KR20240020695A - Screw rotor for vacuum pump - Google Patents

Abstract

The present invention relates to a screw-type rotor of a vacuum pump that creates a vacuum inside a chamber during a semiconductor manufacturing process.
The present invention is a screw-type rotor that forms the vacuum of a vacuum pump, including an inlet pitch consisting of a variable pitch section with a large thread thickness, an outlet pitch consisting of a back pitch section with a thin thread thickness, etc. By applying a combination of and implementing a new screw rotor designed with an optimal profile shape that theoretically reduces the gap between the threads on both sides where two screws are engaged, the function and durability of the screw rotor are improved, as well as machine tool durability. We provide a screw rotor for a vacuum pump that can present screw modeling that can be manufactured.

Description

Screw rotor for vacuum pump {SCREW ROTOR FOR VACUUM PUMP}

The present invention relates to a screw rotor for a vacuum pump, and more specifically, to a screw-type rotor for a vacuum pump that creates a vacuum inside a chamber during a semiconductor manufacturing process.

Generally, the semiconductor manufacturing process is performed in a process chamber in a closed environment where a predetermined process gas is introduced. The inside of this process chamber must be maintained at a temperature and pressure appropriate for the process conditions.

In particular, the process must be carried out while continuously maintaining a vacuum state in the process chamber to prevent contamination due to particles, etc. At this time, a precise semiconductor manufacturing process can be performed only when the vacuum state is accurately maintained at the set value.

The vacuum pump system for creating a vacuum in the process chamber includes a vacuum pump that creates a vacuum inside the process chamber by sucking air from the process chamber to maintain the forming process of the semiconductor member in a vacuum state.

This vacuum pump is responsible for creating a vacuum inside the process chamber and discharging gaseous substances or process by-products generated in the process chamber to the outside.

In general, dry-type vacuum pumps are mainly used as vacuum pumps for creating and maintaining vacuum in the process chamber. These vacuum pumps usually include roots-type rotors, screw-type rotors, and a combination of roots-type and screw-type rotors. It is being used.

Additionally, recent vacuum pumps are structured to include one or more screw-type rotors to maintain a more perfect vacuum in the process chamber and reduce power costs.

Prior art documents related to this include, Public Patent Publication No. 10-1997-0021753, Public Patent Publication No. 10-2007-0022575, Registered Patent Publication No. 10-0497982, Registered Patent Publication No. 10-0624982, and Registered Patent Publication No. Various screw-type rotors are disclosed in No. 10-0737321, etc.

The present invention is used in a vacuum pump and aims to develop a new screw rotor with improved performance compared to the prior art through optimal thread engagement combination between two screw rotors.

Publication of Patent No. 10-1997-0021753 (May 28, 1997) Public Patent Publication No. 10-2007-0022575 (2007.02.27.) Registered Patent Publication No. 10-0497982 (June 20, 2005) Registered Patent Publication No. 10-0624982 (2006.09.11.) Registered Patent Publication No. 10-0737321 (2007.07.03.)

The present invention was created in consideration of the above points, and is a screw-type rotor that creates a vacuum in a vacuum pump. The inlet pitch consists of a variable pitch section with a large thread thickness, and the thickness of the thread is relatively small. In addition to applying a combination of outlet pitch with a thin back pitch section, a new screw is designed with an optimal profile shape that theoretically makes the gap between the threads on both sides where two screws engage to zero. By implementing a rotor, the purpose is to provide a screw rotor for a vacuum pump that can improve the function and durability of the screw rotor, as well as provide screw modeling that can be manufactured with machine tools.

In order to achieve the above object, the screw rotor for a vacuum pump provided by the present invention has the following characteristics.

The screw rotor for a vacuum pump according to an embodiment of the present invention is a screw rotor for a vacuum pump in which two screw rotors (10) engage and rotate to form a vacuum, and the screw rotor (10) determines the maximum intake amount of gas. Cell V1, which compresses the gas to create a specific compression ratio and primarily distributes the compression heat to prevent the screw rotor in the V3 area from rapidly expanding due to the compression heat, and Cell V2, which compresses the gas to create a specific compression ratio and distributes the compression heat. An inlet pitch section (L2) consisting of a variable pitch section and including cell V3, which disperses and prevents the screw rotor in the V4 to VN region from rapidly expanding due to compression heat, and a cell that seals the sucked gas to form a constant vacuum degree. It includes an outlet pitch section (L1) including V4 to VN and consisting of an equal pitch section, the volume of the cell V3 is set to 1.03 to 1.10 times the volume of the cell V4, and the volume of the cell V2 is the volume of the cell V3. It is set to 1.90 to 2.50 times, and the volume of cell V1 is set to 1.40 to 1.70 times the volume of cell V2, so that the compression ratio between the variable pitch section and the constant pitch section is set to 4.1:1 to 6.3:1, so that the absolute temperature and It is characterized by reducing the increase in temperature deviation and minimizing the generation of compression heat.

In a preferred embodiment, the ratio of the outer diameter (D) and the inner diameter (d) of the threads of the inlet pitch section (L2) and the outlet pitch section (L1) may be set to 1.5 to 2, and the inlet pitch section (L2) and the length ratio of the outlet pitch section (L1) can be set to 0.6 or more, and the lead angle of the inlet pitch section (L2) is set to 90 to 100°, and the lead angle of the outlet pitch section (L1) is set to 90 to 100°. Can be set to 95°.

Here, the pressure value at the beginning of the inlet pitch section (L2) is sensed, and the degree of vacuum can be adjusted by adjusting the rotation speed using an inverter using the sensed pressure value.

And the outer diameter (D') of at least one thread of the outlet pitch section (L1) adjacent to the inlet pitch section (L2) is set to be relatively smaller than the outer diameter (D) of the remaining threads of the outlet pitch section (L1), thereby compressing This can solve the problem of collision as the rotor expands due to heat generation.

This screen rotor for a vacuum pump may further include a lobe device that is directly connected to the screw rotor or is coupled with a partition wall to increase the vacuum efficiency of the pump.

In a preferred embodiment, a hole parallel to the axis is formed in the screw rotor, and an oil supply pipe is installed inside the hole, and the oil supplied from the oil supply device is supplied to the oil supply pipe. The screw rotor can be cooled by flowing into the hole of the screw rotor.

In addition, the screw rotor for a vacuum pump according to another embodiment of the present invention is a screw rotor for a vacuum pump in which two screw rotors (10) engage and rotate to form a vacuum, wherein the screw rotor (10) generates a maximum amount of gas. Cell V1 determines the suction amount, cell V2 compresses the gas to create a specific compression ratio and primarily distributes the compression heat to prevent the screw rotor in the V3 area from rapidly expanding due to the compression heat, and cell V2 compresses the gas to create a specific compression ratio. An inlet pitch section (L2) consisting of a variable pitch section and including cell V3, which distributes compression heat and prevents the screw rotor in the V4 to VN region from rapidly expanding due to compression heat, and seals the sucked gas to maintain a constant vacuum level. At least one thread outer diameter (D') of the outlet pitch section (L1) adjacent to the inlet pitch section (L2), including cells V4 to VN and comprising an outlet pitch section (L1) composed of equal pitch sections. It is characterized by setting it to be relatively smaller than the remaining thread outer diameter (D) of the outlet pitch section (L1), so as to solve the problem of collision as the rotor expands due to heat generation due to compression.

The screw rotor for a vacuum pump provided by the present invention has the following effects.

First, the cells between the threads (V0, V1, V2, V3) include an inlet pitch section (L2) made up of a variable pitch section and an outlet pitch section (L1) where the cells between the threads (V4 to VN) are made of an equal pitch section. By applying a screw rotor, it is possible to simplify the structure, reduce the size, and realize a highly efficient screw rotor.

Second, by limiting the ratio between the screw diameter and the shaft diameter, limiting the lead angle of the equal pitch section and the variable pitch section, and limiting the ratio of the inlet pitch section and the outlet pitch section, the gap between the threads on both sides where the two screws are engaged is theoretically By implementing the optimal profile to achieve zero, there is an effect of improving durability as well as improving the function of the screw rotor.

Third, by designing the optimal profile model and making it possible to manufacture it with a cutting machine tool, there is an effect of economically manufacturing the screw rotor, such as improving manufacturability and reducing manufacturing costs.

Fourth, by cooling the rotor area and bearing area of the screw rotor using the oil circulation method, the stability of process performance and equipment operation can be ensured, such as preventing a rapid increase in temperature of the screw rotor, and the temperature of the screw rotor can be ensured. It has the effect of being able to be set according to process characteristics.

1 is a cross-sectional view showing a vacuum pump including a screw rotor according to an embodiment of the present invention.
Figure 2 is a front view showing a screw rotor for a vacuum pump according to an embodiment of the present invention.
Figure 3 is a perspective view showing the separated volume of the cell in the screw rotor for a vacuum pump according to an embodiment of the present invention.
Figure 4 is a schematic diagram showing the lead angle of the variable pitch section and the lead angle of the constant pitch section in the screw rotor for a vacuum pump according to an embodiment of the present invention.
Figure 5 is a front view showing the state of thread polishing in the equal pitch section in the screw rotor for a vacuum pump according to an embodiment of the present invention.
Figure 6 is a perspective view showing the coupled state of lobes in a screw rotor for a vacuum pump according to an embodiment of the present invention.
Figure 7 is a cross-sectional view showing a cooling structure in a screw rotor for a vacuum pump according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. The specific structural or functional descriptions presented in the embodiments of the present invention are merely illustrative for the purpose of explaining the embodiments according to the concept of the present invention, and the embodiments according to the concept of the present invention may be implemented in various forms. In addition, the invention should not be construed as limited by the embodiments described in this specification, and should be understood to include all changes, equivalents, and substitutes included in the spirit and technical scope of the present invention.

Meanwhile, in the present invention, terms such as first and/or second may be used to describe various components, but the components are not limited by the terms. The above terms are used only for the purpose of distinguishing one component from other components, for example, without departing from the scope of rights according to the concept of the present invention, a first component may be named a second component, Similarly, the second component may also be referred to as the first component.

When a component is referred to as being “connected” or “connected” to another component, it should be understood that it may be directly connected or connected to the other component, but that other components may exist in between. something to do. On the other hand, when a component is referred to as being “directly connected” or “in direct contact” with another component, it should be understood that there are no other components in between. Other expressions to describe the relationship between components, such as “between” and “immediately between” or “adjacent to” and “directly adjacent to”, should be interpreted similarly.

Like reference numerals refer to like elements throughout the specification. The terminology used herein is for describing embodiments and is not intended to limit the invention. In this specification, singular forms also include plural forms unless specifically stated in the phrase. As used in the specification, “comprises” and/or “comprising” means that a referenced component, step, operation and/or element is present in one or more other components, steps, operations and/or elements. or does not rule out addition.

1 is a cross-sectional view showing a screw rotor for a vacuum pump according to an embodiment of the present invention.

As shown, the screw rotor for a vacuum pump includes a housing 14 as a component that accommodates the screw rotor 10.

This housing 14 is formed with an inlet 15 connected to the process chamber for suction of fluid and an outlet 16 connected to the atmosphere or post-processing equipment for discharge of fluid.

In addition, the screw rotor for a vacuum pump includes a pair of screw rotors 10 as a means of substantially forming a vacuum.

The screw rotor 10 is installed in a structure supported by a shaft inside the housing 14, and a vacuum is formed by rotating the pair of screw rotors 10 inside the housing 14.

Additionally, the screw rotor for a vacuum pump includes a pair of shafts 17 that support the screw rotor 10.

Each shaft 17 is installed in a structure where it passes through the center of each screw rotor 10 and is supported via a bearing on the housing 14 side. This pair of shafts 17 are connected to each other by electric gears ( 18), of which one shaft 17 is connected to the shaft of the motor 19.

In addition, the screw rotor for a vacuum pump includes a motor 19 as a means of providing power for rotation of the screw rotor 10.

The motor 19 may be installed on one external side of the housing 14, and may be connected to the one shaft 17 via a separate coupler 20, or may be directly connected to the shaft 17.

Accordingly, when the motor 19 is driven, the shaft 17 and the screw rotor 10 rotate and a vacuum can be formed.

Since the basic structure and operating method of the screw rotor for a vacuum pump is the same as that of the screw rotor for a vacuum pump disclosed in Patent No. 10-1712962, detailed description will be omitted.

On the other hand, the screw rotor for a vacuum pump according to the present invention can be formed with an optimal profile in which the gap between the threads (cells) on both sides of the two screws is theoretically zero when the two screws are engaged, and this profile It has the feature of being able to be manufactured with a cutting machine tool by setting the desired gap value.

For this purpose, as shown in FIGS. 2 to 4, the screw rotor for a vacuum pump according to the present invention is a screw type in which two screw rotors (reference numeral '10' in FIG. 1) engage and rotate to form a vacuum. It consists of a rotor.

The screw rotor 10 has an inlet pitch section (L2) in which each cell (V0, V1, V2, V3) between threads is a variable pitch section, and each cell (V4 to VN) between threads is an equal pitch section. It includes an outlet pitch section (L1) consisting of.

Here, the thickness of the thread of the inlet pitch section (L2) is thicker than the thickness of the thread of the outlet pitch section (L1), and each thread belonging to the inlet pitch section (L2) at this time has a different thickness. Each thread belonging to the outlet pitch section L1 may have the same thickness.

This inlet pitch section (L2) may include cells V0, V1, V2, V3, etc. in FIGS. 2 and 3, and the outlet pitch section (L1) may include cells V4 to VN in FIGS. 2 and 3. In this case, the uses of cells V0 to V4, etc. are as follows.

The V0 is a cell that is exposed to the inlet 15 and inhales gas, and is a cell that has a slightly different shape (volume) in order to inhale gas and adjust the overall center of gravity of the product.

The V1 is a cell that determines the maximum intake amount of gas (vacuum efficiency: pumping speed).

The V2 is a cell that compresses the gas to create a specific compression ratio and primarily distributes the compression heat to prevent the screw rotor in the V3 area from rapidly expanding due to the compression heat.

The V3 is a cell that compresses gas to create a specific compression ratio and disperses compression heat to prevent the screw rotor in the V4 to VN regions from rapidly expanding due to compression heat.

The V4 is a cell that seals the sucked gas and forms a certain degree of vacuum.

In particular, the pressure distribution between P1 and P2 varies depending on the number of cells (V4 ~ VN) in the outlet pitch section (L1), and the maximum vacuum (base vacuum) can be maintained lower as the number of cells increases, and the screw rotor and The screw rotor gap and the screw rotor and housing (stator) gap can also be widened.

Here, P1 means the pressure of the VAC area at the front of the inlet pitch section (L2) (e.g., 1×10^1 ~ 1×10^-3 Torr), and P2 is the pressure of the waiting area at the back of the outlet pitch section (L1). It means pressure (e.g., 7.6×10^3 Torr).

The number of cells V4 must be set according to the maximum vacuum degree and the degree of heat generation within the screw rotor. About 3 to 8 cells can be used without problems considering the maximum vacuum degree and the heat of compression within the screw rotor.

For example, the number of cells in the outlet pitch section (L1) can be set within the range of 3 to 7 cells depending on the vacuum degree. If the vacuum degree is 1.7 torr, the number of cells in the outlet pitch section (L1) can be set to 3. If the vacuum degree is 0.14 torr, the number of cells in the outlet pitch section (L1) can be set to 6, and if the vacuum degree is 0.069 torr, the number of cells in the outlet pitch section (L1) can be set to 7.

In this way, by adjusting the number of cells in the outlet pitch section (L1) to an appropriate number according to various vacuum degrees, the optimal number of cells suitable for the efficiency of the vacuum pump required by the user can be provided.

In addition, the number of cells must be determined considering economics and durability.

For example, if the number of cells (V4 ~ VN) in the outlet pitch section (L1) is small, the vacuum degree is bad, but it is advantageous in terms of durability and economic efficiency (processing time), and if the number of cells (V4 ~ VN) is large, the vacuum degree is excellent, but It is disadvantageous in terms of durability and economic efficiency (processing time).

Considering these characteristics, it is necessary to consider setting the compression ratio (variable pitch section) and the number of cells (equal pitch section) according to the volume of each cell. If you want to set the number of cells to be small, set the variable pitch section relatively small to reduce the compression ratio.

In addition, by setting the equal pitch section to be large to generate less compression heat (e.g., reducing compression heat generation and speeding up gas exhaust), the gap between the screw rotor and the screw rotor and the housing can be narrowed, allowing the maximum Vacuum degree and vacuum efficiency can be maintained.

And by setting each cell (V1 to V3) of the inlet pitch section (L2) to an optimal volume, the ideal compression ratio in each cell can be determined.

For example, based on the starting point (Vs) of the variable pitch section, the empty space screw rotor volume V3 when one rotation is made, the empty space screw rotor volume V2 when one rotation is made again, and the empty space screw rotor volume once again. The ideal volume of volume V1 is:

As can be seen from [Table 1] to [Table 4] below, the volume of cell V3 can be set to 1.20 times or less, preferably 1.03 to 1.10 times the volume of cell V4 (V3/V4 = 1.03 to 1.10).

In addition, the volume of cell V2 can be set to 2.6 times or less than the volume of cell V3, preferably 1.90 to 2.50 times (V2/V3 = 1.90 to 2.50), and the volume of cell V1 is 1.8 times or less than the volume of cell V2. Preferably, each can be set to 1.40 to 1.70 times (V1/V2 = 1.40 to 1.70).

As a result, compression heat generation can be minimized by setting the compression ratio of the screw rotor to an optimal compression ratio, for example, 'compression ratio of variable pitch section: constant pitch section = 4.1:1 ~ 6.3:1', preferably 4.5:1. This can prevent collisions between screw rotors or between screw rotors and housings, and ultimately eliminate the cause of vacuum pump failure.

[Table 1]

[Table 2]

[Table 3]

[Table 4]

Here, [Table 1] and [Table 4] represent normal samples, and [Table 2] and [Table 3] represent samples that had problems due to high temperature. The highest heating temperature of sample 1 was about 100°C, The highest heating temperature of Sample 2 was approximately 180℃, that of Sample 3 was approximately 122℃, and that of Sample 4 was approximately 96℃.

And as can be seen in [Graph 1] and [Graph 2] below, and [Figure 1], appropriately setting the compression ratio in relation to the volume limitation of the cell as above can reduce the increase in absolute temperature and temperature deviation. (Refer to [Graph 1]), if the compression heat increases rapidly, failure may occur due to collision between the screw rotor and the screw rotor or the screw rotor and the housing (Refer to [Graph 2]). According to the configuration of the present invention, there is a great advantage that the gas temperature rise is small at the same capacity.

[Graph 1]

[Graph 2]

[Figure 1]

Here, T1 is the temperature measured at about the 3rd to 4th cell position from the end of the screw, and T2 is the temperature measured at about the 2nd to 3rd cell position from the end of the screw.

In addition, the ratio (D/d) between the outer diameter (D) and the inner diameter (d) of the threads in the inlet pitch section (L2) and the outlet pitch section (L1) is preferably set to 1.5 to 2.

As an example, if the outer diameter (D) of the thread is 150 mm and the inner diameter (d) is 80.4 mm, the ratio (D/d) of the outer diameter (D) of the thread and the inner diameter (d) at this time can be 1.8657. there is.

As another example, if the screw thread outer diameter (D) is 130 mm and the inner diameter (d) is 82 mm, the ratio (D/d) of the screw thread outer diameter (D) and inner diameter (d) can be 1.5854. there is.

As another example, if the outer diameter (D) of the thread is 120 mm and the inner diameter (d) is 79.56 mm, the ratio (D/d) of the outer diameter (D) of the thread and the inner diameter (d) is 1.5083. It can be.

As another example, if the screw thread outer diameter (D) is 92 mm and the inner diameter (d) is 57.4 mm, the ratio (D/d) of the screw thread outer diameter (D) and inner diameter (d) is 1.6028. It can be.

In this way, the ratio of the inner diameter (d) to the outer diameter (D) of the screw thread of the screw rotor can be set to 1.5 or more, and the larger it is set as much as processing allows, the better.

This is more efficient as the overall volume within the screw rotor increases as the inner diameter (d) increases, improving the vacuum degree and vacuum efficiency. As the inner diameter (d) decreases, the thermal expansion distance becomes shorter when the screw rotor generates heat. This is because it has the advantage of stably securing the space between the screw rotors.

For example, [Graph 3] below shows the thermal expansion between the actual screw rotor and the screw rotor when the temperature of the screw rotor with a thread outer diameter (D) of 150 mm increases to 150℃ (e.g., generally increases to 150℃). It represents the distance. When the outer diameter (D) of the thread is 150mm, the expansion distance is limited to about 0.2mm, so D/d is more than 1.5 times appropriate. If it is limited to more than 0.2mm, the vacuum degree and vacuum efficiency will rapidly deteriorate. .

[Graph 3]

And as shown in [Table 5] below, it is desirable to set the length ratio of the inlet pitch section (L2) and the outlet pitch section (L1) to 0.6 or more.

[Table 5]

In [Table 5] above, 7 cells and 6 cells mean the number of cells of the screw rotor in the outlet pitch section (L1), that is, the equal pitch section.

As an example, when the thread outer diameter (D) is 150 mm (7 cells), the length of the outlet pitch section (L1) is 161.2 mm, and the length of the inlet pitch section (L2) is 214 mm, the inlet pitch section at this time The length ratio (L1/L2) of (L2) and the outlet pitch section (L1) may be 0.753.

As another example, when the thread outer diameter (D) is 150 mm (6 cells), the length of the outlet pitch section (L1) is 140.6 mm, and the length of the inlet pitch section (L2) is 214 mm, the inlet pitch section at this time The length ratio (L1/L2) of (L2) and the outlet pitch section (L1) may be 0.657.

As another example, when the thread outer diameter (D) is 120mm (7 cells), the length of the outlet pitch section (L1) is 106.5mm, and the length of the inlet pitch section (L2) is 129.7mm, the inlet at this time The length ratio (L1/L2) of the pitch section (L2) and the outlet pitch section (L1) may be 0.821.

As another example, when the thread outer diameter (D) is 120 mm (6 cells), the length of the outlet pitch section (L1) is 91.7 mm, and the length of the inlet pitch section (L2) is 129.7 mm, the inlet at this time The length ratio (L1/L2) of the pitch section (L2) and the outlet pitch section (L1) may be 0.707.

As can be seen in these various examples, the length ratio (L1/L2) of the inlet pitch section (L2) and the outlet pitch section (L1) can be set to be 0.6 or more, and the inlet pitch section (12) and the outlet pitch section ( By adopting the length ratio (L1/L2) of 13), the generation of compression heat due to rapid compression can be reduced while maintaining the degree of vacuum, thereby achieving effects such as preventing collision of the screw rotor.

Additionally, the lead angle of the inlet pitch section L2 is preferably set to 90 to 100°, and the lead angle of the outlet pitch section L1 is preferably set to 90 to 95°.

That is, the lead angle of the thread in the variable pitch section is set to 90 to 100°, preferably 92 to 98°, and the lead angle of the thread in the equal pitch section is set to 90 to 95°, preferably 90 to 92°. It is desirable to set it to .

Here, if the lead angle of the screw rotor is set large, the gap between the screw rotors can be made smaller, but the screw rotor profile has a relatively long overall length.

Ultimately, the smaller the lead angle is set, the overall length can be reduced with the same number of cells, which significantly reduces the processing time, making it more economical.

Meanwhile, the screw rotor for the vacuum pump includes a control method that can adjust the degree of vacuum according to the internal pressure of the screw rotor.

For this purpose, a pressure sensor (not shown) is installed at the beginning of the inlet pitch section (l2) of the screw rotor 10, and the pressure value at the beginning of the inlet pitch section (L2) is sensed with the installed pressure sensor. In addition, the pressure value sensed at this time is provided to the controller (not shown).

Subsequently, the controller controls the inverter (not shown) with the pressure value input from the pressure sensor to adjust the rotation speed of the screw rotor 10, thereby adjusting the vacuum level of the vacuum pump appropriately, for example, to suit various operating conditions. The degree of vacuum can be easily adjusted.

Figure 5 is a front view showing the state of thread polishing in the equal pitch section of the screw rotor for a vacuum pump according to an embodiment of the present invention.

As shown in FIG. 5, the outer diameter (D') of at least one thread of the outlet pitch section (L1) adjacent to the inlet pitch section (L2), for example, the two threads (21a, 21b), is the outlet pitch section (L2). It may be set to be relatively smaller than the thread outer diameter (D) of the remaining threads (21c to 21f) in the pitch section (L1).

Accordingly, the compression heat after compression in the inlet pitch section (L2) immediately meets the screw thread in the outlet pitch section (l1), which has a smaller outer diameter of the thread, so that the problem of the screw rotor colliding as it expands due to heat generation due to compression can be solved. do.

At this time, the screw threads 21a and 21b, whose outer diameter is set to be relatively small, can be made by grinding the diameter to about 0.2 mm through a polishing process.

In this way, according to the screw rotor for a vacuum pump of the above configuration, a variable pitch section that increases pumping efficiency by sucking in a large amount of gas and a pitch section that discharges the sucked gas in a constant amount are applied, The capacity of the pump is made larger in the variable pitch section (the pump can be made smaller when the capacity is the same), and in the equal pitch section, gas is only transported through pressure distribution (appropriate pressure distribution and heat generation can be adjusted), generating a lot of heat. It has the effect of preventing you from doing it.

In addition, cells V1, V2, and V3 areas inevitably generate compression heat due to significant gas intake, and if the compression ratio between V1 vs. V2, V2 vs. V3, and V3 vs. V4 is significantly different, the compression heat of the gas is easily lost. It cannot escape and accumulates inside the cell. In the present invention, by setting the optimal volume ratio between cells V1 vs. V2, V2 vs. V3, and V3 vs. V4, the compression heat of the gas can easily escape while maintaining the vacuum, thereby reducing the generation of compression heat. There is an effect that can be minimized.

For example, graphs 4 to 6 below show the rotor with various samples applied to ensure the thermal stability of the rotor (e.g., temperature 80 to 120°C during rotor operation) required by vacuum pump manufacturers as well as vacuum pump consumers. This is data measuring the temperature of .

The results in Graph 4 show that the volume ratio of V2/V3 and V3/V4 are fixed to the volume ratio range suggested by the present invention (V2/V3 = 2.4, V3/V4 = 1.06), and the volume ratio of V1/V2 is variously changed. This is the result of measuring the temperature, and the result in Graph 5 is V2 with the volume ratio of V1/V2 and V3/V4 fixed to the volume ratio range suggested by the present invention (V1/V2 = 1.64, V3/V4 = 1.03). This is the result of measuring the temperature by varying the volume ratio of /V3.

Likewise, the results in Graph 6 show that the volume ratio of V3/V4 is varied while the volume ratio of V1/V2 and V2/V3 are fixed to the volume ratio range suggested by the present invention (V1/V1=1.67, V2/V3=2.31). This is the result of measuring the temperature by changing the temperature.

The volume of cell V1 is set to 1.40 to 1.70 times the volume of cell V2, the volume of cell V2 is set to 1.90 to 2.50 times the volume of cell V3, and the volume of cell V3 is set to 1.03 to 1.10 times the volume of cell V4. It can be seen that the sample of the present invention satisfies the temperature of 120°C or less, but it can be seen that there is a limit to reducing the heat generation of the rotor in the case of the sample outside the volume ratio range of the cell of the present invention.

[Graph 4]

[Graph 5]

[Graph 6]

In addition, in constructing the screw rotor for a vacuum pump according to the present invention, it is important to set a volume ratio combination that can maintain the temperature of the rotor below 120°C, that is, a volume ratio combination of V1/V2, V2/V3, and V3/V4. Importantly, maintaining the temperature of the rotor below 120°C means maintaining the temperature of the gas below 120°C when the vacuum pump operates.

The reason why the temperature of the rotor and the temperature of the gas must be maintained below 120°C will be explained with reference to Tables 6 to 8 below.

[Table 6]

[Table 7]

Table 6 shows the thermal expansion value of the radius according to each gas temperature by rotor (rotor) size (in the case of dry vacuum pumps used in semiconductor processes, a screw rotor (rotor) with an outer diameter of about 90 to 150 mm is used), As the temperature increases, the size of the outer diameter increases.

As shown in Table 7, the temperature of the stator (housing) is fixed at 80 degrees Celsius (a temperature often used in semiconductor processes, and typically up to 130 degrees Celsius is used), and the thermal expansion values of the rotor and stator (housing) are applied. In this case, when the temperature of the gas exceeds 130℃, it can be seen that the gap between the rotor and the stator is reduced to less than 0.1mm in some sizes.

When the gap is reduced to less than 0.1mm (i.e. 100㎛), considering the bearing gap that supports the rotor rotating at high speed (usually over 6,000RPM), the gap in the bearing housing, and the vibration of the rotor, the gap between the rotor and the rotor is reduced. It is unsuitable for dry vacuum pumps that require a gap of 100㎛ or more because it causes interference between electrons or between rotor and stator, resulting in collision.

Of course, it is possible to adjust the outer diameter of the rotor, the inner diameter of the stator, etc. to make various sizes to suit each temperature range, but in the case of semiconductor processing, the same pump (same stator and rotor size) must be used for various temperature bands, so it is compressed as much as possible. Since heat must be reduced so that multiple bands can be used, there is an advantage of lower maintenance costs because multiple models are not produced.

[Table 8]

In addition, in the case of a dry vacuum pump, the larger the spatial area is within the range allowed by the vacuum level, the longer the lifespan increases. However, if the gap decreases due to an increase in gas temperature, the lifespan also decreases accordingly.

For example, in the case of a rotor with an outer diameter of 120 mm, the space area increases by 22% when the gas temperature is 80°C compared to when the gas temperature is 120°C, which means that the life of the vacuum pump increases by more than 22%.

In the screw rotor for a vacuum pump according to the present invention, the variable pitch section increases pumping efficiency by sucking in a large amount of gas, and the equal pitch section allows the sucked gas to be discharged in a constant amount while appropriately distributing the pressure in the pump. It can be used to do this.

In addition, in the present invention, a combination of a variable pitch section and a constant pitch section is provided to control the amount of heat generated through appropriate pressure distribution, and the volume between each cell is adjusted so that the compression ratio between each cell in the variable pitch section does not differ significantly. It is set appropriately so that the compression heat of the gas can easily escape.

In addition, by setting the length ratio (L1/L2) of the inlet pitch section (L2) and the outlet pitch section (L1) to 0.6 or more, there is an effect of reducing compression heat generation due to rapid compression while maintaining the degree of vacuum. .

In other words, the L1/L2 ratio directly affects cells V1 to V4 (compression ratio), but the number of cells is also determined by how to distribute pressure within the pump, so about 7 cells are used. However, when reducing the number of cells, the cell (pitch) size must be increased (screw lengthened) and gas discharge must be increased to maintain vacuum and remove compression heat. At that time, L1 is The length ratio must be set to at least 0.6.

In addition, from the viewpoint of process applicability (semiconductor process, etc.) (pump life and safety), according to the present invention, it is easy to set partial pressure with equal pressure distribution in the back pitch section (the pressure of the cell is 1/2 of the back cell, For example, the last cell is 760 Torr, the previous cell is 380 Torr), and the N ₂ purge location (for gas dilution) and amount can be easily selected, so it can be used advantageously in process applications.

From the viewpoint of machinability (cost), in the present invention, only the variable pitch section must maintain a constant angle, so the processing speed of the milling equipment is slow, but the equal pitch section can process a large amount at once, which can shorten the processing time and assembly. From a performance standpoint (cost and quality), it has the advantage of being simple to assemble and making it easy to adjust the gap between the screw cell and the cell.

In this way, in the present invention, the combination of the variable pitch section and the back pitch section directly related to securing the capacity of the pump, distributing pressure, minimizing compression heat generation, etc., the relative volume ratio between each cell in the variable pitch section, and the ratio of the inlet pitch section and the outlet pitch section. The length ratio is presented, and as described above, through appropriate pressure distribution in the back pitch section, it is possible to prevent a lot of heat from being generated by only allowing gas to be transported, and cells V1 vs V2, V2 vs V3, and V3 vs V4. By reducing the difference in compression ratio between the two sections, the compression heat of the gas can be easily escaped while maintaining the vacuum. By appropriately setting the length ratio of the inlet pitch section and the outlet pitch section, the generation of compression heat due to rapid compression can be reduced while maintaining the vacuum degree. there is.

Figure 6 is a perspective view showing the coupled state of the lobe device in the screw rotor for a vacuum pump according to an embodiment of the present invention.

As shown in FIG. 6, a vacuum pump combining a screw rotor 10 and a lobe device 22 is shown.

The lobe device 22 may be directly connected to the screw rotor 10 or may be coupled with a partition wall. The lobe devices 22 combined in this way create a vacuum while rotating together at the tip of the screw rotor 10, thereby further increasing the vacuum efficiency of the vacuum pump.

As an example, the lobe device 22 includes a casing 23 with an inlet and an outlet formed on both sides of the space, and is rotatably installed inside the casing 23 to receive power from the motor 19. It may include a pair of lobes 24 that engage and rotate with each other.

Figure 7 is a cross-sectional view showing the cooling structure of the screw rotor in the screw rotor for a vacuum pump according to an embodiment of the present invention.

As shown in FIG. 7, a hole (not shown) parallel to the axis is formed in the screw rotor 10, and an oil supply pipe 12 is installed inside the hole thus formed.

Here, the distal end of the oil supply pipe 12 maintains a gap with the closed end of the hole in the screw rotor, and at the same time, the outer circumference of the oil supply pipe 12 also maintains a gap with the inner peripheral surface of the hole, and accordingly, the oil supply pipe 12 ) The oil that escapes through the tip of the oil flows backwards through the gap between the oil supply pipe (12) and the hole, falls into the inside of the housing (14), and is then recovered into the oil pan (11).

And the oil sent from the oil supply device 13 is supplied to the oil supply pipe 12, and the supplied oil flows inside the hole 11 to cool the screw rotor 10.

This oil supply device 13 includes an oil pan 11 for storing a certain amount of oil, and an oil pump (not shown) that is operated by output control of the microprocessor 25 and pumps the oil in the oil pan 11. , a heat exchanger 26 for heat exchange of the oil pumped by the oil pump and supplied to the oil supply pipe 12, etc.

In addition, the oil line 27 connected from the oil pan 11 leads to the oil pump, and the oil line 27 continues to the heat exchanger 26 through a filter (not shown), and then to the floor switch or It connects to the oil supply pipe (12) through sensors, etc.

Therefore, the oil supply device 13 can cool the screw rotor using an oil circulation line that leads to oil pan → oil pump → heat exchanger → oil supply pipe → inside of housing → oil pan.

By implementing a new system that cools the vacuum pump by controlling the temperature of the screw rotor by circulating oil inside the screw rotor of the vacuum pump, it is possible to prevent a rapid rise in the temperature of the vacuum pump, especially the screw rotor. Furthermore, the stability of process performance and vacuum pump operation can be secured, and the vacuum pump can be maintained and managed economically.

In this way, in the present invention, the thread section of the screw-type rotor that forms the vacuum of the vacuum pump is composed of a combination of a variable pitch section and a constant pitch section, and the gap between the threads on both sides where the two screws are engaged is theoretically set to zero. By providing a new type of screw rotor designed with a profile of , it is possible to not only improve the function and durability of the screw rotor, but also realize a highly efficient screw rotor that can be manufactured with a machine tool.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements can be made by those skilled in the art using the basic concept of the present invention defined in the following claims. Included in the scope of rights of the present invention.

10: screw rotor
11: Oil pan
12: Oil supply pipe
13: Oil supply device
14: housing
15: Entrance
16: exit
17: shaft
18: Electric gear
19: motor
20: coupler
21a ~ 21f: thread
22: Lobe device
23: Casing
24: Lobe
25: microprocessor
26: heat exchanger
27: Oil line

Claims (9)

In the screw rotor for a vacuum pump in which two screw rotors (10) engage and rotate to form a vacuum,
The screw rotor 10 includes a cell V1 that determines the maximum intake amount of gas, and a cell that compresses the gas to create a specific compression ratio and primarily distributes the compression heat to prevent the screw rotor in the V3 area from rapidly expanding due to the compression heat. An inlet pitch section (L2) consisting of a variable pitch section and including cell V3, which compresses gas to create a specific compression ratio and distributes compression heat to prevent the screw rotor in the V4 to VN region from rapidly expanding due to compression heat; , an outlet pitch section (L1) consisting of equal pitch sections and including cells V4 to VN that seal the sucked gas to form a constant vacuum degree,
The volume of the cell V3 is set to 1.03 to 1.10 times the volume of cell V4, the volume of cell V2 is set to 1.90 to 2.50 times the volume of cell V3, and the volume of cell V1 is set to 1.40 to 1.70 times the volume of cell V2. By setting it to double, the compression ratio between the variable pitch section and the constant pitch section is set to 4.1:1 ~ 6.3:1, so that the increase in absolute temperature and temperature deviation can be reduced, thereby minimizing the generation of compression heat. Screw rotor for vacuum pump.
In claim 1,
A screw rotor for a vacuum pump, characterized in that the ratio of the outer diameter (D) and the inner diameter (d) of the threads of the inlet pitch section (L2) and the outlet pitch section (L1) is set to 1.5 to 2.
In claim 1,
A screw rotor for a vacuum pump, characterized in that the length ratio of the inlet pitch section (L2) and the outlet pitch section (L1) is set to 0.6 or more.
In claim 1,
A screw rotor for a vacuum pump, characterized in that the lead angle of the inlet pitch section (L2) is set to 90 to 100°, and the lead angle of the outlet pitch section (L1) is set to 90 to 95°.
In claim 1,
A screw rotor for a vacuum pump, characterized in that the pressure value at the beginning of the inlet pitch section (L2) is sensed and the degree of vacuum can be adjusted by adjusting the rotation speed using an inverter using the sensed pressure value.
In claim 1,
The outer diameter (D') of at least one thread in the outlet pitch section (L1) adjacent to the inlet pitch section (L2) is set to be relatively smaller than the outer diameter (D') of the remaining threads in the outlet pitch section (L1), thereby reducing compression. A screw rotor for a vacuum pump, characterized in that it solves the problem of the rotor colliding while expanding due to heat generation.
In claim 1,
A screw rotor for a vacuum pump, characterized in that it further includes a lobe device (22) that is directly connected to the screw rotor or coupled with a partition wall to increase the vacuum efficiency of the pump.
In claim 1,
In the screw rotor 10, a parallel hole is formed along the axis, and an oil supply pipe 12 is installed inside the hole, and oil sent from the oil supply device 13 is supplied to the oil supply pipe 12, A screw rotor for a vacuum pump, characterized in that the oil supplied through the oil supply pipe (12) flows inside the hole of the screw rotor (10) to cool the screw rotor (10).
In the screw rotor for a vacuum pump in which two screw rotors (10) engage and rotate to form a vacuum,
The screw rotor 10 includes a cell V1 that determines the maximum intake amount of gas, and a cell that compresses the gas to create a specific compression ratio and primarily distributes the compression heat to prevent the screw rotor in the V3 area from rapidly expanding due to the compression heat. An inlet pitch section (L2) consisting of a variable pitch section and including cell V3, which compresses gas to create a specific compression ratio and distributes compression heat to prevent the screw rotor in the V4 to VN region from rapidly expanding due to compression heat; , an outlet pitch section (L1) consisting of equal pitch sections and including cells V4 to VN that seal the sucked gas to form a constant vacuum degree,
The outer diameter (D') of at least one thread in the outlet pitch section (L1) adjacent to the inlet pitch section (L2) is set to be relatively smaller than the outer diameter (D') of the remaining threads in the outlet pitch section (L1), thereby reducing compression. A screw rotor for a vacuum pump, characterized in that it solves the problem of the rotor colliding while expanding due to heat generation.