ELECTRICAL SCREW SPINDLE COOLANT PUMP

Abstract

An electrical screw spindle coolant pump is suitable for conveying a coolant circuit or other corrosive, liquid media. The electrical screw spindle coolant pump has a spindle housing with a spindle chamber and an axially adjacent motor housing. The motor housing has a motor chamber, in which a dry-running electric motor is arranged separated from the flow current. The motor housing has a thermal transition portion through which the flow current flows. The thermal transition portion is arranged between the motor chamber and a component boundary of the motor housing to the spindle housing.

Description

The present invention relates to an electric coolant pump of the screw pump type for delivery of a coolant circulation or the like, in particular for delivering corrosive, liquid media.

Screw pumps are displacement pumps which permit high pressures and high volumetric efficiency. They do not offer adjustment of the geometry in a manner independent of speed but they do comprise a robust rotary piston mechanism which is not sensitive to fouling and which operates without delicate elements such as stop valves or the like. Consequently, mechanically driven screw pumps have to date predominantly been used in large-scale applications such as e.g. oil pumps in stationary installations or ships engines in which they run with relatively constant operating points.

In the area of fuel delivery pumps of vehicles, smaller electrically driven screw pumps have recently become known, these permitting higher pressures than centrifugal pumps. These are installed in a submerged arrangement in the vehicle tank and provide a high input pressure upstream of the high-pressure pump or injection pump in the fuel path. The electric drive of such fuel delivery pumps is designed as a wet-running electric motor without a separating can and so both the rotor and the stator are in contact with the fuel. The temperature of the fuel delivered from the tank generally corresponds to an ambient temperature of the vehicle. As a result, the drive, which heats up owing to electric power dissipation, is easily cooled in such fuel delivery pumps.

Thus US 2018/0216614 A1 describes a screw pump which is provided as a fuel pump. A cover with an axial outlet is attached to a housing of the screw pump. The electric motor is received in an outlet chamber of the cover and fuel flows through it before it leaves the outlet.

DE 10 2015 101 443 B3 describes a fuel pump with a housing in which an electric drive motor is coupled to a screw pump. The fuel flows through the drive motor before it leaves the pressure-side outlet.

WO 2014/138519 A1 describes an electric liquid pump of the screw type. The liquid which flows through an inlet and an outlet also surrounds the motor. A fuel is mentioned as the liquid. A flange plane, which is shown in the illustrated construction between a motor-side housing part and a pump-side housing part, extends between the motor and a pump-side outlet.

DE 10 2017 210 771 A1 describes an electrically driven screw pump as a fuel delivery assembly. A pump housing and an electric motor are received in a casing. In the illustrated embodiment, which does not comprise a separating can on the stator of the electric motor, the electric components of the motor are in direct contact with the fuel within an outlet guide on a pressure side of the spindle chamber.

However, the above-mentioned pumps cannot be transferred to an application as an electric water pump, in particular not as an electric coolant pump. A liquid medium to be delivered, such as a coolant would corrosively damage the exposed components of the electric motor, in particular the coil windings of the stator.

U.S. Pat. No. 6,371,744 B1 describes an electric vacuum pump of the screw type. The screw spindles are driven by an electric motor which is arranged in a separate housing.

Independently of specific modifications between a screw pump for gasses and a screw pump for liquids, said vacuum pump could not be transferred to an application as an electric coolant pump. In the case of the illustrated arrangement, sufficient cooling of a dry-running electric motor could not be ensured. In a pressurised coolant circulation, a target temperature for a coolant can be in the vicinity of the boiling temperature of the coolant. In this case, in continuous operation, overheating damage to electric or electronic components would occur.

On the basis of the known electric screw pumps of the prior art, which are not suitable for an application as a coolant pump, it is an object of the present invention to provide an electric screw pump which is suitable for delivering corrosive, liquid media and provides cooling of the electric drive.

Another, partial aspect of the object is further to provide a corresponding technical solution such that it can also be inexpensively produced in large numbers by mass production.

The object is achieved by the features of claim 1. The electric screw coolant pump in accordance with the invention for delivering a coolant circulation is characterised in particular in that a motor housing comprises a motor chamber, in which a dry-running electric motor is arranged in such a manner that it is delimited with respect to the delivery flow; and that the motor housing comprises a heat transfer section, through which the delivery flow flows, arranged between the motor chamber and a component boundary between the motor housing and a spindle housing.

Therefore, for the first time, the invention provides a screw pump as a coolant pump.

Furthermore, for the first time, the invention provides a screw pump as an electric liquid pump which is driven by a dry-running electric motor.

Furthermore, for the first time, the invention provides a screw pump as an electric liquid pump, in which a convection-assisted heat transfer from a dry motor chamber to a delivery flow of the liquid medium to be delivered is provided.

The invention permits a coolant pump to be produced with a high level of power density. The screw pump provides the high delivery pressure of a displacement pump but with relatively low pulsation, similar to a centrifugal pump. In connection with an electric drive, the screw pump permits universal installations and applications. The electric screw coolant pump in accordance with the invention is suitable e.g. for use in electric, in particular battery-electric, vehicles, in which no mechanical drive source is provided, and a branched structure of thin or capillary cooling ducts in a battery module or a traction motor requires a high delivery pressure.

From a constructional point of view, the invention is based on a principle of shifting an axial position of a component boundary between a motor housing and a spindle housing from a conventional functional position further in the direction of the spindle chamber. In this way, on the one hand, a region protected from the liquid of the delivery flow is provided and so the electric drive is not exposed to corrosive influences. On the other hand, by reason of the heat transfer section, a liquid-carrying region on the motor housing is provided, which enlarges an internal thermal contact surface with the coolant. Waste heat from electric power dissipation can be effectively carried away from the pump by a heat exchange at the thermal contact surface, thus produced, of the heat-conducting motor housing and convection of the delivery flow, even when there is a small temperature difference between the electric drive and the coolant.

The enlargement of the thermal contact surface is achieved without an increased level of complexity in the structure, as in the form of surface-enlarging structures, flow resistance means or the like. The motor housing is designed as a cast part during product development. As a result, the changed component boundary can be produced on the pump construction in accordance with the invention without considerable outlay or increase in manufacturing costs. By reason of shifting the component boundary of the spindle housing in a complementary manner, substantially no disadvantageous increase in the overall dimensions of the pump arises despite having an increased axial dimension for the motor housing.

Flow losses in the pump are considerably reduced in comparison with a known pump construction with a wet-running electric drive which is exposed in the delivery flow.

The above-mentioned shifting of the component boundary leads to an open spindle chamber cross-section at the end of the spindle housing. Thus the screw spindles can simply be inserted through the open end of the spindle chamber during assembly of the pump.

Advantageous developments of the invention are provided in the dependent claims.

According to one aspect of the invention, the heat transfer section can further comprise the pump outlet. In this way, the flow cross-section of the entire delivery flow can be channelled past the motor chamber. The internal surface of the pump outlet at the heat transfer section further enlarges the thermal contact surface of the heat-conducting motor housing with the delivery flow to a considerable extent.

According to one aspect of the invention, the heat transfer section can comprise a delivery flow chamber which produces a connection between the frontal delimitation of the motor chamber and the spindle chamber. By this design, the heat transfer portion of the heat-conducting motor housing between the electric heat sources in the motor chamber and the delivery flow is shortened further. Furthermore, the internal surface of the delivery flow chamber in the heat transfer section further enlarges the thermal contact surface of the heat-conducting motor housing with the delivery flow.

According to one aspect of the invention, the heat transfer section can comprise a bearing seat for a shaft bearing, which is arranged between the electric motor and the screw spindles. The surface of the bearing seat in the heat transfer section in turn enlarges the thermal contact surface of the heat-conducting motor housing with the delivery flow. Moreover, the integration of a shaft bearing in the axial region of the heat transfer section is favourable to a compact construction for the pump.

According to one aspect of the invention, an electronic system for the electric motor can also be arranged in the motor chamber. A further heat source is therefore incorporated into the inventive cooling of the electric drive. In this way, the power dissipation from power electronics is also discharged via the delivery flow.

According to one aspect of the invention, a stator and/or an electronic system of the electric motor in the motor housing can be in contact with a frontal delimitation of the motor chamber. Therefore, the smallest possible heat transfer portion of the heat-conducting motor housing between the electric heat sources in the motor chamber and the delivery flow is ensured.

According to one aspect of the invention, the heat transfer section can be formed integrally with the motor housing. In this way, an optimised heat transfer portion without boundary surfaces or joints in the material and the lowest possible production costs for the motor housing are ensured.

According to one aspect of the invention, the spindle housing can be formed as one piece. As explained above, the shifting of the component boundary between the motor housing and the spindle housing produces an open cross-section for the spindle chamber. In this way, both for assembly of the pump and also for production of the moulded body of the spindle housing no division into two housing halves is required. The one-piece design of the spindle housing ensures a joint-free internal contour for the spindle chamber without the need for post-processing. The internal contour of the spindle chamber can be produced simply and precisely by bores.

According to one aspect of the invention, the spindle housing can comprise the pump inlet. The spindle housing is designed as a cast part during product development. Consequently, by integration of the pump inlet, the number of components of the pump construction in accordance with the invention can be reduced without considerable outlay.

According to one aspect of the invention, a flange joint consisting of a flange section of the motor housing and a flange section of the spindle housing can be formed at the component boundary between the motor housing and the spindle housing. The flange joint permits a preferred screw connection for assembly of the two housing components, while a corresponding flange plane allows different types of seal.

The invention will be explained hereinafter with the aid of an embodiment and with reference to the accompanying drawing,

FIG. 1 shows a schematic sectional view through a screw coolant pump according to one embodiment of the invention.

In terms of this disclosure, the term ‘screw pump’ is understood to mean skew rotary piston pumps with a thread pitch for displacement of the medium to be delivered. Such types of pump generally comprise a driven screw spindle 2a and at least one further screw spindle 2b which is in coupled motion therewith via engagement of the toothing.

In the embodiment of the schematic illustration of FIG. 1, in a spindle housing 1, a driven screw spindle 2a and a screw spindle 2b in coupled motion are received in a rotatably mounted manner in a spindle chamber 10 of the spindle housing 1. The spindle chamber 10 has a cross-sectional contour in the form of a so-called figure-of-eight housing, i.e. it is formed by two bores in the pump housing 1 with overlapping radii in order to ensure engagement of the screw spindles 2a, 2b. The driven screw spindle 2a is connected to an electric motor 4.

A pressure side of the spindle chamber 10 which communicates with a pump outlet 13 in the form of a pressure connection is located on the drive side of the screw spindles 2a, 2b. A suction side of the spindle chamber 10 is located on the other side of the screw spindles 2a, 2b opposite the electric motor 4. The suction side of the spindle chamber 10 communicates with a pump inlet 11 in the form of a suction connection. In relation to the delivery direction of the screw pump, a liquid medium to be delivered or a coolant is drawn into the spindle chamber 10 from a coolant circulation through the pump inlet 11 on the suction side. A rotational movement of engaged screw profiles of the rotating screw spindles 2a, 2b generates a negative pressure on the suction side of the spindle chamber 10 and a positive pressure on the opposing pressure side of the spindle chamber 10. The medium to be delivered is delivered by continuous displacement along a screw pitch of the engaged screw profiles and ejected from the spindle chamber 10 through the pump outlet 13.

A motor housing 3 adjoins the spindle housing on the pressure side of the spindle chamber 10. The motor housing 3 comprises a flange section 35 which is formed to match a flange section 15 of the spindle housing 1. The flange joint is sealed by a seal. A separated motor chamber 30 is formed in the motor housing 3, in which chamber the dry-running electric motor 4 and an electronic system, in particular power electronics (not shown), for switching the electric power at the electric motor are received. An open end of the motor chamber 30 is closed by a motor cover (not shown). A collar-shaped bearing seat 32 with a though-opening in a frontal delimitation of the motor chamber 30 is formed in the motor housing 3. A common shaft bearing 23 of the electric motor 4 and of the driven screw spindle 2a is fitted in the bearing seat 32. Upstream of the shaft bearing 23, a shaft seal 34 is fitted into the bearing seat 32 and seals the motor chamber 30 against ingress of liquid.

The dry-running electric motor 4 is of the internal rotor type with an internal rotor 42 and an external stator 41. The rotor 42 is coupled to the driven screw spindle 2a. The stator 41 comprises field coils which are actuated by the power electronics and supplied with electric power. The stator 41 of the electric motor 4 is in thermal contact with an internal peripheral surface and with a frontal boundary surface of the motor chamber 30, and so waste heat from the field coils of the stator 41 is transferred to the motor housing 3.

The motor housing 3 consists of a metallic material with a good level of heat conductivity, such as an aluminium cast alloy, and is formed as a one-piece cast part. A heat transfer section 31 of the motor housing 3 extends in an axial section between the motor chamber 30 and the flange section 35. As an integral component of the heat transfer section 31, the pump outlet 13 in the form of a radially discharging pressure connection is arranged between the motor chamber 30 and the spindle chamber 10. A delivery flow chamber 33 is formed within the heat transfer section 31 and has the liquid medium to be delivered flowing through it. The delivery flow chamber 33 produces a connection for the delivery flow of the pump between the pressure side of the spindle chamber 10 and the pump outlet 13. The delivery flow chamber 33 surrounds the collar-shaped bearing seat 32 and carries the pressurised liquid medium to be delivered to the frontal delimitation of the motor chamber 30, with which the stator 41 is in thermal contact.

The heat transfer section 31 constitutes the region of the heat-conducting material volume on the motor housing 3 which is definitively involved in the dissipation of waste heat from the motor chamber 30 into the delivery flow. The internal surface of the pump outlet 13, the internal surface of the delivery flow chamber 33 and the surface of the bearing seat 32 each contribute to enlargement of the thermal contact surface between the motor chamber 30 and the delivery flow within the heat transfer section 31.

The optimised heat transfer limits any temperature difference between a coolant and the motor chamber 30. Consequently, even under high loading with a high operating temperature in a coolant circulation, a critical component temperature of the electric drive, at which overheating damage can occur on the winding insulations of the stator 41 or the electronic system, is reliably prevented.

LIST OF REFERENCE NUMERALS

1 Spindle housing

2a Driven screw spindle

2b Screw spindle in coupled motion

3 Motor housing

4 Electric motor

10 Spindle chamber

11 Pump inlet

13 Pump outlet

15 Flange section of the spindle housing

23 Shaft bearing

30 Motor chamber

31 Heat transfer section

32 Bearing seat

33 Delivery flow chamber

34 Shaft seal

35 Flange section of the motor housing

41 Stator

42 Rotor

Claims

1. An electric screw coolant pump for delivering a coolant circulation comprising:

a spindle housing having a spindle chamber in which at least two screw spindles are rotatably accommodated;

a pump inlet and a pump outlet for guiding a delivery flow through the spindle chamber;

a motor housing arranged axially adjacent to the spindle housing;

wherein

the motor housing includes a motor chamber in which a dry-running electric motor is arranged so the motor chamber is delimited with respect to the delivery flow; and

the motor housing comprises a heat transfer section, through which the delivery flow flows, arranged between the motor chamber and a component boundary between the motor housing and the spindle housing.

2. The electric screw coolant pump according to claim 1, wherein

the heat transfer section includes the pump outlet.

3. The electric screw coolant pump according to claim 1, wherein

the heat transfer section includes a delivery flow chamber that establishes a connection between a frontal delimitation of the motor chamber and the spindle chamber.

4. The electric screw coolant pump according to claim 1, wherein

the heat transfer section includes a bearing seat for a shaft bearing arranged between the electric motor and the screw spindles.

5. The electric screw coolant pump according to claim 1, wherein

an electronic system for the electric motor is arranged inside the motor chamber.

6. The electric screw coolant pump according to claim 1, wherein

a stator and/or an electronic system of the electric motor is in contact with a frontal delimitation of the motor chamber inside the motor housing.

7. The electric screw coolant pump according to claim 1, wherein

the heat transfer section is formed integrally with the motor housing.

8. The electric screw coolant pump according to claim 1, wherein

the spindle housing is formed as one piece.

9. The electric screw coolant pump according to claim 1, wherein

at the component boundary between the motor housing and the spindle housing, a flange joint is formed of a flange section of the motor housing and a flange section of the spindle housing.