Abstract: A fuel vapor treatment system includes a canister containing an adsorbent, a detector detecting a concentration of a fuel vapor, a purge passage for introducing the mixture gas into an engine, and an ECU which controls a purge based on a detected fuel vapor condition quantity and learns a fuel vapor concentration. If a difference between a learned concentration and a detection concentration is not less than a specified value, the ECU performs a purge control based on the learned concentration prior to a purge control based on the detection concentration.

Abstract: A fuel nature measuring device for measuring the nature of fuel stored in a fuel tank includes a measurement passage, a gas flow generator, a pressure detector, an concentration operator, a temperature detector, and a volatility calculator. The measurement passage has an orifice. The gas flow generator generates gas flow in the measurement passage. The pressure detector detects a differential pressure between opposite ends of the orifice. The concentration operator determines a concentration of evaporated fuel in the fuel tank based on the differential pressure detected when the opposite ends of the measurement passage communicate with the fuel tank and the fuel flows in the measurement passage. The temperature detector determines a temperature of the fuel in the fuel tank. The volatility calculator calculates a volatility of the fuel in the fuel tank based on the concentration of the evaporated fuel and the temperature of the fuel in the tank.

Abstract: A fuel vapor treatment system includes a canister containing an adsorbent, a detector detecting a concentration of a fuel vapor, a purge passage for introducing the mixture gas into an engine, and an ECU which controls a purge based on a detected fuel vapor condition quantity and learns a fuel vapor concentration. If a difference between a learned concentration and a detection concentration is not less than a specified value, the ECU performs a purge control based on the learned concentration prior to a purge control based on the detection concentration.

Abstract: A fuel vapor treatment apparatus connects with a fuel tank, which produces fuel vapor to be purged into an intake passage of an internal combustion engine through a purge passage. The fuel vapor treatment apparatus includes a state measuring unit that includes a measurement passage provided separately from the purge passage. When the measurement passage is blocked from the intake passage, the state measuring unit measures a state of fuel vapor by detecting a physical quantity of the fuel vapor in the measurement passage. The physical quantity is correlative to the state of fuel vapor. The fuel vapor treatment apparatus further includes a diagnosis unit for diagnosing a malfunction of at least one of components of the state measuring unit.

Abstract: A fuel nature measuring device for measuring the nature of fuel stored in a fuel tank includes a measurement passage, a gas flow generator, a pressure detector, an concentration operator, a temperature detector, and a volatility calculator. The measurement passage has an orifice. The gas flow generator generates gas flow in the measurement passage. The pressure detector detects a differential pressure between opposite ends of the orifice. The concentration operator determines a concentration of evaporated fuel in the fuel tank based on the differential pressure detected when the opposite ends of the measurement passage communicate with the fuel tank and the fuel flows in the measurement passage. The temperature detector determines a temperature of the fuel in the fuel tank. The volatility calculator calculates a volatility of the fuel in the fuel tank based on the concentration of the evaporated fuel and the temperature of the fuel in the tank.

Abstract: An oscillation-type state measuring apparatus has an oscillation-type sensor, a reference oscillation signal generating circuit for producing reference oscillation signals, a beat signal generating circuit for generating beat signals having a beat frequency by synthesizing the sensor oscillation signals and the reference oscillation signals, a counter for measuring a period of the beat signals, and a physical quantity calculation circuit for calculating a physical quantity from the period of the beat signals and from the period of the reference oscillation signals. The reference oscillation signal generating circuit varies the frequency of the reference oscillation signals, and the physical quantity calculation circuit calculates the physical quantity based on the varied period of the reference oscillation signals.

Abstract: A CPU measures an actual air-fuel ratio based on the signals detected by the air-fuel ratio sensor. When the difference between the actual air-fuel ratio and a target air-fuel ratio is larger than a predetermined value, the computer determines that a fuel vapor amount purged into the intake passage deviates from a target value due to an incorrectness of a reference flow quantity of the purge valve. The computer calculates an actual reference flow quantity based on a measured actual air-fuel ratio, and rewrites the reference flow quantity corresponding to a current intake pressure into the calculated the reference flow quantity. Thereby, the difference between the actual air-fuel ratio and the target air-fuel ratio can be reduced.

Abstract: A butterfly valve restricts flow passage areas of a purge passage and a blow-by gas passage by the same degree. A first pressure sensor detects variation in pressure of the purge gas, which is generated by the butterfly valve. A second pressure sensor detects variation in pressure of the blow-by gas, which is generated by the butterfly valve. Since a fuel vapor concentration of the blow-by gas is lower than that of the purge gas, the blow-by gas can be treated as air of 100%. Hence, the fuel vapor concentration is calculated based on the variations in pressure detected by the first pressure sensor and the second pressure sensor.

Abstract: A fuel vapor treatment apparatus includes a first canister, a purge passage, an atmosphere passage, a first detection passage provided with a restrictor, and a passage-changing valve for changing the connection passage of the first detection passage between the purge passage and the atmosphere passage. The apparatus further includes a second canister connecting with the first detection passage on the opposite side of the passage-changing valve across the restrictor. A differential pressure sensor detects a pressure difference between both ends of the restrictor. An ECU computes the concentration of fuel vapor on the basis of the detection result of the differential pressure sensor.

Abstract: A fuel vapor treatment apparatus includes a first canister purges fuel vapor into an intake passage of an engine through a purge passage, which communicates with a first detection passage having a throttle. A second canister is located on an opposite side of the purge passage with respect to the throttle, and communicates with the first detection passage. A gas flow generating unit generates gas flow by reducing pressure in a second detection passage communicating with the second canister. A pressure detecting unit detects pressure correlated with the throttle and the gas flow generating unit. An exhaust detecting unit detects exhaust of fuel vapor from the second canister to the second detection passage. A purge control unit controls purge of fuel vapor from the purge passage to the intake passage in accordance with detection results of the pressure detecting unit and the exhaust detecting unit.

Abstract: A fuel nature measuring device for measuring the nature of fuel stored in a fuel tank includes a measurement passage, a gas flow generator, a pressure detector, an concentration operator, a temperature detector, and a volatility calculator. The measurement passage has an orifice. The gas flow generator generates gas flow in the measurement passage. The pressure detector detects a differential pressure between opposite ends of the orifice. The concentration operator determines a concentration of evaporated fuel in the fuel tank based on the differential pressure detected when the opposite ends of the measurement passage communicate with the fuel tank and the fuel flows in the measurement passage. The temperature detector determines a temperature of the fuel in the fuel tank. The volatility calculator calculates a volatility of the fuel in the fuel tank based on the concentration of the evaporated fuel and the temperature of the fuel in the tank.

Abstract: A fuel nature measuring device for measuring the nature of fuel stored in a fuel tank includes a measurement passage, a gas flow generator, a pressure detector, an concentration operator, a temperature detector, and a volatility calculator. The measurement passage has an orifice. The gas flow generator generates gas flow in the measurement passage. The pressure detector detects a differential pressure between opposite ends of the orifice. The concentration operator determines a concentration of evaporated fuel in the fuel tank based on the differential pressure detected when the opposite ends of the measurement passage communicate with the fuel tank and the fuel flows in the measurement passage. The temperature detector determines a temperature of the fuel in the fuel tank. The volatility calculator calculates a volatility of the fuel in the fuel tank based on the concentration of the evaporated fuel and the temperature of the fuel in the tank.

Abstract: A leak detecting apparatus includes a canister adsorbing a fuel vapor evaporated in a fuel tank, a measure passage, a pump connected with the canister through the measure passage, and a pressure senor detecting a pressure in the measure passage. The pump depressurizes the measure passage, the canister, and the fuel tank so that a leakage of the fuel vapor is detected. When a blow-by of the fuel vapor is arisen, the pump is stopped to forcibly terminate a depressurization.

Abstract: An oscillation-type state measuring apparatus has an oscillation-type sensor, a reference oscillation signal generating circuit for producing reference oscillation signals, a beat signal generating circuit for generating beat signals having a beat frequency by synthesizing the sensor oscillation signals and the reference oscillation signals, a counter for measuring a period of the beat signals, and a physical quantity calculation circuit for calculating a physical quantity from the period of the beat signals and from the period of the reference oscillation signals. The reference oscillation signal generating circuit varies the frequency of the reference oscillation signals, and the physical quantity calculation circuit calculates the physical quantity based on the varied period of the reference oscillation signals.

Abstract: A fuel nature measuring device for measuring the nature of fuel stored in a fuel tank includes a measurement passage, a gas flow generator, a pressure detector, an concentration operator, a temperature detector, and a volatility calculator. The measurement passage has an orifice. The gas flow generator generates gas flow in the measurement passage. The pressure detector detects a differential pressure between opposite ends of the orifice. The concentration operator determines a concentration of evaporated fuel in the fuel tank based on the differential pressure detected when the opposite ends of the measurement passage communicate with the fuel tank and the fuel flows in the measurement passage. The temperature detector determines a temperature of the fuel in the fuel tank. The volatility calculator calculates a volatility of the fuel in the fuel tank based on the concentration of the evaporated fuel and the temperature of the fuel in the tank.

Abstract: A butterfly valve restricts flow passage areas of a purge passage and a blow-by gas passage by the same degree. A first pressure sensor detects variation in pressure of the purge gas, which is generated by the butterfly valve. A second pressure sensor detects variation in pressure of the blow-by gas, which is generated by the butterfly valve. Since a fuel vapor concentration of the blow-by gas is lower than that of the purge gas, the blow-by gas can be treated as air of 100%. Hence, the fuel vapor concentration is calculated based on the variations in pressure detected by the first pressure sensor and the second pressure sensor.

Abstract: A fuel vapor processing apparatus includes a canister, a purge passage, a detection passage including an atmosphere passage and a restrictor, a passage changing valve for changing the connection passage of the detection passage between the purge passage and the atmosphere passage, a pump connecting with the detection passage on the opposite side of the passage changing valve across the restrictor, a pressure sensor for detecting a pressure between the restrictor and the pump, and an ECU for computing the concentration of fuel vapor. When the passage changing valve causes the purge passage to connect with the detection passage and the pump reduces pressure in the detection passage to pass the air-fuel mixture through the restrictor, the pressure sensor detects the pressure during a detection period of time that elapses after the air-fuel mixture passes through the restrictor until the air-fuel mixture reaches the pump.

Abstract: A fuel vapor treatment apparatus connects with a fuel tank, which produces fuel vapor to be purged into an intake passage of an internal combustion engine through a purge passage. The fuel vapor treatment apparatus includes a state measuring unit that includes a measurement passage provided separately from the purge passage. When the measurement passage is blocked from the intake passage, the state measuring unit measures a state of fuel vapor by detecting a physical quantity of the fuel vapor in the measurement passage. The physical quantity is correlative to the state of fuel vapor. The fuel vapor treatment apparatus further includes a diagnosis unit for diagnosing a malfunction of at least one of components of the state measuring unit.

Abstract: When a gas flow producer is driven, plural kinds of gases flow into a measure-passage at respective timing. An orifice is provided in the measure-passage. The orifice has a diameter-changing portion which restricts a separation of gases from an inner surface of the measure-passage. A pressure sensor is provided in the measure-passage to detect a pressure determined by the orifice and the gas flow producer. A microcomputer calculates a density ratio between the gases based on the detected differential pressure.

Abstract: A sensor device is disclosed that includes a sensor, in which a resistance value is changed in accordance with a change in an environment of the sensor. The sensor device also includes a beat oscillator having plural oscillators of different oscillating frequencies. The beat oscillator generates a beat signal of a frequency lower than the oscillating frequencies. The beat signal corresponds to a difference of the oscillating frequencies. The beat oscillator is electrically connected to the sensor such that the frequency of the beat signal changes in accordance with the changes in the resistance value of the sensor.