Measuring and testing – Dynamometers – Responsive to torque
Reexamination Certificate
1999-09-15
2002-04-16
Fuller, Benjamin R. (Department: 2855)
Measuring and testing
Dynamometers
Responsive to torque
Reexamination Certificate
active
06370966
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an input torque detecting device for power steering, more particularly, an input torque detecting device which converts a relative rotation of an input shaft and an output shaft into a movement in the direction of a shaft so as to detect torque.
BACKGROUND ART
Heretofore, as an input torque detecting device for power steering, for example, a device for detecting input torque by converting the relative rotation of an input shaft and an output shaft resulting from torsion of a torsion bar based on input torque into an amount of slide in the direction of a shaft and detecting the amount of slide as proposed in Japanese Patent Application No. Hei 7-182151 is well known. The input torque detecting device of Japanese Patent Application No. Hei 7-182151 will subsequently be described with reference to
FIGS. 6 through 9
.
As shown in
FIG. 6
, an input shaft
101
in which torque is input from a steering wheel is rotatably held in a gear box
118
through a bearing
121
and also connected to an output shaft
103
through a torsion bar
102
which is connected to the inside of the input shaft
101
. The output shaft
103
is rotatably held in the gear box
118
through a bearing
122
and also engaged with a rack shaft
105
through a pinion gear
104
, whereby input torque is applied to a steered side through the rack shaft
105
.
A cylindrical sleeve
107
is installed at a common outer circumference of the input shaft
101
and the output shaft
103
. As shown in
FIG. 7
, at an inner circumference of the sleeve
107
, a pair of pins
108
are installed as members for engaging with the input shaft
101
at an interval of 180 degrees and also a pair of shaft line direction holes
109
which extend in the direction of a shaft line are formed as members for engaging with the output shaft
103
at an interval of 180 degrees. Incidentally, the pins
108
and the shaft line direction holes
109
are installed in such a manner that they get out of position to each other by 90 degrees.
On the other hand, as shown in
FIGS. 8 and 9
, two spiral grooves
113
which extend in a direction diagonal to a shaft line are formed at an outer circumference of the input shaft
101
as sections for engaging with the pins
108
. Further, pins
114
are formed at the output shaft
103
as members for engaging with the shaft line direction holes
109
.
Further, an annular detection groove
115
is formed at an outer circumference of the sleeve
107
and a detection lever
116
of a sensor
117
(for example, a potentiometer) is engaged with the detection groove
115
.
Due to such constitution, in a conventional input torque detecting device, the input shaft
101
and the output shaft
103
make relative rotations as a result of torsion of a torsion bar which is caused by inputting input torque from a steering wheel in the input shaft
101
. At this time, in a relation to the output shaft
103
, the sleeve
107
is allowed to make a relative movement only in a direction along the shaft line direction holes
109
and is prohibited from making a relative rotation. On the other hand, in a relation to the input shaft
101
, the sleeve
107
makes relative rotations sliding in the direction of a shaft in spiral orbit along the spiral grooves
113
. Thus, an amount of torsion of the torsion bar
102
is converted into an amount of slide of the sleeve
107
, and the amount of slide is detected by the sensor
117
as an amount of operating the detection lever
116
which is engaged with the sleeve
107
. More specifically, input torque is detected by the sensor
117
, and an electric motor or the like which is not shown in the drawings generates auxiliary torque according to the magnitude and direction of the input torque detected.
However, the conventional input torque detecting device is accompanied with the following problems.
First, the conventional input torque detecting device requires that the pins
108
are fitted to the sleeve
107
and the pins
114
to the output shaft
103
, respectively, as engaging members, whereby a large number of parts are used. Further, it requires a process which pin holes for fixing pins are machined in the sleeve
107
and the output shaft
103
and then the pins
108
and
114
are pressed into the pin holes. Surplus manufacturing costs are entailed and man-hours for assembly increase.
Second, due to line contact of the spiral grooves
113
with the cylindrical pins
108
and the shaft line direction holes
109
with the cylindrical pins
114
, operation of the device easily causes abrasion of these pins
108
and
114
.
Third, since the spiral grooves
113
formed at the input shaft
103
are square, plastic working cannot be carried out and machining is required, whereby manufacturing costs become higher.
In this regard, Japanese Patent Application No. Hei 7-182151 discloses an embodiment in which a ball rotatably held at the sleeve
107
is used as an engaging member, but it does not lead to the fundamental solution of the problems described above. Further, in order to prevent the ball from falling from the sleeve
107
, a ball hole must be bored in the sleeve
107
, whereby manufacturing costs are increased again.
The present invention is made in consideration of such problems. An object of the present invention is to provide an input torque detecting device for power steering which is capable of reducing parts in number, facilitating assembly, and decreasing manufacturing costs.
DISCLOSURE OF THE INVENTION
According to the present invention, in an input torque detecting device comprising an input shaft in which torque is input from a steering wheel side, an output shaft being linked to a steered side, a torsion bar to be equipped between the said input shaft and output shaft, a movable body which is slidably arranged at the said input shaft and output shaft in the direction of a shaft, converting means for converting a relative rotation of the said input shaft and output shaft into a slide of the movable body in the direction of a shaft, and detecting means for detecting an amount of slide of the movable bodies, a cylindrical sleeve to be arranged as the said movable body at a common outer circumference of the said input shaft and output shaft is equipped and also a diameter expansion section is installed at any one of the outer circumferences of the said input shaft and output shaft. Further, the said converting means have a plurality of splines which are formed extending in a direction diagonally to a shaft line at the said diameter expansion section and an inner circumference of the said sleeve, respectively, and engagement means which engage either of the input shaft or the output shaft with the said sleeve in such a manner that only a slide in the direction of a shaft is allowed. At least one end of the said splines is opened, an undulation section is installed orthogonally to a shaft center at an outer circumference of the said sleeve, and a detection lever of the detecting means is engaged with the undulation section. Thus, when a relative rotation between the input shaft and the output shaft arises resulting from torsion of the torsion bar based on input torque, in a relation to the input shaft or the output shaft, the sleeve makes relative rotations along a spiral orbit which is determined by a plurality of splines formed extending in a diagonal direction and also makes a relative movement in the direction of a shaft. Input torque is detected by detecting an amount of slide of the sleeve in the direction of a shaft by the detecting means. When auxiliary torque arises based on the magnitude and direction of the input torque, an appropriate power assist can be achieved. In this case, a section engaging the sleeve with the input shaft or the output shaft is composed of a plurality of splines. These splines can be formed in one united body with the sleeve and either the input shaft or the output shaft. Thus any other engaging member of a different kind is not required, whereby the number of parts and the man-hours f
Kugiyama Fusayoshi
Naruse Nobuharu
Tanigawa Naomichi
Fuller Benjamin R.
Kayaba Kogyo Kabushiki Kaisha
Rabin & Berdo P.C.
Thompson Jewell V.
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