JP2000233737A - Antiskid control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure a braking distance by getting the sufficient deceleration even in the case of traveling on a rough road surface such as a gravel road or the like. SOLUTION: At the time point of the starting of decompression, for example, an exceptive decompression value >=PEXC in a degree of 30% of wheel cylinder pressure Pi is set up as an increase/decrease pressure command value >=Pi* whereby decompression is carried out on the basis of the exceptive decompression value ΔPEXC. At this time when wheel acceleration VWi' is less than a positive threshold α for detecting a rough road surface, the count value conformed to the magnitude of the wheel acceleration VWi' is set to a counter C, for counting it down, and when the counter C is C=0 at the time of the starting of decompression the exceptive decompression is carried out, but when the counter C is C>0 at the time of starting of decompression, the exceptive decompression is not carried out, but this exceptive decompression is carried out after the counter C has come to C=0. By postponing the time of carrying out the exceptive decompression, this exceptive decompression is avoided, to be conducted in such a state that the wheel velocity VWi is more than the target wheel velocity VWi*, and an overabundance of decompression for lowering deceleration, is avoided in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anti-skid control device for preventing wheel lock during braking of a vehicle.

[0002]

2. Description of the Related Art As an anti-skid control device of this type, for example, a target increase / decrease of a cylinder pressure for braking is performed based on a target wheel speed and a deviation of the wheel speed and a deviation of the target wheel acceleration and a deviation of the wheel acceleration. 2. Description of the Related Art There has been known an apparatus that calculates an amount and increases or decreases a fluid pressure of a braking cylinder, that is, a braking pressure based on the target increasing / decreasing amount, thereby controlling the braking pressure by proportional / differential control. Further, in order to prevent an increase in slip due to a delay in pressure reduction, for example, as in an anti-skid control device described in JP-A-8-150917, a certain amount of pressure reduction is secured by feedforward control at the start of pressure reduction. Some of them have been proposed.

[0003]

By the way, the traveling road surface of a vehicle is various, and there is a road surface having a lot of unevenness and undulation which is generally called a bad road. When the vehicle travels on such a bad road, so-called pulsation, in which the wheel speed greatly increases and the cycle thereof becomes short, is likely to occur as the wheels bounce and rebound. In such a situation, the wheel acceleration, which is a differential value of the wheel speed, also has a large amplitude and its cycle tends to be short.

As described above, when the amplitude of the wheel acceleration fluctuates and the cycle becomes shorter, in the above-described anti-skid control device, the differential term in the proportional / differential control increases, and this differential term governs the target pressure increase / decrease amount. Therefore, decompression is started before the wheel speed reaches the target wheel speed, and this occurs continuously, so that the braking pressure always tends to be reduced, and the braking force is substantially reduced, and as a result, The braking distance may be lengthened. In particular, when a certain amount of reduced pressure is secured by feedforward control at the start of reduced pressure, there is a problem that excessive reduction in pressure causes excessive reduction in deceleration.

Accordingly, the present invention has been made in view of the above-mentioned conventional problems, and provides an anti-skid control device capable of obtaining a sufficient deceleration even when traveling on a rough road such as a gravel road. It is intended to be.

[0006]

In order to achieve the above object, an anti-skid control device according to claim 1 of the present invention is disposed on a wheel to be controlled based on a master cylinder pressure from a master cylinder. A control valve for controlling the fluid pressure of the braking cylinder; detecting means for detecting the wheel speed and wheel acceleration / deceleration of the control target wheel; detection values of the wheel speed and wheel acceleration / deceleration detected by the detecting means; A target pressure increase / decrease amount calculating means for calculating a target pressure increase / decrease amount of the fluid pressure based on the value, and a control means for controlling the control valve so that the fluid pressure of the brake cylinder changes by the target pressure increase / decrease amount. And an exceptional decompression unit that sets a predetermined pressure reduction amount as the target pressure increase / decrease amount at the start of the pressure reduction of the fluid pressure, wherein the wheel acceleration / deceleration detected by the detection unit is provided. A road surface condition detecting means for detecting the road surface condition of the traveling road surface based on the detected value, and delaying the execution timing of the exceptional pressure reduction by the exceptional pressure reducing device when the road surface condition detecting device detects that the traveling road surface is a rough road surface. Exceptional decompression delay means.

The anti-skid control device according to claim 2, wherein the road surface condition detecting means determines that the road surface is a rough road surface when the wheel acceleration / deceleration exceeds a preset threshold value. It is characterized by becoming. The anti-skid control device according to claim 3 is
The exceptional decompression delay unit is characterized in that, as the wheel acceleration / deceleration increases, the timing of the exceptional decompression by the exceptional decompression unit is delayed.

Further, the anti-skid control device according to claim 4 is characterized in that the threshold value is changed according to a road surface friction coefficient.

[0009]

The anti-skid control device according to claim 1 of the present invention delays the execution timing of the exceptional pressure reduction by the exceptional pressure reduction means when the road surface condition detection means detects that the traveling road surface is rough. Therefore, it is possible to prevent the braking pressure from being excessively reduced when traveling on a rough road surface, and to secure a braking distance.

The anti-skid control device according to claim 2 determines that the traveling road surface is a rough road surface when the wheel acceleration / deceleration exceeds a preset threshold value. Can be easily and accurately detected. Further, the anti-skid control device according to claim 3 delays the execution timing of the exceptional decompression as the wheel acceleration / deceleration increases, so that the execution timing of the exceptional decompression can be delayed according to the road surface condition.

Further, the anti-skid control device according to claim 4 changes the threshold value in accordance with the road surface friction coefficient, so that it is possible to accurately detect the rough road surface in accordance with the road surface condition. Can be.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of a vehicle to which an anti-skid control device according to the present invention is applied. The anti-skid control device is arranged between each of the wheels 1FL to 1RR and the brake operation unit 11. Brake operation unit 11
Are a brake pedal 11a, a booster 11b that amplifies the force of depressing the pedal 11a, a master cylinder 11c that receives the force amplified by the booster 11b and compresses the brake fluid to generate a brake pressure, and stores the brake fluid. And a reservoir tank 11d. And
Each of the wheels 1FL to 1RR is a wheel cylinder 2F.
L-2RR and brake discs 3FL-3RR.

The hydraulic pressure of the wheel cylinders 2FL to 2RR is controlled by inlet valves 12FL to 12RR and outlet valves 14FL to 14RR, which are solenoid valves, similarly to the conventional anti-skid control device. Then, the brake fluid accumulated in the reservoirs 16F and 16R due to the reduced pressure is removed by a pump 20F driven by the motor 18.
And 20R are pumped up into the damper chambers 22F and 22R and returned upstream of the inlet valves 12FL to 12RR.

An inlet valve 24, which is a solenoid valve,
F and 24R are closed to shut off the connection between the master cylinder 11c and the wheel cylinders 2FL to 2RR, and the outlet valves 26F and 26R, which are solenoid valves, are opened to pump up the brake fluid from the reservoir tank 11d. The cylinder pressure can be controlled. Relief valves 28F and 28R are provided in parallel with the inlet valves 24F and 24R.

Then, each of the inlet valves 12FL
-12RR and 24F, 24R and the outlet valves 14FL-14RR, 26F, 26R are controlled by the controller 30. Also,
The position of the vehicle, each wheel of the wheel speed Vw _{i (i} = FL~R
R) Wheel speed sensors 32FL to 32RR for detecting
An acceleration sensor 34 for detecting longitudinal and lateral accelerations X _G and Y _G of the vehicle, and a yaw rate sensor 36 for detecting a yaw rate φ ′ generated in the vehicle.
When the master cylinder pressure sensor 38 for detecting the master cylinder pressure P _MC is provided.

The controller 30 receives a detection signal from each of the above-described sensors, and receives an engine drive torque Te from an engine controller 50 for controlling the engine and a transmission controller 5 for controlling the automatic transmission.
2. A microcomputer for inputting the gear position GR from the microcomputer 2 and performing anti-skid control processing based on these signals to output control signals to the respective inlet valves and outlet valves, and a control signal output from the microcomputer. And a drive circuit for converting the drive signal into a drive signal for the solenoid of the inlet valve and the outlet valve including the above-mentioned electromagnetic valve and the like. And
The microcomputer includes an input interface circuit having an A / D conversion function, an output interface circuit having a D / A conversion function, an arithmetic processing unit including a microprocessor unit MPU, a ROM, a RAM, and the like.
And the like.

Next, an anti-skid control process executed by the microcomputer in the controller 30 will be described with reference to the flowchart of FIG. This anti-skid control process is executed as a timer interrupt every predetermined sampling time.
In the wheel speed Vw _{i (i} = FL~RR) from the wheel speed sensors 32FL～32RR, longitudinal acceleration from the acceleration sensor 34 X _G and the lateral acceleration Y _G, the yaw rate sensor 36
Yaw rate phi ', the master cylinder pressure from the master cylinder pressure sensor 38 P _MC, the engine controller 50 from
And the gear position GR from the transmission controller 52 are read.

[0018] Then, the process proceeds to step S2, and calculates the wheel acceleration Vw _i 'a (i = FL~RR). here,
For example, it is calculated based on the following equation (1). Vw _i '= - Note _{((Vw i1 + Vw i0)} (Vw i4 + Vw i3)) / 2 · ΔT) ...... (1), subscript 0-4 in the formula represent prior to each cycle of the current control cycle For example, the subscript 2 represents two cycles before. ΔT represents a control cycle.

Next, the process proceeds to step S3, where the selected wheel speed _Vfs is calculated. For example, the wheel speed Vw of each wheel
the _i calculated, during acceleration, by performing a filtering process to remove the noise contained in the data in response to deceleration or the like, closer to the vehicle speed speed Vw _fi a (i = FL to RR) for each wheel In addition, depending on the conditions such as braking and non-braking, each Vw _fi
The selected wheel speed V _fs closest to the vehicle speed is calculated by selecting the largest one from among the vehicle speeds.

Next, the process proceeds to step S4 to calculate a wheel load W _i (i = FL to RR) of each wheel. For example, it is calculated according to the following equation (2) based on the longitudinal acceleration X _G and the lateral acceleration Y _G. W _i = W _i0 + kx × X _G + ky _i × Y _G (2) In the expression, W _i0 is the initial load (static load), that is, the weight when the vehicle stops. kx and ky _i are constants determined by the wheelbase, the height of the center of gravity, the tread, and the roll rigidity distribution of the vehicle.

The wheel load W _i may be calculated using, for example, the change amount of the vehicle body speed calculated up to the previous time or the estimated value of the road surface friction coefficient μ. The lateral acceleration Y _G may be estimated from the angle, the vehicle speed and the yaw rate φ ′, or the vehicle speed and the difference between the left and right wheel speeds. Next, the process proceeds to step S5, where the estimated wheel cylinder pressure _Pi is calculated. Specifically, when the control of the wheel cylinder pressure has already been started by the anti-skid control, the control amount, that is, the wheel cylinder pressure increase / decrease amount is grasped in the microcomputer as described later. Since the pressure increase / decrease characteristic of the pressure increase / decrease amount (= valve opening time) with respect to the wheel cylinder pressure is known in advance, for example, the master cylinder pressure at the time when the anti-skid control is started is set as an initial value, and the wheel in the control cycle up to the previous time is used. What is necessary is just to track based on the cylinder increase / decrease amount.

Next, the process proceeds to step S6, where the slip ratio S _i of each wheel is calculated. This for each wheel, on the basis of its wheel speed Vw _i and the vehicle speed V _X, is calculated according to the following equation (3). _{S i = (Vw i -V X} ) / V X ...... (3) Then, the process proceeds to step S7, whether or not the peak value of the road surface friction coefficient of each wheel, i.e., the braking force applied to each wheel Also, it is determined whether or not the state cannot be transmitted to the road surface. Here, it is determined that the wheel acceleration Vw _i 'calculated in the step S2 on the basis of the slip ratio S _i. That is, as shown in FIG. 3, if the wheel state falls within a predetermined area (shaded area in the figure) in the characteristic diagram representing the correspondence between the slip ratio and the absolute value of the wheel acceleration, the road surface friction is increased. It is determined that the coefficient is at the peak. Here, the threshold value for the determination is set to the same value as the control start determination of the anti-skid control. Also, once the anti-skid control is activated, if the exceptional control described later is not performed,
Even if the wheel deviates from the above area, the determination that the road surface friction coefficient is at the peak is continued. Furthermore, even when the wheels are under anti-skid control, there are exceptional cases such as synchronous control of the left and right (or front and rear) wheels (so-called select-low control) and slow pressure increase control (so-called yaw moment control) at the beginning of control. When the control is being performed, it is determined that the wheel is not at the peak of the road surface friction coefficient because the slip ratio does not become a sufficiently large value by these controls.

Next, the process proceeds to step S8, where
It is determined in step S7 that the road surface friction coefficient is at the peak.
Road surface friction coefficient μ_iIs estimated. This
Here, for example, the wheel of each wheel calculated in step S2
Acceleration Vw_i'And the wheel of each wheel calculated in step S4
Load W_iAnd the estimated wheel series estimated in step S5.
Pressure P_iIs calculated from the equation of the rotational motion of the wheel based on
Out, and for the drive wheels,
Using the torque Te and the gear position GR, the rotational operation of the wheels is performed.
According to the equation of motion, according to the following equations (4) and (5)
Road friction coefficient μ _iIs calculated.

[0024] non-driving _{wheels: μ i = (I × Vw} i '+ K × P i × R) / (W i × R 2) ...... (4) driving _{wheels: μ i = (I × Vw} i' + K × P _i × R−k × Te) / (W _i × R ² ) (5) where I is the inertia mass of the tire, and K is the brake specification (friction coefficient of pad, wheel cylinder area, wheel cylinder effective diameter). ), R is the tire effective diameter, k
Is a constant determined according to the transmission gear ratio according to the gear position GR and the final gear ratio of the differential gear.

Next, the process proceeds to step S9, and the variation V _X 'of the vehicle body speed is calculated using the road surface friction coefficient μ _i of each wheel. Here, it is calculated according to the following equation (6) from the average value of the road surface friction coefficient μ of the wheel determined to be at the peak of the road surface friction coefficient and the correction amount ΔV _X ′ of the vehicle body speed change amount described later. V _X ′ = Σμ _i / m + ΔV _X ′ (6) where m is the number of wheels determined to be at the peak of the road surface friction coefficient, and the correction amount ΔV _X ′ of the vehicle speed change amount is constant. Value (for example, 0.1 g (g is gravitational acceleration)). The correction amount [Delta] V _X 'is to detect the estimation error of the vehicle speed V _X, when the vehicle speed V _X than the actual vehicle speed is determined to be large, the correction amount [Delta] V _X' variables such Enlarge It may be. Also, the average value of the road surface friction coefficient μμμ _i /
For m, an acceleration that can occur in the vehicle is limited to, for example, 1.3 g as a maximum value and 0.05 g (g is a gravitational acceleration) as a minimum value. If there is no wheel determined to be at the peak of the road surface friction coefficient, all the wheels have not reached the peak and the anti-skid control is not being performed, so that V _X ′ = 1. 3 g.

The variation V _X 'of the vehicle body speed may be calculated by multiplying a weight corresponding to the wheel load distribution of each wheel, instead of a simple average value of the road surface friction coefficient μ _i of each wheel. That is, when it is determined in step S7 that the front wheel is at the peak of the road surface friction coefficient, the variation V _X 'of the vehicle body speed may be calculated by the following equation (7). V _X ′ = Σ (μ _i × (W _i / W)) (7) where W is the weight of the vehicle. When it is not determined that any of the wheels is at the peak of the road surface friction coefficient, for example, the value of μ _i of the right and left opposite wheels determined to be at the peak is used, or the maximum μ is used. _Using the value of _i , V _X ′ is calculated in accordance with equation (7).

[0027] Then, the process proceeds to step S10, and calculates the lateral velocity V _y of the vehicle. Here, the lateral acceleration Y
_G, the yaw rate phi 'and using the vehicle speed V _X (provided that the value of the previous control cycle) is calculated by performing an integral calculation in accordance with the following equation (8). _{V y (n) = V y} (n-1) + ΔV y × ΔT ...... (8) ΔV y = Y G (n) -φ '(n) × V X (n-1) Note, [Delta] T in the formula Represents a control cycle. Further, n represents the current control cycle, and n-1 represents the previous control cycle. Here, although the calculated lateral velocity V _y of the vehicle by performing the integration calculation based on signals from the sensors, the controller, for example, may be stored vehicle model relationships of the steering angle and the yaw rate, The vehicle side slip angle β may be estimated from the vehicle speed V _X and the steering angle δ, and the product of β and V _X may be used as the lateral speed V _y .

[0028] Then, the process proceeds to step S11, and calculates the vehicle speed V _X. Here, when the anti-skid control is performed, that is, when there is a wheel whose road surface friction coefficient is determined to be at a peak, the vehicle speed V _X (n−1) in the previous control cycle is selected. If the wheel speed is equal to or higher than V _fs (V _X (n−1) ≧ V _fs ), it is determined that the vehicle is decelerating, and the vehicle speed V _X (n) is calculated according to the following equation (9).
Is calculated, and when the vehicle speed V _X (n−1) in the previous control cycle is smaller than the selected wheel speed V _fs (V _X (n−1) <
V _fs ), it is determined that the vehicle is accelerating, and the following equation (1)
0) to calculate the vehicle speed V _X in accordance with. Further, if the anti-skid control is not performed, that is, when the road surface friction coefficient is no wheel is determined that a peak, the select wheel speed V _fs and vehicle speed V _X (n).

V _X (n) = V _X (n−1) −V _X ′ −V _h (9) V _X (n) = V _X (n−1) +5.0 g (10) In the equation, V _X ′ is the change amount of the vehicle body speed calculated in step S9, and V _h is the lateral speed V calculated in step S10.
_The turning correction amount is a product of _y and the yaw rate φ '.

Next, the routine proceeds to step S12, where a target slip ratio S ^* _i is calculated. Here, on a dry road surface, the target slip ratio S ^* _i is set to a predetermined value S ^* ₀ (for example, S ^*
₀ = 0.15), and is set according to the road surface friction coefficient μ _i calculated in step S8, for example, as shown in FIG.
Note that different values may be taken for the front and rear wheels, and the target slip ratio S ^* _i may be changed depending on the turning state of the vehicle. Further, the target slip ratio S ^* _i may be a constant value regardless of the road surface friction coefficient mu _i and turning.

[0031] Then the process proceeds to step S13, and the vehicle speed V _X calculated in step S11, the target wheel speed Vw _i according the following equation (11) and the target slip rate S ^* _i calculated in step S12, to the original Calculate ^* . ^{_{Vw i * = V X × (}} 1-S * i) ...... (11) Then, the process proceeds to step S14, the target wheel speed Vw _i ^*
And calculating the target pressure increase amount [Delta] P _0i according the following equation (12) based on the wheel speed Vw _i.

The _{ΔP 0i = k P × ε +} k D × (dε / dt) ...... (12) ε = Vw i * -Vw i In the formula, a is a proportional control term first term on the right side, the right side second
Term is the derivative control term, k _P is a proportional gain, k _D is a differential gain. These proportional gain k _P and derivative gain k
_D is changed according to the road surface friction coefficient μ, the vehicle speed, and the like.

Next, the process proceeds to step S15, and FIG.
The exception pressure reduction process shown is executed. In this exceptional decompression process,
First, in step S21, the value calculated in step S8 is calculated.
Road friction coefficient μ_iOriginally, for example, the control system shown in FIG.
The threshold α is set according to the threshold. That is, the road
Surface friction coefficient μ_iIs relatively small μ_LWhen:
Threshold value α = α_MIN(About 4.0 [g]),
Road friction coefficient μ _iIs relatively large μ_MAXIn the case above
Threshold value α = α_MAX(About 8.0 g)
And road friction coefficient μ_iIs μ_MIN<Μ_i<Μ_MAXWhen
Is μ_iSo that the threshold α increases as
To α_MIN<Α <α_MAXSet within the range. And the threshold
Value α_H= Α + 2.0 [g], threshold α_M= Α_,Shiki
Value α_L= Α-2.0 [g]. This
Is determined to be running on rough road such as gravel road
Is a possible value. In other words, when driving on rough roads
In this case, the fluctuation of the wheel speed Vw becomes large and the recovery speed of the wheel speed Vw is increased.
Speed, ie positive wheel acceleration Vw_i′ Becomes bigger
This wheel acceleration Vw_i'On a rough road due to the size of
Can be determined.

Next, the process proceeds to step S22, in which the wheel acceleration V calculated in step S2 in the previous control cycle.
Based on w _i ′ (n−1) and the wheel acceleration Vw _i ′ (n) calculated in step S2 in the current control cycle,
And it determines whether the same or increased and the previous value wheel acceleration Vw _i 'is a positive value. And the wheel acceleration V
w _i '> 0 a is and _{Vw i' (n) ≧ Vw} i '(n-
1 when) is, the process proceeds to step S23, the wheel acceleration Vw _i 'is determined whether greater than the threshold value α _H, Vw _i' the counter C goes to step S24 when it is> alpha _H C = C _H (about 15 msec)
After setting the flag F _H to F _H = 1, the process proceeds to step S41 described later.

The process proceeds to step S25 when at the step S23 not Vw _i '> α _H, the wheel acceleration V
determine whether w _i ′ is greater than threshold α _M ,
The counter C then proceeds to step S26 when a Vw _i '> α _M is set to C = C _M (10 msec considerable), after setting the flag F _M to F _M = 1, proceeds to step S41 described later I do. Vw _i 'in the step S25
> Alpha proceeds to step S27 when not _M, the wheel acceleration Vw _i 'is determined whether greater than the threshold value _{α L, Vw i'> α} C the counter C goes to step S28 when a _L = C _L (approximately 5 msec)
After setting the flag _FL to _FL = 1, the process proceeds to step S41 described later. Vw in step S27
_{If i} ′> α _L is not satisfied, the process directly proceeds to step S41.

[0036] Incidentally, the C _H, C _M, C _L is 'a value set according to the wheel acceleration Vw _i' wheel acceleration Vw _i when decelerating from the state of the wheel speed Vw _i is This is a value corresponding to a time predicted to be equal to or lower than the target wheel speed Vw ^* (hereinafter referred to as a delay time). Further, the respective flags F _H, F _M, F _L is set to zero at startup.

On the other hand, in step S22, the wheel acceleration V
When it is determined that w _i ′ has decreased, step S31 is performed.
Proceeds to the flag F _H is determined whether the F _H = 1, the process proceeds to step S32 when the flag is F _H = 1. In step S32, the wheel acceleration Vw _i 'is determined whether greater than the threshold value α _H, Vw _i'>
If α _H , the process proceeds to step S41 described below. When not Vw _i '> α _H in the step S32 proceeds to step S34, after updating the counter C to C = C-1, the process proceeds to step S41 described later. In addition,
The minimum value of the counter C is set to zero, and when the counter C is already zero, no update is performed.

Then, in step S31, the flag F is set._H
Is F_HIf it is not 1, the process proceeds to step S35, and
Lug F_MIs F_MIt is determined whether or not = 1. flag
Is F _M= 1, the process proceeds to step S36,
Wheel acceleration Vw_i′ Is the threshold α_MIs greater than
And Vw_i'> Α_MIf this is the case,
The process proceeds to step S41, and in step S36, Vw_i'> Α_Mso
If not, the process proceeds to step S34.

The flag F _M at step S35 is F _M =
Proceeds to step S38 when not 1, the flag F _L
Is determined whether or not _FL = 1, and the flag _FL is set to _FL =
When not 1 proceeds directly to step S41 described later, when the flag F _L is F _L = 1, the step S
Move to 39. Then, the wheel acceleration Vw _i 'it is determined whether or not greater than the threshold value _{α L, Vw i'> α} L
If it is, the process proceeds to step S41 described below. Then, the wheel acceleration Vw _i 'is Vw _i' in the step S39
If not> α _L , the process proceeds to step S34.

[0040] At step S41, the flag F _EXC is determined whether the F _EXC = 1, the flag is F _EXC =
If it is not 1, the flow shifts to step S42, and it is determined whether or not it is the time to start the pressure reduction to shift to the state of reducing the wheel cylinder pressure. This is, for example, the pressure increase / decrease command value ΔP _i ^* (n−1) set in the previous control cycle is a positive value including zero, and the target pressure increase / decrease amount ΔP _0i (in the current control cycle calculated in step S14) It is determined whether n) is a negative value. If it is not the time of the start of pressure reduction, that is, if pressure reduction is to be performed continuously or pressure increase or pressure holding is performed, the process proceeds to step S43, and the target pressure increase / decrease amount ΔP _0i (n) calculated in step S14 is calculated. The current pressure increase / decrease command value ΔP _i ^* is set, and step S1 in FIG.
Move to 6.

On the other hand, in step S42, the wheel cylinder
It is determined that it is time to
If the connection has been disconnected, the process proceeds to step S44,
It is determined whether or not the counter C is C = 0. And mosquito
When the counter C is 0, the process proceeds to step S45.
However, in the same manner as a known anti-skid control device,
For example, the estimated wheel cylinder pressure P at the start of pressure reduction_i
Of the exceptional pressure reduction amount ΔP_EXCCalculated as
Next, the routine proceeds to step S46, where the exceptional pressure reduction amount ΔP
_EXCTo the pressure increase / decrease command value ΔP_i ^*Set as Also, each
Flag F_H, F _M, F_L, F_EXCReset to zero,
It moves to step S16 of No. 2.

If the counter C is not C = 0 at the step S44, the process goes to a step S47.
After updating the flag F _EXC to F _EXC = 1, the process _proceeds to step S43. This flag F _EXC is set to F _EXC = 0 at startup. Step S1 in FIG.
In 6, calculates a valve drive time Tp _i corresponding to decreasing pressure command value [Delta] P _i ^*. Here, the upstream pressure P of each solenoid valve
_U and the downstream pressure P _L and the pressure increase / decrease command value ΔP _i ^* ,
Calculating a valve drive time Tp _i by the following procedure.

For example, when increasing the pressure, the pressure increasing valve (inlet valve) is turned on for a predetermined time ΔTp (for example, 10 msec).
Etc.) When the valve is opened, the flow rate ΔQ _T of the brake fluid is equal to the master cylinder pressure P which is the upstream pressure of the inlet valve.
And _MC, is calculated from the wheel cylinder pressure P _i is the downstream pressure according to the following equation (13). ΔQ _T = k ₁ × (P _MC −P _i ) (13) Here, k _{1 in} the equation is a constant determined by brake specifications and hydraulic characteristics.

Next, the current wheel cylinder pressure P_iBased on
According to the brake characteristic diagram shown in FIG.
Wheel cylinder fluid quantity Q_PiIs calculated. And constant
ΔFlow Q of brake fluid by opening of valve for time ΔTp_TAnd the present
Current wheel cylinder fluid volume Q _PiFrom the sum of
Wheel cylinder fluid amount Q after opening of valve for a fixed time ΔTp<sub>Pi
+ dT</sub>Is estimated. In addition, the estimated wheel
Liquid quantity Q_{Pi + dT}Based on the brake characteristics shown in Fig. 7.
From the figure, the wheel cylinder pressure P after a certain time ΔTp_{i + dT}
Is calculated. Next, the wheel after the predetermined time ΔTp
Cylinder pressure P_{i + dT}From the current wheel cylinder pressure P_iTo
Subtract the wheel cylinder pressure for a certain time ΔTp
Change amount ΔP_dTIs estimated and the pressure increase / decrease
Rep. ΔP_i ^*Valve driving time Tp for realizing_iTo
It is calculated according to the following equation (14).

[0045] _{Tp i = (ΔTp × ΔP i} *) / ΔP dT ...... (14) where the value of the master cylinder pressure P _MC, may it be a value from the master cylinder pressure sensor 38, a brake operation It may be obtained by simple estimation using the time from the start time to the start of the anti-skid control.
Further, the current wheel cylinder pressure P _i is calculated by performing a reverse calculation of the above procedure based on the valve drive time Tp _i up to the previous control cycle. That is, first, based on the valve drive time Tp _i (n-1) in the previous control cycle and the wheel cylinder pressure change amount ΔP _dT in the fixed time ΔTp, the fluid from the previous control cycle is calculated according to the following equation (15). The pressure change amount ΔP _i is calculated.

ΔP _i = (Tp _i (n−1) × ΔP _dT ) / ΔTp (15) Then, this fluid pressure change amount ΔP _i is determined by the wheel cylinder pressure P _i (n−1) in the previous control cycle. To calculate the current wheel cylinder pressure P _i (n). The above procedure shows the case of increasing the pressure. However, when the pressure is reduced, the same procedure is performed with the upstream pressure of the pressure reducing valve (outlet valve) as the wheel cylinder pressure P _i and the downstream pressure as the atmospheric pressure (= 0). What is necessary is just to calculate.

[0047] Then, the process proceeds to step S17, in accordance with the calculated drive time Tp _i, to generate a valve drive signal for controlling each switching valve, and outputs this via the driving circuit. Then, the process returns to the main program (not shown). Here, the inlet valves 12FL to 12RR,
24F and 24R, and outlet valve 14FL-
14RR, corresponding to 26F and 26R are controlled valve, processing for calculating the wheel acceleration Vw _i 'corresponds to the detection means in the process of step S2 of the wheel speed sensors 32FL~32RR and 2, the process of step S14 in FIG. 2 Corresponds to the target pressure increase / decrease amount calculating means, the processing in steps S16 and S17 in FIG. 2 corresponds to the control means, and the processing in steps S45 and S46 through steps S42 to S44 in FIG. 5 corresponds to the exceptional pressure reducing means. Then, steps S23 and S2 in FIG.
5 and S27 correspond to the road surface condition detecting means, and the processes of steps S21 to S39 and step S39 in FIG.
The processing that proceeds to step S43 through steps S44 to S47 corresponds to the exceptional decompression delay means.

[0048] Now, from a state where the vehicle is constant speed running, stop the driver vehicle, or to decelerate, depresses the brake pedal 11a at time t _1, the master cylinder 1
1c is transmitted to each of the wheel cylinders 2FL to 2RR, and as the wheel cylinder pressure rises, this pressure is applied to the brake discs 3FL to 3RR.
And the wheel acceleration V as shown in FIG.
w _i 'is increased in the negative direction, the wheel speed Vw _i decreases as shown by the solid line in FIG. 8 (c), FIG. 8 along with this
Vehicle speed V _X decreases as indicated by a chain line in (c).

In the controller 30, the anti-clock system shown in FIG.
Executes skid control processing at predetermined interrupt timing
And the target wheel speed Vw_i ^*And wheel speed Vw_iAnd based on
According to the expression (12), the target pressure increase / decrease amount ΔP_0iIs calculated
Based on this, the pressure increase / decrease command value ΔP _i ^*And set
Valve drive time Tp_iAccording to the inlet valley
Drive the outlet valve 12i and the outlet valve 14i,
Control the cylinder pressure. That is, the wheel speed Vw_iBut
Target wheel speed Vw_i ^*Below the inlet
The valve 12i is closed and the outlet valve 14i is closed.
Open to reduce wheel cylinder pressure and increase wheel speed
And the wheel speed Vw_iIs the target wheel speed Vw_i ^*Trying to exceed
Then, the wheel speed Vw_iTo reduce the inlet
Open the lube 12i, close the outlet valve 14i
Increase wheel cylinder pressure. Also, at the start of decompression
Then, for example, the wheel cylinder pressure P at this point_i
Exceptional pressure reduction amount ΔP with a value of about 30% of_EXCIncrease
Pressure reduction command value ΔP_i ^*Set as and wheel accordingly
Reduce the cylinder pressure.

[0050] At this time, the Kontora 30 sets the counter C in accordance with the amplitude of the wheel acceleration Vw _i ', is not carried out exceptions decompression when the counter C is C> 0. That is, as shown in FIG. 5, a threshold value α corresponding to the road surface condition is set based on the calculated road surface friction coefficient μ _i , and three threshold values α _H , α _M , α
_L is set (step S21). And while setting the counter C on the basis of the wheel acceleration Vw _i ', when depresses the brake pedal 4 at time t _1, the wheel acceleration V
Since w _i ′ is a negative value, steps S22, S31, S
After going through steps S35 and S38, the process moves to step S41. That is, the counter C is not updated, and C = 0 remains unchanged.
Until the wheel acceleration Vw _i 'is a positive value, the counter C
Is maintained at zero, and the calculated target pressure increase / decrease amount ΔP _0i is maintained at zero. _Therefore , the processing shifts from step S41 to step S43 via step S42, and the target pressure increase / decrease amount ΔP _0i becomes the pressure increase / decrease command value ΔP _i ^*. Is set as

[0051] Then, the wheel cylinder pressure is increased according to the depression amount of the brake pedal 4 Accordingly, the wheel speed Vw _i is trying Shitamawaro the target wheel speed Vw _i ^*, the time t
_When the calculated target pressure increase / decrease amount ΔP _0i becomes a negative value in 2,
In the process of step S42, it is detected that it is time to start depressurization. At this time, since the counter C is zero, the process shifts from step S44 to step S45 to set the predetermined exceptional pressure reduction amount ΔP _EXC as the pressure increase / decrease command value ΔP _i ^* (FIG. 8).
(D)), the pressure is reduced based on this. As a result, the wheel cylinder pressure _Pi is greatly reduced.

Thereafter, steps S41 to S42 are repeated.
Then, the process proceeds to step S43, where the calculated target pressure increase / decrease amount Δ
P_0iTo the pressure increase / decrease command value ΔP_i ^*And based on this
Pressure reduction. Then, this pressure reduction causes the wheel speed Vw_iof
The deceleration becomes smaller and the time t _ThreeAnd the wheel acceleration Vw_i'But
When the value becomes a positive value (FIG. 8B), steps S21 and S22 are performed.
To step S23 through the wheel acceleration V
w_i′ Is the threshold α_H, Α _M, Α_LLower than
After steps S25 and S27, the process proceeds to step S41,
Time t_TwoIs not the time of the start of pressure reduction, so that step S41
From S42 to S43 via S42 and the calculated target
Increase / decrease amount ΔP_0iTo the pressure increase / decrease command value ΔP_i ^*Set as
You.

[0053] Then, the wheel acceleration Vw _i 'is the threshold α
Until exceeds _L, the update of the counter C is not performed at the time t ₄ when the wheel acceleration Vw _i 'exceeds the threshold value alpha _L (FIG. 8 (b)), step S22, S23, S25, S
Then, the process proceeds to step S28 through 27, and the counter C is set to C =
Set as C _L, and sets the flag F _L to F _L = 1 (FIG. 8 (a)).

While the wheel acceleration Vw _i 'is increasing, the counter C is set as C = _CL , and the time t ₅
In the wheel acceleration Vw _i 'exceeds the threshold value alpha _M (FIG. 8
(B)), the process proceeds from step S25 to S26 to set the counter C as C = C _M (FIG. 8 (a)). Since then
Between the wheel acceleration Vw _i 'is increasing counter C =
Set as C _M. Once t ₆ the wheel acceleration Vw _i 'and starts to decrease (FIG. 8 (b)), the process proceeds from step S22 to step S31, since the flag F _H = 1, the process proceeds to step S35, the flag F _M Since F _M = 1, the process proceeds to step S36. Then, since this time the wheel acceleration Vw _i 'is greater than the threshold value alpha _M, and proceeds from step S36 to step S41, updating of the counter C is not performed.

[0055] When the wheel acceleration Vw _i 'is smaller than the threshold value alpha _M at time t ₇ (FIG. 8 (b)), and proceeds from step S36 to step S34, the counter C =
Update to C-1 (FIG. 8A). And time t
_When the target pressure increase / decrease amount ΔP _0i is calculated in step 8 and it is determined that it is the time of the start of pressure reduction, the process proceeds from step S42 to step S44.
Is not C = 0 (FIG. 8 (a)), the flag F _EXC is set to F _EXC = 1 in step S44, and then the process _proceeds to step S43, where the calculated target pressure increase / decrease amount ΔP _{0i is set} to the pressure increase / decrease command value ΔP. _i ^* , and no exceptional decompression is performed (FIG. 8D). Then, in the next control cycle, since the flag F _EXC is set to F _EXC = 1, the process _proceeds to S44.
Since the counter C is not C = 0, steps S44 to S4
Then, the flow shifts to step S43 through step 7, where the target pressure increase / decrease amount ΔP _0i
The pressure is reduced based on.

[0056] Then, when the counter C is gradually decreased with the decrease of the wheel acceleration Vw _i ', where at time t ₉ the counter C becomes C = 0 (FIG. 8 (a)), step S44
Then, the process proceeds to step S45, where the exceptional pressure reduction amount ΔP _EXC is set as the pressure increase / decrease command value ΔP _i ^* (FIG. 8D), and pressure reduction is performed based on this. As a result, the wheel cylinder pressure _Pi is greatly reduced at this point.

Thereafter, the counter C maintains C = 0, and since it is not the time of the start of pressure reduction, the target pressure increase / decrease amount ΔP
_0i is set as the pressure increase / decrease command value ΔP _i ^* , and pressure reduction is performed based on this. And, with this, the wheel acceleration Vw
_i 'is a positive value recovered, it exceeds the threshold value alpha _L at time t ₁₀ (FIG. 8 (b)), the step S from step S27
Moves to 28, but the counter C is set to C = C _L (FIG. 8 (a)), not a pressure-decrease start time, the target pressure increase amount [Delta] P _0i is set as the pressure increase and decrease the command value [Delta] P _i ^* Decompression is performed.

Then, the wheel acceleration Vw_i′ Decreases
t₁₁And the threshold α_L(Fig. 8 (b)).
From step S38 to step S34 via step S39.
And decrement the counter C. And time t₁₂Calculated by
Issued target pressure increase / decrease amount ΔP_0iBecomes a negative value, and
If rejected, step S41 through step S42
The process proceeds to S44, but at this time, the counter C indicates C = 0.
The flag F _EXCTo F_EXC= 1 and calculated
Target increase / decrease amount ΔP_0iThe pressure is reduced based on
(D)). And time t₁₃And the counter C becomes C = 0
Moves from step S44 to step S45
And the predetermined exception pressure reduction amount ΔP_EXCIs the pressure increase / decrease command value ΔP_i ^*
(FIG. 8 (d)).
The decompression is performed.

[0059] Then, although the wheel acceleration Vw _i at time t ₁₄ increases 'is then becomes positive wheel acceleration Vw _i', the counter C is maintained at zero since not exceed the threshold alpha _L.
When it becomes a vacuum beginning at time t _15, therefore,
The process moves from step S41 to step S44 via step S42. At this time, since the counter C is zero, step S4
5 and the exception pressure reduction amount ΔP _EXC is increased by the pressure increase / decrease command value ΔP _i
Set as ^*, performs decompression on the basis of the exception pressure decrease amount [Delta] P _EXC at this time (Fig. 8 (d)).

Therefore, for example, when the vehicle travels on a rough road such as a gravel road, the fluctuation of the wheel acceleration Vw 'becomes large, and when the target pressure increase / decrease amount ΔP _0i is calculated, the differential control term becomes dominant, and the wheel speed Vw _i There vacuum in a state in which exceeds the target wheel speed Vw _i ^* is initiated, resulting braking shortage Pounds and makes braking distance may become longer, further become decompression excessive if the exception vacuum was carried out in this state The braking distance becomes longer. In the above embodiment, the time t ₇ and time t ₁₁
In the wheel acceleration Vw _i falls below the threshold α _M or α _L '
When the vehicle starts to decelerate, the wheel acceleration Vw at that time
count value C corresponding to a delay time corresponding to the magnitude of _i '
_M, Set C _L to the counter until the delay time has elapsed, even when a pressure-decrease start time of starting the decompression, because Separate the exception decompression, the wheel speed V
w _i is an exception decompression is performed from being sufficient deceleration. Thus, avoiding the wheel speed Vw _i is because it is possible to start the pressure reduction at the time when sufficient approached the value of the target wheel speed Vw _i ^* vicinity, by avoiding a braking insufficient Pounds, braking distance is longer can do.

[0061] Also, as shown at time t _14, when the wheel acceleration Vw _i 'does not exceed the threshold value alpha _L, the counter C is set to remain zero, exceptions vacuum when it becomes a vacuum initiated when t ₁₅ To do. In other words, the like when traveling on a rough road surface, as compared to the case of traveling an ordinary flat road such, since the recovery speed of the wheel speed is faster ie positive wheel acceleration Vw _i 'increases, the wheel acceleration Vw _i ′ Is smaller than the threshold value α _L, it means that the vehicle is traveling on a normal road surface. At this time, the exceptional pressure reduction is performed at a normal timing. Therefore, the exceptional pressure reduction must be performed at an appropriate timing according to the road surface condition. Can be.

[0062] In the above embodiment, the threshold alpha _L, alpha _M, the alpha _H provided, and be provided the counter value C _L corresponding to the delay time, C _M, a C _H accordingly Although the case has been described, the present invention is not limited to this, and one threshold α may be provided.
More than this may be provided, and in this case, a counter value corresponding to the delay time according to each threshold value may be set.

[0063] In the above embodiment sets the count value C _H corresponding to the delay time which the wheel speed Vw _i is expected to fall below the target wheel speed Vw _i ^*, C _M, the C _L,
There has been described a case where the delay time is to perform an exception decompression after a lapse, the wheel speed Vw _i is the target wheel speed V
to detect whether or not lower than the w _i, may be carried out an exception under reduced pressure when the wheel speed Vw _i is less than the target wheel speed Vw _i.

Further, in the above embodiment, the case where the delay time is measured using the down counter has been described. However, the up counter is activated when the threshold value is exceeded by using the up counter. Exceptional pressure reduction may be performed when a count value corresponding to the delay time is reached.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention.

FIG. 2 is a flowchart illustrating an example of a processing procedure of an anti-skid control process in the controller of FIG. 1;

FIG. 3 is a characteristic diagram illustrating a relationship between a slip ratio and wheel acceleration.

FIG. 4 is an explanatory diagram showing a relationship between a road surface friction coefficient and a target slip ratio.

FIG. 5 is a flowchart illustrating an example of a processing procedure of an exceptional decompression process in step S15 of FIG. 2;

FIG. 6 is a control map showing a correspondence between a road surface friction coefficient μ and a threshold value α.

FIG. 7 is a brake characteristic diagram showing a correspondence between a wheel cylinder pressure and a wheel cylinder liquid amount.

FIG. 8 is an explanatory diagram for explaining the operation of the present invention;

FIG. 9 is an explanatory diagram for explaining a conventional operation.

[Explanation of symbols]

 1FL-1RR Wheel 2FL-2RR Wheel cylinder 11a Brake pedal 11c Master cylinder 30 Controller 32FL-32RR Wheel speed sensor 34 Acceleration sensor 36 Yaw rate sensor 38 Master cylinder pressure sensor

Claims (4)

[Claims] 1. A control valve for controlling a fluid pressure of a brake cylinder disposed on a control target wheel based on a master cylinder pressure from a master cylinder, and detecting a wheel speed and a wheel acceleration / deceleration of the control target wheel. Detecting means for detecting the wheel speed and wheel acceleration / deceleration detected by the detecting means, and a target pressure increase / decrease amount calculating means for calculating a target pressure increase / decrease amount of the fluid pressure based on these target values; Control means for controlling the control valve so that the fluid pressure of the cylinder for use changes by the target pressure increase / decrease amount; exceptional pressure decrease means for setting a predetermined pressure decrease amount as the target pressure increase / decrease amount at the start of the pressure reduction of the fluid pressure An anti-skid control device comprising: a road surface condition detecting device that detects a road surface condition of a traveling road surface based on a wheel acceleration / deceleration detection value detected by the detecting device; An anti-skid control device comprising: an exceptional decompression delay unit that delays the execution timing of the exceptional decompression by the exception decompression unit when detecting that the traveling road surface is a rough road surface. 2. The road surface condition detecting means is configured to determine that the road surface is rough when the wheel acceleration / deceleration exceeds a preset threshold value. An anti-skid control device as described. 3. The anti-diagnosis device according to claim 1, wherein the exception pressure reduction delay means delays the timing of the exception pressure reduction by the exception pressure reduction means as the wheel acceleration / deceleration increases. Skid control device. 4. The anti-skid control device according to claim 2, wherein the threshold value is changed according to a road surface friction coefficient.