Ball screw pair and linear actuator

Abstract

The utility model discloses a ball screw pair and a linear actuator, belonging to the transmission structure technical field, the ball screw pair comprises a nut, a screw rod and a ball arranged in a raceway, the axial length of the nut is greater than the axial length of a transmission part, the outer peripheral surface of the transmission part is embedded with a return block, and the return block is embedded in the screw rod. The outer side of the return block is provided with a return groove with the rotating direction opposite to that of the roller path, the roller path is divided into a plurality of single-circle closed circulation loops with spiral sections through the return groove, and the balls move along the circulation loops so as to convert rotating 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 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 set on the nut, the internal thread on 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. 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, which divides the raceway into several 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 utility model provides a ball screw pair, comprising:

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

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

[0009] The first spiral groove and the second spiral groove cooperate to form a spiral 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 circumference 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 several single-turn closed circulation loops with spiral segments through the return groove. The balls move along the circulation loops 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 several return grooves are provided on the outside thereof and are distributed along the axial direction. 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, and 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 a spiral segment that is consistent with the number of raceways, and the shape of each spiral segment is consistent.

[0013] Preferably, the return grooves on the same return block are distributed in parallel and spaced apart along the axial direction, and the circulation loops are correspondingly distributed in parallel and spaced apart 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, and a return groove is provided on the outside of each return block. The raceway is provided with a circle whose head and tail ends 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 along the circumference of the transmission part.

[0017] Preferably, the raceways are provided with several raceways with the same rotation direction and independent of each other, and the return blocks are arranged in arrays 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 the parts on a certain circle of each raceway are connected in sequence through the return groove on the outside of the return block of 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 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.

[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 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 several single-turn closed circulation loops with spiral segments through the return groove. After the balls move to the end of the spiral in the spiral segment, they can return to the beginning of the spiral through the return groove, so that the balls always circulate back and forth in the closed circulation loop. The spiral segment gives the single-turn circulation loop a certain lead. The balls circulating back and forth 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 balls are always located in the circulation loop between the transmission part and the nut, which can effectively prevent the balls 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 a corresponding return block can be provided. Several return grooves can be provided on the return block. The ends of several turns in the raceway are connected through the corresponding return grooves to form a circulation loop. In this case, each circulation loop has only one spiral segment. Several raceways can also be provided, and several return blocks can be provided accordingly. Several return grooves can be provided on each return block. Parts of a certain turn in each raceway are connected in sequence through the corresponding return grooves on each return block to form a closed circulation loop. In this case, each loop has spiral segments that match the number of raceways, and the shapes of the spiral segments are consistent. The number of return blocks should be reasonably determined according to the number of raceways so that the raceways can be smoothly divided into circulation loops. When two or more raceways are provided so that each circulation loop has spiral segments that match 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. A single raceway can be provided, with multiple return blocks, each with a return groove. The leading and trailing ends of a particular raceway turn are connected through the return groove on the corresponding return block, forming a circulation loop. In this case, each circulation loop has only one helical segment. Alternatively, multiple raceways can be provided, with the return blocks spaced axially in arrays, with the number of return blocks in each group matching the number of raceways and evenly spaced along the axial direction of the transmission unit. Each return block has a return groove, and portions of a particular raceway turn are connected sequentially through the return grooves on the return blocks in the same group, forming a circulation loop. In this case, each circulation loop has the same number of helical segments as the number of raceways, and the number of helical segments is consistent. The return blocks are distributed appropriately based on the number of raceways, so that the raceways can be smoothly divided into circulation loops. When two or more raceways are provided, with each circulation loop having the same number of helical segments as the number of raceways, the raceway lead is increased, effectively increasing the linear motion speed of the lead screw, thereby enabling the ball screw pair to better meet the requirements 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 ensuring the structural strength of the return block.

[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 circulate back and forth smoothly in the circulation loop, thereby ensuring that the ball screw pair can be transmitted smoothly.

[0026] 6. 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

[0027] Figure 1 This is an overall schematic diagram of the ball screw pair in Example 1;

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

[0029] Figure 3 An axial cross-sectional view of the nut of the ball screw pair in Example 1;

[0030] Figure 4 An axial cross-sectional view of the nut and the screw rod of the ball screw pair in Example 1;

[0031] Figure 5 This is a diagram showing the matching structure of the screw, return block and ball of the ball screw pair in Example 1;

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

[0033] Figure 7a Schematic diagram of the trajectory of one circle of the original raceway in the circumferential direction in Example 1;

[0034] Figure 7b Schematic diagram of the trajectory of the ball screw pair's circulation loop in the circumferential direction in Example 1;

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

[0036] Figure 9 This is a diagram showing the matching structure of the lead screw in Example 1 and a return block using another solution;

[0037] Figure 10 Exploded view of the screw and return block of the ball screw pair in Example 2;

[0038] Figure 11a Schematic diagram of the trajectories of two adjacent circles of the original two raceways in the circumferential direction in Example 2;

[0039] Figure 11b Schematic diagram of the trajectory of the ball screw pair's circulation loop in the circumferential direction in the second embodiment;

[0040] Figure 12 This is a partial structural diagram of the ball screw pair in Example 3;

[0041] Figure 13 Exploded view of the screw and return block of the ball screw pair in Example 3;

[0042] Figure 14 This is a partial structural diagram of the ball screw pair in Example 4;

[0043] Figure 15 This is an exploded view of the screw and return block of the ball screw pair in Example 4.

[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-roller, 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 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.

[0048] Example 1

[0049] Combine Figures 1 to 6 The first embodiment of the present invention provides a ball screw pair 100, comprising:

[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 portion 121 that cooperates with the nut 110, and a second spiral groove 122 is provided on the outer circumference of the transmission portion 121;

[0052] The first spiral groove 112 and the second spiral groove 122 cooperate to form a spiral rolling track 130 , in which a ball 140 is disposed;

[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 return groove 151 divides the raceway 130 into several single-turn closed circulation loops 131 with spiral segments 1311. The balls 140 move along the circulation loops 131 to convert the rotational motion of the nut 110 into linear motion of the screw rod 120.

[0054] The balls 140 always circulate back and forth within the closed loop 131. The spiral segment 1311 gives the single-turn loop 131 a certain lead. The balls 140 reciprocating within the loop 131 can smoothly convert the spiral motion of the nut 110 into the linear motion of the screw 120, allowing the ball screw pair 100 to meet the transmission requirements. Because the return block 150 with the return groove 151 is embedded in the outer circumference 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 balls 140 are always located within the loop 131 between the transmission part 121 and the nut 110, which can effectively prevent the balls 140 from falling out of the 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 also be greatly reduced, and the difficulty of assembling the ball screw pair 100 can also 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 to avoid friction caused by contact between the hole wall of the through hole 111 and the outer peripheral surface of the transmission part 121 during relative movement, so that the nut 110 and the screw rod 120 can move smoothly relative to each other. The screw rod 120 also includes a rod portion 123 connected to the transmission part 121 as an integral structure, and the end of the rod portion 123 away from the transmission part 121 can be connected to the object to be actuated. The rod portion 123 and the transmission part 121 can be formed as one piece, or they can be formed separately and then fixed together. The outer diameter of the rod portion 123 is not larger than the outer diameter of the transmission part 121, that is, the outer diameter of the rod portion 123 can be consistent with the outer diameter of the transmission part 121, or the outer diameter of the rod portion 123 can 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 portion 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 wall of the through hole 111. The axial length of the first spiral groove 112 is substantially the same as the axial length of the nut 110. Correspondingly, the transmission portion 121 is provided with a second spiral groove 122 on its outer circumference. The axial length of the second spiral groove 122 is substantially the same as the axial length of the transmission portion 121. The first and second spiral grooves 112, 122 follow the same spiral trajectory and have substantially the same groove depth and width. The first and second spiral grooves 112, 122 cooperate to form a helically extending raceway 130. Raceway 130 has a single-thread structure with multiple turns. The depth of raceway 130 is substantially the same as the diameter of ball 140, and the axial length of raceway 130 is determined by the axial length of the second spiral groove 122. In this embodiment, a 360° circumferential extension of raceway 130 is defined as one turn.

[0058] In this embodiment, a return block 150 is provided. A plurality of return grooves 151 are provided on the outer side of the return block 150, spaced apart along the axial direction. The first and last ends of several turns of the raceway 130 are connected through corresponding return grooves 151 to form circulation loops 131. Each circulation loop 131 has a spiral segment 1311. Specifically, the number of 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 along the circumferential direction. Point A and point B represent the 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 figure shows the trajectory of the circulation loop 131 after it is expanded along the circumferential direction. A certain circle of the raceway 130 spirally extends from the head end shown at point A to the tail end shown at point D. The tail end shown at 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 shown at point A and the other end of the return groove 151 is connected to the head end shown at 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. Because the extension distance of the spiral segment 1311 is less than the extension distance of one complete circle of the original raceway 130, the lead P1 of the circulation loop 131 is slightly less 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 circumference of the transmission portion 121 is axially opposite to the spiral direction of the raceway 130.

[0059] In order for the ball 140, having moved to the rear end of the spiral segment 1311, to smoothly return to the front end of the spiral segment 1311 through the return groove 151, the two ends of the return groove 151 must be smoothly connected to the front and rear ends of the spiral segment 1311. Specifically, the return groove 151 includes a main groove segment 151a and transition segments 151b disposed at both ends of the main groove segment 151a. The two ends of the main groove segment 151a are smoothly connected to the front and rear ends of the spiral segment 1311 through the transition segments 151b.

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

[0061] In this embodiment, the leading and trailing ends of adjacent turns of the raceway 130 are connected via return grooves 151 on the return block 150. Therefore, multiple return grooves 151 are provided on the return block 150 at intervals along the axial direction. To accommodate the return block 150, a groove 124 is provided on the outer circumference of the transmission portion 121 to accommodate the return block 150. The return block 150 is embedded in the groove 124, with the outer surface of the return block 150 substantially aligned with the outer circumference of the transmission portion 121. Furthermore, to reduce the difficulty of molding the return block 150 and the groove 124, in this embodiment, the groove 124 extends along the axial direction of the transmission portion 121. Accordingly, the return block 150 is in the shape of an elongated strip extending along the axial direction. The elongated return block 150 has two parallel, opposing side surfaces that are both parallel to the axial direction of the transmission portion 121, and the return groove 151 extends from one side surface to the other. 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. 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 configured in other reasonable shapes such as a spiral shape.

[0062] To ensure smooth passage of the ball 140 through the return groove 151, the depth of the return groove 151 is slightly greater than the depth of the second spiral groove 122. This prevents the ball 140 moving within the return groove 151 from becoming stuck between the spiral teeth on the inner wall of the through hole 111 and being unable to move. This ensures that the ball 140 can smoothly reciprocate within the circulation loop 131, thereby ensuring smooth transmission of the ball screw assembly 100. The depth of the return groove 151 can be reasonably determined based on 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 portion 121. The return block 150 is then installed into the groove 124. The return block 150 is temporarily positioned in the groove 124 due to the adhesion of the grease. The ball 140 is then adhered to the second spiral groove 122 and the return groove 151 by the grease. Finally, the transmission portion 121 with the ball 140 and return block 150 adhered thereto is screwed into the nut 110. Of course, the assembly method of the ball screw pair 100 is not limited to this. This is merely an illustrative example. Other reasonable assembly methods may also be used for the ball screw pair 100.

[0064] Combine Figure 8 This embodiment also 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.

[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 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 wall 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.

[0066] 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.

[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 about its own central axis. The rotating nut 110 drives the screw rod 120 to move axially via the balls 140, thereby achieving the extension and retraction of the screw rod 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 spiral section 1311 of the raceway circulation loop 131, causing the screw rod 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 spiral section 1311 of the circulation loop 131, causing the screw rod 120 to retract relative to the nut 110.

[0068] 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.

[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] Combine Figure 9 In other solutions of this embodiment, the return grooves 151 on the outer side of the return block 150 are arranged relative to the spacers of the raceway 130. Accordingly, the odd-numbered or even-numbered races of the raceway 130 form a circulation loop 131 through the corresponding return grooves 151. By forming the circulation loop 131 with the spacers of the raceway 130, the number of return grooves 151 on the return block 150 is reduced, and the thickness of the portion of the return block 150 between two adjacent return grooves 151 is increased, thereby ensuring the structural strength of the return block 150.

[0071] Example 2

[0072] In this embodiment, two first spiral grooves with the same rotation direction and independent of each other are provided on the wall of the through hole of the nut. Correspondingly, two second spiral grooves with the same rotation direction and independent of each other are provided 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 fast linear actuation.

[0073] Combine Figure 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. Accordingly, 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] Figure 11a It is a schematic diagram of the trajectory of two adjacent circles on the original two raceways 130 after being expanded along the circumferential direction, where points A1 and B1 represent the two terminal positions of a circle in one of the original raceways 130, and points A2 and B2 represent the two terminal positions of a circle in the other original raceway 130. The two circles are arranged adjacent to each other, and the straight line A1B1 is parallel to the straight line A2B2. 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. Figure 11b The figure shows a schematic diagram of the trajectory of the circulation loop 131 of this embodiment after being unfolded along the circumferential direction, in which a circle in one of the raceways 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. The 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 the adjacent circles of the two raceways 130 pass through the return grooves 151 on the two return blocks 150 to form a closed circulation loop 131 in the circumferential direction. 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 this 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 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 distributed along the axial direction. The number of spiral sections 1311 and return grooves 151 on each circulation loop 131 is consistent with the number of raceways 130, and the spiral sections 1311 and return grooves 151 on the same circulation loop 131 are staggered one by one along the circumference.

[0076] In other schemes of this embodiment, the return groove 151 on the outside of each return block 150 can be set 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, the 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] Example 3

[0080] Combine Figure 12 、 Figure 13 In this embodiment, in order to ensure the structural strength of the return block 150, the return block 150 adopts a structure with multiple dispersed distribution. Specifically, the return block 150 is block-shaped and is provided with a plurality of 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 a circle and the first and tail ends of the 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 diagram of the circulation loop 131 along the circumferential direction is basically the same as that of the embodiment. Figure 7b The embodiment is consistent with the above, and will not be further illustrated in detail.

[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. Correspondingly, 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, the 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] Example 4

[0085] Combine Figure 14 、 Figure 15 In this embodiment, the raceway is provided with two independent raceways of the same rotation direction, that is, the raceway adopts a double-threaded structure. Accordingly, an array of return blocks 150 is provided along the axial direction, and each group of return blocks 150 has two return blocks 150. 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 of a circle in the second raceway through the 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 the return groove 151 on another return block 150 in the same group, thereby forming a closed circulation loop. The trajectory diagram of the circulation loop unfolded along the circumferential direction is basically the same as Figure 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 axially adjacent groups of return blocks 150 are staggered along the circumference of the transmission part 121. Correspondingly, the return grooves 151 on each circulation loop 131 are staggered along the circumference of the transmission part 121.

[0087] In other schemes of this 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 distributed along the axial direction. The number of spiral sections and return grooves 151 in each circulation loop is consistent with the number of raceways 130, and the spiral sections 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, the 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 methods. Those skilled in the art can make various changes and modifications based on the present invention. As long as they do not depart from the spirit of the present invention, they should all fall within the scope defined in the claims of the present invention.

Claims

1. A ball screw pair, comprising: A nut having a through hole and a first spiral groove provided on a wall of the through hole; The screw rod is provided with a transmission portion cooperating with the nut, and a second spiral groove is provided on the outer circumference of the transmission portion; The first spiral groove and the second spiral groove cooperate to form a spiral 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 several single-turn closed circulation loops with spiral segments through the return groove, and the balls move along the circulation loops to convert the rotational motion of the nut into the linear motion of the screw rod.

2. A ball screw pair according to claim 1, characterized in that: The raceway is provided with one return block and a plurality of return grooves spaced apart along the axial direction are provided on the outer side of the return block. The first and last ends of the 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. The ball screw pair according to claim 1, characterized in that: The raceways are provided with several independent raceways with the same rotation direction. 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 that are 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 distributed in parallel and spaced apart along the axial direction, and the circulation loops are correspondingly distributed in parallel and spaced apart along the axial direction.

5. The 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. The 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 provided on the outside of each return block. The raceway is provided with a circle whose first and last ends 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. The ball screw pair according to claim 1, characterized in that: The raceways are provided with several independent raceways with the same rotation direction, and the return blocks are arranged in arrays 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. The parts on a certain circle of each raceway are connected in sequence through the return grooves on the outside of the return blocks in the same group to form a circulation loop. Each circulation loop has spiral segments that are consistent with the number of raceways, and the shapes of the spiral segments are consistent.

9. The 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 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 according to 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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