JP2007270651A - Compressor for fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compressor for a fuel cell advantageous to use in high speed rotation, and superior in durability. <P>SOLUTION: A bearing device 14 supports a rotary shaft 13 of the compressor 1 for the fuel cell, and has a pair of radial foil bearings 21 and 22 concentrically arranged on the rotary shaft 13 and supporting the rotary shaft 13 from the radial direction, and an axial magnetic bearing 23 opposed from the axial direction to the rotary shaft 13 and supporting the rotary shaft 13 from the axial direction. A control device 61 has a rotating speed determining means setting the lowest rotating speed of the rotary shaft 13 to a value larger than a floating rotating speed of the radial foil bearings 21 and 22, and the lowest rotating speed maintaining means maintaining a rotating speed of the rotary shaft 13 to the lowest rotating speed or more by detecting the rotating speed by a rotation sensor 36. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a compressor for a fuel cell that is installed on an oxygen supply side of a fuel cell device that generates energy from hydrogen and oxygen and supplies compressed air to the fuel cell, and more particularly, a fuel suitable for mounting in a fuel cell vehicle. The present invention relates to a battery compressor.

  A prototype of a fuel cell vehicle that travels with a fuel cell has already been manufactured. Patent Document 1 discloses a scroll that is suitable for a compressor for supplying compressed air to a fuel cell of a fuel cell vehicle. One with a mold compressor has been proposed.

In addition to the scroll type, the compressor is referred to as a turbine compressor having an impeller at one end and a rotating shaft that rotates inside the casing, and compresses air in the space in the gas circulation portion of the casing by the rotation of the impeller. A centrifugal compressor is also known (Patent Document 2).
JP 2002-70762 A Japanese Patent Application Laid-Open No. 7-91760

  In a fuel cell device used in a fuel cell vehicle, downsizing, cost reduction, and weight reduction are important issues, and further downsizing of the compressor is required.

  Therefore, in place of the scroll compressor of Patent Document 1 which is a kind of positive displacement compressor, it is conceivable to use a non-displacement centrifugal compressor which is free from fluctuations in compression and can be downsized. In the centrifugal compressor, the axial direction force acting on the impeller is largely fluctuated, so that it is a problem to ensure the durability of the bearing device. In addition, in fuel cell vehicles, the low-speed rotation during idling and the high-speed rotation during normal running are repeated continuously, which is advantageous for use at high-speed rotation and excellent durability. It is required to be.

  In view of the above circumstances, the object of the present invention is to reduce the size by using a centrifugal compressor, and to absorb fluctuations in the axial direction force accompanying the rotation of the impeller, which becomes a problem at that time. It is another object of the present invention to provide a compressor for a fuel cell which is advantageous in use and excellent in durability.

  A compressor for a fuel cell according to the present invention includes a rotating shaft that has an impeller at one end and rotates inside the casing, a bearing device that supports the rotating shaft, and a control device that controls the rotating shaft. In a fuel cell compressor that compresses air in a space in a gas circulation part of a casing and supplies the fuel cell to a fuel cell, the bearing device is provided concentrically with the rotating shaft and supports a pair of radials from the radial direction. It is equipped with a foil bearing and a control type axial magnetic bearing that is opposed to the rotating shaft in the axial direction and supports the rotating shaft from the axial direction, and the control device sets the minimum rotational speed of the rotating shaft to the floating rotation of the radial foil bearing. A rotational speed determining means for making the value larger than the speed, and a minimum rotational speed maintaining means for detecting the rotational speed of the rotary shaft with a rotational sensor and maintaining the rotational speed to be equal to or higher than the minimum rotational speed And it is characterized in that it has.

  The radial foil bearing is, for example, a flexible bearing foil having a bearing surface that is radially opposed to the rotating shaft, an elastic body that supports the bearing foil, and the bearing foil and the elastic body are held between the rotating shaft. And a bearing housing.

  As the control type axial magnetic bearing, various types used in the 5-axis control type magnetic bearing device can be used. For example, the control type axial magnetic bearing may be composed of a permanent magnet and an axial electromagnet. It may be composed of a pair of axial electromagnets.

  According to the bearing device described above, the radial foil bearing is supported by the radial foil bearing, and the surrounding air is drawn between the bearing foil and the rotating shaft during the rotation of the rotating shaft to generate pressure (dynamic pressure). The rotating shaft is held by contact. Further, the axial magnetic bearing is responsible for supporting in the axial direction, and the current flowing through the axial electromagnet is controlled to hold the rotating shaft in a non-contact manner.

  Since the centrifugal compressor rotates the rotating shaft at a high speed with a motor, air is introduced into the impeller provided at one end of the rotating shaft from the axial direction, and compressed air is discharged in the radial direction. A large force in the axial direction acts on. Therefore, when the axial direction support is performed by the axial foil bearing, the rigidity of the bearing may be insufficient. On the other hand, by supporting the axial direction with the axial magnetic bearing, the load capacity is increased, and the control current is changed according to the fluctuation of the axial force, so that the axial direction is also applied to the rotational load fluctuation. Non-contact support is ensured.

  The clearance between the rotating shaft and the top foil of the radial foil bearing gradually increases from 0 as the rotational speed increases at the initial stage of rotation, and increases rapidly at a certain rotational speed. And move to a completely non-contact state. Therefore, in the rotational speed determination means, the rotational speed at which the clearance starts to increase suddenly is set as the floating rotational speed, and the compressor rotational area where the rotational speed slightly higher than this is set as the minimum rotational speed is set, and in the minimum rotational speed maintaining means The non-contact state can be reliably maintained by detecting the rotation speed of the rotation shaft with the rotation sensor and maintaining the rotation speed at or above the minimum rotation speed.

  The control type axial magnetic bearing is composed of, for example, an impeller-side permanent magnet and an anti-impeller-side axial electromagnet that are opposed to each other via a flange portion of a rotating shaft. Thereby, the axial electromagnet is arranged so that its attractive force is opposite to the direction of the axial force generated by the rotation. In this way, the axial length can be shortened compared to an axial magnetic bearing that normally has a pair of axial electromagnets, thereby increasing the natural frequency of the rotating shaft and rotating at high speed. As well as being smaller and lighter. Then, by passing a control current through the electromagnet coil of the axial electromagnet, the rotating shaft is attracted to the anti-impeller side.

  When the axial magnetic bearing is composed of a permanent magnet and an axial electromagnet, the axial electromagnet paired with the permanent magnet is composed of an electromagnet yoke and an electromagnet coil, and of course it may be separated from the radial foil bearing. It may be integrated into one of the radial foil bearings.

  By integrating the axial electromagnet with the radial foil bearing, the length in the axial direction can be further shortened, and the size can be further reduced. A bearing in which an electromagnet of an axial magnetic bearing is integrated with a radial foil bearing has a flexible bearing foil having a bearing surface radially facing the rotating shaft, and holds the bearing foil between the rotating shaft and An outer ring having an annular recess formed on the end surface, and an electromagnet coil that is fitted in the recess of the outer ring that also serves as an electromagnet yoke and forms an axial electromagnet together with the outer ring are provided. An axial electromagnet composed of an outer ring that also serves as an electromagnet yoke and an electromagnet coil is opposed to a permanent magnet provided in a casing via a flange portion, and an axial magnetic bearing is formed by the axial electromagnet and the permanent magnet.

  When the axial magnetic bearing is composed of a pair of axial electromagnets, it is preferable that each axial electromagnet is integrated with each radial foil bearing, whereby the length in the axial direction can be suppressed. It is possible to ensure miniaturization using an axial electromagnet.

  According to the fuel cell compressor of the present invention, the rotating shaft is supported by the radial foil bearing (dynamic pressure gas bearing) from the radial direction and is supported by the control type axial magnetic bearing from the axial direction. The reduction in the fatigue life of the bearing due to the above is suppressed, and the function for circulating the oil for lubrication becomes unnecessary, so that the size of the compressor can be reduced. Furthermore, the axial load generated by the rotation of the impeller of the centrifugal compressor is received by the control type axial magnetic bearing, so that the load capacity (axial rigidity) is increased, the rotational stability is improved, and the axial contact is improved. As a result, no load is generated on the radial foil bearing, so that the durability of the radial foil bearing is also improved.

  Furthermore, since the minimum rotational speed of the rotating shaft is maintained at a value larger than the floating rotational speed of the radial foil bearing, the burden on the radial foil bearing can be reduced and the bearing life can be prevented from being shortened.

  Embodiments of the present invention will be described below with reference to the drawings. In the following description, the right in FIG. 1 is the front and the left is the back.

  FIG. 1 shows a schematic configuration of a first embodiment of a fuel cell compressor according to the present invention. A fuel cell compressor (1) is a non-displacement centrifugal compressor, which is horizontally arranged in the front-rear direction. A substantially cylindrical hermetic casing (11) disposed on the shaft, a horizontal shaft-shaped rotating shaft (13) having an impeller (12) at the rear end and rotating inside the casing (11), and a rotating shaft ( A bearing device (14) for supporting 13), and a control device (61) for controlling the rotating shaft (13) and the bearing device (14).

  The casing (11) is composed of a front rotary shaft support portion (11a) that supports the rotary shaft (13) and a rear gas flow portion (11b) on which the impeller (12) is disposed.

  The rotating shaft (13) has a stepped shaft shape and is disposed in a space in the rotating shaft support (11a).

  A built-in motor (20) that rotates the rotating shaft (13) at a high speed on the inner periphery of the rotating shaft support (11a), and a pair of front and rear radial foil bearings (21) that support the rotating shaft (13) from the radial direction. 22) and a set of control type axial magnetic bearings (23) for supporting the rotating shaft (13) from the axial direction (front-rear direction).

  The motor (20) includes a stator (20a) provided on the rotary shaft support portion (11a) side and a rotor (20b) provided on the rotary shaft (13) side.

  The bearing device (14) includes front and rear radial foil bearings (21) and (22) and an axial magnetic bearing (23).

  A gas inflow passage (11c) is provided at the rear end of the space in the gas circulation part (11b). When the rotating shaft (13) rotates, the impeller (12) rotates.By the rotation of the impeller (12), air is transferred from the gas inflow path (11c) to the space (11d) in the gas circulation part (11b). It flows in, is compressed in the space (11d), and is discharged through a gas outflow path (not shown) that leads to the space (11d). A gap of a predetermined size is formed between the inner surface of the gas flow part (11b) and the impeller (12) to ensure compression performance.

  The stepped rotary shaft (13) is connected to the large-diameter portion (31) where the rotor (20b) of the motor (20) is provided at the intermediate portion in the axial direction and to the outside in the front-back direction of the large-diameter portion (31) It consists of front and rear small diameter portions (32), (33) and a flange portion (34) provided in the axially intermediate portion of the front small diameter portion (32). The impeller (12) is attached to the rear end portion of the rear small diameter portion (33), and the radial foil bearings (21) and (22) are provided at both end portions of the large diameter portion (31).

  As shown in FIG. 2, each radial foil bearing (21) (22) has a flexible top foil that is arranged on the radially outer side of the rotary shaft large diameter portion (31) with a bearing gap (44) therebetween. (Bearing foil) (41), a bump foil (elastic body) (42) disposed on the radially outer side of the top foil (41), and an outer ring disposed on the radially outer side of the bump foil (42) ( Bearing housing) (43).

  The top foil (41) is made of a strip-shaped stainless steel plate, and the strip-shaped stainless steel plate is formed into a cylindrical shape without overlapping in the circumferential direction by roll processing so that both ends in the longitudinal direction are adjacent to each other. It is formed by cutting both ends in the axial direction of one end of the steel plate in the radial direction and bending the tip. The cylindrical portion (41a) other than the cut and raised portion is a main portion of the top foil, and the cut and raised portion (41b) is an engaging portion of the top foil (41).

  The bump foil (42) includes a cylindrical portion (42a) formed of a corrugated plate made of stainless steel into a cylindrical shape, and an engaging portion that is connected to one end of the cylindrical portion (42a) and located on the radially outer side of the cylindrical portion (42a). (42b).

  On the inner peripheral surface of the outer ring (43), an engagement groove (43a) extending in a substantially radial direction is formed. Then, the cylindrical portion (42a) of the bump foil (42) is arranged along the inner peripheral surface of the outer ring (43), and the engaging portion (42b) is formed in the engaging groove (43a) of the outer ring (43). By being engaged, the bump foil (42) is attached to the outer ring (43), and the cylindrical portion (41a) of the top foil (41) is provided between the bump foil (42) and the rotary shaft large diameter portion (31). ) And the engaging portion (41b) is engaged with the engaging groove (43a) of the outer ring (43), so that the top foil (41) is attached to the outer ring (43).

  Radial foil bearings (21) and (22) have a top foil (41) that is formed into a cylindrical shape that does not overlap in the circumferential direction by roll processing so that both ends in the longitudinal direction are adjacent to each other in the longitudinal direction. Since the radius is constant and the roundness is high, the support performance of the rotary shaft (13) is high and the floating characteristics of the rotary shaft (13) are also good.

  Although not shown in the drawings, the radial foil bearings (21) and (22) are not limited to those described above, and the radial foil bearing is composed of a plurality of flexible foil pieces having a bearing surface facing the rotating shaft. The bearing foil which consists of, and the outer ring | wheel which hold | maintains a bearing foil between rotating shafts may be provided.

  The axial magnetic bearing (23) includes an axial electromagnet (24) and a permanent magnet provided on the rotating shaft support (11a) of the casing (11) so as to face each other via the flange (34) of the rotating shaft (13). (25). The axial electromagnet (24) includes a yoke (24a) and a coil (24b). The direction of the force acting on the impeller (12) by the rotation is backward (leftward in FIG. 1). Correspondingly, the permanent magnet (25) is arranged on the rear side of the flange portion (34) and is axial. The electromagnet (24) is disposed on the front side of the flange portion (34) so that its attractive force is opposite to the direction of the axial force generated by the rotation.

  On the rear surface of the front wall of the rotating shaft support portion (11a) of the casing (11), a target portion made of soft magnetic stainless steel (35) concentrically provided at the front end portion of the small diameter portion (32) of the rotating shaft (13). ) Is provided with an axial position sensor (26) for detecting the position of the rotary shaft (13) in the axial direction. The rear surface of the front wall of the rotating shaft support portion (11a) of the casing (11) is further faced by a recess (37) provided on the outer periphery of the front surface of the target portion (35) to reduce the rotational speed of the rotating shaft (13). A rotation sensor (36) for detection is provided. Although only one recess (37) is shown in the figure, a plurality of recesses (37) may be provided at equal intervals.

  Based on the position of the rotary shaft (13) detected by the position sensor (26) and the rotational speed detected by the rotation sensor (36) by the control device (61), the electromagnetic coil of the axial magnetic bearing (23) The current flowing through (24b) is controlled. The current flowing in the coil (24b) is controlled so that an attractive force that is balanced with the force acting on the impeller (12) and the attractive force of the permanent magnet (25) by the rotation is generated in the axial electromagnet (24). The rotation shaft (13) is supported in a non-contact manner at a predetermined position in the axial direction.

  As shown in FIG. 3, the controller (61) can be a motor drive circuit (62), a magnetic bearing drive circuit (63), a position sensor drive circuit (64), a rotation sensor drive circuit (65), and a software program. A DSP (66), an AD converter (67), and a DA converter (68) are provided as digital processing means. The DSP is an abbreviation for a digital signal processor. The digital signal processor refers to dedicated hardware that can input a digital signal and output the digital signal, can be software-programmed, and can perform high-speed real-time processing.

  The position sensor drive circuit (64) calculates the position of the rotary shaft (13) in the axial direction based on the distance signal that is the output of the position sensor (26), and converts the position signal that is the result of the calculation into an AD converter ( 67) to the DSP (66).

  When the size of the gap (gap) with the target (35) changes with an alternating current flowing through the coil of the axial position sensor (26), an inductance change occurs, and the axial position sensor (26) A distance signal proportional to the size of the gap is output. The position sensor drive circuit (64) sets the displacement when the rotating shaft (13) is at the target flying position to 0, and uses a signal proportional to the axial displacement of the rotating shaft (13) relative to the target flying position as a position signal. Output.

  The output of the rotation sensor (36) also changes in proportion to the size of the gap with the target (35), and the part other than the recess (37) of the target (35) faces the rotation sensor (36). And when the recess (37) faces the rotation sensor (36), the size of the gap between the rotation sensor (36) and the target (35) is different, so the output of the rotation sensor (36) is It changes each time the recess (37) comes to the opposite position. Therefore, the rotation sensor (36) generates the same number of pulses as the number of recesses (37) during one rotation of the rotation shaft (13), and the output of the rotation sensor (36) rotates as a speed detection signal. The signal is output from the sensor drive circuit (65) to the DSP (66).

  The DSP (66) is an axial magnetic bearing (7) based on the rotational speed input from the rotation sensor drive circuit (65) and the digital position signal indicating the position of the rotary shaft (13) input from the AD converter (67). The excitation current signal for the electromagnet (24) is output to the magnetic bearing drive circuit (63) via the DA converter (68). Then, the drive circuit (63) supplies the excitation current based on the excitation current signal from the DSP (66) to the electromagnet (24) of the corresponding magnetic bearing (7), whereby the rotating shaft (13) is lifted to the target surface. Non-contact support in position.

  The DSP (66) also calculates the rotation speed of the rotation shaft (13) from the rotation speed detection signal of the rotation sensor drive circuit (65), and controls the rotation speed of the motor (20) based on this. The command signal is output to the motor drive circuit (62). The motor drive circuit (62) includes an inverter and controls the rotation speed of the motor (20) based on the rotation speed command signal. As a result, the rotating shaft (13) is rotated at high speed by the motor (20) while being supported in a non-contact manner at the target floating position by the radial foil bearings (21), (22) and the axial magnetic bearing (23). .

  The rotary shaft (13) and the top foil (41) of the radial foil bearing (21) (22) are, when the rotary shaft (13) is not rotating, the top foil (41) Due to the eccentricity, contact is made at one place on the circumference. Then, the clearance W between the rotating shaft (13) and the top foil (41) shown in FIG. 4 (b) (defined by “the median value of the clearance = (top foil inner diameter−rotating shaft outer diameter) / 2”). Increases as the rotation speed (the number of rotations per hour) of the rotating shaft (13) increases. This clearance W has the characteristics shown in FIG. 4 (a). In the initial stage of rotation, the clearance W gradually increases from 0 as the rotational speed increases, and increases rapidly at a certain rotational speed. The rotating shaft (13) and the top foil (41) shift to a completely non-contact state. Therefore, the rotational speed at which the clearance starts to increase suddenly is defined as the floating rotational speed of the radial foil bearings (21) and (22). The contact state can be reliably maintained.

 Based on the above knowledge, as shown in FIG. 5, the control of the rotational speed of the rotary shaft (13) and hence the rotational speed of the motor (20) is performed as follows.

  First, when setting initial conditions, the floating rotational speed of the radial foil bearings (21) and (22) to be used is determined (step 1 (S1)). Further, the minimum rotation speed and the maximum rotation speed of the rotation shaft (13) are set. The minimum rotational speed Rmin is obtained as Rmin = Rf + ΔR by adding a safety allowance ΔR based on the floating rotational speed Rf of the radial foil bearings (21) and (22) (step 2 (S2)). By turning on the engine of the fuel cell vehicle for which this setting has been completed, the fuel cell starts operating, and the rotating shaft (13) rotates (step 3 (S3)). Here, when an operation end operation for turning on the engine is performed (step 4 (S4)), the operation is stopped (step 10 (S10)). Otherwise, the rotation speed of the rotating shaft 13 is detected by the rotation sensor 36 (step 5 (S5)), and at the minimum and maximum rotation speeds set in step 2 (S2). Based on this, the rotation axis (13) is controlled to be maintained within these ranges (step 6 (S6)). This rotational speed maintenance control is applied not only during traveling but also during so-called idling stop. During the rotation speed maintenance control, it is always determined whether or not the minimum rotation speed is greater than or equal to the setting (step 7 (S7)), and a warning is issued when the current rotation speed falls below the minimum rotation speed (step 7). 9 (S9)). If the current rotational speed is equal to or higher than the minimum rotational speed, the operation of the fuel cell is continued (step 8 (S8)), and the loop for maintaining the rotational speed from step 4 (S4) to step 7 (S7) is repeated. Further, the rotation speed equal to or higher than the minimum rotation speed Rmin is maintained.

  Thus, the rotating shaft (13) is controlled so as to always rotate at a rotational speed larger than the floating rotational speed of the radial foil bearings (21) and (22) when traveling or idling (standby state). As a result, the burden on the radial foil bearings (21) and (22) can be reduced, and the bearing life can be prevented from decreasing.

  According to the fuel cell compressor (1) of the first embodiment, the radial shaft bearings (21) and (22) support the radial direction of the rotary shaft (13), and the rotary shaft (13) During rotation, the foil bearings (21) and (22) are supported in the radial direction in a non-contact manner by the dynamic pressure generated by the foil bearings (21) and (22). Also, the axial support of the rotary shaft (13) is handled by the axial magnetic bearing (23) .If the axial force acting on the impeller (12) fluctuates, the corresponding attractive force will be applied. Generated in the axial electromagnet (24). As a result, the rotary shaft (13) is stably supported in a non-contact manner without being affected by fluctuations in the rotational load, and its smooth rotation is guaranteed and durability (life) is excellent.

  FIG. 6 shows a schematic configuration of a second embodiment of the fuel cell supercharger according to the present invention. This compressor for a fuel cell (1) is constructed such that the axial electromagnet (24) is a radial fill bearing in that the axial electromagnet (56) of the axial magnetic bearing (55) is integrated with one radial foil bearing (51). (21) This is different from the first embodiment provided separately from (22). In the following description, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  In FIG. 6, the rear radial foil bearing (51) is an axial electromagnet integrated bearing. The flange portion (52) of the rotating shaft (13) is provided at the rear end portion of the large diameter portion (31) of the rotating shaft (13). A radial foil bearing (51) integrated with an axial electromagnet (56) includes a flexible top foil (41) having a bearing surface opposed to the rotating shaft (13) in the radial direction, and a top foil (41). Bump foil (42) to support, outer ring (53) holding top foil (41) and bump foil (42) between rotating shafts (13), and annular formed on the rear end surface of outer ring (53) And an electromagnet coil (56a) fitted in the recess (54). The annular recess (54) of the outer ring (53) is provided so as to face the flange portion (52) of the rotating shaft (13). The outer ring (53) is made of a magnetic material and also serves as an electromagnet yoke for the axial electromagnet (56). A permanent magnet (57) is provided on the rear wall of the rotating shaft support portion (11a) of the casing (11) so as to face the outer ring (53) via the flange portion (52). Thus, an axial electromagnet (56) is formed by the outer ring (53) of the rear radial foil bearing (51) and the electromagnet coil (56a) fitted in the annular recess (54), and this axial electromagnet (56 ) And a permanent magnet (57) opposed thereto, form an axial magnetic bearing (55).

  According to the fuel cell compressor (1) of the second embodiment, the radial shaft bearings (21) and (51) support the radial direction of the rotary shaft (13), and the rotary shaft (13) During rotation, the foil bearings (21) and (51) are supported in the radial direction in a non-contact manner by the dynamic pressure generated by the foil bearings (21) and (51). The axial support of the rotary shaft (13) is supported by the axial magnetic bearing (55), and if the axial force acting on the impeller (12) fluctuates, the corresponding attractive force will be applied. Generated in the axial electromagnet (56). As a result, the rotary shaft (13) is stably supported in a non-contact manner without being affected by fluctuations in the rotational load, and its smooth rotation is guaranteed and durability (life) is excellent. In the second embodiment, the axial electromagnet (56) of the axial magnetic bearing (55) is integrated with the rear radial foil bearing (51), so that it is compared with that of the first embodiment. The axial length of the axial electromagnet is shortened by the axial length, the natural frequency is increased and high-speed rotation is possible, and a more compact fuel cell compressor (1) Is obtained.

  Further, the control device (61) of the second embodiment is the same as that of the first embodiment, and by this control device (61), the rotational speed always higher than the floating rotational speed of the radial foil bearings (21) (51). The rotating shaft (13) is controlled so as to rotate at a speed. As a result, the load on the radial foil bearings (21) and (51) is reduced, and the bearing life can be prevented from being reduced.

  Instead of the radial radial bearing (51) on the rear side, the radial radial bearing (21) on the front side can also be an axial magnetic bearing integrated bearing. In this case, the flange of the rotating shaft (13) The part (52) is arranged near the rotor (20b) at the front part of the rotating shaft (13), and in the same manner as shown in FIG. 6, a permanent magnet (57) is arranged at the rear side of the flange part and an axial part is arranged at the front side. An electromagnet (56) is arranged.

  In the first and second embodiments, the axial magnetic bearings (7) and (55) are composed of permanent magnets (25) and (57) and electromagnets (24) and (56). (56) It may be composed of (56). The embodiment is shown in FIG.

  In this embodiment, the fuel cell compressor (1) includes an axial electromagnet (56) in which the permanent magnet (57) disposed on the rear side in the second embodiment is integrated with the radial foil bearing (51) on the front side. ) Is different from the second embodiment. In the following description, the same components as those of the second embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  7, the front radial foil bearing (51) is an axial electromagnet integrated bearing. Accordingly, the permanent magnet (57) arranged on the rear side in FIG. 6 is omitted, and the rotating shaft ( A flange portion (58) where the axial electromagnet (56) is exposed is added to the front end portion of 13). A radial foil bearing (51) on the front side integrated with an axial electromagnet (56) is the one provided on the rear side of the second embodiment, which is used in the reverse direction, and has a diameter on the rotating shaft (13). Flexible top foil (41) having bearing surfaces facing from the direction, bump foil (42) supporting the top foil (41), and the top foil (41) and the bump foil (42) are connected to the rotating shaft (13 Between the outer ring (53) and the annular recess (54) formed in the front end surface of the outer ring (53) and facing the flange (58) of the rotating shaft (13). And an electromagnet coil (56a). The outer ring (53) also serves as an electromagnet yoke of the axial electromagnet (56), and the electromagnet coil (56a) fitted into the outer ring (53) of the front radial foil bearing (51) and its annular recess (54) Thus, a front axial electromagnet (56) is formed, and an axial magnetic bearing (55) is formed by the front axial electromagnet (56) and the rear axial electromagnet (56).

  According to the fuel cell compressor (1) of the third embodiment, each radial foil bearing (51) supports the radial direction of the rotary shaft (13). When the rotary shaft (13) rotates, These are supported in the radial direction in a non-contact manner by the dynamic pressure generated in each foil bearing (51). The axial support of the rotary shaft (13) is supported by the axial magnetic bearing (55), and if the axial force acting on the impeller (12) fluctuates, the corresponding attractive force will be applied. Generated in the axial electromagnet (56). As a result, the rotary shaft (13) is stably supported in a non-contact manner without being affected by fluctuations in the rotational load, and its smooth rotation is guaranteed and durability (life) is excellent. In the third embodiment, the pair of axial electromagnets (56) of the axial magnetic bearing (55) is integrated with the radial foil bearings (51), respectively. The axial length of the axial electromagnet is shorter than the axial length of the axial electromagnet, and the natural frequency increases, enabling high-speed rotation and a more compact fuel cell compressor ( 1) is obtained.

  Further, the control device (61) of the third embodiment is the same as that of the first embodiment, and the control device (61) always rotates at a rotational speed higher than the floating rotational speed of the radial foil bearing (51). Thus, the rotary shaft (13) is controlled, and as a result, the load on the radial foil bearing (51) can be reduced, and the bearing life can be prevented from decreasing.

FIG. 1 is a longitudinal sectional view schematically showing a first embodiment of a fuel cell compressor according to the present invention. FIG. 2 is a cross-sectional view showing a radial foil bearing used in the fuel cell compressor according to the present invention. FIG. 3 is a block diagram schematically showing the overall configuration of the control device. FIG. 4 is a graph showing an example of the relationship between the clearance and the rotation speed. FIG. 5 is a flowchart showing a main part of the control device. FIG. 6 is a longitudinal sectional view schematically showing a second embodiment of the fuel cell compressor according to the present invention. FIG. 7 is a longitudinal sectional view schematically showing a third embodiment of the fuel cell compressor according to the present invention.

Explanation of symbols

(1) Fuel cell compressor
(11) Casing
(12) Impeller
(13) Rotating shaft
(14) Bearing device
(21) (22) Radial foil bearing
(23) Control type axial magnetic bearing
(24) Axial electromagnet
(25) Permanent magnet
(34) Flange
(51) Radial foil bearing
(52) (58) Flange
(55) Axial magnetic bearing
(56) Axial electromagnet
(57) Permanent magnet

Claims (1)

  A rotating shaft that has an impeller at one end and rotates inside the casing, a bearing device that supports the rotating shaft, and a control device that controls the rotating shaft are provided, and air is moved in the space in the gas circulation portion of the casing by the rotation of the impeller. In a compressor for a fuel cell that is compressed and supplied to a fuel cell, the bearing device includes a pair of radial foil bearings that are provided concentrically with the rotating shaft and support the rotating shaft from the radial direction, and an axial direction from the axial direction to the rotating shaft. A control type axial magnetic bearing that is opposed to support the rotating shaft from the axial direction, and the controller determines the rotational speed so that the minimum rotational speed of the rotating shaft is larger than the floating rotational speed of the radial foil bearing. And a minimum rotation speed maintaining means for detecting the rotation speed of the rotating shaft with a rotation sensor and maintaining the rotation speed above the minimum rotation speed. Use compressor.

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