JP4529129B2 - Hydrostatic air bearing spindle - Google Patents

Description

  The present invention relates to a hydrostatic air bearing spindle that is suitable for, for example, a high-precision rotary spindle such as a precision processing machine and supports a main shaft in a non-contact state by supplying compressed air to a bearing gap between the main shaft and the bearing.

  Conventionally, a hydrostatic air bearing spindle configured to support a main shaft in a non-contact manner by supplying compressed air from an air supply nozzle to a minute bearing gap provided between the main shaft and the bearing is as shown in FIG. . FIG. 7 is a side sectional view of a hydrostatic air bearing spindle showing the prior art.

  In FIG. 7, 1 is a housing, 2 is a main shaft, 2a is a thrust disk, 3 and 4 are hydrostatic air journal bearings provided on the anti-load side and load side, and 5 and 6 are provided on the anti-load side and load side, respectively. Static pressure air thrust bearing, 7 spacer, 8 compressed air supply path, 9 motor, 9a motor rotor, 9b motor stator, 10 sleeve, 11, 12 supply nozzle, 13 exhaust passage, 15 exhaust Clearances 16, 17 and 18 are exhaust paths, 19 is a magnetic gap between the motor rotor 9a and the motor stator 9b, 20 is a back plate, and 20a is an exhaust hole. The housing 1, the hydrostatic air thrust bearings 5 and 6, and the communication portion of the spacer 7 which are parts constituting the compressed air supply passage 8 and the exhaust passage 13 are sealed using an O-ring (not shown).

  The hydrostatic air bearing spindle basically includes a main shaft 2 housed in a cylindrical housing 1 having a hollow cross section, two hydrostatic air journal bearings 3 and 4 that support the radial direction of the main shaft 2, and a main shaft. 2 are opposed to both sides of the spacer 7 formed in the radial direction of the thrust disk 2a provided on the load side, and are opposed to the double-sided hydrostatic thrust bearings 5 and 6 that support the thrust direction of the main shaft 2. It is configured. The static pressure air journal bearings 3 and 4 are provided with an air supply nozzle 11 communicating with a compressed air supply path 8 provided in the housing 1, and the compressed air thrust bearings 5 and 6 are similarly provided with a compressed air supply path 8. An air supply nozzle 12 communicating with the air supply nozzle 12 is provided. A motor rotor 9a is integrally attached to the opposite end of the main shaft 2 by bonding or the like. Further, a motor stator 9b is disposed opposite to the motor rotor 9a via a magnetic gap 19. The motor stator 9b is integrally attached to the inner peripheral side of the sleeve 10 fitted to the housing 1 by bonding or the like, and the motor 9 serving as a driving source of the main shaft is constituted by both the motor rotor 9a and the motor stator 9b. To do.

Next, the operation will be described.
In the hydrostatic air bearing spindle, when compressed air is supplied to the compressed air supply passage 8, the compressed air passes through the air supply nozzles 11 and 12, and the bearing clearance between the main shaft bearing portion 2b and the hydrostatic air journal bearings 3 and 4 is increased. The main shaft 2 is supported in a non-contact manner in the radial direction and the thrust direction by flowing into the bearing gaps between the thrust disk 2a and the hydrostatic air thrust bearings 5 and 6 to form gas films. Thus, the main shaft 2 is directly driven by the motor 9 while being supported in a non-contact manner by the hydrostatic air bearing.

  On the other hand, the flow of compressed air exhausted with respect to the compressed air supplied to the bearing portion is as follows. That is, part of the air supplied to the load-side static pressure air thrust bearing 6 is exhausted from the load-side exhaust gap 15 to the outside of the housing 1. Further, a part of the air supplied to the anti-load side static pressure air thrust bearing 5 passes through the exhaust passage 16, passes through the exhaust passage 13, flows into the exhaust passage 18, and is also loaded on the load side static pressure air journal bearing. Part of the air supplied to 4 flows into the exhaust path 18 through the exhaust path 17 and the exhaust path 13. Furthermore, a part of the air supplied to the anti-load side hydrostatic air journal bearing 3 flows directly into the exhaust path 18. Thus, when the air flowing into the exhaust path 18 passes through the magnetic gap portion 19, the heat generated in the motor stator 9b is cooled by heat transfer accompanied by forced convection, and is then transferred to the outside of the housing 1 through the exhaust hole 20a. Dissipates heat.

  Here, the heat generated in the motor stator 9b has the following two paths in addition to the path taken by the air passing through the magnetic gap portion 19 described above. That is, the heat generated in the motor stator 9b is conducted to the housing 1 through the sleeve 10 and is radiated from the outer surface of the housing 1 to the air, and the heat generated in the motor stator 9b passes through the magnetic gap portion 19. The radiant heat is transmitted to the main shaft 2 through the main shaft 2 and spreads throughout the main shaft 2, and then is radiated directly from the shaft end surface of the main shaft 2 to the air, or is transmitted to the bearing through the bearing gap, and then passes through the housing 1 There is a path for heat radiation from the outer surface of the housing 1 to the air.

Next, the assembly procedure will be described.
First, the anti-load side hydrostatic air journal bearing 3 is inserted from the anti-load side of the housing 1, and the load-side hydrostatic air journal bearing 4 is inserted from the load side. Then, the anti-load side static pressure air thrust bearing 5 is attached to the housing 1, and the main shaft 2 in which the motor rotor 9 a is integrated is inserted into the static pressure air journal bearings 3 and 4 from the load side. Further, after the spacer 7 and the load side static pressure air thrust bearing 6 are attached to the load side of the housing 1, the sleeve 10 in which the motor stator 9 b is integrated is inserted into the opposite side of the housing 1. Finally, the back plate 20 is attached. If a problem such as contact between the main shaft 2 and the hydrostatic air journal bearings 3 and 4 occurs, the hydrostatic air journal bearings 3 and 4 must be removed from the housing 1 for repair. Therefore, when removing the hydrostatic air journal bearings 3 and 4, especially when removing the anti-load side hydrostatic air journal bearing 3, it is necessary that the sleeve 10 can be easily removed from the housing 1. The attachment to the gap is a clearance fit (see, for example, Patent Document 1).
Japanese Patent Laying-Open No. 2001-304259 (Specification, page 4, FIG. 1)

  In the conventional hydrostatic air bearing spindle, since the sleeve 10 is attached to the housing 1 with clearance gaps, there is a fitting gap between both parts, the thermal resistance from the sleeve 10 to the housing 1 increases, and the contact heat transfer coefficient. Becomes smaller. Therefore, the amount of heat transmitted to the sleeve 10 among the heat generated in the motor stator 9b is reduced. Here, if the amount of heat taken away by the air passing through the magnetic gap 19 is constant, the amount of heat transferred to the main shaft 2 increases, and the temperature rise of the main shaft 2 increases. As a result, when the main shaft 2 is thermally expanded and a tool or a workpiece is attached to the main shaft 2 to perform processing or the like, elongation occurs in the axial direction, resulting in a problem that processing accuracy is lowered.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a hydrostatic air bearing spindle that reduces the amount of heat transmitted to the main shaft and reduces the axial extension of the main shaft.

  In order to solve the above problem, the present invention is configured as follows.

The invention according to claim 1 is a cylindrical housing having an air supply passage and an exhaust passage for compressed air, a main shaft housed in the housing, a hydrostatic air journal bearing that supports a radial direction of the main shaft, A hydrostatic air thrust bearing that supports the thrust direction of the main shaft, a motor rotor attached to the opposite end of the main shaft, a motor rotor and a magnetic gap that are disposed opposite to each other, and an inner peripheral side of the housing A hydrostatic air bearing spindle provided with a motor stator attached to a sleeve on the outer diameter side of the end portion on the load side of the sleeve, provided with a stepped portion cut out in a substantially ring shape, Yes forming an air passage communicating with the exhaust passage of the housing in a space surrounded between the stepped portion of the sleeve and the housing, the housing of the sleeve Of the opposing side, the through air passage and the communication is characterized by comprising at least one groove passing through in the axial direction.

  According to a second aspect of the present invention, in the hydrostatic air bearing spindle according to the first aspect, the stepped portion is provided with at least one air hole communicating from the air passage side toward the main shaft side. It is characterized by being.

According to a third aspect of the present invention, in the hydrostatic air bearing spindle according to the first aspect, a plurality of the concave grooves are provided at equal intervals in the circumferential direction.
It is.

  According to a fourth aspect of the present invention, in the hydrostatic air bearing spindle of the second aspect, a plurality of the air holes are provided at equal intervals in the circumferential direction.

  According to a fifth aspect of the present invention, in the hydrostatic air bearing spindle according to the second or fourth aspect, the air holes are arranged at different angular positions along the circumferential direction with respect to the concave groove. It is characterized by that.

  According to a sixth aspect of the present invention, in the hydrostatic air bearing spindle of the first aspect, a thermal conductive grease is filled between the sleeve and the housing.

  According to the first aspect of the present invention, since the air that has passed through the exhaust passage is blocked by the stepped portion of the sleeve, the air passage extends in the circumferential direction and passes through the groove of the sleeve, so that the outer periphery of the sleeve Cool down. For this reason, the heat transmitted from the motor stator to the sleeve is also deprived by the air passing through the concave groove in addition to being transmitted to the housing, and the amount of heat transmitted from the motor stator to the sleeve is larger than in the conventional case. . As a result, since the amount of heat transferred from the motor stator to the main shaft is reduced, it is possible to provide a hydrostatic air bearing spindle in which the temperature rise of the main shaft is suppressed and the main shaft is less elongated in the axial direction.

  According to the second aspect of the present invention, the heat transmitted from the motor stator to the sleeve is transmitted to the housing or taken away by the air passing through the concave groove, and also by the air passing through the air hole of the stepped portion. The amount of heat transferred from the motor stator to the sleeve is further increased than in the case of the invention described in claim 1. As a result, since the amount of heat transferred from the motor stator to the main shaft is further reduced, the temperature rise of the main shaft can be suppressed, and the hydrostatic air bearing spindle in which the main shaft is less stretched in the axial direction than in the case of the invention of claim 1. Can be provided.

  According to the third aspect of the present invention, since air passes through the sleeve at equal intervals, the outer periphery of the sleeve is uniformly and uniformly cooled. For this reason, the heat transmitted from the motor stator to the sleeve can be efficiently taken, and the amount of heat transmitted from the motor stator to the sleeve becomes larger than when the concave grooves are provided unevenly. As a result, since the amount of heat transferred from the motor stator to the main shaft is reduced, it is possible to provide a hydrostatic air bearing spindle in which the temperature rise of the main shaft is suppressed and the main shaft is less elongated in the axial direction.

  According to the fourth aspect of the present invention, since air passes through the air holes at equal intervals, the stepped portion of the sleeve is uniformly and uniformly cooled. For this reason, the heat transmitted from the motor stator to the stepped portion of the sleeve can be efficiently taken, and the amount of heat transmitted from the motor stator to the sleeve becomes larger than when the air holes are provided unevenly. As a result, since the amount of heat transferred from the motor stator to the main shaft is reduced, it is possible to provide a hydrostatic air bearing spindle in which the temperature rise of the main shaft is suppressed and the main shaft is less elongated in the axial direction.

  According to the fifth aspect of the present invention, air surely flows into both the concave groove and the air hole, and the heat transmitted from the motor stator to the stepped portion of the sleeve can be efficiently and reliably taken away.

  According to the sixth aspect of the present invention, contact heat transfer between the sleeve and the housing can be improved, and heat can be efficiently radiated to the outside of the housing.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, the same code | symbol is attached | subjected about the same component of this invention as a prior art, the description is abbreviate | omitted, and only a different point is demonstrated.

  1 is a side sectional view of a hydrostatic air bearing spindle according to a first embodiment of the present invention, FIG. 2 is a front sectional view taken along line AA of FIG. 1, and FIG. It is a figure explaining the sleeve to be used, Comprising: (a) is the side view, (b) is the front view seen from the arrow B of (a).

  In the figure, 10a is a stepped portion, 10b is a concave groove, and 10c is a protruding portion.

  The present invention is different from the prior art as follows.

  That is, in the hydrostatic air bearing spindle, as shown in FIG. 1, a part of the end of the sleeve 10 on the load side is connected adjacent to the end of the hydrostatic air journal bearing 3 on the non-load side. A stepped portion 10a having an outer diameter side cut out in a substantially ring shape so as to form an air passage 14 communicating with the exhaust passage 13 between the sleeve 10 and the housing 1; Is provided with at least one concave groove 10b communicating with the air passage and penetrating in the axial direction. In addition, the sleeve 10 has the outer peripheral portion of the protrusion 10c excluding the concave groove 10b attached to the housing 1 by a gap fit, and between them, a heat conducting grease is provided for the purpose of improving contact heat transfer. Filled.

  Here, as shown in FIGS. 2 and 3, the groove 10b and the exhaust passage 13 are equally spaced at the same angle around the central axis so that air passing through the exhaust passage 13 can easily flow into the groove 10b. It is desirable to arrange a plurality. Further, the sleeve 10 is made of a material having a high thermal conductivity such as an aluminum material A2017 in order to increase the heat transfer coefficient.

Next, the operation will be described.
The path of the air exhausted from each hydrostatic air bearing includes the path exhausted to the outside of the housing 1 from the exhaust gap 15 on the load side, and the housing 1 via the exhaust path 18 via the magnetic gap 19 and the exhaust hole 20a. In addition to the path exhausted to the outside, there is a path that flows into the exhaust passage 13 via the exhaust path 16 or the exhaust path 17. Among them, the air flowing into the exhaust passage 13 flows into the air passage 14 formed by the anti-load side surface of the anti-load side hydrostatic air journal bearing 3, the load side surface of the sleeve 10, and the stepped portion 10 a of the sleeve 10. Then, since it is blocked by the stepped portion 10 a, it spreads in the circumferential direction along the air passage 14. Thereafter, the air flows from the load side to the anti-load side along one or a plurality of concave grooves 10b provided on the circumference of the outer periphery of the sleeve 10, and is exhausted from the exhaust hole 20a to the outside of the housing 1. At that time, the outer periphery of the sleeve 10 is cooled by the air passing through the concave groove 10b. Here, the path of the heat generated in the motor stator 9 b is transmitted to the sleeve 10, transmitted to the main shaft 2 via the magnetic gap 19, or taken away by the air passing through the magnetic gap 19. There are three ways. Of these, the heat transferred to the sleeve 10 is also transferred to the housing 1 and also taken away by the air accompanying the forced convection passing through the concave groove 10 b, and is taken away by the air passing through the magnetic gap 19. When the amount of heat is constant, the amount of heat transferred from the motor stator 9b to the sleeve 10 is greater than when there is no conventional groove 10b.

  Thus, by making the sleeve 10 into a stepped shape in the first embodiment, the heat transfer coefficient of the sleeve 10 can be increased, so that the amount of heat transferred to the main shaft 2 can be reduced. As a result, the temperature rise of the main shaft 2 can be suppressed, and the elongation of the main shaft 2 in the axial direction can be reduced.

  4 is a sectional side view of a hydrostatic air bearing spindle according to a second embodiment of the present invention, FIG. 5 is a front sectional view taken along line CC of FIG. 4, and FIG. 6 is a perspective view of the hydrostatic air bearing spindle in FIG. It is a figure explaining the sleeve to be used, Comprising: (a) is the side view, (b) is the front sectional view seen from the arrow D of (a). Note that the description of the components of the second embodiment that are the same as those of the first embodiment will be omitted, and different points will be described.

  In FIG. 4, 10d is an air hole. The communicating parts of the parts constituting the compressed air supply path 8 and the exhaust path 13 are sealed with an O-ring (not shown) as in the first embodiment.

  As shown in FIGS. 4 to 6, the second embodiment is different from the first embodiment in that it communicates with the stepped portion 10 a of the sleeve 10 so that air flows from the air passage 14 side toward the main shaft 2 side. The air hole 10d is provided.

  Here, as shown in FIG. 5, it is desirable that a plurality of the concave grooves 10b and the air holes 10d be arranged at different angles around the central axis at equal intervals along the circumferential direction. That is, when the concave groove 10b and the air hole 10d are arranged at the same angle around the central axis, for example, most of the air flows into the concave groove 10b and almost no air flows into the air hole 10d. This is to ensure that air flows to both the concave groove 10b and the air hole 10d.

  Next, the operation will be described.

  Of the air exhausted from each static pressure air bearing, the air that spreads in the circumferential direction along the air passage 14 via the exhaust passage 13 is divided into two paths. The first path is a path that passes through the concave groove 10b described in the first conventional example. In the second path, one or more airs are provided on the circumference of the sleeve stepped portion 10a. The air passes through the air hole 10 d and is exhausted from the exhaust hole 20 a to the outside of the housing 1 through the exhaust path 18 and the motor gap 19. At that time, the heat transmitted to the stepped portion 10a is taken away by the air passing through the air hole 10d. That is, the heat transmitted from the motor stator 9b to the sleeve 10 is transmitted to the housing 1 or is taken away by the air accompanying the forced convection passing through the concave groove described in the first embodiment, and the air hole of the stepped portion. When the amount of heat taken away by the air passing through the magnetic gap 19 is constant, the amount of heat transferred from the motor stator 9b to the sleeve 10 is further increased than in the first embodiment. Become more.

  As described above, in the second embodiment, the sleeve 10 has a stepped shape and the air hole is provided, so that the heat transfer coefficient of the sleeve 10 can be made larger than that in the first embodiment. The amount of heat transferred to 2 can be further reduced. As a result, the temperature rise of the main shaft 2 can be suppressed, and the elongation of the main shaft 2 in the axial direction can be reduced.

  Since the axial extension of the spindle of the hydrostatic air bearing spindle is reduced, it can be applied to an apparatus such as a precision processing machine that needs to minimize the displacement of the spindle during operation.

1 is a side sectional view of a hydrostatic air bearing spindle showing a first embodiment of the present invention. Front sectional view along line AA in FIG. It is a figure explaining the sleeve used for the static pressure air bearing spindle in FIG. 1, Comprising: (a) is the side view, (b) is the front view seen from the arrow B of (a). Side sectional view of a hydrostatic air bearing spindle showing a second embodiment of the present invention. Front sectional view taken along line CC in FIG. It is a figure explaining the sleeve used for the static pressure air bearing spindle in FIG. 4, Comprising: (a) is the side view, (b) is the front sectional view seen from the arrow D of (a). Side view of a conventional hydrostatic air bearing spindle

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Housing 2 Main shaft 2a Thrust disk 2b Main shaft bearing part 3 Hydrostatic air journal bearing (anti-load side)
4 Hydrostatic journal bearing (load side)
5 Hydrostatic air thrust bearing (anti-load side)
6 Hydrostatic thrust bearing (load side)
7 Spacer 8 Compressed air supply passage 9 Motor 9a Motor rotor 9b Motor stator 10 Sleeve 10a Stepped portion 10b Recessed groove 10c Projection portion 10d Air holes 11, 12 Air supply nozzle 13 Exhaust passage 14 Air passage 15 Exhaust gaps 16, 17, 18 Exhaust path 19 Magnetic gap 20 Back plate
20a Exhaust hole

Claims (6)

A cylindrical housing having a compressed air supply passage and an exhaust passage;
A main shaft housed in the housing;
A hydrostatic air journal bearing that supports a radial direction of the main shaft;
A hydrostatic air thrust bearing that supports a thrust direction of the main shaft;
A motor rotor attached to the opposite end of the main shaft;
A motor stator that is disposed opposite to the motor rotor via a magnetic gap, and is attached to the inner peripheral side of the housing via a sleeve;
In a hydrostatic air bearing spindle with
A stepped portion notched in a substantially ring shape is provided on the outer diameter side of the end portion on the load side of the sleeve, and the exhaust of the housing is formed in a space surrounded by the stepped portion of the sleeve and the housing. An air passage communicating with the passage is formed,
A hydrostatic air bearing spindle characterized in that at least one concave groove communicating with the air passage and penetrating in the axial direction is provided on the surface of the sleeve facing the housing.   The hydrostatic air bearing spindle according to claim 1, wherein the stepped portion is provided with at least one air hole communicating from the air passage side toward the main shaft side.   The hydrostatic air bearing spindle according to claim 1, wherein a plurality of the concave grooves are provided at equal intervals in the circumferential direction.   3. The hydrostatic air bearing spindle according to claim 2, wherein a plurality of the air holes are provided at equal intervals in the circumferential direction.   5. The hydrostatic air bearing spindle according to claim 2, wherein the air holes are arranged at different angular positions along a circumferential direction with respect to the concave groove. 6.   2. The hydrostatic air bearing spindle according to claim 1, wherein thermal grease is filled between the sleeve and the housing.

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