JP2005067244A - Brake control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a brake control device for preventing excessively increased pressure on a wheel cylinder as a result of the inertial rotation of a pump upon starting holding during ABS control. <P>SOLUTION: The brake control device comprises an excessively increased pressure preventing means for preventing pressure generated by the inertial rotation of a pump motor from acting on the wheel cylinder upon starting holding control at least during ABS control. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention provides a brake capable of performing so-called brake-by-wire control, which includes a hydraulic pressure source other than the master cylinder pressure generated by a driver's operation and generates brake hydraulic pressure from the hydraulic pressure source according to the driver's intention. The present invention relates to a control device.
[0002]
[Prior art]
Conventionally, in a brake control device, a technique in which a pump is disposed between a master cylinder and a wheel cylinder and the increase / decrease of the wheel cylinder is controlled by the rotation of the pump is disclosed in Patent Document 1.
[0003]
[Patent Document 1]
JP-A-5-147524 (see FIG. 1).
[0004]
[Problems to be solved by the invention]
However, in the above-described prior art, pump rotation does not stop immediately due to the inertial force of the pump motor when shifting from pressure increasing control to holding control, and the wheel cylinder pressure becomes excessively increased during holding control. There was a risk that the accuracy of the would decrease.
[0005]
The present invention has been made paying attention to the above-mentioned problems, and provides a brake control device capable of preventing an excessive increase in wheel cylinder pressure caused by inertial rotation of a pump motor at the start of holding during ABS control. The purpose is to do.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, in the present invention, there is provided an overpressure prevention means for preventing the pressure generated by inertial rotation of the pump motor from acting on the wheel cylinder at least at the start of the holding control during the ABS control.
[0007]
Therefore, it is possible to prevent an excessive increase in the wheel cylinder pressure due to inertial rotation of the pump motor, and an appropriate brake braking force can be obtained.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
(Embodiment 1)
(Brake-by-wire control)
FIG. 1 is a hydraulic circuit diagram for performing brake-by-wire control in Embodiment 1 of the present invention. First, the configuration will be described. Between the oil passage 46 and the oil passage 48, the gear pump 10 is provided as a hydraulic pressure source. A gear pump 11 is provided between the oil passage 47 and the oil passage 49. The gear pumps 10 and 11 are driven by pump motors 12 and 13 based on command values from the control unit.
[0009]
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.
[0010]
When the stroke sensor 2 detects the depression of the brake pedal 1, the depression amount is transmitted to the control unit. When the pump motors 12 and 13 are driven based on a command from the control unit, the gear pumps 10 and 11 are driven to supply hydraulic pressure to the wheel cylinders 8 and 9. 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).
[0011]
Thus, a hydraulic pressure source other than the master cylinder pressure (gear pumps 10 and 11 in this embodiment) is provided, and brake hydraulic pressure is supplied from the hydraulic pressure source to the wheel cylinders 8 and 9 according to the driver's intention. Then, the brake-by-wire control for performing the braking control is executed.
[0012]
A pressure reducing valve 14 is provided between the oil passage 34 and the oil passage 40. A pressure reducing valve 15 is provided between the oil passage 35 and the oil passage 45. When the power is OFF, the shut-off valves 6 and 7 are opened, and the pressure reducing valves 14 and 15 are closed. At this time, when the brake pedal 1 is depressed, the stroke sensor 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.
[0013]
A relief valve 16 is provided between the oil passage 36 and the oil passage 38. A relief valve 17 is provided between the oil passage 37 and the oil passage 39. The allowable hydraulic pressure value of the relief valves 16 and 17 is set to the required maximum hydraulic pressure in the hydraulic circuit.
[0014]
A one-way valve 18 is provided on the oil passage 46. A one-way valve 19 is provided on the oil passage 47. This is to prevent the hydraulic pressure from returning to the gear pumps 10 and 11 side by providing these one-way valves 18 and 19 when the gear pumps 10 and 11 are driven to supply a necessary amount of 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.
[0015]
Between the gear pumps 10 and 11 and the wheel cylinders 8 and 9, there is provided an isolation valve 20 that can communicate and block the oil passages for each wheel. The isolation valve 20 is in a closed state (so-called normally closed type) when not energized (OFF).
[0016]
(Proportional control of pressure reducing valve)
In the ABS control, even if the gear pumps 10 and 11 are turned off at the start of the holding control after the pressure increasing control, the rotation of the gear pumps 10 and 11 does not stop immediately due to the inertial force of the pump motors 12 and 13. Therefore, there is a problem that the wheel cylinder pressure is excessively increased. Therefore, overpressure was eliminated by performing pressure reduction control. The pressure reduction control is performed by proportionally controlling the pressure reducing valve based on the pressure reduction amount calculated from the pump rotation speed.
[0017]
FIG. 2 is a flowchart showing the proportional control of the pressure reducing valves 14 and 15.
In step 101, it is confirmed whether there is a holding request. If there is a holding request, the process proceeds to step 102. If there is no request, this control flow ends.
[0018]
In step 102, the gear pumps 10 and 11 (pump motors 12 and 13) are turned off, and the process proceeds to step 103.
[0019]
In step 103, the amount of reduced pressure is calculated, and the process proceeds to step 104. Note that the amount of pressure reduction is calculated based on the number of rotations of the pump motor when pressure increase control is performed before the holding request.
[0020]
In step 104, proportional control of the pressure reducing valves 14 and 15 is performed, and this control flow ends.
[0021]
Hereinafter, the content of the proportional control of the pressure reducing valves 14 and 15 will be described with reference to the time chart of FIG.
At time T _1, the stroke sensor 2 the braking request of the driver, detects the stop lamp switches, and ON (closed) the shut-off valve 6,7. As the master cylinder pressure increases, the motor speed also increases. At this time, pressure increase control is performed.
[0022]
At time _{T 2,} there are holding request, turning ON the ABS flag. In the flowchart of FIG. 2, the process proceeds from step 101 to step 102. Next, the gear pumps 10 and 11 are turned off by turning off the driving of the pump motors 12 and 13. At this time, the rotations of the gear pumps 10 and 11 do not stop immediately but become excessive pressure increase, so it is necessary to perform pressure reduction control. Therefore, in step 103, the required pressure reduction amount is calculated from the pump speed, and the process proceeds to step 104. In step 104, proportional control of the pressure reducing valves 14 and 15 is performed based on the pressure reduction amount calculated in step 103, and this control flow ends.
[0023]
At time _{T 3,} since there is a reduced pressure demand, pressure reducing valves 14 and 15 continue to ON (open). The gear pumps 10 and 11 are also kept off.
[0024]
At time _{T 4,} because of the holding request, and Step 101 → Step 102 in the flowchart of FIG. The pump motors 12 and 13 are continuously turned off. In step 103, the rotation of the gear pumps 10 and 11 has already stopped, and is not in an overpressure state. Therefore, pressure reduction control is not necessary, and the pressure reduction amount becomes zero. Therefore, in step 104, the pressure reducing valves 14 and 15 are turned off (closed).
[0025]
At time T _5, with the increase of the wheel cylinder pressure, the pressure increase request is issued. Thereby, the pump motors 12 and 13 are driven to perform pressure increase control.
[0026]
At time _{T 6,} since there is a holding request, in the flowchart of FIG. 2, and Step 101 → Step 102. Since the rotation of the gear pumps 10 and 11 does not stop immediately, the wheel cylinder pressure is excessively increased. Therefore, in step 103, the required pressure reduction amount is calculated from the pump speed, and the process proceeds to step 104. Here, proportional control of the pressure reducing valves 14 and 15 is performed based on the pressure reducing amount calculated in step 103.
[0027]
At time T _7, decompression of the wheel cylinder over increasing pressure in the holding control is terminated. Therefore, the pressure reducing valves 14 and 15 are turned off (closed).
[0028]
As described above, in the first embodiment, the wheel cylinder overpressure prevention means is provided at the start of the holding control during the ABS control. At this time, when the pump motors 12 and 13 are turned off and the gear pumps 10 and 11 are stopped, it is possible to prevent the pressure due to the inertial force of the gear pumps 10 and 11 from acting on the wheel cylinders 8 and 9. Therefore, the braking force suitable for the driver's intention can be obtained (corresponding to claim 1).
[0029]
In addition, the pressure reducing valves 14 and 15 are controlled to open for a predetermined time as a means for preventing excessive increase in the wheel cylinder pressure at the start of the holding control during the ABS control. That is, it is possible to prevent the wheel cylinder pressure from being excessively increased only by controlling the pressure reducing valves 14 and 15 used for the ABS control. Therefore, an appropriate braking force can be obtained without newly providing means for preventing excessive pressure increase (corresponding to claim 2).
[0030]
In addition, the predetermined time for performing the valve opening control is calculated based on the pressure reduction amount calculated from the rotation speed of the gear pumps 10 and 11. Accordingly, it is possible to obtain an appropriate amount of pressure reduction according to the brake state, and it is possible to achieve stable brake control without giving the driver a sense of incongruity.
[0031]
Note that the excessive pressure increase prevention means may be performed only at the start of the first holding control during the ABS control. When ABS control is started, it is highly likely that the driver suddenly depresses the brake pedal, and the gear pumps 10 and 11 are rotating at a high speed, so that the wheel cylinder pressure tends to be excessively increased. That is, by applying the excessive pressure increase prevention means at this timing, it becomes possible to prevent the wheel cylinder pressure from being excessively increased very effectively. Therefore, braking without a sense of incongruity can be performed (corresponding to claim 3).
[0032]
In this embodiment, the one-way valves 18 and 19 are provided between the gear pumps 10 and 11 and the oil passages 32 and 33 connected to the wheel cylinders 8 and 9 without providing an electromagnetic valve or the like. That is, although the hydraulic pressure generated by the inertial force of the gear pumps 10 and 11 is supplied to the oil passages 32 and 33, the hydraulic pressure supplied by the overpressure preventing means can be reliably reduced, so that the cost is reduced. It also contributes to reduction.
[0033]
Further, for example, in the configuration described in Patent Document 1, the pressure reducing valve is not provided, and the pressure reducing, holding, and pressure increasing control is performed by changing the rotation direction of the pump, so that an accurate pressure reducing timing can be secured. Have difficulty. On the other hand, in the present embodiment, the gear pumps 10 and 11 are rotated only when the pressure is increased, and the pressure reducing and holding controls are performed by opening the pressure reducing valves 14 and 15. Therefore, the rotation direction of the pump motors 12 and 13 is one direction, and decompression, holding, and pressure increase control can be performed without providing a circuit configuration for controlling the rotation of the pump motors 12 and 13 in the reverse direction. .
[0034]
Furthermore, in the configuration described in Patent Document 1, since a switching valve such as a pressure reducing valve is not provided, pressure reduction at the time of excessive pressure increase is performed by reversing the pump rotation direction. There is a problem that the timing is delayed. On the other hand, in the present embodiment, when the pressure is excessively increased, the pressure reducing valves 14 and 15 are quickly switched to perform pressure reduction, so that it is possible to prevent excessive pressure increase with good timing.
[Brief description of the drawings]
FIG. 1 is a hydraulic circuit diagram for performing brake-by-wire control in an embodiment of the present invention.
FIG. 2 is a flowchart showing proportional control of the pressure reducing valve in the first embodiment.
FIG. 3 is a time chart showing proportional control of the pressure reducing valve in the first embodiment.
[Explanation of symbols]
1 Brake pedal 2 Stroke sensor 3 Master cylinder 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 Isolation valve 21 Reservoir 22, 23 Wheel cylinder pressure sensor

Claims (3)

A wheel cylinder that generates braking force on each wheel;
A pump driven by a pump motor and capable of supplying hydraulic pressure to the wheel cylinder;
A pressure reducing valve interposed in the middle of a brake circuit connecting the wheel cylinder and a reservoir for storing brake fluid, and capable of releasing the brake fluid in the wheel cylinder to the reservoir;
In the brake control device capable of reducing, maintaining, and increasing pressure of the wheel cylinder pressure by driving the pump and the pressure reducing valve,
A brake control device comprising an overpressure prevention means for preventing pressure generated by inertial rotation of the pump motor from acting on the wheel cylinder at least at the start of holding control during ABS control. The brake control device according to claim 1, wherein
The brake control device according to claim 1, wherein the excessive pressure increase preventing means is a means for opening the pressure reducing valve for a predetermined time. The brake control device according to claim 1 or 2,
The brake control device according to claim 1, wherein the over-pressurization preventing means is performed at the first holding control at the start of ABS control.

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