JPH07117651A - Brake controller - Google Patents

Abstract

PURPOSE:To prevent the lock of a wheel by opening an all-time opened solenoid valve interposed between a brake pipe and a wheel cylinder at least on the start of brake application and closing the solenoid valve when the pressure detected by a pressure detecting means increases to the vicinity of the lock pressure. CONSTITUTION:A master cylinder 39 increases the pressure of each brake pipe 41, 42 according to the stepping-on quantity of a brakeo pedal 40, and applies each brake power to wheels 35-38 according to each pressure applied to wheel cylinders 31-34. In this case, an all-time opened solenoid valve 50 and a unidirectional valve 46 are interposed between the brake pipes 41 and 43, and an all-time opened solenoid valves 51 and a unidirectional valve 47 are interposed between the brake pipes 41 and 44. Further, a pressure sensor 49 for detecting the pressure in the brake pipe 41 is installed, and the lock pressure for the wheel is calculated in a control circuit 55 from the output. At least on the start of brake application, the solenoid valves 50 and 51 are set in each opened state, and when the pressure detected by the pressure sensor 49 increases to the value close to the lock pressure, the solenoid valves 50 and 51 are closed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a braking control device for controlling the braking of wheels in a vehicle, such as an anti-skid brake device for preventing slipping of the wheels during braking.

[0002]

2. Description of the Related Art Conventionally, an antiskid brake device has been developed for a vehicle to prevent wheel slippage during braking. In these devices, for example, Japanese Patent Laid-Open No.
As disclosed in Japanese Patent Laid-Open No. 159854, a brake pipe in which internal fluid is pressurized in response to depression of a brake pedal, and a normally open pressure increasing solenoid valve interposed between the brake pipe and a wheel cylinder. , A reservoir capable of accumulating fluid, a normally closed depressurizing solenoid valve interposed between the reservoir and the wheel cylinder, and a fluid in the reservoir interposed between the reservoir and the brake pipe to the brake pipe And a control means connected to the pressure increasing solenoid valve, the pressure reducing solenoid valve, and the pump. When the brake pedal is depressed, the pressure in the brake pipe increases, the internal pressure of the wheel cylinder increases, and the brake is applied. Here, when the pressure increasing solenoid valve is closed and the pressure reducing solenoid valve is opened, the fluid in the wheel cylinder flows to the reservoir, the wheel cylinder internal pressure is reduced, and the braking force is weakened.
The control means controls the solenoid valve for increasing pressure and the solenoid valve for reducing pressure, adjusts the wheel cylinder pressure, and suppresses wheel slip. This adjustment method is, for example, to reduce the wheel cylinder pressure when the wheel deceleration is equal to or higher than a certain level, compare the estimated vehicle body speed with the wheel speed, and increase the wheel cylinder pressure when the wheel speed recovers to the estimated vehicle body speed. I am trying.

[0003]

In the above anti-skid brake device, a solenoid valve for increasing pressure and a solenoid valve for reducing pressure are required for one wheel, and the pressure increase and the pressure decrease are alternately repeated. Since this is also done, a pump is required to return the fluid accumulated in the reservoir to the brake pipe side. Therefore, there is a limit to the cost reduction, which hinders the spread of the anti-skid brake device.

Therefore, an object of the present invention is to reduce the number of solenoid valves and pumps to a minimum and to reduce the cost.

[0005]

In order to solve the above problems, in the present invention, a brake pipe in which internal fluid is pressurized in response to depression of a brake pedal, and pressure detection for detecting pressure in the brake pipe. Means, a normally open solenoid valve interposed between the brake pipe and the wheel cylinder,
It is connected to the pressure detecting means and the solenoid valve, calculates the lock pressure of the wheel, opens the solenoid valve at least at the start of braking, and when the pressure detected by the pressure detecting means rises to near the lock pressure, the solenoid The control means for closing the valve is provided.

[0006]

According to the above means, when the brake pedal is depressed, the internal pressure of the brake pipe increases. Since the solenoid valve is a normally open valve, the internal pressure of the wheel cylinder increases at the same time and the braking force acts on the wheel. On the other hand, the control means calculates the lock pressure of the wheels. The pressure in the brake pipe is detected by the pressure detecting means. Here, when the pressure detected by the pressure detection means rises to the vicinity of the calculated lock pressure, the control means closes the solenoid valve.

As a result, the wheel cylinder pressure is maintained. Since the wheel cylinder pressure is maintained near the lock pressure, the wheels will not lock.

If a one-way valve that moves fluid only from the wheel cylinder to the brake pipe is installed in parallel with the solenoid valve, when the brake pedal is weakened after the solenoid valve is closed, the wheel The cylinder internal pressure can be reduced according to the amount of depression of the brake pedal.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, the braking control device 30 includes a brake pedal 40, a master cylinder 39, and wheel cylinders 31, 32, 33, 34. The master cylinder 39 increases the pressure in the brake pipes 41 and 42 according to the amount of depression of the brake pedal 40. The wheel cylinder 31 increases or decreases the braking force of the front right wheel 35 of the vehicle according to the applied pressure. Similarly, the wheel cylinders 32, 33 and 34 increase / decrease the braking force of the front left wheel 36, the rear right wheel 37 and the rear left wheel 38, respectively. The wheel cylinders 31 and 32 are in communication with the brake pipes 43 and 44, respectively. The wheel cylinders 33 and 34 are brake pipes 4.
It communicates with 5. Brake pipe 41 and brake pipe 4
A normally open solenoid valve 50 and a one-way valve 46 are interposed between the three. The one-way valve 46 allows fluid to communicate only from the brake pipe 43 to the brake pipe 41. Brake pipe 41
A normally open solenoid valve 51 and a one-way valve 47 are interposed between the brake pipe 44 and the brake pipe 44. The one-way valve 47 connects fluid only from the brake pipe 44 to the brake pipe 41.
A normally open solenoid valve 52, a normally closed solenoid valve 53, and a one-way valve 48 are interposed between the brake pipe 42 and the brake pipe 45. The one-way valve 48 allows fluid communication only from the brake pipe 45 to the brake pipe 42. A reservoir 54 is provided in the brake pipe 42. Brake piping 4
1 is provided with a pressure sensor 49 for detecting pressure. Front right wheel 35, front left wheel 36, rear right wheel 37 and rear left wheel 3
8 is a wheel speed sensor 5 for detecting the speed of each wheel.
6, 57, 58 and 59 are provided. Solenoid valve 5
0, 51, 52, 53, wheel speed sensors 56, 57, 5
8, 59 and the pressure sensor 49 are connected to the control circuit 55.

FIG. 2 is a circuit diagram of the control circuit 55. The wheel speed sensors 56, 57, 58 and 59 are connected to the input ports of the microcomputer 69 via the input interfaces 60, 61, 62 and 63, respectively. The pressure sensor 49 is connected to the input port of the microcomputer 69 via the input interface 64.
The solenoid valves 50, 51, 52 and 53 are connected to the output ports of the microcomputer 69 via output interfaces 65, 66, 67 and 68, respectively.

FIG. 3 shows a flow chart of the microcomputer 69. The microcomputer 69 operates according to this flowchart. In FIG. 4, when an ignition switch (not shown) of the vehicle is turned on, first, step 70 is initialized. Next, at step 71, it is judged if the control start condition is satisfied. The control is started depending on whether or not the brake pedal 40 is depressed.
Here, the control is started when the pressure sensor 49 detects the pressure. Step 71 until it is judged that control is started
repeat. When it is determined that the control is started, the friction coefficient μ of the road surface is temporarily substituted as a predetermined value μH in step 72. As the predetermined value μH, a friction coefficient value on a normal road surface such as dry asphalt is given in advance. Friction coefficient μ
Will be reset again in the steps described below. next,
In step 73, the timer t is started. The timer t counts up and the elapsed time after the start is shown.

If the timer t is less than or equal to the predetermined value t1, step 75 is executed. At step 75, the road surface μ is determined. This determination is performed by determining the variable X based on the following mathematical formula and determining the magnitude of μ of the road surface according to the magnitude of the variable X.

[0014]

## EQU1 ## X = V0 / (-μg (1 + R ² M / θ) + Rχ
/ 2θ × t) t Here, μ is given a predetermined value μH as described above. t indicates time, and the value of the above-mentioned timer t is taken. Further, g is the acceleration of gravity, R is the effective diameter of the tire, M is the vehicle weight, θ is the inertia of the tire, and χ is the hydraulic pressure-torque conversion coefficient. These values are obtained in advance as test values. According to the applicant's calculation, X≈100 / 374.
It is 4 μH. When the value of X is larger than the predetermined value α, it is determined that the road surface has a high μ. When the value of X is equal to or smaller than the predetermined value α, it is determined that the road surface is low μ. For the value of α, a value smaller than the predetermined value μH is α = 100 /
It is calculated by substituting 374.4 μa for μa. When it is determined that the friction coefficient μ is high, the predetermined value μH is substituted for the friction coefficient μ again in step 77. When it is determined that the friction coefficient μ is low, a predetermined value μL is substituted for the friction coefficient μ in step 76. As the predetermined value μL, a friction coefficient value on a frozen road or a wet road surface is given in advance.

Next, steps 78 and 79 are successively executed. Here, the brake torque Tb when the wheels are locked is obtained, and the target pressure Pa on the verge of the lock pressure is obtained from the brake torque Tb. The brake torque Tb is calculated by the following mathematical formula.

[0016]

## EQU00002 ## Tb = .mu.g {RM + .theta. / R.times. (1-.lamda.)} Where .mu. Is the value obtained by the above .mu. Determination. Further, the target pressure Pa is calculated by the following mathematical formula.

[0017]

## EQU00003 ## Pa = Tb / .chi..alpha..alpha.
The pressures of 1 and 32 are set so as not to lock when the pressure reaches the target pressure. Note that a constant value may be subtracted instead of multiplying by α. After this,
Return to step 74.

In step 74, when the time t1 has elapsed from the timer start and the timer t becomes larger than the predetermined value t1, step 80 is executed. In step 80, the pressure value measured by the pressure sensor 49 at that time is substituted for the pressure value P1 at time t1. Next, at step 81, the process waits until t2 time has elapsed from the timer start. When the time t2 has elapsed from the timer start and the timer t becomes larger than the predetermined value t2, step 82 is executed. In step 82, the pressure sensor 49 at that time is
The measured pressure value of is substituted for the pressure value P2 at time t2. Next, at step 83, an increase amount (pressure increase rate) ΔS of the pressure per unit time is obtained by the following equation.

[0019]

[Delta] S = (P2-P1) / (t2-t1) Next, at step 84, the time [Delta] t from when the time t2 has elapsed until the pressure of the wheel cylinders 31, 32 reaches the target pressure Pa is calculated by the following equation. Ask by.

[0020]

## EQU4 ## Δt = (Pa−P2) / Δs Next, at step 85, t2 + Δ from the timer start.
The system waits until the time t has elapsed, and then the solenoid valves 50 and 51 are closed in step 86.

Next, in step 87, the wheel speed Vw is calculated, and in steps 88 and 89, the process waits until the wheel speed Vw becomes zero or the measured value of the pressure sensor 49 becomes zero. The valves 50 and 51 are opened, and the process returns to step 71.

The operation of the microcomputer 69 will be described again with reference to the time chart of FIG. When the brake pedal is depressed, the pressure values P1 and P2 of the wheel cylinder after a predetermined time t1 and t2 are measured. In addition, the target pressure value Pa is obtained during this period. This t1, t2, P
1, the time Δt from P2 and Pa until reaching the target pressure Pa is obtained, and after this Δt elapses, the solenoid valve is closed and the pressure of the wheel cylinder is maintained. Since the target pressure Pa is set to a pressure that does not reach the lock pressure, braking is performed without locking the wheels. After that, when the wheel speed becomes zero, the solenoid valve opens, and the wheel cylinder pressure rises to the master cylinder pressure.

[0023]

According to the present invention, since only one solenoid valve is required for each wheel cylinder and no pump is used,
Low cost. Further, the structure is simple and the device becomes compact.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is a circuit diagram of a control circuit according to an embodiment.

FIG. 3 is a flowchart of a microcomputer according to an embodiment.

FIG. 4 is a time chart of an example.

[Explanation of symbols]

30 Braking control device 31, 32, 33, 34 Wheel cylinder 35 Front right wheel 36 Front left wheel 37 Rear right wheel 38 Rear left wheel 39 Master cylinder 40 Brake pedal 41, 42 Brake piping 43, 44, 45
Brake piping 46, 47, 48 One-way valve 49 Pressure sensor (pressure detection means) 50, 51 Electromagnetic valve 52, 53 Electromagnetic valve 54 Reservoir 55 Control circuit (control means) 56, 57, 58, 59 Wheel speed sensor 60, 61 , 62, 63, 64 Input interface 65, 66, 67, 68 Output interface 69 Microcomputer

Claims (1)

[Claims] 1. A brake pipe (41) in which an internal fluid is pressurized in response to depression of a brake pedal, and pressure detection means (49) for detecting the pressure in the brake pipe.
A normally open solenoid valve (50, 51) interposed between the brake pipe and the wheel cylinder; connected to the pressure detecting means and the solenoid valve to calculate a wheel lock pressure; A braking control device comprising: a solenoid valve opened; and a control means (55) closing the solenoid valve when the pressure detected by the pressure detection means rises to near the lock pressure.