Thermostat

Abstract

A thermostat having a hollow body, wherein the hollow body is at least partly filled with a thermosensitive medium. A heating element is provided for heating the thermosensitive medium. The heating element is located outside of the hollow body and is at least partially insulated electrically from the hollow body. The element is connected to the hollow body in a thermally conductive manner.

Claims

1. A thermostat comprising: a hollow body, the hollow body being at least partly filled with a thermosensitive medium; a heating element for heating the thermosensitive medium, the heating element being arranged outside of the hollow body and is at least partially insulated electrically from the hollow body, wherein the heating element is connected to the hollow body in a thermally conductive manner, wherein the hollow body is implemented as multiple parts, wherein a first housing part of the hollow body is configured as a cup-shaped shell that projects into a hollow space of the hollow body, wherein a second housing part is configured as a cup-shaped housing part, wherein the cup-shaped shell and the cup-shaped housing part each have a radially surrounding flange at an open end region thereof, and wherein the cup-shaped shell is positioned in the open end region of the cup-shaped housing part and the flange of the cup-shaped shell is connected to the flange of the cup-shaped housing part.

2. The thermostat according to claim 1, wherein the ratio between an inside diameter of the cup-shaped housing part and an outside diameter of the cup-shaped shell lies in a range from greater than 1 to less than 2.5.

3. The thermostat according to claim 1, wherein the cup-shaped shell is connected to the cup-shaped housing part in a liquid-tight manner, and wherein electrical insulation is arranged between the cup-shaped shell and the cup-shaped housing part.

4. The thermostat according to claim 1, wherein the heating element is a PTC heating element.

5. The thermostat according to claim 1, wherein the heating element is a heating wire and/or a heating sheet arranged on or at a molded article.

6. The thermostat according to claim 1, wherein the heating element is connected to a molded part that has recesses for the electrical contacts of the heating element.

7. The thermostat according to claim 1, wherein the hollow body has an opening that is located essentially opposite the heating element, wherein a piston element that is movably supported in the opening is conducted through the opening, and wherein a force component resulting from a volume change in the thermosensitive medium is transmitted to the piston element.

8. The thermostat according to claim 1, wherein the cup-shaped shell is connected to the cup-shaped housing part in a liquid-tight manner, and wherein electrical insulation is arranged between the flange of the cup-shaped shell and the flange of the cup-shaped housing part.

9. The thermostat according to claim 1, wherein the flange of the cup-shaped shell directly contacts the flange of the cup-shaped housing part.

10. The thermostat according to claim 1, wherein the open end region of each of the cup-shaped housing part and the cup-shaped shell are provided on a same side of the hollow body.

11. A thermostat comprising: a hollow body, the hollow body being at least partly filled with a thermosensitive medium; a heating element for heating the thermosensitive medium, the heating element being arranged outside of the hollow body and is at least partially insulated electrically from the hollow body, wherein the heating element is connected to the hollow body in a thermally conductive manner, wherein the hollow body is implemented as multiple parts, and wherein a first housing part of the hollow body is configured as a cup-shaped shell that projects into a hollow space of the hollow body, wherein the heating element is arranged in a region of the cup-shaped shell that projects into the hollow space, and wherein an electrically insulating layer and/or a thermally conductive layer is arranged between the heating element and the cup-shaped shell.

12. The thermostat according to claim 1, wherein the hollow body is made of a material that has a thermal conductivity of less than 50 W/mK or less than 25 W/mK.

13. A thermostat comprising: a hollow body, the hollow body being at least partly filled with a thermosensitive medium; a heating element for heating the thermosensitive medium, the heating element being arranged outside of the hollow body and is at least partially insulated electrically from the hollow body, wherein the heating element is connected to the hollow body in a thermally conductive manner, and wherein the heating element is attached to an exterior surface of the hollow body via an electrically insulating and thermally conductive adhesive.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein:

(2) FIG. 1 is a schematic sectional view through a hollow body according to an embodiment of the invention with a heating element that is connected by means of an adhesive, wherein the adhesive is electrically insulating and thermally conductive,

(3) FIG. 2 is a schematic sectional view through a multi-part hollow body, wherein a heating element is inserted into the cup-shaped shell, and electrical insulation is provided between the cup-shaped housing part and the cup-shaped shell,

(4) FIG. 3 is a schematic sectional view through a multi-part hollow body from FIG. 2, wherein electrical insulation is only provided between the heating element and the exterior wall of the cup-shaped shell, and

(5) FIG. 4 is a schematic sectional view of a hollow body with a heating element having an ohmic resistance, wherein the hollow body and the heating element are supported by a molded part on a housing.

DETAILED DESCRIPTION

(6) FIG. 1 shows a schematic sectional view of an expansion element 1. The expansion element 1 has a hollow body 2 that is filled with a thermosensitive material 5. The hollow body 2 can advantageously have a cylindrical basic shape. Other designs, such as cuboid or spherical hollow bodies, may also be provided in alternative embodiments.

(7) On its top surface, the hollow body 2 has an opening through which a piston element 6 passes. As a result of a volume change in the thermosensitive medium 5, the piston element 6 can be moved up and down in the interior of the hollow body 2.

(8) Provided beneath the hollow body 2 is a plate-like heating element 3, which is attached to an exterior surface of the hollow body 2 by an adhesive 4. The adhesive 4 in this design is electrically insulating and thermally conductive. In this way, the heat from the heating element 3 can advantageously be transmitted to the hollow body 2 and in particular to the thermosensitive medium 5. At the same time, a short circuit is precluded by the electrical insulation.

(9) In advantageous fashion, the heating element 3 is a PTC heating element. It is connected to a voltage source by a circuit 7.

(10) In alternative embodiments, the heating element 3 can also be implemented with a cup shape, for example, and can include a bottom region of the hollow body 2.

(11) FIG. 2 shows another schematic sectional view of an alternative expansion element 10. The expansion element 10 has a cup-shaped housing part 11 and a cup-shaped shell 12.

(12) The cup-shaped shell 12 is inserted into the cavity formed by the cup-shaped housing part 11 through an open region 19 of the cup-shaped housing part 11. Both the cup-shaped housing part 11 and the cup-shaped shell 12 have a circumferential flange 21 or 22 at their open end regions 19 or 20. The cup-shaped housing part 11 is connected to the cup-shaped shell 12 by means of the two flanges 21 and 22.

(13) Electrical insulation 13 is placed between [the two parts at] the joint. In this way, the cup-shaped shell 12 is electrically insulated from the cup-shaped housing part 11.

(14) Located in the interior of the cup-shaped housing part 11 is a thermosensitive medium 14. Together, the cup-shaped housing part 11 and the cup-shaped shell 12 form the hollow body 23.

(15) Formed between the exterior surface of the cup-shaped shell 12 and the interior surface of the cup-shaped housing part 11 is a circumferential annular gap 17 that is likewise filled with the thermosensitive material 14.

(16) Depending on the design of the cup-shaped shell 12 and the cup-shaped housing part 11, the annular gap 17 can have a cylindrical or other shape resulting from the spacing between the interior surface of the cup-shaped housing part 11 and the exterior surface of the cup-shaped shell 12.

(17) A heating element 15 is inserted in the cup-shaped shell 12. This heating element is connected to a voltage source by an electric circuit 16. An air gap 18 is shown between the heating element 15 and the cup-shaped shell 12. This gap can vary depending on the design of the heating element 5 relative to the cup-shaped shell 12. Due to the electrical insulation 13, the heating element 15 can also rest directly on the cup-shaped shell 12 with full-area contact.

(18) As a result of inserting the heating element 15 into the cup-shaped shell 12, the overall heat exchange area between the heating element 15 and the cup-shaped shell 12, and hence also with the thermosensitive medium 14, increases.

(19) The cup-shaped shell 12 and the cup-shaped housing part 11 can be implemented as a deep-drawn part, a turned part, or a cast part, for example. FIG. 2 does not restrict the possibilities for implementing these two elements.

(20) As shown in FIG. 2, the heating element 15 can likewise be constructed with a cylindrical shape, but it can also be matched to the inside diameter of the cup-shaped shell as a function of the shape of the cup-shaped shell.

(21) In alternative embodiments, it would also be possible, for example, to stagger multiple heating elements, such as those already shown in FIG. 1, inside the cup-shaped shell.

(22) Placement of the heating element 15 in the interior of the cup-shaped shell 12 is especially advantageous, since the heat transmission can thus take place in a direct way through the cup-shaped shell 12 to the thermosensitive medium 14. The proportion of heat that would transfer to a coolant that could possibly be flowing around the expansion element 10 is considerably reduced as a result.

(23) In an especially advantageous embodiment, the cup-shaped shell 12, in particular, has greater thermal conductivity as compared to the cup-shaped housing part 11. This ensures that the heat transfer from the heating element 15 to the thermosensitive medium 14 is improved.

(24) The cup-shaped housing part 11, in turn, has as low a coefficient of thermal conductivity as possible in order to prevent heat from the thermosensitive medium 14 or from the heating element 15 being delivered directly to a coolant that flows around the expansion element 10 during operation.

(25) FIG. 3 shows another schematic, sectional view of an expansion element 30. As already shown in FIG. 2, the hollow body 38 is composed of a cup-shaped housing part 31 and a cup-shaped shell 32 inserted therein. Likewise formed between these two elements is an annular gap 37, which is oriented to the shape of the cup-shaped shell 32 relative to the cup-shaped housing part 31.

(26) Located in the interior of the hollow body 38 is a thermosensitive medium 34.

(27) In contrast to FIG. 2, the flanges of the cup-shaped shell 32 and of the cup-shaped housing part 31 are now connected directly to one another, and are not separated from one another by electrical insulation.

(28) The connection between the cup-shaped housing part 31 and the cup-shaped shell 32 in FIG. 2 through 4 can be accomplished by gluing, welding, flanging, screwing, or locking, for example.

(29) The interior surface of the cup-shaped shell 32 is provided with electrical insulation 33. Here, the term interior surface of the cup-shaped shell 32 describes the surface facing away from the cavity of the hollow body 38. This can be accomplished by means of a film made of Kapton material, for example. The electrical insulation 33 ensures that no electrical short circuit occurs between the heating element 35 inserted in the cup-shaped shell 32 and the cup-shaped shell 32. In addition, Kapton material has the property of not impeding heat transport.

(30) The heating element 35 is connected to a voltage source by a circuit 36. The heating element 35 can likewise be composed of one PTC heating element or of a plurality of PTC heating elements connected to one another.

(31) FIG. 4 shows an alternative embodiment of an expansion element 50. As in the preceding FIGS. 2 and 3, this element is composed of a cup-shaped housing part 51 and a cup-shaped shell 52. The expansion element 50 or the hollow body 53 is filled with a thermosensitive medium 54. A piston element passes through the top surface of the expansion element 50.

(32) In contrast to the preceding figures, the heating element 55 now is not composed of a PTC heating element, but rather a heating wire that is wound around a molded article 63. The heating element 55 thus produces heat as a result of the ohmic resistance of the heating wire. The gap between the heating element 55 and the cup-shaped shell 52 is filled with an electrically nonconductive and thermally conductive material 62. The open region of the cup-shaped shell 52 is closed toward the bottom by a molded part 57. Consequently, the electrically nonconductive and thermally conductive material 62 is held in the region around the heating element 55 enclosed by the cup-shaped shell 52.

(33) In alternative embodiments, a heating sheet or another arrangement of an element that generates heat through an ohmic resistance can also be provided in place of the wound heating wire.

(34) Alternatively, a single PTC heating element or a plurality of PTC heating elements can also be provided.

(35) The molded part 57 has recesses 60 through which pass the electrical contacts of the circuit 56, by which means the heating element 55 is connected to a voltage source. The entirety of the expansion element 50 with the inserted molded part 57 is placed in a housing 59. In this design, it is supported relative to the walls of the housing 59 by a sealing element 61. Provided between the expansion element 50 and the housing 59 is an air gap 58 that constitutes thermal and electrical insulation of the expansion element 50 relative to the environment.

(36) FIG. 2 through 4 have in common that the heating element 15, 35, 55 is inserted into the interior of the cup-shaped shell 12, 32, 52 in each case. As a result, the heat transmission area between the heating element 15, 35, 55 and the cup-shaped shell 12, 32, 52 is enlarged as a whole in each case, and the heat transfer to the applicable thermosensitive medium 14, 34, 54 in the interior of the hollow body 23, 38, 53 is improved. At the same time, unwanted heat loss to a coolant flowing around the applicable expansion elements 10, 30, 50 is minimized.

(37) All the exemplary embodiments shown in FIG. 1 through 4 are by way of example, and serve to describe the inventive concept. They can be combined with one another and do not have any limiting character.

(38) The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims.