Coolant pump having a use-optimised structure and improved thermal efficiency

Abstract

In an electrical coolant pump, preferably for use as an additional water pump in a vehicle, a radial bearing of the shaft is provided by means of a radial slide bearing lubricated with coolant on the separating element which is disposed between the pump impeller and the rotor. A dry-running electric motor has a radially inner stator and a radially outer rotor is accommodated within the motor chamber. A shaft seal is disposed between the radial slide bearing and the motor chamber. The rotor is formed in a cup shape, the inner surface of which faces the shaft seal and is fixed to the shaft in an axially overlapping manner. The motor chamber has an opening to the atmosphere which is closed by a liquid-tight and vapor-permeable pressure equalizing membrane. The separating element is configured as a support flange with a separating portion and an axial projection into the motor chamber, to which the stator is attached. The control unit is disposed between the separating element and the stator in the axial direction.

Claims

1. An electrical coolant pump for conveying coolant within a vehicle, comprising: a pump housing having a pump chamber in which a pump impeller is rotatably located, an inlet and an outlet which are connected to the pump chamber; a separating element between the pump chamber and a motor chamber disposed within the pump housing formed by a motor housing; a shaft onto which the pump impeller is fixed; a control unit disposed in the motor chamber; wherein a radial bearing of the shaft is provided by a radial slide bearing lubricated with coolant on the separating element, which is located between the pump impeller and a radially outer rotor; a dry-running electric motor having a radially inner stator and the radially outer rotor is located within the motor chamber; a shaft seal is disposed between the radial slide bearing and the motor chamber; the rotor is formed in a cup shape, an inner surface of which faces the shaft seal and is fixed to the shaft in an axially overlapping manner; the motor chamber has an opening to the atmosphere which is closed by a liquid-tight and vapour-permeable pressure equalising membrane; the separating element is configured as a support flange with a separating portion and an axial projection into the motor chamber, to which the stator is attached; and the control unit is disposed axially between the separating element and the stator.

2. The electrical coolant pump according to claim 1, wherein a filling material is introduced between the control unit and the separating element as a gap filler.

3. The electrical coolant pump according to claim 1, wherein the separating element is accommodated at least partially within a pump cover of the pump housing in the axial direction.

4. The electrical coolant pump according to claim 2, wherein the separating element is accommodated at least partially within a pump cover of the pump housing in the axial direction.

5. The electrical coolant pump according to claim 1, wherein an axial bearing of the shaft is provided by an axial slide bearing which is disposed upstream of the pump impeller in a flow direction of the coolant.

6. The electrical coolant pump according to claim 5, wherein the axial slide bearing is formed by a free end of the shaft and a run-up surface on the pump housing.

7. The electrical coolant pump of claim 6, wherein the pump housing includes a pump cover on which the run-up surface is located.

8. The electrical coolant pump according to claim 1, wherein an axial slide bearing is formed by a free end of the shaft and a run-up surface on the pump housing.

9. The electrical coolant pump of claim 8, wherein the pump housing includes a pump cover on which the run-up surface is located.

10. The electrical coolant pump according to claim 1, wherein the shaft seal has at least two sealing lips for dynamic sealing on the shaft circumference which are aligned to at least one axial side so as to be seal-effective.

11. The electrical coolant pump according to claim 1, wherein the separating element has at least one lubrication channel which connects the pump chamber to a rear end of the radial slide bearing opposite from the pump chamber.

12. The electrical coolant pump according to claim 11, wherein the at least one lubrication channel includes at least one filter.

13. The electrical coolant pump according to claim 11, wherein the stator of the electric motor is disposed so as to axially overlap the at least one lubrication channel.

14. The electrical coolant pump according to claim 1 as an additional water pump in a coolant-conveying system in a vehicle having an internal combustion engine and a main water pump.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) FIG. 1 is an axial sectional view of a coolant pump according to an embodiment of the invention.

DETAILED DESCRIPTION

(2) The invention will be explained hereinafter with the aid of an exemplified embodiment and with reference to the drawing in FIG. 1.

(3) As can be seen in the axial sectional view in FIG. 1, a pump housing 1 comprises, on a side illustrated on the left, an intake connection 16 and a pressure connection 17 which issue into a pump chamber 10. The intake connection 16 serves as a pump inlet which is attached in the form of a separate pump cover 11 to an open axial end of the pump housing 10 and leads to an end side 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 transitions tangentially to a pressure connection 17 which forms a pump outlet.

(4) The pump impeller 2 is a known radial pump impeller having a central opening adjoining the intake connection. The flow to be conveyed which flows towards the pump impeller 2 through the intake connection 16 is accelerated and diverted by the inner blades radially outwards into the spiral housing of the pump chamber 10.

(5) On a side illustrated on the right, the pump housing 1 comprises a hollow space which is designated as a motor chamber 13 and is separated from the pump chamber 10 by a separating element 12 configured as a support flange 12.

(6) The support flange 12 is produced from a material having a high thermal conductivity, such as e.g. metal, in order to permit effective heat transfer between the motor chamber 13 and the pump chamber 10 or permit effective heat dissipation from the motor chamber 13 to the medium to be conveyed in the pump chamber 10. In the case of the exemplified embodiment shown in FIG. 1, the support flange 12 is produced from an aluminum alloy. The support flange 12 has a separating portion 12a, which provides the separation between the motor chamber 13 and the pump chamber 10, and a projection or projection portion 12b on which the stator 31 is attached or fixed.

(7) As shown in FIG. 1, the pump cover 11 engages around the separating portion 12a of the support flange 12 on an outer circumferential side of the support flange 12 and so the separating portion 12a of the support flange 12 is accommodated at least partially within the pump cover 11 in the axial direction. Disposed between the support flange 12 and the pump cover 11 is a sealing element, such as e.g. an O-ring, in order to prevent a leakage of the medium to be conveyed in the pump chamber 10. As shown in FIG. 1, the sealing element in the case of the present exemplified embodiment is disposed on an outer circumferential surface of the separating portion 12a of the support flange 12, but the sealing element can also be disposed e.g. on the side surface of the separating portion 12a facing the pump cover 11 in the axial direction. The above-described configuration permits simple and exact positioning of the support flange 12 in the radial direction and also a simplified structure and simplified sealing of the pump housing 1 because the entire separating portion 12a of the support flange 12 is located radially inside the connection portion between the pump cover 11 and the motor housing 17 and thus, in comparison with a case in which the pump cover 11 is connected to the motor housing 17 via the separating portion 12a, fewer housing interfaces are present.

(8) A brushless electric motor 3 of the outer-runner type is accommodated in the motor chamber 13. A stator 31 having field coils of the electric motor 3 is fixed around the projection portion 12a of the support flange 12 which has e.g. a cylindrical configuration and so the stator 31 is in contact with the projection portion 12a. This ensures very effective heat dissipation from the stator 31 in the motor chamber 13 via the support flange 12 to the medium to be conveyed in the pump chamber 10. A rotor 32 having permanently magnetic rotor poles is fixed on the shaft 4 so as to be rotatable about the stator 31.

(9) FIG. 1 shows that a control unit or circuit board 18 of the pump including power electronics of the electric motor 3 is disposed in the axial direction between the separating portion 12a of the support flange 12 and the stator 31. By reason of the spatial proximity between the circuit board 18 and the support flange 12 on the one hand and the stator 31 and the circuit board 18 on the other hand, effective heat dissipation from the circuit board 18 via the support flange 12 to the medium to be conveyed is facilitated and good prerequisites are provided for simple and robust contacting or wiring between the circuit board 18 and the electric motor 3.

(10) Disposed in the air gap between the separating portion 12a and the circuit board 18 is a filling material, such as a gap filler, having a high thermal conductivity and so the heat transfer from the circuit board 18 to the medium to be conveyed in the pump chamber 10 can be further improved.

(11) The electric motor 3 is a dry runner type, of which the field coils are exposed in a non-encapsulated or open manner with respect to the motor chamber 13 at the air gap to the rotor 32. The rotor 32 has a cup shape which is typical of an outer runner and is seated on the free end of the shaft 4 illustrated on the right and supports the permanently magnetic rotor poles in the axial region of the stator 31. However, what is not typical of a rotor body is that the rotor 32 preferably has no apertures in a radially extending portion, as is routine in a conventional manner for reducing the accelerated mass on rotating support bodies. Therefore, the cup-shaped rotor 32 has preferably a closed inner side which is open only on the left side for accommodating the stator 31.

(12) The shaft 4 which extends between the pump chamber 10 and the motor chamber 13 is mounted in a radial manner in the support flange 12 by means of a radial slide bearing 41. The slide surfaces at the shaft circumference and at the bearing seat of the slide bearing 41 are lubricated by means of the coolant which is conveyed by the additional water pump and penetrates into the bearing gap between the slide surfaces, as described later.

(13) Moreover, the shaft 4 is mounted in an axial manner on the left, free end. The axial slide bearing 42 is established by means of a slide surface pairing between the end face of the shaft 4 and a run-up surface which is provided positioned accordingly on the pump cover 11 by means of a projection or a strut in the intake connection 16 upstream of the pump impeller 2. During operation, the pump impeller 2 pushes the shaft 4 by means of a suction effect in the direction of the intake connection 16 against the run-up surface and so axial load absorption of the shaft bearing is sufficient in this direction. Since a bearing gap between the slide surfaces is surrounded by the flow to be conveyed, the axial slide bearing 42 is also lubricated with coolant, at least in the form of an initial wetting of the slide surfaces by the coolant and renewed wetting of said slide surfaces under vibration and turbulence.

(14) Disposed between the radial slide bearing 41 and the motor chamber 13 is a shaft seal 5 which seals an open end of the projection portion 12b of the support flange 12 with respect to the shaft 4. The shaft seal 5 is a double-lipped seal which is pressed into the projection portion 12b of the support flange 12, and two sealing lips (not illustrated) which are located one behind the other and are directed in the direction of the radial slide bearing 41 for one-sided dynamic sealing on the shaft circumference.

(15) Furthermore, a lubrication channel 14 is introduced in the wall of the projection portion 12b of the support flange 12 and issues on the one hand on a rear side of the pump impeller 2 into the pump chamber 10 and on the other hand leads to an annular hollow space which surrounds the shaft 4 between the rear end of the radial slide bearing 41 and the shaft seal 5. During operation, coolant flows from the pump chamber 10 through the lubrication channel 14 to the shaft 4 and penetrates, in a manner delimited by the shaft seal 5, into the bearing gap between the shaft circumference and the bearing seat of the radial slide bearing 41 so that it flows back in the opposite direction. The axial circulation of the coolant in combination with the rotational movement between the slide surfaces ensures uniform distribution and lubrication of the bearing gap with the coolant. The coolant contains a frost protection additive having a friction-reducing property, such as e.g. a glycol, silicate or the like. At the same time, particles arising from abrasion of the slide surface pairing are transported away to the pump chamber and into the flow to be conveyed. In the case of the exemplified embodiment in FIG. 1, only one lubrication channel 14 is provided; however, a plurality of such lubrication channels 14 can be provided in the projection portion 12a of the support flange 12.

(16) On the other hand, a filter 15 is disposed in the region where the lubrication channel 14 issues to the pump chamber 10, said filter preventing particulate impurities, such as metallic abrasion or the like, from being flushed from the flow to be conveyed into the bearing gap of the radial slide bearing 41 or into the sealing gap of the shaft seal 5. If the coolant circulates through the lubrication channel 14 and the radial slide bearing 41, the annular hollow space between the radial slide bearing 41 and the shaft seal 5 is subjected to a reduced pressure in comparison with the pump chamber 10 by reason of a flow resistance of the filter 15. Although the reduced pressure, which, in addition to the configuration of the filter, is also adjusted by the number and the flow cross-section of the lubrication channel 14, attenuates the circulation through the radial bearing, it also relieves the shaft seal 5, thus resulting in a longer service life of the sealing lips by virtue of less friction and a smaller leakage.

(17) However, the small unavoidable leakage which passes from the circulation of the lubrication channel 14 in a dropwise manner through the shaft seal 5 over the course of time does not come directly into contact with the field coils or the motor electronics in the motor chamber 13. During operation, the leakage drops pass downstream of the shaft seal 5 to the inner surface of the rotating rotor 32 and are carried radially outwards by the centrifugal force. By reason of swirling movements at the rotor poles or permanent magnets and by reason of 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 being able to exert wetting in a liquid phase, i.e. a corrosive effect, on the radially inner stator 32.

(18) By reason of the closed cup shape of the rotor 32, the leakage drops cannot pass in the axial direction into the motor space 13 but instead are collected on the inner surface of the rotor 32 and directed to the air gap for vaporization. In order to minimize a volume of the air gap, the air gap is configured to be complementary to the circumferences of the stator 32. By reason of the arrangement of the control unit 18 between the support flange 12 and the stator 31, the control unit is protected against the leakage drops or the vaporized leakage.

(19) The transition of leakage drops from the liquid phase to the gaseous phase is associated with a volume increase which, in the case of a closed volume of the motor chamber 13, would lead to a pressure increase, irrespective of a pressure fluctuation which would result by reason of temperature fluctuations between operation and non-operation of the pump.

(20) However, between the motor chamber 13 and the surrounding atmosphere a membrane 6 is provided which is attached to the cup-shaped motor housing 17 in the motor chamber 13. In the case of this exemplified embodiment, the membrane 6 is adhered in a radially central portion of an inner surface of the motor housing 17 facing the rotor in the axial direction and allows the equalization of pressure fluctuations from the motor chamber 13 to the atmosphere. As a result, a cost-effective and large-area adhesive membrane can be used at a protected site. The motor housing 17 has in this region a permeable or open-pored structure which is configured such that the membrane 6 is sufficiently protected and is not damaged during high pressure jet tests. The membrane 6 is semi-permeable in relation to water-permeability, i.e. it does not allow water in a liquid phase to pass through, whereas moisture-laden air can diffuse through up to a limit in relation to a droplet size or a droplet density agglomerating at the membrane surface. Therefore, during a volume expansion caused by vaporization in the motor chamber 13, moisture-laden warm air can pass through the membrane 6 and so vaporized leakage drops are effectively discharged into the atmosphere. In the opposite direction, the membrane 6 protects, in turn, against the ingress of splash water or the like during the drive operation of the vehicle.

(21) Furthermore, a connector for external power supply is disposed on the top side of the pump housing 1.

(22) In addition to the illustrated and described embodiment, the invention can also be carried out using alternative embodiments with additional features or without described features. As is apparent from the explanations relating to the achievement of the object, the pump can likewise be produced without lubrication channels 14 and filters 15 or with an axial bearing other than the slide bearing 42 in the region of the intake connection 16 or with a shaft seal 5 other than the one having two sealing lips. In one case in which no lubrication channels 14 are provided, it is at least possible to utilize static lubrication—which can be adjusted via the bearing gap—of the bearing gap of the radial slide bearing 41 by means of the operating pressure from the pump chamber 10, wherein, again, a reduced pressure in comparison with the pump chamber 10 acts upon the shaft seal 5 downstream of the radial bearing 41.