Patent ID: 7130738

Claim:
An apparatus for measuring oil aeration of an engine, comprising: an oil line connecting a hydraulic pump mounted at the engine and an oil gallery in a cylinder block of the engine; a density sensor mounted on the oil line and measuring oil density of the oil line; a pressure sensor mounted on the oil line and measuring oil pressure of the oil line; a temperature sensor mounted on the oil line and measuring oil temperature of the oil line; and a calculation unit calculating the oil aeration based on the oil density, the oil pressure, and the oil temperature respectively measured by the density sensor, the pressure sensor, and the temperature sensor, wherein said calculation unit is programmed to execute instructions for: calculating density ρ 0 of pure oil based on measured oil pressure P and measured oil temperature T; calculating density ρ a of air based on measured oil pressure P and measured oil temperature T; and calculating oil aeration Ψ based on the measured oil density {overscore (ρ)}, measured oil pressure P, the calculated density ρ 0 of pure oil, and the calculated density ρ a of air; wherein the calculation unit is further programmed to calculate the oil density ρ 0 as ρ 0 (P,T)=ρ 0 (P 0 ,T 0 )+γΔP−βΔT, where in ρ 0 (P 0 ,T 0 ) is the oil density at a predetermined temperature T 0 and a predetermined pressure P 0 , β is a thermal expansion coefficient of pure oil, and γ is a compression ratio of pure oil and a gas constant R of air.