ELECTRIC COOLANT PUMP HAVING A FLOW-COOLED CONTROL CIRCUIT

Abstract

The invention relates to an electric coolant pump for a coolant circuit of an internal combustion engine, having a radially accelerating pump impeller and a spiral housing section of a pump housing. A control circuit is arranged about an inlet on the side of the pump housing opposing the electric engine, and is accommodated in an ECU chamber. An open side of the pump chamber and an open side of the ECU chamber are separated by a heat-exchange cover, which is opened into the pump chamber at a mouth of the inlet, wherein a material from which the ECU chamber is made has a lower heat conductivity than a material from which the heat-exchange cover is made.

Claims

1. An electric coolant pump configured for a coolant circuit of an internal combustion engine, comprising: an electric motor with a pump shaft; a pump impeller which radially accelerates a coolant to be conveyed and which is arranged on the pump shaft and is driven by the electric motor; a pump housing with a pump chamber into which the rotably supported pump shaft extends and in which the pump impeller is accommodated within a spiral housing section that encloses a radial circumference of the pump chamber; a pump inlet which, on the side of the pump housing opposite the electric motor, leads into the pump chamber and is axially directed to the pump impeller as well as an outlet which, at a circumferential section of the spiral housing section, is directed in a tangentially discharging direction; a control circuit which, on the side of the pump housing opposing the electric motor, is situated around the pump inlet and accommodated within an ECU chamber; characterized in that the pump chamber is opened to the side of the pump housing opposing the electric motor and the ECU chamber is opened to the side facing the pump chamber; and the opened side of the pump chamber and the opened side of the ECU chamber are separated by a heat-exchange cover, which is opened at a mouth of the puma inlet into the pump chamber, a material from which the ECU chamber is made having a lower heat conductivity than a material from which the heat-exchange cover and/or the spiral housing section is made.

2. The electric coolant pump according to claim 1, wherein the heat-exchange cover is made of aluminum or an aluminum alloy.

3. The electric coolant pump according to claim 1, wherein the ECU chamber is formed in a molded piece of plastics.

4. The electric coolant pump according to claim 1, wherein the spiral housing section is made of aluminum or an aluminum alloy that is suitable in terms of manufacturing for a pressure die casting process, an injection molding process or a 3D printing process.

5. The electric coolant pump according to claim 1, wherein an unpopulated side of a circuit carrier of the control circuit is in planar contact with the heat-exchange cover.

6. The electric coolant pump according to claim 5, wherein the circuit carrier of the control circuit is a lead frame.

7. The electric coolant pump according to claim 1, wherein the control circuit comprises a printed circuit board that is preferably held in the ECU chamber spaced apart from the circuit carrier by means of a electrically connecting contact pins.

8. The electric coolant pump according to claim 1, wherein the pump impeller as the impeller is formed with a central inflow opening and radial outlet openings and comprises steps formed at a casing portion between the inflow opening and the radial outlet openings in a radial and axial direction; and the heat-exchange cover comprises radially alternating protrusions and recesses, wherein a protrusion and an adjacent recess being respectively radially associated with a step of the pump impeller being arranged axially on the opposite side, and axial shapes of the protrusions being graded to the associated steps in a complementary manner so that a gap is formed between the associated recesses and the steps.

9. The electric coolant pump according to claim 1, wherein the heat-exchange cover comprises a collar that encloses the inlet and/or forms the mouth of the inlet.

10. The electric coolant pump according to claim 1, wherein the ECU chamber and the inlet are formed integrally.

11. The electric coolant pump according to claim 1, further comprising a busbar rail which extends through a channel in the pump housing and establishes an electric connection between the control circuit and a stator of the electric motor.

12. The electric coolant pump according to claim 11, wherein a clearance remains between an internal surface section of the channel and an external surface section of the busbar rail that enables a pressure equalization between an internal space of a motor housing and the ECU chamber.

13. The electric coolant pump according to claim 1, wherein the ECU chamber comprises an opening which is closed by a diaphragm that is impervious to liquids and open to gas.

14. The electric coolant pump according to claim 1, furthermore comprising a metal seal between the pump housing ROM and the heat-exchange cover.

15. The electric coolant pump according to claim 1, furthermore comprising a lip seal between the pump housing and the pump shaft.

16. The electric coolant pump according to claim 1, furthermore comprising an aluminum leakage seal between the pump housing and the electric motor.

17. The electric coolant pump according to claim 1, wherein a motor housing, by means of which the electric motor is attached to the pump housing, is made of aluminum.

18. The electric coolant pump according to claim 1, wherein a leakage chamber is formed between a face side of the electric motor and an opposing outline of the spiral housing section in the pump housing.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The invention is explained in more detail below with reference to the accompanying figures.

[0043] FIG. 1 shows a cross-sectional view of an embodiment of the electric coolant pump;

[0044] FIG. 2 shows a perspective view of the electric coolant pump from FIG. 1;

[0045] FIG. 3 shows a perspective exploded view of the electric coolant pump from FIG. 1;

[0046] FIG. 4 shows a perspective view of the spiral housing section and of the staggered outline of the impeller;

[0047] FIG. 5 shows a perspective view of the control circuit on the heat-exchange cover of the electric coolant pump;

[0048] FIG. 6 shows a perspective view of the sealed motor assembly with the shaft mounting;

[0049] FIG. 7 shows a perspective view of the opened motor assembly;

[0050] FIG. 8 shows a sectional view of the ECU chamber with the diaphragm opening.

DETAILED DESCRIPTION OF THE DRAWINGS

[0051] The structure of an exemplary embodiment of the electric coolant pump according to the invention is explained below with reference to the drawings.

[0052] As may be seen from the FIGS. 1 and 2, the coolant pump consists in the axial direction of the pump of essentially three sections, namely the assembly of electric motor 2, pump housing 1 and control circuit 3 or ECU chamber 30 having an integrated inlet 13. During assembly, the sections are joined using screw bolts 40 that are inserted in the axial direction.

[0053] A separated view of the individual components of the described embodiment is illustrated in FIG. 3.

[0054] An electric motor 2 is attached to one side of pump housing 1 with a stator 25 and a rotor 26. Electric motor 2 is enclosed by a motor housing 27 that is flanged to pump housing 1 using screw bolts 40. Motor housing 27 is opened at the face side facing pump housing 1. A leakage seal 41 is interposed between the motor assembly and the pump housing.

[0055] At stator 25 of electric motor 2, a bus rail 35 extends from the outer circumference of the stator in the axial direction of the pump. Bus rail 35 carries supply lines of electric motor 2 within itself in order to stimulate the stator coils of stator 25 that are driven by power electronics. Pump housing 1 includes a channel 15 into which bus rail 35 is inserted when flanging the motor assembly to pump housing 1. The bus rail extends through channel 15 in the interior of pump housing 1, protected from outer corrosive influences, and provides corresponding supply line contacts of electric motor 2 at the opposing side of pump housing 1.

[0056] Pump housing 1 includes on the side of electric motor 2 a reception for a ball bearing 28 at which pump shaft 21 is supported in an entry area into pump housing 1 against same and rotably mounted. Within pump housing 1, this is followed in the axial direction by a pump chamber 10, into which the free end of pump shaft 21 extends. A radial pump impeller, hereinafter called impeller 20, which is rotably accommodated in pump chamber 10, is fastened at the free end of pump shaft 21. A lip seal 42 is inserted between pump shaft 21 and its entry opening in pump chamber 10.

[0057] Impeller 20 is a radially accelerated pump impeller with a central inflow opening 22 through which the delivery flow is drawn from the inlet 13 of the coolant pump. Around inflow opening 22, a jacket portion of impeller 20 extends radially outward and axially downstream. Chamber-like outlet openings 24 of impeller 20 are situated further downstream from the jacket portion, separated by internal blades that begin below the inflow opening 22 and extend radially outward towards the outlet openings 25.

[0058] Around impeller 20, pump chamber 10 is enclosed by a spiral housing section 11 characteristic for a radial pump. Spiral housing section 11 accommodates the radially accelerated delivery flow from impeller 20 and leads it through the outlet 12 out of the coolant pump inside a circumferential spiral channel. In the present embodiment, spiral housing section 11 as well as outlet 12 and the remaining part of pump housing 1 are made from a pressure die casting alloy.

[0059] Pump chamber 10 is opened on the opposing side of electric motor 2. Between the opened side and inlet 13 of the coolant pump, pump chamber 10 is closed by a pump cover, in the following also called heat-exchange cover 31. Next to the face side end of pump chamber 10, heat-exchange cover 31 provides a mouth receptacle for inlet 13 at an opening upstream from impeller 20.

[0060] Between heat-exchange cover 31 and impeller 20, a staggered labyrinth seal is provided at both components which prevent the delivery flow from bypassing the impeller. For this purpose, radial steps 23 are formed on the face side at the jacket portion of impeller 20 between inflow opening 22 and outlet openings 24, as shown in FIG. 4.

[0061] In the opposing mouth area of inlet 13, radial protrusions 32a and recesses 32b are formed into heat-exchange cover 31 complementary to steps 23 of impeller 20. The staggering of the axial extension of protrusions 32a corresponds to the staggering of steps 23 of impeller 20. Recesses 32b are respectively axially recessed radially outside and adjacent to each of protrusions 32a in heat-exchange cover 31. A radial width of protrusions 32a, recesses 32b and steps 23 is aligned with one another in such a way that respectively one protrusion 32a and one recess 32b of heat-exchange cover 31 are associated with a step 23 of impeller 20.

[0062] As shown in FIG. 1, a gap and an adjacent annular space result at each step 23 between impeller 20 and heat-exchange cover 31. An inner radius of the mouth opening of heat-exchange cover 31 furthermore covers an internal radius of inflow opening 22 of impeller 20. It is thus largely prevented that a portion of the delivery flow drawn in splits off at the inflow opening of the impeller 20 along the jacket portion and bypasses impeller 20 outside of it, as a gap and subsequently a recess with a capillary effect has to be alternatingly and repeatedly passed through when passing through the described labyrinth seal.

[0063] At the same time, the number of protrusions 32a and recesses 32b increases the surface area of heat-exchange cover 31 that is provided for a heat transfer to pump chamber 10 and a filling of the coolant in recesses 32b is subjected to constant exchange due to a leakage stream. Furthermore, heat-exchange cover 31 is machined from aluminum in the present embodiment. Metals having good heat conductivity and corrosion resistance, e.g. aluminum, are also suitable for heat-exchange cover 31.

[0064] A metal seal 43 is interposed between heat-exchange cover 31 and pump housing 1. A fine adjustment of the gap of the labyrinth seal is enabled by a suitable elasticity of metal seal 43 during assembly of heat-exchange cover 31 within a defined tightening torque of screw bolts 40.

[0065] As shown in FIG. 5, control circuit 3 is directly mounted to heat-exchange cover 31 and fixed, for instance, using heat-conducting paste. Instead of a conventional circuit board or a molded circuit in the mentioned related art, a carrier of control circuit 3 is made of a lead frame 34 with a metal core that improves particularly the heat transfer of the power electronics to the heat-exchange cover. In addition to the power electronics, control circuit 3 includes a logical circuit printed on a circuit board 36. Circuit board 36 of the logic printed circuit is electrically connected to lead frame 34 via contact pins 37 and spaced apart from it. Thus the radial end surface to be provided for circuit board 36 is not lost at the surface of the lead frame that has better heat conductivity than the circuit board.

[0066] Control circuit 3 is accommodated in ECU chamber 30 that closes heat-exchange cover 31 to the exterior. In the embodiment shown, ECU chamber 30 is formed monolithically with inlet 13, as shown in FIG. 2, and is made, for instance, of plastics.

[0067] Bus rail 35 extends through openings in heat-exchange cover 31 and lead frame 34. Contacts associated with the supply lines of electric motor 2 are connected via spring contacts to the power electronics of control circuit 3 in a way that is advantageous in terms of assembly.

[0068] As shown in FIG. 6, the motor assembly is sealed by a lip seal 42 and an aluminum leakage seal 41. Lip seal 42 sits on pump shaft 21 between ball bearing 28 and pump chamber 10. Aluminum leakage seal 41 extends in a plane between the motor assembly and pump housing 1 and forms, in the central section, an L shaped collar 44 that radially encloses the accommodation of pump housing 1 for ball bearing 28 and protrudes in a direction towards electric motor 2.

[0069] If, during high load operation of the pump or after increasing wear of lip seal 41, a small amount of leakage occurs at it, droplets may reach through ball bearing 28 of pump shaft 21 to rotor 26 or stator 25 of electric motor 2. The penetrated droplets evaporate in the motor assembly, particularly when they come into contact with components that are at operating temperatures.

[0070] Due to the fact that the air volume in the motor assembly heats more during operation than that in ECU chamber 30 and the pressure thus increases by unequal amounts, channel 15 provides a pressure equalization. An increased pressure in ECU chamber 30 may escape to the outside through diaphragm 38 illustrated in FIG. 8, which is a diaphragm 38 open to gas but impervious to liquids, which closes an opening in ECU chamber 30.

[0071] When, when the pump cools, a partial vacuum is created in the motor assembly, it may in turn be equalized in the reverse order through diaphragm 38 at the ECU chamber and via channel 15 without moisture penetrating into ECU chamber 30.

[0072] As illustrated in FIG. 7, an electric motor 2 with an internal rotor is used in this embodiment. However, in an alternative embodiment, an electric motor 2 with an external rotor may likewise be used as long as a supply line is provided for the central stator at motor housing 27 and pump housing 1 as configured in the illustrated embodiment by bus rail 35. Furthermore, in an alternative embodiment, ECU chamber 30 and the inlet may be separately formed.

[0073] Various modifications to the invention may be apparent to one of skill in the art upon reading this disclosure. For example, persons of ordinary skill in the relevant art will recognize that the various features described for the different embodiments of the invention can be suitably combined, un-combined, and re-combined with other features, alone, or in different combinations, within the spirit of the invention. Likewise, the various features described above should all be regarded as example embodiments, rather than limitations to the scope or spirit of the invention. Therefore, the above is not contemplated to limit the scope of the present invention.