Brake vacuum sensor sticking fault detection device

Abstract

This fixation failure determination device assesses whether there has been a change in a negative pressure value under prescribed conditions, including whether a negative pressure generation request has been transmitted and the number of times a brake has been operated, and determines a fixation failure of a brake negative pressure sensor on the basis of whether an engine is driven and whether the negative pressure value has changed. In the failure determination, it is determined that a failure of fixation of the brake negative pressure sensor is confirmed when it is assessed that there is no change in the negative pressure value while the engine is not being driven, and it is determined that there is uncertainty as to fixation failure, i.e., that there is a possibility that the brake negative pressure sensor has failed to be fixed, when it is assessed that there is no change in the negative pressure value while the engine is being driven.

Description

[Technical Field]

[0001] The present invention relates to a brake vacuum sensor sticking failure determination device. [Background technology]

[0002] Conventionally, braking systems installed in vehicles use a brake booster to assist the brake pedal force. Brake boosters installed in engine-powered vehicles, such as engine vehicles and hybrid vehicles, utilize the negative pressure (intake negative pressure) generated by the engine's intake to assist the brake pedal force (see Patent Document 1).

[0003] For example, a brake booster is divided into two chambers by a partition member attached to the piston: the chamber on the brake pedal side is the variable pressure chamber, and the chamber on the master cylinder side is the vacuum chamber. When the brake pedal is not operated, the variable pressure chamber and the vacuum chamber are in communication with each other, and the pressure in the variable pressure chamber and the vacuum chamber are the same. When the brake pedal is depressed and the piston is moved forward, the variable pressure chamber is cut off from the vacuum chamber and communicates with the atmosphere. This causes the pressure in the variable pressure chamber to approach atmospheric pressure, creating a pressure difference between the variable pressure chamber and the vacuum chamber. This pressure difference pulls the piston toward the vacuum chamber, increasing the force applied to the brake pedal.

[0004] However, in engine-equipped vehicles, it is preferable to stop the engine whenever possible while the vehicle is stopped or moving in order to improve fuel economy. For example, when the engine is stopped due to an idling stop, the intake vacuum caused by the engine is no longer supplied to the vacuum chamber of the brake booster, and the vacuum in the vacuum chamber gradually decreases and approaches atmospheric pressure. This weakens the brake booster's ability to assist the brake pedal.

[0005] Therefore, for example, in the braking system disclosed in Patent Document 1, when the vacuum value in the vacuum chamber of the brake booster becomes smaller than a predetermined reference value, the stopped engine is forced to start, thereby supplying the intake vacuum of the engine to the vacuum chamber and appropriately assisting the brake pedal force. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2004-204724 Summary of the Invention [Problem to be solved by the invention]

[0007] The negative pressure value in the vacuum chamber of the brake booster is detected by, for example, a brake vacuum sensor, but if this brake vacuum sensor cannot detect the correct negative pressure value due to a sticking failure or other reason, it becomes difficult to drive the engine according to the negative pressure value in the vacuum chamber. Therefore, in the past, whether or not the brake vacuum sensor has stuck is determined based on the negative pressure value detected by the brake vacuum sensor.

[0008] However, for example, when the engine is running and the vacuum is consumed by braking, the vacuum chamber may not recover even if the engine is running and vacuum is generated. Also, even if the engine is running, the vacuum chamber may not recover under certain conditions, such as during warm-up. In such cases, the brake vacuum sensor may be determined to have stuck even if it can correctly detect the vacuum value.

[0009] The present invention has been made in consideration of the above circumstances, and aims to provide a brake vacuum sensor sticking failure determination device that, when determining a sticking failure of a brake vacuum sensor, determines whether the brake vacuum sensor is suspected to have stuck or failed, which may indicate that the brake vacuum sensor has actually stuck or failed. [Means for solving the problem]

[0010] In order to achieve the above-mentioned object, one embodiment of the present invention is a brake vacuum sensor sticking failure determination device for determining a sticking failure of a brake vacuum sensor that detects a vacuum value of a brake booster in a vehicle capable of supplying vacuum generated by engine operation to the brake booster, the device comprising: an engine operation determination unit that determines whether the engine is running; a vacuum generation request unit that transmits a vacuum generation request to the engine to generate vacuum according to the vacuum value; and a determination unit that determines whether the vacuum value has changed under predetermined conditions including whether the vacuum generation request has been transmitted and the number of brake operations. and a failure determination unit that determines whether the brake negative pressure sensor has a sticking failure based on whether the engine is being driven by the engine drive determination unit and whether the negative pressure value change determination unit has changed the negative pressure value, wherein the failure determination unit determines that the brake negative pressure sensor has a confirmed sticking failure when it is determined that there is no change in the negative pressure value while the engine is not being driven, and determines that there is a possibility that the brake negative pressure sensor has a sticking failure when it is determined that there is no change in the negative pressure value while the engine is being driven. In addition, one embodiment of the present invention is characterized in that the negative pressure generation request unit sends the negative pressure generation request when the negative pressure value becomes equal to or less than a predetermined start threshold, and stops sending the negative pressure generation request when the negative pressure value becomes equal to or greater than a predetermined stop threshold that is greater than the start threshold, a sticking failure judgment threshold is set between the start threshold and the stop threshold, and when the failure judgment unit determines that there is no change in the negative pressure value while the engine is running and the negative pressure generation request is being sent, if the negative pressure value is equal to or less than the sticking failure judgment threshold, it judges that the sticking failure is confirmed, and if the negative pressure value is greater than the sticking failure judgment threshold and less than the stop threshold, it judges that the sticking failure is suspected. In one embodiment of the present invention, the sticking failure determination threshold is a value that allows recovery until the negative pressure value becomes greater than the stop threshold, regardless of the driving state of the engine. In addition, one embodiment of the present invention is characterized in that the failure determination unit determines that the sticking failure has been confirmed when it is determined that there is no change in the negative pressure value detected while the brake operation is performed a predetermined number of times while the engine is not running. In addition, one embodiment of the present invention is characterized in that the failure judgment unit judges that the sticking failure is suspected when it is determined that there is no change in the negative pressure value detected while the brake operation is performed a predetermined number of times while the engine is running and the negative pressure generation request is not being transmitted. In addition, one embodiment of the present invention is characterized in that when it is determined that the brake negative pressure sensor has confirmed the sticking failure, the negative pressure generation request unit constantly sends the negative pressure generation request to the engine, and when it is determined that the brake negative pressure sensor is suspected of having the sticking failure, the negative pressure generation request unit sends the negative pressure generation request to the engine for a predetermined period of time. [Effects of the Invention]

[0011] According to one embodiment of the present invention, when the failure determination unit determines that there is no change in the vacuum value while the engine is not running, it determines that the brake vacuum sensor has definitely experienced a stuck fault, and when the failure determination unit determines that there is no change in the vacuum value while the engine is running, it determines that there is a possibility that the brake vacuum sensor has experienced a stuck fault, so when determining that there is a stuck fault in the brake vacuum sensor, it is possible to determine that there is a possibility that the brake vacuum sensor has experienced a stuck fault. This makes it possible to avoid determining that a normal brake vacuum sensor has experienced a stuck fault. Furthermore, if the failure judgment unit determines that there is no change in the negative pressure value when the engine is running and a negative pressure generation request is being sent, and if the negative pressure value is less than the sticking failure judgment threshold, it will judge that there is a confirmed sticking failure, and if the negative pressure value is greater than the sticking failure judgment threshold and less than the stop threshold, it will judge that there is a suspected sticking failure.In this way, when judging a sticking failure of the brake negative pressure sensor, it can be determined whether there is a confirmed sticking failure or a suspected sticking failure. Furthermore, if the threshold for determining a sticking failure is set to a value that can be recovered until the negative pressure value becomes greater than the stop threshold, regardless of the engine's operating conditions, it is possible to avoid determining that a sticking failure is suspected when the negative pressure of the brake negative pressure sensor cannot be recovered. Furthermore, if the failure determination unit is configured to determine that a sticking failure has been confirmed when it determines that there is no change in the detected negative pressure value while the brake is operated a predetermined number of times while the engine is not running, it can determine whether the brake negative pressure sensor has a confirmed sticking failure when determining that the brake negative pressure sensor has a sticking failure. Furthermore, if the failure determination unit is configured to determine that a sticking failure is suspected when it determines that there is no change in the detected negative pressure value while the brake is operated a predetermined number of times while the engine is running and a negative pressure generation request is not being sent, it can determine whether the brake negative pressure sensor is suspected of a sticking failure when determining that the brake negative pressure sensor has a sticking failure. Furthermore, if the negative pressure generation request unit is configured to constantly send a negative pressure generation request to the engine when it determines that the brake negative pressure sensor has a confirmed stuck fault, and to send a negative pressure generation request to the engine for a predetermined period of time when it determines that the brake negative pressure sensor is suspected of having a stuck fault, then a negative pressure generation request can be sent in accordance with the respective determination results when it is determined that the brake negative pressure sensor has a confirmed stuck fault or is suspected of having a stuck fault. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is an explanatory diagram showing a configuration of a vehicle according to an embodiment; [Figure 2] 1 is a diagram showing a configuration of a brake system mounted on a vehicle according to an embodiment; [Figure 3] 1 is a functional configuration diagram of a brake negative pressure sensor sticking failure determination device according to an embodiment of the present invention; [Figure 4] 10 is an explanatory diagram of a method for determining whether a brake vacuum sensor has become stuck or malfunctioned when the engine is running and a vacuum generation request is being transmitted. FIG. [Figure 5] FIG. 10 is an explanatory diagram of a method for determining whether a brake negative pressure sensor has become stuck or malfunctioned when the engine is not running. [Figure 6] 10 is an explanatory diagram of a method for determining whether the brake vacuum sensor has become stuck or malfunctioned when the engine is running and no vacuum generation request is being transmitted. FIG. [Figure 7] FIG. 10 is a diagram summarizing the conditions and results of a method for determining a stuck fault in a brake negative pressure sensor. [Figure 8] 3 is a flowchart showing the steps of a method for determining whether a brake negative pressure sensor has become stuck or malfunctioned according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] A brake vacuum sensor sticking failure determination device according to an embodiment of the present invention will now be described with reference to the drawings. First, the configuration of a vehicle 10 equipped with a brake system 60 will be described. FIG. 1 is an explanatory diagram showing the configuration of the vehicle 10 according to this embodiment. In this embodiment, the vehicle 10 will be described as a hybrid vehicle equipped with an engine and a motor, but it is sufficient that the vehicle 10 is equipped with at least an engine, and it may also be an engine vehicle equipped with only an engine. As shown in FIG. 1, the vehicle 10 includes a driving system 20, a power generation system 30, and an ECU 100.

[0014] The driving system 20 is a drive mechanism of the vehicle 10, and includes front wheels 21, rear wheels 22, a motor 23, an inverter 24, an engine 25, a fuel tank 40, and a battery 50.

[0015] The front wheels 21 and the rear wheels 22 are each configured as a pair of wheels in the vehicle width direction. In this embodiment, the front wheels 21 are the driving wheels of the motor 23 and the engine 25.

[0016] The motor 23 is driven using the power stored in the battery 50, and outputs a rotational force (torque) from the output shaft 23A. The rotational force output from the output shaft 23A of the motor 23 is transmitted to the front wheels 21 via a transmission mechanism (not shown). The motor 23 is also capable of generating electricity by using the regenerative force generated when the vehicle 10 decelerates. The electric power generated by the regenerative power generation is supplied to the battery 50 via the inverter 24, and charges the battery 50.

[0017] The inverter 24 adjusts the power supplied from the battery 50 to match a required output value and supplies the adjusted power to the motor 23. The required output value is calculated by the ECU 100 (described later) based on, for example, the depression force of an accelerator pedal (not shown) and the depression force of a brake pedal 62 (see FIG. 2). The ECU 100 controls the inverter 24 based on the calculated driver's required output value.

[0018] The engine 25 is driven by burning fuel supplied from a fuel tank 40 in a combustion chamber. The engine 25 is, for example, a reciprocating engine that uses gasoline as fuel. The rotational force output to an output shaft 25A of the engine 25 is transmitted to the front wheels 21 via a transmission mechanism (not shown). The driving of the engine 25 is controlled by an ECU 100, which will be described later.

[0019] The fuel tank 40 stores fuel (e.g., gasoline) that is the power source for the engine 25. The battery 50 stores electricity that is the power source for the motor 23. A BMU (Battery Monitoring Unit) 50A is connected to the battery 50. The BMU 50A detects the voltage and temperature of the battery 50, the input and output current, etc., and detects the state of the battery 50, including the state of charge (SOC). The BMU 50A transmits the state of the battery 50 (at least the state of charge) to the ECU 100.

[0020] The power generation system 30 is a mechanism for charging the battery 50, and includes an engine 25, a generator 31, and an inverter 24.

[0021] The rotation of the output shaft 25A of the engine 25 is transmitted to the rotary shaft 31A of the generator 31 by a transmission mechanism (not shown). When the generator 31 is placed in a state where it is able to generate electricity under the control of the ECU 100, the rotary shaft 31A rotates in response to the rotation of the output shaft 25A of the engine 25, generating electricity. The generator 31 is connected to the inverter 24, and the AC power generated by the generator 31 is converted to DC power by the inverter 24 and charged into the battery 50. As described above, the battery 50 can also be charged with power generated by regenerative power generation of the motor 23.

[0022] The generator 31 also functions as a starter when starting the engine 25. When starting the engine 25, the ECU 100 controls the inverter 24 to drive the generator 31. When the generator 31 is driven, the rotating shaft 31A rotates. The rotating shaft 31A is connected to the output shaft 25A of the engine 25 via a transmission mechanism (not shown). Therefore, when the generator 31 is driven and the rotating shaft 31A rotates, the output shaft 25A of the engine 25 can be rotated.

[0023] The ECU 100 is a control unit that controls the entire vehicle 10. The ECU 100 includes a CPU (Central Processing Unit), a ROM (Read Only Memory) that stores and memorizes control programs, etc. It is composed of a RAM (Random Access Memory) as the operating area for the control program, an EEPROM (Electrically Erasable Programmable Read Only Memory) that stores various data in a rewritable manner, and an interface section that interfaces with peripheral circuits, etc.

[0024] Next, the brake system 60 of the vehicle 10 will be described. Fig. 2 is an explanatory diagram showing the configuration of the brake system 60. As shown in Fig. 2, the brake system 60 includes a brake pedal 62, a brake booster 64, a master cylinder 66, and a disc brake 68. The vehicle 10 of this embodiment is capable of supplying the brake booster 64 with negative pressure generated by driving the engine 25.

[0025] The brake pedal 62 is installed at the driver's feet and receives braking operation by the driver. When the driver depresses the brake pedal 62, the depression force (push force) drives a piston in a master cylinder 66, which pushes out brake fluid filled in the master cylinder 66. The pushed-out brake fluid is transmitted to the disc brakes 68 of each wheel 21, 22 through hydraulic piping LB.

[0026] The disc brakes 68 are provided on the front wheels 21 and the rear wheels 22, respectively, and include disc rotors and brake calipers (not shown). Brake fluid transmitted to the disc brakes 68 through hydraulic piping LB transmits its pressure to the brake calipers. The brake calipers are provided with brake pads and pistons. In the brake calipers, the pistons are driven by the pressure transmitted to the brake fluid, pressing the brake pads against the disc rotors. Friction between the disc rotors and the brake pads releases the kinetic energy of the front wheels 21 and the rear wheels 22 into the air as heat energy, stopping the rotation of the front wheels 21 and the rear wheels 22 and bringing the vehicle 10 to a halt.

[0027] When the force applied to the brake pedal 62 is transmitted to the master cylinder 66, the brake booster 64 utilizes the negative pressure generated by the intake of the engine 25 to assist the force applied to the brake pedal 62. This allows the brake system 60 to obtain the pressure required to brake the vehicle 10.

[0028] Specifically, brake booster 64 is connected to brake pedal 62 and is provided with a piston (not shown) that holds a partition member (not shown). The interior of brake booster 64 is divided into two chambers by the partition member of the piston, with a variable pressure chamber 70 on the brake pedal side and a vacuum chamber 72 on the master cylinder 66 side. Vacuum chamber 72 is connected to the intake system of engine 25.

[0029] When the brake pedal 62 is not depressed, the variable pressure chamber 70 and the vacuum chamber 72 are in communication with each other, and the pressure in the variable pressure chamber 70 is the same as the vacuum pressure in the vacuum chamber 72. In other words, the variable pressure chamber 70 and the vacuum chamber 72 are at the intake vacuum pressure of the engine 25, which is a pressure on the vacuum side of atmospheric pressure.

[0030] When the brake pedal 62 is depressed and the piston is moved forward, the variable pressure chamber 70 is isolated from the vacuum chamber 72 and is connected to the atmosphere. This causes the pressure in the variable pressure chamber 70 to approach atmospheric pressure, creating a pressure difference between the variable pressure chamber 70 and the vacuum chamber 72, which is the intake vacuum of the engine 25. This pressure difference draws the piston into the vacuum chamber 72, increasing the pressure applied to the brake pedal 62. When the brake pedal 62 is released, the variable pressure chamber 70 is isolated from the atmosphere and reconnected to the vacuum chamber 72, causing the vacuum in the vacuum chamber 72 to approach atmospheric pressure.

[0031] The vacuum chamber 72 of the brake booster 64 is provided with a brake vacuum sensor 74 that detects the vacuum value of the vacuum chamber 72. The smaller the vacuum value detected by the brake vacuum sensor 74, the closer the vacuum chamber 72 is to atmospheric pressure, indicating a state in which the vacuum is insufficient. On the other hand, the larger the detected vacuum value, the closer the vacuum chamber 72 is to a vacuum, indicating a state in which the vacuum is sufficient. The brake vacuum sensor 74 transmits the detected vacuum value (detected value) of the vacuum chamber 72 to the ECU 100.

[0032] Next, the functional configuration of the brake negative pressure sensor sticking failure determination device of this embodiment will be described. The brake negative pressure sensor sticking failure determination device determines a sticking failure of the brake negative pressure sensor 74 that detects the negative pressure value of the brake booster 64 mounted on the vehicle 10. As shown in Fig. 3, the brake negative pressure sensor sticking failure determination device includes the brake negative pressure sensor 74, the engine 25, the engine sensor 26, and an ECU 100. The ECU 100 further includes a drive control unit 102, a braking control unit 104, an engine drive determination unit 106, a negative pressure generation request unit 108, a negative pressure value change determination unit 110, and a failure determination unit 112.

[0033] The drive control unit 102 calculates a required output value based on an accelerator opening detected by an accelerator pedal sensor (not shown). Then, the drive control unit 102 controls the power supplied to the inverter 24 based on the calculated required output value, and controls the ignition mechanism and fuel system of the engine 25 to control the driving of the motor 23 and the engine 25. Furthermore, when a negative pressure generation request unit 108 transmits a negative pressure generation request to the engine 25, the drive control unit 102 drives the engine 25.

[0034] The braking control unit 104 controls the braking of the braking system 60 based on the amount of brake operation detected by a brake pedal sensor (not shown). Furthermore, when determining whether the brake negative pressure sensor 74 has stuck under a predetermined condition, the braking control unit 104 controls the brake operation a predetermined number of times.

[0035] The engine drive determining unit 106 determines whether the engine 25 is driven or not based on the detection value of the engine sensor 26. The engine sensor 26 is provided in the engine 25 and detects the engine 25 rotation speed.

[0036] The negative pressure generation request unit 108 transmits a negative pressure generation request to the engine 25 to generate negative pressure in accordance with the negative pressure value of the brake booster 64. When the negative pressure generation request is transmitted to the engine 25, the engine 25 starts to operate and supplies the negative pressure generated during intake to the negative pressure chamber 72 of the brake booster 64.

[0037] Here, the transmission of the vacuum generation request will be explained. When the driver depresses the brake pedal 62 to perform a braking operation, the vehicle 10 stops, and at this time the vacuum in the brake booster 64 is consumed, decreasing the vacuum value in the vacuum chamber 72. On the other hand, when the engine 25 starts, the vacuum pressure at the time of intake is supplied to the brake booster 64, the vacuum in the brake booster 64 is restored, and the vacuum value in the vacuum chamber 72 increases.

[0038] In this way, the negative pressure of the brake booster 64 is consumed and restored. Therefore, a "start threshold" is set to determine whether to start transmitting a negative pressure generation request when the negative pressure is consumed, and a "stop threshold" is set to determine whether to stop transmitting a negative pressure generation request when the negative pressure is restored. The stop threshold is greater than the start threshold.

[0039] Therefore, when the negative pressure is consumed by braking and the negative pressure value of the brake booster 64 becomes equal to or less than the start threshold, the negative pressure generation request unit 108 transmits a negative pressure generation request to the engine 25 to start driving the engine 25. Then, when the negative pressure value of the brake booster 64 becomes equal to or greater than the stop threshold due to driving of the engine 25, the negative pressure generation request unit 108 stops transmitting the negative pressure generation request to the engine 25. The start threshold and stop threshold are determined based on the speed of the vehicle 10 (vehicle speed).

[0040] In addition, a sticking failure determination threshold (see T2 in FIG. 4(B)) is set between the start threshold and the stop threshold. That is, the sticking failure determination threshold is a value that is greater than the start threshold and less than the stop threshold. The sticking failure determination threshold is a value that allows recovery until the negative pressure value of the brake booster 64 becomes greater than the stop threshold, regardless of the driving state of the engine 25. The sticking failure determination threshold is used when making a determination by the failure determination unit 112, which will be described later.

[0041] Furthermore, when the failure determination unit 112 determines that the brake negative pressure sensor 74 has definitely suffered a sticking failure, the negative pressure generation request unit 108 constantly transmits a negative pressure generation request to the engine 25. Furthermore, when it is determined that the brake negative pressure sensor 74 is suspected of having a sticking failure, the negative pressure generation request unit 108 transmits a negative pressure generation request to the engine 25 for a predetermined time. For example, when it is determined that the brake negative pressure sensor 74 is suspected of having a sticking failure after three braking operations, the predetermined time is set to a time required for recovering the negative pressure required for three braking operations.

[0042] The negative pressure value change determination unit 110 determines whether or not there is a change in the negative pressure value under predetermined conditions, including whether or not a negative pressure generation request has been transmitted and the number of brake operations. Specifically, when the engine 25 is not running, or when the engine 25 is running and a negative pressure generation request has not been transmitted, the negative pressure value change determination unit 110 determines a change in the negative pressure value detected while the brake is operated a predetermined number of times. Furthermore, when the engine 25 is running and a negative pressure generation request has been transmitted, the negative pressure value change determination unit 110 determines a change in the negative pressure value regardless of the brake operation.

[0043] The failure determination unit 112 determines whether the brake negative pressure sensor 74 has a sticking failure based on whether the engine 25 is being driven by the engine drive determination unit 106 and whether there is a change in the negative pressure value by the negative pressure value change determination unit 110. When the failure determination unit 112 determines that there is no change in the negative pressure value while the engine 25 is not being driven, it determines that the brake negative pressure sensor 74 has definitely suffered a sticking failure, and when the failure determination unit 112 determines that there is no change in the negative pressure value while the engine 25 is being driven, it determines that there is a possibility that the brake negative pressure sensor 74 has suffered a sticking failure.

[0044] The determination result by the failure determination unit 112 includes the following states. 1) The brake negative pressure sensor 74 is not stuck. 2) The brake negative pressure sensor 74 is stuck and a stuck fault has been confirmed. 3) A state in which the brake negative pressure sensor 74 is suspected to be stuck.

[0045] In the case of 1) above, the brake vacuum sensor 74 is not malfunctioning and can accurately detect the negative pressure value in the vacuum chamber 72. In the case of 2), the brake vacuum sensor 74 has malfunctioned due to sticking, and the correct negative pressure value in the vacuum chamber 72 cannot be detected, i.e., an incorrect negative pressure value is detected. In the case of 3), the brake vacuum sensor 74 may have malfunctioned due to sticking, and the correct negative pressure value in the vacuum chamber 72 may not be detected, i.e., it is unclear whether the detected negative pressure value is accurate or inaccurate.

[0046] A specific method for determining a brake negative pressure sensor sticking failure performed by the failure determination unit 112 will be described below. First, with reference to FIG. 4, a method for determining a brake negative pressure sensor sticking failure when the engine 25 is running and a negative pressure generation request is transmitted will be described. In FIG. 4, the horizontal axis represents time, with time elapsed toward the right. The vertical axis represents the negative pressure value, with the negative pressure value decreasing upward and increasing downward. Therefore, in FIG. 4, the higher the negative pressure value, the closer the brake booster 64 is to atmospheric pressure, and the lower the negative pressure value, the closer the brake booster 64 is to vacuum. The stop threshold T1 described above is also provided in FIGS. 4(A) and (B). FIG. 4(B) also provides a sticking failure determination threshold T2 that is greater than a start threshold (not shown) and less than the stop threshold T1.

[0047] When the engine 25 is running and a negative pressure generation request is being sent, and the negative pressure value change judgment unit 110 judges that there is no change in the negative pressure value of the brake booster 64, the failure judgment unit 112 judges that a sticking failure has been confirmed if the negative pressure value is equal to or less than the sticking failure judgment threshold T2, and judges that a sticking failure is suspected if the negative pressure value is greater than the sticking failure judgment threshold T2 and less than the stop threshold T1.

[0048] That is, when the engine 25 is running and a vacuum generation request is being transmitted, the vacuum generated by the engine 25 is supplied to the brake booster 64, so that the vacuum in the brake booster 64 is restored. While the vacuum generation request is being transmitted, the vacuum value changes from moment to moment. In Figure 4, the vacuum value changes from a small value to a large value in an inversely proportional manner over time.

[0049] 4A, the negative pressure value remains just above the stop threshold T1, i.e., at a value slightly smaller than the stop threshold T1. Conventionally, if the negative pressure value of the brake booster 64 remains at a value smaller than the stop threshold T1 like this (detected negative pressure value<stop threshold T1) even though the engine 25 is running, it would be determined that the brake negative pressure sensor 74 has failed due to sticking or the like.

[0050] However, even when the engine 25 is running, under certain conditions, such as when the engine 25 is warming up, the supply of vacuum from the engine 25 is small or nonexistent, so the recovery of vacuum in the brake booster 64 may stop and the vacuum may remain just above the stop threshold T1. In other words, even if the vacuum value is smaller than the stop threshold T1, the brake vacuum sensor 74 may not be stuck and may not be at fault.

[0051] In consideration of such a case, in this embodiment, a sticking failure determination threshold T2 is set, which is a value smaller than the stop threshold T1, as shown in Fig. 4(B). As described above, the sticking failure determination threshold T2 is a value that allows recovery until the negative pressure value of the brake booster 64 becomes a value larger than the stop threshold T1, regardless of the driving state of the engine 25.

[0052] 4B, in this embodiment, when the engine 25 is running and a negative pressure generation request is being transmitted, the failure determination unit 112 determines that the brake negative pressure sensor 74 has definitely experienced a sticking failure if the detected negative pressure value is equal to or less than the sticking failure determination threshold T2. Furthermore, when the engine 25 is running and a negative pressure generation request is being transmitted, the failure determination unit 112 determines that the brake negative pressure sensor 74 is suspected of having a sticking failure if the detected negative pressure value is greater than the sticking failure determination threshold T2 and less than the stop threshold T1, since it is not possible to determine whether the problem is due to a sticking failure of the brake negative pressure sensor 74 or the engine 25 being in a warm-up operation. Furthermore, when the engine 25 is running and a negative pressure generation request is being transmitted, the failure determination unit 112 determines that the brake negative pressure sensor 74 has not experienced a sticking failure if the detected negative pressure value is equal to or greater than the stop threshold T1.

[0053] Next, with reference to FIG. 5, a method for determining whether the brake vacuum sensor has stuck or malfunctioned when the engine 25 is not running will be described. In FIG. 5(A), the horizontal axis represents time, with time elapsed as the value moves to the right. The vertical axis represents the brake fluid pressure, with 0.3 MPa representing the value at the start of depression of the brake pedal 62 and 2.0 MPa representing the value at the end of depression of the brake pedal 62. Note that the brake fluid pressure values ​​shown in FIG. 5(A) are merely examples. In FIG. 5(B), the horizontal axis represents time. The vertical axis represents the vacuum value, with the vacuum value decreasing as the value moves upward and increasing as the value moves downward. Therefore, in FIG. 5 as well, the higher the vacuum value, the closer the brake booster 64 is to atmospheric pressure, and the lower the vacuum value, the closer the brake booster 64 is to vacuum.

[0054] The failure determination unit 112 determines that a sticking failure has been confirmed when the negative pressure value change determination unit 110 determines that there is no change in the detected negative pressure value while the brakes are operated a predetermined number of times while the engine 25 is not running. In other words, when the engine 25 is not running, the negative pressure value of the brake booster 64 changes simply by operating the brakes, so whether or not a sticking failure has been confirmed is determined based on the negative pressure value detected while the brakes are being operated.

[0055] Furthermore, depending on the depression amount of the brake pedal 62, a single braking operation may be sufficient with the supply from a vacuum tank (not shown), and the negative pressure value of the brake booster 64 may not fluctuate. For this reason, it is determined whether or not a sticking failure has been confirmed based on the negative pressure value detected while the brake is operated multiple times (N times), for example, three times. Note that if the engine 25 is not running, the negative pressure value of the brake booster 64 will not recover, and therefore it will not be determined that a sticking failure is suspected.

[0056] Therefore, as shown in Fig. 5, in this embodiment, if the negative pressure value detected by the brake negative pressure sensor 74 does not change (see Fig. 5(B)) while the brake is operated a predetermined number of times, for example, three times (N1, N2, and N3 in Fig. 5(A)) when the engine 25 is not running, the failure determination unit 112 determines that the brake negative pressure sensor 74 has definitely suffered a sticking failure. On the other hand, if the negative pressure value detected by the brake negative pressure sensor 74 changes while the brake is operated a predetermined number of times, for example, three times, when the engine 25 is not running, the failure determination unit 112 determines that the brake negative pressure sensor 74 is not stuck.

[0057] Next, with reference to Figure 6, a method for determining whether the brake vacuum sensor has stuck or malfunctioned when the engine 25 is running and no vacuum generation request has been transmitted will be described. In Figure 6(A), the horizontal axis represents time, with time elapsed as it moves to the right. The vertical axis represents the brake fluid pressure, with 0.3 MPa representing the value at the start of depression of the brake pedal 62 and 2.0 MPa representing the value at the end of depression of the brake pedal 62. Note that the brake fluid pressure values ​​shown in Figure 6(A) are an example. In Figure 6(B), the horizontal axis represents time. The vertical axis represents engine operation, which indicates whether the engine is running or not.

[0058] In Figure 6(C), the horizontal axis represents time. The vertical axis represents the negative pressure value, with the negative pressure value decreasing upward and increasing downward. Therefore, in Figure 6, the higher the negative pressure value, the closer the brake booster 64 is to atmospheric pressure, and the lower the negative pressure value, the closer the brake booster 64 is to vacuum. Also in Figure 6(C), the dotted line P1 represents the actual negative pressure value (actual negative pressure value), and the solid line P2 represents the negative pressure value detected by the brake negative pressure sensor 74.

[0059] 6, the engine 25 is not driven (FIG. 6(B)), and the brake operation is performed (FIG. 6(A)), thereby consuming the negative pressure of the brake booster 64 (FIG. 6(C) dotted line P1). Also, the engine 25 is driven (FIG. 6(B)), and the negative pressure of the brake booster 64 is restored (FIG. 6(C) dotted line P1).

[0060] The failure determination unit 112 determines that a sticking failure is suspected when the engine 25 is running and a request for generating negative pressure is not being sent, and the negative pressure value change determination unit 110 determines that there is no change in the detected negative pressure value while the brake operation is performed a predetermined number of times.

[0061] Even if a negative pressure generation request is not transmitted, the engine 25 may be driven depending on the driving state of the vehicle 10. Even if the engine 25 is driven to generate negative pressure, the negative pressure in the brake booster 64 may not be restored if the brakes are applied because the negative pressure in the brake booster 64 is consumed.

[0062] Furthermore, depending on the depression amount of the brake pedal 62, a single braking operation may be sufficient with the supply from a vacuum tank (not shown), and the vacuum value of the brake booster 64 may not fluctuate. For this reason, it is preferable to determine whether or not a sticking failure is suspected based on the vacuum value detected while performing the braking operation multiple times (N times), for example, three times.

[0063] 6, in this embodiment, when the engine 25 is running and a negative pressure generation request has not been transmitted, if the negative pressure value detected by the brake negative pressure sensor 74 does not change while the brake is operated a predetermined number of times, for example, three times (N1, N2, and N3 in FIG. 6A) (see solid line P2 in FIG. 6C), the failure determination unit 112 determines that the brake negative pressure sensor 74 is suspected of having a sticking failure. On the other hand, when the engine 25 is running and a negative pressure generation request has not been transmitted, if the negative pressure value detected by the brake negative pressure sensor 74 changes while the brake is operated a predetermined number of times, for example, three times (see dotted line P1 in FIG. 6C), the failure determination unit 112 determines that the brake negative pressure sensor 74 is not stuck.

[0064] If the engine 25 is running and the vacuum value does not change while the brakes are applied multiple times, it is impossible to determine whether the brake vacuum sensor 74 is stuck or whether the consumption of vacuum due to the brakes and the recovery of vacuum due to the engine are balanced. Therefore, in this case, it is determined that the brake vacuum sensor 74 is suspected of having a stuck fault.

[0065] The conditions and results of the method for determining whether a brake vacuum sensor has stuck or malfunction, as explained above, are summarized in Figure 7. The following is an explanation of Figure 7. R1) Engine is running and vacuum generation is required Threshold for determining sticking fault ≧ negative pressure value ・・・ Sticking fault confirmed Stop threshold > Negative pressure value > Sticking fault judgment threshold...Sticking fault suspected R2) Engine is running, no vacuum generation required The negative pressure value does not change after N brake operations... Suspected brake sticking R3) No engine drive, negative pressure generation required The negative pressure value does not change after N brake operations... A stuck fault has been confirmed. R4) No engine drive, no vacuum generation request The negative pressure value does not change after N brake operations... A stuck fault has been confirmed.

[0066] That is, in the brake vacuum sensor sticking failure determination method of this embodiment, if the engine 25 is running, a vacuum generation request has been transmitted, and the detected vacuum value is greater than the sticking failure determination threshold and less than the stop threshold, the brake vacuum sensor 74 determines that a sticking failure is suspected. Also, if the engine 25 is running, a vacuum generation request has not been transmitted, and the vacuum value does not change during N brake operations, the brake vacuum sensor 74 determines that a sticking failure is suspected. In this way, if the brake vacuum sensor 74 determines that a sticking failure is suspected, transmitting a vacuum generation request for a predetermined time will drive the engine 25 for the requested time and generate vacuum, which is advantageous in improving fuel efficiency.

[0067] Next, the flow of the method for determining whether the brake negative pressure sensor has a stuck fault according to this embodiment will be described with reference to Fig. 8. As shown in Fig. 8, first, the engine drive determination unit 106 determines whether the engine 25 is running (step S10). If the engine 25 is running (step S10: YES), the negative pressure generation request unit 108 determines whether a negative pressure generation request has been sent to the engine 25 (step S12).

[0068] If a negative pressure generation request has not been sent to the engine 25 (step S12: NO (see R2 in FIG. 7)), the braking control unit 104 performs the brake operation N times (for example, three times) (step S14), and the negative pressure value change determination unit 110 determines whether there is a change in the negative pressure value detected during the N brake operation operations (step S16). If there is no change in the negative pressure value (step S16: NO), the failure determination unit 112 determines that the brake negative pressure sensor 74 is suspected of having a sticking failure (step S18).

[0069] If it is determined that the brake negative pressure sensor 74 is suspected of having a sticking failure, the negative pressure generation request unit 108 transmits a negative pressure generation request to the engine 25 for a predetermined time (step S20), and the process returns to step S10. On the other hand, if there is a change in the negative pressure value in step S16 (step S16: YES), the failure determination unit 112 determines that the brake negative pressure sensor 74 is not stuck, and the process returns to step S10.

[0070] In step S12, if a negative pressure generation request has been sent to the engine 25 (step S12: YES (see FIG. 7R1)), the negative pressure value change determination unit 110 determines whether or not there has been a change in the negative pressure value (step S22). If there has been a change in the negative pressure value (step S22: YES), the failure determination unit 112 determines that the brake negative pressure sensor 74 is not stuck, and the process returns to step S10.

[0071] On the other hand, if there is no change in the negative pressure value (step S22: NO), the malfunction determination unit 112 determines whether the detected negative pressure value is greater than the sticking malfunction determination threshold T2 (step S24). If the detected negative pressure value is not greater than the sticking malfunction determination threshold T2, that is, if the detected negative pressure value is equal to or less than the sticking malfunction determination threshold T2 (step S24: NO), the process proceeds to step S32.

[0072] On the other hand, if the detected negative pressure value is greater than the sticking failure determination threshold T2 (step S24: YES), the failure determination unit 112 determines whether the detected negative pressure value is less than the stop threshold T1 (step S26). If the detected negative pressure value is less than the stop threshold T1 (step S26: YES), that is, if the negative pressure value is greater than the sticking failure determination threshold T2 but less than the stop threshold T1, the process proceeds to step S18. On the other hand, if the detected negative pressure value is equal to or greater than the stop threshold T1 (step S26: NO), the process determines that the brake negative pressure sensor 74 is not stuck, and returns to step S10.

[0073] If the engine 25 is not running in step S10 (step S10: NO), the braking control unit 104 performs the brake operation N times (for example, three times) (step S28), and the negative pressure value change determination unit 110 determines whether there is a change in the negative pressure value detected during the N brake operation operations (step S30). If there is no change in the negative pressure value (step S30: NO), the failure determination unit 112 determines that the brake negative pressure sensor 74 has definitely suffered a sticking failure (step S32).

[0074] If it is determined that the brake negative pressure sensor 74 has a confirmed stuck fault, the negative pressure generation request unit 108 constantly transmits a negative pressure generation request to the engine 25 (step S34), and the process returns to step S10. On the other hand, if there is a change in the negative pressure value in step S30 (step S30: YES), the fault determination unit 112 determines that the brake negative pressure sensor 74 is not stuck, and the process returns to step S10.

[0075] As described above, in the brake vacuum sensor sticking failure determination device of this embodiment, when the failure determination unit 112 determines that there is no change in the negative pressure value while the engine 25 is not running, it determines that the brake vacuum sensor 74 has definitely suffered a sticking failure. On the other hand, when the engine 25 is running and it determines that there is no change in the negative pressure value, it determines that there is a possibility that the brake vacuum sensor 74 has suffered a sticking failure. Therefore, when determining that the brake vacuum sensor 74 has a sticking failure, it is possible to determine that there is a possibility that the brake vacuum sensor 74 has suffered a sticking failure. This makes it possible to avoid determining that a normal brake vacuum sensor 74 has suffered a sticking failure. Furthermore, when the failure determination unit 112 determines that there is no change in the negative pressure value while the engine 25 is running and a negative pressure generation request is being sent, if the negative pressure value is equal to or less than the sticking failure determination threshold T2, it determines that a sticking failure has been confirmed, and if the negative pressure value is greater than the sticking failure determination threshold T2 but less than the stop threshold T1, it determines that a sticking failure is suspected. Therefore, when determining that the brake negative pressure sensor 74 has a sticking failure, it can be determined whether the brake negative pressure sensor 74 has a confirmed sticking failure or is suspected of having a sticking failure. Furthermore, the sticking failure judgment threshold T2 is set to a value that can be recovered until the negative pressure value becomes greater than the stop threshold T1, regardless of the driving condition of the engine 25, so that it is possible to avoid judging that a sticking failure is suspected when the negative pressure of the brake negative pressure sensor 74 cannot be recovered. Furthermore, the failure determination unit 112 is configured to determine that a sticking failure has occurred if it is determined that there is no change in the detected negative pressure value while the brake is operated a predetermined number of times while the engine 25 is not running. Therefore, when determining that the brake negative pressure sensor 74 has a sticking failure, it can be determined whether the brake negative pressure sensor 74 has a sticking failure. Furthermore, the failure determination unit 112 is configured to determine that a sticking failure is suspected when it is determined that there is no change in the detected negative pressure value while the brake is operated a predetermined number of times while the engine 25 is running and a negative pressure generation request is not being transmitted. Therefore, when determining that the brake negative pressure sensor 74 has a sticking failure, it can be determined whether the brake negative pressure sensor 74 is suspected of having a sticking failure. Furthermore, the negative pressure generation request unit 108 is configured to constantly send a negative pressure generation request to the engine 25 when it is determined that the brake negative pressure sensor 74 has a confirmed sticking failure, and to send a negative pressure generation request to the engine 25 for a predetermined period of time when it is determined that the brake negative pressure sensor 74 is suspected of having a sticking failure. Therefore, when it is determined that the brake negative pressure sensor 74 has a confirmed sticking failure or is suspected of having a sticking failure, it can send a negative pressure generation request that matches the respective determination result.

[0076] Although various embodiments have been described above, it goes without saying that the present invention is not limited to such examples. It is clear that a person skilled in the art can conceive of various modifications or alterations within the scope of the claims, and it is understood that these also naturally fall within the technical scope of the present invention. Furthermore, the components of the above embodiments may be combined in any manner as long as they do not deviate from the spirit of the invention.

[0077] This application is based on a Japanese patent application (Patent Application No. 2023-51724) filed on March 28, 2023, the contents of which are incorporated herein by reference. [Explanation of symbols]

[0078] 10 vehicles 20 Running System 21 Front wheel 22 rear wheel 23 Motor 24 inverters 25 Engine 26 Engine Sensor 30 Power Generation System 31 Generator 40 Fuel Tank 50 Battery 60 Brake System 62 Brake pedal 64 Brake booster 66 Master cylinder 68 disc brake 70 Transformer Room 72 Negative pressure chamber 74 Brake vacuum sensor 100 ECU 102 Drive control unit 104 Braking control unit 106 Engine drive determination unit 108 Negative pressure generation request unit 110 Negative pressure value change determination unit 112 Failure determination section

Claims

1. 1. A brake negative pressure sensor sticking failure determination device for determining a sticking failure of a brake negative pressure sensor that detects a negative pressure value of a brake booster in a vehicle that can supply negative pressure generated by driving an engine to the brake booster, comprising: an engine running determination unit that determines whether the engine is running; a negative pressure generation request unit that transmits a negative pressure generation request to the engine in response to the negative pressure value; a negative pressure value change determination unit that determines whether or not the negative pressure value has changed under predetermined conditions including whether or not the negative pressure generation request has been transmitted and the number of brake operations; a failure determination unit that determines a sticking failure of the brake negative pressure sensor based on whether or not the engine is being driven by the engine drive determination unit and whether or not the negative pressure value has changed by the negative pressure value change determination unit, The failure determination unit determines that the brake negative pressure sensor has a confirmed sticking failure when it is determined that there is no change in the negative pressure value while the engine is not running, and determines that there is a possibility that the brake negative pressure sensor has a sticking failure when it is determined that there is no change in the negative pressure value while the engine is running. A brake vacuum sensor sticking failure determination device characterized by the above.

2. the negative pressure generation request unit transmits the negative pressure generation request when the negative pressure value becomes equal to or less than a predetermined start threshold, and stops transmitting the negative pressure generation request when the negative pressure value becomes equal to or greater than a predetermined stop threshold that is greater than the start threshold; a sticking failure determination threshold is set between the start threshold and the stop threshold; When it is determined that there is no change in the negative pressure value while the engine is running and the negative pressure generation request is being transmitted, the malfunction determination unit determines that the sticking malfunction is confirmed if the negative pressure value is equal to or less than the sticking malfunction determination threshold, and determines that the sticking malfunction is suspected if the negative pressure value is greater than the sticking malfunction determination threshold and less than the stop threshold.

2. The brake vacuum sensor sticking failure determination device according to claim 1.

3. The sticking failure determination threshold is a value that allows recovery until the negative pressure value becomes greater than the stop threshold value, regardless of the driving state of the engine.

3. The brake vacuum sensor sticking failure determination device according to claim 2.

4. The failure determination unit determines that the sticking failure has been confirmed when it is determined that there is no change in the negative pressure value detected while the brake operation is performed a predetermined number of times while the engine is not running.

2. The brake vacuum sensor sticking failure determination device according to claim 1.

5. The malfunction determination unit determines that the sticking malfunction is suspected when it is determined that there is no change in the detected negative pressure value while the brake operation is performed a predetermined number of times while the engine is running and the negative pressure generation request is not being transmitted.

2. The brake vacuum sensor sticking failure determination device according to claim 1.

6. The negative pressure generation request unit constantly transmits the negative pressure generation request to the engine when it is determined that the brake negative pressure sensor has the confirmed sticking failure, and transmits the negative pressure generation request to the engine for a predetermined period of time when it is determined that the brake negative pressure sensor is suspected of having the sticking failure.

6. The brake negative pressure sensor sticking failure determination device according to claim 1.

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