JP2002029397A - Braking force control device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a braking force control device for a vehicle capable of safely braking. SOLUTION: This braking force control device for the vehicle is provided with pitching detecting means 13 and 15 for detecting whether the vehicle is in a predetermined pitching state or not, a state quantity detecting and estimating means 13 for detecting or estimating pitching state quantity showing a degree of the pitching when the pitching detecting means 13 and 15 detect that the vehicle is in the predetermined pitching state, and braking force- lowering means 9 and 13 for lowering braking force actuating a front wheel based on the pitching state quantity detected or estimated by the state quantity detecting and estimating means 13. The braking force-lowering means 9 and 13 lower the braking force actuating the front wheel in larger quantity when the pitching state quantity is large than when the pitching state quantity is small.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle braking force control system for stabilizing a vehicle braking state.

[0002]

2. Description of the Related Art When the vehicle is decelerated, if the grounding load on the rear wheels falls off, the vehicle posture becomes unstable, and stable braking may not be performed. Specifically, when a vehicle such as a truck is not carrying luggage, the vehicle deceleration increases, and such a phenomenon is likely to occur when the load on the vehicle loses the ground contact load of the rear wheels. JP-A-6-72307 relates to the ABS control, but detects the pitching state of the vehicle from the deceleration acting on the vehicle, and when it is detected that the vehicle is in a predetermined pitching state, the front wheel A braking force control device for reducing the brake hydraulic pressure is described.

[0003]

However, the braking force control device described in Japanese Patent Application Laid-Open No. 6-72307 discloses the following.
The brake hydraulic pressure reduction amount is not adjusted in accordance with the pitching state, and there is a possibility that over-pressure reduction or insufficient pressure reduction may occur. If the pressure is excessively reduced, appropriate braking cannot be performed even if the state of the vehicle is stabilized. Also,
If the decompression is insufficient, the state of the vehicle cannot be stabilized. Accordingly, it is an object of the present invention to provide a vehicle braking force control device that can perform stable braking.

[0004]

A vehicle braking force control device according to the present invention is a vehicle braking force control device for controlling a braking force acting on a vehicle having front wheels and rear wheels. Pitching detection means for detecting whether or not there is, when the pitching detection means is detected as a predetermined pitching state, state amount detection and estimation means for detecting or estimating the pitching state quantity indicating the degree of pitching, Braking force reduction means for reducing the braking force acting on the front wheels based on the pitching state quantity detected or estimated by the state quantity detection and estimation means,
The braking force reduction means increases the amount of reduction in the braking force acting on the front wheels when the pitching state quantity detected or estimated by the state quantity detection / estimation means is large as compared to when the pitching state quantity is small. When the amount is small, the amount of decrease in the braking force acting on the front wheels is smaller than when the pitching state amount is large.

According to the vehicle braking force control device of the present invention,
When the vehicle is in the predetermined pitching state, the braking force on the front wheels is reduced while adjusting the braking force reduction amount on the front wheels according to the degree of pitching, so that stable braking can be performed.

Here, it is preferable that the pitching detecting means detects that the vehicle is in a pitching state when the pitch angle of the vehicle becomes a predetermined angle or more. With this configuration, when it is considered that the braking state of the vehicle becomes unstable, the above-described braking force control can be accurately performed.

Here, the pitching state quantity is preferably a pitching angular velocity. If you do this,
The degree of pitching can be accurately determined from the pitching angular velocity, and accurate braking force control corresponding to the degree of pitching can be performed.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a vehicle braking force control device according to the present invention will be described with reference to the drawings.

FIG. 1 shows the configuration of a braking force control device according to this embodiment. The braking force control device of the present embodiment has a hydraulic brake mechanism that presses a brake pad 3, which is a friction material, against a brake disk 4 coupled to wheels using hydraulic pressure. In the present embodiment, since the brake oil is used as a medium for transmitting the brake fluid pressure, the brake fluid pressure is hereinafter also referred to as a hydraulic pressure. FIG. 1 shows the brake pipes on the front wheel side and the rear wheel side collectively.

The hydraulic pressure generated for braking the vehicle is transmitted to the wheel cylinders 2 of the respective wheels via a brake pipe, which is a hydraulic pressure transmission path, using brake oil as a medium. Brake oil filled in the brake pipe is stored in a reservoir tank 8. A plurality of control valves (solenoid valves) 9 are disposed on the brake pipe. The solenoid valves 9 switch the transmission path of the hydraulic pressure and adjust the hydraulic pressure transmitted to the wheel cylinder 2. The brake pad (friction material) 3 is pressed against the brake disc 4 connected to the wheel by the hydraulic pressure transmitted to the wheel cylinder 2, and the rotation of the wheel is braked to brake the vehicle itself.

The hydraulic brake mechanism performs braking by transmitting hydraulic pressure generated in the master cylinder 5 by operating the brake pedal 10 to the wheel cylinder 2 in the brake caliper 1 during normal braking. On the other hand, when the hydraulic pressure of the wheel cylinder 2 is to be positively increased, held, or reduced, such as during brake hydraulic control or ABS control according to the pitching state, the solenoid valve 9 on the brake pipe is opened and closed to open the wheel cylinder 2. Control the hydraulic pressure transmitted to the vehicle.

A pressure sensor 11 for detecting the oil pressure of the wheel cylinder 2 is also mounted on the brake pipe. The detection result of each pressure sensor 11 is sent to an ECU (Electronic Control Unit) 13 that performs overall brake control. Further, a stop lamp switch 12 for detecting that the brake pedal 10 is operated is connected to the brake pedal 10. The stop lamp switch 12 functions as a switch for turning on a stop lamp attached to the rear of the vehicle when the brake pedal 10 is operated, and the brake pedal 10
A signal is transmitted to the ECU 13 to inform that the is operated.

The pump motor 6 is driven by the electric power of the battery in accordance with a command from the ECU 13, and sends out the brake oil stored in the reservoir tank 8 to the wheel cylinder 2. The front-rear G sensor 15 for detecting the deceleration of the vehicle in the front-rear direction is also connected to the ECU 13. Each solenoid valve 9 on the brake pipe is also connected to the ECU 13, and the opening and closing operation of the solenoid valve 9 is controlled by the ECU 13.

Further, a wheel speed sensor 14 is attached to each wheel to detect the rotation speed of each wheel.
The wheel speed sensor 14 can also detect the rotational position of each wheel. Each wheel speed sensor 14 is also connected to the ECU 13. The above-described ECU 13 is configured by a microcomputer, and controls the braking control of the vehicle and other controls.

When the hydraulic pressure of the wheel cylinder 2 is to be increased using the solenoid valve 9, the pump motor 6 is operated and the holding valve 9a is opened, so that the pump motor 6
Is transmitted to the wheel cylinder 2. At this time, the pressure reducing valve 9b is closed. The degree of pressure increase is adjusted by the open / close duty ratio of the holding valve 9a. When the hydraulic pressure of the wheel cylinder 2 is reduced using the solenoid valve 9, the pressure reducing valve 9b is opened to release the brake oil in the wheel cylinder 2 from the reservoir tank 8.
Reduce pressure by returning to. At this time, the holding valve 9a is closed. The degree of pressure reduction is adjusted by the open / close duty ratio of the pressure reducing valve 9b. When the hydraulic pressure of the wheel cylinder is held using the solenoid valve 9, both the holding valve 9a and the pressure reducing valve 9b are closed.

Next, by the control device having the above-described configuration,
Control for stabilizing the braking state of the vehicle based on the pitching state will be described.

In this control, it is determined whether or not the vehicle is in a predetermined pitching state based on the pitch angle of the vehicle.
Since the pitch angle of the vehicle has a correlation with the longitudinal deceleration acting on the vehicle, this control detects the pitch angle from the longitudinal deceleration acting on the vehicle. That is, G before and after
Sensor 15 or ECU for calculating the pitch angle from this output
13 and the like function as pitching detection means.

Instead of the front and rear G sensor 15, the vehicle body speed may be calculated from the output of the wheel speed sensor 14, and the pitch angle may be obtained based on the vehicle body deceleration obtained by differentiating this vehicle speed. . Also in this case, the calculation of the vehicle speed, the vehicle deceleration, and the pitch angle are performed by the ECU 13, and the wheel speed sensor 14, the ECU 13, and the like function as pitching detection means. FIG. 2 shows an example of the correlation between the longitudinal deceleration of the vehicle and the pitch angle of the vehicle. In the present embodiment, there is a linear function correlation between the longitudinal deceleration of the vehicle and the pitch angle of the vehicle, but there may be other forms of correlation such as a quadratic function. Conceivable.

As described above, the ECU 13 monitors the pitch angle of the vehicle based on the deceleration of the vehicle in the front-rear direction, and constantly determines whether the pitch angle of the vehicle is equal to or greater than a preset threshold value. Has been determined. Here, the predetermined threshold value is set as a value at which when the pitch angle is equal to or greater than the threshold value, it is considered that the vehicle leans forward and the ground contact load of the rear wheels is insufficient. In the present embodiment, the threshold value is fixed, but may be variably controlled. In this case, another information amount (such as a wheel slip ratio or a road surface friction coefficient) may be added to a parameter for determining a threshold value to be variably controlled.

When the pitch angle of the vehicle is equal to or greater than the above threshold value, it is considered that the braking state of the vehicle is unstable. Therefore, the braking force acting on the vehicle is controlled to stabilize the vehicle. In the present invention, in order to stabilize the braking state of the vehicle,
Decrease the braking force of the front wheels.

In this control, the hydraulic pressure transmitted to the front wheels is reduced in order to reduce the braking force of the front wheels. Then, the amount of reduction in the braking force of the front wheels is adjusted according to the degree of pitching, and this adjustment is also made depending on how much the hydraulic pressure transmitted to the front wheels is reduced. In the present embodiment, the above-described pitch angle speed is used as the pitching state quantity indicating the degree of pitching. Here, the pitch angle that is constantly calculated is calculated by the ECU 13.
The pitch angular velocity is obtained by differentiating with time. That is, in the present embodiment, the front and rear G sensor 15 and the EC
U13 also functions as state quantity detection and estimation means.

FIG. 3 shows the relationship between the pitch angular velocity and the amount of pressure reduction of the brake oil pressure (in this embodiment, the opening time of the pressure reducing valve 9b). As shown in FIG. 3, the pressure reduction amount of the brake hydraulic pressure is adjusted according to the pitch angular velocity. When the pitch angular velocity is high, the brake hydraulic pressure reduction amount (acting on the front wheels) is lower than when the pitch angular velocity is low. The amount of braking force drop) increases. In other words, when the pitch angular velocity is small, the amount of decrease in brake oil pressure (the amount of decrease in the braking force acting on the front wheels) is smaller than when the pitch angular velocity is large.

In the case of the present embodiment, the amount of decrease in brake oil pressure is set to a minimum value in a certain range on the low-speed side of the pitch angular velocity, and is set to a maximum value in a certain range on the high-speed side. However, looking at the full range of pitch angular velocity,
When the pitch angular velocity is high, the amount of decrease in brake oil pressure is increased as compared to when the pitch angular velocity is low, and when the pitch angular velocity is small, the amount of decrease in brake oil pressure is reduced as compared to when the pitch angular velocity is high.

When the pressure reduction amount of the brake oil pressure is determined, the above-described solenoid valve 9 is driven based on the pressure reduction amount to reduce the brake oil pressure transmitted to the front wheels, thereby reducing the braking force acting on the front wheels. At this time, the pitch angle,
FIG. 4 is a timing chart showing the relationship between the opening / closing operation of the solenoid valve 9 and the brake oil pressure. As shown in FIG. 4, when the pitch angle becomes equal to or greater than the threshold value, the pressure reduction amount of the brake oil pressure (here,
Times T0, T1, and T2 for opening the pressure reducing valve 9b and shutting off the holding valve 9a are obtained, and the opening and closing of the pressure reducing valve 9b and the holding valve 9a are controlled.

To reduce the brake oil pressure, the holding valve 9a is closed to prevent the oil pressure from the master cylinder 5 from being transmitted to the front wheels, and the pressure reducing valve 9b is opened to reduce the oil pressure already acting on the front wheels. Let it. Thereby, the braking force of the front wheels is reduced. That is, the ECU 13 and the solenoid valve 9 function as braking force reducing means.

At the same time as the control for eliminating the instability of the braking state due to the insufficient ground contact load of the rear wheels, a so-called
Other braking control such as ABS control may be executed.
In this case, the solenoid valve control by other braking control such as the ABS control and the solenoid valve control for stabilizing the braking state are executed in parallel. At that time, in the present embodiment, control of the solenoid valve 9 by ABS control has priority.

The braking force control device for a vehicle according to the present invention includes:
The present invention is not limited to the above embodiment. For example,
In the embodiment described above, the conversion from the pitch angle and the longitudinal deceleration of the vehicle (or the vehicle deceleration) to the pitch angle is performed, but the conversion of the pitch angle and the longitudinal deceleration of the vehicle (the vehicle deceleration) is performed. If the correlation is known in advance, the pitching state can be directly detected based on the longitudinal deceleration of the vehicle (vehicle deceleration) without performing such conversion. In such a case, the longitudinal deceleration of the vehicle (vehicle deceleration) is equal to the pitch angle when detecting the pitching state, and can be said to be the pitch angle referred to here.

Further, in the above-described embodiment, a vehicle having a pair of front wheels and a pair of rear wheels has been described, but another wheel may be arranged between these front and rear wheels. The front wheel in the present invention means a wheel located on the front side of the vehicle among all the wheels.

[0029]

According to the vehicle braking force control device of the present invention, the amount of reduction in the braking force acting on the front wheels is adjusted according to the degree of pitching, so that highly stable braking can be performed.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating a configuration of an embodiment of a vehicle braking force control device of the present invention.

FIG. 2 is a graph showing a correlation between a longitudinal deceleration of a vehicle and a pitch angle.

FIG. 3 is a map showing a relationship between a pitch angular velocity and a pressure reduction amount of a brake oil pressure.

FIG. 4 is a timing chart showing a relationship between a pitch angle, an opening / closing operation of a solenoid valve, and a brake oil pressure.

[Explanation of symbols]

1 ... brake caliper, 2 ... wheel cylinder, 3 ...
Brake pads, 4 ... brake disc, 5 ... master cylinder, 6 ... pump motor, 8 ... reservoir tank, 9 ...
Solenoid valve (braking force reducing means), 10: brake pedal, 11: pressure sensor, 13: ECU (pitching detecting means, state quantity detection estimating means, braking force reducing means), 1
4 wheel speed sensor, 15 front and rear G sensor (pitching detecting means, state quantity detecting and estimating means).

Claims (3)

[Claims] 1. A vehicle braking force control device for controlling a braking force acting on a vehicle having a front wheel and a rear wheel, comprising: a pitching detecting means for detecting whether the vehicle is in a predetermined pitching state; A state quantity detection / estimation means for detecting or estimating a pitching state quantity indicating a degree of pitching when the detection means detects a predetermined pitching state; and a pitching detected or estimated by the state quantity detection / estimation means. Braking force reduction means for reducing the braking force acting on the front wheel based on the state quantity, wherein the braking force reduction means has a large pitching state quantity detected or estimated by the state quantity detection and estimation means. In this case, the amount of reduction in the braking force acting on the front wheels is increased compared to when the pitching state amount is small, Vehicular brake force control apparatus characterized by if the amount is small to reduce the amount of reduction in the braking force acting on the front wheel than when the amount of pitching state is large. 2. The vehicle control system according to claim 1, wherein said pitching detecting means detects that said vehicle is in a pitching state when a pitch angle of said vehicle becomes a predetermined angle or more. Power control device. 3. The vehicle braking force control device according to claim 1, wherein the pitching state quantity is a pitching angular velocity.