JP2540996B2 - Steering device with variable angular velocity ratio - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steering device used in a vehicle such as an automobile, and more particularly, to a steering device that responds to an increase in steering angle from a steering neutral position of a steering wheel. The present invention relates to a variable angular velocity ratio steering device that increases a ratio (turning ratio) between an angle and a turning angle of steered wheels.

[Conventional technology]

A conventional angular velocity ratio variable steering device is shown in FIGS. This angular velocity ratio variable steering device 100
Is an input shaft 103 connected to the steering wheel 101,
An output shaft 107 connected to a rack and pinion gear device 105 for rotatably rotating the front wheels by being rotatable relative to the input shaft 103, and an intermediate shaft 1 arranged in parallel with the both shafts 103, 107.
09, and a pair of elliptical gears 111, 113 provided between the intermediate shaft 109 and the input shaft 103 and facing the gear 111 on the input shaft 103 side in accordance with the rotation amount from the neutral position of the input shaft 103. An angular velocity ratio variable gear train 115 that increases the angular velocity ratio of the gear 113 on the intermediate shaft 109 side, and a pair of large and small circular gears 117 and 119 is provided between the intermediate shaft 109 and the output shaft 107, and the angular velocity ratio variable gear train 115 is provided. And a speed-increasing gear train 121 that accelerates the rotation of the input shaft 103 transmitted through the output shaft 107 by a predetermined amount and transmits it to the output shaft 107. The elliptical gears 111 and 11 of this angular velocity ratio variable gear train 115
As shown in the gear meshing diagram by the pitch circle in FIG. 5, 3 is assembled as shown in FIG. 5 in the steering neutral position. As a result, as shown in FIG. 6, the steering ratio increases non-linearly as the steering angle increases from the steering neutral position to 180 °, and when it exceeds 180 °, the steering angle increases. It decreases in a non-linear manner.

In addition, such an angular velocity ratio variable steering device is
It is disclosed in detail in Japanese Patent Application Laid-Open No. 2-14971 “Name: Steering device for vehicle” before the present application.

[Problems to be Solved by the Invention]

However, in the above-described variable angular speed ratio steering device, since the variable angular speed ratio gear train is composed of a pair of elliptical gears, the relationship between the steering angle of the steering wheel and the steering ratio is as shown in FIG. The steering ratio sharply increases at an angle of around 180 °. As a result, if the driver steers quickly without getting used to the steering wheel, the steered wheels are steered too quickly, which gives a steering feeling that the steering stability is poor.

As a solution to this problem, firstly, the eccentricity ε of the elliptical gear in the variable angular velocity ratio gear train (the eccentricity ε is obtained by ε = β / α in FIG. 5, where c is The focus of the ellipse, d is a pitch circle), and secondly, the speed increasing ratio of the speed increasing gear train provided in series with the variable angular speed ratio gear train is decreased. To be

First, FIG. 7 shows the first method in which the eccentricity of the elliptical gear is reduced. 7A shows the characteristics of the prior art, and B shows the case where the eccentricity is reduced. In this case, it is possible to reduce the steering ratio near the steering angle of 180 °, but on the other hand, the steering ratio near the steering neutral position becomes high, so there is a large amount of steering at the steering neutral position, and high speed steering is possible. At the time of traveling, the steering angle becomes too large and the steering stability deteriorates, although the steering amount is small.

Next, FIG. 8 shows a second method in which the speed increasing ratio of the speed increasing gear train is reduced. 8A shows the characteristics of the prior art, and B shows the case where the speed increasing ratio is reduced. Note that C and D are maximum steering angles, respectively. In this case, the turning ratio becomes small over the entire steering angle of the steering wheel.
As a result, the steering ratio around the steering angle of 180 ° becomes smaller,
The steering stability of the vehicle can be greatly improved. However, if the overall steering ratio is reduced, the maximum steering angle D (maximum rotation angle of the steering wheel) increases, and the operability improvement due to the reduction of the steering angle, which is the original aim of the variable angular speed ratio steering device, is impaired. It will be. Furthermore, as the maximum steering angle increases, the steering ratio during maximum steering becomes considerably smaller than the steering ratio when the steering angle is 180 °. 180
It becomes higher than the effectiveness of the rudder near ゜. Therefore,
A non-linear effect of the steering effect on the steering of the steering wheel is promoted, which deteriorates the steering feeling.

Therefore, in order to explain the above problems, the present invention provides
When the steering angle reaches around 180 °, the angular velocity ratio (steering ratio) on the output shaft side to the gear on the input shaft side in the variable angular velocity ratio gear train is made substantially constant, without impairing operability improvement. , To improve the steering stability.

[Means for solving the problem]

Therefore, the variable angular velocity ratio steering device of the present invention has an input shaft connected to a steering wheel, and an output shaft connected to a steering link mechanism that is disposed so as to be rotatable relative to the input shaft and steers the steered wheels. An angular velocity ratio that has a pair of gears provided between the output shaft and the input shaft and that increases the angular velocity ratio of the gear on the output shaft side facing the gear on the input shaft side according to the amount of rotation from the neutral position of the input shaft. In a variable angular speed ratio steering device including a variable gear train, a gear of an angular speed ratio variable gear train is configured such that an elliptical portion having an axis as a focal point, a circular portion having the axial center as a center, and an interpolation connecting the circular portion and the elliptical portion. The elliptical portions are arranged so as to mesh with each other near the steering angle neutral position, and the respective circular portions are arranged so as to mesh with each other near the steering angle 180 °.

[Action]

In the variable angular speed ratio steering device of the present invention, when the steering wheel is rotated, the input shaft rotates, and the rotation is transmitted to the output shaft via the variable angular speed ratio gear train, and the steering link mechanism operates in accordance with the rotation of the output shaft. The steered wheels are steered through. Then, the angular velocity ratio variable gear train is configured by an elliptical portion having a shaft center as a focal point, a circular portion having the shaft center as a center, and an interpolating portion connecting the circular portion and the elliptical portion, and the elliptical portion is near a steering angle neutral position. Are arranged so that they mesh with each other, and the circular parts are arranged so that they mesh with each other at a steering angle of about 180 °,
In the vicinity of the steering neutral position and when the steering angle is small from the steering neutral position, the angular velocity ratio of the gear on the output shaft side to the gear on the input shaft side can be set to a small value, and the steering ratio becomes small.

Next, when the steering angle increases from the steering neutral position of the steering wheel, the angular velocity ratio of the gear on the output shaft side to the gear on the input shaft side in the variable angular velocity ratio gear train increases non-linearly, that is, the steering ratio increases. It grows non-linearly. Further, when the steering angle reaches around 180 °, the angular velocity ratio of the gear on the output shaft side to the gear on the input shaft side in the variable angular velocity ratio gear train becomes constant, that is, the steering ratio becomes constant.

〔Example〕

Embodiments of the present invention will be described below with reference to the accompanying drawings.

The drawings from FIG. 1 to FIG. 3 show an embodiment of the present invention. FIG. 1 shows a rack and pinion type power steering system for a vehicle equipped with a known power assist mechanism including a hydraulic pump 1, a rotary valve type control valve 3, a power cylinder 5, a reservoir 7 and the like. It shows an implemented steering device with a variable angular velocity ratio. In this variable angular velocity ratio steering device, a valve shaft 9 connected to a steering wheel 8 and an input shaft 11 coaxially and rotatably arranged with respect to the valve shaft 9 are connected by a torsion bar 13. Also, the valve shaft 9 and the input shaft 11
The output shaft 15 is coaxially and relatively rotatably disposed, and the intermediate shaft 17 is parallel to the valve shaft 9 and the input shaft 11 and the output shaft 15 in a parallel position. It is installed in. A pinion 19 is integrally formed on the output shaft 15, and the rack bar 21 also serving as a piston rod of the power cylinder 5 is configured to be moved in the axial direction by the pinion 19. The front wheels are steered by a known steering link mechanism including the above.

Then, in this embodiment, the input shaft 11 and the intermediate shaft 17
A variable angular velocity ratio gear train 31 is provided therebetween, and a speed increasing gear train 41 is provided between the intermediate shaft 17 and the output shaft 15.

As shown in FIGS. 1 and 2, the variable angular speed ratio gear train 31 includes an input gear 33 serration-fitted to the input shaft 11 and an intermediate gear 35 rotatably supported by the intermediate shaft 17. Has been done. The pitch circle 331 of this input gear 33 is 0
Ellipse 331a formed in an ellipse with the axis A as the focal point from a to 100 ° and a from 260 to 360 ° and 140 to 2
A circular portion 331c formed by a circle centered on the axis A in the C region up to 20 °, and b from 100 ° to 140 ° and 220 ° to 260 °
The interpolating part 331b in which the pitch lines of the 1 and b2 regions are formed as continuous curves between the elliptical part 331a and the circular part 31c.
It is composed of 1 and 331b2. Also, this intermediate gear 35
The pitch circle 351 has an elliptic portion 351d formed by an ellipse centering on the axis B at d regions from 0 ° to 80 ° and 280 ° to 360 °, and an e region from 130 ° to 230 °. A circular part 351e formed by a circle around the center and from 80 ° to 130 ° and 230 °
Interpolation parts 351f1 and 351f2 are formed so that the f1 and f2 regions up to 280 ° are formed so that the pitch line has a continuous curve between the circular part 351e and the elliptical part 351d. Then, in this angular velocity ratio variable gear train 31, the neutral position of the input shaft 11,
That is, at the steering neutral position of the steering wheel 8,
The input gear 33 and the intermediate gear 35 are assembled so as to mesh with each other as shown in FIG. 2, and the intermediate gear 35 relative to the input gear 33 increases in accordance with an increase in the steering angle (rotation amount) from the steering neutral position of the input shaft 11. The angular velocity ratio is designed to increase.

The speed increasing gear train 41 is composed of a pair of large and small circular gears 43, 45, and the large diameter gear 43 is integrally formed with the intermediate gear 35 and rotatably mounted on the intermediate shaft 17, and
The small diameter gear 45 rotates integrally with the output shaft 15. In the speed increasing gear train 41, the rotation of the large diameter gear 43 is speeded up by a predetermined amount and transmitted to the output shaft 15.

Further, in this embodiment, the intermediate shaft 17 has the housing 51
It is provided integrally with a carrier 53 that is rotatably assembled to the. The carrier 53 is configured to rotate and revolve around the axes of the valve shaft 9, the input shaft 11 and the output shaft 15, and integrally has a sector gear 55, and a worm gear 57 engaged with the gear 55 It can be rotated within a range until it comes into contact with the housing 51. The worm gear 57 is rotatably assembled to the housing 51, and is rotatably driven by an electric motor (not shown) capable of rotating in the forward and reverse directions. The operation of the electric motor is controlled by the vehicle speed and the steering operation angle of the steering wheel.

Next, the operation and effect of the variable angular velocity ratio steering device according to the embodiment of the present invention will be described.

In this embodiment configured as described above, when the steering wheel 8 is rotated, the valve shaft 9 and the input shaft 11 rotate, and the angular velocity ratio variable gear train 31 and the speed increasing gear train 31 are rotated.
The rack bar 21 is moved in the axial direction according to the rotation of the output shaft 15 via 41, and the front wheels are steered via the steering link mechanism. At this time, the control valve 3 operates according to the steering torque, and the power cylinder 5 assists the axial movement of the rack bar 21.

Thus, in the above transmission system, the variable angular speed ratio gear train 31 is configured to increase the angular speed ratio of the intermediate gear 35 to the input gear 33 in accordance with the amount of rotation of the input shaft 11 from the steering neutral position. When the rotational operation amount from the neutral position of 8 is small (when operating near the neutral position), the angular velocity ratio of the intermediate gear 35 to the input gear 33 is set to a small value. Therefore, the variable angular velocity ratio gear train 31
Even if the rotation of the input shaft 11 transmitted via the speed-increasing gear train 41 is accelerated by a predetermined amount, the rotation amount of the output shaft 15 is the rotation line operation amount of the steering wheel 8 as shown in A of FIG. The steering ratio becomes a small value as shown by A in FIG. 3, and the running stability including high-speed running is remarkably improved. Incidentally, A in FIG. 3 is the characteristic of this embodiment, and B is the characteristic of the prior art.

Next, when the rotational operation amount from the neutral position of the steering wheel 8 increases, the angular velocity ratio of the intermediate gear 35 to the input gear 33 increases accordingly, and the output shaft 15 rotates by synergistic action with the speed increasing gear train 41. The amount increases non-linearly, and as shown in A of FIG. 3, the steering ratio takes a non-linearly large value as the steering angle from the neutral position of the steering wheel 8 increases, and the steering angle decreases. Therefore, the operability is improved.

Further, when the steering operation amount from the neutral position of the steering wheel 8 further increases and the steering angle reaches around 180 °,
Since the input gear 33 and the intermediate gear 35 mesh with each other in the circular portions 331c and 351e, the intermediate gear 35 with respect to the input gear 33 becomes constant at a large angular velocity ratio. As a result, when the steering wheel 8 reaches around 180 °, the steered angle becomes large and constant as shown in FIG. 3A. Even if you steer quickly,
Since the steered wheels are not steered too quickly, a feeling of excessive steering is not produced and steering characteristics are excellent.

The specific embodiment of the present invention has been described above, but the present invention is not limited to this embodiment, and various embodiments are included within the scope of the claims of the utility model. Is.

〔The invention's effect〕

As described above, in the present invention, the turning angle is small near the steering angle neutral, and the turning ratio increases as the steering angle increases, but the turning ratio becomes constant near the steering angle 180 °. As described above, the pitch circle of the pair of gears of the variable angular speed ratio gear train is formed by the combination of the elliptical portion and the circular portion, so that the maximum steering angle is not substantially increased and the rotation around the steering angle of 180 ° is achieved. Since the steering angle can be reduced, the operability is improved by reducing the steering angle, and the operability is surely improved by suppressing the excessive steering effect for steering around the steering angle of 180 °.

[Brief description of drawings]

FIGS. 1 to 3 show an embodiment of the present invention, and FIGS. 4 to 8 show a conventional technique.
FIG. 1 is an overall configuration diagram showing a variable angular velocity ratio steering device according to an embodiment of the present invention, FIG. 2 is a gear meshing diagram showing the shapes of an input gear and an intermediate gear by pitch circles, and FIG. 3 is a steering wheel steering wheel. FIG. 4 is a characteristic diagram showing the turning ratio of the output shaft with respect to the angle, FIG. 4 is an overall configuration diagram showing a conventional angular velocity ratio variable steering device, and FIG. 5 is a diagram showing the shapes of the input shaft side gear and the output shaft side gear. A gear meshing diagram indicated by a circle, FIG. 6 is a characteristic diagram showing the steering ratio of the output shaft with respect to the steering angle of the steering wheel, and FIG. 7 is a characteristic showing the steering ratio of the output shaft with respect to the steering angle of the steering wheel, and the eccentricity. FIG. 8 is a comparison diagram of the characteristics showing the turning ratio of the output shaft with respect to the steering angle of the steering wheel and the characteristics when the speed increasing ratio of the speed increasing gear train is changed. is there. 8 …… Steering wheel 11 …… Input shaft 15 …… Output shaft 21 …… Rack bar (steering link mechanism) 31 …… Angular speed ratio variable gear train 33 …… Input gear (gear) 331a …… Elliptical part 331b …… Interpolation Part 331b2 …… Interpolator 331c …… Circular part 35 …… Intermediate gear (gear) 351d …… Elliptical part 351e …… Circular part 351f1 …… Interpolator 351f2 …… Interpolator

Claims (1)

(57) [Claims] Claim: What is claimed is: 1. An input shaft connected to a steering wheel, an output shaft connected to a steering link mechanism, which is arranged so as to be rotatable relative to the input shaft to steer the steered wheels, and between the output shaft and the input shaft. An angular velocity ratio variable gear train that has a pair of gears provided in and that increases the angular velocity ratio of the gear on the output shaft side facing the gear on the input shaft side according to the amount of rotation from the neutral position of the input shaft. In the variable angular speed ratio steering device, the gear of the variable angular speed ratio gear train is composed of an elliptical portion whose focal point is the axis, a circular portion whose center is the axial center, and an interpolation portion which connects the circular portion and the elliptical portion. A variable angular speed ratio steering device, characterized in that the respective elliptical portions are arranged so as to mesh with each other near a steering angle neutral position, and the respective circular portions are arranged so as to mesh with each other near a steering angle of 180 °. .