U.S. patent application number 15/751752 was filed with the patent office on 2018-08-23 for electric coolant pump having a flow-cooled control circuit.
This patent application is currently assigned to NIDEC GPM GmbH. The applicant listed for this patent is NIDEC GPM GmbH. Invention is credited to Christian BATZ, Jens HOFFMANN, Franz PAWELLEK.
Application Number | 20180238348 15/751752 |
Document ID | / |
Family ID | 56800282 |
Filed Date | 2018-08-23 |
United States Patent
Application |
20180238348 |
Kind Code |
A1 |
PAWELLEK; Franz ; et
al. |
August 23, 2018 |
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.
Inventors: |
PAWELLEK; Franz; (Lautertal,
DE) ; HOFFMANN; Jens; (Schwarzbach, DE) ;
BATZ; Christian; (Sonneberg, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NIDEC GPM GmbH |
Auengrund OT Merbelsrod |
|
DE |
|
|
Assignee: |
NIDEC GPM GmbH
Auengrund OT Merbelsrod
DE
|
Family ID: |
56800282 |
Appl. No.: |
15/751752 |
Filed: |
August 22, 2016 |
PCT Filed: |
August 22, 2016 |
PCT NO: |
PCT/EP2016/069795 |
371 Date: |
February 9, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F04D 29/624 20130101;
F04D 29/5893 20130101; F04D 29/588 20130101; F04D 29/5813 20130101;
F05D 2300/5024 20130101; H02K 11/33 20160101; F04D 29/026 20130101;
F04D 13/0693 20130101; F04D 13/0686 20130101; F01P 2005/125
20130101 |
International
Class: |
F04D 29/58 20060101
F04D029/58; F04D 13/06 20060101 F04D013/06 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 3, 2015 |
DE |
10 2015 114 783.1 |
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
RELATED APPLICATIONS
[0001] 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
[0002] The present invention relates to an electric coolant pump
having a control circuit that is cooled by the delivery flow.
BACKGROUND OF THE INVENTION
[0003] 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.
[0004] 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.
[0005] 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.
[0006] 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.degree. C.
[0007] 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.
[0008] 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.
[0009] 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.
[0010] After passing through the cooler or a heat exchanger with
the surroundings, the coolant should have a maximum temperature of
up to 113.degree. 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.degree. C.
or even 130.degree. C.
[0011] 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.
[0012] 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.
[0013] 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.
[0014] 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
[0015] 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.
[0016] The object is solved according to the invention by an
electric coolant pump according to claim 1. 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.
[0017] 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.
[0018] 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.
[0019] 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.
[0020] 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.
[0021] 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.
[0022] Other advantageous further embodiments of the electric
coolant pump according to the invention are the object of the
dependent claims.
[0023] 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.
[0024] 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.
[0025] 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.
[0026] 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.
[0027] 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.
[0028] 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.
[0029] 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.
[0030] 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.
[0031] 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.
[0032] 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.
[0033] 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.
[0034] 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.
[0035] 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.
[0036] 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.
[0037] 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.
[0038] 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.
[0039] 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.
[0040] 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.
[0041] 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
[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.
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