Speed reducer, speed reducer system

Abstract

A reduction device capable of detecting a rotation reference position with high accuracy is provided. A reduction device (10) of an embodiment has a first gear (82), a second gear (71) that revolves around the axis of the first gear (82), a reduction portion (3) that reduces the rotation of the second gear (71), and a sensor (4) that measures a predetermined position of the second gear (71).

Description

[0001] This application claims priority to Japanese Patent Application No. 2024-209128, filed on November 29, 2024. The entire contents of that Japanese application are incorporated herein by reference. Technical Field

[0002] This invention relates to a speed reduction device and a speed reduction system. Background Technology

[0003] A speed reduction device is known to reduce the rotation of an input gear before outputting a speed reduction output. For example, Patent Document 1 describes an eccentric oscillating gear device comprising: an input gear that receives rotation from a drive device; a plurality of external teeth that oscillate and rotate due to the rotation of the input gear; internal teeth that mesh with the external teeth; and a first plate and a second plate disposed on the sides of the plurality of external teeth. The eccentric oscillating gear device reduces the rotation of the input gear before outputting a speed reduction output.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2016-205601

[0005] The performance characteristics of a speed reducer, such as rigidity or angular transmission error, change with the phase angle of its output component, i.e., its rotational position. To compensate for this, the inventors researched how to obtain the speed reducer's performance data in advance and use this data to correct for variations in the speed reducer's performance.

[0006] Here, when performance data such as rigidity or angular transmission error at each rotational position of the reducer is obtained in advance, using a specific rotational position of the reducer as a reference, if the reference position of the performance data shifts, the position used for correction using the performance data will also shift, making proper correction difficult. Patent Document 1 completely lacks a method for detecting specific rotational positions of the reducer, such as absolute angles, and its disclosure is insufficient from the viewpoint of being able to detect the reference position of rotation with high precision. Summary of the Invention

[0007] The present invention was made in view of the following problem, and its object is to provide a deceleration device that can detect the rotation reference position with higher accuracy.

[0008] To solve the above-mentioned problems, a speed reduction device according to one embodiment of the present invention includes: a first gear; a second gear that revolves around the axis of the first gear; a speed reduction unit that reduces the rotation of the second gear; and a sensor that measures a predetermined position of the second gear.

[0009] Another embodiment of the present invention is a speed reducer system. The system includes: the aforementioned speed reducer; a rotary supply device for supplying rotational energy to a first gear; and a control unit for controlling the rotary supply device, the control unit utilizing measurement results from sensors.

[0010] Furthermore, any combination of the above-mentioned constituent elements, or the substitution of the constituent elements of the present invention with each other in methods, systems, etc., is also effective as an embodiment of the present invention.

[0011] Invention Effects

[0012] According to the present invention, a deceleration device capable of detecting the position of a rotation reference with high precision can be provided. Attached Figure Description

[0013] Figure 1 This is a cross-sectional view schematically showing an example of a speed reducer system equipped with the speed reduction device according to the embodiment.

[0014] Figure 2 This is a diagram illustrating an example of angular transmission error in a speed reduction device.

[0015] Figure 3 It is shown Figure 1 A perspective view of an example of the second gear of a speed reduction device.

[0016] In the diagram: 3-reduction section, 4-sensor, 5-control section, 7-first reduction section, 8-rotary supply device, 10-reduction device, 14-external gear, 16-internal gear, 35-first bracket, 36-second bracket, 40-output component, 42-feature part, 43-protrusion, 71-second gear, 82-first gear, 100-reduction gear system. Detailed Implementation

[0017] Hereinafter, the present invention will be described with reference to the accompanying drawings and according to preferred embodiments. In the embodiments and modifications, the same or equivalent constituent elements and components are labeled with the same reference numerals, and repeated descriptions are omitted where appropriate. Furthermore, for ease of understanding, the dimensions of the components in each drawing are appropriately enlarged and reduced. Also, in each drawing, some components that are not important to the description of the embodiments are omitted.

[0018] Furthermore, terms containing ordinal numbers such as 1 and 2 are used to describe multiple constituent elements, but such terms are used only for the purpose of distinguishing one constituent element from other constituent elements, and the constituent elements are not limited by such terms.

[0019] [Implementation Method]

[0020] refer to Figures 1 to 3The speed reduction device 10 involved in the embodiment will be described. Figure 1 This is a schematic side sectional view showing a speed reducer system 100 equipped with a speed reduction device 10. The speed reducer system 100 includes a speed reduction device 10, a rotary supply device 8, and a control unit 5. The speed reduction device 10 includes a first speed reduction unit 7, a speed reduction unit 3, and a sensor 4 for reducing the input rotation.

[0021] The first deceleration unit 7 in this embodiment includes a second gear 71, which is a spur gear. A sensor 4 measures a predetermined position of the second gear 71. The sensor 4 in this embodiment detects a feature 42 located on the second gear 71 and outputs a pulse-like gear signal S1, for example, at a predetermined rotational position of the second gear 71. The predetermined rotational position is a pre-set position for use, such as the origin position. The deceleration unit 3 decelerates the rotation of the second gear 71 before outputting the signal. The sensor 4 will be described later.

[0022] The rotary supply device 8 is the drive source for the reduction gear 10, and in this embodiment, it is a servo motor. The rotary supply device 8 has an output shaft 81 that outputs rotation. A first gear 82 that meshes with a second gear 71 is provided at the front end of the output shaft 81. The first gear 82 is, for example, a pinion. By rotating the first gear 82 integrally with the output shaft 81, the reduced rotation is transmitted to the second gear 71 that meshes with the first gear 82.

[0023] The control unit 5 uses the encoder signal S2 from the encoder 84 and the gear signal S1 from the sensor 4 to control the torque or speed of the rotary supply device 8. The encoder 84 outputs a pulse signal corresponding to the rotation of the rotary supply device 8. The structure of the encoder 84 is not limited, but in this example, the encoder 84 has a disk (not shown) that rotates integrally with the output shaft 81 and a transmissive optical sensor (not shown) that detects changes in the amount of light through the slit of the transmissive disk. The encoder 84 outputs a pulse signal with a frequency proportional to the rotational speed of the output shaft 81 as the encoder signal S2.

[0024] The reduction unit 3 will be described. In the embodiment, the reduction unit 3 is an eccentric oscillating type reducer that generates the rotation of one of the internal and external gears by oscillating the external gear meshing with the internal gear, and outputs the generated rotational component from the output component to the driven component. In particular, in Figure 1 In the example, the reduction gear 10 is a so-called distributed reduction gear in which the crankshaft is positioned offset from the axis of the internal gear.

[0025] The reduction unit 3 mainly includes a crankshaft 20, external gears 14 and 15, internal gears 16, brackets 35 and 36, housing 6, main bearings 26 and 27, crankshaft bearings 37 and 38, and a second gear 71.

[0026] Hereinafter, the direction along the central axis La of the internal gear 16 will be referred to as the "axial direction," and the circumferential direction and radial direction of the circle centered on the central axis La will be referred to as the "circumferential direction" and "radial direction," respectively. Furthermore, regarding the second gear 71 and its periphery, the circumferential direction and radial direction of the circle centered on the rotation center line Lb of the crankshaft 20 will be referred to as the "circumferential direction" and "radial direction," respectively. For convenience, the side of the axial direction (right side in the figure) will be referred to as the input side, and the other side (left side in the figure) will be referred to as the opposite input side.

[0027] The structure of each part of the reduction unit 3 will be described. The brackets 35 and 36 include a first bracket 35 disposed on the input-opposite side of the external gears 14 and 15, and a second bracket 36 disposed on the input-side side of the external gears 14 and 15. The housing 6 has a cylindrical shape surrounding the reduction device 10, and an internal gear 16 is provided on its inner circumferential surface. The housing 6 supports the outer circumferential sides of the main bearings 26 and 27. From the input-opposite side toward the input side, the housing 6 sequentially includes a second outer circumferential portion 62, a first outer circumferential portion 61, a third outer circumferential portion 63, and an input-side housing 80.

[0028] The input-side housing 80 is a hollow circular component used to connect the rotary supply device 8 and the reduction gear 10. Furthermore, the input-side housing 80 is part of the housing 6 and serves as a connecting adapter for connecting the rotary supply device 8 and the reduction gear 10. The input-side housing 80 has a cylindrical portion 83 connected to the input side of the housing 6 (described later), a disc-shaped portion 85 closing the input-side end of the cylindrical portion 83, an opening 87 surrounding the central axis of the disc portion 85 and through which the output shaft 81 passes, and a boss 86 located radially offset from the central axis of the disc portion 85 and protruding towards the input side. A seal 88 is disposed between the opening 87 and the output shaft 81. The input-side housing 80 is connected to the first outer periphery 61 of the housing 6 by bolt B1. The rotary supply device 8 is screwed into the hole of the boss 86 by bolt B2, thereby connecting to the input-side outer housing 80, i.e., the outer housing 6.

[0029] The main bearings 26 and 27 include a first main bearing 26 disposed on the side opposite to the input side of the external gears 14 and 15, and a second main bearing 27 disposed on the side of the input side of the external gears 14 and 15. The main bearings 26 and 27 support the housing 6. In this example, the main bearings 26 and 27 are angular contact roller bearings, but are not limited to this. The brackets 35 and 36 are rotatably supported on the housing 6 via the main bearings 26 and 27.

[0030] Crankshaft bearings 37 and 38 are disposed between crankshaft 20 and brackets 35 and 36, rotatably supporting crankshaft 20 on brackets 35 and 36. In this example, crankshaft bearings 37 and 38 are tapered roller bearings, but are not limited to this.

[0031] Three crankshafts 20 are arranged at positions offset from the central axis La of the internal gear 16. The three crankshafts 20 are arranged at equal intervals in the circumferential direction. Figure 1 Only one crankshaft 20 is shown. To enable the external gears 14 and 15 to oscillate, the crankshaft 20 has multiple eccentric portions 24 and 25 that are eccentric relative to the rotation center line Lb of the crankshaft 20. In this example, the crankshaft 20 has two eccentric portions 24 and 25 whose eccentric phases are offset from each other by 180°.

[0032] The crankshaft 20 is supported by crankshaft bearings 37 and 38 on the first bracket 35 and the second bracket 36. The crankshaft bearing 37 on the opposite input side is disposed on the opposite input side of the external gears 14 and 15, located between the crankshaft 20 and the first bracket 35. The crankshaft bearing 38 on the input side is disposed on the input side of the external gears 14 and 15, located between the crankshaft 20 and the second bracket 36.

[0033] A second gear 71 is provided at the input side end of each crankshaft 20. Figure 1 In the diagram, only one second gear 71 is shown. Furthermore, the feature 42 described later is only provided on one second gear 71, and not on the other two second gears 71. As described above, the second gear 71 meshes with the first gear 82 of the output shaft 81, and the rotation of the output shaft 81 is input to the second gear 71.

[0034] External gears 14 and 15 are correspondingly arranged with eccentric portions 24 and 25 via eccentric rollers 19, and have three inner pin holes 41 and 42 and three swing holes 45 and 46 arranged at equal intervals in the circumferential direction. An inner pin 48 is inserted into each inner pin hole 41 and 42. The eccentric portions 24 and 25 of the crankshaft 20 are inserted into each swing hole 45 and 46, and multiple eccentric rollers 19 exist between the swing holes 45 and 46 and the eccentric portions 24 and 25. The external gears 14 and 15 are configured to swing by moving simultaneously with the external teeth formed on the outer periphery of the external gears 14 and 15 in contact with the internal gear 16.

[0035] The internal gear 16 has an internal gear body 18 integrated with the inner periphery of the housing 6 and an outer pin 17 disposed in a pin groove formed on the internal gear body 18. The outer pin 17 constitutes the internal teeth of the internal gear 16 and meshes with the external teeth of the external gears 14 and 15. The number of outer pins 17 is only slightly more than the number of external teeth of the external gears 14 and 15 (one more in this example).

[0036] The inner pin 48 extends axially from the first bracket 35 and is fixed to the second bracket 36 by bolt B1. The inner pin 48 is inserted into the inner pin holes 41 and 42 of the external gears 14 and 15 with a clearance.

[0037] One of the first bracket 35 and the housing 6 serves as an output component that outputs rotational power to the driven component (not shown), and the other serves as a fixed component that is fixed to an external component (not shown) for supporting the reduction gear 10. Figure 1 In the example, the first bracket 35 is the output component 40.

[0038] The deceleration operation of the reduction gear 10 will be explained. Rotational power is distributed to three second gears 71 via the first gear 82 of the output shaft 81, and the three second gears 71 rotate in the same phase. When the three second gears 71 rotate, the eccentric portions 24 and 25 of the crankshaft 20 rotate about the rotation center line passing through the crankshaft 20, and the external gears 14 and 15 oscillate through these eccentric portions 24 and 25. As the external gears 14 and 15 oscillate, the meshing positions of the external gears 14 and 15 with the outer pins 17 of the internal gear 16 shift sequentially. As a result, for each revolution of the crankshaft 20, one of the external gears 14 and 15 and the internal gear 16 generates a rotation equivalent to the difference between the number of teeth on the external gears 14 and 15 and the number of outer pins 17 on the internal gear 16. In this embodiment, the external gears 14 and 15 rotate, and the decelerated rotation is output from the first bracket 35, which rotates synchronously with the rotational component of the external gears 14 and 15. The first bracket 35 rotates, and the first bracket 35, as an output component 40, drives the driven component connected to the first bracket 35 to rotate.

[0039] The performance of a speed reduction device, such as rigidity or angular transmission error (hereinafter referred to as "speed reduction device performance"), varies depending on the phase angle of the output component, i.e., the rotational position of the output component (hereinafter simply referred to as "rotational position"). To compensate for this, it is advisable to pre-observe the speed reduction device performance, such as rigidity or angular transmission error, at each rotational position of the output component for one revolution, using a specific rotational position of the speed reduction device as a reference, and store this as performance data. This performance data can then be used to control the torque input to the speed reduction device and to correct for variations in speed reduction device performance.

[0040] Angular transmission error is expressed in angles and refers to the error relative to the theoretical transmission angle. Since it is difficult to measure angular transmission error after assembling the measuring device into the actual device, a dedicated measuring device is used to pre-measure the angular transmission error waveform of the measuring device.

[0041] Figure 2This is a diagram illustrating an example of the angular transmission error of a speed reduction device. In this diagram, the horizontal axis shows the angle (°) of the rotational position of the output component of the speed reduction device during one revolution (360°), and the vertical axis shows the angle of the angular transmission error (arc sec). As shown, the graph g1 of this angular transmission error exhibits a sawtooth-like variation. This angular transmission error depends on the meshing position of the gears inside the speed reduction device, and shows approximately the same change corresponding to the rotational position of the output component with each revolution.

[0042] Therefore, if the angular transmission error of one revolution is obtained in advance, the variation of the angular transmission error can be smoothed by controlling the rotation or torque of the rotary supply device in the direction that cancels out the angular transmission error. Therefore, it is necessary to obtain the rotational reference position of the reduction gear, i.e., the reference position of the output component (hereinafter referred to as the "reference position"), and the angular transmission error of the rotational position one revolution from the reference position as performance data. For example, the reference position can be the origin of the reduction gear's rotation (e.g., the 0° position).

[0043] Here, if the accuracy of the reference position detection is low, a corresponding deviation will occur between the performance data and the actual rotational position, and the rotational supply device will be controlled based on the performance data with this deviation. As a result, the control error increases, and the desired correction effect cannot be obtained. Therefore, it is desirable to be able to detect the reference position with high accuracy.

[0044] To detect the reference position, a sensor measuring the rotational position of the output component of the speed reducer could be considered. However, in this case, interference might occur between the device assembling the speed reducer and the sensor, thus compromising the versatility of the speed reducer. Therefore, the speed reducer 10 of this embodiment has a sensor 4 that measures a predetermined position of the second gear 71, and the reference position of the output component 40 is detected based on this measured predetermined position. In this case, the second gear 71 will hardly interfere with the device, thus ensuring the versatility of the speed reducer 10.

[0045] The second gear 71 rotates about the rotation center line Lb of the crankshaft 20, and rotates integrally with the first bracket 35 and the second bracket 36, which are output components 40, about the central axis La. Therefore, a predetermined position of the second gear 71 approaches the sensor 4 with the same period as the rotation of the output component 40. The predetermined position of the second gear 71, obtained from the measurement results of the sensor 4, has a fixed relationship with the reference position of the output component 40; therefore, the reference position of the output component 40 can be determined based on the predetermined position of the second gear 71.

[0046] Sensor 4 will be described. Sensor 4 measures a predetermined position of the second gear 71. As described above, the reference position of the output component 40 can be determined based on the predetermined position of the second gear 71. Sensor 4 only needs to be able to measure the predetermined position of the second gear 71, and a detection device based on a known principle can be used. Examples of such detection devices include distance sensors, magnetic sensors, proximity sensors, contact sensors, and photoelectric sensors. The sensor 4 in this embodiment is a distance sensor that measures the distance to the object being measured.

[0047] refer to Figure 1 and Figure 3 The feature part 42 of the second gear 71 will be described. Figure 3 This is a perspective view showing an example of the second gear 71, with the teeth omitted. A feature portion refers to a part that can be distinguished from other circumferential positions, especially a part with a shape that can be distinguished from other parts, such as a mark. In the embodiment, a feature portion 42 is provided at the predetermined circumferential position of the second gear 71 for measuring the predetermined position. The feature portion 42 only needs to be able to provide the predetermined position of the second gear 71 to the sensor 4, and a feature portion based on known principles can be used. Examples of such feature portions include convex portions that are more prominent than the surrounding area, concave portions that are more recessed than the surrounding area, and light reflectivity variations such as black and white patterns. Figure 3 As shown, the feature portion 42 in the embodiment is a protrusion 43 extending axially from the second gear 71. The protrusion 43 protrudes from the second gear 71 toward the input side.

[0048] Furthermore, the other circumferential portions of the second gear 71 do not all have the same shape. As long as the other circumferential portions and the feature portion can be distinguished, they can have protrusions different from the feature portion every 90 degrees, or their shape can change continuously in the circumferential direction. However, compared to a continuous change in shape in the circumferential direction, the intermittent changes in shape of the other circumferential portions, such as protrusions different from the feature portion every 90 degrees, make detection easier and simpler for the detection sensor. Moreover, the portions in other circumferential positions other than the feature portion have the same shape or similar form, making detection easier and simpler.

[0049] The configuration of sensor 4 will be described. The configuration of sensor 4 is simply to be capable of measuring a predetermined position of the second gear 71. In this embodiment, sensor 4 includes a first sensor 4a disposed axially outside the feature portion 42 arranged axially outside the second gear 71, and a second sensor 4b disposed on the axial input side of the feature portion 42. Alternatively, the reduction gear 10 may only include one of the first sensor 4a and the second sensor 4b. In particular, the first sensor 4a is disposed radially outside the protrusion 43 extending axially, and the second sensor 4b is disposed on the axial input side of the protrusion 43.

[0050] Alternatively, a dedicated component for holding the sensor 4 may be provided. In this embodiment, the first sensor 4a is supported on the cylindrical portion 83 of the input-side housing 80 surrounding the protrusion 43, and the second sensor 4b is supported on the disc portion 85 disposed near the input side of the protrusion 43. The first sensor 4a is embedded in a hole penetrating the third outer peripheral portion 63 in the radial direction, and the second sensor 4b is embedded in a hole penetrating the disc portion 85 in the axial direction. The first sensor 4a outputs a gear signal S1a, and the second sensor 4b outputs a gear signal S1b. In the following description, unless otherwise specified, the term "sensor 4" is used as a general term for the first sensor 4a and the second sensor 4b, and the term "gear signal S1" is used as a general term for the gear signal S1a and the gear signal S1b.

[0051] refer to Figure 1 The reducer system 100 will be described below. The reducer system 100 includes a reduction gear 10, a rotation supply device 8 that supplies rotation to the second gear 71, and a control unit 5 that controls the rotation supply device 8. The control unit 5 controls the rotation supply device 8 using the measurement results of the sensor 4.

[0052] In this example, the control unit 5 stores the angular transmission error relative to the rotational position of one revolution from the reference position of the reduction gear 10, which is obtained in advance, as performance data. The reference position for obtaining this performance data can be determined according to the measurement results of the sensor 4 as described above. The control unit 5 uses the encoder signal S2 from the encoder 84 and the gear signal S1 from the sensor 4 to supply the rotary supply device 8 with a control signal S3 for controlling the torque or speed of the rotary supply device 8, so as to suppress the change of angular transmission error.

[0053] That is, the control unit 5 determines the absolute rotational position during one revolution by combining the reference absolute rotational position determined by the gear signal S1 and the relative rotational position determined by the encoder signal S2. It reads the angular transmission error corresponding to the absolute rotational position from the performance data and controls the rotation supply device 8 to counteract the read angular transmission error. As a result, the variation of the angular transmission error of the reduction gear 10 can be smoothed out.

[0054] The features of the speed reduction device 10 configured as described above will be explained. The speed reduction device 10 includes a first gear 82, a second gear 71 that revolves around the axis of the first gear 82, a speed reduction unit 3 that reduces the rotation of the second gear 71, and a sensor 4 that measures the predetermined position of the second gear 71.

[0055] According to this structure, the predetermined rotational position of the second gear 71 of the reduction gear 10 can be detected with high precision. Using the predetermined position of the second gear 71 measured by the sensor 4 as a reference position, the speed reducer performance, such as rigidity or angular transmission error, at each rotational position of the speed reducer 10 can be obtained. When the detection accuracy of the predetermined position is low, the deviation between the rotational position and the speed reducer performance will increase; however, according to the speed reducer 10, the deviation between the rotational position and the speed reducer performance can be reduced.

[0056] Based on the pre-acquired and stored information regarding the performance of the reducer at each rotational position, changes in the reducer's performance can be corrected using control methods that can control the torque or speed of the rotational supply device 8. Because the deviation between the rotational position and the reducer's performance is small, changes in the reducer's performance can be corrected with higher precision.

[0057] As an example, the reduction gear 10 has a feature 42 at a predetermined circumferential position of the second gear 71 that can be distinguished from other circumferential positions. At this time, by detecting the feature 42 by the sensor 4, the predetermined position of the second gear 71 can be determined with a simple structure.

[0058] As an example, feature 42 is a protrusion 43 extending along the axial direction. In this case, it can be constructed with almost no increase in the radial space of feature 42, which is beneficial for miniaturization of the device.

[0059] As an example, sensor 4 is disposed radially outside the axially extending protrusion 43. In this case, it can be constructed with almost no increase in the axial space of the protrusion 43, thus facilitating the miniaturization of the device.

[0060] As an example, sensor 4 can be disposed on the axially outer side of feature 42 disposed on the axially outer side of the second gear 71. Since it can be constructed with almost no increase in the axial space of protrusion 43, it is beneficial for miniaturization of the device.

[0061] The above is a description of the implementation method.

[0062] The present invention has been described above based on embodiments. These embodiments are examples, and various modifications and alterations can be made within the scope of the patent claims of the present invention. Such modifications and alterations also fall within the scope of the patent claims of the present invention, as will be understood by those skilled in the art. Therefore, the descriptions and drawings in this specification should not be considered limiting, but rather illustrative.

[0063] (Modified Example)

[0064] The following describes modified examples. In the accompanying drawings and descriptions of the modified examples, the same reference numerals are used to denote the same or equivalent components and parts as in the embodiment. Descriptions that are repeated in the embodiment are omitted where appropriate, and the focus is on describing structures that differ from the embodiment.

[0065] In the above description, an example was shown where the performance data of the controlled object is the angular transmission error relative to the rotational position of the output component 40 of the reduction gear 10, but the present invention is not limited to this. Performance data can be any performance relative to the rotational position of the output component 40 of the reduction gear 10. Examples of such performance include torque variation or torque ripple, loss motion, spring constant, and backlash. Torque ripple, for example, refers to the phenomenon where the torque fluctuates with one peak (one cycle) or two peaks (two cycles) per revolution of the output component 40. The reduction gear system 100 may also be configured to suppress these performance variations with the rotational position of the output component 40.

[0066] In the above description, an example is shown where the protrusion 43 protrudes from the second gear 71 toward the input side, but the invention is not limited thereto. For example, the protrusion may also protrude from the second gear toward the opposite side of the input.

[0067] In the above description, an example was shown where the feature portion 42 is a protrusion 43 that protrudes axially from the second gear 71, but the present invention is not limited thereto. For example, the feature portion may also be a protrusion that protrudes radially from the second gear.

[0068] In the above description, an example of a distribution-type reducer is shown where the reduction unit 3 is arranged with multiple crankshafts 20 at a position offset from the axis of the internal gear 16. However, the present invention is not limited to this, and various reduction mechanisms may be used. For example, the reduction unit may be a so-called center crankshaft type reducer where the crankshaft is arranged at the axis of the internal gear.

[0069] The above description shows an example of a reduction unit having two external gears 14, but the present invention is not limited thereto. The reduction unit may also have one or more external gears.

[0070] The reduction gear has no restrictions on the meshing structure; for example, it can be composed of a reduction mechanism different from planetary gears, such as a traction drive.

[0071] In the above description, an example of the deceleration device 10 being placed laterally with its axial direction extending horizontally is shown, but the present invention is not limited to this. The deceleration device 10 can also be placed longitudinally with its axial direction extending vertically. When the deceleration device 10 is placed longitudinally, since a space can be easily formed on the axially outer side of the feature portion 42 (protrusion 43), the sensor 4 can be arranged in this space.

[0072] These variations also have the same effects as the implementation method.

[0073] Any combination of the above-described embodiments and modifications is also effective as an embodiment of the present invention. New embodiments resulting from combinations possess the effects of both the combined embodiments and modifications.

Claims

1. A speed reduction device comprising: a first gear; a second gear revolving about the axis of the first gear; a speed reduction unit for reducing the rotation of the second gear; and a sensor for measuring a predetermined position of the second gear.

2. The speed reduction device according to claim 1, wherein, The second gear has a feature at a predetermined circumferential position that can be distinguished from other circumferential positions.

3. The speed reduction device according to claim 2, wherein, The feature portion is a convex portion extending along the axial direction.

4. The speed reduction device according to claim 3, wherein, The sensor is disposed on the radially outer side of the axially extending protrusion.

5. The speed reduction device according to claim 2, wherein, The sensor is disposed on the axially outer side of the feature portion arranged on the axially outer side of the second gear.

6. A speed reducer system comprising: the speed reducer of claim 1; a rotary supply device for supplying rotational energy to the first gear; and a control unit for controlling the rotary supply device. The control unit uses the measurement results from the sensor to perform control.

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