Carbon canister for use in evaporative emission control system of internal combustion engine

1. A carbon canister comprising:

first and second chambers which are coaxially arranged and have substantially the same cross sectional area;

first and second activated charcoal masses respectively received in the first and second chambers;

a labyrinth structure arranged between respective first ends of the first and second chambers so that the first and second chambers are connected through a limited fluid communication;

an atmospheric air inlet port provided by a second end of the second chamber;

a third chamber arranged beside the coaxially arranged first and second chambers, the third chamber having a first end positioned near a second end of the first chamber and a second end positioned near the second end of the second chamber;

a third activated charcoal mass received in the third chamber;

a connector passage extending between the second end of the first chamber and the first end of the third chamber to provide a fluid connection between the first and third chambers;

a fuel vapor inlet port provided by the second end of the third chamber; and

a fuel vapor outlet port provided by the second end of the third chamber.

2. A carbon canister as claimed in claim 1 , in which the first, second and third chambers are cylindrical in shape, and in which the first and second cylindrical chambers have substantially the same cross section.

3. A carbon canister as claimed in claim 1 , in which the second activated charcoal mass has a vapor adsorbing/releasing ability that is hither than that of the first activated charcoal mass.

4. A carbon canister as claimed in claim 1 , in which the third activated charcoal mass has substantially the same vapor adsorbing/releasing ability as the first activated charcoal mass.

5. A carbon canister as claimed in claim 1 , in which a passage defined by the second chamber, the labyrinth structure, the first chamber, the connector passage and the third chamber has a generally U-shape.

6. A carbon canister as claimed in claim 2 , in which the following inequalities are satisfied by the first and second cylindrical chambers:

2 ≦L 1 /D 1 ≦5

L 2 /D 2 <1

wherein:

L 1 : axial length of first cylindrical chamber

D 1 : diameter of first cylindrical chamber

L 2 : axial length of second cylindrical chamber

D 2 : diameter of second cylindrical chamber.

7. A carbon canister as claimed in claim 6 , in which the following inequality is further satisfied by the third cylindrical chamber:

2 ≦L 3 /D 3 ≦5

wherein:

L 3 : axial length of third cylindrical chamber

D 3 : diameter of third cylindrical chamber.

8. A carbon canister as claimed in claim 1 , further comprising:

a fourth chamber arranged between the second chamber and the atmospheric air inlet port; and

a fourth activated charcoal mass received in the fourth chamber, the fourth activated charcoal mass having a honeycomb structure.

9. A carbon canister as claimed in claim 8 , in which the fourth chamber is defined by the second chamber, and in which the fourth chamber and the second chamber are partitioned by a filter member.

10. A carbon canister as claimed in claim 8 , in which the fourth chamber is defined in a pipe that extends outward from the atmospheric air inlet port.

11. A carbon canister as claimed in claim 8 , in which the following inequalities are satisfied by the first and second cylindrical chambers:

2 ≦L 1 /D 1 ≦4

2 ≦L 2 /D 2 ≦4

wherein:

L 1 : axial length of first cylindrical chamber

D 1 : diameter of first cylindrical chamber

L 2 : axial length of second cylindrical chamber

D 2 : diameter of second cylindrical chamber.

12. A carbon canister as claimed in claim 11 , in which the following inequality is further satisfied by the third cylindrical chamber:

2 ≦L 3 /D 3 ≦5

wherein:

L 3 : axial length of third cylindrical chamber

D 3 : diameter of third cylindrical chamber.

13. An evaporative emission control system of a motor vehicle powered by an internal combustion engine, comprising:

a carbon canister including first and second chambers which are coaxially arranged and have substantially the same cross sectional area; first and second activated charcoal masses respectively received in the first and second chambers; a labyrinth structure arranged between respective first ends of the first and second chambers so that the first and second chambers are connected through a limited fluid communication; an atmospheric air inlet port provided by a second end of the second chamber; a third chamber arranged beside the coaxially arranged first and second chambers, the third chamber having a first end positioned near a second end of the first chamber and a second end positioned near the second end of the second chamber; a third activated charcoal mass received in the third chamber; a connector passage extending between the second end of the first chamber and the first end of the third chamber to provide a fluid connection between the first and third chambers; a fuel vapor inlet port provided by the second end of the third chamber; and a fuel vapor outlet port provided by the second end of the third chamber;

a charging pipe extending from a fuel tank of the vehicle to the fuel vapor inlet port of the third chamber; and

a purge pipe extending from a negative pressure producing area of an intake pipe of the engine to the fuel vapor outlet port of the third chamber.

14. An evaporative emission control system as claimed in claim 13 , further comprising:

an electromagnetic valve installed in the purge pipe to open and close the same;

an all range type exhaust air/fuel ratio sensor arranged in an exhaust system of the engine; and

a control unit which controls the open/close operation of the electromagnetic valve in accordance with an information issued from the all range type exhaust air/fuel ratio sensor.