Internal-combustion engines – Charge forming device – Fuel flow regulation between the pump and the charge-forming...
Reexamination Certificate
2000-04-10
2001-06-12
Miller, Carl S. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel flow regulation between the pump and the charge-forming...
C123S1980DA
Reexamination Certificate
active
06244253
ABSTRACT:
PRIOR ART
The invention relates to a pressure control valve for a fuel injection apparatus for internal combustion engines, including a housing with a high-pressure connection and a return connection and including a cup-shaped piston. The piston which is disposed in a housing bore and, can be moved axially between a valve seat oriented toward the high-pressure connection and a stop oriented toward the return connection, counter to the spring force of a spring acting in the direction of the valve seat. The piston and has at least one through opening that connects the inside of the cup-shaped piston to the housing bore.
Pressure control valves of this kind have been known for a long time and can be seen, for example, in the German publication “Diesel-Speichereinspritzsystem Common-Rail” [Diesel Common Rail Accumulator Fuel-Injection System] Bosch Technical Instruction No. 1987722054; KH/VDT-0997-DE”.
The function of a pressure control valve of this kind essentially corresponds to that of a pressure relief valve. In the event of a failure of the pressure control. The control valve protects the components from bursting as a result of being overloaded. The pressure control valve limits the pressure in the pressure accumulation chamber, the so-called rail, by virture of the fact that it lifts up from the valve seat in the event of an excessive load and unblocks the through openings. Pressure control valves that are known from the prior art and are described in the above-mentioned publication permit a momentary maximal pressure of 1500 HPa in the pressure accumulation chamber.
This prevents damage to components of the fuel injection system in the event of possible system malfunctions due to an excessive pressure in the fuel injection system. If malfunctions occur which, for example, lead to a continuous full delivery, i.e. at a very high system pressure, which is the case for example in a limp-home program. Then by means of the pressure control valve, through the discharge of a fuel quantity into the tank, a pressure is adjusted in the fuel injection system which on the one hand, prevents damage to any components of the fuel injection system and on the other hand, is at least great enough that an opening of the fuel injection nozzles and consequently a driving operation is possible.
Such a limp-home operation places high demands on the durability of both the spring and the valve in the region of the valve seat. When the pressure control valve is subjected, for example, to a very high pressure that prevails during limp-home operation, a collision of the piston against the valve seat, for example, or a vibration-induced fracture of the spring can occur.
An object of the invention, therefore, is to improve the pressure control valve of this generic type to the extent that on the one hand, in all operating situations, no pulsating pressure is produced in the pressure control valve within predetermined limits and that an impact and/or collision of the piston does not occur either in/against the valve seat or against the stop.
ADVANTAGES OF THE INVENTION
In a pressure control valve of the type described beginning in the, this object is attained according to the invention by virtue of the fact that throttle elements are disposed upstream and/or downstream of the valve seat in the flow direction of the fuel.
The disposition of throttle elements upstream and/or downstream of the valve seat in the flow direction of the fuel has the particularly great advantage that the system pressure is adjusted by means of these throttle elements as a function of the through flow quantity. Furthermore, the throttle elements permit a flow-favorable guidance of the fuel inside the pressure control valve.
A wide variety of embodiments are conceivable with regard to the disposition of the throttle elements. An advantageous embodiment provides that a throttle element is disposed in high-pressure connection. In this instance, the throttle element is disposed upstream of the valve seat and throttles the system pressure prevailing at the valve seat.
Another embodiment provides that a throttle element is disposed in the at least one through opening. This kind of disposition of the throttle elements effectively prevents an impact or collision of the piston against the valve seat.
A particularly advantageous embodiment provides that the cup-shaped piston has an additional piston disposed coaxially in the cup-shaped piston upon which, by means of the spring or by means of an additional spring, a spring force can be exerted in the direction of an additional valve seat embodied on the cup-shaped piston. This additional piston has at least one additional throttle element which can be acted upon by pressurized fuel through the lifting of the additional piston from the additional valve seat. This dual stage pressure control valve has the great advantage that on the one hand, the pressure control valve opens only when a predetermined pressure is exceeded and on the other hand, a “holding pressure” can be set, which can be chosen independently of the opening pressure. The pressure control valve thereby opens only when a high pressure has been exceeded, which is the case, for example, during limp-home operation. The holding pressure, which prevails after the opening of the pressure control valve, prevents the components of the fuel injection apparatus from being continuously loaded with the high opening pressure when the pressure control valve is open. In this connection, the holding pressure can be set to a predetermined value through the selection of the additional throttle elements and the spring force of the spring.
Therefore purely in principle, a wide variety of embodiments are conceivable with regard to the embodiment of the additional throttle elements in the additional piston. One advantageous embodiment provides that the additional throttle elements are through openings in the additional piston. Another advantageous embodiment provides that the additional throttle elements are one or a number of predetermined leaks in the additional valve seat.
The valve seats can be embodied in various ways.
One advantageous embodiment provides that the valve seat is embodied as a conical seat.
Another advantageous embodiment provides that the valve seat is embodied as a spherical seat.
Therefore in the dual stage pressure control valve described above, for example both valve seats can be embodied as conical seats or as spherical seats or can be embodied in alternation as a conical seat and a spherical valve seat.
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Buerkle Frieder
Clauss Helmut
Haeberer Rainer
Rueckle Markus
Greigg Edwin E.
Greigg Ronald E.
Miller Carl S.
Robert & Bosch GmbH
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