JP5133224B2 - Vacuum pump unit - Google Patents

Description

  The present invention relates to a vacuum pump unit having a vacuum ultimate pressure of about 1 Pa.

  A vacuum pump having an exhaust capability with a vacuum ultimate pressure of about 1 Pa is used for applications such as sputtering devices, helium leak detectors, and analysis devices such as SEM. Also, vacuum pumps with the above exhaust capability are used as vacuum pumps for roughing high vacuum pumps such as turbo molecular pumps, and for the purpose of sucking gases such as water vapor, such as vacuum drying and vacuum bonding devices It has been.

  Among these types of vacuum pumps, as a vacuum pump with a relatively high pumping speed (1000 L / min or more) used in semiconductor manufacturing applications, etc., a conventional two-shaft volume transfer type dry vacuum such as a multi-stage roots type or a screw type has been used. A pump is in use. In addition, in order to obtain a vacuum exhaust performance with an ultimate vacuum pressure of 1 Pa or less and a higher exhaust speed, two pumps, a main pump and a booster pump, are connected in series to form one vacuum pump unit. Some are. The biaxial positive displacement dry vacuum pump does not use oil in the gas passage unlike the oil rotary pump, so there is no oil contamination, and non-contact operation is possible without using the tip seal like the scroll type dry vacuum pump. Since it is possible, there is no generation of particles due to wear of the chip seal, and it is suitable for use in semiconductor manufacturing.

  Patent Document 1 discloses a screw-type biaxial volume transfer type dry vacuum pump unit of this type. This dry vacuum pump unit includes a main pump (vacuum pump) disposed on the external pressure side and a booster pump (vacuum pump) disposed on the vacuum side, and the booster pump and the main pump are connected in series. It is configured. Each of the main pump and the booster pump includes a pair of screw type pump rotors, a casing that houses the pair of screw type pump rotors, and a pair of magnet rotors that rotate integrally with the pair of screw type pump rotors. I have. According to this dry vacuum pump, it is possible to reduce the size and size, achieve a sufficient degree of vacuum, low power consumption, no problem of contamination due to oil or chip seals, etc., and exhaust from atmospheric pressure in a short time. It becomes possible.

However, the dry vacuum pump shown in Patent Document 1 needs to rotate its screw type pump rotor at a high speed in order to reduce the size. There was a problem that the load increased and at the same time the temperature became high, and reliability could not be secured.
JP 2007-231935 A

The present invention has been made in view of the above points and its object is also rotation of the screw rotor to speed, to provide a vacuum pump unit that Ru can be sufficiently ensure the reliability of their thrust bearing There is.

The invention according to claim 1 includes a main pump disposed on the external air pressure side, and a booster pump disposed on the vacuum side and connected in series to the main pump, and at least the main pump includes a pair of vertical and screw rotor arranged in parallel, a casing for accommodating the pair of screw rotors, and a pair of b over data that rotates integrally with the pair of screw rotors, the rotary shaft of the pair of screw rotors In addition to being installed vertically in the direction, the intake port provided in the casing is positioned above the exhaust port, and the thrust bearing of the rotary shaft is installed on the intake side above the rotary shaft. in the vacuum pump unit that.

A second aspect of the present invention is the vacuum pump unit according to the first aspect, wherein the rotor is a magnet rotor.

The invention described in the claims 3, the vacuum pump unit according to claim 1 or 2, wherein the thrust bearing is in vacuum pump unit you being a ceramic ball bearing.

According to the invention described in claim 1 or 2, since the main pump is installed vertically so that the intake port of the casing of the main pump is positioned above the exhaust port, the thrust load applied to the pair of screw rotors is It becomes upward and can cancel out with the dead weight (downward) of the screw rotor, and the thrust load can be reduced. At the same time, since the thrust bearing of the rotating shaft is installed on the relatively low temperature intake side where no heat of compression is generated, the temperature of the thrust bearing can be prevented from increasing. And even if a screw rotor rotates at high speed by these synergistic effects, the reliability of those thrust bearings can fully be ensured.

According to the invention described in claim 3 , since the ceramic ball bearing having excellent heat resistance and suitable for high speed rotation is used as the thrust bearing, the reliability of the thrust bearing can be further improved.

Hereinafter, an embodiment of the present invention will be described by taking a dry vacuum pump unit as an example . FIG. 1 is a schematic side view of a dry vacuum pump unit 1 according to an embodiment of the present invention, and FIG. 2 is a schematic diagram of the dry vacuum pump unit 1. As shown in FIG. 1, the dry vacuum pump unit 1 has a main pump 15 and a booster pump 16 attached to a pump installation base 60, and the electrical equipment 17 that drives the dry vacuum pump unit 1 and the pump installation base 60 are connected to a heat sink. The outer case 29 is mounted so as to cover and fix the above-described members.

  The main pump 15 and the booster pump 16 are pumps having the same structure, and both are connected in series. However, the main pump 15 and the booster pump 16 do not necessarily have the same structure. The two pumps 15 and 16 are volumetric transfer type biaxial screw pumps that do not have a compression process, and do not use a timing gear, but use a non-contact magnet coupling to synchronously invert the biaxial pump rotor. And a vacuum pump for transferring gas. The motors 15m and 16m for driving the vacuum pumps 15 and 16 are brushless DC motors in which permanent magnets are arranged on the motor rotor. The motors 15m and 16m are driven by variable speed motor drivers in the electrical equipment 17. Fins 15f and 16f are attached to the outer peripheral side surfaces of the main pump 15 and the booster pump 16 (including motors 15m and 16m), respectively.

  The electrical equipment 17 is for electrically controlling the dry vacuum pump unit 1 to drive it. The motor drivers installed therein are a motor driver for the main pump 15 and a motor driver for the booster pump 16. And each independently drives the main pump 15 and the booster pump 16 to rotate. Both motor drivers are supplied with, for example, 48V DC power from a common DC power supply (AC / DC converter), and each motor driver converts the DC power into a rectangular pulse waveform by PWM. Is supplied to the drive winding. For example, the rotational speed of the vacuum pump (main pump) 15 on the external air pressure side is set to about 13000 rpm, the rotational speed of the vacuum pump (booster pump) 16 on the vacuum side is set to 15000 to 21000 rpm, and the rotational speed of the booster pump 16 is set to the main pump. The rotation speed is higher than 15. Thus, by rotating the vacuum pumps 15 and 16 at a high speed, an ultimate vacuum pressure of 1 Pa or less can be obtained while being small. Here, “outside air pressure” means the pressure in the ambient atmosphere of the vacuum pump unit 1, and more specifically, the pressure in the exhaust side space communicating with the vacuum pump unit 1. Since the ultimate pressure power is about 240 to 300 W, the power consumption is low, and the electric power of the dry vacuum pump unit 1 can be sufficiently supplied by an ordinary single-phase AC power source. For this reason, this dry vacuum pump unit 1 can be used as a portable vacuum pump wherever a single-phase AC power source can be used.

  The main pump 15 and the booster pump 16 are pumps having the same structure, but by operating the booster pump 16 at a higher speed than the main pump 15, a vacuum that cannot be obtained at all by operating this type of vacuum pump. An ultimate vacuum of about 1 Pa or less (0.5 Pa in this embodiment) is obtained on the container side.

  The pump mounting base 60 is formed of a single member made of a material having good thermal conductivity (aluminum in this embodiment), and includes a substantially flat upper plate portion 60a and a top plate portion 60a. The column portion 60b attached to the lower surface is integrally formed. The upper surface of the upper plate portion 60a is substantially horizontal, and the booster pump 16 is attached thereto. The side surface of the support column 60b is a surface that substantially hangs down from the upper surface, and the main pump 15 is attached to one side surface (the surface facing the air discharge port 29b). Inside the pump mounting base 60, a communication passage 61 that communicates between the exhaust port 16 b of the booster pump 16 and the intake port 15 a of the main pump 15, an exhaust port 15 b of the main pump 15, and a check valve 32 described below (see FIG. 2) and a pressure release passage 62 for bypassing the main pump 15 and connecting the communication passage 61 and the exhaust pipe 39. The pressure release passage 62 is further connected to an exhaust pipe 39 communicating with outside air via a pressure release valve (check valve) 31 and a pipe 47. Therefore, when the pressure in the communication path 61 between the main pump 15 and the booster pump 16 is high, the pressure release valve (check valve) 31 opens and communicates with the outside air via the exhaust pipe 39. Here, the pressure release valve (check valve) 31 has a structure in which a valve body pressurized by a spring presses an elastic body such as an O-ring (rubber ring) to seal the flow path, and the communication path It opens only when the pressure in 61 becomes higher than the external pressure. The material of the pump mounting base 60 may be another material such as titanium or stainless steel.

  Thus, when the vacuum vessel to be exhausted to which the suction pipe 34 is connected is exhausted from the outside air pressure, the booster pump 16 and the main pump 15 are connected because the exhaust speed of the booster pump 16 is higher than the exhaust speed of the main pump 15. Although the gas in the communication path 61 is overcompressed, the overcompressed gas can be released into the outside air by the pressure release valve (check valve) 31. Accordingly, the pressure release valve (check valve) 31 prevents gas overcompression and is safe, and at the same time increases the power required for exhausting when the vacuum vessel is at the external pressure (when the intake side pressure is equal to the external pressure). Can be prevented. Further, the operation of the main pump 15 can be continued while maintaining the exhaust speed of the booster pump 16 as it is, and a decrease in the exhaust flow rate at the start-up can be prevented, and a desired degree of vacuum can be reached in a short time.

  That is, when there is no pressure release valve (check valve) 31, in order to avoid overcompression of gas, first, the main pump is evacuated and the booster pump is started after the vacuum state is reached to some extent. The main pump was started while operating at a low rotational speed. In this case, since the exhaust speed at startup is mainly determined by the main pump, there is a problem that the exhaust flow rate is low and a certain amount of time is required to reach a predetermined degree of vacuum. By providing the pressure release valve 31, it is possible to directly exhaust the gas at the external pressure with a booster pump having a high exhaust speed, and it is possible to reach the required vacuum degree in a short time.

  Here, as an operating condition of the pressure release valve 31, when a differential pressure is generated between the upstream side and the downstream side, the valve is immediately closed, and when the differential pressure disappears, the valve is immediately opened. For this reason, when the intake side changes from the external pressure to the vacuum pressure, the valve is quickly closed and there is no loss of exhaust time. Further, during steady operation, the pressure release valve 31 is always closed, so that the exhaust sound of the booster pump 16 does not leak outside.

  On the other hand, the pressure release valve 32 (see FIG. 2; not shown in FIG. 1 because it is located on the back side of the pressure release valve 31) attached to the exhaust passage 63 connected to the exhaust port 15b of the main pump 15 is also a spring. Has a structure in which the pressure-pressed valve body presses the O-ring (rubber ring). As a result, when the inside of the vacuum vessel is in a steady operation state where the vacuum is evacuated, the pressure release valve 32 is almost closed, and the exhaust sound of the main pump 15 can be blocked from leaking to the outside. Even when the operation of the main pump 15 is stopped due to some abnormality, the pressure release valve 32 is closed, so that the vacuum state can be prevented from being broken.

  The heat radiating plate 21 is formed in a substantially rectangular flat plate shape, and an air circulation portion 23 through which air for cooling the heat radiating plate is passed is formed on the lower surface side of the heat radiating plate 21. The front end of the air circulation part 23 (the end on the front side of the electrical equipment 17) is exposed in the vicinity of the lower part of the front surface of the exterior case 29, and the opening is an air inlet (hereinafter referred to as “second air” for introducing air). 23a). The rear end of the air circulation part 23 is an air outlet 23 b that opens at the lower part of the main pump 15. On the upper surface of the heat radiating plate 21, the lower surface of the column portion 60 b of the pump installation base 60 and the lower surface of the electrical equipment 17 are fixed. The outer case 29 is box-shaped, and an air inlet (hereinafter referred to as “first air inlet”) 29a is provided near the upper portion of the front surface (the surface on which the second air inlet 23a is located). In addition, an air discharge port 29 b is provided in the vicinity of the upper portion of the rear surface of the outer case 29. A cooling fan 40 is installed at a position facing the air outlet 29 b in the outer case 29. The cooling fan 40 forcibly discharges air, which has been introduced from the first and second air inlets 29a and 23a and has cooled the internal equipment, to the outside from the air outlet 29b.

  3 is a schematic longitudinal sectional view of the main pump 15, FIG. 4 is a sectional view taken along the line IV-IV of FIG. 3, and FIG. 5 is a schematic longitudinal sectional view of the main pump 15, the booster pump 16 and the pump installation base 60. As shown in these drawings, the main pump 15 is a vacuum pump that uses a pair of non-contact magnet couplings to synchronize and reverse a pair of screw rotors and transfer gas without using a timing gear. This is a volume transfer type twin screw pump. Moreover, as shown in FIG. 5, the main pump 15 is installed vertically and the booster pump 16 is installed horizontally. In this embodiment, since the main pump 15 and the booster pump 16 have the same configuration, only the main pump 15 will be described below.

  As shown in FIGS. 3 and 4, two rotary shafts 51a and 51b are arranged in parallel in the casing 50, and the upper and lower portions of the rotary shafts 51a and 51b are respectively thrust and radial bearings 53-1. And a radial bearing 53-2. As the thrust radial bearing 53-1, which supports the upper portions of the rotary shafts 51a, 51b, a ceramic ball bearing having excellent heat resistance and suitable for high-speed rotation is used. On the other hand, as the radial bearing 53-2 for supporting the lower portions of the rotary shafts 51a and 51b, a similar ceramic ball bearing may be used, or a material other than that may be used. The thrust radial bearing 53-1 is fixed to the casing 50 in both the thrust direction (axial direction) and the radial direction (rotation direction), and the radial bearing 53-2 is fixed only in the radial direction. Is not fixed in the thrust direction. That is, the expansion and contraction of the rotary shafts 51a and 51b in the axial direction is supported by the radial bearing 53-2 moving (vertically moving) in the axial direction.

  A right-handed screw rotor (pump rotor) 52a is fixed to the rotating shaft 51a, and a left-handed screw rotor (pump rotor) 52b is fixed to the rotating shaft 51b. A fluid passage 56 is formed between the screw rotors 52 a and 52 b and the inner surface of the casing 50, an intake port 15 a is provided at the upstream end of the fluid passage 56, and an exhaust port is provided at the downstream end of the fluid passage 56. 15b is provided. The screw rotors 52a and 52b are reversed in contact with each other while maintaining a slight clearance so that the gas sucked from the intake port 15a is transferred to the exhaust port 15b. That is, the main pump 15 is installed vertically with the rotation shafts 51a and 51b of the pair of screw rotors 52a and 52b in the vertical direction (substantially vertical direction in this embodiment), and the intake port 15a provided in the casing 50 is exhausted. Positioned above the port 15b, the thrusts of the rotary shafts 51a and 51b and the radial bearing 53-1 are installed on the intake side above the rotary shafts 51a and 51b. In addition, as a screw rotor 52a, 52b, you may use a pair of screw rotor which has an axial cross-sectional shape which contacts only on a pitch line.

  A pair of magnet rotors 54, 54 having the same configuration are arranged at the shaft ends on the intake side of the rotation shafts 51a, 51b, respectively, and the rotation shafts 51a, 51b are driven in reverse as brushless DC motors. Synchronous reversal of the rotating shafts 51a and 51b is ensured. As shown in FIG. 4, each magnet rotor 54 is provided with a ring-shaped magnet 54a around the outer periphery of a magnetic material yoke 54b. In the present embodiment, a magnet 54a magnetized in six poles is provided on the outer periphery of the magnet rotor 54, facing each other so that the different magnetic poles of the magnet rotors 54 and 54 attract each other, and maintaining a clearance C. Has been placed. The number of poles of the magnet rotor 54 is an even number such as 4, 6, 8, 10, 12.

  The screw rotors 52a and 52b are synchronously rotated in opposite directions by the magnet coupling action of the magnet rotors 54 and 54. Thereby, the screw pump which can perform the stable biaxial synchronous inversion even if there is no gear is comprised. The absence of gear means that no lubricating oil is required, non-contact rotation including a two-shaft perfect synchronization mechanism is possible, and high speed operation of the screw pump is possible. That is, in the contact-type synchronization mechanism using the timing gear, the rotation speed is 6000 to 7000 rpm, but by using the magnet coupling, the synchronous inversion high-speed rotation of about 10000 to 30000 rpm can be stabilized as described above. As a result, even if the vacuum pump is made smaller, an improvement in exhaust performance such as a high degree of vacuum is achieved.

  A three-phase (U, V, W) motor stator 57 including an iron core 57a and a winding 57b is disposed in the vicinity of a part of the outer peripheral surface of each magnet rotor 54. The three-phase motor stator 57 is disposed on the side opposite to the side where the magnet rotors 54 are magnet-coupled with respect to the rotation axis. Thereby, the magnet coupling force that the magnet rotors 54 attract each other can be canceled by the attraction force acting on the magnet rotor 54 and the motor stator core 57a. By supplying a direct current having a required rectangular pulse waveform to the three-phase winding 57b, the two rotating shafts 51a and 51b can be synchronously inverted and driven at an arbitrary rotational speed.

  In the case of a positive displacement screw pump, the gas flows in the axial direction as the screw rotors 52a and 52b rotate. Therefore, as shown in FIG. 3, when the main pump 15 is installed vertically and the exhaust port 15b is disposed below the intake port 15a, the gas is sent downward, and as a reaction, both screw rotors 52a, The thrust load applied to 52b is upward. Therefore, this thrust load can be reduced by canceling between the self-weights (downward) of the screw rotors 52a and 52b. At the same time, since the thrust / radial bearing 53-1 of the rotary shafts 51a and 51b is installed on the relatively low temperature intake side where no compression heat is generated, the temperature of the thrust / radial bearing 53-1 can be prevented from being increased. Because of these synergistic effects, even if the screw rotors 52a and 52b are rotated at high speed, the thrust load applied to the thrust / radial bearing 53-1 is reduced and the high temperature due to the compression heat is also reduced. The bearing 53-1 is not damaged or deteriorated, and its reliability can be sufficiently secured. Furthermore, in this embodiment, since the ceramic ball bearing excellent in heat resistance and suitable for high speed rotation is used as the thrust radial bearing 53-1, the thrust radial bearing 53-1 is not easily damaged or deteriorated. Reliability is improved.

  On the other hand, the structure of the booster pump 16 is the same as the structure of the main pump 15 as described above, and the difference is that the booster pump 16 is installed horizontally (the rotation axes of the pair of screw rotors are substantially horizontal). Only. Therefore, unlike the main pump 15, there is no canceling effect due to the thrust load applied to both screw rotors and its own weight. As will be described below, when the vacuum vessel to which the dry vacuum pump 1 is connected reaches the ultimate vacuum, the thrust load of the booster pump 16 becomes small and the load becomes light, while the main pump 15 The load becomes a rated load operation that is close to the maximum, and a high temperature is also generated due to compression heat. From these, the main pump 15 has a considerably larger thrust load than the booster pump 16 and generates heat. For this reason, in this embodiment, the main pump 15 having a large thrust load and heat generation is installed vertically as described above, and the booster pump 16 having a relatively small thrust load and heat generation is installed horizontally. Of course, the booster pump 16 may be installed vertically.

  Further, since the main pump 15 is installed vertically and the exhaust port 15b is disposed below the intake port 15a, the exhaust port 15b is positioned at the lower end of the fluid passage 56. Therefore, the flow of water (condensed water or the like) into the casing 50 can be prevented by the action of gravity, and overload and corrosion of the main pump 15 can be prevented. Further, since the magnet rotor 54 and the motor stator 57 are located above the screw rotors 52a and 52b (above the fluid passage 56), even if water flows in from the exhaust port 15b, these components come into contact with water. There is nothing. As described above, the main pump 15 is arranged to have an angle with respect to the horizontal direction so that the exhaust port 15b is positioned below the intake port 15a. In the present embodiment, as an example, the screw rotor of the main pump 15 is provided. 52a and 52b are arranged substantially vertically.

  Next, an operation method of the vacuum pump unit 1 configured as described above will be described. First, when an operation button provided at a predetermined position of the outer case 29 is pressed to turn on the power, both the booster pump 16 and the main pump 15 are soft-started and exhausted. Eventually, the rotational speeds of the booster pump 16 and the main pump 15 reach the rotational speeds of the set steady operation, and the exhaust is continued. Since the exhaust speed of the booster pump 16 is higher than the exhaust speed of the main pump 15, the pressure in the communication path 61 increases and the load power of the booster pump 16 also increases. When the pressure in the communication path 61 becomes larger than the external air pressure around the vacuum pump unit 1, the pressure release valve 31 is opened, the pressure in the communication path 61 is released, and the load on the booster pump 16 is constant. Become.

  When the pressure in the vacuum vessel decreases, the pressure in the communication passage 61 also decreases, and the pressure release valve 31 closes. Further, the load on the booster pump 16 is also reduced. When the pressure in the vacuum vessel further decreases and the ultimate vacuum is reached, the pressure difference between the intake side and the exhaust side of the booster pump 16 is small (both the intake and exhaust sides are in a vacuum state), so the booster pump 16 is in a state close to no-load operation. become. On the other hand, in the main pump 15, since the pressure difference between the intake side and the exhaust side is large (the intake side is vacuum and the exhaust side is the external pressure), the load of the main pump 15 is close to the rated value. At this time, even when the main pump 15 is abnormally stopped, the pressure release valve 32 is momentarily closed, so that the vacuum in the vacuum vessel can be prevented from being broken. Thus, as a feature of the vacuum pump unit 1, it is possible to perform start-up and steady operation without a sensor without detecting pressure and flow rate.

  On the other hand, when the power is turned on, the operation of the cooling fan 40 is started, air is introduced from the first and second air introduction ports 29a and 23a, and the introduced air is indicated by arrows in FIGS. The electric equipment 17, the main pump 15, and the booster pump 16 that flow across the internal space of the dry vacuum pump unit 1 are cooled, and then are cooled from the air discharge port 29b of the outer case 29 through the cooling fan 40. To be discharged.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the technical idea described in the claims and the specification and drawings. Is possible. Note that any shape, structure, or material not directly described in the specification and drawings is within the scope of the technical idea of the present invention as long as the effects and advantages of the present invention are exhibited. For example, in the above-described embodiment, the thrust and radial bearings 53-1 and 53-1 are attached to the upper positions of the rotary shafts 51 a and 51 b, but the thrust bearing and the radial bearing are separately installed at the upper positions of the rotary shafts 51 a and 51 b. You may install a bearing, respectively.

1 is a schematic side view of a dry vacuum pump unit 1. FIG. 1 is a schematic diagram of a dry vacuum pump unit 1. FIG. 2 is a schematic longitudinal sectional view of a main pump 15. FIG. FIG. 4 is a cross-sectional view taken along arrow IV-IV in FIG. 3. 3 is a schematic longitudinal sectional view of a main pump 15, a booster pump 16, and a pump installation base 60. FIG.

1 Dry vacuum pump unit 15 Main pump (vacuum pump)
15a Intake port 15b Exhaust port 16 Booster pump (vacuum pump)
17 Electrical Equipment 21 Heat Dissipating Plate 29 Exterior Case 40 Cooling Fan 50 Casing 51a, 51b Rotating Shafts 52a, 52b Screw Rotor 54 Magnet Rotor 53-1 Thrust and Radial Bearing (Thrust Bearing)
53-2 Radial Bearing 56 Fluid Path 60 Pump Installation Base

Claims (3)

A main pump arranged on the outside air pressure side;
A booster pump disposed on the vacuum side and connected in series to the main pump,
At least the main pump has a screw rotor which is arranged in a pair of parallel, a casing for accommodating the pair of screw rotors, a pair of B over data that rotates integrally with the pair of screw rotors, said pair The rotary shaft of the screw rotor is vertically installed with the vertical direction thereof, the intake port provided in the casing is positioned above the exhaust port, and the thrust bearing of the rotary shaft is disposed on the intake side above the rotary shaft vacuum pump unit characterized in that installed in. The vacuum pump unit according to claim 1, wherein
  The vacuum pump unit, wherein the rotor is a magnet rotor. In vacuum pump unit according to claim 1 or 2,
The thrust bearing, vacuum pump unit you being a ceramic ball bearing.

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