Ball screw pair

Abstract

The ball screw pair comprises a lead screw (1) and a nut (2) which are matched with each other, and the length of a threaded roller path of the lead screw (1) is smaller than that of a threaded roller path 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

[0002] The invention relates to the technical field of ball screw pairs, in particular to a ball screw pair which realizes ball return circulation through the interior of a screw. Background Art

[0003] A ball screw pair is generally composed of a screw, a nut, a ball and a return device. It is a spiral transmission element with balls as rolling bodies between the screw and the nut. It can convert rotational motion into linear motion, or convert linear motion into rotational motion.

[0004] The screw of a traditional ball screw pair is longer than the nut. The screw passes through both ends of the nut and cooperates with it. According to the different circulation methods of the balls 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 balls through the return device embedded in the nut raceway. The external circulation is that the balls return to the screw and nut through the spiral groove or cannula on the outer surface of the nut during the circulation process. The ball return circulation device of the traditional ball screw pair is set on the nut.

[0005] With the development of new energy vehicles, people have put forward new and higher requirements for the structure of ball screw pairs in order to realize short-stroke actuators with compact structure and large load. That is, the entire thread stroke of the screw is required to be completely inside the nut, and the ball return circulation must be realized; because the length of the screw thread is less than the length of the nut thread, the use of a traditional ball screw pair to set a ball return circulation device on its nut will cause the ball to detach from the raceway during the stroke and cannot achieve a return circulation, so it is necessary to change the traditional structure. The Chinese patent application with publication number CN118499425A discloses a reverse ball screw pair, which sets a ball return circulation device on the outer cylindrical thread raceway of the screw, and realizes the return of the ball by machining a return channel and setting a ball stopper on the outer cylindrical thread raceway of the screw. However, the circulation method of setting a ball stopper on the thread raceway of this structure will greatly reduce the load-bearing capacity and cause uneven load of the ball on the nut. Because of the number of effective ball circles set on the screw, each circle requires a return channel to realize the return of the ball. In addition to the one-way ball stopper on the outside of the first and last return channels, the middle return channel uses a two-way ball stopper. Since the two-way ball stopper is longer and occupies more thread raceway space, the interval between the effective ball circles is larger. Therefore, under the condition that the total length of the screw remains unchanged, the number of effective ball circles that can be accommodated is greatly reduced, which greatly reduces the bearing capacity of the ball screw pair; on the other hand, each effective ball circle needs to be set with a corresponding return channel. Once the ball enters the return channel, it will no longer contact the nut, that is, it is in an unloaded state and no longer bears load. Each circle of effective ball circles has a gap at the position of the return channel that does not bear the load, which will cause uneven bearing of the ball on the nut; too many return channels also affect the smoothness of the ball operation. In addition, from the aspect of process processing, surface processing of the outer cylindrical thread raceway of the screw will greatly increase the complexity and difficulty of the entire processing process, resulting in increased processing costs. Summary of the invention

[0006] The technical problem to be solved by the present invention is to overcome the shortcomings of the above-mentioned prior art: to provide a ball screw pair with relatively simple process, lower manufacturing cost, uniform and smooth force on the balls, greater load-bearing capacity, and especially the ability to effectively avoid re-processing the curved surface of the outer circle of the screw and the threaded raceway.

[0007] The technical solution of the present invention is as follows: a ball screw pair, comprising a matching screw and a nut, wherein the thread raceway length of the screw is smaller than the thread raceway length of the nut; a plurality of balls are arranged in the thread raceways of the screw and the nut; return device mounting grooves are arranged on both end surfaces of the screw; a ball return channel connecting the return device mounting grooves at both ends of the screw is arranged on the screw; a ball return device is arranged in the return device mounting groove; the ball return device comprises a guide channel, one end of the guide channel is connected to the end of the thread raceway of the screw, and the other end is connected to the ball return channel.

[0008] As an optimization, the inner walls at both ends of the guide channel are tangentially connected to the inner wall of the ball return channel and the threaded raceway of the lead screw to achieve a smooth transition.

[0009] As an optimization, the ball return device is provided with a blocking rib; the blocking rib is provided at the connecting end of the guide channel and the threaded raceway of the lead screw; the outer wall of the blocking rib is in clearance with the threaded raceway of the nut. The function of the blocking rib is to block the ball and guide it into the guide channel, and then enter the ball return channel.

[0010] As an optimization, countersunk holes are provided at both ends of the ball return channel, and a flange that cooperates with the countersunk holes is provided on the lower surface of the ball return device at the end of the guide channel.

[0011] As an optimization, the axis of the ball return hole is perpendicular to the end face of the lead screw.

[0012] As an optimization, the bead return channel is arranged on the bottom surface of the return device installation groove.

[0013] As an optimization, the upper surface of the ball return device is flush with or lower than the end surface of the lead screw.

[0014] As an optimization, a rotating shaft is coaxially provided on the lead screw.

[0015] As an optimization, one end of the nut away from the rotating shaft is closed. A limiting device is provided at the edge of the nut opening to prevent the end face of the lead screw from separating from the open end face of the nut.

[0016] As an optimization, the return device mounting groove is obtained by milling the end face of the screw.

[0017] As an optimization, the ball return device is formed by mold compression or injection molding, and the material of the ball return device is engineering plastic or metal.

[0018] As an optimization, at least one threaded hole for fixedly installing the ball return device is provided at the bottom of the return device installation groove, and a screw hole corresponding to the threaded hole is provided on the ball return device.

[0019] As an optimization, the bottom of the return device mounting groove is provided with at least one positioning hole for positioning the ball return device, and a positioning pin engaged with the ball return device is provided in the positioning hole, or a positioning pin cooperating with the positioning hole is provided on the ball return device.

[0020] The beneficial effects of the present invention are as follows: in view of the technical problems in the prior art such as low load-bearing capacity, low contact rigidity, uneven load-bearing, and the need to process the return raceway on the thread raceway of the outer circle of the screw, which complicates the processing technology and increases the cost, the structural structure of the ball screw pair of the present invention greatly improves the load-bearing capacity, high contact rigidity and uniformity of ball load-bearing, and only needs to mill the end face of the screw, completely avoiding the surface processing on the thread raceway of the outer circle of the screw, and has good processing technology, can use traditional processing technology, mature technology, high processing efficiency and low processing cost. The present invention arranges the ball return circulation device on the end faces of the screw thread raceway at both ends and realizes the return of the ball through the axial through hole. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the three-dimensional structure of the ball screw pair in an embodiment of the present invention.

[0022] Figure 2 It is a schematic diagram of the exploded structure of the ball screw pair in an embodiment of the present invention.

[0023] Figure 3 It is a schematic cross-sectional structural diagram of a ball screw pair in an embodiment of the present invention.

[0024] Figure 4 It is a schematic diagram of the cross-sectional three-dimensional structure of the ball screw pair in an embodiment of the present invention.

[0025] Figure 5 It is a schematic diagram of the exploded structure of the ball screw pair in an embodiment of the present invention.

[0026] Figure 6 It is a schematic diagram of the exploded structure of some components of the ball screw pair in an embodiment of the present invention.

[0027] Figure 7-8 It is a schematic diagram of the exploded structure of the ball return device of the ball screw pair in an embodiment of the present invention.

[0028] Fig. 9 It is a schematic diagram of the front view structure of some components of the ball screw pair in an embodiment of the present invention.

[0029] Fig.10 It is a schematic cross-sectional structural diagram of some components of a ball screw pair in an embodiment of the present invention.

[0030] In the figure: 1, lead screw; 11, return device mounting groove; 12, ball return hole; 2, nut; 3, ball; 4, ball return device; 41, guide hole; 42, blocking rib; 43, flange; 5, rotating shaft; DETAILED DESCRIPTION

[0031] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention. Example

[0032] Now combined Figure 1-10 A ball screw pair is described, comprising a matching screw 1 and a nut 2, wherein the thread raceway length of the screw 1 is shorter than the thread raceway length of the nut 2; that is, during the screwing motion of the screw 1 relative to the nut 2, the thread raceway of the screw 1 can always remain inside the nut 2, and can be used as a short-stroke driving element; the thread raceway of the matching screw 1 and the nut 2 is evenly filled with balls 3; Figure 2 As shown, the balls 3 in this embodiment fill the thread raceway of the lead screw 1; both end surfaces of the lead screw 1 are provided with return device mounting grooves 11; the lead screw 1 is provided with a ball return hole 12 connecting the return device mounting grooves 11 at both ends thereof; the return device mounting groove 11 is provided with a ball return device 4; 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 of which is connected to the ball return channel 12 .

[0033] The two ends of the threaded raceway of the screw 1 are connected to the ball return channel 12 through the two ball return devices 4 to form a closed ball circulation channel. The 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 Fig.10 As shown, the inner walls at both ends of the guide channel 41 are tangentially connected with the inner wall of the ball return channel 12 and the threaded raceway of the screw 1 to achieve a smooth transition. The ball return device 4 at one end of the screw 1 can smoothly guide the balls 3 from one end of the threaded raceway of the screw 1 into the ball return channel 12; and then the ball return device 4 at the other end of the screw 1 smoothly guides the balls 3 from the ball return channel 12 to the other end of the threaded raceway of the screw 1 to achieve a return cycle. In this embodiment, the ball return channel 12 is also evenly filled with balls 3.

[0035] The ball return device 4 is provided with a blocking rib 42; the blocking rib 42 is arranged at the connecting end of the guide channel 41 and the threaded raceway of the screw 1; the outer wall of the blocking rib 42 is matched with the threaded raceway gap of the nut 2, and the gap is smaller than the diameter of the ball 3, so the blocking rib 42 can be used to guide the ball 3 into the guide channel 41, and can also prevent the ball 3 from escaping from the screw 1 and the nut 2 from the end of the threaded raceway.

[0036] Counterbores are provided at both ends of the ball return channel 12, and flanges 43 cooperating with the counterbores are provided at the end of the guide channel 41 on the lower surface of the ball return device 4. Accurate channel docking between the guide channel 41 and the ball return channel 12 can be achieved. Moreover, the provision of the flange 43 can effectively increase the turning R of the guide channel 41 without increasing the thickness of the ball return device 4, thereby increasing the smoothness of ball guiding.

[0037] The axis of the ball return channel 12 is perpendicular to the end face of the lead screw 1. Figure 4 As shown, in this embodiment, the axis of the ball return hole 12 is set to deviate from the axis of the screw 1, and at the same time, the axis of the ball return hole 12 is parallel to the axis of the screw 1, so that the ball return hole 12 can be drilled on the end face of the screw 1 very conveniently and accurately, effectively avoiding the complexity of the processing technology caused by the processing of the outer cylindrical thread raceway of the screw 1.

[0038] The ball return channel 12 is arranged on the bottom surface of the return device installation groove 11 .

[0039] The upper surface of the ball return device 4 is flush with the end surface of the lead screw 1 .

[0040] The screw 1 is coaxially provided with a rotating shaft 5. The rotating shaft 5 and the screw 1 are positioned by a hole axis and connected by thread pre-compression, and anti-loosening measures are provided; the rotating shaft 5 can be used as a driving shaft to drive the nut 2 to move linearly, or as an output shaft of linear motion driven by the nut 2, depending on the actual use.

[0041] In this embodiment, the end of the nut 2 away from the rotating shaft 5 is closed, and the closed end face of the nut 2 may also be provided with a fixed mounting hole, and the opening edge of the nut 2 may also be provided with a limiting device to prevent the end face of the lead screw 1 from being separated from the open end face of the nut 2. The specific limiting device may be a limiting screw, etc., and the limiting device may also be replaced by a mounting end cover of the nut. The mounting hole and the limiting device belong to conventional technology and are not shown in the figure of this embodiment.

[0042] The ball return device 4 is formed by injection molding, and the material of the ball return device 4 is engineering plastic.

[0043] The return device installation groove 11 is obtained by milling the end face of the lead screw 1, which can effectively avoid the complexity of the processing technology caused by processing the outer cylindrical thread raceway of the lead screw 1.

[0044] At least one threaded hole for fixing and installing the ball return device 4 is provided at the bottom of the return device installation groove 11 , and a screw hole corresponding to the threaded hole is provided on the ball return device 4 .

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

[0046] like Figure 7-8 As shown, the ball return device 4 described in this embodiment is composed of two divided parts, and each divided part evenly divides the inner wall of the guide channel 41; it is convenient for mold forming and demoulding. During installation, the upper and lower divided parts of the ball return device 4 are first embedded into a whole, and then embedded into the return device installation groove 11, and then fixed with screws, and then the blocking rib 42 at one end of the screw 1 with the ball return device 4 installed at both ends is screwed into the nut raceway, so that the thread raceway of the screw 1 is aligned with the thread raceway of the nut 2, and then the balls are poured between the thread raceway of the screw 1 and the thread raceway of the nut 2.

[0047] The ball screw pair of the present invention can be used as a short-stroke linear drive element to replace a pneumatic rod or a hydraulic rod, and has good application prospects in new energy vehicle gearboxes or brake systems, etc. The most important thing is that the load-bearing capacity, high contact rigidity and uniformity of ball load-bearing are greatly improved, and the surface processing on the thread raceway of the outer circle of the screw is avoided. The processing process is good, the traditional processing technology can be used, the process is mature, the processing efficiency is high, and the processing cost is low.

[0048] The above are only examples of the features of the present invention and do not constitute any limitation on the protection scope of the present invention. Any technical solution formed by equivalent exchange or equivalent replacement falls within the protection scope of the present invention.

Claims

1. A ball screw pair, comprising a matching screw (1) and a nut (2), characterized in that: The thread raceway length of the lead screw (1) is shorter than the thread raceway length of the nut (2); a plurality of balls (3) are arranged in the thread raceway of the lead screw (1) and the nut (2); return device mounting grooves (11) are arranged on both end surfaces of the lead screw (1); a ball return hole (12) is arranged on the lead screw (1) and is connected to the return device mounting grooves (11) at both ends; a ball return device (4) is arranged in the return device mounting groove (11); the ball return device (4) comprises a guide hole (41), one end of the guide hole (41) is connected to the end of the thread raceway of the lead screw (1), and the other end is connected to the ball return hole (12).

2. The ball screw pair according to claim 1, characterized in that: The inner walls at both ends of the guide hole (41) are tangentially connected to the inner wall of the ball return hole (12) and the thread raceway of the lead screw (1) to achieve a smooth transition.

3. The ball screw pair according to claim 1, characterized in that: The ball return device (4) is provided with a blocking rib (42); the blocking rib (42) is provided at the connecting end of the guide channel (41) and the thread raceway of the lead screw (1); the outer wall of the blocking rib (42) is clearance-matched with the thread raceway of the nut (2).

4. The ball screw pair according to claim 1, characterized in that: Countersunk holes are provided at both ends of the ball return channel (12), and flanges (43) cooperating with the countersunk holes are provided on the lower surface of the ball return device (4) at the end of the guide channel (41).

5. The ball screw pair according to claim 1, characterized in that: The axis of the ball return hole (12) is perpendicular to the end surface of the lead screw (1); the ball return hole (12) is arranged on the bottom surface of the return device installation groove (11).

6. The ball screw pair according to claim 5, characterized in that: The upper surface of the ball return device (4) is flush with the end surface of the lead screw (1) or lower than the end surface of the lead screw.

7. The ball screw pair according to claim 6, characterized in that: The ball return device (4) is formed by mold compression or injection molding, and the material of the ball return device (4) is engineering plastic or metal.

8. The ball screw pair according to claim 7, characterized in that: The return device installation groove (11) is obtained by milling the end surface of the lead screw (1).

9. The ball screw pair according to claim 8, characterized in that: At least one threaded hole for fixing and mounting the ball return device (4) is provided at the bottom of the return device installation groove (11), and a screw hole corresponding to the threaded hole is provided on the ball return device (4).

10. The ball screw pair according to claim 9, characterized in that: At least one positioning hole for positioning the ball return device (4) is provided at the bottom of the return device installation groove (11), and a positioning pin engaged with the ball return device (4) is provided in the positioning hole, or a positioning pin engaged with the positioning hole is provided on the ball return device (4).

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