Optical encoder unit and optical encoder

Abstract

To provide an optical encoder unit capable of being reduced in size.SOLUTION: An optical encoder unit includes: a shaft connected to a rotary machine; an optical scale fixed to an upper 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 a double-row ball bearing in which one inner ring raceway surface is formed on an outer peripheral surface of the shaft and an inner ring having the other inner ring raceway surface externally engages with the outer peripheral surface of the shaft, and which includes an outer ring having a pair of outer ring raceway surfaces.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, with the trend toward smaller robots, there is a demand for smaller optical encoder units.

[0013] The present invention has been made in view of the above-mentioned problems, and has an object to provide an optical encoder unit that can be made smaller. [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 upper 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; a double-row ball bearing having an outer ring fitted with an inner ring having one inner ring raceway surface formed on the outer peripheral surface of the shaft and the other inner ring raceway surface formed on the outer peripheral surface of the shaft, and an outer ring having a pair of outer ring raceway surfaces; An optical encoder unit comprising: [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 present invention, the optical encoder unit can be configured more compactly. [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 a double-row ball bearing 26. 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] The double-row ball bearing 26 has a single outer ring 50 fitted inside the cover 21, balls 52A, 52B arranged in two rows, one above the other, along the shaft 12 extending in the vertical direction, a lower inner ring 51 fitted outside the shaft 12 and against which the lower ball 52B abuts, a pair of upper and lower crown-type cages 53A, 53B that hold the balls 52A, 52B so that they can roll freely, a pair of upper and lower sealing members 54A, 54B attached to both axial ends of the outer ring 50, and a positioning member 55 that abuts against the underside of the lower inner ring 51.

[0021] The outer ring 50 is formed with a pair of outer ring raceway surfaces 50a, 50b on which upper and lower balls 52A, 52B roll. The outer peripheral surface of the shaft 12 is formed with an inner ring raceway surface 12a on which the upper ball 52A rolls, a shoulder portion 12b located above the inner ring raceway surface 12a, and a fitting groove 12c which is a notched groove formed so that the lower inner ring 51A can fit into it. The lower inner ring 51 is formed with an inner ring raceway surface 51a on which the lower balls 52B roll, and a shoulder portion 51b located below the inner ring raceway surface 51a. The outer peripheral surface located below the inner ring raceway surface 12a of the shaft 12 is formed straight from the groove bottom. Also, the outer peripheral surface located above the inner ring raceway surface 51a of the lower inner ring 51 is formed straight from the groove bottom.

[0022] According to this configuration, the inner ring raceway surface 12a and the shoulder portion 12b are integrally molded on the shaft 12, thereby reducing the axial and radial dimensions of the bearing. Also, by making the outer ring 50 a single member on which the pair of outer ring raceway surfaces 50a, 50b are formed, the axial dimension of the bearing can be further reduced. This makes it possible to further reduce the size of the optical encoder unit 31.

[0023] 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 lower crown-shaped holder 53B also holds the lower ball 52B with its opening on the optical scale 11 side.

[0024] Next, the assembly process of the double row ball bearing 26 will be described. First, the upper balls 52A are inserted between the shaft 12, on which the inner ring raceway surface 12a and shoulder portion 12b are formed, and the outer ring 50. Next, an upper crown-type cage 53A is installed to support the underside of the upper balls 52A. Next, grease is injected from above the upper balls 52A. Next, a seal member 54A is installed at the upper end of the double-row ball bearing 26. Next, the lower balls 52B are inserted into the double-row ball bearing 26. Next, the lower inner ring 51A is inserted into the fitting groove 12c of the shaft 12 so as to support the lower balls 52B. A preload is applied to the lower inner ring 51A by pressing the lower inner ring 51A against the shaft 12 (fitting groove 12c) using a positioning member 55. At this time, grease is applied to the lower inner ring 51A in advance. Next, a lower crown-type cage 53B is installed so as to support the lower balls 52B. Next, a seal member 54B is installed at the lower end of the double-row ball bearing 26.

[0025] As described above, the lower inner ring 51A is later assembled, which facilitates assembly of the double-row ball bearing 26. It also facilitates adjustment of the preload (=adjustment of the bearing rigidity).

[0026] 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.

[0027] As described above, the present specification discloses the following: (1) a shaft connected to a rotating machine; an optical scale fixed to an upper 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; a double-row ball bearing having an outer ring fitted with an inner ring having one inner ring raceway surface formed on the outer peripheral surface of the shaft and the other inner ring raceway surface formed on the outer peripheral surface of the shaft, and an outer ring having a pair of outer ring raceway surfaces; An optical encoder unit comprising: According to this configuration, the bearing portion is compact in both the axial and radial directions, allowing the optical encoder unit to be made smaller.

[0028] (2) An optical encoder unit as described in (1), wherein the double-row ball bearing has multiple rows of balls arranged along the shaft and multiple retainers for holding the balls in each row, and the retainer on the optical scale side is open to the optical scale side. 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.

[0029] (3) The optical encoder unit according to (2), wherein the holder is a crown-type holder. This configuration prevents grease from leaking to the optical scale side, and reduces friction torque.

[0030] (4) An optical encoder unit according to any one of (1) to (3), 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]

[0031] 1 Shaft 2 Optical Encoder 3 Arithmetic device (arithmetic means) 11 Optical scale 12 shafts 12a Inner ring raceway surface 12b Shoulder 12c Fitting groove 21 Cover 26 Double row ball bearing (bearing) 31 Optical Encoder Unit 35 Optical sensor unit 50 outer ring 50a, 50b Outer ring raceway surface 51 Lower inner ring (inner ring) 51a Inner ring raceway surface 51b Shoulder 52A, 52B balls 53A, 53B Crown type cage 53a Annular part 53b opening 54A, 54B sealing members 55 Positioning member

Claims

1. a shaft coupled to the rotating machine; an optical scale fixed to an upper 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; a double-row ball bearing having an outer ring fitted with an inner ring having one inner ring raceway surface formed on the outer peripheral surface of the shaft and the other inner ring raceway surface formed on the outer peripheral surface of the shaft, and an outer ring having a pair of outer ring raceway surfaces; An optical encoder unit comprising:

2. The double-row ball bearing has a plurality of rows of balls arranged along the shaft and a plurality of cages for holding the balls in each row, The optical encoder unit according to claim 1 , wherein the holder on the optical scale side is open toward the optical scale side.

3. 3. The optical encoder unit according to claim 2, wherein the holder is a crown-type holder.

4. An optical encoder unit according to any one of claims 1 to 3; 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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