JPH01303313A - Dynamic pressure bearing for pump - Google Patents

Abstract

PURPOSE:To reduce a cost in the whole of the subject pump with a simple structure by forming grooves for generating dynamic pressure on a surface facing to the shaft sleeve of a fixed bearing and thrust receiving plate. CONSTITUTION:Grooves 23 are formed on at least one of the surface facing to the shaft sleeve 21 of a fixed bearing 24 and a thrust receiving plate 22 or the surface facing to the shaft sleeve 21 and the fixed shaft 24 of the thrust receiving plate 22. Air is introduced from the outside of the pump 10 to the grooves 23 through air holes 25 provided on the fixed bearing 24. With this arrangement, it is possible to reduce a cost in the hole of the pump with a simple structure.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to bearings employed in pumps such as turbomolecular pumps and helium compressors for configuring sputtering equipment and CVD equipment, and in particular, The present invention relates to a hydrodynamic bearing for a rotating shaft configured to rotate at an ultra-high speed.

(Prior art) In a turbo-molecular pump or a compressor for helium, etc., by rotating the rotating shaft at high speed, a high vacuum can be created using the rotor 1 blade or impeller that is provided integrally with the rotating shaft. Or one that generates high pressure.

Therefore, it is necessary to employ a bearing for smooth rotation of the rotating shaft.

Conventionally, a bearing is generally used for such a high-speed rotating shaft, and the bearing is configured to supply lubricating oil to the bearing in order to smoothly operate the bearing. However, when it comes to pumps like turbomolecular pumps that create Ifi high vacuum, the lubricating oil for the bearings vaporizes, and not only is it impossible to obtain a complete high vacuum, but the vaporized lubricating oil or the seals also vaporize. This poses a problem of contamination of the vacuum system by flowing into the vacuum system.

On the other hand, pumps that do not use bearings but employ magnetic bearings have also been proposed. However, this magnetic bearing is not only quite expensive, but also has a complicated overall structure, making it unsuitable for so-called industrial use, although it may be suitable for laboratory use.

Therefore, the inventor's calculation is also suitable for industrial use.

As a result of intensive research to develop a bearing for a pump that has a one-minute function, the hydrodynamic bearing of the present invention was completed.

(Invention or problem to be solved) The present invention has been made based on the background described in 1-1 below.The problem to be solved is the high cost and structural complexity of conventional bearings. be.

The purpose of the present invention is to actively form a groove that generates dynamic pressure, which is not only functionally sufficient, but also reduces the cost of the entire pump by providing an in-cylinder structure. The object of the present invention is to provide a dynamic JE bearing for a pump that can be achieved without causing contamination.

(First stage for solving the problem) The first stage taken by the present invention to solve the following 4-aa is explained with reference to the 11th aspect corresponding to the embodiment. A cylindrical shaft sleeve (21) integrally provided on a part of the rotary shaft (15) for rotating the rotor blade (I6);
1), a thrust receiving plate (22) located near the shaft sleeve (21), and the thrust receiving plate (22).
and a fixed bearing (24) fixedly provided on the casing (II) side of the pump (lO).

The surface of this fixed bearing (21) facing the shaft sleeve (21) and thrust receiving plate (22), or the fixed bearing (
24) on at least one of the opposite sides,
Grooves (2 grooves) are formed to generate dynamic pressure.

Furthermore, this ν4 fixed vehicle receiver (24) has a 19-digit air hole (
25) from the outside of the pump (■)).
23), and between the fixed bearing (24) and the shaft sleeve (21),
The dynamic pressure bearing (20)J is characterized by being provided with a gas seal (26) that blocks air introduced from the air hole (25) from moving toward the rotor blade (16).

In other words, the dynamic pressure bearing (20) according to Unreleased II is installed on the rotating shaft (15) constituting the pump (10), such as a turbo molecular pump as shown in 1st r-4, for example. , fixed bearing (24) side, or rotating shaft (15)
Groove 1III (2:
These grooves (
A fixed bearing (24) having a surface facing the pump (23) is fixed to the casing (11) side of the pump (10). This hydrodynamic bearing (20) has each groove groove (2
An air hole (25) is formed in the fixed bearing (24) to supply the air necessary to generate the dynamic pressure in step 3), and a gas seal is provided to prevent this air from flowing into the high negative pressure area. (26) is provided at a location between the shaft sleeve (2) and the fixed bearing (24) and on the movable disk (16) side of the pump (10).

(Operation of the invention) The hydrodynamic bearing (20
), the dynamic pressure bearing (20) is connected to the rotating shaft (1
The operation of the pair of pumps (lO) employed in the sea lion portion of 5) will be explained. In addition, in this explanation, groove III (2:l) or shaft sleeve (21)
This is mainly carried out when the croup groove (23) is provided on the fixed bearing (24) of the thrust receiving plate (22), but when the croup groove (23) is provided on the fixed bearing (24). also has a similar effect, so the explanation in that case will be omitted.

Now, when the motor rotor (14), that is, the rotating shaft (15) starts rotating by energizing the motor stator (13) of the pump (10), the shaft sleeve (2I) integrated with this rotating shaft (+5) and thrust receiving plate (2
2) also starts rotating. These shaft sleeves (21
) and the thrust receiving plate (22), the pump (+1
1) Air from outside or the air hole (2) provided in the fixed bearing (24)
5) begins to be supplied into the hydrodynamic bearing (20).

Note that the supply from the air hole (25), especially the initial supply, can be forcibly performed by a pump (not shown) connected to the air hole (25), as shown in the embodiment, so that one rotation axis (
15) The initial operation is performed more smoothly.

From this state, the rotation axis (+5) of the pump (lO)
When the number of rotations increases further by 1, the pump (In)
More air from outside can be taken in through the air holes (25). As a result, a groove groove (23) is formed between the shaft sleeve (21) and the thrust receiving plate (22), and the constant bearing (24) facing each other.
Dynamic pressure is generated by the air flowing along the path. That is, the shaft sleeve (21) and the fixed bearing (24)
A dynamic pressure that supports the so-called thrust load is generated between the thrust receiving plate (22) and the fixed bearing (24), and a dynamic pressure that supports the so-called radial load is generated between the thrust receiving plate (22) and the fixed bearing (24).

By generating two types of dynamic pressure, the pump (10
) rotates smoothly. In other words, even if the rotating shaft (15) rotates at an extremely high speed, the rotational wobble with respect to its axis will be caused by the thrust bearing plate (22) and the fixed bearing (
24) It is completely suppressed by the 4jjlE generated in between, and almost no load is applied to the F force bearing (19) that basically supports the rotating shaft (15). be. Therefore, this rotating shaft (15) rotates stably and smoothly for the first time without causing abnormality a or increasing power consumption in the motor stator (13).

Furthermore, when the rotating shaft (15) rotates, the fixed bearing (24
) The air supplied into each dynamic pressure bearing (20) from the air hole (25) of the An imperial order! Attempts to move to the (+6) side. However, in the hydrodynamic bearing (20) according to the present invention, the movable roller (+6) of the shaft 1 rib (21) and the fixed bearing (24) is
Since a gas seal (26) is formed on the side, that is, the part shown in FIG. 1, to block the flow of this air, this air does not flow toward the rotor blade (seal 6). In other words, the outside of the motor housing (]+2, i.e. am(+
The side 6) is kept completely airtight, and the function of the pump (10) is not impaired at all.

Furthermore, the hydrodynamic bearing (20) of the present invention has a groove groove (20).
3) and a fixed bearing (24) facing the thrust receiving plate (22), and the fixed bearing (24) and the shaft sleeve (21
), it is sufficient to form a well-known gas seal (26) in the part shown in the figure, so its structure is much more cylindrical than, for example, a magnetic bearing.

(Example) Next, a hydrodynamic bearing (20) according to the invention will be described in detail according to an example shown in one drawing.

FIG. 1 shows a dynamic pressure bearing (20) according to the present invention on a rotating shaft (1).
5) Below is a cross-sectional view of the pump (10) employed. Before explaining the hydrodynamic bearing (20) of the present invention, an outline of this pump (10) will be explained.

This pump (10) forms one airtight space by a casing (11) and a casing (18) airtightly attached to the lower part of the casing (18) having an exhaust port. Inside this airtight space is the motor housing (
A rotating shaft (+5) having a motor stator (13) supported by a motor stator (12) and a motor rotor (14) which receives a repulsive action of this motor stator (13) under one body is arranged. ) is a fixed child support stand (17) having a large number of movable parts i (+6) for generating negative pressure.

Moreover, the rotation shaft (15) of this pump (I t+ ) is
A bearing (19) provided at the end provides basic support for rotation of the motor housing (12) and lower casing (18). A motor rotor (14) integral with this rotating shaft (15)
Two dynamic pressure bearings according to the present invention (2
0) or 0) respectively.

Each hydrodynamic bearing (20) includes a shaft sleeve (21) fixed to the rotating shaft (15) side of the pump (10).
and the thrust receiving plate (22), and the pump (
A fixed bearing (24) fixed to the motor housing (12) side of 10), and a gas seal (26) arranged in a part of the shaft sleeve (21) and the fixed bearing (24) as shown in the figure.
In this embodiment, the fixed bearing (24) of the shaft sleeve (21) and the thrust receiving plate (22)
) A groove (23) is formed on the surface facing the groove (23).

The shaft sleeve (21) is fitted and supported on the lower end of the rotational shaft (+5) so that it has the same weight as the rotational shaft (15), and the outer surface of the lower part of the rotational shaft (+5) as shown in FIG. The so-called herringbone type groove (
23) is the formation. In addition, the thrust receiving plate (22) is also inserted into the rotating shaft (15) in a hole provided at its center and fixed thereto, and the upper surface of the thrust receiving plate (22) has, as shown in FIG. Spiral type groove n C2
3) is formed. These groove grooves (23) are
It may be formed on each surface facing the shaft sleeve (21) and thrust receiving plate (22) of a fixed bearing (24), which will be described later. Note that the shaft sleeve (21) and the thrust receiving plate (22) may be constructed as separate bodies as in this embodiment, or they may be integrally mounted.

The fixed bearing (24) facing the shaft sleeve (21) and the thrust bearing & (22) is cylindrical as shown in Fig. 1, and is attached to the motor housing (+2) of the pump (In). By fixing it to the lower casing (
18) and the casing (1). Also, this fixed bearing (24) has a shaft sleeve (21) and a thrust receiving plate (2) facing it.
Air hole (2) for introducing external air into the space with
In this embodiment, this air hole (25) passes through a passage formed in the motor housing (12) and lower casing (18) of the pump (lO).
10) communicates with the outside. Note that the air outlet (1) introduced from this air hole (25) is provided at a location not shown in the lower casing (18), and the air hole (25) is provided with a A pump (not shown) for forcibly supplying air is connected.

Either the shaft sleeve (21) and the thrust bearing plate (22), which mainly constitute the hydrodynamic bearing (20), or the fixed bearing (24) facing these, are the same as those of this embodiment. In this case, it is made of ceramic material.

That is, in the dynamic pressure bearing (20) according to the present invention 11, it is preferable that at least one of the members making up the dynamic pressure bearing (20) and performing relative rotational motion is made of ceramic. The reason is that this ceramic has high hardness and excellent wear resistance, so it has excellent load resistance.
, TaC.

B < C, WC, Cr :I C= , S I 1
N4,8N.

TiN, AJ, N, TiB2. CrB2. A porous body consisting of ZrBt kosherite, mullite, Tie,
Alternatively, it is preferable to use a composite material in which the open pores are filled with a lubricant. Among them, A12o,, Zr
O2,5iffN4. SiC cordierite is more preferred because it has higher strength and primarily excellent thermal shock properties. Even if one member that performs relative rotational interlocking is made of ceramic and the other member is made of metal, for example, the member made of ceramic is made of phase-L material. This is because it has excellent abrasion resistance against.

Moreover, it is preferable that this ceramic is porous.

This is because ceramic has an M quality with poor self-lubricating properties, which by itself has the disadvantage of excellent wear resistance or a relatively large wear coefficient, whereas ceramic is porous. This is because by filling the open pores with a lubricant, it is possible to impart so-called lubricity.

In this case, the porosity of this ceramic porous body is 10 to 6.
It is preferable that it is Qg arm %. The reason for this is that if the porosity is less than 10% by volume, even if the lubricant is filled, the ceramic sliding surface is larger than the pore surface that has the lubricating properties. This is because the effect cannot be fully demonstrated.

On the other hand, when the porosity of open pores is greater than 60%,
This is because whether the lubricity effect is sufficient or, conversely, the strength of the ceramic porous body will be lowered and the load change resistance will be lowered.
Among these, it is more preferable that the porosity is 20 to b.

Note that the other member may be made of ceramic, porous ceramic material, metal, etc., but the material should be one that causes almost no abrasion on the porous ceramic member. .

The lubricants filled in the open pores of the ceramic porous body as described below include fluorine-based oil, silicone-based oil, mineral oil, and animal oil.

It is preferable that at least one selected from paraffinic oil and naphthenic oil is used. These can be easily impregnated into the pores of the ceramic, and the I
This is because it reacts sensitively to frictional heat, becomes low in viscosity, and is supplied to the FF4 contact surface between each member by the pumping effect, drastically reducing the starting torque. It is more effective to use at least one selected from oil, paraffin oil, and naphthenic oil.

The lubricant has at least a volume of 1 in the pores of the ceramic.
．． )% filling is preferred. The reason for doing this is that if it is less than 10%, it will be difficult to fully demonstrate its lubricating effect.
It is more effective if the volume is less than 0%.

The lubricant can be filled into the pores by heating and melting the lubricant and impregnating it, by dissolving it in a solvent and impregnating it, by impregnating it with a nitrate or a reaction raw material and then reacting it, and by using fine particles. Molecule t! There is a method to remove the dispersion medium by suspending or emulsifying it in medium I and dry-blasting it, and it is also possible to use the method 2 and 1- in combination, and it is also possible to charge it in several batches. can.

Porous ceramic dynamic pressure bearing related to Unexploded 11 (20)
The depth of the croup groove (23) in
It is preferable to keep it within the range of Bm. In other words, if the depth of the groove (23) is less than 3 gm, even though there is a dynamic pressure effect, the performance deteriorates due to clogging of the groove (2) due to abrasion powder during use, and the ceramic・
This is because there are problems such as the grinding of the material being uneconomical. On the other hand, the depth of the croup groove (23) is 5
This is because, if it exceeds 0 gm, it will be impossible to exert a sufficient dynamic pressure effect.

The gas seal (26) provided in the illustrated part of the shaft sleeve (21) and fixed bearing (24) is made of wood! In the embodiment, as shown in FIG.
1) is constructed by forming a spiral groove on the outer periphery of the L portion. That is, this spiral groove rotates with the rotation of the shaft sleeve (21) and 1. It is constructed so that the air between the +4 constant bearings (24) is forcibly sent in the direction shown in the figure.

Of course, this gas seal (26) includes the shaft sleeve (21), the thrust receiving plate (22), and the fixed bearing (2
This is to prevent the air supplied into the space formed by 4) from escaping in the direction F in the figure.
The invention is not limited to the examples described above.

For example, other mechanical seals such as labyrinths may be used.

(Effects of the Invention) As described in detail in 1-1 below, the present invention is as exemplified in Example 1.

[A cylindrical shaft sleeve (21) provided on a part of the rotating shaft (15) that constitutes the pump (Iil) and rotates the dynamic IK (+6), and this shaft sleeve (21). a thrust receiving plate (22) located near the shaft sleeve (21) and the thrust receiving plate (22), and a fixed bearing fixedly provided on the casing (11) side of the pump (lO) and facing the shaft sleeve (21) and the thrust receiving plate (22) at the same time. (24)
and a fixed bearing (21) of the shaft sleeve (21) and the thrust bearing plate (22) facing the shirt sleeve (21) and the thrust bearing plate (22) of the fixed bearing (24).
24) on at least one of the opposite sides,
A croup groove (23) is formed to generate dynamic pressure.

Furthermore, an air hole (25) provided in this fixed bearing (24)
Air is introduced from the outside of the pump (Ill) into the croup grooves (2) through the air hole (25) between the fixed bearing (24) and the shaft sleeve (21). The feature of the configuration lies in the provision of a gas seal (26) that blocks the movement of air toward the + (16) side, which actively forms a croup groove that generates dynamic pressure. Therefore, we provide a dynamic pressure shaft '3 (211) for a pump that is not only efficient in terms of performance, but also reduces the cost of the entire pump due to the mW in the cylinder, and does not cause 7r7 staining. There are things you can do.

That is, according to the hydrodynamic bearing (20) of the present invention, there is no need for lubricating oil, which was required in the past, so there is no adverse effect caused by the vaporization of lubricating oil, and naturally there is no need to replenish the lubricating oil. Such maintenance can be completely eliminated.

Moreover, according to this hydrodynamic bearing (20), mechanical pressure I
Since it can be constructed so that almost no J-friction occurs, for example, when compared with the case of a magnetic bearing, the construction can be placed inside the cylinder and the overall cost can be reduced.

Moreover, since the dynamic pressure bearing (20) has a heavy structure, it does not require a large installation space, and the entire pump (Ill) can be made more compact.

[Brief explanation of the drawing]

1st [7! FIG. 2 is a cross-sectional view of a pump that employs a dynamic pressure bearing according to the present invention, and FIG. 2 is a perspective view of a shaft sleeve and a thrust receiving plate. Explanation of symbols 10...Pump, 15...Rotating shaft, 16・-171
Quality, 20--Dynamic pressure bearing, 21--Shaft sleeve, 22--Thrust receiving plate 2 go...Groove groove, 24
...Fixed bearing, 25...Air hole, 26...Gas seal. On the other side

Claims (1)

[Claims] A cylindrical shaft sleeve integrally provided on a part of a rotating shaft for rotating rotor blades constituting a pump, a thrust receiving plate located near the shaft sleeve, and a fixed bearing that simultaneously faces the shaft sleeve and the thrust receiving plate and is fixedly provided on the casing side of the pump; A groove for generating dynamic pressure is formed on at least one of both surfaces of the receiving plate facing the fixed bearing, and further, a groove for generating dynamic pressure is formed from outside the pump through an air hole provided in the fixed bearing. The rotor blade is configured to introduce air into the rotor blade, and a gas seal is provided between the fixed bearing and the shaft sleeve to block the air introduced from the air hole from moving toward the rotor blade. Pressure bearing.