EDITING STANDARD AND METHOD FOR ITS MANUFACTURING

Abstract

Encoder scale (4) for an encoder (1) with electromagnetic induction, wherein the encoder scale (4) comprises the following: a substrate (41); an electrically conductive layer (42) which has electrical conductivity and is provided on a surface of the substrate (41); a corroding electrical conductor (43A) provided on the electrically conductive layer (42) and forming an induction electrode; and a protective film (45) covering the electrical conductor (43A) and provided by an insulating body, wherein the electrically conductive layer (42) in a top view of the substrate (41) is wider than the electrical conductor (43A) and is partially exposed by the protective film (45), and an earthing conductor (46) is connected to a section of the electrically conductive layer (42) that protrudes beyond the protective film (45).

Description

TECHNICAL AREA

[0001] The present invention relates to an encoder scale and a method for manufacturing the encoder scale. In particular, the present invention relates to an encoder scale for a linear encoder with electromagnetic induction. GENERAL STATE OF THE ART

[0002] A linear encoder is known as a device connected to a manufacturing device or measuring instrument for detecting the position of a linearly moving unit. There are many different types of linear encoders, such as optical linear encoders, capacitive linear encoders, and electromagnetic induction linear encoders, which employ various detection methods. In particular, typical electromagnetic induction linear encoders include, for example, devices disclosed in JP 2009 - 276 306 A and JP 2011 - 247 600 A.

[0003] The electromagnetic induction linear encoder comprises an elongated encoder scale featuring an induction electrode pattern and an encoder head that slides along the encoder scale. An electric current induced in the induction electrode by a sliding movement of the scale relative to the head is detected by an induction coil in the encoder head, and a displacement of the scale is detected, for example, by counting the induction electrode(s) that have passed.

[0004] For a linear encoder using electromagnetic induction, the electrical conductor of the induction electrode should preferably be made of a material with low electrical resistance in order to amplify the electric current induced in the conductor. Accordingly, a metal with high electrical conductivity, particularly copper, is frequently used as the conductor material. Furthermore, a glass substrate is used as the substrate on which the electrical conductor is located.

[0005] Since copper is unlikely to adhere to glass, an adhesive layer is provided between the copper electrode and the glass substrate to improve the reliability of the adhesion. Chromium, which should have an excellent affinity for both copper and glass, is frequently used as an adhesive layer.

[0006] A guide is provided for the encoder head, allowing the encoder head to slide in relation to the encoder scale.

[0007] The guide includes a rotating roller, and a surface of the glass substrate defines a belt-shaped guide area where the glass is exposed without being covered by the adhesive layer. As the roller rolls on the guide area, the encoder head slides smoothly along the length of the encoder scale at a uniform distance relative to the scale.

[0008] However, the rotation of the roller on the guide surface can cause electrostatic charging of the glass substrate. This electrostatic charge, which causes electrical discharges and / or noise, is detrimental to the encoder head. Furthermore, electrostatic charging of the glass substrate often causes dust to adhere to the encoder head, leading to problems such as detection errors. To prevent electrostatic charging of the glass substrate, which causes the aforementioned problems, the glass substrate of a typical encoder scale is equipped with an antistatic electrode.

[0009] Fig. 5A to 5D and Fig. Figures 6A to 6D show an example of processes for manufacturing a typical encoder scale.

[0010] To produce an encoder scale 104, an adhesive layer 142 in the form of a film is first formed on a glass substrate 141, and then an electrode layer 143 is formed on the adhesive layer 142. Subsequently, a resist 144 is applied to the electrode layer 143, and a predetermined mask pattern is formed, for example, by photolithography.

[0011] Fig. 5A shows the state of the workpiece after the above-mentioned processes have been completed.

[0012] As in Fig. As shown in 5B, the electrode layer 143 is then partially removed by etching, using the resist 144 as a mask, thereby forming an electrical conductor 143A and a copper mask 143B.

[0013] As in Fig. As shown in Figure 5C, the adhesive layer 142 is partially removed by etching, using the electrical conductor 143A as a mask. This forms an adhesive body 142A and an antistatic electrode 142B for the electrical conductor 143A. The adhesive body 142A has a shape that matches that of the electrical conductor 143A in a top view of the substrate 141, so that the electrical conductor 143A can serve as a mask. However, the resist 144 continues to adhere to the workpiece in the aforementioned state, so that the resist 144, as shown in Figure 5C, is removed. Fig. 5D shown, removed.

[0014] As in Fig. As shown in Figure 6A, the electrical conductor 143A and the underlying adhesive body 142A are next masked with another resist 147, and then the copper mask 143B is removed by etching. As shown in Figure 6A, the electrical conductor 143A and the underlying adhesive body 142A are masked with another resist 147, and then the copper mask 143B is removed by etching. Fig. As shown in 6B, this exposes the antistatic electrode 142B.

[0015] After the Resist 147, as in Fig. As shown in Figure 6C, the electrical conductor 143A and the underlying adhesive body 142A are covered with a protective film 145A, which may be made of an insulating resin, and an earthing conductor 146 is connected to the exposed antistatic electrode 142B, as shown in Figure 6C. Fig. 6D shown. The encoder scale 104 is thus produced.

[0016] According to a method for producing the typical encoder scale 104, an etchant for etching the electrical copper conductor 143A differs from an etchant for etching the chromium adhesion layer 142, such that the etching process, which in Fig. 5B is shown, and the etching process, which is shown in Fig. 5C is shown, they should be independent of each other.

[0017] Moreover, the additional processes that are in Fig. 6A and Fig. Figure 6B shows the processes required to provide the antistatic electrode 142B for grounding to the substrate 141. Many processes are therefore required to manufacture the typical encoder scale 104.

[0018] JP 2004-198253A describes a magnetic encoder with a scale, comprising a substrate and a plurality of scale coils arranged side by side along a predetermined measuring track on the substrate. Magnetic glass is used as the substrate material.

[0019] US Patent 6,653,828 B2 describes a non-contact analog angle offset sensor of the magnetic induction type. The sensor comprises a first part, forming a detector, with at least one substrate plate supporting at least one flat spiral winding, at least one core layer made of a material with high magnetic permeability and low saturation field on at least a portion of the winding, wherein the detector can interact with a device for processing the electrical signal measured at the terminals of the winding, and two rotors, each comprising at least one magnet arranged on a predetermined angular sector.

[0020] JP 2009 - 276 306 A describes an encoder scale comprising a scale pattern conductor; a glass substrate; a glass contact metal layer provided on a surface of the glass substrate and configured to contain either chromium atoms, molybdenum atoms or titanium atoms and drawing a scale pattern; and a thin copper film laminated onto the glass contact metal layer.

[0021] DE 196 16 707 A1 describes a device consisting of a non-conductive measuring rod which is attached to a carrier and provided with position markings which are scanned by a relatively displaced opto-electronic scanning device in order to provide signals which represent the position of the scanning device. SUMMARY OF THE INVENTION

[0022] The invention is manufactured under the above-mentioned circumstances. An object of the invention is to provide an antistatic encoder scale with a simple arrangement that is capable of being manufactured by a small number of processes, and a method for manufacturing the encoder scale.

[0023] The object of the invention is achieved by the articles having the features disclosed in the independent claims. Further embodiments are defined in the dependent claims.

[0024] A first aspect of the invention relates to an encoder scale for an electromagnetic induction encoder according to independent claim 1.

[0025] The substrate of the encoder scale for the electromagnetic induction encoder should be provided by an insulating body. The substrate material can be glass. The electrical conductor is intended to conduct electricity, and therefore its material should preferably have low electrical resistance. The electrical conductor material can therefore be copper, which has high electrical conductivity.

[0026] However, it is likely that the substrate of the insulating body will become electrostatically charged. An electrostatic charge on the substrate, which causes electrical discharge and / or noise, is undesirable.

[0027] In the first aspect, the electrically conductive layer, provided on one surface of the substrate, attracts electrical charges through the principle of electrostatic induction, even when electricity is generated on that surface of the substrate. This leads to electrical neutralization between the substrate and the conductive layer. The conductive layer therefore acts as a typical antistatic electrode, preventing electrostatic charging of the substrate. The material of the conductive layer can be chromium.

[0028] According to the first aspect of the invention, the material of the electrical conductor, such as copper, is corrosive, and therefore the electrical conductor must be covered with a protective film provided by an insulating body. The electrically conductive layer is covered with the protective film along with the electrical conductor, so that no grounding wire can be connected to the electrically conductive layer. Since the electrically conductive layer is wider than the electrical conductor when viewed from above, in the first aspect the electrical conductor is covered with the protective film, leaving the electrically conductive layer partially exposed. The electrically conductive layer can therefore be easily grounded.

[0029] When copper is used as the electrical conductor material and chromium as the material of the conductive layer, the difference in electrical conductivity between the conductor and the conductive layer is increased. Consequently, while an electric current is induced in the conductor by electromagnetic induction, very little current is induced in the conductive layer. By increasing the difference in electrical conductivity between the conductor and the conductive layer, the need to etch the conductive layer, which is required at a typical encoder scale, is eliminated. The encoder scale can therefore be structurally simplified and manufactured using a small number of processes.

[0030] Furthermore, in cases where it is unlikely that the substrate material and the electrical conductor material will adhere to each other, the electrically conductive layer can be used as a typical adhesive layer to help the substrate and the electrical conductor adhere to each other.

[0031] In the aspect mentioned above, the electrically conductive layer is grounded.

[0032] Since the electrically conductive layer is grounded, the electrical potential of the substrate beneath the electrically conductive layer, as well as that of the electrically conductive layer itself, can be maintained at a reference level.

[0033] In the aspect mentioned above, it is preferred that one area of ​​the substrate has an area that is provided with the electrically conductive layer, and that the rest of the one area is exposed.

[0034] Since the electrically conductive layer is formed on one surface of the substrate over one area, the electrically conductive layer can be formed by a small number of processes compared to an electrically conductive layer that has the same shape as the electrical conductor in a typical electrical conductor.

[0035] The remainder of one surface of the substrate is exposed. If the substrate is, for example, a glass substrate, the exposed surface is sufficiently hard. A guide roller, which helps the induction coil slide relative to the encoder scale, is therefore able to roll on this exposed surface.

[0036] A second aspect of the invention relates to a method for manufacturing an encoder scale for an electromagnetic induction encoder according to independent claim 3.

[0037] In the second step, the electrically conductive layer is formed on the substrate, and the induction electrode layer is formed on top of the electrically conductive layer. The induction electrode layer is then partially covered with a protective film, and the area of ​​the induction electrode layer not covered by the protective film is removed. The encoder scale is thus produced.

[0038] Compared to the process for manufacturing a typical encoder scale, the second aspect of the process does not require multiple processes for forming an antistatic electrode for grounding to the substrate and a process for partially removing the electrically conductive layer. The number of manufacturing processes can therefore be reduced. BRIEF DESCRIPTION OF THE DRAWING(S) Fig. Figure 1 is a perspective view showing a linear encoder according to an exemplary embodiment of the invention. Fig. 2 is a sectional view, viewed from a direction that is in Fig. 1 is indicated by the arrows II-II. Fig. Figure 3 is a perspective view showing a encoder scale. Fig. Figure 4A shows a manufacturing process of the encoder scale. Fig. Figure 4B shows the manufacturing process of the encoder scale. Fig. Figure 4C shows the manufacturing process of the encoder scale. Fig. 4D shows the manufacturing process of the encoder scale. Fig. Figure 5A shows the first part of a manufacturing process for a typical encoder scale. Fig. Figure 5B shows the first part of the manufacturing process of the typical encoder scale. Fig. Figure 5C shows the first part of the manufacturing process of the typical encoder scale. Fig. 5D shows the first part of the manufacturing process of the typical encoder scale. Fig. 6A shows a second part of the manufacturing process, which follows the part shown in Fig. 5A to 5D are shown. Fig. 6B shows the second part of the manufacturing process, which follows the part shown in Fig. 5A to 5D are shown. Fig. 6C shows a second part of the manufacturing process, which follows the part shown in Fig. 5A to 5D are shown. Fig. 6D shows the second part of the manufacturing process, which follows the part shown in Fig. 5A to 5D are shown. DESCRIPTION OF THE FORM(S)

[0039] Exemplary embodiments of the invention are described below with reference to the accompanying drawings.

[0040] Fig. Figure 1 is a perspective view showing a linear encoder 1 with electromagnetic induction, which is provided with an encoder scale 4 according to an exemplary embodiment of the invention. The linear encoder 1 with electromagnetic induction (an electromagnetic encoder) comprises: a main scale 2 extending in a measuring direction X; and an encoder head 3 which is provided to be movable relative to the main scale 2 in the measuring direction X.

[0041] As in Fig. As shown in Figure 2, the encoder scale 4 is provided in the main scale 2, and a section of the encoder head 3 facing the encoder scale 4 is equipped with an induction coil 31. In the linear encoder 1 with electromagnetic induction, electromagnetic induction is generated between the induction coil 31 and an electrical conductor 43A (see Figure 2). Fig. 3 and 4A to 4D) which forms an induction electrode to generate an induced electromotive force in the induction coil 31. A position of the induction coil 31 is detected based on the induced electromotive force generated in the induction coil 31.

[0042] As in the Fig. 1 and Fig. As shown in Figure 2, the main scale 2 has a side surface provided with a slot 21 extending along the measuring direction X, and, for example, urethane lips 22 are provided on both edges of the slot 21 over its entire length. The lips 22 are closed, with their edges abutting each other to prevent foreign matter from entering the main scale 2. When the encoder head 3 is moved in the measuring direction X, the abutting edges of the closed lips 22 are pushed apart by a separating section 32 of the encoder head 3. The separating section 32 has a cross-section in the shape of the underside of a ship (not shown), so that the separating section 32 can easily push the abutting edges of the lips 22 apart.

[0043] As in Fig. As shown in Figure 2, the encoder head 3 comprises a guide 33 arranged in the main scale 2. The guide 33 includes rotatable first and second rollers 34, 35. The first and second rollers 34, 35 each comprise a small-diameter ball bearing shaft. The encoder scale 4 comprises a substrate 41, which defines a guide surface 41A, not covered with an electrically conductive layer 42, and a side surface 41B. During movement of the encoder head 3, the first roller 34 rolls on the guide surface 41A within a region close to the electrically conductive layer 42, and the second roller 35 rolls on the side surface 41B.

[0044] The substrate 41 of the encoder scale 4 can be a glass substrate. Glass has a low coefficient of thermal expansion and is hard. Therefore, the first and second rollers 34, 35 can roll on the surface of the substrate 41 without deforming or damaging it. Moreover, the glass substrate does not absorb moisture and therefore has a constant volume regardless of changes in humidity.

[0045] The electrical conductor 43A determines continuous scale patterns 47 on the substrate 41 at regular intervals in the measuring direction X. As shown in Fig. As shown in Figure 3, the electrical conductor 43A in the exemplary embodiment comprises electrical conductors, each defining a spiral pattern in the form of a rectangular ring, and a pair of electrical conductors oriented in an orthogonal direction to the measuring direction X, defining in combination one of the scale patterns 47. The scale patterns 47 each function as a subdivision of the linear encoder 1 with electromagnetic induction.

[0046] A method for manufacturing the encoder scale 4 with the above-mentioned arrangement is described below with reference to the Fig. Sections 4A to 4D are described. Fig. 4A to 4D are sectional views of the encoder scale 4, taken along a plane orthogonal to the measuring direction X.

[0047] As in Fig. As shown in Figure 4A, the electrically conductive layer 42 is first formed on the substrate 41 by a vacuum deposition process (e.g., vacuum evaporation or sputtering). The electrically conductive layer 42, which is made of electrically conductive chromium, has a thickness in the range of, for example, 50 nm to 100 nm.

[0048] Next, a copper electrode layer 43 is formed on the electrically conductive layer 42. Copper is not inherently a substance that adheres directly to glass. However, with the support of the electrically conductive chromium layer 42, which has an excellent affinity for both copper and glass and is provided between the substrate 41 and the electrode layer 43, the electrode layer 43 can adhere sufficiently firmly to the substrate 41.

[0049] Next, a thin copper film (not shown) is applied to the electrically conductive layer 42, and then copper is further laminated onto the thin copper film to form the electrode layer 43. The thin copper film serves as a sublayer for enlarging the electrode layer 43 by electroplating. The thin copper film allows for easy lamination of copper by electroplating. It should be noted that the electrode layer 43 can be sprayed or printed.

[0050] The thin copper film can have a thickness in the range of 200 nm to 500 nm, and the electrode layer 43 can have a thickness in the range of 1 µm to 100 µm.

[0051] Next, a resist 44 is applied to the electrode layer 43 to form a predetermined pattern. This process can be carried out by lithography.

[0052] Fig. 4A shows the state of the workpiece after the above-mentioned processes have been completed.

[0053] Next, an area not covered by electrode layer 43 and the thin copper film is removed by etching, as shown in Fig. 4B is shown, and then the resist 44 is removed, leaving the workpiece in the Fig. The state shown in 4C is provided. The electrical conductor(s) 43A is / are thus formed by the electrode layer 43.

[0054] As a result, as in Fig. As shown in Figure 4D, an earthing conductor 46 is connected to the electrically conductive layer 42, and the electrical conductor(s) 43A is / are covered with a protective film 45, which can be an insulating body made of an ultraviolet-curing resin or a thermosetting resin. The protective film 45 prevents the oxidation and / or migration of the electrical conductor(s) 43A.

[0055] In the exemplary embodiment, the protective film 45 has the same width as the electrically conductive layer 42, as shown in Fig. 4D shown. In contrast, the protective film is 45, as shown in Fig. Figure 3 shows that the electrically conductive layer 42 is shorter in length in the measuring direction than the electrically conductive layer 42, such that both ends of the electrically conductive layer 42 project beyond the protective film 45 in the measuring direction X. According to the invention, the grounding conductor 46 is connected to the section of the electrically conductive layer 42 that projects beyond the protective film 45.

[0056] It should be noted that the protective film 45, which in the exemplary embodiment is shorter in direction X than the electrically conductive layer 42, may be shorter in a direction orthogonal to direction X.

[0057] In the exemplary embodiment described above, the grounded, electrically conductive layer 42 can electrically neutralize the substrate 41, even at the moment when the rotation of the first and second rollers 34, 35 on the glass substrate 41 generates electricity. The electrical potential of the substrate 41 can therefore be maintained at a reference level to prevent electrostatic charging of the substrate 41.

[0058] Moreover, the electrically conductive layer 42 completely covers an area of ​​the substrate 41, except for a section that defines the guide surface 41A, so that a large area of ​​the substrate 41 can be reliably electrically neutralized by the electrically conductive layer 42.

[0059] However, since glass is exposed on the guide surface 41A of the substrate 41, which is not covered with the electrically conductive layer 42, and on the side surface 41B of the substrate 41, the first and second rollers 34, 35 are allowed to roll directly on the substrate 41.

[0060] Since the electrically conductive layer 42 is made of a non-corrosive material, e.g., chromium, it is not necessary to cover the electrically conductive layer 42 with the protective film 45. Therefore, the grounding conductor 46 can simply be connected to the section of the electrically conductive layer 42 that protrudes beyond the protective film 45.

[0061] The electrically conductive layer 42, which helps the glass substrate 41 and the electrical copper conductor(s) 43A to adhere to each other (to be firmly fixed), also acts as a conductor for electrically neutralizing the substrate 41. An arrangement corresponding to the typical antistatic electrode 142B can therefore be omitted to reduce the number of manufacturing processes.

[0062] Moreover, in the exemplary embodiment, unlike the typical encoder scale 104, the need to etch the electrically conductive layer 42 using the electrical conductor(s) 43A as a mask is eliminated, thus reducing the number of manufacturing processes.

[0063] It is understood that the scope of the invention is not limited by the exemplary embodiment described above, but may include modifications and improvements that are compatible with the invention.

[0064] For example, in the exemplary embodiment, the electrical conductor(s) 43A is / are a spiral pattern in the form of a rectangular ring, but it can / can be in a different shape. For example, the electrical conductor(s) 43A can / can be in the form of a continuous rectangle or circle, or in a zigzag shape that bends to the right and left. In other words, as long as the electrical conductor(s) is / are in an island shape and is / are electrically conductive, the shape of the electrical conductor(s) 43A can differ from the exemplary embodiment.

[0065] The materials of the components of the encoder scale 4 in the exemplary embodiment can be replaced with any other material if required.

[0066] For example, in the exemplary embodiment, the material of the substrate 41 is glass, but it can be any hard insulating material such as ceramic, sapphire, quartz or resin.

[0067] Furthermore, the material of the electrical conductor(s) 43A in the exemplary embodiment is copper, but can be any material with a low electrical resistance, such as gold or silver.

[0068] In the exemplary embodiment, the material of the electrically conductive layer 42 is chromium, but it can be any material, such as nickel or titanium, as long as the material has a higher electrical resistance than the electrical conductor(s) 43A and is unlikely to cause electromagnetic induction.

[0069] The electromagnetic induction encoder is exemplified by the electromagnetic induction linear encoder 1, which, in this exemplary embodiment, detects a linear displacement of an object to be measured. However, the electromagnetic induction encoder can also be an electromagnetic induction rotary encoder, which detects the amount and / or the rotational speed of an object to be measured.

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