GB2436593A

GB2436593A - Internal combustion engine having a fuel injection system

Info

Publication number: GB2436593A
Application number: GB0606185A
Authority: GB
Inventors: Jeffrey Allen
Original assignee: Scion Sprays Ltd
Current assignee: Scion Sprays Ltd
Priority date: 2006-03-28
Filing date: 2006-03-28
Publication date: 2007-10-03
Anticipated expiration: 2026-03-28
Also published as: GB0606185D0; GB2436593B

Abstract

The fuel injection system delivers both air and fuel directly into a combustion chamber (17). The system has a fuel pump (10,21,23-28) which comprises a piston (21) and solenoid (26) and which delivers a fixed amount of fuel in each operation. The fuel is delivered into air supplied from a source of pressurised air and the delivery of fuel and air is controlled by a solenoid operated poppet valve (15). A controller controls the quantity of fuel delivered by the pump in each engine operating cycle and also timing of delivery of fuel and air into the combustion chamber (17). In a modification, the poppet valve 15 is opened briefly when there is high gas pressure in the cylinder 17 and a volume of high pressure gas is trapped in a closed pressure storage vessel (30, fig.2) for use in atomizing the fuel in the next engine cycle. The fuel may be metered directly into the flowing high pressure air as it flows to the combustion chamber via a sonic nozzle (44, fig.3) or a pressure operated poppet valve (54, fig.4).

Description

AN INTERNAL COMBUSTION ENGINE HAVING A FUEL INJECTION SYSTEM

The present invention relates to an internal combustion engine ("IC engine") having a fuel injection system which delivers fuel directly into a combustion chamber of the "IC engine".

Direct injection of fuel into a combustion chamber of a spark-ignition engine requires extremely good atomisation of the fuel to ensure it mixes rapidly and evenly with the air in the cylinder, in a very short time (<lOms), to ensure good combustion and low emissions. One known solution to achieve excellent atomisation is the use of a high pressure gas by a gas-assisted direct injector. When the high pressure gas is passed through small gaps/orifices very high velocities are created and hence high shear can be generated on the fuel as it is combined with the gas, which results in very fine atomisation of the fuel.

As well as atomisation, the control of the correct amount of fuel being delivered into the cylinder is critical. The conventional method of controlling the quantity is a Pulse Width Modulation (PWM) injector. With this PWM the injector is a simple on/off flow valve with a fixed orifice diameter. When a known and precisely controlled pressure difference is maintained between the fuel supply and gas medium, then the amount of fuel injected when the injector is switched on is just a function of the duration of "on" time of the injector. However, in the real world of IC engines it is very difficult to achieve a precisely controlled pressure balance throughout an engine cycle due to the dynamic processes occurring inside the engine. Hence many application use expensive and complex pressure regulation devices in order to achieve this pressure control. This complexity makes this type of atomisation system overly expensive for smaller low cost engines.

The present invention provides an internal combustion engine having fuel injection system which delivers fuel and air directly into a combustion chamber of the engine, the fuel injection system comprising: a source of pressurised gas; a gas flow control valve for controlling flow of pressurised gas from the source of pressurised gas into the combustion chamber; a fuel pump which cyclically draws in an amount of fuel and dispenses the drawn-in fuel, before drawing in a further amount of fuel for dispensing, the amount of fuel dispensed in each dispensing operation being fixed for each and every dispensing operation of the pump; and a controller for controlling operation of the gas flow control valve and the fuel pump; wherein: the controller controls in quantity the fuel delivered in each engine operating cycle by controlling in number the dispensing operations of the pump during the engine operating cycle; the fuel pump dispenses fuel into the pressurised gas flowing from the source of pressurised gas for mixing with the pressurised gas prior to delivery of the fuel and gas into the combustion chamber; and the controller controls operation of the air flow control valve to control timing of delivery of fuel and gas into the combustion chamber in each engine operating cycle.

The present invention proposes the use of a pulse count injection system which does away with the need for pressure regulation as the amount of fuel delivered is purely a function of the geometric size of the pump (or "pulse injector unit") and the number of delivery operations ("pulses") selected per engine cycle. This solution whilst reducing the cost of a straight forward air-assist atomisation system also allows other sources of high-pressure gas to be used or unusual injection timing to be used both of which would normally cause fuel quantity deliver problems due to the unknown pressure fluctuations.

Preferred embodiments of the present invention will now be described with reference to the accompanying drawings, in which: Figure 1 shows schematically a combustion chamber and associated fuel injection apparatus according to a first embodiment of the invention; Figure 2 shows schematically a combustion chamber and associated fuel injection apparatus according to a second embodiment of the invention; Figure 3 shows schematically a combustion chamber and associated fuel injection apparatus according to a third embodiment of the invention; and Figure 4 shows schematically a combustion chamber and associated fuel injection apparatus according to a fourth embodiment of the invention.

In Figure 1 there can be seen an embodiment of an air-assisted gasoline direct injection (?GDI!) injector 9 with a pulse count injector 10 delivering fuel into the top of a gas flow control valve 11. In the figure there can be seen a combustion chamber 17 of an internal combustion engine, an inlet poppet valve 18 controlling flow of air via an inlet runner into the combustion chamber 17 and an exhaust valve controlling flow of combusted gases from the combustion chamber 17 to an exhaust runner. The injector 10 functions as a pump. It has a piston 21 slidable in a bore in a housing 22. The piston is biassed by a biassing spring 23 and when the piston slides axially along the bore under the action of the biassing spring 23 then the piston draws fuel into a fuel chamber 24 from a fuel inlet 13 via a one-way valve 25 which prevents expulsion of fuel from the chamber 24 to the fuel inlet 13. A solenoid 26 is used to drive the piston 21 to expel fuel from the chamber 24 via a one-way valve 27 to a fuel outlet 28; the one-way valve 27 prevents flow back into the chamber 24 from the outlet 28. A plate 29 is affixed to the piston 21 to extend across an end face of the solenoid 26 and assist operation of the solenoid.

With a prior art PWM injector there would be pressure regulators controlling the high pressure air feed and the high pressure fuel feed. With the present invention no pressure regulators are needed. A high pressure gas feed 12 supplies gas from any source (e.g. an air pump) and the supply does not need to be at a constant pressure or precisely controlled.

A fuel supply 13 is connected to the injector 10. A low pressure supply (e.g. directly from a tank) can be used and the injector will still accurately control delivery of fuel into the pressurised air. The precisely controlled amount of fuel delivered by the injector 10 flows along a central passage 14 in a poppet valve 15 in the air control valve 11 S and flows from the passage 14 via apertures 8 provided adjacent a rear face of a valve head 7 of the poppet valve to be mixed with the air. The fuel is finely atomised when a solenoid 6 of the valve 11 is energised and the poppet valve 15 opened and the pressurised gas and fuel pass through a small annular gap 16 defined between the rear face of the valve head 7 of opened poppet valve 15 and a valve seat against which the valve head closes.

If a standard PWM injector was used, as well as needing the pressure regulators, the fuel injection period would be usually restricted to the period when the air valve is closed, this is when the air pressure is at its known stable condition. However, with the use of a pulse count injector the fuel may be injected at any time even when the air solenoid valve 11 is open, as the fuel quantity delivered is not effected by the variations of air pressure that will/may occur during the opening of the air valve. This will lead to an improved atomisation condition as fuel is added to a high velocity moving air stream.

The embodiment has no need for pressure regulators.

The fuel supply pressure can be lower than the air supply pressure. There is no need f or a fuel supply pump. The fuel injection timing can be at any time, not just when the air valve is closed. This is lower cost and gives simpler

control than a prior art gas-assisted injector.

Both the solenoid 6 and the solenoid 26 are controlled by an electronic controller (not shown), which controls the solenoid 6 to control the timing and duration of delivery of fuel/gas charge to the chamber 17 and which controls how much fuel is delivered to the chamber 17 in each operating cycle by controlling the number of pulsed operations of the injector 10 in the cycle.

The Figure 2 embodiment is the same as the Figure 1 embodiment, but has additionally a closed pressure storage vessel 30. In this embodiment, the poppet valve 15 is opened for a brief period during the engine cycle when there is high gas pressure in the cylinder of the engine. This can be during the end period of the compression stroke or during the end of the expansion stroke or beginning of the exhaust stroke on a 4-stroke engine (or similar conditions on a 2-stroke engine) . When this occurs a volume of high-pressure gas flows past via the valve 15 to be trapped in the storage chamber 30. The trapped high pressure gas can then be used to atomise the fuel on the next cycle of the engine. This is normally a very unreliable method of generating gas pressure as the final pressure of the gas is very variable from cycle to cycle and this would make it impossible to accurately control the correct amount of fuel with a conventional PWM injector. However, with the pulse count injector 10 the fuel quantity delivered will always be accurate and independent of the gas pressure allowing a gas assisted injector to be used without the need for an air pump, fuel pump or any regulators.

The Figure 2 embodiment provides an air assist GDI which needs no fuel pump, no air pump and no pressure regulators The Figure 3 embodiment shows an arrangement with a simplified gas flow control valve 40. The gas flow control valve 40 has a pintle 41 operated by a solenoid 42 against a biassing spring 43. It does not form a poppet valve in contact with the combustion chamber. In this arrangement it is proposed that the fuel is metered (by a pulse count injector 45 identical to those described previously) directly into the flowing high pressure air as it flows to the combustion chamber 46 through a "sonic nozzle" 44. As the sonic nozzle 44 is open to the combustion chamber 46 it is likely that there will be pressure fluctuations in an air passage 47 in the nozzle 44 caused by the pressure changes in the combustion chamber 46 during the intake and compression stroke. The use of the pulse count injector 45 means an accurate fuel quantity can be delivered regardless of any pressure fluctuations. This embodiment provides a simplified air control valve 40 with a simple sonic mixing nozzle 44, no need for pressure regulators and achieves a low cost finely atomised GDI system.

In Figure 4, the Figure 3 embodiment is modified with a pressure operated poppet valve 54 in place of the sonic nozzle. This will prevent any possibility of carbon build up inside the air/fuel mixing chamber.

Claims

CLAI MS

1. An internal combustion engine having fuel injection system which delivers fuel and air directly into a combustion chamber of the engine, the fuel injection system comprising: a source of pressurised gas; a gas flow control valve for controlling flow of pressurised gas from the source of pressurised gas into the combustion chamber; a fuel pump which cyclically draws in an amount of fuel and dispenses the drawn-in fuel, before drawing in a further amount of fuel for dispensing, the amount of fuel dispensed in each dispensing operation being fixed f or each and every dispensing operation of the pump; and a controller for controlling operation of the gas flow control valve and the fuel pump; wherein: the controller controls in quantity the fuel delivered in each engine operating cycle by controlling in number the dispensing operations of the pump during the engine operating cycle; the fuel pump dispenses fuel into the pressurised gas flowing from the source of pressurised gas for mixing with the pressurised gas prior to delivery of the fuel and gas into the combustion chamber; and the controller controls operation of the air flow control valve to control timing of delivery of fuel and gas into the combustion chamber in each engine operating cycle.

2. An internal combustion engine as claimed in claim 1 wherein the fuel pump comprises: a piston slidable in a fuel chamber in a housing; a fuel pump solenoid which can drive the piston to slide axially along the chamber; a biassing spring which acts on the piston; a first one-way valve which allows fuel to be drawn into the fuel chamber from a fuel inlet while preventing flow from the fuel chamber to the fuel inlet, and a second one-way valve which allows fuel to be dispensed from the fuel chamber to a fuel outlet while preventing flow from the fuel outlet to the fuel chamber, wherein: in each dispensing operation of the fuel pump fuel is drawn from the fuel inlet into the fuel chamber by motion of the piston under the action of the biassing spring and then the drawn-in fuel is dispensed by motion of the piston driven by the fuel pump solenoid.

3. An internal combustion engine as claimed in claim 2 wherein the gas flow control valve comprises: a poppet valve opening on to the combustion chamber; a biassing spring for biassing a valve head of the puppet valve closed against a valve seat; and an air flow control solenoid for opening the poppet valve by driving the valve head of the poppet valve away from the valve seat against a biassing applied by the biassing spring, wherein: the poppet valve has a valve stem with a central passage running axially therealong through which flows fuel dispensed by the fuel pump; the valve stem has one or more apertures which allow fuel to flow out of the central passage to be entrained in air flowing past the poppet valve; and -10 -the fuel is mixed with the pressurised air as the fuel and air pass through an annular gap defined between a rear face of the poppet valve head and the valve seat.

4. An internal combustion engine as claimed in claim 3 wherein the fuel is drawn from a fuel tank to the fuel pump without being pressurised by an additional pump prior to pressurisation in the fuel pump.

5. An internal combustion engine as claimed in claim 3 or claim 4 wherein the fuel pump dispenses fuel both when the gas flow control valve is closed and also when the gas flow control valve is open.

6. An internal combustion engine as claimed in any of claims 3,4 or 5 wherein the source of pressurised gas is an air pump.

7. An internal combustion engine as claimed in any one of claims 3,4 or 5 wherein the source of pressurised gas is a pressurised gas storage chamber and the gas flow control valve is operated by the controller to open to allow gas pressurised in the combustion chamber to flow from the combustion chamber to the pressurised gas storage chamber to be subsequently returned back into the combustion chamber entraining fuel f or combustion.

8. An internal combustion engine as claimed in claim 2 wherein the gas flow control valve comprises an electrically-operated valve which controls flow of pressurised gas from the source of pressurised gas to a sonic nozzle which opens on to the combustion chamber and -11 -the fuel pump delivers dispensed fuel to the entrained by the pressurised gas flow to pass through the sonic nozzle into the combustion chamber.

9. An internal combustion engine as claimed in claim 2 wherein the gas control valve comprises an electrically operated valve which controls flow of pressurised gas from the source of pressurised gas to a pressure-operated poppet valve via which the pressurised gas is admitted to the combustion chamber; the pressure-operated poppet valve has a valve head biassed by a biassing spring into engagement with a valve seat; and the fuel pump delivers fuel to be entrained by the pressurised gas flowing past the poppet valve into the combustion chamber.

10. An internal combustion engine substantially as hereinbefore described with reference to and as shown in the accompanying drawings. I2

Amendments to the claims have been filed as follows 1. An internal combustion engine having fuel injection system which delivers fuel and air directly into a combustion chamber of the engine, the fuel injection system comprising: a source of pressurised air; an air flow control valve for controlling flow of pressurised gas from the source of pressurised air into the combustion chamber; a fuel pump which cyclically draws in an amount of fuel and dispenses the drawn-in fuel, before, drawing in a further amount of fuel for dispensing, the amount of fuel dispensed in each dispensing operation being fixed for each and every dispensing operation of the pump; and a controller for controlling operation of the air flow control valve and the fuel pump; wherein: the controller controls in quantity the fuel delivered in each engine operating cycle by controlling in number the dispensing operations of the pump during the engine operating cycle; the fuel pump dispenses fuel into the pressurised air flowing from the source of pressurised air for mixing with the pressurised air prior to delivery of the fuel and air into the combustion chamber; the controller controls operation of the air flow control valve to control timing of delivery of fuel and air into the combustion chamber in each engine operating cycle; and the fuel pump comprises: a piston slidable in a fuel chamber in a housing; /3 a fuel pump solenoid which can drive the piston to slide axially along the chamber; a biassing spring which acts on the piston; a first one-way valve which allows fuel to be drawn into the fuel chamber from a fuel inlet while preventing flow from the fuel chamber to the fuel inlet, and a second one-way valve which allows fuel to be dispensed from the fuel chamber to a fuel outlet while preventing flow from the fuel outlet to the fuel chamber, and in each dispensing operation of the fuel pump fuel is drawn from the fuel inlet into the fuel, chamber by motion of the piston under the action of the biassing spring and then the drawn-in fuel is dispensed by motion of the piston driven by the fuel pump solenoid.

2. An internal combustion engine as claimed in claim 1 wherein the air flow control valve comprises: a poppet valve opening on to the combustion chamber; a biassing spring for biassing a valve head of the poppet valve closed against a valve seat; and an air flow control solenoid for opening the poppet valve by driving the valve head of the poppet valve away from the valve seat against a biassing applied by the biassing spring, wherein: the poppet valve has a valve stem with a central passage running axially therealong through which flows fuel dispensed by the fuel pump; the valve stem has one or more apertures which allow fuel to flow out of the central passage to be entrained in air flowing past the poppet valve; and the fuel is mixed with the pressurised air as the fuel and air pass through an annular gap defined between a rear face of the poppet valve head and the valve seat.

3. An internal combustion engine as claimed in claim 2 wherein the fuel is drawn from a fuel tank to the fuel pump without being pressurised by an additional pump prior to pressurisation in the fuel pump.

4. An internal combustion engine as claimed in claim 2 or claim 3 wherein the fuel pump dispenses fuel both when the air flow control valve is closed and aJso when the air flow control valve is open.

5. An internal combustion engine as claimed in any of claims 2,3 or 4 wherein the source of pressurised air is an air pump.

6. An internal combustion engine as claimed in any one of claims 2,3 or 4 wherein the source of pressurised air is a pressurised air storage chamber and the air flow control valve is operated by the controller to open to allow air pressurised in the combustion chamber to flow from the combustion chamber to the pressurised air storage chamber to be subsequently returned back into the combustion chamber entraining fuel for combustion.

7. An internal combustion engine as claimed in claim 1 wherein the air flow control valve comprises an electrically-operated valve which controls flow of pressurised air from the source of pressurised air to a sonic nozzle which opens on to the combustion chamber and the fuel pump delivers dispensed fuel to the entrained by the pressurised air flow to pass through the sonic nozzle into the combustion chamber.

8. An internal combustion engine as claimed in claim 1 wherein the air control valve comprises an electrically operated valve which controls flow of pressurised air from the source of pressurised air to a pressure-operated poppet valve via which the pressurised air is admitted to the combustion chamber; the pressure-operated poppet valve has a valve head biassed by a biassing spring into engagement with a valve seat; and the fuel pump deliveis fuel to be entrained by the pressurised air flowing past the poppet valve into the combustion chamber.

9. An internal combustion engine substantially as hereinbefore described with reference to and as shown in the accompanying drawings.