JP2518028B2 - Anti-lock type brake hydraulic pressure control device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an anti-lock type brake hydraulic pressure control device for a vehicle hydraulic brake that brakes a vehicle while preventing a wheel from falling into a locked state. In particular, an electromagnetic valve device is provided that can switch between a pressure increasing position that allows the hydraulic pressure of the wheel cylinder that operates the brake for suppressing the rotation of the wheels to increase and a pressure reducing position that allows the hydraulic pressure to decrease. It also relates to an anti-lock type brake fluid pressure control device.

[Conventional technology]

Anti-lock control is performed in order to brake the vehicle without impairing driving stability or at a shortest distance possible. In order to perform this antilock control, an electromagnetic valve device is provided between the hydraulic pressure source, the reservoir and the wheel cylinder. Generally, as a hydraulic pressure source, (a) a master cylinder that outputs a hydraulic pressure having a height corresponding to the operating force of a brake operating member such as a brake pedal, (b) a hydraulic pump, a motor, an accumulator, etc. A constant hydraulic pressure source that outputs pressure is used. On the other hand, as an electromagnetic valve device, a pressure increasing position that allows the wheel cylinder fluid pressure to increase by communicating the wheel cylinder with the fluid pressure source, and a wheel cylinder fluid that is disconnected from the fluid pressure source and communicates with the reservoir. A solenoid valve device is used that is switchable to a reduced pressure position that allows the pressure to decrease. In this type of solenoid valve device, in addition to the pressure increasing position and the pressure reducing position, it is possible to switch to the pressure holding position for keeping the wheel cylinder hydraulic pressure constant by disconnecting the wheel cylinder from the hydraulic pressure source and the reservoir. A solenoid valve device is included. Further, the solenoid valve device is configured by a combination of a plurality of valves, such as a combination of two electromagnetic opening / closing valves provided on the hydraulic pressure source side and the reservoir side, and a combination of an electromagnetic directional switching valve and an electromagnetic opening / closing valve. There are also cases.

Then, the wheel cylinder hydraulic pressure is controlled by the electromagnetic valve device controlled by the electric control device so that a frictional force as large as possible is generated between the wheel and the road surface.
The coefficient of friction between the wheel and the road surface becomes maximum when the slip ratio of the wheel with respect to the road surface is within an appropriate range of, for example, 15 to 20%, and therefore the wheel cylinder hydraulic pressure is set so that the slip ratio is maintained within the appropriate range. As a result, the braking force is controlled. Specifically, when the slip ratio increases and a locking tendency occurs that deviates from the proper range, the electric control device enters a pressure reducing mode in which the solenoid valve device is kept in the pressure reducing position. By executing this pressure reducing mode, the wheel cylinder hydraulic pressure is reduced. It is rapidly reduced, the slip ratio is reduced, and the lock tendency is resolved, and eventually it is resolved. If the execution of this pressure reduction mode is further continued, the wheel speed approaches the vehicle speed too much, the slip ratio approaches 0, and the slip ratio deviates from the proper range. Therefore, when the tendency to cancel the lock tendency is generated or the tendency to cancel the lock tendency is canceled, the electric control device increases the solenoid valve device by alternately switching the solenoid valve device between the pressure increasing position and the pressure reducing position. The pressure increasing mode allows the wheel cylinder fluid pressure to increase more slowly than when the wheel cylinder pressure is maintained, and the wheel cylinder fluid pressure is gradually increased by executing this mode.
The slip rate is increased. The electric control device keeps the slip ratio within an appropriate range by alternately repeating the pressure reducing mode and the gradual pressure increasing mode as the lock tendency occurs and disappears.

On so-called low μ roads where the friction coefficient μ is small, such as on icy roads, when the decompression mode is executed, the wheel cylinder fluid pressure is relatively low and the decompression gradient becomes gentle. It takes time to recover to a speed almost equal to. Therefore, on the low μ road, the slow pressure increase mode is started at the time when the tendency of locking the wheels is canceled so that the timing of starting the slow pressure increase does not come too early in relation to the recovery of the wheel speed. It is desirable to be set. On the other hand, on so-called high μ roads with a large friction coefficient μ such as dry asphalt roads, the wheel cylinder hydraulic pressure is relatively high and the pressure decreasing gradient becomes steep during the depressurization mode, so the wheel cylinder hydraulic pressure decreases rapidly. The target hydraulic pressure is reached early. Therefore, on high μ roads, the pressure reduction mode is set at a time when the tendency to cancel the wheel lock tendency occurs so that the timing of pressure reduction end is too early and the wheel cylinder hydraulic pressure does not decrease too much to cause insufficient braking force. It is desirable to set it to end.

However, when the wheel cylinder hydraulic pressure is controlled by switching between the pressure reduction mode and the gradual pressure increase mode, the pressure reduction end timing is necessarily the gradual pressure increase start timing. Therefore, when both the decompression end time and the gentle decompression start time are selected at the time when the wheel locking tendency is eliminated, good braking performance is secured on the low μ road, but on the high μ road, Since the decompression end time is too late, the graph in Figure 13 (b)
The wheel cylinder pressure is
After Pw decreases more than expected and the wheel speed recovers to a speed almost equal to the vehicle speed as indicated by the broken line in the graph (a) of the same figure, the actual vehicle speed decrease gradient becomes gentler than that. The braking force may be insufficient. On the other hand, if both the pressure reduction end time and the gradual pressure increase start time are selected when the tendency to eliminate the wheel lock tendency occurs, high μ
Good braking performance is ensured on roads, but on low-μ roads, the time to start slowly increasing pressure is too early. In the anti-lock type brake fluid pressure control device, generally, the vehicle speed is estimated based on the rotation speed of the reference wheel having the highest rotation speed among the wheels (the wheel estimated to have the smallest slip),
Based on the difference between the estimated vehicle speed and the wheel speed that is the rotation speed of the control wheel that is the control target, it is estimated whether the wheel has a lock tendency or whether the lock tendency has been eliminated.
Therefore, if the slow pressure increase start timing is too early on the low μ road, the slip ratio of the reference wheel also increases, and the estimated vehicle speed becomes inaccurate. Specifically, it becomes too small with respect to the actual vehicle speed. In this case, even though the true slip ratio of the control wheel deviates from the proper range, the wheel speed is close to the estimated vehicle speed, so it is estimated that the slip ratio of the control wheel is in the proper range. It is possible to make a false decision that the lock tendency has been eliminated even though the lock tendency has not been eliminated. As a result, as in the conventional example shown by the broken lines in graphs (a) and (b) of FIG. There is a possibility that the tendency to lock increases and the wheels fall into a locked state.

Therefore, conventionally, if the tendency of canceling the lock tendency of the wheel occurs due to the execution of the pressure reducing mode, the wheel cylinder hydraulic pressure is kept constant until the lock tendency is canceled from that time. Alternatively, a gentle depressurization mode is performed that allows the wheel cylinder hydraulic pressure to be more gently reduced than in the depressurization mode. By controlling the wheel cylinder fluid pressure in this way,
It is possible to avoid the situation where the lock tendency increases on the low μ road and the situation where the braking force becomes insufficient on the high μ road.

The gradient of the wheel cylinder hydraulic pressure in the pressure maintaining mode or the gentle depressurizing mode is the difference in the wheel cylinder hydraulic pressure due to the difference in the friction coefficient μ on the road surface and the output hydraulic pressure of the hydraulic pressure source. Without being affected by the difference of
It is desirable to be on schedule. Therefore, JP-A-56-
As disclosed in Japanese Patent No. 34554 and Japanese Patent Laid-Open No. 57-11142, a solenoid valve device is provided with a pressure holding position for shutting off a wheel cylinder from a hydraulic pressure source and a reservoir, and the solenoid valve device is installed after a pressure reducing mode. When the wheel cylinder fluid pressure is in the decompression mode by maintaining the fluid pressure mode by maintaining the fluid pressure position, or by connecting the solenoid valve device with the fluid passage that is closed to the reservoir by shutting off the wheel cylinder from the fluid pressure source. A gentle decompression position is provided to allow a gradual decrease compared to the above, and a gentle decompression mode is obtained by maintaining the electromagnetic valve device at the gentle decompression position after the decompression mode. When the gentle decompression mode is executed, the decompression gradient of the wheel cylinder hydraulic pressure tends to become steeper as the wheel cylinder hydraulic pressure becomes higher, but the wheel cylinder hydraulic pressure is designed to gradually decrease. The effect of fluctuations in is small.

[Problems to be Solved by the Invention]

In a two-position solenoid valve device having two positions, a pressure increasing position and a pressure reducing position, a pressure holding mode or a slow pressure reducing mode is obtained by repeatedly switching the solenoid valve device between the pressure increasing position and the pressure reducing position for an appropriate time. You can

However, in this case, the gradient of the wheel cylinder hydraulic pressure in the pressure maintaining mode or the gentle depressurizing mode is not always as planned. The friction coefficient μ on the road surface is not constant for each brake operation, and the wheel cylinder hydraulic pressure during antilock control is not constant for each antilock control, and the hydraulic pressure source is, for example, the master cylinder output fluid. When the pressure level changes depending on the brake operating force, the reason is that the output hydraulic pressure of the hydraulic pressure source is not constant for each antilock control. This hydraulic pressure gradient is determined by the ratio of the duration of the pressure increasing position to the duration of the pressure reducing position, and the pressure increasing gradient at the pressure increasing position and the pressure reducing gradient at the pressure reducing position. The pressure increasing gradient becomes steeper as the difference between the wheel cylinder hydraulic pressure and the target hydraulic pressure increasing pressure (generally, the output hydraulic pressure of the hydraulic pressure source substantially matches). The higher the fluid pressure, the steeper. Therefore, even if the output hydraulic pressure of the hydraulic pressure source is constant,
The smaller the friction coefficient μ of the road surface, the steeper the pressure increase gradient and the more gentle the pressure reduction gradient. As a result, the hydraulic pressure gradient inclines toward the pressure increase side, and the magnitude of the friction coefficient μ of the road surface is constant. However, the higher the output hydraulic pressure of the hydraulic pressure source, the steeper the pressure increase gradient, and as a result, the hydraulic pressure gradient inclines toward the pressure increase side. Therefore, the wheel cylinder hydraulic pressure is not always controlled as scheduled by the execution of the pressure maintaining mode or the like, and there arises a problem that the control accuracy of the wheel cylinder hydraulic pressure cannot be sufficiently increased.

Therefore, the present invention provides an anti-lock type brake hydraulic pressure control device including a solenoid valve device having a pressure increasing position and a pressure reducing position, in which the decompression end time is equal to the time when the tendency to cancel the locking tendency of the wheels occurs, If the third mode corresponding to the pressure-holding mode or the slow depressurization mode is executed after the depressurization mode, and the lock tendency is not resolved by executing the third mode, the mode does not shift to the slow pressurization mode and the depressurization is performed. The above problem is solved by sequentially executing the mode and the third mode, and appropriately changing the hydraulic pressure gradient in the third mode this time based on the execution result of the third mode last time. The task was to do.

[Means for solving the problem]

The present invention relates to an antilock brake hydraulic pressure control device including an electromagnetic valve device capable of switching between the pressure increasing position and the pressure reducing position (1) connected to the electromagnetic valve device, and (a) depressurizing the electromagnetic valve device. By alternately switching the pressure reducing mode for maintaining the position to (b) the solenoid valve device between the pressure increasing position and the pressure reducing position,
Slow pressure increasing mode that allows the wheel cylinder fluid pressure to increase more slowly than when the solenoid valve device is kept in the pressure increasing position, and (c) switching the solenoid valve device alternately between the pressure increasing position and the pressure reducing position. This allows the wheel cylinder fluid pressure to decrease or increase more gently on the road surface with a large friction coefficient μ than in the pressure reducing mode or the slowly increasing pressure mode, or the third mode that keeps the wheel cylinder fluid pressure constant. It is possible to switch to and, and when the wheels tend to lock, the pressure reduction mode is set, and when the locking tendency disappears, the mode becomes the third mode. (2) The third mode of this time is the third mode of the previous time. In the third mode, the ratio of the duration of the pressure increasing position to the duration of the pressure reducing position (hereinafter referred to as the duration time ratio) is set to the previous time. The gist of the present invention is to include a ratio decreasing means for decreasing the value of the value of.

It should be noted that, as one mode of the ratio reducing means, there is a form in which the present continuation time ratio is obtained by subtracting a positive correction amount from the previous continuation time ratio value or multiplying the previous value by a correction coefficient smaller than 1. can do. In this case, the correction amount and the correction coefficient are changed in accordance with the length of the last time of the third mode, or are changed as the number of repetitions of the third mode is increased. It can be changed as the number of repetitions of the pressure increasing position and the pressure reducing position increases.

As another aspect of the ratio reducing means, the length of the last time of the third mode, the number of repetitions of the third mode, the number of repetitions of the pressure increasing position and the pressure reducing position in each third mode, etc. are factors. Then, determine the duration ratio corresponding to each value of those factors, and use the predetermined relationship between those factors and the duration ratio, and determine the duration ratio this time according to that relationship. can do. As a predetermined relationship between those factors and the duration ratio, use a function that calculates the duration ratio using those factors as variables, or a table that represents the relationship between these factors and the duration ratio. You can

[Action]

In the anti-lock type brake hydraulic pressure control device according to the present invention, if the tendency of eliminating the locking tendency of the wheels occurs due to the execution of the pressure reducing mode, the mode is shifted to the third mode at that time.

When the third mode is executed on the high μ road, normally,
Since the wheel speed recovers fairly rapidly and the lock tendency is easily eliminated, the slow pressure increasing mode is executed after the execution of the third mode this time. As described above, in the present embodiment, the pressure reducing mode is terminated at the time when the tendency to eliminate the lock tendency occurs, and when the third mode is executed, the wheel cylinder hydraulic pressure is gentler than that in the pressure reducing mode. To the wheel cylinder fluid as shown by the solid lines in graphs (a) and (b) of FIG. The pressure does not decrease too much, and the occurrence of the situation where the braking force is insufficient on the high μ road is avoided.

On the other hand, when the third mode is executed on the low μ road,
Normally, the duration time ratio in the first time of the third mode is not appropriate, and the wheel lock tendency cannot be eliminated by only executing the third mode once. In this case, the pressure reducing mode is executed instead of the gradual pressure increasing mode, and the third mode is executed again when the tendency of eliminating the lock tendency occurs due to this execution.

When the third mode is continuously executed in this way, it is estimated that the duration ratio in the previous third mode is too large in relation to the friction coefficient μ of the road surface. It can be reduced from the previous value. And
If the lock tendency is canceled by executing the third mode this time, the mode is shifted to the slow pressure increasing mode. On the low μ road, the third mode and the pressure reduction mode are alternately repeated until the lock tendency is eliminated. As described above, in the device of the present invention, the mode shifts to the slow pressure-increasing mode after waiting for the lock tendency to be eliminated, so that the low μ road is shown by the solid lines in the graphs (a) and (b) of FIG. As in one example, the slow pressure increasing mode is not executed before the lock tendency is eliminated, and the situation in which the wheels are locked early is avoided.

〔The invention's effect〕

As described above, according to the present invention, regardless of changes in the output hydraulic pressure of the hydraulic pressure source, changes in the road surface friction coefficient μ, etc.
The lock tendency is eliminated early, and the braking distance is not unduly lengthened, so that the braking performance is improved.

According to the present invention, it is possible to obtain an effect that highly accurate hydraulic pressure control can be realized by an inexpensive anti-lock type brake hydraulic pressure control device provided with a two-position solenoid valve device having only two positions, a pressure increasing position and a pressure reducing position. .

The electric control device may be configured to uniformly shift to the third mode after the depressurization mode, or may not be uniformly transitioned to the third mode. If the above is the case, the transition is made, but if not, the transition may not be made. When the locking tendency is small, the execution of the third mode is almost unnecessary. Therefore, if the third mode is executed in such a case, the braking distance may be extended. Therefore,
If the electrical control device is designed to execute the third mode only when the lock tendency is equal to or greater than the reference value, as in the case of the latter aspect, it is possible to avoid the above-described extension of the braking distance. can get.

〔Example〕

Hereinafter, an embodiment in the case where the present invention is applied to an anti-lock type brake hydraulic pressure control device for a hydraulic brake device for a four-wheeled vehicle will be described in detail with reference to the drawings.

In FIG. 2, reference numeral 10 indicates a tandem brake master cylinder (hereinafter simply referred to as a master cylinder) as a hydraulic pressure source. The master cylinder 10 has a brake pedal 12
The hydraulic pressure of the same height is generated in the two independent pressurizing chambers in accordance with the operating force of. The hydraulic pressure in one pressurizing chamber is transmitted to the wheel cylinders of the brakes provided on the left and right front and rear, and the hydraulic pressure in the other pressurizing chamber is transmitted to the wheel cylinders for the left and right rear wheels. Only the wheel cylinder 14 for the left front wheel is shown in FIG. 2, and the following description will be made only for the left front wheel. The wheel cylinder 14 is connected to the master cylinder 10 by liquid passages 18 and 20, and a two-position valve 22 as a solenoid valve device is provided in the middle thereof.

The two-position valve 22 is connected to the reservoir 28 by a reservoir passage 26. The two-position valve 22 is always in the pressure increasing position that allows the hydraulic pressure of the master cylinder 10 to be transmitted to the wheel cylinder 14 by disconnecting the liquid passage 20 from the reservoir passage 26 and communicating with the liquid passage 18. When the solenoid 32 is excited, the liquid passage 20 is shut off from the liquid passage 18
The pressure reducing position is set such that the brake fluid of the wheel cylinder 14 is allowed to be discharged to the reservoir 28 by communicating with the reservoir 26. The brake fluid discharged to the reservoir 28 is pumped up by the pump 36 driven by the motor 34 and returned to the fluid passage 18. The liquid passages 18 and 20 are connected to a recirculation passage 38 that allows the brake fluid to recirculate from the wheel cylinder 14 to the master cylinder 10 by bypassing the two-position valve 22.
The recirculation passage 38 is provided with a check valve 40 that prevents the reverse flow of the brake fluid. Reference numerals 42 and 44 are check valves.

The solenoid 32 is controlled by a controller 50 mainly composed of a computer. The controller 50 includes a rotation sensor 54 that detects the rotation speed of the disk rotor 52 that rotates with the left front wheel, that is, the rotation speed of the left front wheel, a rotation sensor that detects the rotation speed of wheels other than the left front wheel, and the brake pedal 12. The brake switch 58 for detecting the depression of the pedal is connected. The controller 50 also has a function of starting and stopping the motor 34 as needed.

The controller 50 also stores various control programs including the main program shown in the flow charts of FIGS. 3 to 8. Antilock control is performed by executing these control programs.

The state of antilock control will be described. It should be noted that only the antilock control for the left front wheel will be described, and the control for the other wheels will be omitted.

When the ignition switch of the vehicle is not operated, the two-position valve 22 is in the pressure increasing position, and the hydraulic pressure of the master cylinder 10 is transmitted to the wheel cylinder 14 via the two-position valve 22.

When the ignition switch is operated, execution of the main program shown in FIG. 3 is started. First, step S1
(Hereinafter, simply referred to as S1. The same applies to other steps.) The current mode is set to the pre-control mode (a flag indicating that antilock control is not being performed is set), and the demagnetization command is issued to the solenoid 32 in S2. Is issued. The execution of S2 is to confirmably switch the two-position valve 22 to the pressure increasing position in order to avoid the situation where the two-position valve 22 is erroneously switched to the pressure reducing position due to an abnormality in the electric system. In S3, the value of the elapsed time t _A after the slow pressure increasing mode is started and the value of the elapsed time t _H after the pressure maintaining mode is started are both reset to zero.

In S4, a signal is taken in from the rotation sensor 54 or the like, the current wheel speed Vw of the left front wheel, the wheel acceleration Gw and the estimated vehicle speed Vs are calculated from the detection result, and a predetermined slip ratio is set to the estimated vehicle speed Vs. The reference speed Vo is calculated in anticipation.

In S5, it is determined whether or not the brake is operated, that is, whether or not the brake switch 58 is in the ON state, and in S6, whether or not the antilock control is permitted, that is, the estimated vehicle speed Vs is It is determined whether or not the speed has increased above a predetermined control permission speed V _E (a small speed such as several kilometers per hour). When the brake is operated and the estimated vehicle speed Vs is equal to or higher than the control permission speed V _E , the determination results of S5 and S6 are both YES, and S7 is executed.

In S7, it is determined whether or not antilock control needs to be performed on the left front wheel. That is, it is determined whether the wheel speed Vw of the left front wheel is equal to or lower than the reference speed Vo and the wheel acceleration Gw is equal to or lower than the negative reference acceleration G ₁ . In the present embodiment, it is estimated that the wheel tends to lock when the wheel speed Vw becomes equal to or lower than the reference speed Vo and the wheel acceleration Gw becomes equal to or lower than the reference acceleration G ₁ . Therefore, when the brake pedal 12 is operated, the hydraulic pressure in the wheel cylinder 14 is appropriate in relation to the friction coefficient μ of the road surface, and the left front wheel does not tend to lock, the determination result in S7 is NO, and S8 is At, it is determined whether the pre-control mode is set. Since this is the pre-control mode, the determination result is YES, and the process returns to S4. On the other hand, the hydraulic pressure of the wheel cylinder 14 is
Is too high in relation to, and if the left front wheel has a tendency to lock, the determination result in S7 is YES, and thereafter the antilock control is executed. It should be noted that, for example, when antilock control is performed due to a relatively large tendency to lock the left front wheel on a high μ road, the estimated vehicle speed Vs, the wheel speed Vw, the reference speed Vo, the wheel acceleration Gw and the wheel An example of how the hydraulic pressure Pw of the cylinder 14 changes is shown in graphs (a) to (c) of FIG. 9, and antilock control is performed due to a large locking tendency occurring on a low μ road, for example. An example of how the hydraulic pressure Pw of the wheel cylinder 14 changes in the case of the above is shown in the graph of FIG.

In S9, it is determined whether the wheel acceleration Gw is increasing. At present, the left front wheel has a lock tendency, and the lock tendency is increasing, that is, the wheel acceleration Gw is decreasing, so the determination result is NO, and S10 is executed. In S10, it is determined whether or not the mode is the mode for gradually increasing pressure. Since this time it is still in the pre-control mode, the judgment result is NO, and it is judged in S11 whether it is the pressure-holding mode or not.
This determination result also becomes NO, and the pre-control mode is changed to the pressure reduction mode in S12. In S13, the solenoid 32 is excited and the two-position valve 22 is switched from the pressure increasing position to the pressure reducing position. As a result, the brake fluid in the wheel cylinder 14 flows out toward the reservoir 28, and the wheel cylinder 14
Thus, the hydraulic pressure Pw of will decrease rapidly.

The depressurization mode is continued until the tendency to eliminate the lock tendency is generated by the execution of the depressurization mode, that is, in the present embodiment, the wheel acceleration Gw starts to increase and the determination result of S9 becomes YES. If the determination result in S9 is YES, it is determined in S14 whether the mode is the slow pressure increasing mode. Since the pressure reduction mode is currently in effect, the determination result is NO, and in S15, it is determined whether or not the duration time T _R of the pressure reduction mode is equal to or longer than a predetermined reference time T _RO , so that the lock generated on the left front wheel is locked. It is determined whether or not the tendency is strong enough to be the reference value or more.

First, the case where the locking tendency of the left front wheel is small will be described.

In this case, the determination result in S15 is NO, the depressurization mode is changed to the slow pressure increasing mode in S16, and the slow pressure increasing mode is executed in S17.

The execution of the slow pressure increasing mode will be described. First, the outline of execution will be described. In the present embodiment, a state in which the pressure reducing position and the pressure increasing position are sequentially switched once is defined as one control cycle, and the control cycle is repeated many times at a constant cycle time tc to obtain the slow pressure increasing mode. To be
Further, in the present embodiment, the target time T _AO of the slow pressure increasing mode duration time T _A is a situation where the hydraulic pressure gradient in the slow pressure increasing mode of the wheel cylinder 14 is assumed to be the gentlest,
For example, a wheel cylinder that will tend to lock the left front wheel on high μ roads with a fairly large coefficient of friction μ.
A hydraulic pressure slightly higher than the hydraulic pressure Pw of 14 is generated in the master cylinder 10 by the operation of the brake pedal 12, and even when the hydraulic pressure difference between the master cylinder 10 and the wheel cylinder 14 is small, the hydraulic pressure of the wheel cylinder 14 is small. The length is determined so that the braking distance does not greatly increase because it takes an excessive amount of time for the pressure Pw to reach the target hydraulic pressure.

2-position valve while maintaining a constant hydraulic pressure in the master cylinder 10.
When 22 is alternately switched between the pressure increasing position and the pressure decreasing position, if the length of the repetition time is sufficient, the hydraulic pressure Pw of the wheel cylinder 14 will be the hydraulic pressure of the wheel cylinder 14 at the beginning of the repetition. The pressure converges to a constant height regardless of the height of the pressure Pw, and the height of the converged pressure is determined by the height of the hydraulic pressure of the master cylinder 10 and the repeating pattern of the pressure increasing position and the pressure reducing position. It has been known. Therefore, in the present embodiment, the fluid pressure Pw of the wheel cylinder 14 increases to a convergent pressure or does not converge completely but converges before the slow pressure increasing mode continues for a time equal to the target time T _AO. Wheel cylinder 14 in the braking system so that it increases until it almost matches the pressure
The liquid pressure Pw pressure increase and pressure decrease characteristics are set. Therefore, the hydraulic pressure of the wheel cylinder 14 in the pressure reducing mode.
Even if the depressurization amount of Pw varies in each depressurizing mode and the hydraulic pressure Pw at the start of the gradually increasing pressure of the wheel cylinder 14 varies in each gradual increasing pressure mode, the gradual increasing mode duration T _A Will be kept constant with high accuracy.

In the present embodiment, the ratio of the duration of the pressure increasing position to the duration of the pressure reducing position in each slow pressure increasing mode is set to 1
As a one-to-one correspondence, the decompression time t _R , which is the duration of the decompression position in each control cycle, is defined as the cycle time.
A duty ratio D which is a value divided by tc is used. As shown in the graph of FIG. 10, the pattern of the duty ratio D is the elapsed time t _A from the start of execution of each slow pressure increasing mode.
Decreases as the time increases and the elapsed time t _A
It is set to continue decreasing even after _{exceeding AO} and become 0 when the maximum time t _{MAX has} elapsed.

In this embodiment, the predetermined relationship between the duty ratio D corresponding to each control cycle and the elapsed time t _A is stored as a function D (t _A ) having the elapsed time t _A as a parameter. . Therefore, the current value of the elapsed time t _A in the function D (t _A) (provided that the value of the elapsed time t _A is an integer multiple of the cycle time tc, corresponding to each control cycle.)
By substituting for, the duty ratio D corresponding to each control cycle is calculated. Then, the duty ratio D and the cycle time tc are multiplied to obtain the pressure reduction time t _R corresponding to each control cycle.

The execution of the gradual pressure increase mode will be specifically described based on the flowchart shown in FIG. First, in S100, it is determined whether the elapsed time t _A is 0 or not. Since the execution of the slow pressure increasing mode has not started yet and the elapsed time t _A remains 0, the determination result of S100 becomes YES and S101 is executed.

In S101, the depressurization time t _R in one control cycle to which the current execution of S17 belongs is the elapsed time in the function D (t _A ).
It is calculated by substituting the current value of t _A and multiplying the resulting value by the cycle time t c.

In S102, the elapsed time t _A at that time is stored as the start timing ts (the timing at which the pressure reducing position in the previous control cycle is switched to the pressure increasing position in the current control cycle) representing the start timing of one control cycle. In S103, it is determined whether the pressure reduction timing t _R has elapsed from the start timing ts of one control cycle, that is, whether the elapsed time t _A is smaller than the sum of the start timing ts and the pressure reduction time t _R. Since the slow pressure increasing mode is not yet executed and the elapsed time t _A remains 0, the determination result in S103 is YES, the solenoid 32 is excited in S104, and the two-position valve 22 is switched to the pressure reducing position. . The execution of S17 is normally repeated many times until the series of slow pressure increasing modes ends, that is, until the left front wheel locks due to execution of the slow pressure increasing mode. S17
Since the time interval between the previous execution and the current execution of is Δt _A , the elapsed time t _A is increased by Δt _A in S105.

When the above execution is completed, the process returns to S4 in FIG. 3 and again S7.
At, it is determined whether or not the left front wheel has a lock tendency, and if NO, S17 is executed again. Since the elapsed time t _A is Δt _A and is not 0 this time when S100 is executed, the determination result in S100 is NO, and in S106, S1
It is determined whether or not one control cycle is completed in the previous execution of 7, that is, whether the elapsed time t _A is equal to or more than the sum of the start time ts and the cycle time tc. If one control cycle is not yet completed by the previous execution, the determination result of S106 is NO, the execution of S101 and S102 is bypassed, and S103 is executed. In S103, decompression time t _R
Is determined not to expire, and if not expired, S104
Is executed and the two-position valve 22 is maintained at the pressure reducing position, and when it has expired, the solenoid 32 is demagnetized in S107 and the two-position valve 22 is switched to the pressure increasing position. After that, the elapsed time in S105
When t _A is increased, the process returns to S4 in FIG.

After that, S17 is executed many times, and when one control cycle ends, the determination result of S106 becomes YES, and in S101,
A new decompression time t _R in a future control cycle is calculated. In the same manner, S17 is repeated a considerable number of times, the left front wheel is locked, and the determination result of S7 in FIG. 3 is YE.
When S is reached, execution of the slow pressure increasing mode ends.

Thereafter, if it is determined in S9 whether or not the wheel acceleration Gw is increasing, it becomes NO, and in S10, it is determined whether or not the mode is the slow pressure increasing mode. Since the mode is the slow pressure increasing mode this time, the determination result is YES, and the duty ratio D in the slow pressure increasing mode is corrected in S18.

The execution of S18 will be described based on the flowchart shown in FIG. First, in S200, the elapsed time at that time
t _A is stored as the slow pressure increasing mode duration T _A , and the elapsed time t _A is reset to 0 in S201.

In the present embodiment, the duty ratio D in the next slow pressure increasing mode is obtained by adding the correction amount ΔD to the duty ratio D in the last slow pressure increasing mode. As shown in the graph of FIG. 11, the correction amount ΔD increases the difference between the time T _A and T _AO when the previous slow pressure increasing mode duration T _A is longer than the target time T _AO. If the slow pressure increasing mode duration time T _A is shorter than the target time T _AO , on the contrary, the positive value increases as the difference between those times T _A and T _AO increases. It is set to be a value. The two solid lines in the graph of FIG. 11 each show an example of the characteristic of the correction amount ΔD. In the present embodiment, the predetermined relationship between the correction amount ΔD, the slow pressure increasing mode duration time T _A and the elapsed time t _A is the slow pressure increasing mode duration time T _A and the elapsed time t _A. It is stored as a function ΔD (T _A , t _A ) which is a parameter.

In S202, the previous duty ratio D and the correction amount ΔD
Is stored as the duty ratio D corresponding to the elapsed time t _A of the slow pressure increasing mode at this time, and the elapsed time is determined in S203.
t _A is increased by the cycle time t c, and it is determined in S204 whether the elapsed time t _A is greater than the maximum time t _MAX . Until the determination result of S204 becomes YES, S202 and S203
As a result of repeating the execution of, the duty ratio D in each control cycle in the next slow pressure increasing mode is sequentially calculated as the elapsed time t _A increases. Then, as shown in the graph in FIG. 10, the next duty ratio D is on the pressure reducing side when the previous slow pressure increasing mode duration time T _A is shorter than the target time T _{AO, and} on the pressure increasing side when it is long. Will be corrected.

If the decision result in S204 is YES, the elapsed time t _A is reset to 0 in S205, then the depressurization mode is set in S12 of FIG. 3, and the two-position valve 22 is set in the depressurization position in S13, and then S4. Return to execution. Thereafter, unless a situation in which the lock tendency is increased due to some circumstances occurs, the pressure reduction mode and the slow pressure increase mode are alternately repeated while the duty ratio D in the slow pressure increase mode is corrected so as to approach an appropriate value. As a result, the slip ratio of the front left wheel is kept within an appropriate range.

The above description is for the case where the lock tendency occurring in the left front wheel is small, but hereinafter, the case where it is large will be described.

The pressure reduction mode is executed and the hydraulic pressure Pw of the wheel cylinder 14
If the wheel acceleration Gw of the left front wheel starts to increase as a result of a rapid decrease, S9 becomes YES. Then, in S14, it is determined whether or not the mode is the slow pressure increasing mode. Since it is currently in the pressure reducing mode, the determination result is NO, and S15 is executed. Since this explanation is for the case where the lock tendency is large, S1
If it is determined in 5 whether the pressure reduction mode duration time T _R is equal to or longer than the reference time T _RO , the determination result is YES, and S19 is executed.

In S19, as shown in the flowchart in FIG. 6, first, in S300, the wheel acceleration Gw is whether or not the positive reference acceleration G ₂ or more is determined. Currently wheel acceleration
Since Gw is less than or equal to the negative reference acceleration G ₁ , the determination result is NO, and it is determined in S301 whether or not the flag indicating that “wheel acceleration Gw has exceeded the reference acceleration G ₂ ” is set. . At present, the wheel acceleration Gw has never exceeded the reference acceleration G ₂ , and it is estimated that the lock tendency has not been resolved. Therefore, the determination result also becomes NO, and the process proceeds to S20 in FIG. The pressure reducing mode is changed to the pressure maintaining mode in S20, and the pressure maintaining mode is executed in S21.

The execution of the pressure holding mode in S21 will be described. First, the outline of execution will be described. In the present embodiment, a state in which the pressure increasing position and the pressure reducing position are sequentially switched once is defined as one control cycle, and the control cycle has a constant cycle time.
The holding mode is obtained by repeating tc many times. In the present embodiment, the initial value of the duration in each control cycle of the pressure increasing position (= tc-t _R) is, hydraulic pressure gradient is in the pressure-holding mode of the wheel cylinders 14, the high μ
The hydraulic pressure Pw of the wheel cylinders 14 is set to a level that is maintained at a constant height even when the master cylinder 10 is operated with the maximum operating force on the road. Therefore, even in the high μ road, in the master cylinder 10, in the state where the hydraulic pressure slightly higher than the hydraulic pressure of the height that causes the lock tendency in the high μ road, the pressure holding mode is set. If it is executed, the hydraulic pressure Pw of the wheel cylinder 14 will be gradually reduced, and if the pressure maintaining mode is executed on the low μ road, the hydraulic pressure Pw of the wheel cylinder 14 will be rapidly increased or will be moderate. Will increase. The initial value of the duty ratio D in the pressure-holding mode is set so that the braking force does not become insufficient even if the hydraulic pressure Pw of the wheel cylinder 14 decreases on the high μ road.

Next, the execution of the pressure-holding mode will be specifically described with reference to the flowchart shown in FIG. First, in S400, it is determined whether or not the elapsed time t _H from the start of execution of the pressure holding mode is 0. Since the elapsed time t _H is currently 0, the determination result is YES, and in S401, the elapsed time t _H at that time is
Is stored as the start time ts of the control cycle to which this execution belongs. In S402, it is determined whether or not the duration of the pressure increasing position in the control cycle has expired. If not, the solenoid 32 is demagnetized in S403 and the two-position valve 22 switches to the pressure increasing position. The execution of S21 is usually repeated many times, and since the time interval between the previous execution and the current execution is Δt _H , in S404,
The elapsed time t _H is increased by Δt _H.

When the above execution is completed, the process returns to S4 in FIG. 3 and again S7.
At, it is determined whether or not the left front wheel has a lock tendency. If NO, the pressure holding mode is subsequently executed in S21. When S400 is executed this time, the elapsed time
Since t _H is Δt _H and not 0, the determination result of S400 is NO.
Then, in S405, it is determined whether or not one control cycle has ended in the previous execution of S21, that is, whether the elapsed time t _H is equal to or more than the sum of the start time ts and the cycle time tc. If one control cycle is not yet completed by the previous execution, the determination result of S405 is NO, the execution of S401 is bypassed, and S402 is executed. In S402, it is determined whether or not the pressure boosting time has expired. If it does not expire, S403 is executed and the two-position valve 22 is held in the pressure boosting position. If it expires, the solenoid 32 is energized in S406. The position valve 22 switches to the reduced pressure position. After that, the elapsed time t _H is increased in S404, and the process returns to the execution of S4 in FIG.

After that, S21 is executed many times, and when one control cycle ends, the determination result of S405 becomes YES, and in S401,
The elapsed time t _{H at} that time is the start time ts of the next control cycle
And the control cycle is executed in the same manner.

By executing this pressure holding mode, the left front wheel tends to lock and S7 becomes YES, and then S9 becomes YES if the wheel acceleration Gw starts to increase. Since it is currently in pressure holding mode, S14
It becomes NO and the duration T _R of the previous decompression mode is the reference time T _RO
Because of the above, S15 is YES and S19 is executed.

The state of execution of S19 will be described based on a specific example. High μ
If the pressure reduction mode is executed on the road, the hydraulic pressure Pw of the wheel cylinder 14 at that time is relatively high and the pressure reduction gradient becomes steep. Therefore, if the pressure retention mode is executed, the wheel speed Vw of the left front wheel becomes the ninth speed. It recovers rapidly as shown in the figure. As a result, if the wheel acceleration Gw is exceeds the reference acceleration G _2, in the execution of S19, representing the "effect that wheel acceleration Gw becomes reference acceleration G ₂ or more" by S300 is S302 and that a YES is performed Flag is set. Thereafter, at a time when the wheel acceleration Gw has passed the reference acceleration G ₂ decreases through the maximum value, if S19 is executed, S300 is NO, S301 is YES, the flag is reset at S303, FIG. 9 the time indicated by t _3, the S16 proceeds to gentle increase mode to the third view is executed. That is, in the present embodiment, it is presumed that the lock tendency of the left front wheel is canceled when the wheel acceleration Gw has passed the reference acceleration G ₂ once each while the wheel acceleration Gw is increasing and decreasing.

It is estimated that the lock tendency does not occur at the time when the execution of the slow pressure increasing mode is started, S7 is NO, S8 is NO, and S14 is Y.
It becomes ES and the execution of the slow pressure increasing mode is continued. Eventually, if the hydraulic pressure Pw of the wheel cylinder 14 increases and a locking tendency occurs, S7 becomes YES, S9 becomes NO, and S
10 becomes YES, and the duty ratio D in the slow increase mode is corrected in S18, the time indicated by t ₄ in FIG. 9, S1
The depressurization mode is executed in 2 and S13, and then the slowly increasing pressure mode and the depressurizing mode are alternately repeated to keep the slip ratio of the left front wheel within the proper range.

On the high μ road, even if the pressure holding mode is executed due to a large locking tendency, the wheel speed of the left front wheel recovers considerably fast, so immediately after passing through the pressure holding mode without going through the pressure reducing mode. It is normal to shift to the slow boost mode.

The above explanation is about the case where the lock tendency is canceled by executing the pressure-holding mode.However, there is a case where the lock tendency is not canceled by executing the pressure-holding mode, for example, when the lock tendency occurs on a low μ road. Hereinafter, this case will be described.

In this case, the holding mode is executed and the wheel cylinder
Where the hydraulic pressure Pw of 14 should be kept constant, it may actually be increased as in the example shown in the graph of FIG. In such cases, the locking tendency is not resolved,
Since the wheel acceleration Gw cannot exceed the reference acceleration G ₂ , S1
9 does not become YES and the wheel acceleration Gw begins to decrease and S9
Becomes NO. In this case, since the pressure-holding mode is currently set, S10 is NO and S11 is YES, and the duty ratio D in the pressure-holding mode is corrected in S22.

The state of execution of S22 will be described based on the flowchart shown in FIG. First, in S500, a new decompression time
t _R is the current value of the decompression time t _R and a predetermined positive correction amount Δ
This is the sum of t _R and in S501, it is determined whether the pressure reduction time t _R is longer than the cycle time tc. If so, the depressurization time t _R is made equal to the cycle time tc in S502, so that the pressure holding mode is substantially equal to the depressurization mode, otherwise the execution of S502 is bypassed. In other words, by executing S22, the duty ratio D in the pressure maintaining mode is corrected so that the pressure maintaining gradient of the wheel cylinder 14 in the current pressure maintaining mode becomes gentler than the previous time.

Thereafter, at a time indicated by t ₃ in Figure 1, pressure reduction mode is performed by S12 and S13. This depressurization mode ends when the tendency of the left front wheel to cancel the lock tendency occurs and S7 becomes NO. Then, in this case, if the lock tendency at that time is not equal to or greater than the reference value, S15 becomes NO, and the slow pressure increasing mode is executed in S16 and S17. On the other hand, if the degree of locking tendency is greater than the reference value and S15 is YES,
S19 is executed. Wheel acceleration Gw is the determination result is NO reference acceleration G ₂ is less than the S19, the time indicated by t ₄ in the figure, a pressure-holding mode is executed in S20 and S21.
In this pressure maintaining mode, the duty ratio D is the value corrected in S22, and if the duty ratio D in this pressure maintaining mode is appropriate, as shown in FIG.
The hydraulic pressure Pw of the wheel cylinder 14 is kept constant. Such the usual case, since if the locking tendency of the left front wheel is eliminated, S19 becomes YES, and the time indicated by t ₅ in the figure, is executed slow increase mode step S16 and S17 It

If the lock tendency of the left front wheel is not eliminated even by the pressure maintaining mode this time, the duty ratio D in the next pressure maintaining mode is corrected in S22 so that the hydraulic pressure Pw of the wheel cylinder 14 is further reduced. Then, it becomes a proper value.

After that, unless a situation such as a further decrease in the friction coefficient μ of the road surface occurs, the locking tendency of the left front wheel is reliably eliminated even by executing the pressure-holding mode, and the slip ratio of the left front wheel is kept in an appropriate range. Then, the operation of the brake pedal 12 is released and the determination result in S5 becomes NO, or the vehicle speed decreases and the estimated vehicle speed Vs does not exceed the control permission speed V _E , and the determination result in S6 becomes NO. Then, in S23, the pressure reducing mode or the slow pressure increasing mode is returned to the pre-control mode, the demagnetizing command is issued to the solenoid 32 in S24, the two-position valve 22 is returned to the pressure increasing position, and the elapsed time is elapsed in S25. The values of t _A and t _H are both reset to 0, and S4
Return to

As is clear from the above description, in the present embodiment, if the tendency of canceling the locking tendency of the wheels occurs due to the execution of the pressure reducing mode, the pressure reducing mode is switched to the pressure maintaining mode at that time. The situation where the braking force is insufficient due to the timing being too late does not occur.

Further, in this embodiment, the state in which the tendency of locking the wheels is not canceled by executing the pressure-holding mode, that is,
If the duty ratio D in the pressure-holding mode is not appropriate, the depressurization mode and the pressure-holding mode are repeatedly executed without shifting to the slow pressure-increasing mode, and corrected to a value appropriate for eliminating the lock tendency. Therefore, it is possible to avoid the situation where the wheels are locked early on a low μ road, for example.

Further, in the present embodiment, since the duty ratio D in the slow pressure increasing mode is corrected so that the duration T _A thereof in the slow pressure increasing mode becomes equal to the target time T _AO , the slow pressure increasing of the wheel cylinder 14 is performed. The gradient is properly controlled with high accuracy.

The technical idea used to properly control the gradient of the hydraulic pressure Pw of the wheel cylinder 14 in the slow pressure increasing mode, that is, the two-position valve so that the duration of each mode is constant.
The technical idea of controlling the duty ratio D of 22 was previously conceived by the present inventors. And
In order to properly control the hydraulic pressure gradient of the hydraulic pressure Pw of the wheel cylinder 14 in the pressure holding mode,
For example, it may be adopted as follows.

That is, the hydraulic pressure Pw of the wheel cylinder 14 is controlled in two modes, a pressure reducing mode and a slow pressure increasing mode, and the slow pressure increasing mode is divided into a first half portion and a second half portion, and the duty ratio D of the first half portion is changed. The value is set to be the same as that in the pressure maintaining mode in the above-described embodiment, the duty ratio D in the latter half is set to be the same as the original slow pressure increasing mode (slow pressure increasing mode in the first embodiment), and in each slow pressure increasing mode. The first half is executed for a predetermined fixed time. The operation in this case will be described below.

When the wheel tends to lock, the pressure reducing mode is executed, and when the tendency to eliminate the lock tends to occur, the slow pressure increasing mode is executed. On the high μ road, the lock tendency is canceled by executing the first half of the gentle pressure increasing mode, so that the wheel cylinder 14 is gradually increased in pressure when the latter half is executed. However, on the low μ road, the hydraulic pressure Pw of the wheel cylinder 14 increases due to the execution of the first half of the slow pressure increasing mode, and the wheel acceleration Gw decreases without canceling the lock tendency. The mode is canceled midway.
Only the case of the low μ road will be described below.

If the slow pressure increasing mode is stopped, the duty ratio D in the first half of the next slow pressure increasing mode is corrected so as to be increased, and then the pressure reducing mode is executed again.
If the lock tendency is canceled by this execution, the gentle pressure increasing mode is executed again. Here, it is assumed that the lock tendency is canceled by the execution of the first half of the slow pressure increasing mode. In this case, the second half of the slow boost mode is executed subsequently, and this execution causes the wheel cylinder 14
Is gradually increased. If the wheels tend to lock, the pressure reduction mode is executed. If the start time of this pressure reduction mode is appropriate and the pressure reduction mode ends in a short time,
It is estimated that the slip ratio is sufficiently small and the slow pressure increasing mode is executed. However, since the duty ratio D in the first half portion of the slow pressure increasing mode is set properly in the state where the slip ratio is not sufficiently small, the first half portion of the slow pressure increasing mode is in the stage where the slip ratio is sufficiently small. Is executed, the slow depressurization mode is substantially executed as indicated by the broken line in the graph of FIG. 1, and there is a problem that the braking force becomes insufficient.

On the other hand, in this embodiment, the duty ratio D is corrected when the slip ratio is large, that is, the duty ratio D in the pressure holding mode is corrected, and the duty ratio D is corrected when the slip ratio is sufficiently small. That is, since the correction of the duty ratio D in the slow pressure increasing mode is performed independently of each other, the wheel cylinder 14 can be gradually increased in pressure in accordance with the recovery of the wheel speed, and the braking distance can be reduced. The extension can be kept as small as possible.

In the embodiment described in detail above, by combining the pressure increasing position and the pressure reducing position, the hydraulic pressure Pw of the wheel cylinder 14 on the high μ road is increased.
The holding pressure mode set as should be kept constant corresponds to the third mode, and the rotation sensor 54 and the part of the controller 50 that controls the two-position valve 22 constitute an electric control device. The portion of the controller 50 that corrects the duty ratio D relating to the excitation of the solenoid 32 in the pressure-holding mode constitutes ratio reducing means.

In the present embodiment, one control cycle of the pressure-holding mode is set so that the pressure increasing position is switched to the first half and the pressure reducing position is switched to the latter half, but the pressure reducing position is switched to the first half and the pressure increasing position is switched to the second half. Good.

Further, in the present embodiment, the duty ratio D relating to the excitation of the solenoid 32 in the pressure maintaining mode is changed by changing the length of the pressure reducing time t _R while keeping the cycle time tc constant. However, even if the duty ratio D is changed by changing the pressure increasing time and the cycle time tc while keeping the pressure reducing time t _R constant, the pressure increasing time becomes constant. The value of the duty ratio D may be changed by changing the depressurization time t _R and the cycle time tc.

Further, in this embodiment, the hydraulic pressure Pw of the wheel cylinder 14 is 2
The present invention was applied to a so-called reflux type anti-lock type brake hydraulic pressure control device directly controlled by the position valve 22, but the two-position valve 22 and the wheel cylinder 14 are connected via the hydraulic pressure control valve. , A so-called positive displacement anti-lock brake hydraulic pressure control device that indirectly controls the hydraulic pressure Pw of the wheel cylinder 14 by controlling the hydraulic pressure of the hydraulic fluid of the hydraulic pressure control valve by the two-position valve 22. The invention can also be applied.

In the present embodiment, the wheel speed Vw is the reference speed Vo.
When the wheel acceleration Gw is less than or equal to the reference acceleration G ₁ or less, it is estimated that the wheel has a tendency to lock, and the wheel acceleration Gw changes from the decreasing tendency to the increasing tendency. estimated to be state eliminated tendency occurs tendency, through the wheel acceleration Gw is a positive reference acceleration G ₂ in increasing state of the wheel that the wheel acceleration Gw is passing through the reference acceleration G ₂ in reduced Although it is estimated that the lock tendency has been eliminated, the criterion can be changed as necessary.

For example, as shown in graphs (a) and (b) of FIG. 12, the wheel acceleration Gw exceeds a reference acceleration G ₃ smaller than the reference acceleration G ₁ when a predetermined time Ta has elapsed from the start time of the pressure reducing mode, and thereafter, It is estimated that the state in which the reference acceleration G ₃ has increased is the state in which the tendency to cancel the wheel lock tendency has occurred,
The state in which the wheel speed Vw becomes equal to or higher than the reference speed Vo can be estimated as the state in which the wheel lock tendency is eliminated.

Although the embodiments of the present invention have been described in detail with reference to the drawings, the present invention can be carried out in various modifications and improvements based on the knowledge of those skilled in the art.

[Brief description of drawings]

FIG. 1 is a graph for explaining how the wheel cylinder hydraulic pressure Pw is controlled by the anti-lock type brake hydraulic pressure control device of the hydraulic brake device for a four-wheel vehicle according to one embodiment of the present invention. FIG. 3 is a system diagram of the hydraulic brake device, FIGS. 3 to 8 are flow charts showing a control program stored in a computer of the brake hydraulic pressure control device, and FIGS. 9 (a) to 9 (c) are FIG. 10 is a graph for explaining how the wheel speed Vw, the wheel acceleration Gw, and the wheel cylinder fluid pressure Pw are controlled by the brake fluid pressure control device. FIG. 10 is a graph showing the duty ratio D corrected by the brake fluid pressure control device. graph for explaining how to be, Figure 11 is the elapsed time t _a and due to a gentle increase mode duration T _a and the slow increase mode in the above brake fluid pressure control device 6 is a graph for explaining a predetermined relationship between the tee ratio D and a correction amount ΔD.
FIGS. 12 (a) and 12 (b) are graphs for explaining one aspect of the start timing of various modes different from the above embodiment. FIGS. 13 (a) and 13 (b) are graphs for explaining how the wheel speed Vw and the wheel cylinder hydraulic pressure Pw on the high μ road in the device of the present invention are controlled, FIG. 14 (a) and FIG. 3B is a graph for explaining how the wheel speed Vw and the wheel cylinder hydraulic pressure Pw are controlled on a low μ road in the device of the present invention. 10: Master cylinder, 12: Brake pedal 14: Wheel cylinder, 22: 2-position valve 50: Controller, 54: Rotation sensor

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuhiko Kubota 1 Toyota Town, Toyota City, Aichi Prefecture, Toyota Motor Co., Ltd. (72) Inventor Munenori Ishizaka, 1 Toyota Town, Toyota City, Aichi Prefecture 72) Inventor Chisho Hamada 1 Toyota-cho, Toyota-shi, Aichi Toyota Motor Co., Ltd.

Claims (1)

(57) [Claims] 1. A wheel cylinder hydraulic pressure is increased by providing the hydraulic cylinder between a hydraulic pressure source and a reservoir and a wheel cylinder that operates a brake for suppressing rotation of a wheel, and by communicating the wheel cylinder with the hydraulic pressure source. The solenoid valve device that can switch between a pressure increasing position that allows this and a pressure reducing position that allows the wheel cylinder hydraulic pressure to decrease by disconnecting from the hydraulic pressure source and communicating with the reservoir, and the electromagnetic valve device The solenoid valve device is maintained in the pressure increasing position by alternately connecting (a) the pressure reducing mode for keeping the solenoid valve device at the pressure reducing position and (b) alternately switching the solenoid valve device between the pressure increasing position and the pressure reducing position. By gradually switching the solenoid valve device between the pressure increasing position and the pressure reducing position, and the slow pressure increasing mode in which the wheel cylinder hydraulic pressure is allowed to increase gradually. On a road surface having a large friction coefficient μ, the wheel cylinder hydraulic pressure is allowed to gradually decrease or increase as compared with the case of the pressure reducing mode or the slowly increasing pressure mode, or a third mode for keeping the wheel cylinder hydraulic pressure constant. It is possible to switch to the pressure reducing mode when the wheels tend to lock, and the third mode occurs when the tendency to eliminate the lock tends to occur. The electric control device becomes a slow pressure increasing mode when it is canceled and a pressure reducing mode when it is desired to be canceled, and the current third mode goes through the slow pressure increasing mode from the execution of the last third mode. If it is executed without any action, the ratio of the duration of the pressure increasing position to the duration of the pressure reducing position in the third mode this time is decreased from the previous value. Anti-lock type braking fluid pressure control apparatus which comprises a rate reduction unit.