External circulation ball screw

Abstract

The external circulation ball screw of the present invention comprises a screw shaft, a nut, two reflux elements and a cover plate. The nut is arranged on the screw shaft and forms a load channel with the screw shaft. The outer peripheral surface of the nut has two conical grooves. Each reflux element is installed in the conical groove of the nut by a conical portion. The cover plate is arranged on the outer peripheral surface of the nut and presses the two reflux elements. Each reflux element has a first reflux groove, and the cover plate has a second reflux groove. The two first reflux grooves, the second reflux groove and the load channel together form a circulation channel for the ball to run. Therefore, the external circulation ball screw of the present invention uses the method of conical surface matching to quickly complete the assembly and positioning of the reflux element, and can eliminate the step difference between the reflux element and the nut to improve the smoothness of the operation of the ball.

Description

Technical Field

[0001] The invention relates to a ball screw, in particular to an external circulation ball screw. Background Art

[0002] The ball screw disclosed in US 10,035,536 B2 has a reflux groove on the nut, and the two ends of the reflux groove are connected to a mounting groove respectively. A guide is set in each mounting groove, and each guide has a channel connected to the reflux groove, so that the reflux groove and the two channels together constitute a reflux path for the ball to reflux. However, in the aforementioned patent document, a part of the reflux path is set on the nut, resulting in a high degree of fit between the nut and the two guides, otherwise it is easy to have a step difference at the joint and affect the smoothness of the ball running, so it will be relatively difficult to manufacture.

[0003] The external circulation ball screw disclosed in the TW M519199 patent case is provided with two mounting holes in the nut, and each mounting hole is embedded by a guide portion of a guide member and a convex portion of a cover plate. The guide portion of each guide member has a first reflux groove connected to the load channel, each convex portion of the cover plate has an extended guide groove connected to the first reflux groove, and the second abutment plane of the cover plate has a second reflux groove connected to the two extended guide grooves. Thus, the first reflux groove, the two extended guide grooves and the second reflux groove together constitute a reflux path for the ball to reflux. However, in the aforementioned patent document, each guide member is assembled by embedding the guide portion in the mounting hole of the nut. Due to the assembly error or dimensional tolerance between the two, there may be a step difference between the first reflux groove and the load channel, which affects the smoothness of the ball's operation. Summary of the invention

[0004] The main purpose of the present invention is to provide an external circulation ball screw, which is convenient to assemble and easy to position, and can improve the running smoothness of the ball.

[0005] In order to achieve the above main purpose, the external circulation ball screw of the present invention includes a screw shaft, a nut, a reflux unit, and a plurality of balls. The screw shaft has an external thread groove; the nut is sleeved on the screw shaft and can move along the axial direction of the screw shaft, the nut has an internal thread groove, the internal thread groove of the nut and the external thread groove of the screw shaft correspond to each other, so that the two together constitute a load channel, in addition, the outer peripheral surface of the nut has two conical grooves connected to the internal thread groove; the reflux unit has two reflux elements and a cover plate, wherein: each of the reflux elements has a conical portion and a reflux portion connected to the conical portion, and the conical portion of each reflux element is arranged on a conical groove of the nut. The reflux portion of each reflux element is located between the screw shaft and the nut. In addition, each reflux element also has a first reflux groove that runs through the tapered portion and the reflux portion; the cover plate is arranged on the outer circumference of the nut and presses these reflux elements. The cover plate has a second reflux groove. The second reflux groove of the cover plate is connected with the first reflux grooves of the reflux elements at both ends, so that the second reflux groove and the first reflux grooves form a reflux channel. The reflux channel is connected with the load channel at both ends, so that the two together form a circulation channel for the balls to run.

[0006] From the above, it can be seen that the external circulation ball screw of the present invention utilizes the conical surface matching method to quickly complete the assembly and positioning of these return elements, and the return channel is completely configured in the return unit, which can effectively eliminate the connection step difference between each return element and the nut, thereby improving the running smoothness of these balls.

[0007] Optionally, the nut has a first plane on which these conical grooves are arranged, and the groove diameters of these conical grooves gradually decrease in the direction away from the first plane; each of the reflux elements has a second plane, which is connected to the conical portion and penetrated by the first reflux groove, and the outer diameter of the conical portion gradually decreases in the direction away from the second plane; the cover plate has a third plane on which the second reflux grooves are arranged, and the third plane of the cover plate abuts against the first plane of the nut and the second planes of the reflux elements.

[0008] Optionally, an angle is formed between the outer peripheral surface of each conical portion and an imaginary plane, the imaginary plane is parallel to the first plane of the nut and passes through the center of the screw shaft, and the angle is between 40 and 60 degrees, with 45 degrees being the best angle. If the angle is less than 40 degrees, the volume of each conical portion will increase, so that the groove diameter of each conical groove needs to increase accordingly, which will increase the size of the nut; if the angle is greater than 60 degrees, the volume of each conical portion will decrease, so that the return radius of the first return groove will decrease accordingly, so that the speed of the balls passing through the first return groove will increase, so that the impact force exerted by the balls on the cover plate will inevitably increase.

[0009] The detailed structure, features, assembly or use of the external circulation ball screw provided by the present invention will be described in the detailed description of the specific implementation methods in the following. However, those skilled in the art in the field of the present invention should understand that these detailed descriptions and the specific embodiments listed for implementing the present invention are only used to illustrate the present invention, and are not used to limit the scope of protection of the patent application of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a three-dimensional view of the external circulation ball screw according to the first embodiment of the present invention.

[0011] Figure 2 This is a three-dimensional exploded view of the external circulation ball screw according to the first embodiment of the present invention.

[0012] Figure 3 This is a bottom perspective view of the return element provided by the external circulation ball screw according to the first embodiment of the present invention.

[0013] Figure 4 for Figure 1 Sectional view along line 4-4.

[0014] Figure 5 for Figure 1 Section view along line 5-5.

[0015] Figure 6 This is a diagram showing the angle relationship between the nut and the return element provided for the external circulation ball screw according to the first embodiment of the present invention.

[0016] Figure 7 This is a top view of the external circulation ball screw with the cover plate removed according to the first embodiment of the present invention.

[0017] Figure 8 This is a diagram showing the angle relationship between the nut and the return element provided for the external circulation ball screw according to the second embodiment of the present invention.

[0018] Fig. 9 This is a top view of the external circulation ball screw with the cover plate removed according to the second embodiment of the present invention.

[0019] Fig.10 This is a diagram showing the angle relationship between the nut and the return element of the external circulation ball screw provided in the third embodiment of the present invention.

[0020] Fig.11 This is a top view of the external circulation ball screw with the cover plate removed according to the third embodiment of the present invention.

[0021] Fig.12This is a graph of the external circulation ball screw according to the first embodiment of the present invention, mainly showing the impact force applied by the ball to the cover plate when the angle of the tapered portion is 45 degrees.

[0022] Fig.13 This is a graph of the external circulation ball screw according to the second embodiment of the present invention, mainly showing the impact force applied by the ball to the cover plate when the angle of the tapered portion is 40 degrees.

[0023] Fig.14 This is a graph of the external circulation ball screw according to the third embodiment of the present invention, mainly showing the impact force applied by the ball to the cover plate when the angle of the tapered portion is 60 degrees.

[0024] [Explanation of the main component symbols in the accompanying drawings]

[0025] DETAILED DESCRIPTION

[0026] The applicant first explains that in the entire specification, including the embodiments and claims described below, the terms related to directions are based on the directions in the drawings. Secondly, in the embodiments and drawings to be described below, the same element numbers represent the same or similar elements or their structural features.

[0027] Please read first Figure 1 and Figure 2 The external circulation ball screw 10 of the first embodiment of the present invention includes a screw shaft 20, a nut 30, a reflux unit 40, and a plurality of balls 70.

[0028] The nut 30 is sleeved on the screw shaft 20 and can move along the axial direction of the screw shaft 20. The screw shaft 20 has an external thread groove 22, and the nut 30 has an internal thread groove 32. The two correspond to each other to form a load channel 72 (such as Figure 4 In addition, the nut 30 has a first plane 34 and two tapered grooves 36 communicating with the internal thread groove 32 and two screw holes 38 are arranged on the first plane 34, wherein the groove diameter of the tapered groove 36 gradually decreases in the direction away from the first plane 34.

[0029] The return unit 40 has two return elements 50, such as Figure 2 and Figure 3 As shown, each reflux element 50 has a second plane 52, and each reflux element 50 extends downward from the periphery of the second plane 52 to form a tapered portion 54, and the outer diameter of the tapered portion 54 gradually decreases in the direction away from the second plane 52. In addition, each reflux element 50 also has a reflux portion 56, which is integrally connected to the small diameter end of the tapered portion 54 and is penetrated by a first reflux groove 58 together with the second plane 52 and the tapered portion 54. Figure 2 As shown, the reflux unit 40 further has a cover plate 60 , which has a curved surface 62 , a third plane 64 , and two countersunk holes 66 penetrating the curved surface 62 and the third plane 64 , wherein the third plane 64 has a second reflux groove 68 .

[0030] When the reflux unit 40 is used in conjunction with the nut 30, Figure 4 and Figure 5 As shown, the conical portion 54 of each reflux element 50 is disposed in the conical groove 36 of the nut 30, and the reflux portion 56 of each reflux element 50 is located between the screw shaft 20 and the nut 30. Since the conical portion 54 of each reflux element 50 and the conical groove 36 of the nut 30 have the same inclination angle, the two are pressed against each other. Then, two screws S are locked in the two screw holes 38 of the nut 30 through the two countersunk holes 66 of the cover plate 60, so that the cover plate 60 is pressed with the third plane 64 against the first plane 34 of the nut 30 and the second plane 52 of the two reflux elements 50 (as shown in FIG. 1 ). Figure 5 As shown in FIG. 4 , the assembly of the reflux unit 40 is completed. After the assembly is completed, the two first reflux grooves 58 are connected to one end of the second reflux groove 68, respectively, so that the two first reflux grooves 58 and the second reflux groove 68 form a reflux channel 74, and the two ends of the reflux channel 74 are connected to the load channel 72, so that the two together form a circulation channel 76 for the balls 70 to run.

[0031] On the other hand, Figure 6 , Figure 8 and Fig.10 As shown, there is an angle θ between the outer peripheral surface of each tapered portion 54 (equivalent to the groove wall of each tapered groove 36) and the imaginary plane P. The imaginary plane P is parallel to the first plane 34 of the nut 30 and passes through the center C of the screw shaft 20. The angle θ is between 40 degrees and 60 degrees. Figure 6 The 45 degrees shown is the optimal angle. Figure 8 The angle θ shown is 40 degrees. Compared with the angle θ of 45 degrees, the conical portion 54 has a larger volume (eg Figure 6 and Figure 8 As shown), the area of ​​the second plane 52 is also larger (as shown Figure 7 and Fig. 9 As shown in FIG. 5 , the diameter of the tapered groove 36 of the tapered portion 54 also needs to be enlarged. Therefore, if the angle θ is less than 40 degrees, the size of the nut 30 will increase. Fig.10 The angle shown is 60 degrees. Compared with the angle of 45 degrees, the conical portion 54 has a smaller volume (such as Figure 6 and Fig.10 As shown), the area of ​​the second plane 52 is also smaller (as shown Figure 7and Fig.11 As shown in FIG. 5 , the return radius of the first return groove 58 will decrease accordingly. Therefore, the speed of the ball 70 when passing through the first return groove 58 will increase, resulting in a greater impact force applied by the ball 70 to the cover plate 60.

[0032] Please refer to Figure 12 to Figure 14 , simulating the impact force on the cover plate 60 when the angle θ between the outer peripheral surface of the tapered portion 54 and the imaginary plane P is 40 degrees, 45 degrees and 60 degrees respectively. The parameter conditions during the simulation are set to use 39 balls 70, the ball diameter of the balls 70 is 1.5 mm, the outer diameter of the screw shaft 20 is 8 mm, the lead is 4 mm, and the screw shaft 20 rotates at 3000 rpm. This simulation is performed by computer software RecurDyn based on the above parameters. The simulation results are shown in the following table:

[0033]

[0034] It can be seen from the above table that, at a 45-degree angle, a good balance can be achieved between the size of the nut 30 and the impact force on the cover plate 60 .

[0035] In summary, the external circulation ball screw 10 of the present invention utilizes a conical surface fit to quickly complete the assembly and positioning of the return element 50, and the return channel 74 is entirely configured in the return unit 40, which can facilitate processing to reduce costs, and can also effectively eliminate the connection step difference between the return element 50 and the nut 30, thereby improving the running smoothness of the ball 70.

Claims

1. An external circulation ball screw, comprising: A screw shaft having an external thread groove; a nut, sleeved on the screw shaft and movable along the axial direction of the screw shaft, the nut having an internal thread groove and two tapered grooves connected to the internal thread groove, the internal thread groove of the nut and the external thread groove of the screw shaft correspondingly matching each other to form a load channel; A reflux unit, comprising two reflux elements and a cover plate, each of the reflux elements comprising a conical portion, a reflux portion connected to the conical portion, and a first reflux groove penetrating the conical portion and the reflux portion, the conical portion of each of the reflux elements being disposed in the conical groove of the nut, the reflux portion of each of the reflux elements being located between the screw shaft and the nut, the cover plate being disposed on the outer circumference of the nut and pressing the reflux elements, the cover plate comprising a second reflux groove, the two ends of the second reflux groove being connected to the first reflux grooves, so that the second reflux groove and the first reflux grooves form a reflux channel, the two ends of the reflux channel being respectively connected to the load channel to form a circulation channel; and A plurality of balls are disposed in the circulation channel; in, The nut has a first plane on which the tapered grooves are arranged, and the groove diameters of the tapered grooves gradually decrease in a direction away from the first plane; each of the reflux elements has a second plane connected to the tapered portion and penetrated by the first reflux groove, and the outer diameter of the tapered portion gradually decreases in a direction away from the second plane; the cover plate has a third plane on which the second reflux grooves are arranged, and the third plane of the cover plate abuts against the first plane of the nut and the second planes of the reflux elements; There is an angle between the outer peripheral surface of each conical portion and an imaginary plane passing through the center of the nut, the imaginary plane is parallel to the first plane of the nut and passes through the center of the screw shaft, and the angle is between 40 degrees and 60 degrees; the inclination angle of each conical portion is equal to the inclination angle of each conical groove.

2. The external circulation ball screw according to claim 1, wherein: The angle is 45 degrees.

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