JPS5813779B2 - Airtight structure of high-temperature shaft body that performs rotation and linear motion - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high-temperature shaft body sealing structure that combines airtightness of the rotating shaft by an oil seal and airtightness of axial movement by a bellows.

In more detail, the present invention applies to, for example, vacuum melting equipment that requires processing while maintaining a high-temperature special (gas or vacuum) atmosphere inside a container isolated from the outside.
A great effect can be obtained by using it as an airtight part of a shaft that rotates and holds a crucible in a container.

In other words, it is a rotating shaft that has a high-temperature heat source and is in a high temperature state due to heat conduction, and is generally a round bar-shaped metal shaft that is also required to move in the axial direction. By using this in combination with a bellows that serves as an axial seal while protecting the part (contact part with the shaft body) from high temperatures, it provides a structure that achieves movement and maintains airtightness.

The drawing, which will be described in detail later, is a cutaway view of an embodiment of the present invention, in which 5 is a shaft body, 6 is a bellows, 13 and 20 are oil seals, and a is a lip portion thereof.

(The oil seal is regulated by JISB2402, etc., so a description of its structure will be omitted.

) First, the conventional technology will be explained.

The following methods are conventionally known as methods for maintaining airtightness of shaft bodies that require both rotation and axial movement at high temperatures.

(1) Rotating (for) seals and linear motion (for) seals are the same seal body, such as oil seals, Wilson seals, etc.
There are four methods for heat-resistant protection of a seal body, such as an oil seal, using an O-ring.

(a) Method of using a heat-resistant oil seal - This is an oil seal using a soft or silicone material.
The limit temperature for continuous use is 250 to 260°C, and it cannot be used where the temperature of the sealed portion exceeds this temperature.

(b) A method of cooling the oil seal from the outside of the holding container - The oil seal is fixedly held on the container side, a fluid cooling jacket is provided inside the oil seal holding container, and the oil seal is cooled from the outside. In this method, the oil seal retainer (holding part) is cooled and protected, but the lip part that maintains the airtightness of the rotating and linear moving parts is not sufficiently cooled and receives heat directly from the shaft body. However, the disadvantage is that the lubricant deteriorates or evaporates easily, has a weak protective effect, and has a short lifespan.

(c) A method of forced circulation cooling of the lubricating oil in the seal part - This method cools the lubricating oil supplied to the oil seal lip of the shaft body externally and forcibly circulates it, using heat from the shaft body to cool the lubricating oil. It absorbs heat and protects the oil seal lip from heat.

In this case, if cooled lubricating oil is effectively supplied to the lip, the effect is great, but it is generally difficult to effectively supply lubricating oil to the lip due to the unique shape of the oil seal, and the inside of the shaft and the lip Since heat is continuously supplied from the contacting adjacent parts of the parts, one side of the lip part is directly under the influence of heat while forming a thermal boundary at the lip part, and the shaft body performs linear motion. The disadvantage is that the cooling effect is not very effective, and the life of the seal is short due to deterioration of the lubricating oil and insufficient thermal protection of the oil seal.

(d) Method of cooling the shaft by making it hollow and circulating cooling fluid - This method cools the shaft, which is a heat conductor, from within, and is the most effective method for thermally protecting the oil seal. .

However, there are restrictions in hole drilling and increased mounting dimensions, and a rotary seal is required to prevent cooling fluid from leaking when installing a joint to supply and drain cooling fluid inside the shaft as it rotates. , which increases the seal resistance to rotation of the shaft and makes smooth rotation difficult.

In addition, it is necessary to consider the design space occupied by the range of motion of the joint relative to the linear motion of the shaft, and there are many constraints.

Note that in both rotational and linear motion, the seal resistance is large at very low speeds, so linear and rotational stick-slip (
stick slip) may occur, which may impede smooth rotation and linear movement.

To avoid this, it is necessary to reduce the number of seal installation locations to the minimum necessary, but even then, internal cooling is often not possible due to mechanical reasons for shafts that require smooth rotation and linear motion.

(2) Method of configuring the rotary seal and linear motion seal separately - In this case, the seals are configured separately and thermal protection is provided for each seal, but as with method (1), the following four methods are available: be.

(a) Method of using a mechanical seal as a rotary seal The heat resistance temperature varies depending on the combination of materials of the mechanical seal used for the single-turn sliding part.

For example, the combination of ceramic and carbon depends on the degree of cooling of the lubricating oil, but there are examples of it being used in applications where the temperature exceeds 400°C.

It is also the best rotating seal with lower rotational resistance than oil seals.

However, it is expensive and often cannot be used in regular equipment.

(b) Rotating seal, oil seal, Wilson seal,
Method using 0-ring etc. - The drawbacks of this method are the same as those explained in (1).

(/) Straight seal, oil seal, Wilson seal,
Method using 0-ring etc. - The drawbacks of this method are the same as those explained in (1).

(d) Method of using heat-resistant and pressure-resistant bellows for linear seals
This uses bellows to absorb linear motion and handle high-temperature atmospheres using heat-resistant and pressure-resistant materials.

This method is the same as a mechanical seal for rotation, and compared to methods such as oil seals, it has no sliding parts, so it does not cause stick-slip caused by sliding resistance, and is the most excellent linear seal in terms of life. However, the disadvantage is that it is expensive.

The present invention was made in view of the drawbacks of the above-mentioned conventional methods.
A combination of oil seals and bellows, which are relatively easy to obtain and inexpensive, is used to maintain airtightness by insulating the high-temperature shaft that performs rotation and linear motion from the atmosphere inside the high-temperature container through which the shaft passes, without cooling the shaft. The feature is that it is possible.

By the way, the following technical problems are required to be solved by the present invention.

(1) The shaft body is in a high temperature state; that is, one end of the shaft body is in or near a container with a high-temperature heat source, and heat is continuously supplied at all times, and the heat is conducted through the shaft body. The locations where the oil seal as a rotating seal and the bellows as a linear seal are to be installed are exposed to high temperatures that cannot be withstood by the material.

Therefore, it is not possible to have a structure in which an oil seal or the like comes into direct contact with the shaft body.

(2) The shaft body rotates and moves linearly, requires airtightness between the high temperature atmosphere inside the container and the outside, and requires smooth rotation and linear movement at very low speeds.

From the viewpoint of maintenance, it is necessary to minimize the number of seals and reduce seal resistance.

(3) In order to reduce resistance to rotation and linear motion of the shaft and to simplify the structure due to dimensional constraints, it is required that the shaft is not cooled.

Cooling the inside of the shaft is difficult due to the longitudinal dimension of the shaft and processing constraints, and a fluid coupling cannot be used because it increases sealing resistance.

(4) Oil seals require thermal protection to maintain their functions due to the material they are made of, and when cooling, it is more effective if the lip is directly protected from high temperatures.

The main points of the present invention to address the above problems are as follows.

(a) The rotary seal and linear motion shaft end seal are configured to be thermally protected using separate oil seals,
Heat-resistant and pressure-resistant bellows are used for the high-temperature side seal of the shaft against linear motion, and protection from high-temperature atmospheres is not particularly considered.

(b) Protect the rotary seal oil seal as follows.

The number is the number of the drawing. (b1) A bowl-shaped flange 12 is provided to attach the oil seal 13 to the shaft body 5 to alleviate the thermal influence on the oil seal.

The bowl-shaped flange is fixedly fixed to the shaft body and rotates together with the shaft 5, and an oil seal 13 is attached to the tip thereof as shown in the figure.

Heat from the high-temperature molten material 3 is conducted from the shaft body to the flange 12 side, but due to the shape of the flange, the heat dissipation surface expands rapidly, and the heat transfer gradient to the oil seal mounting part is large. The temperature drops significantly.

In addition, by circulating a lubricant around the flange 12 between A and B for lubricating the oil seal, cooling of the flange portion and the influence of heat from the shaft on the oil seal are reduced.

(b2) The partition tube 14 having the cooling fluid jacket 9 is inserted between the rotating shaft body 5 and the bowl-shaped flange 12, and the lip part a of the oil seal 13 (a is the dogleg-shaped part in the figure, b is the dogleg-shaped part in the figure, spring) directly contacts the cooled partition wall tube to maintain airtightness.

In this manner, the lip portion of the oil seal slides in direct contact with the cooled partition wall tube, so that the oil seal is not affected by heat and airtightness is reliably maintained.

The partition tube also has the effect of blocking heat radiation from the shaft body 5, so that the lip portion is doubly protected from heat.

Next, an embodiment of the present invention in which the above measures are taken will be described in more detail.

The drawing is a cross-sectional view of an example of a sealing structure for a high temperature shaft of a vacuum processing device or a semiconductor crystal pulling device that performs processing while maintaining the inside of a container 2 in a high-temperature gas or vacuum atmosphere as described above, and shows a crucible 4 containing a high-temperature melt 3. This figure shows the airtight structure of the holding shaft 5, which functions to slowly rotate and move up and down.

Other symbols in the drawings will be explained first.

1 is a frame for the container 2, 6 is a bellows, 7 is a mounting flange,
8 is an O-ring, 9 is a cooling jacket, 10 is a guide shaft,
11 is a gasket, 12 is a bowl-shaped flange, 13 is an oil seal, 14 is a partition tube, 15 is a housing (protective frame of the device), 16 is a cooling joint, 17 is a lubrication joint, 18
19 is a bearing, 20 is an oil seal, 21 is a worm, 22 is a worm wheel, and 23 is a bearing bush.

The container 2 is attached to the pedestal 1 and is, for example, a device that maintains a high-temperature vacuum atmosphere, and the shaft 5 is in a high temperature state because a high-temperature heat source such as a crucible 4 is mounted on one end.

Further, the shaft body 5 is rotatably supported by a bearing 18 on a housing 15 and held by a guide shaft 10 so as to be able to move in an axial direction relative to the container 2 .

(Although there is a separate power unit that provides this axial movement, it is not shown in the figure.) The bellows 6 and the oil seal 13 seal the atmosphere inside the container 2 from the outside (keep it airtight). The oil seal 13 is in charge of sealing against the linear axial movement of the shaft body 5, and the oil seal 13 is in charge of sealing against the rotational movement of the shaft body 5.

The bowl-shaped flange 12 is engaged and fixed to the shaft body 5, and an oil seal 13 is attached to its tip so that it can rotate together with the shaft body 5.

The lip portion of this oil seal 13 is
The cooling jacket part 9 is integrally fixed to the partition wall cylinder 14 and is arranged between the shaft body 5 and the bowl-shaped flange 12.

The shaft body 5 has a worm wheel 2 attached to its lower end.
The worm 21 is rotated by driving the worm 21 with a motor (not shown) or the like, and the bearing 18 in the housing 15 rotates.
The oil supplied from the lubrication joint 17 provides both lubrication and cooling effects to the oil seal 13 and the shaft body 5.
The bearing 18, the bowl-shaped flange 12, and the oil seal 13 to which heat is conducted are cooled.

Now, when the shaft body 5 rotates, the bowl-shaped flange 12 also rotates, causing the oil seal 13 to rotate, but its lip portion slides in contact with the outer periphery of the bulkhead tube 14 having the cooling jacket 9 attached to the housing 15, thereby resisting the rotation. Maintain airtightness.

Further, the housing 15 can be moved linearly by external power while being positioned on the guide shaft 10, and linear movement in the axial direction can also be performed while rotating the shaft body 5.

The bellows 6 is responsible for keeping the internal atmosphere of the container 2 airtight from the outside during this axial movement.

When the heat transmitted from the shaft 5 using the high-temperature molten material 3 in the crucible 4 as a heat source reaches the bowl-shaped flange 12, the radiation area expands in a plane, the radiation action rapidly increases, and the temperature also drops rapidly.

In addition, cooling is performed by filling the housing 15 with lubricating oil and forcing it to circulate, and the temperature of the holding part of the oil seal 13 is controlled by using a material with low heat resistance such as NBR synthetic rubber (acrylonitrile butadiene rubber) for the oil seal. It is possible to lower the value to a value that is sufficient for use.

Furthermore, the oil seal 13 is not directly exposed to the radiant heat of the shaft body 5 due to the cooling jacketed bulkhead tube 14 .

Therefore, the oil seal 13 is not exposed to high temperatures.
Expected to have a long life.

The bellows 6 receives heat radiation from the shaft 5, and its temperature rises due to heat conduction from the container 2 side, but since bellows made of heat-resistant and pressure-resistant materials are easily available, it is possible to maintain airtightness during linear motion of the shaft. can be maintained reliably.

The oil seal 20 maintains airtightness between the collar 19 at the end of the rotating shaft and the end of the housing 15, and since it is close to the lubricating oil input end and has a low temperature, there is no temperature problem like the oil seal 13.

As explained in detail above, by using the configuration of the present invention, one end of the container that must perform rotation and linear axial movement while airtightly separating the atmosphere inside the container, which has a high-temperature heat source inside, from the outside, can be connected to the high-temperature part of the container. It is possible to use a bellows and an inexpensive oil seal for relatively low temperatures to maintain airtightness of the high-temperature shaft body that protrudes from the shaft, which has significant practical effects such as long service life and economical performance.

The present invention can be used not only in the vacuum melting apparatus and the semiconductor single crystal pulling apparatus but also in high-temperature drying apparatuses, and has a wide range of applications.

[Brief explanation of the drawing]

The drawing is a sectional view showing an example of a seal structure for a high-temperature shaft in which the present invention is implemented. 1... Frame, 2... Container, 3... High temperature melting object,
4... Crucible, 5... Shaft, 6... Bellows, 7
...Flange, 8...0 ring, 9...Cooling jacket, 10...Guide shaft, 11...Gasket, 1
2...Dog-shaped flange, . 13...Oil seal,
14... Partition tube, 15... Housing, 16...
Cooling joint, 17... Lubrication joint, 18... Bearing,
19...Color, 20...Oil seal, 23...
・Push.

Claims (1)

[Claims] 1 The shaft body has an airtight structure to maintain airtightness between the high temperature atmosphere and the outside of the shaft body, which has one end inside or near a container with a high temperature atmosphere and is required to move in the axial direction and rotate around the axis. To maintain airtightness against axial movement, a heat-resistant and pressure-resistant bellows is arranged and fixed between the end of the housing that supports the rotating shaft as a bearing and the above-mentioned high-temperature container so as to surround the shaft, and to maintain airtightness against rotation of the shaft. A partition tube is attached to the bellows terminal side of the housing so as to surround the shaft body through an O-ring, and allows cooling fluid to flow inside, and a partition tube is fitted and fixed to the outer periphery of the shaft body inside the housing. a bowl-shaped flange whose end portion is formed so as to wrap around the partition tube, and a plurality of oil seals that are attached to the flange and whose lip portions are in sliding contact with the cooled partition tube when the shaft rotates. Equipped with
An airtight structure of a high-temperature shaft body that performs rotation and linear motion, characterized in that lubricating oil is sealed or circulated inside the housing.