Development of Fast Response Time PM Sensor 2020-01-0390
From the perspective of air pollution and health damage, the automakers have worked to reduce PM emissions. The mainstream technology is the installation of Filters, and the OBD of the filter itself is required for function monitoring in the market. Therefore, there is a need for high sensitivity PM sensor that detects a few amount of PM leaking from the filter. In addition, due to the detection principle called electrical resistance type that applies the voltage between electrodes, collects PM, forms PM path and outputs it, the electrodes directly are exposed to the exhaust gas environment. Therefore, the poisoning resistance is also essential.
With regard to high sensitivity, in order to form PM path between the electrodes with a few amount PM, we developed the laminated electrodes that enables narrow electrodes gap such as 20 micrometer with Al2O3 sheets printed electrode. In addition, with the electric field simulation, we adopted the electrodes layout separated with +/- electrode pairs for PM approach to the pairs easily.
On the other hand, with regard to poisoning resistance, in order to prevent the poisoning substances from contacting to the electrodes, we developed the unique temperature control using Leidenfrost-phenomenon that liquid-phase poisoning substances repel and Thermophoresis-phenomenon that solid-phase poisoning substances keep away, except for Filter-OBD term. And we confirmed that the durability can be secured under the exhaust gas environment.
Based on these technologies, we developed PM sensor that enables both the frequent filter -OBD and the long-term stable, and started mass-production.
Masahiro Yamamoto, Eriko Maeda, Yusuke Todo, Mitsunobu Nakato