JPH054574A - Antiskid control device - Google Patents

Abstract

PURPOSE:To prevent the occurrence of rapid lock and to ensure stability of a vehicle by performing control based on a reference speed during running on a high mu road surface at a high speed to prevent the increase of a braking distance and performing control based on the peak of a wheel speed during running at a low speed. CONSTITUTION:One of a hydraulic pressure control modes to reduce a brake hydraulic pressure, the mode to hold the brake hydraulic pressure, and the mode to increase the brake hydraulic pressure is set by a hydraulic pressure control mode setting means M7 to drive a hydraulic control device M2. Either a first pressure increase mode to increase a pressure when a wheel speed exceeds a reference speed or a second pressure increase mode to increase a pressure when a wheel speed exceeds a wheel speed at a peak is selected according to the deciding result of a road surface deciding means M6. A hydraulic pressure control mode is switched by a pressure increase mode switching means M8 so that the first pressure increase mode is selected when it is decided that a road surface has a high friction factor at least in a given range and a reference speed is in a high speed area exceeding a given speed, and the second pressure increase mode is selected when the reference speed is below the given speed in a low speed area.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anti-skid control device for controlling a braking force applied to wheels during vehicle braking to prevent the wheels from locking.

[0002]

2. Description of the Related Art It is well known that if the wheels are locked during sudden braking of the vehicle, the directional stability of the vehicle may be lost depending on road surface conditions. Therefore, when the brake fluid pressure to the wheel cylinder during braking is increased, the wheel speed sharply decreases immediately before the friction coefficient μ with respect to the wheel becomes maximum, so that the wheel speed and the wheel acceleration (including deceleration are included). The brake fluid pressure is controlled according to the change of the same), and as a result, the braking force is controlled so that the slip ratio of the wheel becomes around 20%, that is, the maximum friction coefficient is obtained. Specifically, an anti-skid control device is installed to control the braking force by reducing, increasing or maintaining the brake fluid pressure on the wheel cylinder so that the wheels do not lock during sudden braking.

In such an anti-skid control device, generally, the rotation speed of each wheel, that is, the wheel speed is detected, and the estimated vehicle speed is set as the reference speed according to the output of the acceleration detector based on the detected wheel speed. Then, the reference speed is further calculated from the estimated vehicle speed, the latter reference speed is compared with the wheel speed of each wheel, and the brake hydraulic pressure of the wheel cylinder of each wheel is controlled according to the comparison result. For example, as shown in FIG. 11, a reference speed Vsn that follows the estimated vehicle speed Vso with a constant speed difference is set, and the wheel speed Vw is lower than the reference speed Vsn (Vw
<Vsn), and although not shown, when the wheel acceleration Gw falls below the reference acceleration G1 (Gw <G1), the brake fluid pressure in the wheel cylinder is reduced. As a result, when the wheel acceleration Gw becomes equal to or higher than the reference acceleration G1 (Gw ≧ G1) and the wheel speed Vw is detected to change in the recovery direction,
The brake fluid pressure is maintained, the wheel acceleration Gw becomes equal to or higher than the reference acceleration G1 (Gw ≧ G1), and the wheel speed Vw is reached.
When is higher than the reference speed Vsn, the pressure is increased.

The estimated vehicle speed Vso is the wheel speed Vw,
Although it is set based on the output of the acceleration detector, etc., the deceleration rate is set to be larger than the deceleration rate of the actual vehicle body speed, that is, the actual vehicle body speed V, in consideration of errors due to detection errors and disturbances. Has been done. In particular, when the estimated vehicle body speed Vso is set based on the output of an acceleration detector such as an acceleration sensor or an acceleration switch, the estimated vehicle body speed Vso is affected by disturbances such as road inclination and vehicle body vibration. (Deceleration in this case) is set to a deceleration rate with a large margin. Therefore, the wheel speed Vw is controlled so as to decrease at a larger deceleration rate than the actual vehicle body speed V, and is particularly remarkable on a low μ road where the friction coefficient of the traveling road surface (hereinafter referred to as road surface μ) is low.

As described above, when the anti-skid control based on the reference speed Vsn is performed on the low μ road, the wheel speed Vw decreases along the estimated vehicle speed Vso without sufficiently recovering as shown in FIG. This will cause an early lock. In order to prevent this, generally, a method of switching from depressurization to pressure increase at the time when the wheel acceleration Gw changes from a positive value to a negative value (at the time of shifting from acceleration to deceleration). That is, as shown in FIG. 12, the pressure is controlled to increase when the wheel speed Vw peaks. According to this, although it is possible to prevent the early locking on the low μ road, the timing for increasing the brake fluid pressure is delayed and the braking distance is increased on the medium μ or high μ road where the road surface μ is high. In the brake fluid pressure characteristics in FIG. 12, a delay occurs as shown by the solid line in comparison with the original pressure boosting output shown by the broken line. As a result, not only the acceleration of the vehicle (in this case, deceleration) falls and the feeling is impaired, but also the braking distance is extended within the range shown by the diagonal lines in FIG. The increase in the braking distance due to the delay in the timing of increasing the brake fluid pressure is large when the vehicle runs on a high μ road at a high speed, and its influence is small when the vehicle runs on a low μ road or a low speed.

On the other hand, in the anti-skid control method disclosed in Japanese Patent Laid-Open No. 63-195055, the conventional anti-lock control method has a high peak point of the wheel speed Vw regardless of whether the friction coefficient (road surface μ) of the road surface is high or low. Since the pressurization is started at the (convex inflection point), the pressurization timing is delayed on the medium and high μ roads where the road surface μ is relatively high, and the wheel speed Vw overshoots near the high peak point to increase the braking distance. The problem that vehicle body vibration occurs is raised, and in order to cope with this, the start point of pressurization is advanced on the medium and high μ roads. That is, on the medium-high road, the pressurization start time is changed to the time when the wheel speed reaches the reference speed V _T after the low peak point has passed.

[0007]

However, as shown in FIG. 11, when the deceleration rate of the estimated vehicle body speed Vso is higher than the deceleration rate of the actual vehicle body speed V, the reference speed is set as described in the above publication. If the time point at which V _T is reached is taken as the pressurization start time point, the wheel speed Vw decreases along with the estimated vehicle body speed Vso, so there is still a risk of causing an early lock. On the other hand, control using the peak wheel speed is performed. If this is done, the braking distance will be extended, especially when traveling at high speed.

In view of this, the present invention suppresses the extension of the braking distance by controlling based on the reference speed during high speed running while traveling on a high μ road surface, and prevents the early lock by controlling based on the peak wheel speed during low speed traveling. The purpose is to ensure the stability of the vehicle.

[0009]

In order to achieve the above object, the anti-skid control device of the present invention applies a braking force to each wheel RR of a vehicle as shown in the outline of the configuration of FIG. A wheel cylinder 53 and the like, and a hydraulic pressure generator M1 that supplies brake hydraulic pressure to the wheel cylinder 53 and the like,
A hydraulic pressure control device M2 that controls a brake hydraulic pressure by interposing a hydraulic pressure passage that connects the hydraulic pressure generation device M1 and the wheel cylinders 53, and a signal corresponding to the wheel speed to detect the rotational speed of the wheels RR and the like. , A reference speed setting means M4 for setting a reference speed on the basis of the wheel speed detected by at least the wheel speed detection means M3, and a peak for detecting a peak from an increase to a decrease in the wheel speed. A detection means M5, a road surface determination means M6 for determining whether the friction coefficient of the traveling road surface is high or low, and a pressure reduction mode for reducing the brake fluid pressure,
Hydraulic pressure control mode setting means M7 for driving the hydraulic pressure control device M2 by setting either a hydraulic pressure control mode of holding pressure or a pressure increasing mode of increasing pressure, wherein the wheel speed is equal to or higher than the reference speed. Depending on the determination result of the road surface determination means M6, either one of the first pressure increase mode in which the pressure increases when the wheel speed reaches a peak and the second pressure increase mode in which the pressure increases when the wheel speed becomes equal to or higher than the peak wheel speed. And a hydraulic pressure control mode setting means M7 that is selected by selecting. Then, the road surface determination means M
6 is determined to be a road surface with a high friction coefficient within at least a predetermined range,
When it is determined that the reference speed of the reference speed setting means M4 is in the high speed range equal to or higher than the predetermined speed, the hydraulic pressure control mode setting means M7 selects the first pressure increasing mode, and the reference speed falls below the predetermined speed to the low speed range. A pressure increasing mode switching means M8 for switching between the first and second pressure increasing modes so as to select the second pressure increasing mode when it is determined to be present is provided.

[0010]

In the anti-skid control device having the above structure, when the brake fluid pressure is supplied from the fluid pressure generation device M1 to each of the wheel cylinders 53 and the like through the fluid pressure control device M2, each of the wheels RR and the like is provided. Braking force is applied to it.
During this time, the rotation speed of the wheels RR, that is, the wheel speed is detected by the wheel speed detecting means M3.

The wheel speed signal of the wheel speed detecting means M3 is supplied to the reference speed setting means M4, where the reference speed is set based on at least the wheel speed. Further, the peak detecting means M5 detects a peak, that is, a convex inflection point, at which the wheel speed detected by the wheel speed detecting means M3 increases and decreases. Further, the road surface determination means M6 determines whether the friction coefficient of the traveling road surface is high or low based on the wheel acceleration calculated from the wheel speed, for example. The reference speed and the wheel speed are compared in magnitude by the hydraulic control mode setting means M7, and the hydraulic control mode is set according to the result. That is, when the wheel speed falls below the reference speed, one of the pressure reducing mode and the holding mode is set. Further, one of a first pressure increasing mode in which pressure is increased when the wheel speed is equal to or higher than a reference speed, and a second pressure increasing mode in which pressure is increased when the wheel speed is equal to or higher than the wheel speed at the peak. Is set. In these first and second pressure increasing modes, first, the road surface determination means M
According to the determination result of No. 6, for example, when it is determined that the road surface has a high friction coefficient, the first pressure increase mode is selected, and when it is determined that the road surface has a low friction coefficient, the second pressure increase mode is selected. Then, when the road surface determination means M6 determines that the road surface has a high friction coefficient within at least a predetermined range, and the reference speed of the reference speed setting means M4 is determined to be in a high speed range equal to or higher than the predetermined speed, the first pressure increase mode. Is selected and the second pressure increasing mode is selected by the pressure increasing mode switching means M8 so that the second pressure increasing mode is selected when it is determined that the vehicle is below the predetermined speed and is in the low speed range. ..

[0012]

EXAMPLES Examples of the anti-skid control device of the present invention will be specifically described below. FIG. 2 shows a vehicle equipped with an anti-skid control device according to an embodiment of the present invention, which has a hydraulic pressure generating device 2 including a master cylinder 2a and a booster 2b and is driven by a brake pedal 3.

The master cylinder 2a is a so-called tandem type master cylinder, and is a wheel cylinder 5 of wheels FR and FL.
1 and 52 are directly connected to the actuator 30.
And the wheels RR via the proportioning valve 60,
It is connected to the wheel cylinders 53 and 54 of the RL.
Here, the wheel FR indicates the front right wheel when viewed from the driver's seat, hereinafter the wheel FL indicates the front left side, the wheel RR indicates the rear right side, the wheel RL indicates the rear left wheel, and the front wheel side and the rear wheel side are independent. The piping of the front and rear division method is configured. A known transmission 5 is connected to the internal combustion engine 4 mounted on the vehicle of this embodiment, and the transmission 5 is connected to a differential gear 7 via a propeller shaft 6. The wheels RR and RL are connected to the differential gear 7, and the driving force of the internal combustion engine 4 is transmitted.

When a pedal effort is applied to the brake pedal 3, the booster 2b is driven according to this pedal effort, and the booster 2b drives the master cylinder 2a with a double pressure. As a result, brake hydraulic pressure corresponding to the pedaling force of the brake pedal 3 is output from the master cylinder 2a and applied to the wheel cylinders 51 to 54. When the brake fluid pressure is applied to the wheel cylinders 51 and 52, the braking force is applied to the wheels FR and FL, which are the driven wheels, and the wheel cylinders 5 and 5 are driven.
When applied to 3, 54, the braking force is applied to the wheels RR and RL that are the driving wheels.

Actuator 3 which constitutes a hydraulic pressure control device
0 is interposed between the master cylinder 2a and the wheels RR and RL, and is connected to the pump 40 and the reservoir 41. The pump 40 is driven by the internal combustion engine 4, and the reservoir 41
The brake fluid is increased and supplied as power fluid pressure to the actuator 30. The actuator 30 is provided with a pair of electromagnetic switching valves (not shown). These electromagnetic switching valves have the solenoids 31 and 32 shown in FIG. 3 and are driven and controlled by the output signal of the electronic control unit 10.

In the "pressure increasing" mode in which the output hydraulic pressure of the pump 40 is supplied to the wheel cylinders 53, 54 to increase the brake hydraulic pressure, the "pressure reduction" is communicated with the reservoir 41 to reduce the brake hydraulic pressure. The hydraulic pressure control mode of the mode and the "holding" mode in which the brake hydraulic pressure in the wheel cylinders 53 and 54 is held is appropriately selected, and the brake hydraulic pressure is adjusted so that the wheels RR and RL are not locked. Further, the solenoids 31 and 32 are de-energized so that the master cylinder 2a
The "direct connection" mode is set in which the wheel cylinders 53, 54 are directly communicated with each other.

The proportioning valve 60 interposed between the actuator 30 and the wheel cylinders 53 and 54 makes the brake fluid pressure applied to the rear wheel cylinders 53 and 54 constant with respect to the input fluid pressure. It has a function of reducing the pressure by a ratio and approximating the ideal braking force distribution, and in the present embodiment, a so-called load sensing type whose characteristics change according to the supporting load on the wheels RR and RL is used.

A wheel speed sensor 20, which is a wheel speed detecting means, is provided in the differential gear 7 connected to the wheels RR and RL. In the wheel speed sensor 20, the rotation speed of the propeller shaft 6, that is, the rear wheels RR and R that are the driving wheels.
The average wheel speed Vw of L is detected, and the detected wheel speed V
An electric signal corresponding to w is output to the electronic control unit 10.
Further, the acceleration sensor 21 is fixed at an appropriate position where the vibrations from the road surface and the vibrations from the internal combustion engine 4 are difficult to be transmitted, and the acceleration of the vehicle (including deceleration unless otherwise specified) is detected. Estimated vehicle speed Vso
And an electric signal for determining the road surface μ are output to the electronic control unit 10.

A brake switch 22 that opens and closes in conjunction with the brake pedal 3 is provided to detect the operation of the brake pedal 3. The brake switch 22 is turned on when the brake pedal 3 is operated, a stop lamp (not shown) is turned on, and
It is output to the electronic control unit 10 as an electric signal indicating that the brake pedal 3 is in the operated state. Then, the output electric signals of the wheel speed sensor 20, the acceleration sensor 21, and the brake switch 22 are input to the electronic control unit 10.

The electronic control unit 10 is, as shown in FIG.
A microprocessor 11, a waveform shaping circuit 12, input buffers 13, 14, 15 and output buffers 16, 17 are provided. A commercially available one-chip microcomputer is used as the microprocessor 11 of this embodiment, and has a built-in free-run timer for outputting the current time, a ROM storing a program, a RAM necessary for executing the program, and the like.

The waveform shaping circuit 12 includes a wheel speed sensor 20.
A sine-wave voltage signal is input from the processor, converted into a square-wave signal here, and interrupted by the interrupt request terminal I of the microprocessor 11.
Input to RQ. Therefore, an interrupt request is issued to the microprocessor 11 at time intervals according to the wheel speed detected by the wheel speed sensor 20. Also, via the input buffer 13, the input / output port IP of the microprocessor 11 is in the form of a high (H) level when the brake switch 22 is on and a low (L) level when it is off.
Input to 1. Further, the output of the acceleration sensor 21 is input to the input ports IP2 and IP3 of the microprocessor 11 via the input buffers 14 and 15 according to the acceleration of the vehicle.

On the other hand, the output port OP1 of the microprocessor 11 is connected to the actuator 3 via the output buffer 16.
It is connected to the solenoid 31 of one of the 0 electromagnetic switching valves. The output port OP2 is connected to the solenoid 32 of the other electromagnetic switching valve via the output buffer 17. These output buffers 16 and 17 have output ports OP1 and OP2.
The electric signal output from the actuator is amplified and the actuator 30
Is a circuit for exciting the solenoids 31 and 32, respectively.

In the electronic control unit 10, a series of processes for anti-skid control is performed according to the program executed by the microprocessor 11, and electric signals are output from the output ports OP1 and OP2. This program has a main routine shown in the flowchart of FIG. 4 and an interrupt routine shown in the flowchart of FIG. 5 which is executed when an electric signal is input to the interrupt request terminal IRQ.

First, the main routine of FIG. 4 will be described. When the electronic control unit 10 is powered on, initialization processing is performed in step S1. That is, ta, tb and a flag under control which will be described later are cleared to zero. The outputs of the output ports OP1 and OP2 are set so that the solenoids 31 and 32 are not excited. next,
In step S2, the signal indicating the state of the brake switch 22 and the signal corresponding to the acceleration of the vehicle detected by the acceleration sensor 21 are input to the microprocessor 11.

Next, in step S3, the wheel speed Vw of the rear wheels is calculated by the following equation (1) based on the cycle ΔTw of the electric signal output from the wheel speed sensor 20. The period ΔTw is measured in an interrupt routine described later. Vw = K / ΔTw (1) where K is a constant determined by the characteristics of the wheel speed sensor 20.

In step S4, the wheel acceleration Gw is calculated from the wheel speed Vw calculated in step S3 by the following equations (2) and (3). Int = (ΔTw (n) + ΔTw (n-1)) / 2 (2) Gw (n) = (Vw (n) -Vw (n-1)) / Int (3) where Int Indicates an interrupt interval time, and Vw (n),
ΔTw (n) indicates the wheel speed Vw and the cycle ΔTw calculated this time, and Vw (n−1) and ΔTw (n−1) indicate the wheel speed Vw and the cycle ΔTw calculated last time.

In step S5, the acceleration sensor 2
Acceleration Gd of the vehicle detected by 1 and step S3
An estimated vehicle body speed Vso, which is a reference speed, is calculated from the wheel speed Vw calculated in. The estimated vehicle body speed Vso is calculated as follows by the above equation (2) and the following equations (4) and (5). Vd (n) = Vso (n−1) −L · Gd (n) · Int (4) Vso (n) = Max (Vw (n), Vd (n)) (5) where Vd (n ) Indicates the set speed obtained this time, and L is a constant determined by the characteristics of the acceleration sensor 21. Further, Vso (n) indicates the estimated vehicle body speed Vso obtained this time, and Vso (n-1) indicates the estimated vehicle body speed Vso obtained last time.
Indicates. Max (a, b) is a function that gives the larger value of a and b.

Next, the process proceeds to step S6, and step S
3, reference speeds Vsn, Vsn set so as to follow the wheel speed Vw, the wheel acceleration Gw, and the estimated vehicle speed Vso obtained in S4 and S5 with a constant speed difference.
Based on h, how to control the brake fluid pressure in the wheel cylinders 53 and 54 is determined. The process of step S6 will be described later. Then, in step S7, the output signal for driving the solenoids 31 and 32 is output port OP according to the determination result in step S6.
1, OP2, the wheel cylinders 53, 54
The brake fluid pressure applied to is increased, reduced or maintained.

When the steps S1 to S7 are repeatedly executed and the wheel speed Vw is rapidly reduced and the wheels RR and RL have a large slip on the road surface, the brake fluid pressure is reduced to rotate the wheels RR and RL. The slip of the wheels RR and RL with respect to the road surface is suppressed.

FIG. 5 shows the above-mentioned interrupt routine, in which the time interval between the previous interrupt request and the present interrupt request, that is, the period ΔTw of the electric signal output from the wheel speed sensor 20 is measured. First, at step 11, the current time ta is set by the free-run timer. Next, at step S12, the time difference between the time tb when the previous interrupt request is generated and the current time ta is calculated, and the cycle ΔTw of the output electric signal of the wheel speed sensor 20 is set.
Then, in step S13, the time tb is updated and set in preparation for the next interrupt request. Step S1
When the processing of 1 to S13 is executed, the processing of the main routine is executed again.

FIG. 6 shows the subroutine of step S6 of FIG. 4, in which the brake fluid pressure control processing for properly selecting the fluid pressure control modes of pressure reduction, pressure increase, and holding is executed. First, in step 601, it is determined whether or not the start condition of the brake fluid pressure control is satisfied. That is, the estimated vehicle body speed Vso is compared with a predetermined stop determination speed Vo, for example, 5 km / h, and when it is determined that the vehicle is stopped, the process returns to the main routine and the brake hydraulic pressure control is not performed. In step 602, the on / off state of the brake switch 22 is determined, and if it is on, the process proceeds to step 603. When it is off, the routine returns to the main routine and this brake fluid pressure control is not performed. Step 6
In 03, it is judged whether or not the control is in progress by the control flag,
If it is under control, the routine proceeds to step 604, and if it is not under control, the routine returns to the main routine, and this brake fluid pressure control is not performed. The control flag is a flag that is set when the brake fluid pressure control is started, and is maintained in the set state during control.

Next, it is judged whether or not the rear wheels RR and RL which are the driving wheels are slipping. That is, in step 604, it is determined whether the wheel speed Vw of the rear wheels is smaller than the reference speed Vsn (Vw <Vsn). Wheel speed V
When w is smaller than the reference speed Vsn (Vw <Vsn), it is determined that the wheels RR and RL are slipping, and the routine proceeds to step 605. On the other hand, the wheel speed V
When w is equal to or higher than the reference speed Vsn (Vw ≧ Vsn), the process proceeds to step 610 described later.

In step 605, the wheel acceleration G of the rear wheels is
It is determined whether w is smaller than a predetermined reference acceleration G1s. The wheel acceleration Gw is smaller than the reference acceleration G1s (Gw <
G1s), it is determined that the wheels RR and RL are immediately before being locked. At this time, the routine proceeds to step 606, where the pressure reduction mode is output, the routine returns to the main routine, and at step S7 of FIG.
Solenoid 31, so that the brake fluid pressure inside is reduced
The 32 excited and non-excited states are set. That is, when the pressure reduction signal is output in step 606, the actuator 30 causes the wheel cylinders 53 and 54 to communicate with the reservoir 41, and the brake fluid pressure is reduced. On the other hand, the wheel acceleration Gw is greater than or equal to the predetermined acceleration G1s (Gw ≧
G1s), it is determined that the wheels RR and RL are not locked immediately, and the routine proceeds to step 607, where the holding mode is output.

On the other hand, in step 604, the wheel speed V
When it is determined that w is equal to or higher than the reference speed Vsn, the routine proceeds to step 610, where it is determined whether the wheels RR and RL are slipping. Wheel speed V in step 610
When it is determined that w is lower than the reference speed Vsnh, the process proceeds to step 611. Wheel speed Vw is reference speed Vsnh
If it is determined that the above is the case, the process proceeds to step 612.

In step 611, it is determined whether the wheel acceleration Gw is smaller than the predetermined reference acceleration G1h. When the wheel acceleration Gw is equal to or higher than the reference acceleration G1h, the holding mode signal is output in step 607. When it is determined that the wheel acceleration Gw is smaller than the reference acceleration G1h, the process proceeds to step 612, where it is determined whether the road surface μ corresponds to the first high μ value H1, and if so, the process proceeds to step 613. To output a boosting mode signal.
Thus, the above steps 604, 605, 610 and 61.
Depending on the determination result of No. 1, as shown in FIG. 7, one of the pressure increasing, holding and depressurizing modes is selected according to the wheel speed Vw and the wheel acceleration Gw, and so-called map control is performed. As a result, the control characteristics shown in FIG. 9 are obtained, and if it is determined in step 612 that the road surface μ does not correspond to the first high μ value H1, the process proceeds to step 614, and whether the road surface μ corresponds to the second high μ value H2. It is determined whether or not. The determination of the first and second high μ values H1 and H2 is performed based on the output signal of the acceleration sensor 21, and the road surface such as a dry asphalt road has the first high μ value H1 and is wet. On a road surface such as an asphalt road, the second high μ value H2 is set.

When the road surface μ is the second high μ value H2, the estimated vehicle body speed Vso is further changed to the predetermined speed V at step 615.
It is determined whether or not it is less than 1, and when it is determined that the speed is equal to or higher than the predetermined speed V1, the pressure increasing mode signal is output in step 613. When it is determined that the estimated vehicle body speed Vso is lower than the predetermined speed V1, the routine proceeds to step 616, where it is determined whether the wheel speed Vw has reached the peak.
That is, when it is determined that the wheel speed Vw has changed from increasing to decreasing and has reached the high peak of the convex inflection point, the routine proceeds to step 613, where the pressure increase mode signal is output. On the other hand, if the high peak has not been reached, the holding mode signal is output in step 607. Such a pressure increasing method is distinguished from the above map pressure increasing mode as a peak pressure increasing mode.

On the other hand, when it is determined in step 614 that the road surface μ does not correspond to the second high μ value H2, that is, when it is the medium μ value M or the low μ value L, the routine proceeds to step 616, where the peak A determination is made, and a pressure increasing mode signal (step 613) or a holding mode signal (step 607) is output according to the determination result. That is, as shown in FIG. 8, the map pressure increasing mode as the first pressure increasing mode and the peak pressure increasing mode as the second pressure increasing mode are selected according to the value of the road surface μ and the value of the estimated vehicle speed Vso.

FIG. 10 shows an example of a control state at the time of vehicle braking in the present embodiment. Reference speeds Vsn, V follow the estimated vehicle speed Vso with a constant speed difference.
snh is set, and as described above, the reference speed Vsn serves as a criterion for starting pressure reduction, the reference speed Vsnh serves as a criterion for starting pressure increase, and brake fluid pressure control having a hysteresis characteristic is performed. When the estimated vehicle speed Vso after the start of the anti-skid control is equal to or higher than the predetermined speed V1, the pressure is increased based on the map control, and the control is shifted to the peak control at the point P below the predetermined speed V1 and the wheel speed Vw is drastically reduced. It is blocked and is on the way to recovery.

[0039]

Since the present invention is configured as described above, it has the following effects. That is, in the anti-skid control device of the present invention, when the pressure increase mode switching means determines that the road surface has a high friction coefficient and is in the high speed range, the first pressure increase mode is selected and the low pressure range is selected. When it is determined that the second pressure increasing mode is selected, the pressure can be increased at an early timing by the control based on the reference speed when traveling on a road surface having a high friction coefficient at high speed. During low-speed traveling, early locking can be prevented by control based on the peak wheel speed. Thus, the stability and steering of the vehicle can be maintained and good anti-skid control can be performed without increasing the braking distance.

[Brief description of drawings]

FIG. 1 is a block diagram showing an outline of an anti-skid control device of the present invention.

FIG. 2 is an overall configuration diagram of an embodiment of an anti-skid control device of the present invention.

FIG. 3 is a block diagram showing a configuration of the electronic control device of FIG.

FIG. 4 is a flowchart showing a process of a main routine for controlling a braking force in the embodiment of the present invention.

FIG. 5 is a flowchart showing a process of an interrupt routine for controlling braking force according to an embodiment of the present invention.

FIG. 6 is a flowchart showing a process of a subroutine for brake fluid pressure control in one embodiment of the present invention.

FIG. 7 is a graph showing a relationship between a wheel speed and a wheel acceleration in a map pressure increasing mode according to an embodiment of the present invention.

FIG. 8 is a graph showing a relationship between an estimated vehicle body speed Vso and a road surface μ in a peak pressure increasing mode and a map pressure increasing mode in an embodiment of the present invention.

FIG. 9 is a graph showing a control state of brake fluid pressure control in one embodiment of the present invention.

FIG. 10 is a graph showing a control example of the anti-skid control device according to the embodiment of the present invention.

FIG. 11 is a graph showing a control state of map control in the conventional anti-skid control device.

FIG. 12 is a graph showing a control state including a peak pressure increasing mode in a conventional anti-skid control device.

[Explanation of symbols]

 2 hydraulic pressure generating device 2a master cylinder, 2b booster, 3 brake pedal 10 electronic control device 11 microprocessor 20 wheel speed sensor (wheel speed detecting means) 21 acceleration sensor 22 brake switch 30 actuator (hydraulic pressure control device) 31, 32 solenoid 40 Pump 41 Reservoir 51-54 Wheel Cylinder FR, FL, RR, RL Wheel

 ─────────────────────────────────────────────────── ─── Continued front page (72) Inventor Hiroyuki Ichikawa 2-1-1 Asahi-cho, Kariya city, Aichi Prefecture Aisin Seiki Co., Ltd. (72) Inventor Kami Katsu 2-1-1 Asahi-cho, Kariya city, Aichi prefecture Aisin Seiki Co., Ltd. Incorporated (72) Inventor, Itabashi Katsuya 2-1-1 Asahi-cho, Kariya city, Aichi Aisin Seiki Co., Ltd.

Claims (1)

Claim: What is claimed is: 1. A wheel cylinder for applying a braking force to each wheel of a vehicle, a hydraulic pressure generator for supplying a brake hydraulic pressure to the wheel cylinder, the hydraulic pressure generator and the wheel. A hydraulic pressure control device that controls the brake hydraulic pressure by interposing a hydraulic passage that connects between the cylinders, a wheel speed detection unit that detects the rotational speed of the wheel and outputs a signal corresponding to the wheel speed, and at least Reference speed setting means for setting a reference speed based on the wheel speed detected by the wheel speed detecting means,
Peak detection means for detecting a peak from which the wheel speed increases to decrease, road surface determination means for determining whether the friction coefficient of a traveling road surface is high or low, a depressurization mode for reducing the brake fluid pressure, a holding mode for holding pressure and an increase. Hydraulic pressure control mode setting means for setting any one of the hydraulic pressure control modes of the pressure increasing mode to drive the hydraulic pressure control device, wherein the pressure is increased when the wheel speed becomes equal to or higher than the reference speed. 1
Hydraulic control for selecting one of the pressure increasing mode of No. 2 and the second pressure increasing mode of increasing pressure when the wheel speed becomes equal to or higher than the peak wheel speed according to the judgment result of the road surface judging means. In an anti-skid control device including a mode setting means, the road surface determination means determines that the road surface has a high friction coefficient within at least a predetermined range, and the reference speed of the reference speed setting means is in a high speed range of a predetermined speed or more. When it is determined that the hydraulic pressure control mode is set, the hydraulic pressure control mode setting means selects the first pressure increasing mode, and when it is determined that the reference speed is lower than the predetermined speed and is in the low speed range, the second pressure increasing mode is selected. Thus, the antiskid control device is provided with pressure increasing mode switching means for switching the first and second pressure increasing modes.