Internal-combustion engines – Charge forming device – With fuel pump
Reexamination Certificate
1999-06-16
2001-08-28
Dolinar, Andrew M. (Department: 3747)
Internal-combustion engines
Charge forming device
With fuel pump
Reexamination Certificate
active
06279542
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method and arrangement for controlling the pressure when injecting fuel, such as diesel oil, in an engine, whereby the pressure in a conventional way is obtained by a piston which is driven by a cam shaft and which presses oil out through a nozzle connected to a cylinder cavity in which the piston works. The spray nozzle is provided with small narrow holes through which the liquid fuel is atomized.
PRIOR ART
Many different arrangements for injecting diesel oil are known hitherto. They differ substantially from each other but have in common that a high pressure must be obtained so that the liquid is atomized and that the injection must occur quickly and start as a predetermined moment and be completed at a predetermined limited moment. Most arrangement are therefore based on the principle that a piston presses the fuel against a nozzle having holes at such high speed that a pressure of in the order of amount 300 Bar is created, whereby the injection of the fuel starts. This can occur by making the injection holes so small that they cannot allow all fuel which is pressed against them to pass. The pressure continues to rise even though fuel is flowing out from the nozzle. To release the pressure a connection between the pressure chamber and a valve is arranged, which valve opens when the injection is to be completed so that the pressure instantaneously drops to a zero value. The oil which flows through this regulating valve when it is opened flows via a drainage pipe back to the oil store.
The regulating valve is usually actuated by an electromagnet. It is of great importance that this valve works instantaneously since the whole injection cycle takes only time of in the order of 3 ms (milliseconds) having a highest pressure of about 1500 Bar.
The pressure-creating device, usually a piston in a cylinder, has usually a simple construction and the variations of the fuel injection arrangements which are present relate mostly to the controlling or steering valve which is connected to the fuel pressure. Examples of such arrangements are described in the German patent specification 3741526, the international patent application WO 89/00242, the European patent specification 0193788 and the American patent specification 5517973. All these patent descriptions describe quite different arrangements and it is therefore difficult to compare them with each other and with other prior art.
THE TECHNICAL PROBLEM
In the known arrangements having only one controlling valve the fuel pressure is built up quickly to a value of in the order of 300 Bar and it increase thereafter to about 1500 Bar until the pressure is released by means of the control valve. The injection through the injection holes starts at about 300 Bar. At the beginning of the injection cycle the fuel is combusted with relatively large formation of nitrogen oxide (NO
x
), which from an environmental view is a disadvantage. Since the content of nitrogen oxides is limited by law, which law is continually made more stringent the moment of injection and thus the combustion must normally be postponed to reduce the contamination. This postponement has a negative influence on the efficiency of the engine. A further disadvantage with known arrangements is that at high speeds the pressure can be built up too quickly and become too high above the limit which the injection construction allows. It is therefore a requirement to be able to influence the pressure or to relieve it somewhat during the injection cycle at chosen moments, such as at the beginning, in order to decrease the NO
x
emission and at the end to avoid too high pressures.
THE SOLUTION
According to the present invention, the above problem has been solved by a control valve which only closes and opens and an arrangement and a way of regulating the injection pressure of liquid fuel, such as diesel oil, by a nozzle having narrowed injection openings has been brought about, the pressure being created by a quick action from, for example, a piston in a cylinder and a main control valve in connection with the liquid fuel before the nozzle, which main control valve is kept closed during the injection, which method is characterized in that the pressure is relieved at a suitable moment during the injection cycle through a secondary valve.
According to the invention, it is suitable that the injection pressure is relieved at the beginning of the injection cycle for decreasing developed nitrous gases (NO
x
) during combustion.
According to the invention, it may also be suitable that the injection pressure is relieved at the end of the injection cycle to allow higher speeds of the pressure-creating piston or the like.
The invention also comprises an arrangement for regulating the injection pressure of liquid fuel such as diesel oil by a nozzle having narrowed injection openings, whereby the pressure is created by a quick action from, for example, a piston in a cylinder and control valve in connection with the liquid fuel before the nozzle, which main control valve is kept closed during the injection, which arrangement is characterized in that a secondary valve within the main control cylinder for relieving the injection pressure.
According to the invention, the main control valve comprises a moveable valve body, which through an electromagnet, can be moved up and down against a first spring force having an enlargement at its lower part which is intended to co-operate with a surrounding housing to create a valve which can be closed or opened for the flow of liquid between the housing and the valve body, which liquid-flow is connected to the liquid before the liquid injection nozzle, which arrangement is characterized by a moveable rod within the valve body which is attached to the up and down moveable part of the electromagnet and which at its other end carries a second spring abutting against the lower part of the valve body, which second spring is stiffer than the first spring acting on the valve body, wherein radial holes have been made in the valve body inwardly against the rod and in that the rod co-operate with the valve body to make a valve.
According to the invention it is suitable that the radial holes in the valve body are located somewhat above the edge where a narrowing in the rod starts so that passage of liquid through the holes is prevented when the rod is located in its lower position with the stiffer second spring expanded.
It is also possible according to the invention that the radial holes in the valve body end in a ring-shaped part in the valve body around the rod and that the lower part of the ring-shaped part and a circular edge delimiting a narrowing of the rod make a valve.
According to the invention, it is suitable that the outlet side for the flow in both the main valve and the secondary valve drain into the fuel store.
According to the invention, it is suitable that the first spring acting on the valve body abuts with its other end via a support against the upper side of the body and with its second end against a part of the housing.
According to the invention, both springs are suitably co-axial and the electromagnet is arranged to be activated in at least two steps, whereby in the first step the main control valve is closed and in the second step when the main control valve is closed the secondary control valve is opened.
REFERENCES:
patent: 4485969 (1984-12-01), Deckard et al.
patent: 4753212 (1988-06-01), Miyakai
patent: 5443047 (1995-08-01), Ishiwata et al.
patent: 5517973 (1996-05-01), Askew et al.
patent: 5526791 (1996-06-01), Timmer et al.
patent: 37 41 526 C2 (1989-06-01), None
patent: 0 124 191 A2 (1984-11-01), None
patent: 0 193 788 B1 (1986-09-01), None
patent: 0 200 373 A2 (1986-12-01), None
patent: 0 588 475 A2 (1994-03-01), None
patent: 89/00242 (1989-01-01), None
Castro Arnold
Dolinar Andrew M.
Lerner David Littenberg Krumholz & Mentlik LLP
Volvo Lastvagnar AB
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