FR2653400A1 - Anti-lock brake control system - Google Patents

Abstract

Anti-lock brake control system including a feed passage (16) bypassing a flowrate control valve with pressure compensation (13) and a non-return valve (22) which allows the brake fluid to flow only towards one wheel cylinder (3) or only away from this wheel cylinder, is mounted in this feed passage (16) in series with an orifice (15). As a consequence, the anti-lock braking control makes it possible to establish either slow and fast pressurising modes, a fast depressurising mode and a holding mode, or slow and fast depressurising modes, a fast pressurising mode and a holding mode. It is possible to eliminate an abrupt variation in the hydraulic brake pressure by establishing the holding mode when passing from the fast depressurising mode to the fast pressurising mode or vice versa. Owing to the fact that this prevents a wide variation in the adjustment speed, the comfort of driving during braking is improved and the rebound developed in the brake pedal is eliminated.

Description

This invention relates to an anti-lock braking control system in a motor vehicle. More particularly, the invention relates to an anti-lock braking control system having flow passage selection valves and pressure compensated flow control valves; the selection valves switch from a fast depressurization mode to a slow depressurization mode and vice versa, to reduce the hydraulic brake pressure, and from a slow pressurization mode to a rapid pressurization mode to increase the hydraulic braking pressure at the moment of anti-lock braking control.

In general, an anti-lock brake control is designed so that, when it is detected, during braking, the wheel of a vehicle is about to be blocked, the braking force acting on the wheel is reduced to prevent blocking, after which the braking force is increased again. Such a control stabilizes the driving of the vehicle and makes the braking distance as short as possible.

An example of such an anti-lock braking control system for carrying out such a braking control operation is shown in FIG. 5.

As seen in FIG. 5, this anti-lock braking control system has a diagonally formed braking circuit comprising a first braking system.
A and a second braking system B. The first braking system is adapted such that the hydraulic pressure of a hydraulic pressure source 1, comprising a pump 1a and an accumulator 1b, is fed to a wheel cylinder 3 for the right front wheel and a wheel cylinder 4 for the left rear wheel, via a first control valve 2. The second braking system B is adapted so that the hydraulic pressure of the pressure source 1 is fed to a wheel cylinder 6 for the left front wheel and a wheel cylinder 7 for the right rear wheel via a second control valve 5. Due to the fact that the first braking system and the second braking system A and B are made in the same way, we will describe the first braking system A and we will omit the description of the second braking system
B.

In the first braking system A, the first control valve 2 is constituted by a distributor with three orifices and three positions. An outlet port 2a of the control valve 2 and the wheel cylinder 3 for the right front wheel are brought into communication via a first feed passage 8, and the outlet port 2a of the first control valve 2 and the wheel cylinder 4 for the left rear wheel are put into communication via a second feed passage 9.

The first and second feed passages 8, 9 are respectively equipped with a first flow passage selection valve 10 and a second flow passage selection valve 11, each consisting of a solenoid valve. The first and second flow passage selection valves 10, 11 are adapted to collectively switch the respective wheel cylinders 3, 4 so that they communicate with either the outlet ports 2a of the first control valve 2 either with a reservoir 12. In the usual state shown in FIG. 5, the first and second passage selection valves 10, 11 are positioned to communicate the wheel cylinders 3, 4 with the outlet port 2a. and to isolate the wheel cylinders 3, 4 of the tank 12.

The first and second feed passages 8, 9 are further provided, at locations upstream of the first and second flow passage selection valves 10, 11, a first and a second valve. pressure-compensated flow control valves 13, 14, each constituted by a mechanical valve, for selectively communicating the outlet port 2a with the wheel cylinders 3, 4 and isolating them from each other.The first and the second pressure compensated flow control valves 13, 14 are adapted to open the first and second feed passages 8, 9 under the ordinary conditions shown in Fig. 5, and to switch and isolate the first and the second second supply passages 8, 9 when a predetermined pressure difference develops between the pressure on the side of the outlet port 2a and the pressures acting on the wheel cylinders 3, 4.

The outlet port 2a is provided with a first port 15 to communicate with the wheel cylinder 3 via a third supply passage 16 through the first flow passage selection valve 10, which bypasses the first pressure compensated flow control valve 13, and a second port 17 to communicate with the wheel cylinder 4 through a fourth feed passage 18 through the second valve flow passage selection circuit 11, which bypasses the second pressure compensated flow control valve 14.

The second supply passage 9 is equipped with a proportional valve PV 19 at a location between the second flow passage selection valve 11 and the wheel cylinder 4.

The reservoir 12 is connected to the suction side of the pump 1a whose delivery side communicates with the accumulator 1b and with an inlet 2b of the first control valve 2. The first and the second control valves 2, 5 are connected to a brake pedal 21 by means of a balancer device 20. When the brake is inactive, which is the state shown in FIG. 5, the first and second control valves 2, 5 are positioned in a first position for communicating the outlet port 2a with a discharge port 2c. When depressing the brake pedal 21, the valves 2, 5 are positioned in a second position in which the three orifices 2a, 2b, 2c are isolated from each other. By further depressing the brake pedal 21, the valves 2 5 are positioned at a third position in which the outlet port 2a and the inlet port 2b communicate with each other.

Based on the functional states of the first flow passage selection valve 10 and the first pressure compensated flow control valve 13, the anti-lock braking control system is positioned at the control modes indicated on the table 1.

Table 1: ANTI-BLOCKING BRAKE CONTROL MODES

<tb><SEP><SEP> Valves of <SEP><SEP> Selection <SEP> Change <SEP> 10
<tb><SEP> On <SEP> Off
<tb><SEP> valve <SEP><SEP><SEP> Depressurization control
<tb><SEP> On <SEP> Pressurization <SEP> Depressurization
<tb><SEP> speed <SEP> to <SEP> com <SEP> slow <SEP> fast
<tb> thought <SEP> of
<tb><SEP> Shutdown <SEP> Pressurization <SEP> Pressurization
<tb> pressure <SEP> 13 <SEP> slow <SEP> fast
<tb><SEP> slow <SEP> fast
<Tb>
We will now describe the operation of this anti-lock braking control system.

Ordinarily, the valves 10, 11, 13 and 14 are in the states shown in Fig. 5 and the outlet port 2a communicates with the wheel cylinders 3, 4. Accordingly, when the brake pedal 21 is depressed to position the first control valve 2 in the third position at the moment of braking, the hydraulic pressure of the hydraulic pressure source 1 is supplied to the wheel cylinder 3 for the right front wheel and to the wheel cylinder 4 for the left rear wheel, by through the first and second feed passages 8, 9, thus exerting a braking on the right front wheel and the left rear wheel.

When it is detected that the right front wheel is about to be blocked, the solenoid of the first pressure compensated flow control valve 13 is energized in response to the resultant detection signal. The first pressure compensated flow control valve 13 thus closes the first supply passage 8. As a result, the brake fluid is supplied to the wheel cylinder 3 for the right front wheel, only via the third passage supply 16 in which is the orifice 15. As a result, the hydraulic brake pressure exerted on the wheel cylinder 3 increases gradually. This is the slow pressurization mode. If the right front wheel is still about to be blocked, even in the slow pressurization mode, the solenoid of the first passage selection valve 10 is energized to switch this selector valve. and the first pressure compensated flow control valve 13 is switched to the ordinary state. As a result, the outlet port 2a and the wheel cylinder 3 are isolated from each other, the passage of the brake fluid is switched and the first supply passage 8 is opened to make communicating the wheel cylinder 3 with the reservoir 12. As a result, the brake fluid inside the wheel cylinder 3 is rapidly evacuated in the reservoir 12 and the result is that the hydraulic brake pressure of the wheel cylinder 3 This is the fast depressurization mode, in which the brake pressure acting on the right front wheel decreases rapidly. When the hydraulic brake pressure of the wheel cylinder 3 has decreased by a predetermined value, the first pressure compensated flow control valve 13 switches back to close the first supply passage 8. As a result, the braking inside the wheel cylinder 3 is progressively evacuated in the reservoir 12 and it follows that the hydraulic brake pressure of the wheel cylinder 3 decreases gradually. This is the slow depressurization mode, in which the brake pressure acting on the right front wheel gradually decreases.

When the right front wheel is no longer liable to be blocked, the solenoids of the two valves 10, 13 are de-energized to communicate the outlet orifice 2a with the wheel cylinder 3 and the passage of the brake fluid is switched to isolating from one another the wheel cylinder 3 and the reservoir 12 and the first supply passage 8 is open. As a result, the hydraulic pressure of the wheel cylinder 3 increases rapidly to establish the rapid pressurization mode, in which the braking force acting on the right front wheel increases rapidly.

Thus, the hydraulic brake pressure is controlled so as to eliminate the blockage and to make the braking distance as short as possible. The control characteristic, in this case, is shown in FIG.

An anti-lock control is performed in a similar manner each time the other wheels are about to be locked.

However, with this anti-lock braking control system, the control is carried out in the four modes indicated in Table 1 and, therefore, one goes directly from a pressurization mode to a depressurization mode or directly from a depressurization mode to a pressurization mode. As a result, when there is a transition from one mode to another, there is a large fluctuation in the G (the speed of adjustment) and a large fluctuation in the hydraulic brake pressure.

 This results in a large rebound of the brake pedal and a deterioration of road comfort and driving sensation.

In addition, if one seeks to minimize the fluctuation of the hydraulic brake pressure, the flow passage selection valve 10 and the first compensation flow control valve 13 must be finely controlled and, accordingly, the number many times these valves are operated increases. As a result, the flow passage selection valve and the first pressure compensated flow control valve must have a very long service life. As a result, they cost more.

An object of the present invention is to provide an anti-lock braking control system capable of performing an anti-lock control so as to make as low as possible a fluctuation in G (the speed of adjustment).

Another object of the present invention is to provide an anti-lock braking control system designed to minimize the number of times the flow passage selection valves and pressure compensated flow control valves are operated, enabling to manufacture these valves cheaply.

According to the present invention, the above aims are achieved by means of an anti-lock braking control system for a motor vehicle, characterized in that it comprises a first supply passage for communicating the generating means of the hydraulic braking pressure and a wheel cylinder, which cylinder produces a braking force applied to a wheel of the vehicle, a flow passage selection valve mounted in the first supply passage for withdrawing brake fluid which has been supplied to the wheel cylinder and send it to a reservoir when it is actuated when it is detected that the wheel is about to be blocked at the time of braking, a braking compensation flow control valve mounted in the first supply passage in a point between the flow passage selection valve and the wheel cylinder to close the first feed passage only when predetermined control prevails in the anti-lock braking control and to open the first supply passage at all other times, a second supply passage having an orifice provided in parallel with the pressure-compensated flow control valve to bypass the latter and a check valve, arranged in the second supply passage.

In the anti-lock braking control system according to the present invention performed as described above, the check valve is mounted in the second supply passage which bypasses the pressure compensated flow control valve and is in series with the orifice. As a result, either the slow depressurization mode or the slow pressurization mode, in which the hydraulic braking pressure decreases slowly or increases slowly during anti-lock braking control, is set in a holding mode, in which the pressure Hydraulic braking is maintained. By setting the hold mode when there is a transition from the rapid depressurization mode to the rapid pressurization mode or the rapid pressurization mode to the rapid depressurization mode, the sudden fluctuation of the hydraulic braking pressure can be eliminated.

By arranging the check valve so as to allow a flow of the brake fluid only in the direction of the wheel cylinder, the slow and fast pressurization modes, the fast depressurization mode and the holding mode are set. By arranging the check valve to allow a flow of the brake fluid only in the direction away from the wheel cylinder, the slow and fast depressurization modes, the rapid pressurization mode and the holding mode are set. .

As apparent from the foregoing description, the anti-lock braking control system according to the present invention is advantageous in that the holding mode is set when the rapid depressurization mode is switched to the rapid pressurization mode or the pressurization mode. fast pressurization mode to fast depressurization mode.

This makes it possible to eliminate a sudden fluctuation of the hydraulic brake pressure by bringing it back to a relatively low level. As a result, there are no significant fluctuations in G and, as a result, driving comfort during braking control is considerably improved. In addition, because a fluctuation in the brake hydraulic pressure can be kept relatively low, it is also possible to suppress the rebound of the brake pedal and, consequently, the driving feeling is improved.

In addition, reducing the fluctuation of the hydraulic braking force means that the flow passage selection valve and the pressure-compensated flow control valve no longer need to have such a long service life. As a result, these valves can be manufactured cheaper.

The invention will be better understood on reading the detailed description, given below by way of example only, of several preferred embodiments of the invention, in conjunction with the attached drawing in which - FIG. 1 is a diagram of FIG. control circuit schematically showing an embodiment of the anti-lock braking control system according to the present invention - Fig. 2 is a graph showing the control characteristic of this embodiment - Fig. 3 is a control circuit diagram schematically showing a Another embodiment of the anti-lock braking control system according to the present invention - Fig. 4 is a diagram showing the control characteristic of this embodiment - Fig. 5 is a control circuit diagram schematically showing a braking control system anti-lock as an example; and - Figure 6 is a graph showing the control characteristic in this control circuit.

Several embodiments of the present invention will now be described in detail with reference to the drawings.

Figure 1 is a control circuit diagram, similar to that of Figure 5, schematically showing an embodiment of an anti-lock braking control system according to the present invention. The elements identical to those of the anti-lock braking control system of FIG. 5 are designated by the same references and, for reasons of simplicity, these elements will not be described.

Moreover, because the first braking system
A and the second braking system B are identical, as in Figure 5, we will describe only the first braking system A and will not describe the second braking system B.

As seen in FIG. 1, in this embodiment, the third supply passage 16 is equipped with a non-return valve 22 which only allows the brake fluid to flow from the upstream side to the downstream side, namely from the outlet orifice 2a to the wheel cylinder 3. The check valve 22 may be mounted either upstream or downstream of the orifice 15.

Depending on the operating states of the first flow passage selection valve 10 and the first pressure compensated flow control valve 13, the anti-lock braking control system of this embodiment is secured in one. control modes shown in Table 2.

Table 2: ANTI-LOCK BRAKE CONTROL MODES

<tb><SEP><SEP> valve of <SEP> selection <SEP> of <SEP> crossing
<tb><SEP> of <SEP> throughput <SEP> 10
<tb><SEP> On <SEP> Off
<tb><SEP> valve of <SEP> command <SEP> Pressurization
<tb> of <SEP> debit <SEP> to <SEP> com <SEP> On <SEP> Hold <SEP> slow
<tb> thought <SEP> of <SEP> near
<tb><SEP> 13 <SEP> Shutdown <SEP> Depressurization <SEP> Depressurization
<tb><SEP> quick <SEP> fast
<Tb>
Accordingly, in this embodiment, a mode of holding instead of the slow depressurization mode among the control modes in the anti-lock braking control system of the type shown in FIG. 5 is provided.

The operation of this embodiment is the same as that of the anti-lock braking control system of FIG. 5 except that a hold mode is set in place of the slow depressurization mode. Consequently, similar aspects of this operation will not be described again. Furthermore, the control characteristic of this embodiment is such that when the fast depressurization mode is switched to the fast pressurization mode, the hold mode is established, as shown in FIG. 2. Hydraulic brake pressure does not vary as abruptly as before.

Fig. 3 is a control circuit diagram, similar to that of Fig. 5, schematically showing another embodiment of an anti-lock braking control system according to the present invention. The elements identical to those of the anti-lock braking control system of FIG. 5 are designated by the same references and these elements will not be described for the sake of simplicity. Moreover, since the first braking system A and the second braking system B are identical, as in FIG. 5, only the first braking system A will be described and the second braking system B will not be described.

As seen in FIG. 3, in this embodiment, the third feed passage 16 is equipped with a check valve 23 which allows the brake fluid to circulate only from downstream to upstream, to namely from the wheel cylinder 3 to the outlet port 2a. The check valve 23 may be mounted either upstream or downstream of the orifice 15.

Depending on the operating states of the first flow passage selection valve 10 and the first pressure compensated flow control valve 13, the anti-lock braking control system of this embodiment is secured in one. control modes shown in Table 3.

Table 3: INAE-ANTI-BLOCKING CONTROL MODES

<tb><SEP><SEP> valve of <SEP> selection <SEP> of <SEP> crossing
<tb><SEP> of <SEP> throughput <SEP> 10
<tb><SEP> On <SEP> Off
<tb><SEP> valve of <SEP> command
<tb><SEP> On <SEP> Depressurization <SEP> Hold <SEP>
<tb> of <SEP> bit rate <SEP> to <SEP> compen- <SEP> slow <SEP>
<tb> sation <SEP> of <SEP> pressure <SEP> Shutdown <SEP> Depressurization <SEP> Pressurization
<tb> 13 <SEP> fast <SEP> fast
<Tb>
Accordingly, in this embodiment, a hold mode in place of the slow pressurization mode is set among the control modes of the anti-lock braking control system of the type shown in FIG. 5.

The operation of this embodiment is the same as that of the anti-lock braking control system of FIG. 5 except that a hold mode is set in place of the slow pressurization mode. Consequently, similar aspects of this operation will not be described again. Furthermore, the control characteristic of this embodiment is such that, when the rapid pressurization mode is switched to the fast depressurization mode, a holding mode is established, as shown in FIG. 4. the hydraulic braking pressure does not vary as abruptly as before.

Thus, in one or the other of the two embodiments described above, it eliminates a sudden variation in the hydraulic brake pressure by establishing the holding mode, in which the hydraulic braking pressure is maintained, when there a transition from the rapid depressurization mode to the rapid pressurization mode or from the rapid pressurization mode to the rapid depressurization mode.

 It follows that G does not undergo a large fluctuation and that there is not a strong rebound in the brake pedal. As a result, excellent road comfort and excellent driving feeling can be achieved even during anti-lock braking control.

The present invention is not limited to the previous embodiments, but it can be modified in various ways. For example, although the holding mode is established only once in the two previous embodiments, an appropriate number of modes can be combined among those of slow and fast depressurization, slow and fast pressurization and maintenance. By adapting such an arrangement, it is possible to perform a more appropriate anti-blocking control.

Although the check valves 22, 23 are mounted only in the braking system on the front wheel side in the previous embodiments, these check valves can be mounted in the braking system of the rear wheels or in both systems. braking front and rear wheels.

In addition, although the braking line is diagonally disposed in the previous embodiments, the present invention can be applied to other pipe arrangements as well. The present invention is applicable not only to the four-pipe system of the previous embodiments, in which the four wheels constituting the front and rear wheels are independent of each other, but also to other driving systems, such as a system with three ducts, in which the left and right front wheels are independent and the rear wheels are independent of the front wheels but not one of the other.

In addition, although the preceding embodiments relate to a case in which the present invention applies to a dual braking circuit, it goes without saying that the invention can also be applied to a simple braking circuit.

Since the present invention can be implemented in many apparently widely different embodiments, without departing from the spirit or scope of the invention, it is understood that the invention is not limited to previous embodiments specific.

Claims (3)

claims 1. - anti-lock braking control system for a motor vehicle, comprising a feed passage (8) for communicating hydraulic brake pressure generating means (1) and a wheel cylinder (3) which exerts a braking force on a wheel of the vehicle a flow passage selection valve (10) mounted in said supply passage (8) for withdrawing brake fluid, which has been fed to the wheel cylinder, and to send it in a reservoir (12) when it is detected that the wheel is about to be blocked upon braking a pressure compensated flow control valve (13) mounted in said feed passage at a point between said flow passage selection valve and the wheel cylinder for closing said feed passage only when a predetermined control mode prevails in the anti-lock brake control and for opening said feed passage to all other moments a bypass supply passage (16) having an orifice (15) connected in parallel with said pressure compensated flow control valve (13) to bypass said pressure compensated flow control valve, characterized in that a non-return valve (22) is mounted in the bypass supply passage (16). 2. - System according to claim 1, characterized in that the non-return valve (22) is arranged to allow the brake fluid to flow only in the direction of the wheel cylinder (3). 3. - System according to claim 1, characterized in that the nonreturn valve (23) is arranged to allow the brake fluid to circulate only away from the wheel cylinder