The field of this invention is two stroke engines and, more particularly, relates to an air intake porting configuration that allows an increased cylinder bore and facilitates a corresponding power increase for a given exterior cylinder dimension.
In an effort to get more power out of a given frame size for a two stroke engine, one readily apparent way is to simply increase the bore of the cylinders. As a result, the power output increases by the square of the ratio of the new bore divided by the previous bore. The problem with doing this is that the throws on the crankshaft have given spacing, and the enlargement of the bore forces an increase in external dimensions of the cylinder. The existing block may also define limits to any desired increase of the bore, depending on the available spacing between the existing bores, for instance. The problem with expanding the bore size of two stroke engines is that air intake passages to the cylinder require a fair amount of space, because of their location. In the past, air was introduced through passages extending from the crank end of the power cylinder to the intersection of the intake ports with the main bore of the cylinder. Another way was to build an air chest into the engine block around the intake ports for the cylinder. However this method would substantially increase the size of the engine block, which increases the weight of the engine and may not be compatible with the given engine bay, for instance.
While a wholly new engine could be designed, such a process can be expensive and time consuming. It is clearly desirable if the bore size can be increased without major changes to the basic engine structure. In accordance with certain embodiments, the present invention provides methods and apparatus to increase the bore sizes of a given engine design without significant changes to the frame or crankshaft. The invention is put into perspective by a quick review of two stroke engine basics, shown in
Referring to
As will be described below, the present invention, in accordance with certain embodiments, reconfigures the intake air routing to make use of the space formerly occupied by passage 28 to accommodate a bigger piston so that the cylinder housing 14 will fit on the same connection to the block 38. This is made possible by routing the air inlet through the piston skirt, as will be explained below. As will also be explained below, the position adjustment mechanism for the piston will also be explained. This mechanism adjusts the piston position axially without need to rotate the piston.
In accordance with certain embodiments, a two stroke engine of a particular configuration can have its power output increased via a larger cylinder bore and by using ports in the piston skirt through which to conduct compressed air within the skirt through short passages in the cylinder housing that conduct the air from within the skirt to above the piston. As a result, a larger piston can be used for the same spacing and opening size in the block, reducing the need to redesign the block and the crankshaft, for instance. A position adjuster for the piston moves it axially without rotation of the piston ports out of alignment with inlet ports in the housing. The piston rod is held in the crosshead using a flat to prevent rotation while an adjuster nut that is turned creates axial movement in the piston rod with a lock nut securing the final piston position.
These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
Referring to exemplary embodiment of the present invention illustrated in
It is beneficial if the piston position adjustment is able to move the piston 42 axially without rotating it, so as not to misalign circumferentially openings 44 in the skirt 52 with inlets 48 on cylinder housing 58. As shown in
Those skilled in the art will appreciate that the elimination of the air intake passage outside the piston skirt has allowed the piston to take up that space to increase its size for a given opening in the block. For that reason the block and crank don't need to be redesigned and a given engine frame and crank can accommodate a bigger piston to increase the power output. The larger piston now directs the compressed air from within its skirt though skirt openings. As the piston rises the skirt openings come up to align with the openings 48 in passages 46 in the cylinder housing 58. The compressed air passes from below piston 42 to above it. The difference in the designs is that the porting of the air through the skirt 52 allows the piston 42 to occupy space formerly used for air passages 28. As a result, the larger piston 42 can be accommodated in the same mount on an existing block. Additional power output is possible from a known engine block and crankshaft combination. Thus assuming the remaining components can deal with the additional power produced the need for a total redesign to get more power is avoided. What results is the ability to increase piston size to the size of the opening in the block by eliminating air passages outside the skirt and taking advantage of the volume within the skirt to hold the compressed air and deliver it at the proper time when ports are in alignment.
The adjuster mechanism allows axial adjustment of the piston 42 without rotating it so that ports 44 stay in circumferential alignment with inlets 48 while the needed clearance is obtained to set the proper compression ratio with the piston at top dead center.
The above description is illustrative of the preferred embodiment and many modifications may be made by those skilled in the art without departing from the invention whose scope is to be determined from the literal and equivalent scope of the claims below.
Again, the above description is illustrative of exemplary embodiments, and many modifications may be made by those skilled in the art without departing from the invention whose scope is to be determined from the literal and equivalent scope of the claims below.
This application is a continuation of U.S. patent application Ser. No. 11/779,004, filed on Jul. 17, 2007, which is hereby incorporated by reference in its entirety, which is a continuation of U.S. patent application Ser. No. 11/367,136, filed on Mar. 3, 2006, and issued as U.S. Pat. No. 7,258,087, on Aug. 21, 2007, which is hereby incorporated by reference in its entirety.
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Number | Date | Country | |
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20090283081 A1 | Nov 2009 | US |
Number | Date | Country | |
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Parent | 11779004 | Jul 2007 | US |
Child | 12509336 | US | |
Parent | 11367136 | Mar 2006 | US |
Child | 11779004 | US |