FIELD OF INVENTION:

The invention relates to a fuel vapor purging system for an automobile.

BACKGROUND OF THE INVENTION:

Purge control systems to purge the fuel vapors collected in a canister, are known in the prior arts. The US patent 5,273,020 discloses one such system. The Us 5,273,020 discloses a fuel vapor purging system which establishes a pressure difference between upstream and downstream lines of a fuel vapor collection canister sufficient for controlling a pure flow rate.

The US patent 7775195 discloses a method to purge fuel in a hybrid vehicle. The method discloses operating an internal combustion engine; during operation of the internal combustion engine, performing a fuel vapor purge operation based on an amount of liquid fuel in a fuel tank of the hybrid electric vehicle and a duration between liquid fuel filling events.

OBJECT OF THE INVENTION:

The object of the invention is to provide a device and a method for a fuel purging system for a motorbike. The device is simple in nature and does the purging only based on the engine RPM and the engine temperature. The invention makes use of the components which are already available in the vehicle thereby not needing any additional hardware.

ADVANTAGES OF THE INVENTION:

The proposed invention provides a simple device and method to do the fuel vapor purging. By using the already existing components in the vehicle, the invention is cost effective and simple to implement.

By using only the engine RPM and the engine temperature, which are already available in the vehicle, the invention eliminates the need to use data from an oxygen sensor or any other specific sensor for the purpose of fuel vapor purging. This reduces the complexity of the device.

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 a fuel purge system according to the invention. The fuel purge system comprises a controller 10, a purge valve 12, a canister 14, an inlet 16, a purge passage 18 and a purge port 20. The fuel purge system shown in fig.l forms part of the fuel injection system supplying fuel to the internal combustion engine 22. The internal combustion engine 22 may be referred just as engine in the rest f the document.

The typical fuel injection system comprises a fuel tank 24, fuel pumps which are not shown, a fuel supply path 26, a carburetor 28 etc. The preferred embodiment is described with respect to a carburetor based engine. In other embodiments there may be fuel injectors 28 instead of carburetor 28.

In this document only the relevant parts of the fuel injection system and the engine are described. Other parts or components which are commonly known are not described.

The internal combustion engine 22 comprises an intake path 30, an exhaust path 32, a cylinder 34, an ignition system 36 etc. A throttle 38 located in the intake path 30 regulates the amount of air entering into the intake path 30. The engine shown in the fig. 1 has spark plugs 36 disposed in each of the cylinders.

The fuel pump receives the fuel from the tank 24 and pressurizes it. The pressurized fuel is delivered to the engine 22 via the fuel supply path 26 and the intake path 30. The injectors or the carburetor 28 placed in the intake path 30 inject the fuel into the air coming through the intake path 30. The air fuel mixture is drawn into the cylinder 34 during the suction stroke.

The air fuel mixture burns in the cylinder 34 generating power for the motion of the vehicle.

The fuel in the fuel tank 24 vaporizes because of the increase in the temperature experienced by the tank body. The higher the temperature, more being the vaporization. The fuel tank 24 has a purge passage 18 connecting the fuel tank 24 to the canister 14. The vapors formed in the tank 24 in the space above the fuel level, pass through the purge passage 18 and enter into the canister 14. The canister 14 is filled with a substance which absorbs the fuel vapors coming from the tank 24. The canister 14 is connected to a first port of the purge valve 12. The purge valve 12 normally remains closed except during the purge operation. The second port of the purge valve is connected to the purge port 20 which opens into the intake path 30 downstream from the throttle valve 38. The purge port 20 guides the fuel vapors into the intake path 30 during the purge operation.

Air from atmosphere enters into the canister 14 through an air inlet 16. The air passes through the filled substance in the canister 14. The air passing through the canister 14 picks up the fuel vapor stored in the filled substance in the canister. As the purge valve 12 is normally closed, the air passing through the canister 14 is blocked at the purge valve 12.

The control unit 10 continuously receives engine temperature 40 and the engine RPM 42. The control unit 10 controls the opening and closing of the purge valve 12 depending upon the engine temperature 40 and the engine speed 42. The engine speed is also referred as engine RPM.

When the control unit 10 detects that the engine temperature 40 is above a threshold and the variation in engine speed 42 is within a given range, the control unit starts the purge operation. If the variation in engine speed 42 is within a given range for few samples, it indicates that the engine is running more or less at constant speed and there is no acceleration or deceleration of the engine.

The purge operation is referred to the opening of the purge valve 12 to transfer the fuel vapors collected in the canister 14 to the intake path 30. According to the invention the duration of the purge operation depends upon the engine speed 42.

The purge operation is not started if the engine temperature 40 is below a predefined threshold and the few consecutive samples of engine RPM are varying beyond a predefined range. The first condition, i.e. engine temperature should be above a predefined threshold, is to ensure that the warm up phase of the engine is completed. The second condition, i.e. the variation in the engine RPM from few consecutive samples needs to be within a predefined range, indicates that the engine is running more or less at constant speed and there is no acceleration or deceleration of the engine. This criterion is to ensure that the engine performance is not disturbed during acceleration or deceleration of the engine because of the extra amount of air-fuel mixture entering the engine 22 from the canister 14.

The control unit contains a look up table where the values of required opening durations of the purge valve for different engine speeds are stored.

When the control unit 10 needs to start the purge operation, the control unit 10 reads from the look table the duration T for which the purge valve 12 is to be opened, corresponding to the engine RPM 42.
After determining the time T for which the purge valve 12 needs to be kept opened, the control unit 10 generates a signal to the purge valve 12 and the purge valve 12 opens.

Once the purge valve 12 opens, the canister 14 is in fluid communication with the intake path 30 of the engine. Because of the low pressure created in the intake path 30 during the suction stroke, the air rushes from the inlet 16 of canister 14 to the intake path 30, passing through the canister 14. The air rushing through the canister 14 towards the intake path 30 of the engine, carries with it the fuel vapors from the canister 14 which are stored in the filled substance.

As part of the fuel vapors are taken out from the substance filling the canister 14, the filling substance can store more efficiently the fresh vapors coming from the fuel tank 24.

Once the time T for which the purge valve needs to be open expires, the control unit 10 generates a signal to close the purge valve 12 and the purge valve 12 closes.

Thus by using a simple method where only two parameters from the engine, i.e. the engine temperature and the engine RPM, are used along with a look up table, the fuel vapors are purged from the canister.

WE CLAIM:

1. A canister purge system for purging fuel vapors in a carburetor based internal combustion engine, the said canister purge system comprising

- a canister (14) to collect the fuel vapors coming from a fuel tank (24)

- a control unit (10) to read an engine temperature (40) and an engine RPM (42)

- a purge valve (12) to purge the fuel vapors collected in the said canister (14) the said control unit (10) adapted to open the purge valve (12) when the engine temperature (40) is above a predefined threshold and variations in engine RPM (42) are within a predefined range

2. A canister purge system according to claim 1 wherein the control unit (10) opens the purge valve (12), the duration of the opening being dependant on the engine RPM (42).

3. A canister purge system according to claim 1 wherein the control unit (10) contains a look up table storing opening durations of the purge valve (12) for different engine RPMs.

4. A canister purge system according to claim 1 wherein the canister (14) is arranged in a purge passage (18) communicating between the fuel tank (24) and purge valve (12)

5. A canister purge system according to claim 1 wherein the purge valve (12) is arranged in a portion of the purge passage between said canister (14) and the intake path (30) of the engine.

6. A canister purge system according to claim 1 wherein the said canister (14) is provided with an air inlet (16) to receive air from the atmosphere.

7. A canister purge system according to claim 1 wherein the said control unit (10) generates a signal to open the purge valve (12)

8. A canister purge system according to claim 1 wherein the said control unit generates
a signal to close the purge valve (12)

9. A method to purge fuel vapors in a vehicle, the said method comprising the steps:

- reading the engine temperature (40)

- reading the engine RPM (42)

- opening the purge valve (12) if the engine temperature is above a predefined threshold and the variations of the engine RPM (42) are within a predefined range

- closing the purge valve (12) after a predetermined duration, the duration being dependant on the engine RPM (42).