Fluid handling – Line condition change responsive valves – Direct response valves
Patent
1991-05-15
1992-11-10
Rivell, John
Fluid handling
Line condition change responsive valves
Direct response valves
13754323, 123467, F02M 5946
Patent
active
051615720
DESCRIPTION:
BRIEF SUMMARY
STATE OF THE ART
The invention is directed to a pressure valve. In a pressure valve known from DE-AS 1 236 863, a return collar is separated from a second collar by an annular groove, which has at least one excision and in the present case two excisions. This excision is ground and remains within the transit bore in every position of the closing member of the pressure valve. The closing member has a conical sealing surface at the pump working space end and a fixed stop on the spring space side with which it is brought into contact on every opening stroke of the closing member by the action of a very soft compression spring. The excision provided on the closing member which therefore always has a constant flow cross-section, is formed as throttling cross-section. The object of this throttling cross-section is to move the pressure valve closing member more quickly to its closed position at the end of injection after the closing of the injection nozzle, since the pressure waves reflected in the delivery line meet a flow resistance at the throttling cross-section, which has the effect of a closing force on the closing member in support of the compression spring. Due to the different delivery rates or delivery speeds of the fuel through the pressure valve or the delivery line during idling on the one hand and full load operation at high speed on the other hand, the effect of the throttle area on the closing movement of the closing member decreases in the direction of idling as the pressure wave is relatively weak, so that the throttle cross-section offers a lower resistance to this pressure wave and more fuel can flow through the throttle per unit of time. The closing member is accordingly closed more slowly and thus during idling a larger proportion of the volume of the delivery line released by the closing valve is replaced by fuel from the pump working space than is the case during full load or part load operation, so that the reduction of pressure in the delivery line changes from the lowest amount during idling to the largest amount during full load operation.
Such a pressure valve is therefore used to control the residual pressure in the delivery line and to equalise the amount of fuel delivered in dependence on the injected quantity and the speed. The throttle acting during the spill stroke has at the same time an effect on the injection rate during the delivery phase of the fuel injection pump and reduces the quantity of fuel injected at full load with increasing engine speed.
In the case of a known pressure valve, where the closing member has a return collar and which do not come up against a fixed stop during each delivery process, the flow cross-section released in the transit bore by the closing member connected to the return collar on the side of the pump working space is made very large, particularly larger than the free cross-section of the connected delivery line. In such pressure valves, greatly varying quantities are injected when the high pressure delivery of the fuel injection pump is set at constant. These varying fuel injection quantities cannot be corrected by suitable setting of the effective delivery stroke of the pump piston, particularly in the case of a distributor injection pump, as all injection points of the internal combustion engine are supplied alternately from a single pump working space and accordingly the quantity control for all injection points must be equal, provided that no injection quantity control device is furnished which individually controls the injected quantity per delivery stroke of the pump piston. However such a control involves considerable expense. The quantity can also be influenced by other secondary measures, e.g. by limiting the stroke of the pressure valve, which again does not give the desired uniform effect over the whole operating range of the fuel injection pump and is also very expensive.
ADVANTAGES OF THE INVENTION
The pressure valve in accordance has an the advantage that the above-mentioned variations of quantities can be prevented by a simp
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Lutz Rolf
Oberl Johann
Schmidt Hermann
Greigg Edwin E.
Greigg Ronald E.
Rivell John
Robert & Bosch GmbH
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