JPH0939824A - Steering device - Google Patents

Abstract

(57) [Abstract] [Purpose] By correcting the relationship of the steering angle ratio so that the Ackerman or parallel characteristics become stronger as the steering amount in the front wheel steering vehicle and the front and rear wheel steering vehicles becomes larger, the tire slip angle during turning is corrected. (EN) Provided is a steering device which suppresses occurrence and improves maneuverability and operability. A CPU (central processing unit determines a current value to the electric motor 14 based on output signals of a steering angle sensor 18 and a rotation angle sensor 19 of the electric motor 14 which are operated by the rotation of the steering wheel 1, and controls a current driver 20. By driving, the inner / outer wheel steering angle ratio is corrected to be larger or smaller according to the increase of the steering amount, and the correction amount of the inner / outer wheel steering angle ratio is made smaller at the time of high speed turning.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention corrects the relationship between the inner and outer wheel steering angle ratios determined by the steering of the steering wheel, thereby suppressing the occurrence of tire slip angles during turning and improving the steerability and operability. The present invention relates to a steering device.

[0002]

2. Description of the Related Art Generally, in a steering apparatus for an automobile,
In the so-called Ackermann steering mechanism in which the turning centers of the outer wheel and the inner wheel with respect to the turning direction coincide with each other,
The steering angle of the inner wheels is larger than the steering angle of the outer wheels, and when turning at low speeds where centrifugal force can be ignored, there is no side slip of the tires and smooth turning is possible. On the other hand, with the parallel steering mechanism, where there is not much difference between the steering angle of the outer wheels and the steering angle of the inner wheels, the difference in slip angle between the inner and outer wheels becomes smaller during high-speed turning, and the cornering force increases and smooth You can turn to.

By the way, in any of the above steering mechanisms, if the steering angle of the steering wheel is determined, the steering angles of the inner and outer wheels are uniquely determined, and the steerability and operability are improved only under specific conditions. For example, in the Ackermann steering mechanism, if conditions change, such as when making a high-speed turn with large centrifugal force, the slip angle of the inner wheel becomes larger than the appropriate value, and tire wear increases. However, it will lead to squeal of tires and deterioration of steering stability. Further, in the parallel steering mechanism, there is a problem that a slip angle is generated when turning at a low speed, which deteriorates handle operability.

Therefore, in order to solve these problems, for example, as disclosed in Japanese Unexamined Patent Publication No. 62-187653, the steering device is parallel when turning at high speed regardless of the running state of the vehicle. -A steering device has been proposed that improves steering stability and operability by approaching the steering geometry and approaching the Ackermann steering geometry when turning at low speed.

That is, in the conventional steering device including Japanese Patent Laid-Open No. 62-187653, in the case of a front two-wheel steering vehicle (2WS), as shown in FIG. 12, the turning center E0 at the low speed is the rear wheel axle. As above, the front-wheel inner-outer wheel rudder angle ratio (= inner-wheel rudder angle θ ₁ / outer-wheel rudder angle θ ₂ ) is designed. Basically, the front-wheel inner-outer wheel rudder angle ratio> 1 and the steering wheel steering angle Ackerman steering in which the front-to-outer wheel steering angle ratio increases with increasing. Therefore, when there is a relationship of the front wheel inner / outer wheel rudder angle ratio> 1 between the front wheel inner / outer wheel rudder angle ratio and the steering wheel steer angle, there is no excessive slippage on the tires, and the vehicle can smoothly turn. it can.

[0006]

However, the above-described steering device having the conventional structure is a device proposed only for a front two-wheel steering vehicle, and in recent years, a small turn steering at a low speed and a steering operation at a high speed. In the case of a front / rear wheel steering vehicle (4WS) that takes into consideration the improvement of steering performance, the steering operation is used to steer both the front wheels and the rear wheels, and it is assumed that only the front two wheels are steered. In all cases, the mechanism makes it impossible to eliminate the tire slip angle, which causes problems such as tire wear and deterioration of steering stability.

That is, in the front and rear wheel steering vehicle (4WS),
There are an in-phase steering type in which the steering angles of the front and rear wheels are in the same direction, and an antiphase steering type in which the steering angles of the front and rear wheels are in the opposite directions. For example, in an antiphase steering type 4WS, the turning center of the vehicle is E.
Since the turning radius becomes smaller by moving forward than 0 and the turning center of the vehicle moves backward by E0 and the turning center becomes larger in the in-phase steering type, the front-wheel inner-outer wheel steering angle ratio becomes 2WS. The amount of increase in the front-wheel inside-outer-wheel steering angle ratio is determined by the rear-wheel steering angle, but when there is a dynamic characteristic at the location where the rear-wheel steering angle is determined from the steering steering angle, However, there is no one-to-one relationship such as 2WS between the steering angle and the front-wheel / outer-wheel steering angle ratio, and the conventional steering device cannot eliminate the tire slip angle in all cases.

Further, even when there is no dynamic characteristic at the position where the steering angle of the rear wheel determines the steering angle of the rear wheel, the increase rate of the steering angle ratio of the front-wheel / outer-wheel steering angle to the steering wheel steering angle is 2 W.
Since it is larger than S and the shape of the increasing curve is different from 2WS, it is very difficult to eliminate the tire slip angle with the conventional steering device in all cases. Further, when the tire is unevenly worn, the tire has an unnecessary slip angle, so that there is a problem that the steering force is deteriorated by the lateral force in the right and left directions.

The present invention has been made by paying attention to the problems of the above-mentioned conventional structure, and the inner and outer wheel steering angle ratios of the front and rear wheels are adjusted so that the Ackerman or parallel characteristics become stronger as the steering amount in the front and rear wheel steering vehicle increases. By correcting the relationship of, the occurrence of tire slip angle during turning is suppressed,
An object of the present invention is to provide a steering device with improved maneuverability and operability.

[0010]

In order to achieve the above-mentioned object, a steering device according to the present invention is characterized in that, in claim 1, a mechanism for steering front wheels and an inner / outer wheel steering angle ratio (= inner wheel steering angle / In a front and rear wheel steering vehicle having a mechanism for variably controlling the outer wheel steering angle) and a mechanism for steering the rear wheels in antiphase or in phase with respect to the front wheels, the inner and outer wheels of the front wheels are increased as the antiphase steering amount of the rear wheels increases. An inner / outer wheel steering angle ratio control means is provided for correcting the steering angle ratio so as to decrease the steering angle ratio of the front wheels as the steering angle ratio increases or the in-phase steering amount of the rear wheels increases.

Further, in claim 2, the inner-outer wheel steering angle ratio control means for correcting the inner-outer wheel steering angle ratio reduces the correction amount of the inner-outer wheel steering angle ratio of the front wheels in accordance with an increase in vehicle speed, Alternatively, the correction control is stopped.

[0012]

According to the present invention based on such a configuration,
According to the first aspect of the present invention, when the vehicle speed is turning at a low speed within a predetermined value, the turning center can be moved further forward as the amount of rear-wheel anti-phase steering in the front-rear wheel steering vehicle increases. In addition, the ratio of the front and rear wheel rudder angles (= inner wheel rudder angle / outer wheel rudder angle) is increased to enhance the characteristics of the Ackerman steering geometry. Alternatively,
As the rear wheel in-phase steering amount increases, the turning center can be moved further rearward, so to prevent uneven wear on the tires, the steering angle ratio of the front and inner wheels can be reduced to improve the characteristics of the parallel steering geometry. ramp up.

Therefore, according to the present invention, the inner / outer wheel steering angle ratio (= inner wheel steering angle / outer wheel steering angle) is increased in accordance with an increase in the rear wheel anti-phase steering amount or the rear wheel in-phase steering amount in the front and rear wheel steering vehicle. By performing the correction to increase or decrease, it is possible to suppress the occurrence of the tire slip angle at the time of turning and improve the steering stability and operability.

Further, according to the second aspect of the present invention, during high speed turning when the vehicle speed is high and the lateral G is large, a side slip angle is always generated in the tire, so that the inner / outer wheel steering angle for correcting the inner / outer wheel steering angle ratio is maintained. The ratio control means reduces the inner-outer wheel steering angle ratio correction amount during high-speed turning from the correction amount of the inner-outer wheel steering angle ratio during low-speed turning, or stops the correction control to turn the inner and outer wheels during high-speed turning. Increase the force to change lanes smoothly.

[0015]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a schematic configuration diagram showing a main part of a front wheel side steering device according to a first embodiment of the present invention, and FIG. 2 is an explanatory diagram showing a relationship between a steering angle and a turning center.
FIG. 3 is an explanatory diagram showing the relationship between the steering angle and the steering angle ratio of the inner and outer wheels.

The front and rear wheel steering vehicle (4WS) includes an in-phase steering type in which the steering angle of the rear wheels is in the same direction as that of the front wheels, and an antiphase steering in which the steering angle of the rear wheels is in the opposite direction to the front wheels. 2 shows the case of the anti-phase steering type 4WS. In the anti-phase steering type 4WS, the turning center of the vehicle moves to E ₁ ahead of E 0 and turns. Since the radius becomes smaller, the front-wheel inner-outer wheel steering angle ratio becomes larger than 2WS, and the increase in the front-wheel inner-outer wheel steering angle ratio is determined by the rear-wheel steering angle. Further, when there is a dynamic characteristic at a portion where the rear wheel steering angle is determined from the steering steering angle, there is no one-to-one relationship such as 2WS between the steering steering angle and the front wheel / outer wheel steering angle ratio.

Next, in FIG. 1, the rotation of the steering wheel 1 in the vehicle is transmitted to the pinion gear 3 via the steering column shaft 2. A rack shaft 4 arranged horizontally in the vehicle meshes with the pinion gear 3, and the rack shaft 4 can be moved leftward or rightward by rotating the pinion gear 3. The rack shaft 4 moves leftward or rightward to steer the tire 7 leftward or rightward in the traveling direction via the side rods 5 and the knuckle arms 6, depending on the amount of movement of the rack shaft 4. The turning amount of the tire (front wheel) 7 is determined. Therefore, the steering wheel 1, the steering column shaft 2, the pinion gear 3, the rack shaft 4, the side rod 5, the knuckle arm 6, and the like constitute a mechanism for steering the front wheels 7. The rack shaft 4 is laid out in a horizontal direction behind the axle shaft 11 that supports the front tire 7, and the rack housing 8 is laid out.
The rack housing 8 is supported by
It is mounted on the vehicle body side via an actuator 9 and an insulator (not shown) shown in FIG. 4, which will be described later.
The angle δ formed by the side rod 5 and the knuckle arm 6 is set so as to have an Ackermann geometry of 90 degrees or more with respect to the knuckle arm 6.

4 to 6 are detailed explanatory views of the actuator 9 according to the present invention. FIG. 4 is a partially broken plan view, FIG. 5 is a left side view of FIG. 4, and FIG. 6 is IV- of FIG. FIG. 4 is a sectional view taken along line IV.

In the figure, a rack housing 8 arranged in the horizontal direction of the vehicle penetrates the shaft of a hollow gear 12 arranged at the center of an actuator 9 and rotates so as not to receive torque due to rotation of the hollow gear 12. Freely supported. Also, on the left and right sides of the main body of the actuator 9,
A pair of guide members 13 each having a long hole 13a formed in the front-rear direction.
Both ends of the rack housing 8 are installed in the long holes 13a of the pair of left and right guide members 13 so as to be movable only in the front-rear direction. Here, stopper guides 13b are fixed to both ends of the rack housing 8 to prevent the rack housing 8 from moving laterally.

On the other hand, the hollow gear 12 through which the rack housing 8 penetrates is a worm gear 15 which is rotated by a drive shaft of an electric motor 14 arranged in the traveling direction of the vehicle.
And a rack 16 fixed to the main body side of the actuator 9 in the vehicle along the traveling direction. Then, when the electric motor 14 rotates, it is transmitted to the hollow gear 12 by the worm gear 15, but the rack 16 in which the hollow gear 12 is fixed to the main body side is transmitted.
, The hollow gear 12 moves in the front-back direction of the vehicle. Therefore, when the electric motor 14 rotates and the hollow gear 12 moves in the front-rear direction of the vehicle, the rack housing 8 penetrating the shaft of the hollow gear 12 becomes
It moves only in the front-back direction of the vehicle along the inside of the elongated holes 13a of the pair of left and right guide members 13.

FIG. 7 is an explanatory view showing the control system of the electric current of the electric motor 14, in which the CPU (central processing unit) is operated by the output signals of the steering angle sensor 18 and the rotation angle sensor 19 of the electric motor 14 which are operated by the rotation of the steering wheel 1. )
The current value to the electric motor 14 is determined at 17, and the current driver 20 is driven to rotate the electric motor 14 forward or backward. Therefore, the CPU 17, the electric motor 14, and the electric driver 20 constitute the inner / outer wheel steering angle ratio control means A.

Next, the operation of the CPU 17 according to the embodiment of the steering device constructed as described above will be described with reference to the flow chart shown in FIG. FIG. 9 is a characteristic diagram of various steering linkages showing theoretical curves of Ackermann geometry and parallel geometry, and the actual steering geometry of the vehicle is set in a shaded area between the two. It is assumed that the neutral position of the rack housing 8 in the front-rear direction is substantially in the middle of the shaded area shown in FIG.

First, when the control system starts, step S
At 100, all control systems are initialized and the rack housing 8 is set at a neutral position in the vehicle front-rear direction. Next, in step S101, the steering angle, the rear wheel steering angle, and the rotation angle of the electric motor 14 are read, and in step S102, the ideal inner / outer wheel steering angle ratio (= inner wheel steering angle / outer wheel steering angle) is calculated based on the steering angle. To calculate. Next, step S
Proceeding to 103, the position of the rack housing 8 and the steering angle are calculated from the rotation angle of the electric motor 14,
Calculate the actual inner / outer wheel steering angle ratio. Further, step S10
In 4, the drive current of the electric motor 14 is calculated so that the actual value of the inner / outer wheel steering angle ratio approaches the ideal value. When the actual value is smaller than the ideal value (actual value <ideal value), the rack housing 8 is The drive current for moving the vehicle rearward is output to the current driver-20 in step S105. On the contrary, when the actual value is larger than the ideal value (actual value> ideal value), the drive current for moving the rack housing 8 to the front of the vehicle is output to the current driver-20.
Then, since the drive current calculated in step S104 is output to the electric motor 14 via the current driver-20 in step S105, ideal turning corresponding to the steering angle of the steering becomes possible.

As described above, when the vehicle is turning at a low speed within a predetermined value, the turning center moves forward as the amount of rear-phase anti-phase steering in the front and rear wheel steering vehicle increases. It is necessary to increase the wheel steering angle ratio (= inner wheel steering angle / outer wheel steering angle), but by moving the rack housing of the steering device to the rear of the vehicle, the inner wheel is cut off and the outer wheel is cut back, The inner wheel rudder angle / outer wheel rudder angle is increased, the Ackerman steering geometry is strengthened, the occurrence of tire slip angles is suppressed, uneven wear is eliminated, and maneuverability and operability can be improved.

Further, during high speed turning when the vehicle speed is high and the lateral G is large, the side slip angle is always generated in the tire. Therefore, the correction amount of the inner / outer wheel steering angle ratio during high speed turning is adjusted to the inner / outer wheel during low speed turning. Either make the steering angle ratio smaller than the correction amount or stop the correction control and increase the cornering force of the inner and outer wheels during high-speed turning to smoothly change lanes.

FIG. 10 is a schematic configuration diagram showing a main part of a front wheel side steering apparatus according to a second embodiment of the present invention. In the figure, the difference from the first embodiment is that the knuckle side of the side rod 5 is provided. The point is that the joint is laid out so as to be located in front of the vehicle with respect to the axle shaft 11 supporting the front tire 7.

Therefore, in the configuration according to the second embodiment of the present invention, when the rack housing 8 is moved to the front of the vehicle, the inner ring is cut off and the outer ring is cut back, which is the reverse of the first embodiment. Then, the ideal value and the actual value of the inner / outer wheel steering angle ratio are calculated. When the actual value <the ideal value, the rack housing 8 is moved to the front of the vehicle, and when the actual value> the ideal value, By moving the rack housing 8 to the rear of the vehicle, ideal turning corresponding to the steering angle of the steering wheel is possible, and similarly to the first embodiment, the tire slip angle is suppressed and uneven wear is eliminated. In addition, it is possible to improve maneuverability and operability, and to increase the cornering force between the inner wheel and the outer wheel during a high-speed turn to smoothly change lanes.

FIG. 11 is an explanatory view showing the relationship between the steering steering angle and the turning center when the front and rear wheel steering vehicle is in-phase steering in the in-phase steering type. The steering angle θ ₁ / outer wheel steering angle θ ₂ ) is added to the rear-wheel side inner-outer wheel steering angle ratio (θ ₃ ) to move the turning center point from E ₀ to the rear E ₂ to change the turning radius. When the steering angle ratio of the front and inner wheels is reversed from that in the opposite phase, it becomes smaller than 1 as indicated by the alternate long and short dash line in FIG. As a result, the rack housing of the steering device is moved to the front of the vehicle, the front and rear wheel steering angle ratio is reduced to prevent uneven wear of the tires, and the characteristics of the parallel steering geometry are enhanced to improve the tire slip angle. Occurrence can be suppressed, uneven wear can be eliminated, and maneuverability and operability can be improved. In addition, during high speed turning when the vehicle speed is high and the lateral G is large, the sideslip angle of the tire is always generated. Therefore, the correction amount of the inner / outer wheel rudder angle ratio during high speed turning is set to the inner / outer wheel rudder angle ratio during low speed turning. Or the correction control is stopped to increase the cornering force of the inner and outer wheels during high-speed turning to smoothly change lanes.

[0030]

As described in detail above, according to the present invention, in claim 1, when the vehicle speed is low speed turning within a predetermined value, the turning center moves forward as the rear wheel antiphase steering amount increases. Therefore, in order to prevent uneven wear of the tires, the inner-outer wheel steering angle ratio of the front wheels (= inner wheel steering angle / outer wheel steering angle) is reduced,
As the characteristics of Ackerman steering geometry are strengthened or the turning center moves rearward as the rear wheel in-phase steering amount increases, the front and rear wheel rudder angle ratio (= inner wheel rudder angle) / Outer wheel steering angle) to increase the characteristics of the parallel steering geometry, suppress the occurrence of tire slip angles during turning, and improve the steering stability and operability.

In the second aspect of the invention, when the vehicle turns at high speed and the lateral G becomes large, a side slip angle is always generated in the tire. Therefore, the inner / outer wheel steering angle ratio for correcting the inner / outer wheel steering angle ratio is corrected. The control means reduces the correction amount of the inner / outer wheel steering angle ratio during high-speed turning from the correction amount of the inner-outer wheel steering angle ratio during low-speed turning, or stops the correction, so that the cornering force of the inner and outer wheels during high-speed turning is reduced. It is possible to make lanes larger and change lanes smoothly.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a main part of a front wheel side steering device according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a relationship between a steering angle and a turning center.

FIG. 3 is an explanatory diagram showing a relationship between a steering angle and a steering angle ratio between inner and outer wheels.

FIG. 4 is a partially cutaway plan view illustrating details of an actuator according to the present invention.

FIG. 5 is a left side view of FIG. 2;

6 is a sectional view taken along line 6-6 of FIG.

FIG. 7 is an explanatory diagram showing a control system of the electric motor.

FIG. 8 is a flowchart illustrating the operation of the steering device according to the present invention.

FIG. 9 is a characteristic diagram of various steering linkages.

FIG. 10 is a schematic configuration diagram showing a main portion of a front wheel side steering device according to a second embodiment of the present invention.

FIG. 11 is an explanatory diagram showing a relationship between a steering angle and a turning center when steering the front and rear wheels with the same phase.

FIG. 12 is an explanatory diagram showing a relationship between a steering angle and a turning center in a front two-wheel steering vehicle.

[Explanation of symbols]

 A Inner / Outer Wheel Steering Angle Ratio Control Means 1 Steering (Mechanism for Steering Front Wheels) 14 Electric Motor 17 CPU (Central Processing Unit) 18 Steering Angle Sensor 19 Motor Rotation Angle Sensor 20 Electric Driver

Claims (2)

[Claims] 1. A mechanism for steering a front wheel, a mechanism for variably controlling an inner-outer wheel steering angle ratio (= inner wheel steering angle / outer wheel steering angle) of the front wheel, and a rear wheel steering in an opposite phase or the same phase with respect to the front wheel. In a front and rear wheel steering vehicle having a mechanism, the inner-outer wheel steering angle ratio of the front wheels is increased as the anti-phase steering amount of the rear wheels is increased, or the inner-outer side of the front wheels is increased as the in-phase steering amount of the rear wheels is increased. A steering apparatus comprising: inner-outer wheel steering angle ratio control means for correcting the wheel steering angle ratio to decrease. 2. The inner / outer wheel rudder angle ratio control means for correcting the inner / outer wheel rudder angle ratio reduces the correction amount of the inner / outer wheel rudder angle ratio of the front wheels according to an increase in vehicle speed, or stops the correction control. The steering device according to claim 1, wherein the steering device is adapted to be operated.