Air supply device for a fuel cell

Abstract

Air supply device (1) for a fuel cell - with a shaft (2); - with a compressor wheel (4) which is arranged in a compressor housing (3) and which is fastened to one end (5) of the ends (5, 20) of the shaft (2), - with a bearing (6, 7, 8) arranged in a bearing housing (9) for supporting the shaft (2), and - with an electric motor (10) for driving the shaft (2), which is arranged in the bearing housing (9), characterized in that - that the shaft (2) has two shaft bearing sections (11, 12) designed as separate components and a magnet section (13) arranged between the shaft bearing sections (11, 12), forming a separate component and forming a rotor of the electric motor (10), wherein the shaft bearing sections (11, 12) and the magnet section (13) are braced or fixed against one another, and that the shaft bearing sections (11, 12) and the magnet section (13) are centered relative to one another via a centering arrangement (12A, 13F) acting on an outer edge (A), wherein the shaft bearing sections (11, 12) and the magnet section (13) each abut one another axially, wherein the centering arrangement (12A, 13F) comprises an annular circumferential step (13F) of an outer reinforcement (13A) of the magnet section (13) and an axially projecting nose (12A) of the shaft bearing section (11,12) and the nose (12A) engages in the step (13F) and bears against an axial stop surface (13E) of the step (13F), and wherein there is play (S) between the magnet section (13) and the shaft bearing section (11, 12).

Description

[0001] The invention relates to an air supply device for a fuel cell according to the preamble of claim 1.1

[0002] For efficient operation of a fuel cell, it is necessary that it is constantly supplied with a sufficient amount of air. For this purpose, a commercially available, prior art air supply device according to the preamble of claim 1 is known, which provides the air supply via a compressor wheel arranged in a compressor housing and driven by an electric motor.

[0003] However, due to the design of the known air supply device, it has the disadvantage that the electric motor can drive the compressor wheel at maximum speeds of approximately 100,000 rpm. Investigations conducted within the scope of the invention have shown that such speeds cannot fully exploit the potential of modern compressor wheels and compressor housings, so that, at least in some applications, a sufficient air supply to the fuel cell by the known device is not guaranteed, or at least not fully guaranteed.

[0004] US 2011 / 0 243 762 A1 shows a motor-driven centrifugal compressor with air bearings. A hydrodynamic fluid film thrust bearing is shown in US 5 529 398 A. US 2005 / 0 123 417 A1 shows a turbocharger whose turbine wheel and drive are connected by threads. JP 2009 - 257 165 A shows an electric turbocompressor for a fuel cell system. DE 694 05 806 T2 shows a centrifugal compressor with a centrifugal impeller and a vaned diffuser.

[0005] It is therefore an object of the present invention to provide an air supply device of the type specified in the preamble of claim 1 that enables high efficiency and thus the supply of a large amount of air to the fuel cell. Furthermore, the air supply device should be as compact as possible.

[0006] This problem is solved by the features of claim 1.

[0007] Because the shaft of the air supply device according to the invention is divided into three sections, which are formed by two shaft bearing sections and a magnet section forming the rotor of the electric motor, which are clamped against each other in the final assembly state, it is possible to realize a more rigid shaft structure compared to the prior art. This, particularly in conjunction with an air bearing, enables compressor wheel speeds of up to 150,000 rpm. This enables the air supply device according to the invention, again compared to the prior art, to supply significantly higher air mass flows to the fuel cell, while the design of the air supply device according to the invention is more compact and saves material.

[0008] The subclaims contain advantageous developments of the invention.

[0009] Among the particularly noteworthy preferred measures with which further increases in performance of the air supply device according to the invention are possible is the design of the air bearing with preferably two radial air bearings on both sides of the electric motor and one axial air bearing arranged adjacent to the compressor wheel.

[0010] Furthermore, it is possible to utilize the exhaust air or waste heat also generated in fuel cells by additionally providing a turbine wheel on the shaft of the air supply device, which is arranged in a turbine housing, which is preferably provided with a variable turbine geometry (VTG) in order to further increase the efficiency of the turbine.

[0011] In this case, the components “compressor wheel, compressor housing, turbine wheel and turbine housing” can be dimensioned and constructed in the same way as they are designed for conventional exhaust gas turbochargers, which in turn reduces the construction effort of the air supply device according to the invention.

[0012] Among the further preferred features to be emphasized, a cooling device should be mentioned which, in a particularly preferred embodiment, is formed by the outer side of the bearing housing and an outer jacket surrounding this outer side, which delimit a coolant interior space preferably provided with flow guide elements, into which coolant, preferably cooling water, can be introduced.

[0013] In order to be able to cool the axial bearing in particular, it is possible to provide a separate axial bearing cooling section, which can be designed, for example, as a recessed coolant ring formed in the bearing housing and arranged adjacent to the axial bearing.

[0014] Further details, features and advantages of the invention will become apparent from the following description of embodiments with reference to the drawing.

[0015] It shows: Fig. 1A, Fig. 1B schematically slightly simplified longitudinal sectional views through an air supply device according to the invention, which is suitable for fuel cells, but also other devices and apparatuses that must be supplied in particular with increased air quantities, Fig. 2 a detailed view of a part of the shaft of the air supply device in a longitudinal section, and Fig. 3 a perspective view of a blade ring for a diffuser of a compressor housing of the air supply device according to the invention.

[0016] Fig. 1A shows a preferred embodiment of an air supply device 1 according to the invention, which, for example, corresponds to a Fig. 1A, which is not shown in detail, can supply the fuel cell with the air mass flow required for its efficient operation.

[0017] The air supply device 1 has a shaft 2 which extends along a longitudinal axis L of the air supply device 1.

[0018] A compressor wheel 4 is attached to one end 5 of the shaft 2 and is arranged in a compressor housing 3. The compressor housing 3 and the compressor wheel 4 can be designed in accordance with the configuration of a compressor of an exhaust gas turbocharger. In the example shown, a screw connection 23 is provided for fastening. This screw connection has a threaded pin 23A that penetrates the compressor wheel and is screwed with one end into an internal thread of a shaft bearing section 12. A nut 23B is screwed onto the outer end of the screw connection, thereby fastening the compressor wheel 4 to the shaft 2.

[0019] Furthermore, the air supply device 1 has a bearing, which in the example is designed as an air bearing with two radial air bearings 6 and 7 and one axial air bearing 8. The radial air bearings 6 and 7 are arranged on associated shaft bearing sections 11 and the previously mentioned shaft bearing section 12. Between the shaft bearing sections 11 and 12, a magnet section 13 is provided, which forms the rotor of an electric motor 10. The magnet section 13 also includes a coil 14, which forms the stator of the electric motor 10 and, for this purpose, surrounds the magnet section 13 and is guided in a bearing housing 9. Furthermore, guide elements 17 and 18 are provided, which can be designed, for example, as Teflon discs, which rest against the respective end faces 15 and 16 of the coil 14 and which hold the air bearings 6, 7. Furthermore, these guide elements 17 and 18 fulfill a sealing function towards the shaft 2 in order to prevent air from escaping.Finally, the guide elements 17 and 18 serve as emergency bearings.

[0020] Instead of the air bearings described above, other bearings, such as magnetic bearings, are also conceivable.

[0021] How Fig. 1A, due to the provision of the shaft bearing sections 11 and 12 and the magnet section 13, the shaft 2 is divided into three shaft sections, which are formed by the aforementioned shaft bearing sections 11, 12 and the magnet section 13.

[0022] These three sections 11 to 13 are clamped against one another in the final assembly state, for which purpose a tie rod 19 is provided in the example. Sections 11 to 13 are pre-assembled outside the bearing housing on the tie rod 19, for which purpose the tie rod is screwed with its free end section 19A into an internal thread, if necessary with the interposition of a washer, of the shaft bearing section 12. At the left end of the shaft bearing section 11, the arrangement comprising the three sections 11 to 13 is fixed to the tie rod 19 via a shaft nut 20. In this pre-assembled state, this arrangement can be further processed, for example, preferably ground and coated.

[0023] The compressor wheel 4 is then fixed to the shaft bearing section 12 with a first axial bearing half 33, and this assembly is balanced. The second axial bearing half 34 is then placed onto the formed assembly, and the radial bearings 6 and 7 are fixed in the bearing housing. The entire preassembled shaft assembly described above can then be inserted into the bearing housing 9.

[0024] At the Fig. 1A, a turbine wheel 21 is arranged at the end 5 of the shaft 2 opposite the end region of the shaft 2, which is provided with an adjustable turbine geometry 22 to increase efficiency. The naturally provided turbine housing is shown in FIG. 1A for the purpose of better representation of the VTG 22. Fig. 1 is not shown, but is of course provided in the ready-to-use air supply device 1 as is the compressor housing 3.

[0025] For the final clamping of this unit, after placing the turbine wheel 21 on the other free end 19B of the tie rod 19, a nut 19C is screwed onto the tie rod 19, so that the entire shaft assembly consisting of the shaft bearing sections 11 and 12 and the magnet section 13 and the optionally provided turbine wheel 21 is clamped.

[0026] At the Fig. In the embodiment shown in Figure 1A, the compressor wheel 4 is fixed to the shaft 2 by means of the screw connection 23, as already described above. However, it is also possible to connect the compressor wheel 4 to the shaft assembly of the shaft 2 via the tie rod 19 in the manner described above, and accordingly, in this case, the turbine wheel 21 via the screw connection 23.

[0027] Fig. 1A further illustrates that the particularly preferred embodiment of the air supply device 1 shown in this figure further comprises an axial air bearing 8 which is arranged in the bearing housing 9 adjacent to the compressor wheel 4 and cooperates with a radially outwardly projecting shaft collar 31, on both sides of which the axial bearing halves are arranged.

[0028] Finally, Fig. 1A, the preferred embodiment of the air supply device 1 further comprises a cooling device 24, which is defined between the outer side of the bearing housing 9 and an outer jacket 25, which surrounds the bearing housing 9 at a distance. This makes it possible to create a cooling jacket into which coolant, preferably in the form of cooling water, can be introduced in order to provide the components of the air supply device 1 with the required cooling.

[0029] In particular for cooling the axial air bearing 8, the coolant device 24 in the Fig. 1A, the particularly preferred embodiment has an axial cooling bearing section 27 which is formed by an annular channel machined into the bearing housing 9 and provided adjacent to the axial air bearing 8 in order to be able to effect an increased cooling effect there.

[0030] Finally, it should be mentioned that the outer casing 25 is sealed and flexibly supported relative to the bearing housing 9 by an O-ring arrangement 28 and 29, each provided in the end sections of the outer casing 25. A stationary fixing device 36, e.g., in the form of a bearing block for installing the air supply device 1 in a motor vehicle, engages the outer casing 25, so that the previously described O-rings 28 and 29 can also perform a damping function in addition to their sealing function.

[0031] Out of Fig. 1B, which shows a further, but differently positioned longitudinal section through the air supply device 1, it is furthermore clear that in the bearing housing 9 in the particularly preferred embodiment a spring assembly arrangement is provided, of which a spring assembly 35 due to the selected cutting position in Fig. 1B. However, the spring assembly typically comprises at least two such spring assemblies 35. After the previously described insertion of the shaft assembly with the two axial bearing halves 33 and 34, the spring assembly presses the axial bearing half 34 onto the annular disc or the shaft collar 31, which further simplifies assembly.

[0032] The representation of the Fig. 1B also shows in enlarged form the Fig. 1A already described cooling device 24 with its flow guide elements, which in the example case is designed as a spiral channel arrangement, which results in a preferably spiral-shaped coolant flow to increase the cooling effect.

[0033] In order to increase the efficiency of the air supply device 1 according to the invention as explained above, a further supporting feature is provided that the shaft bearing sections 11 and 12 and the magnet section 13 are centered relative to one another at an outer edge of the arrangement, which can be seen from the detailed representation of the Fig. 2 results.

[0034] Fig. 2 shows the magnet section 13, which has an outer annular reinforcement 13A, a sleeve 13B which bears against its inner circumferential ring, and a magnet 13C which in turn bears against the inner circumference of the sleeve 13B and is provided with a central longitudinal through-hole 13D through which the tie rod 19 can be guided. To simplify the illustration and explanation, Fig. 2 only the area of ​​the detail located above the longitudinal axis L of the Fig. 1. Furthermore, the tie rod 19, which consists of Fig. 1 results in Fig. 2 not shown. It is also possible to apply the reinforcement 13A directly to the magnet 13C, i.e. without the sleeve 13B.

[0035] The aforementioned external centering on the outer edge A is achieved by an axially projecting nose 12A, which engages with its inner circumference in a correspondingly formed, annularly circumferential step 13F of the reinforcement 13A, and which has an axial stop surface 13E against which the nose 12A axially rests. To avoid a double fit, a clearance S is provided between the magnet section 13 and the Fig. 2, which includes the nose 12A and a longitudinal through-recess 12B in which an internal thread 12C is provided, into which the Fig. 1 explained first free end section 19A of the tension rod 19 and the threaded rod 23A can be screwed in.

[0036] The centering on the outer edge between the components 12 and 13 results in a higher stability of the shaft, whereby it should be emphasized that the previously explained stabilization naturally takes place in the same way between the shaft bearing section 11 and the magnet section 13, for simplification in Fig. 2 is not shown in detail.

[0037] In order to allow the passage of the tie rod 19, the shaft bearing section 11 naturally also has a longitudinal central bore extending through its entire length corresponding to the through recess 13D or 12B.

[0038] In a further alternative to the arrangement according to Fig. 2, it is possible that the middle part 13B is the magnet and that part 13C represents an inner shaft, so that in this arrangement the magnet 13B is encapsulated between the outer reinforcement 13A and the inner shaft 13C, which is particularly advantageous if the magnet has a relatively porous structure which is stabilized by the sheathing by the reinforcement 13A and the shaft 13C.

[0039] Finally, for a further increase in efficiency, it is possible for the compressor housing 3 to have a diffuser 30 which is provided with blading which is schematically shown in a slightly simplified manner using the Fig. 3, since this blading is due to the Fig. 1 is not visible in this figure. The blading of the diffuser 30 can be designed according to the illustration of Fig. 3 by means of a ring 31' which can be inserted into the diffuser 30 and which is provided with a blade arrangement 32 which can be adapted to the application, as can be seen from the perspective view of the Fig. 3 is an example. How Fig. As Figure 3 particularly shows, the blade arrangement 32 in the particularly preferred arrangement shown therein is designed as a double blade arrangement, which in the example comprises eleven blade pairs. However, the number of blade pairs, their design, alignment with one another, and alignment relative to the ring 31 can be modified depending on the application.

[0040] In addition to the above written disclosure of the invention, reference is hereby explicitly made to the graphic representation according to Fig.1 to 3. Furthermore, any conceivable combinations of the previously described individual components of the invention are possible, so that the invention is not limited to the examples described above. List of reference symbols 1 air supply device 2nd wave 3 Compressor housing 4 Compressor wheel 5 first end of wave 2 6, 7, 8 Air bearing or radial air bearing 6, 7 and axial air bearing 8 9 bearing housing 10 Electric motor 11, 12 shaft bearing sections 12A Nose 12B Longitudinal center recess 12C internal thread 13 Magnet section 13A sleeve-like reinforcement 13B sleeve 13C ring-shaped magnet 13D Longitudinal center recess of the magnet 13C 13E axial stop surface of the reinforcement 13A 13F Level 14 coil 15, 16 End faces of the coil 17, 18 Guide elements (guide discs) 19 tie rods 19A, 19B free ends of the tie rod 19C Mother 20 shaft nut 21 Turbine wheel 22 VTG 23 Screw connection 23A threaded rod 23B screw 24 Cooling device 25 outer shell 26 Flow guide elements of the guide device 24 for generating a preferably circulating, spiral coolant flow 27 Thrust bearing cooling section 28, 29 O-rings 30 diffuser 31 Ring disc / shaft collar 31' ring 32 blading 33, 34 axial bearing halves 35 spring package 36 Fixed fixing device / bearing block L Longitudinal axis S game A outer edge

Claims

[1] Air supply device (1) for a fuel cell - with a shaft (2); - with a compressor wheel (4) which is arranged in a compressor housing (3) and which is fastened to one end (5) of the ends (5, 20) of the shaft (2), - with a bearing (6, 7, 8) arranged in a bearing housing (9) for supporting the shaft (2), and - with an electric motor (10) for driving the shaft (2), which is arranged in the bearing housing (9), characterized by , - that the shaft (2) has two shaft bearing sections (11, 12) designed as separate components and a magnet section (13) arranged between the shaft bearing sections (11, 12), forming a separate component and forming a rotor of the electric motor (10), wherein the shaft bearing sections (11, 12) and the magnet section (13) are braced or fixed against one another, and that the shaft bearing sections (11, 12) and the magnet section (13) are centered relative to one another via a centering arrangement (12A, 13F) acting on an outer edge (A), wherein the shaft bearing sections (11, 12) and the magnet section (13) each abut one another axially, wherein the centering arrangement (12A, 13F) comprises an annular circumferential step (13F) of an outer reinforcement (13A) of the magnet section (13) and an axially projecting nose (12A) of the shaft bearing section (11,12) and the nose (12A) engages in the step (13F) and bears against an axial stop surface (13E) of the step (13F), and wherein there is play (S) between the magnet section (13) and the shaft bearing section (11, 12). [2] Air supply device according to claim 1, characterized by that a coil (14) forming a stator of the electric motor (10) is provided, which is arranged around the magnet section (13) in the bearing housing (9). [3] Air supply device according to claim 2, characterized by that the coil (14) is guided in the bearing housing (9) via two axial guide elements (17, 18) lying on its respective end faces (15, 16). [4] Air supply device according to one of claims 1 to 3, characterized by that the shaft bearing sections (11, 12) and the magnet section (13) are braced against each other via a tie rod (19). [5] Air supply device according to one of claims 1 to 4, characterized bythat a turbine wheel (21) is arranged at the other end (20) of the shaft (2). [6] Air supply device according to claim 5, characterized by that either the compressor wheel (4) or the turbine wheel (21) is connected to the shaft (2) via a screw connection (23), and the other wheel (turbine wheel 21 or compressor wheel 4) is connected to the shaft (2) via the tie rod (19). [7] Air supply device according to claim 5 or 6, characterized by that the turbine wheel (21) is arranged in a turbine housing provided with a variable turbine geometry (22). [8] Air supply device according to one of claims 1 to 7, characterized by that the bearing (6, 7, 8) is designed as an air bearing with two radial air bearings (6 and 7) arranged on the shaft bearing sections (11, 12) on both sides of the electric motor (10) and one axial air bearing (8). [9] Air supply device according to claim 8, characterized bythat the axial air bearing (8) is arranged adjacent to the compressor wheel (4) in the bearing housing (9). [10] Air supply device according to one of claims 1 to 9, characterized by that a cooling device (24) is provided between the bearing housing (9) and an outer casing (25) surrounding it. [11] Air supply device according to claim 10, characterized by that the cooling device (24) has flow guiding elements (26). [12] Air supply device according to claim 11, characterized by that the flow guiding elements (26) are designed as an arrangement of spiral channels. [13] Air supply device according to claim 11 or 12, characterized by that the cooling device (24) has an axial bearing cooling section (27) arranged in the bearing housing (9). [14] Air supply device according to one of claims 11 to 13, characterized by that the outer casing (25) is supported on the bearing housing (9) via O-rings (28, 29). [15] Air supply device according to one of claims 1 to 14, characterized by that the compressor housing (3) has a bladed diffuser (30). [16] Air supply device according to claim 15, characterized by that the diffuser (30) is provided with double blading (32). [17] Air supply device according to claim 9, characterized by that the axial air bearing (8) has two axial bearing halves (33, 34) which are arranged on both sides of a shaft collar (31) and which are preloaded by means of a spring assembly arrangement (35) arranged in the bearing housing (9).

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