Motor vehicles – Steering gear – With electric power assist
Reexamination Certificate
1998-10-30
2001-01-30
Swann, J. J. (Department: 3611)
Motor vehicles
Steering gear
With electric power assist
C180S443000
Reexamination Certificate
active
06179083
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a steering apparatus for a vehicle having a variable transmission ratio of a steer angle of turned wheels to a steering angle of a steering wheel.
2. Related Background Art
In the comparative steering apparatus, rotation of a steering shaft coupled to the steering wheel is normally converted to lateral displacement of a tie rod through a gearing system such as rack and pinion. In order to assure running stability according to vehicle speed on this occasion, the apparatus is provided with a transmission ratio changing mechanism for changing a rotation transmission ratio (gear ratio) between input and output of the gearing system in accordance with vehicle speed.
FIG. 9
illustrates an example of the comparative steering apparatus provided with such a transmission ratio changing mechanism which is similar to a mechanism described in Japanese Laid-open Patent Application No. 62-23869. In this steering apparatus, rotation of steering shaft
102
coupled to the steering wheel is transmitted through input gears
103
,
104
to input shaft
101
, whereby the input shaft
101
rotates in unison with sun gear
105
. The rotation of the sun gear
105
is transmitted through planetary gears
106
, disposed on the outside periphery of the sun gear, to ring gear
107
, and the apparatus is structured to gain rotational output from output shaft
108
which is integral with the ring gear
107
.
On the other hand, rotation of stepping motor
109
is transmitted to carrier
110
, which is rotatable relative to the input shaft
101
, and the carrier
110
supports the planetary gears
106
.
In this setup, when the carrier
110
is rotated by the stepping motor
109
, the planetary gears
106
come to revolve around the sun gear
105
. This action changes an amount of rotation of the planetary gears
106
rotated by the sun gear
105
. The rotation transmission ratio between the input shaft
101
and the output shaft
108
is controlled by this mechanism.
SUMMARY OF THE INVENTION
In the comparative steering apparatus, as shown in
FIG. 10
, when the input shaft
101
rotates in the direction of arrow a, this rotation is transmitted through the sun gear
105
and the planetary gears
106
to the ring gear
107
, but the ring gear
107
rotates in the direction of arrow b, which is opposite to the arrow a. In order to achieve agreement between the rotating direction of the steering wheel and the rotating direction of the output shaft
108
, it was necessary to transmit the rotation of the steering shaft
102
while reversing it accordingly. For this purpose, it was necessary to interpose a pair of input gears
103
,
104
for transmission with reversal of the rotation of the steering shaft
102
on the input side, and they were thus hindered against miniaturization of the steering apparatus.
The present invention has been accomplished to solve this problem and an object of the invention is to provide a steering apparatus for a vehicle that can contribute to miniaturization of the steering apparatus.
A steering apparatus for a vehicle according to the present invention is a steering apparatus for a a vehicle having a variable transmission ratio of an angle of a turned wheel to an angle of a steering wheel, the steering apparatus comprising: an input shaft arranged to rotate in the same direction as the steering wheel does, in conjunction with a rotating operation of the steering wheel; a sun gear disposed concentrically with the input shaft and being capable of being driven to rotate; a planetary gear coupled to the input shaft and arranged to revolve in the same direction as the input shaft does, around the sun gear while being kept in mesh with the sun gear; a ring gear of an annular shape whose inside periphery is in mesh with the planetary gear; and an output shaft arranged to rotate in unison with the ring gear.
With rotation of the input shaft, the planetary gear coupled to this input shaft revolves around the sun gear in the same direction as the input shaft. With the revolving motion of the planetary gear around the sun gear, the ring gear in mesh with the planetary gear is rotated in the same direction as the revolving direction of the planetary gear, whereby the output shaft is rotated in this direction. Therefore, agreement is achieved between the rotating directions of the input shaft and the output shaft.
Rotation of the sun gear changes the rotation amount (angle of rotation) of the planetary gear and in turn also changes the rotation amount of the ring gear. This action can change the rotation transmission ratio of the output shaft to the input shaft.
The steering apparatus for vehicle may comprise: a transmission gear disposed concentrically with the input shaft and driven to undergo rotation by a driving source, thereby transmitting the rotation to the sun gear; first fixing means for fixing the sun gear and transmission gear relative to the input shaft so as to inhibit movement thereof along an axial direction of the input shaft and permit rotation thereof relative to the input shaft; a support member comprised of carrier
1
) for supporting the planetary gear; and second fixing means for fixing the support member relative to the input shaft.
The second fixing means is comprised, for example, of an abutment portion formed between the input shaft and the support member so as to inhibit movement of the support member along the axial direction of the input shaft, and a pushing portion for pushing the support member toward the abutment portion.
In this way the first fixing means fixes the sun gear and transmission gear relative to the input shaft, while the second fixing means, different from the first fixing means, fixes the support member relative to the input shaft. Accordingly, the second fixing means can fix the support member relative to the input shaft, independent of the fixing mechanism of the first fixing means, whereby axial positioning of the support member relative to the input shaft can be carried out independently, which increases degrees of freedom of positioning in assembling operation of the support member.
The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not to be considered as limiting the present invention.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
REFERENCES:
patent: 3286548 (1966-11-01), Baker
patent: 3404584 (1968-10-01), Trautmann
patent: 3427899 (1969-02-01), Gunderson et al.
patent: 3511104 (1970-05-01), Piat
patent: 4530413 (1985-07-01), Buike et al.
patent: 4765425 (1988-08-01), Saito et al.
patent: 4973295 (1990-11-01), Lee
patent: 62-23869 (1987-01-01), None
patent: 62-238166 (1987-10-01), None
Cuff Michael
Oliff & Berridg,e PLC
Swann J. J.
Toyota Jidosha & Kabushiki Kaisha
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