JP5223301B2 - Brake control device - Google Patents

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 In recent years, many electronically controlled brake systems that control the braking force of each wheel so as to give an optimal braking force to the vehicle according to the traveling state of the vehicle have been adopted as a braking device in the vehicle. In such an electronically controlled brake system, an electromagnetic flow control valve is used to monitor the wheel cylinder pressure of each wheel by a pressure sensor and to achieve a target hydraulic pressure calculated based on the brake pedal operation amount of the driver. (See, for example, Patent Document 1).
JP 2004-322843 A

  By the way, such an electronically controlled brake system is usually provided with a liquid level detecting device for detecting the liquid level of the reservoir tank in order to monitor the fluid amount in the reservoir tank. When the liquid level detecting device detects that the liquid level is lower than a predetermined reference liquid level, it is determined that fluid leakage has occurred.

  In the electronically controlled brake system, it is preferable to ensure a sufficient capacity of the reservoir tank in order to provide a sufficient margin for the operation of the liquid level detecting device. If the capacity of the reservoir tank cannot be secured sufficiently, the fluid level detection device will not operate until the liquid level detection device is activated due to variations in fluid injection at the time of shipment from the factory, fluid contraction due to temperature changes in the engine room, and changes in accumulator pressure accumulation. Even if the liquid level is not reduced due to fluid leakage and the fluid level is lowered due to wear of the brake pads, the fluid level detection device detects the fluid leakage. There is a possibility.

  In order to prevent such misjudgment of liquid leakage due to wear of the brake pad, it is conceivable to set the reference liquid level for judging liquid leakage lower than the liquid level that decreases due to wear of the brake pad. May not be able to generate the necessary braking force because sufficient fluid does not remain in the reservoir tank after detecting a liquid leak.

  However, for example, in a small car, it may be difficult to provide a large-capacity reservoir tank due to a problem of engine room space. In recent years, in order to protect pedestrians in the event of a vehicle collision, there is also a demand for ensuring a sufficient space between the hood and the reservoir tank in the engine room, and it has become difficult to provide a large-capacity reservoir tank. Yes.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a brake control device capable of reducing the size of a reservoir tank.

In order to solve the above problems, a brake control device according to an aspect of the present invention includes a plurality of wheel cylinders that apply braking force to a wheel by supplying fluid, a brake operation member that is operated by a driver, and a brake operation member. A master cylinder that generates hydraulic pressure in accordance with the amount of operation, a master cut valve that shuts off the communication between the master cylinder and the wheel cylinder, a reservoir tank that is connected to the master cylinder and that stores fluid, and is connected to the reservoir tank. Further, a pump for pressurizing the fluid, an accumulator for storing the fluid pressurized by the pump, an accumulator pressure control unit for controlling the hydraulic pressure of the accumulator by controlling the pump, and a wheel cylinder and an accumulator are provided. An electromagnetic flow control valve for controlling the hydraulic pressure of the wheel cylinder; Solenoid valve control unit for controlling the operation of the stut cut valve and the electromagnetic flow control valve, a liquid level detection device for detecting the liquid level of the reservoir tank, and a liquid leak detection means for detecting whether or not a liquid leak has occurred And comprising. The accumulator pressure control unit detects that the liquid level of the reservoir tank has become lower than a predetermined reference liquid level by the liquid level detecting device , and the occurrence of liquid leakage is detected by the liquid leak detecting means. If not , increase the fluid pressure of the accumulator more than before the detection of the liquid level drop, and if the fluid leakage detection unit detects that a fluid leakage has occurred after that, the fluid pressure of the accumulator Less than.

  According to this aspect, the liquid level detection device does not determine that the liquid leak has occurred but has actually detected whether or not the liquid leak has occurred. Even if the reservoir tank is downsized, it is possible to suppress erroneous determination of liquid leakage.

  Also, when the liquid level is detected by the liquid level detector, the accumulator fluid pressure is increased from that before the liquid level drop is detected to temporarily increase the accumulated pressure, and then the actual liquid leakage When the occurrence of spillage is detected, the hydraulic pressure of the accumulator is reduced from before the leak detection, and the stored fluid is used for braking, so an appropriate braking force is generated even after the leak. be able to. Since the accumulator is used as a temporary fluid holding means when the liquid level is lowered, it is not necessary to enlarge the reservoir tank in normal times, and the reservoir tank can be downsized.

  When the leak detection unit detects that a leak has occurred, the solenoid valve control unit applies the hydraulic pressure from the master cylinder to some of the wheel cylinders, and the remaining wheel cylinders. May control the master cut valve and the electromagnetic flow control valve so that the hydraulic pressure is applied from the accumulator.

  The pump is driven by a motor, and the accumulator pressure control unit drives the motor when the accumulator hydraulic pressure is lower than a predetermined motor on pressure, and stops the motor when the accumulator hydraulic pressure is higher than the predetermined motor off pressure. The hydraulic pressure of the accumulator may be controlled.

The accumulator pressure control unit detects that the liquid level of the reservoir tank has become lower than a predetermined reference liquid level by the liquid level detecting device , and the occurrence of liquid leakage is detected by the liquid leak detecting means. If not , change the motor-on pressure and motor-off pressure to higher values than before the liquid level drop detection, and then detect that the liquid leak is detected by the liquid leak detector. The pressure may be changed to a value lower than that before detecting the liquid leak.

  ADVANTAGE OF THE INVENTION According to this invention, the brake control apparatus which can reduce a reservoir tank can be provided.

  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 showing 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 brakes the four wheels of the vehicle based on the operation amount of the brake pedal 12 as a brake operation member. It is something to control.

  The brake pedal 12 is connected to a master cylinder 14 that generates a hydraulic pressure in accordance with the depression operation by the driver. When the brake pedal 12 is depressed, the master cylinder 14 sends out fluid as a working fluid. The brake pedal 12 is provided with a stroke sensor 46 for detecting the depression stroke.

  A stroke simulator 24 that creates a reaction force according to the operating force of the brake pedal 12 by the driver is connected to one output port 14 a of the master cylinder 14. A simulator cut valve 23 is provided in the middle of the flow path connecting the master cylinder 14 and the stroke simulator 24. The simulator cut valve 23 is a normally closed electromagnetic on-off valve that is closed when not energized and is switched to an open state when an operation of the brake pedal 12 by the driver is detected.

  The master cylinder 14 is connected to a reservoir tank 26 for storing fluid. Although the detailed configuration of the reservoir tank 26 will be described later, the reservoir tank 26 is provided with a liquid level detecting device for detecting the fluid level of the fluid in the reservoir tank 26.

  A brake hydraulic control pipe 16 for the right front wheel is connected to one output port 14a of the master cylinder 14, and the brake hydraulic control pipe 16 is for the right front wheel that applies a braking force to the right front wheel (not shown). It is connected to the wheel cylinder 20FR. A brake hydraulic control pipe 18 for the left front wheel is connected to the other output port 14b of the master cylinder 14, and the brake hydraulic control pipe 18 applies a braking force to the left front wheel (not shown). Is connected to the wheel cylinder 20FL.

  A right master cut valve 22FR is provided in the middle of the brake hydraulic control pipe 16 for the right front wheel, and a left master cut valve 22FL is provided in the middle of the brake hydraulic control pipe 18 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 16 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 fluid pressure energy into the pressure energy of an enclosed gas such as nitrogen and stores the fluid is employed.

  The accumulator 50 stores fluid that has been pressurized to, for example, about 14 to 22 MPa by the oil pump 34. Further, the valve outlet of the relief valve 53 is connected to the hydraulic supply / discharge pipe 28. When the fluid pressure in the accumulator 50 increases abnormally to, for example, about 25 MPa, the relief valve 53 is opened, and the high-pressure fluid is It 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 fluid pressure in the accumulator 50. The detailed configuration of the accumulator 50 will be described later.

  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.

  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, a wheel cylinder pressure that detects a wheel cylinder pressure, which is a fluid pressure acting on the corresponding wheel cylinder 20, respectively. 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 80 of the brake control device 10. The hydraulic actuator 80 is controlled by an electronic control unit (hereinafter referred to as “ECU”) 200.

  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 above-described master cut valves 22FR and 22FL, simulator cut valve 23, pressure increasing valves 40FR to 40RL, pressure reducing valves 42FR to 42RL, and other hydraulic actuators 80.

  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, the ECU 200 receives a signal indicating the fluid level of fluid from the liquid level detecting device provided in the reservoir tank 26. The ECU 200 is connected to a warning lamp 54 for notifying the driver of a decrease in the liquid level of the reservoir tank 26.

  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 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 master cut valves 22FR and 22FL are closed, and the simulator cut valve 23 is opened. Therefore, the fluid 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.

  FIG. 2 is a diagram for explaining the operation of the brake control device 10 at the normal time. FIG. 2 shows the configuration around the reservoir tank 26 and the accumulator 50. Here, the normal time means a state in which no fluid leaks in the brake control device 10 and sufficient fluid is secured in the reservoir tank 26.

  The main body 140 of the reservoir tank 26 is formed of a synthetic resin and is formed in a bottomed cylindrical shape capable of storing fluid therein. An opening 144 for injecting fluid is formed in the upper part of the main body 140. A cap 142 for closing the opening 144 is fitted and fixed to the opening 144.

  The reservoir tank 26 is provided with a level lowering switch 100 as a liquid level detecting device for detecting the fluid level L of the fluid in the reservoir tank 26. The level lowering switch 100 transmits a liquid level lowering signal to the ECU 200 when the fluid level L of the fluid becomes lower than a predetermined reference liquid level Ls. As the level lowering switch 100, a known one can be used. For example, one that detects the height of the liquid surface using a float or one that optically detects the height of the liquid surface can be used. In the present embodiment, when the magnet fitted in the float passes the reference liquid level Ls, it is switched from the OFF state to the ON state. The reference liquid level Ls is set so as to secure a fluid amount that can stably apply an appropriate braking force to the four wheel cylinders 20. Since the optimal reference liquid level Ls varies depending on the reservoir tank 26 and the hydraulic actuator 80, it may be determined by experiments and simulations as appropriate.

  A first partition 128 and a second partition 130 are formed upward from the bottom surface of the main body 140. The first partition wall 128 and the second partition wall 130 are formed so that the height of the upper end portion is lower than the reference liquid level Ls.

  The first partition 128 and the second partition 130 divide the internal space below the reference liquid level Ls of the main body 140 into three spaces. In other words, the first fluid storage chamber 116 is formed by the first partition wall 128 and the side wall of the main body 140, and the second fluid storage chamber 118 is formed by the first partition wall 128 and the second partition wall 130. A pump chamber 120 is formed by 130 and the side wall of the main body 140.

  A first connecting portion 122 for communicating the first fluid storage chamber 116 with one output port 14 a of the master cylinder 14 is formed on the bottom surface of the first fluid storage chamber 116. A second connection portion 124 is formed on the bottom surface of the second fluid storage chamber 118 to allow the second fluid storage chamber 118 to communicate with the other output port 14 b of the master cylinder 14. On the bottom surface of the pump chamber 120, a third connection portion 126 for communicating the pump chamber 120 with the suction port of the oil pump 34 is formed.

  As shown in FIG. 2, the accumulator 50 is a bellows type and includes a housing 168 and a bellows 160. One end of the bellows 160 is airtightly attached to the housing 168, and an end plate 165 is attached to the other end. By the end plate 165, the internal space of the housing 168 is partitioned into two spaces. In the present embodiment, the inside of the bellows 160 is a gas chamber 164 in which high-pressure gas is accommodated, and the space opposite to the space where the bellows 160 exists is the oil pump of the two spaces partitioned by the end plate 165. The high-pressure fluid discharged from 34 is used as a pressure accumulation chamber 162 in which the fluid is stored under pressure. A high pressure pipe 30 is connected to the pressure accumulating chamber 162, and fluid is sent from the oil pump 34 to the pressure accumulating chamber 162 through the high pressure pipe 30 to accumulate pressure.

  The accumulator pressure P, which is the hydraulic pressure of the accumulator 50, is controlled by the ECU 200. That is, the ECU 200 functions as an accumulator pressure control unit that controls the accumulator pressure P. The accumulator pressure P is detected by the accumulator pressure sensor 51.

  The ECU 200 controls the motor 32 that drives the oil pump 34 so that the accumulator pressure P falls within a range between a predetermined motor-on pressure PON and a predetermined motor-off pressure POFF. That is, when the accumulator pressure P is smaller than the motor-on pressure PON, the ECU 200 drives the oil pump 34 by rotating the motor 32 and increases the accumulator pressure P. On the other hand, when the accumulator pressure P is larger than the motor off pressure POFF, the drive of the oil pump 34 is stopped by stopping the rotation of the motor 32. In this way, a hydraulic pressure equal to or higher than a predetermined value is always accumulated in the accumulator 50.

  In the normal operation of the brake control device 10 shown in FIG. 2, the motor-on pressure PON is set to the standard motor-on pressure PONMed, and the motor-off pressure POFF is set to the standard motor-off pressure POFFMed. Accordingly, the ECU 200 operates the motor 32 so that the accumulator pressure P falls within the range of the standard motor on pressure PONMed and the standard motor off pressure POFFMed. By controlling the motor 32 in this way, as shown in FIG. 2, the pressure accumulation amount V of the accumulator 50 is equal to or greater than the standard motor-on pressure accumulation amount VONMed, which is a pressure accumulation amount corresponding to the standard motor-on pressure PONMed. Is kept within a range equal to or less than the standard motor-off pressure accumulation amount VOFFMed.

  In a normal state, the ECU 200 closes the right master cut valve 22FR and the left master cut valve 22FL, and the pressure increasing valve so that each wheel cylinder 20 has a target hydraulic pressure calculated according to the depression amount of the brake pedal 12. 40, the pressure reducing valve 42 is controlled. This control mode is called a normal control mode. The fluid accumulated in the accumulator 50 increases the wheel cylinder pressure when the brake pedal 12 is stepped on. After that, when the brake pedal 12 is returned, the fluid is reduced and returns to the reservoir tank 26 through the hydraulic supply / discharge pipe 28. . When the accumulator pressure P decreases to a value smaller than the standard motor-on pressure PONMed, the motor 32 is driven, the fluid is supplied from the reservoir tank 26 to the accumulator 50, and the accumulator 50 is accumulated.

  FIG. 3 is a diagram for explaining the operation when the liquid level becomes lower than the reference liquid level. When the liquid level L becomes lower than the reference liquid level Ls, the level lowering switch 100 is switched from the OFF state to the ON state.

  When the level lowering switch 100 is turned on, the ECU 200 increases the accumulator pressure P before the liquid level lowering is detected, here, compared with the normal time. Specifically, when it is detected that the level lowering switch 100 is in the ON state, the ECU 200 changes the motor on pressure PON and the motor off pressure POFF to values higher than those before detection of the liquid level drop. In the present embodiment, the motor on pressure PON is changed to a high motor on pressure PONHi that is higher than the standard motor on pressure PONMed, and the motor off pressure POFF is changed to a high motor off pressure POFFHi that is a value higher than the standard motor off pressure POFFMed. To do. As a result, the ECU 200 drives the motor 32 so that the accumulator pressure P becomes equal to or higher than the high motor-on pressure PONHi, so that the accumulator pressure P increases and the pressure accumulation amount V increases. By controlling the motor 32 in this way, the pressure accumulation amount V of the accumulator 50 is equal to or higher than the high motor-on pressure accumulation amount VONHi, which is a pressure accumulation amount corresponding to the high motor-on pressure PONHi, as shown in FIG. Is kept in a range equal to or less than the high motor-off pressure accumulation amount VOFFHi, which is the pressure accumulation amount corresponding to.

  The ECU 200 may issue a warning to the driver by turning on the warning lamp 54 when a decrease in the liquid level L is detected. Thereby, the driver can take measures such as examining the cause of the liquid level L. The alarm may be due to a sound such as a buzzer.

  FIG. 4 is a diagram for explaining the operation when the occurrence of liquid leakage is detected. In the brake control device 10, it is assumed that liquid leakage has occurred in any of the four wheels. In this case, the liquid level L further decreases and eventually the fluid in the pump chamber 120 disappears. On the other hand, since the right master cut valve 22FR and the left master cut valve 22FL are closed, fluid remains in the first fluid storage chamber 116 and the second fluid storage chamber 118.

  When it is detected by the level lowering switch 100 that the liquid level L is lower than the reference liquid level Ls, the ECU 200 detects whether or not the liquid leakage actually occurs in the brake control device 10. For example, when the accumulator pressure P does not increase even though the pressure increasing valve 40 is all closed and the motor 32 is driven, the ECU 200 detects that a liquid leak has occurred. Moreover, a switch for detecting liquid leakage may be provided between the level lowering switch 100 and the inlet of the oil pump 34 to detect the occurrence of liquid leakage.

  When it is detected that liquid leakage has occurred, the ECU 200 switches the control mode from the normal control mode to the failsafe mode. The fail safe mode is a control mode in which the right master cut valve 22FR and the left master cut valve 22FL are opened, and the pressure increasing valve 40FR, the pressure increasing valve 40FL, the pressure reducing valve 42RL, and the pressure reducing valve 42RR are closed. As a result, the two front wheels of the wheel cylinder 20FR and the wheel cylinder 20FL are separated from the control pressure system, and the wheel cylinder 20FR and the wheel cylinder 20FL are in a static pressure supply state in which the wheel cylinder pressure is controlled using the master cylinder 14 as a hydraulic pressure source. It is said. The left and right rear wheel cylinders 20FR and 20RR are in a control pressure supply state in which the wheel cylinder pressure is controlled using the accumulator 50 as a hydraulic pressure source.

  FIG. 5 is a diagram for explaining the operation after the liquid leakage is detected. When it is detected in the brake control device 10 that a liquid leak has occurred, the ECU 200 decreases the accumulator pressure P than before the liquid leak is detected. Specifically, when the occurrence of liquid leakage is detected, ECU 200 changes motor on pressure PON and motor off pressure POFF to values lower than those before detection of liquid leakage. In the present embodiment, the motor on pressure PON is changed to a low motor on pressure PONLo that is lower than the high motor on pressure PONHi, and the motor off pressure POFF is changed to a low motor off pressure POFFLo that is a value lower than the high motor off pressure POFFHi. To do. As a result, the accumulator pressure P decreases, and the accumulated amount V of the accumulator 50 is equal to or higher than the low motor-on accumulated amount VONLo, which is the accumulated amount corresponding to the low motor-on pressure PONLo, as shown in FIG. It falls to the range below the low motor off pressure accumulation amount VOFFLo which is the corresponding pressure accumulation amount.

  As the pressure accumulation amount V of the accumulator 50 decreases, the fluid corresponding to the decrease in the pressure accumulation amount flows out from the accumulator 50. The fluid that has flowed out of the accumulator 50 returns to the suction port of the oil pump 34 and the reservoir tank 26 through the pressure increasing valve 40, the wheel cylinder 20, and the pressure reducing valve 42. FIG. 5 shows a state in which the liquid level L of the pump chamber 120 has increased due to the decrease in the amount of accumulated pressure in the accumulator 50.

  FIG. 6 is a diagram for explaining the operation in the case where liquid leakage has occurred in the front wheel system. For example, if there is a liquid leak in the system of the wheel cylinder 20FR for the right front wheel, the fluid in the second fluid storage chamber 118 disappears, but the fluid is secured in the first fluid storage chamber 116, so the left front wheel A master cylinder pressure can be applied to the wheel cylinder 20FL. On the other hand, since the fluid accumulated in the accumulator 50 can be supplied to the left rear wheel wheel cylinder 20RL and the right rear wheel wheel cylinder 20RR, the braking force of the left and right rear wheels can be secured.

  FIG. 7 is a diagram for explaining the operation in the case where liquid leakage has occurred in the rear wheel system. If liquid leakage has occurred in any of the left and right rear wheels, the fluid accumulated in the pump chamber 120 and the fluid accumulated in the accumulator 50 will decrease over time, and will eventually disappear, but the first fluid storage chamber Since the fluid is secured in the 116 and the second fluid storage chamber 118, the fluid is supplied from the master cylinder to the wheel cylinders 20FR and 20FL of the left and right front wheels, and a braking force can be generated.

  As described above, according to the brake control device 10 according to the present embodiment, it is determined that the liquid has leaked only when the liquid level L of the reservoir tank 26 is lower than the reference liquid level Ls by the level lowering switch 100. In addition, since it is detected whether or not a liquid leak has actually occurred, erroneous determination of liquid leak can be suppressed even when the reservoir is downsized.

  Further, normally, when it is detected that liquid leakage has actually occurred, there is not much fluid left in the reservoir tank, and it is difficult to generate an appropriate braking force. In the brake control device 10 according to the present embodiment, the pressure accumulation amount V of the accumulator 50 is increased at the time when the level lowering switch 100 detects the decrease in the liquid level L, and the fluid is temporarily stored in the accumulator 50. Thereafter, when the occurrence of liquid leakage is actually detected, the stored fluid is released and used for braking, so that an appropriate braking force can be generated even after the liquid leakage has occurred. Since the accumulator 50 is used as a temporary fluid holding means when the liquid level is lowered, it is not necessary to enlarge the reservoir tank 26 at normal times, and the reservoir tank 26 can be downsized.

  The high motor-on pressure PONHi, the high motor-off pressure POFFHi, the low motor-on pressure PONLo, and the low motor-off pressure POFFLo may be determined as appropriate through experiments and simulations so that the necessary braking force can be secured after the liquid leakage is detected.

  FIG. 8 is a flowchart showing the control of the brake control device 10 according to the present embodiment. This braking control flow is continuously executed at predetermined time intervals. In the normal state, the brake control device 10 is controlled in the normal control mode.

  First, the ECU 200 determines whether or not a level lowering abnormality flag indicating whether or not a liquid level lowering abnormality of the reservoir tank 26 has already occurred is ON (S10).

  When the level decrease abnormality flag is OFF (N in S10), the ECU 200 determines whether or not the level decrease switch 100 is in the ON state (S12).

  When the level lowering switch 100 is in the OFF state (N in S12), it is assumed that there is sufficient fluid in the reservoir tank 26, and the motor on pressure PON and the motor off pressure POFF are the standard motor on pressure PONMed and the standard motor off pressure POFFMed (S14, S16) A braking force is generated in the normal control mode for the four-wheel brake (S18). Thereafter, the process returns to S10 and the control flow is repeated.

  On the other hand, when the level lowering switch 100 is in the ON state (Y in S12), the ECU 200 performs liquid leakage detection (S20). Various methods can be used to detect liquid leakage. Here, when the accumulator pressure P does not increase even though the pressure increasing valve 40 is all closed and the motor 32 is driven, the liquid leakage is detected. Determined to occur.

  The ECU 200 determines whether or not a liquid leak has occurred (S22). If no liquid leak has occurred (N in S22), the ECU 200 sets the motor on pressure PON to a value higher than the standard motor on pressure PONMed. The motor off pressure POFF is changed to a certain high motor on pressure PONHi, and the motor off pressure POFF is changed to a high motor off pressure POFFHi that is higher than the standard motor off pressure POFFMed (S24, S26). Thereby, the pressure accumulation amount V of the accumulator 50 increases. Thereafter, the ECU 200 performs control in the normal control mode (S18). Thereafter, the process returns to S10 and the control flow is repeated.

  If a liquid leak has occurred (Y in S22), the ECU 200 sets the level drop abnormality flag to ON (S28), and sets the motor on pressure PON to the low motor on pressure PONLo, which is a value lower than the high motor on pressure PONHi. The motor off pressure POFF is changed to a low motor off pressure POFFLo that is a value lower than the high motor off pressure POFFHi (S30, S32). As a result, the pressure accumulation amount V of the accumulator 50 decreases, and the fluid corresponding to the decrease in the pressure accumulation amount flows out from the accumulator 50. The fluid that has flowed out of the accumulator 50 returns to the suction port of the oil pump 34 and the reservoir tank 26 through the pressure increasing valve 40, the wheel cylinder 20, and the pressure reducing valve 42.

  If a liquid leak has occurred (Y in S22), the ECU 200 switches the control mode from the normal control mode to the failsafe mode (S34). Thereby, the wheel cylinder 20FR and the wheel cylinder 20RR for the left and right rear wheels are set to the control pressure supply state, and the wheel cylinder 20FR and the wheel cylinder 20FL for the left and right front wheels are set to the static pressure supply state.

  When liquid leakage has occurred in the front wheel system, the fluid temporarily stored in the accumulator 50 can be supplied to the left rear wheel wheel cylinder 20RL and the right rear wheel wheel cylinder 20RR. The braking force of the left and right rear wheels can be ensured. When liquid leakage has occurred in the rear wheel system, fluid is supplied from the master cylinder to the wheel cylinders 20FR and 20FL of the left and right front wheels, and braking force can be generated. Thereafter, the process returns to S10 and the control flow is repeated. In S10, since the level decrease abnormality flag is determined to be ON (Y in S10), steps S30 to S34 are repeatedly executed.

  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.

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 operation | movement of the brake control apparatus in the normal time. It is a figure for demonstrating operation | movement when a liquid level becomes lower than a reference | standard liquid level. It is a figure for demonstrating operation | movement at the time of detecting generation | occurrence | production of a liquid leak. It is a figure for demonstrating the operation | movement after a liquid leak detection. It is a figure for demonstrating operation | movement when the liquid leak has generate | occur | produced in the system | strain of a front wheel. It is a figure for demonstrating operation | movement when the liquid leak has generate | occur | produced in the system | strain of a rear wheel. It is a flowchart which shows control of the brake control apparatus which concerns on this Embodiment.

Explanation of symbols

  10 brake control device, 12 brake pedal, 14 master cylinder, 20 wheel cylinder, 26 reservoir tank, 32 motor, 34 oil pump, 40 pressure increasing valve, 42 pressure reducing valve, 50 accumulator, 51 accumulator pressure sensor, 100 level lowering switch, 200 ECU.

Claims (4)

A plurality of wheel cylinders for applying braking force to the wheels by supplying fluid;
A brake operating member operated by the driver;
A master cylinder that generates a hydraulic pressure according to an operation amount of the brake operation member;
A master cut valve for blocking communication between the master cylinder and the wheel cylinder;
A reservoir tank connected to the master cylinder for storing fluid;
A pump connected to the reservoir tank for pressurizing the fluid;
An accumulator for storing fluid pressurized by the pump;
An accumulator pressure control unit for controlling the hydraulic pressure of the accumulator by controlling the pump;
An electromagnetic flow control valve that is provided between the wheel cylinder and the accumulator, and controls a hydraulic pressure of the wheel cylinder;
An electromagnetic valve control unit for controlling the operation of the master cut valve and the electromagnetic flow control valve;
A liquid level detecting device for detecting the liquid level of the reservoir tank;
A liquid leak detection means for detecting whether or not a liquid leak has occurred;
With
The accumulator pressure control unit detects that the liquid level of the reservoir tank has become lower than a predetermined reference liquid level by the liquid level detection device , and the liquid leakage detection means generates a liquid leak. If it is not detected , the liquid pressure of the accumulator is increased more than before the liquid level lowering detection, and then the liquid leak detection unit detects that a liquid leak has occurred. A brake control device, wherein the pressure is reduced as compared with that before detection of a liquid leak.   When it is detected that the liquid leakage is detected by the liquid leakage detection unit, the solenoid valve control unit is configured such that a part of the plurality of wheel cylinders is given a hydraulic pressure from the master cylinder, The brake control device according to claim 1, wherein the remaining wheel cylinder controls the master cut valve and the electromagnetic flow control valve so that hydraulic pressure is applied from the accumulator.   The pump is driven by a motor, and the accumulator pressure control unit drives the motor when the accumulator fluid pressure is smaller than a predetermined motor-on pressure, and the accumulator pressure control unit operates when the accumulator fluid pressure is greater than a predetermined motor-off pressure. The brake control device according to claim 1 or 2, wherein the hydraulic pressure of the accumulator is controlled by stopping a motor. The accumulator pressure control unit detects that the liquid level of the reservoir tank has become lower than a predetermined reference liquid level by the liquid level detection device , and the liquid leakage detection means generates a liquid leak. If not detected , change the motor-on pressure and the motor-off pressure to a value higher than that before the liquid level level detection, and then, after that, the liquid leak detection unit detects that a liquid leak has occurred, 4. The brake control device according to claim 3, wherein the motor-on pressure and the motor-off pressure are changed to values lower than those before detection of liquid leakage.

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