JP2011168079A - Brake device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress influence on a braking control by pulsation of hydraulic pressure by a drum brake, in a brake device making a disc brake and the drum brake coexist. <P>SOLUTION: In a braking control device 20, ABS boosting valves 51 and 52 are provided to be opened so that working fluid may be supplied to wheel cylinders 23FR and 23FL imparting braking force according to the hydraulic pressure to the disc brake. ABS boosting valves 53 and 54 are provided to be opened so that working fluid may be supplied to wheel cylinders 23RR and 23RL imparting braking force according to the hydraulic pressure to the drum brake. In the ABS boosting valves 51 and 52, normal open valves to be opened by stopping supply of current and to be closed by supplying prescribed current are adopted. In the ABS boosting valves 53 and 54, normal close valves to be closed by stopping supply of current and to be opened by supplying prescribed current are adopted. A brake ECU 70 opens the ABS boosting valves 53 and 54 when total requested braking force of a front wheel is lower than a prescribed value. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a brake device, and more particularly to a brake device in which a disc brake and a drum brake coexist.

  A technique for adjusting the braking force applied to the wheel by controlling the wheel cylinder pressure by controlling the opening and closing of the pressure increasing valve is conventionally known. As such a brake control device, a brake control device employing a so-called normally open valve as a pressure increasing valve has been proposed (see, for example, Patent Document 1).

JP 2009-23386 A

  Generally, there are a disc brake and a drum brake as brakes for vehicles. Even now, for example, there are many vehicles in which a disc brake is provided corresponding to the front wheel and a drum brake is provided corresponding to the rear wheel from the viewpoint of reduction in size and weight. In the future, in order to deploy hybrid technology to a wide range of vehicles, it is necessary to adapt various braking control technologies to drum brakes.

  However, the drum brake has a problem that the wheel cylinder pressure easily pulsates during traveling of the vehicle due to the influence of the eccentricity of the drum due to the characteristics of the hardware configuration. For this reason, for example, in the brake device in which the disc brake and the drum brake coexist as described above, depending on the configuration of the hydraulic actuator for controlling the hydraulic pressure, the brake control of the disc brake is performed by the hydraulic pressure pulsation by the drum brake. May also be affected.

  Accordingly, the present invention has been made to solve the above-described problems, and an object of the present invention is to reduce the influence on the brake control by the pulsation of the hydraulic pressure by the drum brake in the brake device in which the disc brake and the drum brake coexist. It is to suppress.

  In order to solve the above-described problem, a brake device according to an aspect of the present invention includes a first pressure increasing valve that is opened to supply hydraulic fluid to a first wheel cylinder that applies a braking force corresponding to a hydraulic pressure to a disc brake. And a second pressure increasing valve that is opened to supply hydraulic fluid to a second wheel cylinder that applies a braking force according to the hydraulic pressure to the drum brake. The first pressure increasing valve is a normally open valve that is opened when current supply is stopped and closed when a predetermined current is supplied. The second pressure increasing valve is closed when current supply is stopped and a predetermined current is supplied. Is a normally closed valve that opens.

  According to this aspect, it is possible to open only the first pressure increasing valve by not supplying power to both the first pressure increasing valve and the second pressure increasing valve. Therefore, for example, by not supplying power to both the first pressure increasing valve and the second pressure increasing valve in a predetermined case, the braking force can be generated only for the disc brake, and the hydraulic pulsation generated by the drum brake is suppressed. can do. For this reason, it is possible to avoid the influence on the braking control due to the hydraulic pulsation of the drum brake while suppressing the power supplied to the valve.

  The apparatus may further comprise a valve control unit that controls opening and closing of each of the first pressure increasing valve and the second pressure increasing valve by controlling a current supplied to each of the first pressure increasing valve and the second pressure increasing valve. . When the valve control unit acquires the first braking request, the valve control unit opens the first pressure increasing valve and closes the second pressure increasing valve to request a braking force higher than the first braking request. When the second braking request to be obtained is acquired, the first pressure increasing valve may be opened and the second pressure increasing valve may be opened.

  According to this aspect, for example, when a request for generating a high braking force is acquired, the second booster valve is opened so that the braking force can be generated not only by the disc brake but also by the drum brake. Power can be obtained. For this reason, the operation amount of the brake pedal can be suppressed and the vehicle stability can be maintained.

  The second pressure increasing valve is interposed in a liquid path connecting the master cylinder, which is increased according to the operation amount of the brake pedal, and the second wheel cylinder, and when a hydraulic pressure higher than a predetermined pressure is applied. A relief valve that opens to supply hydraulic fluid to the second wheel cylinder may be used.

  According to this aspect, when the brake pedal is strongly depressed, the hydraulic fluid can be supplied from the master cylinder to the second wheel cylinder and the braking force can be generated by the drum brake. For this reason, a shortage of braking force when a high braking force is required can be avoided.

  According to the present invention, in the brake device in which the disc brake and the drum brake coexist, it is possible to suppress the influence on the braking control due to the pulsation of the hydraulic pressure by the drum brake.

It is a systematic diagram which shows the braking control apparatus which concerns on this embodiment. It is a flowchart which shows the control procedure of the braking control apparatus which concerns on this embodiment.

  Hereinafter, embodiments of the present invention (hereinafter referred to as “embodiments”) will be described in detail with reference to the drawings.

  FIG. 1 is a system diagram showing a braking control device 20 according to the present embodiment. The braking control device 20 shown in the figure constitutes an electronically controlled brake system (ECB) for a vehicle, and controls braking force applied to four wheels provided in the vehicle. The braking control device 20 according to the present embodiment is mounted on, for example, a hybrid vehicle that includes an electric motor and an internal combustion engine as a travel drive source. In such a hybrid vehicle, each of regenerative braking that brakes the vehicle by regenerating kinetic energy of the vehicle into electrical energy and hydraulic braking by the braking control device 20 can be used for braking the vehicle. The vehicle in the present embodiment can execute brake regenerative cooperative control that generates a desired braking force by using both the regenerative braking and the hydraulic braking together.

  The brake control device 20 according to the present embodiment is a brake device in which a disc brake and a drum brake coexist. As shown in FIG. 1, the disc brake units 21FR and 21FL, the drum brake units 28RR and 28RL, and the master A cylinder unit 27, a power hydraulic pressure source 30, and a hydraulic actuator 40 are included. Hereinafter, the disc brake units 21FR and 21FL are collectively referred to as “disc brake unit 21” as necessary. The drum brake units 28RR and 28RL are collectively referred to as “drum brake unit 28” as necessary.

  Each of the disc brake units 21FR and 21FL applies a braking force to each of the right front wheel and the left front wheel of the vehicle. Each of the drum brake units 28RR and 28RL applies a braking force to each of the right rear wheel and the left rear wheel of the vehicle. The master cylinder unit 27 as the manual hydraulic pressure source in the present embodiment uses the brake fluid (hydraulic fluid) pressurized according to the amount of operation by the driver of the brake pedal 24 as the brake operation member to the disc brake units 21FR and 21RL. And the drum brake units 28RR and 28RL. The power hydraulic pressure source 30 supplies the brake fluid as the working fluid pressurized by the power supply to the disc brake units 21FR and 21RL and the drum brake units 28RR and 28RL independently from the operation of the brake pedal 24 by the driver. Can be sent out. The hydraulic actuator 40 appropriately adjusts the hydraulic pressure of the brake fluid supplied from the power hydraulic pressure source 30 or the master cylinder unit 27 and sends it to the disc brake units 21FR and FL and the drum brake units 28RR and 28RL. Thereby, the braking force with respect to each wheel by hydraulic braking is adjusted.

  Each of the disc brake units 21FR and 21RL and the drum brake units 28RR and 28RL, the master cylinder unit 27, the power hydraulic pressure source 30, and the hydraulic actuator 40 will be described in more detail below. Each of the disc brake units 21FR and 21R includes a brake disc 22 and wheel cylinders 23FR and 23FL built in the brake caliper, respectively. Each of the drum brake units 28RR and 28RL includes a brake drum 29 and wheel cylinders 23RR and 23RL, respectively. The wheel cylinders 23FR to 23RL are connected to the hydraulic actuator 40 via different fluid passages. Hereinafter, the wheel cylinders 23FR to 23RL are collectively referred to as “wheel cylinders 23” as appropriate.

  In the disc brake units 21FR and 21RL, when brake fluid is supplied to the wheel cylinder 23 from the hydraulic actuator 40, a brake pad as a friction member is pressed against the brake disc 22 that rotates with the wheel. As a result, braking force is applied to the right front wheel and the left front wheel. In the drum brake units 28RR and 28RL, when brake fluid is supplied from the hydraulic actuator 40 to the wheel cylinder 23, a lining as a friction member is pressed against the brake drum 29. As a result, braking force is applied to the right rear wheel and the left rear wheel.

  The wheel cylinder 23FR applies a braking force corresponding to the hydraulic pressure to the brake disc 22 of the disc brake unit 21FR. The wheel cylinder 23FL applies a braking force corresponding to the hydraulic pressure to the brake disc 22 of the disc brake unit 21FL.

  The wheel cylinder 23RR applies a braking force corresponding to the hydraulic pressure to the brake drum 29 of the drum brake unit 28RR. The wheel cylinder 23RL gives a braking force corresponding to the hydraulic pressure to the drum brake unit 28RL.

  In this embodiment, the master cylinder unit 27 is a master cylinder with a hydraulic booster, and includes a hydraulic booster 31, a master cylinder 32, a regulator 33, and a reservoir. The hydraulic booster 31 is connected to the brake pedal 24, amplifies the pedal effort applied to the brake pedal 24, and transmits it to the master cylinder 32. When the brake fluid is supplied from the power hydraulic pressure source 30 to the hydraulic pressure booster 31 via the regulator 33, the pedal effort is amplified. The master cylinder 32 generates a master cylinder pressure having a predetermined boost ratio with respect to the pedal effort.

  A reservoir 34 for storing brake fluid is disposed above the master cylinder 32 and the regulator 33. The master cylinder 32 communicates with the reservoir 34 when the depression of the brake pedal 24 is released. On the other hand, the regulator 33 is in communication with both the reservoir 34 and the accumulator 35 of the power hydraulic pressure source 30, and the reservoir 34 is used as a low pressure source, the accumulator 35 is used as a high pressure source, and the hydraulic pressure is approximately equal to the master cylinder pressure. Is generated. Hereinafter, the hydraulic pressure in the regulator 33 is appropriately referred to as “regulator pressure”. The master cylinder pressure and the regulator pressure do not need to be exactly the same pressure. For example, the master cylinder unit 27 can be designed so that the regulator pressure is slightly higher.

  The master cylinder 32 and the regulator 33 have a so-called idle stroke. The idle stroke is a stroke from when the brake operation is not performed until the brake pedal 24 is depressed and the connection between the master cylinder 32 and the regulator 33 and the reservoir 34 is cut off. During the idle stroke, the fluid pressure in the master cylinder 32 and the regulator 33 does not increase because the reservoir 34 is in communication. The master cylinder unit 27 of the present embodiment is configured such that when the brake pedal is depressed, the idle stroke of the regulator 33 is first reduced as the stroke increases, and then the idle stroke of the master cylinder 32 is reduced. That is, the connection with the reservoir 34 is cut off in the order of the regulator 33 and the master cylinder 32.

  Hereinafter, for the sake of convenience, the pedal stroke when the connection between the regulator 33 and the reservoir 34 is cut off is referred to as a first cut-off stroke, and the stroke when the connection between the master cylinder 32 and the reservoir 34 is cut off is referred to as a second cut-off stroke. Called. In the present embodiment, the second cutoff stroke is larger than the first cutoff stroke. When the pedal stroke is between the first cutoff stroke and the second cutoff stroke, the regulator 33 has a higher pressure than the master cylinder 32 and a differential pressure is generated between the two hydraulic fluid chambers. This is because the regulator 33 is disconnected from the reservoir 34 and the hydraulic fluid is pressurized according to the stroke, whereas the master cylinder 32 is connected to the reservoir 34 and the hydraulic pressure does not increase.

  The power hydraulic pressure source 30 includes an accumulator 35 and a pump 36. The accumulator 35 converts the pressure energy of the brake fluid boosted by the pump 36 into the pressure energy of an enclosed gas such as nitrogen, for example, about 14 to 22 MPa and stores it. The pump 36 has a motor 36 a as a drive source, and its suction port is connected to the reservoir 34, while its discharge port is connected to the accumulator 35. The accumulator pressure is maintained within a set range to be maintained by the pump 36 (this may be referred to as an allowable range in the present specification). Based on the measurement value of the accumulator pressure sensor 72, the brake ECU 70 turns on the pump 36 to increase the accumulator pressure when the accumulator pressure falls below the lower limit of the allowable range, and when the accumulator pressure exceeds the upper limit of the allowable range. The pressurization is finished by turning off the pump 36.

  The accumulator 35 is also connected to a relief valve 35 a provided in the master cylinder unit 27. When the pressure of the brake fluid in the accumulator 35 increases abnormally to about 25 MPa, for example, the relief valve 35 a is opened, and the high-pressure brake fluid is returned to the reservoir 34.

  As described above, the brake control device 20 includes the master cylinder 32, the regulator 33, and the accumulator 35 as a supply source of brake fluid to the wheel cylinder 23. A master pipe 37 is connected to the master cylinder 32, a regulator pipe 38 is connected to the regulator 33, and an accumulator pipe 39 is connected to the accumulator 35. These master pipe 37, regulator pipe 38 and accumulator pipe 39 are each connected to a hydraulic actuator 40.

  The hydraulic actuator 40 includes an actuator block in which a plurality of flow paths are formed, and a plurality of electromagnetic control valves. The flow paths formed in the actuator block include individual flow paths 41, 42, 43 and 44 and a main flow path 45. The individual flow paths 41 to 44 are respectively branched from the main flow path 45 and connected to the corresponding wheel cylinders 23FR, 23FL, 23RR, 23RL of the disc brake units 21FR, 21FL and the drum brake units 28RR, 28RL. Thereby, each wheel cylinder 23 can communicate with the main flow path 45.

  In addition, ABS holding valves 51, 52, 53 and 54 are provided in the middle of the individual flow paths 41, 42, 43 and 44. The ABS pressure increasing valve 51 is opened to supply hydraulic fluid to the wheel cylinder 23FR when increasing the hydraulic pressure of the wheel cylinder 23FR. The ABS pressure increasing valve 52 is opened to supply hydraulic fluid to the wheel cylinder 23FL when increasing the hydraulic pressure of the wheel cylinder 23FL. The ABS pressure increasing valve 53 is opened to supply hydraulic fluid to the wheel cylinder 23RR when increasing the hydraulic pressure of the wheel cylinder 23RR. The ABS pressure increasing valve 54 is opened to supply hydraulic fluid to the wheel cylinder 23RL when increasing the hydraulic pressure of the wheel cylinder 23RL.

  Each of the ABS holding valves 51 to 54 in the opened state can distribute the brake fluid in both directions. That is, the brake fluid can flow from the main flow path 45 to the wheel cylinder 23, and conversely, the brake fluid can also flow from the wheel cylinder 23 to the main flow path 45. When the ABS holding valves 51 to 54 are closed, the flow of brake fluid in the individual flow paths 41 to 44 is blocked.

  Further, the wheel cylinder 23 is connected to the reservoir channel 55 via pressure reducing channels 46, 47, 48 and 49 connected to the individual channels 41 to 44, respectively. ABS decompression valves 56, 57, 58 and 59 are provided in the middle of the decompression channels 46, 47, 48 and 49. Each of the ABS pressure reducing valves 56 to 59 has a solenoid and a spring that are ON / OFF controlled, and is a normally closed electromagnetic control valve that is closed when the solenoid is in a non-energized state. When the ABS pressure reducing valves 56 to 59 are closed, the flow of brake fluid in the pressure reducing flow paths 46 to 49 is blocked. When the solenoid is energized and the ABS pressure reducing valves 56 to 59 are opened, the brake fluid is allowed to flow through the pressure reducing flow paths 46 to 49, and the brake fluid flows from the wheel cylinder 23 to the pressure reducing flow paths 46 to 49 and It returns to the reservoir 34 via the reservoir channel 55. The reservoir channel 55 is connected to the reservoir 34 of the master cylinder unit 27 via a reservoir pipe 77.

  The main channel 45 has a separation valve 60 in the middle. By this separation valve 60, the main channel 45 is divided into a first channel 45 a connected to the individual channels 41 and 42 and a second channel 45 b connected to the individual channels 43 and 44. The first flow path 45a is connected to the front wheel wheel cylinders 23FR and 23FL via the individual flow paths 41 and 42, and the second flow path 45b is connected to the rear wheel wheel cylinder via the individual flow paths 43 and 44. Connected to 23RR and 23RL.

  The separation valve 60 has a solenoid and a spring that are ON / OFF controlled, and is a normally closed electromagnetic control valve that is closed when the solenoid is in a non-energized state. When the separation valve 60 is in the closed state, the flow of brake fluid in the main flow path 45 is blocked. When the solenoid is energized and the separation valve 60 is opened, the brake fluid can be circulated bidirectionally between the first flow path 45a and the second flow path 45b.

  In the hydraulic actuator 40, a master channel 61 and a regulator channel 62 communicating with the main channel 45 are formed. More specifically, the master channel 61 is connected to the first channel 45 a of the main channel 45, and the regulator channel 62 is connected to the second channel 45 b of the main channel 45. The master channel 61 is connected to a master pipe 37 that communicates with the master cylinder 32. The regulator channel 62 is connected to a regulator pipe 38 that communicates with the regulator 33.

  The master channel 61 has a master cut valve 64 in the middle. The master cut valve 64 is provided on the brake fluid supply path from the master cylinder 32 to each wheel cylinder 23. The master cut valve 64 has a solenoid and a spring that are ON / OFF-controlled, and the valve closing state is guaranteed by the electromagnetic force generated by the solenoid when supplied with a prescribed control current, so that the solenoid is in a non-energized state. It is a normally open electromagnetic control valve that is opened in some cases. The master cut valve 64 in the opened state can cause the brake fluid to flow in both directions between the master cylinder 32 and the first flow path 45 a of the main flow path 45. When a prescribed control current is applied to the solenoid and the master cut valve 64 is closed, the flow of brake fluid in the master flow path 61 is interrupted.

  A stroke simulator 69 is connected to the master channel 61 via a simulator cut valve 68 on the upstream side of the master cut valve 64. That is, the simulator cut valve 68 is provided in a flow path connecting the master cylinder 32 and the stroke simulator 69. The simulator cut valve 68 has a solenoid and a spring that are ON / OFF controlled, and the valve opening state is guaranteed by the electromagnetic force generated by the solenoid upon receipt of a specified control current, and the solenoid is in a non-energized state. It is a normally closed electromagnetic control valve that is closed in some cases. When the simulator cut valve 68 is closed, the flow of brake fluid between the master flow path 61 and the stroke simulator 69 is blocked. When the solenoid is energized and the simulator cut valve 68 is opened, the brake fluid can be circulated bidirectionally between the master cylinder 32 and the stroke simulator 69.

  The stroke simulator 69 includes a plurality of pistons and springs, and creates a reaction force corresponding to the depression force of the brake pedal 24 by the driver when the simulator cut valve 68 is opened. As the stroke simulator 69, in order to improve the feeling of brake operation by the driver, it is preferable to employ one having a multistage spring characteristic.

  The regulator flow path 62 has a regulator cut valve 65 in the middle. The regulator cut valve 65 is provided on the brake fluid supply path from the regulator 33 to each wheel cylinder 23. The regulator cut valve 65 also has a solenoid and a spring that are ON / OFF controlled, and the valve closing state is guaranteed by the electromagnetic force generated by the solenoid upon receipt of a specified control current, and the solenoid is in a non-energized state. It is a normally open electromagnetic control valve that is opened in some cases. The regulator cut valve 65 that has been opened can cause the brake fluid to flow in both directions between the regulator 33 and the second flow path 45 b of the main flow path 45. When the solenoid is energized and the regulator cut valve 65 is closed, the flow of brake fluid in the regulator flow path 62 is blocked.

  In the hydraulic actuator 40, an accumulator channel 63 is also formed in addition to the master channel 61 and the regulator channel 62. One end of the accumulator channel 63 is connected to the second channel 45 b of the main channel 45, and the other end is connected to an accumulator pipe 39 that communicates with the accumulator 35.

  The accumulator flow path 63 has a pressure-increasing linear control valve 66 in the middle. Further, the accumulator channel 63 and the second channel 45 b of the main channel 45 are connected to the reservoir channel 55 via the pressure-reducing linear control valve 67. The pressure-increasing linear control valve 66 and the pressure-decreasing linear control valve 67 each have a linear solenoid and a spring, and both are normally closed electromagnetic control valves that are closed when the solenoid is in a non-energized state. In the pressure-increasing linear control valve 66 and the pressure-decreasing linear control valve 67, the opening degree of the valve is adjusted in proportion to the current supplied to each solenoid.

  The pressure-increasing linear control valve 66 is provided as a common pressure-increasing control valve for each of the wheel cylinders 23 provided corresponding to each wheel. Similarly, the pressure-reducing linear control valve 67 is provided as a pressure-reducing control valve common to the wheel cylinders 23. That is, in this embodiment, the pressure-increasing linear control valve 66 and the pressure-reducing linear control valve 67 are a pair of common control valves that control the supply and discharge of the working fluid sent from the power hydraulic pressure source 30 to each wheel cylinder 23. It is provided as. Thus, if the pressure-increasing linear control valve 66 and the pressure-decreasing linear control valve 67 are made common to the wheel cylinders 23, it is preferable from the viewpoint of cost as compared to providing a linear control valve for each wheel cylinder 23.

  Here, the differential pressure between the inlet and outlet of the pressure-increasing linear control valve 66 corresponds to the differential pressure between the pressure of the brake fluid in the accumulator 35 and the pressure of the brake fluid in the main flow path 45, and the inlet / outlet of the pressure-reducing linear control valve 67. The pressure difference therebetween corresponds to the pressure difference between the brake fluid pressure in the main flow path 45 and the brake fluid pressure in the reservoir 34. Further, the electromagnetic driving force according to the power supplied to the linear solenoid of the pressure increasing linear control valve 66 and the pressure reducing linear control valve 67 is F1, the spring biasing force is F2, and the pressure increasing linear control valve 66 and the pressure reducing linear control valve are Assuming that the differential pressure acting force according to the differential pressure between the inlet / outlet of 67 is F3, the relationship of F1 + F3 = F2 is established. Therefore, the differential pressure between the inlet and outlet of the pressure-increasing linear control valve 66 and the pressure-reducing linear control valve 67 is controlled by continuously controlling the power supplied to the linear solenoids of the pressure-increasing linear control valve 66 and the pressure-reducing linear control valve 67. can do.

  In the braking control device 20, the power hydraulic pressure source 30 and the hydraulic actuator 40 are controlled by a brake ECU 70 as a control unit in the present embodiment. The brake ECU 70 is configured as a microprocessor including a CPU, and includes a ROM that stores various programs, a RAM that temporarily stores data, an input / output port, a communication port, and the like in addition to the CPU. The brake ECU 70 can communicate with a host hybrid ECU (not shown) and the like, and based on control signals from the hybrid ECU and signals from various sensors, the pump 36 of the power hydraulic pressure source 30 and the hydraulic pressure The electromagnetic control valves 51 to 54, 56 to 59, 60, and 64 to 68 constituting the actuator 40 are controlled.

  Further, a regulator pressure sensor 71, an accumulator pressure sensor 72, and a control pressure sensor 73 are connected to the brake ECU 70. The regulator pressure sensor 71 detects the pressure of the brake fluid in the regulator flow path 62 on the upstream side of the regulator cut valve 65, that is, the regulator pressure, and gives a signal indicating the detected value to the brake ECU 70. The accumulator pressure sensor 72 detects the pressure of the brake fluid in the accumulator flow path 63, that is, the accumulator pressure on the upstream side of the pressure increasing linear control valve 66, and gives a signal indicating the detected value to the brake ECU 70. The control pressure sensor 73 detects the pressure of the brake fluid in the first flow path 45a of the main flow path 45, and gives a signal indicating the detected value to the brake ECU 70. Since the main flow path 45 is connected to the wheel cylinder 23, the control pressure sensor 73 detects the control pressure acting on the wheel cylinder 23. The detection values of the pressure sensors 71 to 73 are sequentially given to the brake ECU 70 every predetermined time, and are stored and held in a predetermined storage area of the brake ECU 70.

  When the separation valve 60 is opened and the first flow path 45 a and the second flow path 45 b of the main flow path 45 communicate with each other, the output value of the control pressure sensor 73 is the low pressure of the pressure-increasing linear control valve 66. This indicates the hydraulic pressure on the high pressure side of the pressure-reducing linear control valve 67 and the output value can be used to control the pressure-increasing linear control valve 66 and the pressure-reducing linear control valve 67. When the pressure-increasing linear control valve 66 and the pressure-decreasing linear control valve 67 are closed and the master cut valve 64 is opened, the output value of the control pressure sensor 73 indicates the master cylinder pressure. Further, the separation valve 60 is opened so that the first flow path 45a and the second flow path 45b of the main flow path 45 communicate with each other, and the ABS holding valves 51 to 54 are opened, while the ABS pressure reducing valves 56 are opened. When? 59 is closed, the output value of the control pressure sensor 73 indicates the working fluid pressure acting on each wheel cylinder 23, i.e., the wheel cylinder pressure.

  Further, the sensor connected to the brake ECU 70 includes a stroke sensor 25 provided on the brake pedal 24. The stroke sensor 25 detects a pedal stroke as an operation amount of the brake pedal 24 and gives a signal indicating the detected value to the brake ECU 70.

  Further, a stop lamp switch is connected to the brake ECU 70. The stop lamp switch is turned on when the brake pedal 24 is depressed. As a result, the stop lamp is turned on. When the depression of the brake pedal 24 is released, the stop lamp switch is turned off and the stop lamp is turned off. A signal indicating the lighting state of the stop lamp switch is input from the stop lamp switch to the brake ECU 70 every predetermined time, and is stored and held in a predetermined storage area of the brake ECU 70.

  The braking control device 20 configured as described above can execute brake regeneration cooperative control. The braking control device 20 receives the braking request and starts braking. The braking request is generated when a braking force should be applied to the vehicle, for example, when the driver operates the brake pedal 24. In response to the braking request, the brake ECU 70 calculates a required braking force, and calculates a required hydraulic braking force that is a braking force to be generated by the braking control device 20 by subtracting the braking force due to regeneration from the required braking force. Here, the effective value of the braking force due to regeneration is supplied from the hybrid ECU to the braking control device 20. Then, the brake ECU 70 calculates the target hydraulic pressure of each wheel cylinder 23FR to 23RL based on the calculated required hydraulic braking force. The brake ECU 70 determines the value of the control current supplied to the pressure-increasing linear control valve 66 and the pressure-decreasing linear control valve 67 based on the feedback control law so that the wheel cylinder pressure becomes the target hydraulic pressure.

  As a result, in the brake control device 20, the brake fluid is supplied from the power hydraulic pressure source 30 to each wheel cylinder 23 via the pressure-increasing linear control valve 66, and a braking force is applied to the wheels. Further, brake fluid is discharged from each wheel cylinder 23 through the pressure-reducing linear control valve 67 as necessary, and the braking force applied to the wheel is adjusted. In the brake control device 20, the master cylinder unit 27, the power hydraulic pressure source 30, the hydraulic pressure actuator 40, the disc brake unit 21, and the drum brake unit 28 increase or decrease the wheel cylinder pressure by increasing or decreasing the control pressure. Functions as a control system. This wheel cylinder pressure control system performs so-called brake-by-wire braking force control. The braking control device 20 according to the present embodiment can naturally control the braking force by the wheel cylinder pressure control system even when the required braking force is provided only by the hydraulic braking force without using the regenerative braking force. .

  When brake-by-wire braking force control is performed, the brake ECU 70 closes the regulator cut valve 65 so that the brake fluid delivered from the regulator 33 is not supplied to the wheel cylinder 23. Further, the brake ECU 70 closes the master cut valve 64 and opens the simulator cut valve 68. This is because the brake fluid sent from the master cylinder 32 in accordance with the operation of the brake pedal 24 by the driver is supplied not to the wheel cylinder 23 but to the stroke simulator 69. During the brake regeneration cooperative control, a differential pressure corresponding to the magnitude of the regenerative braking force acts between the upstream and downstream of the regulator cut valve 65 and the master cut valve 64. The brake ECU 70 opens the separation valve 60. Thereby, each wheel cylinder pressure is controlled to a common hydraulic pressure.

  If it is determined from the detection result of the stroke sensor 25 that the brake pedal 24 is not depressed, the brake ECU 70 closes the separation valve 60, the pressure-increasing linear control valve 66, and the pressure-decreasing linear control valve 67, and the master cut valve 64 and the regulator cut valve 65 are opened. When it is determined that the brake pedal 24 is depressed, the stroke sensor 25 opens the separation valve 60, the pressure increasing linear control valve 66, and the pressure reducing linear control valve 67, and closes the master cut valve 64 and the regulator cut valve 65. And brake-by-wire braking force control.

  When it is determined that a predetermined abnormal condition has been satisfied during execution of the braking force control of the brake-by-wire system, the brake ECU 70 also determines that the brake pedal 24 has been depressed, the separation valve 60, the pressure-increasing linear control valve 66, The pressure-reducing linear control valve 67 is closed, and the master cut valve 64 and the regulator cut valve 65 are kept open. As a result, the brake fluid can be supplied directly to each of the wheel cylinders 23 by depressing the brake pedal 24.

  The drum brake units 28RR and RL have a problem that the wheel cylinder pressure is likely to pulsate during traveling of the vehicle due to the influence of the eccentricity of the drum due to the characteristics of the hardware configuration. Since the drum brake unit is known, a detailed description of the structure of the drum brake units 28RR and 28RL will be omitted.

  In the brake device in which the disc brake unit 21 and the drum brake unit 28 coexist like the braking control device 20 according to the present embodiment, such pulsation of the hydraulic pressure can be transmitted to the hydraulic pressure path to the disc brake unit 21. There is sex. Particularly in the brake control device 20, when the separation valve 60 is open, the wheel cylinders 23 communicate with each other, so that the hydraulic pressure pulsation caused by the drum brake unit 28 is particularly easily transmitted to the periphery of the disc brake unit 21.

  When such hydraulic pressure pulsation occurs, hunting may occur in which the detected wheel cylinder pressure repeatedly increases and decreases with respect to the target hydraulic pressure. In order to suppress such hunting, a method is considered in which a dead zone is provided with respect to the target hydraulic pressure, and when the detected wheel cylinder pressure deviates from this dead zone, the wheel cylinder pressure is controlled so as to approach the dead zone. It is done. However, when the hydraulic pressure pulsation of the drum brake unit 28 is easily transmitted to the periphery of the disc brake unit 21 as in the present embodiment, the disc brake unit 21 also has a target hydraulic pressure to suppress the influence of the hydraulic pressure pulsation. Therefore, it is necessary to provide a relatively large dead zone.

  When the dead zone is increased in both the drum brake unit 28 and the disc brake unit 21 as in the present embodiment, the response speed of the wheel cylinder pressure becomes slower than in the case where a large dead zone is provided only in the drum brake unit 28, and the brake feeling. There is a risk of having a greater impact. In addition, when a large dead zone is provided, since the pressure reduction is terminated when the dead zone is reached even during the pressure reduction, a residual pressure may be generated in the wheel cylinder pressure. If the dead zone is increased in both the drum brake unit 28 and the disc brake unit 21 as in this embodiment, the disc brake unit 21 may be dragged so that the brake pad contacts the disc rotor. For this reason, the fuel consumption of the vehicle may be a factor.

  For this reason, in the present embodiment, normally open valves are employed for the ABS boost valves 51 and 52, and normally closed valves are employed for the ABS boost valves 53 and 54. The normally open valve is a valve that opens when current supply is stopped and closes when a predetermined current is supplied. The normally closed valve is a valve that closes when current supply is stopped and opens when a predetermined current is supplied.

  By adopting a normally closed valve for the ABS boost valves 53 and 54 as described above, the ABS boost valves 53 and 54 can be closed without supplying electric power to give a braking force only to the front wheels in a predetermined case. it can. For this reason, it is possible to prevent the hydraulic pulsation generated by the drum brake unit 28 from being transmitted to the disc brake unit 21 while suppressing power consumption.

  Further, the ABS pressure increasing valves 51 and 52 are interposed in a liquid path connecting each of the wheel cylinders 23FR and 23FL and the master cylinder 32. Further, the ABS pressure increasing valves 53 and 54 are interposed in a liquid path connecting each of the wheel cylinders 23RR and 23RL and the regulator 33.

  Relief valves are employed for the ABS boost valves 53 and 54. The relief valve is a valve that opens when a hydraulic pressure equal to or higher than a predetermined pressure is applied. Specifically, the relief valve has a ball (not shown), a valve seat (not shown), and a coil spring (not shown). The coil spring applies a biasing force to the ball so as to be seated on the valve seat. Since the relief valve is known, the detailed structure of the relief valve will not be described.

When the brake ECU 70 determines that any abnormality has occurred in the braking control device 20, the brake ECU 70 closes the pressure-increasing linear control valve 66 and the pressure-decreasing linear control valve 67 as described above, and sets the master cut valve 64 and the regulator cut valve 65 as well. Open the valve. As a result, the master cylinder 32 and the ABS pressure increasing valves 51 and 52 communicate with each other, and the regulator 33 and the ABS pressure increasing valves 53 and 54 communicate with each other.
Each of the master cylinder 32 and the regulator 33 is increased in pressure according to the operation amount of the brake pedal 24. When the brake pedal 24 is not depressed and the hydraulic pressure of the regulator 33 is low, the ball is seated on the valve seat by the biasing force of the coil spring, and the relief valve is closed. However, when the brake pedal 24 is depressed and the hydraulic fluid pressure of the regulator 33 exceeds a predetermined value, the force applied to the ball by the hydraulic fluid pressure becomes stronger than the urging force of the coil spring, and the ball is separated from the valve seat. The relief valve opens. By adopting a relief valve for each of the ABS boost valves 53 and 54 as described above, the braking force generated by making the ABS boost valves 53 and 54 normally closed when something abnormal occurs in the brake control device 20. A decrease can be avoided.

  FIG. 2 is a flowchart showing a control procedure of the braking control apparatus 20 according to the present embodiment. The processing in this flowchart starts when the ignition switch of the vehicle is turned on, and is repeatedly executed every predetermined time until the ignition switch of the vehicle is turned off.

  The brake ECU 70 functions as a valve control unit that controls the opening and closing of each of the ABS boost valves 51 to 54 by controlling the current supplied to each of the ABS boost valves 51 to 54. The brake ECU 70 determines whether or not there is a braking request by determining whether or not the brake pedal 24 is depressed using the detection results of the stroke sensor 25 and the control pressure sensor 73 (S10). If there is no braking request (N in S10), the processing in this flowchart is temporarily terminated.

  A vehicle in which the braking control device 20 is mounted is provided with a regenerative braking mechanism that applies a regenerative braking force to the wheels by regenerative control of a motor that is an electric motor. Since such a regenerative braking mechanism is well known, description thereof is omitted. Furthermore, the vehicle according to the present embodiment is a front wheel drive vehicle, and a regenerative braking force is applied to the front wheels, that is, the wheels to which the braking force is applied by the disc brake unit 21. The vehicle according to this embodiment may be a four-wheel drive vehicle. When there is a braking request (Y in S10), the brake ECU 70 determines whether or not the total required braking force of the front wheels to be applied by the disc brake unit 21 and the regenerative braking mechanism is equal to or greater than a predetermined value X1 (S12). This total required braking force for the front wheels may be the sum of the braking forces to be achieved by all wheels.

  In the present embodiment, the brake ECU 70 calculates the friction braking force to be applied to each of the right front wheel and the left front wheel by the disc brake unit 21 using the detection result of the control pressure sensor 73. Further, the brake ECU 70 acquires the braking torque of the motor, and uses this to calculate the regenerative braking force to be applied to each of the right front wheel and the left front wheel. Since the calculation method of such friction braking force and regenerative braking force is well known, description thereof is omitted. The brake ECU 70 compares the sum of the calculated friction braking force and regenerative braking force as a total required braking force for the front wheels with a predetermined value X1.

  Note that the regenerative braking mechanism may not be provided in the vehicle. In this case, the brake ECU 70 uses the detection result of the control pressure sensor 73 to calculate the friction braking force to be applied to each of the right front wheel and the left front wheel by the disc brake unit 21, and uses the calculated friction braking force for the front wheels. The required braking force is compared with a predetermined value X1.

  When the total required braking force of the front wheels is smaller than X1 (N in S12), the processing in this flowchart is temporarily ended. As a result, when the required braking force is relatively low, the braking force is applied to the front wheels by the disc brake unit 21 and the braking force from the drum brake unit 28 is not applied to the rear wheels. For this reason, generation | occurrence | production of the hydraulic pressure pulsation by the drum brake unit 28 can be avoided, and the fall of a brake feeling and vehicle stability can be suppressed.

  When it is determined that the total required braking force of the front wheels is equal to or greater than X1 (Y in S12), the brake ECU 70 opens the pressure increasing valve corresponding to the drum brake unit 28 (S14). Thereby, when the required braking force is relatively high, the braking force can be applied to all the front and rear wheels, and a shortage of the braking force can be avoided.

  As described above, in this embodiment, when the brake ECU 70 acquires the first braking request that requires a relatively weak braking force, the brake ECU 70 opens the ABS boost valves 51 and 52 and opens the ABS boost valves 53 and 54. When the valve is closed and the second braking request that requires a braking force higher than the first braking request is acquired, the ABS pressure increasing valves 51 and 52 are opened and the ABS pressure increasing valves 53 and 54 are also opened. For example, an acceleration sensor that detects acceleration applied to the vehicle in the longitudinal direction of the vehicle may be provided. The brake ECU 70 uses the detection result of the acceleration sensor to determine that the braking force greater than the predetermined value is generated in the vehicle when the absolute value of the deceleration exceeds the predetermined value, and determines that the ABS pressure increasing valve 53 , 54 may be opened. This also makes it possible for the drum brake unit 28 to appropriately generate a braking force when a large braking force is required.

  The present invention is not limited to the above-described embodiment, and an appropriate combination of the elements of this embodiment is also effective as an embodiment of the present invention. Various modifications such as various design changes can be added to the present embodiment based on the knowledge of those skilled in the art, and the embodiments with such modifications can be included in the scope of the present invention.

  20 brake control device, 21FR, 21FL disc brake unit, 23FR, 23FL, 23RR, 23RL wheel cylinder, 24 brake pedal, 25 stroke sensor, 28RR, 28RL drum brake unit, 32 master cylinder, 51, 52, 53, 54 ABS increase Pressure valve, 60 separation valve, 64 master cut valve, 65 regulator cut valve.

Claims (3)

A first pressure increasing valve that is opened to supply hydraulic fluid to a first wheel cylinder that applies a braking force in accordance with the hydraulic pressure to the disc brake;
A second pressure increasing valve that is opened to supply hydraulic fluid to a second wheel cylinder that applies a braking force in accordance with the hydraulic pressure to the drum brake;
With
The first pressure increasing valve is a normally open valve that opens by stopping the supply of current and closes by supplying a predetermined current;
The brake device according to claim 1, wherein the second pressure increasing valve is a normally closed valve that closes when current supply is stopped and opens when a predetermined current is supplied. A valve control unit that controls opening and closing of each of the first pressure increasing valve and the second pressure increasing valve by controlling a current supplied to each of the first pressure increasing valve and the second pressure increasing valve;
The valve control unit
When the first braking request is acquired, the first pressure increasing valve is opened and the second pressure increasing valve is closed,
The second pressure increasing valve is opened and the second pressure increasing valve is opened when a second braking request that requires a braking force higher than the first braking request is acquired. Item 4. The brake device according to item 1.   The second pressure increasing valve is interposed in a liquid path connecting the master cylinder, which is increased according to the operation amount of the brake pedal, and the second wheel cylinder, and when a hydraulic pressure higher than a predetermined pressure is applied. The brake device according to claim 1, wherein the brake valve is a relief valve that opens to supply hydraulic fluid to the second wheel cylinder.

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