Optical encoder

Details Optical encoder Optical encoder

2000-12-05

2002-02-26

Lee, John R. (Department: 2878)

Radiant energy

Photocells; circuits and apparatus

Optical or pre-photocell system

C250S231140

Reexamination Certificate

active

06350984

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to an optical encoder for detecting the rotations of a motor, etc.
BACKGROUND OF THE INVENTION
A prior art optical encoder is constructed as shown in FIG.
2
and
FIG. 3
In the drawings; housing
20
is attached to and fixed at a mount
23
of a bracket
22
of a motor
21
. A rotating shaft
24
is supported at the housing
20
by means of a bearing
25
and is directly connected to the rotating shaft
26
of the motor
21
via a connector
26
a
. A rotary disk
27
has a pattern (not illustrated) composed of a light shielding portion or a light-penetrating portion attached to a transparent member such as glass that is attached to the rotating shaft
24
. A holder
28
is a holder to retain light emitting elements, which is constructed by molding. As shown in
FIG. 3
, the holder
28
is constructed of a supporting portion
28
a
attached to the housing
20
and an attaching portion that attaches the light-emitting element
29
. The light emitting element
29
is attached so as to be inserted into a hole portion secured at the supporting portion
28
a
of the holder
28
. A sub-board
30
has a photo detector element
31
attached to the plate surface of the sub-board
30
. A main board
32
is attached to the housing
20
via a supporting member (not illustrated), and the main board is connected to the sub-board
31
by a connection line (not illustrated), and an electronic component that detects the speed of rotation or position of the rotation is incorporated on the plate surface of the main board
32
. A cover
33
covers up the optical encoder and is fixed at the bracket
22
of the motor
21
. A lead wire
34
comes out of the optical encoder.
Next, a description is given of an assembly process of an optical encoder.
First, the rotating shaft
24
is attached to the bearing
25
attached to the housing
20
, and a rotary disk
27
is fixed at the rotating shaft
24
. Next, the sub-board
30
provided with the photo detector element
31
is attached to the housing
20
, wherein the holder
28
to which the light emitting element
29
is attached is fixed at the housing
20
so that it is opposed to the photo detector element
31
to accommodate the rotary disk
27
therein.
The optical encoder thus constructed is completed so that the cover
33
surrounding the optical encoder is attached to the bracket
22
of the motor
21
after it is attached on the mounting seat of the bracket
22
.
Actually however, since the outer circumferential portion of the rotary disk is made open until the prior art optical encoder is attached to the motor, foreign substances and dust floating in the air may adhere to the rotary disk or foreign substances and/or dust adhered to the cover may drop from the cover due to vibrations during operation and adhere to the rotary disk, thereby making rotation detection impossible.
DISCLOSURE OF THE INVENTION
It is therefore an object of the present invention to provide an optical encoder that is capable of executing accurate rotation detection, free from any adhered foreign substances and/or dust.
In order to solve the abovementioned problems, an optical encoder according to the invention comprises a rotating shaft pivotally supported on a bearing of the housing; a rotary disk fixed at the rotating shaft; a light emitting element attached to the housing; a photo detector element attached to the housing, which can receive light passed through or reflected by the rotary disk from the light emitting element; and a main board incorporating a circuit that detects the speed of rotation and position of rotation from the light received by the photo detector element and is attached to the housing; wherein a holder consisting of a covering portion annularly formed so as to be engaged with the outer circumference of the main board and a light emitting element retaining portion formed at the covering portion is attached to the housing.
Therefore, according to the invention, it is possible to secure a dust-proof structure without hindering the assembly process of an optical encoder and to accurately detect the rotation without permitting foreign substances and/or dust to adhere to the rotary disk.


REFERENCES:
patent: 4214155 (1980-07-01), Jones
patent: 4338517 (1982-07-01), Perrine
patent: 4385234 (1983-05-01), Johnson
patent: 4387374 (1983-06-01), Wiener
patent: 4593269 (1986-06-01), Nakamura et al.
patent: 5773820 (1998-06-01), Osajda et al.
patent: 60-107520 (1985-06-01), None
patent: 61-122519 (1986-06-01), None
patent: 2-89313 (1990-07-01), None

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