Position measuring device

Abstract

To provide an induction type position measuring device for reducing a measurement error.SOLUTION: The position measuring device 100 includes a scale member 130 having a first surface extending in a first direction, a plurality of ring-shaped scale coils 140 arranged side by side in the first direction on the first surface, a slider member 150 having a second surface facing the first surface and relatively movable in the first direction with respect to the scale member 130, excitation coils 160 and 170 provided on the second surface to generate an oscillating magnetic field to cause the scale coils 140 to generate an induced current, a detection coil 180 provided on the second surface to receive an induced magnetic field generated by the induced current and generate a detection voltage, and a detection coil 180 held by the slider member 150 and detecting the induced current.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a position measuring device. [Background technology]

[0002] For example, Patent Document 1 discloses a combination scale having multiple single scales arranged in a row and a common wire, with all the single scale coils connected to the common wire, so that the coils of all the single scales are arranged in parallel. Furthermore, for example, Patent Document 2 discloses an induction linear encoder or rotary encoder having a sensor and a scale arranged so as to be movable relative to each other. The sensor is provided with a drive wire through which an AC current flows and a detection wire that is perpendicular to the drive wire. The scale is provided with a periodic array of closed conductor circuits in the direction of relative movement. The closed conductor circuits generate an induced current due to a first fluctuating magnetic field generated by a drive coil, which in turn generates a second fluctuating magnetic field. The second fluctuating magnetic field causes an induced current to flow in the detection wire of the sensor, which becomes a detection output current. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-133238 [Patent Document 2] Japanese Patent Application Publication No. 11-223505 Summary of the Invention [Problem to be solved by the invention]

[0004] In the case of the combination scale described in Patent Document 1, wiring is required to connect the coils of the individual scales. In contrast, in the case of the induction type encoder described in Patent Document 2, wiring on the scale side is not required. However, in an induction encoder, when multiple individual scales are arranged to extend the scale length, as in the combined scale described in Patent Document 1, an increase in measurement error occurs mainly at the connection points between the individual scales. On the other hand, configurations that avoid an increase in error at the connection points often result in a large overall measurement error.

[0005] Therefore, an object of the present disclosure is to reduce measurement errors in an induction-type position measuring device. [Means for solving the problem]

[0006] One aspect of a position measuring device according to the present disclosure comprises a scale member having a first surface extending in a first direction, a plurality of scale coils, each having an annular shape, arranged in a row in the first direction on the first surface, a slider member having a second surface facing the first surface and movable relative to the scale member in the first direction, an excitation coil provided on the second surface and generating a fluctuating magnetic field to induce an induced current in the scale coil, and a detection coil held by the slider member and having: a first location that receives an induced magnetic field associated with the induced current and generates a detection voltage; a second location that has one end connected to the first location and an opposite end side relative to the one end extending in a direction away from the first surface; and a third location that is connected to the other end side of the second location and extends in a direction along the first surface, the detection coil being held by the slider member and detecting the induced magnetic field. [Effects of the Invention]

[0007] According to the present disclosure, measurement errors are reduced in an induction-type position measuring device. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing an example of installation of a position measurement device. [Figure 2] FIG. 2 is an external view of an embodiment of the position measuring device. [Figure 3] FIG. 3 is a perspective view showing the internal structure of an embodiment of the position measuring device. [Figure 4]FIG. 4 is a perspective view showing the internal structure of an embodiment of the position measuring device. [Figure 5] FIG. 5 is a view showing the underside of the slider member. [Figure 6] FIG. 6 is a perspective view showing the positional relationship of the coils. [Figure 7] FIG. 7 is a plan view showing the positional relationship of each coil. [Figure 8] FIG. 8 is a perspective view showing a first modified example of the position measuring device. [Figure 9] FIG. 9 is a perspective view showing a first modified example of the position measuring device. [Figure 10] FIG. 10 is a perspective view showing a second modified example of the position measuring device. [Figure 11] FIG. 11 is a perspective view showing a second modified example of the position measuring device. [Figure 12] FIG. 12 is a perspective view showing a third modified example of the position measuring device. [Figure 13] FIG. 13 is a perspective view showing a third modified example of the position measuring device. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the position measuring device of the present disclosure will be described in detail with reference to the accompanying drawings. However, to avoid unnecessary redundancy in the following description and to facilitate understanding by those skilled in the art, more detailed description than necessary may be omitted. For example, detailed description of already well-known matters or redundant description of substantially identical configurations may be omitted. Furthermore, elements shown in earlier-described figures may be appropriately referenced in the description of later figures.

[0010] <Structure of position measuring device> FIG. 1 is a diagram showing an example of installation of a position measurement device. As an example, the position measuring device 100 is installed in a machine tool 200. The machine tool 200 is equipped with a table 210 that moves relative to a bench 220, and is a machine that processes a workpiece placed on the table 210. The position measuring device 100 is used, for example, to measure the position of the table 210 relative to the bench 220.

[0011] The position measuring device 100 includes a scale 110 and a slider 120. Unless otherwise clearly indicated by the context, the term "include" in this specification means to include in some form, whether as an independent object or as part of an object. In contrast, the term "have" in this specification generally means to include as part of an object.

[0012] The scale 110 is fixed to a bench 220, and the slider 120 is fixed to a table 210 via a jig 211. The slider 120 is held by the jig 211 at a predetermined distance, for example, 1 mm or less, from the scale 110. When the table 210 moves relative to the bench 220, the slider 120 moves along the scale 110 while maintaining the predetermined distance from the scale 110. The amount of movement of the table 210 relative to the bench 220 can be large, for example, 1 m to 3 m, and the position measuring device 100 is required to be able to measure such large amounts of movement.

[0013] FIG. 2 is an external view of an embodiment of the position measurement device 100. As shown in FIG. In order to measure large amounts of movement, the position measuring device 100 may have multiple scales 110 connected together. In the position measuring device 100, the cable 121 used for inputting and outputting electrical signals for measurement is connected only to the slider 120, and no wiring is required on the scale 110 side.

[0014] 3 and 4 are diagrams showing the internal structure of one embodiment of the position measuring device 100. Fig. 3 shows the internal structure with protective covers and the like provided on the scale 110 and slider 120 removed, and Fig. 4 shows some of the elements of the slider 120 in a see-through manner. Figs. 3 and 4 also show XYZ coordinate axes as directional references for explanation. The X direction is the longitudinal direction of the scale 110, the Y direction is the width direction of the scale 110, and the Z direction is the height direction (thickness direction) of the scale 110.

[0015] The scale 110 includes a scale member 130 and a scale coil 140. The slider 120 includes a slider member 150, excitation coils 160 and 170, and a detection coil 180. The scale member 130 is a member extending in, for example, the X direction, and has an upper surface 131 extending in the X direction. The upper surface 131 faces the +Z direction and faces the slider 120. The upper surface 131 is an example of a first surface in the present disclosure, and the X direction is an example of a first direction in the present disclosure. The scale member 130 is an iron material whose main raw material is, for example, Fe. Note that in this specification, "main raw material" means a raw material component that accounts for more than 50% by mass.

[0016] As shown in FIG. 4, a plurality of scales 110 are connected by joints 111, and gaps are generated at the joints 111 between the scale members 130. A plurality of scale coils 140 are periodically arranged in the X direction on the upper surface 131 of the scale member 130. Each scale coil 140 is a ring-shaped coil that is long in the Y direction and is formed, for example, by a conductor pattern. The scale member 130 and the scale coils 140 are insulated from each other by an insulating film or the like (not shown).

[0017] The slider member 150 has, for example, a rectangular parallelepiped shape and has an upper surface 152 facing the +Z direction and a lower surface 153 facing the -Z direction. The lower surface 153 corresponds to an example of a second surface in the present disclosure, and faces the upper surface 131 of the scale member 130. The slider member 150 is movable relative to the scale member 130 in the X direction by movement of the slider 120. The slider member 150 has a through-hole 151 that extends from an upper surface 152 to a lower surface 153. The slider member 150 is a metal block made primarily of, for example, Fe, and may be a metal block coated with an insulating film (not shown). In other words, the slider member 150 comprises a metal block. The slider member 150 holds excitation coils 160, 170 and a detection coil 180.

[0018] The excitation coils 160, 170 are provided on the lower surface 153 of the slider member 150 and are held in positions facing the scale coil 140. As will be described later, the excitation coils 160, 170 generate a varying magnetic field to induce a current in the scale coil 140. The detection coil 180 has a first location 181 located on the lower surface 153 side of the slider member 150, a second location 182 passing through the through hole 151, and a third location extending on the upper surface 152 side of the slider member 150. The detection coil 180 is held by the slider member 150, and detects an induced magnetic field generated by the scale coil 140 in association with an induced current, as will be described later.

[0019] The excitation coils 160, 170 and the detection coil 180 are insulated from the slider member 150 by an insulating film or the like (not shown). Here, the structure for attaching the detection coil 180 to the slider member 150 will be described with reference to FIG.

[0020] 5 is a diagram showing the lower surface 153 side of the slider member 150. For ease of explanation, the excitation coil is omitted from the illustration in FIG. For example, the first location 181 side and the second location 182 side of the detection coil 180 are produced separately and then connected to each other to be attached to the slider member 150. That is, the second location 182 side of the detection coil 180 is attached to the slider member 150 from the top surface 152 side, or is formed directly on the outer surface of the slider member 150.

[0021] On the other hand, first point 181 of detection coil 180 is formed separately from slider member 150, and is connected to second point 182 from the lower surface 153 side by, for example, a connector. In this way, detection coil 180 is attached to slider member 150. The structure in which the first portion 181 and the second portion 182 are separate makes it easier to create the detection coil 180 held by the slider member 150 than when the first portion 181 and the second portion 182 are integrated. The procedure for attaching detection coil 180 to slider member 150 is not limited to the above. For example, first portion 181 and second portion 182, which are formed separately, may be connected to each other and then attached to slider member 150, for example, from the lower surface 153 side, and then third portion 183 may be attached to slider member 150, for example, from the upper surface 152 side.

[0022] <Measurement principle> Figures 6 and 7 are diagrams showing the positional relationship of each coil. Figure 6 shows a perspective view, and Figure 7 shows a plan view seen from above in the Z direction. For ease of explanation, Figure 7 shows one excitation coil 170 as a representative of the two excitation coils 160, 170.

[0023] The excitation coils 160, 170 have excitation sections 162, 172 that generate a varying magnetic field for the scale coil 140 when a current of an excitation signal flows, and wiring sections 161, 171 that send the excitation signal to the excitation sections 162, 172.

[0024] 7, the excitation section 172 of the excitation coil 170 has a periodic structure that follows the periodic arrangement of the scale coils 140, and generates a magnetic field with a spatial period that is the same as the period of the arrangement of the scale coils 140, for example. The spatial period of the magnetic field generated by the excitation coil 170 may be an integer multiple of the period of the arrangement of the scale coils 140, for example. The varying magnetic field generated by the excitation unit 172 generates an induced electromotive force and an induced current in the scale coils 140. As a result of the induced current flowing through the scale coils 140, an induced magnetic field is generated laterally in the Y direction relative to the arrangement of the scale coils 140.

[0025] A first point 181 of the detection coil 180 is positioned so that its end overlaps the arrangement of the scale coils 140 in the Y direction, and generates a detection voltage when it receives an induced magnetic field caused by an induced current generated in the scale coil 140. The detection voltage generated at the first point 181 is output from the detection coil 180 as a detection signal. Movement of the slider 120 relative to the scale 110 changes the phase between the excitation section 172 of the excitation coil 170 and the scale coil 140. The phase change changes the magnetic coupling between the excitation section 172 and the scale coil 140, and the strength of the induced current and the strength of the detection signal also change.

[0026] That is, when the phases of the excitation unit 172 and the scale coil 140 are the same, the intensity of the detection signal is maximum, and when the phases of the excitation unit 172 and the scale coil 140 are out of phase by half a period, the intensity of the detection signal is minimum. Therefore, the position measuring device 100 can measure the position in units of the arrangement period of the scale coil 140 by counting the periodic intensity changes of the detection signal.

[0027] Furthermore, the position measuring device 100 not only measures the position by counting the signal changes, but also measures the position using the intensity changes of the detection signal within one period of the periodic arrangement of the scale coils 140, thereby achieving high position accuracy. However, if noise is picked up at a location other than the first location 181 of the detection coil 180 or at a portion of the first location 181 that extends away from the scale coil 140, a disturbance known as an interpolation error occurs in the intensity changes of the detection signal, resulting in a position measurement error. In particular, it is desirable to suppress measurement errors caused by large noise generated by gaps in the scale members 130 at the joints 111 between the scales 110.

[0028] <Error suppression structure> 4, the detection coil 180 has a first location 181, a second location 182, and a third location 183, thereby reducing noise picked up by locations other than the first location 181 and suppressing errors. That is, the second location 182 is less likely to pick up noise because one end is connected to the first location 181 and the other end extends in the Z direction away from the top surface 131 of the scale member 130. Furthermore, the third location 183 is less likely to pick up noise because it is connected to the other end of the second location 182 and extends in a direction along the top surface 131 of the scale member 130 on the side of the top surface 152 away from the scale coil 140 in the Z direction.

[0029] Furthermore, as shown in FIG. 4, the slider member 150 is positioned between the first location 181 and the third location 183 of the detection coil 180, so that the third location 183 is held at a position away from the first location 181 and the scale coil 140 by the slider member 150, making it less susceptible to noise pickup. Furthermore, because slider member 150 includes a metal lump, noise is blocked by the metal lump, reducing noise picked up by third point 183. In particular, because the metal lump of slider member 150 is made primarily of Fe, the reduction in noise is remarkable.

[0030] Furthermore, since the slider member 150 has a through hole 151 through which the second point 182 of the detection coil 180 passes, the second point 182 can connect the first point 181 and the third point 183 over a shorter distance than if it passed through the side of the slider member 150, and is less likely to pick up noise.

[0031] 6, detection coil 180 has, as second locations 182, one-end-side second location 182a connected to one end side 181a of first location 181 and another-end-side second location 182b connected to the other end side 181b of first location 181. One-end-side second location 182a and another-end-side second location 182b pass through a common through-hole 151, as shown in FIG. 4. Therefore, the one-end-side second location 182a and the another-end-side second location 182b are close to each other, and noise picked up by second location 182 is further suppressed.

[0032] 7, in the X direction in which the scale coils 140 are arranged, the dimension W1 of the first point 181 of the detection coil 180 is smaller than the dimension W2 of the excitation section 172 of the excitation coil 170. Therefore, the first point 181 is less likely to pick up noise generated at the end of the excitation section 172 in the X direction, thereby suppressing errors.

[0033] 6, one end side 181a and the other end side 181b of the first point 181 extend from a point connected to the second point 182 to opposite sides along the X direction in which the scale coils 140 are arranged. Therefore, the first point 181 can obtain a dimension W1 sufficient to generate a detection signal, improving the signal-to-noise ratio (S / N) and reducing errors.

[0034] As described above, in this embodiment, a number of structural improvements are made to suppress measurement errors caused by interpolation errors. Furthermore, as shown in Figures 4, 6 and 7, the detection coil 180 has first locations 181 on both sides of the arrangement of multiple scale coils 140 in the Y direction, thereby canceling out the effects of tilt or positional deviation on the slider 120 side relative to the arrangement of the scale coils 140, thereby improving measurement accuracy.

[0035] <Modification> Next, modifications of the above-described embodiment will be described. The installation form and appearance of each of the modifications described below are the same as those described in Figures 1 and 2. Furthermore, each of the modifications described below includes a scale 110 similar to that of the above-described embodiment, and the slider 120 includes excitation coils 160 and 170 similar to those of the above-described embodiment. For this reason, the following description will focus on the differences from the above-described embodiment, and redundant description of elements similar to those of the above-described embodiment will be omitted.

[0036] 8 and 9 are diagrams showing a first modified example of the position measuring device. The position measuring device 300 of the first modified example includes a slider member 150 similar to that of the above-described embodiment on the slider 120. The position measuring device 300 of the first modified example also includes a detection coil 180 on the slider 120, and the detection coil 180 has a first location 181, a second location 182, and a third location 183.

[0037] In the first modified example, second location 182 and third location 183 of detection coil 180 have the same shapes as those in the above-described embodiment, but the dimension in the X direction of first location 181 is smaller than that in the above-described embodiment. Even when the dimension in the X direction of first location 181 is small in this way, a sufficient S / N ratio can be obtained if the induced magnetic field generated on the scale 110 side is strong.

[0038] 10 and 11 are diagrams showing a second modified example of the position measuring device. The position measuring device 400 of the second modification includes a slider member 150 similar to that of the above-described embodiment on the slider 120. The position measuring device 400 of the second modification also includes a detection coil 180 on the slider 120, and the detection coil 180 has a first location 181, a second location 182, and a third location 183.

[0039] In the second modified example, second location 182 of detection coil 180 has the same shape as in the above-described embodiment, but as in the first modified example, first location 181 has a smaller dimension in the X direction than in the above-described embodiment. Furthermore, third location 183 of detection coil 180 in the second modified example has a larger dimension in the X direction than in the above-described embodiment. Because slider member 150 is located between first location 181 and third location 183 to block noise, the dimension of third location 183 may be large as in the second modified example.

[0040] 12 and 13 are diagrams showing a third modified example of the position measuring device. The position measuring device 500 of the third modification includes a slider 120, a slider member 150, and a detection coil 180, and the detection coil 180 has a first location 181, a second location 182, and a third location 183.

[0041] The slider member 150 in the third modified example has four through holes 151. A one-end-side second location 182a connected to one end side 181a of the first location 181 and an other-end-side second location 182b connected to the other end side 181b of the first location 181 pass through separate through holes 151. Because air is present inside through-hole 151, when one end side second location 182a and the other end side second location 182b pass through separate through-holes 151, the effect of noise increases compared to when they pass through a common through-hole. However, sufficient error suppression can be expected for position measuring device 500 as a whole.

[0042] Although the above description cites a linear scale that measures a position on a straight line as an example of an application of the position measuring device of the present disclosure, the application of the position measuring device of the present disclosure is not limited to this. For example, the position measuring device may be applied to a rotary scale that measures a position on an arc. That is, the first surface in the present disclosure may be a flat surface or a curved surface. Furthermore, the first direction in the present disclosure may be a linear direction or a curved direction. When the position measuring device of the present disclosure is applied to a rotary scale, the first direction may be an arcuate direction relative to a flat first surface, or the first direction may be a circular direction relative to a cylindrical first surface.

[0043] Furthermore, although the above provides an example of installation of the position measuring device of the present disclosure on a machine tool, the installation of the position measuring device of the present disclosure is not limited to the above, and the position measuring device may be installed on general machinery such as civil engineering machinery and transport machinery. The above-described embodiments should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is defined by the claims, not by the above-described embodiments, and is intended to include all modifications within the meaning and scope of the claims. The present technology can be configured as follows.

[0044] (1) a scale member having a first surface extending in a first direction; a plurality of scale coils, each having an annular shape, arranged side by side in the first direction on the first surface; a slider member having a second surface facing the first surface and movable in the first direction relative to the scale member; an excitation coil provided on the second surface, which generates a varying magnetic field to induce a current in the scale coil; a detection coil that is held by the slider member and detects the induced magnetic field, the detection coil comprising: a first location that receives an induced magnetic field associated with the induced current and generates a detection voltage; a second location that has one end connected to the first location and the other end side extending in a direction away from the first surface; and a third location that is connected to the other end side of the second location and extends in a direction along the first surface; A position measuring device comprising:

[0045] (2) The position measuring device according to (1), wherein the slider member is located between the first location and the third location. (3) The position measuring device according to (2), wherein the slider member comprises a metal mass. (4) The position measuring device according to (3), wherein the metal block is made primarily of Fe.

[0046] (5) The position measuring device according to any one of (1) to (4), wherein the slider member has a through hole through which the second portion passes. (6) the detection coil includes, as the second location, a one-end-side second location connected to one end side of the first location and an other-end-side second location connected to the other end side of the first location, The position measuring device according to (5), wherein the second location on the one end side and the second location on the other end side pass through the common through hole.

[0047] (7) The position measuring device according to (6), wherein the one end side of the first location and the other end side of the first location extend in opposite directions from a point where they connect to the second location along the first direction.

[0048] (8) The position measuring device according to any one of (1) to (7), wherein the dimension in the first direction at the first location is smaller than the dimension in the first direction of the excitation coil.

[0049] (9) The position measuring device according to any one of (1) to (8), wherein the detection coil includes the first locations on both sides of the array of the plurality of scale coils. (10) The position measuring device according to any one of (1) to (9), wherein the first location and the second location are separate and connected to each other. [Explanation of symbols]

[0050] 100, 300, 400, 500: Position measurement device 110: Scale 120: Slider 200: Machine tools 220: Bench 210: Table 121: Cable 130: Scale material 140: Scale coil 150: Slider member 160, 170: Excitation coil 161, 171: Wiring section 162, 172: Excitation section 180: Detection coil 151: Through hole 181: First Place 181a: One end of the first location 181b: The other end of the first location 182: Second Place 182a: Second location on one end 182b: Second location on the other end 183: Third Place W1: Dimension of the first location W2: Dimensions of the excitation part

Claims

1. a scale member having a first surface extending in a first direction; a plurality of annular scale coils arranged side by side in the first direction on the first surface; a slider member having a second surface facing the first surface and movable in the first direction relative to the scale member; an excitation coil provided on the second surface, which generates a varying magnetic field to induce a current in the scale coil; a detection coil that is held by the slider member and detects the induced magnetic field, the detection coil including: a first location that receives an induced magnetic field associated with the induced current and generates a detection voltage; a second location that has one end connected to the first location and the other end side thereof extending in a direction away from the first surface; and a third location that is connected to the other end side of the second location and extends in a direction along the first surface; A position measuring device comprising:

2. 2. The position measuring device according to claim 1, wherein the slider member is located between the first location and the third location.

3. 3. The position measuring device of claim 2, wherein the slider member comprises a metal mass.

4. 4. The position measuring device according to claim 3, wherein the metal mass is made mainly of Fe.

5. The position measuring device according to claim 1 , wherein the slider member has a through-hole through which the second portion passes.

6. the detection coil includes, as the second location, a one-end-side second location connected to one end side of the first location and an other-end-side second location connected to the other end side of the first location, The position measuring device according to claim 5 , wherein the one end side second location and the other end side second location pass through the common through hole.

7. The position measuring device according to claim 6 , wherein the one end side of the first location and the other end side of the first location extend in opposite directions from a location where the one end side of the first location is connected to the second location along the first direction.

8. 2. The position measuring device according to claim 1, wherein the dimension in the first direction at the first location is smaller than the dimension in the first direction of the excitation coil.

9. 2. The position measuring device according to claim 1, wherein the detection coil has the first locations on both sides of the array of the plurality of scale coils.

10. 2. The position measuring device according to claim 1, wherein the first location and the second location are separate and connected to each other.

Images