HK1225432B - Oil diffusion pump and oil vapor generator used therefor - Google Patents

Abstract

Provided is an oil diffusion pump provided with an oil vapor generator capable of eliminating a problem that arises when a heater wire is used as a hydraulic oil heating source. The oil diffusion pump is a vacuum pump in which an oil vapor generator (70) is disposed in a casing (51) and operated, thereby evaporating a hydraulic oil (8) into oil vapor, and the oil vapor is ejected from jets (53, 53a) to discharge an intake gas. The oil vapor generator (70) is provided with a tubular case (71) (object to be heated) that extends in an upright direction, an induction coil (75) wound around the tubular member (71) through an insulating material (73), and a feeding means for applying an alternating current to the induction coil (75). The case (71) and the induction coil (75) are build in the casing in such an arrangement as to be immersed in the hydraulic oil (8) stored in the casing (51). The feeding means is operated to apply the alternating current to the induction coil (75), thereby heating the case (71) itself and thus evaporating the hydraulic oil (8).

Description

Oil diffusion pump and oil vapor generator for the same

Technical Field

The present invention relates to an oil diffusion pump as a vacuum pump connected to a vacuum container constituting various vacuum apparatuses such as a vapor deposition apparatus and a sputtering apparatus, and an oil vapor generator incorporated in the pump, and is suitable for use in evacuating the inside of the container.

Background

In various vacuum apparatuses such as a vapor deposition apparatus and a sputtering apparatus, an oil diffusion pump is used as a vacuum pump used in an exhaust apparatus for evacuating the inside of a vacuum container constituting the apparatus. Among conventional oil diffusion pumps, there are known oil diffusion pumps that: an electric heater having a heater wire is used as a heat source for the working oil stored in the boiler (patent document 1).

Prior art documents

Patent document

Patent document 1: japanese laid-open patent publication No. 2007-23778

Disclosure of Invention

Problems to be solved by the invention

In the case of using a heater wire as a heat source for the working oil, although there is an advantage that the apparatus can be formed inexpensively, there are also factors that can cause the following disadvantages: for example, the heating function is lost due to the breakage of the heating wire; leakage of electricity occurs due to poor insulation of the heater wire; poor contact occurs due to high temperature of the terminal block; and rust on the heated body. Further, since the heating wire generates a high temperature close to the red heat level when the oil diffusion pump is operated, attention must be paid to the installation place thereof, and there is a problem of an installation environment in which the degree of freedom is limited at the installation place depending on the installation place in consideration of the radiant heat from the heating wire.

Further, since the heating wire as the heating source of the working oil also generates heat conduction loss in terms of energy efficiency, there are the following problems in addition to the problem that the heating efficiency is low and energy saving is hindered.

(1) The rising speed of heating is slow (the start time is long),

(2) the thermal responsiveness is poor and it is difficult to control,

(3) it is difficult to selectively heat the object to be heated and also heat the periphery of the object to be heated.

According to one aspect of the present invention, there is provided an oil vapor generator that can solve the problem in using a heater wire as a working oil heating source, and an oil diffusion pump that is provided with the oil vapor generator and can contribute to energy saving during operation.

Means for solving the problems

An oil diffusion pump according to the present invention is a vacuum pump in which an oil vapor generator is disposed in an ejector disposed in a casing, the oil vapor generator is operated to heat working oil and generate oil vapor, the oil vapor in the ejector is ejected from the ejector, and high-vacuum exhaust operation is performed on an intake gas.

The oil vapor generator is provided with: a body to be heated; an induction coil arranged in the vicinity of the object to be heated in an electrically insulated manner; and a power supply unit that applies an alternating current to the induction coil. Further, the power supply unit is operated to apply an alternating current to the induction coil, thereby heating the object to be heated itself and gasifying the operating oil.

The oil vapor generator of the present invention is used for heating the working oil in the oil diffusion pump having the casing and the ejector to generate the oil vapor. The oil vapor generator of the present invention comprises: a heated body disposed in the ejector in the casing so that a part or the whole of the heated body is immersed in the working oil stored in the casing of the oil diffusion pump; an induction coil disposed in the vicinity of the body to be heated so as to be electrically insulated so that a part or the whole of the induction coil is immersed in the working oil stored in the case; and a power supply unit that applies an alternating current to the induction coil. The heating device is characterized in that the power supply unit is operated to heat the object to be heated, thereby gasifying the operating oil.

In the above two inventions, the shape of the object to be heated constituting the oil vapor generator is not particularly limited, and for example, a plate shape, a cylindrical shape, or a combination of a plate shape and a cylindrical shape can be considered. For example, in the case where the object to be heated is formed in a cylindrical shape extending in the standing direction (fig. 3 to 5), the induction coil may be wound around the object to be heated via an insulating material (fig. 3 to 5). When the object to be heated is formed of a plate material such as a disk, the induction coil may be disposed around the object to be heated (for example, on the back surface) with an insulating material interposed therebetween, and when the induction coil and the power supply unit are combined, power may be supplied using 1 induction coil and power supply unit of the system, in addition to using a single induction coil and a plurality of power supply units. In any case, in the present invention, the body to be heated and the induction coil are assembled to the case in such a manner that a part or all of the body to be heated and the induction coil are immersed in the working oil stored in the case.

In the present invention, a flow path of the working oil that can heat the oil vapor generator by operating the oil vapor generator can be provided in the casing of the oil diffusion pump.

In the present invention, the oil vapor generator disposed in the casing can be configured to be thermally insulated from the bottom surface of the casing.

In the present invention, the induction coil of the oil vapor generator can be constituted by an insulated and coated heat-resistant electric wire.

Effects of the invention

The oil vapor generator incorporated in the oil diffusion pump of the present invention is configured to: as the working oil heating source, a heating source (for example, a heating source in which an induction coil is wound around a cylindrical object to be heated with an insulating material interposed therebetween) in which the induction coil is disposed in the vicinity of the object to be heated with the insulating material interposed therebetween is used, and the object to be heated is heated by applying an alternating current to the induction coil, and the working oil is gasified by the heat. The body to be heated and the induction coil are assembled to the bottom of the casing in such a manner as to be immersed in the working oil stored in the casing of the oil diffusion pump.

That is, according to the oil vapor generator incorporated in the oil diffusion pump of the present invention, alternating current is applied to the induction coil, not to heat the induction coil, thereby generating a flux linked in a predetermined direction of the object to be heated (in the case of the above example, in the upper and lower sides in the vertical direction), and the generated flux causes the object to be heated to generate eddy current, which is an induced current, thereby generating joule heat (induction heating). The heat generated heats the object to be heated (the object to be heated itself), thereby heating the working oil.

Therefore, since there is no member which is consumed like the heater wire, the heat generating function is not lost due to the wire breakage. In addition, since all the current is consumed in the object to be heated as the heating element, there occurs no leakage due to insulation failure and no contact failure of the terminal block due to high temperature. Further, there is an advantage that the degree of freedom in selecting the place where the induction coil is disposed is increased according to the nature of the heating source capable of locally heating the working oil.

In addition, according to the oil vapor generator incorporated in the oil diffusion pump of the present invention, the body to be heated and the induction coil are incorporated in such a manner that a part or all of them is immersed in the working oil stored in the casing of the oil diffusion pump. Therefore, even when the temperature of the induction coil increases due to the temperature rise of the object to be heated, the cooling effect of the working oil can be expected, and abnormal heating can be prevented. Therefore, the upper limit temperature of the induction coil can be kept low, for example, as compared with a system in which the induction coil is disposed outside the housing and air-cooled.

In the oil diffusion pump of the present invention, the oil vapor generator of the present invention is incorporated in the casing, and therefore all the current applied to the induction coil of the oil vapor generator can be consumed in the object to be heated which is the heating element. As a result, the heat generating element has high energy efficiency, and electric power can be saved.

By providing a flow path for the working oil for heating by operating the oil vapor generator in the casing of the oil diffusion pump, it is not necessary to provide a pipe for circulating the working oil as a flow path for the working oil on the atmospheric side (outside the casing) of the bottom of the casing, and the casing can be simplified.

By passing the working oil through the flow path heated by the heated body, preliminary heating can be performed in the middle of passage of the flow path in the middle of circulation of the working oil, and a state suitable for generation of oil vapor can be achieved.

In the oil diffusion pump according to the present invention, as described above, the oil vapor generator as the heat source is disposed in the casing, and the oil diffusion pump of the conventional structure does not have the heat source outside the casing including the heat source. Therefore, the bottom of the casing is also substantially flattened, the oil diffusion pump can be placed flat, and convenience can be improved.

Further, according to the example of the oil vapor generator of the present invention, since the upper end of the heating object as the heating element wound with the induction coil in the vertical direction is exposed upward from the oil surface of the working oil in contact therewith, the oil vapor rising from the oil surface is brought into contact with the upper portion of the inner wall of the heating object exposed upward from the oil surface, and is further heated, thereby generating the oil vapor heated sufficiently in a short time. As a result, in the oil diffusion pump incorporating such an oil vapor generator, the temperature rise of the working oil (i.e., the generation of oil vapor) can be performed in a shorter time, and the oil diffusion pump is extremely advantageous in terms of energy efficiency.

Drawings

Fig. 1 is a schematic configuration diagram showing a vacuum apparatus according to an embodiment of the present invention.

Fig. 2 is a schematic cross-sectional view showing an oil diffusion pump used in the vacuum apparatus of fig. 1.

Fig. 3 is a schematic structural cross-sectional view showing an important part of an oil vapor generator as an example used in the oil diffusion pump of fig. 2.

Fig. 4 is a schematic plan view of fig. 3 as viewed from the direction IV.

Fig. 5 is a diagram showing another example of an important part of the oil vapor generator corresponding to fig. 3.

Fig. 6 is a diagram showing another example of the arrangement of the oil vapor generator incorporated in the oil diffusion pump of this example.

Fig. 7 is a diagram showing another example of the arrangement of the oil vapor generator incorporated in the oil diffusion pump of this example.

Description of the reference symbols

1: a vacuum device; 10: a vacuum vessel; 21. 23, 25-29: a pipeline; 31: a main suction valve; 33: a leakage valve; 35: a rough pumping valve; 37: an auxiliary valve; 39: a leakage valve; 50: an oil diffusion pump; 51: a housing; 53: an ejector; 53 a: a nozzle; 55: an air intake portion; 57: an exhaust section; 58: a water-cooled tube; 59: an oil storage tank; 60: a rough pumping pump; 70: an oil vapor generator; 70 a: a support; 71: a case (an example of a body to be heated); 71 a: an inner region; 71 b: an outer region; 72: a base; 72 a: an opening part; 73: an insulating material; 75: an induction coil; 76: a magnetic shield case; 8: working oil; 90: a lower cover (flange); 92: a fastening member.

Detailed Description

An example of the present invention will be described below with reference to the drawings.

As shown in fig. 1, the vacuum apparatus 1 of this example has a vacuum vessel 10. Various devices necessary for forming (depositing) a thin film, such as a deposition source (not shown) such as an evaporation source or a sputtering source, or a substrate holder for holding a substrate to be processed, are disposed inside the vacuum chamber 10. The downstream side of the pipe 21 is connected to the vacuum vessel 10. A vacuum gauge (not shown) is connected to the vacuum container 10, and detects the air pressure (vacuum degree) in the vacuum container 10.

The downstream side of the suction line 23 is connected to the upstream side of the line 21 via a main suction valve 31. The suction line 23 is connected upstream to an intake portion 55 of the oil diffusion pump 50. The downstream side of the branch line 25 is connected to the middle of the line 21. The downstream side of the conduit 26 is connected to a middle portion of the branch conduit 25, and a leak valve 33 is provided on the upstream side of the conduit 26.

The downstream side of the line 27 is connected to the upstream side of the branch line 25 via a roughing valve 35. The upstream side of the line 27 is connected to a roughing pump 60. The downstream side of the line 28 is connected to the middle of the line 27. The upstream side of the pipe line 28 is connected to an exhaust portion 57 of the oil diffusion pump 50 via an auxiliary valve 37. The downstream side of the pipe line 29 is connected to a pipe line 28 connection portion of the pipe line 27, and a leak valve 39 is provided on the upstream side of the pipe line 29. A vacuum gauge (not shown) is connected to the pipe 28 to detect the pressure in the oil diffusion pump 50.

The vacuum apparatus 1 of the present embodiment includes a control device (not shown) for controlling the operation of the apparatus 1 in addition to the above-described configuration. The control device provided in this example includes: a main control circuit (not shown) including various processing circuits; a vacuum gauge drive circuit (not shown) connected to a vacuum gauge connected to the inside of the pipe 21; a rough pump control circuit (not shown) for controlling the operation of the rough pump 60; and an oil diffusion pump control circuit (not shown) for controlling the operation of the oil diffusion pump 50.

The main control circuit is connected with valves (a main suction valve 31, leak valves 33, 39, a rough suction valve 35, and an auxiliary valve 37) which are opened and closed at predetermined timings of the main control circuit. The roughing pump 60 is connected to the oil diffusion pump 50, and the gas discharged from the oil diffusion pump 50 through the auxiliary valve 37 is sucked into the roughing pump 60 and discharged from a path not shown.

As shown in fig. 2, the oil diffusion pump 50 of this example has a cylindrical container (casing) 51 with a closed bottom. An oil vapor generator 70 that heats and vaporizes the working oil 8 is assembled at the bottom in the casing 51, and the bottom of the casing 51 is substantially flat. Details of the oil vapor generator 70 will be described later. An injector 53 is disposed in the casing 51, and the injector 53 takes in oil vapor that has been vaporized and ascended by the working oil 8 (see fig. 3) heated by the oil vapor generator 70, and injects the oil vapor in the rough drawing direction through a nozzle 53 a. An air intake portion 55 is provided at the upper end of the casing 51, and an air discharge portion 57 is provided at the side surface of the casing 51.

Next, the operation of the oil diffusion pump 50 will be described.

When the oil vapor generator 70 is operated after the main suction valve 31 is opened, the working oil 8 is heated to a temperature near the boiling point by the oil vapor generator 70, is vaporized and filled in the injector 53, and is injected from the nozzle 53a to the inner surface of the side wall of the housing 51. The intake gas (air in the vacuum chamber 10) sucked from the intake portion 55 by this injection is sprayed in the traveling direction of the jet flow, and is discharged from the exhaust portion 57. Thereby evacuating the vacuum vessel 10. The "circle (o)" in fig. 2 schematically shows the state of oil vapor produced by gasifying oil. Then, the air inlet 55 is opened after the oil vapor is discharged from the nozzle 53a so that the working oil 8 does not enter the vacuum chamber 10.

Further, since the casing 51 is cooled by the water cooling tube 58, the oil vapor of the working oil 8 adhering to the inner wall of the casing 51 is cooled and condensed, returned to the oil reservoir 59 below the casing 51, heated again by the oil vapor generator 70, and vaporized again, thereby forming a circulating structure.

As shown in fig. 3 and 4, the oil vapor generator 70 of the present example is assembled to the bottom of the casing 51 of the oil diffusion pump 50 shown in fig. 2 via a plate-shaped bracket 70 a. The bracket 70a is supported from the atmosphere side by a lower cover (flange) 90. A heat insulator (not shown) may be interposed between the bracket 70a and the lower cover 90. The lower cover 90 is detachably attached to the bottom surface of the housing 51 by fastening members 92 such as bolts, and the bottom of the housing 51 is formed to be substantially flat on the atmosphere side.

A cylindrical case 71 as an example of a subject to be heated is disposed above the holder 70a (upward in fig. 3). In this example, the lower end of the housing 71 is supported by a base 72 having an opening 72a in the vicinity of the approximate center. The base 72 is supported by the bracket 70a via a leg portion 70b having a predetermined height, and the base 72 is disposed so as to form a gap with the bracket 70a to such an extent that the working oil 8 can pass therethrough. In this example, the gap between the base 72 and the bracket 70a formed by the leg portion 70b functions as a preheating flow path for the working oil. Further, due to the gap, the oil vapor generator 70 disposed in the casing 51 of the oil diffusion pump 50 is thermally insulated from the bottom surface of the casing 51.

A flanged housing (not shown) in which a base 72 having an opening 72a is integrated may be used as the housing 71. The base 72 may be supported above the bracket 70a via an insulating disk member (not shown) of an induction coil 75 described later.

The casing 71 in this example is made of a material to be heated. As the material to be heated, at least one of stainless steel, carbon steel and rolled steel for general structures prescribed in JIS-G3101 can be used.

As the stainless steel, for example, all kinds of SUS such as SUS304, SUS303, SUS302, SUS316L, SUS316J1, SUS316J1L, SUS405, SUS430, SUS434, SUS444, SUS429, SUS430F, and SUS302 can be used. The carbon steel includes low carbon steel with a relatively low carbon content such as soft steel material, and high carbon steel with a relatively high carbon content such as hard steel material. The general rolled steel for the structure includes SS330, SS400, SS490 and SS 540.

Among them, a mild steel material or the like having a resistivity of about 10 × 10 is preferably used^-8Omega m to 20 × 10^-8Omega m of a ferromagnetic material having a low electrical resistance, the housing 71 is formed. When the case 71 is made of a ferromagnetic material (such as mild steel) having a low electric resistance, the amount of eddy current generated by the induction coil 75 increases due to the low electric resistance, and as a result, the self-heating amount of the case 71 itself also increases, and higher efficiency is expected.

It is also preferable that the housing 71 be made of SS400, which is a general steel material and is easily available. In this case, even if the object to be heated is at a high temperature, the object is always immersed in the working oil in a vacuum atmosphere, and therefore, the object can be expected to exhibit rust prevention. In addition, the housing 71 may be formed by a molded product having a coating material on the surface of the material to be heated on the side of the induction coil 75, for example.

In this example, the base 72 for supporting the lower end of the casing 71 may be made of a material to be heated.

The housing 71 has a structure in which a peripheral wall thereof extends in a standing direction (vertical direction). The two regions, i.e., the inner region 71a and the outer region 71b of the casing 71, constitute an oil reservoir 59 (see fig. 2), and the working oil 8 is filled and stored therein. For example, in the case where the casing 71 is formed at a height of 120mm, the working oil 8 is filled so that the oil level L when the oil vapor generator 70 stops operating is about 30 mm. In this case, when the oil vapor generator 70 is started to operate, the oil level L of the working oil 8 is lowered to, for example, about 10 mm.

In this example, in order to realize induction heating (low-frequency induction heating) by low-frequency alternating current as described later, the thickness of the outer shell 71 is preferably formed in a range of 5mm to 12 mm.

In this example, the inner region 71a of the housing 71 communicates with the outer region 71b of the housing 71 via the opening 72a of the base 72 (see fig. 3).

An induction coil 75 is wound around the outer periphery of the case 71 with an insulating material 73 interposed therebetween. Thereby, the induction coil 75 is arranged on the outer periphery (an example of the vicinity) of the case 71 so as to be electrically insulated. The insulating material 73 may be formed of, for example, a polyimide film having a thickness of about 10 to 180 μm, mica, or a thermal spray obtained by thermally spraying an insulating material on the outer surface of the object to be heated.

As the lead wire constituting the induction coil 75, a heat-resistant wire having a small electric resistance and a high heat-resistant temperature and being insulated and coated is used. Examples of such electric wires include aluminum oxide wires obtained by alumite treatment of aluminum wires. The diameter of the wire constituting the induction coil 75 is preferably in the range from 2mm to 4 mm. The number of turns of the induction coil 75 is preferably in the range from 7 layers to 14 layers.

A power supply unit (not shown) for supplying power to the induction coil 75 is connected to the induction coil 75, and a power supply state of the power supply unit is controlled by a control device (not shown).

In this example, since the housing 71 and the induction coil 75 are assembled together in such a configuration that part or all of them are immersed in the hydraulic oil 8, the induction coil 75 is not abnormally heated to a temperature equal to or higher than the temperature of the hydraulic oil 8, and even when the temperature of the induction coil 75 itself rises, the cooling effect of the hydraulic oil 8 can be expected. Moreover, the temperature rise of the induction coil 75 contributes to the heating of the working oil 8, thereby contributing to energy saving.

Next, the operation of the oil vapor generator 70 will be described.

First, the power supply unit is operated to apply an alternating current to the induction coil 75. The frequency of the alternating current applied to the induction coil 75 is not particularly limited, and a low-frequency alternating current of several 10Hz to several 100Hz may be mentioned as an example, but a high-frequency alternating current may be used. Even if a high-frequency alternating current is supplied, the same effect can be obtained. Further, the current control method is adopted for controlling the power supply means, but the power control method may be adopted. Hereinafter, a case where a low-frequency ac power is applied by a current control method will be exemplified.

When the power supply unit is operated to apply an ac power of 50Hz or 60Hz commercial frequency to the induction coil 75, a flux is generated in the vertical direction of the housing 71 so as to be linked up and down, and an eddy current is generated in the housing 71 by the flux, thereby generating joule heat. The casing 71 itself is heated by this heat, thereby directly heating the working oil 8 stored in the inside area 71a of the casing 71. The oil vapor rising from the oil surface in the casing 71 is further heated by contacting a high-temperature portion of the upper portion of the casing 71 exposed upward from the oil surface, and rises in the injector 53 as sufficiently heated high-temperature oil vapor, and is ejected from the nozzle 53 a.

As described above, since the casing 51 of the oil diffusion pump 50 is cooled by the water cooling tube 58, the oil vapor of the working oil 8 adhering to the inner wall of the casing 51 is cooled and condensed, and returns to the outer region 71b (the same as the oil reservoir 59 in fig. 2) of the casing 71 below the casing 51. In this example, since the inner region 71a of the casing 71 communicates with the outer region 71b of the casing 71 through the opening 72a of the base 72 (see fig. 3), the condensed and returned hydraulic oil 8 passes through the gap between the base 72 formed by the leg portion 70b and the bracket 70a, flows through the opening 72a of the base 72 toward the inner region 71a of the casing 71, is reheated by the oil vapor generator 70, and is vaporized again to circulate the hydraulic oil 8.

In this example, when the base 72 supporting the lower end of the case 71 is made of a material to be heated, the base 72 may be used as a body to be heated together with the case 71. In this case, the working oil 8 cooled by the casing 51 and returned to the outer region 71b of the casing 71 can be preheated in the gap (i.e., the flow path) between the base 72 and the bracket 70a, and it can be expected to contribute to improvement in the evaporation efficiency of the working oil 8 when reheating is performed in the inner region 71 a.

When the holder 70a supporting the base 72 from the back surface via the leg portion 70b is made of a material to be heated, as in the case of the case 71 and the base 72, the holder 70a can be expected to function as a body to be heated.

In the oil vapor generator 70 of this example, as the heat source for the working oil 8, a heat source in which an induction coil 75 is wound around the outer periphery of a cylindrical casing 71 made of a material to be heated such as mild steel or SS400 with an insulating material 73 interposed therebetween is used, and the casing 71 is heated by applying low-frequency alternating current to the induction coil 75, and the working oil 8 is vaporized by the heat. Since the induction coil 75 is not heated, there is no problem of wire breakage, and the exhaust function of the oil diffusion pump 50 is not impaired by the heat generating function being lost due to the wire breakage. In addition, leakage due to insulation failure does not occur. Further, since the induction coil 75 itself is not a heating element but is housed in the case 51, a contact failure of the terminal block due to high-temperature deterioration does not occur.

Further, when the pedestal 72 supporting the lower end of the casing 71 is also made of a material to be heated, the pedestal 72 can be heated by applying a low-frequency alternating current to the induction coil 75, and the efficiency of gasification can be improved.

When the holder 70a supporting the base 72 from the back surface is also made of a material to be heated, the holder 70a can be used as a body to be heated by applying a low-frequency alternating current to the induction coil 75, and improvement in vaporization efficiency can be expected. In this case, a heat insulator (not shown) is interposed between the holder 70a and the lower cover 90, whereby the gasification efficiency can be further improved.

Since the oil vapor generator 70 of the present embodiment is incorporated into the oil diffusion pump 50 of the present embodiment, all the current flowing through the induction coil 75 of the oil vapor generator 70 can be consumed by the casing 71 (or the casing 71 and the base 72) itself. As a result, there are the following effects: the energy efficiency is high, energy saving is promoted, and it is possible to contribute to shortening the temperature rise time for heating the working oil 8 (the start time of the oil diffusion pump 50 can be shortened), and the like.

In the oil vapor generator 70 of this example, the main parts (the casing 71, the insulator 73, and the induction coil 75) are assembled to the bottom of the casing 51 with the lower ends thereof disposed above the flat bracket 70a, and therefore the bottom of the casing 51 can be formed to be substantially flat on the atmosphere side. As a result, the oil diffusion pump 50 that can be laid flat can also be provided, improving convenience.

In the oil vapor generator 70 of the present embodiment, the following structure is adopted: since the upper end U of the case 71, which is a heating element and around which the induction coil 75 is wound, in the vertical direction is exposed upward from the oil level L of the working oil 8 in contact therewith, the oil vapor rising from the oil level L is brought into contact with the upper portion of the case 71 exposed upward from the oil level L and is further heated, and thus sufficiently heated oil vapor is generated. As a result, in the oil diffusion pump 50 incorporating the oil vapor generator 70 of the present example, the temperature of the ejected vapor ejected from the injector 53 can be increased, which is very advantageous in achieving an increase in the exhaust gas velocity.

The above examples are described for easy understanding of the present invention, and are not described for limiting the present invention. Therefore, each element disclosed in the above-described embodiments includes all design modifications and equivalents that fall within the technical scope of the present invention.

For example, in the above example, the induction coil 75 is wound around the outer periphery of the housing 71 having a single structure formed of mild steel material, SS400, or the like with the insulating material 73 interposed therebetween, and the outer periphery of the induction coil 75 is exposed (see fig. 3), but the present invention is not limited to this embodiment, and the housing 71 may be formed in a double-layer structure of, for example, a housing inner wall and a housing outer wall, so that the outer region 71 b/the housing outer wall/the insulating material 73/the induction coil 75/the insulating material 73/the housing inner wall/the inner region 71a has a structure, and the operational effects of the present example can be achieved.

In this embodiment, since the hydraulic oil 8 stored in the outer region 71b can be heated together with the hydraulic oil 8 stored in the inner region 71a, the efficiency of heating the hydraulic oil 8 can be expected to be dramatically improved.

The cylindrical object to be heated is not limited to the illustrated plate material, and may be a structure in which a porous metal body or a mesh that can pass the working oil is wound around the object to be heated.

In the above example, the outer peripheral side of the induction coil 75 is exposed (see fig. 3), but the present invention is not limited to this embodiment, and for example, as shown in fig. 5, the following embodiment may be adopted: the induction coil 75 is substantially entirely covered with a magnetic shield case 76 made of a material different from that of the case 71 (except for a part of the lower portion, see fig. 5). Such a configuration is preferable because it can be expected to further improve the heating efficiency when the housing 71 is heated by applying an alternating current to the induction coil 75.

In the above example, the cylindrical casing 71 is used as the object to be heated constituting the oil vapor generator 70, but the present invention is not limited to this embodiment, and a plate material (not shown) such as a disc may be used as the object to be heated, and the plate material may be entirely or partially immersed in the stored working oil 8. In this case, the induction coil 75 may be disposed around the plate material, for example, on the back surface of the plate material (bottom side of the case 51) with the insulating material 73 interposed therebetween. In this manner, the operational effects of the present example can be achieved.

In the above example, 1 oil vapor generator 70 is provided in a single oil diffusion pump 50, but the present invention is not limited to this embodiment, and a plurality of oil vapor generators 70 of the present example may be disposed in the bottom portion of the casing 51 as shown in fig. 6 and 7, for example, when the oil diffusion pump is particularly considered to be large in size.

Examples

Next, examples (embodiments) of the present invention and comparative examples are explained.

[ examples ]

In this example, an oil diffusion pump 50 (fig. 2) as shown below was prepared, and evaluation was performed under the following conditions, wherein 1 oil vapor generator 70 (fig. 3) as a heating source of the working oil was incorporated in the oil diffusion pump 50.

(oil diffusion pump 50)

Diameter of the exhaust port: the thickness of the film is 250mm,

exhaust velocity: at a rate of 2900L/sec,

ultimate pressure in vacuum vessel 6.7 × 10^-6Pa (pascal) or less, and a salt thereof,

the required power: the power of the electric motor is 0.7KW,

working oil: LION S, 1L.

(oil vapor generator 70)

Height of the housing 71: the thickness of the film is 120mm,

oil level L of the working oil: 30mm (at rest) and 10mm (at work).

[ comparative example ]

In this example, an oil diffusion pump of a conventional structure in which an electric heater using a heater wire (nickel wire) as a heating source for working oil was disposed at a pump bottom portion was prepared, and evaluation was performed under the following conditions.

(conventional oil diffusion pump)

Diameter of the exhaust port: the thickness of the film is 250mm,

exhaust velocity: at a rate of 2900L/sec,

ultimate pressure in vacuum vessel 6.7 × 10^-6Pa (pascal) or less, and a salt thereof,

the required power: 2.0KW (200V),

working oil: LION S, 1L.

[ evaluation ]

The operating power was measured using the oil diffusion pumps of the respective examples. Specifically, the parts to which electric power was supplied to the nickel wire (comparative example) and the induction coil (example) were measured by a ammeter, and the electric power (power at startup and power at operation) was calculated from the voltage, current, and power factor, and the ratio between the example and the comparative example (ratio to the conventional one) was calculated. As a result, the operating power of the example was reduced by 40% at the time of startup and 65% at the time of operation, which revealed that significant power reduction could be achieved at both the time of startup and the time of operation.

The temperature (side surface, bottom surface) was measured for each oil diffusion pump. As a result, the side surface temperature (atmosphere side) of the example was 170 ℃. This was reduced by 26% as compared with comparative example (230 ℃ C.), and it was confirmed that: the heating can be concentrated on the boiler inner cylinder, which is helpful for reducing power consumption. In addition, the bottom surface temperature of the example was 120 ℃. It is found that heat loss can be significantly suppressed as compared with a comparative example (red heat state) in which the red heat heating block is exposed and has a very high temperature. In addition, it is known to be able to reach a level where damage to the floor is not a concern.

Claims (9)

1. An oil diffusion pump in which an oil vapor generator is disposed in an ejector disposed in a casing of the oil diffusion pump, the oil vapor generator is operated to heat working oil and generate oil vapor, the oil vapor in the ejector is ejected from the ejector and a high-vacuum exhaust operation is performed on an intake gas,

the oil vapor generator is provided with:

a body to be heated;

an induction coil arranged in the vicinity of the object to be heated in an electrically insulated manner; and

a power supply unit that applies an alternating current to the induction coil,

the body to be heated and the induction coil are assembled to the case in such a configuration that a part or the whole of the body to be heated and the induction coil are immersed in the working oil stored in the case,

the oil diffusion pump is configured to gasify the operating oil by operating the power supply unit to heat the object to be heated.

2. The oil diffusion pump of claim 1,

the oil vapor generator has a cylindrical body extending in the vertical direction, and an induction coil is wound around the cylindrical body with an insulating material interposed therebetween.

3. The oil diffusion pump of claim 1,

the oil vapor generator has a plate-like body to be heated, and an induction coil is disposed around the plate-like body to be heated with an insulating material interposed therebetween.

4. The oil diffusion pump according to any one of claims 1 to 3,

the casing has a working oil flow path.

5. The oil diffusion pump according to any one of claims 1 to 3,

there is no heating source on the atmospheric side of the bottom of the housing.

6. The oil diffusion pump according to any one of claims 1 to 3,

the oil diffusion pump is configured to thermally insulate an oil vapor generator disposed in the casing from a bottom surface of the casing.

7. The oil diffusion pump according to any one of claims 1 to 3,

the induction coil is composed of a heat-resistant wire which is coated with an insulation.

8. A vacuum apparatus having an exhaust device for evacuating the interior of a vacuum container,

use of the oil diffusion pump according to any one of claims 1 to 7 as the exhaust means.

9. An oil vapor generator for generating oil vapor by heating working oil in an oil diffusion pump having a casing and an ejector,

the oil vapor generator is used by being assembled to a casing inside the oil diffusion pump,

the oil vapor generator is provided with:

a heated body disposed in the injector so that a part or the whole of the heated body is immersed in the working oil stored in the case;

an induction coil disposed in the vicinity of the body to be heated so as to be electrically insulated so that a part or the whole of the induction coil is immersed in the working oil stored in the case; and

a power supply unit that applies an alternating current to the induction coil,

heating the heated body by operating the power supply unit, thereby gasifying the operating oil.