GB2279994A

GB2279994A - I.c.engine fuel injection gas supply system.

Info

Publication number: GB2279994A
Application number: GB9314310A
Authority: GB
Inventors: Thomas Tsoi-Hei Ma
Original assignee: Ford Motor Co
Current assignee: Ford Motor Co
Priority date: 1993-07-10
Filing date: 1993-07-10
Publication date: 1995-01-18
Also published as: GB9314310D0

Abstract

Each engine combustion chamber 10 is connected by way of a respective non-return valve 20 to a common pressure reservoir 28 and a pressure regulator 30 provides gas at a regulated pressure to the fuel injection system via outlet pipe 46. The regulated pressure may be varied by changing the force of the spring 40, varying the pressure in the spring chamber or by an electrical signal to a regulator electromagnet. <IMAGE>

Description

Internal Combustion Engine Field of the invention The present invention relates to an internal combustion engine having a source of compressed gas to assist in fuel injection.

Background of the invention Various forms of fuel injection system are used in internal combustion engines that require a source of compressed gas.

Examples of these are air-assisted and air-forced fuel injectors as used in both 4-stroke and 2-stroke engines.

To provide a supply of compressed gas, a special compressor is required that is driven by the engine. This in itself adds to the cost of the fuel injection system. The complexity of the engine is still further increased because steps must be taken during starting to pressurise the air rail in a minimum of time.

Obiect of the invention The present invention seeks to provide an engine having a simpler and less costly compressed gas supply for use by the fuel injection system.

Summarv of the invention According to the present invention, there is provided a fuel injected internal combustion engine in which each engine combustion chamber is connected by way of a respective non-return valve to a common pressure reservoir and a pressure regulator is connected to the pressure reservoir to supply gas at a regulated pressure to the fuel injection system.

In the invention, the engine itself acts as the compressor in that the pressure in the combustion chambers is supplied to the pressure reservoir through the non-return valves. In the first few operating strokes of the engine, the pressure reservoir reaches the peak pressure developed in the combustion chambers and thereafter only the volume of gas consumed by the fuel injection system is drawn in each cycle.

Apart from the advantage of providing a convenient and inexpensive supply of compressed gas, the invention offers the advantage that because the compressed gas is drawn from downstream of the intake throttle, the gas used by the fuel injection system is effectively contained in a closed circuit and does not interfere with the engine idling speed control. This is to be contrasted with the prior art arrangements in which the gas used in the assisted or forced fuel injection is ambient air that constitutes an air leak bypassing the intake throttle. Limits must in this case be placed on the air used in the fuel injection system if the idling speed is not to be raised.

Brief description of the drawing The invention will now be described further, by way of example, with reference to the accompanying drawing which is a schematic section through an engine cylinder, a pressure reservoir and a regulator.

Detailed description of the drawing The drawing shows one cylinder 12 of an internal combustion engine having a combustion chamber 10 and a piston 14. The intake and exhaust systems are not shown in the drawing in the interest of clarity. A one-way valve 20 formed of a ball 22 urged against a valve seat 24 by means of a spring 26 is mounted in the combustion chamber to allow gases from the combustion chamber 10 to flow only outwards via a conduit 28 into a pressure regulator 30. The volumes of all the conduits 28 and that of the small chamber within the regulator 30 that interconnects them constitute a pressure reservoir that in operation is pumped to the peak pressure attained within the combustion chambers 10 during operation.

The pressure regulator 30 comprises a poppet valve 32 that interacts with a valve seat 34 to regulate the delivery pressure supplied via a chamber 36 to an outlet pipe 46 that leads to the fuel injection system. The other end of the poppet valve 32 is connected to a piston 38 (or better still a diaphragm to avoid leakage) which is acted upon on the one side by the delivery pressure in the chamber 36 and on the other side by a spring 40 acting between the piston 38 and an adjustable end stop 42. The pressure in the chamber containing the spring 40 may either be ambient pressure or it may itself be a regulated reference pressure supplied to the chamber by way of an inlet pipe 44.

The operation of the regulator 30 is in itself conventional and need only be described in brief outline. The piston 38 is acted on by the delivery pressure in the chamber 36 in the direction to close the valve 32. As the delivery pressure rises the valve 32 closes to reduce the flow through the valve and thereby reduce the pressure in the chamber 36. Conversely as the delivery pressure drops below the value set by the reference pressure and the force of the spring 40 the piston 38 moves in the direction to increase the delivery pressure. In this way negative feedback is established to maintain the delivery pressure constant at a value dictated by the reference pressure and the spring 40 regardless of the peak combustion pressure stored within the reservoir formed by the conduits 28 and the rate at which gases are drawn by the fuel injection system.

The gases drawn from the combustion chamber will consist of a mixture of air and fuel and possibly burnt gases but its chemical constitution is not of importance as it forms only a recirculating flow that does not interfere with the average mixture setting. Because of this a higher rate of flow can be used by the forced or assisted fuel injection system to achieve optimum charge preparation. Furthermore this gas will be hotter than ambient air and will still further improve charge preparation by vaporising the fuel.

In the first few cycles of operation of the engine a relatively large volume will be drawn from the combustion chamber but by maintaining the reservoir volume 28 as small as possible the adverse effect on engine starting can be minimised. The reservoir volume can in fact be maintained small because the pressure within it can be significantly higher than the air rail pressure conventionally used in the fuel injection system so the stored air mass can still be sufficient to meet the needs of the fuel injection system.

During operation, the air drawn from the combustion chambers is only the volume required by the fuel injection system and the consequential loss in engine power is lower than would be required to operate a separate compressor as all friction and thermodynamic losses are avoided.

Because the pressure stored in the reservoir 28 is the peak combustion pressure, it is sufficiently high to permit forced injection directly into the combustion chamber not only early in the compression stroke but even when the piston 14 approaches top dead centre. This is important in direct injection engines in which charge stratification is required.

It will be appreciated that other forms of regulator valve may be used in place of that described. For example, an electromagnet may be used within the regulator to allow the delivery pressure to be varied in response to an electrical input signal, this being desirable if it is required to vary the gas pressure in the fuel injection system as a function of engine operating conditions, for example under the control an electronic engine management system.

The invention is not restricted to any particular form of fuel injection system but may be applied to any system in which a pressurised gas supply is required. For this reason, it is felt that a detailed description of knownair-forced and air-assisted fuel injection systems is not required within the present context.

Claims

1. A fuel injected internal combustion engine in which each engine combustion chamber is connected by way of a respective non-return valve to a common pressure reservoir and a pressure regulator is connected to the pressure reservoir to supply gas at a regulated pressure to the fuel injection system.

2. An internal combustion engine as claimed in claim 1, wherein the regulated pressure is adjustable by varying the compression of a spring within the regulator.

3. An internal combustion engine as claimed in claim 1 or claim 2, wherein means are provided to supply a variable reference pressure to the regulator to vary the regulated pressure supplied to the fuel injection system.

4. An internal combustion engine as claimed any preceding claim, wherein the regulator comprise means for enabling the regulated delivery pressure to be varied in response to an electrical input signal.

5. An internal combustion engine constructed, arranged and adapted to operate substantially as herein described with reference to and as illustrated in the accompanying drawing.