Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
2001-08-20
2002-07-23
Miller, Carl S. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel injection system
C123S300000
Reexamination Certificate
active
06422209
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a magnet injector for fuel reservoir injection systems, having:
a fuel inlet and a fuel outlet; a control chamber, which communicates with the inlet; a nozzle, which communicates with the inlet; and a nozzle needle, which has a tip for closing the nozzle opening and has a shaft end that borders on the control chamber; and
a magnet valve, which has a first electromagnet, an armature, a valve chamber that communicates with the outlet via a first passage and with the control chamber via a second passage, and a throttle body which is located in the valve chamber and is connected to the armature,
wherein the throttle body, in the state of repose of the injector, is kept in a first terminal position, in which it blocks one of the two passages, and is moved toward a second terminal position, in which it opens this passage, by triggering of the first magnet. To make shorter switching times possible, the magnet valve has a second electromagnet, which upon triggering acts on the armature oppositely from the first electromagnet.
2. Description of the Prior Art
A magnet injector of this kind is already known from the book entitled “Dieselmotor-Management/Bosch” [Bosch Diesel Engine Management System], pages 274-277 (2nd Edition, 1998, published by Robert Bosch GmbH, ISBN 3-528-03873-X). At present, fuel reservoir injection systems are predominantly used in diesel engines. Along with the injectors for the cylinders, they also have a high-pressure reservoir (common rail) and a high-pressure pump for the fuel. The high-pressure pump compresses the fuel in the reservoir to the so-called system pressure, which at present can be as high as 1350 bar. This reservoir communicates with the fuel inlet of the injector.
In the known magnet injector, the magnet valve has a single electromagnet; the throttle body in its first terminal position blocks the second passage by way of which the valve chamber communicates with the control chamber, and the first passage, by way of which the valve chamber communicates with the outlet, is disposed such that it cannot be blocked by the throttle body. When the magnet is triggered, it attracts the armature, which carries the throttle body along with it until it is in its second terminal position, in which both the second passage to the control chamber and the first passage to the outlet are open.
The mode of operation of the known magnet injector, when the engine is running, can be summarized as follows.
In the state of repose, the injector is closed, and so the fuel cannot pass through the nozzle to reach the combustion chamber of the cylinder. To that end, the electromagnet of the magnet valve is not triggered, and so a valve spring keeps the throttle body in the first terminal position, in which it blocks the second passage to the control chamber. Thus the system pressure applied by the high-pressure reservoir prevails in the control chamber and also prevails in the nozzle. Since the nozzle needle borders on the control chamber with its shaft end that is opposite its tip, the pressure in the control chamber acts on the shaft end, so that a force in the direction of the tip is exerted on the nozzle needle. A nozzle spring, which serves to prestress the tip into the nozzle opening and thus to close the injector when the engine is not running and high pressure in the high-pressure reservoir is thus absent, likewise exerts a force in the direction of the tip on the nozzle needle. These two closing forces, in the state of repose, exceed the opening force also engaging the nozzle needle; this force originates in the pressure in the nozzle on the tip, which narrows at that point, of the nozzle needle.
At the onset of injection, the injector opens because the magnet valve is triggered. To that end, the so-called attracting current is carried through the electromagnet, which serves to bring about rapid opening of the magnet valve. The magnet valve then exerts a force on the armature, which exceeds the opposite force of the valve spring, so that along its motion toward the electromagnet the armature carries the throttle body along with it and puts it in its second terminal position. As a result, the second passage, by way of which the valve chamber communicates with the control chamber, is opened. Fuel can now flow out of the control chamber through this second passage into the valve chamber and can flow on out through the first passage to the fuel outlet, which communicates with the fuel tank. The pressure in the control chamber consequently drops and is rapidly lower than the pressure in the nozzle, which still is equivalent to the system pressure. Since this reduced pressure in the control chamber is now exerted on the shaft end of the nozzle needle, this closing force on the nozzle needle drops as well, and thus because of the system pressure in the nozzle the opening force predominates, and the nozzle needle is pulled out of the nozzle opening. The fuel at system pressure can now pass through the nozzle opening to emerge from the injector, and the injection begins.
The opening speed of the nozzle needle is determined by the difference between the flow from the fuel inlet into the control chamber and the flow out of the control chamber through the second passage and to the valve chamber. The shaft end of the nozzle needle penetrates into the control chamber far enough that the closing and opening forces on the nozzle needle are equalized, and it then remains in place on a cushion of fuel. This cushion is created by a fuel flow that comes to be established in the control chamber. The nozzle is now fully open, and the fuel is injected into the combustion chamber at a pressure that is approximately equal to the system pressure in the high-pressure reservoir.
At the end of the injection, the magnet valve is no longer triggered, and so the armature is forced away from the electromagnet by the force of the valve spring, and the throttle body again blocks the second passage. Consequently, as a result of the fuel continuing to flow in from the inlet, the system pressure builds up again in the control chamber. This rising pressure causes an increasing force on the nozzle needle. As soon as this closing force from the control chamber and the force of the nozzle spring exceed the opening force from the nozzle, the nozzle needle is moved toward the nozzle opening, until the nozzle opening is again closed by the tip. The closing speed of the nozzle needle is determined by the flow of fuel from the inlet into the control chamber. The injection ends when the nozzle needle reaches its bottom stop and its tip is seated in the nozzle opening. A disadvantage of this known magnet injector, however, is that its switching times are too long to enable a preinjection with replicable, small preinjection quantities of 1 mm
3
and less. This is because the magnet valve used allows only a limited armature speed. The speed can be increased by increasing the attracting current, but then armature recoiling occurs to an increasing extent, which causes a ballistic mode of operation with fluctuations in quantity of up to ±50% of the injected quantity. Increased exhaust emissions and fluctuations in constant-velocity operation are the consequence.
SUMMARY OF THE INVENTION
It is therefore the object of the present invention to make a magnet injector of the type defined at the outset available that makes shorter switching times possible, so that even small injection quantities of less than 1 mm
3
can be replicably defined.
This object is attained in that:
the magnet valve has a second electromagnet, which upon triggering acts on the armature oppositely from the first electromagnet; and
the throttle body is embodied such that in its second terminal position, it blocks the other of the two passages and along the way between its two terminal positions opens both passages.
Consequently, this magnet injector has a magnet valve with two oppositely acting electromagnets and with one common armature. In addition, the
Greigg Ronald E.
Miller Carl S.
Robert & Bosch GmbH
LandOfFree
Magnet injector for fuel reservoir injection systems does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Magnet injector for fuel reservoir injection systems, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Magnet injector for fuel reservoir injection systems will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2820387