Claims:We claim:
1. A canister purge system(100), said system comprises a reed valve (110) positioned between said canister (106) and an intake manifold (112) of an engine to control purging of fuel vapors from said canister (106), said reed valve (110) is designed to operate based on air pressure difference between said intake manifold (112) and atmosphere, characterized in that,
said reed valve (110) openable in a direction towards said canister (106) on movement of a throttle valve (116) from a first position through a second position.

2. The canister purge system (100) as claimed in claim 1, wherein said reed valve (110) is part of a Throttle Body Unit (TBU) (120).

3. The canister purge system (100) as claimed in claim 1, wherein a flap (124) of said reed valve (110) comprises a bent profile.

4. The canister purge system (100) as claimed in claim 1, wherein said reed valve (110) is open when said engine is OFF.

5. The canister purge system (100) as claimed in claim 1, wherein said reed valve (110) is closed when said throttle valve (116) is opened till a first position.

6. The canister purge system (100) as claimed in claim 1, wherein said first position is a position at which said reed valve (110) starts opening.

7. The canister purge system (100) as claimed in claim 1, wherein an opening of said reed valve (110) varies as per the pressure inside said intake manifold (112).

8. The canister purge system (100) as claimed in claim 1, wherein said canister (106) is purged during intermediate to high load conditions of said engine.

9. The canister purge system (100) as claimed in claim 1, wherein said system is implemented for a vehicle selected from a group comprising a motorcycle, a scooter, an auto-rickshaw, and a vehicle with at least four wheels.

10. The canister purge system (100) as claimed in claim 1, wherein said system is implemented for a hand-held engine operated power tool.

, Description:Complete Specification:
The following specification describes and ascertains the nature of this invention and the manner in which it is to be performed:

Field of the invention:
[0001] The present invention relates to a canister purge system.

Background of the invention:
[0002] According to a prior art US2002083931 a canister purge system is disclosed. The canister purge system for throttle less internal combustion engine intake systems includes a plurality of purge ports, each of which is adapted for connection to an intake port of an internal combustion engine. An evaporative emissions canister is in fluid connection with each purge port. Each purge port includes a valve responsive to pressure changes in the intake port and permitting vapor flow from the evaporative emissions canister into the intake port when a vacuum condition is present in the intake port. The valves prevent flow from the intake port to the evaporative emissions canister when a vacuum is not present in the intake port.

Brief description of the accompanying drawings:
[0003] An embodiment of the disclosure is described with reference to the following accompanying drawing,
[0004] Fig. 1 illustrates a canister purge system with a modified reed valve, according to an embodiment of the present invention.

Detailed description of the embodiments:
[0005] Fig. 1 illustrates a canister purge system with a modified reed valve, according to an embodiment of the present invention. A fuel intake system 100 for a vehicle comprises an air filter 102 at the inlet of the intake manifold 112. A Throttle Body Unit 120, comprising a throttle valve 116 and a bypass path 118 along with respective actuator, is positioned to connect with the intake manifold 112. The TBU 120 is either independent unit separate from the intake manifold 112 or is integrated with the intake manifold 112. Further, a fuel tank 104 in fluid communication with a canister 106 is shown. A conduit 108 fluidly couples the canister 106 to the intake manifold 112. A reed valve 110 (also known as one way valve) is positioned between the canister 106 and the intake manifold 112 of an engine of a vehicle to control purging. The reed valve 110 is designed to operate based on air pressure difference between the intake manifold 112 and an atmosphere. The canister purge system 100 is characterized by, the reed valve 110 openable in a direction towards the canister 106 (in contrast to the prior art) on movement of the throttle valve 116 from a first position through a second position. A pair of right arrows in the intake manifold 112 represents the flow direction of the intake air to the engine, through an intake valve 114. Similarly, a down arrow beside the conduit 108 represents direction of flow of the fuel vapors purged from the canister 106. Purging the canister 106 corresponds to purging the fuel vapors adsorbed inside the activated carbon canister 106.

[0006] In accordance to an embodiment of the present invention, the reed valve 110 is positioned in the conduit 108 between the canister 106 and the intake manifold 112. In an alternative embodiment, the reed valve 110 is integrated with the TBU 120, where the conduit 108 connects to the reed valve 110, i.e. the reed valve 110 is a part of the TBU 120.

[0007] The reed valve 110 comprises a flap 124 and a rest 122. The flap 124 of the reed valve 110 comprises a bent profile. The reed valve 110 is kept in open position by default. The Fig. 1 further shows the canister purge system 100, where the flap 124 of the reed valve 110 undergoes different positions due to the pressure difference. In a first case 140, the reed valve 110 is open, i.e. the flap 124 is open. The terms reed valve 110 and the flap 124 are used interchangeably. The first case 140 is achieved during the shutdown or OFF period of the engine, because the air pressure inside the intake manifold 112 is almost close to the atmosphere. Hence, the reed valve 110 is in open position. The reed valve 110 is open when the engine is OFF and the throttle valve 116 rests against a stop.

[0008] As the throttle valve 116 is moved from the rest position to the first position, the reed valve 110 closes, as represented by the second case 150. The closure of reed valve 110 is due to very low pressure due to the engine start. When the engine is started, the suction pressure caused by the movement of the piston creates low pressure in the intake manifold 112. Due to high air pressure difference between the intake manifold 112 and the atmosphere, the reed valve 110 closes. The reed valve 110 is closed when the throttle valve 116 is opened till the first position. The first position is also referred to as the threshold position.

[0009] When the throttle valve 116 is moved further from the first position towards the second position, the reed valve 110 starts opening again. The first position is the position at which the reed valve 110 or the flap 124 starts opening. The same is represented by the third case 160.

[0010] When the throttle valve 116 is moved to extreme open position, such as Wide Open Throttle (WOT), the reed valve 110 completely opens as represented in a fourth case 170. The air pressure in the intake manifold 112 is close to the atmospheric pressure. The second position is any position above the first position until WOT.

[0011] In accordance to an embodiment of the present invention, an opening of the reed valve 110 varies as per the air pressure inside the intake manifold 112 with respect to the atmospheric pressure.

[0012] In accordance to another embodiment, the canister 106 is purged during intermediate to high load conditions. It is undesirable to inject fuel vapors or fumes from the canister 106 into the intake manifold 112 during low load operations. Because at lower load operation, purging of fuel vapors to the intake manifold 112 significantly affects the engine operation. The rich fumes interferes with the intake mass flow and alters the combustion lambda. But at higher loads, the air flow to the combustion chamber of the engine is so high that addition of the purged fuel vapors causes marginal change in in-cylinder air-fuel ratio. The same fumes are injected during high load operation points of the engine, then the large quantity of intake mass flow dilutes the fumes concentration. Thus, a simple reed valve 110 is able to control purging that operates only when the intake manifold pressure is closer to the atmospheric pressure.

[0013] The canister purge system 100 is implemented for a vehicle selected from a group comprising a motorcycle, a scooter, an auto-rickshaw, and a vehicle with at least four wheels. The reed valve 110 is also applicable for a hand held power tools such as chainsaw operated with smaller engine as compared to the engine used in the vehicle.

[0014] According to the present invention, a working of the invention is described. The reed valve 110 is designed such that it is normally open. The reed valve 110 closes only when the suction pressure inside the intake manifold 112 is high. When the engine is operating at low load, the pressure in the intake manifold 112 is lower compared to atmospheric pressure. Due to high pressure difference, the reed valve 110 closes. As the load increases, the pressure inside the intake manifold 112 increases and crosses the threshold opening pressure. At this instant, the flap 124 or the reed valve 110 begins to open since the air pressure difference is not high enough to close the flap 124. The reed valve 110 slightly opens allowing purging. When the load tends towards high load conditions, the pressure inside the intake manifold 112 tends towards the atmospheric pressure, yet slightly below the atmospheric pressure. At this point the reed valve 110 is fully open and allows purging. Also, since reed valve 110 is entirely mechanical, as the pressure builds, there is slow ramping of purge mass flow thus allowing the system 100 to keep up with the fuel vapor intake.

[0015] In accordance to another embodiment of the present invention, a reed valve 110 for canister purge system 100 is provided. The reed valve 110 comprises a bent profile which corresponds to the reed valve 110 being open at rest or default position. The reed valve 110 is usable in the canister purge system 100 of the vehicle or the power tool. An active control is achieved by the use of passive reed valve 110. The term passive signifies that there is no electricity based control of the valve. The functioning of the reed valve 110 is completely mechanical.

[0016] In accordance to an embodiment of the present invention, a fuel intake system 100 without an active purge valve is provided. The present invention eliminates the use of an electronic component that requires associated controller and control strategy and calibration efforts. In contrast to conventional system, in the present invention, the electronic component, such as a solenoid valve, is eliminated. Instead a passive reed valve 110 is used and actuated only when the pressure inside the intake manifold 112 tends to atmospheric pressure.

[0017] Further, in case the vehicle is still (engine not in operation), the pressure inside the intake manifold 112 is approximately same as atmospheric pressure, at which point the reed valve 110 opens. But in this scenario the fumes (or fuel vapors) that build up in the fuel tank 104 passes through the activated carbon canister 106. The canister 106 adsorbs these fumes. But in a case, where the concentration of fumes are much higher than what the canister 106 is capable to store, the fumes passes via the reed valve 110 to the intake manifold 112 and eliminates any pressure build up in the system 100 due to fumes. In contrast, in a conventional system once the canister 106 is filled with fumes, the pressure builds up and the fumes escapes to the environment/ atmosphere through an outlet in the canister 106. If there are no outlet, then the pressure build up within the canister 106 is not conducive.

[0018] It should be understood that embodiments explained in the description above are only illustrative and do not limit the scope of this invention. Many such embodiments and other modifications and changes in the embodiment explained in the description are envisaged. The scope of the invention is only limited by the scope of the claims.