Ball screw structure with retainer and linear actuator

Abstract

The utility model discloses a ball screw structure with a retainer and a linear actuator, and belongs to the technical field of transmission structures, the ball screw structure comprises a nut and a screw rod, a first spiral groove and a second spiral groove are matched to form a spiral raceway, a plurality of balls distributed in an extending mode are arranged in the raceway, and the retainer is arranged in the screw rod. The ball screw structure further comprises a retainer arranged between the transmission part and the nut, the retainer is provided with a containing part used for containing the ball, and a limiting part used for limiting the ball between the retainer and the nut is arranged on the inner wall of the containing part. The linear actuator comprises the ball screw structure. The ball is maintained between the nut and the retainer through the limiting part, the ball is prevented from being separated from the raceway and falling out when the transmission part is partially separated from the nut, and the transmission stability of the ball screw structure is guaranteed.

Description

Technical Field

[0001] The utility model relates to the technical field of transmission structures, in particular to a ball screw structure with a retaining frame. In addition, the utility model also relates to a linear actuator adopting the ball screw structure. Background Art

[0002] The ball screw structure generally includes a screw rod, a nut and a ball arranged between the two. A spiral raceway for the ball to move is formed between the outer circumference of the screw rod and the inner circumference of the nut. The movement of the ball converts rotational motion into linear motion, or converts linear motion into rotational motion.

[0003] During ball screw operation, the balls move unidirectionally within a spiral raceway. To ensure that balls reaching the end of the raceway can return to the raceway, a return structure is typically installed on the nut. The two ends of the return structure are connected to the two ends of the raceway. Balls reaching the end of the raceway are returned to the beginning of the raceway through the return structure, allowing the balls to circulate. To ensure that the balls can smoothly return to the raceway through the return structure, the return structure has high structural and precision requirements. This makes its processing more difficult, hindering product production and assembly efficiency.

[0004] In addition, when the nut is used as the active part, the screw rod's screwed-in part must not be separated from the nut, otherwise the ball between the screw rod and the nut will be separated from the raceway and fall out, which will affect the normal transmission cooperation between the nut and the screw rod and is not conducive to ensuring the transmission function of the ball screw structure. Utility Model Content

[0005] In order to solve the shortcomings and deficiencies in the above-mentioned prior art, the utility model provides a ball screw structure with a retaining frame, which maintains the ball between the nut and the retaining frame through a limiting part, preventing the ball from falling out of the raceway when the transmission part partially disengages from the nut, thereby ensuring the transmission stability of the ball screw structure.

[0006] In order to achieve the above technical objectives, the present invention provides a ball screw structure with a cage, comprising:

[0007] A nut having a through hole and a first spiral groove provided on a wall of the through hole;

[0008] The screw rod is provided with a transmission portion cooperating with the nut, and a second spiral groove is provided on the outer circumference of the transmission portion;

[0009] The first spiral groove and the second spiral groove cooperate to form a spiral raceway, in which a plurality of balls are arranged in a longitudinal direction. The balls move along the raceway to transmit power from the screw or nut to the other.

[0010] The ball screw structure also includes a retaining frame arranged between the transmission part and the nut. The retaining frame is provided with a receiving portion for installing the ball. The inner wall of the receiving portion is provided with a limiting portion for limiting the ball between the retaining frame and the nut.

[0011] Preferably, the receiving portion is a receiving hole provided on the retaining frame, a plurality of receiving holes are provided at intervals along the same spiral track as the raceway, and the limiting portion is provided on the hole wall of the receiving hole.

[0012] Preferably, the receiving hole is conical and the hole wall of the receiving hole is a conical surface, the inner diameter of the receiving hole facing the nut is D1, the inner diameter of the receiving hole facing the transmission part is D2, the diameter of the ball is d, D1>d>D2, and the conical surface is a limiting part.

[0013] Preferably, the limiting portion is a limiting protrusion provided on the wall of the receiving hole.

[0014] Preferably, the receiving portion is a receiving groove provided on the retaining frame, the receiving groove extends along the same spiral track as the raceway, and the limiting portion is provided on the groove wall of the receiving groove.

[0015] Preferably, at least one side wall of the receiving groove is a spiral inclined surface inclined relative to the groove width direction of the receiving groove, the groove width of the receiving groove facing the nut side is W1, the groove width of the receiving groove facing the transmission part side is W2, the diameter of the ball is d, W1>d>W2, and the spiral inclined surface is a limiting part.

[0016] Preferably, the receiving groove extends continuously along the same spiral track as the raceway; or, the receiving groove is provided with at least two sections at intervals along the same spiral track as the raceway.

[0017] Preferably, the screw rod further includes a rod portion, the transmission portion is provided at one end of the rod portion, and the outer diameter of the transmission portion is equal to or greater than the outer diameter of the rod portion.

[0018] The present invention also provides a linear actuator, including a housing, a stator module and the above-mentioned ball screw structure. The ball screw structure is arranged in the housing and the screw can extend out of the housing. The nut is axially positioned and rotatably mounted in the housing, and the stator module is axially positioned and sleeved on the outside of the nut.

[0019] Preferably, the actuated rotating nut drives the screw and the retaining frame to move axially through the ball bearings. The axial length of the nut is L1, and the axial length of the retaining frame is L2. The axial distance that the screw is driven to move when the nut rotates one circle is S, and the axial distance that the retaining frame follows the movement when the nut rotates one circle is n×S, where n is 0.5~0.8, and the length of the transmission part is L3, L3=(L1-L2) / n.

[0020] After adopting the above technical solution, the utility model has the following advantages:

[0021] 1. The present invention provides a ball screw structure comprising a retainer disposed between the nut and the transmission portion of the screw. The retainer is provided with a receiving portion, and a stopper is disposed on the inner wall of the receiving portion. The receiving portion is used to accommodate balls, and the stopper is used to confine the balls between the retainer and the nut. If the transmission portion partially escapes the nut, the balls are restrained by the stopper and prevented from falling out of the raceway, ensuring that the balls remain within the raceway. When the screw returns to its original position, the balls can reengage the transmission portion, ensuring stable transmission between the screw and nut. Because the retainer is disposed between the transmission portion and the nut, when the nut or screw is actuated, the balls moving along the raceway push the retainer in a spiral motion, ensuring that the balls remain within the retainer. This eliminates the need for a conventional return mechanism on the nut, significantly reducing the structural and precision requirements of the ball screw structure and improving production efficiency. Because the stopper is disposed on the inner wall of the receiving portion, the inner and outer circumferential surfaces of the retainer are smooth, thus preventing increased friction between the retainer and the nut or between the retainer and the transmission portion.

[0022] 2. The receiving portion can be receiving holes spaced apart along the same spiral track as the raceway, or a receiving groove extending along the same spiral track as the raceway. Part of the ball is located in the receiving hole or the receiving groove, and the ball moving along the raceway can simultaneously rotate in the receiving hole or in the receiving groove, thereby reducing the friction between the ball and the nut and the screw rod, which is beneficial to improving the transmission efficiency.

[0023] 3. The receiving hole can be configured as a tapered hole, with the wall of the receiving hole being a tapered surface, with D1 > d > D2. At least one side of the receiving groove can be configured as a spiral slope, with W1 > d > W2. A reasonable relationship should be established between the inner diameter of the receiving hole and the ball diameter, or between the width of the receiving groove and the ball diameter. The tapered surface or spiral slope should be used to form a retaining element. When the transmission unit partially disengages from the nut, the ball will not fall out of the receiving hole or groove due to the restraining effect of the tapered surface or spiral slope, thus preventing the ball from escaping the raceway and falling out.

[0024] 4. The limiting portion can also be a limiting protrusion provided on the wall of the receiving hole or the wall of the receiving groove. The limiting protrusion is used to prevent the balls located in the receiving hole or the receiving groove from falling out when the transmission part is partially separated from the nut, thereby always keeping the balls between the nut and the retaining frame.

[0025] 5. The linear actuator provided by the present invention uses a ball screw structure as a rotor module. The screw of the ball screw structure can move forward or backward when the linear actuator is working. The push-pull action can be achieved by utilizing the movement of the screw. This not only reduces the assembly workload of the linear actuator structure, but also can reasonably and linearly reduce the axial length of the actuator structure, so that the linear actuator can better meet the linear actuation requirements in a small space. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 1 is a structural diagram of the ball screw structure in Example 1;

[0027] Figure 2 An exploded view of the ball screw structure in Example 1;

[0028] Figure 3 This is an axial cross-sectional view of the ball screw structure in Example 1;

[0029] Figure 4 for Figure 3 Enlarged view of point A in the middle;

[0030] Figure 5 is an axial cross-sectional view of the nut in Example 1;

[0031] Figure 6 1 is an axial cross-sectional view of the nut and the screw rod in Example 1;

[0032] Figure 7 This is a structural diagram of the retainer in Example 1;

[0033] Figure 8 for Figure 7 Enlarged view of point B in the middle;

[0034] Figure 9 A structural diagram of a portion of the retainer and the balls in Example 1;

[0035] Figure 10 is an axial cross-sectional view of the linear actuator in Example 1;

[0036] Figure 11 A structural diagram of a portion of the cage and the balls in Example 2;

[0037] Figure 12 This is a first structural diagram of the retainer in Example 3;

[0038] Figure 13 This is a second structural diagram of the retaining frame in Example 3.

[0039] In the figure, 100-ball screw structure,

[0040] 10-nut, 11-through hole, 12-first spiral groove, 20-screw, 21-transmission part, 22-second spiral groove, 23-rod, 30-raceway, 40-ball, 50-cage, 51-accommodation part, 51a-accommodation hole, 51b-accommodation groove, 52-limiting part, 52a-conical surface, 52b-limiting protrusion, 52b-spiral inclined surface,

[0041] 1000-Linear Actuator,

[0042] 200- housing, 210- main housing, 220- front cover, 230- rear cover, 240- support frame, 250- oil filling hole, 300- stator module, 410- front connector, 420- rear connector, 500- encoder, 600- control board. DETAILED DESCRIPTION

[0043] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that the following terms indicating orientations or positional relationships, such as "upper," "lower," "left," "right," "longitudinal," "lateral," "inner," "outer," "vertical," "horizontal," "top," and "bottom," are based solely on the orientations or positional relationships shown in the accompanying drawings and are intended solely for the purpose of facilitating and simplifying the description of the present invention. They do not indicate or imply that the device or element referred to must have a specific orientation or be constructed or operated in a specific orientation, and therefore should not be construed as limiting the present invention.

[0044] Example 1

[0045] Combine Figures 1 to 9 The ball screw structure 100 with a retainer provided in the first embodiment of the present invention includes:

[0046] The nut 10 is provided with a through hole 11 and a first spiral groove 12 provided on the wall of the through hole 11;

[0047] The screw rod 20 is provided with a transmission portion 21 that cooperates with the nut 10, and a second spiral groove 22 is provided on the outer circumference of the transmission portion 21;

[0048] The first spiral groove 12 and the second spiral groove 22 cooperate to form a spiral raceway 30. A plurality of balls 40 are disposed in the raceway 30. The balls 40 move along the raceway 30 to transmit power from the screw 20 or the nut 10 to the other.

[0049] The ball screw structure 100 also includes a retaining frame 50 arranged between the transmission part 21 and the nut 10. The retaining frame 50 has a receiving portion 51 for installing the ball 40. The inner wall of the receiving portion 51 is provided with a limiting portion 52 for confining the ball 40 between the retaining frame 50 and the nut 10.

[0050] When the transmission part 21 partially escapes from the nut 10, the ball 40 will not fall out of the raceway 30 due to the limiting effect of the limiting part 52, ensuring that the ball 40 is always located in the raceway 30. When the screw 20 returns to its original position, the ball 40 can re-engage with the transmission part 21 to ensure the stability of the transmission between the screw 20 and the nut 10. Since a retaining frame 50 is provided between the transmission part 21 and the nut 10, when the nut 10 or the screw 20 is actuated, the ball 40 moving along the raceway 30 pushes the retaining frame 50 to move axially, and the ball 40 is always located on the retaining frame 50. There is no need to provide a conventional returner on the nut 10, which can greatly reduce the structural requirements and precision requirements of the ball screw structure 100, and is conducive to improving production efficiency. Since the limiting part 52 is provided on the inner wall of the receiving part 51, the inner and outer peripheral surfaces of the retaining frame 50 are smooth surfaces, which can avoid increasing the friction between the retaining frame 50 and the nut 10 or between the retaining frame 50 and the transmission part 21.

[0051] In this embodiment, the screw rod 20 also includes a rod portion 23. The rod portion 23 and the transmission portion 21 can be formed as one piece, or they can be formed separately and then fixed together. The retaining frame 50 is hollow and cylindrical. In order to prevent the retaining frame 50 from interfering with the transmission between the nut 10 and the screw rod 20, the inner diameter E1 of the retaining frame 50 is slightly larger than the outer diameter C1 of the transmission portion 21, and the outer diameter E2 of the retaining frame 50 is slightly smaller than the inner diameter C2 of the through hole 11, that is, C1<E1<E2<C2. Specifically, E1-C1 can be set to a reasonable size such as 0.5mm, 0.7mm, 1mm, 1.2mm, 1.5mm, etc., and C2-E2 can be set to a reasonable size such as 0.5mm, 0.7mm, 1mm, 1.2mm, 1.5mm, 1.7mm, 2mm, etc. In this embodiment, the outer diameter of the transmission part 21 is larger than the outer diameter of the rod part 23 , and the single-side difference between the two is larger than the depth of the second spiral groove 22 . The outer diameter of the transmission part 21 is the outer diameter C1 of the screw rod 20 .

[0052] In this embodiment, the receiving portion 51 is a plurality of receiving holes 51a provided on the retainer 50. The plurality of receiving holes 51a are spaced apart along the same spiral trajectory as the raceway 30, thereby allowing the balls 40 mounted on the retainer 50 to be simultaneously located within the raceway 30. The spiral trajectory of the receiving holes 51a is consistent with the spiral trajectory of the raceway 30, meaning that the helical directions and helix angles of the two helices are consistent.

[0053] In this embodiment, the receiving hole 51a is a tapered hole, and the hole wall of the receiving hole 51a is a tapered surface 52a, which constitutes the limiting portion 52. The inner diameter of the receiving hole 51a facing the nut 10 is D1, and the inner diameter of the receiving hole 51a facing the transmission part 21 is D2. The diameter of the ball 40 is d, and D1>d>D2. The size relationship between the inner diameter of the receiving hole 51a and the diameter of the ball 40 is reasonably set, and the tapered surface 52a is used to form the limiting portion 52. When the transmission part 21 partially detaches from the nut 10, the ball 40 will not fall out of the receiving hole 51a due to the restraining effect of the tapered surface 52a, and the ball 40 will be confined between the nut 10 and the retaining frame 50, thereby preventing the ball 40 from detaching from the raceway 30 and falling out. Specifically, the slope α of the tapered surface 52a can be set to a reasonable value such as 70°, 71°, 72°, 73°, 74°, 75°, 76°, 77°, 78°, 79°, 80°, etc. In addition, the tapered receiving hole 51a can be formed by stamping the retainer 50.

[0054] To ensure effective transmission between the nut 10 and the screw rod 20 via the ball 40, the ball 40 mounted in the receiving hole 51a protrudes inwardly relative to the inner circumference of the retainer 50 by a height h1, and protrudes outwardly relative to the outer circumference of the retainer 50 by a height h2. The ratio h1 / d is approximately 30% to 35%, and the ratio h2 / d is approximately 30% to 35%. This ensures the proper height of the ball 40 in the first and second spiral grooves 12 and 22, respectively, and thus the proper height of the ball 40 in the raceway 30. For example, when the diameter d of the ball 40 is set to 3.5 mm, h1 can be set to any value within the range of 1.05 mm to 1.3 mm, and h2 can be set to any value within the range of 1.05 mm to 1.3 mm.

[0055] When assembling the ball screw structure 100, first insert one end of the retaining frame 50 into the nut 10, and then insert the balls 40 into the receiving holes 51a one by one along the spiral trajectory. While inserting the balls 40, the retaining frame 50 is further screwed into the nut 10 so that the inserted balls 40 are confined between the nut 10 and the retaining frame 50. After all the receiving holes 51a are filled with balls 40, the retaining frame 50 is also completely screwed into the nut 10. Finally, the transmission part 21 of the screw 20 is screwed into the retaining frame 50 so that the balls 40 are embedded in the second spiral groove 22. After assembly is completed, the balls 40 are located in both the raceway 30 and the receiving holes 51a. When the screw 20 or the nut 10 is actuated, the balls 40 moving along the raceway 30 can simultaneously rotate in the receiving holes 51a.

[0056] When the screw rod 20 is actuated as the active part, the axial length of the transmission part 21 is greater than the axial length of the nut 10, and the axial length of the retaining frame 50 can be approximately equal to or slightly less than the axial length of the nut 10. The actuated screw rod 20 drives the nut 10 to move through the cooperation of the balls 40 and the raceway 30, and the balls 40 moving in the raceway 30 drive the retaining frame 50 to perform spiral motion, that is, the retaining frame 50 performs axial movement and circumferential rotation at the same time.

[0057] When the nut 10 is actuated as an active part, the axial length of the nut 10 is greater than the axial length of the transmission part 21, and the axial length of the retaining frame 50 can be approximately equal to or slightly less than the axial length of the transmission part 21. When the nut 10 rotates, the screw rod 20 is driven to move through the cooperation between the balls 40 and the raceways 30. The balls 40 moving in the raceways 30 drive the retaining frame 50 to perform spiral motion, that is, the retaining frame 50 performs axial movement and circumferential rotation at the same time.

[0058] Combine Figure 10 This embodiment also provides a linear actuator 1000, comprising a housing 200, a stator module 300, and the aforementioned ball screw structure 100. The ball screw structure 100 is disposed within the housing 200, and the screw 20 can extend out of the housing 200. The nut 10 is axially positioned and rotatably mounted within the housing 200, and the stator module 300 is axially positioned and sleeved on the exterior of the nut 10. The ball screw structure 100 is directly used as the rotor module of the linear actuator 1000. The screw 20 of the ball screw structure 100 can advance or retract when the linear actuator 1000 is in operation, and the movement of the screw 20 can achieve a push-pull action. This not only reduces the assembly workload of the linear actuator structure, but also reasonably reduces the axial length of the actuator structure, enabling the linear actuator 1000 to better meet the linear actuation requirements in a small space.

[0059] Specifically, the housing 200 includes a main housing 210, a front cover 220 fixed to the front end of the main housing 210, and a rear cover 230 fixed to the rear end of the main housing 210. The nut 10 is rotatably mounted within the housing 200 and axially positioned via two spaced-apart bearings. The front end of the screw rod 20 extends out of the housing 200 and is connected to a front connector 410. The rear cover 230 is connected to a rear connector 420. The stator module 300 is sleeved outside the central area of the nut 10 and is located on the inner circumference of the housing 200. The stator module 300 can adopt a conventional structure consisting of a stator core and stator windings. The housing 200 also includes a support bracket 240 clamped between the main housing 210 and the rear cover 230. The linear actuator 1000 also includes an encoder 500 located behind the support bracket 240. A control board 600 is located behind the ball screw structure 100 within the rear end of the housing 200. The encoder 500 and the control board 600 can communicate with each other to ensure the precise operation of the linear actuator 1000. Furthermore, an oil filling port 250 is provided on the front or side wall of the housing 200. This port allows lubricating oil or grease to be added to the interior of the linear actuator 1000 after a period of operation. This ensures smooth transmission within the linear actuator 1000 and facilitates regular maintenance of the linear actuator 1000.

[0060] During operation, the rear joint 420 of the linear actuator 1000 is hingedly or fixedly connected to another object, while the front joint 410 is connected to the object being actuated. When the linear actuator 1000 is in operation, switching the direction of current flowing through the stator module 300 changes the rotation direction of the nut 10, causing the lead screw 20 to extend forward or retract backward, thereby enabling the actuated object to perform the corresponding action or execute the corresponding command. As an alternative to this embodiment, the front joint 410 and / or the rear joint 420 can also be eliminated.

[0061] When the linear actuator 1000 is in operation, the nut 10 rotates about its own central axis under the action of the stator module 300. The rotating nut 10 drives the screw 20 and retainer 50 axially via the balls 40. The length of the nut 10 is L1, and the axial length of the retainer 50 is L2. The axial distance S (one lead) of the screw 20 caused by one rotation of the nut 10 is affected by factors such as the size and distribution density of the balls 40. The axial distance n×S caused by the retainer 50 following one rotation of the nut 10 is affected by factors such as the size and distribution density of the balls 40. The axial distance n×S, where n is any value between 0.5 and 0.8, is the maximum axial movement distance of the retainer 50. To prevent the balls 40 from falling out, the retainer 50 must not fall out of the nut 10. The maximum axial movement distance of the retainer 50 is L1-L2. The length of the transmission portion 21 is L3. Therefore, L3 = (L1-L2) / n. As a feasible solution for this embodiment, L2 / L1 can be set to any ratio between 2:1 and 5:1.

[0062] It is understandable that the transmission portion 21 and the rod portion 23 may also be arranged with the same diameter, that is, the outer diameter of the transmission portion 21 is consistent with the outer diameter of the rod portion 23 .

[0063] Example 2

[0064] Combine Figure 11 In this embodiment, the limiting portion 52 is a limiting protrusion 52b provided on the wall of the receiving hole 51a. Specifically, the diameter D of the receiving hole 51a is slightly larger than the diameter d of the ball 40. The wall of the receiving hole 51a is a cylindrical surface. The limiting protrusion 52b can be formed on the wall of the receiving hole 51a by spot welding or other methods. The surface of the limiting protrusion 52b facing the center of the receiving hole 51a can be set as an inclined surface or an arc-shaped surface that matches the ball 40. The limiting protrusion 52b is used to limit the ball 40 installed in the receiving hole 51a, preventing the ball 40 from escaping from the receiving hole 51a, thereby keeping the ball 40 in the raceway 30. In order to improve the limiting effect, the limiting protrusions 52b can be evenly spaced along the circumference of the receiving hole 51a in a reasonable number such as two, three, or four.

[0065] The other structures of the ball screw structure are the same as those in the first embodiment and will not be described in detail here.

[0066] The other structures of the linear actuator except the ball screw structure are the same as those in the first embodiment and are not described in detail here.

[0067] Example 3

[0068] Combine Figure 12 In this embodiment, the receiving portion 51 is a receiving groove 51b provided on the retainer 50. The receiving groove 51b extends along the same spiral trajectory as the raceway 30, and the limiting portion 52 is provided on the groove wall of the receiving groove 51b. Specifically, at least one side of the groove wall of the receiving groove 51b is a spiral slope 52b arranged obliquely relative to the groove width of the receiving groove 51b. The spiral slope 52b constitutes the limiting portion 52. The groove width of the receiving groove 51b facing the nut 10 is W1, and the groove width of the receiving groove 51b facing the transmission portion 21 is W2. The diameter of the ball 40 is d, where W1>d>W2. The relationship between the groove width of the receiving groove 51b and the diameter of the ball 40 is appropriately determined, and the spiral slope 52b forms the limiting portion 52. When the transmission portion 21 partially detaches from the nut 10, the ball 40 is restrained by the spiral slope 52b and prevents it from falling out of the receiving groove 51b, thereby preventing the ball 40 from detaching from the raceway 30. Specifically, W1-d can be set to a reasonable size such as 0.5mm, 0.7mm, 0.9mm, 1mm, 1.2mm, 1.5mm, etc., and d-W2 can be set to a reasonable size such as 0.5mm, 0.7mm, 0.9mm, 1mm, 1.2mm, 1.5mm, etc.

[0069] As a feasible solution of this embodiment, Figure 12 As shown, the receiving groove 51b can extend continuously along the same spiral track as the raceway 30, that is, the receiving groove 51b adopts a one-stage structure; or, as shown in FIG. Figure 13 As shown, the receiving groove 51b can also be provided with at least two sections along the same spiral track as the raceway 30, that is, the receiving groove 51b adopts a segmented structure.

[0070] As a feasible solution of this embodiment, only one side wall of the receiving groove 51b can be set as a spiral inclined surface 52b, and the other side wall can be set perpendicular to the groove width direction of the receiving groove 51b; or, both side walls of the receiving groove 51b can be set as spiral inclined surfaces 52b.

[0071] As an alternative to this embodiment, the width W of the receiving groove 51b is slightly larger than the diameter of the ball 40, and a plurality of spaced-apart limiting protrusions are provided on at least one side of the groove wall of the receiving groove 51b. The limiting protrusions constitute a limiting portion 52. The distance between two adjacent limiting protrusions on the same side groove wall is smaller than the diameter d of the ball, and the limiting portion is constituted by the limiting protrusions.

[0072] The other structures of the ball screw structure are the same as those in the first embodiment and will not be described in detail here.

[0073] The other structures of the linear actuator except the ball screw structure are the same as those in the first embodiment and are not described in detail here.

[0074] In addition to the above preferred embodiments, the present invention has other implementation methods. Those skilled in the art can make various changes and modifications based on the present invention. As long as they do not depart from the spirit of the present invention, they should all fall within the scope defined in the claims of the present invention.

Claims

1. A ball screw structure with a cage, comprising: A nut having a through hole and a first spiral groove provided on a wall of the through hole; The screw rod is provided with a transmission portion cooperating with the nut, and a second spiral groove is provided on the outer circumference of the transmission portion; The first spiral groove and the second spiral groove cooperate to form a spiral raceway, in which a plurality of balls are arranged in a longitudinal direction. The balls move along the raceway to transmit power from the screw or nut to the other. It is characterized in that the ball screw structure also includes a retaining frame arranged between the transmission part and the nut, the retaining frame is provided with a receiving portion for installing the ball, and the inner wall of the receiving portion is provided with a limiting portion for confining the ball between the retaining frame and the nut.

2. The ball screw structure with a cage according to claim 1, characterized in that: The receiving portion is a receiving hole provided on the retaining frame. A plurality of receiving holes are provided at intervals along the same spiral track as the raceway. The limiting portion is provided on the hole wall of the receiving hole.

3. The ball screw structure with a retainer according to claim 2, characterized in that: The receiving hole is conical and the hole wall of the receiving hole is a conical surface. The inner diameter of the receiving hole facing the nut is D1, the inner diameter of the receiving hole facing the transmission part is D2, the diameter of the ball is d, D1>d>D2, and the conical surface is the limiting part.

4. The ball screw structure with a retainer according to claim 2, characterized in that: The limiting portion is a limiting protrusion arranged on the wall of the receiving hole.

5. The ball screw structure with a cage according to claim 1, characterized in that: The receiving portion is a receiving groove provided on the retaining frame, the receiving groove extends along the same spiral track as the raceway, and the limiting portion is provided on the groove wall of the receiving groove.

6. The ball screw structure with a retainer according to claim 5, characterized in that: At least one side of the receiving groove wall is a spiral inclined surface inclined relative to the groove width direction of the receiving groove. The groove width of the receiving groove facing the nut is W1, and the groove width of the receiving groove facing the transmission part is W2. The diameter of the ball is d, W1>d>W2, and the spiral inclined surface is a limiting part.

7. The ball screw structure with a retainer according to claim 5, characterized in that: The receiving groove extends continuously along the same spiral track as the raceway; or, the receiving groove is provided with at least two sections at intervals along the same spiral track as the raceway.

8. The ball screw structure with a cage according to claim 1, characterized in that: The screw rod further includes a rod portion, a transmission portion is provided at one end of the rod portion, and an outer diameter of the transmission portion is equal to or greater than an outer diameter of the rod portion.

9. A linear actuator comprising a housing and a stator module, characterized in that: It also includes a ball screw structure with a retaining frame as described in any one of claims 1 to 8 above, the ball screw structure is arranged in the casing and the screw can extend out of the casing, the nut is axially positioned and rotatably mounted in the casing, and the stator module is axially positioned and sleeved on the outside of the nut.

10. The linear actuator according to claim 9, wherein: The actuated rotating nut drives the screw and the retaining frame to move axially through the ball bearings. The axial length of the nut is L1, and the axial length of the retaining frame is L2. The axial distance that the screw moves when the nut rotates one circle is S, and the axial distance that the retaining frame follows the movement when the nut rotates one circle is n×S, where n is 0.5~0.

8. The length of the transmission part is L3, and L3=(L1-L2) / n.

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