JP2010254261A - Brake control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve pedal feeling in brake operation. <P>SOLUTION: The brake control device includes: a wheel cylinder which gives a wheel a braking force with the supply of operating oil; a brake pedal which is operated by a driver; a master cylinder which can supply the operating oil pressured in according to the stepping on the brake pedal to the wheel cylinder; a master cut valve which is provided between the master cylinder and the wheel cylinder; and a master cylinder pressure sensor which detects oil pressure inside the master cylinder. The ECU opens the master cut valve if the detected oil pressure inside the master cylinder is not more than the predetermined value when the brake pedal is returned. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a brake control device that controls braking force applied to wheels provided in a vehicle.

  2. Description of the Related Art Conventionally, there is known a brake control device configured to pressurize a hydraulic pressure in a master cylinder in accordance with an operation amount of a brake pedal and supply the pressure to a wheel cylinder (for example, see Patent Document 1).

JP-A-11-286269

  By the way, the master cylinder used in such a brake control device is provided with a coupling and a groove for accommodating the coupling in order to seal the hydraulic oil in the master cylinder. In the master cylinder, a gap is usually formed between the coupling and the groove in a state where the coupling is accommodated in the groove in consideration of the air bleeding performance of the brake. By forming a gap between the coupling and the groove portion, the hydraulic oil can be satisfactorily sucked through the gap when air is released.

  However, when a gap is provided between the coupling and the groove in this way, the coupling slightly slides back and forth in the groove when the brake pedal is depressed and returned. This may cause a phenomenon in which the balance of the amount of oil discharged from the master cylinder does not match between when the brake pedal is depressed and when the brake pedal is returned, resulting in a negative pressure in the master cylinder immediately before the brake pedal is fully returned. When the pressure in the master cylinder becomes negative, the return speed of the brake pedal decreases, and there is a possibility that a feeling of strangeness may occur in the pedal feeling immediately before the brake pedal is fully returned.

  In particular, in a brake control device of a brake-by-wire (also referred to as an electronically controlled brake system), the master cylinder is not provided with a booster mechanism, so the reaction force of the return spring of the master cylinder is less than that of the vacuum booster brake. It is set small. Therefore, in the electronically controlled brake system, the return speed of the brake pedal is greatly reduced due to negative pressure, and the driver tends to feel uncomfortable with the pedal feeling.

  This invention is made | formed in view of such a condition, The objective is to provide the brake control apparatus which can improve the pedal feeling in brake operation.

  In order to solve the above problems, a brake control device according to an aspect of the present invention includes a wheel cylinder that applies a braking force to a wheel by supplying hydraulic oil, a brake pedal that is operated by a driver, and a depression of the brake pedal. A master cylinder capable of supplying hydraulic oil pressurized accordingly to the wheel cylinder, and an opening means for releasing the hydraulic pressure in the master cylinder when the brake pedal is returned.

  According to this aspect, since the negative pressure generated when the brake pedal is returned can be eliminated, the return speed of the brake pedal can be prevented from being lowered, and the pedal feeling can be improved.

  The above-described brake control device includes a master cut valve provided between the master cylinder and the wheel cylinder, and a power hydraulic pressure source capable of sending hydraulic oil pressurized by power supply independently from operation of the brake pedal. , The electromagnetic flow control valve provided between the power hydraulic source and the wheel cylinder, and when the brake pedal is depressed, the master cut valve is closed and the opening of the electromagnetic flow control valve is adjusted to adjust the wheel cylinder Control means for controlling the hydraulic pressure of the cylinder, and the release means is a means for detecting the hydraulic pressure in the master cylinder, and the detected hydraulic pressure in the cylinder when the brake pedal is returned is below a predetermined threshold value And a means for opening the master cut valve.

  According to this aspect, the negative pressure generated when the brake pedal is returned can be eliminated in the electronically controlled brake system. Thereby, the fall of the return speed of a brake pedal can be prevented, and pedal feeling can be improved.

  Further, in this aspect, since it is only necessary to control the timing at which the master cut valve is opened, there is no need to add new components or change the components in the existing electronically controlled brake system. Therefore, a brake control device with improved pedal feeling can be realized at low cost.

  ADVANTAGE OF THE INVENTION According to this invention, the brake control apparatus which can improve the pedal feeling in brake operation can be provided.

It is a figure which shows the structure of the brake control apparatus which concerns on embodiment of this invention. It is a figure for demonstrating the structure of a master cylinder. It is an enlarged view of the periphery of the fourth coupling. It is a figure for demonstrating the flow of the hydraulic fluid at the time of air bleeding of a brake. FIGS. 5A to 5H are diagrams for explaining a phenomenon in which the second master hydraulic chamber becomes negative pressure. It is a flowchart for demonstrating negative pressure generation | occurrence | production suppression control.

  The best mode for carrying out the present invention will be described below in detail with reference to the drawings.

  FIG. 1 is a diagram illustrating a configuration of a brake control device 10 according to an embodiment of the present invention. A brake control device 10 shown in FIG. 1 constitutes an electronically controlled brake system (ECB) for a vehicle, and optimally controls the brakes of the four wheels of the vehicle based on the amount of operation of the brake pedal 12 by the driver. Is.

  The brake pedal 12 is connected to a master cylinder 14 that sends hydraulic oil in response to a depression operation by the driver. The brake pedal 12 is provided with a stroke sensor 46 for detecting the depression stroke.

  The master cylinder 14 includes two hydraulic chambers, a first master hydraulic chamber 78 and a second master hydraulic chamber 80. The second master hydraulic chamber 80 of the master cylinder 14 is connected to a stroke simulator 24 that creates a pedal stroke in accordance with the depression force of the brake pedal 12 by the driver via the second output port 14b.

  A simulator cut valve 23 is provided in the middle of the flow path connecting the second master hydraulic chamber 80 of the master cylinder 14 and the stroke simulator 24. The simulator cut valve 23 is a normally-closed electromagnetic on-off valve that opens when energized during normal operation and closes when de-energized such as during an abnormality. The master cylinder 14 is connected to a reservoir tank 26 for storing hydraulic oil.

  The first master hydraulic chamber 78 of the master cylinder 14 is connected to the brake hydraulic control pipe 18 for the right front wheel via the first output port 14a, and the brake hydraulic control pipe 18 applies a braking force to the right front wheel. It is connected to the wheel cylinder 20FR for the right front wheel to be applied. Further, the second master hydraulic chamber 80 of the master cylinder 14 is connected to the brake hydraulic control pipe 16 for the left front wheel via the second output port 14b, and the brake hydraulic control pipe 16 controls the left front wheel. It is connected to a wheel cylinder 20FL for the left front wheel that applies power.

  A right master cut valve 22FR is provided in the middle of the brake hydraulic control pipe 18 for the right front wheel, and a left master cut valve 22FL is provided in the middle of the brake hydraulic control pipe 16 for the left front wheel. These right master cut valve 22FR and left master cut valve 22FL are both normally open solenoid valves that are open when not energized and switched to closed when energized.

  A right master pressure sensor 48FR for detecting the master cylinder pressure on the right front wheel side is provided in the middle of the brake hydraulic control pipe 18 for the right front wheel. A left master pressure sensor 48FL for measuring the master cylinder pressure on the left front wheel side is provided.

  In the brake control apparatus 10, when the brake pedal 12 is depressed by the driver, the stroke operation amount is detected by the stroke sensor 46. The master detected by the right master pressure sensor 48FR and the left master pressure sensor 48FL is detected. The depressing operation force (depressing force) of the brake pedal 12 can also be obtained from the cylinder pressure. As described above, it is preferable from the viewpoint of fail-safe that the master cylinder pressure is monitored by the two pressure sensors 48FR and 48FL on the assumption of the failure of the stroke sensor 46. Hereinafter, the right master pressure sensor 48FR and the left master pressure sensor 48FL are collectively referred to as a master cylinder pressure sensor 48 as appropriate.

  On the other hand, one end of a hydraulic supply / discharge pipe 28 is connected to the reservoir tank 26, and a suction port of an oil pump 34 driven by a motor 32 is connected to the other end of the hydraulic supply / discharge pipe 28. . The discharge port of the oil pump 34 is connected to a high pressure pipe 30, and an accumulator 50 and a relief valve 53 are connected to the high pressure pipe 30. In the present embodiment, a reciprocating pump having two or more pistons (not shown) that are reciprocally moved by the motor 32 is employed as the oil pump 34. As the accumulator 50, an accumulator 50 that converts the pressure energy of hydraulic oil into pressure energy of an enclosed gas such as nitrogen is stored.

  The accumulator 50 stores the hydraulic oil whose pressure has been increased to about 14 to 22 MPa by the oil pump 34, for example. Further, the valve outlet of the relief valve 53 is connected to the hydraulic supply / exhaust pipe 28. When the pressure of the hydraulic oil in the accumulator 50 increases abnormally to, for example, about 25 MPa, the relief valve 53 is opened and the high pressure operation is performed. The oil is returned to the hydraulic supply / discharge pipe 28. Further, the high-pressure pipe 30 is provided with an accumulator pressure sensor 51 that detects an outlet pressure of the accumulator 50, that is, a pressure of hydraulic oil in the accumulator 50. The motor 32, the oil pump 34, the accumulator 50, and the like function as a hydraulic power source that can send hydraulic oil pressurized by the power supply independently from the operation of the brake pedal 12.

  The high-pressure pipe 30 is connected to the right front wheel wheel cylinder 20FR, the left front wheel wheel cylinder 20FL, the right rear wheel wheel cylinder 20RR, and the left rear wheel through the pressure increasing valves 40FR, 40FL, 40RR, 40RL. It is connected to the cylinder 20RL. Hereinafter, the wheel cylinders 20FR to 20RL will be collectively referred to as “wheel cylinders 20”, and the pressure increase valves 40FR to 40RL will be appropriately collectively referred to as “pressure increase valves 40”. Each of the pressure increasing valves 40 is a normally closed electromagnetic flow control valve (linear valve) that is closed when not energized and is used to increase the pressure of the wheel cylinder 20 as necessary. A disc brake unit is provided for each wheel of the vehicle (not shown), and each disc brake unit generates a braking force by pressing the brake pad against the disc by the action of the wheel cylinder 20.

  Further, the wheel cylinder 20FR for the right front wheel and the wheel cylinder 20FL for the left front wheel are connected to the hydraulic supply / discharge pipe 28 via the pressure reducing valve 42FR or 42FL, respectively. The pressure reducing valves 42FR and 42FL are normally closed electromagnetic flow control valves (linear valves) used for pressure reduction of the wheel cylinders 20FR and 20FL as necessary. On the other hand, the wheel cylinder 20RR for the right rear wheel and the wheel cylinder 20RL for the left rear wheel are connected to the hydraulic supply / discharge pipe 28 via a pressure reducing valve 42RR or 42RL which is a normally open electromagnetic flow control valve. . Hereinafter, the pressure reducing valves 42FR to 42RL are collectively referred to as “pressure reducing valve 42” as appropriate.

  Wheel cylinders for detecting the wheel cylinder pressure, which is the pressure of the hydraulic oil acting on the corresponding wheel cylinder 20, in the vicinity of the wheel cylinders 20FR to 20RL for the right front wheel, the left front wheel, the right rear wheel, and the left rear wheel Pressure sensors 44FR, 44FL, 44RR and 44RL are provided. Hereinafter, the wheel cylinder pressure sensors 44FR to 44RL are collectively referred to as “wheel cylinder pressure sensor 44” as appropriate.

  The right master cut valve 22FR and the left master cut valve 22FL, the pressure increasing valves 40FR to 40RL, the pressure reducing valves 42FR to 42RL, the oil pump 34, the accumulator 50, and the like constitute the hydraulic actuator 100 of the brake control device 10. The hydraulic actuator 100 is controlled by an electronic control unit (hereinafter referred to as “ECU”) 200.

  The ECU 200 functions as a control unit that controls the wheel cylinder pressure in the wheel cylinders 20FR to 20RL. The ECU 200 is a nonvolatile memory such as a CPU that executes various arithmetic processes, a ROM that stores various control programs, a RAM that is used as a work area for data storage and program execution, and a backup RAM that can retain stored contents even when the engine is stopped. An A / D converter for converting an analog signal input from a memory, an input / output interface, various sensors, and the like into a digital signal and taking it in, a timer for timing, and the like are provided.

  The ECU 200 is electrically connected to various actuators including the hydraulic actuator 100 such as the right master cut valve 22FR, the left master cut valve 22FL, the simulator cut valve 23, the pressure increasing valves 40FR to 40RL, and the pressure reducing valves 42FR to 42RL. ing.

  The ECU 200 is electrically connected to various sensors / switches that output signals for use in control. That is, a signal indicating the wheel cylinder pressure in the wheel cylinders 20FR to 20RL is input to the ECU 200 from the wheel cylinder pressure sensors 44FR to 44RL.

  Further, a signal indicating the pedal stroke of the brake pedal 12 is input from the stroke sensor 46 to the ECU 200, and signals indicating the master cylinder pressure are input from the right master pressure sensor 48FR and the left master pressure sensor 48FL, and from the accumulator pressure sensor 51. A signal indicating the accumulator pressure is input.

  Further, although not shown, ECU 200 receives a signal indicating the wheel speed of each wheel from a wheel speed sensor installed for each wheel, a signal indicating a yaw rate from the yaw rate sensor, and a steering wheel from the steering angle sensor. A signal indicating the steering angle is input.

  In the brake control device 10 configured as described above, when the brake pedal 12 is depressed by the driver, the ECU 200 calculates the target deceleration of the vehicle from the pedal stroke representing the depression amount of the brake pedal 12 and the master cylinder pressure. Then, a target hydraulic pressure that is a target value of the wheel cylinder pressure of each wheel is obtained in accordance with the calculated target deceleration. Then, the ECU 200 controls the opening degree of the pressure increasing valve 40 and the pressure reducing valve 42 so that the wheel cylinder pressure of each wheel becomes the target hydraulic pressure.

  On the other hand, at this time, the right master cut valve 22FR and the left master cut valve 22FL are closed, and the simulator cut valve 23 is opened. Therefore, the hydraulic oil sent from the master cylinder 14 by the depression of the brake pedal 12 by the driver flows into the stroke simulator 24 through the simulator cut valve 23.

  When the accumulator pressure is less than the lower limit value of the preset control range, the oil pump 34 is driven by the ECU 200 to increase the accumulator pressure. When the accumulator pressure enters the control range, the drive of the oil pump 34 is stopped. Is done.

  FIG. 2 is a diagram for explaining the configuration of the master cylinder 14. In the present embodiment, the master cylinder 14 is configured integrally with the stroke simulator 24.

  In the master cylinder 14, a first piston 62 and a second piston 64 are slidably accommodated in a master cylinder hole 61 formed in the master cylinder body 60. By inserting the two pistons into the master cylinder hole 61 in this way, a first master hydraulic chamber 78 is formed between the first piston 62 and the second piston 64, and the second piston 64 and the master cylinder hole 61. A second master hydraulic chamber 80 is formed between the bottom of the first master hydraulic chamber 80 and the second master hydraulic chamber 80. The stroke simulator 24 is disposed in the second master hydraulic chamber 80 so as to communicate therewith.

  The master cylinder hole 61 is a cylindrical hole whose front is closed. A first annular groove 81 and a second annular groove 82 are formed on the inner peripheral surface of the master cylinder hole 61 near the position where the first piston 62 is disposed. A first coupling 71 is accommodated in the first annular groove 81 located at the rear, and a second coupling 72 is accommodated in the second annular groove 82 located at the front. In this specification, “front” refers to the direction in which the first piston 62 moves when the brake pedal is depressed, and “rear” refers to a predetermined initial state after the depression of the brake pedal is released. This is the direction in which the first piston 62 moves when the position returns.

  The first coupling 71 and the second coupling 72 are cross-sectional cup-shaped seal members formed of an elastic material such as rubber. The first coupling 71 and the second coupling 72 are provided so that the inner surface of the cup faces the front, and the first atmospheric pressure chamber 75 is provided between the first coupling 71 and the second coupling 72. Is formed.

  A third annular groove 83 and a fourth annular groove 84 are formed on the inner peripheral surface of the master cylinder hole 61 near the position where the second piston 64 is disposed. A third coupling 73 is accommodated in the third annular groove 83 located at the rear, and a fourth coupling 74 is accommodated in the fourth annular groove 84 located at the front.

  The third coupling 73 is provided such that the inner side surface of the cup faces rearward, and the fourth coupling 74 is provided such that the inner side surface of the cup faces frontward. A second atmospheric pressure chamber 76 is formed between the third coupling 73 and the fourth coupling 74.

  Further, on the inner peripheral surface of the master cylinder hole 61, the first input port 85 that communicates the first atmospheric pressure chamber 75 and the reservoir tank (not shown), and the second atmospheric pressure chamber 76 and the reservoir tank are communicated. A second input port 86 is formed.

  The first piston 62 is provided with a piston rod 70 that connects the first piston 62 and a brake pedal (not shown) at the rear end. A first cylindrical portion 89 that opens forward is formed at the front end of the first piston 62. A first relief port 87 that communicates the inside and the outside of the first tubular portion 89 is formed on the side surface of the first tubular portion 89. The second piston 64 also has a second cylindrical portion 90 that opens forward at the front end. A second relief port 88 that communicates the inside and the outside of the second cylindrical portion 90 is formed on the side surface of the second cylindrical portion 90.

  A first spring 66 is provided between the first piston 62 and the second piston 64 via a retainer 91, and a second spring 68 is provided between the second piston 64 and the bottom of the master cylinder hole 61. Is provided.

  As described above, the stroke simulator 24 creates a pedal stroke according to the depression force of the brake pedal by the driver. In the stroke simulator 24, a piston 162 is slidably accommodated in a stroke simulator hole 161 formed in the stroke simulator body 160 via a coupling 172. In the present embodiment, stroke simulator body 160 is formed integrally with master cylinder body 60.

  In the stroke simulator 24, a simulator hydraulic chamber 178 and a simulator atmospheric pressure chamber 180 are formed in the stroke simulator body 160 by a piston 162. The simulator atmospheric pressure chamber 180 is provided with a first simulator spring 166 and a second simulator spring 167 so as to urge the piston 162 toward the simulator hydraulic chamber 178 side. The simulator hydraulic chamber 178 of the stroke simulator 24 communicates with the second master hydraulic chamber 80 of the master cylinder 14 via the brake hydraulic control pipe 16. The simulator atmospheric pressure chamber 180 of the stroke simulator 24 communicates with the reservoir tank via an output port (not shown). 2, illustration of a simulator cut valve provided between the master cylinder 14 and the stroke simulator 24, a first output port communicating with the first master hydraulic chamber 78, and the like is omitted.

  FIG. 3 is an enlarged view around the fourth coupling 74. When the brake pedal is not depressed and the second piston 64 is in the initial position, the rear end portion of the fourth coupling 74 is positioned in front of the rear end portion of the second relief port 88 as shown in FIG. is doing. That is, the opening of the second relief port 88 is not covered by the inner peripheral surface of the fourth coupling 74, and the second master hydraulic chamber 80 communicates with the second atmospheric pressure chamber 76. Here, the interval from the rear end portion of the fourth coupling 74 to the rear end portion of the second relief port 88 is referred to as a port idle Dpi.

  When the brake pedal is depressed to move the second piston 64 forward and the port idle Dpi is closed, the opening of the second relief port 88 is covered by the inner peripheral surface of the fourth coupling 74, and the second master hydraulic chamber 80 And the communication with the second atmospheric pressure chamber 76 are blocked. As a result, a positive pressure is generated in the second master hydraulic chamber 80, the target hydraulic pressure of the wheel cylinder pressure is set as described above, and the pressure increasing valve 40 and the pressure reducing valve 42 of each wheel are controlled using the target hydraulic pressure as a target value. The Further, the piston 162 of the stroke simulator 24 is pushed against the urging force of the first simulator spring 166 and the second simulator spring 167 by the generated positive pressure, and the pedal is depressed by the first simulator spring 166 and the second simulator spring 167. Reaction force is created.

  In the master cylinder 14, the groove width of the fourth annular groove portion 84 is slightly larger than the width of the fourth coupling 74. Therefore, as shown in FIG. 3, a gap 92 is formed between the side surface of the fourth annular groove 84 and the fourth coupling 74 in a state where the fourth coupling 74 is accommodated in the fourth annular groove 84.

  In the master cylinder 14, the inner peripheral surface of the fourth coupling 74 is in contact with the outer peripheral surface 90a of the second cylindrical portion 90 of the second piston 64, and the outer peripheral surface of the fourth coupling 74 is the fourth. It is in contact with the bottom surface 84 a of the annular groove 84. The frictional force acting when the second piston 64 moves is greater than the contact portion 93 between the outer peripheral surface of the fourth coupling 74 and the bottom surface 84a of the fourth annular groove portion 84, and the inner peripheral surface of the fourth coupling 74. The contact portion 94 between the second piston 64 and the outer peripheral surface 90a of the second cylindrical portion 90 is formed to be larger.

  Therefore, when the second piston 64 moves, the fourth coupling 74 is dragged by the second cylindrical portion 90 of the second piston 64 and moves in the fourth annular groove portion 84. By the movement of the fourth coupling 74, the gap 92 is formed on the front side, the rear side, or both the front side and the rear side according to the position of the fourth coupling 74 in the fourth annular groove portion 84. .

  FIG. 4 is a diagram for explaining the flow of hydraulic oil when the brake is bleeding. In FIG. 4, the arrow represents the flow of hydraulic oil. When the air is released from the brake, the fourth coupling 74 is positioned so that a gap 92 is formed on both the front side and the rear side of the fourth coupling 74. Further, the outer lip portion 74 a of the fourth coupling 74 is bent inward, and a gap is formed between the bottom surface of the fourth annular groove portion 84 and the outer peripheral surface of the fourth coupling 74. Brake air can be released by sucking the hydraulic oil from the reservoir tank through the gap around the fourth coupling 74 thus formed. As described above, in order to ensure the suction performance of the hydraulic oil during air bleeding, it is necessary to form the gap 92 between the side surface of the fourth annular groove 84 and the fourth coupling 74.

  However, when the gap 92 is provided between the side surface of the fourth annular groove 84 and the fourth coupling 74, the fourth coupling 74 moves back and forth in the fourth annular groove 84 when the brake pedal is depressed and returned. Slide slightly. For this reason, the balance of the amount of oil discharged from the master cylinder 14 does not match between when the brake pedal is depressed and when the brake pedal is returned, and a phenomenon occurs in which the pressure inside the master cylinder 14 becomes negative just before the brake pedal is fully returned.

  FIGS. 5A to 5H are diagrams for explaining a phenomenon in which the inside of the master cylinder 14 becomes negative pressure. First, a phenomenon when the brake pedal is depressed will be described with reference to FIGS.

  FIG. 5A shows a state where the brake pedal is not depressed and the second piston 64 is in the initial position. At this time, the second master hydraulic chamber 80 is at atmospheric pressure because the second master hydraulic chamber 80 communicates with the second atmospheric pressure chamber 76 via the second relief port 88.

  FIG. 5B shows a state in which when the brake pedal is depressed, the second relief port 88 moves forward and the fourth coupling 74 moves forward by being dragged by the second piston 64. At this time, the second master hydraulic chamber 80 is at atmospheric pressure because the second master hydraulic chamber 80 is still in communication with the second atmospheric pressure chamber 76 via the second relief port 88.

  FIG. 5C shows a state in which the second relief port 88 moves forward until the opening of the second relief port 88 is covered with the inner peripheral surface of the fourth coupling 74, that is, until the port idle is closed. . Until the port idle is closed, the hydraulic pressure in the second master hydraulic chamber 80 is atmospheric pressure.

  FIG. 5D shows a state in which the second relief port 88 further moves forward after the port idle is closed. At this time, since communication between the second master hydraulic chamber 80 and the second atmospheric pressure chamber 76 is blocked, a positive pressure is generated in the second master hydraulic chamber 80, and hydraulic oil is discharged from the master cylinder 14. Further, the positive pressure in the second master hydraulic chamber 80 causes the fourth coupling 74 to receive a rearward force and move rearward.

  Next, the phenomenon when the brake pedal is returned will be described with reference to FIGS.

  FIG. 5E shows a state when the brake pedal is started to be returned. When the brake pedal is returned, the second piston 64 moves rearward by the biasing force of the second spring. At this time, the hydraulic oil begins to return to the master cylinder 14, and the positive pressure in the second master hydraulic chamber 80 gradually decreases.

  FIG. 5F shows a state in the middle of returning the brake pedal. At this time, since the fourth coupling 74 has moved rearward, the balance of the discharge oil amount of the master cylinder 14 matches before the second relief port 88 moves to the position at which the port idle opens, and the first 2 The inside of the master hydraulic chamber 80 is at atmospheric pressure.

  FIG. 5G shows a state immediately before the brake pedal returns to the initial position. At this time, the second relief port 88 is retracted to the position when the port idle is opened. Since the second piston 64 is further retracted from the stage of FIG. 5 (f) where the inside of the second master hydraulic chamber 80 is at atmospheric pressure, negative pressure is generated in the second master hydraulic chamber 80. Yes.

  FIG. 5 (h) shows the state when the brake pedal returns to the initial position. At this time, the second master hydraulic chamber 80 is at atmospheric pressure because the second master hydraulic chamber 80 communicates with the second atmospheric pressure chamber 76 via the second relief port 88.

  As described above with reference to FIGS. 5A to 5H, when a gap is provided between the side surface of the fourth annular groove 84 and the fourth coupling 74, the brake pedal returns to the initial position. A phenomenon occurs in which the pressure in the second master hydraulic chamber 80 becomes negative just before it is possible. In the above description, the phenomenon in which negative pressure is generated in the second master hydraulic chamber 80 has been described. However, negative pressure is generated in the first master hydraulic chamber 78 as well. That is, the master cylinder 14 pressure becomes a negative pressure. When the master cylinder pressure becomes negative, the return speed of the brake pedal decreases, and there is a possibility that a feeling of strangeness may occur in the pedal feeling immediately before the brake pedal is fully returned. Therefore, in the brake control device 10 according to the present embodiment, negative pressure generation suppression control is performed.

  FIG. 6 is a flowchart for explaining negative pressure generation suppression control. The control according to the flowchart shown in FIG. 6 is repeatedly executed every predetermined time.

  First, the ECU 200 determines whether or not the brake pedal 12 has been returned based on the pedal stroke information detected by the stroke sensor 46 (S10). If the brake pedal 12 has not been returned (N in S10), the control flow ends.

  When the brake pedal 12 is returned (Y in S10), the ECU 200 determines whether or not the master cylinder pressure detected by the right master pressure sensor 48FR and / or the left master pressure sensor 48FL is equal to or less than a predetermined threshold value Pth. Determine (S12). This threshold value Pth may be set to a value slightly higher than atmospheric pressure, for example, about 0.1 to 0.3 Pa higher than atmospheric pressure, in order to reliably prevent the master cylinder pressure from becoming negative. preferable. If the master cylinder pressure is greater than the threshold value Pth (N in S12), the control flow is terminated.

  When the master cylinder pressure is equal to or less than the threshold value Pth (Y in S12), the ECU 200 determines whether the pedal stroke is equal to or less than a predetermined threshold value Sth based on the pedal stroke information detected by the stroke sensor 46 (S14). ). This threshold value Sth is set to a stroke amount immediately before the brake pedal 12 has completely returned, that is, a stroke amount slightly larger than zero. In the present embodiment, by confirming the pedal stroke in this way, it is surely determined whether or not it is immediately before the brake pedal 12 is fully returned. If the pedal stroke is greater than the threshold value Sth (N in S14), the control flow is terminated.

  When the pedal stroke is equal to or less than the threshold value Sth (Y in S14), the ECU 200 opens the pressure reducing valve 42 (S16). Subsequently, the ECU 200 opens the right master cut valve 22FR and the left master cut valve 22FL that have been closed after the brake pedal 12 is depressed (S18). Accordingly, the first master hydraulic chamber 78 and the second master hydraulic chamber 80 of the master cylinder 14 are communicated with the reservoir tank 26 via the hydraulic supply / discharge pipe 28, so that the hydraulic pressure in the master cylinder 14 is released. That is, the master cylinder pressure becomes atmospheric pressure, and the generation of negative pressure is suppressed.

  As described above, according to the negative pressure generation suppression control according to the present embodiment, by opening the pressure reducing valve 42, the right master cut valve 22FR, and the left master cut valve 22FL immediately before the brake pedal 12 has completely returned, Since the hydraulic pressure in the master cylinder 14 is released, the negative pressure generated when the brake pedal 12 is returned can be eliminated.

  In the electronically controlled brake system, since the master cylinder 14 is not provided with a booster mechanism, the reaction force of the first spring 66 and the second spring 68 of the master cylinder 14 is set smaller than that of the vacuum booster brake. Therefore, in a normal electronically controlled brake system, the return speed of the brake pedal 12 is greatly reduced due to negative pressure, and the driver tends to feel uncomfortable with the pedal feeling. However, according to the brake control device 10 according to the present embodiment, since the generation of negative pressure is suppressed, it is possible to prevent the return speed of the brake pedal 12 from being lowered and to improve the pedal feeling.

  In this embodiment, it is only necessary to control the opening timing of the pressure reducing valve 42, the right master cut valve 22FR, and the left master cut valve 22FL. There is no need to change the element. Therefore, the brake control apparatus 10 with improved pedal feeling can be realized at a low cost.

  The present invention has been described above based on the embodiment. It should be understood by those skilled in the art that these embodiments are exemplifications, and that various modifications can be made to the combination of each component and each processing process, and such modifications are also within the scope of the present invention.

  In the above-described embodiment, the case where the present invention is applied to an electronically controlled brake system has been described, but the present invention provides an opening means for releasing the hydraulic pressure in the master cylinder when the brake pedal is returned, For example, it can be applied to a vacuum booster and a brake.

  10 brake control device, 12 brake pedal, 14 master cylinder, 26 reservoir tank, 34 oil pump, 40 pressure increasing valve, 42 pressure reducing valve, 48FL left master pressure sensor, 48FR right master pressure sensor, 50 accumulator, 66 first spring, 68 Second spring, 71 First coupling, 72 Second coupling, 73 Third coupling, 74 Fourth coupling, 75 First atmospheric pressure chamber, 76 Second atmospheric pressure chamber, 78 First master hydraulic chamber, 80 A second master hydraulic chamber; 81 a first annular groove; 82 a second annular groove; 83 a third annular groove; 84 a fourth annular groove.

Claims (2)

A wheel cylinder that applies braking force to the wheel by supplying hydraulic oil;
A brake pedal operated by the driver;
A master cylinder capable of supplying hydraulic oil pressurized in response to depression of the brake pedal to the wheel cylinder;
Opening means for releasing the hydraulic pressure in the master cylinder when the brake pedal is returned;
A brake control device comprising: A master cut valve provided between the master cylinder and the wheel cylinder;
A hydraulic power source capable of sending hydraulic oil pressurized by the supply of power independently from the operation of the brake pedal;
An electromagnetic flow control valve provided between the power hydraulic source and the wheel cylinder;
Control means for closing the master cut valve when the brake pedal is depressed and controlling the hydraulic pressure of the wheel cylinder by adjusting the opening of the electromagnetic flow control valve;
The opening means is
Means for detecting the hydraulic pressure in the master cylinder;
Means for opening the master cut valve when the detected hydraulic pressure in the master cylinder is less than or equal to a predetermined threshold when the brake pedal is returned;
The brake control device according to claim 1, further comprising:

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