rotary encoder

Abstract

To provide a rotary encoder that can surely prevent entrance of dust by preventing increase of the outer diameter.SOLUTION: A cylindrical body 11 has an opening part 11f. A shaft 12 is arranged in the opening part. Bearings 13, 14 are arranged in the body and hold the shaft rotatably. A seal member 20 is arranged in the body, the shaft penetrates through the center part, and the outer diameter is equal to the diameter of the bearings.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] An embodiment of the present invention relates to a rotary encoder that converts the mechanical displacement of a rotating shaft into an electrical signal. [Background technology]

[0002] A rotary encoder (hereinafter simply referred to as an encoder) converts the direction and angle of rotation of a rotating shaft (hereinafter simply referred to as a shaft) into an electrical signal and outputs the signal. Encoders are used in a variety of environments. For example, if an encoder is used continuously in a dusty environment, dust may get into the bearings that hold the shaft, such as ball bearings, and interfere with the rotation of the shaft. For this reason, technologies have been developed to prevent dust from getting into the bearings (see, for example, Patent Document 1 and Patent Document 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 11-37793 [Patent Document 2] JP2008-2977 Public Relations Summary of the Invention [Problem to be solved by the invention]

[0004] To prevent deterioration of the bearing's functionality, it is necessary to provide a seal member inside the encoder to prevent dust from entering. However, because encoders are required to be smaller, simply providing a seal member is not possible.

[0005] The embodiments of the present invention provide a rotary encoder that can prevent the outer diameter from increasing and reliably prevent dust from entering the bearing. [Means for solving the problem]

[0006] This embodiment is a rotary encoder that converts the mechanical displacement of a shaft into an electrical signal, the rotary encoder comprising: a cylindrical body having a first end and a second end in an axial direction and an opening at the first end; a shaft having a third end and a fourth end in the axial direction, the shaft being disposed within the opening along the axial direction, the third end being disposed from the opening to the outside of the body, and the fourth end being disposed within the second end; a bearing disposed within the body between the first end and the second end and rotatably holding the shaft; a seal member disposed within the body and having a fifth end and a sixth end in the axial direction, the shaft being disposed in a central portion thereof passing through the fifth end and the sixth end, the outer diameter of the fifth end being smaller than the outer diameter of the sixth end, the inner surface of the fifth end being in contact with the periphery of the shaft; and a seal member having a first surface and a second surface that are parallel to each other and an outer circumferential surface connecting the first surface and the second surface, the outer diameter of the sixth end being equal to the diameter of the bearing. a plurality of first protrusions disposed within the first end of the body and inside the opening, and in contact with the first surface of the sixth end of the seal member; and a plurality of second protrusions disposed within the first end of the body and inside the opening, and in contact with the second surface of the sixth end of the seal member. It is equipped with: [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a perspective view showing the appearance of a rotary encoder according to an embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view taken along line II-II in FIG. [Figure 3] Cross-sectional view along line III-III in Figure 1. [Figure 4] FIG. 4 is a cross-sectional view showing a seal member applied to the rotary encoder of the present embodiment. [Figure 5] FIG. 2 is a plan view showing the main body of the rotary encoder of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments will be described with reference to the drawings, in which the same parts are designated by the same reference numerals.

[0009] 1 to 3 show a rotary encoder 10 according to this embodiment. The rotary encoder 10 includes a cylindrical main body 11, a shaft 12 that is rotatable relative to the main body 11, two bearings 13 and 14 that hold the shaft 12, a coil spring 15, a disk 16, a holder 17, a printed circuit board 18, a washer 19, and a dustproof seal member 20.

[0010] The main body 11 has a first end 11a and a second end 11b in the axial direction (longitudinal direction), and a printed circuit board 18 is attached to the inside of the second end 11b. The main body 11 has a cylindrical body 11c inside. The cylindrical body 11c is arranged concentrically with the main body 11 and is connected to the main body 11 by a plurality of beams 11d. Two beams 11d arranged in the diameter direction are each provided with a screw hole 11e. The main body 11 can be attached to a device (not shown) by screwing a screw (not shown) into the screw hole 11e.

[0011] In this embodiment, the cylindrical body 11c is not necessarily required, and the cylindrical body 11c can be omitted by providing the screw hole 11e on the outside of the main body 11. In this case, the main body 11 functions in the same way as the cylindrical body 11c.

[0012] The shaft 12 is inserted into the cylindrical body 11c. That is, the main body 11 has an opening 11f of the cylindrical body 11c at the center of the plane of the first end 11a, and the shaft 12 is inserted into the opening 11f.

[0013] As shown in Figures 2 and 3, two bearings 13 and 14 and a coil spring 15 are arranged inside the cylindrical body 11c. The outer diameters of the bearings 13 and 14 are equal to the inner diameter of the cylindrical body 11c, and the outer diameter of the coil spring 15 is smaller than the inner diameter of the cylindrical body 11c. The bearings 13 and 14 may be, for example, ball bearings or oil-impregnated bearings. The bearing 13 is arranged on the first end 11a side of the main body 11, and the bearing 14 is arranged on the second end 11b side of the main body 11. The coil spring 15 is arranged between the bearings 13 and 14.

[0014] Shaft 12 is disposed through the center of bearings 13 and 14 and coil spring 15 and is rotatably held by bearings 13 and 14. Third end 12a of shaft 12 is located outside main body 11, and fourth end 12b of shaft 12 is located on the side of second end 11b of main body 11. Holder 17 is fixed to fourth end 12b of shaft 12. Bearing 13 is positioned inside cylindrical body 11c by washer 19 fixed on the side of third end 12a of shaft 12, and bearing 14 is positioned by holder 17. Specifically, bearing 13 is pressed against washer 19 by coil spring 15, and bearing 14 is pressed against holder 17 by coil spring 15.

[0015] The disk 16 is fixed to a holder 17 and rotated together with the shaft 12. The rotary encoder of this embodiment is, for example, an optical rotary encoder, and the disk 16 has, for example, a slit (not shown).

[0016] The printed circuit board 18 is disposed inside the main body 11 on the second end 11b side and closes the second end 11b. The printed circuit board 18 is equipped with, for example, a light receiving element (not shown) that constitutes a sensor together with the disc 16. The light emitting element (not shown) is disposed opposite the light receiving element with the disc 16 sandwiched between them. The light receiving element receives light from the light emitting element that passes through a slit as the disc 16 rotates. The printed circuit board 18 is equipped with a signal processing circuit (not shown), which lights up the light emitting element, processes the signal from the light receiving element, and converts the amount of rotation of the disc 16 into an electrical signal for output.

[0017] This embodiment is not limited to an optical rotary encoder, but may be a magnetic rotary encoder.

[0018] Furthermore, a dustproof seal member 20 is disposed inside the opening 11f inside the cylindrical body 11c. The seal member 20 is made of an elastic material, such as rubber. The seal member 20 is substantially annular, and the shaft 12 is inserted into the center portion.

[0019] As shown in FIG. 4, the seal member 20 has a fifth end 20a and a sixth end 20b in the axial direction. An opening 20c is provided in the center of the fifth end 20a and the sixth end 20b to allow the shaft 12 to pass through. The fifth end 20a of the seal member 20 has a substantially truncated cone cross section, with the opening 20c provided in the center. The diameter (outer diameter) D1 of the truncated cone bottom of the fifth end 20a is smaller than the diameter (outer diameter) D3 of the sixth end 20b. The sixth end 20b is substantially cylindrical and has a first surface (lower surface) 20d, a second surface (upper surface) 20e, and an outer peripheral surface 20f connecting the first surface 20d and the second surface 20e.

[0020] The shape of the seal member 20 will be further described. At the fifth end 20a, the diameter D1 of the bottom of the truncated cone is larger than the diameter D2 of the top of the truncated cone and smaller than the diameter D3 of the sixth end 20b. The diameter D3 of the sixth end 20b is equal to or slightly larger than the inner diameter of the cylindrical body 11c. In other words, the diameter D3 of the sixth end 20b is equal to or larger than the diameter of the bearings 13 and 14. Therefore, when the seal member 20 is disposed inside the cylindrical body 11c, the sixth end 20b side of the seal member 20 is pressed against the interior of the cylindrical body 11c. Therefore, there is no gap between the circumferential surface of the sixth end 20b and the inner surface of the cylindrical body 11c, which enhances the dustproof effect.

[0021] Furthermore, since the thickness T2 of the sixth end 20b is greater than the thickness T1 of the fifth end 20a, the contact area between the fifth end 20a and the inner surface of the cylindrical body 11c can be increased, thereby further improving the dustproof effect.

[0022] The inner diameter (opening) D4 of the fifth end 20a of the seal member 20 is approximately equal to the diameter of the shaft 12. Therefore, when the shaft 12 is inserted into the opening 20c of the seal member 20, there is almost no gap between the periphery of the shaft 12 and the inner surface of the opening 20c, which can improve the dustproof effect.

[0023] Furthermore, thickness T1 of fifth end 20a of seal member 20 is thinner than thickness T2 of sixth end 20b, and inner diameter D5 of sixth end 20b is larger than the diameter of shaft 12 (diameter D4 of opening 20c of fifth end 20a). Therefore, seal member 20 contacts shaft 12 only within the range of thickness T1 of fifth end 20a, and does not contact the inner surface of sixth end 20b. Therefore, the contact area between seal member 20 and shaft 12 is small, reducing the frictional force between seal member 20 and shaft 12 and improving the operability of shaft 12.

[0024] A pair of first protrusions 11g and a pair of second protrusions 11h that determine the axial position of the seal member 20 are provided inside the cylindrical body 11c. The number of first protrusions 11g and second protrusions 11h is not limited to one pair, and three or more of each may be provided. As shown in FIG. 3, the first protrusions 11g are provided at a position that holds a first surface (lower surface) 20d of the sixth end portion 20b of the seal member 20, and the second protrusions 11h are provided at a position that contacts a second surface (upper surface) 20e of the sixth end portion 20b of the seal member 20, as shown in FIG. 2. Therefore, the seal member 20 is held in place inside the cylindrical body 11c by the first protrusions 11g and the second protrusions 11h.

[0025] Furthermore, as shown in FIG. 5, the pair of first protrusions 11g and the pair of second protrusions 11h are arranged at different positions within the cylindrical body 11c and do not overlap with each other. That is, the pair of first protrusions 11g and the pair of second protrusions 11h are arranged within the opening 11f of the cylindrical body 11c, spaced apart by a distance L in the circumferential direction of the opening 11f. Therefore, when manufacturing the main body 11 including the cylindrical body 11c, for example, from resin, it is possible to manufacture it using a mold with a simple configuration. If the first protrusions 11g and the second protrusions 11h were arranged without any gaps around the entire circumference of the cylindrical body 11c, a mold with a slide mechanism would be required to manufacture the main body 11 including the cylindrical body 11c. This would increase manufacturing costs.

[0026] (Effects of the embodiment) According to this embodiment, a seal member 20 is provided on the shaft 12 held by the bearings 13 and 14. The seal member 20 includes a fifth end 20a and a sixth end 20b. The diameter D4 of the opening 20c of the fifth end 20a is equal to the diameter of the shaft 12, and the diameter (outer diameter) D3 of the sixth end 20b is equal to or greater than the inner diameter of the cylindrical body 11c in which the bearings 13 and 14 are disposed. This provides close contact between the shaft 12 and the fifth end 20a of the seal member 20, and between the sixth end 20b of the seal member 20 and the cylindrical body 11c. This reliably prevents dust from entering the bearings 13 and 14 through the opening 20c of the cylindrical body 11c, thereby achieving excellent dustproofing.

[0027] The thickness T2 of the sixth end 20b of the seal member 20 is greater than the thickness T1 of the fifth end 20a. This ensures a sufficient contact area between the seal member 20 and the inner surface of the cylindrical body 11c. This further enhances the effect of preventing dust from entering the bearings 13 and 14.

[0028] The diameter (outer diameter) D3 of the sixth end 20b of the seal member 20 is set equal to the diameter of the bearings 13, 14. Therefore, the distance between the pair of screw holes 11e arranged on the outside of the cylindrical body 11c can be determined by the diameter of the bearings 13, 14. This makes it possible to prevent the outer diameter of the rotary encoder from becoming too large. Note that, similarly to the above, it is also possible to prevent the outer diameter of the rotary encoder from becoming too large when the bearings 13, 14 and the seal member 20 are arranged directly inside the cylindrical main body 11 without using the cylindrical body 11c.

[0029] The thickness T1 of the fifth end 20a of the seal member 20 is thinner than the thickness T2 of the sixth end 20b, the inner diameter D4 of the fifth end 20a is equal to the diameter of the shaft 12, and the inner diameter D5 of the sixth end 20b is larger than the inner diameter D43 of the fifth end 20a. Therefore, the seal member 20 and the shaft 12 contact only within the range of the thickness T1 of the fifth end 20a, and do not contact the inner surface of the sixth end 20b. This reduces the contact area between the seal member 20 and the shaft 12, and reduces the frictional force between the seal member 20 and the shaft 12. This improves the operability of the shaft 12.

[0030] A pair of first protrusions 11g provided on the inner surface of the cylindrical body 11c contact a first surface (lower surface) 20d of the sixth end 20b of the sealing member 20, and a pair of second protrusions 11h contact a second surface (upper surface) 20e of the sixth end 20b of the sealing member 20, thereby holding the sealing member 20 from above and below. Therefore, no additional adhesive or fixing tool is required, and the number of assembly steps can be reduced.

[0031] The pair of first protrusions 11g and the pair of second protrusions 11h are arranged at different positions in the inner circumferential direction of the cylindrical body 11c, and further, the pair of first protrusions 11g and the pair of second protrusions 11h are provided at positions where they do not overlap with each other. Therefore, the main body 11 can be manufactured without using a complicated mold such as a slide mechanism, and manufacturing costs can be reduced.

[0032] Furthermore, the present invention is not limited to the above-described embodiments, and in the implementation stage, the components can be modified and embodied without departing from the spirit of the invention. Furthermore, various inventions can be formed by appropriately combining multiple components disclosed in the above-described embodiments. For example, some components may be omitted from all the components shown in the embodiments. Furthermore, components from different embodiments may be appropriately combined. [Explanation of symbols]

[0033] 10...rotary encoder, 11...main body, 11a...first end, 11b...second end, 11f...opening, 11g...first protrusion, 11h...second protrusion, 12...shaft, 12a...third end, 12b...fourth end, 13, 14...bearing, 16...disk, 18...printed circuit board, 20...sealing member, 20a...fifth end, 20b...sixth end, 20d...first surface, 20e...second surface.

Claims

1. A rotary encoder that converts a mechanical displacement of a shaft into an electrical signal, a cylindrical body having a first end and a second end in an axial direction, the first end having an opening; a shaft having a third end and a fourth end in the axial direction, the shaft being disposed within the opening along the axial direction, the third end being disposed from the opening to the outside of the body, and the fourth end being disposed within the second end; a bearing disposed within the body between the first end and the second end, the bearing rotatably holding the shaft; a seal member disposed inside the body, having a fifth end and a sixth end in the axial direction, the shaft disposed at a central portion thereof penetrating the fifth end and the sixth end, the outer diameter of the fifth end being smaller than the outer diameter of the sixth end, the inner surface of the fifth end being in contact with the periphery of the shaft, the sixth end having parallel first and second surfaces and an outer peripheral surface connecting the first and second surfaces, the outer diameter of the sixth end being equal to the diameter of the bearing; a plurality of first protrusions disposed within the first end of the body and inside the opening, the first protrusions contacting the first surface of the sixth end of the sealing member; a plurality of second protrusions disposed within the first end of the body and inside the opening, the second protrusions contacting the second surface of the sixth end of the sealing member; A rotary encoder comprising:

2. 2. The rotary encoder according to claim 1, wherein the inner surface of the fifth end of the seal member contacts the shaft, and the inner diameter of the sixth end is larger than the diameter of the shaft.

3. 3. The rotary encoder of claim 2, wherein the fifth end of the seal member is frustoconical and the sixth end is cylindrical.

4. A rotary encoder as described in claim 1, characterized in that the multiple first protrusions and the multiple second protrusions are arranged in positions that do not overlap each other in the direction around the axis.

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