JPH01127447A - Antiskid control valve - Google Patents

Abstract

PURPOSE:To carry out optimum antiskid control by setting a new desired slip rate in accordance with an output from a comparator means for comparing a desired slip rate having previously been set with a computed wheel slip rate with a reference level. CONSTITUTION:In an antiskid control device 1, a computing section 6 calculates a wheel slip rate from a vehicle speed and a wheel speed detected by sensors and computing sections 3, 5. Further, a wheel slip rate trigger section 8 compares an output from a wheel acceleration computing section 7 with an internally held basic level. As a result, the wheel slip rate is delivered to a comparing change-over section 9 for comparing the wheel slip rate with a previously set desired slip rate and for selectively delivering either one of them as a new slip rate to a control section 10. With this arrangement, the desired slip rate is changed in accordance with a condition of a road surface, and it is possible to perform optimum antiskid control in accordance with the road surface.

Description

TECHNICAL FIELD The present invention relates to an anti-skid control device which is suitably implemented in, for example, an automobile, and which prevents wheels from becoming locked due to operation of a brake pedal.

BACKGROUND ART It is generally known that the dynamic friction coefficient is smaller than the static friction coefficient. For example, when operating a brake pedal in a car to stop the car, the rotation of the wheels is completely stopped and the wheels are locked. Rather than doing this, braking distance will be shorter if the wheel slip ratio of the wheels relative to the road surface is kept constant and the wheels are allowed to rotate to a certain extent.

The wheel slip rate S can be expressed as S=(VS-VW)/VS (1) using the vehicle speed VS and the wheel speed VW. In typical prior art, a target value for this wheel slip rate S (hereinafter referred to as target slip rate) is set in advance, and calculated from the vehicle body speed ■S and the preset target slip rate. The anti-skid control of the wheels is configured to be performed based on a comparison between the target slip distance (wheel speed for realizing a drifting slip ratio) and the wheel speed VW.

FIG. 5 is a diagram for explaining the anti-skid control according to the prior art described above during braking of an automobile. In FIG. 5, the curve p1 indicates the vehicle speed ■S, and the curve p1
2 indicates the wheel speed VW. In addition, in response to the change in vehicle speed ■S shown by curve 11, the change in target slip speed to achieve the target slip rate is shown by curve 11.
3.

The wheel speed VW decreases by operating the brake pedal,
When the wheel speed VW falls below the target slip speed shown by the curve 13 at time t1, the wheel speed VW rapidly decreases, and at time t
2, the shape becomes a lock-B. In such a situation, the prior art anti-skid control device reduces the braking force on the wheels, thereby increasing the wheel speed VW. Then, at time t3, when the wheel speed VW exceeds the target slip speed shown by the curve 13, the braking force on the wheels is increased again, and thereby the wheel speed VW starts to decrease again. In this way, anti-skid control is performed by bringing the wheel speed VW closer to the target slip speed corresponding to the target slip rate.

Problems to be Solved by the Invention The braking distance of an automobile can be minimized by setting the target slip ratio so that the frictional force between the road surface and the wheels is maximized. However, the condition of the road surface is not necessarily constant, and it is not always possible to perform ideal anti-skid control depending on a constant target slip ratio.

FIG. 6 shows the relationship between the wheel slip rate S and the frictional force between the road surface and the wheels when the road surface condition changes. Curve 14 corresponds to a relatively slippery road surface, and is a curve! 5 is suitable for relatively slippery roads.

In curve 14, the frictional force is maximum at wheel slip rate S1, whereas in curve ! In No. 5, the friction force is maximum at the wheel slip rate S2, which is a smaller value than the wheel slip rate S1. Therefore, for example, in case 6 where the target slip rate is set equal to the wheel slip rate S1, it is not possible to sufficiently cope with the road surface shown by the curve 15, and the braking distance of the vehicle cannot be made the shortest.

SUMMARY OF THE INVENTION An object of the present invention is to provide an anti-skid control device that can change a target slip ratio in accordance with road surface conditions, and therefore can perform optimal anti-skid control.

Means for Solving the Problems The present invention provides the following features: vehicle speed detection means; wheel speed pressure detection means; calculation means for calculating wheel acceleration based on the output of the wheel speed detection means; vehicle speed detection means and wheels. wheel slip rate calculation means for calculating a wheel slip rate based on each output from the speed calculation means; a comparison means for comparing the output of the calculation means with a predetermined reference level; and a new target slip rate at the timing of the output of the comparison means. This anti-skid control device is characterized in that it includes a selection means for setting a new target slip ratio based on a previously set target slip ratio and an output of the comparison means.

In the present invention, the vehicle speed is detected by the vehicle speed detection means, and the wheel speed is detected by the wheel speed detection means. Based on the output of the wheel speed detection means, the wheel acceleration is calculated by the calculation means, and the wheel slip rate calculation means calculates the wheel slip rate based on the respective outputs of the vehicle body speed detection means and the wheel speed detection means. The output of the calculation means is compared with a predetermined reference level in the comparison means, and based on the comparison result, the comparison means provides the output of the wheel slip ratio calculation means to the selection means.

In the selection means, a new stray slip ratio is set based on the previously set target slip ratio and the output of the wheel slip ratio calculation means provided from the comparison means.

As a result, the target slip ratio is changed in accordance with the road surface condition, and therefore, optimal anti-skid control corresponding to the road surface can be performed.

Embodiment FIG. 1 is a block diagram showing the basic configuration of an anti-skid control device 1 which is an embodiment of the present invention. The output of the vehicle speed sensor 2, which is realized by a spatial filter type and Doppler type detection device, an acceleration sensor, etc., is given to a vehicle speed calculation section 3. Further, the output of the wheel speed sensor 4, which is realized by a detection device or the like that outputs a signal with a frequency corresponding to the rotational speed of the wheel, is given to the wheel speed calculation section 5. Vehicle speed calculation unit 3 and wheel speed calculation unit 5
The output of is given to the wheel slip rate calculation unit 6 in parallel,
In the wheel slip rate calculation section 6, the wheel slip rate S is calculated based on the first equation. A vehicle speed detection means includes the vehicle speed sensor 2 and the vehicle speed calculation section 3, and a wheel speed detection means includes the wheel speed sensor 4 and the wheel speed calculation section 5.

The output of the wheel speed calculation section 5 is also given to the wheel acceleration calculation section 7, and the wheel acceleration α is calculated based on the rate of change of the output of the wheel speed calculation section 5. The output of the wheel acceleration calculating section 7 is given to a wheel slip rate trigger section 8 which is a comparison means, and the wheel slip rate S is given to the wheel slip rate trigger section 8 from the wheel slip rate calculating section 6.

The wheel slip rate trigger section 8 has a reference level K inside it.
Based on the comparison result between this reference level KG1 and the output of the wheel acceleration calculation section 7, the output of the wheel slip ratio calculation section 6 is intermittently applied to the comparison switching section 9, which is a selection means. The comparison switching unit 9 compares the previously set target slip rate S1 with the wheel slip rate calculation unit 6.
A comparison is made with the wheel slip rate S provided via the wheel slip rate trigger section 8, and one of the two is selectively given to the control section 10 as a new target slip rate S1. The control unit 10 is further given the vehicle speed ■S from the vehicle speed calculation unit 3, the wheel slip rate S from the wheel slip rate calculation unit 6, and the wheel acceleration α from the wheel acceleration calculation unit 7, and based on these, Then, control data is selectively read out from the internal memory 11, and braking its corresponding to the target slip ratio S1 is controlled.

When the wheel slip rate S increases beyond the optimum value corresponding to the road surface, the wheel speed VW begins to decrease rapidly.
Therefore, wheel acceleration α decreases. That is, it can be considered that the frictional force between the road surface and the wheels is at its maximum at the moment when the wheel acceleration α falls below a certain constant value.

In the wheel slip rate trigger section 8, when the wheel acceleration α falls below the reference level KGI by comparing the output of the wheel acceleration calculation section 7 with the reference level KG1 held internally, the wheel slip rate trigger section 8 synchronizes with this and triggers a wheel slip. The output of the rate calculation section 6 is given to the comparison switching section 9. As a result, the signal corresponding to the wheel slip rate S given from the wheel slip rate trigger unit 8 to the comparison switching unit 9 can be considered to correspond to the optimum value of the target slip rate S1.

In the comparison switching section 9, the difference between the wheel slip rate S given from the wheel slip rate trigger section 8 and the previously set target slip rate S1 is calculated, and when this calculation result is smaller than a predetermined value, the target slip is set. If the ratio S1 is not changed and is large, the currently given wheel slip ratio S is newly set as the target slip ratio S1. Due to such processing in the comparison/switching section 9, the processing of the control section 10 is the same as long as the road surface condition does not change beyond a certain level, and thereby the processing is simplified.

FIG. 2 is a diagram for explaining the processing performed in the control unit 10, and shows the contents stored in the memory 11.

As described above, the control unit 10 is given the body speed ■S, wheel slip rate S, wheel acceleration α, and target slip rate S1, and based on these, parameters Vl and V2 regarding the wheel speed that satisfy the second equation below are given. ．． V3 is set. The control unit 10 also includes a parameter Gl regarding the wheel acceleration α.

G2. G3 is set, and these satisfy the third equation below.

V 1 ]> V 2 ;・■3...
(2) Gl<G2<03 (3) Parameter (2) is a parameter corresponding to the slip speed that is the wheel speed that realizes the target slip ratio S1. Further, the parameters Gl, G2°G3 are, for example, -2, 5G, -1, OG, respectively.

+5. It is a parameter corresponding to the capacitance of QG (where G is gravitational acceleration). The parameter G1 is the reference level K (31
It corresponds to the wheel acceleration corresponding to .

In FIG. 2, addresses of memory 11 are shown in parentheses. The braking mechanism of an automobile is realized by, for example, a hydraulic brake, and is configured to apply braking force by increasing hydraulic pressure. The symbol shown at the 11th address in the memory 11 indicates a pulse-like increase in the hydraulic pressure, the symbol shown at the 4th address indicates a continuous pressure increase, and the symbol shown at the 5th address indicates a pulse-like increase in the hydraulic pressure. The symbol shown at address 6 indicates pressure reduction, and the symbol shown at address 9 indicates neither pressure increase nor reduction, and the symbol shown at address 9 indicates continuous pressure reduction.

For example, if the wheel speed VW is V1)VW)V2-...
When (4) is satisfied and the wheel acceleration α satisfies G 2 < α < G 3 . Control is performed to increase the pressure.

FIG. 3 is a flowchart 1 for explaining the operation of the anti-skid control device 1. step r+l
In this step, the vehicle speed calculating section 3 calculates the vehicle speed vS. Further, in step n2, the wheel speed calculating section 5 calculates the wheel speed VW. The output of the wheel speed calculation unit 5 is given to the wheel acceleration calculation m7, and in the Stella 7n3, the wheel acceleration (l) is calculated.Furthermore, in step n4
In the wheel slip rate calculation section 6, a wheel slip 2vS is calculated based on the outputs of the vehicle speed calculation section 3 and the wheel speed calculation section 5.

In step n5, the wheel slip rate trigger unit 8 compares the wheel acceleration α given from the wheel acceleration calculation unit 7 with the reference level K G 1, and when the wheel acceleration α is larger than the reference level K G 1, In step n6, the flag F1 for instructing the output to the comparison switching section of the wheel slip rate trigger section 8 is reset, and thereby the wheel slip rate h trigger section 8 is reset.
, no output is made to the ratio axis switching section 9. step r
+ 5, the wheel acceleration α reaches the reference level [(G 1
If 1' is determined to be less than
'11 was cut off. If flag F1 is set, the process returns to step r+1; if flag F1 is not set, flag F1 is set in step rIS.
1 is sent to Sera 1. As a result, the wheel slip rate l-
The trigger section 8 supplies the wheel slip '\' to the output ratio calibration switching section 9 of the calculation section 6.

In step n7 described above, the flag F1 is set when the wheel acceleration α is below the reference level 1 (G1) and the target slip ratio S1 has already been set.

In step rI9, the comparison switching section 9 calculates the wheel slip rate S given from the vehicle RTh slip 11 and the rigging section 8.
Then, the difference between the current slip rate S1 and the current slip rate S1 is calculated, and in step r1]0 it is determined whether the calculation result is equal to or higher than the reference level I(S held in the comparison switching unit 9).In step [110] Wheel slip rate S
If it is determined that the difference between the slip rate and the target slip rate S1 is less than the reference level KS, the process returns to step C''. In other words, when the difference between the TI transport slip rate S and the target slip rate 81 is relatively small, the target slip rate 8
It will be determined that change 1 is unnecessary.

In step ri 10, +5-31. If it is determined that l≧KS (6), the process moves to step r11.1.
The comparison switching unit outputs the currently given wheel slip rate S as the target slip rate S1. After this,
The process returns to step n1.

FIG. 4 is a diagram for explaining the anti-skid control l performed in the anti-skid control device 1. Fourth
Figure (1) shows vehicle speed ■S, wheel speed VW, and parameter V.
l, V2. It is a graph showing each change of V3,
They are in turn curve LL.

L2. L3. L4. Compatible with L5. Also, Figure 4 (
2) shows the change in wheel acceleration α.

In No. 4117I, the address of the memory 11 read by the control unit 10 is shown in parentheses at the reference numeral indicating each period.

The hydraulic pressure of the braking mechanism is increased by the operation of the brake pedal by the driver of the automobile, and the wheel speed V is increased at time t1.
W is less than parameter ■1. Period Wl before time 1
, the wheel speed VW exceeds the parameter (1), and the acceleration α is between the parameters G1 and G2. Therefore, the control unit 10 reads the data at the second address of the memory 11. As a result, the control unit 10 controls the braking mechanism so that its oil pressure is increased in a pulse-like manner during the period W1. After time t1, the wheel speed VW takes a value between the parameters V1 and V2, so the control unit 10 starts reading the data at the sixth address in the memory 11.

At time t2, when the wheel acceleration α falls below the parameter G1, the output of the wheel slip rate trigger section 8 is given to the comparison switching section 9, and after comparison with the previously set target slip rate S1 in the comparison switching section 9, A new target slip rate S1 is given to the control unit 10 (assuming that the above equation 6 holds true at time t2), at this time,
(Part 1 10 is the parameter Vl, V2.y3z is changed as shown in Fig. 1 (1>
becomes the value of parameter ■2. Note that the parameters V1. in the periods Wl and W2. V2. The value of V3 is determined based on the previously set target slip ratio S1.

During the period W3 from time t2 until the wheel speed VW falls below the parameter V3 at time 3, the memory 1
During the period W5 from time 073 when the data at the 9th address of 1 is read until the wheel acceleration α exceeds the parameter G1, the data at the 13th address of the memory 11 is read. During the period W4 from time t11 until the acceleration α exceeds the parameter G2, the first -
Data at address 1 is being read. In this way, the control unit 1O outputs a control signal to the braking mechanism while sequentially specifying addresses in the memory 11. Thereafter, in the same manner, the wheel speed VW is changed to the parameters Vl, V2 . V3 or below, and the wheel acceleration α is determined by the parameters Ql, Q2 . Q3, the read address of the memory 11 is changed, and the t1-th address is changed in the period W6 to W21.
The contents of the ataxes shown in parentheses in 2) in the figure are sequentially read out. In this way, the wheel speed VW is
As shown in Figure 1 (1), there will be an abnormality.

At time t12, parameters Vl, V2. The reason why V3 did not change is because the above-mentioned formula 6 did not hold, and the previously set value was used as the target slip ratio 51.

As described above, in this embodiment, when the wheel acceleration α falls below the reference level KGI, the wheel slip rate S is input from the wheel slip rate calculation unit 6 to the comparison switching unit 9 in synchronization with this. The wheel slip rate S input at this time is considered to be the optimum wheel slip rate corresponding to the road surface condition at that time. This wheel slip rate S is compared with the previously set target slip rate SL in Himakiri 1 negative section 9, and the wheel slip is 8$S jump from the target slip rate S1).
In case 3 where the difference is relatively small and does not satisfy the sixth equation above,
The target slip IsI is not changed, and the difference between the wheel slip rate S and the target slip rate VSI is relatively large, and the sixth
When the formula is satisfied, the currently obtained wheel slip fiS is output as a new target slip ratio S1. This perforated plate slip rate S1 is given to the control unit 10,
A braking mechanism is controlled. In this way, the target slip ratio S1 is changed every time the road surface condition changes, and therefore, it is possible to optimally control the anti-slip ratio corresponding to the road surface condition.

The above-described processing by the comparison switching section 9 suppresses variations in the target slip ratio S1 to some extent, and therefore the processing in the control section 10 is a simple process with relatively few changes.

In the above-mentioned embodiment, although the change in the target slip ratio S1 was suppressed in the comparison switching section 9,
The output of the wheel slip rate trigger section 8 may be directly sent to the control section 10.

Effects As described above, according to the present invention, an optimal anti-skid system corresponding to all road surface conditions can be realized, so that, for example, the braking distance of a car can always be minimized. .

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the basic configuration of an anti-skid control device 1 which is an embodiment of the present invention, FIG. 2 is a diagram for explaining processing in the control unit 10, and FIG. 3 is an anti-skid control FIG. 4 is a flow chart for explaining the operation of the anti-skid control device 1; FIG. 5 is a flowchart for explaining the operation of the anti-skid control device 1; FIG. Figure 6 is a diagram for explaining the control, and is a diagram for explaining changes in the optimum wheel slip rate due to changes in road surface conditions. 61. Anti-skid control section π, 2. Vehicle speed sensor, 3.・
・Vehicle speed calculation unit, 4...Wheel speed sensor, 5...
Wheel speed calculation section, 6... Wheel slip rate calculation section, 7.
...Wheel acceleration calculation section, 8..Wheel slip rate trigger section, 9..Comparison switching section Agent Patent attorney Keibu Saikyo Part 3 Fig. 5 Fig. 60 Keiki-cho Surisif ℃ bank S

Claims (1)

[Scope of Claims] Vehicle speed detection means; Wheel speed detection means; Calculation means for calculating wheel acceleration based on the output of the wheel speed detection means; Outputs of the vehicle speed detection means and the wheel speed calculation means. a wheel slip ratio calculation means for calculating a wheel slip ratio based on the calculation means; a comparison means for comparing the output of the calculation means with a predetermined reference level; and a selection means for setting a new target slip ratio at the timing of the output of the comparison means. 1. An anti-skid control device comprising: selection means for setting a new target slip ratio based on the previously set target slip ratio and the output of the comparison means.