OIL DIFFUSION PUMP AND OIL VAPOR GENERATOR USED THEREFOR

Abstract

Provided is an oil diffusion pump equipped with an oil vapor generator capable of eliminating a problem that arises when a heater wire is used as a heating source for a hydraulic oil. The oil diffusion pump is a vacuum pump in which an oil vapor generator (70) is arranged in a casing (51) and operated to vaporize a hydraulic oil (8) and produce oil vapor, and this oil vapor is sprayed from a jet (53, 53a) to exhaust an intake air. The oil vapor generator (70) comprises a tubular case (71) (object to be heated) extending in an upright direction, an induction coil (75) wound around the tubular member (71) via an insulating material (73), and a power supply means for applying an alternating current to the induction coil (75). The case (71) and the coil (75) are installed in the casing so as to be immersed in the hydraulic oil (8) stored in the casing (51). The power supply means is operated to apply an alternating current to the induction coil (75) to heat the case (71) itself and thus vaporize the hydraulic oil (8).

Claims

1. An oil diffusion pump, configured that an oil vapor generator is arranged in a jet provided in a casing, the oil vapor generator is operated to heat a hydraulic oil to produce oil vapor, and the oil vapor in the jet is sprayed from the jet to exhaust an intake air in a high vacuum, wherein: the oil vapor generator comprises an object to be heated, an induction coil arranged near the object to be heated in an electrically insulated way, and a power supply means for applying an alternating current to the induction coil; wherein the object to be heated and induction coil are installed in the casing such that a part or all thereof is immersed in the hydraulic oil stored in the casing; and the power supply means is operated to heat the object to be heated and vaporize the hydraulic oil.

2. The oil diffusion pump according to claim 1, wherein the object to be heated in the oil vapor generator is tubular and extending in an upright direction, and an induction coil is wound around the tubular object to be heated via an insulating material provided therebetween.

3. The oil diffusion pump according to claim 1, wherein an object to be heated in the oil vapor generator has a plate shape, and an induction coil is arranged around the plate-shaped object to be heated via an insulating material provided therebetween

4. The oil diffusion pump according to claim 1, wherein a flow path for a hydraulic oil is provided in the casing.

5. The oil diffusion pump according to claim 1, wherein a heating source is not provided on an atmosphere-side bottom portion of the casing.

6. The oil diffusion pump according to claim 1, configured to thermally insulate between the oil vapor generator arranged in the casing and a bottom surface of the casing.

7. The oil diffusion pump according to claim 1, wherein the induction coil is formed by a heat-resistant electric wire covered with an insulator.

8. A vacuum device comprising an exhaust device for evacuating inside a vacuum container, wherein the oil diffusion pump according to claim 1 is used as the exhaust device.

9. An oil vapor generator for heating a hydraulic oil to produce oil vapor in an oil diffusion pump comprising a casing and a jet, installed and used in the casing in the oil diffusion pump, comprising: an object to be heated provided in the jet such that a part or all thereof is immersed in the hydraulic oil stored in the casing, an induction coil provided near the object to be heated in an electrically insulated way such that a part or all thereof is immersed in the hydraulic oil stored in the casing, and a power supply means for applying an alternating current to the induction coil; and configured to heat the object to be heated by operating the power supply means and thus vaporize the hydraulic oil.

10. The oil diffusion pump according to claim 2, wherein a flow path for a hydraulic oil is provided in the casing.

11. The oil diffusion pump according to claim 3, wherein a flow path for a hydraulic oil is provided in the casing.

12. The oil diffusion pump according to claim 2, wherein a heating source is not provided on an atmosphere-side bottom portion of the casing.

13. The oil diffusion pump according to claim 3, wherein a heating source is not provided on an atmosphere-side bottom portion of the casing.

14. The oil diffusion pump according to claim 4, wherein a heating source is not provided on an atmosphere-side bottom portion of the casing.

15. The oil diffusion pump according to claim 2, configured to thermally insulate between the oil vapor generator arranged in the casing and a bottom surface of the casing.

16. The oil diffusion pump according to claim 3, configured to thermally insulate between the oil vapor generator arranged in the casing and a bottom surface of the casing.

17. The oil diffusion pump according to claim 4, configured to thermally insulate between the oil vapor generator arranged in the casing and a bottom surface of the casing.

18. The oil diffusion pump according to claim 2, wherein the induction coil is formed by a heat-resistant electric wire covered with an insulator.

19. The oil diffusion pump according to claim 3, wherein the induction coil is formed by a heat-resistant electric wire covered with an insulator.

20. The oil diffusion pump according to claim 4, wherein the induction coil is formed by a heat-resistant electric wire covered with an insulator.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0027] FIG. 1 is a schematic diagram showing a vacuum device according to an embodiment of the present invention.

[0028] FIG. 2 is a sectional schematic diagram showing an oil diffusion pump as an example used in the vacuum device in FIG. 1.

[0029] FIG. 3 is a sectional schematic diagram showing a key part of an oil vapor generator as an example used in the oil diffusion pump in FIG. 2.

[0030] FIG. 4 is a schematic plan view seeing FIG. 3 from the IV direction.

[0031] FIG. 5 is a view showing another example of a key part of an oil vapor generator corresponding to FIG. 3.

[0032] FIG. 6 is a view showing another example of an arrangement mode of an oil vapor generator incorporated in the oil diffusion pump of the present example.

[0033] FIG. 7 is a view showing another example of an arrangement mode of an oil vapor generator incorporated in the oil diffusion pump of the present example.

DESCRIPTION OF NUMERICAL NOTATIONS

[0034] 1 . . . vacuum device, 10 . . . vacuum container, 21, 23 and 25 to 29 . . . pipe, 31 . . . main evacuation valve, 33 . . . leak valve, 35 . . . rough evacuation valve, 37 . . . auxiliary valve, 39 . . . leak valve,

[0035] 50 . . . oil diffusion pump, 51 . . . casing, 53 . . . jet, 53a . . . jet nozzle, 55 . . . intake part, 57 . . . exhaust part, 58 . . . water cooling pipe, 59 . . . oil storage,

[0036] 60 . . . rough evacuation pump,

[0037] 70 . . . oil vapor generator, 70a . . . pedestal, 71 . . . case (an example of an object to be heated), 71a . . . inner region, 71b . . . outer region, 72 . . . base, 72a . . . opening portion, 73 . . . insulating material, 75 . . . induction coil, 76 . . . magnetic shield case,

[0038] 8 . . . hydraulic oil,

[0039] 90 . . . lower lid (flange), 92 . . . engaging means

EXEMPLARY MODE FOR CARRYING OUT THE DISCLOSED SUBJECT MATTER

[0040] Below, an example of the present invention will be explained based on the drawings.

[0041] As shown in FIG. 1, a vacuum device 1 of the present example comprises a vacuum container 10. Inside the vacuum container 10, a variety of equipment necessary for forming a thin film (film formation) in general are arranged, such as a film formation source (illustration omitted) like a vapor source and sputter source, and a substrate holder for holding a substrate to be subjected to a treatment, etc. The vacuum container 10 is connected with a downstream side of a pipe 21. The vacuum container 10 is connected with a vacuum gauge (illustration omitted) to detect an atmospheric pressure (vacuum degree) inside the vacuum container 10.

[0042] The upstream side of the pipe 21 is connected to a downstream side of the intake pipe 23 via a main evacuation valve 31. The upstream side of the intake pipe 23 is connected to an intake part 55 of an oil diffusion pump 50. The middle of the pipe 21 is connected to the downstream side of a branch pipe 25. The middle of the branch pipe 25 is connected to the downstream side of a pipe 26, and a leak valve 33 is provided on the upstream side of the pipe 26.

[0043] The upstream side of the branch pipe 25 is connected to the downstream side of the pipe 27 via a rough evacuation valve 35. The upstream side of the pipe 27 is connected to a rough evacuation pump 60. The middle of the pipe 27 is connected to the downstream side of the pipe 28. The upstream side of the pipe 28 is connected to an exhaust part 57 of the oil diffusion pump 50 via an auxiliary valve 37. A joint part of the pipe 27 and the pipe 28 is connected to the downstream side of the pipe 29, and the upstream side of the pipe 29 is provided with a leak valve 39. A vacuum gauge (illustration omitted) is connected inside the pipe 28 to detect a pressure inside the oil diffusion pump 50.

[0044] In addition to the above, the vacuum device 1 of the present example is provided with a control device (illustration omitted) for controlling an operation of the device 1. The control device provided in the present example is configured to comprise a main control circuit (illustration omitted) including a variety of processing circuits, a vacuum gauge drive circuit (illustration omitted) connected with a vacuum gauge connected inside the pipe 21, a rough evacuation pump control circuit (illustration omitted) for operating and controlling the rough evacuation pump 60 and an oil diffusion pump control circuit (illustration omitted) for operating and controlling the oil diffusion pump 50.

[0045] The main control circuit is connected to respective valves (main evacuation valve 31, leak valves 33 and 39, rough evacuation valve 35 and auxiliary valve 37), and those valves are opened/closed in accordance with a predetermined sequence of the main control circuit. The oil diffusion pump 50 is connected to a rough evacuation pump 60, and an exhaust air from the oil diffusion pump 50 through the auxiliary valve 37 is sucked by the rough evacuation pump 60 and exhausted from a not shown path.

[0046] As shown in FIG. 2, the oil diffusion pump 50 of the present example has a tubular container (casing) 51 having a closed bottom. On the bottom inside the casing 51, an oil vapor generator 70 for heating and vaporizing a hydraulic oil 8 is installed. The bottom of the casing 51 is formed to be substantially planar. The detailed explanation on the oil vapor generator 70 will be made later on. Inside the casing 51, a jet 53 is arranged where oil vapor, which is the hydraulic oil 8 (refer to FIG. 3) heated by the oil vapor generator 70, vaporized and convected upward is taken in and sprayed through a nozzle 53a to the rough evacuation direction. The upper end of the casing 51 is provided with an intake part 55 and the side surface of the casing 51 is provided with an exhaust part 57.

[0047] Next, an operation of the oil diffusion pump 50 will be explained.

[0048] When the oil vapor generator 70 is operated after opening the main evacuation valve 31, the hydraulic oil 8 is heated to around a boiling temperature to be oil vapor by the oil vapor generator 70 and fills inside the jet 53 and is sprayed from the nozzle 53a to the inner sidewall of the casing 51. An air taken in from the intake part 55 (air inside the vacuum container 10) is blown to the jet flow direction by the spray and discharged from the exhaust part 57. Thereby, evacuation inside the vacuum container 10 is carried out. In FIG. 2, circle () schematically indicates a state of oil vapor, which is vaporized oil. Note that after spraying the oil vapor from the jet nozzle 53a, the intake part 55 is opened so that the hydraulic oil 8 does not come into the vacuum container 10.

[0049] Also, the mechanism is that the casing 51 is cooled by the water cooling pipe 58, so that the oil vapor of the hydraulic oil 8 adhered to the inner wall of the casing 51 is cooled and condensed, returns to an oil storage 59 at a lower portion of the casing 51 and reheated by the oil vapor generator 70 to circulate.

[0050] As shown in FIG. 3 and FIG. 4, the oil vapor generator 70 in the present example is installed via a plate-shaped pedestal 70a on the bottom portion inside the casing 51 of the oil diffusion pump 50 shown in FIG. 2. The pedestal 70a is supported by a lower lid (flange) 90 from the atmosphere side. A heat insulating material (illustration omitted) may be provided between the pedestal 70a and the lower lid 90. The lower lid 90 is attached to the bottom surface of the casing 51 by an engaging means 92, such as a bolt, in a detachable way, and the atmosphere-side bottom portion of the casing 51 is formed to be substantially planar.

[0051] Above the pedestal 70a (the upper direction in FIG. 3), a tubular case 71 is arranged as an example of an object to be heated. A lower end of the case 71 is supported by a base 72 having an opening portion 72a near its substantial center. The base 72 is supported by the pedestal 70a via leg portions 70b having a predetermined height, so that it is arranged to form a space of allowing the hydraulic oil 8 to flow between the pedestal 70a and itself. In this example, the space between the base 72 and the pedestal 70a formed by the leg portions 70b functions as a preheating flow path of the hydraulic oil. Also, by providing this space, it is configured to secure heat insulation between the oil vapor generator 70 arranged in the casing 51 of the oil diffusion pump 50 and the bottom surface of the casing 51.

[0052] As the case 71, a flanged case (illustration omitted) formed integrally with the base 72 having an opening portion 72a may be used, as well. Alternatively, the base 72 may be supported above the pedestal 70a via an insulating disk member (illustration omitted) of an induction coil 75, which will be explained later on.

[0053] The case 71 in the present example is formed by a material to be heated. As the material to be heated, at least any one of stainless steel, carbon steel, rolled steel for general structure specified in JIS-G3101 may be used.

[0054] As stainless steel, all kinds of SUS may be used, for example, SUS304, SUS303, SUS302, SUS316, SUS316L, SUS316J1, SUS316J1L, SUS405, SUS430, SUS434, SUS444, SUS429, SUS430F AND SUS302, etc. Carbon steel includes low carbon steel with a little carbon amount, such as soft steel materials, and high carbon steel with a large amount of carbon, such as hard steel materials. The rolled steel for general structure includes SS330, SS400, SS490 and SS540.

[0055] Among them, it is preferable to configure the case 71 with a ferromagnetic material having low electric resistance with resistivity of 1010.sup.8 m to 2010.sup.8 m or so, such as a soft steel material. When the case 71 is configured by a ferromagnetic material (soft steel, etc.) having low electric resistance, since electric resistance is low, an eddy current amount generated by application to the induction coil 75 becomes large, consequently, a self-heating amount by the case 71 itself becomes large and a high efficiency can be expected.

[0056] It is also preferable to configure the case 71 by an easily available general steel SS400. In that case, even if it is an object to be heated, whose temperature becomes high, a rust prevention property can be expected because it is always immersed in the hydraulic oil in a vacuum atmosphere. Other than the above, the case 71 may be formed, for example, by a mold provided with a clad member on a surface on the induction coil 75 side of a material to be heated.

[0057] In the present example, the base 72 for supporting the lower end of the case 71 may be formed by a material to be heated.

[0058] The case 71 is configured to have a circumferential wall extending in the upright direction (vertical direction). In the case 71, both of an inner region 71 and outer region 71b configure the oil storage 59 (refer to FIG. 2), where the hydraulic oil 8 is filled and stored. For example, when forming the case 71 to be 120 mm height, the hydraulic oil 8 is filled such that an oil surface L level of the oil vapor generator 70 becomes 30 mm or so during an operation stop. In that case, when the operation of the oil vapor generator 70 starts, the oil surface L level of the hydraulic oil 8 decreases, for example, to 10 mm or so.

[0059] In the present example, it is preferable that the case 71 is formed to have a thickness in a range of 5 mm to 12 mm so as to realize induction heating with a low frequency alternating current (low frequency induction heating).

[0060] Note that, in the present example, the inner region 71a of the case 71 is connected with the outer region 71b of the case 71 via the opening portion 72a of the base 72 (refer to FIG. 3).

[0061] An induction coil 75 is wound around the case 71 via an insulating material 73. Thereby, the induction coil 75 is arranged in an electrically insulated way on the outer circumference (an example of periphery) of the base 71. The insulating material 73 may be configured, for example, by a polyimide film, mica or thermal spraying material of an insulating material to the outer surface of an object to be heated, etc. having a thickness of 10 m to 180 m or so.

[0062] As a conducting wire composing the induction coil 75, an insulator-coated heat-resistant electric wire having small electric resistance and high heat resistance may be used. For example, an alumite electric wire, which is an aluminum wire subjected to an anodizing treatment, may be mentioned. A diameter of the conducting wire constituting the induction coil 75 is preferably in a range of 2 mm to 4 mm. The number of wound layers of the induction coil 75 is preferably in a range of 7 to 14 layers.

[0063] The induction coil 75 is connected with a power supply means (illustration omitted) for providing power to the induction coil 75 and a condition of power supply by the power supply means is controlled by a control device.

[0064] In the present example, since the induction coil 75 together with the case 71 is installed in an arrangement so that a part or all thereof is immersed in the hydraulic oil 8, the induction coil 75 is not heated abnormally to be higher than a temperature of the hydraulic oil 8 and, even when the temperature of the induction coil 75 itself becomes high, a cooling effect by the hydraulic oil 8 can be expected. Furthermore, temperature rise of the induction coil 75 helps to heat the hydraulic oil 8, which contributes to the energy saving effect.

[0065] Next, an operation of the oil vapor generator 70 will be explained.

[0066] First, the power supply means is operated to apply an alternating current to the induction coil 75. A frequency of the alternating current to be applied to the induction coil 75 is not particularly limited and low frequency currents of several tens of Hz to several hundreds of Hz may be mentioned, or it may be a high frequency alternating current. The same effects can be obtained by supplying a high frequency alternating current, as well. Also, the current control method is used to control the power supply means, however, it may be a power control method. The case of applying a low frequency alternating current by using the current control method will be explained as an example below.

[0067] When operating the power supply means to apply to the induction coil 75 an alternating current with a commercial frequency of 50 Hz or 60 Hz, a magnetic flux interlinked with the vertical upright direction of the case 71 arises, and the flux generates an eddy current in the case 71 so as to generate Joule heat. This heat heats the case 71 itself and, thereby the hydraulic oil 8 stored in the inner region 71a in the case 71 is heated directly. An oil vapor rising from the oil surface in the case 71 is furthermore heated by contacting with a high-temperature portion at the upper portion of the case 71 exposed above the oil surface, becomes a sufficiently heated high-temperature oil vapor, convects upward inside the jet 53 and is sprayed from the nozzle 53a.

[0068] As explained above, since the casing 51 of the oil diffusion pump 50 is cooled by the water-cooling pipe 58, oil vapor of the hydraulic oil 8 adhered to the inner wall of the casing 51 is cooled to be condensed and returns to the outer region 71b of the case 71 (same as the oil storage chamber 59 in FIG. 2). In the present example, since the inner region 71a of the case 71 is connected with the outer region 71b of the case 71 via the opening portion 72a of the base 72 (refer to FIG. 3), the hydraulic oil 8 after condensing and returning passes through the space between the base 72 and the pedestal 70a formed by the leg portions 70b, flows to the inner region 71a in the case 71 through the opening portion 72a of the base 72, reheated by the oil vapor generator 70, and the hydraulic oil 8 is vaporized again so as to circulate.

[0069] In the present case, when the base 72 for supporting the lower end of the case 71 is formed by a material to be heated, the base 72 portion together with the case 71 can be also used as an object to be heated. In that case, the hydraulic oil 8 cooled in the casing 51 and returned to the outer region 71b of the case 71 can be preheated in the space between the base 72 and the pedestal 70a (namely, the flow path), so that it can contribute to an improvement of efficiency in vaporizing the hydraulic oil 8 when reheating in the inner region 71a.

[0070] When the pedestal 70a for supporting the base 72 from the back surface via the leg portions 70b is formed by a material to be heated as well as the case 71 and the base 72, it is expected that the pedestal 70a also serves as an object to be heated.

[0071] In the oil vapor generator 70 of the present example, the heating source for the hydraulic oil 8 to be used is obtained by winding the induction coil 75 around the tubular case 71 formed by a material to be heated, such as a soft steel and SS400, via an insulating material 73 provided therebetween, the case 71 is heated by applying a low frequency alternating current to the induction coil 75, and the heat vaporizes the hydraulic oil 8. Because the induction coil 75 is not heated, a disconnection problem is prevented, which means that the exhaustion function of the oil diffusion pump 50 is not lost due to a loss of the heating function caused by disconnection. Also, an electric leakage caused by an insulation defect does not arise. Furthermore, the induction coil 75 itself does not become a heating body and a contact defect of a terminal board due to a deterioration caused by a high temperature does not arise because it can be accommodated in the casing 51.

[0072] Furthermore, when the base 72 supporting the lower end of the case 71 is also formed by a material to be heated, the base 72 can be also heated by applying a low frequency alternating current to the induction coil 75 and the efficiency of vaporization can be improved.

[0073] When the pedestal 70a supporting the base 72 from lower side surface is also formed by a material to be heated, there is a possibility that the pedestal 70a can be used as an object to be heated by applying a low frequency alternating current to the induction coil 75, so that an improvement of the vaporization efficiency can be expected. In that case, by providing a heat shielding material (illustration omitted) between the pedestal 70a and the lower lid 90, the vaporization efficiency may be improved furthermore.

[0074] Since the oil vapor generator 70 of the present example is installed in the oil diffusion pump 50 of the present example, all of the current supplied to the induction coil 75 of the oil vapor generator 70 can be consumed by the case 71 (or the case 71 and the base 72). Consequently, there arise effects of improving the energy efficiency, accelerating energy saving and contributing to a reduction of heat rising time of the hydraulic oil 8 (shortening start-up time of the oil diffusion pump 50), etc.

[0075] In the oil vapor generator 70 of the present example, a key part thereof (the case 71, insulating material 73 and induction coil 75) is installed at the bottom portion of the casing 51 in a state where the lower end is arranged above the pedestal 70a, so that the atmosphere-side bottom portion of the casing 51 can be formed to be substantially planar. As a result, the oil diffusion pump 50 able to be placed flatly can be provided and the convenience is enhanced.

[0076] The oil vapor generator 70 of the present example is configured that the upper end U in the upright direction of the case 71 as a heating body wound by the induction coil 75 is exposed above an oil surface L of the contacting hydraulic oil 8, so that oil vapor rising from the oil surface L is furthermore heated as a result of contacting with the upper portion of the case 71 exposed above the oil surface L and sufficiently heated oil vapor is generated. Consequently, in the oil diffusion pump 50 incorporating the oil vapor generator 70 of the present example, the temperature of the vapor to be sprayed from the jet 53 can be made high, which is extremely advantageous for attaining an improvement of an exhausting speed.

[0077] Note that the examples above are described to facilitate understanding of the present invention and are not to limit the present invention. Accordingly, respective elements disclosed in the above examples include all design modifications and equivalents belonging to the technical scope of the present invention.

[0078] For example, in the example above, the induction coil 75 was provided via the insulating material 73 around the single-structured case 71 formed by a soft steel material or SS400, etc. and the outer circumferential part of the induction coil 75 was exposed (refer to FIG. 3), however, it is not limited to this mode and the effects of the present example may be also obtained, for example, by forming the case 71 to have a double structure of a case inner wall and a case outer wall and configuring to have the structure of an outer region 71b/case outer wall/insulating material 73/induction coil 75/insulating material 73/case inner wall/inner region 71a.

[0079] In that mode, a hydraulic oil 8 stored in the outer region 71b can be also heated together with the hydraulic oil 8 stored in the inner region 71a, so that a drastic improvement of the heating efficiency of the hydraulic oil 8 can be expected.

[0080] The tubular object to be heated is not limited to the plate material as in the example and may be a wound porous metal body or net, through which the hydraulic oil can pass through in the configuration using a material to be heated.

[0081] In the above-explained example, the outer circumferential side of the induction coil 75 was exposed (refer to FIG. 3) but it is not limited to this mode and, for example, as the mode shown in FIG. 5, almost all of the induction coil 75 (except for a part at a lower portion: refer to FIG. 5) may be covered with a magnetic shield case 76 formed by a different material from that of the case 71. That mode is preferable as a further improvement of the heating efficiency can be expected thereby when heating the case 71 by applying an alternating current to the induction coil 75.

[0082] In the above-explained example, the tubular case 71 was used as a material to be heated to constitute the oil vapor generator 70, however, it is not limited to this mode and a plate material (illustration omitted), such as a disk shape, may be used as a material to be heated and arranged so that a part or a whole of the plate material may be immersed in the stored hydraulic oil 8. In that case, the induction coil 75 may be provided around the plate material, for example, on the back surface of the plate material (the bottom portion side of the casing 51) via an insulating material 73. The effects of the present example can be also obtained in such a mode.

[0083] Also, one oil vapor generator 70 was provided to single oil diffusion pump 50 in the example explained above, however, it is not limited to this mode and, particularly in the case of seeking for a larger oil diffusion pump, for example as shown in FIG. 7 and FIG. 8, a plurality of oil vapor generators 70 of the present example may be provided at the bottom of the casing 51.

EXAMPLES

[0084] Next, an explanation will be made on an actual example (example) and a comparative example of the present invention.

Example

[0085] In the present example, an oil diffusion pump 50 (FIG. 2) explained below incorporating the oil vapor generator 70 (FIG. 3) as a heating source for a hydraulic oil was prepared and evaluated under the condition below.

[0086] (Oil Diffusion Pump 50) [0087] Diameter of Exhaust Port: 250 mm [0088] Exhaust Rate: 2900 L/sec. [0089] Ultimate Pressure in Vacuum Container: 6.710.sup.6 Pa or lower [0090] Necessary Electric Power: 0.7 KW [0091] Hydraulic Oil: Lion S, 1 L

[0092] (Oil Vapor Generator 70) [0093] Height of Case 71: 120 mm [0094] Oil Surface L Level of Hydraulic oil: 30 mm (during stop), 10 mm (during operation)

Comparative Example

[0095] In the present example, an oil diffusion pump of the conventional configuration was prepared, wherein an electric heater using a heater wire (nichrome wire) as a heating source for hydraulic oil was arranged at the bottom of the pump, and evaluation was made under the condition below.

[0096] (Conventional Oil Diffusion Pump) [0097] Diameter of Exhaust Port: 250 mm [0098] Exhaust Rate: 2900 L/sec. [0099] Ultimate Pressure in Vacuum Container: 6.710.sup.6 Pa or lower [0100] Necessary Electric Power: 2.0 KW (200 V) [0101] Hydraulic Oil: Lion S, 1 L

[Evaluation]

[0102] An operation power was measured by using an oil diffusion pump in each example. Specifically, power supply parts to the nichrome wire (the comparative example) and induction coil (the example) were measured by a clamp ammeter, a power (start-up power, operation power) was calculated from the voltage, current and power factor, and a ratio of the example to the comparative example (comparison with conventional one) was calculated. The result was that the operation power in the example was decreased by 40% at start-up and decreased by 65% during operation from those in the conventional one, and it revealed that a significant power reduction was attained both at start-up and in operation.

[0103] Temperatures (side surface and bottom surface) were measured on the oil diffusion pumps in the respective examples. The result was 170 C. on the side surface (on the atmosphere side) in the example. It was decreased by 26% comparing with that in the comparative example (230 C.), and it was confirmed that a boiler inner tube was heated intensively, which can contribute to a power reduction. Also, the bottom surface temperature in the example was 120 C. It turned out that a heat loss was suppressed significantly comparing with the comparative example (red heat state), wherein a red heat heater block was exposed and at a very high temperature. It also turned out that a level of not needing to consider damages on the floor was attainable.