JP3770048B2 - Steering device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a steering device capable of individually steering left and right wheels according to a steering state of a driver.
[0002]
[Prior art]
For example, JP-A-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 the left and right rear wheels are individually steered. This steering device assists the rear wheels, but it can also be applied to general main steering wheels, that is, front wheels. In this case, for example, the front or rear of the left and right front wheels instructed to be rotatable around the steering shaft are individually steered by pushing or retracting them in the vehicle width direction by individual actuators. Is possible.
[0003]
[Problems to be solved by the invention]
However, in the case where the conventional rear wheel steering device is deployed on the steering device as a front wheel, the actuators are arranged symmetrically with respect to the vehicle longitudinal axis direction, but the driving directions of the left and right steering actuators coincide. Therefore, the driving reaction force also acts in the same direction.For example, when steering the front wheel at extremely low speeds, the vehicle body is steered around the center of rotation determined by the torsional rigidity of the rear tire. Rotate in the direction. In this case, the actual steering angle between the vehicle body and the left and right front wheels becomes small, and there arises a problem that steering responsiveness is lowered.
[0004]
The present invention has been developed in view of these problems. When steering the front left and right wheels with individual steering actuators, the steering that can prevent and suppress the rotation of the vehicle body in the steering direction even when the vehicle is stationary. The object is to provide an apparatus.
[0005]
[Means for Solving the Problems]
In order to solve the above object, a steering apparatus according to claim 1 of the present invention includes a left steering actuator and a right steering actuator that individually steer left and right wheels, and a steering state that detects a steering state by a driver. Detection means, 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 detection means. The left steering actuator and the right steering actuator The left steering actuator and the right steering actuator are electric actuators, and the control means is configured so that the drive amounts of the left steering actuator and the right steering actuator are when it is more than a predetermined amount, also and drives both alternately It is.
[0006]
According to a second aspect of the present invention, in the steering device according to the first aspect, any one of the left steering actuator and the right steering actuator is disposed rearward of the steering target axle position. The other is characterized in that it is arranged in front of the vehicle from the steering target axle position.
According to a third aspect of the present invention, in the steering device according to the second aspect, the left steering actuator and the right steering actuator are equidistant or substantially equal to each other from the steering target axle position in a plan view of the vehicle. It is arrange | positioned in the position of distance.
[0008]
According to a fourth aspect of the present invention, the steering apparatus according to the first to third aspects is characterized in that the left steering actuator and the right steering actuator have the same configuration.
[0009]
【The invention's effect】
Thus, according to the steering apparatus of the first aspect of the present invention, the left steering actuator and the right steering actuator are disposed on the vehicle body so that the driving reaction forces on the vehicle body during steering are opposite to each other. Thus, the drive reaction forces of the two steering actuators cancel each other, and the vehicle body can be prevented from rotating during steering.
In addition, since the left steering actuator and the right steering actuator are electric actuators, and when the driving amounts of the left steering actuator and the right steering actuator are equal to or greater than a predetermined amount, both the steering actuators are driven alternately. There is no need to unnecessarily increase the capacity of the supply source, and it is possible to reduce energy consumption. If the alternate drive timing is shortened, the left and right wheels are steered in the same way while reducing energy consumption. can do.
[0010]
According to the steering device of the present invention, the left steering actuator or the right steering actuator is arranged behind the steering target axle position, and the other is set as the steering target axle. By arranging in front of the vehicle from the position, both steering actuators are asymmetrical with respect to the longitudinal axis of the vehicle even in plan view of the vehicle, canceling the driving reaction force and simultaneously canceling out the moment to rotate the vehicle body at the same time. can do.
[0011]
In the steering device according to claim 3 of the present invention, the left steering actuator and the right steering actuator are disposed at equidistant or substantially equidistant positions from the steering target axle position in plan view of the vehicle. Thus, the driving reaction force can be canceled and the moment to rotate the vehicle body can be canceled .
[0012]
Further, according to the steering device according to claim 4 of the present invention, since the left steering actuator and the right steering actuator have the same configuration, it is possible to equalize parts and reduce costs and parts types. .
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of a steering device of the present invention will be described with reference to the accompanying drawings.
First, FIG. 1 briefly shows the overall configuration of a four-wheel steering apparatus. In the figure, 10FL and 10FR are left and right front wheels which are steering wheels, and 10RL and 10RR are left and right rear wheels which are not individually steered. Among these, the front wheels 10FL and 10FR are supported by the axles 11FL and 11FR so as to be rotatable around the steering shaft with respect to the vehicle body. The front wheels 10FL and 10FR are not mechanically connected to the steering wheel 15 as in a general vehicle.
[0014]
As shown in FIG. 2, of the two front wheels, one end of a tie rod 13 is swingably connected to the axle 11FR of the front right wheel 10FR at the front end of the vehicle, and is connected to the axle 11FL of the front left wheel 10FL. Is connected to the front end of the vehicle in such a manner that one end of the tie rod 13 can swing. The other end of each tie rod 13 is swingably connected to the drive rod 16 of actuators 14FR and 14FL attached to the front and rear of the suspension member 13, that is, the front and rear of the front axle.
[0015]
These actuators 14FR and 14FL have the same structure, and, as shown in FIG. 3, the drive rod 16 is moved in the vehicle width direction, that is, in the left-right direction in the drawing, by the rotation of the motor 20. That is, the motor 20 includes a brush 20B, a stator 20S, and a rotor 20R. A rotating shaft 21 of the rotor 20 is a hollow cylindrical tube, and a drive rod 16 is inserted into the hollow cylindrical tube. The drive rod 16 is rotatably supported by a bearing 26, and the rotating shaft 21 of the motor 20 is rotatably supported by the bearing 22. A ball screw nut 23 is formed on the diameter-expanded portion of the rotating shaft 21. A male screw portion 24 of a ball screw is formed on the outer peripheral portion of the drive rod 16, and a ball 25 is interposed therebetween. 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. Therefore, the drive rod 16 is moved in the vehicle width direction in the axial direction, that is, in the horizontal direction in the figure. Thus, by making the left and right actuators 14FL and 14FR have the same structure, the types of parts can be reduced and the cost can be reduced. Reference numeral 27 in the figure denotes a steering angle sensor for detecting the steering angles δ _fL and δ _fR of the front left and right wheels 10FL and 10FR from the rotation angle of the nut 23 of the ball screw, that is, the rotor 20R of the motor 20. is there.
[0016]
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 left steer is steered. Further, when the front left wheel actuator 14FL is extended, the front left wheel 10FL is steered to the right, and when contracted, the left steer is steered. Therefore, hereinafter, the front right steering actuator 14FR and the front left steering actuator 14FL are also simply described.
[0017]
The relative positional relationship between the axles 11FR and 11FL and the steering actuators 14FR and 14FR in this embodiment 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 is disposed at an equidistant position from the front axle across the front axle that is symmetrical with respect to steering. In addition, both the steering actuators 14FL and 14FR are extended when the front left and right wheels 10FL and 10FR are steered to the right, and are both contracted when the left steering is steered.
[0018]
On the other hand, the steering shaft 17 that supports the steering wheel 15 has a steering torque sensor 18 that detects steering torque, a steering angle sensor 19 that detects a steering angle, and steering that applies a steering reaction force from the steering shaft 17 to the steering wheel 15. A reaction force motor 9 is attached. A vehicle speed sensor 4 for detecting the vehicle speed is attached to the vehicle.
[0019]
Further, the vehicle is provided with a control unit 3 for controlling the steering angle of the front wheels 10FL and 10FR and controlling the steering reaction force to the steering wheel 15. The control unit 3 includes an input interface circuit having an A / D conversion function, a microcomputer having a central processing unit (CPU), a storage device (ROM, RAM), an output interface circuit having a D / A conversion function, etc. The drive circuit is configured to convert an output signal from the microcomputer into a drive signal for driving each actuator.
[0020]
Next, arithmetic processing for front wheel steering control executed by the microcomputer of the control unit 3 will be described based on the flowchart of FIG. This calculation process is executed as a timer interrupt process every predetermined control time ΔT (for example, 10 msec.). In this arithmetic processing, there is no particular communication step, but the program stored in the ROM of the storage device, the map, various data stored in the RAM, etc. are always stored in the buffer of the arithmetic processing device, etc. Each calculation result calculated by the calculation processing device is also stored in the storage device as needed.
[0021]
In this calculation process, first, in step S1, the vehicle speed V _SP from the vehicle speed sensor 4, the steering angle θ from the steering angle sensor 19, the front left wheel steering angle δ _fL from the front wheel steering angle sensor 27, the front right wheel steering. Read the angle δ _fR .
Next, the process proceeds to step S2, and the time differential value of the steering angle θ, that is, the steering angular velocity θ ′ is calculated in accordance with individual calculation processing performed in the step. Specifically, for example, to a difference value between the steering angle theta _(n) in the steering angle θ _(n-1) and the current control time at the previous control time may be divided by the control time [Delta] T, the process proceeds appropriate phase High pass filter processing having characteristics may be performed.
[0022]
Next, the process proceeds to step S3, and in accordance with the vehicle speed V _SP , the steering angle θ read in step S1, and the steering angular speed θ ′ calculated in step S2, according to individual calculation processing performed in the step. The target front wheel rudder angle δ _f ^* is calculated. Specifically, it is natural that the larger the steering angle θ is, the larger the target front wheel steering angle δ _f ^* is set. However, for example, when the vehicle speed V _SP is high, the target front wheel steering angle δ _f ^* is considered in consideration of stability ^. Is set slightly smaller, or when the steering angular velocity θ ′ is large, the target front wheel steering angle δ _f ^* is set slightly larger in consideration of responsiveness.
[0023]
Next, the process proceeds to step S4, and the front left and right wheel steering angle differences Δδ _fL and Δδ _fR are calculated in accordance with individual calculation processing performed in the step. Specifically, the front left wheel steering angle difference Δδ _fL is a value obtained by subtracting the front left wheel steering angle δ _fL from the target rear wheel steering angle δ _f ^* , and the front right wheel steering angle difference Δδ _fR is the target rear wheel steering angle δ _It consists of the value obtained by subtracting the front right wheel steering angle δ _fR 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. If not, the process proceeds to step S7.
[0024]
In the step S6, it is determined whether the left wheel steering angle difference .DELTA..delta _fL before calculated in step S4 is relatively preset large predetermined front wheel steering angle difference value .DELTA..delta _f0 above, the front left wheel steering angle difference .DELTA..delta _{If fL} is greater than or equal to the predetermined front wheel steering angle difference value Δδ _f0 , the process proceeds to step S8, and if not, the process proceeds to step S9.
In step S9, it is determined whether or not 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. If it is greater than or equal to the steering angle difference value Δδ _f0 , the process proceeds to step S8, and if not, the process proceeds to step S7.
[0025]
In step S8, current value control signals corresponding to the front left and right wheel steering angle differences Δδ _FL and Δδ _fR are alternately supplied to the left and right steering actuators 14FL and 14FR every short time in accordance with individual calculation processing performed in the same step. To return to the main program.
On the other hand, in step S9, current value control signals corresponding to the front left and right wheel steering angle differences Δδ _FL and Δδ _fR are simultaneously output to the left and right steering actuators 14FL and 14FR in accordance with individual calculation processing performed in the same step. Then return to the main program.
[0026]
Incidentally, in this control unit 3, in addition to this calculation processing, control of the steering reaction force torque is also performed. In this steering reaction force torque control, for example, the target steering reaction force torque is set based on the vehicle speed V _SP , the steering angle θ, the steering angular velocity θ ′, and the like so that the steering reaction force torque is generated. The reaction force motor 9 is driven.
[0027]
According to the calculation process of FIG. 5, various detection values are read in step S1, the steering angular velocity θ ′ is calculated in step 2, the target front wheel steering angle δ _f ^* is calculated in step S3, and further in step S4. The front left and right wheel steering angle differences Δδ _fL and Δδ _fR are calculated. When the vehicle speed V _SP is greater than the low speed predetermined vehicle speed value V _SP0 , or both the front left and right wheel steering angle differences Δδ _fL and Δδ _fR are less than the relatively large predetermined front wheel steering angle difference value Δδ _f0. In step S7, the current value control signals corresponding to the front left and right wheel steering angle differences Δδ _fL and Δδ _fR are simultaneously output to the left and right steering actuators 14FL and 14FR.
[0028]
At this time, as shown in FIG. 6, for example, when the front left and right wheels 10FL and 10FR are steered to the right when the target front wheel steering angle δ _f ^* is the right steering state, both the left and right steering actuators 14FL and 14FR are extended. . A driving reaction force acts on the vehicle body, specifically, the front suspension member 13 in a direction opposite to the extending direction of the steering actuators 14FL and 14FR. However, as shown in FIG. 6, the driving of both steering actuators 14FL and 14FR is performed. The reaction forces N _FL and N _FR are opposite to each other, and since the two actuators 14FL and 14FR have the same structure, the reaction forces N _FL and N _FR are equal in magnitude. Accordingly, the driving reaction forces N _FL and N _FR of the two steering actuators 14FL and 14FR cancel each other. Further, since the left and right steering actuators 14FL and 14FR are disposed at equal distances from the front axle, when steering the front left and right wheels 10FL and 10FR, they are generated around the ground contact points, that is, approximately at the front axle position. Since the magnitude of the moment due to the driving reaction force is the same, the moment is also cancelled.
[0029]
FIG. 10 shows a steering apparatus in which steering actuators ACT _FL and ACT _FR are both disposed rearward from the front axle and equidistant from the front axle with respect to the front left and right axles AX _FL and AX _FR . . _{Assume that} the configurations of both actuators ACT _FL and ACT _FR are the same as those in the above embodiment. In such a steering apparatus, for example, when the front left and right wheels W _FL and W _FR are steered to the right, as shown in FIG. 11, the front right steering actuator ACT _FR must contract and the front left steering actuator ACT _FL must expand. However, at that time, the driving reaction forces N _FL and N _FR of the actuator generated in the vehicle body both act in the same direction, in this case, in the right direction. O in the figure (same in FIG. 6) indicates the vehicle body rotation center determined according to the torsional rigidity of the rear wheel tire. For example, the front left and right wheels W _FL and W _FR When the vehicle must be steered greatly, the driving force generated by the left and right steering actuators ACT _FL and ACT _FR is naturally increased and the driving reaction forces N _FL and N _FR are also increased. Therefore, the vehicle body is centered on the rotation center O. It rotates in the steering direction, that is, in this case, to the right. If the steering direction of the front left and right wheels W _FL and W _FR is right and the vehicle body is also rotated to the right, the actual steering angle of the front left and right wheels W _FL and W _FR becomes smaller, and the response to steering is reduced. Will do.
[0030]
In the present embodiment, as described above, the driving reaction forces N _FL and N _FR cancel each other and their moments are also cancelled. Therefore, the vehicle body does not rotate around the rotation center O at the time of steering. Responsiveness can be ensured.
On the other hand, when the vehicle speed V _SP is equal to or lower than the low-speed predetermined vehicle speed value V _SP0 and any of the front left and right wheel steering angle differences Δδ _fL and Δδ _fR is equal to or greater than the relatively large predetermined front wheel steering angle difference value Δδ _f0. Then, the process shifts to step S8 of the calculation process of FIG. 5, and current value control signals corresponding to the front left and right wheel steering angle differences Δδ _fL and Δδ _fR are alternately directed to the left and right steering actuators 14FL and 14FR every short time. Output. That is, in this case, as shown in FIG. 7, for example, even when the front left and right wheels 10FL and 10FR are steered to the right, for example, the front left steering actuator 14FL is first extended to slightly steer the front left wheel 10FL to the right. Next, the front left steering actuator 14FL is stopped, the front right steering actuator 14FR is extended and the front right wheel 10FR is slightly steered to the right, then the front right steering actuator 14FR is stopped, and the front left steering actuator 14FL is stopped. The front left wheel 10FL is steered slightly to the right by repeating the operation, and the front left and right wheels 10FL, 10FR are steered alternately little by little.
[0031]
Thus, by alternately operating the left and right steering actuators 14FL and 14FR, the maximum current value, that is, the energy consumption can be reduced. That is, as shown in FIG. 8, if the energy consumed when driving the left and right steering actuators 14FL and 14FR simultaneously, that is, the current value is a large value as shown by the broken line, the left and right steering actuators 14FL and 14FR can be driven alternately. The energy consumption, that is, the current value may be a value that is about half that of 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 energy saving can be achieved at the same time.
[0032]
However, when the left and right steering actuators 14FL and 14FR are alternately driven in this way, the vehicle body may be vibrated in the rotational direction about the rotation center O determined by the torsional rigidity of the rear tire. The resonance frequency in this case is the square root of the 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, so that, for example, the inertia moment J of the vehicle body is 800 kg / m ² and the rear wheel If the torsional rigidity G of the tire is 12 kgf / deg., The resonance frequency is 5 Hz. Therefore, if the left and right steering actuators 14FL and 14FR are alternately driven at a frequency higher than this resonance frequency, the vehicle body will not be vibrated.
[0033]
In the above embodiment, the microcomputer is applied as the control unit 3. However, instead of this, an electronic circuit such as a counter and a comparator may be combined.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing an embodiment of a steering apparatus of the present invention.
FIG. 2 is a configuration diagram of main components of the steering device of FIG. 1;
3 is an explanatory diagram of the structure 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 of FIG. 2;
FIG. 5 is a flowchart of calculation processing performed by the control unit of FIG. 1;
6 is an explanatory diagram of steering by the calculation process of FIG. 5. FIG.
7 is an explanatory diagram of steering by the calculation process of FIG. 5. FIG.
8 is an explanatory diagram of a current value control signal to the steering actuator by the calculation process of FIG.
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 apparatus in which a steering actuator is disposed on the same side with respect to a steering symmetrical axle.
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 / right axle 13 is a tie rod 14FL, 14FR is a front left / right steering actuator 15, a steering wheel 16 is a drive rod 17 is a steering shaft 18 is The steering torque sensor 19 is a steering angle sensor 20 is a motor.

Claims (4)

A left steering actuator and a right steering actuator that individually steer each of the left and right wheels; a steering state detection unit that detects a steering state by a driver; and at least the left in accordance with the steering state detected by the steering state detection unit and control means for driving the steering actuator and the right steering actuator, the left steering actuator and the right steering actuator, driving reaction force with respect to the vehicle body during steering is arranged on the vehicle body so as to be opposite to each other, and the left The steering actuator and the right steering actuator are electric actuators, and the control means alternately drives both the left steering actuator and the right steering actuator when the drive amounts of the left steering actuator and the right steering actuator are equal to or larger than a predetermined amount. .   One of the left steering actuator and the right steering actuator is disposed behind the steering target axle position, and the other is disposed ahead of the steering target axle position. Item 2. The steering device according to Item 1.   The steering apparatus according to claim 2, wherein the left steering actuator and the right steering actuator are disposed at equidistant or substantially equidistant positions from the steering target axle position in a plan view of the vehicle. The steering apparatus according to any one of claims 1 to 3 , wherein the left steering actuator and the right steering actuator have the same configuration.

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