JP2009113693A - Braking force control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a braking force control device capable of realizing the control operation matched with the operation of a driver. <P>SOLUTION: The braking force control device has a brake ECU 32 which holds the braking force according to the brake operation when a vehicle stops on an uphill road, and performs the pressurized holding of the braking force for holding the vehicle by increasing the braking force when the slip of the vehicle occurs when holding the braking force. The brake ECU 32 releases the holding of the braking force when the accelerator operation by a driver is detected during the pressurized holding of the braking force. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention belongs to the technical field of a braking force control device having a slope start assist function that suppresses vehicle slippage when a driver switches from a brake pedal to an accelerator pedal when starting on an uphill road.

Conventionally, in this type of braking force control device, when the vehicle stops on an uphill road, the brake fluid is sealed in the wheel cylinder by turning on the brake switch to hold the braking force, and then the braking force is held by turning off the brake switch. It has been released. In this prior art, when a vehicle slippage is detected during braking force holding, the vehicle sliding down is minimized by performing braking force pressurization holding to pressurize the inside of the wheel cylinder ( For example, see Patent Document 1.)
JP 2002-104147 A

  However, in the above prior art, since the braking force holding is released based on the brake switch being turned off, the driver once releases the brake pedal during the braking force pressurization holding, and then the vehicle slides down. When the driver depresses the brake again with the braking force increased due to the above, the brake circuit may not be depressed and the brake switch may not be turned on because the hydraulic circuit is at a high pressure. Therefore, since holding of the braking force is released by continuing the brake switch OFF, there is a problem that the driver's braking intention is not reflected in the control operation, and the operation of the driver and the control operation do not match.

  The present invention has been made paying attention to the above problem, and an object of the present invention is to provide a braking force control device capable of realizing a control operation that matches the operation of the driver.

In order to achieve the above object, in the present invention, the slope start assisting means releases the braking force holding when the driver's accelerator operation is detected while the braking force is being pressed and held.
The driver's intention to start can be determined by an accelerator operation. If there is no accelerator operation, the driver can determine that the vehicle has a willingness to stop. In the present invention, the braking force pressurization holding is continued until the driver's accelerator operation, that is, the driver's intention to start, is detected, so that the release of the braking force holding contrary to the driver's will can be avoided.
As a result, a control operation that matches the operation of the driver can be realized.

  Hereinafter, the best mode for realizing the braking force control apparatus of the present invention will be described based on Example 1 shown in the drawings.

First, the configuration will be described.
FIG. 1 is a system configuration diagram of the braking force control apparatus according to the first embodiment.
The hydraulic unit (hereinafter referred to as “HU”) 31 is a wheel cylinder W / C (FL) for the left front wheel FL and a wheel cylinder W / C (RR) for the right rear wheel RR based on a command from a brake controller (hereinafter referred to as “brake ECU”) 32. ), Holding, increasing or reducing the hydraulic pressure of the wheel cylinder W / C (FR) of the right front wheel FR and the wheel cylinder W / C (RL) of the left rear wheel RL.

  The brake ECU 32 includes an acceleration sensor (hereinafter referred to as G sensor) 33, a wheel speed sensor 34, an engine controller (hereinafter referred to as ENGCU) 35, and information obtained from the automatic transmission controller (hereinafter referred to as ATCU) 36 through CAN communication, Based on the information from the brake switch (brake operation detecting means) BS, it is determined whether to execute the braking control. During the execution of the control, the wheel cylinder hydraulic pressure is maintained and an increase / decrease command is generated.

  The brake pedal BP is operated when the driver performs braking, and generates a braking force according to the operation amount. The brake switch BS is turned on when the driver depresses the brake pedal BP for a certain amount. The brake ECU 32 determines that there is a driver brake operation when the brake switch BS is ON, and no brake operation when the brake switch BS is OFF.

  Each wheel cylinder W / C brakes the corresponding wheel. The wheel speed sensor 34 detects the wheel speed of each wheel. The brake ECU 32 makes a stop determination based on the wheel speed of each wheel.

  The G sensor 33 detects acceleration in the vehicle longitudinal direction. When paying particular attention to slopes, the G sensor 33 detects the occurrence of longitudinal acceleration in accordance with the gradient. In the first embodiment, the gradient detection is performed using the acceleration generated when the vehicle is stopped as the gradient in the vehicle traveling direction.

  The accelerator pedal AP performs vehicle acceleration / deceleration control by the driver's operation. The ENGCU 35 controls the engine 37 from the driver's accelerator pedal operation. In addition, the generated torque of the engine 37 and information on the accelerator pedal operation amount are output by communication (CAN). The ATCU 36 controls the automatic transmission 38. Further, a gear position signal (range position of the automatic transmission 38) is output by communication (CAN).

  FIG. 2 is a hydraulic circuit diagram of the HU 31 according to the first embodiment. The HU 31 according to the first embodiment has a piping structure called an X piping that includes two systems, a P system and an S system.

  The P system is connected to the wheel cylinder W / C (FL) for the left front wheel and the wheel cylinder W / C (RR) for the right rear wheel. The wheel cylinder W / C (FR) for the right front wheel is connected to the S system. The wheel cylinder W / C (RL) on the left rear wheel is connected. Each of the P system and the S system is provided with a pump PP and a pump PS, and the pump PP and the pump PS are driven by one motor M. In addition, a plunger pump, a gear pump, etc. are suitably mounted as a pump. In terms of cost, a plunger pump is desirable, and in terms of smoothness (controllability), a gear pump is desirable.

  Master cylinder M / C and the suction side of pumps PP and PS (hereinafter referred to as pump P) are connected by conduits 11P and 11S (hereinafter referred to as conduit 11). On each pipeline 11, gate-in valves 2P and 2S, which are normally closed solenoid valves, are provided.

  Further, on the pipeline 11, between the gate-in valves 2P and 2S (hereinafter referred to as gate-in valve 2) and the pump P, check valves 6P and 6S (hereinafter referred to as check valve 6) are provided. The check valves 6 allow the brake fluid to flow in the direction from the gate-in valve 2 to the pump P, and prohibit the flow in the opposite direction.

  The discharge side of each pump P and each wheel cylinder W / C are connected by pipelines 12P and 12S (hereinafter referred to as pipeline 12). On each pipe 12, solenoid-in valves 4FL, 4RR, 4FR, 4RL (hereinafter referred to as solenoid-in valves 4), which are normally open solenoid valves corresponding to the respective wheel cylinders W / C, are provided. ing.

  In addition, check valves 7P and 7S (hereinafter referred to as check valves 7) are provided on the pipes 12 and between the solenoid-in valves 4 and the pumps P. The brake fluid flow in the direction from the pump P toward the solenoid-in valve 4 is allowed, and the flow in the opposite direction is prohibited.

  Furthermore, each pipeline 12 is provided with pipelines 17FL, 17RR, 17FR, and 17RL (hereinafter referred to as pipeline 17) that bypass each solenoid-in valve 4, and this pipeline 17 includes a check valve 10FL. , 10RR, 10FR, 10RL (hereinafter referred to as check valve 10). Each check valve 10 allows the flow of brake fluid in the direction from the wheel cylinder W / C toward the pump P, and prohibits the flow in the opposite direction.

  Master cylinder M / C and pipe 12 are connected by pipes 13P and 13S (hereinafter referred to as pipe 13), and pipe 12 and pipe 13 are connected between pump P and solenoid-in valve 4. Join. On each pipeline 13, gate-out valves 3 </ b> P and 3 </ b> S (hereinafter referred to as gate-out valves 3) that are normally open solenoid valves are provided.

  Each pipeline 13 is provided with pipelines 18P and 18S (hereinafter referred to as pipelines 18) that bypass each gate-out valve 3, and the pipeline 18 includes check valves 9P and 9S (hereinafter referred to as pipelines 18). A check valve 9). Each check valve 9 permits the flow of brake fluid in the direction from the master cylinder M / C side toward the wheel cylinder W / C, and prohibits the flow in the opposite direction.

  On the suction side of the pump P, reservoirs 16P and 16S (hereinafter referred to as the reservoir 16) are provided, and the reservoir 16 and the pump P are connected by pipe lines 15P and 15S (hereinafter referred to as the pipe line 15). ing. Check valves 8P and 8S (hereinafter referred to as check valves 8) are provided between the reservoir 16 and the pump P, and each check valve 8 flows brake fluid in a direction from the reservoir 16 to the pump P. Is allowed and flow in the opposite direction is prohibited.

  The wheel cylinder W / C and the pipeline 15 are connected by pipelines 14P and 14S (hereinafter referred to as pipeline 14), and the pipeline 14 and pipeline 15 merge between the check valve 8 and the reservoir 16. To do. Each pipeline 14 is provided with solenoid-out valves 5FL, 5RR, 5FR, and 5RL (hereinafter referred to as solenoid-out valves 5), which are normally closed solenoid valves.

  The brake ECU 32 calculates the normal brake control according to the driver's operation based on the input signal of each sensor and the driver's brake pedal operation state, anti-skid brake control (ABS), vehicle behavior stabilization control (VDC), and inter-vehicle distance. Performs calculations to control tire slip and vehicle behavior using vehicle information such as control and obstacle avoidance control, calculates braking force (all wheels) required for the vehicle, and required braking force for each wheel Calculate the target value.

  The brake ECU 32 holds the braking force according to the driver's braking operation by stopping the vehicle on the uphill road, and increases and holds the braking force when the vehicle slides down the uphill road while holding the braking force. Slope start assist control is performed (slope start assist means). During the slope start assist control, the solenoid-in valve 4 is kept open and the solenoid-out valve 5 is kept closed as in the normal brake control.

  The ECU 32 switches the gate-out valve 3 from the open state to the closed state when performing slope start assist control. At this time, the gate-in valve 2 maintains a closed state. Thus, the wheel cylinder hydraulic pressure sent from the master cylinder M / C to each wheel cylinder W / C according to the brake operation amount of the driver is maintained.

  When the vehicle slips down during the slope start assist control, the gate-in valve 2 is switched from the closed state to the open state, and the pump P is driven. Thereby, each wheel cylinder hydraulic pressure is pressurized.

[Slope start assist control processing]
FIG. 3 is a flowchart showing the flow of the slope start assist control process executed by the brake ECU 32 of the first embodiment. Each step will be described below. This control process is repeatedly executed at a predetermined calculation cycle.

  In step S1, it is determined whether or not slope start assist control is being performed. If YES, the process proceeds to step S2, and if NO, the process proceeds to step S6.

  In step S2, a control end condition determining process for determining the end condition of the slope start assist control is executed. Details of this control end condition determination processing will be described later.

  In step S3, it is determined whether or not vehicle movement (sliding down) has occurred in the brake OFF state. If YES, the process proceeds to step S4. If NO, the process proceeds to step S5. Here, the brake OFF is determined from the signal of the brake switch BS. In addition, when the vehicle is detected to move down from the wheel speed sensor 34 in a state where the operation of the accelerator pedal AP is not detected, it is determined that the vehicle has moved.

  In step S4, the gate-in valve 2 is closed to open, the motor M is actuated, the pressure of each wheel cylinder is increased by the pump P, and thereafter the pressurization control (second holding mode) is executed, and the return Migrate to

  On the other hand, in step S5, the gate-out valve 3 is changed from open to closed, holding control (first holding mode) for holding each wheel cylinder hydraulic pressure is continued, and the process proceeds to return.

  In step S6, it is determined whether or not the driver is stepping on the brake pedal BP based on whether or not the signal of the brake switch BS is ON. If YES, the process proceeds to step S7. If NO, the process proceeds to return.

  In step S7, it is determined whether or not the vehicle is stopped based on whether or not the state in which the signal from the wheel speed sensor 34 is zero has continued for a predetermined time (Δt, for example, 0.2 seconds). If YES, the process proceeds to step S8, and if NO, the process proceeds to return.

  In step S8, it is determined based on the signal from the G sensor 33 whether the slope of the uphill road is equal to or greater than a threshold value. Here, the traveling direction of the vehicle is detected from the range position which is information from the ATCU 36, and when the traveling direction is uphill from the range position and the inclination direction of the road surface, and the road surface gradient is equal to or larger than the threshold value, the step is performed. The process proceeds to S9, otherwise the process proceeds to step S10.

  In step S9, the gate-out valve 3 is changed from open to closed, holding control (first holding mode) for holding each wheel cylinder hydraulic pressure is performed, and the process proceeds to return.

[Control end condition judgment processing]
FIG. 4 is a flowchart showing the flow of the control end condition determination process executed in step S2 of FIG. 3, and each step will be described below.

  In step S10, the driver depresses the accelerator pedal AP and determines whether or not the vehicle can start based on the accelerator pedal operation amount or the engine torque from the ENGCU 35 (accelerator operation detecting means). If YES, the process proceeds to step S11. If NO, the process proceeds to step S12.

  In step S11, when the operation current of the gate-out bell 3 is gradually decreased and the operation current becomes zero, the slope start assist control is terminated, and the process proceeds to the return of FIG.

  In step S12, it is determined whether or not a predetermined time (for example, 2 seconds) has continued since the driver's brake operation was turned off. If YES, the process proceeds to step S13. If NO, the process proceeds to step S3 in FIG.

  In step S13, it is determined whether or not the pressurization control is prohibited (the first holding mode is being executed). If YES, the process proceeds to step S11. If NO, the process proceeds to step S3 in FIG.

Next, the operation will be described.
[Slope start assisting action]
With conventional braking force control devices, when the vehicle stops on an uphill road, the brake fluid is sealed in the wheel cylinder to maintain the braking force, thereby preventing the vehicle from sliding down when the pedal is switched when starting. is doing. Further, when the vehicle slips while holding the braking force, the wheel cylinder is pressurized to increase the braking force, thereby minimizing the vehicle slipping.

  However, in the conventional braking force control device, the driver's intention to start is determined by turning off the brake switch, and the holding of the braking force is released after a predetermined time has elapsed since the brake switch is turned off. It may not be possible to accurately determine whether or not there is an operation.

  That is, after pressurization in the wheel cylinder, the driver may not be able to depress the brake pedal because the pressure between the wheel cylinder and the master cylinder is in the hydraulic circuit. At this time, since the brake switch is not turned on unless the brake pedal is depressed more than a predetermined amount, the holding of the braking force is released against the driver's braking intention.

  On the other hand, in the brake ECU 32 of the first embodiment, when the driver's accelerator operation is detected during the second holding mode in which the braking force pressurization is held when the start condition is determined in step S10, the process proceeds to step S11. Release the braking force. On the other hand, if the driver's accelerator operation is not detected, the process proceeds to step S10 → step S12 or step S10 → step S12 → step S13 to complete the start condition establishment determination, and then step S3 → step S4 or step S3 → Proceed to step S5 to continue holding the braking force.

  That is, in the first embodiment, the driver's intention to start is determined based on the accelerator operation, not the brake operation. Therefore, when the driver has the intention to start, the holding of the braking force is released, and the driver has the braking intention. The brake control according to the will of the driver can be performed by continuing the holding of the braking force.

  Further, the brake ECU 32 performs step S10 → step S12 → step when the non-detection of the brake operation continues for a predetermined time even when the start condition is not satisfied in step S10 during the execution of the first holding mode. Proceeding from S13 to step S11, the braking force holding is released.

  That is, if the first holding mode continues for a predetermined time without shifting to the second holding mode after the brake is turned off, it can be determined that the vehicle does not slide down. Therefore, in this case, by canceling the braking force holding, the braking force holding is continued unnecessarily, so that the heat generated by the braking control device can be kept small.

The brake ECU 32 gradually reduces the operating current of the gate-out valve 3 when releasing the braking force holding in step S11.
For example, if the operating current of the gate-out valve 3 is set to zero at a time when releasing the braking force holding, a sufficient starting torque does not rise immediately after the accelerator pedal AP starts to be depressed. May occur. This phenomenon is a particularly significant problem in an idle stop vehicle that stops the engine while the vehicle is stopped.

  On the other hand, in the first embodiment, when releasing the braking force hold, the wheel cylinder hydraulic pressure is gradually released, so that the vehicle can be prevented from slipping down due to the start-up torque rising delay.

[Slope start assist control action]
FIG. 5 is a time chart showing the slope start assist control operation of the first embodiment.
At time t1, the driver depresses the brake pedal BP while traveling on the uphill road and starts braking. At this time, the brake switch BS changes from OFF to ON. In the section between time points t1 and t2, the wheel speed decreases as the amount of depression of the brake pedal BP of the driver increases, and at time point t2, the wheel speed becomes zero.

At the time point t3, since the state of zero wheel speed continues for a predetermined time (Δt, for example, 0.2 seconds), it is determined that the vehicle is stopped, and the conditions for implementing the slope start assist control are satisfied. At this time, in the flowchart of FIG. 3, the process proceeds from step S1, step S6, step S7, step S8, and step S9. In step S9, the gate-out valve 3 of the HU 31 is opened and closed to start holding control. Here, the operation current of the gate-out valve 3 is a minimum current value that can maintain the closed state.
In the section between time points t3 and t4, the flow of going from step S1, step S2, step S3, and step S5 is repeated, and the braking force holding is continued.

  At time t4, the driver's brake operation is turned OFF during the slope start assist control, and at time t5, since the vehicle has been detected to fall without starting operation (accelerator pedal operation amount is zero), step S1 → The flow proceeds from step S2 to step S3 to step S4. In step S4, the gate-in valve 2 is closed to open, and the pump P is driven to perform pressurization control. At this time, the operation current of the gate-out valve 3 is increased so that the closed state of the gate-out valve 3 is reliably maintained. In the section between time points t4 and t5, since the vehicle continues to slide down, pressurization control is continued.

  At time t6, since the vehicle has stopped (wheel speed = 0), the flow is switched again to step S1, step S2, step S3, step S5, the pump P is stopped, and the gate-in valve 2 is opened to closed. Switch from pressure control to holding control.

  At time t7, the driver depresses the accelerator pedal AP, the amount of accelerator pedal operation increases, and the vehicle can start.Therefore, in the control end condition determination process of step S2, the process proceeds from step S10 to step S11, and the gate The operating current of the out valve 3 is gradually decreased. At time t8, since the operating current of the gate-out valve 3 becomes zero, the slope start assist control is terminated.

  As described above, the braking force control apparatus according to the first embodiment has the effects listed below.

  (1) Holding the braking force according to the braking operation by stopping the vehicle on the uphill road, and holding the braking force under pressure to increase and hold the braking force when the vehicle slips while holding this braking force In the braking force control apparatus including the ECU 32 that performs the above, the brake ECU 32 releases the holding of the braking force when the driver's accelerator operation is detected while the braking force is being pressed and held. Thereby, the braking control according to the driver's braking or starting intention can be realized.

  (2) Brake operation detection means (brake switch BS) that detects the driver's brake operation is provided, and the brake ECU 32 responds to the amount of brake operation when the driver's brake operation is detected when the vehicle stops on an uphill road. In the first holding mode for holding the braking force, and when the brake operation is not detected while the braking force is being held and the vehicle is detected to fall, the braking force that is held until the vehicle stops is increased. And a second holding mode for performing power pressurization holding. As a result, the vehicle can be prevented from sliding down when the vehicle is started on the uphill road.

  (3) The brake ECU 32 releases the braking force holding when the non-detection of the brake operation continues for a predetermined time during the first holding mode. Thereby, it is possible to suppress unnecessary holding of the braking force, and it is possible to reduce heat generated by the braking control device and improve durability.

  (4) Since the brake operation detection means is the brake switch BS attached to the brake pedal BP, the brake of the driver can be constructed with a cheaper configuration compared to the case where other brake operation detection means such as a master cylinder pressure sensor are provided. An operation can be detected.

  (5) A normally open gate-out valve 3 is provided on the pipeline 13 between the master cylinder M / C and the wheel cylinder W / C, and the brake ECU 32 operates the gate-out valve 3 when releasing the braking force holding. Gradually reduce the current. As a result, the vehicle can be prevented from slipping down due to the start-up torque delay.

(Other examples)
The best mode for carrying out the present invention has been described based on the first embodiment. However, the specific configuration of the present invention is not limited to the configuration shown in the first embodiment. Design changes and the like within a range that does not depart from the gist are also included in the present invention.

  For example, in the first embodiment, an example in which the hydraulic unit 31 capable of executing anti-skid brake control (ABS), vehicle behavior stabilization control (VDC), etc. is used as the hydraulic unit is shown. If the pressure increase / decrease is possible, the configuration of the hydraulic unit is arbitrary.

  In the first embodiment, the hydraulic pressure of the four wheels is controlled by one hydraulic unit 31. However, even if the hydraulic units 31 are provided separately on the front wheel side and the rear wheel side, The same control as in the first embodiment can be executed in the unit.

1 is a system configuration diagram of a braking force control apparatus according to Embodiment 1. FIG. 1 is a hydraulic circuit diagram of a hydraulic unit 31 according to a first embodiment. 6 is a flowchart illustrating a flow of a slope start assist control process executed by the brake ECU 32 according to the first embodiment. It is a flowchart which shows the flow of the control end condition judgment process performed by step S2 of FIG. 3 is a time chart illustrating a slope start assist control operation according to the first embodiment.

Explanation of symbols

AP accelerator pedal
BS brake switch
BP brake pedal
M / C master cylinder
P pump
M motor
W / C Wheel cylinder 2 Gate in valve 3 Gate out valve 4 Solenoid in valve 5 Solenoid out valve 31 Hydraulic unit 32 Brake controller 33 Acceleration sensor 34 Wheel speed sensor 35 Engine controller 36 Automatic transmission controller 37 Engine 38 Automatic transmission

Claims (5)

Slope start assistance that holds the braking force according to the braking operation by stopping the vehicle on the uphill road and holds the braking force pressurization to increase the holding force when the vehicle slips down while holding this braking force In the braking force control device comprising means,
Accelerator operation detection means for detecting the driver's accelerator operation,
The braking force control device according to claim 1, wherein the slope start assisting means releases the braking force holding when the driver's accelerator operation is detected while the braking force is being pressed and held. In the braking force control device according to claim 1,
Brake operation detection means for detecting the driver's brake operation,
The slope start assistance means is:
A first holding mode for holding a braking force in accordance with the amount of brake operation when a driver's brake operation is detected when the vehicle stops on an uphill road;
A second holding mode for holding a braking force pressurizing and holding to increase a braking force to be held until the vehicle stops when a braking operation is not detected while the braking force is being held and a vehicle slippage is detected;
A braking force control device comprising: The braking force control apparatus according to claim 2,
The braking force control device according to claim 1, wherein the slope start assisting unit releases the braking force holding when the non-detection of the brake operation is continued for a predetermined time during the first holding mode. The braking force control apparatus according to claim 2 or 3,
The braking force control device according to claim 1, wherein the brake operation detecting means is a brake switch attached to a brake pedal. In the braking force control device according to any one of claims 1 to 4,
A normally open solenoid valve is provided on the brake line that connects the master cylinder and the wheel cylinder.
The braking force control device, wherein the slope start assisting means gradually reduces the operation current of the solenoid valve when releasing the braking force holding.

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