Vacuum pump device

Abstract

To provide a vacuum pump device that keeps the inside of a rotor chamber of a pump casing at a high temperature, and allows a heater to be easily attached and detached.SOLUTION: A vacuum pump device comprises a pump casing 2, a pump rotor 5 arranged in a rotor chamber 1, a rotating shaft 7 to which the pump rotor 5 is fixed, an electric motor 8 connected to the rotating shaft 7, side covers 10A and 10B forming end surfaces 31a of the rotor chamber 1, housing structures 14 and 16 located outside the side covers 10A and 10B in an axial direction of the rotating shaft 7, and cartridge heaters 70A and 70B arranged in the side covers 10A and 10B, and detachably attached. The cartridge heaters 70A and 70B each comprise a heater 71, and a heater casing 72 covering at least a portion of the heater 71. The heater casing 72 comprises a slit 72a extending from one end thereof to the other end.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a vacuum pump device, and more particularly to a vacuum pump device suitably used for exhausting process gases used in the manufacture of semiconductor devices, liquid crystals, LEDs, solar cells, and the like.

Background Art

[0002] In the manufacturing 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 rotor chamber in opposite directions to transfer gas.

[0003] The process gas may contain by-products with a high sublimation temperature. When the temperature in the rotor chamber of the vacuum pump device is low, the by-products may solidify in the rotor chamber and deposit on the pump rotor and the inner surface of the pump casing. The solidified by-products inhibit the rotation of the pump rotor, causing a decrease in the speed of the pump rotor and, in the worst case, the operation stop of the vacuum pump device. Therefore, in order to prevent the solidification of the by-products, a heater is attached to the outer surface of the pump casing to heat the rotor chamber.

[0004] On the one hand, it is necessary to cool the electric motor that drives the pump rotor and the gear fixed to the rotating shaft of the pump rotor. Therefore, the above-described vacuum pump device usually includes a cooling system for cooling the electric motor and the gear. The cooling system is configured to cool the electric motor and the gear, for example, by circulating a coolant through cooling pipes provided in a motor housing that houses the electric motor and cooling pipes provided in a gear housing that houses the gear. Such a cooling system can prevent overheating of the electric motor and the gear and achieve stable operation of the vacuum pump device.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] The heater attached to the pump casing has a structure sandwiched between side covers. Therefore, when replacing the heater due to its lifespan or the like, it is necessary to disassemble the vacuum pump device, and the heater cannot be easily replaced.

[0007] Therefore, the present invention provides a vacuum pump device that can maintain a high temperature inside the rotor chamber of the pump casing and can easily attach and detach the heater.

Means for Solving the Problems

[0008] In one aspect, there is provided a pump casing having a rotor chamber therein, a pump rotor disposed in the rotor chamber, a rotating shaft to which the pump rotor is fixed, an electric motor connected to the rotating shaft, a side cover forming an end face of the rotor chamber, a housing structure located outside the side cover in the axial direction of the rotating shaft, and a cartridge heater disposed in the side cover or in the pump casing and detachably attached to the side cover or the pump casing. The cartridge heater has a heater and a heater casing covering at least a part of the heater, and the heater casing has a slit extending from one end to the other end. and is made of a material having a higher coefficient of linear expansion than the material constituting the outer shell of the heater , a vacuum pump device is provided.

[0009] One In one aspect, the heater casing is made of any one of an aluminum alloy, aluminum, copper, and magnesium. In one aspect, the side cover or the pump casing has a hole that opens on an outer surface of the side cover or the pump casing and extends linearly, and the cartridge heater has a rod shape and is disposed in the hole. In one aspect, the vacuum pump device further includes a fixing mechanism for detachably fixing the cartridge heater to the side cover or the pump casing.

Advantages of the Invention

[0010] According to the present invention, by attaching the cartridge heater in the side cover or in the pump casing, the inside of the rotor chamber can be maintained at a high temperature. The slit formed in the heater casing can absorb the thermal expansion of the heater and the heater casing. Thereby, deformation of the cartridge heater due to secular deformation of the heater can be prevented, and the cartridge heater can be easily taken out from the side cover or the pump casing. The heater casing is made of a material with a higher coefficient of linear expansion than the material forming the outer shell of the heater, and the gap between the side cover or pump casing and the heater can be filled by the thermal expansion of the heater casing. Therefore, heat can be efficiently transferred from the cartridge heater to the side cover or pump casing.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Modes for Carrying Out the Invention

[0012] Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing an 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 FIG. 1 is a so-called dry vacuum pump device that does not use oil in the gas flow path. Since the vaporized oil does not flow upstream in the dry vacuum pump device, it can be suitably used in a manufacturing apparatus for semiconductor devices that requires a high degree of cleanliness.

[0013] As shown in FIG. 1, the vacuum pump device includes a pump casing 2 having a rotor chamber 1 therein, a pump rotor 5 disposed in the rotor chamber 1, a rotating shaft 7 to which the pump rotor 5 is fixed, and an electric motor 8 connected to the rotating shaft 7. The pump rotor 5 and the rotating shaft 7 may be an integral structure. In FIG. 1, only one pump rotor 5 and one rotating shaft 7 are depicted, but a pair of pump rotors 5 are disposed in the rotor chamber 1 and are respectively fixed to a pair of rotating shafts 7. The electric motor 8 is connected to one of the pair of rotating shafts 7. In one embodiment, the electric motor 8 may be such that a pair of electric motors 8 are respectively connected to the pair of rotating shafts 7.

[0014] The pump rotor 5 of the present embodiment is a Roots-type pump rotor, but the type of the pump rotor 5 is not limited to the present embodiment. In one embodiment, the pump rotor 5 may be a screw-type pump rotor. Further, the pump rotor 5 of the present embodiment is a single-stage pump rotor, but in one embodiment, the pump rotor 5 may be a multi-stage pump rotor.

[0015] 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 the present embodiment, the side covers 10A and 10B are fixed to the end face of the pump casing 2 by screws (not shown).

[0016] The rotor 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 the process chamber of a semiconductor device manufacturing apparatus, and the vacuum pump device is used for exhausting the process gas introduced into the process chamber.

[0017] The vacuum pump device further includes a motor housing 14 and a gear housing 16 as housing structures located outside the side covers 10A and 10B in the axial direction of the rotating shaft 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.

[0018] The rotating shaft 7 is rotatably supported by a bearing 17 held by the side cover 10A and a bearing 18 held by the side cover 10B. The motor housing 14 houses a motor rotor 8A and a motor stator 8B of the electric motor 8 inside thereof. The motor housing 14 and the gear housing 16 are examples of housing structures, and the housing structure is not limited to this embodiment. For example, the housing structure may be a bearing housing that holds bearings.

[0019] A pair of gears 20 meshing with each other are arranged inside the gear housing 16. Note that only one gear 20 is depicted in FIG. 1. The electric motor 8 rotates 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.

[0020] In one embodiment, a pair of electric motors 8 respectively connected to a pair of rotating shafts 7 may be provided. The pair of electric motors 8 rotate in opposite directions synchronously by a motor driver (not shown), and rotate the pair of rotating shafts 7 and the pair of pump rotors 5 in opposite directions synchronously. The role of the gear 20 in this case is to prevent the out-of-phase rotation of the synchronous rotation of the pump rotor 5 due to sudden external factors.

[0021] When the pump rotor 5 is rotated by the electric motor 8, gas is sucked into the pump casing 2 from the intake port 2a. The gas is transferred from the intake port 2a to the exhaust port 2b by the rotating pump rotor 5.

[0022] A cooling flow path 21 is provided in the motor housing 14. Similarly, a cooling flow path 22 is provided in the gear housing 16. The cooling flow path 21 extends along the entire peripheral wall of the motor housing 14, and the cooling flow path 22 extends along the entire peripheral wall of the gear housing 16. The cooling flow path 21 and the cooling flow path 22 are connected to a coolant supply source (not shown). The coolant is supplied from the coolant supply source to the cooling flow path 21 and the cooling flow path 22. The coolant flowing through the cooling flow path 21 cools the motor housing 14, and thereby can cool the electric motor 8 and the bearing 17 disposed in the motor housing 14. The coolant flowing through the cooling flow path 22 cools the gear housing 16, and thereby can cool the gear 20 and the bearing 18 disposed in the gear housing 16.

[0023] Some of the process gases handled by the vacuum pump device contain by-products that solidify as the temperature drops. During the operation of the vacuum pump device, the process gas is compressed as it is transferred from the intake port 2a to the exhaust port 2b by the pump rotor 5. Therefore, the inside of the rotor chamber 1 becomes hot due to the compression heat of the process gas. The side cover 10A is configured to reduce heat transfer from the pump casing 2 to the motor housing 14, and the side cover 10B is configured to reduce heat transfer from the pump casing 2 to the gear housing 16. Therefore, the side covers 10A and 10B can maintain the inside of the rotor chamber 1 at a high temperature. In particular, while cooling the motor housing 14 and the gear housing 16 with the coolant flowing through the cooling channels 21 and 22, the side covers 10A and 10B can maintain the inside of the rotor chamber 1 at a high temperature.

[0024] In this embodiment, the pump casing 2 and the side covers 10A and 10B that form the rotor chamber 1 are made of cast iron. In one embodiment, the side covers 10A and 10B may be made of a material having a lower thermal conductivity than cast iron.

[0025] The vacuum pump device further includes cartridge heaters 70A and 70B respectively disposed inside the side covers 10A and 10B. The cartridge heaters 70A and 70B are detachably attached to the side covers 10A and 10B. Details of the configuration of the cartridge heaters 70A and 70B will be described later.

[0026] Since the side covers 10A and 10B basically have the same configuration, and the cartridge heaters 70A and 70B basically have the same configuration, the side cover 10A and the cartridge heater 70A will be described below. FIG. 2 is a side view of the side cover 10A according to the embodiment shown in FIG. 1. FIG. 3 is a cross-sectional view taken along line A-A of FIG. 2. The side cover 10A has a through hole 27 through which the rotating shaft 7 passes. The through hole 27 communicates with the rotor chamber 1.

[0027] The side cover 10A has an inner wall portion 31 that forms the end face 31a of the rotor chamber 1, an outer wall portion 32 that is located outside the inner wall portion 31 in the axial direction of the rotary shaft 7, and a plurality of spacers 34 sandwiched between the inner wall portion 31 and the outer wall portion 32. The inner wall portion 31 and the outer wall portion 32 are separated from each other by the spacers 34. The inner wall portion 31 is connected to the pump casing 2 (see FIG. 1), and the outer wall portion 32 is connected to the motor housing 14. The outer wall portion 32 has a recess (not shown) in which the bearing 17 is accommodated. A heat insulating material may be disposed between the outer wall portion 32 and the motor housing 14.

[0028] The inner wall portion 31 of the side cover 10A has a hole 31b that opens on the outer surface of the side cover 10A (more specifically, the outer surface of the inner wall portion 31). The hole 31b extends linearly. The cartridge heater 70A has a linearly extending rod-like shape and is disposed in the hole 31b. The vacuum pump device of the present embodiment can locally attach the cartridge heater 70A by providing the hole 31b at a location where the cartridge heater 70A is to be attached.

[0029] In the present embodiment, two cartridge heaters 70A are arranged so as to sandwich the rotary shaft 7 (see FIG. 1). In one embodiment, only one cartridge heater 70A may be provided, or three or more cartridge heaters 70A may be provided. In the present embodiment, the inner wall portion 31 and the outer wall portion 32 are separated, but in one embodiment, the inner wall portion 31 and the outer wall portion 32 may be integrally formed without providing the spacers 34. Further, in one embodiment, a hole 31b may be formed on the outer surface of the side cover of an existing vacuum pump device, and the cartridge heater 70A may be inserted into the hole 31b.

[0030] The cartridge heater 70A is fixed to the side cover 10A by a screw 45 as a fixing mechanism while being inserted into the hole 31b. More specifically, the inner wall portion 31 of the side cover 10A has a screw hole 46 communicating with the hole 31b. When the screw 45 is screwed into the screw hole 46, the tip of the screw 45 presses the cartridge heater 70A in the hole 31b against the inner wall portion 31. Thereby, the position of the cartridge heater 70A is fixed. When the screw 45 is loosened, the cartridge heater 70A can be taken out from the hole 31b. Since the hole 31b opens on the outer surface of the side cover 10A, the cartridge heater 70A can be taken out from the side cover 10A without disassembling the vacuum pump device. Therefore, when a problem occurs in the cartridge heater 70A, it can be easily replaced with a new cartridge heater.

[0031] Next, the configuration of the cartridge heater 70A will be described. FIG. 4 is a perspective view of the cartridge heater 70A. FIG. 5 is a cross-sectional view taken along line B-B of FIG. 4. The cartridge heater 70A has a heater 71 and a heater casing 72 that covers at least a part of the heater 71. The heater 71 has a heating element 71a and an outer shell 71b that surrounds the heating element 71a. The outer shell 71b is made of metal and has a function of protecting the heating element 71a and transmitting the heat generated by the heating element 71a. The cartridge heater 70A is a heating device in which the heater 71 is inserted inside the heater casing 72. The type of the heater 71 is not particularly limited, but a sheathed heater, which is a type of electric heater, can be used as the heater 71. The heater 71 is a rod-shaped heater that extends linearly.

[0032] The heater casing 72 has a cylindrical shape with both ends open and a cylindrical space provided inside. The heater casing 72 has a slit 72a extending from one end to the other end. The slit 72a extends over the entire length of the heater casing 72. The cross-section of the heater casing 72 has an annular shape with a slit 72a of width s1 open. In the present embodiment, the overall length of the heater casing 72 is the same as the overall length of the heater 71, and the heater casing 72 covers the entire heater 71. In one embodiment, the overall length of the heater casing 72 may be longer than the overall length of the heater 71.

[0033] FIG. 6 is an enlarged cross-sectional view of the cartridge heater 70A inserted into the hole 31b. Before the heater 71 generates heat, as shown in FIG. 6, the inner diameter φ1 of the hole 31b of the side cover 10A is larger than the outer diameter φ2 of the heater casing 72. Therefore, when the cartridge heater 70A is inserted into the hole 31b, a gap is formed between the side cover 10A (more specifically, the inner wall constituting the hole 31b) and the heater casing 72. Before the heater 71 generates heat, the inner diameter φ3 of the heater casing 72 is larger than the outer diameter φ4 of the heater 71. Therefore, before the heater 71 generates heat, a gap is formed between the heater 71 and the heater casing 72.

[0034] In the present embodiment, the outer shell 71b of the heater 71 is made of stainless steel. Stainless steel has a higher coefficient of linear expansion than the cast iron constituting the pump casing 2 and the side covers 10A and 10B. The heater casing 72 is made of a material having a higher coefficient of linear expansion than the outer shell 71b of the heater 71. More specifically, the heater casing 72 is made of a metal having a higher coefficient of linear expansion than the outer shell 71b of the heater 71. Examples of metals having a higher coefficient of linear expansion than the stainless steel constituting the outer shell 71b of the heater 71 include aluminum alloy, aluminum, copper, magnesium, and the like.

[0035] When heat is generated from the heater 71, the heat is transferred from the side cover 10A to the rotor chamber 1 (see FIG. 1) via the heater casing 72, and the rotor chamber 1 can be heated. As a result, the inside of the rotor chamber 1 can be maintained at a high temperature, preventing the by-products in the process gas from solidifying.

[0036] The heater 71 may be heated up to about 600° C., and the heater 71 itself thermally expands. When the heater 71 is repeatedly heated over a long-term operation, the entire heater 71 may be deformed. As a result, there is a problem that the heater 71 cannot be removed from the side cover 10A, and when a problem occurs in the heater 71, the heater 71 cannot be easily replaced. Considering the deformation of the heater 71, if the inner diameter φ1 of the hole 31b of the inner wall portion 31 is increased, heat cannot be efficiently transferred from the heater 71 to the side cover 10A. Therefore, the power consumption of the heater 71 increases, and the operating cost increases.

[0037] FIG. 7 is an enlarged cross-sectional view of the cartridge heater 70A during heating. According to the present embodiment, since the cartridge heater 70A includes the heater casing 72 that covers the heater 71, when the heater 71 generates heat, the heater 71 and the heater casing 72 thermally expand. As a result, the gap between the heater 71 and the heater casing 72 becomes smaller. More specifically, the inner diameter φ3 of the heater casing 72 is equal to the outer diameter φ4 of the heater 71. The heater casing 72 having the slit 72a can absorb the secular deformation of the heater 71. Therefore, the overall deformation of the cartridge heater 70A due to the secular deformation of the heater 71 can be prevented, and the cartridge heater 70A can be easily removed from the side cover 10A.

[0038] The heater casing 72 made of a material with a higher coefficient of linear expansion than the outer shell 71b of the heater 71 thermally expands more than the heater 71. The heater casing 72 expands until it contacts the inner wall that forms the hole 31b of the side cover 10A. More specifically, the outer diameter φ2 of the heater casing 72 becomes equal to the inner diameter φ1 of the hole 31b. In this way, the thermally expanded heater casing 72 can fill the gap between the side cover 10A (more specifically, the inner wall that forms the hole 31b) and the heater 71. Therefore, heat can be efficiently transferred from the cartridge heater 70A to the side cover 10A.

[0039] As can be seen from the comparison between FIGS. 6 and 7, the thermal expansion of the heater casing 72 after contacting the hole 31b is absorbed by the slit 72a of the heater casing 72. More specifically, while the thermal expansion of the heater casing 72 is restricted by the hole 31b, the heater casing 72 expands in the direction in which the slit 72a becomes narrower. As a result, the stress generated in the heater casing 72 is reduced, and deformation and breakage of the heater casing 72 are prevented.

[0040] When the heat generation of the heater 71 stops and the temperatures of the heater 71 and the heater casing 72 decrease, the heater 71 and the heater casing 72 contract, and a gap is formed again between the side cover 10A (more specifically, the inner wall that forms the hole 31b) and the heater casing 72. Therefore, the cartridge heater 70A can be easily attached to and detached from the side cover 10A.

[0041] FIG. 8 is a cross-sectional view showing another embodiment of the vacuum pump device. FIG. 9 is a cross-sectional view taken along line C-C of FIG. 8. Since the configuration of this embodiment not particularly described is the same as that of the embodiment described with reference to FIGS. 1 to 7, the overlapping description thereof will be omitted. In the vacuum pump device shown in FIG. 8, a cartridge heater 70 is disposed in the pump casing 2. The cartridge heater 70 is detachably attached to the pump casing 2. The details of the configuration of the cartridge heater 70 are the same as those of the cartridge heater 70A described with reference to FIGS. 4 and 5.

[0042] The cartridge heaters 70 are disposed on both sides of the intake port 2a and both sides of the exhaust port 2b of the pump casing 2. As shown in FIG. 9, the pump casing 2 has a hole 2c that opens on the outer surface of the pump casing 2. The hole 2c extends linearly. The cartridge heater 70 has a linearly extending rod shape and is disposed in the hole 2c. In the vacuum pump device of this embodiment, by providing the hole 2c at a location where the cartridge heater 70 is to be attached, the cartridge heater 70 can be locally attached. In this embodiment, four cartridge heaters 70 are disposed so as to sandwich the intake port 2a and the exhaust port 2b of the pump casing 2. In one embodiment, three or less, or five or more cartridge heaters 70 may be provided.

[0043] The cartridge heater 70 is fixed to the pump casing 2 by a screw 45 as a fixing mechanism while being inserted into the hole 2c. More specifically, the pump casing 2 has a threaded hole 46 communicating with the hole 2c. When the screw 45 is screwed into the threaded hole 46, the tip of the screw 45 presses the cartridge heater 70 in the hole 2c against the pump casing 2. Thereby, the position of the cartridge heater 70 is fixed. When the screw 45 is loosened, the cartridge heater 70 can be taken out of the hole 2c. Since the hole 2c opens on the outer surface of the pump casing 2, the cartridge heater 70 can be taken out of the pump casing 2 without disassembling the vacuum pump device. Therefore, when a problem occurs in the cartridge heater 70, it can be easily replaced with a new cartridge heater.

[0044] The relationship between the inner diameter of the hole 2c of the pump casing 2, the outer diameter and inner diameter of the heater casing 72 of the cartridge heater 70, and the outer diameter of the heater 71 in the present embodiment is the same as the relationship between the inner diameter φ1 of the hole 31b of the side cover 10A, the outer diameter φ2 and inner diameter φ3 of the heater casing 72 of the cartridge heater 70A, and the outer diameter φ4 of the heater 71, which was described with reference to FIGS. 6 and 7. Therefore, the overlapping description thereof is omitted.

[0045] When heat is generated from the heater 71, the heat is transferred from the pump casing 2 to the rotor chamber 1 (see FIG. 8) through the heater casing 72, and the rotor chamber 1 can be heated. Thereby, the inside of the rotor chamber 1 can be maintained at a high temperature, and it is possible to prevent the by-products in the process gas from solidifying.

[0046] According to this embodiment, since the cartridge heater 70 includes a heater casing 72 that covers the heater 71, when the heater 71 generates heat, the heater 71 and the heater casing 72 thermally expand. As a result, the gap between the heater 71 and the heater casing 72 becomes smaller. More specifically, the inner diameter of the heater casing 72 becomes equal to the outer diameter of the heater 71. The heater casing 72 having the slit 72a can absorb the secular deformation of the heater 71. Therefore, the overall deformation of the cartridge heater 70 due to the secular deformation of the heater 71 is prevented, and the cartridge heater 70 can be easily removed from the pump casing 2.

[0047] The heater casing 72 made of a material having a higher coefficient of linear expansion than the outer shell 71b of the heater 71 thermally expands more than the heater 71. The heater casing 72 expands until it contacts the inner wall that forms the hole 2c of the pump casing 2. More specifically, the outer diameter of the heater casing 72 becomes equal to the inner diameter of the hole 2c. In this way, the thermally expanded heater casing 72 can fill the gap between the pump casing 2 (more specifically, the inner wall that forms the hole 2c) and the heater 71. Therefore, heat can be efficiently transferred from the cartridge heater 70 to the pump casing 2.

[0048] When the heat generation of the heater 71 stops and the temperatures of the heater 71 and the heater casing 72 decrease, the heater 71 and the heater casing 72 contract, and a gap is formed again between the pump casing 2 (more specifically, the inner wall that forms the hole 2c) and the heater casing 72. Therefore, the cartridge heater 70 can be easily attached to and detached from the pump casing 2.

[0049] In one embodiment, the vacuum pump device may further include cartridge heaters 70A and 70B in the side covers 10A and 10B in the same manner as the embodiment described with reference to FIGS. 1 to 7, in addition to the cartridge heater 70 in the pump casing 2 described above.

[0050] FIG. 10 is a cross-sectional view showing still another embodiment of the vacuum pump device. FIG. 11 is a side view of the side cover according to the embodiment shown in FIG. 10. FIG. 12 is a view seen from the direction indicated by arrow D in FIG. 11. FIG. 13 is a perspective view of the side cover 10A shown in FIG. 11. The configuration of this embodiment not particularly described is the same as that of the embodiment described with reference to FIGS. 1 to 7, and thus the overlapping description thereof is omitted. The side covers 10A and 10B of the vacuum pump device shown in FIG. 10 further include a constricted portion 33 and a heater housing 35. The cartridge heaters 70A and 70B are detachably attached to the heater housings 35 of the side covers 10A and 10B, respectively. The details of the configuration of the cartridge heaters 70A and 70B are the same as the configuration of the cartridge heater 70A described with reference to FIGS. 4 and 5.

[0051] The side cover 10A of this embodiment has an inner wall portion 31 that forms the end face 31a of the rotor chamber 1, an outer wall portion 32 that is located outside the inner wall portion 31 in the axial direction of the rotating shaft 7, and a constricted portion 33 that is located between the inner wall portion 31 and the outer wall portion 32. The inner wall portion 31 is connected to the pump casing 2, and the outer wall portion 32 is connected to the motor housing 14. The outer wall portion 32 has a recessed portion 32a in which the bearing 17 is accommodated. A heat insulating material may be disposed between the outer wall portion 32 and the motor housing 14.

[0052] The inner wall portion 31, the outer wall portion 32, and the constricted portion 33 are integrally formed. In this embodiment, the inner wall portion 31, the outer wall portion 32, and the constricted portion 33 are integrally formed castings. Since the side cover 10A thus includes an integrally formed object, it is not necessary to separately create a plurality of members and assemble them. As a result, the manufacturing cost can be reduced.

[0053] The constricted portion 33 has an outer peripheral length shorter than the outer peripheral lengths of the inner wall portion 31 and the outer wall portion 32. That is, the constricted portion 33 has a cross-sectional area smaller than the cross-sectional areas of the inner wall portion 31 and the outer wall portion 32. The inner wall portion 31, the outer wall portion 32, and the constricted portion 33 are made of the same material, but since the cross-sectional area of the constricted portion 33 is smaller than the cross-sectional areas of the inner wall portion 31 and the outer wall portion 32, heat is less likely to be transferred from the inner wall portion 31 through the constricted portion 33 to the outer wall portion 32. Although the description is omitted, the side cover 10B basically has the same configuration. The side covers 10A and 10B having such a constricted portion 33 have high heat insulation performance, so the inside of the rotor chamber 1 can be maintained at a high temperature. Further, it is possible to prevent the cooling of the pump casing 2 by the coolant flowing through the cooling channels 21 and 22.

[0054] The side cover 10A has two heater housings 35 each having a hole 35a. The two heater housings 35, the inner wall portion 31, the outer wall portion 32, and the constricted portion 33 are integrally formed. Each hole 35a opens on the outer surface of the side cover 10A (more specifically, the outer surface of the heater housing 35), and the cartridge heater 70A is disposed in the hole 35a. In the present embodiment, the two cartridge heaters 70A are disposed so as to sandwich the rotation shaft 7. In one embodiment, only one cartridge heater 70A may be provided, or three or more cartridge heaters 70A may be provided.

[0055] The hole 35a extends linearly, and the cartridge heater 70A is also a rod-shaped heater that extends linearly. The cartridge heater 70A is fixed to the side cover 10A by a screw 45 as a fixing mechanism while being inserted into the hole 35a. More specifically, the heater housing 35 has a screw hole 46 that communicates with the hole 35a. When the screw 45 is screwed into the screw hole 46, the tip of the screw 45 presses the cartridge heater 70A in the hole 35a against the heater housing 35. Thereby, the position of the cartridge heater 70A is fixed. When the screw 45 is loosened, the cartridge heater 70A can be taken out of the hole 35a. Since the hole 35a opens on the outer surface of the side cover 10A, the cartridge heater 70A can be taken out of the side cover 10A without disassembling the vacuum pump device. Therefore, when the cartridge heater 70A fails, it can be easily replaced with a new cartridge heater.

[0056] The relationship between the inner diameter of the hole 35a of the heater housing 35, the outer diameter and inner diameter of the heater casing 72 of the cartridge heater 70A, and the outer diameter of the heater 71 in this embodiment is the same as the relationship between the inner diameter φ1 of the hole 31b of the side cover 10A, the outer diameter φ2 and inner diameter φ3 of the heater casing 72 of the cartridge heater 70A, and the outer diameter φ4 of the heater 71 described with reference to FIGS. 6 and 7. Therefore, the overlapping description is omitted.

[0057] When heat is generated from the heater 71, the heat is transferred from the heater 71 to the heater housing 35 and the inner wall portion 31 through the heater casing 72 to the rotor chamber 1 (see FIG. 10), and the rotor chamber 1 can be heated. Thereby, the inside of the rotor chamber 1 can be maintained at a high temperature, and it is possible to prevent the by-products in the process gas from solidifying. In particular, since the heater housing 35 and the inner wall portion 31 are integrally formed, the heat conduction efficiency from the cartridge heater 70A to the inner wall portion 31 is improved.

[0058] As shown in FIG. 13, at least a part of the heater housing 35 is separated from the outer wall portion 32. Although not shown, the entire heater housing 35 may be separated from the outer wall portion 32. With such a configuration, the heat generated from the heater 71 and transmitted through the heater casing 72 is less likely to be transmitted to the outer wall portion 32. Therefore, the cartridge heater 70A can prevent the heating of the motor housing 14 (see FIG. 10), which is a housing structure connected to the outer wall portion 32, while heating the rotor chamber 1.

[0059] According to the present embodiment, since the cartridge heater 70A includes the heater casing 72 that covers the heater 71, when the heater 71 generates heat, the heater 71 and the heater casing 72 expand thermally. As a result, the gap between the heater 71 and the heater casing 72 becomes smaller. More specifically, the inner diameter of the heater casing 72 becomes equal to the outer diameter of the heater 71. The heater casing 72 having the slit 72a can absorb the secular deformation of the heater 71. Therefore, the overall deformation of the cartridge heater 70A due to the secular deformation of the heater 71 can be prevented, and the cartridge heater 70A can be easily removed from the heater housing 35.

[0060] The heater casing 72 made of a material having a higher coefficient of linear expansion than the outer shell 71b of the heater 71 expands thermally more than the heater 71. The heater casing 72 expands until it contacts the inner wall that forms the hole 35a of the heater housing 35. More specifically, the outer diameter of the heater casing 72 becomes equal to the inner diameter of the hole 35a. In this way, the thermally expanded heater casing 72 can fill the gap between the heater housing 35 (more specifically, the inner wall that forms the hole 35a) and the heater 71. Therefore, heat can be efficiently transferred from the cartridge heater 70A to the heater housing 35.

[0061] When the heating of the heater 71 stops and the temperatures of the heater 71 and the heater casing 72 decrease, the heater 71 and the heater casing 72 contract, and a gap is formed again between the heater housing 35 (more specifically, the inner wall forming the hole 35a) and the heater casing 72. Therefore, the cartridge heater 70A can be easily attached to and detached from the heater housing 35.

[0062] As shown in FIG. 10, a cartridge heater 70B is also disposed within the side cover 10B. The descriptions with reference to FIGS. 11 through 13 are also applicable to the side cover 10B and the cartridge heater 70B disposed therein, and thus the overlapping descriptions thereof are omitted.

[0063] In one embodiment, the vacuum pump device may further include a cartridge heater 70 within the pump casing 2, in addition to the cartridge heaters 70A and 70B within the side covers 10A and 10B described above, in the same manner as the embodiment described with reference to FIGS. 8 and 9.

[0064] The above-described embodiments are described for the purpose of enabling a person having ordinary skill in the art to which the present invention pertains to practice the present invention. Various modifications of the above embodiments can be naturally made by those skilled in the art, and the technical idea of the present invention can be applied to other embodiments. Therefore, the present invention is not limited to the described embodiments, but is to be construed in the broadest scope in accordance with the technical idea defined by the claims.

Explanation of Reference Numerals

[0065] 1 Rotor chamber 2 Pump casing 2a Intake port 2b Exhaust port 2c Hole 5 Pump rotor 7 Rotation shaft 8 Electric motor 8A Motor rotor 8B Motor stator 10A, 10B Side covers 14 Motor housing (housing structure) 16 Gear housing (housing structure) 17, 18 Bearings 20 Gear 21, 22 Cooling channels 27 Through-hole 31 Inner wall portion 31a End face 31b Hole 32 Outer wall portion 32a Depression 33 Constriction 34 Spacer 35 Heater housing 35a Hole 45 Screw 46 Threaded hole 70, 70A, 70B Cartridge heater 71 Heater 71a Heating element 71b Outer shell 72 Heater casing 72a Slit

Claims

1. A pump casing having a rotor chamber inside, A pump rotor disposed in the rotor chamber, A rotating shaft to which the pump rotor is fixed, An electric motor connected to the rotating shaft, A side cover forming an end face of the rotor chamber, A housing structure located outside the side cover in the axial direction of the rotating shaft, Comprising a cartridge heater disposed inside the side cover or inside the pump casing and detachably attached to the side cover or the pump casing, The cartridge heater has a heater and a heater casing covering at least a part of the heater, The heater casing has a slit extending from one end to the other end and is made of a material having a higher linear expansion coefficient than the material constituting the outer shell of the heater. A vacuum pump device.

2. The vacuum pump device according to claim 1, wherein the heater casing is made of any one of aluminum alloy, aluminum, copper, and magnesium.

3. The side cover or the pump casing has a hole that opens on the outer surface of the side cover or the pump casing and extends linearly, The vacuum pump device according to any one of claims 1 or 2, wherein the cartridge heater has a rod shape and is disposed in the hole.

4. The vacuum pump device according to any one of claims 1 to 3, further comprising a fixing mechanism for detachably fixing the cartridge heater to the side cover or the pump casing.

Images