Hitachi, Ltd.

Kaori Kashio

Noboru Tokuyasu

Hiroaki Hoshika

Yoshihiro Sukegawa

Shiro Yamaoka

Daisuke Terada

Keiji Hanzawa

Jun Kubo

Katsuaki Fukatsu

Hiroshi Onuki

Eiichiro Ohata

Toshiki Otsuki

Takanori Kokubu

Mituharu Osaka

Toshiki Ohtsuki

A fluid flow rate measurement apparatus prevents accumulation of pollutional substances in a sub-passage to enable high-accuracy fluid flow rate measurement. A heater pattern is formed on the surface of a cylindrical rod. When electricity is conducted in the heater pattern and heat is generated, the heat is transmitted to the sub-passage through an insulating layer. The heat is gradually transmitted up to the leading end of the sub-passage, and burns out pollutional substances adhering to the sub-passage. In this way, accumulation in the sub-passage of pollutional substances can be prevented, thus attaining a fluid flow rate measurement apparatus that enables high-accuracy fluid flow rate measurement.

Fluid flow rate measurement apparatus

A control apparatus of an EGR control valve has an EGR control valve has an exhaust gas recirculation passage to circulate exhaust gas of an combustion engine from an exhaust gas passage to an intake air passage. A measurement unit measures a flow rate of EGR gas flowing in the exhaust gas recirculation passage, and a controller receives an input from the measurement unit and closes the EGR control valve if the EGR-gas flow rate is smaller than a predetermined threshold value when the EGR gas is flowing from the exhaust side to the intake side of the internal combustion engine.

Control apparatus of EGR control valve

A thermal flow meter corrects flow rate detection errors produced by vaporization of liquid phase components included in a gas to be measured. The thermal flow meter includes a correction circuitthat applies respectively different predetermined voltages to heating resistors consisting of first heating resistor Rhand second heating resistor Rhof a sensor element disposed in the gas to be measured to set a first temperature state and a second temperature state, calculates a first flow rate value Qof the gas to be measured in the first temperature state and a second flow rate value Qof the gas to be measured in the second temperature state, and calculates a flow rate correction value &#x394;Q based on a ratio (Q/Q) between the first flow rate value and second flow rate value or a fourth-power value (Q/Q)of the ratio to correct a flow rate of the gas to be measured.

Thermal flow meter, thermal flow meter control method, and sensor element of thermal flow meter

An engine that re-circulates its exhaust gas suffers decreased accuracy in estimating an EGR rate real-time especially while the operating state of the engine is in a transitional state, which often results in torque fluctuations and deteriorated exhaust gas. A sensor for directly detecting an EGR flow rate is disposed in an EGR path. An EGR rate and in-cylinder oxygen concentration are calculated from the output value of that sensor. In addition, when this EGR rate calculation method is used, the calculation is properly switched between a steady operation state characterized by a low load and small rotational fluctuations and a transitional operating state including the acceleration and deceleration. This makes it possible to correctly estimate the EGR rate and the in-cylinder oxygen concentration under a wide range of engine operation conditions, and thereby to avoid the fluctuation of torque and the deterioration of exhaust gas.

Engine control system and control method thereof

In a gas flowmeter in which a rod and a sensor element are formed as a single body, for preventing heat of the sensor element from flowing into a sensor probe through a substrate (rod) so as to suppress considerable power consumption, and for obtaining a necessary response speed with respect to a flow rate of gas to be measured or a change in temperature, the gas column (rod) is made of an insulating material on a center axis of the sensing probe and is formed with a conductor pattern on its surface, and the sensing probe connects the sensor element disposed in a pipe through which the gas to be measured flows and a harness terminal through the conductor on the surface of the rod, so as to measure a gas flow rate by using the sensing prove.

Heating resistor-type gas flowmeter

A thermal gas-flow measuring instrument has a first heating resistor placed in the gas to be measured. A temperature sensing resistor is positioned upstream or downstream of the first heating resistor and generates signals relating to the flow rate. Between the first heating resistor and the support for supporting the first heating resistor is a second heating resistor that is electrically insulated from the first heating resistor. The second heating resistor suppresses the heat being transferred from the first heating resistor to the support. A control circuit controls the temperatures of the first heating resistor and the second heating resistor so that the operational temperature range of the second heating resistor or the temperature range at the joint section between the first heating resistor and the second heating resistor is at or above the temperature at which water droplets evaporate to disappear by film boiling.

Thermal type flow meter including a secondary heating device to suppress heat transfer

A flow rate measuring element of a thermal type flow sensor is placed in the fluid to be measured. The element includes: a first heating resistor for measuring a flow rate; a second heating resistor for heating a support for the first heating resistor; and current control circuits and which control heating resistor supply current so that the temperature of the second heating resistor is higher than the temperature of the first heating resistor.

Thermal type flow sensor having a second control circuit to control a second heating resistor above the first heating temperature

A thermal type gas flowmeter comprising a sensor element which, in turn, comprises at least one first heating resistor, two or more resistors in fluid and a second heating resistor which is disposed between the first heating resistor and a housing supporting the sensor element. The first and second heating resistors are electrically independent from each other. A temperature sensing unit is provided between the first and second heating resistors. A temperature of the first or second heating resistor is controlled by a temperature sensed by the temperature sensing unit.

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Sakura, Japan

Kaori Kashio