Precision cycloidal pinwheel reducer

Abstract

A precision cycloidal pinwheel reducer, which uses free eccentric shafts (3) and a suspended input shaft (4). Each free eccentric shaft (3) is sleeved on a rotating arm shaft (21) through a hollow shaft hole thereof, and each cycloidal gear (5) is sleeved on eccentric shaft sections of the free eccentric shafts (3) through shaft holes thereof, thereby forming inner and outer rotational connections. The suspended input shaft (4) is only directly rotationally connected to cycloidal gears (5) at eccentric shaft sections, and is not directly rotationally connected to a base (1) or a planet carrier (2), thus remaining suspended over the base (1) and the planet carrier (2). Such a special design can reduce the radial force borne by the input shaft and allow for the use of a thinner input shaft, and also has a long service life and low requirements for manufacturing precision.

Description

Precision cycloidal pinwheel reducer Technical Field

[0001] This application relates to speed reducers, and more particularly to cycloidal pinwheel speed reducers. Background Technology

[0002] This section is intended to provide background or context for the embodiments of this application as set forth in the claims. The content in this section is for reference only and does not constitute an admission or confirmation that it is prior art that has been disclosed.

[0003] Cycloidal pinwheel drive technology was first invented in Germany in 1937, and after Japan purchased the patent rights in 1939, it successfully manufactured cycloidal pinwheel reducers with large transmission ratios. This technology has been widely used in various industries worldwide and continues to be used today. Its working principle is as follows: the cycloidal wheel, driven by a central input eccentric shaft, oscillates along an eccentric circumference, meshing with the pin teeth. Based on the principle of small tooth difference, one rotation of the cycloidal wheel will drive relative rotation between it and the pin tooth housing, with the rotation angle corresponding to the small tooth difference. This rotation can be transmitted to the planetary carrier output through the swing arm shaft in the cycloidal wheel. Cycloidal pinwheel reducers are widely used due to their high transmission ratio, high efficiency, and long service life. However, because it must withstand enormous radial forces, the central input eccentric shaft needs to be made very large, at the cost of occupying valuable effective area of ​​the cycloidal wheel, preventing further increases in the diameter of the swing arm hole and limiting further improvements in output capacity.

[0004] To address this issue, Teijin Seiki (now Nabtesco Corporation) developed the RV reducer in 1985. This device, while retaining the cycloidal pinwheel reducer, eliminated the central input eccentric shaft and introduced a parallel double-crank (or parallel four-bar) mechanism, unifying input and output onto multiple crankshafts surrounding the cycloidal wheel. This improvement, eliminating the central eccentric shaft, gave the RV reducer the highest output capacity and rigidity currently available. Furthermore, to achieve synchronous drive of multiple cranks, the RV reducer added a front-stage spur gear reduction section, which simultaneously drives multiple planetary spur gears via a sun gear, driving their respective cranks to achieve synchronous input. While this design solved the synchronous input problem, it also introduced an over-constraint (or over-positioning) problem: the shaft holes on the cycloidal wheel already constrained the cranks to maintain phase synchronization, and the rigid transmission through the meshing of the front-stage sun gear and planetary gears further constrained the phase of each crankshaft, resulting in over-constraint. This design not only requires extremely high manufacturing precision, but may also affect the service life, so that even the best-made RV reducer has a service life of only 6,000 hours, far less than the tens of thousands of hours of service life of traditional cycloidal pinwheel reducers.

[0005] The industry is seeking to develop a new type of precision cycloidal pinwheel reducer that combines the advantages of traditional cycloidal pinwheel reducers and RV reducers. Specifically, this new reducer needs to possess the following characteristics: compared to traditional cycloidal pinwheel reducers, its input bearing experiences less radial force, allowing for a thinner input shaft to provide more space for the output mechanism; simultaneously, compared to RV reducers, this new reducer should have a longer service life and lower manufacturing precision requirements to reduce production costs and increase production efficiency. Such technological innovation will provide more efficient and economical power transmission solutions for various industries.

[0006] Summary of the Invention

[0007] The purpose of this application is to provide a precision cycloidal pinwheel reducer that not only reduces the radial force on the input shaft, allowing the use of a thinner input shaft, but also has a long service life and lower requirements for manufacturing precision.

[0008] This application discloses a precision cycloidal pinwheel reducer, comprising: a base, multiple cycloidal wheels, a suspended input shaft, a planetary carrier having multiple rotating arm shafts, and a free eccentric shaft sleeved on each of the rotating arm shafts; the base includes a pin tooth shell, the inner wall of which is provided with multiple pin teeth; the edge of each cycloidal wheel includes multiple cycloidal teeth that mate with the pin teeth, the number of cycloidal teeth being less than the number of pin teeth; the free eccentric shaft includes a through hollow shaft hole and a number of first eccentric shaft segments equal to the number of cycloidal wheels, each first eccentric shaft segment corresponding to one cycloidal wheel; the cycloidal wheel is provided with a shaft hole that mates with the first eccentric shaft segment. The rotating arm shaft passes through the hollow shaft hole of the free eccentric shaft; the free eccentric shaft passes through the shaft hole of each of the cycloidal wheels in each of its first eccentric shaft sections, forming a rotational connection between the inner and outer layers; the suspended input shaft includes a central shaft and a number of second eccentric shaft sections equal to the number of cycloidal wheels, each of the second eccentric shaft sections passing through the center of one of the cycloidal wheels and being rotatably connected to that cycloidal wheel; the central shaft is used to input external torque to drive each of the second eccentric shaft sections to rotate; the suspended input shaft is only directly rotatably connected to each of the cycloidal wheels in each of the second eccentric shaft sections, and the suspended input shaft is not directly rotatably connected to the base or the planetary carrier.

[0009] In a preferred embodiment, when the suspended input shaft rotates, each of the second eccentric shaft segments on the suspended input shaft drives each of the cycloidal wheels to oscillate along the eccentric circumference, causing the cycloidal teeth on the edge of the cycloidal wheel to contact and mesh with the needle teeth on the needle tooth shell, resulting in the cycloidal wheel rotating. When the cycloidal wheel oscillates, it drives each of the free eccentric shafts passing through the shaft hole of the cycloidal wheel to rotate synchronously, and applies radial force and planetary torque to each of the free eccentric shafts. Each of the free eccentric shafts further transmits planetary torque to the rotating arm shaft passing through its center, causing the rotating arm shaft to rotate as well. The torques on each of the rotating arm shafts are combined to form the output torque of the planetary carrier.

[0010] In a preferred embodiment, the planet carrier further includes an output shaft for outputting the output torque of the planet carrier outward.

[0011] In a preferred embodiment, a rolling bearing is provided between the base and the output shaft of the planetary carrier, the inner ring of the rolling bearing being fixedly connected to the output shaft, and the outer ring of the rolling bearing being fixedly connected to the base.

[0012] In a preferred embodiment, the rolling bearing is a crossed roller bearing.

[0013] In a preferred embodiment, the cycloidal wheel comprises three cycloidal wheels, wherein the two side cycloidal wheels located on both sides have the same eccentric angle and differ from the eccentric angle of the central cycloidal wheel by 180°; the two side cycloidal wheels have equal thickness and are half the thickness of the central cycloidal wheel.

[0014] In a preferred embodiment, each of the first eccentric shaft segments and each of the second eccentric shaft segments has the same eccentricity.

[0015] In a preferred embodiment, the number of shaft holes on each of the cycloidal wheels that mate with the first eccentric shaft segment of the free eccentric shaft is equal to the number of the swivel arm shafts.

[0016] In a preferred embodiment, a multi-stage reduction mechanism is included, wherein the pin tooth housing is shared by the multi-stage reduction mechanism, and the planetary carrier of the adjacent pre-stage reduction mechanism is fixedly connected to the suspended input shaft of the subsequent stage reduction mechanism and rotates coaxially. Each stage reduction mechanism includes multiple cycloidal wheels and multiple free eccentric shafts belonging to that stage.

[0017] In a preferred embodiment, the number of cycloidal teeth differs between different grades of cycloidal wheels.

[0018] In the embodiments of this application, the free eccentric shaft is fitted onto the rotating arm shaft through its hollow shaft hole, and each cycloidal wheel is fitted onto its respective eccentric shaft segment through its shaft hole, forming an inner and outer layer of rotational connection (the inner layer of rotational connection is between the free eccentric shaft and the rotating arm shaft, and the outer layer of rotational connection is between the free eccentric shaft and the cycloidal wheel). Furthermore, the suspended input shaft is only directly rotatably connected to each cycloidal wheel in each eccentric shaft segment, and not directly rotatably connected to the base or planetary carrier, thus being suspended above the base and planetary carrier. This special design greatly reduces the maximum radial force that the input shaft may bear, allowing for a smaller input shaft diameter, which in turn allows for a corresponding reduction in the diameter of the cycloidal wheel. As a result, the diameter and weight of the entire cycloidal pinwheel reducer are reduced, resulting in a higher torque density, which is extremely important for applications requiring high precision, such as robots and surgical instruments. In comparison, the input shaft of a traditional cycloidal pinwheel reducer is not only directly connected to the cycloidal wheel, but also needs to be connected to the base or planetary carrier. During operation, the input shaft must bear the entire radial force from the pin teeth, which can sometimes even lead to the input shaft breaking. To prevent this, the input shaft usually needs to be designed to be larger, occupying more central space of the cycloidal wheel, forcing the cycloidal wheel to be designed to be larger, thus increasing the diameter and weight of the entire device.

[0019] Furthermore, simply adding a cycloidal wheel and a cascaded planetary carrier can add a reduction stage, thus realizing a cascaded cycloidal pinwheel reducer. By using cycloidal wheels with different tooth differences (such as one-tooth difference, two-tooth difference, three-tooth difference, etc.) in different stages of the reduction mechanism, a diverse series of transmission ratios can be constructed, thereby directly replacing the existing cascaded involute gear planetary reducers.

[0020] The various technical features disclosed in the above-described invention, the various technical features disclosed in the following embodiments and examples, and the various technical features disclosed in the accompanying drawings can be freely combined to form various new technical solutions (all of which should be considered as having been recorded in this specification), unless such a combination of technical features is technically infeasible. For example, in one example, feature A+B+C is disclosed, and in another example, feature A+B+D+E is disclosed. Features C and D are equivalent technical means that serve the same function, and technically only one needs to be used; it is impossible to use both simultaneously. Feature E can be technically combined with feature C. Therefore, the solution A+B+C+D should not be considered as having been recorded because it is technically infeasible, while the solution A+B+C+E should be considered as having been recorded. Attached Figure Description

[0021] Figure 1 is a simplified kinematic diagram of the transmission mechanism of a precision cycloidal pinwheel reducer according to an embodiment of this application;

[0022] Figure 2 is an external view of a precision cycloidal pinwheel reducer according to an embodiment of this application;

[0023] Figure 3 is a part drawing of a precision cycloidal pinwheel reducer according to an embodiment of this application;

[0024] Figure 4 is a horizontal cross-sectional view of a precision cycloidal pinwheel reducer according to an embodiment of the present application;

[0025] Figure 5 is a vertical cross-sectional view of a precision cycloidal pinwheel reducer according to an embodiment of the present application;

[0026] Figure 6 is a simplified kinematic diagram of the transmission mechanism of a cascaded cycloidal pinwheel reducer according to an embodiment of this application;

[0027] Figure 7 is a structural diagram of the cascaded planetary carrier of a cascaded cycloidal pinwheel reducer according to an embodiment of this application.

[0028] The reference numerals used in the various figures are summarized as follows: 1: Base; 11: Needle housing; 12: Needle; 13: Rear cover; 14: Rolling bearing; 15: Clearance; 16: Output bearing; 2: Planetary carrier; 21: Rotary arm shaft; 22: Output shaft; 3: Free eccentric shaft; 4: Suspended input shaft; 5: Cycloidal wheel; 6: First-stage reduction mechanism; 7: Second-stage reduction mechanism; 8: Cascaded planetary carrier; 81: Rear stage input shaft; 82: Front stage rotary arm shaft. Detailed Implementation

[0029] In the following description, many technical details are presented to help the reader better understand this application. However, those skilled in the art will understand that the technical solutions claimed in this application can be implemented even without these technical details and various variations and modifications based on the following embodiments.

[0030] To make the objectives, technical solutions, and advantages of this application clearer, the embodiments of this application will be described in further detail below with reference to the accompanying drawings.

[0031] The embodiments of this application relate to a precision cycloidal pinwheel reducer, as shown in Figures 1-5. The precision cycloidal pinwheel reducer includes a base 1, multiple cycloidal wheels 5, a suspended input shaft 4, a planetary carrier 2 with multiple rotating arm shafts 21, and a free eccentric shaft 3 sleeved on each rotating arm shaft 21.

[0032] The base 1 includes a needle-tooth shell 11, and a plurality of needle teeth 12 are provided on the inner wall of the needle-tooth shell 11.

[0033] The edge of the cycloidal wheel 5 includes multiple cycloidal teeth that mate with the needle teeth 12, and the number of cycloidal teeth is less than the number of needle teeth 12. The difference can be one tooth, two teeth, three teeth, etc.

[0034] The free eccentric shaft 3 includes a through hollow shaft hole and a number of first eccentric shaft segments equal to the number of cycloidal wheels 5, with each first eccentric shaft segment corresponding to one cycloidal wheel 5. Each cycloidal wheel 5 has a shaft hole that mates with one of the first eccentric shaft segments. The rotating arm shaft 21 passes through the hollow shaft hole of the free eccentric shaft 3. The free eccentric shaft 3 has its first eccentric shaft segments passing through the shaft holes of each cycloidal wheel 5, forming a two-layer rotational connection. The number of shaft holes on each cycloidal wheel 5 that mate with the first eccentric shaft segments of the free eccentric shaft 3 is equal to the number of rotating arm shafts 21.

[0035] The suspended input shaft 4 includes a central shaft and a number of second eccentric shaft segments equal to the number of cycloidal wheels 5. Each second eccentric shaft segment passes through the center of a cycloidal wheel 5 and is rotatably connected to that cycloidal wheel 5. Each first eccentric shaft segment and each second eccentric shaft segment has the same eccentricity. The central shaft refers to the non-eccentric shaft end connected to an external power component (e.g., an electric motor), used to input external torque to drive the rotation of each second eccentric shaft segment. The suspended input shaft 4 is only directly rotatably connected to each cycloidal wheel 5 in each of the second eccentric shaft segments; the suspended input shaft 4 is not directly rotatably connected to the base 1 or the planetary carrier 2.

[0036] Existing cycloidal pinwheel reducers typically have an input shaft that is not only rotatably connected to the cycloidal wheel but also directly rotatably connected to the base or planetary carrier via bearings. However, the suspended input shaft of this embodiment is only directly rotatably connected to the cycloidal wheel, while leaving a gap between it and the base (e.g., the pin gear housing cover), without contact or direct connection. The advantage of this is that when the input shaft is subjected to radial force, it will undergo slight displacement and deformation, allowing most of the radial force to be borne by the free eccentric shaft. This ingenious design significantly reduces the stress on the input bearing, thereby reducing the shaft diameter and allocating the effective area of ​​the cycloidal wheel to the swing arm hole, enabling the use of a larger swing arm shaft and greatly improving output capacity.

[0037] When the suspended input shaft 4 is driven to rotate by an external motor component, each second eccentric shaft segment on the suspended input shaft 4 drives each cycloidal wheel 5 to oscillate along an eccentric circumference, causing the cycloidal teeth on the edge of the cycloidal wheel 5 to engage with the needle teeth 12 on the needle tooth housing 11, resulting in the rotation of the cycloidal wheel 5. As the cycloidal wheel 5 oscillates, it drives each free eccentric shaft 3 passing through the shaft hole of the cycloidal wheel 5 to rotate synchronously, applying radial force and planetary torque to each free eccentric shaft 3. Each free eccentric shaft 3 further transmits planetary torque to the rotating arm shaft 21 passing through its center, causing the rotating arm shaft 21 to rotate as well. The combined torque on each rotating arm shaft 21 constitutes the output torque of the planetary carrier 2.

[0038] The planet carrier 2 also includes an output shaft 22, which is used to output the output torque of the planet carrier 2 outward.

[0039] In the examples of Figures 3 and 4, the planet carrier 2 has three swivel shafts 21. In other embodiments, there may be more swivel shafts 21.

[0040] This embodiment eliminates the over-constraint problem of the RV reducer by using a structure with a free eccentric shaft and a suspended input shaft, while also solving the problem of an excessively large input shaft in the cycloidal pinwheel reducer. Specifically, the centrally located suspended input shaft drives the cycloidal wheel to oscillate eccentrically (this shaft is eccentric, only rotatably connected to the cycloidal wheel, maintaining a gap with the base and not directly connected to the planetary carrier, "suspended" above the base and planetary carrier). The free eccentric shafts on each swing arm rotate synchronously with the oscillation of the cycloidal wheel, bearing enormous radial force and output torque; the suspended input shaft is only responsible for transmitting the oscillation torque to the cycloidal wheel and no longer bears the enormous radial force (the central axis of the free eccentric shaft is a hollow shaft hole, rotatably connected to the swing arm shaft passing through the shaft hole, allowing free rotation around it). In this way, the central suspended input shaft no longer needs a large diameter, freeing up valuable effective area of ​​the cycloidal wheel. Thanks to this, the cycloidal wheel has a large-diameter swing arm hole, thus greatly improving the output capacity. At the same time, it is easy to see that since the front reduction section has been removed, the over-constraint of RV reducers no longer exists, which greatly improves the service life.

[0041] Preferably, in one embodiment, the precision cycloidal pinwheel reducer includes three cycloidal wheels 5, wherein the two side cycloidal wheels 5 located on both sides have the same eccentric angle, and their eccentric angle differs from that of the central cycloidal wheel 5 by 180°. The two side cycloidal wheels 5 have equal thicknesses, which are half the thickness of the central cycloidal wheel 5. Optionally, in one embodiment, all cycloidal wheels 5 are made of the same material. Optionally, in one embodiment, the cycloidal wheels 5 may also be made of different materials, and the mass of the central cycloidal wheel 5 is equal to the sum of the masses of the two outer cycloidal wheels 5, and the thicknesses of the two outer cycloidal wheels 5 may not be equal. Optionally, in one embodiment, two or more cycloidal wheels 5 may also be used.

[0042] Currently, most cycloidal pinwheel reducers on the market use a configuration of two cycloidal wheels paired with an eccentric shaft 180° out of phase, which can offset most radial vibrations. However, since the radial force does not act on the same point, a certain bending moment still exists. This bending moment acts at the root of the swing arm, still affecting output capacity and stiffness. This application proposes a "sandwich" three-cycloidal wheel combination structure, consisting of one central cycloidal wheel and two side cycloidal wheels. The eccentric angle of the eccentric shaft segment corresponding to the two side cycloidal wheels is the same, and it differs from the central eccentric shaft segment by 180°. The thickness of the two side cycloidal wheels is equal and half the thickness of the central cycloidal wheel. This structure completely offsets all vibrations and bending moments, thus allowing for very smooth and quiet operation. Although it slightly increases complexity, it does not increase size or weight, making it very suitable for high-precision applications such as robotics. Under the same conditions, the "sandwich" three-cycloidal wheel structure can significantly improve the backlash accuracy of the reducer.

[0043] Optionally, in one embodiment, a rolling bearing 14 is provided between the base 1 and the output shaft 22 of the planetary carrier 2. The inner ring of the rolling bearing 14 is fixedly connected to the output shaft 22, and the outer ring of the rolling bearing 14 is fixedly connected to the base 1. Preferably, the rolling bearing 14 can be a crossed roller bearing. Using a crossed roller bearing for the output bearing between the planetary carrier 2 and the base 1 can achieve higher transmission accuracy and stronger bending resistance. This structure allows external impact forces to be directly transmitted between the output shaft 22 and the base 1 without affecting the precision cycloidal wheel structure, greatly improving rigidity and impact resistance. Of course, in some embodiments, other types of rolling bearings can also be used.

[0044] In the embodiments of this application, the free eccentric shaft is an assembly of multiple eccentric shafts with a hollow central shaft hole, and the number of segments of the eccentric shaft is equal to the number of cycloidal wheels. The cycloidal wheels are fitted onto the rotating arm shaft and are rotatably connected to the rotating arm shaft. The cycloidal wheels have corresponding shaft holes through which the free eccentric shaft passes and is rotatably connected to the cycloidal wheels. The suspended input shaft is a solid shaft and is an assembly of multiple eccentric shafts, with the number of segments of the eccentric shaft equal to the number of cycloidal wheels. All eccentric segments have the same eccentricity, and each eccentric segment corresponding to the same cycloidal wheel has the same eccentricity angle. It is easy to imagine that when the external input source drives the suspended input shaft to rotate, it will cause each cycloidal wheel to oscillate (translate) around the eccentric circumference, further causing the cycloidal teeth on the edge of the cycloidal wheel to contact and mesh with the corresponding needle teeth on the needle tooth shell. At the same time, according to the principle of planetary transmission with small tooth difference, the cycloidal wheel will rotate slowly at a planetary speed. When the cycloidal wheel oscillates once, it synchronously rotates through the number of teeth less than the total number of needle teeth at a slow planetary speed. On the other hand, when the cycloidal wheel oscillates, it drives each free eccentric shaft to rotate synchronously, applying radial force and planetary torque to the free eccentric shaft. The free eccentric shaft then transmits the planetary torque to the rotating arm shaft passing through its center, and the torque received by each rotating arm is combined to form the output torque of the planetary carrier.

[0045] To those skilled in the art, an eccentric shaft is generally understood as a device that converts the torque of a central shaft into eccentric circular motion, thus implying a fixed connection between the eccentric shaft and the central shaft. This application, however, breaks with conventional thinking by using a hollow, "free" eccentric shaft that can rotate freely around a central shaft. This design offers the following advantages compared to the eccentric shaft in an RV reducer:

[0046] 1. By separating the input and output, the structure of the previous sun gear driving the planetary gear input can be eliminated.

[0047] 2. The rotating arm shaft runs through it, providing reliable support for the cycloidal wheel's movement and enabling a single-sided planetary carrier. In contrast, the RV reducer uses planetary carriers on both sides, with holes drilled in the cycloidal wheel and a through-hole reinforced connecting shaft to securely connect the front and rear planetary carriers. This increases the difficulty of machining and installation, occupies valuable effective area of ​​the cycloidal wheel, and limits output capacity.

[0048] 3. A single-sided planetary carrier and pin gear housing can be rotatably connected using cross-roller bearings. This allows the impact force from external bending moments to be transmitted directly between the pin gear housing and the planetary carrier, avoiding the need for the precision cycloidal gear and pin gears. In contrast, the RV reducer has a parallelogram structure where the front and rear planetary carriers are connected by a through-core reinforced connecting shaft. External bending moment impacts would inevitably be transmitted through the front and rear planetary carriers, causing the parallelogram to twist and deform, which would then affect the cycloidal gear and pin gears. Therefore, the seemingly simple free eccentric shaft hollow bore design solves a crucial problem.

[0049] Optionally, in one embodiment, the precision cycloidal pinwheel reducer may include multi-stage reduction mechanisms to form a cascaded cycloidal pinwheel reducer. The basic structure of each stage of the reduction mechanism is similar to that in Figure 1. The pin gear housing is shared by each stage of the reduction mechanism, and the planetary carrier of the adjacent preceding stage reduction mechanism is fixedly connected to the suspended input shaft of the following stage reduction mechanism and rotates coaxially.

[0050] Figure 6 shows a two-stage cascaded cycloidal pinwheel reducer, including two-stage reduction mechanisms 6 and 7. Reduction mechanisms 6 and 7 each include multiple cycloidal wheels 5 and multiple free eccentric shafts 3 belonging to their respective stages. The pin gear housing 11 is shared by both stages of reduction mechanisms 6 and 7. As shown in Figure 7, the cascaded planetary carrier 8 includes the swing arm shaft 82 of the preceding stage and the input shaft 81 of the following stage.

[0051] Those skilled in the art will understand that more stages of reduction gears can also be cascaded in a manner similar to Figure 6.

[0052] In the multi-stage reduction mechanism of the cascaded cycloidal pinwheel reducer, the number of cycloidal teeth of each cycloidal wheel 5 inside each stage of the reduction mechanism is equal and less than the number of pin teeth 12 in the pin tooth housing 11. However, the number of cycloidal teeth between different stages can be the same or different, so that various different transmission ratios can be combined.

[0053] The advantage of the cascaded cycloidal pinwheel reducer in this application embodiment is that it only requires adding a cycloidal pinwheel and a cascaded planetary carrier to add a reduction stage. By flexibly configuring cycloidal pinwheels with different tooth counts (one-tooth difference, two-tooth difference, three-tooth difference, etc.) in different stages of the reduction mechanism, a rich series of transmission ratios can be formed, which can directly replace existing cascaded involute gear planetary reducers. Cycloidal pinwheels are more suitable for molding with materials such as nylon than involute gears, thus having broad market prospects.

[0054] Compared with existing cycloidal pinwheel reducers and RV reducers, it is easy to see that the present invention effectively combines the advantages of these two types of reducers and successfully eliminates their respective disadvantages, making it superior to existing products in all aspects.

[0055] In summary, by eliminating the front involute spur gear reduction section, thereby eliminating over-constraint; and further eliminating the rear planetary carrier and the reinforced connecting shaft of the through-cycloidal wheel connecting the front and rear planetary carriers, the embodiments of this application have the following advantages compared to existing RV reducers:

[0056] 1. Long service life, reaching the same level as cycloidal pinwheel reducers, i.e., tens of thousands of hours.

[0057] 2. Output capability has been further improved.

[0058] 3. The simplified structure greatly reduces the difficulty of processing and assembly, thus lowering costs.

[0059] 4. Significantly improves bending moment stiffness and torsional stiffness, further enhancing impact resistance.

[0060] 5. The use of a sandwich-type triple cycloidal wheel further increases output capacity, improves transmission accuracy, and reduces vibration and jitter. It is ideal for high-precision applications such as robotics.

[0061] 6. Multi-stage reducers employing cascaded planetary carriers can flexibly configure transmission ratios through the sharing of pinion gears, resulting in a diverse product line. Furthermore, they can be mass-produced using compression molding. With their absolute advantages in output capacity, transmission accuracy, transmission efficiency, and impact resistance, they can completely replace existing multi-stage involute gear planetary reducers.

[0062] It should be noted that, in this disclosure, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one" does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. In this application, if reference is made to performing an action based on an element, it means performing the action at least based on that element, including two cases: performing the action only based on that element, and performing the action based on that element and other elements. Expressions such as "multiple," "repeatedly," and "various" include two, two times, two kinds, and more than two, more than two times, and more than two kinds.

[0063] This specification includes combinations of various embodiments described herein. Individual references to embodiments (e.g., “one embodiment”, “some embodiments”, or “preferred embodiments”) do not necessarily refer to the same embodiment; however, these embodiments are not mutually exclusive unless indicated to be mutually exclusive or are readily apparent to those skilled in the art. It should be noted that the word “or” is used in a non-exclusive sense throughout this specification unless the context explicitly indicates or requires it.

[0064] All references to this application are considered to be incorporated in their entirety into the disclosure of this application so that they can serve as a basis for modifications if necessary. Furthermore, it should be understood that after reading the contents of this application, those skilled in the art can make various alterations or modifications to this application, and these equivalent forms also fall within the scope of protection claimed in this application.

Claims

1. A precision cycloidal pinwheel reducer, characterized in that, include: The base, multiple cycloidal wheels, a suspended input shaft, a planetary carrier with multiple rotating arm shafts, and a free eccentric shaft sleeved on each of the rotating arm shafts; The base includes a needle-tooth shell, and the inner wall of the needle-tooth shell is provided with a plurality of needle teeth; The edge of the cycloidal wheel includes multiple cycloidal teeth that mate with the needle teeth, the number of cycloidal teeth being less than the number of needle teeth; the free eccentric shaft includes a through hollow shaft hole and a number of first eccentric shaft segments equal to the number of cycloidal wheels, each first eccentric shaft segment corresponding to one cycloidal wheel; the cycloidal wheel is provided with a shaft hole that mates with the first eccentric shaft segment; the rotating arm shaft passes through the hollow shaft hole of the free eccentric shaft; the free eccentric shaft passes through the shaft holes of each cycloidal wheel in each of its first eccentric shaft segments, forming a rotational connection of inner and outer layers; The suspended input shaft includes a central shaft and a number of second eccentric shaft segments equal to the number of cycloidal wheels. Each second eccentric shaft segment passes through the center of one of the cycloidal wheels and is rotatably connected to that cycloidal wheel. The central shaft is used to input external torque to drive each of the second eccentric shaft segments to rotate. The suspended input shaft is only directly rotatably connected to each of the cycloidal wheels in each of the second eccentric shaft segments, and the suspended input shaft is not directly rotatably connected to the base or the planetary carrier.

2. The precision cycloidal pinwheel reducer as described in claim 1, characterized in that, When the suspended input shaft rotates, each of the second eccentric shaft segments on the suspended input shaft drives each of the cycloidal wheels to oscillate along the eccentric circumference, causing the cycloidal teeth on the edge of the cycloidal wheel to contact and mesh with the needle teeth on the needle tooth shell, resulting in the rotation of the cycloidal wheel; when the cycloidal wheel oscillates, it drives each of the free eccentric shafts passing through the shaft hole of the cycloidal wheel to rotate synchronously, and applies radial force and planetary torque to each of the free eccentric shafts; each of the free eccentric shafts further transmits planetary torque to the rotating arm shaft passing through its center, causing the rotating arm shaft to rotate as well; the torques on each of the rotating arm shafts are combined to form the output torque of the planetary carrier.

3. The precision cycloidal pinwheel reducer as described in claim 1, characterized in that, The planetary carrier also includes an output shaft for outputting the output torque of the planetary carrier outward.

4. The precision cycloidal pinwheel reducer as described in claim 3, characterized in that, A rolling bearing is provided between the base and the output shaft of the planetary carrier. The inner ring of the rolling bearing is fixedly connected to the output shaft, and the outer ring of the rolling bearing is fixedly connected to the base.

5. The precision cycloidal pinwheel reducer as described in claim 4, characterized in that, The rolling bearing is a crossed roller bearing.

6. The precision cycloidal pinwheel reducer as described in claim 1, characterized in that, Each of the first eccentric shaft segments and each of the second eccentric shaft segments has the same eccentricity.

7. The precision cycloidal pinwheel reducer as described in claim 1, characterized in that, The number of shaft holes on each of the cycloidal wheels that mate with the first eccentric shaft segment of the free eccentric shaft is equal to the number of the swivel arm shafts.

8. The precision cycloidal pinwheel reducer as described in claim 1, characterized in that, It includes three cycloidal wheels, wherein the two side cycloidal wheels located on both sides have the same eccentric angle and differ from the eccentric angle of the central cycloidal wheel by 180°; the two side cycloidal wheels have the same thickness and are half the thickness of the central cycloidal wheel.

9. The precision cycloidal pinwheel reducer as described in any one of claims 1-8, characterized in that, It includes a multi-stage reduction mechanism, the pin tooth housing is shared by the multi-stage reduction mechanism, the planetary carrier of the adjacent front-stage reduction mechanism is fixedly connected to the suspended input shaft of the rear-stage reduction mechanism and rotates coaxially, and each stage reduction mechanism includes multiple cycloidal wheels and multiple free eccentric shafts belonging to this stage.

10. The precision cycloidal pinwheel reducer as described in claim 9, characterized in that, Different grades of cycloidal wheels have different numbers of cycloidal teeth.

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