Intake air meter for an internal combustion engine
US4815324A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 15, 1987 |
| Grant date | Mar 28, 1989 |
| Priority date | — |
| Expiry date | Apr 15, 2007 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01F1/3282
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
An intake air meter for measuring the intake air of an internal combustion engine operates on the principle of an ultrasonic Karman vortex flowmeter. A Karman vortex shedder is disposed in the main intake air passageway of an engine. Ultrasonic waves which are generated by an ultrasonic transmitter are phase modulated by the Karman vortex street which is shed by the vortex shedder. An ultrasonic receiver receives the ultrasonic waves and produces a phase modulated output signal, which is demodulated using a phase locked loop and a low-pass filter. The output of the low-pass filter can be used to count the rate of which Karman vortices are generated by the vortex shedder. A pressure-dependent component in the output signal from the low-pass filter which is caused by pressure variations within the main intake air passageway is removed by compensating means comprising a pressure sensor which measures the air pressure in the vicinity of the vortex shedder, an amplifier which amplifies the AC component of the output of the pressure sensor to equal the amplitude of the pressure-dependent component, an inverter which inverts the amplified output, and a waveform shaper which sums the inver…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.