JPS61205543A - Running control device for car - Google Patents

Abstract

PURPOSE:To finely control the braking force and improve the reliability by providing a piezoelectric piston mechanism in a wheel cylinder, controlling oil pressure, and monitoring the electromotive force generated when the oil pressure is increased in the piezoelectric element. CONSTITUTION:A piezoelectric piston mechanism 23 is installed at the inner part of a wheel cylinder 18 and this piezoelectric piston mechanism 23 is formed by stacking two or more thin plate type piezoelectric elements 231 and 232 and covering them with an expandable moving body 27. In addition, the wheel cylinder 18 and a master cylinder 12 are connected by an oil path 19 and a switching control valve 20 is interposed in this oil path 19. When wheels are locked, the switching control valve 20 is closed and the piezoelectric piston mechanism 23 is actuated, then the braking force is controlled. Besides, the normality and normality of the piezoelectric piston mechanism 23 are determined by comparing the electromotive force and preset value corresponding to the stepping-in of a brake pedal 11 generated in the piezoelectric piston mechanism 23. When the abnormality is assumed, the braking force control is released.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention is particularly applicable to a braking device that applies braking force to wheels, in which anti-skid control, etc., is effectively controlled, and the driving stability of a vehicle is improved. The present invention relates to a vehicle travel control device that improves vehicle performance.

[Background Art] As means for controlling the running state of a vehicle, there is a braking device that applies a braking force to the rotation of wheels to control the vehicle to stop. Such a braking device is configured to push out brake oil set in a master cylinder by operating a brake pedal, and supply this brake oil to a wheel cylinder set for each wheel. . In the wheel cylinder to which this brake fluid is supplied, the supplied hydraulic pressure drives a brake piston, and this brake piston applies braking force to a brake disc that rotates coaxially with the wheel. There is.

In such a braking device for a vehicle, when the brake pedal is depressed with a large force, a large braking force that locks the rotation of the wheels may be applied. In such a locked state, slippage occurs between the wheels and the ground, impairing the running stability of the vehicle. Therefore, when such a wheel slip condition occurs, it is necessary to reduce the braking force on the wheel where the slip has occurred to avoid the slip condition and to obtain a stable running condition. This kind of braking force control can be performed to some extent by controlling the operating force of the brake pedal based on the driver's sense, but by detecting this slip condition, it is possible to automatically control the braking force to the wheel that has caused the slip. It is desirable to control the amount to reduce it.

As a means for executing such anti-skid control, there is known a means for controlling the 1iia switching valve by detecting a locked state and controlling the oil pressure supplied from the smarter cylinder to the wheel cylinder. However, with this type of control means, it is necessary to control a large amount of oil due to the expansion of the piping from the solenoid switching valve to the wheel cylinder and the compressibility of the oil, which requires a large solenoid valve and hydraulic pump. This increases the size and complexity of the device, and it is difficult to set its responsiveness to a good state.

[Problems to be Solved by the Invention] This invention has been made in view of the above-mentioned points, and is designed to be easily constructed. By finely controlling the braking force acting on the wheel with response speed, braking force control is executed with sufficient responsiveness to effectively release the slip condition, and the running stability of the vehicle is ensured. It is an object of the present invention to provide a vehicle travel control device that ensures secure control.

Further, in the present invention, in the braking mechanism section where the braking force control is executed, it is possible to effectively monitor the occurrence of a failure to determine whether or not the braking control is reliably executed. It is an object of the present invention to provide a travel control device that can effectively improve reliability.

[Means for Solving the Problems] That is, in the vehicle travel control device according to the present invention, a plurality of piezoelectric elements are connected to the wheel cylinders constituting the braking mechanism set respectively for each wheel. A piezoelectric piston mechanism configured by stacking the above is provided, and a switching control valve is provided for partitioning the wheel cylinder portion for an oil passage that supplies hydraulic pressure to the wheel cylinder, and the switching control valve is closed. In this state, the voltage applied to the piezoelectric piston mechanism is controlled so that the braking force is finely controlled by the voltage. Further, in the piezoelectric element constituting the piezoelectric piston mechanism, the electromotive force generated when the oil pressure in the wheel cylinder increases is monitored, thereby making it possible to monitor the occurrence of a failure in the piezoelectric piston mechanism.

[Function] In the travel control device configured as described above, when a wheel slips and becomes locked due to strong brake pedal operation, for example, the piezoelectric piston of the braking mechanism corresponding to the wheel A high voltage signal is applied to the mechanism to set the piston mechanism in extension. Then, the switching control valve is closed to set the wheel cylinder section, and the voltage signal to the piezoelectric piston mechanism is switched to a low state, and the piston mechanism is set in a compressed state.
The hydraulic pressure in the wheel cylinder is reduced to reduce the braking force on the wheel that has generated slip, so that the wheel can be released from the slip state. Therefore, anti-skid control with sufficiently excellent responsiveness can be performed with a very limited and simple configuration.

In addition, since the oil pressure in the wheel cylinder is high during braking, pressure acts on the piezoelectric element that makes up the piezoelectric piston mechanism, and this piezoelectric element generates an electromotive force. It has become. Therefore, by comparing the voltage value obtained by this electromotive force with a reference value, it is possible to confirm the normal state of the piezoelectric element, and by monitoring the electromotive force, it is possible to check whether each braking mechanism is normal or abnormal. This allows the status to be monitored.

[Example code] Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

Figure 1 shows the braking control system for the front wheels FL, FR1 and rear wheels RL and RR set for the vehicle.
A braking mechanism is set for each wheel. Each braking mechanism is provided with a piston mechanism driven by a brake pedal 11, and this hydraulic pressure is distributed and supplied to a master cylinder 12 that generates hydraulic pressure corresponding to the depression of the pedal 11. There is. Note that this figure particularly shows the brake mechanism corresponding to the right rear wheel RR in detail, and the brake mechanisms corresponding to the other wheels are similarly configured. In the explanation, only the braking mechanism of the right rear wheel RR will be explained in detail.

A brake disc 14 is provided to rotate coaxially with the wheel shaft 13 of the right rear wheel.

The inner pad 15a and the outer pad 15b are set to sandwich the brake disc 14, and the outer pad 15b is attached to the brake caliper 16.
The inner pad 15a is attached to the brake piston 17, and is pressed against the brake disc 14 in response to the movement of the piston 17.

The brake piston 17 is set within the wheel cylinder 18 so as to be freely movable in its axial direction, and is normally set in a state in which the pad 15a is separated from the disc 14. Then, when the oil pressure inside the wheel cylinder 18 increases, the inner pad 15a is pressed against the brake disc 1.
The brake piston 1 is pressed against the brake piston 1.
7 is driven.

The wheel cylinder 18 has a brake caliper 16
The oil pressure from the master cylinder 12 is set to be supplied through an oil passage 19 formed inside, and a switching control valve 20 is set to the oil passage 19. This control valve 20 is driven and controlled by a command from an engine control unit 21, and is driven by the oil passage 1.
9, and is normally set to open the oil passage 19.

In this case, the control unit 21 is supplied with the rotational speed detection signal of each wheel, the ground speed detection signal of the vehicle, etc. in order to detect the slip state of the wheels, and based on these signals, When a slip condition occurs in each wheel, especially when a wheel lock condition is detected, a command is given to the switching control valve 2G of the braking mechanism section of the wheel where the slip is occurring based on the detection signal, and the oil passage 19 is closed. It is controlled as follows.

Further, a check valve 22 is set to bypass this switching control valve 20. This check valve 22 is set to only allow oil to flow from the wheel cylinder 18 side to the master cylinder 12 side, and is in a state where the oil pressure of the wheel cylinder 18 is sufficiently larger than the oil pressure of the master cylinder 12. When the brake pedal 11
When the operation is released, the braking force is reliably reduced.

A piezoelectric piston mechanism 23 is set inside the wheel cylinder 18. This piezoelectric piston mechanism 23 is constructed by laminating a plurality of thin plate-like piezoelectric elements 231, 232, . The movable body 24 covers one end of the stack in the stacking direction.

This movable body 24 faces the inside of the wheel cylinder 18, and the hydraulic pressure of the wheel cylinder 18 acts on this movable body 24, causing the piezoelectric piston mechanism 2
3 is pressed against the casing 25.

Here, the plurality of piezoelectric elements 231 .
232, . . . are stacked one after another with electrode plates in between, and the piezoelectric elements are connected in parallel by the electrode plates.

FIG. 2 shows an example of a voltage application control circuit for a group of piezoelectric elements 230 connected in parallel in this way, in which a voltage signal from a power source is taken out via a diode D, and a capacitor C
The battery is set to be charged in a high voltage state. In this case, the power source may be a power supply device that boosts the power from a vehicle-mounted battery, a voltage signal source generated by another vehicle-mounted electromagnetic device, or the like. The capacitor C is configured to be discharged via transistors Tr1 and Tr2, and these transistors Tr1 and Tr2
are supplied with first and second control input signals, respectively.

That is, the first control input signal causes the transistor T
If only r1 is controlled to conduct, the discharge high voltage signal from the capacitor C will be applied to the piezoelectric element group 230, and the piezoelectric element group 230 will expand and move the movable body 24 into the wheel cylinder 18. By pushing out the wheel cylinder 18, the volume of the wheel cylinder 18 is reduced. Also, the second
When the conduction of the transistor r2 is controlled by the control input signal, no voltage is applied to the piezoelectric element group 230, and the piezoelectric element group 230 is set to be reduced.

Further, in this piezoelectric element group 230, when oil pressure is set to the wheel cylinder 18, that pressure is supplied and set via the movable body 24. The electric element group 230 generates an electromotive force when pressure is set to be supplied due to its nature, and the voltage signal generated by this electromotive force is taken out from the monitor terminal Mt and sent to the engine control unit 21 as appropriate. will be supplied to

The above description shows the braking mechanism corresponding to the right rear wheel RR, but the other wheels FL and FR are also applicable.

The braking mechanism section corresponding to RL is similarly configured,
Corresponding components are given the same reference numerals and detailed explanations will be omitted.

That is, in the braking mechanism configured as described above, if the control unit 21 detects, for example, a slip state of the right rear wheel RR while the brake pedal 11 is strongly depressed, this wheel first Piezoelectric piston mechanism 23 piezoelectric element group 230 of the braking mechanism corresponding to
A high voltage signal is applied to it to put it in an extended state. In this state, the wheel cylinder 18 is in communication with the master cylinder 12 via the oil passage 19, so the oil pressure does not fluctuate due to the expansion of the piezoelectric piston mechanism 23. Then, a command is given to the switching control valve 20,
The oil passage 19 is closed to separate the wheel cylinder 18 section from the master cylinder 12 section. Then, in this state, the voltage applied to the piezoelectric element group 230 of the piezoelectric piston mechanism 23 is switched to a low state, and the piezoelectric piston mechanism 23
The volume of the wheel cylinder 18 is expanded by reducing the volume of the wheel cylinder 18, and the hydraulic pressure applied to the brake piston 17 is controlled to be reduced. That is, the braking force fF for the right rear wheel RR is reduced, this wheel is released from the slip state, and anti-skid control is executed.

Such control is performed by the piezoelectric piston mechanism 23 associated with the wheel cylinder 18 configured inside the brake caliper 16, so it is effectively performed by simple voltage control. It can be extremely responsive. In particular, since there is no part that expands when large hydraulic pressure is applied, braking force control can be achieved by small volume control using piezoelectric elements, and it is possible to realize fine braking force control and pulse-based control in addition to responsiveness. It is possible to realize control such as
This makes it possible to effectively deal with wheel slippage.

In addition, with such a braking mechanism, if a lateral shake occurs when the vehicle is moving steadily, for example, the output of the yaw rate sensor will apply brakes to the wheels on the inside in the direction of the shake to prevent the shake. Yaw rate control can also be performed.

This control is performed by first closing the switching control valve 20 and then issuing an extension command to the piezoelectric piston mechanism 23, contrary to the above-mentioned anti-skid control.

When configuring the braking device in this way, in the braking mechanism sections that are set independently for each wheel, even if a failure occurs in the piezoelectric piston mechanism 23 in one of the mechanism sections, the above-mentioned It is necessary to cancel the braking control. As a means for monitoring the occurrence of such a failure, a monitor terminal M in the applied voltage control circuit of the piezoelectric element group 230 is used.
The monitor signal from t is used. That is,
When the brake pedal 11 is depressed, an electromotive force corresponding to the depression force is generated in the piezoelectric element group 230 as described above. This electromotive force is then compared with a preset value that corresponds to each wheel to determine the state of each braking mechanism, thereby making it possible to determine an abnormality.

FIG. 3 explains the abnormality determination means set for the control unit 21. First, in step 100, the brake switch 3 is set corresponding to the master cylinder 12.
From the state of 0, it is determined whether the brake switch is in the on state. If the brake switch 30 is not in the on state, no electromotive force is generated in the piezoelectric element group 230, so this determination means is immediately terminated. If the ON state of the brake switch 30 is confirmed, the process proceeds to the next step 101, in which it is determined whether the slip ratio is greater than the set value S, and it is determined whether or not sufficient oil pressure is set. . Then, when it is determined that sufficient oil pressure is set for each wheel cylinder 18, step 1 is performed.
Proceed to step 02 and check the monitor voltage Vfr, V corresponding to each wheel.
Take in fl, ■rr, and Vfl.

Then, in steps 103 to 106 that follow, the set values Vf and vr set corresponding to the front wheels and rear wheels are compared with the above monitor values, and if the monitor values are small, an abnormality is determined in step 107. Make sure to do the following. If it is determined that all the monitor values in steps 103 to 1061' are large, the abnormality determination is canceled in step 108 to confirm that the system is in a normal operating state.

That is, if there is no abnormality in the piezoelectric elements constituting the piezoelectric piston mechanism 23 in all the braking mechanism parts, it is determined that the piezoelectric elements are in a normal state, and braking control using the piezoelectric elements is executed. If any of the above occurs in any of the piezoelectric elements, rNOJ is determined in one of steps 103 to 106, and an abnormal state is determined.

In the above example, only a simple distinction between normal and abnormal states was made, but if an abnormality is detected in the monitor output voltage of only one piezoelectric element, it is determined to be abnormal, and the other piezoelectric elements are determined to be normal. It's okay.

The braking control using the piezoelectric element is set to be canceled when two or more of the piezoelectric elements are determined to be abnormal.

[Effects of the Invention] As described above, the vehicle travel control device according to the present invention can perform braking control such as anti-skid with sufficient response speed while being simple and compact. In particular, since this control can be performed by simple control of the voltage applied to the piezoelectric element, the control means can also be sufficiently simplified. In addition, when a piezoelectric element is used to execute braking control in the braking mechanism set for each wheel, it is possible to maintain the control state even if a failure occurs in the braking mechanism. If this is not done, problems will occur in running balance, but since the properties of this piezoelectric element are effectively used to monitor its normal operating state, reliable braking control can be achieved. This is effective in improving driving stability as well as performance.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram illustrating a travel control device according to an embodiment of the present invention, FIG. 2 is a diagram illustrating an applied voltage control circuit for a piezoelectric element used in the above embodiment, and FIG. It is a flowchart explaining the flow of operation of the piezoelectric element (2 monitoring means. 11... Brake pedal, 12... Master cylinder, 14... Brake disc, 17... Brake piston, 18... Wheel Cylinder, 19...Oil passage, 20...Switching control valve, 21...Engine control unit, 23...Piezoelectric piston mechanism, 230...
Piezoelectric element group. Applicant's agent Patent attorney Takeshi Suzue Foolish plan 2
Figure 3

Claims (1)

[Scope of Claims] A brake piston is provided, in which a brake control mechanism is set for each wheel set on the vehicle, and a brake piston is set to transmit hydraulic pressure from a master cylinder portion to apply a braking force to each wheel. A plurality of wheel cylinders, a switching control valve provided for an oil passage formed for each of the wheel cylinders and controlling the opening and closing of the oil passage, and an inside of the wheel cylinder divided by the switching control valve. a plurality of piezoelectric piston mechanisms constituted by laminating a plurality of piezoelectric elements, each of which controls the hydraulic pressure of each of the plurality of piezoelectric piston mechanisms by a voltage signal; A vehicle running control device comprising: means for detecting an electromotive force of an element and monitoring its operating state.