JP3704985B2 - 4-wheel independent brake force control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention belongs to a technical field of a four-wheel independent brake force control device called a brake-by-wire that generates a brake fluid pressure to a wheel cylinder without depending on a master cylinder during braking.
[0002]
[Prior art]
Conventionally, as a four-wheel independent brake force control device, for example, a device described in JP-A-6-191393 is known.
[0003]
In FIG. 2 of this publication, a pedaling force detection device that detects an operation force on a brake pedal, a vehicle height sensor that detects a motion state of a vehicle, a front and rear G sensor, a lateral G sensor, and an external liquid that does not depend on a brake operation. A hydraulic pressure source by a pump for generating pressure, a brake hydraulic pressure system for generating wheel cylinder pressure to a four-wheel wheel cylinder based on a master pressure from the hydraulic pressure source, a detected pedal depression force and a vehicle motion state Accordingly, there is described a four-wheel independent brake force control device including a control device that independently controls the wheel cylinder pressure generated by the brake hydraulic pressure system so that the actual deceleration matches the target deceleration.
[0004]
[Problems to be solved by the invention]
However, in the above conventional four-wheel independent brake force control device, during braking, the hydraulic pressure generated from the hydraulic pressure source is similar to the master cylinder pressure generated by the mechanical brake using the master cylinder. Since the hydraulic pressure is generally in accordance with the above, there are problems described below.
[0005]
For example, when braking while operating the ABS on a low μ road, if the driver's pedal effort (or brake stroke) is depressed more than the pedal effort (or stroke) sufficient to generate the lock hydraulic pressure, Since the generated hydraulic pressure is too much higher than the hydraulic pressure required for ABS control, the differential pressure between the upstream and downstream of the ABS control valve is generated more than necessary, and unpleasant fluid pulsation such as hydraulic pulsation is generated. In view of the durability of the hydraulic pressure control valve that variably controls the four-wheel hydraulic pressure (cup erosion, etc.), this is not preferable.
[0006]
In the present invention, the problem of fluid noise generation and valve durability, and brake-by-wire, it is necessary to drive a pump from a normal brake, and a large pump is required. It was made by paying attention to the point that the hydraulic pressure smaller than usual is sufficient at the time of ABS operation to suppress the brake lock. The purpose is to prevent the generation of fluid noise such as unpleasant hydraulic pulsation and the liquid An object of the present invention is to provide a four-wheel independent brake force control device capable of stabilizing the durability of the pressure control valve.
[0007]
[Means for Solving the Problems]
As shown in the claim correspondence diagram of FIG. 1, the invention according to claim 1 includes a brake operation force equivalent value detecting means b for detecting a brake operation force equivalent value by the driver for the brake operation member a,
Vehicle motion state detection means c for detecting the motion state of the vehicle;
A hydraulic pressure source d for generating an external hydraulic pressure according to the brake operating force equivalent value by pump driving without brake operation ;
A brake hydraulic pressure system i for generating wheel cylinder pressures to the four wheel cylinders e, f, g, h based on the hydraulic pressure from the hydraulic pressure source d;
A four-wheel independent brake force control means j for independently controlling the wheel cylinder pressure produced by the brake hydraulic pressure system i according to the detected brake operation force equivalent value and the motion state of the vehicle;
In the four-wheel independent brake force control device with
Between the hydraulic pressure source d and the brake hydraulic system i, there is provided a master pressure variable means k for variably controlling the master pressure that is the input pressure to the brake hydraulic system i,
When controlling the four-wheel independent braking force according to the vehicle motion state, the command for controlling the master pressure to the minimum required hydraulic pressure to secure the maximum wheel cylinder pressure, which is the braking lock pressure determined by the road surface friction coefficient, is variable. A master pressure control means m for outputting to the means k is provided.
[0008]
The invention according to claim 2 is the four-wheel independent brake force control device according to claim 1, as shown in the claim correspondence diagram of FIG.
The master pressure control means m inputs the estimated value of the four-wheel road surface friction coefficient, estimates the maximum required pressure value of the four-wheel wheel cylinder according to the estimated value of the four-wheel road surface friction coefficient, and requires the four-wheel wheel cylinder. The master pressure variable is a command that matches the master pressure sensor value from the master pressure sensor n with the master pressure target value, which is obtained by adding the pressure difference required for pressure increase to the pressure value selected by the maximum pressure select high. A means for outputting to the means k is a feature.
[0009]
The invention according to claim 3 is the four-wheel independent brake force control device according to claim 1 or 2, as shown in the claim correspondence diagram of FIG.
The master pressure control means m is a means for inputting an operation signal of an anti-lock brake system (hereinafter referred to as ABS) and executing master pressure control when the ABS is operated.
[0010]
The invention according to claim 4 is the four-wheel independent brake force control device according to claim 3, as shown in the claim correspondence diagram of FIG.
The master pressure control means m is a means for making the master pressure control uncontrolled when the ABS is not operating and using the input pressure from the hydraulic pressure source d corresponding to the brake operation force equivalent value as it is as the master pressure. .
[0011]
Operation and effect of the invention
According to the first aspect of the present invention, the master pressure control means m is required to ensure the maximum wheel cylinder pressure that is the braking lock pressure determined by the road surface friction coefficient when controlling the four-wheel independent braking force according to the vehicle motion state. A command for controlling the master pressure is output to the master pressure varying means k. In the four-wheel independent brake force control means j, the master pressure controlled according to the brake operation force equivalent value detected by the brake operation force equivalent value detection means b and the vehicle movement state detection means c and the movement state of the vehicle. The wheel cylinder pressure is generated by the brake hydraulic pressure system i using the pressure as the base pressure, and the wheel cylinder pressure is controlled independently for the four wheels.
Therefore, at the time of four-wheel independent brake force control according to the motion state of the vehicle, the differential pressure between the upstream master pressure and the downstream wheel cylinder pressure of the brake hydraulic system i can be suppressed to a small level. Generation of unpleasant fluid noise caused by hydraulic pulsation or the like generated accordingly is prevented. In addition, the hydraulic pulsation can be suppressed, and the durability of the hydraulic control valve used in the brake hydraulic system i can be stabilized by reducing the input pressure (master pressure) of the brake hydraulic system i.
[0012]
In the invention according to claim 2, in the master pressure control means m, the estimated value of the road surface friction coefficient of the four wheels is input, and the wheel cylinder required pressure maximum value of the four wheels according to the estimated value of the road surface friction coefficient of the four wheels. The master pressure target value is obtained by adding the pressure difference required for pressure increase to the pressure value obtained by selecting the maximum required pressure value for the four wheel cylinders of the four wheels, and the master pressure sensor value from the master pressure sensor n is used as the master pressure value. A command to match the pressure target value is output to the master pressure varying means k.
Therefore, it is possible to obtain a master pressure target value corresponding to the braking lock pressure being determined by the road surface friction coefficient, thereby obtaining a high fluid sound generation preventing effect and a durable quality stabilizing effect of the hydraulic pressure control valve.
[0013]
In the invention described in claim 3, in the master pressure control means m, the ABS operation signal is inputted, and the master pressure control is executed when the ABS is operated.
Therefore, when braking while operating the ABS on a low μ road where the maximum pressure of the wheel cylinder pressure is low, the input pressure of the brake hydraulic system i can be surely suppressed to a low pressure in response to a request for preventing the generation of fluid noise. it can.
[0014]
In the invention according to claim 4, in the master pressure control means m, the master pressure control is not controlled when the ABS is not operated, and the input pressure from the hydraulic pressure source d corresponding to the brake operation force equivalent value is used as it is. Pressure.
Therefore, during normal braking, where high wheel cylinder pressure is required, the wheel cylinder pressure can be increased to a hydraulic pressure corresponding to the brake operation force equivalent value, ensuring braking performance that matches the driver's braking requirements. can do.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
(Embodiment 1)
The first embodiment is a four-wheel independent brake force control device corresponding to the inventions described in claims 1 to 4. First, the configuration will be described.
[0016]
FIG. 2 is an overall system diagram showing the four-wheel independent brake force control apparatus according to the first embodiment. 1 is a brake pedal (brake operation member), 2 is a brake stroke sensor (brake operation force equivalent value detecting means), and 3 is front and rear. Sensors such as G sensor (vehicle motion state detecting means), 4 is a hydraulic pressure source, 5, 6, 7, and 8 are wheel cylinders, 9 is a brake hydraulic pressure system, 10 is a brake hydraulic pressure control unit (four-wheel independent brake) Force control means), 11 is a master pressure control valve (master pressure variable means), 12 is a master pressure controller (master pressure control means), 13 is a master pressure sensor, 14 is a master cylinder, 15 is a reservoir tank, and 16 is a pedal stroke. Simulators 17, 18, 19, and 20 are wheel speed sensors.
[0017]
The brake stroke sensor 2 detects a brake operation amount S by a driver with respect to the brake pedal 1.
[0018]
The sensors 3 such as the front / rear G sensor are sensors for detecting a vehicle movement state such as braking / deceleration. A detection signal from the sensors 3 is input to the brake fluid pressure control unit 10.
[0019]
The hydraulic pressure source 4 is a hydraulic pressure source that generates an external hydraulic pressure by driving the pump without depending on a brake operation, and includes an electric oil pump 4a, a pump motor 4b, an accumulator 4c, and a reserve tank 4d. ing.
[0020]
The brake hydraulic pressure system 9 is a four-wheel wheel based on the first master pressure P _M1 (hydraulic pressure of the hydraulic pressure source 4) or the second master pressure P _M2 (valve control pressure) from the master pressure control valve 11. In a system for generating wheel cylinder pressure to the cylinders 5, 6, 7, and 8, a right front wheel hydraulic pressure control unit 95 having a first pressure sensor 95a and a first proportional solenoid valve 95b, a second pressure sensor 96a and a second proportional A left front wheel hydraulic pressure control unit 96 having a solenoid valve 96b, a right rear wheel hydraulic pressure control unit 97 having a third pressure sensor 97a and a third proportional solenoid valve 97b, a fourth pressure sensor 98a and a fourth proportional solenoid valve 98b. A left rear wheel hydraulic pressure control unit 98.
The brake hydraulic pressure system 9 is switched to a two-position switching position in which the operation of the pedal stroke simulator 16 is ensured during the brake operation, and the operation of the pedal stroke simulator 16 is ensured after the brake operation is completed and the simulator 16 oil is returned to the reservoir tank 15. A solenoid 9a is provided. In addition, as a fail-safe mechanism that applies the master cylinder pressure from the master cylinder 14 to the left and right front wheel cylinders 5 and 6 when the brake fluid pressure control system fails, an oil pressure converter 9b that transmits the oil pressure by separating the fluid pressure system, 9c, a two-position switching solenoid 9d that switches to a communication position (energization OFF) at the time of failure, and a master cylinder pressure sensor 9e are provided.
[0021]
The brake hydraulic pressure control unit 10 receives a detected brake operation amount S, detection signals from sensors 3 such as front and rear G sensors, and wheel speed signals from wheel speed sensors 17, 18, 19, 20. This is a means for independently controlling the optimum wheel cylinder pressure generated by the brake hydraulic system 9 according to the operation amount S and the motion state of the vehicle. In this brake hydraulic pressure control unit 10, as shown in FIG. 4, the pump motor control is performed so that the first master pressure P _M1 corresponds to the brake operation amount S, and the calculated road surface friction coefficient estimated value μ of each wheel. ₁ , μ ₂ , μ ₃ , μ ₄ and an ABS operation flag are output to the master pressure controller 12.
[0022]
The master pressure control valve 11 is provided in an oil passage between the hydraulic pressure source 4 and the brake hydraulic pressure system 9, and the first master pressure P _M1 on the upstream side is an input pressure to the brake hydraulic pressure system 9. 2 A means using a proportional solenoid valve or the like for controlling to the master pressure P _M2 .
[0023]
The master pressure controller 12 sends a command to control the minimum hydraulic pressure (second master pressure P _M2 ) to ensure the maximum wheel cylinder pressure of each wheel cylinder pressure applied to the four wheels when the ABS is operated. A means for outputting to the control valve 11.
[0024]
Next, the operation will be described.
[Master pressure control operation]
FIG. 3 is a flowchart showing the flow of the master pressure control operation performed by the master pressure controller 12 (performed every 10 ms to 20 ms), and each step will be described below.
[0025]
In step 100, the estimated road surface friction coefficient values μ ₁ , μ ₂ , μ ₃ and μ _{4 of} the four wheels, the ABS operation flag, and the second master pressure sensor value P _M2 from the master pressure sensor 13 are input.
Here, the road surface friction coefficient estimated value μ is estimated and calculated by the following equation.
μ = (T _B −I · ω) / W · r ₀
However, T _B : Brake torque I: Tire inertia ω: Tire rotation angular speed W: Wheel load r ₀ : In the tire radius step 101, according to the road surface friction coefficient estimated values μ ₁ , μ ₂ , μ ₃ and μ ₄ of the four wheels 4-wheel wheel cylinder required pressure Te maximum _{P 1, P 2, P 3} , to estimate the P _4, the wheel cylinder required pressure maximum of the four wheels _{P 1, P 2, P 3} , the pressure by a select-high P ₄ A value obtained by adding the pressure difference P ₀ required for pressure increase to the value Max (P ₁ , P ₂ , P ₃ , P ₄ ) is determined as the master pressure target value P _M2 ^* .
[0026]
In step 102, it is determined whether the ABS is operating (ABS operating flag = 1) or the ABS is not operating (ABS operating flag = 0) based on the sign of the ABS operating flag.
[0027]
In step 103, when the ABS is not operating as determined in step 102, the master pressure control is not controlled, and the first master pressure P _M1 shown in FIG. 4 is set as the second master pressure P _M2 as it is.
[0028]
In step 104, when the ABS is in operation as determined in step 102, the differential pressure between the master pressure target value P _M2 ^* determined in step 101 and the second master pressure sensor value P _M2 value from the master pressure sensor 13 is determined. ΔP is obtained. When ΔP> 0, a pressure increase command is output to the master pressure control valve 11, and when ΔP <0, a pressure decrease command is output to the master pressure control valve 11.
[When ABS is not operating]
When the ABS is not operating, the flow proceeds from step 100 to step 101 to step 102 to step 103 in the flowchart of FIG. 3, master pressure control is not controlled, and the first pressure from the hydraulic pressure source 4 corresponding to the pedal stroke S is changed. The one master pressure P _M1 is directly used as the second master pressure P _M2 .
Therefore, the wheel cylinder pressures of the wheel cylinders 5, 6, 7, and 8 can be increased up to the hydraulic pressure corresponding to the pedal stroke S during normal braking in which a high wheel cylinder pressure is required.
[At the time of ABS operation]
At the time of ABS operation, in the flowchart of FIG. 3, the flow proceeds from step 100 → step 101 → step 102 → step 104, master pressure control is executed, and the maximum wheel cylinder pressure of each wheel cylinder pressure applied to the four wheels is increased. The minimum required hydraulic pressure to be secured (second master pressure P _M2 ) is controlled. The brake fluid pressure control unit 10 executes ABS control for preventing braking lock.
Therefore, the differential pressure between the upstream master pressure and the downstream wheel cylinder pressure of the brake fluid pressure control unit 10 is kept small, and the occurrence of hydraulic pulsation or the like generated according to the magnitude of the differential pressure is prevented. The input pressure to each proportional solenoid valve 95b, 96b, 97b, 98b of the hydraulic pressure control unit 95, 96, 97, 98 used in the brake hydraulic system 9 is set to a low pressure.
[0029]
FIG. 5 (a) shows the vehicle speed characteristics and hydraulic pressure characteristics during ABS operation on the conventional high μ road and low μ road without master pressure control, and FIG. 5 (b) shows the high pressure with master pressure control of the present invention. It is a time chart which shows the vehicle speed characteristic and hydraulic pressure characteristic at the time of ABS operation | movement on a micro road and a low micro road.
As is apparent from this time chart, the second master pressure P _M2 is suppressed to a low pressure especially during ABS operation on a low μ road, and the second master pressure P _M2 and the wheelie cylinder pressure P W / C are lower than in the past. It can be seen that the differential pressure is reduced.
[0030]
Next, the effect will be described.
(1) By adding the master pressure control valve 11 and the master pressure controller 12, the differential pressure between the second master pressure P on the upstream side of the brake fluid pressure system 9 and the wheel cylinder pressure on the downstream side is small during ABS operation. It is suppressed and the generation | occurrence | production of the unpleasant fluid sound resulting from the hydraulic pulsation etc. which generate | occur | produce according to the magnitude | size of a differential pressure is prevented. In addition, since the hydraulic pulsation is suppressed and the input pressure (second master pressure P _M2 ) of the brake hydraulic pressure system 9 is reduced, the proportional solenoid valves 95b, 96b, 97b, 98b used in the brake hydraulic pressure system 9 are reduced. The durability quality can be stabilized.
By the way, when the full stroke is depressed and the road surface μ is μ = 0.1, the noise level is 72 dB without master pressure control, while the noise level is 60 dB with master pressure control. A significant noise reduction effect of about 12 dB was confirmed.
(2) the master pressure control, four-wheel road friction coefficient estimating value _{μ 1, μ 2, μ 3} , the maximum value 4-wheel wheel cylinder required pressure in accordance with _{μ 4 P 1, P 2,} P 3, P 4 And the pressure required to increase the pressure value Max (P ₁ , P ₂ , P ₃ , P ₄ ) by the select high of the maximum required pressure values P ₁ , P ₂ , P ₃ , P ₄ of the _four wheel cylinders since the value obtained by adding the difference P ₀ to perform the control as the master pressure target value P _M2 ^*, it is possible to obtain a master pressure target value P _M2 ^* corresponding to the braking lock pressure is determined by the road surface friction coefficient mu, As a result, a high fluid sound generation preventing effect and a durable quality stabilizing effect of the hydraulic pressure control valve can be obtained.
(3) Since the master pressure control is performed only when the ABS is operated, when braking while operating the ABS on the low μ road where the maximum wheel cylinder pressure is low, the low μ road fluid shown in FIG. As is apparent from the pressure characteristics, the input pressure of the brake hydraulic system 9 can be surely suppressed to a low pressure in response to the request for preventing the generation of fluid noise.
(4) Because the master pressure control is not controlled when the ABS is not operated, and the first master pressure P _M1 (FIG. 4) from the hydraulic pressure source 4 corresponding to the pedal stroke S is used as the second master pressure P _M2 as it is. During normal braking, where high wheel cylinder pressure is required, the wheel cylinder pressure can be increased to the hydraulic pressure corresponding to the pedal stroke S, thereby ensuring braking performance that meets the driver's braking requirements. it can.
[Brief description of the drawings]
FIG. 1 is a claim correspondence diagram showing a four-wheel independent brake force control device of the present invention.
FIG. 2 is an overall system diagram showing the four-wheel independent brake force control apparatus of the first embodiment.
FIG. 3 is a flowchart showing a flow of a master pressure control operation performed by a master pressure controller of the four-wheel independent brake force control apparatus according to the first embodiment.
FIG. 4 is a diagram showing a first master pressure characteristic from a hydraulic pressure source according to a pedal stroke S of the four-wheel independent brake force control apparatus of the first embodiment.
FIGS. 5A and 5B show vehicle speed characteristics and hydraulic pressure characteristics during ABS operation on a high μ road and a low μ road without conventional master pressure control, and FIG. 5B shows a high pressure with master pressure control according to the present invention. It is a time chart which shows the vehicle speed characteristic and hydraulic pressure characteristic at the time of ABS operation | movement on a micro road and a low micro road.
[Explanation of symbols]
a brake operation member b brake operation force equivalent value detection means c vehicle motion state detection means d hydraulic pressure source e, f, g, h wheel cylinder i brake hydraulic pressure system j four-wheel independent brake force control means k master pressure variable means m Master pressure control means n Master pressure sensor

Claims (4)

Brake operation force equivalent value detection means for detecting a brake operation force equivalent value by the driver for the brake operation member;
Vehicle motion state detection means for detecting the motion state of the vehicle;
A hydraulic pressure source that creates an external hydraulic pressure corresponding to the brake operating force equivalent value by pump driving without brake operation ;
A brake hydraulic pressure system for generating wheel cylinder pressure to the four wheel cylinders based on the hydraulic pressure from the hydraulic pressure source;
4-wheel independent brake force control means for independently controlling the wheel cylinder pressure generated by the brake hydraulic pressure system in accordance with the detected brake operation force equivalent value and the motion state of the vehicle;
In the four-wheel independent brake force control device with
Provided between the hydraulic pressure source and the brake hydraulic pressure system is a master pressure variable means for variably controlling a master pressure that is an input pressure to the brake hydraulic pressure system,
When controlling the four-wheel independent braking force according to the vehicle motion state, the command for controlling the master pressure to the minimum required hydraulic pressure to secure the maximum wheel cylinder pressure, which is the braking lock pressure determined by the road surface friction coefficient, is variable. A four-wheel independent brake force control device, characterized in that a master pressure control means for outputting to the means is provided. The four-wheel independent brake force control device according to claim 1,
The master pressure control means inputs the estimated value of the road surface friction coefficient of the four wheels, estimates the required value of the wheel cylinder for the four wheels according to the estimated value of the road surface friction coefficient of the four wheels, and calculates the required pressure of the wheel cylinder of the four wheels. The command that controls the master pressure sensor value from the master pressure sensor to match the master pressure target value is the master pressure target value obtained by adding the pressure difference required for pressure increase to the pressure value by the maximum select high. A four-wheel independent brake force control device characterized in that it is a means for outputting to the pressure variable means. In the four-wheel independent brake force control device according to claim 1 or 2,
The four-wheel independent brake force control device characterized in that the master pressure control means is a means for inputting an operation signal of an anti-lock brake system (hereinafter referred to as ABS) and executing master pressure control when the ABS is operated. . In the four-wheel independent brake force control device according to claim 3,
The four-wheel vehicle characterized in that the master pressure control means is a means for disabling the master pressure control when the ABS is not operating and using the input pressure from the hydraulic pressure source corresponding to the brake operation force equivalent value as it is as the master pressure. Independent brake force control device.

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