WO2019072798A1 - METHOD FOR MANUFACTURING A TANK HEATING AND TANK HEATING - Google Patents

Abstract

Disclosed is a method for producing a tank heater, wherein a PTC heater, which includes a PTC heating resistor (1), with a housing part (6) which is a cast metal part, and then connected housing part (6) and PTC heater be covered with plastic. According to the invention, before the PTC heater is connected to the housing part (6), the housing part (6) is processed by applying a heat transfer surface of the housing part (6) via the heat generated by the PTC heating resistor (1) the housing part (6) passes over is leveled. In addition, a tank heater is described.

Description

 Method for producing a tank heater and tank heater

description

A tank heater and a method for producing a tank heater with the features specified in the preamble of claim 1 is known from DE 10 2014 212 544 A1. Tank heaters for heating liquids in motor vehicles, such as urea solution or water, have a metal housing in which a PTC heater is arranged with a PTC heating resistor and a contact element, and a plastic sheath, which protects the metal housing from contact with liquid. For the metal housing extruded profiles, such as in the known from DE 1 1 2006 001 103 B4 tank heater, or castings, such as in the known from DE 10 2014 212 544 A1 tank heater can be used.

Extruded profiles allow a very good thermal coupling of the PTC heating resistor to the metal housing by simple means by the Extruded profile is pressed after inserting the PTC heater. However, the possible shapes of the metal housing are limited, which is why increasingly castings for metal housing of tank heaters are used. Castings also allow the use of less expensive alloys, but make it difficult a good thermal coupling of the PTC heater to the metal housing, in particular because no channels or pockets can be produced with low-cost alloys, record the PTC heater and then can be pressed. In the tank heater known from DE 10 2014 212 544 A1, therefore, a steel spring plate is used, which is fixed to retaining ribs of the housing part, wherein the retaining ribs are compressed after setting to press the PTC heater with sufficient pressure against a heat transfer surface of a housing part and so make a sufficient thermal contact between PTC heater and metal housing.

Object of the present invention is to show a way, as in a tank heater whose metal housing is a casting, the heat coupling of the PTC heater can be improved.

This object is achieved by a method having the features specified in claim 1 and by a tank heater according to claim 12. Advantageous developments of the invention are the subject of dependent claims. According to the invention, in the manufacture of the tank heater, the casting, before being connected to the PTC heater, is machined by flattening the heat transfer surface of the housing part, via which heat generated by the PTC heating resistor passes to the housing part. Preferably, the housing part is flattened by plastic deformation, for example by pressing a punch by means of a rolling tool. The housing part of the tank heater therefore preferably has a heat transfer surface leveled by plastic deformation. Another possibility is the leveling over a machining such as milling or grinding. The casting can be made for example by die casting, such as an alloy based on aluminum. The surfaces of a casting are generally not as flat or smooth as in an extruded profile. By machining the casting, it is therefore possible to achieve improved thermal contact between the PTC heater and the housing part. The inventively preferred leveling of the thermal contact surface by pressing a stamp can be carried out with little effort, optionally, the force acting on the heat contact surface punch can be supplemented by a matching formed to the opposite surface of the housing part lower punch.

The PTC heater may include one or more PTC heating elements and one or more contact elements. In the simplest case, the metal housing is used for electrically contacting the PTC heating element or the PTC heating elements, so that a single contact element, for. B. a contact plate, sufficient. When the metal shell is electrically isolated from the PTC heater (s), two contact elements are needed. PTC heating element (s) and contact element (s) can be held by a plastic frame, which can also support an insulator, which electrically isolates the or one of the contact elements of the metallic housing part. The insulator may be, for example, a ceramic plate, such as alumina, or a plastic film. But it is also possible to use two electrically insulated housing parts for electrical contacting of the PTC heating element or the PTC heating elements. In order to further improve the heat coupling, a spring element, which generates a spring force which presses the PTC heater against the heat transfer surface, can be fastened to the housing part prior to the sheathing. The spring element is preferably made of an alloy based on aluminum. Aluminum alloys have a good thermal conductivity, so that heat generated by the PTC heater can advantageously also be dissipated via the spring element.

An advantageous development of the invention provides that the spring element is locked or caulked to the housing part. For example, that can Spring element are attached to the housing part by being clipped onto the housing part. Advantageously, such a simple production can be realized. A further advantageous embodiment of the invention provides that the housing part on opposite sides of the heat transfer surface has walls which have an undercut, with which the spring element is hooked. The spring element may for example have two strips with latching hooks, between which extends a resilient lid surface. The spring element can thus form part of the housing in this way and allow easy assembly of the housing.

A further advantageous development of the invention provides that the spring element is an extruded profile. In this way, a cost-effective production is possible. Advantageously, an extruded profile can also be well rounded prior to assembly, so that no more sharp edges are present when encapsulating with plastic.

The features and feature combinations mentioned above in the description as well as the features and feature combinations mentioned below in the description of the figures and / or in the figures alone can be used not only in the respectively specified combination but also in other combinations or in isolation, without the scope of To leave invention.

Further details and advantages will be explained with reference to embodiments of the invention with reference to the accompanying drawings. Identical and corresponding components are provided therein with matching reference numerals. Show it:

Fig. 1 is a sectional view of a tank heater;

FIG. 2 shows the tank heater of FIG. 1 without plastic jacket and spring element; FIG. FIG. 3 shows the spring element of the tank heater shown in FIG. 1; FIG.

FIG. 4 shows a perspective longitudinal section along the line A - A through the casting of the tank heater shown in FIG. 1; FIG.

Fig. 5 is a sectional view of another embodiment of a tank heater;

Fig. 6 is a sectional view of another embodiment of a tank heater;

7 shows an embodiment of a housing part for caulking with a spring element; and FIG. 8 shows a further embodiment of a tank heater without the plastic jacket.

The tank heater illustrated in a sectional view in FIG. 1 contains a PTC heater which contains at least one PTC heating resistor 1 and may additionally comprise, for example, a contact element 2 and an insulator 3 and a plastic frame 4 which holds the various components of the PTC heater , The PTC heater is pressed by a spring element 5 against a heat transfer surface 66 of the housing part 6, passes over the heat generated by the PTC heating resistor 1 to the housing part 6.

In the embodiment shown, the PTC resistor 1 lies flat against the heat transfer surface 66 of the housing part, since the PTC resistor 1 is electrically contacted via the housing part 6. In another embodiment, for example when the PTC heating resistor is electrically insulated on both sides of the housing and is electrically contacted by two contact elements, but also another component of the PTC heater can be applied flat against the heat transfer surface 66, such as a ceramic plate or other insulator. The housing part 6 is a casting, which has been produced for example by die casting. Before the PTC heater is connected to the housing part 6, the heat transfer surface 66 of the housing part 6, leveled by plastic deformation, for example by pressing a punch. In this way, the heat coupling of the PTC heater to the housing part 6 is improved.

After flattening the heat transfer surface 66 of the housing part 6 of the PTC heater is placed on the heat transfer surface 66 and the spring element 5 aufküst on the housing part 6. Thereafter, the housing part 6 and the spring element 5 and the PTC heater arranged between them are encapsulated with plastic, so that they are then protected by a plastic jacket 7 from contact with a liquid to be heated. The housing part 6 has on opposite sides of the heat transfer surface 66 walls 61, which have an undercut, with which the spring element 5 is hooked. The undercut can be formed for example by a groove 62 in the respective side wall 61. In this case, an upper, the undercut forming boundary surface 64 of the groove 62 extends parallel to the heat transfer surface 66 and a lower boundary surface 65 of the groove 62 obliquely to the upper boundary surface of the groove 62. In other words, the groove 62 so spreads in its longitudinal direction. In this way, the housing part 6 is easier to remove from its mold. 4, the hidden cut edges of a longitudinal section through the housing part 2 are shown by dashed lines in a sectional view of the housing part 2, to illustrate this.

The spring element 5 shown isolated in Fig. 3 is locked to the housing part 6. The corresponding positive fit acts perpendicular to the heat transfer surface of the housing part 6. The spring element 5 may have two strips 51 with latching hooks 52, which hook with the undercut of the opposite side walls 61 of the housing part 6. For this purpose, the boundary surface 64, and / or the contact surface 54, which is in engagement with the delimiting surface, of the latching hooks 52 is advantageously inclined to Heat transfer surface 66 running so that the spring element 5 can remain securely locked. Between the strips 51, a resilient ceiling wall 53 extends, which presses against the PTC heater, for example, against an insulator 3, such as a ceramic plate or plastic. The spring element 5 thus has a basically U-shaped configuration. Advantageously, the ceiling inner surface 55, at least before fastening a curved toward the center of the PTC heater out contour, which is at least the central region of the PTC heater securely entangled with the heat transfer surface 66 and the spring element 5 after entanglement.

Both the spring element 5 and the housing part 6 may be made of an aluminum-based alloy. While a low-cost standard casting alloy can preferably be used for the casting, the spring element 5 is preferably produced from a spring-hard alloy such as, for example, an AlMgSi alloy. The spring element 5 can be produced by extrusion, so be an extruded profile. Unlike a thin steel spring plate, where it is difficult to avoid sharp edges, an aluminum-based alloy spring element can easily have rounded edges. Is the spring element z. B. produced as an extruded part, so the edges after cutting can be such z. B. be reworked by sandblasting that the edges are rounded afterwards. As a result, the danger that the plastic sheath in contact with the edges ruptures at these edges is significantly reduced. The housing part 6 may have further walls, for example a rear wall 63 which extends transversely to the opposite side walls 61 which have the undercut. As a result, the PTC heater is adequately protected against the high-pressure injection-molded material from three sides. The remaining open front is largely covered by the front wall of the plastic frame 4, so that here too the PTC heater is sufficiently protected. Otherwise, namely the pressure during encapsulation of the spring force of the spring element 5 could counteract. 5 shows a sectional view of a further exemplary embodiment of a tank heater, which differs from the exemplary embodiment discussed above essentially by the orientation of the latching hooks 52 of the spring element 5 and the cooperating undercut of the side walls 62. While in the embodiment of Figures 1 to 4, the latching hooks 52 of the spring element 5 are directed inward and facing each other, the latching hooks are in the embodiment of FIG. 5 directed to the outside and facing away from each other. Nevertheless, in order to be able to tightly surround the PTC heater with side walls 61 and a rear wall, the undercuts are not attached to the side walls 61, but to further outer side walls 67

Fig. 6 shows a sectional view of another embodiment of a tank heater. This embodiment differs from the embodiments described above essentially in that the spring element 5 is fixed by caulking to the housing part 6. In the embodiment shown, the housing part 6 has protruding pins 8, preferably on the front side of the walls 61. The pins pass through 8 openings in the spring element 5 and are caulked on the top under bias with a tool such that a positive connection is created. In Fig. 6, only one pin 8 can be seen on each end face. Several pins 8 on each side are also possible. The pins 8 may be integrally formed with the housing part 6 or made separately. It is particularly preferred that the pins 8 are arranged laterally offset.

In Fig. 7, an alternative embodiment is shown in which on each side of a single, elongated pin 8 with slightly tapered side surfaces engages through an elongated opening in the spring element. It is also possible, however, a variant of FIG. 8, in which the spring element 5 between the spring element 5 superior rails 9 is inserted and the rails 9 are partially caulked at the edge in such a way that the caulked areas 10 engage over the spring element 5 under bias on the edge and fix it. LIST OF REFERENCE NUMBERS

1 PTC heating resistor

2 contact element

 3 insulator

 4 plastic frames

 5 spring element

 6 housing part

 7 plastic jacket

 8 pen

 9 rail

 10 caulked area

51 bar

 52 snap hooks

 53 ceiling wall

 54 contact surface

 55 ceiling inside

61 side wall

 62 groove

 63 rear wall

 64 upper boundary surface

65 lower boundary surface

66 heat transfer surface

67 additional sidewall

Claims

claims Method for producing a tank heater, wherein  a PTC heater including a PTC heating resistor (1) connected to a housing part (6) which is a metal casting and thereafter encasing the housing part (6) and PTC heater with plastic,  characterized in that  the housing part (6), before the PTC heater is connected to the housing part (6), is processed by a heat transfer surface (66) of the housing part (6), via the heat generated by the PTC heating resistor (1) on the housing part (6) is leveled. A method according to claim 1, characterized in that the heat transfer surface (66) is leveled by plastic deformation, preferably by pressing a punch or by a rolling tool. A method according to claim 1 or 2, characterized in that before the sheathing with plastic on the housing part (6) a spring element (5) is fixed, which generates a spring force which presses the PTC heater against the heat transfer surface (66). A method according to claim 3, characterized in that the spring element (5) is fixed to the housing part (6) by being locked or caulked with the housing part (6). A method according to claim 3 or 4, characterized in that the housing part (6) on opposite sides of the heat transfer surface (66) side walls (61, 67) which have an undercut, with which the spring element (5) is hooked. A method according to claim 5, characterized in that the undercut in each of the opposed side walls (61, 67) is formed by a groove (62), an upper undercut forming surface (64) of the groove (62) being parallel to the heat transfer surface runs and one lower boundary surface (65) of the groove (62) extends obliquely to the upper boundary surface (64) of the groove (62). 7. The method of claim 1, 2 or 3, characterized in that the housing part (6) has protruding pins which are caulked on the housing side facing away from the upper side of the spring element (5) under prestress. 8. The method according to any one of the preceding claims, characterized in that the PTC heater comprises a plastic frame (4), which the PTC Heating element (1), a contact element (2) and a on the side facing away from the PTC heating element (1) side of the contact element (2) insulator (3) holds. 9. The method according to claim 3 and 8, characterized in that the spring element (5) rests against the insulator (3). 10. The method according to any one of the preceding claims, characterized in that the spring element (5) has been produced by extrusion. 1 1. Method according to one of the preceding claims, characterized in that the spring element (5) has two strips (51) with latching hooks (52), between which a resilient ceiling wall (55) extends. 12. Tank heating with  a PTC heater including a PTC heating resistor (1) and a contact element (2),  a housing part (6) made of metal,  a spring element (5), and  a plastic jacket (7) surrounding the housing part (6), the spring element (5) and the PTC heater,  characterized in that the housing part (6) has a heat transfer surface (66) leveled by plastic deformation or by a machining process. has, over the heat generated by the PTC heating resistor (1) on the housing part (6) passes and against which one of the spring element (5) generated spring force presses the PTC heater.