Two-cycle combustion engine with air scavenging system having pressure reducing device

1. In a two-cycle combustion engine with an air scavenging system, the improvement of a pressure reducing device, in the combustion engine, comprising:

a delivery passage for introducing air into a combustion chamber prior to an air-fuel mixture, the delivery passage having a downstream opening through which the air is introduced into the combustion chamber by way of a scavenging port; and

a decompressing hole defined for communicating the combustion chamber to a portion of the delivery passage;

the decompressing hole being closed by a piston then ascending, at a timing delayed relative to closure of an exhaust port, wherein the decompressing hole is defined at a position confronting the exhaust port.

2. The two-cycle combustion engine with the air scavenging system as claimed in claim 1 , further comprises a cylinder block, a fuel supplying device and an insulator provided between the fuel supplying device and the cylinder block, and wherein the decompressing hole is disposed in the cylinder block at a location confronting to the insulator so that removal of the insulator can result in exposure of the decompressing hole.

3. The two-cycle combustion engine with the air scavenging system as claimed in claim 2 , the decompressing holes is employed in a plural number.

4. The two-cycle combustion engine with the air scavenging system as claimed in claim 1 , wherein the decompressing hole is oriented upwardly towards the combustion chamber.

5. The two-cycle combustion engine with the air scavenging system as claimed in claim 1 , further comprising a first scavenging passage communicating the combustion chamber to a crank chamber for supplying an air-fuel mixture within the crank chamber towards the combustion chamber, and a second scavenging passage fluidly connected with the downstream opening of the delivery passage for supplying an air, introduced into the delivery passage, towards the combustion chamber.

6. The two-cycle combustion engine with the air scavenging system as claimed in claim 5 , wherein the second scavenging passage communicates the combustion chamber with the crank chamber through a crankshaft bearing.

7. The two-cycle combustion engine with the air scavenging system as claimed in claim 5 , further comprising an air passage for introducing the air into the delivery passage and wherein the delivery passage extends from the air passage to the second scavenging passage after having passed radially outwardly of the first scavenging passage.

8. In a two-cycle combustion engine with an air scavenging system, the improvement of a pressure reducing device, in the combustion engine, comprising:

a delivery passage formed in a cylinder block for introducing air into a combustion chamber prior to an air-fuel mixture, the delivery passage having a downstream opening through which the air is introduced into the combustion chamber by way of a scavenging port;

a decompressing hole defined for communicating the combustion chamber to a portion of the delivery passage, the decompressing hole being closed by a piston then ascending, at a timing delayed relative to closure of an exhaust port; and

a lid member for covering a portion of the delivery passage, which is exposed bare to an outside when the lid member is removed.

9. The two-cycle combustion engine with the air scavenging system as claimed in claim 8 , wherein the decompressing hole is disposed in the cylinder block at a location such that removal of the lid member can result in exposure of the decompressing hole.

10. The two-cycle combustion engine with the air scavenging system as claimed in claim 9 , further comprising a fan drivingly coupled with a crankshaft of the combustion engine for producing a stream of air and wherein the decompressing hole is defined in a portion block close to the fan.

11. In a two-cycle combustion engine with an air scavenging system, the improvement of a pressure reducing device in the combustion engine, comprising:

a delivery passage for introducing air into a combustion chamber prior to an air-fuel mixture, the delivery passage having a downstream opening through which the air is introduced into the combustion chamber by way of a scavenging port;

a decompressing hole defined for communicating the combustion chamber to a portion of the delivery passage, the decompressing hole being closed by a piston then ascending, at a timing delayed relative to closure of an exhaust port;

a first scavenging passage communicating the combustion chamber to a crank chamber for supplying an air-fuel mixture within the crank chamber towards the combustion chamber; and

a second scavenging passage fluidly connected with the downstream opening of the delivery passage for supplying an air, introduced into the delivery passage, towards the combustion chamber.

12. The two-cycle combustion engine with the air scavenging system as claimed in claim 11 , wherein the second scavenging passage provides communication between the combustion chamber and the crank chamber through a crankshaft bearing.

13. The two-cycle combustion engine with the air scavenging system as claimed in claim 11 , further comprising an air passage for introducing the air into the delivery passage and wherein the delivery passage extends from the air passage to the second scavenging passage after having passed radially outwardly of the fist scavenging passage.

14. The two-cycle combustion engine with the air scavenging system as claimed in claim 11 , wherein the decompressing hole is oriented upwardly towards the combustion chamber.