AU2010101401B4

AU2010101401B4 - Two Stroke Induction Ports

Info

Publication number: AU2010101401B4
Application number: AU2010101401A
Authority: AU
Inventors: Yi Bo Wu
Original assignee: Individual
Current assignee: Individual
Priority date: 2010-01-02
Filing date: 2010-12-13
Publication date: 2011-09-01
Anticipated expiration: 2018-12-13
Also published as: AU2010257317A1; AU2010101401A4

Abstract

A two-stroke internal combustion motor with one or more conventional pistons reciprocating within a block having one or more intake charging passages for each piston formed in the block adapted to transport a combustible charge from the crankcase to the combustion chamber; the charging passages, when viewed in a cross section perpendicular to the direction of piston travel at a portion of their length being openable to the combustion chamber via a port, characterized in that the charging passages have a lobe adjacent one end of their length; the lobe being open to the remaining length of the passage but not otherwise directly open to the combustion chamber via the port.

Description

2 Field of the Invention The present invention relates to two-stroke motors and in particular to the configuration of the charging ports and passages associated therewith in the block. Background of the Invention In recent years great attention has been paid to charging of combustion chambers of two-stroke (and 4 stroke) motors in an effort to increase efficiency and to obtain the maximum amount of power from each charge of combustible fuel introduced into the combustion chamber and hence each power stroke of the engine. Considerable effort has also been paid to reducing noxious emissions from internal combustion motors and in particular two-stroke internal combustion engines which have a reputation for polluting more than their 4 stroke equivalents. It ha% long been appreciated that the velocity, direction and pressure at which a charge is introduced into a combustion chamber and hence the distribution, orientation and concentration of cormbustible fuel and air within the combustion chamber is of critical importance. The charge's orientation with respect to left over spend gases and the spark plug is also of critical importance. Whilst much work has been directed towards charging or four-stroke rotors recent advances in relation to two-stroke motors have been the subject of less research. Often efficient charging of a combustion chamber and/or a decrease in noxious emissions is achieved by a trial and error process wherein the shape and orientation of various components is modified, not necessarily in response to a particular theory, and the results assessed. In this sense design of efficient, low emission, combustion chambers and associated charging ports is often seen as an "art" rather than necessarily a strict "science". Object of the Invention It is an object of the present invention to provide an intake or "charging" passage for a two-stroke motor which exhibits increased efficiency and/or lower ermisSions over prior art configurations. Short Summary of the Invention 3 According to the present invention there is provided a two-stroke internal combustion motor with one or more conventional pistons reciprocating within a block; there being one or more intake charging passages (for each piston) formed in the block adapted to transport a combustible charge from the crankcase to the combustion chamber; the charging passages, when viewed in a cross section perpendicular to the direction of piston travel at a portion of their length openable to the combustion chamber via a port, having a lobe of the passage adjacent one end of it is length (length being normal to the circumference of the bore); the lobe being open to the remaining area of the passage but not otherwise directly open to the combustion chamber via the port. According to a second aspect of the present invention the lobe comprises between 15 and 25% of the volume of the passage when viewed in such two dimensional cross-section adjacent the port . According to a third aspect of the present invention the blank end of the lobe is of radiused as opposed to angular in configuration. According to a fourth aspect of the present invention the lobe adjacent the port extends for 20% to 30% of the overall length of the port as measured along a radius to the bore According to a fifth aspect of the present invention the ratio of the width of the charging passage, as measured radially from the port openings to their radially outermost walls, to the length of the charging passage when viewed in a cross-section perpendicular to the direction of piston travel and adjacent its intake port is between 1: 4 and 1: 5 with the length of the lobe being included in the overall length. Brief Description of the Drawings One embodiment of the present invention will now be described with reference to the accompanying drawings in which: Figure 3 is a cross-section through a block of a single cylinder two-stroke motor having charging passages in accordance with the present invention; the cross section being perpendicular to the direction of piston travel and at the height of the intake port just below top dead centre. Figures 1 and 2 are each perspective views of a block similar to the block of figure 3 having charging passages in accordance with the present invention.

4 Preferred Mode of Car rying out the Invention One erbodiment Of the present invention will now he described with reference to the emltbodirmlents of figures 1, 2 and 3. Figure 3 depicts in cross section a block 1 of a single cylinder two stroke internal combustion motor having two intake charging passages 2. It will be observed that the depicted cross section is perpendicular to the direction of piston travel at a height on the block just below top dead centre so that the passages 2 are open to the bore 6 via charging ports 4 ; the ports being depicted as dotted radiused lines 4 in figure 1. It will be noted that the depicted block 1 is of the simple air cooled variety having peripheral cooling fins 3 peripherally radiating from the block. rhe charging passages 2 are adapted to transport a combustible charge from the crankcase (not shown) to the combustion chamber (not shown) in the conventional manner. The charging passages 2 however, in accordance with the present invention and when viewed in the depicted cross section adjacent ports 4, each have a lobe 5 adjacent one end of it their length (length being normal to the circumference of the bore and perpendicular to the direction of piston travel); the lobes being open to the remaining length of the passage but riot otherwise directly open to the combustion chamber via the ports 5. The lobes 5 comprise between 15 and 25% of the volume of the passage when viewed in such two dimensional cross-section and extend for 20% to 30% of the overall length of the port as measured along a radius to the bore. It will be noted that the blank ends 7 of the lobes are of radiused as opposed to angular configuration, it has been found that extension of the intake charging passages 2 past the actual port openings so as to form the depicted lobes results in decreased emissions as well as increased efficiency. I he relatively slimline configuration of the charging passages adjacent the charging ports as compared with prior art configurations also assists emissions and efficiency. The ratio of the width of the charging passages 2, as measured radially from the port openings to their radially outermost walls, to the length of the passages as measured along a radius to the bore should be between 1:4 and 2:5, 5 The same features as above described will be evident from figures 1 and 2 hereof using the same reference numerals for each integer/feature.

Claims

1. A two-stroke internal combustion motor with one or more conventional pistons reciprocating within a bore of a block having one or more intake charging passages for each piston formed in the block adapted to transport a combustible charge from the crankcase to the combustion chamber; the charging passages, when viewed in a cross section perpendicular to the direction of piston travel at a portion of their length being openable to the combustion chamber via a port, characterized in that the charging passages have a lobe adjacent one end of their length; the lobe being open to the remaining length of the passage but not otherwise directly open to the combustion chamber via the port: the lobe comprising an extension of the charging passage substantially along a circumferential path around the outside of the bore as opposed to along a radial path with respect to the cylinder bore; the radially outermost extension of the lobe from the )m eing 1 i c 11eer than 10% greater than that of the non lobe portion of the charging passage.

2. A two-stroke internal combustion motor in accordance with claim I wherein the lobe comprises between 15 and 25% of the volume of the passage when viewed in such two dimensional cross-section adjacent the port .

3. A two-stroke internal combustion motor in accordance with claim I wherein the blank end of the lobe is of concave inwardly facing radiused configuration as opposed to of angular configuration.

4. A two-stroke internal combustion motor in accordance with claim 1 wherein the lobe adjacent the port extends for 20% to 30% of the overall length of the port as measured along a radius to the bore

5. A two-stroke internal combustion motor in accordance with claim I wherein the ratio of the width of the charging passage to the length, along a radius to the bore, of the charging passage when viewed in a cross-section perpendicular to the direction of piston travel and adjacent the intake port is between 1: 4 and 1: 5 with the length of the lobe being included in the overall length. DATED this 1 8th day of August 2011.