JPS61191431A - Driving force distribution control device for 4-wheel-drive vehicle - Google Patents

Abstract

PURPOSE:To remove the necessity of using various sensors, reducing the manufacturing cost of a 4-wheel-drive vehicle, and to prevent the occurrence of such troubles as the spin of wheels and the like by controlling the distribution of driving force to front and rear wheels on the basis of the difference in the rotational speed of the front and rear wheels. CONSTITUTION:Front and rear wheels 11 and 12, respectively, are coupled with an engine 13, one directly and the other through a clutch 14. The distribution ratio of driving force to the front and rear wheels 11 and 12, respectively, is changed by varying transmitting torque of the clutch 14. Front and rear wheel speed detectors 15 and 16 are provided for detecting the rotational speed of the front and rear wheels 11 and 12, respectively. The difference in the rotational speed of the front and rear wheels 11 and 12, respectively, is calculated by rotational speed difference calculating means 17. Based on the difference in the rotational speed, pressure control means 18 changes the transmitting torque of the clutch 14, controlling the distribution ratio of the driving force.

Description

Detailed Description of the Invention (Industrial Application Field) This invention is a four-wheel drive system in which the distribution of driving force between the front and rear wheels can be changed by changing the torque transmitted from the engine to either the front wheels or the rear wheels using a clutch. The present invention relates to a driving force distribution control device for a vehicle, and particularly relates to a driving force distribution control device that controls driving force distribution between front and rear wheels based on a rotational speed difference between the front and rear wheels.

(Prior art) In a 4-wheel drive vehicle capable of running in 4-wheel drive, in which both the front and rear wheels are driven, the driving force is distributed to the front and rear wheels during 4-wheel drive running. This allows it to exhibit excellent driving performance even on low-friction coefficient roads.However, on the other hand, when driving in four-wheel drive, the front and rear wheels are integrally connected, making it difficult to turn on high-friction coefficient roads. Inconveniences such as corner braking phenomena occur. Therefore, in recent years, four-wheel drive vehicles have been proposed that automatically control switching between two-wheel drive driving, in which only one of the front wheels or rear wheels is driven, and four-axle drive driving, according to vehicle driving conditions. Conventionally, the method disclosed in Japanese Unexamined Utility Model Publication No. 58-1-00132 was known as described in Japanese Unexamined Utility Model Publication No. 58-139226.

For example, the system described in Japanese Utility Model Application Publication No. 58-100132 uses a rain sensor to detect rain, and when the friction coefficient of the road surface decreases due to rain, the system changes from two-wheel drive to four-wheel drive.
The system switches to wheel drive driving to prevent the drive wheels from spinning and improve drive performance. Furthermore, the system disclosed in Japanese Utility Model Application Publication No. 5.8-139226 detects a large steering turn of the vehicle using the hydraulic pressure of a hydraulic power steering device, and when the large steering turn occurs, the system changes from 4-wheel drive to 4-wheel drive.
This switches to wheel drive driving and prevents tight corner braking from occurring.

(Problems to be Solved by the Invention) However, in order to achieve perfection as a four-wheel drive vehicle, it is necessary to It is not enough to simply prevent the spin of the drive wheels as described in Japanese Patent No. 100132;
It is not enough to prevent the occurrence of tight corner braking as described in Japanese Utility Model Application No. 58-139226, and therefore, the method described in Japanese Utility Model Application No. 58-100132 and the method described in Japanese Utility Model Application No. 58-139226 are not enough. By combining the methods described in the above publication, it is necessary to achieve both prevention of spin and prevention of the tight corner braking phenomenon. However, such a
The one described in Publication No. 132 and Utility Model Application Publication No. 58-139226
The product obtained by combining the products described in the above publication requires various types of detectors such as a rain sensor, an oil pressure switch, and a vehicle speed sensor, which has the problem of increasing manufacturing costs.

Furthermore, since the methods described in the above-mentioned Japanese Utility Model Application Publication No. 58-100132 and Japanese Utility Model Application Publication No. 58-139226 only selectively switch between two-wheel drive driving and four-wheel drive driving, There has been a problem in that the steering characteristics of the vehicle may suddenly change during switching, which may impair steering stability.

(Means for Solving the Problems) This invention aims to solve the above problems, and as shown in FIG. At the same time, the other of the front wheel 1 or the rear wheel 12 is connected to the engine 13 via the clutch 14,
In a driving force distribution control device for a four-wheel drive vehicle that changes the transmission torque of the clutch 14 to change the distribution ratio between the driving force of the front wheels 11 and the driving force of the rear wheels 12, the front wheel speed detects the rotational speed of the front wheels 11. a detector 15, a rear wheel speed detector 16 that detects the rotational speed of the rear @ 12, and a front wheel speed detector 15.
A rotational speed difference calculation means 1 that calculates the rotational speed difference between the front wheel 11 and the rear wheel 12 based on the rotational speed of the front wheel 11 detected by the front @ 11 and the rotational speed of the rear wheel 12 detected by the rear wheel speed detector 16.
7, the transmission torque of the clutch 14 is changed based on the rotational speeds of the front wheels 11 and the rear wheels 12 calculated by the rotational speed difference calculation means 17, and the driving force of the front wheels 11 and the driving force of the rear wheels 12 are distributed. A fastening force adjusting means 18 for controlling the ratio is provided.

(Function) This driving force distribution control device for a four-wheel drive vehicle calculates the rotational speed difference between the front and rear wheels 11 and 12 by processing each output signal of the front wheel speed detector 15 and the rear wheel speed detector 16, The transmission torque of the clutch 14 is changed according to this rotational speed difference between the front and rear wheels 11.12 to control the driving force distribution between the front and rear wheels 11.12. That is, the torque transmitted from the engine 13 to either the front wheels 11 or the rear wheels 12 is changed by the clutch 14 based on the rotational speed difference between the front and rear wheels 11.12 calculated from the output signals of the two detectors 15.16. to control driving force distribution. Therefore, there is no need for various types of detectors such as rain sensors as in the conventional device described above, and manufacturing costs can be reduced.

In addition, in this device, control of driving force distribution, that is, switching between two-wheel drive driving and four-wheel drive driving is performed by front and rear tllJ1.
Since this is carried out gradually by changing the transmission torque of the clutch 14 according to the difference in rotational speeds between the wheels 1 and 12, a sudden change in steering characteristics can be prevented and a decrease in steering stability can be prevented.

(Example) Embodiments of the present invention will be described below based on the drawings.

FIGS. 2 to 6 are diagrams showing one embodiment of the present invention.

First, an overview of a four-wheel drive vehicle will be explained with reference to FIG. is a rear wheel propeller shaft 24R and a front wheel propeller shaft 24 via a transfer 23 for switching between two-wheel drive and four-wheel drive.
Connected to F. The rear wheel propeller shaft 24R is
Rear wheel differential 25R and left and right axles 26RL, 2
Similarly, the front wheel propeller shaft 24F is connected to the left and right front wheels 27FL and 27FR via the front wheel differential bag [2SF and the left and right axles 26FL and 26FR. There is.

As shown in FIG. 3, in the transfer 23, an input shaft 30 connected to the output shaft of the transmission 22 is rotatably housed in a transfer case 28 formed by joining two members 28a and 28b with bolts 29. Also,
Rear export force shaft 31 connected to rear wheel propeller shaft 24
is rotatably supported by a bearing 32. The input shaft 30 and the rear export force shaft 31 are each coaxially spline-coupled to a substantially pipe-shaped joint member 33 and connected to rotate integrally through the joint member 33. The joint member 33 is.

A drum 44 of a hydraulic multi-disc clutch 49, which will be described later, is provided on the outer periphery of the transfer case 28.
It is rotatably inserted into a cylindrical bearing holder 34 fixed by a bolt 34a.

A first hollow shaft 38 is rotatably inserted into the input shaft 30 on the left side in FIG. It is rotated and extrapolated. A drive gear 38a meshing with a counter gear 40a is integrally formed on the outer periphery of the first hollow shaft 38. This counter gear 40
A is integrally formed with a counter shaft 40 rotatably supported by the transfer case 28 via a bearing 41, and meshes with a driven gear 42 provided on a front export force shaft connected to the front wheel propeller shaft 24F. The second hollow shaft 39 has a hub 39a that is integrally formed and projects radially outward, and the hub 39a and the drum 4 described above
A friction multi-disc clutch 49 is installed between the clutch 4 and the clutch 4.

The friction multi-disc clutch 49 includes a plurality of drive plates 45 spline-coupled to the inner peripheral wall of the drum 44, and a plurality of drive plates spline-coupled to the hub 39a of the second hollow shaft 39 and arranged alternately in the axial direction with the drive plates 45. A substantially annular piston 48 is attached to the plate 46, the drum 44 and the joint member 33, and the piston 48 has an approximately annular piston 48 whose inner and outer surfaces are in liquid-tight and axially slidable contact with the drum 44 and the joint member 33 to define an oil chamber 47, respectively. - A spring 53 is compressed between the attached retainer 52 and the piston 48 and biases the piston 48 toward the oil chamber 47. The oil chamber 47 receives the oil pressure of the transfer case 28 through a first oil passage 35a formed in the joint member 33, a second oil 135b formed in the bearing holder 34, and a third oil passage 3Sc formed in the transfer case 28. It communicates with port 35d. This friction multi-disc clutch 49 is connected to a hydraulic port 35d and a first. 2nd and 3rd oil passages 35 a
, 35b, , When high pressure oil is supplied to the oil chamber 47 through 35C, the piston 48 moves to the left in the figure against the elastic force of the spring 53, bringing the drive plate 45 and the driven plate 46 into frictional contact. and the joint member 33 and the second
The input shaft 30 is connected to the hollow shaft 39, that is, the input shaft 30 and the front export force shaft.

Note that 30a is a first lubricating oil passage formed in the input shaft 30;
31a is a second lubricating oil passage formed in the rear export force shaft 31;
9b is a first clutch lubricating oil passage formed in the second hollow shaft 39; 39c is a second clutch lubricating oil passage formed in the hub 39a of the second hollow shaft 39; and 44a is a third clutch lubricating oil passage formed in the drum 44. The first and second lubricating oil passages 30a and 31a supply lubricating oil to the needle bearing 43, etc., and the first, second and third clutch lubricating oil passages 39b, 39a and 44a supply lubricating oil to the needle bearing 43, etc. Lubricating oil is supplied to the sliding contact portion between the drive plate 45 and the driven plate 46 of the multi-plate clutch 49.

Further, 36 is a pinion for speed detection.

Again, in FIG. 2, 51 is a control device, and this control device 51 includes a front wheel speed detector 54 that detects the rotational speed of the front wheels 27FL and 27FR, and a front wheel speed detector 54 that detects the rotational speed of the front wheels 27FL and 27FR.
A rear wheel speed detector 55 that detects the rotational speed of R is connected to the rear wheel speed detector 55. The front wheel speed detector 54 detects the front wheels 27FL, 2
A control device that sends a pulse signal with a frequency corresponding to the rotation speed (number of rotations) of the 7FR! 51, and so on.

The rear wheel speed detector 55 outputs to the control device 51 a pulse signal having a frequency corresponding to the rotational speed (number of rotations) of the rear wheels 27RL and 27RR. Note that the front wheel speed detector 54 is connected to the front export force shaft of the transfer 23 or the countershaft 4.
It may be configured to detect a rotation speed of 0, and similarly,
The rear wheel speed detector 55 is connected to the rear export force shaft 3 of the transfer 23.
It is also possible to configure the rotation speed of 1 to be detected.

As shown in FIG. 4, the control device 51 includes a hydraulic circuit 56 (corresponding to a fastening force adjusting means) that supplies pressure oil to the oil chamber 47 of the friction multi-disc clutch 49, and controls the hydraulic pressure generated by the hydraulic circuit 56. An electric control circuit (corresponding to a rotational speed difference calculation means) 57 is provided. As shown in the figure, the hydraulic circuit 56 includes a pump 59 that pressurizes and discharges oil in the reservoir tank 58, and a discharge port of the pump 59 is connected to the oil chamber 47 of the friction multi-disc clutch 49. Also, the solenoid valve 6
0 to the reservoir tank 58. The solenoid 60a of the solenoid valve 60 is connected to an electric control circuit 57, and the electric control circuit 57 opens the oil chamber 47, that is, the pump 5, at an opening degree according to the current value supplied to the solenoid 60a.
9 is communicated with the reservoir tank 58, and the oil chamber 4 is connected to the reservoir tank 58.
Change the oil pressure (clutch pressure) supplied to 7. That is, this solenoid valve 60 has a spool that responds to, for example, the discharge pressure of the pump 59 and the electromagnetic force of the solenoid 60a.

The clutch pressure supplied to the oil chamber 47 is maintained at a value corresponding to the current value supplied to the solenoid 60a with the characteristics shown in FIG.

The electric control circuit 57 includes a first counter 61 that converts the pulse signal output from the front wheel speed detector 54 into a signal Nf with a potential corresponding to the frequency, and a first counter 61 that converts the pulse signal output from the front wheel speed detector 54 into a signal Nf with a potential corresponding to the frequency. A second counter 62 converts into a potential signal Nr, and each output signal Nf, Nr of the first counter 61 and second counter 62 is subtracted to calculate the rotational speed difference between the front wheels 27FL, 27FR and the rear wheels 27RL, 27RR. A signal ΔN (ΔN=N f−N r
) and the output signal ΔN of the subtracter 63
An arithmetic circuit 64 that calculates and outputs a control signal (V) according to the following equation, and an excitation current of a current value (V) corresponding to the control signal V outputted by the arithmetic circuit 64 is applied to the solenoid 60 of the solenoid valve 60.
It has a drive circuit 65 that outputs to a.

V=K・ΔN+Vo ・・・・・・(Formula) However, K
, Vo: the number of settings.

That is, this electric control circuit 57 is connected to the front wheel 27FL.

Rotational speed difference ΔN between 27FR and rear wheels 27RL and 27RR
The solenoid 60a of the solenoid valve 60 is
The solenoid valve 60 controls the clutch pressure P to have the characteristics shown in FIG. 6 with respect to the rotational speed difference ΔN.

Next, the effect will be explained.

The driving force distribution control device of this four-wheel drive vehicle is for the front wheel 27FL.
, rotational speed difference Δ between 27FR and rear wheels 27RL and 27RR
Based on N, the clutch pressure P, that is, the friction multi-disc clutch 4
The transmission torque of No. 9 is controlled to have the characteristics shown in FIG. 6, and the driving force distribution ratio thereof is controlled.

Therefore, this driving force distribution control device does not require a variety of detectors unlike the conventional device described above, making it possible to reduce manufacturing costs. Also, there is no sudden change in steering characteristics.

Below, we will explain in detail each case when driving. First, when driving on a low friction coefficient road surface, rear @ 27RL, 27
In a two-wheel drive mode where only the RR is driven, the rear wheel 27R
L, 27RR suffered ground slip and the rear wheels 27RL, 27
Rotational speed difference ΔN between RR and front wheels 27FL and 27FR
When this occurs, the latch pressure P is supplied to the oil chamber 47 of the friction multi-disc clutch 49 as shown in FIG. 6, and the friction multi-disc clutch 49 applies a driving force corresponding to the clutch pressure P to the front wheels 27F.
L, transmit to 27FR. In other words, the driving force of the vehicle is also distributed to the front wheels 27FL and 27FR, so the rear wheel 27R
The L and 27RR will no longer cause ground slip (spin).

In addition, in this state, the rear wheels 27RL and 27R
Similarly, if R slips on the ground, the front wheel 27RL
, 27RR is transmitted to the rear wheels 27RL, 27RR by the friction multi-disc clutch 49, as shown in FIG.
ground slip is prevented.

On the other hand, the friction multi-disc clutch 49 causes the front wheels 27FL, 27
During four-wheel drive driving with the FR connected to the engine 21, when turning with a small radius on a road surface with a high friction coefficient, the rotational speed of the front wheels 27FL and 27FR will decrease because the turning radius of the front wheels 27FL and 27FR is large as a characteristic of the vehicle. It becomes larger and causes the front wheels 27RL and 27FR to slip on the ground. As a result, the front wheels 27FL, 27FR and the rear wheels 27RL, 27
A rotational speed difference ΔN occurs between the clutch and the RR, and as shown in FIG. 6, the clutch pressure P decreases in response to the rotational speed difference ΔN.
The transmission torque of the friction multi-disc clutch 49 becomes smaller. That is, front wheels 27FL-27FR and rear wheels 27RL and 27R.
Since the driving force distribution ratio with R becomes smaller and the vehicle shifts to two-wheel drive mode, the front wheels 27FL and 27FR will no longer experience ground slip, that is, tight corner braking.

Also, in each of the above cases, the friction multi-disc clutch 4
The transmission torque of 9, that is, the driving force distribution between the front wheels 27FL, 27FR and the rear wheels 27RL, 27RR is as shown in Fig. 6: front @ 27FL, 27FR and rear wheel 27RL.

Since it changes according to the rotational speed difference ΔN with respect to 27RR, the steering characteristics do not suddenly change.

FIGS. 7 and 8 show other embodiments of the invention. Hereinafter, the same parts as in the embodiment described above will be given the same numbers and the explanation will be omitted.

In FIG. 7, reference numeral 70 denotes a road surface detector that detects the condition of the road surface on which the vehicle is traveling, and is composed of, for example, an ultrasonic sensor. The road surface detector 70 is connected to the arithmetic circuit 64 of the electric control circuit 57, and outputs to the arithmetic circuit 64 a signal indicating the road surface condition, such as the presence or absence of unevenness or wetness (snow) on the road surface. The arithmetic circuit 64 changes the constant K in the above-mentioned equation based on the output signal of the road surface detector 70, and outputs a control signal V, that is.

Calculate clutch pressure P. That is, this device changes the transmission torque (clutch pressure) P of the friction multi-disc clutch 49 within the shaded area in FIG. 8 based on the road surface condition and the rotational speed ΔN of the front and rear wheels, and distributes the driving force between the front and rear wheels. Control.

This driving force distribution control device for a four-wheel drive vehicle reduces the absolute value of the constant in the equation when there is snow on the driving road surface and the coefficient of friction is small, and the friction multi-disc clutch 49 is adjusted to the rotational speed difference ΔN. The clutch pressure is controlled, for example, according to the characteristics shown by the solid line A in FIG.

Therefore, the driving force can be distributed on a road surface with a low coefficient of friction where the axle tends to slip on the ground without giving the driver a sense of discomfort, and better maneuverability can be obtained.

The road surface detector in this embodiment can also be configured to detect the operation of a wiper switch or the vertical acceleration of the vehicle body.

(Effects of the Invention) As described above, the driving force distribution control device for a 4@drive vehicle according to the present invention is configured to control the driving force distribution between the front and rear wheels based on the rotational speed difference between the front and rear wheels. This makes it possible to reduce manufacturing costs by eliminating the need for multiple types of detectors, eliminates problems such as axle spin or tight corner braking, and prevents sudden changes in steering characteristics. be done.

Furthermore, in another embodiment shown in FIG. 7, the rate of change in the driving force distribution with respect to the rotational speed difference between the front and rear wheels is changed depending on the condition of the road surface, so that more stable steering performance can be obtained.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a driving force distribution control device for a 4@drive vehicle according to the present invention. 2 to 6 are diagrams showing a driving force distribution control device for a four-wheel drive vehicle according to an embodiment of the present invention, in which FIG. 2 is an overall schematic diagram and FIG. 3 is a sectional view of main parts of the mechanism. , Fig. 4 is a circuit diagram of the control section, Fig. 5 is a diagram showing the clutch pressure with respect to the excitation current to the solenoid of the solenoid valve, and Fig. 6
The figure is a diagram showing the clutch pressure with respect to the rotational speed difference between the front and rear wheels. 7 and 8 are diagrams showing a driving force distribution control device for a four-wheel drive vehicle according to another embodiment of the present invention, FIG. 7 is a circuit diagram of the control section, and FIG. FIG. 3 is a diagram showing clutch pressure with respect to rotational speed difference. 11.27FL, 27FR...Front wheel, 12.27R
L, 27RR... Rear wheel. 13.21...Engine, 14.49...Clutch, 15.54...Front wheel speed detector, 16, 55...Rear wheel speed detector, 17・・・・・・
...Rotational speed difference calculation means, 18... Fastening force adjustment means. Figure 2 Figure 4 7 Figure 5 Figure 6 O Rotational speed difference (JN) Figure 7 Figure 8 0 Rotational speed difference (#)

Claims (2)

[Claims] (1) One of the front wheels or the rear wheels is directly connected to the engine, and the other of the front wheels or the rear wheels is connected to the engine via a clutch, and the transmission torque of the clutch is changed to differentiate the driving force of the front wheels and the driving force of the rear wheels. In a driving force distribution control device for a four-axle drive vehicle that changes the distribution ratio of a vehicle, a front wheel speed detector detects the rotational speed of the front wheels, a rear wheel speed detector detects the rotational speed of the rear wheels, and a front wheel speed detector. rotational speed difference calculation means for calculating a rotational speed difference between the front wheel and the rear wheel based on the rotational speed of the front wheel detected by the front wheel and the rotational speed of the rear wheel detected by the rear wheel speed detector;
A fastening force adjusting means for controlling the distribution ratio between the driving force of the front wheels and the driving force of the rear wheels by changing the transmission torque of the clutch based on the rotational speed difference between the front wheels and the rear wheels calculated by the rotational speed difference calculation means. A driving force distribution control device for a four-axle drive vehicle, comprising: (2) The fastening force adjusting means changes the transmission torque of the clutch so that the distribution ratio becomes smaller when the rotational speed of the front wheels is higher than the rotational speed of the rear wheels, and when the rotational speed of the front wheels is smaller than the rotational speed of the rear wheels. The driving force distribution control device for a four-wheel drive vehicle according to claim 1, wherein the transmission torque of the clutch is changed so that the distribution ratio becomes larger.