JP2001260845A - Hydraulic control device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic control device for a vehicle for driving a motor for a hydraulic pump at all times during antiskid control, keeping the rotating speed of the motor as constant as possible, while restricting energy consumption, and reducing noises with the rotation of the motor. SOLUTION: A pressure is reduced by storing a brake liquid in a wheel cylinder WC for a wheel WL in a reservoir RS via a modulator MD, and the brake liquid in the reservoir is returned between a master cylinder MC and the modulator MD by the hydraulic pump HP driven by the motor M. The motor M is driven at all times during antiskid control. When the quantity of the brake liquid in the reservoir RS is less than a first threshold value, the motor M is driven at a preset minimum rotating speed. When the quantity of the brake liquid in the reservoir is not less than the threshold value, the motor M is driven at a preset rotating speed faster than the minimum rotating speed until the quantity of the brake liquid in the reservoir is less than a second threshold value smaller than the first threshold value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention reduces the pressure of a brake fluid in a wheel cylinder of each wheel by storing the brake fluid in a reservoir through a modulator, and the brake fluid in the reservoir is reduced by a motor-driven hydraulic pump to a master cylinder and a hydraulic cylinder. The present invention relates to a hydraulic pressure control device for a vehicle of a type of returning between modulators.

[0002]

2. Description of the Related Art Various devices are known as a vehicle hydraulic pressure control device. Among them, a brake fluid in a wheel cylinder is stored in a reservoir via a modulator to reduce the pressure, and a hydraulic pump is provided. There is a hydraulic pressure control device configured to return the brake fluid in the reservoir between the master cylinder and the modulator, and to perform anti-skid control, for example, disclosed in Japanese Patent Application Laid-Open No. 09-267736.

[0003] The above publication discloses an anti-lock brake device that detects or estimates the amount of hydraulic oil discharged from a brake cylinder to a reservoir for the purpose of avoiding wasteful energy consumption and preventing generation of vibration and noise. It has been proposed to control the rotation speed of a pump motor so that the entire amount of the hydraulic oil is pressure-fed to a master cylinder within a predetermined time.

[0004]

However, in the apparatus described in the above publication, the rotational speed of the pump motor fluctuates finely at every control cycle during the antilock control as shown in the lowermost part of FIG. 3 of the publication. As a result, the motor driving sound is not stable, and the timbre changes. Although this has a great effect of suppressing energy consumption, it is not enough in terms of preventing noise generation because timbre changes caused by frequent fluctuations in the motor rotation speed cause new noise. It can not be said.

In view of the above, the present invention provides a vehicle hydraulic pressure control device that drives a motor for a hydraulic pump during anti-skid control at all times while keeping the motor speed as constant as possible while suppressing energy consumption. It is an object to reduce noise caused by the noise.

[0006]

According to a first aspect of the present invention, there is provided a motor vehicle comprising: a wheel cylinder mounted on each wheel of a vehicle and a master cylinder; A modulator for adjusting the brake fluid pressure in the wheel cylinder, a reservoir for storing the brake fluid discharged from the wheel cylinder via the modulator, and a fluid for sucking the brake fluid in the reservoir and returning it between the master cylinder and the modulator A pressure pump,
A fluid pressure control device for a vehicle, comprising: a motor for driving the fluid pressure pump; fluid amount estimating means for estimating a brake fluid amount in the reservoir; and motor control means for constantly driving the motor during anti-skid control. When the brake fluid amount in the reservoir estimated by the fluid amount estimating means is less than a first threshold value, the motor control means drives the motor at a predetermined minimum rotation speed to estimate the fluid amount. If the amount of brake fluid in the reservoir estimated by the means is equal to or greater than the first threshold, the amount of brake fluid in the reservoir estimated by the fluid amount estimating means is smaller than the first threshold. The motor is configured to be driven at a predetermined rotation speed higher than the minimum rotation speed until the motor speed becomes lower than a second threshold value.

The motor control means drives the motor at the maximum number of revolutions from the start of driving the hydraulic pump until a predetermined target discharge amount is reached after the driving of the hydraulic pump. Preferably, the motor is driven at the minimum speed after reaching the quantity.

Further, as set forth in claim 3, there is provided a vehicle speed detecting means for detecting a vehicle speed of the vehicle, and the motor control means is provided in accordance with the detected vehicle speed of the vehicle speed detecting means. The first and second thresholds may be set. For example, the first and second thresholds may be set so as to become smaller as the vehicle speed detected by the vehicle speed detector increases.

Further, the motor control means is based on the first and second threshold values when the vehicle speed detected by the speed detection means is lower than a predetermined reference speed. The drive control of the motor may be prohibited.

According to a fifth aspect of the present invention, the vehicle further comprises a friction coefficient estimating means for estimating a friction coefficient of a traveling road surface of the vehicle. The reference speed may be set according to the determined friction coefficient. For example, the reference speed may be set to increase as the friction coefficient estimated by the friction coefficient estimating unit increases.

[0011]

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows a hydraulic pressure control device for a wheel cylinder WC of a wheel WL representing each wheel according to an embodiment of the present invention. The master cylinder MC outputs a brake hydraulic pressure in response to an operation of a brake pedal BP. And a modulator MD for adjusting the brake fluid pressure in the wheel cylinder WC is interposed between the master cylinder MC and the wheel cylinder WC.

The modulator MD is connected to the reservoir RS so that brake fluid discharged from the wheel cylinder WC via the modulator MD is stored in the reservoir RS. As shown in FIG. 1, the modulator MD of the present embodiment is a normally-open two-port two-position solenoid valve PCa (hereinafter simply referred to as a valve PCa).
And a normally closed two-port two-position solenoid on-off valve PCb (hereinafter simply referred to as on-off valve PCb) interposed in a hydraulic pressure passage connecting the reservoir RS between the on-off valve PCa and the wheel cylinder WC.
).

A hydraulic pump H driven by a motor M
P is disposed, and the suction side thereof is connected to the reservoir RS. The brake fluid is sucked by the hydraulic pump HP and returned between the master cylinder MC and the modulator MD. The reservoir RS is provided with a piston and a spring in a housing, a spring side communicates with the atmosphere, a liquid chamber for containing brake fluid is formed between the housing and the piston, and the capacity thereof is variable. .

Further, a pressure sensor PS is provided between the master cylinder MC and the modulator MD, and detects a master cylinder hydraulic pressure. A wheel speed sensor WS is arranged near the wheel WL, and detects a wheel speed. An electronic control unit ECU is provided, and a microcomputer including a CPU, a ROM, a RAM, an input port, an output port, and the like, which are connected to each other via a bus, although illustration of the configuration is omitted, Detection signals from the pressure sensor PS, the wheel speed sensor WS, and the like are input through an input port, and a drive signal is output to the motor M through an output port.

The electronic control unit ECU comprises a fluid amount estimating means for estimating the brake fluid amount in the reservoir RS, and a motor controlling means for constantly driving the motor M during the anti-skid control. When the estimated amount of brake fluid in the reservoir RS is less than the first threshold,
When the motor M is driven at a predetermined minimum rotation speed and the amount of brake fluid in the reservoir estimated by the fluid amount estimating means is equal to or greater than a first threshold value, the amount of brake fluid in the reservoir estimated by the fluid amount estimating means Until the motor M reaches a predetermined rotation speed higher than the minimum rotation speed until the rotation speed of the motor
Is configured to be driven.

Further, the electronic control unit ECU includes, for example, a vehicle speed detecting means for detecting the vehicle speed by estimating and calculating the vehicle speed based on the output of the wheel speed sensor WS, and a friction coefficient of the road surface of the vehicle. A friction coefficient estimating means for estimating is configured. Thus, the first and second thresholds are set according to the detected vehicle speed by the vehicle speed detecting means. Further, when the detected vehicle speed becomes lower than the predetermined reference speed, the drive control of the motor M based on the first and second threshold values is prohibited, and the friction coefficient estimated by the friction coefficient estimating means is reduced. The reference speed is set accordingly.

In this embodiment constructed as described above, the electronic control unit ECU performs brake fluid pressure control for anti-skid control.
A description will be given based on the flowchart of FIG. When an ignition switch (not shown) is closed, initialization is first performed, various operation values are cleared, and various flags are reset. Thereafter, in step 101, the pressure sensor P
S, a detection signal from the wheel speed sensor WS and the like are read, and an actual current when the motor M is driven is read. Next, the process proceeds to step 102, where the wheel speeds Vw of the respective wheels are calculated based on the detection signals from the wheel speed sensors WS and the like. Including wheel deceleration).

Subsequently, the process proceeds to step 104, where the estimated vehicle speed Vs is obtained based on the wheel speed Vw of each wheel. In step 105, the estimated vehicle speed Vs is differentiated, and the estimated vehicle speed Vs is estimated. DVs (including deceleration) is calculated. In step 106, the road friction coefficient μ is estimated and calculated. Then, the wheel speed V of each wheel obtained in the above steps 102 to 105
Based on w, the estimated vehicle speed Vs, and the like, hydraulic pressure control for anti-skid control (ABS control) is performed in steps 107 to 113.

First, at step 107, it is determined whether or not anti-skid control (ABS control) is being executed.
If the ABS control is being performed, the routine proceeds to step 108, where the slip ratio Sn is compared with a predetermined value k1. The slip ratio Sn is determined based on the wheel speed Vw of each wheel and the estimated vehicle speed Vs.
n = (Vs−Vw) / Vs. If the slip ratio Sn is equal to or more than the predetermined value k1, step 109 is further executed.
Is compared with the predetermined value k2. If the wheel acceleration DVw is equal to or larger than the predetermined value k2, step 110 is executed.
And the wheel acceleration DVw is set to the predetermined value k.
If it is less than 2, the routine proceeds to step 111, where the pressure reduction mode is set.

On the other hand, if it is determined in step 108 that the slip ratio Sn is less than the predetermined value k1, the routine proceeds to step 112, where the pulse pressure increasing mode is set. If it is determined in step 107 that the ABS control is not being performed, the process proceeds to step 113, and the normal (sudden) pressure increase mode is set.
Specifically, the on-off valves PCa and PCb in FIG. 1 are controlled to open and close in accordance with the respective hydraulic modes, and the brake hydraulic pressure (wheel cylinder hydraulic pressure) in the wheel cylinder WC is increased, pulse increased, reduced or maintained. Is done.

Subsequently, the routine proceeds to step 114, where the liquid amount Ar of the reservoir RS is estimated. For this, various estimating means and methods are well known, and any of them may be employed, so that the description will be omitted. Then, in step 115, the motor M is controlled. Hereinafter, the control of the motor M will be described with reference to FIG.

First, in step 201, when the ABS control is being performed or the brake fluid remains in the reservoir RS, the process proceeds to step 202 or later, but otherwise, the process proceeds to step 221 or later. In step 202, for example, based on the map shown in FIG.
A first threshold h and a second threshold i for r are set. In the present embodiment, as shown in FIG. 4, as the estimated vehicle speed Vs obtained in step 104 increases,
The first threshold value h is set to gradually decrease as shown by a solid line, and the second threshold value i is set to a constant value smaller than the first threshold value h as shown by a broken line.

Subsequently, in step 203, the reservoir liquid amount Ar estimated in step 114 is input.
Subsequently, in step 204, it is determined whether or not the target discharge amount fixing flag C (hereinafter, referred to as flag C) is in a reset state (0). If the flag is in the reset state, the process proceeds to step 205, where the reservoir liquid amount in the present calculation cycle is determined. Ar (n) is compared with the reservoir liquid amount Ar (n-1) in the previous calculation cycle. If the current reservoir liquid amount Ar (n) is equal to or greater than the previous reservoir liquid amount Ar (n-1), steps 207 and 208 are performed.
The target discharge amount Qp and the target current f are updated.

That is, first, at step 207, the target pump discharge amount c per 12 V of the applied voltage of the motor M is set based on the current reservoir liquid amount Ar (n). In the present embodiment, as shown in FIG. 5, the target pump discharge amount c is set as shown by a solid line according to the reservoir liquid amount Ar (n) input in step 203. As shown in FIG. 6, a variable coefficient d corresponding to the pump discharge side pressure (hereinafter, simply referred to as a pump coefficient d) is set according to the master cylinder hydraulic pressure Pm detected by the hydraulic pressure sensor PS. Then, based on these values c and d, the target discharge amount Qp of the hydraulic pump HP is calculated as Qp = c · (V / 12) · d.
Here, V is a power supply voltage for the motor M. next,
In step 208, the target current f is set (updated) based on the target discharge amount Qp of the above calculation result based on the map of FIG. That is, the target current f for driving the motor M is set as shown in FIG. 7 according to the target discharge amount Qp.

On the other hand, if it is determined in step 205 that the current reservoir liquid amount Ar (n) is smaller than the previous reservoir liquid amount Ar (n-1), the flag C is set in step 206 (1). ), And thereafter, the target discharge amount Qp is fixed to the final set (updated) value, and as a result, the target current f is also fixed to the final set (updated) value.

Then, the process proceeds to a step 209, wherein the motor M
Is compared with the target current f. If the actual current Ima is equal to or higher than the target current f, the process proceeds to step 210, where the estimated vehicle speed Vs is compared with the reference speed j. If the actual speed Ima is equal to or higher than the reference speed j, the state of the flag B is determined in step 211. Here, the flag B is for setting the hysteresis in the determination at the time of the duty control described later. If it is determined that this is not set (1), the process proceeds to step 212, where the reservoir liquid amount Ar is set to the first value. 1
Is compared with the threshold value h.

In step 212, the reservoir liquid amount Ar
Is smaller than the first threshold value h, the target duty g of the motor M is set to a value corresponding to the target current f based on the map of FIG. Thus, after the flag C is set in step 206,
If the reservoir liquid amount Ar is less than the first threshold value h, the rotation speed of the motor M is maintained at the minimum rotation speed.

On the other hand, if it is determined in step 211 that the flag B is set (1),
The process proceeds to step S14, and further, the reservoir liquid amount Ar becomes the second threshold value i.
Is compared to If it is determined that the reservoir liquid amount Ar is equal to or larger than the second threshold value i, the routine proceeds to step 215, where the flag B is set (1). At step 216, the target duty g is set to 100% (maximum value). Is set to Thus, the motor M is driven at the maximum rotation speed. Similarly, when it is determined in step 212 that the reservoir liquid amount Ar is equal to or greater than the first threshold value h, the process proceeds to step 216, where the target duty g is set to 100%, and the motor M is driven at the maximum rotational speed. You.

In step 210, the estimated vehicle speed Vs
Is smaller than the reference speed j, and step 21
When it is determined in step 4 that the reservoir liquid amount Ar is less than the second threshold value i, the routine proceeds to step 217, where the flag B is reset (0). In step 218, the target duty g is set based on the map of FIG. Is set. Also,
If the actual current Ima of the motor M is less than the target current f in step 209, it is immediately after the start of driving. Therefore, the process proceeds to step 219, and the flag B is reset (0). %, And the motor M is driven at the maximum rotation speed.

When the ABS control is not being performed and the brake fluid does not remain in the reservoir RS, the process proceeds from step 201 to step 221 and the reservoir fluid amount Ar
Is cleared (0), the flags B and C are reset (0) in steps 222 and 223, and the target duty g is cleared (0) in step 224. Then, the process returns to the main routine.

As described above, the target duty g of the motor M is set based on the map of FIG. 9 or set to 100% (maximum value) according to various conditions.
This will be described with reference to the time charts of FIGS. FIG. 10 shows the estimated vehicle speed Vs and the wheel speed Vw at the uppermost stage, whether or not ABS control is being performed (flag 1 or 0) at the next stage, the hydraulic pressure mode at the lower stage, and the lower level. The change of the estimated liquid amount Ar in the reservoir is shown in the row. 10 show changes in the target discharge amount Qp by the hydraulic pump HP, the target duty g of the motor M, and the drive duty of the motor M.

In FIG. 10, when the anti-skid control is started at t1, the motor M is driven at a duty of 100%. Then, the calculation of the target discharge amount Qp of the hydraulic pump HP starts, and the target duty g of the motor M is sequentially set based on the target discharge amount Qp. At t2 after the start of the motor M, if the reservoir liquid amount Ar is less than the first threshold value h, the target set according to the first estimated reservoir liquid amount Ar based on the maps of FIGS. Fixed to duty. Accordingly, the rotation speed of the motor M is maintained at the minimum rotation speed and is constant, so that the tone does not change and no new noise is generated.

On the other hand, as shown in FIG. 11, when the reservoir liquid amount Ar becomes greater than or equal to the first threshold value h at time t3, the rotation speed of the motor M is increased to a rotation speed greater than the minimum rotation speed (in this embodiment, the maximum rotation speed). (Set to the number of rotations), the drive duty of the motor M is set to 100%, and is maintained at 100% until the reservoir liquid amount Ar becomes less than the second threshold value i at t4. However, if the estimated vehicle speed Vs is lower than the reference speed j, such as after time t5, the drive duty of the motor is not changed even if the reservoir liquid amount Ar becomes the first threshold value h or more at time t6, as shown in FIGS. 9, the motor M is driven at the minimum rotation speed.

[0034]

The present invention has the following effects because it is configured as described above. That is, in the hydraulic pressure control device according to the first aspect, when the brake fluid amount in the reservoir estimated by the fluid amount estimating means is less than the first threshold value,
When the motor is driven at a predetermined minimum number of revolutions and the amount of brake fluid in the reservoir is equal to or greater than a first threshold, a second threshold in which the amount of brake fluid in the reservoir is smaller than the first threshold. The motor is configured to be driven at a predetermined rotation speed higher than the minimum rotation speed until the rotation speed becomes less than the minimum rotation speed, and the rotation speed of the motor is reduced except for an exceptional range defined by the first and second threshold values. Is maintained at a predetermined minimum rotation speed, so that fluctuations in motor rotation speed are minimized while suppressing energy consumption,
Noise associated with the rotation of the motor can be reduced.

Further, in the hydraulic control apparatus according to the second aspect, the motor is driven at the maximum rotational speed until the predetermined target discharge amount is reached after the driving of the hydraulic pump is started, and the target discharge amount is reached. Since the motor is configured to be driven at the minimum rotation speed later, good responsiveness at the start of control can be ensured.

Further, in the hydraulic pressure control device according to the third aspect, the first pressure is controlled in accordance with the vehicle speed detected by the vehicle speed detecting means.
And the second threshold value is set, so that the motor drive at the minimum rotation speed can be set as long as possible, and thus the noise accompanying the rotation of the motor can be reduced more appropriately. .

In the hydraulic pressure control device according to the present invention, when the speed of the vehicle detected by the speed detecting means is lower than a predetermined reference speed, the motor is driven based on the first and second threshold values. Since the control is prohibited, fluctuations in the number of rotations of the motor during low-speed running can be suppressed, and noise caused by rotation of the motor can be reduced.

Further, in the hydraulic control device according to the fifth aspect, the reference speed is set according to the friction coefficient estimated by the friction coefficient estimating means. Thus, it is possible to appropriately suppress fluctuations in the number of rotations of the motor during low-speed running, and reduce noise caused by rotation of the motor.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a basic configuration of a vehicle hydraulic pressure control device according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a brake fluid pressure control process for anti-skid control according to an embodiment of the present invention.

FIG. 3 is a flowchart illustrating a motor control process according to an embodiment of the present invention.

FIG. 4 is a graph used for a map for setting a threshold value in one embodiment of the present invention.

FIG. 5 is a graph used for a map for setting a target pump discharge amount in one embodiment of the present invention.

FIG. 6 is a graph used for a map for setting a pump coefficient in one embodiment of the present invention.

FIG. 7 is a graph used for a map for setting a target current of a motor in one embodiment of the present invention.

FIG. 8 is a graph used for a map for setting a reference speed in one embodiment of the present invention.

FIG. 9 is a graph used for a map for setting a target duty of a motor in one embodiment of the present invention.

FIG. 10 is a time chart illustrating an example of a driving state of a motor according to the embodiment of the present invention.

FIG. 11 is a time chart showing another example of the driving state of the motor according to the embodiment of the present invention.

[Explanation of symbols]

MC master cylinder, BP brake pedal, W
L wheel, ECU electronic control unit, M motor, H
P hydraulic pump, RS reservoir, MD modulator, WC wheel cylinder

Claims (5)

[Claims] 1. A modulator disposed between a wheel cylinder mounted on each wheel of a vehicle and a master cylinder for adjusting a brake fluid pressure in the wheel cylinder, and a brake discharged from the wheel cylinder via the modulator. A reservoir for storing fluid, a hydraulic pump for sucking brake fluid in the reservoir and returning it between the master cylinder and the modulator, a motor for driving the hydraulic pump, and a fluid for estimating a brake fluid amount in the reservoir. In a fluid pressure control device for a vehicle, comprising: a volume estimating unit; and a motor control unit that constantly drives the motor during anti-skid control, wherein the motor control unit includes a brake fluid in the reservoir estimated by the fluid amount estimating unit. When the amount is less than the first threshold, the motor is driven at a predetermined minimum number of revolutions, and If the amount of brake fluid in the reservoir estimated by the determining means is equal to or greater than the first threshold, the amount of brake fluid in the reservoir estimated by the fluid amount estimating means is smaller than the first threshold. The vehicle hydraulic pressure control device is configured to drive the motor at a predetermined rotation speed greater than the minimum rotation speed until the rotation speed is less than a second threshold value. 2. The motor control means drives the motor at the maximum number of revolutions after starting driving the hydraulic pump until a predetermined target discharge amount is reached, and controls the motor after reaching the target discharge amount. The vehicle hydraulic pressure control device according to claim 1, wherein the vehicle is driven at the minimum rotation speed. 3. A vehicle speed detecting means for detecting a vehicle speed of the vehicle, wherein the motor control means sets the first and second threshold values in accordance with the detected vehicle speed of the vehicle speed detecting means. The hydraulic pressure control device for a vehicle according to claim 1, wherein the control unit is configured to set the hydraulic pressure. 4. The motor control means for prohibiting drive control of the motor based on the first and second threshold values when the detected vehicle speed detected by the speed detection means becomes lower than a predetermined reference speed. 4. The vehicle hydraulic pressure control device according to claim 3, wherein: 5. A vehicle comprising: a coefficient of friction estimating means for estimating a coefficient of friction of a traveling road surface of the vehicle;
The hydraulic pressure control device for a vehicle according to claim 4, wherein the reference speed is set according to the friction coefficient estimated by the friction coefficient estimation unit.