Ball screw set and linear actuator

Abstract

The utility model discloses a ball screw pair and linear actuator belongs to transmission structure technical field, the ball screw pair includes nut, screw and ball, first spiral groove and second spiral groove cooperate to form spiral raceway, be equipped with a plurality of ball in the raceway, the axial length of nut is greater than the axial length of transmission portion, and the screw is equipped with the ball. A groove is formed in the peripheral face of the transmission part, a return block is embedded in the groove, a part of the second spiral groove is formed in the outer side surface of the return block, a return channel communicated with the roller path is arranged between the inner side of the return block and the transmission part, and the balls moving to one end of the roller path return to the other end of the roller path through the return channel. The linear actuator adopts the ball screw pair. The balls complete circulation in the transmission part, a return structure does not need to be arranged on the nut, the structure of the nut can be simplified, the appearance of the nut is kept regular, and the balls cannot fall out of the roller path.

Description

Technical Field

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

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

[0003] During the operation of the ball screw pair, since the balls move unidirectionally in the spiral raceway, a return channel is generally provided on the nut so that the balls that move to the end of the raceway can return to the channel. The two ends of the return channel are respectively connected to the two ends of the raceway. The balls that move to the end of the raceway return to the starting end of the raceway through the return channel, thereby allowing the balls to circulate.

[0004] When the axial length of the nut is greater than the axial length of the external thread on the screw, if the return channel is still provided on the nut, the balls will fall out of the return channel when the internal thread on the nut cannot fully engage with the external thread on the screw. Not only will the fallen balls be unable to return to the raceway to participate in the transmission, but they will also interfere with the transmission between the nut and the screw, which is not conducive to ensuring the transmission stability of the structure. In addition, because the return channel is provided on the nut, the nut structure is relatively complex and generally forms a protruding structure on the outer surface of the nut, which is not conducive to the nut and other components to cooperate. 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 pair, in which the balls complete the circulation inside the transmission part, and there is no need to set a return structure on the nut. The structure of the nut can be simplified and the shape of the nut can be kept regular, and the balls will not fall out of the raceway.

[0006] In order to achieve the above technical objectives, the ball screw pair provided by the present invention includes:

[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 part cooperating with the nut, and a second spiral groove is provided on the outer circumference of the transmission part.

[0009] The first spiral groove and the second spiral groove cooperate to form a spiral rolling track, and a plurality of balls are arranged in the rolling track.

[0010] The axial length of the nut is greater than the axial length of the transmission part. A groove is provided on the outer peripheral surface of the transmission part, and a return block is embedded in the groove. Part of the second spiral groove is provided on the outer surface of the return block. A return channel connected to the raceway is provided between the inner side of the return block and the transmission part. The balls moving to one end of the raceway return to the other end of the raceway through the return channel.

[0011] Preferably, a return groove is provided on the inner side of the return block, and the return channel is formed by the return groove and the bottom wall of the groove; or, a first groove body is provided on the inner side of the return block, and a second groove body corresponding to the first groove body is provided on the bottom wall of the groove, and the return channel is formed by the first groove body and the second groove body.

[0012] Preferably, there is one raceway, one groove and one return block; or, the raceway is provided with at least two raceways having the same rotation direction and being independent of each other, the number of grooves and return blocks is consistent with the number of raceways, and a return channel connected to different raceways is formed between the inner side of each return block and the transmission part.

[0013] Preferably, the return channel includes a main body section and transition sections provided at both ends of the main body section, and a connecting groove for connecting the raceway and the transition section is provided on the transmission part.

[0014] Preferably, the transition section extends from the end of the main section to the lateral surface of the return block, and the connecting groove extends from the outer peripheral surface of the transmission part to the side groove wall of the groove.

[0015] Preferably, the extending direction of the transition section is substantially consistent with the extending direction of the connecting groove, so that the transition section and the connecting groove are smoothly connected.

[0016] Preferably, the main body section extends along the axial direction of the screw rod.

[0017] Preferably, the groove extends along the axial direction of the screw rod, and the return block is in the shape of an elongated strip.

[0018] Preferably, the width of the return block is W, the diameter of the ball is d, and 2.5≤W / d≤4.

[0019] The utility model also provides a linear actuator, including a housing, a stator module and the ball screw pair described above, the ball screw pair is arranged in the housing and the screw can extend out of the housing, the nut can be rotatably mounted in the housing, and the stator module is axially positioned and sleeved on the outside of the nut.

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

[0021] 1. The ball screw pair provided by the present invention has a return block provided on the outer peripheral surface of the transmission portion, a portion of the second spiral groove is provided on the outer surface of the return block, a return channel is provided between the inner side of the return block and the transmission portion, and the return channel is connected to the raceway. The balls moving to one end of the raceway can return to the other end of the raceway through the return channel, so that the balls can circulate back and forth in the raceway, thereby enabling the balls to meet the power transmission requirements between the nut and the screw. Since the return channel is provided between the inner side of the return block and the transmission portion, the balls complete the circulation inside the transmission portion, and there is no need to provide a return structure on the nut. This can simplify the structure of the nut and keep the nut's shape regular, making it easier to match the nut with other components, and also reduce the difficulty of processing the return raceway. Since the axial length of the nut is greater than the axial length of the transmission portion and since the balls complete the circulation inside the transmission portion, the balls will not fall out of the raceway, thus preventing the fallen balls from interfering with the transmission coordination between the screw and the nut, thereby ensuring the transmission stability of the ball screw pair.

[0022] 2. The return channel can be formed by the return groove on the inner side of the return block and the bottom wall of the groove. The return channel can also be formed by the first groove body on the inner side of the return block and the second groove body on the bottom wall of the groove. The specific forming structure of the return channel is reasonably set to reduce the processing difficulty of the return channel.

[0023] 3. The raceway can be single, or two or more. The number of grooves and return blocks matches the number of raceways. Return channels, connected to different raceways, are formed between the inner side of each return block and the transmission unit. This allows balls that reach the end of a channel to return to the beginning of that channel through the corresponding return channel. When two or more raceways are provided, the lead of the transmission unit per one rotation is significantly increased, significantly increasing the axial speed of the screw.

[0024] 3. The return channel consists of a main section and a transition section. A connecting groove is provided on the transmission unit to connect the end of the raceway with the transition section. Balls that reach the end of the raceway enter the return channel through the connecting groove. After passing through the return channel, the balls re-enter the raceway from the connecting groove, allowing the balls to circulate within the raceway. The specific structure of the return channel and transmission unit is rationally designed to ensure that the balls can smoothly return to the raceway through the return channel.

[0025] 4. The extension direction of the transition section is preferably basically consistent with the extension direction of the connecting groove, so that the transition section and the connecting groove can be smoothly connected, so that the balls can move smoothly between the connecting groove and the transition section, avoiding the situation where the movement of the balls between the connecting groove and the transition section is blocked, resulting in obstruction of the ball screw pair transmission or transmission failure.

[0026] 5. The main section of the return channel preferably extends along the axial direction of the screw rod, so that the length of the return channel can be shortened as much as possible, thereby shortening the movement path length of the ball returning to the raceway through the return channel as much as possible, so that the ball moving to the end of the raceway can return to the starting end of the raceway as soon as possible through the return channel.

[0027] 6. The groove preferably extends along the axial direction of the screw rod. Accordingly, the return block is in the shape of an elongated strip. Reasonable design of the shapes of the groove and the return block can not only reduce the processing difficulty of the groove and the return block, but also reduce the assembly difficulty of the return block and the groove.

[0028] 7. The linear actuator provided by this utility model directly utilizes the aforementioned ball screw pair as the rotor module. The screw can advance or retract during operation, and the movement of the screw can achieve push-pull motion. Using the ball screw pair as the rotor module not only reduces the assembly workload of the linear actuator structure but also reasonably reduces the axial length of the linear actuator structure, enabling the linear actuator to better meet the requirements of linear actuation in small spaces. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of the structure of the ball screw pair in Example 1;

[0030] Figure 2 1 is an exploded view of the ball screw pair in Example 1;

[0031] Figure 3 This is an axial cross-sectional view of the ball screw assembly structure in Example 1;

[0032] Figure 4 An axial cross-sectional view of the ball screw assembly structure in Example 1, which deviates from the central axis;

[0033] Figure 5 is an axial cross-sectional view of the nut in Example 1;

[0034] Figure 6 1. It is an exploded view of the screw rod and the return block in Example 1;

[0035] Figure 7 This is a structural diagram of the return block in Example 1;

[0036] Figure 8 It is a partial structural diagram of the screw rod in Example 1;

[0037] Figure 9 is an axial cross-sectional view of the linear actuator in Example 1;

[0038] Figure 10 This is a partial structural diagram of the screw rod in Example 2;

[0039] Figure 11This is an axial cross-sectional view of the ball screw pair structure in Example 2.

[0040] In the figure, 100-ball screw pair, 110-nut, 111-through hole, 112-first spiral groove, 120-screw, 121-transmission part, 122-second spiral groove, 122a-main groove section, 122b-connecting groove section, 123-groove, 123a-bottom wall, 123b-side groove wall, 124-connecting groove, 125-rod, 126-second groove body, 130-roller, 140-ball, 150-return block, 151-outer surface, 152-inner surface, 153-return groove, 154-lateral surface, 155-first groove body, 160-return channel, 161-main section, 162-transition section,

[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 8 The ball screw pair 100 provided in the first embodiment of the present invention includes:

[0046] The nut 110 is provided with a through hole 111 and a first spiral groove 112 provided on the wall of the through hole 111;

[0047] The screw rod 120 is provided with a transmission part 121 that cooperates with the nut 110. The outer peripheral surface of the transmission part 121 is provided with a second spiral groove 122.

[0048] The first spiral groove 112 and the second spiral groove 122 cooperate to form a spiral raceway 130 , in which a plurality of balls 140 are arranged in a longitudinal distribution;

[0049] The axial length of the nut 110 is greater than the axial length of the transmission part 121. A groove 123 is provided on the outer peripheral surface of the transmission part 121, and a return block 150 is embedded in the groove 123. A part of the second spiral groove 122 is provided on the outer surface 151 of the return block 150. A return channel 160 connected to the raceway 130 is provided between the inner side of the return block 150 and the transmission part 121. The ball 140 that moves to one end of the raceway 130 returns to the other end of the raceway 130 through the return channel 160.

[0050] Because the return channel 160 is provided between the inner side of the return block 150 and the transmission portion 121, the balls 140 complete their circulation within the transmission portion 121, eliminating the need for a return structure on the nut 110. This simplifies the structure of the nut 110 and maintains a regular shape, facilitating the coordination of the nut 110 with other components and reducing the difficulty of machining the return raceway 130. Since the balls 140 complete their circulation within the transmission portion 121, they will not fall out of the raceway 130, preventing any interference with the transmission coordination between the screw rod 120 and the nut 110 caused by the fallen balls 140, thereby ensuring the transmission stability of the ball screw assembly 100.

[0051] In this embodiment, the side facing the central axis of the screw rod 120 is defined as the inner side, and the side facing away from the central axis of the screw rod 120 is defined as the outer side. The inner diameter of the through hole 111 is slightly larger than the outer diameter of the transmission portion 121 to prevent friction between the hole wall of the through hole 111 and the outer peripheral surface of the transmission portion 121 during relative motion, thereby allowing the nut 110 and the screw rod 120 to move smoothly relative to each other. The axial length of the first spiral groove 112 is substantially consistent with the axial length of the nut 110, and the axial length of the second spiral groove 122 is substantially consistent with the axial length of the transmission portion 121. The spiral trajectories of the first spiral groove 112 and the second spiral groove 122 are consistent, and the groove depth and groove width of the first spiral groove 112 and the second spiral groove 122 are also substantially consistent. The depth of the raceway 130 formed by the first spiral groove 112 and the second spiral groove 122 is substantially consistent with the diameter of the ball 140. The ball 140 rotates while performing spiral motion along the transmission raceway 130.

[0052] In this embodiment, the raceway 130 utilizes a single-thread structure, meaning only one raceway 130 is provided. Accordingly, only one groove 123 and one return block 150 are provided. The groove 123 is recessed from the outer circumference of the transmission portion 121 toward the central axis of the screw rod 120. The depth of the groove 123 is substantially consistent with the thickness of the return block 150. The outer surface 151 of the return block 150 is curved and has a diameter substantially consistent with the diameter of the transmission portion 121. The second spiral groove 122 comprises a main groove section 122a provided on the outer circumference of the transmission portion 121 and a connecting groove section 122b provided on the outer surface 151 of the return block 150. The main groove section 122a and the connecting groove section 122b combine to form a spiral groove. Furthermore, the groove 123 extends along the axial direction of the screw rod 120, and accordingly, the return block 150 is in the shape of an elongated strip. Properly designing the shapes of the groove 123 and the return block 150 not only reduces the difficulty in machining the groove 123 and the return block 150, but also reduces the difficulty in assembling the return block 150 and the groove 123. As an alternative to this embodiment, the groove 123 may also be designed in other reasonable shapes, such as a spiral shape, and the shape of the return block 150 may be consistent with that of the groove 123.

[0053] In this embodiment, a return groove 153 is provided on the inner surface 152 of the return block 150, and the return channel 160 is formed by the return groove 153 and the bottom wall 123a of the groove 123. In this way, only the return groove 153 needs to be machined on the return block 150, which can reduce the machining difficulty.

[0054] In this embodiment, the return channel 160 includes a main section 161 and transition sections 162 disposed at both ends of the main section 161. The transmission portion 121 is provided with connecting grooves 124 for connecting the raceway 130 with the transition sections 162. Specifically, the main section 161 preferably extends axially along the screw rod 120. This minimizes the length of the return channel 160, thereby minimizing the motion path of the balls 140 returning to the raceway 130 through the return channel 160. One transition section 162 extends from the end of the main section 161 to one of the lateral surfaces 154 of the return block 150, and the other transition section 162 extends from the end of the main section 161 to the other lateral surface 154 of the return block 150. In other words, the two transition sections 162 extend from the ends of the main section 161 to two opposing lateral surfaces 154 of the return block 150, respectively. The connecting groove 124 extends from the outer circumferential surface of the transmission portion 121 to the side groove wall 123b of the groove 123. Specifically, two connecting grooves 124 are provided, each corresponding to two transition sections 162. One connecting groove 124 extends from the second spiral groove 122 to the side groove wall 123b on one side of the groove 123 and connects with one transition section 162. The other connecting groove 124 extends from the second spiral groove 122 to the side groove wall 123b on the other side of the groove 123 and connects with the other transition section 162. The ball 140 that moves to one end of the raceway 130 enters the return channel 160 through one connecting groove 124. After passing through the return channel 160, the ball 140 returns to the other end of the raceway 130 through the other connecting groove 124, thereby achieving reciprocating circulation of the ball 140. As an alternative to this embodiment, the main section 161 can also be configured in other reasonable shapes such as an S-shape or a spiral shape.

[0055] To allow the ball 140 to smoothly pass through the connecting groove 124 and enter the return channel 160, the extension direction of the transition section 162 is substantially aligned with the extension direction of the connecting groove 124. This eliminates the corner between the connecting groove 124 and the transition section 162, allowing the transition section 162 and the connecting groove 124 to smoothly connect, thereby allowing the ball 140 to move smoothly between the connecting groove 124 and the transition section 162. Specifically, the connecting groove 124 and the transition section 162 at one end extend generally along the direction indicated by the straight line E1, while the connecting groove 124 and the transition section 162 at the other end extend generally along the direction indicated by the straight line E2. Furthermore, the extension directions of the two transition sections 162 are generally parallel, and the extension directions of the two connecting grooves 124 are also generally parallel, that is, the straight line E1 is generally parallel to the straight line E2. In a specific structure, due to factors such as processing errors, the extension direction of the transition section 162 may be at a certain angle to the extension direction of the connecting groove 124. This angle can be within 2°. As an alternative to this embodiment, provided that the ball 140 can move smoothly, the transition section 162 and the connecting groove 124 at the same end can also extend in an angled manner. As an alternative to this embodiment, the two transition sections 162 can also extend in non-parallel directions, and the two connecting grooves 124 can also extend in non-parallel directions.

[0056] To ensure that the ball 140 can move smoothly in the return channel 160, in this embodiment, the width K and depth H of the return channel 160 are both greater than the diameter d of the ball 140. Specifically, the difference between the width K of the return channel 160 and the diameter d of the ball 140 can be set to a reasonable value such as 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, or 1 mm, and the difference between the depth H of the return channel 160 and the diameter d of the ball 140 can be set to a reasonable value such as 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, or 1 mm.

[0057] Since the return groove 153 is completely located on the return block 150, in order to minimize the size of the return block 150 while ensuring its structural strength, the outer dimensions of the return block 150 must be appropriately configured. The width of the return block 150 is W, the maximum thickness is T, and the diameter of the ball 140 is d. 2.5 ≤ W / d ≤ 4, and 2 ≤ T / d ≤ 3. In this embodiment, W / d is approximately 3, and T / d is approximately 2.5. As an alternative to this embodiment, W / d can also be set to other reasonable values, such as 2.5, 2.8, 3.1, 3.3, 3.5, 3.7, or 4, and T / d can also be set to other reasonable values, such as 2, 2.2, 2.4, 2.6, 2.8, or 3.

[0058] In this embodiment, the nut 110 is actuated as an active member, and when the nut 110 rotates, the screw rod 120 is driven to move axially through the ball 140. The screw rod 120 also includes a rod portion 125, and the end of the rod portion 125 away from the transmission portion 121 can be connected to the driven object, and the object can be driven to move back and forth through the ball screw pair 100. The rod portion 125 and the transmission portion 121 can be integrally formed, or the rod portion 125 and the transmission portion 121 can be separately formed and then assembled together. In this embodiment, the outer diameter of the rod portion 125 can be smaller than the outer diameter of the transmission portion 121, and the outer diameter of the rod portion 125 can also be equal to the outer diameter of the transmission portion 121.

[0059] During assembly, grease is first applied to the return block 150 and the transmission portion 121. The return block 150 is then installed into the groove 123. The return block 150 is temporarily positioned in the groove 123 due to the adhesion of the grease. The balls 140 are then adhered to the second spiral groove 122 using the grease. Alternatively, some of the balls 140 can be inserted into the return raceway 130. Finally, the transmission portion 121 with the balls 140 adhered is screwed into the nut 110. Of course, the assembly method of the ball screw pair 100 is not limited to this. This is only for illustrative purposes. Other reasonable assembly methods can also be used for the ball screw pair 100.

[0060] Combine Figure 9 This embodiment further provides a linear actuator 1000, comprising a housing 200, a stator module 300, and the aforementioned ball screw pair 100. The ball screw pair 100 is disposed within the housing 200, and a screw rod 120 can extend out of the housing 200. A nut 110 is rotatably mounted within the housing 200, and the stator module 300 is axially positioned and sleeved on the exterior of the nut 110. The ball screw pair 100 is directly used as the rotor module of the linear actuator. The screw rod 120 of the ball screw pair 100 can extend or retract into the housing 200 when the linear actuator 1000 is operating. The movement of the screw rod 120 can achieve a push-pull action, which not only reduces the assembly workload of the linear actuator structure, but also reduces the axial length of the linear actuator structure, enabling the linear actuator to better meet the linear actuation requirements in a small space.

[0061] 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 110 is rotatably mounted within the housing 200 and axially positioned via two spaced-apart bearings. The front end of the screw rod 120 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 110 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, which is clamped between the main housing 210 and the rear cover 230. The linear actuator 1000 also includes an encoder 500, which is located behind the support bracket 240. A control board 600 is located within the rear end of the housing 200, behind the ball screw assembly 100. 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.

[0062] 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 110, causing the lead screw 120 to extend forward or retract backward, thereby enabling the actuated object to perform a corresponding action or execute a corresponding instruction.

[0063] In this embodiment, the nut 110 is actuated as the active element, and the screw 120 is a driven element. When the nut 110 is actuated, the nut 110 rotates about its own central axis. The rotating nut 110 drives the screw 120 to move axially via the balls 140, thereby achieving the extension and retraction of the screw 120. For example, when the nut 110 is actuated to rotate in the forward direction, the balls 140 move from back to front within the raceway 130, causing the screw 120 to extend relative to the nut 110. When the nut 110 is actuated to rotate in the reverse direction, the balls 140 move from front to back within the raceway 130, causing the screw 120 to retract relative to the nut 110.

[0064] In this embodiment, the ratio of the axial lengths of the nut 110 and the transmission portion 121 can be set to a range of 1.5:1 to 8:1. Specifically, the axial length ratio of the nut 110 and the transmission portion 121 can be set to a reasonable value such as 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, 5.5:1, 6:1, 6.5:1, 7:1, 7.5:1, 8:1, etc., and the second spiral groove 122 can be set to a reasonable number of turns such as 2 turns, 3 turns, 4 turns, 5 turns, 6 turns, 7 turns, 8 turns, 9 turns, 10 turns, etc.

[0065] As a further solution of this embodiment, for the nut 110 with a larger axial length, in order to reduce the difficulty of processing the first spiral groove 112 on the wall of the through hole 111, the nut 110 can adopt a multi-section combination structure.

[0066] In other schemes of this embodiment, two first spiral grooves 112 with the same rotation direction and independent of each other are provided on the wall of the through hole 111, and two second spiral grooves 122 with the same rotation direction and independent of each other are provided on the outer peripheral surface of the transmission part 121. Accordingly, the two first spiral grooves 112 and the two second spiral grooves 122 cooperate to form two raceways 130 with the same rotation direction and independent of each other. The starting point of each raceway 130 is staggered in the circumferential direction, and the end point of each raceway 130 is also staggered in the circumferential direction, and each raceway 130 is provided with a ball 140, that is, the raceway 130 adopts a double-line thread structure. Correspondingly, the outer circumference of the transmission portion 121 is provided with two grooves 123. Two return blocks 150 are also provided, each embedded in one of the grooves 123. A return channel 160 is provided between the inner side of one return block 150 and the transmission portion 121, communicating with one of the raceways 130. A return channel 160 is provided between the inner side of the other return block 150 and the transmission portion 121, communicating with the other raceway 130. Balls 140 that have reached the end of a raceway 160 return to the beginning of that raceway 150 through its corresponding return channel 160. In this case, the two return blocks 150 are preferably evenly spaced along the circumference of the transmission portion 121. Alternatively, the raceways 130 may be provided with three, four, or other suitable numbers of mutually independent, identical rotational directions. The number of grooves 123 and return blocks 150 matches the number of raceways 130. Each return block 150 forms a return channel 160 corresponding to that raceway 130 between the return block 150 and the transmission portion 121.

[0067] Example 2

[0068] Combine Figure 10 、 Figure 11In this embodiment, a first groove body 155 is provided on the inner surface of the return block 150, and a second groove body 126 corresponding to the first groove body 155 is provided on the bottom wall 123a of the groove 123. The return channel 160 is formed by the first groove body 155 and the second groove body 126.

[0069] The other structures of the ball screw pair 100 are the same as those in the first embodiment and will not be described in detail here.

[0070] The other structures of the linear actuator except the ball screw pair 100 are the same as those in the first embodiment and are not described in detail here.

[0071] 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. Ball screw pair, including: 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 part cooperating with the nut, and a second spiral groove is provided on the outer circumference of the transmission part. The first spiral groove and the second spiral groove cooperate to form a spiral rolling track, and a plurality of balls are arranged in the rolling track. It is characterized in that the axial length of the nut is greater than the axial length of the transmission part, a groove is provided on the outer peripheral surface of the transmission part, a return block is embedded in the groove, a part of the second spiral groove is provided on the outer surface of the return block, and a return channel connected to the raceway is provided between the inner side of the return block and the transmission part, and the balls moving to one end of the raceway return to the other end of the raceway through the return channel.

2. The ball screw pair according to claim 1, characterized in that: A return groove is provided on the inner side of the return block, and the return channel is formed by the return groove and the bottom wall of the groove; or, a first groove body is provided on the inner side of the return block, and a second groove body corresponding to the first groove body is provided on the bottom wall of the groove, and the return channel is formed by the first groove body and the second groove body.

3. The ball screw pair according to claim 1, characterized in that: There is one raceway, one groove and one return block; or, there are at least two raceways with the same rotation direction and independent of each other, the number of grooves and return blocks is consistent with the number of raceways, and a return channel connected to different raceways is formed between the inner side of each return block and the transmission part.

4. The ball screw pair according to claim 1, characterized in that: The return channel includes a main body section and transition sections arranged at both ends of the main body section, and a connecting groove for connecting the raceway and the transition section is provided on the transmission part.

5. The ball screw pair according to claim 4, characterized in that: The transition section extends from the end of the main section to the lateral surface of the return block, and the connecting groove extends from the outer peripheral surface of the transmission part to the side groove wall of the groove.

6. The ball screw pair according to claim 5, characterized in that: The extending direction of the transition section is substantially consistent with the extending direction of the connecting groove, so that the transition section and the connecting groove are smoothly connected.

7. The ball screw pair according to claim 4, characterized in that: The main body section extends along the axial direction of the screw rod.

8. The ball screw pair according to claim 1, characterized in that: The groove extends along the axial direction of the screw rod, and the return block is in the shape of a long strip.

9. The ball screw pair according to claim 1, characterized in that: The width of the return block is W, the diameter of the ball is d, and 2.5≤W / d≤4.

10. A linear actuator comprising a housing and a stator module, characterized in that: It also includes the ball screw pair according to any one of claims 1 to 9 above, the ball screw pair is arranged in the casing and the screw rod can extend out of the casing, the nut can be rotatably mounted in the casing, and the stator module is axially positioned and sleeved on the outside of the nut.

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