JPS60121162A - Antiskid control apparatus - Google Patents

Abstract

PURPOSE:To stabilize control on low mu road by continuing the reduction of liquid pressure for a predetermined time when wheel speed value right before locking is at least a predetermined value in which the wheel can be safely stopped even by erecting a wheel lock when the wheel lock is detected. CONSTITUTION:When produced pseudo-vehicle speed Vi does not have gradient adapted to a low mu road during braking, control mode right after pressure reduction is liable to be changed over to pressure increasing by a comparative calculation. However, if wheel speed value right before locking exceeds a predetermined value in which the wheel can be stopped safely even by erecting the wheel lock, comparators 25, 26 generate the output of H level and a counter 28 begins the counter operation. And the H level outputs are given respectively to OR gates 18, 21 through AND gate 27 and the reduction of braking liquid pressure is continued during a set time To. Thus, liquid pressure in a wheel cylinder is reduced to the min. value and the rotation of wheels under the locked condition is resumed even on the low mu road to restore the wheel speed Vi.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an anti-skid control device that controls brake fluid pressure so as to maintain braking stability and obtain a short braking stopping distance during sudden braking.

(Prior art) Conventionally, during sudden braking where the braking deceleration exceeds a predetermined deceleration rate, the shortest braking distance can be obtained without causing wheel lock by repeatedly increasing, holding, and decreasing the control mJ pressure. In an anti-skid control device that uses full pressure control (Ill) during braking, when the wheel deceleration is large, the system switches to control 14IIe and pressure reduction (Special Publication No. 50-34185).
Or, create a pseudo vehicle speed signal that decreases at a predetermined slope,
When the slip rate or slip amount calculated from the pseudo vehicle speed signal and the wheel speed signal is greater than a predetermined value, is the control pressure determined? ll
- A method in which pressure is reduced, and a method in which a straight line is generated as a total pseudo vehicle speed that is sequentially connected to the value of the wheel speed when the set deceleration is obtained, and the reduction in brake fluid pressure is determined from the ratio of wheel acceleration/deceleration and slip ratio. (Japanese Unexamined Patent Publication No. 56-53944) is known.

Fig. 1 shows the hydraulic system used in such an anti-skid control device together with the control circuit. Braking hydraulic pressure from the mask cylinder is transferred to the wheel cylinder 3 via the EV valve (inflow valve) 2. In addition, the outlet side of the E valve 2 is connected to a liquid output pump 5 via an AV (outflow valve) 4, and an akinimulator 6 having a pressure accumulating function is provided on the inlet side of the hydraulic pump 50. , l The outlet side of the Asada pump 5 is drained into the mask cylinder 1 via a check valve 7.

On the other hand, 8 is an anti-skid control circuit, which inputs the detection signal JSi' of the wheel speed sensor 10 provided on the wheel 9, and determines the control mode of the brake fluid pressure by calculation according to the above-mentioned methods. Decide whether to increase, maintain, or decrease the pressure, and
■Valve 2 and Av valve 4 are operating.

That is, when increasing the pressure, EV valve 2 is opened to supply mask hydraulic pressure to the wheel cylinder 3, when holding, both EV valve 2 and AV4 valve are closed to seal the current hydraulic pressure in the wheel cylinder 3, and when the pressure is decreasing, the mask hydraulic pressure is supplied to the wheel cylinder 3. The AV valve 4 is opened at the same time as the E-valve 2 is closed, and the hydraulic pressure in the wheel cylinder 3 is quickly discharged to the mask cylinder 1 side by the hydraulic pump 5.

However, in the brake pressure control system shown in Fig. 1, the braking torque T over time when the brake fluid discharge pressure is reduced
The changes in , are shown in Fig. 2, and the braking torque ゛II
, produces a drag torque ΔT, which is not zero at the tip. (Note that due to the structure of the actuator, the wheel cylinder brake itself may not become zero due to residual pressure.) Therefore, as shown in Figure 3,
For example, the wheel speed Vw decreases due to anti-skid control on a low μ road surface.

If the wheel speed is locked while increasing or holding the brake fluid pressure, a method that reduces the pressure when the wheel deceleration is large will cause a large vehicle & [T to be between point a and point b where speed is obtained.
Even if the brake fluid pressure is reduced for only one hour and the pressure is reduced when the wheel speed Vw is equal to or higher than the predetermined slip rate, the threshold value for giving the predetermined slip rate is less than or equal to 0 from point a. The brake fluid pressure is reduced only during the 12 hours leading up to the point.

If the decompression time when the wheels lock is short like this,
According to the pressure reduction characteristics shown in Figure 2, the brake fluid pressure is not sufficiently reduced, and due to the influence of brake drag torque, the wheel speed vw does not recover even if the brake fluid pressure is reduced, and the vehicle speed is relatively high. There was a problem in that the wheels would lock up at this stage.

On the other hand, in a method that generates a pseudo vehicle speed as a straight line that sequentially connects the wheel speed values when the set deceleration is obtained, and determines the brake fluid pressure reduction from the wheel acceleration/deceleration and slip ratio, It is possible to prevent wheel locking at high vehicle speeds by generating an appropriate pseudo-vehicle speed according to the vehicle speed, but as shown in Figure 4, when the vehicle approaches a stopped state, the road surface changes from a high μ road direction to a low μ road surface. In this case, the simulated vehicle speed when entering the low-μ road surface becomes a pseudo-vehicle speed based on the previous high-μ road direction. There was a problem that it caused a lock.

(Object of the Invention) The present invention has been made in view of the above-mentioned conventional problems, and it is possible to recover the wheel speed even if the wheel locks from a relatively high vehicle speed immediately before braking and stopping using anti-skid control. An object of the present invention is to provide an amplifier skid control device that performs pressure reduction control to improve control stability and reliability on low μ road surfaces.

(Structure of the Invention) In order to achieve this object, the present invention, when a wheel lock is detected, detects the value of the wheel speed immediately before the lock, that is, the wheel speed or the peak value of the wheel speed when the set deceleration is obtained. but,
It is determined whether the brake fluid is above a predetermined value that allows a safe stop even if the wheels are locked, and if the brake fluid is above the predetermined value, the braking fluid is It is designed to be generated on a signal that causes the pressure to continue to decrease.

(Example) Is Fig. 5 an example of the present invention? FIG. 3 is a circuit block diagram shown in FIG.

First, to explain the configuration, 10 is a wheel speed sensor that outputs an AC signal with a frequency proportional to the number of rotations of the wheel, and 11 is a wheel speed sensor 10 that detects the wheel speed Vw as a voltage signal proportional to the frequency of the AC signal. wheel speed detection circuit, 12
is an acceleration/deceleration detection circuit that detects wheel acceleration/deceleration αw(i) by differentiating the wheel speed VW or the like.

A pseudo vehicle speed generating circuit 13 generates a pseudo vehicle speed Vi that approximates the vehicle speed every time the set deceleration b1 is obtained.

This spring-like vehicle continuous generation circuit 13 may be configured to generate a pseudo-vehicle speed 1 with a predetermined slope each time the set deceleration b1 is obtained, or the value of the wheel speed when the set redundant speed bl is obtained. A method is used in which the pseudo vehicle speed ■1 is generated as a straight helix that is sequentially connected.

Reference numeral 14 is a target wheel speed generation circuit, which determines the value of the slip ratio λ that provides the maximum braking efficiency at a constant vehicle speed vI, for example, λ=
Since it is 0.15 to 0.2, the relationship ii! 1.0.8
Generate 1″ with the target wheel speed set to the value 0.85Vi multiplied by 5.
Ru.

15, 16.17 are comparators, and the wheel acceleration/deceleration αW is input to the comparator 15, and when the wheel acceleration/deceleration αW becomes equal to or less than the set deceleration b1 (=-o, lG), it outputs 1 level. will occur. Further, the wheel speed vw and the target wheel speed 0.85 V + are input to the comparator 16, and when the wheel speed Vw is less than the target wheel speed 0.85 VI, it produces an output of 1 level. Furthermore, the wheel acceleration/deceleration αW is input to the comparator 17, and the wheel acceleration/deceleration αW is set as the set acceleration al (=0.6
0) or higher, an H level output is generated.

The valley outputs of the comparators 15, 16 and 17 are input to the OR gate 18, which supplies EV1g to the EV valve 2 in the hydraulic system shown in FIG. 1 through the amplifier 19 tray. The outputs of the ratio converters 16 and 17 are input to an AND gate 20, and the input of the comparator 17 is an inverted input, and the output of the AND gate 20 is inputted to an AND gate 20 via an OR gate 21 and an amplifier 22. It is supplied as the AY1 valve to the AV valve 4 in the enemy's Doitohiro shown in Figure 1.

The cycle w6 consisting of the ratio softeners 15 to 17, or game) 18, 21, and anime game) 22 determines the control mode of brake fluid output by comparing the wheel acceleration/deceleration and the slip rate, that is, soil reinforcement, holding, or The control pattern, which has a time M function that largely determines the depressurization and is determined by the wheel acceleration/deceleration αW and the slip rate λ, is shown in the table below.
It becomes as shown in 1. 'Table-1 Also, E obtained by soft calculation according to the pattern in Table-1
14II with a lot of braking due to the combination of V Yugo and AY Tsukugo
The J control mode is as shown in Jiroku-2.

Table 2 Next, the circuit section for preventing wheel lock on low μ road surfaces will be explained.

This circuit section includes a sample and hold circuit and a comparator. 2
6. Consists of an AND gate 27 and a kakunta feather.

That is, the wheel speed vw flaw signal is input as a sample hold signal to the zangle hold circuit B, and the sample hold of the wheel speed vw is performed by setting the 14 level output when the set deceleration bi is obtained from the comparator J5. Z me,
The sample hold circuit holds and outputs the value of the wheel speed vw when the set deceleration b1 is obtained. In addition, a reset signal is supplied to the sample hold circuit 23 through an OR gate 24, and one of the OR gates 24 is supplied with a Km signal by operating an ignition switch when the vehicle is in use.
The l Lebel Ig signal that is turned on is given as a reset signal, and the other side of the or gate is connected to the or gate 21.
The output of the retrigger timer 29 is given, which is retriggered every time the yori no hei is turned off and generates a timer output until the anti-skid control ends, and when the retrigger timer 29 is restored at the end of the anti-skid control, the OR gate 2
The timer output for 4 becomes H level, and the sample and hold circuit section is reset.

The retrigger timer 29 is provided to generate a motor signal (M, it times signal) for running the hydraulic pump 5 of the ratio system shown in FIG. 1 during anti-skid control. In this case, the output of the retrigger timer 29 that generates the motor signal is used to reset the sample and hold circuit.

The output of the sample and hold circuit is given to the comparator 5,
A threshold speed v1 is set in this specific softener section, and a threshold speed V
l is set larger than the speed at which the final wheel lock occurs immediately before the vehicle stops during anti-skid control; for example, as the threshold speed V1, V 1 = 1tJ
Km/11 Values below are used. Therefore, the comparator δ produces an l-i level output when the sampled and held wheel speed Vw is greater than or equal to the threshold speed Vi.

On the other hand, the comparator section is provided to determine whether the wheels are locked, and compares the wheel speed V'w with the threshold speed Vo, and determines that the wheels are locked when the wheel speed Vw is less than the threshold speed ■o. H level output sound is generated. Therefore, the value Vo=IKm/b is set as the dark value speed Vo for the comparator.

Furthermore, the counter has a function that outputs a signal to forcefully continue reducing the brake fluid pressure for a fixed period of time, for example, 2 seconds after the wheels are locked.

It starts with the H level output of the comparator 16, that is, the level output (obtained when the wheel speed Vw becomes below the target wheel speed 0.85V+), and continues for a predetermined set time '1''. During this time, 1 level output is generated. Further, the counter 16 has a retrigger function where the output of the comparator 16 is obtained, which clears all the contents of the count up to that point and performs the 64-minute operation again.

The outputs of the comparators A and 26 and the counter section are input to an AND gate 27, which outputs the B level output of the comparator 5 and the B level output, that is, the sampled and held wheel speed vw. (IKIII/II
) When the wheel lock is detected in the above state, it becomes a permissible state, and the counter path is 1 lbel, and the output t or gate 18.21 sends out the E and AV times signals, as shown in Table 1 above. ni, i! A signal output state is created in which the braking fluid pressure continues to be reduced during the output of the counter unit for a certain period of time with 1V=AV=H level.

Next, the operation sounds of the embodiment shown in FIG. 5 will be explained with reference to the timing chart shown in FIG.

In addition, in the time chart of FIG. 6, t is 11η.

The control between t and t is the anti-skid control according to the comparison 7 calculation in Table 1 above, and from time t onward, the control in Table 1 is based on the detection of wheel lock according to calculation A. -C represents the reduction in brake fluid pressure.

First, time 1. Then, due to the anti-skid control up to that point, the wheel speed was gradually drawn into a skid cycle, and the set rectangular deceleration Ill was reached at time t due to the pressure increase of the brake fluid, and the H level output of the specific softener 15 caused the gv- ll level, AV,
=1. Level side J! Switches to holding I+U expression. However, time 1. When the dynamic pressure is maintained, the wheel speed Vw rapidly drops because the road surface roughness ridges μ are small, causing the wheels to lock.

On the other hand, the detection of the set g speed b1 and the marker wheel speed at time t1 are generated. Also, the H level output of the comparator 15 is given to the Zumble hold circuit B, and the output at time 1. Wheel speed Vw Iiii? i me sample hold comparator δ
Since the value of the sampled and held wheel speed Vw is equal to or higher than the j-value speed V+ (for example, 10 Km/b), the output of the ratio softener section becomes H level.

Next, time 1 in the process of wheel locking. When the wheel speed vw falls below the target wheel speed 0.85VI, the output of the comparator J becomes H level, and as a result, EV=AV=1 level, and the brake fluid pressure is switched to decrease at time t2. Further, the counter train starts counting operation with the output of the ratio e unit 16 at time t2, the output of the comparator 5 is already at the ll level, and the output of the comparator 26 becomes 1 at the time t3 when locking of the wheels is detected. (Since the output from the counter 2811111 is at the level t3, the output from the counter 2811111 is pulled by the AND gate 27 and supplied to the OR gate 18.21. The circuit also separately reduces the brake fluid pressure.

Due to such a pressure reduction in the brake fluid ratio, the once locked wheel speed starts to recover again, and at time t4, the output of the comparator 26 becomes L.
When the set acceleration a1 is obtained in the process of recovering the wheel speed, the output of the comparator 17 becomes the H level, and the output of the comparator 17 becomes the H level. By setting the = b level, the brake fluid ratio is switched to maintenance. At the same time, the wheel speed Vw recovers and the target wheel speed O becomes 5svt? If it exceeds this, the output of the comparison 616 also goes to L level, and the brake fluid ratio is switched to pressure increase.

Due to this pressure increase, the wheel speed Vw starts to decelerate again, and at time t,
When the set deceleration b1 is obtained, the occurrence and time of the target vehicle e 0.85Vl based on the pseudo vehicle speed v1 [.

A sample hold of the wheel speed at time t is performed, and the wheel speed at time t
, the comparator 16 generates an H level output sound, and the counter is retriggered to start counting again from 3AIILa.

This time 1. If the simulated vehicle speed Vt generated by Vt does not have an inclination suitable for a low-μ road surface during braking, but has a slope corresponding to a high-μ road surface, then in the state of wheel lock immediately after time %lt, The value of the pseudo vehicle speed Vt becomes approximately zero, and when the control mode is determined by the comparison calculation shown in Table 1, the braking fluid ratio is switched to an increased pressure state where EV=AV=L level. Therefore, the pressure reduction time of the brake fluid ratio after time t is too short, and during this pressure reduction time, residual pressure remains in the wheel cylinder, causing the wheel speed to become locked. It continues.

On the other hand, in the embodiment shown in FIG. 5, the start of the counter operation of the counter δ at time [6 causes the OR gate 1L2
H level output is given to each of 1 and -1.
It is not possible to control the pressure reduction of braking 1 reaction pressure by the comparison calculation of (
However, the output from the counter obtained through the AND gate 27f creates a signal output state that continues the pressure reduction of the brake fluid ratio from time [6 to set time +110°, for example, for 2 seconds.

Therefore, the braking fluid ratio continues to be reduced by the output of the counter measurement for the set time TOK, and during this time the fluid pressure in the wheel cylinder decreases to the residual pressure that remains as the minimum value.
When the brake fluid pressure becomes approximately zero, the rotation of the wheels in the locked state is restarted even on a low μ road surface, and the wheel speed Vi is restored.

The time chart in Fig. 6 shows a case where noise is generated in the wheel speed Vw due to unevenness of the road surface in the wheel lock state after time [,], and at this time, the output of the comparator section is close to the L level. As a result, the AND gate 27 becomes stopped and the brake fluid ratio cannot be maintained temporarily, but when the noise disappears, the brake fluid ratio is reduced again by the output of the counter.
It will continue.

Due to the pressure reduction of the brake fluid ratio in the locked state of the vehicle after time IIl, the wheel speed recovers and the brake fluid ratio increases again, and the set deceleration b1 is achieved at time t8. and the pseudo vehicle speed Vi is generated, 1 of the wheel speed VW sampled and held at time t8.
Direct is the threshold speed V in the comparator section.

Since the following is true, the output of the comparator section becomes L level,
The value of the wheel speed immediately before the wheel lock occurs is the threshold speed v1 at which the brake can be safely stopped even if the wheel lock occurs.
From the following, the AND gate 27 is L of the comparator section.
The inhibited state is maintained by the level output, and the brake control of the vehicle is brought to a halt using the comparison calculation shown in Table 1 above.

On the other hand, when the vehicle finally comes to a busy stop, since there is no H level input from AVi to the IJ) trigger timer 29, the timer operation is stopped after a certain period of time after the last time the retrigger timer was retriggered, and the timer operation is stopped. The output of the retrigger timer 29 when the operation is stopped is or game) 2
4' to reset the sampling hold circuit ↓, even if counter 4 has a counter output in the state where the braking is stopped, the AND gate 27 sample hold circuit 2 is reset and the braking is stopped. Afterwards, the problem caused by the continuation of the reduced state of money has been resolved.

In addition, as another example in FIG. 5, the signal line 30 shown as broken
Instead of using the output of the retrigger timer 29 to reset the sample and hold times W&B as shown in FIG.

Further, as another embodiment of FIG. 5, the counter is not activated by the comparator 16, but by the H level output of the comparator 15 that detects the set deceleration b1, as shown by the signal line 31 indicated by a broken line. You can also do it.

FIG. 7 is a circuit block diagram showing another embodiment of the present invention, and the main feature of this embodiment is that the peak value of the wheel speed is detected as the wheel speed immediately before the wheel locks. .

That is, in the embodiment of FIG. 7, a peak hold circuit %32 is used instead of the sample and hold circuit in the embodiment of FIG.
is provided, and the peak hold circuit 32 detects and outputs the peak value of the wheel speed obtained when the wheel speed recovered by the depressurization of the water outlet is in a state where the wheel speed is stopped from being depressurized to being maintained.
The peak value of vehicle ¥A included just before the lock detected by this peak hold circuit 32 is input to the ratio softener δ and the threshold speed &V
1 when the peak value is equal to or higher than the threshold speed v1
−It is possible to obtain a level output. The other circuit configurations are the same as those in the embodiment shown in FIG. 4, and the operation thereof is the same as that in the embodiment shown in FIG. 5 except that the peak value of the wheel speed is detected.

In this way, if the peak value of the wheel speed just before the lock is detected, the wheel speed when the set deceleration is obtained in the actual km example in Figure 5 is set to a value slightly lower than the peak value. Therefore, it is possible to guarantee a safer braking stop sound after wheel locking in the first stage of anti-skid control by using the peak value laterally.

(Effects of the Invention) As explained above, according to the present invention, the wheel lock r
At the time of detection, if the wheel speed value immediately after lock detection is equal to or higher than a predetermined speed at which the wheel can be stopped safely even if a wheel lock occurs, the oil reduction basin oil connection on the braking ridge is activated for a predetermined period of time. Since the signal sound is generated,
Even if a wheel lock occurs from a relatively high speed when the vehicle approaches a 1 [I] motion stop state, the brake fluid pressure continues to be reduced for a sufficient period of time to restore the vehicle's engine speed. Therefore, once the wheel speed is locked, it starts to recover again with a light reduction in the pressure of the wheel cylinder, and the braking stability is impaired and the braking stopping distance is shortened while the wheels are still locked from the speed on a low μ road surface. It is possible to precisely prevent this from happening, and it is possible to perform highly accurate amplifier skid control even on a single road surface.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing the dispersion system of a conventional anti-skid control device together with the control circuit, Fig. 2 is a graph showing time reduction of wheel cylinder pressure during pressure reduction, and Fig. 3 is a conventional device. Fig. 4 shows the lock state t7r when the road is concave, and the timing chart of Fig. 4.
Timing chart showing the lock state between roads, No. 5
Is the figure one embodiment of the present invention? ! 6IA is a timing chart showing the control system on a low μ road surface according to the embodiment of FIG. 5, and FIG. 7 is a circuit block diagram showing another embodiment of the present invention. l...Mask cylinder 2...kVVB2...Wheel cylinder 4...AVVS2...Accumulator 7...Check valve 8...Anti-skid control circuit 9...Wheel 10...Wheel speed control circuit/ 11...Wheel, speed detection circuit Work 2...Wheel acceleration/deceleration detection circuit 13.
...Pseudo vehicle speed generation circuit 14...Measure wheel connection generation circuit 15, 16.17.25.2...Comparator i8.21
．． 24...ORKATE, 27...AND gate 19, 22...Amplifier R...Sample hold circuit A...Counter 32...Peak hold circuit Fig. 1 Fig. 2 B Fig. 8 υ

Claims (2)

[Claims] (1) In an anti-skid control device that controls brake fluid pressure based on wheel acceleration/deceleration and/or wheel slip rate, the wheel lock detection means detects vehicle lock due to increase or maintenance of brake fluid pressure; A depressurization signal generating means is provided which generates a depressurization signal that continues the depressurization of the brake fluid for a predetermined period of time when the lock detecting means or the wheel speed immediately before detecting the lock of the wheel is equal to or higher than a predetermined value. Anti-skid control device that makes it easy to use. (2) The acid ratio signal generating means generates a pressure reduction signal at a predetermined time when the wheel speed when the set deceleration immediately before the wheels lock is obtained or the peak value of the wheel speed is equal to or higher than a predetermined value. Claim 1 characterized in that it occurs in
Anti-skid control device as described in section.