JP4994159B2 - Optical rotary encoder - Google Patents

Description

  The present invention relates to an optical rotary encoder, and more particularly, to an optical rotary encoder that is used for detecting a rotational position of a servo system and has an extremely high resolution and detects an absolute position of a machine tool or the like with high accuracy.

  Conventionally, an optical device in which a central portion on the back surface of a rotary code board (pulse disc) having no shaft hole in the central portion and a mounting surface at the top of the rotating shaft are fixed via an adhesive in a concave portion of the mounting surface. A rotary encoder is known (see, for example, Patent Document 1).

Japanese Patent Publication No. 8-12086

  However, in the conventional optical rotary encoder, the adhesive shrinks in the axial direction when the adhesive in the recess is cured and the pulse disk is adhesively fixed to the mounting surface of the top of the rotating shaft. Due to the axial contraction of the adhesive, the central part of the pulse disk is drawn into the concave part, and the central part is displaced into the concave part rather than the part in contact with the edge of the concave part.

  Due to the displacement of the central part of the pulse disk into the recess, the position detection pattern of the outer periphery of the pulse disk is warped so as to float up to the opposite side, and the position detection pattern of the pulse disk and the index scale There is a problem that a setting gap (for example, 160 μm) between them is out of order, and the modulation rate of the light intensity that is transmitted (or reflected) through the pulse disk decreases (changes) and the detection accuracy of the optical rotary encoder decreases. .

  In addition, due to the temperature change of the optical rotary encoder, the adhesive contracts or expands in the axial direction and the amount of warpage of the outer periphery of the pulse disk varies, and the position between the pulse disk position detection pattern and the index scale is changed. There was a problem that the gap fluctuated and the detection accuracy of the optical rotary encoder was lowered similarly.

  The present invention has been made in view of the above, and reduces the amount of warpage of the position detection pattern on the outer periphery of the pulse disk by reducing the amount of axial shrinkage or expansion of the adhesive in the recess. Accordingly, an object of the present invention is to obtain an optical rotary encoder that suppresses a decrease in detection accuracy.

In order to solve the above-described problems and achieve the object, the present invention provides a pulse disk on which a position detection pattern is formed and a housing rotatably held by the housing, and the pulse disk is bonded to the disk holding portion . A rotating shaft to be held, a light emitting element that irradiates light to the position detection pattern of the pulse disk, and a light receiving element that receives light from the light emitting element through the position detection pattern of the pulse disk In this optical rotary encoder, a concave portion is provided in the central portion of the disk holding portion of the rotating shaft, and a convex portion whose height from the bottom surface of the concave portion is lower than the depth of the concave portion is provided in the central portion of the concave portion. Providing the adhesive in the concave portion including on the convex portion, and applying the pulse disc to the outer top of the concave portion to adhere the pulse disc to the adhesive, and the central portion of the adhesive layer. The thickness of the periphery of the central portion And wherein the Ri that thin was.

  According to the present invention, since the thickness of the central portion of the adhesive layer for bonding the pulse disk to the top of the rotating shaft is made thinner than the thickness around the central portion of the adhesive layer, the thinned central portion is bonded. The amount of contraction or expansion in the axial direction of the agent layer is reduced, and the amount of warpage of the position detection pattern on the outer peripheral portion of the pulse disk is reduced, thereby reducing the detection accuracy. Moreover, since the center part of the pulse disk is bonded by the thinned adhesive layer, the adhesive strength of the pulse disk does not decrease.

  Embodiments of an optical rotary encoder according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a longitudinal sectional view showing an optical rotary encoder according to a first embodiment of the present invention, and FIG. 2 shows an adhesive that connects the rotating shaft and the pulse disk of the optical rotary encoder according to the first embodiment. It is a longitudinal cross-sectional view which shows the state which adhere | attached.

  As shown in FIG. 1, the optical rotary encoder 100 according to the first embodiment includes a housing 1 in which a module installation portion 1 a that is a plane perpendicular to the axis is formed, and coaxial first and second bearing holes 1 b of the housing 1. Of the first and second bearings 3 and 4 respectively fitted to 1c, the rotatable shaft 2 held by the inner rings 3b and 4b of the first and second bearings 3 and 4, and the rotating shaft 2 A hub 6 that fits into a hub fitting portion 2d as a rotation input portion, a pulse disc 7 that is bonded and held to a disc-like disc holding portion 2a as a top portion of the rotating shaft 2, and a module installation portion 1a The light emitting element module (LED module) 8 installed and held on the stage, the index scale 9 installed on the top 8a of the light emitting element module 8, and the circuit board attached to the column 1d erected on the housing 1 (Control board) 10 Includes a light-receiving element 11, a facing the outer peripheral portion of the pulse disk 7 is. The light emitting element module 8 irradiates the pulse disk 7 with light through the index scale 9. The index scale 9 is not essential and may not be installed.

  Next, an assembly method of the optical rotary encoder 100 according to the first embodiment and a detailed structure of each part will be described. First, an adhesive is applied to the bearing fitting portion 2c of the rotating shaft 2, the inner ring 3b of the first bearing 3 is fitted to the bearing fitting portion 2c, and the first bearing is located below the disc holding portion 2a. 3 is brought into contact with the inner ring 3b, and the first bearing 3 is positioned and mounted on the rotary shaft 2. As the adhesive, a thermosetting type or an adhesive that cures after a certain period of time is used so as not to immediately solidify.

  Before and after the above steps, the light emitting element module 8 is installed on the step of the module installation portion 1a of the housing 1 (fixed with screws). Further, the preload spring 5 is disposed on the inner flange 1 e on the first bearing hole 1 b side of the housing 1. Further, an adhesive is applied to the first bearing hole 1b.

  Next, the rotating shaft 2 to which the first bearing 3 is mounted is inserted into the first and second bearing holes 1b and 1c from the rotation input portion (hub fitting portion) 2d side, and is inserted into the first bearing hole 1b. The outer ring 3a of the first bearing 3 is fitted. Next, an adhesive is applied to the second shaft hole 1 c and the bearing fitting portion 2 c of the rotary shaft 2, and the outer ring 4 a of the second bearing 4 is set to the second bearing hole 1 c and the inner ring 4 b is set to the rotary shaft 2. It is made to fit in the bearing fitting part 2c.

  Thereafter, the top 2t of the disk holding portion 2a is pressed, the preload spring 5 is compressed by the outer ring 3a of the first bearing 3, and the rotary shaft 2 is pushed downward while preloading the first bearing 3, The axial gap between the top portion 2t of the plate holding portion 2a and the top portion 8a of the light emitting element module 8 is precisely adjusted.

  Next, with the hub fitting portion (rotation input portion) 2d of the rotating shaft 2 abutting the top portion of the hub 6 against the inner ring 4b of the second bearing 4, the hub 6 is mounted in a state where the adhesive is not cured. It is shrink fit and maintains an axial gap adjusted to high precision dimensions. Thereafter, the adhesive is cured, and the rotary shaft 2 and the inner rings 3b and 4b of the first and second bearings 3 and 4 and the first and second bearing holes 1b and 1c and the first and second bearings 3 are obtained. The four outer rings 3a and 4a are fixed.

  Next, referring to FIG. 2, the structure of the bonding portion between the rotating shaft 2 and the pulse disk 7, which is a characteristic configuration of the optical rotary encoder 100 of the first embodiment, will be described. As shown in FIG. 2, a circular recess 2aa is provided at the center of the top 2t of the disc holding portion 2a as the top of the rotating shaft 2. A convex portion 2ab having a height from the bottom surface of the concave portion 2aa lower than the depth of the concave portion 2aa is provided at the central portion of the concave portion 2aa.

  The depth d of the concave portion 2aa is d≈150 μm, and the depth t of the convex portion 2ab is t = 10 to 50 μm. The glass pulse disc 7 is bonded and fixed to the top 2t of the disc holding portion 2a with the top 2t outside the recess 2aa as the contact surface with the pulse disc 7 and in the recess 2aa including the top of the projection 2ab. , A light curable adhesive 15 such as a UV curable adhesive is filled so that the upper surface of the adhesive 15 does not become higher than the contact surface, a thin adhesive layer 15 is formed at the center, and the adhesive layer 15 The pulse disk 7 is precisely positioned so that the center mark of the pulse disk 7 is aligned with the rotation center of the rotation shaft 2 on the top 2t of the disk holding portion 2a of the rotation shaft 2, and the photo-curing adhesive 15 is irradiated with light. Curing is performed. The thickness of the central portion of the adhesive layer 15 is approximately 1/15 to 1/3 of the thickness around the central portion of the adhesive layer 15.

  In the process of curing the photocurable adhesive 15, before the adhesive 15 is cured, the contact surface and the upper surface of the adhesive 15 of the recess 2aa are in contact with the pulse disk 7 at the same height. Accordingly, the central portion of the pulse disk 7 is pulled and deformed in the contraction direction of the adhesive 15, so that the outer periphery of the pulse disk 7 (position detection pattern forming portion) is opposite to the contraction direction. Warp in the direction.

  Further, since the adhesive center portion farther from the contact surface is not supported by the contact surface, the amount of deformation due to the adhesive curing shrinkage of the adhesive 15 is larger. Since the diameter of the position detection pattern and the warpage amount are proportional, the warpage amount (deviation from the normal position) increases toward the outer periphery of the pulse disc 7 on which the position detection pattern is formed. As a result, the encoder 100 The position detection accuracy will be reduced.

  Therefore, it is important to reduce the amount of warpage of the pulse disc 7, and as described above, the thickness (10 to 50 μm) of the central portion of the adhesive layer 15 is made thinner than the surrounding thickness (150 μm). It is good. Thereby, in the center part of the adhesive bond layer 15, the amount of hardening shrinkage and the amount of expansion / contraction due to temperature change are reduced, and the amount of warpage of the pulse disk 7 can be reduced.

  As a specific means for making the thickness of the central portion of the adhesive layer 15 thinner than the surrounding thickness, one is the central portion (φ4) of the concave portion 2aa filled with the adhesive 15 from the contact surface outside the concave portion 2aa. It is only necessary to provide a convex step (convex portion) that does not become too high (from the viewpoint of adhesive strength, the outer peripheral portion of the adhesive layer 15 requires a portion with a thickness of about 150 μm, and the whole cannot be thinned. .)

  For example, the thickness of the central part (outer diameter φ4) of the adhesive layer 15 is 10 μm to 50 μm (1/15 relative to the thickness of the outer peripheral part) with respect to the thickness of 150 μm at the outer peripheral part (outer diameter φ12) of the adhesive layer 15. ~ 1/3), the amount of warping of the outer periphery of the pulse disc 7 (thickness 1 mm, outer diameter φ50) is reduced to about 1/6 to 1/2 compared to the case where it is not thinned. The

  Next, as shown in FIG. 1, the index scale 9 is precisely positioned on the top 8a of the light emitting element module 8 and fixed with an adhesive or the like. Finally, the circuit board 10 to which the light receiving element 11 is attached is fixed to the column 1d erected on the housing 1, and the optical rotary encoder 100 according to the first embodiment is completed. The completed optical rotary encoder 100 is attached to a housing of a servo motor (not shown), the hub 6 is connected to the rear end of the output shaft of the servo motor, and becomes a servo motor including the optical rotary encoder 100.

  The rotational position of the output shaft of the servo motor is detected as follows. When the power is turned on and the light emitting element (LED) installed in the light emitting element module 8 emits light, the light passes through the slit window group formed in the index scale 9, and then the slit window ( The light-receiving element 11 is irradiated as a light signal. The light receiving element 11 generates a current proportional to the amount of light irradiated.

  When the output shaft of the servo motor rotates and the rotary shaft 2 of the optical rotary encoder 100 rotates, the light emitted from the light emitting element 8 is a pattern of a pulse disk 7 that is a rotary scale and an index scale 9 that is a fixed scale. The intensity of light is modulated by the relative position change, and the amount of light reaching the light receiving element 11 becomes an optical signal whose amplitude changes sinusoidally. The light emission current by this optical signal is converted into a voltage by a waveform shaping circuit, shaped into a pulse waveform, and output to the outside.

  According to the optical rotary encoder 100 of the first embodiment described above, the concave portion 2aa is provided in the central portion of the top portion 2t of the rotating shaft 2, and the height from the bottom surface of the concave portion 2aa is the concave portion 2aa at the central portion of the concave portion 2aa. The convex part 2ab lower than the depth of the convex part 2ab is provided, and the adhesive 15 is filled in the concave part 2aa including the convex part 2ab to form the adhesive layer 15 having a thin central part. 2 is bonded to the top portion 2t, the amount of shrinkage or expansion of the adhesive 15 at the center in the recess 2aa is reduced, and the amount of warping of the position detecting pattern portion at the outer peripheral portion of the pulse disc 7 is reduced, and the optical A decrease in detection accuracy of the rotary encoder 100 can be suppressed.

Embodiment 2. FIG.
FIG. 3 is a longitudinal sectional view showing a state in which the rotating shaft and the pulse disk, which are the main parts of the optical rotary encoder according to the second embodiment of the present invention, are bonded with an adhesive. The optical rotary encoder 200 of the second embodiment is different from the optical rotary encoder 100 of the first embodiment only in the form of the rotary shaft 22 and the pulse disk 27 shown in FIG. Description of other parts is omitted.

  As shown in FIG. 3, a circular recess 22aa is provided at the center of the top 22t of the disc holding portion 22a as the top of the rotating shaft 22. The height from the surface (lower surface) of the area facing the recess 22aa of the pulse disk 27 is lower than the depth of the recess 22aa at the center of the area facing the recess 22aa on the lower side of the transparent disk pulse disk 27. A convex portion 27ab is provided.

  The depth d of the concave portion 22aa is d≈150 μm, and the axial distance s between the convex portion 27ab and the bottom surface of the concave portion 22aa is s = 10 to 50 μm. The concave portion 22aa including the bottom of the convex portion 27ab is filled with the photocurable adhesive 25 to form an adhesive layer 25 having a thin central portion, and the pulse disc 27 is attached to the disc holding portion of the rotating shaft 22 by the adhesive layer 25. It is precisely positioned and bonded to the top 22t of 22a so that the center mark of the pulse disk 27 is aligned with the center of rotation of the rotating shaft 22. The thickness of the central portion of the adhesive layer 25 is 1/15 to 1/3 of the thickness of the peripheral portion of the adhesive layer 25.

  The amount of contraction or expansion in the axial direction of the thin adhesive layer 25 in the central portion is smaller than when the convex portion 27ab is not provided, and the amount of warpage of the outer peripheral portion of the pulse disc 27 is reduced. ing.

  According to the optical rotary encoder 200 of the second embodiment described above, the concave portion 22aa is provided in the central portion of the top portion 22t of the rotating shaft 22, and the pulse circle is formed in the central portion of the region facing the concave portion 22aa of the pulse disc 27. A convex portion 27ab whose height from the surface (lower surface) of the region of the plate 27 facing the concave portion 22aa is lower than the depth of the concave portion 22aa is provided, the adhesive 25 is filled into the concave portion 22aa including under the convex portion 27ab, and the concave portion 22aa The convex portion 27ab is inserted into the adhesive layer 25 to form a thin central portion, and the pulse disk 27 is adhered to the top portion 22t of the rotating shaft 22 by the adhesive layer 25, so that the central portion in the concave portion 22aa is formed. The amount of warpage of the outer peripheral portion of the pulse disk 27 can be reduced by reducing the amount of contraction or expansion of the adhesive 25, and the decrease in detection accuracy of the optical rotary encoder 200 can be suppressed.

Embodiment 3 FIG.
FIG. 3 is a longitudinal sectional view showing a state in which the rotating shaft and the pulse disk, which are the main parts of Embodiment 3 of the optical rotary encoder according to the present invention, are bonded with an adhesive. The optical rotary encoder 300 of the third embodiment is different from the optical rotary encoder 100 of the first embodiment only in the form of the rotary shaft 32 shown in FIG. Description is omitted.

  As shown in FIG. 4, a circular recess 32aa is provided at the center of the top 32t of the disc holding portion 32a as the top of the rotating shaft 32, and a protrusion lower than the depth of the recess 32aa at the center of the recess 32aa. 32ab is provided. An annular groove 32ac is formed on the outer periphery of the recess 32aa.

  The depth d of the concave portion 32aa is d≈150 μm, and the depth t of the convex portion 32ab is t = 10 to 50 μm. The depth of the annular groove 32ac may be deeper, shallower or the same as the depth of the recess 32aa. A light curable adhesive 35 is filled in the concave portion 32aa including the convex portion 32ab to form an adhesive layer 35 having a thin central portion, and the pulse disc 7 is attached to the disc holding portion of the rotary shaft 32 by the adhesive layer 35. It is precisely positioned and bonded to the top 32t of 32a.

  When the adhesive 35 filled in the concave portion 32aa becomes a large amount and is somewhat piled up due to the surface tension, when the pulse disk 7 is bonded, the excess pile portion flows into the annular groove 32ac and enters the annular groove 32ac. Be contained. Therefore, the adhesive 35 does not enter between the top portion 32t of the disc holding portion 32a and the pulse disc 7, and does not hinder the precise positioning of the pulse disc 7. Instead of providing the convex portion 32ab in the concave portion 32aa, a convex portion may be provided on the lower surface of the pulse disk 7.

  According to the optical rotary encoder 300 of the third embodiment described above, the concave portion 32aa is provided in the central portion of the top portion 32t of the rotating shaft 32, and the convex portion 32ab lower than the depth of the concave portion 32aa is provided in the central portion of the concave portion 32aa. An adhesive 35 is filled in the concave portion 32aa including the convex portion 32ab to form an adhesive layer 35 having a thin central portion, and the pulse disk 7 is adhered to the top portion 32t of the rotating shaft 32 by the adhesive layer 35. Since the surplus portion 35 is accommodated in the annular groove 32ac, the pulse disc 7 is precisely positioned on the rotary shaft 32, and the amount of contraction or expansion of the adhesive 35 in the central portion in the recess 32aa is reduced to reduce the pulse circle. The amount of warpage of the outer peripheral portion of the plate 7 can be reduced, and a decrease in detection accuracy of the optical rotary encoder 300 can be suppressed.

  As described above, the optical rotary encoder according to the present invention is used for detecting the rotational position of a servo system, has an extremely high resolution, and is useful as an encoder that detects an absolute position of a machine tool or the like with high accuracy.

It is a longitudinal cross-sectional view which shows Embodiment 1 of the optical rotary encoder concerning this invention. It is a longitudinal cross-sectional view which shows the state which adhere | attached the rotating shaft and pulse disc of the optical rotary encoder of Embodiment 1 with the adhesive agent. It is a longitudinal cross-sectional view which shows the principal part of Embodiment 2 of the optical rotary encoder concerning this invention. It is a longitudinal cross-sectional view which shows the principal part of Embodiment 3 of the optical rotary encoder concerning this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Housing 1a Module installation part 1b 1st bearing hole 1c 2nd bearing hole 1d support | pillar 1e Inner flange 2,22,32 Rotating shaft 2a, 22a, 32a Disk holding | maintenance part 2aa, 22aa, 32aa Concavity 2ab, 32ab Convex part 2d Hub fitting part (rotation input part)
2t, 22t, 32t Top portion 3 First bearing 4 Second bearing 5 Preload spring 7, 27 Pulse disc 27ab Protruding portion 8 Light emitting element module (light emitting element)
8a Top 9 Index scale 10 Circuit board (control board)
11 light receiving element 15, 25, 35 photo-curing adhesive (adhesive layer)
100, 200, 300 Optical rotary encoder

Claims (4)

A pulse disk on which a position detection pattern is formed;
A rotation shaft that is rotatably held in a housing and holds the pulse disk by adhering to the disk holding part ;
A light emitting element for irradiating light to the position detection pattern of the pulse disc;
A light receiving element that receives light from the light emitting element through a position detection pattern of the pulse disk;
In an optical rotary encoder comprising:
A concave portion is provided at a central portion of the disk holding portion of the rotating shaft, a convex portion having a height from the bottom surface of the concave portion lower than the depth of the concave portion is provided at the central portion of the concave portion, and includes on the convex portion. Adhesive is filled in the recess, and the pulse disc is applied to the top of the outer side of the recess to adhere the pulse disc to the adhesive, and the thickness of the central portion of the adhesive layer is set to An optical rotary encoder that is thinner than the surrounding thickness. A pulse disk on which a position detection pattern is formed;
A rotation shaft that is rotatably held in a housing and holds the pulse disk by adhering to the disk holding part;
A light emitting element for irradiating light to the position detection pattern of the pulse disc;
A light receiving element that receives light from the light emitting element through a position detection pattern of the pulse disk;
In an optical rotary encoder comprising:
A concave portion is provided in the central portion of the disc holding portion of the rotating shaft, and the height from the surface of the region facing the concave portion of the pulse disc is at the central portion of the region facing the concave portion of the pulse disc. A convex part lower than the depth of the concave part is provided, an adhesive is filled in the concave part including the lower part of the convex part, and the pulse disk is adhered to the adhesive by applying the pulse disk to the outer top of the concave part. An optical rotary encoder characterized in that the thickness of the central portion of the adhesive layer is made thinner than the thickness around the central portion . Optical rotary encoder according to claim 1 or 2 wherein the thickness of the center portion of the adhesive layer, characterized in that the thickness of 1/15 to 1/3 of the thickness of the outer peripheral portion. The optical groove according to claim 1 or 2 , wherein an annular groove into which an excess of the adhesive filled in the concave portion flows is formed in an outer peripheral portion of the concave portion of the disk holding portion of the rotating shaft. Rotary encoder.

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