Transmission structure and electric power tool

Abstract

The application discloses a transmission structure and electric tool, which comprises a transmission shaft, which comprises a transmission section and a support section in sequence along the axial direction, the support section is cylindrical, the transmission section has a transmission surface for transmitting torque, and the radial dimension of the transmission surface is smaller than the radius of the support section; a bearing, the inner ring of which is sleeved on the support section; a transmission part, which is provided with an axial sliding hole, the sliding hole comprises a through hole matched with the cross-sectional shape of the transmission section and an oil groove communicated with the through hole, and the transmission section can slide in the through hole along the axial direction; wherein, in any projection plane perpendicular to the axis of the transmission shaft, the projections of the transmission section and the support section are located inside the projection contour of the sliding hole. The transmission structure and electric tool have high transmission reliability and good lubricity.

Description

Technical Field

[0001] This application relates to the field of power tool technology, and in particular to a transmission structure and a power tool. Background Technology

[0002] In the field of power tools, especially under high-impact load conditions such as electric hammers, the reliability and durability of power transmission are crucial. Currently, the transmission system of electric hammers typically transmits torque and engages via clutches and drive gears on the drive shaft. Specifically, the inner bore of the clutch or drive gear and the transmission section (such as a flat groove or keyway) on the drive shaft employ a sliding fit to achieve axial separation and engagement.

[0003] However, such transmission structures are prone to wear and jamming in practical applications. Electric hammers operate in harsh environments with intense vibrations and large load variations. Under frequent high-torque impacts and sliding friction, the transmission surfaces are highly susceptible to excessive wear. Wear leads to increased clearance, resulting not only in impact noises and reduced transmission efficiency, but more seriously, the metal shavings produced by wear mix with lubricating grease to form an abrasive paste, further exacerbating wear on the transmission surfaces and mating holes, creating a vicious cycle.

[0004] As wear continues to intensify, the clearance between transmission components is disrupted, hindering the originally smooth axial sliding. Especially during reversing or clutch engagement, the worn transmission shaft is prone to misalignment or seizing with the inner bore of the clutch or drive gear, ultimately leading to poor sliding or even complete jamming, causing the entire impact transmission mechanism to fail and severely affecting the reliability and service life of the electric hammer.

[0005] Therefore, there is an urgent need for a transmission structure that can significantly improve the wear resistance of the transmission surface, avoid jamming due to wear, and extend the service life of power tools. Utility Model Content

[0006] The technical problem to be solved by this utility model is to overcome the defects in the transmission structure of existing electric hammers and other power tools, and to provide a new type of transmission structure and power tool, which can effectively reduce the wear of the transmission surface and avoid the problems of jamming and poor sliding between the transmission shaft and the clutch or drive gear due to wear.

[0007] In a first aspect, this application provides a transmission structure for torque transmission in power tools, comprising: A drive shaft includes a drive section and a support section in sequence along the axial direction. The support section is cylindrical. The drive section has a drive surface for transmitting torque, and the radial dimension of the drive surface is smaller than the radius of the support section. The bearing, the inner ring of which is fitted into the support section; The transmission component is provided with an axially penetrating sliding hole, the sliding hole including a through hole adapted to the cross-sectional shape of the transmission section and an oil groove communicating with the through hole, the transmission section being able to slide axially within the through hole; In any projection plane perpendicular to the axis of the transmission shaft, the projections of the transmission section and the support section are both located inside the projection contour of the sliding hole.

[0008] By adopting the above technical solution, the transmission section and the support section are designed with differentiated radial dimensions. This preserves the good fit between the complete cylinder of the support section and the inner ring of the bearing. Furthermore, by bringing the transmission surface closer to the center of the transmission shaft, the effective torque contact area between the transmission surface and the sliding hole of the transmission component is increased. This significantly improves the stability and reliability of torque transmission by reducing surface pressure and reduces wear on the transmission surface under torque. On the other hand, this design increases the effective lever arm of the transmission force, reduces stress concentration on the transmission surface, reduces the risk of deformation under stress, and thus extends the overall service life of the transmission shaft.

[0009] The special structural design of the oil groove has multiple functions: First, it provides a stable space for lubricating grease, which can continuously lubricate the transmission surface and also has the function of washing away wear debris and impurities, ensuring smooth sliding; Second, the oil groove provides an unobstructed axial passage for the support section, which greatly facilitates the assembly process of the transmission components and the transmission shaft; Third, the reasonable layout of the oil groove reduces the sliding contact area between the transmission surface and the through hole, which helps to reduce sliding friction resistance; Finally, the oil groove structure has low requirements for machining accuracy, which reduces the manufacturing difficulty of the sliding hole of the transmission component, and has good manufacturability and economy while ensuring functionality.

[0010] In conjunction with the first aspect, in a further embodiment, the transmission section further includes a cylindrical surface that contacts the transmission surface, the diameter of which is larger than the diameter of the support section.

[0011] By adopting the above technical solution, the enlarged cylindrical surface can serve as an axial positioning reference for the transmission shaft, and can also share part of the radial load during transmission, reducing the stress on the transmission surface and further extending the service life of the transmission surface.

[0012] In conjunction with the first aspect, in a further embodiment, the transmission segment includes two transmission surfaces, which are spaced apart.

[0013] By adopting the above technical solution, the arrangement of dual transmission surfaces provides a more balanced torque transmission path, effectively improves the stress state of the transmission shaft, reduces the possibility of unilateral wear, and improves the smoothness and reliability of the transmission.

[0014] In conjunction with the first aspect, in a further embodiment, the two transmission surfaces are arranged symmetrically with respect to the axis of the transmission shaft.

[0015] By adopting the above technical solution, the symmetrically distributed transmission surfaces ensure the balance of torque transmission, avoid abnormal wear and vibration caused by off-center loading, and at the same time help reduce noise during the transmission process.

[0016] In conjunction with the first aspect, in a further embodiment, the through hole of the transmission component includes a plane that slides with the transmission surface and an arc surface that slides with the cylindrical surface, and a clearance groove is provided at the junction of the plane and the arc surface.

[0017] By adopting the above technical solution, the design of the relief groove eliminates the stress concentration point at the intersection of the plane and the arc surface, provides the necessary tolerance compensation space for the assembly and sliding process, and ensures the smooth sliding of the transmission component on the transmission section.

[0018] In conjunction with the first aspect, in a further embodiment, the clearance groove extends outward from the plane so that the plane completely covers the transmission surface in the radial direction.

[0019] By adopting the above technical solution, it is ensured that the clearance groove provides a sufficiently large clearance space so that the plane of the transmission component can completely cover the transmission surface, ensuring the effective contact area for torque transmission, while avoiding edge interference problems caused by manufacturing tolerances.

[0020] In conjunction with the first aspect, in a further embodiment, the transmission component is a clutch or a drive gear. A clutch and a drive gear can be provided simultaneously in the transmission section. The drive gear and the clutch are provided with axially penetrating sliding holes. The drive gear slides with the transmission section through the sliding holes, and the sliding hole structure of the drive gear is the same as that of the clutch.

[0021] By adopting the above technical solution, the drive gear and clutch use the same sliding hole structure, which realizes the standardized design of components, simplifies the production and assembly process, and ensures that the drive gear and clutch have the same smooth sliding and anti-jamming performance, realizing the clutch engagement and disengagement and the drive gear drive corresponding functions. The two functions can be operated independently to achieve their respective functions.

[0022] In conjunction with the first aspect, in a further embodiment, the cross-section of the transmission segment is polygonal, and the radial dimension of at least two sides is greater than the radius of the support segment.

[0023] By adopting the above technical solution, the polygonal cross section provides a stable torque transmission capability. The design of the specific side length not only ensures sufficient transmission strength and axial positioning, but also provides a clear passage for the sliding parts through the size difference, preventing motion interference.

[0024] In conjunction with the first aspect, in a further embodiment, the cross-section of the transmission section is rectangular, and the radial dimension of its two opposite sides is greater than the radius of the support section.

[0025] By adopting the above technical solution, the rectangular cross-section structure is simple and easy to process. The double-sided transmission design makes the force more balanced. The design of the two opposite side dimensions of the non-transmission surface can better provide axial positioning and torque transmission. At the same time, the transmission area and the passage area are clearly defined, further optimizing the transmission efficiency and anti-jamming performance.

[0026] Secondly, this application provides an electric tool including the transmission structure described in the first aspect.

[0027] By adopting the above technical solution and applying this transmission structure to power tools, the reliability and durability of the power tool transmission system are significantly improved. It is particularly suitable for high impact load conditions such as electric hammers, and effectively extends the service life of the entire machine.

[0028] In summary, this application has at least one of the following beneficial technical effects: 1. By innovatively setting the radial dimension of the transmission surface to be smaller than the radius of the support section, and in conjunction with a special oil groove design, the dual effects of reducing wear and preventing jamming are achieved, solving a technical problem that has long plagued this field.

[0029] 2. The unique relief groove and sliding hole structure design ensures that the transmission components and drive gears always have sufficient clearance during axial sliding, reducing the friction contact area and making the movement smooth and reliable.

[0030] 3. The differentiated dimensional design of the transmission surface and the support section ensures torque transmission efficiency while reducing surface pressure and stress concentration, significantly extending the service life of key components.

[0031] 4. The overall structure is compact and reasonable, making it particularly suitable for power tool applications with limited space. It is also easy to process and manufacture, and has good prospects for industrialization. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the transmission structure of a traditional power tool; Figure 2 This is a schematic diagram of the drive shaft connection part in a traditional transmission structure. Figure 3 This is a schematic diagram of an embodiment of the transmission structure of this application; Figure 4 This is a schematic diagram of the disassembled transmission part of the transmission structure in this application; Figure 5 This is a schematic diagram of the transmission structure after the bearings have been removed. Figure 6 yes Figure 5 Enlarged structural diagram of area A in the middle; Figure 7 This is a three-dimensional structural diagram of the cross-section of the drive gear; Figure 8 This is a three-dimensional structural diagram of the cross-section of the clutch; Figure 9 This is a front view of the transmission structure of this application after the bearing has been removed; Figure 10 yes Figure 9 Enlarged structural diagram of region B in the middle; Figure 11 This is a structural diagram showing the clutch and drive shaft assembled and in the engaged state, and the drive gear and bearing in the state to be assembled. Figure 12 This is a schematic diagram of the internal structure of the power tool of this application.

[0033] Figure label: 100. Transmission structure; 1. Bearing; 2. Drive gear; 21. Sliding hole; 211. Arc surface; 212. Relief groove; 213. Oil groove; 214. Flat surface; 3. Transmission shaft; 31. Transmission section; 311. Transmission surface; 312. Cylindrical surface; 32. Support section; 4. Clutch; 5. Swing bearing; 6. Rocker arm; 7. Power gear; 8. Rotating mechanism; 81. Rotating assembly; 82. Large gear; 9. Motor; 200. Housing. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the application will be further described in detail below with reference to the accompanying drawings. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0035] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0036] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0037] In the description of this application, it should be understood that the terms "upper", "lower", "left", "right", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and 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, and therefore should not be construed as a limitation of this application.

[0038] like Figure 1 and Figure 2 As shown, the existing transmission structure generally includes a transmission shaft 3, a clutch 4, a drive gear 2, and a bearing 1. The clutch 4 and drive gear 2 are slidably connected to the transmission section 31 of the transmission shaft 3, and the bearing 1 is connected to the support section 32 of the transmission shaft 3. The clutch 4 has splined teeth, and the oscillating bearing 5 has internal splines that mate with it. The clutch 4 slides on the transmission shaft 3 to achieve engagement and disengagement with the oscillating bearing 5, and the oscillating bearing 5 drives the rocker arm 6 to oscillate. The motor 9 transmits power to the transmission shaft 3 through the power gear 7. The transmission shaft 3 drives the clutch 4 and drive gear 2 to rotate. The transmission shaft 3 achieves torque transmission by machining a flat square shape on the shaft body.

[0039] Please see Figure 2 In existing transmission shafts, the flat plane 214 of the transmission section 31 of the transmission shaft 3 is higher than the support section 32. This means the radial dimension of the flat transmission surface 311 from the center of the transmission shaft 3 is greater than the radius of the support section 32. This facilitates the passage of the support section 32 of the transmission shaft 3 through the through hole at the center of the clutch 4 and the drive gear 2 during assembly; otherwise, assembly would be impossible. However, this structure results in a relatively small transmission surface 311. Under high operating torque or long operating times, this can easily lead to deformation and misalignment of the transmission surface 311, causing the transmission shaft 3 to jam with the clutch 4 and the drive gear 2, preventing the clutch 4 and the drive gear 2 from sliding. To address this defect, after long-term research and numerous experimental tests, the inventors finally broke through the bottleneck of existing technology and developed a transmission structure. This structure improves the lifespan and performance of the transmission shaft 3, reduces the risk of failure, and reduces the need for complex heat treatment and other processes to enhance the strength of the transmission shaft 3.

[0040] The following detailed description of some embodiments of this application is provided in conjunction with the accompanying drawings. Unless otherwise specified, features in the following embodiments can be combined with each other.

[0041] The power tools in this application include electric hammers, screwdrivers, electric drills, etc.

[0042] Example 1

[0043] Please see Figures 3-11This embodiment provides a transmission structure 100 for torque transmission in power tools, particularly suitable for tools with high torque and high vibration conditions such as electric hammers and impact drills. This structure aims to solve the problems of wear and jamming caused by contact stress concentration in traditional transmission structures 100, as well as sliding and jamming caused by debris accumulation.

[0044] Please see Figure 3 and Figure 4 The transmission structure 100 mainly consists of three parts: transmission shaft 3, bearing 1, and transmission components.

[0045] The drive shaft 3 is a stepped shaft structure, comprising a drive section 31 and a support section 32 along the axial direction. The support section 32 is a precision cylinder with a hardened surface, exhibiting high dimensional accuracy and wear resistance, and is used to support and position the bearing 1. The drive section 31 is adjacent to the support section 32, and its core feature is the inclusion of a drive surface 311 for transmitting torque. The maximum radial dimension of this drive surface 311 (i.e., the distance between the farthest point on the drive surface 311 from the shaft center and the shaft center) is intentionally designed to be smaller than the radius of the support section 32. This design significantly increases the actual effective contact area between the drive surface 311 and the inner hole of the transmission component, thereby reducing surface pressure and improving wear resistance. Furthermore, the drive surface 311 is designed to have a larger area closer to the shaft center, and its radial dimension is designed to be slightly smaller than the radius of the support section 32. This not only further increases the contact area but also increases the power transmission arm, improving torque transmission efficiency and reducing bending stress on the drive surface 311. In the actual design process, the radial dimension of the transmission surface 311 cannot be too small, as this will affect the strength of the transmission shaft 3. Therefore, in this embodiment, the radial dimension of the transmission surface 311 is 80%-95% of the radius of the support section 32, preferably 85%-95%, and optimally 92%-93%.

[0046] Please see Figures 4-6 The transmission section 31 is specifically constructed as follows: it includes two transmission surfaces 311 spaced a certain distance apart axially. These two transmission surfaces 311 are preferably arranged symmetrically about the axis of the transmission shaft 3 to ensure balanced torque transmission and avoid uneven wear and vibration. Between the two transmission surfaces 311 and on the outer side of the transmission surfaces 311, the transmission section 31 also includes a cylindrical surface 312 that contacts the transmission surfaces 311. A key design feature is that the diameter of this cylindrical surface 312 is set to be larger than the diameter of the support section 32. This enlarged cylindrical surface 312 serves as an axial positioning element and can share part of the radial load during transmission.

[0047] Bearing 1 is a deep groove ball bearing 1, whose inner ring is fixedly fitted onto the support section 32 of the drive shaft 3 by an interference fit, while the outer ring is fitted with the tool housing (not shown in the figure). The installation position of bearing 1 ensures the stable rotation of the drive shaft 3.

[0048] Please see Figures 6-8 In this embodiment, "transmission component" is a broad concept, referring to all parts that cooperate with the transmission shaft 3 through the sliding hole 21 and can slide axially, specifically the clutch 4 or the drive gear 2. The transmission component has an axially penetrating sliding hole 21. This sliding hole 21 is one of the core innovations; its shape is not a simple circle, but rather consists of two functional areas: one is a through hole precisely adapted to the cross-sectional shape of the transmission section 31, and the other is an oil groove 213 communicating with this through hole.

[0049] The shape of the through hole is complementary to the cross-sectional shape of the transmission section 31. Specifically, it includes a plane 214 that slides with the transmission surface 311 and an arcuate surface that slides with the cylindrical surface 312 on the transmission section 31. To ensure fitting accuracy and avoid interference, a relief groove 212 is preferably machined at the intersection of the plane 214 and the arcuate surface. This relief groove 212 extends outward from the plane 214 (away from the axial direction), and its depth and width ensure that the plane 214 of the clutch 4 can completely cover and fit the transmission surface 311 in the radial direction, providing the necessary tolerance clearance for assembly and movement, and eliminating stress concentration points.

[0050] The oil groove 213 is another key design element. Its dimensions and location are precisely planned to fulfill at least two core functions: First, it serves as a reservoir for lubricating oil, providing continuous lubrication to the friction pair between the transmission surface 311 and the through hole, and allowing the flow of lubricating oil to remove metal debris generated by wear, thus playing a cleaning role. Second, and more importantly, its width and depth are designed to provide an unobstructed axial passage for the support section 32. This means that when the transmission component needs to slide across the support section 32, the support section 32 can be completely embedded within the space of the oil groove 213, thereby avoiding mechanical interference and jamming. An additional advantage is that the presence of the oil groove 213 naturally reduces the total sliding contact area between the transmission component and the transmission shaft 3, helping to reduce sliding friction resistance. At the same time, the oil groove 213 has relatively low requirements for machining precision, reducing the manufacturing cost of the transmission component.

[0051] Please see Figure 9 and Figure 11 An important overall fit relationship is that, within any projection plane 214 perpendicular to the axis of the drive shaft 3, the projections of both the transmission section 31 and the support section 32 are completely located within the projection contour of the sliding hole 21. This spatial relationship ensures that the transmission components will not collide or interfere with the drive shaft 3 during the entire axial sliding process and assembly.

[0052] Please see Figure 11 The clutch 4 is provided with spline teeth, and the swing bearing 5 is provided with internal splines that cooperate with it. The clutch 4 slides on the transmission shaft 3 to achieve the engagement and disengagement of the swing bearing 5.

[0053] Example 2

[0054] This embodiment provides another way of implementing the transmission segment 31, which differs from the first embodiment mainly in the cross-sectional shape of the transmission segment 31.

[0055] In this embodiment, the cross-section of the transmission segment 31 is a polygon (simple structure, not shown in the figure). Preferably, the polygon is rectangular, hexagonal, or D-shaped. The key design feature is that the distance from the midpoint of at least one side (or a pair of sides) of the polygon to the axis (i.e., the radial dimension) is greater than the radius of the support segment 32. This allows the side to form an effective transmission surface 311, while the other parts of the polygon provide the necessary structural strength.

[0056] As a preferred embodiment, the transmission section 31 has a rectangular cross-section. The distance from the midpoint of the two short sides of the rectangle to the axis is set to be greater than the radius of the support section 32, so that these two short sides serve as the main sliding connection, reinforcement, and guide, and provide part of the torque. The surface where the long side of the rectangle connects is the transmission surface 311. This rectangular cross-section structure is simple, easy to process, and can provide stable and balanced double-sided transmission, effectively avoiding unilateral wear.

[0057] The remaining parts of Embodiment 2, including the bearing 1, the design of the sliding hole 21 of the transmission component (clutch 4 or drive gear 2) (including through hole and oil groove 213), and the overall projected fit relationship, are the same as those of Embodiment 1, and can bring the same technical effects, namely, reducing wear, avoiding jamming, and facilitating assembly.

[0058] Example 3

[0059] Please see Figure 3 , Figure 4 , Figure 12 This embodiment discloses a power tool, specifically an electric hammer. The electric hammer includes a housing 200, a motor 9, an impact mechanism, a rotating mechanism 8, and a transmission structure 100 as described in Embodiment 1 or Embodiment 2. The impact mechanism includes a swing bearing 5 and a swing rod 6 connected to the swing bearing 5. A drive shaft 3 is also connected to a power gear 7. The motor 9 drives the drive shaft 3 to rotate via the power gear 7, which in turn drives the clutch 4 and the drive gear 2 to rotate. The rotating mechanism 8 includes a rotating component 81 and a large gear 82, which drives the rotating component 81 to rotate.

[0060] The transmission structure 100, as the core transmission component of the electric hammer, connects the output shaft of the motor 9 to the impact mechanism. Its working process is as follows: After the motor 9 starts, the torque is transmitted to the transmission section 31 of the transmission shaft 3 through the power gear 7, causing the transmission shaft 3 to rotate. When the clutch 4 slides and connects with the swing bearing 5, it drives the impact mechanism to generate an impact action. When it is necessary to stop the impact, the clutch 4, as a transmission component, slides axially along the transmission shaft 3 under the action of the operating mechanism, disengaging from the swing bearing 5 and cutting off the power. The drive gear 2 slides on the transmission shaft 3 to engage with the large gear 82 of the rotating mechanism 8. The large gear 82 drives the rotating component 81 to rotate. Through the cooperation of the clutch 4 and the drive gear 2, separate or synchronized rotation and impact actions can be achieved, realizing different functions.

[0061] Thanks to the aforementioned transmission structure 100, this electric hammer exhibits exceptional reliability. The increased contact area of ​​the transmission surface 311 and continuous lubrication significantly reduce the wear rate under high impact torque, extending the service life of the entire machine and key components. More importantly, the unique oil groove 213 clearance design ensures that the clutch 4 can pass over the support section 32 without obstruction during installation, improving the ease of assembly.

[0062] The foregoing has shown and described the basic principles, main features, and advantages of this utility model. Those skilled in the art should understand that this utility model is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of this utility model. Various changes, modifications, substitutions, and variations can be made to this utility model without departing from its spirit and scope, and all such changes, modifications, substitutions, and variations fall within the scope of the claimed utility model.

Claims

1. A transmission structure, characterized in that, include: A drive shaft includes a drive section and a support section in sequence along the axial direction. The support section is cylindrical. The drive section has a drive surface for transmitting torque, and the radial dimension of the drive surface is smaller than the radius of the support section. The bearing, the inner ring of which is fitted into the support section; The transmission component is provided with an axially penetrating sliding hole, the sliding hole including a through hole adapted to the cross-sectional shape of the transmission section and an oil groove communicating with the through hole, the transmission section being able to slide axially within the through hole; In any projection plane perpendicular to the axis of the transmission shaft, the projections of the transmission section and the support section are both located inside the projection contour of the sliding hole.

2. The transmission structure according to claim 1, characterized in that, The transmission section also includes a cylindrical surface that is in contact with the transmission surface, and the diameter of the cylindrical surface is larger than the diameter of the support section.

3. The transmission structure according to claim 1 or 2, characterized in that, The transmission section includes two transmission surfaces, which are spaced apart.

4. The transmission structure according to claim 3, characterized in that, The two transmission surfaces are symmetrically arranged with respect to the axis of the transmission shaft.

5. The transmission structure according to claim 4, characterized in that, The through hole of the transmission component includes a plane that slides with the transmission surface and an arc surface that slides with the cylindrical surface, and a clearance groove is provided at the junction of the plane and the arc surface.

6. The transmission structure according to claim 5, characterized in that, The clearance groove extends outward from the plane so that the plane completely covers the transmission surface in the radial direction.

7. The transmission structure according to claim 1, characterized in that, The transmission component is a clutch or a drive gear.

8. The transmission structure according to claim 1, characterized in that, The cross-section of the transmission section is polygonal, and the radial dimension of at least two sides is greater than the radius of the support section.

9. The transmission structure according to claim 8, characterized in that, The cross-section of the transmission section is rectangular, and the radial dimension of its two opposite sides is greater than the radius of the support section.

10. A power tool, characterized in that, Includes the transmission structure as described in any one of claims 1-9.

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