Takao Sasayama

Highly reliable silicon micromachined physical sensors in mass production

Abstract Silicon micromachined physical sensors such as silicon pressure sensors and accelerometers are now in mass production in response to the strong market demands. In the design of such sensors, it is most important to guarantee high reliability as well as low cost. To respond to these demands for microsensors, the designs of device structure, production processes and packaging have been investigated in detail.

Optical fiber gyroscope for automotive navigation

The use of an optical fiber gyroscope in automotive navigation is reported. The performance requirements for a navigational gyroscope are discussed in terms of the input range, resolution, and bias and scale errors. The OFG-3, an automotive optical fiber gyroscope prototype, is introduced, and its error sources are related to the gyroscope designs. The gyroscope is made of polarization maintaining fibers and incorporates optical phase modulation and synchronous demodulation techniques. The gyroscope electronics restrict the resolution and the bias error, while the optics dominate the scale error. The microcomputer in the electronics compensate for the scale error, and the OFG-3 meets navigational requirements. Automotive navigation has been demonstrated using the gyroscope in combination with a map-matching algorithm. >

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.

Knocking Detection of a Gasoline Engine by Utilizing an Optical Fiber with Specific Refractive-index Composition.

Abnormal combustion of a gasoline engine is often accompanied by a sharp metallic noise called knocking. A recently proposed method of in-cylinder pressure measurement is applied to detect the knocking, where the bending power loss of a single-mode fiber with specific refractive-index composition is utilized. The high-frequency response of a prototype sensor is obtained with a small structure to utilize the bending mechanism that is installed into an engine head gasket. Knocking signals are detected in a wide range of trace- to heavy-knock conditions.

Recent developments of optical fiber sensors for automotive use

Abstract Optical fiber sensing technologies are expected to apply for many future electronic control systems in automobiles, because of their inherent outstanding features, such as high noise immunity, high heat resistance, and flexible light propagation paths which can be applied to measure the movements and directions of the mobiles. In this paper, two typical applications of fiber sensing technologies in automobiles are described in detail. The combustion flame detector is one of the typical applications of a fiber spectroscopic technology which utilizes the feature of high noise and heat resistibility and remote sensibility. Measurement of engine combustion conditions, such as the detonation, the combustion initiation, and the air-fuel ratio, have been demonstrated in an experimental fiber sensing method. Fiber interferometers, such as a fiber gyroscope, have great possibilities in future mobile applications because they are applicable to many kinds of measurements for movements and physical variables...

A solid-state air flow sensor for automotive use☆

Abstract A new wire-wound type hot-wire air flow sensor was designed for automotive applications. The sensing probe of the sensor is formed from a small platinum wire-round resistor and installed in the bypass of the measuring air stream in order to protect the sensing probe from surface contamination by dust and mechanical damage by a burst reverse flow which are common in such applications. In the design of the bypass passage, its length and the pressure loss in it are selected to get precise measurements in pulsating flow conditions. A new electronic control method was applied to the solid-state hot-wire sensor to allow the dynamic range to be increased from full scale/40 to full scale and the operating temperature range from −40 to 125 °C. An electronic control circuit for the hot-wire sensor is fabricated on an alumina substrate using thick film technology, and the sensing probes are connected to this substrate directly. This integrated solid-state air flow sensor shows a deviation of the measured mass air flow value of less than 4% of the indicated value.

An advanced engine control system using combustion pressure sensors

While investigating high-efficiency responsive driveability accompanied by low exhaust emissions, a new concept in engine control has been developed. The method is based on the direct monitoring and controlling of combustion conditions in engines, using a newly developed combustion pressure sensor. Fibre-optic technology is adapted to this sensor to produce a high noise immunity and a simple structure that facilitates applications in automotive engines. A sensing method to obtain information on engine output, knocking or detonation and the combustion temperature from the signal of the combustion pressure sensor has been proposed. A control system for the engine and powertrain control using this sensing method has been put forth to provide a remarkable improvement in engine and powertrain characteristics.

Recent Developments Of Optical Fiber Sensors For Automotive Use

Optical fiber sensing technologies are expected to apply for many future electronic control systems in automobiles, because of their original outstanding features, such as high noise immunity, high heat resistance, and flexible light propagation paths which can be applicable to measure the movements and directions of the mobiles. In this paper, two typical applications of fiber sensing technologies in automobiles have been described in detail. The combustion flame detector is one of the typical applications of a fiber spectroscopic technology which utilizes the feature of high noise and heat resistibility and remote sensibility. Measurements of engine combustion conditions, such as the detonation, the combustion initiation, and the air-fuel ratio, have been demonstrated in an experimental fiber sensing method. Fiber interferometers, such as a fiber gyroscope, have a lot of possibilities in future mobile applications because they are expandable to many kinds of measurements for movements and physical variables. An optical fiber gyroscope utilizing the single polarized optical fiber and optical devices has been developed. Quite an accurate measurement of vehicle position was displayed on a prototype navigation system which installed the fiber gyroscope as a rotational speed sensor.

Multiplex in-cylinder pressure measurement utilizing an optical fiber with specific refractive-index composition

An approach to multiplex in-cylinder pressure measurement that utilizes a single-mode optical fiber with specific refractive-index composition has been proposed. The sensing fiber has been designed to show a certain amount of optical power loss with a small change in the fiber-local-bend radius. Along with pressure-transferring diaphragms the sensing fiber was embedded into the head gasket of a four-cylinder gasoline engine. The internal-pressure change in each combustion chamber was detected on the basis of bending power loss in the fiber. Combustion pressure peaks for each cylinder were clearly observed.

Multiplexed Optical Transmission System For Automobiles Using Polymer Fiber With High Heat Resistance

A multiplexed optical transmission system for automobiles utilizing newly developed polymer fiber has been proposed. The system is composed with a star-shaped optical network, in which the ootical signals can be transmitted bi-directionally through polymer optical fiber and optical branches with the central and local controllers. The polymer fiber has been developed for this purpose in order to overcome the conventional problems which prevented its wide use for a long time. The new polymer fiber is fabricated with a thereto-setting resin for core which is pushed out from heating furnace after the process of polymerization. The fiber shows the desirable characteristics for this application, that is, the heat resistance is as high as 200°C, and the transmission loss is as low as 0.5003/m at 660 nm wavelength.