Heating rod

Abstract

Disclosed is a heating rod comprising a tubular housing (1) made of metal, a plurality of ceramic heating elements (3) arranged within the housing (1), a plastic frame (2) holding the heating elements (3), and a metal strip (4) electrically insulated from the housing (1) and in electrical contact with the heating elements (3). The housing (1) has a crimping section which fixes the plastic frame (2) inside the housing (1).

Description

Technical Field

[0001] The utility model relates to a heating rod. Background Art

[0002] US11197349B2 discloses a heating rod, which includes a tubular shell made of metal, a plurality of ceramic heating elements, a plastic frame and a metal strip. The plurality of ceramic heating elements are arranged in the shell, the plastic frame holds the heating elements, and the metal strip is electrically insulated from the shell and electrically in contact with the heating elements.

[0003] Such heating rods are used in cabin heaters for automobiles. It has been found that malfunctions of such heating rods are sometimes caused by relative movements between the tubular housing and the components inside the tubular housing, which can damage the electrical insulation. In prior art heating rods, such relative movements are usually caused by different thermal expansions of the tubular housing and the components arranged therein. Utility Model Content

[0004] Therefore, an object of the present invention is to provide a heating rod with an improved lifespan.

[0005] This object is achieved by a heating rod according to the present invention.

[0006] In the heating rod according to the invention, the tubular housing is crimped, thereby preventing or at least severely limiting the movement of the plastic frame holding the ceramic heating element relative to the tubular housing. In this respect, crimping means that the tubular housing is plastically deformed by squeezing or compression, whereby the inner cross-section of the tubular housing is locally reduced and a stopper is thereby created that blocks the movement of the frame relative to the housing.

[0007] In an advantageous development of the present invention, there are two crimping sections, one adjacent to each end of the tubular housing. In such an embodiment, all ceramic heating elements are arranged between the crimping sections.

[0008] In another advantageous development of the invention, the plastic frame has a recess, in which one of the crimping sections engages. The recess can be a groove, for example a circumferential groove, a groove on one side of the plastic frame or a groove on the opposite side of the plastic frame. During the crimping process, the material of the tubular housing is pressed inwardly into the recess. Thus, an absolute lock can be produced that fixes the plastic frame relative to the tubular housing. The plastic frame can have only one such recess, or the plastic frame can have two or more such recesses, which are engaged by the crimping section of the tubular housing.

[0009] In addition to the recesses or as an alternative to the recesses engaged by the crimping sections of the tubular housing, the ends of the plastic frame can be arranged between a crimping section and a plurality of ceramic heating elements. The crimping sections then form a seat for the adjacent ends of the plastic frame. In a modified embodiment of the utility model, the plastic frame can have an increased width and / or thickness between such crimping sections and a plurality of heating elements. The increased thickness and / or width of the plastic frame protects the ceramic heating elements during the crimping process and can prevent cracking of the ceramic heating elements.

[0010] The plastic frame may be provided with steps in order to locally increase the thickness and / or the width. However, if the plastic frame tapers from its increased thickness and / or width in the direction towards the ceramic heating element, the ceramic heating element can be better protected from mechanical stresses during the crimping process. In order to increase the protection of the ceramic heating element, the tapered section may extend over a length that is greater than the maximum width of the tubular housing. The cone angle, i.e. the angle enclosed by the longitudinal direction and the tapered surface, may be relatively small, for example 10° or less.

[0011] In one embodiment of the present invention, the plastic frame may have a recess, in particular a groove, in a portion adjacent to each end. In another embodiment of the present invention, the plastic frame may have a recess (e.g., a groove) adjacent to one end, and an increased width and / or thickness adjacent to the opposite end of the tubular housing.

[0012] The crimping section of the tubular housing can prevent relative movement between the plastic frame holding the ceramic heating element and the tubular housing. Different thermal expansions may also cause relative movement between the metal band electrically contacting the ceramic heating element and the insulating layer electrically isolating the metal band from the tubular housing. Damage due to such relative movement may be prevented by providing a contact band with a plurality of slits extending in pairs from opposite edges over two-thirds of the width of the band, for example over 80% to 90% of the width of the band. Such slits greatly increase the flexibility of the band, making it easy to extend or contract in the length direction, thereby relieving any thermal stress. If the slit widens at its end away from its starting edge, the flexibility of the band can be further increased. For example, the slit may end with a circular hole, for example a hole with a diameter of 2.0 mm to 4.0 mm. Additionally or in an alternative, the flexibility of the band may be further improved if the slit comprises a first section bent in a first direction and a second section bent in the opposite direction. For example, the slit may be S-shaped.

[0013] In an advantageous further development of the invention, the slit may have a width of 0.7 mm to 1.3 mm. Since the two ends of the slit may widen, the width of the slit is measured in the central portion connecting the ends of the slit. The central portion extends over at least 90% of the total length of the slit.

[0014] In an advantageous further development, the slits are parallel to one another and the distance between a pair of slits can be two to three times greater than the slit width. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Further details and advantages of the invention are explained by means of illustrative embodiments in conjunction with the drawings.

[0016] Figure 1 An exploded view of the heating rod is shown;

[0017] Figure 2 schematically shows a cross-sectional view of a first end of a heating rod;

[0018] Figure 3 schematically shows a cross-sectional view of a second end of the heating rod;

[0019] Figure 4 Shows Figure 1 metal strips; and

[0020] Figure 5 Shows Figure 4 details. DETAILED DESCRIPTION

[0021] Figure 1 1 . The heating rod shown in exploded form in FIG. 1 comprises a tubular housing 1 made of metal, a plastic frame 2 holding a ceramic heating element 3 (e.g. a PTC heating resistor), a metal strip 4 in electrical contact with the heating element 3, and an insulating layer 5 electrically isolating the metal strip 4 from the housing 1. In the embodiment shown, the insulating layer 5 can be a ceramic layer. There can be one or more additional insulating layers 6, 9, for example insulating layers made of plastic (e.g. polyimide). The tubular housing 1 can be closed at one or both ends with a plug, a cap or a sealant, for example a silicone sealant 7, 8.

[0022] In the embodiment shown, the tubular housing 1 is shaped as a flat tube, i.e. it has two opposite wide sides connected by a narrow side. The wide sides of the tubular housing 1 are provided with fins 16 in order to facilitate the transfer of heat generated by the heating element 3 to the surrounding air. Such fins 16 can be provided integrally with the tubular housing 1 by cutting technology, or can be attached to the tubular housing as a separate component.

[0023] In the embodiment shown, there is only a single metal strip 4 which is in electrical contact with the ceramic heating element 3. The bulk of the contacts of the ceramic heating element 3 are provided by the tubular housing 1. A second metal strip which is electrically insulated from the housing may also be provided. The heating element 3 is then arranged between these metal strips and thus connected to the potential and mass.

[0024] During assembly, the ceramic heating elements 3 held by the plastic frame 2, the tape 4 and any insulating layers 5, 6, 9 form a stack. If the ceramic heating elements are not in electrical contact with the tubular housing 1, the stack may include a second metal tape and one or more additional insulating layers. The stack is then inserted into the tubular housing 1. The tubular housing 1 may then be compressed in order to improve the thermal contact of the stack with the tubular housing 1 by applying pressure to the wide sides of the tubular housing 1. The wide sides of the tubular housing 1 are provided with fins 16 and face the main sides of the plate-shaped ceramic heating elements 3.

[0025] Figure 2 Schematically shown is a first end of a tubular housing 1, in which the inserted stack comprises a plastic frame 2. The first end of the tubular housing 1 is the end from which the electrical terminals 4a protrude, for example an extension of the metal strip 4. Also shown is a pressing tool 10 for compressing the tubular housing 1 and thereby improving the thermal contact of the ceramic heating element 3 with the tubular housing 1.

[0026] By crimping portions of the tubular housing 1 , particularly portions adjacent to the ends of the tubular housing 1 , movement of the plastic frame 2 within the tubular housing 1 can be minimized. Figure 2 Schematically shown is a tool 11 for crimping a portion of the tubular housing 1. The plastic frame 2 has a recess 12, such as a groove. The tool 11 crimps a portion of the tubular housing 1 by pressing the housing material inwardly into the recess 12. As a result, the crimping section of the tubular housing 1 engages the recess 12. Thereby, a positive lock is produced between the tubular housing 1 and the plastic frame 2.

[0027] Figure 3 The second end of the tubular housing 1 is schematically shown with the inserted stack comprising the plastic frame 2 and a pressing tool 10 for compressing the tubular housing 1. A tool 13 for crimping the end of the tubular housing 1 in order to minimize movement of the plastic frame 2 relative to the tubular housing 1 is also shown.

[0028] The plastic frame 2 has a section 2a with increased thickness. In the embodiment shown, the thickness of the plastic frame 2 increases towards the end as it moves away from the ceramic heating element. That is, the plastic frame 2 tapers towards the ceramic heating element. The tool 13 is used to crimp the end of the tubular housing 1, thereby forming a seat for the plastic frame 2.

[0029] Figure 2 and 3 Different possibilities are shown for shaping the plastic frame 2 to prevent movement inside the tubular housing 1. Figure 2 Construct one end of the heating rod and Figure 3 Construct the other end, but it is also possible to provide both ends according to Figure 2 or provide a recess at both ends according to Figure 3 The increased thickness.

[0030] In accordance with Figure 2 and 3 In the heating rod of , all ceramic heating elements are arranged between two crimping sections, which are arranged at or near the ends of the heating rod. These crimping sections prevent or at least reduce the movement of the plastic frame 2 inside the tubular housing 1, and thus improve the life of the heating rod.

[0031] Figure 4 A metal strip 4, for example made of aluminum or copper, for electrically contacting the ceramic heating element is shown. The metal strip 4 has a plurality of slits 14 extending in pairs from opposite edges over two thirds of the width of the strip 4, which increase the flexibility of the strip 4. Thus, by longitudinal expansion or compression of the metal strip 4, mechanical stresses caused by different thermal expansions of the various components of the heating rod, in particular the metal strip 4, the ceramic heating element, the insulating layer and the tubular housing, can be more easily relieved.

[0032] Figure 5 Shows Figure 4 Detail A. As shown in the figure, the slit 14 widens at its end away from its starting edge. The widened end can be provided as a circular hole 15 having a diameter greater than the width of the slit 14, for example, two to four times larger. In addition, the slit 14 includes a first section bent in a first direction and a second section bent in the opposite direction. Thus, the slit 14 is S-shaped. The curved section can be connected to the straight section of the slit 14. As shown in FIG. Figure 5 As shown, these straight sections form an angle α with the longitudinal direction of the strip 14 that is less than 90°, for example 55° to 80°.

[0033] Both the widened ends and the curved sections increase the flexibility of the metal strip 4, thereby helping to relieve mechanical stress. The curved section of the slit may have a width d1 of, for example, 0.7 mm to 1.3 mm. For example, the widened ends or circular holes at the ends of the slit 14 may have a diameter d2 of 2.0 mm to 4.0 mm.

[0034] The slits 14 are arranged so that they each cover only one of the ceramic heating elements 3. That is, the slits 14 do not cross from one ceramic heating element 3 to the adjacent heating element. For example, the slits 14 can be arranged in the central part of the ceramic heating element 3. In this way, a good electrical contact between the metal strip 4 and the ceramic heating element 3 is ensured. In the embodiment shown, the slits 14 extend in pairs from opposite edges over two-thirds of the width of the strip 14, for example over 80% to 90% of the width of the strip 14. Each pair of slits 14 can be parallel to each other and arranged at a distance d3, which is two to three times greater than the width d1 of the slits 14. Between the centers of the circular holes 15 at the ends of a pair of slits 14 can be a distance d4 measured in a direction perpendicular to the longitudinal direction of the strip 14, the distance d4 being, for example, 55% to 70% of the width of the strip 14.

[0035] For example, the slits 14 may be cut into the strip 4 using a laser or mechanically.

[0036] The plastic frame 2 can be made of plastic, in particular fiber reinforced plastic, such as polyphenylene sulfide, in particular a fiber content of 10% to 50%, such as 10% to 50% by weight of glass fiber or 10% to 40% by weight of carbon fiber.

[0037] The metal strip 4 may be made of an aluminum or copper based material, such as an aluminum-magnesium Al—Mg alloy, a copper-nickel Cu—Ni alloy, or a copper-iron Cu—Fe alloy.

[0038] List of reference numerals:

[0039] 1 tubular housing,

[0040] 2 plastic frames,

[0041] 2a Section of plastic frame

[0042] 3 Ceramic heating elements

[0043] 4 Metal belt

[0044] 4a terminal

[0045] 5. Isolation Layer

[0046] 6 Isolation layer

[0047] 7 End cap

[0048] 8. Sealant

[0049] 9 Isolation layer

[0050] 10 Tools

[0051] 11 Tools

[0052] 12 recesses

[0053] 13 Tools

[0054] 14 Slit

[0055] 15 holes

[0056] 16 fins

Claims

1. Heating rod, including A tubular housing (1) made of metal, a plurality of ceramic heating elements (3), wherein the plurality of ceramic heating elements (3) are arranged in the housing (1), a plastic frame (2) which holds the heating element (3), and a metal strip (4), the metal strip (4) being electrically insulated from the housing (1) and being in electrical contact with the heating element (3), It is characterized in that The housing (1) has a crimping section for fixing the plastic frame (2) inside the housing (1).

2. The heating rod according to claim 1, wherein all ceramic heating elements (3) are arranged between the crimping sections.

3. The heating rod according to claim 1, wherein the plastic frame (2) has a recess (12), with one of the crimping sections engaging with the recess.

4. The heating rod according to claim 3, wherein the recess (12) is a groove.

5. The heating rod according to claim 1, wherein the plastic frame (2) has a section (2a) with increased thickness between one of the crimping sections of the housing (1) and the plurality of ceramic heating elements (3).

6. The heating rod according to claim 5, wherein the plastic frame (2) tapers gradually from the increased thickness section (2a) toward the plurality of ceramic heating elements (3).

7. The heating rod according to claim 1, wherein the housing (1) is a flat tube.

8. The heating rod according to claim 1, wherein the housing (1) has opposite broad sides connected by narrow sides, wherein the fins are arranged at the broad sides.

9. The heating rod according to claim 1, wherein the metal strip (4) has a plurality of slits (14) extending in pairs from opposite edges and widening at the ends of the slits away from the edge from which the slits start.

10. The heating rod according to claim 9, wherein the slit (14) comprises a first section bent in a first direction and a second section bent in an opposite direction.

11. The heating rod according to claim 9, wherein each slit (14) covers only one of the ceramic heating elements (3).

12. The heating rod according to claim 9, wherein the widened end of the slit (14) is provided as a circular hole (15) having a larger diameter than a cross section of the slit (14) leading to the end.

13. The heating rod according to claim 9, wherein the slit (14) comprises a straight line section enclosing an angle (α) of less than 90° with the longitudinal direction of the strip (4).

14. The heating rod according to claim 1, wherein the plastic frame (2) is made of fiber-reinforced polyphenylene sulfide.

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