JPS61193931A - Driving force distributing controller for four wheel driving vehicle - Google Patents

Abstract

PURPOSE:To prevent the wheel spin and the one sided wheel lock slip by increasing the distribution of driving force to the wheel which has small rotation number in accordance with increase of the difference of rotation number between the front and rear wheels. CONSTITUTION:A variable torque clutch 4 alters the distribution of driving force to a front wheel 1 and a rear wheel 2 by the control actuation of an actuator 3. On the other hand, the signals from rotation sensors 5, 6 provided in a driving force transmission system for the front wheel 1 and the rear wheel 2 are inputted to a control means 7, and the control means operates the difference between the rotation numbers in the driving force transmission system for the front wheel 1 and rear wheel 2. And the distribution of driving force to the wheel which has small rotation number is increased in accordance with increase of the difference of the rotation number, and the fastening force of the clutch is rapidly increased when exceeding given difference value of the rotation number. And the difference of the rotation number which starts the increase of fastening force of the clutch is increased in accordance with increase of vehicle speed.

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 drive force distribution control device for a four-wheel drive vehicle, a device such as that described in Japanese Patent Application Laid-Open No. 56-26636 is known.

This conventional device has a transmission configuration in which power is directly transmitted to one of the front and rear wheels in a transmission, and power is also transmitted to the other of the front and rear wheels via a hydraulic clutch type transfer clutch,
Normally, the clutch is in a half-clutch state where it can slip using a spring, and if slippage occurs between the front and rear wheels, the clutch is controlled in two stages so as to be in a fully integrated engaged state by suppressing the piston. It was characterized by this.

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 a driving force distribution state (two-wheel drive ), and when the slip between the front and rear wheels reaches a predetermined value,
The transfer clutch was fully engaged and the vehicle was in full four-wheel drive.

(Problems to be Solved by the Invention) However, in such a conventional driving force distribution control device, as shown in FIG.
0N-OF from 2-wheel drive state to 4-wheel drive state after 1
Because the drive force distribution was switched in a F-like manner, the steering characteristics suddenly changed when turning, and the drive force distribution was not necessarily the best depending on the driving condition, which could result in drive loss. There was a problem.

On the other hand, in order to solve the above-mentioned problem, the present applicant increases the distribution of driving force to the wheel with the lower rotation speed as the rotation speed difference between the front and rear wheels increases, and also increases the driving force distribution to the wheel with the lower rotation speed. An application was previously filed in which the clutch engagement force is suddenly increased when the rotational speed difference is exceeded. (Japanese Patent Application No. 59-27 However, the clutch engagement force is increased when the rotational speed difference ΔN between the front and rear wheels reaches a predetermined rotational speed difference ΔNa, and the transmission torque characteristics are shown in FIG. 9. As such, it exhibited uniquely defined characteristics regardless of the magnitude of the driving force or vehicle speed.

Therefore, despite the large driving force, the rotational speed difference ΔN
In region A (at low vehicle speed), the transmitted torque is small and the state is close to two-wheel drive, which tends to cause wheel spin, and even though the driving force is small, the rotational speed difference ΔN In large region B (at high vehicle speeds), the transmission torque is large and the vehicle is in a state similar to four-wheel drive, leaving the problem that the four wheels tend to drift and drift out.

(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 solution of the present invention will be explained with reference to the conceptual diagram of the claim shown in FIG. A variable torque clutch 4 that can change the distribution of driving force to the front and rear wheels by actuation,
Rotation sensors 5 and 6 installed in the drive power transmission system of the front and rear wheels 1.2
Input the rotation signals ■ and ■ from , calculate the rotation speed difference of the drive power transmission system between the front and rear wheels 1 and 2, and increase the drive force distribution to the wheel with the lower rotation speed as the rotation difference increases. A control means 7 is provided which outputs a control signal @ to the actuator 3 to rapidly increase the clutch engagement force when a predetermined rotational speed difference is exceeded, and inputs a vehicle speed signal (2) from a vehicle speed sensor 8. The rotational speed difference at which the clutch engagement force starts to increase is changed from a small rotational speed difference to a large rotational speed difference as the vehicle speed increases.

(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 driving force between the front and rear wheels is adjusted according to the difference in the rotational speed of the driving force transmission system between the front and rear wheels. distribution is controlled,
As the rotational speed difference increases, the driving force distribution can be made closer to perfect four-wheel drive.

This drive force distribution control allows the drive force distribution to change smoothly depending on the degree of rotational speed difference between the front and rear wheels, preventing sudden changes in steering characteristics when cornering, and providing appropriate drive according to the driving and road conditions. Power distribution is obtained.

Furthermore, when a predetermined rotational speed difference is exceeded, the clutch engagement force is suddenly increased to increase the transmitted torque.
Even when the rotational speed difference becomes very large or the large rotational speed difference continues for a long time, heat generation due to slippage of the variable torque clutch can be prevented.

In addition, the engine speed difference at which the clutch engagement force starts to increase is changed according to the vehicle speed, so at low vehicle speeds, regardless of the driving force, even if the engine speed difference is small, the rotation speed difference is changed, so that the 4-wheel drive direction is quickly turned on. The driving force distribution is controlled, and
At high vehicle speeds, the drive force distribution can be controlled so that the transition to four-wheel drive is delayed even if the difference in one rotational speed is large regardless of the drive force.

(Example) Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

In describing this embodiment, a driving force distribution control system 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.

10 is a driving force distribution device, as shown in FIG.
Drive input shaft 11. Transmission 12, input shaft 13
．． Rear wheel side drive shaft 14. Multi-plate friction clutch 15. Oil pump 16. Pressure oil discharge pipe 17, oil suction pipe 18. Reserve tank 19. Gear train 20. A front wheel side drive shaft 21 is provided.

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

The transmission 12 changes the speed of 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 provided on two parallel shafts. I am using a similar type.

The north input shaft 13 is a shaft for inputting the rotational driving force from the transmission 12 to the multi-disc friction clutch 15 as a transfer.

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-disc friction clutch 15 can change the driving force transmitted to the front wheels by means of clutch engagement pressure. 15a and a friction plate 15b that is rotationally engaged with the input shaft 13.
A clutch hub 15c rotatably supported on the outer periphery of the clutch hub 15c, a friction disk 15d rotationally engaged with the clutch hub 15c, and a friction plate 15b and a friction disk 15d arranged alternately. It includes a clutch piston 15e and a cylinder chamber 15f formed between the clutch piston 15e and the clutch drum 15a.

The oil pump 16 is a pump that sucks oil in the reserve tank 19 through an oil suction pipe 18, pressurizes it, and supplies it to a pressure oil discharge pipe 17, which is communicated with the cylinder chamber 15f. When pressurized oil is supplied from the oil pump 16, a clutch engagement pressure P is applied to the clutch piston 15e to press the friction plate 15b and the friction disc 15d into contact with each other, thereby transmitting the driving force from the input shaft 13 to the front wheels. let

The gear train 20 includes a first gear 20a provided on the clutch hub 15C, a second gear 20c provided on the intermediate shaft 20b, and a third gear 20d provided on the front wheel drive shaft 21. , is means for transmitting the driving force to the front wheels by engaging the multi-disc friction clutch 15.

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

Incidentally, FIG. 3 shows a specific example of the transfer, in which the multi-disc friction clutch 15 is installed in the transfer case 22.
It houses gears, shafts, etc.

In Figure 3, 15g is a dish plate, 23 is a return spring, and 24 is a control pressure oil input boat.

25 is a control pressure oil passage, 26 is a rear wheel side output shaft, 27 is a lubricating oil passage, and 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. Rear wheel side rotation sensor 42. Vehicle speed sensor 43. Proportional constant setting means 44. Control Uni 7) 45. Valve solenoid 46. It is equipped with an electromagnetic proportional control relief valve 479 and a branch drain pipe 48.

The front wheel rotation sensor 41 and the rear wheel rotation sensor 42 are provided in the middle of the front wheel drive shaft 21 and the rear wheel drive shaft 14, respectively, and are connected to a rotary plate fixed to the shaft and the hole position of the rotary plate. The rotation sensors 41 and 42 generate rotation signals (nf) and (n
r) is output.

The vehicle speed sensor 43 detects the speed of the vehicle using a pulse signal corresponding to the rotation of the drive system and outputs a vehicle speed signal (V). The rotation signal (nr) may be used to substitute the number of rotations for each predetermined time period as the vehicle speed.

Since the difference ΔN between the rotational speed Nr of the rear wheels and the rotational speed Nf of the front wheels is influenced by the operating conditions of the driver, the road surface friction coefficient, etc., the proportionality constant setting means 44 is adapted to take account of these influencing factors. It is set up so that it can be done.

As shown in FIG. 5, the torque transmitted to the front wheels ΔT is expressed as a function of the rotational speed difference ΔN as shown in the following equation.
By changing the proportionality constant K, the relationship between the transmission torque 8T and the rotational speed difference ΔN can also be changed.

ΔT=−func (ΔN) K: Proportional constant The specific proportional constant setting means 44 may be one that can be set appropriately by the driver using a manual dial switch, etc., or a road surface friction coefficient sensor, etc. It may also be possible to use means to automatically change the proportionality constant using .

The L control unit 45 includes the rotation sensor 41
, 42, the vehicle speed signal (V) from the vehicle speed sensor 43, and the proportional constant signal (k) from the proportional constant setting means 44. drive shaft? Calculate the rotation speed difference ΔN from ■, and calculate the rotation speed difference ΔN.
The pulp solenoid outputs a control signal (C) that brings the driving force distribution closer to a four-wheel drive state as N increases, and when a predetermined rotational speed difference ΔNn is exceeded, rapidly increases the clutch engagement force to increase the transmission torque ΔT. 46, as shown in the fourth rgJ, the count circuit 451
, 452, 458, clock circuit 453, RAM 454
, ROM455, CPU456, control signal generation circuit 45
It has 7.

The predetermined rotational speed difference ΔNn at which the clutch engagement force starts to increase is controlled to change from a small rotational speed difference to a large rotational speed difference as the vehicle speed V increases, as shown in FIG. .

Count circuits 451, 452, 458 convert the rotation signals (nf), (nr) and heavy speed signal (V) input from the respective rotation sensors 41, 42 and vehicle speed sensor 43 into digital signals, and convert them into digital signals. This is a circuit that generates signals that can be processed by arithmetic operations.

The clock circuit 453 gives time instructions and
This is a circuit for performing the arithmetic processing in 456 at predetermined time intervals.

The above RAM 454 (random access memory) is a memory that can be written to and read from.
4 is a rotation signal (nf) that is input while the CPU 456 is performing calculation processing.

This is a circuit that temporarily stores the count number of the vehicle speed signal (nr) and the vehicle speed signal (V).

The F ROM 455 (read-only memory) is a read-only memory, and as shown in FIG. (varies depending on the speed) is stored in advance in the form of a table, and after the rotational speed difference ΔN is calculated by the CPU 456, a table lookup is performed.

The relationship between the rotational speed difference ΔN and the transmitted torque ΔT is a proportional relationship with the same slope up to a predetermined rotational speed difference ΔNn, but once the rotational speed difference ΔNn is exceeded, the slope suddenly rises and the rotational speed difference ΔN The rate of increase in the transmission torque ΔT increases.

The above cPU456 (Central Processing Unit) is a central processing unit that performs arithmetic processing.
PU456 calculates the rotation speed difference ΔN between the front and rear wheels, and calculates the RA
Performs reading from M454 and ROM455,
The resulting signal is output to the control signal generation circuit 457.

The L control signal generation circuit 457 is a circuit that outputs a control signal (C) according to the result signal from the CPO 456 to the valve solenoid 46, which is an actuator.

The valve solenoid 46 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 pressure oil discharge pipe 17 to the reserve tank 19, and does not output a control signal (C). In this case, the relief valve 47 is opened by the hydraulic pressure from the check oil passage 49 and the clutch is released, but the control signal (
When there is an output of C), the relief valve 47 moves in the closing direction, and the discharge pressure from the oil pump 16 is set to the clutch engagement pressure P according to the control signal (C).

Note that the clutch engagement pressure P is expressed by the following formula.

P=ΔT/ (g・A−2n−Rm) Le: Coefficient of friction of the clutch plate A: Area of pressure action on the piston n: Number of friction discs Rm: Effective radius of torque transmission of the friction discs Therefore, increase the transmitted torque ΔT Then, the clutch engagement pressure P also increases proportionally.

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 signal (nf) input to the control unit 45 ,,(n
There is no difference in r) either.

For this reason, the electromagnetic proportional relief valve 47 remains open, and high hydraulic pressure is not supplied to the multi-disc 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-disc friction clutch 15, resulting in a mostly rear wheel drive state.

(b) When a rotation difference occurs between the front and rear wheels: During sudden acceleration, braking, or when driving on a road with a low friction coefficient, one wheel may slip or lock, causing a rotation speed difference 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 speed difference ΔN by the control signal (c) from the control unit 45, the drain amount of pressurized oil from the oil pump 16 is adjusted, and the clutch engagement pressure is P is increased to bring 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, and the driving force distribution between the front and rear wheels is such that the larger the rotational speed difference ΔN, the more the driving force is directed to the front wheels. The distribution increases to a state close to full four-wheel drive.

At this time, the rotational speed difference ΔNn at which the multi-disc friction clutch 15 starts to increase the engagement force is also controlled by the vehicle speed signal (V) from the vehicle speed sensor 43. For example, as shown in FIG. When ■ is a low vehicle speed, the rotational speed difference ΔN1 is small, and as the vehicle speed V increases, the rotational speed difference ΔNn becomes
It increases as ΔN1 → ΔN2 → ΔN3.

Due to this driving force distribution control action, at low vehicle speeds where the rotational speed difference ΔN is small despite the large driving force, the driving force distribution control is quickly performed to a state close to four-wheel drive even if the rotational speed difference ΔN is small. Drive force distribution control can prevent wheel spin, and at high vehicle speeds where the rotation speed difference ΔN is large despite the low driving force, the transition to four-wheel drive is delayed even if the rotation speed difference ΔN is large. was done, 4
It is possible to prevent the wheels from drifting out.

As shown in Fig. 6, driving force distribution control basically changes the driving force distribution gradually depending on the degree of occurrence of the rotational speed difference ΔN. There is no sudden change, and no drive loss occurs.

In addition, if the predetermined rotational speed difference ΔNn is exceeded, the multi-disc friction clutch 15 is engaged by the strong clutch engagement pressure P, so for example, the rotational speed difference ΔN becomes very large, or Even if the condition continues for a long time, the multi-disc friction clutch 15 can be prevented from slipping.
Heat generation due to slipping and fluctuations in the transmitted torque ΔT (desired driving force distribution ratio not achieved) can be reduced.

Next, the aforementioned driving force distribution control action 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, in step 200, the front wheel rotation sensor 4
1 and the rotation signal input from the rear wheel side rotation sensor 42 (
nf) and (nr), the respective counts Nf and Nr within a predetermined time are read, and the count number (indicating the vehicle speed) of the vehicle speed signal (V) from the vehicle speed sensor 43 within a predetermined time is read.

In step 201, the rotation speed difference Δ is determined based on the count numbers Nf and Nr read in step 200.
Calculate N.

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

In step 202, based on the rotational speed difference ΔN calculated in step 201, a plurality of relational tables (same relationship as the graph in FIG. ), look up the transmitted torque ΔT in the table.

For example, as shown in FIG.
If the vehicle speed is low, the transmission torque ΔT will be ΔTrz, and if the rotational speed difference ΔN is ΔN2 and the vehicle speed is high, the transmission torque ΔT will be ΔTn2.

In step 203, the proportional constant signal (k) from the proportional constant setting means 44 is input, and the transmitted torque ΔT in step 202 is corrected.

In step 204, the control signal generation circuit 457 is caused to output a result signal corresponding to the transmission torque ΔT' corrected in step 203.

Note that the above-described process is repeatedly performed by the clock circuit 453 at every set predetermined time.

Although the embodiments of the present invention have been described in detail with reference to the drawings, the specific configuration is not limited to these embodiments, and the present invention may be modified without departing from the gist of the present invention. include.

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 is Nf- Nr
It can be calculated as

In addition, in the embodiment, the relationship between the transmitted torque ΔT and the rotational speed difference ΔN is set so as to obtain a directly proportional characteristic, but it is not necessary to be limited to this relationship in particular, and even if it is a viscous clutch characteristic etc. good.

Further, the clutch engagement pressure control means is not limited to the electromagnetic proportional relief valve of the embodiment, and 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.

(Effects of the Invention) As explained hereafter, in the driving force distribution control device for a four-wheel drive vehicle of the present invention, as the rotation speed difference between the front and rear wheels increases, the heavier wheel with the smaller rotation speed is Since the configuration is configured to increase the distribution of driving force to the two wheels, it is possible to achieve an effect that the distribution of driving force can be made appropriate depending on the driving state or driving conditions in which a difference in the number of revolutions occurs.

As a result of the above-mentioned effects, it is possible to prevent wheel spin during sudden acceleration or starting, to prevent one wheel from locking during sudden braking, and to prevent slipping when driving on a road with a low friction coefficient. There are no adverse effects caused by sudden changes.

In addition, since the clutch engagement force is suddenly increased when a predetermined rotational speed difference is exceeded, even when the rotational speed difference becomes very large or a large rotational speed difference continues for a long time, It is possible to prevent the variable torque clutch from slipping, prevent fluctuations in transmission torque due to temperature rise, and improve control performance.

In addition, the rotation speed difference at which the clutch engagement force starts to increase is
As the vehicle speed increases, the rotation speed difference changes from a small rotation speed difference to a large rotation speed difference, so it is possible to prevent wheel spin at low vehicle speeds where the rotation speed difference is small despite the large driving force. It is possible to prevent the four wheels from drifting out at high vehicle speeds when the difference in rotational speed is large despite the small force.

[Brief explanation of the drawing]

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. 3 is a transfer diagram of the embodiment device. FIG. 4 is a block diagram showing the control unit of the embodiment device, and FIG. 5 shows the relationship between the rotational speed difference and the transmitted torque stored in advance in the control unit of the embodiment device. 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 in the embodiment device, and FIG. A graph showing the relationship between the slip rate (rotational speed difference) and the driving force distribution ratio in the conventional device, and FIG. 9 is a graph showing the transmission torque characteristics in the prior art. l...Front wheel 2...Rear wheel 3...Actuator 4...Variable torque clutch 5.6...Rotation sensor 7...Control means 8...Vehicle speed sensor・Rotation signal■...Control signal■...Vehicle speed signal Patent application Nissan Motor Co., Ltd. Figure 4 Figure 5 (Nr-Nf) ΔN (Nr-Nf) (ΔS) Rotation speed view ΔN□

Claims (1)

[Claims] 1) In a four-wheel drive vehicle equipped with a transfer in the middle of the drive power transmission system to the front and rear wheels, the transfer is a variable torque clutch that can change the drive power distribution to the front and rear wheels by control operation of an actuator. The rotation signal from the rotation sensor installed in the drive power transmission system of the front and rear wheels is input, the rotation speed difference between the front and rear drive power transmission systems is calculated, and as the rotation speed difference increases, the drive is directed to the wheel with the lower rotation speed. A control means is provided for outputting a control signal to the actuator that increases the force distribution and rapidly increases the clutch engagement force when a predetermined rotational speed difference is exceeded, and inputs a vehicle speed signal from a vehicle speed sensor to control the clutch engagement force. A driving force distribution control device for a four-wheel drive vehicle, characterized in that a rotational speed difference at which an increase in fastening force is started is changed from a small rotational speed difference to a large rotational speed difference as the vehicle speed increases.