Electrical resistors – Mechanically variable – Movable contact electrically adjustable over length of...
Reexamination Certificate
2000-06-20
2004-05-04
Easthom, Karl D. (Department: 2832)
Electrical resistors
Mechanically variable
Movable contact electrically adjustable over length of...
C338S175000
Reexamination Certificate
active
06731194
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a rotary sensor, for example, a throttle position sensor mounted in a vehicle and used for the purpose of detecting the position of the throttle valve according to the amount of pushing the gas pedal and, in particular, to a rotation shaft bearing structure which prevents the sensor rotation shaft from becoming eccentric.
2. Description of the Related Art
FIGS. 30 and 31
illustrate a conventional rotary sensor of this type. The conventional rotary sensor comprises a cup-shaped housing
31
formed of synthetic resin. An annular wall portion
31
is integrally formed with a cylindrical external connection portion
33
, and three lead-through terminals
34
(only one of which is shown) are mounted by insert molding. The interior of the annular wall
32
constitutes an accommodating portion
35
, the end portions of the three lead-through terminals
34
being arranged in the accommodating portion
35
and the external connection portion
33
.
In the bottom wall portion
36
of the housing
31
, a metal bearing
37
is mounted by insert molding, and a plate-like rotating member accommodated in the accommodating portion
35
and formed of an insulating resin has a rotation shaft
38
a
rotatably supported by the bearing
37
, forked sliders
39
formed of a conductive material being supported by the rotating member
38
. And, to the forward end portion of the rotation shaft
38
a
, there is firmly attached a lever member
40
outside the housing
31
, and due to this lever member
40
, the rotation shaft
38
a
is prevented from being detached.
Further, on the inner peripheral surface of the annular wall portion
32
of the housing
31
, there is formed a step portion
32
a
, and a circuit board
41
formed of synthetic resin or ceramic abuts this step portion so as to be fixed in the accommodating portion
35
such that it is opposed to the rotating member
38
. And, on the surface of the circuit board
41
, there are formed by printing a resistor pattern
42
which is arcuate around the rotation shaft
38
a
and a collector pattern
43
, and the sliders
39
are in contact with them to establish electrical connection between the resistor pattern
42
and the collector pattern
43
. Further, eyelet-like terminals
44
(only one of which is shown) are fixed to the circuit board
41
at both ends of the resistor pattern
42
and one end of the collector pattern
43
, and one end of each of the three lead-through terminal
34
is soldered to the forward end portion of each of them.
Further, in the bottom wall portion
36
of the housing
31
, there is formed on the opposite side of the accommodating portion
35
a recess
45
so as to be opposed to the lever member
40
, and a coil spring
46
is accommodated in the recess
45
such that a part of the bearing
37
is accommodated in the winding portion thereof, the free ends
46
a
and
46
b
of the coil spring
46
being engaged with the recess
45
and the lever member
40
.
Further, a cover
47
formed of synthetic resin is fitted into the opening
35
a
of the housing
31
on the back side of the circuit board
41
, and this cover
47
is supported by the housing
31
by crushing the periphery of the opening
35
a
of the housing
31
by heat caulking, thereby enclosing the interior of the accommodating portion
35
.
In the rotary sensor, constructed as described above, the lever member
40
is connected through a drive pin
49
a
to a rotary disc
49
fastened to a drive shaft
48
, which rotates by a predetermined angle in accordance with the position or opening angle of the throttle valve of an internal combustion engine (not shown), a predetermined voltage being applied to both ends of the resistor pattern
42
through a connector (not shown) fitted into the external connection portion
33
, the lead-through terminals
34
and the terminals
44
.
And, when the rotation of the drive shaft
48
is transmitted to the lever member
40
through the rotary disc
49
and the drive pin
49
a
, the rotation shaft
38
a
and the rotating member
38
rotate integrally with the lever member
40
, and, with that, the sliders
39
slide on the resistor pattern
42
and the collector pattern
43
. As a result, a voltage according to the position or opening angle of the throttle valve is generated in the terminal
44
fastened to one end portion of the collector pattern
43
. This voltage is output to the exterior of the sensor through the connector, and used as a throttle valve position signal for controlling an internal combustion engine or the like.
As shown in
FIG. 31
, in the above-described conventional rotary sensor, a little clearance t is provided between the rotation shaft
38
a
and the inner peripheral surface of the bearing
37
so that the rotation shaft
38
can rotate. Thus, when the rotation shaft
38
a
rotates in a condition in which it s radially eccentric (in the directions of the arrows A), the rotation of the rotating member
38
as a result of the rotation of the rotation shaft
38
a
causes the rotating member
38
to rotate in an eccentric state, so that the sliders
39
are deviated from the regular circular paths. As a result, the linearity characteristics of the throttle posit on signal (linear change in the output voltage according to the rotation of the lever member
40
) deteriorate. Further, hysteresis is generated in the throttle valve position signal, making it impossible to correctly detect the position or opening angle of the throttle valve.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above problem in the prior art. Accordingly, it is an object of the present invention to provide a highly reliable rotary sensor in which radial eccentricity of the rotation shaft is prevented, making it possible to perform correct detection.
To achieve the above object, there is provided, in accordance with the present invention, a rotary sensor comprising a rotating member having a rotation shaft, rotation detecting means for detecting the rotation of the rotating member, a bearing having a shaft hole into which the rotation shaft is inserted and which rotatably supports the rotation shaft integrally with the rotating member, and biasing means for imparting a biasing force in a thrust direction to the rotation shaft, wherein there is formed in the periphery of one end portion of the shaft hole a beveled portion inclined so as to be outwardly flared in the radial direction of the shaft hole, and wherein the rotating member is provided with a tapered surface corresponding to the beveled portion, the tapered surface being held in press contact with the beveled portion by the biasing force.
In the above construction, there are provided a housing having an accommodating portion accommodating the rotation detecting means and a lever member adapted to rotate integrally with the rotation shaft, the bearing being provided in the bottom wall portion of the housing, the accommodating portion communicating with the exterior of the housing by the bearing, the lever member being arranged on the opposite side of the accommodating portion, the bottom wall portion having a recess accommodating the biasing means on the opposite side of the accommodating portion, the biasing means biasing the rotation shaft through the lever member.
Further, in the above construction, the rotating member is accommodated in the accommodating portion, and wherein, in the radial direction of the hole portion, on the outside of the beveled portion of the bearing and the tapered surface of the rotating member, the biasing member biases the lever member such that it is separated from the accommodating portion, thereby bringing the beveled portion into press contact with the tapered surface in the accommodating portion.
Further, in the above construction, the biasing means is formed by a single coil spring, the bearing being accommodated in the winding portion of the coil spring.
Further, in the above construction, the free ends of the coil sprin
Alps Electric Co. ,Ltd.
Easthom Karl D.
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