ROTARY ENCODER

Abstract

A rotary encoder is incorporated in an annular space formed between a hollow rotating shaft and an encoder case. The rotary encoder has an annular printed wiring substrate, a plurality of mounting substrates that are outward from the printed wiring substrate in the radial direction and are arranged in the circumferential direction, and inter-substrate wiring cables bridged between the printed wiring substrate and each of the mounting substrates in the radial direction. Power supply to the mounting substrates and signal transmission and reception between the mounting substrates can be accomplished without routing around the wiring cables. It is possible to achieve a rotary encoder that is suitable for being incorporated in a narrow annular space.

Claims

1. A rotary encoder comprising: an encoder circuit substrate provided with a plurality of mounting substrates; an annular printed wiring substrate; and inter-substrate wiring cables that interconnect the printed wiring substrate and each of the mounting substrates, wherein the mounting substrates are positioned adjacent to the printed wiring substrate on a radially outer or inner side thereof, and are arranged along the printed wiring substrate in a circumferential direction thereof; the inter-substrate wiring cables are bridged in the radial direction between the printed wiring substrate and each of the mounting substrates; and the printed wiring substrate is provided with a wiring pattern for supplying power to each of the mounting substrates, and a wiring pattern for transferring signals between at least two of the mounting substrates.

2. The rotary encoder according to claim 1, wherein the mounting substrates is disposed on the radially outer side of the printed wiring substrate.

3. The rotary encoder according to claim 1, further comprising: a hollow rotating shaft; an encoder case that surrounds the hollow rotating shaft; and an annular space formed between the hollow rotating shaft and the encoder case, wherein the printed wiring substrate, the mounting substrate and the inter-substrate wiring cables are disposed in the annular space.

4. The rotary encoder according to claim 2, further comprising: a hollow rotating shaft; an encoder case that surrounds the hollow rotating shaft; and an annular space formed between the hollow rotating shaft and the encoder case, wherein the printed wiring substrate, the mounting substrate and the inter-substrate wiring cables are disposed in the annular space.

5. A motor comprising: a motor output shaft; and the rotary encoder according to claim 1 to detect rotational information of the motor output shaft.

6. The motor according to claim 5, wherein the mounting substrate is disposed on the radially outer side of the printed wiring substrate.

7. The motor according to claim 5, further comprising: a hollow rotating shaft; an encoder case that surrounds the hollow rotating shaft; and an annular space formed between the hollow rotating shaft and the encoder case, wherein the printed wiring substrate, the mounting substrate and the inter-substrate wiring cables are disposed in the annular space.

8. The motor according to claim 6, further comprising: a hollow rotating shaft; an encoder case that surrounds the hollow rotating shaft; and an annular space formed between the hollow rotating shaft and the encoder case, wherein the printed wiring substrate, the mounting substrate and the inter-substrate wiring cables are disposed in the annular space.

9. An actuator comprising: a motor; a reducer to reduce speed of output rotation of the motor; and the rotary encoder according to claim 1 to detect rotational information of an output shaft of the reducer.

10. The actuator according to claim 9, wherein the mounting substrate is disposed on the radially outer side of the printed wiring substrate.

11. The actuator according to claim 9, further comprising: a hollow rotating shaft; an encoder case that surrounds the hollow rotating shaft; and an annular space formed between the hollow rotating shaft and the encoder case, wherein the printed wiring substrate, the mounting substrate and the inter-substrate wiring cables are disposed in the annular space.

12. The actuator according to claim 10, further comprising: a hollow rotating shaft; an encoder case that surrounds the hollow rotating shaft; and an annular space formed between the hollow rotating shaft and the encoder case, wherein the printed wiring substrate, the mounting substrate and the inter-substrate wiring cables are disposed in the annular space.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] FIG. 1(a) is a schematic diagram showing a hollow motor provided with a rotary encoder to which the present invention is applied, and FIG. 1(b) is an illustrative diagram showing the arrangement state of mounting substrates, etc., of the rotary encoder;

[0021] FIG. 2 is an illustrative diagram showing the effect of the rotary encoder in FIG. 1; and

[0022] FIG. 3 is an illustrative diagram showing the arrangement state of mounting substrates of a prior-art rotary encoder.

MODE FOR CARRYING OUT THE INVENTION

[0023] A hollow motor provided with a rotary encoder according to embodiments of the present invention is described below with reference to the accompanying drawings.

[0024] FIG. 1(a) is a schematic diagram showing the hollow motor, and FIG. 1(b) is an illustrative diagram showing the arrangement state of an encoder substrate, etc., of the rotary encoder. The hollow motor 1 is provided with a cylindrical motor case 2. A hollow motor shaft 3 that extends through the center of the motor case 2 is disposed inside the motor case 2. The hollow motor shaft 3 is rotatably supported, at portions located to the front and rear along the direction of a central axis 1a, by the motor case 2 via bearings. A motor rotor (not shown) is attached to the hollow motor shaft 3, and a motor stator (not shown) is attached to the side of the motor case 2 in a state of coaxially surrounding the motor rotor.

[0025] A rotary encoder 10 is attached to the rear end of the motor case 2. The rotary encoder 10 is provided with a hollow rotating shaft 11 that is formed integrally with an axial end section of the hollow motor shaft 3, and a cup-shaped encoder case 12 that surrounds the hollow rotating shaft 11. A circular hollow section 14 that extends through a central portion of the motor in the direction of the central axis 1a is formed by the hollow motor shaft 3 and the hollow rotating shaft 11. Additionally, in the rotary encoder 10, an annular space 15 is formed between the hollow rotating shaft 11 and a cylindrical portion 12a of the encoder case 12. The constituent components of the rotary encoder 10 are incorporated into the annular space 15.

[0026] An actuator provided with the rotary encoder according to the present invention is configured such that, for example, a reducer 90 is assembled at the front portion of the hollow motor 1, as indicated by virtual lines in FIG. 1(a). For example, a strain wave gearing is used as the reducer 90. In the case of a hollow actuator, a hollow reducer provided with a hollow section 91 extending through the center thereof is used as the reducer 90. An actuator hollow section extending through the center of the actuator is formed by the hollow section 91 and the circular hollow section 14 of the hollow motor 1.

[0027] In the hollow motor 1, the rotary encoder 10 is, e.g., an absolute encoder provided with a magnetic encoder section 20 and an optical encoder section 30. The magnetic encoder section 20 is provided with a two-pole magnetized magnet ring 21 that is coaxially secured to the hollow rotating shaft 11, and a mounting substrate 22 (MT substrate) that is attached to the side of the encoder case 12. A magnetic sensor such as a Hall element, or another electronic component, is mounted on the mounting substrate 22. The optical encoder section 30 is provided with a slit disc 31 that is coaxially attached to the hollow rotating shaft 11, and a mounting substrate 32 (ST substrate) that is attached to the side of the encoder case 12. A light-emitting element, a light-receiving element, a control circuit component for these elements, etc., is mounted on the mounting substrate 32.

[0028] The rotary encoder 10 is additionally provided with: a mounting substrate 41 on which is mounted, for example, an electronic component constituting, inter alia, a signal processing circuit for processing detection signals obtained from the magnetic encoder section 20 and the optical encoder section 30; and a mounting substrate 42 on which is mounted, for example, an electronic component constituting, inter alia, an interface circuit that transmits and receives signals to and from an external unit.

[0029] The rotary encoder 10 is furthermore provided with: an annular printed wiring substrate 50 on which wiring patterns for interconnecting the mounting substrates 22, 32, 41, 42 are printed; and a terminal section 70 to which are connected four inter-substrate wiring cables 60 that interconnect the printed wiring substrate 50 and each of the mounting substrates 22, 32, 41, 42, a power-supply wiring cable 71 that is drawn in from the exterior and that is for supplying electric power, and a wiring cable 72 for outputting encoder signals. Power-supply wiring patterns for distributing externally supplied electric power to the mounting substrates 22, 32, 41, 42, and signal-transfer wiring patterns that transmit and receive signals to and from the mounting substrates 22, 32, 41, 42, are mounted on the annular printed wiring substrate 50.

[0030] The annular printed wiring substrate 50 is disposed in a state of coaxially surrounding the hollow rotating shaft 11. The mounting substrates 22, 32, 41, 42 are of an arcuate form that is suited to arrangement in the annular space 15, the mounting substrates 22, 32, 41, 42 being arranged at prescribed intervals in a circumferential direction on the outer peripheral side of the printed wiring substrate 50. The four mounting substrates 22, 32, 41, 42 and the one printed wiring substrate 50 are attached to substrate supports 80 that are attached to the encoder case 12.

[0031] In the printed wiring substrate 50, cable connectors 61 are mounted at locations respectively facing each of the mounting substrates 22, 32, 41, 42 in a state in which the cable connectors 61 face radially outward. Cable connectors 62 are mounted on the mounting substrates 22, 32, 41, 42 in a state in which the cable connectors 62 face radially inward. The inter-substrate wiring cables 60 are bridged in the radial direction between the cable connectors 61 of the printed wiring substrate 50 and the cable connectors 62 of the mounting substrates 22, 32, 41, 42.

[0032] In the rotary encoder 10 according to the present example, an A-phase signal and a B-phase signal are generated respectively on the basis of detection signals from the magnetic encoder section 20 and the optical encoder section 30. The absolute rotational position of the hollow motor shaft 3 within a single rotation, the number of rotations of the hollow motor shaft 3 from an origin-point position, etc., are calculated on the basis of these encoder signals.

[0033] The rotary encoder 10 according to the present example is provided with the plurality of mounting substrates 22, 32, 41, 42 (i.e., four mounting substrates) arranged in the circumferential direction, the annular printed wiring substrate 50 that is disposed on the radially inner side of the plurality of mounting substrates 22, 32, 41, 42, and the four inter-substrate wiring cables 60 interlinking the mounting substrates 22, 32, 41, 42 and the printed wiring substrate 50, these components being provided within the annular space 15. Unlike the prior-art case shown in FIG. 3, it is unnecessary for wiring cables for connecting the mounting substrates 22, 32, 41, 42 to be routed in the circumferential direction, and the mounting substrates are electrically interconnected via the annular printed wiring substrate 50.

[0034] For example, externally supplied electric power is distributed to the mounting substrates 22, 32, 41, 42 via the printed wiring substrate 50. The need for wiring cables for supplying electric power, etc., to the mounting substrates, and the need for a space for installation of such wiring cables, are both obviated. An operation for hard-wiring a plurality of divided substrates disposed in the narrow annular space 15 is facilitated, and any deterioration in the quality of signals transferred via long wiring cables can be minimized.

[0035] It is also unnecessary to ensure space for disposing cable connectors, wiring cables, etc., between adjacent mounting substrates 22, 32, 41, 42. Due to it being unnecessary to widen gaps between the adjacent divided substrates, a narrow annular space 15 can be effectively utilized.

[0036] Furthermore, the mounting substrates 22, 32, 41, 42 are wired to the annular printed wiring substrate 50 from the radially outer side. Because the cable connectors are to be attached to and detached from the printed wiring substrate and the divided substrates from the radial direction, the cable connectors are easily attached and detached.

[0037] In the case of a rotary encoder having the prior-art configuration shown in FIG. 3, it is necessary to specially design wiring cable lengths for each size of motor. Additionally, when the rotary encoder is applied to a small-sized motor, the degree of freedom in design decreases because it is necessary to design the rotary encoder in consideration of a mounting area for the cable connectors. Moreover, as a result of increases in cable length in a large-sized motor, the risk of deterioration in the quality of signals increases. However, the rotary encoder 10 according to the present example presents advantages in that the components thereof (divided substrates, printed wiring substrate, and inter-substrate wiring cables) can be standardized and in that production management is facilitated, irrespective of the size of the motor.

[0038] FIG. 2 is an illustrative diagram showing one example of a case in which the rotary encoder 10 is incorporated into a large-sized hollow motor provided with an annular space 15A having a larger diameter than in the case shown in FIG. 1. The mounting substrates 22, 32, 41, 42, the printed wiring substrate 50, and the inter-substrate wiring cables 60 can be used without modification. Even when the rotary encoder 10 is applied to a large-sized motor, it is possible to minimize the length of the wiring cables, and to satisfactorily maintain signal quality.

[0039] For example, when the mounting substrates 42, 32 are interconnected using a wiring cable, the wiring length could increase, as indicated by the dash-dotted line in FIG. 2. In the present example, because the substrates are connected via the annular printed wiring substrate 50 as indicated by the dashed line, the wiring length can be dramatically shortened.

Other Embodiments

[0040] Although a hollow motor provided with a rotary encoder to which the present invention is applied was described above, it shall be apparent that the rotary encoder according to the present invention can be applied in a similar manner to a hollow actuator provided with a hollow motor and a hollow strain wave gearing or other hollow gear drive.

[0041] Additionally, the rotary encoder 10 described above is provided with four mounting substrates as encoder substrates. The number of mounting substrates is not limited to four. Moreover, the mounting substrates are not limited to being of arcuate form.

[0042] Furthermore, in the example described above, the annular printed wiring substrate was disposed on the radially inner side relative to the mounting substrates. The printed wiring substrate can also be disposed on the radially outer side relative to the mounting substrates. Additionally, the printed wiring substrate can be disposed on the side of the mounting substrates, i.e., adjacent to the mounting substrates in the direction of the central axis of the encoder.