Denso Corporation has developed the world’s first passenger vehicle air conditioning system using new ‘ejector’ technology.
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The ejector, a small refrigerant injector, contributes to an overall reduction in power consumption. The system made its production debut in the redesigned Prius hybrid, launched in Japan by Toyota last month and now being rolled out in global markets.
“With increasing demand for technologies to reduce carbon dioxide emissions and preserve the environment, Denso has been accelerating its efforts to develop more efficient air conditioning systems,” said Akio Shikamura, managing officer of the supplier’s thermal systems business group.
“The new air conditioning system reduces the compressor’s power consumption by up to about 25%, compared to conventional car air conditioning systems, and thus contributes to fuel savings.”
According to Denso, much of the energy consumed by a vehicle’s air conditioning system is used by the compressor to compress the refrigerant. In conventional air conditioning systems, an expansion valve is used to reduce the pressure of the refrigerant before passing it through the evaporator to cool the air.
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By GlobalDataThe new system uses an ejector, instead of an expansion valve, which recovers expansion energy previously lost in the expansion valve and converts it into pressure energy. This, reduces the compressor’s workload and helps reduce the air conditioner’s overall power consumption, Denso said.
It has previously applied ejector technology to truck refrigeration units and household CO2 heat-pump water heaters but the conventional ejector was not small enough to be installed in vehicle air conditioning systems until now.
Denso said it overcame this challenge by integrating the ejector into the evaporator tank. This new design eliminates the need for the ejector to have a thicker structure to withstand external pressure and also eliminates pipe connection parts needed to connect the ejector with the evaporator, which helps reduce the size of the ejector.
The ejector cycle system evaporator (ECS evaporator), which is equivalent to the size of a conventional evaporator, can also be applied to conventional air conditioning systems, the supplier said.
The new Prius is also available with remote air conditioning control, which Toyota claimed was a world first.
Using power available from the hybrid system battery, the Denso-supplied system can run for up to three minutes before the car is occupied (such a system could not be supported by a conventional 12V car battery). It is activated by pressing the A/C button on the remote key fob for one second.
The model is also offered with optiona solar panels, neatly integrated into a sliding sunroof, powering an electric air circulation fan. Running independently from the engine, it can cool cabin temperature down from 80 to 45°C, so there is less need for the air conditioning to be used when passengers return to the vehicle.
The system can be activated as the driver leaves the car. One minute after the ignition is turned off, the air intake mode switches to ‘outside air ventilation’ and the blower mode switches to ‘face’ to ensure the most efficient performance.
To avoid cabin air that has already been cooled being vented straight away, the system starts operating after 10 minutes, continuing until it is switched off, or the ignition is turned on.
Denso also developed the ultra-compact air conditioning/heater unit for Toyota’s tiny iQ city car.
Engineers repositioned it, freeing up leg and knee room in the front section of the cabin, reducing the unit’s dimensions by 20% overall while maintaining performance. Rerouting the internal passages improved airflow and a more compact filter was used, which in turn allowed a smaller blower fan to be used.
As a result, the passenger side of the dashboard is slimmer than that in front of the driver, and is positioned further forward and towards the centre of the windscreen. This gives the dashboard an asymmetrical shape.
