Mixture-lubricated four-stroke engine

Patent metadata

Field	Value
Publication number	US-2019218961-A1
Application number	US-201916249693-A
Country	US
Kind code	A1
Filing date	Jan 16, 2019
Priority date	Jan 17, 2018
Publication date	Jul 18, 2019
Grant date	—

Abstract

A mixture-lubricated four-stroke engine has a cylinder and a piston. On the piston, at least one piston ring is arranged. Between valve drive chamber and crankcase interior, at least one first channel is arranged. The first opening of the first channel lies in the bottom dead center position of the piston below each piston ring. At the first opening, the first channel defines a first middle flow direction for mixture flowing into the crankcase interior. The first middle flow direction extends inclined towards the combustion chamber and in a viewing direction perpendicular to the cylinder longitudinal plane intersects the longitudinal center axis above the first opening of the first channel.

First claim

What is claimed is:

1 . A mixture-lubricated four-stroke engine comprising:
a cylinder; a piston; at least one piston ring arranged on said piston; said cylinder and said piston conjointly delimiting a combustion chamber; a piston pin; a crankpin; a connecting rod mounted on said piston pin and said crankpin; a crankcase defining a crankcase interior; a crankshaft arranged in said crankcase interior and defining a crankshaft axis; said piston being configured to drive said crankshaft via said connecting rod; an inlet valve; an outlet valve; a valve control for said inlet valve and said outlet valve; said crankshaft being configured to drive said valve control for said inlet valve and said outlet valve; a mixture preparation unit; an intake channel; said inlet valve being connected to said mixture preparation unit via said intake channel; a valve drive chamber; said crankcase interior being flow-connected to said intake channel via said valve drive chamber; at least one first channel being part of the flow-connection and being arranged between said valve drive chamber and said crankcase interior; said at least one first channel defining a first opening which opens into said crankcase interior and a second opening which opens into said valve drive chamber; said cylinder having a cylinder bore defining a longitudinal center axis; said longitudinal center axis and said crankshaft axis conjointly defining a cylinder longitudinal plane; said piston having a bottom dead center position; said first opening of said at least one first channel lying below each of said at least one piston ring in said bottom dead center position of said piston; said at least one first channel, at said first opening, defining a first middle flow direction for mixture flowing into said crankcase interior; and, said first middle flow direction extending inclined towards said combustion chamber and, in a viewing direction perpendicular to said cylinder longitudinal plane, intersecting said longitudinal center axis above said first opening of the at least one first channel.

2 . The four-stroke engine of claim 1 , wherein, in the viewing direction perpendicular to said cylinder longitudinal plane, said first middle flow direction encloses an angle α of at most 85° with said longitudinal center axis.

3 . The four-stroke engine of claim 1 , wherein said piston includes a piston skirt; and, said first middle flow direction in said bottom dead center position of said piston extends through a space enclosed by said piston skirt.

4 . The four-stroke engine of claim 1 , wherein said piston has a piston bottom; and, said first middle flow direction intersects said piston bottom in said bottom dead center position of said piston.

5 . The four-stroke engine of claim 1 , wherein:
said piston has a top dead center position; and, said first middle flow direction intersects said piston pin in said top dead center position of said piston.

6 . The four-stroke engine of claim 1 , wherein, in at least one piston position, a negative pressure in said crankcase interior is such that mixture from said intake channel is drawn in via said valve drive chamber through said at least one first channel into said crankcase interior.

7 . The four-stroke engine of claim 1 , wherein:
said at least one first channel has a first opening area at said first opening; and, said first opening area is greater than 5% of a cross-sectional area of said cylinder bore disposed perpendicularly relative to said longitudinal center axis.

8 . The four-stroke engine of claim 1 , wherein said at least one first channel, starting from said second opening of said at least one first channel, tapers towards said first opening of said at least one first channel.

9 . The four-stroke engine of claim 1 further comprising:
a second channel having a first second channel opening and a further second channel opening;
said crankcase interior and said valve drive chamber being flow-connected by said second channel; and,
wherein said first second channel opening of said second channel opens into said crankcase interior and said further second channel opening opens into said valve drive chamber.

10 . The four-stroke engine of claim 9 , wherein:
said second channel, at a center point of said first second channel opening, defines a second middle flow direction; and, said first middle flow direction and said second middle flow direction, in a viewing direction perpendicular to said cylinder longitudinal plane, enclose an angle β of at least 10°.

11 . The four-stroke engine of claim 9 , wherein:
said second channel, at a center point of said first second channel opening, defines a second middle flow direction; said piston has a top dead center position; and, said second middle flow direction, in said top dead center position of said piston, intersects said crankpin.

12 . The four-stroke engine of claim 9 , wherein:
said first opening of said first channel has a first center point; said first second channel opening of said second channel has a second center point; and, said first center point is at a shorter distance from said cylinder longitudinal plane than said second center point.

13 . The four-stroke engine of claim 9 , wherein:
said first opening of said first channel has a first center point; said first second channel opening of said second channel has a second center point; said crankshaft defines a crankshaft longitudinal plane disposed perpendicularly relative to said longitudinal center axis and containing said crankshaft axis; and, a distance of said crankshaft longitudinal plane to said first center point of the first opening of the first channel is greater than to said second center point.

14 . The four-stroke engine of claim 9 , wherein:
said piston has a top dead center position; said crankshaft defines a crankshaft longitudinal plane disposed perpendicularly relative to said longitudinal center axis and containing said crankshaft axis; said second channel, at a center point of said first second channel opening, defines a second middle flow direction; and, said second middle flow direction in the viewing direction perpendicular to the crankshaft longitudinal plane is inclined relative to said cylinder longitudinal plane in such a manner that a flow of the mixture flowing through said second channel into said crankcase interior has a directional component in the top dead center position which is directed against a movement direction of said crankpin.

15 . The four-stroke engine of claim 1 further comprising:
a seal;
a crankshaft bearing arranged in said crankcase between said crankcase interior and said valve drive chamber; and;
said crankshaft bearing being sealed via said seal.

16 . The four-stroke engine of claim 1 further comprising:
a third channel having a first third channel opening and a further third channel opening;
said crankcase interior and said valve drive chamber being flow-connected by said third channel; and,
wherein said first third channel opening opens into said crankcase interior and said further third channel opening opens into said valve drive chamber.

Assignees

• Stihl Ag & Co Kg Andreas

Inventors

• Groskopf Gordon
• Dangelmaier Manuel

Classifications

• F02B2075/027

  four · CPC title

• F01M1/04

  using pressure in working cylinder or crankcase to operate lubricant feeding devices · CPC title

• F02B33/30

  Control of inlet or outlet ports · CPC title

• F02B33/26 Primary

  Four-stroke engines characterised by having crankcase pumps · CPC title

• F01M3/00

  Lubrication specially adapted for engines with crankcase compression of fuel-air mixture or for other engines in which lubricant is contained in fuel, combustion air, or fuel-air mixture (separating lubricant from air or fuel-air mixture before entry into cylinder F01M11/08) · CPC title