EP4374077A1

EP4374077A1 - Automotive electric side-channel liquid pump with motor cooling

Info

Publication number: EP4374077A1
Application number: EP21748571.3A
Authority: EP
Inventors: Alessandro MALVASI
Original assignee: Pierburg Pump Technology GmbH
Current assignee: Pierburg Pump Technology GmbH
Priority date: 2021-07-21
Filing date: 2021-07-21
Publication date: 2024-05-29
Also published as: WO2023001370A1

Abstract

The invention is related to an automotive electric side-channel liquid pump (10; 10') for providing liquid within a vehicle system, with a pump housing (12) defining both a pump chamber (18) in which the liquid is pressurised by a rotating pump wheel (15; 15'), and a motor chamber (16) for housing an electric drive motor (30), the pump chamber (18) comprising a side-channel (183), a low-pressure liquid inlet zone (181) and a high-pressure liquid outlet zone (182), the motor chamber (16) comprising a rotor chamber (161) for housing a motor rotor (31) of the electric drive motor (30) and a stator chamber (162) for housing a motor stator (32) of the electric drive motor (30), the rotor chamber (161) and the stator chamber (162) being fluidically separated by a separating means (17), a printed circuit board (40) being provided with power electronic components (45) for driving the electric drive motor (30), wherein the rotor chamber (161) is fluidically connected to the pump chamber (18) by a rotor chamber inlet channel (21) branching off of the side-channel (183) or the following high-pressure liquid outlet zone (182) downstream of the low-pressure liquid inlet zone (181) for flooding the rotor chamber (161) with the pumped liquid, and wherein the rotor chamber (161) is fluidically connected to the pump chamber (18) by a rotor chamber outlet channel (22) fluidically connecting the rotor chamber (161) with the side-channel (183) or the low-pressure inlet zone (181). Thereby a relatively large pressure gradient is provided between the inlet zone (181) and the outlet zone (182) which ensures a constant cooling flow through the rotor chamber (161). The specifically designed pump wheel (15; 15') avoids relevant leakages or shortcuts between the inlet zone (181) and the outlet zone (182).

Description

D E S C R I P T I O N

AUTOMOTIVE ELECTRIC SIDE-CHANNEL LIQUID PUMP WITH MOTOR COOLING The invention is related to an automotive electric side-channel liquid pump for providing liquid within a vehicle system, in particular to an automotive electric side-channel oil pump for providing oil within an automatic transmission. Electric pumps which can be driven by an electronically commutated electric drive motor are provided with power electronic components for driving the electric drive motor. The power electronics components are mounted on a printed circuit board being arranged within the pump's housing. During the operation of the pump, the power electronic components and the electric drive motor generate relatively large heat amounts which are typically dissipated via the pumped liquid. In this type of pumps, the motor rotor and the motor stator are, for example, flu id ica lly separated by a separating means which can be a can or a tube for defining a wet rotor chamber and a dry stator/electronics chamber within the pump housing. The rotor chamber is fluidically connected to a pump chamber, wherein a pump wheel rotates for conveying the liquid through the liquid circuit so that the rotor chamber is completely flooded by a partial volume flow branching off of the liquid flowing through the pumping chamber. The circulation of this partial volume flow is initiated by the pressure gradient between a high-pressure zone and a low-pressure zone of the pump chamber. By arranging the heat-generating components close to the rotor chamber the heat is convectively transferred to the liquid and thereby transported out of the rotor chamber. An example for such a pump is disclosed in DE 100 52 797 Al. The document discloses a centrifugal coolant pump, wherein the discharge side of the pump chamber is fluidically connected to the axially adjacent rotor chamber by a connection channel. The cool liquid enters the rotor chamber through the connection channel, flows axially along the rotor to the opposite end of the rotor chamber. At this opposite end of the rotor chamber, a separating wall fluidically separates the wet rotor chamber from the axially adjacent dry electronics chamber in which the printed circuit board is arranged in a heat-transferring contact to the separating wall. The cool liquid flows along the heated separating wall and absorbs the heat. From there, the heated liquid flows back to the suction side of the pump chamber through a hollow drive shaft. At the suction side of the pump chamber, the heated liquid is mixed with cool liquid being sucked in by the pump wheel. Thereby a simple pump internal cooling circuit is defined which is provided with the pumped coolant.

Generally, a relatively high delta pressure is necessary for ensuring a sufficient partial volume flow flowing through the rotor chamber. The cooling circuit of the pump disclosed in DE 100 52 797 A1 is provided with a relatively large pressure gradient, but this type of cooling circuit cannot simply be copied to a side-channel pump. A hollow drive shaft is not directly fluidically connectable to the suction side of a side channel pump. Further, the outlet pressure of a side-channel pump is significantly higher than the outlet pressure of a centrifugal pump. Due to the adjacent arrangement of the inlet zone and the outlet zone, the risk of a short cut between the inlet zone and the outlet zone resulting from cooling circuit is relatively high so that the cooling circuit of a side-channel pump requires a modification of its flow pattern.

WO 2015/197467 A1 discloses a multi-stage side-channel coolant pump with several serially connected pump-stages. All pump wheels are arranged on a common drive shaft so that the pump wheels are co-rotatably connected to each other. Each pump stage is fluidically connected to the adjacent one by an axial ring gap surrounding the drive shaft. The axial ring gap is connected to an outlet zone of each pump chamber by a radial ring gap between the respective pump wheel and the pump housing. The last pump stage is fluidically connected to a rotor chamber via a ring gap surrounding the drive shaft. As a result, a partial flow of the pumped liquid flows through the axial gap from one pump stage to the adjacent one and from there to an axially adjacent rotor chamber. The liquid thereby defines a cooling flow which flows axially from a first axial end along the rotor to an end wall at the second opposite axial end of the rotor chamber.

The end wall fluidically separates the rotor chamber from the axially adjacent electronics chamber at the other side of the end wall. In the electronics chamber several power electronic components are arranged in a heat transferring contact with the axial end wall so that the cooling flow within the rotor chamber cools the power electronic components indirectly. From this axial end of the rotor chamber, the cooling flow flows into a ring- shaped high-pressure discharge channel which circumferentially surrounds the rotor chamber. Accordingly, the pump is provided with a modified flow pattern, wherein the cooling flow does not flow back to the inlet/suction side of the pump, but flows directly into the outlet port so that a short-cut between the inlet and the outlet can be avoided.

As the cooling flow flows directly into the outlet, the cooling flow is not caused by the pressure gradient, but is pumped through the rotor chamber directly into the outlet being fed by the volume flow flowing through the ring gap. As a result, the relatively small cooling flow is not very constant so that the cooling performance is relatively poor an is in particular not suitable for a single-stage side-channel pump.

It is an object of the invention to provide a simple and relatively cost-efficient automotive electric side-channel liquid pump which provides a constant and reliable cooling flow for cooling the electric motor and/or the power electronic components. This object is achieved with an automotive electric side-channel liquid pump according to the invention with the features of main claim 1.

An automotive electric side-channel liquid pump according to the invention - also known as automotive electric regenerative liquid pump - is provided with a pump housing which defines a pump chamber comprising a side- channel, a low-pressure liquid inlet zone and a high-pressure liquid outlet zone. A liquid is conveyed within the pump chamber by a rotating pump wheel. This pump wheel is preferably provided with a disc-type shaped pump wheel body comprising a plurality of substantially radially oriented blades being moved through the side-channel. The axial extension of the blades is smaller than the axial extension of the side-channel so that the blades do not cover the complete side-channel cross-section. Thereby, a blade-free volume is defined within the side-channel. The liquid which is preferably oil enters the side-channel at the inlet zone through a preferably axial inlet duct of the pump.

The liquid is carried by the blades in a vortex-type manner through the side-channel to the liquid outlet zone and is pumped out of the side-channel at the liquid outlet zone through a preferably tangential outlet duct of the pump. Accordingly, the liquid outlet zone is defined by that part of the pump chamber where the circular side-channel transitions into the preferably tangential outlet duct. The liquid outlet zone extends from that transition part downstream through the tangential outlet duct. The liquid inlet zone is defined by the part of the side-channel where the side-channel transitions into the preferably axial inlet duct. The liquid inlet zone accordingly extends from this transition part upstream through the axial inlet duct. The pump housing houses the internal pump components and flu id ically separates the inside of the pump from the outside. The pump housing can be defined by one or more pump housing components. The pump housing further comprises a motor chamber for housing an electric drive motor which drives the pump wheel. The electric drive motor comprises a rotatable motor rotor and a static motor stator. The motor chamber comprises a rotor chamber for housing the motor rotor and a stator chamber for housing the motor stator. The motor stator is circumferentially surrounding the motor rotor such that a circumferential gap is provided between the motor rotor and the motor stator. A separating means is arranged within the gap for flu id ically separating the rotor chamber from the stator chamber and thereby defining a wet zone and a dry zone within the pump housing.

The automotive electric side-channel liquid pump further comprises a printed circuit board which is provided with several power electronic components for driving the electronically-commutated electric drive motor.

The rotor chamber is flu id ically connected to the pump chamber by a first rotor chamber inlet channel. The rotor chamber inlet channel branches off of the pump chamber through a rotor chamber inlet channel opening. The rotor chamber inlet channel opening is arranged downstream of the low-pressure liquid inlet zone within the side-channel or within the high-pressure liquid outlet zone. The position of the rotor chamber inlet channel opening is determined by a simulation software to find the position within the side-channel or the high-pressure liquid outlet zone, where the pressure is relatively high, where the pressure losses resulting from the branch-off are relatively low and where a relatively short and direct connection between the pump chamber and the rotor chamber can be easily manufactured.

A partial volume flow branches off of the main liquid flow being carried through the pump chamber via the rotor chamber inlet channel, and enters the rotor chamber. Thereby, the rotor chamber is flooded with the pumped liquid so that the motor rotor is rotating within the wet zone as a wet running rotor. The liquid entering the rotor chamber defines a cooling flow for cooling the heat-generating components of the automotive electric side-channel liquid pump, in particular for cooling the electric drive motor and the power electronic components being arranged at the printed circuit board. The cooling flow enters the rotor chamber preferably at a first axial end being adjacent to the pump chamber and is guided through the rotor chamber substantially in axial direction preferably towards the other axial end of the rotor chamber. The heat-generating components are arranged within the dry zone of the pump housing adjacent to the separating means which can be, for example, a separating can with an integral axial separating wall or alternatively can be a separating tube with a separate axial separating wall. Preferably, the heat-generating components directly contact the separating means in a heat-transferring manner. The cooling flow contacts the separating means within the wet zone and absorbs the heat being transferred from the heat-generating components to the separating means. Thereby the heat-generating components are cooled. After absorbing the heat, the cooling flow is guided to a rotor chamber outlet channel which fluidically connects the rotor chamber with the low-pressure inlet zone so that the warmed-up cooling flow flows to the inlet zone and mixes-up with the liquid being sucked into the pump chamber.

Due to the fluidic connection between a high-pressure part of the pump chamber and a low-pressure part of the pump chamber through the rotor chamber, the cooling flow is caused by the pressure difference between the rotor chamber inlet channel and the rotor chamber outlet channel so that a constant and sufficient cooling flow is provided for cooling the heat-generating components, in particular for cooling the power electronic components of the pump. Resulting from the high outlet pressure of the side-channel pump, only a relatively small diameter of the rotor chamber inlet channel is necessary for providing a sufficient cooling flow entering the rotor chamber. The cooling flow is at maximum 10% of the main liquid flow, preferably less than 3% of the main liquid flow. In a preferred embodiment, the side-channel is arranged at the same axial side of the pump wheel as the rotor chamber, i.e. the blade-free volume is arranged adjacent to the rotor chamber. As a result, the rotor chamber inlet channel is permanently supplied with liquid swirling through the blade-free volume of the side-channel. If the rotor chamber inlet channel opening is arranged at the radial inner side of the side-channel, a relatively short and direct fluidic connection between the side-channel and the rotor chamber is provided.

Preferably the printed circuit board is arranged in a separate electronics chamber within the pump housing. The separate electronics chamber is flu id ica lly separated from the rotor chamber. The electronics chamber is preferably arranged axially adjacent to the rotor chamber at the opposite axial end of the pump referring to the pump chamber. The electronics chamber is separated from the rotor chamber by the axial separating wall of the separating means. The printed circuit board is preferably arranged adjacent to the separating wall in a heat transferring manner. Further, the power electronic components are at the printed circuit board arranged such that that the heat being generated by the power electronic components at the printed circuit board is transferred to the separating wall. For example, the power semiconductors are arranged in that area of the separating wall which is at the opposite side of the separating wall directly contacted by the cooling flow. Preferably, the power semiconductors at the printed circuit board are arranged centrically referring to the separating wall. The cooling flow flowing through the rotor chamber contacts the separating means, absorbs the heat from the separating means and transports the heat to the liquid inlet zone, where the warmed-up liquid is cooled by the liquid being sucked into the pump chamber. Thereby, the power electronic components are sufficiently cooled by the cooling flow. In a particularly preferred embodiment, the pump is provided with a hollow drive shaft. The hollow drive shaft connects the motor rotor with the pump wheel for transferring the rotational movement of the rotor to the pump wheel. The hollow drive shaft is provided with a backflow channel. The backflow channel extends axially through the hollow drive shaft to provide a liquid backflow from the rotor chamber to the rotor chamber outlet channel. Accordingly, the liquid for cooling the heat-generating components enters the backflow channel at the opposite axial end of the pump referring to the pump chamber and flows through the hollow drive shaft towards the pump chamber. At the downstream end of the backflow channel, the liquid enters the rotor chamber outlet channel and flows into the liquid inlet zone.

The cooling flow is guided by the backflow channel from the axial end of the rotor chamber being adjacent to the pump chamber axially along the separating means to the separating wall at the opposite axial end of the rotor chamber. From there, the cooling flow enters the hollow drive shaft and flows axially back towards the pump chamber so that a permanent circulation of the cooling flow within the rotor chamber is ensured. In a preferred embodiment, the pump housing is at one axial side-channel-sided end of the pump defined by a pump cover. Accordingly, the pump housing is defined by at least two separate parts. The pump cover defines the rotor chamber outlet channel and preferably defines the inlet duct so that the rotor chamber outlet channel extends from an axial pump cover sidewall which faces the pump wheel directly to the inlet duct.

Preferably, the pump wheel is provided with a centric cut-out at an axial sidewall of the pump wheel which faces the pump cover. The axial sidewall of the pump cover which faces the pump wheel is provided with a corresponding protrusion which axially extends into the cut-out of the pump wheel. Thereby a labyrinth-type seal is defined between the pump cover and the pump wheel that reduces the leakage of the cooling flow through the radial gap between the pump cover and the pump wheel so that a relevant (non-useful) fluidic shortcut between the pump's cooling circuit and the pump chamber is avoided. Additionally, the protrusion of the pump cover is preferably provided with a recess at an inlet opening of the rotor chamber outlet channel. The recess faces an outlet opening of the backflow channel within the hollow drive shaft so that a transfer volume is defined between the outlet opening of the backflow channel and the inlet opening of the rotor chamber outlet channel The recess additionally reduces the leakage. The liquid flowing out of the backflow channel does not enter the rotor chamber outlet channel at the gap region between the pump wheel and the pump cover, but is flowing into the transfer volume, and flows from there into the rotor chamber outlet channel so that the liquid is not directly guided into the gap between the pump wheel and the pump cover.

In a preferred embodiment the side-channel is a double-flow side-channel. The double-flow side-channel is provided with two blade-free volumes, one blade-free volume at each axial side of the pump wheel so that the volume flow of the pump liquid being carried through the side-channel is almost doubled.

In an alternative embodiment, the drive shaft axially extends into the recess of the pump cover. Thereby, the outlet opening of the backflow channel is arranged such that the cooling flow does not directly pass the gap between the pump wheel the pump cover after flowing out of the backflow channel. As a result, the leakage is further reduced compared to the first embodiment with the recess, because the cooling flow which is not entering the rotor chamber outlet channel directly is multiply redirected before it reaches the gap between the pump wheel and the pump cover. As a result, an additional labyrinth-type seal is defined by the drive shaft extending into the recess. In a preferred embodiment, the angle between a side-channel-sided rotor chamber inlet channel opening and the axial inlet duct is between 250° and 330°. The first reference for the angle is the centreline of the preferably cylindrical axial inlet duct. Referring to this centreline, the angle extends around the central rotation axis of the pump to the position where the rotor chamber inlet channel opening is located within the side-channel. With this angle, a relatively large pressure gradient between the rotor chamber inlet channel and the rotor chamber outlet channel is ensured so that a relatively constant cooling flow flows through the rotor chamber.

With the automotive electric side-channel liquid pump according to the invention, a reliable cooling circuit for cooling the power electronics is applicated to a side-channel pump. The pressure gradient between the rotor chamber inlet channel and the rotor chamber outlet channel resulting from the precisely determined positions of both channels in the high-pressure zone of the pump chamber and in the low-pressure zone of the pump chamber results in a constant and permanent circulation of the liquid through the rotor chamber. Due to the hollow drive shaft, the cooling flow flows axially completely along the separating means and back to the inlet through the backflow channel and the rotor chamber outlet channel. The specifically designed pump wheel and the corresponding pump cover provide a labyrinth seal which avoids a relevant shortcut between the inlet zone and the outlet zone so that the total efficiency of the pump is not relevantly affected by the cooling circuit.

Two embodiments of the invention are described with reference to the enclosed drawings, wherein figure 1 shows a first embodiment of an automotive electric side-channel liquid pump according to the invention with a short drive shaft ending within the pump wheel in a longitudinal sectional view, figure 2 shows the automotive electric side-channel liquid pump of figure 1 and figure 3 in a cross-sectional view through the side-channel, and figure 3 shows a second alternative embodiment of an automotive electric side-channel liquid pump according to the invention with a long drive shaft extending into a recess within the pump cover in a longitudinal and detailed sectional view of the pump-chamber-sided end of the pump. Figure 1 and figure 3 show an automotive electric side-channel oil pump 10; 10' for providing an automatic transmission with pressurized oil. The not shown part of the pump 10' of figure 3 is identical to the pump 10 of figure 1. The automotive electric side-channel oil pump 10; 10' comprises a multi-piece pump housing 12 with a pump cover 13; 13' and an upper flange 11 which together define a pump chamber 18 with a ring-type double-flow side-channel 183 being provided with a substantially oval cross-section. The pump 10; 10' further comprises a disc-type shaped pump wheel 15; 15' with a hub-type hollow-cylindrical pump wheel body 154 and a plurality of substantially rectangular blades 155 extending axially and radially outwards referring to the pump wheel body 154 and being equiangularly arranged over the circumference of the pump wheel body 154. The pump wheel 15; 15' rotates within the pump chamber 18 between the pump cover 13; 13' and the upper flange 11 so that the blades 155 of the pump wheel 15; 15' are moved through the side-channel 183. The axial extension of the double flow side-channel 183 is larger than the axial extension of the blades 155 so that a blade-free volume is defined within the side-channel 183 at both axial sides of the blades 155 which is not roamed by the blades 155. The pump 10; 10' further comprises a motor chamber 16 for housing an electric drive motor 30 with a substantially hollow-cylindrical and rotatable motor rotor 31 and a hollow-cylindrical static motor stator 32 which circumferentially surrounds the motor rotor 31 so that a circumferential ring gap is defined between the motor rotor 31 and the motor stator 32. Within the ring gap, a hollow-cylindrical separating tube 171 axially extends between the motor rotor 31 and the motor stator 32 to flu id ically separate the motor rotor 31 and a motor stator 32 and to thereby define a cylindrical rotor chamber 161 at the radial inside of the separating tube 171. Additionally, the separating tube 171 defines a ring-shaped stator chamber 162 at the radial outside of the separating tube 171. The motor stator 32 is in a direct heat-transferring contact with the separating tube 171 so that the heat which is generated by the motor stator 32 during the operation of the pump 10; 10' is transferred to the separating tube 171. At the first axial pump-chamber-sided end of the rotor chamber 161, the separating tube 171 is connected to the upper flange 11 in a seal-type manner. At the second axial end of the rotor chamber 161, the separating tube 171 is connected to a separating wall 172 in a seal-type manner so that the rotor chamber 161 is hermetically sealed against the stator chamber 162. At the other opposite axial side of the separating wall 172, the pump 10; 10' comprises an electronics chamber 50, wherein a circular printed circuit board 40 is concentrically arranged with respect to the separating wall 172, the printed circuit board 40 being provided with several power electronic components 45. The printed circuit board 40 is in a heat transferring contact with the separating wall 172, so that the heat which is generated by the power electronic components 45, in particular which is generated by the power semiconductor 451 being centrically arranged at the printed circuit board, is transferred to the separating wall 172.

The motor rotor 31 is not contacting the separating tube 171 to allow a resistance-free and friction-free rotation of the motor rotor 31 within the rotor chamber 161. The motor rotor 31 is co-rotatably connected to the pump wheel 15; 15' by a hollow-cylindrical drive shaft 25; 25' being provided with a concentric backflow channel 26; 26' which completely extends through the drive shaft 25; 25' from the first axial drive shaft end to its second axial drive shaft end. The drive shaft 25; 25' extends through the rotor chamber 161 from the second electronic-sided axial end of the rotor chamber 161 towards the pump-chamber-sided axial end of the rotor chamber 161 and extends through an opening in the upper flange 11 into the pump wheel 15; 15'. If the motor rotor 32 of the electric drive motor 30 is driven by the motor stator 31, the pump wheel 15; 15' is rotated within the pump chamber 18.

The pump chamber 18 further comprises a low-pressure liquid inlet zone 181 and a high-pressure liquid outlet zone 182. The liquid inlet zone 181 is arranged at a first circumferential end of the side-channel 183 and extends upstream from a first transition zone wherein the side-channel 183 transitions into an axial tube-shaped inlet duct 14 which is an integral part of the pump cover 13. The liquid outlet zone 182 is shown in figure 2. The liquid outlet zone 182 extends downstream from a second transition zone wherein the side-channel 183 transitions into a tangential and substantially cylindrical outlet duct 19.

If the pump wheel 15; 15' rotates through the side-channel 183 the liquid is sucked-in through the inlet duct 14 into the liquid inlet zone 181 and is carried by the blades 155 of the pump wheel 15; 15' through the side-channel 183 to the liquid outlet zone 182. From the liquid outlet zone 182, the liquid is pushed into the outlet duct 19 by the blades 155 of the pump wheel 15; 15'.

The pump chamber 18 is fluidically connected to the rotor chamber 161 by a rotor chamber inlet channel 21 defined by a borehole extending through the upper flange 11 of the pump housing 12 from the transition zone between the side-channel 183 and the liquid outlet zone 182 to the rotor chamber 161. The angle a between the centreline of the axial inlet duct 14 and a rotor chamber inlet channel opening 211 of the rotor chamber inlet channel 21 is, seen in flow direction F, about 290°. The pump 10; 10' is provided with a second rotor chamber outlet channel 22 which flu id ically connects the rotor chamber 161 with the low-pressure inlet zone 181. The rotor chamber outlet channel 22 is extending from a recess 27; 27' within the pump cover 13; 13', the recess 27; 27' being in fluidic contact with the backflow channel 26; 26' within the hollow drive shaft 25; 25'. The rotor chamber outlet channel 22 extends from the recess 27; 27' through the pump cover 13; 13' into the inlet duct 14. Initiated by the pressure gradient between the inlet zone 181 and the outlet zone 182, a partial flow of the total volume flow being carried through the side-channel 183 enters the rotor chamber inlet channel 21 through the rotor chamber inlet channel opening 211 as a cooling flow and flows into the rotor chamber 161. The cooling flow flows axially along the radial inside of the separating tube 171 through the gap between the separating tube

171 and the rotating motor rotor 31 towards the other axial end of the rotor chamber 161. Thereby the heat which is generated by the motor stator 32 and which is transferred to the separating tube 171 is absorbed by the cooling flow flowing towards the separating wall 172. After the cooling flow has arrived at the separating wall 172, the cooling flow flows along the separating wall 172 radially inwards and absorbs the heat being generated by the power electronic components 45 and being transferred to the separating wall 172. Due to the pressure gradient, the warmed-up cooling flow then flows through the backflow channel inlet opening 261 into the backflow channel 26; 26' of the hollow drive shaft 25; 25' and flows axially through the backflow channel 26; 26' towards the recess 27; 27' within the pump cover 13; 13'. After the cooling flow has entered the recess 27; 27', the under-atmospheric pressure within the inlet duct 14 sucks the cooling flow through the rotor chamber outlet channel inlet opening 221 into the rotor chamber outlet channel 22 and from there into the inlet duct 14. In the inlet duct 14, the cooling flow mixes up with the oil being sucked into the pumping chamber through the inlet duct 14.

The pump-cover-sided axial end of the pump wheel 15, shown in the pump 10 of figure 1, is provided with a centric cylindrical cut-out 151 with a diameter of about 1/3 of the outer pump wheel diameter. The pump-wheel-sided axial end of the pump cover 13 is provided with a centric cylindrical protrusion 132 extending from the axial end wall 131 of the pump cover 13 which faces the pump wheel 15. The cylindrical protrusion 132 is shaped in correspondence to the cylindrical cut-out 151 of the pump wheel 15 so that the protrusion 132 extends into the cylindrical cut-out 151 such that a relatively small gap is defined between the pump wheel 15 and the pump cover 13. Accordingly, the pump wheel 15 does not contact the pump cover 13 at any side of the pump wheel 15.

The axial end of the cylindrical protrusion 132 which faces the pump wheel 15 is provided with a centric cone-type shaped recess 27 with a diameter that substantially corresponds to the outer diameter of the drive shaft 25. Accordingly, the rotor chamber outlet channel 22 which extends substantially from the centre of the pump wheel 15 within the pump cover 13 in fact extends from the inside of the recess 27 through the pump cover 13 directly into the inlet duct 14, i.e., the rotor chamber outlet channel inlet opening 221 is arranged at the tapering sidewall of the conical recess 27. The angle of the cone of the recess 27 corresponds to the angle of the rotor chamber outlet channel 22 within the pump cover 13 so that the inner tapering sidewall of the recess 27 is substantially perpendicularly arranged referring to the extension direction of the rotor chamber outlet channel 22.

The hollow drive shaft 25 extends through the pump wheel 15 about 3/4 of the axial length of the hub-type hollow-cylindrical pump wheel body 154 and flu id ica lly connects the electronic-sided axial end of the rotor chamber 161 with the recess 27 of the pump cover 13 via the concentrical backflow channel 26 within the drive shaft 25.

After the cooling flow has left the backflow channel 26 of the drive shaft 25, the cooling flow passes the gap between the cut-out 151 of the pump wheel 15 and the protrusion 132 of the pump cover 13 so that a relatively small partial flow of the cooling flow flows into the gap between the cut-out 151 of the pump wheel 15 and the protrusion 132 of the pump cover 13. The labyrinth-type seal between the pump wheel 15 and the pump cover 13 which results from the protrusion 132 and the corresponding cut-out 151 reduces the leakage of the partial cooling flow to the pump chamber 18 so that no shortcut occurs between the inlet zone 181 and the outlet zone 182.

Figure 3 shows an alternative embodiment of the automotive electric side-channel oil pump 10'. The pump wheel 15' of the pump 10' is provided with two cylindrical cut-outs 151', 152 at the axial end of the pump wheel 15' which faces the pump cover 13'. The axial depth of the first centric cylindrical cut-out 151' is about 50% of the axial blade length and the diameter of the first cylindrical cut-out 151' is about the double of the outer diameter of the hollow drive shaft 25'.

The second cylindrical cut-out 152 is concentrically arranged to the first 151'. The diameter of the second cylindrical cut-out 152 is about 25% larger than the first cylindrical cut-out 151' and the axial depth of the second cut-out 152 is about 50% of the axial depth of the first cut-out 151'. The pump cover 13' is correspondingly shaped being provided with a first cylindrical protrusion 132' and a second cylindrical protrusion 133 being concentrically arranged to the first protrusion 132'. Both protrusions 132', 133 are shaped such that they correspond to the cut-outs 151', 152 such that a small gap is defined between the pump wheel 15' and the pump cover 13'. The cut-outs 151', 152 and the corresponding protrusions 132', 133 define a labyrinth-type seal which is, compared to the first embodiment of the automotive electric side-channel oil pump 10, provided with an additional labyrinth to increase the sealing effect of the seal.

The pump cover 13' is further provided with a cylindrical recess 27' which is concentrically arranged to the cylindrical protrusion is 132', 133. The axial depth of the recess 27' corresponds to the axial height of the first protrusion 132'. The drive shaft 25' of the pump 10' extends, compared to the first embodiment of the pump 10, through the hub -type hollow cylindrical pump wheel body 154 so that the hollow drive shaft 25' extends into the cylindrical recess 27' about 60% of the axial depth of the recess 27'. As a result, the cooling flow flowing through the backflow channel 26' within the drive shaft 25' enters the cylindrical recess 27' and is sucked through the rotor chamber outlet channel 22 into the inlet duct 14 by the under-atmospheric pressure.

As a result of the drive shaft 25' which extends into the recess 27', the cooling flow which flows out of the backflow channel 26' does not pass the gap between the pump wheel 15' and the pump cover 13' so that no partial flow of the cooling flow flows directly into the gap. In addition, the drive shaft 25' and the recess 27' define an additional labyrinth-type seal so that the partial flow of the cooling flow which does not directly enter the rotor chamber outlet channel 22 is redirected multiple times before entering the gap between the pump wheel 15' and the pump cover 13' and is thereby decelerated. After the partial flow of the cooling flow has entered the gap between the pump wheel 15' and the pump cover 13', the labyrinth-type seal being defined by the cut-outs 151', 152 and the protrusions 132', 133 reduces the leakage to the pump chamber so that no relevant shortcut between the inlet zone 181 and the outlet zone 182 occurs.

Claims

C L A I M S

1. An automotive electric side-channel liquid pump (10; 10') for providing liquid within a vehicle system, with a pump housing (12) defining both a pump chamber (18) in which the liquid is pressurised by a rotating pump wheel (15; 15'), and a motor chamber (16) for housing an electric drive motor (30), the pump chamber (18) comprising a side-channel (183), a low-pressure liquid inlet zone (181) and a high-pressure liquid outlet zone (182), the motor chamber (16) comprising a rotor chamber (161) for housing a motor rotor (31) of the electric drive motor (30) and a stator chamber (162) for housing a motor stator (32) of the electric drive motor (30), the rotor chamber (161) and the stator chamber (162) being fluidically separated by a separating means (17), a printed circuit board (40) being provided with power electronic components (45) for driving the electric drive motor (30), wherein the rotor chamber (161) is fluidically connected to the pump chamber (18) by a rotor chamber inlet channel (21) branching off of the side-channel (183) or the following high-pressure liquid outlet zone (182) downstream of the low-pressure liquid inlet zone (181) for flooding the rotor chamber (161) with the pumped liquid, and wherein the rotor chamber (161) is fluidically connected to the pump chamber (18) by a rotor chamber outlet channel (22) fluidically connecting the rotor chamber (161) with the side-channel (183) or the low-pressure inlet zone (181).

2. The automotive electric side-channel liquid pump (10; 10') according to claim 1, wherein the pumped liquid is oil.

3. The automotive electric side-channel liquid pump (10; 10') according to claim 1 or 2, wherein the side-channel (183) is arranged at the same axial side of the pump wheel (15; 15') as the rotor chamber (161).

4. The automotive electric side-channel liquid pump (10; 10') according to one of the preceding claims, wherein the printed circuit board (40) is arranged in a separate electronics chamber (50) being axially adjacent to and fluidically separated from the rotor chamber (161) by a separating wall (172).

5. The automotive electric side-channel liquid pump (10; 10') according to claim 4, wherein the electronics chamber (50) is arranged at the opposite axial end of the pump (10) referring to the pump chamber (18).

6. The automotive electric side-channel liquid pump (10; 10') according to claim 4 or 5, wherein the liquid flows through the rotor chamber (161) along the separating wall (172) for cooling the printed circuit board (40) and the power electronic components (45).

7. The automotive electric side-channel liquid pump (10; 10') according to one of the preceding claims, wherein the pump (10; 10') is provided with a hollow drive shaft (25; 25') connecting the motor rotor (31) with the pump wheel (15; 15') and wherein the liquid backflow is provided through a backflow channel (26; 26') within the hollow drive shaft (25;

25').

8. The automotive electric side-channel liquid pump (10; 10') according to claim 7, wherein the pump housing (12) is at one axial side-channel-sided end of the pump (10; 10') defined by a pump cover

(13; 13') which defines the rotor chamber outlet channel (22).

9. The automotive electric side-channel liquid pump (10; 10') according to claim 8, wherein the pump wheel (15; 15') is provided with a centric cut-out (151; 151', 152), and wherein an axial pump cover sidewall (131) which faces the pump wheel (15; 15') is provided with a corresponding protrusion (132; 132', 133) extending axially into the cut-out (151; 151', 152) to define a labyrinth-type seal.

10. The automotive electric side-channel liquid pump (10; 10') according to claim 7, wherein the protrusion of the pump cover (12) is provided with a recess (27; 27') at an inlet opening (221) of the rotor chamber outlet channel (22), the recess (27; 27') facing the backflow channel (26; 26') of the drive shaft (25; 25') and defining a transfer volume between an outlet opening (262) of the backflow channel (26; 26') and the inlet opening (221) of the rotor chamber outlet channel (22).

11. The automotive electric side-channel liquid pump (10; 10') according to one of the preceding claims, wherein the pump cover (13; 13') defines an axial inlet duct (14).

12. The automotive electric side-channel liquid pump (10; 10') according to one of the preceding claims, wherein the separating means (17) is a separating tube (171).

13. The automotive electric side-channel liquid pump (10; 10') according to one of the preceding claims, wherein the side-channel (183) is a double-flow side-channel (183).

14. The automotive electric side-channel liquid pump (10') according to one of the preceding claims, wherein the drive shaft (25') axially extends into the recess (27') of the pump cover (13').

15. The automotive electric side-channel liquid pump (10; 10') according to one of the claims 11-14, wherein the angle (a) between a side-channel-sided rotor chamber inlet channel opening (211) and the axial inlet duct (14) is between 250° and 330°.