JP2960986B2 - Anti-skid control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anti-skid control device for a vehicle, which can control the wheel satisfactorily under the condition that the wheels easily float in the air.

[0002]

2. Description of the Related Art Conventionally, for example, Japanese Patent Application No. 62-207183.
No. (JP-A-1-52566),
Both the calculating wheel deceleration from the signals of wheel speed sensors,
Since it is difficult to obtain the actual vehicle speed, a simulated vehicle speed of the vehicle is estimated, a slip ratio is obtained from the simulated vehicle speed and the wheel speed data of the wheel speed sensor, and the wheel deceleration and the slip ratio are respectively set to threshold values. And according to this result,
2. Description of the Related Art There is known an anti-skid control device that stops a vehicle without locking wheels by reducing, increasing, or maintaining the hydraulic pressure of a wheel cylinder as needed.

[0003] By the way, when a brake is applied to a running wheel, a braking torque exceeds a predetermined amount with respect to a torque for rotating the wheel based on a friction coefficient (road surface μ) between the wheel and the road. In addition, it is known that the lower the road surface μ, the greater the wheel deceleration. That is, when the brake is applied during running and a slip occurs, the wheel deceleration increases as the road surface μ decreases. For this reason, in the first cycle (first cycle) in which the road surface μ cannot be determined in the anti-skid control, the larger the wheel deceleration is,
It is determined that the road surface μ is small, and a simulated vehicle speed with a small inclination is set.

[0004]

In the first cycle (first cycle) of the above-described anti-skid control, the speed of the wheel is reduced during braking, for example, when the wheel floats in the air. Decelerates rapidly, whereby the control device determines that the μ of the road surface is low, and sets a simulated vehicle speed with a small inclination. However, such a situation in which the wheel floats in the air, for example, floating of both rear wheels during linear braking, floating of the inner wheel during turning braking, etc., is a phenomenon that occurs when braking is performed on a high μ road surface,
This phenomenon occurs more remarkably as the μ of the road surface increases. That is, although it is actually a high μ road surface and a simulated vehicle speed with a large inclination is required, it is determined that the road surface is a low μ road, and thereby, anti-skid control according to the low μ road, for example, There was a problem that the brake pressure was set too low because the brake pressure was reduced too much.

The present invention has been made in view of the above circumstances, and in the first cycle (first cycle) of the anti-skid control, the wheel floats in the air on a high μ road surface and the wheel deceleration is reduced. Provided is an anti-skid control device that, when it becomes large, regards this road surface as a low μ road surface and does not erroneously set a simulated vehicle speed with a small inclination, thereby ensuring a sufficient braking force. With the goal.

[0006]

In order to achieve the above object, according to the present invention, there is provided a modulator for setting a brake fluid pressure for a wheel to at least one of a pressure increase and a pressure decrease;
A wheel deceleration is obtained from a signal of the wheel speed sensor, and a simulated vehicle speed is estimated. Further, a slip ratio is calculated from a difference between the simulated vehicle speed and the wheel speed, and at least the modulator is increased from the slip ratio and the wheel deceleration. An anti-skid control device having a controller set to one of a pressure mode and a pressure reduction mode, wherein the controller reduces the wheel deceleration when the wheel deceleration does not exceed a preset wheel deceleration threshold value. The slope of the simulated vehicle speed is set to decrease as the speed increases, and when the wheel deceleration exceeds a preset wheel deceleration threshold, the slope of the simulated vehicle speed increases as the wheel deceleration increases. Is set to be large.

[0007]

According to the present invention, when the wheel deceleration is between 0 and the wheel deceleration threshold value, normal anti-skid control corresponding to μ of the road surface is performed. When operated, when the wheel deceleration is small, it is determined that the road surface has a high μ, and the slope of the simulated vehicle speed is set to be large.When the wheel deceleration is large, the road surface has a low μ. It is determined that there is, and the setting is made such that the slope of the simulated vehicle speed becomes small. On the other hand, if the wheel deceleration was e Yue the wheel deceleration threshold, without normal antiskid control corresponding to the μ of the road surface, it is determined that the wheel is operating in special circumstances, namely,
It is determined that the road surface has a high μ and a phenomenon that the wheels float in the air has occurred. Thereby, when the brake is operated, the road is determined to have a higher μ as the wheel deceleration becomes larger, and the slope of the simulated vehicle speed is set to be larger. Therefore, according to this antiskid control device configured to, when <br/> wheel deceleration was e Yue a predetermined value, the deceleration of the wheel is caused by the wheel has had floated in the air Thus, it is possible to set the simulated vehicle speed to a large inclination.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of an anti-skid control device shown as one embodiment of the present invention will be described below with reference to FIGS. First, the overall configuration of the anti-skid control device will be described with reference to FIGS. Reference numeral 1 denotes a master cylinder, and this master cylinder 1 is a brake pedal 2
The brake pressure is generated by the stepping force. The hydraulic pressure generated by the master cylinder 1 is supplied to wheel cylinders 4 and 5 (not shown) of the left and right front wheel brakes via a modulator 3, and the right and left rear cylinders are controlled via hydraulic pressure control valves 6 and 7. The brake is supplied to the wheel cylinders 8 and 9 of the wheel brakes. The modulator 3 is arranged such that each of the wheel cylinders 4, 5, 8,.
9 provided in the piping system toward
It has a function of restricting an increase in brake fluid pressure or recovering the fluid pressure by a control signal supplied from zero. The details of the modulator 3 will be described later. Each of the wheels is provided with a wheel speed sensor S for detecting its peripheral speed. Wheel speed data obtained from these wheel speed sensors S is supplied to the controller 10. Then, the controller 10 determines whether or not the wheel is slipping based on the wheel speed data, and calculates the degree of the slip by calculation, and performs predetermined anti-skid control on the modulator 3 based on the calculation result. It is made to run.

Next, a specific configuration of each of the modulators 3 will be described with reference to FIG. Reference numerals 11 to 14 denote switching valves that are switched to any of open and closed positions.
Piping systems from the master cylinder 1 to the wheel cylinders 4, 5, 8, 9 are opened and closed by 1 to 14, respectively. The switching valves 11 to 14 are provided with check valves 15 to 18, respectively.
In the "closed" state of Nos. 1 to 14, the flow of liquid in the direction toward the master cylinder 1 is permitted. Further, switching valves 19 to 22 are connected to positions parallel to the switching valves 11 to 14, respectively.
22 open and close to release the hydraulic oil in the wheel cylinders 4.5, 8.9 to the reservoirs 23 and 24, respectively, according to the control signal supplied from the controller 10. Reference numerals 25 and 26 denote pumps driven by a motor 27, respectively.
In response to a control signal supplied from 0, the system is driven to recover the hydraulic pressure of the piping system that has decreased during anti-skid control.

[0010] With the above configuration, the modulator 3 is provided in a piping system from the master cylinder 1 to the wheel cylinders 4, 5, 8, 9.
(A) When switching valves 11 to 14 are "open", switching valves 19 to 22
(B) switching valves 11 to 1
4 is "closed" and the switching valves 19 to 22 are set to one of the pressure reducing mode in which the valves are opened and (c) both the switching valves 11 to 14.19 to 22 are set to one of the holding modes in which the valves are closed. The flow of liquid in the pipeline between each of the wheel cylinders 4, 5, 8, and 9 and the master cylinder 1 is controlled.

In the modulator 3 configured as described above, when the driver depresses the brake pedal 2 to apply the brake, the pressure increasing mode is set, whereby the wheel cylinders 4, 5, 8,. Although the hydraulic pressure is increased by supplying hydraulic oil to 9,
At this time, if a slip occurs on the wheels, the controller 10 performs anti-skid control, and based on the signal supplied from each wheel speed sensor S, sets the modulator 3 from the pressure increasing mode to, for example, the pressure decreasing mode or the pressure decreasing mode. It is set to hold mode. For example, the controller 10 obtains the wheel deceleration from the signal of the wheel speed sensor S and estimates the simulated vehicle speed, further calculates the slip rate from the difference between the simulated vehicle speed and the wheel speed, and calculates the slip rate and the wheel deceleration. Thus, the modulator 3 is set to one of the pressure increasing, holding, and pressure decreasing modes.

Here, the flowchart of FIG. 3 and the flowchart of FIG.
The wheel control will be described step by step with reference to the graph showing the relationship between the magnitude of the wheel deceleration (-AWHEEL) and the slope (-V'REF) in the deceleration of the simulated vehicle speed shown in FIG. It will be used as various judgment data in the following description.
As described above, the wheel acceleration / deceleration (AWHEEL) is calculated based on the wheel speed data output from the wheel speed sensors S, and is composed of a differential value of the wheel speed.
When the value of the wheel acceleration / deceleration AWHEEL is larger than 0 (0 <AWHEEL
EL) indicates acceleration, and if less than 0 (AWHEEL <0)
Represents deceleration. In addition, wheel deceleration (when AWHEEL <0,
In this case, the wheel deceleration threshold value A to be compared with -AWHEEL) and the control content shown in the following flowchart are stored in the controller 10 in advance. The flowchart shown in FIG.
This is the first process (the first cycle of anti-skid control) performed when there is almost no slip or when the wheel suddenly decelerates (slip state or the wheel floats in the air), and the wheel speed is simulated. In the case of a so-called wheel spin exceeding the vehicle speed, the control is performed according to another flowchart.

<Step 1> Immediately after the driver performs the brake operation, the speed of each wheel is
It is determined whether the vehicle is increasing or decreasing. If the vehicle is increasing ( wheel acceleration / deceleration AWHEEL ≧ 0 ), the process proceeds to step 2, and the vehicle is decreasing ( wheel acceleration / deceleration AWHEEL <
0 ), go to step 3. << Step 2 >> The slope of the simulated vehicle speed when the wheels tend to accelerate (V'RE
F) Set. For example, a predetermined large inclination is set. However, the processing content of step 2 may be any commonly performed processing. << Step 3 >> It is determined whether or not the magnitude of the wheel deceleration (-AWHEEL) exceeds the "wheel deceleration threshold value A", and the magnitude of the wheel deceleration is determined.
If (−AWHEEL) does not exceed the “wheel deceleration threshold value A” (≦ A), proceed to step 4 and
If the magnitude (−AWHEEL) exceeds the “wheel deceleration threshold value A” (> A), the routine proceeds to step 5.

<< Step 4 >> The slope of the simulated vehicle speed when the wheels are decelerating (−V′RE
F) is set as in the following equation (1). −V′REF = 1.2 g− (1.2 g / A) · ( −AWHEEL ) (1) (where g indicates the gravitational acceleration, and A indicates the wheel deceleration threshold value shown in step 3) And the above formula (1)
Accordingly, as shown in (a1) in Figure 4, the wheel deceleration larger
As the magnitude (-AWHEEL) increases, the slope (-V'REF)
The simulated vehicle speed is set such that the relationship becomes smaller. << Step 5 >> The slope of the simulated vehicle speed when the wheels are decelerating (−V′RE
F) is set as in the following equation (2). −V′REF = (1.2 g / A) · ( −AWHEEL ) −1.2 g (2) (where “g” indicates the gravitational acceleration and “A” is the wheel deceleration shown in step 3) The threshold value is shown.) Then, according to the above equation (2), as shown by (a2) in FIG. 4, as the magnitude (−AWHEEL ) of the wheel deceleration increases, the slope ( −AWHEEL ) increases.
V'REF) is set so that the simulated vehicle speed becomes large.

[0015] Here, as to calculate the slip ratio from the difference between the simulated vehicle speed and the wheel speed which is determined as described above, and the slip ratio, the car calculated from the signal of the wheel speed sensor
Two examples (a) and (b) of determining the mode of the modulator 3 from the wheel acceleration / deceleration (AWHEEL ) will be described. (A) As shown in Japanese Patent Application No. 62-207183,
In principle, (1) control is performed to reduce the brake pressure when the slip ratio λ exceeds the threshold value λ1, and (2) to increase the brake pressure when the slip ratio λ is less than the threshold value λ1. Control. In this case, when the wheel acceleration / deceleration AWHEEL is smaller than b (generally b ≦ −1) in the above (2), it is determined that there is a tendency for slipping, and the braking force that should be increased is maintained as it is. Hold the brake pressure as much as possible. (B) As shown in Japanese Patent Application No. 1-222728, basically, the slip ratio λ exceeds a predetermined threshold value and the magnitude of wheel deceleration (−AWHEEL) is a predetermined threshold value. When the vehicle speed exceeds the threshold value, the brake fluid pressure is reduced assuming that the wheel is approaching the locked state, and the magnitude of the wheel deceleration (−A
If WHEEL does not exceed a predetermined threshold, the brake fluid pressure is increased.

According to the flowchart shown in FIG. 3 described above , the magnitude of the wheel deceleration (-AWHEE
L) from 0 to a predetermined value (wheel deceleration threshold A)
Normal anti-skid control corresponding to μ of the road surface is performed, that is, when the brake is operated,
When the wheel deceleration A (Wheel) is small, it is determined that the road surface has a high μ, the slope of the simulated vehicle speed (−V′REF) is set to be large, and the magnitude of the wheel deceleration (−
AWHEEL) is determined to be a low μ road surface, and the slope (−V′REF) of the simulated vehicle speed is set to be small. On the other hand, the magnitude of the wheel deceleration (-AWH
If the EEL) exceeds a predetermined value (the wheel deceleration threshold A) does not perform the normal antiskid control corresponding to the μ of the road surface, it is determined that the wheel is operating in special circumstances,
In other words, it is determined that a phenomenon occurs in which the wheel floats in the air due to the high μ road surface. Thus, when the brake is operated, the larger the wheel deceleration (-AWHEEL) is, the higher the road surface is determined to be, and the simulated vehicle speed gradient (-V'REF) is further increased. The settings are as follows.

[0017] Then, according to the anti-skid control apparatus shown in this embodiment, when the wheel deceleration magnitude (-AWHEEL) exceeds a predetermined value (the wheel deceleration threshold A), the deceleration of the wheel Can be determined to be caused by the wheel floating in the air, whereby the simulated vehicle speed is increased by a large slope (−V′REF) according to the above equation (2).
, And an effect that a sufficient braking force can be secured can be obtained.

The flowchart shown in FIG. 3 shows the wheel acceleration / deceleration calculated by a main program (not shown).
(AWHEEL) The processing is performed using (differentiating the signal from the wheel speed sensor S) or the like. After passing through the flowchart shown in FIG. 3, the process returns to the main program. When the pressure is applied (when the second cycle of the anti-skid control is entered), the process does not return to the flowchart shown in FIG. That is, the flowchart shown in FIG. 3 is applied in the first cycle (first cycle) in which the road surface μ cannot be grasped.

In this embodiment, the slope (-V'REF) of the simulated vehicle speed is set as shown in (a1) and (a2) of FIG. 4, but is not limited to this. c)
May be set on the step as shown in FIG.
2) may be set as shown by the dotted line (b).

[0020]

According to the anti-skid control device described in detail above, when the wheel deceleration exceeds a predetermined value, the deceleration of the wheel is caused by the fact that the wheel floats in the air. Can be determined, whereby
As the wheel deceleration increases, the simulated vehicle speed can be set to a larger inclination, and an effect that a sufficient braking force can be secured can be obtained.

[Brief description of the drawings]

FIG. 1 is a piping diagram showing a brake hydraulic system for supplying hydraulic oil to a wheel cylinder of a brake.

FIG. 2 is a piping diagram showing a specific configuration of the modulator of FIG.

FIG. 3 is a flowchart according to the present invention for controlling a modulator.

FIG. 4 is a graph showing the relationship between the magnitude of wheel deceleration (-AWHEEL) and the slope of the simulated vehicle speed (-V'REF).

[Explanation of symbols]

 3 Modulator 10 Controller

Claims (1)

(57) [Claims] 1. A modulator for setting a brake fluid pressure for a wheel to at least one of pressure increase and pressure reduction, a wheel deceleration is obtained from a signal of a wheel speed sensor, and a simulated vehicle speed is estimated. And the slip rate is calculated from the difference between the slip rate and the wheel deceleration,
In an anti-skid control device having a controller that sets the modulator to at least one of a pressure increasing mode and a pressure decreasing mode, the controller includes:
If the wheel deceleration does not exceed the preset wheel deceleration threshold, the slope of the simulated vehicle speed is set to decrease as the wheel deceleration increases, and the wheel deceleration is set to a preset wheel deceleration. An anti-skid control device characterized in that, when the deceleration threshold value is exceeded, the slope of the simulated vehicle speed is set to increase as the wheel deceleration increases.