Power transmission device and assembly method

Abstract

To provide technology for enabling a user to grasp quality of an assembly state during assembly work related to a power transmission device.SOLUTION: The present invention provides a power transmission device that is assembled to an external member and comprises a sensor 50 that detects a state quantity related to the power transmission device. The sensor 50 outputs detection information indicating the state quantity detected by the sensor 50 when the power transmission device is assembled to the external member. The sensor 50 may output the detection information to a control device that controls a controlled device on the basis of the detection information during operation of the power transmission device. The sensor 50 may output the detection information to another information processing device different from the control device when the power transmission device is assembled to the external member.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a power transmission device. [Background Art]

[0002] Patent Document 1 discloses a power transmission device that is assembled to an external member such as an arm member constituting a robot. [Prior Art Literature] [Patent Literature]

[0003] [Patent Document 1] Japanese Unexamined Patent Publication No. 2019-217573 [Summary of the Invention] [Problem to be Solved by the Invention]

[0004] Assembly operations for power transmission devices include an assembly operation of assembling the power transmission device to an external member, an assembly operation between component parts of the power transmission device, and the like. The inventor of the present application has found a new idea for enabling the quality of the assembled state to be grasped when performing such an assembly operation for the power transmission device.

[0005] One of the objects of the present disclosure is to provide a technique for enabling the quality of an assembled state to be grasped when performing an assembly operation for a power transmission device. [Means for Solving the Problem]

[0006] A power transmission device according to one aspect of the present disclosure, which is a power transmission device to be assembled to an external member, comprises a sensor that detects a state quantity related to the power transmission device, and the sensor outputs detection information indicating the state quantity detected by the sensor when the power transmission device is being assembled to the external member.

[0007] An assembly method in one aspect of the present disclosure is an assembly method for assembling an item to be assembled to an assembly partner, wherein the item to be assembled is a power transmission device, and the assembly partner is an external member, and the assembly method includes: an acquisition step of acquiring detection information of a sensor for each of a plurality of different assembly states obtained by adjusting the assembly state of the item to be assembled to the assembly partner; and a determination step of determining one of the plurality of assembly states as the final assembly state based on the acquired detection information of the sensor for each of the plurality of assembly states.

[0008] Another aspect of the present disclosure is an assembly method for assembling an item to be assembled to an assembly partner, wherein the item to be assembled is a power transmission device, and the assembly partner is an external member, and the assembly method includes: an acquisition step of acquiring detection information from a sensor when the item to be assembled is in an assembled state with respect to the assembly partner; a determination step of determining whether the assembled state is good or bad based on the acquired detection information from the sensor; and, if it is determined that the assembled state is good, determining that assembled state as the final assembled state, and if it is determined that the assembled state is not good, adjusting the assembled state of the item to be assembled and repeating the acquisition step and the determination step.

[0009] Another aspect of the present disclosure is a power transmission device comprising a mating part and an assembly part to be assembled to the mating part, the power transmission device comprising a sensor for detecting a state quantity relating to the mating part or the assembly part, the sensor for outputting detection information indicating the state quantity detected by the sensor when the assembly part is being assembled to the mating part.

[0010] Another aspect of the present disclosure is an assembly method for assembling an item to be assembled to a mating part, wherein the item to be assembled is a mating part, and the mating part is an assembly part, and includes an acquisition step of acquiring detection information of the sensor for each of a plurality of different assembly states obtained by adjusting the assembly state of the item to be assembled to the mating part, and a determination step of determining one of the plurality of assembly states as the final assembly state based on the acquired detection information of the sensor for each of the plurality of assembly states.

[0011] Another aspect of the assembly method of the present disclosure is an assembly method for assembling an item to be assembled to an assembly partner, wherein the item to be assembled is a mating part, and the assembly partner is an assembly part, and includes an acquisition step of acquiring detection information of a sensor when the item to be assembled is in an assembled state with respect to the assembly partner, a determination step of determining whether the assembly state is good or bad based on the acquired detection information of the sensor, and if it is determined that the assembly state is good, a decision step of determining that assembly state as the final assembly state, and if it is determined that the assembly state is not good, the assembly state of the item to be assembled is adjusted and the acquisition step and the determination step are performed again. [Effects of the Invention]

[0012] According to this disclosure, it becomes possible to determine the quality of the assembled state when performing assembly work on a power transmission device. [Brief explanation of the drawing]

[0013] [Figure 1] This is a schematic side cross-sectional view showing the power transmission device of the first embodiment. [Figure 2] This diagram schematically shows the intermediate state of the assembly process of the first embodiment. [Figure 3] This is an explanatory diagram of the tolerance range used in the first embodiment. [Figure 4] This is a flowchart showing the assembly procedure for the first embodiment. [Figure 5] This is a flowchart showing the assembly procedure for the second embodiment. [Figure 6] This diagram schematically shows the intermediate state of the assembly work for the power transmission device of the third embodiment. [Figure 7] This is an explanatory diagram of the tolerance range used in the third embodiment. [Figure 8] Figure 8(A) is an explanatory diagram of the starting position for assembly, and Figure 8(B) is an explanatory diagram of the ending position for assembly. [Figure 9] This graph shows the relationship between the position of an assembled component and the state variable detected by a sensor. [Modes for carrying out the invention]

[0014] The embodiments are described below. The same reference numerals are used for identical components, and redundant explanations are omitted. For the sake of clarity, components are omitted, enlarged, or reduced in each drawing. The drawings should be viewed in accordance with the orientation of the reference numerals.

[0015] (First Embodiment) Refer to Figure 1. The power transmission device 10 will be described in detail. The power transmission device 10 is supported by the support member 12 and transmits the power generated by the drive device 14, outputting power to drive the driven member 16. The driven member 16 is, for example, part of industrial machinery (machine tools, construction machinery, etc.), robots (industrial robots, service robots, etc.). Here, we will describe an example in which the power transmission device 10 is incorporated into the joint of a robot arm, and the support member 12 and the driven member 16 are arm members that constitute the robot arm. Hereinafter, the direction along the rotational centerline of the rotating body (the vibrator 22 described later) that constitutes the power transmission device 10 will be called the axial direction, and the radial direction and circumferential direction with the rotational centerline as the center of the circle will be simply called the "radial direction" and "circumferential direction," respectively.

[0016] The power transmission device 10 comprises at least one of a drive device 14 that generates power and a driven device 18 that transmits the power input from the drive device 14 and outputs power to the driven member 16. In this embodiment, the power transmission device 10 does not include a drive device 14, but includes only a driven device 18.

[0017] The driven device 18 of the present embodiment is a gear device 20 serving as a speed reducer. The gear device 20 is a cylindrical strain wave gear device. This gear device 20 comprises: a wave generator 22 rotated by power output from an output shaft 14a of a drive device 14; a flexible external gear 24 that is flexibly deformable by the rotation of the wave generator 22; a wave generator bearing 26 disposed between the wave generator 22 and the external gear 24; and a rigid reduction internal gear 28A and a rigid output internal gear 28B that mesh with the external gear 24.

[0018] The wave generator 22 has an elliptical shape in a cross section orthogonal to the axial direction of the wave generator 22. The term "elliptical" herein is not limited to a geometrically strictly ellipse, and includes substantially elliptical shapes. The reduction internal gear 28A is fixed to the support member 12 by bolts B, and the output internal gear 28B is fixed to the driven member 16 by bolts B. In this example, the number of teeth of the reduction internal gear 28A (for example, 102 teeth) is larger than the number of teeth of the external gear 24 (for example, 100 teeth), and the number of teeth of the output internal gear 28B is the same as the number of teeth of the external gear 24.

[0019] When the wave generator 22 is rotated by the power output from the drive device 14, the external gear 24 is flexibly deformed to form an elliptical shape matching the shape of the wave generator 22. When the external gear 24 is flexibly deformed in this manner, the meshing positions of the external gear 24 with the internal gears 26A and 26B change in the rotation direction of the wave generator 22. As a result, each time the wave generator 22 rotates one revolution, the external gear 24 rotates on its own axis by the difference in the number of teeth between the reduction internal gear 28A and the external gear 24, and this autorotation component is output as output rotation from the output internal gear 28B to the driven member 16.

[0020] The gear device 20 of the present embodiment is of a component type in which the main bearing 30 is omitted, and the main bearing 30 is disposed between the support member 12 and the driven member 16. The gear device 20 may be of a type in which the main bearing 30 is not omitted.

[0021] The support member 12 functions as a first external member 30A to which the power transmission device 10 is assembled, and the driven member 16 functions as a second external member 30B to which the power transmission device 10 is assembled. The power transmission device 10 is detachably assembled by fixing it to the external members 30A and 30B with bolts B. The manner in which the power transmission device 10 is fixed to the external members 30A and 30B is not particularly limited, and may be, for example, a screw structure, a tight fit, friction fastening, etc.

[0022] The power transmission device 10 includes fixing parts 32A and 32B fixed to external members 30A and 30B. The fixing parts 32A and 32B are composed of one or more members. In this embodiment, the fixing parts 32A and 32B include a first fixing part 32A fixed to the first external member 30A (support member 12) and a second fixing part 32B fixed to the second external member 30B (driven member 16). In this embodiment, the first fixing part 32A includes a reduction gear internal gear 28A, and the second fixing part 32B includes an output gear internal gear 28B.

[0023] Each of the external members 30A, 30B and the fixing parts 32A, 32B has contact surfaces 34A, 34B that come into contact with each other when the power transmission device 10 is assembled to the external members 30A, 30B. The contact surfaces 34A, 34B include an axial contact surface 34A that contacts in the axial direction and a radial contact surface 34B that contacts in the radial direction.

[0024] The drive unit 14 in this embodiment is a motor unit. The drive unit 14 functions as a controlled device 36 that operates during the operation of the power transmission unit 10 and is controlled by the control device 38. The control device 38 controls the controlled device 36 based on detection information from the sensor 50, which will be described later, during the operation of the power transmission unit 10. The control device 38 in this embodiment is attached to the drive unit 14, which is the controlled device 36. The control device 38 is composed of, for example, a microcomputer with a driver circuit incorporated into it.

[0025] Refer to Figure 2. Figure 2 schematically shows the intermediate state of the assembly work in this embodiment. In this embodiment, we will describe an example in which the assembly partner 40 in the assembly work is the first external member 30A, and the assembly target 42 to be assembled to the assembly partner 40 is the power transmission device 10. The result obtained by assembling the assembly target 42 to the assembly partner 40 is called the assembly result 46.

[0026] When the part to be assembled 42 is assembled to the mating part 40, the load on the assembled product 46 changes depending on the assembly state of the part to be assembled 42, and an overload may be applied to the assembled product 46. This can occur, for example, when the contact surfaces 34A and 34B of the mating part 40 and the part to be assembled 42 are significantly distorted from the target shape due to manufacturing variations (including processing variations), and the bolt B is tightened to force contact between them. In addition, an overload may be applied to the assembled product 46 if any of the following work defects occur during the assembly process. These work defects include, for example, tightening the bolt B with foreign matter caught between the mating part 40 and the part to be assembled 42, misassembly where the part to be assembled 42 is incorrectly placed in a position different from the target position, or tightening the bolt B too much. Such an overload may adversely affect the specific performance (e.g., lifespan) of the power transmission device 10. Here, we will explain the techniques used to determine the quality of the assembly in relation to the load acting on the resulting assembly 46.

[0027] The power transmission device 10 is equipped with a sensor 50 that detects state quantities related to the power transmission device 10. State quantities related to the power transmission device 10 refer to state quantities acting on the components of the power transmission device 10. The sensor 50 detects state quantities that change according to the assembly state of the assembly target 42 relative to the assembly mat 40. In this embodiment, such state quantities include strain generated in the components of the power transmission device 10 (here, the fixed component 32A). This strain is generated by the load acting on the fixed component 32A and changes in correlation with the load, so the load can be estimated from the amount of strain. In addition, the sensor 50 may also detect state quantities that correlate with specific performance of the power transmission device, as in the third embodiment.

[0028] The specific examples of the state quantities detected by the sensor 50 (hereinafter referred to as "detected state quantities") are not particularly limited and may include strain, stress, load, vibration, temperature, magnetic flux density, etc. The specific examples of the sensor 50 that realize this are not particularly limited and may include strain sensors, stress sensors, load sensors (load cells, etc.), vibration sensors, temperature sensors, magnetic sensors, etc. In addition to the sensor element (strain gauge, etc.) that detects the state quantities, the sensor 50 may also include an amplifier that amplifies the output of the sensor element.

[0029] The sensor 50 outputs detection information indicating the state quantity detected by the sensor 50 when the assembly target product 42 (in this case, the power transmission device 10) is being assembled to the assembly partner 40 (in this case, the first external member 30A). Here, "when assembling" refers to the period from when the assembly of the assembly target product 42 to the assembly partner 40 is started until the assembly is completed. Here, "assembly is completed" refers to determining the final assembly state (described later) in the assembly work and finishing positioning the assembly target product 42 (in this case, the power transmission device 10) at the target position in that determined final assembly state. If the assembly target product 42 has finished positioning at the target position when the final assembly state is determined, then the assembly is completed at the time of determination.

[0030] The detection information from the sensor 50 is mainly used for two purposes. Firstly, the detection information is used to determine the quality of the assembly of the part to be assembled 42 to the mating part 40 when the part to be assembled 42 is being assembled to the mating part 40. In this case, the sensor 50 is connected to an information processing device 54, which is separate from the control device 38, via a transmission member 52, which will be described later, and outputs the detection information to the information processing device 54 via the transmission member 52. Secondly, as shown in Figure 1, the detection information is used for control by the control device 38 while the power transmission device 10 is in operation, that is, while the driven member 16 is being driven. In this case, the sensor 50 is connected to the control device 38 via a wiring member 56 such as a cable while the power transmission device 10 is in operation, and outputs the detection information to the control device 38 via the wiring member 56. Here, the sensor 50 may have an element that stores power to output the detection information, or it may be powered by the control device 38 or the information processing device 54.

[0031] The control method used by the control device 38 with respect to the detection information from the sensor 50 is not particularly limited. For example, the control device 38 may derive the actual torque applied to the components of the power transmission device 10 using relational formulas, tables, etc., based on the strain acting on the components of the power transmission device 10 indicated by the detection information from the sensor 50. The control device 38 may also perform feedback control to control the drive device 14 so that the derived actual torque approaches the target torque. In addition, the control device 38 may detect contact of an obstacle with the driven member 16 based on the detection information from the sensor 50, and control the drive device 14 to stop when contact is detected.

[0032] As shown in Figure 2, the power transmission device 10 is equipped with an output connector 58 for outputting detection information from the sensor 50 to the information processing device 54. The output connector 58 is provided on a component of the power transmission device 10 (in this case, the first fixed component 32A) on which the sensor 50 is installed. The output connector 58 is used only during assembly. The mating connector 52a of a transmission member 52 for transmitting detection information from the sensor 50 to the information processing device 54 is detachably attached to the output connector 58. One of the output connector 58 and the mating connector 52a is a male connector, and the other is a female connector. The transmission member 52 is a wiring member such as a cable for wired connection between the information processing device 54 and the sensor 50. Alternatively, the transmission member 52 may be a wireless communication adapter for wireless connection between the information processing device 54 and the sensor 50. The sensor 50 is electrically connected to the output terminal built into the output connector 58 via internal wiring 60, and outputs detection information to the information processing device 54 via the transmission member 52. Furthermore, the sensor 50 itself may have a function to wirelessly output detection information.

[0033] The information processing device 54 is, for example, an information terminal (PC, tablet, etc.) used by an operator. The information processing device 54 includes a processing unit (CPU, etc.), a storage unit (ROM, RAM, etc.), an input / output interface, an input unit, an output unit, etc. The input unit is, for example, a touch panel, a mouse, a keyboard, a microphone, etc. The output unit is, for example, a touch panel, a display, a speaker, etc. The input / output interface includes a communication interface and is connected to the sensor 50 by wired or wireless connection. Detection information output from the sensor 50 is input to the processing unit, etc. of the information processing device 54 via the input / output interface.

[0034] Refer to Figure 3. The quality of the assembly is determined using an allowable range 70 set for the detected state quantity detected by the sensor 50. The allowable range 70 refers to the allowable range of the state quantity determined by at least one of the allowable upper limit 70a and the allowable lower limit. In this embodiment, an example is shown where the allowable range 70 is determined only by the allowable upper limit 70a. The allowable range 70 is stored in the storage unit of the information processing device 54.

[0035] The tolerance range 70 is set so that the specifications regarding the specific performance (lifespan, etc.) of the power transmission device 10 are satisfied when the detected state quantity, which changes depending on the load, is within the tolerance range 70. For example, if the detected state quantity Va1 is within the tolerance range 70, it indicates that the assembly state can satisfy the specifications regarding the specific performance. Conversely, if the detected state quantity Va2 is outside the tolerance range 70, it indicates that the assembly state cannot satisfy the specifications regarding the specific performance.

[0036] The degree of the relationship between the detected state quantity and the specific performance of the power transmission device 10 varies depending on the type of power transmission device 10 and the position of the sensor 50. For this reason, it is preferable to set an allowable range 70 for each type of power transmission device 10 and each position of the sensor 50, taking into account the specifications of the power transmission device 10, and to use the allowable range 70 corresponding to that type and position to determine whether the assembly is good or bad. Different types of power transmission devices 10 here refer to those in which any of the hardware components of the power transmission device 10 differ, such as the type, design dimensions, number, or material.

[0037] Refer to Figure 4. The procedure for assembling the part to be assembled 42 to the mating part 40 will be explained. In this embodiment, the process of acquiring detection information from the sensor 50 → determining whether the assembly state is good or bad is repeated, and the final assembly state is determined when a good assembly state is found.

[0038] First, connection step S10 is performed to connect the information processing device 54 and the sensor 50 so that detection information detected by the sensor 50 can be output from the sensor 50 to the information processing device 54. At this time, as described above, the mating connector 52a of the transmission member 52 is attached to the output connector 58 of the power transmission device 10.

[0039] Next, the assembly is performed by assembling the part to be assembled 42 to the assembly partner 40. After this, while the part to be assembled 42 is in the assembled state, an acquisition step S12 is performed to acquire detection information from the sensor 50. The acquisition step S12 is performed by outputting the detection information detected by the sensor 50 to the information processing device 54, and the information processing device 54 acquiring the detection information from the sensor 50. At this time, the sensor 50 may output the detection information to the information processing device 54 under the control of the information processing device 54, or the sensor 50 may automatically output the detection information to the information processing device 54.

[0040] Next, a determination step S14 is performed to determine whether the assembly state of the part to be assembled 42 is good or bad, based on the detection information from the sensor 50. Here, the quality of the assembly state of the part to be assembled 42 is determined based on whether the detected state amount indicated by the detection information is within the allowable range 70. In determination step S14, if the detected state amount is outside the allowable range 70, it is determined that the assembly state of the part to be assembled 42 is not good. Conversely, if the detected state amount is within the allowable range 70, it is determined that the assembly state of the part to be assembled 42 is good.

[0041] In the determination step S14, if it is determined that the assembly state is good (Y in S14), a decision step S16 is performed to determine that assembly state as the final assembly state. Conversely, if it is determined in the determination step S14 that the assembly state is not good (N in S14), an adjustment step S18 is performed to adjust the assembly state of the assembly target product 42. The adjustment step S18 is performed when it is determined that the assembly state is not good in order to bring the detected state quantity within the allowable range 70.

[0042] Adjustment of the assembly state may be performed, for example, by (1) replacing at least one of the mating part 40 or the part to be assembled 42. This is mainly done for the purpose of sizing, which adjusts the dimensions of the mating part 40 or the part to be assembled 42 to be replaced within the range of manufacturing variation. Here, "replacement" means replacing the part to be replaced from the mating part 40 or the part to be assembled 42 with a replacement of the same type manufactured under the same manufacturing conditions as the replacement part. Here, the same manufacturing conditions mean that the design dimensions, processing conditions, materials, and other manufacturing conditions are the same. In this case, instead of replacing the entire mating part 40 or the part to be assembled 42, only some of its components may be replaced. This makes it possible to reduce the deviation from the target shape and bring the detected state amount within the allowable range 70, for example, when a defect in the assembly state is caused by distortion due to manufacturing variation. Furthermore, the replacement part 40 or part 42 is not limited to those manufactured under the same manufacturing conditions; for example, the replacement part 40 or part 42 may be manufactured under different designs or different manufacturing conditions.

[0043] In addition, the assembly condition may be adjusted by, for example, (2) machining a part that affects the assembly condition on at least one of the mating part 40 or the part to be assembled 42. This is mainly done for the purpose of sizing, which adjusts the dimensions of the part that affects the assembly condition. The "part that affects the assembly condition" here refers to, for example, the contact surfaces 34A and 34B of the mating part 40 and the part to be assembled 42. The "machining" here refers to, for example, cutting or grinding. In this case, the part that affects the assembly condition is machined to approach the target shape in the design. As a result, similar to (1), if the assembly condition defect was caused by, for example, distortion due to manufacturing variations, the deviation from the target shape can be reduced, and the detected condition amount can be brought within the allowable range 70.

[0044] In addition, the assembly condition may also be adjusted by (3) disassembling the part to be assembled 42 from the mating part 40 and reassembling the part to be assembled 42 back onto the mating part 40. At this time, after disassembling the part to be assembled 42 from the mating part 40, the presence or absence of foreign matter between the mating part 40 and the part to be assembled 42 is checked before reassembly. This makes it possible to keep the detected condition amount within the allowable range 70 in the event that a defect in the assembly condition is caused by a faulty work such as foreign matter getting caught.

[0045] In addition, adjustment of the assembly state may be achieved by moving at least one of the components of the assembled product 46 without replacing it. Here, "components" include not only the mating partner 40 and the product to be assembled 42, but also fasteners such as bolts B for fixing the product to be assembled 42 to the mating partner 40. This assumes, for example, that if the tightening degree of bolt B is too tight, the tightening degree can be changed by moving bolt B. In addition, this assumes that if the product to be assembled 42 is mistakenly placed in a position different from the target position relative to the mating partner 40, the position of the product to be assembled 42 can be changed to the target position by moving one of the two. Changing the position here means, for example, changing either the axial position or the circumferential position (phase). This makes it possible to bring the detected state amount within the allowable range 70 when the assembly state defect is caused by a work defect such as incorrect assembly. Furthermore, this change of position may be performed not only when the product to be assembled 42 is mistakenly placed in a position different from the target position, but also when it is placed in the target position. This assumes, for example, a case where the circumferential shape of the mating part 40 or the part to be assembled 42 is not constant due to manufacturing tolerances, and the circumferential position (phase) of the part to be assembled 42 relative to the mating part 40 is changed. This makes it possible to keep the detected state quantity within the allowable range 70.

[0046] After the adjustment step S18, the acquisition step S12 and judgment step S14 are performed again with the adjusted assembly state of the part to be assembled 42. This flow of adjustment step S18 → acquisition step S14 → judgment step S12 is continued until it is determined in judgment step S14 that the assembly state is good. As a result, the final assembly state is determined via the decision step S16, and the assembly work of the part to be assembled 42 is completed.

[0047] By following the above procedure, once a good assembly state is determined, the adjustment step S18 becomes unnecessary thereafter, thus reducing the amount of work required while determining the final assembly state.

[0048] The judgment step S14 and the decision step S16 may be performed by either the information processing device 54 or the worker. If the information processing device 54 performs both the judgment step S14 and the decision step S16, information (screen, sound, etc.) indicating the determined final assembly state may be output from the output unit of the information processing device 54 so that the worker can understand the final assembly state. If the worker performs both the judgment step S14 and the decision step S16, confirmation images showing the detected state quantity and the allowable range 70 may be output from the output unit of the information processing device 54 so that the worker can understand them. Alternatively, the information processing device 54 may perform the judgment step S14, output information indicating the judgment result from its output unit, and the worker may perform the decision step based on that output. Furthermore, in the assembly and adjustment step S18 of the part to be assembled 42 to the assembly partner 40, the main operator moving the assembly partner 40 and the part to be assembled 42 may be either a worker (human) or an industrial robot.

[0049] If the steps described above are to be performed by the information processing device 54, the processing program for that purpose should be stored in the memory of the information processing device 54 in advance, and each step can be executed by reading the processing program from the information processing device 54.

[0050] The above assembly work may be performed for each assembly partner 40 and each assembly target 42 if there are multiple assembly partners 40 and assembly target items 42. For example, in this embodiment, there are multiple external members 30A and 30B as assembly partners 40. The above assembly work may be performed not only when assembling the power transmission device 10 (assembly target item 42) to the first external member 30A (assembly partner 40), but also when assembling the power transmission device 10 to the second external member 30B (assembly partner 40). In the latter case, a sensor 50 may be provided on the second fixing part 32B (output internal gear 28B) fixed to the second external member 30B, and acquisition steps, etc., may be performed using the detection information of the sensor 50.

[0051] The effects of the power transmission device 10 described above will now be explained.

[0052] The power transmission device 10 is equipped with a sensor 50 that outputs detection information indicating state quantities related to the power transmission device 10 when the power transmission device 10 is being assembled to the external member 30A. Therefore, when assembling the power transmission device 10, the quality of the assembly can be determined to the extent that it can be grasped using the detection information output from the sensor 50. For example, the sensor 50 in this embodiment detects strain as a state quantity that changes depending on the load acting on the components of the power transmission device 10. Therefore, by using the detection information output from the sensor 50 to grasp the state of the load on the power transmission device 10 which changes according to the assembly state, the quality of the assembly can be determined.

[0053] By allowing the quality of the assembly to be assessed during assembly work, defects in the assembly can be detected early. Furthermore, the detection information output from sensor 50 makes it easy to determine the quality of the assembly.

[0054] Conventionally, when the load, specific performance, etc. of the power transmission device 10 changes depending on the assembly state, there was no means for the user, who received the power transmission device 10 from the manufacturer, to know whether the assembly state was good in relation to the load, specific performance, etc. In this regard, according to this embodiment, when the user of the power transmission device 10 performs assembly work, the user can use the detection information output from the sensor 50 to know whether the assembly state is good in relation to the load, specific performance, etc. Therefore, by adjusting the assembly state using the detection information output from the sensor 50, the user can improve the performance and durability of the power transmission device 10 themselves.

[0055] The manufacturer of the power transmission device 10 typically produces the device with high product precision, taking into account the large variations in the assembly state of external components 30A etc. by the user of the power transmission device 10. In this respect, according to this embodiment, the user can adjust the assembly state of the power transmission device 10 themselves, thereby reducing variations in the assembly state by the user. Therefore, the required product precision for the power transmission device 10 can be relaxed, and the manufacturing cost of the power transmission device 10 can be reduced accordingly.

[0056] The sensor 50 outputs detection information to the control device 38, which controls the controlled device 36 based on the detection information while the power transmission device 10 is in operation. Therefore, the sensor 50 used to control the control device 38 can also serve as the sensor 50 for determining whether the assembly is good or bad. Consequently, it is not necessary to incorporate a dedicated sensor for determining whether the assembly is good or bad into the power transmission device 10, and the configuration of the power transmission device 10 can be simplified.

[0057] When the sensor 50 is assembling the assembly target 42 (in this case, the power transmission device 10) to the assembly partner 40 (in this case, the external component 30A), it outputs detection information to the information processing device 54. Therefore, the control device 38 does not need to store information (tolerance range 70, processing program, etc.) for determining whether the assembly is good or bad using the detection information, and the functions of the control device 38 can be simplified.

[0058] The power transmission device 10 is equipped with an output connector 58. Therefore, when assembling the assembly target 42 (in this case, the power transmission device 10) to the assembly mat 40 (in this case, the external member 30A), the transmission member 52 is attached to the output connector 58, and detection information can be output via the transmission member 52. Furthermore, after the assembly work is completed, the transmission member 52 can be removed from the output connector 58 to avoid interference between the transmission member 52 and surrounding objects.

[0059] (Second Embodiment) Refer to Figure 5. Other work procedures for the assembly method of assembling the part to be assembled 42 to the mating part 40 will be described. Here again, an example will be described in which the part to be assembled 42 is the power transmission device 10 and the mating part 40 is the first external member 42A. In this embodiment, an assembly method will be described in which detection information from the sensor 50 is acquired in advance for each of the multiple assembly states, and then the final assembly state is determined.

[0060] First, as in the first embodiment, a connection step S10 is performed to connect the information processing device 54 and the sensor 50.

[0061] Next, an acquisition step S20 is performed to acquire detection information from the sensor 50 for each of several different assembly states obtained by adjusting the assembly state of the part to be assembled 42 with respect to the assembly partner 40. The adjustment of the assembly state is achieved, for example, by performing one of the steps described in (1) to (4) above. The acquisition step S20 repeats the process of acquiring detection information from the sensor 50 and adjusting the assembly state of the part to be assembled 42 until the detection information from the sensor 50 for a predetermined number of assembly states has been acquired.

[0062] Next, a decision step S22 is performed to determine one of the multiple assembly states as the final assembly state based on the detection information from the sensors 50 for each assembly state that has been acquired. At this time, as in the first embodiment, a determination step is performed for each assembly state to determine whether the assembly state of the product to be assembled 42 is good or bad based on the detection information from the sensors 50 that has been acquired. The content of this determination step is the same as in the first embodiment.

[0063] After this, the final assembly state is determined based on the judgment results of the judgment step performed for each assembly state. At this time, if only one assembly state is determined to be good by the judgment step, that assembly state is determined to be the final assembly state. If there are multiple assembly states that are determined to be good by the judgment step, any of them may be determined to be the final assembly state. In addition, a specific assembly state may be determined to be the final assembly state according to predetermined determination criteria. For example, a target value for the detected state quantity may be set within the allowable range 70, and the assembly state in which the detected state quantity closest to the target value was obtained may be determined to be the final assembly state. In addition, if there are no assembly states that are determined to be good by the judgment step, detection information of the sensor 50 for an additional predetermined number of assembly states may be obtained, and then the determination step S22 may be performed again.

[0064] In the decision step S22, if the assembly state differs from the determined final assembly state at that time, the parts to be assembled 42 are assembled to the mating parts 40 so that they reach the determined final assembly state. On the other hand, if the final assembly state is already determined at that time, the parts are actually used in that final assembly state.

[0065] By following the above procedure, the assembly state that is determined to be the best among multiple assembly states can be selected as the final assembly state. In other respects, the same effects as in the first embodiment can be obtained.

[0066] (Third Embodiment) Refer to Figure 6. Next, we will describe the assembly work assumed between the components of the power transmission device 10. The power transmission device 10 comprises a mating component 80 and assembly components 82A and 82B that are assembled to the mating component 80. Both the mating component 80 and the assembly components 82A and 82B are composed of one or more members.

[0067] The mating part 80 in this embodiment comprises a vibrator 22, an external gear 24, and a vibrator bearing 26. The assembly parts 82A and 82B in this embodiment include a first assembly part 82A and a second assembly part 82B. The first assembly part 82A comprises a reduction internal gear 28A, and the second assembly part 82B comprises an output internal gear 28B. Each of the mating part 80 and the assembly parts 82A and 82B comprises individual gears that constitute a gear pair 84 that mesh with each other. In this embodiment, the individual gears are the external gear 24 in the mating part 80 and the internal gears 28A and 28B in the assembly parts 82A and 82B.

[0068] In this embodiment, the assembly method describes an example where the mating part 40 in the assembly work is the mating part 80, and the item to be assembled 42 is the first assembly part 82A. When the item to be assembled 42 is assembled to the mating part 40, the specific performance of the power transmission device 10 may change depending on the assembly state of the item to be assembled 42. In this embodiment, when the first assembly part 82A, which has an internal gear 28A, is assembled to the mating part 80, which has an external gear 24, the backlash at the meshing portion of the gear pair 84 consisting of the external gear 24 and the internal gear 28A may change due to the influence of manufacturing variations (dimensional variations), etc. Here, we will explain the measures taken to determine the quality of the assembly state in relation to the backlash, which is a specific performance of the power transmission device 10.

[0069] The power transmission device 10 includes a sensor 50 that detects state quantities relating to the mating part 80 or the assembly part 82A. The state quantities relating to the mating part 80 or the assembly part 82A refer to state quantities acting on the mating part 80 or the assembly part 82A. Similar to the first embodiment, the sensor 50 detects state quantities that change according to the assembly state of the assembly target 42 relative to the assembly mating part 40. The sensor 50 detects such state quantities that are correlated with the specific performance of the power transmission device 10. This specific performance, like the state quantities detected by the sensor 50, changes according to the assembly state of the assembly target 42 (here, the assembly part 82A). In this embodiment, this "specific performance" refers to the backlash at the meshing portion of the gear pair 84, and the state quantities correlated with it refer to strain, stress, load, etc. acting on either the mating part 80 or the assembly part 82A. There is a negative correlation between backlash and strain, where the greater the backlash, the less the strain, and the smaller the backlash, the greater the strain. In this embodiment, the sensor 50 will be described as detecting strain acting on the first assembly part 82A (reduction internal gear 28A) as such a state quantity.

[0070] Refer to Figure 7. This embodiment shows an example where the allowable range 70 is determined by both an allowable upper limit 70a and an allowable lower limit 70b. The allowable range 70 set for a detected state quantity is set so that the specifications for the specific performance (in this case, backlash) of the power transmission device 10 are satisfied when the detected state quantity, which is correlated with that specific performance, is within the allowable range 70. Here, we consider the case where the specification range for backlash is set by upper and lower limits as the "specifications for the specific performance". As mentioned above, there is a negative correlation between backlash and the detected state quantity (strain). Therefore, in this case, the allowable upper limit 70a of the allowable range 70 set for the detected state quantity is set as a condition to keep the backlash above the lower limit of the specification range. Also, the allowable lower limit 70b of the allowable range 70 set for the detected state quantity is set as a condition to keep the backlash below the upper limit of the specification range.

[0071] For example, if the detected state quantity Vb1 is within the allowable range 70, it indicates that the assembly state can satisfy the specifications regarding a specific performance (backlash). Conversely, if the detected state quantities Vb2 and Vb3 are outside the allowable range 70, it indicates that the assembly state cannot satisfy the specifications regarding a specific performance (backlash). For example, consider the case where the detected state quantity Vb2 exceeds the allowable upper limit 70a of the allowable range 70, that is, the detected state quantity such as strain has an excessive effect on the assembled part 82A. In this case, it indicates that the backlash becomes excessively small, resulting in an assembly state where the backlash may fall below the lower limit of the specification range. Also, consider the case where the detected state quantity Vb3 falls below the allowable lower limit 70b of the allowable range 70, that is, the detected state quantity such as strain has an insufficient effect on the assembled part 82A. In this case, it indicates that the backlash becomes excessively large, resulting in an assembly state where the backlash may exceed the upper limit of the specification range.

[0072] Next, the assembly method for the components of the power transmission device 10 will be described. In this embodiment as well, the assembly method can be carried out using the same work procedure as in the first embodiment (see Figure 4) or the second embodiment (see Figure 5). Here, with reference to Figure 5, the flow when the work procedure is carried out using the same procedure as in the second embodiment will be briefly explained.

[0073] First, a connection step S10 is performed to connect the information processing device 54 and the sensor 50, similar to the second embodiment. Next, an acquisition step S20 is performed to acquire detection information from the sensor 50 for each of several different assembly states obtained by adjusting the assembly state of the product to be assembled 42 (here, the assembled part 82A) with respect to the mating partner 40 (here, the mating part 80). The adjustment of the assembly state may be performed, for example, by replacing at least one of the mating partner 40 or the product to be assembled 42, as described in (1) above. At this time, the internal gear 28A which becomes the product to be assembled 42 may be replaced, or the external gear 24 which is a component of the mating partner 40 may be replaced. This is mainly done for the purpose of sizing, which adjusts the dimensions of the meshing part of the gear pair 84 within the range of manufacturing variation. This makes it possible to find a combination of external gear 24 and internal gear 28A with dimensions suitable for achieving backlash within the specification range. Subsequently, following the same procedure as in the second embodiment, a decision step S22 is performed to determine one of the multiple assembly states as the final assembly state based on the detection information from the sensors 50 for each of the multiple assembly states acquired. Note that this is not limited to adjusting the dimensions of the meshing portion of the gear pair 84 within the range of manufacturing variation; for example, the mating part 40 or the assembly target part 42 manufactured with different dimensions may also be replaced.

[0074] As described in the first embodiment, the above assembly work may be performed for each assembly partner 40 and each assembly target 42 if there are multiple assembly partners 40 and assembly target items 42. For example, in this embodiment, there are multiple assembly parts 82A and 82B as assembly target items 42. Therefore, the assembly work may be performed not only when assembling the first assembly part 82A to the mating part 80, but also when assembling the second assembly part 82B to the mating part 80. In the latter case, a sensor 50 may be provided on the second assembly part 82B, and acquisition steps, etc., may be performed using the detection information of the sensor 50.

[0075] Furthermore, while the sensor 50 has so far been described as detecting state quantities related to assembly parts 82A and 82B, it may also detect state quantities acting on the mating part 80. In this case, the sensor 50 may be provided on the mating part 80 instead of the assembly parts 82A and 82B.

[0076] The effects of the power transmission device 10 described above will now be explained.

[0077] The power transmission device 10 of this embodiment includes a sensor 50 that outputs detection information indicating a state variable related to either the mating part 80 or the assembly part 82A when the assembly part 82A is being assembled to the mating part 80. Therefore, as described above, when assembling the assembly part 82A, the quality of the assembly can be determined to the extent that it can be grasped using the detection information output from the sensor 50. For example, the sensor 50 of this embodiment detects a state variable that is correlated with a specific performance of the power transmission device 10. Therefore, by using the detection information output from the sensor 50 to grasp the state of the specific performance of the power transmission device 10 (in this case, backlash) which changes according to the assembly state, the quality of the assembly can be determined.

[0078] In addition, this embodiment can also obtain the same effects as those described earlier in the first embodiment.

[0079] Furthermore, as in this embodiment, when the individual gears of the gear pair 84 are provided in both the mating part 40 and the part to be assembled 42, the following advantages are available. The following procedure is assumed for assembling a gear pair 84 with good backlash. The quality of the backlash is determined by the combination of predetermined gear dimensions of each gear constituting the gear pair 84. The predetermined gear dimensions are, for example, OBD (over ball diameter) for external gears and BBD (between ball diameter) for internal gears. Therefore, a table is created in advance that defines the combination of gear dimensions of each gear that can obtain good backlash. Next, a first gear is selected from a first group of gears manufactured under the same manufacturing conditions, and the first gear dimension of the selected first gear is measured. Next, using the table created in advance, the second gear dimension of the second gear corresponding to the measured value of the first gear dimension is identified. Next, a second gear having the identified second gear dimension is found from a second group of gears manufactured under the same manufacturing conditions. At this point, the process of selecting a second gear from the group of second gears and measuring its second gear dimension is repeated until a second gear with the specified second gear dimension is found on the table. Next, the gear pair 84 is assembled by combining the selected first gear and the found second gear.

[0080] When following this procedure, the gear dimensions of each gear must be measured in advance for each assembly operation of the gear pair 84. Furthermore, the quality of the backlash of the gear pair 84 obtained after assembly cannot usually be determined until a shipping inspection is conducted on the power transmission device 10 incorporating the gear pair 84, which checks for backlash performance (e.g., hysteresis loss). If the shipping inspection determines that the backlash performance is poor, the assembled power transmission device 10 must be disassembled and the gear pair 84 reassembled, leading to an increase in labor costs.

[0081] In this respect, according to this embodiment, when assembling the part to be assembled 42 to the mating part 40, the quality of the assembly can be determined in relation to the backlash using the detection information from the sensor 50. Therefore, it is possible to eliminate the need to measure the gear dimensions of each gear in advance for each gear pair assembly operation in order to achieve an assembly state that can obtain good backlash. Furthermore, the quality of the assembly can be determined in relation to the backlash when assembling the part to be assembled 42 to the mating part 40 before the shipment inspection of the power transmission device 10. Therefore, the risk of disassembly after the shipment inspection of the power transmission device can be reduced, and the resulting increase in work hours can be avoided.

[0082] Refer to Figures 8 and 9. Other uses of the detection information output from sensor 50 will be explained. Consider the position of the mating part 80 relative to the mating part 82A when assembling the mating part 82A to the mating part 80.

[0083] In this embodiment, the assembly part 82A, which is equipped with an internal gear 28A, is assembled to the mating part 80, which is equipped with an external gear 24, by moving the assembly part 82A, which is equipped with an internal gear 28A, relative to the mating part 80, which is equipped with an external gear 24, in the axial direction X. The position of the assembly part 82A at which a detection amount within the allowable range 70 begins to be detected during the process of moving the assembly part 82A relative to the mating part 80 is called the assembly start position Pa1. In addition, the position at which the target assembly state is achieved at that point, regardless of whether it is the final assembly state or not, when moving the assembly part 82A relative to the mating part 80 is called the assembly end position Pa2. Figure 8(A) shows the state in which the assembly part 82A is at the assembly start position Pa1, and Figure 8(B) shows the state in which the assembly part 82A is at the assembly end position Pa2. Hereinafter, the range in which the assembly part 82A moves from the assembly start position Pa1 to the assembly end position Pa2 is called the movement range R1.

[0084] The sensor 50 outputs detection information multiple times or continuously from the assembly start position Pa1 until the assembled part 82A reaches the assembly end position Pa2. In this embodiment, the sensor 50 continuously outputs detection information over the entire range from the assembly start position Pa1 to the assembly end position Pa2. Alternatively, the sensor 50 may output detection information multiple times from the assembly start position Pa1 to the assembly end position Pa2. In this case, the detection information of the sensor 50 may be output periodically at predetermined output intervals.

[0085] This allows the state of the assembled part 82 relative to the mating part 80 to be determined using the detection information output from the sensor 50 at each point in time when the sensor 50 outputs detection information. For example, in the example of the dashed line La in Figure 8, the detected state amount is within the allowable range 70 for a while after passing the assembly start position Pa1, and then exceeds the allowable upper limit at the intermediate position Pb1 within the movement range R1. This indicates that the backlash is within the specified range until position Pb1 is reached, and after reaching position Pb1, it may become a small backlash outside the specified range. This indicates, for example, that in the gear pair 84, there is a point where meshing begins after reaching position Pb1 that could cause a defect in the assembly state (for example, a point where the tooth thickness becomes excessively thick).

[0086] Furthermore, in the example of the dashed line Lb in Figure 8, the detected state quantity remains within the allowable range of 70 for a while after passing the assembly start position Pa1, and then falls below the allowable lower limit of 70b at the intermediate position Pb2 within the movement range R1. This indicates that the backlash is within the specified range until position Pb2 is reached, and after reaching position Pb2, it may become a large backlash outside the specified range.

[0087] Furthermore, the direction of movement of the assembled part 82A from the assembly start position Pa1 to the assembly end position Pa2 is not limited to the axial direction X only. This direction of movement may be a combination of the axial direction X and the circumferential direction, for example.

[0088] The specific examples of combinations of mating part 80 and assembly parts 82A and 82B are not particularly limited. When the driven device 18 is a gear device 20, the mating part 80 and assembly parts 82A and 82B may include individual gears that constitute a gear pair 84, regardless of the type of gear device 20. The specific examples of individual gears that constitute a gear pair 84 here are not particularly limited, and may include external gears, internal gears as in the embodiment, as well as a pair of external gears, a pair of bevel gears, a rack and pinion, etc.

[0089] Next, we will describe the transformation forms of each component described so far.

[0090] The specific examples of the power transmission device 10 are not particularly limited. The power transmission device 10 may consist of only one of the driven device 18 and the drive device 14, or it may consist of both the drive device 14 and the driven device 18. If both are included, the power transmission device 10 may be, for example, an electric actuator, a fluid actuator (hydraulic actuator, pneumatic actuator, etc.), etc.

[0091] The specific examples of the drive device 14 are not particularly limited and may include a motor device, a fluid drive device using a pump, etc. The specific examples of the driven device 18 are not particularly limited and may include a gear device 20, a traction drive, etc.

[0092] The specific types of gear units 20 are not particularly limited. These types may include flexible meshing gear units, eccentric oscillating gear units, simple planetary gear units, right-angle gear units, parallel-axis gear units, and the like. The specific types of eccentric oscillating gear units are also not particularly limited and may include center crank type, split type, and the like. The specific types of flexible meshing gear units are also not particularly limited and may include cylindrical type, cup type, top hat type, and the like.

[0093] Although an example has been described in which the controlled device 36 is a motor device that becomes the drive device 14, the specific example is not particularly limited. The controlled device 36 may be, for example, a fluid drive device used in a fluid actuator. In addition, the controlled device 36 may be, for example, a brake that brakes the power transmission member (rotating shaft, etc.) of the power transmission device 10.

[0094] Unlike the embodiment, the power transmission device 10 may include a control device 38. In this case, the control device 38 may be provided integrally with the power transmission device 10, or it may be provided separately from the power transmission device 10.

[0095] The sensor 50 does not need to output detection information to the control device 38 while the power transmission device 10 is in operation. The sensor 50 may also be provided separately from the sensors used for control by the control device 38 and function as a dedicated sensor for determining the quality of the assembly.

[0096] The control device 38 may also function as an information processing device 54. The sensor 50 may also output detection information to the control device 38, which also functions as an information processing device 54, when the part to be assembled 42 is being assembled to the mating part 40.

[0097] The power transmission device 10 does not necessarily need to have an output connector 58. In this case, the destination of the wiring member 56 connecting the sensor 50 and the control device 38 may be changed from the control device 38 to the information processing device 54, and the detection information from the sensor 50 may be output to the information processing device 54 via the wiring member 56. Alternatively, a wireless communication module for wireless connection with the information processing device 54 may be incorporated into the sensor 50, and the detection information from the sensor 50 to the information processing device 54 may be output without using the transmission member 52. It can be said that the method of outputting detection information from the sensor 50 to the information processing device 54 is not particularly limited.

[0098] The embodiments and variations described above are illustrative. The abstract technical ideas derived from them should not be interpreted restrictively to the content of the embodiments and variations. Many design changes are possible, such as changes, additions, and deletions of components, in the embodiments and variations. In the embodiments described above, the content that allows for such design changes is emphasized with the notation "embodiment." However, design changes are also permitted even in content without such notation. The hatching applied to the cross-sections in the drawings does not limit the material to which the hatching is applied.

[0099] Any combination of the above components is also valid. For example, any description of another embodiment may be combined with an embodiment, and any description of both an embodiment and another embodiment may be combined with a modified form. A component composed of a single member in an embodiment may be composed of multiple members. Similarly, a component composed of multiple members in an embodiment may be composed of a single member. Furthermore, any substitution of any of the components and expressions of this disclosure between methods, apparatus, systems, etc., is also valid as an embodiment of this disclosure. [Explanation of symbols]

[0100] 10...Power transmission device, 30A, 30B...External components, 36...Controlled device, 38...Control device, 40...Mate, 42...Part to be assembled, 50...Sensor, 54...Information processing device, 58...Output connector, 80...Mate component, 82A, 82B...Assembly component.

Claims

1. A power transmission device which is at least part of an actuator assembled to an external member, The system includes a sensor that detects state variables related to the power transmission device, The aforementioned state quantity is a state quantity that changes according to the assembly state of the power transmission device with respect to the external member. The sensor outputs detection information indicating the state quantity detected by the sensor when the power transmission device is assembled to the external member. The sensor is a power transmission device that outputs the detection information to a control device that controls a controlled device based on the detection information while the power transmission device is in operation.

2. The power transmission device comprises a pair of gears that mesh with each other, The power transmission device according to claim 1, wherein the sensor detects a state quantity correlated with the backlash at the meshing portion of the gear pair.

3. The power transmission device according to claim 1, wherein the sensor outputs the detection information to an information processing device separate from the control device when the power transmission device is assembled to the external member.

4. The power transmission device according to claim 3, further comprising an output connector for outputting the detection information to the information processing device.

5. An assembly method for assembling an item to be assembled to a mating partner, The mating part is an external member according to any one of claims 1 to 4, and the part to be assembled is a power transmission device according to any one of claims 1 to 4. An acquisition step of acquiring detection information from the sensor for each of several different assembly states obtained by adjusting the assembly state of the product to be assembled with respect to the assembly partner, An assembly method comprising: a decision step of determining one of the multiple assembly states as the final assembly state based on the detection information of the sensor for each of the multiple assembly states acquired.

6. An assembly method for assembling an item to be assembled to a mating partner, The mating part is an external member according to any one of claims 1 to 4, and the part to be assembled is a power transmission device according to any one of claims 1 to 4. An acquisition step in which detection information of the sensor is acquired when the product to be assembled is in an assembled state with respect to the assembly partner, A determination step is to determine whether the assembly state is good or bad based on the detection information of the acquired sensor, The process includes a determination step in which, if it is determined that the aforementioned assembly state is good, that assembly state is determined to be the final assembly state, An assembly method in which, if it is determined that the assembly state is not good, the assembly state of the parts to be assembled is adjusted, and the acquisition step and the determination step are performed again.

7. A power transmission device that is at least part of an actuator comprising a mating part and an assembly part that is assembled to the mating part, The system includes a sensor that detects a state quantity relating to the mating part or the assembly part, The aforementioned state quantity is a state quantity that changes according to the assembly state of the assembly part relative to the mating part. The sensor outputs detection information indicating the state quantity detected by the sensor when the assembly part is being assembled to the mating part. The sensor is a power transmission device that outputs the detection information to a control device that controls a controlled device based on the detection information while the power transmission device is in operation.

8. The power transmission device according to claim 7, wherein the sensor outputs detection information from the sensor multiple times or continuously from the assembly start position to the assembly end position when assembling the assembly part to the mating part.

9. The power transmission device comprises a pair of gears that mesh with each other, The power transmission device according to claim 7, wherein the sensor detects a state quantity correlated with the backlash at the meshing portion of the gear pair.

10. The power transmission device according to claim 7, wherein the sensor outputs the detection information to an information processing device separate from the control device when the assembly part is being assembled to the mating part.

11. An assembly method for assembling the part to be assembled to the part to be assembled, The part to be assembled is a mating part according to any one of claims 7 to 10, and the mating part is an assembly part according to any one of claims 7 to 10. An acquisition step of acquiring detection information from the sensor for each of several different assembly states obtained by adjusting the assembly state of the product to be assembled with respect to the assembly partner, An assembly method comprising: a decision step of determining one of the multiple assembly states as the final assembly state based on the detection information of the sensor for each of the multiple assembly states acquired.

12. An assembly method for assembling the part to be assembled to the part to be assembled, The part to be assembled is a mating part according to any one of claims 7 to 10, and the mating part is an assembly part according to any one of claims 7 to 10. An acquisition step in which detection information of the sensor is acquired when the product to be assembled is in an assembled state with respect to the assembly partner, A determination step is to determine whether the assembly state is good or bad based on the detection information of the acquired sensor, The process includes a determination step in which, if it is determined that the aforementioned assembly state is good, that assembly state is determined to be the final assembly state, An assembly method in which, if it is determined that the assembly state is not good, the assembly state of the parts to be assembled is adjusted, and the acquisition step and the determination step are performed again.

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