JPH044925Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an anti-skid device for a four-wheel drive vehicle with a center differential, and more particularly to an anti-skid device for a four-wheel drive vehicle with a center differential that prevents wheel locking detected based on wheel speed by controlling brake fluid pressure.

An anti-skid device is known that detects the deceleration or slip rate of the wheels when braking the vehicle, and operates a modulator as a brake pressure regulator in the brake hydraulic system of the vehicle according to this detected value to prevent wheel lock. . When such an anti-skid device is installed on a vehicle, a wheel speed sensor and a modulator are installed on each wheel to prevent each wheel from locking up during braking.
It is desirable to shorten the braking distance. but,
Attaching wheel speed sensors and the like to all wheels would result in a significant increase in costs, so improvements are desired.

By the way, during braking, a four-wheel drive vehicle with a center differential is considered to produce one-wheel lock, two-wheel lock with one front and rear left and right wheels, two-wheel lock with one front and rear wheel, three-wheel lock, and four-wheel lock. In this case, there are problems such as an increase in braking distance and a loss of straight-line performance.

However, if there is no center differential, or if the center differential locks and becomes directly connected, a four-wheel drive vehicle exhibits the following special behavior when braking.
In other words, (1) When only one of the four wheels locks, the locking wheel and the wheels on the left and right opposite sides will operate at twice the rotational speed of the wheels on the opposite side due to the operation of the front and rear differentials. , such a situation rarely occurs in practice. (2) If two of the four wheels, front and rear, left and right are locked at the same time, the propulsion shaft will be locked, and the pair of front and rear opposite wheels will not rotate, and this condition will not occur. (3) If one of the four wheels is locked at the same time, the front and rear wheels on the opposite side of the locking wheel will rotate approximately twice as much as before locking due to the differential operation of the front and rear differentials. This state may occur transiently. (4) If three of the four wheels lock at the same time, this condition will not occur because the remaining one wheel is directly connected to the propulsion shaft and will always lock. (5), the state in which all four wheels lock simultaneously passes through the transitional state of (3),
Or it can occur directly.

In this way, in a four-wheel drive vehicle, when the center differential locks, the propulsion shaft becomes directly connected.
If braking is started in such a state, only a two-wheel lock, in which one front and rear wheel locks temporarily, or a four-wheel lock, which occurs directly and simultaneously, will occur. Therefore, if two-wheel locks consisting of one front and rear wheels are detected by a pair of left and right speed sensors, and four-wheel locks are detected by signals from both speed sensors and an acceleration/deceleration sensor, vehicle skids can be easily avoided. be considered.

By the way, a limit slip differential is used to regulate the differential operation, but the applicant has previously developed a differential device with a variable differential limiting device that can increase or decrease the differential operation by adding a differential limiting torque. Proposed. This is a differential gear with a variable differential limiter for vehicles and an anti-skid device for four-wheel drive vehicles equipped with this differential gear (patent application filed on May 31, 1980).
will be disclosed within. If this device is used as a center differential to generate a differential lock during braking, the wheels will always behave in the same way as a four-wheel drive vehicle that is directly connected to the propulsion shaft during braking. That is, if the center differential is locked when the brakes are applied and the propulsion shaft is directly connected when braking in a four-wheel drive vehicle, it is considered that control during braking will be simplified.

This invention uses only a pair of left and right speed sensors and acceleration/deceleration sensors to detect the locking tendency of the wheels.
It is an object of the present invention to provide an anti-skid device for a four-wheel drive vehicle with a center differential that does not require any other sensor.

In order to achieve the above object, the present invention provides a differential device with a variable differential differential limiting device that is used as a center differential of a four-wheel drive vehicle and is hydraulically controlled so that the differential operation is limited during vehicle braking, and a pair of left and right speed sensors that send signals corresponding to the front or rear left and right wheel speeds, an acceleration/deceleration sensor that sends signals corresponding to the acceleration/deceleration of the vehicle, and front and rear wheel brakes generated by the master cylinder. A modulator that controls brake fluid pressure, and detects whether or not the wheels are in a state of locking based on signals from the pair of speed sensors and acceleration/deceleration sensors, and operates the modulator in accordance with this locking tendency. It is characterized by having a controller.

Such an anti-skid device for a four-wheel drive vehicle with a center differential first performs a center differential lock process when the vehicle is braked, and can release the four-wheel lock or the two-wheel lock consisting of one wheel each in the front and rear prior to this.

FIG. 1 shows an apparatus according to an embodiment of the present invention.
This is installed in a four-wheel drive vehicle with a center differential in which a front propulsion shaft 1 and a rear propulsion shaft 2 are connected to a transfer 71 via a center differential 3 serving as an intermediate actuating device main body. In this vehicle, driving torque is transmitted from the engine to the front propulsion shaft 1 via the transfer 71 and the center differential 3, is transmitted to the front wheels FW via the front differential 4 having a known structure, and is then transmitted to the rear propulsion shaft 2. The driving torque is transmitted to the rear wheels RW via a rear differential 5 having a known structure.

Here, the center differential 3 is formed as a differential device with a variable differential limiting device, and will hereinafter be simply referred to as an intermediate variable LSD 3. Although the front and rear differentials 4 and 5 are normal differentials in the embodiment shown in FIG. 1, front and rear variable LSDs can be used instead of these, and here, instead of the intermediate variable LSD 3, the differentials shown in FIG. 3 are used. The rear variable LSD 5' is variable in the middle.
I will explain using LSD3 instead.

The rear variable LSD 5' has a differential case 6, which is pivotally supported in a differential carrier (not shown) via a bearing (not shown). The differential case 6 can rotate integrally with a ring gear 7 that meshes with a drive pinion (not shown), and has four pinion gears 9 pivotally connected to a cruciform pinion shaft 8 inside. These pinion gears 9 are connected to the axle shaft 1
It meshes with side gears 12 and 13 which are spline-coupled to gears 0 and 11, respectively. Furthermore, differential case 6
Inside, two left and right pressure rings 14 and 15 are disposed on both sides of the pinion shaft 8, and the rings are splined to the differential case 6 so as to be movable in the axial direction of the axle shaft.
Clutches 16 and 17 are interposed between the pressure rings 14 and 15 and the inner wall of the differential case 6. Each clutch 16, 17 consists of a friction disk 18 spline-coupled to the side gears 12, 13 so as to be movable in the axial direction, and a friction plate 19 spline-coupled to the differential case 6 so as to be movable in the axial direction. A V-shaped cam 20 is formed at each end of the pinion shaft 8 (see FIG. 4), and a V-shaped groove 21 facing the cam 20 is formed on the opposing surfaces of the pressure rings 14 and 15, respectively. (See Figure 4).

Furthermore, as shown in FIG. 3, an annular groove is formed in the surface of the differential case 6 facing the clutch, and an annular piston 23 is mounted within this groove so as to be movable in the axial direction and engages with the friction plate 19. , whereby a pressure chamber 22 is formed within the groove. This pressure chamber is connected to the hydraulic control valve 2 via a case oil passage 24, a shaft oil passage 25, and a carrier oil passage 26.
Connected to 7. This hydraulic control valve 27 is an electromagnetic three-way valve, with an inlet 30 connected to a pump 29 via a pipe line 28 and a pressure chamber 2 via a pipe line 31.
The outlet 32 connected to the reservoir 34 and the return port 35 connected to the reservoir 34 via the conduit 33 are sequentially switched and connected. That is, the hydraulic control valve 27 switches the spool 38 using solenoids 271 and 272, and has a neutral or non-operating position A (indicated by a solid line), an operating position B that applies hydraulic pressure to the pressure chamber 22, and a pressure chamber 22 can be switched to the hydraulic pressure holding position C in which it is closed. Note that the reference numeral 37 in FIG. 3 indicates a check valve.

Solenoids 271, 27 of hydraulic control valve 27
The output signal that excites controller 2 is the controller 3 which will be described later.
It is sent from 6. That is, the controller 36 issues a drive signal according to the input voltage, moves the hydraulic control valve 27 from the neutral position A to the operating position B, maintains this position for a predetermined period of time until a predetermined hydraulic pressure is generated, and then changes the valve to the hydraulic control valve 27. Move to holding position C.
This results in a constant flow rate from the reservoir 34 to the pump 29.
The hydraulic oil pressure-fed through the hydraulic control valve 27
The oil pressure is adjusted to a predetermined oil pressure and acts on the pressure chamber 22, thereby applying a predetermined pressing force to the clutch 16.

Next, the operation of the rear variable LSD 5' (this operation is simultaneously performed in the intermediate variable LSD 3) will be explained. First, when the hydraulic control valve 27 is in the neutral position A and the vehicle is traveling straight, when the differential case 6 is rotated, the pressure rings 14,1
The V-shaped groove 21 of 5 is the V-shaped cam 2 of the pinion shaft.
Press 0. As a result, both the clutches 16 and 17 are pressed, the left and right side gears 12 and 13 rotate integrally with the differential case 6 side, and the same driving torque is transmitted to the left and right rear wheels RW.

On the other hand, when the vehicle turns, the inner side gear 12 or 13 rotates slower than the differential case 6 due to the differential operation due to the difference in road resistance.
The outer wheel side gear 13 or 12 rotates faster than the differential case 6. Therefore, due to the action of the clutches 16 and 17 in the engaged state, the outer wheel side gear is braked, while the inner wheel side gear is pulled in the driving direction, and the friction torque due to the braking of the outer wheel side clutch is applied to the differential case 6 and the inner wheel side gear. It is transmitted to the same side gear via the clutch. As a result, the outer wheel drive torque is reduced by the friction torque, and conversely the inner wheel drive torque is increased by the friction torque. Therefore, this friction torque constitutes a differential limiting torque that limits the differential operation of the rear variable LSD 5', and the value of this torque is determined by the pressing force of the clutches 16 and 17 as described above.

By the way, a brake switch 41 is connected to the controller 36, and in response to an input signal from the brake switch 41, the controller 36 issues an output signal when the vehicle speed is higher than a predetermined speed, moves the hydraulic control valve 27 to the operating position B, and operates at a predetermined level. The valve is held at this position B until oil pressure is generated, and then the valve is moved to the oil pressure holding position C. As a result, pump 2
The hydraulic oil from 9 is adjusted to a predetermined hydraulic pressure by a hydraulic control valve 27 and acts on the pressure chamber 22 . The oil pressure value at this time is set to a value equivalent to creating a differential lock that eliminates the difference in rotation between the left and right wheels.

This four-wheel drive vehicle includes a pair of brake pipes 43, 44 that are X-piped from a master cylinder 42 to each brake 51, 52 of the front and rear wheels, modulators 45, 46 attached to these, and a In addition to detecting the rotational speed, the brakes are operated in conjunction with two left and right speed sensors 73 and 74 supported by the axle housing on both sides of the rear differential 5, an acceleration/deceleration sensor (hereinafter simply referred to as a G sensor) 48, and a brake pedal 49. a brake switch 41 that senses the operation of the ignition switch 5;
It operates when 0 is turned on, and the sensors 48, 73, 7
The controller 36 controls the operation of the modulators 45 and 46 in response to signals from the switch 4 and the switch 41. Here, the speed sensors 73 and 74 may be of a known structure, and the modulators 45 and 4
6 is of a known structure, such as a hydraulic or pneumatic type that controls brake fluid pressure using hydraulic pressure or pneumatic pressure by operating a solenoid, or an electric type that directly controls brake fluid pressure by operating a solenoid,
Detailed explanations of these will be omitted.

The controller 36 is a well-known microcomputer and mainly consists of a central processing unit, memory, and interface. The interface includes speed sensors 73, 74 and clutch switch 4.
1 and the ignition switch 50, and the analog signal from the G sensor 48 is converted into a digital signal by an A/D converter (not shown) and input. A program for controlling the central processing unit is written in the memory in the controller 36, and a data table containing each setting value is stored and processed.

A flowchart of the program written in the memory is shown in FIGS. 5a and 5b. In addition, the relationship between the deceleration of the rear wheel RW and time when the vehicle is controlled during braking according to the program is shown in the sixth section.
Shown in the figure.

The operation of this device will be explained below according to the program. When the program starts, controller 3
6, first, whether or not the vehicle is in a predetermined running state;
Alternatively, preprocessing is performed to determine whether the amount of oil in the brake hydraulic system is at least a predetermined amount and whether other mechanisms are normal (step 1). Next, the controller determines whether or not the brake pedal is depressed and the brake switch 41 is on. If NO, control is stopped (step 3), and if YES, the process proceeds to step 4. Here, first, based on the signals from the pair of speed sensors 73 and 74, the wheel with the faster speed is set as the high-speed wheel.
The slower one is defined as the low speed wheel. In step 5, the deceleration signal -g0, which is constantly input from the G sensor 48, is
Based on the wheel speed signals from the pair of speed sensors 73 and 74, the deceleration setting range G stored in advance as a data table is called up.
Then, decelerations -g1 and -g2 are calculated from the speed changes of the high-speed wheels and the low-speed wheels. Next step 6
Now, after the deceleration -g1 on the low speed side increases as shown as part a in Fig. 6, check whether it exceeds the deceleration setting range G on the deceleration side (shown as part b in Fig. 6). Make a judgment, and if No, proceed to step 7; if YES, proceed to step 8. Similarly, the deceleration -g2 on the high speed side is processed in the same way. In step 7, the deceleration of the detection wheel -g
This is a case where it is determined that the speed is in the direction of the broken line (shown as part C in Fig. 6), and the normal brake operation is continued and the speed drops below the low speed value Vo at which control is stopped in step 9. to judge. and,
YES to stop the control in step 3, NO to start the step
Each of the ten brake switches 41 is determined to be on or not. If the brake switch is depressed, the process returns to step 6, and if the brake switch is depressed, the process proceeds to step 3, where the control is terminated.

In step 8, it is determined whether the low and high wheel speeds have fallen below the low speed value Vo at which control is terminated.If YES, the process proceeds to step 3; if NO, the process proceeds to step 22. Here, the output signal is sent to the hydraulic control valve 2 for a predetermined time.
7, thereby generating a high-level differential limiting torque, defrocking the intermediate variable LSD 3, directly connecting the propulsion shaft, and proceeding to step 11. step
At step 11, the drive signal stored in the data table in advance is applied to the modulator 45 or 46 in the brake system on the low-speed wheel side, which is the lock detection wheel side.
Loosen the brake fluid pressure on the lock side. Moreover, when the high-speed wheel side (-g2) similarly advances to step 11 (in the case of a tendency for all four wheels to lock simultaneously), a drive signal is also given to the other modulator 46 or 45,
Loosen both the left and right wheels. On the other hand, when only the high-speed wheel side has not exceeded the deceleration setting range G to the deceleration side, the control of this non-detection wheel side repeats steps 7, 9, and 10 from step 6, and the modulator 4
6 or 45 will keep the status quo. Through these processes, the brake fluid pressure of at least the low-speed wheel, that is, the lock detection wheel, is reduced and the reduced brake fluid pressure is maintained, thereby reducing the deceleration -g1 that had progressed to part b (in Fig. 6). In other words, the tendency of the lock wheel to rapidly lock is suppressed. After this, it is determined whether the speed has fallen below the low speed value Vo at which control is stopped, and YES
If the answer is No, go to step 13 (Step 12). In step 13, brake switch 41
Determine whether or not it continues to be on, and if NO, proceed to step 3; if YES, proceed to step 14. step
In step 14, as in step 6, it is again determined whether the decelerations -g1 and -g2 of the detected wheels exceed the deceleration setting range G on the deceleration side, and if YES, the process returns to step 11, as shown in section d. , deceleration −g
Loosen the brake fluid pressure on the locking wheel side to prevent the increase in pressure, and proceed to step 15 with No. In step 15, it is determined whether the decelerations -g1 and -g2 of the detection wheels have fallen below the deceleration setting range G to the acceleration side, that is, whether they have entered part e (in Fig. 6). step
16, No, proceed to step 17. In addition, step 14,
Comparisons of 15 are made on both the low-speed and high-speed wheel sides. In step 16, the drive signal to the modulator 45 or 46 on the detection wheel side is stopped, and the hydraulic pressure from the master cylinder 42 is again supplied to the brakes 51, 52 on the detection wheel side to replenish the brake fluid pressure. An operation is performed to increase a certain deceleration -g1 or -g2. Note that when the non-detection wheel -g1 (or -g2) side has not proceeded to step 16, the brake fluid pressure on the non-detection wheel side is maintained. As a result, the detection wheel deceleration -g1 (or -g
2) is on an increasing trend (see section f in Figure 6).
On the other hand, in step 17, since the deceleration on the detection wheel side (-g1 only or including -g2 side) is within the deceleration setting range G, the modulators 45 and 46
The drive signal continues to be sent to the front and rear wheel brakes 51 and 52, and the current brake fluid pressure on the detection wheel side is maintained. After the processing in steps 16 and 17, both enter the same pattern as after the preprocessing S1, and both proceed to step 18. In step 18, it is determined again whether or not the speed has fallen below the low speed value Vo at which control is stopped.If YES, the process proceeds to step 3; if NO, the process proceeds to step 19. In step 19, it is determined again whether or not the brake has been depressed, and if No, the process goes to step 3, and if YES, the process goes to step 20. In step 20, the pair of speed sensors 7
Based on the wheel speed signals from 3 and 74, a high speed wheel side -g2' and a low speed wheel side -g1' are determined. At this point T, the previous deceleration setting range G is erased, and in its place, a new deceleration setting range is set again in step 21.
G' is called (see FIG. 6), and the process proceeds to step 14, whereupon the control is repeated until the low speed value Vo is lowered. In addition, in FIG. 6, the actual vehicle body speed V1 and the lock detection wheel speed V0 on the low-speed wheel side are shown along the above-mentioned control process.

In this way, the anti-skid device for a four-wheel drive vehicle with a center differential shown in FIG. By outputting a signal and operating the lock wheel sides of two modulators 45 and 46 in two separate brake pipes 43 and 44, the vehicle can be controlled with a short braking distance while suppressing slippage. In addition, for vehicles equipped with two brake pipe systems in the X type, when braking, one of the four wheels in the two brake pipe system is crossed, or one wheel each in the front and rear is locked together on the left and right. 2 in certain cases
It is possible to reliably prevent wheel locking and even simultaneous four-wheel locking. In addition, a pair of left and right speed sensors 73, 74
Even if it is attached to the front and rear opposite sides of each embodiment, it can function in the same way.

Furthermore, two modulators 4 are installed in the brake piping.
5,46, but as shown in Figure 2,
An integrated two-system control modulator 53 may be installed in two systems of the X-shaped brake piping.

Furthermore, as shown in FIG. 7, two modulators 56, 57, 58 are arranged at the front and one at the rear of the brake piping 54, 55, which are front and rear independent piping.
These may be controlled by the controller 36. In this case, the rear modulator 58 is connected to the controller so as to receive the same control as the front reference wheel side (select high) modulator 56 or 57. Furthermore, as shown in FIG.
An integrated two-system control modulator 59 may be attached to the system and controlled by the controller 36. In these cases as well, operations similar to those shown in FIGS. 1 and 2 are performed. Note that the rear differential 5 may be replaced with a rear variable LSD 5'. In this case, there is no two-wheel lock, only four-wheel lock, and control is further simplified.

In the above-mentioned place, the hydraulic control valve 27 is an on-off type, and the pressure chamber 22 can be controlled by adjusting the opening time.
The oil pressure value on the side was being increased or decreased, but instead of this,
A duty control type hydraulic control valve 60 as shown in the figure may also be used. This hydraulic control valve 60
is provided with an inlet 61 connected to a constant rotation constant flow type hydraulic pump 29, an outlet 62 connected to the pressure chamber 22, a return port 63 connected to the reservoir 34, and a spool 67 in the valve body 64 equipped with a solenoid 6.
5 is connected, and a displacement sensor 66 is connected to the opposite end.
is installed. The solenoid 65 is connected to the controller 36, and the controller sends a drive pulse signal to the solenoid based on input signals from the speed sensor 47 and the G sensor 48. When the solenoid 65 is not energized, the spool 67 is in the neutral position (the position shown by the solid line), but when the solenoid is energized, the land 68 moves to the left against the return spring 69, and the orifice 70 closes to the operating position. Reach B. At this time, the controller 36 determines the energization time t1 per unit time t based on the input signal (see FIG. 10), and energizes the solenoid 65 accordingly. As a result, the spool 67 is displaced, and the displacement x is fed back to the controller 36 by the displacement sensor 66, and the controller 36 corrects the energization time to the solenoid 65 so that the actual displacement x matches the set value.
Thereby, a predetermined amount of differential limiting torque can be applied to the intermediate variable LSD 3 with high precision at a predetermined time.

As described above, in the anti-skid device for a four-wheel drive vehicle with a center differential according to the present invention, since the intermediate variable LSD 3 defrocks during braking, control during braking is facilitated, and only a pair of left and right speed sensors 73, 74 and G sensor 48 are used. 2-wheel and 4-wheel locks are detected, and the controller 36 can reliably perform anti-skid control on the modulators 45, 46, etc. on the locked wheel side.

For this reason, only a relatively small number of sensors are used.
It can be immediately applied to wheel locks and four-wheel locks, and the control is simplified and quickly achieved, and there is also a cost reduction effect.

[Brief explanation of drawings]

1, 2, 7, and 8 are schematic configuration diagrams of anti-skid devices for four-wheel drive vehicles with a center differential as different embodiments of the present invention, and FIG. 3 is an intermediate variable speed control device in FIG. 1. 4 is a partial plan view of the pressure ring in FIG. 3, and FIGS. 5 a and b are the control program for the anti-skid device described above. 6 is a diagram showing the response of the same device as deceleration and speed, and FIG. 9 is a sectional view of a duty-controlled hydraulic control valve used in place of the hydraulic control valve in FIG. 3. , and FIG. 10 show voltage characteristic diagrams of input signals to the hydraulic control valve of FIG. 9, respectively. 3... Intermediate variable LSD, 4... Front differential,
5...Rear differential, 5'...Rear variable LSD, 36...
... Controller, 42 ... Master cylinder, 47
...Speed sensor, 48...G sensor, 51...Front wheel brake, 52...Rear wheel brake, 45,4
6, 53, 56, 57, 58, 59...modulator, FW...front wheel, RW...rear wheel.

Claims (1)

[Scope of utility model registration request] A differential gear with a variable differential differential limiting device is used as a center differential in a four-wheel drive vehicle and is hydraulically controlled to limit the differential operation during vehicle braking, and a differential gear with a variable differential limiting device is used as a center differential in a four-wheel drive vehicle and is used to control the speed of the front or rear left and right wheels of the vehicle. a pair of left and right speed sensors that respectively send out corresponding signals, an acceleration/deceleration sensor that sends out signals that correspond to the acceleration/deceleration of the vehicle, and a modulator that controls the brake fluid pressure of the front and rear wheel brakes generated by the master cylinder; 4 with a center differential, which has a controller that detects whether or not the wheels are in a state of locking based on signals from the pair of speed sensors and the acceleration/deceleration sensor, and operates the modulator according to this locking tendency.
Anti-skid device for wheel drive vehicles.