CN102179532B - Ultrahigh-precision aerostatic bearing main shaft system - Google Patents

Abstract

An ultra-high-precision aerostatic bearing spindle system, which includes a rotating shaft (1), a spindle box (2) and a headstock end cover (3), wherein the rotating shaft (1) is installed in the headstock (2), relying on aerostatic Supported and rotated relative to the headstock (2), the hydrostatic pressure bearing is integrated in and integral with the headstock (2), allowing for the simplest configuration. A thrust boss (28) is arranged in the spindle box (2) to connect the spindle box end cover (3) and form the axial air film gap of the thrust bearing. The inner surface (2a) of the main bore of the spindle box (2) is provided with a vacuum annular groove (25), the vacuum annular groove (25) is located between the two exhaust grooves (24), and the spindle box (2) is provided with The vacuum port (29), together with the radial hole (13) and the central hole (11) on the rotating shaft (1), forms a connected vacuum air passage, which can be used to absorb workpieces when a vacuum chuck is installed on the end face of the rotating shaft.

Description

Ultra-high precision aerostatic bearing spindle system

technical field

The invention relates to a spindle system of a machine tool, in particular to an ultra-high-precision aerostatic pressure bearing spindle system.

Background technique

In ultra-precision machining machine tools, the spindle system is the core component of the machine tool, and its accuracy directly affects the machining accuracy of the parts. Aerostatic bearings are widely used in the spindle system of ultra-precision machine tools due to their high rotation accuracy, small temperature rise and small thermal deformation errors during high-speed rotation. In the design of the spindle system of ultra-precision machine tools, the principles of simple structure, few parts, good assembly performance, and good dimensional stability should be followed, so that the spindle system can achieve extremely high rotation accuracy and stability. Commonly used aerostatic bearings are divided into two types according to the structural shape of the shaft: T-type and H-type. The former is suitable for high-precision fields, and the latter is suitable for fields with high diagonal rigidity requirements. Chinese patent CN101229590A discloses an ultra-precision aerostatic piezoelectric spindle, which uses an H-shaped rotating shaft and has a relatively large angular stiffness, but it is difficult to adjust the clearance of the thrust bearing, and the rotating shaft is composed of multiple parts, which is difficult to achieve. Especially high precision requirements and dynamic balance requirements; in addition, the aerostatic pressure bearing needs a shaft support or a headstock to support, and sealing needs to be considered between the aerostatic pressure bearing and the headstock. Fig. 1 shows a kind of conventional ultra-precision aerostatic pressure bearing spindle system, which adopts T-shaped rotating shaft, including rotating shaft 100, aerostatic pressure bearing 200, spindle box 300, thrust washer ring 400, and thrust plate 500. Screws 600 (or other connection methods) securely connect the aerostatic bearing 200, the thrust washer 400 and the thrust plate 500 to the headstock 300, and the rotating shaft 100 is suspended on the aerostatic bearing 200 and the thrust plate 500 by high-pressure gas In the gas bearing structure formed, it rotates relative to the headstock; at the same time, between the aerostatic bearing 200 and the headstock 300, there is generally an annular groove 202 for supplying air to the orifice, so on the outer surface of the aerostatic bearing A sealing element 201 needs to be added between the inner hole of the headstock and the headstock to prevent leakage of high-pressure gas. For ultra-precision equipment, few parts and simple assembly can achieve high precision and precision retention. Therefore, the structure of the conventional ultra-precision air static pressure bearing spindle system shown in Figure 2 is complicated. Chinese patent CN2810824Y discloses a super-precision high-speed air-bearing electric spindle, which also adopts a T-shaped spindle, but its structure is more complicated, and the coaxiality of the front and rear bearings is difficult to guarantee. Similar problems also exist in the ultra-precision aerostatic bearing spindle system disclosed in Chinese patent CN101780547A.

Contents of the invention

The purpose of the present invention is to provide an aerostatic bearing spindle system with simple structure, few parts, good structural stability and ultra-high precision, which is used to solve the problem of complex structure of the spindle system in existing ultra-precision machine tools, many parts, Some problems with high assembly requirements and poor accuracy retention.

The technical solution adopted by the present invention to solve the technical problem is: an ultra-high-precision aerostatic bearing spindle system, which includes a rotating shaft, a spindle box, and a spindle box end cover, wherein the rotating shaft is T-shaped and supported by an aerostatic bearing. For rotation in the headstock, the aerostatic bearing is integrated in and with the headstock, which has the advantage that a compact design can be achieved and the number of parts used can be minimized.

The aerostatic bearings referred to in this specification include axial aerostatic bearings which may function as thrust bearings.

In the technical solution of the present invention, the structural elements of the aerostatic pressure bearing, including the journal bearing surface and its radial restrictor, the thrust bearing surface and its axial restrictor, are used to form the axial air film gap The thrust washer ring and the necessary gas flow passages are all integrated on the headstock, thus realizing the compact and stable structural features, as detailed below.

There is a main cavity in the spindle box, the inner surface of the main cavity is cylindrical, which can be used as a journal bearing surface after precision machining, and the rotating shaft can be installed in it. The rotating shaft has a cylindrical shape facing the inner surface of the main cavity. On the outer circular surface, one end surface of the rotating shaft can be connected with a motor or other power mechanism to drive the rotating shaft to rotate relative to the headstock. There are two exhaust grooves on the inner surface of the main bore. These two exhaust grooves divide the journal bearing surface into two parts, or into two journal bearings. These two exhaust grooves are responsible for receiving the two The gas that flows out from the corresponding parts of the journal bearings, and the gas is discharged to the outside of the headstock through the corresponding exhaust flow passage.

The headstock in this specification may have a substantially polyhedral shape or a substantially cylindrical shape.

A thrust boss is arranged on the spindle box, and the thrust boss has a flange plane perpendicular to the axis of the inner surface of the main bore. The function of the thrust boss is similar to that of the thrust washer ring of the conventional aerostatic pressure bearing, which is used to connect the headstock end cover and form the air film gap of the thrust bearing.

The spindle box is also provided with a plane perpendicular to the axis of the inner surface of the main bore, which can be used as a thrust surface of the thrust bearing after precision machining. The main shaft box also includes an end cover of the main shaft box, and one end plane of the end cover can be used as another thrust surface of the thrust bearing after precision machining. These two thrust surfaces constitute a closed aerostatic thrust bearing.

A radial restrictor is arranged on the inner surface of the main bore in the spindle box, and the high-pressure gas enters the gap between the inner surface of the main bore and the outer circular surface of the rotating shaft through the radial restrictor, forming a journal air film, Can withstand radial loads.

An axial throttling device is arranged on the thrust surface perpendicular to the axis of the inner surface of the main bore in the main shaft box; an axial throttling device is also arranged on the thrust surface of the end cover of the main shaft box. The high-pressure gas enters the gap between the two thrust surfaces and the thrust plate of the rotating shaft through the axial restrictor, forming a thrust gas film, which can bear the axial load.

The radial restrictors and axial restrictors referred to in this specification may be small hole restrictors, slit restrictors, or porous restrictors.

There are air inlets and corresponding gas flow passages in the spindle box, which can deliver high-pressure gas to the radial restrictors and axial restrictors; at the same time, there are exhaust flow passages to discharge the gas out of the spindle box. .

The above technical features can integrate the headstock and the aerostatic bearing, thereby reducing the number of parts and simplifying the assembly process, thereby achieving the purpose of compact structure and simple assembly.

The air static pressure bearing spindle system of the present invention may also include a vacuum port and a corresponding gas flow channel, and the gas flow channel is used to connect the vacuum port and the vacuum chuck. Under the joint action of the vacuum port and the gas flow channel, the vacuum chuck can absorb the workpiece. The workpiece in this manual can be other parts that need to be clamped.

The main advantages of the present invention are: the number of parts is small, the structure is simple, and ultra-high rotation accuracy can be realized. According to the current manufacturing level of parts, the rotation accuracy can reach 0.02 μm, and it has the advantages of simple assembly and good precision retention. , can be used in various processing forms of ultra-precision machine tools, including but not limited to ultra-precision lathes, ultra-precision milling machines and ultra-precision grinding machines.

Description of drawings

Figure 1 shows a cross-sectional view of a conventional ultra-precision aerostatic bearing spindle system.

Fig. 2A shows the external view of the ultra-high-precision aerostatic bearing spindle system implementing the present invention;

Figure 2B shows a cross-sectional view of the ultra-high precision aerostatic bearing spindle system implementing the present invention;

Detailed ways

1. Figure 2A and Figure 2B show the ultra-high-precision aerostatic bearing spindle system of the present invention, which includes a rotating shaft 1, a spindle box 2 and a spindle box end cover 3, and the rotating shaft 1 is installed in the spindle box 2, Supported and rotated relative to the headstock 2 by means of an aerostatic bearing integrated in and with the headstock 2, thereby achieving the simplest configuration.

Main shaft box 2 is provided with a main cavity, the inner surface 2a of the main cavity is cylindrical and can be used for the journal bearing surface of an aerostatic bearing, the axis of the inner surface 2a of the main cavity is 12, the main cavity The inner surface 2 a faces the corresponding cylindrical outer surface 1 a of the rotating shaft 1 . Two exhaust grooves 24 and corresponding exhaust flow passages 24a may be provided on the inner surface 2a of the main bore, and the two exhaust grooves 24 divide the bearing surface of the journal into two parts, or in other words, into two journals. Bearings, the two exhaust grooves 24 are responsible for receiving the gas flowing out from the corresponding parts of the two journal bearings, and discharging the gas to the outside of the headstock 2 through the exhaust flow channel 24a. Radial restrictors 21a and 21b are arranged on the inner surface 2a of the main bore, through which high-pressure gas is supplied to the gap between the inner surface 2a of the main bore and the outer circular surface 1a of the rotating shaft to form a journal air film. The outlets of the radial restrictors 21a and 21b are evenly distributed along the circumferential direction of the inner surface 2a of the main bore, and the radial restrictors distributed on a circumferential line of the inner surface 2a of the main bore form a series, or called for a row. In the direction of the axis 12 of the inner surface 2a of the main bore, there are four rows of radial restrictors, of which two rows of radial restrictors 21a form the sum of throttling of a journal bearing, and two rows of radial restrictors 21b The throttling sum that makes up the other journal bearing.

The headstock 2 is provided with a thrust boss 28 having a flange plane 2c perpendicular to the axis 12 of the inner surface 2a of the main bore. The function of the thrust boss 28 is equivalent to the thrust washer of the conventional aerostatic shafting system, and is used to connect the headstock end cover 3 and form the air film gap of the thrust bearing. The thrust boss 28 is integrated with the headstock 2, the purpose of which is to reduce the number of components and improve precision and dimensional stability.

The spindle box 2 is provided with a thrust surface 2b, which is flat and perpendicular to the axis 12 of the inner surface 2a of the main cavity; the spindle box end cover 3 is provided with another thrust surface 3a, which is 3a is also a plane and fits with the flange plane 2c of the thrust boss 28, and the headstock end cover 3 and the headstock 2 are connected by screws 4. The thrust surface 2b faces the rotating shaft thrust disk surface 1e, and the thrust surface 3a faces the rotating shaft thrust disk surface 1d. An axial restrictor 27 is arranged on the thrust surface 2b, and the outlet of the restrictor 27 is evenly distributed on a circumferential line around the axis 12 of the inner surface 2a of the main bore, and is directed toward the thrust surface 2b and the rotating shaft. The gap between the push plate surfaces 1e is supplied with high-pressure gas to form a thrust gas film; an axial restrictor 31 is arranged on the thrust surface 3a, and the outlet of the restrictor 31 is also around the inner surface of the main cavity 2a. The axis 12 is evenly distributed on a circumferential line, and supplies high-pressure gas to the gap between the thrust surface 3a and the thrust disk surface 1d of the rotating shaft to form another thrust gas film. These two thrust air films can bear bidirectional load along the axial direction, forming a closed thrust bearing.

A radial gas flow channel 22a and an axial gas flow channel 22b are provided in the headstock 2 , and an axial gas flow channel 32a , a radial gas flow channel 32b and an axial gas flow channel 32c are provided in the headstock end cover 3 . Since both the radial restrictors and the axial restrictors are evenly distributed around the axis 12 of the inner surface 2a of the main bore, these radial gas flow channels and axial gas flow channels are also distributed around the axis 12 of the inner surface 2a of the main bore. The axes 12 are evenly distributed. For these radial gas passages, axial gas passages, radial restrictors 21a and 21b, and axial restrictors 27 and 31 located in the same axial section, gas can communicate with each other. The headstock end cover 3 is provided with a sealing cover plate 33, and the sealing cover plate 33 and the headstock end cover 3 together form an annular gas flow channel 34 around the axis 12 of the inner surface 2a of the main bore cavity. The gas flow channel 34 All the axial gas passages 32c in different axial sections communicate with each other, so all the radial gas passages and axial gas passages in different axial sections communicate with each other. An air inlet 26 is arranged in the main shaft box 2, and the air inlet 26 can be connected with any gas flow passage. Flow and axial restrictors supply air to the aerostatic bearings. The headstock 2 and the end cover 3 of the headstock are provided with seals 23 to prevent the high-pressure gas in the gas passage from leaking.

The shaft has two end faces 1b and 1c. One end surface of the rotating shaft is used to connect with a motor or other power mechanism, thereby driving the rotating shaft to rotate relative to the headstock; the other end surface of the rotating shaft is used to connect with a vacuum chuck, which absorbs workpieces on the vacuum chuck. One of the two end faces of the rotating shaft is connected to the motor and the other is connected to the vacuum chuck. For example, if the end face 1b is connected to the motor, then the end face 1c is connected to the vacuum chuck; if the end face 1c is connected to the motor, then the end face 1b is connected to the vacuum chuck.

The headstock 2 is provided with a vacuum port 29 for connecting to a vacuum pump. A vacuum annular groove 25 is provided on the inner surface 2 a of the main bore of the spindle box 2 , and the vacuum annular groove 25 is located between the two exhaust grooves 24 . A radial hole 13 and an axial hole 11 are provided on the rotating shaft 1, the radial hole 13 and the axial hole 11 communicate with each other, and the radial hole 13 is located at a position opposite to the vacuum annular groove 25, and the central hole 11 communicates with the rotating shaft 1 Attach the end faces of the vacuum cups. The vacuum port 29, the vacuum annular groove 25, the radial hole 13 and the center hole 11 on the rotating shaft 1 jointly form a connected vacuum air passage. The vacuum pump connected to the vacuum port 29 is continuously pumped away, so that the gas pressure in the channel is maintained at a certain value lower than the air pressure outside the headstock 2, so that the workpiece is adsorbed on the surface of the vacuum chuck, and the workpiece is clamped. . The central hole 11 of the rotating shaft 1 can be a through hole communicating with two end faces, or a blind hole only communicating with the end face where the vacuum chuck is installed. The length of the radial hole 13 provided on the rotating shaft 1 can be equal to the diameter of the rotating shaft, or can be equal to the radius of the rotating shaft.

Specific Embodiment 2. This embodiment is described with reference to FIG. 2B . In this embodiment, the radial restrictors 21 a provided on the inner surface 2 a of the main bore of the headstock 2 are arranged in a row along the direction of the axis 12 .

Specific Embodiment 3. This embodiment is described with reference to FIG. 2B . In this embodiment, the radial restrictors 21 b provided on the inner surface 2 a of the main bore of the headstock 2 are arranged in a row along the direction of the axis 12 .

Claims (7)

1. An ultra-high-precision aerostatic bearing spindle system, which includes a rotating shaft (1), a spindle box (2) and a headstock end cover (3), wherein the rotating shaft (1) is installed in the headstock (2), relying on The aerostatic pressure bearing supports and rotates relative to the headstock (2). The aerostatic pressure bearing is integrated in the headstock (2) and integrated with the headstock (2). It is characterized in that: the headstock (2) is equipped with a cylindrical shaped main cavity, the inner surface (2a) of the main cavity can be used as the journal bearing surface, and the inner surface (2a) of the main cavity of the headstock (2) is provided with two exhaust grooves (24), two row The air groove (24) divides the journal bearing surface into two parts, and the main shaft box (2) is provided with a thrust boss (28) used as a thrust washer, and the thrust boss (28) is connected with the main shaft box (2) Integrated design, the headstock (2) is also provided with a thrust surface (2b) perpendicular to the axis (12) of the inner surface (2a) of the main cavity, and one of the headstock end covers (3) The end plane is used as another thrust surface (3a) of the thrust bearing, and these two thrust surfaces (2b, 3a) constitute a closed type aerostatic thrust bearing. 2. The ultra-high precision aerostatic bearing spindle system according to claim 1, characterized in that a radial restrictor (21a, 21b), wherein, two rows of radial restrictors (21a) are distributed on one journal bearing surface, and the other two rows of radial restrictors (21b) are distributed on the other journal bearing surface, and the high-pressure gas passes through the radial The restrictors (21a, 21b) enter the gap between the inner surface (2a) of the main cavity and the outer circular surface (1a) of the rotating shaft to form a journal air film and can bear radial loads. 3. The ultra-high-precision aerostatic bearing spindle system according to claim 1, characterized in that, an axial throttle (27) is arranged on the thrust surface (2b) of the spindle box; 3) The thrust surface (3a) is also provided with an axial restrictor (31), and the high-pressure gas enters the gap between the two thrust surfaces and the shaft thrust plate through the axial restrictor (27, 31). The gap forms a thrust air film, which can bear axial load. 4. The ultra-high-precision aerostatic bearing spindle system according to claim 2, characterized in that, the radial restrictor is a small hole restrictor, a slit restrictor, or a porous restrictor. 5. The ultra-high-precision aerostatic bearing spindle system according to claim 1, characterized in that, an air inlet and a corresponding gas flow channel are provided in the spindle box (2), and the high-pressure gas can be delivered to each diameter Restrictor and axial restrictor; at the same time, there is an exhaust flow channel, which can discharge the gas out of the headstock. 6. The ultra-high-precision aerostatic bearing spindle system according to claim 1, characterized in that the rotating shaft (1) is provided with a radial hole (13) and a central hole (11), and the main hole of the spindle box (2) The inner surface of the chamber (2a) is provided with a vacuum annular groove (25), which is located between two exhaust grooves (24), and the headstock is provided with a vacuum port (29), and the vacuum annular groove (25 ) together with the vacuum port (29) and the radial hole (13) and central hole (11) of the rotating shaft (1) form a connected vacuum air passage. When the end face of the rotating shaft is equipped with a vacuum chuck and a workpiece, the The gas can be continuously pumped away by the vacuum pump, so that the gas pressure in the channel is maintained at a certain value lower than the air pressure outside the spindle box, so that the workpiece is adsorbed on the surface of the vacuum chuck to realize the clamping of the workpiece. 7. The ultra-high-precision aerostatic bearing spindle system according to claim 3, wherein the axial restrictor is a small-hole restrictor, a slit restrictor, or a porous restrictor.

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