Electric high-speed gas flow pump arrangement

Abstract

The invention refers to an electric high-speed gas flow pump arrangement (100) with an electric motor (110) driving a flow pump rotor (80), comprising a motor housing body (40) supporting a first rolling bearing (31), and a bearing shield body (50) supporting a second rolling bearing (30), wherein a rotor shaft (39) co-rotatably supporting a motor rotor (74) and the flow pump rotor (80) is rotatably supported by the two rolling bearings (30, 31), wherein the motor housing body (40) and the bearing shield body (50) are co-axially directly assembled to each other by a cylindrical press-fitted connection (10) defined by an outside cylindrical friction surface (12) and an inside cylindrical friction surface (11), and wherein a separate circular fluid sealing arrangement (20) comprising an elastic sealing ring (59) is provided axially adjacent to the cylindrical press-fitted connection (10).

Description

[0001] Electric high-speed gas flow pump arrangement

[0002] The invention refers to an electric high-speed gas flow pump arrangement with an electric pump motor driving a flow pump rotor. In particular, the invention refers to an electric hydrogen pump arrangement for pumping hydrogen, for example as a recirculation pump in a hydrogen fuel cell circuit.

[0003] A gas flow pump is generally suitable to pump relatively high volumes of gas and is driven at high rotational speed to provide sufficient outlet pressure. Therefore, the electric gas flow pump arrangement is driven with rotational speeds of far above 10,000 rpm so that the motor shaft co- rotatably supporting the motor rotor and the pump rotor is supported by rolling bearings, not by friction bearings.

[0004] In automotive truck applications, the typical required lifetime of a recirculation gas flow pump is 40,000 hours so that the mechanical wearing of the electric high-speed gas flow pump arrangement must be reduced to a minimum. The rolling bearings are the most sensible mechanical part due to the high rotational speed.

[0005] It is an object of the invention to provide an electric high-speed gas flow pump with high long-term durability.

[0006] This object is solved with an electric high-speed gas flow pump with the features of claim 1. The electric high-speed gas flow pump arrangement according to the invention is provided with an electric motor directly driving a flow pump rotor with a rotational speed of above 10,000 rotations per minute (rpm). The gas flow pump arrangement comprises a motor housing body surrounding the electric motor and supporting a first rolling bearing, and comprises a separate bearing shield body directly or indirectly supporting a second rolling bearing. The two rolling bearings rotatably support a rotor shaft which co-rotatably supports a motor rotor of the electric motor and co-rotatably supports the flow pump rotor.

[0007] The motor housing body and the bearing shield body are coaxially directly assembled to each other by a cylindrical press-fitted connection at the circumferential portions of the bearing shield body and the motor housing body. The cylindrical press-fitted connection is defined by an outside cylindrical friction surface and an inside cylindrical friction surface, both of which define a force-fit axial connection of the motor housing body and the bearing shield body. The diameter difference of the cylindrical friction surface in the non-assembled state of the bearing shield body and the motor housing body is at least 0.1 mm, and preferably is at least 0.2 mm.

[0008] The cylindrical press-fitted connection of the bearing shield body and the motor housing body has primarily the function of perfectly axially aligning the first rolling bearing with the second rolling bearing so that the misalignment of the two rolling bearings with respect to each other is less than 0.5°. The low misalignment of the rolling bearings results in very low misalignment-caused friction losses in the rolling bearings so that the wear of the rolling bearings is reduced to a minimum. As a result, the electric high speed gas flow pump arrangement has a very good long-term durability. Generally, the outside cylindrical friction surface can be provided at the motor housing body or at the bearing shield body whereas the inside cylindrical friction surface can be provided at the bearing shield body or at the motor housing body. Preferably, the outside cylindrical friction surface is provided at the bearing shield body, whereas the inside cylindrical friction surface is provided at the motor housing body.

[0009] A separate circular fluid sealing arrangement comprising an elastic and compressed sealing ring is provided axially adjacent to the cylindrical press-fitted connection. The circular fluid sealing arrangement provides an additional fluid sealing and protection of the cylindrical press-fitted connection against any ingress of the fluid housed inside the motor housing body so that the outside cylindrical friction surface and the inside cylindrical friction surface are not exposed to any fluid housed by the motor housing body which fluid could affect the friction surfaces and thereby could cause a misalignment of the two rolling bearings with respect to each other. Additionally, any crevice corrosion of the cylindrical press-fitted connection caused by that fluid is avoided.

[0010] The circular fluid sealing arrangement preferably is arranged axially between the motor housing body interior and the cylindrical press-fitted connection.

[0011] The fluid sealing arrangement is provided adjacent to the cylindrical press- fitted connection which means that the press-fitted connection and the fluid sealing arrangement are provided somehow next to each other but not necessarily directly adjacent to each other. Preferably, the axial distance between the press-fitted connection and the fluid sealing arrangement is less than 15 mm, more preferably less than 12 mm. Preferably, the motor housing body defines a cooling liquid ring chamber which is axially closed by an axial bearing shield body section that also defines one cylindrical friction surface. This axial bearing shield body section therefore has three functions, i.e. defining one side of the cylindrical press-fitted connection, defining one side of the circular fluid sealing arrangement and defining a ring-shaped closing means for closing the cooling liquid ring chamber of the motor housing body. The cooling liquid ring chamber allows to constantly cool the complete pump arrangement so that the rolling bearings, the electromagnetic motor stator and the motor electronics are constantly cooled down to an acceptable temperature. As a result, the lifetime of the rolling bearings is potentially increased.

[0012] Preferably, the circular fluid sealing arrangement is provided with a circular ring groove provided adjacent to one of the cylindrical friction surfaces, whereas the compressed elastic sealing ring is seated in the circular ring groove. A ring chamfer is provided adjacent to the other cylindrical friction surface having a chamfer angle of less than 30° with respect to the cylindrical friction surfaces. The ring chamfer facilitates the assembly of the motor housing body with the bearing shield body and in particular avoids a jamming and a uncontrolled deformation of the elastic sealing ring during the axial assembly movement. Preferably, the sealing ring is additionally provided with a non-frictional coating which additionally reduces the likelihood of jamming of the elastic sealing ring during the axial assembly movement of the motor housing body and the bearing shield body.

[0013] Preferably, the specific surface roughness of both cylindrical friction surfaces of the press-fitted connection is below Rz=70, and preferably is below Rz=25. The low roughness of the cylindrical friction surfaces allows a relatively smooth and easy axial assembly of the bearing shield body and the motor housing body, and additionally causes a very high alignment precision.

[0014] Preferably the pump rotor is provided with numerous side channel pump blades rotating in a side channel. The pump part of the gas flow pump arrangement defines a side channel pump which is a flow pump type allowing relatively high volumetric pump rates and also allows to provide high gas outlet pressures which are necessary in the hydrogen circuit of a fuel cell arrangement. Preferably, the bearing shield body defines a side channel cavity in which the side channel pump blades of the pump rotor rotate.

[0015] Preferably, the bearing shield body is made of a hydrogen-resistive metal, for example is made of a ductile titan alloy.

[0016] Preferably, the electric motor is provided with electromagnetic motor stator coils and with a motor electronics comprising high-voltage semiconductors for driving the electromagnetic motor stator coils. The electric high-speed gas flow pump arrangement preferably is a hydrogen recirculation pump which has a performance of at least several kW so that it is advantageous to drive the electric motor with a high-voltage above 60V. Since the standard system voltage of automotive traction batteries is 400 V or 800 V, it is advantageous to use the high system voltage of an automotive device to directly energize the electric high-speed gas flow pump arrangement used as a hydrogen recirculation pump.

[0017] One embodiment of the invention is explained with reference to the enclosed drawings, wherein figure 1 shows a schematic longitudinal section of an electric high-speed gas flow pump arrangement with a motor housing body and a bearing shield body being fixed to and axially aligned with each other by a cylindrical press-fitted connection, and figure 2 is an enlarged view II of the cylindrical press-fitted connection of figure 1.

[0018] Figure 1 schematically shows a longitudinal section of an electric highspeed gas flow pump arrangement 100 which is used as a hydrogen recirculation pump in a hydrogen fuel cell circuit of an automotive device having a system voltage of 400 V. The gas flow pump arrangement 100 is provided with an electric motor 110 directly and coaxially driving a rotor 38, which rotor 38 comprises a rotor shaft 39 co-rotatably supporting a flow pump rotor 80 and a permanently magnetized motor rotor 74. The rotor 38 including the rotor shaft 39 rotates around a longitudinal rotation axis A. The gas flow pump arrangement 100 is configured to rotate with a nominal maximum rotation speed of up to 40,000 rpm.

[0019] The electric motor 110 comprises an electromagnetic motor stator 76 with numerous electromagnetic stator coils 77 surrounding the motor rotor 74. The motor stator 76 and the motor rotor 74 are fluid ically separated from each other by a cylindrical separation can 72.

[0020] The gas flow pump arrangement 100 comprises a complex motor housing body 40 directly supporting a first rolling bearing 31 and comprises a separate bearing shield 70 being defined by a bearing shield section 50 and a bearing support section 60, whereas the bearing support section 60 directly supports a second rolling bearing 30. The rolling bearings 30, 31 have a nominal axial distance a3 to each other of 60 mm. Every rolling bearing 30, 31 comprises an outside bearing ring 34, an inside bearing ring 33 and several bearing balls 32. Three of the four bearing rings 33, 34 are fixed by press-fit connections PC at corresponding cylindrical surfaces of the motor housing body 40 and of the rotor shaft 39, and one of the bearing rings 34 is supported with a axially loose connection LC at the corresponding cylindrical surface 64 of a ring-like portion 62 of the separate bearing support body 60.

[0021] The gas flow pump arrangement 100 also comprises a pumping chamber cover 90 defining a first side channel 85 and comprises an electronics chamber cover 92 defining a fluidically closed electronics chamber 96 housing a high-voltage motor electronics 94. The high-voltage motor electronics 94 comprises several high-voltage semiconductors 95 for electrically driving the motor stator coils 77. A second side channel 84 is defined by a distal portion of the bearing shield body 50. The flow pump rotor 80 is provided with two rings of side channel pump blades 82 rotating within the side channels 84, 85 thereby defining a pump device of the side channel type.

[0022] As shown in figure 1, the motor housing body 40 is provided with a substantially cylindrical housing wall 49 and with a substantially parallel cylindrical cooling chamber wall 48 provided radially proximally of the cylindrical housing wall 49. The cylindrical housing wall 49 and the cylindrical cooling chamber wall 48 together define a cylindrical cooling liquid ring chamber 46 which is axially closed by an axial bearing shield body section 51 which is substantially hollow-cylindrical in shape. The liquid ring chamber 46 is filled with a circulating cooling liquid 46' when the gas flow pump arrangement 100 is active. The motor housing body 40 and the bearing shield body 50 are co-axially directly assembled to each other by a cylindrical press-fitted connection 10 which is shown in greater detail in figure 2. Basically, the cylindrical press-fitted connection 10 is defined by an outside cylindrical friction surface 12 of the cylindrical housing wall 49 and an inside cylindrical friction surface 11 of the cylindrical axial bearing shield body section 51. The inner diameter rll of the inside cylindrical surface 11 is at least 0.1 mm smaller than the outer diameter rl2 of the outside cylindrical friction surface 12 in the disassembled state of the bearing shield body and the motor housing body. Both cylindrical friction surfaces 11, 12 have a specific surface roughness of Rz=20 or less.

[0023] A separate circular fluid sealing arrangement 20 is provided axially adjacent to the cylindrical press-fitted connection 10 and axially between the cylindrical press-fitted connection 10 and the cooling liquid ring chamber 46. The circular fluid sealing arrangement 20 is defined by a circumferential ring groove 16 at the outside surface of the axial bearing shield body section 51, by an elastic sealing ring 59 which is provided with a non-frictional coating 24 and which is provided in the circumferential ring groove 16, and by the cylindrical inside surface 43 being parallel to the inside cylindrical friction surface 11. The axial bearing shield body section 51 has a ring-like front surface 56 lying in a radial plane, which front surface 56 is in axial contact with a corresponding and parallel ringstage-defining surface 44 of the cylindrical housing wall 49.

[0024] The front end surface 42 of the cylindrical housing wall 49 is in contact with a corresponding ring surface 53 of a ring extension 52 of the axial bearing shield body section 51. The cylindrical housing wall 49 is provided with a ring chamfer 14 adjacent to the inside cylindrical friction surface 11. The ring chamfer 14 has a chamfer angle a of 25° with respect to the cylindrical friction surfaces 11, 12. Another elastic sealing ring 26 is provided between an inner surface 22 of the axial bearing shield body section 51 and an outer surface 28 of the cylindrical cooling chamber wall 48 to fluidically seal the cooling liquid ring chamber 46.

Claims

CLAIMS1. An electric high-speed gas flow pump arrangement (100) with an electric motor (110) driving a flow pump rotor (80), comprising a motor housing body (40) supporting a first rolling bearing (31), and a bearing shield body (50) supporting a second rolling bearing (30), wherein a rotor shaft (39) co-rotatably supporting a motor rotor (74) and the flow pump rotor (80) is rotatably supported by the two rolling bearings (30, 31), wherein the motor housing body (40) and the bearing shield body (50) are co-axially directly assembled to each other by a cylindrical press-fitted connection (10) defined by an outside cylindrical friction surface (12) and an inside cylindrical friction surface (11), and wherein a separate circular fluid sealing arrangement (20) comprising an elastic sealing ring (59) is provided axially adjacent to the cylindrical press-fitted connection (10).

2. The electric high-speed gas flow pump arrangement (100) of claim 1, wherein the motor housing body (40) defines a cooling liquid ring chamber (46) which is axially closed by an axial bearing shield body section (51) that also defines one cylindrical friction surface (12).

3. The electric high-speed gas flow pump arrangement (100) of one of the preceding claims, wherein the circular fluid sealing arrangement (20) is provided with a circular ring groove (16) located adjacent to one of the cylindrical friction surfaces (12), whereas a ring chamfer (14) is provided adjacent to the other cylindrical friction surface(11), the ring chamfer (14) having a chamfer angle (a) of less than 30° with respect to the cylindrical friction surfaces (11, 12).

4. The electric high-speed gas flow pump arrangement (100) of claim 1, wherein the sealing ring (59) is provided with a non-frictional coating (24).

5. The electric high-speed gas flow pump arrangement (100) of one of the preceding claims, wherein the specific surface roughness Rz of both cylindrical friction surfaces (11, 12) of the press-fitted connection (10) is below 70, and is preferably below 25.

6. The electric high-speed gas flow pump arrangement (100) of one of the preceding claims, wherein the flow pump rotor (80) is provided with side channel pump blades (82) rotating within a side channel (84, 85).

7. The electric high-speed gas flow pump arrangement (100) of one of the preceding claims, wherein the bearing shield body (50) defines the side channel (84).

8. The electric high-speed gas flow pump arrangement (100) of one of the preceding claims, wherein the bearing shield body (50) is made of a hydrogen-resistive metal.

9. The electric high-speed gas flow pump arrangement (100) of one of the preceding claims, wherein the electric motor (110) is provided with motor stator coils (77) and with a motor electronics (94)comprising high-voltage semiconductors (95) for driving the motor stator coils (77).

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