JP4400435B2 - Brake control device - Google Patents

Description

The present invention relates to a so-called brake-by-wire, which is a brake control device capable of controlling supply of working fluid pressure to a brake cylinder of each wheel by a driving source different from a master cylinder that outputs working fluid pressure by depressing a brake pedal.

  In general, a brake-by-wire is equipped with a master cylinder that generates a master cylinder pressure for braking according to the depression of the brake pedal and a hydraulic pump that is another drive source. When the system is normal, the master cylinder and the wheel cylinder are disconnected. The hydraulic pump is operated to control the supply of hydraulic fluid pressure to the wheel cylinder, and when the system is abnormal, the master cylinder and the wheel cylinder are connected to control the supply of the master cylinder pressure directly to the wheel cylinder pressure. Yes.

In such a brake-by-wire, an invalid stroke area of the master cylinder at the initial depression of the brake pedal is provided, and no master cylinder pressure is generated even when the depression is started, and the brake operability is reduced by reducing the pedal depression force. Are known (see, for example, Non-Patent Document 1).
Toyota Motor Corporation September 2004 Prius Electronic Technical Manual

However, the above-described brake control device of Non-Patent Document 1 does not generate a master cylinder pressure in the invalid stroke region at the initial depression of the brake pedal even when the system is abnormal. As a result, when the master cylinder pressure is directly supplied to the wheel cylinder pressure, the pedal stroke for generating the wheel cylinder pressure is increased by the invalid stroke area when the brake pedal is depressed, and the pedal stroke increases. There is an unresolved issue.
Therefore, the present invention has been made to eliminate such inconveniences, and improves the pedal operability until the brake pedal depression amount reaches a predetermined value when the system is normal, and increases the pedal stroke when the system is abnormal. An object of the present invention is to provide a brake control device that can be prevented.

In order to solve the above problems, the brake control apparatus according to the present invention includes a master cylinder for outputting a working fluid pressure according to the depression of the brake pedal, and a wheel cylinder for braking a wheel, the said master cylinder wheel In a brake control device that communicates with a cylinder and supplies a working fluid pressure output from the master cylinder to the wheel cylinder, a first hydraulic fluid is generated by a piston that connects the master cylinder to the brake pedal. A fluid movement control means that divides the fluid chamber and a second fluid chamber on the brake pedal side and restricts the movement of the working fluid from the first fluid chamber to the second fluid chamber; The piston is spaced apart from each other in the moving direction of the piston, and communicates the first fluid chamber and the second fluid chamber on the brake pedal side. And a mechanism that restricts the flow of fluid in the bypass passage, and determines whether any of the brake control devices is normal or abnormal. Control was made to allow movement of the working fluid from the fluid chamber to the second fluid chamber and to restrict movement of the working fluid from the first fluid chamber to the second fluid chamber in the event of an abnormality.

According to the brake control device of the present invention, in the first half of the depression of the brake pedal , the movement of the working fluid from the first fluid chamber to the second fluid chamber is allowed in the normal state , and the working fluid pressure is not generated in the first fluid chamber. , or working increase in fluid pressure is suppressed results depression force of the brake pedal is reduced, it is possible to improve the pedal operation of the first half depression of the brake pedal, the abnormal second fluid chamber from the first fluid chamber As a result, the working fluid pressure corresponding to the stroke of the brake pedal is generated in the first fluid chamber, and the wheel cylinder pressure can be generated immediately as there is no initial invalid stroke. In this way, an increase in pedal stroke can be prevented.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of the brake control device according to the first embodiment. In the figure, reference numeral 2 denotes a brake pedal, and reference numeral 4 denotes a master cylinder whose pressure is increased according to the depression amount of the brake pedal 2. .
The master cylinder 4 has two output systems, and outputs the working fluid pressure to these two output systems. Hereinafter, one of the two output systems is referred to as a primary output system, and the other is referred to as a secondary output system.

  These primary output system and secondary output system are provided with master cylinder pressure sensors 6a and 6b which are pressure sensors for detecting the working fluid pressure, and the working fluid pressure of the primary output system and the secondary output system is The master cylinder cut valves 8a and 8b and the normally open solenoid valves 10a and 10b are supplied to wheel cylinders 14a and 14b that generate braking force on the wheels 12a and 12b.

  A pump 18 is connected to the reservoir 16 arranged in parallel with the master cylinder 4. The pump 18 includes an electric motor 18a and a hydraulic pump 18b that is rotationally driven by the electric motor 18a. The brake fluid pressure output from the pump 18 is a normally open type when the system is in a normal state with the master cylinder cut valve 8a. It is supplied to the fluid path between the solenoid valve 10a. The fluid path between the master cylinder cut valve 8a and the solenoid valve 10a and the fluid path between the master cylinder cut valve 8b and the normally open solenoid valve 10b when the system is normal are normally closed when the system is normal. It is connected via a system shut-off valve 20 which is an electromagnetic on-off valve.

The wheel cylinders 14a and 14b and the reservoir 16 are connected to each other via normally closed electromagnetic valves 22a and 22b when the system is normal, and are configured to control the discharge of fluid from the wheel cylinders 14a and 14b to the reservoir 16. Has been.
A stroke simulator 26 is connected to the upstream side of the master cylinder cut valve 8b in the primary output system of the master cylinder 4 via a stroke simulator cut valve 24 which is a normally closed electromagnetic on-off valve when the system is normal. The stroke simulator cut valve 24 is opened when the master cylinder cut valves 8a and 8b are closed and as a result the master cylinder 4 is disconnected from the line, and connects the primary output system and the stroke simulator 26. When the stroke simulator cut valve 24 is open, the stroke simulator 26 is configured to absorb the working fluid pressure output from the master cylinder 4.

The stroke simulator 26 includes a cylinder body, a piston 26a slidably disposed in the cylinder, and a coil spring 26b that urges the piston 26a, and a pedal reaction force corresponding to the stroke of the brake pedal 2. Is generated.
Further, the brake control device of the present embodiment includes a stroke sensor 41 for detecting the depression amount of the brake pedal 2 and wheel cylinder pressure sensors 42a and 42b for detecting the working fluid pressure of the wheel cylinders 14a and 14b. I have.

FIG. 2 shows details of the master cylinder 4 in a non-braking state in which the stepping force by the brake pedal 2 is zero.
The master cylinder 4 includes a cylinder body 4a, two first and second pistons 4b and 4c slidably disposed in the cylinder body 4a, and the first and second pistons 4b and 4c. The primary pressure generating chamber 4d and the secondary pressure generating chamber 4e formed in the above, the springs 4f and 4g respectively disposed in the primary pressure generating chamber 4d and the secondary pressure generating chamber 4e, the first piston 4b and the brake pedal 2 are connected. The output system from the primary pressure generation chamber 4d is a primary output system, and the output system from the secondary pressure generation chamber 4e is a secondary output system.

The primary piston 4b and the back pressure chamber 4i on the brake pedal 2 side (see FIG. 3) are partitioned by the first piston 4b.
The springs 4f and 4g urge the first and second pistons 4b and 4c toward the brake pedal 2 according to the depression of the brake pedal 2. In the non-braking state shown in FIG. 2, the second piston 4b is located at the approximate center in the longitudinal direction of the cylinder body 4a, and the first piston 4b is located at one end in the longitudinal direction of the cylinder body 4a. Here, the position of the first piston 4b in the non-braking state is referred to as an initial position H of the first piston 4b.

  The master cylinder 4 is supplied with working fluid from the reservoir 16 via the first to third reservoir communication passages 28, 30, and 32. That is, the cylinder body 4a of the master cylinder 4 is provided with three ports 34, 36, and 38 that are spaced apart from each other in the axial direction. One end of the third reservoir communication path 32 is connected to the port 38 provided at the position farthest from the initial position H of the first piston 4 b, and the other end of the third reservoir communication path 32 is connected to the reservoir 16.

  One end of the second reservoir communication path 30 is connected to the port 34 provided at the position closest to the initial position H of the first piston 4b, and the position away from the port 34 with respect to the initial position H of the first piston 4b. One end of the first reservoir communication path 28 is connected to the port 36 provided in the port 36. The other end of the first reservoir communication path 28 is connected to the reservoir 16, and the other end of the second reservoir communication path 30 is connected to a path in the middle of the first reservoir communication path 28. The port 34 may not be provided in the axial direction of the master cylinder 4 but may be provided on the side surface in the axial direction on the brake pedal 2 side. In this case, the invalid stroke until the piston 4b passes through the port 34 is minute but can be reduced.

The first reservoir communication path 28 has a communication path shut-off valve 40 that is a normally closed electromagnetic on-off valve when not energized on the port 36 side from the position where the other end of the second reservoir communication path 30 is connected. It is intervened. The communication path cutoff valve 40 is configured to operate when a predetermined condition described later is satisfied, and to block the flow of the working fluid in the first reservoir communication path 28.
As shown in FIG. 2, when the master cylinder 4 is in a non-braking state in which the stepping force by the brake pedal 2 is zero, the first and second ports 34 and 36 communicate with the primary pressure generating chamber 4d, The 3 port 38 communicates with the secondary pressure generating chamber 4e.

The first piston 4b corresponds to the piston of the present invention, the primary pressure generation chamber 4d corresponds to the first fluid chamber of the present invention, and the back pressure chamber 4i corresponds to the second fluid chamber.
Further, the first fluid communication path 28, the second reservoir communication path 30, and the communication path shut-off valve 40 do not satisfy the predetermined condition until the depression amount of the brake pedal of the present invention reaches a predetermined value. Fluid movement control means for allowing movement of the working fluid from the chamber to the second fluid chamber and restricting movement of the working fluid from the first fluid chamber to the second fluid chamber when it is determined that the predetermined condition is satisfied. Equivalent to. The first reservoir communication path 28 and the second reservoir communication path 30 correspond to the bypass path of the present invention, and the communication path cutoff valve 40 corresponds to the cutoff mechanism of the present invention.

Here, until the brake pedal depression amount reaches a predetermined value in the present embodiment, it means the initial depression of the brake pedal 2.
In addition, the state in which the predetermined condition described above is satisfied in the present embodiment means that any one of various sensors (master cylinder pressure sensors 6a, 6b, etc.) provided in the system and an actuator (pump 18 etc.) provided in the system is abnormal ( This is a state in which a failure) has occurred and it is determined that the fail-safe mode should be entered.

  The master cylinder cut valves 8a and 8b, the normally open solenoid valves 10a and 10b when the system is normal, the system shutoff valve 20, the normally closed solenoid valves 22a and 22b, the stroke simulator cut valve 24, and the communication path shut off when the system is normal Each valve 40 is controlled in its open / closed state by a control signal from the control unit 44 supplied to the solenoid, and is in a normal state when the control signal is in an off state, and is switched to an offset position when the control signal is in an on state. It is configured as follows.

  The control unit 44 is configured via an arithmetic processing device such as a microcomputer, for example. Then, the control unit 44 closes the master cylinder 4 and the wheel cylinders 14a and 14b by closing the master cylinder cut valves 8a and 8b between the master cylinder 4 and the wheel cylinders 14a and 14b in a normal state. The working fluid pressure supplied to the wheel cylinders 14a and 14b by the pump 18 is generated. That is, the control unit 44 calculates the brake fluid pressure command value based on the detected value of the stroke sensor 41 and the detected value of the master cylinder pressure sensor 6b, and operates the pump 18 based on the brake fluid pressure command value. Then, a working fluid pressure is generated and introduced into the wheel cylinders 14a and 14b. Then, the normally open solenoid valves 10a and 10b and the normally closed solenoid valves 22a and 22b when the system is normal and the normally closed solenoid valves 22a and 22b are controlled so that the working fluid pressure becomes the brake fluid pressure command value.

  Further, the control unit 44 opens the stroke simulator cut valve 24 and absorbs the depression of the brake pedal 2 by the stroke simulator 26. Further, by opening the communication passage cutoff valve 40 interposed in the first reservoir communication passage 28 between the master cylinder 4 and the reservoir 16, the first reservoir communication passage 28 and the second reservoir communication passage 30 are opened. Keep in communication.

  When an abnormality occurs, the master cylinder cut valves 8a and 8b are opened to communicate the master cylinder 4 and the wheel cylinders 14a and 14b, and the wheel cylinder pressure of the wheel cylinders 14a and 14b is directly increased by the master cylinder pressure of the master cylinder 4. generate. At this time, by closing the system shutoff valve 20, the primary pressure generating chamber 4d and the secondary pressure generating chamber 4e of the master cylinder 4 independently generate fluid pressure. Further, by closing the communication passage cutoff valve 40 of the first reservoir communication passage 28, the back pressure from the primary pressure generating chamber 4 d is blocked by blocking between the first reservoir communication passage 28 and the second reservoir communication passage 30. The movement of the working fluid to the chamber 4i is prohibited. Further, the stroke simulator cut valve 24 is closed to prevent the brake fluid from flowing into the stroke simulator 26, thereby preventing a loss stroke caused by the stroke simulator 26.

Next, the operation of the present embodiment will be described with reference to FIGS.
Now, it is assumed that the driver is not operating a brake and is in a normal non-braking state. In this case, since the brake pedal 2 is not depressed, the master cylinder 4 is in the state shown in FIG. At this time, the master cylinder cut valves 8a and 8b are closed, and the system cutoff valve 20, the stroke simulator cut valve 24, and the communication path cutoff valve 40 are open.

  When the driver starts to depress the brake pedal 2 from this state (the first half of depressing the brake pedal 2), the first piston 4b to which the depressing force of the brake pedal 2 is transmitted moves toward the second piston 4c. At this time, as shown in FIG. 3, when the first piston 4b moves to a predetermined stroke S1 located between the port 34 and the port 36, the port 36 communicates with the primary pressure generating chamber 4d, and the port 34 Since the piston 4b communicates with the back pressure chamber 4i on the brake pedal 2 side, the working fluid in the primary pressure generating chamber 4d passes through the open communication passage shut-off valve 40, and the first reservoir communication passage 28 is passed. And it flows to the back pressure chamber 4i side via the second reservoir communication passage 30.

Thus, when the brake pedal 2 is in the first half of depression, the working fluid in the primary pressure generating chamber 4d flows into the back pressure chamber 4i, so that no primary pressure is generated in the primary pressure generating chamber 4d or the primary pressure rises. Is suppressed, and the depression force of the brake pedal 2 is reduced.
Since the master cylinder cut valve 8a is closed, the secondary pressure generating chamber 4e of the master cylinder 4 is not displaced. Further, since the primary pressure is not output from the primary pressure generating chamber 4d, the stroke simulator 26 does not generate a pedal reaction force corresponding to the stroke S1 (pedal stroke) of the first piston 4b.

  From this state, the driver further depresses the brake pedal 2, and the first piston 4b moves to a predetermined stroke S2 (S2> S1) where the port 36 and the back pressure chamber 4i communicate with each other as shown in FIG. Then (in the latter half of the stepping), the working fluid does not flow from the primary pressure generating chamber 4d to the back pressure chamber 4i. The working fluid flows from the reservoir 16 through the second reservoir communication passage 30 and the first reservoir communication passage 28 into the back pressure chamber 4i.

  In this state, a primary pressure is generated in the primary pressure generating chamber 4d by the stroke of the first piston 4b, and this primary pressure is output to the primary output system. Thus, the stroke simulator 26 generates a pedal reaction force corresponding to the depression amount (stroke S2) of the first piston 4b and absorbs and consumes the primary pressure output from the primary pressure generating chamber 4d. Ensure that the pedal 2 is depressed.

On the other hand, if an abnormality has occurred, as described above, the master cylinder cut valves 8a and 8b are opened, the stroke simulator cut valve 24 is closed, and the communication passage shut-off valve 40 is closed. The reservoir communication path 30 is shut off.
In this state, as shown in FIG. 5, when the driver starts the depression of the brake pedal 2 and performs braking (in the first half of the depression at the time of abnormality), the first piston 4 b is located between the port 34 and the port 36. Even if the stroke moves to the predetermined stroke S3, the working fluid does not flow from the primary pressure generation chamber 4d to the back pressure chamber 4i because the first reservoir communication passage 28 and the second reservoir communication passage 30 are blocked. . The working fluid that has passed through the second reservoir communication path 30 flows from the reservoir 16 through the middle path of the first reservoir communication path 28 to the back pressure chamber 4i. Further, since the master cylinder cut valve 8b is controlled in the open state, the secondary pressure generating chamber 4e of the master cylinder 4 is displaced.

  Thus, during the first half of the depression of the brake pedal 2 at the time of abnormality, the working fluid in the primary pressure generating chamber 4d does not flow into the back pressure chamber 4i, and the primary pressure corresponding to the stroke S3 of the first piston 4b is the primary pressure generating chamber. It occurs at 4d. Therefore, since the wheel cylinder pressure (braking force) corresponding to the stroke S3 can be generated immediately, an increase in the pedal stroke can be prevented.

  Therefore, in this embodiment, when the brake pedal 2 is normally depressed in the first half, the primary pressure is set via the first reservoir communication passage 28 and the second reservoir communication passage 30 by opening the communication passage cutoff valve 40. Since the generation chamber 4d and the back pressure chamber 4i communicate with each other and the working fluid in the primary pressure generation chamber 4d flows into the back pressure chamber 4i, primary pressure is not generated in the primary pressure generation chamber 4d or the primary pressure is reduced. Ascent is suppressed and the depression force of the brake pedal 2 is reduced. Thereby, the pedal operability in the first half of the depression of the brake pedal 2 at the normal time can be improved.

In the first half of the depression of the brake pedal 2 at the time of abnormality, the primary pressure generation chamber 4d and the back pressure chamber 4i are disconnected from each other by closing the communication passage shut-off valve 40, and the stroke of the brake pedal 2 is reduced. The corresponding primary pressure is generated in the primary pressure generating chamber 4d and the wheel cylinder pressure (braking force) can be generated immediately, so that an increase in pedal stroke can be prevented.
That is, it is possible to reduce the pedaling force in the first half of the depression of the brake pedal 2 at the normal time, and to improve both the brake pedal operability and the prevention of the pedal loss stroke at the abnormal time.

In addition, since the communication passage shut-off valve 40 is a closed electromagnetic on-off valve when not energized, the communication passage shut-off valve 40 is closed even in the case of an abnormal situation where power cannot be obtained, such as when the power fails. As a state, the first reservoir communication path 28 and the second reservoir communication path 30 can be shut off, and an increase in the pedal stroke of the brake pedal 2 can be prevented even during a failure during traveling.
In the above-described embodiment, the configuration in which the other end of the second reservoir communication path 30 is connected to the path in the middle of the first reservoir communication path 28 is shown, but the gist of the present invention is not limited to this. For example, as shown in FIG. 6, even if the other end of the second reservoir communication path 30 is directly connected to the reservoir 16, the same effect can be obtained.

  Further, in the present embodiment, when the predetermined condition is satisfied (the first half of the depression of the brake pedal 2 at the time of abnormality), the non-energized closed type that blocks the flow of the working fluid in the first reservoir communication path 28 Although the flow of the working fluid from the primary pressure generating chamber 4d to the back pressure chamber 4i is limited using the communication passage cutoff valve 40, the gist of the present invention is not limited to this, and for example, satisfies a predetermined condition. Even when a control valve having a throttle mechanism for reducing the flow of working fluid from the primary pressure generating chamber 4d to the back pressure chamber 4i is used, the invalid stroke is reduced and the increase in the pedal stroke is suppressed. be able to.

The fluid movement control means of the present invention is configured by the first reservoir communication path 28, the second reservoir communication path 30, and the communication path shut-off valve 40 that connect the master cylinder 4 and the reservoir 16, but the gist of the present invention is as follows. For example, the first piston 4b may be provided with fluid movement control means for controlling the movement of the working fluid from the primary pressure generating chamber 4d to the back pressure chamber 4i.
In the above-described embodiment, the case where the hydraulic pump 18b driven by the electric motor 18a is applied has been described. However, the present invention is not limited to this, and the hydraulic pump is driven to rotate by using the rotational force of the engine. It may be.

It is a schematic structure figure showing one embodiment of a brake control device of the present invention. It is a figure which shows the principal part of the brake control apparatus of the non-braking state at the time of normal. It is a figure which shows the operation | movement at the time of initial depression of the brake pedal at the time of normal. It is a figure which shows the operation | movement in the middle or the latter period of depression of the brake pedal at the normal time. It is a figure which shows the operation | movement of the initial depression of the brake pedal at the time of abnormality. It is a figure which shows the other example of the fluid movement control means which comprises the brake control apparatus of this invention.

Explanation of symbols

2 Brake pedal 4 Master cylinder 4b First piston (piston)
4d Primary pressure generation chamber (first fluid chamber)
4i Back pressure chamber (second fluid chamber)
6a, 6b Master cylinder pressure sensors 8a, 8b Master cylinder cut valves 10a, 10b Normally open solenoid valves 12a, 12b Wheels 14a, 14b Wheel cylinder 16 Reservoir 18 Pump 20 System shutoff valves 22a, 22b Normally when the system is normal Closed solenoid valve 24 Stroke simulator cut valve 26 Stroke simulator 28 First reservoir communication path 30 Second reservoir communication path 40 Communication path shutoff valve (shutoff mechanism)
42a, 42b Wheel cylinder pressure sensor 44 Control unit

Claims (1)

A master cylinder that outputs a working fluid pressure corresponding to depression of a brake pedal; and a wheel cylinder that brakes a wheel; the master cylinder and the wheel cylinder communicate with each other , and the working fluid pressure output from the master cylinder is In the brake control device for supplying to the wheel cylinder,
The master cylinder, is divided into a first fluid chamber and the second fluid chamber of the brake pedal side, wherein the working fluid pressure by the piston coupled to the brake pedal occurs,
Fluid movement control means for restricting movement of the working fluid from the first fluid chamber to the second fluid chamber;
The fluid movement control means is spaced apart from each other in the movement direction of the piston, and communicates the first fluid chamber and the second fluid chamber on the brake pedal side, and restricts the flow of fluid in the bypass passage. And a mechanism for
It is determined whether any of the brake control devices is normal or abnormal, and the first half of depression of the brake pedal allows the working fluid to move from the first fluid chamber to the second fluid chamber when normal, and when the abnormality occurs, A brake control device controlled to limit the movement of the working fluid from the first fluid chamber to the second fluid chamber .

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