A distance measuring device, a reducer box assembly line, and a cushion selection method

Abstract

The application provides a distance measuring device, a reducer box assembly line and a pad selecting method. The distance measuring device comprises a comparison instrument, a bearing part and a calibration part. The comparison instrument comprises a detection head. The bearing part is arranged opposite to the comparison instrument in a first direction. An area for passing through a conveying line is formed between the comparison instrument and the bearing part. The conveying line is used for conveying a detection target. The calibration part is located on one side of the comparison instrument in a second direction. The calibration part is used for calibrating the comparison instrument. The calibration part comprises a first calibration surface and a second calibration surface. The first calibration surface and the second calibration surface are perpendicular to a detection direction. The distance between the first calibration surface and the second calibration surface is equal to the theoretical distance between a first detection surface and a second detection surface of the detection target. The material of the calibration part is the same as that of the detection target, so as to compensate for the thermal deformation of the detection target. The distance measuring device can improve the accuracy of distance measurement.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of reducer gasket selection, and in particular to a distance measuring device, a reducer box assembly line and a gasket selection method. BACKGROUND

[0002] When assembling a front box and a rear box of a reducer, it is particularly important to select a gasket with a proper thickness, which is used to compensate for an axial gap caused by machining errors or other factors.

[0003] For example, the distance a between the end face of a bearing located in the front box and the joint surface of the front box and the rear box, and the distance b between the gasket mounting surface of the rear box and the joint surface of the front box and the rear box need to be measured, and a gasket is selected according to the difference between the two distances, so as to eliminate the axial gap between the bearing and the rear box after the front box and the rear box are assembled.

[0004] The related art currently adopts online measurement. The front box and the rear box reach a measurement station along a conveying line, and a contact type displacement sensor arranged at the measurement station is moved and contacted with a surface to be measured, so as to measure the distance from the zero point to the surface to be measured, and then the distance between the surfaces to be measured is converted.

[0005] Since this measurement method needs to use multiple contact type displacement sensors, each sensor itself has a certain error, and therefore the errors are easily amplified by superposition, and the contact type displacement sensor cannot compensate for thermal expansion and contraction caused by temperature changes, resulting in inaccurate measurement results. SUMMARY

[0006] The present application aims to at least solve one of the technical problems existing in the prior art. To this end, the present application provides a distance measuring device, a reducer box assembly line and a gasket selection method, which can improve the accuracy of distance measurement.

[0007] According to the distance measuring device provided by the present application, the distance measuring device comprises a comparison instrument, a bearing and a calibration piece. The comparison instrument comprises a detection head. The bearing is arranged opposite the comparison instrument in a first direction. An area for passing through a conveying line is formed between the comparison instrument and the bearing. The conveying line is used to convey a detection target. The calibration piece is located on one side of the comparison instrument in a second direction. The calibration piece is used to calibrate the comparison instrument. The calibration piece comprises a first calibration surface and a second calibration surface. The first calibration surface and the second calibration surface are perpendicular to the detection direction. The distance between the first calibration surface and the second calibration surface is equal to the theoretical distance between a first detection surface and a second detection surface of the detection target. The material of the calibration piece is the same as the material of the detection target, so as to compensate for the thermal deformation of the detection target.

[0008] According to the distance measuring device provided in the application, at least the following technical effects are achieved: on the one hand, the detection target is detected by the comparison instrument, and different sampling points are detected by the same detection head, which can reduce the risk of error superposition and amplification; on the other hand, since the material of the calibration piece is consistent with the detection target, the sensitivity of the calibration piece and the detection target to temperature is basically consistent, so that the size change of the calibration piece at different temperatures can reflect the size change of the detection target, and then the calibration piece can compensate the influence of the thermal deformation of the detection target on the detection result of the comparison instrument, so that the distance measuring device can improve the accuracy of distance measurement.

[0009] According to some embodiments of the application, the calibration piece includes a first calibration column and a second calibration column, an end face of the first calibration column serves as the first calibration face, and an end face of the second calibration column serves as the second calibration face.

[0010] According to some embodiments of the application, the distance measuring device includes a first driving member and a first mounting seat, the calibration piece is mounted on the first mounting seat, and the first driving member is connected to the first mounting seat and is used to drive the first mounting seat to move in the second direction.

[0011] According to some embodiments of the application, the distance measuring device includes a second driving member and a second mounting seat, the second driving member is connected to the second mounting seat and is used to drive the second mounting seat to move in the first direction, and the comparison instrument is mounted on the second mounting seat.

[0012] According to some embodiments of the application, the distance measuring device includes a third driving member, the third driving member is used to drive the carrier to move in the first direction to lift or release the detection target located on the conveying line.

[0013] The reducer box assembly line provided in the application includes a conveying line and the distance measuring device provided in the application, the conveying line includes a measuring station, and the distance measuring device is located at the measuring station.

[0014] According to some embodiments of the application, the reducer box assembly line includes a tray, the tray is placed on the conveying line, the tray is used to carry a reducer box, the tray includes a first positioning part, the carrier includes a second positioning part, and the first positioning part and the second positioning part are oppositely arranged in the first direction.

[0015] According to some embodiments of the application, the conveying line includes conveying rollers, two groups of the conveying rollers are oppositely arranged, and an avoiding area for the carrier to pass through is formed between the two groups of the conveying rollers.

[0016] According to the reducer box gasket selecting method provided in the application, the reducer box assembling line provided in the application is used, and the reducer box gasket selecting method comprises the following steps:

[0017] receiving the reducer box;

[0018] measuring the calibration piece by the comparison instrument, and recording a first actual distance;

[0019] measuring the reducer box by the comparison instrument, and recording a second actual distance;

[0020] calculating and recording the gasket thickness according to the theoretical distance, the first actual distance and the second actual distance;

[0021] sending out the reducer box.

[0022] According to some embodiments of the application, when the comparison instrument measures the calibration piece, the calibration ambient temperature is recorded, and in response to the difference between the current ambient temperature and the calibration ambient temperature exceeding a set range, the comparison instrument re-measures the calibration piece, and updates the first actual distance.

[0023] The reducer box assembling line of the application comprises the distance measuring device provided in the application, the reducer box gasket selecting method of the application uses the distance measuring device provided in the application, so that the reducer box assembling line and the reducer box gasket selecting method both have the beneficial effects brought by the distance measuring device, which will not be described here. BRIEF DESCRIPTION OF DRAWINGS

[0024] The above and / or additional aspects and advantages of the application will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings, in which:

[0025] Figure 1 is a three-dimensional schematic view of a partial structure of the reducer box assembling line of the embodiment of the application;

[0026] Figure 2 is a three-dimensional schematic view of a partial structure of the reducer box assembling line of the embodiment of the application;

[0027] Figure 3 is a flowchart of the reducer box gasket selecting method of the embodiment of the application.

[0028] REFERENCE NUMERALS:

[0029] the first frame body 110, the second frame body 120,

[0030] the comparison instrument 210, the detection head 211, the first platform 212, the second platform 213, the telescopic piece 214, the second driving piece 220, the second mounting seat 230, the second guide piece 240,

[0031] Support component 310, third drive component 320, third guide component 330,

[0032] Calibration component 410, first calibration post 411, second calibration post 412, first drive component 420, first mounting base 430, first guide component 440

[0033] Conveyor line 510, conveyor roller 511, pallet 520

[0034] First box 910, second box 920. Detailed Implementation

[0035] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0036] In the description of this application, it should be understood that the orientation descriptions, such as up, down, front, back, left, right, etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0037] In the description of this application, "several" means one or more, "more than" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0038] In the description of this application, unless otherwise expressly defined, terms such as "setup," "installation," and "connection" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this application in conjunction with the specific content of the technical solution.

[0039] Reference Figure 1 and Figure 2 The reducer assembly line provided in this application includes the distance measuring device and the conveyor line 510 provided in this application. The conveyor line 510 includes a measuring station, and the distance measuring device is located at the measuring station.

[0040] The measuring station is used for online inspection of the gearbox to determine the thickness of the shims that match the gearbox. After inspection, conveyor line 510 continues to send the gearbox downstream for assembly.

[0041] It can be understood that the reducer box is usually composed of a first box body 910 and a second box body 920 (also referred to as a front box and a rear box), and the reducer box is internally assembled with rotating shafts, bearings and other components. Due to design allowance, machining error and other reasons, the bearings have an axial gap after assembly, and therefore it is necessary to calculate the axial gap by measuring the end face distance, and then select a suitable gasket to fill the axial gap. On the one hand, the gasket should be able to limit the axial freedom of the bearing, and on the other hand, the thickness of the gasket cannot be too thick, so as to avoid affecting the normal work of the bearing.

[0042] In the related art, the distance measuring device uses a contact displacement sensor for measurement. Taking detection of the second box body 920 as an example, the contact displacement sensor is arranged in advance in the measuring device, wherein the positions of one group of contact displacement sensors correspond to the joint surface of the second box body 920 and the first box body 910, and the positions of the other group of contact displacement sensors correspond to the end face to be measured. When the second box body 920 reaches the set position of the measuring station, the contact displacement sensor moves and contacts the second box body 920, at which time one group of contact displacement sensors obtains the distance between the joint surface and the initial position, and the other group of contact displacement sensors obtains the distance between the end face to be measured and the initial position, so that the distance between the joint surface and the end face to be measured can be calculated.

[0043] The problem in the related art is that, on the one hand, the contact displacement sensor has a measurement error, and the errors of different contact displacement sensors are not the same, so if the error of the contact displacement sensor for detecting the joint surface is large, and the error of the contact displacement sensor for detecting the end face to be measured is small, the superposition of errors will occur when calculating, and the superimposed error is easy to exceed the tolerance range of the gasket. On the other hand, the reducer box has a thermal expansion and contraction phenomenon, although the reducer assembly line is usually placed in a constant temperature workshop, but the influence of thermal deformation cannot be completely eliminated, and the contact displacement sensor cannot compensate for the thermal deformation. The above reasons make the thickness of the gasket not accurate enough, affecting the product quality of the reducer box.

[0044] Continuing to refer to Figure 1 and Figure 2The distance measuring device provided in the present application comprises a comparison instrument 210, a carrier 310 and a calibration instrument 410. The comparison instrument 210 comprises a detection head 211. The carrier 310 is arranged opposite to the comparison instrument 210 in a first direction. An area for passing a conveying line 510 is formed between the comparison instrument 210 and the carrier 310. The conveying line 510 is used for conveying a detection target. The calibration instrument 410 is located on one side of the comparison instrument 210 in a second direction. The calibration instrument 410 is used for calibrating the comparison instrument 210. The calibration instrument 410 comprises a first calibration surface and a second calibration surface. The first calibration surface and the second calibration surface are perpendicular to the detection direction. The distance between the first calibration surface and the second calibration surface is equal to the theoretical distance between a first detection surface and a second detection surface of the detection target. The material of the calibration instrument is the same as the material of the detection target, so as to compensate for the thermal deformation of the detection target.

[0045] In Figure 1 and Figure 2 the embodiment, the detection target is a reducer box. The first detection surface and the second detection surface respectively refer to a joint surface and a to-be-detected end surface of the reducer box. During operation, the carrier 310 first holds the reducer box sent by the conveying line 510, then the comparison instrument 210 detects the reducer box, and finally the carrier 310 puts the reducer box back to the conveying line 510. The detection head 211 has a spatial movement freedom, so after contacting the joint surface, the detection head 211 can directly move to the to-be-detected end surface, so as to directly measure the distance between the joint surface and the to-be-detected end surface without needing to be converted by the initial position.

[0046] According to the distance measuring device provided in the present application, on the one hand, the comparison instrument 210 is used to detect the reducer box. The same detection head 211 is used to detect different sampling points, so as to reduce the risk of error superposition and amplification. On the other hand, since the material of the calibration instrument 410 is consistent with that of the reducer box, the sensitivity of the calibration instrument 410 and the reducer box to temperature is basically consistent, so that the size change of the calibration instrument 410 at different temperatures can reflect the size change of the reducer box, and then the calibration instrument 410 can compensate the influence of the thermal deformation of the reducer box on the detection result of the comparison instrument 210. The distance measuring device can improve the accuracy of distance measurement.

[0047] The reducer box assembly line provided in the present application uses the distance measuring device provided in the present application, so it has the beneficial effects brought by the distance measuring device. In the reducer box assembly line, the distance measuring device can be used to measure the first box body 910 and / or the second box body 920. One second calibration surface corresponds to one to-be-detected end surface. According to the number of rotating shafts of the reducer box, the number of to-be-detected end surfaces can be one or more, so the number of second calibration surfaces can also be one or more.

[0048] It can be understood that, in order to avoid the interference of the calibration member 410 with the conveying of the reducer box on the conveying line 510, the section of the conveying line 510 where the measuring station is located extends in the third direction, and the calibration member 410 is located on one side of the conveying line 510. The distance measuring device further comprises a rack, and the comparison instrument 210, the carrier 310, and the calibration member 410 are mounted on the rack.

[0049] With reference to Figure 1 and Figure 2 In the assembly process of the reducer box, the first box body 910 and the second box body 920 are usually placed with the openings facing upwards, and the conveying line 510 is usually arranged in the horizontal direction, so the first direction is the vertical direction (that is, the Z direction) in the corresponding embodiment. Figure 1 and Figure 2 In some other possible embodiments, the detection direction can also point to other directions according to the placement mode of the first box body 910 and the second box body 920, and the first direction can also point to other directions according to the arrangement mode of the conveying line 510.

[0050] In addition, in the corresponding embodiment of Figure 1 and Figure 2 , the second direction points to the X direction, and the third direction points to the Y direction.

[0051] The shape of the calibration member 410 can adopt different designs. It is considered that the shape also affects the thermal deformation range of the first calibration surface and the second calibration surface to a certain extent, so theoretically, the reducer box with the same size as the theoretical size as the calibration member 410 can achieve better calibration effect. However, such ideal reducer box is difficult to process, and is not easy to replace after being damaged, so it is difficult to meet the calibration needs in the assembly of a large batch of assembly lines. In order to balance the calibration effect and feasibility, in some embodiments, the calibration member 410 comprises a first calibration column 411 and a second calibration column 412, and the end surface of the first calibration column 411 serves as the first calibration surface, and the end surface of the second calibration column 412 serves as the second calibration surface. In this way, on the one hand, it is convenient to replace the first calibration surface or the second calibration surface separately, and on the other hand, the cylindrical shape can facilitate processing and improve processing precision.

[0052] In some embodiments, the distance measuring device comprises a first driving member 420 and a first mounting seat 430, the calibration member 410 is mounted on the first mounting seat 430, and the first driving member 420 is connected to the first mounting seat 430 and is used to drive the first mounting seat 430 to move in the second direction. The calibration member 410 is mounted on the first mounting seat 430. When calibration is not needed, the first driving member 420 moves the calibration member 410 away from the conveying line 510, reducing the risk of accidental damage to the calibration member 410.

[0053] With reference to Figure 1, the distance measuring device further comprises a first guide 440 extending in the second direction, and the first mounting base 430 is connected to the first guide 440, so as to ensure the movement accuracy of the first mounting base 430. The frame comprises a first frame body 110, and the first driving member 420 and the first guide 440 are mounted on the first frame body 110. The first guide 440 can adopt a guide rail in Figure 1 , and in other embodiments, a guide column, a guide groove or the like can also be adopted.

[0054] In some embodiments, the distance measuring device comprises a second driving member 220 and a second mounting base 230, the second driving member 220 is connected to the second mounting base 230, and the second driving member 220 is used to drive the second mounting base 230 to move in the first direction. The comparison instrument 210 is mounted on the second mounting base 230. The second driving member 220 can drive the comparison instrument 210 to avoid interference and reduce the conveying of the reducer box.

[0055] Referring to Figure 2 , the distance measuring device comprises a second frame body 120, and the second driving member 220 is mounted on the top of the second frame body 120. The distance measuring device further comprises a second guide 240 extending in the first direction, and the second mounting base 230 is connected to the second guide 240, so as to ensure the movement accuracy of the second mounting base 230. The second guide 240 can adopt a guide column in Figure 2 , and in other embodiments, a guide rail, a guide groove or the like can also be adopted.

[0056] In some embodiments, in order to improve the repeatability of the comparison instrument 210, reduce the effect of inertia and reduce power consumption, the comparison instrument 210 adopts a non-Cartesian coordinate system structure to control the movement of the detection head 211. For example, referring to Figure 2 , the comparison instrument 210 comprises a first platform 212, a second platform 213 and a telescopic member 214. The first platform 212 is mounted on the second mounting base 230, the detection head 211 is mounted on the second platform 213, and the telescopic member 214 is connected between the first platform 212 and the second platform 213 through a universal joint. Three groups of telescopic members 214 are connected between the first platform 212 and the second platform 213, and the detection head 211 moves in space through the extension and contraction of the telescopic members 214.

[0057] Referring to Figure 2 , in some embodiments, the distance measuring device comprises a third driving member 320, and the third driving member 320 is used to drive the carrier 310 to move in the first direction, so as to lift or release the detection target located on the conveying line 510. The distance measuring device further comprises a third guide 330 extending in the first direction, and the carrier 310 is connected to the third guide 330, so as to ensure the movement accuracy of the carrier 310. The third guide 330 can adopt aFigure 2 In some embodiments, the guide column in the guide rail is also designed as a guide rail, a guide groove, etc.

[0058] Referring to Figure 1 In some embodiments, the reducer box assembly line includes a tray 520 placed on the conveying line 510, the tray 520 is used to carry the reducer box, the tray 520 includes a first positioning part, the carrier 310 includes a second positioning part, and the first positioning part and the second positioning part are oppositely arranged in the first direction. The first positioning part and the second positioning part match each other, so that the carrier 310 can accurately position the tray 520.

[0059] In order to enable the carrier 310 to smoothly pass through the conveying line 510, in some embodiments, the conveying line 510 includes conveying rollers 511, two groups of conveying rollers 511 are oppositely arranged, and an avoidance area for the carrier to pass through is formed between the two groups of conveying rollers 511.

[0060] According to the reducer box gasket selection method provided by the present application, the reducer box assembly line provided by the present application is used.

[0061] Referring to Figure 3 The reducer box gasket selection method includes the following steps:

[0062] Step S100: receiving a reducer box;

[0063] Step S200: the comparison instrument 210 measures the calibration piece 410, and records the first actual distance;

[0064] Step S300: the comparison instrument 210 measures the reducer box, and records the second actual distance;

[0065] Step S400: according to the theoretical distance, the first actual distance and the second actual distance, the gasket thickness is calculated and recorded;

[0066] Step S500: sending out the reducer box.

[0067] According to the reducer box gasket selection method provided by the present application, by using the calibration piece 410 to calibrate the comparison instrument 210, the measurement error caused by temperature change can be compensated, so that the selection of the gasket is more accurate and reasonable, thereby improving the product quality of the reducer box. In the reducer box assembly line, steps S100 to S500 are repeated, so as to sequentially measure each reducer box passing through the measurement station.

[0068] It is understandable that performing calibration with each measurement would ensure optimal accuracy in thickness calculation, but it would affect the operating efficiency of the gearbox assembly line. When temperature changes are small, the impact of thermal deformation on dimensions is within an acceptable range. Therefore, in some embodiments, when the comparator 210 measures the calibration part 410, the calibration ambient temperature is recorded. In response to the difference between the current ambient temperature and the calibration ambient temperature exceeding a set range, the comparator 210 remeasures the calibration part 410 and updates the first actual distance. That is, a judgment step is added before step S200. When the set conditions are met, step S200 is skipped, improving the operating efficiency of the gearbox assembly line. The judgment step can be located between steps S100 and S200, or before step S100. Generally, the set range can be ±2℃ to balance measurement accuracy and operating efficiency; alternatively, ±1℃ or ±5℃ can also be used.

[0069] The theoretical distance, the first actual distance, and the second actual distance can be defined as L1, L2, and L3, respectively. In step S400, different calculation methods can be used to calculate the gasket thickness.

[0070] For example, in some embodiments, the difference between L3 and L2 is directly used as the shim thickness. Alternatively, in other embodiments, the deformation coefficient of the reducer box is calculated based on the theoretical temperature, current temperature, L1, and L2. A data table mapping the deformation coefficient is constructed. Based on L2 and L3 measured during the current calibration and the contents of the data table, the distance L4 between the mating surface and the end face to be measured of the reducer box at the theoretical temperature is calculated. The difference between L4 and L1 is used as the shim thickness. The data table can be stored in memory and retrieved and the results output by the controller, or it can be retrieved and the results output manually by searching through paper data tables or electronic documents.

[0071] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0072] In some alternative embodiments, the functions / operations referred to in the block diagrams can occur in an order other than the order referred to in the operational illustrations. For example, two blocks shown in succession can in fact be executed substantially concurrently or the blocks sometimes be executed in reverse order, depending on the functions / operations involved. Also, the embodiments presented and described in the flowcharts in this application are only examples. The steps presented and described in the flowcharts are only some (and sometimes all) of the possible various embodiments. Alternative embodiments can be conceived and carried out by a person of ordinary skill in the art, and are within the scope of the application. The disclosed methods are not limited to the operations and logical flows presented in this application. Alternative embodiments are contemplated, in which the order of various steps is changed and in which sub-steps of described larger operations are performed independently.

[0073] While embodiments of the application have been shown and described, it is to be understood that the embodiments described are only examples of the principles of the application and are not intended to limit the scope of the application to these specific embodiments. Many modifications, variations, alterations, and equivalents can be made to the described embodiments without departing from the scope of the application as defined by the claims and their equivalents.

Claims

1. A distance measuring device, characterized in that, The distance measuring device comprises a comparison instrument, a carrier arranged opposite to the comparison instrument in a first direction, a distance between the comparison instrument and the carrier forming an area for a conveying line to pass through, the conveying line being used to convey a detection target, a calibration member located on one side of the comparison instrument in a second direction, the calibration member being used to calibrate the comparison instrument, the calibration member comprising a first calibration surface and a second calibration surface, the first calibration surface and the second calibration surface being perpendicular to a detection direction, a distance between the first calibration surface and the second calibration surface being equal to a theoretical distance between a first detection surface and a second detection surface of the detection target, a material of the calibration member being the same as a material of the detection target to compensate for thermal deformation of the detection target. The calibration member comprises a first calibration column and a second calibration column, an end surface of the first calibration column serving as the first calibration surface, and an end surface of the second calibration column serving as the second calibration surface. The distance measuring device comprises a first driving member and a first mounting seat, the calibration member being mounted on the first mounting seat, and the first driving member being connected to the first mounting seat and used to drive the first mounting seat to move in the second direction. The distance measuring device comprises a second driving member and a second mounting seat, the second driving member being connected to the second mounting seat and used to drive the second mounting seat to move in the first direction, and the comparison instrument being mounted on the second mounting seat.

2. The distance measuring device according to claim 1, characterized in that The distance measuring device comprises a third driving member used to drive the carrier to move in the first direction to lift or release the detection target located on the conveying line.

3. The distance measuring device according to claim 2, characterized in that The reducer box assembly line comprises a conveying line and the distance measuring device according to any one of claims 1 to 5, the conveying line comprising a measurement station, and the distance measuring device being located at the measurement station.

4. The distance measuring device according to claim 1, characterized in that The reducer box assembly line comprises a tray placed on the conveying line, the tray being used to carry a reducer box, the tray comprising a first positioning part, and the carrier comprising a second positioning part, the first positioning part and the second positioning part being arranged opposite to each other in the first direction.

5. The distance measuring device according to claim 1, characterized in that The conveying line comprises conveying rollers, two groups of the conveying rollers being arranged opposite to each other, and an avoiding area for the carrier to pass through being formed between the two groups of the conveying rollers.

6. A reducer box assembly line characterized by, The reducer box gasket selecting method uses the reducer box assembly line according to any one of claims 6 to 8, and comprises the following steps:

7. The reducer box assembly line of claim 6, wherein, receiving a reducer box; 8. The reducer box assembly line of claim 7, wherein, measuring the calibration member by the comparison instrument and recording a first actual distance; 9. A method of selecting pads for a reducer case, the method comprising: measuring the reducer box by the comparison instrument and recording a second actual distance; calculating and recording a gasket thickness according to a theoretical distance, the first actual distance, and the second actual distance; sending out the reducer box. When the comparison instrument measures the calibration member, a calibration ambient temperature is recorded, and in response to a difference between a current ambient temperature and the calibration ambient temperature exceeding a set range, the comparison instrument re-measures the calibration member and updates the first actual distance. ​ ​ 10. The method of claim 9, wherein, ​

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