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The invention refers to an automotive electric liquid pump, for example to an electric coolant or lubricant pump.

Conventional automotive electric liquid pumps are provided with a rotor shaft co-rotatably supporting a motor rotor and a pump rotor. The pump lo rotor can be part of a positive displacement pump or of a flow pump. The rotor shaft is rotatably supported with two separate roller or slide bearings which are arranged at one free end of the rotor shaft and between the motor rotor and the pump rotor.

It is an object of the invention to provide a compact automotive electric i s liquid pump.

This object is achieved with an automotive electric liquid pump with the features of claim 1.

The automotive electric liquid pump according to the invention is provided with a pump rotor and a motor rotor, both co-rotatably supported by a0 rotor shaft. The electric motor of the pump is provided as a so-called can motor. The motor rotor is rotating In a separation can which fluidically separates the wet motor rotor chamber from the dry part of the pump and in particular fluidically separates the motor rotor from the motor stator comprising electromagnetic stator coils. The radial outside of the motor5 rotor is provided with a cylindrical bearing ring and the radial inside of the separation can is provided with a corresponding static and cylindrical bearing ring. The cylindrical rotor bearing ring and the cylindrical static bearing ring together define a radial slide bearing. The radial slide bearing is arranged within the axial extension of the motor rotor and is not0 arranged axially outside of the motor rotor. Therefore, the total axial housing. Beside of the radial bearings also the axial bearing is provided as a slide bearing which does not need much installation space.

According to a preferred embodiment, the rotor shaft supporting the motor rotor and the pump rotor is provided with a continuous central cooling bore. The liquid pumped by the pump rotor is pushed through the cooling bore from the pump rotor end of the shaft to the other axial end of the shaft, from where the liquid is radially flowing outwardly and axially flowing back through the bearing gap back to the pump section. The liquid can circulate within the motor section of the pump to realize a continuous axial flow of the liquid through the bearing gap between the rotor bearing ring and that static bearing ring.

Preferably, the motor control electronics is provided in a control electronics chamber which is separated from the motor rotor rotating in the liquid by a single transversal separation wall. The liquid flowing through the shaft bore impinges against the transversal separation wall so that the separation wall is continuously cooled by the liquid radially flowing from the axial center to the outside where the liquid axially flows into the radial bearing gap. Therefore, the secondary liquid circuit defined by the shaft cooling bore and the radial bearing gap has a double function, i.e. cooling of the separation wall and lubrication of the bearing gap. Preferably, the electronics, and in particular the power semiconductors, are provided in heat-conductive contact with the separation wall, for example by using a heat-conductive adhesive.

According to a preferred embodiment, the rotor bearing ring is made out of metal. The rotor bearing ring it can be defined by the motor rotor itself and, for example, can be a polished section of the motor rotor. Preferably, the static bearing ring is made of plastic, and preferably is made of PTFE (polytetrafiuoroethylene) or PA (polyamide). The material pairing of metal, preferably steel, at one side and of a suitable plastic material, for example PTFE at the other side, provides a slide bearing with high mechanical and abrasive stability and low friction. According to a preferred embodiment, a circular ring groove is provided at the radial inside of the separation can between the two static bearing rings. The ring groove separates the two static bearings rings from each other. The axial length of the ring groove preferably is identical with the axial distance of the corresponding static bearings rings. The ring groove provides a very low fluidic resistance in a section where no narrow gap is needed and thereby reduces the total axial flow resistance in the bearing gap over the entire length of the motor rotor.

Preferably, a longitudinal flow groove is provided at the radial inside of the separation can. The longitudinal flow groove can be orientated precisely axially. Alternatively, the longitudinal flow groove can, for example, have a helical orientation with a substantive axial component. The longitudinal flow groove improves the lubrication of the radial slide bearings because the liquid can flow into the bearing gap also from a circumferential/tangential direction coming from the longitudinal flow groove, not only from an axial direction as it would be without a longitudinal flow groove. Additionally, the longitudinal flow groove reduces the total axial flow resistance. Preferably, two or even more longitudinal flow grooves can be provided.

A description of one embodiment of the invention is described with reference to the drawing, wherein the figure shows a longitudinal cross section of an automotive electric liquid pump with two radial slide bearings and one axial slide bearing.

The figure shows an electric automotive liquid pump 10 which is configured as a flow pump, for example as a coolant pump or as a fuel pump. The liquid pump 10 can alternatively also be realized as a positive displacement pump, for example for pumping a lubricant for lubrication of an internal combustion engine.

The liquid pump 10 is provided, seen in axial direction, with a pump section 20, a motor section 22 and a control section 24. The pump section 20 is provided with a pump rotor 21 which is, in this embodiment, an impeller wheel with an axial inlet opening. The pump rotor can alternatively be designed and provided as a part of a positive displacement pump, for example a gerotor pump, a vane pump or another rotating displacement pump.

The pump rotor 21 is supported by a co- rotating the rotor shaft 80 which is co-rotatably fixed to the motor rotor 32. The motor rotor 32 is defined by a motor rotor body 38 made out of a ferromagnetic material and being permanently magnetized. The motor rotor 32 is magnetically driven by a motor stator which is defined by a number of motor stator coils 48 which generate a rotating magnetic field which is followed by the permanently magnetized motor rotor 32. The motor section 22 is designed as a canned motor with a cylindrical separation can 50 separating the wet motor rotor 32 from the dry motor stator coils 48. The separation 50 is defined by a cylindrical can body 51 made out of plastic.

The control section 24 is defined by control electronics 90 arranged within a control electronics chamber 92. The control electronics 90 is defined by a printed circuit board 91 comprising power semiconductors 94 for electrically switching the stator coils 48. The control electronics chamber 92 is separated from the motor section 22 by a transversal separation wall 96. The printed circuit board 91 is fixed to and thermally connected to the separation wall 96 by a heat-conductive adhesive 98 or paste which is applied in particular opposite to the power semiconductors 94.

The motor rotor 32 is rotatably supported by two radial slide bearings 61, 62 and by one axial slide bearing 70. The first radial slide bearing 61 is defined by a cylindrical static bearing ring 54 at the radial inside of the plastic separation can 50 and a corresponding cylindrical rotor bearing ring 34 at the radial outside of the motor rotor 32. The second radial slide bearing 62 is, as well, defined by a cylindrical static bearing ring 56 at the radial inside of the plastic separation can body 50 and a corresponding rotor bearing ring 36 at the radial outside of the motor rotor 32. The radial bearing gap G between the bearing surfaces 34,54;36,56 of both radial sliding bearings 61, 62 is about 0,1 mm.

The rotor bearing rings 34, 36 are defined by the polished cylindrical surface of the motor rotor body 38 made out of ferromagnetic steel or of another ferromagnetic metal. The static bearings rings 54, 56 are defined by a cylindrical inner surface of the can body 51 which is made out of plastic, preferably made out of PTFE. The two radial slide bearings 61, 62 are axially separated by a circumferential ring groove 42 with a radial depth of more than 0,5 mm. The separation can 50 is also provided with two parallel longitudinal flow grooves 44 which axially overlap the two radial slide bearings 61, 62. The radial depth of the longitudinal flow grooves is more than 0,5 mm.

The axial bearing 70 is defined by a separate ring body 71 which is fixed to the motor rotor body 38. The axial bearing ring body 71 is made out of PTFE and is provided with 3 radial slits 76. The axial bearing ring body 71 defines an axial bearing ring 72 which is cooperating with a corresponding static bearing ring 74 defined by a transversal wall 14 between the motor section 22 and the pump section 20.

The transversal wall 14 and the separation wall 96 are part of a pump housing 12 which is made out of metal, preferably made out of aluminium. The separation can body 51 is hold in corresponding circumferential grooves of the separation wall 96 and the transversal wall 14.

The rotor shaft 18 is provided with a continuous central cooling bore 82 which allows the liquid to flow from the pump rotor section 20 to the separation wall 96 where the liquid flows radially to the outside and then axially back through the radial bearing gap G of both radial slide bearings 61, 62 to the pump section 20.