Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Reexamination Certificate
2001-07-16
2003-04-29
Porta, David (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
C250S231160
Reexamination Certificate
active
06555808
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to apparatuses for detecting a rotational angle, and, more particularly to apparatuses detecting the rotational angle of a steering wheel of a vehicle.
FIG. 6
shows a prior art rotational angle detecting apparatus
51
. The rotational angle detecting apparatus
51
includes a first detecting piece
54
and a second detecting piece
55
, which oppose each other. A rotary disk
53
is located between the first and second detecting pieces
54
,
55
and is secured to a steering shaft
52
. An opening group
56
is located at an outer circumferential portion of the rotary disk
53
. The opening group
56
is used for detecting a relative angle of the steering shaft
52
, or the angle by which the rotary disk
53
is rotated relative to a reference position. The opening group
56
is located along a circle the center of which corresponds to point O. The opening group
56
includes a plurality of openings
56
a
that extend through the rotary disk
53
and are separated from adjacent openings
56
a
at equal intervals. As shown in
FIG. 8
, the circumferential dimension W
1
of each opening
56
a
is equal to the interval W
2
between adjacent openings
56
a
. As shown in
FIGS. 6 and 7
, an opening
57
extends through the rotary disk
53
and is located radially inward from the opening group
56
. That is, the opening
57
is located on a circle that is coaxial with the circle along which the openings
56
a
are located. The opening
57
is used or determining the reference position of the rotary disk
53
. The first detecting piece
54
includes a first light emitting element
58
a
and a second light emitting element
59
a
. The first and second light emitting elements
58
a
,
59
a
are located at positions corresponding to a path defined by the opening group
56
when the rotary disk
53
rotates. The first piece
54
includes a third light emitting element
60
a
located at a position corresponding to a path defined by the opening
57
when the rotary disk
53
rotates. The second detecting piece
55
includes a first light receiving element
58
b
and a second light receiving element
59
b
, which oppose the first light emitting element
58
a
and the second light emitting element
59
a
, respectively. The second detecting piece
55
includes a third light receiving element
60
b that opposes the third light emitting element
60
a.
The first light emitting element
58
a
and the first light receiving element
58
b
form a first detector
58
. In the same manner, the second light emitting element
59
a
and the second light receiving element
59
b
form a second detector
59
. The first and second detectors
58
,
59
form a rotational angle sensor
61
that detects the angle by which the steering shaft
52
, or the rotary disk
53
, is rotated. Further, the third light emitting element
60
a
and the third light receiving element
60
b
form a reference position sensor
60
. The reference position sensor
60
detects that the rotary disk
53
is located at the reference position.
The first detector
58
of the angle sensor
61
generates a binary code depending on whether or not the rotary disk
53
blocks the first light emitting element
58
a
from the first light receiving element
58
b
. Likewise, the second detector
59
of the angle sensor
61
generates a binary code depending on whether or not the rotary disk
53
blocks the second light emitting element
59
a
from the second light receiving element
59
b
. Thus, the rotational angle sensor
61
generates a two-bit code depending on whether or not each detector
58
,
59
faces any opening
56
a
of the opening group
56
.
The first and second detectors
58
,
59
are located relative to each other such that the phase of the binary code emitted by the second detector
59
is offset from the phase of the binary code emitted by the first detector
58
by a quarter cycle. More specifically, if the first and second detectors
58
,
59
both face corresponding openings
56
a
, as shown in FIG.
8
(
a
), the rotational angle sensor
61
generates a two-bit code “1·1”. If the rotary disk
53
rotates from this state in a direction indicated by the arrow of FIG.
8
(
a
) to block the first light emitting element
58
a
from the first light receiving element
58
b
, as shown in FIG.
8
(
b
), the rotational angle sensor
61
generates a two-bit code “0·1”. If the rotary disk
53
further rotates in the same direction to block both the first and second light emitting elements
58
a
,
59
a
from the associated light receiving elements
58
b
,
59
b
, as shown in FIG.
8
(
c
), the rotational angle sensor
61
generates a two-bit code “0·0”. If the rotary disk
53
further rotates in the same direction to block the second light emitting element
59
a
from the second light receiving element
59
b
, as shown in FIG.
8
(
d
), the rotational angle sensor
61
generates a two-bit code “1·0”.
If the rotary disk
53
further rotates in the same direction, the first and second detectors
58
,
59
both face corresponding openings
56
a
, thus restoring the state of FIG.
8
(
a
). In other words, when the rotary disk
53
rotates in the direction indicated by the arrows of FIGS.
8
(
a
) to
8
(
d
), the rotational angle sensor
61
successively generates two-bit codes “1·1”, “0·1”, “0·0”, and “1·0” in this order in a repeated manner. If the rotary disk
53
rotates in an opposite direction, the angle sensor
61
successively generates the two-bit codes in the opposite order.
Accordingly, the rotational direction of the rotary disk
53
is determined in accordance with the order in which the angle sensor
61
generates the two-bit codes. Further, the rotational angle of the rotary disk
53
is also detected in accordance with the angle of motion required to change the two-bit code. That is, if the rotational angle sensor
61
is configured to generate a two-bit code each time the rotational angle of the rotary disk
53
varies by one degree, the resolution of the rotational angle detecting apparatus
51
is one degree.
The reference position sensor
60
generates a binary code depending on whether or not the rotary disk
53
blocks the third light emitting element
60
a
from the third light receiving element
60
b
. More specifically, if the opening
57
is located between the third light emitting element
60
a
and the third light receiving element
60
b
, the reference position sensor
60
generates a binary code “1”. Otherwise, the reference position sensor
60
generates a binary code “0”.
In the rotational angle detecting apparatus
51
, which is constructed as described above, operation is initiated by the reference position sensor
60
. More specifically, if the reference position sensor
60
detects that the opening
57
is located between the third light emitting element
60
a
and the third light receiving element
60
b
, the corresponding angle at which the rotary disk
53
is rotated is defined as the reference angle (which is, for example, zero degrees). A memory of the rotational angle detecting apparatus
51
is thus initialized. Subsequently, the rotational angle sensor
61
generates a two-bit code depending on whether or not each detector
58
,
59
faces any opening
56
a
. The rotational angle detecting apparatus
51
thus computes the rotational angle of the rotary disk
53
with respect to the reference angle in accordance with the two-bit code generated by the rotational angle sensor
61
.
However, in the rotational angle detecting apparatus
51
, the reference angle of the rotary disk
53
is determined only in accordance with the position of the opening
57
. Thus, the memory of the rotational angle detecting apparatus
51
may not be initialized unless the rotary disk
53
is rotated at substantially 360 degrees. This complicates the initialization.
BRIEF SUMMARY OF THE INVENTION
Accordingly, it is an objective of the present invention to provide a rotational angle detecting apparatus that easily initializes a memory regarding a rotational angle o
Ohno Kouichi
Takeuchi Shuichi
Kabushiki Kaisha Tokai Rika Denki Seisakusho
Lee Patrick J.
Porta David
Synnestvedt & Lechner LLP
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