Internal-combustion engines – Charge forming device – Fuel flow regulation between the pump and the charge-forming...
Patent
1997-05-15
1998-06-16
Moulis, Thomas N.
Internal-combustion engines
Charge forming device
Fuel flow regulation between the pump and the charge-forming...
123519, F02M 3704
Patent
active
057655383
DESCRIPTION:
BRIEF SUMMARY
PRIOR ART
The invention is based on a pump device for a fuel vapor retention system of an internal combustion engine. A pump device has already been disclosed (WO 94/15090) which is provided for leak testing a fuel vapor retention system in order to deliver a definite volume of air via a ventilation connection of an adsorption filter to a fuel tank of the engine by means of the pump device so that a pressure increase is produced. In order to determine whether the fuel vapor retention system is pressure tight, some time is allowed to pass after the pressure increase finishes in order to indicate a leak when there is a pressure decrease in the fuel vapor retention system, wherein the time elapsed for the pressure decrease is a measure for the size of the leakage opening. Furthermore, the fuel vapor retention system includes a regenerating valve provided between the adsorption filter and an intake pipe of the engine to introduce the fuel vapor temporarily stored in the adsorption filter into the intake pipe by means of the regenerating valve.
The pump device disclosed in the prior art has a pump membrane which is acted upon alternatingly with vacuum and ambient pressure to drive the pump device. When the engine is running, the vacuum is taken from the intake pipe of the engine via a vacuum hose, and via an on-off valve, which is embodied for example in the form of a solenoid valve, is delivered to a pump chamber of the pump device, which chamber is defined by the on-off valve and the pump membrane. By switching the on-off valve, vacuum and ambient pressure are alternatingly set in the pump chamber. When the pump chamber is acted upon with vacuum, the pump membrane moves counter to the compression force of a pump spring, wherein air flows out of a delivery line into a supply chamber disposed opposite the pump chamber, which supply chamber is closed off by the pump membrane and two stop valves, a suction relief valve and a pressure relief valve. With the subsequent impingement of ambient pressure on the pump chamber, the pump membrane moves in the opposite direction, supported by the compression force of the pump spring, wherein the air enclosed in the supply chamber is compressed. When a certain excess pressure is reached in the supply chamber, the pressure relief valve opens so that the ambient air compressed in the supply chamber flows into the ventilation connection of the adsorption filter via the feed pipe in order to produce a pressure increase in the fuel tank.
In the prior art indicated, the switching process by means of the on-off valve is controlled by a so-called reed switch, which is known to one skilled in the art. The reed switch is actuated by magnetic forces and is attached for example to an outer surface of a sleeve in which a pump plunger attached to the pump membrane is guided so that the pump plunger can move longitudinally. A permanent magnet is provided on an end of the sleeve opposite from the reed switch in order to produce a corresponding change of the magnetic field of the permanent magnet on the reed switch depending on the position of the pump plunger in the sleeve so that when the end position of the pump plunger is reached, the reed switch is correspondingly actuated. The position determination of the pump plunger by means of the reed switch, though, is connected with high tolerances and thus does not permit a precise determination of the position of the pump membrane or the position of the pump plunger in the sleeve so that the determination of the size of the leakage opening is only possible in an imprecise manner.
A pump device driven by a vacuum prevailing in the intake pipe is usually provided in the vicinity of the adsorption filter, which is preferably disposed in the region of the fuel tank of a vehicle. The fuel tank is ordinarily accommodated in the rear region of the vehicle, resulting in a relatively long vacuum hose from the pump device on the adsorption filter to the intake pipe of the engine. Since a leak or a tear in the vacuum hose would put the pump device out o
REFERENCES:
patent: 5499614 (1996-03-01), Busato et al.
patent: 5603359 (1997-02-01), Harris
patent: 5635630 (1997-06-01), Dawson et al.
patent: 5651350 (1997-07-01), Blomquist et al.
Blumenstock Andreas
Denz Helmut
Krimmer Erwin
Kuhnt Winfried
Miehle Tilman
Greigg Edwin E.
Greigg Ronald E.
Moulis Thomas N.
Robert & Bosch GmbH
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