JP2007008333A - Preceding vehicle follow-up control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To relieve a burden of a brake actuator during automatic stop control. <P>SOLUTION: This preceding vehicle follow-up control device, which stops a vehicle by operating the brake actuator when it follows up a preceding vehicle for automatic running to stop the preceding vehicle, controls creep force according to road characteristics of a stopping position. If the stopping position is on uphill, for example, a creep force is generated so as to cancel a force working on the vehicle. If a stopping position is on downhill or a flat road, on the other hand, the vehicle is controlled so as not to generate a creep force. This can relieve a burden of the brake actuator in stopping and maintaining the vehicle. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a preceding vehicle follow-up control device that performs traveling control such as automatic stop and automatic start following a preceding vehicle.

  Conventionally, in a system in which an actuator is operated to automatically drive a brake, a brake actuator corresponding to each wheel so that three or two of the four wheels are alternately operated when the vehicle is stopped. A technique is known that reduces the load on the brake actuator by actuating (see Patent Document 1).

JP 2000-247216 A

  However, in the conventional technology, since control for reducing the braking force for stopping and holding the vehicle is not performed, there is a problem that the braking force necessary for stopping the vehicle reliably does not change.

  The preceding vehicle follow-up control device according to the present invention controls the creep force generated in the vehicle based on the road characteristics of the stop position, and the brake hydraulic pressure required to stop and hold the vehicle in a state where the creep force is controlled. Controlling the brake actuator to generate.

  According to the preceding vehicle follow-up control device according to the present invention, the creep force generated in the vehicle is controlled based on the road characteristic of the stop position, so that the braking force required to stop and hold the vehicle is reduced, and the brake actuator Can be reduced.

  FIG. 1 is a diagram illustrating a configuration of a preceding vehicle follow-up control device according to an embodiment. The preceding vehicle following control device in one embodiment includes an inter-vehicle distance sensor 1, a vehicle speed sensor 2, a hydraulic pressure sensor 3, a throttle actuator 4, a brake actuator 5, an automatic transmission 6, and a control device 10. Prepare.

  The inter-vehicle distance sensor 1 includes a radar device, sends a laser beam to a predetermined range in front of the vehicle at predetermined intervals, and receives reflected light that is reflected back to the preceding vehicle, thereby allowing the inter-vehicle distance to the preceding vehicle. Is detected. The vehicle speed sensor 2 detects the speed of the host vehicle. The hydraulic pressure sensor 3 detects the brake hydraulic pressure of the hydraulic brake provided on each wheel.

  The throttle actuator 4 controls acceleration / deceleration of the vehicle by controlling opening / closing of a throttle valve (not shown) based on a command from the control device 10 described later. The brake actuator 5 controls the braking force of the hydraulic brake based on a command from the control device 10. The automatic transmission (automatic transmission) 6 performs a shift based on a command from the control device 10.

  The control device 10 includes a CPU, a ROM, a RAM, and the like. The control device 10 detects a preceding vehicle based on the laser light transmitted and received by the inter-vehicle distance sensor 1, and the host vehicle automatically follows the detected preceding vehicle. Car follow-up control is performed. That is, based on the inter-vehicle distance detected by the inter-vehicle distance sensor 1 and the speed of the own vehicle detected by the vehicle speed sensor 2, the throttle is set so that the inter-vehicle distance between the own vehicle and the preceding vehicle is maintained at a constant distance. The actuator 4 and the brake actuator 5 are controlled.

  In the preceding vehicle following control, when the preceding vehicle decelerates, the host vehicle is decelerated by operating the brake actuator 5, and when the preceding vehicle stops, the own vehicle is also stopped. At this time, the engine speed and the automatic transmission 6 are controlled so that the brake fluid pressure required to stop and hold the vehicle by the hydraulic brake is minimized.

  FIG. 2 is a flowchart showing the contents of processing performed by the preceding vehicle follow-up control device in one embodiment. When the host vehicle stops in response to the stop of the preceding vehicle while the preceding vehicle following control is being performed, the control device 10 starts the process of step S10.

  In step S10, the road characteristic at the stop position is determined. Here, the road gradient at the stop position is estimated. The road gradient can be estimated based on, for example, a torque command value for the engine and an actual output torque. For example, if the output torque is low with respect to the torque command value, it can be determined that the vehicle is stopped on an uphill, and the relationship between the torque command value, the output torque, and the road gradient is obtained in advance through experiments or the like. If it is, the road gradient can be estimated. When the road gradient is estimated, the process proceeds to step S20.

  In step S20, the force acting on the vehicle is calculated based on the road gradient calculated in step S10. For example, if the road at the stop position is an uphill, gravity acts toward the rear of the vehicle, so the force acting on the vehicle is calculated based on the road gradient calculated in step S10. However, if the road at the stop position is a flat road without a slope or a downhill, the force acting on the vehicle is set to zero. It should be noted that the force acting on the vehicle may be obtained by previously obtaining a table of the relationship between the road gradient and the force acting on the vehicle and using this table.

  In step S30 following step S20, the shift position of the automatic transmission 6 and the engine speed are controlled so that the creep force that cancels the force calculated in step S20 is generated.

  FIG. 3 shows an example of the relationship between the shift position of the automatic transmission 6, the engine speed, the creep force generated in the vehicle, and the brake fluid pressure corresponding to the creep force when the vehicle stops on a road with a slope of 1%. FIG. When the engine speed (idle speed) at a stop is 800 (rpm), the creep force generated in the vehicle decreases as the shift position changes to 1st speed, 2nd speed, and 3rd speed. Therefore, the brake fluid pressure required to stop the vehicle is also reduced against the creep force generated in the vehicle.

  When the engine speed is decreased to 800 (rpm), 700 (rpm), and 600 (rpm) with the shift position at the time of stopping fixed at the third speed, the creep force generated in the vehicle is 210 (Nm ), 160 (Nm), and 110 (Nm). Therefore, the brake fluid pressure required to stop the vehicle is also reduced against the creep force generated in the vehicle. Although FIG. 3 shows an example in which the engine speed is changed with the shift position fixed at the third speed, the engine speed is decreased with the shift position fixed at the first speed or the second speed. Even in this case, the creep force and the brake fluid pressure required to stop the vehicle are reduced.

  When the road at the stop position is uphill, the shift position of the automatic transmission 6 and the engine speed are controlled so that a creep force that cancels the force calculated in step S20 is generated. Also here, the shift position corresponding to the creep force and the engine speed are obtained in advance by experimentation or the like, and the shift position of the automatic transmission 6 and the engine speed are obtained based on this table. Further, when the road at the stop position is a downhill or on a flat road, the shift position of the automatic transmission 6 is set to neutral so that creep force is not generated. In this case, the engine speed (idle speed) is not changed.

  In other words, when the road at the stop position is uphill, control is performed so that a creep force that counteracts the gravity acting on the vehicle is generated so that the brake fluid pressure necessary to stop and hold the vehicle is minimized. To do. Further, when the road at the stop position is a downhill or a flat road, a creep force is not generated so that the brake fluid pressure necessary to stop and hold the vehicle is minimized.

  In step S40 following step S30, the brake fluid pressure necessary to stop and hold the vehicle is calculated, and the brake actuator 5 is operated so that the calculated brake fluid pressure is generated. In step S30, when the stop position is uphill, the shift position of the automatic transmission 6 and the engine speed are controlled so that a creep force that cancels the force acting on the vehicle is generated, and the stop position is lowered. In the case of slopes and flat roads, the shift position is set to neutral so that creep force is not generated. As a result, the braking force required to stop and hold the vehicle decreases, so the brake fluid pressure required to stop and hold the vehicle is greater than the brake fluid pressure immediately after the host vehicle is stopped in the preceding vehicle following control. Lower. That is, in step S40, the brake hydraulic pressure is reduced to a value necessary to stop and hold the vehicle by operating the brake actuator 5.

  Even when the stopping position is uphill, the force acting on the vehicle is balanced with the creep force, and even when the stopping position is on a flat road and no creep force is generated, the brake actuator 5 is used for safety. To activate the brake.

  In step S40, when the brake fluid pressure is reduced to a value necessary for stopping and holding the vehicle, the process proceeds to step S50. In step S50, it is determined whether or not the vehicle is securely held and stopped, that is, whether or not the vehicle is moving. This determination is made based on the vehicle speed detected by the vehicle speed sensor 2. If it is determined that the vehicle is moving and the vehicle is not reliably stopped and held, the process proceeds to step S60. In step S60, the brake actuator 5 is operated so that the brake fluid pressure increases by a predetermined amount, and the process returns to step S50.

  If it is determined in step S50 that the vehicle is not moving and the vehicle is securely held and stopped, the process proceeds to step S70. In step S70, it is determined whether or not the preceding vehicle has started based on the information on the inter-vehicle distance from the preceding vehicle input from the inter-vehicle distance sensor 1. If it is determined that the preceding vehicle has not started, the process returns to step S50, and if it is determined that the preceding vehicle has started, the process proceeds to step S80.

  In step S80, a target torque required to start the host vehicle is calculated based on the road gradient estimated in step S10 and the acceleration at the start of the preceding vehicle. The acceleration of the preceding vehicle can be calculated based on the inter-vehicle distance detected by the inter-vehicle distance sensor 1 a plurality of times. When the target torque at the start is calculated, the process proceeds to step S90. In step S90, the brake fluid pressure required to stop and hold the host vehicle is calculated with respect to the target torque calculated in step S80, and the brake actuator 5 is controlled so that the calculated brake fluid pressure is generated. This brake fluid pressure is a brake fluid pressure necessary to suppress the driving force of the vehicle at this time, assuming that the calculated target torque is generated in the vehicle.

  In step S100 following step S90, the shift position of the automatic transmission 6 is controlled based on the target torque calculated in step S80. When the shift position is controlled, the process proceeds to step S110. In step S110, the brake actuator 5 is actuated to cause a creep phenomenon so that the brake fluid pressure is gradually reduced. Thereafter, the throttle actuator 4 is controlled so as to travel following the preceding vehicle. The follow-up running may be started after the driver gives a start instruction operation.

  According to the preceding vehicle follow-up control device in one embodiment, the road characteristic of the stop position is determined, the creep force generated in the vehicle is controlled based on the determined road characteristic, and the creep force is controlled in the vehicle Since the brake actuator is controlled so that the brake fluid pressure necessary for stopping and holding the vehicle is generated, the brake fluid pressure necessary for stopping and holding the vehicle is reduced, and the load on the brake actuator 5 is reduced. be able to. Moreover, since the load applied to the brake actuator 5 can be reduced, the limit of the vehicle stop holding time can be increased.

  According to the preceding vehicle follow-up control device in one embodiment, when the stop position is uphill, the creep force is controlled so that the creep force that cancels the force acting on the vehicle in the stop state is generated. It is possible to reduce the brake fluid pressure necessary for stopping and holding. In addition, when the stop position is downhill or on a flat road, the creep force is prevented from being generated. Therefore, compared with the case where the creep force is generated, the brake fluid pressure required to stop and hold the vehicle is reduced. Can be reduced.

  According to the preceding vehicle follow-up control device in one embodiment, the creep force generated in the vehicle is controlled by controlling the shift position of the automatic transmission and the engine rotational speed. It can be controlled appropriately.

  Further, according to the preceding vehicle follow-up control device in one embodiment, the target torque at the start of the vehicle is calculated, and before the start of the host vehicle, the brake fluid pressure corresponding to the calculated target torque is generated. The brake actuator is controlled, and then the shift position of the automatic transmission is controlled based on the target torque, and then the brake fluid pressure is gradually reduced to start the vehicle. That is, before controlling the shift position of the automatic transmission based on the target torque at the time of starting, the brake actuator is controlled so that the brake fluid pressure corresponding to the target torque is generated, thereby holding the vehicle stopped. As a certain state, it is possible to prevent the vehicle from inadvertently starting when the shift position is changed.

  The present invention is not limited to the embodiment described above. For example, in order to control the creep force, the shift position of the automatic transmission 6 and the engine rotation speed (idle rotation speed) are controlled, but either the shift position of the automatic transmission 6 or the engine rotation speed is controlled. You may make it do. Further, as long as the creep force can be controlled, other than the shift position of the automatic transmission 6 and the engine speed may be controlled.

  The transmission mounted on the vehicle may be a continuously variable transmission (CVT) instead of a stepped transmission. In this case, when the gear ratio of the transmission is reduced, the creep force generated in the vehicle is reduced. When the stop position is uphill, the smaller the road gradient, the smaller the force acting on the vehicle. Therefore, the smaller the road gradient, the smaller the gear ratio of the continuously variable transmission.

  The road gradient is estimated based on the torque command value for the engine and the actual output torque. However, the road gradient can be estimated by other methods, or a sensor for detecting the road gradient may be provided.

  The brake actuator 5 is not limited to the one that controls the braking force of the hydraulic brake, and for example, an electric brake using an electric motor, a mechanical brake using a wire, or the like can be used.

  The correspondence between the constituent elements of the claims and the constituent elements of the embodiment is as follows. That is, the control device 10 constitutes road characteristic determination means, creep force control means, brake actuator control means, and target torque calculation means. In addition, the above description is an example to the last, and when interpreting invention, it is not limited to the correspondence of the component of said embodiment and the component of this invention at all.

The figure which shows the structure of the preceding vehicle follow-up control apparatus in one embodiment. The flowchart which shows the processing content performed by the preceding vehicle follow-up control apparatus in one embodiment The figure which shows an example of the relationship of the brake fluid pressure according to the shift position of an automatic transmission, an engine speed, the creep force which generate | occur | produces in a vehicle, and a creep force when it stops on the road where a gradient is 1%.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Vehicle distance sensor, 2 ... Vehicle speed sensor, 3 ... Fluid pressure sensor, 4 ... Throttle actuator, 5 ... Brake actuator, 6 ... Automatic transmission, 10 ... Control device

Claims (8)

In the preceding vehicle follow-up control device that automatically runs following the preceding vehicle and stops the vehicle by operating the brake actuator when the preceding vehicle stops,
Road characteristic determination means for determining the road characteristic of the stop position when the host vehicle stops following the preceding vehicle;
A creep force control means for controlling a creep force generated in the vehicle while the vehicle is stopped based on the road characteristic determined by the road characteristic determination means;
Brake actuator control means for controlling the brake actuator so that the brake fluid pressure necessary for stopping and holding the vehicle is generated in a state where the creep force is controlled by the creep force control means. A preceding vehicle following control device. In the preceding vehicle follow-up control device according to claim 1,
The creep force control means controls the creep force so that a creep force is generated that cancels the force acting on the vehicle in the stopped state when the road characteristic determining means determines that the road at the stop position is uphill. A preceding vehicle follow-up control device. In the preceding vehicle follow-up control device according to claim 2,
The road characteristic determining means detects a road gradient at a stop position,
The preceding vehicle follow-up control device, wherein the creep force control means controls a creep force generated in the vehicle based on a road gradient detected by the road characteristic determination means. In the preceding vehicle follow-up control device according to any one of claims 1 to 3,
The creep force control means performs control so that creep force is not generated when the road characteristic determination means determines that the road at the stop position is a downhill or a flat road without a gradient. A preceding vehicle following control device. In the preceding vehicle follow-up control device according to any one of claims 1 to 4,
The preceding vehicle follow-up control device, wherein the creep force control means controls a creep force generated in the vehicle by controlling at least one of a shift position of the automatic transmission and an engine speed. In the preceding vehicle follow-up control device according to any one of claims 1 to 5,
A target torque calculating means for calculating a target torque at the start of the vehicle;
The brake actuator control means controls the brake actuator so that a brake fluid pressure corresponding to the target torque calculated by the target torque calculation means is generated before the vehicle starts. Control device. In the preceding vehicle follow-up control device according to claim 6,
The shift position of the automatic transmission is controlled based on the target torque calculated by the target torque calculation means after the brake actuator is controlled by the brake actuator control means so that the brake hydraulic pressure corresponding to the target torque is generated. A preceding vehicle follow-up control device further comprising shift position control means for controlling the vehicle. In the preceding vehicle follow-up control device that automatically runs following the preceding vehicle and stops the vehicle by operating the brake actuator when the preceding vehicle stops,
Based on the road characteristics at the position where the vehicle stops following the preceding vehicle, the creep force generated on the vehicle is controlled while the vehicle is stopped, and the vehicle is stopped and held in a state where the creep force is controlled. A preceding vehicle follow-up control device that controls a brake actuator so that a necessary brake fluid pressure is generated.

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