FIELD OF INVENTION:

The invention relates to a fuel injection system in general and relates to fuel injection for enhanced starting of the engine in particular.

BACKGROUND OF THE INVENTION:

Fuel injection systems for enhanced starting of the engines are already known. The US patent 5934259 discloses one such system. The US patent discloses a fuel injection system to control timing for injecting fuel into each of the cylinders. A crank angle signal is generated each time the crank shaft rotates a first predetermined angle. Fuel is supplied to the cylinders after the first reference signal is generated for the first time after the internal combustion engine is started. The fuel is sequentially injected into each of the cylinders in a predetermined order in synchronization with a rotation of the crank angle

OBJECT OF THE INVENTION:

It is an object of the invention to provide a method for enhanced starting of an internal combustion engine. The proposed method injects fuel into the intake manifold of the engine, for every alternate crank shaft reference position, the quantity of fuel being proportionate to the amount of the air mass sucked into the engine. An ignition pulse is generated for every crank shaft reference position till the engine phase detection. The fuel enters into the cylinder during the next suction stroke and ignites with the next ignition pulse. Thus a faster start of the engine is achieved.

ADVANTAGES OF THE INVENTION:

The proposed method ensures that the cylinder receives full quantity of fuel for first compression / combustion. As the full quantity of fuel is available for first combustion, there is no wastage of fuel. Also as the fuel is not wasted, there are lesser emissions. As the combustion happens with first ignition pulse after the fuel is sucked into the cylinder, the engine starts faster.

The proposed method makes use of the existing hardware without needing any modifications or additions to the hardware.

BRIEF DESCRIPTION OF THE DRAWINGS:-

FIG. 1 shows a schematic of the invention

DETAILED DESCRITPION OF THE INVENTION:

The present invention is described in the preferred embodiment as follows:-

Shown in Fig. 1 is an engine control unit 10 controlling an internal combustion engine 12 according to the invention. The internal combustion engine 12 comprises a cylinder 14, a piston 15, an intake port 16, exhaust port 18, an injector 20 whose tip is located in the intake manifold 22, a spark plug 24 whose tip is located inside the cylinder 14. The ECU is supplied with crank shaft position signal 26 from a crank shaft position sensor which is not shown. The ECU is supplied with engine operating conditions 28 like load on the engine, vehicle speed, air mass sucked in, temperature of the coolant, temperature of the ambient air, air pressure in the intake manifold etc. but not limited only to these. The engine has a single cylinder.

The engine control unit 10 keeps monitoring the operating conditions 28 of the engine 12. When an user cranks the engine, a starter motor which is not shown starts rotating. As the starter motor rotates, it turns the flywheel, which is not shown. As the flywheel rotates, the crank shaft rotates thereby moving the piston in linear motion inside the cylinder. The crank shaft position sensor detects the movement of the crank shaft and starts generating the crank shaft position signal 26 comprising a stream of pulses. A reference position of the crank shaft is identified by a reference pulse generated by the crank shaft position sensor. Typically this reference position is indicated by a missing pulse in the stream of pulses. For easier understanding the reference pulse is indicated as high level pulse in the graph 2A and 2d in fig. 2. This reference pulse in 2A indicates a reference position of the piston close to the Top Dead Centre (TDC). The piston reaches the TDC twice in a working cycle of the engine, i.e. once during compression stroke and once during exhaust stroke.

Shown in fig 2 are the timing diagrams of the crank shaft position signal, different strokes, ex. exhaust stroke ExS, intake stroke IS, compression stroke CS and expansion stroke ES. The X axis represents the time and the Y axis represents the presence of different signals, "^ injection signal which activates injection of the fuel, ignition signal which ignites the fuel.

When the user starts the engine, the crank shaft starts rotating and the crank shaft position sensor starts generating crank shaft position signal. When the piston is at a known position from the TDC a reference pulse is generated in the crank shaft position signal.

There may be two scenarios:

Scenario 1 represented by graphs 2A, 2B and 2C: The first reference pulse from the crank shaft position signal corresponds to TDC position of the piston of an exhaust stroke.

The first reference pulse PI detected, as shown in 2A, may correspond to a reference position of the piston when it is approaching TDC during an exhaust stroke ExS. When this reference pulse is detected, the ECU injects a pre-computed quantity of fuel into the intake manifold. This injection pulse Ij1 is shown in 2B. Also the ECU generates an ignition pulse Ig1 at the same time. This ignition pulse is shown in 2C. The pre-computed quantity of the fuel depends upon the engine operating conditions. The fuel remains in the intake manifold till an intake stroke begins. As the fuel is still in intake manifold, the ignition pulse Ig1 fails to combust the air in the cylinder.

The intake stroke IS begins after the exhaust stroke. The air and fuel is sucked into the cylinder and gets mixed in the cylinder. After intake stroke the compression stroke begins. At the reference position near the TDC a reference pulse P2 is generated. After P2 is detected, at a predefined position an ignition pulse Ig2 is generated. As the air fuel mixture is available in the cylinder, the combustion takes place. Once the combustion takes place, the speed of the crank shaft increases. This is detected by the ECU. Once the combustion is detected, the ECU determines the phase of the engine, i.e. the TDC corresponding to the compression stroke. The phase of the engine is used to determine the injection and ignition timings. This is shown by the injection pulse Ij2 and ignition pulse Ig3. It is observed that Ij2 and Ig3 have an offset of 360 degrees of the crank shaft angle.

Thus the invention provides a method where a faster start of the engine is achieved. In the above scenario, there is no misfire, hence there is no wastage of fuel and no harmful emissions.

Scenario 2 represented by graphs 2D, 2E and 2F: The first reference pulse from the crank shaft position signal corresponds to TDC position of the piston of a compression stroke.

The first reference pulse PI' detected, as shown in 2D, is assumed to correspond to a position of the piston when it is approaching TDC during compression stroke. When this reference pulse is detected, the ECU injects a pre-computed quantity of fuel into the intake manifold. This injection pulse Ij1' is shown in 2E. Also the ECU generates an ignition pulse Ig1' at the same time. This ignition pulse Ig1' is shown in 2F. The pre-computed quantity of the fuel depends upon the engine operating conditions. The fuel remains in the intake manifold till an intake stroke begins. As the fuel is still in intake manifold, the ignition pulse Ig1' fails to combust the air in the cylinder.

After compression stroke CS there is an expansion stroke ES where the piston moves towards bottom dead centre. Then exhaust stroke begins where the piston starts moving towards the TDC. A reference pulse P2' is generated at reference position as the piston approaches TDC. ECU generates an ignition pulse Ig2' after detecting the reference pulse P2'. But as the fuel is still in intake manifold, the combustion does not occur.

After the exhaust stroke, the intake stroke begins. The fuel which is still in intake manifold, is sucked along with the air into the cylinder. After the intake stroke, the compression stroke begins where the piston starts moving towards TDC.

A reference pulse P3' is generated at a reference position when the piston approaches TDC. After detecting the reference pulse P3', at a predefined time the ignition pulse Ig3' is generated. As the compressed mixture of air and fuel is available in the cylinder, the mixture combusts and the speed of the piston increases. This is detected by the ECU. Once the ECU detects that the combustion occurred in the cylinder, it determines the correct phase of the engine to inject the fuel and ignite it.

Thus according to the invention, in first scenario, the combustion starts after the detection of the second reference pulse of the crank shaft position sensor. And in the second scenario, the combustion starts after the detection of the third reference pulse of the crank shaft position sensor. There are no misfires in either of the above scenarios. As there are no misfires, the fuel wastage is avoided and also the unnecessary emissions. Once the combustion is detected, the ECU determines the correct phase of the engine for injection and ignition of the fuel. This is shown by Ig4'.

Thus the invention provides a sure method of starting the combustion latest after detection of the third reference pulse of the crank shaft position sensor.

WE CLAIM:

1. A method to enhance start of an internal combustion engine comprising a single
cylinder, the said method comprising the steps:

- injecting an amount of fuel proportionate to air mass, into an intake manifold of the said internal combustion engine for every alternate reference pulse indicative of Top Dead Centre position of a piston of the said internal combustion engine till a correct phase of the said engine is detected

- generating ignition signal for every reference pulse indicative of Top Dead Centre position of the said piston of the said internal combustion engine till a correct phase of the said engine is detected

- correcting the timing of the injection of fuel and ignition pulse on detection of correct phase of the said internal combustion engine

2. An Engine Control Unit (ECU) to enhance start of an internal combustion engine
comprising a single cylinder, the said ECU adapted to :

- inject an amount of fuel indicative of air mass, into an intake manifold of the said internal combustion engine for every alternate reference pulse indicative of Top Dead Centre position of a piston of the said internal combustion engine till a correct phase of the said engine is detected

- generate ignition signal for every reference pulse indicative of Top Dead Centre position of the said piston of the said internal combustion engine till a correct phase of the said engine is detected

- correct the timing of the injection of fuel and ignition pulse on detection of correct phase of the said internal combustion engine

3. An ECU according to previous claim wherein the correct phase of the said internal combustion engine is when the piston is at a known reference position from the TDC during a compression stroke of the said internal combustion engine.

4. An ECU according to previous claim wherein the ECU receives crank shaft position signal 26.

5. An ECU according to previous claim wherein the ECU receives engine operating conditions.

6. An ECU according to previous claim wherein the operating conditions comprise one of load on the engine, vehicle speed, engine speed, air mass sucked in, temperature of the coolant, temperature of the ambient air, air pressure in the intake manifold.

7. An ECU according to previous claim wherein the ECU determines reference position of the piston by detecting a reference pulse from the crank shaft position signal 26

8. An ECU according to previous claim wherein the ECU computes amount of fuel to be injected into the said cylinder in dependence of the engine operating conditions.

9. An ECU according to previous claim wherein the ECU controls the timing for injection of fuel.

10. An ECU according to previous claim wherein the ECU controls the timing for ignition of fuel.