WO2008052246A1

WO2008052246A1 - Internal combustion engine and method

Info

Publication number: WO2008052246A1
Application number: PCT/AU2007/001592
Authority: WO
Inventors: James Richard Hunt
Original assignee: Turner, Geoffrey Russell
Priority date: 2006-10-31
Filing date: 2007-10-19
Publication date: 2008-05-08

Abstract

An internal combustion engine is disclosed which has a cylinder (14) in which a piston (16) reciprocates. The engine has a cylinder head (13) which has a chamber (50) which communicates with the cylinder (14) via a jet port (70). A spark plug (60) is arranged for igniting fuel and therefore forced into the chamber (50) through the jet port (70) by movement of the piston so that a flame created by ignition of the fuel in the chamber (50) expands through the jet port (70) to ignite fuel in the cylinder (14) to increase the burn time of the fuel in the cylinder.

Description

INTERNAL COMBUSTION ENGINE AND METHOD

Field of the Invention

This invention relates to an internal combustion engine and also to a method of converting a diesel engine for spark ignition.

Background of the Invention

As is well known, diesel engines generally comprise a diesel injector which injects diesel fuel into a combustion cylinder of an engine. The fuel is ignited by compression of fluid within the cylinder. Generally diesel fuel is injected into the engine when the piston is slightly before top dead centre, and injection of fuel continues until the crank shaft is at about the 90° position or the cylinder is about H of the way through its cycle. This happens by injecting the fuel for a relatively lengthy period so that, notwithstanding the fact that the fuel ignites substantially immediately upon injection, injection of fuel continues so that much of the fuel is burnt at about the 90° position, thereby providing relatively high torque output.

Spark ignition internal combustion engines generally operate by igniting fuel with a spark plug in the cylinder when the piston is slightly before top dead centre. Ignition of fuel generally stops slightly after top dead centre .

As is also well known, it is desirable to reduce pollution and, in particular, greenhouse gases by providing alternative fuels for use in internal combustion engines . Such fuels include bio-fuels, methane and the like. These types of fuels are not readily usable with diesel engine because the fuels generally require spark ignition and such fuels are difficult to supply by conventional diesel fuel injection systems. Furthermore, such fuels burn very quickly and therefore comparable torque output is not achieved if the fuel is ignited in the same manner as occurs in conventional spark ignition engines .

Summary of the Invention

The object of the invention is therefore to provide an internal combustion engine which overcomes these problems and a method of converting a diesel engine to spark ignition .

The invention in a first aspect may be said to reside in an internal combustion engine, comprising: at least one cylinder; a piston for movement in the cylinder; a spark ignition device for igniting fuel in the cylinder; characterised by an ignition chamber having an outlet which communicates the chamber with the cylinder; and the spark ignition device being located for igniting fuel in the chamber which is provided to the chamber, from fuel and air delivered to the chamber from the cylinder, by movement of the piston, so that a flame created by ignition of the fuel in the chamber by the spark ignition device expands through the outlet into the cylinder to ignite fuel in the cylinder to increase the burn time of the fuel in the cylinder .

Because the fuel is initially ignited in the chamber and the flame expands out through the outlet, the expansion time of the burnt fuel is relatively long, thereby providing a relatively long ignition source for fuel in the cylinder. This means that the piston in the cylinder can move to the 90° position before the burn time of the fuel ceases , thereby taking advantage of the torque characteristics which occur when fuel is burnt with the piston at the 90° position of the cycle. Furtherstill, because the fuel is actually ignited by a spark ignition device , cleaner fuel such as bio-fuels , methane and the like, can be used and delivered to the cylinder in the same manner as occurs in conventional spark ignition engines , thereby avoiding the need to supply the fuel by a diesel fuel injector. Thus, a conventional diesel engine can be converted to operate with such fuels whilst still obtaining the advantages of a diesel engine in terms of torque output by providing the chamber, the spark ignition device for igniting fuel in the chamber, and the chamber communicating with the cylinder by the outlet.

Preferably the engine includes an inlet port for supply of air and fuel to the cylinder, an inlet valve for closing and opening the inlet port to the cylinder, an exhaust port and an exhaust valve for opening the exhaust port to the cylinder for escape of combustion gases .

Preferably the engine includes a block and a cylinder head and the chamber is located in the cylinder head.

Preferably the outlet is a jet port for providing slow escape or expansion of a flame created in the chamber through the port to the cylinder.

The invention also provides a method of converting a diesel engine to a spark ignition engine, comprising: providing a chamber in the engine which communicates with a cylinder of the engine; providing a spark ignition device for igniting fuel in the chamber; and wherein the spark ignition device is for igniting fuel in the chamber, which is provided to the chamber from fuel and air delivered to the chamber from the cylinder by movement of a piston located in the cylinder, so that a flame created by ignition of the fuel in the chamber by the spark ignition device, expands through the outlet into the cylinder to ignite fuel in the cylinder, to increase the burn time of the fuel in the cylinder .

Preferably the outlet is a jet outlet for providing slow expansion of the flame from the chamber into the cylinder.

Preferably the spark ignition device comprises a spark plug.

Brief Description of the Drawings

Preferred embodiments of the invention will be described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a view of a conventional diesel engine systern;

Figure 2 is an enlarged view of part of the system of Figure 1 ;

Figure 3 is a cross-sectional view of a first embodiment of the invention;

Figure 4 is a cross-sectional view through a second embodiment of the invention; and

Figures 5 and 6 are cross-sectional views through a third and fourth embodiment of the invention respectively .

Detailed Description of the Preferred Embodiments

Figures 1 and 2 show in schematic form a diesel combustion engine which has a block schematically represented at 12 and a cylinder head schematically represented at 13. A cylinder 14 is located in the block 12 and a piston 16 is located in the cylinder 14. In Figure 2 the piston is not shown for clarity. The piston 16 is connected to a crank shaft 18 by a connecting rod 20 so that the piston can reciprocate in the cylinder 14.

The head 13 has an inlet port 22 and an inlet valve 24 for — R ^■—

opening the inlet portion 2 to the cylinder 14. The cylinder head 13 also has an exhaust port 26 and an exhaust valve 28 for opening the exhaust port 26 to the cylinder 14 for escape of combustion gases.

A diesel injector 25 is located in the head 13 for supplying diesel fuel to the engine. As is known, diesel fuel is injected into the cylinder 14 and is ignited by compression of gases within the cylinder 14 as the piston 16 moves in the cylinder. Typically ignition takes place slightly before top dead centre and fuel is continually delivered by the injector 25 until the piston reaches about the 90° position throughout its cycle, so the connecting rod 20 is rotated 90° from the position shown in Figure 1. This enables a large amount of torque to be generated because of the position of the connecting rod 20 and the effective lever which is created whilst fuel is still supplied to the cylinder from the injector 25 and ignited in the cylinder 12.

Figures 3 to 6 show embodiments of the present invention . Only the head 13 of the engine is shown. It should be understood that the engine includes a piston, connecting rod and crank shaft, as is conventional.

In the embodiments of Figures 3 to 6 , air and fuel is delivered in the same manner as a conventional spark ignition engine from a fuel injector (not shown) or the like which supplies fuel to the inlet portion 22 which in turn travels to the cylinder 14 when the inlet valve 24 is opened.

In the embodiments of Figures 3 to 5, a chamber 50 is formed generally in the position which was occupied by the injector 25 in the diesel engine shown in Figures 1 and 2. Thus , when converting a diesel engine to a spark ignition engine of the preferred embodiment of the invention, the injector 25 is removed and the port in which the injector was located is bored out to receive the chamber 50.

The chamber 50 is provided with a spark plug 60 for igniting fuel and air in the chamber 50. When fuel and air are delivered to the cylinder 14 and the cylinder is performing its compression stroke, fuel and air is forced from the cylinder through outlet port 70 into chamber 14. When the cylinder reaches its usual position for ignition of fuel, such as about 10° before top dead centre, the spark plug 60 is operated in the conventional way to create a spark to ignite the fuel and air in the chamber 50. The fuel and air therefore burns to form a flame which expands out of the chamber 50 through outlet port 70 into the cylinder 14.

Because the port 70 is relatively small, the flame takes some time to expand out of the chamber 50 into the cylinder, thereby creating a source of ignition in the cylinder 14 for a relatively long period compared to that which occurs with conventional spark ignition systems . This therefore enables the piston to travel to the 90° position referred to above whilst fuel is still being ignited, thereby providing comparable torque characteristics to that which are achieved by a conventional diesel engine .

In the embodiment of Figure 3, the chamber 50 is formed from a peripheral chamber wall 51 and a top wall 53 in which the spark plug 60 is mounted. A tappet cover 54 is provided over the spark plug. The spark plug is connected to the ignition system of the engine in the conventional way so that the engine electronic ignition system under the control of the engine ECU can operate the spark plug to create a spark to ignite the fuel in the manner referred to above . — 1 —

Figure 4 shows a slight modification to the embodiment of Figure 3 in which the outlet 70 communicates with an outlet passage 74 which is elongate and of slightly bent configuration .

In Figure 5 the wall 53 of Figures 3 and 4 is omitted.

Figure 6 shows an embodiment similar to Figures 3 and 4 except that the outlet port 70 is connected to a bifurcated passage 72.

The size and configuration of the chamber 50 can be selected to provide a certain amount of additional capacity to the cylinder so that the compression ratio of the diesel engine converted according to the method of the preferred embodiment is reduced. Further reduction in compression ratio by increasing the size of the cylinder can be achieved by shaving the crown of the piston 16 if desired.

Since modifications within the spirit and scope of the invention may readily be effected by persons skilled within the art, it is to be understood that this invention is not limited to the particular embodiment described by way of example hereinabove.

In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprise", or variations such as

"comprises" or "comprising", is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.

Claims

1. An internal combustion engine, comprising: at least one cylinder; a piston for movement in the cylinder; a spark ignition device for igniting fuel in the cylinder; characterised by an ignition chamber having an outlet which communicates the chamber with the cylinder; and the spark ignition device being located for igniting fuel in the chamber which is provided to the chamber, from fuel and air delivered to the chamber from the cylinder, by movement of the piston, so that a flame created by ignition of the fuel in the chamber by the spark ignition device expands through the outlet into the cylinder to ignite fuel in the cylinder to increase the burn time of the fuel in the cylinder .

2. The engine of claim 1 wherein the engine includes an inlet port for supply of air and fuel to the cylinder, an inlet valve for closing and opening the inlet port to the cylinder, an exhaust port and an exhaust valve for opening the exhaust port to the cylinder for escape of combustion gases .

3. The engine of claim 1 wherein the engine includes a block and a cylinder head and the chamber is located in the cylinder head.

4. The engine of claim 1 wherein the outlet is a jet port for providing slow escape or expansion of a flame created in the chamber through the port to the cylinder .

5. A method of converting a diesel engine to a spark ignition engine, comprising: providing a chamber in the engine which communicates with a cylinder of the engine; providing a spark ignition device for igniting fuel in the chamber; and wherein the spark ignition device is for igniting fuel in the chamber, which is provided to the chamber from fuel and air delivered to the chamber from the cylinder by movement of a piston located in the cylinder, so that a flame created by ignition of the fuel in the chamber by the spark ignition device, expands through the outlet into the cylinder to ignite fuel in the cylinder, to increase the burn time of the fuel in the cylinder.

6. The method of claim 5 wherein the outlet is a jet outlet for providing slow expansion of the flame from the chamber into the cylinder .

7. The method of claim 6 wherein the spark ignition device comprises a spark plug.