JP2005119424A - Brake control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a brake control device capable of eliminating shortage of initial braking force while the durability of a liquid pressure source is enhanced. <P>SOLUTION: The brake control device is structured so that a shutoff valve installed between a master cylinder and each wheel cylinder is left open for a certain period of time from the start of the pressurization of the master cylinder when a pump as the liquid pressure source is to be driven at the time of starting the pressurization of the master cylinder while the durability is enhanced by using a gear pump as the liquid pressure source. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a brake control device that includes a hydraulic pressure source different from a master cylinder and performs brake-by-wire control.

Conventionally, in a brake control device, a technique for detecting a stroke of a brake pedal and the like, shutting off a master cylinder and a wheel cylinder at the time of braking, and obtaining a braking force by pressure accumulated in a hydraulic pressure source is disclosed in Patent Document 1. Is disclosed.
JP-T-2001-526150 (see FIG. 1).

  However, in the above-described prior art, when performing brake-by-wire braking, an accumulator is used as a hydraulic pressure source. There was a problem that the durability of the hydraulic pressure source was reduced. Therefore, a method of using an electric pump advantageous in terms of durability as a hydraulic pressure source can be considered. However, when the braking force generation operation by the electric pump, that is, pump braking, is performed, the rise of the pump motor drive tends to be delayed, and the hydraulic pressure is insufficient at the initial stage of pump braking, and the braking force may be insufficient.

  The present invention has been made paying attention to the above-mentioned problems, and provides a brake control device capable of eliminating deficiencies in driving force at the initial stage of pump braking while improving the durability of the hydraulic pressure source. With the goal.

  In order to achieve the above object, in the present invention, in the brake control device, when the pump is driven at the start of pressurization of the master cylinder, the shut-off valve provided between the master cylinder and the wheel cylinder is opened for a predetermined time from the start of pressurization of the master cylinder. It was decided to.

  As a result, the master cylinder pressure generated by the driver's operation can be supplied to the wheel cylinder in the early stage of pump driving, and it is possible to compensate for the lack of hydraulic pressure generation in the early stage of pump rotation. The shortage of braking force at the initial stage of pump braking due to can be solved.

  Hereinafter, the best mode for realizing the brake control device of the present invention will be described based on Example 1 shown in the drawings.

  FIG. 1 is a system diagram showing the overall configuration of the brake control device according to the first embodiment of the present invention. First, the configuration will be described. When the brake pedal 1 is depressed, brake fluid as fluid is supplied to the wheel cylinders 8 and 9 as braking force generating means via the oil passages 24 and 25. The wheel cylinder 8 is on the FL side (left front wheel side), and the wheel cylinder 9 is on the FR side (right front wheel side). The master cylinder 3 is provided with a reservoir tank 20 for storing brake fluid.

  Master cylinder pressure sensors 4 and 5 for detecting the master cylinder pressure are provided between the master cylinder 3 and the oil passages 24 and 25. In the first embodiment, the master cylinder pressure is detected by the sensors 4 and 5. However, the present invention is not limited to this configuration, and may be estimated by, for example, an estimator. A shutoff valve 6 is provided between the oil passage 24 and the oil passage 26. A shutoff valve 7 is provided between the oil passage 25 and the oil passage 27. A wheel cylinder 8 that communicates from the shutoff valve 6 to the oil passage 26 → the oil passage 28 is provided. A wheel cylinder 9 that communicates from the shutoff valve 7 to the oil passage 27 → the oil passage 29 is provided.

  A pressure reducing valve 14 is provided between the oil passage 38 and the oil passage 40. A pressure reducing valve 15 is provided between the oil passage 39 and the oil passage 47. When not energized (OFF), the shutoff valves 6 and 7 are opened, and the pressure reducing valves 14 and 15 are closed. When the brake pedal 1 is depressed, the brake switch 2 is set to ON and pressure is generated in the master cylinder 3. The pressure generated in the master cylinder 3 is transmitted to the wheel cylinder 8 in the order of the oil passage 24 → the shut-off valve 6 → the oil passage 26 → the oil passage 28. Further, the oil is transmitted to the wheel cylinder 9 in the order of the oil passage 25 → the shut-off valve 7 → the oil passage 27 → the oil passage 29.

  A relief valve 16 is provided on the oil passage 43. A relief valve 17 is provided on the oil passage 44. The allowable hydraulic pressure value of the relief valves 16 and 17 is set to the required maximum hydraulic pressure in the hydraulic circuit, and the brake fluid returns to the reservoir tank 20 via the oil passages 45, 46, and 42 when the valve is opened.

  A gear pump 10 is provided on the oil passage 32. A gear pump 11 is provided on the oil passage 33. The gear pumps 10 and 11 are driven by pump motors 12 and 13 based on command values from the control unit, and suck the brake fluid in the reservoir tank 20 into the gear pump through the oil passages 30 and 31.

  A one-way valve 18 is provided on the oil passage 34. A one-way valve 19 is provided on the oil passage 35. This is to prevent the hydraulic pressure from returning to the gear pumps 10 and 11 by providing the one-way valves 18 and 19 when the gear pumps 10 and 11 are driven to supply the necessary hydraulic pressure. Accordingly, the hydraulic pressure can be maintained without further driving the gear pumps 10 and 11, and the hydraulic pressure can be supplied by driving the minimum necessary gear pumps 10 and 11.

  Between the oil passages 49 and 50, an isolation valve 48 capable of communicating and blocking the oil passage for each wheel is provided. The isolation valve 48 is in a closed state (so-called normally closed type) when not energized (OFF).

(Brake-by-wire control)
In the first embodiment, brake-by-wire control is executed. That is, when the ignition is turned on by the driver's key operation, the shutoff valves 6 and 7 are closed. Then, the driver's intention to operate the brake is detected from the master cylinder pressure or the like, and a desired brake fluid pressure is generated by the gear pumps 10 and 11 in accordance with the intention and the running situation. The driver's intention to operate the brake can be detected by detecting the stroke of the brake pedal or the master cylinder.

FIG. 2 is a flowchart showing the control contents of the brake-by-wire control that is the hydraulic pressure control means.
In step 101, it is confirmed whether or not the brake switch 2 is in the ON state. When the brake switch 2 is ON, the process proceeds to step 102.

  In step 102, it is determined whether or not the brake switch 2 has been switched from the previous OFF to the current ON. Proceeds to step 104.

  In step 103, an initial braking control process is performed, and the process proceeds to step 104. The processing content of the initial braking control will be described later.

In step 104, it is determined whether or not the master cylinder pressure change rate is smaller than -ΔP ₀ . If it is smaller, the process proceeds to Step 108, and if it is larger, the process proceeds to Step 105.

In step 105, the master cylinder pressure change rate is determined whether greater than [Delta] P _1. If larger, the process proceeds to Step 107, and if smaller, the process proceeds to Step 106.

  In step 106, the gear pumps 10 and 11 are stopped, and this control flow is ended.

  In step 107, the gear pumps 10 and 11 are driven, and this control flow ends.

  In step 108, the gear pumps 10 and 11 are stopped and the routine proceeds to step 109.

  In step 109, the pressure reducing valves 14 and 15 are driven, and this control flow ends.

(Initial braking control process)
FIG. 3 is a flowchart showing the control contents of the initial braking control process in step 103.

  In step 201, the shutoff valves 6 and 7 are set to OFF (open), and the process proceeds to step 202.

In step 202, the valve opening time T of the shut-off valve 6, 7 is determined whether more than a predetermined time T _R, the following cases T _R to step 203, if more than T _R proceeds to step 204.

In step 203, the valve opening time T of the shutoff valves 6 and 7 is counted up, and the routine proceeds to step 202. Open time T of the shut-off valve 6, 7 is determined whether more than a predetermined time T _R at step 202, if more than the predetermined time T _R repeats step 203 until the following T _R.

  In step 204, the shutoff valves 6 and 7 are set to ON (closed), and this control flow is ended.

  FIG. 4 is a diagram showing the relationship between the pressure of the gear pumps 10 and 11 and time. In the initial stage of pressurization of the master cylinder, since the start of driving of the pump motors 12 and 13 is delayed, the initial discharge capacity of the gear pumps 10 and 11 is low and the pressure rises slowly. Therefore, the above-described braking initial control is executed in order to compensate for the lack of hydraulic pressure at the beginning of braking. Hereinafter, the flowcharts of FIGS. 2 and 3 will be described based on the time chart of FIG. 5.

FIG. 5 is a time chart when the initial braking control is executed.
At time T _1, when detecting an increase in the master cylinder pressure, the process proceeds to check that the brake switch 2 is ON in step 101 in the flowchart of FIG. 2 to step 102, the brake switch is in this ON in the previous OFF Check whether or not. Since the condition is satisfied, the process proceeds to step 103 and the initial braking control process of FIG. 3 is performed.

In step 201 of the flowchart of FIG. 3, the shut-off valve 6 in the OFF (opened), the flow proceeds to step 202, the valve opening time T of the shut-off valve 6, 7 counts up until a predetermined time _{T R} elapses.

At time _{T 2,} the valve opening time of the shut-off valve 6, 7 confirms that the predetermined time _{T R} elapsed, the process proceeds to step 204. In step 204, the shutoff valves 6 and 7 are turned ON (closed), the control flow in FIG. 3 is terminated, and the process proceeds to step 104 in the flowchart in FIG.

Since the master cylinder change rate is larger than -ΔP _{0 at} time T ₃ , the process proceeds to step 105. Here, the process proceeds to step 106 for the master cylinder change rate is less than [Delta] P _1, for holding the wheel cylinder pressure by the gear pump 10, 11 to OFF.

At time _{T 4,} because the brake switch is ON at step 101 of FIG. 2, the process proceeds to step 102. In step 102, since both the brake switch last time and this time are ON, the process proceeds to step 104. In step 104, because the master cylinder pressure change rate is smaller than -DerutaP _0, the process proceeds to step 108. In step 108, the gear pumps 10 and 11 are stopped and the routine proceeds to step 109. In step 109, the pressure reducing valves 14 and 15 are driven, and the brake fluid in the wheel cylinder is returned to the reservoir 20 through the oil passages 36, 40, 41, 42 and the oil passages 37, 47, 41, 42. Reduce power.

At time T _5, since the brake switch is OFF at step 101, this control is terminated.

As described above, in the first embodiment of the present invention, in the brake device that executes the brake-by-wire control, the durability is improved by providing the gear pumps 10 and 11 instead of the accumulator as the hydraulic pressure source. Can be planned. In general, when the brake fluid pressure is generated by a pump, there is a possibility that the responsiveness is deteriorated as compared with the accumulator. In contrast, the shut-off valve 6 for blocking the passage between the master cylinder 3 and the wheel cylinders 8 and 9, it was decided to the predetermined time T _R released immediately after the start of driving of the pump motors 12 and 13. Thereby, the master cylinder pressure generated by the driver's brake operation can be supplied to the wheel cylinder. Therefore, it is possible to compensate for the rise delay of the discharge of the gear pumps 10 and 11 in the initial stage of braking, and it is possible to achieve stable brake-by-wire control without giving the driver a sense of incongruity (corresponding to claim 1).

Next, Example 2 will be described.
FIG. 6 is a system diagram illustrating the overall configuration of the brake control device according to the second embodiment. Since the basic configuration is the same as in FIG. 1 of the first embodiment, only different points will be described.

  In the second embodiment, wheel cylinder pressure sensors 22 and 23 for detecting the wheel cylinder pressure are provided. In the second embodiment, the opening and closing of the shutoff valves 6 and 7 are controlled using the wheel cylinder pressure sensors 22 and 23.

  A stroke sensor 21 is provided for detecting the driver's intention to brake. This stroke sensor 21 achieves brake-by-wire control by generating wheel cylinder pressure according to the driver's control intention. Needless to say, the wheel cylinder pressure may be controlled based on the master cylinder pressure as described in the first embodiment.

  FIG. 7 is a flowchart showing the initial braking control using the master cylinder pressure.

  In step 301, it is determined whether or not the master cylinder pressure is greater than a threshold value A. Here, the threshold value A is a value at which it is determined that the driver has stepped on the brake pedal 1. When the master cylinder pressure is larger than the threshold value A, the process proceeds to step 302. When the master cylinder pressure is smaller, the present control is terminated.

  In step 302, the shutoff valves 6 and 7 are set to OFF (open), and the process proceeds to step 303.

  In step 303, it is determined whether the wheel cylinder pressure is greater than a threshold value B. Here, the threshold value B is a value at which the target wheel cylinder pressure can be sufficiently secured by driving the pump. When the wheel cylinder pressure is larger than the threshold value B, the process proceeds to step 304, and when it is smaller, the present control flow is terminated.

  In step 304, the shutoff valve is set to ON (closed), and this control flow ends.

  Hereinafter, the initial braking control process in the second embodiment will be described based on the time chart of FIG.

FIG. 8 is a time chart showing the initial braking control using the master cylinder pressure.
At time T _1, when detecting an increase in the master cylinder pressure, to verify that the brake switch 2 is in the ON state, the brake switch in step 102 performs a determination whether this is ON in the previous OFF. At this time, since the brake has been depressed, the brake switch 2 has been switched from the OFF state to the ON state, and thus the process proceeds to step 103, and the shutoff valves 6 and 7 are turned off (opened) as the initial braking control process of FIG. And As a result, the master cylinder pressure flows into the wheel cylinder side to compensate for the rise delay of the pump motors 12 and 13, and the shortage of initial discharge of the gear pumps 10 and 11 is resolved.

At time T _2, the wheel cylinder pressure is determined to be larger than the threshold B in step 303, the process proceeds to step 304, the shut-off valve in the ON (closed), and terminates the initial braking control process shown in FIG. 7, the steps of FIG. 2 Proceed to 104.

At time _{T 3,} since the master cylinder pressure change rate is greater than -DerutaP _0, the process proceeds to step 105, because the master cylinder pressure change rate is smaller than [Delta] P _0, the process proceeds to step 106 to stop the gear pump 10 and 11, the brake Hold fluid pressure.

At time _{T 4,} because the brake switch is ON at step 101 of FIG. 2, the process proceeds to step 102. In step 102, since both the brake switch last time and this time are ON, the process proceeds to step 104. Since the master cylinder change rate is smaller than −ΔP ₀ , the process proceeds to step 108, the gear pumps 10 and 11 are stopped, and the process proceeds to step 109. In step 109, the pressure reducing valves 14 and 15 are driven.

  As described above, in the second embodiment, the wheel cylinder pressure sensors 22 and 23 are provided, and the closing timing of the shutoff valves 6 and 7 is determined based on the detected wheel cylinder pressure. Specifically, until the wheel cylinder pressure exceeds the threshold value B, the start-up delays of the pump motors 12 and 13 are compensated by the master cylinder pressure by opening the shut-off valves 6 and 7, and the gear pumps 10 and 11 are initialized. The shortage of discharge is solved. Therefore, it is possible to reliably supply the pressure from the master cylinder up to a threshold value at which a sufficient hydraulic pressure can be secured by the pump. Furthermore, when the hydraulic pressure is secured, it is possible to return to normal brake-by-wire control, and brake-by-wire control can be executed while securing a sufficient initial braking force. When closing the shutoff valves 6 and 7, proportional control may be used. In this case, since the pressure change acting on the brake pedal 1 can be made gentle, it is possible to prevent a feeling of strangeness of the pedal.

It is a system configuration figure of the brake control device in Example 1 of the present invention. 3 is a flowchart showing the control content of initial braking control in brake-by-wire control in the first embodiment. 4 is a flowchart showing the control content of an initial braking control process in brake-by-wire control in the first embodiment. It is a figure which shows the relationship between the wheel cylinder pressure in Example 1, and time. 3 is a time chart when executing initial braking control in the first embodiment. It is a system figure showing the whole brake control unit composition in Example 2. 6 is a flowchart illustrating initial braking control using a master cylinder pressure in the second embodiment. 6 is a time chart showing initial braking control using the master cylinder pressure in the second embodiment.

Explanation of symbols

1 Brake pedal 2 Brake switch 3 Master cylinder 4, 5 Master cylinder pressure sensor 6, 7 Shut-off valve 8 Wheel cylinder (FL)
9 Wheel cylinder (FR)
10, 11 Gear pump 12, 13 Pump motor 14, 15 Pressure reducing valve 16, 17 Relief valve 18, 19 One-way valve 20 Reserve tank 21 Stroke sensor 22, 23 Wheel cylinder pressure sensor 48 Isolation valve

Claims (2)

A master cylinder that generates hydraulic pressure according to the brake operation force of the driver;
A wheel cylinder that uses at least the master cylinder as a hydraulic pressure source and generates braking force on each wheel; and
A hydraulic pressure source for generating a predetermined hydraulic pressure;
Hydraulic pressure control means capable of arbitrarily controlling the wheel cylinder pressure;
A shutoff valve that shuts off an oil passage between the master cylinder and the wheel cylinder;
In a brake control device comprising:
A pump is provided as the hydraulic pressure source,
The hydraulic pressure control means supplies brake hydraulic pressure to the wheel cylinder by driving the pump according to a driver's brake operation, and opens the shut-off valve for a predetermined period from the start of pump driving. Brake control device. The brake control device according to claim 1, wherein
A wheel cylinder pressure detecting means for detecting the wheel cylinder pressure is provided;
The hydraulic pressure control means shuts off the master cylinder and the wheel cylinder regardless of the opening time of the shut-off valve when the detected wheel cylinder pressure is not less than a predetermined value.

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