Reciprocating balancing device for power tools

Abstract

This application relates to a reciprocating balancing device for power tools, belonging to the field of power tool technology. The device includes a drive motor, a crankshaft, a reciprocating rod assembly, a first balance block, and a second balance block. The crankshaft is driven to rotate by the drive motor and has first, second, and third transmission parts arranged sequentially along the rotation axis and offset from the rotation axis. The reciprocating rod assembly has a slide rail, and the second transmission part slides within the slide rail to drive the reciprocating rod assembly to reciprocate. The first and second balance blocks are respectively located on both sides of the reciprocating rod assembly and are driven by the first and third transmission parts to reciprocate in opposite directions. This application can reduce tool vibration by eliminating the connecting rod structure, allowing the balance blocks to be close to the reciprocating rod assembly, reducing the moment arm between inertial forces, and achieving near-collinear inertial force cancellation.

Description

Technical Field

[0001] This invention relates to the field of power tool technology, and more specifically to a reciprocating balancing device for power tools. Background Technology

[0002] Reciprocating saws, reciprocating chisels, and other power tools use a reciprocating rod assembly to drive the working head in a linear reciprocating motion to cut or chisel workpieces. During operation, the reciprocating rod assembly and the working head it holds undergo high-frequency reciprocating motion in one direction, generating significant unbalanced inertial forces and causing severe overall tool vibration. Prolonged use can lead to hand numbness, fatigue, and other discomfort, and may even cause occupational health damage. Therefore, effectively reducing the unbalanced inertial forces generated by reciprocating motion has been a continuous area of ​​focus for those skilled in the art.

[0003] To reduce vibration, existing technologies include placing counterweights on both sides of the reciprocating rod assembly. These counterweights reciprocate in the opposite direction to the reciprocating rod assembly to counteract unbalanced inertial forces. One typical approach uses a crank to drive both the reciprocating rod assembly and the counterweights simultaneously via a connecting rod. In this approach, one end of the connecting rod is connected to an eccentric portion on the crank, and the other end is connected to the reciprocating rod assembly. Therefore, the connecting rod itself needs to occupy a certain thickness in the crankshaft axis, and it also needs to allow for oscillation clearance during movement. These two space requirements force the eccentric portions driving the counterweights to move axially outwards towards both ends of the crankshaft. Consequently, the counterweights driven by these eccentric portions are also forced away from the central plane of the reciprocating rod assembly.

[0004] When the counterweight is far from the reciprocating rod assembly, the inertial force generated by the counterweight and the inertial force generated by the reciprocating rod assembly, although opposite in direction, are not on the same straight line in space, forming a torque arm between them. These two opposing forces no longer constitute ideal collinear cancellation, but instead form an eccentric moment, causing the machine housing to experience additional torsional vibration. The presence of the eccentric moment weakens the counterweight's vibration-canceling effect, resulting in noticeable vibration in the tool during actual use even with double-sided counterweights, affecting operating comfort and work accuracy.

[0005] Therefore, it is necessary to provide a reciprocating balancing device for power tools that has a compact structure and can effectively reduce eccentric torque, in order to solve the problems existing in the prior art. Summary of the Invention

[0006] The purpose of this invention is to provide a reciprocating balancing device for power tools, which can achieve better vibration reduction and balancing effects while simplifying the transmission structure and reducing the number of parts.

[0007] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution: A reciprocating balancing device for a power tool, comprising: Drive motor; The crankshaft is driven by a drive motor to rotate around its own axis. The crankshaft is provided with a first transmission part, a second transmission part and a third transmission part arranged sequentially along the direction of the rotation axis. The first transmission part, the second transmission part and the third transmission part are all offset from the rotation axis. A reciprocating rod assembly is provided with a slide rail, and the second transmission part is slidably engaged in the slide rail to drive the reciprocating rod assembly to reciprocate along a first direction; The first balance block is disposed on one side of the reciprocating rod assembly. The first transmission part is connected to the first balance block to drive the first balance block to reciprocate along a second direction opposite to the first direction. The second balance block is disposed on the other side of the reciprocating rod assembly, and the third transmission part is connected to the second balance block to drive the second balance block to reciprocate along the second direction.

[0008] In the reciprocating balancing device of the aforementioned power tool, the center of mass of the first transmission part and the center of mass of the third transmission part are located on the same straight line parallel to the axis of rotation.

[0009] In the reciprocating balancing device of the aforementioned power tool, the distance from the center of mass of the second transmission part to the axis of rotation is equal to the distance from the center of mass of the first transmission part to the axis of rotation.

[0010] In the reciprocating balancing device of the aforementioned power tool, the sum of the mass of the first balance block and the mass of the second balance block is equal to the mass of the reciprocating rod assembly.

[0011] In the reciprocating balancing device of the above-mentioned power tool, the crankshaft includes a first component and a second component that are detachably connected. The first component is provided with a first transmission part and a transmission shaft, and the second component is provided with a third transmission part and a transmission hole. The transmission shaft and the transmission hole cooperate to form the second transmission part.

[0012] In the reciprocating balancing device of the aforementioned power tool, the second component is further provided with a joint, the transmission hole is opened in the joint, the transmission shaft is at least partially inserted into the transmission hole of the joint, and the outer peripheral surface of the joint is slidably engaged with the slide rail.

[0013] In the reciprocating balancing device of the aforementioned power tool, the crankshaft includes a first rotating body, a first crankshaft body, a second crankshaft body, and a second rotating body arranged sequentially along the rotation axis. Both the first and second rotating bodies are rotating bodies about the rotation axis and each has a shaft protruding in opposite directions. The first crankshaft body includes a first transmission part and a first transmission member. The first transmission part deviates from the rotation axis in a direction perpendicular to it and extends towards the first rotating body along the rotation axis, connecting to the first rotating body. The first transmission member has opposite deviation and protrusion directions to the first transmission part. The second crankshaft body includes the third transmission part and a second transmission member. The third transmission part deviates from the rotation axis in a direction perpendicular to it and extends towards the second rotating body along the rotation axis, connecting to the second rotating body. The second transmission member has opposite deviation and protrusion directions to the third transmission part. The first transmission member and the second transmission member cooperate to form the second transmission part.

[0014] In the reciprocating balancing device of the above-mentioned power tool, the first crankshaft body further includes a first connecting body, the first transmission part and the first transmission component are respectively disposed at both ends of the first connecting body, and the center of gravity of the first connecting body is located on the rotation axis; the second crankshaft body further includes a second connecting body, the third transmission part and the second transmission component are respectively disposed at both ends of the second connecting body, and the center of gravity of the second connecting body is located on the rotation axis.

[0015] In the reciprocating balancing device of the aforementioned power tool, the thickness of the first transmission part, the third transmission part, the first transmission member, and the second transmission member is equal along the direction of the rotation axis.

[0016] In the reciprocating balancing device of the aforementioned power tool, the widths of the first transmission section, the second transmission section, and the third transmission section are all equal along the direction perpendicular to the rotation axis.

[0017] In the reciprocating balancing device of the above-mentioned power tool, a first ring sleeve, a second ring sleeve, and a third ring sleeve are respectively fitted on the outer peripheral surfaces of the first transmission part, the second transmission part, and the third transmission part, and the weight of the second ring sleeve is equal to the sum of the weights of the first ring sleeve and the third ring sleeve.

[0018] In the reciprocating balancing device of the aforementioned power tool, the crankshaft is an integral structure.

[0019] Compared with the prior art, the advantages of the present invention are: The reciprocating rod assembly is equipped with a slide rail, within which the second transmission unit slidably engages. The crankshaft rotation directly drives the reciprocating rod assembly to reciprocate along a first direction. This eliminates the need for the connecting rod mechanism linking the crank and the reciprocating rod in traditional designs. By replacing the connecting rod with a sliding pair, the tangential component of the second transmission unit's circular motion directly pushes against the slide rail sidewall as the crankshaft rotates, converting rotational motion into linear reciprocating motion without the need for intermediate oscillating components for motion decomposition. This design reduces the number of transmission stages and components, resulting in a more compact axial structure, which is beneficial for tool miniaturization and weight reduction. Simultaneously, the rigid sliding engagement provides a shorter transmission path and more direct motion response, reducing potential backlash and wear from multi-stage transmissions, thus improving the reliability and service life of the mechanism.

[0020] The first balance block reciprocates along a second direction opposite to the first direction, and the second balance block also reciprocates along the second direction, meaning the motion directions of the two balance blocks are exactly the same. This solves the problem in existing technologies where the eccentric parts driving the two balance blocks are not arranged on the same side, resulting in the actual reciprocating axes of the two balance blocks being non-parallel, and the motion directions having an angle or even being opposite, thus failing to form a unified, unidirectional inertial force resultant force. By arranging the first and third transmission parts driving the two balance blocks on the same side of the crankshaft, the phase and trajectory of the driving forces acting on them are kept spatially collinear, kinematically ensuring that the velocity and acceleration directions of the two balance blocks are completely consistent at any given time. The inertial forces of the two balance blocks are always superimposed in the same direction, forming a definite and unified resultant force. This resultant force is always opposite in direction to the inertial force of the reciprocating rod assembly, significantly reducing the high-frequency vibration of the tool and improving operating comfort and long-term safety.

[0021] By eliminating the connecting rod, the second transmission unit fits into the slide of the reciprocating rod assembly only as a cylindrical journal, without occupying additional axial width. This structural freedom provides space for the first and third transmission units to retract inward along the rotation axis, allowing them to be positioned closer to the second transmission unit. This enables the first and second balance blocks to be close to the sides of the reciprocating rod assembly. When the two balance blocks are as close to the reciprocating rod as possible, the balancing inertial force and the reciprocating rod inertial force approach the same straight line in space, the torque arm approaches zero, and the two opposing forces form a near-ideal collinear cancellation, resulting in significant improvements in both miniaturization and low vibration of the power tool.

[0022] Furthermore, the center of mass of the first transmission unit and the center of mass of the third transmission unit are located on the same straight line parallel to the axis of rotation. The inertial forces of the two balance blocks are not only completely consistent in direction, but also form a pair of parallel force vectors in space, providing a precise geometric premise for the superposition of inertial forces in the same direction and subsequent collinear cancellation, further improving the certainty and reliability of the balancing effect.

[0023] Furthermore, the distance from the center of mass of the second transmission unit to the axis of rotation is equal to the distance from the center of mass of the first transmission unit to the axis of rotation. When the eccentricities of the three transmission units are equal, the reciprocating rod assembly and the two balance blocks have equal reciprocating stroke and velocity amplitude at the same rotational speed. The amplitude of the inertial force depends only on their respective masses, without the need to introduce additional stroke conversion coefficients or nonlinear corrections. This greatly simplifies the matching calculation of balance parameters, making complete dynamic balancing easier to achieve and debug in engineering.

[0024] Furthermore, the sum of the masses of the first and second balance blocks is equal to the mass of the reciprocating rod assembly. Setting the sum of the masses of the two balance blocks equal to the mass of the reciprocating rod assembly ensures that the resultant inertial force generated by the movement of the two balance blocks in the second direction is exactly equal in amplitude to the inertial force generated by the movement of the reciprocating rod assembly in the first direction, while their directions are always opposite. This minimizes unbalanced inertial forces, reducing tool vibration and the resulting noise and operational discomfort to the greatest extent possible, achieving optimal vibration reduction and balancing quality.

[0025] Furthermore, the crankshaft includes a detachably connected first component and a second component. The first component is provided with a first transmission part and a transmission shaft, and the second component is provided with a third transmission part and a transmission hole. The transmission shaft and the transmission hole cooperate to form the second transmission part. By splitting the crankshaft into two independent components at the second transmission part, during assembly, the transmission shaft of the first component can be passed through one side of the slide rail first, and then the transmission hole of the second component can be aligned with the transmission shaft and sleeved and fixed. This allows the second transmission part to be reassembled after passing through the slide rail, thereby bypassing the assembly interference caused by the eccentric structure of the integral crankshaft mid-section not being able to pass through the slide rail, thus greatly reducing the assembly difficulty and improving the assembly efficiency.

[0026] Furthermore, the second component also has a joint, with the transmission hole located within the joint. The transmission shaft is at least partially inserted into the transmission hole of the joint, and the outer circumferential surface of the joint slidably engages with the slide rail. By placing the transmission hole within a separate joint, the inner hole of the joint is specifically designed for precise positioning and fastening of the transmission shaft, while the outer circumferential surface of the joint is specifically designed for sliding engagement with the slide rail. Simultaneously, the axial length of the joint can be independently designed, and the engagement length between the transmission shaft and the transmission hole is no longer limited by the thickness of the component body, resulting in greater connection rigidity and alignment accuracy. The connection between the transmission shaft and the joint is more secure and reliable, and the sliding engagement between the outer circumferential surface of the joint and the slide rail is smoother and more wear-resistant. The coaxiality of the first and second components is better guaranteed, further improving the assembly accuracy and operational stability of the split crankshaft and extending the overall service life of the transmission pair.

[0027] Furthermore, the crankshaft includes a first rotating body, a first crankshaft body, a second crankshaft body, and a second rotating body arranged sequentially along the rotation axis; both the first rotating body and the second rotating body are rotating bodies about the rotation axis, and each has a shaft body protruding in opposite directions; the first crankshaft body includes a first transmission part and a first transmission member; the first transmission part deviates from the rotation axis in a direction perpendicular to the rotation axis, and extends towards the first rotating body along the rotation axis and connects to the first rotating body; the first transmission member has opposite deviation and protrusion directions to the first transmission part; the second crankshaft body includes the third transmission part and the second transmission member; the third transmission part deviates from the rotation axis in a direction perpendicular to the rotation axis, and extends towards the second rotating body along the rotation axis and connects to the second rotating body; the second transmission member has opposite deviation and protrusion directions to the third transmission part; the first transmission member and the second transmission member cooperate to form the second transmission part. This invention solves the problem that when the crankshaft adopts an integral or simple split structure, the second transmission unit, as a mid-section eccentric structure, cannot pass through the slide rail for assembly. Furthermore, using a single-sided insertion split structure easily leads to asymmetrical support at both ends of the crankshaft and rotational wobble. The crankshaft is split into two mirror-symmetrical sub-assemblies at the second transmission unit: the first rotating body and the first crankshaft body form one side sub-assembly, and the second rotating body and the second crankshaft body form the other side sub-assembly. During assembly, the first and second transmission components of the two sub-assemblies are inserted from opposite sides of the slide rail and meet and connect within the slide rail to form the second transmission unit, completely eliminating the assembly obstacle of the slide rail. Simultaneously, the first and second rotating bodies are located at the two ends of the crankshaft, and their opposing convex shafts provide double-point simply supported beam support for the entire crankshaft. As rotating bodies about their own axis of rotation, the rotating bodies do not generate eccentric inertial forces when rotating. Thus, the ease of assembly and rotational stability of the crankshaft are simultaneously guaranteed: the split structure solves the assembly interference problem, the mirror symmetry layout ensures that the crankshaft mass distribution is symmetrical about the middle plane, and the double support improves the crankshaft's bending stiffness and rotational accuracy, making the compact transmission scheme of direct drive without connecting rods highly feasible in terms of manufacturing process and operational reliability.

[0028] Furthermore, the first crankshaft body also includes a first connecting body, with the first transmission part and the first transmission component respectively disposed at both ends of the first connecting body, and the center of gravity of the first connecting body located on the rotation axis; the second crankshaft body also includes a second connecting body, with the third transmission part and the second transmission component respectively disposed at both ends of the second connecting body, and the center of gravity of the second connecting body located on the rotation axis. This solves the problem that in a mirror-symmetric split architecture, if the center of gravity of the connecting body connecting the various transmission parts deviates from the rotation axis, the connecting body itself will generate additional eccentric inertial force when rotating with the crankshaft. This additional inertial force is superimposed on the driving force generated by the transmission part, complicating the overall unbalanced force system of the crankshaft and increasing the difficulty and uncertainty of subsequent dynamic balancing matching using balance weights. By precisely positioning the centers of gravity of the first and second connecting bodies on the axis of rotation, the connecting bodies themselves become self-balancing components rotating around the axis of rotation. During rotation, no eccentric inertial forces are generated. The unbalanced force during crankshaft rotation is entirely generated by four eccentric blocks intentionally deviating from the axis of rotation: the first transmission unit, the first transmission component, the third transmission unit, and the second transmission component. The force source is clear and singular. Thus, the crankshaft's own unbalanced force system is simplified into a set of concentrated eccentric inertial forces with a clear source and definite direction. Designers only need to perform balancing calculations and match balancing blocks for these four transmission units with known eccentricities and masses, without needing to consider the additional unbalance introduced by the connecting bodies, significantly reducing the complexity of dynamic balancing design.

[0029] Furthermore, the thicknesses of the first transmission part, the third transmission part, the first transmission component, and the second transmission component are equal along the axis of rotation. This solves the problem that, under the premise that the connecting body has achieved self-balancing and the eccentricity of each transmission part is equal, if the thicknesses of the four transmission parts are inconsistent, even if the materials are the same, the masses of each transmission part will still be unequal. This leads to unequal centrifugal forces between the first transmission part and the first transmission component on the first crankshaft body, and unequal centrifugal forces between the third transmission part and the second transmission component on the second crankshaft body. As a result, the crankshaft generates internal torque during rotation, its own dynamic balance is disrupted, and an additional design burden is added to the balance weight. All four transmission parts are eccentric structures offset from the axis of rotation. Under the conditions of equal eccentricity and identical materials, the mass of a transmission part depends only on its thickness along the axis of rotation and its cross-sectional area perpendicular to the axis of rotation. When the thickness is also equal, the mass of the first transmission part is exactly equal to that of the first transmission component, and the mass of the third transmission part is exactly equal to that of the second transmission component. The centrifugal forces of the two opposing transmission parts on each crankshaft body are equal in magnitude and opposite in direction, thus canceling each other out within the crankshaft body. The crankshaft itself does not generate internal torque during rotation. Therefore, the crankshaft not only achieves self-balancing of the connecting body, but also achieves self-balancing of the internal force system between the transmission parts through the constraint of equal thickness. The entire crankshaft is in a state of complete dynamic balance before the addition of balance weights. The balance weights are only used to counteract the inertial force of the reciprocating rod assembly and do not need to share the unbalance of the crankshaft itself. This makes the overall balance design single-objective, simple to calculate, and easy to debug. Complete dynamic balance can be accurately and reliably achieved in engineering.

[0030] Furthermore, the widths of the first, second, and third transmission parts along the direction perpendicular to the rotation axis are all equal. This solves the problem that, even with equal thickness and material, if the widths of the four transmission parts in the direction perpendicular to the rotation axis are inconsistent, the cross-sectional areas of each transmission part will still be unequal, leading to mass differences. This also prevents the centrifugal forces of the two opposing transmission parts protruding from the crankshaft from precisely canceling each other out, leaving residual internal torques on the crankshaft and affecting dynamic balance accuracy. The mass of the transmission part is determined by the material density, eccentricity, thickness, and cross-sectional area perpendicular to the rotation axis. By further ensuring equal widths based on equal material, eccentricity, and thickness, the four transmission parts (first, third, first transmission component, and second transmission component) have completely identical cross-sectional dimensions and areas in the direction perpendicular to the rotation axis, thus achieving perfectly equal volume and mass for all four transmission parts. Because the first transmission part and the first transmission component bulge outwards and have opposite centrifugal force directions, and the third transmission part and the second transmission component bulge outwards and have opposite centrifugal force directions, the fact that the four transmission parts have completely equal mass means that the centrifugal forces of the two opposing transmission parts on each crankshaft body are not only opposite in direction but also precisely equal in magnitude, completely canceling each other out inside the crankshaft body. The entire crankshaft achieves strict mirror symmetry in geometry and dimensions. The crankshaft itself has no internal torque or residual imbalance when rotating, achieving an ideal self-balancing state. The entire mass of the balance block only needs to be used to counteract the inertial force of the reciprocating rod assembly, without bearing any additional counterweight to correct the crankshaft's own imbalance. This simplifies the matching work of complete dynamic balancing to a precise calculation of a single target, making the debugging process more convenient, mass production consistency higher, and vibration reduction effect more stable and reliable.

[0031] Furthermore, a first ring sleeve, a second ring sleeve, and a third ring sleeve are respectively fitted onto the outer peripheral surfaces of the first, second, and third transmission parts. The weight of the second ring sleeve is equal to the sum of the weights of the first and third ring sleeves. This solves the problem that when the transmission part of the crankshaft directly contacts the inner bore of the connecting rod or the slide of the reciprocating rod assembly, the outer peripheral surface of the transmission part gradually wears under long-term high-frequency sliding friction, leading to increased clearance, decreased transmission accuracy, and increased vibration and noise. Replacing worn parts requires replacing the entire crankshaft, resulting in high maintenance costs. By fitting three ring sleeves onto the outer peripheral surfaces of the three transmission parts, the outer peripheral surfaces of the ring sleeves bear the frictional load instead of the transmission part body. The ring sleeves and transmission parts are relatively fixed and do not move relative to each other. Wear only occurs at the contact interface between the ring sleeves and the connecting rod or slide. When the ring sleeves wear beyond the limit, only disassembly and replacement of the ring sleeves are needed to restore the fit accuracy, and the crankshaft body remains intact. Meanwhile, since the first and third transmission parts are located on the same side of the rotation axis, and the second transmission part is located on the other side, they form a 180° opposite phase relationship. The weight of the second ring sleeve is equal to the sum of the weights of the first and third ring sleeves. This ensures that after adding the ring sleeves, the additional mass on both sides of the rotation axis remains symmetrical in the direction of centrifugal force. The resultant centrifugal force generated by each ring sleeve rotating with the crankshaft is zero, and the introduction of the ring sleeves will not disrupt the original dynamic balance of the crankshaft. The resulting effect is that, while significantly extending the crankshaft's service life and reducing maintenance costs, no additional eccentric inertial force is introduced, the dynamic balance accuracy of the crankshaft is fully maintained, and the vibration reduction and noise reduction effects are not affected by the addition of the ring sleeves, achieving a balance between wear resistance and dynamic balance performance.

[0032] Furthermore, the crankshaft is a one-piece structure. This solves the problem that when the crankshaft adopts a split assembly structure, the various transmission parts are assembled with the crankshaft body through key connections, pin connections, or interference fits, resulting in assembly surfaces. Under long-term high-speed operation and alternating loads, these surfaces may experience fretting wear, increased clearance, or even loosening, causing the relative phase angle between the transmission parts to drift. This disrupts the precise 180° anti-phase relationship between the first, third, and second transmission parts, leading to the balance weight and reciprocating rod assembly no longer having strictly opposite motion phases, and the balancing effect gradually deteriorating. The one-piece crankshaft is directly machined from a single blank through processes such as turning, milling, or forging. The first, second, and third transmission parts are all part of the crankshaft body material, and there are no assembly surfaces between the transmission parts and the crankshaft body. The relative spatial positions and phase relationships between the three transmission parts are determined once during the manufacturing stage and remain unchanged throughout their service life, unaffected by vibration, impact, and temperature changes. Therefore, the phase accuracy and eccentricity accuracy between the three transmission parts are guaranteed by the manufacturing process in one go. In long-term use, there will be no performance degradation due to wear or loosening of the assembly joint surface. The long-term stability of transmission synchronization and balance effect is fundamentally guaranteed. At the same time, the number of parts and assembly steps are reduced, the overall rigidity and fatigue life of the crankshaft assembly are improved, and a solid structural foundation is provided for the long-term reliable operation of the reciprocating balancing device under high-speed and high-frequency conditions. Attached Figure Description

[0033] Figure 1 This is a cross-sectional view of an electric tool employing the reciprocating balancing device of the present invention; Figure 2 An exploded view of a power tool employing the reciprocating balancing device of the present invention; Figure 3 This is a perspective view of the reciprocating balancing device of the present invention; Figure 4 This is a cross-sectional view of the crankshaft in Embodiment 1 of the present invention; Figure 5 This is an exploded view of the crankshaft in Embodiment 2 of the present invention; Figure 6 This is a cross-sectional view of the crankshaft in Embodiment 2 of the present invention; Figure 7 This is a schematic diagram of the structure of each transmission part after being fitted with a sleeve ring in this invention.

[0034] The attached figures are labeled as follows: 100. Drive motor; 200. Crankshaft; 210. First transmission part; 220. Second transmission part; 221. Transmission shaft; 222. Joint part; 223. Transmission hole; 230. Third transmission part; 240. First component; 250. Second component; 260. First rotating body; 270. First crankshaft body; 271. First connecting body; 272. First transmission component; 280. Second crankshaft body; 281. Second transmission component; 282. Second connecting body; 290. Second rotating body; 300. Reciprocating rod assembly; 310. Slide rail; 320. Rod body; 330. Clamping part; 400. First balance block; 500. Second balance block; 610. First ring sleeve; 620. Second ring sleeve; 630. Third ring sleeve. Detailed Implementation

[0035] A reciprocating balancing device for a power tool, comprising: Drive motor 100; The crankshaft 200 is driven by the drive motor 100 to rotate around the rotation axis X1. The crankshaft 200 is provided with a first transmission part 210, a second transmission part 220 and a third transmission part 230 arranged sequentially along the rotation axis X1. The first transmission part 210, the second transmission part 220 and the third transmission part 230 are all offset from the rotation axis X1. A reciprocating rod assembly 300 is provided with a slide rail 310, and the second transmission part 220 is slidably engaged in the slide rail 310 to drive the reciprocating rod assembly 300 to reciprocate along a first direction; The first balance block 400 is disposed on one side of the reciprocating rod assembly 300. The first transmission part 210 is connected to the first balance block 400 to drive the first balance block 400 to reciprocate along a second direction opposite to the first direction. The second balance block 500 is disposed on the other side of the reciprocating rod assembly 300, and the third transmission part 230 is connected to the second balance block 500 to drive the second balance block 500 to reciprocate along the second direction.

[0036] The reciprocating rod assembly 300 is provided with a slide rail 310, and the second transmission part 220 is slidably fitted within the slide rail 310. The crankshaft 200 directly drives the reciprocating rod assembly 300 to reciprocate along the first direction. This eliminates the need for the connecting rod mechanism that connects the crank and the reciprocating rod in traditional solutions. By replacing the connecting rod with a sliding pair, when the second transmission part 220 rotates with the crankshaft 200, the tangential component of its circular motion directly pushes against the side wall of the slide rail 310, converting the rotational motion into linear reciprocating motion without the need for intermediate oscillating components to decompose the motion. This solution reduces the number of transmission stages, decreases the number of parts, and makes the axial structure more compact, which is beneficial for miniaturization and weight reduction of tools. At the same time, the transmission path of the rigid sliding fit is shorter, the motion response is more direct, and the backlash and wear that may occur in multi-stage transmissions are reduced, thus improving the reliability and service life of the mechanism.

[0037] The first balance block 400 reciprocates along a second direction opposite to the first direction, and the second balance block 500 also reciprocates along the second direction, meaning the motion directions of the two balance blocks are exactly the same. This solves the problem in the prior art where the eccentric parts driving the two balance blocks are not arranged on the same side, resulting in the actual reciprocating motion axes of the two balance blocks being non-parallel, and the motion directions having an angle or even being opposite, thus failing to form a unified, unidirectional inertial force resultant force. By arranging the first transmission part 210 and the third transmission part 230 driving the two balance blocks on the same side of the crankshaft 200, the phase and trajectory of the driving force they receive are kept spatially collinear, kinematically ensuring that the velocity direction and acceleration direction of the two balance blocks are completely consistent at any given time. The inertial forces of the two balance blocks are always superimposed in the same direction, forming a definite and unified resultant force. This resultant force is always opposite in direction to the inertial force of the reciprocating rod assembly 300, significantly reducing the high-frequency vibration of the tool and improving operating comfort and long-term safety.

[0038] By eliminating the connecting rod, the second transmission unit 220 fits within the slide rail 310 of the reciprocating rod assembly 300 only in the form of a cylindrical journal, without occupying additional axial width. This structural freedom provides space for the first transmission unit 210 and the third transmission unit 230 to retract inward along the rotation axis X1, allowing them to be arranged closer to the second transmission unit 220. This enables the first balance block 400 and the second balance block 500 to be close to the sides of the reciprocating rod assembly 300. When the two balance blocks are as close to the reciprocating rod as possible, the balancing inertial force and the reciprocating rod inertial force tend to be on the same straight line in space, the moment arm approaches zero, and the two opposing forces form a near-ideal collinear cancellation, resulting in significant improvements in both miniaturization and low vibration of the power tool.

[0039] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0040] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," 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 invention 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 invention.

[0041] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0042] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0043] Example 1: See Figures 1 to 4This embodiment provides a reciprocating balancing device for power tools, including a drive motor 100, a crankshaft 200, a reciprocating rod assembly 300, a first balancing block 400, and a second balancing block 500. The crankshaft 200 is driven by the drive motor 100 to rotate around its rotation axis X1. The crankshaft 200 is provided with a first transmission part 210, a second transmission part 220 and a third transmission part 230 arranged sequentially along the rotation axis X1. The first transmission part 210, the second transmission part 220 and the third transmission part 230 are all offset from the rotation axis X1. The reciprocating rod assembly 300 is provided with a slide rail 310. The second transmission part 220 is slidably fitted in the slide rail 310 to drive the reciprocating rod assembly 300 to reciprocate along a first direction. The first balance block 400 is disposed on one side of the reciprocating rod assembly 300. The first transmission part 210 is drivenly connected to the first balance block 400 to drive the first balance block 400 to reciprocate along a second direction opposite to the first direction. The second balance block 500 is disposed on the other side of the reciprocating rod assembly 300. The third transmission part 230 is drivenly connected to the second balance block 500 to drive the second balance block 500 to reciprocate along a second direction.

[0044] The drive motor 100 can be a DC motor, AC motor, or brushless DC motor, etc., which serves as a power source to output rotational torque to drive the crankshaft 200 to rotate. The output shaft of the drive motor 100 is directly connected to the crankshaft 200 or connected through a reduction mechanism to provide continuous rotational power for the entire reciprocating balancing device.

[0045] The crankshaft 200 is a rotating shaft with multiple eccentric structures, driven by the drive motor 100 to rotate around its own rotation axis X1. A first transmission section 210, a second transmission section 220, and a third transmission section 230 are arranged sequentially along the rotation axis X1 on the crankshaft 200. These three transmission sections are all offset from the rotation axis X1, meaning their centers of mass or geometric centers are not located on the rotation axis X1, thus generating centrifugal force or thrust during rotation. The specific shape, size, and eccentricity of the first transmission section 210, the second transmission section 220, and the third transmission section 230 can be set according to actual conditions; for example, they can be cylindrical eccentric journals or block-shaped eccentric protrusions. As the core transmission hub, the crankshaft 200 decomposes the single rotational input of the drive motor 100 into three independent reciprocating motion outputs: the middle second transmission section 220 drives the reciprocating rod assembly 300, while the first transmission sections 210 and the third transmission sections 230 on either side drive the first balance block 400 and the second balance block 500, respectively. Since the three transmission units are integrated on the same crankshaft 200, their relative phase relationship is permanently locked, ensuring the synchronicity and coordination of the movement of each component.

[0046] The reciprocating rod assembly 300 is a component used to clamp the working head and perform linear reciprocating cutting or scraping operations. The reciprocating rod assembly 300 has a slide rail 310, which can be a through slot extending perpendicular to the reciprocating motion direction of the reciprocating rod assembly 300. The second transmission part 220 is slidably fitted within the slide rail 310, meaning that the outer peripheral surface of the second transmission part 220 is in direct contact with and can slide relative to the inner wall of the slide rail 310. When the crankshaft 200 rotates, the component of the second transmission part 220 that deviates from the axis and performs circular motion within the slide rail 310 pushes against the side wall of the slide rail 310, thereby driving the reciprocating rod assembly 300 to perform linear reciprocating motion along the first direction. The specific structural form of the slide rail 310 can be set according to actual conditions; for example, it can be a rectangular transverse groove, a circular through hole, or an arc-shaped guide rail, as long as it can achieve a sliding fit with the second transmission part 220. The reciprocating rod assembly 300 and the second transmission unit 220 form a direct sliding pair transmission, eliminating the need for a traditional linkage mechanism, resulting in a shorter transmission path and a more compact structure.

[0047] The first balance block 400 is a mass block disposed on one side of the reciprocating rod assembly 300, used to generate a reverse inertial force to counteract the inertial force of the reciprocating rod assembly 300. The first transmission unit 210 is connected to the first balance block 400 via a direct sliding fit, hinge, or intermediate connecting member, as long as the driving force can be transmitted. When the crankshaft 200 rotates, the first transmission unit 210 drives the first balance block 400 to reciprocate along a second direction, which is opposite to the first direction of motion of the reciprocating rod assembly 300. The mass, shape, and stroke of the first balance block 400 can be set according to actual conditions; for example, it can be a cuboid, cylinder, or irregular shape, and its mass must be matched with the mass of the reciprocating rod assembly 300. The function of the first balance block 400 in the system is to work in conjunction with the second balance block 500 to generate a resultant force opposite to the direction of the inertial force of the reciprocating rod assembly 300, thereby achieving dynamic balance.

[0048] The second balance block 500 is a mass block disposed on the other side of the reciprocating rod assembly 300, arranged symmetrically or asymmetrically with the first balance block 400. The third transmission unit 230 is connected to the second balance block 500, driving the second balance block 500 to reciprocate in a second direction opposite to the first direction. The first balance block 400 and the second balance block 500 move in the same direction (both in the second direction), while the reciprocating rod assembly 300 moves in the first direction, and the two directions are opposite. The specific implementation of the second balance block 500 can refer to the description of the first balance block 400, and its mass and position can be adjusted according to actual balancing requirements. The second balance block 500 cooperates with the first balance block 400 so that the inertial forces of the two balance blocks can be superimposed in the same direction to form a definite resultant force, so as to more effectively counteract the unbalanced inertial force generated by the reciprocating rod assembly 300.

[0049] The core innovation of this power tool's reciprocating balancing device lies in its direct-drive balancing system based on a single crankshaft 200 with multiple transmission parts. By arranging the first transmission part 210, the second transmission part 220, and the third transmission part 230 sequentially along the crankshaft 200 axially, and utilizing the direct sliding engagement of the second transmission part 220 with the slide rail 310 on the reciprocating rod assembly 300, the traditional linkage mechanism is eliminated. This structure not only reduces the number of parts and axial space occupation, but more importantly, it frees up the arrangement space for the first transmission part 210 and the third transmission part 230, allowing them to be placed closer to the central second transmission part 220. This, in turn, drives the first balance block 400 and the second balance block 500 to be arranged closer to the reciprocating rod assembly 300, significantly reducing the torque arm between the balanced and unbalanced forces.

[0050] After the drive motor 100 starts, it drives the crankshaft 200 to rotate around its rotation axis X1. As the crankshaft 200 rotates, the second transmission unit 220, located in the middle, due to its eccentric setting, continuously pushes against the side wall of the slide rail 310 on the reciprocating rod assembly 300 during rotation, converting the rotational motion into linear reciprocating motion of the reciprocating rod assembly 300 along the first direction, thereby driving the working head to perform operations. At the same time, the first transmission unit 210 and the third transmission unit 230 located on both sides also rotate synchronously with the crankshaft 200, driving the first balance block 400 and the second balance block 500 to reciprocate along the second direction opposite to the first direction, respectively. Since the three transmission units are integrated into the same crankshaft 200, their motion phases are strictly synchronized, ensuring that at any given moment, the direction of the resultant inertial force generated by the two balance blocks is always opposite to the direction of the inertial force of the reciprocating rod assembly 300, thereby achieving dynamic balance.

[0051] Taking a handheld reciprocating saw as an example of a power tool. The drive motor 100 is installed inside the handle housing, and its output shaft is connected to one end of the crankshaft 200 via a gear assembly. The second transmission section 220 in the middle section of the crankshaft 200 is an eccentric cylindrical journal that passes through a transverse slide 310 formed at the tail of the reciprocating rod assembly 300. The front end of the reciprocating rod assembly 300 holds the saw blade. On opposite sides of the reciprocating rod assembly 300 along the direction of movement, a first balance block 400 and a second balance block 500 are respectively provided, and they are restricted to moving only in the second direction by guide sliders or guide grooves. The first transmission section 210 and the third transmission section 230 on the right side of the crankshaft 200 are two eccentric blocks, which are respectively embedded in the drive holes or slide grooves on the first balance block 400 and the second balance block 500. When the motor drives the crankshaft 200 to rotate at high speed, the central eccentric journal pushes the reciprocating rod assembly 300 to reciprocate back and forth for cutting. At the same time, the eccentric journals on both sides push the two balance blocks to move backward (relative to the forward movement of the rod 320 of the reciprocating rod assembly 300) or forward (relative to the backward movement of the rod 320 of the reciprocating rod assembly 300). Because the connecting rod is removed, the two balance blocks can be very close to the center of gravity plane of the reciprocating rod assembly 300, so that the opposing inertial forces cancel each other out almost on the same straight line, greatly reducing the vibration felt in the hand.

[0052] Through the above technical solution, since the second transmission part 220 on the crankshaft 200 directly slides into the slide rail 310 of the reciprocating rod assembly 300, the connecting rod mechanism in the traditional solution is eliminated. Therefore, the transmission structure is more compact, the number of parts is reduced, the assembly difficulty and cost are reduced, and the rigidity and reliability of the mechanism are improved. Since there is no need for the connecting rod to occupy axial space, the first transmission part 210 and the third transmission part 230 can retract inward along the axial direction of the crankshaft 200, so that the first balance block 400 and the second balance block 500 can... By arranging the reciprocating rod assembly 300 close to the crankshaft, the torque arm between the balancing inertial force and the reciprocating rod inertial force is significantly reduced, making the two opposing forces nearly collinear and canceling each other out. This effectively eliminates the eccentric torque and greatly reduces the vibration and noise of the entire machine. In addition, since the first transmission unit 210, the second transmission unit 220 and the third transmission unit 230 are integrated on the same crankshaft 200, the strict synchronization between the reciprocating rod assembly 300 and the movement of the two balance blocks is ensured, making the inertial force cancellation effect more stable and accurate, and improving the operating comfort and work accuracy.

[0053] The specific structure of each component will be described below: The crankshaft 200 can be structured in the following way: the center of mass of the first transmission part 210 and the center of mass of the third transmission part 230 are located on the same straight line X2 parallel to the axis of rotation X1.

[0054] The center of mass of the first transmission unit 210 refers to the equivalent concentration point of its mass distribution during rotation. The position of this center of mass depends on the specific geometry, size, and material density distribution of the first transmission unit 210, and can be set according to actual conditions. In this embodiment, the first transmission unit 210 is used to drive the first balance block 400 to move, and the spatial position of its center of mass directly determines the trajectory axis of the reciprocating motion of the first balance block 400.

[0055] Similarly, the center of mass of the third transmission unit 230 refers to the equivalent concentration point of its mass distribution during rotation. Likewise, the position of this center of mass depends on the structural parameters of the third transmission unit 230; for example, it could be the geometric center of a cylindrical eccentric journal or the weighted average position of irregularly shaped protrusions. The third transmission unit 230 drives the second balance block 500, and the spatial position of its center of mass directly determines the trajectory axis of the reciprocating motion of the second balance block 500.

[0056] Parallel to the rotation axis X1 can refer to a straight line that maintains a constant spatial distance from the rotation center line of the crankshaft 200 and never intersects it. On the same straight line X2 means that the centers of mass of the first transmission unit 210 and the third transmission unit 230 coincide in spatial projection on a straight line X2 parallel to the rotation axis X1. This means that, viewed from the axial perspective of the crankshaft 200, the eccentric directions of the first transmission unit 210 and the third transmission unit 230 are completely consistent, and there is no lever arm deviation caused by circumferential phase difference or axial misalignment.

[0057] The collinear arrangement of the centers of mass of the first transmission unit 210 and the third transmission unit 230, serving as power input ends, forms the geometric basis for the synchronous movement of the two balance blocks. When the crankshaft 200 rotates around the rotation axis X1, since the centers of mass of the two transmission units are located on the same straight line parallel to the rotation axis X1, the centrifugal force components or pushing force components they generate at the same moment have exactly the same direction vector in the plane perpendicular to the rotation axis X1. This coordination ensures that when the first balance block 400 and the second balance block 500 are driven, their instantaneous velocity direction and acceleration direction always remain parallel and in the same direction, thereby ensuring that the inertial forces generated by the two balance blocks form a unified resultant force in space, rather than a dispersed force system that cancels each other out or generates torsional torque.

[0058] Specifically, when the crankshaft 200 rotates, driving the first transmission unit 210 and the third transmission unit 230 to move, since their centers of mass are always on the same plane parallel to the rotation axis X1, the first balance block 400 moves along the second direction, and the second balance block 500 also moves strictly along the same second direction. The displacement, velocity, and acceleration of both remain in phase at any given moment. This motion state allows the inertial force vectors of the two balance blocks to be linearly superimposed, forming a total balancing force with a larger amplitude and a definite direction. This total balancing force is used to precisely counteract the inertial force generated by the reciprocating rod assembly 300 moving along the first direction, avoiding torsional vibration of the housing caused by asynchronous movement or non-parallel lines of action of the two balance blocks.

[0059] Because the centers of mass of the first transmission unit 210 and the third transmission unit 230 are located on the same straight line parallel to the rotation axis X1, the motion trajectory and force direction of the two balance blocks are kept highly consistent in space. This solves the problem in the prior art that the inertial force vector is not collinear due to the asymmetrical position of the drive eccentric part, and the eccentric torque is easily generated. It achieves the technical effect of improving the superposition effect of the balance resultant force, eliminating torsional vibration components and improving the smoothness of tool operation.

[0060] Furthermore, such as Figure 4 As shown, the distance a1 from the center of mass of the second transmission unit 220 to the rotation axis X1 is equal to the distance a2 from the center of mass of the first transmission unit 210 to the rotation axis X1.

[0061] The distance from the center of mass of the second transmission unit 220 to its rotation axis X1 refers to the radial eccentricity formed by its center of mass relative to the rotation axis X1 of the crankshaft 200 during rotation. This distance determines the stroke range when the second transmission unit 220 drives the reciprocating rod assembly 300 in reciprocating motion. The distance from the center of mass of the first transmission unit 210 to its rotation axis X1 refers to the radial eccentricity formed by its center of mass relative to the rotation axis X1 of the crankshaft 200 during rotation. This distance determines the stroke range when the first transmission unit 210 drives the first balance block 400 in reciprocating motion.

[0062] Setting these two distances equal means that the power source driving the reciprocating rod assembly 300 and the power source driving one of the balance blocks have the same geometric eccentricity parameters. This arrangement allows the second transmission unit 220 and the first transmission unit 210 to generate radial displacement components of the same amplitude when rotating with the crankshaft 200 around the rotation axis X1. Consequently, when converted into linear reciprocating motion along the axial or radial direction, both have completely identical reciprocating stroke, peak speed, and peak acceleration.

[0063] Specifically, when the crankshaft 200 is driven to rotate by the drive motor 100, since the distance from the center of mass of the second transmission unit 220 to its rotation axis X1 is equal to the distance from the center of mass of the first transmission unit 210 to its rotation axis X1, the displacement curve of the second transmission unit 220 pushing the reciprocating rod assembly 300 within the slide rail 310 is strictly synchronized in amplitude with the displacement curve of the first transmission unit 210 pushing the first balance block 400. At this time, although the reciprocating rod assembly 300 and the first balance block 400 move in opposite directions, the length of their motion trajectory, the magnitude of their velocity at any given moment, and the magnitude of their acceleration all depend only on their respective mass differences, and are no longer affected by stroke differences. This linkage eliminates the stroke correction coefficient in the calculation of the inertial force amplitude caused by different eccentricities, allowing the system to focus only on mass matching when performing dynamic balancing design. If the distances are not equal, the reciprocating strokes of the reciprocating rod assembly 300 and the counterweight will be inconsistent. Even if the mass matching is perfect, the difference in acceleration amplitude will prevent the inertial force from being completely offset, resulting in residual vibration. By setting the distances between the two to be equal, the basic geometric conditions for offsetting the inertial force are ensured, the adjustment process of the balance parameters is simplified, and the predictability of the vibration reduction effect is improved.

[0064] Because the eccentricity of the second transmission unit 220 is equal to that of the first transmission unit 210, the reciprocating rod assembly 300 and the balance block have the same reciprocating stroke and acceleration amplitude. This simplifies the balance control of inertial force to a simple mass matching problem, solves the technical problem of inaccurate compensation for inertial force amplitude mismatch caused by inconsistent stroke, and achieves the technical effect of simplifying the dynamic balance design difficulty and improving the consistency and reliability of vibration reduction effect.

[0065] Furthermore, the sum of the mass of the first balance block 400 and the mass of the second balance block 500 is equal to the mass of the reciprocating rod assembly 300.

[0066] The sum of the masses of the first balance block 400 and the second balance block 500 can refer to the cumulative scalar value of the two balance blocks' physical mass properties. The first balance block 400 and the second balance block 500 are respectively positioned on both sides of the reciprocating rod assembly 300 and reciprocate in the opposite direction to the movement of the reciprocating rod assembly 300. The setting of this sum of masses aims to adjust the total inertial parameter of the two balance blocks so that the resultant force of their opposing inertial forces generated during motion corresponds specifically in amplitude to the positive inertial force generated by the reciprocating rod assembly 300. This mass parameter setting directly determines the magnitude of the counteracting force that the balance block system can provide during high-speed reciprocating motion and is a key variable for achieving overall dynamic balance.

[0067] The mass of the reciprocating lever assembly 300 can refer to the total mass of all components constituting the reciprocating lever assembly 300 (including the lever body 320, clamping part 330, etc.). The reciprocating lever assembly 300 is the core moving component performing cutting or shaving operations, and it generates a large unbalanced inertial force when it performs high-frequency reciprocating motion along the first direction. This mass value is the benchmark for calculating the required balancing force. Specifically, the mass of the reciprocating lever assembly 300 can be set according to its structural dimensions, material selection, and the type of work head it clamps, based on actual conditions; for example, for different specifications of power tools, the length, diameter, and material of the lever body 320 may differ, resulting in differences in its mass. Using the mass of the reciprocating lever assembly 300 as a reference standard to define the total mass configuration of the two side balance blocks ensures the targetedness and accuracy of the balancing system design.

[0068] Based on the aforementioned constraint of equal eccentricity of the transmission components, when the crankshaft 200 rotates to drive the reciprocating rod assembly 300 and the two balance blocks to move with the same stroke and frequency, the amplitude of the inertial force generated by each component mainly depends on its mass. By setting the total mass of the two balance blocks to be strictly equal to the mass of the reciprocating rod assembly 300, the resultant inertial force generated by the movement of the two balance blocks in the second direction is numerically exactly equal to the inertial force generated by the movement of the reciprocating rod assembly 300 in the first direction. This equal mass configuration, combined with the collinear arrangement in space, allows the two inertial forces in opposite directions to form an ideal canceling state, thereby eliminating the residual excitation force caused by mass mismatch at the dynamic level.

[0069] Specifically, the drive motor 100 drives the crankshaft 200 to rotate, and the first transmission section 210, the second transmission section 220, and the third transmission section 230 on the crankshaft 200 rotate accordingly. Since the distance from the center of mass of the first transmission section 210 and the third transmission section 230 to the rotation axis X1 is equal to the distance from the center of mass of the second transmission section 220 to the rotation axis X1, the reciprocating rod assembly 300 and the first and second balance blocks 500 are driven to perform reciprocating motion with the same frequency and stroke. During this process, the reciprocating rod assembly 300 generates an inertial force pointing in the first direction, while the first balance block 400 and the second balance block 500 generate a resultant inertial force pointing in the second direction (opposite to the first direction). According to Newton's second law, when the acceleration amplitude is the same, the magnitude of the force is proportional to the mass. Since this embodiment limits the sum of the masses of the first balance block 400 and the second balance block 500 to equal the mass of the reciprocating rod assembly 300, the resultant force of the reverse inertial force generated by the balance block system is exactly equal in amplitude to the positive inertial force of the reciprocating rod assembly 300. These two forces, equal in magnitude and opposite in direction, act near the same axis and cancel each other out, causing the net inertial force of the entire device to approach zero during operation.

[0070] Since the sum of the masses of the first balance block 400 and the second balance block 500 is precisely set to be equal to the mass of the reciprocating rod assembly 300, when the crankshaft 200 drives the three components to perform reciprocating motion with the same stroke and frequency, the resultant force of the reverse inertial force generated by the balance block system is exactly equal in amplitude to the positive inertial force generated by the reciprocating rod assembly 300. Thus, complete dynamic balance is theoretically achieved, unbalanced inertial forces are eliminated to the maximum extent, the vibration intensity and noise level of the power tool during high-frequency operation are significantly reduced, and the operating comfort and equipment stability are improved.

[0071] Based on any of the above embodiments, the first transmission part 210, the second transmission part 220 and the third transmission part 230 are eccentric journals or eccentric protrusions formed on the crankshaft 200.

[0072] The first transmission section 210, the second transmission section 220, and the third transmission section 230 can be integral structures directly machined onto the crankshaft 200 body, or protruding parts formed by precision forging and machining processes and fixedly connected to the crankshaft 200 body. This structure ensures that the relative phase relationship between the first transmission section 210, the second transmission section 220, and the third transmission section 230 is permanently locked after manufacturing, preventing loosening, offset, or angular errors due to long-term high-frequency operation.

[0073] The specific implementation of the eccentric journal can be a cylindrical segment on the crankshaft 200 whose diameter changes and whose axis deviates from the rotation axis X1. For example, it can be a journal structure formed by integral forging and grinding, or it can be a wear-resistant shaft segment that has undergone surface hardening treatment. The eccentric protrusion can be a block-shaped structure that protrudes radially from the surface of the crankshaft 200. For example, it can be a boss welded and fixed to the body of the crankshaft 200, or it can be a pin structure that is pressed into a preset hole in the crankshaft 200 by interference fit.

[0074] Because the first transmission unit 210, the second transmission unit 220 and the third transmission unit 230 adopt an eccentric journal or eccentric protrusion structure integrally formed on the crankshaft 200, the phase relationship between each transmission unit is fixed and cannot be adjusted. This solves the phase drift problem caused by wear of parts or assembly errors in the traditional split structure, and achieves the technical effects of high transmission synchronization, high mechanism rigidity and long-term stable operation under high speed and high frequency conditions.

[0075] Furthermore, the second transmission part 220 is a cylindrical journal disposed on the crankshaft 200, and the outer peripheral surface of the cylindrical journal is slidably and rotatably engaged with the groove wall of the slide 310.

[0076] The second transmission unit 220 is a cylindrical journal, whose geometry can be a standard cylindrical structure or a boss structure with an arc-shaped outer surface designed according to actual force requirements. The outer circumferential surface of this cylindrical journal forms a mating relationship with the groove wall of the slide 310 formed on the reciprocating rod assembly 300. This mating relationship is configured to allow the cylindrical journal to slide linearly relative to the slide 310 along the length of the groove, and also to allow the cylindrical journal to rotate relative to the slide 310 about its own axis. The cylindrical journal converts the rotational motion of the crankshaft 200 into the linear reciprocating motion of the reciprocating rod assembly 300, while adapting to changes in the contact point during the motion through its own rotational degree of freedom. When the crankshaft 200 rotates, the outer circumferential surface of the cylindrical journal pushes against the groove wall of the slide rail 310, driving the reciprocating rod assembly 300 to move in the first direction. During this process, the contact point between the cylindrical journal and the groove wall changes continuously with the crankshaft 200's rotation angle, and the cylindrical journal can rotate accordingly, thereby converting some sliding friction into rolling friction or compound friction. Through the above-mentioned cooperation, the cylindrical journal moves smoothly within the slide rail 310, avoiding jamming caused by a single sliding fit, and making the wear distribution on the contact surface more uniform. The specific dimensions, material, and surface roughness of the cylindrical journal can be set according to the actual situation. For example, it can be made of hardened alloy steel or carbon steel with a surface anti-friction coating; its diameter and length can be adjusted according to the power level and spatial layout of the power tool.

[0077] Because the second transmission part 220 adopts a cylindrical journal and forms a sliding and rotatable fit with the groove wall of the slide 310, the transmission pair can adaptively adjust the contact state during the movement, transforming pure sliding friction into rolling-sliding compound friction. This solves the technical problems of jamming, severe local wear and high frictional resistance that are easy to occur in traditional rigid sliding fits, reduces transmission energy consumption, extends the service life of components and improves the smoothness of tool operation.

[0078] Alternatively, the second transmission part 220 may have the following structure: the crankshaft 200 includes a first component 240 and a second component 250 that are detachably connected. The first component 240 is provided with a first transmission part 210 and a transmission shaft 221, and the second component 250 is provided with a third transmission part 230 and a transmission hole 223. The transmission shaft 221 and the transmission hole 223 cooperate to form the second transmission part 220.

[0079] A detachable connection can refer to a connection between the first component 240 and the second component 250 formed by means of threaded fastening, keying, interference fit, or snap locking. This connection method allows the two to be separated during the assembly stage and reassembled into a whole rotating component after a specific assembly path is completed. In this embodiment, the first component 240 carries the first transmission part 210 that drives the first balance block 400 and extends to a transmission shaft 221 for constructing an intermediate drive node; the second component 250 carries the third transmission part 230 that drives the second balance block 500 and has a transmission hole 223 for receiving the transmission shaft 221. The cooperation between the first component 240 and the second component 250 decomposes the original eccentric structure of the integral crankshaft 200, which was originally large in axial dimension and could not directly pass through the slide 310 of the reciprocating rod assembly 300, into two independent components with smaller axial dimensions, thereby changing the assembly difficulty.

[0080] The drive shaft 221 on the first component 240 refers to a columnar protrusion or an independently mounted shaft extending from the body of the first component 240 along the rotation axis X1. Its outer diameter is designed to be smaller than the minimum cross-section of the slide rail 310 on the reciprocating rod assembly 300. The drive shaft 221 serves as a half-body or spindle of the second transmission unit 220, acting as a guide and connecting medium during assembly. It is fixed to the same rigid body as the first transmission unit 210, ensuring phase locking between the drive source of the first balance block 400 and the intermediate drive node. In the system linkage, the drive shaft 221 first passes through the slide rail 310 of the reciprocating rod assembly 300 alone, avoiding interference from the large-sized eccentric structure, and then combines with the second component 250 to form a complete second transmission unit 220, thereby transmitting driving force to the reciprocating rod assembly 300.

[0081] The transmission hole 223 on the second component 250 refers to a through hole or blind hole formed inside the body of the second component 250 or the joint 222 integrated on the second component 250. Its diameter matches the outer diameter of the transmission shaft 221 to achieve coaxial fixation between the two. After the transmission shaft 221 passes through the slide 310, the second component 250 is sleeved on the transmission shaft 221 through the transmission hole 223. This fit allows the second component 250 to rotate synchronously with the first component 240 and transmit the motion of the third transmission part 230 to the second balance block 500. At the same time, the combined structure drives the reciprocating rod assembly 300.

[0082] The second transmission unit 220 is a composite structure formed by the engagement of the transmission shaft 221 and the transmission hole 223, and its function is equivalent to the eccentric journal or eccentric protrusion in the integral crankshaft 200. When the first component 240 and the second component 250 are locked, the second transmission unit 220 rotates as a whole with the crankshaft 200, and its outer peripheral surface contacts the inner wall of the slide 310 on the reciprocating rod assembly 300. As the crankshaft 200 rotates, the eccentric part of the second transmission unit 220 pushes against the side wall of the slide 310, converting the rotational motion into linear reciprocating motion of the reciprocating rod assembly 300 along the first direction.

[0083] Specifically, during the assembly stage, the operator first inserts the first component 240, which has a first transmission part 210 and a transmission shaft 221, into one side of the reciprocating rod assembly 300, so that the transmission shaft 221 passes smoothly through the slide rail 310 on the reciprocating rod assembly 300; then, the second component 250, which has a third transmission part 230 and a transmission hole 223, is aligned with the transmission shaft 221 that has passed through the slide rail 310 from the other side, and the transmission hole 223 is fitted into the end of the transmission shaft 221; finally, the first component 240 and the second component 250 are fixed together by fasteners or interference fit, at which point the joint between the transmission shaft 221 and the transmission hole 223 forms a complete second transmission part 220.

[0084] The crankshaft 200 is split into two independent components at the second transmission part 220. During assembly, the transmission shaft 221 of the first component 240 can be passed through one side of the slide 310 first, and then the transmission hole 223 of the second component 250 can be aligned with the transmission shaft 221 and sleeved and fixed. This allows the second transmission part 220 to be reassembled after passing through the slide 310, thereby bypassing the assembly interference caused by the eccentric structure in the middle section of the integral crankshaft 200 not being able to pass through the slide 310. This significantly reduces the assembly difficulty and improves the assembly efficiency.

[0085] Furthermore, the second component 250 is also provided with a joint 222, a transmission hole 223 is opened in the joint 222, the transmission shaft 221 is at least partially inserted into the transmission hole 223 of the joint 222, and the outer peripheral surface of the joint 222 is slidably engaged with the slide 310.

[0086] The joint 222 is an independent structural component or an integrally formed component disposed on the second member 250, serving as a functional carrier for transmission connection and sliding guidance. The inner cavity of the joint 222 forms a transmission hole 223 for accommodating and fixing the transmission shaft 221 from the first member 240; the outer peripheral surface of the joint 222 directly forms a sliding interface that mates with the slide rail 310 on the reciprocating rod assembly 300. The joint 222 decouples the two functions of fastening the transmission shaft 221 and sliding the slide rail 310: the transmission shaft 221 is at least partially inserted into the transmission hole 223 of the joint 222, and the first member 240 and the second member 250 are circumferentially locked and axially positioned by means of interference fit, key connection or threaded connection, thereby transmitting driving torque and forming the second transmission part 220 of the crankshaft 200; at the same time, the outer peripheral surface of the joint 222 reciprocates linearly within the slide rail 310, undertaking the function of supporting the reciprocating rod assembly 300 and bearing lateral forces. This design allows the mating length between the drive shaft 221 and the drive hole 223 to be no longer limited by the thickness of the second component 250. The axial length of the joint 222 can be set according to actual conditions to obtain greater connection rigidity and alignment accuracy. The material of the joint 222 can be wear-resistant alloy steel, engineering plastic, or surface-hardened metal material, such as a quenched steel sleeve, or a composite joint 222 inlaid with self-lubricating material.

[0087] The transmission hole 223 is a through hole or blind hole formed inside the joint 222, and its geometry can match the outer contour of the drive shaft 221. The transmission hole 223 provides insertion space for the drive shaft 221 and forms a reliable connection interface. When the drive shaft 221 is inserted into the transmission hole 223, the hole wall of the transmission hole 223 fits tightly against the outer peripheral surface of the drive shaft 221, preventing relative rotation or axial movement between the two and ensuring that the first component 240 and the second component 250 can rotate synchronously. The positional accuracy of the transmission hole 223 directly affects the overall coaxiality of the crankshaft 200, so its machining accuracy can be set according to actual assembly requirements, for example, it can be formed by reaming, grinding or precision casting processes.

[0088] The fit between the slide rail 310 and the outer peripheral surface of the joint 222 is a sliding fit, allowing the joint 222 to move freely within the slide rail 310 along the direction of movement of the reciprocating rod assembly 300, while restricting its displacement perpendicular to the direction of movement. The outer peripheral surface of the joint 222 can be a smooth cylindrical surface or other curved surfaces adapted to the shape of the slide rail 310. Its surface roughness can be set according to tribological requirements, such as polishing or applying an anti-friction coating. Through the direct fit between the outer peripheral surface of the joint 222 and the slide rail 310, the driving force generated when the crankshaft 200 rotates acts directly on the reciprocating rod assembly 300, eliminating the need for additional intermediate connecting parts and shortening the force transmission path.

[0089] During assembly, the drive shaft 221 of the first component 240 is first inserted into the slide rail 310 of the reciprocating rod assembly 300 from one side, so that the end of the drive shaft 221 extends out of the other side of the slide rail 310. Then, the joint 222 is fitted onto the extended end of the drive shaft 221 and inserted, so that the drive shaft 221 is fully inserted into the drive hole 223 of the joint 222. At this time, the outer peripheral surface of the joint 222 is located inside the slide rail 310, forming a sliding pair with the groove wall of the slide rail 310.

[0090] The joint 222 is designed so that the mating area between the drive shaft 221 and the drive hole 223 can be specially optimized to ensure connection rigidity, and the outer peripheral surface of the joint 222 can be specially optimized to ensure sliding wear resistance. This solves the problems of insufficient rigidity at the connection and unstable sliding fit in the split crankshaft 200. Because the axial length of the joint 222 can be designed independently, the support span of the sliding fit is increased, thereby improving the coaxiality and running smoothness between the crankshaft 200 and the reciprocating rod assembly 300, and extending the service life of the transmission mechanism.

[0091] Based on any of the above embodiments, the slide 310 is a horizontal groove formed on the reciprocating rod assembly 300, and the length direction of the horizontal groove is perpendicular to the reciprocating motion direction of the reciprocating rod assembly 300.

[0092] A transverse groove is a through or non-through groove-like structure formed on the body of the reciprocating rod assembly 300, and its extension direction (i.e., the length direction) is configured to be orthogonal to the linear reciprocating motion trajectory of the reciprocating rod assembly 300. The transverse groove serves as the motion guiding constraint interface of the second transmission unit 220, receiving the driving force generated by the rotation of the crankshaft 200 and converting this force into a linear thrust that drives the reciprocating rod assembly 300 to move along a first direction. A sliding fit relationship is formed between the transverse groove and the second transmission unit 220. When the second transmission unit 220 rotates with the crankshaft 200, its outer peripheral surface slides on the inner wall surface of the transverse groove, and the side wall of the transverse groove applies a reaction force to the second transmission unit 220. The component of this reaction force is along the motion axis direction of the reciprocating rod assembly 300, thereby driving the reciprocating rod assembly 300 to perform reciprocating linear motion. Since the length direction of the transverse groove is perpendicular to the reciprocating motion direction, the motion trajectory of the second transmission unit 220 in the transverse groove is restricted to a plane perpendicular to the output shaft. This allows the tangential component of the second transmission unit 220 in the circular motion to be effectively converted into an effective driving force along the axial direction of the reciprocating rod assembly 300, while the radial component is balanced and canceled out by the side wall of the transverse groove, thus avoiding the generation of lateral torque.

[0093] The specific implementation of the transverse groove can be determined according to the actual situation. For example, the transverse groove can be a through groove extending through the thickness direction of the reciprocating rod assembly 300. The cross-sectional shape of the transverse groove can be rectangular, arc-shaped, or trapezoidal, as long as its inner wall surface can form a stable sliding contact with the outer peripheral surface of the second transmission part 220. The width of the transverse groove can be set according to the size and fitting tolerance requirements of the second transmission part 220, and is usually slightly larger than the diameter of the second transmission part 220 to reserve a lubrication gap.

[0094] Since the slide rail 310 is specifically defined as a transverse groove with its length direction perpendicular to the reciprocating motion direction, the driving force of the second transmission unit 220 on the reciprocating rod assembly 300 can be directly transmitted along the motion axis, avoiding the lateral force loss caused by the change of swing angle in the traditional linkage mechanism, thus significantly improving the transmission efficiency. At the same time, since the force direction is clear and stable, the contact stress distribution on the side wall of the transverse groove is more uniform, reducing the risk of local wear and jamming, thereby extending the service life of the transmission pair and improving the smoothness and reliability of the mechanism operation.

[0095] Regarding the specific structure of the reciprocating rod assembly 300, the reciprocating rod assembly 300 in this embodiment includes a rod body 320, one end of the rod body 320 is provided with a clamping part 330 for connecting the working head, and a slide 310 is formed on the other end of the rod body 320.

[0096] The rod body 320 is the main structural component of the reciprocating rod assembly 300. Its material can be set according to actual conditions; for example, it can be high-strength alloy steel or heat-treated carbon steel. In the overall technical solution, the rod body 320 is responsible for transmitting driving force and supporting the working head. One end of it cooperates with the drive mechanism, and the other end connects to the working head. The length, cross-sectional shape, and dimensions of the rod body 320 can be designed according to the specific power level and application scenario of the power tool. For example, it can be a cylindrical long rod or an irregularly shaped rod with reinforcing ribs, as long as it meets the strength and rigidity requirements during reciprocating motion.

[0097] The clamping part 330 refers to the connection structure located at the end of the rod 320 for fixing and locking the working head (such as a saw blade, shovel, etc.). The specific implementation of the clamping part 330 can be selected according to the interface standard of the working head. For example, it can be a clamp structure with fastening bolts, a spring-loaded snap-fit ​​structure controlled by a quick-release button, or a threaded connection interface. The clamping part 330 is located at the end of the rod 320 away from the slide rail 310. This layout ensures that the working area of ​​the working head maintains a sufficient distance from the crankshaft 200 and the second transmission part 220, and other driving components, along the length of the rod 320. When the rod 320 performs high-frequency reciprocating motion in the first direction, the clamping part 330 synchronously drives the working head to move. Heat, wear debris, or lubricating grease generated by the driving components are not easily diffused to the working end where the clamping part 330 is located, thus avoiding contamination or thermal interference of the working head clamping interface by the driving mechanism, ensuring the reliability of the clamping connection and the working accuracy of the working head.

[0098] The slide rail 310 is a guide structure formed on the rod 320 to accommodate and guide the movement of the second transmission unit 220. In this embodiment, the slide rail 310 is specifically formed at the other end of the rod 320, that is, on the side opposite to the end where the clamping part 330 is located. This structure with two ends distributed achieves functional zoning: the slide rail 310 focuses on receiving driving force, and the clamping part 330 focuses on performing processing operations. The two do not interfere with each other, which optimizes the force transmission path and improves the overall structural compactness and safety of the machine.

[0099] Through the above technical solution, the motion input end and output end are physically isolated on the rod body 320. Since the slide rail 310 is opened at one end of the rod body 320 and the clamping part 330 is set at the other end, an effective space buffer is formed between the drive component and the working head. This solves the problems of heat interference, debris contamination and inconvenient maintenance caused by the drive component being close to the working area in the traditional structure. Thus, it achieves the functions of ensuring a clean and reliable clamping interface, improving working accuracy and facilitating quick replacement of the working head.

[0100] Example 2: The difference from Embodiment 1 lies in the specific structure of the crankshaft 200, such as... Figure 5 , Figure 6 As shown, the crankshaft 200 includes a first rotating body 260, a first crankshaft body 270, a second crankshaft body 280, and a second rotating body 290 arranged sequentially along the axis of rotation. The first rotating body 260 and the second rotating body 290 are both rotating bodies about their own rotation axis, and each is provided with a shaft protruding in opposite directions; The first crankshaft body 270 includes a first transmission part 210 and a first transmission member 272; the first transmission part 210 deviates from the rotation axis in a direction perpendicular to the rotation axis and extends toward the first rotating body 260 in the direction of the rotation axis and is connected to the first rotating body 260; the first transmission member 272 deviates from and protrudes in the opposite direction to the first transmission part 210. The second crankshaft body 280 includes a third transmission part 230 and a second transmission member 281; the third transmission part 230 deviates from the rotation axis in a direction perpendicular to the rotation axis and extends toward the second rotating body 290 in the direction of the rotation axis and is connected to the second rotating body 290; the second transmission member 281 deviates in the opposite direction and protrudes in the opposite direction to the third transmission part 230. The first transmission component 272 and the second transmission component 281 cooperate to form the second transmission part 220.

[0101] The first rotating body 260 and the second rotating body 290 are reference components used for support and positioning at both ends of the crankshaft 200. Both the first rotating body 260 and the second rotating body 290 are rotating bodies that rotate about their own axes of rotation, and their geometric center lines coincide with the axis of rotation of the crankshaft 200. Each of the first rotating body 260 and the second rotating body 290 has a back-protruding shaft, which can be used to mate with bearings or bushings on the power tool housing to provide double-point support for the entire crankshaft 200. One of the rotating bodies is also connected to the drive motor 100 to receive the driving force transmitted by the drive motor 100, thereby rotating the entire crankshaft 200.

[0102] The first rotating body 260 is located at one end of the crankshaft 200, and the second rotating body 290 is located at the other end of the crankshaft 200. The two bodies axially clamp the intermediate transmission structure, forming a support structure similar to a simply supported beam. This arrangement gives the crankshaft 200 good bending stiffness and rotational accuracy during high-speed rotation, effectively suppressing yaw vibrations caused by the cantilever effect. The specific shapes of the first rotating body 260 and the second rotating body 290 can be set according to actual conditions; for example, they can be cylindrical, stepped shaft-shaped, or other rotating body shapes suitable for mounting bearings.

[0103] The first crankshaft body 270 is a transmission conversion component located between the first rotating body 260 and the middle of the crankshaft 200. The first crankshaft body 270 includes a first transmission section 210 and a first transmission member 272. The first transmission section 210 is offset from the rotation axis in a direction perpendicular to the rotation axis, meaning its geometric center is not on the rotation axis, thus generating eccentric motion when the crankshaft 200 rotates. The first transmission section 210 extends towards and connects to the first rotating body 260 along the rotation axis, transmitting the rotational motion of the first rotating body 260 to the first transmission section 210. The first transmission member 272 is also located on the first crankshaft body 270, but its offset direction and protrusion direction are opposite to those of the first transmission section 210. This means that if the first transmission section 210 protrudes to one side of the rotation axis, the first transmission member 272 protrudes to the other side of the rotation axis, and the two are 180 degrees out of circumferential phase. Figure 5 From the perspective of the image, the first transmission unit 210 rotates 180 degrees around the center of the first crankshaft body 270 and then coincides with the first transmission component 272. The first crankshaft body 270 can be integrally formed by casting, forging or machining, or it can be formed by fixing multiple sub-components together.

[0104] The second crankshaft body 280 is a transmission conversion component located between the second rotating body 290 and the middle of the crankshaft 200. Its structure is mirror-symmetrical or approximately mirror-symmetrical with the first crankshaft body 270. The second crankshaft body 280 includes a third transmission section 230 and a second transmission member 281. The third transmission section 230 is offset from the rotation axis in a direction perpendicular to the rotation axis and extends towards and connects to the second rotating body 290 in the direction of the rotation axis. The third transmission section 230 is used to drive the second balance block 500 disposed on the other side of the reciprocating rod assembly 300. The offset direction and protrusion direction of the second transmission member 281 are opposite to those of the third transmission section 230, that is, the second transmission member 281 extends towards the middle region of the crankshaft 200, and its eccentric direction is opposite to that of the third transmission section 230. Figure 5 From the perspective of the media, the third transmission unit 230 rotates 180 degrees around the center of the second crankshaft body 280 and then coincides with the second transmission component 281.

[0105] The second transmission component 281 and the first transmission component 272 are spatially opposite each other, and together they form the second transmission section 220. When the first transmission component 272 and the second transmission component 281 are engaged, they can be fixed together by means of key connection, pin connection, or threaded connection, forming an integral intermediate transmission shaft 221 neck. The combined second transmission section 220 is slidably engaged within the slide rail 310 of the reciprocating rod assembly 300. When the crankshaft 200 rotates, the first transmission component 272 and the second transmission component 281 move in a circular motion within the slide rail 310 as a whole, and their radial component pushes the side wall of the slide rail 310, thereby driving the reciprocating rod assembly 300 to perform linear reciprocating motion along the first direction. This split-type engagement of the second transmission section 220 solves the technical problem that the eccentric structure of the middle section of the integral crankshaft 200 cannot pass through the narrow slide rail 310 for assembly. The specific mating dimensions, tolerance grades, and connection methods of the first transmission component 272 and the second transmission component 281 can be set according to the actual situation, as long as the connection strength and coaxiality under high-speed rotation can be guaranteed.

[0106] Specifically, the working process and principle of this embodiment are as follows: The drive motor 100 drives the crankshaft 200 to rotate around its axis of rotation. Since the first rotating body 260 and the second rotating body 290 are both rotating bodies and their centers of gravity are located on their axes of rotation, they do not generate eccentric inertial forces during rotation and mainly play a supporting role. As the crankshaft 200 rotates, the first transmission part 210 on the first crankshaft body 270 drives the first balance block 400 to reciprocate along the second direction, and the third transmission part 230 on the second crankshaft body 280 drives the second balance block 500 to reciprocate along the second direction. At the same time, the first transmission member 272 on the first crankshaft body 270 and the second transmission member 281 on the second crankshaft body 280 rotate synchronously, and the second transmission part 220, which together constitutes the second transmission part 220, rotates within the slide rail 310 of the reciprocating rod assembly 300. Because the second transmission unit 220 is offset from its rotation axis, it continuously changes its radial position relative to the center of the slide rail 310 during rotation. By compressing the inner wall of the slide rail 310, it converts the rotational motion into linear reciprocating motion of the reciprocating rod assembly 300 along the first direction. During this process, the first transmission member 272 and the second transmission member 281 remain relatively stationary and cooperate in bearing the load required to drive the reciprocating rod assembly 300. Since the first transmission member 272 is arranged in opposite directions to the first transmission unit 210, and the third transmission unit 230 is arranged in opposite directions to the second transmission unit 281, the centrifugal force of the crankshaft 200 itself is partially or completely canceled out internally, reducing the vibration sources transmitted to the housing.

[0107] During the assembly phase, the operator first inserts the first sub-assembly, containing the first rotating body 260 and the first crankshaft body 270, into one side of the slide rail 310 of the reciprocating rod assembly 300, so that the first transmission member 272 extends into the slide rail 310 but does not completely pass through. Then, the second sub-assembly, containing the second rotating body 290 and the second crankshaft body 280, is inserted into the slide rail 310 from the other side, so that the second transmission member 281 extends into the slide rail 310 and mates with the first transmission member 272. Next, the first transmission member 272 and the second transmission member 281 are fixedly connected by a fastening device to form a complete second transmission section 220. Finally, the shafts at both ends are installed into the bearing housing to complete the final assembly. In the working state, assuming the crankshaft 200 rotates clockwise, the first transmission section 210 pushes the first balance block 400 to the left, while the third transmission section 230 pushes the second balance block 500 to the left, and the second transmission section 220, after being joined in the middle, pushes the reciprocating rod assembly 300 to the right. Since the first transmission component 272 and the second transmission component 281 converge in the slide rail 310, their equivalent point of action is located near the center plane of the reciprocating rod assembly 300, so that the line of action of the driving force is as collinear as possible with the line of action of the inertial force of the balance block, thereby minimizing the eccentric torque.

[0108] Because it adopts a split structure with the first rotating body 260, the first crankshaft body 270, the second crankshaft body 280, and the second rotating body 290 arranged in sequence, and the first transmission component 272 and the second transmission component 281 cooperate in opposite directions to form the second transmission part 220, the problem that the traditional integral crankshaft 200 cannot pass through the slide rail 310 for assembly is solved, and the asymmetrical support defect caused by single-sided insertion is also avoided; because the first rotating body 260 and the second rotating body 290 are located at both ends and provide opposing protruding shafts as double-support points, thus forming The stable simply supported beam structure significantly improves the bending stiffness and rotational accuracy of the crankshaft 200, reducing yaw vibration during operation. Because the first transmission component 272 is opposite to the first transmission part 210 and the second transmission component 281 is opposite to the third transmission part 230, the mass distribution of the crankshaft 200 is more uniform, and the internal centrifugal forces cancel each other out, reducing the imbalance of the crankshaft 200. This allows the balance block to focus more on counteracting the inertial force of the reciprocating rod assembly 300, improving the overall vibration reduction and balance effect and running stability of the machine.

[0109] Furthermore, the first crankshaft body 270 also includes a first connecting body 271, a first transmission part 210 and a first transmission member 272 respectively disposed at both ends of the first connecting body 271, and the center of gravity of the first connecting body 271 is located on the rotation axis; the second crankshaft body 280 also includes a second connecting body 282, a third transmission part 230 and a second transmission member 281 respectively disposed at both ends of the second connecting body 282, and the center of gravity of the second connecting body 282 is located on the rotation axis.

[0110] The first connecting body 271 is a structural component used to connect the first transmission part 21021 and the first transmission member 27234. Its function is to provide rigid support and position fixation for the two transmission members that are offset from the rotation axis, maintaining a predetermined relative positional relationship between them on the first crankshaft body 270. The center of gravity of the first connecting body 271 is located on the rotation axis, meaning that when this component rotates around the rotation axis, its mass distribution is symmetrical about the center of rotation, generating no additional centrifugal force or eccentric inertial torque. In the specific implementation of the first connecting body 271, its shape can be set according to actual conditions, for example, it can be cylindrical, disc-shaped, or a plate-like structure with a specific contour, as long as its geometric center or center of mass falls on the rotation axis; its material can be, for example, high-strength alloy steel, cast iron, or engineering plastics. The first connecting body 271 can be connected to the first transmission part 210 and the first transmission member 272 by welding, integral casting, bolting, or interference fit to ensure structural stability during high-speed rotation. By placing the center of gravity of the first connecting body 271 on the axis of rotation, when the first crankshaft body 270 rotates, only the first transmission part 210 and the first transmission component 272, which are intentionally off-axis, generate centrifugal force, while the connecting body itself is in a self-balancing state. This avoids interference force sources introduced by the eccentricity of the connecting body's own mass, thereby simplifying the dynamic balance calculation model of the first crankshaft body 270.

[0111] The second connector 282 is a structural component used to connect the third transmission part 230 and the second transmission member 281. Its function is similar to that of the first connector 271, aiming to maintain the relative positions of the third transmission part 230 and the second transmission member 281 on the second crankshaft body 280. The center of gravity of the second connector 282 is also located on its rotation axis, ensuring that it does not generate additional unbalanced inertial forces when rotating with the crankshaft 200. The connection between the second connector 282 and the third transmission part 230 and the second transmission member 281 can also be achieved through welding, threaded fastening, or integral molding. Because the second connector 282 achieves self-balancing, the unbalanced force system during the rotation of the second crankshaft body 280 originates entirely from the third transmission part 230 and the second transmission member 281. This makes the force state of the second crankshaft body 280 clear and definite, facilitating precise counterweight adjustment or balance block matching during the assembly stage.

[0112] Specifically, the first connecting body 271 and the second connecting body 282, as key load-bearing components inside the crankshaft 200, work in conjunction with their respective eccentric transmission components. When the drive motor 100 drives the crankshaft 200 to rotate around its axis of rotation, the first connecting body 271 and the second connecting body 282 maintain their rotational balance because their centers of gravity are located on the axis, and do not output vibration excitation externally. At the same time, the first transmission part 210, the first transmission component 272, the third transmission part 230, and the second transmission component 281 located at their ends generate centrifugal force due to their deviation from the axis. This structural design strictly limits the unbalanced force source of the crankshaft 200 to four specific transmission components, eliminating the random or complex unbalanced components that may be introduced by the connecting bodies themselves. The first connecting body 271, together with the first transmission part 210 and the first transmission component 272, constitutes the first crankshaft body 270. The second connecting body 282, together with the third transmission part 230 and the second transmission component 281, constitutes the second crankshaft body 280. The two work together to form a complete crankshaft 200 transmission chain, which not only ensures the spatial position accuracy of the transmission components, but also realizes the self-balancing of the main body of the crankshaft 200. This provides a pure and controllable mechanical basis for the subsequent counterbalancing of the inertial force of the reciprocating rod assembly 300 by the first balance block 400 and the second balance block 500.

[0113] Since the centers of gravity of the first connecting body 271 and the second connecting body 282 are precisely positioned on the axis of rotation, these two connecting bodies do not generate any eccentric inertial force during rotation. This solves the problem of uncontrollable variables introduced by the offset of the center of gravity of the connecting bodies, which leads to the complexity of dynamic balance design. It achieves the effect of making the source of the unbalanced force of the crankshaft 200 clear and singular, facilitating accurate modeling and balance calculation, and improving the certainty and reliability of the overall dynamic balance design.

[0114] Furthermore, the thicknesses of the first transmission part 210, the third transmission part 230, the first transmission member 272, and the second transmission member 281 are equal along the rotation axis. For example... Figure 6 As shown, the thickness of the first transmission part 210 is c3, the thickness of the third transmission part 230 is c4, the thickness of the first transmission component 272 is c1, and the thickness of the second transmission component 281 is c2, then c1=c2=c3=c4.

[0115] The requirement that the thickness of the four transmission components be equal is intended to complement the previous requirement of equal eccentricity. This ensures that, given consistent material density, if the cross-sectional shape and area of ​​each transmission component perpendicular to the axis of rotation are also consistent or matched, the opposing transmission components (i.e., the first transmission component 210 and the first transmission member 272, and the third transmission component 230 and the second transmission member 281) have equal or approximately equal masses. This symmetry in mass ensures that the centrifugal forces generated inside the first crankshaft body 270 by the first transmission component 210 and the first transmission member 272 are equal in magnitude and opposite in direction, thus locally canceling each other out. Similarly, the centrifugal forces generated inside the second crankshaft body 280 by the third transmission component 230 and the second transmission member 281 also locally cancel each other out. This structural design eliminates the internal torque of the crankshaft 200 caused by inconsistent thicknesses of the various transmission components, achieving self-balancing of the crankshaft 200 during rotation. This eliminates the need for the external balancing block to additionally correct the crankshaft 200's own imbalance; it can focus solely on counteracting the inertial force of the reciprocating rod assembly 300. The specific thickness can be set according to the power tool's power rating, spatial layout, and material properties.

[0116] Specifically, when the drive motor 100 drives the crankshaft 200 to rotate, the thicknesses of the first transmission section 210, the third transmission section 230, the first transmission component 272, and the second transmission component 281 along the rotation axis are defined to be equal. Combined with the fact that the center of gravity of each of the preceding transmission sections is equidistant from the rotation axis and that the center of gravity of the connecting sections is located on the rotation axis, the centrifugal force vectors generated by the various eccentric mass blocks inside the crankshaft 200 can form a precise mutual cancellation relationship during high-speed rotation. The centrifugal force generated by the first transmission section 210 and the centrifugal force generated by the first transmission component 272 constitute a pair of balanced force systems within the first crankshaft body 270, and the centrifugal force generated by the third transmission section 230 and the centrifugal force generated by the second transmission component 281 constitute another pair of balanced force systems within the second crankshaft body 280. This self-balancing mechanism of the internal force systems avoids the crankshaft 200 itself generating additional vibration sources or torsional torques, ensuring that the driving force transmitted to the reciprocating rod assembly 300 and the balance block is pure and stable, thereby improving the operational smoothness and dynamic balance accuracy of the entire reciprocating balancing device.

[0117] By using the above technical solution, since the thicknesses of the first transmission part 210, the third transmission part 230, the first transmission component 272 and the second transmission component 281 are equal along the axis of rotation, the masses of the opposing transmission parts can be precisely matched based on the same material and equal eccentricity. This allows the centrifugal force to be self-cancelled within the crankshaft 200 body, eliminating the internal torque of the crankshaft 200 itself and achieving the self-balancing effect of the crankshaft 200 body. This simplifies the difficulty of overall dynamic balancing and improves the operational stability of the power tool.

[0118] Furthermore, the widths of the first transmission section 210, the second transmission section 220, and the third transmission section 230 are all equal along the direction perpendicular to the rotation axis. For example... Figure 6 As shown, the width of the first transmission part 210 and the third transmission part 230 is b2, and the width of the second transmission part 220 is b1, so b1=b2.

[0119] The equal widths of the first transmission section 210, the second transmission section 220, and the third transmission section 230 along the direction perpendicular to the rotation axis mean that the cross-sectional dimensions of the three transmission sections are consistent in the direction perpendicular to the rotation axis of the crankshaft 200. In this embodiment, the first transmission section 210 drives the first balance block 400, the third transmission section 230 drives the second balance block 500, and the second transmission section 220 (formed by the cooperation of the first transmission member 272 and the second transmission member 281) directly drives the reciprocating rod assembly 300. This width characteristic is designed to further ensure the geometric symmetry of each transmission section, in conjunction with the previous constraints on equal eccentricity and equal thickness. Specifically, when the first transmission section 210, the third transmission section 230, and the first transmission member 272 and the second transmission member 281 constituting the second transmission section 220 have the same material density, equal eccentricity, and equal axial thickness, and their widths perpendicular to the axis of rotation are also equal, the cross-sectional areas of these four key eccentric components will be completely identical, thus making their volume and mass precisely equal. This uniformity of geometric parameters ensures that the centrifugal forces generated by the opposing first transmission section 210 and the first transmission member 272 on the first crankshaft body 270 are strictly equal in magnitude and opposite in direction, and the centrifugal forces generated by the opposing third transmission section 230 and the second transmission member 281 on the second crankshaft body 280 are strictly equal in magnitude and opposite in direction. As a result, during the rotation of the crankshaft 200, the inertial forces generated by each transmission section are completely vector-canceled within the crankshaft 200.

[0120] When the crankshaft 200 rotates at high speed around its axis of rotation, the first transmission section 210, the second transmission section 220, and the third transmission section 230, which are offset from the axis of rotation, all generate centrifugal force. Since the widths of the first transmission section 210, the second transmission section 220, and the third transmission section 230 along the direction perpendicular to the axis of rotation are all equal, combined with the previously defined conditions of equal thickness and equal eccentricity, all components constituting the eccentric structure of the crankshaft 200 (i.e., the first transmission section 210, the first transmission member 272, the third transmission section 230, and the second transmission member 281) have a completely uniform mass distribution. Therefore, within the first crankshaft body 270, the centrifugal force generated by the first transmission section 210 and the centrifugal force generated by the first transmission member 272 are mutually balancing forces; within the second crankshaft body 280, the centrifugal force generated by the third transmission section 230 and the centrifugal force generated by the second transmission member 281 are mutually balancing forces. This internal self-balancing state eliminates any internal torque or residual imbalance that may be generated when the crankshaft 200 rotates, ensuring that the crankshaft 200 is in an ideal dynamic balance state even before the balance weights are installed. At this point, the first balance weight 400 and the second balance weight 500, located on both sides of the reciprocating rod assembly 300, are only required to counteract the inertial force generated by the reciprocating motion of the reciprocating rod assembly 300, without needing to share the task of correcting the crankshaft 200's own imbalance. This simplifies the overall dynamic balancing design logic and improves the stability and mass production consistency of the vibration reduction effect.

[0121] Through the above technical solution, this application achieves a strict mirror symmetry in the mass distribution of all eccentric components on the crankshaft 200 because the widths of the first transmission part 210, the second transmission part 220, and the third transmission part 230 are all equal along the direction perpendicular to the rotation axis. This eliminates the internal torque caused by uneven mass within the crankshaft 200, allowing the crankshaft 200 to achieve an ideal self-balancing state. Consequently, the design of the balance block only needs to focus on counteracting the inertial force of the reciprocating rod assembly 300, avoiding the coupling interference of multiple unbalanced factors. Ultimately, this achieves the effects of improving the dynamic balancing accuracy of power tools, reducing overall machine vibration and noise, and improving mass production consistency.

[0122] Based on any of the above embodiments, such as Figure 7 As shown, each transmission part can also be fitted with a ring, that is, a first ring 610 is fitted on the outer circumferential surface of the first transmission part 210, a second ring 620 is fitted on the outer circumferential surface of the second transmission part 220, and a third ring 630 is fitted on the outer circumferential surface of the third transmission part 230, and the weight of the second ring 620 is equal to the sum of the weights of the first ring 610 and the third ring 630.

[0123] The first ring sleeve 610, the second ring sleeve 620, and the third ring sleeve 630 are annular wear-resistant components respectively fitted onto the outer circumferential surfaces of the first transmission part 210, the second transmission part 220, and the third transmission part 230. The first ring sleeve 610 can be interference-fitted or bonded to the first transmission part 210, the second ring sleeve 620 is fixed to the second transmission part 220, and the third ring sleeve 630 is fixed to the third transmission part 230, so that there is no relative rotation or axial displacement between the ring sleeve and the corresponding transmission part. The material of these ring sleeves can be high-strength alloy steel, bearing steel, or metal materials with surface carburizing and quenching treatment, or other wear-resistant materials selected according to actual working conditions. The first ring sleeve 610, the second ring sleeve 620, and the third ring sleeve 630 bear the main frictional load generated during the rotation and reciprocating motion of the crankshaft 200. When the tool operates at high frequency for extended periods, wear primarily occurs on the outer surfaces of the first ring sleeve 610, the second ring sleeve 620, and the third ring sleeve 630, thus protecting the first transmission part 210, the second transmission part 220, and the third transmission part 230 on the crankshaft 200 body from wear. This fit ensures that when the ring sleeves wear beyond the limit, only the corresponding ring sleeves need to be disassembled and replaced to restore transmission accuracy, without having to replace the entire crankshaft 200, thereby reducing maintenance costs and extending service life.

[0124] The weight of the second ring 620 is equal to the sum of the weights of the first ring 610 and the third ring 630. Since the first transmission unit 210 and the third transmission unit 230 are located on one side of the crankshaft 200's rotation axis, while the second transmission unit 220 is located on the other side, the three are arranged axially with opposite eccentric directions, forming an approximately 180° phase distribution. In this arrangement, the centrifugal forces generated by the first ring 610 and the third ring 630 are in approximately the same direction, while the centrifugal force generated by the second ring 620 is in the opposite direction. By setting the weight of the second ring 620 to be equal to the sum of the weights of the first ring 610 and the third ring 630, the added mass on both sides of the rotation axis remains symmetrically balanced in the direction of centrifugal force after the rings are added. This technical feature closely matches the eccentric structure of the crankshaft 200, ensuring that the resultant centrifugal force generated by the three components as the crankshaft 200 rotates is zero, avoiding disruption of the original dynamic balance of the crankshaft 200 due to the introduction of the rings, and preventing the generation of new unbalanced inertial forces.

[0125] During the operation of the power tool, the drive motor 100 drives the crankshaft 200 to rotate, and the first transmission part 210, the second transmission part 220, and the third transmission part 230 rotate eccentrically accordingly. At this time, the first ring sleeve 610, the second ring sleeve 620, and the third ring sleeve 630, which are sleeved on the crankshaft, also rotate synchronously and undergo high-frequency sliding friction with the slide rail 310 of the reciprocating rod assembly 300 or other transmission mating surfaces. Since the ring sleeves are made of wear-resistant materials, the friction loss is mainly concentrated on the surface of the ring sleeves. As the service time increases, if the ring sleeves wear and the mating clearance increases, the operator can replace the first ring sleeve 610, the second ring sleeve 620, or the third ring sleeve 630 individually, while the crankshaft 200 body remains intact. Meanwhile, thanks to the design that the weight of the second ring 620 is equal to the sum of the weights of the first ring 610 and the third ring 630, even under high-speed rotation conditions, the centrifugal forces generated by the three rings can cancel each other out, maintain the dynamic balance accuracy of the crankshaft 200 system, and ensure that the motion stability of the reciprocating rod assembly 300, the first balance block 400 and the second balance block 500 is not affected, thereby continuously and effectively counteracting the unbalanced inertial force.

[0126] Because replaceable first ring sleeves 610, second ring sleeves 620, and third ring sleeves 630 are respectively provided on the outer periphery of the first transmission part 210, the second transmission part 220, and the third transmission part 230, friction and wear are concentrated on the ring sleeves rather than the crankshaft 200 body, thus significantly extending the service life of the crankshaft 200 and reducing maintenance costs. At the same time, since the weight of the second ring sleeve 620 is limited to the sum of the weights of the first ring sleeve 610 and the third ring sleeve 630, the additional centrifugal forces on both sides of the crankshaft 200 after the ring sleeves are installed can cancel each other out. Therefore, the problem of disrupting the dynamic balance of the crankshaft 200 due to the introduction of wear-resistant parts is avoided, ensuring low vibration performance and operating comfort of the power tool under long-term high-frequency operation.

[0127] In addition to the split-type splicing structure used in the above embodiments, the crankshaft 200 can also adopt an integrated structure.

[0128] The crankshaft 200 being a single-piece structure can mean that the first transmission section 210, the second transmission section 220, and the third transmission section 230, along with the remaining body parts of the crankshaft 200, are directly formed from the same blank material through machining or forging processes. There are no assembly joint surfaces between these parts formed by key connections, pin connections, threaded connections, or interference fits. In this structure, the first transmission section 210, the second transmission section 220, and the third transmission section 230, as organic components of the crankshaft 200 body, have their positions relative to the axis of rotation, eccentricities, and phase angles relative to each other precisely fixed during the manufacturing stage. By eliminating the assembly gaps and fretting wear risks common in split structures, this single-piece structure ensures that during long-term high-speed operation of the power tool and under high-frequency alternating loads, the first transmission section 210, the third transmission section 230, and the second transmission section 220 maintain a strict relative positional relationship, particularly ensuring that the motion phases of the drive balance block and the drive reciprocating rod assembly 300 are strictly opposite (e.g., 180° out of phase). This rigid connection method gives the crankshaft 200 higher overall stiffness and fatigue strength, effectively preventing phase drift caused by loosening of the mating surfaces. This ensures that the resultant inertial forces generated by the first balance block 400 and the second balance block 500 are always opposite in direction and collinearly cancel each other out with the inertial force generated by the reciprocating rod assembly 300, maintaining the long-term vibration damping balance performance of the device. This integrated structure can be precision machined after forging from a single piece of steel, or it can be directly CNC machined from bar stock.

[0129] When the drive motor 100 rotates the crankshaft 200 of the integrated structure, since there is no possibility of relative displacement between the first transmission part 210, the second transmission part 220, and the third transmission part 230, the sliding trajectory of the second transmission part 220 in the slide rail 310 always maintains a preset phase difference with the trajectory of the first transmission part 210 and the third transmission part 230 driving the first balance block 400 and the second balance block 500. Even after long-term high-load operation, there will be no lag or advance of the balance block movement due to wear at the transmission part connection, ensuring real-time and accurate cancellation of the reverse inertial force.

[0130] Because the crankshaft 200 adopts an integrated structure, the assembly mating surfaces are eliminated, thus fundamentally preventing the transmission phase drift problem caused by wear of the mating surfaces, increased clearance, or loose connections due to long-term operation. This ensures that the relative positional relationship between the first transmission part 210, the third transmission part 230, and the second transmission part 220 remains constant throughout their service life. Consequently, it guarantees that the motion phase between the first balance block 400, the second balance block 500, and the reciprocating rod assembly 300 is always strictly opposite, maintaining the best vibration cancellation effect. At the same time, the integrated structure reduces the number of parts and assembly processes, improves the overall rigidity and fatigue resistance of the crankshaft 200 assembly, and enhances the operational reliability and service life of the power tool under high-frequency reciprocating conditions.

[0131] The above description is only a specific embodiment of the present invention, but the technical features of the present invention are not limited thereto. Any changes or modifications made by those skilled in the art within the scope of the present invention are covered by the patent scope of the present invention.

Claims

1. A reciprocating balancing device for power tools, comprising a drive motor, characterized in that, Also includes: The crankshaft is driven by a drive motor to rotate around its own axis. The crankshaft is provided with a first transmission part, a second transmission part and a third transmission part arranged sequentially along the direction of the rotation axis. The first transmission part, the second transmission part and the third transmission part are all offset from the rotation axis. A reciprocating rod assembly is provided with a slide rail, and the second transmission part is slidably engaged in the slide rail to drive the reciprocating rod assembly to reciprocate along a first direction; The first balance block is disposed on one side of the reciprocating rod assembly. The first transmission part is connected to the first balance block to drive the first balance block to reciprocate along a second direction opposite to the first direction. The second balance block is disposed on the other side of the reciprocating rod assembly, and the third transmission part is connected to the second balance block to drive the second balance block to reciprocate along the second direction.

2. The reciprocating balancing device for a power tool according to claim 1, characterized in that, The center of mass of the first transmission unit and the center of mass of the third transmission unit are located on the same straight line parallel to the axis of rotation.

3. The reciprocating balancing device for a power tool according to claim 2, characterized in that, The distance from the center of mass of the second transmission unit to the axis of rotation is equal to the distance from the center of mass of the first transmission unit to the axis of rotation.

4. The reciprocating balancing device for a power tool according to claim 3, characterized in that, The sum of the mass of the first balance block and the mass of the second balance block is equal to the mass of the reciprocating rod assembly.

5. The reciprocating balancing device for a power tool according to claim 1, characterized in that, The crankshaft includes a first component and a second component that are detachably connected. The first component is provided with a first transmission part and a transmission shaft, and the second component is provided with a third transmission part and a transmission hole. The transmission shaft and the transmission hole cooperate to form the second transmission part.

6. The reciprocating balancing device for a power tool according to claim 5, characterized in that, The second component is also provided with a joint, the transmission hole is opened in the joint, the transmission shaft is at least partially inserted into the transmission hole of the joint, and the outer peripheral surface of the joint is slidably engaged with the slide rail.

7. The reciprocating balancing device for a power tool according to claim 1, characterized in that, The crankshaft includes a first rotating body, a first crankshaft body, a second crankshaft body, and a second rotating body arranged sequentially along the axis of rotation; Both the first rotating body and the second rotating body are rotating bodies about the axis of rotation, and each is provided with a shaft protruding in opposite directions; The first crankshaft body includes the first transmission part and the first transmission member; the first transmission part deviates from the rotation axis in a direction perpendicular to the rotation axis, and extends toward the first rotating body in the direction of the rotation axis and is connected to the first rotating body; the first transmission member has the opposite deviation direction and protrusion direction to the first transmission part; The second crankshaft body includes the third transmission part and the second transmission member; the third transmission part deviates from the rotation axis in a direction perpendicular to the rotation axis, and extends toward the second rotating body in the direction of the rotation axis and is connected to the second rotating body; the second transmission member has the opposite deviation direction and protrusion direction to the third transmission part; The first transmission component and the second transmission component cooperate to form the second transmission part.

8. The reciprocating balancing device for a power tool according to claim 7, characterized in that, The first crankshaft body also includes a first connecting body, the first transmission part and the first transmission component are respectively disposed at both ends of the first connecting body, and the center of gravity of the first connecting body is located on the rotation axis; The second crankshaft body also includes a second connecting body, the third transmission part and the second transmission component are respectively disposed at both ends of the second connecting body, and the center of gravity of the second connecting body is located on the rotation axis.

9. A reciprocating balancing device for a power tool according to claim 8, characterized in that, The thickness of the first transmission part, the third transmission part, the first transmission member, and the second transmission member is equal along the direction of the rotation axis.

10. A reciprocating balancing device for a power tool according to claim 8 or 9, characterized in that, The widths of the first transmission part, the second transmission part, and the third transmission part are all equal along the direction perpendicular to the axis of rotation.

11. A reciprocating balancing device for a power tool according to claim 1, characterized in that, A first ring, a second ring, and a third ring are respectively fitted on the outer peripheral surfaces of the first transmission part, the second transmission part, and the third transmission part. The weight of the second ring is equal to the sum of the weights of the first ring and the third ring.

12. The reciprocating balancing device for a power tool according to claim 1, characterized in that, The crankshaft is a one-piece structure.

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