JPH10218001A - Steering device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steering device for a vehicle having a natural steering sense without generating a feeling of physical disorder. SOLUTION: A device comprises a steering means 2 not mechanically connected to a steering mechanism 1 for changing a direction of a wheel 10, steering angle detection means 33 for detecting a steering angle of the steering means 2, and a reaction force giving means 3 giving reaction force toward a neutral position to the steering means 2. In accordance with a steering angle detected by the steering angle detection means 33, a steering angle of the steering mechanism 1 is controlled to be adjusted. A setting means 4 is provided, which, in a prescribed range including the neutral position of steering angle detected in the steering angle detection means 33, sets a dead band without giving reaction force by the reaction force giving means 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle steering system for steering a vehicle according to a driver's operation.

[0002]

2. Description of the Related Art Steering of a vehicle is performed by operating a steering means disposed inside the vehicle compartment, for example, by rotating a steering wheel, by steering a steering wheel (generally, a front wheel). Is transmitted to a steering mechanism arranged outside the vehicle. In recent years, an actuator for assisting steering such as a hydraulic cylinder and an electric motor is arranged in the middle of the steering mechanism, and the actuator is driven based on a detection result of an operating force applied to a steering wheel for steering. 2. Description of the Related Art A power steering device (power steering device), which is configured to assist the operation of a steering mechanism in accordance with the rotation of a steering wheel with a force generated by an actuator to reduce a driver's labor burden for steering, has become widespread. ing.

However, in such a conventional steering apparatus for a vehicle, a mechanical connection between a steering wheel, which is a steering means, and a steering mechanism is required, and the position of the steering wheel in the vehicle interior is limited. There is a problem that the connection to the steering mechanism outside the vehicle compartment is limited, and even if the steering wheel is arranged to be connectable, complicated connection is required to realize the connection. This requires a structure, which is a factor that hinders weight reduction of the vehicle and simplification of the assembly process.

[0004] For example, Japanese Utility Model Publication No. 2-29017 discloses a steering device for a vehicle which is a linkless power steering device for solving such a problem. This steering apparatus for a vehicle arranges a steering wheel separately from a steering mechanism, and similarly to an actuator for steering assistance in a power steering apparatus, an electric motor as a steering actuator is provided in the middle of the steering mechanism. The electric motor is driven based on the detection result of the operation direction and the operation amount of the steering wheel, thereby performing steering according to the operation of the steering wheel.

A steering wheel not mechanically connected to a steering mechanism is provided with a reaction actuator having a motor. The reaction force actuator applies a reaction force toward the neutral position to the steering wheel by driving the motor based on the detection result of the vehicle speed and the steering angle of the steering wheel. As shown in FIG. 4 which is a characteristic diagram in which a reaction force indicating torque-steering angle is obtained for each vehicle speed on the vertical axis-horizontal axis, the reaction force is large and small according to the vehicle speed and the steering angle. It has the following characteristics. In such a vehicle steering system, the torque applied to the steering wheel is detected against the reaction force, and the motor current of the electric motor for steering is increased or decreased according to the detection result. Increase or decrease the steering force. As a result, steering can be performed with the same feeling as a general vehicle steering device (connection type steering device) in which the steering wheel and the steering mechanism are mechanically connected.

[0006] The vehicle steering system of the separated type configured as described above increases the degree of freedom in arranging the steering wheel.
In addition to the above-mentioned objectives such as reducing the weight of the vehicle, realization of new steering means such as levers and pedals instead of the steering wheel, detection of guidance signs on the road surface, reception of satellite information, etc. It is useful for the future development of automobile technology such as realization.

[0007]

FIG. 4 is a characteristic diagram in which the vertical axis-horizontal axis shows the reaction force indicating torque-steering angle for each vehicle speed, as described above. The reaction force applied to the steering wheel is shown in FIG. Indicates that the increase / decrease is controlled in accordance with the vehicle speed and the steering angle. However, the neutral position of the steering angle is
Since the reaction force is estimated during the steering operation and is not always fixed, if the direction of the reaction force is switched at the neutral position (estimated position) of the steering angle, the reaction force is changed at a position other than the true neutral position. May be switched, giving the driver an uncomfortable feeling. Further, when the direction of the reaction force is switched at one point at the neutral position, and the direction of the reaction force changes suddenly, the movement of the steering wheel may not be smooth and may give a sense of incongruity. On the other hand, when the steering wheel rotates lightly at high speed, the steering feeling is not good, so it is better to always apply a reaction force at high speed.

In order to eliminate the sense of discomfort generated in the steering wheel, the dead zone of the assist torque with respect to the steering torque is widened as the vehicle speed increases.
There is an electric power steering apparatus disclosed in Japanese Patent Application Laid-Open No. 81866. However, this electric power steering apparatus expands or contracts the width of a dead zone of assist torque, and does not require a reaction force because it is not a linkless power steering apparatus. .
The present invention has been made in view of the above circumstances,
It is an object of the present invention to provide a vehicle steering device having a natural steering feeling that does not cause discomfort.

[0009]

According to a first aspect of the present invention, there is provided a steering apparatus for a vehicle, wherein the steering means is not mechanically connected to a steering mechanism for changing the direction of wheels, and a steering angle of the steering means is determined. A steering angle detecting means for detecting the steering angle, a reaction force applying means for applying a reaction force toward the neutral position to the steering means, and a steering angle of the steering mechanism according to the steering angle detected by the steering angle detecting means. A vehicle steering device that controls increase / decrease of the steering angle, wherein a setting unit for setting a dead zone in which the reaction force applying unit does not apply a reaction force is provided in a predetermined range including a neutral position of the steering angle detected by the steering angle detection unit. Features.

In this vehicle steering system, the setting means sets a dead zone in which the reaction force applying means does not apply the reaction force to a predetermined range including the neutral position of the steering angle detected by the steering angle detection means. As a result, the neutral position (estimated position) of the steering angle can be absorbed in the dead zone, so that the direction of the reaction force does not switch at a position other than the true neutral position, and the steering wheel moves smoothly. Thus, a vehicle steering device having a natural steering feeling without causing a sense of discomfort can be realized.

A vehicle steering apparatus according to a second aspect of the present invention includes a vehicle speed detecting means for detecting a running speed of the vehicle, and the setting means increases or decreases the width of the dead zone in accordance with the running speed detected by the vehicle speed detecting means. It is characterized by comprising means for performing.

In this vehicle steering system, the vehicle speed detecting means detects the running speed of the vehicle, and the increasing / decreasing means in the setting means adjusts the steering angle according to the detected running speed, and the reaction force applying means changes the reaction force. Increase or decrease the width of the dead zone not provided. This makes it possible to reduce the width of the dead zone to a level that does not cause discomfort when driving at high speeds, where it is dangerous for the steering wheel to rotate lightly, realizing a vehicle steering system that has a natural steering feeling that does not cause discomfort. it can.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings showing an embodiment. FIG. 1 is a block diagram showing the overall configuration of a vehicle steering system according to the present invention. The vehicle steering system includes a steering mechanism 1 for causing a pair of steering wheels 10, 10 arranged on the left and right sides of a vehicle body (not shown) to perform a steering operation, and a steering mechanism separated from the steering mechanism 1. A steering wheel 2, a reaction actuator 3 for applying a reaction force to the steering wheel 2, and a steering control unit 4 using a microprocessor. By operation, the steering motor 5 arranged in the middle of the steering mechanism 1 is driven to operate the steering mechanism 1.

As is well known, the steering mechanism 1 includes both ends of a steering shaft 11 that extends in the left-right direction of the vehicle body and slides in the axial direction, and knuckle arms 12 that support the wheels 10, 10.
12 are connected by separate tie rods 13, 13, respectively.
The tie rods 13 and 1 are moved by sliding the steering shaft 11 in both directions.
The knuckle arms 12, 12 are pushed and pulled via 3 to steer the wheels 10, 10 to the left and right. This steering is performed by the steering motor 5, which is coaxially formed in the middle of the steering shaft 11. The rotation is converted into sliding of the steering shaft 11 by an appropriate motion conversion mechanism.

The rotation of the steering shaft 11 around the axis thereof is restricted by rotation restricting means (not shown) interposed between the steering shaft 11 and the steering shaft housing 14. And the steering (steering of the steering wheels 10, 10) according to the rotation of the steering motor 5 is performed. The steering angles of the wheels 10, 10 steered in this way are determined by the relative sliding position between the steering shaft housing 14 on one side of the steering motor 5 and the steering shaft 11 as a medium. The output of the steering angle sensor 16 is provided to the steering control unit 4 together with the output of the rotary encoder 15 for detecting the rotational position of the steering motor 5.

The reaction force actuator 3 which is a reaction force applying means for applying a reaction force to the steering wheel 2 is an electric motor (for example, a three-phase brushless motor),
The casing is fixedly attached to an appropriate portion of a vehicle body (not shown). Steering wheel 2
Is coaxially fixed to a protruding end on one side of the rotating shaft 30, and the other end has a torsion spring 31 having a predetermined elasticity.
Thus, it is connected to an appropriate portion of the vehicle body (not shown).

The reaction force actuator 3 includes a drive circuit 3a corresponding to a reaction force instruction torque signal given from the steering control unit 4.
When the steering wheel 2 is mounted on one end of the rotating shaft 30, a force (reaction force) in a direction opposite to the operation direction is applied to the steering wheel 2 attached to one end of the rotating shaft 30. Therefore, it is necessary to apply a steering torque against the reaction force generated by the reaction force actuator 3 to the rotation operation of the steering wheel 2.
Is detected by a torque sensor 32 attached to the reaction force actuator 3. Further, the operation amount (steering angle) of the steering wheel 2 is detected including the operation direction by a rotary encoder 33 which is a steering angle detecting means attached to the reaction force actuator 3, and the detection result is based on the steering angle. It is provided to the control unit 4. Further, a current flowing from the drive circuit 3 a to the reaction force actuator 3 is detected by the current sensor 3 b and provided to the steering control unit 4.

The torsion spring 31 interposed between the other end of the rotating shaft 30 and a part of the vehicle body causes the rotating shaft 30 to rotate due to its elasticity when the rotating operation performed as described above is stopped. Thus, the steering wheel 2 returns to a predetermined neutral position. This return is necessary for returning the steering wheel 2 in accordance with the return operation of the wheels 10, 10 in the straight traveling direction, which occurs on the steering mechanism 1 side that is not mechanically connected.

As described above, the steering state actually occurring on the steering mechanism 1 side is given to the steering control unit 4 as an input from the rotary encoder 15 and the steering angle sensor 16. Steering wheel 2 as
Is provided as inputs from the torque sensor 32 and the rotary encoder 33. In addition to these, the output of the vehicle speed sensor 6 for detecting the running speed of the vehicle is provided to the input side of the steering control unit 4. Has been given.

On the other hand, as described above, the output of the steering control unit 4 is transmitted to the reaction force actuator 3 for applying a reaction force to the steering wheel 2 and the steering motor 5 for causing the steering mechanism 1 to perform a steering operation. The reaction force actuator 3 and the steering motor 5 perform different operations in response to an instruction signal from the steering controller 4.

The steering control unit 4 includes the steering wheel 2
Is determined, and a reaction force control for generating a reaction force instruction torque signal to the reaction force actuator 3 to generate a reaction force is performed. The reaction force to be applied to the steering wheel 2 has a dead zone where the reaction force becomes zero in a predetermined range including the neutral position of the steering angle of the steering wheel 2 as shown in FIG. The width of the dead zone decreases and increases in accordance with the level of the vehicle speed (running speed) and the steering angle given as an input of the vehicle, and in accordance with the level of the vehicle speed. .

This characteristic is stored in the steering control unit 4 as a table of steering angle-reaction force instruction torque for each vehicle speed.
The steering control unit 4 selects a table of steering angle-reaction force indicating torque according to the vehicle speed from the vehicle speed sensor 6 and sends a reaction force indicating torque signal to the reaction force actuator 3 so as to generate a reaction force according to the characteristics of the table. Emits.

The steering control unit 4 recognizes the operation angle including the operation direction of the steering wheel 2 based on the input from the rotary encoder 33 and recognizes the operation angle based on the input from the steering angle sensor 16 attached to the steering mechanism 1. A steering angle deviation from the actual steering angle is calculated, and the steering angle deviation is corrected so as to be larger or smaller according to the vehicle speed given as an input from the vehicle speed sensor 6 to obtain a target steering angle. The steering control operation for driving the steering motor 5 is performed until the following is obtained. At this time, an input from the rotary encoder 15 is used as a feedback signal for checking whether or not the steering motor 5 has reached a desired rotational position.

Hereinafter, a vehicle according to the present invention having such a configuration will be described.
The operation of the dual-purpose steering system is described based on a flowchart showing the operation.
It will be explained. FIG. 3 shows a vehicle steering system according to the present invention.
It is a flowchart which shows an operation. The steering control unit 4
The vehicle speed is read from the vehicle speed sensor 6 (S2).
Select a table of steering angle-reaction force instruction torque according to speed
(S4). Next, the steering control unit 4 selects the selected (S4).
From the table, detected by the rotary encoder 33
Reaction force indicating torque according to steering angle of steering wheel 2
K T _MIs read (S6) and operated by the torque sensor 32.
Rudder torque T_SIs detected (S8). Next, the reaction force indicating torque
K T_MAnd steering torque T_SAnd the torque deviation ΔI_n= T_M−
T _SIs calculated (S10), and the integral element I of the reaction force control is calculated._n= Δ
I_n× K_I(K_I: Predetermined integration constant) (S1)
2).

Next, the proportional element P _n = (ΔI _n -Δ
I _n-1 ) × K _P (ΔI _n-1 : torque deviation of previous cycle, K
_P: calculates a predetermined proportional constant) (S14), the electric motor of the target current of the reaction force actuator 3 (reaction force motor target _{current) J M = J 0 + I} n + P n (J 0: target current of the previous cycle) Is calculated (S16). Next, the current sensor 3b detects the current J _S of the electric motor of the reaction force actuator 3 (S18), and the current deviation ΔI _n '= J _M − between the target current J _M of the electric motor and the actual current J _{S. JS} is calculated (S20).

Next, the steering control unit 4 determines whether to integrate the reaction force control.
Element I_n'= ΔI_n'× K_I'(K_I': Predetermined integration constant
Number) (S22), and the proportional element P_n'= (ΔI_n′
-ΔI _n-1') × K_P'(ΔI_n-1': Current of previous cycle
Deviation, K_P': A predetermined proportional constant) (S2
4). Next, the target of the electric motor of the reaction force actuator 3
Voltage (reaction motor target voltage) V_M= V₀+ I_n'+
P_n′ (V₀: Target voltage of the previous cycle) (S2
6) The target voltage V is applied to the drive circuit 3a._MAnd output
The electric motor of the reaction force actuator 3 is driven.

Next, the target current J _M target current J ₀ of the previous period, the target voltage V _M to the target voltage V ₀ which last cycle, the torque deviation [Delta] I _n the torque deviation [Delta] I _n-1 of the previous cycle, The current deviation ΔI _n ′ is transferred to the current deviation ΔI _n−1 ′ of the previous cycle (S28), and the process returns. The above embodiment shows an example of the vehicle steering apparatus according to the present invention, and does not limit the configurations of the reaction force actuator 3 and the steering motor 5. Needless to say, other operation means such as a lever and a pedal can be used instead of 2. Further, although the example in which the width of the dead zone is increased or decreased according to the level of the vehicle speed as shown in FIG. 2 has been described, the width of the dead zone may be increased or decreased in another manner according to the level of the vehicle speed.

[0028]

According to the vehicle steering system of the first aspect of the present invention, the neutral position (estimated position) of the steering angle can be absorbed in the dead zone, so that the reaction force is generated at a position other than the true neutral position. Is not switched, the movement of the steering wheel is smooth, and a steering apparatus for a vehicle having a natural steering feeling without causing discomfort can be realized.

According to the vehicle steering system of the second aspect,
During high-speed driving, where it is dangerous to rotate the steering wheel lightly, it is possible to reduce the width of the dead zone to a degree that does not cause discomfort, and it is possible to realize a vehicle steering device that has a natural steering feeling that does not cause discomfort.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an overall configuration of a vehicle steering system according to the present invention.

FIG. 2 is a graph showing characteristics of a reaction force to be applied to a steering wheel of the vehicle steering system according to the present invention.

FIG. 3 is a flowchart showing the operation of the vehicle steering system according to the present invention.

FIG. 4 is a graph showing characteristics of a reaction force to be applied to a steering wheel of a conventional vehicle steering system.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 steering mechanism 2 steering wheel (steering means) 3 reaction force actuator (reaction applying means) 3a drive circuit 3b current sensor 4 steering control unit (setting means, increasing / decreasing means) 5 steering motor 6 vehicle speed sensor (vehicle speed detecting means) 32 Torque sensor 33 Rotary encoder (steering angle detecting means)

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroshi Kawaguchi 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation

Claims (2)

[Claims] 1. A steering device that is not mechanically connected to a steering mechanism that changes the direction of a wheel, a steering angle detection device that detects a steering angle of the steering device, and a reaction force of the steering device toward a neutral position. And a reaction force imparting means for imparting a steering angle, wherein the steering angle detecting means detects and detects the steering angle of the steering mechanism in accordance with the steering angle detected by the steering angle detecting means. A vehicle steering system comprising: a setting unit that sets a dead zone in which the reaction force applying unit does not apply a reaction force in a predetermined range including a neutral position of a steering angle. 2. The vehicle according to claim 1, further comprising: vehicle speed detecting means for detecting a running speed of the vehicle, wherein said setting means includes means for increasing or decreasing the width of said dead zone in accordance with the running speed detected by said vehicle speed detecting means. Vehicle steering system.