JP2001187582A - Power steering - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power steering capable of providing a semi-automated steering feeling by appropriately assisting steering in deviating from a lane. SOLUTION: When a vehicle deviates to the left side of a lane, a target current corresponding to leftward steering torque is diminished, and a target current corresponding to rightward steering torque is enlarged. When the vehicle deviates to the right side of the lane, the target current corresponding to the rightward steering torque is diminished, and the target current corresponding to the leftward steering torque is enlarged. A corrective steering burden for keeping the lane can thereby be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power steering device mounted on a vehicle and used.

[0002]

2. Description of the Related Art Conventionally, there has been a power steering apparatus that transmits a generated torque of an electric motor to a steering mechanism of a vehicle or incorporates a hydraulic cylinder to provide a steering assisting force to a steering mechanism according to steering by a steering wheel. Used. In such a power steering device, for example, a steering assist force according to a steering torque, which is a torque applied to a steering wheel, is generated from an actuator such as an electric motor or a hydraulic cylinder. It is generated symmetrically for left steering and right steering.

However, when the vehicle deviates from the lane,
Steering assistance in the direction of returning to the original lane is more important. On the other hand, there has been proposed an automatic steering system for automatically controlling a steering mechanism. However, in such an automatic steering system, a driver only needs to temporarily steer at the time of emergency avoidance or the like. Problems such as reduced sleepiness and drowsiness.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a power steering apparatus capable of giving a semi-automated steering feeling by appropriately performing steering assist when the vehicle departs from the lane.

[0005]

Means for Solving the Problems and Effects of the Invention The invention according to claim 1 for achieving the above object is used mounted on a vehicle, and is used in accordance with steering by a steering means (1). In the power steering device for applying the steering assist force to 3), an actuator (M) for applying the steering assist force to the steering mechanism and whether or not the vehicle deviates from the lane or tends to deviate from the lane is detected. A lane departure detecting means (11) for detecting a vehicle deviating from the lane or having a tendency to deviate from the lane; Control means (12, 14) for driving and controlling the actuator so as to increase the steering assist force for steering in the direction of returning to the normal state. It is a word steering apparatus. It should be noted that the alphanumeric characters in parentheses represent corresponding components in the embodiments described later.

The device of the present invention provides a basically manual steering system in which a steering assisting force is applied to a steering mechanism in accordance with steering by a steering means. However, this does not prevent the present invention from being applied in the manual mode in the automatic steering system. According to the invention,
If it is detected that the vehicle has deviated from the lane or is likely to deviate from the lane, the steering assist force in the direction of returning to the original lane is larger than the steering assist force in the direction of departure from the lane. The actuator is controlled so that As a result, the steering in the correct traveling direction is supported by the strength of the steering assist, and the steering load for maintaining the lane is reduced, and a semi-automated steering feeling is obtained.

[0007] Since the steering system is basically a manual steering system, an appropriate sense of tension is maintained for the driver, and the above-mentioned problems in the automatic steering system are eliminated.

[0008]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a block diagram showing an electrical configuration of a power steering device according to one embodiment of the present invention. A steering torque applied to a steering wheel 1 as a steering means is transmitted to a steering mechanism 3 via a steering shaft 2. A steering assist force is transmitted to the steering mechanism 3 from an electric motor M as an actuator.

The steering shaft 2 is divided into an input shaft 2A connected to the steering wheel 1 side and an output shaft 2B connected to the steering mechanism 3 side.
The input shaft 2A and the output shaft 2B are connected to each other by a torsion bar 4. Torsion bar 4
Generates twist in accordance with the steering torque, and the direction and amount of the twist are detected by the torque sensor 5.

The torque sensor 5 is, for example, an input shaft 2A
It is of a magnetic type that detects a magnetic resistance that changes according to a change in the positional relationship between the motor and the output shaft 2B in the rotation direction. The output signal of the torque sensor 5 is input to an electronic control unit 10 (ECU) including a microcomputer and the like. The electronic control unit 10 includes an image signal from an in-vehicle camera 6 that captures an image in front of the vehicle equipped with the electric power steering device, an output signal of a vehicle speed sensor 7 for detecting the speed of the vehicle, and Is entered.

The electronic control unit 10 uses the image in front of the vehicle captured by the on-board camera 6 or the vehicle speed detected by the vehicle speed sensor 7 to determine whether the vehicle has deviated from the lane or has a tendency to deviate from the lane. A lane departure detection unit 11 is provided for detecting whether the lane departure has occurred. The lane departure detection unit 11
A lane marking indicating lane division on the road surface is extracted by image recognition processing, and based on this, it is detected whether the vehicle has deviated from the lane or has a tendency to deviate from the lane. Such processing includes, for example, Japanese Patent Application Laid-Open No. 9-254.
The technique disclosed in JP-A-803-803 can be used.

The electronic control unit 10 further stores an assist table storing an assist table for determining a target current of the electric motor M in accordance with the steering torque detected by the torque sensor 5 and the vehicle speed detected by the vehicle speed sensor 7. A section 12 is provided. The motor driver 13 for driving the electric motor M is controlled based on the target current determined by the assist table in the assist table storage unit 12.

The assist table storage unit 12 is constituted by using a part or the whole storage area of a memory element such as a nonvolatile memory, and stores an assist table storing a target current value corresponding to each value of the steering torque. Are stored. Then, one of the assist tables is selected and used by the control unit 14. The control unit 14 selects one of the assist tables according to the detection result of the lane departure detection unit 11.

FIGS. 2A, 2B, and 2C are diagrams illustrating a plurality of assist tables stored in the assist table storage unit 12, and are drawn in the form of a graph representing a target current with respect to a steering torque. ing. In FIG. 2, the steering torque in the right direction is represented by a positive value, and the steering torque in the left direction is represented by a negative value. Similarly, a target current that generates steering assist in the right direction is represented by a positive sign, and a target current that generates steering assistance in the left direction is represented by a negative sign.

When the lane departure detecting unit 11 does not detect a deviation from the lane or its tendency, the first assist table shown in FIG. 2A is used. The first assist table is set so as to generate a steering assist force symmetrically with respect to left and right steering torques. That is,
The relationship between the absolute value of the steering torque and the absolute value of the target current is the same for both left and right steering. When the lane departure detecting unit 11 detects the lane departure to the left or the tendency thereof, the control unit 14 employs the second assist table shown in FIG. In the second assist table, a first assist table (FIG.
(a)), the steering assist force (absolute value of the target current) for leftward steering is reduced,
The steering assist force (the absolute value of the target current) for the rightward steering is increased. The steering assist force is set to be generated asymmetrically with respect to the left and right steering torques. That is, the absolute value of the target current corresponding to the steering torque in the direction deviating from the lane (in this case, the left direction) is determined by the target current corresponding to the steering torque in the direction of returning to the original lane (in this case, the right direction). It is smaller than the absolute value.

On the other hand, when the lane departure detecting unit 11 detects the lane departure to the right or its tendency, the control unit 14
The third assist table shown in FIG. 2C is employed. In the third assist table, the steering assist force (the absolute value of the target current) for the rightward steering is reduced as compared with the first assist table (FIG. 2A) which is normally applied. The steering assist force (the absolute value of the target current) for the leftward steering is increased. The steering assist force is set to be generated asymmetrically with respect to the left and right steering torques. That is, the absolute value of the target current corresponding to the steering torque in the direction deviating from the lane (in this case, rightward) is determined by the target current corresponding to the steering torque in the direction of returning to the original lane (in this case, leftward). It is smaller than the absolute value.

Thus, according to this embodiment,
When the deviation from the lane or its tendency is detected, the steering assist force in the direction to return to the lane becomes larger than the steering assist force in the direction to deviate from the lane, so that the return to the lane is improved. Can be assisted. As a result, a semi-automated steering system based on the manual steering system can be realized, and the correction steering load for maintaining the lane can be reduced. As compared with a completely automated steering system, a driver can maintain a moderate tension, and a highly safe steering system can be provided.

Although the embodiment of the present invention has been described above, the present invention can be embodied in other forms.
For example, in the above-described embodiment, three assist tables are switched and used in response to normal driving, lane departure to the left side, and lane departure to the right side. The same processing can be performed by correcting the target current output from the assist table.

In the above-described embodiment, the power steering device using an electric motor as an actuator is taken as an example. However, the present invention can be applied to, for example, a device using a hydraulic cylinder as an actuator. In addition, various design changes can be made within the scope of the matters described in the claims.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a conceptual configuration of a power steering device according to an embodiment of the present invention.

FIG. 2 (a) Normal time, (b) Left lane departure, and
(c) is a graph illustrating an assist table used when the vehicle departs from the lane to the right.

[Explanation of symbols]

 Reference Signs List 1 steering wheel 3 steering mechanism M electric motor 6 vehicle-mounted camera 7 vehicle speed sensor 10 electronic control unit 11 lane departure detection unit 12 assist table storage unit 13 motor driver 14 control unit

Claims (1)

[Claims] 1. A power steering device mounted on a vehicle for applying a steering assist force to a steering mechanism in response to steering by steering means, comprising: an actuator for applying a steering assist force to the steering mechanism; A lane departure detecting means for detecting whether the vehicle has deviated or is likely to deviate from the lane; and Control means for controlling the drive of the actuator such that the steering assist force for steering in the direction of returning to the lane becomes larger than the steering assist force for steering in the direction of turning.