Linearenkoder

Abstract

Linear encoder comprising a scale (2) and a frame (1) in which the scale (2) is held, the linear encoder being characterized in that the frame (1) has an opening (1a) extending in a longitudinal direction of the frame (1), the linear encoder includes a pair of elongated dustproof members (4, 5) arranged to face each other in the opening (1a), at least a part of each dustproof member (4, 5) being elastically deformable, each dustproof member (4, 5) including a first end portion (4a, 5a) in a transverse direction of the dustproof member (4, 5), a first projecting portion (4c, 5c) disposed at the first end portion (4a, 5a), and a second end portion in the transverse direction, the opening (1a) having a pair of fitting recesses (1b1, 1b2) formed therein, the first end portion (4a, 5a) of each dustproof member (4, 5) is fitted into a corresponding one of the fitting recesses (1b1, 1b2), the first end portion (4a, 5a) of each dustproof member (4, 5) is adapted to rotate in the fitting recess (1b1, 1b2) when the second end portion of the dustproof member (4, 5) is pivotally deformed in the transverse direction, and the first projecting portion (4c, 5c) contacts the corresponding one of the fitting recesses (1b1, 1b2) in a state in which the first end portion (4a, 5a) of each dustproof member (4, 5) is rotated.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention

[0001] The present invention relates to a linear encoder. 2. Description of related technology

[0002] A linear encoder mounted in a machine tool or the like is an example of a measuring device. First, a general structure of a linear encoder will be described. Fig. Figure 1 is a schematic diagram illustrating a general linear encoder. Fig. Figure 6 is a sectional view of the general linear encoder. In the following description, the longitudinal direction, the transverse direction, and the thickness direction of a scale included in the linear encoder are referred to as the X-axis direction, the Y-axis direction, and the Z-axis direction, respectively, for convenience (see Fig. 6).

[0003] As it is in Fig. 1 and Fig. As shown in Figure 6, in a general linear encoder, a scale 2 is held in a frame 1, and an opening 1a is formed in the frame 1 so as to extend in the X-axis direction. The scale 2 and a detector 3 are moved relative to each other while the detector 3 is inserted through the opening 1a, and the detector 3 receives position information from the scale 2 (see, for example, Japanese Unexamined Patent Application Publication JP 2008-267989 A).

[0004] In this structure, to prevent oil, dust, including machine dust, etc., from entering the frame 1 through the opening 1a, the frame 1 is provided with a first dustproof member 101 and a second dustproof member 102 arranged to face each other across the opening 1a in the Z-axis direction. The first dustproof member 101 and the second dustproof member 102 are arranged with the detector 3 therebetween. When the scale 2 and the detector 3 are moved relative to each other, the detector 3 moves along the opening 1a of the frame 1 in the X-axis direction while pushing the first dustproof member 101 and the second dustproof member 102 aside.

[0005] Now, the structure of each of the first dustproof member 101 and the second dustproof member 102 will be described. Fig. 7 illustrates a structure of the first dustproof member 101 before it is deformed. Fig. 8 illustrates the manner in which the first dustproof member 101 and the second dustproof member 102 cover the opening 1a of the frame 1 in a region where the detector 3 is not inserted through the opening 1a. Fig. 9 illustrates the manner in which the first dustproof member 101 and the second dustproof member 102 cover the opening 1a of the frame 1 in a region where the detector 3 is inserted through the opening 1a.

[0006] The first dustproof member is made of a flexible material. The length of the first dustproof member 101 in the X-axis direction is substantially equal to the length of the opening 1a of the frame 1 in the X-axis direction. As shown in Fig. 7, the first dustproof member 101 includes a base portion 101a, a tongue portion 101b, and a projecting portion 101c.

[0007] The base portion 101a is fitted into a first fitting recess 1b1. In order for the base portion 101a to be easily inserted into the first fitting recess 1b1 of the frame 1, the base portion 101a has a size smaller than that of the first fitting recess 1b1 of the frame 1 when viewed in the X-axis direction. Therefore, the base portion 101a and the first fitting recess 1b1 of the frame 1 are not in close contact with each other, and a gap is easily formed between the base portion 101a and the first fitting recess 101b of the frame 1.

[0008] The tongue portion 101b has a plate-like shape and protrudes from the base portion 101a. When the base portion 101a is fitted into the first fitting recess 1b1 of the frame 1, the tongue portion 101b protrudes from the opening of the first fitting recess 1b1.

[0009] The protruding portion 101c is formed on a surface of the tongue portion 101b facing the positive Y-axis direction. The protruding portion 101c has a substantially right-angled triangular shape when viewed in the X-axis direction. A surface of the protruding portion 101c near the tip of the first dustproof member 101 is substantially perpendicular to the tongue portion 101b.

[0010] The second dustproof member 102 will not be described in detail because its structure is similar to that of the first dustproof member 101. The second dustproof member 102 includes a base portion 102a fitted into a second fitting recess 1b2 of the frame 1, a tongue portion 102b protruding from the base portion 102a, and a protruding portion 102c formed on a side of the tongue portion 102b facing the positive Y-axis direction. When the base portion 102a is fitted into the second fitting recess 1b2 of the frame 1, the tongue portion 102b protrudes through the opening of the second fitting recess 1b2.

[0011] The first fitting recess 1b1 and the second fitting recess 1b2 are formed in the frame 1 so as to face each other in the Z-axis direction with the opening 1a of the frame 1 between them. The length of the first fitting recess 1b1 and the length of the second fitting recess 1b2 in the X-axis direction are each substantially equal to the length of the opening 1a in the X-axis direction.

[0012] In the region where the detector 3 is not inserted through the opening 1a of the frame 1 as shown in Fig. 8, the tongue portion 101b of the first dustproof member 101 and the tongue portion 102b of the second dustproof member 102 contact each other to close the opening 1a of the frame 1 in such a state that the first dustproof member 101 and the second dustproof member 102 are warped.

[0013] At this time, for example, the tongue portion 102b of the second dustproof member 102 is engaged with the protruding portion 101c of the first dustproof member 101, and the tongue portion 101b of the first dustproof member 101 is engaged with the tip of the tongue portion 102b of the second dustproof member 102. Even if the first dustproof member 101 or the second dustproof member 102 attempts to rotate in the negative Y-axis direction, the first dustproof member 101 or the second dustproof member 102 is restrained by the restoring force thereof.

[0014] In the region where the detector 3 is inserted through the opening 1a of the frame 1, as shown in Fig. As shown in Figure 9, the tongue portion 101b of the first dustproof member 101 and the tongue portion 102b of the second dustproof member 102 surround the detector 3 in such a state that the first dustproof member 101 and the second dustproof member 102 are warped. At this time, the projecting portion 101c of the tongue portion 101b of the first dustproof member 101 and the projecting portion 102c of the tongue portion 102b of the second dustproof member 102 contact the detector 3.

[0015] As described above, in the dustproof structure of a general linear encoder, gaps are likely to form between the base portion 101a of the first dustproof member 101 and the first fitting recess 1b1 of the frame 1, and between the base portion 102a of the second dustproof member 102 and the second fitting recess 1b2 of the frame 1. Therefore, dust and the like are likely to enter the frame 1 from the outside.

[0016] DE 10 2007 031 976 A1 describes a length measuring device consisting of an encapsulated scale and a sensor chip of a scanning unit that scans the scale. A driver is coupled to the scanning unit via a coupling, rigid in the measuring direction and movable transversely to it.

[0017] DE 41 01 579 A1 describes encapsulated position measuring devices with a housing with a longitudinal slot, sealed by sealing lips. The sealing lips are made of elastic plastic and feature a tensile thread or wire embedded in the sealing lip base.

[0018] US 2004 / 0 065 486 A1 describes a scale device comprising a housing element having a guide opening formed therein, sealing lip elements, a carrier unit having sealing lip pressure means formed thereon, and a coupling element which slides within and relative to the guide opening. SUMMARY OF THE INVENTION

[0019] The present invention has been made to solve the problems described above, and it is an object of the present invention to provide a linear encoder which can prevent dust and the like from entering the frame.

[0020] This object is achieved by a linear encoder having the features disclosed in the independent claims. Preferred embodiments are defined in the dependent claims.

[0021] A linear encoder according to a first aspect of the present invention includes a scale; a frame in which the scale is held, the frame having an opening extending in a longitudinal direction of the frame; and a pair of elongated dustproof members arranged to face each other in the opening. At least a part of each dustproof member is elastically deformable. Each dustproof member includes a first end portion in a transverse direction of the dustproof member, a first projecting portion disposed at the first end portion, and a second end portion in the transverse direction. The opening has a pair of fitting recesses formed therein. The first end portion of each dustproof member is fitted into a corresponding one of the fitting recesses, and the first projecting portion contacts the corresponding one of the fitting recesses.

[0022] A linear encoder according to a second aspect of the present invention includes a scale; a frame in which the scale is held, the frame having an opening extending in a longitudinal direction of the frame; and a pair of elongated dustproof members arranged to face each other in the opening. At least a part of each dustproof member is elastically deformable. Each dustproof member includes a first end portion in a transverse direction of the dustproof member and a second end portion in the transverse direction. The opening has a pair of fitting recesses formed therein, and each fitting recess has a second projecting portion formed therein. The first end portion of each dustproof member is fitted into a corresponding one of the fitting recesses, and the first end portion contacts the second projecting portion.

[0023] In the linear encoder described above, the first projecting portion preferably has an arcuate cross-sectional shape.

[0024] In the linear encoder described above, the second projecting portion preferably has an arcuate cross-sectional shape.

[0025] In the linear encoder described above, a pair of the first projecting portions are preferably arranged on both surfaces of the first end portion of each dustproof member.

[0026] In the linear encoder described above, a pair of the second projecting portions are preferably arranged on surfaces of each fitting recess facing both surfaces of the first end portion of each dustproof member.

[0027] In the linear encoder described above, each dustproof member preferably further includes a third projecting portion disposed at the second end portion, the third projecting portion having an arcuate cross-sectional shape.

[0028] In the linear encoder described above, one end of the second end portion of each dustproof member preferably has an arcuate cross-sectional shape.

[0029] The present invention provides a linear encoder that can prevent dust and the like from entering the frame. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic perspective view of a general linear encoder. Fig. 2 is a schematic sectional view of a first dustproof member of a dustproof structure according to a first embodiment. Fig. 3 is a schematic sectional view illustrating the manner in which a first dustproof member and a second dustproof member of the dustproof structure according to the first embodiment cover an opening of a frame in a region where a detector is not inserted through the opening. Fig. 4 is a schematic sectional view illustrating the manner in which the first dustproof member and the second dustproof member of the dustproof structure according to the first embodiment cover the opening of the frame in a region where the detector is inserted through the opening. Fig. 5 is a schematic partial sectional view of a dustproof structure according to a second embodiment. Fig. 6 is a schematic sectional view of a general linear encoder. Fig. 7 is a schematic sectional view of a first dustproof member of a dustproof structure of the general linear encoder. Fig. 8 is a schematic sectional view illustrating the manner in which the first dustproof member and a second dustproof member of the dustproof structure of the general linear encoder cover an opening of a frame in a region where a detector is not inserted through the opening. Fig. 9 is a schematic sectional view illustrating the manner in which the first dustproof member and the second dustproof member of the dustproof structure of the general linear encoder cover the opening of the frame in a region where the detector is inserted through the opening. DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] Embodiments of the present invention will now be described with reference to the drawings. However, the present invention is not limited to the embodiments. For ease of understanding, the following description and the drawings are simplified as appropriate. First embodiment

[0031] First, the basic structure of a linear encoder of the present embodiment will be described. The dustproof structure of the present embodiment can also be applied to a measuring device other than a linear encoder.

[0032] Although a structure of a linear encoder has been described above in the Background of the Invention section, it will be briefly described again with reference to Fig. 1 and Fig. 6. According to the illustration in Fig. 1 and Fig. 6, in a general linear encoder, a scale 2 is held in a frame 1, and an opening 1a is formed in the frame 1 so as to extend in the X-axis direction (the longitudinal direction of the scale 2). The scale 2 and the detector 3 are moved relative to each other in the longitudinal direction while the detector 3 is inserted through the opening 1a, and the detector 3 receives position information from the scale 2.

[0033] In this structure, in order to prevent dust and the like from entering the opening 1a of the frame 1, the frame 1 is provided with a pair of dustproof members (a first dustproof member 4 and a second dustproof member 5).

[0034] The scale 2 can be, for example, an optical scale or an electromagnetic induction scale for a general linear encoder. The detector 3 is configured to be able to obtain the position information from the scale 2.

[0035] The structure of frame 1 will now be briefly described. Frame 1 is essentially in the shape of a rectangular parallelepiped or cuboid with a predetermined thickness. The longitudinal direction of frame 1 is the X-axis direction, and the width direction of frame 1 is the Y-axis direction.

[0036] A space is formed in the frame 1, and the scale 2 and the detector 3 can be held in the space. In a surface of the frame 1 parallel to the X-axis direction (the lower surface in Fig. 6) The opening 1a is formed to extend in the longitudinal direction. The space formed in the frame 1 is connected to the outside through the opening 1a. The width of the opening 1a (the dimension in the Z-axis direction) is smaller than the width of the space (the dimension in the Z-axis direction).

[0037] As in Fig. As shown in Figure 3, the opening 1a is formed between walls facing each other along the longitudinal direction (along the XY plane). A first fitting recess 1b1 and a second fitting recess 1b2 are formed in the walls, respectively, extending in the longitudinal direction. Base portions 4a and 5a of the first dustproof member 4 and the second dustproof member 5, which will be described below, are fitted into the first fitting recess 1b1 and the second fitting recess 1b2, respectively.

[0038] In this structure, the first dustproof member 4 and the second dustproof member 5 are arranged to face each other in the opening 1a of the frame 1.

[0039] Now the first dustproof member 4 and the second dustproof member 5 will be described. Fig. 2 shows the shape of the first dustproof member 4 when viewed in the X-axis direction (the shape of a cross section perpendicular to the X-axis). Fig. 3 illustrates the manner in which the first dustproof member 4 and the second dustproof member 5 cover the opening 1a of the frame 1 in a region where the detector 3 is not inserted through the opening 1a. Fig. 4 illustrates the manner in which the first dustproof member 4 and the second dustproof member 5 cover the opening 1a of the frame 1 in a region where the detector 3 is inserted through the opening 1a.

[0040] At least a part of each of the first dustproof member 4 and the second dustproof member 5 is elastically deformable. The first dustproof member 4 and the second dustproof member 5 of the present embodiment are made of a flexible material. For example, the first dustproof member 4 and the second dustproof member 5 are made of urethane, nitrile rubber, nitrile butadiene rubber (NBR), or fluorocarbon rubber. A wire 6 made of a metal or synthetic fiber and extending in the longitudinal direction is disposed in each of the first dustproof member 4 and the second dustproof member 5, so that extension of the dustproof members 4 and 5 due to oil or the like can be prevented.

[0041] According to the presentation in Fig. 2, the first dustproof member 4 includes the base portion 4a, a tongue portion 4b, first protruding portions 4c, and a second protruding portion 4d. The first dustproof member 4 has an elongated, substantially plate-like shape. The length of the first dustproof member 4 in the X-axis direction, as described in detail below, is set so that the opening 1a of the frame 1 can be reliably covered by the first dustproof member 4 and the second dustproof member 5.

[0042] The length of the base portion 4a in the X-axis direction is substantially equal to the length of the opening 1a of the frame 1 in the X-axis direction. The base portion 4a is configured to fit into the first fitting recess 1b1 of the frame 1. When viewed in the X-axis direction, the base portion 4a of the present embodiment has a substantially rectangular shape and has a size such that the base portion 4a can fit into the first fitting recess 1b1 of the frame 1. The shape of the base portion 4a is not particularly limited as long as the first dustproof member 4 can be supported by the first fitting recess 1b1 of the frame 1.

[0043] The first fitting recess 1b1 of the frame 1 is arranged to face the second fitting recess 1b2 across the opening 1a of the frame 1 in the Z-axis direction. The first fitting recess 1b1 has a substantially rectangular shape when viewed in the X-axis direction and has a first opening 1c1 facing the opening 1a. The shape of the first fitting recess 1b1 is not limited as long as the base portion 4a of the first dustproof member 4 can be properly fitted into the first fitting recess 1b1.

[0044] The first opening 1c1 of the first fitting recess 1b1 is partially covered by a first side wall 1d1 that protrudes in the positive Y-axis direction from a part of the frame 1 near the opening 1a of the first fitting recess 1b1. Preferably, the tip portion of the first side wall 1d1 has an arcuate cross-sectional shape so as not to damage the first dustproof member 4 when the first dustproof member 4 contacts the tip portion.

[0045] Regarding the first dustproof member 4, the tongue portion 4b is formed to extend over substantially the entirety of the base portion 4a in the longitudinal direction and protrudes from the base portion 4a. The tongue portion 4b of the present embodiment has a plate-like shape, and a base end of the tongue portion 4b is connected to a corner portion of the base portion 4a adjacent to the opening 1a. When the tongue portion 4b is not deformed and the first dustproof member 4 is fitted into the first fitting recess 1b1 of the frame 1, the tongue portion 4b extends substantially in the Z-axis direction and protrudes through the first opening 1c1 into the opening 1a. As will be described below, the distanceDistance by which the tongue portion 4b projects into the opening 1a, that is, the width of the tongue portion 4b, is set so that the opening 1a of the frame 1 can be reliably covered by the first dustproof member 4 and the second dustproof member 5 which are opposite to each other.

[0046] The first protruding portions 4c are formed to extend over substantially the entirety of the base portion 4a in the longitudinal direction. The first protruding portions 4c contact the first fitting recess 1b1 of the frame 1 when the tip portion of the first dustproof member 4 is pivotally deformed in the negative Y-axis direction. The shapes and the like of the first protruding portions 4c will be described below.

[0047] The second protruding portion 4d is formed to extend over substantially the entirety of the tongue portion 4b in the longitudinal direction. The second protruding portion 4d protrudes from a part of a surface of the tongue portion 4b near the tip portion, with the surface facing in the positive Y-axis direction. The function of the second protruding portion 4d will be described below.

[0048] A detailed description of the second dustproof member 5 will be omitted because the structure of the second dustproof member 5 is substantially the same as that of the first dustproof member 4. The second dustproof member 5 includes the base portion 5a fitted into the second fitting recess 1b2 of the frame 1, a tongue portion 5b projecting from the base portion 5a, first projecting portions 5c formed on the base portion 5a, and a second projecting portion 5d formed on the tongue portion 5b.

[0049] According to the presentation in Fig. 3, the first fitting recess 1b1 and the second fitting recess 1b2 of the frame 1 are linearly symmetrical with respect to a line L1 passing through the center of the opening 1a of the frame 1 in the Z-axis direction and extending in the Y-axis direction. A second opening 1c2, facing the opening 1a, is partially covered by a second side wall 1d2. The tongue portion 5b of the second dustproof member 5 protrudes into the opening 1a through the second opening 1c2.

[0050] According to the presentation in Fig. 3, where the first dustproof member 4 and the second dustproof member 5 have the above-described structures, in the region where the detector 3 is not inserted through the opening 1a of the frame 1, the tip portion of the first dustproof member 4 and the tip portion of the second dustproof member 5 contact each other to close the opening 1a of the frame 1 in such a state that the first dustproof member 4 and the second dustproof member 5 are distorted. In this state, the base portion 4a of the first dustproof member 4 is engaged with the first side wall 1d1 of the frame 1, the base portion 5a of the second dustproof member 5 is engaged with the second side wall 1d2 of the frame 1, and the tip portion of each of the dustproof members 4 and 5 is pivotally deformed in the negative Y-axis direction.

[0051] In the present embodiment, since the tip portion of the second dustproof member 5 is engaged with the second projecting portion 4d of the first dustproof member 4 and the tip portion of the first dustproof member 4 is engaged with the tip portion of the second dustproof member 5, the first dustproof member 4 and the second dustproof member 5 are maintained in a distorted state.

[0052] At this time, the first dustproof member 4 exerts a restoring force in a direction such that the second dustproof member 5 is pushed, and the second dustproof member 5 exerts a restoring force in a direction such that the first dustproof member 4 is pushed. Even if the tip portion of the first dustproof member 4 or the tip portion of the second dustproof member 5 attempts to be pivotally deformed in the negative Y-axis direction to change the state of the tip portion of the first dustproof member 4 and the tip portion of the second dustproof member 5 from the closed state to an open state, the first dustproof member 4 or the second dustproof member 5 is restrained by the restoring force thereof. Therefore, dust or the like can be prevented from entering the frame 1.

[0053] In the region where the detector 3 is inserted through the opening 1a of the frame 1, as shown in Fig. 4, the tongue portion 4b of the first dustproof member 4 and the tongue portion 5b of the second dustproof member 5 surround the detector 3 to close the opening 1a of the frame 1 in such a state that the first dustproof member 4 and the second dustproof member 5 are distorted.

[0054] In the present embodiment, the first dustproof member 4 and the second dustproof member 5 are maintained in a warped state because the second projecting portion 4d of the first dustproof member 4 contacts a surface of the detector 3 facing in the positive Z-axis direction, and the second projecting portion 5d of the second dustproof member 5 contacts a surface of the detector 3 facing in the negative Z-axis direction.

[0055] At this time, the first dustproof member 4 exerts a restoring force in a direction such that the detector 3 is pushed, and the second dustproof member 5 also exerts a restoring force in a direction such that the detector 3 is pushed. Even if the tip portion of the first dustproof member 4 or the tip portion of the second dustproof member 5 attempts to be pivotally deformed in the negative Y-axis direction to change the state of the second projecting portion 4d of the first dustproof member 4 and the detector 3 or the state of the second projecting portion 5d of the second dustproof member 5 and the detector 3 from the closed state to an open state, the first dustproof member 4 or the second dustproof member 5 is restrained by the restoring force thereof.Therefore, dust or the like can be prevented from entering the frame 1.

[0056] When the first dustproof member 4 and the second dustproof member 5 are held in the warped state as described above, the first projecting portions 4c of the first dustproof member 4 contact the first fitting recess 1b1 of the frame 1, and the first projecting portions 5c of the second dustproof member 5 contact the second fitting recess 1b2 of the frame 1.

[0057] Thus, a gap between the base portion 4a of the first dustproof member 4 and the first fitting recess 1b1 of the frame 1, as well as a gap between the base portion 5a of the second dustproof member 5 and the second fitting recess 1b2 of the frame 1, are continuously closed in the X-axis direction. Therefore, dust and the like can be prevented from entering the frame 1 through the gaps.

[0058] Preferably, each of the first protruding portions 4c of the first dustproof member 4 and the first protruding portions 5c of the second dustproof member 5 includes a curved portion (having an arc-like shape) when viewed in the X-axis direction. Preferably, the curved portion is formed over the entirety of each of the first protruding portions 4c of the first dustproof member 4 and the first protruding portions 5c of the second dustproof member 5 in the X-axis direction.

[0059] In the present embodiment, each of the first protruding portions 4c of the first dustproof member 4 and the first protruding portions 5c of the second dustproof member 5 has a substantially semicircular shape when viewed in the X-axis direction. When the first protruding portions 4c of the first dustproof member 4 contact the first fitting recess 1b1 of the frame 1 and when the first protruding portions 5c of the second dustproof member 5 contact the second fitting recess 1b2 of the frame 1, the first protruding portions 4c and 5c are easily deformed due to stress concentration.Furthermore, the contact area between the first protruding portions 4c of the first dustproof member 4 and the first fitting recess 1b1 of the frame 1 and the contact area between the first protruding portions 5c of the second dustproof member 5 and the second fitting recess 1b2 of the frame 1 can be increased. Therefore, dust and the like can be more reliably prevented from entering the frame 1.

[0060] Preferably, one of the first protruding portions 4c of the first dustproof member 4 protrudes from a surface of the base portion 4a of the first dustproof member 4 facing the negative Y-axis direction. Similarly, one of the first protruding portions 5c of the second dustproof member 5 protrudes from a surface of the base portion 5a of the second dustproof member 5 facing the negative Y-axis direction. In this case, the intrusion of dust and the like can be prevented at a position farther from the inside of the frame 1, so that dust and the like are less likely to intrude into the inside of the frame 1.

[0061] The number of first protruding portions 4c of the first dustproof member 4 may be one or more. Preferably, a plurality of the first protruding portions 4c are formed at the base portion 4a of the first dustproof member 4. Similarly, the number of first protruding portions 5c of the second dustproof member 5 may be one or more. Preferably, a plurality of the first protruding portions 5c are formed at the base portion 5a of the second dustproof member 5. In this case, the intrusion of dust and the like into the frame 1 at a plurality of positions can be prevented.

[0062] In the present embodiment, two first protruding portions 4c are formed on the base portion 4c of the first dustproof member 4, and two first protruding portions 5c are formed on the base portion 5a of the second dustproof member 5. More specifically, the two first protruding portions 4c of the first dustproof member 4 are formed on a part of a surface of the base portion 4a facing in the positive Y-axis direction, the part being farther from the opening 1a, and on a part of a surface of the base portion 4a facing in the negative Y-axis direction, the part being closer to the opening 1a, respectively, so as to be substantially symmetrical with respect to a line passing through the rotation center of the base portion 4a of the first dustproof member 4 and extending in the X-axis direction.

[0063] The two first projecting portions 5c of the second dustproof member 5 are formed on a part of a surface of the base portion 5a facing in the positive Y-axis direction, the part being farther from the opening 1a, and on a part of a surface of the base portion 5a facing in the negative Y-axis direction, the part being closer to the opening 1a, so as to be substantially symmetrical with respect to a line passing through the rotation center of the base portion 5a of the second dustproof member 5 and extending in the X-axis direction.

[0064] Thus, the rotational diameters of the base portion 4a of the first dustproof member 4 and the base portion 5a of the second dustproof member 5 can be increased, and therefore the first protruding portions 4c and 5c can be deformed to a greater extent. As a result, dust and the like can be more reliably prevented from entering the frame 1.

[0065] Preferably, each of the second protruding portion 4d of the first dustproof member 4 and the second protruding portion 5d of the second dustproof member 5 has a curved portion (having an arc-like shape) when viewed in the X-axis direction. Preferably, the curved portion is formed over substantially the entirety of each of the second protruding portion 4d of the first dustproof member 4 and the second protruding portion 5d of the second dustproof member 5 in the X-axis direction.

[0066] In the present embodiment, each of the second protruding portion 4d of the first dustproof member 4 and the second protruding portion 5d of the second dustproof member 5 has a substantially semicircular shape when viewed in the X-axis direction. When the second protruding portions 4d and 5d contact the detector 3, the second protruding portions 4d and 5d are easily deformed due to stress concentration, and the contact area between the detector 3 and each of the second protruding portions 4d and 5d can be increased. Therefore, the intrusion of dust and the like into the frame 1 can be more reliably prevented.

[0067] Preferably, the second projecting portions 4d and 5d are formed so that the tip portion of the first dustproof member 4 and the tip portion of the second dustproof member 5 contact the detector 3 when the second projecting portion 4d of the first dustproof member 4 and the second projecting portion 5d of the second dustproof member 5 contact the detector 3 and are deformed.

[0068] In this case, preferably, at least parts of the tip portions of the first dustproof member 4 and the second dustproof member 5 near the positions where the tip portions contact the detector 3 each include a curved portion (arc-like portion) when viewed in the X-axis direction. In the present embodiment, the tip portion of the first dustproof member 4 and the tip portion of the second dustproof member 5 each have a substantially semicircular shape when viewed in the X-axis direction.

[0069] When the tip portion of the first dustproof member 4 and the tip portion of the second dustproof member 5 contact the detector 3, the tip portions are easily deformed due to stress concentration, and therefore, the contact area between the detector 3 and the tip portion of each of the first dustproof member 4 and the second dustproof member 5 can be increased. Furthermore, the intrusion of dust and the like into the frame 1 can be prevented in two steps: contact between the detector 3 and the tip portion of each of the first dustproof member 4 and the second dustproof member, and contact between the detector 3 and each of the second projecting portions 4d and 5d. Second embodiment

[0070] Fig. 5 is an enlarged view showing a region near a first fitting recess of a frame of a dustproof structure according to a second embodiment. Since the dustproof structure of the present embodiment is substantially similar to that of the first embodiment, redundant description will be omitted, and the same elements will be denoted by the same reference numerals.

[0071] In the dustproof structure of the first embodiment, the first projecting portions are formed on each of the first dustproof member 4 and the second dustproof member 5. As shown in Fig. 5, protruding portions 1e may be formed in the first fitting recess 1b1 of the frame 1. The protruding portions 1e contact the base portion 4a of the first dustproof member 4 when the first dustproof member 4 is distorted to close the opening 1a of the frame 1 together with the second dustproof member 5. Thus, with the dustproof structure of the first embodiment, dust and the like can be prevented from entering the frame 1.

[0072] Although only a region near the first pass recess 1b1 in Fig. 5, projecting portions are also formed in the second fitting recess 1b2, and the projecting portions contact the base portion 5a of the second dustproof member 5 in a distorted state.

[0073] Although in Fig.5, two protruding portions 1e are formed, the number of protruding portions is not limited and may be one or more than one. The dustproof structure of the second embodiment and the dustproof structure of the first embodiment can be used in combination.

[0074] The present invention is not limited to the embodiments described above, and suitable modifications are possible within the scope of the present invention.

[0075] In the first embodiment, the first protruding portions 4c and 5c are formed integrally with the base portions 4a and 5a and other members of the same material. However, the first protruding portions 4c and 5c and the base portions 4a and 5a may be made of different materials. In this case, the first protruding portions 4c and 5c are preferably made of a material that is more easily deformable than that of the base portions 4a and 5a.

[0076] In the first embodiment, the second protruding portions 4d and 5d are formed integrally with the base portions 4a and 5a and other members from the same material. However, the second protruding portions 4d and 5d and the base portions 4a and 5a may be made of different materials. In this case, the second protruding portions 4d and 5d are preferably also made of a material that is more easily deformable than that of the base portions 4a and 5a.

[0077] Accordingly, a linear encoder is described including a scale 2; a frame 1 in which the scale 2 is held, the frame 1 having an opening 1a extending in a longitudinal direction of the frame 1; and a pair of elongated dustproof members 4, 5 arranged to face each other in the opening 1a. At least a part of each dustproof member 4, 5 is elastically deformable. Each dustproof member 4, 5 includes a first end portion 4a, 5a in a transverse direction of the dustproof member 4, 5, a first projecting portion 4c, 5c arranged at the first end portion 4a, 5a, and a second end portion in the transverse direction. The opening 1a has a pair of fitting recesses 1b1, 1b2 formed therein.The first end portion 4a, 5a of each dustproof member is fitted into a corresponding one of the fitting recesses 1b1, 1b2, and the first projecting portion 4c, 5c contacts the corresponding one of the fitting recesses 1b1, 1b2.

Claims

[1] Linear encoder comprising a scale (2) and a frame (1) in which the scale (2) is held, wherein the linear encoder characterized by is that the frame (1) has an opening (1a) extending in a longitudinal direction of the frame (1), the linear encoder includes a pair of elongated dustproof members (4, 5) arranged to face each other in the opening (1a), at least a part of each dustproof member (4, 5) being elastically deformable, each dustproof member (4, 5) including a first end portion (4a, 5a) in a transverse direction of the dustproof member (4, 5), a first projecting portion (4c, 5c) disposed at the first end portion (4a, 5a), and a second end portion in the transverse direction, the opening (1a) having a pair of fitting recesses (1b1, 1b2) formed therein, the first end portion (4a, 5a) of each dustproof member (4, 5) is fitted into a corresponding one of the fitting recesses (1b1, 1b2), the first end portion (4a, 5a) of each dustproof member (4, 5) is adapted to rotate in the fitting recess (1b1, 1b2) when the second end portion of the dustproof member (4, 5) is pivotally deformed in the transverse direction, and the first projecting portion (4c, 5c) contacts the corresponding one of the fitting recesses (1b1, 1b2) in a state in which the first end portion (4a, 5a) of each dustproof member (4, 5) is rotated. [2] Linear encoder comprising a scale (2) and a frame (1) in which the scale (2) is held, wherein the linear encoder characterized by is that the frame (1) has an opening (1a) extending in a longitudinal direction of the frame (1), the linear encoder includes a pair of elongated dustproof members (4, 5) arranged to face each other in the opening (1a), at least a part of each dustproof member (4, 5) being elastically deformable, each dustproof member (4, 5) including a first end portion (4a, 5a) in a transverse direction of the dustproof member (4, 5), and a second end portion in the transverse direction, the opening (1a) having a pair of fitting recesses (1b1, 1b2) formed therein, and each fitting recess having a second projecting portion (1e) formed therein, the first end portion (4a, 5a) of each dustproof member (4, 5) is fitted into a corresponding one of the fitting recesses (1b1, 1b2), the first end portion (4a, 5a) of each dustproof member (4, 5) is adapted to rotate in the fitting recess (1b1, 1b2) when the second end portion of the dustproof member (4, 5) is pivotally deformed in the transverse direction, and the first end portion (4a, 5a) contacts the second projecting portion (1e) in a state in which the first end portion (4a, 5a) of each dustproof member (4, 5) is rotated. [3] A linear encoder according to claim 1, wherein the first projecting portion (4c, 5c) has an arc-like cross-sectional shape. [4] A linear encoder according to claim 2, wherein the second projecting portion (1e) has an arc-like cross-sectional shape. [5] A linear encoder according to claim 1 or 3, wherein a pair of first projecting portions (4c, 5c) are arranged on both surfaces of the first end portion (4a, 5a) of each dustproof member. [6] A linear encoder according to claim 2 or 4, wherein a pair of said second projecting portions (1e) are arranged on surfaces of each fitting recess facing both surfaces of the first end portion (4a, 5a) of each dustproof member. [7] A linear encoder according to any one of the preceding claims, wherein each dustproof member (4, 5) further includes a third projecting portion (4d, 5d) disposed at the second end portion, the third projecting portion having an arc-like cross-sectional shape. [8] A linear encoder according to any one of the preceding claims, wherein one end of the second end portion of each dustproof member (4, 5) has an arcuate cross-sectional shape.

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