JPH03249424A - Hydrostatic gas bearing - Google Patents

Abstract

PURPOSE:To suppress self-excited vibration, and to improve the rigidity of a bearing by forming a bearing surface out of soft alloy, by providing a slit grove thereon, and by providing a control restrictor for which a plate spring is used, between the slit groove and a compressed gas supply source. CONSTITUTION:A housing 19 is composed of an inner cylinder 20, an outer cylinder 21, a rotational member 22, and of bearing members 24a, 24b. Bearing surfaces 25a, 25b are made of soft alloy of aluminium or of copper, including at least carbon fiber or graphite, form slit grooves 26a, 26b comprising multiple concentric arcs as well as of a radial part that connects them together, and are communicated with a compressed air supply source through a communicating hole 44, distribution channels 27a, 27b, a control restrictor 28, and through an air supply channel 29. The control restrictor 28 for which a diaphragm 31 is used, is provided on a recessed part 30 formed on the outer circumferential surface of the outer cylinder 21. The generation of self-excited vibration can be suppressed thereby, and the rigidity of the bearing can be improved.

Description

Detailed Description of the Invention (Field of Application in Industry A) The static pressure gas bearing of the present invention is used to support rotating parts of precision machine tools, etc. The purpose is to improve the rigidity of gas bearings.

(Prior Art) Hydrostatic gas bearings have been widely used in the past, which are incorporated into precision machine tools and support rotating members such as rotating shafts that rotate at high speed using the force of compressed gas such as air.

10 and 11 show a hydrostatic gas bearing described in Japanese Patent Publication No. 45-37683 as an example of such a conventionally known hydrostatic gas bearing.

In FIG. 10, reference numeral 1 denotes a bearing member whose inner peripheral surface has a cylindrical bearing surface 2, and a rotary shaft 3 is inserted into the inside of this bearing member 1. Recesses 4a, 4b, 5a, and 5b are formed at four positions on the upper, lower, right, and left sides of the bearing surface 2, and each recess 4
By feeding compressed gas into a, 4b, 5a, and 5b, the rotating shaft 3 is supported inside the bearing member 1 in a non-contact manner.

Of the four recesses 4a, 4b, 5a, and 5b, the recesses 4a and 4b located at two positions above and below are controlled via the first control throttle valve 6, and the recesses 5a and 5b located at two positions on the left and right are controlled by the second control. Each of them is connected to a compressed gas supply source such as a compressor via a throttle valve 7.

The first and second control throttle valves 6.7 have upper and lower recesses 4a, 4 so that the bearing surface 2 and the outer peripheral surface of the rotating shaft 3 are concentric.
This is for adjusting the amount and pressure of compressed gas sent to b1 or the left and right recesses 5a and 5b, and is configured as shown in FIG. 11, for example.

A first boat 9 and a recess 4a (
5a) is connected to the first supply pipe 10, and the second boat 11 provided in the center of the other side and the recessed portion 4b (5b) are connected to the second supply pipe 12.
This allows them to communicate with each other. A diaphragm 15 is provided in the middle of the housing 8 to divide the inside of the housing 8 into a first chamber 13 on the first boat 9 side and a second chamber 14 on the second boat 11 side. Compressed gas is fed into both the first and second chambers 13, 14 from a compressed gas supply source.

On the inner surface of the housing 8, the first and second side boats 9.1
The positions surrounding the opening of 1 are made to protrude inwardly over the entire circumference, and on both sides of the diaphragm 15 are first and second side boats 9.11 and first and second chambers 13.14. First and second side throttle channels 16 and 17 are respectively formed between them.

Since it is configured as described above, based on the displacement of the rotating shaft 3,
When the outer circumferential surface of the rotating shaft 3 and the bearing surface 2 are no longer concentric, the amount of compressed air sent into the recesses 4a, 4b, 5a, and 5b is reduced by the action of the first and second control throttle valves 6.7. The pressure is adjusted appropriately, and the outer peripheral surface of the rotating shaft 3 and the bearing surface 2 become concentric.

For example, when the rotating shaft 3 is displaced downward in FIG. 11, the bearing gap 18 between the outer peripheral surface of the rotating shaft 3 and the bearing surface 2
The dimensions of are smaller at the bottom and larger at the top. Along with this dimensional change, the pressure inside the lower recess 4b (5b) becomes high, the pressure inside the upper recess 4a (5a) decreases, and the second supply pipe 12 communicates with the recess 4b (5b). The pressure inside the second boat 11 increases, and the first supply pipe 10 causes the recess 4 to
The pressure in the first boat 9 communicating with a (5a) decreases.

As a result, the diaphragm 15 that partitions the first and second side boats 9.11 is displaced upward, and the second throttle channel 17 is widened.
The first throttle channel 16 becomes narrower, and the lower recess 4b (5
b) the amount and pressure of compressed gas fed into the
The amount and pressure of the compressed gas sent into the upper recess 4a (5a) are reduced, and the rotating shaft 3 is pushed upward in FIG. 11, thereby eliminating the displacement of the rotating shaft 3.

(Problems to be Solved by the Invention) However, the conventional hydrostatic gas bearing that is configured and operates as described above has the following problems.

That is, in the case of the conventional structure, since the recesses 4a, 4b, 5a15b for supplying compressed gas to the bearing gap 18 were large recesses, the compressed gas sent into these recesses 4a, 4b15a, 5b caused self-support vibration. This is likely to occur, and when it occurs, it becomes impossible to stably operate a machine tool or the like incorporating a static pressure gas bearing.

In particular, as shown in FIGS. 10 and 11, both the first and second chambers are provided for communicating the first and second control throttle valves 6.7 with the respective recesses 4a, 4b, 5a, and 5b. When 1310.12 becomes long, the responsiveness of flow rate control deteriorates, and self-excited vibrations as described above are likely to occur.

In addition, in the case of conventional hydrostatic gas bearings, the bearing surface 2 is made of hardened steel, so even if the bearing gap 18 becomes clogged with a small amount of dirt, the rotating shaft 3 may seize or otherwise become irreparable. Failures were likely to occur.

The hydrostatic gas bearing of the present invention solves the above-mentioned problems.

(Means for Solving the Problems) The hydrostatic gas bearing of the present invention includes a housing, a rotating member that faces a bearing surface provided on the housing with a bearing clearance, and a rotating member that is formed on the bearing surface and that is A slit groove that communicates with a supply source of compressed gas via an air flow path is provided between the slit groove and the supply source, and the amount of compressed gas supplied to the slit groove is controlled based on the elastic displacement of a leaf spring. and a control throttle valve to adjust.

If necessary, the bearing surface is made of an aluminum-based or copper-based soft alloy containing at least one of carbon fiber and graphite.

(Function) In the case of the hydrostatic gas bearing of the present invention configured as described above, compressed gas for supporting the rotating member is sent into the bearing gap through the control throttle valve and the slit groove, and supports the rotating member. Supports the housing in a non-contact manner.

In the case of the hydrostatic gas bearing of the present invention, the dynamic stiffness characteristics are improved by using a slit groove for the compressed gas blowout part, and the static stiffness characteristics are improved by providing a control throttle valve, so that the overall Improves rigidity properties.

In addition, the volume of the slit groove is smaller than that of the concave part in conventional structures, and the damping surface is sharp, making it difficult for self-supporting vibrations to occur, making it possible to stabilize the operation of devices incorporating hydrostatic gas bearings. It can be done in the state.

Furthermore, when 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 becomes clogged with dirt,
It is less likely to lead to irreparable failures such as burn-in.

(Example) Next, the present invention will be explained in more detail while explaining the illustrated embodiment.

1-3 show a first embodiment of the invention.

In FIG. 1, inner cylinders 20 each formed into a short cylinder shape.
The outer cylinder 21 is externally fitted and fixed. Inside the inner cylinder 20,
A circular tubular rotating member 22 is inserted therethrough, and flange pieces 23a are fixed to both ends of the rotating member 22, respectively.
23b, and bearing surfaces 25a of bearing members 24a and 24b fixed to the end surfaces of the inner cylinder 20 and outer cylinder 21,
25 b are facing each other. Then, the inner cylinder 20 and the outer cylinder 2
1 and bearing members 24a and 24b constitute a bouncing 19.

Each bearing member 24a is sandwiched between the inner cylinder 20 and the outer cylinder 21 and fixed to the end faces of these two members 20 and 21.
, 24b have respective outer surfaces as bearing surfaces 25a, 25b.
At least each bearing surface 25a, 25b is made of an aluminum-based or copper-based soft alloy containing at least one of carbon fiber and graphite. And, on each bearing surface 25a, 25b, '4'
As shown in FIG. 2, the slit groove isa, 26b is formed of a plurality of concentric arc portions and a radial portion that connects the plurality of concentric arc portions. The width of each slit groove 26a, 26b is approximately 0.8 to 2 mm, and the depth is approximately 50 to 300 μm. Moreover, the inner diameter of the through holes 44.44 communicating with each slit groove 26a, 26b is 1
It is approximately 2 mm.

Each slit groove 26a, 26b is connected to the through hole 44, respectively.
．． 44, and distribution channels 27a and 2 with an inner diameter of about 2 to 4 mm.
7b, a control throttle valve 28 provided in the outer cylinder 21, and an air supply flow path 29, which communicate with a compressed gas supply source such as a compressor, and feed compressed gas into each slit groove 26a, 26b. As a result, the rotating member 22 is supported by the housing 19 in a non-contact manner.

That is, due to the compressed gas sent into each of the slit grooves 26a, 26b, both members 22, 19 are moved together through the bearing gap between the bearing surfaces 25a, 25b and the inner surfaces of the flange pieces 23a, 23b. They are designed to rotate without touching each other.

Distribution channel 27a communicating with each slit groove 26a, 26b,
The control throttle valve 28 provided between the air supply flow path 27b and the air supply flow path 29 is the same as the control throttle valve 6.27b in the conventional structure described above.
7 (see FIGS. 10 and 11), it adjusts the amount and pressure of compressed gas supplied to both slit grooves 26a and 26b, and controls the pressure between the inner surface of the flange piece 23a and the bearing surface 25a. This is done so that the size of the bearing gap and the size of the bearing gap between the inner surface of the flange piece 23b and the bearing surface 25b do not differ greatly.

In the case of this embodiment, such a control throttle valve 28 is
A diaphragm 31 made of a metal plate spring, as shown in FIG.
A pair of valve seat plates 32 and 32 sandwiching this diaphragm 31 are fitted, and the opening of the recess 30 is closed with a cover plate 43. A part of the distribution channel 27b communicating with the slit groove 26b is formed in the cover plate 43, so that the pair of distribution channels are connected to the control throttle valve 28 from both sides. Note that the basic configuration and function of this control throttle valve 28 are the same as those of the first and second control throttle valves 6.7 described above, so a detailed explanation will be omitted.

In the case of the hydrostatic gas bearing of the present invention configured as described above, compressed gas for supporting the rotating member 22 is supplied to each slit groove 2.
6 a, 26 b, each flange piece 23a, 2
3b and the bearing surfaces 25a, 25b, and supports the rotating member 22 in a non-contact state, and when the rotating member 22 is displaced in the axial direction (horizontal direction in FIG. 1) Then, this deviation is corrected by the action of the control throttle valve 28.

Furthermore, in the case of the hydrostatic gas bearing of the present invention, the slit groove 28a
, 26b improves the characteristics in a relatively high frequency range, and the function of the control throttle valve 28 improves the characteristics in a relatively low frequency range, so the characteristics are sufficient in almost the entire frequency range. can be obtained.

For example, according to experiments conducted by the present inventor, when a slit groove is formed on the bearing surface and no control throttle valve is provided, the compliance, which is the reciprocal of the bearing stiffness K (=load capacity/displacement), and the vibration frequency The relationship between the In this case, the above relationship changed as shown by the chain line in the figure. Furthermore, as shown in the zi diagram, in the case of a structure in which slit grooves were formed on the bearing surface and a control throttle valve was provided, the above relationship changed as shown by the solid line C in the diagram.

As is clear from FIG. 4, the static pressure gas bearing of the present invention can obtain sufficient characteristics in almost the entire frequency range.

Furthermore, the control throttle valve 28 is built into the housing 19, and the distribution channels 27a and 27b connecting the control throttle valve 28 and each slit groove 26a and 26b are shortened, so that the hydrostatic gas bearing itself can be made smaller. In addition, 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, it is easy to form each slit groove 26a and 26b, and even if foreign matter such as dust gets into the bearing gap, the coefficient of friction is small. Causes of irreparable failures such as burn-in are less likely to occur.

In addition, slit grooves 26a, 26b are formed on the bearing surfaces 25a, 25b.
By forming a large number of bearings, compressed gas is sent into the bearing gap, making the pressure distribution relatively flat throughout the bearing gap, ensuring sufficient load capacity and sufficient damping area. , it is possible to obtain a static pressure gas bearing that does not easily generate self-supporting vibrations.

Next, FIGS. 5 to 7 show a second embodiment of the present invention.

In the case of this embodiment, the inner cylinder 20 constituting the housing 19 is made of an aluminum-based or copper-based soft alloy containing at least one of carbon fiber and graphite, and the rotating member 22 and flange pieces 23a, 23b are Steel is used to improve strength and durability. The inner circumferential surface of the inner cylinder 20 is a bearing surface 42, and the bearing surface 42 is provided with 1 as shown in Figure N7.
A slit groove 33.33 in the shape of a Japanese character is formed. As shown in FIG. 5.6.9, a control throttle valve 34.34 is built in a recess 30.30 formed on the outer circumferential surface of the outer cylinder 21.
Compressed gas is supplied to each slit groove 33, 33 through the slit groove.

The work of forming the above-mentioned slit grooves 33, 33 on the bearing surface 42 of the inner peripheral surface of the inner cylinder 20 can be performed by various conventionally known processing methods. In this case, for example, JP-A-63-23
By using a rolling method such as that shown in Japanese Patent No. 0219, each slit groove 33, 33 can be easily formed.

That is, as shown in FIG. 8, the steel balls 37 and 37 held removably in the holding holes 36 and 36 of the cylindrical holder 35 are
If the pressing rod 38 is rotated or displaced in the axial direction while pressing the bearing surface 42 with the outer circumferential surface of the pressing rod 38, a slit groove is formed in the bearing surface 42 based on the impression of the steel balls 37, 37. 33.33 can be formed.

Also, in a part of the housing 19, the control throttle valve 34.3
An exhaust flow path 41 is provided in a portion away from the 4-installation portion, so that the compressed gas discharged from each slit groove 33, 33 into the bearing gap can be freely discharged to the outside.

In the case of the radial bearing shown in the second embodiment, as well as in the case of the thrust bearing shown in the first embodiment described above, good characteristics are achieved due to the cooperative action of the slit groove 33 and the control throttle valve 34. You can get it.

It should be noted that if the bearing surfaces 25a, 25b, 42 are made of a copper alloy containing carbon fiber, lead, tin, etc., it has the advantage of being softer than steel and easier to process.

A copper alloy containing carbon fiber intended to improve sliding properties and wear resistance contains 1 to 10% by weight of carbon fiber. still,
If the carbon fiber content is less than 1% by weight or more than 10% by weight, the sliding properties will be low.

If sliding properties are not important, the amount may be less than 1% by weight, or, conversely, may be more than 10% by weight.

Furthermore, the bearing surfaces 25a, 25b, and 42 may be formed of a copper alloy containing graphite instead of carbon fiber. Graphite is added with the intention of improving sliding properties and wear resistance, and the amount added is 1 to 10% by weight. If the graphite content is less than 1% by weight, the sliding properties will be low. If the graphite content is more than 10% by weight, the strength will be weakened. but,
The graphite content may be less than 1% by weight when sliding properties are not important, and it may be greater than 10% by weight when strength is not important.

Graphite is more easily released from metal than carbon fiber. Therefore, a copper alloy containing carbon fibers has higher strength than a copper alloy containing graphite.

Furthermore, if an aluminum alloy is used as the material of the bearing surfaces 25a, 25b, 42, there is an advantage that it is easier to process since it is softer than steel.

For example, an aluminum alloy containing carbon fiber intended to improve sliding properties and wear resistance and to reduce weight has a silicon content of 9 to 1.
6% by weight, copper 1-4% by weight, magnesium 1-3% by weight, iron 1-5% by weight, carbon fiber 1-10% by weight,
The balance is made up of aluminum.

Note that if the carbon fiber content is less than 1% by weight, or conversely if it is more than 10% by weight, the sliding properties will be low.

However, if carbon fiber does not place much emphasis on sliding properties, 1
It may be less than 10% by weight or more than 10% by weight.

Further, the material of the bearing surfaces 25a, 25b, and 42 may be an aluminum alloy containing graphite instead of carbon fiber. Intended to improve sliding properties and abrasion resistance, and reduce weight.
An aluminum alloy containing graphite contains, for example, 9 to 16% by weight of silicon, 1 to 4% by weight of copper, 1 to 3% by weight of magnesium, 1 to 5% by weight of iron, and 1% by weight of graphite.
~10% by weight, and the balance is aluminum.

Note that if the graphite content is less than 1% by weight, the sliding properties will be low. On the other hand, if the graphite content is more than 10% by weight, the strength will be weakened. However, graphite may be less than 1% by weight if sliding properties are not important, or 10% by weight if strength is not important.
4 degrees is also good.

Graphite is carbon! It is easier to release from metal than a-fiber.

Therefore, an aluminum alloy containing carbon fiber has higher strength than an aluminum alloy containing graphite.

Further, the cross-sectional shape of the slit grooves 26a, 26b, and 33 may be arcuate or rectangular.

(Effects of the Invention) Since the hydrostatic gas bearing of the present invention is configured and operates as described above, it is difficult to generate self-support vibrations due to the compressed gas for supporting the rotating member. Machines, etc. can be operated stably, and bearing rigidity can be made sufficiently high.

[Brief explanation of drawings]

1 to 3 show a first embodiment of the present invention, FIG. 1 is a sectional view, and FIG. 2 is a parent view taken along line AA in FIG. 1, showing the shape of the slit groove formed on the bearing surface. , FIG. 3 is an exploded perspective view of the control throttle valve, FIG. 4 is a diagram showing the difference in characteristics between the conventional static pressure gas bearing and the static pressure gas bearing of the present invention, and FIGS. Embodiment 2 is shown, FIG. 5 is a sectional view, FIG. 6 is a sectional view taken along line B-B in FIG. 5, and FIG. 7 is a sectional view of FIG. C-C view, FIG. 8 is a sectional view showing an example of a method for forming slit grooves, FIG. 9 is a D-D parent view of FIG. 1, and FIG. 10 is a diagram of a conventional hydrostatic gas bearing. A sectional view showing an example, FIG. 11 is a sectional view showing a control circuit using a control throttle valve. 1: Bearing member, 2: Bearing surface, 3: Rotating shaft, 4a, 4b,
5a, 5b: recess, 6: first control throttle valve, 7: second control throttle valve, 8: housing, 9: first boat, 10:
First supply pipe, 11: Second boat, 12; Second supply pipe, 1
3: 1st chamber, 14: 2nd chamber, 15: diaphragm, 16
: First throttle flow path, 17: Second throttle flow path, 18: Bearing gap, 19: Housing, 20: Inner cylinder, 21: Outer cylinder, 22:
Rotating member, 23a, 23b: Flange piece, 24a, 24
b Two bearing members, 25a, 25b: bearing surface, 26a, 26
b Nislit groove, 27a, 27b; Distribution channel, 28: Control throttle valve, 29: Air supply channel, 30: Recess, 31; Diaphragm, 32: Valve seat plate, 33 Nislit groove, 34: Control throttle valve, 35: Holder, 36: Holding hole, 37: #4 ball,
38: Pressing rod, 41: Exhaust channel, 42: Bearing surface, 43:
Lid plate, 44: Through hole.

Claims (3)

[Claims] (1) a housing, a bearing surface provided on the housing, a rotating member facing the bearing surface through a bearing gap, and a slit groove formed on the bearing surface and communicating with a compressed gas supply source via an air supply flow path; A static pressure gas bearing comprising a control throttle valve that is provided between the slit groove and the supply source and that adjusts the amount of compressed gas supplied to the slit groove based on the elastic displacement of the leaf spring. (2) The hydrostatic gas bearing according to claim 1, wherein the bearing surface is made of an aluminum-based or copper-based soft alloy containing at least one of carbon fiber and graphite. (3) The hydrostatic gas bearing according to claim 1 or 2, wherein the control throttle valve is incorporated into the housing.