JPH06270708A - Vehicle differential limiting device - Google Patents

Abstract

(57) [Abstract] [Purpose] In a vehicle equipped with a differential device having differential limiting means, the differential limiting means limits the relative motion of the left and right drive wheels relatively quickly. During a sharp turn,
The purpose is to prevent oversteering of steering characteristics due to engine brake operation. [Structure] In a structure in which a differential limiting clutch is provided in a differential device 5 that splits and transmits the input torque from a power unit 3 to the left and right drive wheels 8 and 9, a throttle opening sensor 12 and a steering angle are provided. When a signal from the sensor 14 is input and the engine is in a brake state where the throttle opening is equal to or less than a predetermined value while the steering angle is equal to or greater than a predetermined value,
The left and right drive wheels 8 and 9 are reduced by reducing the engagement force of the clutch.
The control unit 10 is provided for canceling the limitation of the differential operation for

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a differential limiting device for a vehicle, and more specifically to limiting the differential operation of a differential device that splits the input torque from a power unit and transmits the split torque to the left and right driving wheels according to the driving condition. The present invention relates to a differential limiting device.

[0002]

2. Description of the Related Art Generally, in a vehicle, input torque from a power unit composed of an engine and a transmission is absorbed through a differential device in order to absorb a rotational speed difference between left and right wheels during turning. Is configured to communicate to
In this case, when one driving wheel enters a road surface having an extremely low friction coefficient such as muddy, torque is transmitted only to this driving wheel side and the driving wheel slips, so that the vehicle runs. It may be impossible. Therefore, in order to prevent such a situation, this type of differential device limits the differential operation when the slip ratio of one of the driving wheels or the rotational speed difference between the left and right driving wheels exceeds a predetermined value. A differential limiting device is usually provided.

According to Japanese Unexamined Patent Publication No. 59-11922, for example, the slip ratio for limiting the differential operation of the differential device can be set arbitrarily, and at the time of turning, the differential limit slip ratio is increased. Good turning performance is ensured by setting and allowing the differential operation sufficiently.Also, when traveling on a slippery road surface such as a snowy road, the differential limiting slip ratio is set to be low to allow the differential operation. Disclosed is a differential limiting device which is limited to obtain a required forward force.

Further, this differential limiting device switches between allowing the differential operation of the differential device completely or prohibiting it completely and rotating the left and right drive wheels at the same rotational speed. However, in recent years, in order to improve the traveling property during turning, a differential limiting device in which the differential limiting force is variably controlled according to the input torque to the differential device has been put into practical use.
According to this, the larger the input torque, the stronger the differential limiting force and the higher the turning limit, so that good acceleration response can be obtained when the accelerator pedal is depressed during turning.

[0005]

By the way, during the turning traveling in the state where the differential operation of the differential device is limited by the differential limiting device as described above, the accelerator pedal is returned and the engine brake is operated. When this is done, a phenomenon occurs in which the steering characteristic changes to the oversteer side depending on the magnitude of the steering angle at that time. This is because the reverse torque due to the engine braking, that is, the torque in the direction to brake the vehicle body is mainly transmitted to the inner wheel side having a low rotation speed, and the braking force on the inner wheel side becomes relatively large. And this phenomenon is
This is especially noticeable in rear-drive vehicles, but the same tendency also occurs in front-engine / front-drive vehicles, and in either case, running stability during turning deteriorates.

In view of this, the present invention prevents the above steering characteristic from changing to the oversteer side when the engine brake is actuated during turning traveling in a state where the differential operation of the differential device is limited. Therefore, it is an object to improve the running stability in such a case.

[0007]

In order to solve the above problems, a vehicle differential limiting device according to the present invention is characterized in that it is configured as follows.

First, the invention according to claim 1 of the present application (hereinafter,
According to the first invention), a differential device that divides and transmits the input torque from the power unit to the left and right drive wheels is provided with differential limiting means for limiting the differential operation, and the differential limiting device is provided during turning. In a configuration provided with a control means for controlling the differential limiting force generated by the means, a rudder angle detection means for detecting the rudder angle, an engine brake detection means for detecting the operation of the engine brake, and a rudder angle having a predetermined value. It is characterized in that differential limiting force reducing means for reducing the differential limiting force is provided during the above turning and when the engine brake is operating.

The invention according to claim 2 (hereinafter referred to as the second invention) is a differential device that divides the input torque from the power unit into the left and right driving wheels and transmits the divided torque. A steering angle detecting means for detecting a steering angle in a structure including a motion limiting means and a control means for controlling a differential limiting force generated by the differential limiting means according to the input torque during turning. And an engine brake detection means for detecting the operation of the engine brake, and when the steering angle is equal to or greater than a predetermined value and the engine brake is operating, the differential limiting force is set to a magnitude corresponding to the input torque. The differential limiting force reducing means for reducing

The invention according to claim 3 (hereinafter, referred to as the third
In the first invention or the second invention, the differential device is arranged at the rear portion of the vehicle body, and the input torque from the power unit arranged at the front portion of the vehicle body is divided and transmitted to the left and right rear wheels. It is characterized by being applied to configured vehicles, that is, front engine / rear drive vehicles.

[0011]

According to the above construction, according to any of the first to third aspects of the present invention, the left and right driving by the differential device is performed by the differential limiting device while the steering angle is relatively steep turning over a predetermined value. When the engine brake is activated by returning the accelerator pedal while the vehicle is traveling with the differential movement of the wheels limited, the differential limiting force reducing means reduces the differential limiting force to drive the left and right wheels. Differential motion of the wheel will be allowed or restrictions will be relaxed. Therefore, it is possible to avoid oversteering of the steering characteristic due to the operation of the engine brake while the differential limiting force is applied.

Further, according to the second aspect of the invention, the above-mentioned operation is realized in the vehicle which controls the differential limiting force according to the input torque to the differential device. , The effect of improving the acceleration responsiveness and the like during turning by controlling the differential limiting force according to the input torque and the effect of avoiding the oversteering of the steering characteristic at the time of engine braking described above can be obtained at the same time. Will be done.

According to the third aspect of the invention, the effect of avoiding oversteering of the steering characteristic is obtained in a front engine / rear drive vehicle in which oversteering tends to be a problem because neutral steering is originally set. It will be.

[0014]

EXAMPLES Examples of the present invention will be described below.

As shown in FIG. 1, the vehicle according to this embodiment is a front engine / rear drive vehicle in which a power unit 3 consisting of an engine 1 and a transmission 2 is arranged at the front of the vehicle body, and the power unit The torque output from 3 is input via a propeller shaft 4 to a differential device 5 arranged at the rear part of the vehicle body, and is further divided by the differential device 5, and left and right via left and right drive shafts 6 and 7. It is adapted to be transmitted to the rear wheels 8 and 9. As will be described later, the differential device 5 has a differential limiting function for limiting its differential operation, and a differential limiting function for controlling the differential limiting function according to the operating state of the vehicle. A dynamic control unit 10 is provided.

The control unit 10 includes an engine rotation sensor 1 for detecting the rotation speed of the engine 1.
1 from the throttle valve, a signal B from a throttle opening sensor 12 that detects the opening of a throttle valve (not shown) provided in the intake passage of the engine 1, and a steering wheel that detects the steering angle of the steering wheel 13. The signal C from the angle sensor 14 is input.

Further, the vehicle according to this embodiment is provided with an anti-skid brake system (hereinafter referred to as ABS), and the ABS control unit 15 is provided with rear left and right wheels 8 and 9 and left and right front wheels 16 and 17. The signals D1 to D4 from the wheel speed sensors 18, 19, 20, 21 respectively detecting the rotation speeds are input, and among the wheel speed signals D1 to D4, the rear wheels 8 and 9 are input.
Signals D1 and D2 from the ABS control unit 15 to the differential control unit 10
To be transferred to.

The differential control control unit 10 sets the differential limiting force in the differential device 5 based on the input signals A, B, C, D1 and D2, and the set differential limiting force. The control signal E is output to the differential device 5 so that

Next, the structure of the differential device 5 will be described with reference to FIG.

The differential device 5 is arranged on the axes of the small-diameter first bevel gear 31 provided at the rear end of the propeller shaft 4 and the drive shafts 6 and 7 for the rear wheels.
A differential case 34 driven by the output torque of the power unit 3 shown in FIG. 1 via a final reduction gear 33 composed of a second bevel gear 32 meshed with a bevel gear 31 is provided, and a double pinion is provided in the differential case 34. Type planetary gear mechanism 35
A pilot clutch 36, a main clutch 37, and a cam mechanism 38, which are arranged on both sides of the planetary gear mechanism 35, are arranged.

The planetary gear mechanism 35 includes a sun gear 35a arranged on the axes of the drive shafts 6 and 7.
A first pinion gear 35c rotatably supported by the pinion carrier 35b and meshed with the sun gear 35a;
Similarly, a second pinion gear 35d rotatably supported by the pinion carrier 35b and meshed with the first pinion gear 35c, and a ring gear 35e fixed to the inner peripheral surface of the differential case 34 and meshed with the second pinion gear 35d. It is composed of.

The sun gear 35a is connected to the drive shaft 6 for the left rear wheel, and the pinion carrier 35b is connected to the drive shaft 7 for the right rear wheel.

As a result, the left and right rear wheels 8 and 9 shown in FIG.
When the loads acting on the ring gears are equal, the rotation input from the differential case 34 to the ring gear 35e is evenly transmitted to the left and right rear wheels 8 and 9 via the drive shafts 6 and 7, and during turning. When the loads acting on the left and right rear wheels 8 and 9 are not equal, the planetary gear mechanism 35
Alternatively, the differential device 5 operates differentially so that the outer rear wheel having a small load rotates at a higher speed than the inner rear wheel having a large load.

The pinion carrier 35b is movably supported in the axial direction within a certain range.

The pilot clutch 36 is driven by a driving clutch plate 36a engaged with the differential case 34 and a clutch hub 36b rotatably supported on the right rear wheel drive shaft. Side clutch plate 36c, and the solenoid 39 and the armature 40 are arranged to face each other with the clutch plates 36a and 36c sandwiched therebetween. Then, the armature 40 is attracted by a force corresponding to the magnitude of the current applied to the solenoid 39,
The driving side and driven side clutch plates 36a and 36c are fastened by a force corresponding to the magnitude of the current.

The clutch hub 36b is supported so as not to move in the axial direction.

Further, the main clutch 37 includes a drive side clutch plate 37a engaged with the pinion carrier 35b of the planetary gear mechanism 35 and a driven side clutch plate engaged with the drive shaft 6 for the left rear wheel. 37
b and a pressure plate 37c for fastening them. And this pressure plate 3
7c is formed integrally with the pinion carrier 35b. The pinion carrier 35b and the pressure plate 37c are moved to the left side in the drawing so that the drive side and driven side clutch plates 37a and 37b are fastened. It has become.

In addition to the above construction, the end surface of the clutch hub 36b constituting the pilot clutch 36 and the pinion carrier 3 in the planetary gear mechanism 35 are also provided.
A cam mechanism 38 is provided between the end face of 5b and
Next, the structure of the cam mechanism 38 will be described.

As shown in the schematic structure of FIGS. 3 and 4, the cam mechanism 38 includes a pair of ring members 38a and 38b fixedly provided on the opposed end surfaces of the clutch hub 36b and the pinion carrier 35b, respectively. Ring member 38
38c arranged at equal circumferential positions between a and 38b, and each ball member 3
8c is held between recessed portions 38a 'and 38b' formed of two inclined surfaces which are provided facing each other at equal circumferential positions of the ring members 38a and 38b.

When the pilot clutch 36 is released, the rotation of the pinion carrier 35b causes the ring member 38b on the side of the carrier 35b, each ball member 38c, and the ring member 38a on the side of the clutch hub 36b. Even when the clutch hub 36b and the clutch plate 36c on the driven side of the pilot clutch 36 rotate together, and when the pilot hub 36b is engaged and the clutch hub 36b rotates integrally with the differential case 34, the differential case 34 and the pinion carrier 35 are also rotated.
When b is rotating at the same speed, clutch hub 3
Ring member 38 on the 6b side and the pinion carrier 35b side
Since a and 38b also rotate at the same speed, the cam mechanism 38 maintains the state shown in FIG.

On the other hand, the pilot clutch 3
The differential case 34 (ring gear 35e) is operated by the differential operation of the planetary gear mechanism 35 in a state where 6 is fastened.
When relative rotation occurs between the ring member 38a on the side of the clutch hub 36b and the ring member 38b on the side of the pinion carrier 35b, when relative rotation occurs between the ring member 38b on the side of the clutch hub 36b and the recesses 38a ', 38 facing each other.
The position of b'is displaced. Therefore, the ball member 38c held between the respective facing recesses 38a ', 38b' is moved along the slope to form these recesses 38a ', 38b'.
The pinion carrier 35b, which can be moved in the axial direction, is moved so as to be pushed out from the clutch hub 3 in which the axial movement is blocked.
It moves in the direction away from 6b (left side in FIG. 2). Then, the main clutch 37 is engaged by the movement of the pinion carrier 35b.

In this case, the engaging force of the main clutch 37 corresponds to the force of the cam mechanism 38 for axially pressing the pinion carrier 35b, and the pressing force corresponds to the engaging force of the pilot clutch 36. However, the engagement force of the pilot clutch 36 is as described above.
Since it corresponds to the magnitude of the current supplied to the solenoid 39, the engagement force of the main clutch 37 is eventually controlled by controlling the supplied current. The engagement force of the main clutch 37 limits the differential operation between the sun gear 35a of the planetary gear mechanism 35 and the pinion carrier 35b, that is, the drive shafts 6,7.
That is, the differential limiting force limits the differential operation of the left and right rear wheels 8 and 9.

Next, the operation of the differential control control unit 10 for controlling the energization current of the solenoid 39 will be described with reference to the flowchart of FIG.

First, in step S1, the control unit 10 outputs the signals A, B and C from the sensors 11, 12 and 14 shown in FIG.
Engine speed N by the signals D1 and D2 from
E, throttle opening TVO, steering wheel steering angle θ, left rear wheel rotation speed NRL and right rear wheel rotation speed NRR are input, and then engine torque T is set in step S2.

Here, the engine torque T is not the actual output torque of the engine 1 but an alternative characteristic thereof.
The map is set in advance as shown in FIG. 6, and the alternative value T of the engine torque corresponding to the engine speed NE at that time is read from this map.

Next, the control unit 10 sets the gear ratio G of the transmission 2 in step S3.

That is, first, the calculated gear ratio S is calculated according to the following equation based on the engine rotation speed NE and the left and right rear wheel rotation speeds NRL and NRR. Here, GF is a gear ratio of the final reduction gear 33 shown in FIG.

S = NE / [(NRL + NRR) GF / 2] Then, the calculated gear ratio S is used as an actual gear ratio G1, G2, G3, G of each speed stage of the transmission 2 from the first speed to the fifth speed.
4, threshold values a, b set as respective intermediate values of G5 values,
c, d (G1>a>G2>b>G3>c>G4>d> G
5), and the current gear stage of the transmission is determined according to the result. Then, the actual gear ratio (any one of G1 to G5) of the determined gear is set as the value of the transmission gear ratio G.

Thereafter, the control unit 10 determines in step S4 whether the rate of change ΔTVO of the throttle opening TVO is not 0, that is, whether the engine 1 is in the acceleration / deceleration state or in the steady state. Then, as the correction coefficient K of the output current value to the solenoid 39, when in the acceleration / deceleration state, the correction coefficient at the time of acceleration / deceleration is obtained from the map of FIG. 7 in step S5, and when in the steady state, in step S6. The correction coefficient in the steady state is obtained from the map of FIG.

In this case, as shown in FIG. 7, the map during acceleration / deceleration shows that the throttle opening change rate ΔTVO is a positive predetermined value ΔT when the steering angle θ is a predetermined value θ1 or more.
The correction coefficient K is set to 0 in a range larger than VO1 and a range smaller than a negative predetermined value ΔTVO2, and the correction coefficient K is set to 1 in other ranges.

As shown in FIG. 8, the map in the steady state has the correction coefficient K set to 0 in the range where the throttle opening TVO is smaller than the predetermined value TVO1 when the steering angle θ is equal to or larger than the predetermined value θ2. , The correction coefficient K is 1 in other ranges
Is set to.

Then, the control unit 10 sets the value of the correction coefficient K based on either the map of FIG. 7 or FIG. 8, and then, in step S7, the current value I output to the solenoid 39 is as follows. Calculate to.

That is, first, the input torque (T × G) of the differential device 5 is calculated from the engine torque (alternative value) T and the transmission gear ratio G that have already been calculated, and the function value f of this input torque is calculated.
The basic current value I0 is calculated as (T × G). Then
By multiplying the basic current value I0 by the correction coefficient K obtained in step S5 or step S6, the output current value I to the solenoid 39 is obtained.

Here, the function value f of the basic current value I0
(T × G) is the input torque (T × G) as shown in FIG.
The larger G) is, the larger the value is set.

Then, the control unit 10 outputs the current value I obtained as described above in step S8 as the control signal E to the solenoid 39 of the differential device 5, whereby the pilot clutch 36 or the main clutch 37 is driven. The fastening force, in other words, the differential limiting force is controlled. In that case, since the output current value I to the solenoid 39 is set as described above, it is different in each operating state. The following effects are obtained.

First, the throttle opening change rate ΔTVO is 0.
However, it is not during sudden acceleration or sudden deceleration but during relatively gentle acceleration / deceleration, that is, the throttle opening change rate ΔTV.
When O is larger than the negative predetermined value ΔTVO2 and smaller than the positive predetermined value ΔTVO1, and when the steering angle θ is relatively small (θ <θ1) even during sudden acceleration or sudden deceleration. ), The control unit 1
0 sets the correction coefficient K to 1 from the map of FIG. 7, so the current value I output to the solenoid 39 becomes equal to the basic current value I0 shown in FIG. 9, and the input torque ( It becomes a value according to T × G). As a result, the larger the input torque, the stronger the differential limiting force, and the higher the turning limit, so that good acceleration responsiveness during turning corresponding to the depression of the accelerator pedal can be obtained.

Further, when the steering angle θ is larger than a predetermined value θ1 and is relatively steeply turning, and the throttle opening change rate ΔTVO is larger than a positive predetermined value ΔTVO1, during sudden acceleration, and the change rate ΔTVO. At the time of sudden deceleration in which is smaller than the predetermined negative value ΔTVO2, the control unit 10 sets the correction coefficient K to 0 based on the map of FIG. 7, so that the current value I output to the solenoid 39 also becomes 0. Therefore, in these cases, the main clutch 37 is not engaged and the differential limitation is released, so that the differential operation of the left and right drive wheels by the differential device 5 is completely permitted.

As a result, at the time of sudden acceleration, the steering characteristic suddenly changes to the understeer side due to the abrupt increase of the input torque while the differential operation is restricted, and the vehicle body moves from the predetermined turning posture to the straight ahead side accordingly. The operation called pushing under, which behaves in the direction of, will be avoided. In addition, during sudden deceleration, the steering characteristic suddenly changes to the oversteer side due to the sudden engine braking with the differential operation limited, and as a result, the car body further turns inward in the turning direction. The so-called motion is avoided, and a sudden change in the steering characteristic and an unnecessary behavior of the vehicle body at the time of such a rapid change of the throttle opening during such a relatively sharp turn are avoided.

On the other hand, the throttle opening change rate ΔTVO is 0.
In the steady state, the steering wheel steering angle θ is larger than the predetermined value θ2 and the throttle opening TVO is the predetermined value TVO1.
When the engine brake is operating during a relatively steep turn, the control unit 10 sets the correction coefficient K to 0 based on the map of FIG.
To Therefore, as in the case described above, the main clutch 37 in the differential device 5 is released, and the differential operation is completely permitted.

Therefore, it is possible to prevent the steering characteristic from changing to the oversteer side due to the limitation of the differential operation of the differential device 5 while the engine brake is operating during a relatively sharp turn. become. As a result, the steering characteristic is maintained substantially in the neutral steer even during the operation of the engine brake, and good traveling stability during turning is maintained.

In the above embodiment, the signals D1 and D2 from the wheel speed sensors 18 and 19 used in the ABS system are used to determine the gear position of the transmission 2. A sensor for detecting the shift speed may be provided in the second gear.

[0052]

As described above, according to the present invention, the differential device that divides and transmits the input torque from the power unit to the left and right drive wheels is provided with the differential limiting means for limiting the differential operation. In the vehicle described above, when the engine braking is activated during relatively steep turning travel in a state where the differential limiting device limits the differential operation of the left and right driving wheels by the differential device, the differential limiting is performed. Since the differential limiting force generated by the means is reduced, it is possible to prevent the steering characteristic from being over-steered due to the operation of the engine brake while the differential operation is limited. As a result, even in such a case, the steering characteristic is maintained substantially in neutral steering, and good running stability can be obtained when the engine brake is operated during turning.

[Brief description of drawings]

FIG. 1 is a control system diagram of a vehicle according to an embodiment of the present invention.

FIG. 2 is a skeleton diagram showing a configuration of a differential gear in the embodiment.

FIG. 3 is an enlarged right side view in vertical section of the cam mechanism in FIG.

FIG. 4 is a plan view of the cam mechanism seen from the X direction in FIG.

FIG. 5 is a flowchart showing an operation of differential limitation control.

FIG. 6 is a characteristic diagram of engine torque used in the control.

FIG. 7 is a map of correction coefficients during acceleration / deceleration.

FIG. 8 is likewise a map of correction coefficients during steady state.

FIG. 9 is likewise a characteristic diagram of a basic current value.

[Explanation of symbols]

3 power unit 5 differential device 8, 9 drive wheel (rear wheel) 10 control means, differential limiting force reducing means (control unit) 12 engine brake detection means (throttle opening sensor) 14 steering angle detection means (steering angle sensor) 37 Differential limiting means (main clutch)

Claims (3)

[Claims] 1. A differential device that divides and transmits an input torque from a power unit to the left and right drive wheels is provided with differential limiting means for limiting the differential operation thereof, and the differential limiting means is used when turning. A differential limiting device in a vehicle including control means for controlling a generated differential limiting force, wherein a steering angle detecting means for detecting a steering angle, an engine brake detecting means for detecting an operation of an engine brake, Difference in vehicle characterized in that differential limiting force reducing means for reducing the differential limiting force is provided when the steering angle is equal to or greater than a predetermined value and the engine brake is operating. Motion limiter. 2. A differential device that divides an input torque from a power unit into left and right driving wheels and transmits the divided torque, and differential limiting means for limiting the differential operation is provided, and the differential limiting means is used when turning. A differential limiting device in a vehicle equipped with a control means for controlling the generated differential limiting force according to the input torque, wherein the steering angle detecting means detects a steering angle and the operation of engine brake is detected. Engine brake detection means and differential limiting force reducing means for reducing the differential limiting force below a magnitude corresponding to the input torque when the steering angle is equal to or greater than a predetermined value and the engine brake is operating. And a differential limiting device for a vehicle. 3. The differential device is arranged at a rear portion of a vehicle body, and the input torque from a power unit arranged at a front portion of the vehicle body is divided into left and right rear wheels to be transmitted. A differential limiting device for a vehicle according to item 1.