Fluid pump and fuel cell system

Abstract

The invention relates to a fluid pump (9) for pumping a coolant (6) for a fuel cell system (1), comprising a pump unit (13) for pumping the coolant (6) and a motor unit (14) for driving the pump unit (13). The pump unit (13) has a pump housing (15) and an impeller (16) for driving the coolant (6). The motor unit (14) has a metallic motor housing (20) and an electric motor (22) for driving the impeller (16). The electric motor (22) has a rotor shaft (25) which is non-rotatably connected to the impeller (16).The safe operation of the fuel cell system (1), in particular the isolation of the high-voltage voltage from the vehicle chassis, can be improved by the pump housing (15) comprising a pump housing base (27) which has a pump housing opening (29) on an axial side facing the motor housing (20), and a pump housing cover (28) which rests axially against both the motor housing (20) and the pump housing base (27) and closes the pump housing opening (29), wherein the pump housing base (27) and the pump housing cover (28) are made of an electrically insulating material. Furthermore, the rotor shaft (25) is designed in multiple parts and comprises a metallic bearing shaft section (30) rotatably mounted on the motor housing (20) and a drive shaft section (31) made of an electrically insulating material, which is rotationally fixed to the bearing shaft section (30) and to the impeller (16).

Description

[0001] The present invention relates to a fluid pump for conveying a coolant for a fuel cell system, according to the preamble of claim 1. The invention further relates to a fuel cell system equipped with such a fluid pump.

[0002] In a fuel cell system, particularly in a vehicle application, a cooling circuit can be used to cool a fuel cell stack. Such a fuel cell stack comprises several fuel cells, each of which has an electrolyte plate or bipolar plate that separates an anode from a cathode within the respective fuel cell. The cooling system can be configured so that a liquid coolant circulating in the cooling circuit is in direct contact with the bipolar plates, which form one electrical pole of the fuel cell stack. Even though a high-resistance coolant is typically used, the coolant creates an electrically conductive connection between the bipolar plates of the fuel cell stack and a fluid pump that circulates the coolant within the cooling circuit.For reasons of strength, a high-performance fluid pump has a metallic housing that can be touched by a person, especially in vehicle applications of fuel cell systems. In high-voltage applications, i.e., applications with AC voltages above 30 V up to 1 kV or with DC voltages above 60 V up to 1.5 kV, accessible components must be electrically connected to a potential equalization conductor to ensure protection against electric shock. An insulation monitoring device, or insulation monitor, continuously monitors the insulation resistance of the high-voltage system and generates an error message as soon as the monitored electrical resistance is no longer high and falls below a threshold, for example, 500 ohms / volt. However, the thresholds can deviate significantly from this value in individual cases based on specific requirements of the vehicle manufacturer, and can be considerably higher.If the value of 500 ohms / volt applies to the entire vehicle, a single component might, for example, have a limiting resistance of 50 megaohms at a test voltage of 1000 volts. Monitoring the high-voltage system with such an insulation monitor ensures the necessary protection against electric shock.

[0003] If a compact design is required for the fuel cell system, the fluid pump is located relatively close to the fuel cell stack, allowing the coolant lines of the cooling circuit to be comparatively short. It has been observed that, despite the use of a low-resistance or poorly conductive coolant, the relatively large cross-sections used in the coolant lines can cause the electrical resistance between the fuel cell stack and the fluid pump to drop so low during operation that the insulation resistance sensor is triggered and generates an error message, thus compromising touch protection. This problem is exacerbated if multiple fuel cell stacks are connected in parallel or series within the system, as the electrical resistance of the parallel coolant circuits is correspondingly reduced in this case.

[0004] A fluid pump of this type is known, for example, from DE 10 2022 206 143 A1 and comprises a pump unit for conveying the coolant and a motor unit for driving the pump unit. The pump unit has a pump housing and an impeller for driving the coolant. The pump housing contains an impeller chamber and has a coolant inlet and a coolant outlet connected fluidically to the impeller chamber. The impeller is rotatably arranged in the impeller chamber about an axis of rotation. The rotating impeller draws in the coolant at the coolant inlet and expels it at the coolant outlet. The motor unit has a metallic motor housing that is rigidly connected to the pump housing and contains a motor chamber. The motor unit also has an electric motor arranged in the motor chamber for driving the impeller.The electric motor has a rotor with a rotor shaft, the rotor shaft being rotatably mounted on the motor housing about the axis of rotation, extending axially through a rotary seal into the impeller chamber, and being rotationally fixed to the impeller there. In the known fluid pump, the rotor shaft is a one-piece metallic component. In the known fluid pump, the rotary seal is located on an end face of the motor housing axially facing the pump housing. The pump housing has an open side on an axial side facing the module unit, which is closed in the assembled state by the axial end face of the motor housing. In the known fluid pump, the motor housing contains a cooling channel system through which a coolant can flow and which serves to cool the motor unit.In the known fluid pump, this cooling channel system of the motor unit is fluidically connected to the pump housing on the inlet side in the area of ​​a pressure side of the impeller and fluidically connected to the pump housing on the outlet side in the area of ​​a suction side of the impeller. This allows the coolant driven by the fluid pump to be used simultaneously for cooling the motor unit.

[0005] Other fluid pumps of this type are known, for example, from DE 10 2022 206 140 A1, from DE 10 2022 206 141 A1 and from DE 10 2023 200 129 A1.

[0006] The present invention addresses the problem of providing an improved or at least a different embodiment for a fluid pump of the type described above or for a fuel cell system equipped therewith, which is characterized in particular by improved contact protection.

[0007] According to the invention, this problem is solved by the subject matter of the independent claim. Advantageous embodiments are the subject matter of the dependent claims.

[0008] The invention is based on the general concept of manufacturing the pump housing from an electrically insulating material, so that the coolant, from the coolant inlet to the coolant outlet, is in contact exclusively with electrically insulating components of the pump housing. This provides touch protection for the fluid pump in the area of ​​the pump housing and prevents high voltage from coming into contact with the vehicle chassis. The fundamental principle is therefore that all components in contact with the coolant are sufficiently insulated from components that are accessible or connected to an equipotential bonding system.

[0009] Furthermore, the invention proposes electrically insulating or galvanically isolating the metallic motor housing from the pump housing. To this end, it is proposed that the rotor shaft, at least in the area exposed to the coolant where the impeller is located, be manufactured from an electrically insulating material, thus electrically isolating this area of ​​the rotor shaft. Consequently, an electrical voltage carried by the coolant can no longer be transmitted to the motor housing via the rotor shaft. In this way, contact protection can also be achieved for the motor housing, even if the motor housing is still made of a metallic material, such as aluminum or an aluminum alloy.In an uncooled motor housing, there is no fluidic coupling with the coolant pumped in the pump housing, so the metallic pump housing is not in contact with the coolant. Therefore, despite the transport of electrical voltage in the coolant, the motor housing remains highly resistive and can be touched.

[0010] Specifically, the invention proposes that the pump housing comprises a pump housing base with coolant inlet and coolant outlet, and a pump housing cover. The pump housing base has a pump housing opening on an axial side facing the motor housing, through which, for example, the impeller can be inserted into the impeller chamber. The pump housing cover rests axially against both the motor housing and the pump housing base and closes the pump housing opening. In other words, in the fluid pump according to the invention, the pump housing opening is not closed by the axial end face of the electrically conductive motor housing, but by the pump housing cover. The invention also provides that the pump housing base and the pump housing cover are each made of an electrically insulating material. Plastics are preferably used for this purpose.In particular, this can be polyphenylene sulfide, or PPS for short, and / or fiber-reinforced plastics, especially glass fiber-reinforced plastics. Glass fiber-reinforced PPS, especially PPS-GF40, is particularly suitable. It is advantageous for the pump housing body and the pump housing cover to be made of the same material, but this is not mandatory.

[0011] In the fluid pump according to the invention, the rotor shaft is designed in multiple parts, comprising a metallic bearing shaft section and an electrically insulating drive shaft section. The bearing shaft section is rotatably mounted on the motor housing about the axis of rotation. The drive shaft section consists of an electrically insulating material, for example, a ceramic or a plastic. The drive shaft section extends axially through a through-opening formed in the pump housing cover into the impeller chamber and is rotationally fixed to the bearing shaft section on one side and to the impeller on the other.

[0012] According to an advantageous embodiment, the rotary seal can be arranged in or on the through-opening in the pump housing cover and axially spaced from the motor housing. Rotary seals with high sealing performance can contain metallic components. Furthermore, leakage is virtually unavoidable with rotary seals. By arranging the rotary seal on the pump housing cover and by spacing the rotary seal from the metallic motor housing, electrical contact between the rotary seal, which is exposed to the coolant in or on the impeller chamber, and the metallic motor housing can be prevented. In particular, the drive shaft section and the bearing shaft section can be designed to ensure that the rotary seal maintains a safe axial clearance from the bearing shaft section.With the aid of such an axial safety distance, for example, a creepage distance for electrical voltages and / or currents, which depends on the expected electrical voltage, can be increased to such an extent that an unwanted voltage transmission from the rotary seal along the drive shaft part to the electrically conductive bearing shaft part can be prevented.

[0013] In another advantageous embodiment, the coolant pumped by the fluid pump constitutes a primary coolant, and a cooling channel system is provided on and / or in the engine housing, through which a secondary coolant can flow. The cooling channel system can have several cooling channels in the engine housing through which the secondary coolant can flow, and at least two coolant connections on the engine housing, fluidically connected to the cooling channels, for supplying and discharging the secondary coolant. Furthermore, the cooling channel system is configured such that the fluid pump can be traversed by the primary and secondary coolants in a fluid-separated manner. In other words, the primary coolant pumped by the pump unit and flowing through the pump housing is fluidically separated from the secondary coolant, which cools the engine unit, within the fluid pump.In this way, the transfer of electrical voltage from the primary coolant to the secondary coolant can also be prevented. In principle, the primary and secondary coolants can be fluids of the same composition. Preferably, however, they can be different fluids. For example, the primary coolant is a high-resistance or poorly conductive coolant, exhibiting, for instance, an electrical conductivity of no more than 20 µS / cm, preferably no more than 10 µS / cm, while the secondary coolant can be a conventional coolant, which may be more or less electrically conductive.

[0014] In the present context, a “configuration” is synonymous with a “design” and / or “setup”, so that the phrase “configured so that” is synonymous with the phrase “designed so that” and / or “set up so that”.

[0015] According to an advantageous embodiment, the pump housing base can be axially attached to the motor housing by means of a mounting zone that circumferentially surrounds the pump housing base in a closed manner around the axis of rotation. The pump housing cover can extend radially into the mounting zone and be axially clamped there between the pump housing base and the motor housing. For example, several screw connections distributed circumferentially can be formed in the mounting zone, with one screw of each connection penetrating the pump housing cover, for example, through a through-hole formed at the edge of the pump housing cover. This eliminates the need for separate screw connections of the pump housing cover to the pump housing base and / or the motor housing.

[0016] According to an advantageous embodiment, the mounting zone can be sealed off from the impeller chamber. The seal is achieved in such a way that the coolant flowing through the pump housing base cannot penetrate into the area of ​​the fixing mechanism that secures the pump housing base to the engine housing within the mounting zone. This seal is achieved, in particular, by means of a circumferentially continuous gasket between the pump housing cover and the pump housing base. This allows the use of metal screws for creating bolted connections, which can be used to fix the pump housing base to the engine housing within the mounting zone.

[0017] According to an advantageous embodiment, a leakage collection chamber can be provided axially between the pump housing and the motor housing to collect any leakage of the coolant pumped by the fluid pump that penetrates the rotary seal. The leakage collection chamber is bounded by the pump housing cover and by an axial end face of the motor housing facing the pump housing. Furthermore, at least one fluid connection can be provided on the pump housing cover and / or the motor housing, fluidically connecting the leakage collection chamber to the fluid pump's surroundings. Coolant that reaches the leakage collection chamber through the rotary seal during operation of the fluid pump can evaporate due to the temperatures prevailing in the leakage collection chamber during operation and escape into the surroundings as vapor or gas through the fluid connection.The respective fluid connection can be configured as a labyrinth, for example to prevent dirt from the environment from entering the leakage collection chamber.

[0018] According to an advantageous embodiment, the leakage collection chamber can be enclosed circumferentially by the mounting zone. This allows the leakage collection chamber to extend radially to the mounting zone, thus providing a comparatively large volume, so that leakage within the collection chamber can spread over a large area and evaporate easily.

[0019] According to an advantageous embodiment, the coolant inlet can be arranged axially and concentrically to the axis of rotation, while the coolant outlet is arranged tangentially to the axis of rotation. In particular, the pump housing body can be designed as a volute and thus have a helical or spiral configuration. Such a configuration is characterized by high flow rate and efficiency.

[0020] According to another advantageous embodiment, the bearing shaft section can be mounted on the motor housing by means of a front bearing facing axially towards the pump housing and a rear bearing facing axially away from the pump housing. Mounting the bearing shaft section on two axially spaced bearings results in a particularly stable mounting for the rotor of the electric motor. In particular, the front bearing can be larger and therefore more stable and designed for higher forces, so that the front bearing essentially acts as a main bearing.

[0021] According to an advantageous embodiment, the motor housing may have a circumferentially closed metallic housing shell, a metallic front motor housing cover facing axially towards the pump housing, and a metallic rear motor housing cover facing axially away from the pump housing. The housing shell has a front motor housing opening facing axially towards the pump housing and a rear motor housing opening facing axially away from the pump housing. The front motor housing cover closes the front motor housing opening. The rear motor housing cover closes the rear motor housing opening. The housing shell being open on both sides axially simplifies the assembly of the motor unit.

[0022] A particularly advantageous configuration is one in which the front bearing is located on the front engine casing cover, while the rear bearing is located on the rear engine casing cover. This simplifies the assembly of the engine unit.

[0023] According to an advantageous embodiment, the fluid pump can also have a metallic electronics housing in which electronics for operating the electric motor are arranged. The electronics can, for example, include a control unit and / or power electronics, in particular an inverter. The electronics housing can be rigidly connected to the motor housing on a side facing axially away from the pump housing. Since the motor housing is electrically insulated from the coolant, the electronics housing is also electrically insulated from the coolant and automatically provides sufficient protection against accidental contact. According to an advantageous embodiment, the electronics housing can have at least one cooling channel that is fluidically connected to the cooling channel system of the motor housing. This allows the electronics to be efficiently cooled using the secondary coolant.

[0024] A fuel cell system according to the invention, which is particularly suitable for use in a motor vehicle, comprises a fuel cell stack having several fuel cells, a primary cooling circuit for cooling the fuel cell stack and a fluid pump of the type described above, which is integrated into the primary cooling circuit by means of the coolant inlet and the coolant outlet and serves to pump the coolant in the primary cooling circuit.

[0025] According to an advantageous embodiment of the fuel cell system, the fluid pump can be configured such that the coolant pumped by the fluid pump forms a primary coolant, that a cooling channel system is formed on and / or in the engine housing through which a secondary coolant can flow, that the cooling channel system in the engine housing has several cooling channels through which the secondary coolant can flow, and at least two coolant connections on the engine housing fluidically connected to the cooling channels for supplying and discharging the secondary coolant, and that the cooling channel system is configured such that the fluid pump can be traversed by the primary coolant and the secondary coolant in a media-separated manner. Furthermore, in this embodiment, the fuel cell system can be provided with a circuit that is electrically or...The motor housing has a galvanically isolated secondary cooling circuit for cooling the motor casing, wherein the cooling channel system of the motor casing is integrated into the secondary cooling circuit via the coolant connections of the fluid pump. The secondary cooling circuit may, in particular, include a separate coolant pump for driving the secondary coolant within the secondary cooling circuit.

[0026] Further important features and advantages of the invention will become apparent from the dependent claims, the drawings and the associated description of the figures based on the drawings.

[0027] It is understood that the features mentioned above and those to be explained below can be used not only in the combinations specified, but also in other combinations or individually, without departing from the scope of the invention as defined by the claims. Components of a higher-level unit, such as a device, apparatus, or arrangement, mentioned above and those to be mentioned below, which are designated separately, can form separate parts or components of this unit or be integral areas or sections of this unit, even if this is depicted differently in the drawings.

[0028] Preferred embodiments of the invention are shown in the drawings and are explained in more detail in the following description, wherein identical reference numerals refer to identical or similar or functionally identical components.

[0029] They show, schematically, Fig. 1. A highly simplified, circuit diagram-like schematic representation of a fuel cell system, Fig. 2 an isometric sectional view of a fluid pump, Fig. 3 a half longitudinal section of the fluid pump, Fig. 4 an isometric view of the fluid pump, Fig. 5 an enlarged view of the fluid pump in an area V in Fig. 4, Fig. 6 an enlarged view of the fluid pump in area VI in Fig. 4.

[0030] Accordingly Fig. Figure 1 comprises a highly simplified fuel cell system 1, which can be used in a stationary or mobile application, such as in a motor vehicle, and includes at least one fuel cell stack 2, which has several fuel cells 3. Each fuel cell 3 contains a bipolar plate 4, which separates an anode side from a cathode side within the respective fuel cell 3 and forms an electrical pole within the fuel cell stack 2 during operation of the fuel cell system 1. The fuel cell system 1 also has a primary cooling circuit 5 for cooling the fuel cell stack 2. A coolant 6, which can also be referred to as the primary coolant 6, circulates in the primary cooling circuit 5. A distribution pipe 7 supplies the primary coolant 6 to the bipolar plates 4. A collecting pipe 8 carries the primary coolant 6 away from the bipolar plates 4.The primary cooling circuit 5 includes a fluid pump 9 configured to drive the primary coolant 6. The fuel cell system 1 is also equipped with a secondary cooling circuit 10, which contains a separate or additional coolant pump 11 with respect to the fluid pump 9. The coolant pump 11 drives a secondary coolant 12 that circulates in the secondary cooling circuit 10. The primary cooling circuit 5 may include a primary radiator 61 for dissipating heat from the primary coolant 6. The secondary cooling circuit 10 may include a secondary radiator 62 for dissipating heat from the secondary coolant 12. Heat dissipation 63 from the respective radiator 61, 62 into the surroundings of the fuel cell system 1 is indicated by an arrow.

[0031] The fluid pump 9 for pumping the coolant 6 or the primary coolant 6 is described below based on the Fig. 2, Fig. 3, Fig. 4 to Fig. 5 explained in more detail. The fluid pump 9 has a pump unit 13 for pumping the coolant 6 and a motor unit 14 for driving the pump unit 13. The pump unit 13 has a pump housing 15 and an impeller 16 for driving the coolant 6. The pump housing 15 contains an impeller chamber 17 and has a coolant inlet 18 fluidically connected to the impeller chamber 17 and a coolant outlet 19 fluidically connected to the impeller chamber 17. The impeller 16 is arranged in the impeller chamber 17 and is rotatable there about an axis of rotation R. This axis of rotation R defines an axial direction extending parallel to the axis of rotation, a radial direction that runs transversely to the axial direction and is perpendicular to the axis of rotation R, and a circumferential direction U that rotates around the axis of rotation R.

[0032] The motor unit 14 has a metallic motor housing 20, which is rigidly connected to the pump housing 15 and contains a motor compartment 21. The motor unit 14 also includes an electric motor 22 for driving the impeller 16. The electric motor 22 is located in the motor compartment 21. The electric motor 22 has a stator 23, which is rigidly connected to the motor housing 20, and a rotor 24, which is rotatably mounted about the axis of rotation R relative to the stator 23. The rotor 24 has a rotor shaft 25, which is rotatably mounted on the motor housing 20 about the axis of rotation R. The rotor shaft 25 extends axially through a rotary seal 26 and into the impeller compartment 17, where it is rotationally fixed to the impeller 16.

[0033] In the fluid pump 9 presented here, the pump housing 15 comprises a pump housing base 27 and a pump housing cover 28. The pump housing base 27 has the coolant inlet 18 and the coolant outlet 19. The pump housing base 27 is open on one axial side facing the motor housing 20 and is accordingly equipped with a pump housing opening 29 there. The pump housing cover 28 closes the pump housing opening 29 and, in the assembled state of the fluid pump 9, rests axially against the pump housing base 27 on one side and against the motor housing 20 on the other. The pump housing base 27 and the pump housing cover 28 are made of an electrically insulating material.

[0034] The rotor shaft 25 is designed in at least two parts, comprising a metallic bearing shaft section 30 and an electrically insulating drive shaft section 31. The bearing shaft section 30 is rotatably mounted on the motor housing 20 about the axis of rotation R. The drive shaft section 31 consists of an electrically insulating material and extends through a through-opening 32 formed in the pump housing cover 28 into the impeller chamber 17. The drive shaft section 31 is rotationally fixed to the bearing shaft section 30 on one side and to the impeller 16 on the other. The rotary seal 26 is designed according to the Fig. 2 and Fig. 3 is attached in the through-opening 32 on the pump housing cover 28, such that it is axially spaced from the motor housing 20. The rotary seal 26 can be positioned according to Fig. 3 to the bearing shaft section 30 must have an axial safety distance 33, which is selected to be greater than an electrical creepage distance that depends on the electrical voltage at the fuel cell stack 2 of the fuel cell system 1. The axial safety distance 33 must, in particular, be selected to ensure the required insulation resistance of the fluid pump 9.

[0035] In the preferred example of the fluid pump 9 shown here, a cooling channel system 34 is formed on or in the motor housing 20, through which a secondary coolant 12 can flow. This cooling channel system 34 has several cooling channels 35 in the motor housing 20 through which the secondary coolant 12 can flow, and at least two coolant connections 36 fluidically connected to the cooling channels 35, which serve to supply and discharge the secondary coolant 12. In the sectional views of the Fig. 2 and Fig. 3 shows only one inlet-side coolant connection 36 for supplying the secondary coolant 12. In Fig. 4 also shows an outlet-side coolant connection 36 for discharging the secondary coolant 12. The cooling channel system 34 is configured within the fluid pump 9 such that the fluid pump 9 can be supplied with fluids separated by the primary coolant 6 and the secondary coolant 12.

[0036] According to the Fig. 2, Fig. 3, Fig. 4 to Fig. In the embodiment shown here, the pump housing base 27 is axially attached to the motor housing 20 by means of a mounting zone 37. The mounting zone 37 extends circumferentially in the direction U. The pump housing cover 28 extends radially into this mounting zone 37 and is held there axially between the pump housing base 27 and the motor housing 20, preferably clamped. The attachment of the pump housing base 27 to the motor housing 20 by means of the mounting zone 37 can be effected, for example, by means of several screw connections 38, some of which are shown in the sectional views of the Fig. 2 and Fig. 3 only one is recognizable in each case, whereby the isometric view of the Fig. Figure 4 shows several such screw connections 38. A metallic screw 39 of each screw connection 38 penetrates the pump housing base 27 and the pump housing cover 28 in a through-opening and is screwed into a threaded opening formed on the motor housing 20. The fastening zone 37 is sealed against the impeller chamber 17. For this purpose, a circumferential seal 40 can be provided, which seals the pump housing cover 28 against the pump housing base 27. Another circumferential seal 41 can be formed between the pump housing cover 28 and the motor housing 20.

[0037] According to the Fig. 2 and Fig. 3. A leakage collection chamber 42 can be formed axially between the pump housing 15 and the motor housing 20, configured to receive any leakage of the coolant 6, i.e., the primary coolant 6, that penetrates the rotary seal 26. The leakage collection chamber 42 is bounded by the pump housing cover 28 and by an axial end face 43 of the motor housing 20 facing the pump housing 15. Within the leakage collection chamber 42, there is an axial distance between the pump housing 15 and the motor housing 20, thus providing a volume for collecting the leakage. According to the Fig. 4, Fig. 5 to Fig. 6. Several fluid connections 44 can be formed on the pump housing cover 28, fluidically connecting the leakage collection chamber 42 with the surroundings 45 of the fluid pump 9. Advantageously, several such fluid connections 44 are arranged distributed in the circumferential direction U. In particular, these fluid connections 44 can be configured as a labyrinth and / or covered with a cap (not shown here) to prevent the ingress of dirt from the surroundings 45 into the leakage collection chamber 42. At least one such fluid connection 44 can be arranged according to Fig. 5. The fluid connection 44 is positioned on the pump housing cover 28 and / or on the motor housing 20 such that, in the properly functioning or correctly installed state of the fluid pump 9, it is located relatively high up, so that the fluid connection 44 serves as a vent opening 64 through which, when the fluid pump 9 is functioning correctly, evaporated coolant 6 can escape into the environment 45. The vent opening 64 is shown in the example of the Fig. 5 exclusively on the pump housing cover 28. At least one such fluid connection 44 can be formed according to Fig. 6. The fluid connection 44 is positioned on the pump housing cover 28 and / or on the motor housing 20 such that, in the functional or properly installed state of the fluid pump 9, it is located laterally and / or at a mid-height, so that the fluid connection 44 serves as an overflow opening 65 through which, in the event of a malfunction, e.g., of the rotary seal 26, coolant 6, which enters the leakage collection chamber 42 through the rotary seal 26, can escape from the leakage collection chamber 42 into the surroundings 45. The overflow opening 65 is, in the example of the Fig. 6 exclusively on the pump housing cover 28.

[0038] In the example shown here, the leakage collection chamber 42 is formed by a corresponding shape of the pump housing cover 28. The leakage collection chamber 42 is enclosed by the mounting zone 37 in the circumferential direction U.

[0039] According to the Fig. 2, Fig. 3 to Fig. 4 The coolant inlet 18 is arranged axially and concentrically to the axis of rotation R. The coolant outlet 19, on the other hand, is arranged tangentially to the axis of rotation R. The pump housing body 27 is designed here as a volute and thus has a helical or spiral configuration, which in Fig. 4 is particularly easy to recognize.

[0040] According to the Fig. 2 and Fig. 3. The bearing shaft section 30 can be advantageously supported on the motor housing 20 by means of a front bearing 46 axially facing the pump housing 15 and by means of a rear bearing 47 axially facing away from the pump housing 15 and axially spaced from the front bearing 46. The front bearing 46 is significantly larger and more robustly dimensioned than the rear bearing 47. In the example shown here, the motor housing 20 has a circumferentially continuous metallic housing shell 48, which has a front mounting opening 49 facing the pump housing 15 and a rear mounting opening 50 axially facing away from the pump housing 15. The cooling channel system 34 can form a cooling jacket in this housing shell 48 through which the secondary coolant 12 flows.The motor housing 20 also has a metallic front motor housing cover 51 facing the pump housing 15, which closes the front mounting opening 49, and a metallic rear motor housing cover 52 facing axially away from the pump housing 15, which closes the rear mounting opening 50. The front bearing 46 is attached to the front motor housing cover 51, while the rear bearing 47 is attached to the rear motor housing cover 52. The front motor housing cover 51 can be removed according to... Fig. 3 be attached to the housing shell 48, e.g. by means of screws 59. Furthermore, the front motor housing cover 51 can be sealed against the housing shell 48 by means of a circumferential seal 60 that is closed in the circumferential direction U.

[0041] In the embodiment shown here, the fluid pump 9 also has a preferably metallic electronics housing 53 in which electronics 54 are arranged, configured to operate the electric motor 22. The electronics 54 can include power electronics, in particular an inverter. The electronics housing 53 is fixedly connected to the motor housing 20 on a side facing axially away from the pump housing 15. Thus, within the fluid pump 9, the motor housing 20 is located axially between the pump housing 15 and the electronics housing 53. According to the sectional views of the Fig. 2 and Fig. 3. The electronics housing 53 can have at least one cooling channel 55 which is fluidically connected to the cooling channel system 34 of the motor housing 20. The cooling channel 55 of the electronics housing 53 is advantageously arranged so that it can transfer heat to the secondary coolant 12, which is generated at or in the electronics 54 during the operation of the fluid pump 9.

[0042] According to Fig. 1 The fluid pump 9 presented here can be integrated into the primary cooling circuit 5 of the fuel cell system 1 by connecting the primary cooling circuit 5 to the coolant inlet 18 and the coolant outlet 19. Furthermore, the cooling channel system 34 of the motor unit 14 or the motor housing 20 is integrated into the secondary cooling circuit 10. For this purpose, the secondary cooling circuit 10 is connected to the two coolant connections 36 of the motor unit 14, which are located on the motor housing 20. According to Fig. 1. The metallic motor housing 20 is expediently electrically connected to a potential equalization bar 56, for example by means of a suitable electrical conductor 57. The electrical conductor 57 is electrically connected to a corresponding potential connection 58 on the motor housing 20. One possible position for such a potential connection 58 is shown in Fig. 4 recognizable. Reference symbol list 1 Fuel cell system 2 fuel cell stacks 3 Fuel cell 4 Bipolar plate 5 Primary cooling circuit 6 primary coolant 7 Distribution pipe 8 Collector pipe 9 Fluid pump 10 Secondary cooling circuit 11 Coolant pump 12 secondary coolant 13 Pump unit 14 Motor unit 15 pump housings 16 impellers 17 Impeller room 18 Coolant inlet 19 Coolant outlet 20 engine housings 21 Engine compartment 22 Electric motor 23 Stator 24 Rotor 25 Rotor shaft 26 Rotary seal 27 Pump housing base 28 Pump housing covers 29 Pump housing opening 30 Bearing shaft part 31 Drive shaft part 32 Passage opening 33 Safety distance 34 Cooling duct system 35 Cooling channel 36 Coolant connection 37 Mounting zone 38 screw connection 39 screw 40 Seal 41 Seal 42 Leakage collection chamber 43 Front 44 Fluid connection 45 surroundings 46 front bearing 47 rear camp 48 Housing shell 49 front case opening 50 rear case opening 51 front engine casing cover 52 rear engine casing cover 53 electronic housings 54 Electronics 55 Cooling channel 56 Potential equalization rail 57 electrical line 58 Potential connection 59 screw 60 Seal 61 primary radiator 62 secondary radiator 63 Heat dissipation 64 Vent opening 65 Overflow opening QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2022 206 143 A1

[0004] DE 10 2022 206 140 A1

[0005] DE 10 2022 206 141 A1

[0005] DE 10 2023 200 129 A1

[0005]

Claims

Fluid pump (9) for pumping a coolant (6) for a fuel cell system (1),- comprising a pump unit (13) for pumping the coolant (6),- comprising a motor unit (14) for driving the pump unit (13),- wherein the pump unit (13) comprises a pump housing (15) containing an impeller chamber (17) and having a coolant inlet (18) and a coolant outlet (19), and an impeller (16) for driving the coolant (6), which is rotatably arranged in the impeller chamber (17) about an axis of rotation (R),- wherein the motor unit (14) comprises a metallic motor housing (20) fixedly connected to the pump housing (15) and comprising a motor chamber (21), and an electric motor (22) arranged in the motor chamber (21) for driving the impeller (16),- wherein the electric motor (22) comprises a rotor (24) with a rotor shaft (25) which is connected to the Motor housing (20) is rotatably mounted about the axis of rotation (R),extending axially through a rotary seal (26) into the impeller chamber (17) and is rotationally fixed to the impeller (16), characterized in that: - the pump housing (15) has a pump housing base body (27) having the coolant inlet (18) and the coolant outlet (19), which has a pump housing opening (29) on an axial side facing the motor housing (20), and a pump housing cover (28) which abuts axially on the motor housing (20) and on the pump housing base body (27) respectively and closes the pump housing opening (29), - the pump housing base body (27) and the pump housing cover (28) are made of an electrically insulating material, - the rotor shaft (25) is designed in multiple parts and has a metallic bearing shaft part (30) which is rotatably mounted on the motor housing (20) about the axis of rotation (R), and a drive shaft part (31) which is made of an electrically insulating material consists,extends through a through-opening (32) formed in the pump housing cover (28) into the impeller chamber (17) and is rotationally fixed to the bearing shaft part (30) and to the impeller (16). Fluid pump (9) according to claim 1, characterized in that the rotary seal (26) is arranged in or on the through-opening (32) on the pump housing cover (28) and is axially spaced from the motor housing (20). Fluid pump (9) according to claim 2, characterized in that the rotary seal (26) has an axial safety distance (33) from the bearing shaft part (30). Fluid pump (9) according to one of the preceding claims, characterized in that: - the coolant pumped by the fluid pump (9) forms a primary coolant (6); - a cooling channel system (34) is formed on and / or in the motor housing (20) through which a secondary coolant (12) can flow; - the cooling channel system (34) in the motor housing (20) has several cooling channels (35) through which the secondary coolant (12) can flow, and at least two coolant connections (36) on the motor housing (20) which are fluidically connected to the cooling channels (35) for supplying and discharging the secondary coolant (12); - the cooling channel system (34) is configured such that the fluid pump (9) can be supplied with fluids separated from the primary coolant (6) and the secondary coolant (12). Fluid pump (9) according to one of the preceding claims, characterized in that the pump housing base body (27) is axially attached to the motor housing (20) by means of a circumferentially circumferentially circumferentially circumferentially (U) around the axis of rotation (R), and that the pump housing cover (28) extends radially into the fastening zone (37) and is axially clamped between the pump housing base body (27) and the motor housing (20). Fluid pump (9) according to claim 5, characterized in that the mounting zone (37) is sealed against the impeller chamber (17). Fluid pump (9) according to one of the preceding claims, characterized in that a leakage collection chamber (42) is formed axially between the pump housing (15) and the motor housing (20) for receiving a leakage of the coolant (6) pumped by the fluid pump (9) that penetrates the rotary seal (26), which is bounded by the pump housing cover (28) and by an axial end face (43) of the motor housing (20) facing the pump housing (15), that at least one fluid connection (44) is formed on the pump housing cover (28) and / or on the motor housing (20) which fluidically connects the leakage collection chamber (42) with an environment (45) of the fluid pump (9). Fluid pump (9) according to claim 7 and according to claim 5 or 6, characterized in that the leakage collection chamber (42) is enclosed by the mounting zone (37) in the circumferential direction (U). Fluid pump (9) according to one of the preceding claims, characterized in that the coolant inlet (18) is arranged axially and concentrically to the axis of rotation (R), and that the coolant outlet (19) is arranged tangentially to the axis of rotation (R). Fluid pump (9) according to one of the preceding claims, characterized in that the bearing shaft part (30) is mounted on the motor housing (20) by means of a front bearing (46) facing the pump housing (15) and a rear bearing (47) facing away from the pump housing (15). Fluid pump (9) according to one of the preceding claims, characterized in that the motor housing (20) has a circumferentially closed metallic housing shell (48) which has a front motor housing opening (49) facing the pump housing (15) and a rear motor housing opening (50) facing away from the pump housing (15), a metallic front motor housing cover (51) facing the pump housing (15) which closes the front motor housing opening (49), and a metallic rear motor housing cover (52) facing away from the pump housing (15) which closes the rear motor housing opening (50). Fluid pump (9) according to claims 10 and 11, characterized in that the front bearing (46) is arranged on the front motor housing cover (51), and that the rear bearing (47) is arranged on the rear motor housing cover (52). Fluid pump (9) according to one of the preceding claims, characterized in that the fluid pump (9) also has an electronics housing (53) in which an electronics unit (54) for operating the electric motor (22) is arranged, and that the electronics housing (53) is firmly connected to the motor housing (20) on a side axially away from the pump housing (15). Fuel cell system (1), in particular for a motor vehicle,- with a fuel cell stack (2) comprising several fuel cells (3),- with a primary cooling circuit (5) for cooling the fuel cell stack (2),- with a fluid pump (9) integrated into the primary cooling circuit (5) by means of the coolant inlet (18) and the coolant outlet (19) according to one of the preceding claims for pumping a coolant (6) in the primary cooling circuit (5). Fuel cell system (1) according to claim 14, characterized in that the fluid pump (9) is configured according to claim 4, the fuel cell system (1) has a secondary cooling circuit (10) for cooling the motor housing (20) that is separate from the primary cooling circuit (5), and the cooling channel system (34) is integrated into the secondary cooling circuit (10) by means of the coolant connections (36).

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