POSITION TRACKING SYSTEM AND ACTUATOR

Abstract

This position sensing system (1) comprises a primary encoder (15) that detects the position of a motor shaft (13) of a motor (10), a secondary encoder (25) that detects the position of an output shaft (23) of a reduction gear (20), and an additional reduction gear (30, 30') arranged between the output shaft (23) and the secondary encoder (25). The reduction ratio of the additional reduction gear is set such that a rotating disk (25A) for the secondary encoder is located within a single revolution of the entire range of motion of a machine equipped with the motor and the reduction gear.

Description

Technical area

[0001] The present invention relates to a position detection system and an actuator. State of the art

[0002] Actuators consist of a servomotor and a reduction gear connected to each other. A primary encoder is connected to a motor shaft of the servomotor to detect an absolute position within one revolution of the motor shaft and the total number of revolutions of the motor shaft. Similarly, a secondary encoder is connected to an output shaft of the reduction gear to detect an absolute position within one revolution of the output shaft and the total number of revolutions of the output shaft (see, for example, Japanese Unreviewed Patent Publication (Kokai) No. 2007-113932). The information detected by each encoder is stored in a memory.

[0003] In certain situations, such as when the servo motor stops and the reducer output shaft rotates by inertia, the total number of revolutions of the primary encoder can be determined from the absolute position information of the secondary encoder, as long as the reducer output shaft rotates within one revolution. In this case, any encoder can be used for continuous operation without the need for an additional battery.

[0004] PTL 1: Unexamined Japanese Patent Publication (Kokai) No. 2007-113932 Summary of the inventionTechnical problem

[0005] The actuator described above can be installed in a specific machine, such as a robot, that has a shaft that can rotate between ±360° and ±720° (between one and two revolutions). If the shaft rotates between one and two revolutions, an additional battery must be provided to continue using each encoder.

[0006] Therefore, an encoder is desirable that can be used over the entire range of motion of a shaft without an additional battery. Solution to the problem

[0007] According to a first aspect of the present disclosure, a position sensing system is provided, comprising a primary encoder for detecting a position of a motor shaft of a motor, a secondary encoder for detecting a position of an output shaft of a reduction gear coupled to the motor, and an additional reduction gear arranged between the output shaft of the reduction gear and the secondary encoder, wherein a reduction ratio of the additional reduction gear is set such that a rotating disk for the secondary encoder rotates within one revolution over the entire range of motion of a machine comprising the motor and the reduction gear.

[0008] Furthermore, according to another aspect, an actuator is provided which comprises a motor, a reduction gear coupled to the motor, a primary encoder for detecting a position of a motor shaft of the motor, a secondary encoder for detecting a position of an output shaft of the reduction gear, and an additional reduction gear arranged between the output shaft of the reduction gear and the secondary encoder, wherein a reduction ratio of the additional reduction gear is set such that a rotating disk for the secondary encoder rotates within one revolution over the entire range of motion of a machine which comprises the motor and the reduction gear.

[0009] The subject matter, features, and advantages of the present disclosure will become more apparent from the following description of the embodiments taken in conjunction with the accompanying drawings. Brief description of the drawings [ Fig. 1] Fig. 1 is a schematic side view of a position detection system based on a first embodiment of the present disclosure. [ Fig. 2] is a front view of the Fig. 1 shown additional reduction gear. [ Fig. 3] Fig. 3 is a schematic side view of a position detection system based on a second embodiment of the present disclosure. [ Fig. 4] Fig. 4 is a diagram showing an example of change of Fig. 3 shows. Description of the embodiments

[0010] The embodiments of the present disclosure are described below with reference to the accompanying drawings. In the drawings, similar components are provided with the same reference numerals. Fig. 1 is a schematic side view of a position detection system based on a first embodiment of the present disclosure. The position detection system 5 is installed in a machine 3 having a shaft, for example, a propeller shaft of a robot 3. Although the case where the position detection system 5 is installed in the robot 3 will be described below, the same applies to the case where the position detection system 5 is installed in another machine 3 having a shaft, for example, a machine tool.

[0011] In Fig. 1, an actuator 6 arranged in a link 1 comprises a motor 10, e.g., a servomotor, and a reduction gear 20 connected to a motor shaft portion 13 of the motor 10. The motor 10 includes a rotor 12 that rotates integrally with the motor shaft 13, and a stator 11 arranged to surround the rotor 12. The tip of an output shaft 23 of the reduction gear 20 is connected to a link 2. Thus, the actuator 6, consisting of the motor 10 and the reduction gear 20, rotates the link 2 relative to the link 1 within a predetermined operating range to control their positioning. The reduction ratio of the reduction gear 20 is, for example, 1:50.

[0012] The motor shaft 13 is, for example, a hollow shaft with a primary encoder 15 mounted at its rear end. The primary encoder 15 is, for example, an incremental encoder and outputs A-phase, B-phase, and Z-phase signals. The output signals are detected by a detection unit 16, which detects an absolute position PA1 within one revolution of the motor shaft 13 and a total number of revolutions PB1 of the motor shaft 13 using a known method. The detected information is stored in a memory 7, e.g., a volatile memory.

[0013] The output shaft 23 extends through the hollow motor shaft 13 toward the motor 10, and a rear end of the output shaft 23 is connected to a secondary encoder 25 via an additional reduction gear 30, which will be described later. The secondary encoder 25 is, for example, an incremental encoder and outputs A-phase, B-phase, and Z-phase signals. The output signals are detected by a detection unit 26, which detects an absolute position PA2 within one revolution of the output shaft 23 and a total number of revolutions PB2 of the output shaft 23 according to a known method. The detected information is stored in a memory 7, for example, a volatile memory. The primary encoder 15 and the secondary encoder 25 comprise, as is known, the respective rotating disks 15A, 25A.

[0014] The information stored in the memory 7 can be stored for a certain time thanks to a battery 8, e.g. a button battery or a capacitor. Fig. 1, the primary encoder 15 and the secondary encoder 25 are equipped with a common memory 7 and a common battery 8. However, the primary encoder 15 and the secondary encoder 25 may each have a separate memory and a separate battery.

[0015] The information stored in memory 7 is supplied to a controller 9 for controlling machine 3. Controller 9 may be an LSI attached to encoders 15 and 25. Based on the supplied information, controller 9 drives and controls motor 10 and performs a positioning operation to position link 2 at a target position relative to link 1. Furthermore, a built-in brake 50 provided on the outer surface of motor shaft 13 is activated in response to a command from controller 9 to decelerate motor shaft 13. In addition, controller 9 also serves to turn on primary encoder 15 and secondary encoder 25 during operation of machine 3 with links 1 and 2.

[0016] Fig. 2 is a front view of the Fig. 1. The additional reduction gear 30 of the first embodiment is a planetary gear. In this case, the additional reduction gear 30 can be manufactured at a relatively low cost. However, reduction gears other than planetary gears, such as a stress wave reduction gear or a cycloidal reduction gear, can also be used as the additional reduction gear 30.

[0017] The Fig. The additional reduction gear 30 shown in Fig. 2 comprises a sun gear 19 fixed to the rear end of the motor shaft 13, a plurality (e.g., four) planetary gears 32 meshing with the sun gear 19, an outer ring 31 surrounding the plurality of planetary gears 32, and a carrier 35 rotatably meshing with each central shaft of the plurality of planetary gears 32. As can be seen from Fig. 1, a shaft portion extending from the center of the support 35 is coaxial with the motor shaft 13 of the motor 10 and the output shaft 23 of the reduction gear 20 and is connected to the rotating disk 25A of the secondary encoder 25.

[0018] As from Fig. As can be seen in Figure 1, the additional reduction gear 30 is arranged between the output shaft 23 of the reduction gear 20 and the secondary encoder 25. The actuator 6, composed of the motor 10 and the reduction gear 20, can be arranged in a specific machine 3, e.g., a robot 3, with a shaft portion 23 that can rotate within a range of ±360° to ±720° (one revolution or more and two revolutions or less).

[0019] In this case, the reduction ratio of the additional reduction gear 30 is set so that the rotating disk 25A for the secondary encoder 25 rotates within one revolution over the entire travel range of the machine 3 with the motor 10 and the reduction gear 20.

[0020] In one embodiment, the outer diameter D1 of the sun gear 19 is 16 mm, and the inner diameter D2 of the outer ring 31 is 26 mm. The rotational speed of the output shaft 23 is equal to the rotational speed V1 of the sun gear 19, and the rotational speed V2 of the outer ring 31 is equal to the rotational speed of the rotating disk 25A of the secondary encoder 25. The rotational speed V2 of the outer ring 31 can therefore be expressed as D1 / D2 × V1 = 0.615 × V1.

[0021] If the additional reduction gear 30 is not present, the rotating disk 25A of the secondary encoder 25 also rotates ±540° (one revolution or more and two revolutions or less) when the machine 3 travels within a range of ±540° (±1.5 revolutions). In this case, the secondary encoder 25 cannot be used continuously.

[0022] However, in an embodiment in which the additional reduction gear 30 is provided, the ±540° range of motion of the machine 3 is converted to ±332° (=540 × 0.615), and thus the rotating disk 25A of the secondary encoder 25 rotates ±332°. In other words, due to the additional reduction gear 30, the rotating disk 25A of the secondary encoder 25 rotates within one revolution (within ±360°).

[0023] In other words, the outer diameter D1 of the sun gear 19 and the inner diameter of the outer ring 31 should be selected so that the following conditions (1) and (2) are met: ±360°×D1 / D2 is a value greater than ±zero, and ±720°×D1 / D2 is equal to or less than ±360°.

[0024] As long as these conditions are met, the secondary encoder 25 can be used continuously over the entire moving range of the output shaft 23 without requiring an additional battery, even when the shaft part 23 performs a rotational operation of one to two revolutions. Specifically, in one embodiment of the present disclosure, it is possible to provide a position detection system 5 that can be used continuously over the entire moving range of the output shaft 23 without requiring a battery, even when the shaft part 23 performs a rotational operation of ±360° to ±720° (one revolution or more and two revolutions or less). Note that the primary encoder 15 can also be used continuously over the entire moving range of the output shaft 23.

[0025] Preferably, the position detection system 5 is integrated into the joint shaft of the robot 3. The joint shaft of the robot 3 typically rotates between ±360° and ±720° (one revolution or more and two revolutions or less). Therefore, it is particularly advantageous in this case that the position detection system 5 can be operated continuously without a battery within the aforementioned rotational range of the joint shaft.

[0026] Fig. Figure 3 is a schematic side view of a position detection system according to a second embodiment of the present disclosure. The additional reduction gear 30' of the second embodiment is a combination of two spur gears and a two-stage gear. As shown in Fig. 3, the additional reduction gear 30' comprises a spur gear 39 which is fixed to the rear end of the motor shaft 13, a two-stage gear 35 with a gear 31 with a large diameter and a gear 32 with a small diameter, and a spur gear 29. As can be seen from Fig. 3, the spur gear 39 and the large diameter gear 31 of the two-stage gear 35 mesh with each other, and the small diameter gear 32 of the two-stage gear 35 and the spur gear 29 mesh with each other.

[0027] In Fig. 3, the secondary encoder 25 is arranged on the end face of the large diameter gear 31. The Fig. The secondary encoder 25 shown in Figure 3 thus detects the speed of the output shaft 23 reduced by the first reduction ratio.

[0028] Fig. 4 is a diagram showing an example of change of Fig. 3 shows. In Fig. 4, the same additional reduction gear 30' as described above is provided. The secondary encoder 25 is arranged on the end face of the spur gear 29. The Fig. The secondary encoder 25 shown in Figure 4 thus detects the speed of the output shaft 23 reduced by the first reduction ratio and the second reduction ratio.

[0029] In the second embodiment, the rotational speed of the output shaft 23 is reduced by the first reduction ratio between the spur gear 39 and the large-diameter gear 31 of the two-stage gear 35, and the rotational speed of the output shaft 23 is reduced by the second reduction ratio between the small-diameter gear 32 of the two-stage gear 35 and the spur gear 29. As described above, the reduction ratio of the additional reduction gear 30' (the product of the first reduction ratio and the second reduction ratio) is set so that the rotating disk 25A for the secondary encoder 25 rotates within one revolution over the entire range of motion of the machine 3 including the motor 10 and the reduction gear 20. It is understood that the same effects as described above are achieved. Aspects of this disclosure

[0030] According to a first aspect, a position detection system is provided comprising a primary encoder for detecting a position of a motor shaft of a motor, a secondary encoder for detecting a position of an output shaft of a reduction gear coupled to the motor, and an additional reduction gear arranged between the output shaft of the reduction gear and the secondary encoder, wherein a reduction ratio of the additional reduction gear is set such that a rotating disk for the secondary encoder rotates within one revolution over the entire range of motion of a machine comprising the motor and the reduction gear.

[0031] According to a second aspect, the additional reduction gear is a planetary gear, a stress wave reduction gear, a cycloidal reduction gear or a combination of a spur gear and a two-stage gear.

[0032] According to a third aspect, the position detection system in the first or second aspect is mounted on a robot.

[0033] According to a fourth aspect, an actuator is provided comprising a motor, a reduction gear coupled to the motor, a primary encoder for detecting a position of a motor shaft of the motor, a secondary encoder for detecting a position of an output shaft of the reduction gear, and an additional reduction gear arranged between the output shaft of the reduction gear and the secondary encoder, wherein a reduction ratio of the additional reduction gear is set such that a rotating disk for the secondary encoder rotates within one revolution over the entire range of motion of a machine comprising the motor and the reduction gear.

[0034] According to a fifth aspect, the additional reduction gear is a planetary gear, a stress wave reduction gear, a cycloidal reduction gear or a combination of a spur gear and a two-stage gear.

[0035] According to a sixth aspect, the actuator is mounted on a robot.

[0036] Although the embodiments of the present disclosure have been described in detail, the present disclosure is not limited to the individual embodiments described above. Various additions, replacements, changes, or partial deletions may be made to these embodiments within the spirit of the invention or within the scope of the idea and intent of the present invention, which can be understood from the contents described in the claims and their equivalents. For example, the order of each operation and the order of each method of the above-described embodiments are presented as examples and are not limited to them. The same applies when numerical values ​​or formulas are used in the description of the above-described embodiments.Furthermore, suitable combinations of some of the embodiments described above are included within the scope of the present disclosure. List of reference symbols 1, 2 connecting link 3 Machine (robot) 5 Position detection system 6 Actuator 7 storage 8 Battery 9 Control 10 Engine 11 Stator 12 Rotor 13 Motor shaft 15 primary encoder 16 Recording unit 20 reduction gears 23 Output shaft 25 secondary encoder 26 Recording unit 30, 30' additional reduction gear 50 built-in brake QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 2007-113932 [0002, 0004]

Claims

[1] Position detection system, comprising: a primary encoder for detecting a position of a motor shaft of a motor, a secondary encoder for detecting a position of an output shaft of a reduction gear coupled to the motor, and an additional reduction gear arranged between the output shaft of the reduction gear and the secondary encoder, wherein a reduction ratio of the additional reduction gear is set so that a rotating disk for the secondary encoder rotates within one revolution over the entire moving range of a machine comprising the motor and the reduction gear. [2] The position detecting system according to claim 1, wherein the additional reduction gear is a planetary gear, a stress wave reduction gear, a cycloidal reduction gear, or a combination of a spur gear and a two-stage gear. [3] A position detection system according to claim 1 or 2, wherein the position detection system is mounted on a robot. [4] Actuator comprising: an engine, a reduction gear coupled to the motor, a primary encoder for detecting a position of a motor shaft of the motor, a secondary encoder for detecting a position of an output shaft of the reduction gear, and an additional reduction gear arranged between the output shaft of the reduction gear and the secondary encoder, wherein a reduction ratio of the additional reduction gear is set such that a rotating disk for the secondary encoder rotates within one revolution over the entire movable range of a machine comprising the motor and the reduction gear. [5] Actuator according to claim 1, wherein the additional reduction gear is a planetary gear, a stress wave reduction gear, a cycloidal reduction gear or a combination of a spur gear and a two-stage gear. [6] Actuator according to claim 1 or 2, wherein the actuator is mounted on a robot.

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