[AEE] Plastic Halves Weight of Panoramic Roof
May 28, 2008 19:11
Tatsuhiko Hayashi, Nikkei Automotive Technology
Integration of fitting parts for reduction in number of parts
Toyota Industries Corp exhibited a plastic panoramic roof that is much lighter than a glass roof at Automotive Engineering Exposition 2008. The company aims to commercialize it in about 2010.
The prototype of the roof exhibited at the exposition was employed in Toyota RAV4. The roof would weigh 20kg if it was made of glass. But the prototype only weighs 11kg.
The roof, made of polycarbonate (PC), was manufactured by coinjection molding. A transparent portion of the roof is first formed from plastic. Then, after the mold is rotated, a black edge portion is injected around the transparent plastic. With the use of silicon wet coat, the new roof features an improved weather resistance.
The method developed by Exatec is known as one of the coating techniques for plastic windows. According to this method, the PC surface is coated with a glass component by chemical vapor deposition (CVD) using plasma. But Toyota Industries did not adopt Exatec's method.
To begin with, the company is reportedly planning to employ the roof on Toyota cars. Toyota has a very strict requirement for weather resistance. Specifically, resistance for 10 years is demanded even in an extremely hot climate such as in Arizona. Because PC has a problem of discoloration due to ultraviolet light, the company is now conducting an accelerated test to determine whether the roof has a sufficient performance to prevent such a defect.
In addition to checking the weather resistance, cost reduction is another task for the company. The cost would rise if the structure used for a glass roof was simply applied to a plastic roof as-is. Thus, component integration should be promoted in the design to combine the fitting bosses and ribs together, thereby reducing the number of required parts.
The company also plans to incorporate a structure that can absorb the deformation that occurs when the roof is in use.
The plastic roof has to be thicker because its strength is lower than that of a glass roof. But it is easier to control the thickness of each portion of the plastic roof because it is manufactured by injection molding. Therefore, the increase can be minimized by making only the necessary portions thicker, the company said.
Toyota Industries hopes to commercialize the roof in some models in about 2010, and then in several models in about 2012. |
