VACUUM PUMP APPARATUS AND METHOD OF OPERATING THE SAME

Abstract

 A vacuum pump that can reduce deposition of by-product in a pump chamber caused by a process gas, can prevent an unintended stop of a vacuum pump apparatus, and can ensure restarting of the vacuum pump apparatus is disclosed. The vacuum pump apparatus includes: a pump casing (2) having a pump chamber (1) therein; a pump rotor (5A-E) arranged in the pump chamber; a rotation shaft (7) to which the pump rotor is secured; a bearing (17, 18) that rotatably supports the rotation shaft; a side cover (10A, 10B) coupled to the pump casing; a heater (35) attached to the side cover (10A); and a heater controller (40) configured to instruct the heater to generate heat intermittently when the pump rotor is rotating. The bearing (18) is coupled to the side cover (10A).

Description

BACKGROUND OF THE INVENTION

Field of the Invention:

[0001] The present invention relates to a vacuum pump apparatus and a method of operating the same, and more particularly to a vacuum pump apparatus and a method of operating such a vacuum pump apparatus suitable for use in exhausting a process gas used in manufacturing of semiconductor devices, liquid crystals, LEDs, solar cells, or the like.

Description of the Related Art:

[0002] In process of manufacturing semiconductor devices, liquid crystal panels, LEDs, solar cells, etc., a process gas is introduced into a process chamber to perform a certain type of process, such as etching process or CVD process. The process gas that has been introduced into the process chamber is exhausted by a vacuum pump apparatus. Generally, the vacuum pump apparatus used in these manufacturing processes that require high cleanliness is so-called dry vacuum pump apparatus that does not use oil in gas flow passages. One typical example of such a dry vacuum pump apparatus is a positive-displacement vacuum pump apparatus having a pair of pump rotors in a pump chamber which are rotated in opposite directions to deliver the gas.

[0003] The process gas introduced into the process chamber may form solidified by-product through reaction within the chamber as a temperature of the process gas is decreased or increased. When a large amount of solidified by-product accumulates in the vacuum pump apparatus, the solidified by-product may impede the rotation of the pump rotors and may cause the vacuum pump apparatus to suddenly stop. Such an unexpected operation stop of the vacuum pump apparatus can damage products, such as semiconductor devices, which are being manufactured.

[0004] The above-described by-product is also deposited in a pipe coupling the process chamber and the vacuum pump apparatus, and in a pipe coupling the vacuum pump apparatus and an abatement device disposed downstream of the vacuum pump apparatus. For this reason, pipe maintenance is conducted regularly. During the pipe maintenance, the vacuum pump apparatus is stopped, and after the pipe maintenance is completed, the vacuum pump apparatus is restarted. However, if a large amount of by-product accumulates in the pump chamber, a resistance to the rotation of the pump rotor is so large that the vacuum pump apparatus cannot restart.

Citation List

Patent Literature

[0005] Patent document 1: Japanese laid-open patent publication No. 2009-097349

[0006] Therefore, a pump-stop method has been proposed in which by-product accumulated in the pump chamber is gradually scraped away by the pump rotors by repeating rotation and stop of the pump rotors when the operation of the vacuum pump apparatus is to be stopped, (the patent document 1). This method can remove the by-product from the pump chamber and can allow the vacuum pump apparatus to restart.

[0007] However, this pump-stop method takes a long time (for example, about three hours) to complete and lowers a throughput of manufacturing products, such as semiconductor devices. For this reason, this method may not be accepted by users.

SUMMARY OF THE INVENTION

[0008] Accordingly, the present invention provides a vacuum pump that can reduce deposition of by-product in a pump chamber caused by a process gas, can prevent an unintended stop of a vacuum pump apparatus, and can ensure restarting of the vacuum pump apparatus. The present invention further provides a method of operating such a vacuum pump.

[0009] In an embodiment, there is provided a vacuum pump apparatus comprising: a pump casing having a pump chamber therein; a pump rotor arranged in the pump chamber; a rotation shaft to which the pump rotor is secured; an electric motor coupled to the rotation shaft; a bearing that rotatably supports the rotation shaft; a side cover coupled to the pump casing, the bearing being coupled to the side cover; a heater attached to the side cover; and a heater controller configured to instruct the heater to generate heat intermittently when the pump rotor is rotating.

[0010] In an embodiment, the side cover forms an end surface of the pump chamber.

[0011] In an embodiment, the pump casing forms an end surface of the pump chamber.

[0012] In an embodiment, the vacuum pump apparatus further includes a bearing housing that holds the bearing, and the bearing housing is held by the side cover.

[0013] In an embodiment, the side cover comprises: a side wall forming the end surface of the pump chamber; and a spacer made of the same material as the side wall or made of a material having a larger coefficient of linear expansion than that of the side wall, the heater being arranged in the spacer.

[0014] In an embodiment, the side cover comprises: a side wall forming the end surface of the pump chamber, the side wall being made of the same material as the rotation shaft or made of a material having a larger coefficient of linear expansion than that of the rotation shaft; and a spacer holding the bearing, the heater being arranged in the side wall.

[0015] In an embodiment, the side cover comprises: a side wall coupled to the pump casing; and a spacer made of the same material as the side wall or made of a material having a larger coefficient of linear expansion than that of the side wall, the heater being arranged in the spacer.

[0016] In an embodiment, the side cover comprises: a side wall coupled to the pump casing, the side wall being made of the same material as the rotation shaft or made of a material having a larger coefficient of linear expansion than that of the rotation shaft; and a spacer that holds the bearing, the heater being arranged in the side wall.

[0017] In an embodiment, the vacuum pump apparatus further comprises: a first temperature sensor configured to measure a temperature of the pump casing; and a second temperature sensor configured to measure a temperature of the side cover, wherein the heater controller is configured to determine a target temperature based on the temperature of the pump casing, and control the heater such that the temperature of the side cover reaches the target temperature.

[0018] In an embodiment, the heater controller is configured to instruct the heater to stop the heat generation or lower the temperature of the heat generation of the heater after the temperature of the side cover reaches the target temperature.

[0019] In an embodiment, the vacuum pump apparatus further comprises a displacement sensor configured to measure an axial displacement of the bearing, wherein the heater controller is configured to instruct the heater to stop the heat generation when the axial displacement of the bearing reaches a threshold value.

[0020] In an embodiment, the vacuum pump apparatus further comprises a second heater attached to the pump casing.

[0021] In an embodiment, the vacuum pump apparatus further comprises a cooler attached to the pump casing.

[0022] In an embodiment, there is provided a method of operating a vacuum pump apparatus, comprising: intermittently generating heat by a heater when evacuating a process gas by rotating a pump rotor arranged in a pump chamber of a pump casing, the pump rotor being secured to a rotation shaft which is rotatably supported by a bearing, the bearing being coupled to a side cover which is coupled to the pump casing, the heater being attached to the side cover.

[0023] In an embodiment, the side cover forms an end surface of the pump chamber.

[0024] In an embodiment, the pump casing forms an end surface of the pump chamber.

[0025] In an embodiment, the bearing is held by a bearing housing, and the bearing housing is held by the side cover.

[0026] In an embodiment, the side cover comprises: a side wall forming the end surface of the pump chamber; and a spacer made of the same material as the side wall or made of a material having a larger coefficient of linear expansion than that of the side wall, the heater being arranged in the spacer.

[0027] In an embodiment, the side cover comprises: a side wall forming the end surface of the pump chamber, the side wall being made of the same material as the rotation shaft or made of a material having a larger coefficient of linear expansion than that of the rotation shaft; and a spacer holding the bearing, the heater being arranged in the side wall.

[0028] In an embodiment, the side cover comprises: a side wall coupled to the pump casing; and a spacer made of the same material as the side wall or made of a material having a larger coefficient of linear expansion than that of the side wall, the heater being arranged in the spacer.

[0029] In an embodiment, the side cover comprises: a side wall coupled to the pump casing, the side wall being made of the same material as the rotation shaft or made of a material having a larger coefficient of linear expansion than that of the rotation shaft; and a spacer that holds the bearing, the heater being arranged in the side wall.

[0030] In an embodiment, the method of operating the vacuum pump apparatus further comprises: determining a target temperature based on a temperature of the pump casing; and controlling the heater such that a temperature of the side cover reaches the target temperature.

[0031] In an embodiment, the method of operating the vacuum pump apparatus further comprises stopping the heat generation of the heater or lowering a temperature the heat generation of the heater after the temperature of the side cover reaches the target temperature.

[0032] In an embodiment, the method of operating the vacuum pump apparatus further comprises stopping the heat generation of the heater when an axial displacement of the bearing reaches a threshold value.

[0033] In an embodiment, the method of operating the vacuum pump apparatus further comprises heating the pump casing by a second heater attached to the pump casing.

[0034] In an embodiment, the method of operating the vacuum pump apparatus further comprises cooling the pump casing by a cooler attached to the pump casing.

[0035] When the heater generates the heat intermittently during the rotation of the pump rotor, the side cover repeats thermal expansion and contraction, which cause the rotation shaft to reciprocate in an axial direction via the bearing coupled to the side cover. As the rotation shaft reciprocates in the axial direction, the pump rotor also reciprocates in the axial direction, so that the rotating pump rotor can scrape off by-product deposited in the pump chamber. As a result, the pump rotor can rotate smoothly.

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] 

FIG. 1 is a cross-sectional view showing an embodiment of a vacuum pump apparatus;

FIG. 2 is an enlarged cross-sectional view showing a side cover, a bearing housing, and a bearing at an exhaust side;

FIG. 3 is a cross-sectional view showing a state in which the pump rotor is moved in an axial direction due to thermal expansion of the rotation shaft;

FIG. 4 is a cross-sectional view showing a state in which the pump rotor is moved toward the side cover due to thermal expansion of a spacer caused by heat generation of the heater;

FIG. 5 is a cross-sectional view showing an embodiment having a displacement sensor for measuring a displacement of the bearing;

FIG. 6 is a cross-sectional view of an embodiment of a side cover constructed from a single piece of material;

FIG. 7 is a cross-sectional view showing an embodiment in which the bearing is held directly on the side cover;

FIG. 8 is a cross-sectional view showing another embodiment in which the bearing is held directly on the side cover;

FIG. 9 shows an embodiment of a vacuum pump apparatus having a second heater attached to a pump casing;

FIG. 10 shows an embodiment of a vacuum pump apparatus having a cooler attached to the pump casing;

FIG. 11 is a cross-sectional view showing another embodiment of the vacuum pump apparatus;

FIG. 12 is a cross-sectional view showing still another embodiment of the vacuum pump apparatus; and

FIG. 13 is a cross-sectional view showing still another embodiment of the vacuum pump apparatus.

DESCRIPTION OF EMBODIMENTS

[0037] FIG. 1 is a cross-sectional view showing an embodiment of a vacuum pump apparatus. The vacuum pump apparatus of the embodiment described below is a positive-displacement vacuum pump apparatus. In particular, the vacuum pump apparatus shown in FIG. 1 is a so-called dry vacuum pump apparatus that does not use oil in its flow passages for a gas. Since a vaporized oil does not flow to an upstream side, the dry vacuum pump apparatus can be suitably used for a semiconductor-device manufacturing apparatus that requires high cleanliness.

[0038] As shown in FIG. 1, the vacuum pump apparatus includes a pump casing 2 having a pump chamber 1 therein, pump rotors 5A to 5E arranged in the pump chamber 1, rotation shafts 7 to which the pump rotors 5A to 5E are secured, and electric motor 8 coupled to the rotation shaft 7. The pump rotors 5A to 5E and each rotation shaft 7 may be an integral structure. Although only one set of pump rotors 5A to 5E and only one rotation shaft 7 are depicted in FIG. 1, a pair of pump rotors 5A to 5E are arranged in the pump chamber 1, and are secured to a pair of rotation shafts 7, respectively. The electric motor 8 is coupled to one of the pair of rotation shafts 7. In one embodiment, a pair of electric motors 8 may be coupled to the pair of rotation shafts 7, respectively.

[0039] The pump rotors 5A to 5E of the present embodiment are Roots-type pump rotors, while in one embodiment the pump rotors 5A to 5E may be claw-type pump rotors. Further, the pump rotors 5A to 5E may be a combination of Roots-type and claw-type pump rotors. Although the pump rotors 5A to 5E of the present embodiment are multi-stage pump rotors, in one embodiment the pump rotors may be single-stage pump rotors.

[0040] The vacuum pump apparatus further includes side covers 10A and 10B located outwardly of the pump casing 2 in an axial direction of the rotation shafts 7. The side covers 10A and 10B are provided on both sides of the pump casing 2 and are coupled to the pump casing 2. In the present embodiment, the side covers 10A and 10B are fixed to end surfaces of the pump casing 2 by not-shown screws.

[0041] The pump chamber 1 is formed by an inner surface of the pump casing 2 and 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 coupled to a chamber (not shown) filled with gas to be delivered. In one example, the intake port 2a may be coupled to a process chamber of a semiconductor-device manufacturing apparatus, and the vacuum pump apparatus may be used for evacuating a process gas from the process chamber.

[0042] The vacuum pump apparatus further includes a motor housing 14 and a gear housing 16 which are housing structures located outwardly of the side covers 10A and 10B in the axial direction of the rotation shafts 7. The side cover 10A is located between the pump casing 2 and the motor housing 14, and the side cover 10B is located between the pump casing 2 and the gear housing 16.

[0043] The motor housing 14 accommodates a motor rotor 8A and a motor stator 8B of the electric motor 8 therein. Inside the gear housing 16, a pair of gears 20 that mesh with each other are arranged. In FIG. 1, only one gear 20 is depicted. The electric motor 8 is rotated by a not-shown motor driver, and one rotation shaft 7 to which the electric motor 8 is coupled rotates the other rotation shaft 7 to which the electric motor 8 is not coupled in an opposite direction via the gears 20.

[0044] In one embodiment, a pair of electric motors 8, which are coupled to the pair of rotation shafts 7, respectively, may be provided. The pair of electric motors 8 are synchronously rotated in opposite directions by a not-shown motor driver, so that the pair of rotation shafts 7 and the pair of pump rotors 5A to 5E are synchronously rotated in opposite directions. In this case, the role of the gears 20 is to prevent loss of the synchronous rotation of the pump rotors 5 due to a sudden external cause.

[0045] In the embodiment shown in FIG. 1, the motor housing 14 is arranged outwardly of the side cover 10A, and the gear housing 16 is arranged outwardly of the side cover 10B, while configurations of the vacuum pump apparatus are not limited to this embodiment. In one embodiment, the gear housing 16 may be arranged outwardly of the side cover 10A, and the motor housing 14 may be arranged outwardly of the side cover 10B. Further, in one embodiment, both the motor housing 14 and the gear housing 16 may be located outwardly of either the side cover 10A or the side cover 10B.

[0046] When the pump rotors 5A to 5E are rotated by the electric motor 8, a gas is sucked into the pump casing 2 through the intake port 2a. The gas is sequentially compressed by the rotating pump rotors 5A to 5E, delivered to the exhaust port 2b, and discharged from the pump chamber 1 through the exhaust port 2b.

[0047] Each rotation shaft 7 is rotatably supported by bearings 17 and 18 . The bearing 17 is held by a bearing housing 24, and the bearing 18 is supported by the side cover 10B. The bearing 17 is coupled to the side cover 10A via the bearing housing 24. More specifically, the bearing housing 24 is held by the side cover 10A, and positions of the bearing housing 24 and the bearing 17 are fixed by the side cover 10A. Since an inner race of the bearing 17 is fixed to the rotation shaft 7, an axial position of a portion of the rotation shaft 7 held by the bearing 17 is fixed.

[0048] In contrast, the bearing 18 is axially movably supported by the side cover 10B. More specifically, an inner race of the bearing 18 is fixed to the rotation shaft 7, while an outer race of the bearing 18 is not fixed to the side cover 10B, and simply supported by the side cover 10B. Therefore, the bearing 18 is axially movable together with the rotation shaft 7.

[0049] A bearing housing holding the bearing 18 may be disposed 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 race of the bearing 18 is not fixed to the bearing housing, and is simply supported by the bearing housing, so that the bearing 18 can move axially together with the rotation shaft 7.

[0050] During operation of the vacuum pump apparatus, the gas is compressed by the pump rotors 5A to 5E while the gas is being transferred from the intake port 2a to the exhaust port 2b. Therefore, the rotation shaft 7 located in the pump chamber 1 thermally expands due to compression heat of the gas. The axial position of the bearing 17 is fixed, whereas the bearing 18 is movable in the axial direction. Accordingly, the rotation shaft 7 thermally expands in the axial direction beginning from the bearing 17, and the bearing 18 moves in the axial direction as the rotation shaft 7 thermally expands.

[0051] FIG. 2 is an enlarged sectional view showing the side cover 10A, the bearing housing 24, and the bearing 17 at the exhaust side. As shown in FIG. 2, the pump casing 2 has a partition wall 36 therein, and the pump rotor 5E is arranged between the partition wall 36 and the side cover 10A. In this embodiment, the side cover 10A includes a side wall 31 forming an end surface of the pump chamber 1 and a spacer 32 made of the same material as the side wall 31 or made of a material having a larger coefficient of linear expansion than that of 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 coupled to the side wall 31 via the spacer 32.

[0052] The vacuum pump apparatus has a heater 35 attached to the side cover 10A. In this embodiment, the heater 35 is arranged in the 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 made of metal having a coefficient of linear expansion larger than that of the side wall 31. For example, when 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 having a larger coefficient of linear expansion than that of cast iron. When the heater 35 generates heat, the spacer 32 thermally expands, and the bearing housing 24 held by the spacer 32 moves in the axial direction. In particular, the spacer 32 has a shape that surrounds the bearing housing 24 and is prone to the thermal expansion in the axial direction.

[0053] A process gas treated by the vacuum pump apparatus may form solidified by-product through reaction in the chamber as the temperature of the process gas decreases or increases. Such by-product gradually accumulates in the pump chamber 1 as the vacuum pump apparatus operates. FIG. 3 is a cross-sectional view showing a state in which the pump rotor 5E is moved in the axial direction due to the thermal expansion of the rotation shaft 7. As described above, the high-temperature rotation shaft 7 thermally expands in the axial direction, and as a result, the pump rotor 5E is moved in a direction away from the side cover 10A forming the end surface of the pump chamber 1. By-product 100 is gradually deposited in a gap between the pump rotor 5E and the side cover 10A. Such by-product 100 impedes the rotation of the pump rotor 5E, and may cause an unintended operation stop of the vacuum pump apparatus, or may prevent the vacuum pump apparatus from restarting.

[0054] Thus, as shown in FIG. 4, the heater 35 generates heat that causes the thermal expansion of the spacer 32, which moves the bearing housing 24 and the bearing 17 in the axial direction, thereby moving the pump rotor 5E toward the side cover 10A. As the rotating pump rotor 5E moves toward the side cover 10A (i.e., toward the end surface of the pump chamber 1), the rotating pump rotor 5E gradually scrapes off the by-product 100 deposited in the gap between the pump rotor 5E and the side cover 10A.

[0055] The heat generation of the heater 35 is stopped when the pump rotor 5E reaches an initial position shown in FIG. 2. The initial position of the pump rotor 5E is a position of the pump rotor 5E when the entire vacuum pump apparatus has a room temperature. When the heat generation of the heater 35 is stopped, the temperature of the spacer 32 gradually decreases and the spacer 32 gradually contracts. As the spacer 32 contracts, the pump rotor 5E is moved in a direction away from the side cover 10A, and the gap between the pump rotor 5E and the side cover 10A increases as shown in FIG. 3. Since the by-product 100 gradually accumulates in this gap, the heater 35 generates heat again to thermally expand the spacer 32. As shown in FIG. 4, as the rotating pump rotor 5E moves toward the side cover 10A (i.e., toward the end surface of the pump chamber 1), the rotating pump rotor 5E gradually scrapes off the by-product 100 deposited in the gap between the pump rotor 5E and the side cover 10A.

[0056] Similarly, the by-product 100 deposited between the partition wall 36 and the pump rotor 5E is gradually scraped off by the rotating pump rotor 5E after the heat generation of the heater 35 is stopped and when the pump rotor 5E is moved in a direction away from the side cover 10A (i.e., toward the partition wall 36).

[0057] In this way, while the vacuum pump apparatus is in operation (i.e., while the process gas is being exhausted or evacuated), the heat generation and stoppage of the heat generation of the heater 35 are repeated to cause the rotating pump rotor 5E to reciprocate in the axial direction, so that the rotating pump rotor 5E can scrape off the by-product deposited in the pump chamber 1. With the similar mechanism, the rotating pump rotors 5A to 5D can also scrape off by-product deposited in the pump chamber 1. As a result, the by-product is removed from the pump chamber 1, and the pump rotors 5A to 5E can rotate smoothly.

[0058] In a conventional pump, pump rotors do not reciprocate during operation as described above. As a result, a large amount of by-product may be deposited near the pump rotors during operation, and the pump rotors bite the large amount of by-product at a certain moment, causing sudden stop of the pump. According to the present invention, the pump rotors 5A to 5E constantly repeat the reciprocating motion, which makes it possible to create a condition in which almost no by-product is accumulated in the pump chamber 1, particularly near the pump rotors 5A to 5E. As a result, sudden stop of the pump can be prevented.

[0059] As shown in FIG. 2, the vacuum pump apparatus includes a heater controller 40 configured to control the heat generation of the heater 35. The heater controller 40 is configured to intermittently instruct the heater 35 to generate the heat (i.e., periodically repeat heat generation and stop of the heat generation of the heater 35) while the pump rotors 5A to 5E are rotating. The heater controller 40 includes a memory 40a storing programs therein, an arithmetic device 40b configured to perform arithmetic operations according to instructions included in the programs, and a power source 40c configured to supply electric power to the heater 35. The heater controller 40 includes at least one computer. The memory 40a includes a main memory, such as a random access memory (RAM), and an auxiliary memory, such as a hard disk drive (HDD) or solid state drive (SSD). Examples of the arithmetic device 40b include a CPU (central processing unit) and a GPU (graphic processing unit). However, the specific configurations of the heater controller 40 are not limited to these examples.

[0060] The vacuum pump apparatus further includes a first temperature sensor 45 configured to measure a temperature of the pump casing 2 and a second temperature sensor 46 configured to measure a 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 an outer surface of the pump casing 2 or may be embedded in the pump casing 2. This first temperature sensor 45 is provided to indirectly measure the temperature of the rotation shaft 7. Specifically, the temperature of the rotation shaft 7 arranged in the pump casing 2 can be estimated from the temperature of the pump casing 2 measured by the first temperature sensor 45.

[0061] The second temperature sensor 46 is fixed to the side cover 10A. The second temperature sensor 46 may be fixed to an outer surface of the side cover 10A or may be embedded in the side cover 10A. In the embodiment shown in FIGS. 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 in the spacer 32.

[0062] The heater controller 40 is configured to determine a target temperature of the spacer 32, i.e., a 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 rotation shaft 7, a degree of thermal expansion of the rotation shaft 7 (i.e., an axial movement distance of the pump rotor 5E from its initial position) can be estimated from the temperature of the pump casing 2. Therefore, the heater controller 40 can determine the target temperature of the spacer 32 required to return the pump rotor 5E, which has been moved by the thermal expansion of the rotation shaft 7, to the initial position.

[0063] The heater controller 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, an axial thickness of the spacer 32, and the coefficient of linear expansion of the spacer 32. A relationship between a movement distance of the pump rotor 5E and the temperature of the spacer 32 may be obtained by experiment or simulation, and the target temperature of the spacer 32 may be determined from the relationship obtained.

[0064] The heater controller 40 is configured to control the heater 35 such that the temperature of the spacer 32 reaches the determined target temperature. 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 is heated, the bearing housing 24, the bearing 17, the rotation shaft 7, and the pump rotor 5E are moved axially. When the spacer 32 is heated to the target temperature, the pump rotor 5E returns to its initial position shown in FIG. 4. Thereafter, the heater controller 40 instructs the heater 35 to stop its heat generation. In one embodiment, the heater controller 40 may instruct the heater 35 to lower the temperature of its heat generation after the spacer 32 is heated to the target temperature. Furthermore, the heater controller 40 may instruct the heater 35 to stop the heat generation after instructing the heater 35 to lower the temperature of the heat generation of the heater 35.

[0065] In this manner, the heater controller 40 instructs the heater 35 to generate heat intermittently, thereby causing the pump rotor 5E to reciprocate between the initial position shown in FIG. 4 and the thermal expansion position shown in FIG. 3. With this operation, 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 in the pump chamber 1 in the axial direction while the pump rotors 5A to 5E are rotating, the pump rotors 5A to 5E can scrape off the by-product deposited in the pump chamber 1.

[0066] In one embodiment, as shown in FIG. 5, the vacuum pump apparatus includes a displacement sensor 49 configured to measure an axial displacement of the bearing 17. The displacement sensor 49 is attached to the side wall 31 of the side cover 10A and arranged so as to face the bearing housing 24 holding the bearing 17. Therefore, the displacement sensor 49 measures the axial displacement of the bearing 17 by measuring an axial displacement of the bearing housing 24. In one embodiment, the displacement sensor 49 may be arranged to directly measure the axial displacement of the bearing 17.

[0067] The displacement sensor 49 is electrically coupled to the heater controller 40. The heater controller 40 is configured to instruct the heater 35 to stop the heat generation when the axial displacement of the bearing 17 reaches a threshold value. Such controlling of the heat generation of the heater 35 based on the axial displacement of the bearing 17 can prevent the pump rotor 5E from contacting the inner surface of the side cover 10A (i.e., the end surface of the pump chamber 1).

[0068] In one embodiment, as shown in FIG. 6, the side cover 10A may be constructed from a single material. More specifically, a part of the side cover 10A forms the end surface of the pump chamber 1, and other part 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 made of a material having a larger coefficient of linear expansion than that of the pump casing 2. For example, when the pump casing 2 is made of cast iron, the entire side cover 10A is made of cast iron, or made of stainless steel, aluminum, aluminum alloy, or copper having a larger coefficient of linear expansion than that of the pump casing 2. In the embodiment shown in FIG. 6, the rotating pump rotors 5A to 5E can scrape off the by-product deposited in the pump chamber 1 by repeating the heat generation and stop of the heat generation of the heater 35 as well as the previous embodiments.

[0069] In one embodiment, the bearing housing 24 may be omitted, as shown in FIG. 7. In the embodiment shown in FIG. 7, the bearing 17 is held directly on the side cover 10A. More specifically, the bearing 17 is directly held by the spacer 32 of the side cover 10A. Further, in one embodiment, as shown in FIG. 8, the side cover 10A may be constructed from a single piece of material and the bearing housing 24 may not be provided. The embodiment shown in FIG. 8 is a combination of the embodiment shown in FIG. 6 and the embodiment shown in FIG. 7. The bearing 17 is directly held by the side cover 10A. In the embodiments shown in FIGS. 7 and 8, the rotating pump rotors 5A to 5E can scrape off the by-product deposited in the pump chamber 1 by repeating the heat generation and stop of the heat generation of the heater 35 as well as the previous embodiments.

[0070] In one embodiment, as shown in FIG. 9, the vacuum pump apparatus may further include a second heater 50 attached to the pump casing 2 in order to prevent deposition of the by-product in the pump chamber 1 due to a decrease in temperature of the process gas. A certain type of process gas may form by-product as a temperature of the process gas rises. When the vacuum pump apparatus is used for evacuating such a process gas, the vacuum pump apparatus may further include a cooler 51 attached to the pump casing 2, as shown in FIG. 10. The cooler 51 may be a water-cooled cooler. The second heater 50 shown in FIG. 9 and the cooler 51 shown in FIG. 10 may be attached to the outer surface of the pump casing 2 or may be embedded in the pump casing 2.

[0071] According to the embodiments shown in FIGS. 9 and 10, the combination of the axial reciprocation of the pump rotors 5A to 5E by the intermittent operation of the heater 35 and the second heater 50 or the cooler 51can reliably prevent the deposition of the by-product.

[0072] FIG. 11 is a cross-sectional view showing another embodiment of the vacuum pump apparatus. As shown in FIG. 11, in the vacuum pump apparatus of this embodiment, lubricating oil 110 for lubricating and cooling the bearing 17 is stored at a bottom of the motor housing 14. Configurations and operations of this embodiment, which will not be particularly described, are the same as those of the embodiments described with reference to FIGS. 1 to 4, and redundant descriptions thereof are omitted.

[0073] The vacuum pump apparatus of this embodiment includes rotary disks 60 configured to supply the lubricating oil 110 to the bearing 17 and a partition wall 62 arranged between the electric motor 8 and the bearing housing 24. Each rotary disk 60 is coupled to each of the pair of rotation shafts 7 and rotates together with each rotation shaft 7. In one embodiment, a rotary disk 60 may be coupled to one of the pair of rotation shafts 7 and may rotate together with that rotation shaft 7 coupled to the rotary disk 60. The rotation of the rotary disk 60 splashes up the lubricating oil 110 onto the bearing 17.

[0074] The partition wall 62 is fixed to the inner surface of the motor housing 14 and has through-holes (not shown) through which the rotation shafts 7 extend. The partition wall 62 is configured to separate a space in which the lubricating oil 110 is stored from a space in which the electric motor 8 is disposed, and is provided to prevent the lubricating oil 110 from contacting the electric motor 8.

[0075] The lubricating oil 110 in the motor housing 14 is always in contact with the spacer 32 of the side cover 10A. If the heater 35 is arranged in the spacer 32, the temperature of the lubricating oil 110 rises due to the heat generated by the heater 35, and a sufficient cooling effect for the bearing 17 may not be obtained. Therefore, in the embodiment shown in FIG. 11, the heater 35 is arranged in the side wall 31 of the side cover 10A.

[0076] The side cover 10A has the side wall 31 forming the end surface of the pump chamber 1 and the spacer 32 holding the bearing 17. The spacer 32 is coupled 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 coupled to the side wall 31 via the spacer 32. The bearing 17 is coupled to the spacer 32 via the bearing housing 24. The spacer 32 holds the bearing 17 via the bearing housing 24.

[0077] The side wall 31 is made of the same material as a material of the rotation shaft 7 or made of metal having a larger coefficient of linear expansion than that of the rotation shaft 7. For example, when the rotation shaft 7 is made of cast iron, the side wall 31 is made of cast iron, or stainless steel, aluminum, aluminum alloy, or copper having a larger coefficient of linear expansion than that of cast iron. In one embodiment, the side wall 31 may be made of the same material as the material of the pump casing 2 and/or the spacer 32, or may be made of metal having a larger coefficient of linear expansion than that of the pump casing 2 and/or the spacer 32.

[0078] When the heater 35 generates heat, the side wall 31 thermally expands, and the spacer 32 coupled to the side wall 31 moves axially. As a result, the bearing housing 24 and the bearing 17 held by the spacer 32 move axially, and the pump rotor 5E moves toward the side cover 10A. When the rotating pump rotor 5E moves toward the side cover 10A (i.e., toward the end surface of the pump chamber 1), the rotating pump rotor 5E can gradually scrape off the by-product deposited in the gap between the pump rotor 5E and the side cover 10A.

[0079] When the heat generation of the heater 35 is stopped, 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 in a direction 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 FIG. 11, the rotating pump rotors 5A to 5E can scrape off the by-product deposited in the pump chamber 1 by repeating the heat generation and stop of the heat generation of the heater 35, as well as the embodiments described with reference to FIGS. 3 and 4.

[0080] FIG. 12 is a cross-sectional view showing still another embodiment of the vacuum pump apparatus. Configurations and operations of this embodiment, which will not be particularly described, are the same as those of the embodiments described with reference to FIGS. 1 to 4, and redundant descriptions thereof are omitted. As shown in FIG. 12, the pump casing 2 of this embodiment has casing side walls 70A and 70B that form end surfaces of the pump chamber 1. 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. The side covers 10A, 10B are provided on both sides of the pump casing 2 and coupled to the pump casing 2. More specifically, the side wall 31 of the side cover 10A is coupled to the casing side wall 70A of the pump casing 2, and the side cover 10B is coupled to the casing side wall 70B of the pump casing 2. The rotation shafts 7 extend through the casing side walls 70A and 70B of the pump casing 2.

[0081] The side cover 10A includes the side wall 31 coupled to the casing side wall 70A of the pump casing 2, and further includes the spacer 32 made of the same material as the side wall 31 or made of a material having a larger coefficient of linear expansion than that of 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 coupled to the side wall 31 via the spacer 32. In this embodiment, the heater 35 is arranged in the spacer 32 of the side cover 10A. In the embodiment shown in FIG. 12, the rotating pump rotors 5A to 5E can scrape off the by-product deposited in the pump chamber 1 by repeating the heat generation and stop of the heat generation of the heater 35, as well as the previous embodiments.

[0082] FIG. 13 is a cross-sectional view showing still another embodiment of the vacuum pump apparatus. In the vacuum pump apparatus of this embodiment, lubricating oil 110 for lubricating and cooling the bearings 17 is stored at the bottom of the motor housing 14, as in the embodiment described with reference to FIG. 11. Configurations and operations of this embodiment, which will not be particularly described, are the same as those of the embodiment described with reference to FIG. 11, and redundant descriptions thereof will be omitted. As shown in FIG. 13, the pump casing 2 of this embodiment has casing side walls 70A and 70B that form end surfaces of the pump chamber 1. 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. The side covers 10A, 10B are provided on both sides of the pump casing 2 and coupled to the pump casing 2. More specifically, the side wall 31 of the side cover 10A is coupled to the casing side wall 70A of the pump casing 2, and the side cover 10B is coupled to the casing side wall 70B of the pump casing 2. The rotation shafts 7 extend through the casing side walls 70A and 70B of the pump casing 2.

[0083] The side cover 10A includes the side wall 31 coupled to the casing side wall 70A of the pump casing 2, and further includes the spacer 32 holding the bearing 17. The side wall 31 is made of the same material as a material of the rotation shaft 7 or made of metal having a larger coefficient of linear expansion than that of the rotation shaft 7. In this embodiment, the heater 35 is arranged in the side wall 31 of the side cover 10A. In the embodiment shown in FIG. 13, the rotating pump rotors 5A to 5E can scrape off the by-product deposited in the pump chamber 1 by repeating the heat generation and stop of the heat generation of the heater 35, as well as the previous embodiments.

[0084] The previous description of embodiments is provided to enable a person skilled in the art to make and use the present invention. Moreover, various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles and specific examples defined herein may be applied to other embodiments. Therefore, the present invention is not intended to be limited to the embodiments described herein but is to be accorded the widest scope as defined by limitation of the claims.

Claims

1. A vacuum pump apparatus comprising:

a pump casing having a pump chamber therein;

a pump rotor arranged in the pump chamber;

a rotation shaft to which the pump rotor is secured;

an electric motor coupled to the rotation shaft;

a bearing that rotatably supports the rotation shaft;

a side cover coupled to the pump casing, the bearing being coupled to the side cover;

a heater attached to the side cover; and

a heater controller configured to instruct the heater to generate heat intermittently when the pump rotor is rotating.

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

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

4. The vacuum pump apparatus according to claim 1, further comprising a bearing housing that holds the bearing, the bearing housing being held by the side cover.

5. The vacuum pump apparatus according to claim 2, wherein the side cover comprises:

a side wall forming the end surface of the pump chamber; and

a spacer made of the same material as the side wall or made of a material having a larger coefficient of linear expansion than that of the side wall, the heater being arranged in the spacer.

6. The vacuum pump apparatus according to claim 2, wherein the side cover comprises:

a side wall forming the end surface of the pump chamber, the side wall being made of the same material as the rotation shaft or made of a material having a larger coefficient of linear expansion than that of the rotation shaft; and

a spacer holding the bearing, the heater being arranged in the side wall.

7. The vacuum pump apparatus according to claim 3, wherein the side cover comprises:

a side wall coupled to the pump casing; and

a spacer made of the same material as the side wall or made of a material having a larger coefficient of linear expansion than that of the side wall, the heater being arranged in the spacer.

8. The vacuum pumping apparatus according to claim 3, wherein the side cover comprises:

a side wall coupled to the pump casing, the side wall being made of the same material as the rotation shaft or made of a material having a larger coefficient of linear expansion than that of the rotation shaft; and

a spacer that holds the bearing, the heater being arranged in the side wall.

9. The vacuum pump apparatus according to claim 1, further comprising:

a first temperature sensor configured to measure a temperature of the pump casing; and

a second temperature sensor configured to measure a temperature of the side cover,

wherein the heater controller is configured to determine a target temperature based on the temperature of the pump casing, and control the heater such that the temperature of the side cover reaches the target temperature.

10. The vacuum pump apparatus according to claim 9, wherein the heater controller is configured to instruct the heater to stop the heat generation or lower the temperature of the heat generation of the heater after the temperature of the side cover reaches the target temperature.

11. The vacuum pump apparatus according to claim 1, further comprising a displacement sensor configured to measure an axial displacement of the bearing,
wherein the heater controller is configured to instruct the heater to stop the heat generation 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. A method of operating a vacuum pump apparatus, comprising:
intermittently generating heat by a heater when evacuating a process gas by rotating a pump rotor arranged in a pump chamber of a pump casing, the pump rotor being secured to a rotation shaft which is rotatably supported by a bearing, the bearing being coupled to a side cover which is coupled to the pump casing, the heater being attached to the side cover.

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

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

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

18. The method of operating the vacuum pump apparatus according to claim 15, wherein the side cover comprises:

a side wall forming the end surface of the pump chamber; and

a spacer made of the same material as the side wall or made of a material having a larger coefficient of linear expansion than that of the side wall, the heater being arranged in the spacer.

19. The method of operating the vacuum pump apparatus according to claim 15, wherein the side cover comprises:

a side wall forming the end surface of the pump chamber, the side wall being made of the same material as the rotation shaft or made of a material having a larger coefficient of linear expansion than that of the rotation shaft; and

a spacer holding the bearing, the heater being arranged in the side wall.

20. The method of operating the vacuum pump apparatus according to claim 16, wherein the side cover comprises:

a side wall coupled to the pump casing; and

a spacer made of the same material as the side wall or made of a material having a larger coefficient of linear expansion than that of the side wall, the heater being arranged in the spacer.

21. The method of operating the vacuum pump apparatus according to claim 16, wherein the side cover comprises:

a side wall coupled to the pump casing, the side wall being made of the same material as the rotation shaft or made of a material having a larger coefficient of linear expansion than that of the rotation shaft; and

a spacer that holds the bearing, the heater being arranged in the side wall.

22. The method of operating the vacuum pump apparatus according to claim 14, further comprising:

determining a target temperature based on a temperature of the pump casing; and

controlling the heater such that a temperature of the side cover reaches the target temperature.

23. The method of operating the vacuum pump apparatus according to claim 22, further comprising stopping the heat generation of the heater or lowering a temperature the heat generation of the heater after the temperature of the side cover reaches the target temperature.

24. The method of operating the vacuum pump apparatus according to claim 14, further comprising stopping the heat generation of the heater when an axial displacement of the bearing reaches a threshold value.

25. The method of operating the vacuum pump apparatus according to claim 14, further comprising heating the pump casing by a second heater attached to the pump casing.

26. The method of operating the vacuum pumping apparatus according to claim 14, further comprising cooling the pump casing by a cooler attached to the pump casing.

Drawing