JP3979094B2 - Travel control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a travel control device that performs vehicle speed control, and more particularly to a travel control device that controls vehicle speed by applying a braking force.
[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]
However, the technique disclosed in Japanese Patent Application Laid-Open No. 10-278825 only prompts the driver to operate, and it is difficult to reliably guard the vehicle speed below the upper limit. Further, when the braking force is applied with the set vehicle speed as a threshold value, control is performed when the set vehicle speed is exceeded, so that hunting occurs due to a brake shock at the start and end of the control, resulting in a decrease in ride comfort.
[0004]
Accordingly, an object of the present invention is to provide a travel control device that is suitable as upper limit vehicle speed control particularly during slow speed travel and that can reliably perform an upper limit vehicle speed guard without deteriorating riding comfort.
[0005]
[Means for Solving the Problems]
In order to solve the above-described problems, the travel control device according to the present invention performs vehicle speed control so that the braking force is applied to the vehicle using a braking system so that the vehicle speed is less than or equal to a set upper limit vehicle speed determined by the engine speed during idling. In the travel control device, when the vehicle speed during creep travel exceeds a control start vehicle speed lower than the upper limit vehicle speed, a braking force is applied according to the deviation between the upper limit vehicle speed and the current vehicle speed. Thus, by applying the braking force from the control start vehicle speed lower than the upper limit vehicle speed, the vehicle speed becomes difficult to reach the upper limit vehicle speed, and reliable upper limit vehicle speed guard control can be performed.
[0006]
When there is no other braking force application request, it is preferable to perform control so that the vehicle speed converges to a braking force that matches the upper limit vehicle speed. This is preferable because the vehicle speed range up to the set upper limit vehicle speed can be used effectively.
[0007]
When another braking force application request is detected during traveling control, it is preferable to perform control to apply the requested maximum braking force. In this way, the deceleration operation intended by the driver can be reliably performed, and the vehicle speed can be controlled from the stop state to the set upper limit vehicle speed only by the brake operation.
[0008]
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.
[0009]
FIG. 1 is a system configuration diagram of a travel control apparatus 100 according to the present invention. The traveling control device 100 also serves as a braking control device that controls the braking force applied to each wheel by electronic control. The ECU 1 serving as a control unit includes a CPU, a ROM, a RAM, an input signal circuit, an output signal circuit, a power supply circuit, and the like, and stores therein a braking control routine and an upper limit vehicle speed control routine.
[0010]
The braking device 2 is a hydraulic brake system capable of independently controlling the braking force applied to each wheel. The wheel cylinder 22 is disposed on each wheel and operates a hydraulic brake (not shown), and the wheel. An actuator 20 that independently adjusts the hydraulic pressure applied to each of the cylinders 22; and a master cylinder 23 that is connected to the brake pedal 25 and applies hydraulic pressure to the actuator 20 according to the driver's brake operation. An output signal of the hydraulic pressure sensor 24 that detects the hydraulic pressure and the hydraulic pressure sensor 22 that detects the pressure supplied to the wheel cylinder 22 in the actuator 20 is input to the ECU 1. The ECU 1 further receives an output signal of a wheel speed sensor 3 that is disposed on each wheel and detects the wheel speed.
[0011]
Next, the upper limit vehicle speed guard process in this travel control device will be specifically described. FIG. 2 is a flowchart thereof. This process is repeatedly executed at a predetermined timing from when the upper limit vehicle speed guard is set by the ECU 1 until it is released. This upper limit vehicle speed guard is a control in a slow running mode in which the vehicle speed during creep running is maintained below a predetermined upper limit vehicle speed Vref, and the vehicle speed V can be adjusted between 0 and Vref by operating only the brake pedal 25. It is.
[0012]
In step S1, the vehicle speed V is first calculated based on each wheel speed read from the wheel speed sensor 3. Next, in step S2, dev1 and dev2 which are deviations between the vehicle speed V, the upper limit vehicle speed Vref and the control start vehicle speed Vctrl are calculated.
[0013]
In step S3, the obtained deviation dev2 is determined. If the deviation dev2 is positive, that is, if the vehicle speed V exceeds the control start vehicle speed Vctrl, the routine proceeds to step S4, where the deviation dev1, its differential value Δdev1, and the target control oil pressure P1 at the previous time step are used for the current target control. Set the hydraulic pressure P1. In setting, for example, when dev1 is positive, that is, when the vehicle speed V is less than Vref, P1 is increased faster as dev1 is closer to 0 and the approaching speed is faster, and dev1 is negative, that is, the vehicle speed V exceeds Vref. For this reason, it is preferable to perform control so that P1 increases faster as dev1 increases and increases or decreases toward zero.
[0014]
If the deviation dev2 is not positive, that is, if the vehicle speed V is less than or equal to the control start vehicle speed Vctrl, the process proceeds to step S5 and 0 is set to the target control oil pressure P1.
[0015]
In either case after steps S4 and S5, the process proceeds to step S6, and the calculated target control oil pressure P1 and the master cylinder oil pressure generated in the master cylinder 23 when the driver operates the brake pedal 25 are detected by the oil pressure sensor 24. A higher value is set as the value of the control oil pressure Pt among the braking oil pressure P2 obtained based on the braking force requested by the driver and the required braking force such as ABS, VSC, etc. In step S7, the actuator 20 is controlled to adjust the brake hydraulic pressure applied to each wheel cylinder 22 so that the control hydraulic pressure Pt thus obtained is achieved.
[0016]
FIG. 3 is a time chart showing an example of the processing result. The control hydraulic pressure P1 by the vehicle speed control is applied from the time t1 when the vehicle speed V exceeds Vctrl. The control hydraulic pressure increases as the vehicle speed increases, and the braking force is increased to suppress the vehicle speed from exceeding Vref. When the vehicle speed exceeds Vref, the vehicle speed is controlled to be kept below Vref by applying a larger braking force. Here, when the driver starts operating the brake pedal 25 from time t2, P1 is preferentially applied until time t3 when the braking hydraulic pressure P2 obtained from the required braking force is smaller than P1, but P2 is applied. If P1 exceeds P1, P2 is preferentially applied, so that a braking force in accordance with the driver's intention can be applied, thereby improving the controllability of the vehicle.
[0017]
In this way, the braking force for actual upper limit vehicle speed control is applied not from the time when the upper limit vehicle speed Vref is exceeded, but from the lower vehicle speed Vctrl, so that the vehicle speed does not cause hunting in the vicinity of the upper limit vehicle speed. Can be suppressed. Further, it becomes difficult to exceed the upper limit vehicle speed Vref, and the driver can utilize the entire vehicle speed region up to the vicinity of the upper limit vehicle speed. For this reason, it is effective as the upper limit vehicle speed control in the slow running mode. It is preferable that the torque increase process is performed in this slow speed running mode to increase the engine speed during idling so that the upper limit vehicle speed Vref can be shifted to the high speed side.
[0018]
【The invention's effect】
As described above, according to the present invention, since vehicle speed control is performed so that the braking force is applied from the time when the vehicle speed lower than the upper limit vehicle speed is exceeded, the vehicle speed hunting occurs near the upper limit vehicle speed. This improves the ride comfort and improves the driver's control of the vehicle speed.
[Brief description of the drawings]
FIG. 1 is a system configuration diagram of a travel control device according to the present invention.
FIG. 2 is a flowchart showing an upper limit vehicle speed guard process in the apparatus of FIG. 1;
FIG. 3 is a time chart showing an example of the processing result of FIG. 2;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... ECU, 2 ... Braking device, 3 ... Wheel speed sensor, 20 ... Actuator, 21, 24 ... Hydraulic sensor, 22 ... Wheel cylinder, 23 ... Master cylinder, 25 ... Brake pedal, 100 ... Travel control device.

Claims (3)

In a travel control device that performs vehicle speed control so as to be equal to or lower than a set upper limit vehicle speed determined by an engine speed during idling by applying a braking force to the vehicle using a braking system,
A travel control device that applies braking force according to a deviation between the upper limit vehicle speed and a current vehicle speed when a vehicle speed during creep travel exceeds a control start vehicle speed lower than the upper limit vehicle speed.   2. The travel control device according to claim 1, wherein when another braking force application request is detected during the vehicle speed control, a control for applying the requested maximum braking force is performed.   3. The travel control device according to claim 2, wherein when there is no other braking force application request, vehicle speed control is performed so that the vehicle speed converges to a braking force that matches the upper limit vehicle speed.

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