JP4847031B2 - Optical encoder - Google Patents

Description

  The present invention relates to an optical encoder provided with a reflective scale having a curved shape or a V-shape.

  FIG. 21 is a perspective view of a conventional optical reflective encoder, and FIG. 22 is a YZ sectional view orthogonal to the displacement detection axis (X axis in the coordinate system). Of the radiated light beam from the light source 1 composed of an LED chip, the reflected light beam from the reflection scale 2 is received by the light receiving element 3 formed of a photo IC chip incorporating a light receiving unit and a signal processing circuit. The semiconductor elements of the light source 1 and the light receiving element 3 are die-bonded on the substrate 4 and are further covered with a translucent resin 5 and a transparent glass 6, and the light source 1, the light receiving element 3, the substrate 4, the resin 5, The detection head 7 is composed of the transparent glass 6. On the other hand, the reflective scale 2 includes a reflective layer forming portion 11 including a reflective scale substrate 8, a reflective layer 9, and a reflective layer 10. Such a reflective encoder is disclosed in Patent Document 1, for example.

JP 2003-337052 A

  In the reflective encoder having such a configuration, in the XZ sectional view including the displacement detection axis in FIG. 23, the angle θ1 is an effective light beam guided from the light source 1 to the light receiving region of the light receiving element 3 through the reflective scale 2. In this case, only a small amount of the light flux emitted from the light source 1 is used, and most of the light flux becomes an invalid component, and there is a problem that the light use efficiency is extremely poor.

  In order to expand the effective luminous flux, means for expanding the light receiving area of the light receiving element 3 can be easily considered. However, the size of the light receiving element 3 increases the size of the entire detection head 7 and increases the cost. Not. In order to make up for the slight amount of light that reaches the light receiving element 3, it is easy to increase the amount of light emitted from the light source 1. In this case, however, the power consumption increases and an excessive current flows through the light source 1. There arises a problem that the life of the light source 1 is shortened.

  Further, although means for amplifying the signal in the signal processing circuit is conceivable, this method also increases the noise component and does not become a substantially effective means, which affects the detection accuracy and is not a preferable means.

  Inexpensive flexible reflective scales are also considered, but there is also a drawback that deformation is likely to occur and position detection errors are likely to occur due to this deformation.

  An object of the present invention is to provide an optical encoder that solves the above-described problems, improves the shape of the reflection scale itself against deformation, etc., and greatly reduces detection errors.

Technical characteristics of the optical encoder according to the present invention for achieving the above object, the reflection having a detection head having on the same substrate as the light receiving element light source, a flexible displaced relative to the detection head An optical encoder with a scale,
The reaction force of at least a portion seen including a curved shape or a substantially V-shaped, fixed of the reflective scale, elastic bending deformation of the reflective scale itself sectional shape perpendicular to the detection direction of the relative displacement of the reflective scale It is in using .

  According to the optical encoder of the present invention, it is possible to use a flexible film scale, metal scale, etc., which has a problem in terms of accuracy, while being advantageous in terms of price, and at the same time, Utilization efficiency can be greatly improved, resulting in low price, high accuracy, and low power consumption.

  The present invention will be described in detail based on the embodiment shown in FIGS.

  FIG. 1 is a perspective view showing the configuration of a first embodiment of an optical reflective encoder according to the present invention. The detection head 23 is mainly composed of a semiconductor element of a light receiving element 22 formed of a light source 21 formed of an LED chip, a light receiving unit, and a photo IC chip incorporating a signal processing circuit. In addition to the light source 21 and the light receiving element 22, the detection head 23 is disposed on the sealing resin 25, and a translucent sealing resin 25 sealed so as to cover the wiring substrate 24, the light source 21 and the light receiving element 22. It consists of a transparent glass 26 provided.

  The reflection scale 31 disposed above the detection head 23 is bent so as to cover the detection head 23 by a YZ cross-sectional shape orthogonal to the X axis as shown in FIG. A three-dimensional shape is cut out in parallel with the bus line X0. Further, the radius of curvature of the arcuate section in the YZ section is substantially the distance between the detection head 23 and the reflection scale 31, and the center line of curvature is located approximately in the middle between the light source 21 and the light receiving element 22.

  As shown in FIG. 3, the reflective scale 31 includes a pattern forming sheet 32 and a reflective layer forming sheet 33. The pattern forming sheet 32 is, for example, a transparent PET film for industrial photoengraving film, has a thickness of about 0.1 to 0.2 mm, and is subjected to exposure / development steps by the emulsion layer of the industrial photoengraving film. Necessary patterns are formed. On the base material portion 32a of the pattern forming sheet 32, a pattern composed of the non-reflecting portion 32b and the light transmitting portion 32c of the light absorbing portion is alternately provided.

  On the other hand, in the reflection layer forming sheet 33, a reflection layer 33b made of a vapor deposition film is formed on the lower surface of the reflection layer 33a made of a PET film as a base material. The reflective scale 31 has a structure in which the pattern forming sheet 32 and the reflective layer forming sheet 33 are joined by an adhesive layer 34 made of a transparent adhesive as shown in FIG.

  Such a reflective scale 31 is flexible with a thickness of about 0.2 mm, and is bent by applying a force from the Y-axis direction as shown in FIG. 5A, as shown in FIG. It is inserted into the box-shaped attachment member 35 while being bent. As shown in (c), while being bent and deformed, it is pushed to the abutting position of the mounting member 35 to release the force in the Y-axis direction, and the reflection scale 31 is subjected to the elastic bending deformation reaction force F of the reflection scale 31 itself. 31 is fixed to the mounting member 35. In this case, an adhesive may be used in combination with the abutting site.

  FIG. 6 shows the reflection scale 31 which is attached to the attachment member 35 and bent as described above. FIG. 7 is a YZ sectional view of Example 1 in which the reflection scale 31 with the detection head 23 is combined. A part of the mounting member 35 also serves to limit the luminous flux from the light source 21, and the frame body part 35 a provided at the bottom of the mounting member 35 plays a role of an optical stop.

  The light beam emitted from the light source 21 passes through the pattern forming sheet 32 of the reflective scale 31 as a light beam La as shown in FIG. 4, and a part of the light beam is absorbed by the non-reflecting portion 32 b of the pattern forming sheet 32. On the other hand, the light beam Lb is transmitted through the light transmitting portion 32c and reflected by the reflective layer 33b. The reflected light again passes through the light transmitting portion 32 c, further passes through the base material portion 32 a, and enters the light receiving element 22 in the detection head 23. In the reflection type encoder, the change in the light intensity of the reflected light beam from the reflection pattern portion generated with the relative displacement of the detection head 23 and the reflection scale 31 is converted into an electric signal, and the relative displacement amount is calculated by using a calculation means (not shown). Can be measured.

  FIG. 8 shows the state of ray tracing of the path from the light source 21 to the reflection scale 31 to the light receiving element 22 in the first embodiment. Each state (a) to (f) is a distance from the detection head 23 to the reflection scale 31. In other words, the so-called gap between the sensor and the scale is gradually changed away. Since the radius of curvature of the arc-shaped section in the YZ section is substantially the distance between the detection head 23 and the reflection scale 31, and the center of curvature is located between the light source 21 and the light receiving element 22, radiation from the light source 21 is performed. Most of the light beam can be guided as a convergent light beam on the surface of the light receiving element 22.

  Comparing FIG. 8 showing the light beam path in the first embodiment with FIG. 9 of ray tracing using the conventional reflection scale 2 in which the YZ cross-sectional shape is not curved, FIG. 9 shows the light source 21 in FIG. Among the radiated light beams from, only the light quantity in the angle range of θ3 (≈6 ° to about 10 °) is guided to the light receiving element 22. On the other hand, in the first embodiment, the light amount in the angle range of θ2 (≈12 ° to 20 °) in FIG. 8 is guided to the light receiving element 22, and the received light amount is improved by about twice that of the conventional case. Even if the gap between the head 23 and the reflection scale 31 varies over a wide range, it can be used as a sensor.

  FIG. 10 is a graph showing the situation. In the conventional planar scale, it is necessary to arrange a reflection scale in the vicinity of the detection head. However, in the first embodiment, an effective signal can be obtained over a considerably wide range. .

  As described above, in the first embodiment, the YZ cross-sectional shape of the reflective scale 31 is an arc-shaped cross section that covers the detection head 23, so that the amount of radiated light from the light source 21 is larger than that of the conventional flat reflective scale. The light is guided to the light receiving element 22. In particular, in the first embodiment, the radius of curvature of the arc-shaped section in the YZ section is made substantially equal to the distance between the detection head 23 and the reflection scale 31, and the center line of curvature is located between the light source 21 and the light receiving element 22. Therefore, the radiated light beam diverging from the light source 21 is converted as a convergent light beam onto the surface of the light receiving element 22, and the light amount from the light source 21 can be efficiently taken into the light receiving element 22.

  In the reflection scale 31, it is important that the direction of the bus bar X0 of the cylindrical body coincides with the direction of displacement detection. In the cylindrical body, the bending strength in the direction of the bus bar X0 increases compared to the flat plate. Deformation along the surface displacement detection axis X hardly occurs. This is because when the direction of the displacement detection axis X is arranged in parallel to the direction of the generating line X0 of the cylindrical body and applied to a reflective encoder, the linearity of the displacement detection direction component is improved, and the reflected light flux on the reflective scale 31 is improved. Can be controlled.

  Furthermore, if the reflective scale 31 itself is fixedly supported on the mounting member 35 by the reaction force of the elastic bending deformation, the thickness unevenness of the adhesive layer 34 when the conventional reflective scale is bonded to a reference plane, or the inclusion of foreign matter Etc. will not occur.

  FIG. 11 is a YZ sectional view of the reflective encoder of the second embodiment. Since the main configuration is the same as that of the first embodiment, the description thereof is omitted. However, the difference from the first embodiment is in the shape and mounting method of the mounting member 41 to which the reflective scale 31 is mounted. In the first embodiment, the reflective scale 31 is fixedly supported on the mounting member 35 by its own elastic bending deformation reaction force, but in this second embodiment, the reflective scale 31 is fixed to the mounting member 41 by the adhesive layer 42. Has been.

  In order to make the reflective scale 31 into a curved shape, as shown in FIG. 12, the bonding portion of the reflective scale 31 in the YZ section of the mounting member 41 has a curved shape, and the reflective scale 31 extends along this curved surface. Is pasted. Therefore, the curved shape of the reflective scale 31 can be made a desired shape to some extent by the bonded surface shape of the mounting member 41.

  In the second embodiment, similarly to the first embodiment, when the displacement detection axis X direction is arranged in parallel with the direction of the generatrix X0 and applied to the reflective encoder, the linearity of the displacement detection direction component is improved. In addition, there is an effect that the fluctuation of the reflected light beam on the reflection scale 31 can be suppressed.

  Further, the entire back surface of the reflective scale 31 is not bonded and fixed, but only the portion 41a corresponding to the optical effective range D of the reflective scale 31 is escaped in shape, and is actually bonded and supported. Therefore, the surface deformation at the adhesive layer 42, uneven thickness of the adhesive layer 42, and the inclusion of foreign matter at the time of bonding are avoided, and the rigidity of the curved busbar X0 is improved, so that attachment with substantially no deformation is possible. Become.

  FIGS. 13A to 13C show the light beam path in the case where the reflecting surface sectional shape of the second embodiment is a curved shape, in particular, an arc, and the distance between the detecting head 23 and the curved reflecting scale 31 is 2.5 mm. It is an optical path diagram in the case of 0.0 mm and 3.5 mm. It is explanatory drawing at the time of setting it as a reflective cylindrical surface where the curvature center of a circular arc exists in the approximate middle position of the light source 21 and the light receiving element 22, and the curvature radius R is 3.0 mm.

  14A to 14C show the light beam path in the case where the reflecting surface has a curved cross section, particularly a parabola, and the distance between the detection head 23 and the curved reflection scale 31 is 2.5 mm, 3.0 mm, 3 It is an optical path diagram in the case of .5 mm. The axis n of the paraboloid is set at a substantially intermediate position between the light source 21 and the light receiving element 22 and the shape is optimized so that more light flux from the light source 21 is guided to the light receiving element 22, and the light flux is θ4≈60. Reach °. The use efficiency of the light source quantity is improved by about 5 times compared with the conventional reflection scale in the parallel plate state.

  15 (a) to 15 (c) show light beam paths when the reflecting surface has a curved cross-sectional shape, particularly an ellipse, and the intervals between the detection head 23 and the curved reflecting scale 31 are 2.5 mm, 3.0 mm, and 3. It is an optical path figure at the time of setting to 5 mm. The minor axis n of the ellipse is a substantially intermediate position between the light source 21 and the light receiving element 22, and the reflected light beam from the reflection scale 31 is incident on the light receiving element 22 as a substantially parallel light beam.

  As described above, as Example 2, it is shown that various reflection light paths can be designed by giving the curved surface not only a circular arc but also a parabola, an ellipse, and other hyperbola. In any case, as shown in FIG. 10, the light utilization efficiency is greatly improved as compared with the conventional flat reflection scale. Further, in the second embodiment, similarly to the first embodiment, in any surface shape, the displacement detection axis direction is arranged in parallel with the direction of the generatrix X0 and applied to the reflective encoder. The linearity of the detection direction component is improved, and the fluctuation of the reflected light beam at the reflection scale 31 is suppressed.

  FIG. 16 shows a ray path diagram of the third embodiment. In the third embodiment, the YZ cross-sectional shape of the reflection scale 31 is a shape having a structure bent in a substantially V shape. In this case, the V-shaped bending is performed so that the light beams from the two reflection planes overlap. The angle is selected, and the utilization efficiency of the light amount of the light source 21 is improved.

  In actual bending, a slight amount of R is generated in the bent portion, so that it can be handled as a hyperbolic section in the second embodiment. FIG. 17 shows a case where the reflection scale 31 is attached to the outside of the attachment member 51. The reflective scale 31 is bent on both sides in addition to the V-shaped bent portion, and is fixed to the block-shaped attachment member 51 with an adhesive layer 52.

  Also in the third embodiment, the linearity of the displacement detection direction component is improved when the displacement detection axis X direction is arranged in parallel with the bending portion ridge line direction of the bending structure and applied to the reflection type encoder as in the first embodiment. Thus, the fluctuation of the reflected light beam at the reflection scale 31 is suppressed.

  18 to 20 show a fourth embodiment, in particular, a method for manufacturing a fold scale. In FIG. 18, the pattern forming sheet 32 and the reflective layer forming sheet 33 previously shown in FIG. 3 are each independently molded into a curved shape. The reflective pattern forming sheet 32 and the reflective layer forming sheet 33 having a circular arc cross section having a predetermined radius of curvature are separately manufactured and joined by an adhesive layer 61 as shown in FIG.

  As a joining means, many means other than the adhesive layer 61 are conceivable. As a joining method, for example, the adhesive layer 61 is interposed between the pattern forming sheet 32 and the reflective layer forming sheet 33 as shown in FIG. These laminates can be manufactured by heat-pressing and pressing with the upper die 62 and the lower die 63.

  In the description of the configuration of all the above embodiments, the case of the reflective film scale has been mainly described. However, the present invention can be substantially applied to a reflective metal scale and other reflective scales having no flexibility. It is.

1 is a perspective view of a reflective encoder configuration according to Embodiment 1. FIG. 3 is a cross-sectional view orthogonal to a displacement detection direction axis of Example 1. FIG. It is sectional drawing before adhesion | attachment of the reflective scale of Example 1. FIG. 2 is a cross-sectional view of a reflection scale of Example 1. FIG. It is a figure which shows the attachment method of the reflective scale of Example 1. FIG. It is a perspective view of the state where the reflective scale of Example 1 was attached to the fixed member. 3 is a YZ cross-sectional view of a fixed reflection scale of Example 1. FIG. It is an optical path figure in a YZ section. It is an optical path figure of a planar reflective scale. It is a graph figure of received light quantity with respect to the distance of a detection head and a reflective scale. 6 is a cross-sectional view orthogonal to a displacement detection direction axis of Embodiment 2. FIG. 6 is a perspective view of a fixing member of Example 2. FIG. It is an optical path figure in case a reflection scale is circular arc shape. It is an optical path figure in case a reflection scale is parabolic shape. It is an optical path figure in case a reflection scale is elliptical shape. FIG. 6 is an optical path diagram in the YZ section of Example 3. 6 is a cross-sectional view orthogonal to a displacement detection direction axis of Example 3. FIG. 6 is an explanatory diagram of a method for manufacturing a reflective scale of Example 4. FIG. 6 is an explanatory diagram of a method for manufacturing a reflective scale of Example 4. FIG. 6 is an explanatory diagram of a method for manufacturing a reflective scale of Example 4. FIG. It is a perspective view of the conventional reflective encoder. It is XZ sectional drawing of the conventional reflective encoder. It is YZ sectional drawing of the conventional reflective encoder.

Explanation of symbols

21 Light source 22 Light receiving element 23 Detection head 31 Reflective scale 32 Pattern forming sheet 33 Reflecting layer forming sheet 34, 42, 52, 61 Adhesive layer 35, 41, 51 Mounting member 62 Upper die 63 Lower die

Claims (6)

In an optical encoder comprising a detection head provided with a light source and a light receiving element on the same substrate, and a reflective scale having flexibility for relative displacement with respect to the detection head,
Look including a curved shape or a substantially V-shaped in at least a portion of the cross section perpendicular to the detection direction of the relative displacement of the reflective scale,
The reflection scale is fixed using an elastic bending deformation reaction force of the reflection scale itself .   2. The optical encoder according to claim 1, wherein a direction of the bent bus of the reflection scale and the displacement detection direction are arranged in parallel. The curvature radius of the curved shape is substantially equal to the distance from the reflection scale to the detection head, and the curvature center line of the curved shape is located between the light source and the light receiving element. The optical encoder according to claim 2.   The optical encoder according to claim 1, wherein the substantially V-shaped bending ridge line direction of the reflection scale and the displacement detection direction are arranged in parallel.   The optical encoder according to claim 1, wherein the reflection scale is fixed to an attachment member by escaping from a back surface corresponding to an optical effective range. In an optical encoder comprising a detection head provided with a light source and a light receiving element on the same substrate, and a reflective scale having flexibility for relative displacement with respect to the detection head,
Including a curved shape in at least a part of a cross-sectional shape orthogonal to the detection direction of the relative displacement of the reflective scale;
The curved shape of the reflective scale is produced by separately forming an arc-shaped reflective layer forming sheet having a predetermined radius of curvature and an arc-shaped reflective pattern forming sheet having a predetermined radius of curvature, respectively, and forming the reflective layer An adhesive layer is interposed between the sheet and the reflective pattern forming sheet, and is formed by pressure-bonding the reflective layer forming sheet and the reflective pattern forming sheet by heating and pressing with an upper die and a lower die. An optical encoder.

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