JPH06104445B2 - Anti-skidding control device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an anti-skid control device for a vehicle, and more specifically,
In an electronically controlled anti-skid control device that switches the brake fluid pressure between pressure increase mode and pressure reduction mode based on the wheel rotation speed signal during sudden braking, when the rotation speed signal is disturbed during braking, the brake fluid pressure is changed. The present invention relates to an anti-skid control device that prevents the adjustment of (1) from not being performed properly.

[Prior Art] When a running vehicle is suddenly braked, the wheel speed normally decreases rapidly, but there is a limit to the friction between the road surface and the tires, which causes a locked state of the wheels, resulting in a skid phenomenon. Invite.

In order to prevent this skid phenomenon, the detection means for detecting the rotation speed of the wheel and the wheel acceleration / deceleration value and the virtual vehicle body speed value are calculated based on the detected wheel speed, and the data are used to determine the braking time. In the electronically controlled system, the brake fluid pressure is alternately increased, held or reduced so that the slip ratio has a high frictional force, and a control signal for outputting a control signal to that effect to an actuator for brake pressure reduction adjustment. Antiskid controls have been developed.

However, in such an anti-skid controller,
At the time of control, the detection means detects a detection signal including a fluctuation component due to resonance of the suspension system, a bad road surface, etc. As a result, it becomes difficult for the control means to perform good brake hydraulic pressure control. It is known that improvement is hindered.

That is, generally, in order to improve the responsiveness, if the decompression determination level is made sensitive to the slip ratio variation and the acceleration variation of the wheel, the control performance is improved, but the control performance is improved even on the bad road or the vibration of the suspension system. There is an adverse effect that the necessary decompression is performed and the braking distance is rather extended.

That is, as illustrated in FIG. 10 as its explanatory view,
When sudden braking is started, the wheel cylinder hydraulic pressure P _B exerting the braking force draws a curve as shown by the solid line in the figure, and then, as shown by the broken line in the figure, the wheel cylinder hydraulic pressure is high in the region of the vehicle. Although it is desirable for braking to perform control to the extent that locking is not achieved, due to resonance of the suspension or the like near the point a in the figure, road surface fluctuations, etc., the acceleration G reduces the brake fluid pressure in the depressurization mode, as indicated by b and c. It becomes smaller than the reference acceleration Gs to be switched to, and unnecessary depressurization mode is switched, and the control hydraulic pressure becomes the state shown by the solid line d, which is not desirable in terms of braking efficiency.

As a means for dealing with such a problem, for example, Japanese Patent Laid-Open No.
As disclosed in Japanese Patent Laid-Open No. 59-140154, it is known that the brake fluid pressure is switched to the depressurization mode only when the reference speed value Vs shown by the alternate long and short dash line in the figure is dropped.

[Problems to be Solved by the Invention] However, in the above conventional technique, the reference value Vs depending on the vehicle speed is used.
Since the switching control is performed by using, the responsiveness to the true depression must be sacrificed constantly, and the reference can be obtained based on all wheels and only the relative value between each wheel can be obtained. It cannot be perfect because it cannot be done.

The present invention has been made in order to solve the above-mentioned conventional problems, and unnecessary decompression of the actuator against disturbance of the output of the wheel speed detection sensor due to resonance of the suspension system in anti-skid control, vibration received from the road surface, etc. An object of the present invention is to provide an anti-skid control device that can prevent switching to a mode in advance and can perform pressure increase / decrease control promptly or without impairing responsiveness.

[Means for Solving the Problems] The anti-skid control device of the present invention made to achieve the above object detects the rotation speed of the wheel and calculates the wheel speed, as illustrated in FIG. Wheel speed calculating means A, wheel acceleration calculating means B for calculating wheel acceleration based on the wheel speed, and brake pressure adjusting means C for adjusting brake pressure acting on the wheel according to a control signal. An anti-skid comprising at least a control means D for judging a slip state of a wheel based on the wheel acceleration and outputting a control signal for reducing the brake pressure to the brake pressure adjusting means C according to the slip state. In the control device, the wheel acceleration exceeds a first predetermined value corresponding to a predetermined positive acceleration, and then a second smaller value than the first predetermined value.
Determination means E for determining whether or not the acceleration is less than or equal to a predetermined value, and the determination means E determines that the acceleration exceeds the first predetermined value and then becomes equal to or less than the second predetermined value. A period determination means F for determining whether or not a predetermined period has elapsed from the time, and until the period determination means F determines that the predetermined period has elapsed, it is difficult for the brake pressure of the wheels to be reduced. Further, the control means D is provided with a pressure reduction level lowering means G for lowering a judgment level for the wheel acceleration for outputting the pressure reduction control signal.

[Operation] With the above configuration, the slip state of the wheel is determined based on at least the wheel acceleration, and the brake pressure is adjusted according to the slip state.

Here, for example, vibration occurs in the suspension system when the wheel recovers from the slip state during anti-skid control, or the wheel acceleration fluctuates when the vehicle travels on a rough road. In the present invention, when the wheel acceleration undergoes a predetermined change (when it exceeds a first predetermined value that is a positive acceleration and then changes to a second predetermined value that is smaller than this), such vibration or It is considered that the fluctuation has occurred, and the judgment level for reducing the brake pressure is lowered. Therefore, it is possible to prevent the brake pressure from being erroneously reduced due to the above-mentioned vibration or fluctuation, and there is no problem that the braking distance of the vehicle is extended. Further, when the above-mentioned vibration or fluctuation does not occur, it is not necessary to lower the determination level, and therefore the responsiveness of the anti-skid control performed in the normal state is not sacrificed.

[Embodiment] Next, an anti-skid control device of the present invention will be described with reference to the drawings with reference to an embodiment.

FIG. 3 is a system diagram schematically showing the overall configuration of an anti-skid control device mounted on a rear-wheel drive vehicle.

In the figure, 1 to 4 represent respective wheels of a vehicle, 1 is a right front wheel, 2 is a left front wheel, 3 is a right rear wheel, and 4 is a left rear wheel. Reference numerals 5 to 7 are electromagnetic pickup type or photoelectric conversion type vehicle speed sensors for detecting wheel speeds. Of these, 5 is mounted near the right front wheel 1 and generates a signal in response to rotation of the right front wheel 1. The right front wheel vehicle speed sensor, 6 is mounted near the left front wheel 2, and generates a signal in response to the rotation of the left front wheel 2, and 7 is a power source for driving the right rear wheel 3 and the left rear wheel 4. Is a rear wheel vehicle speed sensor which is attached to the propeller shaft 8 for transmitting the signal, and which generates a signal according to the rotation of the propeller shaft 8 corresponding to the average rotational speed of the right rear wheel 3 and the left rear wheel 4. Reference numerals 9 to 12 are hydraulic braking devices, respectively, in which the hydraulic braking device 9 is on the right front wheel 1, the decompression braking device 10 is on the left front wheel 2, the hydraulic braking device 11 is on the right rear wheel, and the hydraulic braking device 12 is on the left. Each of the rear wheels 4 is arranged. 13 is the brake pedal, 14
Is a stop switch for detecting when braking or not braking according to the state of the brake pedal 13, 15 is a hydraulic cylinder that generates brake hydraulic pressure when the brake pedal 13 is depressed, and 17 to 19 are hydraulic cylinders. An actuator that adjusts the hydraulic pressure from 15 according to the output from an electronic control circuit 26 described later and sends it to the hydraulic braking devices 9 to 12,
17 is a right front wheel actuator corresponding to the hydraulic brake device 9 for the right front wheel 1, 18 is a left front wheel actuator corresponding to the hydraulic brake device 10 for the left front wheel 2, 19 is a hydraulic brake device 11 for the rear wheels 3, 4, It is a rear wheel actuator corresponding to 12. 20 to 23 are hydraulic lines for guiding the adjusted hydraulic pressure from the actuators 17 to 19 to the hydraulic braking devices 9 to 12, 20 of which is the hydraulic braking device 9 for the right front wheel actuator 17 and the right front wheel 1. And 21 are hydraulic lines, 21 is a hydraulic line provided between the left front wheel actuator 18 and the hydraulic brake device 10 of the left front wheel 2, and 22 is a rear wheel actuator 19 and the right rear wheel 3. A hydraulic line provided between the hydraulic brake device 11 and 23 is a hydraulic line provided between the rear wheel actuator 19 and the hydraulic brake device 12 of the left rear wheel 4. 24 is a main relay that switches the connection between the electromagnetic solenoids of the actuators 17 to 19 and the power supply source according to the output of the electronic control circuit 26; 25 is an anti-skid control device when the electromagnetic solenoid is disconnected or the stop switch 14 is disconnected. An indicator lamp for notifying the driver that an abnormality has occurred in the system according to the output of the electronic control circuit 26 when a failure occurs in the vehicle. 26
Is an electronic control circuit that receives signals from the vehicle speed sensors 5 to 7 and the stop switch 14 and performs arithmetic processing for anti-skid control and controls the actuators 17 to 19, the main relay 24 and the indicator lamp 25. Represents what produces an output.

Above right front wheel actuator 17, left front wheel actuator 1
As shown in FIG. 4, the rear wheel actuator 8 and the rear wheel actuator 19 respectively hold an electromagnetic solenoid portion 27 for increasing / decreasing, holding or switching the hydraulic pressure, and temporarily storing the brake hydraulic fluid when the brake hydraulic pressure is reduced. After that, it is equipped with a reservoir and a motor unit 28 that returns to the master cylinder side, and the hydraulic pressure output from each actuator is supplied to the brake wheel cylinder of each hydraulic brake device via each hydraulic pressure line. It is transmitted and brakes each wheel. The electromagnetic solenoid for increase / decrease control is designed to reduce the hydraulic pressure when energized, for example.

The electronic control circuit 26 has a circuit configuration as shown in FIG. 5. Reference numerals 30 to 32 in the drawing are waveform shaping amplifier circuits, respectively. The waveform shaping amplifier circuit 30 processes the signal of the vehicle speed sensor 5 by the microcomputer 35. And the other waveform shaping amplifier circuits 31 and 32 are also configured to have similar pulse signals. 33 is a buffer circuit electrically connected to the stop switch 14, 34 is a microcomputer 35 when the ignition switch 41 is turned on.
A power supply circuit for supplying a constant voltage to the CPU 35, the CPU 35a,
It represents a microcomputer including a ROM 35b, a RAM 35c, an I / O circuit 35d, and the like. Reference numerals 36 to 40 denote drive circuits that output according to control signals from the microcomputer 35. Of these, 36 is a drive circuit for the front right wheel actuator for driving the electromagnetic solenoid of the front right wheel actuator 17, and 37 is a front left wheel. Left front wheel actuator drive circuit for driving the electromagnetic solenoid of the actuator 18, 38 is a rear wheel actuator drive circuit for driving the electromagnetic solenoid of the rear wheel actuator 19, 39 is a coil 24b of the main relay 24 having a normally open contact 24a Is a main relay drive circuit for energizing the switch to turn on the normally open contact 24a, and 40 is an indicator lamp drive circuit for lighting the indicator lamp 25.

Next, the processing and operation of the anti-skid control device thus configured will be described.

When the ignition switch 41 is turned on, the power circuit 34
The constant voltage is applied to the microcomputer 35 and the like, and the CPU 35a of the microcomputer 35 starts execution of arithmetic processing according to a program preset in the ROM 35b.

FIG. 6 is a schematic flow chart showing the main part of this arithmetic processing. In this processing, first, at the start of processing, initialization processing for subsequent processing is performed in step 101, for example, resetting of various flags described later. And so on.

After that, depending on the determination result of step 107, a series of processes including step 102 and step 103, step 104, step 105, step 106, and step 107, or step 102, step 103, and step 103
A series of processes including 104, step 105, step 106, step 107, step 108, and step 109 is repeatedly executed until the ignition switch 41 is turned off.

In the series of processes, the control permission process and the control start determination process are executed in step 102. That is, when the estimated vehicle body speed is calculated in the estimated vehicle body speed calculation processing step 104, which will be described later, the permission flag Fact for instructing the selection change of the wheel speed which is one of the plurality of estimated vehicle body speed candidates is set. While performing the reset process,
Instructions for changing the processing content of the traveling road discrimination processing step 103 described later, instructions for permitting or prohibiting execution of the actuate pattern selection step 206 in the timer interrupt routine, which will be described later, and criteria to be calculated in the reference speed calculation processing step 105, which will be described later. Performs set / reset processing of start flag Fsta for instructing speed selection.

Next, at step 103, the type of road on which the vehicle is currently traveling, the friction coefficient based on the road surface condition, and the unevenness of the road surface are estimated, and the road is a high μ road such as dry concrete, wet asphalt. Intermediate μ road, such as
Or it is a low μ road typified by an icy road, a so-called good road where the degree of unevenness is extremely gentle, a so-called bad road where the degree of unevenness is severe to a certain extent, or a degree of unevenness is extremely severe and it interferes with anti-skid control. A traveling road discrimination process is executed to discriminate the property of the road itself according to a specific condition such as an easy so-called bad road (including a wavy road).
The content of this determination processing will be described in brief. Corresponding wheel speed Vw data calculated based on the signals from the individual vehicle speed sensors 5, 6, 7 (however, for the wheel speed of the rear wheel, the right rear wheel 3 And the actual wheel speed, and the average wheel speed of the left rear wheel 4 and the actual wheel speed.), Wheel acceleration w data, reference acceleration data of a plurality of levels stored in advance in the ROM 35b, and a reference. Based on the plurality of reference speed data calculated in the speed calculation processing step 105, the processing corresponding to the size comparison by various combinations of the wheel speed, the wheel acceleration, and the reference speed, the reference acceleration is performed for each individual wheel. In addition, it increments according to the processing result,
The value of the decremented counter is compared with a preset value, and the road is finally discriminated based on the comparison result.

Next, in step 104, the estimated vehicle body speed calculation processing is executed. The outline of this process is as follows. When creating the estimated vehicle speed data, three candidate speeds, that is, calculated wheel speeds and running accelerations that can be obtained from the actual vehicle running state (including braking) are included. 2 based on the upper and lower limits, estimated vehicle speed calculated by the previous estimated vehicle speed calculation process, etc.
An intermediate value of the speeds composed of the first and second estimated vehicle body speeds calculated by each of the three arithmetic expressions is determined as the estimated vehicle body speed. In this case, the wheel speed, which is one of the candidate speeds, has an intermediate value among the three wheel speeds during the period in which the permission flag Fact as described above in the control permission / start determination processing step 102 is in the reset state. The wheel speed to be taken is selected as a candidate, while the wheel speed that takes the maximum value is selected as a candidate while the permission flag Fact is in the set state.

Next, in step 105, a reference speed calculation process is executed.
The outline of this processing content is that the control start determination reference speed is calculated until the start flag Fsta is reset from the reset state to the set state, that is, until the pressure reduction is started (also referred to as control start), and the start flag Fsta is calculated. After setting, that is, after starting the control, the road speed noise (vehicle body vibration) countermeasure reference speed for preventing malfunction of the actuators 17 to 19 due to road surface noise, electric noise, etc., and pressure reduction that is one reference for starting pressure reduction At least the estimated vehicle body speed should be the data corresponding to the determination reference speed, the intermediate μ determination reference speed that is the reference for determining the intermediate μ road, and the low μ determination reference speed that is the reference for determining the low μ road. It is created from a predetermined arithmetic expression including. Regarding the control start determination reference speed, in particular, in order to prevent undesired depressurization of at least one of the actuators 17 to 19 due to a gentle brake on a bad road, the traveling road determination processing step 103 The value of the subtracted number in the arithmetic expression is made variable according to the property of the road itself discriminated in. Also for the road noise (vehicle body vibration) countermeasure reference speed and the decompression determination reference speed, the values of the subtracted numbers in the corresponding arithmetic expressions are variable, and the decompression acceleration reference is switched according to the condition of the bad road. Thus, it is possible to prevent excessive decompression due to overcontrol.

Next, in step 106, a system abnormality check is executed. In this process, the data stored in the ROM 35b corresponding to the operating state of the system element at the time of normal system operation and the data representing the operating state of the system element taken at the time of the process are compared and examined, and the system abnormality is detected. If it is determined that the abnormality flag is set, the abnormality flag indicating the system operation state is set. On the other hand, if it is determined that there is no abnormality, the abnormality flag is maintained or inverted to the reset state.

Next, at step 107, it is judged whether or not there is a system abnormality by looking at the abnormality flag. If it is determined that the abnormality flag is not set, that is, if the system is operating normally, the process proceeds to the control permission / start determination processing step 102 as described above. On the other hand, if it is determined that the abnormality flag is set, that is, if the system has an abnormality or is operating abnormally, step 108 and step 109 are sequentially executed, and then the control permission and start determination are performed. Proceed to processing step 102.

Step 108 is a step for notifying the driver that an abnormality has occurred in the system and confirming that the anti-skid control is not effective.
In 8, the control signal for turning on the indicator lamp is output to the indicator lamp driving circuit 40 only when it is first judged that the system abnormality has occurred by executing the judgment step 107 as described above. The indicator lamp drive circuit 40, to which this control signal is input, latches this control signal so that the indicator lamp 25 keeps lighting.
In step 108, after the control signal is output as described above, a process of outputting a control signal for turning on the indicator lamp 25 to the indicator lamp drive circuit 40 when the system automatically returns to the normal operation state is also included. You may make it execute.

Step 109 is a step for performing fail-safe processing at the time of abnormal system operation. In this step 109, the increase / decrease control electromagnetic solenoids of the three actuators 17, 18 and 19 are respectively operated at the respective driving states at that time point. Outputs a control signal for cutting off energization to the coil 24b of the main relay 24 in order to switch to the non-anti-skid control mode, i.e., the normal mode in which braking is performed by the brake fluid pressure according to the depression of the brake pedal 13 regardless of the situation. Processing is performed.
When the coil 24b is no longer energized, the normally open contact 24a that has been closed until then is switched to the normal open state, whereby the power supply to the electromagnetic solenoid in each of the actuators 17, 18, 19 is cut off, and at least Brake braking is normally performed until the system abnormality is cleared. In this system fail-safe processing step 109, the power supply is cut off as described above to further improve safety, and a control signal for turning off the electromagnetic solenoid is output to each actuator drive circuit 36, 37, 38. The processing to be performed may be executed together.

FIG. 7 is a flowchart schematically showing a timer interrupt routine which is started in a predetermined cycle during the execution of the main arithmetic processing as described above with reference to FIG.

In this timer interrupt routine, first, step 201
At, the process of calculating the wheel speed for each wheel is executed.
In this wheel speed calculation step 201, a predetermined value including a difference between the count value of the vehicle speed pulse in the current process execution and the count value of the vehicle speed pulse in the previous process execution, a time interval, and a constant. Is calculated, and if necessary, filter processing, that is, processing for averaging wheel speeds obtained by a plurality of successive arithmetic expression calculations is also performed. The counting of the vehicle speed pulse is executed in a vehicle speed interrupt routine described later.

Next, at step 202, a process of calculating the wheel acceleration for each wheel is executed. In this wheel acceleration calculation step 202, the wheel speed calculated by executing the wheel speed calculation step 201 and the previous wheel speed calculation step 201
The speed difference with the wheel speed calculated by, the time, and a predetermined arithmetic expression including a constant, as well as, if necessary, substantially the same processing as the filter device as described above is performed together with the wheel speed, The pulsating component of wheel acceleration is damped.

Next, at step 203, the permission flag F described above with reference to FIG.
It is determined whether act is set and permission flag Fac
If t is not set, that is, stop switch 14
If is not turned on, the process proceeds to step 204, while if the permission flag Fact is set, the route including steps 205 to 208 is sequentially executed.

In the above step 204, all actuators 17, 18, at the time of the first processing after the reset of the permission flag Fact,
In order to return 19 to the non-operating state, a process for outputting a control signal therefor to each of the actuator drive circuits 36, 37, 38 is performed. Each of the actuator drive circuits 36, 37, and 38 to which this control signal is input holds the state corresponding to this control signal, stops energizing the electromagnetic solenoid of the corresponding actuator, and the brake hydraulic pressure control is performed in the normal mode. To do so. Note that the permission flag
The output processing as described above may not be performed in the second and subsequent processing after the Fact reset. This output step
After 204, the process of FIG. 6 during which the process is interrupted is normally executed.

On the other hand, step 20 executed when the permission flag Fact is set
5, the wheel speeds and the wheel accelerations calculated in the wheel speed calculation step 201 and the wheel acceleration calculation step 202, and the various reference values calculated in the reference speed calculation processing step 105 in FIG. A process of comparing the speed and various preset reference accelerations is executed.

Next, in step 206, a process of selecting a drive pattern of the increase / hold / reduction control electromagnetic solenoid based on the result obtained in the comparison step 205 is executed. Various drive patterns corresponding to each solenoid are ROM3
Pre-stored in 5b.

Next, at step 207, the continuous time of the pressure increasing mode and the pressure reducing mode is monitored, and if the pressure reducing mode continues for a time longer than the expected time from normal anti-skid control, the permission flag is set. Even if Fact is set, it is judged that the system is abnormal, and in the next step 208, all the actuators 17, 18 and 19 are forced to be in the non-actuated state.
The process of changing the drive pattern selected in 6 is executed.

Next, at step 208, the control signal corresponding to the final drive pattern is sent to the corresponding actuator drive circuits 36, 3
The process of outputting to 7 and 38 is executed. The actuator drive circuits 36, 37, 38 to which this control signal is input respectively respond to the corresponding actuator 1 by the control signal.
Performs drive output that determines the drive state of 7, 18, and 19. After passing through this output step 208, normally, the sixth process during the process interruption is performed.
The processing shown in the figure continues to be executed.

FIG. 8 shows a vehicle speed interrupt routine that is executed in a one-to-one correspondence with each of the vehicle speed sensors 5, 6, and 7. This vehicle speed interrupt routine sends a vehicle speed pulse through the vehicle speed sensor and the waveform shaping amplifier circuit. When input to the microcomputer 35, the processing of FIG. 7 described above is interrupted and execution is started. In this case, needless to say, the three vehicle speed interrupt routines are given priorities in consideration of the case where two or more vehicle speed pulses simultaneously generate an interrupt instruction.

In this vehicle speed interrupt routine, step 301 is executed to count vehicle speed pulses. The count value is used when the wheel speed calculation step 201 is executed in the timer interrupt routine as described above.

The overall configuration and processing operation of the present anti-skid control device have been schematically described above. Next, the main processing according to the present invention will be described with reference to FIG.

The flowchart shown in FIG. 9 represents a part of the processing executed in step 205 in FIG. 7 described above.

First, after initial setting is executed in step 400, the acceleration G is detected based on the detection signals from the vehicle speed sensors 5 and 6 (Fig. 3).
(See FIG. 2) is calculated (step 402). In the next step 404, it is determined whether or not the acceleration G is equal to or higher than the vibration detection reference value GV, and when it is determined to be equal to or higher than the reference value GV, a flag indicating this is set (step 40).
6).

At the next step 408, it is judged whether the signal for switching the brake fluid pressure to the pressure reducing mode is ON, that is, the first reference value.
It is determined whether G1 or the second reference value G2 corresponding to the negative acceleration whose absolute value is larger than the first reference value G1 is set. When it is determined in step 408 that the value is at the first reference value G1, the determination of whether or not the acceleration is zero and the determination of whether or not the flag of step 406 is set are executed,
(Steps 410, 412) If both are "YES", the switching signal for changing to the second reference value G2 is output, and then the flag is reset.

That is, when the first reference value G1 is set and the acceleration exceeds the vibration detection reference value GV and further goes from zero to a negative value, it is switched to the second reference value G2. As a result, even if the pulsational acceleration G is detected because the reference level is lowered, the value below the second reference value G2 is not easily reached, so that unnecessary switching to the pressure reduction mode is prevented.

On the other hand, the restoration from the second reference value G2 to the first reference value G1 is performed in steps 408 and 420-432. That is, if it is determined in step 408 that the switching signal is in the ON state, then in step 420, determination of the flag is performed. Here, since the flag is reset in step 416 after the switching signal has already been turned on, it is determined to be "NO", the count is incremented in step 428, and then the second reference value G2 is set in step 430. It is determined whether or not T1 time has elapsed after switching. If "YES" in this step 430, the switching signal is turned off, and the second reference value G2 is restored to the first reference value G1.

As described above, the switching signal is output so as to return to the original when the predetermined time T1 has passed, but as a compensating means when detecting an acceleration exceeding the vibration detection reference value GV during switching, Steps 420-426 are provided.

That is, when the switching signal is turned on and the flag is set exceeding the vibration detection reference value GV (step 40
4,406), this flag is determined in step 420, and when the acceleration reaches zero, the counter is cleared,
From this point, the time of the switching signal is newly set. Then, the flag is reset to prepare for the next vibration detection (step 426).

Therefore, with the above configuration, when the pulsating acceleration that adversely affects the anti-skid control is detected, the reference value for switching to the pressure reducing mode is lowered, so that it is possible to prevent unnecessary switching to the pressure reducing mode.

Next, the operation of the above embodiment will be described with reference to FIG.

As shown in FIG. 2, when the braking of the vehicle is started by abruptly depressing the brake pedal at time t1, the hydraulic pressure of the actuators 17 to 19 increases and the vehicle speed (wheel speed) V is increased.
Is reduced. This deceleration is detected by the vehicle speed sensors 5 to 7 and input to the electronic control circuit 26. The electronic control circuit 26 calculates the acceleration G from the vehicle speed V. Then, the electronic control circuit 26 determines that the acceleration G becomes lower than the first reference value G1 and then switches the actuators 17 to 19 to the pressure reducing mode via the holding mode (time t2). As a result, the vehicle speed V increases. The first reference value G1 is a reference value for pressure reduction and a reference value for pressure increase. Therefore, when the acceleration G becomes G1 or less and then exceeds G1 again, pressure increase is executed.

On the other hand, after the acceleration G further increases and exceeds the positive first value GV, the acceleration G starts to decrease and then becomes the second reference value OG.
When = 0 or less (time t3), the reference value for increase / decrease is decreased to the second reference value G2. The state of switching to G2 is continued for a certain period of time and then returned to G1.

The acceleration G fluctuates beyond GV which is the vibration detection reference value or below OG like after time t2 in Fig. 2 because the suspension system resonance or the road surface after the wheel recovers from the lock tendency. This is because the wheel rotation speed vibration with a positive acceleration is generated depending on the state of.

In the present embodiment, as described above, when it is considered that such vibration is occurring, the reference value for switching the increase / decrease mode is set.
Since it is changed to G2 <G1 instead of G1, it becomes difficult to shift to the decompression mode. That is, at time t4, the mode switching reference is
If it is still G1, it will be switched to the decompression mode, but in the present embodiment, it will be switched to G2, so it cannot be switched to the decompression mode at time t4.

This eliminates unnecessary switching to the decompression mode even when the acceleration associated with the vibration of the suspension system, the vibration of the vehicle speed sensor, or the acceleration pulsating due to the vibration received from the road surface is detected. High efficiency,
In addition, highly reliable anti-skid control can be performed.

As shown in FIG. 2, when the acceleration G crosses the first reference value G1 at time t2, a hysteresis is provided to the first reference value G1 to prevent chattering.

[Advantages of the Invention] As described above, according to the present invention, the vehicle speed increases due to the vibration caused by the reaction force from the road surface to the wheels generated by the increase or decrease of the brake fluid pressure during the anti-skid control and the resonance of the suspension system. Even if the pulsating acceleration is detected by receiving the vibration of the detecting means, it is possible to prevent the unnecessary reduction of the brake fluid pressure, and the responsiveness in the normal state is not deteriorated.

[Brief description of drawings]

FIG. 1 is a block diagram showing the structure of the present invention, FIG. 2 is an explanatory view for explaining the operation of the present invention, FIGS. 3 to 9 show an embodiment of the present invention, and FIG. FIG. 4 is a system diagram showing the overall configuration of the example anti-skid control device.
5 is a block diagram showing the main configuration of the actuators 17 to 19, FIG. 5 is a block diagram showing the circuit configuration of the electronic control circuit 26 in FIG. 3, and FIG. 6 is a main part of the microcomputer 35 shown in FIG. FIG. 7 is a flow chart showing a timer interrupt routine, FIG. 8 is a flow chart showing a vehicle speed interruption routine, and FIG. 9 is a flow chart showing main arithmetic processing according to the present invention. The figure is an explanatory view for explaining the operation of the conventional anti-skid control device. A: Wheel speed calculation means B: Wheel acceleration calculation means C: Brake pressure adjustment means D: Control means E: Judgment means F: Period judgment means G: Reduced pressure level lowering means

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shoichi Masaki 1-1, Showa-cho, Kariya city, Aichi Prefecture Nihon Denso Co., Ltd. (72) Inventor Satoshi Hirano 1-1-1, Showa-cho, Kariya city, Aichi prefecture Nidec Corporation Co., Ltd. (72) Inventor Ken Asami, 1 Toyota Town, Toyota City, Aichi Prefecture, Toyota Motor Corporation (72) Inventor, Kazunori Sakai, 1 Toyota Town, Toyota City, Aichi Prefecture, Toyota Motor Corporation (56) References JP-A-60-107440 (JP, A)

Claims (1)

[Claims] 1. A wheel speed calculation means for detecting a wheel rotation speed to calculate a wheel speed, a wheel acceleration calculation means for calculating a wheel acceleration based on the wheel speed, and a wheel speed calculation means according to a control signal. Brake pressure adjusting means for adjusting the brake pressure acting on the wheels, and a control signal for determining the slip state of the wheels based on at least the wheel acceleration and reducing the brake pressure according to the slip state. In the anti-skid control device including a control unit for outputting to the adjusting unit, the wheel acceleration exceeds a first predetermined value corresponding to a predetermined positive acceleration, and then a second smaller value than the first predetermined value.
From the time when the acceleration exceeds the first predetermined value and thereafter becomes equal to or less than the second predetermined value. A period determining means for determining whether or not a predetermined period has elapsed, and the control means for preventing the brake pressure of the wheels from being easily reduced until the period determining means determines that the predetermined period has elapsed. 2. An anti-skid control device, comprising: a pressure reduction level lowering unit for lowering a determination level for the wheel acceleration for outputting the pressure reduction control signal.