JP3089271B2 - Hydrostatic gas bearing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[Industrial applications]

The hydrostatic gas bearing to which the present invention is applied is used for supporting a rotating part of a precision machine tool or the like. In particular, the present invention
The rigidity of such a static pressure gas bearing is improved.

[0002]

[Prior art]

2. Description of the Related Art Static pressure gas bearings that support a rotating member such as a rotating shaft that rotates at a high speed and that is incorporated in a precision machine tool or the like by the force of a compressed gas such as air have been widely used. FIG. 10-
11 is an example of such a static pressure gas bearing,
1 shows a hydrostatic gas bearing utilizing the structure described in Japanese Patent No. 37683.

As shown in FIG. 10, a rotating shaft 3 is inserted inside a bearing member 1 having an inner peripheral surface having a cylindrical bearing surface 2.
A recess is provided at each of four positions of the bearing surface 2 in the upper, lower, left and right directions
4a, 4b, 5a, 5b are formed, and these concave portions 4a, 4b, 5a, 5b are formed.
The rotating shaft 3 is supported inside the bearing member 1 in a non-contact state by sending compressed gas into the bearing member 1.

Of the four recesses 4 a, 4 b, 5 a, 5 b, two recesses 4 a, 4 b at upper and lower positions are provided via a first control throttle valve 6 to the left and right sides.
The recesses 5a, 5b at the position are provided via the second control throttle valve 7,
Each is connected to a compressed gas supply source such as a compressor. These first and second control throttle valves 6 and 7 are provided with upper and lower concave portions so that the bearing surface 2 and the outer peripheral surface of the rotary shaft 3 are concentric.
It is for adjusting the amount and pressure of the compressed gas sent to the recesses 4a, 4b or the left and right recesses 5a, 5b, and is configured, for example, as shown in FIG.

That is, a first port 9 provided at the center of one surface of a housing 8 constituting a first (second) control throttle valve 6 (7) and a recess
4a (5a) is formed by the first supply pipe 10, and the second port 11 and the recess 4b (5b) provided in the center of the other surface are formed by the second supply pipe 12.
Each is in communication. A diaphragm 15 is provided at an intermediate portion of the housing 8, and the inside of the housing 8 is divided into a first chamber 13 on the first port 9 side and a second chamber 14 on the second port 11 side. A compressed gas is supplied to the first and second chambers 13 and 14 from a compressed gas supply source. The positions surrounding the openings of the first and second ports 9 and 11 on the inner surface of the housing 8 are respectively protruded inward over the entire circumference. The first and second throttle passages 16 and 17 are formed between the second ports 9 and 11 and the first and second chambers 13 and 14, respectively.

With the above-described configuration, based on the displacement of the rotating shaft 3,
When the outer peripheral surface of the rotating shaft 3 and the bearing surface 2 are not concentric, the amount of compressed air sent into the recesses 4a, 4b, 5a, 5b by the action of the first and second control throttle valves 6, 7 And the pressure are appropriately adjusted, so that the outer peripheral surface of the rotating shaft 3 and the bearing surface 2 are concentric.

For example, when the rotating shaft 3 is displaced downward in FIG. 11, the size of the bearing gap 18 between the outer peripheral surface of the rotating shaft 3 and the bearing surface 2 is small on the lower side and larger on the upper side. . Along with this dimensional change, the pressure in the lower recess 4b (5b) increases, the pressure in the upper recess 4a (5a) decreases, and the second supply pipe 12 communicates with the recess 4b (5b). The pressure in the two ports 11 increases, and the pressure in the first port 9 communicated with the recess 4a (5a) by the first supply pipe 10 decreases.

As a result, the diaphragm 15 that partitions the first and second ports 9 and 11 is displaced upward, the second throttle channel 17 is widened, the first throttle channel 16 is narrowed, and the lower concave portion is formed. The amount and pressure of the compressed gas sent into 4b (5b) increases, and the upper concave portion 4a
The amount and pressure of the compressed gas sent into (5a) decreases, and the rotating shaft 3 is pushed upward in FIG. 1 ', so that the displacement of the rotating shaft 3 is eliminated.

[0009]

[Problems to be solved by the invention]

However, the conventional hydrostatic gas bearing configured and operated as described above has the following problems. That is, in the case of the conventional structure, since the concave portions 4a, 4b, 5a, 5b for supplying the compressed gas to the bearing gap 18 were large concave portions, the compressed gas sent to these concave portions 4a, 4b, 5a, 5b was used. As a result, self-excited vibration is likely to occur, and if it occurs, the operation of a machine mechanism or the like incorporating the hydrostatic gas bearing cannot be stably performed. In particular, as shown in FIGS. 10 and 11, the first and second control throttle valves 6 and 7 communicate with the respective recesses 4 a, 4 b, 5 a and 5 b.
When the first and second supply pipes 10 and 12 are long, the response of the flow control is deteriorated, and the self-excited vibration as described above is easily generated. Further, in the case of the conventional hydrostatic gas bearing, since the bearing surface 2 is made of hardened steel, even if a small amount of dust is clogged in the bearing gap 18, it is impossible to repair the seizure of the rotating shaft 3 and the like. Trouble was easy to occur. The hydrostatic gas bearing of the present invention solves any of the above problems.

[0010]

[Means for solving the problem]

An aerostatic gas bearing according to the present invention includes a housing, a rotating member opposed to a bearing surface provided in the housing via a bearing gap, and a distribution flow path formed on the bearing surface so as to face each other and independent of each other. A plurality of independent sets of slit grooves, which are provided through the downstream end of each other, and provided between each of these distribution channels and an air supply passage leading to a compressed gas supply source,
Based on the elastic displacement of a leaf spring arranged in a state of partitioning a pair of air chambers communicating with the upstream end of each of the distribution channels, the supply amount of compressed gas to the slit grooves of each of the sets is determined by one of the slits. A control throttle valve for adjusting the supply amount of the compressed gas to the other slit groove in a state of decreasing the supply amount of the compressed gas to the other slit groove as the supply amount of the compressed gas to the groove increases. The bearing surface is made of an aluminum-based or copper-based soft alloy containing at least one of carbon fiber and graphite.

[0011]

[Action]

In the case of the hydrostatic gas bearing of the present invention configured as described above, the compressed gas for supporting the rotating member is sent into the bearing gap through the control throttle valve and the slit groove, and the rotating member is moved relative to the housing. Support in a non-contact state. In the case of the hydrostatic gas bearing of the present invention, the dynamic stiffness characteristics are improved by forming the blowout portion of the compressed gas as slit grooves, and the static stiffness characteristics are improved by providing the control throttle valve. The rigidity characteristics can be sufficiently increased at a practically satisfactory level. In addition, the volume of the slit groove is smaller than that of the concave part in the conventional structure, and the large damping surface prevents self-excited vibration, and stabilizes the operation of equipment incorporating a static pressure gas bearing. It can be done in the state. In addition, the response to the change in the flow rate of the compressed gas that supports the rotating member is improved by providing the control throttle valve for the static pressure gas bearing using the conventional differential pressure principle (without the control throttle valve). I do. By improving the static stiffness characteristics based on the improvement of the response, the bearing clearance can be set wider, and the processing industry of each component of the bearing can be facilitated. Furthermore, since the bearing surface is made of an aluminum-based or copper-based soft alloy containing at least one of carbon fiber and graphite, even if the bearing gap is clogged with dust, unrecoverable failure such as seizure occurs. Is difficult to connect to.

[0012]

【Example】

1 to 3 show a first embodiment of the present invention. FIG.
As shown in the figure, the outer cylinder is
21 is externally fitted and fixed. A cylindrical rotary member 22 is inserted inside the inner cylinder 20, and inner surfaces of flange pieces 23a and 23b fixed to both ends of the rotary member 22, the inner cylinder 20 and the outer cylinder, respectively. Bearing member 24 fixed to end face with 21
The bearing surfaces 25a and 25b of a and 24b face each other. The housing 19 is constituted by the inner cylinder 20, the outer cylinder 21, and the bearing members 24a and 24b.

Each of the bearing members 24 a, 24 b fixed to the end surfaces of these two members 20, 21 so as to be sandwiched between the inner cylinder 20 and the outer cylinder 21.
Has outer surfaces thereof as bearing surfaces 25a and 25b. At least each of the bearing surfaces 25a and 25b is made of an aluminum-based or copper-based soft alloy containing at least one of carbon fiber and graphite. As shown in FIG. 2, slit grooves 26a and 26b are formed on each of the bearing surfaces 25a and 25b. The slit grooves 26a and 26b include a plurality of concentric arc portions and a radiating portion that connects the plurality of concentric arc portions. ing. Each of the slit grooves 26a and 26b has a width of about 0.8 to 2 mm and a depth of about 50 to 300 μm. Also, slit groove 26
The inside diameters of the through holes 44, 44 communicating with the a, 26b are about 1-2 mm.

Each of the slit grooves 26a, 26b is formed with a corresponding one of the through holes 44,
44 and an independent distribution channel 27 having an inner diameter of about 2 to 4 mm
Through a and 27b, a control throttle valve 28 provided in the outer cylinder 21, and an air supply passage 29, the air communicates with a compressed gas supply source such as a compressor. By sending compressed gas into the slit grooves 26a and 26b, the rotating member 22
At 19, it is supported in a non-contact state. That is, the compressed gas sent into each of the slit grooves 26a, 26b causes the two members 22, 19 to pass through the bearing gap between the bearing surfaces 25a, 25b and the inner surfaces of the flange pieces 23a, 23b. They rotate without touching each other.

A pair of distribution channels 27 communicating with the slit grooves 26a and 26b
a control throttle valve 28 provided between a, 27b and one air supply passage 29
Functions in the same manner as the first and second control throttle valves 6 and 7 (see FIGS. 10 and 11) in the aforementioned conventional structure. Then, the supply amount and pressure of the compressed gas to both slit grooves 26a and 26b are adjusted, and the size of the bearing gap between the inner surface of the flange piece 23a and the bearing surface 25a, and the inner surface of the flange piece 23b and the bearing are adjusted. The size of the bearing gap with the surface 25b should not be significantly different.

In the case of the present embodiment, the control throttle valve 28 as described above is provided in a recess 30 formed on the outer peripheral surface of the outer cylinder 21, as shown in FIG. A diaphragm 31 and a pair of valve seat plates 32, 32 sandwiching the diaphragm 31 are fitted, and the opening of the recess 30 is closed by a cover plate 43. In the cover plate 43, a part of the distribution channel 27b communicating with the one slit groove 26b is formed, and the pair of distribution channels 27a, 27
b is connected to the control throttle valve 28 from both sides. Since the basic configuration and operation of the control throttle valve 28 are the same as those of the first and second control throttle valves 6 and 7 described above, detailed description will be omitted.

In the case of the hydrostatic gas bearing of the present invention configured as described above, the compressed gas for supporting the rotating member 22 passes through the slit grooves 26a and 26b and the inner surfaces of the flange pieces 23a and 23b. And into the bearing gap between the bearing surfaces 25a and 25b. When the rotating member 22 is supported in a non-contact state and the rotating member 22 is displaced in the axial direction (the left-right direction in FIG. 1),
This shift is corrected by the operation of the control throttle valve 28.

Further, in the case of the hydrostatic gas bearing of the present invention, the characteristics in a relatively high frequency range are improved by the action of each of the slit grooves 26a and 26b, and the relatively low frequency Since the characteristics are improved in the frequency range, sufficient characteristics can be obtained at a practically satisfactory level in almost all frequency ranges.

For example, according to an experiment performed by the present inventors, when a slit groove is formed in a bearing surface and a control throttle valve is not provided,
The relationship between the compliance, which is the reciprocal of the bearing stiffness K (= load capacity / displacement), and the vibration frequency has changed as shown by the broken line a in FIG. In the case where a throttle valve was provided and a simple concave portion was formed on the bearing surface, the above relationship changed as shown by a chain line b in FIG. Further, as shown in FIG. 1, in the case of a structure in which a slit groove is formed in the bearing surface and a control throttle valve is provided, the above relationship changes as shown by a solid line c in FIG.

As is clear from FIG. 4, the hydrostatic gas bearing of the present invention can obtain sufficient characteristics at a practically satisfactory level in almost all frequency ranges. That is, in the above regions (f _p in FIG. 4) excitation frequency f is a certain frequency, improved dynamic stiffness characteristics by the effect of the slit groove, the vibration frequency f is close to 0 (f ≒ 0)
In the region, the static stiffness characteristics can be very large.

In the illustrated example, the control throttle valve 28 is built in the housing 19, and the distribution flow paths 27a and 27b connecting the control throttle valve 28 and the respective slit grooves 26a and 26b are shortened. Not only can the compressed gas bearing itself be miniaturized, but also the responsiveness of the control throttle valve 28 when the rotating member 22 is displaced is improved.

Furthermore, since the bearing surfaces 25a and 25b are made of a soft alloy, the work of forming the respective slit grooves 26a and 26b is easy, and even when foreign matter such as dust enters the bearing gap, the friction coefficient is reduced. Since it is small, the cause of an unrecoverable failure such as burn-in hardly occurs.

Since a plurality of slit grooves 26a, 26b are formed in the bearing surfaces 25a, 25b to feed the compressed gas into the bearing gap, the pressure distribution is made relatively flat over the entire bearing gap, and It is possible to obtain a hydrostatic gas bearing in which self-excited vibration is unlikely to occur while ensuring a sufficient load capacity and a sufficient damping area. Furthermore, the static rigidity characteristics are improved as compared with the conventional hydrostatic gas bearing using the principle of differential pressure, so that the bearing clearance can be set wider and the work of processing each component of the bearing can be facilitated. I can do it.

Next, FIGS. 5 to 7 show a second embodiment of the present invention. In the case of this embodiment, the inner cylinder 20 forming the housing 19 is made of an aluminum-based or copper-based soft alloy containing at least one of carbon fiber and graphite.
The rotating member 22 and the flange pieces 23a and 23b are made of steel in order to improve strength and durability. The inner peripheral surface of the inner cylinder 20 is formed as a bearing surface 42, and the bearing surface 42 is provided with a “day” as shown in FIG.
Formed slit grooves 33, 33 are formed. As shown in FIGS. 5, 6, and 9, a concave portion formed on the outer peripheral surface of the outer cylinder 21 is formed.
Compressed gas is supplied to each slit groove 33, 33 through a control throttle valve 34, 34 built in the 30, 30.

The operation of forming the above-described slit grooves 33 on the bearing surface 42 on the inner peripheral surface of the inner cylinder 20 can be performed by various conventionally known processing methods. In particular, when the bearing surface 42 is made of a soft alloy, for example, Japanese Patent Application Laid-Open No. 63-230219
By using a rolling process as disclosed in Japanese Patent Application Laid-Open Publication No. H11-107, each slit groove 33, 33 can be easily formed.

That is, as shown in FIG. 8, the holding hole 3 of the cylindrical holder 35 is formed.
The steel balls 37, 37 rollably held by
If the pressing rod 38 is rotated or displaced in the axial direction while pressing against the bearing surface 42 on the outer peripheral surface thereof, the slit grooves 33, 33 based on the indentations of the steel balls 37, 37 are formed on the bearing surface 42. Can be formed.

An exhaust passage 41 is provided in a part of the housing 19 that is separated from the control throttle valves 34, 34, and the compression blows out from each slit groove 33, 33 into the bearing gap. Gas can be discharged to the outside. In the case of the radial bearing shown in this example, which is configured as described above, similarly to the case of the thrust bearing shown in the first embodiment, by the cooperative action of the slit groove 33 and the control throttle valve 34, Good characteristics can be obtained.

When the material of the bearing surfaces 25a, 25b, 42 is a copper alloy containing carbon fiber, lead, tin, or the like, there is an advantage that the material is softer than steel and can be easily processed. A copper alloy containing carbon fibers intended to improve slidability and wear resistance contains 1 to 10% by weight of carbon fibers. still,
If the carbon fiber content is less than 1% by weight or more than 10% by weight, the slidability is low. When the slidability is not so important, it may be at least better than 1% by weight, and conversely, may be more than 10% by weight.

The bearing surfaces 25a, 25b, 42 may be formed of a copper alloy containing graphite instead of carbon fibers. Graphite is added for the purpose of improving slidability and abrasion resistance, and its addition amount is 1 to 10% by weight. If the amount of graphite is less than 1% by weight, the slidability is reduced. If the graphite content is more than 10% by weight, the strength becomes weak. However, graphite may be less than 1% by weight when slidability is not so important, and when strength is not so important, etc.
It may be more than 10% by weight. Graphite is easier to release from metal than carbon fiber.
Therefore, the strength of the copper alloy containing carbon fibers is higher than that of the copper alloy containing graphite.

Further, if an aluminum alloy is used as the material of the bearing surfaces 25a, 25b, and 42, the material is softer than copper, so that there is an advantage that processing is easy. Aluminum alloys containing carbon fibers intended to improve slidability and abrasion resistance and to reduce weight are, for example, silicon having 9 to 9%.
16% by weight, 1 to 4% by weight of copper, 1 to 3% by weight of magnesium, 1 to 5% by weight of iron, 1 to 10% by weight of carbon fiber, and the balance of aluminum. In addition, even if the carbon fiber content is less than 1% by weight or more than 10% by weight, the slidability is lowered. However, the carbon fiber may be less than 1% by weight or less than 10% by weight when the slidability is not so important.

The material of the bearing surfaces 25a, 25b, 42 may be an aluminum alloy containing graphite instead of carbon fibers. Aluminum alloys containing graphite intended to improve slidability and abrasion resistance and reduce weight are, for example, 9% silicon.
~ 16 wt%, copper is 1-4 wt%, magnesium is 1-3
% By weight, 1 to 5% by weight of iron, 1 to 10% by weight of graphite, and the balance of aluminum. If the amount of graphite is less than 1% by weight, the slidability is reduced. Conversely, if the content of graphite is more than 10% by weight, the strength becomes weak. However, graphite may be less than 1% by weight when slidability is not important, and 10% by weight when strength is not important.
May be more. Graphite is more easily released from metal than carbon fiber. Therefore, an aluminum alloy containing carbon fibers has a higher strength than an aluminum alloy containing graphite. Further, the cross-sectional shape of the slit grooves 26a, 26b, 33 may be an arc shape or a rectangular shape.

[0032]

【The invention's effect】

Since the hydrostatic gas bearing of the present invention is configured and operates as described above, self-excited vibration by the compressed gas for supporting the rotating member is unlikely to occur, and operation of a machine tool or the like incorporating the hydrostatic gas bearing is difficult. And the bearing rigidity can be sufficiently increased to a practically satisfactory level. Further, the bearing clearance can be set wide, and the work of processing each component of the bearing can be facilitated. Further, even when dust is clogged in the bearing gap, it is difficult to cause an unrecoverable failure such as seizure, so that the reliability of the machine tool or the like can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a first embodiment of the present invention.

FIG. 2 shows the shape of a slit groove similarly formed on a bearing surface,
AA view of FIG.

FIG. 3 is an exploded perspective view of the control throttle valve.

FIG. 4 is a diagram showing a difference in characteristics between a conventional hydrostatic gas bearing and the hydrostatic gas bearing of the present invention.

FIG. 5 is a sectional view showing a second embodiment of the present invention.

FIG. 6 is a sectional view taken along line BB of FIG. 5;

7 shows the shape of a slit groove also formed on the bearing surface, FIG.
CC view of FIG.

FIG. 8 is a sectional view showing an example of a method for forming a slit groove.

FIG. 9 is a DD view of FIG. 1;

FIG. 10 is a sectional view showing an example of a conventional hydrostatic gas bearing.

FIG. 11 is a sectional view showing a control circuit using a control throttle valve.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Bearing member 2 ... Bearing surface 3 ... Rotating shaft 4a, 4b, 5a, 5b ... Concave part 6 ... First control throttle valve 7 ... Second control throttle valve 8 ... Housing 9 ... First port 10 First supply pipe 11 Second port 12 Second supply pipe 13 First chamber 14 Second chamber 15 Diaphragm 16 First throttle channel 17 Second throttle channel 18 Bearing clearance 19 Housing 20 Inner cylinder 21 Outer cylinder 22 Rotating member 23a, 23b Flange piece 24a, 24b Bearing member 25a, 25b Bearing surface 26a, 26b Slit groove 27a, 27b Distribution flow path 28 Control throttle valve 29 Supply air flow path 30 Recess 31 Diaphragm 32 Valve seat plate 33 Slit groove 34 Control Throttle valve 35 Holder 36 Holding hole 37 Steel ball 38 Pressing rod 41 Exhaust flow path 42 Bearing surface 43 Cover plate 44 Through hole

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F16C 32/06

Claims (2)

(57) [Claims] 1. A housing, a rotating member opposed to a bearing surface provided in the housing via a bearing gap, and a downstream end of a distribution channel formed opposite to the bearing surface and independent of each other. A plurality of sets of slit grooves independent of each other and a pair of air provided between each of these distribution channels and an air supply passage communicating with a supply source of compressed gas, and communicating with an upstream end of each of the distribution channels. Based on the elastic displacement of the leaf springs arranged so as to partition the chambers, the supply amount of the compressed gas to each of the above-described slit grooves is increased by increasing the supply amount of the compressed gas to one of the slit grooves. A control throttle valve for adjusting the amount of compressed gas supplied to the slit groove in a reduced state, wherein the bearing surface includes at least one of carbon fiber and graphite, and is made of an aluminum-based or copper-based soft alloy. hand Hydrostatic gas bearing that. 2. A control throttle valve incorporated in a housing.
The hydrostatic gas bearing according to claim 1.