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: An evaporative fuel treatment apparatus is disclosed that includes a fuel tank and a purge passage that fluidly couples the intake path of an internal combustion engine and the fuel tank. The apparatus also includes a purge valve that is installed in the purge passage and controls the quantity of evaporative fuel purged from the fuel tank into the intake path. Furthermore, the apparatus includes an evaporative fuel status measuring device that measures a density-based status of evaporative fuel in the fuel tank. Additionally, the apparatus includes a purge valve controlling device that controls the purge valve based on the density-based status of the evaporative fuel measured by the evaporative fuel status measuring device.

Abstract: A pump generates a gas flow within a measurement passage having an orifice. A differential pressure sensor detects a pressure difference between both ends of the orifice. Switching valves are disposed in the measurement passage to create a first concentration measurement state in which the measurement passage is opened at both ends thereof and the gas flowing through the measurement passage is the atmosphere, and a second concentration measurement state in which the measurement passage is in communication at both ends thereof with a canister and the gas flowing through the measurement passage is a fuel vapor-containing air-fuel mixture provided from the canister. An ECU calculates a fuel vapor concentration by based on a pressure difference detected in the first concentration measurement state and a pressure difference detected in the second concentration measurement state.

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 PCV valve is arranged in an outflow passage. An ECU controls rotation of a motor such that an opening degree of the PCV valve increases in response to an increase in an opening degree of a throttle valve. The outflow passage connects an interior of a head cover of an engine to a portion of an intake air passage located on a downstream side of the throttle valve. The outflow passage recirculates blow-by gas leaked from a combustion chamber into an interior of a crankcase to the portion of the intake air passage located on the downstream side of the throttle valve. An inflow passage connects the interior of the head cover to a portion of the intake air passage located on an upstream side of the throttle valve. The inflow passage conducts intake air from the intake air passage to the interior of the head cover.

Abstract: An evaporative fuel treatment system is disclosed that includes a canister, a detection passage having a reduced area portion, and switching device that switches fluid communication. Also included is a depressurizing device for depressurizing the detection passage coupled to the detection passage on a side of the reduced area portion opposite to the switching device, and a pressure detecting device. Moreover, the system includes an evaporative fuel state calculating device for calculating an evaporative fuel state in the mixture based on a cutoff pressure, an air pressure, and a mixture pressure of a mixture of air and the evaporative fuel. In one embodiment, the cutoff pressure, the air pressure, and the mixture pressure are detected independently and discontinuously. In another embodiment, the cutoff pressure and the air pressure are detected on a continual basis during purge of the evaporative fuel.

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.

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 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: 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 pump generates a gas flow within a measurement passage having an orifice. A differential pressure sensor detects a pressure difference between both ends of the orifice. Switching valves are disposed in the measurement passage to create a first concentration measurement state in which the measurement passage is opened at both ends thereof and the gas flowing through the measurement passage is the atmosphere, and a second concentration measurement state in which the measurement passage is in communication at both ends thereof with a canister and the gas flowing through the measurement passage is a fuel vapor-containing air-fuel mixture provided from the canister. An ECU calculates a fuel vapor concentration by based on a pressure difference detected in the first concentration measurement state and a pressure difference detected in the second concentration measurement state.

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 leakage inspection apparatus utilizes a fuel tank, an adsorption container which houses an adsorbent for adsorbing fuel vapor generated in the fuel tank, and an exhaust device for communicating between the adsorption container and an intake pipe. Furthermore, the apparatus utilizes a pressure means that pressurizes or depressurizes a fuel vapor path formed from the fuel tank through the adsorption container to the exhaust device. A leakage detection means detects leakage from the fuel vapor path after the fuel vapor path is pressurized or depressurized by the pressure means while a calculation means calculates an amount of fuel vapor adsorbed, and a control means determines if the pressure means should execute leakage inspection of the fuel vapor path in accordance with the amount of the fuel vapor calculated by the calculation means.

Abstract: A pump generates a gas flow within a measurement passage having an orifice. A differential pressure sensor detects a pressure difference between both ends of the orifice. Switching valves are disposed in the measurement passage to create a first concentration measurement state in which the measurement passage is opened at both ends thereof and the gas flowing through the measurement passage is the atmosphere, and a second concentration measurement state in which the measurement passage is in communication at both ends thereof with a canister and the gas flowing through the measurement passage is a fuel vapor-containing air-fuel mixture provided from the canister. An ECU calculates a fuel vapor concentration by based on a pressure difference detected in the first concentration measurement state and a pressure difference detected in the second concentration measurement state.

Abstract: An apparatus detects leak in a fuel vapor treatment system which is referred to as an evaporation system. The apparatus measures a required time T2 that is required for decreasing pressure in the evaporation system from P0 to P1 while opening a base leak hole that provides known amount of leak. Then, a required time T1 that is required for decreasing pressure from P0 to P1 is measured while closing the base leak hole. The apparatus compares the required times T1 and T2 in order to detect a leak other than the base leak hole. In this process, a specified coefficient that is defined in accordance with the base leak hole is taken into consideration. It is possible to detect the leak of the evaporation system with high accuracy even when the amount of remaining fuel is extremely large.

Abstract: A fuel vapor leakage inspection apparatus utilizes a fuel tank, an adsorption container which houses an adsorbent for adsorbing fuel vapor generated in the fuel tank, and an exhaust device for communicating between the adsorption container and an intake pipe. Furthermore, the apparatus utilizes a pressure means that pressurizes or depressurizes a fuel vapor path formed from the fuel tank through the adsorption container to the exhaust device. A leakage detection means detects leakage from the fuel vapor path after the fuel vapor path is pressurized or depressurized by the pressure means while a calculation means calculates an amount of fuel vapor adsorbed, and a control means determines if the pressure means should execute leakage inspection of the fuel vapor path in accordance with the amount of the fuel vapor calculated by the calculation means.

Abstract: A pump generates a gas flow within a measurement passage having an orifice. A differential pressure sensor detects a pressure difference between both ends of the orifice. Switching valves are disposed in the measurement passage to create a first concentration measurement state in which the measurement passage is opened at both ends thereof and the gas flowing through the measurement passage is the atmosphere, and a second concentration measurement state in which the measurement passage is in communication at both ends thereof with a canister and the gas flowing through the measurement passage is a fuel vapor-containing air-fuel mixture provided from the canister. An ECU calculates a fuel vapor concentration by based on a pressure difference detected in the first concentration measurement state and a pressure difference detected in the second concentration measurement state.

Abstract: A fuel vapor leakage inspection apparatus utilizes a fuel tank, an adsorption container which houses an adsorbent for adsorbing fuel vapor generated in the fuel tank, and an exhaust device for communicating between the adsorption container and an intake pipe. Furthermore, the apparatus utilizes a pressure means that pressurizes or depressurizes a fuel vapor path formed from the fuel tank through the adsorption container to the exhaust device. A leakage detection means detects leakage from the fuel vapor path after the fuel vapor path is pressurized or depressurized by the pressure means while a calculation means calculates an amount of fuel vapor adsorbed, and a control means determines if the pressure means should execute leakage inspection of the fuel vapor path in accordance with the amount of the fuel vapor calculated by the calculation means.

Abstract: An apparatus detects leak in a fuel vapor treatment system which is referred to as an evaporation system. The apparatus measures a required time T2 that is required for decreasing pressure in the evaporation system from P0 to P1 while opening a base leak hole that provides known amount of leak. Then, a required time T1 that is required for decreasing pressure from P0 to P1 is measured while closing the base leak hole. The apparatus compares the required times T1 and T2 in order to detect a leak other than the base leak hole. In this process, a specified coefficient that is defined in accordance with the base leak hole is taken into consideration. It is possible to detect the leak of the evaporation system with high accuracy even when the amount of remaining fuel is extremely large.

Abstract: When purge control of fuel vapor, which is released from a fuel tank and is then adsorbed and retained in a fuel adsorption layer of a canister, is performed through ON/OFF control of a purge valve, ON/OFF of a heater plate received in the canister is controlled based on a purge fuel vapor concentration estimated through air-fuel ratio control operation of an engine. In this way, a sensor for measuring the purge fuel vapor concentration of the fuel vapor conducted from the canister to an intake passage of the engine can be eliminated.