JPH0424253B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a driving force distribution control device for a four-wheel drive vehicle that controls the distribution of driving force to front and rear wheels according to predetermined control conditions.

(Prior Art) As a conventional driving force distribution control device for a four-wheel drive vehicle, a device as described in, for example, Japanese Patent Laid-Open No. 56-26636 is known.

This conventional device is configured to transmit power directly to one of the front and rear wheels in a transmission, and also to the other of the front and rear wheels via a hydraulic clutch type transfer clutch, and the clutch is usually operated by a spring. A slippery half-clutch is brought into an engaged state, and if a slip occurs between the front and rear wheels, the two-stage control is performed so that the fully integrated engaged state is achieved by pressing a piston. It was hot.

Therefore, in the conventional device, when the slip between the front and rear wheels is less than a predetermined value, the transfer clutch is in a half-engaged state and the drive force distribution state ( When the slip between the front and rear wheels exceeds a predetermined value, the transfer clutch is fully engaged, resulting in a complete four-wheel drive state.

(Problems to be Solved by the Invention) However, in the case of such a conventional driving force distribution control device, as shown in _FIG . Since the drive force distribution was switched ON and OFF to the wheel drive state, the steering characteristics suddenly changed when turning, and the drive force distribution was not necessarily the best depending on the driving condition. There was a problem that losses could occur.

(Means for Solving the Problems) The present invention has been made for the purpose of solving the above-mentioned problems, and in order to achieve this purpose, the present invention employs the following solving means. did.

The solving means of the present invention will be explained with reference to the conceptual diagram of the claim shown in FIG. The difference in rotational speed between the front and rear wheels is calculated based on rotation signals from a variable torque clutch 4 whose transmission torque can be changed by controlling the actuator 3 and rotation sensors 5 and 6 provided in the drive power transmission system for the front and rear wheels. a front and rear wheel rotational speed difference calculation means 7; a control coefficient setting means 8 that sets a control coefficient, which is a change gradient of the transmitted torque with respect to the front and rear wheel rotational speed difference, in accordance with an influencing factor of the front and rear wheel rotational speed difference;
Driving force distribution control means 9 that outputs to the actuator 3 a control signal that increases the transmission torque to the clutch-engaged drive wheels as the difference in rotational speed between the front and rear wheels increases, and increases the transmission torque increase ratio as the control coefficient increases. It is characterized by having the following.

Incidentally, the influencing factors of the difference in rotational speed between front and rear wheels refer to the road surface friction coefficient, the driver's accelerator operating characteristics, etc., and the control coefficient setting means 8 is a means for automatically setting the value using a road surface friction coefficient detection means. Alternatively, a means such as a manual dial switch or the like that can be set appropriately by the driver may be used.

(Function) Therefore, in the driving force distribution control device for a four-wheel drive vehicle of the present invention, by using the above-mentioned means, the difference in rotational speed between the front and rear wheels increases in the driving force distribution control means 9 during driving. Accordingly, a control signal is output to the actuator 3 that increases the torque transmitted to the clutch-engaged driving wheels and increases the transmission torque increase ratio as the control coefficient increases, and the variable torque clutch 4 is actuated.

The above-mentioned driving force distribution control is provided in the middle of the driving force transmission system from one of the front and rear wheels 1 and 2 that is directly connected to the engine to the other clutch-engaged driving wheel, and the transmission torque is changed by the control operation of the actuator 3. Since drive force distribution control is performed by the variable torque clutch 4, the variable torque clutch 4 gradually changes the drive force distribution ratio between the front and rear wheels, and there is no sudden change in steering characteristics or drive loss when turning. .

Further, since the front and rear wheel drive force distribution ratio is controlled according to the occurrence of the front and rear wheel rotation difference and the set control coefficient, the following operation is shown.

When the control coefficient is set to a low value, the speed at which the clutch engages the torque to be transmitted to the drive wheels increases as the rotational difference between the front and rear wheels increases is low, and the drive force distribution ratio between the front and rear wheels is equally distributed with low response and small transmitted torque. By controlling the direction, it is possible to suppress the tight corner braking phenomenon that occurs when the front and rear wheels are directly connected, for example, when making a small radius turn on a high friction coefficient road that generates a rotation difference between the front and rear wheels. like,
While retaining the characteristics of a two-wheel drive vehicle, the engine-directly connected drive wheels are prevented from slipping or locking up.

When set to a high control coefficient, the clutch engages the clutch and increases the transmission torque to the drive wheels quickly in response to an increase in the rotational difference between the front and rear wheels, and the drive force distribution ratio between the front and rear wheels is equally distributed with high response and large transmission torque. For example, by being controlled in the direction, it is possible to prevent wheel spin during sudden acceleration or starting, to prevent one wheel from locking on one of the front and rear wheels during sudden control, and to prevent slipping when driving on a road with a low friction coefficient. Priority is given to the characteristics of a complete four-wheel drive vehicle, and driving stability is achieved by quickly suppressing slippage and locking of the engine-directly connected drive wheels.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.
In describing this embodiment, a driving force distribution control device for a four-wheel drive vehicle based on rear wheel drive will be taken as an example.

First, the configuration of the embodiment shown in FIGS. 2 to 5 will be explained.

Reference numeral 10 denotes a driving force distribution device, which, as shown in FIG.
2, input shaft 13, rear wheel drive shaft 14, multi-disc friction clutch 15, oil pump 16, hydraulic discharge pipe 1
7, an oil suction pipe 18, a reserve tank 19, a gear train 20, and a front wheel drive shaft 21.

The drive input shaft 11 is a shaft to which the driving force that has passed through the engine and clutch is input.

The transmission 12 changes the rotational driving force from the drive input shaft 11 according to a gear position selected by a shift operation, and in the embodiment, gear sets with different gear ratios are mounted on two parallel shafts. I am using a type that has a

The input shaft 13 is connected to the transmission 12 to a multi-plate friction clutch 15 as a transfer.
This is the shaft to which the rotational driving force is input.

The rear wheel drive shaft 14 is coaxially and directly connected to the input shaft 13, and the rotational driving force from the input shaft 13 is directly transmitted thereto.

The multi-plate friction clutch 15 is a clutch that can change the driving force transmitted to the front wheels by the clutch engagement pressure, and includes a clutch drum 15a fixed to the input shaft 13 and the rear wheel drive shaft 14, and a clutch drum 15a fixed to the input shaft 13 and the rear wheel drive shaft 14. A friction plate 15b rotationally engaged with the input shaft 15a, a clutch hub 15c rotatably supported on the outer circumference of the input shaft 13, and a friction disk 15d rotationally engaged with the clutch hub 15c. Friction plate 15b and friction disk 1 arranged
Clutch piston 1 provided on one end side with 5d
5e, and a cylinder chamber 1 formed between the clutch piston 15e and the clutch drum 15a.
5f.

The oil pump 16 has a reserve tank 19
This pump sucks in oil from the oil suction pipe 18, pressurizes it, and supplies it to the pressure oil discharge pipe 17. This pressure oil discharge pipe 17 is connected to the cylinder chamber 15f, and the pressurized oil from the oil pump 16 is At the time of supply, clutch engagement pressure is applied to the clutch piston 15e to press the friction plate 15b and friction disk 15d into pressure contact, thereby transmitting the driving force from the input shaft 13 to the front wheels.

The gear train 20 includes the clutch hub 1
5c, a second gear 20c provided on the intermediate shaft 20b, and a third gear 20d provided on the front wheel drive shaft 21. This is a means of transmitting driving force to the front wheels by tightening the wheels.

The front wheel drive shaft 21 is a shaft that transmits rotational driving force to the front wheels of the vehicle.

FIG. 3 shows a specific example of a transfer, in which the multi-plate friction clutch 15, gears, and shafts are housed in a transfer case 22.

In Fig. 3, 15g is a dish plate, 23 is a return spring, 24 is a control pressure oil input port,
25 is a control pressure oil path, 26 is a rear wheel side output shaft, 27 is a lubricating oil path, 28 is a speedometer pinion,
29 is an oil seal, 30 is a bearing, 31 is a needle bearing, 32 is a thrust bearing, and 33 is a joint flange.

40 is a driving force distribution control device, which includes a front wheel rotation sensor 41, a rear wheel rotation sensor 42, an ignition switch 43, a proportional constant setting means 44, a control unit 45, and a valve solenoid 4.
6, an electromagnetic proportional control relief valve 47 and a branch drain pipe 48 are provided.

Front wheel rotation sensor 41 and rear wheel rotation sensor 4
2 is provided in the middle of the front wheel drive shaft 21 and the rear wheel drive shaft 14, respectively, and rotates by a rotary plate fixed to the shaft and a phototube and a photoelectric element arranged in the hole position of the rotary plate. A sensor or the like is used, and both rotation sensors 41 and 42 output rotation signals nf and nr in the form of pulse signals corresponding to shaft rotation.

The ignition switch 43 is closed by inserting a key into the key cylinder and rotating it to the engine starting position, and outputs an ON signal i.

The control coefficient setting means 44 is provided so that the rotation speed difference ΔN between the front and rear wheels is influenced by the operating conditions of the driver, the road surface friction coefficient, etc., and can be adapted to these influencing factors. be.

As shown in Fig. 5, the transmission torque ΔT to the front wheels is expressed as a function of the rotational speed difference ΔN as shown in the following equation, and by changing the control coefficient K,
The relationship between the transmission torque ΔT and the rotational speed difference ΔN can also be changed.

ΔT=k・func(ΔN)k; Control coefficient The specific control coefficient setting means 44 may be one that can be set appropriately by the driver using a manual dial switch or the like; 160629
The control constant k may be automatically changed to a larger value on a road surface with a low friction coefficient where the rotational speed difference ΔN is likely to occur using a road surface friction coefficient detection means known in No. 1, etc.

The control unit 45 inputs rotation signals nf and nr from the rotation sensors 41 and 42, an ON signal i from the ignition switch 43, and a control coefficient signal k from the control coefficient setting means 44, and drives the front and rear wheels. Difference in rotational speed between shafts 21 and 14 △N (Nr-
Nf) and outputs a control signal c to the valve solenoid 46 that brings the driving force distribution closer to the four-wheel drive state as the rotational speed difference ΔN increases.As shown in FIG. 451,
452, clock circuit 453, RAM454,
ROM455, CPU456, control signal generation circuit 4
It is equipped with 57.

Count circuits 451 and 452 receive rotation signals nf and 452 input from rotation sensors 41 and 42, respectively.
This circuit converts nr into a digital signal and makes it a signal that can be processed by the CPU 456.

The clock circuit 453 is a circuit for giving time instructions and causing the CPU 456 to perform arithmetic processing at predetermined time intervals.

The above RAM 454 (random access memory) is a memory that can be written to and read from.
The RAM 454 is a circuit that temporarily stores the count numbers of the rotation signals nf and nr that are input while the CPU 456 is performing arithmetic processing.

The above ROM455 (read-only memory) is a read-only memory.
As shown in the fifth solid line, the basic relationship between the rotational speed difference ΔN and the torque transmitted to the front wheels ΔT is stored in advance in the form of a table, and the CPU 45
After the rotational speed difference ΔN is calculated in step 6, a table search is performed.

The CPU 456 (Central Processing Unit) is a central processing unit that performs arithmetic processing. This CPU 456 calculates the rotational speed difference ΔN between the front and rear wheels, reads data from the RAM 454 and the ROM 455, and controls the resulting signals. It is output to the signal generation circuit 457.

The control signal generation circuit 457 provides control to the CPU 4 for the valve solenoid 46 which is an actuator.
This circuit outputs a control signal c according to the result signal from 56.

The valve solenoid 46 is connected to the pressure oil discharge pipe 17
This is an actuator that drives an electromagnetic proportional control relief valve 47 provided in the middle of a branch drain pipe 48 branched from the reserve tank 19 to the reserve tank 19. If the control signal c is not output, check the oil passage 49.
The relief valve 47 is opened by the hydraulic pressure from the oil pump 16, and the clutch is opened, but when the control signal c is output, the relief valve 47 moves in the closing direction, and the discharge pressure from the oil pump 16 is controlled by the control signal c. Adjust the hydraulic pressure accordingly.

The clutch engagement pressure P is expressed by the following equation.

P=ΔT/(μ・A・2n・Rm) μ: Coefficient of friction of clutch plate A: Area of pressure acting on piston n: Number of friction discs,
Rm: Effective torque transmission radius of friction disk Next, the operation of the embodiment will be explained.

(b) When there is no rotation difference between the front and rear wheels When driving straight on a dry road where the tires do not slip, there is almost no difference in the rotation speed between the front and rear wheels, and the rotation signals nf, nr are input to the control unit 45. There is no difference.

For this purpose, the electromagnetic proportional relief valve 47
remains open, and high oil pressure is not supplied to the multi-plate friction clutch 15, resulting in the clutch being in an open state.

Therefore, almost no driving force from the input shaft 13 is transmitted to the front wheels via the multi-plate friction clutch 15, resulting in almost a rear wheel drive state.

(b) When a difference in rotation occurs between the front wheels: During sudden acceleration, braking, or when driving on a road with a low friction coefficient, one wheel may slip or lock, causing a difference in rotation speed between the front and rear wheels. A difference also occurs in the rotation signals nf and nr input to the control unit 45.

For this purpose, the electromagnetic proportional relief valve 47
is closed according to the rotational difference in accordance with the control signal c from the control unit 45, and the amount of pressurized oil drained from the oil pump 16 is adjusted, increasing the clutch engagement pressure P and bringing the clutch into the engaged state.

Therefore, the driving force from the input shaft 13 is also transmitted to the front wheels via the multi-plate friction clutch 15.
As for the distribution of driving force between the front and rear wheels, the greater the difference in rotational speed, the more the distribution of driving force to the front wheels increases, resulting in a state close to full four-wheel drive.

This driving force distribution control function can prevent wheel spin during sudden acceleration or turning, prevent one wheel from locking during sudden braking, and can also prevent wheels from locking on one wheel during sudden braking. Wheel slips can be prevented on roads with low friction coefficients.

As shown in Fig. 6, the driving force distribution control function gradually changes the driving force distribution depending on the degree of rotational speed difference between the front and rear wheels. Furthermore, there is no drive loss.

Next, the aforementioned driving force distribution control operation will be explained with reference to a flowchart (FIG. 7) showing the flow of operations in the CPU 456 of the control unit 45.

First, turn on the ignition switch 43.
The program is executed by the signal i.

Then, in step 200, the respective counts Nf and Nr within a predetermined time are read based on the rotation signals nf and nr input from the front wheel rotation sensor 41 and the rear wheel rotation sensor 42, respectively.

In step 201, a rotational speed difference ΔN is calculated based on the counts Nf and Nr read in step 200 (corresponding to front and rear wheel rotational speed difference calculating means in the claims).

Note that the arithmetic expression is ΔN=Nr−Nf.

In step 202, based on the rotational speed difference ΔN calculated in step 201, the ROM 4 is
The transmission torque ΔT is looked up from the relationship table between the rotational speed difference ΔN and the transmission torque ΔT (same function as the graph in FIG. 5) stored in advance in the controller 55.

For example, as shown in FIG. 5, if the rotational speed difference ΔN is ΔNn, the transmitted torque ΔT becomes ΔTn.

In step 203, the control coefficient setting means 4
Input the control coefficient signal k from step 4 and
The transmission torque ΔT at 202 is corrected.

In step 204, a result signal corresponding to the transmission torque ΔT' corrected in step 203 is outputted to the control signal generation circuit 457. Note that steps 202 to 204 correspond to driving force distribution control means in the claims.

Incidentally, the above-mentioned processing is repeatedly performed by the clock circuit 453 at every set predetermined time.

Although the embodiments of the present invention have been described above in detail with reference to the drawings, the specific configuration is not limited to these embodiments, and even if the design is changed within the scope of the gist of the present invention, the present invention may be modified. included.

For example, although the embodiment shows a four-wheel drive vehicle based on a rear-wheel drive vehicle, it may also be a four-wheel drive vehicle based on a front-wheel drive vehicle. In that case, the rotational speed difference ΔN may be calculated as Nf - Nr.

Further, in the embodiment, the relationship between the transmitted torque ΔT and the rotational speed difference ΔN is set so as to obtain the characteristics of a viscous clutch, but there is no need to limit it to this relationship, for example, a proportional relationship, It is also possible to establish a relationship in which the increase rate of the transmitted torque with respect to the increase in the rotational speed difference ΔN increases as the rotational speed difference ΔN increases.

Further, the means for controlling the clutch engagement pressure is not limited to the electromagnetic proportional relief valve of the embodiment, but other means may be used.

Further, the mounting position of the rotation sensor is not limited to the mounting position of the embodiment as long as it is provided in the drive transmission system of the front wheel side and the rear wheel side.

Further, as the variable torque clutch, an electromagnetic clutch or the like may be used.

(Effects of the Invention) As explained above, in the drive force distribution control device for a four-wheel drive vehicle of the present invention, one of the front and rear wheels is directly connected to the engine, and the other clutch-engaged drive wheel is The variable torque clutch, which is installed in the middle of the power transmission system and can change the transmitted torque by controlling the actuator, is used to control the drive force distribution, so the variable torque clutch gradually changes the drive force distribution ratio between the front and rear wheels. As a result, the steering characteristics do not suddenly change when turning, and the drive loss does not occur.

In addition, the drive force outputs a control signal to the actuator of the variable torque clutch that increases the torque transmitted to the clutch engagement drive wheels as the difference in rotational speed between the front and rear wheels increases, and increases the transmission torque increase ratio as the control coefficient increases. Since a distribution control means is provided, if the control coefficient is set to a low value,
While retaining the characteristics of a two-wheel drive vehicle, it is possible to prevent slippage and locking of the drive wheels directly connected to the engine.Also, when a high control coefficient is set, the characteristics of a complete four-wheel drive vehicle are given priority, and the drive wheels are directly connected to the engine. By quickly suppressing slippage and locking of the drive wheels, driving stability can be achieved, and by setting control coefficients, it is possible to achieve optimal drive force distribution control according to the driving route and the driving vehicle's preferences. This effect can be obtained.

[Brief explanation of drawings]

FIG. 1 is a conceptual diagram of a claim showing a driving force distribution control device for a four-wheel drive vehicle according to the present invention, FIG. 2 is an overall view showing a driving force distribution control device of an embodiment, and FIG. 4 is a block diagram showing the control unit of the embodiment device, and FIG. 5 is a graph showing the relationship between the rotation speed difference and the transmitted torque stored in advance in the control unit of the embodiment device. , FIG. 6 is a graph showing the relationship between the rotational speed difference and the driving force distribution ratio in the embodiment device, FIG. 7 is a flowchart showing the flow of operation in the control unit of the embodiment device, and FIG. 8 is a conventional device. 3 is a graph showing the relationship between the slip rate (rotational speed difference) and the driving force distribution ratio. DESCRIPTION OF SYMBOLS 1... Front wheel, 2... Rear wheel, 3... Actuator, 4... Variable torque clutch, 5, 6... Rotation sensor, 7... Front and rear wheel rotation speed difference calculation means, 8...
Control coefficient setting means, 9...driving force distribution control means.

Claims (1)

[Scope of Claims] 1. A variable torque that is provided in the middle of the drive power transmission system from one engine-directly coupled drive wheel to the other clutch-engaged drive wheel of the front and rear wheels, and whose transmission torque can be changed by control operation of an actuator. A clutch, a front and rear wheel rotation speed difference calculation means for calculating a front and rear wheel rotation speed difference based on a rotation signal from a rotation sensor provided in a drive power transmission system for the front and rear wheels, and a change in transmission torque with respect to the front and rear wheel rotation speed difference. A control coefficient setting means for setting a control coefficient, which is a gradient, according to an influencing factor of a difference in rotational speed between front and rear wheels; A driving force distribution control device for a four-wheel drive vehicle, comprising: driving force distribution control means for outputting a control signal to the actuator that increases the transmission torque increase ratio as the value increases.