JP2005181022A - Optical encoder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical encoder capable of preventing generation of an environmental stress crack (ESC) of a rotary disk, accompanying the use of a motor over time. <P>SOLUTION: This optical encoder 1 connected directly to the motor 11 is equipped with a photosensor 15, having a light-emitting part 15B and a light-receiving part 15C arranged oppositely across a clearance 15A made to coincide with the optical axis, and the resin rotating disk 13 mounted on a motor shaft 12, wherein a plurality of light-shielding parts and light-transmitting parts crossing on the optical axis following rotation are arrayed alternately. In the encoder 1, an oil return member 2 is disposed in between the motor end face 11A, where the motor shaft 12 on which the rotary disk 13 is mounted is projected and the rotating disk 13. The oil return member 2 is formed to have a reversed cone shape, having a recessed part which is enlarge gradually as going downwardly, in the outside direction from the base around a shaft passing hole. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical encoder directly connected to a motor.

  In a machine tool, a robot having multiple joints, etc., it is necessary to detect the number of rotations of a motor when controlling a motor as a drive unit. Optical encoders are widely used as sensors for detecting the rotational speed, rotational position, and the like of such motors.

As shown in FIG. 3, the conventional optical encoder 10 includes a rotating disk 13 attached to a motor shaft 12 of a motor 11, a printed circuit board 14 that is fixed to the motor end surface 11 </ b> A in the vicinity of the rotating disk 13, and the printed circuit board. 14 between the light-emitting unit 15B and the light-receiving unit 15C disposed so as to face each other so that the optical axes thereof coincide with each other. The rotating disk 13 is attached to the motor shaft 12 so that a part of the circumferential edge of the rotating disk 13 is inserted.
Note that, for example, a plurality of slits are provided on the rotating disk 13 that crosses the optical axis of the photosensor 15 so as to be arranged at desired intervals along the periphery of the rotating disk.

  A driving voltage is applied to the light emitting diode (LED) in the light emitting unit 15B from the outside via a cable 16 connected to the printed board 14, and the output of the light receiving element in the light receiving unit 15C is also externally connected via the cable 16. Is output. The cable 16 is bundled by a tie wrap 17 and attached to the motor 11 at a position close to the connection location with the printed circuit board 14. The member of the code | symbol 18 in a figure is a gearwheel.

  According to such an optical encoder 10, the LED is driven to emit light from the LED in the optical axis direction, and the light from the LED passes through the slit on the rotating disk 13 and enters the light receiving element. . In this state, the motor 11 is driven to interlock with the rotation of the motor shaft 12 so that the slit of the rotating disk 13 is disengaged from the optical axis of the photosensor 15 so that the light from the LED is blocked by the rotating disk. Specifically, the emitted light is blocked by a light shielding portion as a portion between the slit and the slit adjacent thereto, so that light from the LED cannot enter the light receiving element.

When the motor 11 continues to be driven and the rotating disk 13 continues to rotate in conjunction with this, the slits and the light-shielding portions alternately pass on the optical axis of the photosensor 15. Will be received intermittently.
As described above, according to the conventional optical encoder 10, the number of revolutions of the motor 11 can be measured based on whether or not the light that has passed through the slit as the transmission portion is received.

  In such a conventional optical encoder 10, slits are formed by pressing or etching a metal plate, but such processing is not only complicated, but also increases the manufacturing cost.

In recent years, since it has become possible to perform resin molding with high accuracy and low manufacturing cost, resin molded products are widely used as the rotating disk 13. As a material, for example, a polycarbonate resin excellent in molding accuracy and mechanical strength is preferred and generally used.
Further, in the case of the rotating disk 13 formed of a transparent resin such as polycarbonate resin, it is not necessary to structurally form an opening as a slit, and a printing process with a low processing cost is applied to the surface of the rotating disk 13. A light-shielding portion that blocks light from the LED can also be formed.

  However, the polycarbonate resin is excellent in mechanical strength, but has a characteristic of poor resistance to organic solvents, synthetic oils, oils containing additives, and the like.

  The motor 11 to which the rotating disk 13 made of polycarbonate resin is attached uses an oil-impregnated metal for the purpose of improving the wear resistance of the bearing as a constituent member. As the motor shaft 12 rotates, the oil moves along the surface of the motor shaft in the direction of the shaft tip and adheres to the rotating disk 13.

  Depending on the oil component, environmental stress cracking (ESC) may occur around the motor shaft insertion portion of the rotating disk 13 made of polycarbonate resin, that is, the portion where the stress is always applied by the press-fitting of the motor shaft 12. As a result, the rotating disk 13 cannot be fixedly held on the motor shaft 12.

  The present invention has been made in view of the above points, and an object of the present invention is to provide an optical encoder that has been created to prevent the occurrence of ESC of a rotating disk associated with the aging of a motor.

  In order to achieve the above object, an optical encoder according to the present invention includes a light emitting unit and a light receiving unit that are arranged to face each other with their optical axes aligned, and a translucent light that is attached to the motor shaft and transmits light from the light emitting unit. And a resin rotating disk in which a plurality of light shielding parts that block light from the light emitting part are alternately arranged, and is directly connected to a motor, and a motor end surface from which a motor shaft to which the rotating disk is attached projects And an oil return member between the rotating disk and the rotating disk.

  In order to achieve the above object, the optical encoder of the present invention is attached to a motor shaft and a photosensor having a light emitting part and a light receiving part that are arranged to face each other with a gap with the optical axes aligned, and rotates. And a resin-made rotating disk in which a plurality of light-shielding parts and light-transmitting parts crossing the optical axis are alternately arranged, and directly connected to a motor, and the motor shaft to which the rotating disk is attached includes: The oil return member is disposed between the protruding motor end surface and the rotating disk.

  In the optical encoder according to the present invention, preferably, the oil return member is formed in an inverted mortar shape having a concave portion that is expanded outwardly from the base portion around the shaft through hole. Is attached to the motor shaft with the concave side facing toward the motor end surface.

  The oil return member is preferably formed of a resin that is resistant to oil that oozes out of the motor. As the resin for molding the oil return member, any of polyacetal resin, polyamide resin, and polyphenylene sulfide resin can be used. Alternatively, instead of a plastic molded product, a metal member may be used as the oil return member.

  According to the above configuration, the oil return member prevents the oil that has oozed out of the motor from adhering to a rotating disk molded from a resin, for example, a polycarbonate resin. As a result, oil can be prevented from adhering to the resin portion to which the stress of the resin-made rotating disk is applied, and the occurrence of environmental stress cracking can be avoided.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing an optical encoder 1 according to an embodiment of the present invention, and FIG. 2 is a partial cross-sectional view of the optical encoder 1 according to an embodiment of the present invention. In addition, about the member same as the member of the conventional optical encoder 10, it demonstrates using the same code | symbol as a prior art example.

  The optical encoder 1 is mounted on a rotating disk 13 attached to the motor shaft 12, a printed circuit board 14 fixed to the motor end surface 11A by a fixing means such as a bolt in the vicinity of the rotating disk 13, and the printed circuit board 14. The photo sensor 15 is disposed directly connected to the motor 11.

  The rotating disk 13 is formed into a disk shape using a resin, for example, a polycarbonate resin, and has a hole 13A at the center. The rotating disk 13 is attached to the motor shaft 12 by press-fitting the hole 13 </ b> A of the rotating disk 13 through the motor shaft 12.

  Further, the surface of the rotating disk 13 is partially subjected to printing processing to form a light shielding portion. That is, a light shielding portion that blocks light transmission by printing and a light transmitting portion that transmits light (a portion that is not subjected to printing processing between adjacent light shielding portions) have a desired distance along the periphery of the rotating disk 13. Are arranged alternately. The translucent part may be structurally formed as a hole penetrating the rotating disk 13 like a slit provided in a metal plate in the conventional example.

  The photosensor 15 mounted on the printed circuit board 14 includes a light emitting unit 15B and a light receiving unit 15C, and the light emitting unit 15B and the light receiving unit 15C are opposed to each other with a gap 15A with their optical axes aligned. It is arranged.

  Note that the positions of the rotating disk 13 and the photosensor 15 are set so that a part of the circumferential edge of the rotating disk 13 enters the gap 15 </ b> A of the photosensor 15. In other words, the rotary disk 13 and the photosensor 15 are positioned and adjusted so that the respective light shielding parts and the respective light transmitting parts cross the optical axis of the photosensor 15 as the rotary disk 13 rotates.

  A driving voltage is applied to the light emitting diode (LED) in the light emitting unit 15B from the outside via the cable 16 connected to the printed circuit board 14, and the voltage of the photodiode (PD) or phototransistor in the light receiving unit 15C. Similarly, the signal is output to the outside via the cable 16.

  The light receiving unit 15C may be a light receiving element configured to output three types of signals (A phase, B phase, and Z phase) so that the optical encoder 1 is an incremental type. The rotating disk 13 includes a light shielding unit that divides light from the LED into three phases. Further, the cable 16 is bundled by a tie wrap 17 and attached to the motor 11 at a position close to a connection portion with the printed circuit board 14.

  The above configuration is the same as the configuration of the conventional optical encoder 10, but the optical encoder 1 according to the embodiment of the present invention includes a motor end surface 11A from which the motor shaft 12 to which the rotating disk 13 is attached, and a rotating disk. 13, the oil return member 2 is disposed.

  As shown in FIG. 2 (A), the oil return member 2 is formed as a flat plate having a shaft through hole 2A in the center, and the oil return member 2 is inserted into the shaft through hole 2A through and press-fitted into the shaft 2a. Is fixed to the motor shaft 12. The oil return member 2 is preferably formed in the shape of an inverted bowl that expands outward as it goes downward from the base 2B around the shaft through hole 2A, as shown in FIG. 2 (B). Should be used.

  The oil return member 2 may be made of metal, but it is advantageous to use a plastic with a low manufacturing cost. As the plastic, it is preferable to use a resin having solvent resistance. For example, polyacetal resin (polyacetal, abbreviated as POM), polyamide resin (polyamide, abbreviated as PA), and polyphenylene sulfide resin (resin) that are extremely resistant to oil (ester base) that bleeds out of the motor as the motor 11 ages. It is preferable to use any of polyphenylene sulfide (abbreviated as PPS).

According to the optical encoder 1 configured as described above, the oil impregnated in the bearing in the motor 11 bleeds with the aging of the motor 1, and the motor shaft surface rotates with the rotation of the motor shaft 12. Even if the oil moves along the shaft end direction, the oil return member 2 blocks the progress of the oil.
Further, as shown in FIG. 2B, if the oil return member 2 is formed in a reverse mortar shape with the motor end surface 11 </ b> A being recessed, the oil that has oozed out of the motor It stays in a region defined by the concave surface 2C, that is, a concave portion.

  As described above, according to the optical encoder 1 according to the embodiment of the present invention, the oil that has oozed out of the motor is prevented from adhering to the rotary disk 13 molded of polycarbonate resin. Accordingly, it is possible to prevent oil from adhering to the motor shaft fitting portion of the rotating disk 13 made of polycarbonate resin, that is, the resin portion to which stress is always applied by press-fitting of the motor shaft 12, thereby avoiding the occurrence of environmental stress cracking. be able to.

As described above, the present invention can be implemented in various forms without departing from the spirit of the invention. That is, the oil return member may be formed using a resin resistant to the oil that oozes out from the motor, and interposed between the rotating disk 13 and the motor end surface as described above.
In the above description, the light emitting unit 15B and the light receiving unit 15C are integrated as the photosensor 15. However, the light emitting unit 15B and the light receiving unit 15C are disposed opposite to each other with the rotating disk 13 interposed therebetween. Of course, the oil return member 2 described above can also be applied to the motor direct-coupled optical encoder.

It is a figure which shows the optical encoder which concerns on embodiment of this invention. (A) And (B) is a fragmentary sectional view of the optical encoder which concerns on embodiment of this invention, respectively. It is a figure which shows the conventional optical encoder.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical encoder 2 Oil return member 2A Shaft passage hole of oil return member 2B Base part of oil return member 2C Concave surface of oil return member 11 Motor 12 Motor shaft 13 Rotary disk 13A Hole of rotary disk 14 Printed circuit board 15 Photo sensor 15A Gap 15B Light emitting part 15C Light receiving part 16 Cable 17 Tie wrap

Claims (6)

A light emitting portion and a light receiving portion arranged opposite to each other with the optical axes aligned, and
A motor rotating shaft, which is attached to a motor shaft and includes a resin-made rotating disk in which a plurality of light-transmitting portions that transmit light from the light-emitting portion and light-shielding portions that block light from the light-emitting portion are alternately arranged. A directly connected optical encoder,
An optical encoder, wherein an oil return member is disposed between a motor end surface from which a motor shaft to which the rotating disk is mounted projects and the rotating disk. A photosensor having a light-emitting portion and a light-receiving portion that are arranged to face each other with a gap with the optical axes aligned,
An optical encoder that is attached to a motor shaft and includes a resin-made rotating disk in which a plurality of light-shielding portions and light-transmitting portions that alternately cross the optical axis is rotated, and is directly connected to the motor. And
An optical encoder, wherein an oil return member is disposed between a motor end surface from which the motor shaft on which the rotating disk is mounted protrudes and the rotating disk. The oil return member is formed in an inverted mortar shape having a recess, which is expanded outwardly from the base portion around the shaft through hole.
3. The optical encoder according to claim 1, wherein the oil return member is attached to the motor shaft with a concave portion side of the oil return member facing the motor end surface. 4.   The optical encoder according to claim 1, wherein the oil return member is molded using a polyacetal resin.   The optical encoder according to claim 1, wherein the oil return member is formed using a polyamide resin. The optical encoder according to claim 1, wherein the oil return member is molded using polyphenylene sulfide resin.

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