JPH02220953A - Anti-lock controller - Google Patents

Abstract

PURPOSE:To prevent a carwheel lock by conducting a duty control so that a pair of 2 position valves may cut off spaces between a master cylinder and wheel cylinders and also, parts of the 2nd position time when the suction sides of depressurizing pumps are connected with spaces between wheel cylinders, may not overlap each other. CONSTITUTION:Respective wheel cylinders 11, 21, 31 41 are connected with a master cylinder 1 side at the 1st position and with the suction sides of common pumps 51, 52 at the 2nd position, by means of 3 port 2 position valves 15, 25, 35, 45. And, an electronic control means 60 conducts the duty control of 2 position valves 15-45, and also, control is made so that at least parts of time at the 2nd position may not overlap each other, and the brake oil pressure of wheel cylinders 11-41 on a low pressure side is depressurized by means of this unoverlapping time. Thus, a sufficient and also stable anti-lock performance can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an anti-lock control device that prevents wheels from locking during braking of a vehicle, and particularly relates to an anti-lock control device that reduces pressure using a pump during control.

[Conventional technology]

Conventionally, this type of anti-lock control device includes a reservoir for reducing the brake hydraulic pressure of the wheel cylinder and a pump for increasing the pressure.

In addition, a system has been proposed in which the pressure of the brake hydraulic pressure is directly reduced by a pump without releasing it to the reservoir. In a simple example, one pump is commonly used to reduce the pressure in the wheel cylinders of the two rear wheels at the same time, and in another example, an independent pump is arranged for each wheel.

[Problems to be Solved by the Invention] The former problem has a problem in that the mechanical unit in this part cannot be made smaller and lower in cost because of the reservoir.

In addition, although the latter type does not have a reservoir, the brake hydraulic pressure of each wheel cylinder cannot be controlled independently.
When there is a pressure difference in the brake oil pressure between the wheel cylinders, there is a problem in that only the high pressure side can be depressurized and the low pressure side cannot be depressurized.

If a pump is arranged for each wheel cylinder of each wheel, independent control of the brake oil pressure is possible, but the number of pumps increases and miniaturization and cost reduction are insufficient.

The present invention has been made in view of the above points, and an object of the present invention is to provide an anti-lock control device that can be made smaller and lower in cost, and that can reduce pressure even when there is a pressure difference in brake oil pressure between wheel cylinders. shall be.

[Means to solve the problem]

The present invention provides: a hydraulic system that applies brake hydraulic pressure from a master cylinder to the wheel cylinders of a pair of wheels; a common pump provided in this hydraulic system for reducing the brake hydraulic pressure of the pair of wheel cylinders; A pair of 3-point and 2-position valves provided in a brake system, and an electronic control means for controlling the 2-position valve,
The position valves each communicate between the master cylinder and the wheel cylinder at a first position and disconnect between the suction side of the pressure reducing pump and the wheel cylinder, and connect the master cylinder and the wheel cylinder at a second position. The electronic control means is configured to cut off communication between the pressure reducing pump and the wheel cylinder, and to communicate between the suction side of the pressure reducing pump and the wheel cylinder, and the electronic control means controls the time period during which the pair of two-position valves are in the second position. 1 above so that at least a portion of the
A technical measure is adopted in which a pair of two-position valves are configured for duty control to prevent wheel locking.

[Effect]

Each wheel cylinder is connected to the first
It communicates with the master cylinder side at the position, and communicates with the common pump side at the second position. And the pressure reduction of the wheel cylinder is 2
This is done by a common pump when the position valve is in the second position. The electronic control means performs duty control on the two-position valves, and also controls the time when the pair of two-position valves are in the second position so that they do not overlap, so the low pressure is maintained during this non-overlapping time. The brake oil pressure in the side wheel cylinder is reduced.

〔Example〕

The present invention will be explained below with reference to an embodiment shown in the drawings. In FIG. 1, which shows an X-piped two-system hydraulic brake system for a front-wheel drive vehicle, ■ is a master cylinder, and 2 is a brake pedal. Each wheel (front right wheel 11, front left wheel 21, rear right wheel 31, rear left wheel 41) has a wheel cylinder 12, 22, 32, 42 for braking, and further detects the speed of each wheel. Wheel speed sensors 13, 23, 33° 43 are installed.

The master cylinder 1 is a tandem type for the first and second hydraulic systems, and in the first hydraulic system, brake hydraulic pressure is applied to the wheel cylinder 12 of the front right wheel 11 via a fixed throttle 14 and a two-position valve 15. In addition, the provisioning valve (
P pulp and when) 44. Left rear wheel 4 through 2 position valve 45
Brake oil pressure is applied to the wheel cylinder 42 of No. 1. In the second hydraulic system, hydraulic pressure is similarly applied to the wheel cylinder 22 of the left front wheel 21 via the fixed throttle 24.2 position valve 25, and the hydraulic pressure is applied to the wheel cylinder 22 of the left front wheel 21 via the P valve 34.2 position valve 35.
Apply hydraulic pressure to the wheel cylinder 32 of No. 1. Each of the two-position valves 15, 25, and 35.45 is an electromagnetic three-port two-position valve, and each port is connected to the master cylinder side hydraulic piping, and each B boat is connected to the wheel cylinder side. .

Further, the C boats of the two position valves 15.45 are connected to the suction side of the pump 51 through check valves 16.46, respectively.The C boats of the two position valves 25.35 are connected to the pump 51 through check valves 26.36, respectively. connected to the suction side of the

The pumps 51, 52 are structurally integrated,
Commonly driven by one electric motor, the discharge side of which is driven by two
It is connected to the A boat side piping of position valve 15.25,
Further, its position control (on/off) is controlled by an electronic control unit (referred to as ECU) 60.

The ECU 60 has each wheel speed sensor 13, 23°33.4
3, the wheel speed, wheel acceleration, etc. are calculated based on these signals, and the 2-position valves 15, 25, 35, 45 are duty-controlled based on these calculated values, and Commands to drive the pumps 51 and 52.

ECU60 is a microcomputer type, CP
U, ROM that stores control programs and data
, a RAM for temporarily storing calculation data, and an I10 unit connected to each sensor, valve, and pump.

FIG. 2 shows the configuration for one wheel extracted from FIG. 1, and FIG. 3 shows the drive signal waveform and brake pressure waveform. The operation will be explained with reference to FIGS. 2 and 3.

(i) During normal braking, the two-position valve 15 is in the position shown in FIG. 2(A) in a non-energized state, and the pump 51 is also in a non-driven state. Therefore, the brake pressure of the master cylinder 1 generated when the brake pedal 2 is depressed acts directly on the wheel cylinder 12 via the two-position valve 15, and a brake force is generated on the right front wheel 11.

(ii) During anti-lock control When the right front wheel 11 becomes more likely to lock due to brake operation while the vehicle is running, anti-lock control is started. When anti-lock control is started, the ECU 60 outputs an ON command signal to drive the pump 51, as shown in FIG. 3(A). As a result, the pump 51 is always continuously driven during anti-lock control. Furthermore, Fig. 3 (B),
As shown in (C), the ECU 60 duty-controls the two-position valve 15 to control the brake pressure P of the wheel cylinder 12.
, 1 is repeated 8 times.

Here, when the two-position valve 15 is de-energized (first position), the A and B boats are communicated with each other as shown in FIG. Brake oil pressure P- is increased.

On the other hand, the two-position valve 15 is in the position shown in FIG. 2 (B) when energized (second position).
), communication is established between the B and C boats, and as a result,
By driving the pump 51, the brake hydraulic pressure Pw in the wheel cylinder 12 is reduced.

The period T in Fig. 3 is constant (for example, 20 to 50 m5
ec), and by changing the pressure reduction time TI (ON time of the two-position valve 15), the average oil pressure change is controlled and the pressure is gradually increased, lj! Perform depressurization. Hereafter, the ratio of the decompression time T8 to this period 'MT (T, /T)
X 100 (%) is called the duty ratio.

In the duty control of the two-position valve 15, the larger the duty ratio is, the more the pressure decreases, and the smaller the duty ratio is, the more the pressure increases.

Next, an example of the anti-lock control process executed by the ECU 60 is shown in the flowchart of FIG. 4, and will be described in detail below based on this flowchart.

In step 100, initialization is performed, and in step 1Ol, each wheel speed (right front wheel speed V□, left front wheel speed VFL, right rear wheel speed 8. Calculate the left rear wheel speed VIL). In step 102, from the change in each wheel speed calculated in step 101, the acceleration of each wheel w, R, w,
L, wlIR, w, and 1L are calculated. Step 10
3, the estimated vehicle speed V6 and estimated vehicle acceleration W are calculated by the following equations.

Vl(-1-MED (Vll+, 1-11-αI'
L C+ VW@@X+Vl(,1-11+α2・
tc) ・・・・・・・・・(a) Vw--x
””MAX (VFII, VFL, Vllll,
VIIL)・・・・・・・・・(b) Wm = (Vl(11) Ls+r+-+>)
/ tc ・・・・・・・・・(C) Here, MED
means the intermediate value, and MAX means the maximum value. Also, formula (a)
■, -) subscript in, 1. is the value calculated this time,
8 indicates the value calculated last time. And α1
．． α2 is the upper limit of deceleration and upper limit of acceleration of the vehicle body acceleration,
This is to limit the speed difference between the vehicle body speed Vl(n-1) calculated last time and the vehicle body speed VB+19) calculated this time. Note that tc is the cycle for calculating the vehicle speed (for example, 4 to
(predetermined value of 10m5ec).

In step 104, the estimated vehicle speed v calculated in step 103! Based on l, a reference speed ■3 for determining the tendency of wheels to lock is created.

In other words, the estimated vehicle speed V is multiplied by 0 (K, = 0.7~
0.95)L, the speed corresponding to the target slip ratio is determined, and the value obtained by subtracting the offset speed v0 from that speed is set as the reference speed VSN.

V, - to V, -V.・・・・・・
...(d) Here, the estimated vehicle speed ■ is multiplied by 0, and the offset speed ■ is 0■. The purpose of subtracting is to make the estimated vehicle speed ■8 and the reference speed ■ have a speed difference larger than the off-cent speed v0 even when the estimated vehicle speed ■8 becomes small.

In step 105, based on the estimated vehicle acceleration W obtained in steps 103 and 104 and the reference speed ■, a parameter (hereinafter referred to as a wheel parameter) representing the locking tendency of each wheel is calculated using the following formula: calculate.

X**-A ・ (V-* Vs)+B ・ (W-
Ws)・・・・・・・・・(e) Here, the X umbrella of formula (e), and ■9. etc. symbol Yuyu is F
R.

Represents either FL, RR, or RL.

Wheel parameter X0. calculated by equation (e). When XYU〉O, the wheel has a tendency to lock (,X,.

When ≦, it means that there is a tendency to lock, IX.

The value represents the strength of the locking tendency. During anti-lock control, if Xo≦0, the pressure is maintained or reduced.

In step 106, it is determined whether anti-lock control has already started. If anti-lock control has been started, the process proceeds to step 109; if not, step 107
Proceed to.

In step 107, the tendency of each wheel to lock is determined. That is, the wheel parameters W0. of each wheel determined in step 105. and control start level-K.

(Kw: positive constant). As a result, any wheel parameter W0. If it is determined that even one of the values is smaller than -8, the process proceeds to step 108 and anti-lock control is started. Meanwhile, in step 107, all wheel parameters W, l, W, L, WRR.

If it is determined that WRL is greater than or equal to -Kw, it is assumed that none of the wheels have a tendency to lock, and the process returns to step 101.

In step 108, the pump 51 is driven (ON state) by a motor (not shown) to start anti-lock control.

In step 109, all wheel parameters XFII
XFLI XRRI 'The state where XRL is greater than 0 is T.

It is determined whether or not it lasted for more than a second (for example, 0.5 to 2 seconds). If this determination result is affirmative, it is assumed that the tendency of the wheels to lock has been completely suppressed, and the process proceeds to step 110. In step 110, the pump 51 is put into a non-driving state (OFF state), and the energization to the two-position valve 15 is stopped (O
FF state) Finish the anti-lock control and proceed to step 101.
Return to - On the other hand, if the determination result in step 109 is negative, the locking tendency of the wheels has not been completely suppressed, so in step 111 each wheel 11, 21, 31
．． Anti-lock control is executed for 41.

In step 111, the strength of the locking tendency of each wheel lX,
, l, the duty ratio for driving the two-position valves 15.25, 35° 45 is calculated in the order of right front wheel, left front wheel, right rear wheel, and left rear wheel.

In step 112, it is determined whether or not the calculated duty ratio of each wheel needs to be corrected. If correction is necessary, the process returns to step 101; if correction is necessary, the process proceeds to step 113, and the calculated value of the duty ratio is Perform correction and step 1
Return to 01. Specifically, in step 112, it is determined whether the calculated value of the duty ratio is 100%. For example, the calculated value of the duty ratio of the two-position valve 15 for the front right wheel is 10.
If it is 0%, the process proceeds to step 113, where the duty ratio of the two-position valve 45 of the left rear wheel, which is paired with the right front wheel, is forcibly corrected to 0%. Note that when the calculated values of the duty ratios of the two-position valves 15.45 are both 100%, the magnitude of the locking tendency lX, , l is determined, and the wheel side with a greater locking tendency is prioritized and corrected.

The solenoid valves 15, 25, 35, and 45 are sequentially driven by the interrupt routine shown in FIG. 5 in accordance with the duty ratio value. This interrupt routine is activated and executed every time T/4 (T is one cycle of duty control). first,
Step 210 determines the value of counter N, and depending on the value, step 220 (if N=O), step 23
0 (if N=1), step 240 (if N=2)
, step 250 (if N=3).

In step 220, the two-position valve 15 for the right front wheel is energized (O
N) L, 2-position valve 15 corresponding to the calculated value of duty ratio
Set the energization (ON) time to the software timer. Similarly, in steps 230 to 250, the ON signal and ON time of the two-position valves 25, 35, and 45 are controlled.

Thereafter, in step 260, 1 is added to the value of the counter N, and if N=4 is not determined in step 270, the interrupt routine is immediately terminated and the process returns to OUT.If N=4, in step 280, N=0 It exits to OUT.

In addition, four software timers are set, and C
The value of a free running counter built into the PU is monitored, and when the set ON time ends, the drive signal for each 2-position valve is turned off.

In the above configuration, control waveforms during anti-lock control will be explained with reference to FIGS. 6 to 9. First, in Fig. 6, (a) shows the first hydraulic system (front right wheel (FR) and rear left wheel (FR)).
Indicates the wheel cylinder pressure P8 of RL)), and RA) to (
e) are the front right wheel (FR), rear left wheel (RL), and front left wheel (
(FL) and the drive signal for the two-position valve for the right rear wheel (RR).

Here, the front wheel brake pressure is higher than the rear wheel brake pressure? 111 is being sent.

At time L1, the two-position valve 15 is turned on (ON) by step 220 of the interrupt routine, and the brake oil pressure of the right front wheel is set to T as shown in FIG. 6(a).

The amount of time the pressure is decompressed. At this time, the 2-position valve 45 is de-energized (
OFF), and the pressure is increased.

At time t2, which is T/4 hours after time Ll, the two-position valve 25 is turned on in step 230, and the brake pressure on the left front wheel is reduced. Furthermore, from time L2, T
When /4 hours have passed and the clock arrives, the two-position valve 45 is turned on in step 240, and the brake pressure on the left rear wheel is reduced as shown in FIG. 6(a). Further, at time 10, T/4 hours have elapsed, and at time L4, the two-position valve 35 is turned on in step 250, and the brake pressure of the right rear wheel is reduced.

In this state, as shown in Fig. 6(b) and (C), the phase of the duty control of the front right wheel FR and the rear left wheel RL is set to T/2.
The two-position valves 15 and 45 of the first hydraulic system are
Since the N (depressurization) times do not overlap, even the left rear wheel with low brake pressure can be depressurized according to the ON time.

Further, as shown in FIG. 7, when the ON times of the two-position valves 15 and 45 partially overlap, during this overlapping period T, the brake fluid of the right front wheel, which has a higher pressure, is given priority to the pump 51.
The brake pressure on the left rear wheel is as shown in Figure 7 (
As shown in a), the pressure is maintained. However, the two-position valve 15 for the right front wheel is turned OFF, and there is a period T in which they do not overlap.

In such a case, the brake pressure of the left rear wheel is reduced, and even in such a case, the brake pressure of the left rear wheel can be regulated by duty control.

Note that when both two-position valves 15.45 in the first hydraulic system are turned on, brake fluid flows from the wheel cylinder with higher brake pressure to the lower brake cylinder due to the action of check valve 16.46, and the brake fluid pressure increases. trying not to rise.

Further, for example, there are cases where the left rear wheel is on the verge of locking and a sudden pressure reduction is required. If brake pressure is to be maintained in this situation, there is a risk that the desired rapid pressure reduction may not be possible.

In this case, in step 111 shown in FIG.
The duty ratio of the position valve 45 is calculated to be 100%. For this reason, step 112 is passed, and duty ratio correction is performed in step 113. In this correction, the duty ratio of the two-position valve 15 of the right front wheel paired with the left rear wheel of the first hydraulic system is unconditionally corrected to 0%.

That is, as shown in FIG. 8(C), if the drive duty ratio of the 2-position valve 45 is calculated to be 100% at time t, then the drive duty ratio of the 2-position valve 15 is calculated to be 40% at time t. Even if it is calculated, it is corrected to 0% and shown in Figure 8 (
The ON signal shown by the broken line in b) is not output.

In this way, the brake pressure of the left rear wheel, which requires rapid pressure reduction, is prioritized and reduced as shown in FIG. 8(a).

When the brake pressure of the left rear wheel is sufficiently reduced and the two-position valve 45 is turned OFF as shown at time t7, the brake pressure of the right front wheel is subjected to normal duty control both at time and in subsequent cycles.

Incidentally, in step 111, when the calculated values of the duty ratios of the two-position valves 15.45 are both 100%, the larger locking tendency IX, , l is determined, and the larger one is prioritized to reduce the pressure.

In the above embodiment, the phase of the duty control of the four wheels is set to T/4.
By doing so, pressure pulsations in the master cylinder generated by duty control of the two-position valves of each wheel are smoothed out, and brake pedal kickback, vehicle body vibration, and control noise can be reduced.

Further, instead of shifting the phases of the duty control of all four wheels by T/4, it is also possible to make pairs of two wheels, each pair having the same phase, and shifting the phase of the other pair by T/2. In this case as well, the pair may be assembled in any manner. Further, depending on the case, it is not necessary to shift the phase.

〔Effect of the invention〕

As described above, in the present invention, it is possible to eliminate the need for a reservoir, and to reduce the pressure in a pair of wheel cylinders using one common pump, thereby achieving downsizing and cost reduction. Furthermore, the brake oil pressure in the low-pressure wheel cylinder can also be reduced, making it possible to obtain sufficient and stable anti-lock performance.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing the configuration of an embodiment of the present invention, and FIG.
Figures (A) and (B) are configuration diagrams showing one wheel of the embodiment illustrated in Figure 1, Figure 3 is a time chart explaining the operation of the embodiment illustrated in Figure 1, and Figures 4 and 5. is a flowchart showing an example of control, and FIGS. 6 to 8 are time charts for explaining the operation. 1... Master cylinder, 11, 21, 31.41...
・Wheel, 12, 22, 32.42... Wheel cylinder, 15, 25, 35.45... 2 position valve, 51°5
2... Pump, 60... Electronic control unit (electronic control means). Representative Patent Attorney Takashi Okabe (and 1 other person)

Claims (2)

[Claims] (1) a hydraulic system that applies brake hydraulic pressure from a master cylinder to the wheel cylinders of a pair of wheels; a common pump provided in this hydraulic system for reducing the brake hydraulic pressure of the pair of wheel cylinders; and the brake. comprising a pair of 3-port 2-position valves provided in the system, and an electronic control means for controlling the 2-position valves;
The position valves each communicate between the master cylinder and the wheel cylinder at a first position and disconnect between the suction side of the pressure reducing pump and the wheel cylinder, and connect the master cylinder and the wheel cylinder at a second position. The electronic control means is configured to cut off communication between the pressure reducing pump and the wheel cylinder, and to communicate between the suction side of the pressure reducing pump and the wheel cylinder, and the electronic control means controls the time period during which the pair of two-position valves are in the second position. 1 above so that at least a portion of the
An anti-lock control device configured to control the duty of a pair of two-position valves to prevent wheels from locking. (2) When the electronic control means suddenly reduces the brake hydraulic pressure of one of the pair of wheel cylinders, the electronic control means controls one of the two-position valves to the second position, and simultaneously controls the other of the two-position valves to the second position. The anti-lock control device of claim 1, wherein the anti-lock control device is configured to be held in one position.