JPH1178845A - Antiskid controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve antiskid control performance while increasing brake reducing speed by estimating the error of an estimated car speed to a large side and, correcting it so as to increase the changing amount of the car speed estimated value according to the judgment of the estimation. SOLUTION: The changing of a target slip rate is performed by a target slip rate changing means (d) according to the judgment of a wheel speed converging state judging means (c). On the other hand, car body speed estimation is performed by a car speed estimation error judging means (i) for estimating the error of estimated car body speed to a large side, and according to the judgment, by an estimated car speed changing amount correcting means (j), correction is made so as to increase the changing amount of a car body speed estimated value in the car speed estimating means (b) to correct the changing amount of a car body speed such that a reduction in a brake liquid pressure is suppressed to prevent a speed reduction shortage when the upper shifting of the estimated car body speed is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle anti-skid control device.

[0002]

2. Description of the Related Art An anti-skid system of a vehicle avoids wheel lock during braking, stabilizes the vehicle behavior, and shortens the braking distance. Proposals have been made (for example, JP-A-6-298065 (Document 1)).
JP-A-7-237537 (Document 2) and the like.

In the anti-skid control device, when estimating the vehicle speed, which is a basic signal for anti-skid control, it is customary to select the wheel speed of each wheel and use the selected wheel speed after filtering. (For example, the above-mentioned document 1). When the change amount of the selected wheel speed is equal to or larger than the set vehicle body speed change amount, it is general to estimate the vehicle body speed so as to follow the selected wheel speed within the set value (FIG. 18).

[0004]

However, according to the following considerations, there is room (problem) to be improved in the following points. (B) In the conventional vehicle speed estimation using the above-mentioned select wheel speed, the wheel speed of each wheel is selected as the vehicle speed, and the filtered wheel speed is used, and all the wheels are slipping. In this state, accurate vehicle speed cannot be estimated. For this reason, as shown in FIG. 18, which will be referred to also in comparison with the embodiment of the present invention, the vehicle speed (Vi) is generally used.
Is calculated to be smaller than it actually is, resulting in the phenomenon that the wheel slips deeper. Further, in order to prevent the vehicle speed from being calculated extremely low and the wheels from locking early, control is inevitably made to hunt the wheels to some extent, and as a result, the braking force decreases and the braking distance increases. Problems and problems that can be improved in terms of anti-skid control performance, such as the occurrence of such problems, remain.

(B) If the brake fluid pressure is controlled so that the wheel speed converges to the target wheel speed, the braking deceleration is improved and the braking distance is shortened, but accurate estimation of the vehicle speed becomes more difficult. However, there is a high possibility that the estimated vehicle speed will be shifted.

On the other hand, as a countermeasure against deviation of the estimated vehicle speed, a technique for avoiding a decrease in the estimated vehicle speed has been proposed in the above-mentioned document 2. These aims are:
A second target larger than the first target wheel speed for actually converging the target wheel speed and the estimated vehicle speed for correcting a decrease in the estimated vehicle speed ("pseudo vehicle speed" in Document 2). The vehicle speed is switched between two target vehicle speeds in a predetermined cycle, thereby achieving both the wheel convergence and the prevention of the estimated vehicle speed from slipping.

Here, in the above-mentioned document 2, the target wheel speed is switched at a predetermined cycle, and the wheels for changing the target alternate between the front wheels and the rear wheels.

(C) Although the above-described effects can be expected from the change of the target wheel speed, the effect of changing the target wheel speed on the vehicle behavior and deceleration is considered. The following can be said. Generally speaking, anti-skid controlled wheels are usually at the tire limit. Therefore, in such a limit state of the tire, suddenly reducing the slip of the wheel has a considerable effect on the vehicle behavior, and therefore, it is not possible to change the target of the front and rear wheels alternately to a predetermined cycle uniformly in the vehicle. In some cases, the behavior may be adversely affected. FIG.
This is also referred to in comparison with the embodiment of the present invention in the following description. However, when the target change of the wheel speed is performed alternately between the front and rear wheels (switching of the target change flag), the wheel cylinders of the front and rear wheels are simply changed. The (W / C) pressure (brake pressure) is controlled in a transition as shown in the figure, and as a result, the yaw rate may be disturbed as shown in the figure.

(D) On the other hand, in this case, the case where the estimated vehicle speed deviates to a small side is considered, but the case where the estimated vehicle speed deviates to a large side is not considered. If the estimated vehicle speed deviates to the larger side, the so-called "upward slip" occurs, the anti-skid control incorrectly determines that the wheels are in braking slip and reduces the brake fluid pressure. In some cases, a shortage of braking force may occur (FIG. 15). In such a situation, even if the above-mentioned measures to prevent the vehicle speed from slipping down cannot be dealt with, there is still room for improvement in such a point.
There are issues.

It is desirable that, even when the brake pressure of each wheel is controlled so that the wheel speed converges to the target value, the advantage such as the improvement of the braking deceleration is utilized as much as possible and the vehicle body as described above is used. An object of the present invention is to realize anti-skid control performance that is highly responsive in consideration of the effect on deceleration due to a decrease in brake fluid pressure due to a shift in estimated speed. More desirably, while improving the braking deceleration and the like by similarly converging the wheel speed to the target wheel speed, and also improving the anti-skid control performance by estimating the vehicle speed with high accuracy. The above can be realized.

The present invention is based on the above considerations and the following considerations, and seeks to make improvements and improvements from these points. In particular, the present invention provides a target value for which the wheel speed is calculated from the vehicle speed. It is suitable for performing anti-skid control to control the brake pressure of each wheel so that the brake pressure deceleration is improved by taking advantage of the improved braking deceleration as much as possible. This makes it possible to obtain highly responsive anti-skid control performance in consideration of the effect of decompression on deceleration. Also,
Similarly, by converging the wheel speed to the target wheel speed, the braking deceleration is improved, and the anti-skid control performance is improved by estimating the vehicle speed with high accuracy.
It is an object of the present invention to provide an improved anti-skid control device that can appropriately realize the above.

[0012]

According to the present invention, the following anti-skid control device is provided. That is, the anti-skid control device of the present invention is an anti-skid control device including an anti-skid control unit that controls the brake pressure of each wheel so that the wheel speed becomes a target wheel speed calculated from the vehicle speed. Vehicle speed estimation deviation judging means for estimating that the estimation of the vehicle speed is wrong to the larger one, and an estimated vehicle body for correcting the variation of the vehicle body speed estimation value to be large according to the judgment of the vehicle speed estimation deviation judging means And a speed change amount correcting means (FIG. 1).

Further, there is provided a road surface μ estimating means for estimating a road surface friction coefficient (road surface μ), and a vehicle speed estimating means for estimating the vehicle speed using the road surface μ of each wheel estimated by the road surface μ estimating means. An anti-skid control device for setting a target wheel speed of each wheel based on the vehicle speed estimated by the vehicle speed estimating means, and controlling a brake pressure of each wheel so that each wheel speed converges to the target value. A wheel speed convergence state determining means for determining a convergence state of each wheel to a target wheel speed; a vehicle speed estimation deviation determining means for estimating that the estimation of the vehicle body speed is erroneous to a larger one; Target slip ratio changing means for changing the target slip rate of at least one wheel to a shallower one in accordance with the judgment of the speed convergence state judging means; Estimated car that compensates to increase It is characterized in that comprising a quick variation correction means.

In the above, the vehicle speed estimation deviation judging means may determine the vehicle speed based on the time until the wheel speed of the wheel whose target slip ratio has been changed shallowly by the target slip ratio changing device follows the target. The difference is determined.

Further, the estimated vehicle speed change amount correcting means includes:
The estimated vehicle speed change amount is corrected by changing the offset amount added to the vehicle body speed change amount calculated from the road surface μ of each wheel estimated by the road surface μ estimating means to a larger one. is there.

Further, the estimated vehicle speed change amount correction means includes:
The estimated vehicle speed change amount is corrected by changing the offset amount added to the vehicle body speed change amount after the completion of the deviation determination according to the time during which the vehicle speed estimation deviation determination unit makes the deviation determination. Is what you do.

The target slip ratio changing means selects a wheel having the least effect on the vehicle behavior when the slip state of the wheel is changed based on a detected value of the vehicle running state detecting means for detecting the vehicle running state. The slip ratio of the wheel selected by the wheel selecting means is changed.

Further, the wheel speed convergence state judging means judges the convergence state according to a time during which all wheel speeds are smaller than a convergence judgment wheel speed threshold value different from the target wheel speed. It is a feature.

When the target slip ratio is changed to a shallower one, the target slip ratio changing means keeps the target slip ratio in a shallow state until the wheel speed of the wheel follows the target. It is characterized by returning to the target slip ratio.

The road surface μ estimating means includes: a wheel acceleration calculated from a wheel speed detected by the wheel speed detecting means of each wheel; a wheel load detected by the wheel load detecting means of each wheel; Of the brake fluid pressure estimated by the brake fluid pressure estimating means, and for the drive wheels,
Further, the road surface μ is calculated from the driving torque estimated by the driving torque estimating means.

Further, the anti-skid control device of the present invention
Road surface estimating means for estimating the road surface μ, and vehicle body speed estimating means for estimating the vehicle speed using the road surface μ of each wheel estimated by the road surface estimating means. An anti-skid control device that sets the target wheel speed of each wheel based on the vehicle speed, and controls the brake pressure of each wheel so that each wheel speed converges to its target value. A wheel speed convergence state determining means for determining a convergence state to the vehicle body speed estimation deviation determining means for estimating that the estimation of the vehicle body speed is erroneous to a larger one; Target slip rate changing means for changing the target slip rate of at least one wheel to a shallower one and changing the target slip rate to a deeper one according to the judgment by the vehicle speed estimation deviation judging means. Things.

In the above, the target slip ratio changing means changes the vehicle body speed estimation when the target slip ratio of at least one wheel is changed to a shallower one according to the judgment of the wheel speed convergence state judging means. When changing the target slip ratio to a deeper one in accordance with the judgment of the deviation judging means, the target slip ratio is changed to a deeper one only for wheels other than the wheels for which the target slip ratio is changed to a shallower one. Is what you do.

[0023]

According to the present invention, according to the above configuration, anti-skid control for controlling the brake pressure of each wheel so that the wheel speed becomes the target wheel speed calculated from the vehicle speed is performed. The vehicle speed estimation deviation determination for estimating that the estimation of the vehicle speed based on which the calculation is based is incorrect to the larger one is performed. And can cope with the occurrence of a slip on the side of the estimated vehicle body speed which cannot be corrected by the conventional method, thereby making it possible to correct the deviation of the estimated vehicle body speed. . Therefore, even when controlling the brake pressure of each wheel so that the wheel speed converges to a target value calculated from the vehicle body speed, while taking advantage of the improved braking deceleration and the like as much as possible,
It is possible to realize highly responsive anti-skid control performance that also takes into account the effect on deceleration due to pressure reduction of the brake pressure due to deviation of the estimated vehicle speed. Therefore, the above-described problem to be improved can be satisfactorily achieved, and an improved anti-skid control device can be provided.

Further, the present invention provides,
The road surface μ is estimated, the vehicle speed is estimated using the estimated road surface μ of each wheel, and the target wheel speed of each wheel is set based on the estimated vehicle speed, and each wheel speed is While anti-skid control is performed to control the brake pressure of each wheel so that it converges to the target value, the state of convergence of each wheel to the target wheel speed is determined. Vehicle speed estimation deviation judgment to estimate that the vehicle is running, and at least one
The present invention can be suitably implemented as a configuration in which the target slip ratio of the wheel is changed to a shallower one and correction is made so as to increase the amount of change in the estimated vehicle speed in accordance with the determination of the estimated vehicle speed deviation. In this case, similarly, in the case of the anti-skid control in which the brake pressure of each wheel is controlled so that the wheel speed converges to the target value, the vehicle speed estimated value is improved while taking advantage of the improvement of the braking deceleration as much as possible. Highly responsive anti-skid control performance that takes into account the effect of deceleration due to pressure reduction of brake pressure due to ascending can be realized, and braking deceleration etc. is improved by converging the wheel speed to the target wheel speed. In addition, by estimating the vehicle speed with high accuracy, the anti-skid control performance can be improved, and the above can be realized. In addition, in this case, in estimating the vehicle speed, which is the basis for setting the target wheel speed, the road surface μ is estimated, and the amount of change in the vehicle speed is calculated therefrom, and the vehicle speed is calculated based on the amount of change. This is more effective when applied to the case of estimating the vehicle speed. In the case of such a method, when an upward deviation of the estimated vehicle speed occurs,
Since the brake pressure is reduced, the estimated value of the road surface μ is also reduced, and as a result, the amount of change in the vehicle speed is reduced, and the estimated value of the vehicle speed may further deviate, resulting in a vicious circle. It is also possible to prevent the speed estimation value from further shifting upward, and to avoid entering such a vicious circle.

In this case, it is preferable that the vehicle speed estimation deviation judging means determines the vehicle speed in accordance with the time until the wheel speed of the wheel whose target slip ratio is changed to a small value follows the target. The present invention can be suitably implemented as a configuration for judging a deviation of the estimation, and similarly, the above can be realized. In this case, by looking at the time, the target slip ratio is changed to be shallow, the brake pressure of the wheel is reduced, and as a result, although the wheel normally returns to near the vehicle speed, If the vehicle does not return even after the predetermined time, it is determined that the estimated vehicle speed itself may be deviated to a value greater than the actual vehicle speed. This can be easily and appropriately performed using the wheel speed of the vehicle, and it can be estimated that the estimation of the vehicle body speed is erroneous to the larger one.

When the amount of change in the estimated vehicle speed is corrected in accordance with the judgment of the estimated vehicle speed deviation, the correction of the estimated vehicle speed change is performed by the estimated vehicle speed having the structure as described in claim 4 or 5. The present invention can be suitably implemented by the change amount correcting means, and the above can be similarly realized. In this case, according to the fourth aspect, even when the correction amount is changed to be extremely large in order to quickly correct the estimated vehicle body speed, this can be easily responded to and is estimated by the road surface μ estimating means. With this correction to the vehicle speed change amount calculated from the road surface μ of each wheel, it is possible to appropriately and quickly correct the deviation of the estimated vehicle speed. Also,
According to the fifth aspect, for example, once the correction amount is changed to increase the correction amount for the upward correction as described above, when the correction amount is changed, the road surface μ estimation is estimated to be small due to some influence. In addition to this, in addition to this, it is possible to take into account the processing of the vehicle speed change amount after the correction amount change, and in this case, the vehicle body speed estimation deviation determination means makes the deviation determination. The processing can be performed more finely according to the time being performed. Further, by correcting and changing the vehicle speed change amount in this way, it is possible to appropriately prevent the estimated vehicle speed from further deviating upward, and to effectively prevent the above-described vicious circle. It becomes something. The correction of the estimated vehicle body speed change amount according to claim 4 or claim 5 can be performed individually or in a mode in which both are used in combination.

According to a sixth aspect of the present invention, the target slip ratio changing means for changing the target slip ratio of at least one wheel to a shallower one in accordance with the wheel speed convergence judgment is determined by:
When the slip state of the wheel is changed based on the detected value of the vehicle running state detecting means for detecting the vehicle running state, the slip ratio of the wheel selected by the wheel selecting means for selecting the wheel having the least effect on the vehicle behavior is changed. The present invention can be suitably implemented as a configuration that performs the above. In this way, in addition to the above-described operational effects, the target slip ratio is changed in consideration of the traveling state of the vehicle, and the wheel that changes the target slip ratio to a shallower one has the least effect on the vehicle behavior. It is possible to change the target slip ratio of the wheel selected for a small number of wheels to a shallower one, and thus obtain a more responsive anti-skid control performance that also takes into account the effect on vehicle behavior and deceleration. In the case of a downward shift of the estimated vehicle speed, the slip of the estimated vehicle speed can be corrected by restoring the slip of the selected wheel. Therefore, also in this point, the influence on the vehicle behavior which is not taken into consideration by the above-mentioned document 2 and the like is sufficiently considered, and the adverse effect on the vehicle behavior can be avoided. Effectiveness can be further enhanced, and the above-mentioned points can be achieved at the same time, and the above can be appropriately realized. According to a seventh aspect of the present invention, the wheel speed convergence state determining means changes the convergence state according to a time when all the wheel speeds are smaller than a convergence determination wheel speed threshold different from the target wheel speed. The present invention can be suitably implemented as a configuration for judging, and the above can be similarly realized. Further, in this case, when determining the convergence state to the target wheel speed,
By looking at the time during which all the wheel speeds are smaller than the convergence determination wheel speed threshold, if it is long, the anti-skid control for converging the wheel speed has been performed very well for a long time. In addition, it is possible to appropriately determine that there is a possibility that the estimated speed of the vehicle body may be deviated by such a convergence state determination. Then, based on the result of the wheel speed convergence state determination, the target slip ratio can be changed to correct the deviation of the estimated vehicle speed.

Further, regarding the change of the target slip ratio,
When the target slip ratio is changed to a shallower one, the target slip ratio is maintained in a shallow state until the wheel speed of the wheel follows the target, and is returned to the original target slip ratio after following. The present invention can be embodied as more effective as a configuration that takes into account various processes. In this case, once the target slip ratio is changed to be shallow, the brake pressure of the wheel is reduced, but this is maintained until the wheel follows the changed slip ratio, and after that, Since it is returned to the normal target value, it is possible to return to the original target slip ratio at the optimal timing.Therefore, even if the brake pressure is reduced to correct the estimation of the vehicle speed, the effect on deceleration is not affected. Can be smaller.

When the road surface μ is estimated by the road surface μ estimating means and the vehicle body speed is estimated by using the estimated road surface μ of each wheel, The wheel acceleration calculated from the wheel speed detected by the wheel speed detecting means of each wheel, the wheel load detected by the wheel load detecting means of each wheel, and the brake fluid estimated by the brake fluid pressure estimating means of each wheel According to the present invention, the road surface μ is calculated from the wheel acceleration, the wheel load, the estimated brake fluid pressure, and the driving torque estimated by the driving torque estimating means. Can be suitably implemented, and the same can be realized in the same manner. In this case, it is possible to more appropriately calculate the road surface μ of each wheel as a basis for estimating the vehicle body speed, and as a result, it is effective to estimate the vehicle body speed more accurately.

Further, the present invention can be suitably implemented as a configuration as described in claim 10. The configuration according to the configuration employing the estimated vehicle speed change amount correction means as described above is intended to prevent the brake pressure from being reduced by correcting the change amount of the vehicle body speed so that the deceleration does not become insufficient. On the other hand, in the case of the present invention, the target slip ratio of at least one wheel is changed to a shallower one according to the judgment of the wheel speed convergence state judging means, The target slip rate changing means for changing the target slip rate to a deeper one in accordance with the judgment of the above is used. Even in such a case, when it is determined that the estimated vehicle speed is deviated upward, By changing the target slip ratio to a deeper value, it is possible to suppress or prevent the brake pressure from being reduced due to an increase in the estimated vehicle speed, and to avoid insufficient deceleration. Therefore, although the means different from those of the first to ninth aspects can achieve the same function and effect, similarly, the deviation of the estimated vehicle speed can be corrected, and the wheel speed can be adjusted to the target value. Even in the case of anti-skid control that controls the brake pressure of each wheel so that it converges, while taking advantage of the improved braking deceleration as much as possible, the deceleration due to the reduction in the brake pressure caused by the deviation of the estimated vehicle speed is used. The anti-skid control performance with high responsiveness that takes into account the influence of the vehicle speed can be realized, the braking speed is improved by converging the wheel speed to the target wheel speed, and the vehicle speed is estimated with high accuracy. The above can be realized by improving the anti-skid control performance. In this case, preferably, the target slip ratio changing means changes the target slip ratio of at least one wheel to a shallower one in accordance with the judgment of the wheel speed convergence state judging means. If the target slip rate is changed to a deeper one in accordance with the judgment of the vehicle speed estimation deviation judgment means, the target slip rate is changed to a deeper one only for wheels other than the wheels whose target slip rate is changed to a shallower one. The present invention can be suitably implemented as a configuration to be changed. In this case, in addition to the above, if, for example, the target slip ratio is changed to a shallow one wheel, the target slip ratios of the three wheels except for the one wheel are targeted. Can be changed to a deeper value, and accordingly, the brake pressure can be appropriately prevented from being reduced, and insufficient deceleration can be prevented.

[0031]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a diagram showing the configuration of one embodiment of the present invention. In this embodiment, a vehicle (automobile) to which the present invention is applied
Denotes a rear-wheel drive vehicle (AT vehicle, vehicle equipped with a conveyor differential), and anti-skid control (ABS control) assumes a braking device that can independently control the left and right braking forces (braking fluid pressure) for both front and rear wheels. .

In the figure, 1 is a brake pedal, 2 is a booster, 3 is a reservoir, and 4 is a master cylinder. 10 and 20 are left and right front wheels (driven wheels), and 30 and 4
0 indicates left and right rear wheels (drive wheels), respectively. Each wheel is provided with a brake disk 11, 21, 31, 41, and a wheel cylinder (W) that applies a hydraulic pressure to apply frictional force to the brake disk to apply a braking force (braking force) to each wheel.
/ C) 12, 22, 32, 42, and the pressure control unit 5
Each wheel is individually braked when supplied with hydraulic pressure from the vehicle.

The pressure control unit 5 constitutes an anti-skid control device together with a controller to be described later including the pressure control unit 5. The pressure control unit 5 adjusts the hydraulic pressure from the master cylinder 4 according to an input signal, and controls the wheel cylinders 12, 22, 3 of each wheel.
The brake fluid pressure to be supplied to 2, 42 is controlled. The pressure control unit 5 is provided for each hydraulic pressure supply system (each channel) for the front and rear wheels
It is configured to include an actuator individually. As the actuator, an actuator having a pressure-intensifying valve and a pressure-reducing valve as control valves so that pressure-reducing, holding, and pressure-increasing control can be used. Pressure control unit 5 (pressure servo unit)
FIG. 3 shows an example.

In this embodiment, as shown in the figure, the master cylinder 4 and the wheel cylinders 11, 21, 3
Between 1 and 41, an anti-skid device is provided, the control device is therefore a 4ch anti-skid system, thereby avoiding wheel lock when the anti-skid control is activated.

Here, pressure increasing valves 14, 24, 34, 44 as inlet valves and pressure reducing valves 15, 25, 35, as outlet valves are provided in channels for each wheel.
45, and the reservoirs 16 and 17 and the motor 36
Driving pumps 26 and 27 are included as elements, and these are connected and connected by a brake hose or the like as shown in the figure to form a hydraulic circuit.

In the brake fluid pressure system from the master cylinder 4 to the wheel cylinders 11 to 41, in the front wheel (front) brake system, the master cylinder fluid passage connects the pressure boost valves 14 and 24 individually to each other. From the front wheel 10,
20 wheel cylinders 11 and 21. Similarly, in the rear wheel (rear) brake system, the master cylinder fluid path is connected to each of the pressure boosting valves 33 and 44, and from the pressure boosting valves, the rear wheel 3 is passed through the fluid path on each wheel cylinder side.
0 and 40 wheel cylinders 31 and 41, respectively.

Each of the wheel cylinder fluid paths connected to each of the front wheel wheel cylinders 11 and 21 is branched from the middle thereof, and these branch fluid paths are connected to the front wheel reservoir 16 via the pressure reducing valves 15 and 25, and the front wheel is also connected. Through the master pump 26 to the master cylinder fluid path on the upstream side. Similarly, the wheel cylinder fluid passages connected to the wheel cylinders 31 and 41 of the rear wheels are also branched from the middle, respectively, and the branched fluid passages are connected to the rear wheel reservoir 17 via the pressure reducing valves 35 and 45, respectively. Through the rear wheel pump 27, it is connected to the master cylinder fluid path on the upstream side.

The pressure-intensifying valves 14, 24, 34, and 44 are at the positions shown in the figure during normal braking. Pressure reducing valve 1
3, 23, 33, and 43 are normally in the positions shown in the figure, and the connection between the valve input / output ports, and hence the connection with the corresponding reservoirs 16 and 17, is cut off. And thus the position at which the wheel cylinders are connected to the corresponding reservoirs 16,17.
Thus, during anti-skid control, this valve guides the brake fluid of the corresponding wheel cylinder to the reservoir to reduce the wheel cylinder pressure.

In the normal braking state, when the hydraulic pressure from the master cylinder 4 is supplied to each wheel cylinder by the driver's depressing operation of the brake pedal 1 at the illustrated position of each pressure increasing valve and pressure reducing valve, The master cylinder pressure is the master cylinder fluid path, each booster valve,
And through the wheel cylinder fluid path,
Therefore, the brake hydraulic pressure (braking hydraulic pressure P) can be increased toward the master cylinder hydraulic pressure, which is the original pressure, and each wheel is individually braked to perform normal braking.

At the time of such braking, when the pressure reducing valves 15, 25, 35, and 45 of each channel are operated to open and close, the branch fluid paths to the corresponding reservoirs 16 and 17 are opened at the valve open positions. Open during the period of operation, the brake fluid of the corresponding wheel cylinder is guided to the reservoir and drained. In addition, during the period in which the valve is closed, the communication with the reservoir is cut off to cut off the above-mentioned brake fluid pressure. Thus, by such valve opening / closing drive control, a reduced pressure state is established in which the brake fluid pressure is released to the corresponding reservoir and reduced.

The brake fluid accumulated in the reservoirs 16 and 17 due to the pressure reduction is returned to the upstream of the pressure increasing valves 14, 24, 34 and 44 by pumps 26 and 27 driven by a motor 36. Then, the returned brake fluid is used for pressure increase.

Returning to FIG. 2, signals to the control valves of the respective channels of the pressure control unit 5 are supplied from a controller 50. The controller 50 has an acceleration sensor for detecting the front and rear and lateral accelerations Xg and Yg of the vehicle. Signal from 6,
Signals from the yaw rate sensor 7 for detecting the yaw rate φ, and signals Vw1 (front wheel left side) and Vw2 from the wheel speed sensors 13, 23, 33, 43 for detecting the wheel speeds arranged on the respective wheels 10, 20, 30, 40. (Front wheel right side), Vw3 (rear wheel left side), Vw4 (rear wheel right side) and the like are input. Further, in this embodiment, the controller 50 is connected to an engine controller 51 for controlling the engine and an AT controller 52 for controlling the transmission, and the controller 51, 52 controls the engine drive torque Te, Automatic transmission (not shown)
Is also input. Here, the driving torque Te and the gear position GR information are stored in the driving wheels 30, 40.
Can be used as information for estimating the driving torque for

The controller 50 includes a microcomputer, and includes an input detection circuit, an arithmetic processing circuit (CPU), a control program for anti-skid control executed by the arithmetic processing circuit and other control programs, And a storage circuit (RA
M, ROM), and an output circuit that outputs control signals such as pressure increase, pressure decrease, and hold command signals for each channel to the pressure control unit 5.

In the present embodiment, the controller 50 controls the pressure increasing valve and the pressure reducing valve of each channel to prevent the wheel from being locked by braking based on the input information in the braking situation where the anti-skid control is activated during braking. A drive pulse is output to control the brake fluid pressure of each wheel to control the wheel braking force. In this case, in the case of the ABS control of the four-channel four-sensor system as in this example, basically, the wheel speed information Vwi (i = 1 to 4) for each of the four front, rear, right and left wheels is obtained, and the vehicle speed (the vehicle body speed) is obtained. Speed), and in the case of using the wheel acceleration, the wheel acceleration is also calculated from the wheel speed for each wheel, and the target pressure increase / decrease amount is obtained from the wheel speed, the wheel acceleration, and the body speed. By controlling the wheel cylinder hydraulic pressure, it is possible to perform control for avoiding wheel lock during braking.

In the above control, the controller 50 controls the brake fluid pressure of each wheel so that the wheel speed becomes the target wheel speed calculated from the vehicle body speed, and performs anti-skid control in this case to perform braking. To make the best use of the advantages such as the improvement of deceleration as much as possible, and at the same time take into account the effect on deceleration due to the reduction of brake fluid pressure due to vehicle behavior and deviation of estimated vehicle speed. A vehicle speed estimation deviation determination for estimating that the vehicle speed estimation is incorrect to the larger one, and correcting the vehicle speed estimation value so as to increase the amount of change in the vehicle speed estimation value in accordance with the vehicle speed estimation deviation determination Execute the change amount correction processing. In this case, preferably, the road surface μ is estimated, the vehicle speed is estimated using the estimated road surface μ of each wheel, and the target wheel speed of each wheel is set based on the estimated vehicle speed. While controlling the brake pressure of each wheel so that each wheel speed converges to its target value, while performing the wheel speed convergence state determination to determine the convergence state of each wheel to the target wheel speed, and As described above, the vehicle body speed estimation deviation judgment is performed to estimate that the estimation of the vehicle body speed is erroneous to the larger one, and the target slip ratio of at least one wheel is changed to a shallower one according to the wheel speed convergence state judgment. The target slip ratio is changed and, as described above, the estimated vehicle speed change amount correction for correcting the change amount of the estimated vehicle speed value to be large according to the determination of the estimated vehicle speed difference is also performed.

FIG. 4 is a block diagram showing an example of the functions of the system shown in FIG. 2 for the anti-skid control including such estimation of the estimated vehicle speed deviation and correction of the estimated vehicle speed change. It is expressed as In FIG.
a is road surface μ estimating means (estimating unit), b is vehicle speed estimating means (estimating unit), c is wheel speed convergence state determining means (judging unit)
d is a target slip ratio changing means (changing unit), i is a vehicle speed estimated deviation determining means (determining unit), j is an estimated vehicle speed change amount correcting means (correcting unit), and g is an anti-skid control unit. , The pressure control unit 5 as well as these functional elements.

The road surface μ estimating means a is means for estimating the road surface μ, and the vehicle speed estimating means b is means for estimating the vehicle speed using the road surface μ of each wheel estimated by the road surface μ estimating means a. The anti-skid control unit g sets the target wheel speed of each wheel (the target wheel speed calculated from the vehicle speed) based on the vehicle speed estimated by the vehicle speed estimating means b, and sets each wheel speed to the target value. The control method is to control the brake pressure of each wheel so as to converge. In such anti-skid control, the wheel speed convergence state determining means c for determining the convergence state of each wheel to the target wheel speed, and the target slip ratio of at least one wheel are determined in accordance with the determination of the wheel speed convergence state determining means c. A vehicle body having target slip ratio changing means d for changing to a shallower one and executing the change of the target slip ratio, while estimating that the estimation of the vehicle body speed is erroneous to the larger one by the vehicle speed estimation deviation judging means i. An estimated speed deviation is determined, and the estimated vehicle speed change amount correction means j determines, based on the estimated vehicle speed deviation, the brake fluid pressure due to the upward shift when it is determined that the estimated vehicle speed has shifted upward. In order to correct or reduce the change in the vehicle speed so as not to cause the deceleration to be insufficient, the correction is made to increase the change in the estimated vehicle speed by the vehicle speed estimation means b.

In a preferred embodiment, the vehicle speed estimation deviation judging means i determines the vehicle body speed in accordance with the time until the wheel speed of the wheel whose target slip rate has been changed shallowly by the target slip rate changing means d follows the target. A method of judging a shift can be adopted. The estimated vehicle speed change amount correction means j changes the offset amount to a larger one added to the vehicle body speed change amount calculated from the road surface μ of each wheel estimated by the road surface μ estimating means a, thereby obtaining the estimated vehicle speed. The amount of change can be corrected, and the amount of offset to be added to the amount of change in vehicle speed after the end of the deviation determination is changed according to the time during which the deviation determination is made by the estimated vehicle speed deviation determination means i. Thus, the estimated vehicle speed change amount can be corrected.

Further, in a preferred embodiment, the change of the target slip ratio has the most influence on the vehicle behavior when the slip state of the wheels is changed based on the detected value of the vehicle running state detecting means for detecting the vehicle running state. This can be done by changing the slip rate of the wheel selected by the wheel selecting means for selecting fewer wheels, and the target slip rate changing means d has changed the target slip rate to a shallower one. In this case, it is possible to add a method of maintaining the target slip ratio in a shallow state until the wheel speed of the wheel follows the target, and returning to the original target slip ratio after following. Also, regarding the determination by the wheel speed convergence state determination means c,
The convergence state may be determined according to the time during which all wheel speeds are smaller than the target convergence determination wheel speed threshold value. Also, road surface μ estimating means a
In a preferred aspect, the wheel acceleration calculated from the wheel speed detected by the wheel speed detecting means of each wheel, the wheel load detected by the wheel load detecting means of each wheel, and the brake fluid pressure estimation of each wheel The road surface μ can be calculated from the brake fluid pressure estimated by the means, and, for the driving wheels, from them and the driving torque estimated by the driving torque estimating means. In the present embodiment, each of the units a to j can include a corresponding sensor or the like in FIG. 2 and a part of the controller 50.

FIG. 5 is a flowchart of an example of a control program including the above-described judgment of the estimated vehicle body speed deviation, the correction of the estimated vehicle body speed variation, and other processes executed by the controller 50. This process is executed by a periodic interrupt at a fixed time interval by an operating system (not shown).
First, in step S101, each of the sensors 6, 7, 1
Various data from 3, 23, 33, 43, controllers 51, 52 and the like are read. That is, the longitudinal acceleration Xg,
Lateral acceleration Yg, yaw rate φ, each wheel speed Vwi (i = 1
4), the engine drive torque Te and the gear position GR are read.

In the following step S102, the wheel speed Vwi
Is calculated based on the wheel acceleration Vwdi (i = 1 to 4). In this embodiment, it is calculated according to the following equation.

Vwdi = ((Vwi1 + Vwi0) − (Vwi4 + Vwi3)) / 2ΔT (1) Here, the subscripts 0 to 4 indicate the number of cycles before the control cycle the wheel speed. ΔT is a control cycle. If the wheel speed Vwi value in the earlier control cycle period is larger, the wheel is in a state of being decelerated.

In the following step S103, select wheel speed Vfs is calculated. In the present embodiment, the wheel speed Vw of each wheel
A filter is applied to i according to acceleration / deceleration, etc., and Vwfi (i = 1 to 4) closer to the vehicle speed is calculated for each wheel. Depending on conditions such as when the anti-skid control is activated / deactivated, By selecting the largest one from each Vwfi / selecting the average value of the non-driven wheels, the selected wheel speed Vfs closest to the vehicle body speed is calculated.

In the following step S104, the wheel load Wi of each wheel is calculated. In the present embodiment, each wheel load Wfr (front wheel right), the values Xg and Yg of the front and rear G and side G sensors are used.
Wfl (front wheel left), Wrr (rear wheel right), and Wrl (rear wheel left) are calculated according to the following equations. Before and after G and lateral G are used after applying a first-order lag filter.

Wfr = Wfr0 + kx × Xg + kyf × Yg 2a Wfl = Wfl0 + kx × Xg + kyf × Yg 2b Wrr = Wrr0 + kx × Xg + kyr × Yg 2c Wrl = x kx, kyf, and kyr are constants determined by the distribution of the wheel base, the height of the center of gravity, the tread, and the roll rigidity. Wfr0, Wfl0, Wrr0, Wrl0 are initial loads (static loads).

In this embodiment, the front and rear G and side G sensors are used. However, instead of the front and rear G sensor values, the change amount of the vehicle speed calculated up to the previous time (step S109) or
The road surface μ estimated value (step S108) may be used. Instead of the lateral G, the lateral G may be estimated from the vehicle speed and the steering angle, the vehicle speed and the yaw rate, or the vehicle speed and the difference between the left and right wheel speeds.

In the following step S105, an estimated brake fluid pressure Pwsi is calculated. In this embodiment, the brake pressure of each wheel is estimated from the history of the brake fluid pressure increase / decrease pulse output to the pressure control unit 5 for controlling the brake fluid pressure. By performing the reverse of the process of calculating the valve drive time Ti from the pressure increase / decrease amount ΔP ^* (target value) described later,
The actual pressure increase / decrease amount ΔP (change in pressure increase / decrease according to the valve driving time) is calculated, and the current brake fluid pressure P is calculated according to the following equation.
Estimate wsi.

Pwsi = Pwsi (previous value) + ΔP (3)

In the following step S106, the slip ratio Si of each wheel is calculated. In the present embodiment, the wheel speed Vw of each wheel
The slip ratio is calculated by the following equation from i and the vehicle speed Vi calculated last time (the Vi value calculated in step S110 in the previous loop).

## EQU00004 ## Si = (Vi-Vwi) / Vi... 4

In the following step 107, each wheel is set on the road surface μ.
It is determined whether or not the peak value is reached. In this embodiment, it is determined whether or not a peak is obtained from the wheel acceleration Vwdi and the slip ratio Si calculated in the above steps S102 and S106. In other words, when the wheel state is in the set area (shaded area) in the characteristic diagram of the slip ratio and the wheel acceleration (deceleration) shown in FIG. 6, it is determined that the wheel is at the peak value of the road surface μ. . Here, the threshold value for this determination is the same as the control start determination for the anti-skid control. In addition, as an example of each of the values S ₁ , S ₂ , α ₁ , α ₂ applied for setting the determination area in FIG.
₁ = 0.05, S ₂ = 0.15, α ₁ = 3.0, α ₂ =
1.0.

Here, in the anti-skid control, the control is usually performed by the wheel deceleration and the wheel slip ratio. For example, in a typical ABS, the control is performed by a deceleration-slip ratio map as shown in the upper part of FIG. The mode can be determined and the anti-skid control can be executed. That is, in the illustrated example, the pressure is reduced and the anti-skid control is started only when the slip ratio becomes equal to or less than the predetermined value Sx (threshold value). FIG. 6 is the same as changing the threshold value Sx by deceleration. That is, the start timing of the anti-skid control and the determination of the road μ peak are made the same (FIG. 6, FIG. 7, lower part). Conversely, basically, when the anti-skid control operates, it is assumed that the road surface μ is at the peak.

In this way, in the road surface μ peak determination in step S107, this is performed by determining that the road surface μ has the peak value according to the acceleration of each wheel and the slip ratio of the wheel. Then, once the anti-skid control has been activated, if the exceptional control described later is not performed, it is determined that the wheel state is at the peak value of the road surface μ for a while even if the wheel state is out of the above-mentioned region. continue. Here, as means for this, for example, when the wheels are under anti-skid control, once it is determined that the road surface μ is at the peak, the determination threshold values of the wheel acceleration and the slip ratio are changed. Alternatively, a method may be employed in which the determination that the user is at the peak is maintained to some extent by providing a certain set time. When such a method is taken into consideration, for example, the start timing of the anti-skid control and the road surface μ peak determination for obtaining the calculated value for the road surface μ on which the vehicle speed is estimated are made the same, Once the control has been activated,
By continuing the determination that the wheel is at the peak value of, immediately after the relevant wheel is determined to be at the peak of the road surface μ, immediately, a determination result that the wheel is not at the road surface μ peak occurs,
It is properly avoided that the road surface μ on the wheel side becomes inapplicable to the above-mentioned vehicle body speed estimation, there is no undesirable control hunting, and the vehicle body speed is well estimated during anti-skid control. It is possible to make it.

Further, even when the wheels are in the anti-skid control state, the left and right or front and rear wheels are synchronously controlled, ie, so-called select-low control, and the initial pressure is gradually increased, ie, so-called yaw moment control. When exceptional controls are being performed, the slip rate is not sufficiently large due to those controls, and it is meaningless to calculate the road surface μ, so that it is determined that the road surface μ is not at the peak. In the determination of the road surface μ peak in step S107, this processing is also taken into consideration, and therefore, even when the wheels are under the anti-skid control, the slip when the above-described exceptional control is performed is performed. It is determined that the wheel on the side with a lower rate is not on the road surface μ peak.

In the following step S108, the value μi (i = 1 to 4) of the road surface μ is calculated for the wheels for which the road surface μ is determined to be at the peak according to the determination in the above step S107 (therefore, in step S107). If it is determined that all wheels are at the peak of the road surface μ, then all wheels are μi
The corresponding wheel is excluded when it is determined that the road surface μ is not at the peak in the determination processing.) In the present embodiment, each of the above steps S102, S104, S1
Using the wheel acceleration Vwdi, the wheel load Wi, and the estimated brake fluid pressure Pwsi calculated in step S05, and for the drive wheels (30 and 40 in the present embodiment), the above-described step S10 is further performed.
Engine drive torque Te and gear position GR read in
, The road surface μ is calculated for each of the non-driven wheels (10, 20 in this embodiment) and the driven wheels according to the following equation.

[0062]

(5) Non-drive wheel side: μi = (I × Vwdi + K × Pwsi × R) / (Wi × R ² ) 5a Drive wheel side: μi = (I × Vwdi + K × Pwsi × R−k × Te) / (Wi × R ² ) ··· 5b where K is a constant determined by brake specifications (pat μ, wheel cylinder area, wheel cylinder effective diameter), k
Is a constant determined according to the transmission gear ratio corresponding to the gear position GR and the differential final gear ratio, I is the inertial mass of the tire, and R is the tire effective diameter. Here, the calculated road surface μ estimated value may be subjected to, for example, a first-order lag filter process.

In the following step S109, the road surface μ of each wheel
Is used to calculate the vehicle speed change amount Vid. In the present embodiment, the wheel whose road surface μ is determined to be at the peak (therefore, also in this case, the road surface μ is determined in the determination processing in step S107).
Wheel is determined to be not at the peak) is excluded)
And the vehicle speed change amount correction amount ΔVid described later is used to calculate the vehicle speed change amount.

Vid = (Σ (μi)) / n + ΔVid (6) where n is the number of wheels for which the road surface μ is determined to be at the peak. Here, the vehicle body speed change amount Vid calculated using the road surface μ is applied to the vehicle body speed Vi (estimated vehicle speed) calculation in step S112 as described later. By calculating this from equation (6), basically, a process of correcting and changing the change amount of the vehicle body speed (the vehicle body speed change amount) calculated from the road surface μ of each wheel estimated by the road surface μ estimation process is also performed. And the correction ΔVi applied as the addition term of the second term on the right side
It can be changed according to the size of d (step S117).

Here, the average value of the road surface μ (Σ (μ
i)) / n is an acceleration that can be generated by the vehicle body, for example, a maximum limit of 1.3 g as a predetermined upper limit, and 0.0 as a predetermined lower limit for preventing excessive release of brake pressure.
A limit of 5 g is imposed. When there is no wheel whose road surface μ is determined to be the peak, all the wheels have not reached the limit yet, and the anti-skid control has not been operated. Therefore, for example, Vid = 1. 3g
(Predetermined upper limit value).

Here, the basic value of the vehicle speed change amount calculated from the road surface μ (the first term on the right side of the above equation) is not a simple average value of the road surface μ of each wheel, but the wheel load of each wheel. The vehicle speed change amount may be calculated by multiplying the weight according to the distribution. That is, when it is determined in step S107 that all the wheels are at the peak of the road surface μ, the vehicle speed change amount Vid (basic value) is simply calculated using the wheel load Wi calculated in step S104, for example, by the following equation. May be calculated.

Vid (basic value) = Σ (μi × (Wi / W)) 7

However, W is the weight. If any of the wheels is not determined to be the peak of the road surface μ, (A) substitute the μi of the right and left opposite wheels determined to be at the peak, B) Substituting the μi calculated as the largest,
After that, the value Vid is calculated according to the above equation.

Here, this is based on the following viewpoints. That is, in the case of the above equation 6, the average value of each road surface μ (Σ
(Μi)) / n. By the way, when considering whether there is no problem even when the road surface μ estimated for each wheel is significantly different on the so-called right and left split road surfaces when the road surface μ on the left and right of the vehicle is extremely different,
As described above, since the road surface μ of the shallow slip wheel whose right / left wheel is subjected to the select-low control is ignored (step S107), the average value of the road surface μ of the other wheels is calculated as the vehicle speed change amount Vid. There is no problem by applying to.

Although there are not many braking scenes to be encountered, if further consideration is given to the case where the road surfaces μ of the four wheels are largely different, it is more preferable to be able to cope with this. In view of this, in the mode according to the modified example of the above equation 7, the weight of the road surface μ of each wheel is multiplied by a weight corresponding to the wheel load distribution, and the amount of change in the vehicle body speed is calculated. It is applied to. When the control program is executed in this manner, basically, the selected wheel speed Vfs calculated from the wheel speed Vwi is selected.
If there is a wheel whose road surface μ is determined to be at the peak, the road surface μ of each wheel calculated in step S108 is followed by the vehicle speed change amount Vid with a weight corresponding to the wheel load Wi. The vehicle speed Vi is estimated (step S11).
2) It is possible to take into account the case where the road surfaces μ of the four wheels differ greatly from one another, and to cope with this. Therefore, in the vehicle speed change amount calculation processing, this may be performed.

In the following step S110, the lateral speed Vy of the vehicle is calculated. In this embodiment, the vehicle lateral speed V is integrated by using the lateral acceleration Yg, the yaw rate φ, and the vehicle speed Vi (previous value), which are the sensor signals, as in the following equations.
Calculate y.

ΔVy = Yg (n) −φ (n) · Vi (n−1) 8a Vy (n) = Vy (n−1) + ΔVy · ΔT 8b (ΔT is a control cycle, ((N) indicates the current value, (n-1) indicates the previous value)

In this embodiment, the vehicle lateral speed is calculated by integral calculation from each sensor signal. However, a vehicle model is provided in the controller 50, and the vehicle lateral slip is calculated based on the vehicle speed Vi and the steering angle δ. Estimate the angle β, β and Vi
Vy may be calculated by the following equation.

Vy = β × Vi (9)

In the following step S111, the turning correction amount Vh
Is calculated. In this embodiment, the turning correction amount Vh is calculated by the m-th order equation.

Vh = Vy × φ 10

In the following step S112, the vehicle speed Vi is calculated according to the vehicle body shift amount Vid and the turning correction amount Vh. In the present embodiment, when the anti-skid control is activated (when there is a wheel whose road surface μ is determined to be at a peak), the previous value of the vehicle speed Vi and the selected wheel speed Vfs value in step S103 are compared with the previous value. (1) Vi
If (previous value) ≧ Vfs, it is determined that the vehicle body is decelerating, and the vehicle speed Vi is calculated according to the following equation.

11 = Vi (previous value) − ((Σ (μi)) / n + ΔVid) −Vh (11) (2) Vi (previous value) If <Vfs, it is determined that the vehicle is accelerating, and the vehicle speed Vi is calculated according to the following equation.

Vi = Vi (previous value) +5.0 g (12) That is, when Vi (previous value) ≧ Vfs, the vehicle speed V
Each time the execution of this step S112 is performed with respect to the previous value of i,
Then, here, the vehicle speed change amount Vid obtained by using the average value of the road surface μ and the vehicle speed change amount correction amount ΔVid according to the above equation 6 is reduced, and further, the turning correction amount Vh = V
The current value of the vehicle body speed Vi is set in consideration of the correction process using y × φ (the third term on the right side of the above equation). And V
If i (previous value) <Vfs, a predetermined value (5.0 g in this example) is added to the previous value of the vehicle speed Vi each time this step S112 is executed, and the vehicle speed Vi is added.
This time value. In this manner, the vehicle speed Vi can be basically estimated using the road surface μ of each wheel. In this way, when the program is executed, the selected wheel speed Vfs and the road surface μ When there is a wheel determined to be at the peak, the vehicle body speed Vi can be estimated so as to follow with the vehicle body speed change amount according to the average value of the road surface μ. On the other hand, when the anti-skid control is not operating (when there is no wheel whose road surface μ is determined to be the peak), Vi = Vfs.

This makes it more effective in estimating the vehicle speed. That is, when the above-mentioned Vi (previous value) ≧ Vfs, the third term on the right side of the above calculation formula is not applied. Vi = Vi (previous value) −Vid
Although the present invention can be applied to the method according to the method described above, the influence on the vehicle speed due to the lateral force of the tire can be considered more accurately as compared with the method according to The anti-skid control performance can be improved.

In the present embodiment, when the vehicle speed is estimated so that the selected wheel speed calculated from the wheel speed is followed by the vehicle speed change obtained by using the road surface μ, the road surface speed change is used as the vehicle speed change. When there is a wheel whose road surface μ is determined to be at the peak in the μ peak determination, the calculation is performed using the road surface μ of each wheel calculated by the road surface μ calculation, and this is further calculated by the lateral speed Vy of the vehicle. The vehicle speed Vi can be estimated as the corrected vehicle speed change amount corrected by the turning correction amount Vh calculated by the yaw rate φ and the yaw rate φ. On the other hand, in a mode in which the turning correction amount Vh is not applied, When the vehicle speed change amount Vid is calculated in accordance with the estimated road surface μ and the vehicle speed is estimated based on Vi = Vi (previous value) −Vid. The road surface μ is the road surface in the front-rear direction of the tire Although the reaction force is taken into consideration, the effect of the lateral force of the tire on the vehicle speed is not sufficient. Therefore, when further improvement in accuracy is desired, the influence on the vehicle speed due to the lateral force of the tire should be more accurately considered, and this embodiment is also considered. . Further, as in Expression 11b in which Expression 6 is substituted into the second term on the right side of Expression 11a, the value of the vehicle speed change amount correction amount ΔVid is reflected in the estimation of the vehicle speed Vi. The Rukoto. In this case, the estimated vehicle speed Vi is Vi (previous value).
As a result of calculation using − ((Σ (μi)) / n + ΔVid) −Vh, as the larger correction amount ΔVid is applied, the Vi value decreases with a larger reduction rate by the amount of the addition of ΔVid. In this direction, the current estimated vehicle speed Vi value is sequentially corrected, and is applied to the following processing (for example, see FIG. 13 for correction from a state in which the estimated vehicle speed is shifted).

In a succeeding step S113, a convergence state of the wheel speed is determined. This is because, as described above, when the brake fluid pressure is controlled so that each wheel speed becomes the target wheel speed, the wheel speed converges to the target value (the actual value of the wheel speed follows the target value. The anti-skid control so that the deviation is small) is effective in improving braking deceleration and the like, but on the other hand, there is a possibility that the estimated vehicle speed tends to "deviate". In this case, it is determined whether or not such a situation exists in a state where each wheel converges to the target wheel speed.

In this embodiment, a step S119 described later is performed.
, The target wheel speed Vw calculated from the vehicle speed Vi (estimated value)
A threshold value Vwsl (convergence determination wheel speed threshold value) smaller than si is set, and a time Tw during which all wheel speeds Vwi are equal to or less than the threshold value is set value Tss (in this embodiment, a predetermined value). Since the time during which the anti-skid control for converging the wheel speed is extremely well performed when the vehicle speed exceeds a long time, it is determined that there is a possibility that the estimated vehicle speed Vi may be largely deviated. Decide to change the slip rate shallowly. Here, for example, assuming that the target slip ratio Si ^* of the anti-skid control is 0.15, the slip ratio corresponding to the threshold value Vwsl is set to Ssl = 0.1, and is determined according to the following equation.

Vwsl = Vi × (1−Ssl) 13a

In the present embodiment, the time discrimination value Tss relating to the time Tw used for the convergence judgment is set to a predetermined value. It may be smaller.

The "upward" and "downward" of the estimated vehicle speed Vi will be supplementarily described with reference to FIGS. FIG. 18 shows changes in wheel speed, actual vehicle speed, and the like in the case of the conventional example. In the case of FIG. 18, the estimated vehicle speed Vi is basically calculated from the select wheel speed Vfs. Vi is “downhill” and has a larger width than the actual vehicle speed. This is because the wheel speed slips only for the brake. In the figure, in the change relationship between the front wheel speed (solid line) and the rear wheel speed (dashed line), the one obtained by simply selecting the larger one (upper side) is the simple select wheel speed (selection). However, if further filtering is performed on such a simple selected wheel speed (selection), the selected wheel speed becomes the selected wheel speed Vfs as indicated by the thick broken line in the figure.

Here, with respect to the phenomenon of the estimated vehicle speed being “upward” and “downward”, the estimated vehicle speed Vi is calculated based on the actual vehicle speed (V
car) is referred to as “upward” (upwardly (largely deviated in estimation)).
Estimation shifted downward is referred to as “downward shift” (downward shift or small shift in estimation). One of the biggest problems of the ABS control is how to accurately estimate the vehicle speed. When the ABS control is applied to all the wheels, all four wheels are slipping. Therefore, the vehicle speed is unknown only from the signal from the wheel speed sensor, and must be estimated. Then, when the estimation is shifted, what will be concretely considered is as follows.

[Decrease of Vi] For example, as shown in the upper part of FIG. 19, when the estimated vehicle speed Vi decreases, the target value also decreases, so that the wheel speed Vw is controlled by a deep slip.
Locking may occur in the low-speed range (this is early locking). When the ABS operates on all four wheels and the brake fluid pressure is controlled so that the wheel speed Vw converges to the target wheel speed, the braking deceleration is improved and the braking distance is shortened, but accurate estimation of the vehicle speed becomes more difficult. It is highly probable that the estimated vehicle speed is deviated, and therefore, as in (a) discussed at the beginning of the specification, since the accurate vehicle speed cannot be estimated, a large " Downhill
If this occurs and is controlled by a deep slip, this is likely to be a factor of earlier locking.

[Case of Vi shift] On the other hand, as shown in the lower part of FIG. 19, when the estimated vehicle speed Vi increases, the target value also increases, so that the wheel speed Vw is controlled with a shallow slip. Then, when this state continues, the target value becomes larger than the actual vehicle speed Vcar as shown in the figure, and the slip state is established. At this time, the brake pressure continues to be reduced, resulting in an excessively reduced pressure state, resulting in insufficient deceleration (the brake fluid pressure reaches 0 if the pressure is reduced). Therefore, in this sense, "upward" has a greater effect than "downward". As shown in FIG. 15, during braking, the ABS control is operated on the four wheels,
An “upward shift” that shifts to the side where the estimated vehicle speed is higher,
If the brake fluid pressure (W / C pressure) continues to be reduced in all of the front, rear, left, and right wheels even during braking, the deceleration deficiency becomes large. Therefore, even if the brake fluid pressure control is successfully performed so as to converge the wheel speed, and as a result, an estimation deviation in which the estimation of the vehicle body speed is erroneously estimated occurs, in this respect, " The "upshift" phenomenon is in a more severe situation (hence, it can be said that it is better to set the estimation deviation to a smaller side in consideration of safety).

In the present example of the program, however, it is possible to appropriately avoid the "upshift" which may cause the excessive decompression state (insufficient deceleration).
Significant "descent" of estimated vehicle speed Vi as shown in the upper part of FIG.
In order to avoid occurrence of the wheel speed, the above-described wheel speed Vwi
In the determination of the convergence state, the convergence state is determined according to the time Tw in which all the wheel speeds are lower than the threshold value by using the convergence determination wheel speed threshold value. If the time Tw continues for a period exceeding the set value Tss according to the result of the determination, it is determined that there is a possibility that the estimated vehicle body speed Vi is deviated at that time, and the estimated vehicle body speed Vi is largely deviated. In order to prevent this from happening, the process of changing the target slip ratio is determined so as to change the target slip ratio of at least one wheel to a shallower one.

Returning to FIG. 5, in step S114 following step S113, the running state is determined. Here, the detection of the vehicle running state includes the vehicle speed, the longitudinal acceleration Xg, and the lateral acceleration Y
The running state of the vehicle can be detected from at least one of g, yaw rate φ, steering angle δ, wheel load, wheel slip ratio, vehicle body and wheel side slip angle. In the present embodiment, the turning direction is determined based on the output value Yg of the lateral G sensor,
At the same time, the slip state of each wheel is compared based on the slip ratio Si of each wheel. Here, the yaw rate φ, the difference between the left and right wheel speeds (Vw), the steering angle δ, and the side slip angle β may be used for the turning determination. Further, the wheel load Wi estimated above may be used.

In the following step S115, in response to the determination of the change in the slip ratio in the above-mentioned step S113, a wheel having a changed slip ratio is selected according to the running state of the vehicle. In this embodiment, the slip ratio of the inner wheel after turning is normally changed. This is because, after turning, the inner wheel has the smallest wheel load and the smallest tire friction circle, so that the change in the slip ratio has little effect on the vehicle behavior. Thus, when the present program is executed through the processing of step S116 and thereafter, basically, the target slip ratio of only one of the inner wheels after the turning is changed to the shallower one, and the brake hydraulic pressure of the corresponding wheel is changed. Is controlled so that the slip rate of the inner wheel after the turning becomes the target slip rate (in FIG. 12, the right rear wheel speed in the right turning braking, the target change flag, the right rear wheel and the other three wheels). Refer to the W / C pressure, and also refer to, for example, the right rear wheel speed, the target change flag 1, the right rear wheel, and the other three W / C pressures in FIG.

In this embodiment, the inner wheel after turning is selected as the optimum wheel which will have little effect on the vehicle behavior when the slip state of the wheel is changed in accordance with the running state of the vehicle. The slip ratio of the selected inner wheel after turning can be changed. However, in the slip state of each wheel, if the slip of the outer wheel after turning or the inner wheel before turning is within the above-mentioned convergence determination threshold but is the shallowest, the slip ratio of that wheel is changed. In this way, when the target slip ratio of at least one wheel is changed to a shallower one, the target slip ratio of the wheel that has the least effect on the vehicle behavior can be changed from the above-described viewpoint. Here, in the present embodiment, step S115
In the slip ratio changing wheel selection process, the slip ratio of the inner wheel after turning is normally changed.However, the present invention is not limited to this. Of course,
The criterion for the selection is to determine a wheel whose slip ratio is changed according to vehicle characteristics such as a driving method, weight distribution, and roll rigidity distribution.

In the following step S116, a judgment is made as to whether or not the estimation of the vehicle body speed is wrong to the larger one. In this case, the vehicle speed Vi calculated in step S112 by the aforementioned vehicle speed Vi calculation processing is determined. Is determined to be larger.

The determination of the estimated deviation of the vehicle speed may be made by utilizing the change of the target slip ratio. For example, the deviation of the vehicle body speed estimation is determined according to the time until the wheel speed of the wheel whose target slip ratio has been changed shallowly based on the target slip ratio change processing follows the target. In this embodiment, the wheel speed convergence state is determined in step S113,
The set value Tuz is the time Tu during which the slip ratio of the wheel that has the least effect on the vehicle behavior (in this embodiment, usually the inner wheel after turning, for example, the right rear wheel during right turn braking) is changed to the shallower one. When it exceeds (predetermined value in this embodiment), it is determined that the estimated vehicle speed Vi deviates to the larger one. In other words, if the target slip ratio of a certain wheel is changed to a very small value, and as a result the brake fluid pressure of the wheel continues to be reduced for a long time, as a result of the depressurization, the wheel normally moves to the vehicle speed. If the vehicle returns close to the vehicle, but does not return for a long time, it is determined that the estimated vehicle speed (Vi) itself may be deviated to a direction higher than the actual vehicle speed. In this manner, when the estimation of the vehicle body speed Vi is erroneous to the larger one, it is possible to estimate that the estimated vehicle body speed Vi is deviated to the larger one by using the wheel speed of the wheel whose target slip ratio has been changed to be shallower. it can. In addition, the determination of the estimated vehicle body speed deviation is held until the wheel whose target slip ratio has been changed to the shallower one follows the target slip ratio, and the deviation is corrected after the following, and the determination is cleared.

In the present embodiment, the time discrimination value Tuz relating to the time Tu used for judging whether or not the vehicle speed Vi deviates to the higher side as described above is set to a predetermined value. Value Tuz for low μ that is easy to come out or when turning
May be made smaller than in other cases.

In the subsequent step S117, if it is determined in step S116 that the estimation of the vehicle speed is shifted, a correction amount ΔVid of the vehicle speed change amount Vid is calculated. In the present embodiment, when the time Tu exceeds the set value Tuz, the correction amount Δ
Change Vid to be extremely large. This allows
In order to correct the upward movement, the vehicle speed can be corrected so as to increase the amount of change in the estimated vehicle speed. Thus, even in the case of an upward deviation of the estimated vehicle speed, for example, as shown in the first half transition of the estimated vehicle speed in FIG. Value (step S11
2) is corrected immediately downward so as to approach the actual vehicle speed, and the deviation of the estimated vehicle speed is corrected.

For example, the change amount of the vehicle speed is determined in step S10.
8 (road surface calculation) and S109 (vehicle speed change amount calculation), which are basically obtained by using the road surface μ. It is assumed that the estimated vehicle speed change amount is corrected by setting ΔVid as in the following equation.

ΔVid = 0.1 (Tu <Tuz; before the correction amount is changed) 14a = 1.0 (Tu ≧ Tuz) 14b = 0.3 (Tu <Tuz; correction amount is once 14c after being changed)

In this manner, the vehicle speed change amount calculated from the road surface μ of each wheel estimated by the road surface μ estimation is corrected. Here, the correction amount ΔVid is changed, that is, the correction amount ΔVid. Is the ΔV of the expression 14a.
The change from the id to the ΔVid in the equation 14b means that the road surface μ is estimated (step S1).
08) is considered to have been estimated to be small due to some influence. Therefore, in the present embodiment, once the correction amount ΔVid is changed, the correction amount ΔVid is changed to, for example, 0.3 which is larger than 0.1. (Equation 14c). Equation 14b above
In addition to correcting the deviation of the estimated vehicle body speed in the case of an upward deviation by the correction by the change according to
When the processing for the corrected vehicle speed change amount is also taken into account as in the above equation 14c, the brake fluid pressure is reduced when the estimated vehicle speed is shifted upward.
The estimated value of the road surface μ is also reduced, and as a result, the amount of change in the vehicle speed is reduced, and the effect of preventing a vicious cycle in which the estimated value of the vehicle speed further deviates further is exerted.

In the present embodiment, the correction amount ΔVid is a simple change.
u, the correction amount may be increased according to the set value Tuz.

ΔVid = 0.1 + (Tu−Tuz) (Tu ≧ Tuz) 15a = 0.1 (Tu <Tuz) 15b

Further, the correction amount ΔVid may be increased not in a linear function but in a quadratic function according to the time Tu.

Further, the value after the change of the correction amount ΔVid is also simply switched (for example, switched to 0.3 (Equation 14).
c)), instead of starting the vehicle speed estimation according to the switching time Tus (for example, from 0.1 (Expression 14a)) to 1.0 (Expression 14b) and the road surface μ. For example, the characteristic shown in FIG. 8 may be determined according to the time Tabs until the deviation is determined and the correction amount is switched.

FIG. 8 shows the relationship between the ratio Tus / Tabs of the time Tus and the time Tabs to the ΔVid value after the correction amount is changed. Here, when Tus / Tabs is, for example, less than 0.1 as the first predetermined value, its ΔVid
Is set to 0.1 (first predetermined value) and Tus / Tab
When s exceeds, for example, 1.0 as the second predetermined value, ΔVid is set to 1.0 (first predetermined value), and between the first predetermined value and the second predetermined value. When the correction amount is changed, ΔVid increases with Tus / Tabs in accordance with the characteristic tendency shown in FIG.
The Vid value has been set.

As described above, the correction for the vehicle speed change amount once the correction amount ΔVid is changed is not limited to simply applying the uniform set value according to the above equation (14c), but is variably set with such characteristics. When it is possible to change the ΔVid value after the change of the correction amount, the change in the ΔVid value can be appropriately reflected even in accordance with the time Tus. can do. Therefore, as described above, when the correction amount ΔVid is changed, from the viewpoint that the road surface μ estimation is estimated to be small due to some influence, a process for further correcting the vehicle body speed change is added. When you do, you can do this more finely,
The prevention of the vicious circle as described above can be made more appropriate.

Returning to FIG. 5, in the following step S118,
Calculate the target slip ratio Si ^* . In this embodiment, the target slip rate Si ^* is normally set to a predetermined value S0 ^* (for example, S0 ^* = 0.15 as exemplified above), and the target slip rate of the wheel selected in step S115 is shallow ( For example, 0) is changed. Here, the changed slip ratio is not limited to 0 as in the above example, but may be a small slip value such as 0.02, or may be a negative value. At this time, the target is changed, for example, with a first-order delay.

In this embodiment, the target slip ratio Si ^* is normally set to the predetermined value S0 ^* , but may be changed depending on the turning state or the road surface μ. Further, different values may be used for the front and rear wheels. Further, the method of change may be such that no delay is added or a second-order delay is added. These depend on vehicle characteristics (including brake characteristics) and tire characteristics.

Further, once the target slip ratio is changed to be shallow, the wheel is held until the wheel follows the changed slip ratio, and after the change is returned to the normal target value.
In this way, in the process of changing the target slip ratio, the wheel speed of the wheel whose target slip ratio has been changed (in this embodiment, the wheel speed is usually the inner wheel after turning, for example, the right rear wheel speed Vw4 during right turning braking) ) Keeps the target slip ratio (for example, S4 ^* = 0) in a shallow state until the target slip ratio follows the target, and can add processing to return to the original target slip ratio after following the target. (FIGS. 12 and 13).

At the next step S119, the vehicle speed Vi
The target wheel speed Vwsi of each wheel is calculated using (the calculated Vi value in step S112). In the present embodiment, the target slip rate Si ^* set in step S118 (the target slip rate of the wheel selected as the target slip rate change target wheel whose target slip rate is to be changed shallowly (for example, 0 or 0.02) is calculated according to the following equation.

Vwsi = Vi × (1-Si ^* ) 16

In the following step 120, a brake fluid pressure increase / decrease amount ΔP ^* is calculated. In this embodiment, the target wheel speed Vw
ΔP ^* is calculated by the following equation from si and the wheel speed Vwi.

ΔP ^* = k1 × ε + k2 × (dε / dt) 17a ε = Vwsi−Vwi 17b where dε / dt in equation 17a is the actual wheel speed represented by equation 17b. Means the derivative of the deviation ε between the value and the target value.
Further, k1 and k2 are feedback gains (proportional control gain and differential control gain, respectively), and are changed according to the road surface μ and the vehicle speed.

In the following step S121, as described above,
Target increase / decrease amount ΔP^*After calculating the
The process of outputting the drive signal to the control valve (step S122)
The pressure increase / decrease amount ΔP^*Calculate valve drive time Ti according to
Put out. In this embodiment, the upstream pressure Pu of the control valve (the pressure
The master cylinder pressure Pm / c,
Eel cylinder pressure Pw / c) and downstream pressure Pl (for booster valve
Wheel cylinder pressure Pw / c if pressure reduction valve
Pressure) and increase / decrease amount ΔP ^*And valve drive time Ti
formula,

The valve drive time Ti is calculated from the following equation: Ti = f1 (Pu, P1, ΔP ^* ) (18) Graphs of the above relational expressions are shown in FIGS. For example, at the time of pressure increase (FIG. 9), the pressure increase valves (14, 24, 34, 44) to be controlled
Master cylinder pressure Pm / c, which is the upstream pressure (Pu), and the corresponding wheel cylinder pressure Pw / c, which is the downstream pressure (Pl)
And the target pressure increasing amount ΔP ^* , the corresponding drive time T of the pressure increasing valve
i is calculated.

FIG. 9 shows the characteristics when Ti = tu is constant, and the driving times other than tu are obtained by proportionally complementing. Here, in obtaining the value Ti, for example, it can be obtained from a three-dimensional map of Ti = f (Pu, Pl, ΔP), but the following method can be adopted. As shown in FIG. 10, specifically, the calculation is performed by the following method for simplicity. That is,
Assuming that Ti = tu, the pressure increase / decrease amount ΔP at this time is calculated, and the calculation is repeated until this ΔP matches ΔP ^* . That is, ΔP = f2 when Ti = tu (Pu,
Pl, Ti) when ΔP ^* > ΔP (first for ΔP)
When the second calculated value is still less than the target ΔP ^* )
Further, recalculation is performed with Ti = 2tu (1 from the left side of the figure).
First and second black circle points). And ΔP ^*
(Ti = 3tu, 4tu (third and fourth black circles from the left in the figure) until ≤ΔP is satisfied (that is, until ΔP is at least equal to or exceeds ΔP ^* ). Point), 5tu...), And the Ti at this time is defined as the driving time. For example, ΔP (Ti = 3
tu) <ΔP ^* ≦ ΔP (Ti = 4tu), Ti =
4 tu (the case in the figure corresponds to this). Ti may be obtained in this manner. FIG.
0 (at the time of depressurization) shows the characteristics when Ti = tl is constant (in this case, the pressure-reducing valve (15,
(25, 35, 45) is the pressure of the reservoir (16, 17), so that Pl is always 0 (open to the atmosphere).

Here, the master cylinder pressure used in the above calculation, that is, the value of the master cylinder pressure Pm / c as the upstream pressure Pu applied to the calculation of the valve drive time Ti is detected by a master cylinder pressure sensor. It may be a value, but may be calculated by simply estimating the time from the brake start time to the start of the anti-skid control. Further, the downstream pressure Pl or the upstream pressure Pu
As for the current wheel cylinder pressure as

The actual pressure increase / decrease amount is estimated using ΔP = f2 (Pu, Pl, Ti) (19), and is added to the previous estimated wheel cylinder pressure value in accordance with Equation 3 shown in step S105. Is calculated by

Thus, after calculating the valve drive time Ti, the brake fluid pressure control is executed by outputting a valve drive signal to the pressure control unit 5 in this step every time step S122 is executed based on this. The brake fluid pressure of each wheel is controlled such that each wheel speed Vwi converges to a target value (target wheel speed Vwsi) of each wheel set based on the estimated vehicle body speed Vi. The pressure is controlled by controlling the corresponding control valve of each channel.

In the present embodiment, for the anti-skid control portion, feedback control is performed in accordance with the deviation ε between the wheel speed Vwi and the target wheel speed Vwsi, but if the pressure control unit 5 has sufficient responsiveness, The wheel speed Vw is controlled so as to accurately follow the target. When all the wheel speeds converge with a certain deceleration slip in this way, the conventional vehicle speed estimation method uses the "upward" of the estimated vehicle speed.
There is a concern about insufficient deceleration due to deceleration and the occurrence of early locking due to "descent". However, according to this method, the vehicle speed Vi can be accurately estimated even when all wheels are decelerating and slipping, and Even if there is a deviation in the vehicle speed estimation, in the case of a downward deviation, the deviation of the estimated vehicle speed can be corrected by restoring the slip of the wheel that has the least effect on the vehicle behavior and deceleration, and the deceleration is sacrificed. Good anti-skid performance can be demonstrated.

In addition, even in the case of an upward deviation that cannot be corrected by the conventional method, the deviation of the estimated vehicle speed can be corrected.
It is possible to suppress or prevent a decrease in brake fluid pressure caused by an increase in the estimated vehicle speed, and to avoid insufficient deceleration. In particular, in the case of the method of estimating the road surface μ shown in the above-described embodiment, calculating the amount of change in the vehicle speed based on the estimated value, and calculating the vehicle speed from the amount of change (steps S108, S109, S11)
2) When the estimated deviation of the vehicle body speed occurs, the brake fluid pressure is reduced, so that the estimated value of the road surface μ is also reduced. As a result, the amount of change in the vehicle body speed is reduced, and the estimated vehicle speed is further reduced. According to the present embodiment, the vehicle speed estimated value is prevented from further shifting upward by correcting and changing the vehicle speed change amount, thereby preventing the brake fluid pressure from decreasing. Can prevent this vicious circle from entering.

Therefore, according to the present embodiment, the braking speed is improved by converging the wheel speed Vwi to the target wheel speed Vwsi, and the anti-skid control performance is improved by estimating the vehicle speed with high accuracy. Can be improved.

The present invention can be carried out in the following modes in addition to the above embodiment (first embodiment). That is, in the first embodiment, the amount of change in the vehicle body speed is corrected (steps S109 and S117). By changing to the other direction, it is possible to prevent the brake fluid pressure from decreasing and prevent the deceleration from becoming insufficient.

In this embodiment, regarding the system configuration,
This is the same as the case of the first embodiment shown in FIG. FIG. 16 is a functional block diagram showing the basic configuration in the present embodiment. Road surface μ estimating means a for estimating the road surface μ, vehicle body speed estimating means b for estimating the vehicle body speed using the road surface μ of each wheel estimated by the road surface μ estimating means a, and vehicle body speed estimating means b An anti-skid control unit that sets a target wheel speed of each wheel based on the vehicle speed and controls a brake pressure of each wheel so that each wheel speed converges to the target value. Is the same as that of the first embodiment, but in the case of the present embodiment, the wheel speed convergence state determination means c that determines the convergence state of each wheel to the target wheel speed, The target slip ratio of at least one wheel is changed to a shallower one in accordance with the judgment of the vehicle speed estimated deviation determining means i for estimating an error and the wheel speed convergence state determining means c. The target slip ratio changes to a deeper one according to the judgment of i. A configuration including a target slip ratio changing means d 'to. Here, in a preferred embodiment, the target slip rate changing means d 'is adapted to change the estimated vehicle body speed when the target slip rate of at least one wheel is changed to a shallower one according to the judgment of the wheel speed convergence state judging means c. When the target slip ratio is changed to the deeper one in accordance with the judgment of the judgment means i, the target slip ratio may be changed to the deeper one only for wheels other than the wheels whose target slip ratio is changed to the shallower one. it can.

FIG. 17 is a flowchart of an example of a control program executed by the controller 50 in this embodiment. In the figure, the contents of steps S201 to S216 and steps S219 to S222 are the same as those of steps S101 to S222 of the first embodiment.
116 and almost the same as steps S119 to S122, but the calculation of the vehicle body speed change amount Vid in step S209 of the present embodiment is performed in step S10 of the first embodiment.
Unlike the case of Equation 6 of Expression 9, Vid = (Σ (μi)) / n
And does not add ΔVid. Hereinafter, the target slip ratio correction amount Δ in step S217, which is a main part of the present embodiment, will be described.
Si ^* calculation and target slip ratio Si ^{* in} step S218
The contents of the calculation will be described.

[0112] In step S217 in FIG calculates a target slip ratio Si ^* correction amount DerutaSi ^* If it is determined that the shift vehicle speed estimated by the vehicle speed estimation deviation determination in step S216. In the present embodiment, regarding the time Tu and the set value Tuz described in the first embodiment,
The correction amount ΔSi ^* is increased according to Tu and Tuz as in the following equation.

## EQU20 ## ΔSi ^* = Tu−Tuz (Tu ≧ Tuz) 20a = 0 (Tu <Tuz) 20b In the present embodiment, the correction amount ΔSi ^* is a linear function according to the time Tu. Although increased, it may be increased in a quadratic function.

In the following step S218, a target slip ratio Si ^* is calculated. Also in this embodiment, the target slip ratio Si ^* is usually set to a predetermined value S0 ^* (for example, S0 ^* = 0.15).
The target slip ratio of the wheel selected in step S215 (selection of a wheel for changing the slip ratio) is shallow (for example, 0).
Be changed. Here, the changed slip ratio may be a small slip value such as 0.02 instead of 0, or a negative value.

On the other hand, in the present embodiment, if it is determined in step S216 that the estimated vehicle speed is deviated, the target slip rates of the wheels other than the wheels whose target slip rates have been changed to be shallower are determined in step S217. The value is changed according to the following equation according to the calculated slip correction amount ΔSi ^* .

[Expression 21] Si ^* = S0 ^* + ΔSi ^* 21

At this time, the target is changed with a first-order lag, for example. In this embodiment, the target slip ratio Si ^*
Is normally a predetermined value S0 ^* , but may be changed according to the turning state or the road surface μ. Further, different values may be used for the front and rear wheels. Further, the method of change may be such that no delay is added or a second-order delay is added. These depend on vehicle characteristics (including brake characteristics) and tire characteristics. Further, once the target slip ratio is changed to be shallow, the wheel is held until the wheel follows the changed slip ratio, and after the wheel is followed, the wheel is returned to the normal target value. These points may be the same as in the modification of the first embodiment. Then, the subsequent steps S219 to S222 are executed to end the processing of this program in the current loop, and the contents are the same as steps S119 to S222 of the first embodiment.

The present invention corrects the amount of change in the vehicle body speed in the first embodiment, but sets the target slip ratio when it is determined that the estimated vehicle speed is deviating upward as in the present embodiment. By changing to a deeper one, it is possible to prevent the brake fluid pressure from decreasing and prevent the deceleration from becoming insufficient. According to this embodiment, the same operation and effect as those of the first embodiment can be obtained. Further, if the target slip ratio is changed to a deeper value only for wheels other than the wheel whose target slip ratio is changed to a shallower one in accordance with the determination of the estimated vehicle body speed deviation, for example, the target slip ratio is changed to a shallower wheel. Is one wheel (also in the present embodiment, as in the first embodiment, the target wheel is usually the inner wheel after turning according to the determination of the wheel speed convergence state. ), The target slip rates of the other three wheels (front wheel left, front wheel right, rear wheel left) except for the one wheel can be changed to the deeper, To that extent, it is possible to appropriately prevent the brake pressure from being reduced, thereby preventing insufficient deceleration.

FIGS. 12 and 13 are examples of time series graphs showing the operation when the control according to the present invention is performed.
Is mainly used in the case of downward movement, and FIG. 13 also includes the case of occurrence of upward movement.

Here, FIG. 12 shows FIG. 1 as a comparative example.
As in the case of No. 4, the situation of braking from right turning is compared as an example. That is, changes in various amounts such as the wheel speed and the vehicle body speed in the case of this control example are shown, and the actual vehicle speed (broken line) and the estimated vehicle body speed (steps S112 and S212) indicated by the solid line are shown. ), The respective changes in the front wheel right wheel speed (solid line), which is the inner wheel before turning, and the rear wheel right wheel speed (dashed line, dashed line) which is the inner wheel after turning, are shown. Further, according to the present control example, a target change flag applied in a target slip ratio changing process based on the determination of the wheel speed convergence state during the operation of the anti-skid control, a change transition of the generated yaw rate φ during the control, Wheel cylinder pressure of each wheel (W / C pressure)
Are shown. In this control, the braking deceleration is improved by converging the wheel speed to the target wheel speed, and the anti-skid control performance is improved by estimating the vehicle speed with high accuracy.

When the vehicle speed is calculated from the selected wheel speed as mentioned in FIGS. 18 and 19, it is not possible to accurately estimate the vehicle speed when all the wheels are slipping, and the wheel speed converges to the target wheel speed. With anti-skid control,
When the vehicle speed estimation becomes more difficult, as shown in FIG. 12, according to the present logic, in the process of controlling the wheel speed Vw to accurately follow the target wheel speed Vws,
Even during anti-skid control in which all wheels are braking and slipping, the problem of the estimated vehicle speed "falling down" which causes such early lock is also avoided. The difference is small (the downhill is small), and the accuracy of the slip ratio control is greatly improved. In the case of FIG. 18, the estimated vehicle speed is calculated from the selected wheel speed obtained by selecting and filtering the wheel speed of each wheel.
09 (steps S208 and S209), since the calculation is not performed from the wheel speed (that is, to estimate from the road surface μ), basically, the error of the braking slip included in the wheel speed does not enter. The accuracy is improved.

Therefore, in this regard, according to the present control example, even during the anti-skid control in which all the wheels are braking and slipping, it is possible to accurately estimate the vehicle body speed and improve the anti-skid control performance. It is possible to solve the problems discussed in (a) and (b) at the beginning of the specification, to prevent the wheels from slipping deeply and to control the wheels to some extent hunting to prevent early locking. Such a problem of a decrease in the braking force, an increase in the braking distance, and the like can be satisfactorily solved.

Focusing on the braking control scene of an actual vehicle equipped with an anti-skid system, there is always a fine road irregularity on the actual road surface, and it is unlikely that all wheels always converge on the target for a long time. In some cases, one of the wheels may deviate from the target and have a shallow slip. Even in such a state, if the slip of the wheel determined at a predetermined cycle is recovered (the timing of switching the target change flag in FIG. 14), there may be a case where the deceleration is affected. In some cases, the deceleration may be reduced by reducing the brake pressure to recover the slip of the wheel that has converged to the target. It is possible.

In addition to the above, the matters discussed in (c) at the beginning of the specification can be satisfactorily eliminated at the same time. FIG.
In the case of the comparative example of No. 4, even during braking from the same right turn, the target is switched periodically at a predetermined time, and the wheels for changing the target are rear wheels next to the front wheels as shown in the figure. According to the example shown in FIG. 14, the front wheel right wheel speed (solid line) and the rear wheel right wheel speed (bold line dashed line) also change as shown in FIG. The effect of the vehicle behavior is large, and at the same time, the reduction of the W / C pressure of the front left and right wheels and the rear left and right wheels to be changed when the target is changed is also large. At this point, the deceleration also decreases. It is big.

On the other hand, in the case of this control example of FIG.
Such a situation is also avoided, and the wheel speed convergence state determination (steps S113 and S21) is performed during such right-turn braking.
According to 3), the target slip ratio is changed to a shallower one. The wheels targeted for the target slip ratio change are:
As described above, and as shown in the figure, the right rear wheel, which is the inner wheel after turning selected based on the determination of the convergence state of the wheel speed, is the next target. Even if the target slip ratio is changed to change the slip ratio to a shallower one, the rear wheel is right (therefore, it is not a mode in which the front wheel and the rear wheel are alternately performed alternately at a predetermined cycle). Thus, the correction of the downward deviation of the estimated wheel speed is performed at each timing, and at this time, the disturbance of the yaw rate is not large, and at the same time, the estimation of the vehicle speed at the right of the rear wheel, which is the inner wheel after turning, is performed. It can be seen that the reduction in the W / C pressure for correction is also small. Thus, according to this, it is possible to improve the braking deceleration by converging the wheel speed to the target wheel speed, and to improve the anti-skid control performance by estimating the vehicle speed with high accuracy. To be compatible.

Further, as shown in FIG. 13, as shown in the first half, even in the case of upward displacement, the deviation of the estimated vehicle body speed can be corrected. Here, FIG. 13 also shows an example of the case where the downward shift correction of the estimated vehicle body speed as in the case of FIG. 12 is performed at the latter half of the timing. FIG. 13 is similar to FIG. 15 as a comparative example.
The situation of the braking control from the right turn is compared as an example. Furthermore, changes in various amounts such as the wheel speed and the vehicle speed in the case of the present control example are shown, and the actual vehicle speed (broken line) with respect to the vehicle speed and the estimated vehicle speed and the wheel speed before turning with the solid line are shown. The transition of the front wheel left wheel speed (solid line) as the outer wheel, the rear wheel right wheel speed (bold dashed line) as the inner wheel after turning, and the target wheel speed of the front left wheel (thin dashed line) are shown. .

Further, here, the target slip ratio change processing for the rear right wheel based on the judgment of the wheel speed convergence state during the anti-skid control operation (the target slip ratio of at least one wheel according to the judgment of the wheel speed convergence state). Target slip ratio changing process for changing the vehicle speed to a shallower one) a target change flag 1 to be applied, and a target slip ratio changing process for the other three wheels other than the right rear wheel based on the determination of the estimated vehicle speed deviation (the estimated vehicle speed deviation) The target change flag 2 applied in the target slip ratio changing process of changing the target slip ratio to a deeper one according to the determination, and the change transition of the wheel cylinder pressures (W / C pressures) of the front, rear, left, and right wheels are shown. ing.

According to this, it is understood that the matters discussed in (d) at the beginning of the specification can be satisfactorily eliminated at the same time. FIG.
In the case of the comparative example of No. 5, when "upward" of the estimated vehicle speed occurs, the anti-skid control erroneously determines that the wheel is in braking slip, and reduces the brake fluid pressure, resulting in insufficient braking force. Will occur.

On the other hand, in the case of the present control example in FIG.
In addition to the response of the estimated vehicle speed to "downshift", the case where the estimated vehicle speed deviates to the larger side is also considered, and the "upward" of the estimated vehicle speed is corrected in the first half of the figure. Also, in the latter half, the downward shift of the estimated vehicle body speed is corrected by the same operation as in FIG. Therefore, it can be understood that the deviation of the estimated vehicle speed can be corrected in both cases of the upward deviation and the downward deviation of the estimated wheel speed. Therefore, as compared with the case in FIG. 15 in which the braking force is insufficient due to the upward displacement, the pressure reduction in the shaded zone of the W / C pressure of each wheel in FIG. 13 can be prevented well. It is possible to prevent shortage of braking force. Therefore, it is possible to effectively cope with an upward deviation and a downward deviation of the estimated vehicle body speed, improve the braking deceleration by converging the wheel speed to the target wheel speed, and estimate the vehicle body speed with high accuracy. This shows that the anti-skid control performance can be improved.

Note that the present invention is not limited to the above embodiment. For example, in the embodiment, the vehicle to be applied is a rear wheel drive vehicle (AT vehicle, vehicle equipped with a Convedev), but is not limited to this. In addition, the front and rear wheels are 4-channel ABS that can control the left and right brake pressures independently.
However, the present invention is not limited to the three-channel brake system in which the left and right front wheels are independently controlled and the rear two wheels are commonly controlled.

[Brief description of the drawings]

FIG. 1 is a diagram showing a basic conceptual diagram of the present invention.

FIG. 2 is a system diagram showing a configuration of an embodiment of the present invention.

FIG. 3 is a view showing the configuration of the embodiment, and showing an example of an applicable pressure control unit.

FIG. 4 is a functional block diagram illustrating an example of a basic configuration of control contents.

FIG. 5 is a flowchart illustrating an example of a control program executed by a controller.

FIG. 6 is a diagram illustrating an example of a characteristic used for explaining road surface μ peak determination;

FIG. 7 is a diagram also provided for a similar description.

FIG. 8 is a diagram showing an example of a characteristic used for explaining a correction amount calculation of a vehicle body speed change amount.

FIG. 9 is a diagram showing an example of a characteristic used for explaining a valve driving time calculation.

FIG. 10 is a characteristic diagram for the same explanation.

FIG. 11 is a diagram that is also used for the same description and shows an example of a calculation method.

FIG. 12 is a diagram showing a time-series graph used for explaining control contents, and showing an example thereof.

FIG. 13 is a diagram showing a time-series graph for explaining control contents, which is another example.

FIG. 14 is an example of a time series graph in a comparative example, shown in comparison with FIG.

FIG. 15 is an example of a time series graph in a comparative example, shown in comparison with FIG.

FIG. 16 is a functional block diagram showing another embodiment of the present invention and showing an example of a basic configuration thereof.

FIG. 17 is a flowchart showing an example of the control program.

FIG. 18 is a diagram showing changes in wheel speed, actual vehicle speed, and the like in general anti-skid control.

FIG. 19 is a diagram provided for describing an effect of a deviation in estimated vehicle body speed.

[Explanation of symbols]

Reference Signs List 1 brake pedal 2 booster 3 reservoir 4 master cylinder 5 pressure control unit (pressure servo unit) 6 longitudinal / lateral acceleration sensor 7 yaw rate sensor 10, 20, 30, 40 left front wheel, right front wheel, left rear wheel, right rear wheel 11, 21, 31, 41 Brake discs 12, 22, 32, 42 Wheel cylinders 13, 23, 33, 43 Wheel speed sensors 14, 24, 34, 44 Pressure increasing valves (control valves) 15, 25, 35, 45 Pressure reducing valves (control Valve) 16, 17 Reservoir 26, 27 Pump 36 Motor 50 Controller 51 Engine control controller 52 AT control controller

Claims (11)

[Claims] 1. An anti-skid control device including an anti-skid control unit for controlling a brake pressure of each wheel so that a wheel speed becomes a target wheel speed calculated from a vehicle speed, wherein an estimated vehicle speed is larger. Vehicle speed estimation deviation determining means for estimating that the vehicle body speed is incorrect, and estimated vehicle speed change amount correcting means for performing correction so as to increase the amount of change of the vehicle body estimated value in accordance with the determination by the vehicle speed estimation deviation determining means. And an anti-skid control device. 2. A road surface friction coefficient estimating means for estimating a road surface friction coefficient, and a vehicle speed estimating means for estimating a vehicle speed using a road surface friction coefficient of each wheel estimated by the road surface friction coefficient estimating means. An anti-skid control device that sets a target wheel speed for each wheel based on the vehicle speed estimated by the vehicle speed estimation means, and controls a brake pressure of each wheel so that each wheel speed converges to its target value. A wheel speed convergence state determining means for determining a convergence state of each wheel to a target wheel speed; a vehicle speed estimation deviation determining means for estimating that the estimation of the vehicle body speed is erroneous to a larger one; Target slip ratio changing means for changing the target slip ratio of at least one wheel to a shallower one in accordance with the judgment of the convergence state judging means; and increasing the change amount of the estimated vehicle body speed value in accordance with the judgment of the vehicle speed estimation deviation judging means. Make corrections And an estimated vehicle speed change amount correcting means. 3. The vehicle speed estimation deviation determining means determines the deviation of the vehicle speed estimation according to the time until the wheel speed of the wheel whose target slip ratio has been changed shallowly by the target slip ratio changing device follows the target. The anti-skid control device according to claim 2, wherein: 4. The estimated vehicle speed change amount correction means changes the offset amount added to the vehicle body speed change amount calculated from the road surface friction coefficient of each wheel estimated by the road surface friction coefficient estimation means to a larger one. 4. The anti-skid control device according to claim 1, wherein the estimated vehicle speed change amount is corrected by: 5. The estimated vehicle speed change amount correction means changes an offset amount to be added to the vehicle body speed change amount after the end of the deviation determination according to the time during which the deviation determination is made by the estimated vehicle speed deviation deviation determination means. The anti-skid control device according to any one of claims 1 to 3, wherein the estimated vehicle speed change amount is corrected. 6. The target slip ratio changing means selects a wheel having the least effect on vehicle behavior when changing a slip state of a wheel based on a detection value of a vehicle running state detecting means for detecting a vehicle running state. The anti-skid control device according to any one of claims 2 to 5, wherein a slip ratio of a wheel selected by the wheel selecting means is changed. 7. The convergence state judging means judges the convergence state in accordance with a time when all wheel speeds are smaller than a convergence judgment wheel speed threshold different from the target wheel speed. The anti-skid control device according to any one of claims 2 to 6, characterized in that: 8. The target slip ratio changing means, when the target slip ratio is changed to a shallower one, holds the target slip ratio in a shallow state until the wheel speed of the wheel follows the target. The anti-skid control device according to any one of claims 2 to 7, wherein the anti-skid control device returns to a target slip ratio. 9. The road surface friction coefficient estimating means includes: a wheel acceleration calculated from a wheel speed detected by a wheel speed detecting means of each wheel; a wheel load detected by a wheel load detecting means of each wheel; From the brake fluid pressure estimated by the wheel brake fluid pressure estimating means, and, for the drive wheels, from these, and from the driving torque further estimated by the driving torque estimating means,
The anti-skid control device according to claim 2, wherein a road surface friction coefficient is calculated. 10. A road surface friction coefficient estimating means for estimating a road surface friction coefficient, and a vehicle body speed estimating means for estimating a vehicle speed using a road surface friction coefficient of each wheel estimated by the road surface friction coefficient estimating means. An anti-skid control device that sets a target wheel speed for each wheel based on the vehicle speed estimated by the vehicle speed estimation means, and controls a brake pressure of each wheel so that each wheel speed converges to its target value. A wheel speed convergence state determining means for determining a convergence state of each wheel to a target wheel speed; a vehicle speed estimation deviation determining means for estimating that the estimation of the vehicle body speed is erroneous to a larger one; Target slip rate changing means for changing the target slip rate of at least one wheel to a shallower one according to the judgment of the judging means, and changing the target slip rate to a deeper one according to the judgment of the vehicle speed estimation deviation judging means; Including Anti-skid control apparatus according to claim. 11. The target slip ratio changing means, when the target slip ratio of at least one wheel is changed to a shallower one according to the judgment of the wheel speed convergence state judgment means,
When changing the target slip rate to a deeper one in accordance with the determination of the vehicle body speed estimation deviation determining means, only the wheels other than the wheels for which the target slip rate has been changed to the shallower one, change the target slip rate to the deeper one; The anti-skid control device according to claim 10, wherein: