JPS62295766A - Pseudo vehicle speed generator for anti-skid controller - Google Patents

Abstract

PURPOSE:To enable a normal anti-skid control even at a time of a G sensor being abnormal by having a constitution which is switched over so as to calculate a pseudo vehicle speed on the basis of a vehicle wheel speed, at a time of the vehicle-decelerated-speed detecting G sensor being abnormal, instead of this vehicle-decelerated-speed. CONSTITUTION:When a brake operation signal from a brake switch 5 is inputted to an anti-skid control circuit 4, a vehicle-decelerated-speed g from a G sensor 6 is integrated at an integration circuit 8, and this integration value is inputted to a control circuit 4 together with the output Vw of a vehicle wheel speed sensor 7. And at this control circuit 4 is calculated a pseudo vehicle speed, on the basis of which the anti-skid control of a wheel 1 is made to be done. On this occasion, when there occurs abnormality at the G sensor 6, and when the absolute value of a difference between the pseudo vehicle speed and a vehicle wheel speed has become above a set level and also when this condition has continued beyond a set time, a switchover is made so that the calculation of the pseudo vehicle speed is done on the basis of the vehicle wheel speed. By this, a normal anti-skid control is made to be done afterward.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention (Field of Industrial Application) The present invention provides an anti-skid control device that controls brake fluid pressure so that maximum braking efficiency is achieved while preventing wheels from locking. This invention relates to a pseudo vehicle speed generator.

(Prior Art) An anti-skid control device prevents the wheels from locking by reducing the brake fluid pressure when the circumferential speed of the wheels (wheel speed) has a slip relationship of more than a predetermined value with respect to the vehicle speed. In this case, Doppler radar, etc. that directly detects the actual vehicle speed is expensive and impractical, so whenever the wheels tend to lock and the wheel speed suddenly deviates from the actual vehicle speed, that is, the wheel deceleration exceeds the deceleration standard 1st shift. Each time the vehicle speed exceeds the vehicle speed, it is common to find a pseudo vehicle speed of a predetermined deceleration gradient based on the first wheel speed at that time, and use this as the vehicle speed.

To explain this pseudo vehicle speed generation technology and anti-skid control technology, wheel speed 9 and wheel acceleration/deceleration αw are shown in FIG.
A defined by the combination of (negative is deceleration). ,Eight,,
Set four areas B,, B, and vw>viWxQ,
85 (V+W Hata similar vehicle speed, 0.85 C) Wheel slip rate S at which the road surface friction coefficient μ is maximum as shown in Figure 6 by characteristics on frozen roads (a) and characteristics on dry roads (b) 1
Directly, that is, reason, thought soup rate S. = coefficient corresponding to 15%, Vi,
+al is acceleration reference value, -bl is deceleration reference value).

Although the brake fluid pressure is increased in the direction of the master cylinder fluid pressure in the area, locking of the wheels is prevented by maintaining or reducing the brake fluid pressure as shown in the diagram in other areas A1, B, and B. while the maximum braking efficiency is (
Be able to be asked.

This anti-skid control action, together with the pseudo vehicle speed generation action, will be described in detail for the case where the wheel speed Vw is as shown in FIG. 5 (however, vo is the actual vehicle speed shown for reference). Instant t.

At the beginning of the rise in brake fluid pressure P due to the start of braking, naturally,
fart. In this region, the brake fluid pressure Pw is equal to the master turn ring fluid pressure. Due to the start of wheel lock, αyu≦−b1
From the instant t1, v,, (t) −vw ol)−ko(t−ti)
However, V,, (t): momentary pseudo vehicle speed v-(ti
)'Wheel speed ko at instant t1; deceleration setting gradient position -1,: instant 1. due to the elapsed time from instant t1. The subsequent pseudo vehicle speed Viw is determined as shown by the dashed line in FIG. Then, from instant t5 when the next wheel lock starts and α,≦-b1, the pseudo vehicle speed Vi
w is determined as follows: First, 1 pseudo vehicle speed V
Find 1 for the deceleration gradient of Lw, and based on this, v+w(t) -V, (ts)- +(t -ts)
The pseudo vehicle speed Viw is obtained from the calculation. Hereafter, α, ≦−b
A similar calculation is performed each time the value becomes 1, and the pseudo vehicle speed V iw is determined as shown in FIG. However, in V, >Viw, %l
Since WO is closer to the actual vehicle speed VC, it is set as Vlw-Vw. In addition, the above-mentioned coefficient 0.
The target wheel speed viwXO185, which is multiplied by 85, becomes as shown in FIG.

From moment t1 until wheel lock instant L2 when vw ≦Viw Along with making it possible,
To prevent a response delay in anti-skid control to be performed by reducing brake fluid pressure due to a continuous increase in brake fluid pressure.

Instantly, more B. The brake fluid pressure PW is reduced to prevent wheel locking (anti-skid control). As a result, the wheel rotates upward due to the recovery of road friction force, and α
, >+al from the instant t3. Until the instant t when ≦+41, the brake fluid pressure Pw is maintained in the A1 range.

This holding pressure makes it possible to determine the road surface friction condition, and
To prevent a delay in canceling anti-skid control to be performed due to a rise in brake fluid pressure due to a continuous drop in brake fluid pressure.

It can be assumed that the wheel speed vw has recovered to the actual vehicle speed at this instant, and from this moment on, A. brake fluid pressure Pw
By increasing the pressure, it is possible to prevent braking distance from becoming longer due to unnecessary brake fluid pressure increase restrictions. With this pressure increase, α is again
, ≦-b1, the next skid cycle starts, and the same control as described above is repeated, and eventually the brake fluid pressure Pw changes the slip ratio S to the ideal slip ratio S. It is controlled to maintain maximum braking efficiency while preventing wheel locking.

However, in the calculation method of the pseudo vehicle speed ViW as described above, in the first skid cycle) the pseudo vehicle speed ViW
k. Since the pseudo vehicle speed VtW in this skid cycle is determined at a constant value as shown in FIG.
. may not be approximated. In particular, even when the brake fluid pressure Pw is reduced, the wheel speeds V and N are reduced to the actual vehicle speed V due to a low friction road or when a low speed gear with large wheel rotational inertia is selected. If the speed does not recover until close to , the pseudo vehicle speed V1w is the actual vehicle speed V. This will result in a much smaller correction. in this case,
Due to a misjudgment that the wheels are not locked even though the wheels are locked, anti-skid control (reducing the brake fluid pressure PW) is not performed and there is a risk that the wheels will remain locked.

To solve this problem, a calculation method has been proposed in Japanese Patent Application Laid-Open No. 57-111t19, etc., in which the wheel speed at the start of braking is used as an initial value, and the value obtained by subtracting the integral value of vehicle deceleration from this value is used as a pseudo vehicle speed. .

(Problems to be Solved by the Invention) However, in such a device that calculates a pseudo vehicle speed based on vehicle deceleration, if the output value gain of the G sensor that detects vehicle deceleration changes or an offset occurs, It becomes impossible to calculate a correct pseudo vehicle speed.

If the simulated vehicle speed shifts to a higher side, the brake fluid pressure will be reduced unnecessarily even though the wheels are not locked, resulting in a longer braking distance or becoming unable to brake.On the other hand, if the simulated vehicle speed shifts to a lower side, the brake fluid pressure will be reduced unnecessarily even though the wheels are not locked. Even though a lock has occurred, the brake fluid pressure is not reduced and the wheels remain locked.

(Means for Solving the Problems) From the viewpoint that an abnormality in the G sensor is expressed as a signal indicating abnormally large wheel slip, the present invention provides abnormal slip signal detection means for detecting this signal. , a clock means for measuring the duration of the signal, and a switching means for switching to calculate the pseudo vehicle speed based on the wheel speed instead of the vehicle deceleration when the duration continues for a set time or more. It is something.

(Function) The anti-skid control device detects wheel slip from the difference between the pseudo vehicle speed and the wheel speed, and when wheel slip occurs, reduces the brake fluid pressure of the wheel to prevent wheel lock and maximize braking efficiency. be able to do so.

The pseudo vehicle speed is calculated as follows.

When the G sensor that detects vehicle deceleration is normal, even if the abnormal slip signal detection means detects a signal indicating abnormally large wheel slip, the duration of the signal is less than the predetermined time. . Therefore, the timer means for measuring this duration time is set to a state in which the calculation of the pseudo vehicle speed is performed based on the vehicle deceleration by means of the switching means.

By the way, when the G sensor is abnormal, the signal indicating abnormally large slip of the wheel detected by the abnormal slip signal detection means continues for a set time or longer. In response to a signal from the timer for measuring this duration, the switching means switches to calculate the pseudo vehicle speed based on the wheel speed instead of the vehicle deceleration. Therefore, even if there is an abnormality in the G sensor, the calculated value of the pseudo vehicle speed will not become abnormal, and braking efficiency may deteriorate due to an unnecessary decrease in brake fluid pressure even though the wheels are not locked, or the wheels may be locked. However, it is possible to avoid the risk of the brake fluid pressure not being reduced and the wheels remaining locked.

(Example) Hereinafter, the present invention will be described in detail based on illustrated embodiments.

FIGS. 1(a) and 1(b) show an anti-skid control device equipped with a pseudo vehicle speed generating device according to an embodiment of the present invention,
This device applies brake fluid pressure P to the wheel cylinder 2 of the wheel 1. It is assumed that the pressure is appropriately reduced by electronic control of the actuator 3 and the wheels 1 are anti-skid.

An anti-skid control circuit 4 is provided to electronically control the actuator 3, and the following information is input to this circuit. That is, the brake switch 5 closes when the brake is applied.
A G sensor 6 that detects the deceleration g of the vehicle, and a wheel speed sensor 7 that emits a pulse signal of a frequency corresponding to the rotation speed of the wheel 1 are provided. The brake switch 5 inputs a brake activation signal to the anti-skid control circuit 4 and the integration circuit 8, and the G sensor 6 inputs a signal related to vehicle deceleration g to the integration circuit 8. The integral circuit 8 inputs the integral value up to the instant of application of the brake to the anti-skid control circuit 4. Further, the pulse from the wheel speed sensor 7 is inputted to the wheel speed calculation circuit 9, and this circuit calculates the wheel speed 9 from the pulse signal and the rotation radius of the wheel 1, and outputs it to the anti-skid control circuit 4. .

The anti-skid control circuit 4 calculates the pseudo vehicle speed υ゛lW based on the human power information as shown in FIG. shall be carried out.

First, the pseudo vehicle speed calculation function shown in FIG. 1(b) will be explained with reference to FIG. 2. In step 10, it is determined whether the brake switch 5 is ON or not. If it is not ON, braking is not in progress and anti-skid control is started. Since it is not necessary to calculate the vehicle speed or the pseudo vehicle speed, the switching flag CHG, which will be described later, is set in steps 11 and 12.
FLG is reset to 0, and timer T, which will be described later, is also reset to 0, and the control is terminated.

If braking is in progress, that is, at instant t in FIG. Thereafter, it is determined in step 13 whether CHGFLG is 1 or not, but since CHGFLG=p is initially obtained by executing step 11, the control reaches step 14. In step 14, timer T
is the set time T. It is determined whether or not the above is the same, but since T=O due to the execution of step 12, the control goes to step 15.
The process then proceeds to step 16 or 17 and then to step 18. Therefore, at the beginning of braking, the corner step 18 is executed, and in this step, the braking start instant t. before the wheel speed vw (to).

By the way, if an abnormality occurs such as a change in the output value gain of the G sensor 6 or an offset occurs, the pseudo vehicle speed Viw calculated as described above will be at the instant t in FIG. -t4
As shown in the figure, the wheel speed deviates significantly from the wheel speed vw over a long period of time. However, this figure shows a case where the output value g of the G sensor 6 is lower than the actual vehicle deceleration and the pseudo vehicle speed Viw deviates significantly upward from the wheel speed Vw. In this case, the absolute value IAV+ of the difference between the pseudo vehicle speed V iw and the wheel speed Vw is as shown in FIG. 2, and this is the set level AV. While this is the case, step 15 continues to select step 17, and in this step the timer T is incremented. Therefore, the timer T measures the duration of the signal indicating 1AVI≧AVo, that is, an abnormally large slip of the wheel 1, and this duration is the set time T. After the switching flag CHGFLG is set to 1 in step 19 at instant t4, the control proceeds to step 20.

Thereafter, since CHGFLG=l, step 13 continues to select step 20, so that the pseudo vehicle speed L1w is calculated based on the wheel speed vw instead of step 18. The switching instant t of this pseudo vehicle speed calculation method
After 4, the pseudo vehicle speed Vow becomes instantaneous in Fig. 5.

Thereafter, calculations are made in the same manner as described above, resulting in a result as shown in FIG.

The anti-skid control circuit 4 performs the same anti-skid control as described above with reference to FIG. 5 based on the pseudo vehicle speed V iW and the wheel speed vw determined as above, and adjusts the brake fluid pressure P as shown in FIG. 2. Control as shown in . At this time, due to the abnormality of the G sensor 6, the brake fluid pressure P at instant t3. is set to O, and braking becomes temporarily impossible, but
At the instant t4 when T≧To, the abnormality is detected and the pseudo vehicle speed V1 is set.
Since the calculation of w is switched to be performed based on the vehicle's theoretical speed vw, normal anti-skid control can be performed from then on. Therefore, even when the G sensor 6 is abnormal, it is possible to prevent the braking from being disabled from continuing.

Note that while the G sensor 6 is normally detecting the vehicle deceleration g, the pseudo vehicle speeds V and W almost match the actual vehicle speed vc, and the wheel speed vw temporarily changes as shown in FIG. Pseudo vehicle speed V
Even if there is a case where 1AVl≧AVo, which is far away from iw, the duration time (output of timer T) is the set time T due to anti-skid control. less than Because of this,
Step 20 in FIG. 1(b) is not executed,
By executing step 18, the pseudo vehicle speed V1w continues to be calculated. However, since the G sensor 6 that detects the vehicle deceleration g, which is the data for this calculation, is normal, the anti-skid control can be executed normally.

By the way, in the above example, in order to detect a signal indicating an abnormally large slip of the wheel 1 (abnormality of the G sensor 6), the magnitude of l/IVI was determined in step 15 in Fig. 1, etc. , the abnormality is caused by the slip rate S signal of wheel 1, which remains at the set value of 81 or more for a long period of time.
As shown in FIG. 1(C), step 21 is set in place of step 15 in FIG. Needless to say, you can obtain

(Effects of the Invention) Thus, as described above, the pseudo vehicle speed generator of the present invention calculates the pseudo vehicle speed VtW based on the wheel speed Vw instead of this vehicle deceleration when the G sensor 6 that detects the vehicle deceleration g is abnormal. Since the switching is configured, the pseudo vehicle speed Vow will not become abnormal even if the G sensor 6 is abnormal, and the anti-skid control executed based on this can continue to be performed normally.

[Brief explanation of drawings]

FIG. 1(a) is an overall system diagram of an anti-skid control device equipped with a pseudo-vehicle speed generating device of the present invention, FIG. A flowchart showing another example of the vehicle speed calculation function. Figures 2 and 3 are operation time charts when the G sensor of the same side device is abnormal and normal, respectively. Figure 4 is a general area of anti-skid control. Fig. 5 is a general anti-skid control operation time chart, and Fig. 6 is a road surface friction coefficient change characteristic diagram for frozen roads and dry roads. 1... Wheel 2... Wheel cylinder 3... Actuator 4... Anti-skid control circuit 5... Brake switch 6... G sensor 7...
Wheel speed sensor 8...Integrator circuit 9...Wheel speed calculation circuit Patent applicant Nissan Motor Co., Ltd. Fig. 1 (a) Fig. 6 Mushi Mushi Life Three t1' quasi (S) Hin k (Tsumi f! @ S)

Claims (1)

[Claims] 1. An anti-wheel brake system that detects wheel slip from the difference between the pseudo vehicle speed calculated based on the deceleration of the vehicle and the wheel speed, and reduces the brake fluid pressure of the wheel when wheel slip occurs. In the skid control device, an abnormal slip signal detection means for detecting a signal indicating an abnormally large slip of a wheel; a timing means for measuring the duration of the signal; and calculating the pseudo vehicle speed when the duration continues for a set time or more. 1. A pseudo vehicle speed generating device for an anti-skid control device, comprising: a switching means for switching based on the wheel speed instead of the vehicle deceleration.