JPH04243656A - Slip control device for automobile - Google Patents

Abstract

PURPOSE:To improve the safety at the time of failure of the liquid pressure of a hydraulic brake while performing brake control of excellent responsiveness by providing a second brake means obtaining brake force through a piezoelectric element as drive source in addition to a first brake means obtaining brake force using brake pressure. CONSTITUTION:A hydraulic brake serving as a first brake means is provided with a first friction pad 31 and a first piston 33 fittingly inserted into a wheel cylinder 32 formed at a caliper 15, and a brake pipeline 25 is connected to a liquid chamber 34. A second brake means 27 is provided parallel to the first friction pad 31 and the first piston 33 and elongated laterally by applying voltage to a piezoelectric element 36 so as to move a second piston 35 to the left and thereby to press a second friction pad 37 to a disk 14. When liquid pressure failure is generated to a brake liquid pressure system, the piezoelectric element 36 for a wheel of the liquid pressure failure is controlled in such a way as to obtain brake force corresponding to the liquid pressure of the normal braking liquid pressure system.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a slip control device for an automobile.

0002

[Prior Art] Modern automobiles have anti-lock brake control (hereinafter referred to as ABS) that performs slip control.
Many vehicles now perform traction control (hereinafter referred to as TRC control) or traction control (hereinafter referred to as TRC control). This ABS
The control is to prevent the wheels from locking against the road surface due to excessive braking force when applying braking force to the wheels, and when the wheel speed is lower than the vehicle body speed. This is slip control when the value is also small. On the other hand, TRC control prevents the drive wheels from slipping against the road surface due to too large a torque applied to the drive wheels when starting or accelerating. Slip control is performed when is greater than the vehicle speed. And T
In RC control, a braking force is generally applied to the drive wheels in order to reduce excessive torque applied to the drive wheels.

[0003] Automobile brake devices for slowing down or stopping the automobile are generally of the hydraulic type. That is, when the driver presses the brake pedal with his/her foot, brake fluid pressure is generated in the master cylinder as a brake fluid pressure generation source, and this brake fluid pressure is applied to each wheel. Braking force is transmitted to wheel cylinders such as disc brakes and drum brakes, and applies braking force to each wheel. Such a hydraulic brake is not only convenient for obtaining sufficient braking force, but is also advantageous in terms of reliability, brake feeling, etc. For safety reasons, the brake hydraulic pressure system, that is, the brake hydraulic pressure piping system, is usually divided into a plurality of mutually independent systems, such as so-called X piping.

On the other hand, the conventional slip control device is attached to the above-mentioned hydraulic brake, but requires a separate pump for generating brake hydraulic pressure as an attached device. That is, in TRC control, which is based on the assumption that the driver is not applying the brakes, the brake fluid pressure itself is generated, and in ABS control, the brake fluid pressure is first reduced and then the brake fluid pressure is increased again. As mentioned above, a pump was required to increase the pressure. However, the need for a separate pump for slip control means increased weight and
This would result in increased costs and the complexity of the brake fluid system.

[0005] For this reason, recently, AB
It has been proposed to use a piezoelectric element as an actuator for S control (see Japanese Patent Laid-Open No. 63-266266). The system described in this publication incorporates a piezoelectric element into the caliper of a disc brake, and controls the duty of this piezoelectric element to generate a force corresponding to the mechanical displacement of the piezoelectric element, which is obtained according to the duty ratio. This presses the friction pad. In other words, all the brakes used to slow down or stop the car are electronically controlled, and when the driver depresses the brake pedal, an electrical signal corresponding to this depressing is extracted as a brake request signal. Accordingly, a control signal (duty ratio) for the piezoelectric element is determined so that a braking force corresponding to the brake request signal can be obtained. This piezoelectric element is extremely excellent in that its mechanical displacement changes extremely quickly with respect to voltage changes and satisfies responsiveness.

[0006]

[Problem to be Solved by the Invention] However, in the method described in the above publication, the brake pedal and the friction pad are only electrically coupled via a piezoelectric element, which poses a major problem in terms of reliability. . In particular, since the brake is an important safety component, if it is electronically controlled as described above, a fail-safe is definitely required, but setting it is difficult. In addition to this, piezoelectric elements are used to obtain braking force not only during slip control but also during normal braking. Not only is it difficult to obtain force, but it is also difficult to apply brake reaction force to the driver, and even if this point could be satisfied, the overall control would be extremely complicated. Moreover, since the piezoelectric element has the characteristic that its mechanical displacement is small,
It is practically difficult to make adjustments over the entire range of changes in braking force required of ordinary hydraulic brakes.

The present invention has been made in consideration of the above-mentioned circumstances, and while obtaining the advantages of a hydraulic brake, it also achieves responsive slip control with an extremely simple configuration without using a separate pump for slip control. It is an object of the present invention to provide a slip control device for a motor vehicle, which is capable of accomplishing the following and also dramatically increases safety when a hydraulic pressure failure occurs in a brake hydraulic system.

[0008]

[Structure of the Invention] In order to achieve the above object, the present invention has the following structure. In other words, brake fluid pressure is generated by the driver's manual operation.
a brake fluid pressure generating means, and a first brake means provided for each wheel and configured to perform braking in response to the brake fluid pressure generated by the brake fluid pressure generating means, independently of each other. a plurality of brake hydraulic pressure systems for supplying the brake hydraulic pressure generated by the brake hydraulic pressure generating means to any of the first brake means; a second brake means that is configured independently of the pressure system and generates braking force using a piezoelectric element as a drive source; and a first control means that controls the piezoelectric element to prevent the wheels from slipping on the road surface. , a failure detection means for detecting a failure of the hydraulic pressure in the brake hydraulic system, a hydraulic pressure detection means for detecting the hydraulic pressure in the brake hydraulic system, and the failure detection means. When a hydraulic pressure failure in the brake hydraulic system is detected, the piezoelectric element for the second braking means for the wheel of the brake hydraulic system in which the hydraulic pressure has failed; and second control means for outputting a control signal corresponding to the hydraulic pressure of the brake hydraulic system in which the hydraulic pressure detected by the hydraulic pressure detection means has not failed.

[0009]

[Effects of the Invention] According to the present invention, slip control with extremely excellent responsiveness can be performed using piezoelectric elements. The braking force adjustment range by the piezoelectric element is reduced by the amount of braking force obtained by the hydraulic brake, so it can be small, and the small mechanical displacement of the piezoelectric element is not a problem. It becomes something that cannot be. Of course, the advantage of hydraulic brakes is that it is easy to obtain a braking force that corresponds to the driver's delicate braking operations, and it is also possible to obtain an appropriate braking reaction force that corresponds to the driver's subtle braking operations. can be given to the driver.

Furthermore, since the first brake means using hydraulic pressure and the second brake means using piezoelectric elements are provided independently of each other, the second brake means using piezoelectric elements
Even if some abnormality occurs in the hydraulic
This has the advantage of not affecting the function of the brake means in any way, which is preferable in ensuring the original function of the brake, which is to stop or decelerate the automobile.

Furthermore, since the brake hydraulic pressure system is configured as a plurality of systems, safety is essentially enhanced, and in addition, when the hydraulic pressure of the brake hydraulic system fails, Since the braking force for this failed wheel can be obtained using a piezoelectric element, safety is further dramatically improved. Furthermore, the braking force generated by the piezoelectric element for the wheel where the hydraulic pressure has failed is set to an appropriate level corresponding to the normal hydraulic pressure in the brake hydraulic system, so the braking force distribution to each wheel can be optimized. But it will be beneficial.

[0012] The hydraulic pressure for setting the control signal to the piezoelectric element at the time of hydraulic pressure failure, that is, the hydraulic pressure of the normal brake hydraulic pressure system selected for setting the control signal, is the pressure between the left and right front wheels. It is preferable to select between the left and right rear wheels, or between the left and right rear wheels, in order to more fully satisfy the need for appropriate braking force distribution to each wheel. More specifically, for example, when focusing on the front wheels, if the brake fluid pressure of one of the left and right front wheels fails, the piezoelectric element is controlled based on the brake fluid pressure of the other front left and right wheels. Preferably, a signal is set. Such a setting is based on the premise that the brake hydraulic pressures are made independent between the left and right front wheels, and the brake hydraulic pressure systems are made independent between the left and right rear wheels, for example by so-called X piping. When the brake hydraulic system fails, the voltage that must be applied to the piezoelectric element becomes extremely large. From this point of view, as a voltage circuit for the piezoelectric element, in addition to the first voltage circuit, which is a low voltage circuit necessary for slip control,
It is preferable to separately set up a high voltage circuit for use in the event of a hydraulic pressure failure. Preferred embodiments of the invention and its advantages will become apparent from the following description of the examples.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below with reference to the accompanying drawings. In addition, in the following explanation, "FR" is used for the right front wheel.
The front left wheel is distinguished by the "FL" identification code, the right rear wheel by the "RR" identification code, and the left rear wheel by the "RL" identification code. If there is no particular need to distinguish between such items, this identification code will not be used in the explanation. Figure 1 In Figure 1, 1FR is the right front wheel, 1FL is the left front wheel, 1R
R is the right rear wheel, and 1RL is the left rear wheel. Further, 2 is an engine, and the torque generated by the engine 2 is transmitted to the clutch 3,
After being transmitted to the transmission 4, propeller shaft 5, and actuating device 6, it is transmitted to the right rear wheel 1RR via the drive shaft 7R, and to the left rear wheel 1RL via the drive shaft 7L. In the intake passage 8 of the engine 2, a main throttle valve 10 that opens and closes in response to depression of the accelerator pedal 9 is disposed, and a sub-throttle valve 11 is disposed downstream of the main throttle valve 10. There is. This sub-throttle valve 11 is driven to open and close by an electromagnetic actuator 12, and is normally kept fully open, but is driven in the closing direction during TRC control to reduce the torque generated by the engine 2.

Each of the wheels 1FR to 1RL is provided with a brake device 13FR to 13RL, respectively. The brake devices 13FR to 13RL include a disc 14 that rotates integrally with the wheel, and a caliper 15 that includes a wheel cylinder. Reference numeral 21 denotes a master cylinder as a means for generating brake fluid pressure, in which the force of depression of the brake pedal 22 by the driver is inputted via a known booster 23, and the brake fluid is applied in accordance with this depression force. pressure is generated. This master cylinder 21 has two discharge ports 21a and 21
It is said to be a tandem type with b. One outlet 2
Brake pipe 24A extending from 1a is branched into two in the middle, one branch pipe 25FL is connected to the brake device 13FL (wheel cylinder) for the left front wheel, and the other branch pipe 25RR is connected to the front left wheel brake device 13FL. It is connected to the rear wheel brake device 13RR (wheel cylinder). The other outlet 2
Brake pipe 24B extending from 1b is branched into two in the middle, one branch pipe 25FR is connected to the brake device 13FR (wheel cylinder) for the right front wheel, and the other branch pipe 25RL is connected to the left front wheel brake device 13FR. It is connected to the rear wheel brake device 13RL (wheel cylinder). In this way, the branch pipes 24A and 24B constitute mutually independent brake hydraulic pressure systems (two systems).

Control valves 26FR, 26FL, 26RR, or 26R are connected to the branch pipes 25FR to 25RL. In addition, for the rear wheel pipes 25RR and 25RL,
P valves (proportioning valves) 28RR and 28RL are connected to the upstream side of the control valve, and as is known, these are used to reduce the brake fluid pressure for the rear wheels by a predetermined amount below the brake fluid pressure for the front wheels. This is for brake fluid pressure. The caliper 15 of each brake device is also provided with second brake means 27FR to 27RL using piezoelectric elements, which will be described later.

In FIG. 1, S1 to S6 are sensors or switches. Sensors S1 to S4 are connected to each wheel 1FR to 1RL.
This is to detect the rotation speed of. Switch S5 is a brake switch that is turned on when the brake pedal is depressed. The switch S6 is an accelerator switch that is turned on when the accelerator pedal 9 is not depressed, that is, when the main throttle valve 10 is fully closed.

FIG. 2 shows the aforementioned control valves 26FR to 26RL and a hydraulic brake device 13FR as a first brake means.
~13RL and the second brake means 2 incorporated therein
7FR to 27RL are shown in detail, but since these have a common configuration for each wheel, the following description will be made without identifying the left, right, front and rear wheels "FR" to RL. First, the control valve 26 is constituted by a 2-port, 2-position electromagnetic switching valve, and in the position shown in FIG. 2, it is in a closed state. However, in this shut-off state, the control valve 26
A check valve 29 built in allows only flow from the caliper 15 side toward the master cylinder 21. Of course, the control valve 26 can be moved from the position shown in FIG.
It is in the open state at the position where is displaced to the left. In this open state, the control valve 26 upstream pressure (primary hydraulic pressure) P1 and downstream pressure (
(secondary hydraulic pressure) P2 are made equal.

As is known, the hydraulic brake as the first braking means includes a first friction pad 31 and a caliper 1.
The first wheel cylinder 32 is fitted into the wheel cylinder 32 formed in the
The brake piping 25 is connected to a liquid chamber 34 defined to the right of the first piston 33. In this way, the braking force by the first brake means corresponds to the pressure in the liquid chamber 34. In addition, in the liquid chamber 34, liquid pressure detection sensors S7 (there are a total of four for each wheel) made of piezoelectric elements are arranged.

The second brake means 27 is provided in parallel with the first friction pad 31 and the first piston 33. That is, the caliper 15 further holds the second friction pad 37 and is formed with a guide hole 38 having a concave shape and opening toward the second friction pad, and the second piston 35 is inserted into the guide hole 38. It is inserted. and,
A piezoelectric element 36 for driving the second piston 35 is disposed in the guide hole 38 behind the second piston 35 . Now, when a voltage is applied to the piezoelectric element 36, the piezoelectric element expands in the left-right direction and the second piston 35 is moved leftward, thereby pressing the second friction pad 37 against the disk 14, and this pressing force or control is applied. Power is generated by piezoelectric element 3
This corresponds to the magnitude of the applied voltage with respect to 6.

FIGS. 3 and 4 FIGS. 3 and 4 show the control system. This figure 3, figure 4
Since FIG. 3 only shows an outline of the input/output relationship, the details will be explained with reference to FIG. 4. First, 41
, 42 is a CPU, into which signals from each sensor S1 to S7 (S7 is 4 in total as described above) are inputted via an input interface 43. Each of the CPUs 41 and 42 performs slip control, which will be described later, and controls the drive of the control valves 26FR to 26RL (energization control to the solenoids) and the braking force adjustment means 27FR to RL via the output interface 44. control (voltage control for the piezoelectric element 36, in this embodiment, duty control). however,
In FIG. 4, for simplicity, the rear wheel control valves 26RR, 2
6RL and the second brake means (piezoelectric element) 27RR, 2
Only 7RL is shown, and those for the front wheels are omitted.

[0021] The output interface 44 connects both CPUs.
Only when the command signals from 41 and 42 are the same, the control valve 26
FR~26RL, second brake means 27FR~27RL
is driven (energized) by switching transistors TR1~
This is done via TR4 (as mentioned above, the front wheel switching transistor is omitted from illustration). Both CPUs
They mutually monitor each other, and if an abnormality is detected, an alarm 46 such as a warning lamp is activated via the output interface 45 (this also applies when other abnormalities are detected). Note that each of the CPUs 41 and 42 is also monitored for abnormalities by the watchdog timer 50 or 51.

In FIG. 5, 46 is a normal voltage constant circuit (12V in the embodiment), and 47 is a high voltage constant circuit (2V in the embodiment).
4V), 48 is a voltage monitoring circuit, and 49 is a timer and voltage switching circuit. The normal voltage constant circuit 46 is for adjusting the driving voltage for the piezoelectric element 6 during normal operation. The high voltage constant circuit 47 supplies a high voltage to the piezoelectric element 36 (voltage switching is performed by the circuit 49) when an abnormality occurs in the brake fluid system, particularly when a hydraulic pressure failure occurs. This is to obtain good braking force. The voltage monitoring circuit 48 includes each voltage constant circuit 46, 47.
When an abnormality occurs, the CPU 41 shuts down the control system (the control valve 26 is demagnetized and opened). The circuit 49 performs the voltage switching described above, and
When a failure occurs other than a brake fluid system failure, the piezoelectric element 3
This is to gradually reduce the voltage applied to 6 to 0. In this way, when any abnormality occurs, all of the control valves 26FR to 26RL are opened, and the piezoelectric element 36 is returned to its contracted state to apply braking force to each wheel. depends only on the brake hydraulic pressure generated in the master cylinder 21.

FIGS. 5 to 8 FIGS. 5 to 8 show details of slip control by the control unit U, which will be explained below. Note that in the case of ABS control, all vehicles are subject to slip control, but in TRC control, only the driving wheels are subject to control. First, at P (step - same below) 1 in FIG. 5, signals from each sensor S1 to S7 are read, and then at P2, the brake switch is turned ON.
In other words, it is determined whether or not the brake pedal 22 is depressed. When the determination in P2 is YES, it is considered that there is a possibility that ABS control will be performed. At this time, first, at P3, the control voltage V to the piezoelectric element 36 is determined to have a magnitude proportional to the brake fluid pressure detected by the sensor S7. in this case,
As shown in FIG. 8, it is preferable to set the braking force f2 by the second brake means using the piezoelectric element 36 to be smaller than the braking force f1 by the hydraulic brake means.

Next, in P4, a slip value R for ABS control is calculated. This slip value R is calculated, for example, based on the following equation (1), but the vehicle speed used in this equation (1) is a pseudo vehicle speed estimated from each wheel speed, as is commonly done in the past. used. R=(vehicle speed−wheel speed)/vehicle speed (1) After P4, in P5, it is determined whether the ABS flag is 1 or not. When this ABS flag is 1, it indicates that ABS control is currently in progress, and since it is initially initialized to 0, the determination in P4 becomes NO and the process moves to P6. At P6, it is determined whether the slip value R is small, that is, whether the slip value R is smaller than a predetermined threshold value as an ABS control start condition. When the determination in P6 is NO, it means that the wheels are not locked and ABS control is unnecessary, so in P10, the control voltage V determined in P3 is applied directly to the piezoelectric element 3.
Output for 6.

When the determination in P6 is YES, ABS control is required. At this time, first, in P7, the control valve 26 (its solenoid) is energized to be in the cutoff state (the state shown in FIG. 3). Next, after ABS control is performed at P8, the ABS flag is set to 1 at P9. The ABS control at P8 is performed by controlling the duty of the piezoelectric element 36 so that the slip value R becomes a predetermined target value, and the control state is shown in FIG. At this time, it is also possible to perform control using three general modes of ABS control: pressure reduction, pressure increase, and holding (provided that P2≦P1). In ABS control, the left and right front wheels are controlled independently from each other, and the left and right rear wheels are controlled in an integrated manner (either select high or select low). After the above-mentioned processing after P7 is performed, the determination of P5 is Y.
ES, in which case it is determined in P11 whether the slip value R is large, that is, whether the slip value R is larger than a threshold value as an ABS control stop condition. Note that the threshold value of P11 and the threshold value of P6 can be set as equal values or different values.

When the determination in P11 is NO, the process moves to P8 and ABS control is continued. When the determination in P11 is YES, the control valve 26 is opened in P12,
ABS control is stopped at P13, the ABS flag is reset to 0 at P14, and the control voltage V for the piezoelectric element 36 is returned to the value determined at P3 at P15. Note that when the brake pedal 22 is returned during ABS control, secondary hydraulic pressure (
P2) is quickly reduced, resulting in a prompt reduction in braking force.

When the determination in P2 is NO, P in FIG.
Move to 21. In this P21, the accelerator switch S
This P21 is determined whether or not 6 is turned on.
If the determination is YES, this means that the accelerator pedal 9 is not depressed and TRC control is unnecessary. In this case, the voltage to the piezoelectric element 36 is set to 0 in P22, and the TRC flag is reset to 0 in P23. be done. Note that when the TRC flag is 1, it means that TRC control is in progress.

If the determination in P21 is NO, the slip value S for TRC control is calculated in P24 based on the following equation (2), but the vehicle speed used in this equation (2) is The estimated vehicle speed is based on the vehicle speed. S = (driving wheel speed - vehicle speed) / vehicle speed ... (2) P24
After that, in P25, it is determined whether the TRC flag is 1 or not. If the determination of P25 is NO, P2
After setting the voltage to the piezoelectric element 36 to 0 in step 6, P
At step 27, it is determined whether the slip value S is large, that is, whether the slip value S is greater than or equal to a predetermined threshold value set for starting TRC control. This P27
If the determination is NO, it is assumed that TRC control is unnecessary and the process returns as is.

If the determination in P27 is YES, it is time to perform TRC control. At this time, the control valve 26 is first set to the shutoff state in P28, and then the T
RC control is performed and the TRC flag is set to 1 at P30.
is set to The traction control in P29 above is
so that the slip value S of the driving wheels becomes a predetermined target value,
This is done by controlling the duty of the piezoelectric element 36. After the above-mentioned processing from P28 onward, the determination in P25 becomes YES. In this case, in P31, it is determined whether the slip value S is small or not, that is, the slip value S is TRC.
It is determined whether or not the value is smaller than a predetermined threshold value set for stopping control. If the determination in P31 is NO, the process moves to P29 and TRC control is continued. In addition,
The threshold values of P27 and P31 can be set as equal values or different values.

When the determination in P31 is YES, the control voltage for the piezoelectric element 36 is gradually reduced to 0 in P32, and after it is confirmed in P33 that this control voltage has become 0, the TRC flag is set in P34. is reset to 0. Here, in TRC control, the above-mentioned brake
Along with key control, engine control is also performed. In other words, when the drive wheel slip value S is large, the actuator
By controlling the throttle valve 12 and driving the sub-throttle valve 113 in the closing direction, the torque generated by the engine 2 is reduced. In this case, the target value for TRC control by the engine (target slip value for the driving wheels) and the target value for traction control by the brake can be set as equal values or different values. It is preferable to set the target value smaller than the brake target value (TRC control mainly for the engine).

FIG. 9 FIG. 9 shows the content of control when a failure occurs in the brake hydraulic system. First, in P51, it is determined whether the flag is 1 or not. When this flag is 1, it means that slip control is in progress. When the determination in P51 is NO, the hydraulic pressure for the right front wheel, that is, the hydraulic pressure of the branch pipe 25FR, is read as PFR, and the hydraulic pressure for the left front wheel, that is, the hydraulic pressure of the branch pipe 25FL, is read as PFL. In P53, it is determined whether the absolute value of the difference between PFR and PFL is greater than or equal to a predetermined value. When this determination is NO, it is assumed that no hydraulic pressure failure has occurred in the branch pipes 25FR, 25FL, and hence the pipes 24A, 24B, and the valve is returned as is.

If the determination in P53 is YES, this means that a failure has occurred in either the brake hydraulic piping 24A or 24B. At this time, the high voltage circuit 47 is selected as the power supply circuit for the piezoelectric element 36 in P54. Next, connect the brake hydraulic piping 24B (2) for the right front wheel.
5FR) has failed. This determination is made, for example, by checking whether the PFR value is zero even though hydraulic pressure is generated in the master cylinder 21. If P55 is YES, the hydraulic pressure for the left front wheel (hydraulic pressure of branch pipe 25FL) corresponding to the normal brake hydraulic system 24A is determined as PFL.
Also, the hydraulic pressure for the right rear wheel (hydraulic pressure of branch pipe 25RR) is PRR.
is read as . After that, in P57, the control voltage (duty ratio) for the piezoelectric element 36 for the right front wheel where the brake fluid pressure has failed is set as a value proportional to the normal left front wheel fluid pressure PFL, and The control voltage for the failed left rear wheel piezoelectric element 36 is set to be proportional to the normal right rear wheel hydraulic pressure PRR.

[0033] If the determination in P55 is NO, then P58
, P59 is performed, but this is because the relationship between the brake hydraulic piping in which the hydraulic pressure has failed and the normal brake hydraulic piping is just the opposite of the case explained in P56 and P57 above. The redundant explanation will be omitted. P57 or P59
After that, it is determined in P60 whether or not it is time to start slip control. If the determination in P60 is NO, the process returns as is, but if the determination in P60 is YES, a flag is set in P61. is set to 1. P61
After passing through, the determination in P51 becomes YES, and in this case, it is determined in P62 whether or not the slip control has ended. If the determination in P62 is NO, the process returns, and if the determination in P62 is YES, the flag is reset to 0 in P63.

Although the embodiments have been described above, the present invention is not limited thereto, and includes, for example, the following cases. stomach. The control valve 26 may be omitted. B. If the brake hydraulic piping fails, ABS control and T
Each slip control of the RC control may be canceled, and although the TRC control in which brake hydraulic pressure is not generated may be performed, only the ABS control in which brake hydraulic pressure is generated may be canceled. C. The brake hydraulic piping is not limited to the X piping; for example, the hydraulic pressure supply to the right front and rear wheels is shared, the left front and rear wheels are shared (two systems), and the hydraulic pressure to each wheel is shared. All pressure supplies may be made independent (4 systems). D. The control signal for the piezoelectric element for the wheel in which the hydraulic pressure has failed may be determined based on the hydraulic pressure in the master cylinder 21 as the hydraulic pressure generation source.

[Brief explanation of the drawing]

FIG. 1 is an overall system diagram showing one embodiment of the present invention.

FIG. 2 is a diagram showing details of a control valve, first brake means, and second brake means.

FIG. 3 is a diagram showing the above-mentioned input/output relationship to the control unit.

FIG. 4 is a diagram showing details of the control unit shown in FIG. 3;

FIG. 5 is a flowchart showing a control example of the present invention.

FIG. 6 is a flowchart showing a control example of the present invention.

FIG. 7 is a diagram schematically showing the contents of ABS control.

FIG. 8 is a diagram showing a preferred setting example of the braking force by the first brake means and the braking force by the second brake means.

FIG. 9 is a flowchart showing a control example of the present invention.

[Explanation of symbols]

1FR, 1FL Front wheels 1RR, 1RL Rear wheels (drive wheels) 13FR to 13RL First brake means 15 Caliper 21 Master cylinder (brake hydraulic pressure generation means) 22
Brake pedal 24A Brake piping (second system) 24B Brake piping (second system) 25FR~25RL Brake piping (branch pipe) 26F
R~26RL Control valve 27FR~27RL Second brake means 31 First
Friction pad 33 First piston 35 Second piston 36 Piezoelectric element 37 Second friction pad 46 Low voltage circuit 47 High voltage circuit 49 Voltage circuit switching circuit S7 Sensor (brake hydraulic pressure) U Control unit

Claims (5)

[Claims] 1. A brake hydraulic pressure generating means for generating brake hydraulic pressure by manual operation by a driver; a first brake means that performs braking in response to brake fluid pressure;
a plurality of brake hydraulic pressure systems configured independently from each other for supplying the brake hydraulic pressure generated by the brake hydraulic pressure generation means to any of the first brake means; a second brake means that is configured independently of the brake hydraulic system and generates braking force using a piezoelectric element as a drive source; and a second brake means that controls the piezoelectric element to prevent the wheels from slipping on the road surface. 1 control means, failure detection means for detecting failure of hydraulic pressure in the brake hydraulic system, and failure detection means for detecting failure of the hydraulic pressure in the brake hydraulic system;
a hydraulic pressure detecting means for detecting the hydraulic pressure of the brake hydraulic system; The hydraulic pressure detected by the hydraulic pressure detection means corresponds to the hydraulic pressure of the brake hydraulic system that has not failed with respect to the piezoelectric element for the second brake means for the wheels of the brake hydraulic system. A slip control device for an automobile, comprising: second control means for outputting a control signal. 2. In claim 1, a first voltage circuit and a second voltage circuit having a higher voltage than the first voltage circuit are set as a power supply circuit for the piezoelectric element, and the first voltage circuit is controlled by the first control means. A switching means is provided for selecting the first voltage circuit when performing control and selecting the second voltage circuit when performing control by the second control means. 3. In claim 1, the brake hydraulic system is set such that the left and right front wheels are independent of each other and the left and right rear wheels are independent of each other, and the second control means is configured to control the left and right front wheels independently of each other. When one brake hydraulic system loses hydraulic pressure, the control signal is output based on the hydraulic pressure of the other brake hydraulic system for the left and right front wheels, and the brake fluid for one of the left and right rear wheels is reduced. The control signal is set to be output based on the hydraulic pressure of the other brake hydraulic pressure system for the left and right rear wheels when the hydraulic pressure system fails. 4. In claim 3, the brake hydraulic system includes a first brake hydraulic system for the left front wheel and the right rear wheel, and a first brake hydraulic system for the right front wheel and the left rear wheel. It is configured as two systems, including a second brake hydraulic system. 5. In claim 1, the control signals for the piezoelectric element from the first control means and the second control means are set as duty signals indicating voltage signals, and the control signals from the second control means are set as duty signals indicating voltage signals. The duty ratio is set to be approximately proportional to the normal hydraulic pressure of the brake hydraulic system.