Two Cycle Internal Combustion Engine

This invention relates to a new and improved method of operating a two-stroke high torque and high speed gas or diesel fueled multi-cylinder internal combustion engine utilizing an air blower or turbo charger combination connected in series, and having a new and improved design of the internal moving parts, more specifically to the design of the scavenging valves which are opened and closed by the relatively wide area of cam lobes of a cam shaft and related mechanisms all assembled in the cylinder head. Also of importance is the piston assembly having a novel feature of design. A recirculating type pressure lubrication system is used to lubricate all the vital and critical moving parts, making this invention an efficient device. The design and location also of the exhaust ports in each of the cylinders provides the most efficient operation of this machine.

It is an object of this invention therefore to disclose its design, its novel features, its advantages, its efficiency and method of operation.

Among the objects of this invention is how to eliminate the many disadvantages, limitations, difficulties and inefficient operations of most two-stroke engines specially when pressure lubrication is used.

Another object of this invention is to disclose and provide a device of the character herewithin described in which a new and improved design of the scavenging valves which are opened and closed by cam lobes of special design having relatively wide area of contact for longer duration of valve opening period. The valves and related mechanisms are assembled and installed in the cylinder head.

Still another object of this invention is to disclose and provide a device of the character herewithin described in which a new and improved design of the piston assembly, having novel features that reduces and controls pressure lubrication problems.

Still another object of this invention is to disclose a new and improved design of the piston assembly, the design of the scavenging valves and related mechanisms and the design and location of the exhaust port openings in each cylinder and the application of an air blower which together leads to this relatively cleaner exhaust gas emission characteristic.

Still another object of this invention is to provide an engine capable of producing high torque and high revolution per minute because of less moving parts and compact assembly.

Still another object of this invention is to provide a device of the character herewithin described which may include the design of the air blower assembly having a scoop-type impeller and a compressor rotor that are bolted together to a common shaft supported with ball bearings that can be driven by means of a gear or by a belt pulley.

Still another object of this invention is to provide a device of the character herewithin described which is compact in design, economical in manufacture and otherwise well suited to the purpose for which it is designed.

In accordance with the invention there is provided a two-stroke supercharged multi-cylinder internal combustion engine, with inline or V-type configuration and including a pressure lubrication system; comprising in combination a cylinder block having cylinder bores formed therein, a cylinder head on the upper end of the cylindrical bores and closing same and defining a combustion chamber at the upper end of each cylindrical bore, a piston assembly in each of said bores including a piston having a domed head and a connecting rod operatively connected to said piston for reciprocating same between top dead centre and bottom dead centre, a crankshaft mounted for rotation at the base of said block, said connecting rods being operatively connected to said crankshaft an an oil pan enclosing the lower end of the cylinder bores and said crankshaft, said cylinder head including a cam shaft mounted for rotation thereon and being operatively connected to said crankshaft, at least one inlet-and-scavenger valve mounted on said cylinder head and being operatively connected with said combustion chamber of each of said cylindrical bores, a rocker arm operatively mounted on said cylinder head and operatively engaging said inlet-and-scavenger valve by one end thereof, a cam lobe for each rocker arm formed on said cam shaft operatively connected with the other end of said rocker arm, said cam lobes having a relatively wide area of contact with said rocker arm to control the opening, closing and duration of opening of said inlet-and-scavenger valve and exhaust port located in the lower side of the cylinder walls of the cylinder bores inclining downwardly and outwardly through the cylinder walls and being covered and uncovered by the reciprocating piston passing thereby.

With the foregoing in view, and other advantages as will become apparent to those skilled in the art to which this invention relates as this specification proceeds, the invention is herein described by reference to the accompanying drawings forming a part hereof, which includes a description of the best mode known to the applicant and of the preferred typical embodiment of the principles of the present invention, in which:

FIG. 1 is a schematic partially sectioned side elevation of one cylinder and a piston assembly showing the piston position in the latter part of the power stroke with the scavenging valve or intake valve already partly opened.

FIG. 2 is a view similar to FIG. 1 but showing the piston position at bottom dead centre with the intake valve fully opened.

FIG. 3 is a view similar to FIG. 1 but showing the exhaust port covered by the piston at the beginning of the compression stroke with the intake valve still partly opened.

FIG. 4 is a view similar to FIG. 1 but showing the piston position at top dead centre of its compression stroke.

FIG. 5 is a fragmentary cross sectional view of the piston and connecting rod assembly per se.

FIG. 6 is a schematic side elevation partially sectioned showing a turbo charger connected to the engine.

FIG. 7 is a view similar to FIG. 6 but showing a V-type configuration.

FIG. 8 is a fragmentary cross sectional view of the preferred air blower construction.

FIG. 9 is a view from the left hand side of FIG. 8.

FIG. 10 is an example of the valve and port diagram of the engine.

In the drawings like characters of reference indicate corresponding parts in the different figures.

Proceeding therefore to describe the invention in detail, reference should first be made to FIGS. 1 to 4 in which reference character 10 illustrates generally a cylinder including a cylinder wall 11, water cooling passages 12 formed therein and a cylinder head assembly 13 secured to the upper side of the cylinder by conventional means (not illustrated).

A valve casing 14 surmounts the cylinder head and is once again connected by conventional means not shown.

A piston assembly is reciprocal within said cylinder, said piston assembly being generally designated by reference character 15 and including a piston collectively designated 16 and a connecting rod collectively designated 17, details of which will hereinafter be described.

An exhaust port 18 is formed through the wall of the cylinder 11 on one side thereof, said exhaust port preferably being of rectangular configuration and inclining downwardly and outwardly through the wall as clearly shown in FIGS. 1 to 4.

An exhaust conduit 19 leading to an exhaust manifold 20 (see FIG. 6) is secured to the exhaust port on the outer side thereof by means of flange 21 and bolts 22 and this exhaust conduit 19 extends outwardly and downwardly at an inclined angle similar to the inclined angle of the exhaust port through the cylinder wall 11 to facilitate the exit of exhaust gases as will hereinafter be described.

At least one and preferably two or more air intake and scavenging valves 23 are provided within the cylinder head 13 normally seated on valve seats 24 and being retained therein by means of valve springs 25 on the upper ends 26 of the valve stems which engage through valve guides 27 within the head 13 in a conventional manner.

These valves are preferably operated by an overhead cam shaft 28 supported for rotation in a conventional manner (not illustrated) and being operatively connected to the crankshaft (not illustrated) which is also conventional.

However, the cam lobes 29 of the cam shaft are shaped with a relatively wide contact area 30A to control the duration of the opening of the air intake valves 33 and also the time that they are opened and closed.

The cam lobes 29 engage rocker arms 30 pivoted by one end thereof to rocker arm bearings 31 and engaging the upper ends 26 of the valve stems by the other ends 32A in a conventional manner.

FIGS. 1 to 4, an air blower assembly collectively designated 32 is provided and is operatively connected to the engine in a conventional manner to supply air under superatmospheric pressure to the air inlet valve 23 via passages 33 which may be connected to an intake manifold if a plurality of pistons and cylinders are utilized.

Details of the preferred embodiment of the air blower assembly are shown in FIGS. 8 and 9 and comprises a cylindrical casing 34 within which a fan blade assembly collectively designated 35 is supported for rotation upon a shaft 36 supported with bearings 37 and driven from the engine by means of gear 38 or gear belt (not illustrated) either of which is operatively connected to the cam shaft in a conventional manner by means of a gear chain or cog belt.

The blower includes the aforementioned combination fan assembly 35 with an outer set of impeller blades 39 and an inner set of screw or compressor blades 40. Rotation of the fan assembly in the direction of arrow 41, draws air through the central intake 42 in the centre of the front wall of the casing, compresses same and ejects it from the discharge end 43 which is operatively connected to the air intake valves 23 as hereinafter described.

Reference should be made to the piston assembly illustrated in detail in FIG. 5. The piston is preferably formed from aluminum alloy and includes a piston head 44, a piston head crown 45 and a surrounding cylindrical skirt portion 46.

The piston crown 45 is domed as illustrated by reference character 47 and is convexly curved with the side of the crown 48 towards the exhaust port 18 curving down to a point 48 which is lower than the junction of the crown to the head on the opposite side as illustrated by reference character 50 so that the apex 51 of the dome is offset from the vertical centre line of the piston, towards the side 50 which is diametrically opposite to the lower side 49 on the exhaust port side of the cylinder when assembled.

This facilitates the flow of exhaust gases from the combustion chamber 52 assisted by the air entering via the blower assembly 32.

A pair of opposed piston bosses 53 are formed within the wall of the piston in a conventional manner and a wrist pin 54 bearingly engages these bosses and also bearingly engages the wrist pin end 55 of the connecting rod 17.

It is desirable to seal the outer ends of the bosses 53 to prevent lubricating oil from being discharged therethrough and in this connection a tie rod or pin 56 extends freely through the wrist pin 54 which is hollow, and is secured as by brazing to two concave sealing end caps 57, one being situated slightly within each outer end 58 of the wrist pin bosses of the piston as clearly shown.

A pair or more of compression piston rings 59 are seated within the piston ring grooves 60 around the piston adjacent the upper end of the head thereof and an oil scraper ring 61 is installed within an annular groove 62 adjacent the base of the skirt of the piston with oil return apertures 63 being formed through the skirt at the base of the groove in a conventional manner.

Of importance is the fact that the oil scraper ring always remains below the lower side 18A of the exhaust port when the piston is in the top dead centre position as illustrated in FIG. 4.

The exhaust port 18 design is such that it inclines downwardly and outwardly on the walls of the cylinder and the attaching exhaust conduit is preferably rectangular in configuration and may be provided with one or more vertical bars 64 to guide the compression rings past the exhaust port and to prevent them catching on the edges of the walls defining the port.

In operation to this point, reference should be made of FIGS. 1 to 4.

In FIG. 1, the piston 15 is approaching the lower end of the power stroke and the scavenging valve is just beginning to open. In FIG. 2, the piston is at the lower end of the power stroke with the exhaust port 18 being uncovered and air passing through the now fully opened scavenging or inlet valve, being supplied in sufficient volume by the blower assembly 32, to complete scavenge the exhaust gases through the exhaust port facilitated by the common angle of the piston head crown at this point and downwardly inclining exhaust port 18 and exhaust conduit 19.

In this position, the piston is at the bottom dead centre and in FIG. 3 it is commencing to move upwardly on the compression stroke having covered the exhaust port 18 although the scavenging valve is still slightly open to ensure that a full charge of air is supplied within the combustion chamber 52.

The scavenging or intake valve 23 now closes as the piston continues to move upwardly on the compression stroke to the top dead centre position as shown in FIG. 4. With the piston at this position, it will be noted that the aforementioned oil scraper ring 61 always remains below the lower edge 18A of the exhaust port so that the lubricating oil cannot escape through this port.

Within a few degrees of the piston reaching the top dead centre of its travel as shown in FIG. 4, an atomized spray of fuel is injected via a conventional fuel injector assembly 65 which ignites due to the highly compressed air between the crown of domed piston head and the combustion chamber of the cylinder head, in a conventional manner with the scavenging valve 23 being completely closed at this point. The ignited fuel and highly compressed air mixture expands and pushes the moving piston downwardly performing the power or expansion stroke to the position shown in FIG. 1 and the cycle of operation is repeated again and again.

It is to be noted that the scavenging valves 23 are of relatively large diameter to ensure that the air supplied to cylinders 52 is sufficient to completely scavenge and charge its cylinders every time the piston reaches the bottom of its stroke.

It is also to be noted further that the scavenging valves 23 are opened and closed at the correct timing in relation to the piston degrees of travel. In order to achieve this, cam lobes 29 of the cam shaft 28 have a relatively wide area of contact 30A and is designed to correctly time the duration of opening and closing of its scavenging valves 23 in relation to the piston degrees of travel. The scavenging valves 23, the rockers 30 and cam lobes 29 of the cam shaft 28 are mechanically contacting one another and are all assembled upon the cylinder head. The cam shaft 28 is mechanically driven by the crankshaft by means of gears and chain or cogged belt in a conventional manner.

Reference should be made to the novel design of the piston assembly illustrated in detail in FIG. 5. The piston is preferably formed from aluminum alloy and includes a piston head 44, a piston head crown and a surrounding cylindrical skirt portion 46.

As discussed previously, another very important point to be moved is the piston assembly shown in a fragmentary form as in FIG. 5, having a novel design features that controls and reduces lubricating oil problems especially if a pressure lubrication system is utilized in a two-cycle engine. The novel design features of the piston assembly are: the head 45 is dome shaped to facilitate the flow of the scavenging exhaust gases, a pair of compression rings 59 and a pair of sealing caps 57 installed at both ends of the piston bosses. For safety of operation these sealing caps 57 are secured by brazing a pin 56 that extends freely through the wrist pin 54 which is hollow. The sealing caps 57 are installed at each outer end of the piston bosses 58 to prevent any amount of the lubricating oil from being discharged therethrough.

Another important feature of the piston assembly to be noted is the oil scraper ring 61 which is installed close to the base of the piston skirt with oil return holes 63, the function of which is to prevent any amount of lubricating oil from being discharged to the exhaust ports 18 and that said oil scraper 61 always remains below the lower side 18A of the exhaust port when the piston is in the top dead centre position of its stroke.

The exhaust port 18 is located in the side of the cylinder wall adjacent the bottom dead centre position of the piston, the design of which is inclining downwardly and outwardly and is covered and uncovered by the piston, the design of which is to facilitate the flow of exhaust gases more freely into the atmosphere.

As mentioned previously, this invention is suitable for use with single or multi-cylinders either inline or V-type configuration being shown schematically in FIGS. 6 and 7 respectively.

It will also be appreciated that the air blower assembly 32 can be used with all configurations or alternatively, a turbo charger and air blower combination connected in series can be utilized as shown schematically in FIG. 7 collectively designated 66.

Finally, reference should be made of FIG. 10 which shows a valve and port diagram.

The width of the cam lobe 30A is such that the inlet and scavenger valve opens approximately 105.degree. to 110.degree. after top dead centre and closes approximately 70.degree. after bottom dead centre so that it remains open through approximately 140.degree..

The position of the exhaust port relative to the piston is such that the piston uncovers the exhaust port at approximately 115.degree. after top dead centre and covers or closes the exhaust port at approximately 65.degree. after bottom dead centre so that the exhaust port remains uncovered through approximately 130.degree.. The relationship between the exhaust port opening and the inlet-and-scavenger valve opening is such that there is approximately a 5.degree. overlap at either end in which the inlet-and-scavenger valve is open approximately 5.degree. before the exhaust port is uncovered and remains open approximately 5.degree. after the exhaust port is covered or closes.

This provides the necessary control for the opening, closing and duration of opening of the inlet-and-scavenger valve with the piston and position of the exhaust port controlling the opening, closing and duration of opening of the exhaust port.

Since various modifications can be made in my invention as hereinabove described, and many apparently widely different embodiments of same made within the spirit and scope of the claims without departing from such spirit and scope, it is intended that all matter contained in the accompanying specification shall be interpreted as illustrative only and not in a limiting sense.