JPH07277169A - Anti-skid control device for four-wheel drive vehicle - Google Patents

Abstract

PURPOSE:To restrict a lowering of deceleration, and to also restrict the vibration by performing at least one of the prohibition of reduction of the brake pressure and the delay of increase of the brake pressure with a vibration restricting means at the only time when each axle speed of the front wheel side and the rear wheel side has opposite phase vibration. CONSTITUTION:In an anti-skid control device to be applied to a four-wheel drive vehicle, a difference of the rotating speed between each axle of the front wheel side and the rear wheel side is computed by a speed difference computing means. A period that the computed speed difference achieves a predetermined value is computed by a period computing means. Furthermore, when the computed period exists within a predetermined range, a vibration generating means judges that each axle speed of the front wheel side and the rear wheel side has the opposite phase vibration. When the vibration is judged, a vibration restricting means performs at least of the prohibition of reduction of the brake pressure and the delay of increase of the brake pressure performs to at least one of wheels of the front wheel and the rear wheel. Lowering of the deceleration is thereby restricted, and the vibration is also restricted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anti-skid control device for a four-wheel drive vehicle, and more particularly, to a front wheel axle speed and a rear wheel axle speed based on a change in speed difference between a front wheel axle speed and a rear wheel axle speed. The present invention relates to an anti-skid control device for a four-wheel drive vehicle, which determines that the vehicle is in a vibration state in which the speed and the phase are opposite to each other, and performs control for suppressing the vibration only at this determination.

[0002]

2. Description of the Related Art In a four-wheel drive vehicle, when the front wheel axle and the rear wheel axle are directly connected or are connected with each other with a very strong binding force, the front wheel axle speed and A vibration state is likely to occur in the axle speed of the rear wheels, and when this vibration occurs, there is a problem that the braking force becomes excessive or insufficient and the slip deviates from the proper range. This problem is likely to occur especially when traveling on a low μ road.

As an anti-skid control device for a four-wheel drive vehicle, which has heretofore been aimed at suppressing the above-mentioned vibration in a four-wheel drive vehicle, an anti-skid control device for a four-wheel drive vehicle described in Japanese Patent Laid-Open No. 4-50067. It has been known. This anti-skid control device employs a so-called three-channel system in which the brake pressure of the front wheels is controlled independently for each of the left and right front wheels, and the brake pressure of the rear wheels is controlled together for the left and right rear wheels. In synchronization with the pressure reduction, the brake pressure of the front wheel on the same side of the left and right rear wheels as the rear wheel on the locking tendency side is also controlled to be reduced.

[0004]

However, the above-mentioned conventional anti-skid control device always synchronizes the brake pressure of the front wheels when reducing the brake pressure of the rear wheels, regardless of whether or not vibration is generated. Since the vehicle body is decompressed by this, there is a drawback that the deceleration of the vehicle body decreases and the braking distance increases.

Therefore, the anti-skid control device for a four-wheel drive vehicle according to the present invention does not always perform control for suppressing vibration during anti-skid control, but performs control for suppressing vibration only when vibration occurs. Thus, it is an object to suppress the vibration while suppressing the decrease in the deceleration of the vehicle body.

[0006]

For the above object, an anti-skid control device for a four-wheel drive vehicle according to the present invention is an anti-skid control device applied to a four-wheel drive vehicle as shown in FIG. And a speed difference calculation means for calculating a speed difference between the rotation speed of the front wheel side axle and the rotation speed of the rear wheel side axle, and a cycle for the speed difference calculated by the speed difference calculation means to reach a predetermined value. And a cycle calculating means for performing, and the cycle calculated by the cycle calculating means belongs to a predetermined range,
Vibration occurrence determining means for determining that the front wheel axle speed and the rear wheel axle speed are in opposite phase vibration states, and the vibration occurrence determining means causes the front wheel axle speed and the rear wheel axle speed to be in opposite phases. When it is determined that the vehicle is in the state of vibration, at least one of the front wheel and the rear wheel is provided with vibration suppressing means for prohibiting the pressure reduction of the brake pressure and delaying the pressure increase. And

[0007]

As described above, in the anti-skid controller for a four-wheel drive vehicle according to the present invention, as described above, the vibration state of the opposite phase is generated based on the cycle of the speed difference between the front wheel axle speed and the rear wheel axle speed. Since the occurrence of vibration is determined, it is possible to accurately grasp the occurrence of vibration. Then, only when the front wheel axle speed and the rear wheel axle speed are in the opposite phase vibration state, at least one of the front wheel and the rear wheel is prohibited from reducing the brake pressure and delaying the increase in pressure. One is performed, in other words, the vibration suppression control is performed. On the other hand, when it is not in the vibration state, the vibration suppression control is not performed and the normal anti-skid control is performed.

Therefore, when the vibration is generated, the vibration can be suppressed by the vibration suppressing control, and when the vibration is not generated, the deceleration of the vehicle body can be secured by the normal anti-skid control, so that the braking distance can be reduced.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the construction of an anti-skid control device for a four-wheel drive vehicle according to one embodiment.

In FIG. 1, 1 is a left front wheel (FL), 2 is a right front wheel (FR), 3 is a left rear wheel (RL), and 4 is a right rear wheel (R).
R) respectively. Each of the wheels 1 to 4 is driven by a drive system composed of an engine 5, a transmission 6, a center differential 7, a front differential 8, a rear differential 9 and the like.

Each of the wheels 1 to 4 has an electromagnetic pickup type wheel speed sensor 10 for detecting the wheel speed of each of the wheels 1 to 4.
~ 13 are installed and each wheel speed sensor 10 ~ 13
The detection signal of is input to the ECU 14. In addition to these detection signals, a detection signal of a brake signal detector 16 that detects that the brake pedal 15 is depressed is input to the ECU 14. Based on these input signals, the ECU 14 performs braking control for the wheels 1 to 4 as described below.

The braking system for braking each wheel 1 to 4 is composed of two systems, one is a system for supplying the brake fluid pressure of the master cylinder 17 to the left front wheel 1 and the right rear wheel 4,
The other is a system that supplies the brake fluid pressure of the master cylinder 17 to the right front wheel 2 and the left rear wheel 3. The former brake system includes a solenoid valve 18 for the left front wheel that controls the brake fluid pressure for the left front wheel 1 to either increase, maintain, or reduce pressure according to a control signal from the ECU 14, and a brake fluid pressure for the right rear wheel 4. The solenoid valve 19 for the right rear wheel which controls the pressure to be increased, maintained or reduced, the proportioning valve 20 which limits the brake fluid pressure of the right rear wheel 4, and the left front wheel 1 or the right rear wheel 4 at the time of pressure reduction. A reservoir 21 that collects the brake fluid and a pump 22 that returns the brake fluid in the reservoir 21 to the master cylinder 17 are provided. The latter brake system has the same EC
According to the control signal from U14, the solenoid valve 23 for the right front wheel, which controls the brake fluid pressure for the right front wheel 2 to either increase, hold, or reduce, and the brake fluid pressure for the left rear wheel 3, increase, maintain, or reduce. The solenoid valve 24 for the left rear wheel which controls either of the above, the proportioning valve 25 which limits the brake fluid pressure of the left rear wheel 3, and the reservoir 2 which collects the brake fluid of the right front wheel 2 or the left rear wheel 3 when the pressure is reduced.
6 and the brake fluid in the reservoir 26 to the master cylinder 1
A pump 27 for returning to 7 is provided.

The ECU 14 executes the calculation and processing as shown in the flow chart of FIG. The calculation process shown in FIG. 2 is started when the ignition switch is turned on.

The contents of the arithmetic processing shown in FIG. 2 will be described below in order.

(1) Speed difference calculation (step 100) The rotation speed of the front wheel axle 28 (FIG. 1) and the rear wheel axle 2
The speed difference V _D from the rotation speed of 9 is obtained (step 10
0). Specifically, the wheel speed sensors 10 and 11 on the front wheel side
Wheel speed V _FR of the right front wheel 2 calculated based on the detection signal of
And the average value of the wheel speed V _FL of the left front wheel 1 ((V _FR + V _FL )
/ 2) is obtained as the rotation speed of the axle 28 on the front wheel side, and the wheel speed V _RR of the right rear wheel 4 and the left rear wheel 3 calculated based on the detection signals of the wheel speed sensors 12 and 13 on the rear wheel side. The average value ((V _RR + V _RL ) / 2) with the wheel speed V _RL is obtained as the rotation speed of the rear wheel axle 29, and is calculated from the rotation speed of the front wheel axle 28 ((V _FR + V _FL ) / 2). Rear wheel side axle 29
The rotational speed ((V _RR + V _RL ) / 2) is subtracted to obtain the speed difference V _D (= (V _FR + V _FL ) / 2− (V _RR + V _RL ) / 2).

(2) Judgment of Necessity of Vibration Occurrence Judgment (Step 101) Vibration Occurrence Judgment for Judging Whether Anti-phase Vibration Occurs Between Front Wheel Axle 28 and Rear Wheel Axle 29 It is determined whether or not (step 102) needs to be performed (step 101). Specifically, in order to detect the timing when the speed difference V _D reaches the predetermined value KV ₁ , the speed difference V _{D (n-1)} obtained last time is less than the predetermined value KV ₁ and the speed difference V obtained this time is detected. _It is determined whether _{D (n)} is greater than a predetermined value KV ₁ , and the previous speed difference V _{D (n-1)} is less than or equal to the predetermined value KV ₁ and the current speed difference V _{D (n)} is the predetermined value KV _1. If it is larger, it is determined that it is necessary to determine the occurrence of vibration.

(3) Vibration Occurrence Judgment (Step 102) It is judged whether or not an antiphase vibration occurs between the front wheel axle 28 and the rear wheel axle 29 (step 102).
Specifically, the value of the timer CT ₁ is greater than or equal to the predetermined value KT _{1 and} KT ₂
If the value of the timer CT ₁ is greater than or equal to the predetermined value KT _{1 and} less than or equal to KT _2, it is determined that the vibration has occurred.

Here, the timer CT ₁ has a predetermined value K larger than KT ₂ until the first vibration occurrence judgment is made.
Is set to T ₃ (steps 105, 106, 1
07), it is reset when it is judged that the vibration does not occur in the first vibration occurrence judgment (step 10).
4) Then, the step is cyclically advanced until the second vibration occurrence determination is made (step 105). That is, the timer CT ₁ is the time required from the first vibration occurrence determination time to the second vibration occurrence determination time, from the second vibration occurrence determination time to the third vibration occurrence determination time. The time required is ...

The predetermined value KT₁ , KT₂ Is the center
In the locked and free states of the differential 7
Experimentally, the rotational speeds of the axles 28 of the front wheels 1 and 2 and the rear wheels
Speed difference V from the rotational speed of the axles 3 and 4_D The various roads
Surface, the driving method of the vehicle to measure the axle speed of the front wheels and the
Speed difference from axle speed V_D The factor that changes cyclically is
It can be determined whether it is due to vibrations across the rear wheels.
It is set as the time when you can Speed difference V_D Around
Even if it changes over time, the time required for one cycle is KT ₁ Yo
If it is shorter, the cause is the road surface
KT and normal ABS control.₂ Than
If it is too long, the interference of the center differential 7
Because it is weak, the vibration at that time must be dealt with specially
Also converges naturally. The speed difference V_D It takes one cycle
Time, speed difference V_D Is a predetermined value KV₁ When it reached
CT as a reference₁ Is being measured by
Small speed difference V due to factors other than front and rear wheel vibration_D Has occurred
This is because it is removed as noise. Also, predetermined
Value KT₃ Is KT₂ Greater value, vibration suppression
Defined as the time to execute the control (step 110)
Therefore, the vehicle performance is not adversely affected.
It is set within the range that does not cause a black state.

(4) Setting and resetting the flag f ₁ (steps 103, 107) A flag f ₁ for instructing either normal anti-skid control (also called ABS control; step 109) or vibration suppression control (step 110). Is set or reset (steps 103 and 107). Specifically, when it is determined in the vibration occurrence determination (step 102) that the vibration is occurring, the flag f ₁ is set to instruct the vibration suppression control (step 110), and the value of the timer CT ₁ is KT _3. If it is determined to be larger than the above, the flag f ₁ is reset and the normal anti-skid control (step 109) is instructed (step 108).

(5) Normal anti-skid control (step 109) This is executed when the flag f ₁ is in the reset state indicating that the above vibration is not generated, and as is known, the wheel speed V _FR of the right front wheel 2 is known. , The wheel speed V _FL of the left front wheel 1, the wheel speed V _RR of the right rear wheel 4, the wheel speed V _RL of the left rear wheel 3, the vehicle speed V _S, etc., based on the solenoid valves 18, 19, 23, 24.
Is controlled (step 109).

(6) Vibration Suppression Control (Step 110) This is executed when the flag f ₁ is in the set state indicating that the vibration has occurred, and at least one of the front wheels 1 and 2 and the rear wheels 3 and 4 is applied to Thus, the solenoid valves 18, 19, 23, 24 are controlled so as to prohibit at least one of the reduction of the brake pressure and the delay of the pressure increase.

According to the anti-skid control device constructed as described above, as shown in FIG. 3, the brake pressure of the front wheels 1 and 2 is reduced for a predetermined period T ₀ from the time t ₁ when it is judged that vibration has occurred. By prohibiting and delaying the pressure increase, vibration between the wheel speed V _F of the front wheels 1 and 2 and the wheel speed V _R of the rear wheels 3 and 4 came to be damped.

As described above, according to this embodiment,
Only when the front wheel axle speed and the rear wheel axle speed are in the opposite phase vibration state, at least one of the prohibition of brake pressure reduction and the delay of pressure increase is applied to at least one of the front wheel and the rear wheel. In other words, the vibration suppression control is performed. On the other hand, when it is not in the vibration state, the vibration suppression control is not performed and the normal anti-skid control is performed.
Therefore, when the vibration occurs, the vibration can be suppressed by the vibration suppression control, and when the vibration does not occur, the deceleration of the vehicle body can be secured by the normal anti-skid control, so that the braking distance can be reduced.

As the vibration suppression control, in addition to the prohibition of the pressure reduction of the brake pressure and the delay of the pressure increase as described above, a method of synchronizing the pressure increase and the pressure decrease to the front wheels and the rear wheels may be adopted. Good.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an anti-skid control device for a four-wheel drive vehicle according to an embodiment.

FIG. 2 is a flowchart showing a calculation process of the ECU.

FIG. 3 is a waveform diagram for explaining the operation of the anti-skid control device.

[Fig. 4] Claim correspondence diagram

[Explanation of symbols]

 1, 2 front wheels 3, 4 rear wheels step 100 speed difference calculating means step 105 cycle calculating means step 102 vibration occurrence judging means step 110 vibration suppressing means

Claims (1)

[Claims] 1. An anti-skid control device applied to a four-wheel drive vehicle, comprising: speed difference calculation means for calculating a speed difference between a rotation speed of a front wheel side axle and a rear wheel side axle. Cycle calculating means for calculating a cycle in which the speed difference calculated by the speed difference calculating means reaches a predetermined value; and, when the cycle calculated by the cycle calculating means falls within a predetermined range, the front wheel axle speed and the rear wheel. The vibration occurrence judging means for judging that the axle speed is in the opposite phase vibration state, and the vibration occurrence judging means judges that the front wheel axle speed and the rear wheel axle speed are in the opposite phase vibration state. When, for at least one of the front and rear wheels,
An anti-skid control device for a four-wheel drive vehicle, comprising: a vibration suppressing unit that prohibits reduction of brake pressure and delays increase of pressure.