Electricity: measuring and testing – Magnetic – Displacement
Reexamination Certificate
1999-03-17
2001-07-31
Oda, Christine (Department: 2862)
Electricity: measuring and testing
Magnetic
Displacement
C324S207200, C324S207120
Reexamination Certificate
active
06268722
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to sensors for sensing a rotation angle, and more particularly to sensors that sense a rotation angle or open degree of a throttle valve installed in an air intake manifold of an internal combustion engine.
2. Description of the Background Art
Generally speaking, a throttle valve is installed in an air intake manifold of an internal combustion engine, and a rotation angle sensor detects an open angle of the throttle valve. A detecting signal of the rotation angle sensor is routed to an engine control unit, which signal indicates an intake air amount of the engine. The engine control unit calculates a fuel injection amount corresponding to the intake air amount. The rotation angle sensor has a potentiometer, which is comprised of a resistant element and a brush for detecting the open angle of the throttle valve. The brush is connected with a rotational shaft (a throttle shaft). When the brush moves on the resistant element, the open angle of the throttle valve can be detected by a resistant value change of the resistant element. However, because the brush may be isolated from the resistant element, the detecting signal of the rotation angle sensor has the potential for being suddenly interrupted. Also, when the brush or the resistant element is used for a long period of time, the rotation angle sensor cannot keep its durability and life because of the wearing away of the brush or the resistant element.
A Japanese Patent Application First Publication No. Heisei 9-189509, published on Jul. 22, 1997, exemplifies a previously proposed rotation angle sensor with three poles, having a first yoke, a second yoke, and a third yoke surrounding a magnet, and a first Hall element installed between the first yoke and the third yoke, and a second Hall element installed between the second yoke and the third yoke.
In the disclosed Japanese Patent Application First Publication, the rotation angle sensor is shown in
FIG. 9. A
throttle body
1
has a throttle valve (not shown) which rotates with a valve shaft
2
. The throttle body
1
has also a fit portion
1
A, which forms a cylindrical shape surrounding the projection end of the valve shaft
2
. The fit portion
1
A is fixed to a cylindrical portion
3
A of a yoke mounting member
3
. The valve shaft
2
is made of a high strength metal material, which is installed on the bearings in the throttle body
1
.
The yoke mounting member
3
includes a casing in conjunction with the throttle body
1
, which has the cylindrical portion
3
A opening in the downward direction, a partition portion
3
B covering on the top end of the cylindrical portion
3
A, a circuit board installing space
3
C on the upper portion of the partition portion
3
B, a magnet installing space
3
D on the lower portion of the partition portion
3
B, and a connector portion
3
E projecting in the outside diameter direction of the cylindrical portion
3
A.
A magnet
4
is installed in the magnet installing space
3
D of the yoke mounting member
3
. The magnet has circular ended portions in the lengthwise direction, parallel ended portions in the width direction, and a through hole
4
A extending in the axial direction of the valve shaft
2
. By inserting and crimping the projecting end of the valve shaft
2
into the through hole
4
A, the magnet
4
is fixed to the valve shaft
2
.
The first yoke
5
is installed in the yoke-mounting member
3
. The first yoke
5
has a circular magnet portion
5
A opposed to the circular portions of the magnet
4
, and an extending portion
5
B extending from the magnet portion
5
A to the circuit board installing space
3
C, and shaped like a letter L. The extending portion
5
B covers a Hall element
8
from above. The extending portion
5
B of the first yoke
5
leads a magnetic flux from the magnet
4
to the first Hall element
8
.
The second yoke
6
is installed in the yoke-mounting member
3
. The second yoke
6
has a circular magnet portion
6
A opposed to the circular portions of the magnet
4
, and an extending portion
6
B extending from the magnet portion
6
A to the circuit board installing space
3
C, and shaped like a letter L. The extending portion
6
B covers a Hall element
9
from above. The extending portion
6
B of the second yoke
6
leads a magnetic flux from the magnet
4
to the second Hall element
9
.
The third yoke
7
is installed in the yoke-mounting member
3
. The third yoke
7
has a circular magnet portion
7
A opposed to the circular portions of the magnet
4
. An extending portion
7
B extends from the magnet portion
7
A along the surface of a circuit board
10
on the partition portion
3
B of the yoke mounting portion
3
, which extending portion
7
B is installed below the extending portions
5
B,
6
B.
The first Hall element
8
for a first signal output means is installed on the circuit board
10
, which circuit board is positioned between the extending portion
5
B of the first yoke
5
and the extending portion
7
B of the third yoke
7
. The first signal is output proportional to a magnetic flux density through a first closed flux path which is comprised of the magnet
4
, the first yoke
5
, and the third yoke
7
.
The second Hall element
9
for a second signal output means is installed on the circuit board
10
, which stands between the extending portion
6
B of the second yoke
6
and the extending portion
7
B of the third yoke
7
. The second signal is output proportional to a magnetic flux density through a second closed flux path which is comprised of the magnet
4
, the second yoke
6
, and the third yoke
7
.
The circuit board
10
is installed in the circuit board installing space
3
C, which includes an insulating material such as a ceramic. The Hall elements
8
,
9
are positioned on the circuit board
10
. The circuit board
10
is connected to the end of more than one terminal
11
, which extends toward the connector
3
E. The circuit board
10
is connected to a signal processing circuit (not shown) by the terminal
11
.
The circuit installing space
3
C of the yoke-mounting member
3
is sealed with a cover
12
, which may be a resin plate. Packing
13
is installed between the cover
12
and the circuit installing space
3
C, which packing includes an elastic member.
A magnetic shielding plate
14
is buried in the partition portion
3
B of the yoke mounting member
3
, which interrupts a leakage flux and reduces the effect of a leakage magnetic field to the Hall elements
8
,
9
.
In the above-mentioned the rotation angle sensor, when the valve shaft
2
rotates to the throttle valve openings, the magnet
4
which is fixed on the valve shaft
2
also moves. Then, because each area ratio of the circular portion of the magnet
4
relative to the circular magnet portion
5
A or the circular portion of the magnet
4
relative to the circular magnet portion
6
A changes, the magnetic flux density through the yoke
5
,
6
changes.
Each Hall element
8
,
9
outputs a signal proportional to the magnetic flux density to the signal processing circuit through the circuit board
10
and terminal
11
. Therefore, the valve shaft opening is detected by the signal processing circuit.
Incidentally, in the above-mentioned rotation angle sensor, because the magnetic shielding plate
14
is buried in the partition portion
3
B of the yoke mounting member
3
, this requires preparations for many parts. Also, when the yoke-mounting member
3
is made, because the magnetic shielding plate
14
must be molded in the partition portion
3
B, it causes inconvenience in the workability.
In addition, the Hall elements
8
,
9
are contained on the circuit board
10
of the circuit installing space
3
C, which is located above the partition portion
3
B of the yoke mounting member
3
. When the yoke-mounting member
3
is mounted on the cylindrical fit portion
1
A of the throttle body
1
, it results in an undesirably increased size of the sensor.
SUMMARY OF THE INVENTION
It is therefore an object of the pres
Kogure Yoshihiro
Nakazawa Hirotsugu
Foley & Lardner
Oda Christine
Unisia Jecs Corporation
Zaveri Subhash
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