Automotive electric liquid pump

The invention refers to an automotive electric liquid pump comprising a positive displacement pumping part for providing a pressurized pumping liquid, for example pressurized oil, for an automotive lubrication and/or cooling circuit.

Typical automotive electric liquid pumps are disclosed in GB 2558214 A or DE 10 2017 200 485 B3. The automotive electric liquid pump is provided with an electric motor part comprising an electromagnetic motor stator and a permanently magnetized motor rotor. In a dynamic-sealing-free pump concept, the motor rotor is provided in a wet motor rotor chamber being fluidically separated from the dry electromagnetic motor stator by a cylindrical separation wall.

The electromagnetic motor stator is energized by a motor control electronics comprising several power semiconductors. Since the typical performance of an automotive coolant or lubrication pump for a passenger car engine is in the range of 1,0 kW and for a truck engine is in the range of up to 10 kW, the power semiconductors need to be actively liquid-cooled. The active liquid cooling of the motor control electronics can be provided by a pump-internal cooling circuit being provided fluidically in parallel with and in reverse to the general pumping path. The internal parallel cooling circuit must reliably provide sufficient cooling performance but should only minimally short-circuit the general pumping path.

It is an object of the invention to provide an automotive electric liquid pump including an internal electronics cooling circuit of which the flow rate can easily and precisely be defined.

SUBSTITUTE SHEET (RULE 26) This object is, according to the invention, solved with an automotive electric liquid pump with the features of main claim 1.

The automotive electric liquid pump according to the invention provides a pressurized pumping liquid which is preferably oil. The liquid pump can be a pump for pumping a lubrication liquid and/or a cooling liquid for cooling, for example, electric components of an electrically driven vehicle. The liquid pump is provided with a positive displacement pumping section for pumping the pumping liquid with high pressure. The liquid pump is provided with a motor section being arranged in axial alignment with the pumping section.

The motor section comprises a dry electromagnetic motor stator with one or more stator coils which is/are energized by a motor control electronics. The motor section also comprises a wet permanently magnetized motor rotor fluidically separated from the dry motor stator by a substantially cylindrical separation wall. The liquid pump does not comprise any dynamic fluid seal.

The pumping section comprises a positive displacement pump rotor being provided within a pump chamber substantially defined by a pump main housing part. The positive displacement pumping section can be of any positive displacement pump type, but preferably is of the Gerotor type.

The liquid pump is provided with a pump-internal electronics cooling circuit for actively cooling the motor control electronics with the pumping liquid. The internal electronics cooling circuit is provided fluidically in parallel with the general main pumping path comprising the pump rotor and defines a fluidic short circuit of the general main pumping path. The liquid pump is provided with a rotor shaft which co-rotatably supports the pump rotor as well as the motor rotor. The rotor shaft is axially hollow and defines an axial liquid pipe with a motor-sided axial shaft opening at one axial shaft end and with an axial pump-sided shaft opening at the other axial shaft end. The rotor shaft pipe is part of the internal electronics cooling circuit.

The liquid pump is provided with a separate axial pump cover housing part being axially mounted or assembled to the pump main housing. The pump cover housing part is provided with a proximal throttle groove defining a fluid connection between the corresponding axial pump-sided shaft opening and a static low-pressure pump inlet chamber or a static high- pressure pump outlet chamber. The throttle groove substantially defines the flow rate through the internal electronics cooling circuit.

Since the cooling circuit throttle is defined by a simple throttle groove at the pump cover housing part, the precise machining and production of the throttle is simple and easily adaptable to any kind of flow rate to be defined.

Preferably, the throttle groove causes more than 50% of the total fluidic resistance of the complete internal electronics cooling circuit.

Preferably, the throttle groove defines the narrowest cross section of the complete internal electronics cooling circuit.

Preferably, the throttle groove cross section is smaller than 5 mm ² .

Preferably, the throttle groove has a substantially radial orientation and thereby fluidically connects the pump-sided shaft opening with the pump inlet chamber or the pump outlet chamber. The inlet chamber and/or the outlet chamber is a static liquid chamber adjacent to the pump chamber defined by the pump main housing. The outlet chamber is fluidically arranged between the pump chamber and the pump outlet port of the pump, and the inlet chamber is fluidically arranged between the pump inlet port of the pump and the pump chamber. The substantially radial throttle groove fluidically connects the inlet chamber or the outlet chamber with the pump-sided shaft opening, so that the throttle groove is arranged adjacent to and fluidically upstream or downstream of the rotor shaft liquid pipe.

Preferably, the open side of the throttle groove provided in the pump cover housing part is closed by and covered by the pump rotor, and preferably is covered by an axial pump rotor surface lying in a transversal plane.

Preferably, the pump cover housing part defines a pump chamber inlet opening and the fluidically subsequent pump inlet chamber and/or defines a pump chamber outlet opening and the fluidically prevenient pump outlet chamber. The pump chamber inlet opening and the pump chamber outlet opening define the fluidic connection between the pump chamber comprising the pump rotor and the pump inlet chamber/pump outlet chamber.

Preferably, the pumping section defines a Gerotor-type pump with two cooperating pump rotors. Preferably, the inner rotor of the two cooperating pump rotors covers the throttle groove.

Preferably, a motor rotor chamber substantially defined by the pump main housing is axially fluidically closed by a bottom wall substantially lying in a transversal plane. The motor control electronics comprises several power semiconductors which are in direct thermal contact with the bottom wall so that a high cooling performance can be provided for the power semiconductors.

Preferably, the pumping liquid is oil.

An embodiment of the invention is described with reference to the enclosed drawings, wherein figure 1 shows a schematic longitudinal cross-section of an automotive electric liquid pump with a motor section and a pumping section and comprising a fluidically parallel internal electronics cooling circuit with a throttle groove defined in the separate axial pump cover housing part, and figure 2 shows a transversal intersecting plane II-II of the liquid pump of figure 1, showing the proximal surface of the separate axial pump cover housing part including the throttle groove.

Figure 1 shows schematically a longitudinal cross section of an automotive electric liquid pump 10 for pumping a pressurized pumping liquid which is, in the present embodiment, oil for a lubrication circuit of an internal combustion engine. Seen in axial direction, the electric liquid pump 10 substantially is provided with a motor section 40 and a positive displacement pumping section 20 being in axial alignment with the motor section 40.

The motor section 40 comprises a dry electromagnetic motor stator 50, which is a ring-like motor stator, and comprises a wet permanently magnetized internal motor rotor 60 which is fluidically separated from the dry motor stator 50 and the dry motor control electronics 42 by a cylindrical separation wall 55 and a plane and disk-shaped bottom wall 88 lying in a transversal plane. The motor rotor 60 rotates in a wet motor rotor chamber 16. The motor section 20 comprises an inner pump rotor 22 and an outer pump rotor 23 being arranged within a cylindrical pump chamber 26 which is substantially defined by a massive pump main housing 80. The pump rotors 22, 23 together define a Gerotor-type pump.

The electromagnetic motor stator 50 comprises several stator coils 51 which are energized by several power semiconductors 43 being assembled to a printed circuit board of the motor control electronics 42. The motor control power semiconductors 43 are in direct thermal contact with the distal side of the metal bottom wall 88. The motor control electronics 42 is arranged within an electronics chamber 46 which is distally closed by an electronics cover lid 48.

A hollow cylindrical metal rotor shaft 30 is rotatably supported by the body of the pump main housing 80 in a fluid-tight friction bearing and defines an axial liquid pipe 32 with a motor-sided axial shaft opening 34 at one axial shaft end and an axial pump-sided shaft opening 36 at the other axial shaft end. The rotor shaft 30 rotates around a rotational axis 11 and co- rotatably directly supports the motor rotor 60 and the inner pump rotor 22.

A separate axial pump cover housing part 70 is axially mounted to the pump main housing 80. The pump cover housing part 70 is a massive metal part and axially-d istally closes the pump chamber 26. The pump cover housing part 70 defines at its proximal surface 71 a sickle-shaped pump chamber inlet opening 72 and a sickle-shaped pump chamber outlet opening 74 defining the liquid inlet and liquid outlet for the pump chamber 26. The pump chamber outlet opening 74 is defined by a static and sickleshaped pump outlet chamber 84 which is fluid ically connected to a pump outlet port 14. The pump chamber inlet opening 72 is defined by a static and sickle-shaped pump inlet chamber 82 which is fluidically connected to a pump inlet port 12.

The main housing part 80 defines a second pump inlet chamber 182 and defines a second pump outlet chamber 184 axially opposite to the first pump inlet chamber 82 to the first a pump outlet chamber 84. The first and the second pump inlet chambers 82, 182 are fluidically directly connected with each other, as well as the first pump outlet chamber 84 is fluidically directly connected to the second pump outlet chamber 184, whereas the latter fluid connections are not shown in the figures. The second outlet chamber 184 is fluidically directly connected to the motor rotor chamber 16 via a relatively wide connection opening 81.

The proximal surface 71 of the pump cover housing part 70 is provided with a proximal radial throttle groove 90 defining a fluid connection 92 between the shaft opening 36 and the low-pressure pump inlet chamber 82. The cross section A of the throttle groove 90 is about 1,0 mm ² . The open side of the throttle groove 90 is covered by the inner pump rotor 22.

When the motor rotor 60 is driven, the pumping liquid is sucked through the pump inlet port 12 and through the pump inlet chambers 82, 182 into the pump rotor cavity 26, and is pumped by the pump rotors 22, 23 as a pressurized pumping liquid into the high-pressure pump outlet chambers 84, 184. The main liquid current flows from the pump outlet chambers 84, 184 directly to the pump outlet port 14.

A cooling liquid current flows from the second pump outlet chamber 184 through an internal electronics cooling circuit to the first pump inlet chamber 82: a very small share of less than 5% of the total liquid current flows through the connection opening 81 axially into the motor rotor chamber 16, and flows from the motor rotor chamber 16 through the motor-sided shaft opening 34 to the pump-sided shaft opening 36. The liquid flows from the pump-sided shaft opening 36 radially through the throttle groove 90 into the first pump inlet chamber 82. The cooling liquid current thereby defines a fluidic short circuit which is quantitatively restricted and defined by the throttle groove 90 so that under all conditions, a sufficient cooling of the power semiconductors 43 is always guaranteed but with a minimum short circuit liquid flow.