JP2013060197A - Travel control device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid degradation of steering stability felt by a driver when starting after stopping on a gradient travel road.SOLUTION: A travel control device includes a braking force control means (21), a stop holding control means (11) for holding the vehicle in a stopped state through the braking force control means, a driving force control means (23), a start operation detection means (13) for detecting start operation by an occupant, a means (17) for acquiring the gradient of the travel road, and a start control means (13). The start control means, upon detection of start operation while the vehicle is held in the stopped state by the stop holding control means, calculates target drive force for preventing movement of the vehicle by balancing force toward a downward direction of the travel road and the driving force, maintains a driving state by the target drive force until the release of the braking force is completed, and increases the driving force according to the release of the braking force to start the vehicle.

Description

  The present invention relates to an apparatus for controlling traveling of a vehicle.

  The following Patent Document 1 discloses an apparatus for controlling creep running of a vehicle. According to this apparatus, the means for detecting the operation of the brake executes creep control for creeping the vehicle at a predetermined target vehicle speed when detecting the non-operation of the brake. In the creep control, the intake air amount for creep travel is feedforward controlled to the intake air amount control means in accordance with the detected road surface gradient.

Japanese Patent No. 3853447

  However, even if the driving force for creep travel is applied to the vehicle after the brake has been inactivated, at the moment when the brake is inactivated, the traveling direction of the vehicle is Acceleration may occur in the opposite direction. Such acceleration in the reverse direction may impair the driver's feeling (steering stability).

  Accordingly, an object of the present invention is to provide a travel control capable of avoiding the above-described deterioration in feeling when stopping and starting on a traveling road having a gradient.

  The present invention includes a braking force control unit that controls a braking force of a vehicle, a stop holding control unit that holds the vehicle in a stopped state via the braking force control unit, and a driving force control that controls the driving force of the vehicle. A travel control device comprising: means; a start operation detecting means for detecting a start operation of the occupant with respect to the vehicle; and a means for acquiring a gradient of a travel path of the vehicle. The travel control means further has the acquired gradient when the start operation detecting means detects the start operation while the vehicle is held in the stop state by the stop hold control means. And calculating a target driving force for suppressing the movement of the vehicle on the traveling road by balancing the driving force toward the downward direction of the traveling road and the driving force control means. After the vehicle is driven by the target driving force, the braking force is released so as to release the holding state of the vehicle via the braking force control means, and according to the release of the braking force, A start control means is provided for starting the vehicle by increasing the drive force via the drive force control means. The start control means maintains the state in which the vehicle is driven by the target driving force via the driving force control means until the release of the braking force via the braking force control means is completed.

  According to the present invention, when the vehicle is driven by the target driving force that suppresses the movement of the vehicle on the traveling road, the stop state of the vehicle is held by the driving force that balances the gradient, and the stop state is maintained by the braking force. Is not retained. Therefore, even if the braking force is released while the vehicle is driven with the target driving force, the vehicle does not move in the direction opposite to the traveling direction. For this reason, the vehicle can be started smoothly, and the driver's feeling can be prevented from being impaired. Further, since the vehicle is maintained by the target driving force until the braking force is completely released, it is possible to avoid making the driver feel a drag feeling while the braking force is released. .

The block diagram of the traveling control apparatus according to one Example of this invention. The figure for demonstrating the form which advances and starts and the outline | summary of the conventional start control. The figure for demonstrating the outline | summary of start control according to one Example of this invention. The figure which shows the form which reverses and starts. The flowchart of the start control process according to one Example of this invention. The figure which shows the target drive force according to the gradient according to one Example of this invention. The flowchart of the process which calculates the target driving force according to one Example of this invention. The figure which shows performing start control irrespective of the operation amount of an accelerator pedal according to one Example of this invention.

  Next, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing a configuration of a travel control device 10 for controlling travel of a vehicle, which is mounted on the vehicle, according to one embodiment of the present invention. The travel control device 10 can be realized by an electronic control unit (ECU) which is a computer including a central processing unit (CPU) and a memory, and each functional block shown in the figure is realized by the CPU.

  The travel control device 10 includes a stop and hold control unit 11, a start control unit 13, and a travel control unit 15, and also includes a braking force control unit 21 and a driving force control unit 23.

  The stop holding control unit 11 gives an instruction to the braking force control unit 21 so as to hold the stop state of the vehicle. Connected to the braking force control unit 21 is an actuator that controls a mechanical element that applies a braking force to the vehicle (hereinafter referred to as a braking actuator, not shown). The braking force control unit 21 controls the braking actuator so as to hold the stop state of the vehicle in response to an instruction from the stop holding control unit 11. Here, the mechanical element that applies the braking force to the vehicle may be any known element, such as a hydraulic brake device or an electric parking brake.

  If the start control unit 13 detects a start operation of the vehicle performed by the driver while the stop holding control unit 11 holds the stop state of the vehicle, the start holding unit 11 stops the vehicle. In order to release the holding of the vehicle, an instruction is issued to the braking force control unit 21 to release the braking force, and an instruction is issued to the driving force control unit 23 to output a driving force for starting the vehicle. In response to an instruction from the start control unit 13, the braking force control unit 21 controls the braking actuator to release the braking force that has been applied to hold the vehicle in a stopped state.

  The driving force control unit 23 is connected to an actuator (hereinafter referred to as a driving actuator, not shown) that controls a mechanical element that applies a driving force to the vehicle. The driving force control unit 23 controls the driving actuator so as to drive the vehicle in response to an instruction from the start control unit 13. Here, the mechanical element that applies the driving force to the vehicle may be any known element, and may be, for example, a throttle valve or an intake valve that controls the amount of intake air to the engine. The intake air amount can be controlled by adjusting the opening degree of the throttle valve and by adjusting the lift amount of the intake valve. In the case of a vehicle that is driven not only by an engine but also by using a motor, such as a hybrid vehicle, the mechanical element may be the motor. The driving force can be controlled through the control of the motor.

  The travel control unit 15 controls the travel of the vehicle after the start control by the start control unit 13 is completed. Via the braking force control unit 21 and the driving force control unit 23, it is possible to realize constant speed travel, acceleration travel, deceleration travel, and the like of the vehicle.

  In addition, the start operation by the driver may be any appropriate one, for example, an operation on a start switch provided in advance in the vehicle, or an operation in which an accelerator pedal is depressed.

  Regarding the functions of the stop holding control unit 11, the start control unit 13, and the travel control unit 15 described above, the follow-up control in a relatively low vehicle speed range that can stop and start the own vehicle following the preceding vehicle. You may utilize the function of the apparatus which implement | achieves (LSF: Low Speed Following). In this follow-up control, the preceding vehicle is detected by, for example, a radar device, and if the preceding vehicle stops, the own vehicle is stopped and the stopped state is maintained. According to the driver's operation on the start switch, for example, The holding of the stop state is canceled and the vehicle is started, and the vehicle is driven so as to follow the preceding vehicle. Devices for realizing such follow-up control are described in, for example, Japanese Patent Application Laid-Open Nos. 2006-56398, 2006-69420, and 2006-151369.

  Returning to FIG. 1, the traveling control apparatus 10 according to this embodiment of the present invention further includes a gradient acquisition unit 17. The gradient acquisition unit 17 acquires the gradient of the travel path on which the vehicle is traveling. The gradient can be obtained by any suitable technique. In one embodiment, the vehicle is provided with a sensor for detecting the inclination of the road surface (pitch angle of the vehicle), and the gradient acquisition unit 17 acquires the gradient of the road from the detection value of the sensor. In another embodiment, a front-rear G sensor that detects acceleration in the front-rear direction of the vehicle is mounted on the vehicle, and the gradient acquisition unit 17 estimates the inclination of the travel path based on the detection value of the front-rear G sensor. May be. Such an estimation method is described in, for example, Japanese Patent Application Laid-Open No. 2002-162225. In still another embodiment, the gradient acquisition unit 17 can estimate the inclination (gradient) of the travel path based on the output torque, the braking force of the brake, and the like. No. 108589, Japanese Patent Application Laid-Open No. 2007-283882, and the like.

  The start control unit 13 performs the start control as described above. Furthermore, the start control according to the present invention uses the gradient acquired by the gradient acquisition unit 17 to maintain a stop state on a traveling road with a gradient. The vehicle is configured to achieve a smoother start. Here, with reference to FIG. 2 and FIG. 3, the basic concept of the start control of the present invention will be described.

  FIG. 2A shows a state in which the vehicle is stopped on a traveling road having a predetermined slope, and the vehicle is going to start in the upward direction as indicated by an arrow from the stopped state. As indicated by “rear” and “front”, the start is made in the forward direction of the vehicle. It is assumed that the gradient shown in (a) has such a magnitude that the vehicle stop state cannot be maintained only by a predetermined creep force acting on the vehicle.

  FIG. 2B shows a vehicle speed, a braking force (shown by a broken line), and a driving force (shown by a solid line) that can occur when the conventional start control is performed from the state shown in FIG. ) Is shown. The vehicle speed takes a positive value when the vehicle travels in the traveling direction as indicated by an arrow in (a), and takes a negative value when traveling in the direction opposite to the traveling direction.

  In (b), the stop state of the vehicle is maintained by the braking force between times t0 and t1. The driving force is maintained at a low predetermined value (creep force). A dotted line 111 indicates the value of the driving force necessary to balance the gradient. In other words, in order to maintain the vehicle stop-holding state on a traveling road with a gradient, it is necessary to apply a force that counteracts the gravity acting on the vehicle to the vehicle. A dotted line 111 is a line that represents the magnitude of the driving force necessary to maintain the vehicle in the stop-holding state on the traveling road having the gradient when the braking force is not applied.

  At the time t1, the start control is started in response to the start operation performed by the occupant. According to this start control, when the braking force is released and the braking force is completely released (at zero) at time t2, the driving force starts to increase. When the driving force reaches a value balanced with the gradient indicated by the dotted line 111, the vehicle starts in the traveling direction.

  When this type of start control is performed, acceleration is temporarily generated in the direction opposite to the traveling direction, as indicated by reference numeral 101, so that the vehicle temporarily moves in the opposite direction. To do. The driver may momentarily feel that the vehicle slides down the slope, and the driver's feeling may be impaired.

  FIG. 3A shows a vehicle speed, a braking force (shown by a broken line) that can occur when the start control according to the embodiment of the present invention is performed in the state shown in FIG. And the transition of the driving force (indicated by the solid line) is shown. Between times t0 and t1, the vehicle is held in a stopped state by the braking force. At time t1, the start control is started in response to the start operation performed by the occupant. According to this start control, an increase in driving force is started (time point t1), and when the driving force reaches a value that balances the gradient indicated by reference numeral 111 (time point t2), release of the braking force is started. The driving force continues to increase until the braking force is completely released (t2 to t3).

  According to this form of start control, the braking force is released after increasing the driving force, so that the vehicle temporarily moves in the direction of the problem of FIG. 2B, that is, in the direction opposite to the traveling direction. It is possible to prevent the phenomenon of moving to. Therefore, the driver's feeling can be improved as compared with that of (b).

  However, in the case of this start control, there is a possibility that the increase speed of the vehicle speed fluctuates as shown in the region of reference numeral 103. That is, the vehicle speed starts to gradually increase at time t2 when the release of the braking force starts, and the vehicle speed increases rapidly at time t3 when the braking force reaches zero. While the vehicle speed is gradually increasing, there is a risk of causing the driver to feel that the vehicle is being dragged, and a sudden increase in the vehicle speed may cause the driver to feel abruptness.

  Therefore, in a more preferred embodiment of the present invention, start control as shown in FIG. FIG. 3B shows changes in vehicle speed, braking force (indicated by a broken line), and driving force (indicated by a solid line), as in FIG. This start control is also based on the state shown in FIG. Between times t0 and t1, the vehicle is held in a stopped state by the braking force. The start control is started in response to the start operation by the occupant at time t1. In this start control, first, an increase in driving force is started while maintaining the braking force (time point t1). This is the same as (a) of FIG. Further, in this start control, when the driving force reaches a value balanced with the gradient indicated by the dotted line 111 (time t2), the release of the braking force is started. While the braking force is released, the driving force is maintained at a value commensurate with the gradient. When the braking force is completely released (becomes zero) at time t3, the driving force is increased from a value balanced with the gradient, and the vehicle is started.

  By performing such start control, it is avoided that the driving force increase and the braking force decrease occur simultaneously, so that the problem that may occur in FIG. 3A can be solved. That is, in a state where the driving force is maintained at a value that is balanced with the gradient at time t2 to t3, the vehicle can maintain the stop holding state by the action of the driving force, and the maintenance of the stop holding state can be maintained. No braking force is required. Therefore, even if the braking force starts to decrease, the vehicle speed remains zero, and the driver does not feel like dragging the vehicle. When the braking force becomes zero, the driving force starts to increase, so that the vehicle speed can be increased smoothly as shown in the region of reference numeral 105, so that a smooth start can be realized. .

  3A and 3B, the stop holding state during the time t0 to t1 is realized by the stop holding control unit 11, and the start control during the time t1 to t3 is realized by the start control unit 13. The traveling state after the start at time t3 can be realized by the traveling control unit 15.

  In FIG. 3, the case where the vehicle starts while moving forward in the uphill direction is described as an example. However, the same applies to the case where the vehicle starts moving backward in the uphill direction as shown in FIG. The start control is performed. In this case, the force that balances the gradient indicated by the dotted line 111 may be different between forward and reverse. Therefore, as shown in FIG. 1, a detection signal from a shift position sensor that detects a shift position is passed to the start control unit 13, and the start control unit 13 moves the shift position indicated by the detection signal forward (D). A driving force that is balanced with the gradient is calculated as shown by a dotted line 111 depending on whether it indicates retraction (R).

  FIG. 5 is a flowchart of a detailed process by the start control unit 13 shown in FIG. This process is based on the form of start control shown in FIG.

  In step S11, it is determined whether or not a start operation by the passenger is detected. As described above, this determination can be made by detecting whether a predetermined start switch has been operated or whether the accelerator pedal has been depressed. If no start operation is detected, the process is terminated.

  If a start operation is detected, a detection signal from the shift position sensor is acquired in step S12, and whether or not the shift position indicated by the detection signal indicates an in-gear state in which the vehicle can travel, that is, forward travel. It is determined whether either (D) or reverse travel (R) is indicated. If the shift position indicates either forward travel (D) or reverse travel (R), the process proceeds to step S13. If the shift position does not indicate an in-gear state, that is, if the shift position indicates either neutral (N) or parking (P), the process is terminated.

  In step S13, as described above, the gradient of the currently traveling road is acquired based on a detection signal from, for example, an inclination sensor. In step S14, a driving force that balances the gradient as indicated by reference numeral 111 in FIG. 3B is calculated as a target driving force. Details of this calculation process will be described later.

  In step S15, an instruction is given to the driving force control unit 23 so that the current driving force reaches the target driving force. In step S16, it is determined whether or not the current driving force has reached the target driving force. If not, the process returns to step S15 to continue the driving force control. If it reaches, it will progress to step S17 and will instruct | indicate the braking force control part 21 to cancel | release braking force. It is preferable to release the braking force at the fastest possible speed. By doing so, the vehicle can be started more quickly.

  In step S18, it is determined whether the braking force has become zero. If it is not zero, it returns to step S17 and continues braking force control. If it becomes zero, it indicates that the start control is completed. Thereafter, the driving control unit 15 shown in FIG. 1 gradually increases the driving force from the target driving force value (value indicated by the dotted line 111) as shown in FIG. The vehicle can be started smoothly by increasing gradually.

  Next, a method for calculating the target driving force in step S14 will be described with reference to FIG.

  FIG. 6A is a graph showing the relationship between the driving force and acceleration of the vehicle when the traveling direction of the vehicle is forward (when the shift position is D) according to the slope of the slope. Yes. The braking force is zero.

  In the figure, “uphill” indicates a slope whose direction from the rear (rear) to the front (front) of the vehicle is ascending, and the value of the slope is positive. “Downhill” indicates a downhill in which the direction from the rear (rear) to the front (front) of the vehicle is down, and the value of the slope is negative. C1 indicates a gradient that balances a predetermined creep force acting on the vehicle, that is, a gradient value at which gravity acts to cancel the creep force.

  The acceleration when a driving force as shown in the upper graph of the figure is applied to the vehicle is depicted in the lower graph (solid line). The acceleration represents the forward direction of the vehicle as a positive value and the backward direction of the vehicle as a negative value. When the gradient is C1, the acceleration of the vehicle is zero and the vehicle is stopped.

  As indicated by the solid line 201, when the gradient is smaller than C1, the driving force is controlled to zero. Accordingly, as indicated by the solid line 301, the acceleration increases as the gradient value decreases (the descending gradient increases).

  As shown by the solid line 203, when the gradient is C1 or more, the driving force is increased as the value of the gradient increases so that the acceleration becomes zero. As indicated by the solid line 303, the acceleration is maintained at zero.

  A dotted line 305 indicates the acceleration when the driving force is set to zero when the gradient is C1 or more. In this case, the acceleration takes a negative value and represents that the vehicle moves backward. (Indicates that you're going down the hill.) Driving force control as indicated by the solid line 203 can prevent such movement of the vehicle in the direction opposite to the traveling direction.

  In this way, when the vehicle is going to start while moving forward, the target driving force may be set according to the driving force map as shown in the upper part of FIG. As a result, even if the upward gradient is C1 or more, the driving force that balances the upward gradient acts on the vehicle, so that the vehicle can be held in a stopped state even when the braking force is zero.

  FIG. 6B is a graph showing the relationship between the driving force and acceleration of the vehicle when the traveling direction of the vehicle is backward (when the shift position is R) according to the slope of the slope. Yes. In the figure, “uphill” and “downhill” have the same meaning as (a).

  C2 indicates a gradient that balances a predetermined creep force acting on the vehicle, that is, a gradient value at which gravity acts to cancel the creep force. Acceleration is depicted in the lower graph (solid line) when a driving force as shown in the upper graph in the figure is applied to the vehicle. The acceleration represents the backward direction of the vehicle as a negative value, and represents the forward direction of the vehicle as positive. When the gradient is C2, the acceleration of the vehicle is zero, and the vehicle is stopped.

  As shown by the solid line 211, when the gradient is larger than C2, the driving force is controlled to zero. In response to this, as indicated by a solid line 311, the magnitude of acceleration increases as the gradient value increases (the upward gradient magnitude increases).

  As indicated by the solid line 213, when the gradient is equal to or less than C2, the driving force is increased as the value of the gradient decreases so that the acceleration becomes zero. As indicated by the solid line 313, the acceleration is maintained at zero.

  A dotted line 315 indicates the acceleration when the driving force is zero when the gradient is C2 or less. In this case, the acceleration takes a positive value and represents that the vehicle moves forward. (Indicates that you're going down the hill.) Such a movement in the direction opposite to the traveling direction of the vehicle can be prevented by the driving force control as indicated by the solid line 213.

  In this way, when the vehicle is going to start while moving backward, the target driving force may be set according to the driving force map as shown in the upper part of FIG. As a result, even when the downward gradient is C2 or less, the driving force that balances the gradient acts on the vehicle, so that the vehicle can be held in a stopped state even when the braking force is zero.

  FIG. 7 is a flowchart of a process for calculating the target driving force, which is executed in step S13 of FIG. 5, according to the method described with reference to FIG.

  In step S31, it is determined whether the shift position acquired in step S12 (FIG. 5) represents forward travel (shift position is D) or reverse travel (shift position is R). If the shift position represents forward travel, the process proceeds to step S32, and a forward map such as the upper part of FIG. 5A is referred to based on the gradient acquired in step S12, and the corresponding driving force is determined. Obtained as the target driving force. Such a map can be stored in advance in the memory of the travel control device 10.

  On the other hand, if the shift position indicates reverse travel, the process proceeds to step S33, and a reverse map such as the upper part of FIG. 5B is referred to based on the gradient acquired in step S12, and the corresponding drive is performed. The force is obtained as the target driving force. Such a map can also be stored in advance in the memory of the travel control device 10.

  Thus, when the descending direction of the gradient of the travel path is opposite to the direction in which the vehicle is about to start, a target driving force that is balanced with the magnitude of the gradient is calculated. Since such a target driving force acts on the vehicle, the driver can start the vehicle without perceiving the sensation that the vehicle slides down the slope. Since the vehicle is kept stopped by the target driving force until the braking force is completely released, the driver can start the vehicle without feeling uncomfortable.

  With reference to FIG. 8, the relationship between the start control according to the present invention as described above and the operation of the driver with respect to the accelerator pedal will be described. There is a possibility that the accelerator pedal may be operated by the occupant even during the start control by the traveling control device 10. Normally, the driving force of the vehicle is controlled according to the operation amount (opening degree) of the accelerator pedal. However, in the start control according to the present invention, the driving force and the braking force are controlled as shown in FIG. 3A or, more preferably, FIG. 3B, regardless of the operation amount of the accelerator pedal.

  More specifically, FIGS. 8A and 8B show the same diagram as FIG. 3B. The difference is that the accelerator is shown in dotted lines 401 and 403, respectively. It shows the change in the opening of the pedal (more precisely, the driving force that should be generated according to the opening during normal travel).

  In (a), as indicated by the dotted line 401, the accelerator pedal opening is increased by a slight depression of the accelerator pedal, and then the depression of the accelerator pedal is released during time t1 to t2. ing. In this way, in the start control at the times t1 to t3, the driving force is increased to the target driving force (dotted line 111) calculated so as to be balanced with the gradient in spite of the accelerator pedal opening being operated in this way. The target driving force is maintained until the braking force is released to zero.

  In (b), as shown by the dotted line 403, the accelerator pedal opening degree continues to increase from time t to t3 in response to depression of the accelerator pedal. In this way, in the start control at the times t1 to t3, the driving force is increased to the target driving force (dotted line 111) calculated so as to be balanced with the gradient in spite of the accelerator pedal opening being operated in this way. The target driving force is maintained until the braking force is released to zero.

  In this way, even if the accelerator pedal is operated during the start control from time t1 to t3, the start control unit 13 and the driving force control unit 23 are configured not to respond to the operation of the accelerator pedal. ing. After the time point t3 when the start control is completed, the driving force control unit 23 is controlled by the traveling control unit 15 so that the driving force according to the opening degree of the accelerator pedal is generated. Therefore, in the case of (a), since the accelerator pedal is not operated after time t3, the driving force is increased by the travel control unit 15 toward the predetermined vehicle speed (for example, the above-described follow-up). When the control is performed, the vehicle speed is controlled so as to follow the preceding vehicle). In the case of (b), after time t3, the driving force according to the increased accelerator pedal opening is set as the target driving force, and the driving force is generated so as to reach the target driving force.

  As described above, specific embodiments of the present invention have been described. However, the present invention is not limited to these embodiments.

DESCRIPTION OF SYMBOLS 10 Traveling control apparatus 11 Stop holding | maintenance control part 13 Start control part 17 Gradient acquisition part 21 Braking force control part 23 Driving force control part

Claims (1)

Braking force control means for controlling the braking force of the vehicle;
Stop holding control means for holding the vehicle in a stopped state via the braking force control means;
Driving force control means for controlling the driving force of the vehicle;
Start operation detecting means for detecting a start operation for the vehicle of the occupant;
Means for obtaining a gradient of the traveling path of the vehicle;
When a start operation is detected by the start operation detecting means while the vehicle is held in a stopped state by the stop holding control means, the vehicle is moved downward in the travel path based on the acquired gradient. A target driving force for suppressing the movement of the vehicle on the travel path is calculated by balancing the heading force and the driving force, and the vehicle is driven by the target driving force via the driving force control means. After the braking force is released, the braking force is released via the braking force control means to release the holding state of the vehicle, and the driving force is controlled via the driving force control means according to the release of the braking force. Starting control means for starting the vehicle by increasing
With
The start control means maintains the state in which the vehicle is driven by the target driving force via the driving force control means until the release of the braking force via the braking force control means is completed.
Travel control device.

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