Automatic pre-tightening structure for ball screw nut

Abstract

The utility model relates to an automatic pre-tightening structure of a ball screw nut, which comprises a main screw nut and an auxiliary screw nut, the corresponding ends of the main screw nut and the auxiliary screw nut are respectively provided with a force guiding ring, and the auxiliary screw nut is provided with a pre-tightening pressing device for pushing the force guiding rings to move reversely along the axial direction. According to the automatic pre-tightening structure of the ball screw, energy storage of the pressure spring, self-locking of the self-locking nut and matching of the thrust block, the guide groove and the guide inclined face are utilized, the axial positions of the two force guide rings are adjusted, the main nut and the auxiliary nut move in the opposite directions in the axial direction and are kept in the pre-tightening state all the time, and the purpose of automatic pre-tightening is achieved; the automatic pre-tightening structure is simple in structure, convenient to maintain and good in heat dissipation performance.

Description

Technical Field

[0001] The present invention relates to the technical field of ball screw preloading structures, and specifically to an automatic preloading structure for ball screw nuts. Background Art

[0002] After being used for a long time, ball screws will wear, resulting in a decrease in accuracy and stiffness. The purpose of preloading the ball screw is to eliminate the axial clearance between the balls and the screw to improve the transmission accuracy, thereby ensuring the stability and operating accuracy of the entire mechanism. Among the existing preloading methods in the market, the double-nut shim type and the spring type are the most widely used. The shim type preloading structure has strong stiffness but insufficient accuracy, cannot be adjusted during operation, is not easy to operate, and cannot automatically compensate for the clearance. The spring type preloading structure can automatically compensate for the clearance, but has problems such as insufficient return stiffness, easy fatigue of the spring, and unstable preloading force. Therefore, the purpose of the present invention is to design a preloading structure with a simple structure, convenient maintenance, good heat dissipation, easy and stable adjustment of the preloading force, and capable of automatically compensating for the wear clearance. Utility Model Content

[0003] Aiming at the defects existing in the above-mentioned prior art, the technical problem to be solved by the present utility model is how to provide a ball screw preloading structure that can not only automatically adjust the clearance between the balls and the screw, but also stably output the preloading force to ensure the stiffness and accuracy of the ball screw pair.

[0004] The technical solution of the present utility model to solve the above technical problems is: an automatic preloading structure for ball screw nuts, including a main nut and a sub-nut. Guide rings are respectively provided at one end of the main nut and the sub-nut facing each other. The guide rings are respectively fixed on the end faces of the main nut and the sub-nut facing each other by positioning pins, and there is a gap between the two guide rings. A preloading pressing device for pushing the two guide rings to move axially in opposite directions is provided on the sub-nut.

[0005] Further, a plurality of guide grooves are symmetrically arranged on one side of the two guide rings facing each other. The length of the guide groove along the axial direction gradually decreases from the outside to the inside to form an inclined surface. The width of the guide groove is the same from the outside to the inside, so the two sides are parallel. The bottom wall of the guide groove does not penetrate the guide ring. Two guide grooves facing each other on the two guide rings form a group, forming a groove with an isosceles trapezoidal axial cross-section. The small end of the isosceles trapezoidal groove is close to the screw.

[0006] Further, three or four groups of the guide grooves are evenly arranged. Four groups are arranged in both Embodiment 1 and Embodiment 2 of the present utility model.

[0007] Further, the preloading and pressing-down device includes a thrust block that cooperates with a corresponding set of guide grooves. The two axial sides of the thrust block are inclined surfaces. The inclination angles of the two end faces of the thrust block in the axial direction are the same as those of the inclined surfaces of the guide grooves. The thrust block is inserted into two corresponding guide grooves. The thrust block fits into the isosceles trapezoidal groove formed by the two opposite guide grooves and can slide radially along it. There is a radial movement space between the inner small end face (the end face with a smaller surface area at the inner end) of the thrust block and the lead screw. There is a radial movement space between the outer large end face (the end face with a larger surface area at the outer end) of the thrust block and the outer circle of the force guiding ring.

[0008] Further, the large end face of the thrust block is an arc-shaped inclined surface. The preloading and pressing-down device further includes a guiding inclined surface that cooperates with the arc-shaped inclined surface of the thrust block. The inclination angle and radian of the arc-shaped inclined surface of the thrust block are the same as those of the guiding inclined surface. By moving the axial position of the guiding inclined surface towards the main nut, the thrust block can be extruded to move radially towards the lead screw.

[0009] Further, the guiding inclined surface is on the inner wall of the front section of the thrust sleeve and is in an overall tapered shape with a larger front and a smaller rear. The rear section of the thrust sleeve is sleeved on the outer wall of the auxiliary nut and can move axially.

[0010] Further, the guiding inclined surface is on the inner side of the front section of the thrust key. The thrust key is arranged in the positioning sleeve. The positioning sleeve is provided with a guiding space corresponding to the thrust key. The thrust key can move axially in the positioning sleeve. The positioning sleeve is fixedly sleeved on the outer wall of the auxiliary nut. The number of thrust keys is the same as the number of thrust blocks.

[0011] Further, the rear section of the auxiliary nut is connected to a self-locking nut through an external thread. The locking teeth of the self-locking nut are serrated with one side vertical and the other side inclined. A pressure spring is sleeved on the auxiliary nut between the end of the thrust sleeve or the end of the thrust key and the self-locking nut.

[0012] Further, the winding direction of the pressure spring is opposite to the thread direction of the self-locking nut. The front end of the pressure spring is fixedly connected to the end of the thrust sleeve or the end of the thrust key. The end of the pressure spring is movably clamped in the locking teeth of the self-locking nut.

[0013] Further, the two force guiding rings are connected by a connecting key.

[0014] Advantages of the present utility model over the prior art: The automatic preloading structure of the ball screw of the present utility model is driven by a pressurized spring storing energy to axially move the thrust sleeve or thrust key forward. By using the angle matching of the guiding inclined surface with the inclined surfaces of the thrust block and the guiding groove, the axial positions of the two force guiding rings are adjusted, causing the main nut and the auxiliary nut to move in opposite directions axially, thereby automatically compensating for the clearance between the balls and the screw in the nut pair. Compared with the traditional preloading methods using gaskets or springs, the automatic preloading structure of the present utility model not only solves the problem of insufficient spring preloading stiffness but also solves the problem that the gasket preloading has insufficient precision and cannot be preloaded automatically. Due to the triangular force principle used in the present utility model, the reverse stroke stiffness and precision are improved, the spring is less affected by the rebound impact, the preloading is stable, and the vibration is small. At the same time, due to the structures of the guiding groove and the thrust block, a certain distance can be separated between the two force guiding rings, facilitating the heat generated by the friction between the balls and the screw in the nut pair to escape. Description of the Drawings

[0015] Figure 1 Schematic diagram of Embodiment 1 of the present utility model;

[0016] Figure 2 Side view of Embodiment 1 of the present utility model;

[0017] Figure 3 Cross-sectional view of Embodiment 1 of the present utility model;

[0018] Figure 4 Schematic diagram of the force guiding ring of the embodiment of the present utility model;

[0019] Figure 5 Schematic diagram of the thrust sleeve of Embodiment 1 of the present utility model;

[0020] Figure 6 Schematic of Embodiment 2 of the present utility model Figure 1 ;

[0021] Figure 7 Schematic of Embodiment 2 of the present utility model Figure 2 ;

[0022] Figure 8 Schematic diagram of the thrust key of Embodiment 2 of the present utility model;

[0023] Figure 9 Schematic diagram of the self-locking nut and spring of the embodiment of the present utility model.

[0024] Reference numerals: 1. Thrust block, 2. Thrust sleeve, 3. Auxiliary nut, 4. Self-locking nut, 5. Pressurized spring, 6. Force guiding ring, 7. Screw, 8. Main nut, 9. Positioning pin, 10. Connecting key, 11. Guiding groove, 12. Guiding inclined surface, 13. Thrust key, 14. Positioning sleeve. Detailed Embodiments

[0025] The following further describes the embodiments of the present invention in conjunction with the accompanying drawings. However, these embodiments do not limit the present invention. Any similar structures and their similar variations of the present invention shall fall within the protection scope of the present invention.

[0026] Embodiment 1

[0027] As Figure 1 and Figure 2 shown, an automatic preloading structure for a ball screw nut includes a main nut 8 and a sub-nut 3. Guide force rings 6 are respectively provided at one end of the main nut 8 and the sub-nut 3 facing each other. Positioning pins 9 are provided between the two guide force rings 6 and the main nut 8 and the sub-nut 3. A preloading pressing device for pushing the guide force ring 6 to move axially along the screw rod is provided on the sub-nut 3. When the preloading pressing device moves towards the main nut 8, the axial positions of the two guide force rings 6 can be adjusted simultaneously, so that the main nut 8 and the sub-nut 3 move axially in opposite directions, thereby playing a role in adjusting the gap between the balls and the screw rod in the nut pair.

[0028] Specifically, as Figure 3 and Figure 4 shown, a plurality of guide grooves 11 are symmetrically arranged on one side of the two guide force rings 6 facing each other. The length of the guide groove 11 along the axial direction gradually decreases from the outside to the inside to form an inclined surface. The width of the guide groove 11 is the same from the outside to the inside, so the two sides are parallel. The bottom wall of the guide groove 11 does not penetrate the guide force ring 6. Two guide grooves 11 facing each other on the two guide force rings 6 form a set, forming a groove with an isosceles trapezoidal axial cross-section. The small end of the isosceles trapezoidal groove is close to the screw rod 7.

[0029] To cooperate with the use of the guide groove 11, the preloading pressing device includes a thrust block 1 that cooperates with a corresponding set of guide grooves 11. The contact surfaces of the two axial sides of the thrust block 1 and the two guide force rings 6 are inclined, and the inclination angle is the same as the inclination angle of the inclined surface of the guide groove 11. The thrust block 1 is inserted into the corresponding two guide grooves 11, and the upper end of the thrust block 1 is forced to move downward to squeeze the two guide force rings 6 to move axially in opposite directions along the screw rod. To control the thrust block 1 to expand the corresponding two sides of the guide force ring 6 after being inserted into the guide groove 11, the upper end surface of the thrust block 1 is an arc inclined surface, and the preloading pressing device further includes a guide inclined surface 12 that cooperates with the arc inclined surface of the thrust block 1. The axial position of the guide inclined surface 12 is adjusted towards the main nut 8 to press the thrust block 1 to move downward. As Figure 5As shown, the guide bevel 12 is on the inner wall of the front section of the thrust sleeve 2 and is overall in a conical shape with a larger front and a smaller rear section. The rear section of the thrust sleeve 2 is sleeved on the outer wall of the secondary nut 3. The thrust sleeve 2 is adjusted to move in the direction of the main nut 8. The large-end arc inclined surfaces of each thrust block 1 are simultaneously squeezed radially inward by the guide bevel 12, and then each thrust block 1 simultaneously moves radially toward the screw 7 in the guide groove 11, and the guide rings 6 on both sides are stretched open with the cooperation of the inclined surfaces of the guide groove 11, so that the main nut 8 and the secondary nut 3 move in the opposite direction in the axial direction, thereby axially compensating the gap between the ball and the screw.

[0030] like Figure 9 As shown, the tail section of the secondary nut 3 is connected to the self-locking nut 4 through an external thread, and a pressure spring 5 is sleeved on the secondary nut 3 between the self-locking nut 4 and the end of the thrust sleeve 2. The front end of the pressure spring 5 is fixedly connected to the end of the thrust sleeve 2, and the end of the pressure spring 5 is stuck in the locking teeth of the self-locking nut 4. By rotating the self-locking nut 4 in the forward direction, the pressure spring 5 is axially pressed to push the front thrust sleeve 2 to move in the direction of the main nut 8. The front end of the pressure spring 5 is extended for a section and inserted into the positioning hole of the push sleeve 2 to be fixed thereto. The end of the pressure spring 5 is bent into a "7" shape and stuck in the locking teeth of the self-locking nut 4. When in use, the end of the pressure spring 5 is stuck in the locking teeth of the self-locking nut 4. The locking teeth of the self-locking nut 4 are serrated on one side vertical and on the other side inclined. The serration setting direction of the locking teeth facilitates the screwing in of the self-locking nut but limits the screwing out of the self-locking nut. Due to the special shape of the locking teeth, the self-locking nut 4 can only be rotated forward but not reversely. Since the winding direction of the pressure spring 5 is opposite to the thread direction of the self-locking nut 4, when the self-locking nut 4 becomes loose and wants to be rotated out during the operation of the ball screw, the tension of the pressure spring 5 itself and the pulling force of the reverse spiral are used to self-lock the self-locking nut 4.

[0031] Example 2

[0032] like Figure 6 , Figure 7 and Figure 8 As shown, the difference between Example 2 and Example 1 is that the guide bevel 12 is arranged on the inner side of the front section of the thrust key 13, the thrust key 13 is arranged in the positioning sleeve 14, and the positioning sleeve 14 is provided with a guide space corresponding to the thrust key 13, the thrust key 13 can move axially in the positioning sleeve 14, the positioning sleeve 14 is fixedly sleeved on the outer wall of the secondary nut 3, the number of thrust keys 13 is consistent with the thrust block 1, and similarly, the tail section of the secondary nut 3 is connected to the self-locking nut 4 through an external thread, and a pressure spring 5 is sleeved on the secondary nut 3 between the self-locking nut 4 and the end of the thrust key 13, the front end of the pressure spring 5 is fixedly connected to the end of the thrust key 13, and the end of the pressure spring 5 is clamped and connected to the self-locking nut 4.

[0033] Regardless of embodiment 1 or embodiment 2, the two force guiding rings 6 are connected by a connecting key 10, so that the two force guiding rings 6 can be fixed circumferentially and can slide axially.

[0034] Similarly, in order to make the force guide ring 6 evenly stressed, preferably, the guide grooves 11 are evenly arranged in three or four groups, and the two guide grooves 11 facing each other on the two guide rings 6 form a group.

[0035] The automatic pre-tightening structure of the ball screw nut of the utility model can adjust the size of the pre-tightening force of the double nuts of the ball screw by changing the angles of the thrust block 1, the guide groove 11 and the guide bevel 12, and rotating the self-locking nut 4 according to the specific working occasions and equipment of the ball screw and the size of the pre-tightening force. It is suitable for various different equipment. By screwing in the self-locking nut 4, the pressure spring 5 is squeezed to push the thrust sleeve 2 or the thrust key 13 forward, and then each thrust block 1 is moved along the guide bevel 12 toward the screw 7 at the same time, and then the thrust block 1 squeezes and opens the guide rings 6 on both sides in the guide groove 11, so that the main nut 8 and the auxiliary nut 3 move in the axial direction. The axial gap between the ball and the screw in the nut pair is compensated, and the ball screw nut has an automatic pre-tightening effect due to the energy storage of the pressure spring 5 and the self-locking function of the self-locking nut 4.

[0036] The axial direction mentioned in the embodiments of the present invention takes the central axis of the screw rod as a reference line, and the top, bottom, up, down, inside, outside, front and back directions mentioned in the embodiments are all relative positions, and the specific positions are determined according to the contents recorded in the specification and the drawings in the specification.

[0037] The above is only a specific implementation of the utility model, but the protection scope of the utility model is not limited thereto. Any changes or substitutions that are not conceived through creative work should be included in the protection scope of the utility model. Therefore, the protection scope of the utility model should be based on the protection scope defined in the claims.

Claims

1. A ball screw nut automatic pre-tightening structure, comprising a main nut (8) and a secondary nut (3), characterized in that: The main nut (8) and the auxiliary nut (3) are provided with a force guide ring (6) at the opposite ends thereof. The force guide ring (6) is fixed on the opposite end faces of the main nut (8) and the auxiliary nut (3) by a positioning pin (9), and a spacing is left between the two force guide rings (6). The auxiliary nut (3) is provided with a pre-tightening and pressing device for pushing the two force guide rings (6) to move in the opposite direction along the axial direction.

2. The automatic pre-tightening structure for ball screw nut according to claim 1, characterized in that: A plurality of guide grooves (11) are symmetrically arranged on opposite sides of the two force guide rings (6); the guide grooves (11) are gradually reduced in length along the axial direction from the outside to the inside to form an inclined surface; the width of the guide grooves (11) is the same from the outside to the inside and therefore the two sides are parallel; the bottom wall of the guide groove (11) does not penetrate the force guide ring (6); the two guide grooves (11) facing each other on the two force guide rings (6) form a group and form a groove with an axial cross-section in the shape of an isosceles trapezoid, and the small end face of the isosceles trapezoid groove is close to the screw rod (7).

3. The automatic pre-tightening structure for ball screw nut according to claim 2, characterized in that: The guide grooves (11) are evenly arranged in three or four groups.

4. The automatic pre-tightening structure for ball screw nut according to claim 3, characterized in that: The pre-tightening and pressing device comprises a thrust block (1) matched with a corresponding set of guide grooves (11); the thrust block (1) has inclined surfaces on both axial sides; the inclination angles of the two axial inclined surfaces of the thrust block (1) are consistent with the angles of the inclined surfaces of the guide grooves (11); the thrust block (1) is inserted into the corresponding two guide grooves (11); the thrust block (1) fits in the isosceles trapezoidal groove formed by the two opposite guide grooves (11) and can slide radially therein; a radial movement space is reserved between the inner small end face of the thrust block (1) and the screw rod (7); and a radial movement space is reserved between the outer large end face of the thrust block (1) and the guide ring (6).

5. The automatic pre-tightening structure for ball screw nut according to claim 4, characterized in that: The large end surface of the thrust block (1) is an arc inclined surface, and the pre-tightening pressing device also includes a guide inclined surface (12) matched with the arc inclined surface of the thrust block (1). The inclination angle and curvature of the arc inclined surface of the thrust block (1) are consistent with those of the guide inclined surface (12). By moving the axial position of the guide inclined surface (12) in the direction of the main nut (8), the thrust block (1) can be squeezed to move radially in the direction of the screw rod (7).

6. The automatic pre-tightening structure for ball screw nut according to claim 5, characterized in that: The guide slope (12) is located on the inner wall of the front section of the thrust sleeve (2) and is in a cone shape with a larger front section and a smaller rear section. The rear section of the thrust sleeve (2) is sleeved on the outer wall of the secondary nut (3) and is axially movable.

7. The automatic pre-tightening structure for ball screw nut according to claim 6, characterized in that: The guide inclined surface (12) is located on the inner side of the front section of the thrust key (13); the thrust key (13) is arranged in a positioning sleeve (14); a guide space is provided on the positioning sleeve (14) corresponding to the thrust key (13); the thrust key (13) can move axially in the positioning sleeve; the positioning sleeve (14) is fixedly mounted on the outer wall of the secondary nut (3); the number of the thrust keys (13) is the same as the number of the thrust blocks (1).

8. The automatic pre-tightening structure for ball screw nut according to claim 6 or 7, characterized in that: The rear section of the auxiliary nut (3) is connected to the self-locking nut (4) via an external thread; the locking teeth of the self-locking nut (4) are sawtooth-shaped with one side vertical and the other side inclined; a pressure spring (5) is sleeved on the auxiliary nut (3) between the self-locking nut (4) and the end of the thrust sleeve (2) or the end of the thrust key (13).

9. The automatic pre-tightening structure for ball screw nut according to claim 8, characterized in that: The winding direction of the pressure spring (5) is opposite to the thread direction of the self-locking nut (4); the end of the pressure spring (5) is bent into a "7" shape; the front end of the pressure spring (5) is fixedly connected to the end of the thrust sleeve (2) or the end of the thrust key (13); and the end of the pressure spring is movably engaged in the locking teeth of the self-locking nut (4).

10. The automatic pre-tightening structure for ball screw nut according to claim 9, characterized in that: The two force guiding rings (6) are connected via a connecting key (10).

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