JP2015220905A - Pump including electric motor and control method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pump including an electric motor that improves motor efficiency at a time of a light load without reducing motor efficiency at a time of a high load.SOLUTION: A pump 1 includes a pump rotor 13 mounted to two main shafts 15A, 15B. An electric motor 31A for a high load is mounted to one end of the first main shaft 15A. An electric motor 31B for a light load is mounted to the other end part of the first main shaft 15A or the other end part of the second main shaft 15B.

Description

  The present invention relates to a pump, and more particularly, to a pump including two electric motors and a control method thereof.

  In the semiconductor manufacturing process, various types of pumps and electric motors for driving the pumps are used. For example, a vacuum technique is required in various processes, and a vacuum pump is used accordingly. Some examples include vacuum deposition methods for metal thin film formation, plasma etching methods for resist removal and etching processes, ion implantation methods for impurity diffusion processes, silicon oxide film and nitride film formation processes. For example, low pressure CVD or plasma CVD. All of these semiconductor manufacturing processes are performed in a vacuum (or reduced pressure) environment, and the role played by vacuum in the semiconductor manufacturing process is very large.

  As a vacuum pump used in a semiconductor manufacturing apparatus or the like, there is a biaxial synchronous multi-stage root type positive displacement vacuum pump 500 as shown in FIG. 4 (see Patent Document 1). What is shown in this figure is a four-stage vacuum pump 500. That is, a total of eight pump rotors 512 and 522 are provided. The pump rotor rotating shafts 514 and 524 of the vacuum pump 500 are rotated at the same speed in opposite directions by a pair of timing gears 511 and 521. The pump rotors 512 and 522 facing each other, and the pump rotors 512 and 522 and the casing 501 do not contact each other, rotate while maintaining a slight gap, and suck in and discharge the gas to the outside.

  In FIG. 4, electric motors 601 and 602 are installed at the right end. In the electric motors 601 and 602, motor rotors 601a and 602a are attached to pump rotor rotating shafts 514 and 524, and motor stators 601b and 602b are installed around a radial gap around the motor rotors 601a and 602a. Yes. Further, coils for generating magnetic flux from the core are wound around the motor stators 601b and 602b.

  Incidentally, the load applied to the electric motors 601 and 602 varies greatly depending on the operating state of the vacuum pump 500. For example, the load applied to the electric motors 601 and 602 is large when the gas is flowing, at the start-up operation, or when the process gas is discharged. In the case of a general motor, the configuration of the electric motor is designed so that the motor efficiency at the maximum load is the best. In other words, the motor rotor and the motor stator are designed so as to correspond to the electric power required at the maximum load. On the other hand, when the vacuum pump 500 is operated for a predetermined time and the pressure becomes below a certain level, the load applied to the electric motors 601 and 602 decreases. For example, it becomes a light load at the time of reaching operation. The power required for light loads is naturally smaller than the power required for maximum loads.

  In the example shown in FIG. 4 described so far, one motor is a permanent magnet synchronous motor and the other motor is an induction motor. And the electric motor which drives with respect to the change of a driving | running state is switched suitably. In addition, in the present invention, the electric motors 601 and 602 are connected to one end portions of the two pump rotor rotating shafts 514 and 524 so as to be adjacent to each other.

JP 2013-198307 A

  In the invention in which the two motors 601 and 602 are arranged adjacent to each other, the size of the motor is limited so that the high-load electric motor and the light-load electric motor 601 and 601 do not physically interfere with each other. . In particular, an electric motor for high load is often large, and a motor with a large output capacity cannot be freely selected due to the presence of an electric motor for light load. In order to avoid such an inconvenience, it is also conceivable to extend one of the pump rotor rotating shafts 514 and 524 so that the two electric motors 601 and 602 are shifted from each other in the axial direction.

  The present invention has been made in view of the above problems, and it is a problem to be solved by the present invention to provide a pump including an efficient electric motor without sacrificing the degree of freedom of design. is there. In order to solve the problem, the first means is a pump in which a pump rotor is mounted on two main shafts, and an electric motor for high load is connected to one end of the first main shaft, and is used for light loads. The electric motor is connected to the other end of the first main shaft or the other end of the second main shaft.

  By adopting the configuration as described above, when the pump is operated in a high load state, both the high load electric motor and the light load electric motor generate driving force ( 2-axis operation). At this time, since the electric motors are not arranged adjacent to each other, the high-load electric motor and the light-load electric motor do not physically interfere with each other. In addition, when operating in a light load state, the high load electric motor is stopped (the rotor is rotating without being energized), and the pump is driven only by the light load electric motor. Since the permanent magnet is not used in the high load electric motor, the iron loss of the high load electric motor can be reduced when the motor is stopped.

  In addition to the configuration of the first means, the second means adopts a configuration in which at least one of the electric motors is an induction motor and further includes an inverter circuit that adjusts the power supplied to the electric motor. .

  In addition to the configuration of the first means, the third means adopts a configuration in which at least one of the electric motors is an SR motor and further includes an inverter circuit that adjusts the power supplied to the electric motor. .

  The fourth means adopts a configuration in which one electric motor is a PM motor and the other electric motor is an SR motor or an induction motor in addition to the structure of the second means or the third means.

  5. The fifth means according to any one of claims 1 to 4, wherein the high load electric motor is an induction motor or SR motor that does not use a permanent magnet, in addition to any of the first to fourth means. The pump described in.

  The sixth means has a configuration in which the rated output of the high load electric motor with respect to the rated output of the light load electric motor is twice or more in addition to any of the configurations of the first means to the fifth means. Adopted.

In the seventh means, in addition to the configuration of any one of the first means to the sixth means, the rated output of the electric motor for light load corresponds to the load at the time of pump ultimate pressure operation, and The rated output of the electric motor is adapted to correspond to the load at the time of pump maximum load operation. That is, the output ratio of the light motor for the light load and the electric motor for the high load is a ratio of the generated power at the time of pump ultimate pressure operation and the generated power at the maximum pump load. For this reason, at the time of light load, the pump is driven only by the light motor for light load which becomes the highest efficiency point when generating the power necessary for the pump ultimate pressure operation. Further, at the time of high load, the high load electric motor that is the highest efficiency point when the power necessary for the pump maximum load operation is generated is also driven. Thereby, the pump can be driven with high efficiency from a light load to a high load.

  The eighth means adopts a configuration in which the electric motor includes a can for maintaining the airtight state of the space in which the motor rotor is provided, in addition to any one of the first to seventh means. .

  The ninth means further includes a control unit in addition to the configuration of any one of the first means to the eighth means, and the control unit is provided for the high load electric motor when the load applied to the electric motor is lower than a predetermined value. It is configured to stop driving.

  The tenth means is a method of controlling the operation of a pump having a pump rotor mounted on two main shafts. The pump has a high load electric motor connected to one end of the first main shaft and is used for a light load. The electric motor is connected to the other end of the first main shaft or the other end of the second main shaft, and when the load of the electric motor is detected and the detected load falls below a predetermined value, The configuration is such that the electric motor is stopped.

  In the eleventh means, in addition to the configuration of the tenth means, a threshold value of the load applied to the electric motor is set in order to switch the start and stop of the electric motor for high load. The configuration is such that the values are different depending on whether the motor is started or stopped.

It is sectional drawing along the main axis | shaft of the vacuum pump which concerns on one Embodiment of this invention. FIG. 2 (A) is a block diagram of a pump system including a vacuum pump, and FIG. 2 (B) is a diagram for explaining the vacuum pump disclosed in FIG. 1, and FIG. 2 (B) shows the relationship between motor load and operation switching. FIG. It is sectional drawing along the main axis | shaft of the vacuum pump which concerns on the 2nd Embodiment of this invention. It is sectional drawing along the main axis | shaft of the vacuum pump provided with the conventional electric motor.

  Hereinafter, an electric motor and a pump according to an embodiment of the present invention will be described with reference to the accompanying drawings. Hereinafter, a canned motor and a vacuum pump in which the rotor chamber and the stator chamber are separated will be described as specific examples. However, the present invention can also be applied to a motor, a compression pump, or the like in which the rotor chamber and the stator chamber are the same space. Note that an invention in which individual components described below are arbitrarily combined is also included in the technical concept of the present invention.

[Overview]
FIG. 1 shows a vacuum pump 1 including canned motors 31A and 31B according to this embodiment. The vacuum pump 1 includes a vacuum pump main body 11, a canned motor 31 A attached to one end of the vacuum pump main body 11, and a canned motor 31 B attached to the other end of the vacuum pump main body 11. The canned motors 31A and 31B are radial gap motors, and include a motor rotor 41, a stator 51, and a cylindrical can 61 that is disposed between the motor rotor 41 and the stator 51 and maintains a vacuum in a space where the motor rotor 41 exists. I have.

[Vacuum pump body]
The vacuum pump body 11 includes main shafts 15A and 15B to which a plurality of pump rotors 13 are attached, a main casing 17 that houses the pump rotor 13, and a first end casing 19 that is attached to one end face of the main casing 17. And a second end casing 21 attached to the other end face of the main casing 17. Such a vacuum pump 1 is called a biaxial synchronous multistage roots positive displacement pump.

[Spindle]
The main shafts 15A and 15B extend along the axial direction of the vacuum pump main body 11, and are rotatably supported by bearings 19a and 21a of the first and second end casings 19 and 21 at both ends thereof. . Five pump rotors 13 are attached to the two main shafts 15A and 15B of the present embodiment to form a five-stage vacuum pump body 11. For this reason, a total of ten pump rotors 13 are provided. However, the number of stages is merely an example, and a vacuum pump body having a number of stages other than five may be used.

[Main casing]
The main casing 17 has a pump chamber corresponding to each pump rotor 13, and further includes a gas discharge path 23 radially outward with a predetermined partition wall therebetween. Further, the pump chambers of the respective stages are separated from each other by a predetermined partition wall. The pump chamber of each stage is configured such that the width becomes narrower from the upstream side (left side in the figure) to the downstream side (right side in the figure). The main casing 17 is provided with a gas inlet (not shown) for taking gas into the most upstream pump chamber 23a, and has a gas outlet (not shown) for discharging gas from the most downstream pump chamber 23b. Is provided. The gas inlet is connected to a semiconductor manufacturing apparatus or the like that requires a vacuum state. On the other hand, the gas discharge port is connected to a predetermined exhaust gas processing device (not shown). The reason why the gas exhaust port is connected to the exhaust gas processing device is that the gas discharged by the vacuum pump 1 may contain corrosive gas, and it is necessary to appropriately detoxify the gas. is there. However, if the exhausted gas is harmless, it is not necessary to connect an exhaust gas processing device to the gas exhaust port.

[First end casing]
The first end casing 19 is attached to one end of the main casing 17. A stepped through hole is formed at the center of the first end casing 19. Among these, the main shafts 15A and 15B pass through the through hole having a small diameter, and two bearings 19a are provided in the through hole having a large diameter. The main shaft 15A. The one end side of 15B is rotatably supported. However, the number of bearings is an example, and may be one or three or more. In the present embodiment, the main casing 17 and the first end casing 19 are formed separately, but the present invention is not limited to this. That is, the main casing 17 and the first end casing 19 may be integrally formed.

[Timing gear]
Timing gears 42A and 42B attached to the main shafts 15A and 15B are provided outside the first end casing (on the right side in FIG. 1). The timing gears 42A and 42B mesh with each other at the outer peripheral portion. For this reason, when one main shaft 15A rotates, the other main shaft 15B also rotates in the reverse direction at the same rotational speed. The timing gears 42 </ b> A and 42 </ b> B are surrounded by a timing gear cover 45, and the timing gear cover 45 is fixed to the first end casing 19.

[Second end casing]
The second end casing 21 is attached to the other end of the main casing 17. A stepped through hole is also formed at the center of the second end casing 21. Among these, the main shafts 15A and 15B pass through the small diameter through hole, and one bearing 21a is provided in the large diameter through hole. The bearings 21a rotatably support the main shafts 15A and 15B on the other end side. In the present embodiment, the main casing 17 and the second end casing 21 are formed separately, but the present invention is not limited to this. That is, the main casing 17 and the second end casing 21 may be integrally formed.

  A casing cover 29 is attached to the outside (left side in FIG. 1) of the second end casing 21. The casing cover 29 forms a predetermined space between the second end casing 21 and covers the bearing. Lubricating oil is stored in the lower part of the space formed by the casing cover 29 and the timing gear cover 45 so that the bearings 19a and 21a and the gears 42A and 42B can be lubricated. However, when using a bearing filled with grease, lubricating oil is not essential. The casing cover 29 and the timing gear cover 45 are not essential components in the present invention.

[Canned motor]
Next, the canned motors 31 </ b> A and 31 </ b> B that are one of the characteristic parts of the present embodiment will be described. For convenience of explanation, first, a canned motor 31A connected to one end (right end) of the main shaft 15A will be described. Here, the canned motor 31A is a radial gap type motor. The motor rotor 41 of the canned motor 31A is attached around one end of the main shaft 15A. In addition, the stator 51 is disposed so as to surround the motor rotor 41 outside the motor rotor 41 in the radial direction. That is, the motor rotor 41 and the stator 51 are arranged in the radial direction (radial direction), and a gap is formed between the motor rotor 41 and the stator 51.

  The stator 51 includes a stator core 51a and a coil 51b. The periphery of the stator 51 is surrounded by a stator casing 55. Further, one end side (right side in the figure) of the stator casing 55 is a closed end. For this reason, the stator casing 55 has, for example, a dish shape, and the interior of the stator casing 55 is a stator chamber 53. The other end side (left side in the figure) of the stator casing 55 is an open end, but is in contact with the flange portion of the cylindrical can 61.

  A cylindrical can 61 is provided between the motor rotor 41 and the stator 51. One end surface (right end surface) of the can 61 is a closed end, and the other end surface is an open end. A predetermined flange is formed around the open end, and is fixed between the timing gear casing 45 and the stator casing 55 via the flange. Thus, since the can 61 is provided, the airtightness of the rotor chamber 43 is maintained. At this time, since the rotor chamber 43 communicates with the pump chamber (reference numeral 23b in FIG. 1) of the vacuum pump body 11, the motor rotor 41 is exposed to corrosive gas. However, the stator 51 is isolated from the corrosive gas by the sealing function of the can 61. Further, the can 61 is made of a thin metal material or a resin material so as not to affect the magnetic flux generated between the motor rotor 41 and the stator 51 as much as possible. Further, when considering the efficiency of the motor, it is desired to make the motor rotor 41 and the stator 51 as close as possible. For this reason, when a desired strength can be ensured, it is desirable to make it as thin as possible.

As described above, the canned motor 31A is attached to one end (right end) of one of the main shafts 15A. In the present embodiment, the canned motor 31B is also disposed to the other end (left end) of the main shaft 15A. It is attached. The canned motor 31B basically has the same structure as the canned motor 31A. However, the canned motor 31A at one end is a high load motor, whereas the canned motor 31B at the other end is a light load motor. That is, the canned motor 31A is designed to minimize the iron loss during high load operation, and the canned motor 31B is designed to minimize the iron loss during light load operation.

[Operation]
Next, operations of the canned motors 31A and 31B and the vacuum pump 1 according to the present embodiment will be described with reference to FIG. First, FIG. 2 (A) is a block diagram showing a pump system including the vacuum pump main body 11 and the canned motors 31A and 31B according to the embodiment. As shown in FIG. 2A, this pump system controls the operation of the above-described vacuum pump body 11, the canned motors 31A and 31B connected to the vacuum pump body 11, and the canned motors 31A and 31B. And a control unit 62. An inverter circuit 63 connected to an AC power source is provided between the control unit 62 and the canned motors 31A and 31B. The loads of the canned motors 31 </ b> A and 31 </ b> B are transmitted to the control unit 62 through the inverter circuit 63. Of course, the loads of the canned motors 31 </ b> A and 31 </ b> B may be directly transmitted to the control unit 62 without passing through the inverter circuit 63. In the case of two-axis operation, even if there are no timing gears 42A and 42B, a drive current is supplied from the inverter circuit so that the canned motors 31A and 31B rotate at the same speed.

  FIG. 2B is a graph showing the relationship between the load applied to the canned motor 31B and the operation switching control. The vertical axis represents the load applied to the canned motors 31A and 31B, and the horizontal axis represents time. Here, the load applied to the canned motors 31A and 31B does not mean a load applied to the individual canned motors 31A and 31B but a load generated by the vacuum pump main body 11. And the diagram in a graph has shown the fluctuation | variation of the load added to canned motor 31A, 31B. The graph is divided into a 2-axis operation region and a 1-axis operation region. Here, the biaxial operation is an operation state in which the high load and light load canned motors 31A and 31B generate driving force at the same time, and the single axis operation means only the light load canned motor 31B. Is an operating state in which a driving force is generated.

  Further, as shown in FIG. 2B, a load threshold for switching the operation state is provided. In the present embodiment, two threshold values are provided, and the lower threshold value is a trigger when the load decreases and shifts from the two-axis operation to the one-axis operation. On the other hand, the upper threshold value is a trigger when the load increases to shift from the 1-axis operation to the 2-axis operation.

  In FIG. 2B, the canned motors 31A and 31B are operated biaxially from time 0 to time T1. That is, both of the canned motors 31A and 31B generate driving force. The load decreases linearly from time T1 to time T3. Then, at time T2 before time T3, the load becomes smaller than the lower threshold value. This is detected by the control unit 62 and the power supply to the high load canned motor 31A is stopped. For this reason, the vacuum pump body 11 is driven only by the light load canned motor 31B.

  Next, the load is light and constant from time T3 to time T4. For this reason, the uniaxial operation is continued. The load increases from time T4 to time T6. At this time, the load exceeds the upper threshold value at time T5 before time T6. For this reason, the control unit 62 determines that the operation has shifted to the high load operation, supplies power to the high load canned motor 31A, and resumes the two-axis operation. After time T6, the load is constant at a high load, and the biaxial operation is maintained.

FIG. 3 is a diagram showing a vacuum pump 1B according to the second embodiment. In this figure, the vacuum pump body 11 is the same as that disclosed in FIG. On the other hand, a different point is that an electric motor 31B for light load is connected to the other end of the second main shaft 15B. That is, the light load electric motor 31B does not directly apply the driving force to the first main shaft 15A, but the driving force is applied from the second main shaft 15B to the first main shaft 15A via the timing gears 42B and 42A. It is transmitted to the main shaft 15A. For this reason, it will operate | move similarly to the vacuum pump 1 disclosed in FIG.

  The present invention can be used for an electric motor used for a pump.

1, 1B Vacuum pump 11 Vacuum pump body 13 Pump rotor 15A, 15B Main shaft 17 Main casing 19 First end casing 19a Bearing 21 Second end casing 21a Bearing 23 Pump chamber 29 Casing cover 31A, 31B Canned motor 41 Motor rotor 42A, 42B Timing gear 43 Rotor chamber 51 Stator 51a Stator core 51b Coil 53 Stator chamber 55 Stator casing 61 Can 62 Controller 63 Inverter circuit

Claims (11)

  A pump in which a pump rotor is mounted on two main shafts, wherein an electric motor for high load is connected to one end of the first main shaft, and an electric motor for light load is connected to the other end of the first main shaft or the first main shaft. A pump connected to the other end of the two main shafts.   The pump according to claim 1, wherein at least one of the electric motors is an induction motor, and further includes an inverter circuit that adjusts electric power supplied to the electric motor.   The pump according to claim 1, wherein at least one of the electric motors is an SR motor, and further includes an inverter circuit that adjusts electric power supplied to the electric motor.   4. The pump according to claim 2, wherein one electric motor is a PM motor and the other electric motor is an SR motor or an induction motor.   The pump according to any one of claims 1 to 4, wherein the high-load electric motor is an induction motor or SR motor that does not use a permanent magnet.   The pump according to any one of claims 1 to 5, wherein a rated output of the high-load electric motor with respect to a rated output of the light-load electric motor is twice or more.   The rated output of the electric motor for light load corresponds to the load at the time of pump ultimate pressure operation, and the rated output of the electric motor for high load corresponds to the load at the time of pump maximum load operation, The pump according to any one of claims 1 to 6.   The said electric motor is an electric motor as described in any one of Claim 1 to 7 provided with the can for maintaining the airtight state of the space in which the motor rotor was provided.   The control unit according to claim 1, further comprising a control unit, wherein the control unit stops the operation of the high load electric motor when a load applied to the electric motor is lower than a predetermined value. pump. A method of controlling the operation of a pump having a pump rotor mounted on two main shafts, wherein the pump has a high-load electric motor connected to one end of the first main shaft, and a light-load electric motor Connected to the other end of the first main shaft or the second main shaft,
A method of detecting a load of the electric motor, and stopping the electric motor for high load when the detected load falls below a predetermined value.   In order to switch between starting and stopping of the high load electric motor, a threshold value of a load applied to the electric motor is set, and this threshold value is set when the high load electric motor is started and when stopped. The method of claim 10, wherein the values are different.

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