Rotary unit for oil-less vacuum pump

Abstract

The present invention provides a rotary unit for an oil-free vacuum pump installed within the housing of the oil-free vacuum pump, comprising: a cam ring fixedly installed along the inner diameter of the housing; a rotating shaft eccentrically positioned from the center of the cam ring; a rotor coupled to the rotating shaft and rotating together with the rotating shaft, and including a plurality of slot portions; and a plurality of vanes slidably inserted into each of the slot portions and contacting the inner surface of the cam ring according to the rotation of the rotor; wherein the slot portions are formed at an angle of 20 to 70° with respect to a virtual extension line extending radially from the center of the rotor. By doing so, it is possible to obtain a rotary unit for an oil-free vacuum pump designed to be easy to maintain and repair without using oil, and to provide excellent gas suction, isolation, compression, and exhaust.

Description

Technology Field

[0001] The present invention relates to a rotary unit for an oil-less vacuum pump, and more specifically, to a rotary unit for an oil-less vacuum pump designed to be easy to maintain and repair by not using oil, and to provide excellent gas suction, isolation, compression, and exhaust. Background Technology

[0002] Radioactive iodine, radioactive cesium, or radioactive carbon released into the atmosphere from nuclear power plants are harmful radionuclides with long half-lives that emit beta rays; they generally account for the highest contribution to radiation doses resulting from the release of radionuclides from nuclear power plants. These radioactive atoms are generated when carbon, nitrogen, oxygen, and other elements present in nuclear fuel, fuel cladding, coolants, moderators, and other structural materials are activated by neutrons. Among these, radioactive carbon exists in the atmosphere as carbon dioxide when released into the environment, allowing it to be distributed globally; furthermore, due to its long half-life, it does not easily dissipate. Consequently, radioactive carbon is fixed within living organisms through respiration or photosynthesis by animals and plants, and can accumulate in the human body via the food chain; therefore, radioactive atoms, including radioactive carbon, are subject to special management and monitoring.

[0003] Therefore, a radiation monitoring system (RMS) is installed in nuclear power plants to measure and monitor the radioactive levels of gases flowing within installed pipes, and as shown in Fig. 1, a vacuum pump for moving air is installed within the radiation monitoring system. This vacuum pump is a key piece of equipment that creates an environment where radioactive levels can be measured by forcibly transporting gases within the pipes as a rotary assembly rotates, thereby creating and maintaining a vacuum state of 0 to 10 inHG inside the chamber.

[0004] As such, oil-less vacuum pumps must be used to exhaust gases flowing within piping and maintain a vacuum. While oil-less vacuum pumps offer the advantage of preventing process contamination caused by oil backflow, most of them rely on foreign products, making maintenance and repair difficult and leading to instances of discontinuation; therefore, there is a need for the localization of oil-less vacuum pumps. Prior art literature

[0005] Patent No. 10-0983675 registered with the Korean Intellectual Property Office The problem to be solved

[0006] The present invention was devised to solve the above-mentioned problems and aims to provide a rotary unit for an oil-less vacuum pump designed to facilitate maintenance and repair by not using oil, and to provide excellent gas suction, isolation, compression, and exhaust. means of solving the problem

[0007] The above objective is achieved by a rotary unit for an oil-less vacuum pump installed within the housing of the oil-less vacuum pump, comprising: a cam ring fixedly installed along the inner diameter of the housing; a rotating shaft eccentrically positioned from the center of the cam ring; a rotor coupled to the rotating shaft and rotating together with the rotating shaft, and including a plurality of slot portions; and a plurality of vanes slidably inserted into each of the slot portions and contacting the inner surface of the cam ring according to the rotation of the rotor; wherein the slot portions are formed in a state inclined at an angle of 20 to 70° with respect to a virtual extension line extending radially from the center of the rotor.

[0008] Here, the vane includes a curved tip having a radius of curvature (R) of the cam ring to relieve stress concentration that occurs when in contact with the inner surface of the cam ring, and it is preferable that the radius of the cam ring be 52.4 mm, the thickness of the vane be 5 mm, and the width of the vane in contact with the cam ring be 4 mm.

[0009] In addition, it is preferable that the clearance volume (Vc) formed between the cam ring and the rotor be calculated using Equation 1, and that the cam ring be formed with an inner diameter of φ104 to 105.7 mm, and that the rotor be formed with an outer diameter of φ91.6 to 93 mm.

[0010] In addition, the rotary unit has a rotational speed of 1725 to 1750 rpm and a flow rate of 28 m 3 It is preferable that the volumetric efficiency be designed to be 90% or more under the / h condition, the inner diameter (Dc) of the cam ring and the outer diameter (Dr) of the rotor be designed such that Dc / Dr = 1.12 to 1.15, the width of the rotor be 88 mm, and the number of vanes be 4 to 6. Effects of the invention

[0011] As described above, according to the present invention, it is possible to obtain a rotary unit for an oil-less vacuum pump designed to be easy to maintain and repair without using oil, and to provide excellent gas suction, isolation, compression, and exhaust. Brief explanation of the drawing

[0012] FIG. 1 is a configuration diagram of a nuclear radiation monitoring system including an oil-less vacuum pump, and FIG. 2 is a cross-sectional view of a rotary unit for an oil-less vacuum pump, and FIG. 3 is a detailed perspective view of the rotation axis and rotor of a rotary unit, and Figure 4 is a detailed cross-sectional view of the rotor. Specific details for implementing the invention

[0013] Hereinafter, the technical concept of the present invention will be explained in more detail using the attached drawings. The attached drawings are merely examples illustrated to explain the technical concept of the present invention in more detail, and therefore the technical concept of the present invention is not limited to the form of the attached drawings.

[0014] FIG. 1 is a configuration diagram of a nuclear radiation monitoring system including an oil-less vacuum pump, FIG. 2 is a cross-sectional view of a rotary unit for an oil-less vacuum pump, FIG. 3 is a detailed perspective view of the rotating shaft and rotor of the rotary unit, and FIG. 4 is a detailed cross-sectional view of the rotor.

[0016] An oil-less vacuum pump refers to a dry vacuum pump that does not use oil for gas evacuation and vacuuming. This oil-less vacuum pump is a key device that creates and maintains a vacuum state of 0 to 10 inHG inside the housing by forcibly transporting gas within the piping as the rotating shaft and rotor rotate, thereby creating an environment where radiation levels can be measured. More specifically, oil-less vacuum pumps have the advantage of very high vacuum levels and low noise because they utilize dry, low-friction solid lubricants such as graphite, Teflon, or molybdenum disulfite instead of oil. Furthermore, oil-less vacuum pumps are easy to maintain and manage because they do not require oil replacement, and they are characterized by the absence of contamination and the generation of contaminated water.

[0017] An oil-less vacuum pump is a pump that creates a vacuum by using a rotating rotor and vanes to expel gas molecules from within the housing to the outside via an air exhaust method. Because it seals gas molecules without using oil, it is also referred to as a dry pump. The operation of a rotary vane vacuum pump consists of four stages: induction, isolation, compression, and exhaust. The induction stage corresponds to the phase where gas molecules are guided into the housing as the rotor rotates 180° initially, filling the crescent-shaped space created by the rotor. The isolation stage involves vanes positioned close to the inlet blocking the inlet to isolate gas molecules within the housing. The compression stage corresponds to the phase where the volume of the gas injection decreases as the rotor rotates further and the lower vanes gradually rise, causing the gas to be compressed and heated. Finally, the exhaust stage refers to the phase where, once the rotor has fully rotated and the lower vanes are positioned near the exhaust valve, the pressure of the gas molecules increases, forcibly opening the exhaust valve to expel the gas molecules to the outside, where the pressure is lower.

[0018] In order to inhale, isolate, compress, and exhaust gas molecules in this manner, the structural design of the rotor and vanes within the oil-less vacuum pump is very important. Therefore, the present invention describes a rotary unit (10) for an oil-less vacuum pump that is installed within the housing of the oil-less vacuum pump so as to be applicable to the oil-less vacuum pump.

[0020] A rotary unit (10) for an oil-less vacuum pump according to an embodiment of the present invention includes a cam ring (100), a rotating shaft (200), a rotor (300), and a vane (400) as shown in FIG. 2.

[0021] The cam ring (100) is fixedly installed along the inner diameter of the oil-less vacuum pump housing and provides a space for gas compression and discharge. The rotating shaft (200), rotor (300), and vane (400), which will be described later, are arranged inside this cam ring (100), and the performance of the oil-less vacuum pump is determined by the clearance space between the rotor (300) and the cam ring (100).

[0022] The rotation shaft (200) is configured to be rotatably installed inside the cam ring (100) and is installed to be positioned eccentrically from the center of the cam ring (100). By positioning the rotation shaft (200) eccentrically from the center of the cam ring (100), a clearance space can be formed between the cam ring (100) and the rotor (300) to isolate and compress the gas.

[0023] The rotor (300) is configured to be coupled to a rotation axis (200) as shown in FIG. 3 and rotate together with the rotation axis (200), and includes a plurality of slot portions (310) formed at an angle (θ) different from a virtual extension line (L) extending radially from the center of the rotor (300) as shown in FIG. 4. In the case of the rotor (300), a plurality of slot portions (310) are formed so that a vane (400) to be described later can be inserted, and the present invention is characterized in that the slot portions (310) are formed at an angle (θ) different from the extension line (L), rather than on the same line as the virtual extension line (L) extending radially.

[0024] A slot portion (310) has one end formed in an area that engages with a virtual extension line (L) extending radially from the rotation axis (100), and the other end formed in a recessed area that is close to the rotation axis (100) from the one end. As shown in FIG. 4, the slot portion (310) of this structure is formed in a recessed state tilted at an angle (θ) of 20 to 70° relative to the extension line. This design allows the vane to withstand higher gas pressure compared to a slot portion formed radially as in the conventional method, thereby improving the performance of the oil-less vacuum pump.

[0025] Such a rotor (300) is preferably manufactured from stainless steel (SUS304), specifically having a tensile strength of 520 MPa, a yield strength of 205 MPa, a Brinell hardness of 187 HB, and a density of 7930 kg / m³ 3 It is most desirable to use stainless steel made of [material].

[0026] The vane (400) is configured to be slidably inserted into each of the multiple slot portions (310) and to come into contact with the inner surface of the cam ring (100) according to the rotation of the rotor (300), and performs the function of isolating and compressing the gas by repeatedly driving into or out of the slot portions (310). That is, the vane (400) is configured to protrude from the slot portions (310) and come into close contact with the inner surface of the cam ring (100) using centrifugal force due to inertia, and the distance of contact with the cam ring (100) is different due to the eccentric rotation axis (200) and the rotor (300), so that insertion into or out of the slot portions (310) is repeated. It is preferable that such a vane (400) has a thickness of 4 to 5 mm, but is not limited thereto.

[0027] A vane (400) of this type includes a curved tip having a radius of curvature (R) of the cam ring (100) to relieve stress concentration that occurs when in contact with the inner surface of the cam ring (100). The tip of the vane (400) is configured to protrude from the slot portion (310) toward the cam ring (100) and come into contact with the inner surface of the cam ring (100). The inner surface of the cam ring (100) and the tip of the vane (400) repeatedly come into contact and separate, and stress may occur when the tip of the vane (400) comes into contact with the inner surface of the cam ring (100). Therefore, to relieve such stress concentration, it is preferable that the tip of the vane (400) be formed with a curved shape having a radius of curvature of the cam ring (100).

[0028] Here, it is preferable to design the radius of curvature of the cam ring (100) to be 52.4 mm, the thickness of the vane (400) to be 5 mm, and the width of the vane (400) in contact with the cam ring (100) to be 4 mm, but is not limited thereto.

[0029] These vanes (400) are preferably made of carbon steel (S20C), specifically having a tensile strength of 457 MPa, a yield strength of 288 MPa, an elastic modulus of 119 Gpa, an elongation of 15%, and a density of 7850 kg / m³ 3 It is most desirable to use carbon steel made of [material].

[0030] The rotary unit (10) for an oil-less vacuum pump of the present invention, configured as described above, has a clearance space formed between the cam ring (100) and the rotor (300). Since the isolation and compression of gas are achieved through this clearance space, the volume of the clearance space is an important factor when designing an oil-less vacuum pump. Therefore, the clearance volume (V) of the oil-less vacuum pump c ) is calculated through the following Equation 1.

[0032] [Equation 1]

[0033]

[0034] (Here, Vc represents the free space volume, and rpm represents the rotor's rotational speed.)

[0036] The oil-less vacuum pump according to the present invention has a minimum gas flow rate of 28 m 3 Designed to be / h, and the maximum flow rate is 34m, which is a 20% increase in the minimum flow rate. 3 It is set to / h. In this way, the minimum flow rate at 1725 rpm is 28 m 3 The free space volume (V) of the oil-less vacuum pump to enable / h c ) can be calculated as follows using Equation 1, and the calculated value is 1.50×10 5 mm 3 It is obtained as.

[0038]

[0040] Through such calculations, the inner diameter of the cam ring (100) and the outer diameter of the rotor (300) can be designed, with an effective flow rate of 34 m 3 In the case of / h, the minimum and maximum values ​​were verified by calculating for volumetric efficiency of 90% and 85%, resulting in values ​​ranging from 31.1 to 40m as follows. 3 It is derived as / h.

[0042] - Flow rate range at 90% volumetric efficiency: 31.1 to 37.8 m 3 / h

[0043] - Flow rate range at 85% volumetric efficiency: 32.9 to 40.0 m 3 / h

[0045] The flow rate range is 31.1 to 40 m 3 In order to determine the discharge volume range (V) per revolution in a state determined as / h, the rotor rotation speed is set to 1750 rpm and 1725 rpm, respectively, and then the calculation is performed as follows.

[0047] - 1750rpm

[0048] 31.1m 3 / h = V / 2×1750×60×4 → V = 1.48×10 -4m 3

[0049] 40m 3 / h = V / 2×1750×60×4 → V = 1.90×10 -4 m 3

[0050] - 1725rpm

[0051] 31.1m 3 / h = V / 2×1725×60×4 → V = 1.50×10 -4 m 3

[0052] 40m 3 / h = V / 2×1725×60×4 → V = 1.93×10 -4 m 3

[0054] In this way, the minimum value (V) of the discharge volume range per revolution according to the rotational speed of the rotor (300) min ) and maximum value(V max ) are as follows.

[0056] V min = 1.48×10 -4 m 3

[0057] V max = 1.93×10 -4 m 3

[0059] When the width corresponding to the horizontal length of the cam ring (100) and the rotor (300) is set to 88 mm using the volume range (V) obtained as above, the minimum value (A) of the discharge cross-sectional area range min ) and maximum value(A max ) is derived as follows.

[0061] A min = 1.48×10 -4 m 3 / 0.088m = 1.68×10 -3 m 2

[0062] A max = 1.93×10 -4 m 3 / 0.088m = 2.19×10 -3 m 2

[0064] Based on this range of discharge cross-sectional areas, the inner diameter (Dc) of the cam ring (100) and the outer diameter (Dr) of the rotor (300) are combined so that the size of the discharge cross-sectional area is a minimum value (A min ) and maximum value(A max The inner diameter (Dc) of the cam ring and the outer diameter (Dr) of the rotor are selected so as to be within the range. In the present invention, the minimum value (A min ) and maximum value(A max 1.70×10, corresponding to a value close to the range -3 m 2 and 2.18×10 -3 m 2 Using this, the minimum and maximum values ​​for the inner diameter (Dc) of the cam ring and the outer diameter (Dr) of the rotor are derived.

[0066] 1.70×10 -3 m 2 = π / 4×{(Dc) 2 -(Dr) 2} = π / 4×{(0.104m) 2 -(0.093m) 2}

[0067] 2.18×10 -3 m 2 = π / 4×{(Dc) 2 -(Dr) 2} = π / 4×{(0.1057m) 2 -(0.0916m) 2}

[0069] Through the above calculation, the maximum and minimum values ​​for the inner diameter of the cam ring (100) and the outer diameter of the rotor (300) are derived as follows.

[0071] - Cam ring inner diameter (Dc) range: φ104 to 105.7mm

[0072] - Rotor outer diameter (Dr) range: φ91.6 to 93mm

[0074] In this way, it is preferable to design the inner diameter (Dc) of the cam ring and the outer diameter (Dr) of the rotor such that Dc / Dr = 1.12 to 1.15. When designed with this ratio, the gap between the cam ring (100) and the rotor (300) is optimized, thereby minimizing compression efficiency and volume loss simultaneously.

[0075] Finally, the specifications of the rotary unit (10) for an oil-less vacuum pump according to the present invention, obtained through the above calculations, are as shown in Table 1. In particular, when the width of the rotor (300) is 88 mm, the 28 m corresponding to the flow rate condition of the present invention 3 It is possible to secure a sufficient volume relative to the maximum power under / h conditions, and when the vanes (400) are composed of 4 to 6, it is possible to maintain a balance between the rotational force of the rotor (300) and the compression cycle, as well as have the effect of reducing vibration and noise.

[0077] Design factors range Flow rate (m 3 / h) 28 to 34 Rotational speed (rpm) 1725 to 1750 Cam ring inner diameter (mm) φ104 to 105.7 Rotor outer diameter (mm) φ91.6 to 93 Cam ring width (mm) 88 Rotor width (mm) 88 Number of Vayne 4 to 6

[0079] Conventional rotary units for vacuum pumps have slots formed radially, so they do not have excellent efficiency. However, the rotary unit (10) for oil-less vacuum pumps of the present invention exhibits excellent performance through multiple slots (310) formed at different angles from the radial extensions, and the performance of gas suction, isolation, compression, and exhaust can be improved by designing the cam ring (100) and rotor (300) considering the gas flow rate and rotational speed.

[0080] The present invention is not limited to the embodiments described above, and its scope of application is diverse. Furthermore, it is understood that various modifications are possible without departing from the essence of the invention as claimed in the claims. Explanation of the symbols

[0081] 10: Rotary unit 100: Camring 200: Rotation axis 300: Rotor 310: Slot section 400: Vayne

Claims

Claim 1 A rotary unit for an oil-less vacuum pump installed within the housing of the oil-less vacuum pump, comprising: a cam ring fixedly installed along the inner diameter of the housing; a rotating shaft eccentrically positioned from the center of the cam ring; a rotor coupled to the rotating shaft and rotating together with the rotating shaft, comprising a plurality of slot portions; and a plurality of vanes slidably inserted into each of the slot portions and contacting the inner surface of the cam ring according to the rotation of the rotor; wherein the slot portions are formed at an angle of 20 to 70° with respect to a virtual extension line extending radially from the center of the rotor, and the clearance volume (Vc) formed between the cam ring and the rotor is calculated through the following Equation 1. (Here, Vc represents the free space volume, and rpm represents the rotor's rotational speed.) Claim 2 A rotary unit for an oil-less vacuum pump according to claim 1, wherein the vane includes a curved tip portion having a radius of curvature (R) of the cam ring to relieve stress concentration occurring when in contact with the inner surface of the cam ring, and is designed such that the radius of the cam ring is 52.4 mm, the thickness of the vane is 5 mm, and the width of the vane in contact with the cam ring is 4 mm. Claim 3 delete Claim 4 A rotary unit for an oil-less vacuum pump according to claim 1, characterized in that the cam ring has an inner diameter of φ104 to 105.7 mm and the rotor has an outer diameter of φ91.6 to 93 mm. Claim 5 In claim 1, the rotary unit has a rotational speed of 1725 to 1750 rpm and a flow rate of 28 m 3 A rotary unit for an oil-less vacuum pump, characterized by being designed to have a volumetric efficiency of 90% or more under the / h condition, and having an inner diameter (Dc) of the cam ring and an outer diameter (Dr) of the rotor such that Dc / Dr = 1.12 to 1.15, and having a rotor width of 88 mm and a number of vanes of 4 to 6.

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