JPH068099B2 - Four-wheel drive vehicle - Google Patents

Description

Detailed Description of the Invention A. OBJECT OF THE INVENTION (1) Field of Industrial Application The present invention is directed to a power unit being connected to one of the front and rear axles, and the torque transmission amount of the front and rear other axles depending on the relative rotation speed. The present invention relates to a four-wheel drive vehicle that is connected to a power unit via a torque transmission mechanism having a large torque.

(2) Conventional Technology Conventionally, in such a four-wheel drive vehicle, a brake is generally mounted on each wheel.

(3) Problems to be Solved by the Invention By the way, in the above vehicle, since the front and rear axles are always almost rigidly connected, if the braking hydraulic pressure becomes excessive during sudden braking, all the wheels will be locked at the same time. So
Compared to front-wheel or rear-wheel drive vehicles, stability during braking is improved, but stability against disturbance and loss of steerability are not eliminated. Therefore, it is desirable that the brake device has an antilock function.

However, the anti-lock brake basically controls the brake torque for each wheel or each axle to keep the slip ratio of each wheel near an appropriate value, and the speed of each wheel or each axle is It is necessary to be able to change independently. On the other hand, in a vehicle in which the front and rear axles are almost rigidly connected, the front and rear wheels interfere with each other, so antilock control of each brake may not be performed on the wheels with brakes mounted on each wheel as in the conventional case. ,
I cannot get proper control.

On the other hand, if the front and rear axles are almost rigidly connected, the slip ratio of the wheels on the other axle will inevitably be about the proper value if a proper slip rate is applied to the wheels on one axle. is there.

Therefore, if the brakes are attached only to the front wheels to obtain the braking force of all the wheels and the antilock control of those brakes is performed, the above-mentioned problems can be solved, and the present applicant can We propose a four-wheel drive vehicle with various configurations.

However, if the braking of all the wheels is performed only by the brakes of the front wheels, the load on the brakes of the front wheels becomes large, and it may be difficult to increase the capacity in terms of space.

The present invention has been made in view of such circumstances, and a brake is also attached to the rear wheels in order to reduce the load on the brakes of the front wheels, but the antilock control of the brakes of the rear wheels is performed from the rear wheels to the front wheels. An object of the present invention is to provide a four-wheel drive vehicle that is designed to minimize interference.

B. Structure of the Invention (1) Means for Solving the Problems According to the present invention, brakes are mounted on the wheels of both axles, and the brake hydraulic system that controls the hydraulic pressure of each brake puts the wheels in a locked state. An anti-lock control device for controlling the brake hydraulic pressure to be loosened at the time of trying is attached, and the anti-lock control device controls the front wheel brakes individually and the anti-lock control device responds to the possibility of the wheel lock occurring. A rear wheel control unit configured to control the braking of the rear wheels by loosening the brake hydraulic pressure but continuously avoiding an increase in the brake hydraulic pressure until the end of the braking operation even if the possibility of wheel locking is eliminated.

(2) Operation According to the above-mentioned configuration, after the anti-lock control for loosening the brake hydraulic pressure of the rear wheels is generated due to the possibility of rear wheel locking, the brake hydraulic pressure of the rear wheels is kept until the braking operation is completed. It does not increase and the slip ratio of the rear wheels is suppressed, and the interference from the rear wheels to the front wheels is suppressed to a small level.

(3) Example Hereinafter, one example of the present invention will be described with reference to the drawings. First, in FIG. 1, a pair of left and right front wheels Wfl, Wf.
r and a pair of left and right rear wheels Wrl, Wrr are respectively suspended on the front and rear portions of a vehicle body (not shown).

A pair of front axles Afl, Afr connected to the left and right front wheels Wfl, Wfr are mutually connected via a front differential device Df, and a pair of rear axles Arl, Arr connected to the left and right rear wheels Wrl, Wrr are They are interconnected via the rear differential Dr. A power unit P including an engine and a transmission is connected to an input portion of the front differential device Df. Further, the rear propulsion shaft Pr is connected to the input portion of the rear differential device Dr. The rear propulsion shaft Pr is coaxially connected to the front propulsion shaft Pf via a viscose clutch 1 as a torque transmission mechanism, and the driving force of the power unit is transmitted to the front propulsion shaft Pf.

The viscose clutch 1 includes a high-viscosity oil and a small amount of air that allows thermal expansion of the high-viscosity oil in a sealed oil chamber 4 defined between a clutch outer 2 and a clutch inner 3 which are relatively rotatable with respect to each other. And a plurality of outer clutch plates 5 spline-coupled to the clutch outer 2 and a plurality of inner clutch plates 6 spline-coupled to the clutch inner 3. Moreover, each plate 5, 6 is provided with an opening (not shown) that allows passage of oil particles, the clutch outer 2 is integrated with the front propulsion shaft Pf, and the clutch inner 3 is integrated with the rear propulsion shaft Pr. It

In this viscose clutch 1, when relative rotation occurs between the clutch outer 2 and the clutch inner 3, both clutch plates 5 and 6 relatively rotate while shearing the highly viscous oil, and torque between the clutch plates 5 and 6 is increased. Viscous transmission takes place. Further, when the relative rotation speed further increases, a complicated temperature gradient is generated between the clutch plates 5 and 6 due to the increase in the oil temperature, and the strain resulting from this causes a synergistic effect of the increase in the pressure in the sealed oil chamber 4 to cause an adjacent A frictional engagement portion or a portion having a very small gap is formed between the two clutch plates 5 and 6, so that torque friction is transmitted between the clutch outer 2 and the clutch inner 3.

According to such a viscose clutch 1, between the front propulsion shaft Pf and the rear propulsion shaft Pr, that is, the front axle Afl,
The Afr and the rear axles Arl and Arr are always almost rigidly connected, and the front wheels Wfl and Wfr and the rear wheels Wrl and Wrr interfere with each other.

The front wheels Wfl and Wfr are equipped with brakes Bfl and Bfr, and the rear wheels Wrl and Wrr are equipped with brakes Brl and Brr having a relatively small capacity.

In FIG. 2, each brake Brl, Bfr, Brl,
The brake hydraulic device 7 for controlling the hydraulic pressure of Brr includes a tandem master cylinder 8 having a pair of output ports 8a and 8b, a hydraulic pressure supplied from one output port 8a, and a brake Bfl for the front left wheel and a rear right wheel. It includes modules Mfl and Mrr that lead to the wheel brakes Brr and modules Mfr and Mrl that adjust the hydraulic pressure supplied from the other output port 8b and lead to the front right wheel brake Bfr and the left rear wheel brake Brl. The brake hydraulic device 7 is provided with an antilock control device 9 for controlling the operation of the modulators Mfl, Mfr, Mrl, Mrr in order to prevent the wheels from entering the locked state.

The anti-lock control device 9 controls the front wheels Wfl and Wfr individually to control the modulators Mfl and Mfr.
a and the rear wheel Wrl, Wrr modulators Mrl, Mr
a front wheel Wf having a rear wheel control unit 9b for controlling r simultaneously.
Detectors 10l and 10r for detecting wheel speeds of 1 and Wfr
Signals from the rear wheels Wrl,
The signals from the detectors 11l and 11r that detect the wheel speed of Wrr are input to the rear wheel control unit 9b.

Next, the configuration of the front wheel control unit 9a will be described with reference to FIG. 3 as well, but the portion corresponding to the one modulator Mfl and the portion corresponding to the other modulator Mfr have basically the same configuration. Therefore, in the following description, the part associated with one modulator Mfl will be described with the subscript l, and the part associated with the other modulator Mfr will be illustrated with the subscript r.

In order to determine whether the wheel is about to enter the locked state, the wheel speed V _W detected by the detector 10l is
The wheel acceleration _W obtained by the arithmetic circuit 12l is input to the inverting terminal of the first comparator 13l and the wheel acceleration _W obtained by the arithmetic circuit 12l. Input to each terminal.
A reference wheel speed V _R which is inputted to the in the first comparator 13l noninverting terminal, a comparison of the wheel speed V _W is performed, the signal to loosen the brake hydraulic pressure when it is V _R> V _W lambda is the It is output from the 1-comparator 13l. In addition, the second comparator 14
At l, the reference wheel deceleration input to the non-inverting terminal −
A comparison between _WO and the wheel acceleration _W is performed, and −
_{When WO 2} > _W , the signal β for relaxing the braking hydraulic pressure is output from the second comparator 14l. Furthermore, the third comparator 15
At l, the reference wheel acceleration input to the reversing terminal +
Comparison of _WO and wheel acceleration _W is performed, and _W > +
_When it is _WO , the signal α is output from the third comparator 151. This signal α is for determining whether or not the wheel speed Vw is increasing, and the signal α is used to determine the timing for continuing to loosen the braking hydraulic pressure.

The output terminal of the first comparator 13l is connected to the input terminal of the AND gate 16l, and is connected to the input terminal of the OR gate 17l. The output terminal of the second comparator 14l is A
It is connected to the input terminals of the ND gate 16l and the OR gate 17l. Further, the output terminal of the third comparator 15l is OR
It is connected to the input terminal of the gate 17l.

The output terminal of the AND gate 16l is inverted and connected to the input terminals of the AND gates 18l and 19l and to the output terminal 20l. The output terminal of the OR gate 17l is connected to the input terminal of the AND gate 18l, and the output terminal of the AND gate 18l is connected to the output terminal 22l and inverted and connected 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 thus configured, the output terminal 2
A signal for reducing the braking pressure is output from 0l, 20r, a signal for increasing the braking pressure is output from output terminals 21l, 21r, and a signal for holding the braking pressure constant is output from output terminals 22l, 22r. One modulator Mfl is
It operates in response to the signals from the output terminals 20l, 21l, 22l, and the other modulator Mfr has the output terminals 20r, 2l.
It operates in response to signals from 1r and 22r, whereby antilock control of both brakes Brl and Bfr is individually performed.

In FIG. 4, the configuration of the rear wheel control unit 9b will be described. The configuration of the rear wheel control unit 9b is similar to the configuration of the front wheel control unit 9a, and the portion corresponding to the front wheel control unit 9a will be described. The same reference numerals are attached without adding the subscripts l and r, and they are only illustrated.

The rear wheel control unit 9b should be particularly noted in the detectors 11l, 1
The wheel speed detected in 1r is 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. That is, the left and right rear wheels Wrl, Wr
Among r, the anti-lock control is performed according to the wheel that is easier to lock, that is, the wheel whose wheel speed is lower, and the control signals output from the output terminals 20, 21, 22 are used to control both modulators Mrl, Mrr. Operation is controlled at the same time.

Moreover, in the rear wheel control section 9b, the flip-flop 24 is interposed between the output terminal of the first comparator 13 and the input terminal of the OR gate 17. That is, flip-flop 2
The output terminal of the first comparator 13 is connected to the set input terminal S of No. 4, and the set output terminal Q of the flip-flop 24 is connected to the input terminal of the OR gate 17. A braking operation detector 26 that outputs a high level signal when a braking operation by the brake pedal 25 (see FIG. 2) is detected is connected to the reset input terminal R of the flip-flop 24 in an inverted manner.

With such a configuration, when the high-level signal λ is output from the first comparator 13, the output of the braking operation detector 26 becomes a low level when the braking operation is completed, that is, the flip-flop 24 outputs. The set output of the flip-flop 24 is high level until the reset input becomes high level, and therefore the output of the OR gate 17 also connects the high level state. As a result, the output of the AND gate 19, that is, the output of the output terminal 21 does not become high level during the antilock control until the braking operation is completed, and the brake hydraulic pressure of the rear wheel brakes Brl, Brr is reduced or held constant.

Next, the operation of this embodiment will be described. The brakes Bfl, Bfr;
Brake hydraulic pressure is supplied to rl and Brr, and each wheel Wfl,
It is assumed that the brake hydraulic pressure becomes excessive when a braking force is applied to Wfr; Wrl and Wrr. At this time, the rear wheel control unit 9b determines that the rear wheels Wrl and Wrr are likely to lock, outputs signals λ and β, outputs a pressure reduction signal from the output terminal 20, and brakes the rear wheels Wrl and Wrr. Reduce the hydraulic pressure. Moreover, the set output of the flip-flop 24 is also at high level, and the output of the OR gate 17 is at high level.

When there is no possibility of locking the wheels due to the reduction of the brake oil pressure, the signals β and λ become low level and the output terminal 20
Output becomes low level, but the output of the OR gate is high level, the output of the AND gate 18 becomes high level, and a signal for keeping the brake oil pressure constant is output from the output terminal 22. Therefore, the rear wheel Wrl,
The brake hydraulic pressure of Wrr is kept low,
The slip ratio is reduced. As a result, the rear wheels Wrl, W
The interference from rr to the wheels Wfl and wfr is suppressed to a small level, and good antilock control is performed.

By the way, the condition of the road surface may change during braking, and the adhesion coefficient may decrease. In this case, the brake hydraulic pressure may become too high if the brake hydraulic pressure is kept constant as described above. At this time, by determining that the lock is likely to occur again, the high level signals λ and β are output from the first and second comparators 13 and 14, and the brake hydraulic pressure is reduced.

Further, the front wheel control unit 9a includes front wheel modulators Mfl, M.
Since fr is controlled individually, excellent effects can be obtained in terms of braking distance and running stability. That is, the front wheels Wfl,
In a four-wheel drive vehicle in which Wfr and the rear wheels Wrl, Wrr are connected substantially rigidly, the control of the front wheels Wfl, Wfr affects the rear wheels Wrl, wrr. Based on the modulators Mfl and Mfr
With the high-select method that simultaneously controls the
One of the front wheels Wfl and Wfr may be locked, and the effect thereof affects both rear wheels Wrl and Wrr, causing the rear wheels Wrl and Wrr to slip, resulting in poor running stability. In addition, the front wheels Wfl and Wf with high load distribution
At r, both brakes Bfl, based on the low-speed front wheel speed,
It is obvious that the braking distance is extended by adopting the low select system that simultaneously controls Bfr.

In the above embodiments, the rear wheel modulators Mrl and Mr are arranged.
Although r is controlled simultaneously by the row select method, it may be controlled individually. Further, the flip-flop 14 may set the set output to the high level at the falling edge of the signal λ, or may set the set output to the high level at the rising edge or the falling edge of the signal β.

C. EFFECTS OF THE INVENTION As described above, according to the present invention, the brakes are mounted on the wheels of both axles, and the brake hydraulic system that controls the hydraulic pressures of the brakes controls the brake hydraulic pressures when the wheels are about to enter the locked state. An anti-lock control device for controlling to loosen is attached, and the anti-lock control device loosens the brake hydraulic pressure according to the possibility of wheel lock and the front wheel control unit individually controlling the brake of the front wheel, but the wheel lock Even if the possibility of the above is eliminated, the rear wheel control unit that controls the brakes of the rear wheels is configured to continuously avoid the increase of the brake hydraulic pressure until the end of the braking operation, so that the burden of the front wheels is reduced. It is possible to reduce the pressure, and after the possibility of locking the rear wheels, keep the brake hydraulic pressure on the rear wheels loose until the braking operation is completed. In spite of the vehicle in which the rear wheels are connected substantially rigidly, it is possible to obtain good anti-lock control by suppressing the interference from the rear wheels to the front wheels during anti-lock control.

[Brief description of drawings]

The drawings show one embodiment of the present invention. FIG. 1 is a schematic diagram of a drive system, FIG. 2 is a schematic diagram of a brake system, FIG. 3 is a schematic diagram of a front wheel control unit, and FIG. It is a schematic diagram of a wheel controller. 1 ... Viscose clutch as torque transmission mechanism, 7 ...
Brake hydraulic system, 9 ... Anti-lock control system, 9a ...
Front wheel control unit, 9b ... Rear wheel control unit, Afl, Afr, Arl, Arr ... Axle, Bfl, Bf
r ... brake, P ... power unit, Wfl, Wfr,
Wrl, Wrr ... Wheels

Claims (1)

[Claims] 1. A front or rear axle (Afl, Af)
The power unit (P) is connected to r), and the front and rear axles (Arl, Arr) have a torque transmission mechanism (1) that increases the torque transmission amount as the relative rotation speed increases. In a four-wheel drive vehicle that is connected to the power unit (P) via the two axles (Afl, Afr; Arl,
Arr) wheels (Wfl, Wfr; Wrl, Wrr) are equipped with brakes (Bfl, Bfr; Brl, Brr), respectively, and each brake (Bfl, Bfr; Brl, Brr).
The brake hydraulic device (7) for controlling the hydraulic pressure of
An anti-lock control device (9) for controlling the brake hydraulic pressure to be loosened when the wheel is about to enter a lock state is attached, and the anti-lock control device (9) is connected to the front wheel (Wf
The front wheel control unit (9a) for individually controlling the brakes (Brl, Bfr) of (1, Wfr) and the brake hydraulic pressure is loosened in response to the possibility of wheel locking, but the possibility of wheel locking is eliminated. The rear wheels (Wrl, Wr) are configured to avoid increasing the brake hydraulic pressure continuously until the end of the braking operation.
and a rear wheel control unit (9b) for controlling the brakes (Brl, Brr) of r).