JPS61178256A - Anti-lock control device - Google Patents

Abstract

PURPOSE:To make it possible to precisely estimate the speed of a vehicle even during generation of wheel spins, by estimating the vehicle speed in accordance with higher one of the speeds of drive and driven wheels during abrupt braking but in accordance with the speed of the driven wheels during braking other than abrupt braking. CONSTITUTION:When wheel spins are generated at drive wheels on a slippery road surface or during abrupt starting or abrupt acceleration, a first reference wheel speed Vr becomes high if the vehicle speed Vv is estimated in accordance with the speed Vw of the drive wheel since the speed Vw of the drive wheels becomes higher than the actual vehicle speed Vv, and therefore, there is a possibility of such a judgement that the wheels come to be locked. However, the vehicle speed Vv is estimated in accordance with the speed Vw of the driven wheels during braking other than abrupt braking, and therefore, the above- mentioned erroneous judgement may be prevented. Further, during abrupt braking the vehicle speed Vv is estimated in accordance with the higher one of the speeds of the drive and driven wheels, the accuracy of the estimated speed may be enhanced, thereby it is possible to carry out the anti-lock control with a higher degree of accuracy.

Description

[Detailed Description of the Invention] A0 Object of the Invention +l) Industrial Application Field The present invention relates to a wheel brake; a hydraulic control circuit for controlling the supply of braking hydraulic pressure to the wheel brake; a wheel speed detector; The vehicle speed is estimated based on the wheel speed detected by the wheel speed detector, and by comparing the wheel speed with a reference wheel speed based on the estimated vehicle speed, it is determined whether the wheels are likely to lock. and a control means for controlling the hydraulic pressure control circuit to reduce the braking hydraulic pressure applied to the wheel brake when the wheel brake is likely to lock.

(2) Prior Art Conventionally, in such an anti-lock braking device, wheel speed Vw
is detected, wheel acceleration Qw and estimated vehicle speed Vv are calculated from the wheel speed Vw, and a reference wheel speed Vr is set by adding an appropriate slip rate to the reference wheel acceleration and estimated vehicle speed Vv, and the wheel speed Vw and A comparison is made with the reference wheel speed Vr and the wheel acceleration </W is compared with the reference wheel acceleration, and the results are comprehensively judged to determine whether the wheels are likely to lock, and the braking oil pressure of each wheel brake is adjusted. is under control. Moreover, in estimating the vehicle speed Vv from the wheel speed Vw, as shown in FIG. 4, an arithmetic circuit consisting of an ideal diode 44, a memory capacitor 45, and a constant current discharge circuit 46 is used, and as shown in FIG. A temporary vehicle speed Vv is estimated by connecting the valleys of the wheel speed Vw at a constant slope. Furthermore, in order to improve the estimation accuracy, there is also a system in which the higher wheel speed Vw of either the driving wheel or the driven wheel is selected.

(3) Problems to be Solved by the Invention In the conventional anti-lock braking device described above, when starting suddenly on a slippery road surface such as a snowy or frozen road, the wheel speed of the driving wheels Vw as shown in FIG. A phenomenon in which the estimated vehicle speed Vv becomes significantly larger than the actual vehicle speed Vv'' occurs, that is, wheelspin.For this reason, the estimated vehicle speed Vv becomes significantly larger than the actual vehicle speed Vv'', and even after the wheelspin disappears, the same state occurs. continues for a while, and just before the wheel spin subsides, large wheel deceleration also occurs. As a result, the control means determines that the wheels are about to lock and attempts to reduce the braking oil pressure. Therefore, if a braking operation is performed during or immediately after wheel spin (period A in FIG. 9), the braking pressure may drop. This is also the case during sudden acceleration while driving on a slippery road surface, and as shown in Figure 7, the estimated vehicle speed Vv becomes significantly higher than the actual vehicle speed ■v''', and when braking within period A. Braking pressure may decrease.

By the way, when the vehicle speed is estimated based on the wheel speed Vw of the higher of the driving wheels and the driven wheels,
During normal driving other than during sudden braking, the wheel speed Vw of the driven wheels matches the actual vehicle speed Vv''' with sufficient accuracy.Furthermore, wheel spin does not occur during sudden braking.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an anti-lock braking device that can accurately estimate vehicle speed even when wheelspin occurs.

B0 Structure of the Invention (1) Means for Solving the Problems According to the present invention, the wheel speed detector is provided on both the driving wheel and the driven wheel, and the control means controls the driving wheel and the driven wheel during sudden braking. The vehicle speed is estimated based on the higher one of the wheel speeds, and the vehicle speed is estimated based on the wheel speed of the driven wheels except during sudden braking.

(2) Forces that may cause wheelspin (in some cases, the vehicle speed is estimated based on the wheel speed of the driven wheels, so a value close to the actual vehicle speed can be obtained, and sudden braking that does not cause wheelspin) Sometimes, the vehicle speed is estimated based on the higher wheel speed of either the driving wheel or the driven wheel, which improves the estimation accuracy.

(3) Embodiment An embodiment of the present invention will be described below with reference to the drawings. First, in FIG. 1, the brake pedal 1 is operatively connected to the mask cylinder M, and the driver presses the brake pedal When the master cylinder M is stepped on, the master cylinder M generates oil pressure through the oil passage 2t. This oil passage 2 is connected to a hydraulic control circuit 3, and braking oil pressure corresponding to the oil pressure is supplied to the hydraulic control circuit 3.
is output from.

Wheel brakes are mounted on the left and right driving wheels and the 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 front wheel brake Bj is applied to the left and right front wheels as driving wheels. f and right front wheel brake Brf are installed, and left rear wheel brake Bj! is attached to the left and right rear wheels as driven wheels. r' and right rear wheel brake B
rr is attached. Each brake B1f, Brf, B1r
, Brr are drum brakes, for example, and an oil passage 5' from the hydraulic control circuit 3 is communicated with the braking oil chamber 4 of the left front wheel and right front wheel brakes BJf, Br'f, and Brake Bj for right rear wheel! An oil passage 5' from the hydraulic control circuit 3 is communicated with the brake oil chamber 4 of r and Brr.

In each brake B/f, Brf, Bnr, Brr,
When brake oil pressure is supplied to each brake oil chamber 4, the piston 7.
8 operate in the direction away from each other, and the brake shoes 9
, 10 respectively 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 a locked state, the brake hydraulic pressure is reduced by the hydraulic control circuit 3.
This prevents the wheels from becoming locked.

The hydraulic control circuit 3 is a brake B6f for left and right front wheels.

Modulator 11 compatible with BRF and brake B7 for left and right rear wheels! Modulator 11' corresponding to r, F3rr
Since both modulators 11° and 11' have basically the same configuration, the structure of only one modulator 11 will be described in detail.

That is, the modulator 11 has a cylinder portion 14 that 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, and the partition wall 13 is connected between the pistons 15 and 16. A rod 17 is provided, which passes through the rod 17 in a slidable manner in the axial direction. A cylinder chamber between the partition wall 13 and one piston 15 serves as a primary braking hydraulic chamber 18 and communicates with the mask cylinder M via the oil passage 2 . Further, 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 chamber 4 of the left and right front wheel brakes Bnf and Brf. An anti-lock control hydraulic chamber 20 is defined between one end wall of the cylinder section 14 and one piston 15, and a release oil pressure chamber 20 is defined between the other end wall of the cylinder section 14 and the other piston 16. A chamber 21 is defined, and the release oil chamber 21 communicates 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 11.

In the other modulator 11' as well, the primary brake hydraulic chamber 18' is communicated with the mask cylinder M, and the secondary brake hydraulic chamber 19' is connected to the left and right rear wheel brakes B7! through the oil passage 5'. r
, 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 i', and is also connected to an oil tank T via a normally open outlet 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 18
．． When hydraulic pressure is supplied from mask cylinder M to 18',
The volume of the secondary brake hydraulic chamber 19.19' is reduced, and each wheel brake B7! Braking oil pressure corresponding to the oil pressure from the mask cylinder M is supplied to the brake oil chambers 4 of f, Brf, BIlr, and Brr. Therefore, the torque during braking can be freely increased according to the driver's braking operation.

When the outlet valves Vo, Vo' are closed with the inlet valves Vi, Vi' closed, the control oil in the anti-lock control hydraulic chamber 20.20' is locked, so each modulator 11.11' The volume of the secondary brake hydraulic chamber 19.19' remains unchanged regardless of the increase or decrease in the hydraulic pressure supplied to the primary brake hydraulic chamber 18.18', and therefore the torque during braking is dependent on the driver's braking operation. It is kept at a constant size regardless. 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 chamber 20, 20', so that the hydraulic pressure from the mask cylinder M is Despite acting on the primary brake hydraulic chamber 18,18', the volume of the secondary brake hydraulic chamber 19.19' increases, and each wheel brake BIlf.

The oil pressure in the brake oil chambers 4 of Brf, BILr, and Brr decreases, and the braking torque is weakened. Therefore, when the wheel is about to enter the lock state, the inlet throat valve Vi,
By opening Vi' and closing outlet valves Vo and Vo', it is possible to avoid the wheels from entering a locked state.

In FIG. 2, the configuration of the control means 32 will be explained, and one set of wheel brakes B7! A configuration for controlling the inlet valve Vi and the outre throat valve ■0 corresponding to f, B, rf, and the other set of wheel brakes Bj!
Inlet valve ■B and outlet valve V corresponding to r, Brr.

The configuration for controlling ′ is basically the same, so
Here, only the configuration for controlling one inlet valve Vi and outlet valve ■0 will be described.
The main parts related to the other inlet valve Vi and outlet valve y o J will only be illustrated by adding a dash "'" to the reference numerals.

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.

(a) Wheel acceleration QW<Reference wheel deceleration-VW
.

A method that outputs a signal β when

(b) A method of outputting a signal S1 to loosen the braking oil pressure when the relationship of wheel speed VW<first reference wheel speed Vr is established. However, in this case, when the vehicle speed is v1 and the wheel slip rate is λ1, Vr, = Vv・ (l - λI), so when the wheel slip rate is λ, Vw<V
r, is the same as λ>λ1, and Vw<Vr, or λ>
When λ1 is established, a signal Sl is output.

(C) A method in which the braking oil pressure is loosened when either one of the above ta) and (b) is established.

(d) A method in which the braking oil □ pressure is relaxed when the above (a) and (b) are satisfied at the same time.

In the method (a), the reference wheel deceleration -Qwo is set to a value that does not occur during braking in a state where there is no risk of wheel locking, for example, usually -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. Furthermore, when driving on a rough road, the wheel acceleration </W> pulsates finely even during normal braking, and even when there is no fear of wheel locking, the signal β is output, reducing braking efficiency.

Furthermore, in the method (b), even if the slip ratio λ is high, that is, even if the signal Sl 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 is loosened, resulting in a decrease in braking efficiency.

The method (0) above has the drawbacks of (a) and (b).
It is clear that there are shortcomings.

Finally, the above-mentioned method (dl) solves the problem of reduced braking efficiency when driving on rough roads 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 -V W o is set within the range of wheel deceleration that occurs during braking under normal road running conditions, for example -1.
, 0 to OG, preferably -0°3 to -0.6G, the wheel deceleration will be -1.0 to -0.5G during braking operations performed on snowy roads, autobahns, etc. It is also possible to detect a locked condition and loosen the brake hydraulic pressure.

Therefore, the control means 32 includes a wheel speed detector 34 attached to the driving wheel and a wheel speed detector 34 attached to the driven wheel.
', signals corresponding to the wheel speeds Vw are respectively inputted, and these wheel speeds VW and the wheel accelerations Qw calculated based on the respective wheel speeds Vw are calculated from the first
They are compared with the reference wheel speed VrI and the reference wheel deceleration -ΩWo, respectively, and ΩW<-WW.

Vw<Vr.

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

These signals β and Sl 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 SI is output, the transistor 37 becomes conductive, the solenoid 39 is energized, and the outlet valve VO is closed.

By the way, when the braking torque is weakened using the signals β and S1 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 10 m5, 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. In order to eliminate such a phenomenon, when λ>λ, a relaxation signal may be generated until the wheel speed Vw is reliably increased. However, although good control can normally be obtained even if the loosening signal is stopped at </W>-Qw, the loosening signal is continued until </W>0, which reduces the braking torque. There is a drawback that excessive loosening occurs, but this does not pose a practical problem for wheels with a smaller braking load distribution.

Therefore, a second reference wheel speed Vrz corresponding to the second reference slip rate λ2 where λ2>λ1 is set, and 7w<Vr2
That is, only when λ>λ2 and the possibility of locking increases, the loosening signal is maintained until the wheel speed Vw increases. That is, in the judgment circuit 33, Vw<Vr.

Alternatively, it is determined whether λ>λ2, and when the condition is satisfied, the signal S2 is output. In addition, in order to determine that the wheel speed Vw is increasing, the acceleration reference value +
. Set VW>+</W.

When , the signal α is output.

The signal S2 is inputted to one input terminal of the AND gate 40 and inputted to the OR gate 41, and the signal α is inputted to the OR gate 41 and inverted and outputted to the AND gate 4.
It is input to 0. Furthermore, the signal S1 is also connected to the 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 the transistor 36 is input to an OR gate 42, and the output of the OR gate 42 is applied to the base of the transistor 36.

According to such a control means 32, the signals S1°α, S2
When either of them becomes high level, the transistor 37 becomes conductive, the outlet valve VO closes, and the signal β+S+
The inlet valve Vi opens when both are at a high level, or when the signal α is at a high level and the signal α is at a low level.

Next, the method of setting the first and second reference wheel speeds Vr, Vr2 will be explained. These are performed by detecting the vehicle speed V and setting the reference slip ratio λ8. Ideally, it should be determined as shown in the following equation, taking λ2 into consideration.

V r + = V (1-λ,) V r 2 = V (1-λ2) However, no practical means for detecting the vehicle speed ■ has been found so far. Therefore, a method of estimating a temporary vehicle speed Vv from the state of change in the wheel speed Vw is common, and the arithmetic circuit 43 includes an ideal diode 44, a storage capacitor 45, and a constant current discharge circuit 46. In this arithmetic circuit 43, as shown in FIG. 5, the wheel speed V
By touching the valley of w at a constant slope, a temporary vehicle speed ■V is estimated and input to the judgment circuit 33.

Here, the high select circuit 4 is connected to the input terminal of the arithmetic circuit 43.
A diode 48, which is one component of this high select circuit 47, is connected to the wheel speed detector 34 on the driving wheel side via a relay switch 50, and a diode 49, which is the other component, is connected to the wheel speed detector 34 on the driven wheel side. It is connected to the side wheel speed detector 34'. That is, the relay switch 50
is cut off, the wheel speed detector 3 on the driven wheel side
When the wheel speed Vw detected at 4' is manually input to the arithmetic circuit 43 and the relay switch 50 is conductive, either the wheel speed detector 34 on the driving wheel side or the wheel speed detector 34' on the driven wheel side The higher wheel speed Vw is selected by the high select circuit 47 and manually inputted to the arithmetic circuit 43.

As a condition for changing the switching mode of the relay switch 50, it is determined whether the vehicle is under sudden braking. In other words, wheel spin of the driving wheels cannot occur during sudden braking, and when the sudden braking is performed, the vehicle speed Vv is estimated based on the higher wheel speed Vw of either the driving wheel or the driven wheel. This is intended to improve accuracy.

Whether or not it is sudden braking is determined from the start of anti-lock control during braking until the end of the braking operation. Therefore, the output terminals of OR gates 41.41' and 42.42' are respectively input in parallel to the input terminal of OR gate 51, and
The output end of the R gate 51 is connected to a relay coil 53 via a delay circuit 52. The relay coil 53 and the relay switch 50 constitute a relay. After the anti-lock control starts, the relay coil 53 is excited when the time set by the delay circuit 52 has elapsed, and the relay switch 50 is energized accordingly. conducts. Further, after the anti-lock control is completed, the relay coil 53 is demagnetized after a delay time by the delay circuit 52, and the relay switch 50 is cut off.

In this way, during normal driving, the wheel speed V of the driven wheel is
The vehicle speed Vv is estimated based on the wheel speed Vw, and during sudden braking, the vehicle speed Vv is estimated based on the higher wheel speed Vw of the driven wheel and the driving wheel.

Next, the operation of this embodiment will be explained with reference to FIG. This Fig. 3 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 V v 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, speed increase reference value +Qw, and reference wheel deceleration -UWo are shown. , further below there are signals α, β,
The operating states of S1, S2 and solenoids 38 and 39 are shown, and the braking oil pressure Pb is shown at the bottom.

First, at time t=Q, immediately after starting braking, the outputs of the signals α, β, SI, and St are at a low level, and the braking oil pressure pb gradually increases, and along with this, the wheel speed Vw and the wheel acceleration Qw Both gradually decrease.

At time t, wheel acceleration -VW is reference wheel deceleration -
becomes smaller than Qwo (V W < V W ).

), the signal β becomes high level, but at this time, the wheel speed Vw is greater than the first reference wheel speed Vr, so the signal β becomes high level.
1 remains at low level. Therefore, braking oil pressure p
b continues to increase, wheel speed VW and wheel acceleration </W
continues to decline.

At time t2, the wheel speed Vw reaches the first reference wheel speed V.
When it drops below r+, the signal S1 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. This energizes the solenoids 38 and 39, opening the inlet valve Vi and closing the outlet valve Vo. As a result, the braking oil pressure pb begins to decrease, and the wheel acceleration </W changes to the speed increasing side. At this time, the wheel speed Vw continues to decrease.

At time t3, when the wheel acceleration <IIW becomes larger than the reference wheel deceleration -W (Vw>VWo), the signal β becomes a low level, and in response, the AND gate 3
The output of No. 5 becomes low level. 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 t4, wheel acceleration <7w is the speed increase reference value +
When the value becomes greater than <7W0 (tsuW>+tsuw.), the signal α becomes high level. Furthermore, at time t5, the wheel speed V
When w exceeds the first reference wheel speed Vr, the signal S1 becomes low level. Furthermore, at time t6, when the wheel acceleration <7w falls below the speed increase reference value + V W o,
The signal α becomes low level, and the rear l-let valve ■0
opens. Correspondingly, the braking oil pressure pb increases.

At time t7, wheel acceleration W becomes reference wheel deceleration -
Qw. When it becomes smaller than (vw<-Qwo), the signal β
becomes a high level, and at time t8, the wheel speed Vw
is lower than the first reference wheel speed Vr (Vw<Vr+)
Then, the signal S becomes high level, and in response, the signal A becomes high level.
The output of the ND gate 35 becomes high level, the inlet valve ■i closes, and the outlet valve V
.

opens, and the braking 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.

Time t. When the wheel acceleration Qw becomes larger than the reference wheel deceleration -Qw, the signal β becomes low level, but the braking oil pressure Pb further decreases and the wheel speed VW starts increasing.

At time tl+, wheel acceleration <7w is the speed increase reference value + <7w
When it exceeds o, 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 is at a low level, so the solenoid 3 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 Vrz, the signal S2 becomes low level, and when the wheel speed Vw exceeds the first reference wheel speed Vr at time t13, the signal SI becomes low level. However, the braking oil pressure pb is kept almost constant, and a locked state is avoided. Also, at time t14, the wheel acceleration </W is + the speed increase reference value
Qw. When the signal α becomes lower than , the signal α becomes low level,
In response to this, outlet valve Vo opens. Therefore, the braking oil pressure pb starts to increase.

At time t15, wheel acceleration Qw becomes reference wheel deceleration - Qwo
When it becomes smaller than , the signal β becomes a high level, and at the next time t16, the wheel speed Vw decreases below the first reference wheel speed Vrl and the signal S1 becomes a high level, and the inlet valve Vi opens. At the same time, the outlet valve Vo is closed. Therefore, the braking oil pressure pb begins to decrease.

Furthermore, time 1. At □, the wheel acceleration Qw is the reference wheel deceleration -
When ΩWo is exceeded, the outlet valve ■0 opens in response to the signal β becoming low level, and the braking oil pressure pb is maintained constant.

At time t18, the wheel acceleration </W becomes the speed increase reference value + Wo
When the wheel speed Vw exceeds the first reference wheel speed Vrl at time , the signal α becomes a high level, and when the wheel speed Vw exceeds the first reference wheel speed Vrl at time , the signal S+ becomes a low level. Further, at time too, the wheel acceleration W becomes the speed increase reference value W. When the pressure drops below the level, the signal α goes to low level, and accordingly, the outlet valve Vo opens and the braking oil pressure pb starts to drop.

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

Although the anti-lock control on the driving wheel side has been described above, the same applies to the anti-lock control on the driven wheel side.

Next, it is estimated when the drive wheels experience wheel spin due to a sudden start or sudden acceleration on a slippery road such as a snowy or icy road. When this wheel spin occurs, the wheel speed Vw of the driving wheels becomes significantly larger than the actual vehicle speed Vv'''. Therefore, if the vehicle speed Vv is estimated based on the wheel speed VW of the driving wheels, The first reference wheel speed vrI also becomes large, and Vw<
There is a possibility that the condition for Vrl is satisfied and it is determined that the wheels are likely to lock. However, in the present invention, during normal driving other than during sudden braking, the vehicle speed Vv is estimated based on the wheel speed Vw of the driven wheels, so the above-mentioned judgment can be avoided.

Furthermore, during sudden braking, the vehicle speed VV is estimated based on the higher wheel speed Vw of either the driving wheel or the driven wheel, so the estimation accuracy is improved and more precise anti-lock control is possible.

In the above embodiment, OR game) 51 and OR game) 41.
I connected all the output terminals of 41', 42 and 42', but each O
The switching mode of the relay switch 50 may be changed over by at least one of the R gates 41.41' and 42.42'.

C0 Effects of the Invention As described above, according to the present invention, the vehicle speed detector is provided on both the driving wheels and the driven wheels, and the control means controls the driving wheel and the driven wheel, whichever is higher, during sudden braking. Since the vehicle speed is estimated based on the vehicle speed, and the vehicle speed is estimated based on the wheel speed of the driven wheels except during sudden braking, the estimated vehicle speed is This prevents the vehicle speed from becoming significantly higher than the actual vehicle speed, prevents the braking oil pressure from being reduced unnecessarily, and improves the accuracy of estimating the vehicle speed when there is no risk of wheel spin.

[Brief Description of the Drawings] Figures 1 to 3 show one embodiment of the present invention.
Figure 2 is a hydraulic control circuit diagram, Figure 2 is a circuit diagram showing the configuration of the control means, Figure 3 is a characteristic diagram showing the operating state of the Nunchlock, Figures 4 to 7 show the prior art, and Figure 4 shows the conventional technology. is a circuit diagram showing an arithmetic circuit, and Fig. 5 is a characteristic diagram of the arithmetic circuit.
FIG. 6 is a characteristic diagram when wheel spin occurs when the vehicle is moving forward, and FIG. 7 is a characteristic diagram when wheel spin occurs during rapid acceleration. 3... Hydraulic control circuit, 32... Control means, 34.3
4'...Wheel speed detector

Claims (1)

[Claims] a wheel brake; a hydraulic control circuit for controlling supply of braking hydraulic pressure to the wheel brake; a wheel speed detector; estimating a vehicle speed based on the wheel speed detected by the wheel speed detector; The hydraulic control circuit determines whether a wheel is likely to lock by comparing the wheel speed with a reference wheel speed based on the speed, and reduces the braking hydraulic pressure to the wheel brake when the wheel is likely to lock. In the anti-lock braking device, the wheel speed detector is provided on both the driving wheel and the driven wheel, and the control means is configured to detect the speed of either the driving wheel or the driven wheel during sudden braking. An anti-lock braking device characterized in that it is configured to estimate a vehicle speed based on a wheel speed of a driven wheel, and to estimate a vehicle speed based on a wheel speed of a driven wheel except during sudden braking.