JP2002081930A - Unit-type linear scale - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the linearity of scale accuracy from lowering even in the case that the difference between the coefficients of linear expansion of an aluminum frame and an object of fastening is large. SOLUTION: In this unit-type linear scale, an aluminum frame 10 extended in the direction of length measurement in which a main scale is housed is fastened to the object by fastening fixing blocks by screws each directly connected to both end parts in the direction of length measurement. A thermal expansion absorbing mechanism provided with both a reference member 18A with a reference face (A face) and a biasing member 18B is formed in the fixing block 18 on the right side of the end parts. The reference face (A face) is in parallel with the direction of length measurement and in contact with a bush 22 in which a screw 20 spirally inserted in the surface of the object at right angles is inserted for fastening the fixing blocks to the object, and the biasing member 18B biases the bush 22 to the side of the reference face by a pressing face (B face) opposed to the reference face and extended in the direction of length measurement.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a detection head for detecting a lengthwise movement amount of a frame housing a main scale from a relative movement amount of an index scale moving along the scale. The present invention relates to a unit-type linear scale formed integrally.

[0002]

2. Description of the Related Art As a device for detecting a linear displacement of an object (moving body) moving relatively, an elongated frame housing a main scale, and an index scale movable relatively to the frame. A unit-type linear scale in which a detection head accommodating a detection unit such as the above is integrally formed is generally used.

FIGS. 4A, 4B, and 4C show a plan view, a left side view, and a front view, respectively, of an example of such a unit-type linear scale fixed to one object. Things. As shown in this figure, the unit-type linear scale is a main scale (not shown).
Is integrally formed with an aluminum frame (frame body) 10 in which the detection unit (not shown) is accommodated, and the detection head 12 is arranged in the longitudinal direction of the aluminum frame 10. It can be moved along a certain measuring direction.

In this unit type linear scale, the aluminum frame 10 is screwed through a screw hole 14A at a fixing position of a fixing block 14 attached to both ends in the length measuring direction.
The detection head 12 is fixed to the other object (not shown) by screwing it to one object (the opposite surface in the figure) and the detection head 12 is fixed to the other object (not shown). The detection is performed based on the relative movement amount of the detection head 10 and the detection head 12.

As shown in FIG. 5 corresponding to FIG. 4, such a unit-type linear scale fixes the aluminum frame 10 to the object not only by the fixing blocks 14 at both ends in the length measuring direction. In some cases, the fixing position 16A of the fixing member 16 attached in the middle of the longitudinal direction (for example, the central portion which is the center position) is screwed and similarly fixed to the mating surface at three points.

[0006]

SUMMARY OF THE INVENTION According to the present invention, a frame body in which a main scale is accommodated and which extends in a length measuring direction is screwed to fixed blocks directly connected to both ends in the length measuring direction. In the unit-type linear scale to be fixed to, the fixed block on either one of the both ends has a degree of freedom only in the length measurement direction, and a thermal expansion absorption mechanism that absorbs the elongation of the frame is formed. This has solved the above-mentioned problem.

That is, in the present invention, the frame is fixed to the object by screwing the fixed blocks directly connected to both ends in the length measuring direction thereof, and the frame is fixed to one of the fixed blocks. Since the thermal expansion absorption mechanism that absorbs the elongation of the body is formed, even if the thermal expansion coefficients of the frame and the material of the object are significantly different, the elongation can be reliably absorbed, so that the main scale A decrease in the linearity of accuracy can be prevented, and as a result, measurement accuracy can be improved.

According to the present invention, a frame extending in the length measuring direction in which the main scale is accommodated is provided with a fixing block directly connected to both ends in the length measuring direction and a fixing block directly connected in the middle in the length direction. In a unit-type linear scale in which the member is screwed and fixed to the object, the fixed blocks at both ends have a degree of freedom only in the length measurement direction, and a thermal expansion absorption mechanism that absorbs the elongation of the frame body. The above-mentioned problem is similarly solved by being formed.

That is, in the present invention, the frame is fixed in an immovable state in the middle of the length measuring direction, and at both ends in the length measuring direction, the thermal expansion absorbing mechanism can absorb the elongation due to the temperature change. Similarly, deformation of the frame can be prevented.

[0010]

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

FIG. 1 is an enlarged view of an aluminum frame 10 provided in a unit-type linear scale according to a first embodiment of the present invention, in the vicinity of both ends in the length measurement direction as viewed from the same direction as that of FIG. It is shown. However, the other side (object)
Is not shown.

In this embodiment, the right end of the aluminum frame (frame body) 10 constituting the unit type linear scale in the length measurement direction is directly connected to a fixed block 14 similar to the conventional one by screws (not shown). The fixed block 14 is fixed to an object (not shown) by a screw via a fixed position (screw hole) 14A. Therefore, the movement of the aluminum frame 10 is restricted in all three directions, ie, the length measurement direction, the direction perpendicular to the mating surface perpendicular to the measuring surface, and the direction parallel to the mating surface. The part has a fixed end which is fixed in a completely immobile state.

On the other hand, the left end is similarly directly connected to the fixing block 18, but the fixing block 18 itself is formed with a thermal expansion absorbing mechanism, and is a free end. The screw is in a fixed position on the free end side. Hereinafter, this thermal expansion absorbing mechanism will be described in detail with reference to FIG.

FIG. 2A is an enlarged plan view of the fixing block 18, FIG. 2B is a longitudinal sectional view in the X direction passing through the axial center of the fixing screw 20, and FIG. In the direction perpendicular to the axial direction of the fixing screw 20, C- in FIG.
It is a cross-sectional view in the C position (hatching is omitted for easy understanding).

The fixing block 18 is fixed to the target object via a bush (screw member) 22 by the fixing screw 20 which is vertically screwed into the surface of the target object. A spring washer (spring member) 24 is interposed between the fixed block 18 and the flange portion 22A located at the upper end of the bush 22.
8 can be securely brought into close contact with the surface of the object by the urging force of the washer 24 without being completely fastened and fixed by the fixing screw 20, and is regulated in the Y direction.

As shown in FIG. 2C, the fixed block 18 has a reference member (surface A in the figure) which is in contact with the outer peripheral surface of the bush 22 and which is parallel to the length measuring direction. An urging member 18B that urges the bush 22 toward the reference surface of the reference member 18A by a pressing surface 18A and a pressing surface (a surface B in the drawing) that also faces the reference surface and extends in the length measurement direction.
Thus, a compression spring mechanism (thermal expansion absorption mechanism) having a degree of freedom of expansion in the length measurement direction is formed.

That is, in the fixing block 18, at least the urging member 18B can be formed of a material that generates an urging force, for example, a generally available metal such as aluminum, iron, and zinc. The maximum separation distance D between the reference surface (A surface) and the pressing surface (B surface) is formed smaller than the outer diameter φd of the bush 22 indicated by a two-dot chain line, and near the portion directly connected to the aluminum frame 10. The biasing member 18B is formed with a compression spring mechanism centered on the point O in the figure by reducing the thickness thereof, and the fixing block 1 is formed by the spring mechanism.
8 itself is regulated in the X direction in the figure and positioned.

The pressing surface (surface B) of the urging member 18B
Is formed as a curved surface in which the separation distance gradually decreases at the contact angles α and β in the length measurement direction from the position of the maximum separation distance D. Therefore, since the bush 22 is most stable at the position of the maximum separation distance D, when the bush 22 deviates from this position, a tension is applied to the aluminum frame 10 so as to return to the position.

According to the present embodiment described above, when the aluminum frame 10 tries to extend in the Z direction (length measuring direction) due to a temperature change in the measurement environment, the reference surface ( Since the slip occurs on the basis of the (A surface), the elongation can be absorbed. Also, at this time, since the bush 22 is compressed in the reference plane direction and positioned in the X direction by the compression spring mechanism of the fixed block 18, only the elongation of the aluminum frame 10 is absorbed, and thermal expansion occurs. The deformation of the aluminum frame 10 due to the above can be prevented.

The fixing block 18 is provided with a fixing screw 20.
As a result, the object is urged and fixed via the spring washer 24 so that the pressing force of the fixing block 18 against the object in the Y direction in the drawing and the frictional force in the X and Z directions in the drawing are: It can be prevented from being affected by the tightening of the fixing screw 20. Further, by forming the pressing surface of the biasing member 18B with a curved surface having a contact angle set by the angles α and β, the tightening force of the compression spring can be controlled to a position of the dimension D which is stable. To be able to
The degree of freedom in design can be improved.

Further, one end of both ends in the measurement direction is a fixed end,
Since the other side can be set as a free end, it is possible to set a reference point for elongation and a direction of elongation with respect to the aluminum frame 10, thereby improving the linearity of the accuracy of the main scale accommodated. It becomes possible.

FIG. 3 is a plan view, corresponding to FIG. 5, showing a unit-type linear scale according to a second embodiment of the present invention.

The present embodiment is a unit-type linear scale fixed at three points, and has an aluminum frame 1 at the center (in the middle) in the length measuring direction.
Numeral 0 is fixed in a completely immobile state by a fixing member 16, and both ends in the length measurement direction are fixed by a fixing block 18 in which the compression spring mechanism is formed.

According to the present embodiment, the center of the aluminum frame 10 can be a fixed end, and both ends can be free ends. Since it is possible to cause the elongation of the aluminum frame 10, it is possible to prevent a decrease in the linearity of the accuracy of the housed main scale, thereby improving the measurement accuracy.

Although the present invention has been specifically described above, the present invention is not limited to the above-described embodiment, and can be variously modified without departing from the gist thereof.

For example, the specific configuration of the thermal expansion absorbing mechanism formed on the fixed block is not limited to the one shown in the above embodiment. Specifically, the urging member 18B
The screw member biased to the reference surface of the reference member 18A is not limited to the bush described in the above embodiment, and may be a screw itself. The pressing surface of the biasing member 18B may be a flat surface instead of a curved surface.

In the second embodiment, the aluminum frame 10
Is fixed at the center, but there is no particular limitation as long as it is in the length measurement direction.

[0028]

As described above, according to the present invention,
Even if the difference in linear expansion coefficient between the frame body in which the main scale is housed and the object to which the frame body is fixed is large, it is possible to prevent the linearity of the accuracy of the main scale from being reduced,
As a result, measurement accuracy can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic front view showing an aluminum frame included in a unit-type linear scale according to a first embodiment of the present invention.

FIG. 2 is an enlarged plan view, a longitudinal sectional view, and a transverse sectional view showing a fixed block having a thermal expansion absorbing mechanism.

FIG. 3 is a schematic front view showing an aluminum frame included in a unit-type linear scale according to a second embodiment of the present invention.

FIG. 4 is a plan view, a left side view, and a front view showing the appearance of a conventional unit-type linear scale.

FIG. 5 is a plan view, a left side view, and a front view showing the appearance of another conventional unit-type linear scale.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Aluminum frame 12 ... Detection head 14 ... Fixed block 16 ... Fixed member 18 ... Fixed block 18A ... Reference member 18B ... Biasing member A surface ... Reference surface B surface ... Pressing surface 20 ... Fixing screw 22 ... Bush 24 ... Spring Washer (spring member)

Claims (7)

[Claims] 1. A unit-type linear scale for fixing a frame body in which a main scale is accommodated and extending in a length measuring direction to a target object by screwing fixing blocks directly connected to both ends in the length measuring direction. A fixed block on either one of the two end portions, a unit having a degree of freedom only in the length-measuring direction, and a thermal expansion absorbing mechanism for absorbing elongation of the frame body; Linear scale. 2. A frame body, in which a main scale is accommodated, extending in the length measuring direction is fixed to a fixing block directly connected to both ends in the length measuring direction, and a fixing member directly connected in the middle in the side length direction. Then, in the unit-type linear scale to be fixed to the object, the fixed blocks at both ends are provided with a thermal expansion absorbing mechanism that has a degree of freedom only in the length measurement direction and absorbs the elongation of the frame body. A unit type linear scale characterized by the following. 3. The thermal expansion absorbing mechanism according to claim 1, wherein said thermal expansion absorbing mechanism abuts on an outer peripheral surface of a screw member which is vertically screwed into a surface of said object in order to fix said fixing block to said object. A reference member having a stable reference surface, and an urging member that urges the screw member toward the reference surface side by a pressing surface that faces the reference surface and extends in the length measurement direction. The unit-type linear scale according to claim 1. 4. The unit-type linear scale according to claim 3, wherein the fixed block is fixed by the screw member via a spring member for urging the block toward the object. 5. The apparatus according to claim 3, wherein a maximum separation distance between a reference surface of said reference member and a pressing surface of said urging member is formed smaller than an outer diameter of said screw member. Unit type linear scale. 6. The unit-type linear scale according to claim 3, wherein the pressing surface of the urging member is formed so as to gradually decrease in the measurement direction from the position of the maximum separation distance. . 7. A thickness of a portion of the urging member near a portion directly connected to the frame is formed to be thin so that the urging member functions as a compression spring for the reference member. 3. The unit-type linear scale according to 3.