WO2012162717A1

WO2012162717A1 - Air cooled ported piston for internal combustion engines

Info

Publication number: WO2012162717A1
Application number: PCT/AU2011/000692
Authority: WO
Inventors: Peter Selwyn OCAMPO; Paul Jermin OCAMPO
Original assignee: Individual
Current assignee: Individual
Priority date: 2011-06-01
Filing date: 2011-06-01
Publication date: 2012-12-06
Anticipated expiration: 2013-12-01

Abstract

An internal combustion engine implementation utilizing a piston with a port to allow cooling air to flow from the crankcase into the combustion chamber and to facilitate improved scavenging of the cylinder.

Description

AIR COOLED PORTED PISTON FOR INTERNAL COMBUSTION ENGINES

Description

Field of the invention

The invention pertains to the operation of an internal combustion engine. This invention provides improvement to the efficiency of internal combustion engines. By implementing an engine design utilizing a piston with an opening (port) that allows cooling air to flow through the combustion chamber, the operating temperature of the machine is lowered and exhaust gases are escaped effectively from the combustion chamber.

Background of invention

Modern society's reliance on fossil-fuel is ever increasing. At the same time the impact to the environment in the form of air pollution and greenhouse gases can no longer be ignored. Oil deposits are being depleted at a high rate and demand is still expected to grow as nations' requirement for energy continues to increase. According to industry experts, the use of motor vehicles as a mode of transportation contributes to approximately 10% of all greenhouse gases emitted to the environment. The number may not imply a significant figure when compared to other contributing factors but combined with the fact that the oil required to power these vehicles is dwindling in quantity and the growing risk of accelerating the greenhouse effect, it makes a perfect case to look for better ways of running them.

Although alternative methods are becoming available to power motor vehicles, a large percentage of cars on the roads today are still powered by internal combustion engines. The use of an internal combustion engines is the least efficient way to power a car. Most engines were designed during the time when fuel was abundant and the effects of pollution and emission were not a major concern. As a consequence, efficiencies were not maximized.

An internal combustion engine is theoretically a power pump. The efficiency of a power pump is measured by its ability to produce work output relative to the heat input. Heat input is generally derived from the combustion of fossil fuels. There are several factors that can impact efficiency and viability of an engine. Heat transfer, friction, type of fuel, and complexity can all contribute to losses. On the other hand, exhaust gases and quality of combustion have an impact to the environment. While not all of these factors can be addressed in a single solution, certain aspects of the implementation of current conventional engines can be improved to get better results.

The goal of applying thermodynamic principles to a system is to deliver a closed loop cycle. An ideal cycle is a cycle wherein the system is back to the original state at the start of the cycle. A typical internal combustion engine is designed as a close loop system. Pressure, volume and temperature are expected to be at the original state at the start of the process. While most production engine designs aim to get system state wherein these parameters are close to the expected levels at the start of the cycle, in practice is this is rarely achieved. There lies an opportunity to improve the process by addressing the problems preventing the cycle from being perfect.

During combustion event, the temperature in the combustion chamber of an engine increases to a level very close if not equal to the ignition temperature of burning gases. A large amount of heat is developed from the combustion process from which a considerable percentage is used to produce the work output needed. It is the heat transferred to the components of the engine that contributes to the inefficiencies of conventional designs.

An interesting component of this heat is the residual heat deposited to parts of the engine which has a direct influence to the cycle. This pose a problem as it impacts the start of the cycle. If the residual heat is not taken away from these parts, the next cycle starts at a higher temperature. In effect, reduces efficiency therefore results in less than ideal operating temperature.

While dramatic progress in metallurgy has delivered materials in the form of alloys that are effective in addressing strength and weight requirements of engine designs, there is still no material available with minimal heat absorption characteristics that can be used on engines. Conventional engine designs address the problem of residual heat by introducing mechanisms to cool down the engine.

In most cases it is in the form of a medium that absorbs and transports heat away from the engine. Engine oil partly accomplishes this, but mostly, the aspect of cooling is often addressed by the use of a coolant. The coolant in the form of air or fluid which is allowed to pass through cooling fins or cavities in the engine block and cylinder head to eliminate excess heat. This action is intended to bring down the combustion chamber temperature to level close to the start of the cycle and therefore lowering the operating temperature.

In practice, the engine does not get close to the ideal operating temperature. There is a large quantity of residual heat in the piston, cylinder and cylinder head. While most of the heat in the cylinder and cylinder head is eliminated by the coolant, the piston continues to absorb heat during combustion event. When the ratio between the exposed area of the piston to the combustion chamber and the total area of the entire combustion chamber is considered, a substantial amount of heat is expected to be retained in the piston during and after combustion. This is the part of the engine where heat is not effectively reduced. Although there is contact between the piston and cylinder wall through the piston rings and control rings, there is only minimal heat transferred away and removed from the piston.

While the above is mainly evident in four stroke engines, just as equal in a two-stroke engine, there is still substantial amount of heat that remains in the piston. Those familiar with the art of the two-stroke engine will understand the presence of air and fuel mixture in the crankcase is not enough to eliminate considerable percentage of heat deposited in the piston.

Another shortfall of a typical engine design that can be improved is the process of scavenging the cylinder. In this process burnt gases are exchanged with fresh mixture of air and fuel. On most engine designs, there is always an amount exhaust gases remains in the combustion chamber. This presents a disadvantage as it contaminates the air and fuel mixture which decreases the efficiency of combustion. Even in a four-stroke engine wherein a full stroke is allocated to eliminate exhaust gases from the combustion chamber, there is still a quantity of these gases left in the chamber. It is even worse in a two-stroke engine because the slight overlap between the intake and exhaust events exposes the fresh mixture to exhaust gases.

Furthermore, the alignment of the intake and exhaust ports in a large majority of engine designs is less than ideal. Intake and exhaust ports in a four-stroke engine are on the cylinder head. This configuration impedes the efficient flow of air and gases into and out of the cylinder. And, it is a similar case in a two-stroke engine as there is an offset in the alignment of the ports. Combustion inside the engines is a high speed process. The flow of air and gas requires to be maximized in order for the engine to attain highest potentials.

The invention presented in this claim is both a mechanism and a process applied to an internal combustion engine whose objective is to eliminate excess heat from the piston, to allow the effective removal of exhaust gases from the combustion chamber and to improve the rate of gas flow in the cylinder. The principle behind the design is simple yet effective and it can be applied to all types of internal combustion engines.

The key aspect of the design is the introduction of an opening in the form of a port in the piston. The port facilitates the passage of air into the combustion chamber which produces a cooling effect on the piston. The other aspect of the design is the manipulation of the crankcase as a charging cylinder used to pressurized air entering the combustion chamber. The pressure maintained by the air entering the combustion chamber is exploited to effectively expel exhaust gases away from the cylinder.

The implementation also resulted in the axial alignment of the intake and exhaust ports. Although coincidental to the design, the overall effect facilitates a more laminar flow of gases through the cylinder.

The combination of the aspects of the invention outlined above addresses the deficiencies identified in the current designs of internal combustion engines. By allowing air to pass though the piston itself, the heat deposited in the piston is reduced dramatically and the scavenging process is improved. An internal combustion engine implementation incorporating these aspects of the design will run efficiently and emit less air pollution. This engine design also eliminates other known problems such as valve float issues, valve timing issues, pre-detonation/engine knock, valve to piston clearances and the need for heavy lubrication.

Summary of the Invention

The highlight of the invention is the use of the combination of a ported piston and a charged crankcase in a conventional internal combustion engine implementation. The port facilitates the flow of cooling air from the crankcase into the combustion chamber. The effect of the air flowing in the manner as described is the removal of excess heat from the piston.

The use of the crankcase cavity to supplement the operation and events in the combustion chamber is integral to the design. The crankcase cavity serves as a charging pump to compress air during the power event of the cycle. A method of covering the air intake port leading to the crankcase is used to conditionally seal the crankcase allowing pressure to build up when the piston is moving towards the crankshaft. The pressure build up is then used to propel cooling air to flow into the combustion chamber during intake event.

The air traversing through the port also aids in impelling burnt gases out of the cylinder during the exhaust and intake events. This enhancement permits the engine to operate effectively even at low compression ratio, to deliver a higher power output due to reduced stored rotational energy and friction and to run at a lower operating temperature when used with any fuel.

To take advantage of the cooling facility and better scavenging process introduced by the invention, a corresponding cycle integral to the claim was developed. A two-stroke four-event cycle is presented which integrates the ability to lower the operating temperature of the piston and effective scavenging process. The aspects that differentiate the new process from typical engine processes are the first stroke combines the intake and compression events and the second stroke combines the power and exhaust events.

Brief Description of Drawings

Figure 1 illustrates all the key components of the invention

Figure 2 illustrates the key aspects of intake event

Figure 3 illustrates the key aspects of compression event

Figure 4 illustrates the key aspects of power event

Figure 5 illustrates the key aspects of exhaust event

Figure 6 illustrates the details of piston and port

Detailed description of preferred embodiments

With reference to figure (1), a representative spark ignition internal combustion engine is illustrated to demonstrate aspects of the invention. The invention can be applied to any internal combustion engine. In order to simplify the illustration a single piston engine model is demonstrated. It should be noted that the invention can be applied to multiple cylinder engines.

The engine is composed of an engine block (16), a fuel feeder port (2), fuel injection pump/system (4), cylinder head (10) with exhaust ports (14) and valves (5), overhead cam (12), a spark plug (13), a crankcase (9), a crankshaft (15), a connecting rod (11) and a piston (6) with an air intake port/s (8) and valve (1). The combustion chamber (7) is defined by the boundaries of the cylinder walls, the surface of the cylinder head exposed to the chamber and the surface of the piston facing the chamber.

The air intake port (8) is situated on the surface of the piston (6) facing the combustion chamber (7). The port opening (8) is covered by a valve (1)1 or any mechanical instrument which can be actuated to be either in an open or close state depending on the event. In the case when a valve is used, the valve may be actuated mechanically or by the differential in pressure between the combustion chamber and crankcase or the combination of a spring and the differential in pressure between the combustion chamber (7) and crankcase (9).

The fuel feeder port (2) is exclusively used to deliver fuel to the combustion chamber (7). Fuel is delivered into the combustion chamber by a typical fuel injection system (4) used in production engines. With a direct injection system the port may be replaced by a fuel injector (2) directly attached to either the wall of the cylinder or to the cylinder head adjacent to the exhaust port or ports. Fuel delivery is regulated by an electronic control unit (ECU) which determines the amount of fuel necessary to achieve ideal combustion and emission levels.

Air is introduced into the combustion chamber (7) from the crankcase (9) through the port (8) in the piston (6). The port opening which is covered by a valve or any mechanical implement either permits or restricts the flow of air into the chamber depending on the event. Air to be fed in the combustion chamber is firstly compressed in the crankcase. Compression is accomplished by the combination of the use of a reed valve (3) or similar sealing device in the air intake port of the crankcase and the action of the piston moving towards the crankshaft while the valve on the piston is in a closed state.

The piston is connected to the crankshaft (15) by the connecting rod (11). The reciprocating motion of the piston within the cylinder between the top dead centre and bottom dead centre positions allows for the crankshaft to produce rotational movement. This action produces the work output of engine. Combustion is initiated when the spark plug is triggered. The spark ignites the air and fuel mixture in the combustion chamber which creates the chemical reaction to produce heat.

In this demonstration, the exhaust valve (5) is actuated by the overhead cam (12). The valve on the piston (8) is in a 'floating' configuration and it is actuated by the differential in pressure between the combustion chamber and the crankcase. In actual practice, this intake valve can be controlled by a mechanical actuator or can be spring loaded.

The start of the engine cycle is the bottom dead centre position, when the engine crank angle is 180 degrees relative to the top dead centre (0 degrees). This is when the piston is closest to the rotational axis of the crankshaft. This is the intake event wherein cooling air is allowed to enter from the crankcase through the port in the piston into the combustion chamber. At this stage the valve on the piston is in an open state, the reed valve in the crankcase port is in a close state and the exhaust valve is in an open state, as shown in figure 2. During this event compressed air is introduced into the combustion chamber from the crankcase which has a subsequent effect of pushing exhaust gas out of the cylinder.

At any period when exhaust gases has completely escaped the combustion chamber which is between 180 to 300 degrees crank angle, fuel is introduced into the combustion chamber from the fuel port. Once the appropriate amount of fuel has entered the combustion chamber, the compression event begins. At this stage the valve on the piston is in a close state, the reed valve in the crankcase port is in an open state and the exhaust valve is in a close state, as shown in figure 3. This event allows for the air and fuel mixture to compress and ends just before the piston reaches top dead centre.

At top dead centre, 0 degree engine crank angle, when the piston is farthest away from the crankshaft the power event occurs. This is the stage when the the spark plug is triggered and the combination of air and fuel mixture is ignited. As a result of ignition, the piston moves towards bottom dead centre to produce work. At this stage the valve on the piston is in close state, the reed valve in the crankcase port is in close state and the exhaust valve is in a close state, as shown in figure 4. In this event, the charging action in the crankcase also takes palce. The movement of the piston with a closed valve towards the crankcase while the crankcase cavity is sealed by the reed valve allows for the air to be compressed.

At any time after combustion is completed, which is between 45 to 180 degrees, the exhaust event takes place to allow burnt gases to exit. At this stage the valve on the piston is in close state, the reed valve in the crankcase port is in a close state and the exhaust valve is in an open state, as shown in figure 5. When the exhaust valve on the cylinder head is opened exhaust gases commence to escape. This event overlaps with the intake event and ends when exhaust gases are completely scavenge from the combustion chamber.

Claims

1. A method of operating an internal combustion engine wherein at least one piston is implemented with an opening in the form of a port or a number of ports, said port or ports are situated on the surface of the piston facing the combustion chamber, said port's opening or ports' openings are covered by valves or any mechanical instruments which can be actuated to be either in an open or close state depending on the event, and said port or ports are used as passageways for air to flow into the combustion chamber from the crankcase.

2. The internal combustion engine as in claim 1, wherein: when applied to a single cylinder engine, the crankcase is used as a charging pump which operates when air present in the crankcase cavity is compressed while the piston with port closed is in the process of moving towards the crankshaft, during such period the cavity is complementarily sealed by a mechanical instrument in the crankcase intake port allowing pressure to develop and later on allowing the compressed air to be forced into the combustion chamber during intake event.

3. The internal combustion engine as in claim 1, wherein: the crankcase which is used as a charging pump is divided into independent sealable compartment per cylinder when used in multiple cylinder engines and characterized by the process when air in the compartment cavity is compressed when the piston with port closed is in the process of moving towards the crankshaft while the air intake port of the cavity is sealed by a mechanical instrument and such pressure developed allows the air to be forced into the combustion chamber during intake event.

4. The internal combustion engine as in claim 1, and 2 or 3, wherein: the fuel feed system is either a low or high pressure implementation in which the correct amount of fuel is introduced into the combustion chamber to achieve an ideal stoichiometric ratio.

5. The internal combustion engine as in claim 1, and 2 or 3, wherein: the fuel feed system is mechanically or electronically controlled using feedback loop to achieve appropriate air to fuel ratios relevant to different engine operating conditions.

6. The internal combustion engine as in claim 1 and 2 or 3, wherein: the engine operates in a two-stroke four-events cycle in which the first stroke combines the intake and compression events and the second stroke combines the power and exhaust events.

7. The internal combustion engine as in claim 1 and 2 or 3, wherein the start of the cycle is when the piston is close to the bottom dead centre position, which is the intake event when air is allowed to enter from the crankcase through the port in the piston into the combustion chamber, then fuel is allowed to enter the combustion chamber from a separate fuel port at any point in time as necessary to maximize efficiency during this event, once the appropriate amount of fuel to has entered the combustion chamber, the compression event begins, which ends just before the piston reaches top dead centre; and when at top dead centre, when the piston is farthest away from the crankshaft the power event occurs, the combination of air and fuel mixture is ignited, and as a result the piston moves towards bottom dead centre to produce work, and at any time after full combustion, the exhaust event may take place to allow burnt gases to exit the combustion chamber.

8. The internal combustion engine as in claim 1 and 7, wherein an enhancement to the process is introduced such that between the power and exhaust event water is injected in the combustion chamber which allows for further cooling of the piston and at the same time augment the power output of the engine by the action of water expanding during vaporization.

9. The internal combustion engine as in claim 1 and 2 or 3, wherein fuel used is not limited to gasoline.