Compressor for fuel cell system and fuel cell system having same
By adopting a combination design of biaxial air bearings and radial bearings in the compressor of fuel cell system for commercial vehicles, the wear problem caused by excessive axial force is solved, and efficient loading of axial forces in a limited space is achieved and extended The service life is improved and the utilization of structural space is optimized.
Patent Information
- Application Number
- CN202380044970.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2022-06-09
- Filing Date
- 2023-05-16
- Publication Date
- 2025-01-03
AI Technical Summary
The excessive axial force of the compressor in the fuel cell system of commercial vehicles leads to intensified wear of the support, and the dual-stage compressor is not suitable for use in the case of shortage of space, making it difficult to effectively withstand axial forces in a limited space.
A biaxial air bearing design is adopted, wherein the second axial air bearing is arranged spaced from the first axial air bearing for bearing axial force of the compressor shaft and optimizes the rotational mass and Torque balance reduces structural space requirements.
It significantly improves the axial load-bearing capacity of the bearing assembly, extends service life, and optimizes space utilization without adding expensive structures, suitable for single-stage compressors, reducing dependence on special bearings.
Smart Images
Figure CN119256166A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a compressor for a fuel cell system, in particular a compressor for a fuel cell system of a commercial vehicle, the compressor comprising a compressor housing, a compressor wheel, a rotationally driven compressor shaft operatively connected to the compressor wheel, and a support assembly for supporting the compressor shaft in the compressor housing in a manner that allows rotation about a rotation axis, wherein the support assembly comprises an axial air bearing for absorbing a force between the compressor housing and the compressor shaft in the direction of the rotation axis (hereinafter also referred to as: axial force). Background Art
[0002] For correct operation, fuel cell systems usually require controlled air supply on the cathode side in order to be able to maintain an optimal balance of reactants required for the operation of the fuel cell system within the fuel cell (the so-called stack). It is known that the air is compressed by means of one or more compressors and thus a controllable air mass flow or air volume flow is provided for the fuel cell.
[0003] The higher the power to be generated by the fuel cell, the higher the required mass flow or volume flow that must be delivered by the compressor. During compressor operation, due to the suction process of the air, there are axial forces acting on the compressor shaft. As the speed of the compressor shaft and the compressor wheel increases (with a constant cross section), the amount of air sucked in and thus the pressure built up, and thus the axial force, also increases. This effect is more pronounced in single-stage compressors than in two-stage compressors, in which the axial forces are at least partially balanced.
[0004] If the axial forces are too high for the bearings used, this leads to increased wear, especially at the usual rotational speeds. In other words, the axial forces that occur must be absorbed by the bearing assembly in all compressor systems so that undesirably high wear does not occur between the rotating and stationary elements in the compressor. Due to the high rotational speeds of the above-mentioned compressors during operation, it has proven to be feasible to use axial air bearings in the bearing assembly, which are used to absorb the axial forces that occur between the compressor shaft and the compressor housing.
[0005] Two-stage compressors can usually compensate for axial forces to a sufficient extent by using axial air bearings. However, the space occupied by two-stage compressors due to their design principle is considered a challenge, especially against the background of increasingly limited space in vehicles. Therefore, two-stage compressors are mostly not suitable for use in passenger vehicles, and in commercial vehicles, due to technological developments, installation space is also becoming increasingly scarce. Summary of the invention
[0006] Against this background, the object of the present invention is to provide a compressor in which the above-mentioned disadvantages are reduced as much as possible. In particular, the object of the present invention is to improve a compressor of the above-mentioned type in such a way that the axial forces acting on the compressor shaft can be better absorbed and the compressor requires as little structural space as possible. In addition, the object of the present invention is in particular to achieve the above-mentioned object as cost-effectively as possible.
[0007] The present invention achieves its object in that it proposes a compressor according to claim 1. In particular, it is proposed that in a compressor of the type mentioned at the outset, the axial air bearing is a first axial air bearing and that the bearing assembly also has a second axial air bearing, which is arranged spaced apart from the first axial air bearing in the direction of the rotation axis (hereinafter also referred to as: axial direction) and is designed (in addition to the first axial air bearing) to absorb forces between the compressor housing and the compressor shaft in the direction of the rotation axis, i.e. axial forces. In other words, according to the present invention, both the first axial air bearing and the second axial air bearing are now provided to provide an axial bearing function, so that the axial forces introduced by the compressor wheel via the compressor shaft can be absorbed by both axial air bearings.
[0008] The invention is based on the recognition that the use of a second axial air bearing provides an unexpectedly good compromise between increasing the axial load-bearing capacity (i.e. the ability to withstand axial forces) on the one hand and expanding the required structural space on the other hand. Although it seems counterintuitive that the installation of an additional bearing necessarily requires additional structural space, it has been shown that the additional axial structural space required for the second axial air bearing can lead to a significantly more suitable closed volume for the entire compressor than, for example, conventional solutions (e.g. replacing an existing axial air bearing of a known compressor with an axial air bearing of larger radial structure). At the same time, by using multiple bearings, even in the case of bearing types that are simple in design, a significant increase in the axial load-bearing capacity of the support assembly is achieved as a whole, so that it is not necessary to use expensive special bearings, such as spiral groove bearings. Nevertheless, the invention still has the advantage of improving the load-bearing capacity with a moderate increase in structural space even when spiral groove bearings are used.
[0009] Further advantages also result from preferred embodiments and developments of the invention, which will be described below.
[0010] In an advantageous development, the compressor is a single-stage compressor, wherein the compressor wheel is arranged at a first end section of the compressor shaft, and wherein the second axial air bearing is arranged at a second end section of the compressor shaft facing away from the first end section. The arrangement of the compressor wheel on one side and the second axial air bearing on the other side facing away from each other improves the balancing of the rotating masses. In particular in the case of a single-stage compressor, this is a major design advantage, especially for the bearing assembly, which has the effect of promoting a longer service life.
[0011] In a preferred embodiment, the bearing assembly has a radial bearing assembly. Preferably, the radial bearing assembly has a certain number of radial bearings arranged between the first axial air bearing and the second axial air bearing. According to the present invention, "a certain number" refers to a number of 1 or an integer greater than 1.
[0012] Preferably, the radial bearing is arranged between the first axial air bearing and the second axial air bearing.
[0013] Particularly preferably, the bearing assembly has two radial bearings, which can be configured as radial air bearings, for example. By balancing and spacing the axial air bearing and the radial bearing, an advantageous weight distribution can be achieved, and thus also accessibility to the axial air bearing is provided to a good extent for maintenance.
[0014] In a further preferred embodiment, the first axial air bearing has a first working disk which is designed to run in a first air gap, and the second axial air bearing has a second working disk which is designed to run in a second air gap.
[0015] In order to achieve the greatest possible commonality of parts, it may be preferred to manufacture both axial air bearings in the same manner, in particular with regard to their essential elements (foil, foil carrier, working disk). This can increase cost-effectiveness, for example with regard to production costs and assembly costs.
[0016] In an alternative preferred embodiment, one of the working disks (such as the first working disk) is dimensioned to be larger in the radial direction than the other working disk (such as the second working disk). Depending on the degree of the difference, this will result in different load-bearing capacities of the two axial air bearings in the axial direction, which can support the definition of a clear direction of action of the axial bearing.
[0017] In another preferred embodiment, a certain number of radial bearings therefore have a first radial bearing and a second radial bearing, the first radial bearing being arranged to have a first axial spacing from the first axial air bearing, the second radial bearing being arranged to have a spacing from the first radial bearing and to have a second axial spacing from the second axial air bearing, wherein the second axial spacing is different from the first axial spacing.
[0018] Preferably, the second axial spacing is greater than the first axial spacing.
[0019] The compressor wheel is usually also arranged on the side of the compressor shaft on which the first axial air bearing is arranged, so that the rotating mass and the tilting moment on this side of the compressor shaft are expected to be greater than the rotating mass and the tilting moment on the left side. However, by making the distance between the second axial air bearing and the next radial bearing adjacent thereto (i.e., the second radial bearing) larger, at least partial compensation of the tilting moment can be achieved.
[0020] In particular, a first radial force acts on the radial bearing assembly from the first working disk, and a second radial force acts on the radial bearing assembly from the second working disk. A third radial force acts on the radial bearing assembly from a compressor wheel arranged at a third axial distance from the first or second radial bearing. These radial forces and distances respectively result in tilting moments, which act on the radial bearing assembly via the compressor shaft.
[0021] Preferably, the first, second and third distances are dimensioned such that the resulting tilting moments at least partially and preferably completely cancel each other out.
[0022] Alternatively or additionally, the first, second and / or third distance is preferably dimensioned such that equally strong radial forces act in each case on the radial bearing of the bearing arrangement.
[0023] In another preferred embodiment, the first air gap and the second air gap are sized to be different in the direction of the axis of rotation. This is based on the consideration that at low rotation speeds, the working disk of the axial air bearing sometimes still rests on the corresponding bearing part or slips during movement, and only when a predetermined lift-off rotation speed is reached does it occupy a spacing on both sides of the working disk and freely rotate in the air gap. By determining the size of one of the two air gaps to be narrower than the other air gap, for example, by setting a narrower size or a narrower tolerance for the air gap, it is possible to predict which of the two axial air bearings will wear at low rotation speeds. This creates advantages in terms of maintenance planning and prediction of the service life of the support assembly. In addition, making the air gap of one of the axial air bearings larger also has a positive effect on friction losses.
[0024] In another preferred embodiment, the first axial air bearing and / or the second axial air bearing are configured as foil bearings. Preferably, the working disk of each axial air bearing is arranged between two fixed foil disks separated from each other by an air gap. The axial air bearing is preferably configured as a bump-type or other foil bearing type. In combination with the design principle according to the present invention, these cost-effective bearing types have sufficient load-bearing capacity to compensate for axial forces even in single-stage compressors. However, the present invention does not exclude the use of spiral groove bearings and other bearing types. In a preferred embodiment, one of the axial air bearings (such as the first axial air bearing) is configured as a spiral groove bearing, and the other axial air bearing (such as the second axial air bearing) is configured as a foil bearing.
[0025] It is particularly preferred that one of the axial air bearings is designed as a spiral groove bearing and the air gap associated therewith (eg, the first air gap) is larger than the air gap associated with the other axial air bearing (eg, the second air gap).
[0026] The above first aspect of the invention is described with reference to the compressor itself. In a further aspect, the invention also relates to a fuel cell system for driving a vehicle, in particular a commercial vehicle, having a compressor for supplying air to the fuel cell on the cathode side.
[0027] The invention achieves its object in such a fuel cell system in that the compressor is designed according to one of the above-described preferred embodiments. The fuel cell system thus utilizes the same advantages as the compressor according to the first aspect. The preferred embodiments of the compressor are also preferred embodiments of the fuel cell system, and vice versa. Therefore, to avoid repetition, reference is made to the above. BRIEF DESCRIPTION OF THE DRAWINGS
[0028] The present invention will be described in detail below with reference to preferred embodiments in conjunction with the accompanying drawings.
[0029] in:
[0030] Figure 1 shows a schematic diagram of a fuel cell system according to a preferred embodiment; and
[0031] Figure 2 Shown according to Figure 1 Detailed schematic of the compressor shaft of a fuel cell system. DETAILED DESCRIPTION
[0032] exist Figure 1Schematically depicts a fuel cell system 100 for a commercial vehicle 300. The fuel cell system 100 has a fuel cell 101, which is configured to provide electrical energy. For air supply, the fuel cell 101 is operatively connected to a compressor 1, which is configured to suck in and compress an air flow L and deliver it to the fuel cell 101 on the cathode side.
[0033] The compressor 1 has a compressor housing 3, in which a compressor shaft 5 is rotatably supported. The compressor shaft 5 is supported in the compressor housing 3 by means of a bearing assembly 7, wherein the bearing assembly 7 comprises a radial bearing assembly 8. The radial bearing assembly 8 comprises a first radial bearing 7a and a second radial bearing 7b. Preferably, both radial bearings 7a, 7b are designed as radial air bearings, such as foil bearings.
[0034] The support assembly 7 also has a first axial air bearing 7c and a second axial air bearing 7d.
[0035] A compressor wheel 11 is arranged in the first end section 9 of the compressor shaft 5 and is connected to the compressor shaft 5 in a rotationally rigid manner.
[0036] The compressor 1 has an electric motor 13 which can be operated as an electric motor and in this case drives the compressor shaft 5 in rotation, whereby the compressor wheel 11 draws in, compresses and delivers an air flow L in the direction of the fuel cell 101 .
[0037] In the illustrated embodiment, the compressor 1 is constructed as a single-stage compressor. In the second end section 15 opposite to the first end section 9, a second axial air bearing 7d is arranged on the compressor shaft 5. Thus, the second axial air bearing 7d equally imparts several important functions to the compressor 1: On the one hand, the second axial air bearing 7d provides additional bearing force, which significantly increases the axial bearing capacity of the bearing assembly 7, i.e., it bears the axial force F in the direction of the rotation axis A of the compressor shaft 5. axial In addition, the second axial air bearing 7b helps to reduce the radial force acting on the radial support assembly 8 (see Figure 2 ) and tilting moments are at least partially balanced, since the mass from the second axial air bearing 7d acts on the compressor shaft 5 on the side of the radial support assembly 8 away from the compressor wheel 11, and thus in particular the radial forces and tilting moments of the first axial air bearing 7c and the compressor wheel 11 can also be partially balanced.
[0038] The first axial air bearing 7c has a working disk 17 which is connected rotationally rigidly to the compressor shaft 5 and is positioned between two stationary foil disks 19. An air gap 21 is formed between the two foil disks 19.
[0039] The second axial air bearing 7 d also has a working disk 23 which is connected rotationally rigidly to the compressor shaft 5 , wherein the second working disk 23 is arranged between two stationary foil disks 25 , between which an air gap 27 is defined.
[0040] According to a preferred embodiment, the diameter (ie radial extension) of the working disks 17 , 23 can be designed differently to better define the direction of action in the direction of the axis A, or can be designed identically to support the universal component concept. This of course also applies to the foil disks 19 , 25 .
[0041] The air gaps 21, 27 can be designed to be of equal size in the axial direction, but in a preferred embodiment, as described above, one of the two air gaps 21, 27 can be designed to be narrower than the other air gap, so that the wear point is clearly defined and the maintenance prediction can be designed more accurately. For example, this may be the air gap 27. If the bearing assembly 7 has to be maintained, it will be reliably ensured, at least with regard to the axial air bearings 7c, 7d, that the wear occurs at the second axial air bearing 7d. And in order to repair or replace this second axial air bearing, it is not necessary to additionally disassemble the compressor wheel 11.
[0042] Figure 2 The force balance of the compressor shaft 5 and the radial bearing assembly 8 is shown in a rough manner and under the simplified assumption that the compressor shaft 5 is massless. The first radial bearing 7a is subjected to a radial force F R1 Loaded, while the second radial bearing 7b is subjected to radial force F R2 Loading. Radial force F L1 From the first working disk 17 of the first axial air bearing 7c, the radial force F L2 From the second working disk 23 of the second axial air bearing 7d, they act on the compressor shaft 5 respectively. V Coming from the compressor wheel 11 , it also acts on the compressor shaft 5 .
[0043] The centers of the two radial bearings 7a, 7b are spaced apart from each other by a distance L in the direction of the rotation axis A, that is, in the axial direction. R The first working disc 17 has an axial spacing L1 with its closest radial bearing (i.e., the first radial bearing 7a). The second working disc 23 has a spacing L2 with its closest radial bearing (i.e., the second radial bearing 7b). The compressor wheel 11 has a spacing L3 with its center of gravity in the axial direction with its closest radial bearing (i.e., the above-mentioned first radial bearing 7a).
[0044] Based on the force balance and moment balance for this situation, the spacings L1, L2 and L3 as well as L R The radial load F acting on the radial bearing assembly 8 is coordinated with each other.R1 、F R2 In a preferred design, the distance L2 is greater than L3, and L3 is greater than L1. R Preferably larger than L2.
[0045] By means of a structurally advantageous design, for example by minimizing the distances L1 and L3 as much as possible, a very compact bearing concept can be created overall, which provides good utilization of the construction space and at the same time enables a compressor shaft 5 which is balanced purely by air compared to the prior art. Due to the balancing effect from the second axial air bearing 7d, a long service life can be achieved even when a single-stage compressor is used (as in the preferred embodiment here). At the same time, the bearing concept allows the use of simple bearing types for the axial air bearing, for example a wave foil type or other foil bearing types.
[0046] List of reference numerals (part of the description)
[0047] 1 compressor
[0048] 3 Compressor housing
[0049] 5Compressor shaft
[0050] 7 Support components:
[0051] 7a First radial bearing
[0052] 7b Second radial bearing
[0053] 7c First axial air bearing
[0054] 7d Second axial air bearing
[0055] 8 Radial bearing assembly
[0056] 11Compressor wheel
[0057] 13 Machines
[0058] 15 End section
[0059] 17 working tray
[0060] 19 Foil Pan
[0061] 21 Air Gap
[0062] 23 working trays
[0063] 25 foil trays
[0064] 27 Air Gap
[0065] 100 fuel cell systems
[0066] 101 Fuel Cell
[0067] 300 Commercial Vehicles
[0068] A axis of rotation, compressor shaft
[0069] R is the radial direction relative to A
[0070] F R1 、F R2 Radial force of radial bearing
[0071] F L1 、F L2 Radial Forces in Axial Air Bearings
[0072] F V Radial force of compressor
[0073] F axial Axial force
[0074] L Air flow
[0075] L1, L2, L3, L R Axial spacing
Claims
1. A compressor (1) for a fuel cell system (100), in particular a compressor for a fuel cell system (100) for a commercial vehicle (300), the compressor comprising a compressor housing (3), a compressor wheel (11), a rotationally driven compressor shaft (5) operatively connected to the compressor wheel (11), and a bearing assembly (7) for supporting the compressor shaft (5) in the compressor housing (3) in a manner rotatable about a rotation axis (A), wherein: The support assembly (7) has an axial air bearing (7c) for bearing the axial force (F) between the compressor housing (3) and the compressor shaft (5). axial ), The invention is characterized in that the axial air bearing (7c) is a first axial air bearing, and the support assembly (7) further comprises a second axial air bearing (7d), which is arranged to be axially spaced apart from the first axial air bearing (7c) and is configured to bear an axial force (F) between the compressor housing (3) and the compressor shaft (5). axial ).
2. The compressor (1) according to claim 1, It is characterized in that The compressor (1) is a single-stage compressor (1), wherein the compressor wheel (11) is arranged at a first end section (9) of the compressor shaft (5), and wherein the second axial air bearing (7d) is arranged at a second end section (15) of the compressor shaft (5) facing away from the first end section (9).
3. The compressor (1) according to claim 1 or 2, It is characterized in that The support assembly (7) has a radial support assembly (8).
4. The compressor (1) according to claim 3, in, The radial support assembly (8) is arranged between the first axial air bearing and the second axial air bearing (7d).
5. A compressor (1) according to any one of the preceding claims, It is characterized in that The first axial air bearing (7c) has a first working disk (17) which is configured to operate in a first air gap (21), and the second axial air bearing (7d) has a second working disk (23) which is configured to operate in a second air gap (27).
6. The compressor (1) according to claim 5, in, The first working disk (17) is dimensioned to be larger than the second working disk (23) in a radial direction (R).
7. A compressor (1) according to any one of the preceding claims, in, The radial support assembly (8) comprises a first radial bearing (7a) and a second radial bearing (7b), wherein the first radial bearing is arranged to have a first axial spacing (L1) with the first axial air bearing (7c), and the second radial bearing is arranged to have a certain spacing (L2) with the first radial bearing (7a). R ) and has a second axial spacing (L2) with the second axial air bearing (7d), wherein the second axial spacing (L2) and the first axial spacing (L1) are different.
8. The compressor (1) according to claim 7, in, The first radial force (F L1 ) is applied from the first working disk (17) to the radial support assembly (8), and a second radial force (F L2 ) is applied from the second working disk (23) to the radial support assembly (8), and a third radial force (F V ) is applied to the radial bearing assembly (7) from the compressor wheel (11) arranged at a third axial distance (L3) from the first or second radial bearing (7a, 7b).
9. The compressor (1) according to claim 8, in, By radial force (F L1 、F L2 、F V ) and spacing (L1, L2, L3, L R ) respectively result in a tilting moment which acts on the bearing assembly (7) via the compressor shaft (5), wherein the first, second and third distances (L1, L2, L3) are dimensioned such that the resulting tilting moments partially or completely cancel each other out.
10. The compressor (1) according to claim 8 or 9, in, The first, second and third distances (L1, L2, L3) are dimensioned so that radial forces (F R1 、F R2 ) act respectively on the radial bearings (7a, 7b) of the support assembly (7).
11. The compressor (1) according to any one of claims 5 to 10, in, The first air gap (21) and the second air gap (27) are determined to have different sizes in the direction of the rotation axis (A).
12. A compressor (1) according to any one of the preceding claims, in, The first axial air bearing (7c) and / or the second axial air bearing (7d) are configured as foil bearings.
13. A compressor according to any one of the preceding claims, in, One of the axial air bearings (7c, 7d), preferably the first axial air bearing (7c), is configured as a spiral groove bearing, while the other of the axial air bearings (7c, 7d), preferably the second axial air bearing (7d), is configured as a foil bearing.
14. A fuel cell system (100) for driving a vehicle (300), in particular a commercial vehicle, comprising a compressor (1) for supplying air to a fuel cell (101) on the cathode side, It is characterized in that The compressor ( 1 ) is designed according to any of the preceding claims.