JPH08326753A - Static pressure air bearing spindle - Google Patents

Abstract

PURPOSE: To materialize weight reduction and compactification by forming a plurality of restriction holes, which open at the bearing face, within one section orthogonal to the axis, and an intake passage in polygonal form, which makes that restriction holes communicate with one another in the circumferential direction, in a housing, and charging compressed air into the space between the main shaft and a bearing face through the restriction holes so as to support the main shaft without contact. CONSTITUTION: The surface of the bore of a housing 2 is made a journal bearing face 2a opposed through very small journal bearing space to the external face of the main shaft 1, and a plurality of fine restriction holes 2c and 2d are opened here, and a plurality of fine restriction holes 2e are opened at a thrust bearing face 2b, and radial intake passages 2f and 2g, which make these communicate one another, axial intake passages 2h, and further a series of intake passages 2i in the shape of a polygon, which make the restriction holes 2c communicate with one another in the circumferential direction. By the above constitution, the intake passages can be made in the housing 2 of single member by boring, so the rigidity of the bearing and the rotational accuracy of a spindle can be improved, and weight reduction becomes possible by making the housing of low-specific gravity material and thinning it.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a static pressure air bearing spindle device for supporting a main shaft by a static pressure air bearing in a non-contact manner, and can be used as a spindle device for a hole drilling machine, a precision machining machine, an electrostatic coating machine, etc. You can

[0002]

2. Description of the Related Art A hydrostatic air bearing supports a main shaft in a non-contact manner, so that it has a feature that friction loss is small and movement guiding precision is very good. Therefore, it is used as a main shaft bearing of high-speed spindles or precision spindles of hole drilling machines, precision processing machines, electrostatic coating machines and the like.

4 to 6 exemplify a conventional static pressure air bearing spindle using a static pressure air bearing. This static pressure air bearing spindle is an air turbine drive system, that is, a plurality of recesses 2 are formed on the outer periphery of the thrust plate 21a of the main shaft 21.
1a1 is provided, and a turbine nozzle 22 that opens tangentially at a position facing the recess 21a1 is provided, and compressed air supplied from the turbine air supply port 22a is sprayed tangentially from the turbine nozzle 22 to the recess 21a1 of the thrust plate 21a. In this system, the main shaft 21 is rotated.
Then, the main shaft 21 rotationally driven in this manner is supported in a non-contact manner by the bearing portion X and the bearing portion Y described below.

The bearing portion X includes a cylindrical housing 23,
A bearing sleeve 24 fixed to the inner diameter of the housing 23 by an appropriate means such as shrink fitting, press fitting or adhesion.
The inner diameter of the bearing sleeve 24 is provided with a journal bearing surface 24a that faces the outer diameter surface of the main shaft 21 with a minute journal bearing gap, and the rear end of the bearing sleeve 24 has the tip of the thrust plate 21a of the main shaft 21. A thrust bearing surface 24b facing the surface with a small thrust bearing gap is provided. Further, the bearing sleeve 24 has a plurality of fine throttle holes 24c, 24 opened in the journal bearing surface 24a.
d, and a plurality of fine aperture holes 24e opened on the thrust bearing surface 24b. Apertures 24c, 2
4d and 24e are respectively arranged in the same cross section orthogonal to the axis of the bearing sleeve 24.

The bearing portion Y has a cylindrical housing 25 which is coaxially fixed to the rear end of the housing 23 by a plurality of bolts 27 (see FIG. 4b), and the inner diameter of the housing 25 is shrink-fitted, press-fitted or adhered. The bearing sleeve 26 fixed by an appropriate means. A thrust bearing surface 26b is provided at the tip of the bearing sleeve 26 so as to face the rear end surface of the thrust plate 21a of the main shaft 21 with a minute thrust bearing gap therebetween. Further, the bearing sleeve 26 is provided with a plurality of fine throttle holes 26c which are opened in the thrust bearing surface 26b. The throttle hole 26c is arranged in a cross section orthogonal to the axis of the bearing sleeve 26.

Bearing sleeve 24 and bearing sleeve 26
The displacement of the main shaft 21 in the radial direction and the thrust direction is restricted by the compressed air flowing into the bearing gaps from the respective throttle holes (24c, 24d, 24e, 26c). The compressed air for the bearing is supplied from the air supply port 28, and the radial air supply passages 29 and 30 and the axial air supply passages 31 and 3 are provided.
2 through each throttle hole (24c, 24d, 24e, 26
circumferential air supply passages 33, 3 for communicating c) in the circumferential direction
4, 35 (see FIG. 5 and FIG. 6) and enter each aperture (2
4c, 24d, 24e, 26c) into the bearing gap. The compressed air that has flowed into the bearing gap reaches the bearing end through the bearing gap, and from there, directly or through the exhaust passages 36, 37.
Is discharged to the outside of the spindle via. At this time, due to the pressure distribution of the compressed air generated in the bearing clearance, the main shaft 21
Are journal bearing surfaces 24a, thrust bearing surfaces 24b, 2
6b is contactlessly supported.

As described above, in the conventional hydrostatic air bearing spindle, the bearing portion X and the bearing portion Y for supporting the main shaft 21 in a non-contact manner are respectively provided in the housing (23, 25).
And the bearing sleeves (24, 26) are integrated with each other. This is because when the bearing portion (X, Y) has a single cylindrical structure, each throttle hole of the bearing portion (X, Y) is formed. (24c, 24
The main reason is that the circumferential air supply passages (33, 34, 35) for communicating the (d, 24e, 26c) in the circumferential direction cannot be processed.

[0008]

By the way, in the field of the above-mentioned processing machine and the like, recently, there is a tendency to make the spindle positioning more multi-dimensional or to speed it up for the purpose of improving the processing efficiency. Therefore, reducing the weight of the spindle has become an important issue as one of the factors. For example, in electrostatic coating machines, there is an increasing demand to attach a spindle, which was conventionally mounted on a reciprocating table, to an articulated robot in order to perform more flexible and detailed painting work. Due to the above restrictions, further weight reduction of the spindle is a great advantage.

On the other hand, in this kind of spindle, the spindle shape and material are often determined by functional requirements such as load capacity of the spindle, rigidity, elongation due to thermal deformation, wear resistance, etc. The main focus is on reducing the weight of the bearing (housing, bearing sleeve).
As a means for this, the housing is formed of a material having a small specific gravity such as an aluminum alloy, a synthetic resin, or graphite (generally, the housing is often made of stainless steel and the bearing sleeve is made of a bronze alloy), or the housing. It is possible to make the bearing sleeve and bearing sleeve thinner.

However, in the conventional spindle as shown in FIGS. 4 to 6, the bearing portion has a structure in which the housing and the bearing sleeve are fitted together, and is structurally rigid as compared with a single cylindrical structure having the same thickness. Is small. Therefore, if the various means for weight reduction are applied to the conventional spindle as they are,
Due to the decrease in the rigidity of the bearing part (since the low specific gravity material as described above has a smaller elastic coefficient than stainless steel etc., and the rigidity becomes smaller when the housing is made thinner), it is caused by the imbalance of the main shaft during operation. The vibrating force vibrates the entire spindle to expand the whirling of the spindle, resulting in a problem that sufficient rotational accuracy cannot be obtained. Also, if the bearing sleeve is made thin, the inner diameter surface is deformed by the chucking force when the journal bearing surface is machined, so that the journal bearing surface is not finished in an exact circular shape and sufficient bearing accuracy cannot be obtained. The problem arises.

The present invention solves the above problems,
The object is to provide a lightweight, compact and highly accurate hydrostatic air bearing spindle.

[0012]

According to the present invention, there are provided a bearing surface facing the outer surface of the main shaft with a small bearing gap, and a plurality of throttle holes arranged in a cross section orthogonal to the axis line and opened in the bearing surface. , A series of polygonal air supply passages that allow a plurality of throttle holes arranged in the same cross section to communicate in the circumferential direction are directly formed in the housing, and compressed air is flowed into the bearing gap from the plurality of throttle holes, The main shaft is supported in a non-contact manner with the bearing surface of the housing.

The polygonal air supply passage can be constituted by a plurality of linear passage portions that are bored in a predetermined direction from the outer diameter of the housing.

The housing may be made of a low specific gravity material. The low specific gravity material may have self-lubricating property.

Further, a coating having good lubricity or wear resistance may be formed on the bearing surface of the housing.

[0016]

[Operation] A bearing surface facing the outer surface of the main shaft with a small bearing gap, a plurality of throttle holes opened in the bearing surface, and a plurality of throttle holes arranged in the same cross section are made to communicate with each other in the circumferential direction. Since the polygonal air supply passage is directly formed in the housing as the bearing, the rigidity of the bearing is improved as compared with the conventional spindle in which the bearing is integrally formed with the housing and the bearing sleeve. . As a result, not only can the rotation accuracy of the spindle be improved, but also while maintaining the rotation accuracy of the spindle, the housing as the bearing part is made of a material with a low specific gravity, or the weight is reduced to make the housing thinner. It is possible to apply various means of.

By forming a series of polygonal air supply passages for communicating a plurality of throttle holes in the circumferential direction with a plurality of linear passage portions bored in a predetermined direction from the outer diameter of the housing, the air supply passages are formed. Can be formed by making a hole in a housing made of a single member.

When contact between the main shaft and the bearing surface is expected, the housing is formed of a low specific gravity material having self-lubricating property, or a coating having good lubricity or wear resistance is formed on the bearing surface of the housing. By forming it, good durability can be obtained.

[0019]

Embodiments of the present invention will be described below with reference to FIGS.

FIG. 1 shows a longitudinal section along the axis of a hydrostatic air bearing spindle according to this embodiment. The hydrostatic air bearing spindle of this embodiment mainly includes a main shaft 1 that makes a rotary motion, and a housing 2 and a housing 3 as bearing portions that support the main shaft 1 in a non-contact manner. Housing 2 and housing 3 as bearings
Are made of a single member and do not include the bearing sleeves (24, 26) of the conventional spindle shown in FIGS. The drive system of the main shaft 1 is the same air turbine drive system as the conventional spindle shown in FIGS. That is, a plurality of recesses 1a1 are formed on the outer periphery of the thrust plate 1a of the spindle 1.
And a turbine nozzle 4 which is tangentially opened at a position facing the recess 1a1 is fixed to the inner diameter of the housing 3, and is supplied through a turbine air supply port 5 and a turbine air supply passage 6 provided in the housing 3. Air is blown tangentially from the turbine nozzle 4 to the recess 1a1 of the thrust plate 1a to rotate the main shaft 1. Then, the main shaft 1 which is rotationally driven in this manner is supported in a non-contact manner by the housing 2 and the housing 3 as bearing portions.

A journal bearing surface 2a is provided on the inner diameter of the housing 2 so as to face the outer diameter surface of the main shaft 1 with a minute journal bearing gap, and the tip end surface of the thrust plate 1a of the main shaft 1 is provided at the rear end thereof. Thrust bearing surfaces 2b facing each other with a minute thrust bearing gap provided therebetween are provided. The journal bearing surface 2a has a plurality of fine throttle holes 2c and 2d.
, And a plurality of fine throttle holes 2e are opened on the thrust bearing surface 2b. The throttle holes 2c, 2d, and 2e are arranged in the same number (six in this embodiment) in the same cross section orthogonal to the axis of the housing 2. In addition, the housing 2 has aperture holes 2c and 2c of the same vertical cross section.
Radial air supply passages 2f, 2 for communicating d, 2e with each other
g and an axial air supply passage 2h are provided, and
As shown in (transverse cross section AA in FIG. 1), a series of polygonal air supply passages 2i are provided which are generally polygonal in shape and which communicate the respective throttle holes 2c in the circumferential direction. In this embodiment, the polygonal air supply passage 2i has a substantially triangular shape, and has three straight passage portions 2i1 and 2 forming each side.
i2 and 2i3 respectively correspond to the two diaphragm holes 2c, and as a whole, six (all) diaphragm holes 2c are communicated in the circumferential direction. The polygonal air supply passage 2i communicates with an axial air supply passage 2j opened at the rear end of the housing 2.

Each of the radial air supply passages 2f and 2g and the polygonal air supply passage 2i is controlled by feeding a machining tool (a drill or the like) from the outer diameter of the housing 2 to a predetermined position in a respective direction to form a hole. It can be formed by performing processing. Similarly, the axial air supply passages 2h and 2j are
It can be formed by making a hole from the end face of the housing 2 in the axial direction to a predetermined position. In this way, each air supply passage is bored in the housing 2 made of a single member, and if necessary, an opening on the outer diameter side or the end face side is formed by a sealing means 7 such as a plug or a resin mold. It is formed by closing.

At the tip of the housing 3, there is a thrust plate 1a.
A thrust bearing surface 3b is provided which faces the rear end surface with a small thrust bearing gap therebetween. Thrust bearing surface 3
A plurality of fine aperture holes 3c are opened in b. The throttle hole 3c is arranged in a cross section orthogonal to the axis of the housing 3. Further, the housing 3 has an air supply port 3d connected to a compressed air source (not shown) and an axial air supply passage 3e communicating with the axial air supply passage 2j of the housing 2.
And a cross section B- in FIG.
As shown in B), a series of polygonal air supply passages 3 each having a substantially polygonal shape as a whole and connecting the throttle holes 3c in the circumferential direction.
f is provided. In this embodiment, the polygonal air supply passage 3f has a substantially triangular shape, and the three linear passage portions 3f1, 3f2, 3f3 forming each side are respectively
Corresponding to the two diaphragm holes 3c, as a whole, six (all) diaphragm holes 3c are communicated in the circumferential direction. The polygonal air supply passage 3f is connected to the air supply port 3 through the axial air supply passage 3g.
It communicates with d.

The polygonal air supply passage 3f can be formed by carrying out a hole control by feeding a machining tool from the outer diameter of the housing 3 to a predetermined position in the direction of each passage portion 3f1, 3f2, 3f3. . Similarly, the axial air supply passages 3e, 3g can be formed by drilling holes from the end surface of the housing 3 in the axial direction to predetermined positions. In this way, each air supply passage is formed by making a hole in the housing 3 made of a single member, and if necessary, closing the outer diameter side opening with a sealing means 8 such as a plug or a resin mold. Is formed by.

Housing 2 and housing 3 as described above
After assembling the main shaft 1 and the turbine nozzle 4, the end faces of the main shaft 1 and the turbine nozzle 4 are aligned and fixed coaxially by a fixing means such as a bolt.

When compressed air is supplied from the air supply port 3d of the housing 3, the compressed air flows into the journal bearing gap and the thrust bearing gap through the respective air supply passages and throttle holes described above, and directly from the bearing end or the exhaust passage. It is discharged to the outside of the spindle via 9 and 10. At this time, the main shaft 1 is supported in non-contact with the journal bearing surface 2a and the thrust bearing surfaces 2b and 3b by the pressure component of the compressed air generated in the bearing gap.

As described above, in the hydrostatic air bearing spindle of this embodiment, the throttle holes (2c, 2d, 2e, 3c) opened in the bearing surfaces (2a, 2b, 3b) are provided in the polygonal air supply passage (2i). 3f) has a structure in which they are communicated in the circumferential direction, all the air supply passages can be formed by making holes in the housings (2, 3) made of a single member. Therefore, unlike the conventional spindle, it is not necessary to make the bearing part have the fitting integral structure of the housing and the bearing sleeve (as described above, the conventional spindle has the fitting integral structure of the housing and the bearing sleeve. This is because it is necessary to form a circumferential groove that allows the throttle holes to communicate with each other in the circumferential direction.), And the housing can be configured only with the housing (2, 3) made of a single member. The rigidity of the bearing portion can be improved as compared with. Then, the bearing portion (housing 2,
As a result of the improved rigidity of 3), not only the rotation accuracy of the spindle is improved, but also the housing (2, 3) is formed of a low specific gravity material while maintaining the rotation accuracy of the spindle.
Alternatively, it is possible to provide various means for reducing the weight, such as reducing the thickness.

When the housings (2, 3) are made of a low specific gravity material to reduce the weight, aluminum alloy, synthetic resin, graphite or the like may be used as the low specific gravity material. Among them, considering the durability when the main shaft 1 and the bearing surfaces (2a, 2b, 3b) are in contact with each other due to overload, it is preferable to use a synthetic resin having self-lubricating property, graphite or the like. As the synthetic resin having self-lubricating property, for example, fluorine resin, polyamide resin, polyimide resin, ketone resin such as polyether ether ketone, polyphenylene sulfide resin, etc. can be used. Alternatively, on the bearing surfaces (2a, 2b, 3b) of the housings (2, 3), a solid lubricant such as fluororesin, molybdenum disulfide, or hexagonal boron nitride, and further wear resistance such as Si, SiC, or TiC. A film containing a substance having good properties may be formed by a method such as resin coating, dispersion plating, or vapor deposition.

The present invention is not limited to the static pressure bearing spindle of the air turbine drive type, but can be similarly applied to the static pressure bearing spindle of the drive type driven by an electric motor such as an induction motor or various servo motors. Produce the effect of.

[0030]

According to the present invention, a bearing surface facing the outer surface of the main shaft with a small bearing gap, a plurality of throttle holes opened in the bearing surface, and a plurality of throttle holes arranged in the same cross section are circular. Since a series of polygonal air supply passages that communicate with each other in the circumferential direction are directly formed in the housing as a bearing, the bearing has a structure in which the bearing is integrated with the housing and the bearing sleeve. The rigidity of is improved. As a result, not only can the rotation accuracy of the spindle be improved, but while maintaining the rotation accuracy of the spindle,
The housing as the bearing part is made of low specific gravity material,
Alternatively, it is possible to provide various means for reducing the weight, such as reducing the thickness. This makes it possible to provide a lightweight, compact, highly accurate hydrostatic air bearing spindle. Further, since the housing as the bearing portion can be formed of a single member, the number of parts can be reduced, the machining process can be simplified, and the cost can be reduced as compared with the conventional case.

By constructing a series of polygonal air supply passages for communicating a plurality of throttle holes in the circumferential direction with a plurality of linear passage portions bored in a predetermined direction from the outer diameter of the housing, the air supply passages are formed. Can be formed by making a hole in a housing made of a single member.

The housing is made of a low specific gravity material having self-lubricating property, or a coating having good lubricity or wear resistance is formed on the bearing surface of the housing so that the main shaft and the bearing surface are prevented from overloading. Good durability can be obtained even under a use condition in which contact with is expected.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing a spindle according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view taken along the line AA in FIG.

3 is a cross-sectional view taken along the line BB in FIG.

FIG. 4 is a vertical cross-sectional view showing a conventional spindle (FIGS. A and b show different vertical cross-sections).

5 is a cross-sectional view taken along the line AA in FIG.

6 is a horizontal cross-sectional view taken along the line BB in FIG.

[Explanation of symbols]

 1 spindle 2 housing 2a journal bearing surface 2a thrust bearing surface 2c throttle hole 2d throttle hole 2e throttle hole 2i polygon air supply passage 3 housing 3b thrust bearing surface 3c throttle hole 3f polygon air supply passage

Claims (5)

[Claims] 1. A bearing surface facing the outer surface of the main shaft with a small bearing gap, a plurality of throttle holes arranged in a cross section orthogonal to the axis and opening in the bearing surface, and arranged in the same cross section. And a series of polygonal air supply passages that allow the plurality of throttle holes to communicate with each other in the circumferential direction are directly formed in the housing,
A hydrostatic air bearing spindle, wherein compressed air is caused to flow into a bearing gap from the plurality of throttle holes to support the main shaft in a non-contact manner with respect to a bearing surface of a housing. 2. The hydrostatic air bearing spindle according to claim 1, wherein the polygonal air supply passage is composed of a plurality of linear passage portions that are bored in a predetermined direction from the outer diameter of the housing. 3. The hydrostatic air bearing spindle according to claim 1, wherein the housing is made of a low specific gravity material. 4. The hydrostatic air bearing spindle according to claim 3, wherein the low specific gravity material is a self-lubricating material. 5. The hydrostatic air bearing spindle according to claim 1, wherein a coating having good lubricity or wear resistance is formed on the bearing surface of said housing.