JPH05178222A - Steering device - Google Patents

Abstract

PURPOSE:To increase the steering angle characteristic in acceleration form for the steering wheel turning angle, permit the free change of the steering characteristic and facilitate working. CONSTITUTION:A controller 20 installed between an input shaft 11 and an output shaft 13 increases the assistance force which is applied to an output operating member 14 by a boosting device 30 according to the increase of the relative turning angle between both the shafts 11 and 12. The input shaft 11 and output shaft 13 which are connected with a steering wheel are installed in eccentricity by a prescribed quantity, and both the shafts are connected by a steering characteristic applying mechanism 40 which consists of turning members 41 and 41a each of which is connected with one between both the shafts and has a cam groove 43 in the diameter direction formed on the edge surface and projections 44 and 44a which are installed in projection in the axial direction in eccentricity larger than a prescribed quantity on the other between both the shafts and engaged with the cam groove.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steering device for steering front wheels of an automobile, and more particularly to a power steering device.

[0002]

2. Description of the Related Art A conventional steering system operates between an input shaft connected to a handle shaft that rotates together with a steering handle and an output actuating member that steers front wheels via a steering link. The interlocking mechanism is provided, and various interlocking mechanisms such as a rack and pinion type, a ball screw type, and a worm pin type are used. There is also a front wheel steering system using a hydraulic power steering system in which a power cylinder is operated by a servo valve that operates according to a torque applied to an input shaft to give an assist force to an output operating member. There is also a front wheel steering device that uses an electric power steering device instead of a hydraulic type.

[0003]

However, for example, in the rack and pinion type, since the speed reduction ratio of the stroke of the rack bar which is the output actuating member with respect to the rotation angle of the input shaft is constant, steering is performed except near the neutral position of the steering wheel. When the steering wheel is turned, the feeling of turning is insufficient, and the maximum steering wheel rotation angle required to obtain the desired maximum front wheel steering angle is large (for example, 540 degrees). If the speed reduction ratio is reduced in order to solve this problem, there is a feeling of excessive cutting near the neutral position of the steering wheel. The same applies to other types of interlocking mechanisms, because the reduction ratio is almost constant.

On the other hand, as disclosed in JP-A-2-14971, two elliptical gears and two circular gears are provided between the input shaft and the output shaft of the front wheel steering apparatus, and the steering center of the input shaft is provided. There is one in which the speed reduction ratio is gradually reduced according to the increase of the rotation angle from the position. However, since this one uses two elliptical gears, it is difficult to machine and it is not easy to change the characteristics of the reduction gear ratio. Also, depending on the tooth contact state of the four gears when assembled,
It is difficult to obtain the desired handle torque. Further, it is difficult to simultaneously adjust the backlash of the elliptical gear and the backlash of the circular gear.

An object of the present invention is to solve such a problem in a steering device by using an appropriate steering characteristic imparting mechanism.

[0006]

To this end, the steering apparatus according to the present invention has an input shaft 11 connected to a steering wheel shaft that rotates together with a steering wheel, as illustrated in the accompanying drawings.
And the input shaft 1 through the output shaft 13 and the interlocking mechanism 15.
1, an output actuating member 14 that steers the wheels via a steering link, a booster 30 that gives an assisting force to the output actuating member 14, and the booster that operates according to the torque applied to the input shaft 11. 30 is the output operating member 1
In the steering system including a control device 20 for changing the assist force applied to the shaft 4, the input shaft 11 and the output shaft 13 are provided with eccentricity from each other by a predetermined amount.
Is a rotary member 41, 41A which is connected to either one of the shafts and has diametrical cam grooves 43, 43A formed on the end surface.
And a steering characteristic imparting mechanism 4 including protrusions 44 and 44A which are provided on the other of the both shafts so as to be more eccentric than the predetermined amount so as to project in the axial direction and engage with the cam grooves 43 and 43A.
It is characterized by being connected by 0.

[0007]

The rotation of the handle shaft that rotates with the steering wheel is transmitted to the output shaft 13 via the input shaft 11 and the steering characteristic imparting mechanism 40, and the interlocking mechanism 15 and the output actuating member 14 are transmitted.
Steer the wheels through. At this time, as the input shaft 11 rotates from the steering neutral position, the steering characteristic imparting mechanism 40
The protrusion 44 moves in the radial direction along the cam groove 43 of the rotating member 41, whereby the rotation angle of the output shaft 13 is acceleratedly increased in accordance with the increase of the rotation angle of the input shaft 11. The characteristic of this increase is that when the cam groove 43 of the steering characteristic imparting mechanism 40 is provided on the input shaft 11 side, the change in the inclination angle is
As shown in FIG. 5, the rotation angle of the input shaft 11 becomes sharp near the neutral position. On the other hand, when the protrusion 44 of the steering characteristic imparting mechanism 40 is provided on the input shaft 11 side, the change in the inclination angle is caused by the rotation angle of the input shaft 11 being 18 as shown in FIG.
It becomes sharp in the range near 0 degrees.

[0008]

As described above, according to the present invention, since the rotation angle of the output shaft increases at an accelerating rate as the rotation angle of the input shaft increases, the steering angle increases with respect to the rotation angle of the steering wheel. Accordingly, it has a characteristic of acceleratingly increasing. Therefore, in the state where the steering wheel is turned without giving a feeling of excessive cutting near the neutral position of the steering wheel, a sufficient cutting feeling can be given, and the maximum steering wheel rotation angle required to obtain a desired maximum steering angle can be reduced. Can be made

Further, the steering characteristic can be changed by a relatively simple adjustment by changing the ratio of the eccentricity of the output shaft to the input shaft and the eccentricity of the protrusion to the output shaft. Further, the cam groove and the protrusion of the steering characteristic imparting mechanism can be changed. The selection range of the steering characteristics can be widened by changing the characteristic of the rotation angle of the output shaft with respect to the input shaft by selecting which of the two is set as the input shaft side. In addition, machining is easier than that using an elliptical gear mechanism, and backlash can be easily adjusted by simply adjusting the play by changing the gap between the cam groove and the projection.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the first embodiment will be described with reference to FIGS. As shown in FIG. 1, the housing 10 of the steering apparatus of the first embodiment is composed of a valve housing 10a and a rack housing 10b which are screwed and fixed to each other. Input shaft 11 and intermediate shaft 1 arranged coaxially with each other
2 is a valve housing 10a via bearings 17a and 17b.
The shafts 11 and 12 are supported inside and are elastically relatively rotatably connected to each other by a torsion bar 16. The outer ring of the bearing 17b is attached to the valve housing 1 by the bearing retainer 10c.
It is fixed at 0a. The key 41a is provided at the rear end of the intermediate shaft 12.
The outer periphery of an input flange 41 (rotating member 41) of a steering characteristic imparting mechanism 40 (described later) that is coaxially fixed via a shaft is supported by the rack housing 10b via a bearing 17c.

The steering characteristic imparting mechanism 40 is operated via the key 42a.
The output shaft 13 of which the output flange 42 is coaxially fixed to the front end is eccentric in parallel with the intermediate shaft 12, and the bearings 18a, 1
8b is supported by the rack housing 10b, and the eccentric amount between the rotation axes O1 and O2 of the shafts 12 and 13 is e.
Is. A rack bar (output actuating member) 14 is supported on the rack housing 10b so as to move three-dimensionally with the output shaft 13 so as to be axially movable.
It is interlocked by 5. In this embodiment, the interlocking mechanism 15 includes a pinion 15a formed on the output shaft 13,
The rack 15 includes a rack 15b formed on a part of the rack bar 14 and meshing with the pinion 15a. Interlocking mechanism 1
By increasing the speed increasing ratio of 5, the movement amount of the rack bar 14 can be increased with a small steering wheel steering angle.
Both ends of the rack bar 14 are connected to the left and right front wheels (neither is shown) via steering links.

Next, the structure of the steering characteristic imparting mechanism 40 will be described with reference to FIGS. 1 and 2. Input flange 4 as described above
1 and the output flange 42 are coaxially fixed to the rear end of the intermediate shaft 12 and the front end of the output shaft 13 via keys 41a and 42b, respectively. A cam groove 43 extending in the diametrical direction is formed on the rear end surface of the input flange 41 facing the output flange 42. Further, the output flange 42 facing the input flange 41 is provided with a protrusion 44 projecting in the axial direction from the front end face thereof, and the center line O3 thereof is an eccentric amount e between the rotation axis lines O1, O2 of the both shafts 12, 13. Greater distance R than
It is eccentric from the rotation axis O2 of the output shaft 13. This distance R is larger than the amount of eccentricity e between the rotation axis lines O1 and O2 of both shafts 12 and 13. The protrusion 44 has a pin 44a fixed to the output flange 42 in parallel with the rotation axis O2.
A roller 44b is rotatably provided on the pin 44a via a needle roller 44c.
The outer peripheral surface of is engaged in the cam groove 41 so as to be rollable without a gap. In the neutral position shown in FIG. 2, each axis O1, O2,
O3 are aligned on a straight line, and the center line O of the protrusion 44 is opposed to the rotation axis O1 of the rotating member 41 in which the cam groove 43 is formed.
3 and the rotational axis O2 of the output flange 42 provided therewith are located on opposite sides.

Next, the steering characteristic of the first embodiment will be described with reference to FIGS. 4 and 5. As shown in FIG. 4, a line connecting the rotation axis O1 of the rotation member 41 having the cam groove 43 and the rotation axis O2 of the output flange 42 provided with the protrusion 44 is defined as the y-axis, and the line passing through the rotation axis O2 is defined as the y-axis. If the orthogonal line is the x-axis and the rotation angle of the output shaft 13 when the intermediate shaft 12 is rotated by the angle α from the neutral position shown by the solid line is θ, the coordinates (x, y) of the center line O3 of the protrusion 44 are It is as follows.

[0014]

## EQU1 ## x = Rsinθ y = Rcosθ The relationship between the rotation angle α and θ is as follows from FIG.

[0015]

Tan α = R sin θ / (R cos θ−e) = sin θ / (cos θ−r) where r = e / R Therefore, the following is obtained.

[0016]

## EQU3 ## α = tan ^-1 (sin θ / (cos θ-r)) The relationship between the two rotation angles α and θ is as shown in FIG. 5 (a).
The output shaft rotation angle θ is acceleratedly increased as the intermediate shaft rotation angle α is increased from the neutral position. That is, the inclination angle of the characteristic is small near the neutral position, and the intermediate shaft rotation angle α
Increases as the angle approaches 180 degrees. Therefore, the reduction ratio between the intermediate shaft 12 and the output shaft 13 gradually decreases as the intermediate shaft rotation angle α approaches 180 degrees away from the neutral position as shown in FIG. 5 (b). In addition, the ratio r (= e /
As the R) increases, the change in the inclination angle of the characteristic shown in FIG. 5A becomes large, and the reduction ratio also becomes large.

Since the reduction ratio of the steering angle of the front wheels to the rotation angle of the output shaft 13 is almost constant when the steering angle is large, the characteristic of the reduction ratio between the steering wheel rotation angle and the front wheel steering angle is as follows. For example, the curve is as shown in FIG. That is,
At the steering neutral position, the reduction ratio is large, and gradually decreases as the steering wheel rotation angle increases, and the steering wheel rotation angle becomes 18
It becomes the minimum value at the position of 0 degree, and tends to increase at the steering wheel rotation angle beyond that, that is, the opposite characteristic. Figure 3
An example of the case of e = 0.4 is shown, but if the ratio e changes, this characteristic changes similarly to the characteristic shown in FIG. 5 (b). In addition,
The steering wheel is not steered by a stopper beyond a predetermined angle (for example, 240 degrees).

As shown in FIG. 1, the steering system of this embodiment is provided with a power steering system including a servo valve (control system) 20 and a power cylinder (power booster) 30. The rotor valve member 21 of the servo valve 20 is integrally formed on the rear portion of the input shaft 11, and the inner and outer peripheral surfaces of the sleeve valve member 22 are respectively rotatable on the outer peripheral surface of the rotor valve member 21 and the inner peripheral surface of the valve housing 10a. And is connected to the intermediate shaft 12 by an engagement pin 23. The valve housing 10a has four ports of the servo valve 20, namely, the input port 2
5, discharge port 26 and a pair of distribution ports 27a, 27
b is formed.

On the other hand, the power cylinder 30 has a rack bar 14
A cylinder 31 that is provided in the middle of the rack housing 10b and that is formed integrally with the rack housing 10b and that penetrates the rack bar 14 coaxially and liquid-tightly; The piston 32 is configured to separate the inside into left and right working chambers. The left and right working chambers are respectively connected to the distribution ports 27a and 27b of the servo valve 20 by communication passages, and the input port 25 and the discharge port 26 are connected to the supply pump 35 and the reservoir 36 by communication passages, respectively.

The servo valve 20 includes an input shaft 11 and an intermediate shaft 1.
It operates in response to a slight twist of the torsion bar 16 due to the torque acting between the two, and supplies the working fluid from the supply pump 35 to each working chamber of the power cylinder 30 and the working fluid from each working chamber to the reservoir 36. The discharge is controlled via the distribution ports 27a and 27b. As a result, the steering assist force corresponding to the torque is applied to the rack bar 14
Is given to the front wheels via. A reaction force mechanism 29 for changing the power steering characteristic by changing the torsion spring characteristic between the input shaft 11 and the intermediate shaft 12 is provided between the input shaft 11 and the intermediate shaft 12. Omit it. The oil seal 19 that seals between the reaction force mechanism 29 and the steering characteristic imparting mechanism 40 is a bearing retainer 10c that fixes the bearing 17a.
The outer periphery is fitted and fixed in a liquid-tight manner, and the seal lip on the inner periphery is brought into liquid-tight contact with the outer peripheral surface of the boss portion of the input flange 41.

Next, the operation of the first embodiment will be described.
When the input shaft 11 rotates in proportion to the rotation of the steering wheel (not shown), the input flange 41 of the steering characteristic imparting mechanism 40 also rotates via the torsion bar 16 and the intermediate shaft 12.
As the intermediate shaft 12 rotates leftward or rightward from the front wheel steering neutral position shown by the solid lines in FIGS. 2 and 4, the roller 44b of the protrusion 44 rolls radially outward along the cam groove 43 to output the output shaft. 13 rotates, but the intermediate shaft 12 and the output shaft 13
As described above, the speed reduction ratio during the period gradually decreases as the rotation angle of the steering wheel increases from the steering neutral position. The rotation of the output shaft 13 is controlled by the rack bar 14 via the interlocking mechanism 15.
Is converted into the shaft movement of the front wheel, and is converted into steering of the front wheels through a link (not shown). The characteristic of the reduction ratio between the steering wheel rotation angle and the front wheel steering angle is, for example, the curve shown in FIG. 3 as described above.

Due to the speed reduction ratio characteristic between the steering wheel rotation angle and the front wheel steering angle, the front wheel steering angle characteristic becomes a characteristic that the characteristic increases at an accelerating rate as the rotation angle of the steering wheel increases. As a result, although the structure is relatively simple, it is possible to give a sufficient feeling of cutting when the steering wheel is turned without giving a feeling of excessive cutting near the neutral position of the steering wheel, and to obtain a desired maximum front wheel steering angle. It can reduce the maximum steering wheel rotation angle required.
Moreover, the steering characteristic can be changed by a relatively simple adjustment in which the ratio e of the eccentricity e between the input shaft 11 and the output shaft 13 and the eccentric distance R of the protrusion 44 with respect to the output shaft 13 is changed.

Further, the servo valve 20 is a steering characteristic imparting mechanism 4
Since the operation is performed according to the torque applied to the input shaft 11 located on the steering wheel side of 0, the steering wheel torque is not affected by the reduction of the reduction ratio by the steering characteristic imparting mechanism 40 between the intermediate shaft 12 and the output shaft 13. Of the output operating member 14 via the power cylinder 30.
The assisting force that increases in proportion to the increase in the steering wheel torque is given to. Therefore, the steering wheel torque has a characteristic that the steering wheel torque increases almost proportionally with an increase in the steering wheel rotation angle from the steering neutral position, and the steering wheel does not become acceleratingly heavy.

Next, a second embodiment shown in FIGS. 6 to 8 will be described. In the second embodiment, a protrusion 44A of the steering characteristic imparting mechanism 40 is provided on the intermediate shaft 12 side, and a rotary member 41A having a cam groove 43A for engaging the protrusion 44A is provided on the output shaft 13.
The point provided on the side is substantially different from the first embodiment. Similar to the first embodiment, the intermediate shaft 12 and the output shaft 13 are eccentric to each other by a distance e and are supported by the housing 10.
At the rear end of 2 and the front end of the output shaft 13, the keys 42b and 41 are provided.
The input flange 42A and the output flange (rotating member) 41A are coaxially fixed via b. The input flange 42A is supported by a middle housing 10d forming a part of the housing 10 via a bearing 17c,
The output flange 41A is supported by the rack housing 10b via the bearing 18a.

As shown in FIGS. 6 and 7, a cam groove 43A extending in the diametrical direction is formed on the front end surface of the output flange 41A facing the input flange 42A. The input flange 42A facing the output flange 41A is provided with a protrusion 44 axially protruding from the rear end surface thereof by a distance R eccentric from the rotation axis O1 of the input flange 42A. At the steering neutral position, as in the first embodiment,
The center line O3 of the protrusion 44A is the rotation axis O of both shafts 12 and 13.
1, O2 are aligned with each other, and the distance R is larger than the eccentric amount e, but the center line O3 of the protrusion 44A and the input provided with the center line O3 of the rotation member 41A having the cam groove 43A are provided. The rotation axes O1 of the flanges 42A are located on the same side as each other.

Next, the steering characteristics of the second embodiment will be described with reference to FIGS. 7 and 8. As shown in FIG. 7, the cam groove 43A
Of the rotation member 41A and the projection 44A
The line connecting the rotation axis O1 of the input flange 42A provided with is the y-axis, and the line passing through the rotation axis O1 and orthogonal to the y-axis is x.
If the rotation angle of the output shaft 13 when the intermediate shaft 12 is rotated by an angle α from the neutral position indicated by the solid line is θ, then the projection 4
The coordinates (x, y) of the center line O3 of 4 are as follows.

[0027]

## EQU4 ## x = Rsinα y = Rcosα The relationship between the rotation angle α and θ is as follows from FIG.

[0028]

Tan θ = R sin α / (R cos α + e) = sin α / (cos α + r) where r = e / R Therefore, the following is obtained.

[0029]

[Equation 6] θ = tan ⁻¹ (sin α / (cos α + r)) The relationship between the two rotation angles α and θ is basically similar to that of the first embodiment, and the inclination angle of the characteristic is shown in FIG. As shown in (a), it is small near the neutral position and increases as the intermediate shaft rotation angle α approaches 180 degrees, and the reduction ratio between the intermediate shaft 12 and the output shaft 13 is shown in FIG. 8 (b). As shown in, the intermediate shaft rotation angle α gradually decreases as it moves away from the neutral position. Further, as the ratio r (= e / R) increases, the change in the inclination angle of the characteristic of FIG. 8 (a) becomes large, and the reduction ratio also becomes large.

However, the characteristic of the increase of the output shaft rotation angle θ is that in the first embodiment, as shown in FIG. 5, the change of the inclination angle of the characteristic becomes abrupt near the neutral position, whereas in the second embodiment. In the example, as shown in FIG. 8, the change in the inclination angle of the characteristic is rapid when the intermediate shaft rotation angle α is around 180 degrees.
Therefore, in the first and second embodiments, even if the ratio r is the same, the characteristic of the reduction ratio between the intermediate shaft 12 and the output shaft 13, that is, the characteristic of the reduction ratio between the steering wheel rotation angle and the front wheel steering angle is different. Will be things.

Since the structure and operation of the second embodiment other than the above are substantially the same as those of the first embodiment, detailed description thereof will be omitted. Like the first embodiment, the second embodiment has a relatively simple structure and can give a sufficient cutting feeling at a large steering wheel angle without giving an excessive cutting feeling at a small steering wheel angle position. The maximum steering wheel rotation angle required to obtain the desired maximum front wheel steering angle can be reduced, and the steering characteristics can be changed by a relatively simple adjustment of changing the ratio r. It is possible to obtain each effect that the handle does not become heavy due to acceleration. Moreover, since the characteristic of the reduction ratio between the steering wheel rotation angle and the front wheel steering angle is different from that of the first embodiment as described above, the selection range of the steering characteristic can be expanded.

Although each of the above-described embodiments has shown an example in which a hydraulic power steering device is used, the present invention uses a power steering device of another type, for example, an electric power steering device. It can also be carried out. The present invention also relates to the interlocking mechanism 1
It is also possible to implement a steering device using a device other than a rack and pinion type such as a ball screw type and a worm pin type.

[Brief description of drawings]

FIG. 1 is an overall vertical sectional view of a first embodiment of a steering device according to the present invention.

2 is a sectional view taken along line 2-2 of FIG.

FIG. 3 is a diagram showing an example of a reduction ratio characteristic of the first embodiment.

FIG. 4 is an explanatory diagram of the operation of the steering characteristic imparting mechanism of the first embodiment.

5 is a diagram showing characteristics of the steering characteristic imparting mechanism of FIG.

FIG. 6 is a side view in which a main part of a second embodiment of a steering device according to the present invention is cut away.

FIG. 7 is an explanatory diagram of the operation of the steering characteristic imparting mechanism of the second embodiment.

8 is a diagram showing characteristics of the steering characteristic imparting mechanism of FIG. 7. FIG.

[Explanation of symbols]

11 ... Input shaft, 13 ... Output shaft, 14 ... Output actuating member (rack bar), 15 ... Interlocking mechanism, 20 ... Control device (servo valve), 30 ... Booster device (power cylinder), 40 ... Steering characteristic imparting mechanism, 41, 41A ... Rotating member, 43, 43A
... Cam grooves, 44, 44A ... Protrusions.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Masanori Natsume 1-1, Asahi-cho, Kariya city, Aichi Toyota Koki Co., Ltd. (72) Inventor Kuyo Ikusei 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Co., Ltd. (72) Inventor Satoru Niwa 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Co., Ltd.

Claims (1)

[Claims] 1. An input shaft connected to a handle shaft that rotates together with a steering handle, an output operating member connected to the input shaft via an output shaft and an interlocking mechanism, and an output operating member for steering a wheel via a steering link, and an output thereof. A steering device comprising: a booster device that gives an assisting force to an actuating member; and a control device that operates in response to a torque applied to the input shaft to change the assisting force that the booster device gives to the output operating member. The shaft and the output shaft are provided eccentrically with respect to each other by a predetermined amount, and both shafts are connected to either one of the shafts and a rotary member having a diametrical cam groove formed on an end face thereof, and the other of the shafts are provided with A steering device characterized in that the steering device is connected by a steering characteristic imparting mechanism that is provided with a protrusion eccentrically larger than a predetermined amount so as to project in the axial direction and engages in the cam groove.