Two-stroke engine and production series of two-stroke engines

Patent metadata

Field	Value
Publication number	US-10100718-B2
Application number	US-201615299340-A
Country	US
Kind code	B2
Filing date	Oct 20, 2016
Priority date	Oct 20, 2015
Publication date	Oct 16, 2018
Grant date	Oct 16, 2018

Abstract

A two-stroke engine has a cylinder and a transfer channel which, in the region at bottom dead center of a piston, establishes a flow connection between a crankcase interior and the combustion chamber. The crankcase has a crankcase connecting flange for connecting to the cylinder, which has a first connecting opening and a second connecting opening. The transfer channel passes into the crankcase at the first connecting opening or the second connecting opening. At the other of the first and second connecting openings, no transfer channel passes into the crankcase. For a production series of two-stroke engines, provision is made, in one two-stroke engine of the series, which has a first cylinder, for a second connecting opening to be closed off from the cylinder, and, in one two-stroke engine of the series, which has a second cylinder, for the first connecting opening to be closed off by the cylinder.

First claim

What is claimed is:

1. A two-stroke engine comprising: a cylinder defining a longitudinal cylinder axis and having a cylinder bore defining a combustion chamber formed therein; a piston delimiting said combustion chamber and being arranged in said cylinder so as to carry out a reciprocating back and forth movement therein between top dead center and bottom dead center; a discharge opening leading out of said combustion chamber and being controlled by said piston; a crankcase defining a crankcase interior; a crankshaft rotatably journaled in said crankcase so as to be rotatable about a crankshaft rotational axis; a connecting rod connected between said piston and said crankshaft so as to permit said piston to drive said crankshaft in rotation about said crankshaft rotational axis; at least one transfer channel configured to provide a flow connection between said crankcase interior and said combustion chamber when said piston is in a region of said bottom dead center thereof; said at least one transfer channel having a transfer window controlled by said piston; said at least one transfer channel opening into said combustion chamber via said transfer window; said crankcase having a crankcase connecting flange for connecting to said cylinder and said crankcase connecting flange defining a passthrough opening for said connecting rod; said crankcase connecting flange having at least one first connecting opening and at least one second connecting opening; said crankcase having a first fluid connection of said at least one first connecting opening with said crankcase interior and a second fluid connection of said at least one second connecting opening with said crankcase interior; said at least one first connecting opening and said at least one second connecting opening being arranged radially outside of said cylinder bore referred to said longitudinal cylinder axis; and, said at least one transfer channel passing into said crankcase at the at least one first connecting opening or at the at least one second connecting opening and, at the other one of said at least one first connecting opening and said at least one second connecting opening, there is no transfer channel passing into said crankcase.

2. The two-stroke engine of claim 1 , wherein:
said two-stroke engine is dividable into four sectors running parallel to said cylinder longitudinal axis;
a first one of said sectors contains at least one of said transfer windows of at least one of said at least one transfer channels;
a second one of said sectors contains said discharge opening;
said at least one first connecting opening is arranged in said first sector; and,
said at least one second connecting opening is arranged in said second sector.

3. The two-stroke engine of claim 1 , wherein said passthrough opening is connected with at least one of said at least one first connecting openings.

4. The two-stroke engine of claim 3 , wherein:
said crankcase connecting flange has a recess;
said at least one of said at least one first connecting openings is configured at said recess; and,
said recess has a total height (h) and is open to said crankcase interior over said total height (h).

5. The two-stroke engine of claim 1 , wherein said at least one second connecting opening is separated by a strut from said passthrough opening and is connected via a channel segment to said crankcase interior.

6. The two-stroke engine of claim 1 , wherein said two-stroke engine defines a center plane containing said cylinder longitudinal axis; and, said center plane is arranged perpendicularly to said crankshaft rotational axis.

7. The two-stroke engine of claim 6 , wherein:
there are at least two of said transfer channels and at least two of said transfer windows corresponding to respective ones of said at least two transfer channels;
said at least two transfer windows are arranged on mutually opposite sides of said center plane; and,
said at least two transfer channels run symmetrically with respect to said center plane.

8. The two-stroke engine of claim 6 , wherein precisely one of said at least one second connecting opening is provided and which is intersected by said center plane.

9. The two-stroke engine of claim 6 , wherein said crankcase has a first crankcase component and a second crankcase component which are connected to each other on a partition plane running parallel to said center plane.

10. The two-stroke engine of claim 9 , wherein said partition plane is at a distance (c) to said center plane.

11. A two-stroke engine comprising: a cylinder defining a longitudinal cylinder axis and having a cylinder bore defining a combustion chamber formed therein; a piston delimiting said combustion chamber and being arranged in said cylinder so as to carry out a reciprocating back and forth movement therein between top dead center and bottom dead center; a discharge opening leading out of said combustion chamber and being controlled by said piston; a crankcase defining a crankcase interior; a crankshaft rotatably journaled in said crankcase so as to be rotatable about a crankshaft rotational axis; a connecting rod connected between said piston and said crankshaft so as to permit said piston to drive said crankshaft in rotation about said rotational axis; at least one transfer channel configured to provide a flow connection between said crankcase interior and said combustion chamber when said piston is in the region of said bottom dead center thereof; said at least one transfer channel having a transfer window controlled by said piston; said at least one transfer channel opening into said combustion chamber via said transfer window; said crankcase having a crankcase connecting flange for connecting to said cylinder and said crankcase connecting flange defining a passthrough opening for said connecting rod; said crankcase connecting flange having at least one first connecting opening and at least one second connecting opening; said at least one first connecting opening and said at least one second connecting opening being arranged radially outside of said cylinder bore referred to said longitudinal cylinder axis; said at least one transfer channel passing into said crankcase at the at least one first connecting opening or at the at least one second connecting opening and, at the other one of said first and second connecting openings, there is no transfer channel passing into said crankcase; wherein said two-stroke engine defines a center plane containing said cylinder longitudinal axis; wherein said center plane is arranged perpendicularly to said crankshaft rotational axis; and, wherein there are two of said transfer windows arranged in a first sector; said at least one first connecting opening has a width (e) measured parallel to said center plane; said transfer windows each have a width (f, g); and, said width (e) of said at least one first connecting opening is at least 1.5 times said width (f, g) of one of said transfer windows.

12. The two-stroke engine of claim 1 , further comprising first and second crankshaft bearings; said crankshaft is rotatably journaled in said crankshaft bearings; said crankshaft bearings are at a distance (a) away from each other measured parallel to said crankshaft rotational axis; said at least one second connecting opening has a width (d) measured parallel to said crankshaft rotational axis; and, said width (d) of said at least one second connecting opening is less than said distance (a) between the crankshaft bearings.

13. A production series of two-stroke engines comprising:
at least a first cylinder and at least a second cylinder;
at least one crankcase which can be assembled onto said first cylinder or

Assignees

• Stihl Ag & Co Kg Andreas

Inventors

• Thoelking Hannah

Classifications

• F02F7/0082

  Mounting of engine casings · CPC title

• F02F7/0036

  Casings for two-stroke engines with scavenging conduits · CPC title

• F02F7/0004

  Crankcases of one-cylinder engines · CPC title

• F02B33/44

  Passages conducting the charge from the pump to the engine inlet, e.g. reservoirs · CPC title

• F02B33/04 Primary

  with simple crankcase pumps, i.e. with the rear face of a non-stepped working piston acting as sole pumping member in co-operation with the crankcase · CPC title