Ball screw pair

Abstract

The utility model discloses a ball screw pair which comprises a lead screw (1) and a nut (2) which are matched with each other, and the length of a thread raceway of the lead screw (1) is smaller than that of a thread raceway of the nut (2). A plurality of balls (3) are arranged in a threaded roller path where the lead screw (1) is matched with the nut (2); returning device mounting grooves (11) are formed in the two end faces of the lead screw (1). The lead screw (1) is provided with a ball return hole channel (12) communicated with the reverser installation grooves (11) in the two ends of the lead screw (1). The lead screw is simple in manufacturing process, lower in manufacturing cost, uniform and smooth in ball stress and higher in bearing capacity, and particularly, curved surface remachining of the outer circle and the threaded raceway of the lead screw can be effectively avoided.

Description

TECHNICAL FIELD

[0001] The utility model relates to a ball screw pair technology field, specifically is a kind of ball screw pair that ball is returned to cycle by screw rod inside. BACKGROUND

[0002] Ball screw pair is generally by screw rod, nut, ball and return device etc., it is the helical transmission element with ball as rolling body between screw rod and nut, can change rotary motion into linear motion, or change linear motion into rotary motion.

[0003] The length of the screw rod of traditional ball screw pair is greater than the nut, and the two ends of the screw rod penetrating the nut are matched with the nut, according to the different circulation modes of the ball on the nut, the ball screw pair is divided into internal circulation type and external circulation type, the internal circulation type realizes the return circulation of the ball through the return device embedded in the raceway of the nut, and the external circulation is that the ball returns between the screw rod and the nut to realize the return circulation in the circulation process through the helical groove or the insertion pipe on the outer surface of the nut. The ball return circulation device of the traditional ball screw pair is arranged on the nut.

[0004] With the development of new energy vehicles, people want to realize a short stroke actuator with compact structure and heavy load, and new and higher requirements are put forward for the structure of ball screw pair. That is, the whole thread stroke of the screw is completely inside the nut, and the ball needs to be circulated in the reverse direction. Because the length of the screw thread is less than the length of the nut thread, the traditional ball screw pair is provided with a ball reverse circulation device on the nut, which will cause the ball to be separated from the raceway during the stroke and unable to realize the reverse circulation, so the traditional structure needs to be changed. The Chinese patent application with publication number CN118499425A discloses a reverse ball screw pair, which sets the ball reverse circulation device on the outer thread raceway of the screw, and realizes the reverse circulation of the ball by machining the reverse channel on the outer thread raceway of the screw and setting the ball stopper. However, the circulation mode of setting the ball stopper on the thread raceway of this structure will greatly reduce the carrying capacity and the load of the ball on the nut is uneven. Because the effective number of ball circles is set on the screw, each circle needs a reverse channel to realize the reverse circulation of the ball. Except that one-way ball stoppers are used on the outside of the first and last reverse channels, bidirectional ball stoppers are used in the middle reverse channels. Since the bidirectional ball stopper is longer and occupies more space of the thread raceway, the spacing between the effective ball circles is large, so under the condition that the total length of the screw is unchanged, the number of accommodated circles of the effective ball circles is greatly reduced, which greatly reduces the carrying capacity of the ball screw pair. On the other hand, each effective ball circle needs to be correspondingly provided with a reverse channel. Once the ball enters the reverse channel, it is no longer in contact with the nut, i.e. in the unloading state and no longer carries a load. Therefore, each effective ball circle has a gap in the position of the reverse channel and does not bear a load, which will cause the load of the ball on the nut to be uneven. Too many reverse channels will also affect the smoothness of the ball running. In addition, from the aspect of process machining, the curved surface machining of the outer thread raceway of the screw will greatly increase the complexity and difficulty of the whole machining process, causing the machining cost to increase. Practical new type content

[0005] The technical problem to be solved by the present utility model is to overcome the above-mentioned shortcomings of the prior art: to provide a ball screw pair which is relatively simple in process, lower in manufacturing cost, uniform and smooth in ball stress, higher in carrying capacity, and especially capable of effectively avoiding the curved surface reprocessing of the outer circle and thread raceway of the screw.

[0006] The technical solutions of the utility model are as follows: a ball screw pair, comprising a matched screw rod and nut, the thread raceway length of the screw rod is smaller than the thread raceway length of the nut, a plurality of balls are arranged in the thread raceway of the matched screw rod and nut, a return device mounting groove is arranged on the end face of the screw rod, a ball return hole is arranged on the screw rod and is communicated with the return device mounting grooves at both ends of the screw rod, a ball return device is arranged in the return device mounting groove, the ball return device comprises a guide hole, one end of the guide hole is communicated with the end of the thread raceway of the screw rod, and the other end is communicated with the ball return hole.

[0007] As optimization, the inner walls at both ends of the guide hole are respectively tangent to the inner wall of the ball return hole and the thread raceway of the screw rod to smoothly transition.

[0008] As optimization, a blocking rib is arranged on the ball return device, the blocking rib is arranged at the joint end of the guide hole and the thread raceway of the screw rod, and the outer wall of the blocking rib is gap matched with the thread raceway of the nut. The blocking rib blocks the balls and guides the balls into the guide hole, and then the balls enter the ball return hole.

[0009] As optimization, counterbores are arranged at both ends of the ball return hole, and a flange matched with the counterbores is arranged on the lower surface of the ball return device and located at the end of the guide hole.

[0010] As optimization, the axis of the ball return hole is perpendicular to the end face of the screw rod.

[0011] As optimization, the ball return hole is arranged on the bottom face of the return device mounting groove.

[0012] As optimization, the upper surface of the ball return device is flush with or lower than the end face of the screw rod.

[0013] As optimization, a rotating shaft is coaxially arranged on the screw rod.

[0014] As optimization, one end of the nut away from the rotating shaft is closed. Limiting devices are arranged on the open edge of the nut to prevent the end face of the screw rod from being separated from the open end face of the nut.

[0015] As optimization, the return device mounting groove is obtained by milling the end face of the screw rod.

[0016] As optimization, the ball return device is molded or injection molded by a mold, and the material of the ball return device is engineering plastic or metal.

[0017] As optimization, at least one screw hole for fixing and mounting the ball return device is arranged on the bottom of the return device mounting groove, and a screw hole corresponding to the screw hole is arranged on the ball return device.

[0018] As optimization, the bottom of the returner mounting groove is provided with at least one positioning hole for positioning the ball returner, the positioning hole is provided with a positioning pin fitted with the ball returner, or the ball returner is provided with a positioning pin matched with the positioning hole.

[0019] The beneficial effects of the utility model are: aiming at the technical problems of the prior art, such as low bearing capacity, low contact rigidity, uneven bearing, and the need for machining the return raceway and other curved surface structures on the thread raceway of the outer circle of the lead screw, the structure of the ball screw pair greatly improves the bearing capacity, the contact rigidity is high, and the uniformity of ball bearing, and only the end face of the lead screw needs to be milled, the curved surface machining on the thread raceway of the outer circle of the lead screw is completely avoided, the machining process is good, the traditional machining technology can be used, the process is mature, the machining efficiency is high, and the machining cost is low. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 It is a perspective structure schematic view of the ball screw pair in the utility model embodiment.

[0021] Figure 2 It is an explosion structure schematic view of the ball screw pair in the utility model embodiment.

[0022] Figure 3 It is a sectional structure schematic view of the ball screw pair in the utility model embodiment.

[0023] Figure 4 It is a sectional structure schematic view of the ball screw pair in the utility model embodiment.

[0024] Figure 5 It is an explosion structure schematic view of the ball screw pair in the utility model embodiment.

[0025] Figure 6 It is an explosion structure schematic view of the ball screw pair in the utility model embodiment.

[0026] Figures 7-8 It is an explosion structure schematic view of the ball screw pair in the utility model embodiment.

[0027] Figure 9 It is a main view structure schematic view of the partial assembly of the ball screw pair in the utility model embodiment.

[0028] Figure 10 It is a sectional structure schematic view of the partial assembly of the ball screw pair in the utility model embodiment.

[0029] In the diagram: 1. Lead screw; 11. Reverse gear mounting slot; 12. Ball return channel; 2. Nut; 3. Ball; 4. Ball return gear; 41. Guide channel; 42. Blocking rib; 43. Flange; 5. Shaft; Detailed Implementation

[0030] The embodiments of this utility model are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this utility model, and should not be construed as limiting this utility model. Example

[0031] Now combined Figures 1-10 A ball screw assembly is described, comprising a mating screw 1 and a nut 2, wherein the thread raceway length of the screw 1 is shorter than that of the nut 2; that is, during the screw 1's precession relative to the nut 2, the thread raceway of the screw 1 remains within the nut 2, allowing it to be used as a short-stroke drive element; the thread raceway of the screw 1 and the nut 2 is uniformly filled with balls 3; Figure 2 As shown, in this embodiment, the ball bearings 3 fill the thread raceway of the lead screw 1; both ends of the lead screw 1 are provided with return device mounting grooves 11; the lead screw 1 is provided with a ball return channel 12 that connects the return device mounting grooves 11 at both ends; a ball return device 4 is provided in the return device mounting groove 11.

[0032] The ball return device 4 includes a guide channel 41, one end of which is connected to the end of the threaded raceway of the lead screw 1, and the other end is connected to the return ball channel 12.

[0033] The two ends of the threaded raceway of the lead screw 1 are connected to the return ball channel 12 through the two ball return devices 4 to form a closed ball circulation channel. This channel is filled with balls 3 to form a continuous, closed multi-turn ball chain, and there is a certain gap between adjacent balls 3.

[0034] like Figure 10 As shown, the inner walls of both ends of the guide channel 41 are tangentially connected to the inner wall of the return ball channel 12 and the thread raceway of the lead screw 1, respectively, for a smooth transition. The ball return device 4 at one end of the lead screw 1 can smoothly guide the ball 3 from one end of the thread raceway of the lead screw 1 into the return ball channel 12; then, the ball return device 4 at the other end of the lead screw 1 smoothly guides the ball 3 from the return ball channel 12 to the other end of the thread raceway of the lead screw 1, achieving a reverse circulation. In this embodiment, the return ball channel 12 is also uniformly filled with balls 3.

[0035] The ball returner 4 is provided with a blocking rib 42; the blocking rib 42 is arranged at the joint end of the guide hole 41 and the thread raceway of the screw rod 1; the outer wall of the blocking rib 42 is in clearance fit with the thread raceway of the nut 2, and the clearance is smaller than the diameter of the ball 3, so that the blocking rib 42 can be used to guide the ball 3 into the guide hole 41 and prevent the ball 3 from separating from the screw rod 1 and the nut 2 at the end of the thread raceway.

[0036] The ball returner 4 is provided with a blocking rib 42; the blocking rib 42 is arranged at the joint end of the guide hole 41 and the thread raceway of the screw rod 1; the outer wall of the blocking rib 42 is in clearance fit with the thread raceway of the nut 2, and the clearance is smaller than the diameter of the ball 3, so that the blocking rib 42 can be used to guide the ball 3 into the guide hole 41 and prevent the ball 3 from separating from the screw rod 1 and the nut 2 at the end of the thread raceway.

[0037] The axis of the ball return hole 12 is perpendicular to the end face of the screw rod 1. Figure 4 As shown in the embodiment, the axis of the ball return hole 12 is arranged to deviate from the axis of the screw rod 1, and the axis of the ball return hole 12 is parallel to the axis of the screw rod 1, so that the ball return hole 12 can be conveniently and accurately drilled on the end face of the screw rod 1, and the complexity of the machining process caused by the machining of the outer thread raceway of the screw rod 1 can be effectively avoided.

[0038] The ball return hole 12 is arranged on the bottom surface of the returner mounting groove 11.

[0039] The upper surface of the ball returner 4 is flush with the end face of the screw rod 1.

[0040] The screw rod 1 is coaxially provided with a rotating shaft 5. The rotating shaft 5 is in hole-shaft positioning and thread pre-pressing connection with the screw rod 1, and has an anti-loosening measure; the rotating shaft 5 can be used as a driving shaft to drive the nut 2 to move linearly, or can be used as an output shaft of linear motion to be driven by the nut 2, according to the actual use.

[0041] In the embodiment, the end of the nut 2 away from the rotating shaft 5 is closed, and the end face of the closed end of the nut 2 can be further provided with a fixed mounting hole, and the open edge of the nut 2 can be further provided with a limiting device to prevent the end face of the screw rod 1 from separating from the open end face of the nut 2. The specific limiting device can be a limiting screw, and the limiting device can also be replaced by a mounting end cover of the nut. The mounting hole and the limiting device are conventional technologies, and are not shown in the drawings of the embodiment.

[0042] The ball returner 4 is injection molded by a mold, and the material of the ball returner 4 is engineering plastic.

[0043] The return mechanism mounting groove 11 is obtained by milling the end face of the lead screw 1. This effectively avoids the complexity of machining caused by machining the outer diameter thread raceway of the lead screw 1.

[0044] The bottom of the return device mounting groove 11 is provided with at least one threaded hole for fixing the ball return device 4, and the ball return device 4 is provided with screw holes corresponding to the threaded hole.

[0045] The bottom of the return device mounting groove 11 is provided with at least one positioning hole for positioning the ball return device 4, and the positioning hole is provided with a positioning pin connected to the ball return device 4.

[0046] like Figures 7-8 As shown, the ball reversing device 4 described in this embodiment is composed of two segmented parts, each segmented part dividing the inner wall of the guide channel 41; this facilitates mold forming and demolding. During installation, the upper and lower segmented parts of the ball reversing device 4 are first fitted together as a whole, and then embedded into the reversing device mounting groove 11 and fixed with screws. Then, the blocking rib 42 at one end of the lead screw 1 with the ball reversing device 4 installed at both ends is screwed into the nut raceway, so that the thread raceway of the lead screw 1 is aligned with the thread raceway of the nut 2. Then, balls are poured between the thread raceway of the lead screw 1 and the thread raceway of the nut 2.

[0047] This novel ball screw assembly can be used as a short-stroke linear drive element to replace pneumatic or hydraulic rods, and has promising application prospects in new energy vehicle transmissions or braking systems. Most importantly, it significantly improves load-bearing capacity, contact rigidity, and the uniformity of ball bearing, while avoiding the need for surface machining on the threaded raceway of the screw's outer diameter. It offers good machinability, can utilize traditional machining techniques, and boasts mature processes, high processing efficiency, and low processing costs.

[0048] The above are merely exemplary embodiments of this utility model and do not constitute any limitation on the scope of protection of this utility model. All technical solutions formed by equivalent exchange or substitution fall within the scope of protection of this utility model.

Claims

1. A ball screw pair comprising a mating screw (1) and a nut (2), characterized in that: The screw rod (1) is provided with a plurality of balls (3) in the thread raceway matched with the nut (2); the screw rod (1) is provided with a returner installation slot (11) on each end face; the screw rod (1) is provided with a ball returning hole (12) which is communicated with the returner installation slots (11) at both ends; the returner installation slot (11) is provided with a ball returner (4); the ball returner (4) comprises a guide hole (41), one end of the guide hole (41) is communicated with the end of the thread raceway of the screw rod (1), and the other end is communicated with the ball returning hole (12).

2. Ball screw pair according to claim 1, characterized in that The inner walls at both ends of the guide hole (41) are respectively tangent to the inner wall of the ball returning hole (12) and the thread raceway of the screw rod (1) to smoothly transition.

3. The ball screw pair according to claim 1, characterized in that: The ball returner (4) is provided with a blocking rib (42); the blocking rib (42) is arranged at the joint end of the guide hole (41) and the thread raceway of the screw rod (1); the outer wall of the blocking rib (42) is gap matched with the thread raceway of the nut (2).

4. The ball screw pair according to claim 1, characterized in that: The ball returning hole (12) is provided with a counterbore at both ends, and the lower surface of the ball returner (4) is provided with a flange (43) which is matched with the counterbore.

5. The ball screw pair according to claim 1, characterized in that: The axis of the ball returning hole (12) is perpendicular to the end face of the screw rod (1); the ball returning hole (12) is arranged on the bottom face of the returner installation slot (11).

6. Ball screw pair according to claim 5, characterized in that The upper surface of the ball returner (4) is flush with or lower than the end face of the screw rod (1).

7. Ball screw pair according to claim 6, characterized in that The material of the ball returner (4) is engineering plastic or metal.

8. Ball screw pair according to claim 7, characterized in that The bottom of the returner installation slot (11) is provided with at least one threaded hole for fixedly installing the ball returner (4), and the ball returner (4) is provided with a screw hole corresponding to the threaded hole.

9. Ball screw pair according to claim 8, characterized in that The bottom of the returner installation slot (11) is provided with at least one positioning hole for positioning the ball returner (4), the positioning hole is provided with a positioning pin which is embedded in the ball returner (4), or the ball returner (4) is provided with a positioning pin which is matched with the positioning hole.

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