ruler

Abstract

A ruler includes a substrate, a ruler pattern having electrical conductivity and provided on a first main surface of the substrate, and a conductive film provided on a second main surface of the substrate, a base material of the conductive film being a resin material, and a conductive material being added to the base material.

Description

Technical Field

[0001] A particular aspect of the embodiments described herein relates to a scale. Background Technology

[0002] A scale for an electromagnetic induction encoder is disclosed (for example, see Japanese Patent Application Publication No. 2004-294225). Summary of the Invention

[0003] In the scale, the side without the scale pattern (the reverse side) is supported by a support member to allow relative movement along the measurement axis. Depending on the position of the support member, uneven distribution occurs in the eddies generated within it. Therefore, it is possible to form a thick coating on the back of the scale to generate eddies within it. However, depending on the stress of the coating, warping may occur in the scale.

[0004] In one aspect of the invention, an object is to provide a scale capable of suppressing warping and suppressing uneven distribution of eddy currents.

[0005] According to one aspect of the present invention, a ruler is provided, comprising: a substrate; a ruler pattern having conductivity and disposed on a first main surface of the substrate; and a conductive film disposed on a second main surface of the substrate, wherein the substrate of the conductive film is a resin material and the conductive material is added to the substrate. Attached Figure Description

[0006] Figure 1 The structure of an electromagnetic induction encoder using electromagnetic coupling between the detection head and the scale is shown;

[0007] Figure 2 The structure of the scale being supported by supporting members is shown; and

[0008] Figure 3 A schematic cross-sectional view of the scale is shown. Detailed Implementation

[0009] The following is a description of the embodiments with reference to the accompanying drawings.

[0010] Figure 1 The structure of an electromagnetic induction encoder 100 using electromagnetic coupling between a detection head and a scale is shown. (See diagram.) Figure 1 As shown, the electromagnetic induction encoder 100 has a detection head 10 and a scale 20. The detection head 10 moves relative to the scale 20 in the direction of the measuring axis. The detection head 10 and the scale 20 are flat plates and are positioned opposite each other with a predetermined gap. The electromagnetic induction encoder 100 includes a transmission signal generator 30 and a displacement measuring device 40, etc. Figure 1In the diagram, the X-axis represents the displacement direction (measuring axis) of the detection head 10. In the plane formed by the scale 20, the Y-axis is vertical relative to the X-axis.

[0011] The detection head 10 includes a transmitter coil 50, a receiver coil 60, etc. The transmitter coil 50 is a rectangular coil, and its longitudinal direction is the X-axis. For example... Figure 1 As shown, the receiver coil 60 is located inside the transmitter coil 50.

[0012] In scale 20, multiple scale patterns 22 having a rectangular shape are arranged along the X-axis with a fundamental period λ. The scale patterns 22 are electromagnetically coupled to the transmitter coil 50 and also to the receiver coil 60.

[0013] The transmission signal generator 30 generates a single-phase AC transmission signal and supplies the generated transmission signal to the transmitter coil 50. In this case, a magnetic flux is generated in the transmitter coil 50. Therefore, an electromotive force current is generated in the plurality of scale patterns 22. The plurality of scale patterns 22 are electromagnetically coupled to the magnetic flux generated by the transmitter coil 50, and a magnetic flux oscillating in the X-axis direction is generated within a predetermined spatial period. The magnetic flux generated by the scale patterns 22 generates an electromotive force current in the receiver coil 60. The electromagnetic coupling between each coil oscillates according to the displacement of the detection head 10. Thus, a sinusoidal signal with the same period as the fundamental period λ is obtained. Therefore, the receiver coil 60 detects the phase of the magnetic flux generated by the plurality of scale patterns 22. The displacement measuring device 40 can use the sinusoidal signal as a digital quantity with minimum resolution by electrically interpolating the sinusoidal signal. Thus, the displacement measuring device 40 measures the displacement of the detection head 10.

[0014] The scale 20 is supported by a support member, allowing it to move relative to the measuring axis. The side of the scale 20 without a scale pattern (the back side) is also supported by the support member. Figure 2 The structure of scale 20, supported by a supporting member, is shown. As an example, Figure 2 A cross-sectional view of an indicator with a built-in electromagnetic induction encoder is shown.

[0015] like Figure 2 As shown, the indicator includes a main housing 1, a frame 2, a main shaft 3, and an electromagnetic induction encoder 100. The main housing 1 has an open first end. The main housing 1 has a cylindrical shape. The frame 2 is mounted on the first end of the main housing 1 and is rotatable at the first end. The main shaft 3 is supported by the main housing 1 and is movable along its axial direction. The electromagnetic induction encoder 100 detects the amount of displacement of the main shaft 3 in the axial direction.

[0016] The support ring 11 is integrally formed with the central portion of the main body shell 1 at the second end of the main body shell 1. The main shaft protective sleeve 13 is mounted on the upper outer circumference of the main body shell 1 via the connecting member 12. The upper outer circumference is located at... Figure 2 The rod 14 is located on the upper side of the main body shell 1, on its lower outer circumference. The lower outer circumference is located on the upper side of the main body shell 1. Figure 2 The lower side of the shaft. The spindle protection sleeve 13 and the rod 14 are on the same axis. The connecting member 12 and the rod 14 form a bearing.

[0017] Spindle 3 is inserted into rod 14. Spindle 3 can slide within rod 14. Figure 2 The upper head 31 of the spindle 3 engages within the spindle protection sleeve 13 and can slide within it. A probe 32 is positioned at the lower edge of the spindle 3. The lower edge protrudes from the lower end of the rod 14. A support member 33 and a pin 34 engaging with a spring are positioned at the central portion of the spindle 3. The support member 33 and pin 34 are located inside the main body housing 1. A tension spring 35 is positioned between the pin 34 and the inner wall of the main body housing 1. The spindle 3 is pulled towards the main body housing 1 by the tension spring 35. Figure 2 The lower side of the spindle 3 is biased and force is applied. The tension spring 35 prevents the spindle 3 from rotating. The tension spring 35 is extended so that its length is longer than its equilibrium length.

[0018] The plate-shaped retaining member 41 is fixed to the inner wall 17 with screws, the inner wall 17 being located at the first end of the opening of the main body shell 1. Figure 2 As shown, the cutout portion 43 for holding the detection head 10, which will be described later, is formed in the holding member 41.

[0019] The electromagnetic induction encoder 100 has a detection head 10 and a scale 20. The electromagnetic induction encoder 100 is capable of detecting the absolute displacement of the main shaft 3 in the axial direction. The detection head 10 is disposed near the main shaft 3 along its axial direction. The detection head 10 engages with a cutout portion 43 of a retaining member 41 fixed to the main housing 1. The scale 20 is positioned opposite the detection head 10 at predetermined intervals. The scale 20 is fixed to the main shaft 3 by a support member 33.

[0020] The substrate 5 located on the detection side is fixed to the front side of the holding member 41 by the spacer 51. Figure 2 (Right side of the image). The substrate 5 is parallel to the retaining member 41. The substrate 5 has a circular shape along a virtual circular trajectory, the center of which is the axis A around which the frame 2 can rotate. The contact point pattern 52 is formed on the front side of the substrate 5. Figure 2 On the right side of the surface.

[0021] Depending on the material of the support member 33 or the support range of the scale 20 supported by the support member 33, distribution problems (non-uniform distribution) may occur in the eddy currents within the support member 33 because the magnetic flux has penetrated the scale 20. Therefore, the signal strength from the scale 20 may be non-uniform depending on its position. When this distribution (non-uniform distribution) of signal strength occurs, the measurement accuracy of the electromagnetic induction encoder 100 may be affected.

[0022] Therefore, it can be assumed that a copper plating layer with a large thickness, such as 18 micrometers, is formed on the entire back side of the substrate of the scale 20, generating eddy currents in the copper plating layer and reducing the influence of the support member 33. However, when a copper plating layer with a large thickness is provided on the back side of the substrate, the cost may increase. Warping may occur in the scale 20 due to the stress of the copper plating layer with a large thickness. The process for forming the copper plating layer is performed separately from the process for bonding the scale 20 to the support member 33. Therefore, the cost may increase. By dividing the copper plating layer from a continuous layer into a mesh layer, the warping of the scale 20 can be suppressed. However, magnetic flux leaks from the gaps created by the division. Therefore, signal strength distribution may occur.

[0023] Therefore, the scale 20 of this embodiment has a structure for suppressing warping at low cost. A detailed description of the scale 20 will be given below.

[0024] Figure 3 A schematic cross-sectional view of scale 20 is shown. (As shown) Figure 3 As shown, the scale 20 has a structure in which a scale pattern 22 is formed on the substrate 21. The scale pattern 22 has a structure in which a plurality of metal grids are arranged at predetermined intervals.

[0025] The substrate 21 is not limited. For example, the substrate 21 is made of a material other than a metal. For example, the material is a metal oxide material, an organic material, a glass epoxy material, a glass material, etc. A material with a low coefficient of expansion, such as quartz glass (fused synthetic quartz), can be used as a glass material.

[0026] The scale pattern 22 is made of a conductive material such as metal.

[0027] A conductive film 23 is formed on the back side of the substrate 21. The conductive film 23 is a conductive film in which a conductive material is added to a substrate made of a resin material. Examples of resin materials include epoxy, polyurethane, acrylic, and silicone resins. The conductive material is not limited to any material that is conductive. The conductive material is a low-resistance material, such as Ag (silver), Cu (copper), or Au (gold).

[0028] Because the conductive film 23 contains a conductive material, eddy currents may still occur in the conductive film 23 even if the magnetic flux penetrates the scale 20. Therefore, the influence of the support member 33 can be suppressed. Typically, the Young's modulus of the resin material is 1 GPa to 10 GPa, which is less than the Young's modulus of the copper-plated film (10 GPa to 100 GPa). Therefore, warping of the substrate 21 can be suppressed. Thus, uneven distribution of warping and eddy currents can be suppressed.

[0029] The resin material applied to the substrate 21 is a paste-like material. It can be applied to the substrate 21 through simple processes such as screen printing or a dispenser. This reduces costs and eliminates waste liquids such as electroplating waste solutions.

[0030] The conductive material of the preferred conductive film 23 has magnetic shielding properties that prevent magnetic flux from penetrating. When the conductive film 23 is impermeable to magnetic flux, the magnetic flux does not reach the support member 33. Therefore, the influence of the support member 33 can be suppressed. The conductive material with magnetic shielding properties is, for example, permalloy or ferrite.

[0031] Resin materials, such as epoxy resin, polyurethane resin, acrylic resin, and silicone resin, possess adhesive properties. Therefore, resin materials are used to mount integrated circuit chips. When using resin materials, it is not necessary to prepare another adhesive to bond the scale 20 and the support member 33. Therefore, the support member 33 can be bonded to the scale 20 in a single process by applying the resin material.

[0032] Preferably, the conductive film 23 covers the entire back side of the substrate 21. In this case, magnetic flux leakage and the influence of the support member 33 can be suppressed. Regardless of the shape of the support member 33, the support member 33 supports the scale 20 through the conductive film 23. Therefore, the shape of the support member 33 has no effect. For example, even if the position of the scale 20 supported by the support member 33 changes, the problem of eddy current distribution in the support member 33 will be less severe. Preferably, the thickness of the conductive film 23 allows for a sufficient amount of eddy current flow. For example, from the viewpoint of the skin effect, the thickness d of the conductive film 23 is preferably d = √(2ρ / ωμ) or greater. "ρ" is resistivity. "ω" is angular frequency. "μ" is absolute permeability.

[0033] This invention is not limited to the specific embodiments and modifications disclosed, but may include other embodiments and modifications without departing from the scope of this invention.

Claims

1. A ruler, characterized in that, include: A substrate having a conductive scale pattern formed on its first main surface; A conductive film is disposed on the second main surface of the substrate. The substrate of the conductive film is a resin material, and a conductive material is added to the substrate. The conductive film allows at least a portion of the magnetic flux to permeate, generating eddy currents when the magnetic flux permeates. as well as The support member is configured to support a portion of the second main surface. The conductive material is silver, copper, or gold.

2. The scale according to claim 1, wherein, The resin material has adhesive properties between the substrate and the support member.

3. The scale according to claim 1, wherein, The conductive film covers the entire second main surface.

4. The scale according to claim 1, wherein, The upper and side surfaces of the scale pattern, located on the side opposite to the substrate, are exposed to external gas.

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