GB2186323A

GB2186323A - Two-stroke internal combustion engine

Info

Publication number: GB2186323A
Application number: GB08603207A
Authority: GB
Inventors: Antonio Ancheta
Original assignee: Individual
Current assignee: Individual
Priority date: 1982-09-15
Filing date: 1986-02-10
Publication date: 1987-08-12
Also published as: GB8603207D0; DE3606603A1

Abstract

The scavenging and exhaust ports 26 and 29 are formed in the walls of the cylinder above the bottom dead centre position of the piston head. The lower side of the scavenging port opening inclines inwardly and upwardly toward the cylinder wall so that the flow of scavenging air creates a turbulent action as it enters inside the cylinder for efficient scavenging of the exhaust gases. The scavenging port and exhaust ports are both uncovered and covered simultaneously by the reciprocating piston passing thereby. A sealing "O" ring (50, Fig. 6) is installed into an annular groove (51) formed in each boss (47) of the piston adjacent the end portions of the wristpin (48) to prevent the escape of lubricating oil. Fuel may be injected through an opening (25, Fig. 2) immediately above the part 26 beginning 10 DEG before piston closure of the port 26 and ending 5 DEG after closure. The ports 26 and 29 are uncovered for 130 to 140 DEG . <IMAGE>

Description

SPECIFICATION Two-stroke internal combustion engine This invention relates to a new and improved construction and method of operating a superturbocharged two-cycle multi-cylinder diesel or gas fueled internal combustion engine that can be manufactured as an inline or type configuration.

Of importance is the piston assembly having a novel feature of design that overcomes the principal problems and difficulties of equipping a two-cycle multi-cylinder super-turbocharged diesel or gas engine with a re-circulating type constant pressure feed lubrication system to lubricate all the vital and critical moving parts at all times.

This invention is also equipped with a supercharger or turbocharger combination connected in series to provide excellent power and acceleration capabilities. Another unique design feature of this invention is that gas engine fuel injection is used in which the design of the fuel spray nozzle or fuel injector assembly includes a cone-shape needle valve that opens under low pressure to inject metered atomized gaseous fuel at a precise time in relation to the position of the piston head at the scavenging port opening. The location and design of the scavenging port and exhaust port openings of each cylinder permits same to be uncovered and covered simultaneously by the reciprocating piston passing thereby and thus provides the excellent operation of this machine.

In accordance with the invention there is provided a two-stroke multi-cyinder internal combustion engine, having a cylinder block having cylinder bores formed therein, a cylinder head on an upper end of the cylindrical bores defining a main combustion chamber, a piston assembly in each of said cylinder bores and 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 the said cylinder block, characterized by a re-circulating type constant pressure feed oil pump mounted in the base of said cylinder block and being operatively driven by said crankshaft, an oil pan enclosing the lower side of the cylinder block, said crankshaft and said oil pump, said pump being operatively connected to the lubrication system of said engine, said cylindrical bores having individual scavenging port and exhaust port openings formed in the lower side of each cylinder wall in the same plane and axial position, said scavenging port lower side opening inclining inwardly and upwardlytowards the walls of the cylinder, said scavenging port and exhaust port openings being both uncovered and covered simultaneously by the reciprocating piston passing thereby.

For efficient scavenging of the exhaust gases, the design of the lower side of the scavenging port opening is inclining inwardly and upwardlytoward the walls of the cylinder so that when the scavenging port is fully uncovered by the domed head of the piston, the flow of the scavenging air as it enters inside the cylinder creates a swirling turbulent motion in an upward direction to completeiy scavenge the burnt gases.

The duration of the opening period of both the scavenging port and exhaust port for both gas and diesel engine is approximately 1300 to 135" of crankshaft rotation. In a gas engine the duration of injection period for injecting the fuel is approximately 10 to 15 of crankshaft rotation, with the injection of the gas fuel beginning approximately 100 before the head of the piston covers the scavenging port opening.

Description of the Drawings Figure 1 is a general schematic sectional side view of a single cylinder two-stroke diesel engine equipped with super-turbocharger combination connected in series and utilizing a re-circulating type constant pressure lubrication system. This view clearly shows the internal moving parts in general and the position of the piston at the top dead centre of its stroke.

Figure 2 is a schematic sectional side view of a single cyiinder two-stroke gas engine utilizing fuel injection type fuel system and equipped with recirculating type constant pressure lubrication system and also equipped with supercharger. It clearly shows the location of the fuel spray nozzle or fuel injector and the approximate position of the piston head at the scavenging port opening when the spray of fuel begins.

Figure 3 is a view showing the piston position at the bottom dead centre of its stroke. It clearly shows the position of the domed head of the piston in relation to both the scavenging port and exhaust port openings when these are fully uncovered and a blast of super-atmospheric pressure air under swirling turbulent motion enters the cylinder in an upward direction as it is being deflected by the dome of the piston head.

Figure 4 is a view showing the schematic sectional side view of a V-type two-stroke muli-cylinder engine, utilizing pressure feed lubrication and equipped with supercharger or turbocharger combination connected in series.

Figure 5 is a fragmentary cross sectional view of a gas fuel spray nozzle or fuel injector assembly as used in a gas engine.

Figure 6 is a fragmentary cross sectional view of the connecting rod and piston assembly design as used in both gas or diesel engines.

Figure 7 is an example of the timing diagram for the duration of the opening period of both the scavenging port and exhaust port when both are uncovered simultaneously by the head of the piston.

Figure 8 is an example of timing diagram for a gas engine equipped with fuel injection type of fuel system. It shows the approximate duration of injection period of the spray of the gas fuel and the approximate number of degrees of piston travel in relation to the scavenging port opening when the spray of fuel begins and ends. The duration of the opening period and closing period of both the scavenging port and exhaust port openings which are both uncovered and covered simultaneously by the reciprocating piston are identical for both gas and diesel engine.

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

Detailed Description Proceeding therefore to describe the invention in detail, reference should first be made to Figures 1 to 3 in which reference character 10 illustrates generally a cylinder block including a cylinder bore 11,watercooling passages 12formedtherein and a cylinder head 13 having pre-combustion 21, injector 22 and glow plug 23 both installed securely to said pre-combustion chamber. The cylinder head 13 is secured to the upper side of the cylindrical bores by conventional means (not illustrated).

A piston assembly is reciprocal within said cylinder, said piston assembly being generally designated by reference character 14 and including a piston collectively designated 15 and a connecting rod collectively designated 16, details of which will hereinafter be described.

A constant pressure lubricating oil pump 17 which is submerged within an adequate amount of lubricating oil 18, is operatively driven by the crankshaft 19 by means of gears (not illustrated).

The crankshaft 19 is supported with several conventional bearings and is lubricated with filtered lubricating oil under constant pressure at all times.

The spin-on oil filter 20 filters all the lubricating oil before it is supplied to all vital moving parts.

In the diesel engine illustrated in Figures 1 and 3, a pre-combustion chamber 21 is installed into a machined opening formed in the cylinder main combustion chamber of each cylinder. A fuel injector assembly 22 and glow plug 23 are operatively installed in the pre-combustion chamber by conventional means, details of which will hereinafter be described.

In the gas engine shown in Figure 2, a fuel spray nozzle or fuel injector assembly 24 is bolted or screwed into an opening 25 formed in the cylinder close to the upper side of the scavenging port opening 26 of each cylinder, details of which will hereinafter be described.

A streamlined gas conduit 27 leads to an exhaust manifold 28 which is bolted to the cylinder block 10 at the exhaust port opening 29, said exhaust conduit is connected to the turbocharger 30 having a turbine wheel 31 which is mechanically connected to the air compressor wheel 32 by the shaft 33 supported with two oil bathed bearings in a conventional manner (not illustrated).

A supercharger assembly collectively designated 34 (Figures 1 to 4) having a scoop type compressor wheel 34A is operatively connected to the engine and driven by V-belt pulleys or by gears (not illustrated) to supply air under super-atmospheric pressure to the scavenging port 26 which may be connected to an air manifold if a plurality of piston and cylinders are utilized. The scavenging port 26 in the lower side portion 26A inclines inwardly and curves upwardly toward the wall of the cylinder, the purpose of which is so that the scavenging air, as it enters the cylinder, creates a turbulent motion as it swirls in an upward direction and efficiently scavenges the exhaust gases remaining in the cylinder.

A dry type air filter 35 is connected to the air compressor wheel casing 32A of the turbocharger 30 and is provided with air manifold 36 connected to the supercharger, so that filtered air is supplied to scavenge the individual cylinders.

It will also be appreciated that the supercharger 34 can be used with all configurations or alternatively, a turbocharger 30 and supercharger 34 combination connected in series may be utilized as shown schematically in Figures 1 to 4 collectively and designated 30 and 34.

As mentioned previously, this invention is suitable for use with multi-cylinder inline or V-type configurations as shown schematically in Figure 4.

Reference should be made to the spray nozzle or fuel injector assembly 24 designed for use in gas engines equipped with fuel injection types of fuel systems, as illustrated in detail in Figure 5.

The injector body 36 has a calibrated fuel passage 39 with spray nozzle tip 38 having a cone-shape needle valve 41 with its matched seat and details of construction are included later on in the specification.

Said fuel spray nozzle assembly injects metered atomized fuel under low pressure, supplied by the fuel injection system in a conventional manner (not illustrated). The cone-shape design of the needle valve 41 is such that the expansion pressure of the burnt gases cannot escape or back-up into the fuel system through the nozzle assembly.

Details of the preferred embodiment of the piston assembly is illustrated in Figure 6. The piston is preferably formed from aluminum alloy and includes a piston head 42, a piston head crown 43 and a surrounding cylindrical skirt portion 44.

The piston crown 43 is convexedly domed as illustrated by reference character 42 and convexedly curved on both sides 43A and 43B towards the scavenging port 26 and exhaust port 29.

This design of the dome of the piston head facilitates the flow of the scavenging air in an upward direction as it enters the cylinder thus creating a turbulent motion and providing efficient scavenging of the burnt gases. At the same time, the flow of the exhaust gases at the exhaust port, eject freely towards the exhaust manifold 28.

A pair of opposed piston bosses 47 are formed within the wall of the piston in a conventional manner and a wristpin 48 bearingly engages said bosses and also bearingly engages the wristpin end 49 of the connecting rod 16.

It is desirable to seal the outer end portions of the wristpin 48 to prevent the splash of the lubricating oil underside the piston head from being discharged through the bosses 47 supporting the wristpin. An "0" ring type of seal 50, made of materal having a high temperature resistance property is installed in an annular groove 51 formed close to the outer edge portion of each of the bosses of the piston.

For safety of operation and prevent cylinder wall wear, it is desirable to keep the wristpin in its centre position at all times so that a pair of retainer rings or keepers 52 is installed, one each in an annular groove formed close to the outermost edge portion of each of the piston bosses 47 adjacent the annular groove for the sealing ring. The magnified view of the design of the retainer ring 52 is shown as 52 in Figure 6A.

Two or more compression piston rings 54 are seated within the piston ring grooves 55 around the piston ring grooves 55 around the piston adjacent the upper end of the head thereof and an oil scraper ring 56 is installed within an annular groove 57 adjacent the base of the skirt of the piston with oil return apertures 58 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 56 always remains below the lower side 26B and 29A of the scavenging port and exhaust port opening respectively when the piston is at the top dead centre position of its stroke as illustrated in Figure 1.

The design of the scavenging port opening 26 is such that the lower side 26A inclines inwardly and upwardly towards the wall of the cylinder to provide and create turbulent swirling motion of the scavenging air as it enters in the cylinder in an upward direction for efficient scavenging of the burnt gases, when the scavenging port and exhaust port openings are fully uncovered by the reciprocating piston head passing thereby during the scavenging period.

In operation to this point, reference should be made to Figures 1 and 3.

In Figure 1, within a few degrees, before the piston reaches the top dead centre of its stroke, a metered amount of an atomized spray of diesel fuel is injected via a conventional fuel injector assembly 22 in the pre-combustion chamber 21 thus initiating ignition of the highly compressed air inside the cylinder between the main combustion chamber 46 of the cylinder head and the crown of the piston domed head. The expanding, burning gases of the main combustion chamber push the piston downward on the power stroke. As the piston continues its power stroke, at approximately 110 to 1 15" after top dead centre, the dome of the piston head starts to uncoverthe scavenging port 26 and exhaust port 29 openings simultaneously and the scavenging sequence or period commences.

As the piston reaches the bottom dead centre of its downward stroke as shown in Figure 3, both the scavenging port 26 and exhaust port 29 openings are fully uncovered by the dome of the piston head and the full blast of scavenging air supplied by the supercharger 34 enters the cylinder in an upward direction creating a turbulent swirling motion to completely scavenge the burnt but still expanding gases.

When the piston reaches its bottom dead centre of its down stroke as shown in Figure 3, half of its scavenging and exhaust period is already accomplished which is approximately 65" of crankshaft rotation.

Afterthe piston passes bottom dead centre as shown in Figure 3, it commences its upward stroke through the opposite 1800 portion of the crankshaft rotation and as soon as the dome of the piston head 43 starts to cover the scavenging port and exhaust port openings (which point is approximately 65" of crankshaft rotation from bottom dead centre), the scavenging and exhaust period ends and at the same time the compression period begins. As the piston continues its upward travel until it reaches top dead centre of its stroke as shown in Figure 1, one complete cycle of operation is completed and this cycle is repeated again in each cylinder.

It is to be noted that there are four periods of events taking place in one complete 360" cycle of operation, namely one downstroke and one upstroke of the piston. The four periods of events are: power stroke which starts from top dead centre and extends to approximately 1 10" to 1150 after top dead centre. At this point, the scavenging port 26 and exhaust port openings 29 starts to be uncovered simultaneously so that power, exhaust and scavenging events are taking place simultaneously.

Scavenging and re-charging with fresh air extends through approximately 1300 to 140 and extends through bottom dead centre. As the crankshaft continues its rotation through the opposite 1800 rotation after reaching and passing through bottom dead centre, the dome of the piston head starts to cover the scavenging port and exhaust openings simultaneously and the scavenging period ends. As the piston continues its upward stroke towards top dead centre, compression takes place until the piston approaches the top dead centre of its stroke which is approximately 110 to 115 of crankshaft rotation from the end of the scavenging sequence.

It is to be noted further that the scavenging port and exhaust port openings are formed in the same plane in axial position in the lower side of the cylinder which are both uncovered and covered simultaneously by the dome of the piston head passing thereby. The area of the scavenging port 26 and exhaust port 29 openings are in proportion to the piston displacement of the engine so that one or more scavenging port or exhaust port openings may be provided in the cylinder of much larger engines developing more horsepower.

Another important point to be noted is that when the piston reaches the top dead centre position of its stroke as is shown in Figure 1, the aforementioned oil scraper ring 56 always remains below the lower side of the scavenging port 26A and the lower side of the exhaust port 29A openings so that no lubricating oil can escape or discharge through these ports.

In the gas engine as shown in Figure 2, the fuel spray nozzle or fuel injector assembly 24 is of special design that opens under relatively low fuel pressure and is bolted or screwed in into an opening 25 formed into the cylinder adjacent to the upper side of the scavenging port opening so that the duration of the fuel injection period gives the required time for efficient mixing of the metered atomized spray of fuel to the scavenging air.

Reference should be made to the features of the fuel spray nozzle or fuel injector assembly illustrated in detail in Figure 5. The fuel spray nozzle is preferably formed from alloy steel and is accurately machined. It includes a body 36 having a threaded portion 37 for mounting in the cylinder wall. A further screw threaded portion 38 is provided connecting a low pressure line from a fuel distributor pump (not ilustrated).

A calibrated drilled passage 39 extends through the body 36 connecting to a fuel chamber 40 in the opposite end of the body. The cone-shaped desigri of the needle valve 41 which is held in its matched seat 42, is threaded to the body 36. A cone-shape needle valve 41 is held in position relative to its matched seat by means of a coil spring 43 having a predetermined calibrated tension and spring retainer 44 is mounted atthe headed inner end of the cone-shape needle vale to retain the spring in position so that it reacts between the seat and the needle valve normally maintaining the valve upon the seat.

With this design of the fuel spray nozzle, an atomized spray of fuel in metered quantity and supplied by the fuel distributor pump under low fuel pressure, is injected into the cylinder at a precise time when the dome of the piston head position is in a predetermined position relative to the scavenging port opening. The injection of the fuel begins approximately 10 before the dome of the piston head covers the scavenging port opening and ends approximately 5 after the scavenging port opening is covered by the dome of the piston head so that the approximate duration of the fuel injection period is 15" of crankshaft rotation.

Reference should be made to the novel design of the piston assembly illustrated in detail in Figure 6 and described previously. The piston is preferably formed from aluminum alloy and includes a piston head 42, a piston crown 43 and a surrounding cylindrical skirt portion 44.

The exhaust port 29 is formed within the lower side of the cylinder wall and in the same plane and in axial position to the scavenging port. The port conduit inclines downwardly and outwardly from the wall and is being uncovered and covered simultaneously with the scavenging port 26 by the dome of the piston head 42 passing thereby, the design feature of the said exhaust port is to facilitate the exit of the exhaust gases more freely into the atmosphere.

It is to be noted further that in a gas engine, the design features of the piston assembly as well as the construction of the scavenging port and exhaust port, are all identical to a diesel engine and that the constant pressure feed lubrication system is also utilized.

As discussed previously, starting a cold diesel engine is a major problem especially in countries where extremely cold weather conditions is a major problem. The pre-combustion chamber 21 having a small opening to the main combustion chamber, is installed into a port formed and accurately machined in the cylinder head connecting the main combustion chamber 46, said pre-combustion chamber having a fuel injector 22 and glow plug 23 installed therein. During the starting of the cold engine the said glow plug 23 is first turned on several seconds before the engine is started so that the injected atomized diesel fuel in the precombustion chamber ignites readily for ease of starting an extremely cold engine.

As mentioned previously, this invention is suitable for use in diesel or gas fueled engine having a single or multi-cylinder, inline or V-type configuration equipped with a supercharger or turbocharger combination and utilizing a constant feed lubrication system as being shown schematically in Figures 1,3 and 4 respectively.

It will also be appreciated that the supercharger 33 can be used with all configurations or alternatively, a turbocharger or supercharger combination connected in series may be utilized as shown schematically in Figures 1 and 4 and collectively designated 30.

Reference should be made to Figure 7 which shows a timing diagram during the scavenging period and the injection period of fuel as applied in a diesel engine equipped with fuel injection equipment. The location of the scavenging port and exhaust port openings formed in the lower side of the cylinder wall determines the duration of the scavenging period which extends approximately 1300 to 135 of crankshaft rotation. The scavenging port and exhaust port openings are both uncovered by the dome of the piston head simultaneously.

Finally, reference should be made to Figure 8 that shows a timing diagram of the duration of the openings of the scavenging port and exhaust port in relation to the piston degree of travel in a gas engine.

The location of the scavenging port and exhaust port openings formed in the lower side of the cylinder which are uncovered and covered simultaneously by the reciprocating piston that passes therein is shown. The approximate duration of the opening period of the scavenging port and exhaust port is 1300 to 140 of crankshaft rotation.

The scavenging port and exhaust port openings begin to be uncovered approximately 1100 to 115 aftertop dead centre of crankshaft rotation and said port openings are covered approximately 65" to 70" after bottom dead centre of crankshaft rotation.

The duration of fuel injection period is approximately 12" to 15 of crankshaft travel in which injection of the gas fuel begins approximatey 10 before the scavenging port opening is covered by the dome of the piston head and injection ends approximately 2" to 5" after the scavenging port opening is covered bythedome of the piston head so that complete mixing of the atomized spray of the gas fuel and the scavenging air is achieved.

For the excellent power performance of this invention, the size of the area of the scavenging port and exhaust port openings are both calculated or determined by the piston displacement of such engine and one or more port openings can be utilized to each cylinder of such engines developing relatively large horsepower output. The supercharger or turbocharger combination connected in series as used in the invention, supplies sufficient volume of air required for scavenging the exhaust gases and charging each cylinder during the scavenging period.

Claims

1. Atwo-stroke multi-cylinder internal combustion engine, having a cylinder block having cylinders bores formed therein, a cylinder head on an upper end of the cylinder bores defining a main combustion chamber, a piston assembly, in each of said cylinder bores and 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 the said cylinder block, characterized by a re-circulating type constant pressure feed oil pump mounted in the base of said cylinder block and being operatively driven by said crankshaft, an oil pan enclosing the lower side of the cylinder block, said crankshaft and said oil pump, said pump being operatively connected to the lubrication system of said engine, said cylinder bores having individual scavenging port and exhaust port openings formed in the lower side of each cylinder wall in the same plane and axial position, said scavenging port lower side opening inclining inwardly and upwardlytowards the walls of the cylinder, said scavenging port and exhaust port openings being both uncovered and covered simultaneously by the reciprocating piston passing thereby.

2. The invention according to Claim 1 in which said piston uncovers said scavenging port and exhaust port openings simultaneously at approximately 110 to 115 after top dead centre, and said scavenging port and exhaust port openings being covered simultaneously by the piston at approximately 65" to 70 after bottom dead centre, whereby the duration of the opening period for both the scavenging port and exhaust port is approximately 1300 to 140 of crankshaft rotation.

3. The device according to Claims 1 or 2 in which said piston assembly includes means to reduce and control the escape of lubricating oil therepast, said means including said piston assembly having a domed piston head, a piston skirt extending therefrom, a pair of diametrically opposed wristpin bosses in said skirt below said domed head, a wristpin mounted within said bosses with a retainer ring installed in an annular groove formed in an outermost edge portion of each of said bosses adjacent outer ends of the wristpin for restricting endwise movement of said wristpin, said wristpin operatively connecting said connecting rod to said piston, sealing "0" rings having high temperature resistance properties installed in an annular groove formed in each of said bosses of the piston adjacent to each end portion of the wristpin after assembly to prevent the escape and discharge of lubricating oil therepast, at least two compression piston rings situated in spaced and parallel grooves in the head of said piston above said wristpin bosses and at least one oil scraper ring mounted within an annular groove around the skirt close to a lower edge portion of said skirt, drain holes extending from said groove through said skirt to control and prevent the escape of lubricating oil past the individual scavenging port and exhaust port openings, said oil scraper ring always remaining below the lowermost edges of said scavenging port and exhaust port openings when said piston is at top dead centre of its stroke.

4. The invention according to Claim 1, 2 or 3 which includes a re-circulating type constant pressure feed lubrication system in which sufficient lubricating oil is stored in the oil pan being supplied and distributed to all the vital moving parts by means of the pressure feed lubricating pump being operatively driven by the crankshaft by means of gears, said lubrication system using a micronic spinon oil filter to ensure that clean oil is delivered at all times to the vital and critical moving parts.

5. The invention according to any of the preceding claims in which the design of the scavenging port lower side opening being inclined inwardly and upwardly toward the wall of the cylinder, provides a swirling turbulent motion of the scavenging air as it enters inside the cylinder in an upward direction when port opening is fully uncovered, said exhaust port opening being inclined downwardly and outwardly from the lower side of said cylinder wall to facilitate the flow and exit of exhaust gases to atmosphere.

6. The invention according to any of the preceding claims in which said gas fueled engine includes a fuel injector nozzle bolted or screwed into an opening formed in the lower side of the cylinder close to the upper side of each scavenging port opening, said nozzle metering atomized fuel under low fuel pressure supplied by a fuel distributor pump at a precise timing in relation to piston head crown position at the scavenging port opening, the injection of fuel beginning approximately 10 before the scavenging port opening is covered by the crown of the piston head, and injection of the gas fuel ending approximately 5O after the scavenging port opening is covered of the said piston head crown whereby the duration of the fuel injection period is approximately 15 of crankshaft rotation.

7. The invention according to any of the preceding claims which includes a supercharger being operatively driven by said engine and having an air intake and an air outlet, said outlet being operatively connected to an air manifold bolted to each cylinder to supply air under super-atmospheric pressure to scavenge and charge each of said cylinders.

8. The invention according to any of the preceding claims in which the duration of the closing of said scavenging port and exhaust port is approximately 220 to 230 of crankshaft rotation.

9. The invention according to any of the preceding claims in which the injection of the gas fuel commences approximately 10 before the scavenging port is covered and ends approximately 5" after the scavenging port is covered whereby the duration of the fuel injection period is approximately 15 of crankshaft rotation.

10. The invention substantially as illustrated and described.