CONTAINER HEATING, TANK HEATING WITH PTC HEATING ELEMENT

Description

[0001] The invention is based on a container heater having the features specified in the preamble of claim 1, as known, for example, from DE 10 2018 105 222 A1 and DE 10 2014 108 074 A1. Similar container heaters are known from EP 3 428 438 A1 and EP 3 537 849 A1.

[0002] Tank heaters are required in motor vehicles, among other things, for tanks containing corrosive liquids such as urea solution. Such tank heaters have a plastic housing that protects a heater assembly from contact with corrosive liquid and forms a housing for an electrical connector through which the heater assembly can be connected to a power source.

[0003] The object of the present invention is to show a way in which the position of the connector housing of such a container heater can be selected with greater flexibility within the framework of cost-effective production.

[0004] This object is achieved by a container heater having the features specified in claim 1. Advantageous developments of the invention are the subject of subclaims.

[0005] In a container heater according to the invention, the contact between the contact tongue and the contact plate is not established by free wiring, but there is electrical contact via the contact tongues to a metal strip which, in the interior, rests with a front side on a contact plate which electrically contacts a first part of the PTC resistors, and with a rear side on a contact plate which electrically contacts a second part of the PTC resistors.

[0006] In one possible embodiment of the invention, the sheet metal strip has a section located between a first contact plate, which electrically contacts a first part of the PTC resistors, and a second contact plate, which electrically contacts a second part of the PTC resistors. This section rests with its front side against the first contact plate and with its rear side, opposite the front side, against the second contact plate.

[0007] The PTC heating resistors of a container heater according to the invention are thus divided into two groups, each containing at least one PTC heating resistor. Each of these two groups is electrically contacted by two contact plates, between which PTC heating resistors are held.

[0008] The number of PTC heating resistors required for a given heating output can be distributed virtually arbitrarily between these two groups, allowing the location where the contact plates electrically connect the two metal strips to be selected to match the desired position of the connector on the plastic housing of the container heater. This avoids unnecessary lengths of metal strips leading to the contact tabs.

[0009] An advantageous embodiment of the invention relates to a container heater with a heater assembly containing a plurality of ceramic PTC heating resistors, a plastic housing surrounding the PTC heating resistors and forming a housing of an electrical plug-in connector, wherein the housing of the plug-in connector has a base which separates a sealed interior of the plastic housing containing the PTC heating resistors from an exterior space and from which contact tongues of the plug-in connector protrude, characterized in that via the contact tongues there is electrical contact with a metal strip which has a section lying between two contact plates, wherein this section is arranged in the interior with a front side in each case on a first of the two contact plates, which electrically contacts a first part of the PTC heating resistors, and with a rear side in each case on a second of the two contact plates,which electrically contacts a second part of the PTC heating resistors.

[0010] The container heater according to the invention can advantageously be designed such that the current direction in the two groups is exactly reversed. The magnetic fields generated by the heating currents of the two groups then partially compensate each other. This advantageously reduces the strength of the overall magnetic field generated by the heating current and improves the electromagnetic compatibility of the container heater.

[0011] An advantageous development of the invention provides for the metal strips to be welded to the contact plate located on their front and rear sides. This ensures reliable electrical contact and also allows for the pre-assembly of an easy-to-handle unit.

[0012] The contact plates are preferably bent into an L-shape, with a first leg each resting against one of the metal strips and a second leg resting against PTC heating resistors. This ensures that the PTC heating resistors are all arranged in the same geometric plane, facilitating efficient dissipation of the heat they generate. Furthermore, the PTCs can also be arranged close to one another, since the preferred design requires little space in the PTC plane for the connection technology.

[0013] A further advantageous development of the invention provides that the first part of the PTC heating resistors is held in a first plastic frame, and the second part of the PTC heating resistors is held in a second plastic frame. This facilitates pre-assembly into an easily manageable assembly, especially if the metal strips are welded to the contact plates adjacent to them. However, it is also possible to hold all PTC heating resistors in a single plastic frame.

[0014] Preferably, at least one of the two contact plates is latched to a plastic frame, for example, by the contact plate having angled tabs with openings into which the latching projections of the plastic frame engage. It is also possible for both contact plates adjacent to a PTC to be latched to a plastic frame.

[0015] A further advantageous development of the invention provides for the contact tabs to be part of the sheet metal strip to which they make contact. This advantageously simplifies production. However, it is also possible for the contact tabs to make contact with the sheet metal strips via separate conductors.

[0016] The sheet metal strips preferably have sections made of different metals. For example, a front section made of electrically conductive metal such as bronze can form the contact tongues, and a rear section of the sheet metal strips can be made of corrosion-resistant metal, for example stainless steel. In this way, the contact tongues can enable very good electrical contact to a power supply with an advantageously low contact resistance, so that only a small amount of heat is lost in the plug-in housing and damage caused by poor contact is reliably avoided. However, in the interior enclosed by the plastic housing, a material such as copper would be problematic in the event of a leak, as this could lead to an uncontrolled chemical reaction. In the interior of the plastic housing, corrosion-resistant metal such as stainless steel, for example V4A steel, is preferably used.

[0017] The sheet metal strip sections made of corrosion-resistant metal can protrude from the base of the connector. The connection point between the contact tabs and the sheet metal strips is then located outside the container heater. Preferably, the connection point between the contact tabs and the corrosion-resistant sheet metal strips is located in the base of the connector housing, for example, by overmolding the connection point with plastic during the manufacture of the connector housing.

[0018] An advantageous development of the invention provides that the contact tongues made of electrically conductive metal are welded to the sheet metal strip section made of corrosion-resistant metal. Preferably, the end faces of the partial sheet metal strips are welded together. Alternatively, an end section of the contact tongues can also overlap with the sheet metal strips.

[0019] The highly conductive metal from which the contact blades are made preferably has a conductivity of at least 7 mS / m. Copper-based alloys, especially bronze, but also aluminum alloys or highly conductive steel are well suited. The contact blades can be coated with a metallic layer, such as silver, nickel, tin, or gold. This advantageously reduces the contact resistance of the connector.

[0020] Further details and advantages of the invention are explained using an exemplary embodiment with reference to the accompanying drawings. They show: Fig. 1 shows an embodiment of a container heater according to the invention; Fig. 2 shows a sectional view of Fig. 1 ; Fig. 3 the heater assembly of the container heater with contact tongues of the connector; Fig. 4 the heater assembly of the container heater without plastic frame; and Fig. 5 the heater assembly with heat exchanger.

[0021] The Figures 1 and 2 The container heater shown is designed as a tank heater and contains a Fig. 3 shown heater assembly 1, which is mounted on a heat exchanger 2 made of metal, for example aluminum, as shown in Fig. 5 shown, is in contact. The heat exchanger 2 can be formed in one piece or consist of several separate parts. In the exemplary embodiment shown, the heat exchanger 2 is formed from three individual, identical extruded parts 2a, 2b, 2c, each of which forms a passage 7 into which the heater assembly 1 engages. For this purpose, the separate heat exchanger parts 2a, 2b, 2c are each pushed onto the heater assembly 1 with their passage 7 from two end faces. If several heat exchanger parts, here the two parts 2b and 2c, are pushed on from one side, they are preferably pushed on at a distance. After pushing on, the heater assembly 1 is pressed into the passages 7 of the heat exchanger parts 2a, 2b, 2c.

[0022] Heater assembly 1 and heat exchanger 2 are enclosed by a plastic housing 3, which in the illustrated embodiment is composed of several parts, for example, a lower part 31, an upper part 32, and a housing 33 of an electrical connector. The various parts of the plastic housing 3 can be welded together, for example, the lower part 31 with the upper part 32, or connected to one another in a fluid-tight manner. For example, an O-ring 8 is arranged between the housing 33 of the electrical connector and the upper part 32 for sealing.

[0023] The housing 33 of the electrical connector has a base 34 from which contact tabs 4a, 5a protrude, via which the container heater can be connected to a power source. In the housing 33 of the connector, the base 34 thus separates an interior of the container heater, in which the heat exchanger 2 and the heater assembly 1 are arranged, from an exterior space.

[0024] The contact tongues 4a, 5a, made of electrically conductive metal, e.g., copper, are each electrically connected to a sheet metal strip 4b, 5b made of a corrosion-resistant metal, which is arranged in the interior of the plastic housing 3. In the illustrated embodiment, the contact tongues 4a, 5a, together with the sheet metal strips 4b, 5b, each form a composite sheet metal strip 4, 5 that protrudes through the base 34 of the connector housing 33. The contact tongues 4a, 5a each form a front end section of this composite sheet metal strip 4, 5, while a rear end section 4b, 5b made of corrosion-resistant metal is arranged in the interior of the container heater.

[0025] The contact tongues 4a, 5a are made of a highly electrically conductive metal with an electrical conductivity of at least 7 MS / m, for example, a copper-based alloy, while the rear end section 4b, 5b of the composite sheet metal strips 4, 5 is made of a corrosion-resistant metal, for example, stainless steel. The composite sheet metal strips 4, 5 are manufactured by welding a sheet metal strip made of highly electrically conductive metal to a sheet metal strip made of corrosion-resistant metal, in particular by welding at the respective end faces.

[0026] The weld seam 6—or, in the case of another connection, more generally the connection point—between the contact tongues 4a, 5a and the respective end section 4b, 5b made of corrosion-resistant metal is not located in the sealed interior of the plastic housing 3, but is embedded in the base 34 of the connector housing 33 or, together with the contact tongues 4a, 5a, lies in the exterior space. During the manufacture of the connector housing 33, the composite sheet metal strips 4, 5 are overmolded with plastic. In particular, the weld seam 6 between the contact tongues 4a, 5a and the rear section 4b, 5b of the composite sheet metal strips 4, 5 can also be overmolded, so that the weld seam 6 then lies in the base 34.

[0027] The contact tabs 4a, 5a can be provided with a metallic coating to minimize contact resistance of the connector. For example, the contact tabs 4a, 5a can be silver-plated.

[0028] The heater assembly 1 contains several ceramic PTC heating resistors 11 arranged between contact plates 12, 13 and 15, 16, respectively. These contact plates can be electrically insulated from the heat exchanger 2a, 2b, and 2c, respectively, by an insulating layer 14, for example made of ceramic, particularly aluminum oxide. For low-voltage applications, one of the two contact plates can be grounded together with a heat exchanger 2 and then does not need to be electrically insulated from it.

[0029] A portion of the PTC heating resistors 11 is held by a first plastic frame 20, and a second portion by a second plastic frame 21. Each plastic frame 20, 21 thus holds at least one PTC heating resistor 11. Each of the two plastic frames 20, 21 carries two contact plates 12, 13 and 15, 16, respectively, between which the PTC heating resistors 11 held by the respective plastic frame are located. Fig. 4shows the heater assembly 1 without these plastic frames 20, 21 for better understanding.

[0030] The current direction of the PTC heating resistors 11 in the two plastic frames is opposite. Fig. 3 and Fig. 4 As shown, the composite sheet metal strips 4, 5 run between the two plastic frames 20, 21 and are each electrically contacted on their front and rear sides by contact sheets 12, 13 and 15, 16, respectively, which bear against them there. The contact sheets 12, 13 and 15, 16 can advantageously be welded to the intermediate section 4b or 5b of the sheet metal strip 4 or 5, in particular by means of a common welded joint 17. The section 4b or 5b of the sheet metal strip 4 or 5 thus forms a sheet metal stack with the sections of the contact sheets 12, 16 and 13, 15 bearing against it on opposite sides.

[0031] The contact plates 12, 13, 15, 16 are each bent into an L-shape. One of their legs rests against the metal strip 4 or 5, respectively, while the other leg rests against the PTC heating resistor(s) 11 to which they make electrical contact. The current direction in the PTC heating resistor(s) 11 held by the first plastic frame 20 is exactly the opposite of that in the PTC heating resistor(s) 11 held by the second plastic frame 21.

[0032] In the illustrated embodiment, one of the two contact plates 13, 16 of each plastic frame 20, 21 is latched to the plastic frame 20, 21, for example, by the contact plates 13, 16 having angled tabs 22 with openings into which the latching projections of the plastic frames 20, 21 engage. It is also possible for both contact plates 12, 13 or 15, 16 to be latched to the respective plastic frame 20, 21. List of reference symbols

[0033] 1 Heater assembly 2 Heat exchanger 2a Heat exchanger part 2b Heat exchanger part 2c Heat exchanger part 3 Plastic housing 4 Composite sheet metal strip 4a Contact tab 4b Sheet metal strip 5 Composite sheet metal strip 5a Contact tab 5b Sheet metal strip 6 Weld seam 7 Passage 8 O-ring 11 PTC heating resistor 12 Contact plate 13 Contact plate 14 Insulator layer 15 Contact plate 16 Contact plate 17 Welded connection 20 Plastic frame 21 Plastic frame 22 Tab 31 Lower part 32 Upper part 33 Connector housing 34 Base

Claims

1. Container heater with a heater assembly (1) containing a plurality of ceramic PTC heating resistors (11), a plastic housing (3) which surrounds the PTC heating resistors (11) and forms a housing (33) of an electrical plug connector, wherein the housing (33) of the plug connector has a base (34) which separates a sealed inner space of the plastic housing (3) containing the PTC heating resistors (11) from an outer space and from which contact tongues (4a, 5a) of the plug connector protrude, characterised in that electrical contact is made via the contact tongues (4a, 5a) to a respective sheet metal strip (4, 5), each of which in the inner space abuts with a front side a contact plate (12, 13), which electrically contacts a first part of the PTC heating resistors (11), and with a rear side abuts a contact plate (15, 16), which electrically contacts a second part of the PTC heating resistors (11).

2. Container heater according to claim 1, characterised in that the direction of current in the first part of the PTC heating resistors (11) is the reverse of the direction of current in the second part of the PTC heating resistors (11).

3. Container heater according to any one of the preceding claims, characterised in that the metal strips (4, 5) are each welded to the contact plate (12, 13, 15, 16) abutting their front side and to the contact plate (12, 13, 15, 16) abutting their rear side by a common weld (17).

4. Container heater according to any one of the preceding claims, characterised in that the first part of the PTC heating resistors (11) is held in a first plastic frame (20) and the second part of the PTC heating resistors (11) is held in a second plastic frame (21).

5. Container heater according to claim 4, characterised in that the sheet metal strips (4, 5) pass between the two plastic frames (20, 21).

6. Container heater according to any one of the preceding claims, characterised in that the contact tongues (4a, 5a) are each part of the sheet metal strip (4, 5) to which electrical contact is made via them.

7. Container heater according to claim 6, characterised in that the sheet metal strips (4, 5) have a front section, which projects out of the base (34) as a contact tongue (4a, 5a), and a rear section (4b, 5b), against the front and rear sides of which contact plates (12, 13, 15, 16) rest.

8. Container heater according to claim 7, characterised in that the front section (4a, 5a) is made of an electrically highly conductive metal and the rear section (4b, 5b) is made of a corrosion-resistant metal.

9. Container heater according to any one of the preceding claims, characterised in that the contact plates (12, 13, 15, 16) are bent in an L-shape and each abut with a first leg one of the metal strips (4, 5) and with a second leg PTC heating resistors (11).

10. Container heater according to any one of the preceding claims, characterised in that the PTC heating resistors (11) are all arranged in the same plane.

11. Container heater according to any one of the preceding claims, characterised in that a heat exchanger (2) made of metal is arranged in the plastic housing (3), said heat exchanger comprising has a passage (7) with which it is stuck onto the heater assembly (1).

12. Container heater according to claim 11, characterised in that the heat exchanger (2) has a plurality of separate heat exchanger parts (2a, 2b, 2c), each of which has a passage (7) and the heat exchanger parts (2a, 2b, 2c) are stuck onto the heater assembly (1) from two end faces.

13. Container heater according to any one of the preceding claims, characterised in that a first of the sheet metal strips (4) has a section (4b) which lies between the two contact plates (12, 16 or 13, 15) abutting it, and a second of the sheet metal strips (5) has a section (5b) which lies between the two contact plates (13, 15 or 12, 16) abutting it.

14. Container heater according to any one of the preceding claims, characterised in that the contact plates (12, 13, 15, 16) each abut the end section (4b, 5b) of one of the metal strips (4, 5).

15. Container heater according to any one of the preceding claims, characterised in that the sheet metal strips (4, 5) each have only a single section (4b, 5b) which contact plates (12, 13, 15, 16) abut.