Rotation detector operable to measure magnetism direction...

Details Rotation detector operable to measure magnetism direction... Rotation detector operable to measure magnetism direction...

1999-04-27

2001-08-07

Strecker, Gerard R. (Department: 2862)

Electricity: measuring and testing

Magnetic

Displacement

C324S207220, C324S207250

Reexamination Certificate

active

06271663

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a rotation detector, and more specifically, to a rotation detector including a rotor having magnets.
FIG. 1
illustrates how an absolute position detection type detector detects rotational position. The rotation detector includes a rotor
30
, which is fixed on a rotating shaft and integrally rotates with the shaft. An N pole zone
32
and an S pole zone
33
are alternately formed at sixty degree intervals on the rotor
30
in a circumferential direction. In positions facing the rotor
30
, first to third magnetic resistance elements
31
are arranged around the axis O of the rotor
30
at forty-degree intervals. Each of the first to third resistance elements
31
detects the N pole zone
32
and the S pole zone
33
, which alternately pass by the resistance elements
31
at sixty-degree intervals during the rotation of the rotor
30
.
When the N pole zone
32
is detected, the first to third resistance elements
31
respectively output signals SG
1
, SG
2
, SG
3
having an H level. When the S pole zone
33
is detected, the resistance elements
31
respectively output the signals SG
1
, SG
2
, SG
3
having an L level. When the zone detected by each resistance element
31
moves from the N pole zone
32
to the S pole zone
33
, each of the signals SG
1
, SG
2
, SG
3
changes from the H level to the L level. Contrarily, when the zone detected by each resistance element
31
moves from the S pole zone
33
to the N pole zone
32
, each of the signals SG
1
, SG
2
, SG
3
changes from the L level to the H level. As shown in
FIG. 1
, the signals SG
1
, SG
2
, SG
3
of the resistance elements
31
change gradually between the L and H levels. The reason for this is because a direction of magnetic flux changes gradually when the detected zone moves from the N pole zone
32
to the S pole zone
33
. Three comparators (not shown) respectively receive the signals SG
1
-SG
3
and adjust the waveforms of the signals SG
1
-SG
3
, thus generating detection signals S
1
-S
3
, which change sharply between the L and H levels.
More specifically, each of the comparators compares an output signal with a reference value, which is a middle level between the H level and the L level, and generates an H level detection signal S
1
-S
3
when the output signal is greater than the reference value or generates an L level detection signal S
1
-S
3
when the output signal is lower than the reference value. The reference value is the level of the signals SG
1
-SG
3
output when the border between the N pole zone
32
and the S pole zone
33
passes by each of the first to third resistance elements
31
. When any one of the detection signals S
1
-S
3
changes from the L level to the H level or from the H level to the L level, the rotational position of the rotor
30
(or rotation shaft) is determined based on the state of the other detection signals. In the case of
FIG. 1
, the rotational position (absolute position) is detected in the range of zero to 120 degrees at intervals of twenty degrees.
However, it is difficult to precisely form the N pole zone
32
and the S pole zone
33
alternately at sixty-degree intervals on the rotor
30
in the circumferential direction. Accordingly, the rotational position is not detected at twenty-degree intervals with precision at the point when the detection signals S
1
-S
3
change from the L level to the H level or from the H level to the L level.
Furthermore, in the above rotation detector, the levels of the output signals SG
1
-SG
3
may be varied by objects located near the resistance element
31
that can affect magnetic flux. A shielding member may be provided to shield the rotation detector. However, this increases the number of parts, cost and assembly work.
The objective of the present invention is to provide a rotation detector that detects rotational position with high precision.
SUMMARY OF THE INVENTION
To achieve the above objective, the present invention provides a rotation detector. The rotation detector includes a rotor having a shaft. Projections are located at predetermined intervals on the periphery of the rotor and extend in an axial direction. The rotation detector further includes magnets and magnetism detecting elements respectively detecting magnetism of the magnets. At least one of the magnets and the detecting elements are arranged between the projections and the shaft at predetermined intervals.
Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.


REFERENCES:
patent: 4235213 (1980-11-01), Jellissen
patent: 4406272 (1983-09-01), Kiess et al.
patent: 5028868 (1991-07-01), Murata et al.
patent: 5291133 (1994-03-01), Gokhale et al.
patent: 5627464 (1997-05-01), Shinjo et al.
patent: 6064198 (2000-05-01), Wolf et al.
patent: 4241106 (1993-06-01), None
patent: 19629611 (1998-01-01), None
patent: 164832 (1985-12-01), None
patent: 702203 (1995-07-01), None

Affiliated with

Also associated with

Rating

Rotation detector operable to measure magnetism direction... does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Rotation detector operable to measure magnetism direction..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Rotation detector operable to measure magnetism direction... will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2457151