Lineargeber

Abstract

Linear encoder comprising a scale unit (1) and a slider which slides along the scale unit (1), wherein the slide has a slide housing (11) comprising a slide retaining unit (12), a detection head retaining unit (13) mounted within a scale housing (2) of the scale unit (1), and a column (14) extending between the outside and inside of the scale housing (2) to connect these two retaining units (12, 13), and a part of the column (14) that is closer to the detection head holding unit (13), and a part of the detection head holding unit (13) that is closer to the column (14), are drilled out with a thickness that is greater than a thickness of the column (4).

Description

Priority indication

[0001] This application claims priority over Japanese patent application No. 2014-142006, filed on July 10, 2014. Technical field

[0002] The present invention relates to a linear encoder that is installed in a machine tool, a semiconductor manufacturing device or the like for determining the position of a movable shaft. background

[0003] Fig. Figure 3 shows a special structure of a conventional linear encoder. Fig. Figure 4 is a cross-sectional view along line BB' in Fig. 3. As shown in the cross-section in Fig. As shown in 4, one scale unit comprises 1 of the scale shown in Fig. Figure 3 shows a conventional linear encoder comprising a scale housing 2, which is open at and around an edge defined by its lower and rear surfaces, and has a main scale 3 mounted inside the scale housing 2. The main scale 3 is made of glass and has a scale made of a thin metallic film, etched into its surface in a matrix at a constant pitch in the longitudinal direction. A slide unit 20 of the linear encoder comprises a slide housing 21, which approximately includes a slide retainer 22, a detection head retainer 23, and a column 24 connecting the two. The detection head retainer 23 has a detection head mounted thereon, comprising a light-emitting unit 7, a mirror 8, and a light-receiving unit 29.In the detection head, the light emitted by the light-emitting unit 7 is reflected at a right angle onto the mirror 8 to be projected into the matrix section of the main scale 3, and the transmitted light is converted into an electrical signal by the light-receiving unit 29. The slide holder 22 is attached to a movable unit or the like of a machine by means of a screw. The slide holder 22 has a built-in circuit board 27 for converting the electrical signal from the light-receiving unit 29 into a position data signal. A through-hole 26 is formed in the column 24 and the detection head holder 23, so that an electrical wire 28 passes from the detection head through the through-hole 26 to the circuit board 27.The position data signal output by the circuit board 27 is transmitted externally via a waterproof connector 9 mounted on the slide holder 22. A cover 4 is securely attached to the slide holder 22 to protect the circuit board 27 from water, oil, or the like.

[0004] The scale unit 1 and the slider unit 20 are, as in Fig. As shown in Figure 3, the detection head, the detection head holding unit 23, and part of the column 24 are assembled and housed in the scale housing 2. Seals 5 and 6 are firmly attached near the opening of the scale housing 2. The pointed ends of the seals 5 and 6 are in contact with each other to close the opening of the scale housing 2 and prevent the ingress of dust, water, oil, or the like from the outside. The column 24 is long in the longitudinal direction of the scale unit 1 and thin in the transverse direction, and has a cross-section that is ship-like in shape. With this shape, the column 24 moves, while the two seals 5 and 6 oppose each other in the advancing direction when the slide unit 20 moves. Furthermore, with this shape, the opposing pointed ends of the seals 5 and 6 are brought into contact with each other on the opposite side of the advancing direction of the column 24.

[0005] The slide housing 21, which includes the slide retaining unit 22, the detection head retaining unit 23, and the column 24, is formed in one piece using metal, such as aluminum or the like, generally by lost-wax casting, die casting, or the like. However, it is not possible to form the through-hole 26 of the detection head retaining unit 23 and the column 24 by one-piece forming because the diameter of the hole is very small, while its length is as much as five times the hole diameter. Furthermore, if the through-hole is formed during post-processing, only drilling and unloading operations are available, which are costly to machine, and it is necessary to form several holes if there are many wires. In addition, because the column is very thin, a machining defect is likely to be caused during the drilling operation by a hole breaking through the surface of the column.Furthermore, while the process requires passing several electrical wires through the through-hole in the column, soldering to connect the wire leading to the electrical circuit, and pressing the connector terminal to secure it, the number of steps necessary for wiring presents a problem. It should be noted that one method for improving the wiring process is the use of a flexible flat cable (FCC) instead of an electrical wire. However, passing an FCC through the through-hole requires creating a long hole in the column, and creating such a hole during rework necessitates repeated unloading and drilling operations.Furthermore, a method for forming a long hole in a column is available that forms part of the column of the valve body by using two shaped components whose form is divided by a long hole. However, this method has a problem due to the reduced strength of the column that supports the detection head holding unit.

[0006] The present invention was conceived in light of the foregoing, and one object of the present invention is to realize a slide structure of a linear encoder in which a through-hole of a detection head holding unit and a column of a slide housing are formed by one-piece machining by forming or milling in order to create a linear encoder with lower costs. Summary of the invention

[0007] A linear encoder according to the present invention is a linear encoder comprising a scale unit and a slider that slides along the scale unit, the slider comprising a slider holding unit, a detection head holding unit mounted within a scale housing of the scale unit, and a column extending between the outside and inside of the scale housing to connect these two holding units, wherein a portion of the column closer to the detection head holding unit and a portion of the detection head holding unit closer to the column are drilled to a thickness greater than the thickness of the column.

[0008] In this case, drilling into the column can be applied to a part that is closer to the detection head holding unit than a position where a seal attached to the scale housing touches the column when the column is mounted to the scale unit.

[0009] The slide housing can be designed to include a through-hole that is formed in one piece between the part drilled from the column and the slide retaining unit.

[0010] The slide housing may be subject to post-processing by milling to form a through-hole between the part drilled from the column and the slide retaining unit.

[0011] According to the present invention, a portion of the column closer to the detection head holding unit and a portion of the detection head holding unit closer to the column are drilled to a thickness greater than the column. This makes it possible to reduce the length of the through-hole. Thus, it is possible to mold the slide housing containing the through-hole in one piece using lost-wax casting, die casting, or the like. Furthermore, even when one-piece molding is not possible, depending on the length of the through-hole, it is possible to achieve a through-hole that is shorter than that of a conventional slide housing and to make the base section of a milling tool thicker than, or even thicker than, the column thickness, thereby enabling milling to form a through-hole.The foregoing makes it possible to easily create a long hole for an FCC by milling, thereby reducing the number of wiring steps without increasing machining costs. According to the present invention, the foregoing makes it possible to create a slider unit of a linear encoder at a lower cost.

[0012] It should be noted that, according to conventional linear encoders, forming a bored section in a column as in the present invention has been considered pointless. However, an actual analysis of the relationship between a column and a seal proves that the seal in a central section of the column only contacts the column in a portion closer to the slide holder, and that a portion of the column closer to the detection head holder does not contribute to the sealing performance at all. This analysis enables the present invention. Brief description of the drawings

[0013] Preferred embodiments of the present invention will be described in detail with reference to the following figures, wherein: Fig. 1 shows a special structure of a linear encoder according to the present invention; Fig. 2 a cross-sectional view along line AA' in Fig. 1 is; Fig. 3 shows a special structure of a conventional linear encoder and Fig. 4 Cross-sectional view along line BB' in Fig. 3 is. Detailed description of the invention

[0014] The present invention will now be described with reference to the drawings. Fig. Figure 1 shows a special structure of a linear encoder according to the present invention. Fig. 2 is a cross-sectional view along line AA' in Fig. 1. It should be noted that for ease of understanding, the seal 6 and the upper surface of the scale housing 2 (the right end face in Fig. 2) in Fig. 1 are not shown. Fig. 1 and Fig. 2 is an element that has the same function as the one in Fig. 3 and Fig. 4, the same reference numeral is given and is not described. The detection head holding unit 13 of the slide housing 11 and a part of the column 14 have a shape formed by boring out a part to a position immediately before a position where the column 14 contacts the seal 5, 6 on the side of the detection head holding unit 13, with a thickness greater than the thickness of the column 14.

[0015] That is, as is evident from the drawing, the detection head holder 13 is completely enclosed within the hollow space formed inside the scale housing 2. An opening is formed at the edge of the scale housing 2 to allow communication between the outside and the inside of the scale housing 2, and the column 14 extends through this opening. Thus, the detection head holder 13 is not exposed to the outside, while the column 14 is partially exposed. The seals 5 and 6 are attached to the scale housing 2, and their respective tips are in contact with the column 14. A portion of the column 14 that is closer to the detection head holder 13 than the point where the seals 5 and 6 contact the column 14 is not exposed to the outside.

[0016] In this embodiment, a drilled section 15 is formed in a portion of the column 4 that is closer to the detection head holding unit 13 than in a position where the column 14 contacts the seals 5, 6—in other words, a portion of the column 14 that is not exposed to the outside—and in a portion of the detection head holding unit 13 that is closer to the column 14. It should be noted that it is desirable for the drilled section 15 to be located substantially in the center of the column 14 in the longitudinal direction of the scale (the left-right direction). Fig. 1) is formed. As long as it is possible to ensure a seal for the opening of the scale housing 2, the position of the drilled section 15 is not restricted to the center of the longitudinal direction of the scale, but can be in other positions.

[0017] A long through-hole 16 is formed between the bored section 15 of the column 14 and the slide holder unit 12. Within the slide housing 11, the slide holder unit 12, the detection head holder unit 13, the column 14, the bored section 15, and the through-hole 16 are formed in one piece using metal, such as aluminum or the like, by lost-wax casting, die casting, or the like. An FCC connector 18 is connected to the light receiving unit 29 and also to an FPC connector 19 mounted on the circuit board 17, passing through the bored section 15 and the long through-hole 16.

[0018] In the embodiment described in Fig. 1 and Fig.Figure 2 shows an example in which the through-hole 16 of the column 14 is formed in one piece. However, if forming the through-hole 16 in one piece is difficult, the long through-hole 16 can be formed by milling during subsequent machining. Alternatively, the drilled section 15 can be formed not during the one-piece forming process but during subsequent milling. Although an optical linear encoder is described as an example in the preceding embodiment, the present invention can be applied to a magnetic or electromagnetic inductive linear encoder.

Claims

[1] Linear encoder comprising a scale unit (1) and a slider which slides along the scale unit (1), wherein the slide has a slide housing (11) comprising a slide retaining unit (12), a detection head retaining unit (13) mounted within a scale housing (2) of the scale unit (1), and a column (14) extending between the outside and inside of the scale housing (2) to connect these two retaining units (12, 13), and a part of the column (14) that is closer to the detection head holding unit (13), and a part of the detection head holding unit (13) that is closer to the column (14), are drilled out with a thickness that is greater than a thickness of the column (4). [2] Linear encoder according to claim 1, wherein the drilling of the column (14) is applied to a part that is closer to the detection head holding unit (13) than a position where a seal (6) attached to the scale housing (2) contacts the column (14). [3] Linear encoder according to claim 1 or 2, wherein the slide housing (11) is formed such that it includes a through hole (16) which is formed in one piece between the part which is drilled by the column (14) and the slide retaining unit (12). [4] Linear encoder according to claim 1, wherein the slide housing (11) is given a post-processing to form a through hole (16) between the part which is drilled by the column (14) and the slide retaining unit (12) by means of milling. [5] Linear encoder according to claim 2, wherein the slide housing (12) is formed such that it includes a through hole (16) which is formed in one piece between the part which is drilled by the column (14) and the slide retaining unit (12). [6] Linear encoder according to claim 2, wherein the slide housing (12) is post-processed to form a through hole (16) between the part which is drilled by the column (14) and the slide retaining unit (12) by means of milling.

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