Abstract
The demand of fuel efficiency improvement by idling-stop is increasing. In most every case, however, air-conditioner doesn’t work while engine is stopping. Especially in summer, engine restarts quickly to keep the comfort of air-conditioning. Thus, the effect of fuel economy by idling-stop is reduced to keep the air-comfort.
We develop cold-storage evaporator which equips cold storage material (CSM). While engine is running, CSM is cooled by refrigerant. When engine is stopped, the cold-energy stored in CSM is released to cool the automotive cabin. At first, we investigated the drive-pattern of idling-stop vehicles such as appearance ratio of running time and stoppage time. As a result, we could clarify that the appearance ratio of under 60 seconds is a major part of the running time and stoppage time. Thus, it is important for the cold storage evaporator to store the cold energy quickly and release it slowly. To achieve the quick storage, we adopt the structure that the CSM cases are sandwiched by refrigerant tubes. And to enhance the phase-change of CSM, inner fin is arranged in CSM case. This structure enables cold storage evaporator to store the cold energy quickly and release it slowly.
We compared the cold storage evaporator to the current one by measuring time to reach air-flow temperature to discomfort temperature (cooling keep time). The test is performed after running compressor for a constant time (cold storage time). The cooling keep time of the cold storage evaporator is about three times longer than that of current one. The cooling keep time which was measured by changing the cold storage time does not change above 40 seconds of cold storage time. This means that our cold storage evaporator can store the cold energy fully within the target time of 60 seconds.
In an age of rapid expansion of idling-stop vehicles, this product can play a great role in keeping the balance of the air-conditioning comfort with the fuel economy at the same time.
KEYWORDS Air-conditioner, Evaporator, Cold-Storage, Idling-stop, Saving energy