Method and device for introducing a carburetted mixture under pressure in a chamber of a two-stroke engine

Claim 1

A device for introducing a carburetted mixture under pressure into a chamber of a first cylinder of a two-stroke internal combustion engine, the device comprising a valve having a first end cooperating with a seat for closing a feed duct feeding the carburetted mixture into the chamber of the first cylinder, means for returning the valve, an assistance member comprising a separation element cooperating with one end of a stem of the valve opposite said first end, said assistance member separating a first volume and a second volume within each of which a pressure prevails, the separation element being displaceable and causing displacement of the valve under an action of a pressure difference between the pressure of the first volume and the pressure of the second volume, and means for connecting said feed duct to said first volume so that the pressure in said first volume is substantially equal to the pressure in said feed duct.

Claim 2

A device for introducing a carburetted mixture under pressure into a chamber of a first cylinder of a two-stroke internal combustion engine, the device comprising a valve having a first end cooperating with a seat for closing a feed duct feeding the carburetted mixture into the chamber of the first cylinder, means for returning the valve, an assistance member comprising a separation element cooperating with one end of a stem of the valve opposite said first end, said assistance member separating a first volume and a second volume within each of which a pressure prevails, the separation element being displaceable and causing displacement of the valve under an action of a pressure difference between the pressure of the first volume and the pressure of the second volume, and means for connecting said feed duct to said first volume so that the pressure in said first volume is substantially equal to the pressure in said feed duct.

Claim 3

A method for introducing a carburetted mixture under pressure into a chamber of a first cylinder of a two-stroke internal combustion engine, the method comprising the steps of closing a feed duct introducing the carburetted mixture into the chamber of the first cylinder by a valve having a first end cooperating with a valve seat of the feed duct, assisting a displacement of the valve by an assisting member comprising a separation element cooperating with an end of a stem of the valve opposite said first end and separating a first volume and a second volume within each of which prevails a pressure, allowing movement of the separation element under an action of a difference between the pressure of the first volume and the pressure of the second volume, connecting said first volume to said carburetted mixture feed duct so that the pressure in said first volume is substantially equal to the pressure in said feed duct, and providing a valve returning means for enabling a return to an initial position.

Claim 4

A method for introducing a carburetted mixture under pressure into a chamber of a first cylinder of a two-stroke internal combustion engine, the method comprising the steps of closing a feed duct introducing the carburetted mixture into the chamber of the first cylinder by a valve having a first end cooperating with a valve seat of the feed duct, assisting a displacement of the valve by an assisting member comprising a separation element cooperating with an end of a stem of the valve opposite said first end and separating a first volume and a second volume within each of which prevails a pressure, allowing movement of the separation element under an action of a difference between the pressure of the first volume and the pressure of the second volume, connecting said first volume to said carburetted mixture feed duct so that the pressure in said first volume is substantially equal to the pressure in said feed duct, and providing a valve returning means for enabling a return to an initial position.

Claim 7

The device as claimed in one of claims 1, 3 or 4, wherein means are provided for connecting said second volume to an element of the engine having a pressure relative to the pressure of the first volume so as to contribute to the displacement of the valve.

Claim 8

The device as claimed in one of claims 1, 3 or 4, wherein said internal combustion engine comprises at least a third cylinder with a crankcase pump and having a cycle advanced with respect to the cycle of the first cylinder, and wherein means are provided for connecting the crankcase pump of the third cylinder to said second volume.

Claim 9

The device as claimed in one of claims 1, 3 or 4, wherein said separation element is a membrane.

Claim 10

The device as claimed in one of claims 1, 3 or 4, wherein said separation element has a cross-sectional area greater than a cross-sectional area of the valve.

Claim 11

The device as claimed in one of claims 1, 3 or 4, wherein said feed duct comprises a fuel feed member.

Claim 12

The device as claimed in one of claims 1, 3 or 4, wherein said feed duct opens in a vicinity of a cylinder head of said first cylinder.

Claim 13

The device as claimed in one of claims 1 or 3 wherein said internal combustion engine comprises several cylinders, each of said cylinders having a crankcase pump fed with air through an air feed duct, and wherein said air feed duct comprises an element adapted for reducing the air intake, and wherein means are provided for connecting a portion of the air feed duct common to several cylinders and located downstream of said element adapted for reducing the air intake to the second chamber of the assistance member.