JP2018028296A - Compressor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compressor capable of reducing its capacity necessary for an electromagnet of a magnetic bearing part.SOLUTION: A compressor 1 includes impellers 5a, 5b, a shaft 6, and a thrust magnetic bearing part 21 having an axial disc part 23 and a pair of electromagnets 25a, 25b for supporting the shaft 6 in the thrust direction. When one electromagnet for magnetically attracting the axial disc part 23 in a direction opposing gas thrust force generated by the rotation of the impellers is defined as a first electromagnet 25a and the other electromagnet is defined as a second electromagnet 25b, a gap Ga between the axial disc part 23 and the first electromagnet 25a during operation is set to be in a smaller state than a gap Gb between the axial disc part 23 and the second electromagnet 25b.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a compressor.

  Conventionally, a compressor described in Patent Document 1 below is known as a technique in such a field. The compressor includes a motor that rotates the rotating shaft of the impeller, and a magnetic bearing portion that supports the rotating shaft in a non-contact manner. The magnetic bearing portion includes an axial disk portion provided on the rotating shaft and a pair of electromagnets arranged with the axial disk portion sandwiched in the axial direction. In this compressor, the attraction force of the electromagnet that attracts the rotating shaft is adjusted based on the displacement detected by the displacement sensor, and the position of the rotating shaft is controlled to be constant.

JP 2014-43834 A

  In the magnetic bearing portion, the required current increases as the attractive force required for the electromagnet increases. In this case, it is necessary to increase not only the capacity of the electromagnet, but also the capacity of auxiliary devices such as an amplifier for supplying current and a power supply unit, which increases the manufacturing cost of the entire compressor. Therefore, it is desirable to reduce the current required for the electromagnet of the magnetic bearing portion as much as possible.

  An object of this invention is to provide the compressor which can reduce the required capacity | capacitance of the electromagnet of a magnetic bearing part.

  The compressor according to the present invention includes an impeller, an impeller rotation shaft, an axial disk portion provided on the rotation shaft, and an axial disk portion sandwiched in the thrust direction, and magnetically attracts the axial disk portions in opposite directions. A pair of electromagnets, and a magnetic bearing portion that supports the rotating shaft in the thrust direction, and magnetically moves the axial disk portion in a direction that opposes the gas thrust force generated by the rotation of the impeller among the pair of electromagnets. When one electromagnet to be attracted is a first electromagnet and the other electromagnet is a second electromagnet, the gap between the axial disk portion and the first electromagnet during operation is larger than the gap between the axial disk portion and the second electromagnet. It is set to be smaller.

  The compressor of the present invention includes a control unit that operates the magnetic attraction force of the first and second electromagnets so that the position of the predetermined control reference point of the rotating shaft is kept constant, and the axial disk unit has a thrust direction In this case, it may be located between the first electromagnet and the control reference point.

  ADVANTAGE OF THE INVENTION According to this invention, the capacity | capacitance required of the electromagnet of the magnetic bearing part of a compressor can be reduced.

It is sectional drawing which shows the compressor of this embodiment typically. It is a figure which shows typically the component required for position control of a shaft. (A) is a figure which shows the positional relationship of the electromagnet and axial disk part in driving | operation, (b) is a figure which shows the positional relationship of the electromagnet and axial disk part before driving | operation.

  Hereinafter, embodiments of a compressor according to the present invention will be described in detail with reference to the drawings.

  A compressor 1 shown in FIG. 1 is a two-stage compressor in series, and includes a first compressor unit 3a that compresses gas and a second compressor unit 3b that further compresses gas compressed by the first compressor unit 3a. And. The first impeller 5a of the first compressor unit 3a and the second impeller 5b of the second compressor unit 3b are connected via a shaft 6 (rotating shaft), and the first impeller 5a is provided at one end of the shaft 6, The second impeller 5 b is provided at the other end of the shaft 6. The first impeller 5a, the second impeller 5b, and the shaft 6 are integrally rotated around the rotation axis A in the housing 7 of the compressor 1.

  In the following description, the terms “axial direction”, “circumferential direction”, and “radial direction” mean the rotational axis direction of the shaft 6, the rotational circumferential direction of the shaft 6, and the rotational radial direction of the shaft 6, respectively. And In addition, in the following description, when words such as “right direction” and “left direction” are used, the first impeller 5a side is the left side and the second impeller 5b side is the right side, corresponding to the right and left in FIG. .

  The housing 7 of the compressor 1 includes a first housing 7a that houses the first impeller 5a, a second housing 7b that houses the second impeller 5b, and a space between the first housing 7a and the second housing 7b. And a shaft housing 7c. The first housing 7a is formed with a first scroll 9a surrounding the first impeller 5a in the circumferential direction. Similarly, a second scroll 9b that surrounds the second impeller 5b in the circumferential direction is formed in the second housing 7b. The shaft 6 is accommodated in the shaft housing 7c.

  A motor unit 13 that rotates the shaft 6 is provided around the shaft 6 inside the shaft housing 7c. The motor unit 13 includes a rotor 13r fixed to the shaft 6 and a stator 13s fixed to the shaft housing 7c. When current is supplied to the motor coil of the stator 13s, the rotor 13r and the shaft 6 rotate, and the first impeller 5a and the second impeller 5b rotate. Thus, the compressor 1 is a direct drive type compressor in which the rotational force of the motor unit 13 is directly transmitted to the first impeller 5a and the second impeller 5b.

  The gas flowing in the axial direction from the intake port 15a of the first housing 7a is accelerated in the radial direction by the rotating first impeller 5a, and then decelerated and boosted by the first scroll 9a. The gas delivered from the first scroll 9a is introduced in the axial direction from the intake port 15b of the second housing 7b via a connection pipe (not shown). A cooler for cooling the gas may be provided in the middle of the connection pipe. The gas introduced from the intake port 15b is accelerated in the radial direction by the rotating second impeller 5b, decelerated and boosted by the second scroll 9b. Thus, the compressor 1 compresses gas in two stages by the first compressor unit 3a including the first impeller 5a and the second compressor unit 3b including the second impeller 5b.

  Inside the shaft housing 7c, two radial magnetic bearing portions 19a and 19b that support the shaft 6 in the radial direction and one thrust magnetic bearing portion 21 that supports the shaft 6 in the axial direction are provided. The radial magnetic bearing portions 19a and 19b are disposed on the first impeller 5a side and the second impeller 5b side with the motor portion 13 interposed therebetween. The radial magnetic bearing portions 19a and 19b regulate the position of the shaft 6 in the radial direction by a magnetic attractive force in the radial direction, and support the shaft 6 in the radial direction without contact.

  The thrust magnetic bearing portion 21 is disposed between the motor portion 13 and the radial magnetic bearing portion 19a in the axial direction. The thrust magnetic bearing portion 21 includes a disk-shaped axial disk portion 23 provided in a bowl shape so as to project from the shaft 6 in the radial direction, a pair of electromagnets 25a and 25b sandwiching the axial disk portion 23 in the axial direction, It has. The electromagnet 25a (first electromagnet) attracts the axial disk portion 23 toward the first compressor portion 3a by magnetic force. The electromagnet 25b (second electromagnet) attracts the axial disk portion 23 to the second compressor portion 3b side by magnetic force. The axial force of the axial disk portion 23 and the shaft 6 is maintained by controlling the attractive force by the electromagnet 25a and the attractive force by the electromagnet 25b. Supported in the direction.

  Further, in the shaft housing 7c, a touchdown bearing 29a is provided between the radial magnetic bearing portion 19a and the first impeller 5a, and between the radial magnetic bearing portion 19b and the second impeller 5b, A touchdown bearing 29b is provided. The touchdown bearings 29a and 29b are normally not in contact with the shaft 6 and function as a bearing for the emergency shaft 6 when a failure occurs in the radial magnetic bearing portions 19a and 19b. Ball bearings or the like are employed as the touchdown bearings 29a and 29b.

Next, the axial position control of the shaft 6 by the control device 37 (control unit) and the thrust magnetic bearing unit 21 will be described in more detail with reference to FIGS. FIG. 2 is a diagram schematically showing components related to this position control, and FIG. 3 is a diagram showing the positional relationship between the electromagnets 25a and 25b and the axial disk portion 23. As shown in FIG. Moreover, the meaning of each code | symbol shown by FIG. 2 is as follows.
Qa: leftward magnetic attractive force generated by the electromagnet 25a with respect to the axial disk portion 23 Qb: rightward magnetic attractive force generated by the electromagnet 25b with respect to the axial disk portion 23 Ga: gap between the electromagnet 25a and the axial disk portion 23 (gap)
Gb: Gap (gap) between the electromagnet 25b and the axial disk portion 23
Ia: Drive current supplied from the control device 37 to the electromagnet 25a Ib: Drive current supplied from the control device 37 to the electromagnet 25b Note that the electromagnets 25a and 25b are, for example, a coil 25h and a core as shown in FIG. 25j. In this case, strictly speaking, as shown in FIG. 3, the distances between the front end surface of the core 25j and the surface of the axial disk portion 23 correspond to the gaps Ga and Gb.

  In order to control the position of the shaft 6 in the axial direction, the compressor 1 includes displacement sensors 33a and 33b. The displacement sensor 33 a is disposed on the left side of the motor unit 13, and the displacement sensor 33 b is disposed on the right side of the motor unit 13. The displacement sensors 33 a and 33 b detect the axial displacement of the shaft 6. For example, as the displacement sensors 33a and 33b, a sensor that detects the positions of the sensor targets 36a and 36b provided on the outer peripheral surface of the shaft 6 in a non-contact manner may be used.

  The control device 37 acquires a displacement signal indicating the axial displacement of the sensor target 36a from the displacement sensor 33a, and acquires a displacement signal indicating the axial displacement of the sensor target 36b from the displacement sensor 33b. Moreover, the control apparatus 37 can operate the magnetic attraction force of the electromagnets 25a and 25b by operating the supply current to the electromagnets 25a and 25b.

  The control device 37 calculates the axial displacement of the predetermined control reference point 41 set on the shaft 6 by a predetermined calculation based on the displacement signals acquired from the two displacement sensors 33a and 33b. For example, when the control reference point 41 is set at the midpoint between the sensor target 36a and the sensor target 36b, the control device 37 averages the displacement of the sensor target 36a and the displacement of the sensor target 36b to control the control reference point. The axial displacement of the point 41 can be calculated. Based on the obtained displacement of the control reference point 41, the control device 37 operates the current supplied to the electromagnets 25a and 25b so that the displacement of the control reference point 41 becomes zero. That is, during the operation of the compressor 1, feedback control is performed such that the axial position of the control reference point 41 is kept constant with respect to the housing 7. The control reference point 41 on the shaft 6 becomes a stationary point in the axial direction with respect to the housing 7 during operation.

  The control reference point 41 is a virtual point that can be set at an arbitrary position on the shaft 6 in a position control program for executing the position control of the shaft 6. For example, the control device 37 calculates the axial displacement of the control reference point 41 set at an arbitrary position by a weighted average that gives a predetermined weight to each of the displacement of the sensor target 36a and the displacement of the sensor target 36b. can do.

  Here, the gas thrust force generated in the shaft 6 by the rotation of the impellers 5a and 5b will be described. The rotating impeller 5a sucks gas rightward in the axial direction and accelerates radially outward. Due to the reaction from the gas, the impeller 5a receives a leftward thrust force Fa. By the same principle, the impeller 5b receives a rightward thrust force Fb. The resultant force of the thrust force Fa and the thrust force Fb acts on the shaft 6 as the gas thrust force F. For example, in the case of the compressor 1, the gas pressure ratio by the second compressor unit 3b is higher than the gas pressure ratio by the first compressor unit 3a, and Fb> Fa. Therefore, in this case, in the compressor 1, the gas thrust force F acting on the shaft 6 is rightward.

  In order to balance with the rightward gas thrust force F, in the thrust magnetic bearing portion 21, the relationship between the magnetic attractive force Qa of the electromagnet 25a and the magnetic attractive force Qb of the electromagnet 25b needs to satisfy Qa> Qb. is there. That is, the magnetic attractive force Qa of the electromagnet 25a that magnetically attracts the axial disk portion 23 in the direction opposite to the gas thrust force F needs to be larger than the magnetic attractive force Qb of the other electromagnet 25b.

  Here, the magnetic attractive force generated by the electromagnet with respect to the object is inversely proportional to the square of the gap between the electromagnet and the object. Based on this knowledge, as shown in FIG. 3A, the compressor 1 is set so that the gap Ga is smaller than the gap Gb during operation (for example, during rated operation). That is, during operation, the axial disk portion 23 rotates at a position closer to the electromagnet 25a than the electromagnet 25b.

  Specifically, when the control reference point 41 of the shaft 6 during operation is zero displacement, the control reference point is such that the axial disk portion 23 is disposed at a position closer to the electromagnet 25a than the electromagnet 25b. 41, the positional relationship between the displacement sensors 33a and 33b, the electromagnets 25a and 25b, and the axial disk portion 23 is set. During operation, the impellers 5a and 5b and the shaft 6 are heated and thermally expanded due to windage loss during rotation. Therefore, in order to set the above positional relationship, the shaft 6 extends in the axial direction due to thermal expansion. Also included in consideration. Of course, the axial disk portion 23 is set so as not to contact the electromagnet 25a when the shaft 6 is thermally expanded. As shown in FIG. 3B, the gap Ga and the gap Gb may be equal before the operation (when the shaft 6 is not rotating).

  A description will be given of the operational effects due to the gap Ga becoming smaller than the gap Gb during operation. Compared with the operation in which the gap Ga and the gap Gb are made equal, the gap Ga is reduced, whereby the current Ia necessary for the electromagnet 25a to generate the magnetic attractive force Qa can be reduced. On the other hand, since the magnetic attractive force Qb to be generated by the electromagnet 25b is originally relatively small, the increase in the current Ib required due to the increase in the gap Gb is also relatively small. Further, when the gap Ga is smaller than the gap Gb, the sum of the current Ia and the current Ib can be made smaller than when the gap Ga and the gap Gb are equal.

  As described above, according to the configuration in which the gap Ga is smaller than the gap Gb during operation, neither the current Ia nor the current Ib needs to be extremely large, and therefore the current capacity of the electromagnets 25a and 25b is extremely large. There is no need to make it bigger. Therefore, it is possible to reduce the capacity of the amplifier and the power supply unit for supplying current to the electromagnets 25a and 25b. As a result, the manufacturing cost of the compressor 1 can be reduced. Further, as described above, since neither the current Ia nor the current Ib needs to be extremely increased, the power consumption and running cost of the thrust magnetic bearing portion 21 and the compressor 1 are also reduced.

  In the compressor 1, as shown in FIG. 2, there is a positional relationship in which the axial disk portion 23 is positioned between the electromagnet 25 a and the control reference point 41 in the axial direction. The effect obtained by such a positional relationship will be described.

  When the shaft 6 is thermally expanded during operation, the shaft 6 extends left and right around the control reference point 41 that is stationary with respect to the housing 7. And the axial disk part 23 moves to the direction (left direction) which leaves | separates from the control reference point 41, and approaches the electromagnet 25a resulting from the said thermal expansion. That is, the axial disk portion 23 during operation moves to a position closer to the electromagnet 25a as compared to before operation (when no thermal expansion occurs). Accordingly, it is possible to automatically set a phenomenon such that the gap Ga is equal to the gap Gb before the operation and the gap Ga becomes smaller than the gap Gb during the operation using the thermal expansion of the shaft 6. become.

  Although one embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and may be modified without changing the gist described in each claim. You may use combining the structure of each embodiment suitably. For example, in the embodiment, the present invention is applied to a two-stage compressor, but the present invention can also be applied to a one-stage compressor or a multistage compressor having three or more stages. In addition, the axial disk portion 23 is not limited to a disc shape, and may be any shape that can receive an attractive force of an axial component from the electromagnets 25a and 25b.

1 Compressor 5a, 5b Impeller 6 Shaft (Rotating shaft)
21 Thrust magnetic bearing part 23 Axial disk part 25a Electromagnet (first electromagnet)
25b Electromagnet (second electromagnet)
37 Control device (control unit)
41 Control reference point Ga, Gb Gap F Gas thrust force

Claims (2)

Impeller,
A rotating shaft of the impeller;
An axial disk portion provided on the rotating shaft, and a pair of electromagnets arranged so as to sandwich the axial disk portion in a thrust direction and magnetically attract the axial disk portions in directions opposite to each other. A magnetic bearing portion that supports the thrust direction,
Of the pair of electromagnets, when one electromagnet that magnetically attracts the axial disk portion in a direction opposite to the gas thrust force generated by the rotation of the impeller is a first electromagnet and the other electromagnet is a second electromagnet ,
A compressor, wherein a gap between the axial disk portion and the first electromagnet during operation is set to be smaller than a gap between the axial disk portion and the second electromagnet. A controller for operating the magnetic attraction force of the first and second electromagnets so as to keep the position of the predetermined control reference point of the rotating shaft constant;
The compressor according to claim 1, wherein the axial disk portion is located between the first electromagnet and the control reference point in the thrust direction.

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