JPH0270559A - Brake - Google Patents

Abstract

PURPOSE:To simplify the structure of a brake, by making a combination of a variable proportioning valve and a depressurizing means. CONSTITUTION:A variable proportioning valve 220 changes the pressure of brake supplied to a rear wheel wheel cylinder 3c on the basis of the ratio of the pressure of brake sought by means of a control ratio determining means, so the ratio of the pressure of brake of front and rear wheel wheel cylinders 3b, 3c is aptly adjusted. In addition, when the lock tendency of a car wheel is decided by means of a lock deciding means, a control signal is outputted to a depressurizing means 215. On this occasion, the depressurizing means 215 cuts off a master cylinder 2 and a branching off point A, and depressurizes directly the pressure of brake of the rear wheel wheel cylinder 3c at the half way point of a piping between the variable proportioning valve 220 and the rear wheel wheel cylinder 3c. The front wheel wheel cylinder 3b communicating with the branching off point A, is depressurized by the operation of this depressurizing means 215 through the variable proportioning valve 220.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a brake device, and in particular to a brake device with so-called diagonal piping, which is equipped with piping that communicates the wheel cylinders of front wheels and rear wheels located diagonally. This is suitable for vehicles with a system.

[Conventional technology]

2. Description of the Related Art Diagonal piping is known as a brake hydraulic piping system often used in front-wheel drive (FF) vehicles.

As an anti-skid device using such diagonal piping, a simultaneous control system for front and rear wheels (a two-channel system for four-wheeled vehicles) has been proposed in which the hydraulic pressure is controlled for each diagonal piping system.

The hydraulic system of such a two-channel (2ch) type anti-skid device is shown in FIG.

The hydraulic pressure generated by the master cylinder 2 is applied to each hydraulic system connected to the dia-gonal piping. And the right front wheel (
Hydraulic pressure is supplied from one hydraulic system to the wheel cylinder 3a of the front left wheel (FL) and the wheel cylinder 3d of the left rear wheel (RL), and the wheel cylinder 3b of the left front wheel (FL) and the wheel cylinder 3d of the right rear wheel (R
Hydraulic pressure is supplied to the wheel cylinder 3c of R) from the other hydraulic system. Each hydraulic system is provided with a hydraulic control device 1a, Ib, and the oil path to the rear wheel side of each hydraulic system is provided with a proportioning valve (P pulp) 4a, 4b.

[Problem to be solved by the invention]

In such a conventional configuration, the P valves 4a, 4b
Since the characteristics of the vehicle are fixed, problems arise in terms of running stability and braking distance.

In other words, for example, when the road surface on which the vehicle is running changes from a road surface with a high friction force to a straddling road surface (a road surface where the friction coefficients of the road surface for the left and right wheels are different) when the vehicle is braking, the oil pressure of the wheel cylinder on the high μ road side is maintained as it is, It is ideal to reduce the oil pressure of the wheel cylinder on the low μ road side. However, in conventional anti-skid equipment with diagonal piping, P
Since the characteristics of the valves 4a and 4b are fixed, it is impossible to execute the above control, and the braking force of the wheel cylinder on the low μ road side becomes excessive, or the braking force of the wheel cylinder on the high μ road side becomes excessive. The braking force will either be insufficient or insufficient.

Further, the P pulps 4a and 4b have hysteresis between the forward flow from the master cylinder side to the rear wheel side and the reverse flow. Therefore, even if the front wheel side is depressurized by the hydraulic control device 1a, the rear wheel side is depressurized via the P valve (flow in the opposite direction), so there is a delay in the depressurization time. Therefore, the pressure reduction timing of the rear wheel wheel cylinder 3C is delayed than that of the front wheel wheel cylinder 3b.

For this reason, the recovery of the rear wheel speed is slower than that of the front wheel speed, resulting in lower running stability.

The present invention was made in view of the above problems, and is a brake device equipped with diagonal piping that diagonally communicates the wheel cylinders of the front and rear wheels, with a simple configuration that allows the ratio of braking pressure between the front and rear wheels to be adjusted. It is an object of the present invention to provide a device which eliminates the delay in pressure reduction timing between the front and rear wheels during pressure reduction.

[Means to solve the problem]

In order to achieve the above object, the brake device according to the present invention, as shown in FIG.
In a brake device to which braking pressure is supplied from a common master cylinder, a pipe is provided in the middle from the branch point to the wheel cylinder of the rear wheel, and the braking pressure is supplied from the master cylinder to the rear wheel. a variable proportioning valve that changes the ratio of braking pressure supplied to the foil cylinders of the master cylinder in response to a control signal; and a variable proportioning valve that interrupts communication between the master cylinder and the branch point; a pressure reducing means for reducing the braking pressure of the rear wheel side wheel cylinder from the middle of the piping between the rear wheel wheel cylinder, a control ratio determining means for determining the ratio of the braking pressure of the variable proportioning valve, and the front and rear wheel cylinders. a lock determining means for determining a locking tendency of the wheels based on a wheel slip rate; and when the locking tendency of the vehicle is determined by the lock determining means, the master cylinder and the branch point are cut off, and the rear wheel wheel cylinder and control means for outputting a control signal for reducing the braking pressure to the pressure reducing means.

[Effect]

According to the above configuration, the variable proportioning valve changes the braking pressure supplied to the rear wheel wheel cylinders based on the ratio of braking pressures determined by the control ratio determining means. The ratio of braking pressures is adjusted appropriately.

Further, when the lock determining means determines that the wheels tend to lock, a control signal is output to the pressure reducing means.

At this time, the pressure reducing means shuts off the master cylinder and the branch point, and directly reduces the braking pressure of the rear wheel cylinder from the middle of the piping between the variable provisioning valve and the rear wheel cylinder. By the operation of this pressure reducing means, the front wheel wheel cylinder communicating with the branch point is
Vacuum is applied via the variable proportioning valve. At this time, the variable proportioning valve causes a forward flow from the branch point on the master cylinder side to the rear wheel cylinder, so the front wheel cylinder pressure is reduced at the same time without delay compared to the rear wheel cylinder. .

[Effect of the invention] As described above, the present invention provides diagonal piping with
By combining a variable proportioning valve and a pressure reducing means, it is possible to create a more efficient structure than a brake system equipped with an anti-skin device that independently adjusts the wheel cylinder pressures of the four wheels. Moreover, it is possible to adjust the ratio of the braking pressures of the front and rear wheels, and when reducing pressure when a tendency to lock occurs, it is possible to eliminate the delay in pressure reduction timing of the front and rear wheels and to perform pressure reduction at the same time.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 2 is a configuration diagram showing a hydraulic circuit and a control device of a brake device according to a first embodiment of the present invention.

2 is a master cylinder, and hydraulic pressure is supplied from this master cylinder 2 to two hydraulic systems indicated by reference numerals 100 and 200. Branch point B in the middle of the piping of the hydraulic system 100
Hydraulic pressure is supplied to the wheel cylinder 3a of the FR wheel and the wheel cylinder 3d of the RL wheel, and from the branch point A in the piping of the hydraulic system 200 to the wheel cylinder 3b of the FL wheel and the wheel cylinder 3C of the RR wheel. Hydraulic pressure is supplied.

600 is an electronic control unit (ECU), which is composed of a microcomputer, etc., and includes wheel speed sensors 510, 520, 530, . - Input the wheel speed of each wheel from 540, and apply each 2-position valve 110, 115, 21.
0,215, pump motor 400, and each P valve 12
Controls 0,220.

Since each hydraulic system 100, 200 has the same configuration, the following description will focus on the hydraulic system 200. Note that the same configuration of each hydraulic system is given the same reference numeral below the value of 10.

Reference numeral 210 denotes a normally open electromagnetic two-position valve for increasing and shutting off pressure, and is provided in the middle of the piping between the master cylinder 2 and the branch point A. 220 is a variable proportioning (P) valve that connects the rear wheel (RR) wheel cylinder 3 from the branch point A.
It is provided in the middle of the piping leading to c, and changes the ratio of the braking pressure supplied to the rear wheel wheel cylinder 3C with respect to the braking pressure supplied from the master cylinder 2 in accordance with a signal from the ECU 600. 215 is an electromagnetic two-position valve for pressure reduction, which is connected in the middle of the piping between the variable P valve 220 and the rear wheel cylinder 3c, and is connected to the wheel cylinder 3b, 3c.
Reduce the oil pressure at c.

Here, a two-position valve for shutoff 210 and a two-position valve for pressure reduction 215
The combination of these constitutes the pressure reducing means of the present invention. By the combination of opening and closing operations of the two-position valves 210 and 215, three modes are implemented: a pressure increase mode in which the oil pressure of the foil cylinders 3b and 3c is increased, a holding mode in which the oil pressure is maintained, and a pressure reduction mode in which the oil pressure is reduced. Ru. In the pressure increase mode, the two-position shutoff valve 210 serves as the first device A, and the two-position pressure reduction valve 215 serves as the first device C. In hold mode, 2 positions 2
10 and 215 are the first devices C in the second position, respectively. On the other hand, in the pressure reduction mode, the two-position valves 210 and 215 are in the second position.
position, d, the hydraulic pressure of the rear wheel cylinder 3C is released to the reservoir 230, and the hydraulic pressure of the front wheel cylinder 3b is released to the reservoir 2 through the branch point A1 variable P valve 220.
It will be opened to 30. Note that the pump 240 is connected to the reservoir 23
Pressurize 0 brake oil to the piping on the master cylinder 2 side.

Next, the structure of P pulp 220 will be explained in detail.

FIG. 3 is a sectional view showing the structure of the P valve 220.

11 is a non-magnetic housing, in which a passage 21, a passage 22, and two cylindrical spaces are formed;
A spool 12 made of a magnetic material is slidably inserted into this space. This spool 12 has cylindrical parts 12a and 12b at both ends, and a tapered part 12 in the center.
c, and a boss portion 12d. Housing 1
A sheet member 13 is press-fitted into the housing 11 in the center of the cylindrical space of No. 1, and the spool boss portion 12d
A spring 14 is installed between the spool 12 and the spool 12 to urge the spool 12 to the right in the figure. A cover 15 is fixed to the housing 11 with bolts 30. This cover 1
5 has a guide portion 15a, and supports the cylindrical portion 12b of the spool 12 in a slidable manner.

A check valve 16 is also provided within the housing 11. This check valve 16 is composed of a seat 17, a pole stopper 18, a ball 19, and a spring 20, and allows fluid to flow only from a passage 21 formed in the housing 11 to a passage 22. There is.

A coil housing 23 is made of a non-magnetic material, and a coil portion 24 is disposed inside the coil housing. The coil portion 24 includes a coil 25, a plate 26 made of a magnetic material, a side plate 27, a ring 28, and a guide 29 made of a non-magnetic material. 30 is a bolt that connects the housing 11, the cover 15,
The coil housings 23 are each fixed integrally. 31°, 32.33, and 34.35 are O-rings that maintain the sealing properties of each part.

The cylindrical parts 12a and 12b at both ends of the spool 12 have different cross-sectional areas, and as shown in the figure, the cross-sectional area of the right part in the figure is Sl, and that of the left part is 32. Spool 1
2 moves to the left in the figure, the spool taper portion 12
c and the seat portion 13a, which is a corner of the sheet member 13, come into contact with each other, thereby closing the passages 21 and 22. At this time, the cross-sectional area of the contact point between the tapered portion 12c and the sheet portion 13a is S3. Here, there is a relationship of S, < S z < 33.

Next, the operation of the P valve 220 will be explained.

First, a state in which no current is applied to the coil 25 will be described. The pressure applied to the passage 21 is P. , the pressure applied to the passage 22 is P, 4, and the urging force of the spring 14 is F, then the force acting on the spunil 12 is a force F directed to the right in FIG.
,=F, ,force toward the left FL= (S2 Sl
) XPM. As a result, in the case of F,>F, the spool tapered portion 12c and the seat portion 13a do not contact each other, and the passages 21 and 22 communicate with each other, so that P, 1=P.

The force acting on the spool is F,=FL, and the tapered portion 12c and the seat portion 13a come into contact. After that, the pressure P,
As we raise the value, there is a contact point, so the force FR in the right direction becomes F R - F s + (S 3 S z
) x P, 4, the force FL in the left direction is FL = (S3 5l)
xp.

Therefore, the pressure relationship is such that FR=FL holds true. In other words, Fs ten (S3 5Z)XPH= (Si St)xP
The value of w is smaller than l, and as a result, Pl and l rise more slowly than the PM pressure rises.

This situation is represented by the characteristics shown by the solid line in FIG.

Next, when the coil 25 is energized, an attractive force FC is generated between the spool 12 and the plate 26, and a force in the left direction in FIG. 3 is generated. 20 power F. Naturally, this changes depending on the current value applied to the coil 25, and the larger the current value, the larger the attraction force FC becomes.

As described above, when the coil 25 is energized, a force FC in the left direction in FIG. 3 is generated. Therefore, the break point in the broken line characteristic of P pulp shown in FIG. Move to a point. Further, the characteristics after the break point are as shown by the dashed line in FIG.

As the current value applied to the coil 25 increases, the break point moves from point X toward point 0, but eventually reaches point F.

>F, the spool taper part 12c and the seat part 1
3a maintains contact even when the pressure P increases to a certain extent, and the passage 21 and the passage 22 are in a closed state. When the pressure reaches P= or higher, the spool 12 can finally move to the right and the pressure P. begins to rise in proportion to the subsequent rise in pressure P. That is, the characteristics are as shown by the two-dot chain line in FIG.

Here, the cases of normal braking and anti-skid control will be explained based on FIG. 2.

(i) In the case of normal braking When the brake pedal is depressed, brake oil is pumped from the master cylinder 2 to each of the wheel cylinders 3b and 3c, and the pressure in each of the wheel cylinders 3b and 3C increases.

Thereafter, when the brake pedal is released, the pressure in each of the wheel cylinders 3b and 3c is reduced, but at this time, the pressure in the rear wheel cylinder 3c is increased or decreased via the P pulp 220.

(ii) For anti-skid control Each foil cylinder 3b with anti-skid control.

The pressure reduction of 3c is performed via the pressure reduction two-position valve 215. Here, since the pressure reducing two-position valve 215 is connected to the downstream side of the P valve 220, the pressure in the rear wheel cylinder 3C is directly reduced without going through the P valve 220. Then, the pressure of the front wheel wheel cylinder 3b is at the branch point A
, is opened via variable P valve 220. At this time, the variable P valve 220 causes a forward flow in the rear wheel cylinder 3 from the branching point A, so the front wheel wheel cylinder 3
The pressure reduction in b can be performed simultaneously on the rear wheel side without any delay. The characteristics at this time are as shown in Figure 4, and the pressure history when no current is passed through the coil 25 is 0.
→Y-4X-+F→X→Y→O, and the pressure history when current B is applied becomes 0→Z-F'→Z.

Next, the control and operation of the anti-skid device configured as described above will be explained.

In this embodiment, the above-mentioned P valve 120 or 220
The ratio of braking force between the front and rear wheels can be changed by changing the current value passed through the coil 25, and a larger braking force (braking oil pressure) can be applied to the front wheels than before.
A smaller braking force (braking oil pressure) can be applied to the rear wheels.

In the following explanation, a low-select type control will be described in which control is performed based on the lowest wheel speed, with emphasis on the front and rear wheels that have a large tendency to open up. In addition, in the following embodiment, in order to simplify the explanation, control is performed using only the pressure increase mode and the pressure decrease mode.

For example, let's consider a case where the road surface is snowy, the front wheels are flat tires, and the rear wheels are normal tires (this condition is common in winter).

Figure 5 shows changes in each wheel speed etc. due to P valve control when brake operation is performed in this condition.
VB = vehicle speed, VFL: left front wheel speed, VR
R: Right rear wheel speed, PFL: Left front wheel wheel cylinder pressure,
P□: right rear wheel wheel cylinder pressure, VFL: left front wheel acceleration, VRR: right rear wheel acceleration. The pressure in each wheel cylinder increases due to the brake operation, and the wheel speed decreases significantly (between time 0 and T).

Since this control method is low select control, the ECU 600 issues a pressure reduction command to the two-position valves 210 and 215 based on the low-speed rear wheel speed or deceleration signal, and the pressure in each wheel cylinder is reduced. go.

Along with this, each wheel speed recovers (time T1 to Tz
between O). Comparing both axle speeds and wheel accelerations ((b) in Figure 5) during these times (between 0 and T2), it is found that the drop in wheel speed and wheel deceleration is greater for the rear wheels than for the front wheels. (Also, the recovery of the wheels after pressure reduction is slower for the rear wheels than for the rear wheels.In other words, due to these phenomena, the normal P valve characteristics (when the turning point is X in Figure 4) Since the rear wheels show a greater tendency to lock, it is clear that the pressure distribution needs to be made at a corner point closer to the 0 point than the X point shown in FIG.

Therefore, as an information value indicating the degree of excessive braking force of the rear wheels for determining which coil 25 is energized, for example, the difference Δ■ between the maximum drop speeds of the front and rear wheels, the front wheel speed VFL and the vehicle body speed V, There is a difference Δv2 between the front and rear wheel speeds when the vehicle recovers to a certain speed, a difference ΔG between the front and rear wheel decelerations, and a difference ΔG2 between the front and rear wheel accelerations when the wheels recover. Based on one or more of these information values, the current value of the coil 25 is determined before the next pressure increase. That is, the larger the information value is, the larger the current flowing through the coil 25 is, and this control current I (FIG. 5(C)) is determined by the pressure increase start time T.
2, or immediately before it.

This pattern will be explained based on the flowchart of FIG. 5 for the case where the information value is ΔG1.

First, in step 700, each wheel speed VFR+VFL.

VllR+ VRL is read, and in step 710 acceleration V Fil, V FL+ V IIR・V
Calculate IIL. Then, in step 720, for example, in the FL-RR yarn system, it is determined whether the control mode is the pressure increase mode. If the result of this determination is the pressure increase mode, the process proceeds to step 730; otherwise (the pressure reduction mode), the process proceeds to step 790. In step 730, a control mode variable k is determined. Here, when k=1, it indicates that the control mode is the pressure reduction mode, and when k=o, it indicates that the control mode is the pressure increase mode. Then, if k=1, go to step 740, otherwise (k=o) step 750
Proceed to.

In step 740, the current value I that is energized to the coil 25 from the start of the current pressure increase to the start of the next pressure increase is determined by the limit calculated in step 770 during the previous pressure increase. 11 Substitute the current value I. In step 750, the control mode variable k is set to 0 indicating the pressure increase mode. In step 760, based on step 710, a difference ΔG1 (corresponding to ΔG in FIG. 5(b)) between the value where VFL is the smallest and the value where VIIM is the smallest is calculated. In step 770, a value obtained by multiplying the value of ΔG1 by k (constant),
The next control current value 1p is calculated by adding the current value {circle around (2)} currently energized to the coil 25. However, when the current value I has a negative value (when the deceleration of the front wheels is greater than that of the rear wheels), I is set to 0. In step 780, the current value ■ is set to the P pulp 22 only during anti-skid control.
0 coil 25 is energized. In step 790, the control mode variable k is set to l indicating the depressurization mode.

In summary, the control current value I to be applied to the coil 25 of the P pulp 220 during the next pressure increase control and pressure decrease control is determined by the acceleration difference ΔG1 during the current pressure increase control.

is calculated (steps 760, 770), and the control current value Ip is changed to the applied current value I at the start of the next pressure increase control (steps 730, 740).

By repeating such a routine, the current value I is finally controlled such that ΔG1=0.

Note that these controls are performed independently in the FL-RR system and the FR-RL system.

In the above embodiment, a two-position combination was used, but a three-position electromagnetic valve may also be used, as shown in FIG.

Note that Figure 7 shows only the FL-RR system, and the FR-R system
Since the L system has the same configuration, it will be omitted.

2100 is an electromagnetic three-position valve, which is provided between the master cylinder 2 and branch points C and D; position FIA is in the pressure increasing mode, position FIA is in the pressure increasing mode, position A is in the holding mode, and position C is in the pressure reducing mode. 211
0 is a check valve that allows flow only from the master cylinder 2 to the foil cylinders 3b and 3c. 2120 is a check valve, which is provided between the pipe between the variable P valve 220' and the rear wheel cylinder 3b and the branch point;
Allows flow only towards the branch point. The variable P pulp 220' has a configuration in which the check valve 16 of the variable P valve 220 of the aforementioned embodiment is omitted.

Its operation will be briefly explained. During normal braking, the master cylinder 2 to 3 position valve 2100 (position W a )
, through the check valve 2110, the foil cylinder 3b,
3c is increased and when the brake pedal is released, the brake oil in the front wheel cylinder 3c flows through the check valve 2120 together with the brake oil in the rear wheel cylinder 3b via the branch point C1 variable P valve 220'. Return to master cylinder 2 along the route.

Further, during anti-skid control, when the three-position valve 2100 is switched to the pressure reduction mode (position C), the master cylinder 2 and the branch points C and D are cut off. The brake oil in the front wheel cylinder 3C is transferred to the reservoir 230 along with the brake oil in the rear wheel cylinder 3b via the check valve 220 via the branch point C1 variable P valve 220'.
will be opened to

In this way, in this embodiment, the pressure reduction during normal braking and during anti-skid control is performed through the same route, and the variable P valve 220' is connected to the rear wheel cylinder 3C from the branch point on the master cylinder side. Since a flow occurs in the forward direction, the front and rear wheel cylinders 3b and 3c are depressurized simultaneously without delay.

In the basic control method described above, the current value I of the coil 25 is kept constant from the start of the current pressure increase to the start of the next pressure increase, so the ratio of the pressure in the front and rear wheel cylinders is also constant at the time of increase/decrease. The hydraulic characteristics are as follows. Therefore, the current value ■ is changed when increasing the pressure and when decreasing the pressure. Furthermore, we will explain an improved control method that achieves sophisticated control by changing the current value (2) during pressure increase/decrease or while pressure is maintained.

Before showing these control methods, first, how the pressure changes by the above-mentioned control will be explained with reference to the hydraulic circuit shown in FIG. 2.

In FIG. 8, a current value ■2 is applied to the coil 25,
Suppose that the pressure distribution point is located at the point.

At this time, when the current value I is lowered from I2 to I with each of the two-position valves 210 and 215 in the holding mode, the pressure distribution point shifts from the point to the L point, and the front wheel cylinder pressure decreases. , the rear wheel cylinder pressure will increase. To explain this with reference to FIG. 3, by lowering the current value ■, the balance of forces in the left and right directions applied to the spool 12 is disrupted, and the force in the right direction prevails, causing the spool 12 to open. Therefore, the brake oil flows from the front wheel cylinder 3b to the rear wheel cylinder 3C, and the pressure distribution point shifts to point L, which is a new balance point.

On the other hand, when the current value ■ is increased from I2 to ■, the pressure distribution point maintains the position of the point. To explain the reason for this using FIG. 3, it is true that the balance between the left and right forces applied to the spool 12 is disrupted at this time as well, but at this time, the leftward force of the spool 12 is dominant, so the spool 12 remains seated. It is.

Therefore, the pressure distribution point does not move from one point to another.

Therefore, the pressure in the front and rear wheel cylinders is increased and maintained,
When the pressure is controlled to decrease, if the current value 1 applied to the coil is changed between increasing and decreasing the pressure, the pressure changes in the front and rear wheel cylinders will be as shown in Figures 9 and 10, respectively. .

As shown in FIGS. 9(b) and 9(C), when increasing the pressure, the current value is held at I2, and when decreasing the pressure, the pressure in each foil cylinder 3b and 3c is as shown in FIG. 9(a). Looking at the history of this pressure in Figure 8, it changes from O to J-+ →
L→M→0.

In addition, as shown in Fig. 10(b) and (C), when the current value is held at I2 during pressure increase and increased to I during pressure reduction,
The pressure in each foil cylinder 3b, 3c changes as shown in Fig. 10(a), and when looking at the history of this pressure in Fig. 8, 0 → J
−+ becomes −N−+P. What we should pay attention to here is the movement of the pressure distribution point from N to N (period of ΔT in Figure 1O (a)). During this period, the pressure in the front wheel cylinder 3b is kept constant, while the rear wheel Only the pressure in cylinder 3C has decreased.

Also, if the current value I at the time of pressure reduction is changed from I2 to 14, for example, the pressure history changes from 0 → J → → Q, and the pressure in the rear wheel cylinder 3C is reduced to zero while keeping the pressure in the front wheel cylinder 3b constant. It is also possible to do this.

Next, during pressure increase and pressure reduction, the current value I of the coil 25 is
Figures 12 and 13 respectively show the case where
This will be explained based on the diagram. As shown in FIG. 12(b),
The voltage is increased while passing a current of current value I2 through the coil 25, and the voltage is increased for a certain period of time. If the current value I is decreased from 12 to 18 (point S in Figure 11), the current I2 in Figure 11 will be reduced by then.
However, after the current value I changes to 11, the pressure is increased with pressure distribution according to the characteristics according to the current I shown in FIG. As a result, the pressures in the front and rear wheel cylinders 3b and 3c change as shown in FIG. 12(a). Here, the current value I is changed from I2 to 11
The reason why the pressure in the front wheel cylinder 3b does not increase immediately when the pressure is decreased to It works to lower the pressure in the cylinder 3b.

Further, as shown in FIG. 12(d), the pressure is increased while flowing the current value I2, and the current value I is increased from I2 to I at a certain time L2.
, the pressure in the rear wheel cylinder 3C remains constant and only the pressure in the front wheel cylinder 3b increases until the front wheel cylinder pressure becomes distributed according to the characteristics of the current value l. (between S and T in Fig. 11), and after the pressure distribution point of the front and rear wheel wheel cylinders 3b and 3c reaches point T, the pressure is increased with pressure distribution according to the characteristics of the current value I3. As a result, the pressures in the front and rear wheel cylinders 3b and 3c change as shown in FIG. 12(C).

Next, a case will be described with reference to FIG. 13, in which the current value (2) applied to the coil 25 is changed during the pressure reduction.

As shown in FIG. 13(G), the current I2 is applied from the pressure distribution point U to the front and rear wheel foil cylinders 3b.

The pressure at 3c is reduced, and for a certain period of time □ (Fig. 11 V
At point), the current value I is decreased from I2 to 11.

Then, until then, the pressure is reduced according to the pressure distribution according to the characteristics of the current I2 shown in Fig. 11, but after the current value changes to Il, it follows the characteristics of the current I as shown by the dotted line in Fig. 11. Move to pressure distribution. As a result, the pressures in the front and rear wheel cylinders 3b and 3c change as shown in FIG. 13(a).

Also, as shown in Fig. 13(d), when the pressure is reduced while flowing the current value 2, and the current value I is increased from 12 to 13 at a certain time t, 4 (point V in Fig. 11), As shown by the dashed line in Fig. 11, until the pressure in the front and rear wheel cylinders 3b and 3c becomes distributed according to the characteristics of the current value I3, the pressure in the front wheel cylinder 3b remains constant and the pressure in the rear wheel cylinder 3b remains constant. Only the pressure in cylinder 3C is reduced. As a result, the pressures in the front and rear wheel cylinders 3b and 3c change as shown in FIG. 13(C).

As described above, by changing the current value I applied to the coil 25 during pressure increase and pressure reduction, or during pressure increase and decrease, the pressure in the front and rear wheel foil cylinders 3b and 3c can be controlled more skillfully. Can be done.

Hereinafter, anti-skid control using the above-mentioned control will be explained using FIG. 14.

However, even in the anti-skid control that will be explained from now on, it is assumed that low selection type control is performed, and
Retention mode shall not be used for convenience. In addition, the road surface on which the vehicle is traveling is assumed to be a straddle road (for example, an asphalt road surface on the left side and a snowy road surface on the right side) that can be represented by the control method of this embodiment.

On the above road surface, in the pressure systems of the front left wheel and the rear right wheel, as the brake pressure increases, the tendency of the right rear wheel to lock becomes greater than that of the left front wheel. At this time, if the tendency of the left front wheel to lock is very small, there is no need to reduce the pressure in the left front wheel wheel cylinder 3b. With the basic control shown in Fig. 6 mentioned above, the brake pressure of both wheels is reduced even in such a case, but with this control, the brake pressure of both wheels is reduced as shown in Fig. 13 (C).
As explained using a), the front wheel cylinder 3b
Control is used to reduce only the pressure in the rear wheel wheel cylinder 3C while keeping the pressure constant. In other words, Fig. 14 (
As shown in C) and (d), at time T4, the coil current value ■ is switched to a relatively large value 1 ehax to reduce the pressure in the front and rear wheel wheel cylinders 3b and 3c. As a result, while maintaining the braking force of the front wheels, the braking force of only the rear wheels can be reduced, and the wheel speed can be recovered. after that,
When increasing the pressure in the front and rear wheel cylinders 3b and 3c as the wheel speed of the right rear wheel recovers, the pressure is increased while energizing the coil 25 with the current value lc calculated in the same manner as in the basic control described above.

At this time, the current value 1c applied to the coil 25 is as shown in FIG.
It is better not to change stepwise as shown by the two-dot chain line in C). The reason is shown in Figure 12(a).

As explained in (b), the front wheel wheel cylinder 3b
This is because the pressure changes in a peculiar way. Therefore, in this embodiment, as shown by the solid line in FIG. 14(C), the coil 2
The current value 1c applied to 5 is changed at a certain slope.

Further, during the subsequent pressure increase, the current value is corrected at time T during the pressure increase. In other words, Fig. 14(a)
, As shown in (b), the locking tendency of the right rear wheel increases slightly during the pressure increase, so the current value decreases during the pressure increase.
increased. This makes it possible to increase only the pressure in the front wheel cylinder 3b while keeping the pressure in the rear wheel cylinder 3c constant for a predetermined period from time T5. In addition, if the left front wheel tends to lock up during pressure increase, the coil 25
What is necessary is to control the energizing current value I to.

FIG. 15 shows an example of a flowchart for realizing the anti-skid control described using FIG. 14.

The flowchart shown in FIG. 15 is basically the same as the flowchart shown in FIG. 6, so only the different steps will be explained here.

In step 800, the current value I that is currently energizing the coil 25, the control current value ■ calculated in step 770,
It is determined whether the difference between the two values is greater than a predetermined value δ. If the result of this determination is affirmative (Yes), step 810
Proceeding to Step 2, a comparison is made between the energizing current value (■) and the control current value (■). As a result of this comparison, if the control current value {circle over (2)} is large, the process proceeds to step 820 and immediately changes the conduction current value I to the control current value {circle around (2)} in order to increase the current value l flowing through the coil 25. On the other hand, if the control current value (2) is small, the process proceeds to step 830 in order to decrease the current value I flowing to the coil 25. At this time, as described above, it is desirable to gradually decrease the value of the current value (■), so the value of one decrease is set as Δ■ (constant) and the value is decreased in stages.

In step 840, a determination is made as to whether or not the current value {circle around (2)} to be applied to the coil 25 at the start of pressure reduction is to be changed. In other words, at step 770 during pressure increase, the acceleration difference ΔG between the front and rear wheels,
In other words, the difference between the control current value ■2 calculated based on the difference in lock tendency between the front and rear wheels and the current energizing current value I is the predetermined value I.
It is determined whether it is larger than K (>δ). When this determination result is affirmative (Yes), the energizing current value I should be increased, so the process proceeds to step 850, and the energizing current value I is changed to the maximum value [msx]. On the other hand, if the determination result is negative (No), it is assumed that there is no need to change the energizing current value I, and the process directly proceeds to step 780.

Note that this change in the current 1 at the start of pressure reduction is mainly performed during pressure reduction control immediately after anti-skid control is started. This is because in the subsequent anti-skid control, P
This is because the valve 220 is almost completely controlled.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an overview of the present invention, Fig. 2 is a block diagram showing a hydraulic circuit and an electric circuit of an embodiment to which the present invention is applied, and Fig. 3 is a block diagram showing the variable P valve shown in Fig. 2. FIG. 4 is a sectional view showing the structure of the variable P valve (220) in FIG.
20) Characteristic diagrams showing the characteristics of Fig. 5 (a), (b),
(c) is a time chart explaining the basic operation of the embodiment shown in Fig. 2, Fig. 6 is a flowchart for realizing the basic operation shown in Fig. 5, and Fig. 7 is another embodiment. Fig. 8 and Fig. 11 are characteristic diagrams for explaining other improved control, Fig. 9, Fig. 10, Fig. 12, and Fig. 13 show the operation by the improved control. FIG. 14 is a time chart for explaining the operation of the anti-skid control that incorporates the improved control. FIG. 15 is a flow chart for realizing the operation by the improved control shown in FIG. 14. FIG. 16 is a configuration diagram showing general diagonal piping. 1... Hydraulic control mechanism, 2... Master cylinder, 3a
. 3 b, 3 c, 3 d--Wheel cylinder, 4a, 4b...P valve, 100,200...Hydraulic system, ■20220.220'...Variable P valve,
510,520 530.540...Wheel speed sensor, 600...ECU.

Claims (2)

[Claims] (1) In a brake device in which braking pressure is supplied from a common master cylinder through a branch point in the middle of piping that communicates the wheel cylinders of the front wheels and rear wheels located diagonally, the brake pressure is supplied from the branch point to the rear wheel. A variable proportion system is provided in the piping leading to the wheel cylinder of the rear wheel, and changes the ratio of the braking pressure supplied to the wheel cylinder of the rear wheel with respect to the braking pressure supplied from the master cylinder in response to a control signal. the braking pressure of the variable proportioning valve of the rear wheel from the middle of the piping between the variable proportioning valve and the wheel cylinder of the rear wheel; control ratio determining means for determining a locking tendency of the vehicle based on the slip ratios of the front and rear wheels; and locking determining means determining a locking tendency of the vehicle based on the slip ratios of the front and rear wheels; and the branch point,
A brake device comprising: control means for outputting a control signal for reducing the braking pressure of the rear wheel wheel cylinder to the pressure reducing means. (2) The pressure reducing means is provided in the middle of the piping between the branch point and the master cylinder, and further includes a cutoff valve that cuts off communication between the master cylinder and the branch point, and the variable proportioning valve. 2. The brake device according to claim 1, further comprising a pressure reducing valve connected in the middle of a pipe between the rear wheel cylinder and the rear wheel wheel cylinder to reduce the braking pressure of the rear wheel side wheel cylinder.