Ball screw set and linear actuator

Abstract

The invention discloses a ball screw pair and a linear actuator, and belongs to the technical field of transmission structures, the ball screw pair comprises a nut, a screw rod and balls, 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, the axial length of the nut is larger than that of a transmission part, and the screw rod is arranged in the screw rod. 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 present invention relates to the technical field of transmission structures, and in particular to a ball screw pair. In addition, the present invention also relates to a linear actuator using the ball screw pair. Background Art

[0002] A ball screw pair generally includes a screw rod, a nut and a ball disposed therebetween. A spiral raceway is formed between the outer circumference of the screw rod and the inner circumference of the nut for the ball to move. The movement of the ball 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 in order to allow the balls that move to the end of the raceway to 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 beginning 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 set on the nut, the internal thread on the nut cannot fully mesh with the external thread on the screw and the ball will fall out of the return channel. The fallen ball will not only be unable to return to the raceway to participate in the transmission, but 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, since the return channel is set on the nut, the structure of the nut is relatively complex and generally a protruding structure will be formed on the outer surface of the nut, which is not conducive to the nut and other components. Matching. Summary of the invention

[0005] In order to solve the shortcomings and deficiencies in the above-mentioned prior art, the present invention provides a ball screw pair, in which the balls complete 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 comprises:

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

[0008] The screw rod is provided with a transmission part matched with the nut, and a second spiral groove is provided on the outer peripheral surface of the transmission part.

[0009] The first spiral groove cooperates with the second spiral groove to form a spiral rolling track, and a plurality of balls distributed in a continuous manner 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. A 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 cooperation of 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 cooperation of the first groove body and the second groove body.

[0012] Preferably, the raceway is provided with one, and the groove and the return block are provided with one; or, the raceway is provided with at least two raceways with the same rotation direction and independent of each other, the number of the grooves and the return blocks are consistent with the number of the 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 comprises a main section and transition sections arranged at both ends of the main 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 is smoothly connected with the connecting groove.

[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 present invention 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 present invention has the following advantages:

[0021] 1. The ball screw pair provided by the present invention is provided with a return block on the outer peripheral surface of the transmission part, and a part 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 part, and the return channel is connected with 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 and reciprocate in the raceway, so that the balls meet the power transmission requirements between the nut and the screw rod. Since the return channel is provided between the inner side of the return block and the transmission part, the balls complete the circulation inside the transmission part, and there is no need to provide a return structure on the nut, which can simplify the structure of the nut and keep the shape of the nut regular, facilitate the matching of the nut with other components, and reduce the processing difficulty of the return raceway. Since the axial length of the nut is greater than the axial length of the transmission part and since the balls complete the circulation inside the transmission part, the balls will not fall out of the raceway, so as to avoid the dropped balls from interfering with the transmission matching between the screw rod and the nut, and ensure 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 formation structure of the return channel is reasonably set to reduce the processing difficulty of the return channel.

[0023] 3. There can be only one raceway, or two or more raceways. The number of grooves and return blocks is consistent with the number of raceways. The inner side of each return block forms a return channel connected to different raceways with the transmission part, so that the ball moving to the end of a channel can return to the beginning of the raceway through the corresponding return channel. When there are two or more raceways, the lead of the transmission part during one rotation is significantly increased, which can significantly increase the axial movement speed of the screw.

[0024] 3. The return channel includes a main section and a transition section. A connecting groove is provided on the transmission part to connect the end of the raceway with the transition section. The balls moving to the end of the raceway enter the return channel through the connecting groove. The balls passing through the return channel re-enter the raceway from the connecting groove, so that the balls can circulate in the raceway. The specific structure of the return channel and the transmission part is reasonably set so 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 ball can move smoothly between the connecting groove and the transition section, avoiding the situation where the movement of the ball 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 beginning 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 the present invention directly uses the ball screw pair described above as a rotor module. The screw rod can move forward or backward when the linear actuator is working, and the push-pull action can be achieved by the movement of the screw rod. Using the ball screw pair as a rotor module can not only reduce the assembly workload of the linear actuation structure, but also reasonably reduce the axial length of the linear actuation structure, so that the linear actuator can better meet the linear actuation requirements in a small space. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a structural schematic diagram of the ball screw pair in the first embodiment;

[0030] Figure 2 An exploded view of the ball screw pair in the first embodiment;

[0031] Figure 3 It is an axial cross-sectional view of the structure of the ball screw pair in the first embodiment;

[0032] Figure 4 It is an axial cross-sectional view of the ball screw pair structure in the first embodiment deviating from the central axis;

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

[0034] Figure 6 It is an exploded view of the screw rod and the return block in the first embodiment;

[0035] Figure 7 It is a structural diagram of the return block in the first embodiment;

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

[0037] Fig. 9 is an axial cross-sectional view of the linear actuator in Embodiment 1;

[0038] Fig.10 It is a partial structural diagram of the screw rod in the second embodiment;

[0039] Fig.11It is an axial cross-sectional view of the ball screw pair structure in the second embodiment.

[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 is further described below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the following words indicating orientation or positional relationship such as "upper", "lower", "left", "right", "longitudinal", "lateral", "inner", "outer", "vertical", "horizontal", "top", "bottom", etc. are only based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device / element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention.

[0044] Embodiment 1

[0045] Combination 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 matched with the nut 110, and a second spiral groove 122 is provided on the outer peripheral surface of the transmission part 121.

[0048] The first spiral groove 112 cooperates with the second spiral groove 122 to form a spiral raceway 130, and a plurality of balls 140 are arranged in the raceway 130.

[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 moving to one end of the raceway 130 returns to the other end of the raceway 130 through the return channel 160.

[0050] Since the return channel 160 is disposed between the inner side of the return block 150 and the transmission part 121, the ball 140 completes the circulation inside the transmission part 121, and there is no need to provide a return structure on the nut 110, which can simplify the structure of the nut 110 and keep the shape of the nut 110 regular, facilitate the coordination of the nut 110 with other components, and reduce the processing difficulty of the return raceway 130. Since the ball 140 completes the circulation inside the transmission part 121, the ball 140 will not fall out of the raceway 130, which prevents the fallen ball 140 from interfering with the transmission coordination between the screw rod 120 and the nut 110, thereby ensuring the transmission stability of the ball screw pair 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 positioned as the outer side. The inner diameter of the through hole 111 is slightly larger than the outer diameter of the transmission part 121, so as to avoid friction between the hole wall of the through hole 111 and the outer peripheral surface of the transmission part 121 due to contact during relative movement, so that the nut 110 and the screw rod 120 can move relative to each other smoothly. 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 part 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, and the ball 140 rotates while performing spiral movement along the transmission raceway 130.

[0052] In this embodiment, the raceway 130 adopts a single-thread structure, that is, only one raceway 130 is provided, and accordingly, only one groove 123 is provided, and only one return block 150 is provided. The groove 123 is concave from the outer peripheral surface of the transmission part 121 toward the central axis of the screw rod 120, and 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 in an arc shape and its diameter is substantially consistent with the diameter of the transmission part 121. The second spiral groove 122 includes a main groove section 122a provided on the outer peripheral surface of the transmission part 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 are combined 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 a long strip. Reasonable configuration of the shapes of the groove 123 and the return block 150 can not only reduce the processing difficulty of the groove 123 and the return block 150, but also reduce the assembly difficulty of the return block 150 and the groove 123. As an alternative to this embodiment, the groove 123 can also be configured in other reasonable shapes such as a spiral shape, and the shape of the return block 150 is consistent with the shape 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 processed on the return block 150, which can reduce the processing difficulty.

[0054] In this embodiment, the return channel 160 includes a main section 161 and transition sections 162 provided at both ends of the main section 161, and a connecting groove 124 for connecting the raceway 130 and the transition section 162 is provided on the transmission part 121. Specifically, the main section 161 preferably extends along the axial direction of the screw rod 120, so that the length of the return channel 160 can be shortened as much as possible, thereby shortening the length of the movement path of the ball 140 returning to the raceway 130 through the return channel 160. One of the transition sections 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, that is, the two transition sections 162 extend from the end of the main section 161 to the two opposite lateral surfaces 154 of the return block 150, respectively. The connecting groove 124 extends from the outer peripheral surface of the transmission part 121 to the side groove wall 123b of the groove 123. Specifically, there are two connecting grooves 124, which correspond to two transition sections 162 respectively. 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 is connected to 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 is connected to the other transition section 162. The ball 140 moving to one end of the raceway 130 enters the return channel 160 from one of the connecting grooves 124. After passing through the return channel 160, the ball 140 returns to the other end of the raceway 130 from the other connecting groove 124, thereby realizing the reciprocating circulation of the ball 140. As an alternative to this embodiment, the main section 161 can also be set to other reasonable shapes such as S-shaped or spiral.

[0055] In order to allow the ball 140 to smoothly enter the return channel 160 through the connecting groove 124, the extension direction of the transition section 162 is substantially consistent with the extension direction of the connecting groove 124, thereby eliminating the corner between the connecting groove 124 and the transition section 162, so that the transition section 162 and the connecting groove 124 can be smoothly connected, so that the ball 140 can 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 roughly along the direction shown by the straight line E1, and the connecting groove 124 and the transition section 162 at the other end extend roughly along the direction shown by the straight line E2. Further, the extension directions of the two transition sections 162 are roughly parallel, and the extension directions of the two connecting grooves 124 are also roughly parallel, that is, the straight line E1 is roughly parallel to the straight line E2. In the specific structure, due to factors such as processing errors, there may be a certain angle between the extension direction of the transition section 162 and the extension direction of the connecting groove 124, and the angle may be within 2°. As an alternative to this embodiment, under the premise that the ball 140 can move smoothly, the extension directions of the transition section 162 and the connecting groove 124 at the same end can also be set at an angle. As an alternative to this embodiment, the extension directions of the two transition sections 162 can also be non-parallel, and the extension directions of the two connecting grooves 124 can also be non-parallel.

[0056] In order to ensure that the ball 140 can move smoothly in the return channel 160, in this embodiment, the width K and the 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 size such as 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1mm, etc., 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 size such as 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1mm, etc.

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

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

[0059] During assembly, grease is first applied to the return block 150 and the transmission part 121, and then the return block 150 is installed in the groove 123. The return block 150 can be temporarily positioned in the groove 123 under the adhesion of the grease, and then the ball 140 is adhered to the second spiral groove 122 through the grease, or part of the ball 140 can be inserted into the return raceway 130, and finally the transmission part 121 with the ball 140 is screwed into the nut 110. Of course, the assembly method of the ball screw pair 100 is not limited to this, and it is only schematically described here. The ball screw pair 100 can also adopt other reasonable assembly methods.

[0060] Combination Fig. 9 This embodiment also provides a linear actuator 1000, including a housing 200, a stator module 300 and the ball screw pair 100 described above, wherein the ball screw pair 100 is disposed in the housing 200 and the screw rod 120 can extend out of the housing 200, the nut 110 can be rotatably mounted in the housing 200, and the stator module 300 is axially positioned and sleeved on the outside of the nut 110. The ball screw pair 100 is directly used as the rotor module of the linear actuator, and the screw rod 120 of the ball screw pair 100 can extend or retract into the housing 200 when the linear actuator 1000 is working. The movement of the screw rod 120 can realize the push-pull action, which can not only reduce the assembly workload of the linear actuation structure, but also reduce the axial length of the linear actuation structure, so that the linear actuator can 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 in the housing 200 through two front and rear spaced bearings and is axially positioned. The front end of the screw rod 120 extends out of the housing 200 and is connected to a front joint 410. The rear cover 230 is connected to a rear joint 420. The stator module 300 is sleeved outside the middle area of ​​the nut 110 and is located on the inner periphery of the housing 200. The stator module 300 can adopt an existing structure consisting of a stator core and a stator winding. In addition, the housing 200 further includes a support frame 240 clamped between the main housing 210 and the rear cover 230, and the linear actuator 1000 further includes an encoder 500 disposed at the rear side of the support frame 240. A control board 600 located behind the ball screw pair 100 is also disposed in the rear end of the housing 200, and the encoder 500 and the control board 600 can communicate with each other to ensure that the linear actuator 1000 can operate accurately. In addition, an oil filling hole 250 is also disposed on the front wall or side wall of the housing 200, and lubricating oil or grease can be added to the interior of the linear actuator 1000 after the linear actuator 1000 has worked for a period of time through the oil filling hole 250, so that the interior of the linear actuator 1000 is in a state of smooth transmission, and it is also convenient to regularly maintain the linear actuator 1000.

[0062] When in use, the rear joint 420 of the linear actuator 1000 is hinged or fixedly connected to other objects, and the front joint 410 is connected to the object to be actuated. When the linear actuator 1000 is working, switching the direction of the current flowing through the stator module 300 can change the rotation direction of the nut 110, so that the screw rod 120 can extend forward or retract backward, so that the actuated object can complete the corresponding action or execute the corresponding instruction.

[0063] In this embodiment, the nut 110 is actuated as an active member, and the screw rod 120 is a driven member. When the nut 110 is actuated, the nut 110 rotates around its own central axis, and the rotating nut 110 drives the screw rod 120 to move axially through the ball 140, thereby realizing the extension and retraction of the screw rod 120. For example, when the nut 110 is actuated to rotate forward, the ball 140 moves from back to front in the raceway 130 to extend the screw rod 120 relative to the nut 110; when the nut 110 is actuated to rotate reversely, the ball 140 moves from front to back in the raceway 130 to retract the screw rod 120 relative to the nut 110.

[0064] In this embodiment, the ratio of the axial lengths of the nut 110 and the transmission part 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 part 121 can be set to a reasonable size 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 the present embodiment, two first spiral grooves 112 with the same rotation direction and independent of each other are provided on the hole 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. Correspondingly, 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, and 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, two grooves 123 are provided on the outer circumference of the transmission part 121, and two return blocks 150 are also provided and respectively embedded in the two grooves 123. A return channel 160 communicating with one of the raceways 130 is provided between the inner side of one return block 150 and the transmission part 121, and a return channel 160 communicating with another raceway 130 is provided between the inner side of the other return block 150 and the transmission part 121. The ball 140 moving to the end in a raceway 160 returns to the beginning of the raceway 150 through the corresponding return channel 160. At this time, the two return blocks 150 are preferably evenly spaced along the circumference of the transmission part 121. Of course, the raceways 130 can also be provided with three, four or other reasonable numbers of the same rotation direction and independent of each other. The number of each of the grooves 123 and the return blocks 150 is consistent with the number of the raceways 130, and a return channel 160 corresponding to the raceway 130 is formed between each return block 150 and the transmission part 121.

[0067] Embodiment 2

[0068] Combination Fig.10 , Fig.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, and 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 will not be described in detail here.

[0071] In addition to the above preferred embodiments, the present invention has other implementation modes. Those skilled in the art may 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 arranged on the wall of the through hole; The screw rod is provided with a transmission part matched with the nut, and a second spiral groove is provided on the outer peripheral surface of the transmission part. The first spiral groove cooperates with the second spiral groove to form a spiral rolling track, and a plurality of balls distributed in a continuous manner 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, 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: The raceway is provided with one, and the groove and the return block are provided with one; or, the raceway is provided with at least two raceways with the same rotation direction and independent of each other, the number of the grooves and the return blocks are consistent with the number of the 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 comprises 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 arranged 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 is smoothly connected with the connecting groove.

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 as described in any one of claims 1 to 9 above, the ball screw pair is arranged in the casing and the screw 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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