Electric heating device

Abstract

An electric heating device includes a housing having a partition wall which separates a connection chamber from a heating chamber for dissipating heat and from which at least one receiving pocket protrudes into the heating chamber as a heating rib that may taper towards its lower closed end. A PTC heating element is received in the receiving pocket. The PTC element includes at least one PTC element and conductor tracks which energize the PTC element with different polarities which are electrically conductively connected to the PTC element, and which are electrically connected in the connection chamber. A pressure element also is received in the receiving pocket. Heat extraction surfaces of the PTC element are held in the receiving pocket abutting against oppositely disposed inner surfaces of the receiving pocket. The pressure element has at least one cambered surface segment projecting toward the inner surface or toward the PTC element.

Claims

1. An electric heating device comprising: a housing having a partition wall which separates a connection chamber from a heating chamber for dissipating heat and from which at least one receiving pocket protrudes, wherein the receiving pocket protrudes into the heating chamber as a heating rib; a PTC heating element received in the receiving pocket, the PTC heating element including at least one PTC element and conductor tracks which are electrically conductively connected to the PTC element and which are configured to energize the PTC element with different polarities and which are electrically connected in the connection chamber, and a pressure element which is received in the receiving pocket and which holds a plurality of heat extraction surfaces of the PTC heating element abutted against oppositely disposed inner surfaces of the receiving pocket, wherein the pressure element has a wedge-shaped cross-sectional configuration, wherein the wedge shape is formed by opposite main side surfaces of the pressure element, and wherein at least one of said opposite main side surfaces of the pressure element has a cambered surface segment projecting in a direction toward the inner surface of the receiving pocket and/or in a direction toward the PTC element.

2. The electric heating device according to claim 1, wherein at least one respective cambered surface segment of the pressure element is provided on opposite sides of the pressure element.

3. The electric heating device according to claim 1, wherein a cambered surface segment of the pressure element and one of a planar surface segment or a concave surface segment extending in the vertical direction of the receiving pocket are provided consecutively, at least on one side of the pressure element, and wherein the planar or concave surface segment is arranged deeper in the receiving pocket than the cambered surface segment.

4. The electric heating device according to claim 1, wherein at least one of the inner surfaces of the receiving pocket comprises an inner surface segment projecting toward the pressure element.

5. The electric heating device according to claim 1, wherein the cambered surface segment of the pressure element has a radius (R) of between 500 and 1,000 mm.

6. The electric heating device according to claim 1, wherein at least one of the inner surfaces of the receiving pocket projects toward the pressure element.

7. The electric heating device according to claim 1, wherein the cambered surface segment of the pressure element terminates with a spacing from an upper or lower end of the pressure element and transitions via a depression to the cambered surface segment.

8. The electric heating device according to claim 1, wherein at least one of the inner surfaces of the receiving pocket comprises a cambered inner surface segment projecting in the direction toward the pressure element.

9. The electric heating device according to claim 1, wherein the receiving pocket tapers towards a lower, closed end, thereof.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) 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:

(2) FIG. 1 shows a perspective face side view of an embodiment of an electric heating device with the housing partially removed;

(3) FIG. 2 shows a cross-sectional view of a heating rib of the embodiment shown in FIG. 1 with a partially simplified heater casing;

(4) FIG. 3 shows a simplified cross-sectional view approximately according to FIG. 2 before the pressure element is introduced into the receiving pocket;

(5) FIG. 4 shows an enlarged side view of the pressure element according to FIG. 4;

(6) FIG. 5 shows an enlarged detail D according to FIG. 4;

(7) FIG. 6 shows an exaggerated side view of the pressure element;

(8) FIG. 7 shows a cross-sectional view of the receiving pocket in the region of the inner surface for a first variant; and

(9) FIG. 8 shows a cross-sectional view of the receiving pocket in the region of the inner surface for a second variant.

DETAILED DESCRIPTION

(10) FIG. 1 shows an embodiment of an electric heating device with a housing 2 having a housing base 102 and a housing cover 6. The housing base 4 surrounds a heating chamber 8 which is connected via ports, of which only one port 10 is shown, to a line for fluid to be heated. The heating chamber 8 is penetrated by several heating ribs 11 which extend in the longitudinal direction of the housing base 4 and which in the cross-sectional view form a substantially U-shaped, slightly conically tapering receiving pocket 12 and are circumferentially closed with respect to the heating chamber 8. These receiving pockets 12 have a depth that is greater than the extension of PTC heating elements 14 in the longitudinal direction of the receiving pocket 12.

(11) The embodiment of an electric heating device shown has four adjacently disposed receiving pockets 12 which extend substantially over the entire length of the housing base 4. The housing base 4 is formed as a die-cast member made of aluminum. For further details on the electric heating device, reference is made to the applicant's EP 1 921 896 A1.

(12) When the housing cover 6 is removed, several PTC heating elements 14 are introduced one next to one another in the individual receiving pockets 12. Details of these PTC heating elements 14 can be found, for example, in the applicant's EP 2 637 474 A1, the subject matter of which is incorporated by reference. This earlier disclosure also provides details on a pressure element denoted with reference numeral 16 in the drawing.

(13) Like in the disclosure of EP 2 637 474 A1, the pressure element 16 is also wedge-shaped in the present case. The pressure element 16 has a special surface configuration which shall be discussed in more detail below. As illustrated in FIG. 4, the pressure element 16 has a cambered surface segment 18 on each oppositely disposed main sides. A planar surface segment 20 defining the lower end of the pressure element 16 projects over this surface segment 18 at the lower, thinner end of the pressure element 16. Formed at the oppositely disposed end of the pressure element 16 is a further planar surface segment 22 which forms the thicker end of the wedge-shaped pressure element 16. A respective depression 24 is formed between the cambered surface segment 18 and the adjacent planar surface segments 20, 22 and is illustrated in particular in FIG. 5. The depression 24 is formed where the conically formed planar surface segment 20, 22 adjoins the radius of the cambered surface segment 18. The respective surface segments 18, 20, 22 transition steplessly and continuously into one another.

(14) A representation of the respective cross-sectional geometry of the pressure element 16 exaggerating the actual geometric relationships can be gathered from FIG. 6.

(15) The depression 24 forms a receiving region for an adhesive 26 which can be recognized as an adhesive droplet within the receiving pocket 12 in FIG. 3 prior to the assembly of the pressure element 16. The PTC heating element 14 has already been introduced into the receiving pocket 12 shown schematically there. It comprises a single PTC element 28, the main side surfaces of which are each covered with a contact plate 30, which, for forming contact strips 32, are extended beyond a heater casing 34 which joins the PTC element 28 and the contact plates 30 as well as insulating layers denoted with reference number 36 to form one entity. The insulating layers 36 are located between one of the contact plates 30 and an inner surface 38 of the receiving pocket 12; cf. FIG. 2

(16) In the embodiment shown in FIG. 3, the insulating layer 36 is formed by a Kapton film into which the PTC element 28 and the contact plates 30 abutting thereagainst are wrapped.

(17) FIGS. 7 and 8 show conceivable configurations of the inner surface 38 of the receiving pocket 12. According to FIG. 7, a ramp-shaped profile is shown which forms a projection with a planar surface segment 40 of the inner surface 38. When the pressure element 16 is received in the receiving pocket 12, the cambered surface segment 18 of the pressure element 16 abuts against this planar surface segment 40. The two other surface segments 20, 22 are located approximately at the level of a lower or respectively upper surface segment 42, 44 of the inner surface 38.

(18) In the alternative embodiment according to FIG. 8, the central surface segment denoted there with reference numeral 46 is convex and therefore cambered. It extends from lower and upper planar surface segments 42, 44.

(19) Surprisingly, it has been shown that improved heat extraction over the solutions described in prior art can be achieved even with the abutment of two cambered, i.e. each convexly shaped surface segments 18, 46 on both sides of the pressure element 16. The configuration also improves the pressure element 16 from being undesirably forced out of the receiving pocket 12 as a result of vibrations. Because the electric heating device is employed, in particular, as an electric heating device in a motor vehicle. Vibrations in a motor vehicle are a challenge for mechanical connections, also for pressure connections with the aid of a pressure element 16.

(20) FIG. 3 shows the pressure element 16 prior to assembly. When pushing the pressure element 16 into the receiving pocket 12, the adhesive 26 interacts with the oppositely disposed surface, i.e. with the inner surface 38 or respectively an outer surface of the PTC heating element 14 formed by the insulating layer 36. The respective surfaces are there ideally completely wetted. At the end of the insertion motion of the pressure element 16 into the receiving pocket 12, good wetting with adhesive arises accordingly between the components to be adhesively bonded in the receiving pocket 12. The adhesive can be cured with higher strength and/or shorter curing time by applying temperature. For this purpose, the PTC heating element 14 can be energized.

(21) At the end of the assembly, the PTC heating element 14 is wedged in by the pressure element 16, so that the main side surfaces of the PTC element 28 abut against the inner surfaces 38 of the receiving pocket 14 with good thermal conductivity. The contact strips 32 extended beyond the heater casing 34 are exposed in a connection chamber 50 of the housing 2 which is separated in FIG. 1 by a partition wall 48 in front of the heating chamber 8. In this connection chamber 50, the contact strips 32 of each individual PTC heating element 14 are electrically connected in the manner described, for example, in EP 1 921 896 A1, in order to group several of the PTC heating elements 14 to form a heating circuit and/or to connect the PTC heating elements 14 individually or in groups to a control device which is typically also provided in the connection chamber 50.