JP3974783B2 - Travel control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a travel control device including a slow travel mode that facilitates vehicle speed adjustment only by a brake operation during slow travel.
[0002]
[Prior art]
Various techniques are known for controlling the vehicle speed within a predetermined range when the vehicle is running, and in a relatively high speed vehicle speed range, an auto cruise device that obtains a predetermined vehicle speed by automatically adjusting the accelerator opening is known. ing. As a vehicle speed control technique during slow running, for example, a technique disclosed in Japanese Patent Laid-Open No. 10-278825 is known. This technology uses creep driving to perform automatic parking.Vehicle speed control is basically performed by the driver by braking, but when the vehicle speed range suitable for automatic parking is exceeded. Is to notify the driver by a notification means, thereby prompting the driver to perform an appropriate brake operation. Also known is a technique for controlling the vehicle speed by applying a braking force when the vehicle speed exceeds the set vehicle speed as a threshold.
[0003]
[Problems to be solved by the invention]
A technique for performing driving force application control called torque up is known in order to improve the controllability of the vehicle speed and expand the vehicle speed control range when using such creep running. However, when the torque is increased, the required braking force increases compared to when the torque is not increased, which increases the burden on the braking system and increases the amount of braking operation by the driver. End up.
[0004]
Therefore, an object of the present invention is to provide a travel control device that can perform driving force application control without increasing the load on the braking system.
[0005]
[Means for Solving the Problems]
In order to solve the above-described problem, a travel control device according to the present invention provides a slow travel mode that facilitates vehicle speed adjustment by brake operation during slow travel by setting the engine generated torque when the accelerator is off to a predetermined torque-up state. When the vehicle is stopped in the slow driving mode, the torque increase is released or reduced.
[0006]
When the stopped state continues, the braking force necessary for stopping is reduced by releasing or reducing the torque increase, and the load on the braking system is reduced.
[0007]
This slow driving mode is preferably executed during parking assistance by the parking assistance device. If it does in this way, the operativity at the time of parking assistance operation will improve.
[0008]
In the case where the stop state continues after cancellation or reduction of the torque increase, it is preferable to further include notification means for urging the driver to cancel the parking assistance. If the stopped state continues after the torque-up stop, there may be a steep slope or obstacle that the parking support cannot handle, so in this case the parking support is canceled. This is because it is preferable to switch to manual operation by the driver.
[0009]
It is preferable to restore the torque increase when the brake release operation continues and the vehicle moves after the torque increase cancellation or reduction operation. In this way, when the driver temporarily stops due to the presence of a pedestrian on the course, the torque up can be automatically restored after the start, and the torque up and torque down hunting can be performed. Since it can suppress, riding comfort improves.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings. In order to facilitate the understanding of the description, the same reference numerals are given to the same components in the drawings as much as possible, and duplicate descriptions are omitted.
[0011]
FIG. 1 is a block diagram of a parking assistance device 100 including a travel control device 110 according to the present invention. This parking assistance device 100 includes an automatic steering device 120 in addition to the travel control device 110 according to the present invention, and is controlled by a parking assistance ECU 1 that is a control device. The parking assist ECU 1 includes a CPU, a ROM, a RAM, an input signal circuit, an output signal circuit, a power supply circuit, and the like, and includes a travel control unit 10 that controls the travel control device 110 and a steering control unit 11 that controls the automatic steering device. And have. The travel control unit 10 and the steering control unit 11 may be separated in hardware in the parking assist ECU 1, but are separated in software using the same CPU, ROM, RAM, and the like in hardware. Also good.
[0012]
The travel control device 110 includes the travel control unit 10 described above, a braking system, and a drive system. The braking system is an electronically controlled brake (ECB) system in which the braking force applied to each wheel is electronically controlled by the brake ECU 31, and the brake hydraulic pressure applied to the wheel cylinder 38 of the hydraulic brake disposed on each wheel by the actuator 34. Adjust the braking force by adjusting. The brake ECU 31 is disposed in a wheel speed sensor 32 that is disposed on each wheel to detect the wheel speed, an acceleration sensor 33 that detects vehicle acceleration, and an actuator 34, and is added to the inside and the wheel cylinder 38. Each output signal of a master cylinder (M / C) hydraulic sensor 36 that detects the hydraulic pressure of a master cylinder 35 that is connected between the brake pedal 37 and the actuator 34 is not shown. Have been entered.
[0013]
The engine 22 constituting the drive system is controlled by the engine ECU 21, and the engine ECU 21 and the brake ECU 31 communicate with each other and perform cooperative control with the travel control unit 10. Here, the output of the shift sensor 12 that detects the shift state of the transmission is input to the engine ECU 21.
[0014]
The automatic steering device 120 includes a drive motor 42 that also serves as a power steering device disposed between the steering wheel 40 and the steering gear 41, and a displacement sensor 43 that detects a displacement amount of the steering, and the steering control unit 11 is driven. While controlling the drive of the motor 42, the output signal of the displacement sensor 43 is input.
[0015]
The parking support ECU 1 including the travel control unit 10 and the steering control unit 20 includes an input unit 16 that receives an image signal acquired by the rear camera 15 for acquiring an image behind the vehicle and a driver's operation input for parking support. Are connected to a monitor 13 that displays information by an image to a driver and a speaker 14 that presents information by voice.
[0016]
FIG. 2 is a diagram for explaining the outline of parking support control using this apparatus. The case where the vehicle 5 moves from the position shown in the figure to the position shown in 5a and performs so-called parallel parking between the vehicles 61 and 62 parked along the road shoulder 63 will be described as an example.
[0017]
First, after moving the vehicle 5 to the position shown in the figure, the driver operates the input means 16 while viewing the image captured by the rear camera 15 displayed on the monitor 13, and is displayed on the screen. The target parking position is set by moving the parking frame being moved to the position 5a in the figure. Hereinafter, the center of gravity of the vehicle is P (x, y), and the center of gravity of the target parking position 5a is represented by Pt (x _t , y _t ).
[0018]
Parking assist ECU1 calculates a Pt (x _t, y _t) by the image recognition processing. Pt (x _t , y _t ) may be obtained as relative coordinates with the current vehicle position P (x, y) as the origin, for example. Next, the parking assist ECU1 corresponding to P (x, y) from Pt (x _t, y _t) determined the path 51 of the optimum vehicle center of gravity leading to the steering operation and the position of the center of gravity needed to take this path 51 This is calculated as the steering angle change.
[0019]
When the driver depresses the brake pedal 37 and operates the shift lever to set the vehicle back, the travel control unit 10 of the parking assist ECU 1 instructs the engine ECU 21 to torque up the engine 22. As a result, the engine 22 rotates at a higher rotational speed than during normal idling, thereby shifting to a torque-up state with a high driving force. For this reason, the vehicle speed range that can be adjusted only by the brake pedal 37 without performing the accelerator operation is expanded, and the controllability of the vehicle is improved.
[0020]
When the driver returns the brake pedal 37, the wheel cylinder hydraulic pressure (brake hydraulic pressure) applied to the wheel cylinder 38 is adjusted by the actuator 34 according to the pedal opening, and the braking force applied to each wheel is adjusted. To adjust the vehicle speed. At this time, the braking force is applied by adjusting the brake hydraulic pressure applied to each wheel cylinder 38 by the actuator 34 so that the vehicle speed detected by the wheel speed sensor 32 does not exceed the upper limit vehicle speed, so that the vehicle speed becomes lower than the upper limit vehicle speed Vref. Car speed guard is performed. The above travel control is hereinafter referred to as slow travel mode control.
[0021]
While monitoring the output of the displacement sensor 43, the steering control unit 11 controls the drive motor 42 and operates the steering gear 41 to control the steering angle so as to match the steering angle displacement obtained by the parking assist ECU 1. Since the movement along the route set in this way is performed, the driver can concentrate on safety confirmation on the route and vehicle speed adjustment. If there are obstacles, pedestrians, etc. on the path, when the driver depresses the brake pedal 37, the braking force corresponding thereto is applied to the wheel cylinder 38 via the actuator 34 under the control of the brake ECU 31, which is safe. You can slow down and stop.
[0022]
Next, details of the slow running mode control in the present embodiment will be specifically described with reference to FIG. FIG. 3 is a flowchart showing this control. This control is repeatedly executed at a predetermined timing (time step Δt) during the parking assist operation described above.
[0023]
First, in step S1, the vehicle speed V is calculated based on each wheel speed read from the wheel speed sensor 3, and in the next step S2, it is determined whether the vehicle speed V is 0, that is, whether the vehicle is stopped. When the vehicle is stopped, the process proceeds to step S3, and the time of continuous stop is calculated by adding the time step Δt to the stop duration tstop.
[0024]
In the next step S4, it is determined whether torque is being increased. When the torque is being increased, the process proceeds to step S5, and the stop duration tstop is compared with the threshold value tth1. This tth1 is set to 30 seconds, for example. When tstop ≧ tth1, the process proceeds to step S6, the torque-up is released, and the process is terminated. On the other hand, if it is determined in step S5 that tstop <tth1, the process of step S6 is skipped and the process ends. As a result, when the vehicle has been continuously stopped for a longer time than the threshold value tth1, the braking force necessary to stop the vehicle is reduced by releasing the torque increase and changing the driving force to a smaller value. Let This eliminates the need for the driver to continue to depress the brakes, making operation easier and reducing the load on the brake system. Moreover, since excessive torque increase is not performed, useless energy consumption can be suppressed.
[0025]
If it is determined in step S4 that the torque is not being increased, that is, if the vehicle is still stopped after the torque increase is canceled in step S6, the process proceeds to step S7, and the brake pedal 37 is released. It is determined whether or not a return operation is in progress. The determination of the presence / absence of the return operation is performed by, for example, referring to the change in the master cylinder oil pressure measured by the oil pressure sensor 36 and determining that the return operation is being performed when the master cylinder oil pressure has decreased from the previous time step. do it.
[0026]
If it is determined in step S7 that the return operation is not being performed, that is, if the driver has stepped on the brake pedal 37 further than the previous time step, or continues to press in the same manner, the process proceeds to step S8, where the brake return is performed. After the operation duration tbl is initialized to 0, the stop duration tstop is compared with the threshold value tth2 in step S9. tth2 is set longer than tth1, for example, 3 minutes. When it is determined that tstop <tth2, the subsequent processing is skipped and the process is terminated. In the case of tstop ≧ tth2, the process proceeds to step S10, and after the warning process for prompting the driver to cancel the parking assistance is performed by the monitor 13 or the speaker 14, the process is terminated.
[0027]
As a result, if the stopped state continues after the torque-up is released, the torque-up released state continues, and if the stopped state continues for a long time, parking assistance such as obstacles and steep slopes Since it is considered that there may be a situation that cannot be handled by the device, parking support cancellation is urged, so that parking assistance is not continued in a state where the device cannot be handled, and the driver's trust in the device can be ensured.
[0028]
If it is determined in step S7 that the return operation is being performed, the time step Δt is added to the return operation duration tbl in step S11, and tbl and the threshold value tth3 are compared in the next step S12. This tth3 is preferably set shorter as the speed is higher and longer as the speed is lower, for example, according to the speed of the return operation. If it is determined that tbl <tth3, the subsequent process is skipped and the process ends. In the case of tbl ≧ tth3, the process proceeds to step S13 and the torque up is resumed. As a result, when the driver depresses the brake and intentionally stops the vehicle and then releases the brake, the torque can be resumed to increase the driving force and improve the startability. The controllability of the vehicle can be maintained. Further, when the brake return operation is small, the torque-up release state is continued, so that the torque-up does not return suddenly when the driver unintentionally releases the brake temporarily. As a result, the vehicle can be controlled as intended by the driver.
[0029]
If it is determined in step S2 that the vehicle is not stopped, the stop duration tstop is set to 0 and initialized in step S14, and then the process ends. In this case, since the torque-up state is continued, the controllability of the vehicle can be maintained.
[0030]
In the above description, the embodiment in the parking assist device having the automatic steering function has been described. The same can be used in the apparatus. Furthermore, even in the case of the travel control device 110 alone that expands the vehicle speed control range by the brake pedal, it is suitable for the case where the parking operation, the stop, and the movement are repeated.
[0031]
【The invention's effect】
As described above, according to the present invention, torque increase is automatically canceled when the vehicle is stopped due to the driver's intention or due to an external condition such as an obstacle or a steep slope. Torque-up is not continued, and the burden on the braking system can be suppressed and the burden on the driver can be reduced.
[0032]
Furthermore, when the brake release operation continues, the torque-up is restored, so that when the torque-up is necessary, the torque-up state can be surely restored, and the startability and controllability of the vehicle are ensured. be able to.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a parking assistance device including a travel control device according to the present invention.
FIG. 2 is a diagram for explaining an outline of parking support control in the apparatus of FIG. 1;
FIG. 3 is a flowchart showing a process of slow running support control according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Parking assistance ECU, 10 ... Driving control part, 11 ... Steering control part, 12 ... Shift sensor, 13 ... Monitor, 14 ... Speaker, 15 ... Rear camera, 16 ... Input means, 21 ... Engine ECU, 22 ... Engine, DESCRIPTION OF SYMBOLS 31 ... Brake ECU, 32 ... Wheel speed sensor, 33 ... Acceleration sensor, 34 ... Actuator, 35 ... Master cylinder, 36 ... Hydraulic sensor, 37 ... Brake pedal, 38 ... Wheel cylinder, 40 ... Steering wheel, 41 ... Steering gear, DESCRIPTION OF SYMBOLS 42 ... Drive motor, 43 ... Displacement sensor, 5 ... Vehicle, 61, 62 ... Other vehicle, 100 ... Parking assistance apparatus, 110 ... Traveling control apparatus, 120 ... Automatic steering apparatus.

Claims (4)

In a travel control device having a slow travel mode that facilitates vehicle speed adjustment by brake operation during slow travel by setting the engine generated torque when the accelerator is off to a predetermined torque-up state,
A travel control device that releases or reduces torque increase when the vehicle is stopped in a slow travel mode .   The travel control device according to claim 1, wherein the slow travel mode is executed during parking support by a parking support device.   The travel control device according to claim 2, further comprising notification means for urging the driver to cancel the parking assistance when the stop state continues after the torque increase is released or reduced. The travel control device according to any one of claims 1 to 3, wherein the torque increase is restored when the vehicle is moved while the brake release operation is continued after the torque increase cancellation or reduction operation.

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