JP5293418B2 - Brake abnormality detection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To properly detect an abnormality of a wheel cylinder pressure control system. <P>SOLUTION: In a brake abnormality detection device, an abnormality determination part determines that a threshold changing condition is satisfied when both of accumulator pressure and control pressure Pfr are increased during execution of a wheel cylinder pressure control and determines that the threshold changing condition is not satisfied when both of the pressure is reduced. The abnormality determination part sets a value that deviation pressure Pb is deducted from target pressure Pref to an abnormality determination threshold Pmin when the threshold changing condition is not satisfied. The abnormality determination part sets a smaller value, of the abnormality determination threshold Pmin calculated by deducting the deviation pressure Pb from the target pressure Pref and an abnormality determination threshold Pmin calculated by utilizing transformation gradient dPacc/dt of accumulator pressure, to the abnormality determination threshold Pmin, when the threshold changing condition is satisfied. The abnormality determination part determines that an abnormality occurs in the wheel cylinder pressure control system when the control pressure Pfr is lower than the abnormality determination threshold Pmin. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a brake abnormality detection device, and more particularly to a brake abnormality detection device that detects an abnormality in a wheel cylinder pressure control system that increases or decreases a pressure in a wheel cylinder.

  For example, there is known an electronically controlled brake device that controls the operation of a wheel cylinder pressure control system so as to set a target pressure of the wheel cylinder and bring the control pressure acting on the wheel cylinder closer to the target pressure. In such an electronically controlled brake device, the target value immediately after the braking request generally increases linearly, while the control pressure tends to deviate below the target pressure. For this reason, a brake control device that determines whether or not there is an abnormality in the wheel cylinder pressure control system based on a comparison between the control pressure and the reference pressure has been proposed (see, for example, Patent Document 1). In addition, a brake fluid pressure control device that specifies a failure part based on a deviation between a target fluid pressure and a wheel cylinder pressure has been proposed (see, for example, Patent Document 2).

JP 2007-112293 A JP-A-11-180294

  For example, when an abnormality occurs in the wheel cylinder pressure control system, such as a failure of opening of the pressure reducing valve or leakage of hydraulic fluid from the caliper, it may be difficult to appropriately increase the control pressure to the target pressure. For this reason, it is necessary to detect such an abnormality accurately and to promptly shift to the fail process when the abnormality occurs. At this time, for example, when the state in which the control pressure does not increase to the threshold value set to a value lower than the target pressure continues, it is possible to consider that an abnormality has occurred in the wheel cylinder pressure control system.

  However, for example, at a very low temperature, the viscosity of the hydraulic fluid in the wheel cylinder pressure control system becomes high, and it may take time until the control pressure is increased after the braking request is generated. For this reason, when the above-described abnormality determination method is adopted, there is a possibility that it is erroneously determined that an abnormality has occurred in the wheel cylinder pressure control system even when there is no abnormality. In the control when the wheel cylinder pressure control system is abnormal, the brake feeling given to the driver may be different from the control in the normal state. Therefore, the frequency of such erroneous determination needs to be as low as possible.

  Accordingly, the present invention has been made to solve the above-described problems, and an object thereof is to appropriately detect an abnormality in the wheel cylinder pressure control system.

  In order to solve the above-described problem, a brake abnormality detection device according to an aspect of the present invention sets a control pressure detecting unit that detects a control pressure acting on a wheel cylinder, a target pressure of the wheel cylinder, and increases or decreases the control pressure. Wheel cylinder pressure control means for executing wheel cylinder pressure control for controlling the operation of the wheel cylinder pressure control system to cause the control pressure to approach the target pressure, and abnormality determination for determining abnormality of the wheel cylinder pressure control system An abnormality determination unit that sets a threshold and determines whether or not an abnormality has occurred in the wheel cylinder pressure control system based on a comparison between the control pressure and the abnormality determination threshold, and is used for increasing the control pressure Accumulator pressure detecting means for detecting the accumulator pressure. The abnormality determination unit does not satisfy the threshold change condition when a relationship between the accumulator pressure and the control pressure satisfies a threshold change condition for changing the abnormality determination threshold during execution of the wheel cylinder pressure control. The abnormality determination threshold is set to a value different from the time.

  As a result of earnest research and development by the inventor, by paying attention to the relationship between accumulator pressure and control pressure, for example, even when the control pressure does not increase quickly to the target pressure, it is an abnormality in the wheel cylinder pressure control system. It has been found that it is possible to appropriately determine whether it is due to a delay in control pressure increase at extremely low temperatures or the like. Therefore, according to this aspect, it is possible to suppress the frequency of abnormality erroneous determination due to extremely low temperatures and the like, and it is possible to appropriately detect abnormality of the wheel cylinder pressure control system.

  The abnormality determination unit is configured to reduce the abnormality to a value lower than when the threshold change condition is not satisfied when the relationship between the accumulator pressure and the control pressure satisfies the threshold change condition during execution of the wheel cylinder pressure control. A determination threshold value may be set, and it may be determined that an abnormality has occurred in the wheel cylinder pressure control system when the control pressure is lower than the abnormality determination threshold value.

  According to this aspect, it is possible to appropriately detect an abnormality in the wheel cylinder pressure control system in which the control pressure does not increase to the target pressure due to, for example, a failure in opening of the pressure reducing valve or leakage of hydraulic fluid from the caliper.

  The abnormality determining means determines that an abnormality has occurred in the wheel cylinder pressure control system when a state in which the control pressure is lower than the abnormality determination threshold value continues for a preset period during execution of the wheel cylinder pressure control. Also good.

  According to this aspect, for example, it is determined that an abnormality has occurred in the wheel cylinder pressure control system due to the control pressure being lower than the short-term abnormality determination threshold value even though no abnormality has occurred in the wheel cylinder pressure control system. The possibility can be reduced. For this reason, the abnormality of the wheel cylinder pressure control system can be detected more appropriately.

  The abnormality determination means determines that the threshold change condition is satisfied when both the accumulator pressure and the control pressure are increased during execution of the wheel cylinder pressure control, and when both are reduced, It may be determined that the threshold change condition is not satisfied.

  For example, when an abnormality such as a failure in opening of the pressure reducing valve or leakage of hydraulic fluid from the caliper occurs in the wheel cylinder pressure control system, both the accumulator pressure and the control pressure are reduced. On the other hand, as a result of earnest research and development by the inventor, it was confirmed that both the accumulator pressure and the control pressure increase when the control pressure gradually increases at extremely low temperatures. Therefore, according to this aspect, using such a relationship between the accumulator pressure and the control pressure, it is determined whether an abnormality has occurred in the wheel cylinder pressure control system or whether the control pressure has been delayed in an extremely low temperature. Can be carved appropriately.

  The abnormality determination means may set the abnormality determination threshold using the accumulator pressure when the threshold value changing condition is satisfied.

  As a result of earnest research and development by the inventors, it has been found that, for example, the pressure increase characteristic of the control pressure at an extremely low temperature is related to the accumulator pressure. Therefore, according to this aspect, it is possible to easily set an appropriate abnormality determination threshold using the accumulator pressure.

  When the threshold value changing condition is not satisfied, the abnormality determination unit may set a value obtained by subtracting a deviation pressure calculated based on the target pressure from the target pressure as the abnormality determination threshold value.

  According to this aspect, the abnormality determination value can be set easily and appropriately in a normal state that is not at an extremely low temperature.

  The abnormality determination means, when the threshold change condition is satisfied, out of the abnormality determination threshold calculated by subtracting the deviation pressure from the target pressure, and the abnormality determination threshold calculated using the accumulator pressure The smaller one may be set as the abnormality determination threshold.

  According to this aspect, it can be avoided that the abnormality determination threshold value becomes larger when the threshold value changing condition is satisfied than when the threshold value changing condition is not satisfied. For this reason, the abnormality of the wheel cylinder pressure control system can be detected more appropriately.

  According to the present invention, it is possible to appropriately detect an abnormality in the wheel cylinder pressure control system.

It is a systematic diagram showing a braking control device concerning this embodiment. It is a functional block diagram which shows the structure of the brake abnormality detection apparatus which concerns on this embodiment. It is a flowchart which shows the procedure of the abnormality detection process by the brake abnormality detection apparatus which concerns on this embodiment. It is a flowchart which shows the detailed procedure of the abnormality determination threshold value Pmin setting process of S12 in FIG. It is a figure which shows the threshold value change condition of S42 in FIG. It is a figure which shows the change of the control pressure Pfr and the accumulator pressure Pacc when a braking request | requirement is given in a normal environment when abnormality has arisen in the wheel cylinder pressure control system. It is a figure which shows the change of the control pressure Pfr and the accumulator pressure Pacc when a braking request | requirement is given under extremely low temperature when there is no abnormality in a wheel cylinder pressure control system. It is a figure which shows the change of the control pressure Pfr and the accumulator pressure Pacc when a braking request | requirement is given under extremely low temperature when there is no abnormality in a wheel cylinder pressure control system.

  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.

  As shown in FIG. 1, the brake control device 20 includes disc brake units 21FR, 21FL, 21RR, and 21RL provided for each wheel (hereinafter collectively referred to as “disc brake unit 21” as necessary). A master cylinder unit 27, a power hydraulic pressure source 30, and a hydraulic 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 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 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 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 braking control device 20, the master cylinder unit 27, the power hydraulic pressure source 30, the hydraulic pressure actuator 40, and the disc brake unit 21 function as a wheel cylinder pressure control system that increases or decreases the wheel cylinder pressure by increasing or decreasing the control pressure. . 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.

  Here, for example, when an abnormality occurs in the wheel cylinder pressure control system, such as failure of opening of the pressure-reducing linear control valve 67 or leakage of hydraulic fluid from the caliper of each disc brake unit, the control pressure is appropriately increased to the target pressure. There may be cases where you do not. For this reason, a vehicle equipped with the braking control device 20 is provided with a brake abnormality detection device to detect such an abnormality.

  FIG. 2 is a functional block diagram illustrating a configuration of the brake abnormality detection device 100 according to the present embodiment. In FIG. 2, the brake ECU 70 depicts functional blocks realized by cooperation of hardware such as CPU, ROM, RAM, and software. Therefore, these functional blocks can be realized in various forms by a combination of hardware and software.

  The brake abnormality detection device 100 includes a brake ECU 70, a stroke sensor 25, a regulator pressure sensor 71, an accumulator pressure sensor 72, and a control pressure sensor 73. The brake ECU 70 includes a wheel cylinder pressure control unit 102 and an abnormality determination unit 104.

  The wheel cylinder pressure control unit 102 sets a target pressure using detection results of the stroke sensor 25, the regulator pressure sensor 71, and the like when a braking request is made. The wheel cylinder pressure control unit 102 executes wheel cylinder pressure control that controls the operation of the hydraulic actuator 40 and the motor 36a to bring the control pressure closer to the target pressure. Since the calculation method of the target pressure and the increase / decrease method of the control pressure are known, the description thereof is omitted.

  The wheel cylinder pressure control unit 102 determines that there is a braking request when it is determined that the brake pedal 24 is depressed based on the detection result of the stroke sensor 25. Of course, it is not limited to this case that it is determined that there is a braking request. For example, when it is determined by the behavior control of the vehicle that it is necessary to apply a braking force to the wheel regardless of the detection result of the stroke sensor 25 or the like, the wheel cylinder pressure control unit 102 may determine that there is a braking request. Such vehicle behavior control is also well known and will not be described.

  The abnormality determination unit 104 sets an abnormality determination threshold value for determining abnormality of the wheel cylinder pressure control system using the set target pressure, the detection result of the acquired accumulator pressure Pacc, and the like. The abnormality determination unit 104 determines whether an abnormality has occurred in the wheel cylinder pressure control system based on a comparison between the control pressure detected by the control pressure sensor 73 and the set abnormality determination threshold. Specifically, the abnormality determination unit 104 determines that an abnormality has occurred in the wheel cylinder pressure control system when the control pressure is lower than the abnormality determination threshold.

  FIG. 3 is a flowchart showing a procedure of abnormality detection processing performed by the brake abnormality detection device 100 according to the present embodiment. The processing in this flowchart starts when the ignition switch of the vehicle is turned on, and is then repeatedly executed every predetermined time until the ignition switch of the vehicle is turned off.

  The abnormality determination unit 104 determines whether there is a braking request using the detection result of the stroke sensor 25 or the like (S10). When there is a braking request (Y in S10), the abnormality determination unit 104 executes the abnormality determination threshold Pmin setting process to set the abnormality determination threshold Pmin (S12). The abnormality determination threshold value Pmin setting process will be described later.

  When the abnormality determination threshold value Pmin is set, the abnormality determination unit 104 determines whether or not the control pressure Pfr is lower than the abnormality determination threshold value Pmin (S14). When the control pressure Pfr is lower than the abnormality determination threshold value Pmin (Y in S14), the abnormality determination unit 104 determines that the quasi-abnormal state indicates that an abnormality may have occurred in the wheel cylinder pressure control system. If it is determined that the quasi-abnormal state is present, the abnormality determination unit 104 increments the abnormality determination counter Nc held by itself (S16), and determines whether or not the abnormality determination counter Nc is greater than the reference number Nref. It is determined whether or not the state has continued for a preset period (S18). When the abnormality determination counter Nc is equal to or smaller than the reference number Nref (N in S18), it is determined that the quasi-abnormal state does not continue until a preset period, and the subsequent processing is skipped.

  When the abnormality determination counter Nc exceeds the reference number Nref (Y in S18), the abnormality determination unit 104 determines that the quasi-abnormal state has continued for a preset period, and an abnormality has occurred in the wheel cylinder pressure control system. Determine (S20). As described above, the abnormality determination unit 104 determines that an abnormality has occurred in the wheel cylinder pressure control system when a state in which the control pressure Pfr is lower than the abnormality determination threshold Pmin continues for a preset period during execution of the wheel cylinder pressure control. . Thereby, it can be avoided that it is determined that an abnormality has occurred in the wheel cylinder pressure control system due to a temporary decrease in the control pressure Pfr.

  When it is determined that an abnormality has occurred in the wheel cylinder pressure control system, the wheel cylinder pressure control unit 102 performs a fail process. In this fail process, the wheel cylinder pressure control unit 102 closes the pressure-increasing linear control valve 66 and opens the regulator cut valve 65. As a result, the wheel cylinder pressure can be directly increased through the regulator channel 62 by the depression of the brake pedal 24. Since such a fail process is known, a description thereof will be omitted. When the fail process is executed, the braking control by the pressure-increasing linear control valve 66 and the like is finished.

  When there is no braking request (N in S10), or when the control pressure Pfr is greater than or equal to the abnormality determination threshold Pmin (N in S14), the abnormality determination unit 104 determines whether or not the abnormality determination counter Nc is greater than zero ( S22). If the abnormality determination counter Nc is greater than zero (Y in S22), the abnormality determination unit 104 resets the abnormality determination counter Nc to zero (S24). When the abnormality determination counter Nc is zero (N in S22), the abnormality determination counter Nc is maintained as it is.

  FIG. 4 is a flowchart showing a detailed procedure of the abnormality determination threshold value Pmin setting process of S12 in FIG. The abnormality determination unit 104 first inputs the target pressure Pref into a preset function and calculates the deviation pressure Pb (S40). The deviation pressure Pb may be a value calculated by multiplying the target pressure Pref by a predetermined value, for example. Since such a method for setting the deviation pressure Pb is known, a description thereof will be omitted. When the deviation pressure Pb is calculated, the abnormality determination unit 104 determines whether or not a threshold value changing condition is satisfied (S42).

  FIG. 5 is a diagram showing the threshold value changing condition of S42 in FIG. In FIG. 5, dPacc / dt is the transformation gradient of the accumulator pressure Pacc, and dPfr / dt is the transformation gradient of the control pressure Pfr. The abnormality determination unit 104 samples and holds the accumulator pressure Pacc and the control pressure Pfr at every repetition interval t1 of the abnormality determination process of FIG. The abnormality determination unit 104 calculates the accumulator pressure transformation gradient dPacc / dt and the control pressure transformation gradient dPfr / dt by the method of least squares using the sampled accumulator pressure Pacc and control pressure Pfr. Of course, these calculation methods are not limited to the method of least squares.

  In FIG. 5, “+” indicates a positive value, and “−” indicates a negative value. In FIG. 5, zero is included in the positive value. As described above, the abnormality determination unit 104 determines that the threshold change condition is satisfied when both the accumulator pressure and the control pressure are increased during execution of the wheel cylinder pressure control, and changes the threshold when both are reduced. It is determined that the condition is not satisfied.

  For example, when an abnormality such as a failure in opening of the pressure reducing valve or leakage of hydraulic fluid from the caliper occurs in the wheel cylinder pressure control system, both the accumulator pressure and the control pressure are reduced. On the other hand, when the viscosity of the hydraulic fluid becomes high, for example, at an extremely low temperature, the control pressure Pfr does not rapidly increase but gradually increases even if the pressure increasing linear control valve 66 is opened. In such a case, it has been confirmed as a result of earnest research and development by the inventors that both the accumulator pressure Pacc and the control pressure Pfr are increased. Therefore, by using the relationship between the accumulator pressure Pacc and the control pressure Pfr as described above, it is possible to easily determine whether or not the environment where the vehicle is placed is extremely low.

  In this embodiment, the environment in which the vehicle is placed is the same regardless of whether the accumulator pressure transformation gradient dPacc / dt and the control pressure transformation gradient dPfr / dt are a combination of plus and minus or a combination of minus and plus. The threshold change condition is assumed to be at a very low temperature.

  Returning to FIG. When the threshold change condition is not satisfied during execution of the wheel cylinder pressure control that brings the control pressure Pfr closer to the target pressure Pref (N in S42), the abnormality determination unit 104 determines that the normal state is not extremely low, and the target pressure Pref A value obtained by subtracting the deviation pressure Pb from is set as the abnormality determination threshold value Pmin (S48).

  FIG. 6 is a diagram showing changes in the control pressure Pfr and the accumulator pressure Pacc when a braking request is given under a normal environment when an abnormality occurs in the wheel cylinder pressure control system. In FIG. 6, the horizontal axis indicates time t, and the vertical axis indicates pressure P. In a normal environment where the temperature is not extremely low, the abnormality determination threshold value Pmin is set to a value obtained by subtracting the deviation pressure Pb from the target pressure Pref as shown in FIG.

  For example, when an abnormality such as leakage of hydraulic fluid occurs in any of the wheel cylinder pressure control systems, the control pressure Pfr cannot reach the target pressure Pref and gradually decreases. At this time, the accumulator pressure Pacc gradually decreases. The abnormality determination unit 104 determines that an abnormality has occurred in the wheel cylinder pressure control system when the period during which the control pressure Pfr is less than the abnormality determination threshold Pmin has reached the reference time Tref (Tref = Nref × t1).

  FIG. 7 is a diagram showing changes in the control pressure Pfr and the accumulator pressure Pacc when a braking request is given at an extremely low temperature when there is no abnormality in the wheel cylinder pressure control system. At an extremely low temperature, the viscosity of the hydraulic fluid in the wheel cylinder pressure control system becomes high, and the control pressure Pfr gradually increases as shown in FIG. 7 even when a braking request is generated. In this case, if the abnormality determination threshold value Pmin is set as in the normal environment, the control pressure Pfr may be less than the abnormality determination threshold value Pmin even though there is no abnormality in the wheel cylinder pressure control system. Furthermore, if the state continues for the reference time Tref, it may be determined that an abnormality has occurred in the wheel cylinder pressure control system.

  Returning to FIG. Therefore, the abnormality determination unit 104 is different from the case where the threshold change condition is not satisfied when the relationship between the accumulator pressure and the control pressure satisfies the threshold change condition for changing the abnormality determination threshold during the execution of the wheel cylinder pressure control. Sets the abnormality determination threshold value. Specifically, when the threshold change condition is satisfied during execution of the wheel cylinder pressure control (Y in S42), the abnormality determination unit 104 first calculates the minimum supply capacity pressure Px using the accumulator pressure Pacc (S44). . In this embodiment, the abnormality determination unit 104 calculates the minimum supply capacity pressure Px by subtracting a predetermined pressure from the accumulator pressure Pacc. Next, the abnormality determination unit 104 calculates MIN (Pref−Pb, Px), that is, the abnormality determination threshold Pmin calculated by subtracting the deviation pressure Pb from the target pressure Pref, and the abnormality determination threshold Pmin calculated using the accumulator pressure Pacc. Is set as the abnormality determination threshold value Pmin. (S46).

  FIG. 8 is a diagram showing changes in the control pressure Pfr and the accumulator pressure Pacc when a braking request is given at an extremely low temperature when there is no abnormality in the wheel cylinder pressure control system. The abnormality determination unit 104 sets the abnormality determination threshold value to a lower value when the threshold change condition is satisfied during execution of the wheel cylinder pressure control than when the threshold change condition is not satisfied. At this time, the abnormality determination threshold value Pmin is set as a threshold value that gently inclines as shown in FIG. 8 using the accumulator pressure Pacc. As a result, even if the control pressure Pfr is gradually increased, if the wheel cylinder pressure control system is normal, it can be avoided that the control pressure Pfr is lower than the abnormality determination threshold value Pmin, and the occurrence frequency of abnormality determination at an extremely low temperature can be suppressed. be able to.

  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, 23 wheel cylinder, 25 stroke sensor, 35 accumulator, 66 pressure-increasing linear control valve, 67 pressure-decreasing linear control valve, 70 brake ECU, 71 regulator pressure sensor, 72 accumulator pressure sensor, 73 control pressure sensor, 100 brake An abnormality detection device, 102 a wheel cylinder pressure control unit, 104 an abnormality determination unit.

Claims (7)

Control pressure detecting means for detecting a control pressure acting on the wheel cylinder;
Wheel cylinder pressure control means for setting a target pressure of the wheel cylinder and controlling the operation of a wheel cylinder pressure control system for increasing or decreasing the control pressure to execute the wheel cylinder pressure control to bring the control pressure close to the target pressure;
An abnormality determination threshold value for determining an abnormality in the wheel cylinder pressure control system is set, and it is determined whether an abnormality has occurred in the wheel cylinder pressure control system based on a comparison between the control pressure and the abnormality determination threshold value. An abnormality determination means;
An accumulator pressure detecting means for detecting an accumulator pressure used for increasing the control pressure;
With
The abnormality determination unit does not satisfy the threshold change condition when a relationship between the accumulator pressure and the control pressure satisfies a threshold change condition for changing the abnormality determination threshold during execution of the wheel cylinder pressure control. A brake abnormality detection device, wherein the abnormality determination threshold value is set to a value different from the time.   The abnormality determination unit is configured to reduce the abnormality to a value lower than when the threshold change condition is not satisfied when the relationship between the accumulator pressure and the control pressure satisfies the threshold change condition during execution of the wheel cylinder pressure control. The brake abnormality detection device according to claim 1, wherein a determination threshold value is set, and it is determined that an abnormality has occurred in the wheel cylinder pressure control system when the control pressure is lower than the abnormality determination threshold value.   The abnormality determining means determines that an abnormality has occurred in the wheel cylinder pressure control system when the state in which the control pressure is lower than the abnormality determination threshold value continues for a preset period during execution of the wheel cylinder pressure control. The brake abnormality detection device according to claim 2.   The abnormality determination means determines that the threshold change condition is satisfied when both the accumulator pressure and the control pressure are increased during execution of the wheel cylinder pressure control, and when both are reduced, The brake abnormality detection device according to claim 2 or 3, wherein it is determined that the threshold change condition is not satisfied.   5. The brake abnormality detection device according to claim 2, wherein the abnormality determination unit sets the abnormality determination threshold using the accumulator pressure when the threshold change condition is satisfied.   6. The abnormality determination unit, when the threshold change condition is not satisfied, sets a value obtained by subtracting a deviation pressure calculated based on the target pressure from the target pressure as the abnormality determination threshold. The brake abnormality detection device described in 1.   The abnormality determination means, when the threshold change condition is satisfied, out of the abnormality determination threshold calculated by subtracting the deviation pressure from the target pressure, and the abnormality determination threshold calculated using the accumulator pressure The brake abnormality detection device according to claim 6, wherein the smaller one is set as the abnormality determination threshold value.

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