JPH0971258A - Steering device of vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a play feeling of steering in the direction having the posibility of collision, and to improve the steering feeling, by providing a means to suppress the steering when the steering torque is at a set value or higher, and the possibility of collision is generated, and setting to increase the set value of the steering torque when the car speed is increased. SOLUTION: A set value Ta of the steering torque is made constant when the car speed is less than a certain speed va requiring no steering suppression, and the set value Ta is increased proportionally with the car speed v when the car speed is at the speed va or higher. When the detected torque T is at the set value Ta or higher, the steering direction is decided by the signal from a torque sensor 3. And by the obstacle detecting signals from sensors 53, 54, 55, and 56 in the steering direction, the possibility of collision of a vehicle 10 and an obstacle is decided. When it is decided that there is a possibility of collision, the steering is suppressed. When the steering torque T required to the steering in the direction having the possibility of collision is less than the set value Ta, the steering is not suppressed, and as a result, a play feeling of steering can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steering system capable of preventing a running vehicle from colliding with an obstacle.

[0002]

2. Description of the Related Art In order to prevent a vehicle from colliding with an obstacle such as a side or rear side guardrail or another vehicle at the time of a lane change or the like, there is a possibility of collision between the vehicle and the obstacle. Based on this, a steering device that suppresses steering has been proposed. For example, when the obstacle is detected on the rear side of the vehicle, the application of the steering assist force is released, the steering suppression force is applied in the direction opposite to the direction in which the vehicle is trying to steer, or the lane currently being driven is maintained. It has been proposed to control the steering device in order to suppress steering and allow the driver to recognize the presence of an obstacle (Japanese Patent Laid-Open No. 5-29425).
No. 0, JP-A-4-19274).

[0003]

However, when such a possibility of collision occurs, even if the current lane is maintained without actually changing the lane in the direction of the possibility of collision. , When the steering is suppressed, the feeling of play of steering in the direction in which there is a possibility of collision disappears,
There is a problem that the steering feeling is deteriorated.

An object of the present invention is to provide a vehicle steering system that can solve the above problems.

[0005]

A vehicle steering system according to the present invention comprises means for detecting a steering torque, means for determining whether or not the steering torque is equal to or greater than a set value, and an obstacle detected in the steering direction. Means for determining whether or not there is a possibility of collision with the vehicle, and the steering torque is equal to or greater than a set value, and
And means for suppressing steering when a possibility of collision occurs,
The set value of the steering torque is set to increase as the vehicle speed increases.

According to the configuration of the present invention, if the steering torque required for steering in the direction in which there is a possibility of collision is less than the set value, steering is not suppressed, so steering in the direction in which there is a possibility of collision. It is possible to obtain a feeling of play and to prevent deterioration of steering feeling. Further, as shown in the comparative example of FIG. 10, when the set value Tc of the steering torque is constant with respect to the vehicle speed v, the play range of the steering becomes small at the time of high speed traveling, and the steering feeling is sufficiently lowered. Cannot be prevented. This is because when the vehicle speed increases, the self-aligning torque that acts on the tire from the road surface increases and the torque required for steering increases even when the steering angle is the same as during low-speed traveling. On the other hand, according to the configuration of the present invention, since the set value of the steering torque increases as the vehicle speed increases, it is possible to prevent the steering play range from decreasing even if the self-aligning torque increases during high-speed traveling. However, it is possible to sufficiently prevent deterioration of steering feeling.

A means for controlling the actuator for generating a steering assist force by a control value according to the detected steering torque, and the steering torque is equal to or more than a set value, and
Preferably, the control value is changed so as to suppress steering when a collision possibility occurs, and the rate of increase of the steering assist force with respect to the steering torque is preferably set to decrease as the vehicle speed increases. .

By applying the present invention to the power steering device, the steering restraining force can be applied by the steering assist force generating actuator. The rate of increase of the steering assist force with respect to the steering torque decreases as the vehicle speed increases, so that traveling stability is improved at high speeds and turning performance is improved at low speeds. In this case, since the steering assist force decreases at high speed, the torque required for steering increases even when the steering angle is the same as during low speed traveling. According to the configuration of the present invention, since the set value of the steering torque increases as the vehicle speed increases, it is possible to prevent the steering play range from decreasing even during high-speed traveling.
It is possible to sufficiently prevent the steering feeling from deteriorating, and to improve the running stability at high speed and the turning performance at low speed.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

The rack and pinion type electric power steering system 1 shown in FIG. 1 includes an input shaft 2 connected to a steering wheel H of a vehicle 10 and an output shaft 4 connected to the input shaft 2 via a torque sensor 3. Is equipped with. The output shaft 4 is connected to a pinion 6 via a universal joint 5, and a steering wheel 8 is connected to a rack 7 that meshes with the pinion 6. As a result, the steering torque is transmitted to the rack 7 via the steering wheel H, the input shaft 2, the torque sensor 3, the output shaft 4, and the pinion 6, and the movement of the rack 7 steers the vehicle 10.

As shown in FIG. 2, the torsion bar 11 is inserted into the input shaft 2 and the output shaft 4, and the pin 1 is inserted.
It is connected by 8 and 19. The input shaft 2
Is configured by connecting the first shaft 2a on the steering wheel H side and the second shaft 2b on the torque sensor 3 side by a pin 18. As a result, the input shaft 2 and the output shaft 4 relatively rotate in accordance with the steering torque. One end of the input shaft 2 is inserted into a recess 4a formed at one end of the output shaft 4, and as shown in FIG. 3, a part of the outer peripheral surface of the input shaft 2 and a part of the inner peripheral surface of the recess 4a. Are non-circular portions 2'and 4'opposed to each other. By contacting the non-circular portion 2'on the input shaft 2 side and the non-circular portion 4'on the output shaft 4 side,
The relative rotatable amount of the input shaft 2 and the output shaft 4 is regulated within a certain range, and damage to the torsion bar 11 is prevented. A worm wheel 12 is fitted on the outer circumference of the output shaft 4, and a worm gear 15 that meshes with the worm wheel 12 is provided.
Is connected to a steering assist force generating motor (actuator) 13 as shown in FIG.

As shown in FIG. 2, the torque sensor 3
Includes a housing 16 fitted to the input shaft 2 and the output shaft 4 so as to be rotatable relative to each other. A first detection ring 21 made of a magnetic material is fitted to the outer circumference of the input shaft 2, and a second detection ring 23 made of a magnetic material is fitted to the outer circumference of the output shaft 4 so as to rotate together. The one end surface of the first detection ring 21 and the other end surface of the second detection ring 23 are arranged so as to face each other, and each of the detection rings 21, 23
A plurality of teeth 21a and 23a are respectively provided on the facing end surfaces of the above along the circumferential direction. The other end side of the first detection ring 21 is a small diameter portion 21b having an outer diameter smaller than that of the one end side. Each of the detection rings 21 and 23 is attached to the housing 16.
The first detection coil 33 that covers the facing portion and the second detection coil 34 that covers the small-diameter portion 21b of the first detection ring 21 are held, and the detection coils 33 and 34 configure the signal processing circuit shown in FIG. . That is, the first detection coil 33 has the resistor 4
Is connected to the oscillator 46 via the second detection coil 34.
Is connected to an oscillator 46 via a resistor 47, and the detection coils 33 and 34 are connected to a differential amplifier circuit 48.

The transmission of the steering torque from the input shaft 2 to the output shaft 4 causes the torsion bar 11 to elastically twist, and
When the detection ring 21 and the second detection ring 23 rotate relative to each other, the facing areas of the teeth 21a and 23a of the detection rings 21 and 23 change. Due to the area change, the tooth 21
Since the magnetic resistance between a and 23a facing each other changes, the output of the first detection coil 33 changes according to the change, and the steering torque is detected corresponding to the output. As a result, the torque sensor 3 can detect the steering torque up to the detection limit at which the non-circular portion 2'on the input shaft 2 side and the non-circular portion 4'on the output shaft 4 contact each other. Further, by setting the outer diameter of the small diameter portion 21b so that the magnetic resistance on the side of the first detection coil 33 and the magnetic resistance on the side of the second detection coil 34 become equal in the state where no steering torque is applied, The output variation of the first detection coil 33 due to the temperature variation is made equal to the output variation of the second detection coil 34 due to the temperature variation, and is canceled by the differential amplifier circuit 48, and the temperature variation of the detected value of the transmission torque is compensated. The output of the torque sensor 3 becomes zero at the midpoint where steering is not performed, and the absolute value of the output at the detection limit during right steering and the absolute value of the output at the detection limit during left steering become equal. As described above, in the assembling process, after the relative positions of the input shaft 2 and the output shaft 4 are determined, they are connected by the torsion bar 11 via the pins 18 and 19.

As shown in FIG. 1, the torque sensor 3
Is connected to a controller 50 mainly composed of a computer. The controller 50 includes a motor 13, a vehicle speed detection sensor 51, and a plurality of obstacle detection sensors 53, 54, 55 attached to the vehicle 10.
56 is connected. Those obstacle detection sensors 53, 5
Reference numerals 4, 55, and 56 are for detecting obstacles such as other vehicles or guardrails on the left and right sides and the left and right rear sides of the vehicle 10, and are transmitters that emit radar waves such as lasers and ultrasonic waves from the vehicles. And a receiver for the radar wave and an amplifier for the received radar wave, and the controller 50 calculates the distance to the obstacle based on the time difference from the transmission to the reception of the radar wave. .

The controller 50 calculates a control value I corresponding to the drive current of the steering assisting force generating motor 13 based on the output of the torque sensor 3 and the vehicle speed, and drives the motor 13 by the calculated control value I. Control. That is, FIG. 5 shows the relationship between the steering torque and the control value I when steering assist is performed. When the steering torque increases, the control value I, that is, the steering assist force increases, and the rate of increase is large at low speed and small at high speed. Become. As a result, the turning performance at low speed and the running stability at high speed are improved. When the controller 50 performs steering assist, the controller 50 shown in FIG.
The control value I is calculated so as to satisfy the relationship shown in (1), and when the possibility of collision occurs, the control value I is changed to suppress the steering. The relationship between the steering torque and the control value I shown in FIG. 5 is an example, and the present invention is not limited to this. For example, not only the vehicle speed but also the steering angle is detected, and the control value I is calculated as the steering angle. In a large low speed state, the steering assist force may be increased to improve the turning performance of the vehicle, and in a high speed state where the steering angle is small, the steering assist force may be decreased to improve the running stability.

A control procedure based on the control program of the controller 50 will be described with reference to the flowchart shown in FIG.

First, the torque sensor 3 and the vehicle speed detection sensor 5
1 and the signals from the obstacle detection sensors 53, 54, 55, 56 are read, the steering torque and the vehicle speed are obtained, and the distance to the obstacle is calculated (step 1).

Next, the detected torque T is set to the set value T.
It is judged whether or not it is a or more (step 2). The set value T
It is assumed that a increases as the vehicle speed increases. In the present embodiment, as shown in FIG. 7, the set value Ta is constant below a constant vehicle speed va that does not require steering suppression, and the set value Ta is increased in proportion to the vehicle speed v at or above the constant vehicle speed va.

When the detected torque T is less than the set value Ta, the control value I of the steering assisting motor 13 is calculated as described above (step 3), and the motor 13 is controlled by the control value I.
To assist the steering (step 4), and the process returns to step 1.

When the detected torque T is equal to or larger than the set value Ta, the steering direction is judged by the signal from the torque sensor 3, and the sensors 53, 54, 55, 5 in the steering direction are determined.
The obstacle detection signal from 6 determines the possibility of collision between the vehicle 10 and the obstacle (step 5). For example, when an obstacle is detected within a predetermined distance in the steering direction, it is determined that there is a possibility of collision.

If there is no possibility of collision, step 3,
In step 4, steering assist is performed, and the process returns to step 1.

When it is determined in step 5 that there is a possibility of collision, steering is suppressed (step 6) and the process returns to step 1. The method of suppressing the steering is not particularly limited,
For example, the application of the steering assist force is released, or the steering restraining force is applied in the direction opposite to the direction in which the steering is attempted.

According to the above configuration, if the steering torque T required for steering in the collision-prone direction is less than the set value Ta, steering is not suppressed, so steering in the collision-prone direction. It is possible to obtain a feeling of play and to prevent deterioration of steering feeling. Further, since the set value Ta of the steering torque increases as the vehicle speed v increases, even if the self-aligning torque increases during high speed traveling,
Even when improving the running stability at high speeds and the turning performance at low speeds by reducing the rate of increase of the steering assist force with respect to the steering torque by increasing the vehicle speed, the steering play range at high speeds Can be prevented from becoming small, and the steering feeling can be sufficiently prevented from deteriorating.

The present invention is not limited to the above embodiment. For example, as shown in the first modification of FIG.
It is possible to increase a as a quadratic function of the vehicle speed v.
Further, as shown in the second modified example of FIG. 9, the set value Ta can be increased stepwise with respect to the vehicle speed v. Further, the obstacle detecting means is not particularly limited, and for example, the presence or absence of the obstacle approaching the vehicle may be determined based on the image around the vehicle by the CCD camera. Further, the steering direction detecting means is not particularly limited, and may be detected by a winker operation signal, for example.

[0025]

According to the vehicle steering system of the present invention, when a possibility of collision with an obstacle occurs, a feeling of steering play can be properly secured in accordance with the vehicle speed, and a reduction in steering feeling can be prevented. Further, by applying the present invention to the power steering device, while improving the running stability at high speeds and the turning performance at low speeds, a proper play feeling of the steering is ensured and deterioration of the steering feeling is prevented. it can.

[Brief description of drawings]

FIG. 1 is a structural explanatory view of a power steering device according to an embodiment of the present invention.

FIG. 2 is a sectional view of a torque sensor according to an embodiment of the present invention.

FIG. 3 is a sectional view taken along line III-III in FIG. 2;

FIG. 4 is a circuit diagram of a torque sensor according to an embodiment of the present invention.

FIG. 5 is a diagram showing a relationship between a control value and a steering torque according to the embodiment of the present invention.

FIG. 6 is a flowchart showing a control procedure of the power steering device according to the embodiment of the present invention.

FIG. 7 is a diagram showing a relationship between a torque setting value and a vehicle speed according to the embodiment of the present invention.

FIG. 8 is a diagram showing a relationship between a torque setting value and a vehicle speed according to a first modified example of the present invention.

FIG. 9 is a diagram showing a relationship between a torque set value and a vehicle speed according to a second modified example of the present invention.

FIG. 10 is a diagram showing a relationship between a torque set value and a vehicle speed in a comparative example of the present invention.

[Explanation of symbols]

 1 Power Steering Device 3 Torque Sensor 13 Motor (Actuator) 50 Controller 51 Vehicle Speed Detection Sensor 53, 54, 55, 56 Obstacle Detection Sensor

Claims (2)

[Claims] 1. A means for detecting a steering torque, a means for judging whether or not the steering torque is equal to or more than a set value, and a means for judging the possibility of collision between an obstacle detected in the steering direction and a vehicle. And a means for suppressing steering when the steering torque is equal to or greater than a set value and a collision possibility occurs, and the set value of the steering torque is set to increase as the vehicle speed increases. Vehicle steering system. 2. A means for controlling an actuator for generating a steering assist force according to a control value according to a detected steering torque, and steering suppression when the steering torque is equal to or more than a set value and a collision possibility occurs. 2. The vehicle steering system according to claim 1, further comprising means for changing the control value so that the steering assist force increases with respect to the steering torque so as to decrease as the vehicle speed increases.