Electric fluid pump

The invention is directed to an electric fluid pump, in particular to a self- cooling automotive electric liquid pump.

An electric fluid pump comprises several power electronic components for driving the electric drive motor. These power electronic components can generate critical heat quantities within the plastic pump housing so that an effective heat dissipation system is required to prevent the pump housing and the temperature sensitive components from an overheating.

The electric drive motor is typically arranged within a motor chamber being arranged adjacent to an electronics chamber for housing the power electronic components. The motor chamber is fluidically connected to the pumping chamber so that a partial volume flow of the pumped fluid flows through the motor chamber and preferably flows along a separating wall between the motor chamber and the electronics chamber. Thereby the heat is convectively transferred from the separating wall to the fluid and is dissipated by the fluid.

The separating wall is a separate component being typically made of a heat conductive material preferably a heat conductive metal which allows a sufficient heat transfer from the electronics chamber to the motor chamber. Since the electronics chamber must be sealed against the fluid within the motor chamber, a separate sealing element is required at the contacting surfaces of both the metallic separating wall and the plastic pump housing.

It is an object of the present invention to provide an electric fluid pump within effective and cost-efficient heat dissipation system for dissipating the heat from the electronics chamber. This object is achieved by an electric fluid pump according to the invention with the features of main claim 1.

An electric fluid pump according to the invention comprises a pump housing defining a pumping chamber, a motor chamber and an electronics chamber. The pumping chamber is flu id ica lly connected to the motor chamber so that a partial volume flow of the pumped fluid is guided into and through the motor chamber. An electric drive motor comprising a motor stator a motor rotor is arranged within the motor chamber so that the electric drive motor is at least partially in direct contact with the fluid within the motor chamber. Preferably, at least the motor rotor is as a so-called wet running rotor in direct contact with the fluid.

The pump housing defines a plastic separating ring wall between the motor chamber and the electronics chamber. The separating ring wall supports a metal heat-transfer center wall, both the separating ring wall and the supported metal heat-transfer center wall fluidically separating the electronics chamber and the motor chamber. The metal heat-transfer center wall is preferably made of a relatively heat conductive metal which allows an extremely effective heat transfer. Ideally, the power electronic components for driving the electric drive motor are arranged adjacent to the metal heat-transfer center wall so that the generated components' heat is transferred to the metal heat-transfer center wall at a relatively short distance.

The metal heat-transfer center wall is preferably in a direct contact with the fluid within the motor chamber, so that the heat is convectively transferred from the metal heat-transfer center wall to the fluid flowing through the motor chamber and is thereby transported out of the motor chamber and out of the pump housing into a connected fluid circuit. Thereby, a relatively effective heat dissipation system is provided which allows a precise heat transfer from the power electronic components via the metal heat-transfer center wall to the fluid within the motor chamber and thereby prevents the power electronic components, the pump housing and in particular the plastic separating ring wall from an overheating.

The metal heat-transfer center wall and the plastic separating ring wall are preferably connected without any additional connection means. Preferably, the metal heat-transfer center wall is supported such that a form-fitted and fluid-tight connection is defined between the metal heat-transfer center wall and the separating ring wall. The metal heat-transfer center wall, for example, can be integrally fixed to the plastic separating ring wall by an injection moulding process which defines an integral fluid tight connection so that no additional sealing elements are required to seal the electronics chamber against the fluid within the motor chamber. As a result, the manufacturing process of the electric fluid pump is significantly simplified, and the sealing reliability is significantly increased compared to the application of the separate sealing element.

In a preferred embodiment of the present invention, the electric fluid pump comprises a separating tube for fluidically separating the motor stator and the motor rotor of the electric drive motor. The separating tube preferably surrounds the motor rotor at the radial inside of the motor stator so that the separating tube substantially extends through the so-called air gap defining an inner rotor chamber and an outer stator chamber within the motor chamber. The separating tube thereby defines a wet zone and a dry zone both within the motor chamber, wherein the wet zone is preferably the rotor chamber being fluidically connected to the pumping chamber but being fluidically separated from the stator chamber housing the dry motor stator. Accordingly, the motor rotor is a so-called wet running rotor which is in direct fluidic contact with the fluid being branched off of the pumping chamber. In a preferred embodiment of the invention, a substantially axial collar protrudes from the metal heat-transfer center wall. The axial collar preferably protrudes towards the separating tube so that the separating tube can be supported by the axial collar. The separating tube can either surround the axial collar or can be surrounded by the axial collar so that the separating tube is either supported at its radial outside or at its radial inside.

In a preferred embodiment of the invention, the electric fluid pump comprises a printed circuit board which is arranged within the electronics chamber. The printed circuit board supports the power electronic components for driving the electric drive motor. The printed circuit board is preferably arranged such that it is in a heat transferring contact with the metal heat-transfer center wall, for example, the printed circuit board can be arranged adjacent and parallel to the metal heat-transfer center wall to guarantee a relatively large heat transfer surface. In addition, a heat- conducting paste can be applicated between the printed circuit board and the metal heat-transfer center wall to improve the heat transfer.

The metal heat-transfer center wall is preferably arranged concentrically to the electric drive motor. The wet running rotor guarantees a proper circulation of the fluid along the metal heat-transfer center wall so that a relatively effective convective heat transfer is provided between the metal heat-transfer center wall and the flowing fluid.

In a preferred embodiment of the invention, the electric fluid pump is a liquid pump, for example, a coolant pump or an oil pump. Liquids are due to their relatively large heat-transfer coefficient particularly suitable for a convective heat transfer so that a relatively effective heat dissipation can be realised by guiding the pumped liquid through the motor chamber along the metal heat-transfer center wall. Alternatively, the electric fluid pump could be a gas pump. Furthermore, the electric fluid pump could be a flow pump, a positive-displacement pump or any other suitable pump for pumping liquid or gas.

In a preferred embodiment of the present invention, the electric fluid pump comprises a hollow drive shaft. The hollow drive shaft fluidically connects the motor chamber with the pumping chamber in addition to the already existing fluidic connection between the pumping chamber and the motor chamber, for example, via a connection channel in the pump housing so that a complete cooling circuit is provided guaranteeing a continuous and homogeneous fluid flow through the pump housing.

The electric fluid pump according to the invention is preferably suitable for an automotive application, since one major requirement for an automotive electric fluid pump is a lightweight construction using preferably plastic components where applicable. The usage of plastic components only is costefficient, if the electric fluid pump is mass-produced in a relatively large quantity which is in particular usual in the automotive industry.

An embodiment of the electric fluid pump is described with reference to the enclosed drawing, wherein figure 1 shows a schematic longitudinal cross-sectional view of an electric fluid pump according to the invention.

Figure 1 shows an automotive electric coolant pump 10 of the centrifugal type for supplying a coolant circuit of a vehicle. The automotive electric coolant pump 10 comprises a multipiece pump housing 12 with a plastic pumping chamber cover 121 and a plastic pumping chamber flange 122 both defining a pumping chamber 15 within the pump housing 12.

The pump housing 12 further comprises a motor housing 123, which can be for example made of plastic or metal, and a plastic motor housing cover 124, the pumping chamber flange 122, the motor housing 123 and the motor housing cover 124 together defining a motor chamber 17 within the pump housing 12. The motor chamber 17 is arranged axially adjacent to the pumping chamber 15.

The pump housing 12 further comprises a plastic electronics chamber coverl25 which defines an electronics chamber 19 together with the motor housing cover 124. The electronics chamber 19 is arranged axially adjacent to the motor chamber 17 at the axial opposite side of the pumping chamber 15

The automotive electric coolant pump 10 comprises a pump wheel 13 being rotatably arranged within the pumping chamber 15 for pumping a coolant from a pumping chamber inlet 151 to a pumping chamber outlet (not shown).

The automotive electric coolant pump 10 further comprises an electric drive motor 30 with a static motor stator 31 and a rotatable motor rotor 32. The motor rotor 32 is co-rotatably connected to the pump wheel 13 via a hollow drive shaft 14. The energised electric drive motor 30 thereby rotates the pump wheel 13 within the pumping chamber 15 during the operation of the automotive electric coolant pump 10. The electric drive motor 30 is arranged within the motor chamber 17, wherein the outer motor stator 31 circumferentially surrounds the inner motor rotor 32.

The automotive electric coolant pump 10 comprises a hollow-cylindrical separating tube 28 which axially extends through the so-called air gap between the motor stator 31 and the motor rotor 32 so that the separating tube 28 circumferentially surrounds the motor rotor 32. The motor rotor 32 is not in a frictional contact with the separating tube 28. The separating tube 28 defines a rotor chamber 17A and a stator chamber 17B within the motor chamber 17, wherein the rotor chamber 17A houses the motor rotor 32 and the stator chamber 17B houses the motor stator 31.

The electronics chamber 19 houses a printed circuit board 40 comprising several power electronic components 35 for driving the electric drive motor 30. The plastic motor housing cover 124 defines an integral circular plastic separating ring wall 21 extending radially inwards with respect to the radial outside of the pump housing 12.

The automotive electric coolant pump 10 further comprises a circular discshaped metal heat-transfer center wall 25 which is made of a particularly heat-conducting metal. Both the plastic separating ring wall 21 and the metal heat-transfer center wall 25 fluidically separate the motor chamber 17 and the electronics chamber 19. The metal heat-transfer center wall 25 is arranged concentrically to the electric drive motor 30 and is further provided with an axial extending circumferential collar 251 which protrudes at the outer edge of the metal heat-transfer center wall 25 towards the motor chamber 17.

The metal heat-transfer center wall 25 comprises a circumferential ring groove 252 at its radial outside, the ring groove 252 facing the radial inside of the separating ring wall 21. The motor housing cover 124 is manufactured by an injection moulding process, wherein the motor housing cover 124 is moulded around the metal heat-transfer center wall 25. Thereby the separating ring wall 21 integrally fixes the metal heat-transfer center wall 25 via a form-fitted and fluid-tight connection 27 by extending into the circumferential ring groove 252 of the metal heat-transfer center wall 25. Accordingly, no additional connection means are required for connecting the metal heat-transfer center wall 25 to the separating ring wall 21. The separating tube 28 is at its pumping-chamber-sided end supported by an axial ring collar 1221 at the pumping chamber flange 122, the axial ring collar 1221 protruding axially towards the motor chamber 17, wherein the separating tube 28 circumferentially surrounds the axial ring collar 1221. The separating tube 28 is at its electronics-chamber-sided end supported by the axial collar 251 of the metal heat-transfer center wall 25, wherein the separating tube 28 circumferentially surrounds the axial collar 251. The separating tube 28 thereby flu id ica lly separates the motor chamber 17 in a wet zone 171 and a dry zone 172.

The wet zone 171, i.e., the rotor chamber 17A is flu idically connected to the pumping chamber 15 via a connection channel 1222 extending from the pumping chamber 15 through the pumping chamber flange 122 into the rotor chamber 17A. In particular, the connection channel 1222 is fluidically connected to the high-pressure discharge zone DZ of the pumping chamber 15. Thereby, a partial volume flow is branched off of the main coolant flow being pumped through the pumping chamber 15.

The rotor chamber 17A is further fluidically connected to the pumping chamber 15 via a backflow channel 141 extending axially through the hollow drive shaft 14. The backflow channel 141 in particular connects the electronics-chamber-sided end of the rotor chamber 17A to the low- pressure suction zone SZ of the pumping chamber 15. The resulting pressure gradient between the discharge zone DZ and the suction zone SZ forces the branched-off coolant to flow through the wet zone 171 from the high-pressure discharge zone DZ to the low-pressure suction zone SZ of the pumping chamber 15.

In detail, the branched-off coolant flows through the connection channel 1222 along the radial inside of the separating tube 28 towards the electronics chamber 19. The branched-off coolant flows further directly along the metal heat-transfer center wall 25 and thereby absorbs the heat being generated by the power electronic components 35 and being transferred to the metal heat-transfer center wall 25 via the printed circuit board 40 which is arranged in a direct heat-transferring contact to the metal heat-transfer center wall 25. At the metal heat-transfer center wall 25, the coolant enters the backflow channel 141 within the hollow drive shaft 14 and flows towards the pumping chamber 15 and into the suction zone SZ of the pumping chamber 15, where the heated coolant mixes with cooler coolant being sucked into the pumping chamber 15 through the pumping chamber inlet 151 so that an extremely effective cooling circuit is provided which significantly benefits from the application of the metal heat-transfer center wall 25 within the plastic separating ring wall 21.