PTC heating device

Abstract

A PTC heating device (2) comprising several PTC elements (4) and electrical conductors (6, 10) between which the PTC elements (4) are provided and which are electrically connected to the PTC elements (4), and a frame (14) forming at least one receptacle (16) for the PTC elements (4), which is provided between the electrical conductors (6, 10). To adjust the heating power of the PTC heating device, the present invention proposes providing at least two conductors (6a, 6b) on at least one side of the PTC elements (4), which are electrically connected to different PTC elements (4).

Description

[0001] The present invention relates to a PTC heating device with multiple PTC elements and electrical conductors between which the multiple PTC elements are arranged. The PTC elements are electrically connected to the conductors so that the PTC elements can be energized with different polarities.

[0002] The PTC heating element also has a frame to hold the PTC elements. This frame has at least one recess for this purpose. The frame is usually positioned between the electrical conductor tracks.

[0003] A generic PTC heating device is disclosed, for example, in DE 10 2019 204 472 A1. In this prior art, several PTC heating devices of the aforementioned type are used in a water heater that includes heating fins projecting into a heating chamber, each of which accommodates the PTC heating device or several such PTC heating devices. Generic PTC heating devices are also used in an air heater. An example of this is given in EP 1 564 503 A1. In this prior art, the PTC elements are normally arranged one behind the other in receptacles in the frame.

[0004] The present invention aims in particular to disclose a PTC heating element of the aforementioned type, which is used in an electric heating device in a motor vehicle. Previous solutions typically disclose a connection chamber provided opposite the heating chamber, in which contact tongues, electrically connected to electrical conductors of the PTC heating elements, are exposed. The PTC heating elements are thus typically connected in the connection chamber. The connection chamber can also accommodate a control unit that activates and controls different PTC heating elements of the heating device (see, for example, DE 20 2011 003 209 U1 or EP 3 731 595 A1).

[0005] Each PTC heating element is controlled individually. A single PTC heating element with multiple PTC elements can be controlled uniformly. To adjust the desired heating power, several PTC heating elements of a heating device are typically combined in a heating circuit, which can be switched on or off and whose heating power is usually regulated by power transistors, so that the actual heating power of the heating device can be adjusted via the control device.

[0006] Nevertheless, there is a need for further, possibly more differentiated, adjustment of the heating output.

[0007] The present invention addresses the problem of providing a PTC heating device of the type mentioned above, whose heating power can be adjusted in a more differentiated manner.

[0008] From EP 3 410 818 A1 a PTC heating device is known in which at least two conductor tracks are provided on at least one side of the PTC elements, which are electrically conductively contacted with different PTC elements.

[0009] Thus, within the PTC heating device, different conductor tracks are assigned to the PTC elements provided in the frame, which, through adapted current supply, each only energize a portion of the total PTC elements provided in the PTC heating device.

[0010] In a manner known per se, the PTC elements are held in a positioning frame. This positioning frame has recesses adapted to the size of the at least one PTC element located in the recess. In a manner known per se, several PTC elements can also be provided in a single recess. The PTC element(s) provided in the recess are positioned above the positioning frame. Similarly, the at least two conductor tracks provided on one side of the PTC element are also held in a predetermined position. Through their interaction with the positioning frame, selected PTC elements can be spatially assigned to specific conductor tracks, via which these PTC elements are contacted and energized on one side.

[0011] One side can be designated as the positive or negative terminal, or as a ground. The opposite side typically features a single conductor track that serves all PTC elements. However, this side may also have further, spatially differentiated contacts for the PTC elements.

[0012] In the following description, it is assumed that the PTC elements are cuboid in shape with a relatively low height, such that the opposing main face surfaces of the PTC elements have a significantly larger surface area than the surface sections of the surrounding edge. The surface area of ​​the main face sections is typically five times larger than the largest surface segment of the cuboid contained within the surrounding edge. This description serves to clarify the invention. Of course, the invention can also be implemented with end-face current applied to the PTC elements. With such current application, the conductor tracks are in contact with the surrounding edge, so that heat dissipation from the PTC element via the main face surface does not have to occur through the conductor track.

[0013] In a simple design where the switching of different PTC elements within a single PTC heating device is achieved solely via the corresponding contacts on one side, a single conductor track is provided on the opposite side to electrically connect all PTC elements. If a different electrical connection for the PTC elements is also chosen on the opposite side, the heating power of the PTC device can sometimes be more finely tuned with a simpler design.

[0014] According to the present invention, a PTC heating device according to claim 1 is proposed, in which several conductive traces are provided on one side of the PTC elements and several opposing conductive traces are provided on the opposite side. The conductive traces and the opposing conductive traces are each assigned to several PTC elements. The conductive trace provided on one side is electrically connected to at least several PTC elements, which are electrically connected to different opposing conductive traces on the opposite side.

[0015] Particularly in confined spaces, it is possible that several electrical conductors on one side may overlap a single PTC element, but only one of these conductors is intended to supply power to that specific PTC element. In such a case, the other conductor leads to a different PTC element and is therefore not assigned to the single PTC element. Such overlapping can also occur due to inaccurate positioning during assembly or changes in the conductors' position during operation. The PTC heating device of the present invention is used particularly in motor vehicles that are subject to significant vibrations.Therefore, it can also be advantageous to insulate one or more electrical conductors opposite at least one of the PTC elements. This insulation prevents electrical contact between the conductor and the designated PTC element, while the conductor opposite another PTC element is not insulated, allowing the conductor to be electrically connected to that element. Depending on the selected power current for energizing the PTC elements, an insulating layer can be provided on the side of the electrical conductors opposite the PTC elements, covering this opposite side. Typically, both outer surfaces of the PTC heating element are covered with such an insulating layer. These insulating layers can be attached to the frame, for example, by gluing.It is also possible to overmold the frame and the insulating layers with a plastic material to form a frame-shaped housing that encloses the frame, the PTC elements, and the conductor tracks, essentially covering the insulating layers only at their edges. This means that the insulating layers at least partially form the outer surface of the PTC heating device, particularly opposite the main side surfaces of the PTC elements, which dissipate the majority of the heat generated by the PTC elements. In this respect, reference can be made to EP 3 334 242 A1. The PTC heating device according to the invention can also be realized using the design described therein.

[0016] Further details and advantages of the present invention will become apparent from the following description of an exemplary embodiment in conjunction with the drawing.

[0017] This shows: Fig. 1 a perspective exploded view of a first embodiment; Fig. 2 the in Fig. 1 The illustrated embodiment in the assembled state; Figs. 3a-3d show different variants for conductor tracks provided on one side; Fig. 4 shows a cross-sectional view of a part of an electric heating device that has been created using a PTC heating device according to the invention; Fig. 5 shows a perspective side view of an embodiment of a PTC heating device that is incorporated into the electric heating device according to the invention. Fig. 4 is used; and Fig. 6 a sectional view along line VI-VI according to the illustration in Fig. 4 .

[0018] In Fig. 1 Reference numeral 2 designates a PTC heating device with several, in this case six, PTC elements 4. On the in Fig. 1 On the left side of the PTC elements 4, two conductor tracks 6a and 6b are provided. These conductor tracks consist of stamped metal strips and have contact tongues 8 at one free end. On the opposite side of the PTC elements 4, there is only one uniform conductor track 10. This conductor track 10 covers the main side faces of all PTC elements 4.

[0019] The PTC elements 4 are arranged in two adjacent rows, R1 and R2. Each row, R1 and R2, comprises three PTC elements 4.

[0020] The elongated conductor track 6a covers the PTC elements 4 of the first row R1. The other conductor track 6b covers the other row R2. The conductor track 10 covers all PTC elements 4 on the opposite side. All conductor tracks 6a, 6b, and 10 are in direct electrical contact with the main side faces of the PTC elements 4. The PTC elements 4 are ceramic components whose main side faces are provided with an electrode layer for electrical contact, which is applied, for example, by vapor deposition. On the side opposite the PTC elements 4, the conductor tracks 6a and 6b are each covered with an insulating layer 12, in this case in the form of a ceramic plate.

[0021] Below this layered structure is in Fig. 1 A frame marked with reference numeral 14 can be identified. This frame 14 has several receptacles 16. Each of the receptacles 16 is designed to receive one of the PTC elements 4. In the illustrated embodiment, the receptacles 16 are all the same size. PTC elements 4 with identical dimensions are used.

[0022] The PTC elements 4 are located in the recesses 16 and within the plane of the frame 14. The PTC elements 4 are thicker than the frame 14, so that the conductor tracks 6a, 6b, 10 accommodate the frame 14 between them, while being in direct electrical contact with the PTC elements 4. The insulating layers 12 are each placed directly against the outer surface of the conductor tracks 6a, 6b, and 10, respectively.

[0023] The Fig. 3a shows a first modification to the one in the Fig. 1 und 2 The illustrated embodiment also features two rows R1, R2, each with three PTC elements 4 arranged one above the other. However, the PTC elements 4 are of different sizes. The PTC elements of the first row R1 are smaller than the PTC elements of the second row R2. The same applies to the base area of ​​the two conductor tracks 6a, 6b.

[0024] While in the exemplary embodiment according to the Fig. 1 und 2 Since an identical heating power could be switched on and off by switching conductor tracks 6a and 6b respectively, the heating power in the exemplary embodiment can be determined according to Fig. 3a Additionally, it can be controlled depending on which of the two conductor tracks 6a, 6b is switched on or controlled.

[0025] In the exemplary embodiment according to Fig. 3b The conductor track marked with reference numeral 6a covers only one PTC element 4 on one side. The other PTC elements 4 are assigned to the heating circuit that can be controlled via the contact tongue 8 of conductor track 6b.

[0026] In the exemplary embodiment according to Fig. 3c On one side, three conductor tracks 6a, 6b, 6c are provided, each of which is assigned to three PTC elements 4 arranged one above the other.

[0027] Another option is conceivable and in Fig. 3d As shown, three conductor tracks 10a to 10c are provided on the opposite side, covering the PTC elements arranged in a row R1, R2, R3 and making electrically conductive contact with them. The conductor tracks 6a, 6b provided on one side correspond to the embodiment shown in the illustration. Fig. 3b .

[0028] Except for the one in Figur 3d The PTC element 4 shown in the upper left is connected to all other PTC elements 4 on one side via conductor 6b. On the opposite side, the conductors of the first row R1 are connected to the opposite conductor 10a. Thus, the PTC elements 4 in row R1 are electrically connected on the opposite side via a single conductor 10a, but on the opposite side via two conductors 6a and 6b. The PTC elements in rows R2 and R3 are connected in the opposite way. They are electrically connected to conductor 6b on one side and to different conductors 10b and 10c on the opposite side.

[0029] By selectively controlling the individual conductor tracks 6a, 6b, 10a, 10b, 10c, the heating power output of the PTC heating element 2 can be adjusted. Individual heating circuits can simply be switched on or off, or they can be controlled via a power transistor, so that the heating power of individual heating circuits can essentially be controlled from 0 to 100% of the heating power of the respective heating circuits. A heating circuit is formed by those PTC elements 4 that are arranged between two conductor tracks 6, 10.

[0030] Reference number 20 are in Figur 1 The profile elements 20 are characterized by extruded profile elements that incorporate the layered structure consisting of the insulating layers 12, the conductive tracks 6a, 6b, 10 provided within these layers, the frames 14, and the PTC elements 4. The profile elements 20 are made of extruded aluminum. The profile elements 20 are contained in a heating device, which is discussed below. Figuren 4 bis 6 The electric heating device 98 is designated with reference numeral 98. The electric heating device 98 has a housing 100. The housing 100 forms a wall 104 that completely surrounds a heating chamber 102. Fig. 1 The heating chamber 102 is still open at the bottom, since a base closing the housing 100 at the bottom is in Fig. 1 not shown. The same applies to a control housing cover, which is connected to the housing 100 on the opposite side to cover and surround a connection chamber designated by reference numeral 106. Between the heating chamber 102 and the connection chamber 106, the housing 100 forms a partition 108 in one piece. Heating fins 110 project from this partition 108 into the heating chamber 102. The heating fins 110 are closed at their lower end, which projects into the heating chamber 102. As the hatching in Fig. 4 To clarify, the heating fins 110 together with the partition 100 and the wall 104 are formed from a one-piece die-cast aluminum housing 100.

[0031] The heating fins 110 form a wedge-shaped, downwardly tapered receiving pocket 112. A PTC heating element 2 is received in each of the receiving pockets 112.

[0032] How especially the Fig. 5 and 6 Each of the profile elements 20 is U-shaped in cross-section. The cheek surfaces, marked with reference numeral 114, have outwardly projecting groove-limiting projections 116, which enclose a groove 118 between each pair. As in particular Fig. 6 As illustrated, the cheek surface 114 has a multitude of identically shaped grooves 118. The grooves 118 extend in the insertion direction of the receiving pocket 112, which is located in Fig. 4 is marked with reference numeral E.

[0033] Spring projections 120 protrude from the inside of the receiving pocket 112. These spring projections 120 are integrally formed with the die-cast housing 100. As shown in the cross-sectional view according to Fig. 6 The spring projections 120 taper wedge-shaped towards their free ends. Similarly, the groove-limiting projections 116 also taper wedge-shaped towards their free front ends. It is understood that only the surfaces of the groove-limiting projections 116 that define the groove 118 have this shape. To illustrate this, the following are shown in Fig. 6 The spring protrusions on the right side were omitted (120).

[0034] During the assembly of the exemplary embodiment, the PTC heating element 2 is first positioned between the profile sections 20. The pre-assembled unit is then inserted into the receiving pocket 112. The spring projections 120 engage in their corresponding grooves 118. A comparison of the right and left sides reveals... Fig. 6 Deformation is visible in the area of ​​the groove limit projections 116. This results in a certain tolerance compensation and consequently an elastic deformation of the tongue-and-groove structure on the cheek surfaces 114 of the profile elements 20 and the associated spring projections 120 of the housing 100. This positions the PTC heating device 2 under preload in the receiving pocket 112 and thus ensures good thermal conductivity.

[0035] Remaining cavities in the receiving pocket 112 can be filled with a highly thermally conductive material, for example a curing plastic compound filled with thermally conductive particles.

[0036] The housing can also be formed by an extruded profile that creates a receiving pocket open on both sides. The inner surface of the receiving pocket is formed by a partition that creates a heating chamber extending parallel to the receiving pocket, which guides the fluid to be heated. Several profiles can be arranged side by side in this way, so that a parallel flow of the fluid to be heated is guided past different receiving pockets, as is known, for example, from EP 0 899 985 A1. The receiving pocket can be formed between two joined profiles.The PTC heating device can thus be incorporated into the extruded profile together with the profile parts, each of which is provided with spring projections designed in the manner described above and which interact with the groove limiting projections of the profile elements to clamp the layers of the PTC heating device against each other. Reference symbol list

[0037] 2PTC heating element 4PTC element 6, 6a, 6b, 6c Conductor track on one side 8 Contact tongue 10, 10a, 10b, 10c Conductor track on the opposite side 12 Insulation layer 14 Frame 16 Receptacle 20 Profile element 98 Heating device 100 Housing 102 Heating chamber 104 Wall 106 Connection chamber 108 Partition 110 Heating fin 112 Receptacle pocket 114 Side surface 116 Groove limiting projection 118 Groove 120 Spring projection Insertion direction R Series

Claims

1. PTC heating device (2) with multiple PTC elements (4) and electrical conductor tracks (6, 10), between which the PTC elements (4) are provided and which are electrically conductively connected to the PTC elements (4), and a frame (14) forming at least one receptacle (16) for the PTC elements (4) which is provided between the electrical conductor tracks (6, 10), wherein at least two conductor tracks (6a, 6b) are provided on one side of the PTC elements (4) and are electrically conductively connected to different PTC elements (4), characterized in that a plurality of opposite conductor tracks (10a, 10b, 10c) are provided on the opposite side and that at least one of the conductor tracks (6a, 6b) is electrically conductively connected to a plurality of PTC elements (4) which are electrically conductively connected to different opposite conductor tracks (10a, 10b, 10c) on the opposite side.

2. PTC heating device (2) according to claim 1, characterized in that several conductor tracks (6a, 6b) are provided on one side of the PTC elements (4) and a single opposite conductor track (10) is provided on the opposite side.

3. PTC heating device (2) according to one of the previous claims, characterized by electrical insulating layers (12) which cover the electrical conductor tracks (4) on a side opposite the PTC elements (4).

4. PTC heating device (2) according to one of the previous claims, characterized in that the electrical insulating layers (12) are each connected to the frame (14).

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