JPH0367765A - Anti-skid control device - Google Patents

Abstract

PURPOSE:To cancel out the lack of braking forces by permitting wheel cylinder fluid pressure to be reduced during the course of satisfying predetermined requirements for starting pressure reduction if the time needed for the requirements for starting pressure reduction is less than a predetermined time, and inhibiting control of a brake fluid pressure control means after the requirement for starting pressure reduction are not satisfied. CONSTITUTION:An anti-skid control device 100 for controlling the braking fluid pressure of driving wheels RR, RL has an actuator 12 interposed between fluid pressure piping 7 and 8 for guiding the braking pressure of a master cylinder 3 to a rear wheel cylinder 10, 11 and uses the actuator 12 to adjust braking pressure to be applied to the wheel cylinder 10, 11. In an ECU for controlling the actuator 12, it is determined according to the wheel speed whether or not predetermined requirements for starting pressure reduction are satisfied, and when the predetermined requirements for starting pressure reduction are satisfied and the time that was needed for the requirements to be satisfied is more than a set time, control of the braking fluid pressure is permitted. When the time needed for the requirements to be satisfied is less than the set time, control of the braking fluid pressure is inhibited after the requirements for starting pressure reduction are not satisfied.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention provides a system for controlling braking force on wheels during vehicle braking,
The present invention relates to an anti-skid control device that prevents wheels from locking.

(Prior Art) It is well known that when the wheels of a vehicle lock during sudden braking, the vehicle may become unstable in driving or lose steering performance depending on road surface conditions. For this reason, in order to prevent the wheels from locking during sudden braking, anti-skid control devices are used that control the braking force by reducing, increasing, or maintaining the brake fluid pressure in the wheel cylinders, and are also called anti-lock control devices. being called. Anti-skid control of wheels includes rear wheel control and front and rear wheel control.

That is, there is four-wheel control. The former prevents the rear wheels from rolling, ensuring running stability and shortening the braking distance, while the latter prevents the front wheels from locking, thereby maintaining steering performance.

In an anti-skid control device, the rotational acceleration (including deceleration) of the wheel is calculated based on the fact that when the brake fluid pressure to the wheel cylinder is increased, the wheel speed suddenly decreases just before the friction coefficient μ for the wheel reaches its maximum. (The same applies hereafter) The brake fluid pressure is controlled so that the slip rate of the wheels becomes around 20%, that is, the braking force is controlled so that the maximum coefficient of friction is obtained.

As this kind of conventional unskid control device, for example,
There is one shown in Japanese Patent Publication No. 4B-44236.

When this control device detects a locked state of the wheels because the rate of decrease in wheel speed becomes equal to or higher than a set value due to sudden braking, it starts anti-skid control and first reduces the brake fluid pressure in the wheel cylinders. Then, when the wheel speed recovers due to pressure reduction and the rate of decrease in wheel speed becomes less than the set value, the brake fluid pressure in the wheel cylinder is increased until the time corresponding to the wheel angular acceleration stored during the pressure reduction stroke during sudden braking. After that, the brake fluid pressure is increased much more slowly than the brake fluid pressure corresponding to the angular acceleration.

(Problems to be Solved by the Invention) In the conventional control device described above, when the rate of decrease in wheel speed exceeds a set value, a locked state of the wheels is detected and anti-skid control is started. A decrease in wheel speed due to a momentary drop in wheel speed that occurs when driving on rough roads, when a wheel runs over a protrusion, or due to gear backlash in the power train in an anti-skid control device that prevents only the drive wheels from locking. If the ratio exceeds the set value, the locked state of the wheels may be erroneously detected, and anti-skid control may be started. As a result, if this false detection is made immediately after the start of braking, anti-skid control will be started before the brake fluid pressure in the wheel cylinders has risen sufficiently, and the pressure increase gradient of the brake fluid pressure in the wheel cylinders will be slow. This results in insufficient braking force and an increase in braking distance.

Therefore, the technical object of the present invention is to prevent the initiation of anti-skid control due to the above-mentioned erroneous detection of the locked state of the wheels, thereby preventing the occurrence of insufficient braking force.

[Structure of the invention]

(Means for Solving the Problems) The measures taken to solve the above-mentioned technical problems are such that the anti-skid control device is connected to a brake fluid pressure source that generates high pressure and low pressure, and a brake fluid pressure source that generates high pressure and low pressure. a switching valve means provided between the cylinder and the wheel cylinder for selectively supplying either the high pressure or the low pressure to the wheel cylinder; a wheel speed detecting means for detecting the rotational speed of the wheel; and the wheel speed detecting means a calculation means for determining whether a predetermined pressure reduction start condition is satisfied based on the detected wheel speed; and a calculation means for determining whether or not a predetermined pressure reduction start condition is satisfied based on the detected wheel speed; a brake fluid pressure control means for controlling the brake fluid pressure of the wheel cylinder to increase or decrease the brake fluid pressure of the wheel cylinder, and comparing a time during which the predetermined pressure reduction start condition is satisfied with a set time to determine that the predetermined pressure reduction start condition is satisfied. When the time is longer than the set time, control of the brake fluid pressure control means is allowed, and when the time during which the predetermined pressure reduction start condition is satisfied is less than the set time, the brake fluid pressure is controlled after the predetermined pressure reduction start condition is not satisfied. The invention also includes a prohibition means for prohibiting control of the hydraulic pressure control means.

(Operation) According to the above-described means, the brake fluid pressure applied to the wheel cylinder is increased or decreased by the switching valve means. That is, when the switching valve means communicates the wheel cylinder with the high pressure of the brake fluid pressure source, the brake fluid pressure of the wheel cylinder is increased, and conversely, it communicates the wheel cylinder with the low pressure of the brake fluid pressure source. If so, the brake fluid pressure in the wheel cylinder is reduced. Furthermore, the brake fluid pressure in the wheel cylinders can be maintained by sealing the brake fluid pressure applied to the wheel cylinders by the switching valve means or by repeatedly switching the switching valve means at high speed. Therefore, the brake fluid pressure in the wheel cylinder can be increased, decreased, and maintained by the switching valve means.

Further, according to the above-described means, when the calculation means determines that a predetermined pressure reduction start condition is satisfied during braking based on the wheel speed detected by the wheel speed detection means, the brake fluid is The pressure control means controls the switching valve means to supply optimum brake fluid pressure to the wheel cylinders. Therefore, according to the above-described means, locking of the wheels is prevented.

Furthermore, according to the above-mentioned means, the time during which the predetermined pressure reduction start condition is met by the inhibiting means is compared with the set time. The inhibiting means determines that the wheels tend to lock due to braking and the predetermined pressure reduction start condition is satisfied when the time period during which the predetermined pressure reduction start condition is satisfied is longer than the set time. Based on the result of this determination, the inhibiting means allows the above-described brake fluid pressure control means to control when the time during which the predetermined pressure reduction start condition is satisfied is longer than the set time. Therefore,
When the time during which the predetermined pressure reduction start condition is satisfied is longer than the set time, the brake fluid pressure control means supplies the optimum brake fluid pressure to the wheel cylinders, thereby preventing the wheels from locking. In addition, the prohibition means is an anti-skid control device that prevents only the driving wheels from locking when the time for which the predetermined decompression start condition is satisfied is less than the set time, when the vehicle is driving on a rough road, when the vehicle rides on a wheel protrusion, or when only the drive wheels are locked. It is determined that the predetermined pressure reduction start condition is satisfied when the rate of decrease in wheel speed exceeds a set value due to an instantaneous drop in wheel speed caused by gear backlash in the power train. Based on this judgment result, the inhibiting means prohibits the control of the brake fluid pressure control means after the predetermined pressure reduction start condition is not satisfied when the time during which the predetermined pressure reduction start condition is satisfied is less than the set time, and the inhibition means prohibits the control of the brake fluid pressure control means after the predetermined pressure reduction start condition is not satisfied, and the normal control is applied to the wheel cylinder. Provides brake fluid pressure for braking action. Therefore, if the time during which the predetermined pressure reduction start condition is satisfied is less than the set time, the brake fluid pressure in the wheel cylinder is reduced only during the time when the predetermined pressure reduction condition is satisfied, and then the brake fluid pressure in the wheel cylinder is immediately reduced by normal braking operation. The brake fluid pressure in the cylinder increases rapidly. Therefore, it is possible to prevent anti-skid control from being started due to erroneous detection of the locked state of the wheels, and to prevent insufficient braking force from occurring.

(Embodiment) Hereinafter, one embodiment of an anti-skid control device according to the present invention will be described based on the accompanying drawings.

FIG. 1 is a block diagram showing an outline of an anti-skid control device 100 of this embodiment. The anti-skid control device 100 of this embodiment controls only the brake fluid pressure of each wheel cylinder 10 and 11 of rear wheels RR and RL which are driving wheels of an FR vehicle, and each wheel cylinder 5 of each wheel cylinder 5 of front wheels FR and FL which are driven wheels. and 6 are directly connected to the mask cylinder 3 and do not control its brake fluid pressure. Such a device is suitable for a vehicle 9 in which the load supported by the rear wheels RR and RL varies greatly, such as a small truck or a microbus. Incidentally, the present invention can also be applied to the anti-skid control device for front and rear wheel control described above.

The driver's depression force applied to the brake pedal 1 is boosted by the negative pressure booster 2, and the mask cylinder 3 is operated by the boosted depression force, and generates brake pressure according to the depression force. do. In this embodiment, the mask cylinder 3 is of a tandem type, and one system is connected to the wheel cylinder 5.6 via the hydraulic piping 4, and the brake of the mask cylinder 3 is connected to the wheel cylinder 5.6. When the pressure is applied, the front right wheel FR and the front left wheel FL are respectively put into a braking state. Further, the other system of the mask cylinder 3 is connected to the wheel cylinder 10 via hydraulic piping 7, 8.9.
．． 11, and when the brake pressure of the mask cylinder 3 is applied to the wheel cylinder 10.11, the right rear wheel RR
, the left rear wheel RL enters the braking state.

An actuator 12 is interposed between the hydraulic pipes 7 and 8. Actuator 12 is actuated by hydraulic pressure generated by hydraulic pump 13 driven by engine 15, and adjusts the brake pressure applied to wheel cylinder 10.11 according to instructions from electronic control unit ECU. Furthermore, in this embodiment, a load-responsive hydraulic control valve (LSPV) 14 is interposed between the hydraulic piping 8 and 9.
The upward slope of the wheel cylinder 1011 relative to the upward slope of the brake pressure of the mask cylinder 3 is kept small in accordance with the load of the vehicle.

A transmission I6 is connected to the engine 15 and changes the reduction ratio between the engine 15 and the propeller shaft 18 in order to obtain the requested driving force.

The output rotation of the transmission 16 is transmitted to the differential gear 19 via the propeller shaft 18. The differential gear 19 further reduces the rotation of the propeller shaft 18 and transmits it to the rear wheels RR, RL via the axles 17a, 17b. A wheel speed sensor 20 is disposed on the differential gear 19 . Wheel speed sensor 2
0 is the rotational speed of the propeller shaft 18, that is, the right rear wheel R
The average wheel speed of R and left rear wheel RL is detected.

Further, in order to detect the acceleration of the vehicle, an acceleration sensor 21 is fixedly installed at an appropriate position on the vehicle.
1 is a well-known mercury switch type or pendulum hole type, and is fixed in a position where vibrations from the road surface and vibrations from the engine 15 are difficult to be transmitted.

Further, a brake indicator light switch 22 is disposed near the brake pedal 1 to detect that the brake pedal 1 has been depressed by the driver. Note that the brake indicator light switch 22 is turned on when the brake pedal 1 is operated.

Electric signals are input to the electronic control unit ECU from a wheel speed sensor 20, an acceleration sensor 21, and a brake indicator light 22. Further, the electronic control unit ECU outputs an electric signal for controlling the actuator 12.

Next, the actuator 12 in this embodiment will be explained with reference to FIG. Actuator 12 is hydraulic supply/discharge valve 3
0 and a regulator valve 31, the regulator valve 31 is an oil pump 1.
The hydraulic pressure generated by the mask cylinder 3 is adjusted so as to always have a constant ratio to the brake pressure generated by the mask cylinder 3. The hydraulic pressure regulated by the regulator valve 31 is transferred to the hydraulic piping 32.
and is supplied to the hydraulic piping 34 through the liquid chamber 33.

The hydraulic pressure supplied to the hydraulic piping 34 is guided to the liquid chamber 37 by the switching solenoid valve 34. At this time, the brake fluid pressure generated by the mask cylinder 3 is as follows: hydraulic piping 7 → hydraulic piping 40 → bypass valve 41 → hydraulic piping 42 → cut valve 43 → hydraulic piping 4
4 → guided to the wheel cylinders to, ii via a path comprising hydraulic piping 8.

The switching solenoid valve 35 connects the hydraulic piping 34 and the liquid chamber 37 when the solenoid 36 is not energized.
6 is energized, the hydraulic piping 38 connected to the reservoir 39 and the liquid chamber 37 are communicated with each other. When the solenoid 36 of the switching solenoid valve 35 is energized, the hydraulic pressure in the liquid chamber 37 is discharged to the reservoir 39 through the hydraulic piping 38 . At this time, as the liquid pressure in the liquid chamber 37 decreases, the pressure reducing piston 45 moves to the left in the figure, and the volume of the liquid chamber 37 decreases. When the pressure reducing piston 45 moves to the left in the drawing, the ball 46 blocks the cut valve 43 and the hydraulic pipe 44 . Liquid chamber 37
When the hydraulic pressure therein further decreases, the volume on the wheel cylinder 1011 side increases due to the movement of the pressure reducing piston 45, and the brake hydraulic pressure applied to the wheel cylinder 10.11 is reduced.

When the solenoid 36 is de-energized in this state, the switching solenoid valve 35 communicates the liquid chamber 37 with the hydraulic piping 34.
The liquid pressure within the liquid chamber 37 increases. Due to the increase in the fluid pressure in the fluid chamber 37, the pressure reducing piston 45 moves to the right in the drawing, the volume on the wheel cylinder 10.11 side is reduced, and the brake fluid pressure applied to the wheel cylinder 10.11 is increased. As a result, when the solenoid 36 of the switching solenoid valve 35 is energized, the brake fluid pressure applied to the wheel cylinders 10 and 11 is reduced;
When the wheel cylinder 10.1 is de-energized, the wheel cylinder 10.1
The brake fluid pressure applied to 1 is increased.

Therefore, in this embodiment, the Solenoid 3 of the switching solenoid valve 35 is
The brake fluid pressure applied to the wheel cylinder 10.11 is controlled by the duty ratio of the electric signal supplied to the wheel cylinder 6.

Next, the electronic control unit ECU will be explained with reference to FIG.

The electronic control unit ECU includes a microprocessor MPU, a waveform shaping circuit 51, input buffers 52, 53, 54, and an output buffer 55.

A large number of microprocessors MPU are currently on sale1.
It uses a chip microcomputer. The microprocessor MPU of this embodiment has a built-in free-run timer that outputs the current time, a ROM that stores programs, a RAM that is necessary for program execution, and a solenoid timer that determines the energization time for the solenoid 36. ing.

The characteristics of the waveform shaping circuit 51 are shown in FIG. The waveform shaping circuit 51 converts the sine wave transmitted from the wheel speed sensor 20 into a square wave, which is input to the interrupt request terminal IRQ of the microprocessor MPU. Therefore, an interrupt request is sent to the microprocessor MPU at time intervals corresponding to the rotational speed of the wheel detected by the wheel speed sensor 20.

Table 1 shows the characteristics of the input buffer 52. The input buffer 52 turns the brake indicator light switch 22 ON and OFF.
The status is input to the input port (IPI) of the microprocessor MPU.

Next, the characteristics of the input buffers 53 and 54 are shown in Table 2. The acceleration sensor 21 detects the acceleration of the vehicle with 2 bits, and the detection signal is sent to each terminal 031. Input buffer 53 via GS2
．． 54 to the input port IP2.54 of the microprocessor MPU. Input to IP3.

Table 2 Also, an output buffer 55 is connected to the output port OP1 of the microprocessor MPU.

The output buffer 55 is a circuit that amplifies the power of the electrical signal output from the output port OPI and excites the solenoid 36 of the actuator 12.

The electrical signals output from the output port OP1 are controlled by a program executed by the microprocessor MPU. FIGS. 5, 8, and 9 are flowcharts outlining programs executed by the microprocessor MPU. The program executed by the microprocessor MPU is the main routine and the interrupt request terminal IR.
It has an interrupt routine that is executed when an electrical signal is input to Q.

First, the main routine shown in FIG. 5 will be explained. When the electronic control unit ECU is powered on, the microprocessor MPU starts processing from step S1.

In step S1, initialization processing is performed.

When step S1 is executed, the flags ta, tb and the under control flag are set to zero. Also, output port) OP
1 is set so that the solenoid 36 is de-energized.

In step S2, the state of the brake indicator light switch 22 is input to the microprocessor MPU.

Furthermore, in step S3, the magnitude of the acceleration detected by the acceleration sensor 21 is input to the microprocessor MPU.

Next, in step S4, the input port IP2. of the microprocessor MPU is input in step S3. The road surface condition (
μ) is determined.

In step S5, the wheel speed V8 of the rear wheels is calculated based on the period ΔTw of the electric signal output by the wheel speed sensor 20. The period ΔT1 of the electrical signal output by the wheel speed sensor 20 is measured by an interrupt routine (described in detail later). Rear wheel rotation speed V. is calculated by equation (1).

Wheel speed - ・ ・ ・ ・ (1) ΔT1 However, K is a constant determined by the characteristics of the wheel speed sensor 20.

In step S6, the rotational acceleration G of the rear wheel is calculated from the wheel speed V of the rear wheel calculated in step S5. is calculated. The rear wheel acceleration G8 is calculated using equations (2) and (3).

Interrupt interval! nt=-(ΔTW(n)+ΔTwtn-n
)・・・・(2) V H(, l, V H(n−11 Rotational acceleration CyW(□,=nt・・・・(3) However, vl'l (71) + ΔTW(a) was calculated this time The wheel speed ■ of the rear wheels and the period ΔTw of the electric signal are shown, and VW (n-1>+ ΔTW axis-1) shows the previously determined wheel speed ■ of the rear wheels and the period ΔTw of the electric signal.

In step S7, the preset estimated vehicle body acceleration α shown in FIG. 7 is determined according to the road surface μ determined in step S4, and the rear wheel rotation speed ■ calculated in step S5. ■ Estimated vehicle speed from. is calculated. Estimated vehicle speed■,
. is calculated by equation (4).

Estimated vehicle speed ■. ) = Max(Vwtn++ V!O(1%-11
(rowInt) (4) However, Max (a, b) is a function that gives the larger value of a and b.

Furthermore, V. (++1 is the estimated vehicle speed V obtained this time.

Indicates ■,. <21-11 indicates the estimated vehicle speed V3° obtained last time.

In step S8, it is determined how the brake fluid pressure should be controlled based on the rear wheel speed "I11 + rear wheel rotational acceleration G" obtained in steps 35 to S7 and the estimated vehicle speed V. Note that the process of step S8 will be described later with reference to FIG.

In step S9, the determination result in step S8 is output to the solenoid 36, and the brake fluid pressure applied to the wheel cylinder 10.11 is increased, decreased, or held.

By repeatedly executing the processes of steps S1 to S9 described above, the average wheel speed V of the rear wheels RR and RL is
- When the brake fluid pressure suddenly decreases, the brake fluid pressure is reduced to encourage rotation of the rear wheels RR and RL and prevent the rear wheels RR and RL from locking.

Next, the interrupt routine shown in FIG. 8 will be explained. In the interrupt routine, the time interval between the previous interrupt request and the current interrupt request, that is, the period ΔT1 of the electrical signal output by the wheel speed sensor 20 is measured.

In step 311, the current time ta is set by the free run timer.

In step S12, the time difference between the time tb when the previous interrupt request occurred and the current time ta is calculated, and the cycle ΔT of the electric signal output by the wheel speed sensor 20 is set.

In step S13, time tb is updated and set in preparation for the next interrupt request.

After executing the process of step Sll-313, the main routine process shown in FIG. 5 is executed again.

Next, a subroutine for brake fluid pressure control shown in FIG. 9 will be explained.

In step S21, the estimated vehicle speed VW. . , is compared with a first predetermined speed v1. The first predetermined speed Vl is a speed for determining whether or not the vehicle is stopped, and is set to approximately 5 km/h in the case of this embodiment. When the estimated vehicle speed v go (111 is greater than or equal to the first predetermined speed v1), step S22 is executed. Conversely, when the estimated vehicle speed V go
When sO(n) is less than the first predetermined speed V1, step S37 is executed. When the estimated vehicle speed Via(n) is less than the first predetermined speed v1, step S37 is executed and brake fluid pressure control is not executed.

In step S22, it is determined whether the brake indicator light switch 22 is ON. If the brake indicator light 22 is ON, step S23 is executed. Conversely, when the brake indicator light 22 is OFF, step 337 is executed and brake fluid pressure control is not executed.

In step S23, it is determined whether the under control flag is set. If the under-control flag is set, step S32 is executed; conversely, if the under-control flag is not set, step 324 is executed. Note that the under-control flag is a flag that is set in step 32B when brake fluid pressure control is started;
Set continuously.

In step S24, the wheel speed VW(*) of the rear wheels is changed to the reference speed V3N(nl (=estimated vehicle speed VffO(+s
) is less than a predetermined value (value obtained by multiplying <0)). The rear wheel speed VW (fi) is the reference speed VX
N,,1. When it is less than 20%, it is determined that slip has occurred in the rear wheels RR and RL and that the slip rate of the rear wheels is greater than 20%. At this time, step S25 is executed. Conversely, the wheel speed VW(n) of the rear wheels is the reference speed V3H.
(n) or more (VW(n)≧V !N (fl+
), it is determined that no slip has occurred in the rear wheels RR and RL, or that the slip rate of the rear wheels is 20% or less. At this time, step 337 is executed and brake fluid pressure control is not executed. The reference speed VSN (nl) is used to control the braking force so that the slip rate of the rear wheels is around 20%, which is the slip rate of the rear wheels when the friction coefficient μ of the wheels is at its maximum. .

In step S25, the rotational acceleration G of the rear wheel is determined. It is determined whether (7) is less than a predetermined acceleration 61. When the rotational acceleration G1.1 (7) of the rear wheels is less than the predetermined acceleration G1 (Gwt-)<Gl), it is determined that the rear wheels RR and RL are just before locking. At this time, step S26 is executed, and the brake fluid pressure in the wheel cylinders 10.11 of the rear wheels RR and RL is reduced. Conversely, the rotational acceleration G of the rear wheel. When (yi) is greater than or equal to the predetermined acceleration 61 (Gw<n+≧Gl), it is determined that the rear wheels RR and RL will not lock immediately. At this time, step S37 is executed and brake fluid pressure control is not executed.

In step 326, the mode flag is set to reduced pressure. When pressure reduction is set in the mode flag, the brake fluid pressure applied to the wheel cylinders 10.11 is reduced in step 330, which will be described later, and locking of the rear wheels RR and RL is prevented.

In step 327, the process is started when it is determined in step S25 that the rear wheel rotational acceleration G,
< VSN (Ml and Gwt+n < Gl (F
) It is determined whether or not the count of the control start timer that counts the continuous Vt establishment time is equal to or longer than the set time T3.

When the count of the control start timer is equal to or greater than the set time 78, step 328 is executed. Conversely, if the count of the control start timer is less than the set time T8, step S
After step S29 is executed and the count of the control start timer is incremented, step S30 is executed. Therefore, unless the count of the control start timer reaches the set time of 78 or more,
Step 328 is not executed and the under control flag is not set. In this embodiment, the set time T is 40L! is set to .

In step 328, the under control flag is set. The under control flag is the estimated vehicle speed vl. . ) becomes less than the first predetermined speed V1 (step 321) or the brake indicator light switch 22 is turned off (step 522).

In step 330, a solenoid timer is started. The solenoid timer is a timer for controlling the duty ratio of the electrical signal output from the output port OP1, and is built in the microprocessor MPU. The solenoid timer controls the power supplied to the solenoid 36 according to the setting value of the mode flag.

The mode flag settings include 'depressurization', 'pressure increase' and 'hold'.
There are four types: , "direct connection". ``Decompression'' in the mode flag
is set, the actuator 12 controlled by the solenoid timer is activated by the wheel cylinder 10.11.
The brake fluid pressure applied to the brake fluid is reduced. Further, when "pressure increase" is set in the mode flag, the actuator 12 controlled by the solenoid timer increases the brake fluid pressure applied to the wheel cylinder 10.11. Further, when the mode flag is set to "hold", the actuator 12 controlled by the solenoid timer maintains the brake fluid pressure applied to the wheel cylinder 10.11. Furthermore, when the mode flag is set to "direct connection", the actuator 12 controlled by the solenoid timer is connected to the wheel cylinder 10.
11 and the mask cylinder 3 are directly connected.

In step 331, processing for returning to the main routine is performed.

If the under control flag is set in step 323, step S32 is executed. In step S32, the wheel speed VW(a) of the rear wheels is set to the reference speed VSN(a).
The process in step 332, in which it is determined whether or not the value is less than 1, is the same as the process in step 324, so a description thereof will be omitted. The wheel speed of the rear wheels - (7, is the reference speed V 114 (
fi), step S34 is executed. Conversely, the rear wheel speed Vllll(R) is the reference speed VI.
N(+sl or more ("W(++)≧VSN(n
)), step S33 is executed and the mode flag is set to "pressure increase". When "pressure increase" is set in the mode flag, the brake fluid pressure applied to the wheel cylinders 10.11 is increased in step 330.

In step S34, the rotational acceleration G of the rear wheel is determined. It is determined whether or not (n) is less than a predetermined acceleration G1. The process in step 334 is similar to the process in step S25, so a description thereof will be omitted. When the rotational acceleration (G-axis) of the rear wheel is less than the predetermined acceleration 01, step S35 is executed;
The mode flag is set to "depressurization °°". When the mode flag is set to "depressurization", the brake fluid pressure applied to the wheel cylinders 10 and 11 is reduced in step S30. Conversely, the rotation of the rear wheel When the acceleration G is greater than or equal to the predetermined acceleration 01, step 336 is executed;
"Hold" is set in the mode flag.

When the mode flag is set to "hold", step S3
At 0, the brake fluid pressure applied to the wheel cylinder 10.11 is maintained.

By repeatedly executing steps 332 to 336 and executing brake fluid pressure control, the rear wheel RR,
The slip between the RL and the road surface is controlled to be almost constant, providing stable braking force.

In step S21, the estimated vehicle speed V. 1. , ) becomes less than the first predetermined speed v1, or step S22
When the brake indicator light switch 22 is turned OFF, steps 337 and 338 are executed, and the brake fluid pressure control is completed. In step S37, the mode flag is set to "°°direct connection". When the mode flag is set to "direct connection", in step S37, the wheel cylinder 10.1
1 and the mask cylinder 3 are directly connected. Also, step 3
In step S38, the under control flag is cleared, and in step S39
In this case, the count of the control start timer is cleared.

When the count of the control start timer is less than the set time T8 in step S27, the wheel speed Vl (1 of the rear wheel becomes equal to or higher than the reference speed VSM(n) in step S24, or the rotational acceleration G1 of the rear wheel is determined in step S25. ) becomes the predetermined acceleration 01 or more, step 3
37 and 338 are executed, and brake fluid pressure control is prohibited. In step S37, the mode flag is set to "direct connection" and the mode flag is set to "direct connection." When the mode flag is set to "direct connection," the wheel small cylinder 10.11 and the mask cylinder 3 are set in step S37. It is directly connected to perform normal braking operations.

Also, in step 33B, the control flag is cleared, and in step S39, the count of the control start timer is cleared. Note that the steps 323 to S described above
31 and steps 337 to 339 correspond to the prohibition means of the present invention.

As explained above, according to the brake fluid pressure control subroutine shown in FIG. 9, the inhibiting means sets the pressure reduction start condition, that is, V H (*) < V x H (m) and Gw (,
1) <If the continuous satisfaction time of G1 is not longer than the set time T8, the control flag will not be set and brake fluid pressure control will not be executed, and if the continuous satisfaction time of the pressure reduction start condition is less than the set time T8, the mode flag will be directly connected. is set to prohibit brake fluid pressure control and normal braking operations are performed.

In other words, Fig. 10 shows the situation when the vehicle is driving on a rough road or when the vehicle runs over a protrusion on a wheel.

Alternatively, in an anti-skid control device that prevents locking of only the drive wheels, the wheel speed of the rear wheels is shown as a control waveform when the wheel speed vw of the rear wheels momentarily drops due to backlash of the gears in the power train. V. ■ Wheel speed due to momentary drop in . Reference speed Vs, 1(n)
and rotational acceleration G of the rear wheel, 4<predetermined rotational acceleration G
1 is instantaneously established and the continuous satisfaction time of this depressurization start condition is less than the set time Ts, the mode flag is only set to depressurize while the depressurization start condition is satisfied, and control is in progress. No flags are set. Therefore, while the depressurization start condition is continuously satisfied, the wheel cylinder 1
After the brake fluid pressure of 0.11 is reduced, immediately after the pressure reduction start condition is not satisfied, brake fluid pressure control is prohibited, the mode flag is set to direct connection, and the brake fluid pressure of wheel cylinders 10° and 11 is reduced by normal braking operation. is suddenly increased in pressure.

Therefore, as shown in FIG. 10, the pressure reduction start condition is instantaneously established due to the instantaneous drop in the wheel speed V8 as described above, and in the prior art to start anti-skid control (brake fluid pressure control), the wheel cylinder In contrast, in this embodiment, after the pressure reduction start condition is not satisfied, the wheel cylinder 10.
The brake fluid pressure in the wheel cylinders 10 and 11 increases rapidly, and after the pressure reduction start condition is not met, the rising gradient becomes the same as that during normal braking, so there is a delay in the rise in the brake fluid pressure in the wheel cylinders 10 and 11 relative to the rise in the brake pressure in the mask cylinder 3. is extremely short, and the occurrence of insufficient braking force is prevented.

Note that the wheel speed V as described above. In order to prevent the anti-skid control from starting and causing a lack of braking force due to the instantaneous establishment of the depressurization start conditions due to a momentary drop in the One possibility is to reduce the sensitivity of skid control initiation.

However, according to this method, the pressure reduction timing is always delayed, resulting in a large drop in wheel speed Vw and wheel locking. In this embodiment, the wheel speed is V, as shown in FIG. 11, which shows the control waveform of normal anti-skid control. <Reference speed VSM (
, 1) and the rotational acceleration G of the rear wheel. After the pressure reduction start condition that is a predetermined rotational acceleration C1 is satisfied, the mode flag is set to pressure reduction and the brake fluid pressure in the wheel cylinder 10.11 is reduced at least while the pressure reduction start condition is satisfied. As shown in , when the continuous satisfaction time of the pressure reduction start condition is less than the set time Ts, brake fluid pressure control is prohibited without setting the flag under control, and when the continuous satisfaction time of the pressure reduction start condition is longer than the set time T8, the control flag is set. is set and brake fluid pressure control is executed. Therefore, according to this embodiment, the sensitivity for starting anti-skid control is lowered, and the pressure reduction start condition is instantaneously established due to an instantaneous drop in the wheel speed V-, without causing a delay in pressure reduction timing. , anti-skid control is started to prevent insufficient braking force from occurring.

〔Effect of the invention〕

As explained above, according to the present invention, when the time during which the predetermined depressurization start condition is continuously satisfied is less than the set time, the prohibition means is activated when the vehicle is traveling on a rough road or when the vehicle runs over a protrusion of a wheel. Or, it is determined that a predetermined depressurization start condition has been established due to a momentary drop in wheel speed that occurs due to a gear crash in the power train in an anti-skid control device that prevents only the drive wheels from locking. While the pressure reduction start condition is satisfied, the brake fluid pressure of the wheel cylinder is allowed to decrease, and after the pressure reduction start condition is not satisfied, the control of the brake fluid pressure control means is prohibited. Therefore, without reducing the sensitivity of anti-skid control initiation and causing a delay in pressure reduction timing, anti-skid control is started and the braking force is instantaneously established due to a momentary drop in wheel speed. It is possible to prevent shortages from occurring.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an overview of an embodiment of an anti-skid control device according to the present invention, FIG. 2 is a cross-sectional view showing an actuator of an embodiment of the present invention, and FIG. 3 is an embodiment of an embodiment of the present invention. A block diagram showing an example electronic control device, FIG. 4 is a graph showing characteristics of a waveform shaping circuit according to an embodiment of the present invention, and FIG. 5 is a program executed by a microprocessor according to an embodiment of the present invention. FIG. 6 is a characteristic diagram showing road surface judgment criteria in one embodiment of the present invention;
FIG. 7 is a characteristic diagram showing the estimated acceleration setting value of the vehicle body by the acceleration sensor in one embodiment of the present invention, and FIGS.
FIG. 1 is a flowchart showing an outline of a program executed by a microprocessor according to an embodiment of the present invention, and FIGS. 10 and 11 are explanatory diagrams for explaining the present invention. 1... Brake pedal, 3... Master switch,
4...Hydraulic pressure piping, 5, 6...Wheel cylinder, 7
, 8.9... Hydraulic pressure piping, 10, 1]... Wheel cylinder, 12... Actuator (switching valve means), 13
... Hydraulic pressure pump (brake fluid pressure source), 20... Wheel speed sensor (wheel speed detection means), 21... Acceleration sensor, 22... Brake indicator light switch, 30... Hydraulic pressure supply Discharge valve, 31...Regulator valve, 32.34...
Hydraulic pressure piping, 35...Switching valve (switching valve means), 36...
・Solenoid, 37...Liquid chamber, 38...Hydraulic pressure piping,
39...Reservoir (brake fluid pressure fl), 43...
Cut valve, 45... Pressure reducing piston, 51... Waveform shaping circuit, 52.5354... Input buffer, 55...
- Output buffer, ECU...Electronic control unit (calculation means, brake fluid pressure control means, prohibition means).

Claims (1)

[Claims] (1) A brake fluid pressure source that generates high pressure and low pressure, and a switch that is provided between the brake fluid pressure source and the wheel cylinder and selectively supplies either the high pressure or the low pressure to the wheel cylinder. a valve means, a wheel speed detection means for detecting the rotational speed of the wheel, a calculation means for determining whether a predetermined pressure reduction start condition is satisfied based on the wheel speed detected by the wheel speed detection means; brake fluid pressure control means that controls the switching valve means to increase or decrease the brake fluid pressure of the wheel cylinder when the predetermined pressure reduction start condition is determined to be satisfied by the calculation means; The time during which the predetermined pressure reduction start condition is satisfied is compared with a set time, and if the time during which the predetermined pressure reduction start condition is satisfied is equal to or longer than the set time, control of the brake fluid pressure control means is permitted, and the predetermined pressure reduction start condition is satisfied. and prohibiting means for prohibiting control of the brake fluid pressure control means after the predetermined pressure reduction start condition is not satisfied when the period of time for which the brake fluid pressure has been applied is less than the set time.