Internal-combustion engines – Charge forming device – With fuel pump
Patent
1992-11-03
1994-09-06
Miller, Carl S.
Internal-combustion engines
Charge forming device
With fuel pump
123449, F02M 3704
Patent
active
053438450
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a fuel injection pump for internal combustion engines.
More particularly, it relates to a fuel injection pump which has a pump plunger enclosing a pump work space in a pump cylinder and a cam drive controlling the reciprocating movement of the pump plunger.
In such a known fuel injection pump a non-return valve opening into the suction space of a distributor fuel injection pump is arranged in the fuel duct downstream of the magnet valve in the flow direction toward the fuel tank. In addition, the rear of the non-return valve in the filling duct is connected with the fuel duct. The object of this arrangement is to prevent the non-return valve serving to fill the pump work space from opening in the event that the electrically actuated valve remains stuck in its closed position. This would cause an excess quantity of fuel to be delivered with each delivery stroke of the pump plunger since there exists between the electrically actuated valve and the non-return valve of the fuel duct a counter-pressure which is determined by the opening pressure of the non-return valve in the fuel duct and is greater than the opening pressure acting on the non-return valve in the filling duct. Accordingly, the internal combustion engine is protected from damage as a result of defective operation of the electrically actuated valve.
In other fuel injection pumps it is known to fill and also to empty the pump work space via the electrically actuated valve. In so doing, the electrically actuated valve must be outfitted with a sufficiently large opening cross section so that the injection phase can be terminated quickly and the pump work space can be filled from the fuel tank during its filling stroke at a constant pressure. This large cross section increases the cost of the electrically actuated valve which is preferably constructed as a magnet valve. Moreover, at a given electromagnetic force the actuating time increases with the opening cross section, which works to the disadvantage of an exact and quick control in all speed ranges of the internal combustion engine.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a fuel injection pump of the above mentioned general type, which avoids the disadvantages of the prior art.
In keeping with these objects and with others which will become apparent hereinafter, one feature of the present invention resides, briefly stated, in a fuel injection pump in which fuel can flow through a fuel duct which connects the pump work space with a fuel supply and is controlled by an electrically actuated valve, where the electrically control valve is open in the filling position as well as in the emptying position depending on the pump plunger movement.
When the fuel injection pump is designed in accordance with the present invention, it has the advantage over the prior art that the electrically controlled valve need only meet the requirements for relieving the pump work space. For this purpose it is sufficient to lower the pressure in the pump work space to a certain extent to end the injection without the need for the pump work space to take on the pressure of the fuel supply. On the other hand, in addition to the open cross section of the electrically actuated valve, the cross section of the non-return valve in the filling duct is also available for the filling of the pump work space during the suction stroke of the pump plunger. It is accordingly ensured that the pump work space itself is always sufficiently filled to a desired extent even with a small cross section of the electrically actuated valve and accordingly with a small overall height. In so doing, the switching times of the electrically actuated valve can be shorter at a given overall height and expenditure. Expenditure on construction and the energy requirement for the fuel injection pump are improved overall.
The novel features which are considered as characteristic for the invention are et forth in particular in the appended claims.
REFERENCES:
patent: 4597369 (1986-07-01), Yasuhara
patent: 4633837 (1987-01-01), Babitzka
patent: 4643155 (1987-02-01), O'Neill
patent: 4831986 (1989-05-01), Linder
patent: 4884549 (1989-12-01), Kelly
patent: 4974564 (1990-12-01), Laufer
patent: 5186151 (1993-02-01), Schwerdt
Miller Carl S.
Robert & Bosch GmbH
Striker Michael J.
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