JPH0891075A - Vehicle transfer device - Google Patents

Abstract

(57) [Abstract] [Purpose] A vehicle transfer that improves responsiveness while suppressing sudden release of torsion torque and sudden change in steer characteristics of a power train system when switching from a four-wheel drive state to a two-wheel drive state in a turning state. Provide a device. When switching from a four-wheel drive state to a two-wheel drive state, a switching time t is calculated based on a vehicle speed detection value V and a steering angle detection value θ with reference to a storage table (step S6).
By setting the reduction amount ΔD of the duty ratio D for the duty control solenoid valve so as to complete the switching within this switching time t (step S7), and by successively reducing by this reduction amount ΔD (step S8), the tight corner is obtained. The power train system twisting torque due to the braking phenomenon reduces the friction clutch engagement force to prevent shock due to the rapid release of the power train system torsional torque, while shortening the switching time when the tight corner braking phenomenon is small. And improve responsiveness.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle in which the traveling state can be changed from a two-wheel drive state to a full four-wheel drive state by controlling the clutch engagement force of a friction clutch. Regarding the transfer device.

[0002]

2. Description of the Related Art A conventional transfer device for a vehicle is known, for example, as disclosed in Japanese Patent Application Laid-Open No. 62-74721. In this transfer device, the output shaft from the transmission is directly connected to the output shaft from the rear wheels, and the output shaft from the transmission is connected to the output shaft from the front wheels via a friction clutch to continuously transfer the torque transmitted from the friction clutch. A changeable fastening force applying means is provided to gradually change from a four-wheel drive traveling state to a two-wheel drive traveling state or from a two-wheel drive traveling state to a four-wheel drive traveling state. .

[0003]

However, in the above-mentioned conventional transfer device, the two-wheel drive mode is changed from the four-wheel drive mode to the two-wheel drive mode.
When changing to the wheel drive state, the clutch engagement force is gradually reduced. However, since the reduction time of the clutch engagement force is constant regardless of the running state, this switching time is four wheel drive state. In order to prevent a large shock from being caused by the sudden release of the torsional torque acting on the power train system when a tight corner braking phenomenon occurs, it is necessary to set a long time. However, when the degree of the tight corner braking phenomenon is small, there is an unsolved problem that the switching time for switching from the four-wheel drive state to the two-wheel drive state is too long and the responsiveness deteriorates.

Therefore, the present invention has been made by paying attention to the unsolved problem of the above-mentioned conventional example, and changes the switching time from the four-wheel drive state to the two-wheel drive state according to the degree of the tight corner braking phenomenon. An object of the present invention is to provide a transfer device for a vehicle, which can change the optimum switching time to prevent the shock due to the release of the torsion torque of the power train system and improve the responsiveness.

[0005]

In order to achieve the above object, a transfer device for a vehicle according to a first aspect of the present invention has a driving force input from a transmission to an input shaft as shown in the basic configuration diagram of FIG. And a two-wheel / four-wheel switching mechanism for transmitting the driving force transmitted to the first output shaft to the second output shaft via a friction clutch capable of controlling the clutch pressure.
A transfer device for a vehicle, comprising: a traveling state detecting means for detecting a traveling state of the vehicle; and a clutch control means for controlling a clutch engagement force of the friction clutch based on a traveling state detection value of the traveling state detecting means, A turning running state detecting means for detecting a turning running state; a switching time setting means for setting a switching time for switching from a four-wheel driving state to a two-wheel driving state based on a turning state detection value of the turning running state detecting means; When the clutch control means controls from the four-wheel drive state to the two-wheel drive state, a clutch engagement force reducing means for gradually reducing the clutch engagement force corresponding to the switching time is provided.

According to a second aspect of the present invention, in the vehicle transfer apparatus of the first aspect, the turning traveling state detecting means has a vehicle speed detecting means for detecting a vehicle speed and a steering angle detecting means for detecting a steering angle. However, the switching time setting means
A longer switching time is set as the steering angle detection value of the steering angle detection means becomes larger, and a longer switching time is set as the vehicle speed detection value of the vehicle speed detection means becomes smaller even with the same steering angle detection value. It is characterized by

According to a third aspect of the present invention, there is provided a transfer device for a vehicle according to the first aspect, wherein the turning state detecting means detects a lateral acceleration of the vehicle and a longitudinal acceleration of the vehicle. The switching time setting means sets a longer switching time as the lateral acceleration detection value of the lateral acceleration detection means increases, and even if the lateral acceleration detection value is the same, the switching time setting means sets the switching time before and after the longitudinal acceleration detection means. It is characterized in that the larger the detected acceleration value is, the longer the switching time is set.

According to a fourth aspect of the present invention, in the vehicle transfer apparatus of the third aspect, the lateral acceleration detecting means estimates the lateral acceleration based on the difference between the left and right wheel speeds of the driven wheels,
The longitudinal acceleration detecting means is configured to estimate the longitudinal acceleration based on the wheel speed of the driven wheels.

[0009]

According to the first aspect of the invention, when the turning traveling state detecting means detects the turning traveling state, the switching time setting means sets the switching time based on the detected turning traveling state value.
This switching time is set by, for example, judging the degree of tight corner braking phenomenon from the steering angle and vehicle speed, and when the degree of tight corner braking phenomenon is small, a short switching time is set, and the degree of tight corner braking phenomenon is set from this. Becomes longer, the clutch engagement force reducing means changes the engagement force of the friction clutch to the two-wheel drive state by causing the engagement force of the friction clutch to change at the switching time set by the switching time setting means. Therefore, when the degree of tight corner braking is small, the response is improved, and on the contrary, when the degree of tight corner braking is large, the occurrence of shock and sudden change in the steer characteristics of the vehicle due to release of the power train torsion torque are prevented. .

According to the second aspect of the present invention, the degree of tight corner braking phenomenon is estimated by the turning traveling state detecting means from the steering angle detection value and the vehicle speed detection value, and the tighter the steering angle detection value by the switching time setting means, the tighter the steering angle. By determining that the degree of corner braking is large, a long switching time is set, and even if the same steering angle detection value is set, the longer the switching time is set, the longer the switching time is set. Set the time.

According to the third aspect of the present invention, the turning traveling state of the vehicle is estimated from the lateral acceleration and the longitudinal acceleration generated in the vehicle, and the larger the detected lateral acceleration value in the switching time setting means, the larger the steer characteristic change of the vehicle. A long switching time is set based on the judgment, and a longer switching time is set as the longitudinal acceleration detection value increases even with the same lateral acceleration detection value, to prevent sudden changes in steer characteristics during turning and to reduce noise during acceleration / deceleration. And suppress the occurrence of vibration.

According to the fourth aspect of the present invention, the lateral acceleration of the vehicle is detected from the wheel speed difference between the left and right driven wheels, and the longitudinal acceleration of the vehicle is also detected from the wheel speed of the driven wheels. The lateral acceleration and the longitudinal acceleration are estimated without using the sensor and the longitudinal acceleration sensor.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 shows a part-time four-wheel drive vehicle based on the FR (front engine, rear drive) system, which includes an engine 10 as a rotary drive source and a front left-
Rear right wheels 12FL to 12RR, a driving force transmission system 14 capable of changing a driving force distribution ratio to the wheels 12FL to 12RR, and a hydraulic pressure supply for supplying hydraulic pressure to control the driving force distribution by the driving force transmission system 14. The vehicle includes a device 16 and a controller 18 that controls the hydraulic pressure supply device 16.

The driving force transmission system 14 is an automatic transmission 20 that shifts the driving force from the engine 10 at a selected gear ratio.
And the driving force from the automatic transmission 20 is the front wheels 12FL, 1
It has a 2FR and a transfer 22 that distributes to the rear wheels (normally driven wheels) 12RL and 12RR. Then, in the driving force transmission system 14, the front wheel driving force distributed by the transfer 22 is transmitted to the left and right front wheels 12FL, 12FR via the front wheel side output shaft 24, the front differential gear 26 and the front wheel side drive shaft 28. The rear wheel side driving force is transmitted to the left and right rear wheels 12RL and 12RR via the propeller shaft (rear wheel side output shaft) 30, the rear differential gear 32 and the drive shaft 34.

FIG. 3 shows the internal structure of the transfer 22. The input shaft 42 and the first shaft 42 are coaxially butted in the transfer casing 40.
In the output shaft 44, the input shaft 42 is the front casing 40a.
Is rotatably supported by a radial bearing 46 on the first
The output shaft 44 has a radial bearing 48 in the rear casing 40b.
It is rotatably supported via and is arranged so as to be rotatable relative to each other.

Below the front casing 40a and the rear casing 40b, the front casing 40a is parallel to the input shaft 42 and the first output shaft 44, respectively.
And the bearing 50 disposed in the rear casing 40b
The second output shaft 54 is rotatably supported by and 52. The input shaft 42 is the output shaft 5 of the automatic transmission 20.
6, the first output shaft 44 is connected to the rear wheel side output shaft 30, and the second output shaft 54 is connected to the front wheel side output shaft 24.

An auxiliary transmission mechanism 58 is inserted between the input shaft 42 and the first output shaft 44, and the
A two-wheel / four-wheel drive switching mechanism 60 is provided between the output shaft 44 and the second output shaft 54. The subtransmission mechanism 58 includes a planetary gear mechanism 62 and a meshing clutch type high / low speed switching mechanism 64 that is coaxially arranged on the planetary gear mechanism 62.

The planetary gear mechanism 62 includes a sun gear 62a formed on the outer periphery of the input shaft 42 and a front casing 40.
It is composed of an internal gear 62b fixed inside a, a pinion gear 62c that meshes with the sun gear 62a and the internal gear 62b, and a pinion carrier 62d that rotatably supports the pinion gear 62c.

The high / low speed switching mechanism 64 is integrally formed on the left end side with a cylindrical portion 64a ₁ having a spline hole 64b ₁ which engages with a spline shaft portion formed on the outer periphery of the first output shaft 44. A shift sleeve 64b, which is constituted by a flange portion 64a ₂ having external teeth 64b ₂ formed on its surface and is slidable in the axial direction;
4b is formed on the outer peripheral position of the input shaft 42 capable of meshing with the spline hole 64b _{1 of} 4b, and the inner periphery of the pinion carrier 62d capable of meshing with the outer teeth 64b ₂ of the shift sleeve 64b. It is composed of a low speed shift gear 64d.

The shift sleeve 64b is shown in FIG.
As shown, the cylindrical portion 64a₁Formed on the outer peripheral surface of the right end of
The four grooves 64e are arranged in the circumferential groove 64e so as to be slidable in the left-right direction.
The fork 64g formed integrally with the crod 64f is engaged.
This fork rod 64f is combined with the link (not shown).
A rear two-wheel drive Hi-relay installed near the driver's seat via a mechanism.
Range (hereinafter referred to as 2H range), 4-wheel drive high-speed range
(Hereinafter referred to as 4H range), neutral range (hereinafter
Below, referred to as N range) and 4 wheel drive low speed range (hereinafter,
Auxiliary transmission lever that can linearly select 4L range)
Are connected to each other. 2H range with this auxiliary transmission lever
When the 4H range is selected, the spline hole 64
b₁Engages with the high speed shift gear 64c, and the input shaft 42
Driving force transmitted directly to the first output shaft 44
It is moved to the high speed shift position H, and from this state, the auxiliary transmission lever is
-By selecting N range, the spline hole 64
b ₁Is a high speed shift gear 64c and a four-wheel drive gear 80
Of the input shaft 42 and the first output shaft 44 from each other.
Moved to the neutral position N where the connected state is released,
Furthermore, by selecting the 4L range with the auxiliary transmission lever
The lower side of the shift sleeve 64b in FIG.
As shown, spline hole 64b₁High speed shift gear
64c is disengaged, and instead of this, external teeth 64b₂Is low
It engages with the gear 64d for speed shift and has a spline hole 64b.
₁4 wheel drive formed on the first sprocket 68 described later
It is moved to the low speed shift position L that meshes with the gear 80.

Further, the two-wheel / four-wheel drive switching mechanism 60 includes a wet multi-plate friction clutch (hereinafter abbreviated as friction clutch) 66 for changing the driving force distribution ratio to the front and rear wheels, and a first.
The first sprocket 6 rotatably arranged on the output shaft 44.
8, a second sprocket 70 coaxially coupled to the second output shaft 54, and a chain 72 wound between the first and second sprockets 60, 70.

The friction clutch 66 includes the first sprocket 6
8, a clutch drum 66a coupled to the clutch drum 66a, a friction plate 66b splined to the clutch drum 66a, a clutch hub 66c splined to the outer circumference of the first input shaft 44, and a clutch hub 66c integrally coupled to the clutch hub 66c. The friction disc 66d disposed between the friction plates 66b and the first output shaft 44
The rotary member 66e that rotates integrally with the rotary member 66e to bring the friction plate 66b and the friction disk 66d into contact with each other by the axial movement toward the clutch drum 66a, and is mounted on the inner wall of the rear casing 40b to enable the axial movement. The clutch piston 66g, the thrust bearing 66f for transmitting the axial movement of the clutch piston 66g to the rotating member 66e, and the cylinder chamber 6 formed between the inner walls of the clutch piston 66g and the rear casing 40b.
6h, the clutch piston 66 with respect to the rotating member 66e
It is composed of a return spring 66j that applies a biasing force to the g side.

When the clutch pressure P _C is supplied from the hydraulic pressure supply device 16 to the input port 74 formed in the rear casing 40b which communicates with the cylinder chamber 66h, the clutch piston 6 is generated by the pressing force generated in the cylinder chamber 66h.
6g moves to the left side of FIG. 3, and the clutch piston 66
The movement of g is caused by the rotation member 66e via the thrust bearing 66f.
The friction plate 66b and the friction disc 66d, which are transmitted to each other and are separated from each other, come into contact with each other due to the movement of the friction disc 66d, and the clutch engagement force corresponding to the clutch pressure Pc due to the frictional force is applied. As a result, the rotational drive force of the first output shaft 44 passes through the first sprocket 68, the chain 72, and the second sprocket 70 at a predetermined torque distribution ratio according to the clutch engagement force of the friction clutch 66. 54 is transmitted.

Further, when the supplied clutch pressure Pc decreases and the urging force of the return spring 66j moves the rotating member 66e and the clutch piston 66g to the right in FIG. 3, the friction plate 66b and the friction disc 66d are separated from each other. The transmission of the driving force from the first output shaft 44 to the second output shaft 54 is cut off. Further, the first sprocket 68 is provided with the four-wheel drive gear 80 on the outer periphery on the shift sleeve 64b side, and when the shift sleeve 64b is shifted to the low speed position as described above,
The spline hole 64b ₁ meshes with the four-wheel drive gear 80 to forcibly connect the first output shaft 44 and the second output shaft 54. Here, the shift sleeve 64b and the four-wheel drive gear 80 constitute a dog clutch forcibly forming the four-wheel drive state.

Further, inside the front casing 40a, as shown in FIG. 4, a high speed shift position sensor 86 for detecting that the shift sleeve 64b has slid to the high speed shift position H is provided. The detection signal S _H of the sensor 86 is input to the controller 18. Further, the hydraulic pressure supply device 16 supplies a predetermined clutch pressure Pc to the input port 74 of the transfer 22 by the circuit configuration shown in FIG.

This hydraulic pressure supply device 16 includes a first output shaft 44.
Forward / reverse rotation type main pump 10 that is directly connected to and rotationally driven
0 and a positive rotation type sub-pump 104 which is arranged in parallel with the main pump 100 and is rotationally driven by the electric motor 102 as a power source are used as hydraulic pressure sources. The main pump 100 and the sub-pump 102 use a strainer 106a, a strainer 106a, and a hydraulic oil in an oil tank 105 formed in a lower portion of the front casing 40a and the rear casing 40b.
08a, and the discharge side pipes 106b, 108
Discharge to b. An oil element 112 is connected to the converging pipe 110a that converges the pipes 106b and 108b. The oil element 112 is connected to the upstream side (the main pump 100 and the sub pump 104 side) and the other end is connected to the lubrication system supply section 114 side. The relief path 116 to be connected is connected. A line pressure regulating valve 118 is connected to the downstream side of the oil element 112, and pipes 110b, 110c, 11 branching from the converging pipe 110a.
The input sides of the electromagnetic switching valve 120, the clutch pressure adjusting valve 122, and the pressure reducing valve 124 are connected to 0e. When the pilot pressure from the electromagnetic switching valve 120 is supplied to the output side of the clutch pressure adjusting valve 122, the pilot switching valve 1 that supplies the clutch pressure Pc to the transfer 22.
The input side of 26 is connected, and the output side of the pressure reducing valve 124 is
The input side of the duty control solenoid valve 128 is connected. A temperature sensor 130 for detecting the temperature of the hydraulic oil is provided in the oil tank 105, and an output from a hydraulic switch 132 and a pilot switching valve 126 for detecting the pressure set to be reduced by the line pressure regulating valve 118. Pressure switch 13 for detecting the clutch pressure Pc
4 are provided, and these detection signals are output to the controller 18. The hydraulic pressure supply device 16 is arranged inside the transfer 22 in an actual vehicle.
The main pump 100 that sucks the hydraulic oil from the oil tank 105 has a first gear 136a as shown in FIG.
Also, the sub-pump 104 is connected to the first output shaft 44 via the second gear 136b, and is connected to the electric motor 102 externally attached to the rear casing 40b.

Next, each component of the hydraulic pressure supply device 16 will be described in detail with reference to FIG. The main pump 100, which is driven in the normal rotation, sucks the working oil from the oil tank 105 through the strainer 106a connected to the end of the suction pipe 106c, and the sub-pump 104 is also a strainer connected to the end of the suction pipe 108c. The hydraulic oil is sucked from the oil tank 105 via 108a. Then, the converging pipe 110
Check valves 106d and 108d are respectively inserted in the discharge pipes 106b and 108b of each pump connected to a, and a bypass passage is provided between the discharge pipe 106b of the main pump 100 and the suction pipe 108c of the sub pump 104. 140 is connected. This bypass 140 is
It is composed of a bypass pipe 140a and three check valves 140b inserted in the bypass pipe 140a. When the discharge pipe 106b is in a negative pressure state, the check valve 140b is in an open state, and the hydraulic oil is It becomes a communication passage that flows in the direction of the dashed arrow.

The relief passage 116 connected to the convergent pipe 110a on the upstream side of the oil element 112 has a relief pipe 116 having the other end connected to the lubricating system supply section 114 side.
a and two check valves 116b with springs inserted in the relief pipe 116a. Then, when the filter of the oil element 112 is clogged and the pressure on the upstream side of the oil element 112 becomes equal to or higher than a predetermined pressure, the check valve 116b is opened, and the hydraulic fluid flows in the direction of the dashed arrow. Become.

The line pressure regulating valve 118 is composed of an internal pilot and a spring type pressure reducing valve, and has an input port 118 _A connected to the convergent pipe 110a side and a lubricating system 11.
A spool is slidably arranged in a tubular valve housing having internal pilot ports 118 _P1 and 118 _P2 to which primary pressure and secondary pressure are supplied via an output port 118 _B connected to the four side and a fixed throttle. A return spring 118a for urging the spool toward one end is provided. Then, the main pump 100 or the sub pump 1
The line pressure P _L increased by 04 is applied to the line pressure regulating valve 11
The pressure is reduced to a predetermined pressure from No. 8 and is supplied to the electromagnetic opening / closing valve 120, the clutch pressure adjusting valve 122, and the pilot valve 124. The hydraulic oil flowing out from the output port 118 _B when the pressure reduction is set is supplied to the lubrication system supply unit 114.

The clutch pressure adjusting valve 122 is composed of an internal pilot valve, an external pilot valve, and a spring type pressure regulating valve, and is connected to the pipe 110c in the input port 1.
22 _A , an output port 122 _B connected to the pilot switching valve 126, an internal pilot port 122 _P1 to which the secondary pressure is supplied as a pilot pressure via a fixed throttle, and an external pilot to which a control pressure is supplied from the duty control solenoid valve 128. A spool is slidably disposed in a tubular valve housing having a port 122 _P2, and a return spring 122a that biases the spool toward one end is disposed. When the pilot control pressure from the duty control solenoid valve 128 is not supplied, the clutch pressure adjusting valve 122 closes the communication passage between the input port 122 _A and the output port 122 _B and does not output the secondary pressure. When the pilot control pressure is supplied from the control solenoid valve 128, the spool is moved and controlled, and the secondary pressure corresponding to the pilot control pressure is output from the output port 122 _B as the clutch pressure Pc.

The pressure reducing valve 124 is composed of an internal pilot and a spring type constant secondary pressure type pressure reducing valve, and has an input port 124 _A connected to the pipe 110 e and an output port 12 connected to the duty control solenoid valve 128.
4 _B, and the internal pilot port 124 _P to the secondary pressure from the output port 124 _B is supplied as a pilot pressure through a fixed throttle, the spool is slidable in a cylindrical valve housing having a drain port 124 _D And a return spring 12 for urging the spool toward one end.
4a is provided. Then, the spool is moved to a predetermined position by the pilot pressure supplied to the internal pilot port 124 _P , so that the input port 12
The primary pressure supplied from 4 _{A is} supplied to the duty control solenoid valve 128 as a control pressure reduced and adjusted to a predetermined pressure.

The duty control solenoid valve 128 has three
An output port configured to be a port 2 position type and connected to an input port 128 _A connected to the pressure reducing valve 124 side, a drain port 128 _D connected to the drain side, and an external pilot port 122 _P2 of the clutch pressure regulating valve 122. 12
8 _B and, and a return spring 127a, normal position 128b spool disposed within the valve causes communication between the output port 128 _B and the drain port 128 _D
If a valve which is controlled to move the operating position 128c which communicates the input port 128 _A and the output port 128 _B.
Then, when the exciting current i ₀ having a required duty ratio is supplied from the controller 18 to the solenoid 128d, the section return spring 1 in which the exciting current i ₀ is in the ON state.
28a against the normal position 128b to the operating position 12
By controlling the movement of the spool to 8c, the pilot control pressure according to the duty ratio is adjusted to the clutch pressure adjusting valve 12
2 is output. Therefore, the clutch pressure adjusting valve 122
When the pilot control pressure is supplied from the duty control solenoid valve 128 to the external pilot port 122 _P2 , the clutch pressure Pc corresponding to the pilot control pressure is output, and the clutch engagement force of the friction clutch 66 is controlled accordingly. Thus, the drive torque is distributed to the front wheels according to the clutch pressure Pc.

Further, the spring offset type solenoid operated directional control valve 120 is arranged at the position of 3 ports and 2 ports, and the input port 120 _A to which the line pressure is supplied and the pilot directional control valve 12 are provided.
6 and an output port 120 _B to be connected to the external pilot port 126 _P1 of the drain port 120 and a _D, the drain port 120 a spool disposed within the valve shuts off the input port 120 _A and the output port 120 _B a normal position 120b for communicating to _D, the input port 120 _a
And the output port 120 _B are in communication with each other and the drain port 120 _D is shut off. When the exciting current i ₁ is input from the controller 18 to the solenoid 120d, the electromagnetic switching valve 120 controls the movement of the spool against the return spring 120a while the exciting current i ₁ continues to be in the ON state. To the operating position 120c, and the pilot switching valve 1
The pilot control pressure is supplied to the external pilot port 126 _P1 of 26. Further, when the exciting current i ₁ from the controller 18 is turned off, the return spring 120
It is returned to the normal position 120b by the pressing force of a, and the pilot control pressure supplied to the external pilot port 126 _P1 is extinguished through the drain port 120 _D.

As shown in FIG. 6, the pilot switching valve 126 has an input port 126 _A to which the secondary pressure is supplied from the clutch pressure adjusting valve 122 and an output port 126 _B to supply the secondary pressure to the transfer 22. , Electromagnetic switching valve 120
An external pilot port 126 _P1 to which pilot control pressure is supplied when the solenoid 120d is in the energized state,
Cylindrical valve housing 1 with drain port 126 _D
A spool 126e is slidably disposed in 26i,
Further, the valve is provided with a return spring 126a for urging the spool 126e toward one end.

Then, the switch of the pilot switching valve 126
The pool 126e is the external pilot port 126._P1To
If the pilot control pressure is not supplied, input port 1
26 _AAnd output port 126_BAre cut off, and the output
Heart 126_BIs the drain port 126_D2W communicating with
The movement is controlled to the D mode position 126b.
(The state of the left half cross section of FIG. 6). In addition, the solenoid on-off valve 120
Of the solenoid 120d is turned on.
And the spool of the solenoid on-off valve 120 to the second position 120c.
Movement control and external pilot port 126_P1On the pilot
Control pressure is supplied to the input port 126_AAnd output port
126_BMoved to 4WD mode position 126c where
It is designed to be controlled (right half cross section of FIG. 6)
state).

As described above, by driving the pilot switching valve 126 with the pilot control pressure from the electromagnetic switching valve 120, the spool 126e can be driven with a high pilot control pressure, and the sliding passage of the spool 126e is dusted. Even when chips or the like are attached and the sliding resistance of the spool 126e is high, the sliding of the spool 126e can be ensured.

On the other hand, as shown in FIG. 2, the controller 18 is arranged in the high speed shift position sensor 86, for example, the 2H range position of the auxiliary shift lever, and is in the 2-4WD mode which is turned on when the 2H range is selected. A sensor 90, a steering angle sensor 92 and a vehicle speed sensor 94 for detecting a steering angle of a steering wheel of a vehicle as a turning traveling state detecting means of the vehicle, a front wheel side output shaft 24 as a traveling state detecting means.
Detection signal from a front wheel side rotation speed sensor 96 that detects the rotation speed of the front wheel side and a rear wheel side rotation speed sensor 98 that detects the rotation speed of the input shaft 42 connected to the output shaft of the automatic transmission 20 as the rear wheel side rotation speed. Based on the excitation current i to the hydraulic supply device 16
It is a device that outputs ₀ and i ₁ . In this embodiment, the same controller 18 is used for the hydraulic pressure supply device 16
Is also adapted to perform control so that a predetermined line pressure can be maintained.
0 and hydraulic switches 132 and 134, and a motor control signal S _M based on detection signals from these sensors is also sent from the controller 18 to the hydraulic supply device 16 described above.
Is output to.

As shown in FIG. 7, the controller 18 includes a microcomputer 7 for performing the driving force distribution control, a microcomputer 8 for performing the above-mentioned predetermined line pressure holding control, and the microcomputer 7.
The solenoid 128 of the duty control solenoid valve 128 in the hydraulic pressure supply device 16 according to the control signal CS ₀ from
A drive circuit 31a for supplying an exciting current i ₀ having a required duty ratio D to d, and an exciting current i ₁ which is turned on / off in response to a control signal CS ₁ from the microcomputer 7, in an electromagnetic switching valve in the hydraulic pressure supply device 16. A drive circuit 31b for supplying the solenoid 120d of 120, and a motor drive for chopper-controlling the electric motor 102 according to the motor control signal S _M from the microcomputer 8 and controlling the speed to a rotation speed according to the motor control signal S _M. And a circuit 103.

The microcomputer 7 is arranged to
Sensor 86, 90, 92, 94, 96, 98 detection signal
A / D conversion function to read the signal as each detected value
Input interface circuit 7a for performing a predetermined program
Calculation / control processing for driving force distribution control according to
1)) and the like, and an arithmetic processing unit 7b, a ROM, a RAM
Obtained by the storage device 7c such as the above and the arithmetic processing device 7b.
Determine the torque distribution on the front wheel side corresponding to the rotation speed difference ΔN between the front and rear wheels
Clutch pressure P to be determined_COf duty ratio D to command
Signal CS₀And clutch pressure P_CDecide whether to output
Control signal CS₁Output interface for outputting
Circuit 7d. In addition, the micro computer
The computer 8 is provided with the sensors 130, 132, 134.
A / D converter for reading each detection signal as each detection value
Functioning input interface circuit 8a and arithmetic processing unit
The storage unit 8b, the storage device 8c such as ROM and RAM, and
The electric motor rotation speed command value obtained by the arithmetic processing unit 8b
For example, analog voltage signal S _MTo output as D /
Equipped with an output interface circuit 8d having an A conversion function
I am.

The microcomputer 7 is shown in FIG.
In accordance with the arithmetic processing shown in 1, the high speed shift position sensor 86
High-speed shift position detection signal S from_H2-4WD mode
Mode signal D from the sensor 90_nOf the steering angle sensor 92
Steering angle detection signal θ, vehicle speed detection signal from the vehicle speed sensor 94
V, the rotation speed signal N of the front wheel side rotation speed sensor 96_FAnd rear wheels
Rotation speed signal N of the side rotation speed sensor 98_RBased on fast
Shift position detection signal S _HIs on, the front wheel
Luk distribution command value T₂To set the corresponding
Chi pressure P_CCalculate the duty ratio D
Control signal CS corresponding to the command value D₀Output
Control signal CS₁Control to the ON state, and
Signal D_nIs switched from off to on
That is, when the two-wheel drive state is selected from the four-wheel drive state
The steering angle detection signal θ of the steering angle sensor 92 and the vehicle speed sensor.
The switching time t is calculated based on the vehicle speed detection signal V of the service 94.
Then, during this switching time t, the four-wheel drive state is gradually changed to the two-wheel drive state.
Clutch pressure P to drive_CDew to order
Perform 4-2WD switching processing to gradually decrease the tee ratio D.
2-4WD mode signal of the mode sensor 90_nBut
When the two-wheel drive state is represented by
Detection signal S of the sensor 86_HControl when is off
Signal CS₁And CS₀Are turned off and these control signals
CS₀And CS₁The drive circuits 31a and 31b, respectively.
Output to.

The drive circuit 31a is provided with, for example, a pulse width modulation circuit which outputs an exciting current having a duty ratio D corresponding to a command value of a control signal CS ₀ which is an analog voltage signal output from the microcomputer 7. Therefore, the exciting current i ₀ having the duty ratio corresponding to the command value of the control signal CS ₀ is output to the solenoid 128d of the duty control solenoid valve 128.

The drive circuit 31b is the microphone.
Control signal CS output from computer 7₁The electromagnetic
Current value that can excite the solenoid 120d of the switching valve 120
Exciting current i₁Of the electromagnetic switching valve 120
Output to the solenoid 120d. In addition,
Calculation processing performed by the computer 8, that is, the hydraulic pressure supply device 1
The control for enabling 6 to supply a predetermined hydraulic pressure is, for example,
For example, the hydraulic switch 132
On the downstream side of the oil element 112 of the converging pipe 110a
Line pressure P_LDetected that is below the set value
The discharge pressure (oil amount) from the sub-pump 104
Oil temperature detection from the oil temperature sensor 130 for controlling
Value S_YThe control signal that indicates the rotation speed command value set according to
No. S_MIs calculated and is supplied to the motor drive circuit 103.
By controlling the rotation speed of the electric motor 102,
The line pressure P output from the hydraulic pressure supply device 16_LWhere
It maintains a constant pressure. The high-speed shift position
The detection signal of the sensor 86 is on and the hydraulic switch 13
4, the clutch pressure output from the pilot switching valve 126
P _CIs detected to be zero, the pilot is turned off.
It judges that the exchange valve 126 is abnormal and issues an alarm.

Here, the storage device 7c of the microcomputer 7 pre-stores programs and fixed data necessary for executing the processing of the arithmetic processing device 8b, and the processing results can be temporarily stored. There is. Among these, the fixed data includes a storage table corresponding to each control characteristic shown in FIGS. 8 to 11. FIG. 8 shows the transmission torque ΔT to the front wheel side with respect to the front and rear wheel rotation speed difference ΔT.
It shows the control characteristics of. According to this, the driving force distribution is nonlinearly increased in accordance with the increase of the rotational speed difference ΔN of the transmission torque ΔT. Further, FIG. 9 shows the switching valve 126.
It shows the value of the transmission torque ΔT to the front wheels, which increases linearly with the increase of the clutch pressure Pc. FIG.
Is the solenoid 128d of the duty control solenoid valve 128
Clutch pressure regulating valve 12 that increases non-linearly in a parabola in accordance with an increase in duty ratio D of exciting current i ₀ supplied to
The value of the clutch pressure Pc of 2 is shown. Furthermore, FIG.
Is a storage table showing the relationship between the steering angle θ with the vehicle speed V as a parameter and the switching time t from the four-wheel drive state to the two-wheel drive state. When the vehicle speed V is low, the relatively small steering angle θ _S1 The increase rate of the switching time t starts to increase, and as the vehicle speed V increases, the steering angle at which the switching time starts to increase increases, and the increase rate decreases.

Then, when the transmission torque ΔT is determined by referring to the storage table corresponding to FIG. 8 based on the rotational speed difference ΔN between the front and rear wheels in the microcomputer 7, the storage corresponding to FIG. 9 and FIG. The value of the duty ratio D that the controller 18 has to output is calculated backward by sequentially referring to the table. And FIG.
When the clutch pressures P _{1 to} P ₂ according to the duty ratio in the range of D _{1 to} D ₂ are supplied to the friction clutch 66, the torque distribution ratio on the front and rear wheels side according to the engagement force of the friction clutch 66 becomes Rear wheel: Front wheel = 100%: 0-Rear wheel: Front wheel = 50
%: Continuously changed up to 50%. When the duty ratio is D ₁ or less, the clutch pressure P _C is generated and the friction plate 66b of the friction clutch 66 and the friction disc 66d are in pressure contact with each other, but the driving force is not transmitted. In addition, the 2-4WD mode sensor 90
When the mode signal D _n is changed from the off state to the on state and the change from the four-wheel drive state to the two-wheel drive state is selected, within the switching time t determined by referring to the storage table of FIG. The duty ratio D is gradually decreased so that the four-wheel drive state is changed to the two-wheel drive state.

The hydraulic pressure supply control by the microcomputer 7 is executed according to the reference calculation process shown in the flowchart of FIG. The reference calculation process of the hydraulic pressure supply control will be briefly described. The calculation process of FIG. 12 is executed by a timer interrupt every predetermined time (for example, τ = 20 msec). First, in step S1, the 2-4WD mode sensor 90 is used. Read the input mode signal D _n ,
Next, at step S2, it is determined whether or not the switching determination flag F indicating that the four-wheel drive state is being switched to the two-wheel drive state is set to "1". when it is reset to 0 ", the process proceeds to step S3, determines whether or not a changing selection of based on the mode signal D _n from the four-wheel drive mode to the two-wheel drive mode. This determination is that when the mode during the previous processing is the four-wheel drive mode and the mode during the current processing is the two-wheel drive mode, the switching from the four-wheel drive mode to the two-wheel drive mode is performed. The determination is made and the process proceeds to step S4.

In step S4, the switching determination flag F
Is set to "1", then the process proceeds to step S5,
The vehicle speed detection signal V and the steering angle detection signal θ are read, then the process proceeds to step S6, and the switching time t is calculated based on the vehicle speed detection signal V and the steering angle detection signal θ by referring to the storage table of FIG. Next, in step S7, the current duty ratio D stored in the predetermined storage area of the storage device 7c is read out, and based on this, the processing cycle τ and the switching time t, the following formula (1) is calculated. The duty ratio decrease amount ΔD per processing is calculated by performing the above.

ΔD = D / (t / τ) (1) Next, the process proceeds to step S8, and a value obtained by subtracting the duty ratio decrease amount ΔD from the current duty ratio D is set as a new duty ratio D. This is set and updated and stored in a predetermined storage area of the storage device 7c. Then, it is determined in step S9 whether the duty ratio D becomes zero or negative, and D
When> 0, the process proceeds to step S10, the duty ratio D stored in the predetermined storage area of the storage device 7c is read, and the control signal for the duty control solenoid valve 128 having the command value corresponding to the duty ratio D is read. CS
_{After 0} is output to the drive circuit 31a, the timer interrupt process is terminated to return to the predetermined main program, and when D ≦ 0, the process proceeds to step S11 to control the control signal CS ₀ and the electromagnetic switching valve 120. After the signal CS ₁ is turned off, the process proceeds to step S12 and the switching determination flag F
Is reset to "0", the timer interrupt processing is terminated, and the predetermined main program is restored.

On the other hand, when the determination result of step S2 is that the switching determination flag F is set to "1", the process proceeds to step S13, and the mode of the mode signal D _{n is} a mode other than the two-wheel drive mode. If it is in the two-wheel drive mode, the routine proceeds to step S8, where
The switching to the wheel drive mode is continued, and when it is the four-wheel drive mode other than the two-wheel drive mode, the process proceeds to step S14, the switching determination flag F is reset to "0", and then the timer interrupt process is ended. To return to the prescribed main program.

If the result of the determination in step S3 is not at the time of switching from the four-wheel drive mode to the two-wheel drive mode, the process proceeds to step S15 to determine whether or not the four-wheel drive mode is set. In the wheel drive mode, the process proceeds to step S16, the control signals CS ₀ and CS ₁ are turned off as in step S11 described above, the timer interrupt process is terminated, and the predetermined main program is restored. When the vehicle is in the wheel drive state, the process proceeds to step S17, and the detection signal S _H input from the high speed shift position sensor 86 is read.

Next, in step S7, it is determined whether the shift sleeve 64b has moved to the high speed shift position H. If it is determined that the shift sleeve 64b has not moved to the high speed shift position H, the friction clutch 66 must be controlled. Therefore, when the control signal CS ₀ and the control signal CS ₁ are turned off, the main program is restored, and it is determined that the high-speed shift position H is reached, the process proceeds to step S19. The control signal CS ₁ for the electromagnetic switching valve 120 is turned on, and then the process proceeds to step S20 to read the rotational speed detection values N _F and N _R of the front wheel side rotation speed sensor 86 and the rear wheel side rotation speed sensor 88, and then read. In step S21, the rotation speed difference ΔN (= N _R −N _F ) obtained by subtracting the front wheel rotation speed N _F from the rear wheel rotation speed N _R.
After calculating, the process proceeds to step S22.

In step S22, the rotational speed difference ΔN is
Refer to the storage tables of FIGS. 8 to 10 in order.
Therefore, the front wheel side torque distribution ΔT corresponding to the rotational speed difference ΔN
Is calculated, and the friction clutch is calculated based on this front wheel side torque distribution ΔT.
Clutch pressure P of switch 66_CAnd finally
Chi pressure P_CD corresponding to₀~ D₁Duty ratio D in the range
Is calculated and updated in a predetermined storage area of the storage device 7c.
Then, the process proceeds to step S23 and the determined data
Control signal CS of command value corresponding to duty ratio D ₀The drive
Output to the circuit 31a and then return to the main program
It

In the processing of FIG. 12, step S
The processing of S5 and S6 corresponds to the switching time setting means, the processing of steps S2 to S4 and S7 to step S13 corresponds to the clutch engaging force reducing means, the processing of steps S15 to S23 and the electromagnetic switching valve 120, the clutch pressure adjustment. Valve 122, constant secondary side pressure reducing valve 124, pilot switching valve 126,
The duty control solenoid valve 128 corresponds to the clutch control means.

Next, the operation of the above embodiment will be described. now,
It is assumed that the vehicle is stopped, the shift lever of the automatic transmission 20 is in the parking range position, the auxiliary transmission lever is in the 2H range, and the engine 10 is stopped. In this state, when the ignition switch is turned on and the engine 10 is started, the controller 1
8 is turned on and each microcomputer 7, 8 is turned on.
Then, predetermined initialization processing (such as resetting the flag and clearing the duty ratio D to zero) is performed, and then predetermined calculation processing is started.

At this time, the vehicle is stopped and the
Engine 1 with the left lever in the parking range position
The driving force of 0 is not transmitted to the output shaft of the automatic transmission 20,
The input shaft 42 of the transfer 22 and the
1 Since the rotation of the output shaft is stopped, the hydraulic pressure supply device 1
The drive of the main pump 100 of 6 is stopped, and the convergence pipe
110a line pressure P_LIs almost zero and therefore the hydraulic pressure
The switch 132 is in the on state, and the switch
Signal S₁Is input to the microcomputer 8,
Of the oil temperature of the oil temperature sensor 130 by the microcomputer 8 of
Outgoing price S_YThe rotation speed of the electric motor 102 is determined based on
The motor drive control signal S corresponding to this _MThe motor drive
Output to the circuit 103. Therefore, the motor drive circuit 10
The electric motor 102 is rotated at the set rotation speed by 3.
The sub-pump 104 is rotationally driven.
The working oil having a predetermined pressure is discharged, and this is the check valve 108.
By being supplied to the converging pipe 110a via d,
Line pressure P_LIs boosted. And the line pressure P_LSet up
When the constant pressure is reached, the hydraulic switch 132 is turned off.
The rotation of the electric motor 102 is stopped accordingly.
Be done.

On the other hand, in the microcomputer 7, FIG.
The process 2 is executed, but since the auxiliary transmission lever is in the 2H range, the mode signal D _n of the 2-4WD mode sensor 90 is in the ON state, and the switching determination flag F is reset to "0". Therefore, steps S1 to S3
Through step S15 to step S16,
The control signals CS ₀ and CS ₁ are controlled in the off state. Therefore, the exciting current i ₀ from the drive circuits 31a and 31b is
And i ₁ are cut off, and the duty control solenoid valve 12
8 maintains the normal position, the pilot control pressure output from now on becomes atmospheric pressure, and the clutch pressure adjusting valve 12
The clutch pressure P _C output from No. 2 becomes zero, the electromagnetic switching valve 120 maintains the normal position, and the pilot control pressure P _C output from this becomes atmospheric pressure. Accordingly, the pilot switching valve 126 becomes normal. The clutch pressure P _C supplied to the friction clutch 66 is maintained at the atmospheric pressure, the friction clutch 66 is disengaged, and the first output shaft connected to the rear wheels 12RL and 12RR of the input shaft 42 is maintained. It is in the rear two-wheel drive state in which only 44 is connected.

After that, for example, when traveling on a good road,
With the auxiliary transmission lever kept in the 2H range, the vehicle can be started by selecting the D range with the shift lever, releasing the brake, and depressing the accelerator pedal. At this time, when the processing of FIG. 12 is executed, the control signals CS ₀ and CS ₁ continue to be in the off state,
The friction clutch 66 continues to be in the disengaged state. On the other hand, since the auxiliary transmission lever is in the 2H range, the high / low speed switching mechanism 64 of the auxiliary transmission mechanism 62 meshes the spline hole 64b ₁ of the shift sleeve 64b with the high speed shift gear 64c formed on the input shaft 42. Since the state at the high speed position H is continued, when the driving force is transmitted from the automatic transmission 20 to the input shaft 42 of the transfer 22, this driving force is transmitted as it is to the first output shaft 44 via the shift sleeve 64b. , Propeller shaft 30, rear differential gear 32
And the rear left and right wheels 12RL, 1 via the drive shaft 34
The left and right rear wheels 12RL and 12RR are transmitted to the 2RR and the vehicle can be driven forward.

As described above, when the vehicle starts traveling, the first output shaft 44 is rotationally driven, so that the main pump 100 mechanically coupled thereto is rotationally driven, and the main pump 100 is operated. The oil is discharged and supplied as line pressure to the converging pipe 110a via the check valve 106d. When the line pressure P _L is maintained at the set pressure by the discharge pressure of the main pump 100, the hydraulic pressure is changed. When the switch 132 is turned off, the electric motor 10 by the microcomputer 8
2 is stopped.

On the other hand, when traveling on a low friction coefficient road such as off-road, snowy road or freezing road, the auxiliary transmission lever is set to 2
Switch from H range to 4H range. The switching of the auxiliary transmission lever from the 2H range to the 4H range can be performed not only when the vehicle is stopped, but also when the vehicle is traveling, for example, when the vehicle is traveling at a low speed of 40 km / h or less.

Then, when the auxiliary transmission lever is switched to the 4H range, the mode signal of the 2-4WD mode sensor 90 becomes the four-wheel drive mode, and when the processing of FIG. 12 is executed, the steps from step S15 to step S15 are executed. When the detection signal S _H of the high-speed shift position sensor 86 is read in S17 and this is in the ON state, the process proceeds from step S18 to step S19, and the electromagnetic switching valve 1
The control signal CS ₁ for 20 is turned on. Therefore, the electromagnetic switching valve 120 is switched from the normal position 120b to the operating position 120c, so that the line pressure P _L
Is used as it is as pilot control pressure and pilot switching valve 1
26, whereby the pilot switching valve 126
Is switched from the normal position 126b to the operating position 126c, and the clutch control pressure P _C output from the clutch pressure adjusting valve 122 can be supplied to the friction clutch 66.

Next, in step S20, the front wheel side rotation speed
Sensor 96 and rear wheel side rotation speed sensor 98 rotation speed detection value N
_FAnd N_RIs read, and then the process proceeds to step S21.
Then, the front-rear wheel rotation speed difference ΔN is calculated and
Based on step S22, the duty control valve 128 is
Control signal CS₀Determine the duty ratio D of
Control signal CS of command value according to duty ratio D₀Drive times
Output to the path 31a. For this reason, the drive circuit 31a
Excitation current i with duty ratio D₀Is a duty control solenoid valve 1
28, the duty control electromagnetic
Pilot control pressure from valve 128 according to duty ratio D
Is output to the clutch pressure regulating valve 122, and this clutch
From the pressure control valve 122, the clutch corresponding to the pilot control pressure
H control pressure P _CIs output, which is the pilot switching valve 12
Is supplied to the friction clutch 66 via 6, and the friction clutch
The clutch engagement force of the switch 66 is controlled.

Therefore, when the front-rear wheel rotation speed difference ΔN is small, the duty ratio D becomes close to zero, and the ON state section of the exciting current i ₀ output from the drive circuit 31a is compared with the OFF state section. Accordingly, the pilot control pressure output from the duty control solenoid valve 128 is also close to zero in response to this, and the clutch pressure P _C output from the clutch pressure adjusting valve 122 is also close to zero. The clutch engagement force of the friction clutch 66 is controlled to be small. Therefore, the driving force transmitted from the first output shaft 44 of the friction clutch 66 to the first sprocket 68 via the friction clutch 66 is close to zero, and the driving force is not transmitted to the front wheel side, and the rear two-wheel drive is performed. It will be in a state,
From this state, the duty ratio D increases as the front-rear wheel rotation speed difference ΔN increases, and the clutch pressure P _C output from the clutch pressure adjusting valve 122 increases accordingly, so that the clutch of the friction clutch 66 is increased. As the fastening force increases, the friction clutch 66, the first sprocket 6
8, the left and right front wheels 1 via the chain 72, the second sprocket 70, the second output shaft 54, the front wheel side output shaft 24, the front differential gear 26 and the drive shaft 28.
The 2FL and 12FR are rotationally driven to be in the four-wheel drive state. After all, the front / rear wheel drive force distribution ratio is changed from 0: 100 to 50:50 according to the front / rear wheel rotation speed difference ΔN, and a good traveling state can be secured.

When the 4H range is selected by the auxiliary transmission lever and the vehicle is traveling in the four-wheel drive state, when the vehicle travels in a tight corner with a relatively low turning radius at a relatively low speed, a tight corner braking phenomenon occurs. In order to eliminate this, the driver sets the auxiliary transmission lever to 2
When the range is switched to the H range, when the process of FIG. 12 is executed, the process proceeds from step S3 to step S4, the switching determination flag F is set to "1", and then step S5.
The vehicle speed detection signal V and the steering angle detection signal θ are read in and the switching time t is calculated by referring to the storage table of FIG. 11 in step S6. The switching time t at this time becomes longer as the value of the steering angle detection signal θ becomes larger, and becomes longer as the value of the vehicle speed detection signal V becomes smaller even with the same value of the steering angle detection signal θ. The switching time is set according to the degree.

Then, the process proceeds to step S8, the duty ratio reduction amount ΔD corresponding to the set switching time t is calculated, and then the value obtained by subtracting the duty ratio reduction amount ΔD from the current duty ratio D is calculated in step S9. The new duty ratio D is updated and stored (step S8), and the control signal CS having the command value corresponding to the updated duty ratio D is stored.
₀ is output (step S10). Therefore, the pilot control pressure of the duty control solenoid valve 128 is reduced in accordance with the duty ratio reduction amount ΔD, so that the clutch pressure P _C output from the clutch pressure adjustment valve 122 is also reduced. By reducing the clutch engagement force, the torque distribution to the second output shaft 54 side is reduced.

After that, since the switching determination flag F is set to "1", steps S2 to S
By shifting to step S8 via step 13, the duty ratio D is decreased by the duty ratio decrease amount ΔD according to the switching time t set in the previous process, and accordingly, the torque distribution on the front wheel side is gradually decreased. When the duty ratio D becomes zero or negative, the clutch engagement force of the friction clutch 66 becomes zero before that, and the state is switched to the complete two-wheel drive state. In this state, the control signals CS ₀ and CS ₁ are turned off (step S11), and the switching determination flag F is also “0”.
Then, the two-wheel drive state described above is restored.

As described above, in order to avoid the tight corner braking phenomenon when the vehicle is turning, the four-wheel drive mode is set to two.
When the vehicle is switched to the wheel drive mode, the switching time t is set according to the degree of the tight corner braking phenomenon, so that the power train system torsion torque in the four-wheel drive state is gradually released, which causes a sudden change. It is possible to reliably prevent the shock generated by releasing the torque, and when the tight corner braking phenomenon is small, the switching time t is shortened, so that the four-wheel drive state can be switched to the two-wheel drive state quickly. The responsiveness can be improved. Further, since it is possible to gradually switch from the four-wheel drive state to the two-wheel drive state, it is possible to prevent a sudden change in the steer characteristic and improve the steering stability.

When the four-wheel drive mode is selected again by the auxiliary transmission lever during the switching from the four-wheel drive state to the two-wheel drive state, the process proceeds from step S13 to step S14 and the switching determination flag F is selected. Is reset to "0", so when the next processing is executed,
After step S3 and step S15, the process proceeds to step S17, and the above-mentioned clutch pressure control in the four-wheel drive mode is executed.

By the way, when a stack is generated in a traveling state in which the 4H range is selected by the auxiliary transmission lever, or when traveling on sandy sand or the like where the stack is likely to occur, it is necessary to switch the auxiliary transmission lever to the 4L range. However, in this case, when the vehicle is stopped and the shift lever is shifted to the N range or the P range, for example, and the auxiliary transmission lever is shifted to the 4L range in this state, the spline hole 64b of the shift sleeve 64b is provided. ₁ for 1st sprocket 68
The high speed shift gear 80 can be engaged with the shift sleeve 64b and the shift sleeve 64b can be moved from the high speed position H to the low speed position L.

When the 4L range is selected by the auxiliary transmission lever, the driving force of the output shaft of the automatic transmission 20 is decelerated by the auxiliary transmission mechanism 62 via the input shaft 42 of the transfer 22, and the reduced driving force. Is formed on the pinion carrier 62d, the low speed shift gear 64d and the shift sleeve 6
Is transmitted to the shift sleeve 64b via the external teeth 64b ₂ of 4b, while being transmitted to the first output shaft 44 spline-coupled from the shift sleeve 64b thereto, and meshes with the spline hole 64b ₁ of the shift sleeve 64b 4
The second output shaft 5 via the wheel drive gear 80, the first sprocket 68, the chain 72, and the second sprocket 70.
4 and the driving force transmitted to the input shaft 42 is forcibly distributed to the first output shaft 44 and the second output shaft 54, resulting in a direct drive four-wheel drive state.

At this time, by shifting the shift sleeve 64b to the low speed position L, the high speed shift position sensor 8
When the detection signal of 8 is turned off and the processing of FIG. 12 is executed by the microcomputer 7, step S1
By shifting from 8 to step S16, the OFF state of the control signal CS ₁ for the electromagnetic switching valve 120 and the control signal CS ₀ for the duty control electromagnetic valve 128 is continued, and the supply of the clutch pressure P _C to the friction clutch 66 is stopped. Maintain a good condition.

In the first embodiment described above, the case where the duty ratio decrease amount ΔD is calculated based on the switching time t has been described. However, the present invention is not limited to this, and the vehicle speed detection signal V Also, a storage table for directly calculating the duty ratio reduction amount ΔD based on the steering angle detection signal θ may be prepared to calculate the duty reduction amount ΔD. In this case, the four wheels drive state is changed to the two wheels. The switching time changes according to the value of the duty ratio at the time of switching to the drive state, so that the torque of the power train system can be released more smoothly.

Next, a second embodiment of the present invention will be described with reference to FIGS. 13 and 14. The second embodiment is the same as the first embodiment.
Instead of controlling the switching time according to the degree of the tight corner braking phenomenon as in the embodiment, the steer characteristic suddenly changes when the four-wheel drive state is switched to the two-wheel drive state during turning of the vehicle. Is to prevent.

That is, in the second embodiment, as shown in FIG. 13, instead of the steering angle sensor 92 and the vehicle speed sensor 94 in the first embodiment, a lateral acceleration sensor 150 for detecting a lateral acceleration Y _G generated in the vehicle and A longitudinal acceleration sensor 152 for detecting the longitudinal acceleration X _G is provided, and the memory device 7c of the microcomputer 7 stores the memory table shown in FIG. 14 instead of the memory table shown in FIG. It has the same configuration as that of the first embodiment described above except that the control processing shown in 15 is changed.

The memory table of FIG. 14 has a configuration of a characteristic diagram showing the relationship between the lateral acceleration detected value Y _G and the switching time t, which uses the value of the longitudinal acceleration detected value X _G as a parameter. When Y _G is small, the switching time t starts to increase from a relatively large longitudinal acceleration detection value X _G and the rate of increase increases, and before and after the lateral acceleration detection value Y _G increases, the switching time increases. It is represented by a characteristic curve in which the increase rate becomes smaller as the acceleration detection value X _G becomes smaller.

In the control processing of FIG. 15, the processing of steps S5 and S6 in the control processing of FIG. 12 in the first embodiment reads the lateral acceleration detection value Y _G and the longitudinal acceleration detection value X _G in step S25. Except that the processing is changed to step S26 in which the switching time t is calculated by referring to the storage table of FIG. 14 based on the read lateral acceleration detection value Y _G and longitudinal acceleration detection value X _G. The same process as the process of 12 is performed, the same step number is given to the corresponding process, and the detailed description thereof will be omitted.

According to the second embodiment, when the vehicle is running in the four-wheel drive mode by selecting the 4H range with the auxiliary transmission lever, the vehicle enters a turning state, and during this turning, the auxiliary transmission is performed. When the 2H range is switched by the machine lever to switch to the two-wheel drive state, in the process of FIG. 15, the process proceeds from step S3 to step S4, the switching determination flag F is set to "1", and the process proceeds to step S25. Then, the lateral acceleration detection value Y _G and the longitudinal acceleration detection value X _G are read, and then the process proceeds to step S26 to refer to the storage table of FIG. 14 based on the lateral acceleration detection value Y _G and the longitudinal acceleration detection value X _G. Then, the switching time t is calculated.

Therefore, the calculated switching time t is longer as the lateral acceleration detection value Y _G is larger because the longitudinal acceleration detection value X _G is substantially zero in the steady circular turning state.
Steering characteristic change when switched from four-wheel drive state to a two-wheel drive state can improve steering stability becomes moderate, even with the same lateral acceleration detection value Y _G, acceleration or deceleration state Therefore, the larger the longitudinal acceleration detection value X _G becomes, the longer the switching time becomes, and it is possible to suppress the generation of noise and vibration when switching from the four-wheel drive state to the two-wheel drive state during acceleration / deceleration. When the lateral acceleration detection value Y _G is small such as when traveling on a curve with a large turning radius, the switching time t can be minimized to improve the responsiveness.

In the second embodiment, the case where the lateral acceleration and the longitudinal acceleration generated in the vehicle are individually detected by the acceleration sensor has been described, but the present invention is not limited to this, and the front wheels, which are the driven wheels, are not limited thereto. Side wheel speed is detected,
The longitudinal acceleration is estimated from the amount of change in the wheel speed per unit time, and the difference in wheel speed between the left and right front wheels is detected.
It is also possible to estimate the lateral acceleration from the wheel speed difference and calculate the switching time t based on the estimated lateral acceleration and longitudinal acceleration.

In the first and second embodiments, the case where the automatic transmission 20 is applied has been described, but the present invention is not limited to this, and a manual transmission may be applied. Further, in the above-mentioned first and second embodiments, the case where the auxiliary transmission 58 is applied to switch to the three modes of the 2H range, the 4H range and the 4L range has been described, but the present invention is not limited to this, and the auxiliary transmission is not limited thereto. The present invention can be applied to a case where two types of modes, that is, a two-wheel drive mode and a four-wheel drive mode, are omitted by omitting 58, and in this case, a mode changeover switch is provided for mode changeover, The microcomputer 7 may read the switch signal of the mode changeover switch, judge the changeover state based on this switch signal, and perform the changeover control.

Further, in the above-mentioned first and second embodiments, the case where the high / low speed switching mechanism 64 of the auxiliary transmission mechanism 62 is mechanically operated by the auxiliary transmission lever has been described, but the invention is not limited to this. 2H range of auxiliary transmission lever,
A mode selection switch having switching contacts corresponding to the 4H range and the 4L range is arranged, an electric motor for slidingly driving the shift sleeve 64b is provided, and the electric motor is driven according to the mode selected by the mode selection switch. Then, the shift sleeve can be slid.

Furthermore, in the above-mentioned first and second embodiments, the case where the duty control solenoid valve 128 is applied to form the pilot control pressure of the clutch pressure adjusting valve 122 has been described, but the present invention is not limited to this. not,
Instead of the duty control solenoid valve 128, an electromagnetic proportional pressure control valve whose output pressure can be adjusted according to the value of the exciting current supplied to the solenoid can be applied. In this case, the drive circuit 31a is, for example, a floating type. A constant voltage circuit may be used to output the exciting current i ₀ having a current value corresponding to the voltage value of the input control signal CS ₀ .

In the first and second embodiments, the case where the present invention is applied to the rear-wheel drive vehicle-based four-wheel drive vehicle has been described. However, the present invention is not limited to this, and the front-wheel drive vehicle-based four-wheel drive vehicle is used. The present invention can also be applied to a vehicle.

[0082]

As described above, according to the first aspect of the present invention.
According to the invention described above, the switching time setting means sets the switching time from the four-wheel drive state to the two-wheel drive state based on the turning state detection value of the turning traveling state detection means, and the clutch engagement is performed according to this switching time. When the clutch control means controls the switching from the four-wheel drive state to the two-wheel drive state by the force reducing means, the clutch engaging force is gradually reduced in accordance with the switching time. The turning state of the vehicle can be detected from the steering angle, vehicle speed, lateral acceleration, etc., and the optimum switching time can be set accordingly, and the power train system at the time of switching from the four-wheel drive state to the two-wheel drive state. The effect that the responsiveness can be improved while surely preventing the shock and the sudden change of the steer characteristic due to the release of the torsion torque is obtained.

Further, according to the invention of claim 2, in addition to the effect of the invention of claim 1, the turning state detecting means is composed of the vehicle speed detecting means and the steering angle detecting means, and the switching time setting means is A longer switching time is set as the steering angle detection value of the steering angle detection means becomes larger, and a longer switching time is set as the vehicle speed detection value of the vehicle speed detection means becomes smaller even with the same steering angle detection value. Therefore, the optimum switching time can be set according to the tight corner braking phenomenon, and the power train torsion torque of the power train system can be reduced when switching from the four-wheel driving state to the two-wheel driving state in the state where the tight corner braking phenomenon occurs. It is possible to obtain the effect that the responsiveness can be improved while preventing the shock caused by the sudden release.

Further, according to the invention of claim 3, in addition to the effect of the invention of claim 1, the turning state detecting means is composed of the lateral acceleration detecting means and the longitudinal acceleration detecting means, and the switching time setting means. Since the longer the switching time is set as the lateral acceleration detection value of the lateral acceleration detection means becomes larger, and the longer the longitudinal acceleration detection value becomes, the longer the switching time is set even if the lateral acceleration detection value is the same. In addition, it is possible to prevent the steer characteristic from changing suddenly when the four-wheel drive state is switched to the two-wheel drive state during turning, and to improve the responsiveness while suppressing the generation of noise and vibration.

Furthermore, according to the invention of claim 4, in addition to the effect of the invention of claim 3, the lateral acceleration is estimated from the wheel speed difference between the left and right wheels on the driven wheel side, and the wheel on the driven wheel side is estimated. Since the longitudinal acceleration is estimated from the speed, there is an effect that a low-cost system can be configured without using an expensive acceleration sensor.

[Brief description of drawings]

FIG. 1 is a basic configuration diagram showing a schematic configuration of the present invention.

FIG. 2 is a configuration diagram showing an outline of a four-wheel drive vehicle according to a first embodiment of the present invention.

FIG. 3 is a diagram showing an internal structure of a transfer according to the first embodiment.

FIG. 4 is a diagram showing a sliding operation of a shift sleeve of the auxiliary transmission mechanism according to the first embodiment.

FIG. 5 is a circuit diagram showing a hydraulic pressure supply device according to the first embodiment.

FIG. 6 is a diagram showing a switching valve used in the hydraulic pressure supply device according to the first embodiment.

FIG. 7 is a block diagram showing a control means according to the first embodiment.

FIG. 8 is a control characteristic graph of transmission torque to the front wheel side with respect to a front-rear wheel rotation speed difference according to the first embodiment.

FIG. 9 is a control characteristic graph of the transmission torque to the front wheels that changes according to the change in clutch pressure supplied from the hydraulic pressure supply device.

FIG. 10 is a control characteristic graph of clutch pressure that changes according to a command current value.

FIG. 11 is a control characteristic graph showing the relationship between the steering angle detection value and the switching time with the vehicle speed detection value as a parameter.

FIG. 12 is a flowchart showing a hydraulic pressure control process of the control means according to the first embodiment.

FIG. 13 is a block diagram showing a control means according to a second embodiment of the present invention.

FIG. 14 is a control characteristic graph showing a relationship between a lateral acceleration detection value and a switching time with the longitudinal acceleration detection value as a parameter according to the second example.

FIG. 15 is a flowchart showing a hydraulic pressure control process of the control means according to the second embodiment.

[Explanation of symbols]

 16 hydraulic supply device 18 controller 42 input shaft 44 first output shaft 54 second output shaft 58 auxiliary transmission 60 two-wheel-four-wheel drive switching mechanism 66 friction clutch 80 four-wheel drive gear 92 steering angle sensor 94 vehicle speed sensor 96 front wheel Side rotation speed sensor 98 Rear wheel rotation speed sensor 120 Electromagnetic switching valve 122 Clutch pressure adjusting valve 124 Secondary pressure constant type pressure reducing valve 126 Pilot switching valve 128 Duty control solenoid valve 150 Lateral acceleration sensor 152 Longitudinal acceleration sensor

Claims (4)

[Claims] 1. A first output shaft to which a driving force input from a transmission to an input shaft is transmitted, and a driving force transmitted to the first output shaft via a friction clutch capable of controlling a clutch pressure. A two-wheel / four-wheel switching mechanism transmitting to two output shafts, a running state detecting means for detecting a running state of the vehicle, and a clutch engagement force of the friction clutch based on a running state detection value of the running state detecting means. In a vehicle transfer device including a clutch control means, a turning traveling state detecting means for detecting a turning traveling state of the vehicle, and a two-wheel drive from a four-wheel driving state based on a turning state detection value of the turning traveling state detecting means. Switching time setting means for setting a switching time to the state, and when the clutch control means controls from the four-wheel drive state to the two-wheel drive state, the clutch engaging force is gradually reduced corresponding to the switching time. A transfer device for a vehicle, comprising: a clutch engaging force reducing means. 2. The turning traveling state detecting means has a vehicle speed detecting means for detecting a vehicle speed and a steering angle detecting means for detecting a steering angle, and the switching time setting means has a steering angle of the steering angle detecting means. The longer the detection value, the longer the switching time is set,
2. The transfer device for a vehicle according to claim 1, wherein even if the detected steering angle values are the same, the smaller the vehicle speed detection value of the vehicle speed detection means, the longer the switching time is set. 3. The turning traveling state detecting means includes a lateral acceleration detecting means for detecting a lateral acceleration of the vehicle and a longitudinal acceleration detecting means for detecting a longitudinal acceleration of the vehicle, and the switching time setting means is a lateral A longer switching time is set as the lateral acceleration detection value of the acceleration detecting means increases, and a longer switching time is set as the longitudinal acceleration detection value of the longitudinal acceleration detecting means increases even if the lateral acceleration detection value is the same. The transfer device for a vehicle according to claim 1, wherein the transfer device is provided. 4. The lateral acceleration detecting means is configured to estimate the lateral acceleration based on the difference between the left and right wheel speeds of the driven wheels, and the longitudinal acceleration detecting means is configured to estimate the longitudinal acceleration based on the wheel speeds of the driven wheels. The transfer device for a vehicle according to claim 3, wherein: