JPH07329755A - Anti-skid control device - Google Patents

Abstract

PURPOSE:To provide a anti-skid control device capable of preventing the lowering of the reliability of an assumed road surface frictional coefficient. CONSTITUTION:When a speed difference of DELTAV1 or more is present between a rear wheel speed VWR and a front wheel speed VWF (after time t1), the calculation of assumed road surface frictional coefficient mu is already completed when the DELTAV1 is reached. Namely, its duration, i.e., the counted value by a timer counter TKeep is a duration (after time t1) passed after the road surface frictional coefficient is assumed lastly. Thus, when the duration is a specified time T2 or longer, even if the counted value is a proper assumed road surface frictional coefficient mu when it is calculated at a time t1, a long time is passed before it is used fox anti-skid control. Therefore a road surface frictional coefficient muS as a predetermined fixed value is set in place of the road surface frictional coefficient mu when a specified time T2 is continued (at the time t2). Thus an anti-skid control on safe side is assured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anti-skid control device, and more particularly to an anti-skid control device considering the reliability of an estimated road surface friction coefficient.

[0002]

2. Description of the Related Art An anti-skid control device is known which controls the braking pressure of an automobile or the like so as to shorten the braking distance. The adjustment of the brake pressure can be performed as follows. That is, as in Japanese Patent Application No. 5-310457 filed by the present applicant, before the anti-skid control is started, the road surface friction is changed based on the deceleration of the wheel with the smaller deceleration from the change in the front-rear wheel speed difference. The coefficient is estimated, and after the start of the anti-skid control, the brake pressure of each wheel is controlled based on the road surface friction coefficient so that the slip state or the deceleration becomes a suitable state.

As described above, the road surface friction coefficient, which is estimated immediately before entering the antiskid control, is used as the most important parameter for the antiskid control such as the estimated vehicle speed during the antiskid control. Therefore, when the reliability of the estimated road surface friction coefficient is low, an inconvenient value is set for the estimated vehicle body speed and the like, and there is a possibility that the control will not be performed appropriately.

As an anti-skid control device in consideration of the case where the reliability of the estimated road surface friction coefficient is lowered, JP-A-3-2
No. 58649 is proposed. This device assumes that the road surface friction coefficient calculated when spin or drift occurs is unreliable, and further reduces the road surface friction coefficient calculated immediately before spin or drift occurs to reduce the anti-skid control. It is used as an estimated road friction coefficient.

[0005]

However, not only the road surface friction coefficient calculated when the vehicle is running abnormally, but also the estimated road surface friction coefficient is calculated when the running state is not abnormal. However, the above-mentioned conventional techniques cannot deal with this case.

That is, even if the road surface friction coefficient is properly estimated in a normal vehicle traveling state, the road surface state may change before the anti-skid control is performed according to the estimated road surface friction coefficient. For example, if there is loose braking in the turning circuit, or if there is loose braking when the tire diameter of the front wheels is different from that of the rear wheels, there will be a speed difference between the front and rear wheels, and There may be a long-term transition until the start of anti-skid control with almost no change. In such a case, the road surface friction coefficient is estimated once there is a gentle deceleration, but thereafter there is no chance of re-estimation for a long time until the anti-skid control. For this reason, there is a high possibility that the actual road surface friction coefficient changes between the road surface friction coefficient estimation and the start of the anti-skid control. If there is a change in the road surface friction coefficient, even if the accurate road surface friction coefficient is estimated at the time of estimation, as a result, the antiskid control must be performed with an inaccurate road surface friction coefficient. That is, the reliability of the estimated road surface friction coefficient decreases.

In addition, as another case of reliability deterioration during normal running, when braking is applied immediately while accelerating the vehicle, there is already a difference in wheel speed between the driving wheels and the driven wheels during acceleration before braking. Is occurring. In such a state, deceleration from almost the same wheel speed state gradually decelerates the wheel speeds, and assuming that the front and rear wheels have a speed difference equal to or greater than a predetermined speed difference, When the method of estimating the road surface friction coefficient based on the wheel deceleration was adopted, the road surface friction coefficient estimation was unreliable. That is, when shifting from the acceleration state to the deceleration state, there is already a speed difference between the wheels during acceleration, so the road surface friction coefficient can be estimated immediately from the deceleration of the wheel with the smaller deceleration without delay. become.

However, when the road surface friction coefficient is immediately estimated in this manner, unlike the normal estimation, the wheel speed on the side with a smaller deceleration is reached before the wheel speed reaches the deceleration corresponding to the road surface friction coefficient. Since the road surface friction coefficient is estimated by deceleration, the estimated road surface friction coefficient becomes too low and a reliable estimated road surface friction coefficient cannot be obtained.

The present invention provides an anti-skid control device capable of coping with the decrease in reliability of the estimated road surface friction coefficient as described above.

[0010]

The invention according to claim 1 is
As illustrated in FIG. 1, before starting the anti-skid control,
The road surface friction coefficient is estimated based on changes in the wheel speeds of a plurality of wheels, and after the anti-skid control is started, the slip state or deceleration of the control target wheel is set to a suitable state based on the road surface friction coefficient. In the anti-skid control device for controlling the brake pressure of the control target wheel, in the state before the start of the anti-skid control, an estimated post-elapse time measuring means for measuring the time since the road surface friction coefficient was last estimated, When the time measured by the post-estimation elapsed time measuring means is a predetermined time or more, as the road surface friction coefficient used after the start of the anti-skid control, a predetermined road surface friction coefficient is set instead of the estimated road surface friction coefficient. And a predetermined road surface friction coefficient switching means for controlling the anti-skid control device.

According to the second aspect of the present invention, as illustrated in FIG. 2, before the antiskid control is started, the road surface friction coefficient is estimated based on the change in the speed difference between the front and rear wheels, and the antiskid control is started. After that, based on the road surface friction coefficient, in an anti-skid control device that controls the brake pressure of the control target wheel so that the slip state or deceleration of the control target wheel becomes a suitable state, the front and rear wheel speed difference A speed difference determining means for determining whether or not a speed difference equal to or more than a predetermined value exists, and a speed for measuring the duration time during which the speed difference is equal to or more than the predetermined value by the speed difference determining means before starting the anti-skid control. The road surface used after the start of the anti-skid control when the duration measured by the speed difference duration measuring means and the speed difference duration measuring means is a predetermined time or more. As friction coefficient, a anti-skid control device, characterized in that it and a predetermined road surface friction coefficient switching means for setting a predetermined road surface friction coefficient, instead of the estimated road surface friction coefficient.

According to the third aspect of the present invention, as illustrated in FIG. 3, the road surface friction coefficient is estimated based on changes in the wheel speeds of a plurality of wheels before the start of the antiskid control, and after the start of the antiskid control, Based on the road surface friction coefficient, in an anti-skid control device that controls the brake pressure of the controlled wheel so that the slip state or deceleration of the controlled wheel is in a suitable state, before the anti-skid control starts, the wheel Anti-skid control starts when the wheel speed change determination means determines whether the speed has switched from the accelerated state to the decelerated state and the wheel speed change determination means determines that the wheel speed has switched from the accelerated state to the decelerated state. As the road friction coefficient used later, set a predetermined road friction coefficient instead of the above estimated road friction coefficient. A predetermined road surface friction coefficient switching unit that,
An anti-skid control device comprising:

According to a fourth aspect of the present invention, as illustrated in FIG. 4, the road surface friction coefficient is estimated based on changes in wheel speeds of a plurality of wheels before the start of the antiskid control, and after the start of the antiskid control, Based on the road surface friction coefficient, in an anti-skid control device that controls the brake pressure of the controlled wheel so that the slip state or deceleration of the controlled wheel is in a suitable state, before the anti-skid control starts, the wheel Acceleration duration determination means for determining whether or not the speed is in the acceleration state for a predetermined time or longer, and whether or not the wheel speed has been switched from the acceleration state to the deceleration state before starting the anti-skid control. The wheel speed change judging means and the acceleration continuation time judging means judge that the wheel speed is in the acceleration state for a predetermined time or more. When the wheel speed change detection means determines that the wheel speed has switched from the acceleration state to the deceleration state, the road surface friction coefficient used after the start of the anti-skid control is set in advance instead of the estimated road surface friction coefficient. An anti-skid control device comprising: a predetermined road surface friction coefficient switching means for setting a road surface friction coefficient.

The invention according to claim 5 is the anti-skid control device according to claim 3 or 4, further comprising the post-estimation elapsed time measuring means and the predetermined road surface friction coefficient switching means according to claim 1. The invention according to claim 6 is further provided with the speed difference determination means, speed difference duration measuring means and predetermined road surface friction coefficient switching means according to claim 2.
The described anti-skid control device.

According to a seventh aspect of the present invention, the predetermined road surface friction coefficient switching means uses a road surface friction coefficient obtained by correcting the estimated road surface friction coefficient in a high friction direction as a road surface friction coefficient used after the start of anti-skid control. Claim 1 to set
It is an anti-skid control device in any one of-6.

[0016]

According to the first aspect of the invention, the road surface friction coefficient is finally estimated in the state before the antiskid control is started by the predetermined road surface friction coefficient switching means measured by the post-estimation elapsed time measuring means. When the elapsed time is equal to or longer than a predetermined time, a predetermined road surface friction coefficient is set instead of the estimated road surface friction coefficient as the road surface friction coefficient used after the start of the anti-skid control.

That is, the road surface friction coefficient once estimated is
Even if it is an appropriate estimated road surface friction coefficient, if a long time elapses before it is used for anti-skid control, it is highly possible that the road surface state has changed, and the estimated road surface friction coefficient is If used as is, proper anti-skid control may not be performed. It is not possible to use the estimated road surface friction coefficient with low reliability for subsequent anti-skid control.Therefore, by setting a predetermined road surface friction coefficient instead of the road surface friction coefficient, It guarantees anti-skid control in the. In this way, it is possible to cope with the decrease in reliability of the estimated road surface friction coefficient.

According to a second aspect of the present invention, the speed difference continuation time measuring means determines, before the start of the anti-skid control, the continuation time in which the front and rear wheel speed difference has a predetermined speed difference or more by the speed difference determining means. Measured, the predetermined road surface friction coefficient switching means, when the duration measured by the speed difference duration measuring means is a predetermined time or more, as the road surface friction coefficient used after the start of anti-skid control, the estimated road surface friction coefficient Instead, a predetermined road friction coefficient is set.

If there is a speed difference of a predetermined value or more between the front wheel speed and the rear wheel speed before starting the anti-skid control, the estimated road surface friction coefficient is already calculated when the speed difference is reached. It is shown that. That is, the duration is the duration since the road surface friction coefficient was last estimated. Therefore, if the duration is equal to or longer than the predetermined time, as described above, even if it is an appropriate estimated road surface friction coefficient, since a long time has elapsed before it is used for anti-skid control, the road surface The state is likely to have changed, and if the estimated road surface friction coefficient is used as it is, appropriate anti-skid control may not be performed. It is not possible to use the estimated road surface friction coefficient with low reliability for subsequent anti-skid control.Therefore, by setting a predetermined road surface friction coefficient instead of the road surface friction coefficient, It guarantees anti-skid control in the. In this way, it is possible to cope with the decrease in reliability of the estimated road surface friction coefficient.

According to a third aspect of the present invention, when the predetermined road surface friction coefficient switching means determines that the wheel speed has changed from the accelerating state to the decelerating state by the wheel speed change detecting means, the road surface used after the start of the anti-skid control. As the friction coefficient, a predetermined road surface friction coefficient is set instead of the estimated road surface friction coefficient.

If there is an acceleration state before the anti-skid control, there is a high possibility that a certain speed difference has already occurred between the driving wheel and the driven wheel. Therefore, when shifting from this acceleration state to the deceleration state, it is highly possible that the speed difference between the front wheel speed and the rear wheel speed has already become equal to or greater than the predetermined speed difference at the start of deceleration, and as described above, the road surface friction coefficient is The road surface friction coefficient is estimated from the deceleration of the wheel on the side where the deceleration is small, while the deceleration is not sufficiently reflected. Therefore, the estimated road surface friction coefficient becomes unreliable. Therefore, by setting a predetermined road surface friction coefficient instead of the road surface friction coefficient, antiskid control on the safe side is guaranteed. In this way, it is possible to cope with the decrease in reliability of the estimated road surface friction coefficient.

According to a fourth aspect of the present invention, in addition to the structure of the third aspect, an acceleration continuation time determination means is further provided, and the time during which the wheel speed is in the acceleration state before the start of the anti-skid control is a predetermined time or more. Determine whether it is continuing. In the predetermined road surface friction coefficient switching means, the acceleration duration determination means determines that the wheel speed is in the accelerated state for a predetermined time or longer, and the wheel speed change detection means decelerates the wheel speed from the accelerated state. When it is determined that the state is switched to the state, a predetermined road surface friction coefficient is set as the road surface friction coefficient used after the start of the anti-skid control, instead of the estimated road surface friction coefficient.

That is, if the duration of the acceleration state is equal to or longer than the predetermined time, it is considered that the wheel speed difference between the driving wheel and the driven wheel is sufficiently large. Therefore, when shifting from this acceleration state to the deceleration state, it is quite likely that the speed difference between the front wheel speed and the rear wheel speed has already become equal to or greater than the predetermined speed difference at the start of deceleration. Before the coefficient is sufficiently reflected in the deceleration, the road surface friction coefficient is estimated from the deceleration of the wheel on the smaller deceleration side. Therefore, the estimated road surface friction coefficient becomes unreliable. Therefore, by setting a predetermined road surface friction coefficient instead of the road surface friction coefficient, antiskid control on the safe side is guaranteed. In this way, it is possible to cope with the decrease in reliability of the estimated road surface friction coefficient.

Incidentally, the post-estimation elapsed time measuring means and the predetermined road surface friction coefficient switching means according to claim 1 may be combined with the anti-skid control device according to claim 3 or 4. Further, the speed difference determining means, the speed difference duration measuring means, and the predetermined road surface friction coefficient switching means according to claim 2 may be combined with the antiskid control device according to claim 3 or 4. With this arrangement, the actions of the above-mentioned claims are combined, and it is possible to cope with a decrease in the reliability of the estimated road surface friction coefficient in a wider range and to further ensure the antiskid control on the safe side.

It is usually preferable to set the road surface friction coefficient higher than the estimated road surface friction coefficient as the above-mentioned predetermined road surface friction coefficient. That is, as the road surface friction coefficient used after the start of the anti-skid control, a road surface friction coefficient obtained by correcting the estimated road surface friction coefficient in the high friction direction may be used. This is because setting the brake pressure on the high side is on the safe side rather than low.

[0026]

EXAMPLE An example of the present invention is shown in FIG. Figure 5
FIG. 1 is a configuration diagram showing a configuration of an anti-skid control device as an embodiment of the present invention. In FIG. 5, the brake pedal 20 is connected to the master cylinder 28 via a vacuum booster 21. Therefore, the brake pedal 2
By stepping on 0, hydraulic pressure is generated in the master cylinder 28, and this hydraulic pressure is applied to the wheel cylinders 31, 32, 33 provided on each wheel (left front wheel FL, right front wheel FR, left rear wheel RL, right rear wheel RR). , 34, and brake pressure is generated.

The master cylinder 28 has two pressure chambers (not shown) which generate brake hydraulic pressures of the same pressure, and supply pipes 40 and 50 are connected to the respective pressure chambers. The supply pipe 40 is branched into communication pipes 41 and 42. The communication pipe 41 is connected to the brake pipe 43 communicating with the wheel cylinder 31 via the solenoid valve 60a. Similarly, the communication pipe 42 is connected to the brake pipe 44 that communicates with the wheel cylinder 34 via the electromagnetic valve 60c.

The supply pipe 50 also has a connection relationship similar to that of the supply pipe 40 and is branched into communication pipes 51 and 52. Communication pipe 51
Is connected to a brake pipe 53 communicating with the wheel cylinder 32 via an electromagnetic valve 60b. Similarly, the communication pipe 52 is connected to the wheel cylinder 33 via the solenoid valve 60d.
Is connected to a brake pipe 54 communicating with the.

Further, known proportioning valves 59, 49 are installed in the brake pipes 54, 44 connected to the wheel cylinders 33, 34. The proportioning valves 59 and 49 control the brake hydraulic pressure supplied to the rear wheels RL and RR to make the distribution of the braking force of the front and rear wheels FL to RR close to ideal.

An electromagnetic pickup type wheel speed sensor 7 is provided on each of the wheels FL to RR to capture the rotational speed of the wheel.
1, 72, 73, 74 are installed and an electronic control circuit (EC
The signal is input to (U) 80. The ECU 80 outputs a drive signal to the solenoid valves 60a to 60d so as to control the brake hydraulic pressure of each wheel cylinder 31 to 34 based on the input wheel speed of each wheel FL to RR.

Solenoid valves 60a, 60b, 60c, 60d
Is a 3-port 3-position solenoid valve, and at the position A in FIG. 5, the communication pipes 41, 42, 51, 52 and the brake pipe 43,
44, 53, 54, respectively, and at the B position, the communication pipes 41, 42, 51, 52, the brake pipe 43,
All of 44, 53, 54 and branch pipes 47, 48, 57, 58 are shut off. In the C position, the brake pipe 4
3,44,53,54 and branch pipes 47,48,57,58
And communicate with each other.

The branch pipes 47 and 48 are both connected to the discharge pipe 81, and the branch pipes 57 and 58 are both connected to the discharge pipe 91. These discharge pipes 81 and 91 are respectively connected to the reservoir 93.
a, 93b. Reservoirs 93a, 93b
Is for temporarily storing the brake fluid discharged from the wheel cylinders 31 to 34 when the solenoid valves 60a to 60d are in the C position. Therefore, the solenoid valves 60a-60d
Then, the brake hydraulic pressure of the wheel cylinders 31 to 34 can be increased at the A position, the brake hydraulic pressure can be maintained at the B position, and the brake hydraulic pressure can be reduced at the C position.

The pumps 99a and 99b are provided with a reservoir 93.
The brake fluid accumulated in a and 93b is pumped up and returned to the master cylinder 28 side. Also, check valve 97
a, 98a, 97b, 98b are reservoirs 93a, 93
The brake fluid pumped up from b is returned to the reservoir 93 again.
This is to prevent backflow to the a and 93b sides.

The stop switch 10 detects whether or not the driver depresses the brake pedal 20. Next, the anti-skid control executed by the ECU 80 in the present embodiment configured as described above will be described with reference to FIG.
It will be described based on the following flowchart. ECU80
Is a well-known CP configured as a microcomputer.
It is equipped with U, ROM, RAM, and I / O. A program for executing anti-skid control is stored in the ROM.

The processing by this program is executed when an ignition switch (not shown) is turned on.
First, as a predetermined initialization process, processes such as initializing variables on a memory used for calculation, zero-clearing various timer counters described later, or initial position setting of each device used for anti-skid control are performed ( Step 100). After this, it is judged whether or not the conditions for the anti-skid control are satisfied (step 110). When the wheel acceleration becomes smaller than a predetermined deceleration reference value and the wheel speed becomes smaller than a reference speed set based on the estimated vehicle body speed, it is determined that the antiskid control condition is satisfied.

If the condition is satisfied, the brake pressure control (step 120) is performed. Here, it is performed as follows. That is, when the wheel speed VW drops below a decompression reference speed set based on an estimated vehicle speed VB, which will be described later, and the wheel acceleration GW falls below a predetermined reference deceleration, the brake pressure on the wheels is reduced. Then, when the wheel acceleration GW returns to a predetermined range near 0 G (which varies depending on the road surface and the vehicle) by reducing the brake pressure, the brake pressure is maintained. After that, when the wheel speed VW is restored to the pressure increase reference speed set based on the estimated vehicle speed VB, the brake pressure is increased.

Next, the process of setting the estimated road surface friction coefficient, the limit deceleration gradient, etc. used in the brake pressure control of the anti-skid control will be described with reference to FIG.
First, when the process is started, the initial setting of the state is performed (step 200). Next, the output values of the wheel speed sensors 71 to 74 are read (step 210). The wheel speed VW and the wheel acceleration GW are calculated based on this value (step 220).

Next, the speed difference ΔV between the wheel speed VWR of the rear wheels and the wheel speed VWF of the front wheels is calculated as in the following equation 1 (step 222).

[0039]

[Equation 1]

Next, the estimated vehicle speed VB and its acceleration GB
Is required (step 230). This estimated vehicle speed V
B and the estimated vehicle acceleration GB are set to the maximum wheel speed VWMAX of the four wheel speeds VW obtained in step 220 and its acceleration GWMAX. Next, it is determined whether or not anti-skid control has been performed (step 240). This determination is affirmative in step 110 of FIG.
If 0 is being repeatedly executed, it is determined that anti-skid control has not been performed. If step 120 is not being repeatedly executed, it is determined that anti-skid control has not been performed.

If anti-skid control has not been performed, that is, if anti-skid control is in progress, a timer counter TKeep, which will be described later, is cleared to zero (step 242), and the process returns to step 210. Before the anti-skid control, it is determined whether the speed difference ΔV between the wheel speed VWR of the rear wheels and the wheel speed VWF of the front wheels obtained in step 222 is equal to or more than a predetermined value ΔV1 (step 250). If the speed difference ΔV is less than the predetermined value ΔV1, the timer counter TKeep is cleared to zero (step 260), and then the estimated road surface friction coefficient μ is calculated (step 270). Here, the estimated road surface friction coefficient μ is obtained from the deceleration of the front and rear wheels having the smaller deceleration.

Next, based on the estimated road surface friction coefficient μ, the limit deceleration gradient VDOWN is set by a predetermined function f (μ) (step 290). That is, the limit deceleration gradient VDOWN indicates the maximum deceleration of the vehicle (the vehicle body speed descending gradient) obtained when the road surface actually has the same friction coefficient as the estimated road surface friction coefficient μ. It is set according to the magnitude of the road surface friction coefficient μ, and it means that the vehicle cannot decelerate at a deceleration higher than this. Actually, in step 290, a predetermined correction value μ1 is further added to the estimated road surface friction coefficient μ and calculation is performed by a predetermined function f (μ + μ1) to increase the brake pressure and to make the antiskid control safer. Have control.

After this, the process from step 210 is repeated again. If an affirmative decision is made in step 250,
The timer counter TKeep is counted up (step 300). Since this processing is repeated at a predetermined cycle, the timer counter TKeep counts up, and
The duration of the state of V ≧ ΔV1 can be measured.
Next, the count value of the timer counter TKeep becomes the predetermined time T2.
It is determined whether or not the above (step 310). While the determination is negative, the routine proceeds to step 290, but when TKeep ≧ T2 is satisfied due to the count-up of the timer counter TKeep, the estimated road surface friction coefficient μ is set to the road surface friction coefficient μS as a fixed value. (Step 32
0). Thereafter, in step 290, the road surface friction coefficient μ
The limit deceleration gradient VDOWN is set based on S, and brake pressure control as anti-skid control (step 12
0).

As shown in the timing chart of FIG. 12, when there is a speed difference ΔV of a predetermined value ΔV1 or more between the rear wheel and the front wheel, which are the wheels on the smaller deceleration side (time t1
After that, the speed difference ΔV has already been reached (here, at time t1).
It indicates that the estimated road surface friction coefficient μ is calculated when the vehicle arrives at. The duration, that is, the timer counter T
The count value of Keep is the duration (after time t1) since the road surface friction coefficient was last estimated. Therefore, when the duration is equal to or longer than the predetermined time T2, as described above, even if the estimated road surface friction coefficient μ is appropriate when it is calculated in step 270, before it is used for anti-skid control. Since a long time has passed, the condition of the road surface is likely to have changed, and if the estimated road surface friction coefficient μ is used as it is, appropriate anti-skid control may not be performed. Since the estimated road surface friction coefficient μ whose reliability is low in this way cannot be used for the subsequent anti-skid control, when the predetermined time T2 is continued (time t2), the road surface friction coefficient μ is replaced in advance. By setting the road surface friction coefficient μS as a fixed value, the antiskid control on the safe side is guaranteed. It is preferable that the road surface friction coefficient μS be set between the intermediate value and the maximum value. As a result, it is difficult to reduce the pressure on the low friction road surface, that is, the braking force is easily applied, and it is possible to apply the braking force to some extent even on the high friction road surface. During this period, the estimated vehicle body speed VB has the critical deceleration gradient VDOWN increased at time t2 because the estimated road surface friction coefficient μ is changed to the road surface friction coefficient μS on the high friction coefficient side. Further, at this time t2, the estimated vehicle speed VB may be set to the maximum wheel speed (in this case, the rear wheel speed VWR).

In this embodiment, the reliability of the estimated road surface friction coefficient is reduced in this way. It should be noted that, in the above-described embodiment, in step 250, it is determined whether or not the speed difference ΔV between the wheel speed VWR of the rear wheels and the wheel speed VWF of the front wheels is equal to or greater than the predetermined value ΔV1, but instead of this, in FIG. Step 25
As shown in 2, the determination may be made based on whether or not the condition for estimating the road surface friction coefficient is satisfied. The condition for estimating the road surface friction coefficient is, for example, a condition in which the rear wheels are in a decelerating state, and the front wheels are decelerated at a greater deceleration than the deceleration of the rear wheels. If the condition for estimating the road surface friction coefficient is satisfied, the process proceeds to step 260, and if not, the process proceeds to step 300.

Thus, step 250 to step 25
With the configuration of 2, when the time TKeep since the road surface friction coefficient was last estimated in step 270 before the anti-skid control is started is the predetermined time T2 or more, the road surface friction used after the anti-skid control is started. As a coefficient, a predetermined road surface friction coefficient μS is set instead of the estimated road surface friction coefficient. That is, step 2
Even if the road surface friction coefficient estimated at 70 is an appropriate estimated road surface friction coefficient, it is possible that the road surface state has changed if a long time has passed before it is used for anti-skid control. Since the estimated road friction coefficient is used as it is, proper anti-skid control may not be performed. Since it is not possible to use the estimated road surface friction coefficient whose reliability is low for subsequent anti-skid control, setting a predetermined road surface friction coefficient μS in place of that road surface friction coefficient will improve safety. The anti-skid control on the side can be guaranteed. In this way, it is possible to cope with the decrease in reliability of the estimated road surface friction coefficient.

In step 320, the estimated road surface friction coefficient μ already set in step 270 may be corrected to a higher value instead of a fixed value. Another process in place of FIG. 7 is shown in the flowchart of FIG. Note that FIG.
The same processing as that of the above is denoted by the same reference numeral and the description thereof is omitted.

First, in the case where the anti-skid control has not been carried out, an affirmative decision is made in step 240, and the estimated road surface friction coefficient μ
Setting process (step 400) is performed. Details of the setting process (step 400) of the estimated road surface friction coefficient μ are shown in the flowchart of FIG. First, the above step 220
It is determined whether the front wheel acceleration GWF calculated in step S1 is greater than or equal to the predetermined acceleration G1 (step 410) and the rear wheel acceleration GWR is greater than or equal to the predetermined acceleration G1 (step 42).
0) is done. If the front wheel acceleration GWF and the rear wheel acceleration GWR are both equal to or greater than the predetermined acceleration G1, the timer counter TUP is incremented (step 43).
0). Next, it is determined whether the count value of the timer counter TUP is TUP ≧ T1 for a predetermined time T1 (step 44).
0), if TUP ≧ T1 is not satisfied, the process exits from step 400 and proceeds to step 500. GWF ≧ G1, GW
When R ≧ G1 continues to be TUP ≧ T1, the road surface friction coefficient μS is set as a predetermined fixed value for the estimated road surface friction coefficient μ (step 450).

If a negative determination is made in any of steps 410 and 420, the count value of the timer counter TUP is cleared to zero (step 460), and then the wheel speed VWR of the rear wheels calculated in step 222 and the front wheel are calculated. The speed difference ΔV from the wheel speed VWF is ΔV <with respect to the predetermined value ΔV2.
It is determined whether or not ΔV2 (step 470).
If ΔV <ΔV2 and a positive determination is made, the speed difference between the wheel speed VWR of the rear wheels and the wheel speed VWF of the front wheels is still small. Therefore, here, the estimated road surface friction coefficient μ from the deceleration of the wheel speed VWR of the rear wheels. Are calculated (step 480). After that, with anti-skid control not being performed, ΔV <ΔV
As long as it is 2, the estimated road surface friction coefficient μ is continuously calculated in step 480.

When the speed difference ΔV becomes equal to or larger than the predetermined value ΔV2, a negative determination is made in step 470 and the process immediately exits step 400, so that the estimated road surface friction coefficient μ is maintained. That is, when the estimated road surface friction coefficient μ is set to the road surface friction coefficient μS as a fixed value at the time of acceleration at the time of acceleration and then the deceleration is started, a certain speed difference between the front wheels and the rear wheels is already generated. Is usually present. Therefore, a negative determination is made in step 470, and step 400 is skipped without executing step 480. Therefore, the subsequent anti-skid control is performed in step 45.
It is executed based on the road surface friction coefficient μS as a fixed value set at 0.

If the vehicle is decelerated without accelerating, a negative determination is made in either step 410 or 420, and a determination is made in step 470 after step 460. The difference ΔV is usually less than the predetermined value ΔV2. Therefore, an affirmative determination is made in step 470, and the calculation of the normal estimated road surface friction coefficient μ is executed based on the deceleration of the wheel on the side where the deceleration is small.

That is, before the anti-skid control, it is judged whether the estimated road surface friction coefficient μ is the high road surface friction coefficient reference value μHi or more (step 500) and whether the estimated road surface friction coefficient μ is the low road surface friction coefficient reference value μLo or more. Determination of whether or not (step 51
0) is performed and when the estimated road surface friction coefficient μ ≧ μHi, the high deceleration setting value GHi is set in the limit deceleration gradient VDOWN (step 520), and when the estimated road surface friction coefficient μ <μHi and μ ≧ μLo Sets a medium deceleration set value GMed to the limit deceleration gradient VDOWN (step 530), and when the estimated road surface friction coefficient μ <μLo, sets a reduction speed set value GLo to the limit deceleration gradient VDOWN (step 540).

In this way, if the anti-skid control is started, a negative determination is made in step 240 thereafter, the timer counter TUP is cleared to zero (step 550), and the limit deceleration set in any one of steps 520, 530, 540. At the gradient VDOWN, anti-skid control, that is, brake pressure control of step 120 is executed.

As shown in the timing chart of FIG. 13, if the acceleration state is reached after the time t10 and the duration of the acceleration state is the predetermined time T1 or more (after the time t12),
It is considered that the wheel speed difference ΔV between the rear wheels and the front wheels is sufficiently large (here, it is ΔV2 or more after time t11). Therefore, the reliable estimated road surface friction coefficient μ cannot be calculated. Therefore, at time t12, by setting a predetermined road surface friction coefficient μS instead of the road surface friction coefficient, the anti-skid control performed after time t13 can be performed safely. It guarantees to the side. The present embodiment can thus cope with the decrease in reliability of the estimated road surface friction coefficient μ. Even in the decelerated state after acceleration, step 47
If it is determined that ΔV <ΔV2 at 0, step 4
An appropriate road surface friction coefficient can be estimated at 80.

During this period, the estimated wheel speed VB is at time t12.
When the road surface friction coefficient μS is set as the estimated road surface friction coefficient μ, the smaller wheel speed (in this case, the front wheel speed VW
F) is set. This is in consideration of slippage during acceleration, which sets an appropriate estimated vehicle body speed VB.

In the above embodiment, steps 430, 4
By omitting only 40 and 460, both steps 410 and 42
The step 450 may be executed immediately when the affirmative determination is made at 0. That is, even if the duration TUP of the acceleration state is not taken into consideration, the road surface friction coefficient μS as a fixed value is set to the estimated road surface friction coefficient μ only because the vehicle is in the acceleration state immediately before deceleration, that is, immediately before entering the anti-skid control. You can set it, and you can guarantee anti-skid control on the safe side.

Further, instead of step 470, it is judged whether or not step 450 is executed immediately before,
Step 480 may be executed when step 450 has not been executed immediately before. In this case, steps 430, 440, and 460 may be omitted as described above.

Another process in place of FIG. 10 is shown in the flowchart of FIG. First, it is determined whether the front and rear wheels are in a decelerating state (step 600). Unless the vehicle is in the deceleration state, the road surface friction coefficient cannot be estimated from the rotational speed of the wheels.
Exit 0 processing.

When the deceleration state is entered, an affirmative decision is made in step 600, and it is next decided whether or not the wheel speed difference ΔV between the front and rear wheels is less than a predetermined speed difference ΔV3. If it is less than the condition, the condition that the road surface friction coefficient can be estimated based on the deceleration GWMAX of the front and rear wheels where the speed difference ΔV is sufficiently small and the deceleration of the front and rear wheels is small is satisfied. The friction coefficient μ is calculated based on the deceleration GWMAX (step 630). Next, the flag F is set.
In step 620, as long as ΔV <ΔV3, the processes of steps 630 and 640 are executed, and then ΔV ≧ Δ
If it becomes V3, a negative determination is made in step 620, and then it is determined whether or not the flag F is set (step 650). If step 640 is executed at the initial stage of deceleration and flag F is set, step 400 is left as it is. That is, in the determinations in steps 500 and 510, the estimated road surface friction coefficient μ calculated based on the deceleration GWMAX of the wheel on the smaller deceleration side in step 630 is used. Skid control is executed.

If the flag F is not set in the determination in step 650, step 620 is executed at the initial stage of deceleration.
In step 650, a negative determination is made because the vehicle has transitioned to the deceleration state in the state where the affirmative determination is not made, that is, in the state where there is a speed difference of ΔV3 or more, and the estimated road surface friction coefficient μ is a fixed value. The friction coefficient μS is set (step 660).

Thus, at the start of deceleration, the speed difference ΔV between the wheel speed on the side with the smaller deceleration (here, the rear wheel wheel speed VWR) and the other wheel speed (here, the front wheel wheel speed VWF) is already present. When the speed difference is equal to or more than the predetermined speed difference V3, the estimated road surface friction coefficient μ calculated from GWMAX becomes unreliable. Therefore, by setting a predetermined road surface friction coefficient μS instead of the road surface friction coefficient, the antiskid control on the safety side is guaranteed. In this way, it is possible to cope with the decrease in reliability of the estimated road surface friction coefficient μ.

Step 290 in the process of FIG. 7 or FIG.
The process of FIG. 10 or 11 may be added immediately before.
By this combination, the operation of FIGS. 7 and 8 and FIG.
The effects of 1 are combined. This makes it possible to deal with both the case where a long time has passed from the road surface friction coefficient and the case where transition from acceleration to deceleration has occurred, and it is possible to cope with a decrease in reliability of the estimated road surface friction coefficient μ in a wider range. Anti-skid control on the safe side can be made more reliable.

In the above embodiment, steps 252 and 2
60 and 300 correspond to the process as the post-estimation elapsed time measuring means in claim 1, and steps 310 and 320 correspond to claim 1.
Corresponds to the processing as the predetermined road surface friction coefficient switching means.
In the above embodiment, step 250 corresponds to the processing as the speed difference determining means of claim 2, step 300 corresponds to the processing as the speed difference duration measuring means of claim 2, and steps 310 and 320 are claimed. This corresponds to the processing as the predetermined road surface friction coefficient switching means of 2.

In the above embodiment, step 600 corresponds to the processing as the wheel speed change determining means of claim 3,
Steps 650 and 660 correspond to the processing as the predetermined road surface friction coefficient switching means in claim 3. In the above-mentioned embodiment, steps 430 and 440 correspond to the processing as the acceleration duration determination means of claim 4, and steps 410 and 42
0 corresponds to the processing as the wheel speed change determining means in claim 4, and steps 450 and 470 correspond to the processing as the predetermined road surface friction coefficient switching means in claim 4.

[Brief description of drawings]

FIG. 1 is an exemplary diagram of a basic configuration of the invention of claim 1.

FIG. 2 is an exemplary diagram of a basic configuration of the invention of claim 2;

FIG. 3 is an exemplary diagram of a basic configuration of the invention of claim 3;

FIG. 4 is an exemplary diagram of a basic configuration of the invention of claim 4;

FIG. 5 is a configuration diagram of an embodiment of an anti-skid control device.

FIG. 6 is a flowchart of anti-skid control processing performed in the embodiment.

FIG. 7 is a flowchart of a setting process of an estimated road surface friction coefficient, a limit acceleration / deceleration gradient, etc., which is performed in the embodiment.

FIG. 8 is a partial flowchart in which a part of FIG. 7 is modified.

FIG. 9 is a flowchart of another example of the setting process of the estimated road surface friction coefficient, the limit acceleration / deceleration gradient, etc. performed in the embodiment.

FIG. 10 is a flowchart of an estimated road surface friction coefficient μ setting process in FIG. 9.

FIG. 11 is a flowchart of another example of the estimated road surface friction coefficient μ setting process in FIG. 9.

FIG. 12 is a timing chart corresponding to the flowchart of FIG.

13 is a timing chart corresponding to the flowchart in FIG.

[Explanation of symbols]

 20 ... Brake pedal 28 ... Master cylinder 31, 32, 33, 34 ... Wheel cylinder 60a, 60b, 60c, 60d ... Electromagnetic valve 71, 72, 73, 74 ... Wheel speed sensor 80 ... ECU

Claims (7)

[Claims] 1. A road surface friction coefficient is estimated based on changes in wheel speeds of a plurality of wheels before the anti-skid control is started, and after the anti-skid control is started, a slip of a control target wheel is performed based on the road surface friction coefficient. In the anti-skid control device that controls the brake pressure of the control target wheel so that the state or deceleration becomes a suitable state, in the state before the start of the anti-skid control, the road surface friction coefficient after the last estimation is performed. When the time measured by the post-estimation elapsed time measuring means for measuring time and the time measured by the post-estimation elapsed time measuring means is a predetermined time or more, as the road surface friction coefficient used after the start of anti-skid control, the estimated road surface friction A predetermined road surface friction coefficient switching means for setting a predetermined road surface friction coefficient instead of the coefficient; Head controller. 2. A road surface friction coefficient is estimated based on a change in a wheel speed difference between front and rear wheels before the start of anti-skid control, and after the anti-skid control is started, a wheel to be controlled is controlled based on the road surface friction coefficient. In an anti-skid control device that controls the brake pressure of the control target wheel so that the slip state or deceleration of No. 1 becomes a suitable state, it is determined whether or not there is a speed difference equal to or more than a predetermined value in the front and rear wheel speed difference. Speed difference determining means, speed difference continuation time measuring means for measuring the duration during which a speed difference of a predetermined value or more exists by the speed difference determining means before the start of the anti-skid control, and the speed difference duration measuring means. When the duration measured by the means is a predetermined time or more, the estimated road surface friction coefficient is used as the road surface friction coefficient used after the start of the anti-skid control. Antiskid control device characterized by and a predetermined road surface friction coefficient switching means for setting a predetermined road surface friction coefficient instead. 3. A road surface friction coefficient is estimated based on changes in wheel speeds of a plurality of wheels before the anti-skid control is started, and after the anti-skid control is started, slippage of wheels to be controlled is performed based on the road surface friction coefficient. In the anti-skid control device that controls the brake pressure of the control target wheel so that the state or deceleration becomes the appropriate state, whether the wheel speed has switched from the accelerating state to the decelerating state before the anti-skid control is started. When determining that the wheel speed change determining means and the wheel speed change detecting means determines that the wheel speed has switched from the acceleration state to the deceleration state, as the road surface friction coefficient used after the start of the anti-skid control,
An anti-skid control device, comprising: predetermined road surface friction coefficient switching means for setting a predetermined road surface friction coefficient instead of the estimated road surface friction coefficient. 4. A road surface friction coefficient is estimated based on changes in wheel speeds of a plurality of wheels before the anti-skid control is started, and after the anti-skid control is started, a slip of a control target wheel is performed based on the road surface friction coefficient. In the anti-skid control device that controls the brake pressure of the control target wheel so that the state or deceleration becomes the appropriate state, the time when the wheel speed is in the acceleration state continues for a predetermined time or more before the start of the anti-skid control. Acceleration duration determination means for determining whether or not the wheel speed change determination means for determining whether the wheel speed has switched from the acceleration state to the deceleration state before the start of the anti-skid control, and the acceleration duration time determination means It is determined that the wheel speed is in the accelerated state for a predetermined time or longer, and the wheel speed change detection means determines the wheel speed. When it is determined that the acceleration state has been switched to the deceleration state, a predetermined road surface friction coefficient is set instead of the estimated road surface friction coefficient as the road surface friction coefficient used after the start of the anti-skid control. An anti-skid control device comprising: 5. The post-estimation elapsed time measuring means and the predetermined road surface friction coefficient switching means according to claim 1, further comprising:
Or the anti-skid control device described in 4. 6. The anti-skid control device according to claim 3, further comprising a speed difference determination means, a speed difference duration measuring means, and a predetermined road surface friction coefficient switching means according to claim 2. 7. The predetermined road surface friction coefficient switching means, as a road surface friction coefficient used after the start of the anti-skid control,
The anti-skid control device according to any one of claims 1 to 6, wherein a road surface friction coefficient is set by correcting the estimated road surface friction coefficient in a high friction direction.