Patent Application
20080135536
The invention relates to an electric heating system with the features set forth in the preamble of claim 1. Such a heating system is used especially as an auxiliary heating system for automobiles. As a rule, automobile heating systems utilize the waste heat produced by the combustion engine. The continuous increase of the efficiency of combustion engines, however, has resulted in a reduction of the amount of waste heat available for the heating system. This applies in particular to the direct-injection diesel engines especially designed for fuel economy. Because of their reduced waste heat, these engines do not, especially in winter, heat up as rapidly as would be desirable for the defrosting of the front windshield, to prevent fogging up of the front windshield and to heat up the passenger compartment to a comfortable temperature. Because of this reason, it is known from U.S. Pat. No. 6,124,470 to provide an electric auxiliary heating system, presenting typically an output between 250 Watts and 2000 Watts.
From U.S. Pat. No. 6,875,962 an electric auxiliary heating system is known which comprises several heating rods, in which PTC resistances are provided as heating resistances. A number of plates are slipped upon the heating rods, whereby the rods are connected to each other. For this purpose, the plates are provided with rectangular openings, of which their inner width is closely adapted to the cross-section of the heating rods, so that the edges of the openings grip the heating rods. These plates function as heat exchangers. The heating rods transfer the therein produced heat to the plates which convey it to an air flow that passes transversally through the auxiliary heating system. One of the extremities of the heating rods is inside a housing in which is arranged a control circuit with power semiconductors, which circuit controls the heating current for the heating rods. Further, either inside or at the housing is arranged a metal plate by means of which is established a bonding with the outside of the heating rod. The other ends of the heating rods are inserted in a cross-arm that mechanically stabilizes the auxiliary heating system and presents means for the assessing of the auxiliary heating system in the motor vehicle.
For different motor vehicles there are different auxiliary heating systems which can be differentiated according to the type and arrangement of the heating rods as well as according to the type of the metal plates adapted to the heating rods.
The object of the present invention is to rationalize the manufacture of electric auxiliary heating systems for different automobiles.
This object is achieved by means of a heating system with the characteristics set forth in claim 1. Other favorable embodiments of the invention are the subject-matter of the subclaims.
According to the invention, at least part of the slotted holes in each metal plate, namely the same slotted holes in each metal plate, is longer by more than the manufacturing tolerance, than the width of the heating rods measured in the longitudinal direction of the metal plates.
This has the advantage that the heating rods can be transversally displaced in the elongated slotted holes, whereby the distance between the heating rods can be changed. This allows to use the same embodiment for the configuration of different auxiliary heating systems that differ in the distance between their heating rods. Therefore, with respect to prior art, it is possible to reduce the number of different metal plates previously required, thus obtaining a rationalization effect that reduces the cost of manufacture, of the tools required for the manufacture as well as of the stock-keeping of the metal plates.
The elongated slotted holes are preferably 1.5 times as long, even better at least twice as long as the width of the widest heating rods, and not more than four times as long as the width of the widest heating rods. Thus, there is considerable play for the configuration of electric auxiliary heating systems with heating rods that differ with respect to the distances between them and/or to their width.
At least in the case of heating systems that have an even number of heating rods all slotted holes are preferably elongated according to the invention. In the case of an odd number of heating rods it can be disregarded to elongate the central slotted hole because, even with different heating rod distances, the middle heating rod can continue in the same central position.
In the case of an even number of heating rods, the middle slotted holes, namely, the slotted holes for the two central heating rods, can be shorter than the slotted holes for the outer heating rods. In the case of a heating system with four adjacent heating rods it is favorable if the outer slotted holes, namely, the slotted holes for the outer heating rods, are twice the length of the slotted holes for the inner heating rods. This allows that heating rods with distinctly different widths can be inserted into such configured metal plates at equal distances.
The metal plates are advantageously configured either planar or mainly planar. In the slotted holes, tongues form at least on one side of the pertinent slotted hole its longitudinal edge. The tongues can extend along the plane of the metal plates. Preferably, the tongues are all bent off from the plane of the metal plates in the same direction. This facilitates the slipping of the metal plates onto the heating rods that bend the metal plates, so that, because of a springing back of their tongues, the metal plates clamp the heating rods in the slotted holes, i.e. establish a frictional connection with the heating rods. Not only is such a frictional connection favorable for the cohesion of the auxiliary heating system but also for the heat transfer from the heating rods to the metal plates.
In principle, in the slotted holes are not required several tongues in order to establish the frictional connection with the heating rods. By providing several tongues it is possible, however, to obtain a constant cohesion irrespective of the position of the pertinent heating rods in the slotted holes and to obtain a greater rigidity of the metal plates. Especially favorable in this respect is a width of the tongue that corresponds approximately to the average width of the customary heating rods with PTC heating elements. Preferably, the heating rods have a rectangular cross-section.
The metal plates can be out of a sufficiently heat-resisting synthetic material. Preferably, they are made out of sheet metal. This has the advantage that they can be manufactured at low cost as stamped and bent parts and can facilitate a good heat transfer. Furthermore, the metal plates can concomitantly be used to establish a connection to ground. For this purpose, an extra hole is punched into the metal plates, into which a metal bolt, serving as terminal post for the connection to ground, can be inserted into one of the metal plates. As an alternative, the metal plates can also be provided with a connecting lug for the establishing of a connection to ground.
The hereto attached illustrations show an embodiment of the invention.
The auxiliary heating system shown in
Due to the chosen length of the slotted holes 6, the distance between the heating rods vis-à-vis the illustrated assembly can be lengthened by the width of the heating rods 1 or shortened by twice the width of the heating rods 1.
At one corner of the metal plate 2 is provided an additional hole 6 into which can be inserted a bolt as connecting lug for a connection to earth.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2006 055 872.3 | Nov 2006 | DE | national |
