JP2002127884A - Brake hydraulic pressure control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a brake hydraulic pressure control device capable of controlling holding and pressure intensifying time after decompression of brake hydraulic pressure of a wheel to the optimum one. SOLUTION: The brake hydraulic pressure control device to repeat holding and pressure intensification after decompressing hydraulic pressure of a brake 5 of the wheel when it detects a skid state of the wheel constitutes its characteristic feature of furnishing a target slip ratio setting means 25 to set a slip ratio (Vs-Vw)/Vs of each of the wheels at a target slip ratio Sa at the time when wheel acceleration DVw reaches the top point while the brake hydraulic pressure is held after the hydraulic pressure of the brake 5 of the sheel is decompressed and deciding the holding and pressure intensifying time of the hydraulic pressure of the brake 5 of the wheel in accordance with the target slip ratio Sa set by the target slip ratio setting means 25.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a brake fluid pressure control device, and more particularly, to a brake fluid pressure control device used for a vehicle anti-skid control device, a vehicle traction control device, and the like.

[0002]

2. Description of the Related Art A conventional brake fluid pressure control device is disclosed in Japanese Patent Application Laid-Open No. Hei 8-295223.
This is a brake fluid pressure control device that calculates a deviation of the wheel deceleration from the estimated vehicle body deceleration at predetermined time intervals, and controls a holding / pressure increase time after the brake fluid pressure of the wheels is reduced based on the deviation. .

Japanese Patent Application Laid-Open No. 4-345567 discloses that the brake fluid pressure of a wheel is increased, and the holding / pressure increase time after the brake fluid pressure of the wheel is reduced according to a change in a slip ratio before and after the pressure increase. A controlling brake fluid pressure control device is disclosed.

[0004]

However, the coefficient of friction (μ) of the road surface is determined by the type and condition of the road surface, the load conditions of the wheels,
And the calculated values such as the estimated vehicle deceleration calculated during the control are based on the current μ value. It is difficult to control the holding / pressurizing time after the pressure reduction to an optimum value.

Particularly, in the latter prior art, when calculating the change in the slip ratio before and after the increase in the brake fluid pressure of the wheels, it is necessary to always calculate the change in the slip ratio while keeping the pressure increase constant. , Near the peak value of μ, the pressure increase exceeds the peak value of μ, and it is difficult to control the holding / pressure increase time after the pressure reduction of the brake fluid pressure of the wheels to an optimum value.

Accordingly, an object of the present invention is to provide a brake fluid pressure control device capable of controlling the time for maintaining and increasing the brake fluid pressure of the wheel after the pressure is reduced to an optimum value in order to solve the above problems.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, according to the first aspect of the present invention, when a skid condition of a wheel is detected, the brake fluid pressure of the wheel is reduced, and then the brake fluid pressure is repeatedly maintained and increased. In the control device, wheel speed detecting means for detecting a wheel speed of each wheel of the vehicle; estimated vehicle speed calculating means for calculating an estimated vehicle speed from the wheel speed of each wheel detected by the wheel speed detecting means; Slip ratio calculating means for calculating a slip ratio of each wheel from the estimated vehicle speed calculated by the speed calculating means and the wheel speed detected by the wheel speed detecting means; and a wheel speed of each wheel detected by the wheel speed detecting means From the wheel acceleration calculation means for calculating the acceleration of each wheel from, and after reducing the brake fluid pressure of the wheels, while holding the brake fluid pressure, When the wheel acceleration calculated by the wheel acceleration calculating means reaches the highest point, the slip rate of each wheel calculated by the slip rate calculating means is set to a target slip rate. A brake fluid pressure control device is characterized in that the time for maintaining and increasing the brake fluid pressure of the wheels is determined according to the target slip ratio set by the target slip ratio setting means.

According to the first aspect of the present invention, when the wheel acceleration reaches the value of the uppermost point is determined to be the time when μ is the highest, the slip rate at that time is set as the target slip rate, and the target slip rate is set. Accordingly, since the time for maintaining and increasing the brake fluid pressure of the wheel is determined, a brake pressure control device capable of controlling the time for maintaining and increasing the brake fluid pressure of the wheel to an optimum value can be provided.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a brake fluid pressure control device according to an embodiment of the present invention. FIG. 1 shows only one wheel.

In FIG. 1, a master cylinder 1 is connected to a brake pedal 3 to generate a brake hydraulic pressure by transmitting a brake operating force of a vehicle driver. The master cylinder 1 is connected to the wheel brake 5 via the main hydraulic pressure path 7 so that brake hydraulic pressure can be applied to the wheel brake 5. Further, a pressure-intensifying valve 11, which is an electromagnetic valve that is normally open, is provided in the main hydraulic pressure path 7.

The recirculation passage 9 is connected to the main hydraulic pressure passage 7 and to the reservoir 13, and is provided with a pressure reducing valve 15 which is a normally closed solenoid valve.

The electric motor 17 is connected to the hydraulic pump 19 and returns the brake fluid in the reservoir 13 to the main hydraulic pressure path 7. The electric motor 17 is electrically connected to a power supply 23 of the vehicle via the switch element 21.
Is also connected to the controller 25. The wheel speed sensor 27 is installed near a wheel (not shown) of the vehicle, detects a wheel speed, and transmits a wheel speed signal to the controller 25. The pressure increasing valve 11 and the pressure reducing valve 15 are also electrically connected to the controller 25, respectively.

The anti-skid control (ABS control) in the brake fluid pressure control device shown in FIG. 1 will be described. The driver of the vehicle operates the brake pedal 3 to generate hydraulic pressure in the master cylinder 1, and the generated hydraulic pressure of the master cylinder 1 is transmitted to the wheel brake 5 via the main hydraulic pressure path 7 and to the wheels (not shown). Generate braking force.

When an excessive brake fluid pressure is applied to the wheel brake 5 and the wheel speed sensor 27 detects a skid state of a wheel (not shown), ABS control is started, and the controller 25 sends a signal to the solenoid (not shown) of the pressure increasing valve 11. When energized and operated, switching from the open state to the closed state,
The solenoid (not shown) of the pressure reducing valve 15 is energized and operated to switch from the closed state to the open state. Thereby, the communication between the wheel brake 5 and the master cylinder 1 is cut off,
It communicates with the reservoir 13. Therefore, the wheel brake 5
Is discharged to the reservoir 13, and the hydraulic pressure of the wheel brake 5 is reduced.

When the ABS control is started, the switch element 21 is turned on by the controller 25 and a current is supplied from the power supply 23 to the electric motor 17 to be driven. The hydraulic pump 19 is driven by the electric motor 17, and the brake fluid once stored in the reservoir 13 is returned to the master cylinder 1.

When the rotation of the wheels is restored by the pressure reduction of the wheel brake 5, the controller 25 controls the pressure reducing valve 15
Is closed, and the wheel brake 5 is
And not in communication with the reservoir 13, the wheel brake 5
Is maintained. Thereafter, the operation and non-operation of the pressure intensifying valve 11 are repeated by the controller 25 again.
Pressure increase and holding of the wheel brake 5 are repeated.

FIG. 2 is a generic flowchart of the brake fluid pressure control device according to the present invention. Step S10
At 0, the controller 25 calculates the wheel speed (Vw) based on the wheel speed signal transmitted by the wheel speed sensor 27. In step S200, the calculated wheel speed (V
Wheel acceleration / deceleration (DVw) is calculated based on w). Furthermore,
In step S300, an estimated vehicle speed (Vs) is calculated based on the wheel speed (Vw) calculated in step S100. In step S400, based on the estimated vehicle speed (Vs) calculated in step S300, the estimated vehicle acceleration / deceleration (D
Vs) is calculated.

Hereinafter, the target slip calculation in step S500 in FIG. 2 will be described in detail with reference to FIGS. In step S502 in FIG.
It is determined whether the S control is being performed. If the ABS control is being performed, it is determined in step S504 whether there is a pressure reduction output request from the controller 25. If there is a reduced pressure output request, it is determined in step S506 whether or not there has been a previous reduced pressure output request. If there has been a previous pressure reduction output request, it is determined in step S510 whether or not the target slip ratio has been calculated. If it is determined in step S506 that there is no previous pressure reduction output request, it is determined that pressure reduction has started, and step S506 is performed.
At 508, a flag of "no target slip ratio calculation" is set. If it is determined in step S510 that the target slip ratio has not been calculated, it is determined in step S512 whether the target slip ratio has been previously calculated. If there is no previous calculation of the target slip rate, step S514
Whether the wheel speed (Vw) exceeds VwLpeak,
That is, it is determined whether or not the wheel speed (Vw) is in a recovery state. When the wheel speed (Vw) is in the recovery state, step S51
In step 6, the “counter after VwLpeak” is set to +1. If it is determined in step S512 that the target slip ratio has been calculated last time, or if it is determined in step S514 that the wheel speed (Vw) is not in the recovery state, VwLpeak, VwLpeak slip, VwLpeak in step S518.
Update the slip rate and DvwHpeak and set the counter after VwLpeak to 0
And

In step S520, it is determined whether the current wheel acceleration / deceleration (DVw) is smaller than DvwHpeak. In step S518, the initial value of DvwHpeak is set to a value when the wheel speed (Vw) is near the lowest point, that is, substantially zero. Therefore, when the wheel speed (Vw) is in the recovery state, the wheel acceleration / deceleration (DVw) takes a positive value,
In step S520, the wheel acceleration / deceleration (DVw) is DvwHpea.
k is larger than k, and in step S522, Dvw
The value of Hpeak is updated. When the wheel speed (Vw) gradually recovers and the wheel acceleration / deceleration (DVw) approaches the uppermost point, when the wheel acceleration / deceleration (DVw) exceeds the uppermost point, step S5 is performed.
At 20, the wheel acceleration / deceleration (DVw) is DvwHpeak (previous DVw
Is determined to be smaller than the current wheel speed (Vw) in step S524, and the flag of “the target slip ratio is calculated” is set in step S524.
The target slip ratio (Sa) is calculated using the estimated vehicle speed (Vs).

Next, in step S528, the target slip ratio (Sa) and the target slip ratio (Sa) of the opposing wheels (the front right wheel and front left wheel or the rear right wheel and rear left wheel, hereinafter referred to as opposing wheels) are increased by a predetermined amount C. It is determined whether there is a difference exceeding. When there is a difference exceeding C between the target slip ratio (Sa) and the target slip ratio (Sa) of the opposite wheel, the wheel speed is determined in step S530.
The difference between the slip ratio (VwLpeak slip ratio) when the (Vw) is at the lowest point and the target slip ratio (Sa) is compared, and when the difference is less than the predetermined amount e, it is determined that the inner wheel is turning, and S
At 532, a flag indicating "there is a request for correction of the target slip ratio" is set. When the difference is equal to or more than the predetermined amount e, step S5
At 36, a flag of "no target slip ratio correction request" is set. That is, the vehicle is in a turning state when the difference between the target slip rates between the opposed wheels exceeds a predetermined amount, and the difference between the slip rate at the time of maximum drop of the wheels and the target slip rate (Sa) is less than a predetermined value. Judgment is made, and the target slip ratio (Sa) is corrected. On the other hand, when the difference between the target slip rates between the opposing wheels is equal to or less than a predetermined amount, or when it is determined that the difference between the slip rate at the time of maximum wheel drop and the target slip rate (Sa) is equal to or more than a predetermined value. The correction of the target slip ratio (Sa) is not performed. When the target slip ratio (Sa) is corrected, the process proceeds to step S540 via step S538, and the target slip 1 (Sv) is corrected by the predetermined value g and set. Further, in step S542, the target slip 2 (Sv) is corrected and set by the predetermined values j and g. On the other hand, in steps S544 and S546, the target slip 1 (Sv) and the target slip 2 (Sv) are not corrected.
Is calculated.

If it is determined in step S502 that control is not being performed, a flag indicating "no target slip rate calculation" is set in step S548, and the target slip rate (Sa) is set to a predetermined value A in step S550. After that, in step S552, VwLpeak, VwLpeak slip, VwLpeak slip rate, and DvwHpeak are updated, the post-VwLpeak counter is set to 0, and in step S554, a "target slip rate correction request not required" flag is set.

Next, AB in step S600 in FIG.
The S control will be described with reference to FIG. If it is determined in step S602 in FIG. 5 that the ABS control is not being performed, the process proceeds to step S604, in which the slip ratio is set to the target slip ratio.
If (Sa) is exceeded, a control flag is set (step S60).
6) The process proceeds to step S622. If the slip ratio is equal to or less than the target slip ratio (Sa), both the pressure increasing valve 11 and the pressure reducing valve 15 are deactivated in step S608, and the wheel brake 5 communicates with the master cylinder 1 and is disconnected from the reservoir 13. Further, step S61
At 0, the pulse increase output time is set to 0, and at step S612, a flag of "no pressure reduction output request" is set.

If it is determined in step S602 that the ABS control is being performed, it is determined in step S614 whether the current slip amount is equal to or more than the target slip 1 (Sv) calculated in step S540 or step S544.
If the current slip amount is equal to or more than the target slip 1 (Sv), the pulse increase time is set to the predetermined value i in step S616.
It is determined whether it is less than. After the pulse increase mode, if it is determined that the pulse increase time is less than the predetermined value i, in step S618, the current slip amount exceeds the VwLpeak slip, that is, the drop amount of the wheel speed (Vw) is It is determined whether or not the maximum drop amount is exceeded, and if it is determined that it is not more than the previous wheel maximum drop amount, in step S620, the pressure increasing valve 11 is operated and the pressure reducing valve 15 is deactivated, and the wheel brake 5 is turned off. The master cylinder 1 and the reservoir 13 are shut off to maintain the brake fluid pressure. The brake fluid pressure of the wheel brake 5 is maintained until the current slip amount exceeds the VwLpeak slip,
Wheel vibration / disturbance correction is performed.

When the current slip exceeds the VwLpeak slip, the wheel acceleration / deceleration (DVw) is determined in step S622.
Is determined to be a negative value. If the value is a negative value, the pressure-reducing mode is entered in step S624 and the pressure-intensifying valve 1
1 and the pressure reducing valve 15 are both activated, the wheel brake 5 is cut off from the master cylinder 1 and communicated with the reservoir 13. Thereafter, in step S626, a flag of "request for pressure reduction output" is set, and in step S628, the pulse pressure increase output time is set to 0. As can be seen from the above, the start timing of the pressure reduction mode during the ABS control is determined by comparing the current slip ratio and the target slip ratio (Sa) in step S604 or the current slip amount and the target slip 1 (Sv) in step S614. ) Will be determined by the comparison result.

On the other hand, if it is determined in step S614 that the current slip amount is less than the target slip 1 (Sv), it is determined in step S630 whether or not the pressure reduction mode has been set. After it is determined in step S630 that the mode is the pressure reduction mode, if it is determined in step S632 that the target slip ratio (Sa) has been calculated, step S632 is performed.
At 634, the current slip amount is equal to the target slip 2 (SV).
When it is less than the target slip 2 (SV), it is determined that the pressure is to be increased, and the process proceeds to step S700 to start the pulse increasing control. This will be described later. Then, in step S636, the pulse increase output time counter is set to +1.
In step S638, it is determined whether or not the increased pulse output time exceeds h. If the increased pulse output time exceeds h, a flag outside the control is set in step S640, and the process proceeds to step S608. If the pulse increase output time is equal to or less than h, the process proceeds to step S612.

In step S632, the target slip ratio
If it is determined that (Sa) has not been calculated, the wheel acceleration / deceleration (DVw)
Is determined to have passed the uppermost point, and in step S622, a determination of holding or pressure reduction is made.

If it is determined in step S634 that the current slip amount is equal to or greater than the target slip 2 (SV), it is determined that the wheel speed has not recovered due to the slip amount that can be increased, and in step S620 Brake fluid pressure is maintained.

Next, the pulse increase control in step S700 in FIG. 5 will be described with reference to FIG. Step S
At 702, it is determined whether or not the wheel acceleration / deceleration (DVw) is less than a predetermined value q (for example, 3G). If it is not less than q, at step S710, the holding time is small and the pressure increasing time is large (for example, 20 ms The time is set to 5 ms), and the extreme pulse increasing mode is executed. If it is determined that the wheel acceleration / deceleration (DVw) is less than q and that the ratio of the current slip amount to the target slip 1 (SV) is equal to or less than the predetermined value m in step S704, the holding time is determined in step S712. During pressure increase time (for example, hold time 20ms, pressure increase time 4m
s), and the rapid pulse increase mode is executed. The ratio of the current slip amount to the target slip 1 (SV) is a predetermined value m
When it is determined in step S706 that it is less than the predetermined value n, the holding time is set to be small and the pressure increasing time is small (for example, the holding time is 20 ms and the pressure increasing time is 3 ms) in step S714. The pulse increase mode is executed. In addition, the ratio of the current slip amount to the target slip 1 (SV) exceeds the predetermined value n, and step S708
When it is determined in step S716 that the pressure is equal to or less than the predetermined value p, in step S716, the holding time is set to medium and the pressure increasing time is short (for example, the holding time is 100 ms and the pressure increasing time is 3 ms), and the slow pulse increasing mode is executed. Further, when it is determined that the ratio of the current slip amount to the target slip 1 (SV) exceeds the predetermined value p, in step S718, the holding time is large and the pressure increasing time is small (for example, the holding time 250 ms and the pressure increasing time). 3 ms), and the extremely slow pulse increasing mode is executed.

Although the anti-skid control has been mainly described in the above embodiment, the present invention is not limited to this, and can be applied to traction control and the like.

[0030]

According to the present invention, when the wheel acceleration reaches the value of the highest point as described above, it is determined that μ is the highest, and the slip ratio at that time is set as the target slip ratio. The time to maintain and increase the brake fluid pressure of the wheels is determined according to the rate, so the time to maintain and increase the brake fluid pressure of the wheels can be controlled to an optimum value, and the highly safe brake fluid pressure control It can be a device.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a brake fluid pressure control device according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a generic flowchart of a brake fluid pressure control device according to the embodiment of the present invention.

FIG. 3 is a diagram illustrating a state of wheels and a vehicle body during braking.

FIG. 4 is a diagram illustrating a flowchart relating to a target slip calculation of the brake fluid pressure control device according to the embodiment of the present invention.

FIG. 5 is a diagram illustrating a flowchart relating to ABS control of the brake fluid pressure control device according to the embodiment of the present invention.

FIG. 6 is a diagram illustrating a flowchart relating to pulse increase control of the brake fluid pressure control device according to the embodiment of the present invention.

[Explanation of symbols]

 5: Wheel brake Vw: Wheel speed Vs: Estimated vehicle speed DVw: Wheel acceleration / deceleration VwLpeak: Wheel speed lowest point value DVwHpeak: Wheel acceleration / deceleration highest point value Sa: Target slip ratio SV ・ ・ ・ Target slip

Claims (3)

[Claims] 1. A wheel speed detecting means for detecting a wheel speed of each wheel of a vehicle in a brake fluid pressure control device which repeats holding and increasing pressure after reducing the brake fluid pressure of the wheel when detecting a skid state of the wheel. Estimated vehicle speed calculating means for calculating an estimated vehicle speed from the wheel speed of each wheel detected by the wheel speed detecting device; estimated vehicle speed calculated by the estimated vehicle speed calculating device and detected by the wheel speed detecting device Slip rate calculating means for calculating the slip rate of each wheel from the detected wheel speed; wheel acceleration calculating means for calculating the acceleration of each wheel from the wheel speed of each wheel detected by the wheel speed detecting means; After the pressure has been reduced, the wheel acceleration calculated by the wheel acceleration calculating means is at the highest point while the brake fluid pressure is maintained. And a target slip rate setting means for setting the slip rate of each wheel calculated by the slip rate calculation means to a target slip rate when the target slip rate is reached. A brake fluid pressure control device that determines the time for maintaining and increasing the brake fluid pressure of the wheels in response to the determination. 2. The brake hydraulic pressure satisfying claim 1, further comprising: determining a pressure reduction start timing of the wheel brake hydraulic pressure according to the target slip ratio set by the target slip ratio setting means. Control device. 3. The brake fluid pressure control device according to claim 1, wherein when the vehicle is determined to be in a turning state, the target slip ratio is corrected.