JPH0563343B2 - - Google Patents

Description

Detailed Description of the Invention A. Object of the Invention (1) Industrial Application Field The present invention provides a vehicle in which a front axle and a rear axle are connected to a power unit via a differential device having a locking mechanism, and the wheels of each axle are The brake hydraulic system that controls the hydraulic pressure of the brakes installed on the vehicle is equipped with an anti-lock control device that reduces the brake hydraulic pressure when the wheels are about to enter a lock state.A four-wheel drive vehicle with an anti-lock brake system. Regarding.

(2) Conventional technology Conventionally, four-wheel drive vehicles have been developed to improve the vehicle's maneuverability and performance on roads with a low friction coefficient. Attempts have also been made to equip devices.

(3) Problems to be Solved by the Invention However, when the lock mechanism is in an inoperative state, there is no problem even if the conventional anti-lock brake device is used as is. When driving, conventional antilock brake systems have disadvantages. That is, during direct four-wheel drive, the front wheels and rear wheels interfere with each other, making it impossible to obtain a sufficient anti-lock effect.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a four-wheel drive vehicle with an anti-lock brake device that can effectively perform anti-lock control on front wheels and rear wheels during direct four-wheel drive. With the goal.

B. Structure of the Invention (1) Means for Solving the Problems According to the present invention, the antilock control device includes a front wheel control section that controls the brake hydraulic pressure of the front wheels, and a rear wheel control section that controls the brake hydraulic pressure of the rear wheels. and has
The front wheel drive section and the rear wheel control section are configured to reduce the pressure of the brake hydraulic pressure of the front wheels only when the locking mechanism is activated and the pressure of the brake hydraulic pressure of the front wheels continues for a certain period of time or more and when the rear wheels are likely to lock up. .

(2) Effect When using direct four-wheel drive, the rear brake hydraulic pressure is reduced only when the front wheels are likely to lock for a certain period of time and the rear wheels are also likely to lock. Sometimes the front wheels interfere with the rear wheels, so anti-lock control of the front wheels alone can prevent the rear wheels from entering a locked state.

(3) Embodiment An embodiment of the present invention will be explained below with reference to the drawings. First, in Fig. 1, a pair of left and right front wheels are shown.
Wfl, Wfr and a pair of left and right rear wheels Wrl, Wrr are suspended at the front and rear of a vehicle body (not shown), respectively.

A pair of front axles Afl and Afr connected to left and right front wheels Wfl and Wfr, respectively, are connected to each other via a front actuating device Df, and a pair of rear axles Afl and Arr connected to left and right rear wheels Wrl and Wrr, respectively, are connected to each other via a front actuating device Df. Actuation device
They are interconnected via Dr. A front propulsion shaft Pf and a rear propulsion shaft Pr are connected to the input parts of the front and rear actuators Df and Dr, and these propulsion shafts Pf and Pr are interconnected via a central actuator Dc. Ru. The input part of this central actuating device Dc is a power unit P including an engine and a transmission.
is connected.

The central actuating device Dc is equipped with a lock mechanism 1, and when the lock mechanism 1 is in operation, a four-wheel drive state is established in which the front and rear propulsion shafts Pf and Pr are directly connected. The operation of this lock mechanism 1 is detected by an operation detector 2.

Brakes Bfl, Bfr; Brl, Brr are attached to the front wheels Wfl, Wfr and the rear wheels Wfl, Wfr.

In Figure 2, each brake Bfl, Bfr, Brl,
The brake hydraulic system 7 that controls the hydraulic pressure of Brr has a tandem master cylinder 8 having a pair of output ports 8a and 8b, and adjusts the hydraulic pressure supplied from one output port 8a to adjust the hydraulic pressure supplied from the left front wheel brake Bfl and the right rear wheel. Modulator leading to wheel brake Brr
Mfl, Mrr, and a modulator Mfr that adjusts the hydraulic pressure supplied from the other output port 8b and guides it to the right front wheel brake Bfr and the left rear wheel brake Brr,
Equipped with Mrl. This brake hydraulic system 7 includes
An anti-lock control device 9 is provided which controls the operation of modulators Mfl, Mfr, Mrl and Mrr in order to prevent the wheels from entering a locked state.

The anti-lock control device 9 includes a front wheel control section 9a that individually controls modulators Mfl and Mfr for the front wheels Wfl and Wfr, and modulators Mrl and Mfr for the rear wheels Wrl and Wrr.
A detector 10 has a rear wheel control section 9b that simultaneously controls Mrr, and detects the wheel speed of the front wheels Wfl and Wfr.
Signals from the rear wheels Wrl and 10r are input to the front wheel control section 9a, and signals from detectors 11l and 11r for detecting the wheel speeds of the rear wheels Wrl and Wrr are input to the rear wheel control section 9b. Further, a detection signal from the operation detector 2 which detects whether the lock mechanism 1 is activated is input to the rear wheel control section 9b.

Next, the configuration of the front wheel control section 9a will be explained with reference to FIG. 3, but the portion corresponding to one modulator Mfl, Mfr and the portion corresponding to the other modulator Mfr are basically the same configuration. Therefore, in the following, parts related to one modulator Mfl will be described with the subscript l, and parts related to the other modulator Mfr will only be illustrated with the subscript r.

In order to determine whether the wheels are about to enter a lock state, the wheel speed V _W detected by the detector 10l is input to the inverting terminal of the first comparator 13l, and is also input to the arithmetic circuit 12l.
The wheel acceleration V〓 _W obtained by this calculation circuit 12l is the inverting terminal of the second comparator 14l and the third comparator 1
The signals are respectively input to the non-inverting terminals of 5l. The first comparator 13l compares the reference wheel speed V _R input to its non-inverting terminal with the wheel speed V _W , and when V _R > V _W , the signal λ for relaxing the braking oil pressure is set at the first comparator 13l. 1 comparator 13l. Also the second
The comparator 14l compares the reference wheel speed −V〓 _WO inputted to the non-inverting terminal with the wheel acceleration V〓 _W , and when −V〓 _WO >V〓 _W , the brake hydraulic pressure is changed. A relaxing signal β is output from the second comparator 14l. Furthermore, the third comparator 15l compares the reference wheel acceleration +V〓 _WO inputted to the inversion terminal with the wheel acceleration V〓 _W , and when V〓 _W > +V〓 _WO , the third comparison is performed. A signal α is output from the device 15l. This signal α is used to determine whether the wheel speed V _W is increasing, and the timing to continue loosening the braking oil pressure is determined based on this signal α.

The output terminal of the first comparator 13l is AND gate 1
6l, and is also connected to the input terminal of OR gate 17l. Further, the output terminal of the second comparator 14l is connected to the AND gate 16l and
It is connected to the input terminal of OR gate 17l. Furthermore, the output terminal of the third comparator 15l is the OR gate 17
It is connected to the input terminal of l.

The output terminal of AND gate 16l is inverted and
It is connected to the input terminals of AND gates 18l and 19l, and is also connected to the output terminal 20l. Also, the output terminal of OR gate 17l is AND gate 18
The AND gate 18l is connected to the input terminal of the AND gate 18l.
The output terminal of is connected to the output terminal 22l and inverted to the input terminal of the AND gate 19l. Further, the output terminal of the AND gate 19l is connected to the output terminal 21l.

In the front wheel control section 9b configured in this way, a signal for reducing the braking pressure is output from the output terminals 20l, 20r, a signal for increasing the braking pressure is output from the output terminals 21l, 21r, and a signal for increasing the braking pressure is output from the output terminals 22l, 20r.
2r outputs a signal to keep the braking pressure constant. One modulator Mfl has output terminal 20
Operates in response to signals from l, 21l, 22l,
The other modulator Mfr has output terminals 20r and 21
It operates in response to signals from brakes Bfl and 22r, whereby anti-lock control of both brakes Bfl and Bfr is performed individually.

Furthermore, the output terminals of the AND gates 16l and 16r are also connected to the input terminals of the timer circuits 24l and 24r. These timer circuits 24l, 24r are the fourth
When a signal as shown in Figure a is input, a high level signal is output with a certain time T delay from the rise of the signal, and the output signal falls in response to the fall of the input signal. Also, both timer circuits 2
The output terminals of 4l and 24r are respectively connected to the input terminal of an OR gate 25.

Due to the function of both timer circuits 24l and 24r, when the signal for reducing the brake hydraulic pressure of both brakes Bfl and Bfr in the front wheel control unit 9a continues for a certain period of time T or more, the output of the OR gate 25 becomes high level, and this OR The output of the gate 25 is transmitted through a line 26 to the rear wheel control section 9b.

In FIG. 5, the configuration of the rear wheel control section 9b will be explained. The configuration of the rear wheel control section 9b is similar to the configuration of the front wheel control section 9a, and the parts corresponding to the front wheel control section 9a are as follows. Subscript l, r
They are only illustrated with the same reference numerals without the .

Particularly noteworthy in the rear wheel control section 9b is the detector 1
The wheel speeds detected at 1l and 11r are input to the low select circuit 23, and the lower wheel speed selected by the low select circuit 23 is input to the first comparator 13 and the calculator 12. .
In other words, anti-lock control is performed in accordance with the wheel that is more likely to lock among the left and right rear wheels Wrl and Wrr, that is, the wheel that has a lower wheel speed.
The operations of both modulators Mrl and Mrr are simultaneously controlled by control signals output from output terminals 20, 21, and 22.

Furthermore, in this rear wheel control section 9b, the output terminal of the AND gate 16 is connected to the input terminals of AND gates 27 and 28, and the operation detector 2 is connected to the input terminal of the AND gate 28, and the output terminal is inverted.
Connected to the input terminal of AND gate 27. Also, a line 26 from the front wheel control section 9a is connected to an input terminal of an AND gate 28, and both AND gates 27,
The output terminals of 28 are connected to the input terminals of an OR gate 29, respectively. Further, the output terminal of the OR gate 29 is connected to the output terminal 20 and
It is inverted and connected to the input terminals of gates 18 and 19.

Therefore, in the rear wheel control section 9b, during direct four-wheel drive, only when the front wheel control section 9a is reducing the brake pressure in at least one of the brakes Bfl and Bfr by connecting it for a certain period of time T or more.
It is possible to reduce the brake hydraulic pressure of the rear wheels Wrl and Wrr.

Next, to explain the operation of this embodiment, when the lock mechanism 1 is operating, the front wheels Wfl,
When Wfr has a tendency to lock, the rear wheels
There is always a locking tendency in Wrl and Wrr, and in this case, by relaxing the brake hydraulic pressure of the front wheels Wfl and Wfr with the front wheel control unit 9a, the locking tendency of both the front wheels Wfl and Wfr and the rear wheels Wrl and Wrr can be alleviated. Ru. Moreover, the brakes Bfl and Bfr of the front wheels Wfl and Wfr are individually controlled by the front wheel control section 9a, so the front wheels
Even if only one of Wfl and Wfr has a tendency to lock, anti-lock control can be performed without any problem.

When the locking tendency of the rear wheels Wrl, Wrr is not resolved even if the brake hydraulic pressure of the front wheels Wfl, Wfr is decreased, that is, even if the signal for reducing the brake hydraulic pressure in the front wheel control section 9a continues for a certain period of time T or more, When the locking tendency of wheels Wrl and Wrr is not eliminated, the output of the AND gate 28 in the rear wheel control section 9b becomes high level. Therefore, the rear brake
The brake hydraulic pressure of Brl and Brr is reduced, and the rear wheel Wrl,
The tendency of Wrr to lock is resolved.

Also, when only the rear wheels Wrl and Wrr tend to lock, the rear wheels Wrl and Wrr are affected by the front wheels Wfl and Wfr, so the lock tendency of the rear wheels Wrl and Wrr does not become stronger and can be ignored. It is.

C. Effects of the Invention As described above, according to the present invention, only when the rear wheels tend to lock while the front wheel brake hydraulic pressure is maintained at a reduced pressure for a certain period of time during direct four-wheel drive, the rear wheels are Since the brake oil pressure is reduced, anti-lock control can be performed efficiently and effectively by utilizing the mutual interference between the front wheels and the rear wheels.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, in which Fig. 1 is a schematic diagram of the drive system, Fig. 2 is a schematic diagram of the brake system, Fig. 3 is a schematic diagram of the front wheel control section, and Fig. 4 is a schematic diagram of the timer. The characteristic diagram of the circuit, FIG. 5, is a schematic diagram of the rear wheel control section. 1... Lock mechanism, 7... Brake hydraulic system,
9...Antilock control device, 9a...Front wheel control unit, 9b...Rear wheel control unit, Afl, Afr, Arl, Arr
... Axle, Bfl, Bfr ... Brake, Dc ... Differential gear, P ... Power unit, Wfl, Wfr, Wrl,
Wrr...wheels.

Claims (1)

[Claims] 1 The front axle and the rear axle are connected to the power unit via a differential device with a locking mechanism, and the brake hydraulic system that controls the hydraulic pressure of the brakes attached to the wheels of each axle has a locking mechanism. In a four-wheel drive vehicle equipped with an anti-lock brake system, the anti-lock control system is equipped with a front wheel control unit that controls the brake oil pressure of the front wheels, and a front wheel control unit that controls the brake oil pressure of the front wheels. and a rear wheel control section that controls brake hydraulic pressure, and the front wheel control section and the rear wheel control section are configured to detect that when the lock mechanism is activated, the pressure reduction of the front wheel brake hydraulic pressure continues for a certain period of time or more, and the rear wheels are likely to lock. A four-wheel drive vehicle with an anti-lock brake system, characterized in that the vehicle is configured to reduce the brake hydraulic pressure of the rear wheels only occasionally.