JP2004291778A - Brake control system for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a brake control device for a vehicle realizing natural adjustment of assist brake force. <P>SOLUTION: Gain C used when a speed reduction G is set against stepping force f is made variable in response to a variation speed of the vehicle state quantity (for example, vehicle speed v) and a brake operation amount (for example, stepping force f) of a driver. Thereby, a speed reduction characteristic is adjusted. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a vehicle brake control device that controls a braking force applied to wheels in a vehicle.
[0002]
[Prior art]
2. Description of the Related Art Electronically controlled brakes that electronically control a braking force applied to wheels using a computer are known. In such an electronically controlled brake, the braking force actually applied can be made different from the amount of operation of the brake pedal by the driver, and control such as ABS or EBD control is also possible.
[0003]
For example, Patent Literature 1 discloses a technique in which an obstacle in front of a vehicle is detected by a laser radar, and a braking force is changed according to a distance from the obstacle. Japanese Patent Application Laid-Open No. H11-163873 discloses that the control gain, which is the rate of change of the brake pressure with respect to the pedaling force, is made different according to the braking operation state, thereby increasing the assisting amount of the braking force at the time of sudden braking, while increasing the braking force at the time of gentle braking. Appropriate control is performed by suppressing the assist amount.
[0004]
[Patent Document 1]
JP-A-10-297452 (paragraphs 0028 to 0034, FIG. 3)
[Patent Document 2]
JP-A-11-59405 (paragraphs 0021 to 0024, FIG. 3)
[0005]
[Problems to be solved by the invention]
However, in the technology of increasing the boost when the distance to the obstacle is short, if the switching of the boost is performed during braking, the braking force change becomes unnatural, and the driver may feel uncomfortable. is there. Also, in the technology of changing the rate of change of the brake pressure with respect to the pedaling force according to the braking operation state, if the braking operation state changes during braking, the way of increasing the brake pressure becomes discontinuous, and the brake operation (the pedaling force) and the brake pressure May be unnatural, and the driver may feel uncomfortable.
[0006]
Accordingly, an object of the present invention is to provide a vehicular braking control device that enables natural adjustment of an assist braking force.
[0007]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, a vehicle brake control device according to the present invention includes a hydraulic pressure line connecting a wheel cylinder that applies a braking force in a braking device and a master cylinder that generates a hydraulic pressure according to a brake operation force. A vehicle for detecting a vehicle state quantity in a vehicle braking control device including a hydraulic pressure adjusting unit connected to adjust a hydraulic pressure applied to each wheel cylinder, and a control unit controlling operation of the hydraulic pressure adjusting unit. The vehicle further includes a state quantity sensor and a brake operation amount sensor that detects a brake operation amount, the hydraulic pressure adjustment unit includes a fluid pressure adjustment valve, and the control unit responds to the detected vehicle state amount and the brake operation speed. By operating the lever flow control valve, control is performed to change the target deceleration with respect to the brake operation amount.
[0008]
According to the present invention, the target deceleration for the brake operation amount is made variable according to the vehicle state amount and the brake operation speed. Thereby, a plurality of brake operation amounts-target deceleration correspondence table or correspondence prepared according to the vehicle state amount (for example, the vehicle speed at the start of braking or the inter-vehicle distance to the preceding vehicle) and the driver's brake operation speed. By selecting a brake operation amount-target deceleration correspondence table or a correspondence expression having an optimal characteristic from the expression and performing the control, the optimal brake characteristic can be selected, and the driver feels discomfort when switching. There is no.
[0009]
When the target deceleration is G, the brake operation amount is f, C is a gain, and k is a constant, the target deceleration G is given by G = C × f ^k. It is preferable that the target deceleration G with respect to the amount f is variable. This facilitates control.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In order to facilitate understanding of the description, the same components are denoted by the same reference numerals as much as possible in each drawing, and redundant description is omitted.
[0011]
FIG. 1 is a hydraulic system diagram of a braking control device according to the present invention, and FIG. 2 is a control block diagram thereof.
[0012]
As shown in FIG. 1, the brake control device is an electronically controlled brake system 1 for controlling a braking force applied to each wheel by electronic control, and operates in response to a driver's depressing operation of a brake pedal 12. It has a master cylinder 14 for pumping oil. The brake pedal 12 is provided with a pedal stroke sensor 13 for detecting a depression amount of the brake pedal, that is, a pedal stroke.
[0013]
Hydraulic supply conduits 15 and 17 extend from the master cylinder 14, and a stroke simulator 18 is connected to the hydraulic supply conduit 15 via a simulator cut valve 16 which is normally opened. The stroke simulator 18 generates a pedal stroke in accordance with the driver's depression force on the brake pedal 12. On the extension of the hydraulic supply conduits 15, 17 are arranged master cut valves 20, 22 which are normally closed, and upstream of these master cut valves 20, 22, Master pressure sensors 24 and 26 for detecting the fluid pressure are provided, respectively.
[0014]
One end of a hydraulic discharge conduit 32 is connected to the reservoir 28, and a pump 36 driven by a motor 34 is arranged in the middle of a hydraulic supply conduit 30 branched from the hydraulic discharge conduit 32. An accumulator 38 for storing the boosted hydraulic pressure is connected. Further, an accumulator pressure sensor 40 for detecting the internal pressure of the accumulator 38 is disposed in the middle of the hydraulic pressure supply conduit 30. A relief valve 44 is provided between the hydraulic pressure supply conduit 30 and the hydraulic pressure discharge conduit 32 for returning hydraulic oil to the reservoir 28 when the pressure in the hydraulic pressure supply conduit 30 increases. The relief valve 44 is a flow control valve according to the present invention, and here, a proportional flow control valve (linear valve) is used.
[0015]
The other end of the hydraulic pressure supply conduit 30 is branched into four, and each wheel (hereinafter, left and right front wheels are represented by symbols FL and FR, respectively, and left and right rear wheels are represented by symbols RL and RR. Wheels for driving a braking device (not shown) arranged in all of the components corresponding to all four wheels are denoted by the symbols FL to RR. Connected to cylinders 48FL-RR. Hereinafter, these connection paths are referred to as hydraulic supply conduits 46FL to RR. Similarly, the other end of the hydraulic discharge conduit 32 is also branched into four, and is connected in the middle of the hydraulic supply conduits 46FL to RR connected to the wheel cylinders 48FL to RR for the respective wheels. Hereinafter, these connection paths leading to the hydraulic supply conduits 46FL to RR are referred to as hydraulic discharge conduits 50FL to RR.
[0016]
Solenoid valves (holding valves) 52FL to RR are arranged on the upstream side (on the pump 36 side) of the connection with the hydraulic discharge conduits 50FL to RR in the middle of the hydraulic supply conduits 46FL to RR, respectively, and are disposed downstream from the connection. Wheel cylinder (W / C) pressure sensors 56FL to RR for detecting hydraulic pressures applied to the wheel cylinders 48FL to RR are arranged on the (wheel cylinders 48FL to RR side). Solenoid valves (pressure reducing valves) 54FL to RR are disposed in the middle of the hydraulic pressure discharge conduits 50FL to RR, that is, downstream (reservoir 28 side) from the connection with the hydraulic supply conduits 46FL to RR.
[0017]
The hydraulic supply conduits 46FL, 46FR are connected to the hydraulic supply conduits 15, 17 across the master cut valves 20, 22, respectively, on the downstream side of the holding valves 52FL, 52FR. Thereby, the master cylinder 14 and the wheel cylinders 48FL, 48FR are connected with the master cut valves 20, 22 therebetween. A region surrounded by a thick line in the figure, which includes the solenoid valves 44, 52FL to RR, 54FL to RR, the motor 34, the accumulator 38, and the like, corresponds to a hydraulic pressure adjusting unit in the present invention.
[0018]
A brake ECU 8, which is a control unit of the electronic control brake system 1, includes a CPU, a memory, and the like, and controls a braking device by executing a stored brake control program. The brake ECU 8 outputs a signal indicating the pressure in the master cylinder 14 which is an output signal of the master pressure sensors 24 and 26, a signal indicating the pressure in the accumulator 38 which is an output signal of the accumulator pressure sensor 40, and a W / C pressure sensor 56FL. RR indicating the hydraulic pressure applied to the wheel cylinders 48FL-RR, the output signal of the vehicle speed sensor 60 indicating the vehicle speed, and the brake pedal operation amount indicating the output signal of the pedal stroke sensor 13. Each signal is input. The inter-vehicle distance signal from the preceding vehicle determined by the inter-vehicle ECU 70 based on the output of the laser radar 72 disposed on the front of the vehicle is also input to the brake ECU 8. Further, the brake ECU 8 outputs control signals for controlling the operations of the above-described simulator cut valve 16, master cut valves 20, 22, solenoid valves 44, 52FL-RR, 54FL-RR, and motor 34.
[0019]
Next, details of the braking force control according to the present embodiment will be described. FIG. 3 is a flowchart showing a control process of the braking force control. This control is repeatedly executed by the brake ECU 1 at a predetermined timing.
[0020]
First, a vehicle state quantity is detected (step S1). Here, the detected vehicle state quantity includes the vehicle speed v output from the vehicle speed sensor 60, the driver's operation amount of the brake pedal 10 output from the pedal stroke sensor 13, and the outputs from the master pressure sensors 24 and 26. The master pressure (corresponding to the driver's depression force f of the brake pedal 10), the current internal pressure of the accumulator 40 which is the output of the accumulator pressure sensor 40, the wheel cylinder pressure which is the output of the W / C pressure sensors 56FL to RR, and the headway ECU 70 There is distance information to a preceding vehicle or an obstacle ahead of the vehicle obtained based on the output of the laser radar 72.
[0021]
In step S2, it is determined from the operation state of the brake pedal 10 whether or not braking is being performed. This determination may be made based on the output of the pedal stroke sensor 13, the value of the pedaling force f determined from the master pressure, or a combination of both. If it is determined that braking is not being performed, the subsequent processing is skipped and the process ends. When it is determined that the vehicle is braking, the time change (referred to as a stepping speed) of the pedaling force f df / dt and the vehicle state quantity (for example, the vehicle speed v and the relative distance ΔL to an obstacle including a preceding vehicle) are used. The gain C is set (Step S3). FIG. 4 shows an example of setting the gain. Here, conditions other than the vehicle speed v, the stepping speed df / dt, and the stepping force f are the same. The gain C is set larger as the stepping speed is higher, and the gain C is set larger at a higher vehicle speed than at a lower vehicle speed. The area where df / dt is less than the predetermined value A is an area where slow stepping is frequently used in general urban driving, and the gain C is set to a constant reference value 1. The gain C is set to be larger than 1 in a region where df / dt is A or more, and a region where df / dt is A or more and less than B is a region used when the driver wants to actively control the vehicle. Yes, it is desirable to increase the effectiveness of the brake. This is defined as a high gain region. Further, a region where df / dt is equal to or larger than B is a region used for braking or the like to avoid a collision in an emergency, and is called an emergency region. In this emergency region, it is preferable to set the gain C for df / dt larger than in the high gain region.
[0022]
After setting the gain C, the target deceleration G is set using the gain C (step S4). Here, G = C × ^fk . FIG. 5 is a graph showing a setting example of the target deceleration G. When the gain is set to be large, for example, in a high gain region or an emergency region, a large deceleration can be provided even if the pedaling force f itself is small. Therefore, for example, a sufficient deceleration can be obtained without depressing the brake pedal 10 in an emergency, so that appropriate braking control can be performed.
[0023]
After the target deceleration G is determined, a braking oil pressure (wheel cylinder pressure) to be applied to each wheel cylinder necessary to obtain the target deceleration G is calculated (step S5). Then, the respective solenoid valves 44, 52FL to RR, 54FL to RR, and the motor 34 are controlled so that the wheel cylinder pressure becomes the determined target oil pressure.
[0024]
Specifically, the internal pressure of the accumulator 38 is checked from the output of the accumulator pressure sensor 40, and when the target oil pressure to be applied is insufficient, the motor 34 is driven to operate the pump 36 to increase the pressure. On the other hand, when the internal pressure is too high as compared with the hydraulic pressure to be applied, the relief valve 44 is opened to release the hydraulic pressure to the reservoir 28 to reduce the internal pressure.
[0025]
The hydraulic pressure applied to each of the wheel cylinders 48FL to RR can be adjusted by changing the operation state of each of the solenoid valves 52FL to RR and 54FL to RR. Taking the case of the wheel cylinder 48FL as an example, the brake ECU 8 compares the wheel cylinder pressure detected by the W / C pressure sensor 56FL with the target hydraulic pressure, and closes the pressure reducing valve 54FL when pressure is required. Then, the holding valve 52FL is opened. As a result, the hydraulic oil increased in pressure by the accumulator 38 is supplied to the wheel cylinder 48FL via the hydraulic supply conduits 30 and 46FL, so that the hydraulic pressure of the wheel cylinder 48FL increases and the braking force is increased. Conversely, when the wheel cylinder pressure detected by the W / C pressure sensor 56FL is higher than the target hydraulic pressure, the brake ECU 8 determines that pressure reduction is required, closes the holding valve 52FL, and opens the pressure reduction valve 54FL. Give a valve. As a result, part of the hydraulic oil supplied to the wheel cylinder 48FL is returned to the reservoir 28 via the hydraulic discharge conduit 50FL, the pressure reducing valve 54FL, and the hydraulic discharge conduit 32, and is thus provided to the wheel cylinder 48FL. The hydraulic pressure is reduced, and the braking force is reduced. When the wheel cylinder pressure detected by the W / C pressure sensor 56FL substantially matches the target hydraulic pressure, the brake ECU 8 determines that the wheel cylinder pressure needs to be maintained, and the holding valve 52FL and the pressure reducing valve Close 54FL together. As a result, the outflow of the hydraulic oil from the holding valve 52FL and the pressure reducing valve 54FL from the hydraulic supply pipe 46FL on the wheel cylinder 48FL side is stopped, so that the hydraulic pressure applied to the wheel cylinder 48FL is maintained.
[0026]
As described above, the relationship between the pedaling force and the target deceleration, that is, the deceleration characteristic is made variable by changing the gain when obtaining the target deceleration to be applied to the operation amount (the pedaling force) of the brake pedal 10. . By changing this deceleration characteristic according to the vehicle state and the operation speed of the brake pedal 10, when a sudden deceleration is required as in an emergency state, a high deceleration can be obtained from a small depression amount. When slow deceleration is required as in a normal state, optimal characteristics are selected so that the deceleration is set relatively low. Further, by adjusting the deceleration instead of the assist amount of the braking force, sudden deceleration can be reliably obtained with a small stepping amount in an emergency, thereby improving safety. In addition, by setting the deceleration according to the stepping amount and the stepping speed, the driver can easily understand the deceleration adjustment by controlling the brake pedal 10, so that the operation can be performed with a more natural feeling, and a sense of discomfort is felt. No drivability is improved.
[0027]
Here, an example in which the brake operation amount is set by the brake pedal has been described, but the brake operation amount may be input by a lever or the like. Further, the flow control valve is not limited to the relief valve 44. For example, one or both of the holding valve and the pressure reducing valve among the solenoid valves 52FL to RR and 54FL to RR may be used as the flow control valve. These flow control valves may be of the proportional type or of another type.
[0028]
【The invention's effect】
As described above, according to the present invention, the response characteristics of the target deceleration to the brake operation amount can be changed according to the brake operation speed and the vehicle state amount, so that the optimal response characteristics can be used. It is possible to provide a natural feeling of deceleration (application of assist braking force).
[Brief description of the drawings]
FIG. 1 is a hydraulic system diagram of a braking control device according to the present invention.
FIG. 2 is a control block diagram of the apparatus of FIG. 1;
FIG. 3 is a flowchart showing a control process of braking force control in the device of FIG. 1;
FIG. 4 is a graph showing a setting example of a gain set by the control of FIG. 3;
FIG. 5 is a graph showing a relationship between a pedaling force and a deceleration in the control of FIG. 3;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Electronic control brake system, 8 ... Brake ECU, 12 ... Brake pedal, 13 ... Pedal stroke sensor, 14 ... Master cylinder, 15, 17 ... Hydraulic supply conduit, 16 ... Simulator cut valve, 18 ... Stroke simulator, 20, 22 .. Master cut valve, 24, 26 master pressure sensor, 28 reservoir, 30 hydraulic supply conduit, 32 hydraulic discharge conduit, 34 motor, 36 pump, 38 accumulator, 40 accumulator pressure sensor, 44 relief Valves (electromagnetic flow control valves), 46FL-RR: hydraulic supply conduit, 48FL-RR: wheel cylinder, 50FL-RR: hydraulic discharge conduit, 52FL-RR: electromagnetic valve (holding valve), 54FL-RR: electromagnetic valve (decompression) Valve), 56FL-RR ... wheel cylinder (W / C) pressure sensor, 60 ... vehicle speed sensor 70 ... vehicle speed ECU, 72 ... laser radar.

Claims (2)

Hydraulic pressure adjustment that is connected to a hydraulic line that connects a wheel cylinder that applies a braking force in a braking device and a master cylinder that generates a hydraulic pressure according to the brake operation force and that adjusts the hydraulic pressure applied to each wheel cylinder Unit, and a control unit that controls the operation of the hydraulic pressure adjustment unit, a vehicle braking control device including:
The vehicle further includes a vehicle state quantity sensor for detecting a vehicle state quantity, and a brake operation amount sensor for detecting a brake operation amount, wherein the hydraulic pressure adjustment unit includes a flow rate adjustment valve, and the control unit includes a detected vehicle state quantity. And a brake control device for a vehicle that performs control to vary a target deceleration with respect to a brake operation amount by operating the flow rate control valve according to the brake operation speed. When the target deceleration is G, the brake operation amount is f, C is a gain, and k is a constant, the target deceleration G is given by G = C × f ^k. 2. The braking required control device according to claim 1, wherein the target deceleration G with respect to the amount f is variable.

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