JPS63232062A - Antiskid control device - Google Patents

Abstract

PURPOSE:To enable an accurate antiskid control to be continually performed, by generating a pressure reducing instruction of brake fluid discriminating a slip condition of each wheel to be in a specific combination and enabling a condition of pressure reduction to be changed corresponding to the compared result for the reference value of deceleration. CONSTITUTION:Brake units 6-9 of each wheel are connected by piping systems 10A, 10B provided being arranged in a diagonal state, and a control device, which controls actuators 11A, 11b provided in each piping system 10A, 10B by a controller 12, performs an antiskid control reducing a pressure of brake fluid. here the controller 12 is constituted detecting a slip condition of each wheel from a mimic car speed, calculated from an output of each wheel speed sensor 2-5, and the actual car speed and discriminating the slip condition of each wheel to be in a specific combination so as to output a signal of reducing a pressure or releasing the reduction of pressure. While a condition of the pressure reduction or its release can be changed corresponding to the compared result of deceleration, separately calculated, with the reference value.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an undesired skid control device used in a braking device for a four-wheeled vehicle.

"Prior Art" Conventionally, as an example of a braking device that generates braking force by supplying pressure oil to the braking device installed on each wheel of a four-wheeled vehicle, wheels arranged diagonally are connected as one system. There is a so-called X-piping system that controls each system separately, and this X-piping system aims to reduce costs by simplifying the brake fluid pressure control system into two systems.

The following system is known as a conventional example of an undesired control system for this X piping.

(i) Detects whether skid (lock) has occurred for each wheel, and if one wheel (either the front or rear wheel) belonging to a certain system is close to locking, the entire system is depressurized. By reducing the braking force on both wheels, the wheels can be recovered from the locked state and avoided.

(ii) Similarly, it is detected whether or not locking has occurred for each wheel, and when both rear wheels are near-locked, the system to which the front wheels that are near-lock belong is depressurized.

"Problems to be Solved by the Invention" ---By the way, in a vehicle in which the control method (i) or (ii) above is adopted, the left rear wheel belonging to the same hydraulic system locks, and the right front wheel locks. Assuming that the wheel is not locked, in the control method (i) above, the hydraulic pressure in the system to which the left rear wheel belongs is immediately reduced to recover from the lock, but in the control method (ii), , unless the right rear wheel becomes slightly locked, the hydraulic pressure will not be reduced, which may lead to a locked condition.

On the other hand, as shown in Fig. 8, the right half of the vehicle 1 exists in a high μ (μ(SO) is large) region shown by hatching in the figure, and the left half exists in a low μ (μ(So) is small) region. ) exists in the region of (1 mi) (called μ 5 plit), then (
The control method i) results in insufficient braking force.

That is, in the control method (i), even if one of the wheels in each system tries to lock, the hydraulic pressure is reduced to recover it, so the front wheel on the high μ side that is unlikely to lock (actually, It is inevitable that the braking force of the nq wheels (bearing the bulk of the braking force) will be two times smaller than the necessary amount, and that the overall braking force will become small.

On the other hand, in the case of the control method (ii), although there is no shortage of braking force, there is a problem in that the brake is likely to lock.

That is, the front wheels on the high μ side and the rear wheels on the low μ side are connected to the same piping system, and the braking hydraulic pressure of the rear wheels is controlled by the hydraulic pressure control valve provided in the hydraulic system, for example, the 9th Since the characteristics shown in the figure are shown, when the braking hydraulic pressure is low, the hydraulic pressures of the front and rear wheels become equal. Additionally, since each wheel is generally equipped with a braking device of the same specification (a braking device that generates the same braking force with the same hydraulic pressure), if the same pressure is applied to the braking devices of the front and rear wheels, In extremely low μ conditions, such as on frozen roads, the rear wheels are more likely to lock up. In the method (11) above, only one rear wheel is locked, so the brake fluid pressure does not decrease, and therefore, there is a tendency for the vehicle to become extremely close to a completely locked state.

To summarize, in the method (i) above, if the friction coefficient μ between the road surface and the wheels is different on the right and left sides of the vehicle, the lower μ side (because μ is smaller) , the side that is in contact with a road surface that is more prone to slip than the other wheel) is also subjected to pressure reduction control sufficient to recover the wheel on the high μ side from the locked state. Therefore, for the wheels on the high μ side, the braking force is excessively reduced, and there is a problem that it is difficult to achieve the shortest braking distance.

In addition, in the method (ii) above, when the rear wheels lock ahead of the front wheels due to extremely small road conditions such as frozen roads, the rear wheels are very close to being completely locked. Since the hydraulic pressure does not decrease until the temperature reaches 1, there is a problem that the directional stability of the vehicle is likely to be impaired.

The present invention was proposed in view of the above circumstances, and μ 5p
It is an object of the present invention to provide a control device that can perform appropriate anti-skid control even on a road surface that is in a lit state or a road surface with an extremely low μ.

``Means for Solving the Problems'' In order to achieve the second objective, the present invention connects the braking devices of wheels arranged diagonally to the same hydraulic system, and independently controls the hydraulic pressure of each hydraulic system. An anti-skid device installed in a vehicle braking device configured to control the anti-skid device includes a wheel speed sensor provided on each of the wheels, and a controller that controls each hydraulic system based on a signal supplied from the wheel speed sensor. , the controller includes a simulated vehicle speed calculating means for calculating a simulated vehicle speed from the detection data of the wheel speed sensor, and detects the slip state of each wheel from the data supplied from the simulated vehicle speed calculating means and the wheel speed sensor. a slip determination means, a deceleration calculation means for calculating deceleration based on the speed signal obtained from the simulated vehicle speed calculation means, a deceleration comparison means for comparing the calculated deceleration with a reference value, and the slip ratio. a depressurization determining means that determines that the slip states of each wheel obtained by the determining means have a specific combination and outputs a signal to reduce the pressure in the hydraulic system or release the depressurization; and the deceleration comparing means. The apparatus is further provided with an intimidation condition changing means for changing the conditions for reducing the pressure or releasing the reduced pressure in the reduced pressure determining means in accordance with the comparison result.

"Operation" According to the above configuration, for example, when one wheel belonging to a certain system is about to lock, the brake fluid pressure of that system is reduced, and when both rear wheels are about to lock, the brake fluid pressure is reduced, and when both rear wheels are about to lock, the brake fluid pressure is reduced. ``Example'' in which it is possible to instruct pressure reduction in the hydraulic system under optimal conditions by selecting conditions different from the control for reducing the brake fluid pressure on the side to which the surface wheel belongs. An embodiment of the present invention will now be described.

First, the configuration of the entire control device will be explained with reference to FIG.
L, left and right rear wheels RR and rLL are provided (), and these wheels are numbered F'R, FL, RL, and RR in the order of 1 to 4 for convenience of explanation. Wheel speed sensors 2 to 5 are respectively provided to detect the circumferential speed of the wheels. Moreover, the braking devices 6 to 9 that brake each wheel are 1. For FR and RL
, FI, and RR are connected to each other to form a so-called X pipe, and these pipes 10A and
1013 is an actuator I that adjusts the hydraulic pressure inside the pipe.
IA and JIB are provided respectively. In addition, these actuators IIA-11B are
2, respectively. Furthermore, hydraulic pressure control valves 13A and 13B are provided in the pipes, respectively, to control the brake hydraulic pressure of the rear wheels so that it is always lower than the brake hydraulic pressure of the 09th wheel.

Next, the principle of control applied to the controller 12 will be explained.

If the slip ratio S between the wheel speed Rw and the vehicle body speed V is defined as S = 1- (Rw/V), then the road surface friction coefficient μs1 in the longitudinal direction (vehicle traveling direction), which is related to the braking distance, is It is known that there is a relationship as shown in Figure 2 between the road surface friction coefficient μL in the lateral direction (vehicle width direction), which is related to directional stability, and the slip ratio S. In the undesired skid control, the braking distance is minimized by controlling the brake fluid pressure to maintain the slip ratio S at the slip ratio S0 at which the road surface friction μS peaks. That is, the basic control is to maintain the brake fluid pressure when S≧So, and to increase the brake fluid pressure when S<So. Note that even when the wheel speed deceleration R is adopted as a control parameter, the wheel speed deceleration R has a certain proportional relationship to the slip rate, so essentially the slip rate S is This is similar to the case where control is performed to maintain So.

By the way, since a very expensive detection means is required to measure the true speed of a vehicle, a normal undesired device is based on the assumption that the speed of the vehicle decreases according to a predetermined characteristic. , the concept of simulated vehicle speed is adopted.

In other words, ■ The deceleration of the vehicle is dV/dt=-μG (G...
...acceleration of gravity), where 0≦μ≦
1, so the slope of the simulated vehicle speed Vr is dVr/dt
Select from 0 to 1.

■ When the wheels are not braked, the circumferential speed Rω of the wheels and the vehicle speed V match, so at the time of starting braking (1=
Assuming that V is the vehicle speed at 0), V=Rω is set.

■ Time 1=1. Under the condition that V r = nω, 1 = 1. At +Δt, Vr(to +Δt)・V r(to)−dV r/dt
・ Compare Δt and Rω (to + Δt), and in the case of V r> R (JJ, calculate Vr by setting V r = V r; on the other hand, in the case of V rs nω, calculate Vr by setting Vr = Rω. Reset.

(2) By repeating these steps, a simulated vehicle speed as shown in FIG. 3 can be obtained.

The slope dVr/dt of the simulated vehicle speed is usually −IG
Selected nearby. This is because if this slope is made small when μ is high, sufficient braking force cannot be obtained. In this embodiment, since a plurality of (four) sensors are provided to detect the wheel circumferential speed Rω, four types of data regarding Rω can be obtained, but the fastest detected value (generally R
Since ω is smaller than V, the largest Rω value is close to the vehicle speed) will be adopted as the vehicle speed.

Then, the slip rate S of each wheel is set to S in response to the simulated vehicle speed obtained moment by moment using the method described above. If the hydraulic pressure is controlled to maintain the simulated vehicle speed Vr, even if the slope at a certain moment is -IG, the average slope will not be -IG.

In other words, in an attempt to keep the slip rate S at So, the paper S =
Assuming that the slip ratio changes in the range of S o ± ε, the braking force F becomes u (S O - ε)mG≦F≦μ (SO 1ε),
The average brake saw is μ(S o)mG−δ. The deceleration of the vehicle is determined by the sum of the braking forces applied to each axis and the vehicle mass, and the value is approximately μ
. It becomes mG.

On the other hand, the simulated vehicle speed Vr approaches the vehicle body speed because it is successively offset by the above-mentioned (2) and the internal speed of each wheel is also selected from a fast value.

Therefore, from a micro perspective, the simulated vehicle speed drawn by -IG has a slope of μ from a macro perspective. It can be seen that it is proportional to. (See Figure 4) Furthermore, normally, the anti-skid cycle, that is, the time for the slip rate S to reach S0+ε from So-ε is 0.5 sec to 0, Ol 5ec (2Hz to 1
00 Hz), the shortest skid cycle is set to 0.5 scc, and the sampling time that can cope with this is set to 0.5 sec.

Therefore, time Tn=0.5n (n=1, 2.3
-...) by comparing the difference in simulated vehicle speed v r (T n) with the standard value. Knowing the level of
Can be done.

In this example, (V r(T n-+) V r(T
n))/ In the case of 0.5≦0.3G, that is, when the deceleration of the simulated vehicle speed is 0.3G or less, the control method of (i) above is used, that is, one of the wheels for a certain system is locked. Control is performed by reducing the pressure in the system on the condition that the system is about to
．． 5> In the case of 0.3G, that is, when the deceleration of the simulated vehicle speed exceeds 0.3G, the control method of (ii) above,
That is, under conditions where both rear wheels are about to lock, control is performed by reducing the pressure in the system to which the wheel that is about to lock belongs.

Note that the deceleration of 0.3G, which is the criterion, is the point at which the hydraulic pressure control valve starts cutting the hydraulic pressure on the rear wheel side (Fig. 4 P).
This value corresponds to the deceleration caused by the hydraulic pressure of , and generally ranges from 0.2G to 0.4G, and in this example, 0.3G was adopted.

A specific control operation of the controller 12 based on such a control principle will be explained.

The wheel speed sensors 2 to 5 constantly supply wheel speed pulses to the controller 12, and these wheel speed pulses are sent to the controller I2.
The data is manually converted into wheel speed data. Next, the controller 12 calculates a simulated vehicle speed Vr from these wheel speed data.
Calculate the slip rate of each wheel from the simulated vehicle speed Vr according to the following formula: 5i=1-Rωi/Vr where i=
Calculated as 1 to 4. And the piping 10A for each system.
10113, outputs one or both of the signals TrIa and 'mb for depressurizing the respective piping systems. Further, this pressure reduction signal Tna-'mb is discarded according to the following law.

That is, time T n = 0, 5 n (n = 1.2.3, ・
”), (V r('1' n-3) -V r
(T n))/0.5 and (V r(T n-
+) −V r(T n))/ 0.5> 0.3G
-------If SI≧S0 holds true under the condition of 1 equation, 'ma' is output.

If S, ≧S0 holds true, 1'1b is output.

S, ≧S 0% and S4≧S.

If this holds true, Tna or Tnb is output.

Also, (V r (T n-+) - V r (T n)) / 0
．． 5≦0.3G ・-・Under the condition of 1 equation, SL≧S0, or S, ≧S.

If it holds true, 711a is output.

Also, S, ≧S 0% or S4≧S.

If it holds true, 'r11b' is output.

The control program of the microprocessor provided in the controller 12 that executes such control is controlled by the seventh controller.
This will be explained according to the diagram.

Anti-skid control is started when the brake pedal is depressed and the brake switch is turned on.

5Lapl: Set a predetermined time data value (current time in the example) in the area of the memory that stores the time Tn!・Start timing at the same time.

S Lap2: Set simulated vehicle speeds V and r in the area for storing the vehicle speed vn at that time.

S Lep3: Whether or not a predetermined period of time has elapsed, that is,
'r. -1-rll n(Determine ΔT, if NO, go to S Lcp4; if YES, go to 5Lep9
Proceed to each.

5Lep4: Whether the amount of decrease in Vn exceeds a predetermined value, that is, V, -V. 〉Determine ΔV (same meaning as in equation 1 above), and if YES, go to S tap5.
If No, proceed to 5step 8.

5Lcp5: Turn off FLAG.

5Lcl) G: Turn ON FLAG.

S Lcp7: Update the value of T n-+ to 'rn.

S tcp8: Update the value of Vn-+ to Vn.

S Lcp9: Determine the wheel circumferential speed Rω from the detection data of the respective front wheel speed sensors 2 to 5, and determine the slip ratio Si for each wheel.

Staplo: Calculate the simulated vehicle speed Vr from Rω and Si obtained in step 5 above.

5tepH: The slip rate S of the left rear wheel rLL is S. If S3≧So, go to S tap12, S3<S
(If +, proceed to S Lcp14.

5 step 12: Determine whether FLAG/l<ON, and if No, go to S step 13, YE
In the case of S, proceed to step 16.

S Lep13: Set the slip rate S4 of the right rear wheel rtrt to S
Compare with o, if S, ≧S0, go to step 16, S
If 4<So, proceed to step 14.

S step14: Set the slip rate S1 of the left front wheel r"L to S
Compare with o, if S, ≧80, go to S Lep16, S
If + < Sa, proceed to step 15.

Step 15: In order to release the reduced pressure in the piping system 10A, a reduced pressure release signal TI'Ia is output.

S Lcp16: Outputs a pressure reduction signal 'ITla to reduce the pressure in the piping system 10A.

By the above-mentioned second operation, the control for the piping system 10A is completed, and then the piping system 10B is operated, and the
pH~S Step corresponding to Lep14
17 to S tap20, and according to the determination result, S Lcp21: In order to release the reduced pressure in the piping system 10B,
A decompression release signal TlIb is output.

S Lep22: Reduce the pressure in the piping system 10B (output the pressure reduction signal 'ITlb'.

S Lep23: One control of the rewriting pipe system 10A-1013 is completed.

If the brake pedal is still depressed even after Step 23 is completed, the process returns to Step 5 and the anti-skid control is repeated.

Changes in wheel circumferential speed and oil pressure when such control is performed will be explained with reference to FIG.
) shows the change in wheel circumferential speed when the control method of (i) above is adopted on a road surface with high μ on the right side and low μ on the left side, and
FIG. 5(b) shows the change in brake oil pressure accompanying the braking shown in FIG. 5(a). In this case, as can be seen from the fact that there is no extreme drop in wheel circumferential speed, there is no locking. Braking is being performed, but since the braking oil pressure is maintained at a low level, a long braking distance is avoided, as can be seen from the gentle slope in Figure 5(a). I can't.

On the other hand, when anti-skid control is performed by the control device of the present invention under the same conditions as in the above case,
As shown in FIG. 5(b), although the left rear wheel LR is locked, the slip ratios of the other wheels can be maintained appropriately and braking force can be effectively exerted. Note that since the side force generated on the left rear wheel RL is originally only small, even if this left rear wheel locks, sufficient running stability can be obtained with the other wheels.

Furthermore, under extremely low μ conditions such as frozen road surfaces, the above (
When the control method ii) is used, it is unavoidable that the rear wheels will come very close to the fully locked state, as shown in Figure 6(a), and in such a situation close to completely locked, the lateral The friction coefficient μL in the direction becomes small, and running stability deteriorates.

On the other hand, in the control device of the present invention, as shown in FIG.
As shown in b), the braking force is controlled without locking.

In addition, the specific configuration of each device that makes up the hydraulic system, and
Of course, the means for detecting the acceleration speed (in the embodiment, the deceleration is determined from the wheel peripheral speed) is not limited to the embodiment.

``Effects of the Invention'' As is clear from the explanations given below, according to the present invention, suitable undesired skid control can be automatically performed in response to all road conditions such as so-called μ-split conditions or extremely low μ conditions. Since the braking method can be selected, braking distance can be shortened and vehicle running stability can be maintained. This relatively low-cost mechanism (method of controlling two coupled brake piping systems) has the effect of achieving anti-skid characteristics equivalent to a high-grade hydraulic control system such as a 4-sensor 3-channel system.

[Brief explanation of the drawing]

1 to 7 show an embodiment of the present invention,
Fig. 1 is a hydraulic system diagram, Fig. 2 is a μ-8 characteristic diagram, Figs. 3 and 4 are charts showing the principle of setting the simulated heavy speed, and Fig. 5 (a) and (b) are, respectively. Figures 6(a) and 6(b) are graphs showing speed changes when the control of the present invention and the conventional control are performed in the μ5plit state, respectively. Figure 7 is a flowchart showing the control operation of the controller, Figure 8 is an explanatory diagram of the μ5plft state, and Figure 9 is a diagram showing the relationship between rear brake fluid pressure and front brake fluid pressure. This is a chart showing. ■...Vehicle body, 2-5...Wheel speed sensor, 6-9...Braking device, l0A-10B...
...Piping system, 1! A・1113...Actuator, 12...Controller, PL-PR-
RL-1111...Wheel.

Claims (1)

[Claims] In an anti-skid control device installed in a vehicle brake system, in which the brake devices of wheels arranged diagonally are connected to the same hydraulic system and the hydraulic pressure of each hydraulic system is controlled independently, the anti-skid control device is installed in each wheel. and a controller that controls each hydraulic system using signals supplied from the wheel speed sensor, and the controller includes a simulated vehicle speed calculation means that calculates a simulated vehicle speed from the detection data of the wheel speed sensor. and a slip determining means for detecting the slip state of each wheel from data supplied from the simulated vehicle speed calculating means and the wheel speed sensor, and calculating deceleration based on the speed signal obtained from the simulated vehicle speed calculating means. a deceleration calculating means for comparing the calculated deceleration with a reference value, and a deceleration comparing means for comparing the calculated deceleration with a reference value, and determining whether the slip state of each wheel obtained from the slip rate determining means has a specific combination. pressure reduction determination means for outputting a signal to reduce or release the pressure reduction in the hydraulic system;
An anti-skid control device comprising: reduced pressure condition changing means for changing conditions for reducing pressure or releasing reduced pressure in the reduced pressure determining means in accordance with a comparison result of the deceleration comparing means.