Vacuum pump
阅读说明:本技术 真空泵 (Vacuum pump ) 是由 桥本建治 井上英晃 柴山浩司 铃木敏生 于 2018-03-27 设计创作,主要内容包括:本发明提供一种真空泵,其包括具有简便、冷却效率良好、生产率良好的冷却结构的壳体。本发明的一个实施方式的真空泵具有泵壳体和冷却管。所述泵壳体由铸铁构成。所述冷却管具有外周面和内周面,并由不锈钢构成。所述冷却管贯通所述泵壳体,与所述泵壳体密接的所述外周面由敏化层构成。该真空泵是将由铸铁构成的泵壳体铸造在由不锈钢构成的冷却管的周围而形成的。在冷却管的外周面设置敏化层,敏化层与泵壳体密接,泵壳体高效地被冷却。(The invention provides a vacuum pump, which comprises a casing with a simple cooling structure with good cooling efficiency and good productivity. A vacuum pump of one embodiment of the present invention has a pump housing and a cooling tube. The pump housing is constructed of cast iron. The cooling tube has an outer circumferential surface and an inner circumferential surface, and is composed of stainless steel. The cooling pipe penetrates the pump housing, and the outer peripheral surface that is in close contact with the pump housing is formed of a sensitizing layer. The vacuum pump is formed by casting a pump casing made of cast iron around a cooling pipe made of stainless steel. A sensitizing layer is provided on the outer peripheral surface of the cooling tube, and the sensitizing layer is in close contact with the pump casing, so that the pump casing is efficiently cooled.)
1. A vacuum pump, having:
a pump housing made of cast iron; and
and a cooling pipe which has an outer peripheral surface and an inner peripheral surface, is made of stainless steel, penetrates the pump housing, and has a sensitizing layer on the outer peripheral surface which is in close contact with the pump housing.
2. A vacuum pump as claimed in claim 1,
further comprising: a first screw rotor and a second screw rotor housed in the pump housing,
the first screw rotor has a helical first tooth portion, and the second screw rotor has a helical second tooth portion meshing with the first tooth portion.
3. A vacuum pump according to claim 1 or 2,
the cooling pipe has a first cooling pipe portion and a second cooling pipe portion juxtaposed with the first cooling pipe portion,
the first screw rotor and the second screw rotor are sandwiched by the first cooling pipe portion and the second cooling pipe portion.
4. A vacuum pump as claimed in claim 3,
the cooling pipe further includes a connecting pipe portion that connects the first cooling pipe portion and the second cooling pipe portion and is provided outside the pump housing,
the first cooling pipe portion, the connecting pipe portion, and the second cooling pipe portion are sequentially connected in series and are integrally formed.
5. A vacuum pump according to any of claims 1 to 4,
the thickness of the cooling pipe is 1mm to 5 m.
6. A vacuum pump according to any of claims 1 to 5,
the thickness of the sensitiser layer is 0.3 mm.
7. A vacuum pump according to any of claims 1 to 6,
the value obtained by dividing the volume of the pump housing by the product obtained by multiplying the thickness of the cooling pipe by the area where the cooling pipe and the pump housing are in contact with each other is 30 or more and 300 or less.
Technical Field
The present invention relates to a vacuum pump.
Background
As a positive displacement dry vacuum pump, for example, a twin-screw pump is known. Such a screw pump includes a pair of screw rotors, a casing that houses the pair of screw rotors, and a drive mechanism that rotates the pair of screw rotors. When the pair of screw rotors rotate, gas is sent from the inlet port of the housing to the outlet port, and the gas in the vacuum chamber is discharged (see, for example, patent document 1).
Sometimes the casing is heated to a high temperature in a case where the pair of screw rotors operate for a long time. Therefore, the casing is usually cooled by air cooling or water cooling. In addition, when the vacuum pump is desired to be compact, it is important how to form a simple and efficient cooling structure in a casing that is a part thereof.
Disclosure of Invention
Problems to be solved by the invention
Since the cooling structure needs a simple cooling structure, it is necessary to adopt a circulation type cooling structure. In addition, as the cooling medium, water, which has higher cooling efficiency than oil or coolant and is easy to handle, is generally used. Further, if the cooling medium is water, a cooling pipe made of stainless steel having high resistance to water is suitable. However, when a cooling pipe made of stainless steel is used, it is important to uniformly bring the cooling pipe made of stainless steel into close contact with the housing and to prevent sensitization to the inner circumferential surface of the cooling pipe made of stainless steel.
In view of the above circumstances, an object of the present invention is to provide a vacuum pump including a casing having a cooling structure which is simple, excellent in cooling efficiency, and excellent in productivity.
Means for solving the problems
In order to achieve the above object, a vacuum pump according to one embodiment of the present invention includes: a pump housing and a cooling tube. The pump housing is made of cast iron. The cooling pipe has an outer circumferential surface and an inner circumferential surface, and is made of stainless steel. The cooling pipe penetrates the pump housing, and the outer surface that is in close contact with the pump housing is formed of a sensitizing layer.
The vacuum pump is formed by casting a pump casing made of cast iron around a cooling pipe made of stainless steel. Thus, a vacuum pump having a cooling pipe penetrating a pump housing is simply formed. Further, a sensitizing layer is provided on the outer peripheral surface of the cooling tube, and the sensitizing layer is in close contact with the pump casing, whereby the pump casing is efficiently cooled.
The vacuum pump may further include a first screw rotor and a second screw rotor housed in the pump housing, the first screw rotor having a helical first tooth portion, the second screw rotor having a helical second tooth portion meshing with the first tooth portion.
In the vacuum pump, even if the pair of screw rotors are operated for a long time, the pump housing can be efficiently cooled by the cooling pipe provided in the pump housing.
In the vacuum pump, the cooling pipe includes a first cooling pipe portion and a second cooling pipe portion arranged in parallel with the first cooling pipe portion. The first screw rotor and the second screw rotor are sandwiched by the first cooling pipe portion and the second cooling pipe portion.
In the vacuum pump, the first cooling pipe portion and the second cooling pipe portion are provided in the pump housing so as to sandwich the pair of screw rotors. Thereby, the pump casing is uniformly cooled.
In the vacuum pump, the cooling pipe further includes a connecting pipe portion that connects the first cooling pipe portion and the second cooling pipe portion and is provided outside the pump housing. The first cooling pipe portion, the connecting pipe portion, and the second cooling pipe portion are sequentially connected in series and are integrally formed.
In the vacuum pump, the cooling pipe is integrally formed by connecting the first cooling pipe portion, the connecting pipe portion, and the second cooling pipe portion in series, and therefore the cooling pipe has a simple structure.
In the vacuum pump, the cooling pipe may have a thickness of 1mm to 5 mm.
In the vacuum pump of this type, since the thickness of the cooling pipe is set to 1mm or more and 5mm or less, the cooling pipe made of stainless steel is not melted to the inner peripheral surface at the time of casting, and the outer peripheral surface is appropriately melted, and the outer peripheral surface of the cooling pipe is in close contact with the pump housing.
In the vacuum pump, the thickness of the sensitizing layer may be 0.3 mm.
In the vacuum pump of this type, since the cooling pipe is in contact with the molten cast iron at the time of casting the pump casing, the outer peripheral surface of the cooling pipe is sensitized and the inner peripheral surface thereof is not sensitized even if the surface of the cooling pipe is heated. Thereby, a sensitizing layer is formed on the outer peripheral surface of the cooling pipe.
In the vacuum pump, a value obtained by dividing the volume of the pump housing by a product obtained by multiplying the thickness of the cooling pipe by the area where the cooling pipe contacts the pump housing may be 30 or more and 300 or less.
In the vacuum pump of this type, since the value obtained by the division is set to 30 to 300, the cooling pipe made of stainless steel is not melted to the inner peripheral surface during casting, and the outer peripheral surface of the cooling pipe is in close contact with the pump housing.
Effects of the invention
As described above, according to the present invention, there is provided a vacuum pump including a casing having a cooling structure which is simple, excellent in cooling efficiency, and excellent in productivity.
Drawings
Fig. 1 is a schematic perspective view showing a main part of a vacuum pump according to the present embodiment.
Fig. 2 is a schematic cross-sectional view showing an internal main portion of the vacuum pump of the present embodiment.
Fig. 3 is an electron probe microanalyzer result of the vicinity of the outer peripheral surface of the cooling tube.
Fig. 4 is a schematic diagram showing a modification of the cooling pipe of the present embodiment.
Detailed Description
Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each drawing, XYZ-axis coordinates are sometimes introduced.
Fig. 1 is a schematic perspective view showing a main part of a vacuum pump according to the present embodiment.
Fig. 1 shows a
A pump chamber 10p is provided inside the
The
The first housing portion 11 and the
The material of the
A part of the cooling pipe 20A penetrates the
The first
The cooling pipe 20A has a U-shaped outer shape when viewed from the X-axis direction. Here, the first screw rotor 31 and the second screw rotor 32 are sandwiched by the first
The first
For example, a part of the cooling tube 20A is previously set in a mold for forming the
The cooling pipe 20A has an outer
Thereby, the outer
In other words, when the
Fig. 2 is a schematic cross-sectional view showing an internal main portion of the vacuum pump of the present embodiment.
A cross-section in the X-Y plane at a position along line a1-a2 of fig. 1 is shown in fig. 2. Fig. 2 shows the drive mechanism 40 and the intermediate case 50, which are not shown in fig. 1.
The screw rotors 31 and 32 have axes parallel to the X-axis direction. The screw rotors 31 and 32 are adjacent to each other in the Y axis direction and are disposed in the first housing portion 11. The first screw rotor 31 has a helical first tooth 31s, and the second screw rotor 32 has a helical second tooth 32s meshing with the first tooth 31 s. The number of turns of each of the first teeth 31s and the second teeth 32s is not limited to the illustrated number.
The first teeth 31s and the second teeth 32s have substantially the same shape, except that the twisting directions thereof are opposite to each other. The first teeth 31s are wound around the shaft portion 310 of the first screw rotor 31 with the same diameter. The second teeth 32s are wound around the shaft portion 320 of the second screw rotor 32 with the same diameter.
The first teeth 31s and the second teeth 32s are engaged with each other. For example, the first tooth 31s is located at a tooth-to-tooth groove of the second tooth 32 s. A gap is provided between the groove and the first tooth 31 s. Likewise, the second tooth 32s is located at the tooth-to-tooth groove of the first tooth 31 s. A gap is provided between the groove and the second tooth 32 s.
The outer peripheral surface of the first tooth 31s faces the inner wall surface of the
In the
The third housing portion 13 is inserted through the shaft end 311 of the first screw rotor 31 and the shaft end 321 of the second screw rotor 32. Further, a bearing 14a is provided between the shaft end 311 and the third housing portion 13, and a bearing 14b is provided between the shaft end 321 and the third housing portion 13. The shaft end 311 is rotatably supported by the third housing portion 13 via a bearing 14a, and the shaft end 321 is rotatably supported by the third housing portion 13 via a bearing 14 b.
A cover 15 covering the bearings 14a and 14b is fixed to the third casing 13 in an airtight manner by fastening with bolts via a sealing member such as an O-ring. Thereby, airtightness of the pump chamber 10p is ensured.
In the
The intermediate housing 50 is disposed between the
A shaft end 312 of the first screw rotor 31 and a shaft end 322 of the second screw rotor 32 are inserted into the intermediate housing 50. A bearing 15a is provided between the shaft end 312 and the intermediate housing 50, and a bearing 15b is provided between the shaft end 322 and the intermediate housing 50. The shaft end 312 is rotatably supported by the intermediate housing 50 via a bearing 15a, and the shaft end 322 is rotatably supported by the intermediate housing 50 via a bearing 15 b.
The drive mechanism 40 has a motor housing 41, a motor 42, a first timing gear 43a, and a second timing gear 43 b. The motor 42, the first timing gear 43a, and the second timing gear 43b are housed in the motor case 41. The motor case 41 is fixed to the intermediate case 50 in an airtight manner by bolt fastening via a sealing member such as an O-ring.
The motor 42 is constituted by, for example, a Direct Current (DC) motor. The drive shaft 420 of the motor 42 is coupled to the shaft end 312 of the first screw rotor 31. The motor 42 rotates the first screw rotor 31 around its axis at a predetermined rotational speed.
The first timing gear 43a is mounted at the shaft end 312 of the first screw rotor 31. The second timing gear 43b is mounted at the shaft end 322 of the second screw rotor 32. The timing gears 43a and 43b are arranged in the Y axis direction so as to mesh with each other. Thus, when the first screw rotor 31 rotates, the rotational driving force of the first screw rotor 31 is transmitted to the second screw rotor 32.
Here, when a space defined by the third housing part 13, the first housing part 11, the first teeth 31s, and the second teeth 32s is defined as an intake chamber 111, and a space defined by the
The screw rotors 31 and 32 are rotated in opposite directions by driving of the motor 42. The drive mechanism 40 conveys the working space S1 formed between the first screw rotor 31, the second screw rotor 32, and the first housing part 11 from the intake port 110 side to the exhaust port 120 side. Thereby, the gas sucked from the gas inlet 110 is carried through the delivered work space S1 and discharged from the gas outlet 120.
In this case, the gas flowing into the intake chamber 111 from the intake port 110 is transported to the exhaust port 120 side by the screw rotors 31 and 32, and is compressed in the exhaust chamber 121. Here, the working space S1 divided into a plurality has the largest pressure difference in the final stage portion thereof. The pressure of the working space in the preceding stage of the final stage is low, and even if the compression ratio is the same, the temperature of the final stage near atmospheric pressure is more likely to increase due to the heat of compression. As a result, the
Hereinafter, several methods of cooling the
For example, as a comparative example of cooling the
However, this method requires drilling for forming a hole in the
In addition, as another comparative example of cooling the
However, this method does not make the vacuum pump compact, and leads to an increase in the cost of the vacuum pump. In addition, in this method, the cooling efficiency is inferior compared to the method of cooling the
Further, as another comparative example of cooling the
However, this method requires an additional fan mechanism for cooling the heating medium, and requires a duct for circulating the heating medium, which leads to an increase in cost. In this method, since the
In the present embodiment, the vacuum pump 1 in which a part of the cooling pipe 20A is provided in the
Here, as a basis for the outer
For example, FIG. 3 is the result of an electron probe microanalyzer near the outer peripheral surface of the cooling tube. The horizontal axis represents the distance (depth) (mm) in the direction from the inside of the cooling pipe 20A toward the
As shown in fig. 3, the Fe strength and the Cr strength were approximately constant up to the distance of 0.6mm, but when exceeding the distance of 0.6mm, significant fluctuations occurred in the Fe strength and the Cr strength. Further, when the distance is about 0.9mm, the Fe strength and the Cr strength change extremely. When considering that the main component of cast iron is iron and that the product of mixing chromium in iron is stainless steel, the position at a distance of 0.9mm can be said to be the boundary position between the cooling pipe 20A and the
In addition, in the region from the distance of 0.6mm to 0.9mm (the boundary between the cooling pipe 20A and the second housing portion 12), significant fluctuations occur in the Fe strength and the Cr strength. In the region from 0mm to 0.6mm, the Fe strength and the Cr strength were approximately constant, and considering the sensitization phenomenon that chromium bonds with carbon in stainless steel and precipitates chromium carbide along the grain boundary of stainless steel, it can be said that the sensitized layer 20s was formed in the region from 0.6mm to 0.9 mm.
Further, since a trace amount of Cr and Ni in the cooling pipe 20A can be detected even at a position exceeding 0.9mm, it can be said that a solid solution is formed to some extent between the cooling pipe 20A and the
Since the thickness of the sensitizing layer 20s is 1mm or less, the thickness of the cooling tube 20A is preferably 1mm or more and 5mm or less.
If the thickness of the cooling tube 20A is less than 1mm, the most part of the volume of the cooling tube 20A is formed of the sensitized layer 20s, and the cooling tube 20A may be corroded from the inner peripheral surface 202 side, or a part of the cooling tube 20A may be melted when the
On the other hand, if the thickness of the cooling tube 20A is greater than 5mm, the volume of the cooling tube 20A increases, and therefore, the outer
A thickness of the sensitized layer 20s of less than 0.3mm means that the outer
On the other hand, if the thickness of the sensitized layer 20s is greater than 0.3mm, most of the volume of the cooling tube 20A is formed by the sensitized layer 20s, which may cause corrosion of the cooling tube 20A from the inner peripheral surface 202 side.
In the present embodiment, the value a obtained by dividing the volume of the
If the value a is less than 30, the cooling pipe 20A may not be sufficiently heated when the
On the other hand, if the value a is greater than 300, the most part of the volume of the cooling tube 20A is formed of the sensitized layer 20s, and the cooling tube 20A may be corroded from the inner peripheral surface 202 side, or a part of the cooling tube 20A may be melted when the
Further, no sensitizing layer is formed on the inner peripheral surface 202 of the cooling pipe 20A, or it is difficult to form a sensitizing layer on the same level as that on the outer
In addition, from the viewpoint of rust prevention, the sensitization phenomenon itself caused by stainless steel can be avoided by using an iron pipe and forming an electroless nickel plating film on the inner peripheral surface as the cooling pipe 20A. However, the plating film cannot secure adhesion, and when pinholes are generated, the plating film may peel off from the pinhole portion. Further, when the expansion and contraction of the cooling pipe 20A are repeated due to a long thermal history, the plating film is more likely to be peeled off. In addition, it is difficult to form a coating film uniformly on the inner peripheral surface 202 of the cooling pipe 20A in terms of technology and cost.
Therefore, as in the present embodiment, if the cooling tube 20A having a thickness of 1mm or more and 5m or less is cast together with cast iron, the
In addition, according to the present embodiment, since the cooling pipe 20A is in direct contact with the
In addition, according to the present embodiment, in order to integrate the first
In addition, according to the present embodiment, since a part of the cooling pipe 20A is provided in the
In addition, according to the present embodiment, the first
Further, according to the present embodiment, since the thickness of the cooling pipe 20A is configured to be 1mm or more and 5mm or less, it is possible to form a screw thread on the inner circumferential surface 202 of each of the
Fig. 4(a) to 4(c) are schematic views showing modifications of the cooling pipe of the present embodiment.
In the
In the
In the
While the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications can be made. For example, the
Description of the reference numerals
1: vacuum pump
10: pump casing
10 p: pump chamber
11: first housing part
12: second housing part
13: third housing part
14a, 14b, 15a, 15 b: bearing assembly
15: cover
20A, 20B, 20C, 20D: cooling pipe
201: peripheral surface
202: inner peripheral surface
20 s: sensitizing layer
21: first cooling pipe part
21t, 22 t: end part
22: second cooling pipe part
23: connecting pipe part
210: depressions
220: wave structure
230: bending part
31: first screw rotor
31 s: first tooth
310. 320, and (3) respectively: shaft part
311. 312, 321, 322: end of shaft
32: second screw rotor
32 s: second tooth
40: driving mechanism
41: motor casing
42: electric motor
420: drive shaft
43 a: first timing gear
43 b: second timing gear
50: middle shell
110: air inlet
111: air inlet chamber
120: exhaust port
121: exhaust chamber
S1: working space
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