JP4788352B2 - Fuel cell supercharger - Google Patents

Description

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

A prototype of a fuel cell vehicle that travels with a fuel cell has already been manufactured, and Patent Document 1 describes that it is suitable for a supercharger for supplying compressed air to a fuel cell of a fuel cell vehicle. The thing provided with the scroll type compressor is proposed.
JP 2002-70762 A

  In a fuel cell device used in a fuel cell vehicle, downsizing, cost reduction, and weight reduction are important issues, and further miniaturization is required for superchargers. .

  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, since the fluctuation of the axial force acting on the impeller is large, ensuring the durability of the bearing device becomes a problem. In addition, in fuel cell vehicles, the low-speed rotation during idling and the high-speed rotation during normal driving are repeated continuously, which is advantageous for use in high-speed rotation and superior durability for the turbocharger. 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 absorb the fluctuation of the axial force accompanying the rotation of the impeller, which is a problem at that time, thereby achieving high speed rotation. It is another object of the present invention to provide a supercharger for a fuel cell that is advantageous in use and excellent in durability.

  A supercharger for a fuel cell according to the present invention is a supercharger for a fuel cell that compresses and supplies air to a fuel cell, and supports a centrifugal compressor provided in a casing and a rotating shaft of the compressor. The bearing device includes a pair of radial foil bearings concentrically provided on the rotating shaft and supporting the rotating shaft from the radial direction, and the rotating shaft is opposed to the rotating shaft from the axial direction. A control-type axial magnetic bearing supported from the axial direction is provided.

  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. It is assumed that it has an outer ring.

  The control-type axial magnetic bearing may control the force acting between a pair of axial electromagnets, and one of them may be a permanent magnet to control the force acting between the axial electromagnet and the permanent magnet. Sometimes it is said.

  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 electromagnetic coil of 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 axial magnetic bearing preferably has an axial electromagnet and a permanent magnet that are opposed to each other via a flange portion provided on the rotating shaft. In this case, 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.

  It is preferable that the axial electromagnet paired with the permanent magnet is integrated with one of the radial foil bearings. If it does in this way, the length of an axial direction can be shortened further, and it can further reduce in size. A bearing in which an axial electromagnet is integrated with a radial foil bearing is composed of a flexible bearing foil having a bearing surface that is radially opposed to the rotating shaft, and an annular one end surface that holds the bearing foil between the rotating shaft. And an electromagnet coil that is fitted in the recess of the outer ring and faces the permanent magnet provided in the casing via the flange portion.

  In this case, the electromagnet yoke may be a member different from the outer ring of the radial foil bearing, but the outer ring of the radial foil bearing may be made of a magnetic material and may also serve as the electromagnet yoke of the axial electromagnet. preferable.

Further, the axial magnetic bearing has a pair of axial electromagnets facing each other via a flange portion provided on the rotating shaft, and the axial electromagnet is flanged from the axial electromagnet facing surface of the flange portion provided on the rotating shaft. In some cases, a radial suction force generator is formed so that the suction force acting on the portion has a radial suction force. In order to do this, for example, by providing a small-diameter annular groove and a large-diameter annular groove on both front and rear surfaces of the flange portion, an attractive force is generated from the electromagnet radially inward of the large-diameter annular groove. An inner suction portion to be received may be formed, and an outer suction portion for receiving a suction force from the electromagnet may be formed radially outward of the large-diameter annular groove. When the rotary shaft is eccentric, the inner suction portion and the outer suction portion are subjected to a radial suction force that returns the eccentric rotary shaft to a concentric state, thereby increasing the rotational speed of the radial foil bearing. The durability can be improved by lowering the resistance.

  According to the supercharger for a fuel cell of the present invention, the rotating shaft is supported by the radial foil bearing (dynamic pressure gas bearing) from the radial direction and is also supported by the control type axial magnetic bearing from the axial direction. A reduction in the fatigue life of the bearing due to rotation is suppressed, and a function for circulating oil for lubrication becomes unnecessary, so that the supercharger can be downsized. 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 radial foil bearing is durable. It is also advantageous in terms of performance.

  Embodiments of the present invention will be described below with reference to the drawings. In the following description, the right in FIG. 2 is the front and the left is the rear.

  FIG. 1 shows an in-vehicle fuel cell device in which a fuel cell supercharger according to the present invention is used. The fuel cell device (1) includes a fuel cell stack (2) and a fuel cell stack (2). A power control device (3) for controlling the power supplied from the fuel cell stack (2), a high-pressure hydrogen tank (4) and a hydrogen pump (5) for supplying hydrogen to the fuel cell stack (2), and compressed air to the fuel cell stack (2) The supercharger (6) for supplying the fuel, the humidifier (7) for humidifying the compressed air obtained by the supercharger (6), and the cooling for cooling the fuel cell stack (2) and the power control device (3) And an electric motor (9) for driving the vehicle by electric energy obtained by the fuel cell stack (2).

  FIG. 2 shows a schematic configuration of a fuel cell supercharger according to a first embodiment of the present invention. A fuel cell supercharger (6) is a centrifugal compressor (6) provided in a casing (11). 12) and a bearing device (14) for supporting the rotating shaft (13) of the compressor (12).

  The centrifugal compressor (12) is a non-displacement compressor, and the horizontal axis-shaped rotating shaft (13) rotates inside a substantially cylindrical hermetic casing (11) arranged on the horizontal axis in the front-rear direction. .

  The casing (11) is composed of a front rotary shaft support part (11a) and a rear gas flow part (11b).

  The rotating shaft (13) has a stepped shaft shape and is disposed in a space in the rotating shaft support (11a). An impeller (13a) located in the space of the gas circulation part (11b) is fixed to the rear end of the rotating shaft (13).

  A built-in type electric motor (20) that rotates the rotating shaft (13) at a high speed on the inner periphery of the rotating shaft support portion (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 electric motor (20) includes a stator (20a) provided on the rotating shaft support (11a) side and a rotor (20b) provided on the rotating 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). As the rotating shaft (13) rotates, the impeller (13a) rotates, and the rotation of the impeller (13a) causes air to flow from the gas inflow path (11c) to the space (11d) in the gas circulation portion (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).

  The stepped rotary shaft (13) is connected to the large-diameter portion (31) in which the rotor (20b) of the electric motor (20) is provided in the intermediate portion in the axial direction and the front-rear direction outer side of the large-diameter portion (31). It consists of front and rear small diameter portions (32), (33) and a flange portion (34) provided at the axially intermediate portion of the front small diameter portion (32). The impeller (13a) 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. 3, each radial foil bearing (21) (22) is a flexible top foil having a bearing gap (44) disposed radially outside the rotary shaft large diameter portion (31). (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) ( 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. The both ends of the steel plate in the axial direction are cut and raised in the radial direction, and the tip is bent. 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.

  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 (13a) by the rotation is backward (leftward in FIG. 2). 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.

  An axial position sensor (26) for detecting the position of the rotating shaft (13) in the axial direction is provided on the rear surface of the front wall of the rotating shaft support portion (11a) of the casing (11). Based on the position of the rotating shaft (13) detected by the position sensor (26), the current flowing through the electromagnet coil (24b) of the axial magnetic bearing (23) 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 (13a) 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.

  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.

  According to the fuel cell supercharger (6) 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). The axial support of the rotary shaft (13) is handled by the axial magnetic bearing (23), and if the axial force acting on the impeller (13a) 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. 4 shows a schematic configuration of a second embodiment of the supercharger for a fuel cell according to the present invention. This supercharger for a fuel cell (6) has an axial electromagnet (24) that is radially filled with an axial electromagnet (56) that is integrated with one radial foil bearing (51). This is different from the first embodiment provided separately from the bearings (21) and (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. 4, the radial foil bearing (51) on the rear side 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 supercharger (6) 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 (13a) 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 the fuel cell supercharger (6 ) Is obtained.

  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 in the vicinity of the rotor (20b) at the front part of the rotating shaft (13), and as shown in FIG. 4, a permanent magnet (57) is arranged on the rear side of the flange part, and an axial part is placed on the front side. An electromagnet (56) is arranged.

  In the above embodiment, one of the magnets (24), (25), (56), and (57) constituting the set of control type axial magnetic bearings (23) and (55) is an electromagnet (24) (56) and the other is Although the permanent magnets (25) and (57) are used, both may be electromagnets.

  FIG. 5 shows a schematic configuration of a third embodiment of a fuel cell supercharger according to the present invention. In this fuel cell supercharger (6), both of the magnets constituting the set of control type axial magnetic bearings (61) are electromagnets (63) and (64), and the shape of the flange portion (62). Is different from the first embodiment in that a radial suction force generating portion (65) is formed. 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. 5, a pair of axial electromagnets (63) and (64) are provided on the rotating shaft support (11a) of the casing (11) so as to face each other through the flange portion (62) of the rotating shaft (13). Yes. A small-diameter annular groove (66) and a large-diameter annular groove (67) are provided on both front and rear surfaces of the flange portion (62), so that the radially inner side of the large-diameter annular groove (67) is provided. In addition, an inner suction portion (68) that receives a suction force from the corresponding axial electromagnet (63) (64) is formed, and on the outer side in the radial direction of the large-diameter annular groove (67), the corresponding axial electromagnet (63) ( An outer suction portion (69) that receives suction force from 64) is formed. The large-diameter annular groove (67) is provided so as to face the electromagnetic coils (63b) and (64b) of the axial electromagnets (63) and (64) from the axial direction. When the concentric state of the rotating shaft (13) is ensured, the part (69) faces the electromagnet yokes (63a) (64a) and receives a force only in the axial direction. When the rotating shaft (13) is eccentric, a radial force is generated between the axial electromagnets (63) (64) and each suction part (68) (69), and this radial force is in an eccentric state. It acts in the direction which returns the rotating shaft (13) which became to a concentric state. In this way, the inner suction portion (68) and the outer suction portion (69) allow the suction force acting on the flange portion (62) from the axial electromagnets (63) and (64) to have a radial suction force. A radial suction force generating part (65) is configured.

  Although not shown, the axial electromagnets (63) and (64) and the suction portions (68) and (69) may be provided so as to be relatively displaced radially outward or radially inward.

FIG. 1 is a block diagram showing a fuel cell apparatus in which a fuel cell supercharger according to the present invention is used. FIG. 2 is a longitudinal sectional view schematically showing a first embodiment of a fuel cell supercharger according to the present invention. FIG. 3 is a cross-sectional view showing a radial foil bearing used in the fuel cell supercharger according to the present invention. FIG. 4 is a longitudinal sectional view schematically showing a second embodiment of the fuel cell supercharger according to the present invention. FIG. 5 is a longitudinal sectional view schematically showing a third embodiment of the supercharger for a fuel cell according to the present invention.

Explanation of symbols

(2) Fuel cell
(6) Fuel cell supercharger
(11) Casing
(12) Compressor
(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) Flange
(55) Axial magnetic bearing
(56) Axial electromagnet
(57) Permanent magnet
(61) Axial magnetic bearing
(62) Flange
(63) (64) Axial electromagnet
(65) Radial suction force generator

Claims (4)

  A supercharger for a fuel cell that compresses and supplies air to a fuel cell, and includes a centrifugal compressor provided in a casing, and a bearing device that supports a rotating shaft of the compressor. A pair of radial foil bearings concentrically provided on the rotary shaft and supporting the rotary shaft from the radial direction; and a control type axial magnetic bearing which is opposed to the rotary shaft from the axial direction and supports the rotary shaft from the axial direction. A supercharger for a fuel cell, comprising:   2. The supercharger for a fuel cell according to claim 1, wherein the axial magnetic bearing has an axial electromagnet and a permanent magnet facing each other through a flange portion provided on the rotating shaft.   The axial electromagnet is integrated with one of the radial foil bearings. The integrated bearing includes a flexible bearing foil having a bearing surface facing the rotating shaft in the radial direction, and the bearing foil as the rotating shaft. And an outer ring in which an annular recess is formed on one end surface, and an electromagnet coil that is fitted in the recess of the outer ring and faces a permanent magnet provided in the casing via a flange portion. The supercharger for a fuel cell according to claim 2. The axial magnetic bearing has a pair of axial electromagnets facing each other via a flange portion provided on the rotating shaft, and the axial electromagnet-facing surface of the flange portion provided on the rotating shaft extends from the axial electromagnet to the flange portion. 2. The supercharger for a fuel cell according to claim 1, wherein a radial suction force generating portion is formed so that the acting suction force has a radial suction force.

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