A movable tooth reducer with logarithmic spiral tooth profile

Abstract

The present application relates to a kind of logarithmic spiral tooth profile movable tooth reducer, including outer gear, cam and cage, wherein, by cam drive arrangement on the cam several movable teeth that can move radially through cage is generated between outer gear and cage transmission ratio and transmits torque, movable tooth is divided into at least two groups, two groups of movable teeth are kept apart in the axial direction of cam each other, and wherein at least one group of movable teeth acts as the compensation mechanism of harmonic transmission jitter, to compensate the vibration caused by the load borne by cage as output shaft. The present application provides a kind of transmission structure based on logarithmic spiral design, relies on the curvature of the tooth surface of movable tooth and outer gear, can realize face contact in stress state, greatly improves the transmission carrying capacity.

Description

Technical Field

[0001] This invention relates to the field of gear reducer technology, and more particularly to a movable gear reducer with a logarithmic helical tooth profile. Background Technology

[0002] Harmonic drive mechanisms are a new type of mechanism that relies on elastic deformation motion to achieve transmission. They break away from the rigid component mechanism model of mechanical transmission, using a flexible component to achieve mechanical transmission, thus obtaining a series of special functions that are difficult to achieve with other transmission methods. A harmonic drive system has three basic components: a circular spline, a flexible spline, and a wave generator.

[0003] Harmonic gear drives possess outstanding advantages such as compact structure, large reduction ratio, small size, light weight, high load-bearing capacity, small backlash, and high transmission accuracy. They are widely used in industries such as aerospace, marine engineering, bionic machinery, petrochemicals, transportation, and medical devices. Their superiority is particularly evident in systems with high dynamic performance. The principle of harmonic gear drives is that a moving, deformable wave is generated within the flexible gear component through the action of a wave generator, meshing with the teeth of the rigid gear to achieve the transmission purpose.

[0004] CN113503353A discloses a logarithmic spiral conjugate tooth profile harmonic reducer, comprising a rigid wheel, a flexible wheel, a wave generator, and a flexible bearing. The tooth profiles of the rigid wheel and the flexible wheel in the meshing state are designed with two different segments of the same logarithmic spiral curve. The origin of the logarithmic spiral coincides with the rotation center of the flexible wheel, achieving complete conjugation during meshing transmission. The minimum radius of curvature of the rigid wheel tooth profile curve is greater than the maximum radius of curvature of the flexible wheel tooth profile curve. In the meshing state, a gradually narrowing wedge-shaped backlash is formed between the tooth profiles of the rigid wheel and the flexible wheel, and under load, the conjugate tooth profiles achieve approximately surface contact.

[0005] The overall performance control of harmonic drives can be achieved by altering the meshing, contact, and lubrication characteristics between the rigid and flexible gear tooth profiles. For the tooth profiles of harmonic gear drives, existing technologies mostly employ involute tooth profiles, tooth profiles combining circular and elliptical curves, and double circular arc tooth profiles. However, involute tooth profiles suffer from tooth tip interference and edge meshing under load, while circular arc tooth profiles can improve meshing under no-load conditions but suffer from localized high loads. Furthermore, the flexible components used for transmission undergo periodic deformation with the wave generator to drive the output end connected to the flexible component. This places high demands on the material properties and manufacturing requirements of the flexible component, especially under high load and high speed conditions, where fatigue damage can easily occur, leading to harmonic drive failure. Therefore, improvements are needed to the tooth profile curves of harmonic drives and the transmission structure between the flexible component and the wave generator to significantly reduce the probability of fatigue damage in harmonic drives.

[0006] CN101627228A discloses a coaxial transmission mechanism, particularly a hollow shaft transmission mechanism for industrial transmission technology, which includes a driving member, an element, and a driven member. The transmission ratio and transmission of the driving torque between the driving member and the driven member are realized through a plurality of radially movable tooth segments connected to the axis of the transmission mechanism. The tooth profiles between the outer tooth flank profile of the tooth segment and / or the tooth flank profile of the inner tooth of the hollow wheel can achieve planar contact in the meshing region through a structure that is a logarithmic helix. In this patent, the so-called planar contact is a near-ideal meshing state. However, in the actual meshing process, due to the introduction of the driven load, the force on both sides of the tooth segment is not uniform. In particular, long-term high-load use exacerbates the uneven wear on both sides of the tooth segment. This uneven wear makes the tooth segment prone to lateral vibration, which in turn causes the surface contact at some tooth surfaces to become line contact. Therefore, the aforementioned planar contact cannot be uniformly achieved at each tooth segment. Especially when the tooth segment meshes with the internal teeth of the hollow wheel in a step-by-step manner, the aforementioned vibration will continue to accumulate and amplify as the step-by-step contact meshing progresses, making the reducer more prone to obvious harmonic vibration.

[0007] Furthermore, on the one hand, there are differences in understanding among those skilled in the art; on the other hand, the applicant studied a large number of documents and patents when making this invention, but due to space limitations, not all details and contents were listed in detail. However, this does not mean that the present invention does not possess the features of these prior art. On the contrary, the present invention already possesses all the features of the prior art, and the applicant reserves the right to add relevant prior art to the background art. Summary of the Invention

[0008] In view of the shortcomings of the prior art, the present invention provides a novel movable tooth reducer with a logarithmic helical tooth profile, which aims to solve at least one or more technical problems existing in the prior art.

[0009] To achieve the above objectives, the present invention provides a movable gear reducer with a logarithmic helical tooth profile, comprising an external gear ring, a cam, and a cage, wherein a transmission ratio and torque are generated between the external gear ring and the cage by driving a plurality of movable teeth arranged on the cam and capable of moving radially through the cage.

[0010] Preferably, the movable teeth of the present invention may include at least two sets, the two sets of movable teeth being spaced apart from each other in the axial direction of the cam, and at least one set of movable teeth acting as a compensation mechanism for harmonic drive jitter, to compensate for the vibration caused by the load borne by the cage as the output shaft.

[0011] For harmonic drives, harmonic vibrations or jitters often originate from harmonics, subharmonics, or vibrations of unknown frequencies that are not directly identifiable. Therefore, the causes of resonance in the transmission structure are highly complex and not solely caused by the reducer. However, since the reducer is located between the load and the drive equipment, it is precisely the most critical point affected by resonance. Therefore, suppressing resonance at the reducer is the simplest and most effective method. Specifically, in practical applications, the overall mechanical characteristics of two symmetrically arranged transmission structures are inconsistent, which is related to the load introduction direction. When the load is attached to one side of the reducer, due to the different load states on both axial sides, the load is concentrated on one side of the reducer. Therefore, when the reducer is driven by the drive equipment, the load in the load direction will have different degrees of influence on the two simultaneously operating transmission structures. This invention, by setting at least two coaxially arranged transmission mechanisms, can effectively suppress harmonic drive resonance, especially significantly suppressing jitter or vibration generated along the reducer's axial direction.

[0012] Preferably, the two sets of movable teeth are movably arranged on the cam via their respective roller bearings.

[0013] One set of roller bearings is held within a first retaining frame integrally formed with the cam, such that the set of roller bearings can move circumferentially around the cam along the first retaining frame, while also allowing the set of roller bearings to rotate around the shaft head of its connecting movable teeth.

[0014] Another set of roller bearings is held within a second retaining frame mounted axially on the cam end cap of the cam, allowing this set of roller bearings to move circumferentially around the cam along the second retaining frame while also rotating around the shaft head of its connecting movable tooth. This invention replaces the flexspline structure in traditional harmonic drives by using a combination of roller bearings and the cam profile. The sliding friction between the roller bearings and the cam frame accurately transmits the torque transmitted by the cam, making it suitable for heavy-load, low-speed deceleration applications.

[0015] Preferably, one set of roller bearings and a set of connected movable teeth constitute a first transmission structure, while another set of roller bearings and another set of connected movable teeth constitute a second transmission structure. The first and second transmission structures are symmetrically arranged in a mirror image of each other in the axial direction, such that the pairs of roller bearings spaced apart axially bear collinear axial thrust. Specifically, in this invention, "symmetrically arranged in a mirror image of each other in the axial direction" means that the first retaining frame (i.e., the inner contour of the cam) and the second retaining frame (i.e., the outer contour of the end cap) are axially separated, and the movable teeth held by each retaining frame are arranged with their racks facing each other. The slender shaft ends (or shaft heads) of the two sets of roller bearings are arranged opposite each other to reduce the radial dimension of the reducer while only slightly increasing the axial length. Furthermore, the two sets of movable teeth are spaced apart in a substantially adjacent manner, such that the gap between adjacent movable teeth allows the movable teeth to move and / or oscillate slightly due to absorbing harmonic vibrations caused by the cam's axial direction. This movement and / or oscillation allows the movable teeth to release part of the load they absorb or bear, thereby preventing further expansion of the unbalanced torque between the two transmission structures.

[0016] Preferably, the first retaining frame for holding one set of movable teeth is arranged radially outward from the axial center of the cam, such that the root of the movable teeth is substantially located at the axial center of the cam, so that the radial force acts approximately perpendicularly to the axial center of the cam. Specifically, in this invention, the "degree of deviation of the first retaining frame from the axial center" is approximately measured by the axial width of the movable teeth; that is, the first retaining frame radially outward from the cam is lateral. The purpose is to ensure that the root of the movable teeth is substantially located in the axial center region of the cam, thereby generating a force substantially perpendicular to the axial center of the cam on this side of the movable teeth, which is the main transmission structure. This prevents a significant imbalance of torque between the two sides of the single set of movable teeth, which is the main transmission structure, relative to the cam, thus affecting the smooth transmission of the reducer and reducing its transmission performance.

[0017] Preferably, the movable teeth in the first transmission structure and the movable teeth in the second transmission structure have different hardnesses to compensate for the unbalanced torque introduced along the cam axis by the cage, which serves as the output shaft, due to bearing the load. In this invention, the movable teeth of each of the two transmission structures can have different hardnesses relative to the transmitted torque from the load (e.g., formed by materials of different hardnesses), and the hardness of the movable teeth is set in relation to the corresponding load input direction, so that the two sets of movable teeth form different hardnesses relative to the external load. This addresses the influence of different external loads transmitted to the two transmission structures via the load attached to the cage, balances the unbalanced torque that may be generated by the two transmission structures, and in particular slows down the wear and aging process of the movable teeth on the load side, so that the two transmission structures maintain essentially synchronous and stable transmission.

[0018] Preferably, at least one set of movable teeth located near the load-in direction side of the cage, which serves as the output shaft, has lower stiffness than at least another set of movable teeth mirror-symmetrically arranged on the other side of the load-in direction along the cam axis. This allows harmonic drive jitter from the load-in direction of the cage to be at least partially absorbed. As the load amount and load time accumulate, the load near the load input direction will cause more severe disturbance to the movable teeth on the same side compared to the movable teeth on the opposite side of the load. This makes the movable teeth on that side more prone to axial movement and / or deflection. By configuring the movable teeth on that side to be more flexible, they can more gently absorb or mitigate the effects of external loads from the load side, preventing the movable teeth on that side from generating more significant harsh friction with the outer gear ring due to load accumulation, thereby exacerbating the wear of the movable teeth on that side.

[0019] Preferably, the cage for holding the movable teeth, which is located near the load access direction of the cage serving as the output shaft, has less rigidity than the cage frame which is mirror-symmetrically located on the other side of the load access direction of the cage along the cam axis, so that harmonic drive jitter from the load access direction of the cage is at least partially absorbed.

[0020] Preferably, the cam end cap is detachably mounted to the side of the cam face facing the load-in direction of the cage, and a second retaining frame arranged radially outward of the cam holds one set of roller bearings to at least partially absorb the vibrations of these roller bearings caused by harmonic drive jitter along the cam radial direction. In this invention, the outer contour of the cam end cap is more elastic or flexible than the outer contour of the cam used to house the main transmission structure, thereby more smoothly absorbing or mitigating the harmonic drive jitter introduced by the cage, which serves as the output shaft, along the cam axis. This is especially true when the load-in direction is on the detachable cam end cap side, where the harmonic vibrations caused are transmitted to the movable teeth and then to the connected roller bearings. The axial movement of the roller bearings can be absorbed by the relatively flexible outer contour of the end cap and further restricted by the movable teeth defined by the cage. Furthermore, when harmonic vibrations are generated along the cam axis... During vibration, the moving teeth and roller bearings inevitably vibrate radially along the cam. In this invention, the outer contour of the cam end cap is more flexible than the integrally formed outer contour of the cam radially outer side. To address the radial vibration of the roller bearings, the outer contour of the end cap, along with the radial side, axial side, and moving teeth defined by the cage of the roller bearing, forms a three-point stable structure. This limits the large radial displacement of the rolling bearings while effectively absorbing the harmonic drive vibrations generated by the rolling bearings through the relatively flexible outer contour of the end cap, mitigating the imbalance and asynchrony between the two transmission structures caused by load introduction. Furthermore, the separable cam end cap provides convenient assembly options, allowing the moving teeth and roller bearings on that side, which can serve as a compensation mechanism for harmonic drive vibrations, to be easily replaced, thus adapting to harmonic drive vibrations or tremors that may occur under different loads (such as heavy or light loads).

[0021] Preferably, the moving teeth of each of the two sets of transmission structures have different hardnesses relative to the transmitted torque from the cam, formed by using different materials, wherein the hardness of the moving teeth in the two sets of transmission structures is set in relation to the load input direction corresponding to the follower.

[0022] Preferably, the cam includes a base having an inner cam profile and an annular frame formed circumferentially around the base as an outer cam profile. The inner and outer cam profiles together partially surround and define a profile segment of one set of transmission structures formed by a movable tooth and a roller bearing, wherein the roller bearing is partially held within the profile segment. The movable tooth contacts the outer and inner cam profiles based on the roller bearing, allowing the movable tooth to accurately transmit the periodic deformation of the cam transmission based on the defining effect of the outer and inner cam profiles, thus avoiding unintended radial offset or deflection. This reduces transmission friction and makes the transmission smoother.

[0023] Preferably, the movable gear reducer with a logarithmic helical tooth profile provided by the present invention includes a cam end cap detachably mounted on the end face of a cam shaft, having an end cap outer profile adapted to the outer profile of the cam, wherein the end cap outer profile and the inner profile of the cam together partially surround and define a profile segment of another set of transmission structures formed by the connection of movable teeth and roller bearings.

[0024] Preferably, the cage has a plurality of guide holes distributed circumferentially. The movable tooth is defined by the guide holes and can move radially, so that the movable tooth can be driven by a cam to radially pass through the guide holes and periodically mesh with the inner tooth profile of the outer gear ring while being held by the guide holes. In this invention, the movable tooth is assembled in a cage, which is used to limit the radial movement of the movable tooth along the cage under the action of the cam to avoid unintended circumferential offset or deflection; in addition, the movable tooth and the cage adopt a clearance fit, so that there is almost no clearance between them, which greatly improves the bending strength of the movable tooth and enables good power transmission.

[0025] Preferably, the profile curve of one side of the movable tooth conforms to a logarithmic spiral:

[0026] S MT =Re θ / tanβ (-θ b ≤θ≤0)

[0027] In the formula, S MT Let θ be the tooth profile curve of the movable tooth in polar coordinates, θ be the polar angle corresponding to the movable tooth in polar coordinates, R be the reference radius of the movable tooth profile, and β be the reference angle of the movable tooth profile. b This is the polar angle corresponding to the position of the root of the moving tooth.

[0028] Preferably, the internal tooth profile of the external gear ring is solved in the following manner:

[0029] Based on the single-sided tooth profile curve S of the movable tooth MT The theoretical profile S of the cam c The relationship between the transmission ratio i and the motion trajectory of the moving tooth profile is obtained, and the envelope is solved.

[0030] Among them, the set of points on the envelope satisfies

[0031] In the formula, For the normal vector of the active tooth profile, It is the direction vector of the relative motion velocity at the meshing point between the moving tooth and the external gear ring.

[0032] Preferably, the cam transmits torque to the follower through a logarithmic spiral-based surface contact between the movable tooth and the external gear ring, wherein the theoretical profile S of the cam... c It conforms to the following piecewise function:

[0033]

[0034] In the formula, S c φ represents 1 / 4 of the theoretical tooth profile of cam 101 in polar coordinates; φ is the polar angle corresponding to cam 101 in polar coordinates; the first and third curves are correction curves for the cam 101 tip, and the second curve conforms to a logarithmic spiral; a0, a1, a2, a3, b0, b1, b2, and b3 are undetermined coefficients, calculated based on the continuity of the curves, where a0, a1, a2, and a3 are the coefficients of the first segment modification curve of cam 101, and b0, b1, b2, and b3 are the coefficients of the second segment modification curve of cam 101; φ1 and φ2 are the intersection points of the modification segments of cam 101, usually taken as... and i represents the theoretical transmission ratio of the reducer.

[0035] In this invention, the tensioning effect of a specially designed cam ensures that the tooth surfaces on both sides of the external gear ring are in contact with the corresponding moving tooth surfaces at all times, thereby achieving zero backlash transmission.

[0036] Preferably, the inner and outer profiles of the cam conform to the following function:

[0037]

[0038] In the formula, "+" represents the outer contour and "-" represents the inner contour. The theoretical profile S of the cam c The unit normal vector is r, where r is the roller radius.

[0039] This invention provides a novel movable gear reducer with a logarithmic helical tooth profile, wherein the movable teeth, external gear ring, and cam are all designed based on a logarithmic helix. Relying on the approximate curvature of the tooth surfaces of the movable teeth and the external gear ring, surface contact can be achieved under stress, which greatly improves the transmission load capacity. It has a compact structure, a hollow interior, and extremely high power density. The radial movement of several spaced movable teeth realizes the periodic deformation of the cam based on its outer contour, which can replace the continuous structure of the flexspline to effectively improve its transmission state, thereby significantly reducing the probability of fatigue damage to the flexspline. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the overall structure of a speed reducer according to a preferred embodiment of the present invention;

[0041] Figure 2 This is a cross-sectional structural schematic diagram of a speed reducer according to a preferred embodiment of the present invention;

[0042] Figure 3This is a schematic diagram of a speed reducer according to a preferred embodiment of the present invention, wherein a is a cross-sectional view of the speed reducer, and b is a view from the right side after removing the cam end cover and the movable gear that acts as the compensation mechanism. Figure 3 a. Right view of the speed reducer of the present invention obtained;

[0043] Figure 4 This is an exploded view of the structure of a speed reducer according to a preferred embodiment of the present invention;

[0044] Figure 5 This is a schematic diagram of the assembly process of a speed reducer according to a preferred embodiment of the present invention;

[0045] Figure 6 This is a schematic diagram of the assembly structure of the cam and the cam end cap according to a preferred embodiment of the present invention;

[0046] Figure 7 This is the motion profile of a cam according to a preferred embodiment of the present invention.

[0047] List of reference numerals

[0048] 100: Drive unit; 101: Cam; 102: Central shaft; 103: Fixing member; 104: Locating pin; 1011: Cam inner contour; 1012: Cam outer contour; 1013: Cam end cover; 1014: End cover outer contour; 1015: First side wall; 1016: Second side wall; 200: Transmission unit; 201: Roller bearing; 202: Movable gear; 203: External gear ring; 204: Cage; 300: Driven unit. Detailed Implementation

[0049] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby providing a clearer and more explicit definition of the scope of protection of the present invention.

[0050] See Figure 1 The present invention provides a movable gear reducer with a logarithmic helical tooth profile, which may include a drive unit 100 for inputting power, a transmission unit 200 for transmitting power, and a driven unit 300 for outputting power. Specifically, the drive unit 100, the transmission unit 200, and the driven unit 300 are coaxially connected.

[0051] According to a preferred embodiment, such as Figure 2 and Figure 3 As shown, the drive unit 100 may include a cam 101 and a central shaft 102. Specifically, the central shaft 102 may be a solid or hollow shaft, and the central shaft 102 is connected or coupled to a channel or cavity inside the cam 101. Further, as... Figure 3As shown, the cam 101 has an inner cam profile 1011 and an outer cam profile 1012. The inner cam profile 1011 and the outer cam profile 1012 respectively contact the roller bearing 201 to form a rolling space or profile that defines the movement of the roller bearing 201 along the outer periphery of the cam 101.

[0052] According to a preferred embodiment, such as Figure 2 and Figure 3 As shown, the transmission unit 200 may include a roller bearing 201, a movable tooth 202, and an external gear ring 203. Specifically, the roller bearing 201 contacts the inner cam profile 1011 and the outer cam profile 1012 of the cam 101. In other words, the roller bearing 201 can roll circumferentially between the inner cam profile 1011 and the outer cam profile 1012. Further, the end of the roller bearing 201 is connected to or provided with a movable tooth 202 that extends radially along the external gear ring 203 and is movable (see...). Figure 3 a). The end of the movable tooth 202 away from the roller bearing 201 can engage with the inner tooth profile of the outer gear ring 203 under the drive of the cam 101 (see...). Figure 2 (above and below) or disengagement (see above and below) Figure 2 (Left and right sides).

[0053] According to a preferred embodiment, the driven part 300 may include a retainer 204 through which each movable tooth 202 moves. See also Figure 2 The cage 204 rotates in a known harmonic drive manner, for example, in the opposite direction to the rotation direction of the cam 101.

[0054] Specifically, a driveable cam 101 is positioned or held radially inside the cage 204 as the input of driving force, specifically within the annular profile formed by the inner contour 1011 of the cam. This cam 101 is driven to rotate and transmits force or torque to the movable tooth 202 via the roller bearing 201. Further, the movable tooth 202 is driven by the cam 101 and / or the roller bearing 201 to move towards the inner tooth profile of the outer gear ring 203. If the outer gear ring 203 remains fixed, the movable tooth 202 moves radially through the cage 204, thereby periodically or alternately meshing with the inner tooth profile of the outer gear ring 203, causing the cage 204 to rotate in the opposite direction to the rotation of the cam 101 according to a known harmonic drive method. This rotation occurs because a driving force along the circumference of the cage 204 is obtained from the contact surface when the tip of the movable tooth 202 meshes with the inner tooth profile of the outer gear ring 203. On the other hand, it is also because the roller bearing 201 with the corresponding movable teeth can roll circumferentially between the inner contour 1011 and the outer contour 1012 of the cam at this time. Under the action of the circumferential driving force, the movable teeth 202 move circumferentially and are supported by the roller bearing 201 in the radial direction.

[0055] As is known to those skilled in the art, with the cage 204 fixed and the external gear ring 203 rotatable, the rotation of the cam 101 will ultimately drive the external gear ring 203 to perform a corresponding rotation. Therefore, the transmission method employed in this invention is similar to a harmonic transmission method composed of a rigid wheel and a flexible wheel. The fixed cage 204 implies a reversal of roles between the driving part 200 and the driven part 300; the applicant reserves the right to file a divisional application in this regard.

[0056] According to a preferred embodiment, such as Figure 2 and Figure 3 As shown, the movable tooth 202 can engage with the outer gear ring 203. Specifically, the outer gear ring 203 is a cylindrical structure adapted to the shape of the cage 204, and a continuous internal tooth profile is provided on the inner wall of the outer gear ring 203. Furthermore, the movable tooth 202 has an external tooth profile adapted to the shape of the internal tooth profile of the outer gear ring 203, so that the movable tooth 202 can engage with the outer gear ring 203 through the external tooth profile at its end.

[0057] Specifically, the tooth profile of the movable tooth 202 conforms to a logarithmic spiral design. Specifically, the origin of the logarithmic spiral coincides with the rotation center of the cam 101 or the movable tooth 202. Furthermore, when the movable tooth 202 is fully engaged with the outer gear ring 203, the conjugate tooth profiles of the movable tooth 202 and the outer gear ring 203 can achieve approximately curved surface contact.

[0058] See Figure 3 a. The roller bearing 201 contacts the cam 101 through its bearing profile, thereby enabling the movable tooth 202 to be mechanically coupled to the cam 101 via the roller bearing 201. Specifically, during operation, the cam 101 is driven to rotate (e.g., clockwise) by an external actuator. The rotation of the cam 101 is transmitted to the movable tooth 202 via the roller bearing 201, causing the movable tooth 202 to move radially, thus periodically meshing with the outer gear ring 203. Further, driven by the cam 101, the movable tooth 202 moves along the inner tooth profile of the outer gear ring 203, driving the cage 204 to move as an output (e.g., counterclockwise rotation). In particular, the outer tooth profile of the movable tooth 202, designed based on a logarithmic spiral, and the inner tooth profile of the outer gear ring 203 achieve periodic curved surface contact during their meshing process.

[0059] In view of this, the present invention provides a movable tooth reducer with a logarithmic helical tooth profile, which may include:

[0060] The external gear ring 203 has an internal tooth profile arranged on its inner wall;

[0061] The retainer 204, which serves as the output shaft / component, is rotatably held inside the external gear ring 203;

[0062] Several independent movable teeth 202 are arranged radially toward the outer tooth ring 203, configured to be held in the cage 204 through the ring, and have an outer tooth profile adapted to the inner tooth profile.

[0063] The cam 101 is drivably held inside the cage 204 and is mechanically connected to the movable tooth 202, wherein the movable tooth 202 is driven by the cam 101 to periodically mesh with the outer gear ring 203.

[0064] According to a preferred embodiment, throughout the entire motion cycle, the cam 101 drives the roller bearing 201 to move, thereby causing the roller bearing 201 to drive the movable tooth 202 to engage with the external gear ring 203. Theoretically, throughout the entire motion cycle, at least one movable tooth 202 is in contact with the external gear ring 203, and the roller bearing 201 is in contact with the cam 101, thus ensuring that the reducer can move continuously and stably. However, in practice, if there are machining errors, the movable tooth 202 and the external gear ring 203, and the roller bearing 201 and the cam 101 are often in a not completely identical contact state (or even the contact state changes drastically, such as due to wear, heavy load, or load fluctuation). In this case, the roller bearing 201 and the movable tooth 202 may move within the hole of the cage 204, affecting the transmission accuracy and stability. Although the presence of the outer contour 1012 of the cam can restrict the roller bearing 201 between the outer contour 1012 of the cam and the inner contour 1011 of the cam, so that the roller bearing 201 and the cam 101 can always be in contact, this can only reduce the impact of machining errors on transmission performance.

[0065] Specifically, the profile of the cam 101 in contact with the roller bearing 201 and / or the movable tooth 202 is symmetrical about the major and minor axes of the cam 101, respectively. More specifically, the profile of the cam 101 may include the major axis profile segment of the meshing portion of the external gear ring 203 and the movable tooth 202 (e.g., Figure 2 The upper and lower sides of the external gear ring 203 shown), and the short shaft profile section of the part where the external gear ring 203 is disengaged from the movable tooth 202 (as shown). Figure 2 The external gear ring 203 shown includes the left and right sides and four transition profile segments located between the long axis profile segment and the short axis profile segment.

[0066] According to a preferred embodiment, when assembling the transmission structure and reducer provided by the present invention, the roller bearing 201 is first assembled to the movable gear 202 and tightened with a nut. All movable gears 202 are then assembled into the cage 204, and after adjusting the movable gears 202 to a suitable position, the cam 101 is assembled. The assembled cage 204, movable gears 202, and cam 101 are then assembled into the outer gear ring 203. Specifically, the tooth profiles of the movable gear 202, the outer gear ring 203, and the cam 101 are all complex curves related to a logarithmic spiral, requiring high machining accuracy. Considering that the outer gear ring 203 is machined using a wire EDM movable forming milling cutter, the contours of the movable gears 202 and the cam 101 can be machined using a cylindrical milling cutter.

[0067] According to a preferred embodiment, the present invention achieves periodic deformation of the cam 101 based on the radial movement of a plurality of spaced movable teeth 202, which can replace the continuous structure of the flexspline to effectively improve its transmission state and significantly reduce the probability of fatigue failure of the flexspline or tooth segment. Furthermore, the movable teeth 202 are mounted on a cage 204, which limits the movement of the movable teeth 202 in engagement with the external gear ring 203 under the action of the cam 101, thus preventing unintended circumferential offset or deflection.

[0068] Specifically, in this invention, the profile curve of one side of the movable tooth 202 conforms to a logarithmic spiral:

[0069] S MT =Re θ / tanβ (-θ b ≤θ≤0)

[0070] Among them, S MT Let θ be the tooth profile curve of movable tooth 202 in polar coordinates, θ be the polar angle corresponding to movable tooth 202 in polar coordinates, R be the reference radius (logarithmic spiral constant) of the tooth profile of movable tooth 202, determined by design parameters, and β be the reference angle (logarithmic spiral constant) of the tooth profile of movable tooth 202, typically taken between 30° and 35°. b This is the polar angle corresponding to the root position of movable tooth 202. The other side of the tooth profile of movable tooth 202 corresponds to curve S. MT It is a mirror image of the polar axis relative to θ = 0. Specifically, the external tooth profile S of the movable tooth 202... MT It is a logarithmic spiral, similar to the curvature of the external gear ring profile, which facilitates the formation of surface contact.

[0071] Specifically, the movable tooth 202 contacts the outer profile 1012 and the inner profile 1011 of the cam based on the roller bearing 201. The roller bearing 201 serves as the transmission medium, causing it to roll relative to the outer profile 1012 and the inner profile 1011 of the cam. This allows the movable tooth 202 and the roller bearing 201 to accurately transmit the periodic motion transmitted by the cam 101, avoiding unintended radial offset or deflection, reducing transmission friction, and resulting in smooth transmission.

[0072] Specifically, in this invention, the theoretical contour line S of cam 101 c It conforms to the following piecewise function:

[0073]

[0074] Among them, S c φ represents 1 / 4 of the theoretical tooth profile of cam 101 in polar coordinates; R is the reference radius of the tooth profile of movable tooth 202; φ is the polar angle corresponding to cam 101 in polar coordinates; the first and third curves are correction curves for the cam 101 tip, and the second curve conforms to a logarithmic spiral; a0, a1, a2, a3, b0, b1, b2, and b3 are undetermined coefficients, calculated based on the continuity of the curves, where a0, a1, a2, and a3 are the coefficients of the first segment modification curve of cam 101, and b0, b1, b2, and b3 are the coefficients of the second segment modification curve of cam 101; φ1 and φ2 are the intersection points of the modification segments of cam 101, usually taken as... and i represents the theoretical transmission ratio of the reducer.

[0075] Specifically, in this invention, the inner and outer contours of the cam 101 conform to the following function:

[0076]

[0077] Wherein, "+" represents the outer contour. "-" indicates the inner contour The theoretical profile S of cam 101 c The unit normal vector is r, where r is the radius of the roller (e.g., roller bearing 201).

[0078] According to a preferred embodiment of the present invention, the profile of the external gear ring 203 can be solved according to the meshing principle described below: based on the tooth profile S of the movable tooth 202 MT Cam 101 theoretical profile S c The relationship between the transmission ratio i and the motion trajectory of the movable tooth 202 profile is obtained, and the envelope is solved. The set of points on the envelope satisfies the following conditions. in, For the normal vector of the tooth profile of active tooth 202, It is the relative velocity direction vector at the meshing point between the movable tooth 202 and the external gear ring 203.

[0079] According to a preferred embodiment, in this invention, the external gear ring 203 is driven by the rotation of the cam 101 to move the movable tooth 202. The envelope of the motion trajectory of the movable tooth 202 is the inner tooth profile of the external gear ring 203. Due to the modification of the cam 101, the envelope of the motion trajectory of the movable tooth 202 is usually a numerical solution, not a logarithmic spiral. In particular, the linearity of the motion trajectory of the movable tooth 202 conforms to the meshing principle, resulting in optimal theoretical meshing performance between the movable tooth 202 and the external gear ring 203.

[0080] According to a preferred embodiment, such as Figure 7 As shown, if the logarithmic spiral is used as the internal tooth profile of the external gear ring 203, the obtained cam profile, while ensuring correct meshing between the movable tooth 202 and the external gear ring 203, is as follows. Figure 7 As shown by the solid line in the figure, the cam profile has sharp points on its minor and major axes. When the roller bearing 201 moves along the inner profile 1011 of the cam to the sharp point, its speed and acceleration will change abruptly, causing the speed and acceleration of the movable tooth 202 connected to the roller bearing 201 to change abruptly, thus aggravating the wear of the meshing surface between the movable tooth 202 and the external gear ring 203. Therefore, at the sharp point, according to the principle that the first derivative of the profile is continuous and the second derivative is 0, the cam 101 is modified. The modified cam profile is as follows: Figure 7 As shown by the dashed line, the modified cam 101 avoids abrupt changes in the speed and acceleration of the movable tooth 202, thereby reducing wear on the meshing surface between the movable tooth 202 and the external gear ring 203 and improving transmission performance. Subsequently, based on the modified cam profile, the tooth profile of the external gear ring 203 is obtained through the envelope method, ensuring that the external gear ring 203 and the movable tooth 202 can always mesh correctly during transmission.

[0081] According to a preferred embodiment, such as Figure 4 and Figure 5 As shown, in this invention, the transmission structure connecting the movable tooth 202 and the roller bearing 201 can be provided in two sets, and the two sets of transmission structures can be symmetrically arranged as mirror images of each other along the axial direction of the cam 101.

[0082] According to such Figure 4 and Figure 5In the embodiment shown, the transmission structure can be a coaxial reduction transmission, wherein the external gear ring 203 remains unchanged, the input end (or driving element) is the cam 101, and the cage 204 serves as the output end (or driven element). Specifically, the cage 204 is essentially a cylindrical frame, and a plurality of holes for holding the movable teeth 202 are arranged circumferentially on the cylindrical frame. These holes are spaced apart axially and divided into two groups, for example... Figure 4 As shown. The movable tooth 202 is fitted to the cage 204 through a hole in the side wall of the cage 204, so that the rotation of the cam 101 drives the movement of the movable tooth 202, which in turn drives the cage 204 to move (e.g., rotate).

[0083] like Figure 4 As shown, by rotating the cam 101, a plurality of movable teeth 202 arranged on the cam 101 are forced to move back and forth radially, alternating between the long and short axes. This back and forth movement of the movable teeth 202 is performed radially through the cage 204. Through the interaction between the movable teeth 202 and the external gear ring 203, a transmission ratio can be generated between the external gear ring 203 and the cage 204, and torque can be transmitted between the cam and the external gear ring 203 or the cage 204.

[0084] like Figure 4 As shown, the movable teeth 202 are divided into at least two groups. Since the holes for holding the movable teeth 202 are also divided into at least two groups, the movable teeth 202 can be arranged in groups within the holes of the corresponding groups. The two groups of movable teeth 202 are spaced apart from each other in the axial direction of the cam 101. At least one group of movable teeth 202 acts as a compensation mechanism for harmonic drive jitter, used to compensate for the vibration caused by the load borne by the cage 204, which serves as the output shaft.

[0085] According to a preferred embodiment, see Figure 5 ① When assembling the two sets of transmission structures described in this invention, first assemble and connect the two sets of movable teeth 202 to the corresponding roller bearings 201, and then follow the instructions... Figure 5 As shown in ②, the movable teeth 202 are stabilized by the retainer 204. Then, the transmission structure connecting the two sets of movable teeth 202 to the roller bearing 201 is assembled one by one to the designated positions corresponding to the internal tooth profile of the outer gear ring 203 (not shown). Further, the cam 101 is arranged as follows... Figure 5 ③ As shown, the roller bearing 201 is assembled from right to left to approximately the center of the retainer 204, such that the right roller bearing 201 in the two transmission structures is assembled into the first retaining frame formed by the inner profile 1011 and the outer profile 1012 of the cam. On the other hand, the cam end cap 1013 is assembled as shown... Figure 5As shown in ④, the roller bearing 201 is assembled to the left end face of the cam 101 from left to right, so that the left roller bearing 201 in the two transmission structures is assembled into the second retaining frame formed by the inner contour 1011 of the cam and the outer contour 1014 of the end cap of the cam end cap 1013.

[0086] According to a preferred embodiment, see Figure 6 The end faces where the cam 101 and the cam end cover 1013 meet are provided with several locating pins 104. The cam end cover 1013 is positioned against the cam 101 by the locating pins 104 and is assembled to the shaft end face of the cam 101 by fasteners 103 (such as bolts) that cooperate with the locating pins 104. Figure 5 ④ The left end face shown.

[0087] Specifically, such as Figure 6 As shown in (a), the cam 101 includes a cylindrical base with an internal hollow shaft and an annular frame integrally formed in the circumference of the cylindrical base. The circumferential side of the cylindrical base serves as the inner profile 1011 of the cam and contacts the roller bearing 201. The annular frame serves as the outer profile 1012 of the cam and contacts the roller bearing 201. The roller bearing 201 is partially surrounded and defined in the profile segment formed by the inner profile 1011 and the outer profile 1012 of the cam.

[0088] On the other hand, such as Figure 6 As shown, the cam end cap 1013 has an end cap outer contour 1014 that has the same shape as the cam outer contour 1012 of the cam 101 but points in the opposite direction. The end cap outer contour 1014 of the cam end cap 1013 serves as an outer contour for contacting and at least partially covering the roller bearing 201, so that the cam end cap 1013, through its end cap outer contour 1014, together with the cam inner contour 1011 of the cam 101, defines and covers the roller bearing 201. In particular, as Figure 5 As shown in ④, when the present invention is provided with a transmission structure in which two sets of movable teeth 202 are connected to the roller bearing 201, the cam end cap 1013 is used to assemble the left roller bearing 201 between the inner contour 1011 of the cam and the outer contour 1014 of the end cap of the cam end cap 1013, thereby limiting the left roller bearing 201 and accurately transmitting the periodic motion transmitted by the cam 101 to avoid unintended radial offset or deflection. The separable cam end cap 1013 provides simple and convenient operating conditions for the disassembly and replacement of the roller bearing 201 and the movable teeth 202.

[0089] According to a preferred embodiment, the transmission structure of the present invention, which connects two sets of movable teeth 202 to roller bearings 201, can significantly improve the load-bearing capacity of the reducer. Specifically, when only one set of movable teeth 202 connected to roller bearings 201 is provided, the reducer operates by contacting the cam 101 and the external gear ring 203 through the transmission structure connected to the roller bearings 201 to transmit torque / load; while when two sets of movable teeth 202 connected to roller bearings 201 are provided, both sets of transmission structures simultaneously contact the cam 101 and the external gear ring 203 and transmit load, thereby improving the overall load-bearing capacity of the reducer. Specifically, when only one set of movable teeth 202 is set to connect with the roller bearing 201, the root of the movable teeth 202 is basically located in the axial center region of the cam, so that the movable teeth, as the only transmission structure, are subjected to a basically balanced force, so as to prevent the movable teeth, as the only transmission structure, from generating a significant unbalanced torque on both sides of the axial direction relative to the cam, thereby affecting the smooth transmission of the reducer and reducing the transmission performance of the reducer.

[0090] While adding a transmission structure improves the overall load-bearing capacity of the reducer, in practical applications, the overall mechanical characteristics (such as stress state) of two symmetrically arranged sets of transmission structures and / or transmission structures with basically the same shape are not entirely consistent. This is usually related to the specific load input direction. In particular, with Figure 5 ④ As shown in the example, if cam 101 or cam 101 with a drive member is inserted into the center of the reducer from the right to provide driving force, and an external load is attached to the output shaft / component (i.e., cage 204) from the left, then, since the load conditions on both sides of the reducer are different, when the entire reducer is operated by driving cam 101, the load is concentrated on one side of the reducer, so that the side with the load will have different mechanical effects on the two sets of transmission structures that operate at the same time. For example, the left side with the load will first have a significantly greater disturbance to the transmission structure on the left side, which in particular affects the contact meshing between the movable tooth 202 and the external gear ring 203 on that side.

[0091] In particular, as the load attached to the cage 204 increases or the duration of continuous load increases, the harmonic disturbances introduced by the cage 204 in the axial direction may cause the movable tooth 202 to move and / or deflect along the axial direction of the outer gear ring 203 while engaging with the outer gear ring 203 through radial movement. Especially since the movable tooth 202 is in near-point connection or point contact with the roller bearing 201, the movement and / or deflection of the movable tooth 202 along the axial direction of the outer gear ring 203 will produce a pendulum-like motion centered on the connection point with the roller bearing 201. This motion is prone to aggravating the wear of the meshing tooth surfaces of the movable tooth 202 and the outer gear ring 203.

[0092] Furthermore, the torque from the output shaft / component (i.e., the cage 204) or transmitted by the cage 204 is transmitted to the transmission structure on the other side. The transmission structure on the other side is less affected by the load compared to the load side. In addition, the outer profile 1012 of the cam 101 limits the two transmission structures to be affected by load torques of different degrees. This causes the movable tooth 202 held in the cage to experience different degrees of aging and wear relative to the outer gear ring 203. This unbalanced mechanical state will become more and more obvious as the frequency of use of the reducer increases, resulting in a significant decrease in the overall load capacity of the reducer in the later stage. In some cases, the two transmission structures may even produce obvious asynchronous meshing, which seriously affects the normal use of the reducer. In particular, this type of reducer based on logarithmic spiral is often used in precision transmission applications. This means that basically synchronized and stable transmission is the key factor in achieving high-precision transmission ratio and torque.

[0093] In view of this, to accommodate the unbalanced torque that may be generated by the two sets of transmission structures and to maintain the overall transmission stiffness of the reducer, in this invention, the two sets of transmission structures are arranged symmetrically, and at least one pair of roller bearings 201 symmetrical to each other are arranged opposite each other at one end for connecting the movable teeth 202, allowing the movable teeth 202 connected to each other to be spaced apart. Specifically, for example... Figure 5 As shown in ④, the roller bearing 201 has a cylindrical shaft end that is surrounded and defined within the retaining frame of the cam 101 or the cam end cover 1013 and an elongated shaft end (or shaft head) outside the retaining frame for connecting the movable gear 202. When the elongated shaft ends (or shaft heads) of the two sets of roller bearings 201 for connecting the movable gear 202 are arranged facing each other, the overall assembly structure of the reducer can be made more compact, thereby reducing the resonance caused by the unbalanced torque between the two transmission structures.

[0094] On the other hand, compared to a single set of wide-pitch teeth, the adjacent spacing of the two sets of movable teeth 202 creates a gap between their respective contact bearing positions. Surprisingly, this actually increases the overall load-bearing capacity of the reducer and improves transmission stiffness. In particular, arranging the two sets of movable teeth 202 with one set close to the axial center and the other set offset axially from the adjacent spacing allows for slight movement and / or oscillation within a small range while maintaining transmission stiffness. This movement and / or oscillation allows the movable teeth 202 to release part of the load they absorb or bear, thereby avoiding resonance of unbalanced torque between the two transmission structures, or even further amplification of it.

[0095] According to a preferred embodiment, in order to mitigate the unbalanced torque that may be generated by the two transmission structures and reduce the wear and aging process of the movable tooth 202 on the load side relative to the outer gear ring 203, so that the two sets of transmission structures can maintain basically synchronous and stable transmission, in this invention, the movable teeth 202 of the two sets of transmission structures located on the same generatrix of the inner contour 1011 of the cam can be formed of different materials, so that they have different hardness relative to the transmitted torque from the cage 204. The hardness of the movable teeth 202 is set in relation to the load input direction corresponding to the cage 204 as the output shaft / component. In particular, given the different load input directions associated with the cage 204, the two ends of the reducer have different stress states, which will have different effects on the two sets of transmission structures that are mirror images of each other in time and space. Therefore, the movable teeth 202 in the two sets of transmission structures can be formed of different materials to have different hardness, so as to compensate for the unbalanced torque generated by the external load introduced by the cage 204 based on the difference in their strength, thereby avoiding the resonance of the unbalanced torque between the two transmission structures.

[0096] According to a preferred embodiment, in this invention, the movable teeth 202 in the two sets of transmission structures that are closer to (or farther from) the load input direction can have lower hardness. That is, the movable teeth 202 with different hardnesses are divided into at least two sets that are axially spaced but aligned with each other. Specifically, for example... Figure 5 As shown in ④, when the load is attached to the output shaft / component (i.e., the cage 204) from the left side, the movable tooth 202 closer to that side can be configured to have a lower hardness than the movable tooth 202 on the opposite side. More specifically, the movable tooth 202 closer to that side can be formed of a material with lower hardness.

[0097] As the load and loading time accumulate, the load oriented towards the load input direction will cause more severe disturbance to the movable tooth 202 on the same side compared to the movable tooth 202 on the opposite side. This makes the movable tooth 202 on that side more prone to axial movement and / or deflection. Therefore, configuring the movable tooth 202 on that side to have lower hardness, i.e., relatively flexible compared to the movable tooth 202 on the other side, allows it to more gently absorb or mitigate the additional load from the same side. This prevents the movable tooth 202 on that side from generating more significant harsh friction with the outer gear ring 203 due to load accumulation, thus exacerbating the wear of the movable tooth 202 on that side. Furthermore, the movable tooth 202 on the load input side engages with the outer gear ring 203 in a relatively flexible manner. Based on its relatively elastic mechanical properties, it can mitigate the disturbing torque introduced by the load on the same side. This allows it to have essentially the same adaptability as the symmetrically arranged movable tooth 202 on the other side relative to the same load and the unbalanced torque introduced in different spaces. This adaptability is achieved through the hardness characteristics exhibited by different molding materials. The arrangement of the movable teeth 202 away from the load input direction is similar and will not be described in detail here.

[0098] Furthermore, the movable teeth 202 of the present invention are divided into at least two groups that are axially spaced but aligned with each other. Axially aligned means that the two groups of movable teeth 202 are spaced apart from each other axially in the cam 101, but adjacent teeth in each group of movable teeth 202 are located on the same generatrix of the inner profile 1011 of the cam. The movable teeth 202 away from the axial center of the cam 101 can serve as a vibration compensation mechanism to compensate for vibrations caused by the load borne by the cage 204, which acts as the output shaft. Additionally, as... Figure 5 As shown in ④, the cam end cap 1013 can be mounted on the side of the cam 101 facing the load-in direction of the cage 204, and is held by a second retaining frame located radially outward of the cam 101, which serves as a harmonic drive jitter compensation for one of the sets of roller bearings 201. The cam end cap 1013 has lower stiffness compared to the cam 101 mirror-symmetrically positioned on its opposite side. In this case, the elasticity of the cam end cap 1013 is important, such as... Figure 5As shown in ④, the second retaining frame of the cam end cover 1013 elastically blocks the axial movement of the proximal moving tooth 202 from its axial end by means of its second sidewall 1016; while the opposite end is limited by the radial contact portion of the moving tooth 202 penetrating the retainer 204. Furthermore, the second retaining frame of the cam end cover 1013 elastically blocks the radial vibration of the side roller bearing 201 from its radial end by means of its first sidewall 1015, further limiting the vibration of the side moving tooth 202. Since the retainer 204 can act as a transmission output mechanism, the load fluctuations it causes can be compensated for on one side of the cam end cover 1013 by the elasticity of the cam end cover 1013. In addition, since the cam end cover 1013 and the cam 101 are connected by a screw, when maintenance is required after long-term operation, only the cheaper and easier-to-replace cam end cover 1013 needs to be replaced to ensure the reliability of the overall equipment, greatly reducing equipment maintenance costs.

[0099] It should be understood that the material forming the movable teeth 202 is usually an alloy material, and this invention does not intend to limit the specific material type. Those skilled in the art can select the appropriate forming material according to the specific application of the movable tooth reducer. The specific type should generally be determined based on the hardness requirements of the movable teeth 202 of each of the two sets of transmission structures. The purpose is to ensure that the movable teeth 202 in the two sets of transmission structures have different complementary hardnesses, such as hardness, tensile strength, and yield strength. Furthermore, the specific materials and hardness requirements of the two sets of movable teeth 202 can be determined by the designer through experimentation based on different usage scenarios of the reducer. Thus, in the case where the cam end cover 1013 described in this invention is detachable, at least by replacing the movable teeth 202 on one side with different hardnesses, it can adapt to the harmonic transmission vibrations or jitters that may be introduced under different harmonic transmission scenarios. In other words, the elasticity of the cam end cap 1013 and the elasticity of the movable teeth 202 can be a set of empirical data tables that are pre-calculated and configured. That is, there are X*Y different matching methods for X groups of cam end caps 1013 and Y groups of movable teeth 202, which can adapt to the long-term stable operation of different loads with a product of X*Y.

[0100] It should be noted that the specific embodiments described above are exemplary. Those skilled in the art can devise various solutions inspired by the disclosure of this invention, and these solutions all fall within the scope of this invention and its protection. Those skilled in the art should understand that this specification and its accompanying drawings are illustrative and not intended to limit the scope of the claims. The scope of protection of this invention is defined by the claims and their equivalents. This specification contains multiple inventive concepts; terms such as "preferredly," "according to a preferred embodiment," or "optionally" indicate that the corresponding paragraph discloses an independent concept. The applicant reserves the right to file divisional applications based on each inventive concept.

Claims

1. A movable gear reducer with a logarithmic helical tooth profile, comprising an external gear ring (203), a cam (101), and a cage (204), wherein, A transmission ratio is generated and torque is transmitted between the outer gear ring (203) and the cage (204) by driving a plurality of movable teeth (202) arranged on the cam (101) and moving radially through the cage (204). Its features are, The movable teeth (202) are divided into at least two groups, and the two groups of movable teeth (202) are spaced apart from each other in the axial direction of the cam (101). At least one group of the movable teeth (202) acts as a compensation mechanism for harmonic drive jitter to compensate for the vibration caused by the load borne by the cage (204) as the output shaft. The two sets of movable teeth (202) are movably arranged on the cam (101) via their respective roller bearings (201). One set of roller bearings (201) is held in the first retaining frame integrally formed with the cam (101), such that the set of roller bearings (201) can move circumferentially around the cam (101) along the first retaining frame, while also allowing the set of roller bearings (201) to rotate around the shaft head of its connecting movable tooth (202) as the axis. Another set of roller bearings (201) is held in a second retaining frame mounted axially on the cam end cap (1013) of the cam (101), such that the set of roller bearings (201) can move circumferentially around the cam (101) along the second retaining frame, while also allowing the set of roller bearings (201) to rotate around the shaft head of its connecting movable tooth (202).

2. The movable gear reducer according to claim 1, characterized in that, One set of roller bearings (201) and a set of movable teeth (202) connected thereto constitute a first transmission structure, and another set of roller bearings (201) and another set of movable teeth (202) connected thereto constitute a second transmission structure. The first transmission structure and the second transmission structure are symmetrically arranged in a mirror image of each other in the axial direction, so that each pair of roller bearings (201) spaced apart from each other in the axial direction bears a collinear axial thrust.

3. The movable gear reducer according to claim 1, characterized in that, A first retaining frame for holding one set of movable teeth (202) is arranged radially outward of the cam (101) from the axial center, such that the root of the set of movable teeth (202) is substantially located at the axial center of the cam (101), so that the radial force acts approximately perpendicularly to the axial center of the cam (101).

4. The movable gear reducer according to claim 2, characterized in that, The first transmission structure includes a plurality of movable teeth (202) and the second transmission structure includes a plurality of movable teeth (202) with different hardnesses to compensate for the unbalanced torque introduced along the axial direction of the cam (101) by the cage (204) as the output shaft due to bearing the load.

5. The movable gear reducer according to claim 1, characterized in that, At least one set of movable teeth (202) disposed on the load access direction side near the cage (204) has less stiffness than at least another set of movable teeth (202) disposed mirror-symmetrically along the cam (101) axis on the other side of the load access direction of the cage (204), so as to allow harmonic drive jitter from the load access direction of the cage (204) to be at least partially absorbed.

6. The movable gear reducer according to claim 1, characterized in that, The retaining frame for holding the movable tooth (202) provided on the load access direction side near the retainer (204) has less stiffness than the retaining frame provided on the other side of the retainer (204) in a mirror symmetrical manner along the cam (101) axis, so that harmonic drive jitter from the load access direction of the retainer (204) is at least partially absorbed.

7. The movable gear reducer according to claim 1, characterized in that, The cam end cap (1013) is detachably mounted to the side of the cam (101) facing the load access direction of the cage (204) and holds one set of roller bearings (201) by a second retaining frame arranged radially outward of the cam (101) to at least partially absorb the vibration of the set of roller bearings (201) caused radially by harmonic drive jitter along the cam (101).

8. The movable gear reducer according to claim 1, characterized in that, The cam (101) transmits torque to the cage (204) through a logarithmic spiral-based surface contact between the movable tooth (202) and the external gear ring (203), wherein the theoretical profile of the cam (101) is... It conforms to the following function: ， In the formula, This represents 1 / 4 of the theoretical tooth profile of the cam (101) in polar coordinates; The polar angle corresponding to the cam (101) in polar coordinates; the first and third curves are the correction curves for the cam (101) tip, and the second curve conforms to the logarithmic spiral. , , , The first segment of the cam (101) is the shaping curve coefficient; , , , The second segment of the cam (101) is the shaping curve coefficient; and The location of the intersection of the cam (101) trim section; This is the theoretical transmission ratio of the reducer; The reference radius for the profile of the movable tooth; This is the reference angle for the profile of the movable tooth.

9. The movable gear reducer according to claim 1, characterized in that, According to the single-sided tooth profile curve of the movable tooth (202) Theoretical profile of cam (101) Transmission ratio Based on the relationship between the two, the motion trajectory of the movable tooth (202) profile is obtained, and the envelope is solved. Wherein, the set of points on the envelope satisfies , In the formula, For the normal vector of the tooth profile of the active tooth (202), The relative velocity direction vector at the meshing point between the movable tooth (202) and the external gear ring (203).

Images