DE102013209957A1 - PTC heating device - Google Patents

Abstract

The invention relates to a heating device with a PTC element (22) and a first contact pin (24) and a second contact pin (26) for connecting the PTC element (22) to a power source, which are spaced from each other. The heating device (20) is characterized in that the first contact pin (24) and the second contact pin (26) are surrounded by an electrically conductive plastic (28, 28a, 28b) and by means of the electrically conductive plastic (28, 28a, 28b ) an electrical contact between the first contact pin (24) and the PTC element (22) and the second contact pin (26) and the PCT element (22) is realized.

Description

Technical area

The invention relates to a heating device according to the preamble of claim 1 and a method for producing a heating device.

State of the art

A heating device usually has a heat-generating element, such as a resistance heating element, in particular a PTC element. The PTC element has a positive temperature coefficient (PCT) conductive material and is a passive electronic device. The current-carrying material of the PTC element can conduct electricity at low temperatures better than at high temperatures, with its electrical resistance increases with increasing temperature. Therefore, a PCT element is also referred to as a PTC thermistor. The PCT element is thus a temperature-dependent component whose resistance value at certain temperatures (reference temperature, Curie temperature) rises sharply over several orders of magnitude. The characteristic data of the PTC element depend on the material and structure and can be taken from the characteristic diagrams of the respective material of the PTC element.

The opposite of PTC thermistors are thermistors, which are also called NTC resistors or NTC thermistors (negative temperature coefficient), which conduct better at higher temperatures, so have a negative temperature coefficient.

PCT elements may preferably operate as self-regulating heating elements. The potential uses of PTC heating elements are almost limitless. They can be integrated in the smallest space and are characterized by a high power density. For the tempering of solids, containers, liquids and devices they are used in industry, in medicine and personal care as well as in many household appliances. For example, in the automotive field PTC contact heating elements are often used, which are dynamic heating elements, and at the same time include the functions heating and temperature limiting. The respective embodiment depends on the field of application.

From the DE 10 2009 028 113 A1 It is known to use a heater in a device for the treatment of exhaust gases, in particular for the reduction of NO _x in the exhaust gas of an internal combustion engine. The heater is formed by PTC-behaving plastic material formed in a plate-shaped configuration.

The DE 10 2009 045 741 A1 shows a high power PTC heater in which heat radiation fines are adhesively attached to both sides of PTC rods to improve the heat transfer efficiency from the PTC rods to the thermal radiation fins. The thermal jet fins are attached to the PTC rods by means of silicone adhesive.

It is the object of the invention to provide an improved heating device which can ensure a good heat conduction contact between the heating device and an object to be heated under the requirements in the motor vehicle.

This is achieved with a heating device having the features of claim 1.

One embodiment relates to a heating device with a PTC element and a first contact pin and a second contact pin, wherein the contact pins are spaced from each other, and are arranged for connecting the PTC element with a power source, wherein the first contact pin and the second contact pin at least partially are surrounded by an electrically conductive plastic and by means of the electrically conductive plastic, an electrical contact between the first contact pin and the PTC element and the second contact pin and the PCT element is realized. The heater, which is connected in operation by means of the contact pins to a power source, operates as a resistance heater and is therefore also referred to as an ohmic heater. The electrically conductive plastic can realize a current flow between the contact pins and the PTC element. The contact pins can in this case be completely surrounded except for a connection section to the power source of the electrically conductive plastic, which is partially in mechanical and electrical contact with the PTC element. But it is also possible that the contact pins spaced from each other between the PTC element and the electrically conductive plastic are arranged, wherein portions of the electrically conductive plastic, which are associated with the respective contact pin have no direct contact with each other and are electrically insulated from each other. In both embodiments, the contact pins are arranged on the PTC element such that an electrical contact between the first and the second contact pin consists only of the PTC element. It is advantageous to contact the contact pins on the PTC element with the electrically conductive plastic, since the plastic can adapt to the geometry of the PTC element and the contact pins. The electrically conductive plastic can realize both an electrical connection, as well as a mechanical connection.

A mechanical property would be, for example, the production of an adhesive compound. Due to its elastic properties, the plastic can absorb mechanical shocks. As a result, a connection surface is not mechanically stressed and can produce a durable and thus safer connection in a motor vehicle, which is exposed to vibration. In comparison to this, known electrical contacts are more susceptible to breakage by means of soldering.

The PTC element is preferably a ceramic PTC element and has a semiconducting polycrystalline ceramic which may be in the form of a pellet or a tablet. A widely used material is polycrystalline barium titanate (BaTiO ₃ ), which is semiconductive by doping with 3- or 5-valent elements. The ceramic PTC element is known per se in different embodiment and size as well as with different performance data and can be selected according to the requirements. By contacting with the electrically conductive plastic can be used flexibly almost any design of the PTC element.

The ceramic PTC element, the first and second contact pins and the electrically conductive plastic, which realizes the electrical contact between the contact pins and the PTC element, form a heating device.

In the heating device, the electrically conductive plastic is preferably an electrically conductive and heat-conducting plastic. Thus, the entire outer surface of the PTC element or at least most of the outer surface can function as a heat-dissipating or heat-distributing surface and optimally heat an article surrounding the heater.

In one embodiment, the heating device has the heating device surrounding it, which is surrounded by an electrically insulating, thermally conductive plastic, wherein the insulating, heat-conducting plastic surrounds the heating device at least in sections. The heater is thus electrically isolated and thus can be placed on any object without having to use a separate insulating housing. It is preferred that an electrically insulating and thermally conductive plastic casing is formed. This may replace the housing used in the prior art as a heat spreader and insulator. In this case, the contact pins protrude out of the insulating plastic casing for making contact with the current source.

In an embodiment of the heating device, the heating device is completely surrounded by the electrically insulating and thermally conductive plastic and, as it were, an envelope or plastic sheath is formed, with the first contact pin and the second contact pin protruding from the sheath. It is advantageous here that the electrically insulating, heat-conducting plastic can adapt flexibly to different geometric shapes of the object to be heated.

In this case, a thermal contact of the heating device with a component or object, for example in the motor vehicle by means of the thermally conductive and electrically insulating plastic can be optimally realized.

The heating device is preferably produced by encapsulating a ceramic PTC element or generally an ohmic heating element of an electrically insulating and heat-conducting plastic. The geometry of the encapsulation can be carried out arbitrarily. Preferably, the electrically insulating, heat-conducting plastic surrounds the PTC element completely. The wall thickness of the encapsulation can be selected depending on the desired geometry and mechanical strength. The encapsulation preferably has a surface with a pattern which enlarges the surface of the encapsulation. The pattern may be, for example, a honeycomb pattern, preferably a diagonal honeycomb pattern. In this case, openings are recessed, in which in a second method step, a first and a second contact pin are pushed. Thereafter, an electrically conductive plastic is injected or injected into the openings in such a way that the contact pins are electrically connected to the PTC element. Preferably, the electrically conductive plastic is also thermally conductive. It is also possible to use lines connected to the PTC element, preferably flexible copper lines, instead of the contact pins. Flexible leads can be connected to the contact pins for connection to a power source. The thermal conductivity or the thermal conductivity coefficient of both the electrically conductive and the electrically insulating plastic may preferably be in the range of 4 W / mK and larger.

Further advantageous embodiments are described by the following description of the figures and by the subclaims.

Brief description of the drawings

The invention will be explained in more detail on the basis of at least one embodiment with reference to the figures of the drawing. Show it:

1 a heating device with a heating element according to the prior art

2 A first embodiment of a heating device according to the invention in sectional view,

3 a perspective view of a heater with a PTC element and surrounded by an electrically conductive plastic contact pins.

Preferred embodiment of the invention

The 1 shows a heater 10 according to the prior art, which is a housing 12 in which a heating element 14 is introduced. The heating element 14 has a first power supply line 16 and a second power supply line 18 on, by means of the heating element 14 to a power / voltage source (not shown) can be connected. The first and second power supply lines 16 and 18 These are typically electrically connected by gluing or pressing to the heating element, for example a PTC element (not shown), so that current can flow through the heating element and heat it. The heat is applied to the case 12 which is made of a material having high thermal conductivity, for example, an aluminum housing 12 , transferred and transferred to a heating environment or component (not shown).

2 shows a sectional view of a heater according to the invention 20 with a PTC element 22 and a first contact pin 24 and a second contact pin 26 that supplies power to the PTC element 22 serve. The PTC element 22 is an ohmic heater with a positive temperature coefficient. The PTC element 22 is of a thermally conductive and electrically conductive plastic material 28 partially surrounded, in which the first contact pin 24 and the second contact pin 26 are embedded. Thus, the first and second contact pins 24 and 26 electrically conductive with the PTC element 22 connected. The sections with electrically conductive plastic 28 are spaced from each other, at least arranged electrically insulated. Because of the plastic material 28 is also thermally conductive, the heat generated during operation (current flow) from the PTC element 22 removed and transferred to the outside on another device (not shown). The PTC element 22 , the contact pins 24 and 26 as well as the electrically conductive plastic material 28 form a heating device 30 , The contact pins 24 and 26 can be designed both as rigid, rigid pins or pins, as well as flexible electrically conductive lines, such as copper cables. The heater 30 is of an electrically insulating, but thermally conductive plastic material 32 surround. Preferably, the plastic material replaces 32 in its function, the contact area / contact volume of the housing 12 the heater 10 from the prior art and can thus be brought into thermal contact with an object to be heated. The plastic material 32 thus has the same function, the heater 30 electrically isolate from the object to be heated and the temperature of the heater 30 to transfer to this and thus act as a heat spreader. Plastic 32 thus forms a sheath 33 or envelopes 33 the heater 30 , The envelope 33 has the same function as a housing, but with a more flexible and adaptable to the installation space shape. The shape in 2 is intended to illustrate only as an example and does not limit the forms to be implemented for the envelope 33 The envelope 33 has openings 31 on, from which the contact pins 24 and 26 from the envelope 33 protrude.

3 shows a heater 30 seen in perspective from obliquely above. The heater 30 indicates the PTC element 22 on, on its upper PTC surface 34 a plastic block 28a and at its lower, opposite PTC surface 36 a second plastic block 28b are arranged. The plastic blocks 28a and 28b are each formed with a substantially rectangular base. In the plastic block 28a is the contact pin 24 picked up, in the plastic block 28b the contact pin 26 , The heater 30 For installation in or contacting an article, it is generally completely covered by the plastic material 32 be surrounded. The thermal conductivity of the plastic 28 is about 4 W / mK, but may be preferably higher.

Electrically conductive plastics are, for example, intrinsically conductive polymers, also called conductive polymers, whose electrical conductivity is comparable to metals. The conductivity of the polymer is achieved by conjugated double bonds, which allow free mobility of charge carriers in the doped state. Another class of electrically conductive plastics are plastics with additives.

• – Umspritzen der Heizeinrichtung 30 komplett oder zumindest bereichsweise mit einem wärmeleitenden, elektrisch isolierenden Kunststoff 34,
• – Aussparen von kleinen Öffnungen 31 oder Löchern in dem Kunststoff 32,
• – Einbringen von Kontaktstiften 24 und 26 in Öffnungen 31,
• – Einspritzen des Kunststoffs 28, 28a, 28b in die Öffnungen 31, so dass die Kontaktstifte 24, 26 mit dem PTC-Element 22 elektrisch leitend verbunden sind.

The production of the heater 20 with a heater 30 includes the following steps:

• - Overmolding the heater 30 completely or at least partially with a heat-conducting, electrically insulating plastic 34 .
• - Eliminate small openings 31 or holes in the plastic 32 .
• - Insertion of contact pins 24 and 26 in openings 31 .
• - Injecting the plastic 28 . 28a . 28b in the openings 31 so that the contact pins 24 . 26 with the PTC element 22 are electrically connected.

Thus, in the holes or openings are the plastic blocks 28a and 28b formed, which depict the shape of these openings or holes. Consequently, the shape of the plastic blocks 28a and 28b this variable, so not necessarily strictly rectangular plastic blocks 28a and 28b as in 2 represented arise. The contact surfaces 28a and 28b can have any shape that the pins 24 and 26 enclose, and are by the notion plastic block 28a . 28b also includes. It is important here that a sufficient contact surface, or a sufficient contact volume between the contact pins 24 and 26 as well as the PTC element 22 given with a good electrical contact. The contact pins 24 and 26 may also be connected to the PTC element by means of an electrically conductive bonding material which is metallic 22 be attached, for example, be soldered. The geometry of the heater 20 is variable in design here. The outer surface of the plastic 32 is variable in design here. It can be smooth or rough. It may also have a structure whereby the surface area can be increased. For example, a diagonal honeycomb structure may be provided.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102009028113 A1 [0005]
• DE 102009045741 A1 [0006]

Claims (10)

A heating device having a PTC element and a first contact pin and a second contact pin for connecting the PTC element to a current source, which are arranged at a distance from one another, characterized in that the first contact pin ( 24 ) and the second contact pin ( 26 ) of an electrically conductive plastic ( 28 . 28a . 28b ) are surrounded and by means of the electrically conductive plastic ( 28 . 28a . 28b ) an electrical contact between the first contact pin ( 24 ) and the PTC element ( 22 ) and the second contact pin ( 26 ) and the PCT element ( 22 ) is realized. Heating device according to claim 1, characterized in that the PTC element ( 22 ) a ceramic PTC element ( 22 ). Heating device according to claim 1 or 2, characterized in that the PTC element ( 22 ), the first contact pin ( 24 ), the second contact pin ( 26 ) and the electrically conductive plastic ( 28 . 28a . 28b ), at least partially between the PTC element ( 22 ) and the first contact pin ( 24 ) and the PTC element ( 22 ) and the second contact pin ( 26 ), a heating device ( 30 ) form. Heating device according to one of claims 1 to 3, characterized in that the electrically conductive plastic ( 28 . 28a . 28b ) an electrically conductive and heat-conducting plastic ( 28 . 28a . 28b ). Heating device according to one of the preceding claims, characterized in that the heating device ( 30 ) of an electrically insulating, heat-conducting plastic ( 32 ) is surrounded at least in sections. Heating device according to one of the preceding claims, characterized in that the heating device ( 30 ) completely of the electrically insulating and thermally conductive plastic ( 32 ) is surrounded and, as it were, an envelope ( 33 ), wherein the first contact pin ( 24 ) and the second contact pin ( 26 ) from the envelope ( 33 ) protrude. Heating device according to one of the preceding claims, characterized in that a thermal contacting of the heating device ( 20 ) with a component to be heated by means of the thermally conductive and electrically insulating plastic ( 32 ) is feasible. Method for producing a heating device ( 20 ) according to one of claims 1 to 7, comprising a PTC element ( 22 ) and a first contact pin ( 24 ) and a second contact pin ( 26 ) for connecting the PTC element ( 22 ) with a power source, characterized in that the PTC element ( 22 ) with an electrically insulating and heat-conducting plastic ( 32 ) is sprayed over, wherein at least two openings ( 31 ) in plastic ( 32 ) remain. Method according to claim 8, wherein additionally the following steps are provided: introduction of the contact pins ( 24 . 26 ) into the openings ( 31 ), - injection or injection of electrically conductive plastic ( 28 . 28a . 28b ) into the openings ( 31 ). Method according to claim 8, characterized in that the contact pins ( 24 . 28 ) already with the PTC element ( 22 ) and after encapsulation with electrically insulating and thermally conductive plastic ( 32 ) protrude from the openings.

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