JP2599699B2 - Anti-lock braking device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wheel brake, a hydraulic control circuit for controlling the supply of braking oil pressure to the wheel brake, a wheel speed detector, and a wheel speed signal output from the wheel speed detector. A calculation circuit for estimating the vehicle speed based on the estimated vehicle speed, and comparing the reference wheel speed set based on the estimated vehicle speed with the wheel speed signal to determine whether the wheel is in a state in which the wheel is likely to be locked, And control means for controlling the hydraulic pressure control circuit to reduce the hydraulic pressure applied to the wheel brakes when the vehicle is about to lock.

[0002]

2. Description of the Related Art Conventionally, in such an antilock braking device, a wheel acceleration VAw and an estimated vehicle speed Vv are calculated from a wheel speed signal Vw output from a wheel speed detector, and a reference wheel acceleration and an estimated vehicle speed Vv are calculated. The reference wheel speed Vr taking into account the appropriate slip rate is set, the wheel speed signal Vw is compared with the reference wheel speed Vr, and the wheel acceleration VAw is compared with the reference wheel acceleration. Is determined to be likely to lock, and the braking hydraulic pressure of each wheel brake is controlled. In addition, when estimating the vehicle speed Vv from the wheel speed signal Vw, as shown in FIG.
4. An arithmetic circuit including a storage capacitor 45 and a constant current discharging circuit 46 is used. By connecting the valleys of the wheel speed signals Vw with a constant downward slope as shown in FIG. Estimated.

[0003]

The above-mentioned conventional antilock braking device has the following problems when applied to driving wheels. That is, when the vehicle suddenly starts on a slippery road such as a snowy road or a frozen road, a phenomenon in which the wheel speed signal Vw of the drive wheel becomes significantly larger than the actual vehicle speed Vv *, that is, a wheel spin occurs, as shown in FIG. . For this reason, the estimated vehicle speed Vv becomes significantly higher than the actual vehicle speed Vv *, and the same state continues for a while even after the wheel spin disappears, and a large wheel deceleration occurs immediately before the wheel spin stops. Therefore, when a braking operation is performed during and immediately after the occurrence of wheel spin (period A in FIG. 9), a state in which the wheel speed signal Vw is lower than the reference wheel speed Vr and the wheel acceleration VAw is lower than the reference wheel acceleration. This occurs temporarily, and in this state, the control means determines that the wheels are about to be locked and tries to perform anti-lock control on the hydraulic control circuit. This is not a state in which there is a possibility that the hydraulic pressure control circuit should perform anti-lock control. Thus, not only does the anti-lock control of the hydraulic control circuit lower the braking oil pressure, but also the operating noise of the control system. May occur unnecessarily or the durability may be reduced. The above-mentioned problem is also the same at the time of rapid acceleration while traveling on a slippery road surface. When a braking operation is performed during and immediately after the wheel spin occurs (period A in FIG. 10), the hydraulic control is performed in the same manner as described above. The circuit may be unnecessarily subjected to antilock control.

The present invention has been made in view of the above circumstances, and the control means does not need to use a hydraulic control circuit during a sudden spin on a slippery road surface or during a wheel spin during a rapid acceleration or during a braking immediately thereafter. An object of the present invention is to provide an anti-lock braking device that can avoid performing anti-lock control.

[0005]

According to the present invention, there is provided, in accordance with the present invention, a wheel brake; a hydraulic control circuit for controlling the supply of brake hydraulic pressure to the wheel brake; a wheel speed detector; Including an arithmetic circuit for estimating the vehicle speed based on the wheel speed signal output from the wheel speed detector,
By comparing a reference wheel speed set based on the estimated vehicle speed with the wheel speed signal, it is determined whether or not the wheel is likely to lock, and when the wheel is likely to lock, braking to the wheel brake is performed. and control means for controlling the hydraulic control circuit to reduce the hydraulic pressure; in antilock brake system comprising, based on the wheel speed signal
A spin detecting means for detecting the spin state of the wheel based on a comparison between the value obtained by the above and a set reference value is connected to the arithmetic circuit, and the arithmetic circuit is configured to control the spin state when the wheel spins. in order to avoid the said control means and the wheel is about to be locked, it is determined, spin that due to the spin detection means
When the state is detected, the estimated vehicle
The rate of increase of both speeds is calculated from the rate of increase when detecting the non-spin state.
Comprising the estimated vehicle speed increase rate reducing means also reduces.

[0006]

[Operation] Even if the wheel speed suddenly increases due to wheel spin at sudden start or sudden acceleration on a slippery road such as a snowy road or a frozen road, the estimated vehicle speed obtained by the arithmetic circuit during the spin state. locking increasing rate with respect to the wheel speed signal, since the estimated vehicle speed increase rate reducing means responsive to said spin detection means Ru is lower than the non-spin state, the wheel due to the excessive increase in the estimated vehicle speed at the time of wheel spin It is possible to prevent the anti-lock control means from determining that it is likely to occur, and as a result, even if a braking operation is performed during or immediately after the wheel spin, the hydraulic control circuit is not unnecessarily subjected to the anti-lock control. It rises quickly in response to the braking operation, and accordingly, the brake quickly shifts to the operating state. Moreover, the spin by the spin detecting means
Detection of the state and estimation of the vehicle speed by the arithmetic circuit
The wheel speed is determined based on the wheel speed of the wheel.
The system from the speed input to the wheel brake belonging to the relevant wheel
It can self-process within the unit, and
There is no need to send and receive complicated information.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. First, in FIG. 1, a brake pedal 1 is operatively connected to a master cylinder M, and when a driver depresses the brake pedal 1, Master cylinder M generates hydraulic pressure in oil passage 2. The oil passage 2 is connected to a hydraulic control circuit 3, and a brake hydraulic pressure according to the hydraulic pressure is output from the hydraulic control circuit 3.

[0008] The left and right driving wheels and left and right driven wheels of the vehicle wheel brakes are mounted respectively, the braking oil pressure is Ru is supplied from the hydraulic control circuit 3 in their wheel brakes. For example, in a front-wheel drive vehicle, left and right front wheels serving as drive wheels include a left front wheel brake Blf and a right front wheel brake B
rf is mounted, and a left rear wheel brake Blr and a right rear wheel brake Brr are mounted on left and right rear wheels as driven wheels. Each brake Blf, Brf, Blr, Br
r is, for example, a drum brake, and an oil passage 5 from a hydraulic control circuit 3 communicates with a brake oil chamber 4 of the left front wheel brake and the right front wheel brake Blf, Brf, and a left rear wheel brake and a right rear wheel brake Blr are provided. , Brr is connected to an oil passage 5 ′ from the hydraulic control circuit 3.

Each brake Blf, Brf, Blr, Br
r, when the brake oil pressure is supplied to each brake oil chamber 4,
The pistons 7, 8 operate in directions away from each other, and the brake shoes 9, 10 respectively contact a brake drum (not shown) to generate a braking torque. If the brake oil pressure in each brake oil chamber 4 is too large, each brake shoe 9,
The braking torque generated between 10 and the brake drum becomes too large, and as a result, the wheels are locked. For this reason, when the wheel is about to enter the locked state, the brake hydraulic pressure is reduced by the hydraulic control circuit 3, thereby preventing the wheel from being locked.

The hydraulic control circuit 3 includes left and right front wheel brakes B
modulator 11 corresponding to lf, Brf and modulator 11 corresponding to left and right rear wheel brakes Blr, Brr
, And both modulators 11 and 11 ′ have basically the same configuration.
Only the structure will be described in detail.

That is, the modulator 11 has a cylinder portion 1 whose both ends are closed and whose middle is partitioned by a partition 13.
And a rod 17 having a pair of pistons 15 and 16 at both ends thereof and penetrating the partition wall 13 in a portion between the pistons 15 and 16 so as to slide freely in the axial direction. Partition 13
A cylinder chamber between the piston cylinder 15 and one of the pistons 15 is communicated with the master cylinder M via the oil passage 2 as a primary braking hydraulic chamber 18. The cylinder chamber between the partition 13 and the other piston 16 serves as a secondary braking hydraulic chamber 19 through the oil passage 5 and the braking oil chamber 4 for the left and right front wheel brakes Blf, Brf.
Is communicated to. An anti-lock control hydraulic chamber 20 is defined between one end wall of the cylinder portion 14 and one piston 15, and a release oil is provided between the other end wall of the cylinder portion 14 and the other piston 16. The chamber 21 is defined, and the release oil chamber 2
1 is connected to the reservoir R of the master cylinder M. A spring 22 for urging the piston 16 in a direction away from the partition 13 is housed in the secondary braking hydraulic chamber 19, and a spring 23 for urging the piston 15 toward the partition 13 in the anti-lock control hydraulic chamber 20. Is stored.

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

In the other modulator 11 ', 1
The next brake hydraulic chamber 18 'communicates with the master cylinder M,
The next brake hydraulic chamber 19 'communicates with the brake oil chamber 4 of the left and right rear wheel brakes Blr, Brr via the oil passage 5', and the release oil chamber 21 'communicates with the reservoir R. Further, the anti-lock control hydraulic chamber 20 'is provided with a normally closed inlet valve Vi'.
And to the oil tank T via a normally open outlet valve Vo '.

The inlet valves Vi and Vi 'and the outlet valves Vo and Vo' are solenoid valves, and their 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 antilock control hydraulic chambers 20, 20 'are released to the oil tank T and the brake pedal When the hydraulic pressure from the master cylinder M is supplied to the primary brake hydraulic chambers 18 and 18 'by stepping on 1, the volume of the secondary brake hydraulic chambers 19 and 19' is reduced, and the volume of each wheel brake Blf, Brf, Blr and Brr is reduced. The braking oil chamber 4 is supplied with a braking oil pressure according to the oil pressure from the master cylinder M. Therefore, the torque at the time of braking freely increases according to the braking operation of the driver.

When the outlet valves Vo and Vo 'are closed while the inlet valves Vi and Vi' are closed,
Since the control oil in the anti-lock control hydraulic chambers 20 and 20 'is in a locked state, the secondary braking hydraulic chambers 19 and 19' of the modulators 11 and 11 'are changed to the primary braking hydraulic chambers 18 and 1'.
Regardless of the increase or decrease of the hydraulic pressure supplied to 8 ', its volume does not change, so that the braking torque is kept constant regardless of the driver's braking operation. Such an operating condition is adapted when a possibility of locking the wheels arises.

When the inlet valves Vi and Vi 'are opened and the outlet valves Vo and Vo' are closed, the anti-lock control hydraulic pressure is supplied to the anti-lock control hydraulic chambers 20 and 20 '. , The volume of the secondary brake hydraulic chambers 19 and 19 'increases,
The hydraulic pressure in the brake oil chamber 4 of each of the wheel brakes Blf, Brf, Blr, Brr decreases, and the braking torque is weakened. Therefore, when the wheels are about to enter the locked state, the inlet valves Vi and Vi 'are opened and the outlet valves Vo and Vo' are closed, so that the wheels can be prevented from entering the locked state.

Referring to FIG. 2, the structure of the control means 32 will be described. The inlet valve Vi and the outlet valve V corresponding to one set of the wheel brakes Blf and Brf are described.
o and the other set of wheel brakes B
Since the configuration for controlling the inlet valve Vi ′ and the outlet valve Vo ′ corresponding to rr and Brr is basically the same, only the configuration for controlling one of the inlet valve Vi and the outlet valve Vo is described here. I will mention it.

The control means 32 includes a judgment circuit 33 such as a microcomputer. The judgment circuit 33 judges whether or not the wheels are in a locked state, and based on the judgment result, activates the inlet valve Vi and the outlet valve Vo. A signal for opening and closing operation is output.

Here, when considering a criterion for deciding what condition is satisfied to output a signal for antilock control, generally, the following (a) to (a) are considered.
The four methods (d) have been proposed. (a) A method in which the signal β is output when the wheel acceleration VAw <the reference wheel deceleration−VAw ₀ is established, and the braking pressure is reduced. (b) When the wheel speed Vw <the first reference wheel speed Vr ₁ is satisfied, the signal S ₁ is output to release the braking oil pressure.
However, since this case is _{Vr 1 = Vv · (1-} λ 1) when the vehicle speed Vv, and the slip ratio of the wheel set to lambda _1, when the slip ratio of the wheel was lambda, Vw <Vr ₁
Is synonymous with λ> λ ₁ and Vw <Vr ₁ or λ> λ ₁
There signals S ₁ is output when established. (c) A method in which the braking oil pressure is reduced when either one of (a) and (b) is satisfied. (d) A method in which the braking oil pressure is released when the above (a) and (b) are simultaneously established.

In the method (a), the reference wheel deceleration-V
Aw ₀ is a value generated when the wheel goes to lock during braking on a normal running road surface, for example, usually −2.0 to −1.
2G is set. However, in a braking operation performed on a low μ road surface such as a snowy road or an ice burn, a slight
According to the above-described method, the wheel speed is far from the vehicle speed Vv in the latter half of braking, and the wheel lock actually occurs because the wheel may go toward locking at a wheel deceleration of about 1.0 to -0.5 G. In some cases, a signal for reducing the braking oil pressure is not output. Also, when driving on rough roads,
Even during normal braking, the wheel acceleration VAw pulsates finely, and even when there is no concern about wheel locking, the signal β is output and the braking efficiency is reduced.

In the method (b), even if the slip ratio λ is high, that is, even if the signal S ₁ is output, if the wheel speed Vw is increasing, the braking oil pressure is sufficiently released. However, it is determined that the braking oil pressure is loosened even during this period, and the braking efficiency is reduced.

It is obvious that the method (c) has the disadvantages (a) and (b).

Finally, the method (d) solves the problem of a decrease in the braking efficiency when traveling on a rough road and the problem of reducing the braking efficiency by loosening the braking oil pressure while the wheel speed Vw is increasing. You. Further the reference wheel deceleration -VAw _0, the normal set on the road surface in a traveling state within the wheel deceleration generated during braking for example -0.3 to-0.6G, snowy or icy such low μ In the braking operation performed on the road surface, even when the wheels are likely to be locked at a wheel deceleration less than the above set value and about -1.0 G or more, the state of the wheels should be accurately detected and the braking hydraulic pressure should be reduced. Can be.

Therefore, in the present embodiment, the judgment circuit 33
, A signal Vw (hereinafter, referred to as a wheel speed signal Vw) corresponding to a wheel speed is input from a wheel speed detector 34 mounted on a drive wheel, and based on the wheel speed signal Vw and the wheel speed signal Vw. The calculated wheel acceleration VAw is compared with the first reference wheel speed Vr ₁ and the reference wheel deceleration −VAw ₀ as described above, Are established, the judgment circuit 33 outputs high-level signals β and S ₁ , respectively. These signals beta, S ₁ is input to the AND gate 35 becomes conductive the transistor 36 when both signals are high level, Sorenodo 38 is energized, the inlet valve Vi is opened. When the high-level signal S ₁ is output, the transistor 37 is turned on, the solenoid 39 is excited,
The outlet valve Vo is closed.

By the way, when the braking torque is weakened by the signals β and S ₁ as described above, the wheel speed is still decelerating, which means that the braking torque is still larger than the road surface driving torque. At this point, concerns about wheel locks have not been completely eliminated. However, since the system generally has an operation delay of about 10 ms, the braking oil pressure is further relaxed even after the release signal has disappeared. A braking result is obtained and there is no fear of wheel lock. However, at the time of braking on a low μ road surface, in the above-described method, the braking oil pressure is not sufficiently loosened, and the wheels may go directly to the lock. So, to solve such a problem,
lambda> lambda to wheel speed signals Vw when _one starts to reliably accelerated (that is, until the wheel acceleration turns positive) may be to generate a loosened signal, In so doing,
As described above, when braking on a normal road surface having a high μ, V
Even if the release signal is stopped at Aw> -VAw ₀ , although the good braking result is obtained, the release signal is maintained until VAw> 0.
Eventually, a reduction in braking efficiency becomes a problem. However, this is practically no problem for the wheel having a smaller braking load distribution.

Therefore, a second reference wheel speed Vr ₂ corresponding to a second reference slip ratio λ ₂ satisfying λ ₂ > λ ₁ is set,
Only when Vw <Vr _2, that is, λ> λ _2, and the possibility of locking is increased, the loosening signal is maintained until the wheel speed signal Vw starts increasing. That is, the determination circuit 33 determines whether or not Vw <Vr ₂ or λ> λ ₂ , and outputs the signal S ₂ when the condition is satisfied. In order to determine that the wheel speed signal Vw is accelerating, a reference value of accelerating speed + VAw ₀ is set, and
When w> + VAw ₀ , the signal α is output.

The signal S ₂ is input to one input terminal of the AND gate 40 and is also input to the OR gate 41, and the signal α is input to the OR gate 41 and is inverted to A.
Input to ND gate 40. Further, the signal S ₁ is also O
The signal is input to the R gate 41, and the output of the OR gate 41 is supplied to the base of the transistor 37. The outputs of the AND gates 35 and 40 are input to an OR gate 42,
The output of gate 42 is provided to the base of transistor 36.

According to the control means 32, the signal S
_{If any one of 1} , α and S ₂ becomes high level, the transistor 37 becomes conductive and the outlet valve Vo closes,
When both the signals β and S ₁ are at a high level, or when the signal S ₂ is at a high level and the signal α is at a low level, the inlet valve Vi opens.

Next, the first and second reference wheel speeds V
Explaining how to set r ₁ and Vr ₂ , these are ideally determined as follows by detecting the vehicle speed V and adding appropriate reference slip ratios λ ₁ and λ ₂ thereto. .

[0031] However, no practical means for detecting the vehicle speed V has been found so far. Therefore, a method of estimating a temporary vehicle speed Vv from a change state of the wheel speed signal Vw is generally used, and its arithmetic circuit is shown in FIG.

In FIG. 3, the arithmetic circuit 49 is provided with the control means 3
2 and includes an ideal diode 44, a storage capacitor 45, and a constant current discharge circuit 46. The ideal diode 44 is connected to an input terminal 43 for inputting the wheel speed signal Vw, and a normally closed relay switch 48 is interposed between the ideal diode 44 and the storage capacitor 45.
The storage capacitor 45 and the constant current discharging circuit 46 are connected to an output terminal 47 for outputting a temporary vehicle speed Vv.

According to such an arithmetic circuit 49, when the relay switch 48 is on, as shown in FIG. 8, the peak value of the wheel speed signal Vw during the antilock operation is determined by the actual vehicle speed Vv *. , The valley of the wheel speed signal Vw is connected at a constant downward gradient, and the tentative vehicle speed V
v is output.

In order to suppress an increase in the estimated vehicle speed Vv irrespective of an increase in the wheel speed signal Vw, the wheel spin is detected when the vehicle suddenly starts or accelerates on a slippery road such as a snowy road or a frozen road. The spin detector 25 is connected to the arithmetic circuit 49.

Considering how the wheel spin is detected, first, the vehicle speed does not exceed 1.0 G during non-braking, so that the wheel speed VAw also increases unless wheel spin occurs. 1.0 G or less. Therefore, by setting the predetermined reference value for comparison + Vaw ₁ for the wheel up speed Vaw, Vaw during non-braking> + Vaw
_When it becomes ₁ , it can be determined that wheel spin has occurred. At the end of wheel spin, wheel speed signal Vw greatly exceeds actual vehicle speed Vv * (Vw>
Vv *) value, the actual vehicle speed V
In order to approach v *, a large wheel deceleration occurs, and this wheel deceleration is determined by the fact that the wheel speed signal Vw is equal to the actual vehicle speed Vv *.
It disappears when it is almost equal to. Therefore, by setting the predetermined reference value -VAw ₁ for the wheel deceleration, the end of the wheel spin when the wheel deceleration is <again VAw from when -VAw _1> -VAw ₁ once VAw Although it can be determined that the time has elapsed, since the system has a slight operation delay, in the illustrated example, the wheel deceleration is VAw
> + VAw ₁ , the first time VAw <−VAw ₁ is determined as the end time of the wheel spin.

The spin detecting means 25 is constructed based on the above-mentioned viewpoint, and differentiates the wheel speed signal Vw to calculate a wheel acceleration or a wheel deceleration.
6, a first comparator 27 for comparison with the wheel up speed and the reference value + Vaw _1, a second comparator 28 for comparison with the wheel deceleration and the reference value -VAw _1, both the comparators 27 and 28 And a relay coil 30 connected to the set output terminal Q of the flip-flop 29 and forming a relay together with the relay switch 48 of the arithmetic circuit 49.

The differentiating circuit 26 is connected to the input terminal 43, and the output terminal of the differentiating circuit 26 is connected to the non-inverting input terminal of the first comparator 27 and to the inverting input terminal of the second comparator 28. Is done. Further to the inverting input of the first comparator 27 is input a signal indicating the reference value + Vaw _1, the non-inverting input terminal of the second comparator 28 a signal indicating the reference value -VAw ₁ is inputted. Further, the output terminal of the first comparator 27 is connected to the set input terminal S of the flip-flop 29, and the output terminal of the second comparator 28 is connected to the reset input terminal R of the flip-flop 29.

According to such a spin detecting means 25,
In response to VAw> + VAw ₁ , a high-level signal is input from the first comparator 27 to the set input terminal S of the flip-flop 29 and the relay coil 30 is excited, so that the relay switch 48 of the arithmetic circuit 49 is activated. Cut off.
This state is maintained until the output of the second comparator 28 becomes a high level, that is, until VAw <−VAw ₁ . Therefore, the relay switch 48 of the arithmetic circuit 49
Is VAw <+ VAw after VAw> + VAw ₁
Shut off until it becomes ₁ . Thus, the spin detection means 25 a from the wheel acceleration Vaw is a Vaw> Vaw ₁ until VAw <-VAw ₁ determines that the generation period of wheelspin. The relay switch 48
While the spin state is detected by the spin detecting means 25 as described later, against the increase of the wheel speed signals V _W
That the estimated vehicle rate of increase of velocity V _V before the time of detecting the non-spin state
The means for reducing the estimated vehicle speed increase rate of the present invention is configured to reduce the increase rate from the above increase rate .

Next, the operation of this embodiment will be described with reference to FIG. FIG. 4 shows an example of the operation mode of the anti-lock braking device. The horizontal axis indicates the time elapsed after the start of braking, and the vertical axis indicates the actual vehicle speed Vv * and the wheel speed signal at the top. Vw, first reference wheel speed Vr ₁
And a second reference wheel speed Vr ₂ , a wheel acceleration VAw, an acceleration reference value + VAw ₀ and a reference wheel deceleration −VAw ₀ are shown below the position, and signals α, β, S ₁ are further below the wheel acceleration VAw. , the operating state of S ₂ and the solenoid 38 and 39 are shown, and the braking pressure Pb is shown at the bottom.

First, at time t = 0, immediately after the braking is started, the outputs of the signals α, β, S ₁ , S ₂ are at the low level, and the braking oil pressure Pb gradually increases. Both the signal Vw and the wheel acceleration VAw gradually decrease.

The wheel acceleration VAw at time t ₁ is smaller than the reference wheel deceleration -VAw ₀ (VAw <-V
Aw ₀ ) and the signal β goes to a high level. At this time, the signal S ₁ remains at a low level because the wheel speed signal Vw is higher than the first reference wheel speed Vr ₁ . Therefore,
The braking oil pressure Pb continues to increase, and the wheel speed signal Vw and the wheel acceleration VAw also continue to decrease.

At time t ₂ , when the wheel speed signal Vw falls below the first reference wheel speed Vr ₁ , the signal S ₁ goes high and the OR gate 42 responds to the output of the AND gate 35 going high. Goes high and the output of the OR gate 41 goes high. This excites the solenoids 38 and 39, opening the inlet valve Vi and closing the outlet valve Vo. As a result, the braking hydraulic pressure Pb starts to decrease, and the wheel acceleration VAw turns to the speed increasing side. At this time, the wheel speed signal Vw continues to decrease.

[0043] At time t _3, greater than the reference wheel deceleration -VAw ₀ the wheel acceleration VAw (VAw> -VA
w ₀ ), the signal β goes low, and the output of the AND gate 35 goes low 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. That is, the braking torque is kept substantially constant. Thereafter, the wheel speed signal Vw starts to increase.

At time t ₄ , when the wheel acceleration VAw becomes larger than the acceleration reference value + VAw ₀ (VAw> + VAw ₀ ), the signal α goes high. At time t _5, when the wheel speed signals Vw exceeds the first reference wheel speed Vr _1, signal S ₁ is at a low level. At time t ₆
, The wheel acceleration VAw is equal to the acceleration reference value + VAw ₀
When the voltage drops further, the signal α becomes low level, and the outlet valve Vo opens. Accordingly, the braking oil pressure Pb
Increase.

[0045] At time t _7, smaller than the wheel acceleration VAw the reference wheel deceleration -VAw ₀ (VAw <-VA
w ₀ ), the signal β goes to a high level, and at time t ₈
, The wheel speed signal Vw is the first reference wheel speed Vr ₁
When the voltage drops below (Vw <Vr ₁ ), the signal S ₁ goes to a high level, the output of the AND gate 35 goes to a high level in response to this, the inlet valve Vi closes, and the outlet valve Vo opens. , Braking oil pressure Pb
Begins to drop. Then the wheel speed signals Vw at time t ₉ the possibility of wheel locking is large decreases (Vw <Vr ₂₎ than the second reference wheel speed Vr _2, the signal S ₂ becomes high level.

[0046] When the wheel acceleration VAw at time t ₁₀ is larger than the reference wheel deceleration -VAw _0, the signal β becomes low level, the brake hydraulic pressure Pb decreases further, the wheel speed signals Vw turns to accelerated . When the wheel acceleration Vaw at time t ₁₁ exceeds the increased speed reference value + Vaw _0, the signal α becomes high level, 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 output of the OR gate 42 is at a low level, so that the solenoid 38 is demagnetized and the inlet valve Vi
Closes the valve. As a result, the braking oil pressure Pb is kept constant.

[0047] At time t _12, the wheel speed signals Vw exceeds the second reference wheel speed Vr _2, the signal S ₂ becomes a low level, exceeding the wheel speed signal Vw is the first reference wheel speed Vr ₁ at time t ₁₃ If, the signal S ₁ is at a low level brake pressure Pb is kept substantially constant, the locked state is avoided. Further, when the wheel acceleration Vaw at time t ₁₄ becomes lower than the increased reference speed + Vaw _0, the signal α becomes low level, the outlet valve Vo accordingly
Opens. Therefore, the braking oil pressure Pb starts to increase.

[0048] When the wheel acceleration VAw at time t ₁₅ becomes smaller than the reference wheel deceleration -VAw _0, the signal β becomes high level, than the wheel speed signals Vw first reference wheel speed Vr ₁ at the next time t ₁₆ together with signals S ₁ decreases the inlet valve Vi is opened in response to the high level, the outlet valve Vo is closed. Therefore,
The braking oil pressure Pb starts to decrease. Further wheel acceleration VAw at time t ₁₇ exceeds the reference wheel deceleration -VAw _0, the outlet valve Vo is opened in response to the signal β becomes low level, the brake hydraulic pressure Pb is kept constant.

[0049] When the wheel acceleration VAw at the time t ₁₈ is greater than the increase rate of the reference value + VAw _0, signal α becomes a high level,
When the wheel speed signal Vw exceeds the first reference wheel speed Vr ₁ at time _19, the signal S ₁ is at a low level. At time t
When ₂₀ wheel acceleration Vaw becomes lower than increasing the speed reference value + Vaw _0, the signal α becomes low level, the outlet valve Vo is opened brake pressure Pb in accordance with it begins to decrease.

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

Next, it is assumed that a sudden start operation is performed on a slippery road such as a snowy road or a frozen road. If a wheel spin occurs during the sudden start, the wheel speed signal Vw becomes significantly higher than the actual vehicle speed Vv * as shown in FIG. However when the wheel acceleration VAw exceeds the reference value + Vw _1, the relay coil 30 is energized, the relay switch 48 is cut off. Therefore, in the arithmetic circuit 49, the charging of the storage capacitor 45 is stopped, and the output from the discharging is output to the output terminal 47.
And the estimated vehicle speed Vv starts to decrease. This is because the wheel acceleration VAw is equal to the reference value -VAw ₁
And relay switch 48 is turned on in response to relay coil 30 being demagnetized. As a result, in the arithmetic circuit 49, the storage capacitor 4
5, the vehicle speed Vv rises at a relatively large gradient corresponding to the charging characteristic until the estimated vehicle speed Vv coincides with the wheel speed signal Vw which is decreasing, and thereafter, the valley of the wheel speed signal is filled. Since the speed decreases at a constant downward gradient, the gap between the estimated vehicle speed Vv and the wheel speed signal Vw in the latter half of and immediately after the wheel spin becomes smaller than in the conventional example shown in FIG. 9, and accordingly, the wheel speed signal Vw
Becomes greater than the first reference wheel speed Vr ₁ (that is, the slip signal S ₁ is no longer output), so that the judgment circuit 33
It is avoided to determine that the wheels are likely to lock at. Thus, when a wheel spin occurs due to a sudden start on a slippery road surface, when the braking operation is performed in the latter half of or immediately after the wheel spin, the estimated vehicle speed Vv is lower than that of the conventional example (see FIG. 9). Since the pressure decreases, it is possible to prevent the determination circuit 33 from determining that the wheels are likely to be locked, thereby preventing a reduction in the braking pressure.

FIG. 6 shows the operation when a wheel spin occurs when a sudden acceleration operation is performed while the vehicle is running on a slippery road such as a snowy road or an ice barn. In the latter half of or immediately after the wheel spin, the estimated wheel speed Vv is reduced as compared with the conventional example (see FIG. 10), so that the determination circuit 33 is prevented from determining that the wheels are likely to be locked.

As described above, the spin detection means 25
And detection of the emission state, estimated vehicle velocity V _V by the arithmetic circuit 49
A constant is made based on the wheel speed signals V _W of the wheel
By inputting the wheel speed, the vehicle belonging to the wheel
Self-processing within the system up to the wheel brakes,
There is no need to exchange complicated information with other wheel systems. This
This is used for switching the base wheel speed in four-wheel drive vehicles, etc.
Especially when it is impossible (when there is no place to switch)
It is profitable.

In the above embodiment, the spin detecting means 2
In wheel 5, wheel deceleration was VAw> + due to wheel spin.
The time at which VAw <−VAw is first determined after exceeding VAw ₁ is determined to be the end time of the wheel spin. However, if the operation delay of the system is ignored, the wheel deceleration becomes VAw <−VAw ₁ once. VAw> -VA again
It is also possible to determine the time point when w ₁ is the end time of the wheel spin.

In order to improve the accuracy of estimating the vehicle speed Vv, the wheel speed of the driving wheel and the driven wheel may be used. In this case, the wheel spin is detected by the wheel acceleration on the driving wheel side, and the driving wheel is detected. It is sufficient to shut off the charging circuit for the capacitor in the arithmetic circuit for estimating the wheel speed on the side.

[0056]

As described above, according to the present invention, even if wheel spin occurs at the time of sudden start or sudden acceleration on a slippery road such as a snowy road or an icy road, and the wheel speed suddenly increases, the spin state is maintained. Is the wheel speed of the estimated vehicle speed obtained by the arithmetic circuit
The rate of increase with respect to the degree signal is made smaller than the non-spin state by the estimated vehicle speed increase rate reducing means responding to the spin detecting means.
Since the anti-lock control means determines that the wheels are likely to lock due to an excessive increase in the estimated vehicle speed during the wheel spin, braking can be prevented during or immediately after the wheel spin. Even if it is operated, the hydraulic control circuit is not unnecessarily subjected to the antilock control, so that the braking hydraulic pressure can be quickly increased in accordance with the braking operation, and the wheels can be braked accurately. Moreover, by avoiding unnecessary antilock control as described above, it is possible to suppress the generation of the operation noise of the antilock control system and to contribute to the improvement of durability thereof. In addition, the spin detection means
Detection of the vehicle state and estimation of the vehicle speed by the arithmetic circuit
The vehicle speed is determined based on the wheel speed of the wheel.
From the input of the wheel speed to the wheel brake belonging to that wheel
Self-processing can be performed in the system, and it can be
Transmission and reception of complicated information is unnecessary, especially for four-wheel drive vehicles.
When it is not possible to switch the base wheel speed
This is advantageous .

[Brief description of the drawings]

FIG. 1 is a hydraulic control circuit diagram showing an embodiment of the present invention.

FIG. 2 is a simplified circuit diagram showing a configuration of control means of the embodiment.

FIG. 3 is a circuit diagram showing a configuration of an arithmetic circuit and spin detecting means of the embodiment.

FIG. 4 is a characteristic diagram showing an antilock operation state of the embodiment.

FIG. 5 is a characteristic diagram when wheel spin occurs at the time of sudden start in the embodiment.

FIG. 6 is a characteristic diagram when a wheel spin occurs at a sudden acceleration in the embodiment.

FIG. 7 is a circuit diagram showing a conventional arithmetic circuit;

FIG. 8 is a characteristic diagram of a conventional arithmetic circuit.

FIG. 9 is a characteristic diagram when wheel spin occurs at the time of sudden start in the prior art.

FIG. 10 is a characteristic diagram when a wheel spin occurs during rapid acceleration in the prior art.

[Explanation of symbols]

3 Hydraulic control circuit 25 Spin detecting means 32 Control circuit 34 Wheel speed detector 48 Relay as means for reducing estimated vehicle speed increase rate
Switch 49 Arithmetic circuit Blf, Brf, Blr, Brr Wheel brake VA _W Value obtained based on wheel speed signal
Wheel acceleration + VA _W1, -VA _W1 reference value Vr _1, Vr ₂ reference wheel speed Vv estimated vehicle both speed Vw wheel speed signal Te

Claims (1)

(57) [Claims] 1. A wheel brake (Blf, Brf, Bl)
r, Brr); and the wheel brakes (Blf, Brf,
Blr, Brr), a hydraulic pressure control circuit (3) for controlling the supply of braking oil pressure, a wheel speed detector (34), and a wheel speed signal (V) output from the wheel speed detector (34).
w), a reference wheel speed (Vr ₁ , Vr ₂ ) set based on the estimated vehicle speed (Vv) and the wheel speed signal (Vw) to determine whether the wheels are about to lock, and when the wheels are about to lock, the wheel brakes (Blf, Brf, Blr,
Control means (32) for controlling to decrease the brake hydraulic pressure the hydraulic control circuit (3) to brr); the anti-lock brake system comprising, based on the wheel speed signal (V _W)
(VA _W ) and the set reference value (+
VA _W1 , −VA _W1 ), and a spin detecting means (25) for detecting a spin state of the wheel based on a comparison with the arithmetic circuit (49) is connected to the arithmetic circuit (49). in order to avoid the control means and the wheel is about to be locked (32) to determine the wheel speed at the time of the spin state detection the that by the spin detection means (25)
Estimated vehicle speed (V _V ) for increasing signal (V _W )
Rate of increase of the rate of increase in the non-spin state detection
An anti-lock braking device comprising: an estimated vehicle speed increase rate reducing means (48) for causing the vehicle to increase.