Piston for a two-stroke engine operating with advanced scavenging and a two-stroke engine

Patent metadata

Field	Value
Publication number	US-10344707-B2
Application number	US-201715682343-A
Country	US
Kind code	B2
Filing date	Aug 21, 2017
Priority date	Aug 19, 2016
Publication date	Jul 9, 2019
Grant date	Jul 9, 2019

Abstract

A piston for a two stroke engine which operates with advanced scavenging has a piston base and a piston skirt. The center axis of the piston skirt forms a longitudinal center axis of the piston. The piston has two piston pin eyes, in which piston pin receptacles are configured. The center axis of the piston pin receptacles forms a transverse axis of the piston. The piston has at least one piston pocket. At least one piston pin eye is connected via at least one connecting rib to the piston skirt. Here, the connecting rib runs on that side of the piston pocket which faces away from the piston base.

First claim

What is claimed is:

1. A piston for a two-stroke engine operating with advanced scavenging, the piston comprising:
a piston base;
a piston skirt;
said piston skirt defining a first center axis;
said first center axis forming a longitudinal center axis of the piston;
the piston having two piston pin eyes defining a second center axis;
said second center axis defining a transverse axis;
said two piston pin eyes having piston pin receptacles formed therein;
the piston defining a middle plane containing said longitudinal center axis of the piston;
said middle plane being perpendicular to said transverse axis;
the piston having at least one piston pocket;
at least one connecting rib connecting at least one of said two piston pin eyes to said piston skirt;
said piston defining an inner space enclosed by said piston skirt;
said at least one connecting rib running within said inner space of said piston;
said at least one piston pocket having a first side being disposed in spaced relationship to said piston base; and,
said at least one connecting rib being arranged on said first side of said piston pocket.

2. The piston of claim 1 , wherein a deepening is formed between said at least one connecting rib and said piston skirt.

3. The piston of claim 2 , wherein:
said deepening has a depth (c);
the piston has a height (h); and,
said depth (c) is at least 3% of said height (h).

4. The piston of claim 1 , wherein said at least one connecting rib runs parallel to said middle plane.

5. The piston of claim 1 , wherein:
the piston has a diameter (a);
said at least one connecting rib and said middle plane conjointly define a distance (d) therebetween; and,
said distance (d) is at least 20% of said diameter (a).

6. The piston of claim 1 , wherein:
the piston has a diameter (a);
each of said piston pin eyes has an end face;
said end faces of said piston pin eyes face each other;
said at least one connecting rib defines a distance (e) to a corresponding one of said end faces, said distance (e) being measured parallel to said transverse axis; and,
said distance (e) is at least 5% of said diameter (a).

7. The piston of claim 1 , wherein said piston pocket has a rear wall and said at least one connecting rib is arranged in an extension of said rear wall.

8. The piston of claim 1 , wherein said piston skirt has an edge facing away from said piston base.

9. The piston of claim 8 , wherein:
said at least one connecting rib has an end face facing away from said at least one piston pocket;
said end face and said edge define an offset (b) therebetween;
the piston has a height (h);
said offset (b) in the direction of the longitudinal center axis is less than 5% of said height (h) at every location of said end face.

10. The piston of claim 8 , wherein a deepening is formed between said at least one connecting rib and said piston skirt, the piston further comprising:
a web extending between said edge and said at least one piston pocket;
said web having a height (m) in a circumferential area of the piston in which said deepening is disposed;
said web has a smallest height (k); and,
said height (m) is at least 1.5 times said smallest height (k).

11. The piston of claim 1 , wherein said piston pin receptacles are at least partially arranged in said at least one piston pocket.

12. A piston for a two-stroke engine operating with advanced scavenging, the piston comprising:
a piston base;
a piston skirt;
said piston skirt defining a first center axis;
said first center axis forming a longitudinal center axis of the piston;
the piston having two piston pin eyes defining a second center axis;
said second center axis defining a transverse axis;
said two piston pin eyes having piston pin receptacles formed therein;
the piston defining a middle plane containing said longitudinal center axis of the piston;
said middle plane being perpendicular to said transverse axis;
the piston having a first piston pocket and a second piston pocket;
said first piston pocket and said second piston pocket are disposed on opposite sides of said middle plane;
a first connecting rib connecting one of said two piston pin eyes to said piston skirt and a second connecting rib connecting the other one of said two piston pin eyes to said piston skirt;
said first piston pocket and said second piston pocket each having a first side disposed in spaced relationship to said piston base; and,
said first connecting rib being arranged at said first piston pocket on said first side of said first piston pocket and said second connecting rib being arranged at said second piston pocket on said first side of said second piston pocket.

13. The piston of claim 1 , wherein the piston is made of a light metal.

14. A two-stroke engine comprising:
a piston having a piston pocket;
a cylinder having a cylinder bore;
a combustion chamber formed in said cylinder bore and delimited by said piston;
a crankcase defining a crankcase interior;
a crankshaft rotatably mounted in said crankcase;
said piston being configured to drive said crankshaft;
a transfer channel configured to connect said crankcase interior to said combustion chamber in at least one position of said piston;
an air channel configured for supplying advanced scavenging air;
said air channel opening at said cylinder bore with an air inlet;
said transfer channel having a transfer window; and,
said piston pocket being configured to lie so as to at least partially overlap with said air inlet and said transfer window in at least one position of said piston.

15. A piston for a two-stroke engine operating with advanced scavenging, the piston comprising:
a piston base;
a piston skirt;
said piston defining an inner space enclosed by said piston skirt;
said piston skirt defining a first center axis;
said first center axis forming a longitudinal center axis of the piston;
the piston having two piston pin eyes defining a second center axis;
said second center axis defining a transverse axis of the piston;
said two piston pin eyes having piston pin receptacles formed therein;
the piston defining a middle plane containing said longitudinal center axis of the piston;
said middle plane being perpendicular to said transverse axis;
the piston having at least one piston pocket;
at least two ribs extending in said inner space of said piston between said piston base and said piston skirt;
the piston having a top side;
said at least two ribs including a first rib having a first end facing away from said top side;
said first end being at a first distance (g) from said top side;
said at least two ribs including a second rib having a second end facing away from said top side;
said second end being at a second distance (o) from said top side measured parallel to said longitudinal center axis of the piston; and,
said distance (o) being smaller than said distance (g).

16. The piston of claim 15 , wherein:
the piston has an inlet side and an outlet side;
at least one of said at least two ribs extends at said outlet side; and,
at least one of said at least two ribs extends at said inlet side.

17. The piston of claim 16 , wherein:
the piston has two first ribs;
one of said two first ribs is disposed at said inlet side and another one of said two first ribs is disposed at said outlet side;
each of said two first ribs extends along said middle plane and is centrally intersected by said middle plane;
the piston has a plurality of second ribs; and,
said two first ribs each have a second rib dispose

Assignees

• Stihl Ag & Co Kg Andreas

Inventors

• Loew Birger
• Lank Jonas

Classifications

• F02F3/24 Primary

  having means for guiding gases in cylinders, e.g. for guiding scavenging charge in two-stroke engines · CPC title

• F02F3/0076

  the inside of the pistons being provided with ribs or fins · CPC title

• F02F3/0084 Primary

  the pistons being constructed from specific materials · CPC title

• F02B2075/025

  two · CPC title

• F02B75/02

  Engines characterised by their cycles, e.g. six-stroke · CPC title