JPH11165620A - Vehicle brake system - Google Patents

Abstract

(57) [Summary] [PROBLEMS] A bi-wire type vehicle brake device is:
If the brake pedal is excessively operated when the vehicle is stopped, the drag torque remains after the braking force is released, and excessive starting energy is required at the time of starting the vehicle, so that this problem is eliminated. SOLUTION: A by-wire type brake device is provided with means for detecting a driver's intention to stop the vehicle, and braking force limiting means for preventing the generation of a braking force greater than a braking force required for stopping the vehicle when the intention to stop the vehicle is detected. . The device shown in the figure detects that the vehicle is stopped based on a signal from the wheel speed sensor 3, and at this time detects the driver's intention to hold the vehicle based on whether the detection signal of the pedaling force sensor 2 exceeds a certain threshold value. However, when there is a will to stop the vehicle, the current supplied to the motor 12 is controlled to maintain the braking force corresponding to a certain threshold.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called by-wire type vehicle brake device for applying a braking force according to a command signal to wheels using an electric actuator or the like, and more specifically, a drag torque after releasing a braking force. The present invention relates to a brake device that is reduced.

[0002]

2. Description of the Related Art A by-wire type brake device detects a brake operation force or a brake operation amount (for example, a depressing force or a pedal stroke applied to a brake pedal) with a sensor and generates a braking force corresponding to the detection signal. It is.

As a brake device of this type, as shown in Japanese Utility Model Application Laid-Open No. 6-67245, a brake device using a hydraulically-actuated actuator having an electric control hydraulic pressure source is used.
As disclosed in Japanese Utility Model Laid-Open No. 22234/1993, there is an apparatus in which an actuator is directly driven by an electric motor or the like.

[0004]

A conventional by-wire type brake device is designed to provide a brake when a driver excessively depresses a brake pedal to generate a braking force greater than that required for stopping when the vehicle stops. Due to the flexural rigidity of the caliper and the compressive strain of the friction material, the amount of pushing of the friction material by the actuator becomes larger than the return amount at the time of braking release, and a drag torque is generated even after the braking force is released, causing excessive starting energy when starting the vehicle. Will be needed.

[0005] Waste of starting energy causes deterioration of fuel efficiency of the vehicle, an increase in the amount of accelerator operation by the driver, an increase in engine noise, and the like.

Accordingly, an object of the present invention is to reduce the drag torque of the by-wire type brake device when the brake is not applied, in order to eliminate the above-mentioned problems.

[0007]

In order to solve the above-mentioned problems, according to the present invention, a brake operation force or a brake operation amount is detected by a sensor, and a bi-wire for generating a braking force corresponding to a detection signal of the sensor is provided. A vehicle brake system of the type is provided with a driver's intention to stop holding the vehicle, and braking force limiting means for preventing the generation of a braking force higher than the braking force required for stopping the vehicle when the intention to stop the vehicle is detected.

[0008] As a specific example of the stop holding intention detecting means,
For example, a vehicle stop detection unit, when the vehicle stop detection unit detects that the vehicle is stopped, determines whether the detection signal of the sensor has exceeded a certain threshold, and when the threshold exceeds the certain threshold to the driver A circuit that determines that there is an intention to hold the vehicle is considered.

The vehicle stop detecting means can detect the stop / non-stop of the vehicle from the output signal of a sensor such as a wheel speed sensor.

[0010] Such a brake device is provided with means for detecting the slope angle of the slope, and calculates an optimum threshold value suitable for the slope angle of the slope in accordance with the detection output of the slope angle detection means. It is desirable to compare the detection signals of the sensors.

An acceleration sensor can be used as the slope inclination detecting means. Since the output of the acceleration sensor when the vehicle stops is an output dependent only on the gravitational acceleration, the inclination of the slope can be detected based on the magnitude of the output of the acceleration sensor when the vehicle stops, and the threshold value is set to a larger value as the inclination becomes steeper. To eliminate the effects of the slope.

Instead of providing a slope angle detecting means,
A detection signal of a brake operation force or a brake operation amount when the stop of the vehicle is detected may be stored, and the stored value may be used as a threshold value for detecting the intention to hold the vehicle, and in this case, the influence of the slope is also eliminated. .

[0013]

When the driver's intention to stop the vehicle is detected and the braking force generated at that time is limited, no excessive braking force is generated even if the brake pedal is depressed excessively while the vehicle is stopped. Accordingly, excessive pushing of the friction material by the actuator is suppressed, and no drag torque remains after the braking force is released.

The braking force required for stopping the vehicle varies depending on the inclination angle of the road, but a device provided with a slope inclination angle detection means or a brake operation force or a brake operation amount detection signal when the vehicle is stopped is transmitted. The one that is stored and used as the threshold value is that an optimal threshold value that matches the inclination angle of the slope is set, and the detection of the stop holding intention is performed by comparison with the threshold value, and the limiting control of the braking force when the holding intention is detected is performed. There is no excessive braking force on hills, and the starting energy of the car is always minimized.

[0015]

1 and 2 show an embodiment of a brake device according to the present invention. In the figure, 1 is a brake pedal,
2 is a pedaling force sensor for detecting the pedaling force applied to the brake pedal, 3 is a wheel speed sensor, 4 is a disk rotor, 5 is a brake pad (friction material), and 6 controls an actuator 7 based on information from various sensors. It is an electronic control unit.

The actuator 7 of the brake device shown in FIG.
Is a brake caliper 8 (floating type in the figure), a brake piston 9 inserted into the cylinder of the caliper 8 in a non-rotating manner, and is slidable in the brake piston 9 in the axial direction.
A ball nut 10 inserted non-rotatably, a screw shaft 11 screwed to the ball nut 10, an electric motor 12, a pinion gear 13 and a spur gear 14 meshed with each other, and advancement of the ball nut 10 in the brake piston 9. A sleeve 15 for regulating the amount, and a spring 1 for applying a returning force to the ball nut 10 via the sleeve 15
6, the power of a motor 12 is transmitted via a pinion gear 13 and a spur gear 14 to rotate a screw shaft 11, and the rotation of the screw shaft 11 causes the brake piston 9 to propelle and brake. The pad 5 is pressed against the disk rotor 4.

The actuator 7 of the brake device shown in FIG. 2 operates the brake piston 9 inserted into the cylinder of the brake caliper 8 with the hydraulic pressure generated by the electric control hydraulic pressure source.

The electric control hydraulic pressure source includes a motor 17 receiving a drive command from the electronic control unit 6, a pump 18 driven by the motor 17, an accumulator 19, and an electromagnetic switching valve 20.
And a hydraulic pressure absorber 21. The pressure of the pump circuit is introduced into the hydraulic pressure absorber 21 by the electromagnetic switching valve 20, and is indirectly transmitted to the brake caliper 8 via a piston in the hydraulic pressure absorber 21. The brake piston 9 is operated by the pressure to press the brake pad 5.

The brake device shown in FIG. 2 includes a master cylinder 22 and a master cylinder 22 when the electric control hydraulic pressure source is normal so that a braking force can be generated even when the electric control hydraulic pressure source fails. 22 to brake caliper 8
Although a flow control valve 23 for shutting off the liquid passage leading to is provided, it is not the gist of the present invention whether or not these elements are provided.

The actuator used is not limited to those shown in FIGS. The actuator is
The piston may be propelled by a motor-driven screw shaft to generate a brake fluid pressure, and the brake pressure may be operated by the fluid pressure to press a brake pad.

Meanwhile, the actuator 7 of the brake device of FIG. 1 reverses the motor 12 to release the brake piston 9 when the braking is released, while the actuator 7 of the device of FIG. The brake piston 9 is returned by the restoring force. However, in both devices, the amount of return of the brake piston 9 is always set to be constant regardless of the pushing amount at the time of braking. Drag torque remains after release.

In view of the above, the brake devices shown in FIGS. 1 and 2 perform a braking force limiting control when the driver is trying to keep the vehicle stationary, thereby preventing the generation of an excessive braking force. The drag torque at the time of starting the vehicle, which causes waste of the starting energy, is reduced. The braking force is limited when the braking force necessary to maintain the stopped state is obtained. Further, whether or not the braking force necessary to maintain the stopped state is obtained is determined by the pedaling force sensor 2 (a stroke sensor or a sensor that directly detects the force of the brake piston 9 pressing the pad 5). Is detected by comparing the detection signal with the set threshold value.However, the braking force required to hold the stopped state changes depending on the slope degree of the slope, so if the threshold value is fixed, the stop holding on the slope becomes unstable. Become. For this reason, an optimum threshold value suitable for the slope angle of the slope is determined so that stable control is performed even on the slope.

More specifically, an acceleration sensor 25 is provided, the degree of inclination of a slope is detected from the output of the sensor 25, and an optimum threshold value corresponding to the degree of inclination is calculated first. Further, the stop / non-stop of the vehicle is detected from the signal of the wheel speed sensor 3, and when the stop of the vehicle is detected, the detection signal of the pedaling force sensor 2 is set to a certain threshold value (threshold value calculated according to the degree of inclination of the slope). ) Is determined, and if the threshold value is exceeded, it is determined that the driver has the intention to hold the vehicle, and the braking force control corresponding to the detection signal of the pedaling force sensor 2 is stopped, and the threshold value is determined. Thus, even if the brake pedal 1 is depressed excessively while the vehicle is stopped, a braking force greater than the held braking force is not generated.

Although not shown, the electronic control unit 6
Has a built-in circuit for performing braking force control based on, for example, the control flowchart of FIG.

In the apparatus shown in FIG.
In the apparatus shown in FIG. 2, the communication between the pump 18 and the hydraulic pressure absorber 21 is cut off by the electromagnetic switching valve 20.

1 and 2, the output of the treading force sensor 2 when the stop of the vehicle is detected is stored in a storage circuit in the electronic control unit 6, and the stored value is used as a threshold to stop the driver. If the holding intention is detected, the optimum control can be performed without the influence of the slope even without the slope inclination detecting means (the acceleration sensor 25 in the figure). FIG. 4 shows a control flowchart in this case.

The brake device shown in FIG.
A mechanical brake operating mechanism for a parking brake as disclosed in Japanese Patent No. 22234 may be provided. The braking force that can be generated by the mechanical brake operating mechanism is smaller than the braking force by the actuator, and the brake pedal 1 is depressed even if the drag torque remains after the braking force generated by the mechanism is released. Since the occurrence of excessive braking force is prevented in the next and subsequent stop braking, the addition of a mechanical brake operating mechanism does not have a significant adverse effect.

[0028]

As described above, according to the brake device of the present invention, even if the driver performs an excessive braking operation while the vehicle is stopped, excessive braking force is not generated, and drag torque remains after the braking force is released. Therefore, the starting energy of the vehicle can be minimized, and the effects of reducing the fuel consumption of the vehicle, reducing the accelerator operation by the driver, and reducing the engine noise at the time of starting can be expected.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of a brake device of the present invention.

FIG. 2 shows another embodiment.

FIG. 3 is a diagram showing an example of a control flowchart by an electronic control unit.

FIG. 4 is a diagram showing another example of a control flowchart.

[Explanation of symbols]

 Reference Signs List 1 brake pedal 2 pedal force sensor 3 wheel speed sensor 4 disk rotor 5 brake pad 6 electronic control unit 7 actuator 8 brake caliper 9 brake piston 10 ball nut 11 screw shaft 12 motor 13 pinion gear 14 spur gear 15 sleeve 16 spring 17 motor 18 pump 19 Accumulator 20 Electromagnetic switching valve 21 Hydraulic absorber 22 Master cylinder 23 Flow control valve 24 Piston seal 25 Acceleration sensor

Claims (4)

[Claims] 1. A by-wire type vehicle brake device that detects a brake operation force or a brake operation amount by a sensor and generates a braking force corresponding to a detection signal of the sensor. A braking device for a vehicle, comprising: braking force limiting means for preventing a braking force greater than a braking force necessary for stopping the vehicle from being generated when the vehicle stops holding intention is detected by the means. 2. A vehicle stop detecting means, comprising: a vehicle stop detecting means for detecting whether a detection signal of the sensor exceeds a certain threshold value when the vehicle stop detecting means detects that the vehicle is stopped. The circuit according to claim 1, further comprising: a circuit for determining that the driver has a will to hold the vehicle stopped when a predetermined threshold value is exceeded. 3. A means for detecting a slope angle of a slope is added, and an optimum threshold value suitable for the slope angle of the slope is calculated in accordance with a detection output of the slope angle detection means. 3. The vehicle brake device according to claim 2, wherein the signals are compared. 4. The vehicle brake device according to claim 2, wherein a detection signal value of the sensor when the stop of the vehicle is detected is stored, and the stored value is used as the threshold value.