WO1992001146A1

WO1992001146A1 - Pressure charged multi-cylinder 2-stroke engine

Info

Publication number: WO1992001146A1
Application number: PCT/AU1991/000299
Authority: WO
Inventors: Glen A. Dullaway
Original assignee: Dullaway Glen A
Priority date: 1990-07-05
Filing date: 1991-07-05
Publication date: 1992-01-23

Abstract

An internal combustion engine power unit comprising two or more reciprocating piston power cylinders (1) operating on two-stroke cycles with charge air supplied by a crescent chamber type rotary compressor (2) which is driven in timed relation with the crankshaft (3). Charge air transfer and exhaust are by way of valve-controlled ports (15, 19). Also disclosed is an embodiment in which the charge air compressor comprises a reciprocating piston pump driven from the crankshaft (3) via a step-up gear train.

Description

PRESSURE CHARGED MULTI-CYLINDER 2-STROKE ENGINE

TECHNICAL FIELD

This invention relates to reciprocating piston internal combustion engines of the type wherein, atleast the power cylinders operate on two stroke cycles and use reciprocating pistons. A pumping cylinder that is driven from the power cylinder output shaft, and provides atleast most of the intake charge for scavenging and combustion in the power cylinders, communicates with the head of, or high pressure portion of the power cylinder by transfer ports. Said transfer ports serve topass the intake chage to the power cyl inders during the transfer phase , and these are controlled atleast by transfer valves that control communication between the power cylinder and transfer port. Exhaust ports also exit the power cylinders from the head portion thereof, and communication thereto is controlled by exhaust vavles.

BACKGROUND ART

Engines of this type have been disclosed in numerous prior art, with most using reciprocating piston pumping cylinders. These designs are typified by US PAT NO 3,880,126 and

4, 458, 635. However, these designs are very undesireable, as they have the pumping cylinder reducing volume stroke, being the same duration as that stroke of the power cylinders. As this design dictates that an efficient transfer phase to the power cylinders be about the duration of the reducing voume stroke of the pumping cylinder, and the power cylinders operate on two stroke cycles, then a transfer phase which takes the time for about a half of a power cylinder cycle, is far to long and reduces the cycle time available for the other phases which also have to occur within that cycle. Obviously then, the powercylinder cycle is severelly compromised by the use of such a pumping cylinder thereon.

My previously filed PCT application, PCT/AU90/00261 discloses a engine design which has reciprocating piston pumping and power cylinders, and overcomes the above cited major problem by having the pumping piston driven at twice the cyclic velocity as the power pistons, with, the stroke of the pumping cylinder taking a half as long as that of the power cylinders. However, this design is very specific and no disclosure is made in the said PCT application of any other designs which share the designs enviable features. It has sinse been found that there are other designs which share that designs enviable features, and as is obvious from the

disclosure herein, these designs are not obvious from that disclosed in the abovesaid PCT application. These other designs have advantages above those already offered by the design disclosed in the above said PCT application, and these include improved engine operating efficiency by way of improved gas flows during the intake and transfer phases, and an improved power to weight ratio. Also, it has also been found that the design disclosed in the said PCT application is undesireable as disclosed, which is due to an undesirable operating cycle which results in an excess of oxides of nitrogen being emitted at the lower operating loads and speeds.

In the above said PCT application, gas flow through the transfer ports has been a limiting feature of the design and this results from, the restrictive nature of the transfer portand controlling valve, and the transfer ports are undesireable long. If the transfer port flow area is increased to allow for higher speed operation, then an unacceptable increase in the dead volume of the said port occurs due to, the excessive length thereof, as well as the requirement for transfer port commmunication to two power cylinders. A decrease in the cylinder area available for provision of the intake valves is also a result of just increasing the transfer port flow area. An increase in the said dead volume results in the pumping cylinder displacement having to be increased to pass the samevαlume of intake air through the transfer ports, and this has obvious power to weight ratio, and friction disadvantages.

Also, no disclosure is made in the said PCT application of any other means to assist in the transfer of the air to the pumping cylinder, which if successfully incorporated in the design, will increase the engines operating efficiency and power to weight ratio.

DISCLOSURE OF INVENTION

The main object of the presented invention, discloses a engine design which has one or more units, with each said unit comprising of two to four reciprocating piston power cylinders operating on two stroke cycles, and a pumping cylinder which may have any number of pistons. A pumping cylinder with the time required for a reducing volume stroke whilst that stroke is in communication to the transfer ports openings thereinto, is or takes less than 75 percent of the time required for a power piston reducing volume stroke. A transfer phase which takes less than eighty % of the said time, whilst said pumping piston remains in timed relation to the movement of the pistons of the power cylinders. The intake charges are transferred in a sequence to the power cylinder. Said transfer phase occurs atleast mostly during the respective power cylinders reducing volume stroke and before that power piston has moved through to ten percent of the cylinder volume before TDC and it is preferred that a single or dual pumping cylinder cycles provide the intake charge for a pumping cylinder. Said exhaust valves begin to open after the respective power piston has moved through fifty percent of its expansion stroke, and before moving past its BDC position. Atleast substantially, saidexhaust valves remain open for atleast fifty percent of the time required for a power piston stroke, and finally close before said piston moves through to ten percent of the cylinder volume before TDC. Preferably crankshaft and conrod means cause reciprocation of atleast the power cylinders, and poppet type valves are used as the exhaust and transfer valves, whilst substantially atleast, a greater portion of exhaust gas is retained in the power cylinders when the engine is operating at low load and speed, then when it is operating at high load and speed. It is also preferred that the pumping piston reducingvolume stroke takes one half or two thirds of the time required for a power piston reducing volume stroke, and the transfer of atleast ninety percent of the intake charge to a power cylinder is performed during one or two pumping cylinder cycles, which increases the efficiency of the cycle. If the said transfer of the intake charge occurs over two pumping cylinder cycles, then the cycle is further optimised by the final closing of the respective exhaust valves about in the middle αf the two said cycles.

Another object of this invention has the transfer port which communicates the pumping cylinder to a power cylinder, being controlled by two or more poppet type valves, and to have a singular said transfer port opening into the pumping

cylinder, with the port branching into seperate ports to each valve, at a point closer to the transfer valves.

A further object of this invention has the top of the pumping cylinder piston, having different heights, with the highest portions thereof being directly below the transfer port openings thereinto, so that the said highest portions thereof extend up into the said openings to displace volume therein, when the said, piston is about its TDC position.

A still further object of this invention has a said

transfer port having at a point therealong, a smaller flow area than the maximum available at the sealing face of the transfer valves.

An even further object of this invention has the two power cylinders being separated by less than one power cylinder diameter, with the pumping cylinder being positioned to one side of the power cylinders and with a single transfer portopening into the pumping cylinder, and which communicates the pumping cylinder to both power cylinders, after branching into separate ports to each valve.

A further object of this invention then discloses a said engine design which uses a reciprocating piston pumping

cylinder as shown in the above said PCT application, and which has the transfer port openings into the pumping cylinder, that when taken from the mean pumping cylinder height, and with reference to the respective planes which intersect the pumping and a respective power cylinder axis, extend for a distancedown the side of the said cylinder, as well as extending for a distance across the top of the cylinder. Preferably, the transfer ports extend down the pumping cylinder wall to where the top ring reversal point is.

Still even further objects of this invention, have air fuel injector means included thereon, with the air supply being taken from the pumping cylinder, and preferably being taken from about the centre of the cylinder in a reiprocating piston pumping cylinder design, which is where the highest pressures are obtained. Also, the drive to the pumping piston has phase changing means included therein so that the phasing of the pumping pistons relative to the power piston may be altered, and further the use of valves to controll communication of the pumping cylinder to the transfer ports, which also increases the gas flow to the power cylinder for a given pumping cylinder displacement.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG 1 - is a top schematic view of the preferred design, which has a single rotary vane pumping cylinder supplying the intake charge for three inline power cylinders, and shows the cylinder port and valve locations.

FIG 2 - is a cross section through the pumping and head section of the middle power cylinder along line A - A of FIG 1, and through the power cylinder axis in the direction of A-A.

FIG 3 - Is a top schematic view of the alternative design, and shows the cylinder, port, and valve locations.

FIG 4 - is a cross section of the alternative design with the section through the head being along line A - A of FIG 3, and through the cylinder and crankshaft axis but around the pistons and crankshafts thereof.

MODES FOR CARRING OUT THE INVENTION

Refering to FIGS 1 - 2, the preferred design is a naturally aspirated spark ignition version, which has three inline power cylinders 1, and a single rotary vane pumping cylinder 2 which is positioned off to the side of the power cylinders. A single power crankshaft 3 and power conrods 4, cause reciprocation of the power pistons 5 inside a common block 6, and a common head 7 closes adjacent ends of all said power cylinders 1. The power pistons are phased one hundred and twenty power crankshaft degrees apart, and so that at every one hundred and twenty said degrees through out a complete cycle, a power piston of a different cylinder is attaining TDC position. The rotor 8, of the pumping cylinder 2 is fixed to the rotor shaft 9 which is supported for rotation in the pumping cylinder housing 10 by journal means, with said housing 10 being bolted to the head 7. Three equally spaced pumping pistons, being vanes 11, are forced to reciprocate in their slots in the rotor 8 to remain in sealing contact with the inner periperal wall of the pump housing 10, by cam means located on the inside of the said rotor 8, and these are not shown in the drawings. The said rotor is driven to perform two revolutions to a power

crankshaft revolution, by toothed belt means from the power crankshaft, with the toothed belt and pulleys not being shown on the drawings. With this drive and pumping piston 11

locations, two cycles are required to transfer an intake charge to the power cylinders 1, and this occurs over one hundred and twenty power crankshaft degrees. Two idler pulleys which are positioned on the outside of belt, a half way between the said pulleys, are electronically actuated, maintain tension on the said belt, and alter the phasing angle of the pumping pistons 11 relative to the power pistons 5 between sixty and eighty power crankshaft degrees BTDC, so that the optimum said phasing angle for any load and speed operating condition of the engine is obtained. An intake port 14, communicates the pumping cylinder 2 to atmosphere, and transfer ports 15 communicate the pumping cylinder to all of the power cylinders. Control of the said transfer ports 15 at the pumping cylinder end is by non return type reed valves 16, and poppet type transfer valves 17control communication between the transfer ports 15 and

respective power cylinders 1. Exhaust valves 18 which are also of the poppet type, control communication between the power cylinders 1, and the exhaust ports 19. All of the said poppet type valves are forced to open by electronic solenoid type means, and provide for variable said valve timings.

The combustion chambers 12 of all power cylinders 1, remain in constant communication with the respective power cylinder 1, and spark plug means and direct air fuel injection means are located thereinto to respectively, cause ignition of, and tocause the combustible mixture. The spark plugs are located in recesses in the combustion chamber, so that the flow of the transferring intake charge does not pass directly across the spark plug which would reduce longevity thereof.

The method of operation of the preferred design is now described. Intake air is drawn into the pumping cylinder through the intake port 14, as a vacum is created behind the rotating vanes 11. On the other side of the said vanes 11, the induced intake charge is being transferred into the respective power cylinder, through the respective transfer port which has its controlling transfer valve open, and in the case of FIG 2, the second cycle of said intake charge is being transferred to the middle power cylinder. The respective reed valve opens under very little pressure to allow said transfer to proceed. After that pump cycle completes the transfer of the intake charge to the abovesaid power cylinder, the intake charge of the next two pump cycles will be transferred into the right hand side power cylinder of FIG 2, with the following two said cycles having the intake charge induced therein, being

transferred to the power cylinder to the left of FIG 2. This provides for every power cylinder to be charged with a fresh intake charge for every power crankshaft rotation. The

respective transfer valves of a power cylinder close five power crankshaft degrees after the vane 11 moves across the transfer ports 15.

The operation of the power cylinders is the same as each other so description is directed to a single said cylinder. With the transfer valves 15 closed, further compression of the charge therein results. During this time fuel is injected, withfuel injection finishing not latter than fifty power crankshaft degrees BTDC. Spark ignition occurs as the piston thereof is about its TDC position. The piston then moves towards BDC on its power stroke, before at between fifty and seventy degrees before BDC, the exhaust valves open and blow down occurs. The exhaust valves 18 then remain open untill between ninety and one hundred degrees BTDC, and always close before the transfer valves 15 close. The transfer valves 15 open between ten and thirty degrees ABDC, which initiates the transfer scavenging phase thereto. Now with reference to the alternative design disclosed in

FIGS 3 and 4, which shares the same identifying numbers for the same respective components of the preferred design. A

reciprocating piston pumping cylinder 2, which has said

reciprocation being caused by crankshaft and conrod means, respectively 9 and 10, with said pump piston 11 being driven at twice the cyclic speed of the power pistons 5 of the two power cylinders 1, by gears 13 which are fixed to the respective crankshaft. All said cylinders are inline in a common block 6, and a common head 7 closes ad -j9ac-ent ends of all said cylinders. Intake port control to the pumping cylinder is by poppet type intake valves 20. The operation of this alternative design is the same as that disclosed for the preferred design in my abovesaid PCT application, but of note is the transfer ports and openings into the pumping cylinder, as well as the

protrusions 21 on top of the pumping piston. The transfer port 15 which communicates the pumping cylinder 2 to a power

cylinder 1 has a singular port opening into the pumping

cylinder 2, with division thereof into two smaller ports which then communicate to each transfer valve, occuring about one third of the distance from the pumping cylinder to the transfer valves. The said port opening into the pumping cylinder extends down to the top ring reversal point and extends radially inwards for only a short distance so that the area available for provision of the intake valves is not compromised.

The highest portions of the pumping piston 21, appear as protrusions on the top thereof and these displace volume in that portion of the transfer port volume which is over the top of the pumping cylinder, when the piston thereof is about its TDC position, so that the dead volume thereof is reduced. The flow area just inside the transfer port opening into the pumping cylinder is that point therealong which has the

smallest flow area, and this is just before where the singular port splits into two.

Claims

CLAIMS.

1. An internal combustion engine comprising of one or more units, with each said unit consisting of; two or more power cylinders, and a pumping cylinder; said power cylinders operate on two stroke cycles and have reciprocating pistons and

mainshaft means to cause said movement; said power cylinders being within a block, and with adjacent ends thereof closed by a head; the pumping piston of the said pumping cylinder is driven from the power mainshaft or output shaft and the timerequired for a reducing volume stroke whilst that stroke is in communication to the transfer ports, is seventy five percent or less of the time required for a power piston reducing volume stroke; said pumping cylinder communicates with suitable positioned intake and transfer ports, repectively for intake charge induction, and transfer of the induced intake charge to the power cylinders; said transfer ports have transfer valve controlled communication with the head section of said power cylinders, and said transfer valves open to allow said transfer to occur atleast mostly during the respective power cylinders reducing volume stroke and before said piston has moved through to ten percent of the cylinder volume before TDC; valve

controlled exhaust ports exit from the head section of each power cylinder; the intake charges for each power cylinder cycle, are transferred in a sequence to the power cylinders of that unit, with the pumping pistons remaining in timed relation to the movement of the power pistons; said transfer valves remaining open for less than eighty percent of the time

required for a power cylinder reducing volume stroke; said exhaust valves begin to open, after the respective pistonthereof has moved through atleast a half of its expansion stroke, and before moving past its BDC position; said exhaust valves remain open for atleast fifty percent of the time required for a power piston stroke, and atleast untill the respective transfer valve begins to open, and said exhaust valves finally close no later than ten percent of the time required for a power piston stroke before said piston attains its TDC position.

2. The engine of claim 1 and wherein; crankshaft and conrod means cause reciprocation of the said power pistons; poppet type valves are used for atleast the transfer and exhaust valves; the mean height of the transfer valve sealing faces, is above the mean top reversal point of that power piston; a greater volume of exhaust gas is retained in a power cylinder when the engine is operating at a low load and speed operating condition, then when the said engine is operating at a high load and speed operating condition.

3. The engine of claim 2 and wherein; a single pumping cylinder cycle is performed to transfer an intake charge to a power cylinder.

4. The engine of claim 2 and wherein; two pumping cylinder cycles are performed to transfer an intake charge to a power cylinder.

5. The engine of claim 2 and wherein; a pumping piston reducing volume stroke takes one half of the time required for a power piston reducing volume stroke.

6. The engine of claim 2 and wherein; a pumping piston reducing volume stroke takes two thirds of the time required for a power piston reducing volume stroke.

7. The engine of claim 2 and wherein; two or more power cylinders of a unit are positioned close together, with the pumping cylinder being positioned to one side thereof; a singular transfer port opens into the pumping cylinder, and communicates it to both the power cylinders, after the said transfer port branches into the first and second transfer ports, and then into separate ports to each transfer valve.

8. The engine of claim 2 and wherein; two or more poppet type valves controll a transfer port communication to a power cylinder.

9. The engine of claim 7 and wherein; separate ports actually communicate a said transfer port to its controlling valves, but the said transfer port opening into the pumping cylinder is a singular port opening, with division to two ports occuring between the transfer valves and the pumping cylinder.

10. The engine of claim 7 and wherein; the maximum flow area available at the transfer valves, is greater than the flow area available at another point along the transfer port.

11. The engine of claims 5 and 7 combined and wherein; a reciprocating piston pumping cylinder is used; a transfer port which communicates the pumping cylinder to a power cylinder, has its opening into the pumping cylinder, with reference from the mean top of the pumping cylinder and with reference to the respective plane which intersects the pumping and respective power cylinder axis, extends for a distance down the said cylinder wall, as well as extending for a distance across the top of the cylinder.

12. The engine of claim 11 and wherein; a said transfer port extends down the pumping cylinder wall to the top ring reversal point thereof.

13. The engine of claim 7 and wherein; a reciprocating piston pumping cylinder is used; the top of the pumping piston has different heights, with the highest portions thereof being below the transfer port openings, and with said highest portions being contoured so that as the said piston is about its TDC position, the said highest portions extend up into the transfer ports to displace volume therein.

14. The engine of claim 2 and wherein; an air fuel

injeciton system is used with the air supply for the said system being taken from a high pressure portion of the pumping cyunder with communication therebetween being by passage way means; a non return type valve is located within the said passage way, close to the said pumping cylinder, so that it maintains pressure within the said passage way.

15. The engine of claims 5 and 7 and 14 combined and wherein; said take off portion for air supply to said injector, is from about the middle of the head of the pumping cylinder, where the highest pressures are attained.

16. The engine of claim 2 and wherein; a phase changing mechanisn is used on the drive to the pumping piston, so that the phasing angle of the pumping pistons relative to the power pistons may be altered.

17. The engine of claim 2 and wherein; valve controlling means control communication from the pumping cylinder to the transfer ports.

18. The engine of claim 4 and wherein; the exhaust valves of a power cylinder finally close about when or slighly after when the first reducing volume stroke of the pumping cylinder has been transferred thereto.