GB2035451A

GB2035451A - Internal combustion engine fuel evaporation control systems

Info

Publication number: GB2035451A
Application number: GB7938684A
Authority: GB
Original assignee: Motors Liquidation Co
Current assignee: Motors Liquidation Co
Priority date: 1978-11-30
Filing date: 1979-11-08
Publication date: 1980-06-18
Also published as: AU5212479A; FR2442972A1; FR2442972B1; DE2943452A1; JPS6120707B2; CA1124594A; DE2943452C2; JPS5575561A; GB2035451B; AU522505B2

Abstract

A fuel vapour storage canister 38,40 is vented to the engine air cleaner 14, and a supplementary fuel vapour storage bed 68 is disposed in the air cleaner to capture fuel vapour lost from the canister and to be thoroughly purged by engine induction air flow. <IMAGE>

Description

SPECIFICATION Internal combustion engine fuel evaporation control systems This invention relates to internal combustion engine fuel evaporation control systems.

It is known, with present day motor vehicle internal combustion engines, to have the vent lines from the engine fuel tank and carburettee fuel bowl connected to a fuel vapour storage canister. As air and fuel vapour are displaced through the vent lines by increasing ambient temperatures when the engine is not operating, the canister captures the fuel vapour to prevent its loss to the atmosphere.

If the canister in such a system should become saturated with fuel vapour, any additional vapour displaced from the fuel tank or carburetter fuel bowl will travel through the canister and out through its vent to the atmosphere. Moreover, even when the canister is not saturated, the flow of air and fuel vapour through the canister causes some of the fuel vapour previously stored in the canister to be purged by way of the canister vent to the atmosphere.

Early proposals to prevent loss of fuel vapour through the canister have involved either increasing the size of the canister or venting the canister through a supplementary canister.

Although such proposals may prevent saturation of the canister or canisters with fuel vapour, they lead to increased loss of fuel vapour from the canister or canisters due to the flow of air and fuel vapour therethrough.

In accordance with the present invention, such loss is prevented by venting a fuel vapour storage canister to the engine air cleaner and disposing supplementary fuel vapour starage bed in the air cleaner to capture fuel vapour lost from the canister. The supplementary storage bed is thoroughly purged by engine air flow when the engine is operating and the substantially completely purged supplementary storage bed is then able to capture substantially all fuel vapour which may be lost from the canister.

A preferred embodiment of this invention is hereinafter described with reference to the accompanying drawings, in which: Figure 1 is a schematic view of an internal combustion engine with a fuel evaporation control system according to this invention; and Figure 2 is a vertical section through the engine air cleaner, showing the supplementary fuel vapour storage bed and the vent connection for the canister.

Figure 1 shows an internal combustion engine 10 having a carburettor 12 and an air cleaner 14 through which extends an air induction passage 1 6.

Carburetter 1 2 has a fuel bowl 1 8 which receives liquid fuel from a fuel tank 20 through a fuel line (not shown). Fuel bowl 1 8 delivers fuel to the induction passage 1 6 in a conventional manner and has an internal vent 22 to maintain the fuel bowl pressure equal to that in the inlet portion of induction passage 16.

A fuel tank vent line 24 extends from fuel tank 20 to a fuel vapour storage canister 26, and a fuel bowl vent line 28 extends from carburetter fuel bowl 18 to canister 26. Canister 26 will be described here only to the extent necessary for an understanding of this invention.

Canister 26 is formed of a cupped housing 30 closed at the bottom by a grid 32 and a cover 34. An annular partition 36 divides the interior of canister 26 into an inner section 38 and an outer section 40 each of which is filled with activated charcoal to form a main fuel vapour storage bed. Tank vent line 24 opens through a fitting 42 into the upper portion of outer section 40, and fuel bowl vent line 28 is connected through a fitting 44 to the upper porting of inner section 38. A fuel bowl vent valve 46 disposed in fitting 44 is biased by a spring 48 to permit vapour flow from fuel bowl 1 8 through bowl vent line 28 to canister 26 when the engine is not operating.When the engine is operating, a diaphragm 50 responds to the sub-atmospheric pressure in induction passage 1 6 downstream of the throttle 52 and lifts vent valve 46 against the bias of spring 48 to close fitting 44.

Upon an increase in temperature when the engine is not operating, air and fuel vapour are displaced from fuel bowl 1 8 and fuel tank 20 and flow through vent lines 28 and 24 to canister 26. The flow travels downwardly through the inner and outer sections 38 and 40 of the main fuel vapour storage bed, into the plenum 54 between grid 32 and cover 34, and then upwardly through a standpipe 56 and a canister vent line 58 to air cleaner 1 4. The activated charcoal in the fuel vapour storage bed captures the fuel vapour to prevent its loss to the atmosphere.

During engine operation, the sub-atmospheric pressure in induction passage 1 6 downstream of throttle 52 draws air cleaned by the filter element 60 from air cleaner 14 through the canister vent line 58 and standpipe 56 into plenum 54 and then upwardly through the inner and outer sections 38 and 40 of the fuel vapour storage bed to a purge fitting 62. Such air flow purges the fuel vapour from the charcoal so that the charcoal may again absorb fuel vapour when the engine is not operating. The purge air flow rate is determined by a pair of purge orifices 63a and 63b.

If desired, a diaphragm purge valve 64 may close across purge fitting 62 under the bias of a spring 66 during closed throttle engine operation. When throttle 52 is opened, the sub-atmospheric induction passage pressure therebelow lifts diaphragm valve 64 against the bias of spring 66 to open purge fitting 62. An additional purge orifice 63c may bypass purge valve 64 to allow a limited purge flow during closed throttle engine operation.

Canister 26 is highly effective in capturing the fuel vapour displaced from the fuel bowl 18 and fuel tank 20. However, the flow of air and fuel vapour through the fuel vapour storage bed may cause some fuel vapour to be purged from the bed and be carried through plenum 54, standpipe 56, canister vent line 58, and air cleaner 14 to the atmosphere. To capture such fuel vapour, a supplementary fuel vapour storage bed 68 is provided in air cleaner 14. As shown particularly in Fig. 2, the supplementary bed 68 is located inwardly of filter element 60 and has an annular configuration; it is formed of activated charcoal which is retained by inner and outer screens 70 and 72 mounted in upper and lower caps 74 and 76. Bed 68 is secured to lower air cleaner plate 78 and extends upwardly part way to an upper air cleaner plate 80.Thus, a portion of the engine induction air flow passes through bed 68 to purge fuel vapour therefrom while some of the engine induction air flow passes through the space 82 between bed 68 and upper air cleaner plate 80. Fuel vapour stored in bed 68 may therefore be substantially completely purged by air flow through induction passage 1 6 without the bed 68 unduly restricting the induction air flow.

Canister vent line 58 is connected to air cleaner 14 through a fitting 84 disposed inwardly of bed 68. If desired, a diffuser (not shown) may be disposed over fitting 84 ta ensure the dispersion of any fuel vapour passing through canister vent line 58 into bed 68.

Air cleaner 14 includes a thermal sensor 86 and a vacuum operated air intake valve mechanism 88 (Fig. 1), to maintain the induction air flow at a substantially constant temperature.

With this construction, any fuel vapour stored in supplementary bed 68 will be substantially completely purged by engine induction air flow through air cleaner 14 when the engine is operating, thereby enabling substantially all fuel vapour lost from canister 26 to be stored in bed 68 when the engine is not operating.

Claims

1. An internal combustion engine having a fuel tank, a canister containing a main fuel vapour storage bed, a tank vent line for delivering to said bed fuel vapour lost from said tank, an induction passage for delivering air to the engine, and a purge line for delivering to said induction passage fuel vapour stored in said bed, a canister vent line being arranged to deliver fuel vapour lost from said main bed to a supplementary fuel vapour storage bed disposed in said induction passage in a position such that fuel vapour stored in said supplementary bed may be substantially completely purged by air flow through the induction passage when the engine is operating.

2. An internal combustion engine having a main and a supplementary free vapour storage bed constructed and adapted to operate as hereinbefore described with reference to the accompanying drawings.