High-precision heavy-load planetary roller screw electric cylinder

Abstract

The application belongs to the technical field of planetary roller screw actuator, and discloses a high-precision heavy-load planetary roller screw electric cylinder, which comprises a harmonic reducer module, a composite bearing, a screw linear actuator, and a position detection member.

Description

Technical Field

[0001] This invention belongs to the technical field of planetary roller screw actuators, specifically relating to a high-precision heavy-duty planetary roller screw electric cylinder. Background Technology

[0002] Against the backdrop of electrification and high-precision upgrades in industrial equipment, the demand for linear actuators with high load capacity, high precision, and high-speed output capabilities within limited installation space is increasing. Planetary roller screws, due to their multi-threaded meshing and multi-contact force transmission structure, offer higher load-bearing capacity and longer service life than ball screws for the same screw diameter, and are gradually becoming an important transmission form for heavy-duty linear actuators.

[0003] However, when integrating a rotary drive unit with a planetary roller screw into a linear actuator, the support structure at the input end of the screw needs to withstand both axial thrust and radial load simultaneously. Existing technologies typically use crossed roller bearings or angular contact ball bearings to bear the axial and radial loads respectively. The raceways of these bearings are arc-shaped or distributed at 90 degrees, making it difficult to simultaneously achieve high rotational accuracy and large radial load capacity under conventional machining conditions. Furthermore, the separate arrangement of multiple bearings leads to an increase in axial dimensions, which is not conducive to achieving high-precision heavy-load output in a compact space.

[0004] In addition, the position feedback of existing linear actuators is usually taken from the rotary drive end, and the output end position is indirectly obtained through lead screw conversion. Under heavy load conditions, the elastic deformation, thermal deformation and backlash accumulation of the transmission chain will cause deviation between the converted position and the actual output position, making it difficult to meet the requirements of high-precision positioning control. Summary of the Invention

[0005] In view of this, and in response to the problem that existing heavy-duty linear actuators cannot simultaneously handle large loads, high precision, and high-speed response within a limited space, the present invention aims to provide a high-precision heavy-duty planetary roller screw electric cylinder that integrates a composite bearing, a linear screw actuator, and an output position detection component into one unit, thereby achieving high-precision heavy-duty linear output within a limited space.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A high-precision, heavy-duty planetary roller screw electric cylinder includes: Harmonic reduction module is used to provide rotational power after reduction and torque amplification; A composite bearing includes an outer ring, an axial bearing component, a radial bearing component, and an inner ring. The outer ring is fixedly connected to the fixed flange of the harmonic deceleration module via a connecting flange. The axial bearing component and the radial bearing component are both disposed between the outer ring and the inner ring, and provide axial rotational support and radial rotational support for the inner ring, respectively. A linear actuator with a lead screw includes a housing, a lead screw shaft, and an output nut. The housing is fixedly connected to the outer ring of the bearing. The outer ring of the input flange of the lead screw shaft is fixedly connected to the inner ring of the bearing. The inner ring of the input flange is fixedly connected to the output flange of the harmonic reduction module. The output screw of the lead screw shaft is threadedly engaged with the output nut. When the lead screw shaft rotates, it drives the output nut to move linearly along the axial direction. The position detection component includes a moving component and a reading component. The moving component is fixed to the output nut and moves linearly synchronously with the output nut. The reading component is fixed to the housing and detects the linear position of the moving component.

[0007] Preferably, the outer ring of the input flange is provided with an outer ring cavity for fitting the inner ring of the bearing, and the inner ring of the input flange is provided with an inner ring cavity for fitting the output flange, and a convex ring is formed between the outer ring cavity and the inner ring cavity.

[0008] Preferably, the axial bearing member includes a first axial bearing member and a second axial bearing member, the bearing inner ring is embedded in the annular raceway formed by the first axial bearing member, the second axial bearing member and the radial bearing member, and the two end faces of the bearing inner ring are respectively in rolling contact with the first axial bearing member and the second axial bearing member, and the outer side of the bearing inner ring is in rolling contact with the radial bearing member.

[0009] Preferably, the bearing outer ring includes a first bearing outer ring and a second bearing outer ring. The first bearing outer ring has a stepped hole. The first axial bearing member is embedded in one end of the stepped hole. The second axial bearing member is embedded at one end of the stepped hole. The second bearing outer ring is fixedly connected to one end face of the first bearing outer ring to provide support for the second axial bearing member.

[0010] Preferably, the second bearing outer ring includes an outer ring portion fixedly connected to the first bearing outer ring and an inner ring portion fixedly connected to the housing, and a first sealing ring is provided between the outer ring portion and the second bearing outer ring.

[0011] Preferably, a second sealing ring is provided between the outer ring of the bearing and the connecting flange, a third sealing ring is provided between the outer ring of the bearing and the housing, and a fourth sealing ring is provided between the housing and the output nut.

[0012] Preferably, the housing includes a main housing and a housing end cover. The outer ring of the bearing is connected to both ends of the main housing and the housing end cover respectively. A fifth sealing ring is provided between the housing end cover and the main housing. A movable gap for storing lubricating grease is reserved between the main housing and the output nut. A support ring is provided on the inner ring of the front end cover of the housing end cover. The inner circumferential surface of the support ring is slidably supported on the outer circumferential surface of the output nut.

[0013] Preferably, an annular space is formed between the lead screw shaft and the output nut. A plurality of planetary rollers are mounted in the annular space by a cage and are evenly distributed circumferentially. The threaded sections of the planetary rollers respectively mesh with the external thread of the lead screw shaft and the internal thread of the output nut. The inner ring of the output nut is symmetrically provided with internal gear rings at both ends. The threaded sections of the planetary rollers are symmetrically provided with involute external gears that mesh with the internal gear rings.

[0014] Preferably, a axial stop step is provided on one end face of the cage, and a retaining ring that mates with the axial stop step is embedded in the mounting groove of the internal gear ring to limit the axial displacement of the planetary roller.

[0015] Preferably, the output nut is connected to an oil scraper and a nut end cap at both ends, the oil scraper is threaded to the lead screw shaft, and the nut end cap is provided with an anti-collision pad facing the end face of the lead screw shaft; the nut end cap is threaded to the output nut, and the output surface of the nut end cap is configured as a spherical surface.

[0016] Preferably, the moving part is fixed to the outer circumferential surface of the output nut by a bracket, and the housing is provided with a sliding groove through which the bracket can pass; the reading element is fixedly connected to the housing by a protective cover, and the protective cover covers the moving part, the reading element and the sliding groove.

[0017] Compared with the prior art, the present invention has the following advantages: (1) The high-precision heavy-duty planetary roller screw electric cylinder of the present invention integrates the harmonic reduction module, the composite bearing and the linear actuator of the screw in a coaxial manner, thereby effectively shortening the power transmission path and enhancing the overall structural rigidity; the composite bearing simultaneously bears axial and radial loads, effectively suppressing the deflection and vibration of the screw shaft under heavy load; the position detection component directly feeds back the actual displacement of the output nut, realizing precise closed-loop feedback of position under heavy load, and thus achieving a coordinated output of high thrust, high precision and fast response in a compact volume.

[0018] (2) In this invention, an axial positioning structure and a stress isolation zone are formed inside the input flange by means of a convex ring structure, so that the mounting surfaces of the bearing inner ring and the output flange of the harmonic deceleration module are independent of each other, avoiding mutual interference of the assembly preload, thereby improving the coaxiality and repeatability of the rotating support.

[0019] (3) In this invention, the two end faces of the bearing inner ring are provided with bidirectional axial rolling support by the first axial bearing member and the second axial bearing member, respectively, and the outer side of the bearing inner ring is provided with radial rolling support by the radial bearing member, so that the bearing inner ring can maintain high rotational accuracy while bearing bidirectional axial thrust and radial load. Compared with crossed roller or angular contact bearings, it can withstand higher composite loads under the same outer diameter, and has low operating temperature rise and good accuracy retention.

[0020] (4) In this invention, the continuous self-lubrication of the lead screw pair is achieved by storing oil in the active gap, which reduces wear and heat generation; the output nut is provided with additional radial guidance by the support ring, which suppresses its swaying in reciprocating motion and further improves the stability and guiding accuracy of linear motion.

[0021] (5) In this invention, the retaining ring is embedded in the mounting groove of the internal gear ring and cooperates with the shaft stop step of the cage, thereby accurately axially limiting the planetary rollers and their cage, preventing them from moving under high-speed start-stop or impact load, ensuring stable meshing relationship, and avoiding transmission failure or abnormal wear. Attached Figure Description

[0022] Figure 1 This is a three-dimensional structural diagram of the high-precision heavy-duty planetary roller screw electric cylinder of the present invention; Figure 2 This is a three-dimensional sectional view of the high-precision heavy-duty planetary roller screw electric cylinder of the present invention. Figure 3 This is a planar sectional view of the high-precision heavy-duty planetary roller screw electric cylinder of the present invention. Figure 4 This is a three-dimensional sectional view of the composite bearing in this invention; Figure 5 This is a three-dimensional sectional view of the assembly of the lead screw shaft and the output nut in this invention; In the diagram: 1-Harmonic reducer module, 2-Axial bearing component, 3-Radial bearing component, 4-Bearing inner ring, 5-Connecting flange, 6-Fixed flange, 7-Main housing, 8-Lead screw shaft, 9-Output nut, 10-Input flange, 11-Output flange, 12-Moving component, 13-Reading component, 14-Outer ring cavity, 15-Inner ring cavity, 16-Convex ring, 17-First bearing outer ring, 18-Second bearing outer ring, 19-First sealing ring, 20-Second sealing ring, 21-Third sealing ring, 22-Fourth sealing ring, 23-Shell end cap, 24-Fifth sealing ring, 25-Support ring, 26-Planetary roller, 27-Internal gear ring, 28-Cage, 29-Retaining ring, 30-Oil scraper, 31-Nut end cap, 32-Anti-collision pad, 33-Bracket, 34-Protective cover. Detailed Implementation

[0023] To further understand the content of this invention, a detailed description of the invention is provided in conjunction with the accompanying drawings and embodiments. The structures, proportions, sizes, etc., depicted in the accompanying drawings are merely for illustrative purposes and to aid those skilled in the art, and are not intended to limit the implementation conditions of the invention. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to size, without affecting the effects and objectives of the invention, should still fall within the scope of the technical content disclosed in this invention. Furthermore, terms such as "upper," "lower," "left," "right," and "middle" used in this specification are merely for clarity and not intended to limit the scope of implementation. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention. It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this application described herein.

[0024] like Figures 1-5 As shown, the high-precision heavy-duty planetary roller screw electric cylinder provided by the present invention includes a harmonic reduction module 1, a composite bearing, a linear actuator, and a position detection component. Specifically, the harmonic reduction module 1 provides rotational power after reduction and torque amplification, provides rotational support for the linear actuator, the linear actuator performs axial linear motion under the drive of the rotational power, and the position detection component detects the linear motion position in real time.

[0025] In one specific embodiment, the harmonic reduction module 1 includes a power component and a harmonic reduction output component. The harmonic reduction output component is connected to the power shaft of the power component to reduce the rotational power provided by the power component, increase the torque, and then output it outward. Specifically, the power component is usually a servo motor, whose high-speed, low-torque output characteristics are converted into low-speed, high-torque rotational motion through the harmonic reduction output component (harmonic reducer), directly driving the subsequent lead screw pair. This effectively eliminates intermediate transmission links such as couplings and synchronous belts, significantly shortening the axial dimension.

[0026] In one specific embodiment, the composite bearing includes an outer ring, an axial bearing member 2, a radial bearing member 3, and an inner ring 4. The outer ring is fixedly connected to the fixed flange 6 of the harmonic deceleration module 1 via a connecting flange 5. The axial bearing member 2 and the radial bearing member 3 are both disposed between the outer ring and the inner ring 4, and provide axial rotational support and radial rotational support for the inner ring 4, respectively.

[0027] In this embodiment, the bearing outer ring includes a first bearing outer ring 17 and a second bearing outer ring 18. The second bearing outer ring 18 is fixedly connected to one end face of the first bearing outer ring 17. The axial bearing member 2 and the radial bearing member 3 are defined between the first bearing outer ring 17 and the second bearing outer ring 18. A second sealing ring 20 is provided between the first bearing outer ring 17 and the connecting flange 5. The second bearing outer ring 18 includes an outer ring portion fixedly connected to the first bearing outer ring 17. A first sealing ring 19 is provided between the outer ring portion and the second bearing outer ring 18. Both the first sealing ring 19 and the second sealing ring 20 are static seals, mainly used to prevent external dust and moisture from seeping into the precision raceway area inside the bearing along the installation interface.

[0028] In this embodiment, the axial support member 2 includes a first axial support member and a second axial support member. The bearing inner ring 4 is embedded in the annular raceway formed by the first axial support member, the second axial support member, and the radial support member 3. The two end faces of the bearing inner ring 4 roll against the first axial support member and the second axial support member, respectively, and the outer side of the bearing inner ring 4 rolls against the radial support member 3. Both the first and second axial support members include a radial roller cage and radial rollers. The radial roller cage is embedded in the bearing outer ring, and the radial rollers are rotatably embedded in pockets on the end faces of the radial roller cage, fixed at intervals by the radial roller cage. The axis of the radial rollers is parallel to the radial line of the bearing outer ring. Multiple radial rollers are evenly distributed circumferentially around the radial roller cage; their function is to prevent mutual compression of the radial rollers during rolling, maintain a constant spacing, and ensure that the radial rollers have an exposed portion after being pressed into the pockets, thus supporting the cage and preventing contact with the raceway. Furthermore, the radial section of the radial roller cage is T-shaped, and the protruding portion of the T-shaped section of the radial roller cage serves to retain lubricating grease. The radial bearing member 3 is a full-fill cylindrical axial roller structure, arranged on the outer circumferential surface of the bearing inner ring 4; the axial rollers are embedded in the radial raceways on the inner diameter of the bearing outer ring, the radial raceways are annular grooves, and the axis of the radial raceways coincides with the axis of the bearing outer ring, while the center surface of the axial rollers coincides with the center surface of the bearing inner ring.

[0029] Furthermore, a stepped hole is provided in the outer ring 17 of the first bearing. The first axial support member is embedded in one end of the stepped hole, and the second axial support member is embedded at the opening of one end of the stepped hole. The second outer ring 18 of the second bearing is fixedly connected to one end face of the outer ring 17 of the first bearing, providing support for the second axial support member. During assembly, the first axial support member can be placed at the bottom of the stepped hole of the outer ring 17 of the first bearing first, and then the radial support member 3, the inner ring 4 of the bearing, and the second axial support member can be installed in sequence. Finally, the second outer ring 18 of the second bearing is fastened to the end face of the outer ring 17 of the first bearing with screws. The end face clamping force is used to achieve precise pre-tightening of the internal rollers. The stepped hole and the second outer ring 18 cooperate to form a closed raceway space, which effectively prevents the rollers from coming out during operation.

[0030] In one specific embodiment, the lead screw linear actuator includes a housing, a lead screw shaft 8, and an output nut 9. The housing is fixedly connected to the outer ring of the bearing. The outer ring of the input flange 10 of the lead screw shaft 8 is fixedly connected to the inner ring 4 of the bearing. The inner ring of the input flange 10 is fixedly connected to the output flange 11 of the harmonic reduction module 1. The output screw of the lead screw shaft 8 is threadedly engaged with the output nut 9. When the lead screw shaft 8 rotates, it drives the output nut 9 to move linearly along the axial direction.

[0031] It should be noted that the outer ring of the input flange 10 is provided with an outer ring cavity 14 for fitting the inner ring 4 of the bearing, and the inner ring of the input flange 10 is provided with an inner ring cavity 15 for fitting the output flange 11. A convex ring 16 is formed between the outer ring cavity 14 and the inner ring cavity 15. Specifically, the input flange 10 effectively isolates the mounting surface of the inner ring 4 of the bearing from the connecting surface of the output flange 11 through the convex ring 16. The outer ring cavity 14 is specifically used to position and press the inner ring 4 of the bearing, while the inner ring cavity 15 is used to accommodate and fix the output flange 11 of the harmonic reduction module. This ensures that the bearing preload and the locking force at the output end of the reducer are independent of each other in the transmission path, avoiding micro-deformation problems caused by assembly stress coupling. For example, when the output torque of the reducer fluctuates or the lead screw shaft 8 is subjected to reverse impact load, the convex ring 16 can act as a stress buffer to prevent the elastic deformation of the mounting surface from being directly transmitted to the bearing raceway, thereby significantly improving the coaxiality of the rotary support and the accuracy retention during long-term operation.

[0032] In this embodiment, an annular space is formed between the lead screw shaft 8 and the output nut 9. Multiple planetary rollers 26, evenly distributed circumferentially, are mounted within this annular space via a cage 28. The threaded sections of the planetary rollers 26 mesh with the external thread of the lead screw shaft 8 and the internal thread of the output nut 9, respectively. Internal gear rings 27 are symmetrically arranged at both ends of the inner ring of the output nut 9, and involute external gears corresponding to the internal gear rings 27 are symmetrically arranged at both ends of the threaded sections of the planetary rollers 26. When the lead screw shaft 8 rotates, the rotational motion is converted into high-precision linear motion of the output nut 9 through meshing with the planetary rollers 26 inside the output nut 9. Specifically, the planetary rollers 26 do not rely solely on the threaded pair to transmit motion, but rather rely on the dual constraints of threaded meshing and gear meshing to achieve power transmission. In this process, the threaded section in the middle of the planetary roller 26 forms a multi-line helical surface contact with the external thread of the lead screw shaft 8 and the internal thread of the output nut 9. At the same time, the involute external gears set at both ends of the planetary roller 26 precisely mesh with the internal gear ring 27 fixed on the inner wall of the output nut 9. The function of this gear pair is to forcibly constrain the axial degree of freedom of the planetary roller 26 relative to the output nut 9, so that it does not slip axially during revolution and rotation, thereby realizing pure rolling transmission.

[0033] Furthermore, a axial stop step is provided on one end face of the cage 28, and a retaining ring 29 that mates with the axial stop step is embedded in the mounting groove of the internal gear ring 27 to limit the axial displacement of the planetary rollers 26. During the operation of the electric cylinder, especially during rapid acceleration or deceleration, inertial forces may attempt to push the planetary rollers 26 to move slightly axially. Once the amount of movement exceeds the gear meshing clearance or thread lead tolerance, it will lead to meshing misalignment, transmission jamming, or even tooth surface peeling. In this embodiment, the retaining ring 29 is usually an elastic steel wire retaining ring or a metal stamping retainer, which is embedded in the preset annular mounting groove of the internal gear ring 27 and forms a rigid abutment with the axial stop step on the end face of the cage 28, locking the planetary rollers 26 and their cage 28 in a preset position to prevent axial movement.

[0034] Furthermore, the housing includes a main housing 7 and a housing end cover 23. The bearing outer ring and the housing end cover 23 are respectively connected to the two ends of the main housing 7. A third sealing ring 21 is provided between the bearing outer ring and the main housing 7. A fifth sealing ring 24 is provided between the housing end cover 23 and the main housing 7. A fourth sealing ring 22 is provided between the housing end cover 23 and the output nut 9. A movable gap for storing lubricating grease is reserved between the main housing 7 and the output nut 9. A support ring 25 is provided on the inner ring of the front end cover of the housing end cover 23. The inner circumferential surface of the support ring 25 is slidably supported on the outer circumferential surface of the output nut 9. Among them, the third sealing ring 21 and the fifth sealing ring 24 are both static seals. The third sealing ring 21 is located at the connection interface between the second bearing outer ring 18 and the main housing 7 to prevent foreign objects from entering the screw drive cavity from the assembly gap between the power input end and the execution end. The fifth sealing ring 24 ensures the static sealing integrity of the housing itself. The fourth sealing ring 22 is located between the inner wall of the end cap 23 and the outer circumferential surface of the reciprocating output nut 9. It is a dynamic seal, which not only continuously scrapes away impurities adhering to the nut surface during the high-speed linear motion of the output nut 9, but also effectively prevents the leakage of lubricating grease from the cavity. The support ring 25, which is embedded in the inner ring of the end cap 23, is usually made of wear-resistant engineering plastic or copper alloy. Its inner hole forms a precise sliding fit with the outer circle of the output nut 9, which effectively suppresses the radial sway and vibration of the output nut 9 when subjected to eccentric loads or high-speed reversal, and improves the smoothness and guiding accuracy of linear motion.

[0035] It should be understood that the sealing rings used for static sealing in this application can all be in the form of O-rings, Y-rings, V-type combination seals or labyrinth seals, and the sealing rings used for dynamic sealing are preferably Glyd rings.

[0036] Furthermore, the output nut 9 is connected to a scraper 30 and a nut end cap 31 at both ends, respectively. The scraper 30 is threadedly engaged with the lead screw shaft 8, and the nut end cap 31 has an anti-collision pad 32 facing the end face of the lead screw shaft 8. Specifically, the scraper 30 is usually made of wear-resistant engineering plastic or bronze, and its inner hole is machined with an internal thread that matches the direction of the external thread of the lead screw shaft 8. When the output nut 9 reciprocates axially, the scraper 30 moves accordingly and forms a spiral scraping action with the surface of the lead screw shaft 8, pushing excess grease and any small particulate impurities that may be mixed in onto the surface of the lead screw shaft 8 back into the oil storage gap inside the main housing 7. This not only prevents grease leakage and pollution of the external environment, but also realizes the recycling of the lubricating medium and avoids the risk of dry friction caused by grease loss. The anti-collision pad 32 is usually made of elastic and energy-absorbing materials such as polyurethane, rubber or nylon. When the electric cylinder runs to the limit position or an overtravel impact occurs due to abnormal control, the anti-collision pad 32 first contacts the end face of the lead screw shaft 8. The impact kinetic energy is absorbed by the elastic deformation of the material, effectively avoiding direct rigid collision between metal parts, thereby protecting precision transmission components such as lead screw threads, planetary rollers 26 and bearings from damage.

[0037] It should also be noted that the nut end cap 31 is threadedly connected to the output nut 9, and the output surface of the nut end cap 31 is configured as a spherical surface. This threaded connection facilitates the disassembly and replacement of the nut end cap 31, the output nut 9, the planetary rollers 26, and other structures. The spherical surface can form a spherical pair connection with the matching concave surface on the external tooling or load connector, enabling the output end of the overall electric cylinder to have a certain angle of self-aligning capability. When there is a slight angular deviation between the installation reference of the external load and the axis of the electric cylinder, the spherical pair can automatically compensate for the deviation, avoiding additional bending moment and lateral force caused by forced alignment.

[0038] In one specific embodiment, the position detection component includes a moving component 12 and a reading component 13. The moving component 12 is fixed to the output nut 9 and moves linearly synchronously with the output nut 9. The reading component 13 is fixed to the housing and detects the linear position of the moving component 12.

[0039] In this embodiment, the moving component 12 is fixed to the outer circumferential surface of the output nut 9 by a bracket 33, and the housing is provided with a groove through which the bracket 33 can pass. The reading component 13 is fixedly connected to the housing by a protective cover 34, which covers the moving component 12, the reading component 13, and the groove. Specifically, the bracket 33 is usually an L-shaped or U-shaped metal component, one end of which is rigidly fixed to the outer circumferential surface of the output nut 9 by screws or pins, and the other end extends to the outside of the housing through a pre-set axial groove for mounting the moving component 12. The moving component 12 is preferably the code disk of a linear grating ruler or the magnetic strip of a magnetic grating ruler, which moves linearly synchronously with the output nut 9, while the reading component 13 (such as a grating reading head or a magnetic sensor) is fixedly installed on the inner wall of the protective cover 34 to read the position information of the moving component 12 in real time in a non-contact manner. The protective cover 34 is typically a long strip-shaped shell made of stainless steel or aluminum alloy. It is fixed to the outside of the housing by screws or clips, completely covering the moving part 12, the reading part 13, and the sliding groove opening on the housing, forming a closed protective cavity. The protective cover 34 can not only effectively block external contaminants such as chips, dust, oil, and coolant from entering the precision sensing area, but also prevent mechanical collisions or human touch from damaging the sensor, ensuring the long-term stable operation of the position detection component in harsh industrial environments.

[0040] In summary, during equipment operation: The harmonic reducer output unit receives the rotary input from the power unit. After internal reduction and torque amplification, it transmits the high-precision, high-torque rotary motion to the input flange 10 of the lead screw shaft 8 via the output flange 11. The lead screw shaft 8 rotates under the support of a composite bearing. The external thread on its output screw first meshes with the external threads of the circumferentially distributed planetary rollers 26, which then pushes the external threads of the planetary rollers 26 to mesh with the internal threads of the output nut 9, converting the rotational motion of the lead screw shaft 8 into the linear motion of the output nut 9. Simultaneously, the involute external gears symmetrically arranged at both ends of the planetary rollers 26 mesh with the internal gear ring 27 fixed on the output nut 9, resulting in no relative axial displacement between the planetary rollers 26 and the output nut 9. The planetary rollers 26 can repeatedly circulate within the closed annular space formed by the lead screw shaft 8 and the output nut 9, achieving continuous motion and power transmission through rolling and sliding friction.

[0041] Under heavy-load conditions, the working reaction force is transmitted to the lead screw shaft 8 through the output nut 9 and planetary rollers 26, and then to the bearing inner ring 4 through the input flange 10. In the composite bearing, the axial bearing component 2 simultaneously bears both positive and negative axial thrust, while the radial bearing component 3 bears the radial load caused by stamping eccentricity or installation errors. The bearing inner ring 4 maintains high rotational accuracy under the combined action of bidirectional axial rolling support and radial rolling support. Since both the axial bearing component 2 and the radial bearing component 3 have regular planar raceways that mate with the inner and outer circular raceways, they can effectively achieve high operating accuracy and a large axial and radial load capacity, thereby ensuring the rotational support stiffness of the lead screw shaft 8 during operation.

[0042] A bracket 33 is mounted on the outer circumference of the output nut 9. The moving part 12 is fixed to the side of the bracket 33 and moves linearly and reciprocally in sync with the output nut 9. The reading element 13 is fixed on the protective cover 34 and directly detects the actual linear position of the output nut 9, meeting the high-precision requirements under high-speed and heavy-load conditions.

[0043] In the description of this invention, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0044] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which is determined by the scope of the appended claims.

Claims

1. A high-precision, heavy-duty planetary roller screw electric cylinder, characterized in that, include: Harmonic reduction module is used to provide rotational power after reduction and torque amplification; A composite bearing includes an outer ring, an axial bearing component, a radial bearing component, and an inner ring. The outer ring is fixedly connected to the fixed flange of the harmonic deceleration module via a connecting flange. The axial bearing component and the radial bearing component are both disposed between the outer ring and the inner ring, and provide axial rotational support and radial rotational support for the inner ring, respectively. A linear actuator with a lead screw includes a housing, a lead screw shaft, and an output nut. The housing is fixedly connected to the outer ring of the bearing. The outer ring of the input flange of the lead screw shaft is fixedly connected to the inner ring of the bearing. The inner ring of the input flange is fixedly connected to the output flange of the harmonic reduction module. The output screw of the lead screw shaft is threadedly engaged with the output nut. When the lead screw shaft rotates, it drives the output nut to move linearly along the axial direction. The position detection component includes a moving component and a reading component. The moving component is fixed to the output nut and moves linearly synchronously with the output nut. The reading component is fixed to the housing and detects the linear position of the moving component.

2. The high-precision heavy-duty planetary roller screw electric cylinder according to claim 1, characterized in that: The input flange has an outer ring cavity on its outer ring for fitting the bearing inner ring, and an inner ring cavity on its inner ring for fitting the output flange. A convex ring is formed between the outer ring cavity and the inner ring cavity.

3. A high-precision heavy-duty planetary roller screw electric cylinder according to claim 1, characterized in that: The axial bearing member includes a first axial bearing member and a second axial bearing member. The bearing inner ring is embedded in the annular raceway formed by the first axial bearing member, the second axial bearing member, and the radial bearing member. The two end faces of the bearing inner ring are respectively in rolling contact with the first axial bearing member and the second axial bearing member, and the outer side of the bearing inner ring is in rolling contact with the radial bearing member.

4. A high-precision heavy-duty planetary roller screw electric cylinder according to claim 2, characterized in that: The bearing outer ring includes a first bearing outer ring and a second bearing outer ring. A stepped hole is provided in the first bearing outer ring. The first axial bearing member is embedded in one end hole of the stepped hole. The second axial bearing member is embedded at one end opening of the stepped hole. The second bearing outer ring is fixedly connected to one end face of the first bearing outer ring to provide support for the second axial bearing member. The second bearing outer ring includes an outer ring portion fixedly connected to the first bearing outer ring and an inner ring portion fixedly connected to the housing. A first sealing ring is provided between the outer ring portion and the second bearing outer ring.

5. A high-precision heavy-duty planetary roller screw electric cylinder according to claim 1, characterized in that: A second sealing ring is provided between the outer ring of the bearing and the connecting flange, a third sealing ring is provided between the outer ring of the bearing and the housing, and a fourth sealing ring is provided between the housing and the output nut.

6. A high-precision heavy-duty planetary roller screw electric cylinder according to claim 1, characterized in that: The housing includes a main housing and a housing end cover. The outer ring of the bearing is connected to both ends of the main housing and the housing end cover respectively. A fifth sealing ring is provided between the housing end cover and the main housing. A movable gap for storing lubricating grease is reserved between the main housing and the output nut. A support ring is provided on the inner ring of the front end cover of the housing end cover. The inner circumferential surface of the support ring is slidably supported on the outer circumferential surface of the output nut.

7. A high-precision heavy-duty planetary roller screw electric cylinder according to claim 1, characterized in that: An annular space is formed between the lead screw shaft and the output nut. Multiple planetary rollers are evenly distributed circumferentially within the annular space via a cage. The threaded sections of the planetary rollers mesh with the external thread of the lead screw shaft and the internal thread of the output nut, respectively. The inner ring of the output nut is symmetrically provided with internal gear rings at both ends. The threaded sections of the planetary rollers are symmetrically provided with involute external gears that mesh with the internal gear rings.

8. A high-precision heavy-duty planetary roller screw electric cylinder according to claim 7, characterized in that: The cage has a axial stop step on one end face, and a retaining ring that mates with the axial stop step is embedded in the mounting groove of the internal gear ring to limit the axial displacement of the planetary roller.

9. A high-precision heavy-duty planetary roller screw electric cylinder according to claim 1, characterized in that: The output nut is connected to an oil scraper and a nut end cap at both ends. The oil scraper is threaded with the lead screw shaft. The nut end cap is provided with an anti-collision pad facing the end face of the lead screw shaft. The nut end cap is threadedly connected to the output nut, and the output surface of the nut end cap is configured as a spherical surface.

10. A high-precision heavy-duty planetary roller screw electric cylinder according to claim 1, characterized in that: The moving component is fixed to the outer circumferential surface of the output nut by a bracket, and the housing is provided with a sliding groove through which the bracket can pass; the reading component is fixedly connected to the housing by a protective cover, and the protective cover covers the moving component, the reading component and the sliding groove.

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