Electric Heating Device And Method For Its Manufacture

Abstract

Electric heating device and method for its manufacture An electric heating device a housing with a partition wall which separates a connection chamber from a heating chamber for dissipating heat and from which at least one PTC heating element with a heating element casing protrudes in the direction toward the heating chamber. At least one PTC element and conductor tracks, electrically connected in the connection chamber for energizing the PTC element with different polarities and connected to the PTC element in an electrically conductive manner, are supported in the heating element casing an insulated manner. For improved support of the PTC heating element, a holding element, engaging around the heating element casing, is connected to the partition wall on its side facing the heating chamber and is connected to the heating element casing. Also disclosed is a method for the manufacture of such an electric heating device.

Claims

1. An electric heating device comprising: a housing with a partition wall which separates a connection chamber from a heating chamber for dissipating heat; at least one PTC heating element having a heating element casing that protrudes in a direction toward the heating chamber; at least one PTC element and conductor tracks supported in the heating element casing an insulated manner, wherein the conductor tracks are electrically connected in the connection chamber for energizing the PTC element with different polarities, and wherein the conductor tracks are connected to the PTC element in an electrically conductive manner; and a holding element engaging around the heating element casing, wherein the holding element is connected to the partition wall on a side facing the heating chamber, and wherein the holding element is connected to the heating element casing.

2. The electric heating device according to claim 1, wherein the holding element is connected, at least in a force-fit manner, to the partition wall.

3. The electric heating device according to claim 1, wherein the holding element is connected, at least in a force-fit manner, to the heating element casing.

4. The electric heating device according to claim 1, wherein the holding element is connected, at least in a force-fit manner, to the partition wall and the heating element casing.

5. The electric heating device according to claim 1, wherein the heating element casing comprises a heating element shield that shields the PTC element electromagnetically, and wherein the heating element shield is electrically connected to the holding element.

6. The electric heating device according to claim 5, wherein the heating element shield is formed by an envelopment enclosing the PTC element.

7. The electric heating device according to claim 6, wherein the connection chamber is provided with a connection chamber shield that shields the connection chamber electromagnetically and that is electrically conductively connected to the holding element.

8. The electric heating device according to claim 7, wherein the housing forms at least one locking projection which surrounds the holding element on an outside and that the holding element, and forms a connection housing connection strip which abuts against the locking projection under preload.

9. The electric heating device according to claim 8, wherein the connection housing connection strip abuts, in an electrically conductive manner, against the locking projection.

10. The electric heating device according to claim 9, wherein the partition wall forms a collar which circumferentially surrounds the at least one heating element casing and which has the holding element engaging around it.

11. The electric heating device according to claim 9, wherein the holding element is an integrally formed sheet metal element that is punch-processed to form a receiving opening for the heating element.

12. The electric heating device according to claim 11, wherein the holding element is substantially planar.

13. The electric heating device according to claim 11, wherein at least one contact strip, which is integrally formed on the sheet metal element, is exposed in the receiving opening and abuts against the heating element casing under resilient preload.

14. A method for the manufacture of an electric heating device in which first a housing having a partition wall which separates a connection chamber from a heating chamber for dissipating heat, and in which at least one PTC heating element with at least one heating element casing are manufactured, in which heating element casing at least one PTC heating element and conductor tracks are supported in an insulated manner, with the conductor tracks being arranged for energizing the PTC element with different polarities, and with the conductor tracks being connected to the PTC element in an electrically conductive manner, the method comprising: introducing the PTC heating element into a heating element receptacle of the partition wall so that the heating element protrudes from the partition wall in a direction towards the heating chamber; pushing a holding element, interacting with the heating element casing, over the heating element casing; and connecting the holding element to the partition wall on side thereof facing the heating chamber.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Further details and advantages of the present invention shall become apparent from the following description of an embodiment in combination with the drawing, in which:

[0025] FIG. 1 shows a perspective side view of an embodiment of a holding element;

[0026] FIG. 2 shows a perspective side view of a housing which forms a partition wall and which is fitted several PTC heating elements before the holding element is pushed on;

[0027] FIG. 3 shows a representation according to FIG. 2 after the holding element has been pushed on;

[0028] FIG. 4 shows detail D according to FIG. 3 in an enlarged view;

[0029] FIG. 5 shows a perspective side view after the holding element has been pushed on, where some of the heating elements have been removed for better illustration of the situation;

[0030] FIG. 6 shows detail F according to FIG. 5 in an enlarged view and

[0031] FIG. 7 shows a perspective explosion view of the PTC heating element of the embodiment.

DETAILED DESCRIPTION

[0032] FIG. 1 shows an embodiment of a holding element 2 formed by punching and bending which comprises a plurality of receiving openings 4 which extend parallel to one another and are designed as an elongated hole into which contact strips 6 respectively protrude on oppositely disposed longitudinal sides of the receiving openings 4. Housing connection strips 8 are provided on the rear longitudinal edge of the holding element 2 in FIG. 1. Three housing connection strips 8 are presently provided there. Located on oppositely disposed transverse sides of the holding element 2, the base area of which is configured as a parallelogram, is a further housing connection strip 8.

[0033] The holding element 2 is formed by punching and bending sheet metal material. The housing connection strips 8 and the contact strips 6 protrude from one side of the planar sheet metal material, whereas a fully circumferentially closed circumferential edge 10 protrudes from the other side and is formed from the plane of the sheet metal material by bending the same.

[0034] As can be seen in particular from FIG. 4, the contact strips 6 have an end on the attachment side which is connected to the edge of the receiving opening 4 and projects therefrom, and a free end which is opposite a web-shaped section which is bent again obliquely from the plane of the sheet metal material and extends substantially at a right angle to the plane of the sheet metal material. The free end of the contact strip 6 can terminate with a sharp edge.

[0035] The holding element 2 can be formed from brass, steel, copper or aluminum. A material should be selected which, firstly, exhibits good electrical conductivity and, secondly, has a certain spring rigidity so that the contact strips can abut against the heating element casing with good contact pressure.

[0036] The PTC heating elements are identified in FIG. 2 with reference numeral 12. They have a heating element casing 14 which is formed from sheet metal and fully circumferentially encloses electrically conductive conductor tracks in the form of contact plates which are typically contacted to mutually oppositely disposed side surfaces of a PTC element, likewise not shown. Details of such a configuration can be gathered from EP 3 334 242 A1. There is also an insulation within the heating element casing 14 which prevents the contact plates from electrically contacting the inner surface of the heating element casing 14. Because the sheet metal material forming the heating element casing 14 is electrically conductive and forms a circumferential envelopment that shields the PTC element circumferentially. The PTC element and the contact plates are also encapsulated by this envelopment from the medium to be heated, and separated according to which flows against the outside of the heating element casing for heating purposes in order to absorb and dissipate the heat generated by the PTC element. The PTC heating elements protrude from a housing 16 which forms a heating element receptacle 18 for each PTC heating element 12. The end of the PTC heating element 12 on the connection side is inserted into this heating element receptacle 18. For this purpose, the heating element casing 14 is typically provided on its outer circumference with a circumferential seal which abuts in a sealed manner against the walls of the housing 16 defining the heating element receptacle, cf. EP 3 334 242 A1.

[0037] The housing 16 can be a metal pressure die-cast housing. To form a connection chamber shield, the housing 16 can equally well be an injection-molded plastic housing into which a shield is incorporated or connected to the plastic housing, for example, by way of injection mold coating with the plastic material. Connected to the housing 16 at diagonally opposite corners of the housing 16, which is basically formed with a rectangular base area, is, firstly, a connector casing 20 for the power current and, secondly, a connector casing 22 for control signals. The two connector casings 20, 22 are made of plastic material and are connected to the housing 16 with the interposition of a seal.

[0038] The housing 16 is basically bowl-shaped, where a base of the bowl forms a partition wall 24 in which the heating element receptacles 18 are recessed. This partition wall 24 is circumferentially surrounded by a circumferential housing wall 26 which encloses a receiving chamber. Exposed in this connection chamber identified by reference numeral 28 are the respective contact plates of the individual PTC heating elements 12 for the electrical connection to the power current. The connection chamber 28 typically also accommodates a control device which controls all the PTC heating elements and, possibly, groups them into different heating circuits.

[0039] A heating chamber is indicated with reference numeral 30 on the side of the partition wall 24 opposite the connection chamber 28. In the embodiment shown, this heating chamber 30 is completed by a further housing element, not shown, which encloses all the PTC heating elements 12, with the exclusion of the connector casings 20, 22, and comprises a base so that a circulation chamber is formed as a heating chamber which is accessible via inlet and outlet ports from the outside for circulating a medium to be heated in the circulation chamber and to pass it along the surfaces of the PTC heating elements 12 in order to heat the medium.

[0040] The holding element 2 according to FIG. 1 is provided in FIG. 2 as an extension of the free ends of the PTC heating elements 12. The direction line P indicates the assembly direction. The holding element 2 is then pushed over the individual heating element casings 14. The contact strips 6 there abut against the outer surface of the heating element casings 14 and contact them electrically. They scrape against the outer surface of the heating element casing 14 when the holding element is mounted.

[0041] FIG. 3 shows the installation position of the holding element 2. In the installed position, this holding element 2 engages with its edge 10 around a collar that surrounds the partition wall 24 circumferentially and is identified with reference numeral 32 in FIG. 2. As a result, the holding element 2 is positioned relative to the partition wall 24 and therefore to the housing 16. In this installed position, the contact strips 6 provided on the oppositely disposed longitudinal sides of the elongated holes each contact the oppositely disposed main side surfaces of the heating element casings 14. This then results in electrical contact between these heating element casings 14 and the holding element 2, which can also be effected in a positive-fit manner with the contact strip 6 tapering sharply.

[0042] FIGS. 5 and 6 in particular show that the housing 16 has several locking projections 34 which protrude from the partition wall 24 in the direction toward the heating chamber 30 and which presently are formed integrally with the pressure die-cast housing. The housing connection strips 8 abut against these locking projections 34 in an electrically conductive manner. When the holding element 2 is pushed on, the housing connection strips 8 scrape along the surface of the locking projections 34 so that, firstly, a positive-fit, sometimes also a clawing and therefore force-fit connection arises which also establishes electrical contact between the holding element 2 and the housing 16.

[0043] A force-fit and/or positive-fit connection arises between the holding element 2 and the housing 16 due to, firstly, the circumferential edge 10 of the holding element 2 engaging around the collar 32 projecting from the partition wall 24 in the direction toward the connection chamber 28 and, secondly, the locking projections 34 interacting with the housing connection strips 8. This connection is also electrically conductive. The connection between the holding element 2 and the heating element casing 14 is also electrically conductive. The electrically conductive properties of the housing 16 give rise to a circumferential shield which accommodates the PTC elements of the PTC heating elements 12 and circumferentially surrounds the connection ends of the contact strips for the electrical connection of the PTC elements in the region of the connection chamber 28. Once a cover for the connection chamber 28 is mounted, all current-carrying components of the embodiment are shielded electromagnetically.

[0044] The electrical connections required for this can be established simply by pressing the holding element 2, firstly, onto the heating element casing 14 and, secondly, onto the housing 16. No further fastening devices or the like are required for firmly connecting the holding element 2 to the housing 16.

[0045] FIG. 7 illustrates details of the PTC heating element 12 which presently comprises only one PTC element 40 which at its oppositely disposed main side surfaces 42 is covered with an insulating layer 44. The insulating layers 44 are presently formed from a plastic film, for example made of Kapton. The PTC element 40 is configured as a platelet having a width B or a length L, respectively, that is greater by the factor of at least 10 than a thickness that corresponds to the distance between the two main side surfaces 42. Provided on oppositely disposed main side surfaces 42 are metal sheet contact plates defining conductor tracks 48 in the meaning of the invention which conductor tracks 48 can be adhesively bonded to the PTC element 40 and thereby be connected in an electrically conductive manner to a surface metallization of the ceramic PTC element 40 which can be applied as a layer by way of PVD or CVD. The conductor tracks 48 can also only merely be placed onto the PTC element 40. Each conductor track 48 forms a contact surface 50 which is abutted in an electrically conductive manner against the main side surface 42 of the PTC element 40 and a contact strip 52 projecting on one side above the PTC element 40. The contact surface 50 is presently provided coinciding with the main side surface 42 of the PTC element 40. The insulating layer 44 lies on the side facing away from the PTC element 40 on the contact plate 48 and covers the latter.

[0046] The PTC element 40 is received in a frame 56 which for this purpose comprises a frame opening 58. An upper cross tie member 62 of said frame 56 is formed integrally with a passage element base 68 which together with a passage segment lid 66 forms a kind of plug over which a stop collar 68 projects. The passage segment lid 66 comprises bores 70 and half shells 72 that are aligned with them and the passage element base 64 sandwich the contact strips 52.

[0047] After assembly, the contact strips 52 of each conductor tracks 48 projects the upper cross tie member 62. The unit thus produced is inserted into a deep-drawn part marked with reference numeral 74 which is formed from sheet metal by deep drawing and provided with a single opening 76, which opening is surrounded by a seal element 78 overmolded over the frame 56. The contact strips 52 are provided for plug connection within the connection chamber 28. The seal element 78 is sealingly received in the heating element receptacle 18.