Sadayasu Ueno

Semiconductor capacitance-type accelerometer with PWM electrostatic servo technique

Abstract A new semiconductor capacitance-type accelerometer utilizing a pulse width modulation (PWM) electrostatic servo technique has been developed. Highly accurate detection of feeble and low frequency acceleration became possible with the PWM sensing method. The limited air gaps between the movable and fixed electrodes ensured compatibility between high sensitivity and durability, while transverse sensitivity was reduced due to the symmetric structure of the sensing part.

Thick-Film Zirconia Air-Fuel Ratio Sensor with a Heater for Lean Mixture Control Systems

This paper describes the design and operation of a thick-film zirconia air-fuel ratio sensor with a heater. This sensor is composed of two zirconia plate cells, a stoichiometric cell and a lean cell, laminated on the platinum heater. It is fabricated as one body using a thick-film process. The pair of cells has a gas diffusion chamber and a slit type gas diffusion aperture. The sensing principle is based on the rate-determining diffusion of oxygen molecules at the gas diffusion aperture. By using an oxygen pumping phenomenon, air- fuel ratios of the stoichiometric and lean regions can be detected. As this sensor is heated to a high constant temperature, it has sufficient accuracy without any additional temperature compensation. Its starting time is short and response time is very quick.

ANTI-DIRT PROPERTY OF HOT-WIRE AIR FLOW METER

Hitachi has recently developed a hot-wire air flow meter which uses a temperature-sensitive resistor of an extremely thin platinum wire wound around a ceramic bobbin and coated with glass. This temperature-sensitive resistor, or a hot wire, is located in a bypass of the intake air passage of an engine and responds exactly for the effective control of engine operation. The flow meter of this construction is sturdy enough to withstand impacts of backfires and vibration and reduces variation in engine output characteristic likely to be caused by dust and dirt present in the intake air. Furthermore, this device requires no cleaning or other maintenance.