JPH09290733A - Road surface frictional coefficient acquiring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve estimating precision for a road surface μ by correcting the road surface μ estimation value when an abnormal condition, which is not generated if the road surface μ estimation value is normal one, is generated in a wheel or in an antilock controller during antilock control. SOLUTION: A road surface frictional coefficient acquiring device, which is used with an antilock controller controlling a braking pressure for a wheel on the basis of the wheel condition and a road surface μ, estimates a road surface μ on the basis of vehicle body deceleration during antilock control so as to feed the road surface μ estimation value to the antilock controller. In this case, a boosting lack tendency is generated in the wheel during the antilock control, and if a duration of a small slip condition is prolonged abnormally in the same wheel (S3), or if a duration of a pulse boosting mode selection condition as a gentle boosting mode in the same wheel is prolonged abnormally (S4), an increase Δ is added to a vehicle deceleration DVS0 substituted for the road surface μ estimation value (S5).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention acquires a road surface μ, which is a friction coefficient of a road surface on which a vehicle is traveling, and obtains the acquired road surface μ based on the state of the wheel and the road surface μ. The present invention relates to a road surface friction coefficient acquisition device that supplies a controlled wheel control device, and particularly to a technique for improving the reliability of an acquired road surface μ.

[0002]

2. Description of the Related Art In order to improve various performances such as braking performance, acceleration performance, turning performance, etc. of a vehicle, it is expressed by the state of wheels, that is, the braking force, driving force, lateral force, etc. acting between the wheel and the road surface. There is already known a technique which should be called a wheel control for controlling a controllable control. Further, if the friction coefficient μ of the road surface on which the vehicle is traveling changes, the state of the wheels also changes, which in turn changes the control characteristics suitable for controlling the state of the wheels. Therefore, in this wheel control,
It is important to determine the control characteristics of the wheel condition in consideration of the road surface μ.

This will be specifically described with respect to an antilock control device which is an example of a slip control device as an example of a wheel control device.

As is well known, this anti-lock control device is a device for controlling the brake pressure of the wheels so that the slip of the wheels does not become excessive during vehicle braking. In this anti-lock control device, the road surface μ
When is high, the brake pressure is also high, so if the wheel slips and the pressure reduction is started for that wheel, the brake pressure will quickly drop even if the pressure is reduced for a short time.
When the road surface μ is low, the brake pressure is also low, so that the decompression time required to eliminate the slip of the wheels becomes longer than that on the high μ road. Therefore, in antilock control, it is important to determine the control characteristics of the state of the wheels in consideration of the road surface μ.

Against the background of such circumstances, there is already known a technique for changing the control characteristic by following the change of the road surface μ during wheel control. This is a technique described in Japanese Patent Application Laid-Open No. 2-267064 of the applicant of the present invention. In the antilock control device, the road surface μ increases rapidly during the antilock control, and the braking pressure of the wheels tends to be insufficient. If the following occurs, the next time the pressure is increased for a longer time than usual, the technology to eliminate the insufficient pressure increase, or if the road surface μ is suddenly decreased and the wheel brake pressure tends to be insufficiently reduced, This is a technique for eliminating the insufficient decompression by performing the next decompression for a longer time than usual.

According to this conventional technique, as a result, the road surface μ
Is reflected in the control characteristics. However, with this conventional technique,
The road surface μ is not used as a basic value when determining the control characteristic, and the road surface μ is only taken into consideration only for the pressure increasing time which is one of the control characteristics. The road surface μ is
It is a basic parameter to obtain the desired control effect by correctly grasping the state of the wheel moving in contact with the road surface and controlling it correctly.From such a meaning, in the wheel control, the road surface μ itself is It is desirable to determine the control characteristics based on this.

Based on such knowledge, it has already been used to use a wheel control device together with a road surface friction coefficient acquisition device. As an example of the road surface friction coefficient acquisition device, the state of the wheel (for example, rotation state, slip state, wheel restoring force, etc.)
Or a vehicle state (for example, vehicle body deceleration or vehicle body acceleration that is a rate of change of vehicle body speed, vehicle body yaw rate, vehicle body lateral acceleration, etc.), a state of a wheel control device (for example, a plurality of wheel states for controlling a state of a wheel, Road surface μ based on the selected mode, solenoid valve, etc., signal output to the actuator, etc.)
An indirect acquisition type (road surface μ estimation device) is already known. Furthermore, information related to road surface μ is directly input from the road surface, and what is the state of the wheel, the state of the vehicle, and the state of the wheel control device? A direct acquisition type (road surface μ detection device) that independently detects the road surface μ is already known.

[0008]

However, the road surface μ is not always normally acquired in any of the formats.

For example, in the case where the road surface friction coefficient acquisition device is an indirect acquisition type that acquires the road surface μ so that it becomes lower as the vehicle deceleration decreases during antilock control, the wheels are road surface projections and manhole covers. When passing through a partially low μ road such as a puddle, wheel slip suddenly increases, the vehicle body deceleration rapidly decreases, and the acquired road surface μ also rapidly decreases. Partial low μ
After passing the road, the acquired road surface μ should be immediately high μ
It is desirable to return to the road surface μ, which represents a road.
However, since it takes time to restore the state of the wheels and the state of the vehicle itself, it takes time to restore the acquired road surface μ, and when the acquired road surface μ is updated based on the past acquired road surface μ, Since the influence of the past acquired road surface μ will extend to the future acquired road surface μ, it will take time to restore the acquired road surface μ, so that the acquired road surface μ will continue to be lower than the original road surface μ. It can happen.

Further, when the road surface friction coefficient acquisition device is of the direct acquisition type for detecting the road surface μ, the problem as in the case of the indirect acquisition type does not occur, but the device itself fails, It is possible that a value different from the road surface μ is detected temporarily or continuously.

In any case, in the wheel control device used together with the road surface friction coefficient acquisition device, if the acquisition of the road surface μ becomes abnormal, normal wheel control is not guaranteed. In the case of the anti-lock control device, there is a possibility that a situation such as insufficient pressure increase or insufficient pressure decrease may occur. Therefore, when the acquired road surface μ becomes abnormal, it is necessary to eliminate the abnormality early.

Against the background of these circumstances, the first to fourth inventions according to claims 1 to 4 feed back the control state based on the acquired road surface μ to change the acquired road surface μ, thereby making the acquired road surface μ abnormal. It was made to solve the problem.

In particular, the second aspect of the present invention is intended to change the obtained road surface μ by feeding back the state of wheel slip as a control state in the first aspect of the invention.

A third aspect of the present invention is intended to change the obtained road surface μ by feeding back a control mode selection state as a control state in the first and second aspects.

The fourth aspect of the present invention is intended to provide a desirable mode of changing the acquired road surface μ in the first to third aspects of the invention.

According to a fifth aspect of the present invention, the partial road surface μ after the wheel has passed the partial low μ road is eventually returned to the acquired road surface μ before the passage, so that the partial low road surface μ is restored. The problem was to avoid unscheduled wheel control by the μ road.

[0017]

In order to solve the problem, the first invention acquires a road surface μ which is a friction coefficient of a road surface on which a vehicle is traveling, and acquires the acquired road surface μ.
In a road surface friction coefficient acquisition device that supplies the wheel control device that controls the state of the wheel based on the state of the wheel and the road surface μ, in the operation of the wheel control device, the state of the wheel and the wheel control device. When the control state, which is at least one of the states 1 and 2, does not occur when the acquired road surface μ is normal, a changing unit that changes the acquired road surface μ is provided.

Since the state of the wheels is influenced by the true road surface μ and the state of the wheel control device is influenced by the state of the wheel, both of them are consequently influenced by the true road surface μ. Further, since the state of the wheel control device is influenced by the acquired road surface μ, and the state of the wheel is influenced by the state of the wheel control device, both of them are eventually influenced by the acquired road surface μ. . Also, the acquired road surface μ is the true road surface μ
The phenomenon that appears in the control state (hereinafter simply referred to as "control state") that is the state of the wheels or the state of the wheel control device at the time of an abnormality that does not substantially match
The phenomenon that appears in the control state differs depending on whether the acquired road surface μ is lower or higher than the true road surface μ, and the phenomenon that appears in the control state in each case can be grasped in advance. Therefore, by monitoring the actual control state in relation to the target control state, it is possible to estimate the relationship between the acquired road surface μ and the true road surface μ, that is, whether the acquired road surface μ is lower or higher than the true road surface μ. .

Based on such knowledge, in the road surface friction coefficient acquisition device according to the first aspect of the present invention, when the wheel control device is in operation, the control state does not occur when the acquired road surface μ is normal. Then, the acquired road surface μ is changed.

For example, in the road surface friction coefficient acquiring device according to the first aspect of the present invention, the change of the acquired road surface μ is performed by changing the acquired road surface μ.
There is a case where it is performed as a correction of, or a case where it is performed as a change to a predetermined standard value. When it is performed as a correction, when the control state becomes a state that occurs when the acquired road surface μ is lower than the normal value during the operation of the wheel control device, the acquired road surface μ is corrected to the increasing side and the reverse. In addition, when the control state becomes a state that occurs when the acquired road surface μ is higher than the normal value, the acquired road surface μ is corrected to the decreasing side. Also,
If it is performed as a change to the standard value, during operation of the wheel control device, if the control state becomes a state that occurs when the acquired road surface μ is not normal, regardless of the true road surface μ, The acquired road surface μ is changed to a standard value, for example, a value indicating a high μ road or a value indicating a low μ road.

Therefore, according to the first aspect of the invention, since the control state based on the acquired road surface μ is fed back and the acquired road surface μ is changed, the abnormality of the acquired road surface μ is eliminated,
The effect that the abnormality of the wheel control based on the abnormality is also eliminated is obtained.

By the way, when the road surface friction coefficient acquisition device is an indirect acquisition type that acquires the road surface μ based on the state of the vehicle (for example, the rate of change of the vehicle speed), the change in the actual value of the road surface μ is the estimated value of the road surface μ. It takes time to appear in. This is because when the actual value of the road surface μ changes, the state of the wheels changes first, and then the state of the vehicle changes, and for the first time, it appears as a change in the rate of change of the vehicle body speed. On the other hand, according to the first aspect of the present invention, the information other than the rate of change of the vehicle speed, that is, the information in which the change in the actual value of the road surface μ appears earlier, that is, the state of the wheel and the state of the wheel, is used. The acquired road surface μ is changed based on a control state that is at least one of the changing wheel control state. Therefore, according to the first aspect of the present invention, when the road surface friction coefficient acquisition device is an indirect acquisition type that acquires the road surface μ based on the state of the vehicle, the road surface μ can be acquired earlier and accurately. You can also get the effect.

The “acquired road surface μ” in the first aspect of the invention is, for example, a road surface μ acquisition value that continuously represents the height of the road surface μ, two levels of high and low, and three levels of high, medium and low. , Or a road surface μ acquisition level represented by a higher level.

The "wheel control device" includes, for example, a slip control device for controlling wheel slip as a wheel condition such as antilock control and traction control, and a wheel longitudinal force between left and right wheels as a wheel condition. And a vehicle behavior control device that controls vehicle behavior by controlling the vehicle lateral force and the lateral force of the wheels.

The "road surface friction coefficient acquisition device" may be, for example, the above-mentioned indirect acquisition type or direct acquisition type. For the indirect acquisition type, for example, a device that estimates the vehicle body speed change rate from the wheel speed and uses the estimated vehicle body speed change rate as the road surface μ, or directly detects the vehicle body speed change rate, and outputs the detected value. There is a device (for example, an acceleration sensor) having a road surface μ. The direct acquisition type includes, for example, a device that radiates ultrasonic waves to the road surface and detects the road surface μ based on the reception state (for example, reception intensity, change state, etc.) of the reflected wave.

[0026]

[Means for Solving the Problem, Action and Effect of the Second Invention] A second invention is, in order to solve the problem, a road surface friction coefficient acquiring device according to the first invention, wherein the wheel control device is configured to slip the wheel. Is a device for controlling the wheel as a state of the wheel, and the changing means is in a state in which the state of slip of the wheel does not occur when the acquired road surface μ is normal during the operation of the wheel control device. In this case, it is characterized by including means for changing the acquisition road surface μ.

Therefore, according to this second invention, the first
As a preferred embodiment of the invention, the state of wheel slip as the state of the wheel is fed back to obtain the road surface μ
The effect that the one that changes is provided is obtained.

In the second aspect of the present invention, "when the state where the wheel slip does not occur when the acquired road surface μ is normal" is, for example, the duration of the state where the wheel slip is smaller than the appropriate amount. Is defined as exceeding the set time (corresponding to an example of insufficient pressure boosting condition),
When the duration of the state where the wheel slip is larger than the appropriate amount exceeds the set time (corresponding to an example of insufficient pressure reduction state)
Can be defined as

[0029]

[Means for Solving the Problem, Action and Effect of the Third Invention] In order to solve the problem, a third aspect of the present invention is a road surface friction coefficient acquiring device according to the first or second invention, wherein the wheel control device is the Based on the state of the wheel and the road surface μ, a mode is selected from a plurality of modes for controlling the state of the wheel, and is a device for controlling the state of the wheel in the selected mode, When the changing means is in a state where the selected state of the mode as the state of the wheel control device does not occur during operation of the wheel control device when the obtained road surface μ is normal, the acquisition It is characterized in that it includes means for changing the road surface μ.

Therefore, according to the third invention, the first
Alternatively, as a desirable embodiment of the second aspect of the invention, it is possible to provide an effect that the obtained road surface μ is changed by feeding back the selection state of the control mode by the wheel control device as the state of the wheel control device.

In the third aspect of the present invention, "when the selected state of the mode does not occur when the acquired road surface μ is normal", for example, when the wheel control device performs antilock control, traction control, etc. In the case of a slip control device that controls the brake pressure of the wheels in a plurality of modes to control the slip of the wheels, for example, the duration of the state in which the pressure increasing mode or the holding mode is selected for the same wheel is set to a set time. Defined as exceeding (corresponding to another example of insufficient pressure increase condition), or when the duration of the condition that the decompression mode is selected for the same wheel exceeds the set time (in another example of insufficient pressure decrease condition, Applicable).

[0032]

A fourth aspect of the present invention is a road surface friction coefficient acquisition device according to any one of the first to third aspects of the present invention, wherein the changing means is A change means for changing the acquired road surface μ to the same direction until the control state becomes a state that occurs when the acquired road surface μ is normal, thereby correcting the acquired road surface μ. To do.

In the road surface friction coefficient acquiring apparatus according to the fourth aspect of the present invention, when the control state based on the acquired road surface μ indicates that the acquired road surface μ is lower than the actual road surface μ, the acquired road surface μ increases. The increase is terminated when the control state based on the acquired road surface μ becomes normal. When the control state based on the acquired road surface μ indicates that the acquired road surface μ is higher than the actual road surface μ, the acquired road surface μ is decreased and the control state based on the acquired road surface μ becomes normal. When that happens, the reduction ends.

As described above, according to the fourth aspect of the present invention, the control state based on the acquired road surface μ is fed back to correct the acquired road surface μ, whereby the acquired road surface μ is the actual value of the road surface μ. The change can be quickly followed, the response of the acquired road surface μ is improved, and the accuracy of acquiring the road surface μ is improved.

[0035]

[Means for Solving the Problem, Action and Effect of the Fifth Aspect of the Invention] In order to solve the problem, a fifth aspect of the present invention relates to a wheel based on the condition of the wheel and a road surface μ which is a friction coefficient of a road surface on which the vehicle is traveling. Used with a wheel controller to control the state of
The road surface μ is acquired based on a control state that is at least one of the state of the wheel, the state of the vehicle, and the state of the wheel control device, and the obtained road surface μ is supplied to the wheel control device. In the device, when the acquisition road surface μ is decreased because the wheel has passed the partial low μ road, as a result, the acquisition road surface μ after passing the partial low μ road
However, before the control state returns to the state before the passage of the partial low μ road, a returning means for changing the obtained road surface μ so as to substantially return to the obtained road surface μ before the passage is provided. And

While the vehicle is traveling on a high μ road, it may pass through a partial low μ road where the road surface μ locally decreases. in this case,
Since the road surface after passing is a high μ road, the wheel control device is not a wheel control suitable for a low μ road, for example, if it is an antilock control, it is not a brake pressure control closer to a pressure reduction but a wheel control suitable for a high μ road. For example, in the case of antilock control, it is desirable to perform brake pressure control near the pressure increase. Then, in order to avoid performing unscheduled wheel control suitable for the low μ road after passing through the partial low μ road, the acquired road surface μ is immediately restored to the original road surface μ after passing through the partial low μ road. It is necessary.

However, the road surface friction coefficient acquisition device determines the road surface μ based on a control state (hereinafter, simply referred to as "control state") that is at least one of the state of the wheel, the state of the vehicle, and the state of the wheel control device. In the case of the indirect acquisition type, the acquired road surface μ does not recover until the wheel condition, vehicle condition, or wheel control device condition is recovered, and the acquired road surface μ is lower than the original road surface μ. The condition may last long.

Therefore, in the road surface friction coefficient acquiring apparatus according to the fifth aspect of the present invention, when the acquired road surface μ is decreased because the wheel has passed the partial low μ road, as a result, after the partial low μ road has passed. Before the control state returns to the state before the passage of the partially low μ road, the obtained road surface μ is changed so as to substantially return to the value before the passage. Wheel is partially low μ
If the passage of the road is detected by some method, the acquired road surface μ can be returned to the value before the passage before the control state is recovered.

Therefore, according to the fifth aspect of the present invention, the road surface friction coefficient acquisition device is an indirect acquisition type that acquires the road surface μ based on the control state, but the effect of passing the partially low μ road is obtained. It is avoided that it remains for a long time, and the partial low μ
The effect that unscheduled wheel control by the road is avoided can be obtained.

[0040]

Supplementary Explanation of the Invention Hereinafter, the present invention will be supplementarily described by listing other embodiments in the same expression form as the claims. (1) The road surface friction coefficient acquisition device according to any one of claims 1 to 5, wherein the wheel control device (a) detects a rotation state of each of a plurality of wheels of the vehicle. , (B) a brake pressure control device that controls the brake pressure of each wheel, and (c) a controller that controls the brake pressure of each wheel by electrically controlling the brake pressure control device. Characteristic road surface friction coefficient acquisition device. In addition, here "wheel rotation state detection means"
Is an example of a wheel speed sensor that detects the wheel speed that is the peripheral speed of the wheel, and an example of a "brake pressure control device" is
This is a solenoid valve that controls the brake pressure of each wheel. (2) The road surface friction coefficient acquisition device according to the embodiment (1), wherein the controller prevents the slip of each wheel from becoming excessive by controlling the brake pressure of each wheel during vehicle braking. An apparatus for obtaining a road surface friction coefficient, which is an anti-lock control device for controlling. (3) The road surface friction coefficient acquisition device according to the embodiment (1) or (2), wherein the controller is at least one of a state of the wheels, a state of the vehicle, and a state of the wheel control device. Based on the state, there are a plurality of modes for controlling the brake pressure of the wheels, including a pressure reducing mode, a holding mode, a moderate pressure increasing mode for gradually increasing pressure, and a rapid pressure increasing mode for rapidly increasing pressure. A braking system characterized in that one of the modes is selected and the brake pressure of the wheel is controlled in the selected mode. (4) The road surface friction coefficient acquisition device according to the embodiment (3), wherein the changing unit is set in a case where the duration of the state in which the slow pressure increasing mode is selected for the same wheel exceeds a set time, A road surface friction coefficient acquisition device comprising means for changing the acquired road surface μ. (5) The road surface friction coefficient acquisition device according to claim 5, wherein the returning means controls the acquired road surface μ when the acquired road surface μ is decreased because the wheel has passed a partially low μ road. The state is changed to the same direction until the state occurs when the acquired road surface μ is normal, whereby the acquired road surface μ after passing the partial low μ road eventually becomes the acquired road surface μ before passing. An apparatus for obtaining a road surface friction coefficient, characterized in that it includes a changing means for substantially returning. (6) The road surface friction coefficient acquisition device according to any one of the embodiments (1) to (5), wherein the changing unit has a control state in which the acquired road surface μ is lower than a normal value while the antilock control device is operating. The road surface friction coefficient acquisition device is characterized in that the acquired road surface μ is changed to an increasing side when the vehicle deceleration of the vehicle tends to increase. (7) The road surface friction coefficient acquisition device according to any one of claims 1 to 5 and embodiments (1) to (6), wherein the wheel control device prevents excessive slip of the wheels during vehicle braking. When the anti-lock control device for controlling the slip of the wheel to an appropriate amount is included, the changing means is operating the anti-lock control device, and when the control state is such that the obtained road surface μ is higher than a normal value. A road surface friction coefficient acquisition device, wherein the acquired road surface μ is changed to a decreasing side when a state occurs. (8) The road surface friction coefficient acquisition device according to claim 5, wherein the returning means determines whether or not the wheel has passed through a front low μ road based on the state of the wheel, and determines that the wheel has passed. In this case, the estimated road surface μ after passing is replaced with the estimated road surface μ before passing, whereby the acquired road surface μ after passing through the partially low μ road is positively changed to the acquired road surface μ before passing. An apparatus for obtaining a road surface friction coefficient, which comprises a replacement means for substantially returning. (9) The road surface friction coefficient acquisition device according to the embodiment (8), wherein the replacement means comprehensively determines whether or not the wheel has passed a partial low μ road from a plurality of wheel-related information at a plurality of determination times. A passage determination unit that determines, (a) a passability determination unit that determines whether or not the wheel may have passed a partial low μ road, based on the wheel-related information at the previous determination time,
(b) A road surface friction characterized by including a passage confirmation determination unit that determines whether or not the wheel has definitely passed a partial low μ road, based on wheel-related information at a later determination time. Coefficient acquisition device. (10) The road surface friction coefficient acquiring device according to the embodiment (9), wherein the replacing means further determines that the road surface μ at that time is determined to be passable by the passability determining unit.
A road surface friction coefficient acquisition device comprising: a road surface μ estimated value storage unit that stores an estimated value in a memory as a road surface μ before passing through a partially low μ road. (11) The road surface friction coefficient acquisition device according to the embodiment (10), wherein the replacement unit is further determined by the passage confirmation determination unit to be deterministic that the wheel has passed a partial low μ road. In the case where the road surface μ estimated value stored as the pre-passage road surface μ is read from the memory, the read road surface μ estimated value is replaced with the road surface μ estimated value calculated this time. A road surface friction coefficient acquisition device comprising a road surface μ estimated value replacement unit for forcibly returning the road surface μ estimated value after passing a partial low μ road to the value before passing. (12) The road surface friction coefficient acquisition device according to the embodiment (11), wherein the replacement unit further replaces the road surface μ estimated value replacement unit with the road surface μ estimated value by the road surface μ estimated value replacement unit from the wheel-related information. A road surface friction coefficient acquisition apparatus including a replacement end determination unit that determines whether or not to stop performing. (13) In the brake pressure control device that estimates the road surface μ based on the rate of change of the vehicle body speed and increases or decreases the brake pressure of the wheels based on the estimated road surface μ, the pressure increase time is equal to or longer than the set time. In the case of, the brake pressure control device is provided with means for correcting the estimated road surface μ to the high μ side.

[0041]

BEST MODE FOR CARRYING OUT THE INVENTION An antilock brake system including a road surface friction coefficient estimating device, which is a more specific embodiment of the present invention, will be described below in detail with reference to the drawings.

First, the mechanical structure of the brake system will be described. In FIG. 1, reference numeral 10 indicates a master cylinder. The master cylinder 10 is a tandem type in which two independent pressure chambers are arranged in series. The master cylinder 10 is linked to a brake pedal 14 as a brake operating member via a booster 12,
When the driver depresses the brake pedal 14, hydraulic pressures of the same height are mechanically generated in the two pressurizing chambers.

In one pressurizing chamber of the master cylinder 10,
A brake cylinder for activating the brake of the left front wheel FL and a brake cylinder for the brake of the right rear wheel RR are connected to each other, and the other pressurizing chamber has a brake cylinder for the brake of the right front wheel FR and a brake cylinder for the left rear wheel RL. Brake cylinders are respectively connected. Master cylinder 1
The two brake systems extending from each of the zero pressure chambers are diagonally configured independently of each other. Less than,
Only one brake system will be described in detail, and the other brake systems have the same configuration in common, so description thereof will be omitted.

One pressurizing chamber of the master cylinder 10 is connected to a front wheel brake cylinder (a brake cylinder for the right front wheel FR in the example in the figure) 22 by a front wheel brake passage 20. A rear wheel brake passage 24 is branched from the middle of the front wheel brake passage 20, and a rear wheel brake cylinder (a brake cylinder for the left rear wheel RL in the example in the figure) is provided at the tip thereof.
26 is connected.

A first solenoid valve 30 is provided in the portion of the front wheel brake passage 20 on the master cylinder 10 side from the branch position to the rear wheel brake passage 24. The first solenoid valve 30 is a normally open solenoid valve. This first solenoid valve 30
Is connected to a return passage 31 with a check valve, which promotes the return of the brake fluid from each brake cylinder 22, 26 to the master cylinder 10.

On the other hand, the rear wheel brake passage 24 is provided with a second electromagnetic valve 32 which is a normally open electromagnetic opening / closing valve. Further, a reservoir passage 34 is connected to a portion of the rear wheel brake passage 24 between the second electromagnetic valve 32 and the rear wheel brake cylinder 26. The reservoir passage 34 extends from the reservoir 36, and a third solenoid valve 38, which is a normally closed solenoid valve, is provided in the middle of the reservoir passage 34.

From the reservoir 36 is also a pump passage 40.
Is also extended. A reservoir 36 is provided in the middle of the pump passage 40.
A pump 42 for pumping the brake fluid is provided. The pump 42 is driven by a motor 44.
The brake fluid discharge port of the pump passage 42 is connected to the master cylinder 10 from the second solenoid valve 32 in the rear wheel brake passage 24.
Is connected to the part on the side of.

The second solenoid valve 3 in the rear wheel brake passage 24
A proportioning valve (hereinafter, simply referred to as “P valve”) 46 is provided in a portion between the rear wheel brake cylinder 26 and the rear wheel brake cylinder 26. As is well known, the P valve 46 transmits the input pressure as it is to the rear wheel brake cylinder 26 as the output pressure before the input pressure (master cylinder pressure or pump discharge pressure) reaches the break point pressure. After the input pressure reaches the break point pressure, in order to avoid the rear wheel lock due to the load movement to the front of the vehicle, the rear wheel brake cylinder 26 uses the hydraulic pressure obtained by reducing the input pressure at a constant ratio as the output pressure. introduce.

The second solenoid valve 3 in the rear wheel brake passage 24
The part between 2 and the P valve 46 is formed by the return passage 48.
The master cylinder 10 and the first of the front wheel brake passage 20
It is connected to a portion between the electromagnetic valve 30 and the solenoid valve 30. A check valve 50 is provided in the return passage 48. Check valve 50
Is from the master cylinder 10 to the rear wheel brake cylinder 26.
The flow of the brake fluid in the direction of is blocked, but the flow in the opposite direction is allowed. The check valve 50 is provided to prevent a residual pressure from being generated in the rear wheel brake cylinder 26 due to the valve opening pressure of the first check valve 54 described later.

The pump passage 4 of the rear wheel brake passage 24
A pressure reducing device 52 is provided in a portion closer to the master cylinder 10 than the connection position with zero. The decompression device 52 is configured such that a first check valve 54 whose valve opening pressure is not substantially 0 and a second check valve 56 whose valve opening pressure is substantially 0 are connected in opposite directions and in parallel. It is a thing. In the present embodiment, since the pump 42 is basically used as a pressure source in the antilock control state, the first check valve 54 sets the flow of the brake fluid in the direction from the pump 42 to the front wheel brake cylinder 22. Functions as a check valve that allows pressure above pressure.

Here, the master cylinder 10 and the pump 4
2, the flow of the brake fluid between the front wheel brake cylinder 22 and the rear wheel brake cylinder 26 will be described.

In the normal braking state, the first solenoid valve 3
0 is in the open state, so the brake fluid from the master cylinder 10 passes through the first solenoid valve 30 and the front wheel brake cylinder 2
It is also supplied to the rear wheel brake cylinder 26 via the first solenoid valve 30 and the second check valve 56. Since the valve opening pressure of the second check valve 56 is substantially 0,
Eventually, brake pressures of the same height are generated in the front wheel brake cylinder 22 and the rear wheel brake cylinder 26.

On the other hand, in the antilock control state,
Basically, the first solenoid valve 30 is closed, and the brake fluid discharged from the pump 42 is stored in the front wheel brake cylinder 22.
Is supplied via the first check valve 54 to the rear wheel brake cylinder 26 (P valve 46). Since the valve opening pressure of the first check valve 54 is not substantially 0, the pressure that is lower than the rear wheel brake pressure by the valve opening pressure of the first check valve 54 is eventually supplied to the front wheel brake cylinder 22. Become. As a result, the front-rear braking force distribution of the vehicle is optimized, and in the loaded state, the rear wheel braking pressure, that is, the rear wheel braking force can be rapidly increased from the light braking area which is an area below the break point of the P valve 46. , The braking distance is shortened.

Next, the electrical construction of the brake system will be described. The first solenoid valve 30, the second solenoid valve 32, the third solenoid valve 38 and the motor 44 are controlled by the controller 60. As shown in FIG. 2, the controller 60 is mainly composed of a computer 68 including a CPU (an example of a processor) 62, a ROM (an example of a memory) 64 and a RAM (another example of a memory) 66. RO
Various programs for executing the antilock control are stored in advance in the M64, and the antilock control is executed by the CPU 62 executing the various programs while using the RAM 66.

The anti-lock control is a control for preventing each wheel from being locked when the vehicle is braked. The operation of the brake pedal 14 by the driver is detected by the brake switch 70 and supplied to the controller 60. The wheel speed, which is the peripheral speed of, is detected by each wheel speed sensor 72 and supplied to the controller 60. Further, on the output side of the controller 60, the first solenoid valve 30 and the second solenoid valve 32 that constitute an actuator in each brake system are provided.
And a third solenoid valve 38 are connected, and a motor 44
Is also connected.

Here, the outline of the control by the controller 60 will be explained based on the functional block diagram shown in FIG.

The wheel speed calculator 80 sequentially calculates the wheel speed V _W of each wheel based on the output signal from each wheel speed sensor 72. The wheel speed calculator 80 has
The vehicle body speed estimation unit 82, the wheel acceleration calculation unit 84, and the slip amount calculation unit 86 are connected to each other.

The vehicle body speed estimation unit 82 uses a plurality of wheel speeds V.
Based on _W , the estimated vehicle speed V _S0 is sequentially calculated at the cycle t. The vehicle body speed estimation unit 82, for example, sets the current estimated vehicle body speed V _{S0 (n)} to the maximum value V _{W MAX} of the four wheel speeds V _W for the four wheels, and the previous estimated vehicle body speed V V. _{From S0 (n-1)} , the upper limit deceleration α of the vehicle
_The value obtained by subtracting the product of _DW (fixed value) and the calculation cycle t and the previous estimated vehicle body speed V _{S0 (n-1 )} are added to the upper limit acceleration α _{UP of the} vehicle.
The intermediate value of the value obtained by adding the product of the (fixed value) and the calculation cycle t is determined.

The wheel acceleration calculation unit 84 calculates the wheel acceleration DV _W for each wheel by _obtaining the difference between a plurality of wheel speeds V _W periodically supplied to the same wheel from the wheel speed calculation unit 80. .

The slip amount calculating unit 86 is also connected to the vehicle body speed estimating unit 82, and calculates the slip amount S of each wheel by subtracting the estimated vehicle body speed V _S0 from the wheel speed V _W of each wheel. Is.

The vehicle body speed estimation unit 82 calculates the vehicle body deceleration.
Portion 88 is also connected. This vehicle deceleration calculation unit 88
Is basically the estimated vehicle speed V_S0Vehicle deceleration based on
Degree DV _S0Is calculated sequentially.
Will be described later.

A control mode selection unit 94 is connected to each of the wheel acceleration calculation unit 84, the slip amount calculation unit 86, and the vehicle body deceleration calculation unit 88.

The control mode selection unit 94 includes the left and right front wheels and
Wheel acceleration DV for each of the left and right rear wheels_WAnd slip amount
S and are used, and the vehicle body deceleration DV_S0The road surface μ
Decompression mode and holding mode
This time we will realize the brake fluid pressure from the pressure increasing mode.
Select the control mode to be used. For example, vehicle body deceleration DV _S0
If it is large, the road surface μ is expected to be high and the brake fluid
High μ by controlling the pressure to the pressure increasing side or making the pressure increasing gradient steep.
Select the appropriate control mode to control the condition suitable for the road
On the other hand, vehicle deceleration DV_S0Is small, the road surface μ
Is expected to be low, control the brake fluid pressure to
Low μ due to steep pressure gradient or gentle pressure increase gradient
Select the appropriate control mode to control the condition suitable for the road
I do.

Incidentally, regarding the "pressure increasing mode",
There are three types: master cylinder pressure increasing mode, pump pressure increasing mode, and pulse pressure increasing mode. The “master cylinder pressure increasing mode” means opening the first solenoid valve 30 to open the master cylinder 1
0 means a mode in which the brake cylinders 22 and 26 are suddenly increased in pressure. The “pump pressure increasing mode” is a mode in which the first solenoid valve 30 is closed and the pump 42 gradually increases the pressure of the brake cylinders 22 and 26 in the master cylinder pressure increasing mode. Further, the "pulse pressure increasing mode" means that the brake cylinders 22 and 26 are pressure-increased in a pulse manner by the pump 42 while the first electromagnetic valve 30 is closed and the second electromagnetic valve 32 is duty-controlled.
This is a mode in which the pressure is gradually increased in the pump pressure increasing mode.

A control state selection unit 96 is connected to the control mode selection unit 94. This control state selection unit 96
Selects the control state to be realized by each solenoid valve 30, 32, 38 based on the control mode selected for each wheel.

The ROM 64 stores in advance the relationship between the front wheel and rear wheel control modes and the control states of the first to third solenoid valves 30, 32, 38. This relationship is shown in tabular form in FIG. In the figure, "Fr" represents the front wheels, "Rr" represents the rear wheels, "M / C boost" represents the master cylinder boost mode, and "○" represents each solenoid valve 30,3.
2 and 38 are in an open state, and “x” is in a closed state.

When the front wheels are in the master cylinder pressure increasing mode (Nos. 1 to 3 in the figure), the first solenoid valve 30 is
Regardless of the control mode of the rear wheel, it will be in the open state. However, the second solenoid valve 32 and the third solenoid valve 38 differ depending on the rear wheel control mode, and when in the master cylinder pressure increasing mode (No. 1 in the figure), the second solenoid valve 3
2 is in the open state, the third solenoid valve 38 is in the closed state, and in the holding mode (No. 2 in the figure), the second solenoid valve 3
In the pressure reducing mode (No. 3 in the figure), the second electromagnetic valve 32 is closed and the third electromagnetic valve 38 is open. When the front and rear wheels are both in the master cylinder boost mode (N
o. 1) corresponds to normal braking.

When the front wheels are in the pump boost mode (No. 4, 5 in the figure), the first solenoid valve 30
Is closed regardless of the control mode of the rear wheels.
However, when the rear wheels are in holding mode (No.
In 4), both the second solenoid valve 32 and the third solenoid valve 38 are in the closed state, and in the pressure reducing mode (No. 5 in the figure), the second solenoid valve 32 is in the closed state and the third solenoid valve 38 is in the closed state. Is open.

When the front wheels are in the holding mode and the rear wheels are in the pump pressure increasing mode (No. 6 in the figure), the first solenoid valve 30 is in the closed state, the second solenoid valve 32 is in the open state, and the second solenoid valve 32 is in the open state. Three
The solenoid valve 38 is closed.

When both the front wheels and the rear wheels are in the pressure reducing mode (No. 7 in the figure), the first solenoid valve 30 is closed, and the second solenoid valve 32 and the third solenoid valve 38 are open. Become.

The mode table in the figure shows the solenoid valve control state (No. 8 in the figure) in which all the solenoid valves 30, 32, 38 are in the open state. It is provided to replenish the emptied reservoir 36 with brake fluid from the master cylinder 10 during the control so as to ensure the pressure increase by the pump 42.

Although not shown in this mode table, when the front wheels or the rear wheels are in the pulse pressure increasing mode, the first solenoid valve 30 is closed and the second solenoid valve 32 is opened and closed. A duty control state in which the state and the state are repeated alternately,
The solenoid valve 38 is closed.

In accordance with such a relationship, the control state selection unit 9
6 selects the control state corresponding to the control mode finally selected for each wheel from the open state and the closed state for each solenoid valve 30, 32, 38.

An actuator control unit 98 is connected to the control state selection unit 96. The actuator control unit 98 outputs a drive signal corresponding to the command signal input from the control state selection unit 96 to each of the solenoid valves 30, 3 based on the command signal.
Supply to 2,38 solenoids.

Here, the vehicle body deceleration calculation unit 88 will be described in detail. The vehicle body deceleration calculation unit 88, as shown in FIG.
The vehicle body deceleration calculation unit 90, the reference vehicle body deceleration calculation unit 91, and the corrected vehicle body deceleration calculation unit 92 are included.

The raw vehicle deceleration calculation unit 90 sequentially calculates the current raw vehicle deceleration DV _{S0X (n)} at the cycle t based on the estimated vehicle body speeds V _S0 acquired before this time. For example, the value obtained by subtracting the current estimated vehicle body speed V _{S0 (n )} from the previous estimated vehicle body speed V _{S0 (n-1)} divided by the calculation cycle t is the current vehicle body deceleration DV _{S0X (n)} . decide.

The reference vehicle body deceleration calculation unit 91 successively calculates the current reference vehicle body deceleration DV _{S0 (n)} based on at least the current vehicle body deceleration DV _{S0X (n)} . The reference vehicle body deceleration calculation unit 91 uses, for example, the current vehicle body deceleration DV _{S0X (n)} and the previous reference vehicle body deceleration DV _{S0 (n-1).}
Based on the pressure increase time and the pressure decrease time, the current reference vehicle body deceleration DV _{S0 (n)} is calculated.

Specifically, the reference vehicle body deceleration calculation unit 91 firstly calculates the reference vehicle body deceleration DV _{S0 (n-1) of the} current time reference vehicle body deceleration DV _{S0 (n) to} be obtained by calculation. The guard value of the increasing side change amount and the guard value of the decreasing side change amount are calculated respectively. The reference vehicle body deceleration calculation unit 92
The increase side change amount guard value is calculated for each calculation cycle t,
And, if the boosting mode is not selected from the previous calculation timing to the current calculation timing,
When the pressure boosting mode is selected, on the other hand, the longer the integrated value of the time, the larger the calculation.
The reference vehicle body deceleration calculation unit 91 further calculates the decrease side variation amount guard value for each calculation cycle t, and the depressurization mode has not been selected from the previous calculation timing to the current calculation timing. In this case, the value becomes 0. On the other hand, when the decompression mode is selected, the longer the integrated value of the time, the larger the calculation.

The reference vehicle body deceleration calculation unit 91 subsequently changes the current reference vehicle body deceleration DV _{S0 (n) based} on the current raw vehicle body deceleration DV _{S0X (n)} , that is, the previous range. With reference to the reference vehicle body deceleration DV _{S0 (n-1)} , the increase side change amount guard value and the decrease side change amount guard value are set to values within the respective ranges. The reference vehicle body deceleration calculation unit 91 uses, for example, the current vehicle body deceleration DV.
_{When S0X (n)} exceeds the sum of the previous reference vehicle body deceleration DV _{S0 (n-1)} and the increasing side change amount guard value, the current reference vehicle body deceleration DV _{S0 (n) is changed} to the previous reference vehicle deceleration. Vehicle body deceleration DV
_A value equal to the sum of _{S0 (n-1)} and the increasing side change amount guard value is determined. If the current vehicle body deceleration DV _{S0X (n)} is _less than the previous reference vehicle body deceleration DV _{S0 (n-1)} minus the decrease side variation guard value, the current vehicle body deceleration DV _{S0 (n)} is determined to be equal to the previous reference vehicle body deceleration DV _{S0 (n -1)} . Also, this time the vehicle deceleration DV
_{When S0X (n)} is within the change range, the current reference vehicle body deceleration DV _{S0 (n) is changed} to the current raw vehicle deceleration DV
Determine the value equal to _{S0X (n-1)} .

By the way, for example, as shown in the graph of FIG. 5, when a certain wheel passes through a projection as a partial low μ portion of the road surface during anti-lock control, the wheel temporarily stops after passing through the projection. When the vehicle is floated in the air, the force for turning the wheel is not applied from the road surface, the wheel speed V _W of the wheel suddenly decreases, the gradient of the vehicle speed becomes gentle, and the vehicle deceleration decreases. On the other hand, the controller 6
At 0, the reference vehicle body deceleration DV _S0 , which is a calculated value, functions as a road surface μ estimation value, and the reference vehicle body deceleration DV
_S0 drops after the wheels pass the bumps, so in the end
The estimated road surface μ value also decreases as the wheels pass through the protrusion.

After the wheel has passed the projection, the wheel has returned to the original portion of the road surface, that is, the high μ portion, and the actual road surface μ of the road contacted by the wheel is almost the same height as the road surface μ before the passage. Has recovered. However, the road surface μ estimated value cannot rapidly change to follow such an actual change of the road surface μ, and it takes time to return to a value representing a high μ road.

The reason why it takes time to restore the estimated road surface μ value is as follows. If the actual value of the road surface μ changes, the change first appears in the condition of the wheels and then in the condition of the vehicle. Therefore, the reference vehicle body deceleration DV as the state of the vehicle
_When the road surface μ estimated value is calculated based on _S0 , it takes time until a change in the actual value of the road surface μ appears in the road surface μ estimated value.

Further, in the calculation of the road surface μ estimation value based on the vehicle deceleration, the slip of the wheels during the calculation is an appropriate amount,
If the braking force of the wheels shows the maximum value under the road surface μ, it is premised on the fact that the vehicle body is decelerated in an amount corresponding to the road surface μ. That is, in order to accurately match the road surface μ estimated value with the actual road surface μ and quickly follow the actual change of the road surface μ, the slip of the wheel is always kept at an appropriate amount, and the brake pressure of the wheel is always appropriate. The assumption is that On the other hand, when the control characteristics of the antilock control are determined based on the road surface μ estimated value, if the road surface μ estimated value is lower than the actual value of the road surface μ, the control characteristic will be closer to the decompression and the wheel brake pressure will decrease. It is lower than the height suitable for the actual value of μ. As a result, the slip of the wheel becomes smaller than an appropriate amount, and only a braking force smaller than the magnitude corresponding to the actual value of the road surface μ is generated on the wheel, and as a result, the reference vehicle body deceleration DV _S0 becomes the actual value of the road surface μ. It will be lower than the corresponding size.

That is, when the road surface μ estimation value is calculated based on the reference vehicle body deceleration DV _S0 as the vehicle state, and the control characteristic of the antilock control is determined based on the road surface μ estimation value. , In addition to the reason that it takes time for the change in the actual value of the road surface μ to appear in the road surface μ estimated value, the road surface μ is reduced because the wheel brake pressure becomes lower than the height corresponding to the actual value of the road surface μ. It takes time for the estimated value to return to the value before passing.

Therefore, if the reference vehicle body deceleration DV _S0 is supplied as it is to the control mode selection unit 94 and the control mode is selected based on the reference vehicle body deceleration DV _S0 , the braking force due to the passage of the protrusion is reduced. There may be a shortage. In this sense, the decrease in the road surface μ estimation value due to the passage of the partial low μ portion is not desirable in relation to the antilock control, and originally, as shown by the broken line in the figure, It is desirable that the μ estimation value be maintained at a constant value regardless of the passage of the partial low μ portion.

In view of such circumstances, in the present embodiment, in order to eliminate the insufficient pressure increase due to the passage of the partially low μ road, the vehicle body deceleration calculation unit 88 is provided with the corrected vehicle body deceleration calculation unit 9
2 is provided, the correction vehicle body deceleration calculation unit 92 causes the estimated value of the road surface μ to return to the value before the passage of the protrusion early after the wheel has passed the protrusion on the road surface. Then, the reference vehicle body deceleration DV _S0 is corrected. That is, the corrected vehicle body deceleration calculation unit 92 determines that the duration of the state in which the slip of the same wheel is below the appropriate amount (hereinafter, referred to as the small slip state duration) is a phenomenon indicating that the pressure increase of each wheel is insufficient. When the set time T ₁ is exceeded and the pulse pressure boosting mode (an example of a slow pressure boosting mode which is an example of the pressure boosting mode) is selected for the same wheel (hereinafter, referred to as a pulse pressure boosting mode duration time). .) Respectively exceeds the set time T ₂ , and every time the small slip state duration exceeds the set time T ₁ or the pulse boosting mode duration exceeds the set time T ₂ , The increment Δ is added to the reference vehicle body deceleration DV _S0 , and the addition is finished when the small slip state is finished and the selection of the pulse pressure boosting mode is finished for the wheel,
Thereby, the corrected vehicle deceleration DV _S0 is calculated.

In other words, in the present embodiment, the slip small state duration for the same wheel exceeds the set time T ₁ and the pulse pressure increase mode duration for the same wheel exceeds the set time T ₂ . Claim 1
The invention corresponds to "a case where the control state does not occur when the acquired road surface μ is normal". Further, in the case where the duration of the small slip state exceeds the set time T ₁ for the same wheel, "when the state of the wheel slip does not occur when the acquired road surface μ is normal," It corresponds to ". Further, in the case where the pulse pressure increasing mode duration for the same wheel exceeds the set time T ₂ "when the selected mode does not occur when the obtained road surface μ is normal," It corresponds to ".
The invention according to claim 4, wherein the increment Δ is added to the reference vehicle body deceleration DV _S0 , and the addition is ended when the small slip state ends and the pulse pressure increasing mode selection ends for the wheel. It corresponds to “changing the acquired road surface μ in the same direction until the control state becomes a state that occurs when the acquired road surface μ is normal”.

The outline of the antilock control by the controller 60 has been described above, but the controller 60 executes a program for controlling the antilock control as a whole.
Although it is stored in M64 in advance, a portion of the program related to the reference vehicle body deceleration calculation unit 91 and the corrected vehicle body deceleration calculation unit 92 is shown in a flowchart in FIG. 7 as a road surface μ estimation routine. Hereinafter, the reference vehicle body deceleration calculation unit 91 and the corrected vehicle body deceleration calculation unit 92 will be described more specifically based on this flowchart.

This road surface μ estimation routine is executed at regular time intervals. In each execution, first, in step S1 (hereinafter, simply referred to as S1; the same _{applies to} other steps), the current raw vehicle body deceleration DV _{S0X (n)} and the previous reference vehicle body deceleration DV _{S0 ( n-1)} and the pressure increase time and the pressure decrease time based on the current standard vehicle body deceleration DV _{S0 (n)}
Is calculated.

Next, in S2, the number x representing each of the four wheels is set to 1. The number x is, for example, 1 for the left front wheel, 2 for the right front wheel, 3 for the left rear wheel,
It is 4 for the right rear wheel. Then, in S3,
It is determined whether or not the slip small state duration of the wheel whose number is x exceeds the set time T ₁ . "Slip" is here, for example, is obtained by dividing the value obtained by subtracting the wheel speed V _W of the wheel from the estimated vehicle velocity V _S0 at the estimated vehicle speed V _S0. This time, assuming that the duration of the small slip state does not exceed the set time T ₁ , the determination is NO, and the process proceeds to S4.

At S4, it is determined whether or not the duration of the pulse pressure increasing mode exceeds the set time T ₂ for the wheel with the number x. This time, assuming that the pulse pressure boost mode duration does not exceed the set time T ₂ , the determination is N
O, and the value of the number x is the maximum value N (=
4) is determined. This time it is 1, so
The determination is NO, the value of the number x is incremented by 1 in S7, and the process returns to S3.

After that, similar processing is executed for the other wheels. However, for a certain wheel, the first small pressure increase state in which the small slip duration time exceeds the set time T ₁ and the pulse pressure increase mode continues for the certain wheel. When at least one of the second insufficient pressure increase state in which the time exceeds the set time T ₂ is satisfied, the determination in S3 or S4 is YES, and S5
In, the incremental Δ is added to the reference body deceleration DV _S0, the reference vehicle body deceleration DV _S0 is corrected. The reference vehicle deceleration DV _S0 is incremented by Δ each time the small slip duration exceeds the set time T ₁ or the pulse pressure increasing mode duration exceeds the set time T ₂ for each wheel. Then, it transfers to S6.

After that, this routine is re-executed for the same wheel, and if the first or second insufficient pressure-increasing state is established even during the execution of this routine, the determination at S3 or S4 becomes YES, and at S5. again, by the increment Δ is added to the reference body deceleration DV _S0, the reference vehicle body deceleration DV _S0 is corrected. That is, the correction is performed until neither the first or the second pressure increase insufficient condition is satisfied, and as a result, the reference vehicle body deceleration DV _S0 is gradually increased by the increment Δ.

Therefore, for example, as shown in FIG.
For the same wheel, when the pulse pressure increasing mode duration exceeds the set time T ₂ , the reference vehicle body deceleration DV _S0 as the road surface μ estimated value is increased by the increment Δ. If the pulse pressure increasing mode ends due to the increase of the reference vehicle body deceleration DV _S0 and the pump pressure increasing mode or the master cylinder pressure increasing mode is entered, the brake pressure is sharper than that when not corrected as shown by the broken line in the graph. The pressure is increased at a certain gradient, and the wheel speed and the vehicle body speed are reduced at a steeper gradient than when not corrected as shown by the broken line in the graph, and the insufficient pressure increase is eliminated. Further, with such an increase in the wheel speed and the gradient of the vehicle body speed, the reference vehicle body deceleration DV _S0 calculated in S1 increases itself toward the actual value of the road surface μ.

That is, in this embodiment, the part of the computer 68 that executes the unillustrated raw vehicle deceleration calculation routine constitutes the above-mentioned raw vehicle deceleration calculation part 90, and the part that executes S1 of FIG. The reference vehicle body deceleration calculation unit 91 is configured, and the portion that executes S2 to S7 in the figure constitutes the corrected vehicle body deceleration calculation unit 92.

As is clear from the above description, according to the present embodiment, the road surface μ estimated value can be quickly returned to the value before the passage after the wheel has passed through the partial low μ road. It is possible to prevent the vehicle braking force from decreasing due to passage of the μ portion.

It should be noted that not only when the wheel passes through the partial low μ road, but also when the road surface changes from the low μ road to the high μ road during a series of antilock control and the road surface μ increases, FIG. With the road surface μ estimation routine of (3), it is also avoided that the road surface μ estimated value changes in quick response to the actual change of the road surface μ and the vehicle braking force decreases.

As is apparent from the above description, in the present embodiment, the portion of the controller 60 that constitutes the vehicle body deceleration calculation unit 88 cooperates with the four wheel speed sensors 72, and any one of claims 1 to 5 is adopted. An example of the road surface friction coefficient acquisition device that is each invention of the above is configured, and among them, S2 to S7 of FIG.
The portion for executing the above constitutes one example of each of the "changing means" in the inventions of claims 1 to 3, the "correcting means" in the invention of claim 4 and the "recovering means" in the invention of claim 5. Is there. Further, four wheel speed sensors 72, first to third solenoid valves 30, 32, 38 as actuators, a pump 42 and a motor 44.
Of the controller 60, the control mode selection unit 94,
The control state selecting unit 96 and the portion forming the actuator control unit 98 cooperate with each other to form an example of the "wheel control device" in the invention of each claim.

In the present embodiment, it is judged whether or not there is a tendency for insufficient pressure increase for each wheel, and if so, the estimated road surface μ value is increased. It is determined whether or not there is a tendency to increase the road surface μ, and the road surface μ estimation value is increased if there is a tendency for pressure increase to be insufficient for the front wheels, but the present invention is configured in a form in which the road surface μ estimation value is not increased even if there is a tendency to increase pressure for the rear wheels. It is feasible. This is because the tendency of insufficient pressure increase appears relatively prominently in the front wheel where the ground load is larger than in the rear wheel.

Further, in the present embodiment, when the small slip duration exceeds the set time T ₁ or the pulse pressure increasing mode duration exceeds the set time T ₂ , the estimated road surface μ value increases immediately. However, for example, when the current value of the vehicle body deceleration becomes equal to or greater than the previous value, for example, the current raw vehicle body deceleration DV _{S0X (n)} is changed to the previous reference vehicle body deceleration DV _{S0 (n-1).} When the above is the case, the present invention can be implemented in a mode in which the road surface μ estimated value this time is increased.
If the actual value of road surface μ is lower than the estimated value of road surface μ,
This is because if the estimated road surface μ value is corrected to the increasing side, the wheel slip will become excessive. Therefore, after confirming that the wheel slip does not become excessive even if the vehicle surface deceleration tends to increase and the control characteristic of the brake pressure is changed to the pressure increase side by increasing the road surface μ estimated value, the road surface μ estimated value is If is corrected to the increasing side, the effect that the slip of the wheels becomes excessive due to the correction of the road surface μ estimated value can be reliably avoided.

Next, another embodiment will be described. Note that this embodiment is different from the previous embodiment in the road surface μ estimation routine,
Since the other parts are common, only the road surface μ estimation routine will be described in detail.

The road surface μ estimation routine in the above embodiment corrects the road surface μ estimation value by feeding back both the wheel condition and the anti-lock control device. When the road surface μ estimated value is lowered due to passing, the road surface μ estimated value is returned to the value before passing as an early result.

On the other hand, the road surface μ estimation routine according to the present embodiment directly determines whether or not the wheel has passed the partial low μ road, and when it determines that the wheel has passed, it outputs the road surface μ estimated value before the passage. It positively restores the value of.

This road surface μ estimation routine will be roughly described, as shown in FIG.
, Passability determination unit 112, and road surface μ estimated value storage unit 1
14, a passage confirmation determination unit 116, a road surface μ estimated value replacement unit 118, and a replacement end determination unit 120.

The road surface μ estimated value calculation unit 110 successively estimates the road surface μ based on at least one of the state of the vehicle and the state of the antilock control device, as in S1 of the above embodiment.

The passability determination unit 112 determines from the state of the wheel whether or not the wheel may have passed the partial low μ road. It is difficult to accurately determine whether or not the wheel has passed the partial low μ road, only from the information at one time. Therefore, in the present embodiment, it is comprehensively determined from the information at the two determination times, and specifically, whether or not the wheel may have passed the partial low μ road is determined from the information at the previous determination time. Is determined, and then it is determined from the information at the later determination time whether the wheel has definitely passed the partial low μ road. And
The passability determination unit 112 determines whether or not the wheel may have passed the partial low μ road, based on the information at the previous determination time.

The road surface μ estimated value storage unit 114 stores the road surface μ estimated value at that time in the RAM 66 when it is determined by the passability determination unit 112 that there is a possibility of passing, before passing the partial low μ road. The road surface μ is stored.
Immediately after the wheel has passed the partial low μ road, the state of the wheel is considerably close to the state before the passage, and the time close to that time is the earlier determination time of the two determination times, Therefore, the road surface μ estimated value at the subsequent determination time is stored in the RAM 66 as the road surface μ before passage.
However, this routine does not change the road surface μ estimated value by the road surface μ estimated value calculation unit 110 and changes the anti-lock control device without changing the road surface μ estimated value calculation unit 110 unless it is determined that the wheel has passed the partial low μ road. It is designed to supply the anti-lock control device after supplying it and determining that the passage is deterministic, after changing the road surface μ estimation value.

The passage confirmation determining unit 116 determines whether or not the wheel has definitely passed the partial low μ road, based on the information at the determination time after the two determination times. .

The road surface μ estimated value replacement unit 118 is stored as the road surface μ before passing when the passage confirmation determination unit 116 determines that the wheel has passed the partially low μ road is deterministic. The road surface μ estimated value is read from the RAM 66, and the read road surface μ estimated value is replaced with the road surface μ estimated value calculated this time by the road surface μ estimated value calculation unit 110, thereby passing through a partially low μ road. This is to force the subsequent road surface μ estimation value to return to the value before passing.

From the state of the wheels, the replacement end determination unit 120 causes the road surface μ estimated value replacement unit 118 to determine the road surface μ.
The road surface μ estimated value calculated this time by the estimated value calculation unit 110 is replaced with the road surface μ before passing, that is, it is determined whether or not the correction of the road surface μ estimated value should be ended. Even if the wheel passes through a partially low μ road and the influence of the passage does not appear on that wheel, continuing the correction of the road μ estimation value may rather reduce the accuracy of the road μ estimation value. Is.

The specific contents of this road surface μ estimation routine are shown in the flow chart of FIG. This routine is also executed at regular intervals. When executing each time, first, S10
1, in the same manner as S1, the raw vehicle body deceleration DV
_The current reference vehicle body deceleration DV _{S0 (n)} is calculated based on _{S0X and the} like. Next, in S102, the wheel speed V of each wheel
_W and the wheel acceleration DV _W are input respectively.

Subsequently, in S103, it is determined whether or not it is currently determined that each wheel has a possibility of passing the partial low μ road. Specifically, when it is ON, it indicates that it is possible to pass each wheel.
In the FF, it is determined whether or not the passability flag indicating that there is no passability is ON. This passability flag is reset to OFF when the power of the computer 68 is turned on, and assuming that this execution is the first time after the power of the computer 68 is turned on,
Since the passability flag is OFF, the determination in S103 is NO.

Thereafter, in S104, it is determined whether or not there is a possibility of passing each wheel. For example, when the wheel speed V _{W of} each wheel decreases and the wheel acceleration DV _W becomes smaller than the first negative set value, it is determined that there is a possibility of passing through each wheel. Assuming that there is no possibility of passing this time, the determination is NO, and one execution of this routine ends.

On the other hand, assuming that there is a possibility of passing this time, the determination in S104 is YES, and in S105, the current reference vehicle body deceleration DV _{S0 (n)} is stored in the RAM 66 as the road surface μ before passage. It Then, in S106, the passability flag is turned ON. This completes one execution of this routine.

When this routine is subsequently executed,
Since the passability flag is ON, the determination in S103 is YES, and the process proceeds to S107 and subsequent steps.

First, in step S107, regarding the wheel determined to have a possibility of passing, a confirmation waiting state is waited until it is determined that the wheel has passed the partial low μ road is deterministic. It is determined whether or not there is. Specifically, it is determined whether or not the wheel is in the confirmation waiting state when ON, and the confirmation waiting flag indicating that the wheel is not in the confirmation waiting state is ON when OFF. Assuming that the confirmation waiting flag is OFF, the determination is NO, and whether or not it is deterministic that the wheel has passed the partial low μ road with respect to the wheel determined to have a possibility of passing in S108. Is determined. For example, from the time when it is determined that there is a possibility of passing (the previous determination time), the set time T
_When the absolute value of the wheel acceleration DV _W of the wheel becomes equal to or less than the second negative setting value larger than the first setting value within ₃ , it is definite that the wheel has passed the partial low μ road. It is determined that there is. Assuming that the passage is not deterministic this time, the determination is NO, and it is determined in S109 whether or not the determination that there is a possibility of passage was an error. Even if the set time T ₃ has elapsed from the time when it is determined that there is a possibility of passing, it is determined whether or not the determination in S108 is YES, and if it is not YES, then it is possible to pass. It is determined that there is an error in determining that there is a property. This time, assuming that the set time T ₃ has not elapsed from the time when it is determined that there is a possibility of passing, the determination becomes NO, and one execution of this routine ends.

After that, as a result of the execution of this routine being repeated several times, the wheels that are determined to be passable before the set time T ₃ has passed from the time when it is determined to be passable. Assuming that the wheel acceleration DV _W is less than or equal to the second set value, the determination in S108 is YES and S
At 110, the pre-passage DV _S0 is read from the RAM 66, and the current reference vehicle body deceleration DV _{S0 (n)} is replaced with it. The reference vehicle body deceleration DV _{S0 (n)} is forcibly returned to the value before passing. After that, in S111, the confirmation waiting flag is turned ON, and one execution of this routine ends.

When this routine is subsequently executed, both the passability flag and the confirmation waiting flag are ON this time, so the determinations in S103 and S107 are YES,
The process moves to S112 and subsequent steps.

In S112, the pre-passage DV _S0 is read from the RAM 66, and the reference vehicle body deceleration DV of this time is read.
_{S0 (n)} is replaced by it. Standard vehicle deceleration DV _{S0 (n)}
Is forcibly changed to the pre-passage value, which causes the wheel state to be substantially restored to the pre-passage state after the passage is determined to be deterministic. The final calculated value of the vehicle body deceleration DV _{S0 (n)} is fixed to DV _S0 before passage and is prohibited from changing. That is, this S
112 is the vehicle body deceleration DV for each time during the passage of the partial low μ road.
The final calculated value of _{S0 (n) (} supplied to the anti-lock control device) is prohibited from changing, and as a result, it functions as a change prohibiting means that prohibits changing the road surface μ estimated value. is there.

Then, in S113, it is determined whether or not the replacement of the current reference vehicle body deceleration DV _{S0 (n) with} the before-passage DV _S0 should be ended. If the state of the wheels determined to have the possibility of passing has returned to the state before passing,
This is because, thereafter, the reference vehicle body deceleration DV _{S0 (n)} should not be replaced with the pre-passage DV _S0 . For example, it is determined that the state of the wheel has been restored when the wheel speed V _W of the wheel becomes equal to or higher than the set value. This time, assuming that the state of the wheels has not returned, the determination is NO, and one execution of this routine ends. On the other hand, assuming that the state of the wheels has been restored this time, the determination is YES, the passability flag is set to OFF in S114 in preparation for the next execution of this routine, and in S115, The confirmation waiting flag is turned off, and the one-time execution of this routine is completed.

That is, of the computer 68, S1
The part that executes 01 functions as the road surface μ estimated value calculation part 110, and the part that executes S102 to S104 and S106 functions as the passability determination part 112,
The part that executes S105 is the road surface μ estimated value storage unit 1
Functioning as 14, and S107 to S109 and S110
The portion that executes the above function as the passage confirmation determination unit 116, the portion that executes S110 and S112 functions as the road surface μ estimated value replacement unit 118, and S113 to S11.
The part that executes 5 functions as the replacement end determination unit 120.

As is clear from the above description, in the present embodiment, the controller 60 of the controller 60, S10 of FIG.
The portion that executes 2 to S115 constitutes an example of the "returning means" in the invention of claim 5.

Although the two embodiments of the present invention have been described in detail with reference to the drawings, various modifications and improvements can be made based on the knowledge of those skilled in the art without departing from the scope of the claims. It is needless to say that the present invention can be carried out in the form in which the above is applied.

[Brief description of drawings]

FIG. 1 is a system diagram showing an antilock brake system including a road surface friction coefficient estimating device according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating an electrical configuration of the brake system.

FIG. 3 is a system configuration diagram showing a controller 60 in FIG.

FIG. 4 is a diagram showing, in a tabular form, a relationship between a control state of each solenoid valve stored in advance in a ROM 64 in FIG. 2 and pressure control modes of front wheel brakes and rear wheel brakes.

FIG. 5 is a graph showing an example of temporal changes in wheel speed, vehicle body speed, brake pressure, and road surface μ estimated value when antilock control is performed based on a reference vehicle body deceleration.

FIG. 6 is a graph showing an example of temporal changes in wheel speed, vehicle body speed, brake pressure, and road surface μ estimated value when antilock control is performed based on the corrected vehicle body deceleration obtained by correcting the reference vehicle body deceleration. is there.

7 is a flowchart showing a road surface μ estimation routine stored in advance in a ROM 64 in FIG.

FIG. 8 is a functional block diagram showing a road surface friction coefficient estimating device which is another embodiment of the present invention.

FIG. 9 is a flowchart showing a road surface μ estimating routine in the road surface friction coefficient estimating device.

[Explanation of symbols]

 10 master cylinder 22 front wheel brake cylinder 26 rear wheel brake cylinder 30 first solenoid valve 32 second solenoid valve 38 third solenoid valve 42 pump 60 controller 72 wheel speed sensor

Claims (5)

[Claims] 1. A wheel control device for acquiring a road surface μ, which is a friction coefficient of a road surface on which a vehicle is traveling, and controlling the acquired road surface μ based on the wheel condition and the road surface μ. In the road surface friction coefficient acquisition device to be supplied to, during the operation of the wheel control device, if the control condition that is at least one of the state of the wheel and the wheel control device is the obtained road surface μ is normal, A road surface friction coefficient acquisition device, characterized in that a change means is provided for changing the acquired road surface μ when a state in which it does not occur. 2. The road surface friction coefficient acquisition device according to claim 1, wherein the wheel control device is a device that controls slip of the wheel as a state of the wheel, and the changing means includes:
During operation of the wheel control device, when the state of the slip of the wheels does not occur when the acquired road surface μ is normal, including a means for changing the acquired road surface μ, Road surface friction coefficient acquisition device. 3. The road surface friction coefficient acquisition device according to claim 1, wherein the wheel control device controls a plurality of modes of the wheel based on the state of the wheel and the road surface μ. Is a device for selecting one of the modes, and controlling the state of the wheel in the selected mode, wherein the changing means is the state of the wheel control device while the wheel control device is operating. A road surface friction coefficient acquisition device comprising means for changing the acquired road surface μ when the selected state does not occur when the acquired road surface μ is normal. 4. The road surface friction coefficient acquisition device according to claim 1, wherein the changing means includes the acquired road surface μ.
Is changed to the same direction until the control state becomes a state that occurs when the acquired road surface μ is normal, and the road surface friction coefficient acquisition is characterized by including a correction means for correcting the acquired road surface μ. apparatus. 5. A wheel control device for controlling the state of a wheel based on the state of the wheel and a road surface μ, which is a friction coefficient of a road surface on which the vehicle is traveling, and the state of the wheel and the state of the vehicle. In the road surface friction coefficient acquisition device that acquires the road surface μ based on a control state that is at least one of the state of the wheel control device, and supplies the acquired road surface μ to the wheel control device, the wheel has a partial low μ The acquired road surface μ
If, as a result, the acquisition road surface μ after passing through the partial low μ road is returned to the acquisition road surface μ before passing through before the control state returns to the state before the passage of the partial low μ road. A road surface friction coefficient acquisition device, characterized in that a recovery means is provided for changing the acquired road surface μ so as to substantially recover.