Electricity: measuring and testing – Magnetic – Displacement
Reexamination Certificate
1998-10-14
2001-12-04
Patidar, Jay (Department: 2862)
Electricity: measuring and testing
Magnetic
Displacement
C324S207250
Reexamination Certificate
active
06326779
ABSTRACT:
BACKGROUND OF THE INVENTION
1. [Field of the Invention]
The present invention relates to a magnetic detector for detecting a magnetic field and, more specifically, to a magnetic apparatus for detecting changes in magnetic field caused by the rotation of a magnetic material or the like and to a production process therefor.
2. [Description of the Prior Art]
FIGS.
8
(
a
) and
8
(
b
) are structural diagrams of a magnetic detector of the prior art, FIG.
8
(
a
) is a top view and FIG.
8
(
b
) is a sectional view taken on line A—A of FIG.
8
(
a
). This magnetic detector comprises a magnetic resistance element for detecting a magnetic field (to be referred to as “MR element” hereinafter), a magnet
2
for providing a bias magnetic field to the MR element
1
, a protection circuit
4
composed of a plurality of electronic parts
3
for removing external noise from the output waveform of the MR element
1
, a lead frame
5
for mounting the electronic parts
3
, a base
6
for holding the MR element
1
, the magnet
2
and the lead frame
5
, a case
7
for protecting the base
6
, and a connector
8
, integrated with the base
6
, for outputting the output signal of the MR element
1
to the outside.
The base
6
is insert molded together with the magnet
2
after the electronic parts
3
forming the protection circuit
4
are mounted on the lead frame
5
, and the MR element
1
is soldered to an element attachment portion
5
k
of the lead frame
5
exposed on the base
6
integrated with the connector
8
after the formation of the base
6
.
After the attachment of the MR element
1
, the base
6
is press fitted in a press-in hole
7
k
of the case
7
and fixed at a press-in portion
6
k
formed at an upper portion (left side of FIG.
8
(
b
)) of the base
6
. Liquid packing P is coated on the outer periphery of the press-in portion
6
k
to cover up tight an inside portion
7
s
of the case
7
. Further, to fix the base
6
to the case
7
firmly, an upper portion of the case
7
is filled with a thermosetting resin adhesive
9
(shown by slant lines of FIG.
8
(
b
)).
As shown in
FIG. 9
, the MR element
1
has a thin film magnetic resistance pattern
1
b
made from a magnetic material having a large magnetic resistance effect, such as permalloy, formed on the substrate
1
a
made from ceramic or the like. The resistance value of the magnetic resistance pattern
1
b
changes according to the size of a magnetic field applied to the magnetic resistance pattern
1
b
. Then, the MR element
1
is arranged next to a magnetic rotor
50
having an irregular surface on the outer periphery and rotating around a rotation axis J with predetermined spacing therebetween to detect changes in the strength of a magnetic field it receives from the magnetic rotor
50
, whereby the rotation position or rotation speed of the magnetic rotor
50
can be obtained.
However, in the above magnetic detector of the prior art, since the connector
8
and the base
6
are integrated with each other, the shape of the magnetic detector is complex and the production cost of a mold used to produce the magnetic detector is high. In addition, when the shape of the connector
8
or the position of the connector
8
with respect to the case
7
is changed, a mold for producing the base
6
and the connector
8
integrally must be newly fabricated, thereby further boosting equipment costs.
When the base
6
is to be press fitted in the case
7
, since the inside of the case
7
is empty and the base
6
is covered up tight in the case
7
, the liquid packing P must be coated on the outer periphery of the press-in portion
6
k
to protect the MR element
1
in the case from moisture, dust and the like. Thereby, productivity deteriorates and costs rise.
Further, when the thermosetting resin adhesive
9
is to be injected into the upper portion of the case
7
, the resin adhesive
9
often overflows from the case
7
and adheres to the side surface of the case
7
. Therefore, a checking step must be provided to remove the adhered resin adhesive
9
, thereby boosting the production cost.
To improve the characteristic properties of the magnetic detector, the MR element
1
must be arranged in front of the magnet
2
. However, as the MR element
1
and the base for holding the magnet
2
are produced as separate units, the MR element
1
must be soldered to the lead frame
5
exposed on the base
6
while it is located at a predetermined position in front of the magnet
2
, thereby reducing productivity and boosting costs.
Moreover, as shown in FIGS.
10
(
a
) and
10
(
b
), solder S for mounting electronic parts
3
(shown by slant lines in FIG.
10
(
b
) previously coated on a land portion
5
a
of the lead frame
5
may flow away at the time of soldering the electronic parts
3
, thereby reducing the reliability of the apparatus. For comparison, the shape of the lead frame
5
of FIGS.
10
(
a
) and
10
(
b
) is made similar to that of the lead frame of the present invention which will be described hereinafter.
SUMMARY OF THE INVENTION
The present invention has been made to solve the above problems and it is an object of the present invention to provide a low-cost magnetic detector having high productivity and high reliability.
According to a first aspect of the present invention, there is provided a process for producing a magnetic detector which comprises the steps of:
producing a base for holding a magnetic detection element for detecting a magnetic field and a connector for outputting the output signal of the magnetic detection element to the outside as separate units; and
electrically interconnecting the magnetic detection element and the connector.
According to a second aspect of the present invention, there is provided a magnetic detector comprising:
a base for holding a magnetic detection element;
a case for housing the base; and
a connector, produced as a separate unit from the base and having a connection portion with the base, for outputting the output signal of the magnetic detection element to the outside.
According to a third aspect of the present invention, there is provided a magnetic detector, wherein a resin is injected into the case.
According to a fourth aspect of the present invention, there is provided a magnetic detector, wherein a press-in hole for press fitting the base is formed in the case and a cut-out portion or a through hole for injecting the resin is formed in the press-in portion of the base.
According to a fifth aspect of the present invention, there is provided a magnetic detector, wherein a tapered portion is formed in an uneven portion of the base.
According to a sixth aspect of the present invention, there is provided a magnetic detector, wherein a recess is formed near an opening portion of the case.
According to a seventh aspect of the present invention, there is provided a magnetic detector, wherein a cut-out is formed between the opening portion of the case and the recess.
According to an eighth aspect of the present invention, there is provided a magnetic detector, wherein the base is constructed such that the resin forming the base does not exist between the magnetic detection element and the output terminal of the magnetic detection element.
According to a ninth aspect of the present invention, there is provided a magnetic detector, wherein a land portion of the lead frame is made double-structured by forming a bent portion connected to the land portion and placing it upon the land portion.
According to a tenth aspect of the present invention, there is provided a magnetic detector, wherein a metal having high solder wettability is adhered to the land portion of the lead frame.
According to an eleventh aspect of the present invention, there is provided a magnetic detector, wherein an area having lower solder wettability than the land portion is formed around the land portion of the lead frame.
According to an eleventh aspect of the present invention, there is provided a magnetic detector, wherein the area having low solder wettability is formed by a
Hatazawa Yasuyoshi
Hiraoka Naoki
Nada Takuji
Shinjo Izuru
Mitsubishi Denki & Kabushiki Kaisha
Patidar Jay
Sughrue Mion Zinn Macpeak & Seas, PLLC
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