A hub connection structure and a speed reducer

Abstract

The utility model relates to a kind of axle hub connecting structure and speed reducer in the technical field of speed reducer, the axle hub connecting structure includes drive shaft and drive hub, outer spline is set on drive shaft, inner spline is set in the center of drive hub, the thickness of gear body gradually increases along the assembly direction on the axial direction of drive shaft, the width of gear slot gradually decreases along the assembly direction on the axial direction of drive hub, gear body and gear slot cooperate, when drive shaft and drive hub are assembled together, along respective assembly direction assembly is carried out, first tooth side wall in gear body is constantly close to and adhere to third gear slot side wall in corresponding gear slot, similarly, second tooth side wall is constantly close to and adhere to fourth gear slot side wall, thus both eliminate the side gap between gear body and gear slot, and increase the contact area between both, while improving the transmission torque, transmission accuracy, response speed, stiffness life and vibration noise are improved.

Description

Technical Field

[0001] This utility model relates to the field of speed reducer technology, and in particular to a shaft hub connection structure and a speed reducer. Background Technology

[0002] In the field of speed reducer technology, the RV reducer is a precision reducer widely used as a joint reducer in articulated industrial robots. It boasts advantages such as small size, light weight, high load capacity, long lifespan, high precision, high rigidity, and a wide transmission ratio range. The RV reducer is a two-stage reducer composed of a pinwheel meshing reduction mechanism and a planetary meshing reduction mechanism. In existing reducers, the motor drives the input shaft in forward and reverse rotation during operation. The input shaft, through external gear meshing, drives the planetary gears in forward and reverse rotation. The planetary gears, through spline connections, drive the eccentric shaft in forward and reverse rotation. Due to backlash in the connection between the external spline of the eccentric shaft and the internal spline of the planetary gears, and due to manufacturing errors, the backlash varies between each set of planetary gears and the eccentric shaft. These factors directly affect the reducer's transmission accuracy, response speed, rigidity, lifespan, and vibration noise. Utility Model Content

[0003] The technical problem to be solved by this utility model is that in the prior art, there is a backlash in the inner and outer spline connection of the shaft hub connection structure. Due to the existence of manufacturing errors, the size of the backlash varies, which directly affects the overall transmission accuracy, response speed, stiffness, life and vibration noise of the reducer. Therefore, a shaft hub connection structure and reducer are provided.

[0004] This utility model aims to provide a shaft-hub connection structure, including: A drive shaft, on which an external spline is provided; The drive hub has an internal spline at its center; The thickness of the external spline teeth gradually increases along the axial direction of the drive shaft assembly direction, and the width of the internal spline tooth groove gradually decreases along the axial direction of the drive hub assembly direction. The drive shaft is assembled with the drive hub, and there is an assembly position where the tooth body and the tooth groove fit together without any side clearance.

[0005] In some embodiments, the drive shaft has a first end and a second end, and the thickness of the tooth body of the external spline at the second end is greater than the thickness at the first end; The drive hub has a third end and a fourth end, and the width of the tooth groove of the internal spline at the fourth end is greater than the width of the third end; The thickness of the tooth body at the second end is greater than or equal to the width of the tooth groove at the fourth end, and the thickness of the tooth body at the first end is less than the width of the tooth groove at the third end. When the drive shaft is assembled with the drive hub, the first end of the external spline of the drive shaft is inserted into the fourth end of the internal spline of the drive hub until the tooth body and the tooth groove are in a fit position without any side clearance, and the assembly is completed.

[0006] In some embodiments, the tooth body has a tooth top wall and a first tooth side wall located on a first side of the tooth top wall, and a second tooth side wall located on a second side of the tooth top wall; The first tooth sidewall is configured as an inclined wall that is inclined along the axial direction of the drive shaft, and the second tooth sidewall is configured as an inclined wall that is inclined along the axial direction of the drive shaft. The first side and the second side are the two opposite sides of the tooth top wall.

[0007] In some embodiments, the tooth groove has a tooth groove bottom wall, a third tooth groove side wall located on the third side of the tooth groove bottom wall, and a fourth tooth groove side wall located on the fourth side of the tooth groove bottom wall; The third tooth groove sidewall is constructed as an inclined wall that is inclined along the axial direction of the drive hub, and the fourth tooth groove sidewall is constructed as an inclined wall that is inclined along the axial direction of the drive hub. The third side and the fourth side are the two opposite sides of the bottom wall of the tooth groove.

[0008] In some embodiments, the inclination angles of the first tooth sidewall and the third tooth groove sidewall are both θ; And / or, the inclination angles of the second tooth sidewall and the fourth tooth groove sidewall are both θ; Where 1°≤θ≤2.5°.

[0009] In some embodiments, the cross-section of the tooth body is designed to be trapezoidal, and the cross-section of the tooth groove is designed to be trapezoidal.

[0010] In some embodiments, the tooth body has an effective length L along the axial direction of the drive shaft, the effective length L being the distance between the first end and the second end; The thickness of the drive hub in the axial direction is B; Where L > B.

[0011] In some embodiments, a speed reducer is provided, comprising: The above-mentioned shaft-hub connection structure.

[0012] In some embodiments, the drive shaft is configured as an eccentric shaft, and the drive hub is configured as a planetary gear; the reducer further includes: An input shaft that meshes with the planetary gears via external teeth; The cycloidal wheel and planetary carrier are provided, wherein the input end of the cycloidal wheel is connected to the output end of the eccentric shaft, and the output end of the cycloidal wheel is connected to the input end of the planetary carrier.

[0013] In some embodiments, the reducer is a rotary vector reducer.

[0014] The solution provided by this utility model has the following advantages compared with the prior art: The thickness of the tooth body on the drive shaft is designed to gradually increase along the axial direction of the drive shaft assembly, while the tooth groove on the drive hub is designed to gradually decrease along the axial direction of the drive hub assembly. Thus, the tooth body and tooth groove cooperate, so that when the drive shaft and drive hub are assembled together, they are assembled along their respective assembly directions. This results in the first tooth sidewall in the tooth body continuously approaching and fitting with the third tooth groove sidewall in the corresponding tooth groove. Similarly, the second tooth sidewall continuously approaches and fits with the corresponding fourth tooth groove sidewall. This eliminates the backlash between the tooth body and the tooth groove, increases the contact area between them, improves the torque transmission, and also improves the transmission accuracy, response speed, stiffness, lifespan, vibration, and noise. Attached Figure Description

[0015] The accompanying drawings, as part of this utility model, are used to provide a further understanding of the present utility model. The illustrative embodiments and descriptions of the present utility model are used to explain the present utility model, but do not constitute an undue limitation of the present utility model. Obviously, the drawings described below are merely some embodiments; those skilled in the art can obtain other drawings based on these drawings without creative effort. In the drawings: Figure 1 It is an existing internal and external spline connection structure; Figure 2 This is a schematic diagram of the drive shaft structure shown in an embodiment of the present invention; Figure 3 yes Figure 2 Enlarged view of point A in the middle; Figure 4 This is a cross-sectional view of the drive shaft shown in an embodiment of the present invention; Figure 5 yes Figure 4 Sectional view along the GG direction; Figure 6 This is a schematic diagram of the drive hub structure shown in an embodiment of the present invention; Figure 7 yes Figure 6 Enlarged view of point C in the middle; Figure 8 This is a cross-sectional view of the drive hub shown in an embodiment of the present invention; Figure 9 yes Figure 8 Sectional view along the HH direction; Figure 10 This is a schematic diagram of the tooth body and tooth groove mating shown in an embodiment of the present invention; Figure 11 This is a cross-sectional view of the reducer shown in an embodiment of the present invention; Figure 12 This is a side view of the reducer shown in an embodiment of the present invention.

[0016] In the diagram: 1'-external spline, 2'-internal spline, 3'-side clearance, 1-drive shaft, 101-tooth body, 1011-tooth top wall, 1012-first tooth side wall, 1013-second tooth side wall, 1014-second end, 1015-first end, 2-drive hub, 201-tooth groove, 2011-tooth groove bottom wall, 2012-third tooth groove side wall, 2013-fourth tooth groove side wall, 2014-fourth end, 2015-third end, 3-input shaft, 4-cycloidal wheel, 5-planetary carrier.

[0017] It should be noted that these accompanying drawings and textual descriptions are not intended to limit the scope of the present invention in any way, but rather to illustrate the concept of the present invention to those skilled in the art by referring to specific embodiments. Detailed Implementation

[0018] In the description of this utility model, it should be noted that the terms "inner" and "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. They are only for the convenience of describing this utility model 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 utility model.

[0019] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," "contact," and "communication" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0020] like Figure 1As shown, in the existing reducer, the motor drives the input shaft to rotate back and forth in both directions during operation. The input shaft, through external gear meshing, drives the planetary gears to rotate back and forth in both directions. The planetary gears, through spline connection, drive the eccentric shaft to rotate back and forth in both directions. Due to the backlash 3' present when the external spline 1' of the eccentric shaft and the internal spline 2' of the planetary gears are connected, and due to manufacturing errors, the backlash size varies for each set of planetary gears and the eccentric shaft. These factors directly affect the reducer's transmission accuracy, response speed, stiffness, lifespan, and vibration noise.

[0021] Based on this, the following embodiments are proposed.

[0022] Example 1: like Figure 2-10 As shown, this embodiment provides a shaft-hub connection structure, including: a drive shaft 1, on which an external spline is provided; a drive hub 2, on which an internal spline is provided at the center; the thickness of the tooth body 101 of the external spline gradually increases along the axial direction of the drive shaft 1, and the width of the tooth groove 201 of the internal spline gradually decreases along the axial direction of the drive hub 2; the drive shaft 1 and the drive hub 2 are assembled, and there is an assembly position where the tooth body 101 and the tooth groove 201 fit together without any side clearance.

[0023] In this embodiment, the thickness of the tooth 101 on the drive shaft 1 is designed to gradually increase along the axial direction of the drive shaft 1 during assembly, such as... Figure 2 The arrows indicate the axial assembly direction of drive shaft 1. This axial assembly direction refers to the mounting direction of other components such as hubs or gears when mounted on drive shaft 1. In this direction, the thickness of the tooth body 101 refers to the distance between two opposing sidewalls, the first tooth sidewall 1012 and the second tooth sidewall 1013, with the thickness gradually increasing. This can also be understood as the tooth tip wall 1011 of the tooth body 101 being trapezoidal, with a gradually increasing base in the axial assembly direction of drive shaft 1. Similarly, the tooth groove 201 on drive hub 2 is designed to gradually decrease in size along the axial assembly direction of drive hub 2. Figure 6The arrows indicate the axial assembly direction of the drive hub 2. This axial assembly direction refers to the installation direction when other shaft components are inserted into the shaft holes of the drive hub 2. In this direction, the width of the tooth groove 201 refers to the distance between two opposing sidewalls on the tooth groove 201, specifically the third tooth groove sidewall 2012 and the fourth tooth groove sidewall 2013. The width increases with distance between them. Alternatively, the bottom wall 2011 of the tooth groove 201 can be trapezoidal, with a gradually decreasing bottom edge in the axial assembly direction of the drive hub 2, thereby allowing the tooth body 101 to mate with the tooth groove 201. This allows the drive shaft 1 and drive hub 2 to be assembled along their respective assembly directions when they are assembled together. This results in the first tooth sidewall 1012 in the tooth body 101 continuously approaching and fitting with the third tooth groove sidewall 2012 in the corresponding tooth groove 201. Similarly, the second tooth sidewall 1013 continuously approaches and fits with the corresponding fourth tooth groove sidewall 2013. This eliminates the side clearance between the tooth body 101 and the tooth groove 201 and increases the contact area between them. This improves the torque transmission while also improving transmission accuracy, response speed, stiffness, lifespan, vibration, and noise.

[0024] Optionally, such as Figure 4 , 5 As shown in Figures 8 and 9, in one implementation of this embodiment, the drive shaft 1 has a first end 1015 and a second end 1014, and the thickness of the tooth body 101 of the external spline located at the second end 1014 is greater than the thickness located at the first end 1015. The drive hub 2 has a third end 2015 and a fourth end 2014, and the width of the tooth groove 201 of the internal spline at the fourth end 2014 is greater than the width of the third end 2015. The thickness of the tooth body 101 at the second end 1014 is greater than or equal to the width of the tooth groove 201 at the fourth end 2014, and the thickness of the tooth body 101 at the first end 1015 is less than the width of the tooth groove 201 at the third end 2015. When the drive shaft 1 is assembled with the drive hub 2, the first end 1015 of the external spline of the drive shaft 1 is inserted into the fourth end 2014 of the internal spline of the drive hub 2 until the tooth body 101 and the tooth groove 201 are in a fit position without any side clearance, and the assembly is completed.

[0025] In this embodiment, preferably, the axial assembly direction of the drive shaft 1 is along the direction from the first end 1015 to the second end 1014; the axial assembly direction of the drive hub 2 is along the direction from the fourth end 2014 to the third end 2015; when the drive shaft 1 and the drive hub 2 are assembled, the tooth body 101 is inserted into the corresponding tooth groove 201 along the direction from the fourth end 2014 to the third end 2015, or the tooth groove 201 is fitted into the corresponding tooth body 101 along the direction from the first end 1015 to the second end 1014.

[0026] In this embodiment, the thickness of the second end 1014 is a2, which is the large end of the tooth body; the thickness of the first end 1015 is a1, which is the small end of the tooth body; the thickness of the tooth body 101 gradually increases from the first end 1015 to the second end 1014; the width of the fourth end 2014 is A2, which is the large end of the tooth groove; the width of the third end 2015 is A1, which is the small end of the tooth groove; the width of the tooth groove 201 gradually increases from the third end 2015 to the fourth end 2014. When the drive shaft 1 is assembled with the drive hub 2, the tooth body 101 is inserted into the tooth groove 201 along the fourth end 2014 to the third end 2015. Preferably, the second end 1014... End 1014 is the termination position, the first end 1015 is the starting position, the fourth end 2014 is the widest part of the tooth groove 201, and the third end 2015 is the narrowest part of the tooth groove 201. Under this condition, the thickness a2 of the second end 1014 is greater than the width A2 of the fourth end 2014. The drive hub 2 moves along the axial direction of the drive shaft 1 to the termination position. At this point, the thickness of the tooth body 101 is greater than the widest width of the tooth groove 201, and the tooth groove 201 cannot continue to move on the tooth body 101, thus being limited to the termination position. This design makes the assembly between the drive shaft 1 and the drive hub 2 have a clear termination position, making the assembly more precise and convenient. The tooth groove 201 is fitted into the tooth body 101 along the first end 1015 to the second end 1014. The thickness a1 of the first end 1015 is less than the width A1 of the third end 2015, allowing the tooth body 101 to be inserted into the corresponding tooth groove 201. That is, during the assembly process of the drive shaft 1 and the drive hub 2, when the drive shaft 1 is inserted along the axial direction of the drive hub 2, the tooth body 101 can completely penetrate the tooth groove 201, so that the drive hub 2 is completely located on the drive shaft 1, ensuring the reliability of the assembly of the two.

[0027] In this embodiment, at the termination position in the axial assembly direction of the drive shaft 1, the thickness of the tooth body 101 is greater than the width of the widest part of the tooth groove 201, so as to limit the drive hub 2 at the termination position. That is, during the assembly process of the drive shaft 1 and the drive hub 2, the drive hub 2 moves to the termination position along the axial assembly direction of the drive shaft 1. At this position, the thickness of the tooth body 101 is greater than the widest width of the tooth groove 201, and the tooth groove 201 cannot continue to move on the tooth body 101, thus being limited at the termination position. This design makes the assembly between the drive shaft 1 and the drive hub 2 have a clear termination position, making the assembly more precise and convenient. At the starting position of the assembly direction along the axial direction of the drive shaft 1, the thickness of the tooth body 101 is less than the width of the narrowest part of the tooth groove 201, so as to allow the tooth body 101 to be inserted into the corresponding tooth groove 201. That is, during the assembly process of the drive shaft 1 and the drive hub 2, when the drive shaft 1 is inserted along the axial direction of the drive hub 2, the tooth body 101 can completely penetrate the tooth groove 201, so that the drive hub 2 is completely located on the drive shaft 1, ensuring the reliability of the assembly of the two.

[0028] Optionally, such as Figure 2 , 3 As shown, in one implementation of this embodiment, the tooth body has a tooth top wall 1011, a first tooth side wall 1012 located on a first side of the tooth top wall 1011, and a second tooth side wall 1013 located on a second side of the tooth top wall 1011; the first tooth side wall 1012 is constructed as an inclined wall in an inclined state along the axial direction of the drive shaft 1, and the second tooth side wall 1013 is constructed as an inclined wall in an inclined state along the axial direction of the drive shaft 1; wherein, the first side and the second side are respectively two opposite sides of the tooth top wall 1011.

[0029] In this embodiment, by constructing the first tooth sidewall 1012 as an inclined wall that gradually tilts towards the first side along the axial assembly direction of the drive shaft 1, and constructing the second tooth sidewall 1013 as an inclined wall that gradually tilts towards the second side along the axial assembly direction of the drive shaft 1, the thickness of the tooth body 101 gradually increases along the axial assembly direction of the drive shaft 1. Thus, when the tooth body 101 mates with the tooth groove 201, they are assembled along their respective assembly directions, forming the first tooth sidewall 1012 in the tooth body 101 continuously approaching and fitting with the third tooth groove sidewall 2012 in the corresponding tooth groove 201. Similarly, the second tooth sidewall 1013 continuously approaches and fits with the corresponding fourth tooth groove sidewall 2013. This not only eliminates the side clearance between the tooth body 101 and the tooth groove 201, but also increases the contact area between them. While improving the transmission torque, the transmission accuracy, response speed, stiffness life, and vibration noise are all improved.

[0030] Optionally, such as Figure 6 , 7As shown, in one implementation of this embodiment, the tooth groove 201 has a tooth groove bottom wall 2011, a third tooth groove side wall 2012 located on the third side of the tooth groove bottom wall 2011, and a fourth tooth groove side wall 2013 located on the fourth side of the tooth groove bottom wall 2011; the third tooth groove side wall 2012 is constructed as an inclined wall in an inclined state along the axial direction of the drive hub 2, and the fourth tooth groove side wall 2013 is constructed as an inclined wall in an inclined state along the axial direction of the drive hub 2; wherein, the third side and the fourth side are respectively two opposite sides of the tooth groove bottom wall 2011.

[0031] In this embodiment, by constructing the third tooth groove sidewall 2012 as an inclined wall that gradually slopes towards the fourth side along the axial assembly direction of the drive hub 2, and constructing the fourth tooth groove sidewall 2013 as an inclined wall that gradually slopes towards the third side along the axial assembly direction of the drive hub 2, the width of the tooth groove 201 gradually decreases along the axial assembly direction of the drive hub 2. Thus, when the tooth body 101 and the tooth groove 201 mate, they are assembled along their respective assembly directions, forming that the first tooth sidewall 1012 in the tooth body 101 continuously approaches and fits against the third tooth groove sidewall 2012 in the corresponding tooth groove 201. Similarly, the second tooth sidewall 1013 continuously approaches and fits against the corresponding fourth tooth groove sidewall 2013. This eliminates the side clearance between the tooth body 101 and the tooth groove 201, increases the contact area between them, improves the torque transmission, and also improves the transmission accuracy, response speed, stiffness life, and vibration noise.

[0032] Optionally, such as Figure 5 , 9 As shown, in one implementation of this embodiment, the inclination angles of the first tooth sidewall 1012 and the third tooth groove sidewall 2012 are both θ; and / or, the inclination angles of the second tooth sidewall 1013 and the fourth tooth groove sidewall 2013 are both θ; wherein, 1°≤θ≤2.5°.

[0033] In this embodiment, for example, the inclination angles of the first tooth sidewall 1012, the second tooth sidewall 1013, the third tooth groove sidewall 2012, and the fourth tooth groove sidewall 2013 are all designed to be θ. During the assembly process of the drive shaft 1 and the drive hub 2, the drive hub 2 moves to the termination position along the axial assembly direction of the drive shaft 1. During this process, the third tooth groove sidewall 2012 in the tooth groove 201 and the first tooth sidewall 1012 in the corresponding tooth body 101 continuously approach each other until they fit together, and the fourth tooth groove sidewall 2013 in the tooth groove 201 and the second tooth sidewall 1013 in the corresponding tooth body 101 continuously approach each other until they fit together. This eliminates the side clearance between the tooth body 101 and the tooth groove 201, increases the contact area between them, and limits θ to a small angle. The small angle design can avoid the problem of the tooth body 101 being too thin and easily broken, and also avoid the drive hub 2 being subjected to a large force from the drive shaft 1 in the axial direction during the driving process, which would cause axial sliding.

[0034] Optionally, such as Figure 5 , 9 As shown, in one implementation of this embodiment, the cross-section of the tooth body 101 is designed as a trapezoid, and the cross-section of the tooth groove 201 is designed as a trapezoid.

[0035] In this embodiment, for example, the tooth top wall 1011 is designed as a trapezoid, so that the thickness of the tooth body 101 gradually increases along the axial direction of the drive shaft 1. This allows the tooth body 101 to mate with the tooth groove 201 along their respective assembly directions, resulting in the first tooth sidewall 1012 in the tooth body 101 continuously approaching and fitting against the third tooth groove sidewall 2012 in the corresponding tooth groove 201. Similarly, the second tooth sidewall 1013 continuously approaches and fits against the corresponding fourth tooth groove sidewall 2013. This eliminates the side clearance between the tooth body 101 and the tooth groove 201 and increases the contact area between them. To increase the contact area, the bottom wall 2011 of the tooth groove is designed as a trapezoid, so that the width of the tooth groove 201 gradually decreases along the axial direction of the drive hub 2. Thus, when the tooth body 101 and the tooth groove 201 are engaged, they are assembled along their respective assembly directions, so that the first tooth sidewall 1012 in the tooth body 101 continuously approaches and fits the third tooth groove sidewall 2012 in the corresponding tooth groove 201. Similarly, the second tooth sidewall 1013 continuously approaches and fits the corresponding fourth tooth groove sidewall 2013. This eliminates the side clearance between the tooth body 101 and the tooth groove 201 and increases the contact area between them.

[0036] Optionally, such as Figure 4 , 8As shown in Figure 9, in one implementation of this embodiment, the tooth body 101 has an effective length L along the axial direction of the drive shaft 1, and the effective length L is the distance between the first end 1015 and the second end 1014; the thickness of the drive hub 2 in the axial direction is B; wherein, L > B.

[0037] In this embodiment, by limiting the effective length L of the tooth body 101 along the axial direction of the drive shaft 1 to be greater than the thickness B of the drive hub 2, that is, by limiting the effective length L of the tooth body 101 along the axial direction of the drive shaft 1 to be greater than the length B of the tooth groove 201 along the axial direction of the drive shaft 1, when the drive shaft 1 is inserted along the axial direction of the drive hub 2, the tooth body 101 can completely penetrate the tooth groove 201, so that the drive hub 2 is completely located on the drive shaft 1, ensuring the reliability of the assembly of the two.

[0038] Example 2 like Figure 11 , 12 As shown, this embodiment provides a speed reducer, including the shaft-hub connection structure of Embodiment 1. Specifically, the drive shaft 1 is constructed as an eccentric shaft, and the drive hub 2 is constructed as a planetary gear. The speed reducer also includes: an input shaft 3, which meshes with the planetary gear through external teeth; a cycloidal wheel 4 and a planetary carrier 5, wherein the input end of the cycloidal wheel 4 is drive-connected to the output end of the eccentric shaft, and the output end of the cycloidal wheel 4 is drive-connected to the input end of the planetary carrier 5.

[0039] In this embodiment, the reducer is an RV reducer, i.e., a rotary vector reducer, which includes the shaft hub connection structure in Embodiment 1. It realizes a backlash-free connection between the internal spline of the planetary gear and the external spline of the eccentric shaft, improves the accuracy and rigidity of the reducer, reduces impact and vibration, extends the overall machine life, and reduces the overall machine noise.

[0040] This embodiment provides a high-precision and low-noise RV reducer with a backlash-free connection between planetary gears and the internal and external splines of the eccentric shaft. It solves the problems of transmission accuracy, response speed, stiffness, lifespan and vibration noise caused by backlash between planetary gears and the internal and external splines of the eccentric shaft. The internal spline grooves of the planetary gears and the external spline teeth of the eccentric shaft are designed as trapezoidal structures with the same angle. The thickness of the external spline teeth of the eccentric shaft is greater than the width of the internal spline grooves of the planetary gears. The larger end of the thickness of the external spline teeth of the eccentric shaft is greater than the larger end of the internal spline grooves of the planetary gears. The smaller end of the thickness of the external spline teeth of the eccentric shaft is smaller than the smaller end of the internal spline grooves of the planetary gears. This ensures that the eccentric shaft and the planetary gears achieve a backlash-free fit when connected, and also increases the contact area and improves the transmission torque.

[0041] This invention provides a high-precision, low-noise RV reducer with a backlash-free connection between the internal spline of the planetary gear and the external spline of the eccentric shaft, while the rest of the components are no different from ordinary RV reducers.

[0042] In this embodiment, the power of the motor in the reducer is transmitted to the input shaft 3. The input shaft 3 transmits the power to the drive hub 2, i.e., the planetary gear, through external gear meshing. The planetary gear transmits the power to the drive shaft 1, i.e., the eccentric shaft, through the eccentric movement of the eccentric part, transmits the power to the cycloidal wheel 4 through the bearing hole of the cycloidal wheel 4. The cycloidal wheel 4 meshes with the needle teeth and the needle tooth housing to generate rotation and transmit the power to the planet carrier 5. The planet carrier 5 outputs the power through bolt connection.

[0043] Since the reducer provided in this embodiment includes the shaft-hub connection structure in Embodiment 1, the reducer in this embodiment has all the beneficial effects of the shaft-hub connection structure in Embodiment 1, and will not be described again.

[0044] In summary, the ingenious design of the shaft-hub connection structure lies in: First, the thickness of the tooth body on the drive shaft is designed to gradually increase along the axial direction of the drive shaft assembly, while the tooth groove on the drive hub is designed to gradually decrease along the axial direction of the drive hub assembly. Thus, the tooth body and tooth groove cooperate, so that when the drive shaft and drive hub are assembled together, they are assembled along their respective assembly directions. This results in the first tooth sidewall in the tooth body continuously approaching and fitting with the third tooth groove sidewall in the corresponding tooth groove. Similarly, the second tooth sidewall continuously approaches and fits with the corresponding fourth tooth groove sidewall. This eliminates the backlash between the tooth body and the tooth groove, increases the contact area between them, improves the torque transmission, and also improves the transmission accuracy, response speed, stiffness, lifespan, vibration, and noise.

[0045] Furthermore, at the termination position in the axial assembly direction of the drive shaft, the tooth thickness is greater than the width of the widest tooth groove, which limits the drive hub to the termination position. The drive hub moves along the axial assembly direction of the drive shaft to the termination position, where the tooth thickness is greater than the widest tooth groove, preventing the tooth groove from moving further on the tooth body and thus limiting it to the termination position. This design provides a clear termination position for the assembly between the drive shaft and the drive hub, making the assembly more precise and convenient. During the assembly process of the drive shaft and the drive hub, when the drive shaft is inserted along the axial assembly direction of the drive hub, the tooth body can penetrate the entire tooth groove, ensuring that the drive hub is completely located on the drive shaft, thus ensuring the reliability of the assembly.

[0046] Secondly, the inclination angles of the first tooth sidewall, the second tooth sidewall, the third tooth groove sidewall, and the fourth tooth groove sidewall are all designed to be θ. The θ is limited to a small angle. The design of a small angle can avoid the problem of the tooth body being too thin and easy to break, and also avoid the drive hub being subjected to a large force from the drive shaft in the axial direction during the driving process, which would cause axial slippage.

[0047] It can be further understood that in this disclosure, "many" refers to two or more, and other quantifiers are similar. "And / or" describes the relationship between related objects, indicating that three relationships can exist; for example, A and / or B can represent: A alone, A and B simultaneously, and B alone. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. The singular forms "a," "the," and "the" are also intended to include the plural forms unless the context clearly indicates otherwise.

[0048] It is further understood that the terms "first," "second," etc., are used to describe various types of information, but this information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another, and do not indicate a specific order or degree of importance. In fact, the expressions "first," "second," etc., are completely interchangeable. For example, without departing from the scope of this disclosure, first information can also be referred to as second information, and similarly, second information can also be referred to as first information.

[0049] It is further understood that although operations are described in a specific order in the accompanying drawings in the embodiments of this disclosure, this should not be construed as requiring these operations to be performed in the specific order or serial order shown, or requiring all of the shown operations to be performed to obtain the desired result. In certain environments, multitasking and parallel processing may be advantageous.

[0050] Other embodiments of this disclosure will readily occur to those skilled in the art upon consideration of the specification and practice of the utility models disclosed herein. This application is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this disclosure are indicated by the following claims.

[0051] It should be understood that this disclosure is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this disclosure is limited only by the appended claims.

Claims

1. A shaft-hub connection structure, characterized in that, include: Drive shaft (1), on which an external spline is provided; Drive hub (2), the center of which is provided with an internal spline; The thickness of the tooth body (101) of the external spline gradually increases along the axial assembly direction of the drive shaft (1), and the width of the tooth groove (201) of the internal spline gradually decreases along the axial assembly direction of the drive hub (2). The drive shaft (1) is assembled with the drive hub (2), and there is an assembly position where the tooth body (101) and the tooth groove (201) fit together without any side clearance.

2. The shaft-hub connection structure according to claim 1, characterized in that, The drive shaft (1) has a first end (1015) and a second end (1014), and the thickness of the tooth body (101) of the external spline at the second end (1014) is greater than the thickness at the first end (1015). The drive hub (2) has a third end (2015) and a fourth end (2014), and the width of the tooth groove (201) of the internal spline at the fourth end (2014) is greater than the width of the third end (2015). The thickness of the tooth (101) at the second end (1014) is greater than or equal to the width of the tooth groove (201) at the fourth end (2014), and the thickness of the tooth (101) at the first end (1015) is less than the width of the tooth groove (201) at the third end (2015). When the drive shaft (1) is assembled with the drive hub (2), the first end (1015) of the external spline of the drive shaft (1) is inserted into the fourth end (2014) of the internal spline of the drive hub (2) until the tooth body (101) and the tooth groove (201) are fitted together without any side clearance, and the assembly is completed.

3. The shaft-hub connection structure according to claim 1, characterized in that, The tooth body (101) has a tooth top wall (1011) and a first tooth side wall (1012) located on the first side of the tooth top wall (1011) and a second tooth side wall (1013) located on the second side of the tooth top wall (1011). The first tooth sidewall (1012) is configured as an inclined wall that is inclined in the axial direction of the drive shaft (1), and the second tooth sidewall (1013) is configured as an inclined wall that is inclined in the axial direction of the drive shaft (1). The first side and the second side are the two opposite sides of the tooth top wall (1011).

4. The shaft-hub connection structure according to claim 3, characterized in that, The tooth groove (201) has a tooth groove bottom wall (2011) and a third tooth groove side wall (2012) located on the third side of the tooth groove bottom wall (2011) and a fourth tooth groove side wall (2013) located on the fourth side of the tooth groove bottom wall (2011). The third tooth groove sidewall (2012) is constructed as an inclined wall that is inclined in the axial direction of the drive hub (2), and the fourth tooth groove sidewall (2013) is constructed as an inclined wall that is inclined in the axial direction of the drive hub (2). The third side and the fourth side are the two opposite sides of the tooth groove bottom wall (2011).

5. The shaft-hub connection structure according to claim 4, characterized in that, The inclination angles of the first tooth sidewall (1012) and the third tooth groove sidewall (2012) are both θ; And / or, the inclination angles of the second tooth sidewall (1013) and the fourth tooth groove sidewall (2013) are both θ; Where 1°≤θ≤2.5°.

6. The shaft-hub connection structure according to claim 1, characterized in that, The cross-section of the tooth body (101) is designed to be trapezoidal, and the cross-section of the tooth groove (201) is designed to be trapezoidal.

7. The shaft-hub connection structure according to claim 2, characterized in that, The tooth (101) has an effective length L along the axial direction of the drive shaft (1), and the effective length L is the distance between the first end (1015) and the second end (1014); The thickness of the drive hub (2) in the axial direction is B; Where L > B.

8. A speed reducer, characterized in that, include: The shaft hub connection structure as described in any one of claims 1-7.

9. The reducer according to claim 8, characterized in that, The drive shaft (1) is configured as an eccentric shaft, and the drive hub (2) is configured as a planetary gear; the reducer further includes: Input shaft (3), which meshes with the planetary gear through external teeth; Cycloidal wheel (4) and planetary carrier (5), the input end of the cycloidal wheel (4) is connected to the output end of the eccentric shaft, and the output end of the cycloidal wheel (4) is connected to the input end of the planetary carrier (5).

10. The reducer according to claim 8, characterized in that, The reducer is a rotary vector reducer.

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