Electricity: measuring and testing – Magnetic – Displacement
Reexamination Certificate
2002-04-16
2004-01-13
Snow, Walter E. (Department: 2862)
Electricity: measuring and testing
Magnetic
Displacement
C324S207200, C174S050510
Reexamination Certificate
active
06677747
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a rotation sensor for sensing the speed of rotation of a gear type magnetic rotor, for instance, and a mold for manufacturing the rotation sensor.
2. Description of the Related Art
FIG. 7
is a side view showing the conventional rotation sensor.
FIG. 8
is a cross-sectional view of the rotation sensor taken along the line B—B in
FIG. 7
, and
FIG. 9
is a front view of a sensor main body as shown in FIG.
8
. As shown in these figures, the rotation sensor comprises the sensor main body
1
made of an insulating resin with the electronic parts mounted, and a case
2
made of insulating resin for tightly covering the sensor main body
1
. Further, the sensor main body
1
comprises a main body portion
1
a
, a board portion
1
b
, an intermediate portion
1
c
, and a connector portion
1
d
. The main body portion
1
a
has mounted a Hall element
3
for detecting the rotation of a magnetic rotor, a permanent magnet
4
for applying a magnetic field to the Hall element
3
, and a circuit substrate
7
having mounted the electronic parts
5
for processing an output signal of the Hall element
3
and formed with a circuit pattern
6
.
The main body portion la is shaped like a substantially slender plate and has one end connected perpendicularly to a principal plane of the board portion
1
b
. And the circuit board
7
is mounted on the principal plane on one side. The permanent magnet
4
is mounted on the other end portion of the main body portion
1
a
perpendicularly to the main body portion
1
a
, and the Hall element
3
that is a sensor element for detecting the approaching magnetic substance is disposed on the principal plane outside the permanent magnet
4
.
Also, the connector portion
1
d
is extended from the other end face of the intermediate portion
1
c
. The connector portion
1
d
extends from the other end face of the intermediate portion
1
c
perpendicularly to the main body portion
1
a
. A terminal
8
that is electrically connected to the circuit pattern
6
of the main body portion
1
a
is buried in the connector portion
1
d
. At a top end portion of L-character shape, a concave engagement portion connected to an external apparatus is formed, and the terminal
8
protrudes into the engagement portion.
The case
2
is composed of a cylindrical sheath portion
2
a
with a bottom, a flange portion
2
b
with an opening end portion of the sheath portion
2
a
thickened radially, a support portion
2
c
with a part of the flange portion
2
b
protruding radially outwardly, and a holding portion
2
d
protruding on the principal plane of the flange portion
2
b
in parallel to the sheath portion
2
a.
The rotation sensor with the above constitution is attached at a predetermined position of the vehicle. With the rotation of the rotor like a gear, for example, that is the magnetic substance provided against the Hall element
3
of the rotation sensor, a concave portion and a convex portion of the rotor alternately come closer to the Hall element
3
. If a magnetic field from the permanent magnet
4
to be applied to the Hall element
3
varies, the Hall element
3
detects a variation in the magnetic field as a voltage change. The voltage change produced in the Hall element
3
is converted into a pulse wave by the electronic parts
5
, and then this electrical signal is sent via the terminal
8
of the connect or portion
1
d
to the external apparatus, not shown, so that the speed of rotation of the rotor is detected.
In a manufacturing method for the rotation sensor, first of all, the sensor main body
1
is produced by molding integrally the main body portion
1
a
, the board portion
1
b
, the intermediate portion
1
c
, and the connector portion
1
d
with the terminal
8
and the permanent magnet
4
buried.
FIGS. 10A and 10B
are views for explaining the molding of the conventional rotation sensor.
FIG. 10A
is across-sectional view, and
FIG. 10B
is a perspective view.
FIG. 11
is a side view showing the permanent magnet after molding and its surroundings, and
FIG. 12
is a lower view of the permanent magnet as seen from a direction of the arrow in FIG.
11
.
In the figures, a molding apparatus
10
is composed of a first metal mold
11
and a second metal mold
12
, in which the first metal mold
11
has a magnet stage portion
11
a
for laying the permanent magnet
4
in molding, and each of the first metal mold
11
and the second metal mold
12
has a main body portion molding space
12
a
that becomes the main body portion
1
a
of the rotation sensor after molding. The permanent magnet
4
is inserted into and laid on the magnet stage portion
11
a
of the first metal mold
11
, and then the second metal mold
12
is engaged with the first metal mold
11
to fill a resin into the main body portion molding space
12
a
, whereby the permanent magnet
4
and the main body portion
11
a
of the rotation sensor are molded integrally as shown in FIG.
11
.
Thereafter, the Hall element
3
and the circuit board
7
are mounted on the main body portion
1
a
to produce the sensor main body
1
. On the other hand, the case
2
is also produced as a piece by molding. And the case
2
is covered over the sensor main body
1
, an upper edge part
2
g
of the holding portion
2
d
for the case
2
is caulked thermally, so that the sensor main body
1
and case
2
are fully integrated.
However, the conventional rotation sensor suffers from such a problem that the edge part of the permanent magnet
4
is likely to chip or break off, when the permanent magnet
4
is laid on the magnet stage portion
11
a
of the first metal mold
11
. That is, since an opening portion
11
b
of the magnet stage portion
11
a
in the first metal mold
11
has a right angled edge, as shown in
FIGS. 10A and 10B
, the edge part of the permanent magnet
4
makes contact with the opening portion
11
b
to chip or break off, when the permanent magnet
4
is inserted into the magnet stage portion
11
a.
Also, when the permanent magnet
4
is laid on the magnet stage portion
11
a
, the permanent magnet
4
makes contact with a bottom portion
11
c
of the magnet stage portion
11
a
to chip or break off at the edge part of the permanent magnet
4
due to a pressing force applied when the second metal mold
12
is engaged with the first metal mold
11
.
SUMMARY OF THE INVENTION
This invention has been achieved to solve the above-mentioned problem, and it is an object of the invention to provide a rotation sensor in which the permanent magnet is prevented from chipping or breaking off. Also, it is another object of the invention to provide a mold for manufacturing the rotation sensor that can manufacture the rotation sensor in which the permanent magnet is prevented from chipping or breaking off.
To achieve the above problem, a rotation sensor according to the present invention comprises a sensor element for sensing a magnetic substance that is approaching, a permanent magnet that is provided adjacent to the sensor element for applying a magnetic field to the sensor element, and a main body portion made of a resin and mounting the sensor element, the permanent magnet and the electronic parts electrically connected to the sensor element, characterized in that the resin is swollen in a taper manner in a boundary region between the permanent magnet and the main body portion, and the resin is swollen at a corner portion of the permanent magnet.
A mold for manufacturing a rotation sensor according to this invention comprises a first metal mold having a magnet stage portion with a porous bottom for placing a permanent magnet, and a second metal mold having a space for forming a main body portion of the rotation sensor with the first metal mold, in which the permanent magnet and the main body portion are integrally molded by filling a resin into the space, characterized by comprising a taper around an opening portion of the magnet stage portion, and a magnet stage plane for laying the permanent magne
Mitsubishi Denki & Kabushiki Kaisha
Snow Walter E.
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