Six-stroke engine and method of operating six-stroke engine

Patent metadata

Field	Value
Publication number	US-9945296-B2
Application number	US-201414902691-A
Country	US
Kind code	B2
Filing date	Jun 20, 2014
Priority date	Jul 9, 2013
Publication date	Apr 17, 2018
Grant date	Apr 17, 2018

Abstract

A six-stroke engine includes a cylinder, a piston, a cylinder head, a combustion chamber, an intake port, an exhaust port, an intake valve, an exhaust valve, a fuel injector, and an ignition plug. The six-stroke engine includes a valve gear that operates the intake valve and the exhaust valve to execute an intake stroke, a compression stroke with ignition, an expansion stroke with combustion, an exhaust stroke, an expansion stroke without combustion, and a compression stroke without ignition. The valve gear opens, only for a predetermined period of time while the piston is located at top dead center, at least one of the intake valve and the exhaust valve within a period from the exhaust stroke to the intake stroke. A valve overlap state is produced at least once within the period from the exhaust stroke to the intake stroke.

First claim

The invention claimed is:

1. A six-stroke engine comprising:
a cylinder;
a piston inserted into the cylinder and that reciprocates between a bottom dead center and a top dead center;
a cylinder head attached to the cylinder;
a combustion chamber defined by the cylinder, the piston, and the cylinder head;
an intake port in the cylinder head and including a downstream end open to the combustion chamber;
an exhaust port in the cylinder head and including an upstream end open to the combustion chamber;
an intake valve provided in the cylinder head and that opens/closes the intake port;
an exhaust valve provided in the cylinder head and that opens/closes the exhaust port;
a fuel injector that injects fuel into at least one of the combustion chamber and the intake port;
an ignition plug attached to a wall of the combustion chamber; and
a valve gear that operates the intake valve and the exhaust valve to execute six strokes including an intake stroke, a compression stroke with ignition, an expansion stroke with combustion, an exhaust stroke, an expansion stroke without combustion, and a compression stroke without ignition, in this order; wherein
within a period from the exhaust stroke to the intake stroke, the valve gear opens at least one of the intake valve that was closed in the exhaust stroke and the exhaust valve that was closed in the intake stroke only for a predetermined period of time, which includes a period when the piston is located on a side of the top dead center during a period from the exhaust stroke to the intake stroke, and then closes the at least one of the intake valve and the exhaust valve to produce a valve overlap state in which both the intake valve and the exhaust valve are open;
the valve overlap state is produced at least once within the period from the exhaust stroke to the intake stroke, and
the intake valve is closed during the exhaust stroke except for the predetermined period of time.

2. The six-stroke engine according to claim 1 , wherein the valve gear opens and closes the intake valve so as to produce the valve overlap state within a period of time after a position of the piston has passed a position of 90° after the bottom dead center in the exhaust stroke until the position of the piston reaches a position of 90° after the top dead center in the expansion stroke without combustion.

3. The six-stroke engine according to claim 1 , wherein the valve gear opens and closes the exhaust valve so as to produce the valve overlap state within a period of time after a position of the piston has passed a position of 90° after the bottom dead center in the compression stroke without ignition until the position of the piston reaches a position of 90° after the top dead center in the intake stroke.

4. The six-stroke engine according to claim 1 , wherein the valve gear opens and closes the intake valve so as to produce the valve overlap state within a period of time after a position of the piston has passed a position of 90° after the bottom dead center in the exhaust stroke until the position of the piston reaches a position of 90° after the top dead center in the expansion stroke without combustion, and opens and closes the exhaust valve so as to produce the valve overlap state within a period of time after the position of the piston has passed the position of 90° after the bottom dead center in the compression stroke without ignition until the position of the piston reaches the position of 90° after the top dead center in the intake stroke.

5. The six-stroke engine according to claim 1 , wherein, based on a rotation speed and a load of the engine, the valve gear operates in at least one of:
a first operation mode in which the intake valve is opened and closed so as to produce the valve overlap state within a period of time after a position of the piston has passed a position of 90° after the bottom dead center in the exhaust stroke until the position of the piston reaches a position of 90° after the top dead center in the expansion stroke without combustion; and
a second operation mode in which the exhaust valve is opened and closed so as to produce the valve overlap state within a period of time after the position of the piston has passed the position of 90° after the bottom dead center in the compression stroke without ignition until the position of the piston reaches the position of 90° after the top dead center in the intake stroke.

6. A method of operating a six-stroke engine including
a cylinder; —a piston inserted into the cylinder and that reciprocates between a bottom dead center and a top dead center; a cylinder head attached to the cylinder; a combustion chamber defined by the cylinder, the piston, and the cylinder head; an intake port in the cylinder head and including a downstream end open to the combustion chamber; an exhaust port in the cylinder head and including an upstream end open to the combustion chamber; an intake valve in the cylinder head and that opens/closes the intake port; an exhaust valve in the cylinder head and that opens/closes the exhaust port; a fuel injector that injects fuel into at least one of the combustion chamber and the intake port; and an ignition plug attached to a wall of the combustion chamber; the method comprising the steps of:
executing, for the engine, six strokes including an intake stroke, a compression stroke with ignition, an expansion stroke with combustion, an exhaust stroke, an expansion stroke without combustion, and a compression stroke without ignition, in this order; and
opening at least one of the intake valve that was closed in the exhaust stroke and the exhaust valve that was closed in the intake stroke only for a predetermined period of time, which includes a period when the piston is located on a side of the top dead center during a period from the exhaust stroke to the intake stroke, and then closing the at least one of the intake valve and the exhaust valve to produce a valve overlap state in which both the intake valve and the exhaust valve are open at least once during the period from the exhaust stroke to the intake stroke, the intake valve being closed during the exhaust stroke except for the predetermined period of time.

7. The method of operating a six-stroke engine according to claim 6 , wherein the valve overlap state is produced by opening and closing the intake valve within a period of time after a position of the piston has passed a position of 90° after the bottom dead center in the exhaust stroke until the position of the piston reaches a position of 90° after the top dead center in the expansion stroke without combustion.

8. The method of operating a six-stroke engine according to claim 6 , wherein the valve overlap state is produced by opening and closing the exhaust valve within a period of time after a position of the piston has passed a position of 90° after the bottom dead center in the compression stroke without ignition until the position of the piston reaches a position of 90° after the top dead center in the intake stroke.

9. The method of operating a six-stroke engine according to claim 6 , wherein the valve overlap state is produced:
by opening and closing the intake valve within a period of time after a position of the piston has passed a position of 90° after the bottom dead center in the exhaust stroke until the position of the piston reaches a position of 90° after the top dead center in the expansion stroke without combustion; and
by opening and closing the exhaust valve within a period of time after the position of the piston has passed the position of 90° after the bottom dead center in the compression stroke without ignition until the position of the piston reaches the position of 90° after the top dead center

Assignees

• Yamaha Motor Co Ltd

Inventors

• Tsukahara Ei

Classifications

• F02D13/0261 Primary

  Controlling the valve overlap · CPC title

• F01L1/047

  Camshafts · CPC title

• F02B1/00

  Engines characterised by fuel-air mixture compression (characterised by both fuel-air mixture compression and air compression, or characterised by both positive ignition and compression ignition F02B11/00) · CPC title

• F02B3/06

  with compression ignition (compression ignition engines using air or gas for blowing fuel into compressed air in cylinder F02B13/02) · CPC title

• F02B1/04

  with fuel-air mixture admission into cylinder · CPC title