Internal-combustion engines – Charge forming device – Fuel flow regulation between the pump and the charge-forming...
Reexamination Certificate
1999-04-30
2001-03-06
Yuen, Henry C. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel flow regulation between the pump and the charge-forming...
C123S467000, C137S493300
Reexamination Certificate
active
06196201
ABSTRACT:
PRIOR ART
The invention is based on a pressure control valve for a fuel system of a vehicle. A pressure control valve of this kind that has been disclosed by the reference DE 42 40 302 is inserted into a supply line between a pump work chamber of a fuel injection pump and an injection point in the internal combustion engine to be supplied by it. The pressure control valve has a valve body that is inserted into a tubular fitting, which constitutes a valve housing, and this valve body has an axial through conduit and constitutes a first valve seat with its end face remote from the pump work chamber. A pressure control valve closing member that opens in the direction of the injection point is guided in the axial through conduit of the valve body and is held with a sealing face against the first valve seat by means of the force of a first valve spring. An axial through bore is disposed in the pressure control valve closing member and can be closed by a back-flow valve that opens in the direction of the pump work chamber. During the operation of the fuel injection pump, the pressure control valve closing member is lifted from the first valve seat counter to the force of the first valve spring by means of a medium under high pressure, which is supplied to the pressure control valve from the pump work chamber by way of the supply line, by means of which the pressure control valve opens in the direction of the injection point. At the end of the high-pressure delivery, the pressure control valve closing member returns to its valve seat. At the same time, an injection valve closes at the injection point, which causes pressure waves to travel back and forth in the volume enclosed between the pressure control valve and the injection valve, which waves are in a position to open the injection valve again. In order to prevent this, the back-flow valve disposed in the pressure control valve closing member now opens, by way of which the pressure level in the supply line can be reduced, even after the closing of the pressure control valve closing member, to a standing pressure which can be adjusted by means of the initial stress of the second valve spring of the back-flow valve.
As a result, however, the known pressure control valve of the constant-pressure valve construction has the disadvantage that the fuel flowing from the pump work chamber in the direction of the injection point and the fuel flowing back must respectively flow through the first or the second valve spring radially inward from the outside. As a result, however, the gap measurement between the individual spring coils of the valve springs changes as a function of the opening stroke of the respective valve member so that an undesirable throttling action occurs when there is flow through the valve springs. This throttle effect, which changes as a function of the opening stroke of the valve members, thereby impairs the through flow behavior of the fuel in the pressure control valve, which can have a negative effect on the course of injection at the injection valve of the injection point.
ADVANTAGES OF THE INVENTION
The pressure control valve according to the invention has the advantage over the prior art that the fuel supplied by the fuel injection pump does not flow radially through the valve springs so that an unthrottled flow through the pressure control valve is assured. As a result, the fuel is advantageously conveyed past the valve springs, radially outside them, wherein a fuel conduit with a large cross section is embodied between the radially outer circumference surfaces of the valve springs and a housing wall encompassing them and the fuel can flow through this fuel conduit in an unthrottled fashion.
As a result, it is particularly advantageous to dispose the pressure control valve closing member and the back-flow valve axially one behind the other, wherein the pressure control valve closing member, with its end face oriented toward the pump work chamber, simultaneously constitutes a second valve seat for the valve member of the back-flow valve. In this connection, the opening stroke movements of the pressure control valve closing member and the valve member of the back-flow valve are advantageously each limited by means of a stop piece, which simultaneously reduces the dead or clearance volume in the pressure control valve. For an unhindered fuel flow, these stop pieces thereby have recesses on their circumference surface on their ends remote from the valve members, which recesses are connected by way of lateral bores or lateral openings to an axial blind bore in the end face remote from the valve member, and which, together with this blind bore, are respectively connected to the supply line. Furthermore, the spring plate of the back-flow valve and the part of the pressure control valve closing member protruding into the valve body have axial recesses, preferably ground sections, which at the same time as permitting a favorable guidance of the components in the valve body, also permit an unthrottled through flow of fuel. As a result, the second stop piece of the back-flow valve can be advantageously press-fitted into the axial through conduit of the valve body, wherein the maximal opening stroke path of the back-flow valve can be adjusted by way of the press-fitting depth. The recesses or ground sections on the stop pieces, on the spring plate of the back-flow valve, and on the pressure control valve closing member can thus have all shapes that permit an unthrottled fuel flow while at the same time permitting a sufficient axial guidance of the components in the valve body or in the valve housing. Alternatively, it is possible to provide the first stop piece of the pressure control valve closing member with an axial through bore which directly connects the injection side part of the supply line to the through bore in the pressure control valve closing member so that the returning fuel also does not have to flow through any valve spring and can flow unhindered onward to the back-flow valve.
Other advantages and advantageous embodiments of the subject of the invention can be inferred from the drawings, the description, and the claims.
REFERENCES:
patent: 4577606 (1986-03-01), Bohringer et al.
patent: 4926902 (1990-05-01), Nakamura et al.
patent: 5033506 (1991-07-01), Bofinger et al.
patent: 5293897 (1994-03-01), Warga et al.
patent: 5295469 (1994-03-01), Kariya et al.
patent: 5365906 (1994-11-01), Deweerdt
patent: 5839414 (1998-11-01), Klinger et al.
patent: 5950669 (1999-09-01), Fehlmann et al.
Fehlmann Wolfgang
Fuchs Walter
Henning Ruben-Sebastian
Jonas Stephan
Ogata Kiyotaka
Castro Arnold
Greigg Edwin E.
Greigg Ronald E.
Robert & Bosch GmbH
Yuen Henry C.
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