Hydraulically adjustable ball screw pair

Abstract

This invention relates to a hydraulically adjustable ball screw assembly, comprising a screw, two nuts cooperating with the screw, and a hydraulic adjustment unit disposed between the two nuts. The hydraulic adjustment unit is sleeved on the screw and includes a relatively slidable annular base and an annular washer. An annular hydraulic cavity is formed between the base and the washer. The base has a piston groove communicating with the hydraulic cavity, and the piston groove is filled with hydraulic oil. An adjusting piston is screwed to the opening of the piston groove. When the adjusting piston is turned, the hydraulic oil enters the hydraulic cavity and acts evenly on the washer and the base, pushing the washer and the base to slide relative to each other. The washer and the base push the two nuts respectively, generating a preload. This invention, by setting a hydraulic adjustment unit between the two nuts, realizes continuous adjustment of the axial preload of the ball screw assembly, improves the accuracy of preload adjustment, and enables uniform and stable axial loading, making the force on the two nuts more uniform, thereby improving the transmission stiffness and operational stability of the ball screw assembly.

Description

Technical Field

[0001] This invention relates to a hydraulically adjustable ball screw assembly, belonging to the technical field of ball screw assemblies. Background Technology

[0002] A ball screw assembly is a device that drives the linear motion of a nut through the rotation of a screw, and is commonly used in transmission and positioning fields. With the increasing demand for high-precision and high-efficiency machining in the manufacturing industry, ball screw assemblies have been widely used in CNC machine tools, aerospace equipment, precision instruments, and other fields.

[0003] In practical applications, to improve the transmission stiffness and positioning accuracy of ball screw assemblies and eliminate axial backlash, it is usually necessary to apply a certain axial preload to the ball screw assembly. In existing technologies, double-nut preloaded ball screw assemblies are widely used due to their mature structure and relatively simple implementation. This structure typically uses preload shims between the two nuts, and the preload is set by adjusting the thickness or number of shims.

[0004] However, the above-mentioned shim pre-tightening method still has certain limitations in actual use: on the one hand, the adjustment of the pre-tightening force depends on the discrete changes in the thickness of the shim, and the adjustment process requires repeated disassembly and assembly, which is cumbersome and makes it difficult to achieve continuous and precise adjustment of the pre-tightening force; on the other hand, during the long-term operation of the equipment, the contact state between the balls and the raceway will change due to factors such as temperature rise, wear and load changes, and the original pre-tightening force may be weakened or shifted, and the traditional shim pre-tightening structure is difficult to compensate online or dynamically after assembly. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention proposes a hydraulically adjustable ball screw pair with uniform loading on two nuts. To achieve the above objectives, the technical solution proposed by this invention is as follows: A hydraulically adjustable ball screw assembly includes a screw, two nuts cooperating with the screw, and a ball recirculation chain disposed between the screw and the nuts. The ball screw assembly also includes a hydraulic adjustment unit disposed between the two nuts. The hydraulic adjustment unit is sleeved on the screw and includes a relatively slidable annular base and an annular washer. An annular hydraulic cavity is formed between the base and the washer. The base has a piston groove communicating with the hydraulic cavity, and the piston groove is filled with hydraulic oil. An adjusting piston is screwed to the opening of the piston groove. When the adjusting piston is turned, hydraulic oil enters the hydraulic cavity and acts evenly on the washer and the base, pushing the washer and the base to slide relative to each other. The washer and the base respectively push the two nuts, generating a preload.

[0006] A further design of the above technical solution is as follows: one end of the substrate is provided with an annular groove, one end of the gasket is embedded in the groove and slidably connected to the groove, the hydraulic cavity is surrounded by the groove wall and the end face of the gasket, and the hydraulic oil in the hydraulic cavity acts evenly on the end face of the gasket and the groove wall of the substrate.

[0007] Furthermore, both the gasket and the adjusting piston are equipped with sealing rings.

[0008] Furthermore, the two nuts and the side wall of the base are provided with keyways at corresponding positions, and flat keys are embedded in the keyways.

[0009] Furthermore: the two nuts are a flange nut and a cylindrical nut.

[0010] Furthermore, both ends of the two nuts are equipped with a reversing device and a dustproof device.

[0011] Furthermore: the inner wall of the nut is provided with an inner raceway, the outer wall of the lead screw is provided with a lead screw raceway, and the reversing device is provided with a reversing raceway. The inner raceway of the nut, the lead screw raceway, and the reversing raceway together form a ball raceway, and the ball circulation chain is located within the ball raceway.

[0012] Compared with the prior art, the present invention has the following advantages: This invention achieves continuous adjustment of the axial preload of the ball screw pair by setting a hydraulic adjustment unit between the two nuts, thus improving the accuracy of preload adjustment. The hydraulic adjustment unit of this invention has an annular hydraulic chamber, which allows the thrust of the hydraulic oil to be evenly applied to the base and the gasket, thereby achieving uniform and stable axial loading. This makes the force on the two nuts more even, and ensures that they only receive axial force, thereby improving the transmission stiffness and operational stability of the ball screw pair.

[0013] This invention achieves nut spacing adjustment through hydraulic transmission, avoiding the need for traditional shim replacement and repeated disassembly and assembly, thus improving the assembly and debugging efficiency of ball screw pairs. Furthermore, the preload can be readjusted or compensated during equipment use, which helps reduce the impact of wear and temperature changes on transmission accuracy.

[0014] This invention has a compact structure and a simple implementation method. While maintaining the reliability of the original double-nut structure, it improves the applicability of the ball screw pair under high-precision and high-dynamic working conditions. Attached Figure Description

[0015] Figure 1 This is an overall schematic diagram of the ball screw assembly of the present invention; Figure 2 for Figure 1 A quarter section view; Figure 3 for Figure 1 Exploded view; Figure 4 This is an overall sectional view of the ball screw assembly of the present invention; Figure 5 This is an isometric view of the flange nut. Figure 6 for Figure 5 Exploded view; Figure 7 This is an isometric view of a straight-tube nut. Figure 8 for Figure 7 Exploded view; Figure 9 An isometric view of the hydraulic adjustment unit; Figure 10 This is a cross-sectional view of the hydraulic adjustment unit; Figure 11 Right view of the hydraulic adjustment unit; Figure 12 This is a longitudinal section view of the hydraulic adjustment unit; In the diagram: 1-lead screw, 2-flange nut assembly, 21-flange nut, 22, 23-dustproof device, 24, 25-return device, 26-ball circulation chain, 3-straight cylinder nut assembly, 31-flange nut, 32, 33-dustproof device, 34, 35-return device, 36-ball circulation chain, 4-hydraulic adjustment unit, 41-base, 42-gasket, 43-adjusting piston, 5-flat key. Detailed Implementation

[0016] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0017] In the description of the embodiments of the present invention, it should be understood that the terms "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings. They are used only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. The accompanying drawings are schematic diagrams or conceptual diagrams, and the relationships between the thickness and width of each part, as well as the proportional relationships between each part, etc., are not entirely consistent with their actual values. Example

[0018] The hydraulically adjustable ball screw pair in this embodiment, such as Figure 1 As shown, it includes a lead screw 1, a flange nut assembly 2 that mates with the lead screw 1, and a straight nut assembly 3. Combined Figure 2 , Figure 3 and Figure 4As shown, the two nuts are fitted onto the lead screw 1 and connected by a ball bearing chain. The outer wall of the lead screw 1 is provided with a lead screw raceway. Rotation of the lead screw 1 can drive the two nuts to make linear motion.

[0019] A hydraulic adjustment unit 4 is also provided between the two nuts. The hydraulic adjustment unit 4 is sleeved on the lead screw 1 and rotates with the nuts relative to the lead screw 1. The two nuts and the side wall of the hydraulic adjustment unit 4 are provided with keyways at corresponding positions. A flat key 5 is embedded in the keyway. The flat key 5 is used to fix the flange nut assembly 2, the straight nut assembly 3 and the hydraulic adjustment unit 4, so that these three parts will not rotate relative to each other.

[0020] like Figure 5 and Figure 6 As shown, the flange nut assembly 2 is one of the components of the ball screw pair. After being driven by the rotation of the screw, it can move linearly, thereby driving the upper worktable to move linearly.

[0021] The flange nut assembly 2 includes a flange nut 21, which serves as the main body of the circulation assembly and is used to connect with the upper-level components. Driven by the lead screw 1, it drives the upper-level components to perform linear motion. The inner wall of the flange nut 21 has an inner raceway, which cooperates with the lead screw raceway to form a cavity for ball circulation. Ball return devices 24 and 25 are installed at both ends of the flange nut 21. The return devices have return raceways to ensure that the balls form a loop. The inner raceway, lead screw raceway, and return raceway together form a ball raceway that accommodates the ball circulation chain 26. Dustproof devices 22 and 23 are also installed at both ends of the flange nut 21 to prevent external dust from entering the interior. The outer wall of the flange nut 21 has a keyway near the other nut for cooperation with other components.

[0022] like Figure 7 and Figure 8 As shown, the straight nut assembly 3 and the flange nut assembly 2 cooperate to provide preload, and the structure is basically the same as that of the flange nut assembly 2, except that it lacks the flange for connection with the upper-level components. Specifically, the straight nut assembly 3 includes a straight nut 31, which is the main body of the bearing circulation assembly. The inner wall of the straight nut 31 is provided with an inner raceway, which cooperates with the lead screw raceway to form a cavity for ball circulation. Ball return devices 34 and 35 are installed at both ends of the straight nut 31. The return devices are provided with return raceways to ensure that the balls form a loop. The inner raceway, the lead screw raceway, and the return raceway together form a ball raceway that accommodates the ball circulation chain 36. Dustproof devices 32 and 33 are also installed at both ends of the straight nut 31 to prevent external dust from entering the interior. The outer wall of the straight nut 31 is provided with a keyway near the other nut for cooperation with other components.

[0023] like Figure 9 , Figure 10 , Figure 11 and Figure 12As shown, the hydraulic adjustment unit 4 includes an annular base 41 and an annular gasket 42. One end of the base 41 is provided with an annular groove. One end of the gasket 42 can be embedded in the groove and slidably connected to the groove. The groove wall and the end face of the gasket embedded in the groove form an annular hydraulic cavity. The base 41 is also provided with a piston groove that communicates with the hydraulic cavity. The piston groove is filled with hydraulic oil. An adjusting piston 43 is screwed to the opening of the piston groove. The adjusting piston 43 is embedded in the piston groove and does not exceed the outer circumference of the base. The outer end of the adjusting piston 43 is provided with a hexagon or cross for turning the adjusting piston 43. Both the gasket 42 and the adjusting piston 43 are provided with sealing rings to achieve sealing of the hydraulic cavity and the piston groove.

[0024] Turning the adjusting piston 43 pushes the hydraulic oil in the piston groove into the hydraulic chamber. The hydraulic oil in the hydraulic chamber pushes the gasket 42 and the base 41 to move linearly relative to each other. The gasket 42 and the base 41 push the two nuts respectively, opening the flange nut assembly and the straight cylinder nut assembly, thereby generating a preload. The preload can be continuously adjusted by adjusting the screwing distance of the piston 43.

[0025] In this embodiment, because the thrust is generated by hydraulic oil being pressed into the annular hydraulic chamber, the thrust generated at all points on the annular washer end face and the annular groove wall is the same. This ensures that the thrust is evenly applied to the annular washer end face and the annular groove wall, thereby achieving uniform and stable axial loading. This makes the double nut more evenly stressed, and it only experiences axial force, preventing radial component forces caused by uneven force distribution. This improves the transmission stiffness and operational stability of the ball screw pair.

[0026] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A hydraulically adjustable ball screw assembly, comprising a screw, two nuts cooperating with the screw, and a ball recirculation chain disposed between the screw and the nuts, characterized in that: It also includes a hydraulic adjustment unit disposed between the two nuts. The hydraulic adjustment unit is sleeved on the lead screw and includes a relatively slidable annular base and an annular washer. An annular hydraulic cavity is formed between the base and the washer. The base is provided with a piston groove communicating with the hydraulic cavity. The piston groove is filled with hydraulic oil. An adjusting piston is screwed to the opening of the piston groove. When the adjusting piston is turned, the hydraulic oil enters the hydraulic cavity and acts evenly on the washer and the base, pushing the washer and the base to slide relative to each other. The washer and the base push the two nuts respectively, generating a preload force.

2. The hydraulically adjustable ball screw assembly according to claim 1, characterized in that: The base has an annular groove at one end, and the gasket is embedded in the groove at one end and slidably connected to the groove. The hydraulic chamber is formed by the groove wall and the end face of the gasket at that end. The hydraulic oil in the hydraulic chamber acts evenly on the end face of the gasket and the groove wall of the base.

3. The hydraulically adjustable ball screw assembly according to claim 2, characterized in that: Both the gasket and the adjusting piston are equipped with sealing rings.

4. The hydraulically adjustable ball screw assembly according to any one of claims 1 to 3, characterized in that: The two nuts and the side wall of the base are provided with keyways at corresponding positions, and flat keys are embedded in the keyways.

5. The hydraulically adjustable ball screw assembly according to claim 4, characterized in that: The two nuts are a flange nut and a cylindrical nut.

6. The hydraulically adjustable ball screw assembly according to claim 5, characterized in that: Both ends of the two nuts are equipped with a reversing device and a dustproof device.

7. The hydraulically adjustable ball screw assembly according to claim 6, characterized in that: The inner wall of the nut is provided with an inner raceway, the outer wall of the lead screw is provided with a lead screw raceway, and the reversing device is provided with a reversing raceway. The inner raceway of the nut, the lead screw raceway, and the reversing raceway together form a ball raceway, and the ball circulation chain is located within the ball raceway.

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