JP6755619B2 - Vehicle braking device - Google Patents

Description

The present invention relates to a vehicle braking device that generates a predetermined brake fluid pressure required to keep a vehicle in a stopped state by a braking means without operating a brake pedal.

A follow-up travel control system that detects the actual vehicle-to-vehicle distance, which is the distance between the own vehicle and the preceding vehicle, and follows the preceding vehicle while maintaining the actual vehicle-to-vehicle distance at a predetermined target vehicle-to-vehicle distance, has been conventionally known. In such a system, when the preceding vehicle decelerates and the actual inter-vehicle distance decreases, the braking means that applies braking force to the wheels is automatically operated to decelerate the own vehicle, and the preceding vehicle accelerates to increase the inter-vehicle distance. When this happens, the braking force is released and the vehicle is automatically accelerated.

Further, in this type of system, as described in Patent Document 1, the braking means is controlled so that the own vehicle automatically stops following the stop of the preceding vehicle. In this case, the own vehicle is also controlled. The braking means are controlled so as to generate a brake fluid pressure that can keep the vehicle in a stopped state.

Japanese Unexamined Patent Publication No. 2001-39182 (see paragraphs 0014-0015, 0042-0043, FIG. 8).

By the way, as described in Patent Document 1 described above, in the follow-up travel control system, when a predetermined brake hydraulic pressure required to keep the vehicle in a stopped state is generated by the braking means without operating the brake pedal, it is usually used. Since there is leakage of the brake fluid pressure from the valves and the like constituting the brake means, the brake means keeps a predetermined brake fluid pressure by repeating the pressurization control of the brake means.

At this time, a hydraulic pressure sensor that constantly detects the brake hydraulic pressure is provided, and the brake means is pressurized and controlled each time the hydraulic pressure sensor detects that the brake fluid pressure has dropped to a predetermined value. Conventionally, the brake means is pressurized and controlled by driving a pump by a motor at predetermined fixed time intervals without providing a hydraulic pressure sensor.

However, in order to detect a decrease in brake fluid pressure by the hydraulic pressure sensor as in the former case, it is necessary to provide a hydraulic pressure sensor on the downstream side of the hydraulic pressure path near the wheel cylinder, which limits the installation location of the hydraulic pressure sensor. In addition, there is a problem that the cost of the hydraulic pressure sensor is high. On the other hand, when the braking means is pressurized and controlled at regular intervals as in the latter case, it is not necessary to provide a hydraulic pressure sensor, but on the other hand, even if the brake hydraulic pressure drops, the braking means can be maintained in a stopped state. Pressurization control may be executed, and as a result of unnecessary pressurization control, there is a problem that the life of the motor that drives the pump is shortened.

An object of the present invention is to enable the vehicle to be kept in a stopped state without operating the brake pedal even if the frequency of pressurization control of the braking means is reduced without adding a hydraulic pressure sensor. ..

In order to achieve the above object, the vehicle braking device of the present invention is a vehicle braking device that generates a predetermined brake hydraulic pressure required to keep the vehicle in a stopped state by the braking means without operating the brake pedal. In the detection means for detecting the start of movement of the vehicle from the stopped state, and the control means for repeating the pressurization control of the brake means so that the brake means maintains the predetermined brake fluid pressure in order to keep the vehicle in the stopped state. The control means executes the pressurization control of the brake means when the detection means detects the start of movement of the vehicle, and repeats the pressurization control according to the distance between the vehicle and the preceding vehicle in the stopped state. It is characterized in that to change the frequency.

According to the present invention, when the detection means detects the start of movement of the vehicle from the stopped state, the control means executes the pressurization control of the brake means. Therefore, as in the conventional case, the downstream of the hydraulic path close to the wheel cylinder. Since it is not necessary to add a hydraulic pressure sensor on the side, it is possible to prevent an increase in cost, and by pressurizing and controlling the braking means only when necessary, there is also a margin that allows for leakage of the brake fluid pressure of the valve. It becomes possible to make it smaller, and it is possible to reduce the frequency of pressurization control and prevent a decrease in the life of the valve or the like.

It is a block diagram of one Embodiment of the vehicle brake device which concerns on this invention. It is an operation explanatory view of FIG.

FIG. 6 shows an embodiment in which the vehicle braking device according to the present invention is applied to a vehicle having a constant-speed traveling / inter-vehicle distance control (ACC: Adaptive Cruise Control) function and an electric parking brake (EPB: Electrical Parking Break) function. It will be described in detail with reference to 1 and FIG.

The vehicle braking device 1 of the present embodiment is configured as shown in FIG. That is, as shown in FIG. 1, the master cylinder 3 is connected to the brake pedal 2, and the master cylinder 3 is connected to the reservoir tank 4 in which the brake fluid is stored, and the brake actuator is connected via the hydraulic path 5. It is connected to No. 6 and supplies a brake fluid pressure corresponding to the amount of depression of the brake pedal 2 by the driver to the brakes of each wheel via the brake actuator 6. The reservoir tank 4 is connected to the brake actuator 6 via the hydraulic path 7.

The brake actuator 6 includes a hydraulic path and a plurality of hydraulic paths connecting the front wheel cylinder of the right front wheel brake mounted on the right front wheel, the front wheel cylinder of the left front wheel brake mounted on the left front wheel, and the master cylinder 3. The wheel cylinder for the rear wheel of the right rear wheel brake mounted on the right rear wheel 8R and the wheel cylinder for the rear wheel of the left rear wheel brake mounted on the left rear wheel 8L, and the master cylinder 3 are provided with an electromagnetic valve. In addition to the hydraulic paths 9R and 9L to be connected and a plurality of solenoid valves, a pump and a motor for driving the pump are provided.

Then, when the brake pedal 2 is depressed by the driver, a brake fluid pressure corresponding to the depression amount is generated in the master cylinder 3, and this brake fluid pressure is applied to the front wheels and the rear through the hydraulic path of the brake actuator 6 and the valve. Normal braking is applied to the left and right front wheel brakes and the left and right rear wheel brakes 10R and 10L by the braking force transmitted to each wheel cylinder of the wheel and corresponding to the brake fluid pressure transmitted to the wheel cylinder corresponding to each wheel.

At this time, the brake pedal switch (not shown) is turned on and off depending on whether or not the brake pedal 2 is depressed, and the on / off signal of the brake pedal switch is sent via the communication bus 12 of CAN (Control Area Network) communication. Then, it is input to the EPBECU (Electronic Control Unit) 13 that controls the electric parking brake (EPB) described in detail later. Then, the EPCECU 13 controls the EPB actuator 15 based on the ON operation of the EPB switch 14 arranged on the instrument panel or the like by the driver, and automatically generates a predetermined braking force on the left and right rear wheel brakes 10R and 10L. Apply the parking brake.

The basic configuration of the parking brake by the EPCECU 13 is an application of the well-known electric parking brake technology. The EPB motor (not shown) is driven by the ON operation of the EPB switch 14, which is a parking brake switch, and the EPB actuator 15 The output shaft of the EPB motor constituting the above rotates in one direction, and the cable 16 is pulled by a predetermined tension by the rotation of the output shaft to generate a predetermined braking force on the left and right rear wheel brakes 10R and 10L. It has become.

Further, as shown in FIG. 1, a VSC (Vehicle Laboratory Control) ECU 18 for preventing and controlling the side slip of the own vehicle is provided, and the side slip of the own vehicle that occurs during cornering on a slippery road surface is not shown. Detected by a sensor or the like, a control command is output to the brake actuator 6 by the VSCECU18, and the brake fluid pressures of the left and right front and rear wheel brakes are individually controlled, and at the same time, the VSCECU18 issues a control command to the engine ECU (not shown). It is output and the engine output is controlled.

Further, as shown in FIG. 1, an ACC ECU 19 for performing constant speed traveling and inter-vehicle distance control is provided, the inter-vehicle distance between the own vehicle and the preceding vehicle is detected by the laser radar 21, and the vehicle speed of the own vehicle is detected by the vehicle speed sensor 22. Is detected, and based on the detected inter-vehicle distance and the vehicle speed of the own vehicle, the ACC ECU 19 outputs a control command to the engine ECU so as to travel at the set speed while maintaining the inter-vehicle distance with the preceding vehicle at the set value. The engine is controlled, and a control command is output to the VSCECU18 to perform brake control.

At this time, when the preceding vehicle is stopped, a control command is output to the VSCECU 18 so that the own vehicle stops at a predetermined distance so as not to collide with the preceding vehicle, and the driver does not have to operate the brake pedal. Brake fluid pressure is applied to the front and rear wheel brakes by the brake actuator 6 to automatically stop the vehicle. Here, the VSCECU18, the brake actuator 6, the left and right front wheel brakes, and the left and right rear wheel brakes 10R and 10L correspond to the braking means in the present invention.

As described above, when the VSCECU18 automatically stops the vehicle by applying the brake fluid pressure to the front and rear wheel brakes by the brake actuator 6 without the driver operating the brake pedal, for example, as shown in FIG. When the initial value Ps is applied as the brake fluid pressure, each valve constituting the brake actuator 6 has its own leakage of the hydraulic pressure, and due to the leakage of this valve, the brake fluid pressure with the passage of time. Decreases from the initial value Ps as shown in the "minimum line" and "maximum line" in FIG. In this case, the leakage characteristic of the valve is experimentally investigated in advance to derive the average value Ap, and the deviation 3σ from the average value Ap is taken to set the “minimum line” and the “maximum line”, respectively.

Since the hydraulic pressure sensor is not provided on the downstream side of the hydraulic pressure path close to the wheel cylinder of the brake actuator 6, the brake actuator 18 is used by the VSCECU 18 at regular intervals to guarantee leakage of each valve of the brake actuator 6. The pressurization control of the brake fluid pressure is repeatedly performed so that the pump drive motor of No. 6 is controlled and reaches the initial value Ps.

At this time, if the conventional method is used, a guaranteed value line is set with a deviation of 5σ exceeding the “maximum line” in anticipation of safety, and the brake fluid pressure for guaranteeing valve leakage is along this guaranteed value line. The time ta for decreasing from the initial value Ps to the pressurization threshold Pt for which additional pressurization should be performed is obtained, and the brake actuator 6 is controlled by the VSCECU 18 for each time ta so that the brake fluid pressure reaches the initial value Ps. While the pressurization control is repeated, in the present embodiment, the time tb for decreasing from the initial value Ps to the pressurization threshold Pt for performing additional pressurization is obtained along the maximum line in FIG. 2, and the VSCECU18 determines. , The brake actuator 6 is controlled every time tb, and the pressurization control of the brake fluid pressure is repeated so as to reach the initial value Ps.

As described above, in the present embodiment, when the brake fluid pressure is applied to the front wheel and rear wheel brakes by the brake actuator 6 to automatically stop the vehicle without the driver operating the brake pedal, the vehicle is longer than the conventional one. Every time tb (> ta), the VSCECU18 controls the pump drive motor of the brake actuator 6 to control the pressurization of the brake fluid pressure, so that the frequency of additional pressurization is reduced and the brake actuator 6 is driven by the pump. The life of the motor can be extended.

Further, in the present embodiment, when the driver automatically stops without operating the brake pedal, in addition to the above-mentioned pressurization control for each time tb, the start of movement of the stopped vehicle is detected and the vehicle starts to move. If there is, the VSCECU 18 immediately controls the brake actuator 6 to control the pressurization of the brake fluid pressure.

That is, the own vehicle depends on whether the distance between the vehicle and the stopped preceding vehicle detected by the laser radar 21 and the ACC ECU 19 changes, and / or whether the vehicle speed of the own vehicle has increased from the zero state by the vehicle speed sensor 22. When the presence or absence of movement of the own vehicle is detected and the movement of the own vehicle is detected, a control command is output from the ACC ECU 19 to the VSCECU 18, the brake actuator 6 is controlled by the VSCECU 18, and the brake fluid pressure is pressurized to control the own vehicle. Pressurization control is performed by the brake actuator 6 so that the brakes of each wheel maintain a predetermined brake fluid pressure in order to keep the vehicle in a stopped state. Here, the ACC ECU 19, the laser radar 21 and / or the vehicle speed sensor 22 constitute the detection means of the present invention, and the VSCECU 18 constitutes the control means of the present invention.

Therefore, according to the above-described embodiment, when the brake fluid pressure is automatically stopped by the brake actuator 6 in addition to the brakes of the front wheels and the rear wheels without the driver operating the brake pedal, the vehicle is stopped from the stopped state. When the movement of the own vehicle is detected, the brake actuator 6 is controlled by the VSCECU18 to pressurize and control the brake fluid pressure. Therefore, as in the conventional case, the hydraulic pressure sensor is placed on the downstream side of the hydraulic pressure path near the wheel cylinder. Since there is no need to add it, it will be cheaper without increasing the cost.

Further, by controlling the pressurization when the movement of the own vehicle from the stopped state is detected, the time for the initial value Ps to decrease to the pressurization threshold value Pt to be additionally pressurized along the maximum line in FIG. It suffices to repeat the pressurization control of the brake fluid pressure for each tb, and it is not necessary to consider the guaranteed value line having a large margin in FIG. 2. It is possible to extend the life of the valve of the brake actuator 6 as compared with the conventional case.

Further, as another embodiment, for example, when the own vehicle automatically stops without the driver operating the brake pedal, the addition is made according to the inter-vehicle distance to the preceding vehicle detected by the laser radar 21. The frequency of pressure control may be changed. That is, when the vehicle-to-vehicle distance is large when the own vehicle is stopped, there is a sufficient distance from the preceding vehicle so that the driver can operate the brake with a margin. Therefore, the valve shown in FIG. From the average value Ap of the leakage characteristics, reset the line of deviation 2σ that is looser than the maximum value line of deviation 3σ, and along this line of deviation 2σ, the brake fluid pressure should be additionally pressurized from the initial value Ps. Pressurization control may be performed every time tk (see FIG. 2) when the value drops to the threshold value Pt. By doing so, the pressurization control is performed every tc longer than the time tb, and the life of the pump drive motor of the brake actuator 6 can be further extended. If the inter-vehicle distance when the own vehicle is stopped is small, it is sufficient to reset the line having a deviation of 4σ or 6σ or more from the average value Ap shown in FIG.

The present invention is not limited to the above-described embodiment, and various modifications other than those described above can be made without departing from the spirit of the present invention.

For example, in the above-described embodiment, the movement of the preceding vehicle is detected from the change in the inter-vehicle distance detected by the laser radar 21 and / or the change in the vehicle speed of the own vehicle by the vehicle speed sensor 22, but the laser radar 21 is used. Alternatively, the movement of the own vehicle may be detected based on the image taken by the in-vehicle camera.

Further, in the above-described embodiment, when the driver automatically stops without operating the brake pedal, in addition to the pressurization control for each time tb shown in FIG. 2, the movement of the own vehicle in the stopped state is detected. Then, if there is a start of movement, the case where the brake actuator 6 is controlled by the VSCECU 18 to control the pressurization of the brake fluid pressure has been described, but the own vehicle in the stopped state starts to move without performing the pressurization control every time tb. When there is, only the pressurization control of the brake fluid pressure by the VSCECU 18 may be performed.

1 ... Brake device 6 ... Brake actuator (brake means)
10R, 10L ... Rear wheel brake (brake means)
18 ... VSCECU (brake means, control means)
19 ... ACC ECU (detection means)
21 ... Laser radar (detection means)
22 ... Vehicle speed sensor (detection means)

Claims (1)

In a vehicle braking device in which the braking means generates a predetermined brake fluid pressure required to keep the vehicle in a stopped state without operating the brake pedal.
A detection means that detects the start of movement of the vehicle from a stopped state,
A control means for repeating pressurization control of the brake means so that the brake means holds the predetermined brake fluid pressure in order to keep the vehicle in a stopped state is provided.
The control means
When the detecting means detects the start of movement of the vehicle, the pressurizing control of the braking means is executed .
A vehicle braking device characterized in that the repetition frequency of the pressurization control is changed according to the distance between the vehicle and the preceding vehicle in a stopped state .

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