EP1507914A1

EP1507914A1 - Household appliance

Info

Publication number: EP1507914A1
Application number: EP03755908A
Authority: EP
Inventors: Harald Schrott
Original assignee: Aweco Appliance Systems GmbH and Co KG
Current assignee: Aweco Appliance Systems GmbH and Co KG
Priority date: 2002-05-29
Filing date: 2003-05-28
Publication date: 2005-02-23
Anticipated expiration: 2023-05-28
Also published as: AU2003243904A1; US7455065B2; EP1507914B1; CN1656277A; CN100402734C; DE20308489U1; DE10324626A1; DE50305906D1; PL372193A1; WO2003102290A1; US20060011221A1

Abstract

The invention relates to a household appliance, particularly a dishwasher, a washing machine or the like, comprising a liquid circuit and a pump, which has a pump housing. Said pump housing contains a heating element (3), which is provided for heating the liquid and which, via a heat-conducting contact surface (20), is adapted to the outer shape (2) of the housing while having an at least partial form-fit therewith. The aim of the invention is to improve the heating efficiency of the inventive household appliance. To this end, the contact surface (20) is at least half as large as the entire outer surface of the heating element.

Description

"Haushaitsmaschine"

The invention relates to a household machine, in particular a washing machine, a dishwasher or the like according to the preamble of claim 1.

With the publication 197 36 794 AI a pump for a dishwasher is known in which the heating element in the form of a water heater has been integrated into the pump. The design described there is associated with adjustments in the machine sump, whereby the pump cannot be handled as a separate component.

A water pump is known from the publication DE 201 07 363 U1, in which a heating element is inserted on the circumference into a circumferential bead.

With the publication DE 199 16 136 AI a liquid pump for a dishwasher has also become known, in which a heating element is also integrated. In this embodiment, the heating element is attached on the outside or on the inside to a pump housing that is closed with the exception of connecting pieces. The on and for the production and assembly is already significantly reduced in this above-described version compared to the older prior art. The object of the invention is to propose a household machine with a liquid pump with outside heating, in which the efficiency of the heating is improved.

This object is achieved on the basis of a household machine of the type mentioned in the introduction by the characterizing features of claim 1.

Advantageous designs and developments of the invention are possible through the measures mentioned in the subclaims.

Accordingly, in a household machine according to the invention, the heating element is at least partially positively adapted to the external shape of the pump housing with a heat-conducting or heat-transferring contact surface, so that the contact surface is at least half as large as the entire outer surface of the heating element. In this way, a large-area direct thermal contact can be established between the heating element and the corresponding housing part of the pump, which increases the efficiency of the heating. The outer shape is preferably provided with a structure that enlarges the contact area. Measures can be considered, such as a structure with an angled or corrugated cross-section.

The efficiency can be further increased by keeping the so-called dead volume V _{t of} the pump, ie the volume of the liquid in the pump (or the total volume of the pump housing minus the volume of the pump wheel) small in relation to the maximum total delivery rate. A ratio of the dead volume to the maximum total delivery rate V _G is preferably selected as follows: V _τ / v _G <0.2, preferably <0.15 or <0.1, with V [cm ³ ] and v _G [cm ³ / sec ]. In an advantageous development of the invention, the pump housing of the liquid pump is provided with an outer recess into which the heating element is inserted.

By inserting into such a recess, the contact area between the corresponding housing part and the heating element is increased, which further increases the efficiency. At the same time, the heating element is integrated into the pump housing from the outside, so that there are no sealing or insulation problems with the heating element.

In an advantageous development of the invention, the outer recess is formed in such a way that a projection forms on the inside of the pump housing. This increases the contact area of the housing with the liquid in the heated area. This measure thus results in a further increase in efficiency.

In this case, the inner projection is preferably aligned along the flow direction in order to disturb this pumping action as little as possible. The dead volume of the pump is reduced by the inner projection, while its alignment, as mentioned above, has little effect on the total delivery rate.

In an advantageous embodiment of the invention, the outer recess is also chosen to be deeper than the corresponding dimension of the heating element, so that the housing protrudes with a protrusion over the heating element inserted into the recess. In this way, the contact area is increased and the heat loss to the outside is reduced, ie the proportion of heat that enters the liquid inside the pump housing through the housing wall increases. This measure also serves to improve the efficiency of the heating. In a further advantageous embodiment of the invention, the heating element is pressed onto the housing, for example in the depression. Such pressing causes a particularly close and flat contact between the heating element and the corresponding housing part and accordingly serves to improve the heat flow from the heating element into the interior of the housing.

In a special embodiment of the invention, a thermally conductive filler is provided between the heating element and the housing wall. Such a filler can also improve thermal contact. This is particularly true where the outer shape of the heating element differs from the shape of the pump housing. Such deviations can hardly be avoided within the framework of normal error tolerances. With the help of a thermally conductive filler, good thermal contact can nevertheless be ensured.

The filler can, for example, be introduced into the recess before the heating element is inserted, so that it is partially displaced again when the heating element is pressed in and, if possible, completely fills up any space between the heating element and the housing wall.

In another embodiment of the invention, such a filler is also provided for fastening the heating element. The filler can be formed, for example, as an adhesive or as a solder, by means of which the heating element is firmly fixed in the housing recess.

The outer shape or the structure of the heating element is preferably designed such that there is an enlarged contact area with the corresponding section of the housing wall and thus with the pump interior. In a particularly simple embodiment, as such structure increasing the contact area, the heating element is designed as a ring segment. A ring segment is particularly advantageous in the case of a cylindrical pump housing. On the one hand, almost the entire circumference of the housing cross section can be covered with the help of a single heating element, on the other hand, the corresponding housing part can be designed as an end cover for the pump housing, which simplifies manufacture and assembly.

The desired contact area can be determined by the design of the cross section of the heating element, e.g. in a triangular, rectangular, square or trapezoidal shape. These cross-sectional shapes allow a large-area form fit.

In addition, production is simplified if the housing recess does not or only slightly behind the heating element, so that the heating element can be inserted into the recess without major deformation of the housing. A slight engagement behind to form a snap connection can be advantageous. It is essential here that the heating element can be inserted after prior separate shaping of the housing.

Another possibility of increasing the contact area between the pump housing and the heating element is to shape the cross section of the heating element in such a way that a larger surface is obtained over the length of the heating element. For example, the cross section can have corrugated or zigzag structures.

Other options for bringing the heating element into a structure with an enlarged contact area consist of forming the heating element in a spiral shape, in the form of a meander and / or in a snake or zigzag shape. All the above-mentioned as well as all other conceivable designs are suitable for forming the large contact area according to the invention. Advantageously, the contact area is made larger than half of the surface of the heating element specified as the minimum size. The efficiency can be further improved if the contact area is greater than 60%, 70%, 80% or even 90% of the total surface of the heating element.

The pump housing is advantageously formed in two parts, the heating element being attached to a housing part. This results in manufacturing advantages. On the one hand, the shape of the depression according to the invention is easier to achieve, and on the other hand, a material different from the rest of the pump housing can be selected for the housing part which carries the heater. For example, a metal can be used for this housing part, which combines good thermal conductivity with high temperature resistance. Such a housing part can e.g. Manufacture inexpensively in large quantities from a flat material by compression molding or deep drawing. A suitable plastic can be used for the rest of the housing, which can be processed, for example, by injection molding.

In a particularly advantageous embodiment of the invention, the pump is designed as a centrifugal pump with an axial inflow and tangential outflow. A centrifugal pump offers good efficiency with regard to the pumping action and can easily be provided with a heating element integrated according to the invention. In the case of a centrifugal pump, on the one hand the drive shaft for the pump wheel must be led out of the housing in a liquid-tight manner and on the other hand the axial inflow is usually provided on the side opposite the drive. The heater according to the invention can in principle be arranged both on the side of the axial inflow and on the drive side. The version with the heating element on the inflow side offers advantages in terms of production technology and design. The dimensions of the drive do not have to be matched to the heating element. In addition, an inflow, for example in the form of a connecting piece, a collar or a flange, can easily be molded into the housing part carrying the heater by means of the same shaping method, with which the depression according to the invention is also applied.

The housing of a centrifugal pump with a heater attached according to the invention can be cylindrical or also helical, as is often the case with centrifugal pumps.

An embodiment of the invention is shown in the drawing and is explained in more detail below with reference to the figures.

Show in detail

FIG. 1 shows a plan view of a housing part for a pump with a heating element integrated according to the invention,

Figure 2 is a side view of a

Housing part according to Figure 1 and

3 shows an enlarged detail of the housing part according to FIG. 1 in section and

Figure 4 is a sectional view of a complete pump. The housing part 1 according to FIG. 1 is designed as a cover for a further housing part of a centrifugal pump containing the pump wheel. It has an outer recess in the form of an annular groove 2, into which a heating element 3 which is bent from a rod-shaped blank to form an annular segment is inserted.

An inflow opening 4 is provided centrally for the axial inflow of the centrifugal pump. The connections 5, 6, which are attached on both sides at the end of the heating element 3, are bent out of the ring plane of the heating element 3, so that they protrude from the ring groove 2 and are therefore easily accessible. The protruding connections 5, 6 are clearly visible in the drawing view according to FIG. 2.

A collar 7 for connecting an inflow line is molded into the housing part 1 around the inflow opening 4.

In the detail enlargement according to FIG. 3 it can be seen that the annular groove 2 is formed in a flat material in such a way that a projection 8 results on the inside. On the one hand, this offers advantages in terms of production technology, in that the housing part 1 can be produced from a flat material, on the other hand, the projection 8 results in an increase in the contact area on the inside of the pump housing formed with the aid of the housing part 1.

Both the base 9 and the side walls 10, 11 of the projection 8 are washed around by the liquid in the interior of the pump to be formed with the housing part 1 and accordingly serve as an inner heating surface. The formation of the annular groove as an inner projection 8 thus almost triples the contact area compared to a heating element placed on a flat housing part. In addition, it can be seen that the heating element 3 and the annular groove 2 are adapted to one another in their cross-sectional shape, so that the heating element 3 lies in the annular groove 2 in a form-fitting manner. This results in large contact areas between the housing part 1 on the one hand and the heating element 3 on the other hand, these contact areas being joined flat to one another. If necessary, a filler material (not shown in detail) can also be provided in order to fill up smaller gaps between the heating element 3 and the housing part 1 in the annular groove 2 and thus to ensure good heat transfer even at such points.

As can be seen from FIG. 3, the annular groove 2 is formed deeper than the corresponding height h of the heating element 3, so that the housing part 1 projects beyond the heating element 3 with a projection a. This results in a contact area 20 of approximately 75% of the total area of the heating element 3 in the substantially square cross section of the heating element in connection with the three-sided heat contact. In addition, the heating element 3 is, as it were, immersed in the annular groove 2. This reduces the amount of heat given off to the outside. The side walls 10, 11, which are available for heat transfer to the liquid, are enlarged by the projection a. The heat flows in the material of the housing part 1 not only perpendicular to the side walls 10, 11 from the heating element 3 into the interior of the pump housing to be closed with the housing part 1, but it also spreads inside the housing part 1, e.g. on the upper extension of the side walls 10, 11. These areas of the side walls 10, 11 are therefore also used for heat transfer to the liquid. Accordingly, the efficiency of the heating element 3 is further improved by this measure.

The connection of the housing part 1, which is preferably made of heat-conducting and temperature-resistant material, for example Metal, is made with at least one further housing part can be carried out in a variety of ways. For example, a releasable connection, such as a snap-in or snap connection, can optionally be provided with appropriate sealing elements. However, a fixed connection to the further housing part is also conceivable, for example by gluing, soldering or welding.

Figure 4 shows a complete pump 12 with drive motor 13 and heating element 3 according to the invention. The housing part 1 described above serves as a cover for another housing part 14. The housing part 14 is penetrated by the drive shaft 15 of the drive motor 13. The passage of the drive shaft 15 is sealed in a manner not shown.

A pump wheel 16 is fastened to the drive shaft 15. The inflow takes place via the inflow opening. The outflow takes place tangentially into an outflow connection 17, where the flow is deflected parallel to the inflow.

In this embodiment, the housing part 1 is firmly connected to the housing part 14. For this purpose, the metal housing part 1 is overmolded in the edge region 18 during the manufacture of the other housing part 14 made of plastic. At this point, however, as mentioned above, detachable variants are also conceivable, which may be additionally sealed.

A variety of further configurations are conceivable compared to the exemplary embodiment shown, it being essential according to the invention that the heating element is inserted into an outer recess in the pump housing. The housing part 1 accordingly closes the pump housing to be sealed. There are no sealing and / or insulation problems in relation to the heating element 2 or its electrical connections 5, 6. In addition, the manufacture of a housing part 1 with a heating element 3 inserted according to the invention is particularly simple and therefore inexpensive.

Reference symbol list:

1 housing part

2 ring groove

3 heating element

4 inflow opening

5 connection

6 connection

7 collar

8 head start

9 base

10 side wall

11 side wall

12 pump

13 drive motor

14 housing part

15 drive shaft

16 impeller

17 drain connector

18 edge area

19 heating element

20 contact area

Claims

Expectations :

1. Household machine, in particular dishwasher, washing machine or the like, with one

Liquid circuit and a pump, which has a pump housing, which comprises a heating element for heating the liquid, which is at least partially positively adapted with a heat-conducting contact surface to the outer shape (2) of the housing (1), characterized in that the contact surface (20) is at least half as large as the entire outer surface of the heating element.

2. Household machine according to claim 1, characterized in that the outer shape of the housing has a surface-enlarging structure.

3. Household machine according to claim 1 or 2, characterized in that the ratio of the dead volume to the total delivery rate V _t [cm ³ ] / V _G [cm ³ / sec] <0.2.

4. Household machine according to one of the preceding claims, characterized in that the heating element (3) is inserted into an outer recess (2) of the pump housing.

5. Household machine according to one of the preceding claims, characterized in that the recess (2) is deeper than the corresponding dimension h of the heating element (3), so that the housing (1) with a protrusion a overhangs the heating element (3) ,

6. Household machine according to one of the preceding claims, characterized in that the outer recess (2) forms a projection (8) on the inside.

7. Household machine according to one of the preceding claims, characterized in that the inner projection is aligned along the flow direction.

8. Household machine according to one of the preceding claims, characterized in that the heating element (3) on the housing (2) is pressed.

9. Household machine according to one of the preceding claims, characterized in that a thermally conductive filler between the heating element (3) and the housing wall (9, 10, 11) is provided.

10. Household machine according to one of the preceding claims, characterized in that the thermally conductive filler is also provided for fastening the heating element (3).

11. Household machine according to one of the preceding claims, characterized in that the heating element (3) is formed from a rod-shaped blank into a ring segment.

12. Household machine according to one of the preceding claims, characterized in that the heating element is spiral.

13. Household machine according to one of the preceding claims, characterized in that the heating element has a meandering, snake or zigzag shape.

14. Household machine according to one of the preceding claims, characterized in that the pump housing is formed in two parts and the heating element (3) is attached to a housing part (1).

15. Liquid pump for a household machine, in particular a dishwasher, a washing machine or the like, which has a pump housing which comprises a heating element for heating the liquid, which is at least partially adapted to the outer shape (2) of the housing (1) with a heat-conducting contact surface is characterized in that the contact area is at least half as large as the entire outer surface of the heating element.