NL1042364B1 - Needle valve controlled pilot valve type fuel injection device - Google Patents

Abstract

The pilot valve fuel injection device according to the invention comprises a fuel injector based on the pilot valve principle for dosage of the fuel that is injected into a combustion chamber. This pilot valve fuel injector is actuated by a spring loaded fuel pressure controlled needie valve, controlling the mass flow and the position of the pilot valve in such a manner that the number of nozzle holes through which fuel is injected into a combustion chamber increases when more engine power and hence more fuel is demanded.

Description

NEEDLE VALVE CONTROLLED PILOT VALVE TYPE FUEL INJECTION DEVICE

FIELD OF THE INVENTION

The present invention relates to a needle valve controlled pilot valve type fuel injection device for internal combustion engines.

BACKGROUND OF THE INVENTION

The fuel injectors for internal combustion engines according to the prior art in general utilize a spring loaded needle with a mating seat, situated close to the tip or nose of the injector to control the fuel dosage to the nozzle holes in the tip through which the fuel enters the combustion chamber of an engine.

Such prior art fuel injectors tend to have a number of drawbacks, such as a high noise level due to oscillation of the spring loaded needle and the relatively small number of nozzle holes through which fuel enters the combustion chamber irrespective of the power demand, hence, irrespective of the amount of fuel that is injected per injection cycle.

Due to the inherently small diameter of the nozzle tip of this type of prior art fuel injector the number of nozzle holes that can be made along the circumference of the tip is limited. Therefore, particularly when more engine power and hence more fuel is demanded, the fuel jet streams exiting the fuel injector tend to become quite massive. This delays the evaporation of the fuel and the mixing with combustion air. As a result the combustion will not be complete and the fuel efficiency will be low while the volume of undesirable byproducts (soot and NOX) will be high. It is therefore that the inventor and the applicant of the present invention recently filed patent applications for an improved fuel injection device comprising a pilot valve (PV) operated fuel injector, hereinafter also referred to as PV fuel injector. Whereas the previous patent applications relating to the PV fuel injector mainly covered the broad concept, there are many aspects of the PV fuel injector that leave room for further detailing with novel and non-obvious characteristics.

SUMMARY OF THE INVENTION

The pilot valve fuel injection device according to the invention comprises a fuel injector based on the pilot valve principle for dosage of the fuel that is injected into a combustion chamber. This pilot valve fuel injector is actuated by a spring loaded fuel pressure controlled needle valve, controlling the mass flow in such a manner that the number of nozzle holes through which fuel is injected increases when more engine power and hence more fuel is demanded.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings, in which: FIG. 1 is a schematic longitudinal section of an embodiment of a pilot valve fuel injector according to the invention with the pilot valve in the fully closed position; FIG. 2 is a schematic longitudinal section of a part of the embodiment of the pilot valve fuel injector according to the invention as shown in FIG. 1 with the pilot valve in the fully opened position; FIG. 3 is a schematic detail of the tip section of the embodiment of the pilot valve fuel injector in the fully opened position as shown in FIG. 2; FIG. 4 is a schematic longitudinal section of the tip of an embodiment of the pilot valve fuel injector with a closed tip; FIG. 5 is a schematic front view of the tip of an embodiment of the pilot valve fuel injector according to the invention; - FIG. 6 is a schematic approximation of the relationship between the fuel pressure (p) and the fuel mass flow (rh fuei) for operation of the fuel injection device according to the invention.

Identical or similar parts have been designated with identical or similar reference numbers in all drawings.

DETAILED DESCRIPTION OF THE INVENTION

The invention provides an injection device ("device") for injecting a fuel into a combustion chamber of an internal combustion engine, wherein a pilot valve, a piston like component, is configured to slide axially inside the bore of an injector tip, also referred to as a sleeve, which protrudes partially into the combustion chamber of an internal combustion engine during operation of the injection device. It is the primary objective of the present invention to provide a fuel injection device using the pilot valve principle for dosage of the injected fuel, whereby the pilot valve is moved by the fuel pressure. FIG. 1 shows a schematic longitudinal section of an embodiment of a pilot valve fuel injector according to the invention with the pilot valve in the fully closed position.

In this embodiment the pilot valve fuel injector comprises the following main components: injector tip (or sleeve) 1 coupling nut 2 body 3 pilot valve 4 needle valve stem 5 locknut 6 valve seat 7 spring 8 fuel conduit 9 fuel chamber 10 shim 11 nozzle holes 12

The injector tip 1 is locked up and connected to the body 3 by the coupling nut 2.

Inside the injector tip 1 a pilot valve 4 can move axially to open or close nozzle holes through which fuel is injected into a combustion chamber. In an embodiment the fuel injection device according to the invention comprises 200 nozzle holes with a diameter of 25 micrometers each, arranged in a plurality of parallel circumferential rows in such a way that upon axial movement of the pilot valve one or more rows of nozzle holes will either be opened or closed, depending on the direction and the extension of the movement of the pilot valve. The number of nozzle holes per row may vary. The embodiment with 200 nozzle holes may comprise for example 10 rows of 10 nozzle holes each. In another embodiment the injection device comprises 100 nozzle holes with a diameter of 50 micrometers each. In yet another embodiment the fuel injection device comprises 40 nozzle holes with a diameter of 60 micrometers each. The pilot valve fuel injection device according to the invention may comprise any number of nozzle holes of any size that is deemed useful or necessary. While conventional needle and seat type fuel injectors usually comprise only for example 8,10 or 12 nozzle holes, the PV fuel injector according to the invention may comprise that number of nozzle holes per row of nozzle holes and comprises a plurality of such rows.

In the embodiment shown schematically in FIG. 1 a first end of a needle valve stem 5, also referred to as needle 5, is screwed into a threaded bore in one end of the pilot valve 4 whereby the connection is secured with a locknut 6. This type of connection between the needle of the needle valve will hereinafter also be referred to as a direct connection. In this embodiment the longitudinal axis of the needle 5 and the longitudinal axis of the pilot valve 4 are essentially in line with each other. The invention includes embodiments wherein the connection between the pilot valve 4 and the needle 5 is not a screwed connection but another type of mechanical direct connection.

In the closed position of the fuel injector the second end of the needle valve stem 5 is pressed onto a valve seat 7 by a spring 8 and fuel entering the injector body 3 through the fuel conduit 9 cannot flow to the injector tip 1. When the needle valve is pushed from the seat, in this case pushed from the seat by fuel pressure, and when at the same time the pilot valve that is rigidly connected to the needle valve moves to bring the fuel chamber 10 into fluidic contact with (some of) the nozzle holes (not shown in FIG. 1) in the injector tip, fuel can flow from the fuel conduit 9 through the bore in the injector body 3 and channels in the pilot valve 4 towards the fuel chamber 10. In order to adjust the preload force with which the needle valve is pressed onto the seat, one or more shims 11 are used in this embodiment of the fuel injection device according to the invention. The invention also comprises embodiments of the fuel injection device wherein for example the needle does not constitute a straight element but comprises one or more angles. In such a case the position of the needle valve seat will not necessarily be in line with the longitudinal axis of the pilot valve. In the remainder of this specification and in the claims, the characterization that the longitudinal axis of the pilot valve and the longitudinal axis of the needle are essentially in line with each other shall also be construed to include embodiments with any other means of actuating the sliding movement of the pilot valve in an axial direction by a movement of the needle of the needle valve in the fuel conduit. Such means may for example also comprise a mechanism with levers.

Various embodiments of the fuel injection device according to the invention comprise a hydraulic actuation of the movement of the pilot valve instead of actuation through a mechanical connection between the needle 5 of the needle valve and the pilot valve 4. This provides for a very flexible configuration of the injection device, since the force on the pilot valve does not have to be transferred directly by a mechanical element but can be transferred by an hydraulic medium that flows through a fluid conduit. The latter form of transfer of a force for (or also referred to as actuation of) the movement on the pilot valve will hereinafter also be referred to as an indirect connection between the needle of the needle valve and the pilot valve. FIG. 2 is a schematic longitudinal section of a part of the embodiment of the pilot valve fuel injector according to the invention as shown in FIG. 1 with the pilot valve in this drawing in the fully opened position. In the longitudinal section shown in FIG. 2 only two sectioned nozzle holes 12 are visible, since the invention envisages that the fuel injector comprises a large number of nozzle holes arranged in a staggered pattern along the circumference of the tip of the injector tip 1. While in FIG. 1 the fuel chamber 10 is visible as a bold line, FIG. 2 clearly shows the fuel chamber 10 in the pilot valve. FIG. 3 is a schematic detail of the tip section of the embodiment of the pilot valve fuel injector as shown in FIG. 2. In this fully opened position of the pilot valve fuel will flow from the fuel chamber 10 in the pilot valve through each of the nozzles holes 12 in the injector tip 1 into the combustion chamber, assuming that the fuel injector is installed in an internal combustion engine. In an embodiment of the fuel injector according to the invention the stroke length of the pilot valve from the fully closed position as shown schematically in FIG. 1 to the fully opened position as shown schematically in FIG. 2 and FIG. 3 comprises only approximately 0,3 millimeters.

The embodiments of the fuel injector device shown schematically in FIG. 1, FIG. 2 and FIG. 3 are of the type wherein the number of nozzle holes that is opened for fuel to be injected into a combustion chamber increases when the pilot valve moves in the direction of the combustion chamber, i.e. to the left in the situation depicted in the drawings, and the number of nozzle holes that is opened decreases when the pilot valve moves in the opposite direction, i.e. to the right in the situation depicted in the drawings. However, the invention includes embodiments wherein the number of nozzle holes that is opened for fuel to be injected into a combustion chamber increases when the pilot valve moves away from the combustion chamber and decreases when the pilot valve moves in the direction of the combustion chamber. FIG. 4 is a schematic longitudinal section of the tip section of an embodiment of the fuel injection device according to the invention, wherein the fuel injection device comprises a closed tip or closed sleeve. In the embodiments shown in the previous drawings the fuel injection device comprised an open-ended sleeve or open tip. FIG. 5 is a schematic front view of the tip of an embodiment of the pilot valve fuel injector according to the invention, whereby the black dots represent the nozzle holes in the injector tip. FIG. 6 is a schematic approximation of the relationship between the fuel pressure (p) and the fuel mass flow (mf) for operation of the fuel injection device according to the invention. In order to push the needle valve from the valve seat a threshold fuel pressure, hereinafter also referred to as the opening pressure, has to be reached. Whereas, normally in a spring loaded valve the required pressure to move the spring loaded stem would increase linearly, in this case the relationship between the fuel pressure and the fuel mass flow is not fully linear. So, only a part of the graph in FIG. 6 has an angle a which corresponds to the spring constant of the pilot valve loading spring 8. This is due to the shape of the needle valve tip which results in a non-linear change of the force exerted on the valve tip by the fuel pressure as the valve moves away from the valve seat. Not shown in FIG. 6 is the relationship between the number of nozzle hole rows and hence the number of nozzle holes that are opened to enable the increase in the fuel mass flow. The higher the fuel mass flow the more nozzle holes are open in order to allow fuel to be injected into the combustion chamber, with all the nozzle holes being opened when the maximum fuel mass flow is reached.

In addition to the stationary embodiments of the pilot valve fuel injector according to the invention shown in the appended drawings, the invention also comprises rotating embodiments of the pilot valve fuel injection device.

As described above, the invention may especially be embodied in the following embodiments, wherein the embodiments are merely numbered for reference reasons: 1. An injection device for the injection of a fuel into the combustion chamber of an internal combustion engine with an injector tip (1), a fuel conduit (9) a pilot valve (4) which pilot valve is slidable in an axial direction, wherein the pilot valve (4) is connected directly or indirectly to a needle (5) of a needle valve that is positioned in the fuel conduit (9). 2. The injection device according to embodiment 1, wherein the longitudinal axis of the needle (5) and the longitudinal axis of the pilot valve (4) are positioned essentially in line with each other.

The term "essentially" herein, such as in "essentially in line", will be understood by the person skilled in the art. The term "essentially" may also include embodiments with "entirely", "completely", etc. Hence, in embodiments the adjective essentially may also be removed. Where applicable, the term "essentially" may also relate to 90% or higher, such as 95% or higher, especially 99% or higher, even more especially 99.5% or higher, including 100%. The term "comprise" includes also embodiments wherein the term "comprises" means "consists of". The term "comprising" may in an embodiment refer to "consisting of" but may in another embodiment also refer to "containing at least the defined species and optionally one or more other species". Use of the verb "to comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim.

The term "and/or" especially relates to one or more of the items mentioned before and after "and/or". For instance, a phrase "item 1 and/or item 2" and similar phrases may relate to one or more of item 1 and item 2.

The devices herein are amongst others described during operation. As will be clear to the person skilled in the art, the invention is not limited to devices in operation.

While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In the device claim enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

The invention further applies to a device comprising one or more of the characterizing features described in the description and/or shown in the attached drawings. The invention further pertains to a method or process comprising one or more of the characterizing features described in the description and/or shown in the attached drawings.

The various aspects discussed in this application can be combined in order to provide additional advantages. Further, the person skilled in the art will understand that embodiments can be combined, and that also more than two embodiments can be combined. Furthermore, some of the features can form the basis for one or more divisional applications.

Claims (2)

An injection device for injecting a fuel into the combustion chamber of an internal combustion engine, wherein the device comprises a fuel inlet channel (9) and an atomizer tip (1) provided with atomizer holes with a metering slide (4) accommodated in the atomizer tip and movable in axial direction characterized in that the metering slide is directly or indirectly connected to the needle (5) of a needle valve located in the fuel inlet channel (9) of the injection device. Injection device according to claim 1, characterized in that the longitudinal axis of the needle (5) and the longitudinal axis of the metering slide (4) are substantially in line with each other.