WO1989002028A1

WO1989002028A1 - Improved internal combustion engine

Info

Publication number: WO1989002028A1
Application number: PCT/IT1988/000061
Authority: WO
Inventors: Pietro Montanari
Original assignee: Pietro Montanari
Priority date: 1987-09-03
Filing date: 1988-09-01
Publication date: 1989-03-09
Also published as: IT1211754B; IT8748348A0

Abstract

An internal combustion engine for automotive vehicles of high performance has a very high cylinder bore to piston stroke ratio and two piston rods (2) engaged with the same piston, which actuate two counter rotating crankshafts (4) engaged through gears (5) with 1:1 driving ratio, so that the large surface of the piston head (6) enables the arrangement of particularly efficient valve and combustion chamber systems combined with an efficiently balanced engine.

Description

"IMPROVED INTERNAL COMBUSTION ENGINE"

DESCRIPTION

The present invention relates to an internal combustion piston engine having high thermal and mechanical effi- ci ency. At present, conventional internal combustion engines, even when technically highly advanced, generally use two valves per cylinder. This does not allow the motor maximum aeration, which obviously reduces power.

Only in particular constructions four or five valves are used, which, however, in view of their inclination, result in a rather elaborate configuration of the combus¬ tion chamber. Moreover, for the balance of the assembly comprising crank-shaft, piston rod and piston, particular*, shafts are provided having counter-rotating masses, entailing obvious complication of the construction.

Additional problems concerning lubri fi cati on and piston side thrust, due to cent ifugal force, with conse¬ quent and again frequent s ezing effects, place limits on the thermodynami c and mechanical efficiency of the conventional engines.

An engine is also known having a piston engaged with two piston rods which actuate two counter rotating shafts. This structure, however, has a cylinder bore/stroke ratio lower than 1. An ob ect of the present invention is an internal combustion engine having one or more pistons slidingly reciprocat ng in a respective cylinder, characterized by the combination comprising: a _cylinder bore/stroke ratio from 2:1 to 6:1, the piston having a depth of the skirt in contact with the cylinder not higher than that sufficient to house the piston rings; a pair of piston rods pivotally connected to the piston by means of parallel piston pins; a pair of crank-shafts, each actuated by one of the piston rods and rotating in oppo¬ site directions, the piston rods having an angle of inclination with respect to the geometrical axis of the cylinder, such that, with the piston at the upper dead center, the distance of the center of the respective crank pin from the cylinder axis is greater than the distance of the center of the respective piston pin from the same cylinder axis; constantly meshed gears rigidly mounted on each respective crank-shaft, having a drive ratio of 1:1, whereby said crank-shafts rotate at the same speed, said piston is constantly maintained aligned with the cylinder axis and the driving torques on said crank-shafts have components directed outwards in opposite directions. The engine of the invention shows the following advan-. tages : the crank case, the cylinder block and the cylinder head can be manufacutred in a monolithic structure in that the wide surface of the cylinder head in combination with the small depth of the cylinder, enables a d rect tool machining in this space; the engine is particularly well balanced in that the synchronism of the two crank-shafts and piston rods does not produce centrifugal thrust; the wide surface of the ceiling of the combustion chamber enables a plurality of valves to be used, particu¬ larly four suction valves and two exhaust valves, which can be controlled by a valve lifter linkage of a simple mechanical structure, thus ensuring an efficient aeration of the engine; the wide surface of the piston head permits a particu¬ larly advantageous configuration of the combustion chamber and the possibility of us ng more than one spark plug; the engine is particularly adapted to operate at a very high revs per m.inute speed Cr/p/m). Description of the drawings

A preferred embodiment of the invention is illustrated in the accompanying drawings, in which: figure 1 is a d agramatic elevation view of the engine

5. according to the invention; figure 2 illustrates a valve arrangement; figure 3 illustrates an embodiment of rocker arm for an arrangement as in figure 2; figure 4 is a side view of a rocker arm; Q. figure 5 is a further arrangement of the valve control; figure 6 is an embodiment of the piston rod; figure 7 is a plan view of the piston head; figure 8 is an isometric view of the piston head and the combustion chamber; 5 figure 9 is a cross-sectional view of the piston^ and the combustion chamber; _ figure 10 s a further embodi ent of piston rod; and figure 11 is a detail showing a bushing of the piston rod.

Referring to the drawings, a preferred embodiment of the present invention is illustrated hereinafter.

The engine can have a plurality of cylinders, as is obvious to those skilled in the art, and since it is a well balanced engine with respect to inertia and centrifugal forces, the engine in particular is adapted to an odd number of cylinders, more in particular three or five cylinders.

In the drawings, the engine is shown in relation to only one cylinder. - -■ -

The piston 1 and the cylinder 18 in which it recipro¬ cates, have a very large diameter with respect to the stroke of the piston 1 in the cylinder 18. The cylinder bore/stroke ratio can range from 2:1 to 6 : and it is preferably comprised between 2,6:1 and 3:1. An engine of the invention having the same displacement as a conventional engine, is provided with a wider surface of the piston head.

An engine having the above indicated features permits the realization of an engine block including the crank case, the cylinder block and the cylinder head in a monolithic structure, in that the wide space available inside the cylinder together with its shallow depth provides easy access for machining parts onto the ceiling of the combustion chamber.

An important additional feature of the invention is that the piston 1 can be made with practically no skirt, in that its balance inside the cylinder 18 is ensured by a double system of connecting rods and cranks. Consequently the depth of the piston skirt is advantage-^- ously made as small as possible, consistently with the presence of piston rings 24. This feature makes the piston lighter, with reduction of stresses due to inertia in the reciprocating motion. The piston 1 is pivotally connected through two piston pins 16 to a pair of piston rods 2.

The small and large ends of the piston rods are advan¬ tageously rigidly united through separate web elements.

Each piston rod can be made of a pair of webs (see figure 6) for compensation of the large width of the piston pins 16 and crank pins 22 with respect to the length of the piston rod. This type of piston rod is preferably connected to a respective crank-shaft by four tightening screws 3. The piston rod can also be made- in .two separate parts, as shown in 2' in figure 10 and the bushings preferably have a plurality of circular grooves 15 (figure 11) for decreasing friction and increasing efficiency of lubrifi cation.. Each piston rod is connected to a respective crank- shaft 4. The engine is consequently provided with two counter-rotating crank-shafts, which are drivingly engaged through g _*ears 5 having a 1 :1 drive ratio.

The arrangement of the engine is such that the thrust of the driving torque has a component directed outwards, in that the axis of the piston rods 2 is inclined towards the longitudinal axis of the cylinder 18. The inclination s such that the distance of the centers of the piston pins 16 from the axis of the cylinder 18 is shorter than the distance of the centers of the crank pins 22 from the same axis. The rotation of the movable members thus results to be smooth in that, besides the balance of the crank-shafts, the masses of which are opposed, it enables the assembly of rods and pistons to move synchroni caI ly, driving the piston inside the cylinder^ without producing dangerous side thrusts. This allows the engine to operate at a rotation speed much higher than that of conventional engines.

The wide surface area. of. the piston head enables the combustion chamber and the valve system to be realized in an advantageous manner in relation to the efficiency of combustion and aeration of the engine.

In one embodiment, the ceiling of the combustion chamber is flat with vert cally arranged valves. As a modification, the ce ling of the chamber can be slightly convex with radially arranged valves.

The seat 6 of the spark plug protrudes towards the center of the combustion chamber to promote the conveying of gas to the plug electrodes. The piston head (figure 7) s prov ded with a peri feral rim having on its inner profile cavities 7 so oriented as to produce, during the compression and final squashing phase, an eddy motion of the gas (indicated by arrows in figures 7, 8 and 9) which makes complete combustion easier by .producing a strong turbulence around the elec- trodes of the spark plug.

As a modification, in addition to the central spark plug, two supplementary spark plugs 14 (figure 9) can be added in diametr cally opposed positions, or with a different angulation, in correspondence with the rim of the piston head, so that the firing of the gas is more rapid and the combustion more perfect.

Preferably six valves are provided on the ceiling of the combustion chamber, namely four suction valves (8) and two exhaust valves (9) which permit the engine to be fed easily through the suction (10) and exhaust (11) conduits.

In the case of the ceiling of the chamber being made with a spherical profile, the valves can be arranged in a radial position with respect to the central sparks plug, with a slight angle of inclination.

*As can be understood, the . selection of the valve arrangement can be very large, and this is a feature of the present invention. Typically, three suction valves and three exhaust valves can be provided, without excluding the possibility of having one suction and one exhaust valve, as seen in conventional engines.

As shown in figures 3, 4 and 5, the valves are control¬ led by means of rocker arms 12 and 13. Preferably, the rocker arm of the suction valve 8 controls two of the four valves and it is provided with two offset disposed screws 20 for tappet adjustment. The rocker arm 12 controls the valves in a first and a second row simultaneously, producing a differential opening of the valves (figure 4),,. .in that the inner screw 20 .produces a lift A shorter than the lift B pro¬ duced by the periferal screw 20.

As a modification, the rocker arm of the suction valves indicated with 12' in figure 5, can be made to control all four suction valves simultaneously and be provided with four screws for tappet adjustment.

As a further modification, rocker arms can be realized provided with three adjustment screws to simultaneously control three suction and three exhaust valves.

In conclusion, by means of a combination of the above illustrated features, an engine is obtained showing a higher volume efficiency, a more complete combustion of the gas mixture and consequently a higher power, in view of a higher pressure applied on a wide surface piston, with division of the load on two crank-shafts, and moreover a more efficient balance of the rotating masses, with the ob ect of obtaining a higher ther o- dynamic and mechanical efficiency with respect to conven- ti ona I engines.

Claims

1. An improved internal combustion engine having one or more pistons slidingly rec procating in a respec¬ tive cylinder, characterized in that it comprises in combination: a cylinder bore to piston stroke ratio from 2:1 to 6:1, said piston having a depth of skirt in contact with said cylinder not larger than that suffi¬ cient for the housing of piston rings; a pair of piston rods pivotally connected to said piston by means of parallel piston pins; a pair of crank-shafts each actuated by one of said piston rods and rotating in opposite directions, said piston rods having an angle of inclina¬ tion with respect to the geometrical axis of said cylin¬ der, such that, with the piston at the upper dead center, the distance of the center of a respective crank pin. from the cylinder axis is greater than the distance of the center of the respective piston pin from the same cylinder axis; and constantly meshed gears rigidly mounted on eac respective crank-shaft having a drive ratio of 1:1, whereby said crank-shafts rotate at the same speed, said piston in constantly maintained alligned with the cylinder axis and the driving torques on said crank-shafts have components directed outwards in opposite di rections. 2. Engine according to claim 1, in which said bore/ stroke ratio is 2,6:1 to 3:1.

3. Engine according to claim 1, in which said piston rods comprise a large end and a small end rigidly con¬ nected by separate web members. 4. Engine according to claim 1., _in which each piston rod comprises two or more separate parallel connecting rods, all pivotally engaged with the same single piston pin and crank pin.

5. Engine according to any one of claims 1 to 4, in which said piston rods are mounted on the piston pin and/or crank pin with the nterposition of bushings having a plurality of circular inner grooves for improving lubri fi cati on and decreasing friction.

6. Engine according to claim 1, comprising a plurality 5 of suction valves and exhaust valves for one cylinder.

7. Engine according to claim 6, in which said valves are arranged vertically on the ceiling of the combustion chamber in a circle concentrical to the axis of the cylinder. Q 8. Engine according to claim 6, in which said valves are arranged regularly on the ceiling of the combustion chamber with respect to the axis of the c linder.

9. Engine according to claim 7 or 8, in which at least two of said valves are controlled by the same 5 rocker arm having lift adjusting screws for a different, tiated lift control of said valves.

10. Engine according to claim 9, in which one rocker arm controls three suction valves and another rocker arm controls three exhaust valves. 0 11- Engine according to claim 9, in which said rocker arm controls four. suction valves.

12. Engine according to claim 1, in which said piston is formed with a concave shaped head and a flat peripheral rim and a plurality of cavities are formed along said 5 rim facing in a direction slightly offset to the center of the head to produce a turbulence of the combustion mixture.

13. Engine according to claim 1, in which the spark plug seat is smoothly protruding at the center of the 0 ceiling of the combustion chamber.. _, _,

14. Engine according to claim 1 or 13, in which two additional spark plugs are arranged in correspondence with the peripheral rim of said piston head.

15. Engine according to claim 1, comprising an engine 5 block formed as an integral monolithic structure, includ- - -

ing a crank case, a cylinder block and a cylinder head.

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