JP7589653B2 - Vehicle brake control device - Google Patents

Description

The present invention relates to determining whether a brake is operated on a vehicle.

Patent document 1 describes a system in which braking control is performed based on the output voltage of a pedal force sensor, and when an abnormality occurs in the pedal force sensor, braking control is performed based on a signal from a brake switch.

Japanese Patent Application Publication No. 4-243648

Instead of the pedal force sensor in Patent Document 1, it is conceivable to provide a sensor that detects the master cylinder pressure of the master cylinder, and to control the brake operation based on the master cylinder pressure detected by that sensor. In such a case, for example, if the master cylinder pressure does not increase due to a mechanical failure of the brake, even if the sensor is normal, the master cylinder pressure will be low, making it impossible to determine whether the brake operation has been performed. In response to this, it is conceivable to determine whether the brake operation has been performed based on the signal from the brake switch, but when determining whether the brake operation has been performed based on the signal from the brake switch, for example, if a failure occurs in which the brake switch is stuck on the ON side (operation side), there is a risk that it will be erroneously determined that the brake operation has been performed when it has not been performed.

The present invention was made against the background of the above circumstances, and its purpose is to provide a braking control device that can accurately determine whether or not the driver has applied the brakes.

The gist of the first invention is a braking control device for a vehicle that (a) determines whether a brake is being operated based on a master cylinder pressure of a master cylinder which is increased in accordance with the amount of brake operation, and if an abnormality occurs in the master cylinder pressure detection means, determines whether the brake is being operated based on an output signal output from a stop lamp switch while the brake pedal is depressed , and (b) when the master cylinder pressure detected by the master cylinder pressure detection means is below a predetermined value, and the output signal of the stop lamp switch changes twice, from a non-output state to an output state and from the output state to a non-output state , a reliability determination flag is raised to determine the reliability of the stop lamp switch, and if the output signal of the stop lamp switch changes from a non-output state to an output state during the period when the reliability determination flag is raised, it is determined that the brake has been operated.

According to the first invention, in a state in which the master cylinder pressure falls below a predetermined value even when the brakes are operated, for example due to a mechanical failure of the brakes, if the output signal of the stop lamp switch changes twice, from a non-output state to an output state and then from the output state to a non-output state , a reliability determination flag is raised, and if the output signal of the stop lamp switch changes from a non-output state to an output state during the period in which the reliability determination flag is raised, it is determined that the brakes have been operated.Therefore, when the stop lamp switch is determined to be normal, it is determined whether the brakes have been operated based on the output signal of the stop lamp switch, thereby preventing erroneous determinations due to the stop lamp switch being stuck, for example.

1 is a diagram showing a schematic configuration of a brake provided in a vehicle to which the present invention is applied and a braking control device that controls the brakes and the like. 4 is a flowchart for explaining a main part of the control operation of the electronic control device, and is a flowchart for explaining the control operation for determining whether the stop lamp switch is normal. 11 is another flowchart for explaining a main part of the control operation of the electronic control device, and is a flowchart for explaining the control operation for determining whether or not a brake operation has been performed. 11 is yet another flowchart for explaining the main control functions of the electronic control device, and is a flowchart for explaining a control operation for determining whether or not to switch the reliability determination flag to "OFF". 4 is a time chart illustrating a control state by an electronic control device.

Here, preferably, when raising the reliability determination flag, the braking control device further determines whether a predetermined time has elapsed since a change occurred in the output signal of the stop lamp switch. In this way, by appropriately adjusting the predetermined time, it is possible to eliminate unintended braking operations by the driver, such as driver erroneous operation, and to accurately determine whether braking operations have been performed.

Preferably, when determining whether the brakes have been operated, during the period in which the reliability determination flag is set, the brake control device determines whether a second predetermined time has elapsed since a change occurred in the output signal of the stop lamp switch. In this way, by appropriately adjusting the second predetermined time, it is possible to determine that the brakes have been operated at the same timing as when the brakes are normal.

The following describes in detail the embodiments of the present invention with reference to the drawings. Note that in the following embodiments, the drawings have been simplified or modified as appropriate, and the dimensional ratios and shapes of each part are not necessarily drawn accurately.

Figure 1 is a diagram showing the schematic configuration of a brake 10 provided on a vehicle to which the present invention is applied, and an electronic control device 12 that controls the brake 10. The brake 10 is composed of a brake pedal 14 operated by the driver, a master cylinder 16 that generates a master cylinder pressure Pm/c that is increased according to the amount of depression (operation amount) of the brake pedal 14 by the driver, an actuator 18 that adjusts the braking force of each wheel, and hydraulic brakes 20a to 20c that are provided on each wheel and actuated by the hydraulic pressure supplied from the actuator 18. Note that the brake 10 is a known technology, so a detailed description of its structure and operation will be omitted.

The electronic control device 12 includes a brake ECU 22 and an SFT-ECU 24. The brake ECU 22 and the SFT-ECU 24 include a so-called microcomputer equipped with, for example, a CPU, RAM, ROM, an input/output interface, etc., and the CPU is configured to execute various vehicle controls, including braking control of the brakes 10, by performing signal processing according to a program previously stored in the ROM while utilizing the temporary storage function of the RAM. The electronic control device 12 corresponds to the vehicle braking control device of the present invention.

The brake ECU 22 has the exclusive function of controlling the brake 10 (braking device) provided on the vehicle, and controls the operating state of the brake 10 based on the driver's depressing the brake pedal 14 and the running state of the vehicle. The brake ECU 22 receives, for example, a hydraulic signal representing the M/C pressure Pm/c from an M/C pressure sensor 28 that detects the master cylinder pressure Pm/c (hereinafter, M/C pressure Pm/c) of the master cylinder 16 that constitutes the brake 10. The brake ECU 22 outputs a command signal Sbrk to various solenoid valves (not shown) that control the brake 10. The M/C pressure Pm/c detected by the M/C pressure sensor 28 is also transmitted to the SFT-ECU 24 via the brake ECU 22. When an abnormality is detected in the M/C pressure sensor 28, information representing the abnormality in the M/C pressure sensor 28 (M/C pressure sensor abnormality information) is transmitted from the brake ECU 22 to the SFT-ECU 24. An abnormality in the M/C pressure sensor 28 is determined, for example, by a self-check function of the M/C pressure sensor 28, or by the brake ECU 22 based on the M/C pressure Pm/c detected by the M/C pressure sensor 28. The M/C pressure sensor 28 corresponds to the master cylinder pressure detection means of the present invention.

The SFT-ECU 24 has the exclusive function of controlling the shift range of the transmission 30 provided in the vehicle, and outputs a command signal to an actuator or the like that switches the shift range of the transmission 30 based on, for example, a shift operation by the driver. The SFT-ECU 24 receives, for example, an output signal Sstp output from a stop lamp switch 32 (also called a brake lamp switch) for switching the operation state of the stop lamp. The SFT-ECU 24 outputs, for example, a parking lock switching signal Spark to the SBW-ACT 34 that switches the transmission 30 to a parking lock state.

For example, if the vehicle is determined to be stopped and the brake pedal 14 is determined to be depressed, and the driver operates the shift lever to the parking position (P position), the SFT-ECU 24 activates the SBW-ACT 34 to switch the shift range to the parking range. Furthermore, if the vehicle is determined to be stopped and the brake pedal 14 is determined to be depressed, and the driver switches the shift lever from the P position to another shift position (such as the D position), the SFT-ECU 24 activates the SBW-ACT 34 to switch the shift range to a range other than the parking range (such as the D range).

When controlling the shift range, the SFT-ECU 24 is functionally equipped with a brake operation determination unit 50 that serves as a brake operation determination means for determining whether the brake pedal 14 is being depressed by the driver, i.e., whether a brake operation is being performed.

The brake operation determination unit 50 performs an operation determination as to whether or not a brake operation has been performed based on whether or not the M/C pressure Pm/c detected by the M/C pressure sensor 28 is higher than a predetermined value α that has been set in advance. Specifically, the brake operation determination unit 50 determines that a brake operation has been performed when the M/C pressure Pm/c becomes higher than the predetermined value α. The predetermined value α is determined in advance experimentally or by design, and is set to a threshold value at which it can be determined that a brake operation has been performed by the driver.

Here, if an abnormality occurs in the M/C pressure sensor 28, it becomes difficult to determine whether a brake operation has been performed based on the M/C pressure Pm/c. In such a case, the brake operation determination unit 50 performs an operation determination as to whether a brake operation has been performed based on an output signal Sstp for switching the operation state of the stop lamp, which is output from the stop lamp switch 32 (hereinafter, stop lamp SW 32). The stop lamp SW 32 is provided, for example, near the brake pedal 14, and is configured to output the output signal Sstp while the brake pedal 14 is depressed by the driver. In addition, the stop lamp SW 32 is configured to output the output signal Sstp even if the brake pedal 14 is slightly depressed. Therefore, it is possible to determine whether a brake operation has been performed based on the output signal Sstp of the stop lamp SW 32. When information indicating an abnormality in the M/C pressure sensor 28 (M/C pressure sensor abnormality information) is transmitted from the brake ECU 22, the brake operation determination unit 50 determines whether the output signal Sstp of the stop lamp SW 32 is being output, and determines that the brake operation is being performed while the output signal Sstp is being output from the stop lamp SW 32.

However, even if the M/C pressure sensor 28 is normal, if the master cylinder 16 has a mechanical failure or the driver does not press the brake pedal 14 deeply enough, and the M/C pressure Pm/c detected by the M/C pressure sensor 28 is below the predetermined value α, making it difficult to determine whether the brake operation has been performed. Even in such a case, it is possible to determine whether the brake operation has been performed using the stop lamp SW 32. However, if an ON failure occurs in which the stop lamp SW 32 is stuck and the output signal Sstp is constantly output from the stop lamp SW 32, it may be erroneously determined that the driver is performing the brake operation even when the brake operation has not been performed. In this case, if the driver operates the shift lever from the P position to another shift position without performing the brake operation, the brake operation may be erroneously determined, and the shift range may be unintentionally switched to a range other than the parking range.

In response to this, the brake operation determination unit 50 sets up a reliability determination flag Ftrust (Ftrust: "ON") for determining the reliability of the stop lamp SW 32 when a change occurs in the output signal Sstp of the stop lamp SW 32 when the M/C pressure Pm/c detected by the M/C pressure sensor 28 is equal to or lower than the predetermined value α, and determines that the brake operation has been performed when the output signal Sstp of the stop lamp SW 32 changes while the reliability determination flag Ftrust is set up. In this way, when the M/C pressure Pm/c is equal to or lower than the predetermined value α, the stop lamp SW 32 is determined to be normal by detecting a change in the output signal Sstp of the stop lamp SW 32, and in a state in which the stop lamp SW 32 is determined to be normal, it is determined whether the brake operation has been performed based on the output signal Sstp of the stop lamp SW 32, thereby preventing erroneous determination of the brake operation due to a malfunction of the stop lamp SW 32. Below, we will explain the control that occurs when the M/C pressure Pm/c detected by the M/C pressure sensor 28 is low (below a predetermined value α), for example, when the master cylinder 16 fails or when the driver does not press the brake pedal 14 deeply.

The brake operation determination unit 50 determines whether or not to raise the reliability determination flag Ftrust, which determines whether the stop lamp SW 32 is normal, based on whether or not all of the following conditions (a) to (d) are satisfied. In addition, when the reliability determination flag Ftrust is "ON", this indicates that the stop lamp SW 32 is normal. Condition (a) is that the M/C pressure Pm/c detected by the M/C pressure sensor 28 is equal to or less than a predetermined value α; condition (b) is that the output signal Sstp of the stop lamp SW 32 is output, i.e., the output signal Sstp switches from "OFF (non-output state)" to "ON (output state)"; condition (c) is that the output signal Sstp of the stop lamp SW 32, which is in the output state, is no longer output, i.e., the output signal Sstp switches from "ON" to "OFF"; and condition (d) is that a predetermined time ta has elapsed since the time when the output signal Sstp of the stop lamp SW 32 switches from "OFF" to "ON", i.e., the time when the output signal Sstp of the stop lamp SW 32 first changed.

Condition (a) is to confirm that even if the M/C pressure sensor 28 is normal, the M/C pressure Pm/c does not increase due to a mechanical failure of the brake 10, or the brake pedal 14 is not depressed enough. Conditions (b) and (c) are to confirm whether a change has occurred in the output signal Sstp of the stop lamp SW 32. Specifically, it is to confirm that the output signal Sstp of the stop lamp SW 32 has switched from " OFF " to " ON ", and further that the output signal Sstp has switched from "ON" to "OFF". That is, it is to confirm that the output signal Sstp of the stop lamp SW 32 has changed twice, from "OFF" to "ON", and from "ON" to "OFF". If these conditions (b) and (c) are satisfied, it can be confirmed that the stop lamp SW 32 is not stuck and operates normally. The condition (d) is a condition for confirming whether the driver intends to apply the brakes based on whether a predetermined time ta has elapsed since the output signal Sstp of the stop lamp SW 32 was switched from "OFF" to "ON". When all of these conditions (a) to (d) are satisfied, the brake operation determination unit 50 determines that the stop lamp SW 32 is normal, and sets the reliability determination flag Ftrust from "OFF" to "ON".

The brake operation determination unit 50 also determines whether a brake operation has been performed based on whether all of the following conditions (e) to (g) are satisfied: Condition (e) is that the reliability determination flag Ftrust is "ON", Condition (f) is that the output signal Sstp of the stop lamp SW32 has switched from "OFF" to "ON", and Condition (g) is that a predetermined time tb has elapsed since the stop lamp SW32 switched from "OFF" to "ON", i.e., a predetermined time tb has elapsed since the output signal Sstp of the stop lamp SW32 first changed during the period in which the reliability determination flag Ftrust is "ON".

Condition (e) is to ensure that the stop lamp SW 32 is normal, i.e., that the reliability of the stop lamp SW 32 is high. Condition (f) is to confirm that the brake operation is performed under a condition in which the stop lamp SW 32 is normal. Condition (g) is a condition for determining that the brake operation is performed at the same timing as when the brake 10 is normal, by confirming that a predetermined time tb has elapsed since the point in time when condition (f) is established. In other words, condition (g) is a condition for giving the driver the same brake operation feeling as when the brake 10 is normal. The predetermined time tb is set, for example, to the time from the point in time when the brake pedal 14 is depressed until the M/C pressure Pm/c becomes equal to or greater than the predetermined value α when the brake 10 is normal.

When all of these conditions (e) to (g) are satisfied, the brake operation determination unit 50 determines that a brake operation has been performed and sets the brake determination flag Fbrk, which indicates that a brake operation is being performed, to "ON". The brake determination flag Fbrk is set to "ON" when all of conditions (e) to (f) are satisfied and it is determined that a brake operation is being performed, and is set to "OFF" when any of conditions (e) to (f) are not satisfied. As a result, when the reliability determination flag Ftrust is "ON", it is determined whether a brake operation has been performed from a change in the output signal Sstp of the stop lamp SW 32, so that a brake operation is determined based on the output signal Sstp of the stop lamp SW 32 when the stop lamp SW 32 is in a normal state.

The brake operation determination unit 50 also determines whether to switch the reliability determination flag Ftrust from "ON" to "OFF" based on whether the following conditions (h) and (i) are all satisfied. Condition (h) is that the reliability determination flag Ftrust is in the "ON" state, and condition (i) is that the brake determination flag Fbrk has switched from "ON" to "OFF." When conditions (h) and (i) are all satisfied, the brake operation determination unit 50 sets the reliability determination flag Ftrust to "OFF."

Figure 2 is a flowchart for explaining the main control operations of the electronic control unit 12, and is a flowchart for explaining the control operations for determining whether the stop lamp switch 32 is normal. This flowchart is executed repeatedly while the vehicle is traveling.

First, in step S10 (hereinafter, step is omitted) corresponding to the control function of the brake operation determination unit 50, it is determined whether all of the conditions (a) to (d) are satisfied. Specifically, it is determined whether the M/C pressure Pm/c detected by the M/C pressure sensor 28 is equal to or lower than a predetermined value α (condition (a)), and the output signal Sstp of the stop lamp SW 32 is switched from "OFF" to "ON" (condition (b)), and the output signal Sstp of the stop lamp SW 32 is switched from a state in which it was switched to "ON" to "OFF" (condition (c)), and a predetermined time ta has elapsed since the output signal Sstp of the stop lamp SW 32 was switched to "OFF" (condition (d)). If the determination in S10 is negative, this routine is terminated. On the other hand, if the determination in S10 is positive, in S11, which corresponds to the control function of the brake operation determination unit 50, the reliability determination flag Ftrust of the stop lamp SW 32 is switched from "OFF" to "ON."

Figure 3 is another flowchart for explaining the main control operations of the electronic control unit 12, and is a flowchart for explaining the control operations for determining whether or not a brake operation has been performed. This flowchart is executed repeatedly while the vehicle is traveling.

First, in S20, which corresponds to the control function of the brake operation determination unit 50, it is determined whether all of the conditions (e) to (g) are satisfied. Specifically, it is determined whether the reliability determination flag Ftrust of the stop lamp SW32 is in the "ON" state (condition (e)), the stop lamp SW32 has switched from "OFF" to "ON" (condition (f)), and a predetermined time tb has elapsed since the stop lamp SW32 switched from "OFF" to "ON" (condition (g)). If the determination in S20 is negative, the brake determination flag Fbrk is set to "OFF" in S22, which corresponds to the control function of the brake operation determination unit 50. In other words, it is determined that the brake operation is not being performed. On the other hand, if the determination in S20 is positive, the brake determination flag Fbrk is set to "ON" in S21, which corresponds to the control function of the brake operation determination unit 50. In other words, it is determined that the brake operation is being performed.

Figure 4 is yet another flowchart for explaining the main control functions of the electronic control unit 12, and is a flowchart for explaining the control operation for determining whether or not to switch the reliability determination flag Ftrust of the stop lamp SW 32 to "OFF". This flowchart is executed repeatedly while the vehicle is traveling.

First, in S30, which corresponds to the control function of the brake operation determination unit 50, it is determined whether or not the condition (h) and the condition (i) are all satisfied. Specifically, it is determined whether or not the reliability determination flag Ftrust of the stop lamp SW 32 is in the "ON" state (condition (h)) and the brake determination flag Fbrk has switched from "ON" to "OFF" (condition i). If the determination in S30 is negative, this routine is terminated. On the other hand, if the determination in S30 is positive, in S31, which corresponds to the control function of the brake operation determination unit 50, the reliability determination flag Ftrust of the stop lamp SW 32 is switched from "ON" to "OFF".

Figure 5 is a time chart that explains the control state by the electronic control unit 12. In Figure 5, the horizontal axis indicates time t, and the vertical axis indicates, from top to bottom, the output signal Sstp of the stop lamp SW 32, the M/C pressure Pm/c of the master cylinder 16, the brake judgment flag Fbrk, and the reliability judgment flag Ftrust of the stop lamp SW 32. The time chart on the left side of Figure 5 shows the judgment of the brake operation under normal conditions when no malfunction occurs in the brake 10. The time chart on the right side of Figure 5 corresponds to the case where the M/C pressure Pm/c is equal to or lower than the predetermined value α due to a mechanical malfunction of the brake 10 or a shallow depression of the brake pedal 14.

First, the time chart on the left side of FIG. 5 will be described. In a normal state, when the brake pedal 14 is depressed at time t1, the output signal Sstp of the stop lamp SW 32 is switched from "OFF" to "ON". At time t2, a predetermined time after time t1, the brake determination flag Fbrk indicating that the brakes have been operated is switched from "OFF" to "ON" on the condition that the M/C pressure Pm/c is equal to or greater than a predetermined value α. At time t3, when the brake pedal is released, the output signal Sstp of the stop lamp SW 32 is switched from "ON" to "OFF", and the M/C pressure Pm/c also decreases. Accordingly, the brake determination flag Fbrk is switched from "ON" to "OFF".

Next, the time chart on the right side of FIG. 5 will be described. When the brake pedal 14 is depressed at time t11, the output signal Sstp of the stop lamp SW 32 is switched from "OFF" to "ON". At this time, due to a failure of the master cylinder 16 of the brake 10 or a light depression of the brake pedal 14, the M/C pressure Pm/c does not increase and does not reach the predetermined value α, which is the judgment value for switching the brake judgment flag Fbrk to "ON". The M/C pressure Pm/c shown by the dashed line in FIG. 5 corresponds to the M/C pressure Pm/c when the brake 10 is normal or the brake pedal 14 is fully depressed. When the brake 10 is normal or the brake pedal 14 is fully depressed, the M/C pressure Pm/c exceeds the predetermined value α at time t12, as shown by the dashed line. However, as shown by the solid line, the M/C pressure Pm/c does not increase, so the brake determination flag Fbrk does not switch from "OFF" to "ON". At time t13, the brake pedal 14 is released, and the output signal Sstp of the stop lamp SW 32 switches from "ON" to "OFF". At this time, the M/C pressure Pm/c is equal to or less than the predetermined value α, and the output signal Sstp of the stop lamp SW 32 switches from "OFF" to "ON" at time t11, and from "ON" to "OFF" at time t13. Furthermore, the elapsed time t from time t11 has passed the predetermined time ta, so that the reliability determination flag Ftrust switches from "OFF" to "ON" at time t13.

At time t14, the brake pedal 14 is depressed, and the output signal Sstp of the stop lamp SW 32 is switched from "OFF" to "ON". At time t15, the reliability determination flag Ftrust is in the "ON" state, the output signal Sstp of the stop lamp SW 32 is switched from "OFF" to "ON", and the elapsed time t from time t14, when the output signal Sstp of the stop lamp SW 32 was switched to "ON", reaches a predetermined time tb, and the brake determination flag Fbrk is switched from "OFF" to "ON". In addition, the predetermined time tb is set to the time from when the brake pedal 14 is depressed to when the M/C pressure Pm/c becomes equal to or greater than the predetermined value α when the brake 10 is normal. As a result, the brake determination flag Fbrk is switched to "ON" at the same timing as when the brake 10 is normal, and the driver can be given the same brake operation feeling as when the brake 10 is normal.

At time t16, the brake pedal 14 is released, causing the output signal Sstp of the stop lamp SW 32 to switch from "ON" to "OFF", and the brake determination flag Fbrk to switch from "ON" to "OFF". At this time, the reliability determination flag Ftrust is in the "ON" state, and because the brake determination flag Fbrk has switched from "ON" to "OFF", the reliability determination flag Ftrust switches from "ON" to "OFF". In this way, when the driver completes the second brake operation, the reliability determination flag Ftrust switches to "OFF".

As described above, according to this embodiment, when the M/C pressure Pm/c is equal to or lower than the predetermined value α even when the brakes are applied due to, for example, a failure of the brake 10, the reliability determination flag Ftrust is raised if a change occurs in the output signal Sstp of the stop lamp SW 32, and if the output signal Sstp of the stop lamp SW 32 changes during the period in which the reliability determination flag Ftrust is raised, it is determined that the brakes have been applied. Therefore, when the stop lamp SW 32 is in a normal state, it is determined based on the output signal Sstp of the stop lamp SW 32 that the brakes have been applied, and erroneous determinations due to the stop lamp SW 32 being stuck or the like can be prevented.

The above describes in detail an embodiment of the present invention based on the drawings, but the present invention can also be applied in other aspects.

For example, in the above embodiment, the brake ECU 22 and the SFT-ECU 24 are provided separately, but they may be configured as a common ECU.

In addition, in the above-described embodiment, the brake 10 is operated by depressing the brake pedal 14, but this is not necessarily limited to the brake pedal 14, and may be manually operated with a lever or the like.

Note that the above is merely one embodiment, and the present invention can be implemented in various forms with various modifications and improvements based on the knowledge of those skilled in the art.

10: Brake 12: Electronic control device (braking control device)
16: Master cylinder 28: M/C pressure sensor (means for detecting master cylinder pressure)
32: Stop lamp switch Pm/c: Master cylinder pressure Sstp: Output signal (output signal of stop lamp switch)
Ftrust: reliability determination flag α: predetermined value

Claims (1)

A vehicle braking control device that performs brake operation determination based on a master cylinder pressure of a master cylinder that is increased in accordance with an amount of brake operation, and when an abnormality occurs in a master cylinder pressure detection means, performs brake operation determination based on an output signal output from a stop lamp switch while a brake pedal is depressed ,
a brake control device for a vehicle, characterized in that when the master cylinder pressure detected by the master cylinder pressure detection means is below a predetermined value and the output signal of the stop lamp switch changes twice, from a non-output state to an output state and from the output state to the non-output state , a reliability determination flag is raised to determine the reliability of the stop lamp switch, and when the output signal of the stop lamp switch changes from the non-output state to the output state during the period in which the reliability determination flag is raised, it is determined that the brakes have been operated.

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