Rotation sensor

Details Rotation sensor Rotation sensor

2002-05-02

2004-08-24

Le, N. (Department: 2862)

Electricity: measuring and testing

Magnetic

Displacement

C324S174000

Reexamination Certificate

active

06781367

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a rotation sensor which detects the rotation number of, for example, a gear-like magnetic rotation body.
2. Description of the Related Art
FIGS. 5A
to
5
C are trihedral diagrams showing a conventional rotation sensor,
FIG. 5A
is a front view (in partial section),
FIG. 5B
is a plan view (in partial section), and
FIG. 5C
is a right side section view. Referring to the figures, the rotation sensor is configured by: a sensor main section
1
on which electronic components are mounted, and which is made of an insulating resin; and a bottomed cylindrical case
2
which hermetically covers the sensor main section
1
, and which is similarly made of an insulating resin. The sensor main section
1
is configured by a main portion
1
a
, a pedestal portion
1
b
, and a connector portion
1
c
. On the main portion
1
a
, mounted are an IC
5
configured by two or more Hall elements
4
which are separated from each other by a predetermined distance in order to detect rotation of a magnetic rotation body
3
, a permanent magnet
6
which applies a magnetic field to the Hall elements
4
, and a terminal
7
on which electronic components for processing output signals of the Hall elements
4
are mounted and a circuit pattern is formed.
The main portion
1
a
has a generally slender plate-like shape. One end of the main portion is perpendicularly connected to the principal face of the pedestal portion
1
b
. The permanent magnet
6
is mounted on the other end of the main portion
1
a
so as to be perpendicular to the main portion
1
a
. The Hall elements
4
which constitute a sensor element for detecting proximity of a magnetic body are arranged on the outer principal face of the permanent magnet
6
.
The connector portion
1
c
elongates from the other end face of the pedestal portion
1
b
. The connector portion
1
c
extends from the other end face of the pedestal portion
1
b
so as to be bent perpendicularly to the main portion
1
a
. The terminal
7
which is electrically connected to the permanent magnet
6
of the main portion
1
a
is embedded in the connector portion
1
c
. A recessed engaging portion which is to be connected to an external apparatus is formed in the tip end portion having an L-like shape. Terminal parts
7
a
of the terminal
7
are projected into the engaging portion.
The thus configured rotation sensor is installed in a predetermined position of a vehicle. When the magnetic rotation body
3
which is a magnetic body disposed in opposition to the Hall elements
4
of the rotation sensor, and which has, for example, a gear-like shape is rotated, concave portions
3
a
and convex portions
3
b
of the magnetic rotation body
3
alternately approach the Hall elements
4
. As a result, the magnetic field which is applied to the Hall elements
4
by the permanent magnet
6
is changed. The change of the magnetic field is detected by the Hall elements
4
as a change of a voltage. The voltage change appearing in the Hall elements
4
is into a pulse wave converted by the electronic components. The electric signal is led out to the terminal parts
7
a
of the terminal
7
in the connector portion
1
c
, and then sent to the external apparatus which is not shown, so that the rotation number of the magnetic rotation body
3
is detected.
However, the conventional rotation sensor has the following problem. As shown in
FIG. 5C
, the connector portion
1
c
is led out in a direction perpendicular to the placement direction of the magnetic rotation body
3
. When there is a structure such as the vehicle body in the direction perpendicular to the placement direction of the magnetic rotation body
3
, therefore, it is impossible to install the rotation sensor, and hence the installation place of such a rotation sensor is limited.
There is no interfering structure in the placement direction of the magnetic rotation body
3
. Consequently, it may be contemplated that the installation direction of the rotation sensor is rotated by 90° to set the lead out direction of the connector portion
1
c
coincident with the placement direction of the magnetic rotation body
3
.
FIG. 6
is a section view showing such a conventional rotation sensor in which the installation direction of the rotation sensor in
FIGS. 5A
to
5
C is rotated by 90° so that the lead out direction of the connector portion
1
c
is coincident with the placement direction of the magnetic rotation body
3
.
In the configuration shown in
FIG. 6
, however, there arises another problem in that the two Hall elements
4
are arranged in a direction which is perpendicular to the placement direction of the magnetic rotation body
3
, and hence it is difficult to detect rotation of the rotation body. This is caused because of the following reason. The difference between the output signals of the two Hall elements
4
is used as the detection output. When the two Hall elements
4
are arranged in a direction which is perpendicular to the placement direction of the magnetic rotation body
3
, therefore, the output signals of the two Hall elements
4
are equal to each other, and there is no difference between the signals.
FIG. 7
is a graph illustrating relationships between a detection GAP ratio and the lead out direction of the connector portion
1
c
in the conventional rotation sensor. In the figure, the ordinate of the graph indicates the detection GAP ratio, and the abscissa of the graph indicates the lead out direction of the connector portion
1
c
. The detection GAP ratio means a ratio of the air gap length (the length of the air gap between the magnetic rotation body
3
and the rotation sensor) at which detection in a certain direction (angle) is enabled, with respect to the air gap length at which detection in an ideal direction (angle) is enabled, and which is set to 1. For example, a detection GAP ratio of 70% means that, when the air gap length at which detection in the ideal direction is enabled is 1, the air gap length at which detection in a certain direction (angle) is enabled is 0.7. The lead out direction of the connector portion
1
c
in a state where the lead out direction of the connector portion
1
c
is coincident with the placement direction of the magnetic rotation body
3
is set to 0°, and that in a state where the connector portion
1
c
is led out perpendicularly to the placement direction of the magnetic rotation body
3
is set to 90°.
As shown in the figure, it will be seen that, in the state where the connector portion
1
c
is led out perpendicularly to the placement direction of the magnetic rotation body
3
, i.e., when the placement direction of the two Hall elements
4
is coincident with that of the magnetic rotation body
3
, the detection GAP ratio is 100%. By contrast, it will be seen that, in the state where the lead out direction of the connector portion
1
c
is coincident with the placement direction of the magnetic rotation body
3
, i.e., when the placement direction of the two Hall elements
4
is perpendicular to that of the magnetic rotation body
3
, the detection GAP ratio is 0%, and the sensor hardly conducts detection.
Therefore, it may be contemplated that the connector portion
1
c
is led out so that the placement direction of the two Hall elements
4
is coincident with that of the magnetic rotation body
3
.
FIGS. 8A and 8B
are trihedral diagrams showing a conventional rotation sensor,
FIG. 8A
is a front view (in partial section), and
FIG. 8B
is a plan view (in partial section). As shown in
FIG. 8A
, however, the three terminal parts
7
a
of the terminal
7
are vertically arranged, and hence the height of the connector portion
1
c
is increased. In this case, therefore, there arises a further problem in that the connector portion interferes with a structure which exists in the vertical direction of the magnetic rotation body
3
.
SUMMARY OF THE INVENTION
The invention has been conducted in order to solve the above-discussed problems. It is an object of the

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