EP3676484A1

EP3676484A1 - Coolant pump with application-optimised design

Info

Publication number: EP3676484A1
Application number: EP18740181.5A
Authority: EP
Inventors: Franz Pawellek; Conrad Nickel; Jens Hoffmann; Robin Büsch; Paul Ludwig; Jakob Schnitzer; Silvio Werner
Original assignee: Nidec GPM GmbH
Current assignee: Nidec GPM GmbH
Priority date: 2017-08-31
Filing date: 2018-07-10
Publication date: 2020-07-08
Anticipated expiration: 2038-07-10
Also published as: CN111033008A; WO2019042638A1; US20210071679A1; EP3676484B1; US11125244B2; CN111033008B; BR112020002880A2; DE102017120039A1

Abstract

The invention relates to an electric coolant pump, preferably for use as a supplementary water pump in a vehicle, characterized in that a radial mounting of the shaft (4) is provided by means of a coolant-lubricated radial sliding bearing (41), which is arranged between the pump impeller (2) and the rotor (32); a dry-running electric motor (3) with a radially inner stator (31) and a radially outer rotor (32) is accommodated in a motor chamber (13) separated from the pump chamber (10); a shaft seal (5) is arranged between the radial sliding bearing (41) and the motor chamber (13); the rotor (32) is in the shape of a bell, the inner surface of which facing the shaft seal (5) and being fixed to the shaft seal (5) so as to axially overlap with the shaft (4); and the motor chamber (13) has an opening to the atmosphere, which is closed by a liquid-tight pressure equalisation membrane (6) that is permeable to vapour.

Description

description

Coolant pump with application optimized design

The present invention relates to a coolant pump whose structure is optimized by a combination of storage, sealing and electric motor in terms of cost, space and life on the application of a make-up water pump.

Such auxiliary electric water pumps are used to circulate portions of a coolant-carrying thermal management system of a vehicle equipped with an internal combustion engine and a main water pump to control so-called hotspots on components such as exhaust gas recirculation, turbocharger, intercooler, or the like such more flexible to cool. Due to the redundancy of the main water pump and the increased number of lines and nodes exist for the type of such additional water pumps a high Preisdruek and high demands on a compact design with small dimensions for integration in a complex packaging modern thermal management systems.

In previously established products of electric auxiliary water pumps, i.a. due to the easier seal in the relatively small pump assembly, wet rotor electric motors of the inner rotor type used. The use of wet-rotor electric motors, in which typically the stator is dry-sealed by a canned or the like relative to the rotor and the rotor and a bearing are designed for operation in the pumped medium, represent a known measure to the problem of a leakage at a Shaft seal and a defect of a shaft bearing counter.

Wet runners, however, have a lower efficiency, since the gap between the stator and the rotor for receiving a split tube larger fails and a field strength acting on the rotor is thereby weakened. In addition, fluid friction occurs on the rotor, which further reduces the efficiency, especially in the relatively small-sized pump drives of additional water pumps. In addition, wet-runners experience problems at low temperatures, such as ice formation in the gap between the stator and the rotor.

On larger pumps such as the electric main water pumps and dry-running electric motors are used due to the better efficiency. For the storage of pump shafts, which are driven by a dry-running electric motor, come predominantly Wälzkörperlager, such as. Ball bearings are used, which absorb both axial and radial loads and achieve low coefficients of friction.

However, rolling element bearings are generally sensitive to moisture penetration because the materials used, particularly suitable rolling element steels, are not sufficiently corrosion resistant for use in moisture. The ingress of moisture leads by corrosion to the reduction of the surface quality of the rolling elements and raceways, which results in a higher friction of the bearing and corresponding heat development and further consequential damage to bearings and seals. As a result, the already costly Wälzkörperlager in pumps on both ends must be provided with even more costly seals that ensure a low-friction and reliable seal against the working pressures occurring in the pump chamber.

In addition to the cost disadvantage of corresponding seals always cause low leakage and often represent the limiting factor of the life of a pump, since they are per se subject to frictional wear and embrittlement due to pressure and temperature fluctuation.

The patent application DE 10 2015 1 14 783 B3 of the same Applicant discloses an electric coolant pump designed for use as a main water pump, in which the pump shaft is connected through a single so-called water pump bearing with two rows of rolling elements between the pump impeller and the electric motor is stored. To counteract the problem of leakage into the bearing and underlying electronic components of a dry-running electric motor, a leakage chamber between a shaft seal and the water pump bearing is provided in the pump housing, in which a leak can be collected and removed without being in contact with the water pump bearing reach. In turn, a leakage seal behind it prevents a collected leak to be discharged from entering a housing section in which the engine components and electronics are accommodated. If a leakage from the leakage chamber directly enter the housing section of the engine, the operating temperature of the motor would cause water vapor to penetrate from the housing section in the opposite direction on the unsealed, unprotected side of the water pump bearing into the bearing and permanently destroy it.

The provision of such a leakage space between pump chamber and drive brings with it the disadvantage of the additional installation space, which increases the axial dimension of the pump structure.

Furthermore, the use and assembly of the shaft seal and the leakage seal are associated with costs that would not be acceptable for products of a make-up water pump. In order to minimize the risk of the water pump oil being damaged by water vapor penetration, it would also be necessary to install and install another bearing seal on the unprotected side of the water pump bearing. From a generic application is also a circulation pump for

Heating systems from the patent application WO 2015/01 1268 AI known, which in turn is driven by a wet rotor electric motor. The pump shaft is supported by a radial slide bearing and an axial bearing arranged behind it with a shaft seal. The slide bearing is lubricated by a supply within the pump shaft with the fluid. An axially adjacent rotor space is separated by a membrane with a static sealing function to a receiving space of the stator. On the problem of leakage at the shaft seal is not discussed in the disclosure. As a critical case, however, a looping of the membrane is called, which leads to a liquid entry into the electrical section of the receiving space, and is to be avoided by a filter in the supply of lubrication.

Based on the problems of the discussed prior art, it is an object of the invention to provide a simple, inexpensive and compact pump construction for a dry-running electric motor.

Another aspect of the invention is to provide a pump assembly in which a leakage space between a shaft seal and the dry-rotor electric motor can be omitted in favor of a shorter axial construction of the pump.

Another aspect of the invention is to provide a low cost and long lasting alternative to the bearing and sealing of a shaft.

The objects are achieved by an electric coolant pump according to claim 1.

The electric coolant pump is characterized in particular by the fact that a radial bearing of the shaft is provided by means of a cooling medium-lubricated radial sliding bearing arranged between the pump impeller and a rotor of a dry-running electric motor; the electric motor is accommodated with a radially inner stator and a radially outer rotor in a motor chamber separated from the pump chamber; a shaft seal is disposed between the radial sliding bearing and the motor chamber; the rotor is formed in a bell shape, the inner surface facing the shaft seal and is fixed axially overlapping with this on the shaft; and the motor chamber an opening to the Atmosphere, which is closed by a liquid-tight and vapor-permeable pressure equalization membrane.

The invention in its most general form, the finding is based on the fact that the inventive selection, combination and arrangement of the individual components of the pump, a complementary chain of action from a pressure reduction to limit leakage to a shaft seal, an optimal evaporation of leakage and discharge a vaporized leakage is achieved by taking advantage of operating conditions in the pump, which also provides the tasks corresponding advantages of a constructive and economic nature.

The invention provides for the first time for a Troekenläufer electric motor to create a pressure-reduced area for a shaft seal in front of a pumped medium, which is formed axially behind a lubricated by the fluid medium slide bearing. By a lower pressure of the pumped medium compared to a corresponding sealing surface within the pump chamber, a leakage that occurs at the shaft seal passes, lower. Furthermore, the invention provides for the first time, behind the shaft seal a

External rotor type trochanter electric motor with a rotor bell to use, whose, preferably closed, inner surface of the shaft seal faces. Thus, liquid droplets of leakage past the shaft seal are forced through the air gap of the dry rotor between the open field coils of the stator and the magnetic poles of the rotor by radial acceleration on the inner surface of the rotor bell before they can pass into a motor chamber with electronics. The leakage drops are vaporized by the operating temperature of the electric motor and by a turbulent turbulence in the air gap. The resulting water vapor then enters the motor chamber and escapes through a membrane into the atmosphere. As a result, encapsulation of the stator and the associated disadvantages of the efficiency of an electric motor of the wet rotor type can be dispensed with. Furthermore, an alternative to the use of cost-intensive Wäl zkörperl agern and a double-sided sealing of the same is created using a dry runner.

As a result, eliminates the disadvantage of a limited life of each bearing seal, which is always present even with complex types of seals, so that a longer life of the additional water pump is expected without defect in the shaft bearing.

At the same time, the elimination of shaft seals and motor seals or a containment shell according to the invention enables a pump design with fewer components and less expensive slide bearings.

Finally, according to the invention, a compact pump construction with a small axial dimension is achieved in which, despite the omission of a leakage space, a permanently safe operating environment for a dry runner in the pump housing is provided.

Advantageous developments of the additional water pump are the subject of the dependent claims.

According to one aspect of the invention, an axial bearing of the shaft can be provided by an axial sliding bearing, which is arranged in a flow direction of the coolant in front of the pump impeller.

As a result, an axial load on the shaft is accommodated by a sliding bearing, whereby a simple, inexpensive shaft bearing is provided in accordance with the task of the invention, which consists exclusively of two lubricated by the coolant plain bearings. According to one aspect of the invention, the axial sliding bearing can be formed by a free end of the shaft and a contact surface on the pump housing, preferably on a pump cover.

During operation, the pump impeller generates a thrust force in the direction of the suction port or inlet of the pump. By a front-side sliding surface of the shaft and a corresponding housing-side contact surface, a particularly simple but sufficient thrust bearing is provided without necessary axial fixation in the opposite direction. Thereby, the structure and the assembly can be further simplified.

According to one aspect of the invention, the shaft seal can have at least two sealing lips for dynamic sealing on the shaft circumference, which are aligned in a sealing manner at least on one axial side.

A double-lip shaft seal provides a favorable and sufficient leakage protection behind the axial plain bearing, which achieves a significantly better sealing compared to glazing joints and allows only a small accumulation of leakage drops to pass. A seal in the opposite direction, as in a pump assembly with a dry rolling bearing, can be omitted due to the wet-running plain bearing.

According to one aspect of the invention, the pump housing may include at least one lubrication channel connecting the pump chamber to a rear end of the radial journal bearing opposite the pump chamber.

By one or more connections from the front and the rear axial end of the sliding bearing to the pumping chamber for lubrication of the sliding bearing can be provided not only a one-sided static loading with funding to the saturation of the bearing gap, but a continuous circulation of funding in the bearing gap. This results in a more even pressure distribution of the Fördenmitteln in the bearing gap and a removal of particles by abrasion of the

Bearing surfaces achieved in favor of better lubrication or lower friction.

According to one aspect of the invention, at least one filter may be associated with the at least one lubrication channel.

Insofar as a circulation direction is provided by the design of the flow paths, in which the fluid initially flows through a lubrication channel and then through the bearing gap, prevents a filter in each lubrication channel or a filter for all lubrication channels that particulate contaminants in the bearing gap or to the shaft seal reach. Due to the nature and thickness of the filter, a suitable pressure drop can be established, which results in a reduced pressure area compared to the pump chamber, which relieves the shaft seal and yet ensures sufficient circulation through the bearing gap.

According to one aspect of the invention, the stator of the electric motor may be arranged in axial overlap with the at least one lubrication channel.

By arranging one or in particular a plurality of radially distributed lubrication channels adjacent to the stator of the electric motor, during operation, a power loss of the field coils of the stator is transferred by a heat transfer in the pump housing to the circulating in the lubrication channels conveyor and discharged to the flow rate in the pump chamber. This advantageous effect can also be utilized at low temperatures between a high cooling temperature and a still higher temperature of the powder swirls.

The invention will be described below with reference to an exemplary embodiment with reference to the drawing in Fig. 1. As the axial sectional views in Fig. 1 it can be seen, comprises a pump housing 1 on a left side shown an intake manifold 16 and a discharge nozzle 17, which open into a pump chamber 10. The intake manifold 16 serves as a pump inlet, which is placed in the form of a separate Pumpcndeekels 1 1 on an open axial end of the pump housing 10 and leads to an end face of a pump impeller 2, which is fixed on a shaft 4. The circumference of the pump chamber 10 is surrounded by a spiral housing, which passes tangentially into a pressure port 17, which forms a pump outlet. The impeller 2 is a known Radialpumpenflügelrad with one of the

Intake manifold adjacent central opening. The flow, which flows against the pump impeller 2 through the intake manifold 16 is accelerated and discharged by the inner wing radially outward into the volute casing of the pump chamber 10.

On a side shown on the right, the pump housing 1 comprises a designated motor chamber 13 cavity which is separated by a partition 12 of the pump housing 1 of the pump chamber 10, and in which a brushless electric motor 3 is taken from the outer rotor type. A stator 31 with field coils of the electric motor 3 is fixed in the motor chamber 13 around a cylindrical portion of the partition 12 of the pump housing 1. A rotor 32 with permanent-magnetic rotor poles is fixed on the shaft 4 rotatably about the stator 31.

An axially open end of the motor chamber 13 is closed by a motor cover of the pump housing 1, in which a control unit or ECU of the pump including a Lcistungselektronik the electric motor 3 is embedded open to the motor chamber 13. Between the power electronics and the stator 31, a cable feedthrough is arranged on an underside of the pump housing 1, which leads the leads to the field coils on the rotor 32 over.

The electric motor 3 is a dry-running type, the field coils of which are unencapsulated or open at the air gap to the rotor 32 to the motor chamber 13. The rotor 32 has a typical for an external rotor bell shape, which sits on the free end of the shaft 4 shown on the right and carries the permanent magnetic rotor poles in the axial region of the stator 31. However, typically for a rotor body, the rotor 32 does not include apertures in a radially extending portion, as is conventionally conventional for reducing the accelerated mass of rotating support bodies. Thus, the bell-shaped rotor 32 preferably forms a closed inner side, which is open only on the left side for receiving the stator 31. The shaft 4, which extends between the pump chamber 10 and the motor chamber 13, is radially supported by a radial sliding bearing 41 in the cylindrical portion of the boundary 12 of the pump housing 1. The sliding surfaces on the shaft periphery and on the bearing seat of the sliding bearing 41 are lubricated by the coolant supplied from the auxiliary water pump, which penetrates into the bearing gap between the sliding surfaces, as will be described later.

In addition, the shaft 4 is axially supported at the left free end. The axial slide bearing 42 comes about by a pair of sliding surfaces between the end face of the shaft 4 and a contact surface, which is provided by a projection or a strut in the intake manifold 16 in front of the pump impeller 2 appropriately positioned on the pump cover 1 1. In operation, the pump impeller 2 pushes the shaft 4 by a suction in the direction of the intake manifold 16 against the contact surface, so that an axial load bearing of the shaft bearing in this one direction is sufficient. Since a bearing gap between the sliding surfaces is surrounded by the flow, and the axial sliding bearing 42 is lubricated with coolant, at least in the form of an initial and re-wetting of the sliding surfaces by the coolant under vibration or turbulence.

Between the radial slide bearing 41 and the motor chamber 13, a shaft seal 5 is arranged, which seals an open end of the cylindrical portion of the partition 12 of the pump housing 1 to the shaft 4. The shaft seal 5 is a double lip seal, which in the cylindrical portion of the partition 12th is pressed, and two successive, directed towards the radial sliding bearing 41 sealing lips (not shown) for unilateral dynamic sealing on the shaft circumference.

In the wall of the cylindrical portion of the partition 12 further lubrication channels 14 are introduced into the pump housing 1, which open on the one hand on a rear side of the pump impeller 2 in the pump chamber 10 and on the other hand lead to an annular cavity, the shaft 4 between the rear end of the radial Slide bearing 41 and the shaft seal 5 surrounds. In operation, coolant flows out of the pumping chamber 10 through the suction chamber 14 to the shaft 4 and, delimited by the shaft seal 5, penetrates into the bearing gap between the shaft circumference and the bearing seat of the radial sliding bearing 41, so that it is in the flows back opposite direction. The axial circulation of the coolant in combination with the rotational movement between the sliding surfaces ensures even distribution and lubrication of the bearing gap with the coolant. The coolant contains a antifreeze additive having a friction reducing property, such as e.g. a glycol, silicate or the like. At the same time particles are removed from an abrasion of Gleitflächenpaarung to the pump chamber and in the flow.

On the other hand, in the region of the mouths of the lubrication channels 14 to the pump chamber 10 filters 15 are arranged to prevent particulate impurities such as metallic abrasion or the like, to be flushed from the flow in the bearing gap of the radial slide bearing 41 or in the sealing gap of the shaft seal 5. When the coolant circulates through the lubrication passages 14 and the radial slide bearing 41, a reduced pressure acts in the annular cavity between the radial slide bearing 41 and the shaft seal 5 due to a flow resistance of the filters 15 compared to the pump chamber 10. The reduced pressure adjacent Although the nature of the filter is adjusted by the number and the flow cross section of the lubrication channels 14, although the circulation through the radial sliding bearing weakens, it also relieves the shaft seal 5, resulting in a longer life of the sealing lips resulting in lower friction and a smaller leakage. However, the small unavoidable leakage that occurs dropwise from the circulation of the lubrication passages 14, the shaft seal 5 in the course of time, does not come into direct contact with the field coils or the engine electronics in the motor chamber 13. In operation, the leakage drops reach behind the shaft seal 5 to the inner surface of the rotating rotor 32 and are carried by the centrifugal force radially outward. By turbulence at the rotor poles or permanent magnets and by the operating temperature resulting from the power loss at the field coils, the leakage drops vaporize in the air gap between the stator 31 and the rotor 32, without on the radially inner stator 32, a wetting in the liquid phase, ie to be able to exert a corrosive action.

Due to the closed bell shape of the rotor 32, the leakage drops can not pass in the axial direction in the engine compartment 13 and the electronics, but are collected on the inner surface of the rotor 32 and fed to the evaporation of the air gap. In order to keep a volume of the air gap small, this is complementary to the circumference of the cylindrical portion of the boundary 12 and the stator 32 is formed stepwise complementary.

The transition from leakage drops of the liquid into the gaseous phase is accompanied by an increase in volume, which would lead to a pressure increase in the case of a closed volume of the motor chamber 13, regardless of a pressure fluctuation that would arise due to temperature fluctuations between operation and standstill of the pump.

However, a diaphragm 6 is provided between the motor chamber 13 and the surrounding atmosphere, which allows a compensation of pressure fluctuations from the motor chamber 13 to the atmosphere. The membrane 6 is semipermeable with respect to water permeability, ie it does not pass water in the liquid phase, whereas moisture-laden air diffuses to a limit with respect to a droplet size or a droplet density that is agglomerated at the membrane surface can. Thus, with a volume expansion by evaporation in the motor chamber 13, a warm air laden with moisture pass through the membrane 6, so that vaporized leakage drops are effectively discharged into the atmosphere. In the opposite direction, the membrane 6 in turn protects against the ingress of spray water or the like during driving of the vehicle.

The diaphragm 6 closes an opening of the pump housing 1, which is arranged in a region of an outlet of the air gap between the stator 31 and the rotor 32 above. At the top of the pump housing 1, a plug for external power supply is further arranged.

In addition to the illustrated and described embodiment, the invention can also be implemented by alternative embodiments with additional features or waiving described features. As can be seen from the explanations for solving the problem, the pump can also be realized without lubrication channels 14 and filter 15, or with a different axial bearing than the sliding bearing 42 in the region of the intake manifold 16, or with a different shaft seal 5 than that with two sealing lips , In a case in which no lubrication channels 14 are provided, at least one adjustable over the bearing gap static lubrication of the bearing gap of the radial slide bearing 41 can be used by the operating pressure from the pump chamber 10, wherein behind the radial slide bearing 41 again a reduced pressure in comparison to the pump chamber 10 acts on the shaft seal 5.

Claims

claims

An electric coolant pump for delivering coolant in a vehicle, comprising: a pump housing (1) having a pump chamber (10) in which a pump impeller (2) is rotatably received, an inlet (16) and an outlet (17) connected to the pump chamber (10); a shaft (4) which is rotatably mounted on the pump housing (1), and on which the pump impeller (2) is fixed; characterized in that a radial bearing of the shaft (4) by means of a coolant-lubricated radial sliding bearing (41) is provided, which between the pump impeller (2) and the rotor (32) is arranged; a dry running electric motor (3) having a radially inner stator (31) and a radially outer rotor (32) is received in a separate from the pump chamber (10) motor chamber (13); a shaft seal (5) is disposed between the radial slide bearing (41) and the motor chamber (13); the rotor (32) is formed in a bell shape whose inner surface faces the shaft seal (5) and is fixed with this axially overlapping on the shaft (4); and the motor chamber (13) has an opening to the atmosphere, which is closed by a liquid-tight and vapor-permeable pressure ausgl ei chsmembran (6).

2. An electric coolant pump according to claim 1, wherein an axial bearing of the shaft (4) is provided by an axial sliding bearing, which is arranged in a flow direction of the coolant in front of the pump impeller (2).

3. An electric coolant pump according to one of claims 1 or 2, wherein the axial sliding bearing (42) by a free end of the shaft (4) and a contact surface on the pump housing (1), preferably a pump cover (1 1) is formed.

4. An electric coolant pump according to claim 1 to 3, wherein the shaft seal (5) has at least two sealing lips for dynamic sealing on the shaft circumference, which are aligned at least on one axial side sealing effect.

5. An electric coolant pump according to one of claims 1 to 4, wherein the pump housing (1) has at least one lubrication channel (14), the pump chamber (10) with a rear, the pump chamber (10) gegenüberl i egendem end of the radial sliding bearing (41 ) connects.

6. An electric coolant pump according to claim 5, wherein the at least one lubrication channel (14) is associated with at least one filter (15).

7. An electric coolant pump according to one of claims 1 to 6, wherein the stator (31) of the electric motor (3) is arranged in axial overlap with the at least one lubrication channel (14).

8. Use of an electric coolant pump according to one of claims 1 to 7 as an additional water pump in a coolant-carrying system in a vehicle with an internal combustion engine and a H auptwasserpumpe.