Optical encoder unit and optical encoder

Abstract

To provide an optical encoder unit which can suppress the adhesion of lubricant to an optical scale, so as to be able to prevent failure such as an error of reading the optical scale.SOLUTION: An optical encoder unit includes: a shaft connected to a rotary machine; an optical scale fixed to an end surface of the shaft; an optical sensor unit for receiving incident light as a light source beam from a light source, which is transmitted or reflected by the optical scale so as to enter the optical sensor unit; and two bearings which align in an axial direction so as to rotatably support the shaft. The bearing on the optical scale side among the two bearings has a holder opening at the optical scale side.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an optical encoder unit and an optical encoder that detects an angle using an optical scale. [Background technology]

[0002] Servo motors used in robots and the like are equipped with optical encoders to detect rotation angles and positions. One known optical encoder unit is described in Patent Document 1. Specifically, as shown in FIG. 2, an optical encoder unit 31 includes a rotor 10 having a shaft 12 connected to a rotating machine such as a motor, a stator 20, and an optical sensor unit 35 capable of reading signal patterns.

[0003] The rotor 10 is made of silicon, glass, a polymer material, or the like, and has a disk-shaped or polygonal optical scale 11. One surface of the optical scale 11 has a signal track. A shaft 12 is attached to the surface of the rotor 10 opposite the surface to which the optical scale 11 is attached.

[0004] The stator 20 includes a cylindrical cover 21 made of a light-blocking material, and a sensor board 23. The cylindrical cover 21 covers the side surface of the sensor board 23 and surrounds the bearing 26, the shaft 12, the optical scale 11, and the optical sensor unit 35.

[0005] The cover 21 rotatably supports the shaft 12 via a bearing 26. The inner periphery of the cover 21 is fixed to the outer ring of the bearing 26, and the outer periphery of the shaft 12 is fixed to the inner ring of the bearing 26.

[0006] When the shaft 12 rotates due to rotation from a rotating machine such as a motor, the optical scale 11 rotates around the center of rotation in conjunction with the shaft 12, and the signal tracks of the optical scale 11 move relative to the optical sensor unit 35. The optical sensor unit 35 is fixed to the sensor substrate 23.

[0007] The optical encoder unit 31 has a connector CNT, which is an input / output terminal, fixed to the flexible substrate 23FP. The connector CNT supplies power to conductive wiring provided on the surface or inside of the flexible substrate 23FP, and can output a detection signal from the optical sensor unit 35 to the outside via a preamplifier AMP.

[0008] Wiring and circuits connected to the wiring 25 are laid on the surface and inside the sensor substrate 23, and one end of a wiring 24 provided along the inside of the cover 21 is electrically connected to the wiring 25 directly or via wiring and circuits connected to the wiring 25. Therefore, the conductive wiring 25 provided on the surface or inside the sensor substrate 23 and the wiring 24 provided along the inside of the cover 21 appropriately connect the connector CNT, the preamplifier AMP, the optical sensor unit 35, and the light source 41.

[0009] The optical scale 11 has a polarizer with a predetermined in-plane polarization direction, which changes with rotation of the shaft 12. The optical sensor unit 35 receives incident light (transmitted light) that is emitted from a light source 41 and passes through the optical scale 11, and can read the signal tracks of the optical scale 11. A light source 41, such as a light-emitting diode or a semiconductor laser light source, is fixed to the surface of the light source substrate 42.

[0010] 3, the optical encoder 2 includes an optical encoder unit 31, a calculation device 3, and a control unit 5 such as an actuator. The calculation device 3 is a computer such as a personal computer, and includes an input interface 4a, an output interface 4b, a CPU 4c, a ROM 4d, a RAM 4e, and an internal storage device 4f. The optical encoder unit 31 detects, by the optical sensor unit 35 , incident light 73 that is incident on the optical scale 11 after the light source light 71 has passed through it. The calculation device 3 receives the detection signal from the optical sensor unit 35, calculates the relative position between the rotor 10 of the optical encoder unit 31 and the optical sensor unit 35, and outputs the relative position information as a control signal to the control unit 5 of a rotating machine such as a motor or other actuator. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Patent No. 6658850 Summary of the Invention [Problem to be solved by the invention]

[0012] However, since the bearings in such optical encoders use lubricants such as grease or oil, if the lubricant leaks and adheres to the optical scale, problems such as reading errors may occur. However, Cited Document 1 does not recognize this problem.

[0013] The present invention has been made in consideration of the above-mentioned problems, and aims to provide an optical encoder unit that can suppress adhesion of lubricant to the optical scale and prevent problems such as reading errors of the optical scale. [Means for solving the problem]

[0014] The above object of the present invention can be achieved by the following configuration [1] or [2].

[0015] [1] A shaft coupled to a rotating machine; an optical scale fixed to an end surface of the shaft; an optical sensor unit that receives incident light that is emitted from a light source and transmitted through or reflected by the optical scale; two bearings arranged in the axial direction and rotatably supporting the shaft; An optical encoder unit comprising: Of the two bearings, the bearing on the optical scale side has an inner ring, an outer ring, rolling elements arranged between the inner ring and the outer ring, sealing members that seal both axial ends of the bearing, and a retainer that has an opening that opens to the optical scale side of the rolling elements and a back portion that closes the side of the rolling elements opposite the optical scale side, an optical encoder unit. [2] The optical encoder unit according to [1]; and a calculation means for calculating a relative movement amount between the optical scale and the optical sensor unit from the light intensity detected by the optical sensor unit. [Effects of the Invention]

[0016] According to the optical encoder unit of the present invention, the bearing on the optical scale side has a retainer that opens to the optical scale side, thereby preventing adhesion of lubricant to the optical scale and preventing problems such as reading errors of the optical scale. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a cross-sectional view showing a rotation mechanism of an optical scale in an optical encoder unit according to this embodiment. [Figure 2] FIG. 2 is a diagram showing the configuration of a conventional optical encoder unit. [Figure 3] FIG. 3 is a block diagram of a conventional optical encoder. DETAILED DESCRIPTION OF THE INVENTION

[0018] An optical encoder unit according to an embodiment of the present invention will be described below. Note that, of the optical encoder unit, the following description will focus on the rotation mechanism of the optical scale of this embodiment, and other configurations will be the same as those of the conventional optical encoder unit and optical encoder in Figures 2 and 3, and descriptions thereof will be omitted or simplified. Therefore, in Figure 1, the light source and the optical sensor unit 35 that receives incident light that is incident on the optical scale 11 after being transmitted through or reflected from the light source are omitted from the optical encoder unit 31. This optical encoder unit 31 is mounted on, for example, a robot body including a robot arm (not shown). The robot arm has a number of joints according to the required tasks and operations, and an actuator such as a motor and the optical encoder unit 31 are provided corresponding to each joint. This enables precise control of the robot arm.

[0019] 1, in the optical encoder unit 31, a hollow shaft 12 connected to a shaft portion 1 of a rotating machine such as a motor is rotatably supported by a cylindrical cover 21 via two bearings 26A and 26B. An optical scale 11 is fixed to the upper end surface of the shaft 12. That is, in this embodiment, the optical scale 11 is disposed above the shaft portion 1 with respect to the shaft 12.

[0020] Both of the two bearings 26A, 26B are deep groove ball bearings, and have an outer ring 50 fitted inside the cover 21, an inner ring 51 fitted outside the shaft 12, balls 52 which are rolling elements arranged between the outer ring 50 and the inner ring 51, a crown-shaped cage 53 which holds the balls 52 so that they can roll freely, and a pair of sealing members 54 attached to both axial ends of the outer ring 50.

[0021] A preload is applied to the two bearings 26A, 26B by a spacer 55 provided between the optical scale 11 and the inner ring 51 of bearing 26A, an inward annular protrusion 56 formed on the inner surface of the cover 21 and positioned between the outer rings 50 of the two bearings 26A, 26B, and a positioning member 57 fixed to the shaft 12 and abutting the end face of the inner ring 51 of bearing 26B.

[0022] Here, the crown-shaped cage 53 of the bearing 26A on the optical scale side has an opening 53b that opens to the optical scale side, and a circular ring portion 53a that is a back surface portion that closes the side opposite the optical scale 11. According to this configuration, it is possible to efficiently prevent grease leaking from the bearing 26A from adhering to the optical scale during low-speed rotation. More specifically, in the crown-type cage 53, the space between the annular portion 53a and the seal member 54 is narrower than the space between the opening 53b and the seal member 54. Therefore, particularly during low-speed rotation, the grease is more likely to leak from the bearing 26A due to shearing between the seal member 54 and the cage 53. In response to this, by arranging the annular portion 53a of the crown-type cage 53 on the side farther from the optical scale 11, it is possible to prevent the grease leaking from the bearing 26A from adhering to the optical scale 11. The crown-shaped cage 53 of the bearing 26B on the motor shaft side also holds the balls 52 with the optical scale side open.

[0023] The present invention is not limited to the above-described embodiments, and can be modified, improved, etc. as appropriate. Furthermore, the embodiments and modifications described in this specification can be combined and applied within the scope of feasibility.

[0024] As described above, the present specification discloses the following: (1) a shaft connected to a rotating machine; an optical scale fixed to an end surface of the shaft; an optical sensor unit that receives incident light that is emitted from a light source and transmitted through or reflected by the optical scale; two bearings arranged in the axial direction and rotatably supporting the shaft; An optical encoder unit comprising: Of the two bearings, the bearing on the optical scale side has an inner ring, an outer ring, rolling elements arranged between the inner ring and the outer ring, sealing members that seal both axial ends of the bearing, and a retainer that has an opening that opens to the optical scale side of the rolling elements and a back portion that closes the side of the rolling elements opposite the optical scale side, an optical encoder unit. According to this configuration, the bearing on the optical scale side has a retainer that opens to the optical scale side, which prevents the adhesion of lubricant to the optical scale and prevents problems such as reading errors of the optical scale.

[0025] (2) The two bearings are deep groove ball bearings, The optical encoder unit according to (1), wherein the holder is a crown-type holder. According to this configuration, an axial load can be applied to the bearing, so that the optical scale can be disposed above the shaft in the vertical direction, preventing grease leakage and reducing friction torque.

[0026] (3) The optical encoder unit according to (1) or (2), and a calculation means for calculating a relative movement amount between the optical scale and the optical sensor unit from the light intensity detected by the optical sensor unit. This configuration can prevent an optical encoder used in any actuator from becoming inoperable due to a malfunction caused by grease leakage. [Explanation of symbols]

[0027] 1 Shaft 2 Optical Encoder 3 Arithmetic device (arithmetic means) 11 Optical scale 12 shafts 21 Cover 26A, 26B deep groove ball bearings (bearings) 31 Optical Encoder Unit 35 Optical sensor unit 50 outer ring 51 Inner circle 52 ball (rolling element) 53 Crown type cage (cage) 53a Circular part (back part) 53b opening 54 Sealing material 55 spacer 56 Annular convex part 57 Positioning member

Claims

1. a shaft coupled to the rotating machine; an optical scale fixed to an end surface of the shaft; an optical sensor unit that receives incident light that is emitted from a light source and transmitted through or reflected by the optical scale; two bearings arranged in the axial direction and rotatably supporting the shaft; An optical encoder unit comprising: An optical encoder unit, wherein of the two bearings, the bearing on the optical scale side has an inner ring, an outer ring, rolling elements arranged between the inner ring and the outer ring, sealing members that seal both axial ends of the bearing, and a retainer that has an opening that opens to the optical scale side of the rolling elements and a back portion that closes the side of the rolling elements opposite the optical scale side.

2. The two bearings are deep groove ball bearings, 2. The optical encoder unit according to claim 1, wherein the holder is a crown-type holder.

3. The optical encoder unit according to claim 1 or 2; and a calculation means for calculating a relative movement amount between the optical scale and the optical sensor unit from the light intensity detected by the optical sensor unit.

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