Two-stage electric cylinder based on planetary roller screw

Abstract

The invention belongs to the technical field of electric cylinder application, and discloses a two-stage electric cylinder based on a planetary roller screw, which comprises a cylinder barrel, a linear transmission part and a power device, the linear transmission part comprises a first-stage transmission assembly, a second-stage transmission assembly and a connecting rod. The first-stage transmission assembly comprises a first-stage hollow lead screw, a first-stage lead screw nut and a first-stage hollow push rod. The second-stage transmission assembly comprises a second-stage hollow lead screw and a second-stage hollow push rod, the second-stage hollow lead screw and the first-stage hollow push rod are assembled into a lead screw nut structure, and the second-stage hollow push rod is rotationally arranged on the periphery of the second-stage hollow lead screw in a sleeving mode through a self-aligning roller bearing and is limited to rotate relative to the first-stage hollow push rod; the rear end of the connecting rod is connected into the first-stage hollow lead screw through a first spline, and the front end of the connecting rod is connected into the second-stage hollow lead screw through a second spline. The two push rods stretch out and draw back at the same time, the size is small, the stroke is large, positioning precision is high, transmission efficiency is high, and synchronism is good.

Description

Technical Field

[0001] This invention belongs to the field of electric cylinder application technology, specifically relating to a two-stage electric cylinder based on a planetary roller screw. Background Technology

[0002] Currently, multi-stage hydraulic cylinders are still used in applications requiring high load capacity and travel distance. However, multi-stage hydraulic cylinders suffer from drawbacks such as complex control, poor sensitivity, low positioning accuracy, limited installation space, and the need for regular maintenance, hindering the miniaturization and lightweighting of mechanical equipment. Electric cylinders, as a new type of electric actuator, offer numerous advantages such as high power density, fast response speed, and good synchronization, and have been widely used in aerospace test benches, multi-degree-of-freedom precision machine tools, and defense equipment. However, single-stage electric cylinders, due to their large size and small extension ratio, cannot be used in applications with limited installation space. Existing multi-stage electric cylinders use nested ball screws as internal linear transmission components, which can be used in small-space applications, but their low load capacity makes them unsuitable for applications with high load capacity requirements. Summary of the Invention

[0003] To address the aforementioned problems, this invention provides a two-stage electric cylinder based on a planetary roller screw, which solves the issues of large size, small extension ratio, and low load-bearing capacity of single-stage electric cylinders and multi-stage electric cylinders.

[0004] To achieve the above objectives, the present invention provides the following technical solution: A two-stage electric cylinder based on a planetary roller screw, comprising: The cylinder has a hollow interior with openings at both ends; Linear transmission components include a primary transmission assembly, a secondary transmission assembly, and a connecting rod; The primary transmission assembly includes a primary hollow screw, a primary screw nut, and a primary hollow push rod. The primary screw nut is helically fitted around the outer periphery of the primary hollow screw and is restricted from rotating relative to the cylinder. The front end of the primary hollow push rod extends out from the hollow front opening, and the rear end is fixedly connected to the primary screw nut. The secondary transmission assembly includes a secondary hollow lead screw and a secondary hollow push rod. The secondary hollow lead screw and the primary hollow push rod are assembled in a lead screw and nut structure, so that the front ends of the secondary hollow lead screw and the secondary hollow push rod extend together from the front end opening of the primary hollow push rod. The secondary hollow push rod is rotatably mounted on the outer periphery of the secondary hollow lead screw through a self-aligning roller bearing and is restricted from rotating relative to the primary hollow push rod. The rear end of the connecting rod is connected to the first-stage hollow screw via a first spline, and the front end is connected to the second-stage hollow screw via a second spline, so as to transmit the torque of the first-stage hollow screw to the second-stage hollow screw. And a power unit, connected to the other end opening of the hollow part, to transmit the torque output by the power unit to the first-stage hollow screw.

[0005] Preferably, the rear end of the connecting rod is connected to the first spline via a first anti-rotation key, and the front end is connected to the second spline via a second anti-rotation key.

[0006] Preferably, the front end of the first-stage hollow screw is provided with a front limiting member adapted to the front end of the connecting rod, and the rear end of the second-stage hollow screw is provided with a rear limiting member adapted to the nut of the first-stage screw.

[0007] Preferably, the primary transmission assembly further includes primary lead screw rollers; the primary lead screw rollers are arranged between the primary lead screw nut and the primary hollow lead screw and distributed on the circumference, and the primary lead screw rollers mesh with the primary lead screw nut and the primary hollow lead screw.

[0008] Preferably, the secondary transmission assembly further includes secondary lead screw rollers; the secondary lead screw rollers are arranged between the primary hollow push rod and the secondary hollow lead screw and distributed on the circumference, and the secondary lead screw rollers mesh with the primary hollow push rod and the secondary hollow lead screw.

[0009] Preferably, a primary retainer and a primary internal gear ring are provided between the primary hollow screw and the primary screw nut. The primary retainer is used to rotatably mount the primary screw roller, and the gear at the end of the primary screw roller meshes with the inner side of the primary internal gear ring.

[0010] Preferably, a secondary retainer and a secondary internal gear ring are provided between the secondary hollow lead screw and the primary hollow push rod. The secondary retainer is used to rotatably mount the secondary lead screw roller, and the end gear of the secondary lead screw roller meshes with the outer side of the secondary internal gear ring.

[0011] Preferably, a first guide keyway is provided on the outer circumferential surface of the first-stage lead screw nut, and a first-stage guide key is provided inside the hollow cylinder to cooperate with the first guide keyway to guide the linear transmission between the first-stage lead screw nut and the first-stage hollow push rod.

[0012] Preferably, a secondary guide keyway is provided on the outer circumferential surface of the secondary hollow push rod, and a secondary guide key is provided at the front end of the primary hollow push rod to cooperate with the secondary guide keyway to guide the linear transmission of the secondary hollow push rod.

[0013] Preferably, the secondary hollow push rod is fixed to the outer ring of the self-aligning roller bearing via a connecting block, and the inner ring of the self-aligning roller bearing is fixed to the secondary hollow lead screw via a bushing and a stop block.

[0014] Preferably, the piston rod head is fixedly connected to the front end of the secondary hollow push rod, and a joint bearing is installed at the front end of the piston rod head by a back-tightening nut.

[0015] Preferably, the power unit includes a housing, a servo motor, a reducer, and a synchronous belt drive component; the servo motor is connected to the reducer, the reducer is fixed to the housing by a vertical plate, and the synchronous belt drive component is installed inside the housing to transmit the torque output by the servo motor after reduction by the reducer to the first-stage hollow lead screw; the synchronous belt drive component includes a first synchronous pulley, a synchronous belt, and a second synchronous pulley, the first synchronous pulley is fixed to the output shaft of the reducer by a flat key and a set screw, the second synchronous pulley is fixed to the rear end of the first-stage hollow lead screw by a flat key and a set screw, and the first synchronous pulley and the second synchronous pulley are connected by a synchronous belt drive.

[0016] Preferably, the rear end of the cylinder is fixedly connected to the vertical plate via a bearing seat, and the shoulder of the first-stage hollow screw is fitted with a bushing that is locked by a lock nut. The bushing is fitted inside the bearing seat, and the bushing and the bearing seat are connected by a support bearing.

[0017] Preferably, a front end cover is fixed to the front end of the cylinder, a first sealing ring is provided between the front end cover and the first-stage hollow push rod, and a second sealing ring is provided between the first-stage hollow push rod and the second-stage hollow push rod.

[0018] This invention also provides a two-stage planetary roller screw electric cylinder transmission method. In the retracted state, after the servo motor is started, the torque of the servo motor is transmitted to the first synchronous pulley through the reducer. Under the action of the synchronous belt, the second synchronous pulley is driven to rotate, which in turn drives the first-stage hollow screw to rotate. At the same time as the first-stage hollow screw rotates, the second-stage hollow screw is driven to rotate simultaneously under the action of the spline connection at both ends of the connecting rod. Under the action of the planetary roller screw pair, the first-stage screw nut, the first-stage hollow push rod, and the second-stage hollow push rod are driven to move. Since the guide keyway on its outer side restricts its circumferential rotation, it can only perform linear motion, thereby realizing the synchronous extension of the first-stage hollow push rod and the second-stage hollow push rod.

[0019] The present invention also provides a two-stage planetary roller screw electric cylinder transmission method. In the extended state, the first-stage hollow screw and the second-stage hollow screw are driven to rotate in opposite directions by the reverse torque of the servo motor, thereby realizing the synchronous retraction of the first-stage hollow push rod and the second-stage hollow push rod.

[0020] Compared with the prior art, the present invention has the following advantages: This invention provides a two-stage electric cylinder structure based on a planetary roller screw, which not only possesses the advantages of a single-stage electric cylinder, such as high positioning accuracy, high transmission efficiency, and good synchronization, but also effectively reduces the overall size of the electric cylinder and increases the extension ratio, providing a solution to the contradiction between limited installation space and large working stroke in practical applications. The use of a high-precision, high-efficiency planetary roller screw as the linear transmission component of the two-stage electric cylinder improves the axial load-bearing capacity and axial rigidity of the electric cylinder. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the initial state of a two-stage electric cylinder structure based on a planetary roller screw according to the present invention. Figure 2 This is a schematic diagram of the extended state of a two-stage electric cylinder structure based on a planetary roller screw according to the present invention. Figure 3 For the present invention Figure 2 Enlarged view of point A in the middle; Figure 4 For the present invention Figure 2 Enlarged view of point B in the middle; In the diagram: Servo motor-1; Reducer-2; Vertical plate-3; Housing-4; First synchronous pulley-5; Synchronous belt-6; Second synchronous pulley-7; Locking nut-8; Bushing-9; Support bearing-10; Bearing seat-11; First anti-rotation key-12; First spline-13; Connecting rod-14; Cylinder-15; Second anti-rotation key-16; Second spline-17; First sealing ring-18; Front end cover-19; Second sealing ring-20; Secondary guide key-21; Piston rod head-22; Back 23. Tightening nut; 24. Spherical bearing; 25. Front end limiter; 26. Rear end limiter; 27. Primary guide key; 28. Primary hollow lead screw; 29. ​​Primary lead screw roller; 30. Primary lead screw nut; 31. Primary internal gear ring; 32. Primary cage; 33. Secondary hollow lead screw; 34. Secondary lead screw roller; 35. Primary hollow push rod; 36. Secondary internal gear ring; 37. Secondary cage; 38. Connecting block; 39. Self-aligning roller bearing; 40. Secondary hollow push rod. Detailed Implementation

[0022] 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.

[0023] like Figures 1 to 4 As shown, the two-stage electric cylinder based on a planetary roller screw proposed in this invention includes a cylinder barrel 15, a linear transmission component, and a power unit. Specifically, the cylinder barrel 15 is a hollow cylindrical structure. The linear transmission component is installed inside the cylinder barrel 15, and the power unit is connected to the rear end of the cylinder barrel 15 to provide driving force for the extension or retraction of the linear transmission component. When the linear transmission component extends, it extends forward from the front opening of the cylinder barrel 15.

[0024] The power unit includes a housing 4, a servo motor 1, a reducer 2, and a synchronous belt drive component. The servo motor 1 is connected to the reducer 2, which is fixed to the housing 4 via a vertical plate 3. The synchronous belt drive component is installed inside the housing 4 to transmit the torque output from the servo motor 1 after reduction by the reducer 2 to the linear transmission component. Specifically, the housing 4 and the cylinder 15 are combined to form an L-shaped structure, thereby achieving a reasonable assembly of the servo motor 1, reducer 2, synchronous belt drive component, and linear transmission component. Notably, the housing 4 has an opening on its front side, and the vertical plate 3 is installed on the front side of the housing 4 to close the opening, thus providing installation protection for the synchronous belt drive component. The rear end of the cylinder 15 is fixedly connected to the vertical plate 3 via a bearing seat 11, and the front end of the cylinder 15 is provided with a front end cover 19, thereby providing installation protection for the linear transmission component and guiding it to perform linear transmission in a preset direction.

[0025] In this embodiment, the housing 4, the upright plate 3, the bearing seat 11, the cylinder 15, and the front cover 19 are combined to form an assembled outer shell structure. The bearing seat 11 and the upright plate 3 are the main load-bearing structures, which can facilitate the installation, debugging, and maintenance of the overall electric cylinder.

[0026] One specific embodiment is provided, wherein the linear transmission component includes a primary transmission assembly. The primary transmission assembly includes a primary hollow lead screw 28, a primary lead screw roller 29, a primary lead screw nut 30, and a primary hollow push rod 35.

[0027] In this embodiment, the rear end of the first-stage hollow lead screw 28 extends into the housing 4. A bushing 9, locked by a locking nut 8, is fitted onto the shoulder of the first-stage hollow lead screw 28. The bushing 9 is assembled inside the bearing housing 11, and the bushing 9 and the bearing housing 11 are connected by a support bearing 10. This allows the torque output from the servo motor 1 after reduction by the reducer 2 to be transmitted to the first-stage hollow lead screw 28 via a synchronous belt drive, thus converting the rotational motion of the servo motor 1's output shaft into the rotational motion of the first-stage hollow lead screw 28. The reducer 2 is used to reduce the rotational speed and increase the torque; specifically, it utilizes the principle of gear transmission, using combinations of gears of different sizes to reduce the rotational speed and amplify the torque, thereby controlling the rotational speed of the first-stage hollow lead screw 28 within a suitable range.

[0028] For example, the synchronous belt drive includes a first synchronous pulley 5, a synchronous belt 6, and a second synchronous pulley 7. The first synchronous pulley 5 is fixed to the output shaft of the reducer 2 by a flat key and a set screw. The second synchronous pulley 7 is fixed to the rear end of the first-stage hollow lead screw 28 by a flat key and a set screw. The first synchronous pulley 5 and the second synchronous pulley 7 are connected by the synchronous belt 6.

[0029] In this embodiment, the first-stage lead screw nut 30 is arranged on the outer periphery of the first-stage hollow lead screw 28 and is restricted from rotating relative to the cylinder 15. The first-stage lead screw rollers 29 are arranged between the first-stage lead screw nut 30 and the first-stage hollow lead screw 28 and are distributed on the circumference. The first-stage lead screw rollers 29 mesh with the first-stage lead screw nut 30 and the first-stage hollow lead screw 28. The front end of the first-stage hollow push rod 35 extends out from the hollow front opening of the cylinder 15, and the rear end is fixedly connected to the first-stage lead screw nut 30. In this structural design, when the first-stage hollow lead screw 28 rotates, the first-stage lead screw nut 30 and the first-stage hollow lead screw 28 will generate a helical drive through the transmission engagement of the first-stage lead screw roller 29. Since the first-stage lead screw nut 30 is restricted from rotating relative to the cylinder 15, according to the motion characteristics of the threaded pair, the first-stage lead screw nut 30 will move axially in a linear motion along the external thread surface of the first-stage hollow lead screw 28, thereby extending or retracting the first-stage hollow push rod 35 from the hollow front end opening of the cylinder 15. Specifically, in actual operation, the extension and retraction of the first-stage hollow push rod 35 can be achieved by controlling the forward and reverse rotation of the servo motor 1.

[0030] To improve the stability of the movement of the first-stage hollow lead screw 28, the first-stage lead screw roller 29, and the first-stage lead screw nut 30, a first-stage cage 32 and a first-stage internal gear ring 31 are provided between the first-stage hollow lead screw 28 and the first-stage lead screw nut 30. The two ends of the first-stage lead screw roller 29 are rotatably mounted on the first-stage cage 32, and the gears at both ends of the first-stage lead screw roller 29 mesh with the inner side of the first-stage internal gear ring 31, thereby achieving stable assembly of the planetary roller lead screw structure. The first-stage lead screw roller 29 converts the original sliding friction into rolling friction, significantly reducing the friction loss of the threaded contact surface, thereby improving transmission efficiency and extending service life.

[0031] To improve the stability of the movement of the primary lead screw nut 30 and the primary hollow push rod 35, a first guide keyway is provided on the outer circular surface of the rear end of the primary hollow push rod 35 and on the outer circumferential surface of the primary lead screw nut 30. A primary guide key 27 is provided inside the hollow cylinder 15, which cooperates with the first guide keyway to guide the linear transmission of the primary lead screw nut 30 and the primary hollow push rod 35. Specifically, the primary guide key 27 extends along the axial length of the cylinder 15, and the length of the primary guide key 27 is approximately equal to the distance between the support bearing 10 and the front opening of the hollow cylinder 15. When the primary hollow lead screw 28 rotates, the cooperation between the primary guide key 27 and the first guide keyway restricts the rotational movement of the primary lead screw nut 30 and the primary hollow push rod 35 relative to the cylinder 15, and guides the primary lead screw nut 30 and the primary hollow push rod 35 to move linearly along the length of the primary lead screw nut 30, effectively avoiding movement deviation caused by insufficient guidance.

[0032] Furthermore, a front end cover 19 is fixed to the front end of the cylinder 15, and a first sealing ring 18 with waterproof and dustproof effects is provided between the front end cover 19 and the first-stage hollow push rod 35. Specifically, the first sealing ring 18 is usually made of a material with good elasticity and sealing performance. These materials can adapt to different working environments and temperature ranges, ensuring that the sealing ring maintains stable performance during long-term use. In practical applications, the first sealing ring 18 relies on its own elastic deformation to form a tight seal at the joint of the equipment, preventing dust, water droplets, and other particulate matter from entering the interior of the cylinder 15 through gaps.

[0033] One specific embodiment is provided, wherein the linear transmission component includes a two-stage transmission assembly. The two-stage transmission assembly includes a two-stage hollow lead screw 33, a two-stage lead screw roller 34, and a two-stage hollow push rod 40.

[0034] In this embodiment, the first-stage hollow push rod 35 is used as the second-stage hollow screw nut adapted to the second-stage hollow screw 33, that is, the inner circumferential wall of the first-stage hollow push rod 35 is provided with threads; the first-stage hollow push rod 35 is arranged on the outer circumference of the second-stage hollow screw 33, and the second-stage screw rollers 34 are arranged between the first-stage hollow push rod 35 and the second-stage hollow screw 33 and distributed on the circumference, and the second-stage screw rollers 34 mesh with the first-stage hollow push rod 35 and the second-stage hollow screw 33; the second-stage hollow push rod 40 is rotatably mounted on the outer circumference of the second-stage hollow screw 33 through the self-aligning roller bearing 39 and is restricted from rotating relative to the first-stage hollow push rod 35. In this structural design, when the secondary hollow screw 33 rotates, the primary hollow push rod 35 and the secondary hollow screw 33 undergo helical transmission through the transmission engagement of the secondary screw roller 34. Based on the motion characteristics of the threaded pair, the secondary hollow screw 33 will undergo a combined rotational and axial movement relative to the primary hollow push rod 35. Under this motion, the secondary hollow push rod 40, mounted outside the secondary hollow screw 33, will extend or retract from the front opening of the primary hollow push rod 35. Specifically, in actual operation, the joint extension and retraction of the secondary hollow screw 33 and the secondary hollow push rod 40 can be achieved by controlling the forward and reverse rotation of the servo motor 1.

[0035] To improve the stability of the movement of the secondary hollow lead screw 33 and the secondary lead screw roller 34, a secondary cage 37 and a secondary internal gear ring 36 are provided between the secondary hollow lead screw 33 and the primary hollow push rod 35. The secondary cage 37 is used to rotatably mount the secondary lead screw roller 34, and the end gear of the secondary lead screw roller 34 meshes with the outer side of the secondary internal gear ring 36, thereby achieving stable assembly of the planetary roller lead screw structure. The secondary lead screw roller 34 converts the original sliding friction into rolling friction, significantly reducing the friction loss of the threaded contact surface, thereby improving transmission efficiency and extending service life.

[0036] To improve the stability of the movement of the secondary hollow lead screw 33 and the secondary hollow push rod 40, a secondary guide keyway is provided on the outer circumferential surface of the secondary hollow push rod 40, and a secondary guide key 21 is provided at the front end of the primary hollow push rod 35 to cooperate with the secondary guide keyway and guide the linear transmission of the secondary hollow push rod 40. Specifically, the secondary guide keyway extends along the axial length direction of the primary hollow push rod 35, and the length of the secondary guide keyway is approximately equal to the length of the primary hollow push rod 35. When the secondary hollow lead screw 33 rotates, the cooperation between the secondary guide key 21 and the secondary guide keyway restricts the rotational movement of the secondary hollow push rod 40 relative to the primary hollow push rod 35, and guides the secondary hollow lead screw 33 and the secondary hollow push rod 40 to move linearly along the length direction of the primary hollow push rod 35, thereby effectively eliminating radial sway caused by the cantilever effect during the movement.

[0037] To further improve the stability of the movement of the secondary hollow push rod 40, it is preferable that the secondary hollow push rod 40 is fixed to the outer ring of the self-aligning roller bearing 39 through the connecting block 38, and the inner ring of the self-aligning roller bearing 39 is fixed to the secondary hollow lead screw 33 through the bushing and the stop block. This ensures that the secondary hollow push rod 40 can rotate relative to the secondary hollow lead screw 33. That is, when the secondary hollow lead screw 33 generates a combined rotational and axial movement relative to the primary hollow push rod 35, the secondary hollow push rod 40 only performs stable axial movement relative to the primary hollow push rod 35.

[0038] In this embodiment, a second sealing ring 20 is provided between the primary hollow push rod 35 and the secondary hollow push rod 40. The second sealing ring 20 seals and fills the gap between the primary hollow push rod 35 and the secondary hollow push rod 40 to prevent dust, water droplets, and other particulate matter from entering the interior of the primary hollow push rod 35 through the gap. A piston rod head 22 is fixedly connected to the front end of the secondary hollow push rod 40. A spherical bearing 24 is installed at the front end of the piston rod head 22 via a tightening nut 23. The piston rod head 22 seals the front end of the secondary hollow push rod 40 to prevent dust, water droplets, and other particulate matter from entering the interior of the secondary hollow push rod 40 through the gap. The spherical bearing 24 allows for a certain degree of relative motion freedom between the connected components, enabling them to swing and rotate at certain angles in different directions. In practical applications, the secondary hollow push rod 40 is connected to other components via the spherical bearing 24.

[0039] In one specific embodiment, the linear transmission component includes a connecting rod 14 that connects the primary transmission assembly and the secondary transmission assembly, thereby achieving synchronous movement between the primary and secondary transmission assemblies and effectively improving the operating speed of the electric cylinder.

[0040] In this embodiment, the rear end of the connecting rod 14 extends into the interior of the first-stage hollow screw 28, and the front end extends into the interior of the second-stage hollow screw 33. By restricting the rotational movement of the connecting rod 14 relative to the first-stage hollow screw 28 and the second-stage hollow screw 33, it can be ensured that the torque of the first-stage hollow screw 28 can be stably transmitted to the second-stage hollow screw 33 through the connecting rod 14.

[0041] Specifically, a first anti-rotation key 12 is installed at the rear end of the connecting rod 14, and a first spline 13 is provided inside the primary hollow screw 28. The connecting rod 14 is connected to the primary hollow screw 28 through the assembly of the first anti-rotation key 12 and the first spline 13; wherein, the first spline 13 is fixedly sleeved on the outside of the first anti-rotation key 12. A second anti-rotation key 16 is installed at the front end of the connecting rod 14, and a second spline 17 is provided inside the secondary hollow screw 33. The connecting rod 14 is connected to the secondary hollow screw 33 through the assembly of the second anti-rotation key 16 and the second spline 17; wherein, the second spline 17 is fixedly sleeved on the outside of the second anti-rotation key 16. This ensures the stability of the connection between the primary hollow screw 28, the connecting rod 14, and the secondary hollow screw 33, and that the connecting rod 14 can... Figure 1 The retraction into the first-stage hollow lead screw 28, as shown, effectively realizes the integrated assembly of the overall structure.

[0042] like Figure 1The diagram shows the initial state (retracted state) of a two-stage electric cylinder structure based on a planetary roller screw according to the present invention. After the servo motor 1 starts, its torque is transmitted to the first synchronous pulley 5 via the reducer 2. Under the action of the synchronous belt 6, the second synchronous pulley 7 rotates, which in turn drives the first-stage hollow screw 28 to rotate. Simultaneously with the rotation of the first-stage hollow screw 28, the second-stage hollow screw 33 rotates due to the connection between the second spline 17 and the first spline 13 at both ends of the connecting rod 14. Under the action of the planetary roller screw pair, the first-stage screw nut 30, the first-stage hollow push rod 35, and the second-stage hollow push rod 40 are driven to move. Because the guide keyway on its outer side restricts its circumferential rotation, it can only perform linear motion, thus stably achieving the synchronous extension of the first-stage hollow push rod 35 and the second-stage hollow push rod 40.

[0043] like Figure 2 The diagram shows the extended state of a two-stage electric cylinder structure based on a planetary roller screw according to the present invention. In this diagram, the servo motor 1 drives the first-stage hollow screw 28 and the second-stage hollow screw 33 to rotate in opposite directions, thereby achieving the synchronous retraction of the first-stage hollow push rod 35 and the second-stage hollow push rod 40.

[0044] During the synchronous extension or retraction of the primary hollow push rod 35 and the secondary hollow push rod 40, preferably, the primary hollow lead screw 28 is provided with a front limiting member 25 adapted to the front end of the connecting rod 14, and the secondary hollow lead screw 33 is provided with a rear limiting member 26 adapted to the primary lead screw nut 30. This further ensures the accurate positioning of the primary and secondary transmission components during synchronous extension or retraction and effectively avoids structural collisions between the primary hollow lead screw 28, the connecting rod 14, and the secondary hollow lead screw 33. Specifically, the front limiting member 25 and the rear limiting member 26 can adopt a physical structure buffer limiting configuration or a displacement signal detection limiting configuration.

[0045] In summary, the two-stage electric cylinder based on a planetary roller screw provided by this invention transmits the push-pull force it bears to the two-stage hollow push rod 40 through the spherical bearing 24 during operation. The push-pull force borne by the two-stage hollow push rod 40 is transmitted to the two-stage hollow push rod 33 through the self-aligning roller bearing 39 connected to the two-stage hollow push rod 33. The push-pull force borne by the two-stage hollow push rod 33 is transmitted to the first-stage hollow push rod 35 through the screw-nut structure formed by the two-stage hollow push rod 33 and the first-stage hollow push rod 35. The push-pull force borne by the first-stage hollow push rod 35 is transmitted to the first-stage hollow push rod 28 through the screw-nut structure formed by the two-stage hollow push rod 35, the first-stage hollow push rod 35, and the first-stage hollow push rod 28. The first-stage hollow push rod 28 is connected to the power device, thereby ensuring that the push-pull force of the two-stage electric cylinder of this invention is transmitted only in the large structural components. Furthermore, in Figure 2In the extended state shown, the cylinder 15 and the first-stage hollow lead screw 28 form a double-layer structure, the first-stage hollow push rod 35 and the connecting rod 14 form a double-layer structure, and the second-stage hollow push rod 40 and the second-stage hollow lead screw 33 form a double-layer structure, thereby effectively improving the load-bearing capacity of the multi-stage electric cylinder.

[0046] 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.

[0047] 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 two-stage electric cylinder based on a planetary roller screw, characterized in that, include: The cylinder has a hollow interior with openings at both ends; Linear transmission components include a primary transmission assembly, a secondary transmission assembly, and a connecting rod; The primary transmission assembly includes a primary hollow screw, a primary screw nut, and a primary hollow push rod. The primary screw nut is helically fitted around the outer periphery of the primary hollow screw and is restricted from rotating relative to the cylinder. The front end of the primary hollow push rod extends out from the hollow front opening, and the rear end is fixedly connected to the primary screw nut. The secondary transmission assembly includes a secondary hollow lead screw and a secondary hollow push rod. The secondary hollow lead screw and the primary hollow push rod are assembled in a lead screw and nut structure, so that the front ends of the secondary hollow lead screw and the secondary hollow push rod extend together from the front end opening of the primary hollow push rod. The secondary hollow push rod is rotatably mounted on the outer periphery of the secondary hollow lead screw through a self-aligning roller bearing and is restricted from rotating relative to the primary hollow push rod. The rear end of the connecting rod is connected to the first-stage hollow screw via a first spline, and the front end is connected to the second-stage hollow screw via a second spline, so as to transmit the torque of the first-stage hollow screw to the second-stage hollow screw. And a power unit, connected to the other end opening of the hollow part, to transmit the torque output by the power unit to the first-stage hollow screw.

2. The two-stage electric cylinder based on a planetary roller screw according to claim 1, characterized in that: The rear end of the connecting rod is connected to the first spline via a first anti-rotation key, and the front end is connected to the second spline via a second anti-rotation key.

3. The two-stage electric cylinder based on a planetary roller screw according to claim 1, characterized in that: The first-stage hollow screw has a front limiting component that matches the front end of the connecting rod, and the second-stage hollow screw has a rear limiting component that matches the nut of the first-stage screw.

4. The two-stage electric cylinder based on a planetary roller screw according to claim 1, characterized in that: The primary transmission assembly further includes primary screw rollers; the primary screw rollers are arranged between the primary screw nut and the primary hollow screw and distributed on the circumference, and the primary screw rollers mesh with the primary screw nut and the primary hollow screw. The secondary transmission assembly further includes secondary lead screw rollers; the secondary lead screw rollers are arranged between the primary hollow push rod and the secondary hollow lead screw and distributed on the circumference, and the secondary lead screw rollers mesh with the primary hollow push rod and the secondary hollow lead screw.

5. The two-stage electric cylinder based on a planetary roller screw according to claim 4, characterized in that: A first-stage retainer and a first-stage internal gear ring are provided between the first-stage hollow screw and the first-stage screw nut. The first-stage retainer is used to rotatably mount the first-stage screw rollers, and the gears at the ends of the first-stage screw rollers mesh with the inner side of the first-stage internal gear ring. A secondary retainer and a secondary internal gear ring are provided between the secondary hollow lead screw and the primary hollow push rod. The secondary retainer is used to rotatably mount the secondary lead screw roller, and the gear at the end of the secondary lead screw roller meshes with the outer side of the secondary internal gear ring.

6. The two-stage electric cylinder based on a planetary roller screw according to claim 1, characterized in that: A first guide keyway is provided on the outer circumferential surface of the first-stage lead screw nut, and a first-stage guide key is provided inside the hollow cylinder to cooperate with the first guide keyway to guide the linear transmission between the first-stage lead screw nut and the first-stage hollow push rod. The outer circumferential surface of the secondary hollow push rod is provided with a secondary guide keyway, and the front end of the primary hollow push rod is provided with a secondary guide key that cooperates with the secondary guide keyway to guide the linear transmission of the secondary hollow push rod.

7. The two-stage electric cylinder based on a planetary roller screw according to claim 1, characterized in that: The secondary hollow push rod is fixed to the outer ring of the self-aligning roller bearing via a connecting block, and the inner ring of the self-aligning roller bearing is fixed to the secondary hollow lead screw via a bushing and a stop block.

8. The two-stage electric cylinder based on a planetary roller screw according to claim 1, characterized in that: The piston rod head is fixedly connected to the front end of the secondary hollow push rod, and a joint bearing is installed at the front end of the piston rod head by tightening a nut.

9. The two-stage electric cylinder based on a planetary roller screw according to claim 1, characterized in that: The power unit includes a housing, a servo motor, a reducer, and a synchronous belt drive component. The servo motor is connected to the reducer, which is fixed to the housing via a vertical plate. The synchronous belt drive component is installed inside the housing to transmit the torque output by the servo motor after reduction by the reducer to the first-stage hollow lead screw. The synchronous belt drive component includes a first synchronous pulley, a synchronous belt, and a second synchronous pulley. The first synchronous pulley is fixed to the output shaft of the reducer via a key and a set screw. The second synchronous pulley is fixed to the rear end of the first-stage hollow lead screw via a key and a set screw. The first synchronous pulley and the second synchronous pulley are connected by a synchronous belt drive.

10. The two-stage electric cylinder based on a planetary roller screw according to claim 9, characterized in that: The rear end of the cylinder is fixedly connected to the vertical plate via a bearing seat. The first-stage hollow screw shaft shoulder is fitted with a bushing that is locked by a lock nut. The bushing is fitted inside the bearing seat, and the bushing and the bearing seat are connected by a support bearing. A front end cover is fixed to the front end of the cylinder. A first sealing ring is provided between the front end cover and the first-stage hollow push rod, and a second sealing ring is provided between the first-stage hollow push rod and the second-stage hollow push rod.

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