Water pump and method for manufacturing a water pump

Abstract

Water pump (2) with a pump impeller (28) driven by an electric machine comprising a housing cover (41) and a spiral (10) with an inlet (12) and an outlet (14) and a cap (20) in which a stator (24) and a rotor (26) of the electric machine and an electronic circuit board (40) are housed, wherein the stator stack (7) is overmolded with a first plastic material (M1) and at least the stator stack (7), the wires (8) and the connectors (9) are overmolded with a second plastic material (M2) to form a cylindrical cap (20) with a cylindrical opening (50) and wherein a heat sink (5) sealing the cylindrical opening (50) of the cap (20) is in contact with the electronic circuit board (40).

Description

Water Pump and Method for Manufacturing Water PumpThe invention relates to a water pump having an impeller driven by an electric machine comprising a housing cover and a scroll having an inlet and an outlet, and a cap housing a stator and a rotor of the electric machine and an electronic board separately fixed to the impeller side and covered by the cap housing, the stator stack being insert molded.The invention further relates to a method for manufacturing the water pump.Prior ArtWater pumps generally include a stator and a rotor. The rotor is in communication with an impeller for moving a fluid. The fluid enters the pump through an inlet in a scroll, is contacted with an impeller, and is moved through an outlet in the scroll. The rotor and the stator are contained in a housing connected to the scroll. Generally, the rotor and the stator are separated by a magnetic air gap, and the rotor and the stator contain rare earth metals such that the magnetic air gap can be bridged between the rotor and the stator such that the rotor is rotated during use and such that the rotor, the stator, or both are isolated from the fluids during use and continue to operate. However, the use of rare earth metals may be affected by the fluid, so that the rare earth metals may require additional encapsulation to prevent damage.US 9360015 B1 discloses an electric water pump and in particular an electric water pump with an improved wet bushing, so that the water pump does not have a housing. The electric water pump includes a pump rotor having a shaft. A wet bushing surrounds the rotor and includes a cover, a bushing housing the rotor, and a seat in communication with the shaft of the rotor such that the seat assists in supporting the shaft on a stator. A scroll surrounding the wet sleeve and the rotor covers an upper portion of the rotor, the wet sleeve, and the stator. The electric water pump further includes a rubber cap covering a lower portion of the rotor, the wet liner, and the stator and communicating with the scroll to form a cover. Further, the water pump includes an electronic board which is fixed on the side separated from the pump impeller and covered by the cap.US 2013 / 0 028 760 A1 discloses a two-part injection molding method for the stator.DE 10 2006 008 423 A1 discloses a motor-driven centrifugal pump with a stator stack of the electric motor injection-molded with plastic, wherein cooling channels through which the delivery medium flows are arranged in the plastic.EP 1 422 809 A2 discloses an electric motor for a pump drive having a stator and a rotor for driving a pump impeller, wherein the stator is embedded in a plastic body and the plastic body together with the stator forms a space in which the rotor is accommodated, wherein the space is closed at a first end of the rotor and the rotor is connected at its opposite second end to the pump impeller.The object of the invention is to provide a water pump with an optimized construction, in particular with integrated parts.The solution provided is a water pump with an impeller driven by an electric machine comprising a housing cover and a scroll with an inlet and an outlet and a cap housing a stator and a rotor of the electric machine and an electronic board separately mounted on the side of the impeller and covered by the cap housing, wherein the stator package is overmoulded with a first plastic material and at least the stator package, the wires and the plugs are overmoulded with a second plastic material to form a cylindrical ring cap and a heat sink sealing a cylindrical opening of the cap.The invention enables a device arrangement with reduced parts and reduced outlay. Due to the fact that parts are completely injection molded, the heat transfer is better. This is also because the dimensions may be reduced and the weight of the water pump is lower compared to standard die cast pumps. The pump has a high vibration resistance.The complete injection molding of the stator eliminates the air enclosed between the components, such as stator package, plugs and copper wires, thus increasing the heat dissipation.It is advantageous that the cooling body is a separate device which carries a rotor shaft. The simple arrangement eliminates at least one seal.Alternatively, it is advantageous that the heat sink is a device which carries a rotor shaft and is formed together with the cap. In this case of a pump variant for a low temperature application, the cooling body is also integrated and two seals could be dispensed with.It is advantageous that the electronic board is injection-molded together with the stator in a method for producing the water pump. The volume of air trapped in the chamber of the electronic board has been reduced for two reasons: increasing heat transfer and reducing the total volume in the event it must be filled with resin to stably hold the components for engine mounting applications.It is advantageous that the cap has an edge which allows connection of the spiral and the cover housing. The connection is made by a snap-fit construction to secure the cover housing and the scroll in a stable position without the need for screw / bolt operations.For this purpose, it is advantageous that the edge comprises at least slots for inserting hooks.The invention further comprises a method for manufacturing a water pump according to the preceding claims, comprising the following steps:• Injection molding a stator core with a first plastic material,• fastening at least wires and plugs,• Injection moulding a second plastic material around the fixed stator to form a cylindrical annular cap with a rim,• Sealing the inner cylindrical opening by a heat sink.DESCRIPTION OF THE INVENTIONThe invention is described in the figures and the following description. FIG. 1 shows a water pump according to the prior art and illustrates a cross-sectional view of a housingless water pump 2, FIG. 2 shows a water pump according to the invention, FIG. 3 is a cross-sectional view of the water pump, FIGS. 4 and 5 show an exploded view, FIG. 6 shows a further view, FIGS. 7, 8, and 9 show the attachment process of the water pump.The water pump 2 includes a scroll 10, a cap 20, and a fastening bracket 22 that fixes the cap 20 and the scroll 10. The scroll 10 includes an inlet 12 and an outlet 14.The scroll 10 is connected to a cap 20 via a mounting bracket 22 to form a cover 4 surrounding the internal components and including a power supply port 16 for accommodating a supply line 46. The internal components of the housingless water pump 2 include a stator 24 that is press fit into the cap 20. The stator 24 surrounds a rotor 26 and the rotor 26 is separated from the stator 24 by a wet bushing 30. The rotor 26 and the stator 24 are separated by a magnetic air gap having a distance (A). The wet sleeve 30 prevents fluid from contacting the stator 24. The rotor 26 includes a shaft 38 and an impeller 28 for moving a fluid as the fluid enters the inlet 12. The pump 28 moves the fluid through the outlet 14 for use. An electronic board 40 is positioned outside the wet can 30 so that the electronic board 40 is separated from any fluids within the housingless pump 2.Figures 2-9 show an embodiment of the water pump with reduced parts, in particular without wet bushing, according to the invention.The pump 2 has a cap 20 that combines various functions: the cap defines the outer periphery of the pump, covers the stator 24, and a wet sleeve function, and houses a rotor 26. A heat sink 5 is mounted in the cap 20 in which a rotor shaft 38 is mounted. A seal 6 in the form of an O-ring seals the heat sink 5 with respect to the inner periphery of the cap 20 in an opening 50.The cap 20 is in the form of a cylindrical ring having the cylindrical opening 50 therein. In the ring, the devices of the stator are positioned in the opening, the rotor 26 is fixed around the shaft 38.The pump cap is formed by overmolding the stator 24, thereby eliminating air gaps between the various components, such as the stator stack 7, the power plugs 9, and the copper wires 8. The injection molding increases the heat dissipation of the stator.During the process, the stator package 7 is encapsulated by injection molding with a first material M 1. The first material is, for example, a plastic material: glass fiber reinforced PA66-GF30. The material is fiber reinforced and has good heat aging resistance. The material M 1 should have high rigidity and dimensional stability and must be specified for the production of electrically insulating parts.After this first step of overmolding the stator stack 7, the supply plugs 9 are inserted and connected to the wires, and the winding of the wires 8 is completed. After the wires and plugs have been contacted and an electrical control system, the assembly is encapsulated by injection molding with a second material M 2. The material M2 is for example PPS-GF34, which has good resistance to ageing, chemicals and radiation and forms a cap which is solid and rigid.After completion of the cap as a molded-on single part, a heat sink 5 carrying a shaft 38 is mounted along the inner periphery of the cap 20.The heat sink 5 is sealed against the cap in the opening 50 by an O-ring 6.Alternatively to the solution with the separate heat sink 5, the bottom of the cap can be closed by the forming process and comprise a seat for the shaft 38.This closed solution could be applied when temperatures are below about 90°, thereby creating a part that reduces the sealing requirement.An electronic board 40 is mounted on the surface of the cap 20 at the heat sink 5 away from the portion of the pump impeller 28. The volume of air enclosed around the electronic board 40 is reduced. This results in an improved heat transfer rate and a reduction in the total volume of the water pump. In cases where it is necessary to fill the volume with plastic molding material to keep the components stable, the electronic board may be mounted before the last overmolding process with the material M 2.The electronic board and a first portion P1 of the length l of the cap is covered with a part of a housing cover 41, a second portion P2 of the length l of the cap is covered with a part of a coil 10. The coil and the cover housing are sealed with rings against the outer periphery of the cap.In Fig. 6, the two central parts, cap 20 and heat sink 6, are shown. Figure 6a shows in an exploded view the cap made of a plastic moulding material, which has a cylindrical opening 50. The opening 50, which can be seen better in FIG. 6 cin the cross section along A-A of FIG. 6 b, is designed to be closed on one side by the cooling body 5, as is shown in FIG. 6 b. Fig. 6e is the situation after installation of the heat sink 5 with the seal 6 in the cap opening. FIG. 6f shows a view from the bottom of the cap after installation of the heat sink. In the embodiment of FIG. 6, a rim 43 is formed during the overmolding process of the stator 24.The rim 43 surrounds the entire periphery of the cap 20 and extends a larger diameter compared to the diameter of the cap. The rim is part of the fastening and fixing devices which will be discussed later. The rim 43 in this embodiment comprises four tabs 42 surrounding slots 44 in the rim. The slots are arranged along a radial length and follow the radii of the cap. The tabs 42 are formed as walls surrounding the slots 44 at the outer periphery of the rim and partially two end sides of the slot.In Figures 4 and 5, the parts of the entire water pump are shown in an exploded diagram. On the right, scroll 10 is shown as part of the finished water pump. This spiral 10 comprises axial hooks 11 arranged on the outer periphery of the device. The axial hooks 11 are defined by L-shaped hook structures 52 and the hooks extend along the diameter of the coil 10. The openings of the hook structures 52 are arranged around the diameter so that the hook openings, the direction of the smaller arm of the L of the two adjacent axial hooks, are all spaced apart from each other and face in the same direction. The hooks 11 do not increase the diameter of the spiral but extend only in the axial direction.For mounting the water pump, the cap 20 has the frame 43 with the slits 44. The cover housing 41 is constructed with radial hooks 45 with the openings of the radial hooks aligned radially outward of the diameter of the cover housing 41.The radial hooks are fixed by tongues 53 fixed to the outside of the cover housing, thereby providing a defined flexibility. Normally, the radial hooks are molded with the lid housing in one step.In FIGS. 7, 8, and 9, the attachment process of the water pump will be explained.In a first step, the spiral 10 with the axial hooks 11 is placed on the cap 20 and the axial hooks 11 enter the slots of the rim 43 of the cap. For easy insertion, the slots 44 have rims 42 for better guiding the axial hooks 11. The insertion of the hooks 11 is so deep that the smaller arms of the L-shaped axial hooks are completely passed through the slots. The slot is wide enough to easily engage the hooks. This insertion is aided by the hooks being designed to follow the circumferential contour of the spiral, Figs. 8a, 8b.In a second step, the two parts, cap 20 and spiral 10, are twisted along their central axis in the direction of the openings of the hooks, such that the smaller arm of the L-shaped axial hooks overlaps the rim of the cap, as can be seen in Figure 8c.The coil is thus fixed to the cap.The slot 44 in the rim 43 remains wide enough for snap-connection with the radial hooks 45 of the lid housing 41.The radial hooks 45 are flexible and it is possible to push them through the remaining space of the slot 44 for fixation by the noses of the hooks which extend outwards.The fastening and fixing method works with the two types of hooks in the two covering parts, which together have a width b1 and b2 for filling the space in the slits in the rim.The hooks of the lid housing block the scroll from rotating back to the attachment start position and complete the water pump mounting process.Reference numerals denote reference numerals2 Water pump 4 Cover 5 Heat sink 6 Seal 7 Stator pack 8 Wires 9 Plug 10 Spiral 11 Axial hook 12 Inlet 14 Outlet 16 Power supply terminal 20 Cap 22 Clip 24 Stator 26 Rotor 30 Wet sleeve 38 Shaft 28 Pump wheel 40 Electronic board 41 Cover housing 42 Tab 43 Rim 44 Slot 45 Radial hook 46 Supply 50 Opening 52 Hook devices 53 Tongue M 1 First material M 2 Second material

Claims

Water pump (2) with an impeller (28) driven by an electric machine comprising a housing cover (41) and a spiral (10) with an inlet (12) and an outlet (14) and a cap (20) in which a stator (24) and a rotor (26) of the electric machine and an electronic board (40) are accommodated, wherein the stator package (7) is injection-coated with a first plastic material (M1) and at least the stator package (7), the wires (8) and the plugs (9) are injection-coated with a second plastic material (M2) to form a cylindrical cap (20) with a cylindrical opening (50) and wherein a cooling body (5) sealing the cylindrical opening (50) of the cap (20) is in contact with the electronic board (40).Water pump (2) according to claim 1, characterised in that the cooling body (5) is a separate device which carries a rotor shaft (38).Water pump (2) according to claim 1, characterized in that the cooling body (5) is a device which carries a rotor shaft (38) and is formed together with the cap (20).Water pump (2) according to Claim 2, characterized in that the cooling body (5) is sealed off by an O-ring (6).Water pump (2) according to Claims 1-4, characterized in that the electronic board (40) is injection-moulded together with the stator (24).Water pump (2) according to any of the preceding claims, characterized in that the cap (20) has a radially extending edge (43) allowing connection of the scroll (10) and the cover housing (41).Water pump (2) according to one of the preceding claims, characterized in that the edge (43) has at least slots (44)Method for manufacturing a water pump (2) according to the preceding claims, comprising the following steps: • overmolding a stator stack (7) with a first plastic material (M1), • fastening at least wires (8) and plugs (9), • overmolding the fastened stator (24) with a second plastic material (M2) to form a cylindrical annular cap (20) with an edge (43), • sealing the inner cylindrical opening (50) by a heat sink (5).The method of claim 8, wherein the heat sink (5) is formed together with the cap (20).The method of claim 8 or 9, wherein the electronic board (40) is over-molded together with the portions of the stator (24).

Images