JP5359436B2 - Brake control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a brake control device making suppression of noise and desired starting performance compatible. <P>SOLUTION: The brake control device retains the brake liquid pressure so as to prevent slide down of a vehicle at stepping-change of a pedal while stopping on a slope. The brake control device is provided with: a pressure reduction control valve for releasing retaining of the brake liquid pressure; and a control part for controlling the pressure reduction control valve such that pressure reduction is continued over an allowance time from starting of releasing of retaining of the brake liquid pressure set based on the desired starting performance to completion of releasing, and that pressure-reduction is completed at the time when the allowance time is passed. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

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

  Patent Document 1 describes a hydraulic brake device for a vehicle that can obtain a parking brake state during non-brake operation. This device increases the hydraulic pressure in the wheel brake side hydraulic pressure path by operating the pump before opening the electromagnetic on-off valve to release the parking brake state. Thereby, it is supposed that generation | occurrence | production of the operation sound at the time of valve opening of an electromagnetic on-off valve and a vibration can be suppressed. Patent Documents 2 and 3 describe a braking force holding device for a vehicle that holds a braking force that prevents movement of the vehicle when the vehicle is stopped and reduces the held braking force when the vehicle starts.

JP 2006-193039 A JP 2004-231155 A JP 2004-203100 A

  Incidentally, abnormal noise may occur in the brake control device. For example, there is an operation sound when the control valve is opened and closed, and a flow sound generated when hydraulic fluid flows through the control valve. If the flow rate is limited, the flow noise can be reduced, but it takes time to release the held braking force. It is desirable that the vehicle can be quickly shifted from the stop to the start according to the driver's request.

  Accordingly, an object of the present invention is to provide a brake control device that realizes both suppression of abnormal noise and desired start performance.

  A brake control device according to an aspect of the present invention includes a wheel cylinder that receives a supply of hydraulic fluid and applies a braking force to a wheel, and a manual that pressurizes the stored hydraulic fluid in accordance with an operation amount of a brake operation member by a driver. A hydraulic pressure source is provided in parallel to the manual hydraulic pressure source with respect to the wheel cylinder, a hydraulic pressure source for accumulating hydraulic fluid by supplying power, and the dynamic hydraulic pressure source as a high pressure source. A wheel cylinder pressure control system that controls the wheel cylinder pressure to follow the pressure, and the manual hydraulic pressure source is shut off from the wheel cylinder while the vehicle is stopped, and is set based on the hydraulic pressure of the manual hydraulic pressure source Of the first target pressure and the second target pressure set based on the inclination of the stop position in order to maintain the stop state, a higher one is used as the target pressure. And a control unit for performing a hydraulic retention control for controlling the Sunda pressure control system, the. The controller is configured to reduce a pressure reduction gradient according to a wheel cylinder pressure at a pressure reduction start time so that the pressure reduction is completed when a preset pressure reduction completion target time elapses when an end condition of the hydraulic pressure holding control is satisfied. To decide.

  According to this aspect, when the hydraulic pressure holding control is terminated, it is guaranteed that the pressure is reduced at the set target time for completion of pressure reduction. Therefore, desired start performance can be realized. Further, the pressure is reduced with a pressure reduction gradient determined according to the wheel cylinder pressure at the time of starting the pressure reduction. Therefore, unlike simply depressurizing at the maximum gradient, that is, at the maximum flow rate, it is possible to reduce the hydraulic fluid flow noise during depressurization.

  The control unit may start depressurization with an initial depressurization gradient smaller than a constant depressurization gradient that completes depressurization at the depressurization completion target time, and the depressurization gradient at the time of completion of depressurization may be a value larger than the constant depressurization gradient. .

  In this way, the flow rate of the hydraulic fluid in the high pressure region can be reduced by setting a small pressure reduction gradient at the beginning of pressure reduction. Abnormal noise can be more effectively suppressed in a high-pressure region where flow noise is likely to occur.

  The controller may control the pressure reduction gradient so that the pressure reduction is completed at the pressure reduction completion target time when an acceleration operation by the driver is started.

  In this way, when an acceleration operation is performed, the completion of pressure reduction at the target time for completion of pressure reduction is guaranteed, and a smooth transition can be made from the end of braking to the start of acceleration. Moreover, when acceleration operation is not performed, it is also possible to set it as the pressure reduction which attached more importance to suppression of abnormal noise.

  Another aspect of the present invention is also a brake control device. This device maintains the brake fluid pressure in order to prevent the vehicle from sliding down when the pedal is changed while the vehicle is stopped on a slope. The brake control device includes a pressure reducing control valve for releasing the holding of the brake fluid pressure, and continues the pressure reduction over an allowable time from the start to the completion of the brake hydraulic pressure holding set based on a desired start performance. And a controller that controls the pressure-reducing control valve so as to complete the pressure-reducing when the time elapses.

  According to this aspect, it is possible to gradually reduce the pressure by making the maximum use of the retained hydraulic pressure release allowable time set based on the desired start performance. For this reason, while suppressing the abnormal noise at the time of pressure reduction, it is possible to realize a quick switch from the slip prevention braking control to the vehicle start.

  According to the present invention, it is possible to achieve both suppression of abnormal noise and desired start performance.

It is a systematic diagram showing a brake control device according to each embodiment of the present invention. It is a figure for demonstrating the wheel cylinder pressure holding | maintenance control for the sliding prevention during the stop which concerns on one Embodiment of this invention. It is a flowchart for demonstrating the cancellation | release process of the hydraulic pressure holding control during a stop which concerns on one Embodiment of this invention.

  In one embodiment of the present invention, a brake control device that prevents a vehicle from sliding down when a driver switches from a brake pedal to an accelerator pedal by maintaining a certain level of brake fluid pressure while stopping on a slope. Is provided. The brake control device determines a decompression profile each time so as to prevent or reduce self-excited vibration in the decompression control valve when releasing the slip prevention control. For example, the holding of the hydraulic pressure is released with a reduced pressure profile having a reduced pressure gradient that is less than the maximum flow rate of the reduced pressure control valve.

  The brake control device may determine the decompression profile based on the retained fluid pressure at the start of decompression and a preset decompression completion target time. The target time for completion of pressure reduction is a time set so as to satisfy a desired start performance, for example, a time allowed as a required time from the start of depression of the accelerator pedal until reaching the brake holding hydraulic pressure release state. . The brake control device may continue the pressure reduction over the target time for completion of pressure reduction and complete the pressure reduction when the target time for completion of pressure reduction has elapsed. Alternatively, when the retentive fluid pressure is sufficiently low, the depressurization may be completed before the depressurization completion target time elapses.

  The control unit of the brake control device may release the holding hydraulic pressure at a constant pressure reduction gradient determined according to the wheel cylinder pressure at the time of starting the pressure reduction so that the pressure reduction is completed at the time when the pressure reduction completion target time has elapsed. The pressure reducing gradient is set to a value smaller than the maximum flow rate of the control valve. Further, the control unit may reduce the pressure at the beginning of pressure reduction at a gentler slope than the constant slope, and increase the pressure reduction gradient toward completion of the pressure reduction. The control unit may determine an initial pressure reduction gradient that is smaller than a certain pressure reduction gradient that completes the pressure reduction at the pressure reduction completion target time, according to the wheel cylinder pressure at the time of starting the pressure reduction. The control unit determines the initial value of the pressure reduction gradient to a value at which the pressure reduction cannot be completed at the target time for completion of pressure reduction. So that the depressurization gradient at the time of depressurization completion is larger than the initial value. The decompression gradient at the time of completion of decompression may be the maximum decompression gradient possible for the decompression control valve.

  The control unit may set the pressure reduction gradient in the hydraulic pressure region where the occurrence of self-excited vibration of the control valve is assumed to a magnitude that guarantees that no self-excited vibration will occur. Usually, the self-excited vibration is likely to occur in a high pressure region, and particularly, the greater the flow rate in the high pressure region, the easier it is to generate. Therefore, the control unit may set a decompression profile in which the pressure is gradually reduced in the region where the self-excited vibration is assumed, and the pressure is reduced more rapidly outside the region where the self-excited vibration is assumed. For example, the pressure is reduced at the first pressure reduction gradient that is guaranteed not to cause self-excited vibration until the self-excited vibration non-occurrence threshold is reduced from the start of pressure reduction, and below the self-excited vibration non-occurrence threshold You may depressurize with the 2nd decompression gradient larger than the 1st decompression gradient.

  In one embodiment, the control unit holds the wheel cylinder pressure while the vehicle is stopped at least at a minimum holding pressure that is set based on the road surface state of the stopping position, for example, the amount of inclination, in order to maintain the stopped state. May be executed. The control unit may set the minimum holding pressure to a constant value regardless of the situation, for example, may be set to a size that keeps the vehicle stopped with the maximum amount of inclination assumed. The control unit may make the wheel cylinder pressure coincide with the operation hydraulic pressure when the operation hydraulic pressure pressurized by the driver's brake pedal operation exceeds the minimum holding pressure.

  The control unit may execute the hydraulic pressure holding control when a start condition including that the driver has depressed the brake pedal more than a predetermined value while the vehicle is stopped is satisfied. Further, the control unit may end the hydraulic pressure holding control when an end condition including that the driver has operated the accelerator pedal is satisfied. The termination condition may include that a predetermined time has elapsed since the driver released the operation of the brake pedal. The control unit may determine the pressure reduction profile and start the pressure reduction of the holding fluid pressure when the end condition of the fluid pressure holding control is satisfied.

  The brake control device may include means for detecting a driver's acceleration request. The control unit may execute the decompression gradient relaxation process when the acceleration request is detected. When the acceleration request is not detected, the control unit may complete the depressurization of the retained hydraulic pressure while maintaining a depressurization gradient that is guaranteed not to cause self-excited vibration, or the depressurization is completed. The holding hydraulic pressure may be reduced over a longer time than the target time.

  FIG. 1 is a system diagram showing a brake control device 20 according to each embodiment of the present invention. A brake 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 on the vehicle. The brake 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 electric energy and hydraulic braking by the brake 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.

  As shown in FIG. 1, the brake control device 20 includes disc brake units 21FR, 21FL, 21RR and 21RL provided for each wheel, a master cylinder unit 27, a power hydraulic pressure source 30, a hydraulic pressure, Actuator 40.

  Disc brake units 21FR, 21FL, 21RR, and 21RL apply braking force to the right front wheel, the left front wheel, the right rear wheel, and the left rear wheel of the vehicle, respectively. The master cylinder unit 27 as the manual hydraulic pressure source in the present embodiment sends the brake fluid pressurized according to the operation amount by the driver of the brake pedal 24 as the brake operation member to the disc brake units 21FR to 21RL. To do. The power hydraulic pressure source 30 can send the brake fluid as the working fluid pressurized by the power supply to the disc brake units 21FR to 21RL independently from the operation of the brake pedal 24 by the driver. is there. 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 to 21RL. Thereby, the braking force with respect to each wheel by hydraulic braking is adjusted.

  Each of the disc brake units 21FR to 21RL, 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 to 21RL includes a brake disc 22 and wheel cylinders 23FR to 23RL incorporated in the brake caliper, 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 to 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 together with the wheel. Thereby, a braking force is applied to each wheel. In the present embodiment, the disc brake units 21FR to 21RL are used, but other braking force applying mechanisms including a wheel cylinder 23 such as a drum brake may be used.

  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 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 wheel cylinders 23FR, 23FL, 23RR, 23RL of the corresponding disc brake units 21FR, 21FL, 21RR, 21RL. 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. Each of the ABS holding valves 51 to 54 has a solenoid and a spring that are ON / OFF controlled, and both are normally open electromagnetic control valves that are opened when the solenoid is in a non-energized state. 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 solenoid is energized and 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 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 brake 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. 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. The output value of the stroke sensor 25 is also sequentially given to the brake ECU 70 every predetermined time, and is stored and held in a predetermined storage area of the brake ECU 70. In the present embodiment, the stroke sensor 25 has two contact points, and can output two measured values to the brake ECU 70 as if they seemed to be two sensors.

  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 brake control device 20 configured as described above can execute brake regeneration cooperative control. The brake control device 20 starts braking in response to a braking request. 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 brake control device 20 by subtracting the braking force due to regeneration from the required braking force. Here, the effective value of the braking force by regeneration is supplied from the hybrid ECU to the brake 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.

  The brake 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. . Regardless of whether or not the brake regeneration cooperative control is executed, the control mode for controlling the braking force by the wheel cylinder pressure control system will be appropriately referred to as a “linear control mode” below. Or it may be called control by brake-by-wire.

  As a result, in the brake control device 20, the brake fluid is supplied from the power hydraulic pressure source 30 to the wheel cylinders 23 via the pressure-increasing linear control valve 66, and 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 present embodiment, a wheel cylinder pressure control system is configured including the power hydraulic pressure source 30, the pressure-increasing linear control valve 66, the pressure-decreasing linear control valve 67, and the like. A so-called brake-by-wire braking force control is performed by the wheel cylinder pressure control system. The wheel cylinder pressure control system is provided in parallel to the brake fluid supply path from the master cylinder unit 27 to the wheel cylinder 23. The brake 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.

  FIG. 2 is a view for explaining wheel cylinder pressure holding control for preventing slippage during stopping according to an embodiment of the present invention. The vertical axis in FIG. 2 indicates the hydraulic pressure, and the horizontal axis indicates time. An example of the time change of the wheel cylinder pressure while the vehicle is stopped is shown by a solid line. In the sliding prevention hydraulic pressure control, the wheel cylinder pressure is controlled to be kept at least at the minimum holding pressure (shown by a one-dot chain line in FIG. 2). Therefore, the brake ECU 70 controls the wheel cylinder pressure in the linear control mode with the higher one of the regulator pressure (indicated by a broken line in FIG. 2) and the minimum holding pressure Pb as the target pressure. The minimum holding pressure Pb is set according to the amount of inclination of the road surface at the stop position, for example. When the brake ECU 70 releases the minimum holding pressure Pb, the brake ECU 70 reduces the pressure with a pressure reduction profile set to prevent self-excited vibration at the pressure reduction linear control valve 67. The decompression profile is determined according to the minimum holding pressure Pb so that decompression is completed at the decompression completion target time T.

  As shown in FIG. 2, when the brake operation is started, the regulator pressure increases according to the operation amount. The brake ECU 70 starts the hydraulic pressure holding control when the hydraulic pressure holding control start condition including that the brake operation amount exceeds the hydraulic pressure holding start threshold value is satisfied while the vehicle is stopped. In FIG. 2, the hydraulic pressure holding control is started when the measured value of the regulator pressure sensor 71 exceeds the hydraulic pressure holding control start hydraulic pressure Pa, and the minimum holding pressure Pb is set. In the present embodiment, the brake ECU 70 uses the hydraulic pressure holding control start condition that the regulator pressure exceeds the hydraulic pressure holding control start hydraulic pressure Pa, but instead of this or together with this, for example, the measured value of the stroke sensor 25 is Exceeding the hydraulic pressure holding start threshold value may be included in the hydraulic pressure holding control start condition.

  At time ta, the regulator pressure reaches the hydraulic pressure holding control start hydraulic pressure Pa, and the hydraulic pressure holding control is started. As described above, the brake ECU 70 controls the wheel cylinder pressure in the linear control mode using the higher one of the regulator pressure and the minimum holding pressure Pb as the target pressure. Normally, as shown in FIG. 2, the regulator pressure is larger than the minimum holding pressure Pb, so the wheel cylinder pressure is controlled through the pressure-increasing linear control valve 66 and the pressure-decreasing linear control valve 67 so as to match the regulator pressure. . In this case, the brake ECU 70 may control the wheel cylinder pressure to the target pressure obtained by correcting the regulator pressure, instead of using the regulator pressure as it is as the target pressure. In addition, before the start of the hydraulic pressure holding control (before ta in FIG. 2), the brake mode in which the regulator cut valve 65 is opened and the regulator pressure is introduced into the wheel cylinder 23 is set, and the hydraulic pressure holding control start condition is satisfied. The brake mode may be switched to the linear control mode.

  The brake ECU 70 determines the minimum holding pressure Pb based on a measurement value of a G sensor (not shown) mounted on the vehicle. That is, the larger the amount of inclination of the stop position obtained from the measured value of the G sensor, the larger the minimum holding pressure Pb, and the smaller the amount of inclination of the stop position, the smaller the minimum holding pressure Pb. For example, the minimum holding pressure Pb is set to a size obtained by adding a predetermined margin to a minimum hydraulic pressure that prevents the vehicle from sliding down and ensures that the vehicle is stopped. This predetermined margin is added in order to give a margin to the minimum necessary hydraulic pressure for maintaining the stop state in consideration of, for example, sensor measurement error.

  FIG. 2 shows an example of a case where the brake operation amount, that is, the regulator pressure is kept constant for a certain period after the start of the hydraulic pressure holding control and then decreases to zero. At time tb, the regulator pressure decreases to the minimum holding pressure Pb, and then becomes zero at time tc. Therefore, the brake ECU 70 holds the wheel cylinder pressure after the time tb at the minimum holding pressure Pb.

  The brake ECU 70 starts depressurization of the wheel cylinder 23 through the depressurization linear control valve 67 when the hydraulic pressure holding control end condition is satisfied. The hydraulic pressure holding control end condition includes, for example, that a predetermined waiting time has elapsed since the release of the brake operation. In FIG. 2, the waiting time elapses at time td and pressure reduction is started. That is, the waiting time is set to the length of time tc-td. The hydraulic pressure holding control end condition may include that the driver has operated the accelerator pedal. In this case, for example, the brake ECU 70 may determine whether or not the accelerator pedal is operated based on an output from a stroke sensor of the accelerator pedal. If it is determined that the accelerator pedal is being operated, the brake ECU 70 starts depressurization without waiting for the above-described waiting time to elapse.

  In the present embodiment, the decompression completion target time T is set in advance. The decompression completion target time T is set based on a desired start performance as a time lag allowed from the start of operation of the accelerator pedal to the actual start of acceleration of the vehicle. The brake ECU 70 reduces the wheel cylinder pressure with the pressure reduction gradient set so that the pressure reduction is completed at the time tf when the pressure reduction completion target time T elapses from the pressure reduction start time td.

  As shown in FIG. 2, the brake ECU 70 controls the pressure-reducing linear control valve 67 so as to reduce the wheel cylinder pressure with, for example, a two-step pressure reduction gradient. At the beginning of the pressure reduction, the pressure is reduced with a relatively gentle pressure reduction gradient, and in the latter half, the pressure is reduced with a relatively large pressure reduction gradient. The initial depressurization gradient is set according to the wheel cylinder pressure (minimum holding pressure Pb in FIG. 2) at the depressurization start time. For example, the initial pressure reduction gradient is set to a value smaller than the gradient Pb / T when the pressure reduction completion target time T is a constant pressure reduction gradient.

  With the first-stage depressurization gradient set in this way, the depressurization linear control valve 67 is depressurized to the wheel cylinder pressure Pc that is guaranteed not to occur. This self-excited vibration non-occurrence threshold value Pc is a value determined experimentally, for example, according to the specification of the pressure-reducing linear control valve 67 and the like. After the time te when the self-excited vibration non-occurrence threshold value Pc is reached, the pressure is reduced with the second pressure reduction gradient so that the pressure reduction is completed at the pressure reduction completion target time T. For example, the second pressure reduction gradient is set to a value larger than the gradient Pb / T when the pressure reduction completion target time T is a constant pressure reduction gradient.

  The break point of the decompression gradient may be set with emphasis on completing the decompression at the decompression completion target time T. That is, when it is necessary to complete the pressure reduction in the remaining pressure reduction time, the pressure reduction gradient may be increased before the wheel cylinder pressure is reduced to the self-excited vibration non-occurrence threshold value Pc.

  Further, instead of the above-described two-stage decompression profile, the decompression may be performed with a constant decompression gradient Pb / T, or the decompression may be performed with a multi-stage decompression profile. The depressurization gradient may be continuously increased as the wheel cylinder pressure decreases.

  FIG. 3 is a flowchart for explaining the release processing of the hydraulic pressure holding control during the stop according to the embodiment of the present invention. The process shown in FIG. 3 is executed at a predetermined control cycle by the brake ECU 70 during execution of the hydraulic pressure holding control. First, the brake ECU 70 determines whether or not a hydraulic pressure holding control end condition is satisfied (S10). As described above, the hydraulic pressure holding control termination condition may be, for example, that a preset waiting time has elapsed since the driver released the operation of the brake pedal 24, or that the accelerator pedal has been operated. Also good. If the hydraulic pressure holding control end condition is not satisfied (N in S10), the brake ECU 70 ends the process as it is and waits until the next process start timing. In this case, the hydraulic pressure holding control is continued.

  On the other hand, when it is determined that the hydraulic pressure holding control end condition is satisfied (Y in S10), the brake ECU 70 determines whether or not the accelerator pedal is operated (S12). For example, the brake ECU 70 determines whether or not the accelerator pedal is operated based on an output from a stroke sensor of the accelerator pedal. If it is determined that the accelerator pedal is being operated (Y in S12), the brake ECU 70 executes a wheel cylinder pressure corresponding pressure reduction control (S14). That is, the brake ECU 70 determines the initial pressure reduction gradient based on the current wheel cylinder pressure, and reduces the wheel cylinder pressure so that the retained hydraulic pressure is completely released at the pressure reduction completion target time T. For example, as described with reference to FIG. 2, the pressure is reduced with a pressure reduction profile having a two-stage pressure reduction gradient.

  If it is determined that the accelerator pedal is not operated (N in S12), the brake ECU 70 executes the reduced pressure gradient control (S16). Specifically, the brake ECU 70 may, for example, use the wheel cylinder pressure until the retained hydraulic pressure is completely released with a pressure reduction gradient that guarantees that no self-excited vibration is generated in the pressure reduction linear control valve 67 by the wheel cylinder pressure at the time of the pressure reduction start. Reduce pressure. For example, the holding fluid pressure may be reduced uniformly with the initial pressure reduction gradient in the wheel cylinder pressure-related pressure reduction control (S14). Alternatively, the pressure may be reduced with a preset pressure reduction gradient that ensures that no self-excited vibration is generated. If an accelerator pedal operation is detected during the reduced pressure gradient control, the brake ECU 70 may switch to the wheel cylinder pressure corresponding pressure reduction control to complete the remaining pressure reduction.

  As described above, according to the present embodiment, when the hydraulic pressure holding control is terminated, it is possible to gradually reduce the pressure by making the maximum use of the holding hydraulic pressure release allowable time set based on the desired start performance. Become. For this reason, while suppressing the abnormal noise at the time of pressure reduction, it is possible to realize a quick switch from the slip prevention braking control to the vehicle start.

  In the above-described embodiment, the example in which the depressurization gradient relaxation control is applied when the hydraulic pressure holding control is finished has been described. However, it is also possible to apply to other cases. For example, it is possible to apply the pressure reduction gradient relaxation control when the operating hydraulic pressure is reduced toward the minimum holding pressure due to a decrease in the brake operation amount of the driver. In this case, for example, the control unit may determine the depressurization gradient according to the wheel cylinder pressure at the depressurization start time so as to reach the minimum holding pressure when the preset depressurization completion target time has elapsed from the depressurization start point. Good.

  20 brake control device, 23 wheel cylinder, 27 master cylinder unit, 32 master cylinder, 33 regulator, 34 reservoir, 60 separation valve, 65 regulator cut valve, 66 pressure-increasing linear control valve, 67 pressure-reducing linear control valve, 70 brake ECU, 73 Control pressure sensor.

Claims (1)

A wheel cylinder that receives a supply of hydraulic fluid and applies braking force to the wheel;
A manual hydraulic pressure source that pressurizes the stored hydraulic fluid according to the amount of operation of the brake operation member by the driver;
A power hydraulic pressure source that is provided in parallel to the manual hydraulic pressure source with respect to the wheel cylinder, and accumulates hydraulic fluid by supplying power;
A wheel cylinder pressure control system that controls the wheel cylinder pressure so as to follow the target pressure using the power hydraulic pressure source as a high pressure source,
While the vehicle is stopped, the manual hydraulic pressure source is disconnected from the wheel cylinder, and the first target pressure set based on the hydraulic pressure of the manual hydraulic pressure source is set to the inclination of the stop position to maintain the stopped state. A control unit that performs hydraulic pressure holding control for controlling the wheel cylinder pressure control system with the higher one of the second target pressures set based on the target pressure,
The control unit ends the hydraulic pressure holding control when an acceleration operation by a driver is detected during the hydraulic pressure holding control or when a predetermined time has elapsed since the operation of the brake operation member was released. ,
When the predetermined time has elapsed without the acceleration operation being detected, the control unit reduces the wheel cylinder pressure over a longer time than a preset pressure reduction completion target time,
Wherein, if the previous SL acceleration operation is detected, it starts decompression of the wheel cylinder pressure with a small initial pressure gradient than a certain pressure gradient complete vacuum in the vacuum target completion time, the decompression completion A brake control device, wherein a pressure reduction gradient at the time of completion of pressure reduction is set to a value larger than the constant pressure reduction gradient so that pressure reduction is completed at a target time.

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