Ball screw structure with embedded ball returning device

Abstract

The ball screw structure comprises a nut and a screw shaft, a central threaded hole is formed in the nut, the nut is in threaded fit with the screw shaft through the central threaded hole, a roller path groove is formed in the inner wall of the central threaded hole, a cylindrical groove corresponding to the roller path groove is formed in the inner wall of the central threaded hole of the nut, and a ball return device is arranged in the cylindrical groove. A ball returning device is embedded in the cylindrical groove, a positioning groove is formed in the end face of the ball returning device, the ball returning device is radially positioned through matching of a cylindrical pin or / and a set screw and the positioning groove, the outer side wall of the ball returning device is a cylindrical surface, a ball returning groove is formed in the inner side wall of the ball returning device, and the ball returning groove is communicated with the roller path groove. The cylindrical surface on the outer side of the ball returning device is a positioning surface, the positioning contact surface is large, the impact resistance is good, the ball returning device is not easy to damage, and a higher rotating speed can be borne; the positioning surface of the ball returning device is easy to process and convenient to detect, and quality control during batch production is facilitated; the outer circle surface of the nut is not damaged, and the application scene is wider.

Description

Technical Field

[0001] The utility model belongs to the technical field of ball screws, in particular to a ball screw structure with an embedded ball return device. Background Art

[0002] As a key element of the transmission device, ball screws play a vital role in modern industrial production. The common application is that the motor is used as input to drive the screw to rotate, and then the nut moves linearly with the rotation of the screw. They can often be seen in various actuators, automation equipment, and conveying equipment. In addition, ball screws have the characteristics of high precision, high efficiency, and reversibility. They are also widely used in aerospace, precision testing, and automotive fields.

[0003] Ball screws generally include parts such as screws, nuts, ball returners, and balls. Depending on whether the balls are separated from the screw during operation, they are divided into two structures: internal circulation and external circulation. The internal circulation structure is further divided into internal and external types. The internal type generally uses the contact between the nut raceway and the two bosses extending from the ball returner for positioning, while the external type generally uses a recessed groove machined on the outer circle of the nut for positioning. The positioning surface of the internal bead returner is a spiral surface, which is not easy to detect in size, so quality control is more difficult during mass production; in addition, the diameter of the two bosses extending from the internal bead returner is smaller than that of the ball, and the contact area with the middle part of the bead returner is relatively small. Under conditions of high speed or large impact, the boss strength is not enough and it is easy to break, resulting in the phenomenon of the ball screw pair getting stuck and failing. After the external bead return device is installed in the nut sink groove, fillers must be added between the bead return device and the outer circle of the nut to fix it, usually by gluing. This structure is prone to glue shedding under conditions of high speed, large impact or high temperature, resulting in failure of the ball screw pair. In addition, whether it is an internal or external bead return device, the outer circle of the nut must be destroyed, which is extremely unfriendly to some occasions where the integrity of the outer surface of the nut needs to be ensured. For example, in the actuator used in the field of automobile braking, the outer surface of the nut is generally not allowed to be damaged because of the need to ensure sealing.

[0004] Therefore, how to solve the defects of the above-mentioned prior art has become the direction of efforts of technicians in this field. Utility Model Content

[0005] The purpose of the utility model is to provide a ball screw structure with a built-in ball return device, which can completely solve the shortcomings of the above-mentioned prior art.

[0006] The purpose of the utility model is achieved through the following technical solutions:

[0007] A ball screw structure with an embedded ball returner, comprising a nut and a screw shaft. A central threaded hole is provided on the nut, and the nut is in threaded fit with the screw shaft through the central threaded hole. A raceway groove is provided on the inner wall of the central threaded hole. A cylindrical groove is provided on the inner wall of the central threaded hole of the nut corresponding to the raceway groove. A ball returner is embedded in the cylindrical groove. A positioning groove is provided on the end face of the ball returner, and the ball returner is radially positioned by cooperating with the positioning groove through a cylindrical pin or / and a set screw. The outer side wall of the ball returner is a cylindrical surface, and a ball return groove is provided on the inner side wall. The ball return groove is communicated with the raceway groove.

[0008] Preferably, the bottom surface of the cylindrical groove is a cylindrical surface matching the outer wall of the ball returner, and the left and right side walls of the cylindrical groove are flat surfaces perpendicular to the central axis of the nut.

[0009] Preferably, pin holes communicating with the cylindrical groove are provided at both ends of the nut, a cylindrical pin is fitted in the pin holes, and the bottom end of the cylindrical pin is fitted in the positioning groove.

[0010] Preferably, the coaxiality of the pin holes at both ends of the nut is the same.

[0011] Preferably, a threaded section is provided at the end of the pin hole, and a set screw is fitted in the threaded section.

[0012] Preferably, thread sealant is applied to the set screw.

[0013] Preferably, a flat surface is provided at the top end of the outer wall of the ball returner.

[0014] Compared with the prior art, the beneficial effects of the present utility model are as follows:

[0015] 1. The cylindrical surface and its two side surfaces outside the ball returner are positioning surfaces, with a large positioning contact surface, good anti-impact performance, not easily damaged, and can withstand higher rotational speeds;

[0016] 2. The positioning surface of the ball returner is easy to machine, convenient to detect, and is conducive to the quality control during mass production;

[0017] 3. There is no need to damage the outer circular surface of the nut, and the application scenario is more extensive, especially suitable for some occasions where the integrity of the outer surface of the nut needs to be ensured. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a three-dimensional structural schematic diagram of the present utility model;

[0019] Figure 2 is a sectional view of the present utility model;

[0020] Figure 3 is a matching relationship diagram of the nut and the ball returner in the present utility model;

[0021] Figure 4It is a three-dimensional structural schematic diagram of the nut in the present utility model;

[0022] Figure 5 It is a three-dimensional structural schematic diagram of the ball returner in the present utility model;

[0023] Figure 6 It is a three-dimensional structural schematic diagram of the ball returner from another angle in the present utility model. Detailed implementation manners

[0024] The present utility model will be further described below in conjunction with specific embodiments and the accompanying drawings.

[0025] As Figures 1 to 6 shown, a ball screw structure with an embedded ball returner includes a nut 1 and a lead screw shaft 2. A central threaded hole 3 is formed in the nut 1, and the nut 1 is in threaded cooperation with the lead screw shaft 2 through the central threaded hole 3. A raceway groove is provided on the inner wall of the central threaded hole 3. A cylindrical groove 4 is formed in the inner wall of the central threaded hole 3 of the nut 1 corresponding to the raceway groove. A ball returner 5 is embedded in the cylindrical groove 4. The width of the cylindrical groove 4 is the same as the height of the cylindrical surface of the ball returner 5, which is used for axially positioning the ball returner 5. Positioning grooves 6 are provided on both end faces of the ball returner 5. Pin holes 7 communicating with the cylindrical groove 4 are axially formed at both ends of the nut 1. A cylindrical pin 8 is fitted in the pin hole 7, and the bottom end of the cylindrical pin 8 is fitted and abutted against the inner bottom surface of the positioning groove 6, which is used for radially positioning the ball returner 5. The size of the pin hole 7 can be slightly larger than that of the cylindrical pin 8 to eliminate the influence caused by machining errors. A threaded section 9 is provided at the end of the pin hole 7, and a set screw 10 is fitted in the threaded section 9 to prevent the cylindrical pin 8 from falling off. If the length of the nut 1 is short, the cylindrical pin 8 can also be cancelled, and the ball returner 5 can be directly fixed by the set screw 10.

[0026] A plurality of cylindrical grooves 4 are provided. Corresponding cylindrical grooves 4 are machined on the inner wall of the central threaded hole 3 of the nut 1 according to the quantity and size of the ball returners 5. The machining methods such as circumferential milling or boring can be adopted, or the cold heading forming method can also be used.

[0027] The coaxiality of the pin holes 7 at both ends of the nut 1 is the same. Specifically, the pin holes 7 on both sides of the cylindrical groove 4 are preferably machined in a way of drilling through to the end, so as to ensure the same coaxiality of the pin holes 7 at both ends. In the case where the destruction of one side end face is not allowed, only the pin hole 7 at one end can also be opened; a threaded section 9 is machined at the top end of the pin hole 7.

[0028] The outer side wall of the ball returner 5 is a cylindrical surface 12, and a ball return groove 11 is provided on the inner side wall. The ball return groove 11 is communicated with the raceway groove, which is used for the circulation of the balls in the raceway groove.

[0029] In this embodiment, the inner bottom surface of the cylindrical groove 4 is a cylindrical surface matching the outer wall of the ball returner 5, and the left and right side walls of the cylindrical groove 4 are flat surfaces perpendicular to the central axis of the nut.

[0030] In some occasions with relatively harsh working conditions, thread sealant is applied to the set screw 10 to improve the strength of the set screw.

[0031] The outer wall top of the ball returner 5 is provided with a flat surface. Specifically, the ball returner 5 can be formed by machining or powder metallurgy. When machining is adopted, in order to facilitate the positioning of the ball returner 5, a flat surface can be machined at the top of the cylindrical surface 12 in contact with the cylindrical groove 4 of the nut 1, but attention should be paid to controlling the size of this flat surface to ensure that there is a certain thickness between the bottom of the ball return groove and this flat surface.

[0032] In the present utility model, the cylindrical surface 12 on the outside of the ball returner 5 and its two side surfaces are positioning surfaces. The positioning contact surface is large, the impact resistance is good, it is not easy to be damaged, and it can withstand higher rotational speeds; the positioning surface of the ball returner 5 is easy to machine, convenient to detect, and is convenient for controlling the quality during mass production; the present utility model does not need to damage the outer circular surface of the nut 1, and has a wider range of application scenarios, especially suitable for some occasions where the integrity of the outer surface of the nut needs to be ensured.

[0033] The above are only the preferred embodiments of the present utility model and are not intended to limit the present utility model. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present utility model shall be included within the protection scope of the present utility model.

Claims

1. A ball screw structure with an embedded ball return device, comprising a nut and a screw shaft, wherein a central threaded hole is provided on the nut, the nut is threadedly matched with the screw shaft through the central threaded hole, and a rolling groove is provided on the inner wall of the central threaded hole, wherein: A cylindrical groove is provided on the inner wall of the central threaded hole of the nut corresponding to the rolling groove, a bead return device is embedded in the cylindrical groove, a positioning groove is provided on the end face of the bead return device, and the bead return device is radially positioned by a cylindrical pin and / or a set screw in cooperation with the positioning groove. The outer wall of the bead return device is a cylindrical surface, and a bead return groove is provided on the inner wall, and the bead return groove is connected to the rolling groove.

2. The ball screw structure with a built-in ball return device according to claim 1, characterized in that: The inner bottom surface of the cylindrical groove is a cylindrical surface matching the outer wall of the bead return device, and the left and right side walls of the cylindrical groove are flat surfaces perpendicular to the central axis of the nut.

3. The ball screw structure with a built-in ball return device according to claim 2, characterized in that: Pin holes communicating with the cylindrical groove are arranged at both ends of the nut, a cylindrical pin fits in the pin hole, and the bottom end of the cylindrical pin fits in the positioning groove.

4. The ball screw structure with a built-in ball return device according to claim 3 is characterized in that: The coaxiality of the pin holes at both ends of the nut is consistent.

5. The ball screw structure with a built-in ball return device according to claim 4, characterized in that: The end of the pin hole is provided with a threaded section, and a set screw is matched with the threaded section.

6. The ball screw structure with a built-in ball return device according to claim 5, characterized in that: Thread glue is applied on the set screw.

7. The ball screw structure with a built-in ball return device according to claim 6, characterized in that: The top end of the outer wall of the bead return device is provided with a plane.

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