Vacuum pump device and its operating method

Abstract

To provide a vacuum pump device that reduces accumulation of a by-product caused by process gas, in a pump chamber, is prevented from being unintentionally stopped, and can be reliably restarted.SOLUTION: A vacuum pump device comprises a pump casing 2 internally comprising a pump chamber 1, a pump rotor 5E arranged in the pump chamber 1, a rotating shaft 7 to which the pump rotor 5E is fixed, a bearing 17 rotatably supporting the rotating shaft 7, a side cover 10A connected to the pump casing 2, a heater 35 attached to the side cover 10A, and a heater control unit 40 for making the heater 35 intermittently produce heat when the pump rotor 5E is rotating. The bearing 17 is connected to the side cover 10A.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a vacuum pump device and an operation method thereof, and more particularly to a vacuum pump device and an operation method thereof that are suitably used for exhausting process gases used in the manufacture of semiconductor devices, liquid crystal panels, LEDs, solar cells, and the like.

Background Art

[0002] In the process of manufacturing semiconductor devices, liquid crystal panels, LEDs, solar cells, etc., process gases are introduced into a process chamber to perform various processes such as etching and CVD processes. The process gas introduced into the process chamber is exhausted by a vacuum pump device. Generally, the vacuum pump device used in these manufacturing processes that require a high degree of cleanliness is a so-called dry vacuum pump device that does not use oil in the gas flow path. As a representative example of such a dry vacuum pump device, there is a positive displacement vacuum pump device that rotates a pair of pump rotors arranged in a pump chamber in opposite directions to transfer gas.

[0003] The process gas introduced into the process chamber may form solidified by-products when its temperature decreases or increases after undergoing a reaction in the chamber. If a large amount of solidified by-products accumulates in the vacuum pump device, it may inhibit the rotation of the pump rotor and cause the vacuum pump device to suddenly stop. If the vacuum pump device stops unexpectedly, it will damage products such as semiconductor devices being manufactured.

[0004] The above-mentioned by-products also accumulate in the pipes connecting the process chamber and the vacuum pump device, and in the pipes connecting the vacuum pump device and the decontamination device on its downstream side. Therefore, pipe maintenance is regularly performed. At this time, the vacuum pump device is stopped, and when the pipe maintenance is completed, the vacuum pump device is restarted. However, if a large amount of by-products accumulates in the pump chamber, the resistance to the rotation of the pump rotor may be large, and the vacuum pump device may not be restarted. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2009-97349 [Overview of the project] [Problems that the invention aims to solve]

[0006] Therefore, a pump stopping method has been proposed in which, when stopping the operation of a vacuum pump device, the pump rotor is repeatedly rotated and stopped to gradually scrape off by-products accumulated in the pump chamber (see Patent Document 1). According to this method, by-products are removed from the pump chamber, and the vacuum pump device can be restarted.

[0007] However, this pump shutdown method took a long time to complete (for example, around 3 hours), which reduced the throughput of product manufacturing, such as semiconductor devices, and was therefore sometimes unacceptable to users.

[0008] Therefore, the present invention provides a vacuum pump and a method for operating the vacuum pump that can reduce the accumulation of by-products caused by process gas in the pump chamber, prevent unintended shutdowns of the vacuum pump system, and ensure restart of the vacuum pump system. [Means for solving the problem]

[0009] In one embodiment, a vacuum pump device is provided, comprising a pump casing having a pump chamber inside, a pump rotor disposed within the pump chamber, a rotating shaft to which the pump rotor is fixed, an electric motor connected to the rotating shaft, a bearing that rotatably supports the rotating shaft, a side cover connected to the pump casing, a heater attached to the side cover, and a heater control unit that intermittently heats the heater when the pump rotor is rotating, wherein the bearing is connected to the side cover. In one embodiment, the side cover forms the end face of the pump chamber. In one embodiment, the pump casing forms the end face of the pump chamber.

[0010] In one embodiment, the vacuum pump device further comprises a bearing housing that holds the bearing, and the bearing housing is held by the side cover. In one embodiment, the side cover comprises a side wall forming the end face of the pump chamber and a spacer made of the same material as the side wall or a material with a higher coefficient of thermal expansion than the side wall, and the heater is disposed within the spacer. In one embodiment, the side cover forms the end face of the pump chamber and includes a side wall made of the same material as the rotating shaft or a material with a higher coefficient of thermal expansion than the rotating shaft, and a spacer for holding the bearing, and the heater is arranged within the side wall. In one embodiment, the side cover comprises a side wall connected to the pump casing and a spacer made of the same material as the side wall or a material with a higher coefficient of thermal expansion than the side wall, and the heater is disposed within the spacer. In one embodiment, the side cover is connected to the pump casing and comprises a side wall made of the same material as the rotating shaft or a material with a higher coefficient of thermal expansion than the rotating shaft, and a spacer for holding the bearing, with the heater located within the side wall.

[0011] In one embodiment, the vacuum pump device further includes a first temperature sensor for measuring the temperature of the pump casing and a second temperature sensor for measuring the temperature of the side cover, and the heater control unit determines a target temperature based on the temperature of the pump casing and controls the heater so that the temperature of the side cover reaches the target temperature. In one embodiment, the heater control unit is configured to stop the heater from generating heat or to lower the heater's heating temperature after the temperature of the side cover reaches the target temperature. In one embodiment, the vacuum pump device further includes a displacement sensor for measuring the axial displacement of the bearing, and the heater control unit is configured to stop heating the heater when the axial displacement of the bearing reaches a threshold value. In one embodiment, the vacuum pump device further comprises a second heater attached to the pump casing. In one embodiment, the vacuum pump device further comprises a cooler attached to the pump casing.

[0012] In one embodiment, a method for operating a vacuum pump device is provided, wherein a pump rotor located in the pump chamber of a pump casing is fixed to a rotating shaft, the rotating shaft is rotatably supported by a bearing, the bearing is connected to a side cover connected to the pump casing, and a heater attached to the side cover is intermittently heated when process gas is exhausted by the rotation of the pump rotor. In one embodiment, the side cover forms the end face of the pump chamber. In one embodiment, the pump casing forms the end face of the pump chamber.

[0013] In one embodiment, the bearing is held in a bearing housing, and the bearing housing is held in a side cover. In one embodiment, the side cover comprises a side wall forming the end face of the pump chamber and a spacer made of the same material as the side wall or a material with a higher coefficient of thermal expansion than the side wall, and the heater is disposed within the spacer. In one embodiment, the side cover forms the end face of the pump chamber and includes a side wall made of the same material as the rotating shaft or a material with a higher coefficient of thermal expansion than the rotating shaft, and a spacer for holding the bearing, and the heater is arranged within the side wall. In one embodiment, the side cover comprises a side wall connected to the pump casing and a spacer made of the same material as the side wall or a material with a higher coefficient of thermal expansion than the side wall, and the heater is disposed within the spacer. In one embodiment, the side cover is connected to the pump casing and comprises a side wall made of the same material as the rotating shaft or a material with a higher coefficient of thermal expansion than the rotating shaft, and a spacer for holding the bearing, with the heater located within the side wall.

[0014] In one embodiment, the operating method further includes determining a target temperature based on the temperature of the pump casing and controlling the heater so that the temperature of the side cover reaches the target temperature. In one embodiment, the operating method further includes stopping the heating of the heater or lowering the heating temperature of the heater after the temperature of the side cover has reached the target temperature. In one embodiment, the operating method further includes stopping the heating of the heater when the axial displacement of the bearing reaches a threshold. In one embodiment, the operating method further includes heating the pump casing with a second heater attached to the pump casing. In one embodiment, the operating method further includes cooling the pump casing with a cooler attached to the pump casing. [Effects of the Invention]

[0015] As the pump rotor rotates and the heater intermittently generates heat, the side cover repeatedly expands and contracts due to the heat, causing the rotating shaft to reciprocate axially via the bearing connected to the side cover. This axial reciprocating motion of the rotating shaft also causes the pump rotor to reciprocate axially, allowing the rotating rotor to scrape off by-products accumulated in the pump chamber. As a result, the pump rotor can rotate smoothly. [Brief explanation of the drawing]

[0016] [Figure 1] It is a cross-sectional view showing an embodiment of a vacuum pump device. [Figure 2] It is an enlarged cross-sectional view showing a side cover, a bearing housing, and a bearing on the exhaust side. [Figure 3] It is a cross-sectional view showing a state in which the pump rotor has moved axially along with the thermal expansion of the rotating shaft. [Figure 4] It is a cross-sectional view showing a state in which the spacer is thermally expanded by the heat generation of the heater, and the pump rotor is moved toward the side cover. [Figure 5] It is a cross-sectional view showing an embodiment provided with a displacement sensor for measuring the displacement of the bearing. [Figure 6] It is a cross-sectional view showing an embodiment of a side cover composed of a single material. [Figure 7] It is a cross-sectional view showing an embodiment in which the bearing is directly held by the side cover. [Figure 8] It is a cross-sectional view showing another embodiment in which the bearing is directly held by the side cover. [Figure 9] It is a view showing an embodiment of a vacuum pump device provided with a second heater attached to the pump casing. [Figure 10] It is a view showing an embodiment of a vacuum pump device provided with a cooler attached to the pump casing. [Figure 11] It is a cross-sectional view showing another embodiment of the vacuum pump device. [Figure 12] It is a cross-sectional view showing still another embodiment of the vacuum pump device. [Figure 13] It is a cross-sectional view showing still another embodiment of the vacuum pump device.

Embodiments for Carrying Out the Invention

[0017] Figure 1 is a cross-sectional view showing one embodiment of a vacuum pump device. The vacuum pump device of the embodiment described below is a positive displacement vacuum pump device. In particular, the vacuum pump device shown in Figure 1 is a so-called dry vacuum pump device that does not use oil in the gas flow path. Since vaporized oil does not flow upstream, a dry vacuum pump device can be suitably used in semiconductor device manufacturing equipment that requires a high degree of cleanliness.

[0018] As shown in Figure 1, the vacuum pump device comprises a pump casing 2 having a pump chamber 1 inside, pump rotors 5A to 5E arranged inside the pump chamber 1, a rotating shaft 7 to which the pump rotors 5A to 5E are fixed, and an electric motor 8 connected to the rotating shaft 7. The pump rotors 5A to 5E and the rotating shaft 7 may be an integrated structure. In Figure 1, only one set of pump rotors 5A to 5E and a rotating shaft 7 is depicted, but a pair of pump rotors 5A to 5E are arranged inside the pump chamber 1 and fixed to a pair of rotating shafts 7, respectively. The electric motor 8 is connected to one of the pair of rotating shafts 7. In one embodiment, a pair of electric motors 8 may be connected to a pair of rotating shafts 7, respectively.

[0019] In this embodiment, the pump rotors 5A to 5E are Roots-type pump rotors, but in one embodiment, the pump rotors 5A to 5E may be claw-type pump rotors. Furthermore, the pump rotors 5A to 5E may be a combination of a Roots-type pump rotor and a claw-type pump rotor. In this embodiment, the pump rotors 5A to 5E are multi-stage pump rotors, but in one embodiment, the pump rotor may be a single-stage pump rotor.

[0020] The vacuum pump device further includes side covers 10A and 10B located outside the pump casing 2 in the axial direction of the rotating shaft 7. The side covers 10A and 10B are provided on both sides of the pump casing 2 and are connected to the pump casing 2. In this embodiment, the side covers 10A and 10B are fixed to the end faces of the pump casing 2 by screws (not shown).

[0021] The pump chamber 1 is formed by the inner surface of the pump casing 2 and the inner surfaces of the side covers 10A and 10B. The pump casing 2 has an intake port 2a and an exhaust port 2b. The intake port 2a is connected to a chamber (not shown) filled with the gas to be transferred. In one example, the intake port 2a is connected to a process chamber of a semiconductor device manufacturing apparatus, and the vacuum pump apparatus is used to exhaust process gas from the process chamber.

[0022] The vacuum pump device further comprises a motor housing 14 and a gear housing 16, which are housing structures located outside the side covers 10A and 10B in the axial direction of the rotating shaft 7. Side cover 10A is located between the pump casing 2 and the motor housing 14, and side cover 10B is located between the pump casing 2 and the gear housing 16.

[0023] The motor housing 14 houses the motor rotor 8A and motor stator 8B of the electric motor 8. Inside the gear housing 16 are a pair of gears 20 that mesh with each other. Note that only one gear 20 is shown in Figure 1. The electric motor 8 is rotated by a motor driver (not shown), and one rotating shaft 7 to which the electric motor 8 is connected rotates the other rotating shaft 7, to which the electric motor 8 is not connected, in the opposite direction via the gear 20.

[0024] In one embodiment, a pair of electric motors 8 may be provided, each connected to a pair of rotating shafts 7. The pair of electric motors 8 rotate synchronously in opposite directions by a motor driver (not shown), causing the pair of rotating shafts 7 and the pair of pump rotors 5A to 5E to rotate synchronously in opposite directions. In this case, the role of the gear 20 is to prevent the synchronous rotation of the pump rotors 5 from being lost due to sudden external factors.

[0025] In the embodiment shown in Figure 1, the motor housing 14 is located outside the side cover 10A and the gear housing 16 is located outside the side cover 10B, but the configuration of the vacuum pump device is not limited to this embodiment. In one embodiment, the gear housing 16 may be located outside the side cover 10A and the motor housing 14 may be located outside the side cover 10B. Furthermore, in one embodiment, both the motor housing 14 and the gear housing 16 may be located outside either the side cover 10A or the side cover 10B.

[0026] When the electric motor 8 rotates the pump rotors 5A to 5E, gas is drawn into the pump chamber 1 of the pump casing 2 through the intake port 2a. The gas is sequentially compressed by the rotating pump rotors 5A to 5E and transferred to the exhaust port 2b, where it is discharged from the pump chamber 1.

[0027] The rotating shaft 7 is rotatably supported by bearings 17 and 18. Bearing 17 is held in a bearing housing 24, and bearing 18 is supported in a side cover 10B. Bearing 17 is connected to the side cover 10A via the bearing housing 24. More specifically, the bearing housing 24 is held in the side cover 10A, and the positions of the bearing housing 24 and bearing 17 are fixed by the side cover 10A. Since the inner ring of bearing 17 is fixed to the rotating shaft 7, the axial position of the portion of the rotating shaft 7 held in bearing 17 is fixed.

[0028] On the other hand, the bearing 18 is supported by the side cover 10B so as to be movable in the axial direction. More specifically, the inner ring of the bearing 18 is fixed to the rotating shaft 7, but the outer ring of the bearing 18 is not fixed to the side cover 10B, but is simply supported by the side cover 10B. Therefore, the bearing 18 is movable in the axial direction integrally with the rotating shaft 7.

[0029] A bearing housing that holds the bearing 18 may be positioned between the side cover 10B and the bearing 18. In this case, the bearing housing is fixed to the side cover 10B, but the outer ring of the bearing 18 is not fixed to the bearing housing, but is merely supported by the bearing housing, and the bearing 18 can move axially together with the rotating shaft 7.

[0030] During operation of the vacuum pump system, the gas is compressed as it is transferred from the intake port 2a to the exhaust port 2b by the pump rotors 5A to 5E. Therefore, the rotating shaft 7 located inside the pump chamber 1 undergoes thermal expansion due to the heat of gas compression. Since the axial position of bearing 17 is fixed while bearing 18 is movable in the axial direction, the rotating shaft 7 undergoes thermal expansion in the axial direction starting from bearing 17, and bearing 18 moves in the axial direction in conjunction with the thermal expansion of the rotating shaft 7.

[0031] Figure 2 is an enlarged cross-sectional view showing the side cover 10A, bearing housing 24, and bearing 17 on the exhaust side. As shown in Figure 2, the pump casing 2 has a partition wall 36 inside, and the pump rotor 5E is positioned between the partition wall 36 and the side cover 10A. In this embodiment, the side cover 10A comprises a side wall 31 that forms the end face of the pump chamber 1, and a spacer 32 made of the same material as the side wall 31, or a material with a higher coefficient of thermal expansion than the side wall 31. The spacer 32 is positioned between the side wall 31 and the bearing housing 24. The bearing housing 24 is held by the spacer 32, and the bearing housing 24 is connected to the side wall 31 via the spacer 32.

[0032] The vacuum pump device includes a heater 35 attached to the side cover 10A. In this embodiment, the heater 35 is located within a spacer 32 of the side cover 10A. The spacer 32 is made of the same material as the side wall 31 and the pump casing 2, or a metal with a higher coefficient of thermal expansion than the side wall 31. For example, if the side wall 31 and the pump casing 2 are made of cast iron, the spacer 32 is made of cast iron, or stainless steel, aluminum, aluminum alloy, or copper with a higher coefficient of thermal expansion than cast iron. When the heater 35 generates heat, the spacer 32 expands due to thermal expansion, and the bearing housing 24 held by the spacer 32 moves axially. In particular, the spacer 32 has a shape that surrounds the bearing housing 24 and is prone to thermal expansion in the axial direction.

[0033] The process gas handled by the vacuum pump system may form solidified by-products as its temperature decreases or increases after reactions within the chamber. Such by-products gradually accumulate in the pump chamber 1 as the vacuum pump system operates. Figure 3 is a cross-sectional view showing the pump rotor 5E moving axially due to the thermal expansion of the rotating shaft 7. As described above, the high-temperature rotating shaft 7 expands axially, and as a result, the pump rotor 5E moves away from the side cover 10A that forms the end face of the pump chamber 1. The by-products 100 gradually accumulate in the gap between the pump rotor 5E and the side cover 10A. Such by-products 100 obstruct the rotation of the pump rotor 5E, causing unintended shutdowns of the vacuum pump system or preventing the vacuum pump system from restarting.

[0034] Therefore, as shown in Figure 4, the heat generated by the heater 35 causes the spacer 32 to expand, which moves the bearing housing 24 and the bearing 17 in the axial direction, and moves the pump rotor 5E toward the side cover 10A. As the rotating pump rotor 5E moves toward the side cover 10A (the end face of the pump chamber 1), it gradually scrapes off the by-products 100 that have accumulated in the gap between the pump rotor 5E and the side cover 10A.

[0035] When the pump rotor 5E reaches the initial position shown in Figure 2, the heater 35 stops generating heat. The initial position of the pump rotor 5E is the position of the pump rotor 5E when the entire vacuum pump system is at room temperature. When the heater 35 stops generating heat, the temperature of the spacer 32 gradually decreases, and the spacer 32 gradually contracts. As the spacer 32 contracts, the pump rotor 5E moves away from the side cover 10A, and the gap between the pump rotor 5E and the side cover 10A increases, as shown in Figure 3. By-products 100 gradually accumulate in this gap, so the heater 35 is heated again to cause thermal expansion of the spacer 32. As shown in Figure 4, the rotating pump rotor 5E moves toward the side cover 10A (the end face of the pump chamber 1), gradually scraping off the by-products 100 accumulated in the gap between the pump rotor 5E and the side cover 10A.

[0036] Similarly, the by-products 100 deposited between the bulkhead 36 and the pump rotor 5E are gradually scraped off by the rotating pump rotor 5E when the heating of the heater 35 is stopped and the pump rotor 5E moves away from the side cover 10A (towards the bulkhead 36).

[0037] In this way, during the operation of the vacuum pump system (i.e., during the exhaust of process gas), the heater 35 is repeatedly heated and then stopped, causing the rotating pump rotor 5E to reciprocate in the axial direction, thereby scraping off by-products accumulated in the pump chamber 1. By a similar mechanism, the rotating pump rotors 5A to 5D can also scrape off by-products accumulated in the pump chamber 1. As a result, by-products are removed from the pump chamber 1, and the pump rotors 5A to 5E can rotate smoothly.

[0038] In conventional pumps, the pump rotor did not reciprocate as described above during operation. As a result, a large amount of by-products accumulated near the pump rotor during operation, and at some point, the pump would suddenly stop due to the accumulation of a large amount of by-products. According to the present invention, since the pump rotors 5A to 5E constantly reciprocate, a state can be created in the pump chamber 1, particularly near the pump rotors 5A to 5E, where almost no by-products accumulate, thus preventing the sudden stopping of the pump.

[0039] As shown in Figure 2, the vacuum pump device includes a heater control unit 40 that controls the heat generation of the heater 35. The heater control unit 40 is configured to intermittently generate heat in the heater 35 (periodically repeating the heating and stopping of the heater 35) when the pump rotors 5A to 5E are rotating. The heater control unit 40 includes a storage device 40a in which a program is stored, an arithmetic unit 40b that performs calculations according to the instructions contained in the program, and a power supply 40c that supplies power to the heater 35. The heater control unit 40 includes at least one computer. The storage device 40a includes a main memory such as random access memory (RAM) and an auxiliary storage device such as a hard disk drive (HDD) or solid state drive (SSD). Examples of arithmetic units 40b include a CPU (central processing unit) and a GPU (graphics processing unit). However, the specific configuration of the heater control unit 40 is not limited to these examples.

[0040] The vacuum pump device further includes a first temperature sensor 45 for measuring the temperature of the pump casing 2 and a second temperature sensor 46 for measuring the temperature of the side cover 10A. The first temperature sensor 45 is fixed to the pump casing 2. The first temperature sensor 45 may be fixed to the outer surface of the pump casing 2 or embedded inside the pump casing 2. This first temperature sensor 45 is provided to indirectly measure the temperature of the rotating shaft 7. That is, the temperature of the rotating shaft 7 located inside the pump casing 2 can be estimated from the temperature of the pump casing 2 measured by the first temperature sensor 45.

[0041] The second temperature sensor 46 is fixed to the side cover 10A. The second temperature sensor 46 may be fixed to the outer surface of the side cover 10A, or it may be embedded inside the side cover 10A. In the embodiments shown in Figures 2 to 4, the second temperature sensor 46 is fixed to the spacer 32 of the side cover 10A. Therefore, the second temperature sensor 46 can measure the temperature of the side cover 10A (more specifically, the temperature of the spacer 32). The second temperature sensor 46 may be embedded inside the spacer 32.

[0042] The heater control unit 40 is configured to determine the target temperature of the spacer 32, i.e., the target temperature of the side cover 10A, based on the temperature of the pump casing 2 measured by the first temperature sensor 45. Since the temperature of the pump casing 2 indirectly indicates the temperature of the rotating shaft 7, the degree of thermal expansion of the rotating shaft 7, i.e., the axial distance traveled by the pump rotor 5E from its initial position, can be estimated from the temperature of the pump casing 2. Therefore, the heater control unit 40 can determine the target temperature of the spacer 32 necessary to return the pump rotor 5E, which has moved due to the thermal expansion of the rotating shaft 7, to its initial position.

[0043] The heater control unit 40 determines the target temperature of the spacer 32 required to return the pump rotor 5E to its initial position, based on the temperature of the pump casing 2, the axial thickness of the spacer 32, and the coefficient of linear expansion of the spacer 32. Alternatively, the relationship between the distance traveled by the pump rotor 5E and the temperature of the spacer 32 may be determined by experimentation or simulation, and the target temperature of the spacer 32 may be determined from the obtained relationship.

[0044] The heater control unit 40 is configured to control the heater 35 so that the temperature of the spacer 32 reaches the target temperature determined above. The temperature of the spacer 32 is measured by the second temperature sensor 46, and the spacer 32 is heated to the target temperature. As the spacer 32 heats up, the bearing housing 24, bearing 17, rotating shaft 7, and pump rotor 5E move axially. When the spacer 32 has reached the target temperature, the pump rotor 5E returns to the initial position shown in Figure 4. After that, the heater control unit 40 stops the heating of the heater 35. In one embodiment, after the spacer 32 has reached the target temperature, the heater control unit 40 may reduce the heating temperature of the heater 35. Furthermore, after reducing the heating temperature of the heater 35, the heater control unit 40 may stop the heating of the heater 35.

[0045] In this way, the heater control unit 40 intermittently heats the heater 35, causing the pump rotor 5E to reciprocate between the initial position shown in Figure 4 and the thermal expansion position shown in Figure 3. As a result, the other pump rotors 5A to 5D also reciprocate in the axial direction in the same manner. Since the pump rotors 5A to 5E reciprocate axially within the pump chamber 1 while rotating, they can scrape off by-products accumulated in the pump chamber 1.

[0046] In one embodiment, as shown in Figure 5, the vacuum pump device includes a displacement sensor 49 for measuring the axial displacement of the bearing 17. The displacement sensor 49 is mounted on the side wall 31 of the side cover 10A and is positioned facing the bearing housing 24 that holds the bearing 17. Thus, the displacement sensor 49 measures the axial displacement of the bearing 17 by measuring the axial displacement of the bearing housing 24. In one embodiment, the displacement sensor 49 may be positioned to directly measure the axial displacement of the bearing 17.

[0047] The displacement sensor 49 is electrically connected to the heater control unit 40. The heater control unit 40 is configured to stop heating the heater 35 when the axial displacement of the bearing 17 reaches a threshold. In this way, by controlling the heating of the heater 35 based on the axial displacement of the bearing 17, it is possible to prevent the pump rotor 5E from coming into contact with the inner surface of the side cover 10A (the end face of the pump chamber 1).

[0048] In one embodiment, as shown in Figure 6, the side cover 10A may be made of a single material. More specifically, a portion of the side cover 10A forms the end face of the pump chamber 1, and the other portion of the side cover 10A holds the bearing housing 24. The side cover 10A is made of the same material as the pump casing 2, or a material with a higher coefficient of thermal expansion than the pump casing 2. For example, if the pump casing 2 is made of cast iron, the entire side cover 10A is made of cast iron, or stainless steel, aluminum, aluminum alloy, or copper with a higher coefficient of thermal expansion than the pump casing 2. In the embodiment shown in Figure 6, the heater 35 repeatedly generates heat and stops generating heat, allowing the rotating pump rotors 5A to 5E to scrape off by-products accumulated in the pump chamber 1.

[0049] In one embodiment, as shown in Figure 7, the bearing housing 24 may be omitted. In the embodiment shown in Figure 7, the bearing 17 is directly held by the side cover 10A. More specifically, the bearing 17 is directly held by the spacer 32 of the side cover 10A. Furthermore, in one embodiment, as shown in Figure 8, the side cover 10A is made of a single material and the bearing housing 24 may be omitted. The embodiment shown in Figure 8 is a combination of the embodiment shown in Figure 6 and the embodiment shown in Figure 7, in which the bearing 17 is directly held by the side cover 10A. In the embodiments shown in Figures 7 and 8, the heater 35 repeatedly generates heat and stops generating heat, allowing the rotating pump rotors 5A to 5E to scrape off by-products accumulated in the pump chamber 1.

[0050] In one embodiment, as shown in Figure 9, the vacuum pump system may further include a second heater 50 attached to the pump casing 2 to prevent the accumulation of by-products in the pump chamber 1 due to a decrease in the temperature of the process gas. Some process gases generate by-products as their temperature rises. When used for exhausting such process gases, the vacuum pump system may further include a cooler 51 attached to the pump casing 2, as shown in Figure 10. The cooler 51 is, for example, a water-cooled cooler. The second heater 50 shown in Figure 9 and the cooler 51 shown in Figure 10 may be attached to the outside of the pump casing 2 or embedded inside the pump casing 2.

[0051] According to the embodiments shown in Figures 9 and 10, the intermittent operation of the heater 35 causes the axial reciprocating movement of the pump rotors 5A to 5E, and the combination with the second heater 50 or cooler 51 reliably prevents the accumulation of by-products in the pump chamber 1.

[0052] Figure 11 is a cross-sectional view showing another embodiment of the vacuum pump device. As shown in Figure 11, in the vacuum pump device of this embodiment, lubricating oil 110 for lubricating and cooling the bearing 17 is stored at the bottom of the motor housing 14. The configuration and operation of this embodiment, which are not specifically described, are the same as those of the embodiment described with reference to Figures 1 to 4, so redundant descriptions are omitted.

[0053] The vacuum pump device of this embodiment includes a rotating disc 60 that supplies lubricating oil 110 to a bearing 17, and a partition wall 62 positioned between the electric motor 8 and the bearing housing 24. The rotating disc 60 is connected to each of a pair of rotating shafts 7 and rotates together with the rotating shafts 7. In one embodiment, the rotating disc 60 may be connected to one of the pair of rotating shafts 7 and rotate together with the connected rotating shaft 7. The lubricating oil 110 is scooped up by the rotation of the rotating disc 60 and supplied to the bearing 17.

[0054] The partition wall 62 is fixed to the inner wall of the motor housing 14 and has a through hole (not shown) through which the rotating shaft 7 passes. This partition wall 62 is configured to separate the space in which the lubricating oil 110 is stored from the space in which the electric motor 8 is housed, and is provided to prevent the lubricating oil 110 from coming into contact with the electric motor 8.

[0055] The lubricating oil 110 inside the motor housing 14 is in constant contact with the spacer 32 of the side cover 10A. If a heater 35 is placed inside the spacer 32, the heat from the heater 35 may raise the temperature of the lubricating oil 110, and the cooling effect of the bearing 17 may not be sufficiently obtained. Therefore, in the embodiment shown in Figure 11, the heater 35 is placed inside the side wall 31 of the side cover 10A.

[0056] The side cover 10A comprises a side wall 31 that forms the end face of the pump chamber 1 and a spacer 32 that holds the bearing 17. The spacer 32 is connected to the side wall 31 and is located between the side wall 31 and the bearing housing 24. The bearing housing 24 is held by the spacer 32, and the bearing housing 24 is connected to the side wall 31 via the spacer 32. The bearing 17 is connected to the spacer 32 via the bearing housing 24. The spacer 32 holds the bearing 17 via the bearing housing 24.

[0057] The side wall 31 is made of the same material as the rotating shaft 7, or a metal with a higher coefficient of thermal expansion than the rotating shaft 7. For example, if the rotating shaft 7 is made of cast iron, the side wall 31 is made of cast iron, or stainless steel, aluminum, aluminum alloy, or copper, which has a higher coefficient of thermal expansion than cast iron. In one embodiment, the side wall 31 may be made of the same material as the pump casing 2 and / or spacer 32, or a metal with a higher coefficient of thermal expansion than the pump casing 2 and / or spacer 32.

[0058] When the heater 35 generates heat, the side wall 31 expands due to thermal expansion, causing the spacer 32 connected to the side wall 31 to move axially. This causes the bearing housing 24 and bearing 17 held by the spacer 32 to move axially, moving the pump rotor 5E toward the side cover 10A. As the rotating pump rotor 5E moves toward the side cover 10A (the end face of the pump chamber 1), it can gradually scrape off by-products accumulated in the gap between the pump rotor 5E and the side cover 10A.

[0059] When the heater 35 stops generating heat, the temperature of the side wall 31 gradually decreases, and the side wall 31 gradually contracts. As the side wall 31 contracts, the pump rotor 5E moves away from the side cover 10A, and the gap between the pump rotor 5E and the side cover 10A increases. In the embodiment shown in Figure 11, as in the embodiments described with reference to Figures 3 and 4, the repeated heating and stopping of the heater 35 allows the rotating pump rotors 5A to 5E to scrape off the by-products accumulated in the pump chamber 1.

[0060] Figure 12 is a cross-sectional view showing yet another embodiment of the vacuum pump device. The configuration and operation of this embodiment, which are not specifically described, are the same as those of the embodiments described with reference to Figures 1 to 4, and therefore redundant descriptions are omitted. As shown in Figure 12, the pump casing 2 of this embodiment has casing side walls 70A, 70B that form the end faces of the pump chamber 1, and the pump casing 2 covers the entire pump chamber 1. The pump chamber 1 is formed by the inner surface of the pump casing 2. Side covers 10A, 10B are provided on both sides of the pump casing 2 and are connected to the pump casing 2. More specifically, the side wall 31 of side cover 10A is connected to the casing side wall 70A of the pump casing 2, and the side cover 10B is connected to the casing side wall 70B of the pump casing 2. The rotating shaft 7 extends through the casing side walls 70A, 70B of the pump casing 2.

[0061] The side cover 10A comprises a side wall 31 connected to the casing side wall 70A of the pump casing 2, and a spacer 32 made of the same material as the side wall 31, or a material with a higher coefficient of thermal expansion than the side wall 31. The spacer 32 is located between the side wall 31 and the bearing housing 24. The bearing housing 24 is held by the spacer 32, and the bearing housing 24 is connected to the side wall 31 via the spacer 32. In this embodiment, the heater 35 is located within the spacer 32 of the side cover 10A. In the embodiment shown in Figure 12, the heater 35 repeatedly generates heat and stops generating heat, allowing the rotating pump rotors 5A to 5E to scrape off by-products accumulated in the pump chamber 1.

[0062] Figure 13 is a cross-sectional view showing yet another embodiment of the vacuum pump device. In the vacuum pump device of this embodiment, as in the embodiment described with reference to Figure 11, lubricating oil 110 for lubricating and cooling the bearing 17 is stored at the bottom of the motor housing 14. The configuration and operation of this embodiment, which are not specifically described, are the same as in the embodiment described with reference to Figure 11, and therefore their redundant descriptions are omitted. As shown in Figure 13, the pump casing 2 of this embodiment has casing side walls 70A, 70B that form the end faces of the pump chamber 1, and the pump casing 2 covers the entire pump chamber 1. The pump chamber 1 is formed by the inner surface of the pump casing 2. Side covers 10A, 10B are provided on both sides of the pump casing 2 and are connected to the pump casing 2. More specifically, the side wall 31 of side cover 10A is connected to the casing side wall 70A of the pump casing 2, and the side cover 10B is connected to the casing side wall 70B of the pump casing 2. The rotating shaft 7 extends through the casing side walls 70A and 70B of the pump casing 2.

[0063] The side cover 10A comprises a side wall 31 connected to the casing side wall 70A of the pump casing 2, and a spacer 32 that holds the bearing 17. The side wall 31 is made of the same material as the rotating shaft 7, or a metal with a higher coefficient of thermal expansion than the rotating shaft 7. In this embodiment, the heater 35 is located inside the side wall 31 of the side cover 10A. In the embodiment shown in Figure 13, the heater 35 repeatedly generates heat and stops generating heat, allowing the rotating pump rotors 5A to 5E to scrape off by-products accumulated in the pump chamber 1.

[0064] The embodiments described above are intended to enable persons with ordinary skill in the art to implement the present invention. Various modifications of the above embodiments can be made naturally by those skilled in the art, and the technical idea of ​​the present invention can be applied to other embodiments as well. Therefore, the present invention is not limited to the embodiments described, but is to be interpreted in the broadest sense according to the technical idea defined by the claims. [Explanation of Symbols]

[0065] 1 Pump Room 2 Pump casing 2a Intake 2b Exhaust port 5A~5E Pump Rotor 7 Rotation axis 8 Electric motor 10A, 10B Side Cover 14 Motor Housing 16 Gear Housing 17,18 Bearings 20 gears 24 Bearing Housing 31 Side wall 32 Spacers 35 Heater 40 Heater control unit 45. First temperature sensor 46. ​​Second temperature sensor 49 Displacement Sensor 50 Second heater 51 Cooler 60 Rotating Disks 62 Partition Wall 70A, 70B Casing sidewalls 100 By-products 110 Lubricating oil

Claims

1. A pump casing having a pump chamber inside, A pump rotor arranged inside the pump chamber, The pump rotor is fixed to a rotating shaft, The electric motor connected to the aforementioned rotating shaft, A bearing that rotatably supports the aforementioned rotating shaft, A side cover connected to the pump casing, The heater attached to the aforementioned side cover, The heater control unit is provided to intermittently generate heat in the heater while the pump rotor is rotating, causing the side cover to repeatedly expand and contract due to thermal stress, thereby causing the pump rotor to reciprocate in the axial direction. The aforementioned bearing is connected to the side cover of the vacuum pump device.

2. The vacuum pump apparatus according to claim 1, wherein the side cover forms the end face of the pump chamber.

3. The vacuum pump apparatus according to claim 1, wherein the pump casing forms the end face of the pump chamber.

4. The vacuum pump device further comprises a bearing housing that holds the bearing, The vacuum pump device according to claim 1, wherein the bearing housing is held by the side cover.

5. The aforementioned side cover is The side wall forming the end face of the pump chamber, The spacer is made of the same material as the side wall, or of a material with a higher coefficient of thermal expansion than the side wall. The vacuum pump device according to claim 2, wherein the heater is disposed within the spacer.

6. The aforementioned side cover is The end face of the pump chamber is formed by a side wall made of the same material as the rotating shaft, or a material with a higher coefficient of thermal expansion than the rotating shaft, It includes a spacer that holds the bearing, The vacuum pump device according to claim 2, wherein the heater is located within the side wall.

7. The aforementioned side cover is The side wall connected to the pump casing, The spacer is made of the same material as the side wall, or of a material with a higher coefficient of thermal expansion than the side wall. The vacuum pump device according to claim 3, wherein the heater is located within the spacer.

8. The aforementioned side cover is A side wall connected to the pump casing and made of the same material as the rotating shaft, or a material with a higher coefficient of thermal expansion than the rotating shaft, It includes a spacer that holds the bearing, The vacuum pump device according to claim 3, wherein the heater is located within the side wall.

9. A first temperature sensor for measuring the temperature of the pump casing, The system further includes a second temperature sensor for measuring the temperature of the side cover, The vacuum pump apparatus according to claim 1, wherein the heater control unit determines a target temperature based on the temperature of the pump casing and controls the heater so that the temperature of the side cover reaches the target temperature.

10. The vacuum pump device according to claim 9, wherein the heater control unit is configured to stop the heater from generating heat after the temperature of the side cover reaches the target temperature, or to stop the heater from generating heat after the heating temperature of the heater has been reduced.

11. The bearing is further provided with a displacement sensor for measuring the axial displacement of the bearing. The vacuum pump device according to claim 1, wherein the heater control unit is configured to stop heating the heater when the axial displacement of the bearing reaches a threshold value.

12. The vacuum pump apparatus according to claim 1, further comprising a second heater attached to the pump casing.

13. The vacuum pump apparatus according to claim 1, further comprising a cooler attached to the pump casing.

14. The pump rotor, located inside the pump chamber of the pump casing, is fixed to the rotating shaft. The aforementioned rotating shaft is rotatably supported by a bearing, A method for operating a vacuum pump device, wherein the bearing is connected to a side cover connected to the pump casing, and when exhausting process gas by the rotation of the pump rotor, a heater attached to the side cover is intermittently heated, causing the side cover to repeatedly expand and contract due to thermal stress, thereby causing the pump rotor to reciprocate in the axial direction.

15. The method for operating a vacuum pump apparatus according to claim 14, wherein the side cover forms the end face of the pump chamber.

16. The method for operating a vacuum pump apparatus according to claim 14, wherein the pump casing forms the end face of the pump chamber.

17. The bearing is held in the bearing housing. The method for operating a vacuum pump apparatus according to claim 14, wherein the bearing housing is held by the side cover.

18. The aforementioned side cover is The side wall forming the end face of the pump chamber, The spacer is made of the same material as the side wall, or of a material with a higher coefficient of thermal expansion than the side wall. The method for operating a vacuum pump apparatus according to claim 15, wherein the heater is located within the spacer.

19. The aforementioned side cover is The end face of the pump chamber is formed by a side wall made of the same material as the rotating shaft, or a material with a higher coefficient of thermal expansion than the rotating shaft, It includes a spacer that holds the bearing, The method for operating a vacuum pump apparatus according to claim 15, wherein the heater is located within the side wall.

20. The aforementioned side cover is The side wall connected to the pump casing, The spacer is made of the same material as the side wall, or of a material with a higher coefficient of thermal expansion than the side wall. The method for operating a vacuum pump apparatus according to claim 16, wherein the heater is located within the spacer.

21. The aforementioned side cover is A side wall connected to the pump casing and made of the same material as the rotating shaft, or a material with a higher coefficient of thermal expansion than the rotating shaft, It includes a spacer that holds the bearing, The method for operating a vacuum pump apparatus according to claim 16, wherein the heater is located within the side wall.

22. The target temperature is determined based on the temperature of the pump casing. A method for operating a vacuum pump apparatus according to claim 14, further comprising controlling the heater so that the temperature of the side cover reaches the target temperature.

23. A method for operating a vacuum pump apparatus according to claim 22, further comprising stopping the heating of the heater after the temperature of the side cover reaches the target temperature, or stopping the heating of the heater after the heating temperature of the heater has been reduced.

24. A method for operating a vacuum pump apparatus according to claim 14, further comprising stopping the heating of the heater when the axial displacement of the bearing reaches a threshold.

25. A method for operating a vacuum pump apparatus according to claim 14, further comprising heating the pump casing with a second heater attached to the pump casing.

26. A method for operating a vacuum pump apparatus according to claim 14, further comprising cooling the pump casing with a cooler attached to the pump casing.

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