CN114673770A

CN114673770A - External circulation type ball screw

Info

Publication number: CN114673770A
Application number: CN202011556310.3A
Authority: CN
Inventors: 杨家铭
Original assignee: Hiwin Technologies Corp
Current assignee: Hiwin Technologies Corp
Priority date: 2020-12-24
Filing date: 2020-12-24
Publication date: 2022-06-28

Abstract

The external circulation type ball screw of the invention comprises a screw shaft, a screw cap, two backflow 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 is provided with two conical grooves, each backflow element is arranged in the conical groove of the nut by utilizing a conical part, and the cover plate is arranged on the outer peripheral surface of the nut and abuts against the two backflow elements. Each backflow element is provided with a first backflow groove, the cover plate is provided with a second backflow groove, and the two first backflow grooves, the two second backflow grooves and the load channel jointly form a circulation channel for the running of the balls. Therefore, the external circulation type ball screw of the invention utilizes the conical surface matching mode to quickly complete the assembly and positioning of the backflow element, and can eliminate the section difference between the backflow element and the screw cap so as to improve the operation smoothness of the ball.

Description

External circulation type ball screw

Technical Field

The present invention relates to a ball screw, and more particularly to an external circulation type ball screw.

Background

The ball screw disclosed in US10,035,536B 2 is provided with a backflow groove at the nut, the two ends of the backflow groove are respectively communicated with a mounting groove, a guide member is arranged in each mounting groove, each guide member is provided with a channel communicated with the backflow groove, so that the backflow groove and the two channels jointly form a backflow path for backflow of the balls. However, in the above patent documents, a part of the backflow path is disposed on the nut, which results in a high degree of matching between the nut and the two guiding members, otherwise, a step difference is easily generated at the joint to affect the smooth operation of the ball, and thus, the manufacturing is relatively difficult.

The TW M519199 patent discloses an external circulation ball screw having two mounting holes on a nut, each of the two mounting holes being embedded by a guide portion of a guide member and a protrusion of a cover plate. The guide portion of each guide member has a first return groove engaging the load channel, each protrusion of the cover plate has an extended guide groove engaging the first return groove, and the second abutting surface of the cover plate has a second return groove engaging the two extended guide grooves. Therefore, the first backflow groove, the two extension guiding grooves and the second backflow groove form a backflow path for backflow of the balls together. However, in the above patent documents, the guiding portions of the guiding members are embedded in the mounting holes of the nuts to complete the assembly, and the assembly error or the dimensional tolerance between the guiding members may cause a step difference between the first backflow groove and the load channel, which affects the smoothness of the ball.

Disclosure of Invention

The main objective of the present invention is to provide an external circulation type ball screw, which is easy to assemble and position, and can improve the smoothness of the operation of the balls.

To achieve the above objective, the external circulation type ball screw of the present invention includes a screw shaft, a nut, a recirculation unit, and a plurality of balls. The screw shaft has an external thread groove; the screw cap is sleeved on the screw shaft and can move along the axial direction of the screw shaft, the screw cap is provided with an internal thread groove, the internal thread groove of the screw cap and the external thread groove of the screw shaft are correspondingly matched with each other, so that the internal thread groove and the external thread groove jointly form a load channel, and in addition, the outer peripheral surface of the screw cap is provided with two conical grooves communicated with the internal thread groove; the reflow unit has two reflow elements and a cover plate, wherein: each backflow element is provided with a conical part and a backflow part connected with the conical part, the conical part of each backflow element is arranged in a conical groove of the screw cap, the backflow part of each backflow element is positioned between the screw shaft and the screw cap, and in addition, each backflow element is also provided with a first backflow groove penetrating through the conical part and the backflow part; the cover plate is arranged on the peripheral surface of the screw cap and is abutted against the backflow elements, the cover plate is provided with a second backflow groove, two ends of the second backflow groove of the cover plate are connected with the first backflow grooves of the backflow elements, so that the second backflow groove and the first backflow grooves form a backflow channel, two ends of the backflow channel are connected with the load channel, and the backflow channel and the load channel jointly form a circulation channel for the balls to operate.

Therefore, the external circulation type ball screw of the invention rapidly completes the assembly and positioning of the backflow elements by the way of conical surface matching, and the backflow channels are all configured in the backflow unit, so that the connecting section difference between each backflow element and the nut can be effectively eliminated, and the running smoothness of the balls is further improved.

Optionally, the nut has a first plane in which the tapered grooves are provided, the groove diameters of the tapered grooves gradually decreasing away from the first plane; each backflow element is provided with a second plane which is connected with the conical part and penetrated by the first backflow groove, and the outer diameter of the conical part is gradually reduced towards the direction far away from the second plane; the cover plate is provided with a third plane provided with the second backflow groove, and the third plane of the cover plate is abutted against the first plane of the screw cap and the second planes of the backflow elements.

Optionally, an included angle is formed between the outer peripheral surface of each of the tapered portions and an imaginary plane, which is parallel to the first plane of the nut and passes through the center of the screw shaft, and the included angle is between 40 degrees and 60 degrees, wherein 45 degrees is an optimal angle. If the angle is less than 40 degrees, the volume of each tapered portion will be increased, so that the groove diameter of each tapered groove needs to be increased, which will increase the size of the nut; if the angle is larger than 60 degrees, the volume of each conical part is reduced, so that the backflow radius of the first backflow groove is reduced, the speed of the balls passing through the first backflow groove is increased, and the impact force applied to the cover plate by the balls is increased.

The invention is described in the following detailed description of specific embodiments of the invention in relation to the detailed construction, features, assembly or use of external recirculating ball screws. However, it will be understood by those skilled in the art that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.

Drawings

Fig. 1 is a perspective view of an external circulation type ball screw according to embodiment 1 of the present invention.

Fig. 2 is an exploded perspective view of an external circulation type ball screw according to embodiment 1 of the present invention.

Fig. 3 is a bottom perspective view of a recirculation element provided in the external circulation type ball screw according to embodiment 1 of the present invention.

Fig. 4 is a cross-sectional view taken along line 4-4 of fig. 1.

Fig. 5 is a cross-sectional view taken along line 5-5 of fig. 1.

Fig. 6 is a diagram illustrating an angular relationship between a nut and a return element provided in the external circulation type ball screw according to embodiment 1 of the present invention.

Fig. 7 is a plan view of the external circulation type ball screw removing cover plate according to embodiment 1 of the present invention.

Fig. 8 is a diagram illustrating an angular relationship between a nut and a return element provided in the external circulation type ball screw according to embodiment 2 of the present invention.

Fig. 9 is a plan view of the external circulation type ball screw of embodiment 2 of the present invention with the cover plate removed.

Fig. 10 is a diagram illustrating an angular relationship between a nut and a return element provided in the external circulation type ball screw according to embodiment 3 of the present invention.

Fig. 11 is a plan view of the external circulation type ball screw of embodiment 3 of the present invention with the cover plate removed.

Fig. 12 is a graph showing an impact force applied to the cover plate mainly when the angle of the tapered portion is 45 degrees, in the external circulation type ball screw according to embodiment 1 of the present invention.

Fig. 13 is a graph showing an impact force applied to the cover plate when the angle of the tapered portion is 40 degrees, in the outer circulation type ball screw according to embodiment 2 of the present invention.

Fig. 14 is a graph showing an external circulation type ball screw according to embodiment 3 of the present invention, in which the impact force applied to the cover plate is mainly shown in the case where the angle of the tapered portion is 60 degrees.

[ description of main reference symbols in the drawings ]

10 external circulation type ball screw

20 screw shaft

22 external thread groove

30 nut

32 inner thread groove

34 first plane

36 tapered groove

38 screw hole

40 reflux unit

50 reflow element

52 second plane

54 taper portion

56 return part

58 first return chute

60 cover plate

62 arc surface

64 third plane

66 countersunk holes

68 second recirculation tank

70 ball

72 load channel

74 Return channel

76 circulation channel

S screw

P imaginary plane

Center of C nut

Angle theta

Detailed Description

Applicants first describe herein, throughout this specification, including the examples and claims that follow, directional terminology will be used with reference to the orientation of the figures. Next, in the embodiments and the drawings to be described below, the same element numbers denote the same or similar elements or structural features thereof.

Referring to fig. 1 and 2, an external circulation type ball screw 10 according to embodiment 1 of the present invention includes a screw shaft 20, a nut 30, a reflow unit 40, and a plurality of balls 70.

The nut 30 is fitted over the screw shaft 20 and is movable in 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, which are fitted to each other to form a load passage 72 (see fig. 4). In addition, the nut 30 has a first plane 34, and two tapered grooves 36 and two threaded holes 38 are provided in the first plane 34, wherein the groove diameter of the tapered groove 36 decreases away from the first plane 34.

The reflow unit 40 has two reflow elements 50, as shown in fig. 2 and 3, each reflow element 50 has a second plane 52, each reflow 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 a direction away from the second plane 52. Each return element 50 also has a return portion 56, the return portion 56 being integrally connected to the small diameter end of the tapered portion 54 and being intersected by a first return groove 58 with the second plane 52 and the tapered portion 54. As further shown in fig. 2, the reflow unit 40 further has a cover plate 60, the cover plate 60 has an arc surface 62, a third plane 64 and two counter bores 66 penetrating the arc surface 62 and the third plane 64, wherein the third plane 64 has a second reflow groove 68.

When the reflow unit 40 is used with the nut 30, as shown in fig. 4 and 5, the tapered portion 54 of each reflow element 50 is disposed in the tapered groove 36 of the nut 30, and the reflow portion 56 of each reflow element 50 is located between the screw shaft 20 and the nut 30, so that the tapered portion 54 of each reflow element 50 and the tapered groove 36 of the nut 30 have the same inclination angle, and they abut against each other. Then, two screws S are locked in the two screw holes 38 of the nut 30 through the two counter bores 66 of the cover plate 60, so that the cover plate 60 presses the first plane 34 of the nut 30 and the second planes 52 of the two reflow elements 50 (as shown in fig. 5) by the third plane 64, thereby completing the assembly of the reflow unit 40. After the assembly is completed, the two first return grooves 58 respectively engage with one end of the second return groove 68, so that the two first return grooves 58 and the second return groove 68 form a return channel 74, and two ends of the return channel 74 engage with the load channel 72, so that the two return channels together form a circulation channel 76 for the operation of the balls 70.

On the other hand, as shown in fig. 6, 8 and 10, the outer peripheral surface of each tapered portion 54 (equivalent to the groove wall of each tapered groove 36) and an imaginary plane P, which is parallel to the first plane 34 of the nut 30 and passes through the center C of the screw shaft 20, have an angle θ between 40 degrees and 60 degrees, with 45 degrees as shown in fig. 6 being the optimum angle. Furthermore, the angle θ shown in fig. 8 is 40 degrees, which is larger in the tapered portion 54 (as shown in fig. 6 and 8) and larger in the area of the second plane 52 (as shown in fig. 7 and 9) compared to the angle θ shown in fig. 8 of 45 degrees, so that the groove diameter of the tapered groove 36 of the matching tapered portion 54 also needs to be larger. Therefore, if the included angle θ is less than 40 degrees, the size of the nut 30 will increase. In addition, the included angle shown in fig. 10 is 60 degrees, compared to the form with the included angle of 45 degrees, although the tapered portion 54 has a smaller volume (as shown in fig. 6 and 10) and the area of the second plane 52 is smaller (as shown in fig. 7 and 11), the backflow radius of the first backflow groove 58 is smaller. Therefore, the speed of the balls 70 when passing through the first return grooves 58 is increased, resulting in an increase in the impact force applied to the cover plate 60 by the balls 70.

Referring to fig. 12 to 14 again, the impact force applied to the cover plate 60 is simulated under the condition that the included angles θ between the outer peripheral surface of the tapered portion 54 and the imaginary plane P are 40 degrees, 45 degrees and 60 degrees, respectively, and the parameter conditions during the simulation are set to use 39 balls 70, the ball diameter of the ball 70 is 1.5mm, the outer diameter of the screw shaft 20 is 8mm, the lead is 4mm, and the screw shaft 20 rotates at 3000rpm, and the simulation is performed by the computer software RecurDyn according to the above parameters, and the simulation results are shown in the following table:

from the above table, it can be seen that at 45 degrees, a good balance can be obtained between the size of the nut 30 and the impact force applied to the cover plate 60.

In summary, the external circulation ball screw 10 of the present invention utilizes the taper fit to quickly complete the assembly and positioning of the reflow element 50, and the reflow channels 74 are all disposed in the reflow unit 40, so as to facilitate the processing to reduce the cost, and simultaneously effectively eliminate the connection section difference between the reflow element 50 and the nut 30, thereby improving the smoothness of the operation of the balls 70.

Claims

1. An external circulation ball screw comprising:

a screw shaft having an external thread groove;

the screw cap is sleeved on the screw shaft and can move along the axial direction of the screw shaft, the screw cap is provided with an internal thread groove and two conical grooves communicated with the internal thread groove, and the internal thread groove of the screw cap and the external thread groove of the screw shaft are correspondingly matched with each other to jointly form a load channel;

A backflow unit having two backflow elements and a cover plate, each backflow element having a tapered portion, a backflow portion connected to the tapered portion, and a first backflow groove penetrating through the tapered portion and the backflow portion, the tapered portion of each backflow element being disposed in the tapered groove of the nut, the backflow portion of each backflow element being located between the screw shaft and the nut, the cover plate being disposed on the outer circumferential surface of the nut and abutting against the backflow elements, the cover plate having a second backflow groove, two ends of the second backflow groove being engaged with the first backflow grooves, so that the second backflow groove and the first backflow grooves form a backflow channel, and two ends of the backflow channel being engaged with the load channel to form a circulation channel; and

a plurality of balls disposed in the circulation passage.

2. An external circulation type ball screw according to claim 1, wherein the nut has a first plane in which the tapered grooves are provided, the groove diameters of the tapered grooves gradually decreasing in a direction away from the first plane; each backflow element is provided with a second plane which is connected with the conical part and penetrated by the first backflow groove, and the outer diameter of the conical part is gradually reduced towards the direction far away from the second plane; the cover plate is provided with a third plane provided with the second backflow groove, and the third plane of the cover plate is abutted against the first plane of the screw cap and the second planes of the backflow elements.

3. An external circulation type ball screw according to claim 2, wherein an angle is formed between an outer peripheral surface of each of the tapered portions and an imaginary plane passing through a center of the nut, the imaginary plane being parallel to the first plane of the nut and passing through a center of the screw shaft, the angle being between 40 degrees and 60 degrees; the inclination angle of each conical part is equal to that of each conical groove.

4. An external circulation ball screw according to claim 3, wherein the included angle is 45 degrees.