Internal-combustion engines – Charge forming device – Having fuel vapor recovery and storage system
Patent
1997-02-28
1998-03-24
Moulis, Thomas N.
Internal-combustion engines
Charge forming device
Having fuel vapor recovery and storage system
F02M 3302
Patent
active
057301077
DESCRIPTION:
BRIEF SUMMARY
PRIOR ART
The invention is based on a pump device for a fuel vapor trapping system, and on a fuel vapor trapping system, respectively. A pump device is already known (International Patent Disclosure WO 94/15090) that is intended for checking the tightness of a fuel vapor trapping system, so that by means of the pump device a defined volume of air can be delivered, via an aeration connection of an adsorption filter, to a fuel tank of the internal combustion engine to bring about a pressure increase. In order to ascertain whether the fuel vapor trapping system is pressure-tight, one waits for plenty of time after the pressure buildup has been concluded in order to determine whether there is a leak upon a pressure reduction in the fuel vapor trapping system; the time elapsed for the pressure reduction is a measure of the size of the leakage opening. The fuel vapor trapping system also includes a regeneration valve, which is provided between the adsorption filter and an intake tube of the engine, so that the fuel vapor temporarily stored in the adsorption filter can be introduced into the intake tube by means of the regeneration valve.
The pump device disclosed in the prior art has a pump diaphragm, which is acted upon in alternation with negative pressure and ambient pressure for its drive. The negative pressure is drawn, with the engine running, from the engine intake tube via a negative pressure hose, and it is delivered via a switching valve, which is embodied for instance as an electromagnetic valve, to a pump chamber, defined by the switching valve and the pump diaphragm, of the pump device. By switching of the switching valve, negative pressure and ambient pressure are established in alternation in the pump chamber. When the pump chamber is acted upon with negative pressure, the pump diaphragm moves upward counter to the pressure force of a pump spring; air from a supply line flows into a feed chamber opposite the pump chamber; air from a supply line flows into a feed chamber, facing the pump chamber, that is closed off by the pump diaphragm and two shutoff valves, that is, one overpressure valve and one negative pressure valve. In the ensuing imposition of ambient pressure on the pump chamber, the pump diaphragm, reinforced by the pressure force of the pump spring, moves in the opposite direction, compressing the air enclosed in the feed chamber. When a certain overpressure is reached in the feed chamber, the overpressure valve opens, so that the ambient air compressed in the feed chamber can flow via the feed line into an aeration line of the adsorption filter, in order to bring about a pressure increase in the fuel tank. Only during operation of the pump device does the shutoff valve, connected between the supply line and the feed line parallel to the shutoff valves, assume a closing position, in which a connection of the supply line with the feed line is broken. If operation of the pump device or a check of the fuel vapor trapping system for tightness is not contemplated, then the shutoff valve remains in an open position, so that in the open position ambient air can be introduced, for instance via an ambient-air filter provided in the supply line, into the adsorption filter for regeneration thereof.
A pump device that furnishes an overpressure for a tightness checking is also known from International Patent Application WO 94/17298; in it, a blower motor is provided as the pump device. The blower motor is connected to an aeration connection of the adsorption filter via a line and a check valve. At the aeration connection, an electromagnetically actuatable shutoff valve is also provided, which is connected to the line parallel to the blower motor. When the blower motor is in operation, the shutoff valve assumes a closing position, so that an overpressure in the fuel tank can be built up by means of the blower motor.
A common feature of all the pump devices of this kind, which by the process described above furnish an overpressure for purposes of checking tightness, is that a connection of the adsorp
REFERENCES:
patent: 5411004 (1995-05-01), Busato
patent: 5474050 (1995-12-01), Cook et al.
patent: 5499614 (1996-03-01), Busato et al.
Greigg Edwin E.
Greigg Ronald E.
Moulis Thomas N.
Robert & Bosch GmbH
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