Precision cycloid reducer

Abstract

A precision cycloid pinwheel reducer uses a free eccentric shaft (3) and a suspended input shaft (4). The free eccentric shaft (3) is sleeved on a rotating arm shaft (21) through its hollow shaft hole, and each cycloid wheel (5) is sleeved on each eccentric shaft segment of the free eccentric shaft (3) through its shaft hole, forming an inner and outer two-layer rotation connection. In addition, the suspended input shaft (4) is directly rotationally connected to each cycloid wheel (5) only at each eccentric shaft segment, and is not directly rotationally connected to a base (1) or a planetary carrier (2), thereby being suspended from the base (1) and the planetary carrier (2). This special design not only reduces the radial force borne by the input shaft, allowing the use of a thinner input shaft, but also has a long service life and low manufacturing precision requirements.

Description

Technical Field

[0001] The present application relates to a reducer, and in particular to a cycloid pinwheel reducer. Background Art

[0002] This section is intended to provide a background or context for the embodiments of the present application as stated in the claims. The contents in this section are for reference only and do not constitute an admission or confirmation that they are prior art that has been disclosed.

[0003] Cycloidal pinwheel transmission technology was originally invented in Germany in 1937. After Japan acquired the patent rights in 1939, it successfully developed cycloidal pinwheel reducers with high transmission ratios. This technology has been widely used in various industries worldwide and continues to be used today. Its operating principle is that the cycloidal wheel, driven by a central input eccentric shaft, oscillates along an eccentric circle, meshing with the pinion teeth. Based on the principle of small tooth difference, each rotation of the cycloidal wheel causes relative rotation between it and the pinion housing, with the rotation angle corresponding to the small tooth difference. This rotation is transmitted to the planetary carrier output via the cycloidal 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 they must withstand significant radial forces, the central input eccentric shaft must be extremely large. This, in turn, consumes valuable effective area of ​​the cycloidal wheel, preventing further increases in the diameter of the arm hole, thus limiting further increases in output capacity.

[0004] To address this issue, Teijin Seiki (now Nabtesco Corporation) developed the RV reducer in 1985. While retaining the cycloid pinwheel reducer, this device eliminated the central input eccentric shaft and introduced a parallel double crank (or parallel four-bar linkage) mechanism, unifying the input and output onto multiple crankshafts surrounding the cycloid gear. This improvement, by eliminating the central eccentric shaft, gave the RV reducer the highest output capacity and stiffness 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 through the sun gear, driving each crank to achieve synchronous input. While this design solved the synchronous input problem, it also introduced an overconstraint (or over-positioning) problem: the axial hole in the cycloid gear already constrained the phase synchronization of the cranks, 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 overconstraint. This design not only requires extremely high manufacturing precision, but may also affect the service life, so that even the most well-made RV reducer has a service life of only 6,000 hours, which is far lower than the tens of thousands of hours of service life of traditional cycloid pinwheel reducers.

[0005] The industry is seeking to develop a new type of precision cycloid reducer that combines the advantages of traditional cycloid reducers and RV reducers. Specifically, this new reducer needs to have the following features: Compared with traditional cycloid reducers, its input shaft is subject to less radial force, allowing the use of a thinner input shaft, leaving more space for the output mechanism. Furthermore, compared with RV reducers, this new reducer should have a longer service life and lower manufacturing precision requirements to reduce production costs and improve production efficiency. Such technological innovations will provide more efficient and economical power transmission solutions for various industries. Summary of the Invention

[0006] The purpose of this application is to provide a precision cycloid pinwheel reducer, which not only reduces the radial force borne by the input shaft and allows the use of a thinner input shaft, but also has a long service life and low manufacturing precision requirements.

[0007] The present application discloses a precision cycloid pinwheel reducer, comprising: a base, a plurality of cycloid wheels, a suspended input shaft, a planetary carrier with a plurality of swing arm shafts, and a free eccentric shaft sleeved on each of the swing arm shafts; the base comprises a pin gear housing, a plurality of pin teeth are provided on the inner wall of the pin gear housing; the edge of the cycloid wheel comprises a plurality of cycloid teeth matching the pin teeth, the number of the cycloid teeth being less than the number of the pin teeth; the free eccentric shaft comprises a through hollow shaft hole and a number of first eccentric shaft segments equal to the number of the cycloid wheels, each first eccentric shaft segment corresponds to one of the cycloid wheels; the cycloid wheel is provided with a shaft hole matching the first eccentric shaft segment ; The swing arm shaft passes through the hollow shaft hole of the free eccentric shaft; the free eccentric shaft passes through the shaft hole of each cycloid wheel at its each first eccentric shaft segment respectively, forming an inner and outer two-layer rotation connection; the suspended input shaft includes a central shaft and second eccentric shaft segments equal in number to the cycloid wheels, each of the second eccentric shaft segments passes through the center of a cycloid wheel and is rotationally connected to the cycloid wheel; the central shaft is used to input external torque to drive each second eccentric shaft segment to rotate; the suspended input shaft is directly rotationally connected to each cycloid wheel only at each second eccentric shaft segment, and the suspended input shaft is not directly rotationally connected to the base or the planetary carrier.

[0008] In a preferred example, when the suspended input shaft rotates, the second eccentric shaft segments on the suspended input shaft drive the cycloid wheels to swing along the eccentric circle, so that the cycloid teeth on the edge of the cycloid wheel contact and engage with the needle teeth on the pinion housing, causing the cycloid wheel to rotate; when the cycloid wheel swings, it drives the free eccentric shafts passing through the axial hole of the cycloid wheel to rotate synchronously, and applies radial force and planetary torque to each free eccentric shaft; each free eccentric shaft further transmits the planetary torque to the swing arm shaft passing through its center, so that the swing arm shaft also rotates accordingly; the torque applied to each swing arm shaft is synthesized into the output torque of the planetary carrier.

[0009] In a preferred example, the planet carrier further includes an output shaft for outputting the output torque of the planet carrier outward.

[0010] In a preferred example, 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.

[0011] In a preferred example, the rolling bearing is a cross roller bearing.

[0012] In a preferred embodiment, three cycloid wheels are included, wherein the eccentric angles of the two side cycloid wheels on both sides are the same and differ by 180° from the eccentric angle of the middle cycloid wheel in the center; the thickness of the two side cycloid wheels is equal and is half the thickness of the middle cycloid wheel.

[0013] In a preferred example, each of the first eccentric shaft segments and each of the second eccentric shaft segments have the same eccentricity.

[0014] In a preferred embodiment, the number of shaft holes on each of the cycloid wheels that cooperate with the first eccentric shaft segment of the free eccentric shaft is equal to the number of the rotating arm shafts.

[0015] In a preferred example, it includes a multi-stage reduction mechanism, the pinion housing is shared by the multi-stage reduction mechanism, the planetary carriers of the adjacent front-stage reduction mechanism are fixedly connected to the suspended input shaft of the rear-stage reduction mechanism and rotate coaxially, and each stage of the reduction mechanism includes multiple cycloid wheels and multiple free eccentric shafts belonging to this stage.

[0016] In a preferred embodiment, the numbers of cycloid teeth of cycloid wheels at different stages are different.

[0017] In an embodiment of the present application, the free eccentric shaft is sleeved on the arm shaft through its hollow shaft hole, and each cycloid wheel is sleeved on each eccentric shaft segment of the free eccentric shaft through its shaft hole, forming an inner and outer rotational connection (the inner rotational connection is between the free eccentric shaft and the arm shaft, and the outer rotational connection is between the free eccentric shaft and the cycloid wheel). In addition, the suspended input shaft is directly rotationally connected to each cycloid wheel only at each eccentric shaft segment, and is not directly rotationally connected to the base or the planetary carrier, thereby being suspended above the base and the planetary carrier. This special design greatly reduces the maximum radial force that the input shaft may withstand, allowing the input shaft diameter to be relatively small, and thus allowing the cycloid wheel diameter to be reduced accordingly. As a result, the diameter and weight of the entire cycloid pinwheel reducer are reduced, and it has a higher torque density, which is extremely important for applications requiring high precision such as robots and surgical machinery. In comparison, the input shaft of a traditional cycloid reducer is not only directly connected to the cycloid gear but also to the base or planetary carrier. During operation, the input shaft must withstand the full radial force from the pinion teeth, sometimes even causing the input shaft to break. To prevent this, the input shaft is typically designed to be thicker, occupying a larger portion of the cycloid gear's center space. This forces the cycloid gear to be larger, increasing the diameter and weight of the entire device.

[0018] Furthermore, simply by adding a cycloid gear and a cascade planetary carrier, a reduction mechanism can be added, creating a cascaded cycloid reducer. By using cycloid gears with different tooth differences (e.g., one, two, or three) in the reduction mechanisms at different stages, a diverse range of transmission ratios can be constructed, directly replacing existing cascaded involute planetary reducers.

[0019] The various technical features disclosed in the above invention content, the various technical features disclosed in the various embodiments and examples below, and the various technical features disclosed in the accompanying drawings can be freely combined with each other to form various new technical solutions (all of which should be deemed to have 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 play the same role. Technically, only one of them needs to be used, and it is impossible to use them at the same time. Feature E can be technically combined with feature C. In this case, the solution of A+B+C+D should not be deemed to have been recorded because it is technically infeasible, while the solution of A+B+C+E should be deemed to have been recorded. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a simplified motion diagram of the transmission mechanism of a precision cycloid pinwheel reducer according to one embodiment of the present application;

[0021] Figure 2This is an appearance diagram of a precision cycloid pinwheel reducer according to one embodiment of the present application;

[0022] Figure 3 This is a parts diagram of a precision cycloid pinwheel reducer according to one embodiment of the present application;

[0023] Figure 4 is a horizontal cross-sectional view of a precision cycloid pinwheel reducer according to one embodiment of the present application;

[0024] Figure 5 is a vertical cross-sectional view of a precision cycloid pinwheel reducer according to one embodiment of the present application;

[0025] Figure 6 This is a simplified motion diagram of the transmission mechanism of the cascade cycloid pinwheel reducer according to one embodiment of the present application;

[0026] Figure 7 This is a structural diagram of a cascade planetary carrier of a cascade cycloid pinwheel reducer according to an embodiment of the present application.

[0027] The reference numerals used in the drawings are summarized as follows:

[0028] 1: Base

[0029] 11: Needle gear housing

[0030] 12: Needle teeth

[0031] 13: Back cover

[0032] 14: Rolling bearings

[0033] 15: Gap

[0034] 16: Output bearing

[0035] 2: Planet carrier

[0036] 21: Arm shaft

[0037] 22: Output shaft

[0038] 3: Free eccentric shaft

[0039] 4: Suspended input shaft

[0040] 5: Cycloid wheel

[0041] 6: One-stage reduction mechanism

[0042] 7: Two-stage reduction mechanism

[0043] 8: Cascade planetary carrier

[0044] 81: Rear stage input shaft

[0045] 82: Front stage arm shaft DETAILED DESCRIPTION

[0046] In the following description, many technical details are provided to help readers better understand this application. However, those skilled in the art will understand that even without these technical details and various changes and modifications based on the following embodiments, the technical solutions claimed in this application can be implemented.

[0047] In order to make the objectives, technical solutions and advantages of this application clearer, the implementation methods of this application will be further described in detail below with reference to the accompanying drawings.

[0048] The embodiment of the present application relates to a precision cycloid reducer, such as Figure 1-Figure 5 As shown, the precision cycloid pinwheel reducer includes a base 1, a plurality of cycloid wheels 5, a suspended input shaft 4, a planetary carrier 2 with a plurality of rotating arm shafts 21, and a free eccentric shaft 3 sleeved on each rotating arm shaft 21.

[0049] The base 1 includes a needle tooth housing 11 , and a plurality of needle teeth 12 are provided on the inner wall of the needle tooth housing 11 .

[0050] The edge of the cycloid wheel 5 includes a plurality of cycloid teeth that match the needle teeth 12, and the number of the cycloid teeth is less than the number of the needle teeth 12. It can be one tooth difference, two teeth difference, three teeth difference, etc.

[0051] 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. Each first eccentric shaft segment corresponds to a cycloidal wheel 5. The cycloidal wheels 5 are provided with shaft holes that mate with the first eccentric shaft segments. The pivot arm shaft 21 passes through the hollow shaft hole of the free eccentric shaft 3. The free eccentric shaft 3, in each of its first eccentric shaft segments, passes 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 pivot arm shafts 21.

[0052] 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 rotationally connected to the cycloidal wheel 5. Each first eccentric shaft segment and each second eccentric shaft segment have the same eccentricity. The central shaft refers to the non-eccentric shaft end connected to an external power component (such as an electric motor) and is used to input external torque to drive the rotation of each second eccentric shaft segment. The suspended input shaft 4 is directly rotationally connected to each cycloidal wheel 5 only at each second eccentric shaft segment. The suspended input shaft 4 is not directly rotationally connected to the base 1 or the planetary carrier 2.

[0053] The input shaft of an existing cycloid pinwheel reducer is usually not only rotationally connected to the cycloid wheel, but also directly rotationally connected to the base or planetary carrier through bearings and the like. However, the suspended input shaft of the embodiment of the present application is only directly rotationally connected to the cycloid wheel, and a gap is left between it and the base (such as the back cover of the pinion housing, etc.), with no contact and no direct connection. The advantage of this is that when the input shaft is subjected to radial force, it will produce a slight displacement and deformation, so that most of the radial force is borne by the free eccentric shaft. This ingenious design greatly reduces the stress on the input shaft, thereby reducing the shaft diameter, giving the effective area of ​​the cycloid wheel to the swing arm hole, and enabling the use of a thick swing arm shaft, which greatly improves the output capacity.

[0054] When the suspended input shaft 4 is rotated by external motor components, the secondary eccentric shaft segments on the suspended input shaft 4 drive the cycloid wheels 5 to oscillate along an eccentric circle, causing the cycloid teeth on the edge of the cycloid wheels 5 to engage with the pin teeth 12 on the pinion housing 11, causing the cycloid wheels 5 to rotate. As the cycloid wheels 5 oscillate, they drive the free eccentric shafts 3 passing through the axial holes of the cycloid wheels 5 to rotate synchronously, applying radial forces and planetary torques to each free eccentric shaft 3. Each free eccentric shaft 3 further transmits the planetary torque to the pivot arm shaft 21 passing through its center, causing the pivot arm shaft 21 to rotate accordingly. The torques acting on each pivot arm shaft 21 are combined to form the output torque of the planetary carrier 2.

[0055] The planet carrier 2 further includes an output shaft 22 for outputting the output torque of the planet carrier 2 outward.

[0056] exist Figure 3 and Figure 4 In the example shown in FIG, the planet carrier 2 has three rotating arm shafts 21 . In other embodiments, the planet carrier 2 may have more rotating arm shafts 21 .

[0057] The embodiment of the present application eliminates the over-constraint problem of the RV reducer through the structure of a free eccentric shaft and a suspended input shaft, and also solves the problem of the cycloid pinwheel reducer input shaft being too thick. Specifically, the suspended input shaft in the center drives the cycloid wheel to swing along an eccentric circle (the shaft is an eccentric shaft, which is only connected to the cycloid wheel for rotation, and maintains a gap with the base, and is not directly connected to the planetary carrier, and is "suspended" on the base and the planetary carrier). The free eccentric shafts on each arm shaft rotate synchronously with the swing of the cycloid wheel, and are subjected to huge radial forces and output torques; the suspended input shaft is only responsible for transmitting the swing torque to the cycloid wheel, and no longer bears huge radial forces (the central axis of the free eccentric shaft is a hollow shaft hole, which is connected to the arm shaft passing through the shaft hole for rotation and can rotate freely around it). In this way, the suspended input shaft in the center no longer needs a large diameter, which frees up the valuable effective area of ​​the cycloid wheel. Thanks to this, the cycloid wheel has a large diameter arm hole, which greatly improves the output capacity. At the same time, it is easy to imagine that since the front-stage reduction part is removed, the over-constraint similar to the RV reducer no longer exists, which greatly improves the service life.

[0058] Preferably, in one embodiment, the precision cycloid pinwheel reducer includes three cycloid wheels 5, wherein the eccentric angles of the two side cycloid wheels 5 located on both sides are the same, and differ by 180° from the eccentric angle of the middle cycloid wheel 5 in the center. The thickness of the two side cycloid wheels 5 is equal and is half the thickness of the middle cycloid wheel 5. Optionally, in one embodiment, all cycloid wheels 5 use the same material. Optionally, in one embodiment, the cycloid wheels 5 can also use different materials, and the mass of the middle cycloid wheel 5 is equal to the sum of the masses of the two outer cycloid wheels 5, and the thickness of the two outer cycloid wheels 5 may not be equal. Optionally, in one embodiment, 2 or more cycloid wheels 5 can also be used.

[0059] Currently, most cycloidal pinwheel reducers on the market utilize a two-cycloidal gear configuration, coupled with eccentric shafts offset by 180°, to offset most radial vibrations. However, because the radial forces do not act at the same point, a certain bending moment still exists. This bending moment, acting at the base of the swing arm, can still affect output capacity and stiffness. This application proposes a "sandwich" structure combining three cycloidal gears: a central cycloidal gear and two side cycloidal gears. The eccentric shaft segments corresponding to the two side cycloidal gears have the same eccentric angle and are 180° offset from the central eccentric shaft segment. The thickness of the two side cycloidal gears is equal and half that of the central cycloidal gear. This structure completely offsets all vibrations and bending moments, resulting in very smooth and quiet operation. While slightly more complex, it does not increase volume or weight, making it ideal for high-precision applications such as robotics. Under the same conditions, the use of a "sandwich" three-cycloidal gear structure can significantly improve the backlash accuracy of the reducer.

[0060] 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, a cross-roller bearing can be used as the rolling bearing 14. Using a cross-roller bearing as 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 transmitted directly between the output shaft 22 and the base 1 without affecting the precise cycloid gear structure. This greatly improves rigidity and impact resistance. Of course, in some embodiments, other types of rolling bearings can also be used.

[0061] In the embodiments of the present application, the free eccentric shaft is a combination of multiple eccentric shafts with a hollow central axis. The number of eccentric shaft segments is equal to the number of cycloidal wheels. The cycloidal wheel is mounted on the pivot arm shaft and is rotationally connected to the pivot arm shaft. The cycloidal wheel has a corresponding axial hole through which the free eccentric shaft passes and is rotationally connected to the cycloidal wheel. The suspended input shaft is a solid shaft, a combination of multiple eccentric shaft segments. The number of eccentric shaft segments is 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 eccentric angle. It is easy to imagine that when an external input source drives the suspended input shaft to rotate, it drives each cycloidal wheel to oscillate (translate) along the eccentric circumference, further causing the cycloidal teeth on the edge of the cycloidal wheel to contact and engage with the corresponding pin teeth on the pinion housing. At the same time, based on the principle of small tooth difference planetary transmission, the cycloidal wheel rotates at a slow planetary speed. As the cycloidal wheel oscillates one circle, it synchronously rotates through the number of teeth that are less than the total number of pin teeth in a slow planetary rotation. On the other hand, when the cycloid wheel swings, it drives the free eccentric shafts to rotate synchronously, applying radial force and planetary torque to the free eccentric shafts. The free eccentric shafts further transmit the planetary torque to the arm shaft passing through their center. The torque received by each arm is combined to form the output torque of the planetary carrier.

[0062] For those skilled in the art, an eccentric shaft is generally understood as a device that converts central shaft torque into eccentric circular motion, and therefore the eccentric shaft is necessarily fixedly connected to the central shaft. However, this application breaks with conventional thinking and uses a hollow, "free" eccentric shaft that can rotate freely around the central shaft. This design has the following advantages over the eccentric shaft of an RV reducer:

[0063] 1. The input and output are separated, eliminating the structure where the front-stage sun gear drives the planetary gear input.

[0064] 2. The arm shaft runs through it, providing reliable support for the cycloid gear's movement and achieving a single-sided planetary carrier. The RV reducer, on the other hand, uses two-sided planetary carriers, with holes drilled in the cycloid gear and a through-hole reinforced connecting shaft installed to securely connect the front and rear planetary carriers. This makes processing and installation difficult, occupies valuable cycloid gear area, and limits output capacity.

[0065] 3. The single-sided planetary carrier and pinion housing can be rotatably connected using a cross-roller bearing. This allows external bending moment impact forces to be transmitted directly between the pinion housing and the planetary carrier, avoiding the delicate cycloid gear and pinion gears. However, in an RV reducer, the front and rear planetary carriers are connected by a through-core reinforced connecting shaft to form a parallelogram. External bending moment impacts are inevitably transmitted through the front and rear planetary carriers, causing distortion of the parallelogram and, in turn, affecting the cycloid gear and pinion gears. Therefore, the seemingly simple design of a free eccentric shaft with a hollow shaft hole solves a critical problem.

[0066] Optionally, in one embodiment, the precision cycloid reducer may include a multi-stage reduction mechanism to form a cascade cycloid reducer. The basic structure of each stage reduction mechanism is Figure 1 The pinion gear housing is shared by all levels of reduction mechanisms, and the planetary carriers of the adjacent front-stage reduction mechanisms are fixedly connected to the suspended input shafts of the rear-stage reduction mechanisms and rotate coaxially.

[0067] Figure 6 The figure shows a two-stage cascade cycloid pinwheel reducer, which includes two-stage reduction mechanisms 6 and 7. The reduction mechanisms 6 and 7 respectively include multiple cycloid wheels 5 and multiple free eccentric shafts 3 belonging to the same stage. The pin gear housing 11 is shared by the two-stage reduction mechanisms 6 and 7. Figure 7 As shown, the cascade planet carrier 8 includes a swing arm shaft 82 of the previous stage and an input shaft 81 of the next stage.

[0068] Those skilled in the art will appreciate that similar Figure 6 More stages of reduction mechanisms are cascaded in a manner.

[0069] In the multi-stage reduction mechanism of the cascaded cycloid pinwheel reducer, the number of cycloid teeth of each cycloid wheel 5 inside each stage of the reduction mechanism is equal and is smaller than the number of pin teeth 12 in the pin gear housing 11, but the number of cycloid teeth between different stages can be the same or different, so that various transmission ratios can be combined.

[0070] The advantage of the cascaded cycloid reducer in the embodiments of the present application is that a single reduction stage can be added simply by adding a cycloid gear and a cascaded planetary carrier. By flexibly configuring cycloid gears with varying tooth counts (e.g., one-, two-, or three-tooth differences) at different reduction stages, a rich range of transmission ratios can be created, allowing for direct replacement of existing cascaded involute planetary reducers. Cycloid gears are more suitable for molding with materials such as nylon than involute gears, and therefore have broad market prospects.

[0071] Compared with the existing cycloid pinwheel reducers and RV reducers, it is easy to see that the present invention well combines the advantages of these two types of reducers and successfully eliminates their respective shortcomings, and is superior to the existing products in all aspects.

[0072] In summary, since the front-stage involute spur gear reduction unit is removed, thereby eliminating overconstraint, and the rear planetary carrier and the reinforced connecting shaft that connects the front and rear planetary carriers and passes through the cycloid gear are further removed, the embodiment of the present application has the following advantages over the existing RV reducer:

[0073] 1. Long service life, which can reach the same level as the cycloid pinwheel reducer, that is, tens of thousands of hours.

[0074] 2. Output capacity is further improved.

[0075] 3. The structure is simplified, the difficulty of processing and assembly is greatly reduced, and the cost is reduced.

[0076] 4. The bending moment rigidity and torque rigidity are greatly improved, and the impact resistance is further improved.

[0077] 5. The use of a sandwich-type three-cycloid wheel can further increase output capacity, improve transmission accuracy, and reduce vibration and jitter. It is very suitable for high-precision applications such as robots.

[0078] 6. Multi-stage reducers using cascade planetary carriers can flexibly configure transmission ratios by sharing pin gears, creating a rich 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 are poised to replace existing multi-stage involute gear planetary reducers.

[0079] It should be noted that, in the disclosure, relational terms such as first and second are merely used to distinguish one entity or operation from another, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprise," "include," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article, or device. Without further restriction, an element defined by the phrase "comprising a" does not exclude the presence of other identical elements in the process, method, article, or device comprising the element. In this application, if it is mentioned that an action is performed according to a certain element, it means that the action is performed at least according to that element, including two situations: performing the action only according to that element, and performing the action according to that element and other elements. Expressions such as "multiple," "multiple," and "multiple" include 2, 2 times, 2 kinds, and more than 2, more than 2 times, and more than 2 kinds.

[0080] This specification includes combinations of the various embodiments described herein. Separate references to an embodiment (e.g., "one embodiment" or "some embodiments" or "preferred embodiments") do not necessarily refer to the same embodiment; however, these embodiments are not mutually exclusive unless indicated as such or clear to one skilled in the art. It should be noted that the word "or" is used in this specification in a non-exclusive sense unless the context clearly indicates or requires otherwise.

[0081] All documents mentioned in this application are considered to be included in their entirety in the disclosure of this application so that they can be used as a basis for modification when necessary. In addition, it should be understood that after reading the contents of this application, those skilled in the art may make various changes or modifications to this application, and these equivalent forms also fall within the scope of protection claimed in this application.

Claims

1. A precision cycloid pinwheel reducer, characterized in that: include: A base, a plurality of cycloid wheels, a suspended input shaft, a planet carrier having a plurality of rotating arm shafts, and a free eccentric shaft sleeved on each of the rotating arm shafts; The base includes a needle tooth housing, and a plurality of needle teeth are provided on the inner wall of the needle tooth housing; The edge of the cycloid wheel includes a plurality of cycloid teeth that cooperate with the needle teeth, and the number of the cycloid teeth is less than the number of the 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 the cycloid wheels, and each first eccentric shaft segment corresponds to one of the cycloid wheels; the cycloid wheel is provided with a shaft hole that cooperates 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 cycloid wheels at each of its first eccentric shaft segments, forming a rotational connection between the inner and outer layers; The suspended input shaft includes a central shaft and second eccentric shaft segments equal in number to the cycloidal wheels, each of the second eccentric shaft segments passes through the center of a cycloidal wheel and is rotatably connected to the cycloidal wheel; the central shaft is used to input external torque to drive the second eccentric shaft segments to rotate; the suspended input shaft is directly rotatably connected to the cycloidal wheels only at 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 cycloid reducer according to claim 1, characterized in that: When the suspended input shaft rotates, the second eccentric shaft segments on the suspended input shaft drive the cycloid wheels to swing along the eccentric circle, so that the cycloid teeth on the edge of the cycloid wheel are in contact and mesh with the pin teeth on the pin gear housing, causing the cycloid wheel to rotate. When the cycloid wheel swings, it drives the free eccentric shafts passing through the axial hole of the cycloid wheel to rotate synchronously, and applies radial force and planetary torque to each free eccentric shaft. Each free eccentric shaft further transmits the planetary torque to the swing arm shaft passing through its center, causing the swing arm shaft to rotate accordingly. The torque applied to each swing arm shaft is synthesized into the output torque of the planetary carrier.

3. The precision cycloid reducer according to claim 1, characterized in that: The planet carrier further includes an output shaft for outputting the output torque of the planet carrier outward.

4. The precision cycloid reducer according to 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 cycloid reducer according to claim 4, characterized in that: The rolling bearing is a cross roller bearing.

6. The precision cycloid reducer according to claim 1, characterized in that: Each of the first eccentric shaft segments and each of the second eccentric shaft segments have the same eccentricity.

7. The precision cycloid reducer according to claim 1, characterized in that: The number of shaft holes on each cycloid wheel that cooperate with the first eccentric shaft section of the free eccentric shaft is equal to the number of the rotating arm shafts.

8. The precision cycloid reducer according to claim 1, characterized in that: The invention comprises three cycloid wheels, wherein the eccentric angles of the two side cycloid wheels on both sides are the same and differ by 180° from the eccentric angle of the middle cycloid wheel in the middle; the thickness of the two side cycloid wheels is equal and is half of the thickness of the middle cycloid wheel.

9. The precision cycloid reducer according to any one of claims 1 to 8, characterized in that: It includes a multi-stage reduction mechanism, the pin gear housing is shared by the multi-stage reduction mechanism, the planetary carriers of the adjacent front-stage reduction mechanism are fixedly connected to the suspended input shaft of the rear-stage reduction mechanism and rotate coaxially, and each stage of the reduction mechanism includes multiple cycloid wheels and multiple free eccentric shafts belonging to this stage.

10. The precision cycloid reducer according to claim 9, characterized in that: The number of cycloid teeth of cycloid wheels of different stages is different.

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