Ball screw pair 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 arranged in a raceway, the axial length of the nut is larger than that of a transmission part, a return block is embedded in the peripheral surface of the transmission part, a return groove with the rotating direction opposite to that of the raceway is formed in the outer side of the return block, and the screw rod is arranged in the return groove. The roller path is divided into a plurality of single-circle closed circulation loops with spiral sections through the return grooves, and the balls move along the circulation loops so as to convert rotary motion of the nut into linear motion of the lead screw. The linear actuator comprises a casing, a stator module and the ball screw pair. The roller path is divided into a plurality of single-circle closed circulation loops with the spiral sections through the return grooves in the return blocks, the balls always move in the circulation loops, and the situation that the balls fall out of the roller path to affect the transmission stability of the structure is avoided.

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 of the nut cannot fully engage 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. 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, which divides the raceway into a number of single-turn closed circulation loops with spiral segments through the return groove on the return block. The balls always move in the circulation loop to prevent the balls from falling out of the raceway and affecting the transmission stability of the structure.

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

[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 ball is arranged in the rolling track;

[0010] The axial length of the nut is greater than the axial length of the transmission part. A return block is embedded on the outer circumferential surface of the transmission part. A return groove with a rotation direction opposite to that of the raceway is provided on the outer side of the return block. The raceway is divided into a plurality of single-turn closed circulation loops with spiral segments through the return groove. The ball moves along the circulation loop to convert the rotational motion of the nut into the linear motion of the screw rod.

[0011] Preferably, the raceway is provided with one, the return block is provided with one and the outer side thereof is provided with several return grooves distributed along the axial direction at intervals, the head and tail ends of several circles in the raceway are connected through the corresponding return grooves to form a circulation loop, and each circulation loop has a spiral section.

[0012] Preferably, the raceways are provided with several raceways with the same rotation direction and independent of each other, the number of return blocks is consistent with the number of raceways and the return blocks are evenly spaced along the circumference of the transmission part, the outer side of each return block is provided with several return grooves spaced along the axial direction, the parts on a certain circle of each raceway are connected in sequence through the corresponding return grooves to form a circulation loop, each circulation loop has spiral segments consistent with the number of raceways, and the shapes of each spiral segment are consistent.

[0013] Preferably, the return grooves on the same return block are spaced and distributed in parallel along the axial direction, and the circulation loops are correspondingly spaced and distributed in parallel along the axial direction.

[0014] Preferably, the return block is in the shape of a long strip extending along the axial direction.

[0015] Preferably, several return blocks are arranged at intervals along the axial direction of the transmission part, a return groove is provided on the outer side of each return block, a raceway is provided and the head and tail ends of a certain circle are connected through the return groove on the corresponding return block to form a circulation loop, and each circulation loop has a spiral section.

[0016] Preferably, the two return blocks adjacent to each other in the axial direction are staggered and distributed along the circumference of the transmission part.

[0017] Preferably, the raceways are provided with a number of raceways with the same rotation direction and independent of each other, and an array of return blocks are arranged at intervals along the axial direction. The number of return blocks in each group is consistent with the number of raceways and are evenly spaced along the circumference of the transmission part. A return groove is provided on the outside of each return block, and a part of a circle in each raceway is connected in sequence through the return groove on the outside of the return block in the same group to form a circulation loop. Each circulation loop has a spiral segment that is consistent with the number of raceways, and the shape of each spiral segment is consistent.

[0018] Preferably, the depth of the return groove is greater than the depth of the second spiral groove; and / or the screw rod further includes a rod portion connected to the transmission portion, and an outer diameter of the rod portion is not greater than an outer diameter of the transmission portion.

[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 has a return block with a return groove embedded on the outer peripheral surface of the transmission part. Since the rotation direction of the return groove is opposite to that of the raceway, the raceway can be divided into a number of single-turn closed circulation loops with spiral sections through the return groove. After the ball moves to the end of the spiral in the spiral section, it can return to the beginning of the spiral through the return groove, so that the ball always circulates back and forth in the closed circulation loop. The spiral section makes the single-turn circulation loop have a certain lead. The ball reciprocating in the circulation loop can smoothly convert the rotational motion of the nut into the linear motion of the screw rod, so that the ball screw pair can meet the transmission requirements. Since the return block with the return groove is embedded on the outer peripheral surface of the transmission part, when the axial length of the nut is greater than the axial length of the transmission part, the ball is always located in the circulation loop between the transmission part and the nut, which can effectively prevent the ball from falling out of the circulation loop and interfering with the rotation of the ball screw pair. In addition, since the return groove is arranged on the return block which is independently formed relative to the transmission part, the difficulty of forming the transmission part and the return block can be greatly reduced, the difficulty of processing the return groove can be greatly reduced, and the difficulty of assembling the ball screw pair can be appropriately reduced.

[0022] 2. Only one raceway can be provided, and one return block is provided accordingly. Several return grooves are provided on the return block. The first and last ends of several circles in the raceway are connected through the corresponding return grooves to form a circulation loop. At this time, each circulation loop has only one spiral segment. Several raceways can also be provided, and several return blocks are provided accordingly. Several return grooves are provided on each return block. Parts of a certain circle in each raceway are connected in sequence through the corresponding return grooves on each return block to form a closed circulation loop. At this time, each loop has spiral segments consistent with the number of raceways, and the shapes of each spiral segment are consistent. The number of return blocks is reasonably determined according to the number of raceways, so that the raceways can be smoothly divided into circulation loops. When more than two raceways are provided so that each circulation loop has spiral segments consistent with the number of raceways, the lead of the raceway increases, which can effectively increase the linear motion speed of the screw rod, so that the ball screw pair can better meet the needs of fast linear actuation.

[0023] 3. The return block is preferably configured as a long strip extending along the axial direction, so that the return grooves on the same return block can be distributed in parallel and spaced apart along the axial direction. The shape of the return block and the distribution of the return grooves are reasonably configured to reduce the difficulty of forming the return block and the difficulty of processing the return grooves.

[0024] 4. Only one raceway can be provided, and several return blocks are provided. A return groove is provided on each return block. The first and last ends of a circle in the raceway are connected through the return groove on the corresponding return block to form a circulation loop. At this time, each circulation loop has only one spiral segment. Several raceways can also be provided. The return blocks are arranged in an array along the axial interval. The number of return blocks in each group is consistent with the number of raceways and is evenly spaced along the axial direction of the transmission part. A return groove is provided on each return block. The local part of a circle in each raceway is connected in sequence through the return groove on the return block in the same group to form a circulation loop. At this time, each circulation loop has a spiral segment consistent with the number of raceways, and the number of each spiral segment is consistent. The distribution mode of the return blocks is reasonably determined according to the number of raceways, so that the raceways can be smoothly divided into circulation loops. When more than two raceways are provided so that each circulation loop has a spiral segment consistent with the number of raceways, the lead of the raceway increases, which can effectively increase the linear motion speed of the screw rod, so that the ball screw pair can better meet the needs of fast linear actuation. In addition, since each return block is provided with only one return groove, the difficulty of forming the return block can be reduced while the structural strength of the return block can be ensured.

[0025] 5. The depth of the return groove is greater than the depth of the second spiral groove, which prevents the ball moving in the return groove from being stuck with the spiral teeth on the inner wall of the through hole and unable to move, ensuring that the ball can reciprocate smoothly in the circulation loop, thereby ensuring that the ball screw pair can be transmitted smoothly.

[0026] 6. 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 moving the screw rod. Using the ball screw pair as a rotor module can not only reduce the assembly workload of the linear actuator structure, but also reasonably reduce the axial length of the linear actuator structure, so that the linear actuator can better meet the linear actuation requirements in a small space. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is an overall schematic diagram of the ball screw pair in the first embodiment;

[0028] Figure 2 An exploded view of the ball screw pair in Example 1;

[0029] Figure 3 It is an axial cross-sectional view of the nut of the ball screw pair in the first embodiment;

[0030] Figure 4 It is an axial cross-sectional view of the cooperation between the nut and the screw of the ball screw pair in the first embodiment;

[0031] Figure 5 This is a diagram showing the matching structure of the screw, return block and ball of the ball screw pair in the first embodiment;

[0032] Figure 6 An exploded view of the screw and return block of the ball screw pair in Example 1;

[0033] Figure 7a It is a schematic diagram of the trajectory of one circle of the original raceway in the first embodiment unfolded along the circumferential direction;

[0034] Figure 7b It is a schematic diagram of the trajectory of the circulation loop of the ball screw pair in the first embodiment unfolded along the circumferential direction;

[0035] Figure 8 is an axial cross-sectional view of the linear actuator in Embodiment 1;

[0036] Fig. 9 It is a diagram showing the matching structure of the lead screw in the first embodiment and the return block using another solution;

[0037] Fig.10 An exploded view of the screw and return block of the ball screw pair in the second embodiment;

[0038] Fig.11a It is a schematic diagram of the trajectory of two adjacent circles of the two original raceways in the second embodiment unfolded along the circumferential direction;

[0039] Fig.11b It is a schematic diagram of the trajectory of the circulation loop of the ball screw pair in the second embodiment unfolded along the circumferential direction;

[0040] Fig.12 It is a partial structural diagram of the ball screw pair in the third embodiment;

[0041] Fig.13 The exploded view of the screw and return block of the ball screw pair in the third embodiment;

[0042] Fig.14 It is a partial structural diagram of the ball screw pair in the fourth embodiment;

[0043] Fig.15 It is an exploded view of the screw and return block of the ball screw pair in the fourth embodiment.

[0044] 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, 123-rod, 124-groove, 130-raceway, 131-circulation loop, 1311-spiral section, 140-ball, 150-return block, 151-return groove, 151a-main groove section, 151b-transition section,

[0045] 1000 - Linear Actuator,

[0046] 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

[0047] 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.

[0048] Embodiment 1

[0049] Combination Figures 1 to 6 , a ball screw pair 100 provided in the first embodiment of the present invention includes:

[0050] 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;

[0051] 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;

[0052] The first spiral groove 112 cooperates with the second spiral groove 122 to form a spiral raceway 130 , and a ball 140 is disposed in the raceway 130 ;

[0053] The axial length of the nut 110 is greater than the axial length of the transmission part 121. A return block 150 is embedded on the outer peripheral surface of the transmission part 121. The outer side of the return block 150 is provided with a return groove 151 whose rotation direction is opposite to that of the raceway 130. The raceway 130 is divided into a plurality of single-turn closed circulation loops 131 having spiral segments 1311 through the return groove 151. The ball 140 moves along the circulation loop 131 to convert the rotational motion of the nut 110 into the linear motion of the screw rod 120.

[0054] The ball 140 always reciprocates in the closed circulation loop 131, and the spiral section 1311 makes the single-turn circulation loop 131 have a certain lead. The ball 140 reciprocating in the circulation loop 131 can smoothly convert the spiral motion of the nut 110 into the linear motion of the screw 120, so that the ball screw pair 100 can meet the transmission requirements. Since the return block 150 with the return groove 151 is embedded on the outer peripheral surface of the transmission part 121, when the axial length of the nut 110 is greater than the axial length of the transmission part 121, the ball 140 is always located in the circulation loop 131 between the transmission part 121 and the nut 110, which can effectively prevent the ball 140 from falling out of the circulation loop 131 and interfering with the rotation of the ball screw pair 100. In addition, since the return groove 151 is arranged on the return block 150 which is independently formed relative to the transmission part 121, the difficulty of forming the transmission part 121 and the return block 150 can be greatly reduced, the difficulty of processing the return groove 151 can be greatly reduced, and the difficulty of assembling the ball screw pair 100 can be appropriately reduced.

[0055] In the following description, 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.

[0056] In this embodiment, 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 smoothly move relative to each other. The screw rod 120 also includes a rod 123 connected to the transmission part 121 as an integral structure, and the end of the rod 123 away from the transmission part 121 can be connected to the actuated object. The rod 123 and the transmission part 121 can be integrally formed, or they can be separately formed and fixed together. The outer diameter of the rod 123 is not larger than the outer diameter of the transmission part 121, that is, the outer diameter of the rod 123 can be consistent with the outer diameter of the transmission part 121, and the outer diameter of the rod 123 can also be slightly smaller than the outer diameter of the transmission part 121. As a specific solution of this embodiment, the cross-sectional shape of the rod 123 perpendicular to the axial direction can be set to a reasonable shape such as a circle, a rectangle, an oblate circle, etc., which is not limited here.

[0057] In this embodiment, the nut 110 is provided with a first spiral groove 112 on the hole wall of the through hole 111, and the axial length of the first spiral groove 112 is substantially consistent with the axial length of the nut 110. Correspondingly, the transmission part 121 is provided with a second spiral groove 122 on the outer peripheral surface, 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 first spiral groove 112 and the second spiral groove 122 cooperate to form a spirally extended raceway 130, which is a single-line thread structure with multiple turns. The depth of the raceway 130 is substantially consistent with the diameter of the ball 140, and the axial length of the raceway 130 depends on the axial length of the second spiral groove 122. In this embodiment, the raceway 130 extending 360° in the circumferential direction is defined as one turn.

[0058] In this embodiment, there is one return block 150, and a plurality of return grooves 151 are arranged on the outer side of the return block 150 and are spaced apart along the axial direction. The first and last ends of several turns of the raceway 130 are connected through the corresponding return grooves 151 to form a circulation loop 131, and each circulation loop 131 has a spiral section 1311. Specifically, the number of the return grooves 151 is less than or equal to the number of turns of the raceway 130. Figure 7a The schematic diagram shows the trajectory of one circle of the original raceway 130 after being expanded in the circumferential direction. Point A and point B represent two terminal positions of one circle of the original raceway 130 . The horizontal distance L between point A and point B is substantially equal to the circumference CF of the transmission part 121 . Figure 7b The schematic diagram shows the trajectory of the circulation loop 131 after being expanded along the circumferential direction. A certain circle of the raceway 130 spirally extends from the head end indicated by point A to the tail end indicated by point D. The tail end indicated by point D is connected to one end of the return groove 151. Since the rotation direction of the return groove 151 is opposite to the spiral direction of the raceway 130, the return groove 151 extends toward the head end indicated by point A and the other end of the return groove 151 is connected to the head end indicated by point A, so that the head and tail ends of one circle of the raceway 130 are connected to each other through the return groove 151. A part of one circle of the original raceway 130 constitutes a spiral section 1311. The spiral section 1311 and the return groove 151 together constitute the circulation loop 131. The circulation loop 131 in this embodiment has a spiral section 1311 and a return groove 151. Since the extension distance of the spiral section 1311 is smaller than the extension distance of a complete circle in the original raceway 130, the lead P1 of the circulation loop 131 is slightly smaller than the lead P0 of the original raceway 130. In this embodiment, the rotation direction of the return groove 151 is opposite to the spiral direction of the raceway 130, which means that the direction in which the return groove 151 extends along the outer circumferential surface of the transmission part 121 is opposite to the spiral direction of the raceway 130 in the axial direction.

[0059] In order to allow the ball 140 that moves to the tail end of the spiral segment 1311 to smoothly return to the head end of the spiral segment 1311 through the return groove 151, the two ends of the return groove 151 need to be smoothly connected to the head and tail ends of the spiral segment 1311. Specifically, the return groove 151 includes a main groove segment 151a and transition segments 151b provided at both ends of the main groove segment 151a, and the two ends of the main groove segment 151a are smoothly connected to the head and tail ends of the spiral segment 1311 through the transition segment 151b.

[0060] In order to ensure the lead P1 of the circulation loop 131, the arc length ratio of the return groove 151 in the circumferential direction relative to the circulation loop 131 should not be too large, and the arc length ratio of the return groove 151 and the spiral segment 1311 can be set to a reasonable size such as 1:6, 1:7, 1:8, 1:9, 1:10, etc. Since the return groove 151 is short, the main groove segment 151a of the return groove 151 can be set to a straight groove segment or a spiral groove segment.

[0061] In this embodiment, the first and last ends of the adjacent multiple turns in the raceway 130 are connected to each other through the return grooves 151 on the return block 150, so the return grooves 151 on the return block 150 are arranged in parallel and spaced along the axial direction. In order to install the return block 150, a groove 124 adapted to the return block 150 is arranged on the outer circumference of the transmission part 121, and the return block 150 is embedded in the groove 124, and the outer surface of the return block 150 is basically aligned with the outer circumference of the transmission part 121. Further, in order to reduce the difficulty of forming the return block 150 and the groove 124, in this embodiment, the groove 124 extends along the axial direction of the transmission part 121, and accordingly, the return block 150 is in the shape of a long strip extending along the axial direction, and the long strip return block 150 has two parallel and opposite side surfaces that are both parallel to the axial direction of the transmission part 121, and the return groove 151 extends from one side surface to the other side surface. As a specific solution of this embodiment, the length of the groove 124 can be less than the axial length of the transmission part 121 so that at least one end of the groove 124 is closed, and the length of the groove 124 can also be equal to the axial length of the transmission part 121 so that the groove 124 axially penetrates the transmission part 121. As an alternative to this embodiment, the groove 124 and the return block 150 can also be set in other reasonable shapes such as a spiral shape.

[0062] In order to allow the ball 140 to smoothly pass through the return groove 151, the depth of the return groove 151 is slightly greater than the depth of the second spiral groove 122, so as to avoid the situation where the ball 140 moving in the return groove 151 is stuck with the spiral teeth on the inner wall of the through hole 111 and cannot move, so as to ensure that the ball 140 can smoothly reciprocate in the circulation loop 131, thereby ensuring that the ball screw pair 100 can smoothly drive. The depth of the return groove 151 can be reasonably determined according to factors such as the diameter of the ball 140, the inner diameter of the through hole 111, and the size of the raceway 130.

[0063] 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 124. The return block 150 can be temporarily positioned in the groove 124 under the adhesion of the grease, and then the ball 140 is adhered to the second spiral groove 122 and the return groove 151 through the grease, and finally the transmission part 121 with the ball 140 and the return block 150 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.

[0064] Combination Figure 8 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 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 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 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.

[0065] 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 through the oil filling hole 250 after the linear actuator 1000 has worked for a period of time, so that the interior of the linear actuator 1000 is in a state of smooth transmission, and it is also convenient for regular maintenance of the linear actuator 1000.

[0066] 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.

[0067] 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 spiral section 1311 of the raceway circulation loop 131, so that the screw rod 120 extends relative to the nut 110; when the nut 110 is actuated to rotate reversely, the ball 140 moves from front to back in the spiral section 1311 of the circulation loop 131, so that the screw rod 120 retracts relative to the nut 110.

[0068] 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.

[0069] 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.

[0070] Combination Fig. 9 In other schemes of this embodiment, the return groove 151 on the outer side of the return block 150 is arranged relative to the raceway 130 spacer, and accordingly, the odd-numbered or even-numbered raceways 130 form a circulation loop 131 through the corresponding return groove 151. By making the raceway 130 spacer form a circulation loop 131, the number of return grooves 151 on the return block 150 is reduced, and the thickness of the part between two adjacent return grooves 151 on the return block 150 is increased, thereby ensuring the structural strength of the return block 150.

[0071] Embodiment 2

[0072] In this embodiment, two first spiral grooves with the same rotation direction and independent of each other are arranged on the wall of the through hole of the nut, and correspondingly, two second thread grooves with the same rotation direction and independent of each other are arranged on the outer peripheral surface of the transmission part. The two first spiral grooves and the two second spiral grooves are combined to form two raceways with the same rotation direction and independent of each other, that is, the raceways adopt a double-line thread structure, and the lead of the double-line thread raceway can be twice that of the single-line thread raceway, so that the ball screw pair can better meet the requirements of rapid linear actuation.

[0073] Combination Fig.10 In order to enable the raceway 130 to form a circulation loop 131, in this embodiment, two return blocks 150 are provided, and the two are symmetrically distributed along the circumference of the transmission part 121. Correspondingly, two symmetrically distributed grooves 124 are provided on the outer circumference of the transmission part 121, and the two return blocks 150 are respectively embedded in the two grooves 124. The outer side of each groove 124 is provided with a plurality of return grooves 151 evenly spaced along the axial direction.

[0074] Fig.11a It is a schematic diagram of the trajectory of two adjacent circles on the two original raceways 130 after being expanded along the circumferential direction, point A1 and point B1 represent the two terminal positions of a circle in one of the original raceways 130, point A2 and point B2 represent the two terminal positions of a circle in the other original raceway 130, the two circles are arranged adjacent to each other, straight line A1B1 is parallel to straight line A2B2, and the horizontal distance L1 between point A1 and point B1 and the horizontal distance L2 between point A2 and point B2 are basically equal to the circumference CF of the transmission part 121. Fig.11b The schematic diagram shows the trajectory of the circulation loop 131 of the present embodiment after being unfolded along the circumferential direction, wherein a circle in one raceway 130 spirally extends from the position indicated by point E1 to the position indicated by point E2, and the end indicated by point E2 is connected with a position on a circle in another raceway 130 indicated by point F1 through a return groove 151 on one of the return blocks 150, and a circle in the raceway 130 spirally extends from the position indicated by point F1 to the position indicated by point F2, and the end indicated by point F2 is connected with the position indicated by point E1 through a return groove 151 on another return block 150, so that adjacent circles of the two raceways 130 pass through the return grooves 151 on the two return blocks 150 to form a circulation loop 131 closed in the circumferential direction, and the circulation loop 131 has two spiral sections 1311 and two return grooves 151, and the two spiral sections 1311 and the two return grooves 151 are staggered one by one in the circumferential direction.

[0075] In other schemes of the present embodiment, the specific number of raceways 130 can be set to three, four or other reasonable numbers of the same rotation direction and independent of each other in combination with factors such as the radial size of the transmission part 121. Accordingly, the number of return blocks 150 is consistent with the number of raceways 130 and is evenly spaced along the circumference of the transmission part 121. All raceways 130 pass through the return grooves 151 on the return blocks 150 to form multiple circles of circulation loops 131 spaced apart along the axial direction. The number of spiral segments 1311 and return grooves 151 on each circulation loop 131 is consistent with the number of raceways 130, and the spiral segments 1311 and return grooves 151 on the same circulation loop 131 are staggered one by one along the circumferential direction.

[0076] In other schemes of this embodiment, the return groove 151 on the outer side of each return block 150 can be arranged relative to the raceway 130 spacer, thereby increasing the local thickness of the return block 150 located between two adjacent return grooves 151, thereby ensuring the structural strength of the return block 150.

[0077] The other structures of the ball screw pair are the same as those described in the first embodiment and will not be described in detail here.

[0078] This embodiment further provides a linear actuator. Except for the ball screw pair, other structures of the linear actuator are the same as those described in the first embodiment and will not be described in detail here.

[0079] Embodiment 3

[0080] Combination Fig.12 , Fig.13 In this embodiment, in order to ensure the structural strength of the return block 150, the return block 150 adopts a structure of several scattered distribution. Specifically, the return block 150 is block-shaped and is provided with several return blocks 150 at intervals along the axial direction of the transmission part 121. The outer side of each return block 150 is provided with only one return groove 151. The raceway 130 is provided with one and the first and last ends of a certain circle are connected through the return groove 151 on the corresponding return block 150 to form a circulation loop 131. Each circulation loop 131 has a spiral section 1311 and a return groove 151. The trajectory schematic diagram of the circulation loop 131 along the circumferential direction is basically the same as Figure 7b The embodiment is consistent with the above, and will not be shown in detail in this embodiment.

[0081] In order to ensure the number of circulation loops 131 , two axially adjacent return blocks 150 are staggered along the circumference of the transmission part 121 . Accordingly, the return grooves 151 on each circulation loop 131 are staggered along the circumference of the transmission part 121 .

[0082] The other structures of the ball screw pair are the same as those described in the first embodiment and will not be described in detail here.

[0083] This embodiment further provides a linear actuator. Except for the ball screw pair, other structures of the linear actuator are the same as those described in the first embodiment and will not be described in detail here.

[0084] Embodiment 4

[0085] Combination Fig.14 , Fig.15 In this embodiment, the raceway is provided with two raceways with the same rotation direction and independent of each other, that is, the raceway adopts a double-threaded structure. Correspondingly, an array of return blocks 150 is arranged at intervals along the axial direction, and the number of return blocks 150 in each group is two. A part of a circle in the first raceway spirally extends from the first position to the second position, and the second position is connected to the third position on a circle in the second raceway through a return groove 151 on one of the return blocks 150 in the same group. A part of a circle in the second raceway extends from the third position to the fourth position, and the fourth position is connected to the first position on the first raceway through a return groove 151 on another return block 150 in the same group, thereby forming a closed circulation loop. The trajectory schematic diagram of the circulation loop unfolded along the circumferential direction is basically the same as Fig.11b Each circulation loop has two spiral segments and two return grooves 151, and the two spiral segments and the two return grooves 151 are staggered in the circumferential direction.

[0086] In order to ensure the number of circulation loops 131 , two groups of return blocks 150 adjacent in the axial direction are staggered along the circumference of the transmission part 121 . Accordingly, the return grooves 151 on each circulation loop 131 are staggered along the circumference of the transmission part 121 .

[0087] In other schemes of the present embodiment, the specific number of raceways 130 can be set to three, four or other reasonable numbers with the same rotation direction and independent of each other in combination with factors such as the radial size of the transmission part 121. Accordingly, the number of return blocks 150 in each group is consistent with the number of raceways 130 and is evenly spaced along the circumference of the transmission part 121. All raceways 130 pass through the return grooves 151 on the return blocks 150 to form multiple circles of circulation loops spaced along the axial direction. The number of spiral segments and return grooves 151 in each circulation loop is consistent with the number of raceways 130, and the spiral segments and return grooves 151 on the same circulation loop are staggered one by one along the circumference.

[0088] The other structures of the ball screw pair are the same as those described in the first embodiment and will not be described in detail here.

[0089] This embodiment further provides a linear actuator. Except for the ball screw pair, other structures of the linear actuator are the same as those described in the first embodiment and will not be described in detail here.

[0090] 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. A ball screw pair, comprising: 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 ball is 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 return block is embedded on the outer circumferential surface of the transmission part, and a return groove with a rotation direction opposite to that of the raceway is provided on the outer side of the return block. The raceway is divided into a number of single-turn closed circulation loops with spiral segments through the return groove, and the ball moves along the circulation loop to convert the rotational motion of the nut into the linear motion of the screw.

2. A ball screw pair according to claim 1, characterized in that: The raceway is provided with one return block and the return grooves are provided on the outer side thereof and are spaced apart along the axial direction. The first and last ends of several circles in the raceway are connected through the corresponding return grooves to form a circulation loop, and each circulation loop has a spiral section.

3. A ball screw pair according to claim 1, characterized in that: The raceway is provided with several raceways with the same rotation direction and independent of each other. The number of return blocks is consistent with the number of raceways and the return blocks are evenly spaced along the circumference of the transmission part. The outer side of each return block is provided with several return grooves spaced along the axial direction. The parts on a certain circle of each raceway are connected in sequence through the corresponding return grooves to form a circulation loop. Each circulation loop has spiral segments consistent with the number of raceways, and the shapes of each spiral segment are consistent.

4. A ball screw pair according to claim 2 or 3, characterized in that: The return grooves on the same return block are spaced and distributed in parallel along the axial direction, and the circulation loops are correspondingly spaced and distributed in parallel along the axial direction.

5. A ball screw pair according to claim 4, characterized in that: The return block is in the shape of a long strip extending along the axial direction.

6. A ball screw pair according to claim 1, characterized in that: The return blocks are arranged at intervals along the axial direction of the transmission part, and a return groove is arranged on the outer side of each return block. The raceway is provided with one and the first and tail ends of a circle are connected through the return groove on the corresponding return block to form a circulation loop, and each circulation loop has a spiral section.

7. A ball screw pair according to claim 6, characterized in that: The two return blocks adjacent to each other in the axial direction are staggered and distributed along the circumference of the transmission part.

8. A ball screw pair according to claim 1, characterized in that: The raceways are provided with a number of raceways with the same rotation direction and independent of each other, and an array of return blocks is arranged at intervals along the axial direction. The number of return blocks in each group is consistent with the number of raceways and is evenly spaced along the circumference of the transmission part. A return groove is provided on the outside of each return block, and a part of a circle in each raceway is connected in sequence through the return groove on the outside of the return block in the same group to form a circulation loop. Each circulation loop has a spiral segment that is consistent with the number of raceways, and the shape of each spiral segment is consistent.

9. A ball screw pair according to claim 1, characterized in that: The depth of the return groove is greater than the depth of the second spiral groove; and / or the screw rod further includes a rod portion connected to the transmission portion, and the outer diameter of the rod portion is not greater than the outer diameter of the transmission portion.

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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