JP3221697B2 - Vehicle slip control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle slip control device provided with anti-skid control means for controlling wheel slip by controlling wheel brake pressure.

[0002]

2. Description of the Related Art Conventionally, as disclosed in Japanese Patent Application Laid-Open No. 57-130754, for example, during braking, an excessive brake pressure locks the wheels and slips, thereby impairing braking performance and directional stability. Anti-skid control is known in which the brake pressure of the wheels is controlled to appropriately control the slip ratio of the wheels in order to prevent the slipping. The brake pressure control is
Usually, a control phase such as a pressure increasing phase or a pressure decreasing phase is set, and the control is performed by appropriately increasing or decreasing the brake pressure based on the control phase.

In the above-described anti-skid control, various control thresholds (thresholds for judging a shift to each control phase) are usually determined according to road surface conditions in order to improve control accuracy. Then, transition to each control phase, that is, increase / decrease of the brake pressure is performed based on the control threshold value. However, the road surface condition, typically, the road surface friction coefficient (road surface μ) is estimated based on the wheel speed change state under the condition where the brake pressure is increased or decreased by the anti-skid control. Therefore, such an actual road surface condition cannot be known at the beginning of the control, and therefore, based on a control threshold value determined based on preset fixed road surface information (information on road surface conditions such as road surface μ). It is considered that control is performed (initial control stage), and thereafter control is performed based on a control threshold value determined based on actual road surface information obtained under anti-skid control (continuous control stage). .

[0004] In the initial control stage, even if the slip tendency is predicted from the wheel deceleration or the slip ratio, the slip condition may not be known because the road surface condition is not yet known or the brake pressure fluctuates greatly while the brake is being depressed. May become larger or smaller from now on, but it may not always be as expected.

On the other hand, in the above continuous control stage, the actual road surface condition can be referred to, or the brake pressure has already been depressed, and there is no fluctuation in the brake pressure due to the depressing of the brake. It is possible to predict the tendency of slipping to some extent from the speed and the slip rate.

[0006]

When the anti-skid control is performed separately in the initial control stage and the continuous control stage as described above, control thresholds such as a wheel deceleration threshold and a slip ratio threshold are set. If the values are uniformly set, that is, set to the same value in any control stage, the following problem occurs.

That is, in the anti-skid control,
Basically, it is desirable to perform anticipated control of predicting a slip tendency and increasing / decreasing and holding the brake pressure at an early stage because of good controllability. Therefore, the control threshold value is set to a value for such anticipated control. It is desirable. For example, taking the control threshold value when shifting to the depressurization phase because the slip increased in the holding phase as an example, the slip is not so large yet, but is set to a value that can be predicted that a large slip will occur in the future. It is desirable to do.

However, for example, if the control threshold value is set to such a value for anticipation control, appropriate anticipation control is performed in the above-described continuous control stage to improve controllability. Even if the expected control is performed with the threshold value, the slip does not always change as expected, and consequently there is a problem that the control is confused. If it is set to a value that decreases or holds the degree of expectation after confirming to some extent, that is, a value that reduces the degree of expectation, it is convenient in the initial control stage, but it is not possible to perform appropriate forecast control in the continuous control stage, and the controllability is reduced. There is a problem of lowering.

SUMMARY OF THE INVENTION In view of the above circumstances, it is an object of the present invention to provide a vehicle slip control device capable of realizing both reliable control in an initial control stage and appropriate expectation control in a continuous control stage.

[0010]

Means for Solving the Problems In order to achieve the above object, the present invention has the following configuration. That is, anti-skid control means for controlling wheel slip by controlling wheel brake pressure and estimating road surface information corresponding to an actual road surface based on wheel behavior under control, Is configured to selectively execute each control phase of the braking force holding phase, the pressure increasing phase, and the pressure reducing phase by comparing the wheel behavior with a predetermined control threshold value, and after the first pressure reduction from the control start. Until the braking force holding phase elapses, the control threshold value is determined based on preset fixed road surface information, and after passing the holding phase after the pressure reduction, a surface corresponding to the actual road surface is determined. A vehicle slip control device configured to determine the control threshold value based on information, wherein the anti-skid control means includes: The control threshold value when performing the brake pressure control based on the road surface information is smaller than the control threshold value when performing the brake pressure control based on the road surface information corresponding to the actual road surface. The configuration is such that the transition between phases is unlikely to occur. As described above, the transition of the control phase is less likely to occur in the initial control stage than in the continuous control stage, and the transition of the control phase is delayed.

According to the present invention, since the control threshold value in the initial control stage is set so as to be less likely to be shifted to the control phase than the control threshold value in the continuous control stage, the control threshold value is expected in the continuous control stage. The control can improve controllability, and in the initial control stage, it is necessary to fully observe how the slip changes and to increase and decrease the slip and maintain it securely to prevent confusion of control due to misunderstanding. Can be.

[0012]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic plan view of a vehicle provided with one embodiment of the present invention.

<Structure of Slip Control Apparatus> As shown in FIG. 1, in a vehicle equipped with this embodiment, left and right front wheels 1 and 2 are driven wheels, left and right rear wheels 3 and 4 are drive wheels, and an engine is provided. 5 is transmitted from the automatic transmission 6 to the left and right rear wheels 3, 4 via the propeller shaft 7, the differential device 8, and the left and right drive shafts 9, 10.

The wheels 1 to 4 have these wheels 1 to 4 respectively.
4 and the disks 11a to 14a rotating integrally with the disk 4 and receiving the braking pressure (brake pressure).
Brake devices 11 to 14 each including caliper 11b to 14b for braking the rotation of 14a are provided, and a brake control system 15 for controlling these brake devices 11 to 14 is provided.

The brake control system 15 includes a booster 17 for increasing the depression force of the brake pedal 16 by the driver,
A master cylinder 18 for generating a braking pressure according to the stepping force increased by the booster 17. The front-wheel braking pressure supply line 19 led from the master cylinder 18 is branched into two paths.
a, 19b are the brake devices 11, 1 on the left and right front wheels 1, 2.
2 are connected to the calipers 11b and 12b, respectively, and are connected to one of the lines 19 leading to the brake device 11 of the left front wheel 1.
a is an electromagnetic on-off valve 20a and an electromagnetic relief valve 20b
The first valve unit 20 is installed, and the other line 19b which leads to the brake device 12 of the right front wheel 2 is also provided.
Similarly to the first valve unit 20, the electromagnetic on-off valve 21
A second valve unit 21 including a and an electromagnetic relief valve 21b is provided.

On the other hand, like the first and second valve units 20, 21, an electromagnetic opening / closing valve 23a and an electromagnetic relief valve are connected to the rear wheel braking pressure supply line 22 led from the master cylinder 18. A third valve unit 23 comprising a valve 23b and a rear wheel braking pressure supply line 22
Are branched into two paths on the downstream side of the third valve unit 23, and the rear-branch braking pressure lines 22a and 22b are connected to the calipers of the brake devices 13 and 14 in the left and right rear wheels 3 and 4, respectively.
13b and 14b, respectively.

That is, the brake control system 15 in the present embodiment comprises a first channel for variably controlling the braking pressure of the brake device 11 on the left front wheel 1 by the operation of the first valve unit 20, and an operation of the second valve unit 21. The second channel for variably controlling the braking pressure of the brake device 12 on the right front wheel 2 and the two brake devices 13 on the left and right rear wheels 3 and 4 by the operation of the third valve unit 23
Fourteenth channels for variably controlling the braking pressure are provided, and the first to third channels are independently subjected to anti-skid control.

The brake control system 15 has the first
A control unit 24 as anti-skid control means for performing anti-skid control on the third channel.
A brake signal from a brake switch 25 for detecting ON / OFF of the vehicle and a wheel speed signal from a wheel speed sensor 26 to 29 for detecting a rotation speed of each wheel are input, and a braking pressure control according to these signals is performed. By outputting a signal to each of the first to third valve units 20, 21, and 23, anti-skid control for the slip of the left and right front wheels 1, 2 and the rear wheels 3, 4 is performed in parallel for each of the first to third channels. Do it. That is, based on the wheel speeds indicated by the wheel speed signals from the wheel speed sensors 26 to 29, the control unit 24 communicates with the on-off valves 20a, 21a, 23a in the first to third valve units 20, 21, and 23 and the reliefs. Valves 20b, 21b, 23b
Are controlled by duty control to apply a braking force to the front wheels 1 and 2 and the rear wheels 3 and 4 with the braking pressure according to the slip state. In addition, the first to third
Each relief valve 20b, 2 in the valve units 20, 21, 23
The brake oil discharged from 1b and 23b is returned to the reservoir tank 18a of the master cylinder 18 via a drain line (not shown).

In the anti-skid non-control state, the control unit 24 does not output a braking pressure control signal. Therefore, as shown in the figure, the relief valves 20b, 20b, 21b,
23b are held closed and the on-off valves 20a, 21a,
23a are held open, and the braking pressure generated in the master cylinder 18 in response to the depression force of the brake pedal 16 is applied to the braking devices 11 to
The braking force corresponding to the braking pressure is directly applied to each of the wheels 1 to 4.

<Outline of Anti-Skid Control> Next, an outline of anti-skid control performed by the control unit 24 will be described.

[F _ABS . F _LOK . F _CON ] In the following description, the anti-skid control flag F _ABS , the lock flag F _LOK , and the continuation control flag F _CON are used.

F _ABS indicates whether or not anti-skid control is being performed. F _ABS = 0 indicates non-control, and F _ABS = 1 indicates control. F _ABS is the F of any of the channels described below.
_It is set to 1 when _LOK is set to 1, and is reset to 0 when a predetermined anti-skid control end condition such as switching of the brake switch 25 from ON to OFF is satisfied.

F _LOK is set for each channel, and indicates whether the wheel of each channel has entered the locked state. F _LOK = 0 indicates an unlocked state, and F _LOK = 1 indicates a locked state. When it is determined that the wheel of each channel has entered the locked state based on a predetermined lock determination condition, _{FLOK of} that channel is set to 1. The lock determination will be described later. When it is determined that the wheel of each channel has entered the locked state, the anti-skid control is started for that channel. Therefore, when _{FLOK of} any channel is set to 1, F _ABS is set to 1 as described above.

It should be noted, F _LOK is set for each channel, thus F _LOK1 to represent each channel, F
Subscripts 1, 2, and 3 are added like _LOK2 and _FLOK3 . F _LOK
In addition, the subscripts 1, 2, and 3 are similarly attached to those set for each channel.

F _CON is set for each channel, and indicates whether the anti-skid control of each channel is an initial control stage (including a non-control state) or a continuous control stage. F _CON
= 0 indicates an initial control stage or a non-control state, and F _CON
= 1 indicates a continuous control stage. That is, in the present anti-skid control, the increase / decrease control of the brake pressure is performed based on various control threshold values determined according to the road surface μ in order to improve the control accuracy. In this case, the road surface μ is estimated based on the wheel speed change state under the anti-skid control as described below. Therefore, such an actual traveling road surface μ cannot be known at the beginning of the control, so that the road surface μ
Is assumed to be high μ, control is performed based on a control threshold value determined based on high μ, and when this initial control is performed and an actual road surface μ can be obtained, The control unit 24 constituting the continuation control stage transition determination unit determines that the transition from the initial control stage to the continuation control stage is performed, whereby F _CON is set to 1 and the control threshold determined based on the above estimated road surface μ. Continuous control is performed based on the value.

[Calculation of Wheel Acceleration and Deceleration] The control unit 24 calculates the acceleration and deceleration of each wheel based on the wheel speed indicated by the signals from the sensors 26 to 29, respectively. The control unit 24 determines the difference between the current value of the wheel speed and the previous value of the wheel speed by a sampling period Δt.
(For example, 7 ms), and a value obtained by converting the result into a gravitational acceleration is updated as the current acceleration or deceleration.

The control unit 24 selects the rear wheels 3 and 4 representing the wheel speed and acceleration / deceleration for the third channel. In the present embodiment, the smaller one of the two wheel speeds is selected as the rear wheel speed in consideration of the detection error of the two wheel speed sensors 28 and 29 of the rear wheels 3 and 4 during slip. The acceleration and deceleration obtained from the wheel speed are selected as rear wheel acceleration and rear wheel deceleration.

[Determination of bad road]
24 determines whether or not the traveling road surface is a rough road. This rough road determination processing is executed, for example, as follows. That is, if the number of times the deceleration or acceleration of the rear wheels 3 and 4 exceeds a predetermined upper limit or lower limit within a predetermined time is within a set value, the control unit 24 determines that the road is not a rough road and determines that the road is not a rough road. If F _AKR is maintained at 0 and the number of times that the values indicating the acceleration and the deceleration exceed the upper limit value and the lower limit value within a certain period of time are equal to or greater than a set value, it is determined that the road is a bad road and the bad road flag F
Set _AKR to 1.

[Calculation of slip ratio] The control unit 24 controls the rear wheel speeds determined from the signals from the wheel speed sensors 28 and 29 and the left and right front wheels 1 indicated by the signals from the wheel speed sensors 26 and 27. , 2 and the pseudo vehicle speed (the pseudo vehicle speed is calculated by the control unit 24 and will be described later), and the slip ratio indicating the degree of slip is calculated for each of the first to third channels. . In this embodiment, the slip ratio is calculated using the following relational expression: slip ratio = (wheel speed / pseudo vehicle speed) × 100. That is, as the deviation of the wheel speed from the pseudo vehicle speed increases, the slip ratio decreases, and the tendency of the wheels to slip increases.

"Estimation of road surface friction coefficient (road surface μ)"

The control unit 24 successively estimates the road surface μ for each channel and updates it. The estimation of the road surface μ is performed as described above when FABS = 0.
Therefore, it is assumed that the road surface μ value MU1 = 3 (3 indicates a high friction road surface).

When FABS = 1, MU1 is set to MU1 based on the wheel deceleration DW1 and the wheel acceleration AW1 before each estimation.
MU1 = 1 (1 indicates a low friction road surface), MU1 = 2 (2 indicates a medium friction road surface), and MU1 = 3.

Even when F _ABS = 1, it is assumed that the road surface is a high friction road surface during the initial control stage in which the road surface μ cannot be estimated or the estimation accuracy is low, and MU ₁ is set in advance. Is set to 3, which is the fixed value obtained. Also,
MU ₁ case of bad road (F _AKR = 1) is set to automatically 3. This is based on the assumption that the road surface is a high friction road surface in order to control the vehicle on a rocky road because the braking performance can be enhanced by controlling the vehicle on a rough road when the vehicle is controlled on a rough road.

[Calculation of pseudo vehicle speed] The control unit 24 calculates the pseudo vehicle speed. The process of calculating the pseudo vehicle speed is performed as follows, for example, according to the flowchart of FIG. That is, the control unit 24 determines that T1
To read various data, and at T2, the maximum wheel speed W _MX from the wheel speeds W _{1 to} W ₄ indicated by the signals from the sensors 26 to 29.
And at T3, a sampling period Δt of the wheel speed W _MX.
Per wheel speed change amount ΔW _MX is calculated.

[0035] Then, read the vehicle speed correction value C _VR corresponding to the representative value of the coefficient of friction from the map shown in FIG. 4 at T4 MU (minimum value of the _{MU 1, MU 2, MU 3} ), the wheel speed change amount T5 It is determined whether ΔW _MX is equal to or less than the vehicle speed correction value C _VR . When the wheel speed change amount ΔW _MX is equal to or _smaller than the vehicle speed correction value C _VR , a value obtained by subtracting the vehicle speed correction value C _VR from the previous value of the pseudo vehicle speed V _R at T6 is replaced with the current value. Therefore, the pseudo vehicle speed V _R decreases at a predetermined gradient according to the vehicle speed correction value C _VR .

On the other hand, in the above T5, the wheel speed change amount ΔW
_{When MX} is judged greater than vehicle speed correction value C _VR, that is, when the maximum wheel speed W _MX showed excessive change value obtained by subtracting the maximum wheel speed W _MX from the pseudo vehicle body speed V _R in T7 predetermined determines whether the value greater than or equal _to V _0. In other words, it is determined whether or not there is a large opening between the highest wheel speed W _MX and the pseudo-vehicle-speed V _R. Then, when there is no large gap replaces the value obtained by subtracting the vehicle speed correction value C _VR from the previous value of the estimated vehicle speed V _R proceeds to the T6 to time value. Further, when a large opening than the predetermined value V ₀ between the highest wheel speed W _MX and the pseudo vehicle body speed V _R occurs, replace the maximum wheel speed W _MX pseudo vehicle body speed V _R proceeds to T8 from T7.

Thus, the pseudo vehicle speed V of the vehicle
_R is the sampling period Δt according to each wheel speed W _{1 to} W ₄
It is updated every time.

[Setting of Control Phase] The control unit 24 includes the first to third valve units 20, 21,
A control phase setting process for defining a control amount for 23 is performed. An outline of the control phase setting process will be described. The control unit 24 includes a control threshold value (control threshold value will be described in detail later) set according to the driving state of the vehicle, a wheel acceleration / deceleration, and a slip. By comparison with the rate, the phase 0 indicating the anti-skid non-control state, the phase 1 indicating the increased pressure state during the anti-skid control, the phase 2 indicating the holding state after the increased pressure, the phase 3 indicating the reduced pressure state, and the phase 3 indicating the reduced pressure state Phase 5 indicating the holding state is selected.

The control unit 24 sets a control amount according to the phase value set for each channel, and then sends a braking pressure control signal according to the control amount to the first to third valve units 20, Output to 21 and 23 respectively. Thereby, the first to third valve units 20, 2
A branch braking pressure line for front wheels 19a, 1 downstream of 1, 23
The braking pressure in the 9b and the rear-wheel branch braking pressure lines 22a, 22b is increased or decreased, or is maintained at the increased or decreased pressure level.

[Setting of Control Threshold] The control unit 24 sets various control thresholds used for the brake pressure control of the first to third channels. The control threshold value setting process is performed as follows according to the flowchart of FIG. The setting process of the control threshold value is performed independently for each channel. Here, the setting process for the first channel for the front left wheel will be described. Note that the control threshold value is similarly set for the second and third channels.

The control unit 24 first reads various data at U1. At U2, it reads the friction coefficient value MU ₁ from the preset parameter selection table shown in FIG.
And selecting parameters corresponding to the pseudo vehicle body speed V _R. When pseudo vehicle body speed V _R is middle speed range in friction coefficient value MU ₁ = _1, LM2 for medium-speed low-friction road surface as the parameter is selected. Further, the control unit 24, if a rough road (F _AKR = 1), as shown in FIG. 6, to select the parameter corresponding only to the pseudo vehicle body speed V _R, the parameter value of the coefficient of friction MU ₁ = 3 Are set the same as the parameters in the case of. That is, for example, when the pseudo vehicle speed V _R belongs to the middle speed range, the HM2 for the middle speed high friction road surface is forcibly selected as the parameter. This, MU ₁ as described above at the time of running on a rough road is because is automatically set to 3.

When the selection of the parameters is completed, the process proceeds to U3, where the control threshold values corresponding to the selected parameters are read from the control threshold value table shown in FIG. Here, as shown in FIG. 7, the control threshold value is 1-2 for determining the shift from phase 1 to phase 2.
Intermediate deceleration threshold B _'12, Phase from Phase 2 3
2-3 intermediate slip ratio threshold value B ' _SG for determining transition to
And 5- for determining the shift from phase 5 to phase 1
One intermediate slip ratio threshold value _{B'SZ and the} like are set for each parameter. In this case, the deceleration threshold value, which greatly affects the braking force, is set to the friction coefficient value MU ₁ in order to achieve a high level of both the braking performance when the road surface μ is large and the control responsiveness when the road surface μ is small. Is set so as to approach 0 G as the level of the road surface becomes smaller, that is, as the road surface μ becomes smaller.

When the control unit 24 selects LM2 for a medium-speed and low-friction road surface as the above-mentioned parameter, the control unit 24 sets L in the control threshold value table of FIG.
As shown in the column _{M2, B '12, B'} SG, as B _'SZ, reads -0.5G, 90%, 90% of each value respectively.

Next, it is determined whether or not the friction coefficient value MU ₁ = 3 in U4, in U5 when the MU ₁ = 3 F _AKR = ₁
Is determined, and when F _AKR = 1, a correction process of the control threshold value at the time of a rough road is performed at U6. This correction process is performed based on, for example, the final threshold value table shown in FIG.
Set the intermediate deceleration threshold B 'minus the ₁₂ from 1.0 G as the final 1-2 deceleration threshold B _12, also 2-
3 The value obtained by subtracting 10% from the intermediate slip ratio threshold value _B'SG and the 5-1 intermediate slip ratio threshold value _B'SZ
Set as 3 slip rate threshold value B _SG and final 5-1 slip rate threshold value B _SZ . This is because the wheel speed sensors 26 to 29 are likely to make an erroneous detection when traveling on a rough road, so that the response of the control is delayed to ensure good braking performance. If MU ₁ = 1,2 and MU ₁ = 3 and F _AKR = 0, each intermediate threshold is set as it is as the final threshold.

In addition to the control threshold values shown in FIGS. 7 and 8, the control unit 24 has a lock determination fixed deceleration threshold value which is a lock determination threshold value for starting anti-skid control. [-3.0G], 2-3 slip ratio [B _SG -5%] for determining transition from phase 2 to phase 3 in the initial control stage (for determining transition from phase 2 to phase 3 in the continuous control stage) The above-mentioned 2-3 slip ratio threshold value _BSG itself is used as the threshold value), and phase 3 to phase 5 in the initial control stage.
3-5 fixed deceleration threshold value [OG], which is a threshold value for determining the shift to the shift, and 3-5 fixed deceleration, which is a threshold value for determining the shift from the phase 3 to the phase 5 in the continuous control stage The threshold value [-1.0G] and the threshold value for determining the shift from phase 5 to phase 1 in the initial control stage, ie, the 5-1 fixed slip ratio threshold value [95%] (in the continuous control stage, The above-mentioned 5-1 slip ratio threshold value B _SZ is used as the threshold value for determining the shift to the phase 1).

[Lock Judgment] Control Unit 24
Determines whether the wheels are locked for each channel. For example, in the lock determination for the first channel for the left front wheel, the control unit 24 first sets the current value of continuation flag F _CON1 for the first channel as a previous value, then the pseudo vehicle body speed V _R and the wheel speed W ₁ is a predetermined condition (for example, V <5 km / H, W ₁ <2.5 km /
H) is determined, and when these conditions are satisfied, the continuation flag F _CON1 and the lock flag F _LOK1 are each reset to 0. If not, the lock flag F _LOK1 is set to 1. It is determined whether or not it has been performed. If the lock flag F _LOK1 is not set to 1, when a preset lock determination condition is satisfied (in the present embodiment, when the wheel deceleration DW ₁ ≦ −3.0 G is satisfied).
_Is determined to be locked, and F _LOK1 is set to 1. Note that the lock determination process is similarly performed on the second and third channels.

<Specific Contents of Anti-Skid Control> FIG.
5 is a flowchart showing one embodiment of the anti-skid control according to the present invention. In this embodiment, control is performed to repeat a cycle in which pressure increase phase 1, pressure increase hold phase 2, pressure decrease phase 3 and pressure decrease hold phase 5 are sequentially performed in this order (however, the first cycle is the hold after pressure increase). (Starting from phase 2). Such control will be described with reference to the flowchart of FIG. 9 taking the case of the first channel as an example.

The control unit 24 reads various data in Q1 and determines whether or not F _ABS = 0 in Q2.
When _ABS = 0 determines whether Q3 on whether the wheel deceleration DW ₁ is fixed deceleration threshold -3.0 G or less for the lock determination.
If the value is greater than -3.0 G, the process proceeds to return. If the value is less than -3.0 G, a lock determination is made, anti-skid control is started, F _ABS is set to 1, and the initial control stage is entered.
That, DW ₁ moves the holding phase intensifying After depressurization by setting the control phase value P ₁ to 2 with Q4 When equal to or less than -3.0G.

[0049] Subsequently, the slip ratio S ₁ is determined whether 2-3 slip rate threshold B _SG -5% smaller than or at Q5. While S ₁ is B _SG -5% or more, the process returns to Q 4 to maintain the holding phase, and when it becomes small, the process proceeds to Q 6,
Set the P ₁ to 3 shifts to the vacuum phase. After transition to Q6 decompression phase, it is determined whether the DW ₁ in Q7 has reached the 3-5 fixed deceleration threshold OG, DW ₁
There the P ₁ set in 5 proceeds to Q8 as they become 0G, shifts the holding phase after pressure reduction. Subsequently, it is judged whether large or not than 95% slip ratio S ₁ is 5-1 fixed slip ratio threshold at Q9, the phase value P ₁ until the large-5
, And when it exceeds 95%, proceed to Q10, where P ₁
Is set to 1 and the process proceeds to the pressure increasing phase.

Simultaneously with the shift to the pressure increasing phase 1, Q11
At F _CON1 is set to one. That is, Q8
Is the initial control stage until the end of the holding phase after the pressure reduction in step S10. After the transition to the pressure increasing phase in Q10, the process shifts to the continuous control stage. In the above initial control stage, the friction coefficient value MU ₁ as described above is set to a fixed value 3 set in advance, thus the threshold value [B
B _SG in _SG -5%] value of the selected B _SG on the basis of FIG. 6, 7 and 8 under the condition that MU ₁ = 3 is used in the subsequent continuous control step, the threshold value B _12, B _SG, B _SZ is DW ₁ and AW B _12, which is actually selected under the MU ₁ that is estimated based on the _1, B _SG, the value of B _SZ used.

After proceeding to Q11 and proceeding to the continuous control stage, the process returns to Q1 and proceeds to Q2.
= 1, NO in Q2, proceed to Q12 to determine whether DW1 is smaller than B12, maintain the pressure increasing phase until it becomes small, and proceed to Q13 when it becomes small, Therefore, P1 is set to 2 and the process shifts to the holding phase after pressure increase. Next, in Q14, it is determined whether or not S1 is smaller than the 2-3 slip ratio threshold value BSG. When the value becomes smaller, the process proceeds to Q15, P1 is set to 3, and the process proceeds to the pressure reduction phase. Next, in Q16, it is determined whether or not DW1 has reached the 3-5 fixed deceleration threshold value -1.0G. At that time, the process proceeds to Q17, where P1 is set to 5, and the phase shifts to the holding phase after decompression. I do. Next, in Q18, it is determined whether or not S1 has exceeded the 5-1 slip ratio threshold value BSZ. At the time, the program proceeds to Q19, in which P1 is set to 1, and the process proceeds to the pressure increasing phase. Next, in Q20, it is determined whether or not the anti-skid control has been completed. If it has not been completed, the process proceeds to return and repeats Q12 to Q20. If completed, the process proceeds to Q21 to reset FABS to 0 and then proceed to return. . In addition,
The termination condition of the anti-skid control is, for example, a change from ON to OFF of the brake switch as described above.

Next, the above control for the first channel will be described more specifically with reference to FIG. In the anti-skid non-control state at the time of deceleration, the brake pressure generated in the master cylinder 18 is gradually increased by the depression operation of the brake pedal 16, and for example, the wheel deceleration DW1 of the left front wheel 1 is reduced as shown in FIG. When it reaches -3G, FLOK1 is set to 1 as shown in FIG.
The anti-skid control is started from the time ta and P1 = 2
(Holding phase), and the braking pressure is held. In the initial control stage immediately after the start of the control, as described above, M
Since U1 = 3, the control unit 24 sets the control parameter to the middle value from the table shown in FIG. 6 when FAKR is not set to 1 and the pseudo vehicle speed VR belongs to the medium speed range, for example. The HM2 for the high-friction road surface is selected, and the BSG value is determined from FIGS. 7 and 8 according to this parameter.
Set “-5%”. Other threshold values are fixed threshold values set in advance, and are used as they are.

[0053] Then, the control unit 24 compares the control threshold value of the S ₁ calculated from the wheel speed W _1, DW _1, AW ₁ and the various, S ₁ is 2-3 slip rate threshold When B _SG becomes smaller than -5%, the relief valve 20b of the first valve unit 20 is set to P ₁ = 3 (pressure reduction phase).
Are turned ON / OFF according to a predetermined duty ratio. As a result, as shown in FIG. _9E , the braking pressure decreases at a predetermined gradient from the time tb, the braking force gradually decreases, and the rotational force of the front wheels 1 starts to recover. Then, further DW ₁ decompression is followed by a braking pressure to the 3-5 fixed deceleration threshold 0G and P ₁ = 5 After Recovery (hold phase after pressure reduction),
Braking pressure from the time t _c is maintained at the level of post-vacuum.

When the state of phase 5 continues and S ₁ exceeds the 5-1 fixed slip ratio threshold value 95%, P ₁ = 1.
As shown in Fig. (B)
As shown in (1), F _CON1 is set to 1 and the _{process proceeds} from the initial control stage to the continuous control stage. Immediately after the transition to the phase 1, the on-off valve 20b of the first valve unit 20 is set to a duty ratio of 100% according to the initial rapid pressure increase time T _PZ set based on the duration of the phase 5 in the initial control stage. And the brake pressure is increased at a steep gradient as shown in FIG. After the initial rapid pressure increase time T _PZ ends,
The on / off valve 20a is turned on / off according to a predetermined duty ratio.
FF is performed, and the braking pressure gradually increases according to a gradient smaller than the above gradient. As described above, immediately after the transition to the continuous control stage, the braking pressure is reliably increased, so that a favorable braking force is secured.

After the transition to the continuous control stage, the changes of phases 1, 2, 3, and 5 as shown in the figure are periodically performed according to the threshold values B ₁₂ , B _SG , −1.0 G, and B _SZ for the continuous control stage. Is repeated. In the continuation control stage, the control threshold value is selected according to MU ₁ indicating the actual road surface condition, so that the precise braking pressure is controlled in accordance with the road surface condition.

<Control Phase Transition Timing> Next, the transition timing to each control phase in the initial control stage and the continuous control stage will be described.

In the present embodiment, as shown in the flow chart shown in FIG. 9, the control thresholds in the initial control stage are smaller than those in the continuous control stage. The value is set so that the transition timing is delayed.

[0058] More specifically, 2-3 slip rate threshold from the holding phase 2 performs shift determination to decompression phase 3, B _SG -5 at the initial control stage while the continuous control stage is B _SG %It has become. The transition from the holding phase to the pressure reduction phase is performed when the slip increases in the holding phase (when the slip ratio decreases). Therefore, as described above, the slip ratio threshold value is set to an initial value as compared with the continuous control stage. By setting the control stage to be smaller, the initial control stage shifts to the pressure reduction phase after the slip becomes larger than the continuous control stage, and the transition timing to the pressure reduction phase is delayed.

Further, the pressure reduction phase 3 to the holding phase 5
The threshold value for 3-5 deceleration for making the transition determination to -1.0 G is -1.0 G in the continuous control stage, whereas it is O in the initial control stage.
It is G. The transition from the decompression phase to the holding phase is performed, for example, at the time when the progress of the slip is substantially stopped in the decompression phase (when the wheel deceleration changes from the negative direction to the positive direction). The initial control stage is set to be larger than the continuous control stage, so that the wheel deceleration becomes larger in the initial control stage as compared with the continuous control stage, that is, the slip progress is more reliably stopped, and then the pressure reduction phase is started. And the transition timing to the pressure reduction phase is delayed.

Further, the 5-1 slip ratio threshold value for determining the shift from the holding phase 5 to the pressure increasing phase 1 is as follows:
B _SZ in the continuous control stage, whereas in the initial control stage
95%. The maximum value of B _SZ is 93% as can be seen from FIGS.
95% is always greater than the threshold of the continuous control phase. The transition from the holding phase to the pressure increasing phase is performed when the slip becomes sufficiently small (when the slip ratio becomes sufficiently large) in the holding phase, and therefore, as described above, the slip ratio threshold value is compared with the continuous control stage. By setting the initial control stage to a large value, the initial control stage shifts to the pressure increasing phase after the slip becomes smaller than that of the continuous control stage, and the shift timing to the pressure increasing phase is delayed.

As described above, by setting the control threshold value in the initial control stage to a value at which the control phase shift timing is later than that in the continuous control stage, that is, to a value that makes it difficult to shift to the next phase, In the continuous control stage, anticipation control can be performed to improve controllability.At the same time, in the initial control stage, how the slip changes can be sufficiently monitored to increase or decrease and the control can be performed. Can be prevented from being confused.

<Modification> The vehicle slip control device according to the present invention is not limited to the above embodiment.
Various modifications can be made without departing from the scope of the invention. For example, in the above embodiment, in the initial control stage, continuous control is performed in all of the transition from the holding phase 2 to the pressure reducing phase 3, the transition from the pressure reducing phase 3 to the holding phase 5, and the transition from the holding phase 5 to the pressure increasing phase 1. The control threshold value is set so that the transition timing is later than the stage, but it is not necessary to set it for all control phase transitions, but only for any control phase transition. It is also possible. Further, when a phase shift different from that of the above-described embodiment, for example, a shift from the holding phase after depressurization to the depressurization phase is set, a control threshold value is set for those phase shifts in the same manner as described above. Can be. Furthermore, the setting of the control threshold value is only required to be set so that the transition timing is later in the initial control stage than in the continuous control stage. It may be something.

[0063]

[Brief description of the drawings]

FIG. 1 is an overall schematic configuration diagram of a vehicle provided with an embodiment of the present invention.

FIG. 2 is a time chart showing an example of anti-skid control.

FIG. 3 is a flowchart illustrating a procedure for calculating a pseudo vehicle body speed.

FIG. 4 is a diagram showing a map used for calculating a pseudo vehicle speed.

FIG. 5 is a flowchart showing a control threshold value setting procedure.

FIG. 6 is a diagram showing a parameter selection table.

FIG. 7 is a diagram showing a control threshold value table.

FIG. 8 is a diagram showing a final threshold value table.

FIG. 9 is a flowchart illustrating a procedure of an embodiment of anti-skid control.

[Explanation of symbols]

 1, 2, 3, 4 wheels 24 anti-skid control means, continuation control stage shift determination unit

Continuation of the front page (72) Inventor Kazutoshi Nobumoto 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Inside Mazda Corporation (56) References JP-A-56-95746 (JP, A) JP-A-1-273759 (JP, A) JP-A-1-106676 (JP, A) JP-A-3-79461 (JP, A) JP-A-64-41454 (JP, A) JP-A-4-201774 (JP, A) JP-A-4-356261 (JP, A) JP-A-4-353061 (JP, A) JP-A-62-2362 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) B60T 8 / 58 B60T 8/66

Claims (1)

(57) [Claims] The present invention controls a wheel slip by controlling a brake pressure of a wheel, and controls a wheel behavior during the control.
Based on road surface information based on actual road surface
A skid control means, wherein the anti-skid control means controls a wheel behavior and a predetermined control.
The braking force holding phase and the pressure increase
Selectively execute each control phase of phase and decompression phase
And after the first decompression from the start of control.
Until the braking force holding phase elapses,
The control threshold is determined based on the fixed road surface information
After passing through the holding phase after the decompression,
The above control threshold is determined based on surface information corresponding to the road surface
The vehicle's slip control device that is configured to
And the anti-skid control means is configured to output the information based on the fixed road surface information.
Control threshold value when performing brake pressure control based on
However, based on the road surface information corresponding to the actual road surface,
Each of the above controls is compared with the control threshold value when performing pressure control.
Is set so that the transition between
That, slip control system for a vehicle, characterized in that.