Patent Description:
An electrical automotive liquid pump according to the state-of-the-art is typically driven by a brushless electric motor being electronically commutated by power electronic components. The power electronic components generate a relatively large heat quantity. In addition, the electric motor in particular the motor stator generates an additional quantity of heat so that an effective heat dissipation within the pump housing is required. The electric motor is therefore designed as a canned electric motor, wherein the motor rotor and the motor stator of the electric motor are fluidically separated by a separating tube being arranged within the gap between the motor rotor and the motor stator.

The fluidic separation of the motor rotor and the motor stator allows to flood the volume at the inside of the separating tube with the pumped liquid which then defines a cooling flow for dissipating the heat being generated by the electric motor and the power electronic components. The volume at the inside of the separating tube therefore defines a wet zone and the motor rotor which is arranged within the wet zone and which is rotating within the liquid is therefore a so-called wet running motor rotor. Due to the fluidic separation provided by the separating tube, the motor stator as well as the power electronic components are not in contact with the pumped liquid so that the volume of the pump housing outside of the separating tube defines a dry zone.

Exemplary electrical automotive liquid pumps are disclosed in <CIT>, in <CIT>, in <CIT>, in <CIT> or in <CIT>.

It is an object of the invention to provide a simple and relatively costefficient electrical automotive liquid pump with an improved cooling flow behavior over the prior art.

This object is achieved with an electrical automotive liquid pump according to the invention with the features of main claim <NUM>.

An electrical automotive liquid pump according to the present invention comprises an electric drive motor with a motor rotor and a motor stator, wherein the motor rotor is co-rotatably connected to a drive shaft being co-rotatably connected to a pump wheel. Accordingly, the motor rotor rotates the pump wheel around a rotor axis for pumping the liquid within the electrical automotive liquid pump. The motor rotor and the motor stator are fluidically separated by a separating tube which is preferably arranged in the gap between the motor rotor and the motor stator. The separating tube thereby defines a wet zone and a dry zone within the pump housing, wherein the wet zone is flooded with liquid being pumped by the pump wheel.

The separating tube is provided with an integral bearing seat structure comprising a bearing seat and a supporting structure. The supporting structure is defined by several blades which connect the bearing seat with the separating tube in particular with the tube-shaped sidewall of the separating tube which radially encloses the motor rotor. The blades of the supporting structure are arranged under a pitch angle with respect to the rotor axis resulting in a turbine-type shaped bearing seat structure, wherein the blades are preferably arranged adjacent and equiangular to each other with a substantially identical pitch angle. The pitch angle substantially depends on the axial extension of the bearing seat structure and the number of the blades. As the blades are preferably circumferentially not overlapping which allows a relatively simple manufacturing of the separating tube, for example by a molding process, an increasing number of blades results in a reduced pitch angle which is disadvantageous for a proper flow deflection.

The turbine-type shaped arrangement of the blades provides a forced axial and circumferential flow guidance of the liquid flowing through the wet zone. The liquid is preferably branched off from a pumping section being arranged at one axial end of the pump housing. From the pumping section, in which the pump wheel rotates, the liquid flows through the wet zone towards the other axial end of the pump housing being opposite to the pumping section. Preferably, at that other axial end of the pump housing, the power electronic components are arranged adjacent to a dry side of a separating wall being part of a separate separating tube cover which preferably axially closes the separating tube. Thereby, the separating tube cover fluidically separates the wet zone from a dry electronics chamber in which the power electronic components are arranged in a preferably heat transferring contact to that side of the separating wall which is not in a fluidic contact with the liquid.

Due to the rotation of the motor rotor, the liquid which is flowing through the wet zone is in addition to its axial flow direction rotated within the wet zone which improves the convective heat transfer between the separating tube and the liquid flowing within the wet zone. However, the rotation of the motor rotor results in a domination of the circumferential flow component so that the axial component of the flow becomes marginal. Accordingly, the blades of the turbine-type shaped bearing seat structure are arranged such that the rotating cooling flow is maintained within the bearing section of the separating tube where the bearing seat structure is arranged, but the flow is redirected more into the axial direction so that the liquid is guided towards the separating wall and is flowing properly along the separating wall for absorbing the heat being transferred to the separating wall by the heat generating pump components.

Compared to a conventional bearing seat structure of a prior art pump with axially oriented ribs for connecting the bearing seat with the separating tube, the cooling flow profile of a pump with a bearing seat structure according to the invention is much more uniform within the bearing section of the separating tube. As a result, the convective heat transfer in particular at the separating wall which is loaded with the heat generated by the power electronic components is relatively large so that the heat dissipation within the bearing section is significantly increased compared to a prior art pump.

Furthermore, the bearing seat is provided with an integral plain bearing shell to directly support the drive shaft within the bearing seat. Accordingly, the bearing seat does not need an additional separate bearing shell so that the direct support of the drive shaft within the bearing seat results in a relatively small required total radial space for the bearing seat. As a result, the turbine-type shaped supporting structure is relatively large compared to a prior art pump with an additional separate bearing shell so that the blades are provided with a relatively large radial extension resulting in an exceptionally good guidance of the cooling flow.

In a particularly preferred embodiment of the invention, the supporting structure comprises at least three blades. By using at least three blades, the deflection of the flow from the substantially circumferential direction to the axial and circumferential direction can be provided sufficiently. As the pitch angle of the blades depends on the axial length of the bearing seat structure and the number of the blades, a number of three or four blades represents a good compromise between a suitable pitch angle and a relatively short axial length of the bearing seat structure.

In a preferred embodiment of the invention, the bearing shell and the separating tube are made of the same material. Preferably, the separating tube and the bearing shell are made of a plastic material with relatively good sliding properties, for example, the separating tube can be made of a Teflon-based plastic material with a relatively small friction coefficient. As a result, a relatively low-friction support of the drive shaft is provided.

In a particularly preferred embodiment of the invention, the blades of the turbine type shaped bearing seat structure are axially overhanging referring to the bearing seat. The axial overhang is provided on that side of the supporting structure which is facing the motor rotor, i.e., the blades are axially extending over the axial end surface of the bearing seat. Preferably, the overhang of the blades is at least <NUM>% of the axial blade length. Accordingly, the overhanging blade tips extend axially into that section where the cooling flow is rotating around the rotor axis initiated by the rotating motor rotor. As a result, the cooling flow which is rotating within the wet zone is caught by the axially overhanging blade tips and is forcibly guided by the blades towards the separating wall. These axial overhanging blades are an independent aspect of the invention and can be provided without an integral plain bearing shell being a part of the bearing seat so that the axial overhang can be alternatively provided in an electrical automotive liquid pump, wherein the bearing seat is provided with a separate bearing shell.

In a preferred embodiment of the invention, the separating tube is at one axial end provided with a mounting section which is provided with a smaller diameter than a diameter of the separating tube motor section defining that section, where the motor rotor is arranged i. e, that section which is arranged in the gap between the motor rotor and the motor stator. The mounting section is preferably arranged at that axial end of the separating tube where the bearing seat structure and the blades are arranged. The reduction of the diameter of the mounting section results in a reduced flow cross-section and therefore results in an acceleration of the cooling flow which in a relatively large convective heat transfer.

Preferably, the mounting section is provided with axial reinforcement ribs at its radial outside. As the separating tube is preferably inserted into a collar of the separating tube cover, the reinforcement ribs on the one hand reinforce the mounting section and thereby reinforce that section where the bearing seat structure is arranged so that the deformation of the bearing seat structure or the sidewall of the mounting section is avoided. As a result, the drive shaft is always exactly positioned without any deviation of the rotor axis. On the other hand, the axial reinforcement ribs are used as a radial supporting structure for supporting and accurately positioning the mounting section within the separating tube cover's collar which preferably encloses the mounting section circumferentially.

In a preferred embodiment of the invention, the blades radially extend over more than <NUM>% of the radius of the mounting section. This results in a relatively large blade surface which is contacting the cooling flow so that a relatively good cooling flow guidance and a relatively good deflection of the cooling flow towards the separating wall is ensured.

In a particularly preferred embodiment of the invention, the axial distance between the bearing seat structure and the separating tube cover is at least <NUM>% of the axial blade length. Thereby, a blade-free section is provided between the bearing seat structure and the heat loaded section of the separating wall so that a uniform and resistance-free rotational movement of the cooling flow within the blade-free section is guaranteed resulting in a proper convective heat transfer between the separating wall and the cooling flow.

The blades are preferably substantially planar which allows a relatively simple manufacturing of the separating tube and which guarantees a sufficient flow deflection with only slight not-useful cooling flow turbulences. Alternatively, the blades can also be provided with an arc -shaped cross section, seen in a tangentially oriented cross plane, that could improve the flow deflection compared to the planar blade.

In a preferred embodiment of the invention, the blades are provided with a profiled surface on that side of the blade which is facing the motor rotor. For example, the blade surface facing the motor rotor could be provided with several substantially parallel flow guiding ribs which extend from the blade surface in axial direction and which extend circumferentially along the blade surface. As a result, the flow guidance of the rotating cooling flow is more laminar resulting in a relatively good heat dissipation.

In a preferred embodiment of the invention, the cross-section of the blades defines an airfoil-shaped profile. The airfoil-shaped profile is arranged such that it is oriented, seen in a tangentially oriented plane, towards the motor rotor. The liquid which is guided by the blades towards the separating tube cover flows along the airfoil-shaped blades so that the flow deflection towards the separating wall is improved compared to a planar or arc-shaped blade.

In a particularly preferred embodiment, the pitch angle of the blades is between <NUM>° and <NUM>° with respect to the rotor axis. As a result, the relation between the circumferential flow component and the axial flow component of the cooling flow is relatively well-balanced resulting in a sufficient flow behavior at the separating wall.

One embodiment of the invention is described with reference to the enclosed drawings, wherein.

<FIG> shows an electrical automotive liquid pump <NUM> which is defined by an electrically driven centrifugal water circulating pump being used for providing a relatively small cooling circuit of an auxiliary unit of a passenger car with water. The electrical automotive liquid pump <NUM> is provided with an electrical drive motor <NUM> comprising a cylindrical motor rotor <NUM> which is arranged at the radial inside of a hollow cylindrical separating tube <NUM> being made of a Teflon-based plastic material. At the radial outside of the separating tube <NUM>, a cylindrical motor stator <NUM> is arranged which circumferentially surrounds the separating tube <NUM> as well as the motor rotor <NUM>. Accordingly, a hollow cylindrical separating tube motor section <NUM> is arranged in the air gap between the motor rotor <NUM> and the motor stator <NUM>.

The separating tube <NUM> is at its both axial ends closed each by one component of a multipiece pump housing <NUM>, wherein at its first axial end, the separating tube <NUM> is closed by a separating flange <NUM> which together with a pump cover <NUM> defines a pumping section <NUM> in which a pump wheel <NUM> is rotating for pumping liquid through a volute <NUM>. The separating flange <NUM> is therefore provided with an axially protruding separating flange collar <NUM> which is inserted into the separating tube <NUM>, wherein a first sealing ring <NUM> is provided between the separating flange collar <NUM> and the separating tube <NUM>. At the other opposite axial end of the separating tube <NUM> being remote from the pump wheel <NUM>, the separating tube <NUM> is closed by a separating tube cover <NUM> comprising a substantially planar separating wall <NUM> and an axially protruding separating tube cover collar <NUM> in which a cylindrical separating tube mounting section <NUM> is inserted. A second sealing ring <NUM> is provided between the separating tube cover collar <NUM> and the separating tube mounting section <NUM> for fluidically separating a wet zone <NUM> at the radial inside of the separating tube <NUM> from a dry zone <NUM> at the radial outside of the separating tube <NUM>. At its radial outside, the mounting section <NUM> is provided with a plurality of equiangularly arranged axial reinforcement ribs <NUM> for reinforcing the mounting section <NUM> and the bearing seat structure <NUM>. The reinforcement ribs <NUM> avoid a deformation of the separating tube <NUM> and support the mounting section <NUM> of the separating tube <NUM> in the separating tube cover collar <NUM>. The diameter d of the separating tube mounting section <NUM> is smaller than the diameter D of the separating tube motor section <NUM>.

The motor rotor <NUM> is rotatably arranged within the wet zone <NUM>, whereas the motor stator <NUM> is arranged within the dry zone <NUM>. The motor rotor <NUM> is co-rotatably connected to a hollow-cylindrical drive shaft <NUM> being provided with an axial backflow channel <NUM> extending completely longitudinally through the drive shaft <NUM>. The drive shaft <NUM> co-rotatably connects the motor rotor <NUM> with the pump wheel <NUM> which is thereby rotated around a rotational axis R for pumping the liquid from a suction port S to a discharge port (not shown). The drive shaft <NUM> is supported at the pumping-chamber-sided end of the separating tube <NUM> by a separate plain bearing <NUM> being supported within the separating tube flange <NUM>. At the other axial end of the separating tube <NUM> where the separating tube mounting section <NUM> is arranged, the drive shaft <NUM> is supported by an integral bearing seat structure <NUM> which is an integral part of the separating tube <NUM>. This bearing seat structure <NUM> comprises a hollow-cylindrical bearing seat <NUM> with an integral plain bearing shell <NUM>. The bearing seat structure <NUM> further comprises three blades <NUM> defining a supporting structure <NUM> which mechanically connects the bearing seat <NUM> with the radial sidewall of the separating tube <NUM>. The bearing seat structure <NUM> and the integral plain bearing shell <NUM> are therefore made of the same Teflon-based material as the separating tube <NUM> is made of.

The rotational motor rotor <NUM> defines a rotational direction RD. When the pump wheel <NUM> rotates, the liquid flows into the pumping section <NUM> through the suction port S, the liquid being axially sucked-in by the pump wheel <NUM>. The liquid thereby defines a flow direction F. Due to the rotation of the pump wheel <NUM>, the liquid is, as a result of the centrifugal force, discharged radially outwards so that the liquid enters the volute <NUM> of the pumping section <NUM>, from where the liquid is pumped into the discharge port (not shown). The pumping section <NUM> is fluidically connected to the wet zone <NUM> by a borehole (not shown) defining a connection channel through the separating tube flange <NUM> so that a relatively small volume flow of the pumped liquid is branched off from the total volume flow being pumped through the pumping section <NUM>. This branched-off cooling flow F enters the wet zone <NUM> and flows axially towards the other axial end of the separating tube <NUM> towards a dry electronics chamber <NUM> being fluidically separated from the wet zone <NUM> by the separating tube cover <NUM>. A printed circuit board <NUM> is arranged within the electronics chamber <NUM>, the printed circuit board <NUM> comprising several power electronic components <NUM> for electronically commutating and for driving the electric motor <NUM>.

As a result of the rotating motor rotor <NUM>, the cooling flow F is rotated in rotational direction RD by the motor rotor <NUM> so that the cooling liquid flows, in addition to its axial flow component, circumferentially at the radial inside of the separating tube motor section <NUM>. Accordingly, the cooling flow F within the wet zone <NUM> absorbs the heat being generated by the electric motor <NUM>, in particular the heat of the motor stator <NUM> which is transferred to the separating tube <NUM>.

The blades <NUM> of the bearing seat structure <NUM> are arranged under a pitch angle c with respect to the rotor axis R, shown in <FIG> and <FIG>. The pitch angle c is <NUM>°. The planar blades <NUM> are with respect to the rotational direction RD of the motor rotor <NUM> arranged such that the substantially circumferentially rotating cooling flow F is deflected more into the axial direction whereas the circumferential flow component is not relevantly affected so that a vortex-type shaped cooling flow F is defined which flows through the bearing seat structure <NUM> vortically towards the separating wall <NUM> of the separating tube cover <NUM>.

As shown in <FIG>, the blades <NUM> are axially overhanging referring to the bearing seat <NUM>. The overhang a which is provided at that side of the bearing seat structure <NUM> which is facing the motor rotor <NUM> is <NUM>,<NUM> wherein the axial blade length L of the blades <NUM> is <NUM>. The axially protruding blade tips <NUM> of the blades <NUM> extend axially into the circumferentially rotating cooling flow F between the motor rotor <NUM> and the bearing seat <NUM> and therefore catch the rotating cooling flow F to forcibly guide the cooling flow F through the bearing seat structure <NUM> towards the separating wall <NUM> of the separating tube cover <NUM>.

As a result of the integral bearing shell <NUM>, the bearing seat <NUM> is radially relatively small so that the radial extension of the blades <NUM> can be relatively large. The blades <NUM> radially extend over <NUM>% of the radius r of the separating tube mounting section <NUM> so that the blades <NUM> allow a sufficient cooling flow F to pass the supporting structure <NUM>. In addition, the blades <NUM> are circumferentially not overlapping, shown in <FIG>, which allows a simple manufacturing of the separating tube <NUM> using one simple molding process.

A blade-free section with an axial length b of <NUM> is provided between the bearing seat structure <NUM> and the separating wall <NUM> of the separating tube cover <NUM>. The printed circuit board <NUM> is arranged next to the separating wall <NUM>, wherein the printed circuit board <NUM> is arranged within the electronics chamber <NUM> in a heat transferring contact to the separating wall <NUM> at that side of the separating wall <NUM> which is not in a direct fluidic contact with the liquid within the wet zone <NUM>. As a result, the vortically rotating cooling flow F flows resistance-free along the separating wall <NUM> resulting in a relatively uniform flow profile which results in a relatively good convective heat transfer between the separating wall <NUM> and the cooling flow F. This relatively good heat transfer allows to absorb a relatively large heat quantity being generated by the power electronic components <NUM>.

Claim 1:
Electrical automotive liquid pump (<NUM>) comprising an electrical drive motor (<NUM>) with a motor rotor (<NUM>) and a motor stator (<NUM>), the motor rotor (<NUM>) being co-rotatably connected to a drive shaft (<NUM>), wherein the drive shaft (<NUM>) is co-rotatably connected to a pump wheel (<NUM>),
the motor rotor (<NUM>) and the motor stator (<NUM>) being fluidically separated by a separating tube (<NUM>) to define a wet zone (<NUM>) and a dry zone (<NUM>) within a pump housing (<NUM>),
the separating tube (<NUM>) being provided with an integral bearing seat structure (<NUM>) with a bearing seat (<NUM>) and a supporting structure (<NUM>), the supporting structure (<NUM>) being defined by several blades (<NUM>) connecting the bearing seat (<NUM>) with the separating tube (<NUM>), and wherein
the bearing seat (<NUM>) is provided with an integral plain bearing shell (<NUM>) to directly support the drive shaft (<NUM>),
characterized in that the blades (<NUM>) are arranged under a pitch angle (c) with respect to a rotor axis (R), so that a turbine-type shaped bearing seat structure (<NUM>) is defined.