Airflow sensor and control circuit
February 27, 2007. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.Patent ReferencesDigital thermodynamic flow-meter Intake air amount detecting system Signal linearizing circuit for internal combustion engines Skin friction gage for time-resolved measurements Gas-flow measuring apparatus and method Apparatus for converting analog-format signals to pulse-format signals Apparatus for measuring a flow rate of intake air for an engine Heat-wire type airflow quantity measuring apparatus Fuel control system for internal combustion engine Control system for an engine having an air intake passage InventorsAssigneeApplicationNo. 019968 filed on 02/27/1987US Classes:702/47, Pressure, resistive, or capacitive sensor73/118.2, Intake air flow73/204.14Including digital or pulse measuring circuitryExaminersPrimary: Lall, Parshotam S.Assistant: Melnick, S. A. Attorney, Agent or FirmInternational ClassG01F 001/68AbstractThe airflow sensor uses a flow sensing bridge having a thermal element which senses airflow as a function of electrical energy applied to the bridge. Energy is applied to the bridge to maintain the thermal element at a constant temperature and constant resistance. A differential amplifier monitors the balanced and unbalanced state of the bridge and controls the application of energy to the bridge to maintain a balanced state. A microcomputer with analog to digital converter senses the level of energy applied to the bridge and converts this energy level to a digital signal indicative of airflow. The raw digital signal is corrected using calibration lookup tables and thermal compensation correction tables in the microcomputer memory circuits. The microcomputer outputs a variable frequency signal indicative of the measured mass airflow. In the alternative to the differential amplifier, the bridge may be balanced using the microcomputer in a sample and hold voltage to current converter configuration.Field of SearchIncluding response characteristic or condition compensationWith distinct heating circuitry for a self-heated sensor Including digital or pulse measuring circuitry Including detail of feedback or rebalancing circuitry Intake air flow Analog input compared with static reference Linearization (e.g., nonlinear transfer characteristic compensates for nonlinear transducer) | |
