JP2996546B2 - Brake control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to inhibiting traction control method slipping of the drive wheels at the time of rapid acceleration of the vehicle
And especially in the working pressure chamber without operating the brake pedal.
Brake booth with valve means for supplying operating pressure
Actuation of the brake pedal to the wheel cylinder
Generate more braking force than can be operated
A brake control method.

[0002]

2. Description of the Related Art In a traction control, when a driving wheel tends to slip due to rapid acceleration of a vehicle, a braking force is applied to the driving wheel to optimize a slip with respect to a road surface, thereby accelerating the wheel. And to improve the stability of the vehicle. In the conventional traction control, for example, as disclosed in JP-A-59-145652, when the wheel speeds of the drive wheel and the driven wheel are detected, and when it is detected that the drive wheel has a slip tendency, Atmosphere is introduced into the working pressure chamber of the brake booster to operate the brake booster, and brake fluid pressure is applied to the wheel cylinder via the master cylinder to generate a braking force.

[0003]

However, since the increasing time of the brake fluid pressure at the start of the traction control is constant, the necessary brake fluid pressure is secured when one of the drive wheels starts the traction control. However, when the traction control of the other drive wheel is started after the traction control of the other drive wheel is started, the brake booster has already been activated and the hydraulic pressure of the master cylinder has been increased. Therefore, if the pressure is increased for a certain period of time in the same manner as in the case of the one drive wheel, there is a problem that the brake fluid pressure becomes excessive and the rotation of the wheels is suppressed more than necessary.

[0004] Further, two threshold values are set for the wheel speed, and when the first threshold value is exceeded, a brake booster is operated to apply brake fluid pressure to a position short of a wheel cylinder. There is also a method in which the brake fluid pressure is applied to the wheel cylinder when the threshold value is exceeded (see Japanese Patent Application No. 1-188341, which is a prior application filed by the present applicant). Since the time from when the threshold value is exceeded to when the second threshold value is reached varies depending on road surface conditions, acceleration conditions, and the like, the same problem remains.

According to the present invention, when such a brake control is started,
The purpose of the present invention is to apply an appropriate braking force in the state described above.

[0006]

SUMMARY OF THE INVENTION A brake control method according to the present invention.
Acts in the working pressure chamber without operating the brake pedal
Brake booster with valve means for supplying pressure
Operating the valve means to operate the brake pedal.
The differential pressure between the constant pressure chamber and the working pressure chamber
The brake fluid from the master cylinder.
To the wheel cylinders provided on the wheels,
The brake fluid pressure acting on the cylinder is
Controlled by a control valve provided between the
In the brake control method,
Measures the operation time and the brake booster is already operating
Pressure increase of brake fluid pressure of wheel cylinder
At the start of operation, the method of driving the control valve according to the operation time
It is characterized by changing the law .

[0007]

According to the brake control method of the present invention , the brake
With the booster not operating, operate the brake pedal.
Valve means for supplying the working pressure to the working pressure chamber regardless of the operation
The brake booster is activated by the operation of
Pressure increase control of the brake fluid pressure acting on the cylinder is started.
Operating pressure chamber without operating the brake pedal
Actuation of the valve means to supply the operating pressure
The booster is activated and the hydraulic pressure of the master cylinder rises.
The brakes acting on the wheel cylinders
Change the drive method of the control valve according to the operation time of the brake booster, such as changing the opening time of the control valve, changing the opening degree of the control valve, etc., when the pressure increase control of the hydraulic pressure is started The brake fluid pressure of the wheel cylinder
Irrespective of the hydraulic pressure of the master cylinder at the start of the pressure increase control , a substantially constant braking force can be applied to the wheels to be controlled.

[0008]

An embodiment of the brake control method of the present invention will be described below.
The traction control method will be described as an example with reference to the drawings.
1 and 2 show examples of a control device to which the traction control method of the present invention is applied. This control device is provided with wheel speed sensors 3 and 4 for detecting the respective wheel speeds in the vicinity of the drive wheel 1 and the driven wheel 2, and also has an operating pressure chamber (described later) of a brake booster 6 for driving the master cylinder 5. A switching valve 7 for selectively connecting a vacuum source such as an intake manifold of an engine and the atmosphere to the working pressure chamber is connected to the first working pressure chamber, while the intake side passage 9 of the engine 8 is connected to the first working pressure chamber. Inside, a main throttle valve 11 operated by the operation of an accelerator pedal 10 and a step motor 1
2 is provided with a sub-throttle valve 13 which is operated by the switching valve 7 and the step motor 12,
The controller 14 controls a control valve and the like to be described later, so that so-called brake control and engine output control can be used together.

In the example of FIG. 2, a tandem type booster is used as the brake booster 6. The structure of the brake booster 6 is an embodiment of a "brake booster" previously filed by the present applicant in Japanese Patent Application No. 2-315195. Is the same as the one disclosed. That is, the inside of the casing 15 is divided into two parts by the center plate 16, and each of the divided parts is further divided by the first diaphragm plate part 18 and the second diaphragm plate part 19 of the power piston 17 into the first constant pressure chamber 20 and the first diaphragm plate part 19. The power piston 17 is divided into a working pressure chamber 21, a second constant pressure chamber 22, and a second working pressure chamber 23.
Are fixed to the valve body 24.
There is provided a constant pressure passage 25 that makes the communication passage 22 communicate with each other, and an operation pressure passage 26 that makes both the operation pressure chambers 21 and 23 communicate with each other. On the other hand, a negative pressure passage 29 is formed inside the valve body 24 in a state where the negative pressure passage 29 is separated from the second constant pressure chamber 22 by a pipe 28 or the like surrounding the output shaft 27. 15 and is connected to a negative pressure source via the switching valve 7;
The second constant pressure chamber 22 is also connected to a negative pressure source separately from the negative pressure passage 29.

At the rear end of the valve body 24, an atmosphere valve 3 for opening and closing between the first working pressure chamber 21 and the atmosphere is provided.
1 and a vacuum valve 32 that opens and closes between the negative pressure passage 29 and the first working pressure chamber 21, and is operated by a brake pedal 33 via an operating rod 34. When the rod 34 advances, the atmosphere valve 31 opens, and the atmosphere is introduced into the first working pressure chamber 21. On the other hand, when the operating rod 34 retreats, the vacuum valve 32 opens, and the first working pressure chamber 21 is connected to the negative pressure passage 2.
9. Then, the driving force of the operating rod 34 is transmitted to the valve plunger 35 incorporated in the valve body 24, and the introduction of the atmosphere into the working pressure chamber 21 causes a boosting action to generate the output shaft 27.
Is transmitted to The reaction force from the output shaft 27 is applied between the output shaft 27 and the valve body 24 by the valve plunger 3.
There is provided a reaction disk 36 for transmitting the signal to the operating rod 34 via the reference numeral 5. Reference numeral 37
Indicates a return spring.

On the other hand, the switching valve 7 is constituted by an electromagnetic valve, and in a normal state (when the power is off), the vacuum source and the negative pressure passage 29 are connected to each other. The connection with the pressure passage 29 is established.
Between the switching valve 7 and the first working pressure chamber 21, there is provided a bypass 38 branched from the negative pressure passage 29 and connected to the first working pressure chamber 21. A check valve 39 is provided to allow only the flow from the switching valve 7 to the first working pressure chamber 21 and prevent the flow in the opposite direction.

When the switching valve 7 is turned on, the negative pressure passage 29 is filled with the atmosphere, but the vacuum valve 32 is closed. The pressure is introduced into the pressure chamber 21 and is guided to the second working pressure chamber 23 through the working pressure passage 26. When the pressure balance between the working pressure chambers 21 and 23 and the constant pressure chambers 20 and 22 is lost, the power piston 17 moves forward to open the vacuum valve 32. Thereby, the atmosphere is introduced into the working pressure chambers 21 and 23 via both the negative pressure passage 29 and the bypass 38, and
Moves further to drive the output shaft 27 and increase the hydraulic pressure of the master cylinder 5. In this state, the switching valve 7 is turned on by the power supply O.
When the negative pressure passage 29 is connected to the vacuum source with the FF, the vacuum valve 32 is open, so that the air in both working pressure chambers 21 and 23 flows out through the negative pressure passage 29 and the power piston 17
Is to be returned backward.

Further, between the master cylinder 5 driven by the brake booster 6 operating as described above and the wheel cylinders 41, 42 of the respective wheels 3, 4, a driving wheel hydraulic system 43 connecting the two, and a driven wheel A hydraulic system 44 is provided, and a drive wheel control valve 45 and a driven wheel control valve 46 for opening and closing the flow path are provided in the middle of the hydraulic systems 43 and 44.

Downstream from the control valves 45 and 46, hydraulic relief systems 47 and 48 for releasing the brake fluid of the wheel cylinders 41 and 42 are connected, respectively. 48 is connected to a reservoir 49 so that the reservoir 49 and each wheel cylinder 41,
The brake fluid of the wheel cylinders 41, 42 is opened by opening the pressure release valves 51, 52 between them.
To escape to. On the other hand, a hydraulic pressure return system 52 is connected so as to communicate between the reservoir 49 and the upstream side of the drive wheel control valve 45, and the hydraulic pressure return system 52
0 is provided. The control valves 45, 46
Is a normally open type solenoid valve which is normally open (when the power is turned off) and closed when the power is turned on. On the other hand, the pressure release valves 50 and 51 are normally (when the power is turned off).
) Is a normally closed solenoid valve which is closed and opened when the power is turned on.

That is, when the master cylinder 5 is driven in a normal state in which the valves 45, 46, 50 and 51 are powered off, the brake fluid is supplied to the wheel cylinder 4
1 and 42, the brake fluid pressure is increased, and when the control valves 45 and 46 are turned on, the wheel cylinder 4
Hydraulic systems 43, 44 between master cylinders 1, 42 and master cylinder 5
Is shut off, and the brake fluid pressure is kept constant irrespective of the operation of the master cylinder 5. The control valve 4
Pressure release valves 50, 5 when power supply is turned on
When 1 is turned on, the brake fluid in the wheel cylinders 41 and 42 is released to the reservoir 49, so that the brake fluid pressure decreases. The pump 60 is driven when returning the brake fluid stored in the reservoir 49 to the hydraulic pressure supply system 43.

Each of the wheel speed sensors 3 and 4 and the switching valve 7, the step motor 12, the control valves 45 and 46, the pressure release valves 50 and 51, and the pump 60 are disposed between the wheel speed sensors 3 and 4. The controller 14 for controlling these based on the signal from the controller 4 is provided to perform anti-skid control at the time of sudden braking or traction control as described later.

Next, a traction control method by the control device having the above configuration will be described with reference to FIGS. In each of the flowcharts of FIGS. 3 to 6, the step number is shown after the symbol of Sp.
FIG. 3 shows a main flowchart of traction control performed on condition that the accelerator pedal 10 is depressed. <Step 1> Initial setting for clearing all flag counters is performed. <Step 2> The time management of the control cycle is started. <Step 3> Signals from wheel speed sensors 3 and 4 are input. <Step 4> The wheel speed and the slip ratio are calculated based on the signals from the wheel speed sensors 3 and 4. <Step 5> Based on the calculation result, the brake fluid pressure increasing / decreasing mode is selected in accordance with the right drive wheel control flow.

<Step 6> In accordance with the left driving wheel control flow, the brake fluid pressure increasing / decreasing mode is selected. <Step 7> The pressure increase / decrease mode of the driven wheel 3 is selected according to the control flow of the driven wheel and the brake booster. <Step 8> The opening of the sub-throttle valve 13 is calculated. <Step 9> The switching valve 7, the control valves 45 and 46, the pressure release valves 50 and 51, and the step motor 12 are controlled. The operation of the brake booster 6 is controlled according to a brake booster flag SRBFLG described later.

In the traction control of this embodiment,
As described above, the brake control and the engine output control can be used in combination. When the slip ratio is relatively small, the opening of the sub-throttle valve 13 is adjusted to perform only the engine output control. When it becomes larger, the control valves 45, 46 and the like are opened and closed to use the brake control together. Modes for the brake control include an UP (pressure increase) mode, a DOWN (pressure reduction) mode, a HOLD (hold) mode, and an OFF (off) mode.

Each mode will be described. As shown in FIG. 7, in the UP (pressure increasing) mode, both the pressure release valve 50 (or 51) and the control valve 45 (or 46) are turned off.
In other words, when the flow path of the hydraulic pressure system 43 (or 44) is open and the flow path of the hydraulic pressure relief system 47 (or 48) is closed, the switching valve 7 of the brake booster 6 is turned on. By driving the master cylinder 5 as described above, the wheel cylinder 41 (or 4
This refers to the control of 2) for increasing the brake fluid pressure. (Each valve has its mode selected separately for the driving wheel or the driven wheel. Hereinafter, unless otherwise limited to control for only one of the driving wheels, the code for the driven wheel is followed by the code for the driven wheel in parentheses. Attached).

In the DOWN mode, both the pressure release valve 50 (51) and the control valve 45 (46) are turned on.
In other words, the flow path of the hydraulic system 43 (44) is closed and the flow path of the hydraulic pressure relief system 47 (48) is open, and the brake fluid of the wheel cylinder 41 (42) is released to the reservoir 49. Control means HOLD mode
When the pressure release valve 50 (51) is OFF and the control valve 45 (46)
Is in an ON state, that is, the flow paths of both the hydraulic system 43 (44) and the hydraulic relief system 47 (48) are closed, and the wheel between the master cylinder 5 and the wheel cylinder 41 (42) is shut off. This refers to control for keeping the brake fluid pressure of the cylinder 41 (42) constant. In the OFF (off) mode, both the pressure release valve 50 (51) and the control valve 45 (46)
This is the state of FF. Here, since the same setting is made in the UP mode and the OFF mode, a braking force is applied when the brake booster 6 is in the OFF mode at the time of operation. In this case, the OFF mode is set to the HOLD mode (or DOWN mode). Control valve 45 (46)
Must be closed. Further, since the traction control is not performed on the driven wheel 4, the HOLD mode (or DOWN mode) is operated while the brake booster 6 is operating.
Mode).

Next, the specific control contents of the right driving wheel control flow in step 5 will be described with reference to FIG. <Step 11> It is determined whether or not the traction control flag FRFLG of the right driving wheel is 1, that is, whether or not the traction control is in operation.
In the case of ES, the process proceeds to step 15. <Step 12> It is determined whether or not to start the traction control. If YES, the process proceeds to Step 13, and if NO, the process proceeds to Step 17. <Step 13> Set the traction control flag FRFLG to 1. <Step 14> Select the pressure increase mode at the start of traction control. <Step 15> It is determined whether or not the traction control has been completed. If YES, the process proceeds to a step 16, and if NO, the process proceeds to a step 20. <Step 16> The traction control flag FRFLG is cleared.

<Step 17> It is determined whether or not the brake booster flag SRBFLG is 1, that is, whether or not the brake booster 6 is operating. If YES, the process proceeds to step 18; if NO, the process proceeds to step 19. If this determination is YES, that is, the brake booster 6 is operating, it means that the traction control is not performed on the right driving wheel to be controlled in this flow, but the traction control is already performed on the left driving wheel. Indicates that <Step 18> Select the HOLD mode. That is, at this time, the brake booster 6 is operated by the traction control of the left driving wheel, and the hydraulic pressure of the master cylinder 5 is increased. Therefore, when the OFF mode is selected in this step, the braking force is applied as described above. Resulting in. Therefore, in this case, the OFF mode is set to HOLD.
In the mode, the connection between the wheel cylinder of the right driving wheel and the master cylinder 5 is shut off so that the hydraulic pressure of the master cylinder 5 does not act on the right driving wheel. <Step 19> Select the OFF mode. In this case, traction control is not performed on any of the left and right drive wheels, and thus the brake booster 6 is not operating. <Step 20> The operation mode is selected. This mode is a conventional normal traction control mode in which control is performed while selecting the increase or decrease of the brake fluid pressure according to the slip state.

FIG. 5 shows the specific contents of the pressure increase mode at the start of traction in step 14 in FIG. 4, and this control is a part according to the present invention. <Step 21> Brake booster flag SRBFLG
Is determined to be 1, that is, whether the brake booster 6 is operating or not.
In the case of O, the process proceeds to step 23. <Step 22> time COUNT from the brake booster 6 is actuated to determine whether the first set time T ₁ is smaller than in the case of YES in step 23, and if NO, it proceeds to step 24. <Step 23> Select the FU ₀ mode. <Step 24> The COUNT is equal to the second set time T ₂
It is determined whether or not it is smaller, and if YES, step 2
If the answer is NO, the process proceeds to step 26. Select <step 25> FU ₁ mode. <Step 26> The COUNT is equal to the third set time T ₃
It is determined whether or not it is smaller, and if YES, step 2
If NO in step S7, the process proceeds to step S28. Select <step 27> FU ₂ mode. Select <step 28> FU ₃ mode.

That is, according to this control flow, when the brake booster 6 is in the non-operation state or when the time after the operation is less than T ₁ , the FU ₀ mode and the operation time T
The FU ₁ mode ₁ exceeds T ₂ less time, exceed T ₂ T
₃ following FU ₂ mode when, T ₃ or more FU ₃ mode is selected. Then, the respective mode is for instructing the pressure increase of the brake fluid pressure, respectively, differ between the pressure increase is shorter in the order of _{FU 0> FU 1> FU 2} > FU 3. That is, the longer the operation time of the brake booster 6 at the start of the traction control, the shorter the pressure increase time. In this case, as a method of changing the pressure increasing time, the time during which the control valve is opened is changed, or the control valve is repeatedly opened and closed during that time even if the entire time of the pressure increasing mode is the same (in this case, open and close the control valve). Pulse slightly longer). The left driving wheel control in step 6 is the same as the right driving wheel control in steps 11 to 28 in FIGS. 4 and 5 for the left driving wheel.

Next, the control flow of the driven wheel and the brake booster in step 7 will be described with reference to FIG. <Step 31> It is determined whether or not either FRFLG or FLFRG is 1, that is, whether or not one of the left and right drive wheels is in traction control operation.
In the case of NO, the process proceeds to Step 32, and in the case of YES, the process proceeds to Step 35. <Step 32> In this case, the traction control is not performed on both the left and right wheels, and SRBFLG indicating the operation of the brake booster 6 is cleared. <Step 33> The time COUNT from the start of the operation of the brake booster is cleared. <Step 34> The OFF mode is selected for the driven wheel. <Step 35> In this case, one of the left and right drive wheels is in the traction control operation state, and the brake booster flag SBRFLG is set. <Step 36> The COUNT is incremented by one. <Step 37> The HOLD mode is selected for the driven wheel. That is, at this time, the brake booster 6 is operated by the traction control of the drive wheels, and the brake fluid pressure of the master cylinder 5 is increasing. Therefore, as in step 18, the fluid pressure does not act on the driven wheels. In addition, the flow path of the hydraulic system between the wheel cylinder and the master cylinder 5 is shut off.

FIG. 8 shows an example of an operation diagram of the brake fluid pressure of the master cylinder 5 and the brake fluid pressure of the wheel cylinder at the driving wheels, which are changed by the traction control as described above. 8, (a) is a wheel speed diagram, (b) is a brake fluid pressure diagram of the master cylinder,
(C) indicates the brake fluid pressure curve diagram of the wheel cylinders in the drive wheels, V _R is the right driving wheel speed, V _L is the left driving wheel speed, the V _a vehicle body (driven wheel) speed, P _M is the master cylinder the brake fluid pressure, P _R is the brake fluid pressure in the wheel cylinder on the right driving wheel, P _L is a brake fluid pressure in the wheel cylinder on the left driving wheel, t denotes time.

[0028] The traction control with respect to the left driving wheel at point A in FIG. 8 is started, the brake booster 6 is actuated to rise brake fluid pressure P _M in the master cylinder 5 is, the brake fluid pressure P _L in the wheel cylinders Is rapidly increasing. (B) As is apparent in the figure, the brake fluid pressure P _M in the master cylinder 5 from the brake booster 6 is activated
Since it takes time to increase the pressure, the pressure is increased by the time t ₀ from the point A to the point B. Then, the traction control is started with respect to the right driving wheel at the point C, the master cylinder 5 brake booster 6 is elapsed t _M time from the actuation
For the brake fluid pressure P _M has already risen, becomes excessive when the brake fluid pressure P _R pressed up the same time as the left driving wheel. Therefore, a possible pressure increase _one hour t by shortening the pressure increasing time, whereby it is possible to suppress the slip to obtain the necessary brake fluid pressure.

In the above embodiment, the pressure increase time at the start of the traction control is set stepwise (four steps in the embodiment), but the pressure increase time is continuously increased in proportion to the increase in the operation time of the brake booster. The pressure time may be changed. The means for changing the driving method of the control valve includes a control valve capable of adjusting the opening degree by a current value or the like in addition to the change of the pressure increasing time (change of the opening time of the control valve, repetition of opening and closing, etc.). To change the opening degree (if the operating time of the brake booster is long, the opening degree is increased). Furthermore, the control method of the present invention is applicable not only to the case where the left and right driving wheels are separately controlled with time as described in the above embodiment, but also to the traction as described in the section of the problem to be solved by the invention. The present invention can also be applied to a case where the brake booster is operated before the control is started. When a certain drive wheel starts the traction control, the brake fluid pressure is set according to the operation time of the brake booster up to that point.

[0030]

As is apparent from the above description, the present invention
According to the brake control method of
When the brake fluid pressure increase control starts, the brake booster is activated.
Is the drive method of the control valve changed according to the time?
Et al., Be any of a state in which the state brake booster is not operated or the brake booster, is already hydraulic pressure of the hydraulic to the master cylinder is increased, substantially constant brake pressure in the wheel cylinder to be controlled and obtained by the action of an effect that it is possible to perform appropriate braking control.

[Brief description of the drawings]

FIG. 1 shows a truck to which a brake control method according to the present invention is applied.
FIG. 2 is a piping system diagram showing an example of an application control method device .

FIG. 2 is a longitudinal sectional view showing an example of a brake booster for driving a master cylinder in FIG.

FIG. 3 is a main flowchart showing one embodiment of the traction control method of the present invention.

FIG. 4 is a flowchart showing specific control contents of step 5 in the flowchart of FIG. 2;

FIG. 5 is a flowchart showing specific control contents of step 14 in the flowchart of FIG. 3;

FIG. 6 is a flowchart showing specific control contents of step 7 in the flowchart of FIG. 2;

FIG. 7 is a table showing a relationship between a control mode of a brake hydraulic pressure, a control valve, and the like.

FIG. 8 is a graph showing the correspondence between the drive wheel speed, the master cylinder hydraulic pressure, and the wheel cylinder hydraulic pressure over time when the control method according to the embodiment of the present invention is performed.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 drive wheel 2 driven wheel 3, 4 wheel speed sensor 5 master cylinder 6 brake booster 7 switching valve 13 controller 17 power piston 20 first constant pressure chamber 21 first working pressure chamber 22 second constant pressure chamber 23 second working pressure chamber 25 Constant pressure passage 26 Working pressure passage 27 Output shaft 29 Negative pressure passage 31 Atmospheric valve 32 Vacuum valve 34 Operating rod 38 Bypass 39 Check valve 41, 42 Wheel cylinder 43, 44 Hydraulic system 45, 46 Control valve 47, 48 Hydraulic relief system 49 Reservoir 50,51 Pressure release valve 52 Hydraulic pressure return system

Claims (1)

(57) [Claims] An operating pressure chamber regardless of operation of a brake pedal.
Brake valve with valve means for supplying working pressure to the inside
The valve means is operated to operate the brake pedal.
A differential pressure is generated between the constant pressure chamber and the working pressure chamber regardless of
Activate the rake booster and brake from the master cylinder.
The liquid is supplied to the wheel cylinder provided on the wheel,
Master cylinder pressure applied to the brake cylinder
Control valve between the rotor and the wheel cylinder.
In the brake control method, the operation time of the brake booster is measured, and the brake
Wheel cylinder when rake booster is active
At the start of the brake fluid pressure increase control,
Characterized in that the method of driving the control valve is changed
Brake control method.