PTC Heating Device and Method of Manufacturing the Same

Abstract

A PTC heating device has a frame surrounding an accommodation space, at least one PTC element accommodated in the accommodation space, and conductor elements, which are connected to the PTC element in an electrically conductive manner and enclose the PTC element between them. Each of the conductor elements is surrounded by a frame segment. The frame segments are welded together to enclose the PTC element in the accommodation space. In the method according to the invention, injection molded plastic frame segments having interacting connection segments are connected to conductor elements. At least one PTC element is then introduced between the frame segments. The frame segments are approached to each other until the connection segments abut against each other. The connection segments are then melted. As a result of this melting, the frame segments are approached further to each other until the conductor elements abut against the PTC element.

Claims

1. A PTC heating device comprising: a frame surrounding an accommodation space and including at least two frame segments; at least one PTC element accommodated in the accommodation space; and conductor elements which are connected to the PTC element in an electrically conductive manner and which enclose the PTC element between them, wherein each of the conductor elements is surrounded at least partially by at least one of the frame segments, and wherein the frame segments are ultrasonically welded together to enclose the PTC element in the accommodation space.

2. The PTC heating device according to claim 1, wherein the frame is formed by two frame segments, each of which surrounds conductor elements abutting against the PTC element and which forms interacting connection segments which are ultrasonically welded to each other.

3. The PTC heating device according to claim 2, wherein a depression, adapted to accommodate melt generated during welding, is formed adjacent to the connection segments on at least one of the frame segments.

4. The PTC heating device according to claim 2, wherein at least one of the frame segments has a pin that is associated with a depression on the other frame segment that holds the pin.

5. The PTC heating device according to claim 2, wherein, adjacent to the connection segments on at least one of the frame segments, a web is formed that is configured to prevent spillover of melt generated during welding over and beyond a contour of the frame.

6. The PTC heating device according to claim 1, wherein each of the conductor elements is sealed in the associated frame segment by overmolding a plastic forming the associated frame segment, and wherein the conductor elements comprise connecting webs protruding from an edge, which connecting webs are covered by positioning projections which are formed on one of the frame segments and which cooperate with associated positioning projection receptacles on the other of the frame segments.

7. The PTC heating device according to claim 6, wherein a contact tongue, protruding externally from the frame, is guided through the frame below one of the positioning projections.

8. A method of manufacturing a PTC heating device, comprising: injection-molding frame segments from a plastic so as to form interacting connection segments on the frame segments; connecting each of the frame segments to a conductor element; introducing at least one PTC element between the frame segments; approaching the frame segments to each other until the connection segments abut against each other; melting the connection segments so as to allow the frame segments to further approach each other until the conductor elements abut against the PTC element.

9. The method according to claim 8, further comprising introducing one of the frame segments into an auxiliary assembly device, which auxiliary heating assembly has a contact surface supporting the frame segment on an underside thereof and which has lateral limiting devices for positioning the frame segment, and subsequently applying the other of the frame segments with enclosure of at least one PTC element between the frame segments, to one of the frame segments with guidance of the lateral limiting devices such that the connection segments provided on the frame segments interlock, and further comprising welding the connection segments to one another to produce the PTC heating device, and then removing the PTC heating device from the auxiliary assembly device.

10. A PTC heating device comprising: a frame surrounding an accommodation space; at least one PTC element accommodated in the accommodation space; and conductor elements which are connected to the PTC element in an electrically conductive manner and which enclose the PTC element between them, wherein each of the conductor elements is sealed in the frame by overmolding a plastic forming the frame, and wherein the conductor elements comprise connecting webs protruding from an edge, which connecting webs are covered by positioning projections which are formed on a portion of the frame and which cooperate with associated positioning projection receptacles on another portion of the frame.

11. The PTC heating device according to claim 10, wherein a contact tongue, protruding externally from the frame, is guided through the frame below one of the positioning projections.

12. The PTC heating device according to claim 10, wherein the frame is formed from first and second frame segments that are ultrasonically welded together to enclose the PTC element in the accommodation space.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Further details and advantages of the present invention will be apparent from the following description of an embodiment in conjunction with the drawing. Therein:

[0025] FIG. 1 shows a perspective exploded view of the embodiment of the PTC heating device;

[0026] FIG. 2 shows a perspective top view of a frame segment of the embodiment according to FIG. 1;

[0027] FIG. 3 shows a perspective top view of the conductor element to the frame segment according to FIG. 2;

[0028] FIG. 4 shows a top view of the embodiment according to FIG. 2;

[0029] FIG. 5 shows a sectional view along line V-V according to the illustration in FIG. 4;

[0030] FIG. 6 shows a sectional view along line VI-VI according to FIG. 4;

[0031] FIG. 6A shows an enlarged detail at the top edge of FIG. 6;

[0032] FIG. 6B shows an enlarged detail at the bottom edge of FIG. 6;

[0033] FIG. 7 shows a perspective sectional view along line VII-VII according to the illustration in FIG. 4;

[0034] FIG. 8 shows a perspective sectional view along line VIII-VIII according to the illustration in FIG. 4;

[0035] FIG. 9A, 9B shows a perspective side view of a device for welding the PTC heating device according to the preceding embodiments in an initial position of a sonotrode (FIG. 9A) and an end position of the sonotrode (FIG. 9B).

DETAILED DESCRIPTION

[0036] FIG. 1 shows an embodiment of a PTC heating device 2 with a two-part frame 4, formed by a first frame segment 4.1 and a second frame segment 4.2. The frame segments 4.1 and 4.2 are configured identically. Accordingly, they form frame halves. In the joined state, the frame segments 4.1 and 4.2 form the entire frame 4 and surround an accommodation space 6. A PTC element 8 is accommodated in this accommodation space. The PTC element 8 is provided as a semiconducting ceramic component with metallizations formed on main side surfaces 10 of the PTC element 8. Between the main side surfaces 10 of the PTC element 8, the latter forms a circumferential edge 12, the respective edge surfaces of which are characterized by reference signs 12.1-12.4.

[0037] Conductor elements characterized by reference sign 14 each form an inner contact surface 16 to the main side surfaces 10. The conductor elements 14 are made of sheet metal. The conductor elements 14 each form a contact tongue 18 by punching. Connecting webs formed by punching and bending are characterized by reference sign 20, each of which projects beyond a lateral edge of the rectangular contact surface 16 and has connecting projections 22 projecting from the plane of the contact surface 16 as a result of bending, which can be seen in particular in FIGS. 3 and 6A. The conductor elements 14 formed by metal sheets further have bores 24 recessed in the area of opposite edges (cf. FIG. 3).

[0038] The connecting webs 20 are each covered by a positioning projection 26 of the frame segment 4.1/4.1, wherein the positioning projection 26 also accommodates the connecting projection 22. The corresponding positioning projection 26 protrudes beyond a frame contact surface characterized by reference sign 28, which is substantially planar and runs around in a plane in the circumferential direction of frame segment 4.1/4.2. To accommodate a single positioning projection 26, the respective other frame segment 4.1 or 4.2 has positioning projection receptacles 30 extending from the frame contact surface 28.

[0039] Complementary projections 26 and holders 30 are provided on longitudinal beams 32 of the frame 4. On an upper cross beam 34, a continuous bore is arranged as a positioning projection receptacle 30 for the round positioning projection 26 provided there. The upper cross beam 34 has an angular recess 36 for holding a cuboid positioning projection 26, which covers the contact tongue 18 and seals in the same.

[0040] Due to the measures described above, the conductor element 14 is solidly connected to the respective frame segment 4.1/4.2. On the other hand, each frame segment 4.1/4.2 can be formed separately with a low height (distance from outer surface to frame contact surface 28). As FIG. 6B illustrates, as a result of the overmolding, the bore 24 is penetrated with melt in each case and solidifies there to form a conical melt plug 41. The bore 24 is conically shaped towards the outside, so that the melt plug 41 also causes a form-fit connection between the respective frame segment 4.1/4.2 and the conductor element 14 at the lower cross beam 34.

[0041] For the welding of the two frame segments 4.1/4.2, these have configurations which are illustrated in FIGS. 7 and 8. The frame segment 4.2 has a projecting pin 40 as connection segment. The lower frame segment 4.1 has a depression 42 formed to be adapted to the pin 40, which forms the other connection segment in the sense of the present invention. As FIG. 7 illustrates, the depression 42 is significantly larger than the base surface of the pin 40. The base surface of the pin 40 is rectangular. A conically projecting tip 44 of the pin 40 protrudes from this rectangular base surface of the pin 40. As FIGS. 7 and 8 illustrate, the depression 42 is significantly larger than the base surface of the pin both along the longitudinal beam 32 and transversely thereto. The depression 42 is dimensioned so as to be able to accommodate these conceivable amounts of melt that may be generated during ultrasonic welding by melting primarily the pin 40. The depression 42 accordingly forms a trough for accommodating conceivable amounts of melt during ultrasonic welding. As a result, the molten plastic mass remains within the respective depression during welding of the two frame segments 4.1/4.2.

[0042] A web 38 protruding from the lower frame segment 4.1 as shown in FIG. 7 or 8 limits the depression 42 on its outside and thus prevents the conceivable escape of melt on the outer circumferential surface of the frame 4.

[0043] In FIGS. 7 and 8, reference sign 38 characterizes a web that protrudes beyond the frame contact surface 28. Correspondingly, the edge surface of the upper frame segment 4.2 is recessed in the area of the web 38 relative to the associated frame contact surface 28 by a web holder 39. This web holder 39 extends uninterruptedly over the entire longitudinal beam 32. With FIGS. 7 and 8, it can be seen that the frame contact surfaces 28 define the parting plane, thus lie at half the height of the joined frame. The web 38 of the lower frame segment 4.1 according to FIGS. 7 and 8 protrudes through the parting plane and ends above the same. The web holder 39 of the upper frame segment 4.2 is recessed relative to the parting plane.

[0044] As FIGS. 2 and 4 convey, two depressions 42 are formed on one of the longitudinal beams 32 and two pins 40 are formed on the opposite longitudinal beam 32, which end on the outside in the web holder 39. The pins 40 and the depression 42 have an overall longitudinal extension that is small in relation to the overall extension of the longitudinal beam 32. The pins 40 may be slightly fin-shaped. In any case, they do not extend over the entire longitudinal extent of the longitudinal beam 32. The opposing cross beams 34 are free of connection segments for welding the two frame segments 4.1/4.2.

[0045] In the course of manufacturing the embodiment shown, two identical conductor elements are first formed by punching and bending a metal sheet. These are inserted into an injection mold and overmolded with the plastic forming the frame segments 4.1 or 4.2. In this process, the connecting projections 22 in particular are sealed in the plastic material. Two of the frame segments 4.1 shown in FIG. 2 are prepared in an identical manner for the PTC heating device 2.

[0046] The lower frame segment 4.1 is introduced for assembly into an auxiliary assembly device, which is characterized by reference sign 46 in FIGS. 9A, 9B. This auxiliary assembly device 46 has a contact surface 48 which is protruded by limiting devices 50. The lower frame segment 4.1 is abutted against the contact surface 48. In this context, the frame segment 4.1 is laterally limited by the limiting devices 50 with a narrow tolerance. Thus, at the end of the insertion movement, the frame segment 4.1 is positioned exactly relative to the auxiliary assembly device 46.

[0047] The PTC element 8 is then placed on the inner contact surface 16 of the corresponding conductor element 14. As FIGS. 7 and 8 show, the PTC element 8 is slightly protruded from the free inner contact surface 16.

[0048] The other of the prepared frame segments 4.2 is then approached to the lower frame segment 4.1 on the auxiliary assembly device 46. The limiting devices 50 also allow good relative positioning of the two frame segments 4.1/4.2. The pins 40 then engage in the associated depressions 42. The state shown in FIGS. 7 and 8 is achieved.

[0049] Thereafter, a sonotrode characterized by reference sign 52 in FIGS. 9A/9B is approached to this layering from the two frame segments 4.1/4.2 and the PTC element 8. Ultrasound is applied to melt the pins 40 in the depressions 42. In this process, the tip 44 of the pin 40 melts first, not so much the surface of the depression 42. Due to a certain pressure applied by the sonotrode 52, the two frame segments 4.1/4.2 approach each other. The joining movement comes to an end when the inner contact surface 16 of the upper frame segment 4.2 is abutted against the upper main side surface 10 of the PTC element 8 in FIGS. 7 and 8. The movement of the sonotrode 52 is usually force-controlled. The higher resistance to progressive approach movement associated with the planar abutment of the conductor element 14 against the PTC element 8 is understood as a signal to stop the feed movement of the sonotrode 52.

[0050] After completion of the ultra-welding process, the melt solidifies. Excess melt from the two connection segments 40/42 is located inside the depression 42.

[0051] After the sonotrode has been moved back to the starting position shown in FIG. 9A, the completed PTC heating device can be removed.