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In a conventional soldering process, solvents, such as chlorofluorocarbons (CFCs), have been necessary to remove the flux-residue after soldering. A new CFC-free fluxless soldering process has been developed to obtain high sealing ability even in a small soldering area. This new process utilizes a reducing atmosphere with an appropriate load and assembly orientation to solder the parts. Under this fluxless condition, it is found that appropriate loading and good solder-wettability of the upper part increase the wettability of the lower part.

We have achieved significant weight reduction for the MS (Multi-Tank Super Slim Structure) Evaporator (1)currently in production at DENSO CORPORATION. The evaporator of HVAC unit, located in the instrument panel, is a component of the aluminum heat exchanger used in automotive air conditioners. The new evaporator uses thinner quad-layer sheet material, thanks to optimization of the electrical potential among its outer filler metal, intermediate anodic layer and core. The evaporator is thus lighter than conventional evaporators, but retains equivalent corrosion resistance.

In conventional automobile designs, a radiator and a condenser are typically configured and mounted independently of each other. We have developed a smaller and more powerful cooling module by integrating these two products into one piece. The new cooling module has been designed to share the fin material and to have an insulating slit and other means for effective prevention of heat loss that occurs due to thermal conduction between the radiator and the condenser1). In addition, as one of the key techniques for integrating fins, we studied thermal spraying of brazing filler to the tube material and were able to achieve a practical-level cooling module through use of high-performance fins, contributing largely to the efforts to create a more compact, higher performance cooling module.

In view of the shorter development period for new automobiles, we have developed a computer-aided engineering (CAE) system to aid in commensurately speedy development of automotive air conditioners. This system consists of three tools: one that calculates various design specifications instantaneously, one that enables designers to easily examine air-conditioner shape, and one that converts shape data into calculable model data to enable 3D (three-dimensional) processing. Effective use of these tools cuts air-conditioner development lead time to half that of the conventional process.

In conventional automobile designs, a radiator for cooling the engine and a condenser for condensing the air-conditioner refrigerant are typically configured independently of each other; they are usually mounted in series in the front of the engine compartment so that they will receive sufficient air flow while the vehicle is running. We have developed a smaller and higher performance cooling module by integrating these two heat exchangers into one unit. (Fig 1) For the heat dissipation fin, we have employed an integral fin construction equipped with an insulating slit, resulting in effective prevention of thermal conduction from the higher temperature radiator side, to the condenser side. We also succeeded in improving heat dissipation performance by making effective use of the connection part of the integral fin.

Having a light weight, a good heat conductivity and a good brazability, aluminum alloy is widely used for automotive heat exchanger systems. The major problem with Aluminum is perforation of the tube by pitting corrosion and corrosion protection is necessary in the field. In radiator and condenser systems using the the Nocolok brazing process given good corrosion resistance using cathodic protection with sacrificial anode made of Zn-sprayed onto tube or low corrosion potential fins etc. On the other hand, in drawn-cup type evaporators, that are fabricated from brazing sheet tubes in vacuum brazing method and then covered low electro-conductive drain water film in operation, the effect of cathodic protection by the anode fin is limited to a very small area. Therefore, this has been studied to improve self-corrosion resistance of the core in the brazing sheet tube.