US3334618A - Four stroke high r.p.m. internal combustion engine for racing purposes - Google Patents

Description

C3. FUNICIELLQ FOUR STROKE HIGH R.P.M.

Aug. 8, 1%"? 3,334,313 INTERNAL COMBUSTION ENGINE FOR RACING PURPOSES 2 Sheets-Sheet 1 Filed. May 14,-1965.

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ataya FUNHCIELLO wmm PM. INTERNAL COMBUSTION ENGINE FOR RACING PURPOSES Aug. 8, 1967 Q FOUR STROKE HIGH R.

2 Sheets-Sheet 2 Filed May 14, 1965 FME PME

PME 00 a s I (X 1 5 INVENTOR- oRH 11c FwpIC/ELLO BY 1 n 3 3 United States Patent 11 Claims. (Cl. 123-75) This invention relates to a four stroke, high r.p.m. internal combustion engine, for racing purposes. In more detail, the invention firstly concerns a lift diagram of inlet and exhaust valves for such engines.

As well known from the literature, the following requirements are to be met for attaining a high specific horsepower: a decrease in the volume and extension of the combustion chamber, thus increasing the so called compactness thereof (defined as the ratio of chamber volume to the area of surface by which the chamber is defined), an increase in the sizes of inlet and exhaust valves; attainment of a good turbulene in the combustion chamber.

In four stroke engines for racing purposes, to which the invention is particularly related, the above requirements are partly met by having recourse to very small piston displacements, i.e. by subdividing the total swept volume into a large number of cylinders. However, such solution results in a number of drawbacks, as: a lower mechanical efficiency, a lower thermal efiiciency, a greater weight, a greater bulk, increased likelihood of troubles and misadjustments, and finally a higher cost.

The ideal solution would be one providing a highly compact combustion chamber, a large valve size and a good turbulence, by simple and reliable means, without having recourse to a large number of cylinders resulting in excessive splitting of total swept volume.

The main purpose of this invention consists in the provision of a design which provides high specific horsepowers by improving the combustion chamber compactness, the turbulence and the size of valve ports, Without having recourse to an excessive splitting-up of the total swept volume, by merely acting on the lift diagram of inlet and exhaust valves, in combination with a very small value of the strokezbore ratio, and with a particular shape of piston dome.

In more detail, the invention proposes to have one or more overhead valves closed or nearly closed at to dead center, in order to allow the piston dome to contact or nearly contact the valve heads at top dead center. Thus, the space that is taken-up by the burning mixture is much smaller than the conventional hemispheric one, which, in the high r.p.m. versions for racing purposes, essentially consists in the space that is leftover, at the top dead center, between the valve and piston dome, and that is necessarily takenup, at overlapped opening of valves at top dead center, by the valves, which at this moment are wide open in a conventional high rpm. engine. That is, while in the latter engine the expanding products of the combustion are compressed essentially in the space which is taken-up by the valves at the top dead center (i.e. that of exhaust stroke end), thereby providing the overlap, in the novel engine of the present invention, the gases are squished from such space (related to one or more valves), and forced into a space that is much smaller than the heads of these valves.

Thus, the magnitude of the actual combustion chamber in the novel engine of the present invention is not depend ent on valve size, whereby recourse can be made to very large valves, fitted in ports that are unusually large with respect to valve stroke, thus obtaining also the well known 3,334,618 Patented Aug. 8, 1967 advantages associated with the very short strokes. The

valves that in the novel engine are closed (or nearly closed) at top dead center and will thereby take-up a portion of opening diagram smaller (by approximately 30%) than in a conventional diagram. However, this reduction is more than balanced by their much greater valve size or geometric section (that may be, in total, double the conventional one).

Moreover, according to a further proposal of the invention, the overlapped intake and exahust openings at top dead center (advance of the inlet opening and scavenging of combustion chamber due to action of exhaust gases) is performed by having the valves, that are closed precisely at the instant of top dead center, again openedbefore or after top dead center, according to the function (inlet or exhaust) of same valves. Otherwise stated, the inlet valve is partially open directly before top outer dead center, and closed again when same center is attained, Whereafter it is wholly opened for the entire time of inlet stroke. Similarly, the exhaust valve is closed at the same dead center, whereafter it is partly opened, and is definitely closed as soon as the pressure in the cylinder is reduced to a value lower than that in the exhaust manifold. In other words, it may be conceived that a maximum is attained by the opening diagram of inlet valve, when the latter valve is additionally opened, while a minimum is attained in the same diagram at the top dead center (which minimum may correspond, e.g., to a zero value of the opening of the valve), whereafter a new maximum distinctly higher than the preceding one is attained after top dead center. By such form of the additional opening diagram, the maximum opening is attained during the additional opening. However, it is to be understood that any other form of additional opening diagram will fall in the range of the invention, on condition that the noun erical requirements, as stated later on, are met. Thus, e.g., the value of maximum of the extra-opening may be equal to the minimum which is attained at the top dead center.

As stated previously, the closing at top dead center may also not be complete, and in such a position, the valve head may be drawn away from its seat by a maximum distance on the order of a few millimeters.

In addition to such additional openings, the overlap may be performed even by other valves, facing the compact combustion chamber, and thus having a conventional opening diagram. Obviously, recourse may be made to a combination of additional opening and conventional valves, as well as to either solution, according to particular operational requirements.

To sum up; the invention proposes to have the well known squish phenomenon realized on one or more valves, by having the opening thereof drastically restricted at the top dead center, without however restricting the opening of said valves before, and after same top dead center; and by the use of further valves, in combination with these valves, but having a conventional opening diagram.

The squish was heretofore present either on stationary sections of head, or even on the valves, being permitted by the fact that the engine, not of the high r.p.rn. type, has a small overlap, and thus a small valve opening at top dead center. Conversely, the novel motor entails a substantial change in the distribution diagram, since it has a large overlap, and simultaneously one or more valves closed, or nearly closed at top dead center, as a result of the above-described additional openings, and by the presence of further valves, having conventional opening diagrams, i.e. diagrams different from those of valves that are closed at top dead center.

The basic features of the engine of the invention are very different from those of conventional engines, namely: a very compact combustion chamber, very large valves, a piston stroke which is very small with respect to cylinder bore, so much so that the stroke/bore ratio which is the most suitable for the engine would be impracticable for a conventional engine, and the shapes and combinations of different valve opening diagrams, which can be summarized as follows:

The condition:

K /sD is met by the distance between the piston dome, and the side of at least one overhead valve facing the same, on attaining top dead center at the end of the exhaust stroke (K said distance; D=Max. lift of related valve from its seat). H

An additional overlap opening is provided, before top dead center of the exhaust stroke, by at least one intake valve, besides the normal opening in the course of inlet stroke, this additional opening being maintained through an angular travel a of crankshaft meeting the following condition:

oc 35 deg.

An additional overlap opening is provided, after top dead center of the exhaust stroke, by at least one exhaust valve, besides the normal opening in the course of exhaust stroke, this additional opening being maintained through .an angular travel of crankshaft, meeting the following condition:

fl 35 deg.

As a result, high specific horsepowers are attained without the necessity of having the total swept volume split into a large number of cylinders, with all related dis advantages, while obviously even higher horsepowers are attained when the invention is carried into practice along with a high splitting-up of swept volume.

The invention will be better appreciated from a consideration of the following detailed description taken with the accompanying drawings, both description and drawings being given as a non-restrictive example only. In the drawings:

FIG. 1 is a diagrammatic axial section of a cylinder with a piston therein, and provided with two inlet valves and two exhaust valves-the structure being shown in the position of combustion at top dead center.

FIG. 2 is a section taken on the line 11-11 of FIG. 1.

FIG. 3 is a section taken on the line IIIIII of FIG. 1.

FIG. 4 shows a possible operating diagram for the valves of the engine as shown in the preceding figures, the valve lifts being plotted on the ordinate, while the angular travel of the crankshaft is plotted on the abscissa.

Referring now to FIGS. 1 to 4 inclusive, 1 is a cylinder, having four valves 2, 2a and 4, 4a at its head. The valves 2 and 2a are located off-center, with respect to the longitudinal axis of the piston, and are respectively designed to operate as an inlet valve and as an exhaust valve. 3 is the inlet pipe, while 3a is the exhaust pipe. The other two valves are: an inlet valve 4, and an exhaust valve 4a, which lead to an offset small combustion chamber 5, wherein the spark plug 6 is located. Said combustion chamber 5 is defined in part by the cylinder head, and in part by a cavity in the dome 9 of piston 8.

The pipes 7 and 7a, that are controlled by the valves 4 and 411, respectively lead into the tubes 3 and 3a (see FIG. 2).

As it can be seen from the figures, the shape of piston dome is partly matched with that of cylinder head, in the section where the valves 2 and 2a are located. In that section, the piston upper side cooperates with the cylinder head inside, and with the valves 2 and 2a to cause, toward the end of the compression stroke, an expulsion of gaseous mass toward the combustion chamber 5 where, as a consequence thereof, a highly efficient turbulence is induced, thus providing a thorough mixing and a quick combustion. Otherwise stated, the so called squish-- 4 well known to the persons skilled in the artis obtained.

The combustion chamber is thus unusually compact. It is faced by both valves 4 and 4a, and by the ignition plug 6.

The sizes of said valves 4 and 4a are smaller than those of both other valves 2 and 2a that are contacted or almost contacted by the piston, with consequent squish and swirl, as indicated by the arrow A.

The axes of both smaller valves 4 and 4a converge at an angle wider than that of larger valves, whereby a common camshaft (not shown) can be used for all valves.

Thus, the engine is characterized by an off-center combustion chamber, by the presence of four valves (i.e. two inlet valves and two exhaust valves), two of the valves being situated at the top of the combustion chamber, while the other two valves are contacted by the piston dome 9 when the top dead center is attained.

According to the invention, a typical and distinctive operating diagram is established for the valves. Such diagram differs from that of conventional valves, due to following basic features:

The additional openings. The material difference between the diagrams of valves 2 and 2a, and the diagrams of valves 4 and 4a.

The coexistence of a marked overlap, with some of the valves closed (or nearly closed) at top dead center.

For a better understanding of the difference in the valve lift diagrams, reference will be made to FIG. 4, which shows a diagram that represents the motion of all four valves (and namely the lifting of the valves from their seats, as a function of the angular travel of the crankshaft, which is plotted on the abscissa). In FIG. 4, the top dead centers and the bottom dead centers of the piston are respectively indicated by the reference letters PME and PMI, while the solid line P and the solid line Q respectively indicate the motions of valves 4 and 4a, i.e. of the valves facing the combustion chamber 5, and the dash lines R, S respectively indicate the motion of valves 2 and 2a.

As it can be readily seen from the above diagram, the valves 2 and 2a are wholly closed at each top dead center, and an additional opening is imparted thereto, while the usual motion is followed by the valves 4 and 4a. According to the invention, the lift of valves 2 and 2a is nil at the top dead center by which the condition K /eD is met (being K=O, while D is the max. lift of valve that is closed at the top dead center). The condition oc 35 is met by the advance at in the opening of inlet valves (in FIG. 4 Ot= deg), and similarly the condition i3 35 deg. is met by the closing delay [3 of the exhaust (in FIG. 4 5:60 deg.

The operation i as follows: the cylinder head is contacted or almost contacted by a large portion of dome of piston 8, when this latter is at top dead center, whereby the gases are expelled, while swirling, into the particularly compact combustion chamber 5, due to the fact that the valves 2 and 2a are closed under such conditions, the overlap being obtained with the valves 4 and 4a, while an overlap is obtained by the valves 2 and 2a due to additional openings.

To prevent the gases which, on attaining the overlap region, are forced by the piston dome & toward the chamber 5 from entering directly into the open port of inlet valve 4, the plane of such valve is set back in respect of that of inlet valve 2, whereby the gas streams that are forced out of the zone wherein the piston dome 9 comes into contact with the cylinder head are not directed toward the valve port, which would prevent an efficient induction. The same effect could however be attained by having a ridge or step formed on the cylinder head, or on the piston dome.

According to another embodiment form (not shown) both piston and cylinder can be formed as shown in the FIGS. 1 to 3, except that the two valves 4 and 41:, facing the combustion chamber 5, are left out; i.e. the cylinder 3 is fitted with the inlet valve 2 and exhaust valve 21, designed to be contacted by the dome 9 of piston 8. In this embodiment, additional openings will necessarily be provided by the valves 2 and 2a (which however would be unnecessary, as previously stated, when the overlap is provided by other valves, with which the engine is fitted, in addition to valves 2 and 2a).

The operation is obvious, namely: about the end of exhaust stroke when, as an effect of the exhaust flow of the column of burnt gases, a vacuum is formed in the cylinder 1 (in the example, at ab. 300 deg), the inlet valve 2 is opened, and is however closed again, together with the exhause valve, when the top dead center is attained by the piston. Then, as soon as the intake stroke is started by the piston 8, which moves away from the outer dead center, both valves are again opened.

However, while the inlet valve is opened up to its maximum lift, the exhaust valve is closed as soon as the vacuum, which is formed in the cylinder, would cause a flow of gas back from the exhaust. In the specific example, this occurs at approximately 420 deg.

As already stated, both valves 2 and 2a may also not be wholly closed at the top dead center, i.e. the invention covers also a solution wherein the piston dome 9 is ridged all around its contour as shown by the dash line 82. Thus, in the latter case, a small intervening space, having a width of the order of some millimeters, i left between the valves 2 and 2a, that at combustion and top dead center are considered as closed, and the piston dome 9 thereby permits valves 2 and 2a to be slightly lifted even at top dead center, whereby a weak overlap is provided by them even in such a position, without however prejudicing the compactness of combustion chamber.

In short, while in the conventional four stroke, high rpm. engines for racing pur oses, very compact combustion chambers, very large valves and very short strokes have been attained by having the whole swept volume split-up into a very large number of cylinders, the very same, or greater, advantages can be obtained by the invention by means of a special timing diagram, in combination with a special shape of piston, and with a very small value of the stroke/ bore ratio.

Thus, it is apparent that the structure of the invention provides, in a four stroke, high rpm. internal combustion engine which operates with spark ignition, a cylinder which has a cylinder head provided with an inner surface of predetermined configuration and a piston which is slidable within this cylinder and which has a dome provided with an upper surface which in part conforms to the configuration of the inner surface of the cylinder head and which at top dead center has this part of the upper surface of the dome located closely adjacent to the inner surface of predetermined configuration of the cylinder head so as to provide squish. The piston and cylinder of course have a common axis and the piston dome and cylinder head define between themselves the combustion chamber whose cross sectional area, in a plane perpendicular to the common axis of the cylinder and piston, is substantially smaller than the cross sectional area of the cylinder, the combustible gases being displaced into the combustion chamber as a result of the squish as the piston approaches top dead center. In accordance with the invention, the engine includes the above-described valve means which is carried by the cylinder head and which communicates with the space between the cylinder head and piston dome for providing for flow of gases into and out of this latter space and for providing overlap of intake and exhaust both before and after the top dead center position of the piston at the end of the exhaust stroke thereof. This valve means of the invention is of course located at least in part directly next to the part of the upper surface of the piston dome which is located directly next to the inner surface of the cylinder head when the piston is at top dead center, and the valve means provides for this latter part thereof a position which is substantially closed at the instant when the piston is at top dead center so as to prevent collision between this part of the valve means and the piston dome. Moreover, in accordance with the present invention, the valve means coacts with the cylinder head for providing for the path of gas flow into and out of the latter a cross sectional area large enough to compensate for the substantially closed position of that part of the valve means which at the instant of top dead center of the piston is located directly next to the latter. As has been indicated above, this large cross sectional area for the path of gas flow into and'out of the cylinder head,

so as to compensate for the closed or substantially closed positions of the valves 2 and 2a at the instant when the piston is at top dead center, is achieved by a number of different features of the invention which may be used either separately or in combination to achieve the results of the invention. Thus, the valves 2 and 2a in and of themselves are of such a large size that they are far greater than normal valves and as a result of their large size pro vide for the large cross sectional area of the gas flow to compensate for the closing or substantial closing'of these valves at the instant of top dead center of the piston. In fact, as has been indicated above, the heads of the valves 2 and 2a are so large that they are in fact larger than the combustion chamber 5, as is apparent from FIG. 1. One of the factors which contributes to the possibility of providing the large valve heads for the valves 2 and 2a is the inclination of these valves, indicated in FIG. 2, the inner surface of the cylinder head having at the region of these valves an inverted V-shaped configuration while the piston dome has at the region of the valves 2 and 2a an upper surface of matching inverted V-shaped configuration, as is also apparent from FIG. 2, so that as a result of this V-shaped configuration there is :an increase in the area of the inner surface of the cylinder head which provides a sufficiently large area to accommodate the very large valve heads of the valves 2 and 2a. Of course, a further feature of the present invention which provides for the path of gas flow a cross sectional area large enough to compensate for the closing or substantial closing of the valves 2 and 2a at the instant of top dead center of the piston is the provision of the additional valve 4 and 4a which communicate only with the combustion chamber so as to be clear of the piston head at top dead center and so as to be capable of providing a continuous uninterrupted overlap in the intake and exhaust through the movement of the piston through the top dead center position thereof at the end of the exhaust stroke. A further feature contributing to the compensation for the closing or substantial closing of the valves 2 and 20! at the instant of top dead center is the extremely small stroke-tobore ratio of the engine of the invention, this extremely small ratio, which has also been referred to above, resulting from the fact that the piston stroke is substantially smaller than the diameter of the cylinder bore.

Obviously, the number of valves, the sizes and location thereof, the additional openings of same valves, and the opening and closing times thereof, may be selected at will, according to the particular requirements: of each application.

Also the shape and arrangement of cylinder head and piston dome may be modified according to the advice of designer, and is intended therefore to cover all such changes and modifications in the appended claims.

What I claim is:

1. In a four stroke, high r.p.m. internal combustion engine which operates with spark ignition, a cylinder having a cylinder head provided with an inner surface of pre. determined configurtaion, a piston slidable in said cylinder and having a dome provided with an upper surface which in part conforms to said configuration of said inner surface of said cylinder head and which at top dead center has said part of said upper surface located closely adjacent to said inner surface of predetermined configuration of said cylinder head to provide squish, said piston and cylinder having a common axis and said piston dome and cylinder head defining between themselves a combus tion chamber whose cross sectional area, in a plane perpendicular to the common axis of said cylinder and piston, is substantially smaller than the crOss sectional area of said cylinder and into which combustible gases are displaced as a result of said squish as said piston approaches top dead center, and valve means carried by said cylinder head and communicating with the space between said cylinder head and piston dome for providing for How of gases into and out of said space and for providing overlap of intake and exhaust both before and after the top dead center position of said piston at the end of the exhaust stroke thereof, said valve means being located at least in part directly next to said part of said upper surface of said piston dome when said piston is at top dead center and said valve means providing for said part thereof a position which is substantially closed at the instant when said piston is at top dead center so as to prevent collision between said part of said valve means and said piston dome, said valve means coacting with said cylinder head for providing for the path of gas flow into and out of the latter a cross sectional area large enough to compensate for the substantially closed position of said part of said valve means at said instant of top dead center of said piston.

2. The combination of claim 1 and wherein said piston has a stroke which is substantally smaller than the diameter of said cylinder.

3. The combination of claim 1 and wherein said valve means includes at least an intake valve and an exhaust valve located directly next to said part of said upper surface of said piston dome when said piston is at top dead center and having substantially closed positions at the instant of top dead center, said intake and exhaust valves respectively having valve heads large enough to provide for said large cross sectional area of the path of gas flow which compensates for the substantially closed positions of said valves at the instant of top dead center of said piston.

4. The combination of claim 3 and wherein said valve heads are larger than said combustion chamber.

5. The combination of claim 3 and wherein said valves respectively have axes which are inclined with respect to the common axis of said piston and cylinder, said part of said upper surface of said piston dome having an inverted, substantially V-shaped configuration and said inner surface of said cylinder head having a matching inverted, substantially V-shaped configuration at least at the region of said inner surface of said cylinder head which is located closely adjacent to said piston dome when said piston is at top dead center, said valve heads being situated at said surface of said cylinder head which is of inverted, substantially V-shaped configuration.

6. The combination of claim 1 and wherein said valve means includes at least one valve situated at and communicating with said combustion chamber and having an open position clear of said piston when the latter is at top dead center at the end of the exhaust stroke.

'7. The combination of claim 6 and wherein said one valve is an intake valve.

8. The combination of claim 6 and wherein said one valve is an exhaust valve.

9. The combination of claim 1 and wherein said valve means includes an intake and an exhaust valve situated at and communicating with said combustion chamber and both having open positions clear of said piston at the top dead center position of the latter at the end of the exhaust stroke.

10. The combination of claim 9 and wherein said part of said valve means is formed by an additional pair of intake and exhaust valves situated directly next to said upper surface of said part of said piston dome when said piston is at top dead center and having substantially closed positions at the instant of top dead center for preventing collision between said piston and said additional pair of valves, said pair of additional valves both having open positions before and after the top dead center position of said piston at the end of the exhaust stroke thereof.

11. The combination of claim 10 and wherein said combustion chamber is offset with respect to and situated to one side of said common axis of said cylinder and piston.

References Cited UNITED STATES PATENTS 2,011,992 8/1935 Aseltine 123-75 2,235,710 3/1941 Hoffman 123-75 2,362,622 11/1944 Fischer 123-193 2,428,886 10/1947 MacPherson 123l9l 2,644,436 7/1953 Berlyn 123-90 2,647,500 8/1953 Lang 123-90 MARK NEWMAN, Primary Examiner.

WENDELL E. BURNS, Examiner.

Claims (1)

1. IN A FOUR STROKE, HIGH R.P.M. INTERNAL COMBUSTION ENGINE WHICH OPERATES WITH SPARK IGNITION, A CYLINDER HAVING A CYLINDER HEAD PROVIDED WITH AN INNER SURFACE OF PREDETERMINED CONFIGURATION, A PISTON SLIDABLE IN SAID CYLINDER AND HAVING A DOME PROVIDED WITH AN UPPER SURFACE WHICH IN PART CONFORMS TO SAID CONFIGURATION OF SAID INNER SURFACE OF SAID CYLINDER HEAD AND WHICH AT TOP DEAD CENTER HAS SAID PART OF SAID UPPER SURFACE LOCATED CLOSELY ADJACENT TO SAID INNER SURFACE OF PREDETERMINED CONFIGURATION OF SAID CYLINDER HEAD TO PROVIDE SQUISH, SAID PISTON AND CYLINDER HAVING A COMMON AXIS AND SAID PISTON DOME AND CYLINDER HEAD DEFINING BETWEEN THEMSELVES A COMBUSTION CHAMBER WHOSE CROSS SECTIONAL AREA, IN A PLANE PERPENDICULAR TO THE COMMON AXIS OF SAID CYLINDER AND PISTON, IS SUBSTANTIALLY SMALLER THAN THE CROSS SECTIONAL AREA OF SAID CYLINDER AND INTO WHICH COMBUSTIBLE GASES ARE DISPLACED AS A RESULT OF SAID SQUISH AS SAID PISTON APPROACHES TOP DEAD CENTER, AND VALVE MEANS CARRIED BY SAID CYLINDER HEAD AND COMMUNICATING WITH THE SPACE BETWEEN SAID CYLINDER HEAD AND PISTON DOME FOR PROVIDING FOR FLOW OF GASES INTO AND OUT OF SAID SPACE AND FOR PROVIDING OVERLAP OF INTAKE AND EXHAUST BOTH BEFORE AND AFTER THE TOP DEAD CENTER POSITION OF SAID PISTON AT THE END OF THE EXHAUST STROKE THEREOF, SAID VALVE MEANS BEING LOCATED AT LEAST IN PART DIRECTLY NEXT TO SAID PART OF SAID UPPER SURFACE OF SAID PISTON DOME WHEN SAID PISTON IS AT TOP DEAD CENTER AND SAID VALVE MEANS PROVIDING FOR SAID PART THEREOF A POSITION WHICH IS SUBSTANTIALLY CLOSED AT THE INSTANT WHEN SAID PISTON IS AT TOP DEAD CENTER SO AS TO PREVENT COLLISION BETWEEN SAID PART OF SAID VALVE MEANS AND SAID PISTON DOME, SAID VALVE MEANS COACTING WITH SAID CYLINDER HEAD FOR PROVIDING FOR THE PATH OF GAS FLOW INTO AND OUT OF THE LATTER A CROSS SECTIONAL AREA LARGE ENOUGH TO COMPENSATE FOR THE SUBSTANTIALLY CLOSED POSITION OF SAID PART OF SAID VALVE MEANS AT SAID INSTANT OF TOP DEAD CENTER OF SAID PISTON.

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