Linear operation type electric part

Details Linear operation type electric part Linear operation type electric part

2001-07-20

2003-01-14

Easthom, Karl D. (Department: 2832)

Electrical resistors

Mechanically variable

Movable contact electrically adjustable over length of...

C338S194000

Reexamination Certificate

active

06507270

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a linear operation type electric part which is provided in an automobile having an engine mounted therein, and which may be preferably used for a sensor for controlling a mixture ratio of fuel and air, a sensor for controlling the amount of exhaust gas to be recycled, and the like.
2. Description of the Related Art
Referring to
FIGS. 11
to
13
, a conventional linear operation type electric part of this kind will be described.
FIG. 11
is a cross-sectional view of a conventional linear operation type electric part as viewed from the side;
FIG. 12
is a cross-sectional view of the conventional linear operation type electric part as viewed from the back; and
FIG. 13
is a cross-sectional view of a flat spring of the conventional linear operation type electric part. In the Figures, a box case
31
includes a housing
31
a
with an opened back portion, a hole
31
b
provided in the front portion that is in communication with the housing
31
a
, and a pair of guide grooves
31
c
provided in the front-to-back direction within the housing
31
a.
Moreover, an insulation substrate
33
having a resistive element
32
provided thereon is attached to the bottom of the housing
31
a
. The inside of the housing
31
a
is hermetically sealed by a sealing part
34
, which closes the opened back portion of the housing
31
a.
A movable member
35
having a pair of shoulder parts
35
a
is accommodated to be linearly movable along the front-to-back direction in the housing
31
a
, with the pair of shoulder parts
35
a
being placed within a corresponding pair of housing guide grooves
31
c
. On the lower part of the movable member
35
is attached, at least one sliding member
36
which slides against and is in electrical contact with the resistive element
32
. Moreover, a flat spring
37
as shown in
FIG. 13
is provided on an upper part of the movable member
35
. The flat spring
37
presses down the movable member
35
so that the lower part of the movable member
35
elastically abuts with the case
31
to prevent backlash along the vertical direction A. At the same time, the flat spring
37
prevents backlash along the horizontal width direction B.
A coil spring
38
, for biasing movable member
35
toward the front of the housing
31
a
and for restoring movable member
35
from backward movement, is placed between the movable member
35
and the sealing part
34
. An operation shaft
39
is inserted into the hole
31
b
such that backward linear movement of the operation shaft
39
along the horizontal front-to-back axial direction of housing
31
a
causes the movable member
35
to also move linearly backward along the axial direction.
Specifically, the spring force of the coil spring
38
acts in the same direction as the axial direction of the operation shaft
39
whereas the spring force of the flat spring
37
acts in directions perpendicular to the axial direction.
Furthermore, the conventional linear operation type electric part operates as follows. First, as the operation shaft
39
is pressed backward along the axial direction, the movable member
35
moves toward the back against the action of coil spring
38
.
Thus, the sliding member
36
moves on the resistive element
32
together with the movable member
35
to produce a varying resistance value, and thus enabling detection of the position of sliding member
36
.
Moreover, during the movement of the movable member
35
, the flat spring
37
moves together with the movable member
35
while sliding along the case
31
. At the same time, the lower part of the movable member
35
moves while in slidable contact with the case
31
.
When the pressure on the operation shaft
39
is released, the movable member
35
on which the sliding member
36
is attached and the operation shaft
39
are pushed frontward by the biasing force of coil spring
38
so as to restore them to their original state.
The conventional linear operation type electric part requires the flat spring
37
to prevent backlash of the movable member
35
along the vertical and horizontal directions in addition to the coil spring
38
for restoring the movable member
35
from its backward movement. In other words, there is a need for two kinds of spring parts, i.e., the coil spring
38
and the flat spring
37
. The increased number of parts leads to an increased cost.
Moreover, placing the flat spring
37
inside the guide grooves
31
c
requires cumbersome attachment work, and thus detracts from fabrication productivity. In addition, the flat spring
37
and the case
31
are in slidable contact with each other, so that the movable member
35
cannot move smoothly.
SUMMARY OF THE INVENTION
In view of above, it is an object of the present invention to provide a linear operation type electric part in which a spring member for restoring the movement of a movable member and a spring member for preventing the backlash of the movable member are formed of the same kind of coil spring, thereby reducing the number of parts used therefore, and enabling lower cost and increased productivity, and in which the movable member can be moved smoothly.
As first means to solve the above-described problems, the structure according to the present invention comprises: an operation shaft linearly movable along an axial direction; a movable member abutting with one end of the operation shaft, the movable member being disposed so as to be linearly movable by the operation shaft; a spring member for biasing the movable member so as to be restored from movement thereof; a case having a guide part for guiding the movable member during the movement thereof; and a detection means disposed on the movable member and operated by the movement of the movable member. The guide part of the case comprises an upper guide sub-part and a lower guide sub-part for guiding surfaces of the movable member from above and below, respectively. The movable member comprises: a lower slide-contact part having the detection means on a lower side thereof and sliding in contact with the lower guide sub-part; and an upper slide-contact part located above and opposing to the lower slide-contact part, the upper slide-contact part sliding in contact with the upper guide sub-part. The upper and lower guide sub-parts and the upper and lower slide-contact parts form a restriction mechanism for restricting the movement of the movable member. The movable member receives from the spring members a turning moment for skewing a center line of the movable member in direction different to the axial direction, the center line extending along a front-to-back direction from a center of the movable member, thus rotating the movable member with respect to the axial direction, the rotation causing the upper and lower slide-contact parts of the movable member to press against and be in contact with their corresponding upper and lower guide sub-parts of the case, respectively. The restriction mechanism restricts the movement of the movable member along the vertical and width directions to prevent a backlash of the movable member. The movable member linearly moves while being skewed with respect to the axial direction.
As second means to solve the problems, the restriction mechanism has inclined planar surfaces on each of the upper and lower guide sub-parts or on each of the upper and lower slide-contact parts.
As third means to solve the problems, the restriction mechanism has inclined planar surfaces on each of the upper guide sub-parts and the upper slide-contact parts or on each of the lower guide parts and the lower slide-contact parts.
As fourth means to solve the problems, the restriction mechanism has s the surfaces of one of either a pair of the upper guide sub-parts and the upper slide-contact parts or a pair of the lower guide sub-parts and the lower slide-contact parts formed of inclined planar surfaces capable of abutting with each other, respectively, while the other pair comprises one arc-shaped surface and one flat surface

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