JPS62227843A - Anti-lock control method - Google Patents

Abstract

PURPOSE:To prevent an unnecessary anti-lock control where the brake is controlled based on the comparison between estimated vehicle speed and vehicle speed by operating vehicle speed based on the wheel speed of a wheel which has notching to do with an idling wheel when the wheel is idling. CONSTITUTION:While a vehicle is running, under a condition that a driving wheel, for example, a front wheel is not idling, vehicle speed Vv2 operated by No.2 operating circuit 52 based on the wheel speed of the driving wheel speed Vwf is used as estimated vehicle speed Vv. And when the driving wheel is idling, and when the wheel speed Vwf of said riving wheel which is greater than the estimated vehicle speed Vv2, is kept continued for more than a certain time, an idling condition is detected by an idling detection circuit 55 for changing a common contact 53c of a change-over switch 53 over to a contact 53a. Owing to this constitution, the use of vehicle speed Vv1 operated by No.1 operating circuit 52 as estimated vehicle speed Vv prevents the estimated vehicle speed Vv from becoming higher than actual vehicle speed for precluding an anti-lock actuation unless it is required.

Description

Detailed Description of the Invention A8 Objective of the Invention (1) Industrial Application Field The present invention estimates vehicle speed based on wheel speed, and compares the wheel speed with a reference value based on the estimated vehicle speed. The present invention relates to an anti-lock control method for controlling the supply of braking hydraulic pressure to wheel brakes.

(2) Prior Art Conventionally, such an anti-lock control method is known, for example, from Japanese Patent Publication No. 56-47010.

(3) Problems to be Solved by the Invention In the above-mentioned prior art, the maximum value of the speeds of a plurality of wheels including the driving wheels is selected as the reference value for estimating the vehicle speed.

However, when wheels, particularly drive wheels, spin, the vehicle speed is calculated based on the speed of the wheels, which results in anti-lock control being performed when unnecessary.

The present invention has been made to solve this problem, and it avoids the estimated vehicle speed being calculated to be higher than the actual vehicle speed even if the wheels spin, and eliminates unnecessary anti-lock activation. It is an object of the present invention to provide an anti-lock control method that prevents the occurrence of locking.

B8 Structure of the Invention (1) Means for Solving the Problems According to the present invention, when a wheel is spinning, the vehicle speed is calculated based on the wheel speed of a wheel different from the wheel that is spinning.

(2) Effect When the wheels are spinning, the vehicle speed is calculated based on the wheel speeds that are not affected by the wheels spinning, so it is possible to avoid estimating the estimated vehicle speed to be higher than the actual vehicle speed.

(3) Examples Examples of the present invention will be explained below with reference to the drawings.
First, in FIG. 1 showing an embodiment of the present invention, a brake pedal 1 is operatively connected to a mask cylinder M, and when a driver depresses the brake pedal 1, the mask cylinder M applies hydraulic pressure to an oil passage 2. occurs. This oil passage 2 is connected to a hydraulic control circuit 3, and a braking hydraulic pressure corresponding to the hydraulic pressure is output from the hydraulic control circuit 3.

Wheel brakes are mounted on the left and right driving wheels and left and right driven wheels of the vehicle, respectively, and braking oil pressure is supplied from the hydraulic control circuit 3 to these wheel brakes. For example, in a front wheel drive vehicle, the left and right front wheels as driving wheels are equipped with a left front wheel brake BNf and a right front wheel brake Brf, and the left and right rear wheels as driven wheels are equipped with a left rear wheel brake Bβr and a right rear wheel. Brake Brr is installed. Each brake Bj! f,Brf,Bj! r and Brr are, for example, drum brakes, and the brake oil chambers 4 of the left front wheel and right front wheel brakes B1f and Brf are communicated with oil passages 5 from the hydraulic control circuit 3, and the brakes for the left rear wheel and the right rear wheel are An oil passage 5' from the hydraulic control circuit 3 is communicated with the brake oil chambers 4 of the brakes Blr and Brr.

When brake oil pressure is supplied to each brake oil chamber 4 in each brake Bef, Brf, BIlt, and Brr, the piston 7
．． The brake shoes 9 and 10 are moved in the direction of moving away from each other, and the brake shoes 9 and 10 each contact a brake drum (not shown) to generate braking torque.

Furthermore, if the braking oil pressure in each brake oil chamber 4 is too large, the braking torque generated between each brake shoe 9, 10 and the brake drum becomes too large, and as a result, the wheels become locked. Therefore, when the wheels are about to enter the locked state, the brake hydraulic pressure is reduced by the hydraulic control circuit 3, thereby preventing the wheels from entering the locked state.

The hydraulic control circuit 3 controls the left and right front wheel brakes Il! r.

Modulator 1) compatible with Brf, and modulator 1) compatible with left and right rear wheel brakes Bffr and Brr.
Since both modulators 1)゜1)' have basically the same configuration, the structure of only one modulator 1) will be described in detail.

That is, the modulator 1) has a cylinder part 14 which is closed at both ends and partitioned in the middle by a partition wall 13, and a pair of pistons 15 and 16 at both ends, with the partition wall 13 in the area between the pistons 15 and 16. and a rod 17 that passes through the shaft so as to be freely slidable in the axial direction. The cylinder chamber between the partition wall 13 and one piston 15 is the primary side mJ + hydraulic chamber 18
It is communicated with the mask cylinder M via the oil passage 2. The cylinder chamber between the partition wall 13 and the other piston 16 serves as a secondary braking hydraulic chamber 19, and is communicated via an oil passage 5 with the braking oil chambers 4 of the left and right front wheel brakes Blf and Brr. One end wall of the cylinder part 14 and one piston 1
An anti-lock control hydraulic chamber 20 is defined between the
A release oil chamber 21 is defined between the other end wall of the cylinder portion 14 and the other piston 16, and the release oil chamber 21 is communicated with the reservoir R of the mask cylinder M. Further, a spring 22 that urges the piston 16 away from the partition wall 13 is housed in the secondary braking hydraulic chamber 19, and a spring 23 that urges the piston 15 toward the partition wall 13 is housed in the anti-lock control hydraulic chamber 20. is stored.

An oil passage 24 is connected to the anti-lock control hydraulic chamber 20, and this oil passage 24 is connected to a hydraulic pump P via a normally closed inlet valve Vi, and is also connected to a hydraulic pump P via a normally open outlet valve Vo. Connected to tank T. Further, an accumulator Ac is connected between the inlet valve Vi and the hydraulic pump P.

Also in the other modulator 1)', the primary braking hydraulic chamber 18' is communicated with the mask cylinder M, and the secondary braking hydraulic chamber 19' is connected to the left and right rear wheel brake Bar through the oil passage 5'.
, Brr, and the release oil chamber 21' is communicated with the reservoir R.

Further, the anti-lock control hydraulic chamber 20' is connected to a hydraulic pump P via a normally closed inlet valve Vi', and to an oil tank T via a normally open outleft valve Vo'.

The inlet valves Vi, Vi' and the outlet valves Vo, Vo' are solenoid valves whose opening and closing operations are controlled by a control means 32.

When the inlet valves Vi, Vi' are closed and the outlet valves Vo, Vo' are open, the anti-lock control hydraulic chamber 20, 20' is open to the oil tank T, and when the brake pedal 1 is depressed, Primary brake hydraulic chamber 1
When hydraulic pressure is supplied from the mask cylinder M to 8.18', the volume of the secondary brake hydraulic pressure chamber 19.19' decreases, and the mask cylinder Braking oil pressure corresponding to the oil pressure from M is supplied. Therefore, the torque during braking can be freely increased according to the driver's braking operation.

When the outleft valves Vo, Vo' are closed with the inlet valves Vi, Vi' closed, the control oil in the anti-lock control hydraulic chambers 20, 20' is locked, so each modulator 1). 1) 'Secondary brake hydraulic chamber 19.19' is the primary brake hydraulic chamber], 8.1.8
Regardless of the increase or decrease in the oil pressure supplied to the brake, its volume remains unchanged, and therefore the torque during braking is maintained at a constant level regardless of the driver's braking operation. Such an operating state is suitable when the possibility of wheel locking arises.

Furthermore, when the inlet valves Vi, Vi' are opened and the outlet valves Vo, Vo' are closed, anti-lock control hydraulic pressure is supplied to the anti-lock control hydraulic chambers 20 and 20'. is acting on the primary brake hydraulic chamber 18.18', 2
Next, the volume of the brake hydraulic chamber 19°19' increases, and each wheel brake Blr.

The oil pressure in the brake oil chamber 4 of Brf, Blr, and Brr decreases,
Braking torque is weakened. Therefore, when the wheels are about to enter the lock state, the inlet valves Vi, Vi
By opening the outlet valves Vo and Vo' and closing the outlet valves Vo and Vo', it is possible to avoid the wheels from entering the locked state.

In FIG. 2, the configuration of the control means 32 will be explained, including a configuration for controlling the inlet valve Vi and outlet valve Vo corresponding to the wheel brakes Blf and Brr of one set, and the wheel brake Blr of the other set, 13
Inlet valve Vi′ and outlet valve V corresponding to rr.

The configuration for controlling ′ is basically the same, so
Here, only the configuration for controlling one of the inlet valves Vi and the outleft valve Vo will be described.

The control means 32 includes a judgment circuit 33 such as a microcomputer, and this judgment circuit 33 judges whether the wheels are in a locked state or not, and opens and closes the inlet valve Vi and the outlet valve VO based on the judgment result. output a signal for

Now, if we consider the criteria for determining which conditions should be met to output a signal for anti-lock control, the following 4 (a) to (d+) are generally considered.
A similar method has been proposed.

(al Wheel acceleration *w Standard wheel deceleration - Q we
A method that outputs a signal β when

(bl A method of outputting a signal S and relaxing the braking oil pressure when wheel speed Vw < first reference wheel speed Vr. However, in this case, the vehicle speed is assumed to be ■■, and the wheel slip rate is λ1. Since Vr,=Vv・(1−λ,), when the wheel slip rate is λ, Vw<
Vrl is the same as λ>λ, and Vw<Vr or λ
>λ, the signal S is output.

(C1 above fat, When either one of (b) is established (This method loosens the braking oil pressure.

fdl A method of relaxing the braking hydraulic pressure when (al, (bl) are established at the same time.

In the method (a), the reference wheel deceleration -9w0 is set to a value that does not occur during braking in a state where there is no risk of wheel locking, for example, normally -2.0 to 1.2G. However, according to this method, -1,0
Wheel deceleration of around -0.5G may occur,
In the latter half of braking, even though the wheels are locked, no signal is output to loosen the brake hydraulic pressure. In addition, when driving on rough roads, the wheel acceleration 9w pulsates finely even during normal braking.
Even when there is no risk of wheel locking, the signal β is output, reducing braking efficiency.

Furthermore, in the above method, even if the slip ratio λ is high, that is, even if the signal S1 is output, if the wheel speed Vw is increasing, it is determined that the braking oil pressure is sufficiently relaxed. However, even within this period, the braking oil pressure will be loosened, resulting in a decrease in braking efficiency.

In the method of fc) above, the drawbacks of (al) and (b)
It is clear that there are shortcomings.

Finally, the fd+ method solves the problem of reduced braking efficiency when driving on a rough road, and the problem of reducing braking efficiency by loosening the brake hydraulic pressure while the wheel speed Vw is increasing. Furthermore, the reference wheel deceleration -QWQ is set within the range of wheel deceleration that occurs during braking under normal road running conditions, for example, from -1.0 to
When set to OG, preferably -0°3 to -0.6G,
In braking operations performed on snowy roads, on the autobahn, etc., even when the wheel deceleration is -1.0 to -0.5 G, a locked state can be detected and the brake hydraulic pressure can be relaxed.

Therefore, a signal corresponding to the wheel speed Vw is inputted from the wheel speed detector 34 to the judgment circuit 33, and the signal corresponding to the wheel speed Vw is inputted to the judgment circuit 33.
w and the wheel acceleration ΩW calculated based on the wheel speed Vw are the first reference wheel speed Vr and the reference wheel deceleration -ΩW, as described above. are compared respectively, and Qw<-*W.

Vw<Vr.

When these are established, high-level signals β and S are output from the judgment circuit 33, respectively.

These signals β and S are input to an AND gate 35,
When both signals are at high level, the transistor 36 becomes conductive, the tube node 38 is energized, and the inlet valve Vi
is opened. Further, when the high level signal S1 is output, the transistor 37 becomes conductive, the solenoid 39 is energized, and the outleft valve Vo is closed.

By the way, when the braking torque is weakened by the signals β and SI as described above, the wheel speed is still decelerating.
This is a state in which the braking torque is still greater than the driving torque on the road surface, and the fear of wheel locking has not been completely eliminated at this point.

However, since the system generally has an operation delay of about 101)13, the braking oil pressure is further loosened even after the loosening signal disappears, so this method usually yields good results. However, depending on road surface conditions, loosening may not be sufficient and the wheel speed may continue to lock. To eliminate this phenomenon, λ〉λ
1, a signal may be generated to slow down the wheel speed Vw until the wheel speed Vw is reliably increased. However, although good control is normally obtained even if the loosening signal is stopped when Qw>-*W, the loosening signal is continued until Qw>Q, so the braking torque may not be loosened too much. However, this is not a practical problem for wheels with smaller braking load distribution.

Therefore, a second reference wheel speed Vrz corresponding to the second reference slip rate λ2 such that λ2 > λ is set, and Vw<Vr
2, that is, when λ>λ2, and the possibility of locking increases, the loosening signal is maintained until the wheel speed Vw increases. That is, the determination circuit 33 determines whether 7w<Vr2 or λ>λ2, and outputs the signal S2 when the condition is satisfied. Further, in order to determine that the wheel speed Vw is increasing, a speed increase reference value +Qw is set, and a signal α is output when Vw>+Wo.

The signal S2 is inputted to one input terminal of the AND gate 40 and also inputted to the OR gate 41, and the signal α is inputted to the OR gate 41 and is inverted and outputted to the AND gate 4.
It is input to 0. Furthermore, the signal S is also OR gate 41
The output of the OR gate 41 is input to the transistor 37.
given on the basis of. Also both AND gates 35.40
The output of is input to the OR gate 42, and the output J of the OR gate 42 is applied to the base of the transistor 3G.

According to such control means 32, the signal S,.

If either α or S2 becomes high level, the transistor 37 becomes conductive and the outlet valve VO closes, and either the signals β and St are both high level, or the signal St is high level and the signal α is low. level, the inlet/throat valve Vi opens.

Next, the method of setting the first and second reference wheel speeds Vrl and Vr2 will be explained. These are performed by detecting the vehicle speed V and setting the reference slip ratio λ3. Ideally, it should be determined as shown in the following equation, taking λ2 into consideration.

Vr,=V(1-λ,) Vr2=V(1-22) However, no practical means for detecting the vehicle speed V has been found so far. Therefore, a temporary vehicle speed Vv is estimated from the change status of the wheel speed Vw, and the calculation circuit thereof is shown in FIG.

In FIG. 3, the first input terminal 51 is connected to the first arithmetic circuit 52.
The second input terminal 51' is connected to the second arithmetic circuit 52'.
connected to. The output terminals of both arithmetic circuits 52 and 52' are connected to individual contacts 53a and 53b of a changeover switch 53, respectively, and a common contact 53c of the changeover switch 53 is connected to an output terminal 54. Moreover, the changeover switch 53 is
The switching is driven by the slip detection circuit 55 connected to the second arithmetic circuit 52'.

The wheel speed Vwr of a driven wheel, such as a rear wheel, is input to the first input terminal 5, and the wheel speed Vwf of a driving wheel, such as a front wheel, is input to a second input terminal 51'.
Arithmetic circuits 52, 52' calculate the wheel speeds Vwr, V
Vehicle speeds Vv, , Vv2 are calculated based on wf, respectively.

In the first arithmetic circuit 52, the input terminal 51 is connected to the comparison circuit 56.
is connected to the inverting input terminal of The output terminal of this comparison circuit 56 is connected to the base terminals of a PNP transistor 52 and an NPN transistor 58, which are connected in series. Also, the DC power supply 59 is connected to the PNP! - It is connected to the emitter terminal of the transistor 57, and the emitter terminal of the NPN transistor 58 is grounded via the constant current circuit 61. A connection point between both transistors 57 and 58 is connected to a non-inverting input terminal of a buffer circuit 62, and a connection between the connection point and the buffer circuit 62 is grounded via a capacitor 63. Moreover, the output terminal of the buffer circuit 62 is connected to one individual contact 53a of the changeover switch 53, and is also connected to the non-inverting input terminal of the comparison circuit 56.

In the first arithmetic circuit 52, when the estimated vehicle speed Vv outputted from the buffer circuit 62 is smaller than the wheel speed Vwr, the output of the comparison circuit 56 becomes low level, the PNP) transistor 57 becomes conductive, and the NPN
Transistor 58 is cut off, and constant current circuit 60 charges capacitor 63 with a constant current. Further, when the estimated vehicle speed Vv1 is larger than the wheel speed Vwr,
The output of the comparator circuit 56 becomes high level, the PNP) transistor 57 is cut off, the NPN l-transistor 58 is made conductive, and the constant current circuit 61 causes the capacitor 63 to become conductive.
A constant current discharge is carried out from. Therefore, when the wheel speed Vwr changes slowly, the estimated vehicle speed Vv,
follows it and changes gradually, but the wheel speed Vwr
When VV suddenly changes, a value obtained by adding or subtracting a predetermined value from the estimated vehicle speed VV is input to the individual contact 53a of the changeover switch 53 as the new estimated vehicle speed VV. That is, when the wheel speed Vwr is larger than the estimated vehicle speed Vv1, the value obtained by adding the speed corresponding to a predetermined value, for example, lG, becomes the new estimated vehicle speed Vv, and when the wheel speed Vwr is smaller than the estimated vehicle speed Vvl, , a value obtained by subtracting a speed corresponding to a predetermined value, for example, IG, becomes the new estimated vehicle speed VvI.

The second arithmetic circuit 52' includes a comparison circuit 56', a PNP transistor 57', an NPNI transistor 58', a DC power supply 59', constant current circuits 60' and 61', a buffer circuit 62' and a capacitor 63'. It is configured similarly to the first arithmetic circuit 52. Moreover, the buffer circuit 62'
The signal outputted from the control unit 53, that is, the estimated vehicle speed Vv2, is input to the individual contact 53b of the changeover switch 53. This second
Also in the calculation circuit 52', when the wheel speed Vwf is larger than the estimated vehicle speed VVZ, a predetermined value, for example, IG
The value obtained by adding the speed corresponding to is the new estimated vehicle speed Vv
2, and when the wheel speed Vvf is smaller than the estimated vehicle speed VV2, a value obtained by subtracting a predetermined value, for example, the speed corresponding to IG, becomes the new estimated vehicle speed Vv2.

The idle detection circuit 55 includes an inversion circuit 64, a timer 65,
A flip-flop 66 is provided. Second arithmetic circuit 52'
The output terminal of the comparison circuit 56' is connected to the base terminals of the PNP transistor 57' and the NPN transistor 58', and is also connected to the inverting circuit 64. The signal inverted by this inverting circuit 64 is sent to the timer 6
5 and the clear input terminal C of the flip-flop 66, and the output of the timer circuit 65 is input to the cent input terminal S of the flip-flop 66. Moreover, the timer 65 keeps the high level signal for a certain period of time, e.g.
When the signal is continuously input for 50m5 or more, a high level signal is output as the certain period of time elapses.

The flip-flop 66 outputs a high-level signal from the set output terminal Q in response to a high-level signal being input to the clear input terminal C and then a high-level signal being input to the cent input terminal S. It is reset when a high level signal is input to the clear input terminal C again. Further, when the output of the set output terminal Q is at a low level, the changeover switch 53 connects the common contact 53C to one individual contact 53b, and when the output of the set output terminal Q is at a high level, the common contact 53C is connected to the other individual contact 53b. It operates to connect to contact 53a.

Therefore, the drive wheels are spinning and the wheel speed Vwf is higher than the estimated vehicle speed VV2 for a certain period of time, for example, 350
If it continues for more than ma, the slip detection circuit 55 detects the slip state, and the estimated vehicle speed VV based on the wheel speed Vwr on the driven wheel side is outputted to the output terminal 5 as the estimated vehicle speed Vv.
It will be output from 4.

Next, the operation of this embodiment will be explained with reference to FIG. This Fig. 4 shows an example of the operating mode of the anti-lock braking system, where the horizontal axis shows the time elapsed after the start of braking, and the vertical axis shows the actual vehicle speed vv'' at the top.
, wheel speed Vw, first reference wheel speed Vr, and second reference wheel speed Vr2 are shown, and below these, wheel acceleration QW, acceleration reference value +*W0, and reference wheel deceleration -ΩW0 are shown, Further below, signals α, β, S1
, S2 and the operating states of solenoids 38 and 39 are shown, and the braking oil pressure pb is shown at the bottom.

First, at time 1=0, immediately after starting braking, the outputs of the signals α, β, St, and Sz are at low level, the braking oil pressure pb gradually increases, and the wheel speed Vw increases accordingly.
and wheel acceleration *W both gradually decrease.

At time, wheel acceleration 9W is reference wheel deceleration - *
When the wheel speed Vv becomes smaller than W0 (9W×ΩW0), the signal β becomes high level, but since the wheel speed Vv is greater than the first reference wheel speed Vr, the signal S remains at a low level. Therefore, the braking oil pressure pb continues to increase, and the wheel speed VW and wheel acceleration *W also continue to decrease.

At time t2, the wheel speed Vw reaches the first reference wheel speed V.
When the signal S, falls below r, the signal S becomes high level,
In response to the output of the AND gate 35 becoming high level, the output of the OR gate 42 becomes high level and the OR gate 42 becomes high level.
The output of gate 41 becomes high level. As a result, the solenoids 38 and 39 are energized, the inlet valve Vi is opened, and the out-left valve 0 is closed. As a result, the braking oil pressure pb begins to decrease, and the wheel acceleration -yw changes to the speed increasing side. At this time, the wheel speed Vw continues to decrease.

At time, the wheel acceleration *W is the reference wheel deceleration -
When it becomes larger than 9W (9w>-9w0), the signal β becomes low level, and the output of the AND gate 35 becomes low level accordingly. Therefore, the solenoid 38 of the inlet valve Vi is demagnetized, the inlet valve Vi is closed, and the braking oil pressure pb is kept constant. In other words, the braking torque is kept substantially constant. After this, wheel speed Vw begins to increase.

At time L4, wheel acceleration 9w is equal to speed increase reference value + Q
When it becomes larger than wo (Qw>+Qw,), the signal α becomes high level. Further, at time t, when the wheel speed Vw exceeds the first reference wheel speed Vr, the signal S1 becomes low level. Furthermore, at time t6, the wheel acceleration *W
decreases from the speed increase reference value + Q w 0, the signal α
becomes low level, and the out left valve Vo opens. The braking oil pressure pb increases accordingly.

At time t7, wheel acceleration *W is equal to reference wheel deceleration -
When the wheel speed Vw becomes smaller than Qwo (9w<-Qwo), the signal β becomes high level, and at time t, when the wheel speed Vw becomes lower than the first reference wheel speed Vr (vw×rl), the signal S, becomes high level, and accordingly AN
The output of the D gate 35 becomes high level, the inlet valve Vi closes, and the out left valve V.

When the valve opens, the brake oil pressure pb begins to decrease. Then time t
, when the wheel speed Vw becomes lower than the second reference wheel speed Vr2 (Vw<Vrz) and the possibility of wheel lock increases, the signal S2 becomes high level.

When the wheel acceleration *W becomes larger than the reference wheel deceleration -ΩW at time L1°, the signal β becomes a low level, but the braking oil pressure pb further decreases and the wheel speed VW starts to increase.

At time tl+, the wheel acceleration 9W becomes the speed increase reference value + Q w,
), the signal α becomes high level and the output of the AND gate 40 becomes low level. At this time, since the output of the AND gate 35 is at a low level, the OR gate 42
The output of solenoid 38 is low level and therefore
is demagnetized and the inlet valve Vi is closed. As a result, the braking oil pressure pb is maintained constant.

At time t1□, when the wheel speed Vw exceeds the second reference wheel speed Vr2, the signal S2 becomes low level, and when the wheel speed Vw exceeds the first reference wheel speed Vr+ at time (I), the signal S1 becomes low level. However, the braking oil pressure pb is kept almost constant, and the lock state is avoided.Furthermore, at time t14, the wheel acceleration ΩW reaches the speed increase reference value + Ω.
When the voltage drops below W0, the signal α becomes low level, and the out-rep valve Vo opens accordingly. Therefore, the braking oil pressure Pb starts to increase.

At time t's, wheel acceleration *W is reference wheel deceleration - *W0
When the signal β becomes smaller than the first reference wheel speed Vr, the signal β becomes high level, and at the next time t16, the wheel speed Vw becomes lower than the first reference wheel speed Vr and the signal S becomes high level, and the inlet valve Vi is opened. At the same time, the outlet valve vO is closed. Therefore, the braking oil pressure pb begins to decrease.

Furthermore, time ti? The wheel acceleration 9W is the standard wheel deceleration -
</W (When it exceeds 1, the out-left valve Vo opens in response to the signal β becoming low level, and the braking oil pressure pb
is maintained constant.

When the wheel acceleration OW exceeds the speed increase reference value +Ωw0 at time t18, the signal α becomes high level, and when the wheel speed Vw exceeds the first reference wheel speed Vr at time y, the signal S
, becomes low level. Furthermore, at time t2°, the wheel acceleration of 9W becomes the speed increase reference value +9W. , the signal α
becomes a low level, the out-left valve Vo opens accordingly, and the braking oil pressure pb begins to decrease.

Thereafter, the above process is repeated in the same way, and the vehicle speed decreases without the wheels locking.

Next, referring to FIG. 5, assume that the wheel speed Vw pulsates during braking while driving on a rough road. At this time, when the driving wheels, for example, the front wheels, are not idling, the vehicle speed Vvz calculated by the second calculation circuit 52' based on the wheel speed Vwf of the driving wheels is used as the estimated vehicle speed Vv.

In such a state, when the wheel speed Vw becomes larger than the estimated vehicle speed Vv, the second calculation circuit 52' calculates the PNP I
- transistor 57' becomes conductive and NPN transistor 58
′ blocks it. Therefore, the capacitor 63' is charged with a constant current, and the value obtained by adding the speed corresponding to IG becomes the new estimated vehicle speed Vv. As a result, the rate of increase in the estimated vehicle speed Vv is suppressed to a low level compared to the wheel speed Vw, and the first and second reference wheel speeds Vr, Vrz are also suppressed to a low level. As a result, the wheel speed Vw is prevented from becoming smaller than the first reference wheel speed Vr, and the braking oil pressure is prevented from decreasing.

Further, in the case where the driving wheels are idling, the idling state is detected by the idling detection circuit 55 when the state in which the wheel speed Vwf of the driving wheels is greater than the estimated vehicle speed Vv2 continues for a certain period of time, for example, 350 ms or more. Then, the changeover switch 53 operates to connect the common contact 53C to the individual contact 53a.

Therefore, the vehicle speed Vv calculated by the first calculation circuit 52 is used as the estimated vehicle speed Vv. As a result, the estimated vehicle speed Vv becomes the actual vehicle speed Vv
” is prevented, and anti-lock activation is prevented from occurring when unnecessary.

FIG. 6 shows another embodiment of the present invention, in which two input terminals 70 and 71 are provided corresponding to the first arithmetic circuit 52, and two input terminals 70 and 71 are provided corresponding to the second arithmetic circuit 52'. Terminals 73, 74 are provided.

The input terminal 70 receives the wheel speed Vvr of the driven wheels, and the input terminal 71 receives the wheel speed Vwf of the driving wheels. The re-input terminals 70 and 71 are connected to the low select circuit 72, and the lower wheel speed is selected and input to the inverting input terminal of the comparator circuit 56 in the first arithmetic circuit 52. That is, the estimated vehicle speed VV is calculated by the first calculation circuit 52 based on the minimum value of the wheel speeds of all wheels.

Input terminals 73 and 74 also contain the wheel speed Vwr of the driven wheel.
and the wheel speeds Vwf of the drive wheels are respectively input, and these wheel speeds Vwr and Vwf are input to the high select circuit 75.
is input. The wheel speed selected by the high select circuit 75, that is, the maximum value of all wheel speeds, is input to the inverting input terminal of the comparison circuit 56' in the second arithmetic circuit 52'.

According to this embodiment, the second calculation circuit 52' calculates the estimated vehicle speed VV based on the maximum wheel speed of each wheel including the driving wheels.
2 is calculated, and when the time during which the maximum wheel speed exceeds the estimated vehicle speed Vv exceeds a certain time T, it is determined that the driving wheels are idling, and in that case, as the estimated vehicle speed Vv,
An estimated vehicle speed Vv, based on the minimum wheel speed, is used. Therefore, even when the vehicle is idling, the estimated vehicle speed Vv is prevented from becoming higher than the actual vehicle speed, and anti-lock control is prevented from being performed when unnecessary.

C9 Effects of the Invention As described above, according to the present invention, when a wheel is spinning, the vehicle speed is calculated based on the wheel speed of a wheel different from the wheel that is spinning, so the vehicle speed estimated when the wheel is spinning is not the actual vehicle speed. It is possible to prevent the vehicle speed from becoming higher than the vehicle speed of the vehicle, and to prevent unnecessary anti-lock operation from occurring.

[Brief explanation of drawings]

1 to 5 show an embodiment of the present invention,
Figure 1 is a hydraulic control circuit diagram, Figure 2 is a simplified circuit diagram showing the configuration of the control means, Figure 3 is a circuit diagram showing the configuration of the calculation circuit and slip detection circuit, and Figure 4 is the anti-lock operating state. FIG. 5 is a characteristic diagram when the wheel speed pulsates, and FIG. 6 is a circuit diagram corresponding to FIG. 3 of another embodiment of the present invention. Bj! f, Br f, Bj! r, Brr...Wheel brake, Vv...Estimated vehicle speed, Vw...At wheel speed Applicant Honda Motor Co., Ltd. 3rd Plan

Claims (3)

[Claims] (1) In an anti-lock control method, the vehicle speed is estimated based on the wheel speed, and the supply of braking hydraulic pressure to the wheel brakes is controlled by comparing the wheel speed with a reference value based on the estimated vehicle speed, An anti-lock control method in which, when a wheel is spinning, the vehicle speed is calculated based on the wheel speed of a wheel different from the wheel that is spinning. (2) In normal times, the vehicle speed is calculated based on the wheel speed of the driving wheels, and when the driving wheels are idling, the vehicle speed is calculated based on the wheel speed of the driven wheels. The anti-lock control method described in (1). (3) Under normal conditions, the vehicle speed is calculated based on the maximum value of multiple wheel speeds including the driving wheels, and when at least one of the wheels is spinning, the vehicle speed is calculated based on the minimum value of each wheel speed. An anti-lock control method according to claim (1), characterized in that: