US 4,995,258 A · Method for determining air mass in a crankcase scavenged two-stroke engine

Abstract

A method is described for determining the cylinder mass of air available for combustion in a crankcase scavenged, two-cycle engine, based upon the Ideal Gas Law relationship and indications of pressure, volume, and temperature of air in the crankcase chamber, at predetermined points in the engine operating cycle. This is achieved by first determining the mass of air trapped and compressed in a crankcase chamber, and thereafter, determining the residual air mass remaining in the crankcase after the transfer of air to the associated combustion chamber. Then, the actual air mass transferred to the combustion chamber is determined as a function of the difference between the trapped and residual air masses. Engine trapping efficiency can be used to correct for air leakage from the combustion chamber prior to cylinder exhaust port closure. The volume of the air within the crankcase chamber is derived as a function of engine cycle position, with crankcase air temperature being derived as a function of intake air temperature. Air pressure in the crankcase is monitored with a pressure transducer.

Claims14

Dependent claims

In a crankcase scavenged two-stroke engine characterized by an operating cycle including portions during which air is inducted into a crankcase chamber, is thereafter trapped and compressed within the shrinking volume of the crankcase chamber, and is then transferred to a combustion chamber;

a method for determining the mass of air transferred to the combustion chamber during the engine cycle, comprising the steps of:
deriving indications of the pressure P, volume V, and temperature T, of air within the crankcase chamber during the engine operating cycle;
determining the mass of air M.sub.T trapped in the crankcase chamber from indicated values of pressure P, volume V, and temperature T derived during that portion of the operating cycle when air is trapped and compressed within the crankcase;
determining the residual mass of air M.sub.R remaining in the crankcase chamber from indicated values of pressure P, volume V, and temperature T derived during that portion of the operating cycle after the transfer of air to the combustion chamber is substantially completed;
and
estimating the mass of air M transferred to the combustion by chamber as a function of the difference between the mass of air M.sub.T trapped within the crankcase chamber and the mass of air M.sub.R remaining within the crankcase chamber.

3 more elements

a method for determining the mass of air trapped in the combustion chamber during the engine cycle, comprising the steps of:
deriving indications of the pressure P, volume V, and temperature T, of air within the crankcase chamber during the engine operating cycle;
determining the mass of air M.sub.T trapped in the crankcase chamber from indicated values of pressure P, volume V, and temperature T derived during that portion of the operating cycle when air is trapped and compressed within the crankcase;
determining the residual mass of air M.sub.R remaining in the crankcase chamber from indicated values of pressure P, volume V, and temperature T derived during that portion of the operating cycle after the transfer of air to the combustion chamber is substantially completed;
estimating the mass of air M transferred to the combustion by chamber as a function of the difference between the mass of air M.sub.T trapped within the crankcase chamber and the mass of air M.sub.R remaining within the crankcase chamber;
determining a trapping efficiency value representing the percentage of the transferred mass of air M, which is trapped in the combustion chamber;
and
adjusting the transferred mass of air M in accord with the determined trapping efficiency value to provide a measure of the air mass trapped in the combustion chamber.

5 more elements

Dependencies are inferred from the claim text.

Method for determining air mass in a crankcase scavenged two-stroke engine

Life of this patent

Method for determining air mass in a crankcase scavenged two-stroke engine

Life of this patent

Abstract

Claims14