JP2008082425A - Magnetic bearing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic bearing device capable of improving durability of a rolling bearing against a load of a thrust load and accurately controlling a magnetic bearing. <P>SOLUTION: This magnetic bearing device uses both rolling bearings 15, 16 and the magnetic bearing. The rolling bearings 15, 16 support a radial load, and the magnetic bearing supports either or both of an axial load and a bearing preload. An electromagnet 17 constituting the magnetic bearing is controlled by a controller 19 according to an output from a force detecting sensor unit 18 for detecting the force of a main shaft 13 in the axial direction. The force detection sensor unit 18 comprises: a pair of ring-shaped sensor targets 31, 32 sandwiching both end faces of an outer ring 16b of the rolling bearing 16; a pair of plate springs 33, 34 supporting each of the sensor targets 31, 32; and a gap sensor 35 for detecting a gap with respect to the sensor targets 31, 32. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a magnetic bearing device used in an air cycle refrigeration cooling turbine unit or the like, and in particular, a rolling bearing and a magnetic bearing are used together so that the magnetic bearing supports one or both of an axial load and a bearing preload. The present invention relates to a magnetic bearing device.

  The use of air as the refrigerant in the refrigeration cooling system is preferable in terms of environmental protection and safety compared to the case of using chlorofluorocarbon or ammonia gas, but is insufficient in terms of characteristics as energy efficiency. However, when used in a facility that can directly blow in air as a refrigerant, such as in a freezer warehouse, the total cost can be reduced to the same level as existing systems by taking measures such as omitting the internal fan and defrost. there is a possibility. At present, the use of chlorofluorocarbon as a refrigerant is already restricted from the environmental viewpoint, and it is desired to avoid using other refrigerant gas as much as possible. Therefore, an air cycle refrigeration cooling system that uses air as a refrigerant has been proposed for the above-described applications (for example, Patent Document 1 and Non-Patent Document 1).

Further, it is stated that the theoretical efficiency of air cooling is equal to or higher than that of chlorofluorocarbon or ammonia gas in a deep coal region of −30 ° C. to −60 ° C. (Non-patent Document 1). However, it is also stated that obtaining the theoretical efficiency of the air cooling is not possible until there is an optimally designed peripheral device. The peripheral device is a compressor, an expansion turbine, or the like.
As the compressor and the expansion turbine, a turbine unit in which a compressor impeller and an expansion turbine impeller are attached to a common main shaft is used (Patent Document 1, Non-Patent Document 1).

In addition, as a turbine compressor which processes a process gas, a turbine impeller is attached to one end of a main shaft, a compressor impeller is attached to the other end, and the main shaft is supported by a journal and a thrust bearing that are controlled by an electromagnet current. A compressor has been proposed (Patent Document 2).
In addition, although it is a proposal for a gas turbine engine, in order to avoid the thrust load acting on the rolling bearing for supporting the main shaft from shortening the bearing life, the thrust load acting on the rolling bearing should be reduced by the thrust magnetic bearing. Has been proposed (Patent Document 3).
Japanese Patent No. 2623202 Japanese Patent Application Laid-Open No. 7-91760 JP-A-8-261237 Magazine, Nikkei Mechanical, “Cooling the Air with Air”, published November 13, 1995, no 467, pp. 46-52

As described above, as the air cycle refrigeration cooling system, in order to obtain the theoretical efficiency of air cooling that is highly efficient in the deep coal region, an optimally designed compressor and expansion turbine are required.
As the compressor and the expansion turbine, a turbine unit in which the compressor wheel and the expansion turbine wheel are attached to a common main shaft as described above is used. In this turbine unit, the compressor impeller can be driven by the power generated by the expansion turbine, thereby improving the efficiency of the air cycle refrigerator.

However, in order to obtain practical efficiency, it is necessary to keep the gap between each impeller and the housing minute. The fluctuation of the gap hinders stable high-speed rotation and causes a decrease in efficiency.
In addition, a thrust force acts on the main shaft by the air acting on the compressor impeller and the turbine impeller, and a thrust load is applied to the bearing that supports the main shaft. The rotation speed of the main shaft of the turbine unit in the air cycle refrigeration cooling system is 80,000 to 100,000 rotations per minute, which is very high compared with a bearing for general use. For this reason, the thrust load as described above causes a decrease in long-term durability and life of the bearing supporting the main shaft, and decreases the reliability of the turbine unit for air cycle refrigeration cooling. Unless such a problem of long-term durability of the bearing is solved, it is difficult to put the air cycle refrigeration cooling turbine unit into practical use. However, the techniques disclosed in Patent Document 1 and Non-Patent Document 2 have not yet been solved for the deterioration of the long-term durability of the bearing against the load of the thrust load under high-speed rotation.

  In the case where the main shaft is supported by a journal bearing and a thrust bearing made of a magnetic bearing, such as the magnetic bearing type turbine compressor of Patent Document 2, the journal bearing does not have a restriction function in the axial direction. Therefore, if there is an unstable factor in controlling the thrust bearing, it is difficult to perform stable high-speed rotation while maintaining a minute gap between the impeller and the diffuser. In the case of a magnetic bearing, there is also a problem of contact when the power is stopped.

  Accordingly, the inventors of the present invention have developed a magnetic bearing device as shown in FIG. 8 in order to solve the above problems. This magnetic bearing device is a turbine unit for air cycle refrigeration cooling in which a compressor impeller 46a of a compressor 46 and a turbine impeller 47a of an expansion turbine 47 are attached to both ends of a main shaft 53. Thus, either or both of the axial load and the bearing preload are supported by the electromagnet 57, and the compressor impeller 46a is rotationally driven by the driving force of the turbine impeller 47a. The electromagnet 57 is disposed so as to face the thrust plate 53a provided perpendicularly and coaxially with the main shaft 53 in a non-contact manner, and according to the output of the force detection sensor unit 58 for detecting the axial force, the magnetic bearing controller 59 is provided. It is controlled by. The force detection sensor unit 58 is fixedly fitted to the outer ring 56a of the rolling bearing 56 and is fitted to the inner diameter surface 54a of the spindle housing 54 so as to be movable in the axial direction. A sensor preload spring that is housed in a housing recess provided in the spindle housing 64 and urges the outer ring 56a of the bearing 56 in the axial direction, interposed between the rod and the electromagnet 57 that is a fixing member. (Not shown), and the axial displacement of the bearing housing 63 is converted into a force by the force detecting element 60 and detected.

  According to the magnetic bearing device having the above configuration, since the thrust force applied to the main shaft 53 is supported by the electromagnet 57, the thrust force acting on the rolling bearings 55 and 56 can be reduced while suppressing an increase in torque without contact. As a result, the minute gaps between the respective impellers 46a and 47a and the housings 46b and 47b can be kept constant, and the long-term durability of the rolling bearings 55 and 56 with respect to the thrust load can be improved.

  However, in the magnetic bearing device configured as described above, when a magnetostrictive material, a giant magnetostrictive material, a strain gauge, a pressure sensitive resistance element, or the like is used as the force detection element 60 constituting the force detection sensor unit 58, the spindle housing 54 is not uniform. There is a problem that accurate force detection is difficult in an environment where there is a temperature change, such as detecting an imbalance of thermal expansion due to a temperature distribution. Further, in order to compensate for the temperature drift of the force detection element 60, it is necessary to provide a separate temperature sensor or to construct a control loop for performing temperature compensation, and there is a problem that the magnetic bearing controller 59 becomes complicated.

  An object of the present invention is to provide a magnetic bearing device capable of improving the long-term durability of a rolling bearing against a thrust load and accurately controlling the magnetic bearing without being affected by thermal expansion imbalance. It is.

The magnetic bearing device of the present invention uses both a rolling bearing and a magnetic bearing, the rolling bearing supports a radial load, the magnetic bearing supports one or both of an axial load and a bearing preload, and the electromagnet is perpendicular to the main shaft and Depending on the output of the force detection sensor unit, which is attached to the spindle housing so as to face the flange-shaped thrust plate made of ferromagnetic material coaxially without contact, and detects the axial force of the main shaft A magnetic bearing device having a controller for controlling an electromagnet, wherein the force detection sensor unit includes a pair of ring-shaped sensor targets sandwiching both end surfaces of the outer ring of the rolling bearing, and a pair of supporting each of these sensor targets. And a gap sensor for detecting a gap with respect to the sensor target. It is characterized in that attached to the sensor target mounted and the inner diameter side portion on the spindle housing in the outer diameter side portion of the main shaft radially.
According to this configuration, since the rolling bearing and the magnetic bearing are used in combination, the rolling bearing supports the radial load, and the magnetic bearing supports one or both of the axial load bearing preloads. Good support can be achieved, long-term durability of the rolling bearing can be ensured, and damage when the power supply is stopped when only the magnetic bearing is supported can be avoided.
Further, in this magnetic bearing device, the electromagnet is controlled by a controller in accordance with the output of the force detection sensor unit that detects the axial force of the main shaft, and the force detection sensor unit is connected to both end faces of the outer ring of the rolling bearing. A pair of ring-shaped sensor targets, a pair of leaf springs that support each of the sensor targets, and a gap sensor that detects a gap with respect to the sensor target, the leaf springs having an outer diameter in the main shaft radial direction. Since the sensor target is attached to the spindle housing at the side portion and attached to the inner diameter side portion, the magnetic bearing can be accurately controlled without being affected by thermal expansion imbalance.

  In the present invention, the leaf spring may be ring-shaped. When a ring-shaped leaf spring is used, a simpler structure is sufficient as compared with the case where a plurality of leaf springs are arranged in the circumferential direction to support the sensor target.

  In the present invention, the gap sensor may be magnetic.

  In the present invention, the gap sensor is a pressure sensor, and introduces compressed air from a compressed air supply source into an air introduction path provided in the spindle housing, and detects a specific position from a gap fluctuation between the center target and the spindle housing. The thrust force may be estimated by detecting the pressure change.

The present invention may be applied to a compression / expansion turbine system in which a compressor side impeller and a turbine side impeller are attached to the main shaft, and the compressor impeller is driven by power generated by the turbine impeller.
In the case of this configuration, a stable high-speed rotation of the main shaft can be obtained while maintaining an appropriate gap between the impellers, and the long-term durability and life of the bearing can be improved.

In this invention, a motor-integrated magnetic bearing device in which the main shaft is provided with the thrust plate and a motor rotor, and a compressor-side impeller and a turbine-side impeller are attached to the main shaft, and motor power and power generated by the turbine-side impeller are provided. It is good also as what is applied to the compression expansion turbine system which drives a compressor side impeller by either or both of these.
In the case of this configuration, a stable high-speed rotation of the main shaft can be obtained while maintaining an appropriate gap between the impellers, and the long-term durability and life of the bearing can be improved. Further, since the main shaft is driven by providing a motor, it is not necessary to provide pre-compression means such as a blower before the compressor.

In the present invention, the compression / expansion turbine system to which the motor-integrated magnetic bearing device is applied includes compression by precompression means, cooling by a heat exchanger, compression by a compressor of a turbine unit, and other heat exchange with respect to inflow air. It may be applied to an air cycle refrigeration cooling system that sequentially performs cooling by a vessel and adiabatic expansion by the expansion turbine of the turbine unit.
When a compression / expansion turbine system to which this magnetic bearing device is applied is applied to such an air cycle refrigeration / cooling system, a stable high-speed rotation of the main shaft can be obtained while maintaining an appropriate clearance between the impellers in the compression / expansion turbine system. The long-term durability of the bearing and the improvement of the service life of the bearing can be obtained, so that the main shaft bearing of the compression / expansion turbine system, which is the bottleneck of the air cycle refrigeration cooling system as a whole, can be obtained. Since stable high-speed rotation, long-term durability and reliability are improved, the air cycle refrigeration cooling system can be put to practical use.

  The magnetic bearing device of the present invention uses both a rolling bearing and a magnetic bearing, the rolling bearing supports a radial load, the magnetic bearing supports one or both of an axial load and a bearing preload, and the electromagnet is perpendicular to the main shaft and Depending on the output of the force detection sensor unit, which is attached to the spindle housing so as to face the flange-shaped thrust plate made of ferromagnetic material coaxially without contact, and detects the axial force of the main shaft A magnetic bearing device having a controller for controlling an electromagnet, wherein the force detection sensor unit includes a pair of ring-shaped sensor targets sandwiching both end surfaces of the outer ring of the rolling bearing, and a pair of supporting each of these sensor targets. And a gap sensor for detecting a gap with respect to the sensor target. Is attached to the spindle housing at the outer diameter side portion in the main shaft radial direction and the sensor target is attached to the inner diameter side portion, so that the long-term durability of the rolling bearing against the load of the thrust load can be improved and the thermal expansion can be improved. The magnetic bearing can be accurately controlled without being affected by the balance.

  An embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a cross-sectional view of a turbine unit 5 incorporating the magnetic bearing device of this embodiment. The turbine unit 5 constitutes a compression / expansion turbine system, and includes a compressor 6 and an expansion turbine 7. The compressor impeller 6 a of the compressor 6 and the turbine impeller 7 a of the expansion turbine 7 are attached to both ends of the main shaft 13, respectively. It has been. Further, the compressor impeller 6a is driven by the power generated in the turbine impeller 7a, and no other drive source is provided.

In FIG. 1, the compressor 6 has a compressor housing 6b facing the compressor impeller 6a with a small gap d1, and compresses air sucked in the axial direction from the suction port 6c in the center by the compressor impeller 6a. And it discharges as shown by the arrow 6d from the exit (not shown) of an outer peripheral part.
The expansion turbine 7 has a turbine housing 7b that is opposed to the turbine impeller 7a via a minute gap d2, and the air sucked from the outer peripheral portion as indicated by an arrow 7c is adiabatically expanded by the turbine impeller 7a, It discharges in the axial direction from the discharge port 7d of the part.

In the magnetic bearing device in the turbine unit 5, the main shaft 13 is supported by a plurality of bearings 15 and 16 in the radial direction, and either or both of the axial load and the bearing preload applied to the main shaft 13 are supported by an electromagnet 17 that is a magnetic bearing. It is supposed to support. The turbine unit 5 includes a force detection sensor unit 18 that detects a thrust force acting on the main shaft 13 by air in the compressor 6 and the expansion turbine 7, and a supporting force by the electromagnet 17 according to the output of the force detection sensor unit 18. And a magnetic bearing controller 19 for controlling the motor.
A pair of electromagnets 17 is installed in the spindle housing 14 so as to face the both surfaces of a flange-like thrust plate 13a made of a ferromagnetic material provided in the center of the main shaft 13 in the non-contact manner.

  The bearings 15 and 16 that support the main shaft 13 are rolling bearings and have a function of restricting the position in the axial direction. For example, a deep groove ball bearing or an angular ball bearing is used. In the case of a deep groove ball bearing, it has a thrust support function in both directions, and has the effect of returning the axial position of the inner and outer rings to the neutral position. These two bearings 15 and 16 are arranged in the vicinity of the compressor impeller 6a and the turbine impeller 7a in the spindle housing 14, respectively.

The main shaft 13 is a stepped shaft having a large-diameter portion 13b at the center and small-diameter portions 13c at both ends. The bearings 15 and 16 on both sides have their inner rings 15a and 16a fitted into the small diameter portion 13c in a press-fit state, and one of the width surfaces engages with a stepped surface between the large diameter portion 13b and the small diameter portion 13c.
The portions of the spindle housing 14 closer to the impellers 6a and 7a than the bearings 15 and 16 on both sides are formed with an inner diameter surface close to the main shaft 13, and non-contact seals 21 and 22 are formed on the inner diameter surface. Yes. The non-contact seals 21 and 22 are labyrinth seals in which a plurality of circumferential grooves are arranged in the axial direction on the inner diameter surface of the spindle housing 14.

The force detection sensor unit 18 is provided on the stationary side of the rolling bearing 16 on the turbine impeller 7a side. As shown in FIG. 2, the force detection sensor unit 18 includes a pair of ring-shaped sensor targets 31 and 32 sandwiching both end surfaces of the outer ring 16 b of the rolling bearing 16, and the sensor targets 31 and 32. And a gap sensor 35 provided on the bearing housing 14a of the spindle housing 14 so as to face each side of the sensor targets 31 and 32 on the bearing facing side. The gap sensor 35 is a sensor that detects a gap with respect to the sensor targets 31 and 32. The outer ring 16b of the rolling bearing 16 is supported on the inner diameter surface of the bearing housing 14a so as to be movable in the axial direction.
The pair of leaf springs 33, 34 are attached to the spindle housing 14 (bearing housing 14 a) at the radially outer diameter side portion of the main shaft 13, and the sensor targets 31, 34 are attached to the inner diameter side portions of the leaf springs 33, 34. 32 is attached. Thereby, a certain amount of movement stroke in the axial direction is given to the outer ring 16 b of the rolling bearing 16. Therefore, when the outer ring 16b of the rolling bearing 16 is displaced in the axial direction by the thrust force acting on the main shaft 13, a gap between each side of the bearing housing 14a and each side of the sensor targets 31 and 32 facing these one side is generated. fluctuate. The pair of leaf springs 33 and 34 are arranged so as to sandwich the rolling bearing 16 in the axial direction, so that the moment disturbance resistance can be improved.

  In the force detection sensor unit 18 configured as described above, the gap between the gap sensor 35 and the sensor targets 31 and 32 that change according to the thrust force acting on the main shaft 13 is detected by the gap sensor 35, and the detected value is obtained. It is converted into a thrust force by the magnetic bearing controller 19. In this case, with respect to the thrust force in one direction, the gaps detected on the left and right in the axial direction across the rolling bearing 16 are opposite to each other. Each output of 35 and 35 is differentially calculated and converted into a thrust force. As described above, by performing the differential operation, the influence of the temperature drift of the gap sensors 35 and 35 generated in the detection result is reduced.

  Even if a plurality of the gap sensors 35 are arranged as shown in FIG. 3A on each side of the bearing housing 14a facing the sensor targets 31, 32, one piece as shown in FIG. 3B. You may arrange them one by one. In the case where a plurality are arranged as shown in FIG. 3A, the detection accuracy can be improved by arranging the detection outputs on each side by arranging them at equidistant positions in the circumferential direction. When one is arranged on each side as shown in FIG. 3B, the gap sensor 35 on one side and the gap sensor 35 on the other side are arranged 180 degrees out of phase with each other in the circumferential direction. Even when the bearing housing 14a is inclined with respect to the main shaft 13, the influence of the inclination generated in the detection result can be canceled.

  In the configuration of the support system for the sensor targets 31 and 32 in the force detection sensor unit 18, it is necessary to shorten the axial length as much as possible due to the problem of the natural frequency. For this reason, the support system needs to have a flat structure. In this embodiment, since the sensor targets 31 and 32 are supported by the leaf springs 33 and 34, a flat structure can be easily realized. For example, when a coil spring is used instead of the leaf springs 33 and 34, the flat structure is provided. It is difficult to realize. Moreover, when the leaf | plate springs 33 and 34 are used, various rigidity can be implement | achieved by adjusting the thickness and inner / outer diameter of a board | plate. A wave washer or a Belleville spring can be used in place of the leaf springs 33 and 34. However, in this case, it is difficult to reduce the spring rigidity because of the structure of the spring member.

As the gap sensor 35, a non-contact type sensor such as a reluctance sensor, an eddy current sensor, an electrostatic sensor, or an optical sensor may be used. However, a reluctance sensor is used here. ing. Optical sensors and electrostatic sensors have a long axial length, making it difficult to make the force detection sensor unit 18 have a flat structure. Although the eddy current sensor is highly sensitive, it is difficult to handle because it detects even scratches on the surface of the sensor targets 31 and 32. On the other hand, since the reluctance sensor detects a change in permeability due to a gap change, it is possible to accurately detect the gap.
Further, when a reluctance sensor is used as the gap sensor 35, a phase detection circuit is used to detect a change in coil inductance, and a change in coil resistance due to a temperature change can be canceled. Thereby, accurate gap detection becomes possible.

  Of the spindle housing 14, at least the gap sensor 35 is provided and the bearing housing 14a serving as the detection portion of the force detection sensor unit 18 is made of a high magnetic permeability material, thereby improving detection sensitivity. In this case, the leaf springs 33 and 34 and the bearing 16 are preferably made of the same material as that of the bearing housing 14a, so that gap fluctuation due to thermal expansion can be minimized.

  FIG. 4 shows another configuration example of the force detection sensor unit 18. In this configuration example, the gap sensor 35 including the reluctance sensor in FIG. 2 is replaced with a gap sensor 35A using a pressure sensor 36. In this case, the gap sensor 35A includes an air introduction path 37 and an air lead path 38 provided in the bearing housing 14a, a pressure sensor 36 communicating with the air lead path 38, and a compression that introduces compressed air into the air introduction path 37. An air supply source 39; In the air introduction path 37, the air introduction hole 37a is opened on the outer diameter surface of the bearing housing 14a, and the air lead-out hole 37b is opened on each side facing the sensor targets 31 and 32 of the bearing housing 14a. The air lead-out path 38 has an air introduction hole 38a opened on one surface of the bearing housing 14a and an air lead-out hole 38b opened on the outer diameter surface of the bearing housing 14a. The pressure sensor 36 is provided in the air lead-out hole 38b. Is in communication. The other configuration is substantially the same as that of the force detection sensor unit 18 in FIG.

  In the force detection sensor unit 18 of this configuration example, the compressed air introduced into the air introduction path 37 from the compressed air supply source 39 causes the bearing housing 14a to move between one side of the bearing housing 14a and the pair of sensor targets 31 and 32 facing each other. On the other hand, a gap of several to several tens of μm is secured, and the gap amount changes according to the thrust force acting on the main shaft 13, and this change causes a pressure change in the gap. The pressure sensor 36 detects the pressure at a specific position of the gap via the air lead-out path 38. The pressure detected in this way is converted by the magnetic bearing controller 19 from gap change amount to thrust force. Thus, by using the pressure sensor 36, it is possible to improve detection accuracy, improve noise resistance, and simplify the detection circuit.

  FIG. 5 shows still another configuration example of the force detection sensor unit 18. In this configuration example, in the configuration of the force detection sensor unit 18 in FIG. 2, a bearing sleeve 40 is interposed between the outer ring 16b of the rolling bearing 16 and the bearing housing 14a. In this case, the outer ring 16b of the rolling bearing 16 is supported in a fixed state on the inner diameter portion of the bearing sleeve 40, and the bearing sleeve 40 is supported on the inner diameter surface of the bearing housing 14a so as to be movable in the axial direction. Other configurations are the same as those in the configuration of FIG.

  In the force detection sensor unit 18 of this configuration example, since the outer ring 16b of the rolling bearing 16 is supported on the bearing housing 14a via the bearing sleeve 40, the force detection sensor unit 18 is moved from the main shaft 13 to the outer diameter side. Can be placed at a distant location. Thereby, interference with the rotation part containing the main axis | shaft 13 and the force detection sensor unit 18 can be avoided, and the length of the main axis | shaft 13 can be shortened. In the high-speed rotating body, the shaft length needs to be as short as possible due to the problem of the main shaft natural frequency. However, the force detection sensor unit 18 of this configuration example can sufficiently meet such a request.

  The turbine unit 5 having this configuration is applied to, for example, an air cycle refrigeration cooling system and compressed by a compressor 6 so that air as a cooling medium can be efficiently heat-exchanged by a subsequent heat exchanger (not shown here). Then, the temperature is increased, and the air cooled by the heat exchanger in the subsequent stage is cooled and discharged by the adiabatic expansion to a target temperature, for example, a very low temperature of about −30 ° C. to 60 ° C., by the expansion turbine 7. used.

In this turbine unit 5, the compressor impeller 6a and the turbine impeller 7a are attached to a common main shaft 13, and the compressor impeller 6a is driven by the power generated in the turbine impeller 7a, so that no power source is required. Cooling can be efficiently performed with a compact configuration.
In order to secure the efficiency of compression and expansion of the turbine unit 5, it is necessary to keep the gaps d1 and d2 between the impellers 6a and 7a and the housings 6b and 7b minute. In the air cycle refrigeration cooling system, ensuring this efficiency is important. On the other hand, since the main shaft 13 is supported by rolling type bearings 15 and 16, the axial direction position of the main shaft 13 is regulated to some extent by the restriction function of the axial direction position of the rolling bearing, and each impeller 6a, 7a and The minute gaps d1 and d2 between the housings 6b and 7b can be kept constant.

However, a thrust force is applied to the main shaft 13 of the turbine unit 5 by the pressure of air acting on the impellers 6a and 7a. Further, the turbine unit 5 used in the air cooling system rotates at a very high speed of about 80,000 to 100,000 rotations per minute, for example. Therefore, when the thrust force acts on the rolling bearings 15 and 16 that rotatably support the main shaft 13, the long-term durability of the bearings 15 and 16 decreases.
In this embodiment, since the thrust force is supported by the electromagnet 17, the thrust force acting on the rolling bearings 15 and 16 for supporting the main shaft 13 can be reduced while suppressing an increase in torque without contact. In this case, a force detection sensor unit 18 that detects a thrust force acting on the main shaft 13 by the air in the compressor 6 and the expansion turbine 7, and the supporting force by the electromagnet 17 is controlled according to the output of the force detection sensor unit 18. Since the magnetic bearing controller 19 is provided, the rolling bearings 15 and 16 can be used in an optimum state with respect to the thrust force according to the bearing specifications.
In particular, the force detection sensor unit 18 includes a pair of ring-shaped sensor targets 31 and 32 sandwiching both end surfaces of the outer ring 16b of the rolling bearing 16 and a pair of leaf springs 33 and 34 that support the sensor targets 31 and 32. And the gap sensor 35 for detecting the gap with respect to the sensor targets 31 and 32, the magnetic bearing can be accurately controlled without being affected by the imbalance of thermal expansion.

  Therefore, stable high-speed rotation of the main shaft 13 can be obtained while maintaining appropriate gaps d1 and d2 between the impellers 6a and 7a, and the long-term durability and life of the bearings 15 and 16 can be improved. Since the long-term durability of the bearings 15 and 16 is improved, the reliability of the entire air cycle refrigeration cooling turbine unit 5 and, as a whole, the air cycle refrigeration cooling system is improved. As described above, stable high-speed rotation, long-term durability, and reliability of the main shaft bearings 15 and 16 of the turbine unit 5 that are the bottleneck of the air cycle refrigeration cooling system are improved. It becomes possible.

  The bearings 15 and 16 are disposed in the vicinity of the compressor impeller 6a and in the vicinity of the turbine impeller 7a, and the main shaft 13 is supported at both ends, so that more stable high-speed rotation is possible.

  Since non-contact seals 21 and 22 are provided between the main shaft 13 and the spindle housing 14 on the end side of the bearings 15 and 16, air passes through the bearings 15 and 16 and the like with the compressor 6. Leakage between the expansion turbines 7 is prevented. Since there is a large pressure difference between the inside of the compressor 6 and the inside of the expansion turbine 7, the inside of each bearing 15, 16 and the surface on which the inner and outer rings 15 a, 16 a of each bearing 15, 16 are fitted to the main shaft 13 and the spindle housing 14 Air leaks are about to occur. Such air leakage causes the efficiency of the compressor 6 and the expansion turbine 7 to decrease, and the air passing through the bearings 15 and 16 contaminates the bearings 15 and 16 when there is dust, or lubricates the bearings. There is a risk that the material may be dried to reduce durability. Such a decrease in efficiency and the fouling of the bearings 15 and 16 are prevented by the non-contact seals 21 and 22.

  FIG. 6 shows another embodiment of the turbine unit 5. In the embodiment shown in FIG. 1, the turbine unit 5 is provided with a motor 25 that rotationally drives the main shaft 13. The motor 25 is provided side by side with the electromagnet 17 and includes a stator 26 provided on the spindle housing 14 and a rotor 27 provided on the main shaft 13. The stator 26 has a stator coil 26a, and the rotor 27 is made of a magnet or the like. The motor 25 is controlled by the motor controller 28.

  In the turbine unit 5, the compressor impeller 6 a is rotationally driven by the driving force of the turbine impeller 7 a generated in the expansion turbine 7 and the driving force of the motor 25. Therefore, the compressor 6 can be driven without a pre-compression stage, and the system can be made compact.

  FIG. 7 shows an overall configuration of an air cycle refrigeration cooling system using the turbine unit 5 of FIG. This air cycle refrigeration cooling system is a system that directly cools air in a space to be cooled 10 such as a freezer as a refrigerant, and an air circulation path from an air intake port 1a to a discharge port 1b respectively opened in the space to be cooled 10 1 In this air circulation path 1, pre-compression means 2, first heat exchanger 3, dehumidifier 4, compressor 6 of air cycle refrigeration cooling turbine unit 5, second heat exchanger 8, intermediate heat exchanger 9, And the expansion turbine 7 of the said turbine unit 5 is provided in order. The intermediate heat exchanger 9 exchanges heat between the inflow air near the intake port 1a in the same air circulation path 1 and the air that has been heated by the subsequent compression and cooled. The air in the vicinity of 1a passes through the heat exchanger 9a.

  The pre-compression means 2 comprises a blower or the like and is driven by a motor 2a. The first heat exchanger 3 and the second heat exchanger 8 have heat exchangers 3a and 8a for circulating a cooling medium, respectively, and a cooling medium such as water and an air circulation path in the heat exchangers 3a and 8a. Heat exchange with 1 air. Each of the heat exchangers 3 a and 8 a is connected to the cooling tower 11 by piping, and the cooling medium whose temperature is increased by heat exchange is cooled by the cooling tower 11.

  This air cycle refrigeration cooling system is a system that keeps the space 10 to be cooled at about 0 ° C. to −60 ° C., from the space to be cooled 10 to the intake 1a of the air circulation path 1 at about 0 to −60 ° C. and 1 atm. Air flows in. Note that the numerical values of temperature and atmospheric pressure shown below are examples that serve as a guide. The air that has flowed into the intake port 1a is used by the intermediate heat exchanger 9 to cool the downstream air in the air circulation path 1 and is heated to 30 ° C. The heated air remains at 1 atm, but is compressed to 1.4 atm by the pre-compression means 2, and the temperature is raised to 70 ° C. by the compression. Since the 1st heat exchanger 3 should just cool the air of 70 degreeC which raised temperature, even if it is cold water about normal temperature, it can cool efficiently and it cools to 40 degreeC. The dehumidifier 4 prevents the moisture in the air in the air circulation path 1 from freezing due to cooling below the freezing point in the subsequent stage and causing clogging of the air circulation path 1 and galling of the expansion turbine 7. Dehumidify the air.

The air at 40 ° C. and 1.4 atm after dehumidification is compressed to 1.8 atm by the compressor 6 of the turbine unit 5, and the second heat exchanger 8 is heated to about 70 ° C. by this compression. To 40 ° C. The 40 ° C. air is cooled to −20 ° C. by the −30 ° C. air in the intermediate heat exchanger 9. The atmospheric pressure is maintained at 1.8 atmospheric pressure discharged from the compressor 6.
The air cooled to −20 ° C. by the intermediate heat exchanger 9 is adiabatically expanded by the expansion turbine 7 of the turbine unit 5, cooled to −55 ° C., and discharged from the outlet 1 b to the cooled space 10. This air cycle refrigeration cooling system performs such a refrigeration cycle.

It is sectional drawing of the turbine unit in which the magnetic bearing apparatus concerning one Embodiment of this invention was integrated. It is sectional drawing which shows one structural example of the force detection sensor unit in the turbine unit. (A) is a front view which shows the example of arrangement | positioning of the gap sensor in the same force detection sensor unit, (B) is a front view which shows the other example of arrangement | positioning of a gap sensor. It is sectional drawing which shows the other structural example of a force detection sensor unit. It is sectional drawing which shows the further another structural example of a force detection sensor unit. It is sectional drawing of the turbine unit concerning other embodiment. FIG. 7 is a system diagram of an air cycle refrigeration cooling system to which the turbine unit of FIG. 6 is applied. It is sectional drawing of a proposal example.

Explanation of symbols

2 ... Pre-compression means 3 ... First heat exchanger 5 ... Turbine unit 6 ... Compressor 6a ... Compressor impeller 7 ... Expansion turbine 7a ... Turbine impeller 8 ... Second heat exchanger 13 ... Main shaft 13a ... Thrust plate 14 ... spindle housing 14a ... bearing housings 15 and 16 ... rolling bearings 17 ... electromagnet 18 ... force detection sensor unit 19 ... magnetic bearing controller 25 ... motor 26 ... motor stator 27 ... motor rotors 31 and 32 ... sensor targets 33 and 34 ... leaf springs 35, 35A ... Gap sensor 90 ... Motor 92 ... Motor rotor

Claims (7)

Rolling bearing and magnetic bearing are used together, the rolling bearing supports the radial load, the magnetic bearing supports the axial load and / or the bearing preload, and the electromagnet is a ferromagnetic body that is perpendicular and coaxial with the main shaft. And a controller that controls the electromagnet according to the output of the force detection sensor unit that detects the axial force of the spindle. A magnetic bearing device,
The force detection sensor unit includes a pair of ring-shaped sensor targets sandwiching both end faces of the outer ring of the rolling bearing, a pair of leaf springs that support the sensor targets, and a gap sensor that detects a gap with respect to the sensor target. The plate spring is attached to the spindle housing at the outer diameter side portion in the main shaft radial direction, and the sensor target is attached to the inner diameter side portion.   2. The magnetic bearing device according to claim 1, wherein the leaf spring has a ring shape.   3. The magnetic bearing device according to claim 1, wherein the gap sensor is a magnetic type.   3. The gap sensor according to claim 1, wherein the gap sensor is a pressure sensor, and introduces compressed air from a compressed air supply source into an air introduction path provided in the spindle housing, and between the center target and the spindle housing. A magnetic bearing device that detects a pressure change at a specific position from a gap fluctuation and estimates a thrust force.   5. The compression / expansion turbine system according to claim 1, wherein a compressor side impeller and a turbine side impeller are attached to the main shaft, and the compressor impeller is driven by power generated by the turbine impeller. Magnetic bearing device to be applied.   The motor-integrated magnetic bearing device according to any one of claims 1 to 4, wherein the main shaft is provided with the thrust plate and a motor rotor, and a compressor-side impeller and a turbine-side impeller are attached to the main shaft. A magnetic bearing device applied to a compression / expansion turbine system in which a compressor side impeller is driven by one or both of motor power and power generated by a turbine side impeller. 7. The compression / expansion turbine system to which the magnetic bearing device is applied according to claim 5 or 6, wherein the inflowing air is compressed by a pre-compression means, cooled by a heat exchanger, compressed by a compressor of a turbine unit, or other heat. A magnetic bearing device that is applied to an air cycle refrigeration cooling system that sequentially performs cooling by an exchanger and adiabatic expansion by an expansion turbine of the turbine unit.

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