Speed ​​reducer, speed reducer system

Abstract

This invention has been made in view of the problems of the prior art, and one of its objectives is to provide a reduction gear capable of accurately detecting the reference position of rotation. [Solution] The reduction gear 10 of the embodiment includes a first gear 82, a second gear 71 that revolves around the axis of the first gear 82, a reduction unit 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

Technical Field

[0001] The present invention relates to a speed reducer and a speed reduction system.

Background Art

[0002] A speed reducer that decelerates and outputs an input rotation is known. For example, in Patent Document 1, an eccentric swing type gear device is described that includes an input gear to which rotation is input from a drive device, a plurality of external teeth that swing and rotate by 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 side portions of the plurality of external teeth, and that decelerates and outputs the rotation of the input gear.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The performance of a speed reducer, such as the rigidity and angular transmission error of the speed reducer, varies depending on the phase angle of the output member of the speed reducer, that is, the rotational position of the output member. To compensate for this, the inventor has considered acquiring the speed reducer performance in advance and correcting the change in the speed reducer performance using the data of this speed reducer performance.

[0005] Here, when acquiring in advance, as performance data, the performance of a speed reducer, such as the rigidity and angular transmission error for each rotational position, based on a specific rotational position of the speed reducer, if the reference position of the performance data is shifted, the position of the correction using the performance data is shifted, and it is difficult to perform appropriate correction. Patent Document 1 does not describe anything about means for detecting a specific position of the rotation of a speed reducer, such as an absolute angle, and is not sufficiently disclosed from the viewpoint of enabling accurate detection of the reference position of the rotation.

[0006] This invention has been made in view of these problems, and one of its objectives is to provide a reduction gear capable of detecting the reference position of rotation with greater accuracy. [Means for solving the problem]

[0007] To solve the above problems, a reduction gear according to one aspect of the present invention comprises a first gear, a second gear that revolves around the axis of the first gear, a reduction unit that reduces the rotation of the second gear, and a sensor that measures a predetermined position of the second gear.

[0008] Another aspect of the present invention is a gearbox system. This system comprises the gearbox described above, a rotational supply device that supplies rotation to a first gear, and a control unit that controls the rotational supply device, the control unit controlling the device using the measurement results of a sensor.

[0009] Furthermore, any combination of the above components, or in which the components or expressions of the present invention are mutually substituted among methods, systems, etc., are also valid embodiments of the present invention. [Effects of the Invention]

[0010] According to the present invention, a reduction gear capable of accurately detecting the reference position of rotation can be provided. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic cross-sectional view showing an example of a gearbox system equipped with a reduction gear according to the embodiment. [Figure 2] This figure shows an example of angular transmission error in a speed reducer. [Figure 3] Figure 1 is a perspective view showing an example of the second gear of a reduction gear. [Modes for carrying out the invention]

[0012] The present invention will be described below with reference to the drawings, based on preferred embodiments. In embodiments and modifications, the same or equivalent components and members will be denoted by the same reference numerals, and redundant explanations will be omitted as appropriate. In addition, the dimensions of the members in each drawing will be enlarged or reduced as appropriate for ease of understanding. Furthermore, some members that are not important for explaining the embodiments will be omitted from the drawings.

[0013] Furthermore, while terms including ordinal numbers such as "first" and "second" are used to describe various components, these terms are used solely to distinguish one component from others, and do not limit the components themselves.

[0014] [Embodiment] The reduction gear 10 according to the embodiment will be described with reference to Figures 1-3. Figure 1 is a schematic side cross-sectional view showing a reduction gear system 100 equipped with the reduction gear 10. The reduction gear system 100 comprises the reduction gear 10, a rotation supply device 8, and a control unit 5. The reduction gear 10 comprises a first reduction unit 7 that reduces the input rotation, a reduction unit 3, and a sensor 4.

[0015] The first reduction unit 7 of the embodiment includes a second gear 71, which is a spur gear. Sensor 4 measures a predetermined position of the second gear 71. Sensor 4 of the embodiment detects a feature portion 42 provided on the second gear 71 and outputs a pulse-like gear signal S1 at a predetermined position of rotation of the second gear 71, for example. The predetermined position of rotation is a position set in advance for use, for example, the origin position. The reduction unit 3 reduces the rotation of the second gear 71 and outputs the signal. Sensor 4 will be described later.

[0016] The rotary feeder 8 is a drive source that drives the reduction gear 10, and in this embodiment, it is a servo motor. The rotary feeder 8 has an output shaft 81 that outputs rotation. A first gear 82 that meshes with the second gear 71 is provided at the tip of the output shaft 81. The first gear 82 is, for example, a pinion gear. As the first gear 82 rotates integrally with the output shaft 81, the reduction rotation is transmitted to the second gear 71 that meshes with the first gear 82.

[0017] The control unit 5 controls the torque or speed of the rotary feeder 8 by using the encoder signal S2 from the encoder 84 that outputs a pulse signal corresponding to the rotation of the rotary feeder 8 and the gear signal S1 from the sensor 4. Although there is no limitation on the configuration of the encoder 84, the encoder 84 in this example includes a disk (not shown) that rotates integrally with the output shaft 81 and a transmissive optical sensor (not shown) that detects a change in the amount of light transmitted through the slit of the disk, and outputs a pulse signal with a frequency proportional to the rotational speed of the output shaft 81 as the encoder signal S2.

[0018] The reduction unit 3 will be described. In the embodiment, the reduction unit 3 is an eccentric swing type reduction gear that causes one of the internal gear and the external gear to rotate by swinging the external gear that meshes with the internal gear, and outputs the generated rotation component from the output member to the driven member. In particular, in the example of FIG. 1, the reduction device 10 is a so-called distribution type reduction device in which the crankshaft is arranged at a position offset from the axis of the internal gear.

[0019] The reduction unit 3 mainly includes a crankshaft 20, external gears 14 and 15, an internal gear 16, carriers 35 and 36, a casing 6, main bearings 26 and 27, crankshaft bearings 37 and 38, and a second gear 71.

[0020] Hereinafter, the direction along the central axis line La of the internal gear 16 is referred to as the "axial direction", and the circumferential direction and the radial direction of the circle centered on the central axis line La are referred to as the "circumferential direction" and the "radial direction", respectively. Also, for the second gear 71 and its periphery, the circumferential direction and the radial direction of the circle centered on the rotation center line Lb of the crankshaft 20 are referred to as the "circumferential direction" and the "radial direction", respectively. Also, hereinafter, for the sake of convenience, one side in the axial direction (the right side in the figure) is referred to as the input side, and the other side (the left side in the figure) is referred to as the anti-input side.

[0021] The structure of each part of the speed reduction unit 3 will be described. The carriers 35 and 36 include a first carrier 35 disposed on the side of the outer gear wheels 14 and 15 opposite to the input side, and a second carrier 36 disposed on the side of the outer gear wheels 14 and 15 on the input side. The casing 6 has a cylindrical shape surrounding the speed reduction device 10, and an internal gear 16 is provided on the inner peripheral surface. The casing 6 supports the outer peripheral sides of the main bearings 26 and 27. The casing 6 includes, in order from the non-input side to the input side, a second outer peripheral portion 62, a first outer peripheral portion 61, a third outer peripheral portion 63, and an input side casing 80.

[0022] The input side casing 80 is a hollow circular member for connecting the rotary supply device 8 to the speed reduction device 10. Also, the input side casing 80 is a part of the casing 6 and is a connecting adapter for connecting the rotary supply device 8 and the speed reduction device 10. The input side casing 80 includes a cylindrical tubular portion 83 connected to the input side of the casing 6 described later, a disc-shaped disc portion 85 closing the input side end of the tubular portion 83, an opening 87 surrounding the central axis of the disc portion 85 through which the output shaft 81 passes, and a boss 86 provided at a position offset in the radial direction from the central axis of the disc portion 85 and protruding toward the input side. A seal 88 is disposed between the opening 87 and the output shaft 81. The input side casing 80 is connected to the first outer peripheral portion 61 of the casing 6 by bolts B1. The rotary supply device 8 is connected to the input side casing 80, that is, the casing 6, by screwing bolts B2 into the holes of the boss 86.

[0023] The main bearings 26 and 27 include a first main bearing 26 disposed on the side of the outer gear wheels 14 and 15 opposite to the input side, and a second main bearing 27 disposed on the side of the outer gear wheels 14 and 15 on the input side. The main bearings 26 and 27 support the casing 6. The main bearings 26 and 27 in this example are angular roller bearings, but are not limited thereto. The carriers 35 and 36 are rotatably supported by the casing 6 via the main bearings 26 and 27.

[0024] The crankshaft bearings 37 and 38 are positioned between the crankshaft 20 and the carriers 35 and 36, and rotatably support the crankshaft 20 relative to the carriers 35 and 36. In this example, the crankshaft bearings 37 and 38 are tapered roller bearings, but are not limited to them.

[0025] 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 shows only one crankshaft 20. The crankshaft 20 has multiple eccentric portions 24, 25 that are eccentric with respect to the rotational centerline Lb of the crankshaft 20 in order to oscillate the external gears 14, 15. In this example, the crankshaft 20 has two eccentric portions 24, 25 that are eccentrically offset from each other by 180°.

[0026] The crankshaft 20 is supported by the first carrier 35 and the second carrier 36 via crankshaft bearings 37 and 38. The crankshaft bearing 37 on the non-input side is located between the crankshaft 20 and the first carrier 35 on the non-input side of the external gears 14 and 15. The crankshaft bearing 38 on the input side is located between the crankshaft 20 and the second carrier 36 on the input side of the external gears 14 and 15.

[0027] The second gear 71 is provided at the input end of each crankshaft 20. Figure 1 shows only one second gear 71. Note that the feature part 42, which will be described later, is provided on only one second gear 71 and not on the other two second gears 71. As mentioned 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.

[0028] The external gears 14 and 15 are provided with eccentric portions 24 and 25 via eccentric rollers 19, and each has three internal pin holes 41 and 42 and three oscillating holes 45 and 46, which are arranged at equal intervals in the circumferential direction. An internal pin 48 is inserted through each internal pin hole 41 and 42. The eccentric portions 24 and 25 of the crankshaft 20 are inserted through each oscillating hole 45 and 46, and a plurality of eccentric rollers 19 are interposed between the oscillating holes 45 and 46 and the eccentric portions 24 and 25. The external gears 14 and 15 are configured to oscillate as the external teeth formed on the outer circumference of the external gears 14 and 15 move in contact with the internal gear 16.

[0029] The internal gear 16 has an internal gear body 18 integrated with the inner circumference of the casing 6, and an external pin 17 positioned in a pin groove formed in the internal gear body 18. The external 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 external pins 17 is slightly greater than the number of external teeth of the external gears 14 and 15 (only one in this example).

[0030] The internal pin 48 extends axially from the first carrier 35 and is fixed to the second carrier 36 by bolt B1. The internal pin 48 is inserted through the internal pin holes 41 and 42 of the external gears 14 and 15 with a gap between them.

[0031] One of the first carrier 35 and the casing 6 becomes an output member that outputs rotational power to a driven member (not shown), and the other becomes a fixed member that is fixed to an external member (not shown) that supports the reduction gear 10. In the example in Figure 1, the first carrier 35 is the output member 40.

[0032] The reduction operation of the reduction gear 10 will now be explained. Rotational power is distributed to the 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. As the three second gears 71 rotate, the eccentric parts 24 and 25 of the crankshaft 20 rotate around the rotational center line passing through the crankshaft 20, and the external gears 14 and 15 oscillate due to these eccentric parts 24 and 25. As the external gears 14 and 15 oscillate, the meshing positions of the external gears 14 and 15 and the external pins 17 of the internal gear 16 shift sequentially. As a result, with each rotation of the crankshaft 20, a rotation occurs in either the external gears 14 and 15 or the internal gear 16 by an amount equivalent to the difference between the number of teeth of the external gears 14 and 15 and the number of external pins 17 of the internal gear 16. In this embodiment, the external gears 14 and 15 rotate on their own, and a reduced rotation is output from the first carrier 35, which rotates in sync with the rotational component of the external gears 14 and 15. As the first carrier 35 rotates, the first carrier 35 acts as an output member 40, and the driven member connected to the first carrier 35 is rotationally driven.

[0033] The performance of a reduction gear, including its rigidity and angular transmission error (hereinafter referred to as "reduction gear performance"), changes depending on the phase angle of the output member of the reduction gear, i.e., the rotational position of the output member (hereinafter simply referred to as "rotational position"). To compensate for this, it is conceivable to acquire the performance of the reduction gear, such as its rigidity and angular transmission error, for each rotational position of the output member, based on a specific rotational position of the reduction gear of the reduction machine, and store this data as performance data. This makes it possible to control the input torque to the reduction gear using this performance data and make corrections to counteract changes in the reduction gear performance.

[0034] Angular transmission error is the transmission error expressed in angle, and refers to the error relative to the theoretical transmission angle. Since it is difficult to measure the angular transmission error after the device is assembled for actual use, the angular transmission error waveform of the measuring device is measured in advance using a dedicated measuring device.

[0035] Figure 2 shows an example of angular transmission error in a speed reducer. In this figure, the horizontal axis represents the rotational position (°) of the output member of the speed reducer during one rotation (360°), and the vertical axis represents the angular transmission error (arc sec). The graph g1 of this angular transmission error shows a sawtooth-like change, as shown in this figure. This angular transmission error depends on the positional relationship of the meshing gears inside the speed reducer and shows almost the same change with each rotation, corresponding to the rotational position of the output member.

[0036] Therefore, by pre-acquiring the angular transmission error for one rotation, the fluctuations in the angular transmission error can be smoothed by controlling the rotation and torque of the rotational supply device in a direction that cancels out this error. For this reason, it is necessary to acquire the reference position of the output member, which is the reference position for the rotation of the reduction gear (hereinafter simply referred to as the "reference position"), and the angular transmission error relative to the rotational position one rotation away from the reference position as performance data. As an example, the reference position may be the origin position of the rotation of the reduction gear (for example, the 0° position).

[0037] If the detection accuracy of the reference position is low, the performance data will deviate from the actual rotational position, and the rotational feed device will be controlled based on this deviated performance data. As a result, the control error will be large, and the desired correction effect cannot be obtained. Therefore, it is desirable to detect the reference position with high accuracy.

[0038] One might consider providing a sensor to measure the rotational position of the output member of the reduction gear in order to detect the reference position. However, in this case, there is a risk of interference between the sensor and the mating device into which the reduction gear is incorporated, which would impair the versatility of the reduction gear. Therefore, the reduction gear 10 of this embodiment has a sensor 4 that measures a predetermined position of the second gear 71, and detects the reference position of the output member 40 based on this measured predetermined position. In this case, there is almost no risk of interference between the second gear 71 and the mating device, so the versatility of the reduction gear 10 can be ensured.

[0039] The second gear 71 rotates around the rotational centerline Lb of the crankshaft 20 and rotates integrally with the output member 40, which consists of the first carrier 35 and the second carrier 36, around the central axis La. Therefore, a predetermined position of one second gear 71 approaches the sensor 4 with the same period as the rotation of the output member 40. Since the predetermined position of the second gear 71 obtained from the measurement results of the sensor 4 has a certain relationship with the reference position of the output member 40, the reference position of the output member 40 can be determined from the predetermined position of the second gear 71.

[0040] Sensor 4 will now be described. Sensor 4 measures a predetermined position on the second gear 71. As mentioned above, the reference position of the output member 40 can be determined from the predetermined position on the second gear 71. Sensor 4 only needs to be capable of measuring a predetermined position on 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. Sensor 4 in this embodiment is a distance sensor that measures the distance to the object to be measured.

[0041] The characteristic part 42 of the second gear 71 will be described with reference to Figures 1 and 3. Figure 3 is a perspective view showing an example of the second gear 71, and the teeth are omitted from the description. A characteristic part is a part that can be distinguished from other circumferential positions, and in particular a part that has a shape that can be distinguished from other parts, and may be a marker, for example. In this embodiment, the characteristic part 42 is located at a predetermined circumferential position of the second gear 71 in order to measure a predetermined position of the second gear 71. The characteristic part 42 only needs to be able to give the sensor 4 a predetermined position of the second gear 71, and a characteristic part based on a known principle can be used. Examples of such characteristic parts include a convex part that protrudes from the surroundings, a concave part that is recessed from the surroundings, and a part with a change in light reflectivity such as a black and white pattern. As shown in Figure 3, the characteristic part 42 of this embodiment is a convex part 43 that extends axially from the second gear 71. The convex part 43 protrudes from the second gear 71 toward the input side.

[0042] Furthermore, the other circumferential parts of the second gear 71 do not necessarily have to have the same shape. As long as the feature part can be distinguished from the other circumferential parts, it is acceptable for the other circumferential parts to have protrusions separate from the feature part every 90 degrees or for the shape to change continuously in the circumferential direction. However, it is easier for the detection sensor to detect the other circumferential parts if their shape changes intermittently, such as having protrusions separate from the feature part every 90 degrees, rather than if their shape changes continuously in the circumferential direction. Moreover, it is even easier to detect the other circumferential parts other than the feature part if they have the same shape or other identical form.

[0043] The arrangement of sensor 4 will now be described. The arrangement of sensor 4 is such that it is possible to measure a predetermined position on the second gear 71. In this embodiment, sensor 4 includes a first sensor 4a, which is arranged on the axially outer side of a feature portion 42, which is arranged on the axially outer side of the second gear 71, and a second sensor 4b, which is arranged on the axial input side of the feature portion 42. Note that the reduction gear 10 may be equipped with only one of the first sensor 4a and the second sensor 4b. In particular, the first sensor 4a is arranged on the radially outer side of a protrusion 43 that extends in the axial direction, and the second sensor 4b is arranged on the axial input side of the protrusion 43.

[0044] A special member may be provided to hold the sensor 4, but in this embodiment, the first sensor 4a is supported by a cylindrical portion 83 of the input-side casing 80 that surrounds the protrusion 43, and the second sensor 4b is supported by a disc portion 85 positioned close to the input side of the protrusion 43. The first sensor 4a is embedded in a hole that penetrates the third outer circumference 63 radially, and the second sensor 4b is embedded in a hole that penetrates the disc portion 85 axially. 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" refers collectively to the first sensor 4a and the second sensor 4b, and the term "gear signal S1" refers collectively to the gear signal S1a and the gear signal S1b.

[0045] The gearbox system 100 will be described with reference to Figure 1. The gearbox system 100 comprises a reduction gear 10, a rotational supply device 8 that supplies rotation to the second gear 71, and a control unit 5 that controls the rotational supply device 8. The control unit 5 controls the rotational supply device 8 using the measurement results from the sensor 4.

[0046] In this example, the control unit 5 stores the angular transmission error of the reduction gear 10 relative to the rotational position of one revolution from the reference position of the reduction gear 10 as performance data, which has been acquired in advance. The reference position when acquiring this performance data can be determined as described above based on the measurement results of the sensor 4. The control unit 5 uses the encoder signal S2 from the encoder 84 and the gear signal S1 from the sensor 4 to supply a control signal S3 to the rotational feed device 8 to control the torque or speed of the rotational feed device 8 in order to suppress changes in the angular transmission error.

[0047] In other words, the control unit 5 determines the absolute rotation position during one rotation by combining the reference absolute rotation position determined by the gear signal S1 and the relative rotation position determined by the encoder signal S2, reads the angular transmission error corresponding to that absolute rotation position from the performance data, and controls the rotation supply device 8 to cancel out the read angular transmission error. As a result, fluctuations in the angular transmission error of the reduction gear 10 can be smoothed out.

[0048] The features of the reduction gear 10 configured as described above will now be explained. The reduction gear 10 includes a first gear 82, a second gear 71 that revolves around the axis of the first gear 82, a reduction unit 3 that reduces the rotation of the second gear 71, and a sensor 4 that measures a predetermined position of the second gear 71.

[0049] This configuration allows for accurate detection of a predetermined position in the rotation of the second gear 71 of the reduction gear 10. Using the predetermined position of the second gear 71 measured by the sensor 4 as a reference position, the reduction gear performance, such as rigidity and angular transmission error, can be acquired for each rotation position of the reduction gear 10. When the detection accuracy of the predetermined position is low, the discrepancy between the rotation position and the reduction gear performance becomes large, but the reduction gear 10 can reduce this discrepancy.

[0050] Based on information obtained and stored in advance regarding the gearbox performance for each rotational position, a control means capable of controlling the torque or speed of the rotational supply device 8 can be used to correct for changes in gearbox performance. Because the discrepancy in the correspondence between rotational position and gearbox performance is small, changes in gearbox performance can be corrected with higher precision.

[0051] As an example, the reduction gear 10 has a feature portion 42 at a predetermined circumferential position of the second gear 71 that can be distinguished from other circumferential positions. In this case, the predetermined position of the second gear 71 can be determined with a simple configuration by detecting the feature portion 42 with the sensor 4.

[0052] As an example, the feature portion 42 is a protrusion 43 extending in the axial direction. In this case, the feature portion 42 can be constructed without significantly increasing the radial space, which is advantageous for miniaturizing the device.

[0053] As an example, the sensor 4 is positioned radially outward of the axially extending protrusion 43. In this case, the configuration can be achieved without significantly increasing the axial space of the protrusion 43, which is advantageous for miniaturizing the device.

[0054] For example, the sensor 4 may be provided on the axially outer side of the feature portion 42, which is located on the axially outer side of the second gear 71. This configuration is advantageous for miniaturizing the device because it can be done without significantly increasing the axial space of the protrusion 43.

[0055] The above is a description of the embodiment.

[0056] The present invention has been described above based on the embodiments. These embodiments are illustrative, and it will be understood by those skilled in the art that various modifications and changes are possible within the scope of the claims of the present invention, and that such modifications and changes are also within the scope of the claims of the present invention. Accordingly, the descriptions and drawings herein should be treated as illustrative rather than limiting.

[0057] (modified version) The following describes modified examples. In the drawings and descriptions of the modified examples, components and parts that are the same or equivalent as those in the embodiments are denoted by the same reference numerals. Descriptions that overlap with those in the embodiments will be omitted as appropriate, and the descriptions will focus on the configurations that differ from those in the embodiments.

[0058] In the above description, an example was shown where the performance data of the controlled object is the angular transmission error with respect to the rotational position of the output member 40 of the reduction gear 10, but the present invention is not limited to this. The performance data may be any performance of the output member 40 of the reduction gear 10 with respect to the rotational position, and examples of such performance include torque fluctuations, torque fluctuations, lost motion, spring constant, backlash, etc. Torque fluctuations refer to a phenomenon in which the torque fluctuates by one peak (one cycle) or two peaks (two cycles) per rotation of the output member 40. The reduction gear system 100 may be configured to suppress fluctuations in these performances with respect to the rotational position of the output member 40.

[0059] In the above description, an example was shown in which the protrusion 43 protrudes from the second gear 71 toward the input side, but the present invention is not limited to this. For example, the protrusion may protrude from the second gear toward the opposite input side.

[0060] In the above description, an example was shown in which the feature portion 42 is a convex portion 43 that protrudes axially from the second gear 71, but the present invention is not limited to this. For example, the feature portion may be a convex portion that protrudes radially from the second gear.

[0061] In the above description, an example was shown in which the reduction unit 3 is a so-called distribution type reduction gear in which multiple crankshafts 20 are arranged at positions offset from the axis of the internal gear 16. However, the present invention is not limited to this, and various reduction mechanisms can be employed. For example, the reduction unit may be a so-called center crank type reduction gear in which a crankshaft is arranged at the axis of the internal gear.

[0062] The above description shows an example in which the reduction gear unit comprises two external gears 14, but the present invention is not limited to this. The reduction gear unit may comprise one or three or more external gears.

[0063] The reduction gear section is not limited to a meshing configuration and may be composed of a reduction mechanism other than planetary gears, such as a traction drive.

[0064] In the above description, an example was shown in which the reduction gear 10 is placed horizontally so that its axial direction extends horizontally, but the present invention is not limited to this. The reduction gear 10 may also be placed vertically so that its axial direction extends vertically. When the reduction gear 10 is placed vertically, space can be easily created on the axial side of the feature portion 42 (protrusion 43), so the sensor 4 can be placed using this space.

[0065] Each of these modifications produces the same functions and effects as the embodiments.

[0066] Any combination of the embodiments and modifications described above is also useful as an embodiment of the present invention. The new embodiments resulting from these combinations possess the combined effects of both the respective embodiments and modifications. [Explanation of Symbols]

[0067] 3 reduction unit, 4 sensor, 5 control unit, 7 first reduction unit, 8 rotational feed device, 10 reduction device, 14 external gear, 16 internal gear, 35 first carrier, 36 second carrier, 40 output member, 42 feature part, 43 protrusion, 71 second gear, 82 first gear, 100 reduction gear system.

Claims

1. A reduction gear comprising a first gear, a second gear that revolves around the axis of the first gear, a reduction unit that reduces the rotation of the second gear, and a sensor that measures a predetermined position of the second gear.

2. The reduction gear according to claim 1, wherein the second gear has a distinguishable feature at a predetermined circumferential position from other circumferential positions.

3. The reduction gear according to claim 2, wherein the aforementioned feature portion is a convex portion extending in the axial direction.

4. The reduction gear according to claim 3, wherein the sensor is disposed radially outward of the protrusion extending in the axial direction.

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

6. The reduction gear according to claim 1, the rotation supply device that supplies rotation to the first gear, and the control unit that controls the rotation supply device, The control unit is a gearbox system that is controlled using the measurement results of the sensor.

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