JPH04258711A - Scale device - Google Patents

Abstract

PURPOSE:To reduce the measurement error and simplify the constitution of a scale device by reducing the mechanical extension or contraction of a scale which is caused by the mechanical extension or contraction due to the thermal expansion or thermal contraction of a scale holding member, in the scale device in which the scale holding member is installed on a base board having the standard surface of the machine tool and a scale is fixed on the scale holding member. CONSTITUTION:A scale holding member 31 is installed on the base board 1 of the machine tool, and when a scale 5 is installed on a scale holding member 31, only a part of the measurement effective length part 5A of the scale 5 is fixed by the scale holding member 31. Accordingly, even if the scale holding member 31 is mechanically extended or contracted by the thermal expansion or contraction, the mechanical extension or contraction of the scale 5 are suppressed to the min. value.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scale device suitable for use as a positioning scale for machine tools, for example.

0002

2. Description of the Related Art Generally, a scale with graduations recorded is attached to the reference surface of a machine tool, etc., and a detection head is attached to the tool stand at a position opposite to the scale. As the tool stand moves, the scale recorded on the scale is read by the detection head, so that the amount of relative movement of the tool stand (tool) can be determined. There are the following four conventional techniques for attaching a scale to the reference surface side (hereinafter referred to as the base) of a machine tool. The first technique is shown in Figure 10.
As shown in the figure, the scale holding member 2 and the brackets 3 and 4 are fixed to the base 1, and tension is applied in the length direction of the scale 5 by the brackets 3 and 4 and the tension adjustment mechanism 15 to move the scale 5 to the base. This is a technology that fixes it to the stand 1. In this case, the scale 5 has an effective length portion 5A whose measurement accuracy is guaranteed (hereinafter referred to as measurement effective length portion as necessary) and an invalid length portion 5B whose measurement accuracy is not guaranteed. The portion 5B is fixed. On the other hand, the effective length 5
A is only placed on the upper surface 2A of the scale holding member 2, but is not fixed. FIG. 11 shows a partial cross section taken along the line AA in FIG. 10. As shown in FIG. 11, the position of the end portion of the scale 5 in the width direction is regulated by the scale holding member 2. As shown in FIG. In this first technique, mechanical strain on scale 5 (
The expansion/contraction) depends on mechanical strain (expansion/contraction) due to thermal expansion/contraction of the base 1. Further, the accuracy of the scale 5 is ensured by adjusting the tension by the tension adjustment mechanism 5 to adjust the elongation of the scale 5. The second technique, as shown in FIG.
0 is fixed, and the scale 5 is attached and fixed to the scale holding member 10. In this second technique, the mechanical expansion and contraction of the scale 5 depends on the mechanical expansion and contraction of the scale holding member 10 due to thermal expansion and contraction. Therefore, it is necessary to match the thermal characteristics of the scale holding member 10 with those of the base 1. This is because there is a risk that the scale 5 will be distorted due to mechanical distortion of the scale holding member 10 (distortion that deforms the outer shape) and a measurement error may occur. Therefore, the scale holding member 10 is generally made of iron, which is the same material as the base 1, or martensitic stainless steel. This is to match the coefficients of thermal expansion. The third technique is a technique in which only one invalid length portion 5B of the scale 5 is fixed to the base 1 using a bracket 4, as shown in FIG. In this example, when the scale 5 expands or contracts due to thermal expansion or contraction, the scale 5 can slide on the upper surface 2A of the scale holding member 2 in the length direction. Moreover, as shown in FIG. 14, the fourth technique directly connects one invalid length portion 5B of the scale 5
It is fixed by a bracket 12 in contact with the base 1. According to these third and fourth techniques, the thermal expansion and contraction of the scale 5 depends on the thermal expansion and contraction of the scale 5 itself.

0003

However, the four techniques of the conventional scale apparatus described above have the following disadvantages. In the first technique (see FIGS. 10 and 11), the scale holding member 2 does not apply mechanical strain to the scale 5, so a relatively lightweight material such as plastic can be used as the material. . On the other hand, there are problems in that the configuration is complicated and it takes a long time to obtain the accuracy of the scale 5. In the second technique (see Fig. 12), it is necessary to use a material with the same thermal characteristics as the base 1 for the scale holding member 10, such as iron or stainless steel, which has a relatively large specific gravity. There is a problem in that the machine tool (not shown) having the base 1 is deformed due to the weight of the member 10, and the accuracy of the machine tool itself is deteriorated. Furthermore, in the third and fourth techniques (see FIGS. 13 and 14), only one end of the scale 5 is fixed, so there is an advantage that the thermal expansion and contraction of the scale 5 is determined by the scale 5 itself. . On the other hand, since only one end of the invalid length portion 5B is fixed, the scale 5 expands and contracts with respect to that fixed point, so there is a slight difference in the coefficient of thermal expansion between the scale 5 and the base 1. Also, since the positional deviation between the unfixed effective length portion 5A and the corresponding base 1 becomes relatively large, the reading accuracy by the detection head (not shown) decreases, and eventually,
This has the disadvantage of causing a decrease in the machining accuracy of the machine tool. The reason for this is that the effective length 5A of the scale 5 is generally located at the center of the X, Y, and Z axes of the machine tool (for example, in the longitudinal direction of the scale attached to the X axis on the movable table in a vertical milling machine). This is because the center part is installed in line with the axis of the spindle head of the vertical milling machine.

The present invention has been made in view of these problems, and has a relatively simple configuration, and can relatively prevent a decrease in measurement accuracy caused by thermal distortion of the scale. The purpose is to provide a scale device.

[0005]

[Means for Solving the Problems] The scale device according to the invention as set forth in claim 1 has, for example, as shown in FIG. The scale 5 includes a scale 5 and a scale holding member 31 on which the scale 5 is placed and held, and only one part of the measurement effective length 5A of the scale 5 is fixed by the scale holding member 31. In the scale device according to the second aspect of the invention, for example, as shown in FIG. 1, one fixed location is approximately the center portion 31M of the scale holding member 31. The scale device according to the third aspect of the invention includes, for example, a scale 39 and at least three scale holding members 44 to 46 on which the scale 39 is placed and held, as shown in FIG. The holding members 44 to 46 are arranged in a line, and the scale 39 is fixed to the scale holding member 45 fixed at the reference position 21 of the base 1 among the scale holding members 44 to 46.
It was designed to be fixed only to

[0006]

[Function] According to the invention as claimed in claim 1, since only one point of the effective measurement length portion 5A of the scale is fixed by the scale holding member 31, the structure is simplified and the scale device has less measurement error. is obtained. According to the invention as claimed in claim 2, since only one point of the effective measurement length portion 5A of the scale is fixed at the approximately central portion 31M of the scale holding member 31, the configuration is simplified and the measurement error is further reduced. Less scale equipment is obtained. According to the invention set forth in claim 3, at least three scale holding members 44-
46, and the scale 39 is fixed only by the central scale holding member 45 among the scale holding members 44 to 46, so that the scale 39 can be held relatively stably and there is no measurement error. It is possible to obtain a scale device with less.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the scale apparatus of the present invention will be described below with reference to the drawings. In the following drawings, the same reference numerals are given to the parts corresponding to those shown in FIGS. 10 to 14 described above.

A. First Embodiment FIG. 2 shows a scale device in which a scale 5 is attached to a scale holding member 31, and FIG. 1 shows a scale device configured as shown in FIG. 2 attached to a base 1 having a reference surface of a machine tool. A schematic cross-sectional configuration of the state is shown. In FIG. 1, 21 is a reference position of the base 1 in the X-axis direction, and the base 1 moves in the X-axis direction with this reference position 21 as the center position (origin of the X-axis). Therefore, scales are formed on the scale 5 in the width direction perpendicular to the X-axis. Note that as the scale 5, a magnetic scale, an optical scale, a capacitive scale, etc. can be adopted. FIG. 3 is a sectional view taken along the line A-A along the reference position 21. As understood from FIGS. 1 and 3, in this example, scale 5
The X-axis of the scale holding member 31 is fixed by the adhesive 22 at approximately the center position 5M in the X-axis direction of the effective length portion 5A (hereinafter simply referred to as effective length portion or measurement effective length portion) where measurement accuracy is guaranteed. The scale holding member 31 is fixed to the base 1 by an adhesive 23 at a substantially central position 31N in the X-axis direction.

In this case, according to the above embodiment, the measurement accuracy of the scale 5 is not guaranteed at the invalid length section 5B, but at one location in the effective measurement length section 5A (in this example, the center position 5M). only at approximately center position 3 of scale holding member 31
Since it is fixed at 1M, there is no need for a bracket as described in the prior art, and the configuration is relatively simple, and at the same time, the thermal expansion standard can be set at the measurement effective length section 5A. . In addition, since the approximate center position 31M of the scale holding member 31 is aligned with the reference position 21 of the base 1, and only the center position 31N is fixed to the base 1, the thermal expansion coefficients of the scale 5 and the base 1 are matched. By doing so, the coefficient of thermal expansion of the material of the scale holding member 31 becomes almost irrelevant. For this reason, the scale holding member 31
For example, the scale holding member 31 can be made of a relatively lightweight material such as aluminum or plastic.
It is possible to suppress the occurrence of mechanical distortion of the base 1 due to the weight of the scale device, and thus a scale device with less measurement error can be obtained. In addition, in the example of FIG. 1, the scale 5 is the adhesive material 22.
Although the scale holding member 31 is fixed to the scale holding member 31, the fixing method is not limited to the method using an adhesive as described above. For example, as shown in FIG. 4, it may be fixed using a caulking portion 26, or as shown in FIG. 5, it may be fixed using a rivet 27. When fixing by caulking part 26, as shown in FIG. The scale 5 is placed on the pedestal portion 33. Then, the caulked portion 26 may be formed by deforming one location of the convex portion 28 facing the side surface of the measurement effective length portion 5A of the scale 5. On the other hand, when fixing with rivets 27, grooves 30 and pedestals 34 are formed in the length direction on both sides of the scale holding member 29 in the width direction, and the scale 5 is placed on the pedestals 34 between the grooves 30. . Then, a rivet 27 may be driven into one location of the groove portion 30 facing the side surface of the measurement effective length portion 5A of the scale 5 to fix it. Convex part 2
8 and the groove 30 can be easily formed by extrusion when aluminum is used as the material for the scale holding members 27 and 29. Note that the material for the scale holding members 27 and 29 is not limited to aluminum.
A plastic material may be used, and when a plastic material is used, the convex portion 28 and the groove portion 30 can be easily formed by molding. When a plastic material is used, the caulked portion 26 can be formed by deformation due to heat or the like. In addition, in FIGS. 4 and 5, a magnetic scale is used as the scale 5. When this magnetic scale is used, the iron-based scale 5 or the scale 5 made of a plastic magnet is replaced by a martensitic stainless steel scale. This thin plate 36 is fixed to the scale holding members 27 and 29 by the caulking portion 26 or the rivet 27.

B. Second Embodiment FIGS. 6 to 8 are diagrams showing the configuration of a second embodiment of the present invention. In this example, in order to place a relatively long scale 39, five scale holding members 43 (53) to 47 (57) are arranged in a line in the length direction of the long scale 39 (FIG.
), and place these five scale holding members 43 (
53) to 47 (57) are each fixed to the base 1. Note that the number of scale holding members is not limited to 5, but may be 3,
At least 3 pieces, such as 4 pieces, 6 pieces, 7 pieces, etc., are sufficient. In addition, these five scale holding members 43 (53) to 4
7 (57) can be easily prepared by cutting one relatively long scale holding member in the width direction at intervals described below. 5 scale holding members 43 (53)
A gap 48 is provided between the opposing surfaces of 47 (57). Scale holding member 43 fixed to base 1
(53) to 47 (57) even if thermal strain (mechanical expansion and contraction) occurs, the scale holding members 43 (53) to 47 (57)
7) This is to reduce distortion compared to the case where only one wire is used. The length of the gap 48 does not need to be constant.

[0011] Also in this second embodiment, the length is increased by the caulking portion 50 (see Fig. 6) provided only at one location of the scale holding member 45 fixed at the reference position 21 (see Fig. 8) of the base 1. A large scale 39 is fixed. Further, the elongated scale 39 is fixed by driving a rivet 51 (see FIG. 7) only at one location of the central scale holding member 55 fixed to the reference position 21 of the base 1. Therefore, the long scale 39 is attached to scale holding members 43 (53), 44 (54), 46 other than the fixed central scale holding member 45 (55).
(56), 47 (57). In other words, the other scale holding members 43 (53), 44 (
54), 46 (56), and 47 (57) only function as guide members. In addition, in FIGS. 6 to 8, a magnetic scale is used as the scale 39,
When this magnetic scale is adopted, the iron-based scale 39 or the scale 39 made of a plastic magnet will
Thin plate 5 of ferromagnetic material, which is martensitic stainless steel
2, and this thin plate 52 is fixed to the scale holding member 45 (55) by the caulking part 50 or the rivet 51.
Fixed. In this case, as shown in FIG. 8, the length L3 of the scale holding member 45 (55) is selected to be a relatively short length that allows thermal distortion (generally, the length L3 is Scale holding members 43 (53), 44 (5
4), 46 (56), 47 (57) lengths L1, L2,
(The length will be shorter than either L4 or L5). With this configuration, measurement errors in this scale device can be reduced by selecting only the material of the central scale holding member 45 (55) that has a coefficient of thermal expansion substantially the same as that of the material of the base 1. be able to. Also in this second embodiment, the mounting structure for the long scale 39 is relatively simple.

FIG. 9 shows that in the first and second embodiments described above, for example, an overhang portion 59 is provided above both sides in the width direction of the scale holding member 27 shown in FIG. 4 to form a scale holding member 62. A thin plate 60 of austenitic non-magnetic material is attached between the overhang portion 59 and the surface 49 of the scale 5. This protects the scale 5 and improves the durability of the scale device. Furthermore, the scale 5 is reliably held in portions other than the caulked portion 26 (see FIG. 4).

It should be noted that the present invention is not limited to the above-described embodiments, and it goes without saying that various configurations can be adopted without departing from the gist of the present invention.

[0014]

As explained above, according to the scale device of the invention as set forth in claim 1, only one part of the effective measurement length of the scale is fixed by the scale holding member, so the configuration is simplified. Moreover, the effect of reducing measurement errors due to thermal factors etc. can be obtained. Furthermore, since the scale and the scale holding member are not fixed on their entire surface, there is an advantage that the range of materials for the scale holding member can be selected is relatively wide. According to the scale device of the invention as set forth in claim 2, since only one part of the effective measurement length of the scale is fixed at approximately the center of the scale holding member, the configuration is simplified and furthermore, thermal factors etc. This has the effect of further reducing measurement errors due to Furthermore, since the scale and the scale holding member are not fixed on their entire surface, there is an advantage that the range of materials for the scale holding member can be selected is relatively wide. According to the invention scale device according to claim 3, at least 3
The scale is held by two scale holding members, and the scale is fixed only by the scale holding member fixed at the reference position of the base among the scale holding members, so the scale can be held relatively stably. Moreover, the effect of reducing measurement errors due to thermal factors etc. can be obtained. In addition, since the scale is fixed only by the scale holding member fixed at the reference position of the base and is not placed on other scale holding members, the range of materials to be selected for other scale holding members is relatively wide. You can also get this advantage.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional diagram showing the configuration of an embodiment of a scale device according to the present invention.

FIG. 2 is a perspective view showing the external configuration of the scale device shown in FIG. 1;

FIG. 3 is a sectional view taken along line A-A of the scale device shown in FIG. 1;

FIG. 4 is a perspective view showing the configuration of another embodiment of the scale device according to the present invention.

FIG. 5 is a perspective view showing the configuration of still another embodiment of the scale device according to the present invention.

FIG. 6 is a perspective view showing the configuration of still another embodiment of the scale device according to the present invention.

FIG. 7 is a perspective view showing the configuration of still another embodiment of the scale device according to the present invention.

FIG. 8 is a longitudinal cross-sectional view of FIGS. 6 and 7;

FIG. 9 is a sectional view showing the configuration of still another embodiment of the scale device according to the present invention.

FIG. 10 is a sectional view showing the configuration of a scale device according to a conventional technique.

11 is a sectional view taken along line AA of the scale device shown in FIG. 10. FIG.

FIG. 12 is a sectional view showing the configuration of a scale device according to another conventional technique.

FIG. 13 is a sectional view showing the configuration of a scale device according to still another conventional technique.

FIG. 14 is a sectional view showing the configuration of a scale device according to still another conventional technique.

[Explanation of symbols]

5 Scale 5A Measurement effective length portion 31 Scale holding members 34, 36 Scale holding members 45, 55 Scale holding member 39 fixed at the reference position of the base Long scale

Claims (3)

[Claims] 1. A scale having an effective measurement length formed at a position excluding the end in the direction in which the scale is formed, and a scale holding member on which the scale is placed and held, the effective measurement length of the scale. A scale device characterized in that only one portion of the scale is fixed using the scale holding member. 2. The scale device according to claim 1, wherein the one fixed location is approximately at the center of the scale holding member. 3. A scale, and at least three scale holding members for mounting and holding the scale, the at least three scale holding members being arranged in a line,
A scale apparatus characterized in that the scale is fixed only by a scale holding member fixed at a reference position of a base among the scale holding members.