JPH06263022A - Braking force control device - Google Patents

Abstract

PURPOSE:To heighten effectiveness in braking control by arranging a threshold value changing means to change a threshold value of mater cylinder pressure in the direction for a control means to become hard to operate according to a detecting signal of a master cylinder pressure detecting means when the master cylinder pressure is zero or extremely low. CONSTITUTION:A controller 16 controls wheel cylinder pressure in a pressure increasing, holding and pressure reducing condition according to detecting signals from wheel speed sensors 19-22. The controller 16 monitors master cylinder pressure on antiskid control, and sets a threshold value of the master cylinder pressure so that control is not operated when a detecting signal of a master cylinder liquid pressure sensor is not more than a preset value. It also carries out threshold value changing control to change the preset threshold value in the direction for the control to become hard to operate when the master cylinder pressure is zero or extremely low.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art As a braking force control device, for example, there is one described in Japanese Patent Application Laid-Open No. 56-53944.
This is to start the anti-skid control when the wheel deceleration reaches a predetermined deceleration during braking of the vehicle. Anti-skid control can be used for low μ
It is effective in preventing wheel lock when braking on the road.

[0003]

By the way, in such control, there is room for improvement in view of the following points. That is, when the vehicle is traveling on a rough road, an irregular road, or the like, when the wheel deceleration reaches the predetermined deceleration, the anti-skid control is started and the braking hydraulic system is controlled. As a result, even when the brake pedal is depressed, the wheel cylinder hydraulic pressure is not transmitted from the master cylinder side, and the brake force may be insufficient.

From this point of view, the present invention improves the braking force control for controlling the fluid pressure of the wheel cylinder to at least one of the pressure reduction, the pressure retention and the pressure increase based on the wheel speed detection signal. A braking force control device capable of appropriately suppressing an early operation of an undesired control that causes a braking force shortage even when traveling on a bad road or the like, and capable of enhancing the effectiveness of the braking force control. Is to provide.

[0005]

According to the present invention, the following braking force control device is provided (FIG. 1). A master cylinder that generates a brake fluid pressure by operating a driver, a wheel cylinder that is arranged on each wheel and that generates a braking force by supplying a brake fluid pressure, and a wheel speed detecting means that detects a rotation speed of a wheel. A braking force control device that includes a control unit that controls the fluid pressure of the wheel cylinder to at least one of pressure reduction, holding, and pressure increase based on the detection signal of the wheel speed detection unit. With the master cylinder pressure detection means to
When the detection signal of the master cylinder pressure detecting means is equal to or lower than a preset value, the control means does not operate. The threshold setting means for setting the threshold of the master cylinder pressure, and the threshold set by the threshold setting means are the master cylinder. The braking force control device is characterized by further comprising threshold changing means for changing the master cylinder pressure to a direction in which the control means is hard to operate when the master cylinder pressure is zero or extremely low based on a detection signal of the pressure detecting means.

[0006]

According to the present invention, the control means is a wheel cylinder which is arranged on each wheel and generates a braking force by the supply of the brake hydraulic pressure based on the detection signal of the wheel speed detecting means for detecting the rotation speed of the wheel. Is controlled to at least one of pressure reduction, holding and pressure increase. Further, master cylinder pressure detection means and master cylinder pressure detection means for detecting the hydraulic pressure of the master cylinder that generates the brake hydraulic pressure by operating the driver. If the detection signal of is less than or equal to a preset value, the control means does not operate, the threshold setting means for setting the threshold of the master cylinder pressure, and the threshold set by the threshold setting means is the detection signal of the master cylinder pressure detecting means. On the basis of the above, when the master cylinder pressure is zero or extremely low pressure, the control means has a threshold changing means for changing to a direction in which it is difficult to operate, Carry out the changes.

Accordingly, the threshold value for controlling the wheel cylinder pressure to be reduced, held, or increased by the control means can be set by the master cylinder pressure, and the threshold value can be switched in the direction in which the control is difficult to be performed at an extremely low pressure. Even if the vehicle is running on a rough road, the threshold value for starting the anti-skid control can be changed based on the master cylinder pressure in the direction in which the control is difficult to start when the master cylinder pressure is zero or extremely low. Prevents early activation of anti-skid control due to running on rough roads and avoids a situation in which the braking force is insufficient.

[0008]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 2 shows the configuration of an embodiment of the device of the present invention.
In this embodiment, the vehicle to be applied is a four-channel vehicle in which the front and rear wheels can control the left and right braking hydraulic pressure.

In the figure, 1L and 1R are front left and right wheels, 2L and 2R are left and right rear wheels, 3 is a brake pedal, and 4 is a tandem master cylinder (M / C). 3a is a booster as a brake booster, and 4a is a reservoir. Each wheel 1L, 1R, 2L, 2R is provided with a wheel cylinder 5L, 5R, 6L, 6R that frictionally holds a brake disc by hydraulic pressure to apply a braking force to each wheel. When the hydraulic pressure from the master cylinder 4 is supplied to (W / C), each wheel is braked individually.

In this embodiment, the brake fluid pressure (braking fluid pressure) system of the braking device is such that the front wheel brake system 7F from the master cylinder 4 has the conduits 8F, 9F, 10F and the fluid pressure control valve 1.
Left and right front wheel cylinders 5L, 5 through 1F, 12F
R, the rear wheel brake system 7R from the master cylinder 4 is connected to the pipelines 8R, 9R, 10R and the hydraulic control valve 11
Left and right rear wheel cylinders 6L, 6R through R, 12R
Lead to.

Hydraulic pressure control valves 11F, 12F, 11R, 12
R is the wheel cylinders 5L and 5L of the corresponding wheels.
By controlling the brake fluid pressure to R, 6L, 6R individually,
Used for anti-skid (ABS) control.
At FF, the brake fluid pressure is increased toward the original pressure in the illustrated pressure increasing position, and the holding (holding pressure) position where the brake fluid pressure does not increase / decrease when the first stage is ON becomes the brake fluid pressure when the second stage is ON. It is assumed that a part of the reservoirs 13F and 13R (reservoir tanks) is in a depressurized position where it is released and lowered.

[0012] Control of these pressure control valve, performed by the appropriate current to the solenoid valve (control valve drive current) I ₁ ~I ₄ from below to the controller (control unit), the current I ₁ ~I ₄ Is 0 A (pressure increasing control signal), the pressure increasing position is above the current I _{1 to} I ₄ is 2 A (holding control signal), and the current holding position is current I _{1 to} I ₄ is 5 A (pressure reducing control signal). At this time, the pressure reduction position is set.

The brake fluid in the reservoirs 13F, 13R is driven by the pump 14 which is driven when the pressure is maintained and the pressure is reduced.
The pipes 8F and 8R are returned to the pipes 8F and 8R by F and 14R, and returned to the accumulators 15F and 15R of these pipes for reuse. Thus, in the brake fluid pressure system, the master cylinder 4 that generates the brake fluid pressure by the driver's operation of the brake pedal 3 and the wheel cylinders 5L and 5R that generate the braking force by the fluid pressure supplied from the master cylinder. Between 6L and 6R, the hydraulic control valves 11F and 1
2F, 11R, and 12R are interposed, and the control valve can switch and control the fluid pressure of each wheel cylinder into three states of pressure reducing, holding, and pressure increasing.

Hydraulic pressure control valves 11F, 12F, 11R, 12
The controller 16 controls ON and OFF by the controller 16, and the controller 16 controls O when the brake pedal 3 is depressed.
Signal from brake switch 18 to N, wheels 1L, 1
The signals from the wheel speed sensors 19 to 22 for detecting the rotational peripheral speeds (wheel speeds) V _{w1 to} V _w4 of R, 2L and 2R are input, respectively.

Further, the controller 16 has a hydraulic pressure P _M of the master cylinder 4 (front wheel hydraulic pressure P _M1 , rear wheel hydraulic pressure P _M2 )
Signals from the hydraulic pressure sensors 33 ₁ and 33 ₂ for detecting the are input. Regarding the master cylinder hydraulic pressure detection, for example, only the front wheel system may be detected and represented. The signal from the wheel speed sensor is used for anti-skid control performed by the controller 16, and the output of the master cylinder hydraulic pressure sensor is used as an input value for setting a variable control threshold in the control as described later.

The controller 16 includes an input detection circuit, an arithmetic processing circuit, and a storage circuit for storing various control programs executed by the arithmetic processing circuit and arithmetic results.
It is composed of a microcomputer including an output circuit for supplying a control signal to the hydraulic pressure control valve. In the arithmetic processing circuit,
Based on the predetermined input information input from the sensors, according to the control program of the anti-skid control described later,
The pressure increasing, pressure reducing, and holding modes are determined, and a control signal corresponding thereto is output to the hydraulic pressure control valve.

In the anti-skid control, basically, in the 4-channel, 4-sensor system as in this example, the wheel speed detection value for each wheel is obtained, and the pressure is reduced so that the slip amount of the corresponding wheel falls within a predetermined range. By controlling the wheel cylinder pressure in the holding and boosting mode (skid cycle), it is possible to perform anti-skid control for each individual wheel, thereby achieving maximum braking efficiency for each wheel.
Avoid wheel locks.

In this way, the controller 16 controls the wheel cylinder pressure to increase, hold, or depressurize based on the detection signal from the wheel speed sensor. Further, the controller 16 is related to the anti-skid control, and is related to the master cylinder. Set the threshold of the master cylinder pressure that monitors the pressure and prevents the control from operating when the detection signal of the master cylinder hydraulic pressure sensor is below a preset value, and the set threshold is the detected master cylinder pressure. On the basis of this, when the master cylinder pressure is zero or extremely low, the threshold value changing control that changes according to the master cylinder pressure is also executed so that the control is changed to a direction in which it is difficult to operate.

In the memory circuit of the controller 16, in addition to the anti-skid control program, for example, a threshold setting map (see FIG. 5) for the threshold changing process applied by the program, and an ABS control map for mode determination ( (See FIG. 6) and the like can be stored in advance.

3 and 4 are flowcharts showing an example of a braking force control program including the threshold value changing process executed by the controller 16, and this program is executed at regular time intervals. In FIG. 3, first, step 1
00, wheel speed sensor, based on the output of the master cylinder pressure sensor, read the wheels 1L, 1R, 2L, wheel speed V _wj of 2R (V _w1 ~V _w4), the master cylinder pressure P _M, respectively. In subsequent steps 101 and 102, the threshold value setting map stored in advance in the storage circuit is checked every time the step is executed, and the control threshold value search and determination processing corresponding to the read master cylinder hydraulic pressure value P _M at that time is performed. Run.

FIG. 5 shows a threshold setting applicable to such processing.
An example of the map is shown, and here, the control threshold α (m /
s²) Is specifically the control valve of the hydraulic control valve shown in FIG.
Wheel addition as a control parameter for control (ABS control table)
It relates to the reference value of wheel acceleration among speed and slip amount.
It is supposed to be. The above processing is provided for hydraulic pressure control
Set the threshold value as a function of the master cylinder pressure,
At extremely low pressure including zero, the threshold value is changed so that it is difficult to control.
And gradually return to the normal threshold value as the hydraulic pressure rises.
This is because the control threshold α is
Normal control threshold α₁And below this
Value α ₀Is defined, and master cylinder pressure P_M(Kgf
/ Cm²), The value α₀To take
In the region of pressure exceeding this value α₀To the value α₁Range between
To take the value of₁To take
The α data is set with the characteristics of the trend as shown in the figure.
ing.

However, after obtaining α according to the master cylinder pressure P _M , every time the step 103 is executed, the retrieved value α is applied as the reference wheel acceleration value, and steps 110 to 113 as shown in FIG. 4 are performed. The hydraulic pressure control routine including is executed. In the hydraulic control routine, the wheel acceleration (differential value of the value V _wj ) for each wheel is based on the read wheel speed V _wj as in the known anti-sud control method using the slip amount and the wheel acceleration as parameters. Then, the slip amount is calculated, the slip amount and the wheel acceleration thus calculated are applied to the ABS control table (step 110), and the wheel for each wheel is calculated.
Decide whether to increase, maintain, or reduce the cylinder pressure (step 1
(11, 112, 113) The braking force is adjusted. In this case, the search value α is used as the reference value with which the calculated wheel accelerations should be compared, and thereby the wheel acceleration reference value is changed.

As shown in FIG. 6, with respect to the wheel acceleration, a reference value α ₂ and another reference value on the negative side are set respectively to define a mode pattern as shown in the drawing, and the calculated slip amount λ and the wheel acceleration are set. By comparing with the reference value,
The anti-sud control is executed according to the control pattern of the control table, but in this control, in that case,
When this is the case, the reference value on the negative side of the wheel acceleration is variable in the range of α _{0 to} α ₁ corresponding to the master cylinder pressure, and the hydraulic pressure control valve is controlled in this manner. It For example, if the calculated wheel acceleration is lower than the variable reference wheel acceleration, the wheel cylinder pressure is considered to be locked and the wheel cylinder pressure is maintained. If it still locks, the pressure is reduced, and when the wheel rotation speed is restored, the hydraulic pressure control valve is increased. Is controlled.

According to the above control, the control threshold value can be appropriately changed by the master cylinder hydraulic pressure,
The driver does not recognize that the brake pedal 3 is stepped on, or the hydraulic control valve is prevented from prematurely operating due to a bad road when the pedal is slightly stepped on. It is possible to achieve compatibility with hydraulic pressure control. More specifically, referring to FIG. 5 and FIG. 6, as shown in FIG. 5, in the region of slow braking (stepping on or stepping on as described above), even if the wheel is on a bad road, Even if rapid decompression is entered, the threshold value α is as low as α = α ₀ ,
That is, it is in a state where it is difficult to maintain the fluid pressure control and reduce the pressure (see α ₀ of the broken line state in FIG. 6). Therefore, at this time, the normal brake (in FIG. 6, the control valve mode is the pressure increasing mode). Will be carried out).

On the other hand, in the case where the driver further depresses the brake pedal 3, and further in the case of the region, the following is performed. That is, in the region, with respect to the threshold value α according to the master cylinder pressure P _M , the early operation of the control valve on a bad road suppresses this, and on the other hand, the soft brake on an icy road or the like is suppressed.
In order to prevent this, the time lock is gradually increased in the range of α ₀ to α to α ₁ , and when reaching the region, α = α ₁ (predetermined value) so that the fluid pressure control is performed at the normal threshold value α. Value). Here, as the α ₁ value itself, AB on the low μ road
The effect of S control can be emphasized and set.

By doing so, as shown in the ABS control table of FIG. 6, in the region of FIG. 5, the reference wheel acceleration which is the threshold value becomes the value α ₀ , and as a result, the pressure increasing mode zone is widened and the holding mode is maintained. The zone becomes narrower. This is A
This means that the BS control is in a direction in which it is difficult to operate. On the other hand, in the region, the master cylinder pressure P _M
Accordingly, the holding mode zone is widened by gradually changing from α ₀ to α ₁ , and in the region, the reference value of the wheel speed acceleration as the threshold value returns to the normal state of the value α ₁ described above.

Thus, in this embodiment, the threshold value α for starting the anti-skid control is set to the master cylinder pressure P _M.
On the basis of the above, when the master cylinder pressure P _M is zero or extremely low, it is possible to realize control in which the control is changed to a direction in which the control is difficult to start. Therefore, when the vehicle is traveling on a bad road or an illegal road, Undesirable early activation of anti-skid control due to running on the road is prevented, and in such a case, the wheel cylinder from the master cylinder side even if the driver depresses the brake pedal, for example, when the driver needs to brake from the state of putting on the foot. A state in which the hydraulic pressure is not transmitted and the hydraulic pressure becomes insufficient can be eliminated.

FIG. 7 shows a wheel speed sensor, a brake switch (S / W), a controller by a microcomputer which outputs a hydraulic pressure control signal using signals from these sensors, and a liquid operated by the output control signal. 9 is a control time chart of a braking force control device including a pressure control valve, which is used when a program as shown in FIG. 8 is created. This does not have the control as described above. That is, FIG. 7A shows the transition of the wheel speed, and FIG. 7B shows the transition of the differential change rate thereof. The comparison value α ₁ in FIG. 7B does not depend on the master cylinder pressure as shown in the figure. 7 is a fixed value fixed in FIG.
In the above case, the switching timing of the hydraulic pressure control valve for depressurizing, holding, and boosting modes and the transition of changes in the master cylinder pressure and the wheel cylinder pressure are shown.

The following is a comparison between this and the control according to the present embodiment. In this case, as shown in the program of FIG. 8, the brake switch signal is used to determine the fluid pressure control, and the brake switch is turned off.
If so, the liquid pressure control is not performed. When it is determined that the brake switch signal is ON / OFF, the braking fluid pressure control routine is passed, and in this state of the brake switch OFF, it is assumed that the brake fluid pressure control routine shown in FIGS. Even if there is a sharp drop in wheel speed, such as
If the braking hydraulic pressure control routine is executed, the early operation of switching the hydraulic pressure control valve from the pressure increasing position to the holding position and the pressure reducing position as shown in FIG. 7C does not occur.

On the other hand, a situation in which the driver predicts braking and only puts his foot on the brake pedal to prepare for it occurs while the vehicle is running, and the master cylinder pressure is 0 (FIG. 7). (See (d)) but when the brake switch is ON, or when the pressure is extremely low (for example,
0~5Kgf / cm ² about the pressure of the state) at a little depressed I state, if, FIG. 7 (a), when occurs rapid deceleration with bad road, such as seen in (b), the brake fluid pressure in FIG. 8 In the control routine, at a timing below a predetermined value α ₁ as shown in FIG. 7C, the hydraulic pressure control valve, which was in the normal pressure increasing position, is switched to the holding position, and further to the pressure reducing position. In this way, the hydraulic control valve is operated. However, in this case, further, if it is the case that the driver who put his foot on the brake pedal depresses the brake pedal with the intention of braking at the timing shown in FIG. Even if the driver starts to depress, the wheel cylinder pressure changes as shown in the figure in response to the rise in the master cylinder pressure, and as a result, in such a situation, the amount indicated by the shaded area is sufficient for the driver's intention. It is difficult to obtain the braking force. On the other hand, in the present embodiment, it is possible to deal with the situation as described above, and it is possible to avoid the state where the hydraulic pressure is insufficient because the wheel cylinder hydraulic pressure is not transmitted from the master cylinder side. Is.

A sensor for detecting the wheel speed and a controller for activating the hydraulic pressure control valve according to the slip state are provided, and the sensor for detecting the hydraulic pressure of the master cylinder is used to activate the hydraulic pressure control valve according to the road surface condition. The present control that can change the threshold value to be used can be used in a method other than the above-described method. For example, in the embodiment, the threshold value α for the reference wheel acceleration is changed, but the slip in the ABS control table of FIG. It is also possible to set the threshold value for the rate λ and change the threshold value λ.

[0032]

According to the present invention, in the braking force control for controlling the fluid pressure of the wheel cylinder to at least one of the pressure reduction, the pressure retention and the pressure increase based on the wheel speed detection signal, the threshold value for starting the control is set to the master cylinder. When the master cylinder pressure is zero or extremely low based on the pressure, the control can be appropriately changed to a direction in which it is difficult to start, and even if the vehicle is traveling on a bad road, undesired control It is possible to prevent an early operation and prevent a situation where the braking force is insufficient. The prevention of early actuation of control due to a bad road or the like and the achievement of sufficient controllability when necessary enhance the effectiveness of such braking force control.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a braking force control device of the present invention.

FIG. 2 is a system diagram of a braking force control device according to an embodiment of the present invention.

FIG. 3 shows an example of a braking force control program executed by a controller, and is a partial flowchart thereof.

FIG. 4 is also another part of the flowchart.

FIG. 5 is a diagram showing an example of a threshold setting map applicable to the program.

FIG. 6 is a diagram similarly showing an example of a hydraulic pressure control map.

FIG. 7 is an example of a time chart in the case of a comparative example shown in comparison with the present embodiment.

FIG. 8 is a control flowchart of the comparative example.

[Explanation of symbols]

 1L, 1R Left and right front wheels 2L, 2R Left and right rear wheels 3 Brake pedal 4 Master cylinder 5L, 5R, 6L, 6R Wheel cylinder 11F, 11R, 12F, 12R Hydraulic control valve 16 Controller 18 Brake switch 19-22 Wheel speed sensor

Front Page Continuation (72) Inventor Shinji Matsumoto 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Nissan Motor Co., Ltd.

Claims (1)

[Claims] 1. A master cylinder that generates a brake fluid pressure by operating a driver, a wheel cylinder that is provided for each wheel and that generates a braking force by supplying a brake fluid pressure, and a rotational speed of a wheel is detected. A braking force control device comprising: a wheel speed detecting means; and a control means for controlling a fluid pressure of a wheel cylinder to at least one of pressure reducing, holding and pressure increasing based on a detection signal of the wheel speed detecting means, And a threshold setting means for setting a master cylinder pressure threshold at which the control means does not operate when the detection signal of the master cylinder pressure detection means is equal to or less than a preset value. A threshold value set by the threshold value setting means based on a detection signal of the master cylinder pressure detection means A braking force control device comprising: threshold changing means for changing the control means in a direction in which the control means is hard to operate when the pressure is zero or extremely low.