EP2331806B1 - Injector with a particle filter arranged before the inlet restrictor - Google Patents

Description

State of the art

The invention relates to an injector, in particular to an injector in a storage injection system of an internal combustion engine having a particle filter for cleaning the high-pressure fuel supplied to a control chamber of the injector according to the preamble of patent claim 1.

Storage injection systems of internal combustion engines, which are also known as common-rail systems, have injectors via which the injection of high-pressure fuel into the combustion chamber of the internal combustion engine is controlled. In common-rail injection systems, a high-pressure pump delivers the fuel under high pressure into a central high-pressure accumulator, which is arranged outside the injector and is also referred to as a rail. From the high pressure accumulator high pressure lines lead to the individual injectors, which are assigned to the cylinders of the internal combustion engine. In the injector, a nozzle needle valve is provided with a pressure chamber which is actuated via a valve control piston. For controlling the Ventifsteuerkolbens, the injector has a control chamber and a control valve associated control valve. During operation of the internal combustion engine, the high-pressure fuel is present in the pressure chamber and on the control valve. With an opening of the control valve, the control piston is relieved, whereby the high-pressure fuel in the pressure chamber raises the nozzle needle, so that the fuel from the pressure chamber at the raised nozzle needle is injected over the injectors into the combustion chamber of the internal combustion engine.

Due to the complex design of injectors, the accuracy and proper operation of this device of the storage injection system is particularly vulnerable to particles that can be supplied to the injector with the fuel. Since the pressure-compensating control valves act as a filter due to a stroke size of 20 to 30 microns for larger particles, particles partially enter the seating area of the control valve and damage it considerably. As has been found from studies of the seat portion of the control valve, the damage occurs mainly on the inner diameter of the seat portion of the control valve, wherein at the inner edge of the seat area strong deformations occur, which can lead to leakage and thus malfunction of the pressure-compensating control valve.

For this purpose, it is known from the prior art to provide the valve seat with a special coating in order to limit damage to the valve seat caused by particles. However, the coating of the valve seat has led to no improvement here. The use of a rod filter in the fuel inlet of the injector has proved to be insufficient due to its gap height of 40 to 80 microns to keep particles smaller size of the control valve away. The fuel filter, which filters particles up to a size of 3 μm and located in front of the high pressure pump, is located too far upstream of the injector so that particles from the high pressure lines and the high pressure pump, despite the fuel filter and the rod filter, enter the injector. Due to the limited space in the injector, the integration of a commercially available filter with a sufficient filter effect from a design point of view is difficult, with the disadvantage that there is a significant pressure loss of the fuel supplied through the filter is to be expected.

Out DE 10 2005 035 347 B3 For example, a fuel injector is known for filtering foreign body particles from fuel in a common rail system. The fuel injector has a socket with an inlet channel, which ensures a fluid connection with a control chamber. On the bush, a filter is further provided, the fuel that flows to the control chamber, cleans of foreign particles. The filtering effect occurs in areas of the filter in which a light area is formed on both sides of the filter. A disadvantage of such a fuel injector is that the filtering effect is limited, and thus the efficiency of the filtering of the fuel entering the control chamber is low.

Disclosure of the invention

The invention has for its object to provide a filter device for an injector, which reliably protects the control valve of the injector against the particles supplied with the fuel and reduces the pressure of the injected fuel within the injector only insignificantly.

According to the invention, the injector comprises an injector housing with a fuel inlet, through which the fuel is preferably supplied from a central high pressure accumulator from the injector under high pressure. The injector is used in such a memory injection or common rail system for controlling the injection process of high-pressure fuel into the combustion chamber of an internal combustion engine. For this purpose, the injector has a high-pressure channel which connects the fuel inlet in terms of flow with a pressure chamber. The fuel is in this case injected from the pressure chamber via injector nozzles in the combustion chamber of the internal combustion engine, wherein the injection process is carried out in dependence on a control valve which is associated with a control chamber of a control piston. The control chamber is in this case hydraulically connected via an inlet throttle with the fuel inlet, so that in addition to the main flow of fuel, which the Pressure space is supplied, a side stream of fuel is passed into the control chamber of the control piston. The nozzle needle driven via the control piston is opened when the fuel pressure in the pressure chamber is greater than the fuel pressure in the control chamber. The control valve is in this case hydraulically connected to a fuel return and therefore serves to regulate the pressure conditions of the fuel located in the control chamber.

In order to prevent a malfunction of the pressure-compensating control valve by an accumulation of particles in the region of the valve seat, it is provided according to the invention that on the side of the inlet throttle associated with the fuel inlet, a particle filter is arranged, the high-pressure fuel before entering the control chamber of the control piston filters.

The inventive arrangement of a particulate filter immediately upstream of the inlet throttle results in the advantage that only that portion of the volume flow of fuel is filtered, which flows via the inlet throttle and the control chamber to the control valve, which is particularly vulnerable to particles. The main stream of fuel, on the other hand, is conducted directly and unfiltered from the fuel feed via the high-pressure passage to the pressure chamber without a pressure loss caused by the particulate filter. As a result, the split-off of the volume flow of fuel into a main flow guided to the pressure chamber and a bypass flow guided to the control chamber is used in an advantageous manner in order to filter only that portion of the volume flow of fuel which flows via the control chamber to the control valve. During operation of the internal combustion engine, the high-pressure fuel flows through the fuel feed into the injector, for example with a flow rate of up to 7 l / min, whereas only maximum flow values of approximately 0.6 l / min occur at the inlet throttle under the same operating conditions. Due to the smaller volume of the particle flow flowing through the secondary flow of fuel, the filter has a high efficiency and a high fatigue strength.

To provide a large filter surface is provided according to the invention that between the high pressure passage and the inlet throttle, a cavity is arranged, which serves to receive the particulate filter. By enlarging the surface of the particulate filter, it is possible to reduce the flow resistance of the particulate filter and thus the pressure loss of the fuel as it flows through the particulate filter.

According to the invention, the cavity is formed as an annular space which surrounds the control chamber in an annular manner. The control room is here separated from the annulus by a control room wall. The control chamber wall, which preferably has the shape of a sleeve and limits the control chamber, in this case comprises the inlet throttle, which connects the control chamber hydraulically via the annular space with the fuel inlet.

In order to further reduce the pressure drop through the filter, it is further provided according to the invention that the particle filter has a hollow cylindrical shape and extends around the circumference of the control chamber wall. Compared to a front filter known from the prior art, whose flow area results from the cross-sectional area of the pipeline, the hollow cylindrical particle filter has a larger flow area, which results from the size of the lateral surface of the hollow cylindrical particle filter.

In order to improve the filtering effect of the particle filter enclosing the control chamber wall, the hollow cylindrical particle filter can subdivide the annular space into a first and a second region. The first region of the annular space in this case faces the fuel inlet, whereas the second region of the control chamber wall is assigned. According to one embodiment of the invention, the first and the second area have the same height. For this purpose, the particle filter preferably extends over the height of the annular space. This results in the advantage that the fuel flows through the particle filter in a substantially radial direction, resulting in an optimal filter effect with only a slight loss of fuel pressure.

According to a further embodiment of the invention, the control chamber wall, the control valve, the control chamber and the inlet throttle is associated with a valve piece which is inserted into the housing of the injector. According to the invention, the particulate filter is fastened between the injector housing and the valve piece. Thus, it is conceivable, for example, that the particle filter is clamped between the injector housing and the valve piece, whereby an additional fixation of the particulate filter within the annular space is unnecessary. In a releasable attachment of the valve member in the injector further results in the advantage that the particulate filter is interchangeable.

According to the invention, the particulate filter can be designed as a fine mesh fabric filter, whereby it can be produced in a simple and cost-effective manner. The particle filter preferably consists of at least one synthetic layer. To reliably prevent damage to the pressure-compensating control valve, it can be provided according to the invention that the particle filter has an opening width which is smaller than the stroke of the control valve. This advantageously prevents that Particles whose size is greater than the stroke of the control valve, can penetrate to this and accumulate in the seating area. The stroke of known from the prior art control valves is in this case usually between 20 and 30 microns.

Moreover, according to the invention, it can be provided that a further particle filter is provided in the injector. The particulate filter can be assigned to both the fuel inlet and the high-pressure line, which connects the pressure chamber hydraulically with the fuel inlet. In addition to the use of a known from the prior art rod filter in the range of fuel inlet, the use of a laser drilled filter in cup form has been found to be particularly advantageous, since in this the pressure loss of the high-pressure fuel is low.

Brief description of the drawings

The invention will be described below with reference to the drawings based on preferred embodiments.

Figur 1

eine Längsschnittansicht eines erfindungsgemäßen Injektors mit einem vor der Zulaufdrossel angeordneten Partikelfilter;

Figur 2

einen Ausschnitt aus einem Längsschnitt durch einen erfindungsgemäßen Injektor mit einem Injektorgehäuse in das ein Ventilstück eingefügt ist, das abschnittsweise von einem Ringraum und einem Partikelfilter umschlossen wird;

Figur 3

eine vergrößerte Längsschnittansicht des erfindungsgemäßen Injektors aus Figur 2 im Bereich der Zulaufdrossel; sowie

Figur 4

eine Querschnittsansicht des erfindungsgemäßen Injektors aus Figur 2 und Figur 3 im Bereich der Zulaufdrossel.

In the drawings show:

FIG. 1

a longitudinal sectional view of an injector according to the invention with a front of the inlet throttle arranged particulate filter;

FIG. 2

a detail of a longitudinal section through an injector according to the invention with an injector in which a valve piece is inserted, which is partially surrounded by an annular space and a particle filter;

FIG. 3

an enlarged longitudinal sectional view of the injector according to the invention FIG. 2 in the area of the inlet throttle; such as

FIG. 4

a cross-sectional view of the injector according to the invention FIG. 2 and FIG. 3 in the area of the inlet throttle.

embodiments

The representation in FIG. 1 is schematically an injector 1 for the injection of high-pressure fuel in a in FIG. 1 To remove not shown combustion chamber of an internal combustion engine.

The injector 1 comprises a housing 2 with a fuel inlet 4, via which high-pressure fuel is supplied to the injector 1. For the supply of high-pressure fuel, the injector 1 via an in FIG. 1 not shown high-pressure line in terms of flow with a central high-pressure accumulator - the so-called rail - connected. The high pressure accumulator is supplied via a high pressure pump fuel under high pressure from a fuel tank. In addition to the in FIG. 1 shown injector 1 may be connected to the central high-pressure accumulator further injectors, which are supplied via further high-pressure lines with fuel.

The fuel supplied to the injector 1 via the fuel inlet 4 is divided into a main and a secondary flow after entering the injector 1, the main flow being conducted via a high-pressure channel 6 to a pressure chamber 8 and the secondary flow via an inlet throttle 16 to a control chamber 12 becomes. The control chamber 12 is arranged above a control piston 14 which is in operative connection with a prestressed nozzle needle 22, which closes the injection nozzles 28 of the injector 1. Via the inlet throttle 16, the control chamber 12 is thus supplied with only a control amount of fuel, which is required to control the control piston 14.

The nozzle needle 22, which is biased by a spring member 24 against the nozzle needle seat in the region of the injection nozzle 28 is lifted from the nozzle needle seat when the fuel pressure in the pressure chamber 8 is greater than the fuel pressure in the control chamber 12 of the control piston 14. To control the injection process the control chamber 12 is associated with a control valve 10, via which the fuel pressure in the control chamber 12 and thus the injection of fuel from the pressure chamber 8 via the injection nozzle 28 is controllable in the combustion chamber of the internal combustion engine. The control valve 10 is in this case connected via an outlet throttle 20 in terms of flow with the control chamber 12. Upon opening of the control valve 10, the fuel flowing through the outlet throttle 20 from the control chamber 12 via a fuel return passage 26 to a in FIG. 1 not shown fuel tank returned. For actuating the control valve 10, an actuator 30 is provided in the injector 1, which opens the control valve 10 against a compression spring force. After the control valve 10 for an exact execution of the injection process of considerable importance it is necessary that the control valve 10 reliably seals the control chamber 12 in the direction of the fuel return 26. In order to prevent damage to the seat region of the control valve 10, a particle filter 18 is arranged between the fuel inlet 4 and the inlet throttle 16, which filters the fuel flow which is supplied to the control chamber 12 in a reliable manner.

By the mentioned separation of the supplied via the fuel inlet 4 to the injector 1 volume flow of fuel into a main and a side stream is filtered by the particulate filter 18, which is provided immediately upstream of the inlet throttle 16, only a fraction of the volume flow of fuel, whereby the led to the pressure chamber 8 main flow of fuel experiences no pressure loss.

FIG. 2 shows a detailed view of an embodiment of the invention, in which a valve piece 32 is received in the housing 2 of an injector 1. After the in FIG. 2 shown in detail injector 1 substantially with the in FIG. 1 For the sake of simplicity, the same reference numbers are used to designate the same parts. Furthermore, in order to avoid repetition, reference is made to the above description of the in FIG. 1 referenced injector referenced.

As from the illustration in FIG. 2 As can be seen, the valve piece 32 has a multi-stepped bore which extends through the valve piece 32 and is closed on the upper side by a valve ball 36. The valve ball 36 is a part of the control valve 10, which is opened or closed depending on the position of the valve ball 36. The valve ball 36 rests in a ball seat and is in the in FIG. 2 illustrated closed state of the control valve 10 is acted upon by an armature 38 with a compressive force. In the arranged between the valve ball 36 and the control chamber 12 portion of the bore an outlet throttle 20 is arranged, which reduces the discharged from the control chamber 12 volumetric flow of fuel via the open control valve 10 to the in FIG. 1 shown fuel return 26 is passed.

The arranged in the valve piece 32 control chamber 12 is bounded by a control chamber wall 40, in which the inlet throttle 16 is arranged. As well as from the representation in FIG. 4 It can be seen, between the valve piece 32 and the injector 2 a cavity designed as an annular space 34 is provided, which surrounds the valve member 32 at the level of the control chamber 12. Between the injector 2 and the valve member 32, the particle filter 18 is disposed within the annular space 34, which surrounds the control chamber wall 40 of the valve member 32 at a distance.

With a supply of high-pressure fuel via the fuel inlet 4 into the annular space 34, the fuel must thus flow through the particle filter 18 in order to reach the control chamber 12 via the inlet throttle 16.

In FIG. 3 the arranged in the annular space 34 particulate filter 18 of the injector 1 is shown in a detailed view. As from the illustration in FIG. 3 As can be seen, the particulate filter 18 divides the annular space 34 provided between the injector housing 2 and the valve piece 32 into a first area 42 and a second area 44. The second area 44 of the annular space 34, which is fluidly associated with the inlet throttle 16 and the control space 12, extends at least over a portion of the height of the particulate filter 18th

As in this context from the in FIG. 4 illustrated cross-sectional view of the injector 1 at the level of the inlet throttle 16, the first and second region 42, 44 of the annular space 34, the particulate filter 18 and the control chamber wall 40 are arranged coaxially to the control chamber 12 of the valve member 32. During operation of the internal combustion engine, the fuel subjected to high pressure initially flows, starting from the fuel inlet 4, into the first region 42 of the annular space 34, from where the fuel flows through the particle filter 18 into the second region 44 of the annular space 34, before passing through the fuel chamber Control chamber wall 40 of the valve member 32 arranged inlet throttle enters the control chamber 12.

The arrangement of the second region 44 of the annular space 34 between the particle filter 18 and the control chamber wall 40, the fuel flows through the particle filter 18 in a substantially radial direction, wherein within the second region 44 of the annular space 34 along the control chamber wall 40 in the direction of the inlet throttle 16th running current exists. The Durchströmfläche of the particulate filter 18 thus corresponds to its lateral surface, so that only a small pressure losses in the supply of highly pressurized fuel into the control chamber 12 by a spaced around the circumference of the control chamber wall 40 of the valve piece 32 arranged particulate filter 18. From the low pressure loss of the fuel when flowing through the particulate filter 18 of the particulate filter 18 is also only slightly stressed, so that there is a high fatigue strength of the particulate filter 18.

For attachment of the particulate filter 18, it may be provided that this is clamped between the injector housing 2 and the valve piece 32.

Claims (7)

1. Injector for injecting fuel into the combustion chamber of an internal combustion engine, comprising an injector housing (2) which has a fuel inlet (4) for the supply of highly pressurized fuel, said fuel inlet being connected in terms of flow via a high-pressure duct (6) to a pressure chamber (8), from where the fuel is injected in a manner dependent on the position of a control valve (10), wherein the control valve (10) is assigned to a control chamber (12) of a control piston (14) which is connected in terms of flow to the fuel inlet (4) via an inlet throttle (16), and a hollow cylindrical particle filter (18) is arranged upstream of the inlet throttle (16) as viewed in the flow direction of the fuel, which particle filter filters the fuel flowing into the control chamber (12), wherein the hollow cylindrical particle filter (18) has a flow passage area defined by the size of an outside surface of the hollow cylindrical particle filter (18), and a cavity (34) is provided between the fuel inlet (4) and the inlet throttle (16), in which cavity the hollow cylindrical particle filter (18) is arranged, wherein the cavity is an annular cavity (34) which surrounds the control chamber (12), wherein the control chamber (12), which is accommodated in a valve piece (32), is delimited by a control chamber wall (40) which comprises the inlet throttle (16) and around the circumference of which the hollow cylindrical particle filter (18) extends, characterized in that the valve piece (32) is inserted into the injector housing (2), wherein the hollow cylindrical particle filter (18) is fastened between the injector housing (2) and the valve piece (32).
2. Injector according to Claim 1, characterized in that the hollow cylindrical particle filter (18) divides the annular chamber (34) into a first region (42), which faces toward the fuel inlet (4), and a second region (44), which faces toward the control chamber wall (40).
3. Injector according to Claim 2, characterized in that the first region and the second region have substantially the same height.
4. Injector according to one of the preceding claims, characterized in that the hollow cylindrical particle filter (18) comprises a fine-mesh fabric.
5. Injector according to one of the preceding claims, characterized in that the hollow cylindrical particle filter (18) has a filter action of up to 15 µm.
6. Injector according to one of the preceding claims, characterized in that the hollow cylindrical particle filter (18) has an opening width of a size smaller than the stroke of the control valve (10).
7. Injector according to one of the preceding claims, characterized in that, within the injector (1), there is provided a further particle filter that filters at least the fuel that is fed to the pressure chamber (8).

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