Linear actuator

Abstract

The linear actuator includes a housing assembly having a first side and a second side; the motor assembly comprises a stator and a rotor; the guide assembly is provided with a first rotation limiting part and comprises an outer sleeve, and the outer sleeve is fixedly connected to the first side of the shell assembly; the lead screw nut assembly is provided with a second rotation limiting part, at least one part of the lead screw nut assembly is arranged in the shell assembly and the guide assembly, the lead screw nut assembly comprises a lead screw, a nut in transmission fit with the lead screw and a push rod for containing at least one part of the lead screw, and the push rod comprises a linear channel, an inner end part and an outer end part; the linear channel allows the lead screw to rotate and linearly move in the linear channel, the inner end is connected with the nut, the outer end is arranged outside the outer sleeve and connected with the connecting assembly, and the first rotation limiting part and the second rotation limiting part are matched to limit rotation of the nut relative to the guiding assembly under constraint. And the screw rod pushes the nut and the push rod to linearly move when rotating.

Description

Technical Field

[0001] The invention relates to a linear actuator and belongs to the technical field of mechanical automation. Background Art

[0002] In the field of modern industrial automation and robotics, linear actuators, as a device that converts electrical energy into linear motion, play a vital role. Linear actuators can provide precise linear motion control and are widely used in robotics, automated production lines, precision positioning systems, medical equipment, aerospace and other fields.

[0003] However, while pursuing high-precision performance, existing linear actuator technologies often face challenges in lightweight design, integration and intelligence, as well as reliability and durability. In addition, the design is too complex, resulting in high costs. For example, the linear actuator module of the Optimus humanoid robot uses a reverse planetary roller screw. Although it provides efficient thrust and torque, it is more expensive than traditional ball screw nuts. Summary of the invention

[0004] The present invention provides a linear actuator, aiming to solve at least one of the technical problems existing in the prior art.

[0005] The technical solution of the present invention relates to a linear actuator on one hand, which includes: a housing assembly, the housing assembly having a first side and a second side; a motor assembly, the motor assembly including a stator and a rotor arranged in the housing assembly; a guide assembly having a first rotation limiting portion, the guide assembly including an outer sleeve, the outer sleeve fixedly connected to the first side of the housing assembly; a lead screw nut assembly having a second rotation limiting portion, at least a portion of the lead screw nut assembly is arranged in the housing assembly and the guide assembly, the lead screw nut assembly includes a lead screw, a nut matched with the lead screw transmission and a push rod accommodating at least a portion of the lead screw, the push rod includes a linear channel, an inner end and an outer end, wherein the linear channel allows the lead screw to rotate and move linearly therein, the inner end is connected to the nut, the outer end is arranged outside the outer sleeve and connected to the connecting assembly, and wherein the first rotation limiting portion and the second rotation limiting portion limit the rotation of the nut relative to the guide assembly under the cooperative constraint, so that the lead screw drives the nut and the push rod to move linearly when rotating.

[0006] According to an embodiment of the present invention, the nut includes an internal threaded hole arranged along the axis, and the push rod includes a shoulder; the inner end of the push rod is fixedly connected to the internal threaded hole of the nut through a thread; and the shoulder is positioned against the orifice surface of the internal threaded hole to allow the axis of the push rod to basically coincide with the axis of the nut.

[0007] According to an embodiment of the present invention, the guide assembly includes an inner sleeve arranged in the outer sleeve and fixed to the outer sleeve, the inner sleeve's inner cylinder cavity is provided with a plane rail to serve as the first rotation limiting portion; the nut of the screw nut assembly includes a radial section to serve as the second rotation limiting portion; during the movement of the nut in the inner cylinder cavity, the plane rail is basically in contact with the radial section to limit the relative rotation between the nut and the inner sleeve.

[0008] According to an embodiment of the invention, the inner sleeve comprises a groove extending along an edge of the planar rail.

[0009] According to an embodiment of the present invention, the hardness of the material of at least the portion of the inner sleeve that contacts the nut is lower than the hardness of the nut.

[0010] According to an embodiment of the present invention, the guide assembly includes a guide plate fixedly connected to the outer sleeve, the guide plate having a non-circular hole to serve as the first rotation limiting portion; the inner end of the push rod of the screw nut assembly is fixedly connected to the nut, and the outer periphery of the outer end of the push rod is formed as a non-circular shaft to serve as the second rotation limiting portion; during the movement of the nut in the outer sleeve, the non-circular shaft continues to pass through the non-circular hole to limit the relative rotation between the nut and the outer sleeve.

[0011] According to an embodiment of the present invention, the guide assembly includes a clamping block allowing the push rod to pass through; the end side of the outer sleeve is provided with a recess for accommodating and positioning at least a portion of the guide piece; the clamping block is fixedly connected to the end side of the outer sleeve so that the guide piece between the clamping block and the outer sleeve is fixed in the recess.

[0012] According to an embodiment of the present invention, the hardness of the material of the guide piece is lower than the hardness of the push rod.

[0013] According to an embodiment of the present invention, the lead screw includes a lead screw portion, a bare rod portion and a first end, wherein the lead screw portion is transmission-coordinated with the nut, the lead screw portion is driven by the rotor of the motor assembly, the bare rod portion and the first end are located in the housing assembly, and the bare rod portion is located between the lead screw portion and the first end.

[0014] According to an embodiment of the present invention, the motor assembly includes a rotor bracket having a through hole, which allows at least a portion of the lead screw to pass through and be positioned so that the rotor bracket and the lead screw rotate together, and the rotor bracket includes: a first frame body, the first frame body is supported by a first bearing; a second frame body, the second frame body is supported by a second bearing; and an intermediate frame body is arranged between the first frame body and the second frame body, and the intermediate frame body is driven by the rotor of the motor assembly.

[0015] According to an embodiment of the present invention, the through hole of the rotor bracket includes a square hole portion, and the lead screw includes a square shaft portion arranged between the lead screw portion and the smooth rod portion of the lead screw, and the square shaft portion cooperates with the square hole portion so that the rotor bracket drives the lead screw to rotate.

[0016] According to an embodiment of the present invention, the housing assembly includes: a first housing, the first housing includes a first cavity and a first inner shoulder, the first cavity accommodates at least part of the electrical component; a second housing, the second housing includes a second cavity and a second inner shoulder, the second cavity accommodates the motor component, wherein the first inner shoulder and the second inner shoulder position the first bearing between the electrical component and the motor component.

[0017] According to an embodiment of the present invention, the electrical component includes: a force sensor, which is connected between the housing component and the connecting component; a circuit board, which is connected to the force sensor and disposed in the housing component; and an encoder, which is connected to the circuit board and is associated with the screw nut assembly to output the rotation amount.

[0018] According to an embodiment of the present invention, the encoder includes: a coding signal receiver, which is fixedly connected to the housing assembly through a support; and a coding signal generator matching the coding signal receiver, which is fixedly connected to the end of the lead screw.

[0019] The linear actuator in the embodiment of the present invention can achieve light weight, low-cost manufacturing, easy maintenance and high reliability while maintaining high precision and high output force performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a stereoscopic diagram of a linear actuator according to an embodiment of the present invention.

[0021] Figure 2 is an exploded view of a linear actuator according to an embodiment of the present invention.

[0022] Figure 3 4 is a partially cut-away stereoscopic view of a linear actuator according to an embodiment of the present invention.

[0023] Figure 4 Yes Figure 3 Cross-sectional view of a linear actuator with a cut-away method.

[0024] Figure 5 Yes Figure 4 Cross-sectional view of the linear actuator at the cutting line AA.

[0025] Figure 6 Yes Figure 4Cross-sectional view of the linear actuator at the cutting line BB.

[0026] Figure 7 Detailed description of the invention The figure is an exploded view of a lead screw nut assembly and its associated parts according to an embodiment of the present invention.

[0027] Figure 8 Detailed description of the invention is given in detail below.

[0028] Figure 9a 3 is a tension and stress analysis diagram of the internal thread connection portion between the nut and the push rod according to an embodiment of the present invention.

[0029] Figure 9b 3 is a stress simulation diagram of a push rod connected to a nut through an internal thread according to an embodiment of the present invention.

[0030] Fig.10a It is a tension and stress analysis diagram of the external thread connection between the nut and the push rod in some technical solutions.

[0031] Fig.10b It is a stress simulation diagram of a push rod connected to a nut through an external thread in some technical solutions.

[0032] Fig.11 It is a schematic diagram of the motion stroke of the screw nut assembly in an embodiment of the present invention.

[0033] Fig.12 is an exploded view of a portion of a linear actuator according to another embodiment of the present invention.

[0034] Fig.13 is a partial cross-sectional view of a linear actuator according to another embodiment of the present invention.

[0035] Fig.14 is a stereoscopic view of a linear actuator according to another embodiment of the present invention.

[0036] Some specific embodiments according to the present invention are described in an exemplary manner in conjunction with the accompanying drawings, in which the same reference numerals represent similar elements. The reference numerals contained in the above drawings and the names of the elements they refer to are as follows:

[0037] 100, housing assembly; 110, first housing; 111, first cavity; 112, first inner shoulder; 113, first line row hole; 120, second housing; 121, second cavity; 122, second inner shoulder; 123, second line row hole;

[0038] 200, motor assembly; 210, stator; 220, rotor; 230, rotor bracket; 231, first frame; 232, second frame; 233, middle frame; 234, square hole portion;

[0039] 300, guide assembly; 310, inner sleeve; 311, inner cylinder cavity; 312, convex edge; 313, plane rail; 314, groove; 320, outer sleeve; 321, gap cavity; 322, convex ring portion; 323, concave portion; 330, guide piece; 333, square hole; 340, pressing block;

[0040] 400, lead screw nut assembly; 410, lead screw; 411, lead screw portion; 412, smooth rod portion; 413, first end; 414, square shaft portion; 415, second end; 420, ball nut; 421, ball sleeve; 422, inner threaded hole; 423, radial section; 430, push rod; 431, linear channel; 432, inner end; 433, shaft shoulder; 434, outer end; 435, square shaft;

[0041] 500, connection assembly; 501, end connection; 502, spherical bearing;

[0042] 600, electrical components; 610, force sensor; 620, circuit board; 630, encoder; 631, encoding signal receiver; 632, support; 633, encoding signal generator;

[0043] 701, first bearing; 702, second bearing; 703, screw; 704, flange nut; 705, anti-drop nut. DETAILED DESCRIPTION

[0044] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0045] It should be noted that, unless otherwise specified, when a feature is referred to as being "fixed" or "connected" to another feature, it may be directly fixed or connected to the other feature, or it may be indirectly fixed or connected to the other feature. In addition, the descriptions of up, down, left, right, top, bottom, etc. used in the present invention are only relative to the relative positional relationship of the components of the present invention in the drawings.

[0046] In addition, unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art. The terms used in this specification are only for describing specific embodiments, not for limiting the present invention. The term "and / or" used herein includes any combination of one or more related listed items.

[0047] It should be understood that, although the terms first, second, third, etc. may be used to describe various elements in the present disclosure, these elements should not be limited to these terms. These terms are only used to distinguish elements of the same type from each other. For example, without departing from the scope of the present disclosure, the first element may also be referred to as the second element, and similarly, the second element may also be referred to as the first element.

[0048] Reference Figure 1 and Fig.12 In some embodiments, the linear actuator according to the present invention includes a housing assembly 100, a motor assembly 200, a guide assembly 300 and a screw nut assembly 400, and may further include a connection assembly 500 and an electrical assembly 600. The housing assembly 100 has a first side (front side, arrow F in the figure points to one side) and a second side (rear side, arrow B in the figure points to one side) facing away from each other, and the guide assembly 300 is fixedly connected to the front side of the housing assembly 100. The guide assembly 300 provides a first rotation limiting portion, and the screw nut assembly 400 provides a second rotation limiting portion, so that the rotation of the nut relative to the guide assembly 300 is limited under the cooperation constraint of the first rotation limiting portion and the second rotation limiting portion, so that the motor assembly 200 (in the housing assembly 100) is arranged in the housing assembly 100. Figure 1 and Fig.12 The guide assembly 300 is shown in dashed outline in FIG. 4 , and drives the lead screw nut assembly 400 so that it moves basically in the guide assembly 300 and outputs linear motion along the guide assembly 300. The connecting assembly 500 serves as an external connecting assembly 500 of the linear actuator. There may be a pair or more connecting assemblies 500, one of which is connected to the output end of the lead screw nut assembly 400, and another connecting assembly 500 is connected to the rear side of the housing assembly, wherein a portion of the electrical assembly 600 is connected between the connecting assembly 500 and the housing assembly for force sensing. Specifically, the electrical assembly 600 may include a force sensor 610, a circuit board 620, and an encoder 630. Specifically, the connecting assembly 500 may include an end connector 501 and a joint bearing 502 disposed in the end connector 501, wherein the end connector 501 is used to connect to the force sensor 610, the housing assembly 100, or the push rod 430, and the joint bearing 502 is used to provide a flexible external connection.

[0049] Reference Figures 2 to 4 In one embodiment, the housing assembly 100 includes a cylindrical first housing 110 and a second housing 120. The first housing 110 includes a first cavity 111 and a first inner shoulder 112, wherein the first cavity 111 accommodates a circuit board 620 and an encoder 630 of the electrical assembly 600. The force sensor 610 connected to the connecting assembly 500 can be implemented in the form of an end cap and fixedly connected to the first housing 110, such as Figure 3 and 4As shown. The force sensor 610 can also be fixed in the first cavity 111 of the first housing 110 while maintaining the sensing of the push and pull forces of the connecting assembly 500. The second housing 120 includes a second cavity 121 and a second inner shoulder 122, wherein the second cavity 121 accommodates the motor assembly 200. Figure 4 The first inner shoulder 112 of the first housing 110 and the second inner shoulder 122 of the second housing 120 position the first bearing 701, and also serve as a separation between the electrical component 600 and the motor component 200. The motor component 200 in the second cavity 121 is generally not directly connected to the electrical component 600 in the first cavity 111 in the housing assembly 100. Preferably, the first housing 110 and the second housing 120 respectively include a first wire row hole 113 connected to the first cavity 111 and a second wire row hole 123 connected to the second cavity 121, the first wire row hole 113 is used to lead wires from the circuit board 620 and / or the encoder 630, and the second wire row hole 123 is used to lead wires from the motor component 200. It can be understood that the housing assembly 100 is divided into two parts of the housing and the bearing is used as a spacer to accommodate relatively small current components (encoding circuits) and relatively large current components (motor windings) in the two cavities, respectively, to better perform electromagnetic and thermal isolation. In addition, it can be understood that the first bearing 701 positioned on the two inner shoulders of the two housings is arranged at the boundary of the two housings, which facilitates the installation and removal of the first bearing 701.

[0050] Continue to refer to Figures 2 to 4 In some embodiments, the motor assembly 200 includes a stator 210 , a rotor 220 , and a rotor support 230 . The lead screw and nut assembly 400 includes a lead screw 410 , a nut, and a push rod 430 .

[0051] Reference Figure 2 and Figure 5 In one embodiment, the motor stator 210 may be frame-shaped and fixed to the second housing 120, while the motor rotor 220 is disposed in the center of the stator 210 and supported by the rotor bracket 230 on its inner wall. Preferably, the stator 210 is composed of coil windings, and the rotor 220 includes magnets. The rotor bracket 230 has a through hole, which allows at least a portion of the lead screw 410 to pass through and be positioned so that the rotor bracket 230 and the lead screw 410 rotate together. In one embodiment, the stator 210 and the second housing 120 are fixed by glue, and the rotor 220 and the rotor bracket 230 are also fixed by glue.

[0052] Reference Figures 4 to 8In one embodiment, the rotor support 230 may be integrally formed, but may also include a first frame 231, a second frame 232, and an intermediate frame 233 disposed between the first frame 231 and the second frame 232. The lead screw 410 includes a first end 413, a bare rod portion 412, a lead screw portion 411, and a second end 415, wherein the diameters of the first end 413 and the bare rod portion 412 are smaller than the diameter of the lead screw portion 411. Figure 4 The second end 415 away from the first end 413 has a clamping surface, which can be used for clamping when installing, adjusting, maintaining, etc. the lead screw 410. Preferably, referring to Figure 7 and Figure 8 The linear actuator according to the present invention may further provide an anti-dropout nut 705, so that the second end 415 can be locked with the anti-dropout nut 705 by means of an external thread. The outer diameter of the anti-dropout nut 705 is slightly smaller than the inner diameter of the linear channel 431, and is larger than the minimum inner diameter between the screw grooves in the screw part 411, so that the anti-dropout nut 705 blocks the end E of the screw groove when it is fixed on the second end 415, preventing the ball nut 420 from exceeding the stroke and falling out.

[0053] The rotor support 230 has a through hole that passes through the first frame 231, the second frame 232 and the intermediate frame 233. The diameter of the through hole in the first frame 231 is substantially equal to or slightly larger than the diameter of the bare rod portion 412 of the lead screw 410 but smaller than the diameter of the lead screw portion 411, while the diameter of the through hole in the second frame 232 and the intermediate frame 233 is larger than the diameter of the lead screw portion 411, so that the lead screw 410 can be positioned in the first frame 231 with the bare rod portion 412 when inserted into the rotor support 230, so that the stepped wall between the lead screw portion 411 and the bare rod portion 412 is closely positioned with the end wall between the first frame 231 and the intermediate frame 233. In addition, the first end 413 of the lead screw 410 after being inserted into the rotor support 230 extends out of the first frame 231.

[0054] In this embodiment, the first frame 231, the second frame 232 and the intermediate frame 233 all have a circumferential outer wall. The outer circumferential wall of the first frame 231 cooperates with the inner ring of the first bearing 701, and the outer ring of the first bearing 701 cooperates with the housing assembly 100. In addition, there is almost no gap left when the light rod portion 412 of the lead screw 410 is inserted into the through hole of the first frame 231. Therefore, the first bearing 701 realizes the main support for the rotor support 230 and the lead screw 410, and can also allow them to rotate. Furthermore, a flange nut 704 can be used to be screwed in through the external thread of the first end 413 to fix the inner ring of the first bearing 701 of the first frame 231 inserted into the rotor support 230, such as Figure 3 and Figure 4In addition, the outer peripheral wall of the second frame 232 cooperates with the inner ring of the second bearing 702, and the outer ring of the second bearing 702 cooperates with the guide assembly 300, so the second bearing 702 provides secondary support for the rotor support 230. The support diagram of the two bearings is shown in FIG. Figure 8 As shown in the dotted box. Preferably, the first bearing 701 used as the main support is a double-row angular contact bearing, and the second bearing 702 used as the secondary support can be a single-row ball bearing. The outer peripheral wall of the intermediate frame 233 is matched and fastened with the inner ring of the motor rotor 220, so that the rotor 220 can drive the intermediate frame 233 to rotate, and then drive the lead screw 410 to rotate.

[0055] In some embodiments, the rotor support 230 includes a non-circular hole surface feature, and the lead screw 410 includes a non-circular shaft surface feature, wherein the non-circular hole surface feature and the non-circular shaft surface feature cooperate to enable the rotor support 230 to transmit a large torque when driving the lead screw 410 inserted therein to rotate. Figure 5 and Figure 8 In a preferred embodiment, a through hole between the first frame 231 and the intermediate frame 233 of the rotor support 230 is provided with a square hole portion 234, and a square shaft portion 414 is provided between the lead screw portion 411 and the smooth rod portion 412 of the lead screw 410, and the square shaft portion 414 is inserted and matched with the square hole portion 234, so that the rotor support 230 drives the lead screw 410 to rotate. It should be understood that the diameter of the first frame 231 is smaller than that of the intermediate frame 233, so the frame structure transitioning from the first frame 231 to the intermediate frame 233 extends radially, thereby forming a solid square hole portion 234 to transmit a larger torque.

[0056] Return to reference Figure 2 and Figure 3 In one embodiment, the encoder 630 includes a coding signal receiver 631 and a coding signal generator 633. The coding signal receiver 631 and the coding signal generator 633 can be readers and code disks in the form of magnetic, photoelectric, capacitive, inductive, etc. The coding signal receiver 631 can be integrated into the circuit board 620 or can be a separate part, which is fixedly connected to the internal structure of the first shell 110 in the first cavity 111 through the support 632. The coding signal generator 633 is close enough to the coding signal receiver 631 so that its movement (rotation) is fully accepted by the coding signal receiver 631. Figure 3 As shown, the coding signal generator 633 is fixedly connected to the first end 413 of the lead screw 410 in a threaded manner through a screw 703. In other embodiments, the coding signal generator 633 can also be connected to the flange nut 704.

[0057] The above embodiments basically describe the arrangement of components and parts of the rear section of the linear actuator, and some of the following embodiments describe in more detail the structure or configuration of the lead screw nut assembly 400 of the front section of the linear actuator.

[0058] In some embodiments, the linear actuator according to the present invention may use a ball-type, T-type, or standard planetary roller-type lead screw nut mechanism as a part of the structure or configuration of the lead screw nut assembly 400. The following embodiments are generally described using a ball-type lead screw nut as an example.

[0059] Reference Figures 2 to 8 , especially with reference to Figure 7 and Figure 8 In one embodiment, in the screw nut assembly 400, the push rod 430 includes a linear channel 431, an inner end 432, a shoulder 433 and an outer end 434. The nut in the screw nut assembly 400 may be a ball nut 420, which includes a ball sleeve 421 and an inner screw hole 422 disposed in the ball sleeve 421. The inner diameter of the inner screw hole 422 is greater than the diameter of the screw 410, and no balls leak out of the inner screw hole 422, so that the screw 410 that is in transmission with the nut does not interfere when passing through the inner screw hole 422. In this embodiment, the inner end 432 of the push rod 430 is fixedly connected to the inner screw hole 422 of the nut through a thread; and the shoulder 433 is positioned against the orifice surface of the inner screw hole 422, so that the axes of the push rod 430, the nut and the screw 410 in the length direction are basically aligned, and then these axes are basically aligned with the rotating shaft of the screw 410. In addition, the shoulder 433 can also strengthen the connection rigidity between the nut and the push rod 430 , while ensuring the axial positioning accuracy of 430 .

[0060] It can be understood that the structural rigidity and precision of the lead screw nut are high. If a tube or rod is directly extended from the lead screw nut in an integral manner as the linear motion output part of the linear actuator, the cost is high. Therefore, for the design requirements of the high load-to-volume ratio of the linear actuator, according to the solution of the present invention, the nut is connected by a separate push rod 430 in the form of an internal thread, which not only makes the overall diameter of the assembly smaller, but also can withstand a larger push-pull load (for example, a load of up to 10KN).

[0061] Figure 9a and Fig.10aIt is a tension and stress analysis diagram of the connection parts between the nut and the push rod 430 with internal threads and external threads respectively. In the figure, Fb is the dominant force generated by the nut being driven by the screw 410, Ft is the force acting on the first end 413 of the push rod 430, and St is the stress at the inner end 432 of the push rod 430. Linear actuators generally have two working conditions: push-out and pull-back. In the pull-back condition, the force load borne by the screw-nut assembly 400 is greater. Therefore, the directions of Fb and Ft in the figure correspond to the directions of the forces of the linear actuator in the pull-back condition. In the pull-back condition, theoretically speaking, if the internal thread fastening method is adopted, the stress generated at the connection part of the push rod 430 tends to cause the end of the push rod 430 to deform inward (such as Figure 9a If the external thread is used for fastening, the stress generated at the connection part of the push rod 430 tends to cause the end of the push rod 430 to deform outward (such as Fig.10a (as shown in the direction of St). Under the premise of the same wall thickness, the deformation of shrinkage is smaller than that of expansion, and it is less likely to break.

[0062] In addition, in order to reduce the volume and dynamic mass, the diameter of the push rod 430 can be as small as possible. Fig.10a and 10b Step rod shown. Figure 9b and Fig.10b For two push rods 430 with basically the same body diameter, finite element stress simulation comparison is performed under the same constraints, materials (such as steel) and tensile loads (such as 10KN) using the vonMises criterion. The push rod 430 with internal thread fastening generates lower stress overall and does not exceed the yield critical value of the push rod 430 material. Therefore, in the linear actuator according to the present invention, the solution of internal thread connection between the nut and the push rod 430 can achieve a compact structure and meet high load requirements. It can be understood that Fig.10a and 10b The weak point of the push rod with external thread is mainly the step transition. If the push rod with external thread is not implemented as a stepped push rod, the push and pull force it is subjected to is the same as that of the push rod with internal thread connection. However, compactness must be considered, and the stepped push rod must use internal threads to ensure strength and compactness.

[0063] In the above embodiments, the lead screw 410, the nut and the inner end 432 of the push rod 430 are arranged in the internal space formed by the housing assembly 100 and the guide assembly 300, and the outer end 434 of the push rod 430 extends out of the guide assembly 300 and is connected to the connecting assembly 500. The lead screw portion 411 of the lead screw 410 can rotate and move linearly in the linear channel 431 of the push rod 430, but does not pass through the outer end 434 of the push rod 430, wherein a small amount of lubricating grease can be arranged in the linear channel 431 of the push rod 430 without leakage and contamination, making the lubrication and maintenance of the lead screw 410 simpler.

[0064] Reference Figure 3 , Figure 4 and Figures 6 to 8 In the first embodiment, the guide assembly 300 includes an inner sleeve 310 and an outer sleeve 320. The outer sleeve 320 can be fixedly connected to the front side of the second housing 120. The outer sleeve 320 is in a stepped cylinder shape, and its cylinder diameter is larger near the housing assembly 100, and its cylinder diameter is smaller away from the housing assembly 100. The inner sleeve 310 is disposed in the outer sleeve 320 and fixed to the outer sleeve 320. The inner sleeve 310 can be in the form of a straight column to allow the nut and the push rod 430 of the screw nut assembly 400 to move linearly therein. Preferably, referring to Figure 4 and Figure 8 The inner sleeve 310 is provided with convex edges 312 at both ends, so as to form a gap cavity 321 between the outer sleeve 320 and the inner sleeve 310 between the convex edges 312 at both ends. In one embodiment, in order to fix the outer and inner sleeves 310, the inner sleeve 310 coated with glue can be inserted into the outer sleeve 320, and the glue can be contained and solidified in the gap cavity 321, so as to be more firm.

[0065] Reference Figures 6 to 8 In one embodiment, the inner cylinder cavity 311 of the inner sleeve 310 is provided with a plane rail 313 as the first rotation limiting portion. Correspondingly, the nut (ball sleeve 421) includes a radial section 423 as the second rotation limiting portion. During the movement of the nut in the inner cylinder cavity 311, the plane rail 313 is substantially in contact with the radial section 423 to limit the relative rotation between the nut and the inner sleeve 310, but allows the nut to move linearly along the plane rail 313. The plane rail 313 can penetrate the inner sleeve 310 all the way, such as Figure 7 Preferably, the axis of the inner sleeve 310 is substantially coincident with the axis of the lead screw nut assembly 400, and the plane rail 313 includes a pair of parallel surfaces that are symmetrical with respect to the axis of the inner sleeve 310. Similarly, the nut is also provided with a pair of radial sections 423 that are symmetrical with respect to the axis, and the distance between the pair of radial sections 423 is substantially equal to the distance between the pair of plane rails 313.

[0066] Reference Figure 6 In a preferred embodiment, the inner sleeve 310 may also be provided with a plurality of grooves 314 extending along the edge of the plane rail 313, and the grooves 314 are arranged on the edge of the plane rail 313. Figure 6 From the cross-sectional observation, the groove 314 is a hollow groove at the contact corner position of the nut and the inner sleeve 310, and can have a rounded cross-sectional profile, which can reduce the friction resistance of the nut when it moves linearly in the inner sleeve 310, while reducing the difficulty of processing and facilitating processing. In addition, the groove 314 can contain lubricating grease to maintain a long-term lubrication effect and reduce wear on parts. Preferably, the hardness of the material of at least the contact portion of the inner sleeve 310 with the nut is lower than the hardness of the nut. For example, the inner sleeve 310 is made of copper alloy, and the nut is made of carbon steel. The separation of the inner sleeve 310 and the outer sleeve 320 into two parts is also based on the fact that the outer sleeve 320 uses harder steel as a support, while the inner sleeve 310 uses a relatively soft copper alloy material, which is suitable for lubrication and wear reduction.

[0067] Therefore, refer to Fig.11 Under the constraints of the planar rail 313 of the inner sleeve 310 and the radial section 423 of the ball nut 420, when the motor rotor 220 drives the lead screw 410 to rotate clockwise and counterclockwise (as shown in the rotation direction R in the figure), the push rod 430 drives the connecting assembly 500 to push out and pull back the linear motion S.

[0068] In addition, return to reference Figure 4 The outer sleeve 320 is provided with a convex ring portion 322 on the side adjacent to the second housing 120 for positioning and supporting the second bearing 702. The second bearing 702 is not positioned and supported by the housing assembly 100 like the first bearing 701, taking into account the convenience of bearing assembly. For example, when the motor rotor 220, the rotor bracket 230, the guide assembly 300, the lead screw nut assembly 400 (including the push rod 430) and the second bearing 702 are assembled together, and then inserted into the first bearing 701 that has been positioned by the second housing 120, it is sufficient to position the guide assembly 300 and the second housing 120 through the barrel shoulder and tighten the screw 703 to install it, thereby saving the alignment of the second bearing 702 and the first bearing 701.

[0069] Now refer to Figure 12 to Figure 14 In the second embodiment, the guide assembly 300 includes an outer sleeve 320 and a guide piece 330 fixedly connected to the outer sleeve 320. Fig.13In one embodiment, the guide assembly 300 may further include a clamping block 340, which allows the push rod 430 to pass through. The end side of the outer sleeve 320 is provided with a recess 323 for accommodating and positioning the guide piece 330, so that the clamping block 340 is fixedly connected to the end side of the outer sleeve 320 so that the guide piece 330 between the clamping block 340 and the outer sleeve 320 is fixed in the recess 323. In other embodiments, the positioning guide piece 330 may be provided with a glue groove (not shown in the figure), and after the positioning guide piece 330 is adjusted to a suitable position with the outer sleeve 320, the glue will adhere to the clamping block 340 after drying. The guide piece 330 has a non-circular hole as the first rotation limiting portion. The outer periphery of the outer end portion 434 of the push rod 430 of the lead screw nut assembly 400 is formed as a non-circular shaft to serve as the second rotation limiting portion. Since the nut is fixedly connected to the inner end 432 of the push rod 430, during the movement of the nut in the outer sleeve 320, the non-circular shaft of the push rod 430 continues to pass through the non-circular hole to limit the relative rotation between the nut and the outer sleeve 320. Fig.12 , the non-circular hole is a square hole 333, the non-circular shaft is a square shaft 435, and the size of the square shaft 435 is substantially equal to or slightly smaller than the size of the square hole 333. Preferably, the hardness of the material of the guide piece 330 is lower than the hardness of the push rod 430. For example, the guide piece 330 is made of copper alloy, and the push rod 430 is made of steel to improve the lubrication effect and reduce wear.

[0070] Therefore, refer to Fig.14 Under the rotation constraint between the guide piece 330 and the push rod 430, when the motor rotor 220 drives the lead screw 410 to rotate clockwise and counterclockwise, the push rod 430 drives the connecting assembly 500 to push out and pull back a linear motion.

[0071] It can be understood that the guide assembly 300 in the first embodiment is generally suitable for use in a linear actuator with a short stroke, while the guide assembly 300 in the second embodiment is generally more suitable for use in a linear actuator with a long stroke.

[0072] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A linear actuator, characterized in that: include: A housing assembly (100), the housing assembly (100) having a first side and a second side; A motor assembly (200), the motor assembly (200) comprising a stator (210) and a rotor (220) disposed in the housing assembly (100); A guide assembly (300) having a first rotation limiting portion, the guide assembly (300) comprising an outer sleeve (320), the outer sleeve (320) being fixedly connected to a first side of the housing assembly (100); A screw nut assembly (400) having a second rotation limiting portion, wherein at least a portion of the screw nut assembly (400) is disposed in the housing assembly (100) and the guide assembly (300), the screw nut assembly (400) comprising a screw (410), a nut drivingly matched with the screw (410), and a push rod (430) accommodating at least a portion of the screw (410), the push rod (430) comprising a linear channel (431), an inner end portion (432), and an outer end portion (434), wherein: The linear channel (431) allows the lead screw (410) to rotate and move linearly therein, the inner end (432) is connected to the nut, the outer end (434) is disposed outside the outer sleeve (320) and connected to the connecting assembly (500), and wherein, The first rotation limiting portion and the second rotation limiting portion cooperate to limit the rotation of the nut relative to the guide assembly (300).

2. The linear actuator according to claim 1, wherein: The nut comprises an inner threaded hole (422) arranged along the axis, and the push rod (430) comprises a shaft shoulder (433); The inner end portion (432) of the push rod (430) is fixedly connected to the inner threaded hole (422) of the nut via a thread; and The shoulder (433) is positioned close to the orifice surface of the internal threaded hole (422) to allow the axis of the push rod (430) to substantially coincide with the axis of the nut.

3. The linear actuator according to claim 1 or 2, wherein: The guide assembly (300) comprises an inner sleeve (310) disposed in the outer sleeve (320) and fixed to the outer sleeve (320); an inner sleeve cavity (311) of the inner sleeve (310) is provided with a plane rail (313) to serve as the first rotation limiting portion; The nut of the screw nut assembly (400) includes a radial section (423) to serve as the second rotation limiting portion; When the nut moves in the inner sleeve cavity (311), the plane rail (313) is substantially in contact with the radial section (423) to limit the relative rotation between the nut and the inner sleeve (310).

4. The linear actuator according to claim 3, wherein: The inner sleeve (310) includes a groove (314) extending along the edge of the planar rail (313).

5. The linear actuator according to claim 3 or 4, wherein: The hardness of the material of at least the portion of the inner sleeve (310) that contacts the nut is lower than the hardness of the nut.

6. The linear actuator according to claim 1, wherein: The guide assembly (300) comprises a guide piece (330) fixedly connected to the outer sleeve (320), and the guide piece (330) has a non-circular hole to serve as the first rotation limiting portion; The inner end portion (432) of the push rod (430) of the screw nut assembly (400) is fixedly connected to the nut, and the outer periphery of the outer end portion (434) of the push rod (430) is formed as a non-circular shaft to serve as the second rotation limiting portion; During the movement of the nut in the outer sleeve (320), the non-circular shaft continues to pass through the non-circular hole to limit the relative rotation between the nut and the outer sleeve (320).

7. The linear actuator according to claim 6, wherein: The guide assembly (300) includes a pressing block (340) that allows the push rod (430) to pass through; The end side of the outer sleeve (320) is provided with a recess (323) for accommodating and positioning at least a part of the guide piece (330); The pressing block (340) is fixedly connected to the end side of the outer sleeve (320) so that the guide piece (330) between the pressing block (340) and the outer sleeve (320) is fixed in the recess (323).

8. The linear actuator according to claim 6 or 7, wherein: The hardness of the material of the guide piece (330) is lower than the hardness of the push rod (430).

9. The linear actuator according to any one of claims 1 to 8, wherein: The lead screw (410) includes a lead screw portion (411), a smooth rod portion (412) and a first end (413), wherein the lead screw portion (411) is in transmission cooperation with the nut, the lead screw portion (411) is driven by the rotor (220) of the motor assembly (200), the smooth rod portion (412) and the first end (413) are located in the housing assembly (100), and the smooth rod portion (412) is located between the lead screw portion (411) and the first end (413).

10. The linear actuator according to any one of claims 1 to 9, wherein: The motor assembly (200) comprises a rotor support (230) having a through hole, wherein the through hole allows at least a portion of the lead screw (410) to pass through and be positioned so that the rotor support (230) and the lead screw (410) rotate together, and the rotor support (230) comprises: A first frame (231), wherein the first frame (231) is supported by a first bearing (701); A second frame (232), wherein the second frame (232) is supported by a second bearing (702); An intermediate frame (233) is arranged between the first frame (231) and the second frame (232), and the intermediate frame (233) is driven by the rotor (220) of the motor assembly (200).

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