JP5290935B2 - Brake hydraulic pressure control device for vehicles - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To concurrently achieve the prevention of erroneous operation of antilock brake control on a rough road or the like and improvement of operation feeling during revolving. <P>SOLUTION: This brake fluid pressure control device for vehicle, controls the fluid pressure of a wheel brake based on a calculation value for the magnitude of a slip amount of respective wheels. This control device includes: a first calculation part (a first slip ratio calculation part 21) for converting the calculation value to a smaller slip amount for calculation; a second calculation part (a second slip ratio calculation part 22) for executing calculation without the conversion; and a pressure control part (a pressure control determination part 24 and a valve drive part 25) for executing decompression control of a wheel brake when a yaw rate deviation &Delta;Y exceeds a yaw rate deviation threshold value and the calculation value calculated by the second calculation part exceeds a second threshold value even if the calculation value calculated by the first calculation part is not in excess of the first threshold value. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a vehicular brake hydraulic pressure control device, and more particularly to a vehicular brake hydraulic pressure control device that achieves both anti-lock brake control malfunction prevention on rough roads and improved driving feeling during turning. .

  In anti-lock brake (ABS) control of a vehicle, a slip ratio serving as a reference (threshold value) for operating ABS control may be changed according to a steering state. For example, in the anti-skid control device of Patent Document 1, a configuration is adopted in which the threshold value is changed based on the deviation between the target yaw rate and the yaw rate detected by the yaw rate detecting means. Thus, by performing ABS control when the vehicle is not turning as much as the driver's intention, the turning force of the vehicle is increased, and the vehicle can behave according to the driver's intention. That is, by using the frictional force of the wheel that has been used for the braking in the front-rear direction to generate the turning force in the lateral direction, it is possible to approach the turning according to the driver's intention.

  On the other hand, when ABS control is activated in a situation other than the original operating situation where the vehicle is likely to slip, such as when the wheel momentarily floats on a rough road surface, etc., the driving feeling will deteriorate, so when calculating the slip ratio, Generally, a configuration is adopted in which the calculated value is offset so that the slip ratio becomes small.

JP-A-4-146863

  However, based on the slip ratio offset so that the value becomes smaller, the slip ratio may become 0 in calculation when the slip ratio is small, such as during braking that is not so strong. If it does so, ABS control cannot be started rapidly by changing a threshold value like a prior art, and driving | operation feeling cannot be improved.

  Accordingly, an object of the present invention is to provide a vehicular brake hydraulic pressure control device that is capable of preventing malfunction of antilock brake control on a rough road and improving driving feeling during turning.

The present invention that solves the above-described problems is capable of controlling the hydraulic pressure of the wheel brake based on the calculated value relating to the magnitude of the slip amount of each wheel calculated from the wheel speed of each wheel, as well as the actual yaw rate and steering of the vehicle. A vehicular brake hydraulic pressure control device capable of obtaining a steering angle, wherein the calculated value is converted into a smaller slip amount and calculated, and the calculated value is converted. A second calculation unit that calculates without any reduction, and executes a wheel brake pressure reduction control when the calculated value calculated by the first calculation unit exceeds a first threshold, and the first calculation unit includes: Even when the calculated value does not exceed the first threshold value, the deviation between the reference yaw rate calculated from the steering angle and the actual yaw rate exceeds the yaw rate deviation threshold value, and the second calculation unit calculates Range calculated value in the case of exceeding the second threshold value have a pressure control unit that performs the decompression control of the wheel brakes, and the yaw rate deviation threshold and the second threshold value, the vehicle speed is higher than a predetermined speed Is characterized in that it is set to a larger value as the vehicle body speed increases .

According to such a vehicular brake hydraulic pressure control device, the pressure control unit sets the calculated value to the first threshold value based on the calculated value converted so that the slip amount calculated by the first calculation unit is reduced. Since the wheel brake pressure reduction control is performed when the pressure exceeds the limit, the pressure reduction control is erroneously performed when the slip amount accidentally increases on a rough road surface as in the case of the vehicle brake hydraulic pressure control device that performs the conventional ABS control. Is prevented. In addition, even when the above condition is not satisfied, the calculated value calculated by the second calculation unit is the value calculated when the deviation between the standard yaw rate calculated from the steering angle and the actual yaw rate exceeds the yaw rate deviation threshold. Under the condition that the threshold value 2 is exceeded, the wheel brake pressure reduction control is executed. In other words, if the direction of the turn by the driver's intention and the actual turning situation of the vehicle deviate greatly, the wheel brake pressure reduction control is executed using the value obtained without converting to the smaller slip amount. Therefore, the frictional force of the wheels can be used for turning, and the driving feeling during turning can be improved.
That is, according to the present invention, it is possible to achieve both prevention of malfunction of antilock brake control on a rough road and the like and improvement of driving feeling during turning.

  In the present invention, the calculated value related to the magnitude of the slip amount includes the slip amount itself (for example, the difference between the vehicle body speed and the wheel speed), the slip ratio (a value obtained by dividing the slip amount by the vehicle body speed), and the like. Moreover, exceeding the threshold value means that the value changes across the threshold value. Depending on how the value is determined to be positive or negative, not only when the value changes from a value smaller than the threshold value to a larger value, but also when the value is larger than the threshold value. In some cases, the value may change to a smaller value.

  In the above-described apparatus, the second calculation unit obtains a ground contact point speed that is a vehicle body speed at each wheel position using the wheel speed and the actual yaw rate, and calculates the contact point speed and the wheel speed of the corresponding wheel. The structure which calculates the said calculated value using a difference may be sufficient.

  In this way, since the calculated value related to the magnitude of the slip amount is obtained using the accurate vehicle speed (contact point speed) in consideration of the position of the wheel in the vehicle body, when the vehicle is in a turning state deviating from the driver's intention Thus, it is possible to detect the slip state of the wheel quickly and execute the pressure reduction control quickly.

  In the above-described apparatus, the pressure control unit may perform a pressure reduction control based on the calculated value calculated by the second calculation unit for only the front wheels outside the turning of the vehicle.

  According to such a configuration, when the vehicle is in an understeer state when turning, by applying the present invention only to the wheel most related to the turning force, the lateral force of the wheel can be quickly recovered, and the understeer state Can be preferably eliminated.

  In the apparatus described above, the pressure control unit is an anti-lock brake control unit that reduces the brake fluid pressure generated in the master cylinder and transmitted to the wheel brake, for example.

  ADVANTAGE OF THE INVENTION According to this invention, the malfunction prevention of the anti-lock brake control on a rough road etc. and the improvement of the driving feeling during turning can be made compatible.

1 is a configuration diagram of a vehicle including a vehicle brake hydraulic pressure control device according to an embodiment of the present invention. It is a block diagram which shows the structure of a hydraulic unit. It is a graph which shows the relationship between the slip ratio of a wheel and frictional force. It is a block diagram which shows the structure of a control part. It is a figure which shows the change of the 1st threshold value according to vehicle body deceleration. It is a figure which shows the change of the 2nd threshold value according to a vehicle body speed. It is a figure which shows the change of the yaw rate deviation threshold value according to a vehicle body speed. It is a flowchart explaining the process of the pressure control of the brake fluid pressure control apparatus for vehicles which concerns on one Embodiment. FIG. 4A is a diagram showing changes with time in wheel speed and vehicle speed, and FIG. 6B is a diagram showing changes in caliper pressure with time.

Next, embodiments of the present invention will be described in detail with reference to the drawings as appropriate.
As shown in FIG. 1, the vehicle brake fluid pressure control device 100 is a device that appropriately controls the braking force applied to each wheel T of the vehicle CR. The vehicle brake hydraulic pressure control device 100 includes a hydraulic unit 10 provided with a hydraulic path and various parts, and a control unit 20 as an example of a control unit for appropriately controlling various parts in the hydraulic unit 10. Mainly prepared.

  Each wheel T is provided with a wheel brake FL, RR, RL, FR, and each wheel brake FL, RR, RL, FR is supplied with a hydraulic pressure supplied from a master cylinder M as an example of a hydraulic pressure source. A wheel cylinder W that generates a braking force is provided. The master cylinder M and the wheel cylinder W are each connected to the hydraulic unit 10. The brake hydraulic pressure generated in the master cylinder M in response to the depression force of the brake pedal P (the driver's braking operation) is supplied to the wheel cylinder W after being controlled by the control unit 20 and the hydraulic pressure unit 10. .

  The control unit 20 includes a pressure sensor 91 that detects the hydraulic pressure in the master cylinder M, a wheel speed sensor 92 that detects the wheel speed of each wheel T, a yaw rate sensor 93 that detects the yaw rate of the vehicle CR, A steering angle sensor 94 that detects the steering angle is connected. The control unit 20 includes, for example, a CPU, a RAM, a ROM, and an input / output circuit, and inputs from the pressure sensor 91, the wheel speed sensor 92, the yaw rate sensor 93, and the steering angle sensor 94, and are stored in the ROM. The control is executed by performing various arithmetic processes based on the programs and data. Details of the control unit 20 will be described later.

  As shown in FIG. 2, the hydraulic unit 10 is disposed between the master cylinder M and the wheel brakes FL, RR, RL, FR. The two output ports M1, M2 of the master cylinder M are connected to the inlet port 121 of the hydraulic unit 10, and the outlet port 122 is connected to each wheel brake FL, RR, RL, FR. In a normal state, the hydraulic pressure path in which the inlet port 121 to the outlet port 122 in the hydraulic pressure unit 10 communicates with each other allows the pedaling force of the brake pedal P to be transmitted to the wheel brakes FL, RR, RL, FR. It has come to be.

  The hydraulic pressure unit 10 is provided with four inlet valves 1, four outlet valves 2, and four check valves 1a corresponding to the wheel brakes FL, RR, RL, FR. In addition, two reservoirs 3, two pumps 4, two dampers 5, and two orifices 5a are provided corresponding to the output hydraulic pressure paths 81 and 82 corresponding to the output ports M1 and M2, respectively. An electric motor 6 for driving is provided.

  The inlet valve 1 is a normally open solenoid valve arranged in a hydraulic pressure path from the master cylinder M to each wheel brake FL, RR, RL, FR (upstream side of each wheel brake FL, RR, RL, FR). . The inlet valve 1 is normally open to allow the brake hydraulic pressure to be transmitted from the master cylinder M to the wheel brakes FL, RR, RL, FR. Further, the inlet valve 1 is blocked by the control unit 20 when the wheel T is about to be locked, thereby blocking the hydraulic pressure transmitted from the brake pedal P to each wheel brake FL, RR, RL, FR.

  The outlet valve 2 is located between each wheel brake FL, RR, RL, FR and each reservoir 3 (on the hydraulic pressure path leading from the hydraulic pressure path on the wheel cylinder W side of the inlet valve 1 to the reservoir 3, the pump 4 and the master cylinder M). ) Is a normally closed solenoid valve. Although the outlet valve 2 is normally closed, the hydraulic pressure applied to each wheel brake FL, RR, RL, FR is supplied to each reservoir by being opened by the control unit 20 when the wheel T is likely to be locked. Escape to 3.

  The check valve 1a is connected to each inlet valve 1 in parallel. This check valve 1a is a valve that allows only the flow of brake fluid from each wheel brake FL, RR, RL, FR side to the master cylinder M side, and an inlet valve when the input from the brake pedal P is released. Even when 1 is closed, the flow of brake fluid from each wheel brake FL, RR, RL, FR side to the master cylinder M side is allowed.

The reservoir 3 has a function of absorbing brake fluid that is released when each outlet valve 2 is opened.
The pump 4 has a function of sucking the brake fluid absorbed in the reservoir 3 and returning the brake fluid to the master cylinder M via the damper 5 and the orifice 5a. As a result, the pressure state of each of the output hydraulic pressure paths 81 and 82 reduced by the absorption of the brake hydraulic pressure by the reservoir 3 is recovered.

  The opening and closing states of the inlet valve 1 and the outlet valve 2 are controlled by the control unit 20 so that the hydraulic pressure in the wheel cylinder W of each wheel brake FL, RR, RL, FR (hereinafter also referred to as “caliper pressure”). To control. For example, in a normal state in which the inlet valve 1 is open and the outlet valve 2 is closed, if the brake pedal P is depressed, the hydraulic pressure from the master cylinder M is transmitted to the wheel cylinder W as it is to increase the pressure. When the valve 1 is closed and the outlet valve 2 is opened, the brake fluid flows out from the wheel cylinder W to the reservoir 3 side to be in a decompressed state. When both the inlet valve 1 and the outlet valve 2 are closed, the caliper pressure (wheel A holding state in which the hydraulic pressure of the cylinder W is held is obtained.

  Next, an outline of control of the apparatus in the present embodiment will be described with reference to FIG. In general, the frictional force in the front-rear direction of the wheel T during braking tends to increase up to a predetermined slip ratio C1, as shown in FIG. 3, and gradually decreases beyond the slip ratio C1. Therefore, in general ABS control, the braking force of each wheel T is controlled so that the slip rate is in the vicinity of the slip rate C1 where the frictional force in the front-rear direction is maximum. On the other hand, since the frictional force in the left-right direction of the wheel T decreases as the slip ratio increases, when the braking force is controlled with the slip ratio C1 as a target, the left-right frictional force, that is, the turning force is slightly increased. May be smaller. Therefore, in the present embodiment, when the driver's intention and the actual turning situation deviate, the target slip rate is set to C2 smaller than C1, so that the frictional force in the left-right direction of the wheel T, that is, Increase the turning force to improve driving feeling. FIG. 3 shows the slip ratio as a representative value for the purpose of explaining the outline of the present embodiment. However, in the following explanation, there are two ways of obtaining the slip ratio. It should be noted that it is difficult to show a unified horizontal axis as shown in FIG. 3 and that FIG. 3 cannot be referred to in the following description.

  Next, details of the control unit 20 will be described. As shown in FIG. 4, the control unit 20 receives the wheel speed from the wheel speed sensor 92, the actual yaw rate Y detected from the yaw rate sensor 93, and the steering angle ST of the steering from the steering angle sensor 94. The The control unit 20 includes a first slip ratio calculation unit 21, a second slip ratio calculation unit 22, a yaw rate deviation calculation unit 23, a pressure control determination unit 24, a valve drive unit 25, and a storage unit 28.

The first slip ratio calculation unit 21 is an example of a first calculation unit, calculates a first slip ratio SL1 as a calculated value related to the magnitude of the slip amount from the wheel speed sensor 92, and outputs the first slip ratio SL1 to the pressure control determination unit 24. It has a function. The first slip ratio SL1 is obtained by the following equation (1) using the vehicle body speed and the offset amount S1 having a predetermined positive value.
SL1 = (body speed−wheel speed−S1) × 100 / body speed (1)

  That is, the difference between the vehicle body speed and the wheel speed means the slip amount, but the first slip rate SL1 is calculated by converting this slip amount so as to be reduced by the offset amount S1. The offset amount S1 here is a malfunction that prevents the ABS control from being erroneously performed even if the slip amount temporarily increases slightly when the wheel T is lifted on a rough road surface or the like. This is a set amount for prevention. The offset amount S1 may be constant regardless of conditions, or may be set so as to change according to other conditions such as the vehicle body speed. Also, as is well known, the vehicle body speed can be estimated by correcting the wheel speed of each wheel T by correcting the upper limit value of the deceleration, for example. More specifically, the vehicle speed is obtained by adding the speed (speed change) changed between the previous time and the current time to the previously obtained body speed, and an upper limit is set for the magnitude of this speed change. . In the present embodiment, the first slip ratio SL1 is calculated for each wheel T. However, in the present specification, no subscript is used, and is simply expressed as the first slip ratio SL1.

  The second slip ratio calculation unit 22 is an example of a second calculation unit, calculates the second slip ratio SL2 without converting the slip amount to be smaller by the offset amount S1 described above, and sends the second slip ratio SL2 to the pressure control determination unit 24. Has a function to output. Further, since the second slip rate SL2 is not converted to a smaller slip amount, in this embodiment, the wheel T in consideration of the position of the wheel T in the vehicle CR so as to be as accurate as possible. Is calculated using the speed of the vehicle body at the position (this is referred to as “contact point speed” in the invention).

Specifically, the second slip ratio SL2 is obtained by the following equation (2).
SL2 = (contact point speed−wheel speed) × 100 / contact point speed (2)

The contact point speed is obtained in the present embodiment as follows.
First, from four wheel speeds V _FL , V _FR , V _RL , V _RR (each of the left front wheel, right front wheel, left rear wheel, and right rear wheel), the vehicle body center speed VG (speed at the center of gravity G of the vehicle body) Center speed candidates VC _FL , VC _FR , VC _RL , and VC _RR are obtained. This calculation is based on the actual yaw rate Y input from the yaw rate sensor, the distances L _FL , L _FR , L _RL , L in the left-right direction between the position of each wheel T stored in advance in the storage unit 28 and the center of gravity G of the vehicle body. _{Using RR} (see FIG. 1), the following equation (3) is obtained.
VC _FL = V _FL + Y × L _FL
VC _FR = V _FR -Y × L _FR (3)
VC _RL = V _RL + Y × L _RL
VC _RR = V _RR -Y × L _RR
The actual yaw rate Y is input as a positive value when turning left.

Of these center speed candidates VC _FL , VC _FR , VC _RL , and VC _RR , the largest one is considered to indicate the value that has the least influence of the locking of the wheel T. The center speed is VG (see the following equation (4)).
VG = max {VC _FL , VC _FR , VC _RL , VC _RR } (4)

Next, contact point speeds VE _FL , VE _FR , VE _RL , VE _RR at the position of each wheel T are obtained from the vehicle body center speed VG. The contact point speeds VE _FL , VE _FR , VE _RL , VE _RR are obtained by using the actual yaw rate Y, distances L _FL , L _FR , L _RL , L _RR in the horizontal direction between the position of each wheel T and the center of gravity G of the vehicle body. Is obtained by the following equation (5).
VE _FL = VG-Y × L _FL
VE _FR = VG + Y × L _FR (5)
VE _RL = VG-Y × L _RL
VE _RR = VG + Y × L _RR

As described above, the contact point speeds VE _FL , VE _FR , VE _RL , VE _RR can be applied to the equation (2) to determine the second slip ratio SL2 for each wheel. That is, the second slip ratio SL2 is obtained for each wheel T. For brake pressure reduction control based on the second slip ratio described below, when the vehicle CR is in the understeer state, the wheel T on the outer side of the turn is set. When the vehicle CR is in an oversteer state, the target is the wheel T on the inner side of the turn. However, in this specification, for the sake of simplicity, the vehicle CR is compared with the front wheel on the outer side of the turn. The brake fluid pressure is controlled to be reduced based on the second slip ratio SL2, and the second slip ratio SL2 is not particularly attached with a subscript indicating the wheel position.

The yaw rate deviation calculating unit 23 calculates the deviation ΔY by subtracting the actual yaw rate Y from the reference yaw rate YS (yaw rate assumed from the steering angle ST) calculated from the steering angle ST input from the steering angle sensor 94, A function of outputting to the pressure control determination unit 24 is provided.
As a method for calculating the reference yaw rate YS from the steering angle ST, for example, a method of multiplying the steering angle ST by a variable that increases as the vehicle body center speed VG increases can be employed.

  Based on the outputs from the first slip rate calculating unit 21, the second slip rate calculating unit 22, and the yaw rate deviation calculating unit 23, the pressure control determining unit 24 increases the caliper pressure of each wheel T in a pressure increasing state, a pressure reducing state, or a holding state. It has the function to determine which one of these is to be selected and to output the determination result to the valve drive unit 25.

  Specifically, the pressure control determination unit 24 first determines pressure control similar to that of the conventional ABS control device based on the first slip ratio SL1 and the first slip ratio threshold SL1th stored in the storage unit 28. It is supposed to do. Here, as illustrated in FIG. 5, the first slip ratio threshold SL1th is set according to the vehicle body deceleration and the vehicle body speed. Whether the vehicle body speed is high speed or low speed can be divided according to a predetermined threshold value. The higher the vehicle body deceleration (road surface friction coefficient), the larger the first slip ratio threshold value SL1th. Value is set. This is because a larger braking force can be obtained with a higher slip ratio when the road surface friction coefficient is higher. Further, comparing the high speed and the low speed, a smaller value is set as the first slip ratio threshold SL1th at the high speed. This is because it is desirable to increase the stability of the vehicle CR at high speeds.

  The pressure control determination unit 24 acquires the first slip ratio threshold value SL1th from the storage unit 28 based on the vehicle body speed and the vehicle body deceleration obtained from the vehicle body speed, and compares it with the first slip ratio SL1. When the first slip ratio SL1 is greater than the first slip ratio threshold SL1th and the wheel acceleration is 0 or less (wheel deceleration is 0 or more), it is determined that the wheel T is likely to be locked, and the caliper pressure is determined. Decide to reduce pressure. Further, when the wheel acceleration is greater than 0, it is determined that the caliper pressure is held, the first slip rate SL1 is equal to or less than the first slip rate threshold SL1th, and the wheel acceleration is equal to or less than 0. Then, the caliper pressure is determined to be increased.

The determination of the pressure control based on the first slip ratio SL1 is the same as the conventional one. In the present embodiment, the pressure control determination unit 24 determines the reduced pressure state when the following first to fourth conditions are satisfied even when the reduced pressure state is not determined in the above determination.
1. Whether the actual yaw rate Y and steering angle ST are normal (is normal)
2. 2. Is the yaw rate deviation ΔY greater than the yaw rate deviation threshold value ΔYth? 3. Is it the front wheel outside the turn? Whether second slip ratio SL2 is greater than second slip ratio threshold SL2th

The determination of the above conditions 1 to 4 may be performed in any order.
As for the first condition, when there is an abnormality in the values of the actual yaw rate Y and the steering angle ST, the reliability of the determination of the second condition is lowered, and thus determination is required.
The second condition is that when the yaw rate deviation ΔY obtained by subtracting the actual yaw rate Y from the reference yaw rate YS is larger than the yaw rate deviation threshold value ΔYth, the driver's intention to steer and the actual turning state of the vehicle CR This is a condition for determining that the deviation is large, that is, the vehicle is in an understeer state.
The third condition is that when the understeer state is determined by the second condition, the understeer state can be eliminated efficiently and quickly by controlling only the front wheels on the outside of the turn most related to the turning force. Judgment is required.
The fourth condition is that, when the second slip ratio SL2 is greater than the second slip ratio threshold SL2th, it is determined that the ratio of the friction force with the road surface of the wheel T in the front-rear direction is relatively large. Is the condition.

Here, the second slip ratio threshold SL2th as the second threshold is a constant value in a range where the vehicle body center speed is small as shown in FIG. 6, and the vehicle body center speed is large in a range equal to or higher than the predetermined vehicle body center speed. The larger the value is set. The larger second slip ratio threshold SL2th is set as the vehicle body center speed increases. For example, when the vehicle body speed (vehicle body center speed) is high in the understeer state, if the caliper pressure is reduced, This is because the vehicle CR suddenly increases the turning force due to the increase of the frictional force and may enter an oversteer state, so that the threshold value is increased to make it difficult to enter the pressure reduction control.

Further, as shown in FIG. 7, the yaw rate deviation threshold ΔYth is set so as to decrease as the vehicle body center speed increases in a predetermined range where the vehicle body center speed is low. This is because when the vehicle body speed (vehicle body center speed) is low, the vehicle will stop soon, so it is more important to stop the vehicle than turning. Therefore, the lower the vehicle body center speed, the larger the threshold value and the lower the pressure. This is to make it difficult to enter the control.
The yaw rate deviation threshold value ΔYth is a constant value up to a higher predetermined speed at a predetermined vehicle body center speed or higher, and is set to take a larger value at a higher speed as the vehicle body center speed increases. This is to prevent the oversteer state from being caused by the pressure reduction at the high speed similarly to the setting at the high speed of the second slip ratio threshold SL2th.

The valve drive unit 25 has a function of outputting a control signal to the inlet valve 1 and the outlet valve 2 in accordance with the instruction of the reduced pressure state, the increased pressure state, or the holding state output from the pressure control determination unit 24. That is, as described above, the inlet valve 1 is closed and the outlet valve 2 is opened to reduce the pressure, and the inlet valve 1 is opened and the outlet valve 2 is closed and held to increase the pressure. In this case, both the inlet valve 1 and the outlet valve 2 are closed.
The pressure control determination unit 24 and the valve drive unit 25 are an example of a pressure control unit.

  A flow of pressure reduction control in the control unit 20 configured as described above will be described with reference to FIG. Note that there is no particular characteristic regarding the pressure increase and holding control, and therefore, only the flow for determining the pressure reduction control is shown in the flow of FIG.

The controller 20 calculates the first slip ratio SL1 corresponding to each wheel T from the wheel speeds V _FL , V _FR , V _RL , V _{RR of} each wheel T by the first slip ratio calculator 21 (S1). ). Further, the second slip ratio calculation unit 22 calculates the contact point speeds VE _FL , VE _FR , VE _RL , VE _RR based on the wheel speeds V _FL , V _FR , V _RL , V _RR and the actual yaw rate Y, the ground point speed _{VE FL, VE FR, VE RL} , VE RR and a wheel speed _{V FL, V FR, V RL} , and a V _RR, and calculates the second slip ratio SL2 for each wheel (S2). Then, the pressure control determination unit 24 acquires the first slip ratio threshold SL1th, the second slip ratio threshold SL2th, and the yaw rate deviation threshold ΔYth from the storage unit 28 based on the current vehicle body speed, vehicle body deceleration, and vehicle body center speed. (S3)

  Then, the pressure control determination unit 24 compares the first slip ratio SL1 and the first slip ratio threshold SL1th (S4), and executes the pressure reduction control when the first slip ratio SL1 is larger (S4, Yes). (S5). On the other hand, when the first slip ratio SL1 is equal to or less than the first slip ratio threshold SL1th (S4, No), it is determined by a known method whether the actual yaw rate Y and the steering angle ST are normal as the first condition (S6). . When the actual yaw rate Y and the steering angle ST are normal (S6, Yes), as a second condition, it is determined whether the yaw rate deviation ΔY obtained by subtracting the actual yaw rate Y from the reference yaw rate YS is greater than the yaw rate deviation threshold value ΔYth. (S7). When the yaw rate deviation ΔY is larger than the yaw rate deviation threshold value ΔYth (S7, Yes), it is determined as a third condition whether the front wheel is outside the turn (S8), and when the front wheel is outside the turn (S8, Yes). As a fourth condition, it is determined whether or not the second slip ratio SL2 is larger than the second slip ratio threshold SL2th (S9). When the second slip ratio SL2 is greater than the second slip ratio threshold SL2th (S9, Yes), the pressure control determination unit 24 determines to perform pressure reduction control (S11). On the other hand, if any one of the first to fourth conditions is not satisfied in steps S6 to S9, it is determined to perform holding or pressure increase control by the same determination method as in the prior art (S10).

  According to such control, if the pressure reduction control is not performed by the determination based only on the first slip rate SL1, the pressure reduction control is performed when the first to fourth conditions are satisfied, When the driver's intention to steer and the turning state of the vehicle deviate greatly, the frictional force in the left-right direction of the wheel T is increased, and the turning feeling of the vehicle is brought closer to the driver's intention to steer. Can be improved.

  In addition, as shown by the broken lines in FIGS. 9A and 9B, the brake fluid pressure control apparatus 100 for a vehicle according to the present embodiment can be used even when the reduction of the caliper pressure is slow. Therefore, since the pressure reduction control is determined based on the accurately calculated second slip rate SL2 of each wheel T without being converted to a method of reducing the slip amount, as shown by the solid line in FIG. Thus, it is possible to quickly eliminate the state where the wheel T is likely to be locked.

  Although the embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment and can be appropriately modified and implemented. For example, in the embodiment, the first to fourth conditions are determined in steps S6 to S9 in FIG. 8, but the determination of the first condition and the third condition may be omitted. . In addition, when other physical property values are acquired, such as when detecting lateral acceleration, control based on the wrong physical property values is performed by determining whether the detected values of those sensors are normal. Can also be prevented.

  In the above-described embodiment, the pressure reduction determination based on the second slip ratio SL2 is performed only on the front wheels on the outer side of the turn in order to eliminate the understeer state of the vehicle. You may make it perform the pressure reduction determination based on 2nd slip ratio SL2 about these wheels. That is, for example, in order to eliminate the oversteer state of the vehicle, the pressure reduction determination based on the second slip ratio SL2 may be performed on the front wheels on the turning inner side.

  In the above embodiment, the actual yaw rate Y is acquired from the yaw rate sensor 93. However, when a lateral acceleration sensor is provided, the actual yaw rate Y may be obtained by calculation from the output from the lateral acceleration sensor. .

DESCRIPTION OF SYMBOLS 20 Control part 21 1st slip ratio calculating part 22 2nd slip rate calculating part 23 Yaw rate deviation calculating part 24 Pressure control determination part 25 Valve drive part 28 Memory | storage part 92 Wheel speed sensor 93 Yaw rate sensor 94 Steering angle sensor 100 Brake fluid for vehicles Pressure control device

Claims (4)

The brake for the vehicle that can control the hydraulic pressure of the wheel brake based on the calculated value of the slip amount of each wheel calculated from the wheel speed of each wheel and can acquire the actual yaw rate of the vehicle and the steering angle of the steering wheel A hydraulic control device,
A first calculation unit that calculates the calculated value in terms of a smaller slip amount;
A second calculation unit that calculates the calculated value without performing the conversion;
While performing the pressure reduction control of the wheel brake corresponding to the case where the calculated value calculated by the first arithmetic unit exceeds the first threshold, the calculated value calculated by the first arithmetic unit exceeds the first threshold Even when there is not, the deviation between the standard yaw rate calculated from the steering angle and the actual yaw rate exceeds the yaw rate deviation threshold value, and the calculated value calculated by the second calculation unit exceeds the second threshold value will have a pressure control unit that performs the decompression control of the wheel brakes,
The vehicle brake fluid pressure control is characterized in that the yaw rate deviation threshold value and the second threshold value are set to increase as the vehicle body speed increases in a range where the vehicle body speed is equal to or higher than a predetermined speed. apparatus.   The second calculation unit obtains a ground contact point speed that is a vehicle body speed at each wheel position by using the wheel speed and the actual yaw rate, and uses the difference between the ground contact point speed and the wheel speed of the corresponding wheel to perform the calculation. The vehicle brake fluid pressure control device according to claim 1, wherein a value is calculated.   3. The pressure control unit according to claim 1, wherein the pressure control unit executes the pressure reduction control based on the calculated value calculated by the second calculation unit only for a front wheel outside the turning of the vehicle. Brake fluid pressure control device for vehicles. 4. The anti-lock brake control unit according to claim 1, wherein the pressure control unit is an anti-lock brake control unit that reduces a brake fluid pressure generated in a master cylinder and transmitted to the wheel brake. 5. The brake fluid pressure control apparatus for vehicles as described.

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