US20180238348A1 - Electric coolant pump having a flow-cooled control circuit - Google Patents

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.

Description

RELATED APPLICATIONS
• This application is a National Phase entry of PCT Application No. PCT/EP2016/069795 filed Aug. 22, 2016 which application claims the benefit of priority to German Application No. 10 2015 114 783.1, filed Sep. 3, 2015, the entire disclosures of which are incorporated herein by reference.
FIELD OF THE INVENTION
• The present invention relates to an electric coolant pump having a control circuit that is cooled by the delivery flow.
BACKGROUND OF THE INVENTION
• In order to maintain the combustion machine within a temperature range optimal for an efficient combustion and low exhaust emissions, the heat delivery of the cooling system is controlled as a function of the present operating state. For this reason, electric coolant pumps are increasingly being used in automotive applications which may be driven independently of the rotation speed of an internal combustion engine and which enable a higher flexibility in controlling a coolant circuit in response to various operating parameters of the internal combustion engine or environmental influences. Thermal management of an internal combustion engine thus provides, for example, that the heat delivery is initially completely and then in part stopped during a cold-start phase.
• One problem when using electric coolant pumps is the sufficient cooling of the control electronics inside the coolant pump, which represents a significant factor for the service life of the coolant pump and also for the operational safety of the internal combustion engine as well as the reliability of the driven vehicle. Under difficult circumstances, the temperature of the coolant may reach a level very close to the permissible maximum temperature of the electronic elements of the control circuit of the pump's electric motor so that, when there is additional waste heat from the electric pump motor itself, there is a risk of the control circuit failing due to overheating.
• When an electric motor is used as a pump motor, it is typically encased together with the control electronics and installed as a motor assembly in order to protect same from outer corrosive influences and dirt during operation. However, by enclosing the electric motor and the electronics as a motor assembly, the electric motor's own waste heat, which is correlated with its power loss, cannot be discharged via an air stream as in other applications. The waste heat of the electric motor thus flows directly into the electronic elements of the control circuit of the coolant pump as heat input.
• In a suitable electric pump motor, the power dissipation is around 20% of the electric power so that a pump motor with 500 W, as is used, for instance, in a coolant pump of a coolant circuit in a passenger vehicle, creates a heat input of 100 W under full-load operation, which is additionally absorbed by the coolant pump via the waste heat of the coolant. The constituent elements of the electric motor reach temperatures of more than 200° C.
• In the related art, coolant pumps are known that use a heat exchange with the coolant of the internal combustion engine in order to maintain the permissible operating temperature of the electronic elements. The coolant has a much higher thermal conduction coefficient of approximately 0.441 W/mK compared to air with 0.0262 W/mK. In addition, it remains within a defined temperature range during the operation of the coolant circuit, while the air temperature varies widely as a function of the surroundings, particularly of the internal combustion engine, and, where applicable, a speed of movement.
• U.S. Pat. No. 6,082,974 B1 describes a motor pump with a chamber that is disposed adjacent to an inlet and an outlet of the pump and which is provided in order to accommodate a controller.
• However, it should be noted that when a pump is used as a coolant pump for an internal combustion engine, the coolant absorbs a high temperature during operation of the internal combustion engine and thus introduces a high heat input itself.
• After passing through the cooler or a heat exchanger with the surroundings, the coolant should have a maximum temperature of up to 113° C. according to the standards of the automobile industry. In applications with particularly high demands, in extreme ambient temperatures or in adverse cases, the coolant in a coolant circuit of an internal combustion engine in a vehicle may however still reach a temperature of, for instance, 120° C. or even 130° C.
• Thus a low difference in temperature of only a few degrees between the coolant temperature and the permissible operating temperature of the electronic elements is available. In order to ensure a reliable operation of the electronic elements in the coolant pump even under difficult conditions as to the operating state of the internal combustion engine or the exterior temperature, there is a technical need to create an efficient heat transport between the electronic elements and the coolant despite the small usable temperature difference.
• In addition, the coolant pump is typically installed in a space-saving manner in the immediate vicinity of the internal combustion engine. The coolant pump is consequently again subjected to heating with considerably higher ambient temperatures due to the waste heat of the internal combustion engine.
• DE 11 2013 003 549 T5 describes a coolant pump for automotive applications with a donut-shaped control circuit which abuts a radial pump chamber at an axial height of an impellant. The pump is equipped with a wet running motor and is separated by a wet bushing from the pump chamber. However, the donut-shaped control circuit is enclosed together with the stator of the wet runner and is thus subjected to its waste heat.
• JP 2004 316548 A shows a liquid pump with a flow-cooled control circuit and a small axial construction height. The control circuit is disposed on the outside of the pump housing around the inlet of the pump on the opposing side of the motor.
SUMMARY OF THE INVENTION
• One object of the present invention is to provide an electric coolant pump that ensures an effective cooling of the control circuit of the electric pump drive via the coolant circuit of an internal combustion engine.
• The object is solved according to the invention by an electric coolant pump according toclaim1. This pump is particularly characterized by the fact that a pump chamber is opened to the side of the pump housing that is opposite of the electric motor, and an ECU chamber is opened to the side that faces 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 an inlet into the pump chamber; a material from which the ECU chamber is made has a lower heat conductivity than a material from which the heat-exchange cover and/or the spiral housing section is made.
• The invention therefore provides, for the first time, that a control circuit that is disposed on the side of the pump housing which is opposite of the electric motor and disposed around the inlet is separated by a heat-exchange cover from the convective delivery flow in the pump chamber.
• The invention further provides that the control circuit is cooled by the delivery flow and is also insulated against the still higher ambient temperatures in the immediate vicinity of the internal combustion engine.
• Due to the increased heat conductivity of the material of the heat-exchange cover, a better heat exchange is created between the delivery flow of the coolant and the control circuit. The disposition of the heat-exchange cover and the control circuit in close vicinity to the impeller further provides a thermal bridge with a short length of the temperature gradient.
• The control circuit is disposed separately and does not absorb any waste heat from the electric motor. In contrast to the mentioned related art, the coolant pump according to the invention furthermore has advantages that enable a simplified assembly thereof. Due to the open-style pump chamber, the electric motor on the one hand and particularly the impeller on the other hand are freely accessible for assembly. When fastening the heat-exchange cover over the impeller, a gap in between may be set more precisely.
• Furthermore, by disposing the control circuit around the inlet of the coolant pump, a smaller axial dimension than when disposing it at an outer surface of the electric motor is realized. This aspect is a considerable advantage in automotive applications, in which there is an increased space constraint due to the increasing number of auxiliary units in an engine compartment.
• Other advantageous further embodiments of the electric coolant pump according to the invention are the object of the dependent claims.
• In an advantageous embodiment, the heat-exchange cover may be made of aluminum or an aluminum alloy. Aluminum is characterized by good heat conductivity and simultaneously has a sufficient corrosion protection.
• In an advantageous embodiment, the ECU chamber may be formed as a molded piece of plastics. An enclosure of plastics with a low heat conductivity may insulate the control circuit from the hot ambient temperatures at the internal combustion engine in a way which is favorable in terms of manufacturing and may isolate it from moisture and dirt.
• In a preferred embodiment, the spiral housing section may be made of aluminum or an aluminum alloy which is suitable in terms of manufacturing for a pressure die casting process, an injection molding process or a 3D printing process. A die casting alloy simplifies the manufacturing of the characteristic shape of the spiral housing. Furthermore, the heat conductivity of the material in the area of the pump housing facilitates a temperature absorption at the interfaces to the motor assembly and the ECU chamber as well as an introduction of the absorbed temperatures into the delivery flow circulating within.
• In a preferred embodiment, an unpopulated side of a circuit carrier of the control circuit may be in planar contact with the heat-exchange cover. In this way, a greatest possible heat exchange area between the control circuit and the delivery flow of the coolant is provided.
• In a preferred embodiment, the circuit carriers of the control circuit may be a lead frame. Using a lead frame instead of a circuit board enables an improved heat transfer of the electronic elements to the heat-exchange cover without any compound, cavities, internal plug connections, crimp connections or clamping connections.
• In another embodiment, the control circuit may have a printed circuit board that is preferably held in the ECU chamber spaced apart from the circuit carrier by means of electrically connecting contact pins. Where the control circuit has a printed circuit board for the component of a logic circuit, shielding of the remaining elements against the heat exchange surface of the heat-exchange cover may be avoided by situating the printed circuit within the space at a distance by means of electrically connecting contact pins.
• In a preferred embodiment, the pump impeller may be formed as an impeller with a central inflow opening and radial outlet openings and may comprise steps formed in a radial and axial direction between the inflow opening and the radial outlet openings. In addition, the heat-exchange cover may have radially alternating protrusions and recesses, one protrusion and one adjacent recess being respectively radially associated with one step of the pump impeller situated axially on the opposite side, and axial shapes of the protrusions being graded towards the associated steps in a complementary manner so that a gap is formed between the associated recesses and the steps.
• The complementary grading in conjunction with the annular recesses create a labyrinth seal between the impeller and the mouth of the inlet in the heat-exchange cover. A leakage stream branching off radially outside at the face side of the impeller from the flowing delivery flow is slowed, when it bypasses the impeller, by radially alternating pressure zones when flowing through the gaps at the protrusions and the adjacent recesses that have a capillary effect. The labyrinth seal likewise counteracts a pressure of the accelerated coolant in the spiral housing so that no return flow is generated past the impeller which would impair the inflow.
• On the one hand, the labyrinth seal improves the volumetric efficiency of the pump. On the other hand, the labyrinth seal improves a heat transfer in an area in which the heat-exchange cover is in close contact with the coolant due to the enlarged surface along the protrusions and recesses.
• In a preferred embodiment, the heat-exchange cover may have a collar that encloses the inlet and/or forms the mouth of the inlet. An indirect and/or direct contact surface for the heat exchange with the coolant may thus be increased. Furthermore, the collar enables the accommodation of a separately produced inlet.
• In a preferred embodiment the ECU chamber and the inlet may be formed monolithically. In this way, the number of components produced and the effort for assembly may be decreased.
• In a preferred embodiment, the electric coolant pump may have a bus 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. The bus rail facilitates the insertion of the pump housing at the motor assembly and in particular the running of the motor supply lines to the opposite side of the pump housing during assembly of the pump.
• In a preferred embodiment, a clearance may remain between an internal surface section of the channel and an external surface section of the bus rail that enables a pressure equalization between an internal space of a motor housing and the ECU chamber. The motor assembly may thus be sealed against external weather conditions, and an excess pressure during its heating may be equalized towards the cooler ECU chamber.
• In a preferred embodiment, the ECU chamber may have an opening which is closed by a diaphragm that is impervious to liquids and open to gas. An excess pressure, which may result in particular from the pressure equalization of the heated motor assembly, may be decreased in the ECU chamber without moisture entering during cooling at a later point in time.
• In a preferred embodiment, the electric coolant pump may have a metal seal between the pump housing and the heat-exchange cover. A metal seal has an elasticity suitable for assembly which enables a precise adjustment of the gap size between the heat-exchange cover and the impeller in the area of the labyrinth seal when tightening the heat-exchange cover by means of flange screws that are distributed around its circumference.
• In a preferred embodiment, the electric coolant pump may have a lip seal between the pump housing and the pump shaft. The lip seal enables a sufficient sealing of the pump chamber below the impeller against the mounting of the pump shaft at the pump housing. In addition, a lip seal is characterized by lower frictional torque than a mechanical seal typically used for water pumps, i.e., a slip ring seal pre-tensioned by a spring.
• In a preferred embodiment, the electric coolant pump may have an aluminum seal against leakage between the pump housing and the electric motor. The housing of the motor assembly thus does not have to be enclosed or closed and a wall for enclosing the motor assembly may be omitted. The aluminum seal which is interposed at the pump housing before assembly of the electric motor closes the opened side to the motor components against a possible leakage of coolant from the pump housing. Furthermore, the heat conductivity of the sealing material at the interface of the pump housing facilitates the heat transfer from the motor assembly to the spiral housing section that is preferably made using aluminum pressure die casting and that introduces the heat further into the delivery flow.
• In a preferred embodiment, a motor housing, by means of which the electric motor is attached to the pump housing, may be made of aluminum. The heat conductivity of the motor housing in turn facilitates the heat delivery from the motor assembly to the pump housing.
• In a preferred embodiment, a leakage chamber may be formed between a face side of the electric motor and an opposing outline of the spiral housing section in the pump housing. The leakage chamber forms a cavity which is separated by the leakage seal from the opened side of the motor assembly. The leakage chamber may achieve a delaying, demoisturizing effect should a small amount of leakage occur in the form of coolant dripping into the motor assembly due to wear of the lip seal.
BRIEF DESCRIPTION OF THE DRAWINGS
• The invention is explained in more detail below with reference to the accompanying figures.
• FIG. 1 shows a cross-sectional view of an embodiment of the electric coolant pump;
• FIG. 2 shows a perspective view of the electric coolant pump fromFIG. 1;
• FIG. 3 shows a perspective exploded view of the electric coolant pump fromFIG. 1;
• FIG. 4 shows a perspective view of the spiral housing section and of the staggered outline of the impeller;
• FIG. 5 shows a perspective view of the control circuit on the heat-exchange cover of the electric coolant pump;
• FIG. 6 shows a perspective view of the sealed motor assembly with the shaft mounting;
• FIG. 7 shows a perspective view of the opened motor assembly;
• FIG. 8 shows a sectional view of the ECU chamber with the diaphragm opening.
DETAILED DESCRIPTION OF THE DRAWINGS
• The structure of an exemplary embodiment of the electric coolant pump according to the invention is explained below with reference to the drawings.
• As may be seen from theFIGS. 1 and 2, the coolant pump consists in the axial direction of the pump of essentially three sections, namely the assembly ofelectric motor2, pumphousing1 andcontrol circuit3 orECU chamber30 having anintegrated inlet13. During assembly, the sections are joined usingscrew bolts40 that are inserted in the axial direction.
• A separated view of the individual components of the described embodiment is illustrated inFIG. 3.
• Anelectric motor2 is attached to one side ofpump housing1 with astator25 and arotor26.Electric motor2 is enclosed by amotor housing27 that is flanged to pumphousing1 usingscrew bolts40.Motor housing27 is opened at the face side facingpump housing1. Aleakage seal41 is interposed between the motor assembly and the pump housing.
• Atstator25 ofelectric motor2, abus rail35 extends from the outer circumference of the stator in the axial direction of the pump.Bus rail35 carries supply lines ofelectric motor2 within itself in order to stimulate the stator coils ofstator25 that are driven by power electronics.Pump housing1 includes achannel15 into whichbus rail35 is inserted when flanging the motor assembly to pumphousing1. The bus rail extends throughchannel15 in the interior ofpump housing1, protected from outer corrosive influences, and provides corresponding supply line contacts ofelectric motor2 at the opposing side ofpump housing1.
• Pump housing1 includes on the side of electric motor2 a reception for aball bearing28 at which pumpshaft21 is supported in an entry area intopump housing1 against same and rotably mounted. Withinpump housing1, this is followed in the axial direction by apump chamber10, into which the free end ofpump shaft21 extends. A radial pump impeller, hereinafter calledimpeller20, which is rotably accommodated inpump chamber10, is fastened at the free end ofpump shaft21. Alip seal42 is inserted betweenpump shaft21 and its entry opening inpump chamber10.
• Impeller20 is a radially accelerated pump impeller with acentral inflow opening22 through which the delivery flow is drawn from theinlet13 of the coolant pump. Aroundinflow opening22, a jacket portion ofimpeller20 extends radially outward and axially downstream. Chamber-like outlet openings24 ofimpeller20 are situated further downstream from the jacket portion, separated by internal blades that begin below theinflow opening22 and extend radially outward towards theoutlet openings25.
• Aroundimpeller20,pump chamber10 is enclosed by aspiral housing section11 characteristic for a radial pump.Spiral housing section11 accommodates the radially accelerated delivery flow fromimpeller20 and leads it through theoutlet12 out of the coolant pump inside a circumferential spiral channel. In the present embodiment,spiral housing section11 as well asoutlet12 and the remaining part ofpump housing1 are made from a pressure die casting alloy.
• Pump chamber10 is opened on the opposing side ofelectric motor2. Between the opened side andinlet13 of the coolant pump, pumpchamber10 is closed by a pump cover, in the following also called heat-exchange cover31. Next to the face side end ofpump chamber10, heat-exchange cover31 provides a mouth receptacle forinlet13 at an opening upstream fromimpeller20.
• Between heat-exchange cover31 andimpeller20, a staggered labyrinth seal is provided at both components which prevent the delivery flow from bypassing the impeller. For this purpose,radial steps23 are formed on the face side at the jacket portion ofimpeller20 between inflow opening22 andoutlet openings24, as shown inFIG. 4.
• In the opposing mouth area ofinlet13,radial protrusions32aand recesses32bare formed into heat-exchange cover31 complementary tosteps23 ofimpeller20. The staggering of the axial extension ofprotrusions32acorresponds to the staggering ofsteps23 ofimpeller20.Recesses32bare respectively axially recessed radially outside and adjacent to each ofprotrusions32ain heat-exchange cover31. A radial width ofprotrusions32a, recesses32band steps23 is aligned with one another in such a way that respectively oneprotrusion32aand onerecess32bof heat-exchange cover31 are associated with astep23 ofimpeller20.
• As shown inFIG. 1, a gap and an adjacent annular space result at eachstep23 betweenimpeller20 and heat-exchange cover31. An inner radius of the mouth opening of heat-exchange cover31 furthermore covers an internal radius of inflow opening22 ofimpeller20. It is thus largely prevented that a portion of the delivery flow drawn in splits off at the inflow opening of theimpeller20 along the jacket portion and bypassesimpeller20 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.
• At the same time, the number ofprotrusions32aand recesses32bincreases the surface area of heat-exchange cover31 that is provided for a heat transfer to pumpchamber10 and a filling of the coolant inrecesses32bis subjected to constant exchange due to a leakage stream. Furthermore, heat-exchange cover31 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 cover31.
• Ametal seal43 is interposed between heat-exchange cover31 and pumphousing1. A fine adjustment of the gap of the labyrinth seal is enabled by a suitable elasticity ofmetal seal43 during assembly of heat-exchange cover31 within a defined tightening torque ofscrew bolts40.
• As shown inFIG. 5,control circuit3 is directly mounted to heat-exchange cover31 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 ofcontrol circuit3 is made of alead frame34 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 circuit3 includes a logical circuit printed on acircuit board36.Circuit board36 of the logic printed circuit is electrically connected to leadframe34 via contact pins37 and spaced apart from it. Thus the radial end surface to be provided forcircuit board36 is not lost at the surface of the lead frame that has better heat conductivity than the circuit board.
• Control circuit3 is accommodated inECU chamber30 that closes heat-exchange cover31 to the exterior. In the embodiment shown,ECU chamber30 is formed monolithically withinlet13, as shown inFIG. 2, and is made, for instance, of plastics.
• Bus rail35 extends through openings in heat-exchange cover31 andlead frame34. Contacts associated with the supply lines ofelectric motor2 are connected via spring contacts to the power electronics ofcontrol circuit3 in a way that is advantageous in terms of assembly.
• As shown inFIG. 6, the motor assembly is sealed by alip seal42 and analuminum leakage seal41.Lip seal42 sits onpump shaft21 between ball bearing28 and pumpchamber10.Aluminum leakage seal41 extends in a plane between the motor assembly and pumphousing1 and forms, in the central section, an L shapedcollar44 that radially encloses the accommodation ofpump housing1 forball bearing28 and protrudes in a direction towardselectric motor2.
• If, during high load operation of the pump or after increasing wear oflip seal41, a small amount of leakage occurs at it, droplets may reach through ball bearing28 ofpump shaft21 torotor26 orstator25 ofelectric motor2. The penetrated droplets evaporate in the motor assembly, particularly when they come into contact with components that are at operating temperatures.
• Due to the fact that the air volume in the motor assembly heats more during operation than that inECU chamber30 and the pressure thus increases by unequal amounts,channel15 provides a pressure equalization. An increased pressure inECU chamber30 may escape to the outside throughdiaphragm38 illustrated inFIG. 8, which is adiaphragm38 open to gas but impervious to liquids, which closes an opening inECU chamber30.
• When, when the pump cools, a partial vacuum is created in the motor assembly, it may in turn be equalized in the reverse order throughdiaphragm38 at the ECU chamber and viachannel15 without moisture penetrating intoECU chamber30.
• As illustrated inFIG. 7, anelectric motor2 with an internal rotor is used in this embodiment. However, in an alternative embodiment, anelectric motor2 with an external rotor may likewise be used as long as a supply line is provided for the central stator atmotor housing27 and pumphousing1 as configured in the illustrated embodiment bybus rail35. Furthermore, in an alternative embodiment,ECU chamber30 and the inlet may be separately formed.
• 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.

Claims (18)

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 toclaim 1, wherein the heat-exchange cover is made of aluminum or an aluminum alloy.

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

4. The electric coolant pump according toclaim 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 toclaim 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 toclaim 5, wherein the circuit carrier of the control circuit is a lead frame.

7. The electric coolant pump according toclaim 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 toclaim 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 toclaim 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 toclaim 1, wherein the ECU chamber and the inlet are formed integrally.

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

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

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

17. The electric coolant pump according toclaim 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 toclaim 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.

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