JP2016068871A - Control device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device for a vehicle which can shorten a slip-down distance at an on-slope start of a vehicle.SOLUTION: After the release of a brake operation in a state that a vehicle is stopped (YES in step S1), a brake force acting on the vehicle is held (step S2). When a vehicle speed of the vehicle exceeds a vehicle speed threshold after the release of the brake operation (YES in step S7), the holding of the brake force is finished, and the brake force acting on the vehicle is reduced. The vehicle speed threshold for use in the determination of the finish of the continuation/finish of the holding of the brake force is set on the basis of the brake force acting on the vehicle and gradient resistance.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a control device applied to a vehicle equipped with a hill hold control function.

  Some vehicles such as automobiles are equipped with a so-called hill hold control (hill start control) function.

  In a vehicle equipped with a hill hold control function, the braking force is maintained even when the driver's foot is released from the brake pedal in order to prevent the vehicle from falling down (retreating) when starting on a hill. Thereafter, when the vehicle speed increases to a constant speed, the holding of the braking force is terminated.

JP 2011-149279 A

  However, the braking force is also released when the vehicle slips and the vehicle speed (minus vehicle speed) increases to a constant speed. In this case, there is a possibility that the sliding distance of the vehicle increases.

  An object of the present invention is to provide a vehicle control device that can reduce a sliding distance.

  In order to achieve the above object, a vehicle control apparatus according to the present invention includes a brake holding unit that holds a braking force acting on a vehicle after release of a brake operation in a state where the vehicle is stopped, and a brake holding unit. If the vehicle speed of the vehicle exceeds the vehicle speed threshold while holding the braking force by the vehicle, vehicle speed condition ending means for ending the holding of the braking force by the brake holding means, and a braking force acquisition means for acquiring the braking force acting on the vehicle, A gradient resistance acquisition unit that acquires gradient resistance acting on the vehicle, and a vehicle speed threshold setting unit that sets a vehicle speed threshold based on the braking force acquired by the brake force acquisition unit and the gradient resistance acquired by the gradient resistance acquisition unit Including.

  According to this configuration, the braking force acting on the vehicle is maintained even after the brake operation is released with the vehicle stopped. Therefore, even if the road surface on which the vehicle is located is an uphill slope, it is possible to suppress the vehicle from sliding down after the brake operation is released until the accelerator operation is performed.

  If the vehicle speed of the vehicle exceeds the vehicle speed threshold after the brake operation is released, the holding of the braking force is terminated and the braking force acting on the vehicle is reduced. As a result, brake drag can be reduced, and the fuel efficiency of the vehicle can be improved.

  The vehicle speed threshold value used for determining whether to continue / end the holding of the braking force is set based on the braking force and the gradient resistance that act on the vehicle. For example, if the value obtained by subtracting the braking force from the gradient resistance is equal to or less than a certain value, the vehicle speed threshold is set to the standard value because the possibility of the vehicle sliding down is low. On the other hand, when the value obtained by subtracting the braking force from the gradient resistance is larger than a certain value, the vehicle is likely to slip down, so the vehicle speed threshold is set to a value larger than the standard value. Thereby, even if the vehicle slips, the vehicle speed can be suppressed from exceeding the vehicle speed threshold. As a result, when the vehicle slides down, it is possible to suppress the holding of the braking force from being finished, and the slipping distance can be reduced as compared with the conventional case.

  The vehicle control device includes a driving force acquisition unit that acquires a driving force input to a wheel from a vehicle engine, and a driving force acquired by the driving force acquisition unit while the braking force is being held by the brake holding unit. When the gradient resistance acquired by the acquisition unit is exceeded, a driving force condition ending unit for ending the holding of the braking force by the brake holding unit may be further provided.

  If the driving force input to the wheels from the engine of the vehicle exceeds the gradient resistance acting on the vehicle, the possibility that the vehicle will subsequently slip down is extremely low. Therefore, in that case, it is preferable that the holding of the braking force is terminated and the braking force is reduced. As a result, brake drag can be reduced, and the fuel efficiency of the vehicle can be improved.

  In the configuration further including the driving force acquisition unit and the driving force condition end unit, when the effect is viewed from another viewpoint, the vehicle speed threshold is set to a value larger than the standard value when the vehicle slips. Therefore, before the vehicle speed exceeds the vehicle speed threshold, the driving force input from the engine of the vehicle to the wheels is made larger than the gradient resistance that acts on the vehicle. Thus, the holding of the braking force can be terminated. As a result, it is possible to reduce the drag of the brake while reducing the sliding distance.

  According to the present invention, it is possible to suppress the vehicle speed from exceeding the vehicle speed threshold value by setting the vehicle speed threshold value to a value larger than a standard value when the vehicle slips. Before the vehicle speed exceeds the vehicle speed threshold, the driving force of the engine can be made larger than the gradient resistance by the accelerator operation, and the holding of the braking force can be ended. Thereby, the drag of the brake can be reduced while the sliding distance can be reduced, and as a result, the fuel consumption of the vehicle can be improved.

It is a block diagram which shows the structure of the principal part of the vehicle by which the vehicle control apparatus which concerns on one Embodiment of this invention is mounted. It is a flowchart which shows the flow of hill hold control. It is a map which shows an example of the relationship between sliding force and a vehicle threshold value. Brake pedal operation (on) / operation release (off), accelerator pedal operation (on) / operation release (off), vehicle speed, driving force input to the wheels from the engine, and braking force applied to the wheels It is a graph which shows an example of change.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a block diagram illustrating a configuration of a main part of a vehicle 1 on which a vehicle control device according to an embodiment of the present invention is mounted.

  The vehicle 1 is an automobile that uses the engine 2 as a drive source.

  The output of the engine 2 is transmitted to drive wheels (for example, left and right front wheels) of the vehicle 1 via a torque converter 3 and a continuously variable transmission (CVT) 4.

  A starter 5 is provided along with the engine 2. The stopped engine 2 starts after cranking by the starter 5.

  An alternator 6 is provided in association with the engine 2.

  The rotation of the output shaft of the engine 2 is transmitted to the rotation shaft (rotor) of the alternator 6. When the rotating shaft of the alternator 6 rotates, the rotation is converted into electric power, and electric power is output from the alternator 6.

  Each wheel of the vehicle 1 (for example, left and right front wheels and rear wheels) is provided with a brake 7. A brake pedal 8 that is operated by a driver's foot is provided in the vehicle interior of the vehicle 1. The brake pedal 8 is connected to a brake booster 10 provided integrally with the master cylinder 9.

  When the brake pedal 8 is depressed, the pedal force input to the brake pedal 8 is transmitted to the brake booster 10. The pedaling force transmitted to the brake booster 10 is amplified (boosted) by the negative pressure of the brake booster 10 and input from the brake booster 10 to the master cylinder 9. In the master cylinder 9, a hydraulic pressure corresponding to the force input from the brake booster 10 is generated.

  The hydraulic pressure in the master cylinder 9 is transmitted to the brake actuator 11. The brake actuator 11 incorporates a valve for controlling the hydraulic pressure of the wheel cylinder provided in the brake 7 of each wheel, a pump for returning the brake fluid to the master cylinder 9, and the like. The hydraulic pressure transmitted from the master cylinder 9 to the brake actuator 11 is distributed and transmitted to the wheel cylinder of each brake 7. A brake force (braking force) is applied from the brake 7 to the wheel by the hydraulic pressure of the wheel cylinder.

  Further, a hydraulic pressure control valve 12 for transmitting the hydraulic pressure to the brake actuator 11 is provided in a system different from the hydraulic pressure of the master cylinder 9. When the hydraulic pressure control valve 12 is opened, the hydraulic pressure is transmitted to the brake actuator 11, and the hydraulic pressure is distributed from the brake actuator 11 to the wheel cylinders of the brakes 7, so that the braking force is automatically applied from the brake 7 to the wheels. Is granted.

  The vehicle 1 is further provided with a battery 13.

  The battery 13 is charged with electric power output from the alternator 6. A starter 5 and the like are electrically connected to the battery 13. Drive power is supplied from the battery 13 to the starter 5. A relay 14 is interposed on the power supply path from the battery 13 to the starter 5.

  The vehicle 1 is also provided with a plurality of ECUs (electronic control units) having a configuration including a CPU and a memory (ROM, RAM, etc.). The ECU includes an engine ECU 21, a CVT (Continuously Variable Transmission) ECU 22, a brake ECU 23, and an idling stop ECU 24. The engine ECU 21, the CVTECU 22, the brake ECU 23, and the idling stop ECU 24 can communicate with each other by a CAN (Controller Area Network) communication protocol.

  The engine 2 is connected to the engine ECU 21 as a control target.

  The CVT ECU 22 is connected to the continuously variable transmission 4 as a control target.

  A brake actuator 11 and a hydraulic pressure control valve 12 are connected to the brake ECU 23 as control targets. A vehicle speed sensor 25, a G sensor (acceleration sensor) 26, and a brake fluid pressure sensor 27 are connected to the brake ECU 23.

  The vehicle speed sensor 25 includes, for example, a rotor made of a magnetic body that rotates as the vehicle 1 travels, and an electromagnetic pickup provided in non-contact with the rotor. Each time the rotor rotates by a certain angle, a pulse signal is output from the electromagnetic pickup, and the pulse signal is input to the brake ECU 23. Since the frequency of the pulse signal corresponds to the vehicle speed, the brake ECU 23 can obtain the frequency of the pulse signal input from the vehicle speed sensor 25 by converting it to the vehicle speed.

  As the G sensor 26, a sensor that outputs a signal corresponding to the displacement of the weight as a detection signal corresponding to the acceleration of the vehicle is employed. When the vehicle speed of the vehicle 1 and / or the gradient of the road surface change, the weight is displaced, and a signal corresponding to the displacement is output from the G sensor 26. The brake ECU 23 acquires the acceleration of the vehicle 1 from the detection signal of the G sensor 26.

  The brake fluid pressure sensor 27 outputs a detection signal corresponding to the fluid pressure (brake fluid pressure) of the master cylinder 9. The brake ECU 23 acquires the hydraulic pressure of the master cylinder 9 from the detection signal of the brake hydraulic pressure sensor 27.

  The relay 14 is connected to the idling stop ECU 24 as a control target.

  The vehicle 1 is equipped with an idling stop (idle stop) function. The idling stop ECU 24 executes idling stop control that is control for the idling stop function. As information necessary for the idling stop control, information such as the number of revolutions of the engine 2 is input from the engine ECU 21 to the idling stop ECU 24, and the vehicle speed and the hydraulic pressure of the master cylinder 9 are input from the brake ECU 23.

  In the idling stop control, when the brake pedal 8 is operated (depressed) while the vehicle 1 is traveling, the idling stop ECU 24 repeatedly determines whether or not a predetermined automatic stop condition is satisfied. The automatic stop condition is, for example, a condition that the vehicle speed is a predetermined vehicle speed (for example, 10 km / h) or less and the brake pedal 8 is operated for a certain time or more. When the automatic stop condition is satisfied, an engine stop request is output from the idling stop ECU 24 to the engine ECU 21, and the engine 2 is automatically stopped (idling stop) by the engine ECU 21.

  While the engine 2 is automatically stopped by the idling stop control, it is repeatedly determined whether or not a predetermined restart condition is satisfied. The restart condition is, for example, a condition that the operation of the brake pedal 8 is released (the driver's foot is released from the brake pedal 8) while the engine 2 is automatically stopped. When the restart condition is satisfied, the relay 14 is turned on by the idling stop ECU 24. When the relay 14 is turned on, the engine 2 is started through cranking by the starter 5.

  Whether the brake pedal 8 is operated or released is determined based on, for example, the hydraulic pressure of the master cylinder 9. That is, if the hydraulic pressure of the master cylinder 9 is equal to or higher than the predetermined pressure, it is determined that the brake pedal 8 is operated. If the hydraulic pressure of the master cylinder 9 is lower than the predetermined pressure, the operation of the brake pedal 8 is released. It is determined that

  FIG. 2 is a flowchart showing the flow of hill hold control.

  The vehicle 1 has a hill hold control function. The brake ECU 23 repeatedly executes hill hold control, which is control for the hill hold control function, while the vehicle 1 is stopped with the brake pedal 8 being operated.

  In the hill hold control, as shown in FIG. 2, the brake ECU 23 first determines whether or not the operation of the brake pedal 8 has been released (step S1).

  When the operation of the brake pedal 8 is not released (NO in step S1), that is, when the brake pedal 8 is operated, the subsequent processing is not performed and the hill hold control is ended. Then, after the hill hold control is completed, the hill hold control is started again.

  When the operation of the brake pedal 8 is released while the vehicle 1 is stopped (YES in step S1), the brake ECU 23 controls the hydraulic pressure control valve 12 to apply a braking force from the brake 7 to the wheel. Thus, the braking force is maintained (step S2). For example, the hydraulic pressure control valve 12 is controlled so that the hydraulic pressure of the master cylinder 9 during operation of the brake pedal 8 is maintained as it is so that the braking force does not change before and after the brake pedal 8 is released.

  When the operation of the brake pedal 8 is released, the brake ECU 23 starts measuring (timekeeping) the elapsed time from the release of the operation (step S3).

  Further, the brake ECU 23 sets a vehicle speed threshold for determining whether to continue or end the holding of the braking force (step S4). The setting of the vehicle speed threshold will be described later.

  Thereafter, the brake ECU 23 determines whether or not the elapsed time from the release of the operation of the brake pedal 8 has reached a certain time (step S5).

  When the elapsed time from the release of the operation of the brake pedal 8 is less than a certain time (NO in step S5), the driving force input to the wheels from the engine 2 by the brake ECU 23 (hereinafter simply referred to as “driving force”). Is greater than the gradient resistance acting on the vehicle 1 (step S6). For this determination, the driving force and the gradient resistance are acquired by the brake ECU 23.

  The driving force is obtained, for example, by obtaining information about the rotational speed of the engine 2 from the engine ECU 21 and calculating the rotational speed of the engine 2 as a parameter. Specifically, the driving force is obtained by multiplying the square value of the rotational speed of the engine 2 by the capacity coefficient of the torque converter 3, the torque ratio of the torque converter 3, and the reduction ratio of the continuously variable transmission 4, and the multiplication value is It is obtained by dividing by the radius of the wheel.

  The gradient resistance is a component in a direction parallel to the road surface (gradient) of gravity acting on the vehicle 1. The gradient resistance is obtained by multiplying the weight of the vehicle 1 by gravitational acceleration and gradient (Sinθ, where the gradient angle is θ).

  The acceleration acquired from the detection signal of the G sensor 26 includes an acceleration component due to a change in the vehicle speed and an acceleration component due to a road surface gradient. On the other hand, the acceleration obtained by differentiating the vehicle speed acquired from the output signal of the vehicle speed sensor 25 is only the acceleration component due to the change in the vehicle speed. Accordingly, by obtaining the difference between the acceleration acquired from the detection signal of the G sensor 26 and the differential value of the vehicle speed, an acceleration component due to the road surface gradient is obtained, and therefore the gradient is estimated based on the acceleration component.

  If the driving force is equal to or less than the gradient resistance (NO in step S6), the brake ECU 23 then determines whether or not the vehicle speed is greater than the vehicle speed threshold (step S7).

  If the driving force is equal to or less than the gradient resistance and the vehicle speed is equal to or less than the vehicle speed threshold value (NO in step S7), whether or not the elapsed time from the release of the operation of the brake pedal 8 has reached a certain time by the brake ECU 23. It is determined again (step S5).

  If the driving force does not exceed the gradient resistance and the vehicle speed does not exceed the vehicle speed threshold and the elapsed time from the release of the operation of the brake pedal 8 has reached a certain time (YES in step S5), the brake ECU 23 determines that a timeout has occurred. Then, the end of the holding of the braking force is determined (step S8). In response to this determination, the brake ECU 23 controls the hydraulic pressure control valve 12 to reduce the braking force applied from the brake 7 to the wheel to zero. Further, when it is determined that the holding of the braking force is finished, the hill hold control is finished.

  Even when the driving force exceeds the gradient resistance until the elapsed time from the release of the operation of the brake pedal 8 reaches a certain time (YES in step S6), the brake ECU 23 determines the end of the holding of the braking force. (Step S8).

  Even when the vehicle speed exceeds the vehicle speed threshold before the elapsed time from the release of the operation of the brake pedal 8 reaches a certain time (YES in step S7), the brake ECU 23 determines the end of holding of the braking force. (Step S8).

  FIG. 3 is a map showing an example of the relationship between the sliding force and the vehicle threshold.

  The sliding force is a value obtained by subtracting the braking force from the gradient resistance acting on the vehicle 1. In the example of the map shown in FIG. 3, a standard value (for example, a predetermined value within a range of 0 to 2 km / h.) For a downward force below a certain value. The value 0 is included.). For a sliding force exceeding a certain value, the vehicle threshold is set to be larger than the standard value in proportion to the sliding force.

  In order to set the vehicle threshold value, the gradient resistance and the braking force acting on the vehicle 1 are acquired. The gradient resistance is obtained by the method described above. The relationship between the hydraulic pressure of the master cylinder 9 and the braking force is stored in the memory, and the relationship is referred to, and the braking force corresponding to the hydraulic pressure of the master cylinder 9 is acquired. Then, the braking force is obtained by subtracting the braking force from the gradient resistance, and the vehicle threshold corresponding to the sliding force is set by referring to the map shown in FIG.

  As described above, the braking force acting on the vehicle 1 is maintained even after the brake operation is released in a state where the vehicle 1 is stopped. Therefore, even if the road surface on which the vehicle 1 is located is an ascending slope, the vehicle 1 can be prevented from sliding down from the release of the brake operation until the accelerator operation is performed.

  When the vehicle speed of the vehicle 1 exceeds the vehicle speed threshold after the release of the brake operation, the holding of the braking force is terminated and the braking force acting on the vehicle 1 is reduced. As a result, brake drag can be reduced, and the fuel efficiency of the vehicle 1 can be improved.

  The vehicle speed threshold value used for determining whether to continue / end the holding of the braking force is set based on the braking force acting on the vehicle 1 and the gradient resistance. Specifically, when the sliding force obtained by subtracting the braking force from the gradient resistance is equal to or less than a certain value, the vehicle 1 is unlikely to slip down, so the vehicle speed threshold is set to the standard value. . On the other hand, when the value obtained by subtracting the braking force from the gradient resistance is larger than a certain value, the vehicle 1 is likely to slip down, so the vehicle speed threshold is set to a value larger than the standard value.

  Thereby, as shown in FIG. 4, even when the vehicle 1 slips, the vehicle speed can be suppressed from reaching the vehicle speed threshold. As a result, when the vehicle 1 slips, the holding of the braking force can be prevented from being finished, and the slip distance can be reduced as compared with the conventional case.

  Further, when the driving force exceeds the gradient resistance, the possibility that the vehicle 1 will subsequently slide down is extremely low. Therefore, in that case, as shown in FIG. 4, the holding of the braking force is terminated and the braking force is reduced. As a result, brake drag can be reduced, and the fuel efficiency of the vehicle 1 can be improved.

  In FIG. 4, time changes in vehicle speed and braking force during the above-described hill hold control are indicated by solid lines, and time changes in vehicle speed and brake force during conventional hill hold control are indicated by broken lines.

  From a different point of view, the above-described effects can be prevented from reaching the vehicle speed threshold by setting the vehicle speed threshold to a value larger than the standard value when the vehicle 1 is slipping down. However, before the vehicle speed reaches the vehicle speed threshold value, the driving force can be made larger than the gradient resistance by the accelerator operation, and the holding of the braking force can be ended. Thereby, the drag of the brake can be reduced while the sliding distance can be reduced, and as a result, the fuel consumption of the vehicle can be improved.

  As mentioned above, although one Embodiment of this invention was described, this invention can also be implemented with another form.

  For example, in the example of the map shown in FIG. 3, the vehicle threshold value is set to be larger than the standard value in proportion to the sliding force for a sliding force exceeding a certain value. However, the present invention is not limited to this, and the vehicle threshold value may be set to a fixed value larger than the standard value for a sliding force exceeding a certain value. Further, the vehicle threshold value may be set to increase stepwise from the standard value as the sliding force increases with respect to the sliding force exceeding a certain value.

  In addition, various design changes can be made to the above-described configuration within the scope of the matters described in the claims.

DESCRIPTION OF SYMBOLS 1 Vehicle 2 Engine 7 Brake 23 Brake ECU (Vehicle control device, brake holding means, vehicle speed condition end means, brake force acquisition means, gradient resistance acquisition means, vehicle speed threshold setting means, driving force acquisition means, driving force condition end means)

Claims (2)

A brake holding means for holding a braking force acting on the vehicle after releasing the brake operation in a state where the vehicle is stopped;
Vehicle speed condition ending means for ending the holding of the braking force by the brake holding means when the vehicle speed of the vehicle exceeds a vehicle speed threshold while holding the braking force by the brake holding means;
Braking force acquisition means for acquiring braking force acting on the vehicle;
Gradient resistance acquisition means for acquiring gradient resistance acting on the vehicle;
And a vehicle speed threshold setting unit configured to set the vehicle speed threshold based on the braking force acquired by the braking force acquisition unit and the gradient resistance acquired by the gradient resistance acquisition unit. Driving force acquisition means for acquiring driving force input to wheels from the engine of the vehicle;
If the driving force acquired by the driving force acquisition unit exceeds the gradient resistance acquired by the gradient resistance acquisition unit while the braking force is being held by the brake holding unit, the braking force is not held by the brake holding unit. The vehicle control device according to claim 1, further comprising driving force condition ending means for ending.

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