JP2005300316A - Displacement measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent thermal strain in the measuring axis direction of a scale, and simultaneously to realize high mounting accuracy in the thickness direction of a scale plate. <P>SOLUTION: The scale 1 is equipped with the scale plate 3 where a gradation 5 extending in the measuring axis direction is formed, and a support 4 for supporting it. As for the scale plate 3, one end in the measuring axis direction is supported by the support through a fixed support part 6, and the other end is supported by the support 4 through an elastic support part 6. The fixed support part 6 defines the distance between the support 4 and the scale plate 3 by fixed spacers 61, 62 projecting from the support 4 toward the scale plate 3. Elastic support parts 7, 8 define the distance between the support 4 and the scale plate 3 by movable spacers 72, 82 projecting from the support 4 toward the scale plate 3. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  Disclosed is a displacement measurement system comprising a scale plate having a scale extending in the measurement axis direction, a scale having a support that supports the scale plate, and a read head that reads the scale opposite the scale. Relates to the device.

Conventionally, in this type of displacement measuring device, when a scale formed with a scale extending in the measurement axis direction is composed of a scale plate made of a low expansion material such as glass and a support that supports the scale, In order to prevent the distortion of the scale due to the difference in thermal expansion coefficient, the scale plate is fixed to the support so as to be movable in the measurement axis direction (Patent Document 1). Specifically, the scale plate has one end fixed to the support via a fixed support and the other end fixed to the support via an elastic support. The fixed support part is realized by a fixed adhesive, and the elastic support part is realized by an elastic adhesive.
Japanese Patent No. 2989140 (paragraph 0008), FIG.

  In the scale disclosed in Patent Document 1 described above, since one end of the scale plate is supported by the support through the elastic support portion, thermal strain in the measurement axis direction between the scale plate and the support is Although there is an effect that the scale plate is absorbed by the elastic support portion, the scale plate is supported by the elastic adhesive also in the thickness direction, so that there is a problem that it is difficult to obtain accuracy in the gap direction with the reading head. is there. In particular, since an elastic adhesive such as silicon shrinks when solidified, it is difficult to accurately manage the gap between the scale plate and the support.

  The present invention has been made in view of these points, and provides a displacement measuring device that can achieve high mounting accuracy in the thickness direction of the scale plate while preventing thermal distortion in the measurement axis direction of the scale. With the goal.

  The displacement measuring apparatus according to the present invention includes a scale plate provided with a scale extending in the measurement axis direction, a scale including a support that supports the scale plate, and the measurement is performed with respect to the scale while facing the scale. In a displacement measuring device that is arranged to be relatively movable in the axial direction and includes a reading head that reads the scale scale, the scale plate has the one end in the measurement axial direction via the fixed support portion. While being supported by the support, the other end in the measurement axis direction is supported by the support via an elastic support, and the fixed support protrudes from the support toward the scale plate and supports the support A first spacer for defining a distance between a body and the scale plate, and a fixed adhesive filled between the support body and the scale plate around the first spacer, and the elastic support Department is in front A second spacer that protrudes from the support body toward the scale plate and defines a distance between the support body and the scale plate, and between the support body and the scale plate around the second spacer. And a filled elastic adhesive.

  According to the present invention, the distance between one end of the scale plate and the support is defined by the first spacer constituting the fixed support, and the distance between the other end of the scale plate and the support is elastically supported. Since the scale plate is defined by the second spacer constituting the part, the scale plate is movable in the measurement axis direction, but is constrained to a predetermined value in the gap direction. For this reason, according to this invention, the high mounting precision to the thickness direction of a scale plate is also realizable, preventing the thermal distortion of the measurement axis direction of a scale.

  Note that, for example, if the scale plate is supported by the support body via the elastic support portion at one or a plurality of positions between the both end portions in the measurement axis direction, even if the scale becomes long, the gap changes due to bending. Can be prevented.

  For example, when the second spacer is a movable spacer whose protrusion amount can be adjusted, the scale plate and the support body due to the shrinkage of the elastic adhesive can be obtained by finely adjusting the movable spacer after the elastic adhesive is solidified. Even if the gap fluctuation occurs, it is possible to set the final gap with high accuracy.

  Furthermore, the movable spacer is in point contact with the scale plate, and the support has protrusions extending in the direction perpendicular to the measurement axis direction on both sides of the measurement axis direction of the movable spacer, and the elastic adhesive is provided with the movable spacer. If it is filled between the projections on both sides and the scale plate, it is possible to improve the accuracy of the gap while enabling stable support.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is an external perspective view of a displacement measuring apparatus (in this example, a linear encoder) according to an embodiment of the present invention.

  The displacement measuring apparatus according to the present embodiment is, for example, a reflective optical encoder, and is opposed to the scale 1 extending in the measurement axis X direction, facing the scale 1 with a predetermined gap, and is measured with respect to the scale 1. The optical read head 2 is arranged so as to be relatively movable in the direction of the axis X. The scale 1 includes a scale plate 3 and a support 4 that supports the scale plate 3.

  The scale plate 3 is a rectangular plate-like body that extends long in the measurement axis X direction. The scale plate 3 is made of a low expansion material such as glass. 5 is formed.

  2 is a view of the portion of the scale 1 from which the reading head is removed from the displacement measuring device shown in FIG. 1 as seen from each direction. FIG. 2A is a view of the scale 1 as seen from above. In order to explain the structure, a part of the scale plate 3 is cut away. The figure (b) is a side view seen from the left side of the figure of (a), the figure (c) is a front view seen from the lower part of the figure of (a), and the figure (d) is from the back side of (a). FIG. The support body 4 is made of a metal plate having a slightly different expansion coefficient from the scale plate 3, and supports the fixed support portion 6 that supports one end portion of the scale plate 3 in the longitudinal direction and the other end portion of the scale plate 3. And an elastic support portion 8 that supports a substantially middle point between both end portions.

  The fixed support portion 6 includes two fixed spacers (first spacers) 61 and 62 that protrude from the support body 4 toward the scale plate 3. The fixed spacers 61 and 62 are protrusions that are spaced apart in the lateral direction of the scale plate 3 and extend in the lateral direction. A rectangular adhesive base 63 having a height lower than that of the fixed spacers 61 and 62 is formed between the fixed spacers 61 and 62, and an epoxy resin or the like is formed between the upper surface of the adhesive base 63 and the lower surface of the scale plate 3. A fixed adhesive 64 is filled. For this reason, the distance between the support 4 and the scale plate 3 is defined by the fixed spacers 61 and 62. These fixed spacers 61 and 62, the adhesive base 63 and the fixed adhesive 64 constitute the fixed support portion 6. As the fixed adhesive 64, Araldite Standard (Tech Jam Co., Ltd.), Cemedine 1500 No. (Cemedine Co., Ltd.), Bond E Set M (Konishi Co., Ltd.), etc., may be used as the epoxy adhesive. it can. In addition, a cement adhesive may be used as the fixed adhesive 64.

  On the other hand, the elastic support portion 7 is screwed into a through hole 71 formed in the support body 4 as shown in an enlarged cross-sectional view in FIG. A driver fitting groove is formed in the part, and a pin-type movable spacer (second spacer) 72 having a thread groove cut in the peripheral surface, which can adjust the protruding amount of the tip part, is provided. Two projecting portions 73 and 74 extending in the short direction of the scale plate 3 are provided on both sides of the movable spacer 72 in the measurement axis X direction, and the upper surface of the projecting portions 73 and 74 and the lower surface of the scale plate 3 are projected. Between them, elastic adhesives 75 and 76 such as a silicone adhesive are filled. Therefore, the scale plate 3 can move within the elastic range of the elastic adhesives 75 and 76 in the measurement axis X direction with respect to the support 4, but is defined by the movable spacer 72 in the gap direction. The movable support 72, the projections 73 and 74, and the elastic adhesives 75 and 76 constitute the elastic support portion 7. Similarly to this, the elastic support portion 8 includes a movable spacer 82 (screwed into the through hole 81), protrusions 83 and 84, and elastic adhesives 85 and 86. Note that the elastic adhesives 75, 76, 85, and 86 contract when they are fixed, and therefore, tensile stress is usually applied to the elastic adhesives 75, 76, 85, and 86. For this reason, the scale plate 3 is not lifted from the tip portions of the movable spacers 72 and 82 even by thermal expansion. As the silicone-based elastic adhesives 75, 76, 85, 86, for example, Shin-Etsu silicone KE-3475T, KE-441T, KE-45B (both Shin-Etsu Chemical Co., Ltd.) and the like can be used.

  The support 4 further has mounting holes 41 and 42 on both sides in the short direction on one end side in the longitudinal direction, and has a mounting hole 43 on one side in the short direction on the other end side in the longitudinal direction. It is fixed to the base 9 or the like of a device that requires displacement measurement through the holes 41 to 43. However, although the mounting hole 42 is for fixed mounting, the mounting hole 41 is formed at the tip of a parallel arm 44 extending in the longitudinal direction, so that the space between the support 4 and the base 9 can be reduced. The mounting hole 43 is formed at the tip of the parallel arm 45 extending in the short direction, so that the heat in the longitudinal direction between the support 4 and the base 9 is absorbed. Absorbs elastic deformation due to differential expansion.

  According to the displacement measuring apparatus configured as described above, the distance between one end of the scale plate 3 and the support 4 is defined by the fixed spacers 61 and 62, and the other end and intermediate portion of the scale plate 3. Since the distance between the support 4 and the support 4 is defined by the movable spacers 72 and 82, the scale plate 3 can move in the measurement axis X direction, but in the gap direction, the fixed adhesive 64 and the elastic adhesive 75, Regardless of adhesion by 76, 85, 86, it is constrained to a predetermined value. For this reason, the high mounting accuracy to the thickness direction of the scale plate 3 is implement | achieved, preventing the thermal distortion of the measurement axis X direction of the scale 1. FIG.

  In the above embodiment, the scale plate 3 is supported by the elastic support portion 8 not only at both ends but also at the middle portion, so that even if the scale 1 is long, the occurrence of errors in the gap direction due to bending is prevented. can do. Note that the movable support portion 8 may be provided not only at one location between both ends in the measurement axis X direction, but also at a plurality of locations as in the present embodiment.

  Needless to say, the present invention is not limited to the type of encoder, and can be applied to scales of other types of encoders such as a magnetic encoder, an electromagnetic induction encoder, and a capacitance encoder.

It is a perspective view showing a schematic structure of a displacement measuring device concerning one embodiment of the present invention. It is the figure seen from each direction of the scale which removed the reading head from the displacement measuring device. It is an expanded sectional view which expands and shows the part of A of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Scale, 2 ... Reading head, 3 ... Scale plate, 4 ... Support plate, 5 ... Scale, 6 ... Fixed support part, 7, 8 ... Elastic support part, 9 ... Base, 61 ... Fixed spacer, 64 ... Fixed adhesion Agent, 72, 82 ... movable spacer, 75, 76, 85, 86 ... elastic adhesive.

Claims (4)

A scale plate formed with a scale extending in the measurement axis direction, and a scale provided with a support that supports the scale plate;
A displacement measuring device comprising: a reading head that faces the scale and is relatively movable in the measurement axis direction with respect to the scale, and that reads a scale of the scale.
The scale plate has one end in the measurement axis direction supported by the support via a fixed support portion, and the other end in the measurement axis direction attached to the support via an elastic support portion. Supported,
The fixed support portion protrudes from the support body toward the scale plate, defines a distance between the support body and the scale plate, and the support body around the first spacer, With a fixed adhesive filled between the scale plate,
The elastic support portion protrudes from the support toward the scale plate, defines a distance between the support and the scale plate, and the support around the second spacer. A displacement measuring device comprising: an elastic adhesive filled between the scale plate.   The displacement measuring device according to claim 1, wherein the scale plate is supported by the support at one or a plurality of positions between both end portions in the measurement axis direction via the elastic support portion. The first spacer is a fixed spacer;
The displacement measuring device according to claim 1, wherein the second spacer is a movable spacer whose protrusion amount can be adjusted. The movable spacer is in point contact with the scale plate,
The support includes protrusions extending in a direction perpendicular to the measurement axis direction on both sides of the movable spacer in the measurement axis direction,
The displacement measuring apparatus according to claim 3, wherein the elastic adhesive is filled between the protrusions on both sides of the movable spacer and the scale plate.

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