JP2010036625A - Brake control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a brake control device inhibiting a drag of a friction member and contributing to prevention of a reduction of fuel consumption with a simple configuration. <P>SOLUTION: When a wheel cylinder 50 is in an unpressurized state, an ECU 36 of the brake control device 34 closes a master cut valve 52 and a reducing valve 80, and drives an oil pump 66 in a state where an admission of brake oil from a reservoir tank 56 is cut off by closing a relief valve 72, thereby absorbing the brake oil from a side of the wheel cylinder 50 to produce a negative pressure state in the wheel cylinder 50. As a result, a brake pad serving as the friction member in the unpressurized state separates from a disk rotor serving as a rotating member, so as to inhibit the drag when the wheel cylinder 50 is in the unpressurized state, and thereby the reduction of the fuel economy is prevented. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a brake control device, and more particularly to a brake control device that can contribute to prevention of fuel consumption reduction.

  One brake device that brakes a vehicle is a disc brake. This disk brake is composed of a disk rotor and a caliper that are rotating members that rotate together with the wheels. The caliper has a housing portion that forms an outer shape and functions as a cylinder. The housing portion includes a piston and a brake pad that is a pair of friction members disposed with the disc rotor interposed therebetween. Then, by introducing hydraulic pressure between the housing part and the piston, the brake pad is pressed against the disk rotor, and the disk rotor is gripped by the pair of brake pads to generate a braking force.

As described above, when generating a braking force, the disc brake causes the disc rotor to press the brake pad by providing hydraulic pressure to the piston. On the other hand, when the brake pad is separated from the disk rotor, only the hydraulic pressure is released, and thereafter, the brake pad is separated using the restoring force at the time of elastic deformation of the piston seal member. Therefore, for some reason, a resistance force greater than the restoring force is generated, and the brake pad may not be separated from the disc rotor. In this case, since the hydraulic pressure is released, a large braking force is not generated, but the brake pad is dragged by the rotating disk rotor, which is one of the causes of a decrease in fuel consumption. In recent years when high fuel efficiency is required, there is a desire to eliminate even a slight fuel consumption reduction factor. Therefore, for example, the brake control device disclosed in Patent Document 1 uses a bidirectional pump to stably maintain a gap between the brake pad and the disk rotor by setting a negative pressure between the wheel cylinder and the hydraulic pressure generation source. The structure is disclosed.
JP 2005-247230 A

  However, the structure of Patent Document 1 requires an increase in component costs such as the need for using a bidirectional pump, complicates the configuration, and requires a change in the design of the hydraulic circuit associated with the use of the bidirectional pump. Therefore, although it can contribute to prevention of fuel consumption reduction, there is a problem that a new problem arises in terms of cost and design. The drum brake device using the brake drum as the rotating member and the brake shoe as the friction member has the same problem. Therefore, there is a demand for a brake control device that can reliably prevent frictional members from being dragged without major design changes or the use of expensive parts, and can contribute to prevention of fuel consumption.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a brake control device that can prevent dragging of a friction member with an easy configuration and contribute to prevention of fuel consumption reduction.

  In order to solve the above problems, a brake control device according to an aspect of the present invention includes a wheel cylinder that generates a braking force by pressing a friction member against a rotating member that rotates together with a wheel, and pressurizing the wheel cylinder. An accumulator for accumulating the hydraulic fluid, a pump for increasing the hydraulic fluid to be accumulated in the accumulator, and an operation for recovering the hydraulic fluid discharged during non-pressurizing operation of the wheel cylinder and supplying the hydraulic fluid to the pump A reservoir tank for storing liquid; a suppression means that is disposed in a flow path connecting the reservoir tank and the pump; and that temporarily suppresses the supply of hydraulic fluid from the reservoir tank to the pump; and the wheel cylinder Detecting means for detecting that the wheel cylinder is in the non-pressurized state, and the detecting means detects the non-pressurized state of the wheel cylinder. Sometimes the suppression means closes the fluid path from the reservoir tank side and drives the pump to suck the hydraulic fluid from the wheel cylinder side, thereby bringing the wheel cylinder into a negative pressure state and rotating the friction member. A separation control unit for separating the member from the member.

  The rotating member may be a disc rotor in the case of a disc brake device, and may be a brake drum in the case of a drum brake device. The friction member may be a brake pad in the case of a disc brake device, and may be a brake shoe in the case of a drum brake device. As the suppression means, a mechanical switch using an electromagnetic valve or a motor that can be controlled for opening and closing can be used. Further, the separation control unit may be configured by a single control unit, or may be configured by adding a function to an existing brake control unit. By driving the pump in a state where the supply of the hydraulic fluid from the reservoir tank to the pump is suppressed, the hydraulic fluid is preferentially sucked from the wheel cylinder side and the inside of the wheel cylinder can be brought into a negative pressure state. As a result, the friction member can be forcedly and reliably separated from the rotating member. That is, dragging of the friction member with respect to the rotating member can be prevented. In addition, since the pump only performs the same operation as the normal pressure accumulation operation at the time of this separation control, it is not necessary to use a pump having a special function, and an effect can be obtained only by adding suppression means and its control unit to the conventional system. . Further, the separation control unit may accumulate the hydraulic fluid sucked from the wheel cylinder side in the accumulator when the liquid passage from the reservoir tank side is closed by the suppressing means. In this case, the accumulator whose pressure accumulation amount has decreased due to the operation of the wheel cylinder can be increased, so that the next operation of the wheel cylinder can be quickly prepared. Moreover, it becomes possible to reduce the pump drive time for pressure accumulation performed when the brake is not operated, and to reduce the uncomfortable feeling of pump drive for the vehicle occupant.

  In the above aspect, the friction member is disposed on an outer peripheral friction portion that can contact the rotating member when the wheel cylinder is in a pressurized state and a non-pressurized state, and an inner peripheral portion of the outer peripheral friction portion. An inner peripheral friction portion that contacts the rotating member when the cylinder is pressurized and is separated from the rotating member when the wheel cylinder is not pressurized may be included. When the wheel cylinder is in a pressurized state, the outer peripheral friction portion and the inner peripheral friction portion are in contact with the rotating member, so that substantially the same braking force as that of a conventional non-separable friction member having the same contact area can be generated. Further, in the non-pressurized state, the inner peripheral friction portion is separated from the rotating member, and only the outer peripheral friction portion can come into contact with the rotating member. As a result, a reduction in fuel consumption due to dragging of the friction member in the non-pressurized state can be greatly suppressed. The outer peripheral friction portion may form an intrusion prevention wall that prevents foreign matter from entering between the rotating member and the inner peripheral friction portion. In this case, the thickness of the intrusion prevention wall in the radial direction of the rotating member may be sufficient to ensure the strength, and the braking force may not be generated or may be generated when contacting the rotating member. Further, it may be formed of a material different from that of the inner peripheral friction portion with emphasis on strength.

  According to the brake control device of the present invention, dragging of the friction member can be prevented with an easy configuration, which can contribute to prevention of fuel consumption reduction.

  Hereinafter, an embodiment of the present invention (hereinafter referred to as an embodiment) will be described with reference to the drawings.

  The brake control device of the present embodiment sucks in hydraulic fluid from the wheel cylinder side preferentially by driving the pump in a state where the supply of hydraulic fluid from the reservoir tank is cut off in a non-pressurized state, and negative pressure is generated inside the wheel cylinder. Put it in a state. As a result, the friction member is separated from the rotating member in the non-pressurized state, and the reduction in fuel consumption due to dragging is prevented in the non-pressurized state of the wheel cylinder. In the following description, a brake control device using a disc brake device as a brake device is shown as an example. In the case of a disc brake device, a disc rotor corresponds to the rotating member, and a brake pad corresponds to the friction member.

  FIG. 1 is a cross-sectional view of a caliper 10 of a disc brake device controlled by the brake control device of the present embodiment. As shown in FIG. 1, the caliper 10 according to the present embodiment is roughly divided into a mounting portion 12 for fixing the caliper 10 to a vehicle side (not shown), a brake pad 14 that is pressed by the disc rotor and generates a braking force. The cylinder portion 16 functions as a pressing means for driving the brake pad 14. The disk rotor 18 that rotates together with the wheels exists between the pair of brake pads 14. As shown in FIG. 1, both side surfaces 18 a of the disk rotor 18 are sliding surfaces, and a pair of brake pads 14 are disposed to face each other. The brake pad 14 includes a friction material 20 that directly contacts the side surface 18 a of the disk rotor 18, and a pad back metal 22 that supports the back side of the friction material 20, that is, the side that does not contact the disk rotor 18.

  The caliper 10 is attached to the vehicle body via a mounting portion 12 so as to be displaceable in the left-right direction in FIG. As shown in FIG. 1, a bottomed hole 24 is formed in the cylinder portion 16 of the caliper 10, and a piston 26 is slidably fitted into the hole 24. A port 28 is provided at the bottom of the hole 24 and is connected to a master cylinder (not shown). When the driver depresses the brake pedal, the brake oil as the working fluid flows into the port 28 from the master cylinder or the accumulator, and the piston 26 is driven. In addition, when an anti-lock brake system (ABS) or the like is operated, the brake oil inflow / outflow from the accumulator to the port 28 is controlled and the braking force adjustment is executed without corresponding to the depression operation of the brake pedal. As a result, the vehicle stable running control is performed.

  When the brake oil flows into the port 28, the piston 26 slides in the left direction in the figure from the non-operating state shown in FIG. 1, and the friction material 20 on the right side in the figure is moved to the disc via the pad back metal 22 on the right side in the figure. The right side surface 18a of the rotor 18 is pressed. When the friction material 20 on the right side in the drawing is pressed against the disk rotor 18, the piston 26 stops sliding. Even after the piston 26 stops sliding, if the brake oil flows into the port 28, the hydraulic pressure in the hole 24 increases. As a result, the stopped piston 26 conversely presses the inner surface of the hole 24 and presses the cylinder housing 16a constituting the cylinder portion 16 rightward in FIG. Since the cylinder housing 16a can be displaced in the left-right direction in the figure, the cylinder housing 16a is displaced in the right direction in the figure as the hydraulic pressure increases.

  A claw 30 is formed on the non-cylinder forming side of the cylinder housing 16a, and the claw 30 moves the friction material 20 on the left side through the pad backing metal 22 on the left side in the figure as the cylinder housing 16a is displaced in the right direction. Press against the left side surface 18 a of the disk rotor 18. Therefore, the disk rotor 18 is pressed and clamped by the pair of friction materials 20, and the disk rotor 18 can be braked efficiently.

  As described above, the friction material 20 is supported by the pad back metal 22, and the pad back metal 22 can come into contact with the torque plate 32 functioning as a torque receiving part constituting a part of the mounting part 12 as shown in FIG. It has become. When the friction material 20 is brought into contact with the rotating disk rotor 18, the friction material 20 is dragged by the disk rotor 18 and receives a tangential force in the tangential direction with respect to the disk rotor 18, that is, braking torque. This tangential force is received by the torque plate 32 via the pad back metal 22. In other words, when the pad backing metal 22 is pressed, the torque plate 32 contacts the end surface of the pad backing metal 22 on the outlet side of the friction material 20 with respect to the rotation direction of the disk rotor 18 and receives the tangential force of the friction material 20. . In FIG. 1, the torque plate 32 is shown only on the back side of the paper with respect to the pad back metal 22, but is also present at a position facing the front side of the paper across the pad back metal 22. As a result, it is possible to receive the braking torque for both the forward rotation and the reverse rotation of the disk rotor 18 and generate both the forward braking force and the reverse braking force.

  FIG. 2 is an explanatory diagram for explaining the overall configuration of the brake control device 34 and the electronic control unit 36 (hereinafter referred to as “ECU 36”) included in the brake control device 34 according to the present embodiment, and operates the caliper 10 of FIG. .

  The brake control device 34 mainly includes an actuator 38 and a master cylinder 44 other than the actuator 38. The brake control device 34 is an ECB system (Electronically Controlled Brake System), which detects the operation amount of the brake pedal with a sensor, calculates the optimum brake oil pressure, and can operate the brakes independently of the four wheels.

  The brake pedal 40 is provided with a stroke sensor 42 that detects the depression stroke. The master cylinder 44 pumps brake oil, which is hydraulic fluid, in response to the driver's depressing operation of the brake pedal 40.

  One end of a brake oil pressure control conduit 46 for the right front wheel (FR) and a brake oil pressure control conduit 48 for the left front wheel (FL) are connected to the master cylinder 44. These brake oil pressure control conduits 46, 48 are respectively connected to the master cylinder 44. These are connected to wheel cylinders 50FR, 50FL for the right front wheel and the left front wheel that exert the braking force of the right front wheel and the left front wheel. A right master cut valve 52FR and a left master cut valve 52FL (sometimes collectively referred to as a master cut valve 52) are interposed in the middle of the brake oil pressure control conduits 46, 48 for the right front wheel and the left front wheel. . The right master cut valve 52FR and the left master cut valve 52FL are electromagnetic valves that are open when de-energized and switch to a closed state when a brake operation is detected (this is referred to as a “normally open type”).

  A right master pressure sensor 54FR and a left master pressure sensor 54FL for measuring the master cylinder fluid pressure on the right front wheel side and the left front wheel side are provided in the middle of the brake oil pressure control conduits 46 and 48, respectively. When the driver depresses the brake pedal 40, the stroke sensor 42 detects the amount of depression, but assuming the failure of the stroke sensor 42, master cylinder fluid by the right master pressure sensor 54FR and the left master pressure sensor 54FL. The depressing operation force of the brake pedal 40 is also detected by measuring the pressure. The master cylinder hydraulic pressure is monitored by two pressure sensors from the viewpoint of fail-safe.

  A reservoir tank 56 is connected to the master cylinder 44. The master cylinder 44 is connected to a stroke simulator 60 that creates a driver's operation amount and reaction force via a simulator cut valve 58. The simulator cut valve 58 is a normally closed solenoid valve that is closed when not energized and switches to an open state when the brake is operated. One end of a hydraulic pressure supply / discharge conduit 62 is connected to the reservoir tank 56. The hydraulic supply / discharge conduit 62 is provided with an oil pump 66 driven by a motor 64. The discharge side of the oil pump 66 is a high-pressure conduit 68, and an accumulator 70 and a relief valve 72 are provided. The accumulator 70 accumulates brake oil that has been brought to a high pressure in the range of, for example, 14 to 22 MPa by the oil pump 66. The relief valve 72 opens when the accumulator pressure is abnormally high, for example, 25 MPa, and releases high-pressure brake oil to the hydraulic pressure supply / discharge conduit 62 side. In addition, a reservoir cut valve 74 is disposed between the oil pump 66 and the reservoir tank 56 on the hydraulic supply / discharge conduit 62 as a suppression means for temporarily suppressing the supply of brake oil from the reservoir tank 56 to the oil pump 66. Has been. The operation of the reservoir cut valve 74 will be described later. When the accumulator pressure becomes abnormally high and the relief valve 72 opens, the reservoir cut valve 74 opens to release brake oil to the reservoir tank 56 side. The reservoir cut valve 74 may be disposed at a position closest to the oil pump 66 on the reservoir tank 56 side.

  The high-pressure conduit 68 is provided with an accumulator pressure sensor 76 that measures the accumulator pressure. Although illustration is omitted, the accumulator pressure that is the output of the accumulator pressure sensor 76 is input to the ECU 36, and the motor 64 is controlled so that the accumulator pressure falls within the control range.

  The high pressure conduits 68 are closed when not energized, and are normally closed electromagnetic flow rate control valves used for pressure increase of the wheel cylinder when necessary, that is, pressure increase valves 78FR, 78FL, 78RR which are linear valves. 78 RL, right front wheel wheel cylinder 50FR, left front wheel wheel cylinder 50FL, right rear wheel wheel cylinder 50RR, left rear wheel wheel cylinder 50RL (hereinafter collectively referred to as "wheel cylinder 50"). It is connected to the. Hereinafter, when the pressure increasing valves 78FR, 78FL, 78RR, and 78RL are collectively referred to, reference numeral 78 is used.

  A disc brake including the caliper 10 shown in FIG. 1 is provided on the right front wheel, the left front wheel, the right rear wheel, and the left rear wheel of the vehicle, and the brake pad 14 is driven by driving the wheel cylinders 50FR, 50FL, 50RR, and 50RL, respectively. Is pressed against the disk rotor 18 to exert a braking force.

  The right front wheel wheel cylinder 50FR and the left front wheel wheel cylinder 50FL are hydraulically supplied via electromagnetic flow control valves used for pressure reduction when necessary, that is, normally closed pressure reduction valves 80FR and 80FL which are linear valves. It is connected to the exhaust conduit 62. Further, the wheel cylinder 50RR for the right rear wheel and the wheel cylinder 50RL for the left rear wheel are connected to the hydraulic pressure supply / discharge conduit 62 through normally open pressure reducing valves 80RR and 80RL, respectively. Hereinafter, when the pressure reducing valves 80FR, 80FL, 80RR, and 80RL are collectively referred to, reference numeral 80 is used.

  Near the right front wheel, left front wheel, right rear wheel, and left rear wheel wheel cylinders 50FR, 50FL, 50RR, 50RL, the right front wheel, the left front wheel, the right rear wheel, Pressure sensors 82FR, 82FL, 82RR, 82RL for the left rear wheel are provided (sometimes collectively referred to as pressure sensor 82).

  The ECU 36 includes a master cut valve 52FR, 52FL, a simulator cut valve 58, a reservoir cut valve 74, a motor 64, four pressure increasing valves 78FR, 78FL, 78RR, 78RL, and four pressure reducing valves 80FR, 80FL, 80RR, 80RL. Control. The ECU 36 includes an arithmetic unit using a microcomputer, a ROM that stores various control programs, and a RAM that is used as a work area for data storage and program execution.

  Although details are not shown, the ECU 36 receives pressures in the right front wheel wheel cylinder 50FR from pressure sensors 82FR, 82FL, 82RR, 82RL for the right front wheel, the left front wheel, the right rear wheel, and the left rear wheel, respectively. A signal, a pressure signal in the left front wheel wheel cylinder 50FL, a pressure signal in the right rear wheel wheel cylinder 50RR, and a pressure signal in the left rear wheel wheel cylinder 50RL are input. Further, the ECU 36 receives a signal indicating the depression stroke of the brake pedal 40 from the stroke sensor 42, a signal indicating the master cylinder hydraulic pressure from the right master pressure sensor 54FR and the left master pressure sensor 54FL, and the accumulator pressure sensor 76. A signal indicating the accumulator pressure is input. Further, a signal indicating whether or not the ignition switch is in an ON state, a signal indicating whether or not the shift lever is in the D range, and the like are also provided to the ECU 36. These sensors can function as detection means for detecting whether the wheel cylinder 50 is currently controlled in a pressurized state or in a non-pressurized state by a single or a plurality of combinations.

  The ROM of the ECU 36 stores a predetermined braking control flow. A target braking amount acquisition unit in the ECU 36 calculates a target braking amount of the vehicle based on the stroke signal and the master cylinder hydraulic pressure signal. Then, the braking control unit calculates the target wheel cylinder hydraulic pressure of each wheel based on the calculated target braking amount, and the pressure increasing valve 78 and the pressure reducing valve 78 so that the wheel cylinder hydraulic pressure of each wheel becomes the target wheel cylinder hydraulic pressure. The valve 80 is controlled.

  The oil pump 66 driven by the motor 64 draws up brake oil from the reservoir tank 56 through the hydraulic supply / discharge conduit 62 and accumulates the brake oil at high pressure in the accumulator 70. The high hydraulic pressure of the accumulator 70 is supplied to each wheel cylinder 50 by controlling opening and closing of the pressure increasing valve 78 in accordance with the target wheel cylinder hydraulic pressure.

  When brake fluid of high hydraulic pressure is consumed from the accumulator 70 by depressing the brake pedal 40, the ECU 36 operates the motor 64 to drive the oil pump 66 so that the pressure of the accumulator 70 is always within the control range. Then, the brake oil at a high pressure is accumulated in the accumulator 70. This pressure accumulation operation is automatically executed according to the detection value of the accumulator pressure sensor 76.

  As shown in FIG. 1, the caliper 10 generates a braking force by pressing the pad back metal 22 with the piston 26 and the claws 30 when high-pressure brake oil is introduced into the port 28. On the other hand, when the pressure reducing valve 80 is opened and the brake oil is returned to the reservoir tank 56 side, an elastic member disposed between the piston 26 and the cylinder portion 16 that has been deformed when the piston 26 is in a pressed state is provided. The shape is restored, and the piston 26 is pushed back to the bottom side of the hole 24 by the restoring force. That is, the pad back metal 22 is released from the pressed state. At this time, if the disk rotor 18 is rotating, the disk rotor 18 repels the friction material 20 and separates them. As a result, the friction material 20 is prevented from being dragged with respect to the disk rotor 18. However, the conduit from the port 28 to the reservoir tank 56 is curved or bent at various locations. There are also many portions where the tube diameter is narrow. As a result, the brake oil may not sufficiently return to the reservoir tank 56 side, and the brake oil may remain in the cylinder portion 16 and the piston 26 may not be sufficiently separated from the pad backing metal 22. In such a case, the brake pad 14 is dragged by the disk rotor 18 and becomes one of the causes of fuel consumption reduction.

  Therefore, the brake control device according to the present embodiment executes drag prevention control for preventing the brake pad 14 from being dragged. Specifically, the ECU 36 closes the reservoir cut valve 74 when the non-pressurized state of the wheel cylinder 50 is detected, closes the liquid path from the reservoir tank 56 side, and drives the oil pump 66 to drive the wheel cylinder. Suction brake oil from the 50 side. Then, separation control for separating the brake pad 14 from the disk rotor 18 by executing the wheel cylinder 50 in a negative pressure state is executed. In this case, the ECU 36 functions as a separation control unit, but a separation control unit may be provided separately from the ECU 36. When the ignition switch is in the ON state, the shift lever is in the D range position, and the stroke sensor 42 is displaced from the ON state to the OFF state, the ECU 36 of the present embodiment controls the all pressure reducing valves 80 to be in the open state. The generation of power is stopped, and the right master cut valve 52FR and the left master cut valve 52FL are closed. Further, the reservoir cut valve 74 is closed. In this state, the ECU 36 drives the motor 64 to drive the oil pump 66 for a predetermined time. As a result, brake oil in the cylinder portion 16 of the wheel cylinder 50 and in the path from the wheel cylinder 50 to the oil pump 66 is sucked up by the oil pump 66 so that at least the inside of the cylinder portion 16 of the wheel cylinder 50 is in a negative pressure state. By making the inside of the cylinder portion 16 into a negative pressure state, the piston 26 is drawn toward the bottom side of the hole 24, and the piston 26 is separated from the pad back metal 22. That is, the pad back metal 22 can be easily repelled by the rotating disc rotor 18 with the brake pad 14 in a completely free state. That is, it is possible to form a state in which the disc rotor 18 and the brake pad 14 can be forcibly separated. As a result, when the generation of braking force is not required, the brake pad 14 is prevented from being dragged to the disc rotor 18 and fuel consumption due to drag can be prevented from being reduced. In the case of the present embodiment, as shown in FIG. 1, the pressure reducing valve 80RL and the pressure reducing valve 80RR are normally closed linear valves. Therefore, when the negative pressure control of the wheel cylinder 50 is performed, the pressure reducing valve 80 It is sufficient to control only the valve 80FR and the pressure reducing valve 80FL.

  Further, once the friction material 20 has been blown off by the disk rotor 18, the high pressure brake oil is again introduced into the port 28, and the posture of the friction material 20 can be maintained as long as it is not pressed by the piston 26. Accordingly, the time for driving the oil pump 66 by closing the right master cut valve 52FR, the left master cut valve 52FL, and the reservoir cut valve 74 is the brake in the cylinder portion 16 and the path from the wheel cylinder 50 to the oil pump 66. A period sufficient to suck up the oil by the oil pump 66 may be sufficient. For example, it may be several seconds, specifically 1 to 2 seconds. The driving time of the oil pump 66 may be changed depending on the length of the path, the flow resistance of the path, the viscosity state of the brake oil, and the like. Further, when there is no brake oil to be sucked up, the driving load of the oil pump 66 increases. Therefore, a threshold value may be provided, and the driving of the oil pump 66 may be stopped when a predetermined threshold value is exceeded. .

  The brake oil sucked up from the wheel cylinder 50 side when the oil pump 66 is driven can be pushed into the accumulator 70. In other words, the driving of the oil pump 66 for preventing the above-described reduction in fuel consumption can be performed as the pressure accumulation operation of the accumulator 70. As a result, the drive of the oil pump 66 for preventing a reduction in fuel consumption can be used for the accumulator operation of the accumulator 70 without waste.

  The fuel consumption reduction prevention control by the drag prevention can be realized only by adding the reservoir cut valve 74 and the control program of the ECU 36, so that there is no significant increase in cost, and a large hydraulic circuit change or system This can be realized without design changes.

  In the above example, the case where the disc brake device is used as the brake device has been described. However, a drum brake device using a brake drum as the rotating member and a brake shoe as the friction member may be employed. Also in this case, as in the case where the disc brake device is employed, the brake shoe is separated from the brake drum in the non-pressurized state, and the fuel consumption can be prevented from being lowered due to dragging.

  By the way, when the brake control device of this embodiment includes a disc brake device, when the friction material 20 of the disc rotor 18 and the brake pad 14 is completely separated from each other, moisture such as rain, snow, and ice enters the formed gap. Sometimes. In that case, the friction state between the disk rotor 18 and the friction material 20 may change, and the initial braking force may change. Although the change in the initial braking force due to the intrusion of moisture does not affect the braking performance of the vehicle only when the braking force rises, it may give a slight change to the brake feeling felt by the driver. Further, when the disc rotor 18 and the friction material 20 of the brake pad 14 are completely separated from each other, foreign matters such as sand and pebbles may enter the gaps formed. If the friction material 20 of the brake pad 14 is pressed against the disc rotor 18 in a state where foreign matter has entered, the side surface 18a of the disc rotor 18 and the friction surface of the friction material 20 may be scratched or damaged.

  Therefore, when the fuel consumption reduction prevention control by the drag prevention described above is performed, a double structure brake pad 84 as shown in FIG. 3 can be employed. FIG. 3A is a side view of the brake pad 84 and the disk rotor 18, and FIG. 3B is a cross-sectional view taken along line AA in FIG. The brake pad 84 can be composed of an outer peripheral pad portion 86 that is an outer peripheral friction portion and an inner peripheral pad portion 88 that is an inner peripheral friction portion. The outer peripheral pad portion 86 has an annular shape that can contact the disk rotor 18 when the wheel cylinder 50 is in a pressurized state and in a non-pressurized state. The inner peripheral pad portion 88 is disposed on the inner peripheral portion of the outer peripheral pad portion 86 and contacts the disc rotor 18 when the wheel cylinder 50 is in a pressurized state, and is separated from the disc rotor 18 when the wheel cylinder 50 is not pressurized. . The outer peripheral pad portion 86 is constantly biased to the side surface 18a of the disk rotor 18 by a low elastic member such as a spring 90 that applies a predetermined biasing force. It is desirable that the urging force at this time is of a magnitude that realizes such a contact that the outer peripheral pad portion 86 makes slight contact with the side surface 18a or does not generate a substantial resistance force. The outer peripheral pad portion 86 may generate a braking force when the wheel cylinder is pressurized. However, when the outer peripheral pad portion 86 generates a braking force, it is necessary to secure a certain thickness in the radial direction of the disc rotor 18. is there. As a result, the drag area in the non-pressurized state increases. Therefore, the outer peripheral pad portion 86 serves as an intrusion prevention wall whose main purpose is to prevent moisture and foreign matter from entering between the disc rotor 18 and the friction material 20, and the radial direction of the disc rotor 18 of the outer peripheral pad portion 86. Is preferably set to such an extent that the strength of the peripheral pad portion 86 can be secured. For example, the thickness is preferably several mm. The outer peripheral pad portion 86 only needs to be able to contact the disk rotor 18 when the wheel cylinder 50 is in a pressurized state and in a non-pressurized state, and does not need to be positively pressed by the piston 26. Further, the outer peripheral pad portion 86 may be formed of a material different from that of the inner peripheral pad portion 88 with emphasis on its strength. In this manner, by reducing the contact area between the outer peripheral pad portion 86 and the disk rotor 18 as much as possible, a reduction in fuel consumption due to drag can be minimized and substantially negligible.

  As with the brake pad 14 shown in FIG. 1, the inner peripheral pad portion 88 is pressed by the piston 26 when the wheel cylinder 50 is in a pressurized state, and generates a predetermined braking force. The fuel consumption reduction prevention control by preventing the drag is performed, and the disk rotor 18 and the inner peripheral pad portion 88 are separated from each other. Note that the brake pad disposed on the claw 30 side similarly operates as a double structure brake pad 84. If the area of the outer peripheral pad portion 86 is made the minimum necessary as a function of the intrusion prevention wall, it is possible to ensure almost the same control performance as that of the non-separable brake pad.

  Thus, the brake pad having a double structure can achieve both the effect of preventing the intrusion of moisture and foreign matter by the conventional drag and the effect of reducing the fuel consumption.

  The present invention is not limited to the above-described embodiments, and various modifications such as design changes can be added based on the knowledge of those skilled in the art. The configuration shown in each figure is for explaining an example, and any configuration that can achieve the same function can be changed as appropriate, and the same effect can be obtained.

It is sectional drawing of the caliper of the disc brake device which the brake control apparatus of this embodiment controls. It is explanatory drawing explaining the whole structure of the brake control apparatus which concerns on this embodiment, and the electronic control unit contained in it. It is explanatory drawing explaining the structure of the brake pad of the double structure of the disc brake device which the brake control apparatus of this embodiment controls.

Explanation of symbols

  10 calipers, 14 brake pads, 16 cylinder parts, 18 disk rotors, 20 friction materials, 26 pistons, 34 brake control devices, 36 ECUs, 38 actuators, 50 wheel cylinders, 52 master cut valves, 56 reservoir tanks, 64 motors, 66 Oil pump, 70 accumulator, 74 reservoir cut valve, 78 pressure increasing valve, 80 pressure reducing valve, 84 brake pad, 86 outer peripheral pad portion, 88 inner peripheral pad portion.

Claims (2)

A wheel cylinder that generates a braking force by pressing a friction member against a rotating member that rotates together with the wheel;
An accumulator for accumulating hydraulic fluid for pressurizing the wheel cylinder;
A pump for increasing the pressure of the hydraulic fluid stored in the accumulator;
A reservoir tank capable of collecting the hydraulic fluid discharged during non-pressurization operation of the wheel cylinder and storing hydraulic fluid supplied to the pump;
A suppression means disposed in a flow path connecting the reservoir tank and the pump, and temporarily suppressing the supply of hydraulic fluid from the reservoir tank to the pump;
Detecting means for detecting that the wheel cylinder is in a non-pressurized state;
When the detection means detects a non-pressurized state of the wheel cylinder, the suppression means closes the liquid path from the reservoir tank side and drives the pump to suck in the hydraulic fluid from the wheel cylinder side. A separation control unit that places the wheel cylinder in a negative pressure state and separates the friction member from the rotating member;
A brake control device comprising:   The friction member is disposed on an outer peripheral friction portion that can contact the rotating member when the wheel cylinder is in a pressurized state and a non-pressurized state, and an inner peripheral portion of the outer peripheral friction portion, and when the wheel cylinder is in a pressurized state The brake control device according to claim 1, further comprising an inner circumferential friction portion that contacts the rotating member and is separated from the rotating member when the wheel cylinder is not pressurized.

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