Electric motor device

Abstract

The invention refers to an electric motor device (10) with a rotatable motor rotor shaft (40) made of an electrically conducting metal and co-rotatably supporting a motor rotor (34) and with a shaft bearing arrangement (100) for rotatably supporting the motor rotor shaft (40) at a static bearing support ring (50) made of an electrically conducting metal, wherein a spiral spring conductor element (60) is provided in a ring gap (54) between the static bearing support ring (50) and the rotatable motor rotor shaft (40), and wherein a fixed spring conductor end (64) of the spiral spring conductor element (60) is fixed in an electrically conductive way to the static bearing support ring (50) and the spiral part (62) of the spiral spring conductor element (60) is radially inwardly pretensioned so that it is always in direct gliding contact with the outside shaft surface (40') of the rotatable motor rotor shaft (40) to thereby define a constant electric connection of the motor rotor shaft (40) and the shaft bearing arrangement (100).

Description

[0001] - 1 - PP.P.23010. WO / EB 26.11.2024

[0002] Electric motor device

[0003] The invention refers to an electric motor device with a rotatable rotor shaft made of an electrically conducting metal and co-rotatably supporting a motor rotor, preferably a permanently magnetized motor rotor without any a mechanical commutator arrangement.

[0004] In many mobile applications, the EMC requirements for an electric motor device are high and can be challenging, for example for an electric motor device driving a secondary device in an automobile or in an airplane.

[0005] The electric motor device is provided with a rotatable rotor shaft made of an electrically conducting metal. To avoid significant electric potential differences between the rotor shaft and other electrically conducting parts of the electric motor device, the rotor shaft must be directly or indirectly electrically connected to an electric ground potential. In many applications, the electric connection between the motor rotor shaft to an electric ground potential is provided by the bearing arrangement which rotatably supports the motor rotor shaft. If the electric motor device is part of an electric fluid pump, the electric ground connection of the motor rotor shaft can be provided by the pumping fluid if the pumping fluid is in contact with the motor rotor shaft and if the pumping fluid is electrically conductive.

[0006] However, if no electrically conductive pumping fluid is present and if the shaft bearing arrangement does not provide a reliable electric connection, the electric potential of the metal motor rotor shaft can cause electromagnetic interferences which can result in a poor EMC quality of the electric motor device.

[0007] It is an object of the invention to provide an electric motor device with a good and reliable EMC characteristics. - 2 - PP.P.23010. WO / EB 26.11.2024

[0008] This object is solved, according to the invention, with an electric motor device with the features of claim 1.

[0009] The electric motor device is provided with a rotatable motor rotor shaft made of an electrically conducting metal. The rotatable motor rotor shaft co-rotatably supports a motor rotor, preferably a permanently magnetized motor rotor without any electromagnetic coils. The electric motor device is provided with a shaft bearing arrangement for rotatably supporting the motor rotor shaft at a static bearing support ring made of an electrically conducting metal.

[0010] The electric motor device is provided with a spiral spring conductor element which is located in a ring gap between the static bearing support ring and the rotatable motor rotor shaft. The spiral spring conductor element is electrically conductive. A fixed spring conductor end of the spiral spring conductor element is fixed in an electrically conductive way to the static bearing support ring. The spiral part of the spiral spring conductor element is, starting from the fixed spring conductor end, radially inwardly pretensioned so that the spiral part is always in direct gliding contact with the outside shaft surface of the rotatable motor rotor shaft to thereby define a constant electric connection of the motor rotor shaft and the static bearing support ring.

[0011] The electric connection provided by the spiral spring conductor element is not necessarily suitable to reliably conduct high electric currents and is not necessarily suitable to provide an electric connection without any short interruptions. But the electric connection provided by the spiral spring conductor element is suitable and sufficiently effective to connect the electrically conductive motor rotor shaft to electric ground potential so that the electric potential of the motor rotor shaft is always substantially at the level of the electric ground potential and does not provide relevant electromagnetic emissions. - 3 - PP.P.23010. WO / EB 26.11.2024

[0012] Preferably, the spiral spring conductor element is designed and pretensioned so that the free end portion of the spiral part of the spiral spring conductor element is always in direct gliding contact with the outside shaft surface. Even if the free end portion of the spiral part of the spiral spring conductor element is subject to some wear over the lifetime, the remaining end portion is always radially pretensioned and, therefore, is always in direct gliding contact with the shaft surface, even at relatively high rotational speed of the pump rotor shaft. Even if the pumping fluid and / or the shaft bearing arrangement preliminarily or constantly cannot provide a reliable electric ground connection, the spiral spring conductor element guarantees that the rotatable motor rotor shaft has always substantially electric ground potential.

[0013] Preferably, the shaft bearing arrangement is a friction bearing and the static bearing support ring is provided with a separate static bearing sleeve. The static bearing sleeve can be of any material which is perfectly suitable for the bearing function and does not necessarily has to have good electric conductive characteristics. As a consequence, the friction bearing sleeve can be made of a suitable plastic material.

[0014] Preferably, the static bearing sleeve is provided axially adjacent to the ring gap where the spiral spring conductor element is located. Even more preferably, the ring gap for the spiral spring conductor element has the same radial extension and the same radius as the static bearing sleeve.

[0015] Preferably, the radial thickness of the spiral part of the spiral spring conductor element is less than the radial thickness of the static bearing sleeve so that the radial thickness of the spiral part of the spiral spring conductor element is less than 50% of the radial extension of the ring gap where the spiral spring conductor element is provided, and even more preferably is less than 25%. - 4 - PP.P.23010. WO / EB 26.11.2024

[0016] Preferably, a motor driving electronics is provided which electrically drives numerous motor stator coils to thereby rotate the motor rotor in a single motor rotation direction, not in both motor rotation directions. The spiral part of the spiral spring conductor element is orientated in that way that it is dragged by the outside surface of the motor rotor shaft which rotates in the single motor rotation direction. Since the spiral part of the spiral spring conductor element is always dragged by the frictional forces of the rotating shaft surface, the spiral part is radially pulled to the rotor shaft so that the electrical connection between the spiral spring conductor element and the shaft surface is improved during rotation of the motor rotor shaft compared to a motor rotor shaft which is not rotating.

[0017] Preferably, the fixed spring conductor end is a radial part of the spiral spring conductor element which radial part is bended outwardly from the spiral part of the spiral spring conductor element. The radial part of the spiral spring conductor element can easily be fixed to a static part of the static bearing support ring by form-fitting, by force-fitting and / or by soldering etc. More preferably, the radially orientated part of the spiral spring conductor element is form-fitting in a radial bore of the static bearing support ring.

[0018] Preferably, the radially orientated radial part of the spiral spring conductor element is inserted into a radial fluidic bypass bore of the static bearing support ring. The radial fluidic bypass bore thereby has two functions, which is the fluidic function and the support function for the fixed spring conductor end.

[0019] Preferably, the specific hardness of the spiral spring conductor element is substantially higher than the specific hardness of the outside shaft surface of the motor rotor shaft. The hardness-pairing of the spiral spring conductor element and of the outside shaft surface makes sure that, over the defined lifetime of the electric motor device, the spiral spring conductor element is not shortened too much due to wearing. The - 5 - PP.P.23010. WO / EB 26.11.2024 circumferential length and the radial pretension of the spiral spring conductor element thereby remain sufficient over the defined lifetime of the electric motor device.

[0020] Preferably, an electric fluid pump pumping for pumping a pumping fluid is provided with electric motor drive. The electric fluid pump is provided with a pump wheel which is co-rotatably supported at and by the motor rotor shaft. The motor rotor is provided in a motor rotor chamber which is filled with the pumping fluid, whereas the pumping fluid is electrically non-conductive. Preferably, the pumping fluid is a liquid, and mor preferably is a cooling liquid. Preferably, the pumping fluid or the cooling liquid is electrically non-conductive, so that the spiral spring conductor element guarantees that the electric potential of the rotatable motor rotor shaft is always at electric ground potential.

[0021] One embodiment of the invention is explained with reference to the enclosed drawings, wherein figure 1 schematically shows a longitudinal section of an electric fluid pump with an electric motor device wherein a spiral spring conductor element is provided axially adjacent to a shaft bearing arrangement, and figures 2 and 3 show a cross section of the shaft bearing arrangement of figure 1.

[0022] The figures show an automotive electric fluid pump 10' for pumping a pumping fluid 11, which pumping fluid 10 in the present embodiment is a cooling liquid which is electrically non-conductive.

[0023] The electric fluid pump 10' is provided with an electric motor device 10 and with a pumping part 20. The pumping part 20 is provided with a pumping part housing 22 defining an axial fluid inlet 12 and a tangential fluid outlet 14. The pump part housing 22 also defines a pump wheel chamber for a flow pump wheel 42 which is designed as an impeller. - 6 - PP.P.23010. WO / EB 26.11.2024

[0024] The electric motor device 10 is provided with a hollow rotatable motor rotor shaft 40 rotating around a rotation axis A and defining a hollow- cylindrical shaft body made of an electrically conductive metal. The hollow rotor shaft 40 defines an axial fluid channel 44 which provides a fluidic connection of the chamber of the pump wheel chamber and the other axial end of the rotor shaft 40.

[0025] The motor rotor shaft 40 is rotatably supported by a pump-wheel-sided shaft bearing 50 and by a shaft bearing arrangement 100 at the free shaft end of the motor rotor shaft 40. The pump-wheel-sided shaft bearing 50 as well as the shaft bearing arrangement 100 both are designed as a friction bearing, respectively. The motor rotor shaft 40 co- rotatably supports the pump wheel 42 as well as a permanently magnetized motor rotor 34 which is surrounded by a dry electromagnetic motor stator defined by several motor stator coils 32. The motor stator coils 32 are electrically driven by a dry motor driving electronics 36 which is provided with several power-semiconductors 37. The motor stator coil 32 and the permanently magnetized motor rotor 34 together define the electromagnetic motor section 30.

[0026] The electric liquid pump 10' is provided with a hollow-cylindrical separating can 24 with a can bottom 25, which can 24 separates a dry motor part comprising the motor stator coils 32 and the motor driving electronics 36 from a wet motor rotor chamber 51 comprising the permanently magnetized motor rotor 34 and the shaft bearing arrangement 100.

[0027] The shaft bearing arrangement 100 is provided with a hollow-cylindrical static bearing support ring 50 made of an electrically conducting metal, a separate static bearing sleeve 56 made of a suitable plastic and the - 7 - PP.P.23010. WO / EB 26.11.2024 outside shaft surface 40' of the motor rotor shaft 40, which outside shaft surface 40' is hardened.

[0028] A circumferential ring gap 54 is provided axially adjacent to the static bearing sleeve 56. The ring gap 54 is radially defined by the static bearing support ring 50 and by the rotatable motor rotor shaft 40. The ring gap 54 is fluid ically connected to the motor rotor chamber 51 by three radial fluidic bypass bores 52, 52'.

[0029] A spiral spring conductor element 60 is provided in the circumferential ring gap 54 which spiral spring conductor element 60 is made of an electrically conductive and hardened metal spring body 61. As can be seen in figure 3, the spiral spring conductor element 60 has a spiral part 62 and a fixed spring conductor end 64 which conductor end 64 is a radial part of the spiral spring conductor element 60. The radial part is bended outwardly from the spiral part 64 in about 90°. The fixed spring conductor end 64 is projecting into one fluidic bypass bores 52 of the static bearing support ring 50, so that the spiral spring conductor element 60 can not rotate. The free end of the spiral part 62 of the spiral spring conductor element 60 is always in direct gliding contact with the hardened outside shaft surface 40' of the motor rotor shaft 40 to thereby define a constant electric connection of the motor rotor shaft 40 with the static bearing support ring 50.

[0030] The specific hardness of the spiral spring conductor element 50 is higher than the specific hardness of the outside shaft surface 40' of the motor rotor shaft 40, and preferably is at least 70% higher. The radial thickness of the spiral part 62 of the spiral spring conductor element 60 is about 10 to 20% of the radial thickness dr54 of the static bearing sleeve 56. The radial thickness dr54 of the static bearing sleeve 56 is identical with the radial extension of the ring gap 54. - 8 - PP.P.23010. WO / EB 26.11.2024

[0031] As shown in figure 3, the motor driving electronics 36 drives the motor stator coils 32 in that way that the motor rotor 34 is always driven and rotated in a single motor rotation direction rd. The spiral part 62 of the spiral spring conductor element 60 is orientated in that way that the free end of the spiral part 62 is dragged, not pushed, by the friction between the outside surface 40' of the rotating motor rotor shaft 40 and the spiral part 62. The spiral part 56 of the spiral spring conductor element 60 has a spiral sector a62 of less than 360°, for example of about 330° when the motor rotor shaft 40 is not rotating. The spiral spring conductor element 60 provides a quasi-constant electric connection of the motor rotor shaft 40 and the static bearing support ring 50.

Claims

- 9 - PP.P.23010. WO / EB 26.11.2024CLAIMS1. An electric motor device (10) with a rotatable motor rotor shaft (40) made of an electrically conducting metal and co-rotatably supporting a motor rotor (34) and with a shaft bearing arrangement (100) for rotatably supporting the motor rotor shaft (40) at a static bearing support ring (50) made of an electrically conducting metal, wherein a spiral spring conductor element (60) is provided in a ring gap (54) between the static bearing support ring (50) and the rotatable motor rotor shaft (40), and wherein a fixed spring conductor end (64) of the spiral spring conductor element (60) is fixed in an electrically conductive way to the static bearing support ring (50) and the spiral part (62) of the spiral spring conductor element (60) is radially inwardly pretensioned so that it is always in direct gliding contact with the outside shaft surface (40') of the rotatable motor rotor shaft (40) to thereby define a constant electric connection of the motor rotor shaft (40) and the static bearing support ring (50).

2. The electric motor device (10) of claim 1, wherein the shaft bearing arrangement (100) is a friction bearing and the static bearing support ring (50) is provided with a separate static bearing sleeve (56) which preferably is provided axially adjacent to the ring gap (54).

3. The electric motor device (10) of one of the preceding claim, wherein the radial thickness of the spiral part (62) of the spiral spring conductor element (60) is less than the radial thickness (dr54) of the static bearing sleeve (56).- 10 - PP.P.23010. WO / EB 26.11.20244. The electric motor device (10) of one of the preceding claims, wherein a motor driving electronics (36) is provided which electrically drives motor stator coils (32) to thereby rotate the motor rotor (34) in a single motor rotation direction (rd), wherein the spiral part (62) of the spiral spring conductor element (60) is orientated in that way that it is dragged by the outside surface (40') of the rotating motor rotor shaft (40).

5. The electric motor device (10) of one of the preceding claims, wherein the fixed spring conductor end (64) is a radial part of the spiral spring conductor element (60) bended outwardly from the spiral part (64) of the spiral spring conductor element (60).

6. The electric motor device of the preceding claim, wherein the fixed spring conductor end (64) is inserted into a radial fluidic bypass bore (52) of the static bearing support ring (50).

7. The electric motor device (10) of one of the preceding claims, wherein the specific hardness of the spiral spring conductor element (60) is higher than the specific hardness of the outside shaft surface (40') of the motor rotor shaft (40).

8. An electric fluid pump (10') with a pump wheel (42) for pumping a pumping fluid (11) and with the electric motor device (10) of one of the preceding claims, wherein the pump wheel (42) is co-rotatably supported at the motor rotor shaft (40), and the motor rotor (34) is provided in a motor rotor chamber (51) which is filled with the pumping fluid (11), which pumping fluid (11) is electrically non-conductive.

9. The electric fluid pump (10') of the preceding claim, wherein the pumping fluid (11) is a liquid, preferably a cooling liquid.

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