Patent Application
20190109516
The present patent application is based on, and claims priority from, German Application No. DE 10 2017 217 788.8, filed Oct. 6, 2017, which is incorporated herein by reference in its entirety.
The invention relates to a fluid pump, having a pump impeller, mounted so as to rotate around an axle, in a conveyed medium and a conductor plate, which is arranged in a dry area sealed off from the conveyed medium, wherein radial forces of the axle are accommodated, on one side, by a separating wall between the dry area and the conveyed medium and by a pump head on the other side.
In what follows, fluid pumps having three-phase motors in a power range of about 30 W to 200 W electric power are considered in particular, without being limited to these.
Fluid pumps of the generic type, particularly motor vehicle water pumps, are often driven by an electronically commutated direct-current motor, which comprises multiple heat-generating components, which primarily include a wound stator and a conductor plate populated with power components. The stator and also the conductor plate are normally arranged directly at a separating wall, which seals off a dry area, in which the heat-generating components are arranged, from a wet area, through which conveyed medium flows. The stator is usually arranged radially with respect to the rotational axis of a pump impeller and the conductor plate is arranged at a right angle to its rotational axis. The pump impeller has, axially offset with respect to a hydraulic part, a magnetic part, which is arranged radially opposite the wound stator. Because the requirements for the power density increase with each product generation, it is necessary to dissipate the heat of the power components as well as possible to the surrounding components or preferably to the conveyed medium. The latter is particularly suited for continuous dissipation of the generated heat on account of the forced flow. In the cooling circuit of a combustion engine, this heat is then emitted, along with the exhaust heat from the combustion engine, to a water-air heat exchanger, which continuously dissipates heat to the environment by means of the headwind.
The transfer of heat from one component to another or to a medium is more successful the larger the surface areas, particularly the contact surfaces, between the areas involved and the better the thermal conductivity value of the materials used. However, dissipating the heat generated to a sufficient degree is frequently unsuccessful. This is because only a small flow of fluid is possible in the magnetically effective area of the wet space due to the narrow flow paths. On the other hand, there is a high volumetric flow, for example, in the intake area. Fluid pumps are also known in which a complex secondary circuit is set up, which diverts a part of the conveyed medium and passes by the heat generators in the electronic system and/or in the stator. However, the hydraulic efficiency is also negatively affected by this. A further disadvantage of a secondary circuit is caused by particles and suspended solids entrained in the conveyed medium. They can clog the secondary circuit and thus stop it up.
The use of high-quality components or the installation of multiple components connected in parallel can reduce the power loss and thus the heat development. Another way would be the use of more temperature-resistant conductor plate materials, e.g. ceramic conductor plates based on Al2O3. These measures, however, are subject to physical and above all cost-related limits.
The object of the invention is thus to provide structural measures to ensure an optimum dissipation of heat from a conductor plate and the power components mounted thereon to the conveyed medium without negatively impacting the hydraulic efficiency of the pump.
Because an essential part of the heat generated by electronic components on the conductor plate is discharged to the cooling medium by means of the heat-conducting path, which has the axle and an axle retainer as components, which transfers the radial forces of the axle from it to the separating wall or the pump head, there is an especially large usable surface area by means of which the heat can be discharged to the conveyed medium.
In a development of the concept of the invention, a provision is that a first axle retainer is fitted against a base of the separating wall, said base being arranged axially to an axis of rotation of the pump impeller. A further provision is that a second axle retainer is arranged in an intake duct of the pump head, and the conveyed medium at least partially flows around it during operation.
In what follows, several options are listed as to how the heat can be efficiently transferred from the power components to the heat-conducting plate. These options can in each case be used singly or in combination with one or more of the other options. First, it is proposed that the conductor plate have a plurality of vias forming a heat-conducting connection of power components through the conductor plate to their opposite side and is in heat-conducting contact with the heat-conducting plate directly there or via a heat-conducting medium.
A further option is that the conductor plate have at least one recess through which a power component extends and is directly in heat-conducting contact with the heat-conducting plate or via a heat-conducting medium.
It is also conceivable that at least one conductor of the conductor plate be directly in heat-conducting contact with the heat-conducting plate or via a heat-conducting medium. The heat-conducting plate preferably consists of aluminum or a material with comparable properties.
Finally, it is also possible for the heat-conducting plate to form at least one electric conductor or a conductor area of the conductor plate.
In principle, all shapes enlarging the surface area are suitable that enable demolding from an injection mold and fulfill the design rules for such shapes. The same applies to manufacture of the heat-conducting plate.
In order to transport as much heat as possible and in order to obtain the largest possible surface area in order to improve the transfer of heat, a provision is that the diameter of the axle be at least 20% of the diameter of the first axle retainer in the area of the contact disk. The axle discharges heat to its environment over its entire length in the conveyed medium; this can be optimized by the pump impeller being mounted on the axle by means of sleeve-like slide bearings, which divert a part of the heat absorbed by the axle to the pump impeller. To ensure this heat diversion is as great as possible, it is proposed that the length of a slide bearing correspond to at least 10% of the length of the axle.
For reasons related to production and cost, the pump head is preferably produced from a plastic material, which can be processed through injection molding. In order to secure the aforementioned advantages, a provision is that the second axle retainer be joined by molding to the pump head, particularly to an intake duct of the pump head. To this end, the thermal expansion coefficients should be as close to one another as possible. This is the case when pairing PPS and aluminum.
As an alternative, the second axle retainer is joined to the pump head, particularly to an intake duct of the pump head, through pressing with force locking and/or positive locking. Preferably, a cone is provided here between the pump head and the component consisting of the intake duct and second axle retainer. In addition, the connection can be secured through bonding, welding, or bolting. If the sealing requirements demand it, an O-ring seal can also be placed between the parts to be joined. Alternatively, a liquid sealant can also be used.
In the optimum case, the intake duct is a single-piece component of the second axle retainer. This enlarges the surface area of the heat-conducting parts again significantly. The intake duct in this case is preferably joined by molding to the pump head, wherein the pump head consists of a plastic material that can be processed using injection molding.
Ideally, at least one or preferably both axle retainers consists of an aluminum material. Essentially, it is important that the ratio between the diameter and length of the axle be greater than 0.1, particularly greater than 0.15, and preferably greater than 0.2. The larger this ratio, the greater the thermal flow and thus the cooling effect which can be achieved.
The exemplary embodiments of the invention are subsequently further explained, based on the drawings. The following is shown:
Note: The reference numbers with subscript and the corresponding reference numbers without subscript refer to details with the same name in the drawings and the drawing description. This reflects use in another embodiment and/or where the detail is a variant.
In describing preferred embodiments of the present invention illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the invention is not intended to be limited to the specific terminology so selected, and it is to be understood that each specific element includes all technical equivalents that operate in a similar manner to accomplish a similar purpose.
Again with reference to
In a development of the concept of the invention, a provision is that the first axle retainer 8 is fitted against the base of the separating wall 6, said base being arranged axially to an axis of rotation of the pump impeller 3. A further provision is that the second axle retainer 9 is arranged in an intake duct 10 of the pump head 7, and the conveyed medium at least partially flows around it during operation.
In order to use the thermal conductivity of the axle retainer to transfer heat, it is intended that the axle retainers 8, 9 consist of a metal material. Preferably, both axle retainers 8, 9 are made of a metal material with particularly good heat conductivity. Aluminum and magnesium are among the most suitable materials.
In what follows again with reference to
A further option is that the conductor plate 4 have at least one recess through which a power component extends and is directly in heat-conducting contact with the heat-conducting plate 11 or via a heat-conducting medium (
It is also conceivable that at least one conductor of the conductor plate 4 be directly in heat-conducting contact with the heat-conducting plate 11 or via a heat-conducting medium. The heat-conducting plate 11 preferably consists of aluminum or a material with comparable properties.
Finally, it is also possible for the heat-conducting plate 11 to form at least one electric conductor or a conductor area of the conductor plate 4.
A good transfer of heat from the conductor plate to the separating wall is achieved in that a heat-conducting plate 11 is arranged to tightly fit between the conductor plate 4 and the separating wall 6 and is a component of the heat-conducting path.
This transfer of heat can be optimized by enlarging the surface area of the heat-conducting plate and the separating wall; to this end the heat-conducting plate 11 has shapes that enlarge its surface area and which are matched to corresponding counter-shapes in the separating wall 6. It is proposed that the shapes consist of circumferential projecting walls 12 (
In principle, all shapes enlarging the surface area are suitable that enable demolding from an injection mold and fulfill the design rules for such shapes. The same applies to manufacture of the heat-conducting plate.
The heat-conducting plate can be further improved in that the first axle retainer has a contact disk 14, whose extensive surface area tightly fits against the separating wall 6, and a retainer sleeve 15 for the axle 2. The retainer sleeve should have as extensive a surface area as possible and fill the existing installation space to the greatest extent possible.
The surface area of the first axle retainer 8 should also be selected to be as large as possible; to this end a support collar 16 connecting to the contact disk 14 is proposed, with the support collar providing radial support in a tube-shaped area 17 of the separating wall 6.
In order to transport as much heat as possible and in order to obtain the largest possible surface area in order to improve the transfer of heat, a provision is that the diameter of the axle 2 be at least 20% of the diameter of the first axle retainer 8 in the area of the contact disk 14. The axle discharges heat to its environment over its entire length in the conveyed medium; this can be optimized by the pump impeller 3 being mounted on the axle 2 by means of sleeve-like slide bearings 18, which divert a part of the heat absorbed by the axle to the pump impeller 3. To ensure this heat diversion is as great as possible, it is proposed that the length of a slide bearing 18 correspond to at least 10% of the length of the axle 2.
Because the axle 2 discharges heat continuously over its entire length, the axle diameter should be particularly large, particularly in the vicinity of the heat source, and can then be selected to be smaller in an area further away; in a development of the invention, the axle 2 should therefore have at least two differently sized diameter ranges, wherein the axle section with the larger diameter is retained in the first axle retainer 8. For reasons of cost, an axle with one single diameter, however, is preferred in many cases.
Because there is an especially high throughput of the conveyed medium in the intake duct, the heat can be discharged most effectively here; it is therefore very important to divert as much of the thermal energy as possible that occurs in the power components of the conductor plate up as far as the intake duct. This is optimized in that the second axle retainer 9 consists of material with good heat conductivity and has one additional slide bearing 31 (
For reasons related to production and cost, the pump head is preferably produced from a plastic material, which can be processed through injection molding. In order to secure the aforementioned advantages, a provision is that the second axle retainer 9 be joined by molding to the pump head 7, particularly to an intake duct 10 of the pump head 7. To this end, the thermal expansion coefficients should be as close to one another as possible. This is the case when pairing PPS and aluminum.
As an alternative, the second axle retainer 9 is joined to the pump head 7, particularly to an intake duct 10 of the pump head 7, through pressing with force locking and/or positive locking. Preferably, a cone is provided here between the pump head 7 and the component consisting of the intake duct 10 and second axle retainer 9. In addition, the connection can be secured through bonding, welding, or bolting. If the sealing requirements demand it, an O-ring seal can also be placed between the parts to be joined. Alternatively, a liquid sealant can also be used.
In the optimum case, the intake duct 10 is a single-piece component of the second axle retainer 9. This enlarges the surface area of the heat-conducting parts again significantly. The intake duct 10 in this case is preferably joined by molding to the pump head 7, wherein the pump head consists of a plastic material that can be processed using injection molding.
The thermal conductivity of the separating wall can also be optimized by modifying the plastic material of which it consists. To this end, additives with good heat conductivity are added to the base material. A very effective way of improving the thermal conductivity of the cooling pad is for the axle to consist of aluminum, particularly an aluminum alloy.
Because aluminum does not have any optimal wear properties, a beneficial provision is that the axle be provided with a wear-resistant layer, particularly a molybdenum, chromium oxide, aluminum oxide, nickel, or bronze layer, at least in the bearing area.
As an alternative and with reference to
Ideally, at least one or preferably both axle retainers 8, 9 consists of an aluminum material. Essentially, it is important that the ratio between the diameter and length of the axle 2 be greater than 0.1, particularly greater than 0.15, and preferably greater than 0.2. The larger this ratio, the greater the thermal flow and thus the cooling effect which can be achieved.
Modifications and variations of the above-described embodiments of the present invention are possible, as appreciated by those skilled in the art in light of the above teachings. It is therefore to be understood that, within the scope of the appended claims and their equivalents, the invention may be practiced otherwise than as specifically described.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2017 217 788.8 | Oct 2017 | DE | national |
