Hydrostatic bearing with an oil-containing surface gas cushion drag reduction structure

Abstract

The application discloses a liquid static pressure bearing with oil sealing surface air cushion drag reduction structure, which comprises a bearing body, an oil sealing surface air cushion drag reduction structure, a circumferential oil return groove and an axial oil return groove. A plurality of oil sealing surface air cushion drag reduction structures are arranged on the circumferential and axial holes of the bearing body. Each oil sealing surface air cushion drag reduction structure is composed of a rectangular oil sealing surface, a rectangular oil inlet groove, an oil inlet hole and a plurality of air inlet holes. The air inlet holes are densely distributed on the rectangular oil sealing surface close to the rectangular oil inlet groove. An air flow control unit is arranged in each air inlet hole. The circumferential oil return groove separates the circumferentially distributed oil sealing surface air cushion drag reduction structures, and the axial oil return groove separates the axially distributed oil sealing surface air cushion drag reduction structures. The oil sealing surface air cushion drag reduction structure can be widely applied to liquid static pressure linear bearings, radial bearings and thrust bearings, has good drag reduction effect and compact structure, and can obtain a liquid static pressure bearing with low heat generation, high stiffness and super-precision.

Description

Technical Field

[0001] This invention relates to hydrostatic bearings, and more specifically to a hydrostatic bearing with an oil-sealing surface air cushion drag-reducing structure. Background Technology

[0002] Machine tools are machines that manufacture machines, with milling and grinding machine tools being the two most important types. With the increasing demand for high-speed, high-efficiency, and high-precision machining, the requirements for spindle accuracy and rigidity in these two types of machine tools are also increasing. Traditional rolling bearing-supported machine tool spindles struggle to meet future machining accuracy requirements, while traditional gas hydrostatic bearing-supported spindles struggle to meet future rigidity requirements. Liquid hydrostatic bearings, due to their advantages of high precision, high rigidity, and high damping, are trending towards replacing these two types of bearings in machine tool spindles. However, the severe oil film shear heating of liquid hydrostatic bearings at high speeds significantly limits their practical application. Summary of the Invention

[0003] The purpose of this invention is to provide a hydrostatic bearing with an oil-sealed air cushion drag reduction structure. It has good drag reduction effect, compact structure, and wide application. It also has three advantages: low heat generation, high rigidity and ultra-precision. When applied to machine tool spindles, it can greatly improve the service performance of the spindle.

[0004] The technical solution provided by this invention is:

[0005] A hydrostatic bearing with an oil-sealing surface air cushion drag reduction structure includes four substructures: the bearing body, the oil-sealing surface air cushion drag reduction structure, the circumferential oil return groove, and the axial oil return groove. Several oil-sealing surface air cushion drag reduction structures are arranged in the circumferential and axial directions of the inner bore of the bearing body. Each oil-sealing surface air cushion drag reduction structure consists of a rectangular oil-sealing surface, a rectangular oil inlet groove, an oil inlet hole, and several air inlets. Several air inlets are densely distributed on the rectangular oil-sealing surface near the rectangular oil inlet groove. Each air inlet hole is equipped with an air flow control unit, which can be a small orifice throttle or a porous throttle.

[0006] Furthermore, the bearing body can be circular or square in shape, with its circumferential oil return groove separating the circumferentially distributed oil sealing surface air cushion drag reduction structure, and its axial oil return groove separating the axially distributed oil sealing surface air cushion drag reduction structure.

[0007] Furthermore, the outer side of the bearing body is provided with several annular air inlet grooves and several axial air passage grooves, which are connected to several air inlet holes, and multiple axial air passage grooves connect adjacent annular air inlet grooves.

[0008] Furthermore, the oil-sealing surface air cushion drag-reducing structure is a basic structural unit, which can be arc-shaped or planar (e.g., planar rectangle and planar sector). It can be widely used in typical hydrostatic bearings such as hydrostatic linear bearings (i.e., guide rails), hydrostatic radial bearings, and hydrostatic thrust bearings. The oil supply method can be constant pressure or constant flow.

[0009] Compared with existing solutions, the advantages of this invention are:

[0010] 1. The oil-sealing surface air cushion drag-reducing structure adopted in this invention works on a principle similar to that of a hovercraft, which significantly reduces the internal friction of oil film shearing in hydrostatic bearings at high speeds, resulting in good drag reduction effect.

[0011] 2. The hydrostatic bearing with oil-sealing surface air cushion drag reduction structure used in this invention has a compact structure with circumferential oil return groove, axial oil return groove and annular air intake groove.

[0012] 3. The oil-sealing surface air cushion drag-reducing structure adopted in this invention is also applicable to typical constant pressure or constant flow hydrostatic bearings such as hydrostatic linear, radial and thrust bearings, and has a wide range of applications.

[0013] 4. This invention can produce a hydrostatic bearing that combines the advantages of low heat generation, high rigidity, and ultra-precision. When applied to machine tool spindles, it can significantly improve the service performance of the spindles. Attached Figure Description

[0014] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0015] Figures 1-3 This is an embodiment of the circular hydrostatic bearing of the present invention. Figure 1 This is a sectional view. Figure 2 Left view, Figure 3 This is a top view (with partial section). It shows: 1. Circular bearing body; 2. Oil sealing surface air cushion drag reduction structure (eight units shown); 2-1. Rectangular oil sealing surface; 2-2. Rectangular oil inlet groove; 2-3. Oil inlet holes (two per unit shown); 2-4. Air inlet holes (fourteen per unit shown); 3. Circumferential oil return groove (eight shown); 4. Axial oil return groove (three shown); 5. Annular air inlet groove (four shown); 6. Axial venting groove (sixteen shown). The axial direction is... Figure 3 The direction perpendicular to the paper surface, and the circumferential direction. Figure 3 In the direction of the middle circumference.

[0016] Figures 4-6 This is an embodiment of the square hydrostatic bearing of the present invention. Figure 4 This is a sectional view. Figure 5 Left view Figure 6This is a top view (with partial sectioning). It shows: 1. Square bearing body; 2. Oil sealing surface air cushion drag reduction structure (eight units shown); 2-1. Rectangular oil sealing surface; 2-2. Rectangular oil inlet groove; 2-3. Oil inlet hole (one per unit shown); 2-4. Air inlet hole (twelve per unit shown); 3. Circumferential oil return groove (eight shown); 4. Axial oil return groove (three shown). The axial direction is... Figure 6 The direction perpendicular to the paper surface, and the circumferential direction. Figure 6 In the direction of the middle circumference.

[0017] Figure 7 shows the arc-shaped and planar embodiments of the single oil-sealing surface air cushion drag-reducing structure of the present invention. Figure 7(a) is the arc-shaped embodiment, suitable for hydrostatic radial bearings; Figure 7(b) is the planar rectangular embodiment, suitable for hydrostatic linear bearings (i.e., guide rails); and Figure 7(c) is the planar sector-shaped embodiment, suitable for hydrostatic thrust bearings. Wherein, 2-1 is the rectangular oil-sealing surface, 2-2 is the rectangular oil inlet groove, 2-3 is the oil inlet hole, and 2-4 is the air inlet hole. Detailed Implementation

[0018] The above-described solution will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. The implementation conditions used in the embodiments may be further adjusted according to the conditions of specific manufacturers, and the implementation conditions not specified are generally those in routine experiments.

[0019] Example 1

[0020] This embodiment describes a circular hydrostatic bearing with a sealing surface air cushion drag reduction structure. The main structure of this structure is as follows: Figures 1-3 As shown, where Figure 1 This is a sectional view. Figure 2 Left view Figure 3 This is a top view. The top view includes a partial section to illustrate the working principle of the single-seal surface air cushion drag reduction structure 2. The axial direction is... Figure 3 The direction perpendicular to the paper surface, and the circumferential direction. Figure 3 In the direction of the middle circumference.

[0021] like Figure 1As shown, the bearing includes four substructures: a circular bearing body 1, an oil-sealing surface air cushion drag-reducing structure 2, a circumferential oil return groove 3, and an axial oil return groove 4. Eight oil-sealing surface air cushion drag-reducing structures 2 are arranged circumferentially and axially within the inner hole of the bearing body 1, serving as the basic structural unit. Each oil-sealing surface air cushion drag-reducing structure 2 consists of a rectangular oil-sealing surface 2-1, a rectangular oil inlet groove 2-2, two oil inlet holes 2-3, and fourteen air inlet holes 2-4. These fourteen air inlet holes 2-4 are densely distributed on the rectangular oil-sealing surface 2-1 near the rectangular oil inlet groove 2-2. Each air inlet hole 2-4 contains an airflow control unit, which can be a small-hole throttle or a porous throttle, etc. The eight oil-sealing surface air cushion drag-reducing structures 2 are divided into two rows along the axial direction, with four units in each row. Three axial oil return grooves 4 separate the two rows of axially distributed oil-sealing surface air cushion drag-reducing structures 2. In each row, four circumferential oil return grooves 3 separate the four circumferentially distributed oil-sealing surface air cushion drag-reducing structures 2. Additionally, to facilitate unified air supply to the densely packed air inlets 2-4, such as... Figure 2 As shown, several annular air inlet grooves 5 and axial ventilation grooves 6 are provided on the outer side of the bearing body 1. They are connected to multiple air inlet holes 2-4, and multiple axial ventilation grooves 6 connect adjacent annular air inlet grooves 5.

[0022] See at work Figure 3 A mandrel is installed in the inner hole of the bearing body 1. The single-sided throttling clearance between the outer circle of the mandrel and the inner hole of the bearing body 1 is generally 0.01~0.1mm. Figure 3To better illustrate the flow of hydraulic oil and air, the mandrel diameter was intentionally reduced and the throttling gap significantly enlarged in the drawing. Since the depth of the rectangular inlet groove 2-2 is typically 1-3 mm, the oil film thickness at the rectangular inlet groove 2-2 is much greater than that at the rectangular sealing surface 2-1. When the mandrel rotates at high speed n, the hydraulic oil between the outer circle of the mandrel and the inner hole of the bearing body 1 generates significant heat through shearing. For the single sealing surface air cushion drag reduction structure 2, hydraulic oil is pumped into the rectangular inlet groove 2-2 through the inlet hole 2-3, then throttled by the rectangular sealing surface 2-1, and flows out from the circumferential return groove 3 and the axial return groove 4. Because the oil film thickness at the rectangular sealing surface 2-1 is significantly less than that at the rectangular inlet groove 2-2, this hydraulic oil shearing heat generation mainly occurs on the rectangular sealing surface 2-1. Without densely distributed air inlets 2-4, the hydraulic oil experiences strong shear adhesion and high internal friction as it flows through the rectangular sealing surface 2-1, resulting in significant heat generation. With densely distributed air inlets 2-4, compressed air flows out through the air flow control unit. When the hydraulic oil flows through the rectangular sealing surface 2-1, it inevitably passes over the dense air cushion formed by the numerous air inlets 2-4. Since the viscosity of the compressed air exiting through the air inlets 2-4 is significantly lower than that of the hydraulic oil, the shear adhesion force experienced by the hydraulic oil flowing through the rectangular sealing surface 2-1 with densely distributed air inlets 2-4 is significantly less than that experienced by the hydraulic oil flowing through the rectangular sealing surface 2-1 without densely distributed air inlets 2-4. This significantly reduces the internal friction of the hydraulic oil, achieving drag reduction, and correspondingly reducing heat generation. This working principle is somewhat similar to the drag reduction principle of hovercraft.

[0023] Optimally, in order to significantly reduce the adhesion area between the hydraulic oil and the rectangular sealing surface 2-1, such as... Figure 1 As shown, multiple air inlets 2-4 are densely distributed around the rectangular oil inlet groove 2-2 on the circumference of the rectangular oil sealing surface 2-1. The purpose of this dense distribution of air inlets 2-4 near the rectangular oil inlet groove 2-2 is to increase the area of ​​the oil sealing surface through which compressed air flows outward, thus reducing the adhesion area. To form a uniformly sized, densely distributed air cushion on the rectangular oil sealing surface 2-1, an air flow control unit with equal air resistance is installed inside each air inlet 2-4 to control the amount of compressed air flowing out. The flow control unit can be a small-hole throttle or a porous throttle, etc. For the bearing body 1, in order to enable the bearing body 1 to have load-bearing characteristics, multiple oil sealing surface air cushion drag-reducing structures 2 can be arranged in the circumferential and axial directions, thereby enabling the bearing body 1 to have radial load-bearing capacity and angular overturning load-bearing capacity. The figure shows four units in the circumferential direction and two rows in the axial direction, for a total of eight units.

[0024] Example 2

[0025] This embodiment describes a square hydrostatic bearing with a sealing surface air cushion drag reduction structure. The main structure of this bearing is as follows: Figures 4-6 As shown, where Figure 4 This is a sectional view. Figure 5 Left view Figure 6 This is a top view. The top view includes a partial section to illustrate the working principle of the single-seal surface air cushion drag reduction structure 2. The axial direction is... Figure 6 The direction perpendicular to the paper surface, and the circumferential direction. Figure 6 In the direction of the middle circumference.

[0026] like Figure 4 As shown, the bearing includes four substructures: a square bearing body 1, an oil-sealing surface air cushion drag-reducing structure 2, a circumferential oil return groove 3, and an axial oil return groove 4. Eight oil-sealing surface air cushion drag-reducing structures 2 are arranged circumferentially and axially within the inner hole of the bearing body 1, serving as the basic structural unit. Each oil-sealing surface air cushion drag-reducing structure 2 consists of a rectangular oil-sealing surface 2-1, a rectangular oil inlet groove 2-2, an oil inlet hole 2-3, and twelve air inlets 2-4. The twelve air inlets 2-4 are densely distributed on the rectangular oil-sealing surface 2-1 near the rectangular oil inlet groove 2-2. Each air inlet 2-4 contains an airflow control unit with equal air resistance, which can be a small-hole throttle or a porous throttle, etc. The eight oil-sealing surface air cushion drag-reducing structures 2 are divided into two rows along the axial direction, with four units in each row. Three axial oil return grooves 4 separate the two rows of axially distributed oil-sealing surface air cushion drag-reducing structures 2. In each row, four circumferential oil return grooves 3 separate the four circumferentially distributed oil sealing surface air cushion drag reduction structures 2. Figure 5 This is the left view.

[0027] See at work Figure 6 A mandrel is installed in the inner hole of the bearing body 1. The single-sided throttling clearance between the outer circle of the mandrel and the inner hole of the bearing body 1 is generally 0.01~0.1mm. Figure 6 To better illustrate the flow of hydraulic oil and air, the mandrel diameter was intentionally reduced and the throttling gap was significantly enlarged in the drawing. Since the depth of the rectangular oil inlet groove 2-2 is typically 1-3 mm, the oil film thickness at the rectangular oil inlet groove 2-2 is much greater than the oil film thickness at the rectangular sealing surface 2-1. The working principle is the same as in Example 1.

[0028] Example 3

[0029] It is worth noting that the surface of the single oil-sealing drag-reducing structure 2 involved in Embodiments 1 and 2 of the present invention is arc-shaped, as shown in Figure 7(a), and is suitable for hydrostatic radial bearings. In the figure, letter n represents the spindle rotation speed. The structure includes a rectangular oil-sealing surface 2-1, a rectangular oil inlet groove 2-2, an oil inlet hole 2-3, and several air inlets 2-4. Several air inlets 2-4 are densely distributed on the rectangular oil-sealing surface 2-1 near the rectangular oil inlet groove 2-2. An air flow control unit is provided in the air inlet hole 2-4, which is not shown in the figure. The air flow control unit can be a small hole directly laser-, EDM-, or milling machined on the oil-sealing surface 2-1, or it can be an embedded or bonded small hole throttle, or it can be an embedded or bonded porous throttle, or a fixed liquid resistance throttle, etc. After making an equivalent transformation of Figure 7(a), it can also be applied to hydrostatic linear bearings (i.e., guide rails) and hydrostatic thrust bearings. Figure 7(b) shows a planar rectangular embodiment, suitable for hydrostatic linear bearings (i.e., guide rails), where the letter u represents the linear velocity in the straight direction. Figure 7(c) shows a planar sector embodiment, suitable for hydrostatic thrust bearings, where the letter u represents the linear velocity in the circumferential direction of the sector. The oil-sealing surface air cushion drag-reducing structure 2 is the basic structural unit, which can be arc-shaped or planar (planar rectangular and planar sector, etc.), and can be widely used in typical constant-pressure or constant-flow hydrostatic bearings such as hydrostatic linear bearings (i.e., guide rails), radial bearings, and thrust bearings.

[0030] In summary, this invention discloses a hydrostatic bearing with a sealing surface air cushion drag reduction structure, and provides an embodiment of a circular hydrostatic bearing ( Figures 1-3 An embodiment of a square hydrostatic bearing ( Figures 4-6 The invention presents three examples of oil-sealing surface air cushion drag reduction structures (Figures 7(a), 7(b), and 7(c)). The invention offers good drag reduction performance, a compact structure, and wide applicability.

[0031] The above examples are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be used to limit the scope of protection of the present invention. All equivalent changes or modifications made according to the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A hydrostatic bearing with an oil-sealing surface air cushion drag-reducing structure, comprising four substructures: a bearing body (1), an oil-sealing surface air cushion drag-reducing structure (2), a circumferential oil return groove (3), and an axial oil return groove (4), characterized in that, Several oil sealing surface air cushion drag reduction structures (2) are provided in the circumferential and axial directions of the inner hole of the bearing body (1). Each oil sealing surface air cushion drag reduction structure (2) consists of a rectangular oil sealing surface (2-1), a rectangular oil inlet groove (2-2), an oil inlet hole (2-3), and several air inlets (2-4). Several air inlets (2-4) are densely distributed on the rectangular oil sealing surface (2-1) near the rectangular oil inlet groove (2-2). The air inlets (2-4) are directly opened on the surface of the rectangular oil sealing surface (2-1) to form a dense air cushion covering the working area of ​​the rectangular oil sealing surface (2-1). An air flow control unit is provided inside each air inlet hole (2-4). The air flow control unit is a small orifice throttle or a porous throttle.

2. The hydrostatic bearing with an oil-sealing surface air cushion drag-reducing structure according to claim 1, characterized in that, The bearing body (1) is round or square in shape. Its circumferential oil return groove (3) separates the circumferentially distributed oil sealing surface air cushion drag reduction structure (2), and its axial oil return groove (4) separates the axially distributed oil sealing surface air cushion drag reduction structure (2).

3. The hydrostatic bearing with a sealing surface air cushion drag reduction structure according to claim 2, characterized in that, The bearing body (1) is provided with several annular air inlet grooves (5) and several axial air passage grooves (6) on its outer side. These grooves are connected to several air inlet holes (2-4), and multiple axial air passage grooves (6) connect adjacent annular air inlet grooves (5).

4. The hydrostatic bearing with a sealing surface air cushion drag reduction structure according to claim 1, characterized in that, The oil sealing surface air cushion drag reduction structure (2) is a basic structural unit, which is arc-shaped or planar, and can be applied to hydrostatic linear bearings, radial bearings and thrust bearings.

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