JPH064410B2 - Anti-skidding control device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an improvement of an anti-skid control device that performs a pressure reduction control of a brake hydraulic pressure when a slip ratio exceeds a predetermined value during braking of a vehicle.

[Conventional technology]

In a vehicle, the friction coefficient μ between the wheel and the road surface is generally 11th.
As shown in the figure, the maximum μ (max) is obtained at a predetermined slip ratio λ ₀ (about 15%), and at this time, the braking efficiency in the vehicle is maximum. Therefore, in a normal anti-skid control device, during braking of the vehicle, the brake fluid pressure is controlled to be increased, reduced, or maintained so that the slip ratio λ of the wheel is always a value near the slip ratio λ _0. It is a thing. As a result, the stopping distance at the time of braking can be shortened and steering stability can be ensured.

Therefore, in the conventional anti-skid control device, when the slip ratio λ becomes equal to or greater than the predetermined slip ratio λ ₀ , the braking hydraulic pressure is controlled to be reduced in order to recover the rotation of the wheels. Specific control is, for example, as shown in FIG. The slip ratio λ is the wheel speed V
_It can be obtained as λ = 1−V _w / V _c based on _w and the vehicle speed V _c , but since it is not easy to detect the vehicle speed V _c at the time of braking, in this example, the vehicle speed is reduced as the vehicle speed V _c. A pseudo vehicle speed (hereinafter referred to as a pseudo vehicle speed V _i ) having a predetermined inclination is generated from the wheel speed V _b when the speed reaches a predetermined value b ₁ .

First, braking is started to increase the braking fluid pressure P, and the wheel speed V
_{When w} decreases and the deceleration also increases to reach the predetermined value b ₁ , the pseudo vehicle speed V _i is sequentially output, while the braking hydraulic pressure P is increased in order to suppress the sudden decrease in wheel speed. The pressure is stopped and the braking hydraulic pressure P is maintained at a relatively high hydraulic pressure.
Then, in this state, the wheel speed V _w decreases, and when the wheel speed V _w reaches V _wo = 0.85 × V _i corresponding to the slip ratio λ ₀ λ ₀ = 1-V _w / V _i = 15%. , Slip ratio λ
Exceeds the predetermined value λ ₀ , the braking fluid pressure P is reduced. After that, when the wheel deceleration decreases due to the reduction of the braking fluid pressure P and the wheel speed V _w is further recovered and the acceleration reaches a ₁ , the braking fluid is suppressed in order to suppress the subsequent rapid increase of the wheel speed. The braking hydraulic pressure P is maintained at a relatively low hydraulic pressure by interrupting the hydraulic pressure P. And the wheel speed V
_{When w} exceeds V _wo = 0.85 × V _i corresponding to the slip ratio λ ₀ and the wheel acceleration falls below a predetermined value a ₁ , the braking hydraulic pressure P
Is controlled to increase, and thereafter, the same braking fluid pressure control as described above is repeatedly performed.

According to the control of the braking fluid pressure P in the above braking,
The pressure reduction control of the brake fluid pressure P in the period E the slip ratio lambda becomes a predetermined value lambda ₀ or more, it is possible to recover the predetermined value a slip ratio lambda became predetermined value lambda ₀ or more.

[Problems to be Solved by the Invention]

By the way, in the control of the braking fluid pressure P as described above, on a road surface (hereinafter, referred to as high μ road surface) where the coefficient of friction μ with the wheel (hereinafter referred to as road surface μ) is relatively large, the hydraulic pressure at which the wheel should be locked. Since the (lock) is high, the braking hydraulic pressure P changes in a relatively high hydraulic pressure region, while on the road surface where the road surface μ is relatively small (hereinafter referred to as low μ road surface), the hydraulic pressure at which the wheels should be locked. Since P (lock) is low, the braking hydraulic pressure P changes in a relatively low hydraulic pressure region.

Further, as shown in FIG. 13, generally, the pressure reducing characteristics of a hydraulic actuator such as a wheel cylinder that transmits the braking hydraulic pressure P to the wheels as a braking force has a large depressurizing rate in a high hydraulic region and a low hydraulic pressure. In the region, the depressurization rate becomes small.

From the above, particularly in braking on a high μ road surface, when the braking hydraulic pressure P is reduced, it is delayed to detect a condition for interrupting the pressure reduction control, for example, that the wheel acceleration has reached the predetermined value a _1. Then, the braking state reaches the low range in the range from the range in FIG. 11 at a stretch. Then, in the low range in this region, as shown in FIG. 11, the change of the friction coefficient (road surface μ) becomes large with respect to the change of the slip ratio λ. That is, if the braking force is affected, and for example, the anti-skid control of the steered wheels is performed independently, there is a possibility that the steering by the steering becomes unstable due to the imbalance of the braking forces of the left and right wheels.

Therefore, in braking on the high μ road surface, pressure reduction control is performed in a relatively high hydraulic pressure region, so that it is conceivable to make the characteristics of the actuator in the hydraulic system as shown by the dotted line in FIG. .

However, when the characteristics of the actuator are changed as a whole in this way, when the hydraulic pressure control is performed in a region where the braking hydraulic pressure P is relatively low on a low μ road surface, the pressure reducing speed in the pressure reducing control is further reduced. May delay the recovery of wheel rotation (wheel speed) on the low μ road surface and lock the wheel.

On the other hand, the decreasing tendency of the vehicle speed V _c during braking changes according to the road surface μ, and the inclination of the vehicle speed V _c is large on the high μ road surface and small on the low μ road surface. Therefore, as the pseudo vehicle speed V _i instead of the vehicle body speed V _c , a predetermined slope, for example, 0.4 G from the detected wheel speed value V _b (0) when the wheel deceleration reaches the predetermined value b ₁ for the first time after starting braking. the speed straight line with an inclination, thereafter, the wheel deceleration is detected wheel speed value for each reaches a predetermined value _{b 1} V b (n), detects the detection wheel speed value V _b (n) and in the initial stage of braking If the speed straight lines having the slope of the straight line connecting the wheel speed value V _b (n) are respectively adopted, the slope information of the pseudo vehicle speed V _i becomes effective as the determination information of the road surface μ (for example, JP-A-56). No. 53944, this publication shows an example in which the pseudo vehicle body speed V _i and the target wheel speed V _wo match.

By the way, on a low μ road surface, the braking fluid pressure P at the initial stage of braking
The recovery of the wheel speed V _w after the wheel speed V _w is reduced by the pressure increase control is slower than the case of the high μ road surface even when the braking fluid pressure is reduced. Thus, in the low μ road surface, once the road irregularities such as shown in FIG. 14 to the extent that the brake initially depressed the wheel speed V _w is gradually restored temporarily wheel speed V _w is lowered The braking hydraulic pressure is increased, and the wheel deceleration may reach the predetermined value b ₁ again. The gradient of the pseudo vehicle speed V _i generated at this time is the wheel speed V _w.
Since the detected wheel speed value V _b (1) becomes a relatively low level value before the recovery of is sufficiently performed, it becomes a relatively large value. As a result, if the road surface μ is determined based on the inclination of the pseudo vehicle speed V _i , the road surface μ may be determined to be a high μ road surface even though the road surface μ is a low μ road surface.

In this way, if an attempt is made to indirectly determine the road surface μ from the state of the wheel, the state of the braking fluid pressure, etc., there is a possibility of misjudging due to various influences.

The present invention has been made in view of the above, and provides an anti-skid control device that enables braking control in a hydraulic region as high as possible on a high μ road surface while appropriately maintaining the pressure reducing characteristics on a low μ road surface. In order to achieve the above object, the means for determining the high μ road surface necessary for realizing the anti-skid control device is a high μ road surface despite the low μ road surface.
A second object is to prevent the situation where the wheels are locked as much as possible by the braking control in the relatively high hydraulic pressure region on the low μ road surface when the road surface is determined.

[Means for Solving the Problems]

In order to achieve each of the above objects, the present invention determines an inclination of a pseudo vehicle speed for each skid cycle in an anti-skid control device that performs pressure reduction control of a braking hydraulic pressure when a slip ratio becomes a predetermined value or more during vehicle braking. Then, the first determination unit 183 that determines that this inclination is larger than a predetermined value,
Based on the determination output from the first determination unit, the control units 184 and 185 that control the pressure reduction control of the braking fluid pressure to a gentle pressure reduction characteristic, and when the inclination of the simulated vehicle speed is smaller than the predetermined value, Prohibition means 182 and 186 for forcibly prohibiting the operation of the control means 184 and 185 are provided.

[Action]

With this configuration, the first determination means 18
If the inclination is determined to be larger than the predetermined value by 3, it means that the friction coefficient μ between the wheel and the road surface is equal to or larger than the predetermined value, and the control means 184 and 185 output the determination output from the first determination means. Based on the above, the pressure reduction control of the braking hydraulic pressure is controlled to a gentle pressure reduction characteristic. When the inclination is equal to or less than the predetermined value, it is determined that the friction coefficient μ is low, and the prohibiting means 182 and 186 forcibly prohibit the operation of the control means 184 and 185 in order to prevent the wheels from locking. .

〔Example〕

 Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the basic configuration of an anti-skid control device according to the present invention. That is, basically, this anti-skid control device (anti-skid control circuit 100) is
During braking, based on a detection signal of a frequency proportional to the rotation speed of the wheel 102 output from the wheel speed sensor 1, an inflow valve 14 (hereinafter referred to as an inflow valve 14 provided in a path from the master cylinder 101 of the braking hydraulic system to the wheel cylinder 103). , EV valve 14) switching control from the wheel cylinder 103 to the reservoir tank 104,
Switching control of the reservoir tank 104 in the hydraulic pressure recovery path to the master cylinder 101 via the hydraulic pressure recovery pump 17 and the outflow valve 15 (hereinafter referred to as the AV valve 15) provided in the preceding stage of the pump 17 is performed. Is. The hydraulic pressure of the wheel cylinder 103, that is, the braking hydraulic pressure, is controlled by the switching signal of the EV valve 14 (hereinafter referred to as EV signal) and the switching signal of the AV valve 15 (hereinafter referred to as AV signal) as shown in the following table. Will be.

Here, the specific configuration of the anti-skid control circuit 100 is as shown in FIG. In the figure, 2 is a wheel speed detection circuit that calculates the wheel speed V _w based on the output signal from the wheel speed sensor 1, and 3 is the wheel speed detection circuit 2 that differentiates the detected wheel speed signal from the wheel speed detection circuit 2, for example. An acceleration / deceleration detection circuit for detecting acceleration and deceleration (negative acceleration).
4 is the pseudo vehicle speed required to detect the slip ratio λ
Pseudo vehicle speed generation circuit that generates V _i (pseudo vehicle speed), 5
Is the reference deceleration b ₁ detected by the acceleration / deceleration detection circuit 3.
It is a comparison circuit that outputs an H level signal (hereinafter referred to as b ₁ signal) when the above is reached, and the pseudo vehicle speed generation circuit 4 has a configuration as shown in FIG. Each time the b ₁ signal is input, a new pseudo vehicle speed V _i is output based on the detected wheel speed output from the wheel speed detection circuit 2 at that time. Reference numeral 6 denotes a target wheel speed generation circuit. This target wheel speed generation circuit 6 is based on the pseudo vehicle speed V _i from the pseudo vehicle speed generation circuit 5 and has a slip ratio λ ₀ λ ₀ = 1- (V _wo / V _i ), which outputs the target wheel speed V _wo that is the control target corresponding to ( _wo / V _i ). Specifically, since λ ₀ is approximately 0.15 (15%), the calculation of V _wo = V _i × 0.85 And outputs the calculated value.

7 inputs the target wheel speed V _wo from the target wheel speed generation circuit 6 and the detected wheel speed V _w from the wheel speed detection circuit 2, and when the detected wheel speed V _w falls below the target wheel speed V _wo , H Comparing circuit for outputting level signal (hereinafter referred to as slip signal), 8
Is the acceleration detected by the acceleration / deceleration detection circuit 3 is the reference acceleration a ₁
A comparator circuit that outputs an H level signal (hereinafter referred to as a ₁ signal) when the above is reached, and 9 is an H level when the detected deceleration from the acceleration / deceleration detection circuit 3 is equal to or greater than the reference deceleration b ₁ like the comparator circuit 5. This is a comparison circuit that outputs a level signal (b ₁ signal).
An AND signal (AV signal) by the AND gate 10 of the inversion signal of the a ₁ signal from the comparison circuit 8 and the slip signal from the comparison circuit 7 is an AV signal adjustment circuit as described later.
The signal is further input to the AV valve 15 via the driver 13 via 18 and the OR signal by the OR gate 11 of the a ₁ signal from the comparison circuit 8, the b ₁ signal from the comparison circuit 9 and the output signal from the AND gate 10. The (EV signal) is input to the EV valve via the driver 12.

16 is a re-trigger that outputs an H level signal (hereinafter referred to as an MR signal) for a predetermined time (for example, about 2 seconds) every time an output signal (AV signal) from the AND gate 10 is input, which is activated at the rising edge thereof. It is a bull timer, and while the MR signal from the retriggerable timer 16 activates the hydraulic pressure recovery pump 17, the pseudo vehicle speed generation circuit 4 is further controlled by the MR signal. There is.

Here, the pseudo vehicle speed generation circuit 4 generates a speed straight line having a predetermined slope, for example, 0.4 G from the detected wheel speed value V _b (0) at that time when the b ₁ signal is output for the first time after starting braking. generated as a pseudo vehicle speed V _i, thereafter, every time the b ₁ signal is generated from the detected wheel speed V _b (n) at that time, the detected wheel speed value V _b (n) and the detected wheel speed value at the initial stage of braking A speed straight line having a slope of a straight line connecting with V _b (0) is generated as the pseudo vehicle speed V _i . To explain its concrete configuration, in FIG. 3, 40a is an inversion signal of the MR signal from the retriggerable timer 16 in FIG. ₂ via the inverter G ₂ and a b ₁ signal from the comparison circuit 5. And a sample hold circuit that extracts and holds the detected wheel speed from the wheel speed detection circuit 2 in synchronization with the AND signal from the AND gate G ₁ and a sample 40b that extracts and holds the detected wheel speed in synchronization with the b ₁ signal. A hold circuit, 41 is a timer counter that increments at a predetermined cycle, and 40c is the AND gate G.
A sample and hold circuit that extracts and holds the numerical value of the timer counter 41 in synchronization with the output signal from ₁ and a sample and hold circuit 40d that extracts and holds the numerical value of the timer counter 41 in synchronization with the b ₁ signal. 42 is a sample hold circuit 40
Sample hold circuit 4 from the sampling wheel speed value V _{o of a}
Subtraction circuit for subtracting the sampled value V _b of 0b, 43 is a subtractor circuit which subtracts the sampled value T _b of the sample-hold circuit 40d from the sampling value T _o of the sample-hold circuit 40c, 44 is subtracted value from the subtraction circuit 42 It is a division circuit that divides (V _o −V _b ) by the subtraction value (T _o −T _b ) from the subtraction circuit 43. Further, 45 is a tilt generation circuit for generating a predetermined wheel speed tilt signal, for example, a tilt signal corresponding to 0.4 G, 46 is a tilt signal from the tilt generation circuit 45 and a calculation output (V _o −V _b from the division circuit 44. ) / (T _o −T _b ), and 47 is the sampling value T held in the sample hold circuit 40b.
A subtraction circuit for subtracting the output value from the timer counter 41 from _b (n), 48 is a subtraction value from the subtraction circuit 47, and a division circuit 44
Is a multiplying circuit for multiplying the divided value from or the gradient value from the gradient generating circuit 45 through the changeover switch 46, and 49 is a calculation from the multiplying circuit 48 from the detected wheel speed value sequentially sampled by the sample hold circuit 40b. It is a subtraction circuit that subtracts the output. Then, 50 is set by the rising edge of the AND signal by the AND gate G ₃ of the b ₁ signal and the MR signal, RS flip-flop which is reset at the falling edge of the MR signal (hereinafter, simply referred to FF50) is, the changeover switch 46 is switched to the inclination generation circuit 45 side when the output Q of the FF 50 is at the L level, and to the division circuit 44 side when the output Q is at the H level.

On the other hand, the AV signal adjusting circuit 18 modulates the pressure reducing characteristic on the high μ road surface, while forcibly prohibiting the modulation operation of the pressure reducing characteristic on the low μ road surface. While the determination is made based on the inclination A of the pseudo vehicle speed V _i from the vehicle speed generation circuit 4, the low μ road surface is determined based on the detected wheel acceleration from the acceleration / deceleration detection circuit 3. Specifically, the wheel acceleration is Predetermined value α _th (eg 3G)
When the value is less than, the road surface is determined to be low μ. The concrete configuration of the AV signal adjusting circuit 18 is as shown in FIG. 4, for example.

In the figure, 181 is a comparison circuit which outputs an H level signal when the detected wheel acceleration α _w from the acceleration / deceleration detection circuit 3 becomes a predetermined value α _th (for example, 3 G) or more, and 182 is a comparison circuit 181.
Is a flip-flop (hereinafter, referred to as FF) which is set at the rising edge of the output of the above and is reset at the rising edge of the MR signal from the retriggerable timer 16. Also, 183
Is the above-mentioned inclination information A from the pseudo vehicle speed generation circuit 4 is a predetermined value A
A comparison circuit that outputs an H level signal when _th (e.g., 0.5 G or more) or more, a pulse generation circuit that outputs a rectangular pulse signal of a predetermined cycle, and a first changeover switch 185 is the first changeover switch. Switch 185 is comparison circuit 1
When the output of 83 is at H level, it is switched to the pulse generation circuit 184 side, and when the output is at L level, the circuit power supply E _cc side is maintained. Further, 186 is a second changeover switch, and this second changeover switch 186 switches to the first changeover switch 185 side when the output Q of the FF 182 is at H level, and when the output is at L level, the power source E It is to maintain the _cc side. Then, the first changeover switch 185 and, or the second changeover switch 186 AND gate 18 that is the gate controlled by a voltage signal of a pulse signal or power E _cc from the pulse generating circuit 184 via the
The AV signal from the AND gate 10 in FIG. 2 is transmitted to the driver 13 via 7.

Next, the operation of this device will be described.

The inclination of the pseudo vehicle speed V _i does not exceed the predetermined value A _th ,
When the first changeover switch 185 maintains the power source E _cc side, the AND gate 187 is always in the allowable state regardless of the state of the second changeover switch 186, and the AV signal from the AND gate 10 is the above-mentioned AND gate. It will be transmitted to the driver 13 as it is via 187, but first,
The operation of the basic anti-skid control in this case will be described.

When the driver depresses the brake pedal to increase the braking hydraulic pressure (the hydraulic pressure in the wheel cylinder 103), the wheel speed is reduced and the wheel deceleration (negative acceleration) is increased accordingly. Here, when the wheel deceleration further increases and reaches the predetermined value b ₁ , the b ₁ signal is output from the comparison circuit 9 and the OR gate 11
The EV valve 14 is actuated by the b ₁ signal (EV signal) via the, and the braking hydraulic pressure is maintained at that time. At this time, when the wheel deceleration reaches the predetermined value b ₁ , the pseudo vehicle speed generation circuit 4 outputs the pseudo vehicle speed V _i having a predetermined inclination from the detected wheel speed at that time, and at the same time, the target wheel Speed generation circuit 6
Target wheel speed corresponding to the slip ratio λ ₀ from _{V wo (= V i × 0} .
85) output sequentially. Then, when the wheel speed is further reduced due to the holding of the brake hydraulic pressure as described above and falls below the target wheel speed V _wo , a slip signal is output from the comparison circuit 7 and the AND gate 10 is operated. The AV valve 15 is operated by the slip signal (AV signal), and the operating state of the EV valve 14 is maintained by the slip signal (EV signal) via the OR gate 11, and the braking hydraulic pressure is reduced.
When the braking fluid pressure is reduced in this way, the wheel speed and the wheel acceleration are restored accordingly, and the wheel acceleration is reduced to a predetermined value a ₁
When reached, output by a ₁ signal from the comparison circuit 8, the a ₁ signal via the OR gate 11 (EV signal) by EV valve 14
While the operation is further sustained, AV valve 15 since the AND gate 10 by the a ₁ signal is disabled state returned to the initial state, the brake fluid pressure is maintained. If the braking hydraulic pressure is maintained even though the hydraulic pressure is relatively low in this way, it starts to decrease again when the wheel speed exceeds the target wheel speed (the slip signal disappears at this point) to some extent. The wheel acceleration also decreases from the value of the predetermined value a ₁ or more. Here, when the wheel acceleration falls below a predetermined value a ₁ , the a ₁ signal from the comparison circuit 8 falls, and the outputs from the comparison circuits 7 and 9 at that time are L level. Thus, the EV signal and the AV signal become L level, and the braking fluid pressure is increased again. Then, the wheel speed and the wheel acceleration further decrease, and thereafter, the same control of the brake hydraulic pressure as described above is sequentially repeated.

That is, the switching control of the braking hydraulic pressure during the braking is performed according to the control mode determined based on the wheel acceleration / deceleration α _w and the slip ratio λ (actually V _w / V _i ) as shown in FIG. .

In such a basic anti-skid control process, the third
The pseudo vehicle speed generation circuit 4 shown in the figure performs the following operations as shown in the timing chart of FIG.

When braking is started, the wheel deceleration is the predetermined deceleration for the first time at time t _0.
When b ₁ is reached, the sample and hold circuits 40a and 40b sample the detected wheel speed from the wheel speed detection circuit 2 as a value V _b (0) = V _o in synchronization with the rising of the b ₁ signal from the comparison circuit 5. with the sample-hold circuit 40c in synchronization with the rise of the b ₁ signal, the count value T (0) from the time counter 41 in the 40d = T _o is sampled. Also,
At this time, the AV signal in the control device is at the L level, so it is not set in the FF 50, and the output Q of the FF 50 holds the L level and the changeover switch 46 is on the side of the inclination generation circuit 45. . Then, with the passage of time until the wheel deceleration reaches the predetermined value b ₁ again, the count value T _c T _c = T−T (0) T: the output of the time counter 41 corresponding to the passage of that time from the subtraction circuit 47. The values are sequentially output, and the multiplication circuit 4 is based on the count value T _c and the inclination value A _o (0.4 G) from the inclination generation circuit 45.
The value A _o × T _c corresponding to the speed decrease value is output sequentially from 8. And _{further, V b (0) -A o} × T c is outputted to the target wheel speed generating circuit 6 as a pseudo vehicle speed V _i from the subtracting circuit 49.

That is, in the first skid cycles until the wheel deceleration again wheel deceleration after reaching a predetermined value b ₁ reaches the b ₁ at time t _0, the detection wheel speed value V at time t ₀ (0) Therefore, the pseudo vehicle speed V _i having the characteristic of decreasing with the slope A _o is output.

Next, when the wheel deceleration reaches the predetermined value b ₁ again at time t ₁ ,
The detected wheel speed value V _b (1) at that time is newly sampled in the sample hold circuit 40b in synchronization with the b ₁ signal, and the count value T _b (1) from the time counter 41 at the same time point. Sample hold circuit 40d in synchronization with the same b ₁ signal
Will be newly sampled. At this time, the MR signal from the retriggerable timer 16 is at H level,
The AND gate G ₁ is disabled and the values V _b (0) and T _b (0) in the sample hold circuits 40a and 40c are further held, and the FF 50 is set and the changeover switch 46 divides. The circuit 44 is switched and held (this state continues thereafter). Here, the difference value [Delta] V _b (1) of the detection wheel speed value V _b from the subtraction circuit 42 by the time t ₀ (0) and the detected wheel speed value V _b at time t ₂ (1) ΔV _{b (1) = V b (0} ) -V b (1) with outputs, the counter value T _b from the subtraction circuit 43 by the time t ₀ (0) the counter value T _b at time t ₂ (1) Difference value ΔT _{b
(1) ΔT b (1)} = T b (0) -T b (1) is output, these differences value _{ΔV b (1), ΔT b} (1) division circuit 44 on the basis of the [Delta] V _b (1 ) / [Delta] T _b performs operation (1), and it outputs the calculated value a ₁ as the slope information, from V _b (0) to V _b (1). Then, with the passage of time until the wheel deceleration further reaches the predetermined value b ₁ , the subtraction circuit 47 sequentially outputs the count value T _c T _c = T−T _b (1) corresponding to the passage of time. , This count value T _c and division circuit
Based on the inclination information A ₁ (A ₁ = ΔV _b (1) / T _b (1)) from 44, the multiplication circuit 48 sequentially outputs the value A ₁ × T _c corresponding to the speed decrease value. Further, the subtraction circuit 49 outputs V _b (1) −A ₁ × T _c as the pseudo vehicle speed.

That is, in the second skid cycles until the wheel deceleration is further again wheel deceleration after reaching a predetermined value b ₁ reaches the b ₁ at time t _1, detection wheel speed value V _b at time t ₁ ( Inclination from 1) A ₁
A pseudo vehicle speed V _i having a characteristic that decreases with is output.

After that, the wheel deceleration is set to the specified value in each skid cycle.
Every time when b ₁ is reached, the slope information is calculated based on the difference between the detected wheel speed value at that time and the detected wheel speed value V _b (0) under the same initial condition and the time interval (count value). Then, until the wheel deceleration reaches the predetermined value b ₁ , the pseudo vehicle speed V _i that decreases from the detected wheel speed value at that time with the above inclination is output.

As described above, the gradient A is sequentially obtained from the pseudo vehicle speed generation circuit 4.
When the wheel speed V _w falls below the target wheel speed V _wo (corresponding to the slip ratio λ ₀ ) determined by the pseudo vehicle speed V _{i with} the generation of the pseudo vehicle speed V _i , the brake fluid pressure P is reduced. Focusing on the above, the operation of the AV signal adjusting circuit 18 will be described with reference to the timing chart shown in FIG.

First, when the slope A of the pseudo vehicle speed V _i output from the pseudo vehicle speed generation circuit 4 is less than a predetermined value A _th (corresponding to 0.5 G), the AND gate 10 is operated based on the slip signal from the comparison circuit 7 in FIG. Although the output becomes the H level, at this time, since the first changeover switch 185 is maintained on the power supply E _cc side, the output from the AND gate 10 is irrespective of the state of the second changeover switch 186. The H level AV signal is transmitted as it is to the driver 13 via the AND gate 187 which is in the allowable state, and the braking fluid pressure P is reduced according to the characteristics of the actuator by the operation of the AV valve 15 accompanying it.

On the other hand, when the gradient A of the pseudo vehicle speed V _i becomes equal to or _larger than the predetermined value A _th , the road surface is usually a high μ road surface, and therefore the peak value of the wheel acceleration when the wheel speed is recovered is the predetermined value α _th (3G). Output of FF182 set at that time exceeds Q (H level)
Thereby, the second changeover switch 186 is changed over to the first changeover switch 185 side. In this state, the output of the AND gate 10 becomes H level based on the slip signal, but at this time, the output of the comparison circuit 183 becomes H level.
Since the changeover switch 185 of the AND gate 10 is changed over to the pulse generation circuit 184 side,
The pulse signal from the pulse generation circuit 184 is transmitted to the driver 13 as an AV signal through the AND gate 187 which is in an allowable state by the output of the signal (1), and the AV valve 15 repeats the ON / OFF operation in synchronization with this pulse signal. As a result, the pressure reduction of the braking hydraulic pressure at this time has a gentle pressure reduction characteristic as shown in FIG.

In addition, even if the road surface involved in braking is a low μ road surface, the pseudo vehicle speed may change due to, for example, the situation shown in FIG.
When the gradient A of V _i is equal to or _larger than the predetermined value A _th and it is determined that the road surface is high μ, the first changeover switch 185 causes the pulse generation circuit 1 to operate.
Although it switches to the 84 side, since the actual road surface μ is low,
The wheel acceleration never exceeds the predetermined value α _th , and FF18
The output Q of 2 is held at the L level, and accordingly, the second changeover switch 186 maintains the power supply E _cc side. Therefore,
Pulse generation circuit 184 via the first changeover switch 185
Is prohibited from being applied to the input terminal of the AND gate 187, and the AND gate 187 holds the allowable state by the application of the power supply E _cc . Therefore, the above pseudo vehicle speed
Similarly to the case where the gradient A of V _i is less than the predetermined value A _th , the output from the AND gate 10 based on the slip signal is directly sent to the driver 13 via the AND gate 187 to the A level of H level.
It is transmitted as a V signal, and the pressure reducing characteristic of the braking fluid pressure P is the same as that of the low μ road surface.

As described above, according to the present embodiment, when the inclination A of the pseudo vehicle speed V _i from the pseudo vehicle speed generation circuit 4 becomes equal to or larger than the predetermined value A _th (corresponding to 0.5 G), it is determined that the road surface is high μ in principle, In the pressure reduction control at this time, since the AV valve 15 is turned on / off in synchronization with the pulse signal from the pulse generation circuit 184, the pressure reduction on the high μ road surface becomes a gentle pressure reduction characteristic, and the braking on the high μ road surface is performed. Then, the braking hydraulic pressure is controlled with a relatively high hydraulic pressure. In addition, even though the road surface is actually low μ, the slope A of the pseudo vehicle speed V _i is
Is erroneously determined to be a high μ road surface with a predetermined value A _th or more, the low μ road surface is determined because the wheel acceleration does not reach the predetermined value α _th (3G). Since the on / off operation synchronized with the pulse signal of the AV valve 15 is forcibly prohibited, the braking fluid pressure on the low μ road surface is relatively high due to the erroneous determination of the high μ road surface. It can be prevented from being controlled.

FIG. 8 is a block diagram showing another concrete configuration example of the AV signal adjusting circuit 18 in FIG.

This is a comparison circuit 181 for comparing the wheel acceleration α _w with a predetermined value α _th, and a rising edge of the output from the comparison circuit 181 as the determination means for the low μ road surface, as in the example shown in FIG. While the FF 182 to be set (which is reset at the rising edge of the MR signal) is provided, the sawtooth wave generation circuit 189 that outputs a sawtooth wave signal, the sawtooth wave signal from the sawtooth wave generation circuit 189, and the pseudo vehicle speed generation circuit 4 A comparison circuit 188 that compares the level with the inclination signal A and outputs an H level signal when the level of the inclination signal A exceeds the level of the sawtooth signal is provided, and the rectangular pulse signal from the comparison circuit 188 is F
It becomes input to one input terminal of the AND gate 187 via a cut-switched selector switch 186 'from the power source E _cc side by H level output of the F 182, the AND gate 187
The output from the AND gate 10 is transmitted to the driver 13 via the.

In this device, especially on a low μ road surface, the output Q of the FF 182 holds the L level and the output Q of the FF 182 holds the L level as in the above embodiment, and the L level of the output Q holds. Since the change-over switch 186 'maintains the power source _Ecc side, the AND gate 187 is always in the allowable state, and the output signal from the AND gate 10 is directly transmitted to the driver 13 via the AND gate 187.
As a result, the pressure reduction of the braking fluid pressure P follows the pressure reduction characteristics of the actuator. On the other hand, when the wheel acceleration reaches the predetermined value α _th which is the criterion for the low μ road surface, the comparison circuit 18
The output of 1 becomes H level, the FF 182 is set and its output Q becomes H level, and the changeover switch 186 'is switched to the comparison circuit 188 side. Then, as shown in FIG. 9, since the level of the tilt signal A at this time is not so high, the duty ratio of the pulse signal output from the comparison circuit 188 becomes relatively large, and the AND gate 10 based on the slip signal. The H level signal from is passed through an AND gate 187 whose gate is controlled by the pulse signal, so that the H level signal is modulated into a pulse signal having a relatively large duty ratio. As a result, the AV valve 15 is turned on and off, and the on time is relatively long, but the pressure reduction of the braking fluid pressure P has a gentler characteristic than the pressure reduction on the low μ road surface. Further, when the road surface becomes a high μ and the level of the inclination signal A becomes high, the changeover switch 186 ′ becomes the side of the comparison circuit 188 similarly to the above, and the duty ratio of the pulse signal output from the comparison circuit 188 becomes small.
The H level signal from the AND gate 10 based on the slip signal is modulated into a pulse signal similar to the above-mentioned relatively small duty ratio by passing through the AND gate 187.
As a result, the ON time of the AV valve 15 which is turned on / off by the pulse signal is shortened, and the pressure reduction of the braking fluid pressure P becomes a gentler pressure reduction characteristic as shown in FIG.

Furthermore, the AV signal adjusting circuit 18 may be configured as shown in FIG. This is a combination of the example shown in FIG. 4 and the example shown in FIG. 8, and when the inclination A of the pseudo vehicle speed V _i is below a predetermined value A _th , the first changeover switch 1
85 keeps the power supply circuit E _cc side and the second changeover switch 1
The AND gate 187 maintains the permissible state regardless of the state of 86, and the AND gate 187 is operated through the AND gate 187.
Is directly transmitted to the driver 13. on the other hand,
When the inclination A becomes equal to or larger than the predetermined value A _th , the first changeover switch 185 is switched to the comparison circuit 188 side, and at this time, the second changeover switch 186 is changed to the first changeover switch 185.
If it is switched to the side, that is, if the output of the FF 182 set at the rising of the output from the comparison circuit 181 becomes the H level and the low μ road surface is not determined,
The comparison output of the comparison circuit 188 between the sawtooth wave signal from the sawtooth wave generation circuit 189 and the inclination signal is the first changeover switch 1
It is input to one input end of the AND gate 187 via the 85 and the second changeover switch 186. In this case, the H level signal from the AND gate 10 based on the slip signal is compared as in the case shown in FIG. The pulse signal from the circuit 188 is modulated by the AND gate 187 which repeats the permitting state and the inhibiting state.

On the other hand, when the road surface is low μ, that is, when the wheel acceleration α _w is less than the predetermined value α _th , the output of the comparison circuit 181 becomes L level and the output Q of the FF 182 becomes L level, and the second switching is performed. Since the switch 186 maintains the power supply E _cc side, the output signal from the AND gate 10 is directly transmitted to the driver 13 via the AND gate 187 regardless of the inclination A of the pseudo vehicle speed V _i .

According to this device, unless the low μ road surface is determined based on the wheel acceleration, when the inclination of the pseudo vehicle speed V _i is equal to or _larger than the predetermined value A _th , the high μ road surface is determined and the AND gate 10 based on the slip signal is used. Is modulated into a pulse signal having the same duty ratio as the pulse signal from the comparison circuit 188, and the AV valve 15 is turned on / off accordingly, so that the brake fluid pressure P is gradually reduced. It becomes a characteristic. In this case, the higher the level of the inclination signal A, that is, the higher the μ road surface, the more the comparison circuit 18
Since the duty ratio of the pulse signal from 8 becomes small, and therefore the ON operation time of the AV valve 15 becomes short, the degree of the gentle pressure reducing characteristic becomes larger.

In each of the above-described embodiments, the determination of the high μ road surface is determined by the pseudo vehicle speed.
Although the case where the determination is performed based on the inclination of V _i has been described, there is a possibility that the determination may be erroneous even if the determination is made on the high μ road surface based on other parameters that indicate the decreasing tendency of the wheel acceleration or the vehicle speed. Also in this case, by providing the low μ road surface determining means, the same effect as in the above-described embodiments can be obtained. The determination of the low μ road surface is not limited to the determination based on the wheel acceleration. For example, focusing on the fact that the braking hydraulic pressure P is controlled in a relatively low region on the low μ road surface, A pressure sensor may be provided and the low μ road surface may be determined based on the sensor output.

〔The invention's effect〕

As described above, according to the present invention, in the anti-skid control device that performs the pressure reduction control of the braking hydraulic pressure when the slip ratio becomes equal to or more than the predetermined value during the braking of the vehicle, the inclination of the pseudo vehicle speed is determined by the first determination means. Is determined to be greater than a predetermined value (high μ road surface), the friction coefficient μ between the wheel and the road surface is equal to or greater than a predetermined value. At this time, the pressure reduction control is controlled to a gentle pressure reduction characteristic. Therefore, while properly maintaining the pressure reduction characteristics on a low μ road surface,
It becomes possible to control the braking in a higher fluid pressure range on a high μ road surface, and, for example, even in the case of independent anti-skid control of the steered wheels, the instability of steering caused by the difference in the braking force on the high μ road surface can be eliminated as much as possible. In addition, the slope of the simulated vehicle speed is smaller than a predetermined value due to the prohibition means (low μ road surface)
When it is determined that the friction coefficient μ between the wheel and the road surface is smaller than a predetermined value, at this time, it is forced to control the pressure reduction of the braking fluid pressure to a gentle pressure reduction characteristic. Even if the low μ road surface is erroneously determined to be a high μ road surface, the braking control in the relatively high hydraulic pressure region on the low μ road surface is prevented, and the occurrence of wheel lock can be effectively prevented. it can. Furthermore, the road surface friction coefficient μ can be determined more accurately by evaluating including the movement of the vehicle body than by determining the magnitude of the wheel speed or the magnitude of the wheel acceleration, and a safer antiskid control device can be obtained. Can be realized.

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of a braking hydraulic system in an anti-skid control device according to the present invention, FIG. 2 is a block diagram showing a basic configuration of an example of an anti-skid control device according to the present invention, and FIG. FIG. 2 is a block diagram showing an example of a specific configuration of the pseudo vehicle speed generating circuit, FIG. 4 is a block diagram showing an example of a specific configuration of the AV signal adjusting circuit shown in FIG. 2, and FIG. 5 is shown in FIG. FIG. 6 is an explanatory view showing a control mode by the device shown in FIG. 6, FIG. 6 is a timing chart showing the operation of the pseudo vehicle speed generating circuit shown in FIG. 3, and FIG. 7 is a timing chart showing the operation of the AV signal adjusting circuit shown in FIG. FIG. 8 is a block diagram showing another example of the concrete configuration of the AV signal adjusting circuit in FIG. 2, and FIG. 9 is an AV shown in FIG.
10 is a timing chart showing the operation of the signal adjusting circuit, FIG. 10 is a block diagram showing still another example of the concrete configuration of the AV signal adjusting circuit in FIG. 2, and FIG. 11 is the friction coefficient μ between the wheel and the road surface and slip. 12 is a graph showing the relationship with the rate λ.
FIG. 13 is an explanatory diagram showing a state of wheel speed, braking fluid pressure, wheel acceleration / deceleration during braking by a conventional anti-skid control device, 13th
Figure is a graph showing the depressurization characteristics of a general actuator provided in the braking hydraulic system, and Figure 14 shows the wheel speed and wheel acceleration / deceleration state during control by a conventional anti-skid controller, especially on low μ road surfaces. It is explanatory drawing which shows an example. 1 ... Wheel speed sensor, 2 ... Wheel speed detection circuit 3 ... Acceleration / deceleration detection circuit, 4 ... Pseudo vehicle speed generation circuit 5, 7, 8, 9 ... Comparison circuit 6 ... Target wheel speed generation circuit 12, 13 ... Driver, 14 ... Inflow valve (EV valve) 15 ... Outflow valve (AV valve), 16 ... Retriggerable timer 17 ... Pump, 18 ... AV signal adjustment circuit 181, 183, 188 ... Comparison circuit 182 ... Flip-flop (FF) 184 ... Pulse generation circuit 185 ... No. 1 of the switch 186 ... second changeover switch 186 '... changeover switch 187 ... aND gates, 189 ... sawtooth generator circuit a ... inclination information (slope) a _th ... predetermined value V _i ... pseudo vehicle speed alpha _w ... detected wheel acceleration α _th … Wheel acceleration (predetermined value) μ… Friction coefficient

Claims (1)

[Claims] 1. An antiskid control device for controlling a brake fluid pressure when a slip ratio exceeds a predetermined value during braking of a vehicle, and determines a pseudo vehicle speed gradient for each skid cycle, and this gradient is a predetermined value. A first determining means (183) for determining that it is greater, and a control means (184, for controlling the brake fluid pressure reduction control to a gentle pressure reduction characteristic based on the determination output from the first determination means). 185) and prohibiting means (182, 186) for forcibly prohibiting the operation of the control means (184, 185) when the inclination of the simulated vehicle speed is smaller than the predetermined value. Skid control device.