US2767695A - Exhaust port cleaner for internal combustion engine - Google Patents

Description

J. H. BUDD Oct. 23, 1956 EXHAUST PORT CLEANER FOR INTERNAL CCMBUSTIONENGINE Filed April" 22,-- 1955 nited States Patent EXHAUST PORT CLEANER FOR INTERNAL COIVIBUSTION ENGINE Joseph H. Budd, Port Chester, N. Y., assignor, by mesne iislsigfiments, to Textron Inc., a corporation of Rhode s an Application April 22, 1955, Serial No. 503,085 Claims. (Cl. 123-65) This invention relates to cylinders of internal combustion engines and is more particularly concerned with cylinders of Z-cycle internal combustion engines.

In conventional 2-cycle engines, the combustion mixture passes into the combustion chamber of the cylinder, during the downward or expansion stroke of the piston following the firing of the previously-charged combustion mixture, through an inlet or transfer port, or ports, communicating with the crank case. The exhaust of the fired combustion mixture takes place through an exhaust port, or ports, also during the downward stroke of the piston, the exhaust ports being opened a predetermined period before the inlet port is uncovered. It is common experience that residual carbonaceous deposits are formed at the rim of each exhaust port so that the time of opening of the exhaust ports in relation to the movement of the piston is changed, and the greater the deposit, the later the opening of the exhaust ports during the downward stroke of the piston. For proper functioning of the engine, the exhaust ports should open at a predetermined time in relation to piston movement and delayed :opening of the exhaust ports reduces the efficiency of the engine and otherwise adversely affects engine operation. Modern fuels and lubricants contain various types of chemical additives which improve their characteristics, but these additives generally involve metallo-organic compounds which tend to leave a metallic residue or deposit upon combustion. In a 2-cycle engine, of course, not only the hydrocarbon fuel but also the crank-case lubricant enter the combustion chamber, and any deposits resulting from combustion of the chemical additives in the fuel and lubricant aggravate any blocking of the exhaust ports which normally occurs as a result of carbon deposition. Consequently the problem of keeping the exhaust ports clean and thus maintaining the time of opening of the exhaust ports in relation to the movements of the piston at the desired value is a very serious one.

Various attempts to overcome this problem have been made but, for the most part, these prior attempts have required periodic disassembly of the engine for cleaning purposes or have involved means which tend to interfere with the proper operation of the engine and are thus of questionable value from a practical standpoint.

It is the principal object of the present invention to provide, in the cylinder of an internal combustion engine having an exhaust port, means for automatically keeping the top or outer edge of the exhaust port clean.

It is a further object of the invention to provide means of the character indicated which are movable with the piston and etfect their cleaning action upon each piston stroke during the operation of the engine.

It is a further object of the invention to provide automatic cleaning means for the exhaust port in the cylinder of an internal combustion engine which is eifective during the normal operation of theengine without adverse eifect upon the engine and which eliminates the 2,767,695 Patented Oct. 23, 1956 need for taking down the engine to clean the exhaust port.

It is another object of the invention to provide a 2- cycle internal combustion engine having a self-cleaning exhaust port.

In accordance with the invention, there is provided a piston and cylinder assembly for a 2-cycle engine which is formed with an axial groove in the wall of the cylinder extending from each exhaust port toward the crank case, and in which each exhaust port has a top or outer edge which is defined by a relatively thin axially-extending lip, and the assembly is further provided With a corresponding slide member receivable in the groove and car ried by the piston. The groove is so formed that the leading edge of the slide member extends substantially to the outer edge of the exhaust port which determines the time of opening of the exhaust port when the piston is in its outermost position at the moment of maximum compression, i. e. the edge away from the crank case.

It is a feature of the invention that each slide member functions as a continuously-acting automatic cleaner by breaking up and dislodging any deposits which may tend to form at the exhaust port edge.

It is another feature of the invention that the continuously-repeated movements :of the slide member during each piston stroke so frequently dislodge deposits that appreciable deposits never have an opportunity to form.

It is another feature of the invention that the momentum of the piston moving in the cylinder is transferred to the slide member and thus dislodgment of the most stubborn deposit is insured.

It is a further feature of the invention that the exhaust port cleaning means of the invention in no Way interferes with proper operation of the engine and in no way damages the parts of the engine.

Other objects and features of the invention will be readily apparent from the following detailed description of an illustrative embodiment of an engine constructed in accordance with the invention and from the drawings, wherein Fig. 1 is a sectional view, partly in elevation, of an internal combustion engine piston and cylinder assembly embodying features of the present invention;

Fig. 2 is a bottom view of the assembly shown in Fig. l with the piston removed, Fig. 1 being taken along the line 1-1 of Fig. 2 and showing the piston in place;

Fig. 3 is a top plan view of the piston shown in Fig. l; and

Fig. 4 is a side elevational view of the piston of Figs. 1 and 3.

Referring LU the drawing, and more particularly to Fig. 1, the reference number 10 designates generally the cylinder and piston assembly of a 2-cycle internal combustion engine, including a cylinder unit 12 which is adapted to be connected with a crank case (not shown) in conventional manner, e. g., by bolting, bolt holes 13 in a bolting flange being provided for this purpose (Fig. 2). The cylinder unit 12 is formed with cooling fins 14, inlet or transfer ports 16 and exhaust ports 18. The cylinder unit 12 is formed in its .outer wall with an opening 20 which communicates with cylinder chamber 19 and in which is positioned bushing 22 which receives the spark plug 24 (partly shown).

Axially movable in the cylinder chamber 19 is a piston 30 formed with peripheral grooves 32 in which are seated the usual piston rings 34. As is customary in a 2-cycle engine, piston 30 has a crown which is provided with a baffle or deflector 35 of any convenient form to deflect the incoming charge and to obstruct its passage in the direction of the exhaust ports during the period in which the exhaust ports are open. The construction of the bafile 35 forms no part of the present invention. The piston 30 is carried in the usual way by a piston rod 36 which is adapted to be connected with the engine crank (not shown) in conventional manner.

As will be seen-by reference to Fig. l, the upper edge of each exhaust port 18 in accordance with the invention, is defined by the lower end of a tall or lip 40 which is defined by cutting away the exhaust port opening exteriorlyof tail 40 as shown in Fig. l. The axial length of lip 40 may vary, e. g. from 0.5 to mnx, but for the best results it should have an axial length of about 3 mm. The exhaust port upper edge defined by the lip 40 lies outwardly of the upper edges 42 of the inlet ports 16 by a predetermined distance a. As a result, the exhaust ports 18 are uncovered, during the expansion stroke of the piston, a predetermined moment in ad vance of the uncovering of the inlet ports through which the next combustion charge will enter. It is the accumulation of residual deposits on the upper edges of conventional exhaust ports which causes the problems which are avoided and solved by the construction of the present invention. Accumulation of deposits on the upper edges of the exhaust ports lowers these edges in the direction of the inlet port edges 42 so that the distance d is reduced and may even be eliminated. Consequently the advance opening of the exhaust ports during the expansion stroke is nullified and engine efiiciency is impaired. In extreme cases, the deposit obstructing the exhaust ports may become so great that the inlet ports are uncovered before the exhaust ports.

To solvethis problem, I provide an automatic exhaust port cleaner which, in the embodiment illustrated, takes the form of plates 45, which are carried by piston 30. As will be seen in Figs. 3 and 4, plates 45 which are conveniently rectangular in outline, have a curvature corresponding to the curvature of piston 30 and are secured to the piston in any suitable manner, as by rivets 46. The plates 45 are mounted on piston 30 in such manner that their upper edges 48 substantially reach the upper edges of the exhaust ports when the piston 3t) is in its maximum outward position at the end of the compression stroke, as shown in Fig. l. A slight clearance of, for example, 0.2 to 0.5 mm. is left to prevent mechanical engagement between the plates 45and the exhaust port edges. To accommodate the plates 45 during reciproca tion of piston 30, grooves 50 are formed in the walls of cylinder chamber 19 which extend from the bottom of the cylinder to the corresponding exhaust port 18. The circumferential dimensions of the plates 45 and of the grooves 50 are selected to correspond to the corresponding dimension of the exhaust port so that each groove 50 merges with its associated exhaust and each plate and each groove has a radial dimension which preferably corresponds to the radial dimension of the exhaust port lip 40, as shown in Fig. 1, although the lip 40 may, if desired, have a slightly smaller radial dimension than the associated plate 45. The radial dimension of the plates is advantageously 0.5 to 10 mm., preferably about 2 mm. The clearance between the plates 45 and their corresponding grooves 50 is the same as that normally present between the piston body and the wallet the associated cylinder, e. g. 0.05 to 0.2 mm. As seen in Figs. 2 and 3, the grooves 50 have the same general outline as that of, the plates.

I have found that plates 45 effect a'continuous, and fully effective cleaning action on the upper edges 40 of the exhaust ports 18 and keep them free from carbonaceous and metallic deposits which tend to form by reason of the residual matter formed during normal combustion of the charge to the engine cylinder. Although the upper edges of the plates 45 do not actually strike the upper edges of the exhaust ports, the plates move with such force and velocity that they shatter and dislodge any deposits which may tend to form and keep the exhaust ports clean. There is, of course, the possibility that there may be some accumulation of residual deposits in the upper portion 52 of the flared mouth 54 of the exhaust ports but this does not create the problem which arises upon obstruction of the upper edges of the exhaust ports since accumulation in portion 52 does not afiect the distance d and the time of opening of the exhaust ports during the expansion stroke of the piston.

It will be apparent to those skilled in the art that vari-- ous changes and modifications may be made in the embodiment of my invention which has been described and illustrated merely by way of example without departing from the scope of the invention as defined in the appended claims. It will be understood, for example, that a plate 45 is provided for each exhaust port and if the number of exhaust ports is greater or less than the number of ports in the embodiment illustrated, the number of plates will change accordingly. Similarly, although rivets are a convenient means of securing the plates to the piston, any other convenient means may be employed. Indeed, the plates 45 may be formed integrally with the piston if this should be desired although, from a practical standpoint, separately-secured plates will generally be found more convenient.

It will be understood, therefore, that I intend that all matter contained in the foregoing description and in the drawing shall be interpreted as illustrative only and not in a limiting sense.

What I claim and desire to secure by Letters Patent 1. In an internal combustion engine having a cylinder and a piston axially movable therein, said cylinder being formed with at least one exhaust port having an upper edge uncovered by the piston during the expansion stroke, means connected to said piston for dislodging deposits tending to accumulate on said upper edge, said means be ing aligned with said exhaust port and said cylinder being formed with a groove for receiving said means.

2. In an internal combustion engine having a cylinder and a piston axially movable therein, said cylinder being formed with at least one exhaust port having an upper edge uncovered by the piston during the expansion stroke, radially extending means carried by said piston for dislodging deposits tending to accumulate on said upper edge, said cylinder wall being formed with an axial groovebelow each exhaust port for receiving said means.

3. In an internal combustion engine having a cylinder and a piston axially movable therein, said cylinder being formed with at least one exhaust port having an upper edge uncovered by the piston during the expansion stroke, plate means secured to said piston for dislodging deposits tending to accumulate on said upper edge, said cylinder being formed with an axial groove below each exhaust port for slidably receiving said plate means upon reciprocation of said piston.

4. In an internal combustion engine having a cylinder and a piston axially movable therein, said cylinder being formed with at least one exhaust port having an upper edge uncovered by the piston during the expansion stroke, plate means secured to said piston for dislodging deposits tending to accumulate on said upper edge, said cylinder being formed with an axial groove below each exhaust port for slidably receiving said plate means upon reciprocation of said piston, said plate means being carried by said piston in such position that its outer edge substantially reaches but does not engage the outer edge of the exhaust port when said piston is in its outermost position.

5. In an internal combustion engine having a cylinder and a piston axially movable therein, said cylinder being formed with at least one exhaust port having an upper edgeuncovered by the piston during the expansion stroke, a plate carried by said piston for each exhaust port for dislodging deposits tending to accumulate on said upper edge, said cylinder being formed with an axial groove below each exhaust port and merging with it for slidably receiving each plate during its entire path of movement upon reciprocation of said piston, the circumferential and radial dimensions of said groove corresponding substantially to those of said plate.

6. In an internal combustion engine having a cylinder and a piston axially movable therein, said cylinder being formed with at least one exhaust port having an upper edge uncovered by the piston during the expansion stroke, a plate carried by said piston for each exhaust port for dislodging deposits tending to accumulate on said upper edge, said cylinder being formed with an axial groove below each exhaust port and merging With it for slidably receiving each plate during its entire path of movement upon reciprocation of said piston, the circumferential and radial dimensions of said groove corresponding substantially to those of said plate, said plate being carried by said piston in such position that its outer edge substantially reaches but does not engage the outer edge of the exhaust port when said piston is in its outermost position.

7. A cylinder and piston assembly for an internal combustion engine comprising in combination, a cylinder, a piston axially movable in said cylinder, said cylinder being formed with at least one exhaust port having an upper edge adapted to be uncovered by the piston during its expansion stroke, and means carried by the side of said piston for mechanically dislodging deposits tending to accumulate on said upper edge, said means being aligned with said exhaust port and said cylinder being formed with a groove for receiving said means.

8. A cylinder and piston assembly for an internal cornbustion engine comprising in combination, a cylinder, a piston axially movable in said cylinder, said cylinder being formed with at least one exhaust port having an upper edge uncovered by the piston during the expansion stroke, a plate carried by said piston for each exhaust port for dislodging deposits tending to accumulate on said upper edge, said cylinder being formed with an axial groove below each exhaust port and merging with it for slidably receiving each plate during its entire path of 6 movement upon reciprocation of said piston, the circuni ferential and radial dimensions of said groove corresponding substantially to those of said plate.

9. A cylinder and piston assembly for an internal combustion engine comprising in combination, a cylinder, a piston axially movable in said cylinder, said cylinder being formed with at least one exhaust port having a lip defining an upper edge uncovered by the piston during the expansion stroke, plate means secured to said piston for dislodging deposits tending to accumulate on said upper edge, said cylinder being formed with an axial groove below each exhaust port for slidably receiving said plate means upon reciprocation of said piston, said lip, said plate means and said groove having substantially uniform axial dimensions.

10. A cylinder and piston assembly for an internal combustion engine comprising in combination, a cylinder, a piston axially movable in said cylinder, said cylinder being formed with at least one exhaust port having a thin, axially-extending lip defining an upper edge uncovered by the piston during the expansion stroke, a plate carried by said piston for each exhaust port for dislodging deposits tending to accumulate on said upper edge, said cylinder being formed with an axial groove below each exhaust port and merging with it for slidably receiving each plate during its entire path of movement upon reciprocation of said piston, the circumferential and radial dimensions of said groove and the lip corresponding substantially to those of said plate.

References Cited in the file of this patent UNITED STATES PATENTS 1,473,688 Thomas Nov. 13, 1923 1,793,685 Edwards Feb. 24, 1931 1,798,399 Clark Mar. 31, 1931 2,056,080 Smith Sept. 29, 1936 2,058,526 Tanner Oct. 27, 1936 2,179,683 Brebeck Nov. 14, 1939 2,660,492 Lewis Nov. 24, 1953

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