Internal-combustion engines – Charge forming device – Having fuel vapor recovery and storage system
Patent
1992-08-26
1993-09-21
Cross, E. Rollins
Internal-combustion engines
Charge forming device
Having fuel vapor recovery and storage system
123533, F02M 3302, F02M 2300
Patent
active
052459748
DESCRIPTION:
BRIEF SUMMARY
This invention relates to the treatment of fuel vapours generated in a fuel tank that provides fuel for an internal combustion engine.
In many countries, regulations relating to emissions from vehicles require the treatment of the vapours generated in the fuel tank to eliminate or substantially reduce the amount of fuel released to the atmosphere by such vapours. It is known that in operating a vehicle the fuel tank can reach temperatures in the order of between 30.degree. C. and 55.degree. C., and accordingly there is significant fuel vapour generated in the fuel tank which would be harmful if released in an untreated manner to atmosphere.
Accordingly, most regulations controlling emissions from vehicles require a suitable form of separator to be provided so that vapours escaping from the fuel tank pass through the separator to remove the fuel therein before the air is released to atmosphere. Usually the separator is of the activated carbon type commonly referred to as the "carbon canister". Such separators operate on the principle of physical adsorption of fuel vapours onto the activated carbon.
Whilst the engine is operating, the air released from the separator is directed to the engine air intake system and accordingly any fuel that may not have been removed in the separator is directed into the engine and is therefore not released to atmosphere. However, when the engine is not operating, particularly immediately after the engine is stopped and the fuel tank temperature is high, the generation of fuel vapour continues and the pressure is sufficient to discharge the vapour into the separator. There is thus an accumulation of fuel in the separator over a significant period of time after the engine has been switched off.
Normally, the separator is designed to have sufficient capacity to retain all the fuel that passes to the separator from the fuel tank after engine shut down, however, this may result in the filter media being loaded with fuel at the time of next start-up of the engine. This fuel in the filter media is drawn into the engine air intake system and can cause the engine on start up to have an oversupply of fuel and hence may produce a high level of hydrocarbon emissions in the exhaust gas. Also this excess fuel supply can cause the engine to run at a speed considerably greater than that as determined by the throttle position and the fuel metering system. This form of operation of the engine after start up is not commercially or environmentally acceptable.
One proposal to deal with this problem is to provide in the vapour control systems a solenoid operated valve that is operated during start-up, so the separator is isolated from the air induction system.
It is the object of the present invention to provide in conjunction with an internal combustion engine a system whereby the fuel accumulated in the separator during engine shut down is disposed of without adverse effects on the operation of the engine.
With this object in view there is provided according to the present invention in an internal combustion engine installation, an air compressor to supply air to effect injection of the fuel for combustion in the engine, a fuel tank wherein fuel for use by the engine is stored, an air/fuel separator to receive vapour generated in the fuel tank and separate the fuel in the vapour from the air, a passage communicating that part of the separator wherein the fuel is held with the inlet port of the compressor so that when the compressor is in operation, at least part of the air taken in by the compressor is drawn through the part of the separator where the fuel is held to thereby extract fuel therefrom.
Conveniently, a check valve is provided between the fuel tank and the separator set so that the valve will remain closed if the pressure in the fuel tank is below a preset figure, for example, 7 kPa, for if the pressure in the fuel tank is too low, excessive fuel vaporisation occurs which would increase the fuel vapour load on the system. Further there is conveniently provided between the check valve a
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Patent Abstracts of Japan, M-245, p. 35, JP,A, 58-110852 Jul. 1983.
Higgins Stuart A.
Sayer Christopher N. F.
Smith Darren A.
Watson Stephen J.
Cross E. Rollins
Moulis Thomas
Orbital Engine Company (Australia) Pty. Limited
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