JPH01301450A - Anti-lock braking controller - Google Patents

Abstract

PURPOSE:To obtain highly efficient braking control function by controlling a brake system in such a way that the four-wheel independent control, the rear wheels select-low control or the front and diagonal wheels low control is selected according to the coefficient of friction with the road surface and the amount of the slippage at the rear wheels. CONSTITUTION:When the turning speed of wheels is reduced by the brake application, an electronic control circuit 10 calculates the estimated wheel speed, the coefficient mu of friction with the road surface and the sum SR of the slip ratio at the rear wheels according to the wheel speeds detected by sensors S1 to S4, and compares the results with related reference values mu0 and THR. If mu>mu0 and SR<mu, the entire wheels are controlled independently, if mu>mu0 and SR>THR, or mu<mu0 and SR<THR, the front wheels FL and FR are controlled independently and the rear wheels RL and RR are placed under the select-low control. If mu<mu0 and SR>THR, the front wheels FL and FR are placed under the diagonal select-low control and the rear wheels RL and RR are under the select-low control. As a result the problems of reduction in direction stability and shortage in braking force are dissolved so that the highly efficient braking control may be executed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an anti-lock brake control device that maximizes braking efficiency when braking the wheels of an automobile.

[Conventional technology]

When applying brakes to the wheels of a car, etc., the H
An anti-lock control system is used to operate the brake system with high efficiency in response to changes in the coefficient of friction. According to this anti-lock control method, the brake pressure in the brake piping is reduced, maintained, or increased even when the brake is applied, and the brake release and braking are repeated within a short period of time, thereby achieving the optimum brake braking action. The brakes are controlled to obtain.

The control device used for the above-mentioned anti-lock control generally uses a wheel speed sensor that detects the wheel speed and calculates the wheel speed, deceleration speed, estimated vehicle speed, slip rate, etc. from the detected wheel speed signal, and uses the result of the calculation. It consists of an electronic control circuit that outputs control signals such as depressurization, holding, and pressurization based on the pressure, and a hydraulic control unit that adjusts the braking pressure from the mask cylinder and sends it to the wheel cylinder based on the control signal from this control circuit. .

When a wheel speed signal is input, the electronic control circuit uses the input information to perform the various calculations described above, and determines whether the braking state of each wheel is in a locking tendency or not based on changes in slip ratio, deceleration value, etc. It is determined whether there is a tendency to recover from the accident, and based on the results, the hydraulic control unit is controlled to reduce, maintain, or maintain pressure.
Or output control signals such as pressurization.

The hydraulic control unit generally includes a solenoid valve (or a cut-off valve or a flow control valve), a check valve, a hydraulic pump and motor, an accumulator, a reserve tank, etc., and is located on the braking path from the mask cylinder to the wheel cylinder. It consists of a hydraulic circuit that opens and closes the flow of braking pressure or pump hydraulic pressure using one of the above-mentioned valves provided in the pump. When applying brakes to each wheel using such a hydraulic circuit, a four-channel system is used in which the above-mentioned solenoid valves are provided for each wheel to control the opening and closing of the flow of hydraulic pressure to the wheel cylinders, and these are controlled independently. , a 3-channel system in which a solenoid valve, etc. is provided for each of the left and right front wheels, and a set of solenoid valves, etc. are provided for the left and right rear wheels to control each, respectively, and a solenoid valve, etc. is provided for each of the left and right front wheels, respectively. There is a two-channel system in which the rear wheels follow the hydraulic pressure to either the left or right front wheels.

As a method of giving a hydraulic pressure control signal to the above hydraulic circuit, the front and left wheels are considered as a pair, and the one of the pair of wheels is controlled with lower hydraulic pressure (lower coefficient of road friction). A control method that reduces the pressure on both sides when the low pressure side moves toward lock based on (hereinafter referred to as select low),
On the other hand, there is a control method that uses the higher hydraulic pressure side as a reference and reduces the pressure on both sides when the high pressure side approaches lock (hereinafter referred to as "select high"), or a method that independently controls the hydraulic pressure of each wheel depending on the road surface condition ( (hereinafter referred to as "Independent") are already known. Furthermore, when braking diagonally located front and rear wheels using the Also known as low.

In general, select low is effective in securing lateral force of the wheels, which affects the directional stability and steering performance of the vehicle, but it has the disadvantage of lengthening the braking distance due to insufficient braking force. On the other hand, while Select High can secure braking force, it has the disadvantage of lacking lateral drag on the wheels. Although independent is more expensive, it has the advantage of being able to make detailed judgments based on the conditions of each road surface. Considering the advantages and disadvantages of each control method, generally speaking, independent or select high is used to ensure braking force for the front wheels, and directional stability is used for the rear wheels. Therefore, select low is considered desirable.

The above conventional technology is generally a front wheel drive (hereinafter referred to as FWD)
Or, it is mainly aimed at rear wheel drive (RWD),
If it is suitable for four-wheel drive (hereinafter referred to as 4WD), it must be devised to be compatible with that drive system. As such a conventional technique, an anti-lock control system has been proposed in Japanese Patent Laid-Open No. 62-238158. This publication describes an anti-lock control method when applied to a vehicle that can freely switch from FWD to 4WD, and the anti-lock control method can also be switched as the drive system is switched. The front wheels of the two
The two rear wheels have a 3-channel control system based on select low, and in 4WD drive mode, the anti-lock control system has a 2-channel control system with a diagonal select low that applies select low to the front and rear wheels diagonally. has been adopted.

[Problem to be solved by the invention]

By the way, 4WD vehicles with viscous couplings generally reduce the driving force when there is a difference in rotational speed between the front and rear axles to prevent the wheels on the low-speed axle from being able to sufficiently transmit the driving force to the road surface. The structure is such that the driving force is increased by transmitting it to other shafts via a viscous coupling, so that the driving force of the four wheels can be used effectively. As long as the rotational speed difference is small, the internal circulation torque transmitted through the viscous joint is small, there is little interference between the axles, and a highly efficient braking effect can be obtained by controlling each wheel independently.

However, as the difference in rotational speed increases, the internal circulating torque increases, which increases the interference between the axles and causes a so-called jerky feeling, and also causes the vehicle to sway, resulting in poor directional stability.

Therefore, in order to eliminate these disadvantages in the prior art mentioned above, a diagonal select low control method is adopted in the 4WD state, and this diagonal select low type control method minimizes the influence of such internal circulation torque. be able to. This is because by performing a select low between diagonally opposite wheels, directional stability is ensured while reducing the pressure based on the pressure on the low speed side, and braking is performed by minimizing the torque difference between the front and rear wheels. .

However, there is a limit to the torque that can be transmitted by a viscous joint, and if such diagonal select low control is performed despite this, the stopping distance may be extended, especially on asymmetrical road surfaces. Further, on a road surface with an extremely low coefficient of friction, even if the diagonal selector is controlled using only one type of diagonal selector, the slip amount of each wheel becomes relatively large, and the running of the vehicle may become unstable.

Despite these various problems, in the prior art, diagonal select low control is always performed in the 4WD state, which is disadvantageous in terms of braking efficiency due to the above problems.

This invention was made in view of the current state of anti-lock brake control technology in conventional four-wheel drive vehicles, and its purpose is to control anti-lock brake control based on the magnitude of the sum of the road surface friction coefficient and rear wheel slip amount. The wheels can be controlled independently, the front wheels can be controlled independently and the rear wheels can be controlled in select low mode, or the front wheels can be controlled in diagonal select low mode and the rear wheels can be controlled in select low mode to achieve the most efficient control depending on each situation. The purpose of the present invention is to provide an anti-lock brake control device that can be used.

[Means to solve the problem]

In this invention, as a means to solve the above problem, a wheel speed sensor that detects the rotational speed of each wheel of a constant all-wheel drive vehicle equipped with a viscous joint between the front axle and the rear wheel, and a Wheel speed, estimated vehicle speed,
an electronic control circuit that calculates deceleration, slip ratio, etc. and outputs a hydraulic control signal based on the calculation results; and a hydraulic control unit that can independently adjust the braking force of each front, rear, left, and right wheel using the control signal. The electronic control circuit has a means for determining a road surface friction coefficient and a means for evaluating the sum of slip amounts of the left and right rear wheels, and when the road surface friction coefficient is low and the sum of the rear wheel slip amounts is small, the four wheels are independently, and when the sum of the rear wheel slip amounts is large, the front wheels are controlled independently regardless of the high or low friction coefficient, and the rear wheels are controlled individually based on information from the lower rotational speed of the two rear wheels. It was adopted.

Furthermore, when the coefficient of friction is small and the sum of slips of the rear wheels is large, the influence of internal circulation torque becomes large. 4 when the rear wheel slip sum is high and the rear wheel slip sum is small.
When the road surface friction coefficient is high and the rear wheel slip sum is large, or when the road surface friction coefficient is low and the rear wheel slip sum is small, the front wheels are set independently.The rear wheel is the one with the lower rotation speed of the two rear wheels. When the road surface friction coefficient is low and the sum of the rear wheel slips is large, the front wheels are controlled by the information from the diagonally opposite rear wheel, which has a lower rotation speed. We adopted a system in which control is performed based on information from the one with a lower rotational speed.

[Effect]

Anti-lock control is started when the brake pedal is depressed. When the wheel speed is reduced due to pressurization due to brake braking, the change in wheel speed is calculated by the electronic control circuit, and the estimated vehicle speed, road surface friction coefficient μ, and rear wheel slip sum SR are calculated based on this wheel speed. Desired. Next, the following case occurs in which μ, S, are compared with respective reference values μ0, THR, and control is performed based on the results.

When μ>μ0 and S++<THR, all wheels are controlled independently. In this case, μ is large and the wheel restraint torque is sufficiently large compared to the internal circulation torque, so independent control of the front wheels is ensured and braking force is effectively transmitted to the road surface. Since the rear wheel slip sum is small and the internal circulation torque is sufficiently small compared to the wheel restraint torque on the road surface, highly efficient braking can be achieved by independently controlling the rear wheels.

Since SR is small, directional stability is not inhibited.

When μ > μ0, SR > THR or μ > μ0, S3<THR, the front wheels are controlled independently, and the rear wheels are controlled selectively for both rear wheels.

Independent control of the front wheels is the same as in the first case above, but for the rear wheels, when the internal circulation torque is smaller than the wheel restraint torque and the rear wheel slip sum is large, the directional stability of the vehicle deteriorates. easy. When the sum of rear wheel slips is small and the internal circulating torque is close to wheel restraint, there is a high risk that the sum of rear wheel slips will become large. Therefore, it is possible to improve directional stability by setting the rear wheels to select low for both rear wheels. can be achieved.

By applying the control according to the first invention as described above, it is possible to perform control that can be applied to road conditions while ensuring sufficient directional stability except in special cases. In addition, the following controls are executed.

When μ is μ0 and Sl>THR, the front wheels are controlled by diagonal select low, and the rear wheels are controlled by select low of both rear wheels.

In this case, the internal circulation torque is close to the wheel restraint torque,
Since the sum of slips of the rear wheels is large, it is possible to avoid interference between the axles by controlling the front wheels diagonally with select low, and to ensure the directional stability of the wheels by controlling the rear wheels with select low of both rear wheels. can.

In each of the above controls, when performing independent control, the detected wheel speed is used as is to determine the slip rate and deceleration, and based on this, the lock tendency or recovery tendency from lock is determined for each wheel. Based on this, a control signal for pressurization, holding, or depressurization is output.

When performing select low control for both rear wheels, replace the high-speed wheel speed of both rear wheels with the low-speed wheel speed to adjust the slip rate,
Find the deceleration and make the same judgment as above based on this,
A control signal based on the determination is output.

In the diagonal select low control, a control signal based on the same judgment as the select low is output between each front wheel and the rear wheel on the diagonal line.

In any of the select low controls, the same results can be obtained by replacing the results of the slip rate, deceleration, etc. with those on the low speed side instead of replacing the wheel speed with those on the low speed side.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

The anti-lock brake control device according to the present invention is provided for a permanent all-wheel drive vehicle shown in FIG. Generally, four-wheel drive vehicles have a viscous joint■ between the front wheel SF and rear wheel S. When the front wheels are no longer able to sufficiently transmit the driving force of engine E to the road surface, the driving force is transmitted to the rear wheels via VC, and the reduced driving force of the front wheels is transferred to the rear wheels by the buffer knob. do.

FIG. 1 is a block diagram schematically showing the electrical control system of the anti-lock brake control device.

The respective wheel speed signals detected by the wheel source sensors S, ~S4 for detecting the rotational state of the front, rear, left, and right wheels of a four-wheel drive vehicle (hereinafter referred to as a 4WD vehicle) are sent to the electronic control circuit 1.
The signal is input to the A/D converter 11 of 0 and converted into a pulse signal, processed by a pulse processing circuit, and then sent to the microcomputer 13.

The microcomputer 13 calculates the estimated wheel speed, deceleration, slip rate, etc. based on the wheel speed pulse signal, and based on the calculation results, the solenoid drive circuit 14
, and the necessary control signals are sent to the motor drive circuit 15, respectively. A fail-safe relay drive circuit 16, a warning lamp drive circuit 17, etc. are provided outside the drive circuit.

W and L are warning lamps.

The solenoid drive circuit 14 sends control signals of four systems as shown in FIG.
By turning ON and OFF 4&l (2-position switching valve), the brake cylinders of each wheel are pressurized and held.
Switch to one of the pressure reduction operation modes and apply the brake.

As shown in FIG. 2, the hydraulic circuit of this embodiment includes a mask cylinder 21 and a 2&[l
It consists of a hydraulic pressure control unit and a wheel cylinder for each wheel, and each hydraulic pressure control unit has a pair of solenoid valves 22 and 22'.
It is equipped with a hydraulic pump 23, a motor 24, an accumulator 25, a reserve tank 26, a check valve 27, etc. The two systems of braking pressure from the mask cylinder 21 are supplied to the left and right front wheels, respectively, and the braking pressure to the left front wheel is branched midway and also sent to the right rear wheel, and the right front wheel is not targeted.
Therefore, the braking pressure system is an X pipe. A pair of solenoid valves 2
2.22', check valve 27 is provided for each wheel, and
Pressure pump 23, accumulator 25, reserve tank 2
Reference numeral 6 is provided for each of the two left and right braking pressure systems, and the motor 24 is of a double-shaft drive type to drive two hydraulic pumps 2.
It is driving 3.

This hydraulic circuit is generally called a circulation type.

Anti-lock control by the anti-lock brake control device is performed as follows (see FIGS. 3 to 6).

When the power is turned on and the car starts, the wheel speed signals of each wheel in motion are input to the electronic control circuit 10, and the microcomputer 13 calculates the wheel speeds VFLII, V of each wheel.
□N, ■RLH, ■+111+1 are calculated. When the brake pedal is depressed and the brake is applied, anti-rotation control is started. As shown in Figure 3,
After calculating the above wheel speed which changes due to braking, further from this wheel speed II constant vehicle speed VREF, road surface friction coefficient μ, rear wheel slip sum SR"= (2Vary
VRLII Vi, lu ), etc. are calculated.

Next, the road surface friction coefficient μ is a predetermined value μ. compared to μ is expressed as the average value of the four wheels. is an appropriate value around which the maximum driving force can be applied to the road surface.

Thereafter, regardless of whether μ is large or small, the rear wheel slip sum S is compared with a reference value THR (threshold).

This THR is a value determined on the basis of whether or not, when all wheels are controlled independently, there is a sufficient influence to impair running stability.

After the above-mentioned comparison of μ and SR is made, four combinations of their magnitudes are generated, so the optimal control for each combination is performed as follows.

In the case of (1), μ is high, so the braking force can be applied to the road surface with high efficiency, and since S is large and small, driving stability is not hindered. Therefore, it is better to brake the four wheels independently. Power can be secured.

In the case of (2), since S is small, the directional stability of the rear wheels is good, but since μ is low, the total slip of the rear wheels tends to increase as a whole due to the influence of internal circulation torque from the front wheels, resulting in poor directional stability. Therefore, it is necessary to independently control the front wheels to ensure braking force, and to obtain directional stability for the rear wheels through select low control 711 of both rear wheels.

In case (3), braking force can be obtained because μ is high, but S.

Because of the large size, the directional stability provided by the rear wheels deteriorates (
It is preferable to use the same control as in 2).

In the case of (4), I is low and SR is large, so braking force cannot be obtained and directional stability also deteriorates. Therefore, first, by setting the rear wheels to select low, interference between the wheels is reduced as much as possible, vehicle stability is obtained, and braking force is secured as much as possible.

In accordance with each of the above cases, the wheel speeds are replaced as shown.

In the case of (1), since each wheel is controlled individually based on the speed information, it passes through the NO line in the judgment loop of μμμ0 and SR>THR, and V(i) (i=1 to 4)
is left unchanged at the value of VFLM~■□□.

In the case of (3), based on the comparison result of ■□M >'VIILH, the input speed information for the front wheels is kept as is, and for the rear wheels, the higher speed is replaced with the lower one based on the lower rotation speed. will be carried out.

In the case of (2), the same speed replacement as in (3) is performed through the No line in the S,>THR judgment loop shown in the figure.

In the case of (4), first V FLII >
The diagonal select low is determined by comparing V++*□ and VFIN>VIILH. As a result, a select low is performed for both rear wheels in each of the four cases, resulting in eight speed replacements.

Since the actual speed state is in one of the above 13 ways, the current V (i) (i=1 to 4) is evaluated again, and the slip ratio, deceleration, etc. are calculated. As a result (θ(i) (i=1 to 4)), if it is determined that the operation mode combination shown in Fig. 4 is in phase I, ■, or ■, the command signal for that determination phase will be sent to the solenoid Ft. , FIIH, RLH, and R□.

FIG. 4 is a detailed flowchart of the evaluation of V(i) in FIG. 3 and the output to the solenoid, and is a program for judgment and output commands used in anti-lock control for boat fishing. In this flowchart, three phases are generally used: a combination of operation modes pressurization, depressurization, and holding; phase I for constant pressurization; phase II for a combination of N pressure and hold command; and phase II for a combination of pressurization and hold command. Phase ■.

The program shown in FIG. 4 is initialized by the main program described later, and since the phase is set to ■, the first phase is naturally ■. In this state of phase r, the presence or absence of a tendency to lock is detected.

To detect this tendency to lock, the deceleration and slip rate are obtained as an evaluation of V (i) (i=1 to 4), and the tendency to lock is determined based on these. If the locking tendency is not detected as a result of the above judgment, a phase I processing command, that is, a constant pressurization command is output to the solenoid. For this reason, the brake remains in a braking state, and as time passes, the brake tends to lock. When a lock tendency is detected, a phase H processing instruction is output,
Depressurization and holding processes are performed. Therefore, as time passes, a lock recovery tendency is detected, and then a processing command for phase (2) is output. With this pressurization and holding command, the pressure is gradually increased, so if this is repeated, the locking tendency will appear again.

When a locking tendency is detected, a phase H processing command is further output, and the process then shifts to phase (2) again, and by repeating these steps, brake braking is performed with high efficiency.

The processing commands in Phases 11 (2) and (2) are used to calculate the resulting θ(i) for each of V(i) = t~4
) (i=1 to 4). Therefore, which phase of processing is performed differs depending on the value of v(1).

FIG. 5 shows an example of the main program. For this main program, the subprograms shown in Figures 3 and 4 are configured as regular interrupt programs, which perform initialization processing after the initial check, set the phase to I, enable interrupts, and then It consists of an infinite loop in which decisions that do not require an emergency are made, and this process is repeated as long as there is no abnormality. When an interrupt occurs at regular intervals, the main loop is temporarily interrupted and the subprogram is executed.

FIG. 6 is another embodiment of the subprogram of FIG. 3. It is basically the same program, but V (i)
(i = 1 to 4) is evaluated first, and the resulting slip rate and deceleration result θ(i) = t to 4.
), when selecting select low for both rear wheels or diagonal select low, after determining μ and S, compare the wheel speeds and convert the above result θ(i) to the low speed result. replace,
The only difference is that processing instructions for each phase are output depending on the result after the replacement.

[Effect] As explained in detail above, in this invention, the four wheels are independently controlled in four cases that occur depending on the magnitude of the road surface friction coefficient μ and the rear wheel slip sum S and l with respect to their respective reference values.
The front wheels are controlled independently, the rear wheels are controlled by select low control of both rear wheels, the front wheels are controlled by diagonal select low control, and the rear wheels are controlled by either select low control of both rear wheels, so all four wheels are controlled at all times. The problems of reduced directional stability and insufficient braking force that occur when using independent control or constant diagonal select low control are resolved by making it possible to perform the above-mentioned optimal control according to each case, and improve high performance. Efficient brake control action can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an electronic control circuit of an embodiment of an anti-lock brake control device according to the present invention, FIG. 2 is a block diagram of a hydraulic circuit, FIG. 3 is a flowchart of a subprogram in the electronic control circuit, and FIG. The figure shows a partial float yard for normal anti-lock control, Figure 5 is a flowchart of the main program, Figure 6 is another embodiment of the flowchart in Figure 3, and Figure 7 is a diagram of the power transmission mechanism of an all-wheel drive vehicle. It is a schematic diagram. 10...Electronic control circuit, 13...Microcomputer, 22.22'
... Solenoid valve, 23 ... Hydraulic pump, S1 to S4 ... Wheel speed sensor, V, ...
・Viscous joint, S,...Front shaft, SA...
- Rear axis. Patent applicant: Sumitomo Electric Industries, Ltd.

Claims (4)

[Claims] (1) A wheel speed sensor that detects the rotational speed of each wheel of a constantly all-wheel drive vehicle equipped with viscous joints between the front wheels and rear wheels, and a wheel speed and estimated vehicle speed based on the detected wheel speed signal. An electronic control circuit that calculates deceleration, slip rate, etc. and outputs a hydraulic control signal based on the calculation results, and a hydraulic control unit that can independently adjust the control force of each front, rear, left, and right wheel using the control signal. The electronic control circuit has a means for determining a road surface friction coefficient and a means for evaluating the sum of slip amounts of the left and right rear wheels, and when the road surface friction coefficient is high and the sum of the rear wheel slip amounts is small, the four wheels are independently, and when the sum of the rear wheel slip amounts is large, the front wheels are controlled independently regardless of the level of the friction coefficient, and the rear wheels are controlled respectively based on information from the lower rotational speed of the two rear wheels. Anti-lock brake control device. (2) The electronic control circuit controls the four wheels independently when the road surface friction coefficient is high and the rear wheel slip sum is small, and controls the rear wheels independently when the road surface friction coefficient is high and the rear wheel slip sum is large, or when the road surface friction coefficient is low and the rear wheel slip sum is small. When the sum of slips is small, the front wheels are driven independently, and the rear wheels are driven diagonally by information from the lower rotational speed of the two rear wheels, and when the road friction coefficient is low and the sum of the rear wheel slips is large, the front wheels are driven diagonally. According to claim 1, the rear wheels are controlled by information from the lower rotational speed of the upper rear wheels, and the rear wheels are controlled by information from the lower rotational speed of the two rear wheels. Anti-lock brake control device as described. (3) The electronic control circuit calculates the wheel speeds of all wheels, estimated vehicle speed, road surface friction coefficient μ, and rear wheel slip sum S_R from the wheel speed signals detected by the wheel speed sensors, μ,
Compare S_R with each reference value μ_0, THR, and find μ>μ_0, S_R<
In the case of THR, the slip rate is determined by the detected wheel speed value.
Determine the deceleration of each wheel and control each wheel independently based on the result, μ>μ_0, S_R>THR or μ>
When μ_0, S_R<THR, the value of the detected wheel speed is used for the front wheels, and the value of the detected wheel speed is used for the rear wheels.The wheel speed of both rear wheels is compared and the high speed wheel speed is replaced with the low speed side, and the slip rate is reduced. Based on the speed, the front wheels are controlled independently, and the rear wheels are controlled in select low mode for both rear wheels, so that μ<μ
When _0, S_R>THR, for the front wheels, the wheel speed on the high speed side is replaced with the wheel speed on the low speed side when compared with the wheel speed of the rear wheel diagonally opposite each front wheel, and for the rear wheels, the select low speed of both rear wheels is changed. Slip rate by replacing the same speed as control,
Deceleration is determined and based on the results, the front wheels are subjected to select low control, and the rear wheels are subjected to select low control for both rear wheels.In each of the above controls, the tendency of each wheel to lock is determined based on the results of determining the slip rate and deceleration. 2. The anti-lock system according to claim 1, wherein a recovery tendency from locking is determined, and a control command for pressurization, holding, or depressurization is output to a solenoid of each wheel according to the determined content. Brake control device. (4) The electronic control circuit calculates the wheel speeds of all wheels, estimated vehicle speed, road surface friction coefficient μ, and rear wheel slip sum S_R from the wheel speed signals detected by the wheel sensors, and calculates the slip rate based on these. , calculate the deceleration to determine the tendency of each wheel to lock or recover from lock, and then compare μ and S_R with respective reference values μ_0 and THR for the four resulting cases. μ>μ_0
, when S_R<THR, each wheel is controlled independently based on the result corresponding to the detected wheel speed value, and when μ>μ_
0, S_R>THR or μ<μ_0, S_R<THR, for the front wheels, the wheel speeds of both rear wheels are compared based on the result corresponding to the detected wheel speed value, and the wheel speed of both rear wheels is compared. By replacing the above results with those on the low speed side, the front wheels are controlled independently and the rear wheels are controlled with select low control for both rear wheels.
When μ<μ_0, S_R>THR, for the front wheels, compare the wheel speed of the rear wheels on the diagonal of each front wheel, replace the high speed result with the low speed result, and for the rear wheels, select both rear wheels. Similar to low control, the results on the high speed side are replaced with those on the low speed side, the front wheels are subjected to diagonal select low control, the rear wheels are subjected to select low control of both rear wheels, and the above respective control signals are output to the solenoids of each wheel. Claim 1 characterized in that any one of pressurization, holding, and depressurization is controlled by
The anti-lock brake control device described in .