JP2001310751A - Steering gear - Google Patents

Abstract

(57) [Problem] To prevent a vehicle body from rotating in a steering direction at the time of stationary steering when front left and right wheels can be individually steered by individual actuators. A left and right steering actuator (14FL, 14) is provided.
The FRs are arranged before and after the front axle and at the same distance from the front axle. The steering actuators 14FL and 14FR have the same structure, so that the driving reaction forces N _FL and N _FR generated at the time of steering are adjusted.
Of each other, and also cancels the moment generated around the front axle. When the steering actuators 14FL and 14FR generate a large driving force at an extremely low speed as in a stationary operation, the left and right steering actuators 14FL and 14FR are alternately driven every short time. The frequency at that time is set to a frequency higher than the resonance frequency determined by the torsional rigidity of the rear tire and the moment of inertia of the vehicle body.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steering device capable of individually steering left and right wheels according to a driver's steering condition.

[0002]

2. Description of the Related Art For example, Japanese Patent Laying-Open No. 8-337106 discloses a steering device in which a part of a link constituting a suspension device is expanded and contracted by an actuator, and right and left rear wheels are individually steered. Although this steering device assists the rear wheels, it can be applied to a general main steering wheel, that is, a front wheel. In this case, for example, the front or rear of the left and right front wheels instructed to be rotatable around the steering axis is individually steered by pushing or retracting the front and rear wheels in the vehicle width direction by individual actuators. Becomes possible.

[0003]

However, in the conventional rear-wheel steering system in which the conventional rear-wheel steering system is applied to the front-wheel steering system, the actuators are arranged symmetrically with respect to the longitudinal direction of the vehicle. Since the driving directions of the steering actuators coincide with each other, the driving reaction force also acts in the same direction. For example, when maneuvering at an extremely low speed or the like, when the front wheels are stationary, it is determined by the torsional rigidity of the rear tires. The vehicle body rotates in the steering direction around the rotation center. In such a case, the actual steering angle between the vehicle body and the left and right front wheels becomes small, and a problem that steering responsiveness is deteriorated occurs.

SUMMARY OF THE INVENTION The present invention has been developed in view of these problems, and when the front left and right wheels are steered by separate steering actuators, it is necessary to prevent the vehicle body from rotating in the steering direction even during stationary operation. It is an object of the present invention to provide a steering device capable of performing the following.

[0005]

According to a first aspect of the present invention, there is provided a steering apparatus comprising: a left steering actuator and a right steering actuator for individually steering left and right wheels; Steering state detecting means for detecting a steering state by a person, and control means for driving the left steering actuator and the right steering actuator according to at least the steering state detected by the steering state detecting means. The right steering actuator is provided on the vehicle body such that driving reaction forces on the vehicle body during steering are opposite to each other.

In the steering apparatus according to a second aspect of the present invention, in the first aspect, one of the left steering actuator and the right steering actuator is located rearward of the vehicle from the position of the axle to be steered. And the other is disposed forward of the vehicle relative to the position of the axle to be steered. In the steering apparatus according to claim 3 of the present invention, in the invention according to claim 2, the left steering actuator and the right steering actuator are:
It is characterized by being disposed at a position equidistant from or substantially equidistant from the position of the axle to be steered in a plan view of the vehicle.

According to a fourth aspect of the present invention, in the steering apparatus according to the first to third aspects, the control means is configured such that a driving amount of the left steering actuator and a right steering actuator is equal to or more than a predetermined amount. Sometimes, they are not driven simultaneously. According to a fifth aspect of the present invention, in the steering apparatus according to the fourth aspect, the control means alternately drives the left steering actuator and the right steering actuator.

According to a sixth aspect of the present invention, in the steering apparatus according to the first to fifth aspects, the left steering actuator and the right steering actuator have the same configuration. It is.

[0009]

According to the steering apparatus of the first aspect of the present invention, the left steering actuator and the right steering actuator are arranged so that the driving reaction forces on the vehicle body during steering are opposite to each other. , The driving reaction forces of the two steering actuators cancel each other, and it is possible to prevent the vehicle body from rotating during steering.

[0010] According to the steering apparatus of the present invention, one of the left steering actuator and the right steering actuator is disposed behind the position of the axle to be steered. By arranging the vehicle ahead of the position of the axle to be steered, even in a plan view of the vehicle, both steering actuators are asymmetric with respect to the longitudinal axis of the vehicle, canceling the driving reaction force, and simultaneously generating a moment for rotating the vehicle body. Can also be almost offset.

According to the steering apparatus of the third aspect of the present invention, the left steering actuator and the right steering actuator are disposed at a position equidistant or substantially equidistant from the position of the axle to be steered in a plan view of the vehicle. With this arrangement, the driving reaction force can be offset, and the moment of rotating the vehicle body can be offset. According to the steering device of the fourth aspect of the present invention, when the drive amounts of the left steering actuator and the right steering actuator are equal to or more than a predetermined amount,
Since both are not driven at the same time, the capacity of an energy supply source such as a power storage device does not need to be increased unnecessarily, and energy consumption can be reduced.

According to the steering apparatus of the present invention, when the driving amounts of the left steering actuator and the right steering actuator are equal to or more than a predetermined amount, the two steering actuators are alternately driven. If the timing of the alternate drive is shortened, the left and right wheels can be steered in the same manner while reducing energy consumption. According to the steering device of the present invention, the left steering actuator and the right steering actuator are configured to be equivalent to each other, so that components can be made identical, and cost and component types can be reduced. .

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the steering device according to the present invention will be described below with reference to the accompanying drawings. First, FIG. 1 briefly shows the overall configuration of a four-wheel steering system. In the figure,
10FL and 10FR are left and right front wheels which are steering wheels,
10RL and 10RR are left and right rear wheels that are not individually steered. The front wheels 10FL and 10FR are supported by the axles 11FL and 11FR so as to be rotatable around the steering axis with respect to the vehicle body. The front wheel 10F
L and 10FR are not mechanically connected to the steering wheel 15 like a general vehicle.

As shown in FIG. 2, of the two front wheels, one end of a tie rod 13 is swingably connected to an axle 11FR of a front right wheel 10FR at a front end of the vehicle.
One end of a tie rod 13 is swingably connected to the axle 11FL of the front left wheel 10FL at the front end of the vehicle. The other ends of the tie rods 13 are connected to actuators 14F attached to the front and rear of the suspension member 13, that is, to the front and rear of the front axle.
The drive rods 16 of the R and 14FL are swingably connected.

These actuators 14FR, 14F
L has the same structure and, as shown in FIG. 3, moves the drive rod 16 in the vehicle width direction, that is, in the left-right direction in FIG. That is, the motor 20 comprises a brush 20B, a stator 20S, and a rotor 20S.
The rotation shaft 21 of the rotor 20 is a hollow cylindrical tube, and the drive rod 16 is inserted therein. The drive rod 16 is rotatably supported by a bearing 26, and the rotating shaft 21 of the motor 20 is
The rotation shaft 21 is rotatably supported. A ball screw nut 23 is formed on the enlarged diameter portion of the rotation shaft 21, and a ball screw external thread portion 24 is formed on the outer peripheral portion of the drive rod 16. A ball 25 is interposed. Therefore,
When power is supplied to the rotor 20R of the motor 20 from the brush 20B, the rotating shaft 21 and the nut 23 of the ball screw rotate together with the rotor 20R, and the thrust of the screw is transmitted to the male screw portion 24 of the ball screw via the ball 25. The drive rod 16 is moved in the axial direction, that is, in the horizontal direction in the drawing, and in the vehicle width direction. Thus, by making the left and right actuators 14FL, 14FR have the same structure,
The types of parts can be reduced, and the cost can be reduced. The reference numeral 27 in the drawing indicates the rotation angle of the nut 23 of the ball screw, that is, the rotor 20R of the motor 20,
Left and right front wheels 10FL, 10FR of the steering angle [delta] _fL, a steering angle sensor for detecting a [delta] _fR.

Accordingly, in FIG. 2, when the front right wheel actuator 14FR is extended, the front right wheel 10FR is steered to the right, and when contracted, the front right wheel 10FR is steered to the left. When the front left wheel actuator 14FL is extended, the front left wheel 10FL is steered right, and when contracted, the front left wheel 10FL is steered left. Therefore, hereinafter, they are also simply referred to as front right steering actuator 14FR and front left steering actuator 14FL.

The axle 11FR in this embodiment,
The relative positional relationship between 11FL and the steering actuators 14FR, 14FR is as shown in FIG. That is, the front right steering actuator 14FR is located at the front of the vehicle, the front left steering actuator 14FL is located at the rear of the vehicle, and the front left axle is arranged at the same distance from the front axle with respect to the front axle which is symmetrical to the steering. And the front left and right wheels 10
The steering actuators 14FL, 14FR are extended when the FL, 10FR is steered to the right, and contracted when steered to the left.

On the other hand, a steering shaft 17 supporting the steering wheel 15 has a steering torque sensor 18 for detecting a steering torque, a steering angle sensor 19 for detecting a steering angle, and a steering reaction force from the steering shaft 17 to the steering wheel 15. Steering reaction force motor 9 to be applied
Is installed. The vehicle is provided with a vehicle speed sensor 4 for detecting the vehicle speed.

The vehicle includes the front wheels 10FL, 10FL.
A control unit 3 for controlling the steering angle of the FR and controlling the steering reaction force to the steering wheel 15
Is provided. This control unit 3
Input interface circuit having / D conversion function, central processing unit (CPU), storage device (ROM, RAM), D
The microcomputer includes a microcomputer having an output interface circuit or the like having an / A conversion function and the like, and a drive circuit for converting an output signal from the microcomputer into a drive signal for driving each actuator.

Next, the arithmetic processing for the front wheel steering control executed by the microcomputer of the control unit 3 will be described with reference to the flowchart of FIG.
This arithmetic processing is performed for a predetermined control time ΔT (for example, 10 mse
c.) Executed as a timer interrupt process for each. In this arithmetic processing, there is no particular step for communication. However, programs and maps stored in the ROM of the storage device or various data stored in the RAM are always stored in a buffer or the like of the arithmetic processing device. The calculation results calculated by the arithmetic processing device are also stored in the storage device at any time.

In this calculation process, first, in step S1
And the vehicle speed V from the vehicle speed sensor 4_SPAnd the steering angle
The steering angle θ from the sensor 19 and the steering angle
Front left wheel steering angle δ_fL, Front right wheel steering angle δ_fRRead. Next,
Move to step S2 and perform individual performances in the same step.
According to the arithmetic processing, the time differential value of the steering angle θ,
The angular velocity θ 'is calculated. Specifically, for example, during the previous control
Steering angle θ_(n-1)And steering at the current control time
Angle θ _(n)May be divided by the control time ΔT.
And high-pass filtering with appropriate phase lead characteristics
May be performed.

Then, the process proceeds to step S3, and the vehicle speed V _SP , the steering angle θ and the steering angle θ read in step S1 are read in accordance with the individual arithmetic processing performed in step S3.
Target front wheel steering angle δ _f corresponding to the steering angular velocity θ ′ calculated in Step 2
Calculate ^* . Specifically, it is natural that the larger the steering angle θ, the larger the target front wheel steering angle δ _f ^* . However, for example, when the vehicle speed V _SP is large, the target front wheel steering angle δ _f ^* is considered in consideration of stability ^. When the steering angular velocity θ ′ is large, the target front wheel steering angle δ _f ^* is set slightly large in consideration of responsiveness.

Next, the process proceeds to step S4, and the front left and right wheel steering angle differences Δδ _fL and Δδ _fR are calculated according to the individual arithmetic processing performed in the step. Specifically, the front left wheel steering angle difference .DELTA..delta _fL is the target rear wheel steering angle [delta] _f ^* from the front left wheel steering angle [delta] _fL
The front right wheel steering angle difference Δδ _fR is the target rear wheel steering angle δ.
_It is a value obtained by subtracting the front right wheel steering angle _δfR from _f ^* . Then control proceeds to step S5, the vehicle speed V _SP is equal to or a preset relatively small predetermined vehicle speed value V _SP0 below, the vehicle speed V _SP is equal to or less than a predetermined vehicle speed value V _SP0 If so, the process proceeds to step S6; otherwise, the process proceeds to step S7.

At step S6, at step S4
It is determined whether or not the front left wheel steering angle difference Δδ _fL calculated in _{Step 2} is equal to or greater than a relatively large predetermined front wheel steering angle difference value Δδ _f0 , and the front left wheel steering angle difference Δδ _fL is determined as the predetermined front wheel steering angle difference value. If it is not less than Δδ _f0 , the process proceeds to step S8; otherwise, the process proceeds to step S9. In step S9,
It is determined whether the front right wheel steering angle difference Δδ _fR calculated in step S4 is equal to or greater than the predetermined front wheel steering angle difference value Δδ _f0 , and the front right wheel steering angle difference Δδ _fR is determined to be the predetermined front wheel steering angle difference value Δδ. If it is not less than _f0 , the process proceeds to step S8; otherwise, the process proceeds to step S7.

In step S8, the front left and right wheel steering angle difference Δ is calculated in accordance with the individual calculation processing performed in step S8.
The current value control signals corresponding to δ _FL and Δδ _fR are alternately output to the left and right steering actuators 14FL and 14FR every short time, and then the process returns to the main program. On the other hand, in step S9, the current value control signals corresponding to the front left and right wheel steering angle differences Δδ _FL , Δδ _fR are sent to the left and right steering actuators 14FL, according to the individual calculation processing performed in the step.
Output to 14FR at the same time and then return to the main program.

Incidentally, the control unit 3 controls the steering reaction torque in addition to the arithmetic processing. In this steering reaction torque control, a target steering reaction torque is set based on, for example, a vehicle speed V _SP , a steering angle θ, a steering angular velocity θ ′, and the like, and the steering is performed such that the steering reaction torque is generated. The reaction force motor 9 is driven.

According to the calculation processing of FIG. 5, step S
After reading various detected values in step 1 and calculating the steering angular velocity θ ′ in step 2, the target front wheel steering angle δ _f ^* is calculated in step S3 ^.
, And in step S4, the front left / right wheel steering angle difference Δδ _fL ,
To calculate the Δδ _fR. The vehicle speed V _SP is greater than the predetermined low speed vehicle speed value V _SP0 or the front left / right wheel steering angle difference Δ
[delta] _fL, if none of the .DELTA..delta _fR is the relatively large than a predetermined front wheel steering angle difference value .DELTA..delta _f0 shifts to step S7,
Here, the current value control signals corresponding to the front left and right wheel steering angle differences Δδ _fL and Δδ _fR are transmitted to the left and right steering actuators 14FL and 14FR.
Are output at the same time.

At this time, for example, as shown in FIG. 6, when the target front wheel steering angle δ _f ^* is steered to the right, the front left and right wheels 10FL, 10FL,
When steering right at 0FR, the left and right steering actuators 1
Both 4FL and 14FR will be extended. The vehicle body, specifically, the front suspension member 13,
A driving reaction force acts in the direction opposite to the direction in which the steering actuators 14FL and 14FR extend, as shown in FIG.
Drive reaction force N of both steering actuators 14FL, 14FR
_FL, N _FR is the opposite directions to each other, yet the two actuators 14FL, since 14FR are the same structure, even equal the magnitude of the reaction force N _FL, N _FR. Therefore, the driving reaction forces N _FL and N _FR of the two steering actuators 14 _FL and 14 _FR cancel each other. Further, since the left and right steering actuators 14FL and 14FR are disposed at the same distance from the front axle, the front left and right wheels 10FL and 10FR are provided.
When the steering wheel is steered, the magnitude of the moment due to the driving reaction force generated around the contact point, that is, at the position of the front axle becomes the same, so that the moment is also canceled.

FIG. 10 shows the front left and right axles AX _FL , AX
_{For FR} , steering actuators ACT _FL , ACT
This is a steering system in which the _FRs are arranged behind the front axle and at the same distance from the front axle. It is assumed that the configuration of both actuators ACT _FL and ACT _FR is the same as that of the above embodiment. In such a steering device, for example, when the front left and right wheels W _FL and W _FR are steered to the right, as shown in FIG.
The front right steering actuator ACT _FR must contract, and the front left steering actuator ACT _FL must extend. At this time, the driving reaction force N _{FL of} the actuator generated on the vehicle body,
The N _FRs act together in the same direction, in this case, to the right.
O in FIG. (FIG. 6 same) shows a vehicle body center of rotation depends on the torsional rigidity of the rear wheel tires, as for example stationary steering, an extremely low speed in the left and right front wheels W _FL, a W _FR When a large steering is required, the driving force generated by the left and right steering actuators ACT _FL and ACT _FR naturally increases, and the driving reaction forces N _FL and N _FR also increase. In the steering direction, that is, in this case, the vehicle rotates rightward. When the steering direction of the front left and right wheels W _FL and W _FR is right and the vehicle body also turns right, the front left and right wheels W
The actual steering angles of _FL and _WFR become smaller, and the response to steering decreases.

In this embodiment, as described above, the driving reaction force N
_FL, N_FRAre offset each other and their moments are also offset
Therefore, the vehicle body is turned around the rotation center O during steering.
Ensure responsiveness to steering without rotating.
Can be. On the other hand, the vehicle speed V_SPIs the low speed predetermined vehicle speed value V
_SP0Hereinafter, the front left and right wheel steering angle difference Δδ _fL, Δδ_fRAny of
Is a relatively large predetermined front wheel steering angle difference value Δδ_f0Is over
In this case, the process proceeds to step S8 of the arithmetic processing in FIG.
And the front left and right wheel steering angle difference Δδ_fL, Δδ_fRCurrent value system according to
The control signal is sent to the left and right steering actuators 14FL and 14FR.
Are output alternately at short intervals. So in this case
As shown in FIG. 7, for example, front left and right wheels 10FL, 1
Even when steering right at 0FR, for example,
Extend the rudder actuator 14FL to move the front left wheel 10FL
Steer a little to the right, then move the front left steering actuator 14FL
Stop and extend the front right steering actuator 14FR
Steer the front right wheel 10FR slightly to the right, and then move the front right steering
The front left steering actuator 1
Extend 4FL and steer the front left wheel 10FL slightly to the right.
The front left and right wheels 10FL and 10FR
Steer alternately.

Thus, the left and right steering actuators 14
By alternately operating the FL and the 14FR, the maximum current value, that is, the energy consumption can be reduced. That is, as shown in FIG. 8, assuming that the consumed energy when driving the left and right steering actuators 14FL and 14FR at the same time, that is, the current value is a large value as indicated by the broken line, the left and right steering actuators 14FL and 14FR are alternately driven. , The consumed energy, that is, the current value may be about half of the value as indicated by the solid line. When the current consumption value is small, the capacity of an energy supply source such as a battery may be small, and at the same time energy saving can be achieved.

However, when the left and right steering actuators 14FL and 14FR are alternately driven in this manner, the vehicle body may be vibrated in the rotational direction about the rotational center O determined by the torsional rigidity of the rear tire. There is. The resonance frequency in this case is a square root of a value obtained by dividing the inertia moment J of the vehicle body by the torsional rigidity G (for two wheels) of the rear wheel tire.
/ m ² and the torsional stiffness G of the rear tire is 12 kgf / deg., the resonance frequency is 5 Hz. Therefore, the left and right steering actuators 14FL,
If the 14FR is alternately driven, the vehicle body will not be vibrated.

Although the above embodiment has been described in connection with the case where a microcomputer is applied as the control unit 3, the control unit 3 may be replaced with an electronic circuit such as a counter and a comparator.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of a steering device of the present invention.

FIG. 2 is a configuration diagram of main components of the steering device of FIG. 1;

FIG. 3 is a structural explanatory view of the steering actuator of FIG. 2;

FIG. 4 is an explanatory diagram of a relative positional relationship between an axle and a steering actuator of the steering device in FIG. 2;

FIG. 5 is a flowchart of a calculation process performed by the control unit of FIG. 1;

FIG. 6 is an explanatory diagram of steering by the calculation processing of FIG. 5;

FIG. 7 is an explanatory diagram of steering by the calculation processing of FIG. 5;

FIG. 8 is an explanatory diagram of a current value control signal to the steering actuator by the arithmetic processing of FIG. 5;

FIG. 9 is an explanatory diagram of setting a frequency when the left and right steering actuators are alternately driven.

FIG. 10 is an explanatory diagram of a relative positional relationship between an axle and a steering actuator of a steering device in which a steering actuator is disposed on the same side with respect to a steering symmetric axle.

FIG. 11 is an explanatory diagram of steering by the steering device of FIG. 10;

[Explanation of symbols]

 3 is a control unit 4 is a vehicle speed sensor 10FL to 10RR is a front left wheel to a rear right wheel 11FL, 11FR is a front left and right axle 13 is a tie rod 14FL, 14FR is a front left and right steering actuator 15 is a steering wheel 16 is a drive rod 17 is a steering shaft 18 The steering torque sensor 19 is a steering angle sensor 20 is a motor

Claims (6)

[Claims] 1. A left steering actuator and a right steering actuator for individually steering left and right wheels, a steering state detecting means for detecting a steering state by a driver, and a steering state detected by at least the steering state detecting means. Control means for driving the left steering actuator and the right steering actuator in accordance with the following. The left steering actuator and the right steering actuator are disposed on the vehicle body such that driving reaction forces on the vehicle body during steering are opposite to each other. A steering device characterized by being performed. 2. One of the left steering actuator and the right steering actuator is disposed behind the vehicle to be steered and the other is disposed ahead of the vehicle to be steered. Claim 1 characterized by the following:
The steering device according to claim 1. 3. The vehicle according to claim 2, wherein the left steering actuator and the right steering actuator are disposed at an equidistant or substantially equidistant distance from a steered axle position in a plan view of the vehicle. A steering device as described. 4. The control device according to claim 1, wherein the control unit does not simultaneously drive the left steering actuator and the right steering actuator when the driving amounts of the left steering actuator and the right steering actuator are equal to or more than a predetermined amount. Steering gear. 5. The steering apparatus according to claim 4, wherein the control unit alternately drives the left steering actuator and the right steering actuator. 6. The steering apparatus according to claim 1, wherein the left steering actuator and the right steering actuator have the same configuration.