Electricity: measuring and testing – Magnetic – Displacement
Reexamination Certificate
2002-08-27
2004-02-10
Le, N. (Department: 2862)
Electricity: measuring and testing
Magnetic
Displacement
C324S207240
Reexamination Certificate
active
06690158
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a position sensor for an electromagnetic actuator which is used in various systems for a vehicle and detects a position of a shaft to be detected which moves axially in synchronization with a movable shaft of the electromagnetic actuator.
BACKGROUND ART
To meet recently-increasing requirement for improving fuel efficiency of a vehicle, various measures directed toward the improvement of the fuel efficiency have been studied. Among them, a high voltage of a battery enables an electromagnetic actuator such as a linear solenoid or the like to have both a great driving force and miniaturization. Consequently, the electromagnetic actuator, which having a higher efficiency to various kinds of electronics systems than a mechanical actuator, has been studied. In order to apply the electromagnetic actuator to these electronics systems, the position of a movable shaft must be controlled accurately. Accordingly, a position sensor becomes important for the accurate position detection of the movable shaft.
With reference to
FIG. 7
, a conventional position sensor (disclosed in Japanese Patent Laid-Open No. 5-264326) for the electromagnetic actuator will be hereinafter described.
FIG.
7
(
a
) is a perspective general view of the conventional position sensor for the electromagnetic actuator.
FIG.
7
(
b
) shows a cross section taken along arrow C—C of the sensor.
FIG.
7
(
c
) is a perspective view detailing a relationship between a magnetoelectric transducer and a magnetic field generator of the sensor.
In FIGS.
7
(
a
),
7
(
b
) and
7
(
c
), reference numeral
100
denotes a shaft to be detected. Reference numeral
100
a
denotes a guide groove formed in a longitudinal direction of the shaft
100
. Reference numeral
110
denotes a magnet
110
polarized magnetically in a thickness direction. Reference numeral
120
denotes a magnetic plate made of a permalloy shaped like an isosceles triangle. Reference numeral
130
denotes a magnetic field generator including the magnet
110
and the magnetic plate
120
attached together in their respective longitudinal direction matching together. Reference numeral
140
denotes a magnetoelectric transducer. Reference numeral
310
denotes a flat surface of the shaft
100
. Reference numeral
320
denotes a slider including an insulating material engages with the guide groove
100
a,
for sliding smoothly relative to the shaft
100
. The magnetoelectric transducer
140
provided at the slider
320
is mounted in parallel with the magnetic field generator
130
provided on the flat surface
310
of the shaft
100
.
An operation of the conventional sensor will be explained below.
The shaft
100
is displaced relative to the slider
320
(in the direction of an arrow D in FIG.
7
(
a
)), the magnetic plate
120
is opposed to the magnetoelectric transducer
140
accordingly with various widths. Consequently, an electric field sensed by the magnetoelectric transducer
140
varies in strength accordingly, thus enabling the sensor to detect the position of the shaft
100
.
The conventional position sensor described above, however, has the following problem. The conventional position sensor for the electromagnetic actuator has a contacting portion functioning as a guide for preventing the magnetoelectric transducer
140
from rotating about an axis of the magnetic field generator
130
. The sensor, if being used over a long period of time, has the contacting portion wearing unevenly and causing backlash, which makes the sensor generate an unstable output.
DISCLOSURE OF THE INVENTION
The present invention addresses the problem discussed above and aims to provide a position sensor for an electromagnetic actuator. The position sensor is capable of accurate non-contacting position detection, not restricting rotation of a shaft to be detected about an axis of the shaft.
To solve this problem, the position sensor of the present invention includes: a first magnet being fixed to the shaft to be detected which moves axially in synchronization with a movable shaft of the electromagnetic actuator, and having a first polarity vector parallel to the axis of the shaft; a second magnet being disposed opposite to the first magnet and having a second polarity vector crossing the first polarity vector substantially orthogonally three-dimensionally; and a magnetoelectric transducer being disposed over the second magnet and having a magnetosensitive axis substantially orthogonal to the first and second polarity vectors. The magnetoelectric transducer generates an output responsive to an axial movement of the shaft. With this configuration, the position sensor for the electromagnetic actuator can detects the position accurately with no contact, not restricting the rotation of the shaft about the axis of the shaft at all.
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patent: 4924696 (1990-05-01), Schroeder et al.
patent: 5570015 (1996-10-01), Takaishi et al.
patent: 6435169 (2002-08-01), Vogt
patent: 1 416 940 (1975-12-01), None
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patent: 59-58305 (1984-04-01), None
patent: 1-203901 (1989-08-01), None
patent: 1-173636 (1989-12-01), None
patent: 5-172504 (1993-07-01), None
patent: 5-280916 (1993-10-01), None
patent: 8-145611 (1996-06-01), None
patent: 10-52019 (1998-02-01), None
patent: 11-215795 (1999-08-01), None
patent: 11-281308 (1999-10-01), None
patent: 11-299269 (1999-10-01), None
patent: 2000-292113 (2000-10-01), None
patent: 2001-221653 (2001-08-01), None
International Search Report corresponding to application No. PCT/JP01/06729 dated Nov. 6, 2001.
English translation of Form PCT/ISA/210.
European Search Report dated Aug. 5, 2003 (3 pages).
European Search Report dated Aug. 5, 2003 (3 pages), EP23804-50.
Jitosho Noriyuki
Matsukawa Yasunori
Matsuura Akira
Saito Kiyoshi
Ueda Shinjiro
Le N.
Matsushita Electric - Industrial Co., Ltd.
RatnerPrestia
Zaveri Subhash
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