EP2029866B1 - Method and device for cleaning valves - Google Patents

Description

State of the art

Out DE 101 18 164 A1 a fuel injection valve for fuel injection systems of internal combustion engines is known. The fuel injection valve comprises an actuator and a valve needle operatively connected to the actuator and acted upon by a return spring in a closing direction for confirming a valve closing body. This forms a sealing seat together with a formed on a valve seat body valve seat. On the downstream side of the valve seat body, a spray perforated disk is arranged, wherein the spray perforated disk is curved in a dotted manner in a flow direction of the fuel.

On self-igniting internal combustion engines, particulate filters, in particular diesel particulate filters, are used due to the higher requirements of emission standards. The particulate filters contain the soot particles contained in the exhaust gas of a self-igniting internal combustion engine, which accumulate in the filter pockets of the diesel particulate filter with the operating time of the self-igniting internal combustion engine. For the regeneration of particulate filters of self-igniting internal combustion engines, the exhaust gas temperature is usually raised by the fact that motor measures are taken. If the exhaust-gas temperature increase required for burning off the soot particles is not possible by engine measures alone, fuel is metered into the exhaust gas by an additional injector provided in the exhaust tract of the self-igniting internal combustion engine, which is catalytically burned on an oxidation catalytic converter. As a result, the heat required to increase the temperature is released. For the additional introduction of fuel into the exhaust tract of the internal combustion engine, the HCI system (Hydro Carbon Injection) was developed. For a good catalytic combustion of the metered into the exhaust gas fuel in the region of the oxidation catalyst a fine distribution of the additionally metered in fuel is required. The generated spray should ideally consist of evenly distributed small droplets. The required spray quality can be achieved by multi-hole nozzles, in which the additionally metered into the exhaust gas fuel is metered through several individual holes in the exhaust. These multi-hole nozzles have a multiplicity of small and minute openings which, however, are deposited on the individual holes by the residual fluid remaining therefrom and the soot accumulating from the exhaust gas at the multi-hole nozzle over the service life of the multi-hole nozzle and clog these gradually. As a result, the additionally metered into the exhaust gas amount of fuel decreases and in particular the fine droplet distribution within the spray decreases drastically. This, in turn, significantly affects the exhaust gas conditioning, so that the effectiveness of the temperature increase generated by the oxidation catalyst is significantly impaired. WO 2005/025725 discloses an electrically controllable heating element which is arranged in front of a metering valve. The heating element can be used to clean the deposit-sensitive parts.

Disclosure of the invention

Following the solution proposed according to the invention, a heating device is provided at an additional injector, via which a spray of finely divided fuel liquid droplets is introduced into the gas. A periodic activation of the heating device can bring about a periodic cleaning or vaporization of soot and fuel deposits on a multi-hole nozzle, so that a long-term constant operation of the additional injector is possible.

At the multi-hole nozzle of the additional fuel injector, which is also referred to as a spray orifice plate, at least one heating wire is integrated. The heating wire representing the additional heating device can on the one hand be on the outside, ie on the side of the multi-hole nozzle or spray perforated disk facing the flow channel. In another embodiment variant, the at least one heating wire that represents the heating device can also be arranged on the inner side, ie the side of the spray perforated disk or the multi-hole nozzle facing away from the exhaust gas flow, and thus be arranged within the injector body of the injector for introducing additional fuel into the exhaust gas flow. At regular intervals by means of the heater, the temperature at the spray perforated disk or the multi-hole nozzle in the immediate vicinity of Spray holes raised to a temperature of over 600 ° C, so that adhering fuel residues and soot particles evaporate or burn.

In order to reduce the thermal load of the fuel injector in the exhaust tract of the internal combustion engine, in particular in its interior, the heater may be insulated inwards by means of a thermal insulation.

Furthermore, the temperature of the spray perforated disk or the multi-hole nozzle can be raised in the short term after the metering of fuel mist one to the particle filter generation to a temperature of for example 400 ° C to evaporate adhering fuel residues quickly. Furthermore, it is also possible by the inventively proposed solution to produce a longer-term increase in temperature to counteract the diffuse deposition of soot particles by thermophoresis or exclude these entirely.

Another additional measure in the form of thermal insulation between the spray perforated disk or the multi-hole nozzle and the injector body of the injector is that a thermal decoupling of the multi-hole nozzle or the spray perforated disk from the injector of the fuel injector is made. While the valve tip is directly exposed to the hot exhaust gas flow in the region of the multi-hole nozzle or the spray perforated disk, the thermal insulation of the spray perforated disk avoids that the heat supplied to it being discharged into the interior of the injector body. Ideally, the spray perforated disk or the multi-hole nozzle assumes the exhaust gas temperature on the side facing the exhaust gas flow.

drawing

With reference to the drawing, the invention will be described below in more detail.

Figur 1

eine schematische Darstellung des Abgastraktes einer selbstzündenden Verbrennungskraftmaschine mit einer einem Oxidationskatalysator vor- geschalteten Eindosierungsstelle für zusätzlichen Kraftstoff in die Ab- gasströmung,

Figur 2

eine erste Ausführungsvariante eines abgasströmungsseitigen Endes eines zusätzlichen Kraftstoffinjektors,

Figur 3

eine weitere Ausführungsvariante des der Abgasströmung zugewandten Endes des zusätzlichen Kraftstoffinjektors und

Figur 4

eine Ausführungsvariante des zusätzlich Kraftstoff in die Abgasströ- mung einbringenden Kraftstoffinjektors mit thermischer Isolation.

It shows:

FIG. 1

1 a schematic representation of the exhaust gas tract of a self-igniting internal combustion engine with an oxidation catalyst upstream injection point for additional fuel into the exhaust gas flow,

FIG. 2

a first embodiment of an exhaust gas flow-side end of an additional fuel injector,

FIG. 3

a further embodiment of the exhaust gas flow facing the end of the additional fuel injector and

FIG. 4

a variant of the additional fuel in the exhaust gas introducing fuel injector with thermal insulation.

variants

The representation according to FIG. 1 is a schematic representation of the exhaust gas tract of a self-igniting internal combustion engine, wherein in the exhaust gas an oxide action catalyst is added, which is preceded by a Einosierungsstelle for additional exhaust gas.

In the exhaust tract 10 of the self-igniting internal combustion engine extends an exhaust pipe 12, via which the exhaust gas of the self-igniting internal combustion engine flows to an oxidation catalyst 18. The exhaust pipe 12 is bounded by a pipe wall 20. An inflow side of the exhaust pipe 12 is denoted by reference numeral 14, and an outflow side of the exhaust gas flow is identified by reference numeral 16. The outflow side 16 of the exhaust pipe 12 represents the inflow side of an oxidation catalyst 18. The exhaust pipe 12 is constructed symmetrically to its symmetry axis 22.

In the pipe wall 20 of the exhaust pipe 12, an injection valve 24 is integrated. The injection valve 24 is connected via a supply line 25, for example, to the fuel tank of the vehicle with a self-igniting internal combustion engine and is supplied via this with fuel.

The injection valve 24 comprises a valve body 26, which penetrates the pipe wall 20 of the exhaust pipe 12 penetrating partially into the exhaust gas flow, which flows through the exhaust pipe 12. Within the valve body 26 is a valve piston 28, indicated only schematically here, in the direction of in FIG. 1 registered double arrow is movable in the vertical direction. The valve piston 28 acts with a valve seat 26 formed in the valve seat 30 together. Below the valve seat 30 is located in the valve body 26 of the injection valve 24 identified by a reference numeral 36 cavity which is adjacent to the valve seat 30 bounded by a spray perforated disk 32.

About the spray perforated disk 32, in which a plurality of smallest openings are designed to produce a finely divided spray, additional fuel, indicated by reference numeral 34, in which the exhaust pipe 12 possierende exhaust gas flow initiated. The smaller the droplet distribution within the spray generated by the spray disk 32, the better the mixing of the additional fuel with the exhaust gas flow and the more uniform combustion can be achieved in the oxidation catalyst 18.

The representation according to FIG. 2 is a section through the exhaust gas flow end facing the injection valve as shown in FIG FIG. 1 refer to.

From the illustration according to FIG. 2 It can be seen that inside the valve body 26 of the injection valve 24, the vertically movable in the direction of the valve piston 28 is located, which cooperates with the likewise formed within the valve body 26 valve seat 30. At the valve seat 30, an opening is formed, which may be circular, for example, and by the valve seat 30 facing end face of the valve piston 28 is closed. Depending on the stroke of the valve piston 28, the opening in the valve seat 30 is fully or partially released, so that additional fuel flows from the interior of the valve body 26 via the open valve seat 30 to the cavity 36.

The valve body 26 is delimited by a spray-bonded disk 32, which is preferably adhesively connected to the valve body 26 at joints 54. The spray perforated disk 32 preferably comprises a multiplicity of individual openings 48. The joints 54 between the valve body 26 and the spray perforated disk 32 may be formed, for example, as welds; Alternatively, it is also possible to screw the spray perforated disk 32 into the valve body 26 or to carry out the valve body 26 with integrated spray perforated disk 32 as an integral component.

From the illustration according to FIG. 2 shows that on the outside of the spray perforated disk 32, with respect to the representation according to FIG. 1 at the exhaust gas flow facing side of the spray perforated disk 32, at this one here as a heating wire 44 formed heating device is assigned. In the illustration according to FIG. 2 is a pitch, which corresponds to the distance of individual heating wires 44 of the heater, indicated by reference numeral 56. The at least one heating wire 44 of the heating device preferably runs such that the at least one heating wire 44 extends over the solid material of the spray perforated disk 32 and does not cover the openings 48 formed in the spray perforated disk 32. Upon activation of the heater formed by the in FIG. 2 heating wires 44 shown, there is a heating of the spray perforated disk 32, so that evaporates remaining in the individual openings 48 fuel and burned on the spray disk 32 in the region of the individual openings 48 accumulating soot particles. By the in FIG. 2 the first embodiment of the heater shown, the quality of the spray generated by the injection valve 24 is permanently secured from additional fuel, since the geometry of the individual openings 48 in the spray perforated disk 32 is not affected by fuel deposits or by the soot particles clogging the individual openings 48. The thickness of the spray perforated disk 32 is indicated by reference numeral 46. The cavity 36 in the injection valve 24 is defined by a first end face 38 of the spray perforated disk 32, an inner wall 42 of the valve body 26, and the valve seat 30 with an opening formed therein. In the in FIG. 2 illustrated embodiment, the heater is located on a second end face 40 of the spray perforated disk 32, that is, at the exhaust gas flow facing surface.

The representation according to FIG. 3 is a further embodiment of the downstream end of an additional fuel in the exhaust flow metering injector.

Unlike in FIG. 2 The heating device comprising at least one heating wire 44 is located on the inside of the spray perforated disk 32, here on the first end face 38 within the cavity 36 in the valve body 26. According to the first embodiment of the injection valve 24 shown FIG. 3 illustrated embodiment of the heating device of the injection valve 24, the at least one heating wire 44 extends to the first end face 38 of the spray perforated disk 32 in a division 56. In the in FIG. 3 illustrated embodiment of a lying inside, ie arranged in the cavity 36 of the valve body 26 heater, comprising at least one heating wire 44, it is achieved that the Heater itself is not contaminated by soot particles contained in the exhaust gas flow of the self-igniting internal combustion engine. By the division 56, in which the at least one heating wire, for example meandering, covers the first end face 38 of the spray perforated disk 32, there is a free inflow cross section to the individual openings 48 formed in the spray perforated disk 32.

When the at least one heating wire 44 of the heating device is supplied with current to the spray perforated disk 32 to a temperature T _max of approximately 600 ° C., evaporation takes place in the individual openings 48 of remaining fuel and combustion of particles contained in the individual openings 48 of the spray perforated disk 32, for example soot particles. As a result, the cross section through which the additional fuel is injected into the exhaust gas flow is maintained. Furthermore, the spray hole geometry remains unchanged over the operating time of the injection valve 24, so that there is no impairment of the area in which the spray is introduced into the exhaust gas flow.

Also in the in FIG. 3 illustrated second embodiment of the injection valve 24 as shown in FIG FIG. 1 is formed in the interior of the valve body 26 of the valve seat 30, the opening of which can be either completely released by the valve piston 28 according to the vertical stroke, fully closed or partially opened. The spray perforated disk 32 according to the in FIG. 3 shown second embodiment of the injection valve 24 may be joined to the valve body 26 at the joints 54 both cohesively and positively inserted in this, for example, be shrunk.

The representation according to FIG. 4 is another embodiment of the in FIG. 1 only to be taken in a schematic representation injector 24 shown.

From the illustration according to FIG. 4 shows that in the cavity 36 between the valve seat 30 and the spray perforated disk 32, a thermal insulation 50 is embedded. The thermal insulation 50 separates the spray hole disk 32 arranged at the exhaust gas flow end from the interior of the valve body 26. The thermal insulation 50 comprises individual openings 52 formed in a partition 58, such that the openings 52 of the thermal insulation 50 communicate with the individual openings 48 of the spray perforated disk 32 are aligned. This is an unobstructed inflow of the stockpiled in the valve body 26 additional fuel with open valve seat 30 to the spray orifice plate 32 possible. In the embodiment according to FIG. 4 is the heater, which is formed by the at least one heating wire 44, omitted.

The in the FIGS. 2 and 3 illustrated embodiments of the heater, which is represented by the at least one heating wire 44, can be energized at regular intervals, so that the temperature at the spray perforated disk 32 in the immediate vicinity of the individual openings 48 to a temperature level of above 600 ° C increases. At this temperature, the outflowing fuel flow obstructing fuel residues evaporates in the individual openings 48. Furthermore, soot particles that have accumulated in the flow cross sections of the individual openings 48 burn at this temperature level. Is the heater from the at least one heating wire 44 at the first end face 38 as shown in FIG FIG. 3 or at the second end face 40 as shown in FIG FIG. 2 arranged, so although in the FIGS. 2 and 3 not shown, in the cavity 36 of the valve body 26, a thermal insulation 50 be added, as in the embodiment according to FIG. 4 shown.

In addition to a uniform temperature of the spray perforated disk 32 by a constant energization of the heater comprising at least one heating wire 44, it is possible to raise the temperature of the spray perforated disk 32 in the short term after metering of fuel to the particle filter regeneration, so for example to a temperature level of about 400 ° C. to evaporate quickly in the individual openings 48 adhering fuel residues. In addition, a prolonged increase in temperature is conceivable in order to counteract the diffuse accumulation of soot particles by means of thermophoresis and, in the ideal case, to completely exclude them.

At the in FIG. 4 In order to increase the temperature of the spray perforated disk 32 to a heating device comprising at least one heating wire 44, it can be completely dispensed with if the temperature increase of the spray perforated disk 32 is brought about by the flow of exhaust gas passing through the exhaust pipe 12. In this case, the interior of the valve body 26 of the injection valve 24 is decoupled from the spray perforated disk 32 by the thermal insulation 50. Preferably, the thermal insulation 50 in the cavity 36 in the valve body 26 introduced, which is bounded by the valve seat 30 on the one hand and the spray hole disk 32 on the other. Since the spray perforated disk 32 is exposed to the hot exhaust gas flow and therefore heats up very strongly, it is achieved via the thermal insulation 50 arranged in the cavity 36 that the temperature level of the spray perforated disk 32 does not act on the valve body 26 of the injection valve 24. Furthermore, it is achieved by the thermal insulation 50 that the heating effect of the exhaust gas flow is limited to the spray perforated disk 32 and this really takes the temperature of the exhaust gas flow after a corresponding heating time. In a variant of the drawing which is not shown in the drawing, the thermal insulation 50 can also be applied to the side of the spray perforated disk 32 facing the exhaust gas flow. In this case, the thermal insulation 50 can be represented by a coating with a ceramic thermal thin layer, wherein it must be ensured that this influences the exhaust gas flow within the exhaust pipe 12 as little as possible. The thermal insulation 50 in the form of a coating with a ceramic thermal thin layer is applied to the spray perforated disk 32 in such a way that the injection openings 48 formed therein are not covered by the ceramic thermal thin layer.

Claims (10)

1. Method for the catalytic combustion of fuel (34), which has been metered into an exhaust section of an internal combustion engine by means of an injection valve (24), using an oxidation catalytic converter (18), having the following method steps:

   a) the metered-in fuel (34) is vaporized in an exhaust-gas flow by means of the injection valve (24),

   b₁) an end (32), which points towards the exhaust-gas flow in an exhaust pipe (12), of the injection valve (24) is heated continuously or periodically by means of a heating device (44), or

   b₂) an end (32), which is thermally decoupled from the injection valve (24), of the injection valve (24) is heated directly by the exhaust-gas flow.
2. Method according to Claim 1, characterized in that, in method step a), the vaporization of the metered-in fuel (34) takes place by means of a spray hole disc (32) which is held on that end of the injection valve (24) which points towards the exhaust-gas flow.
3. Method according to Claim 1, characterized in that, in method step b₁), that end (32) of the injection valve (24) which points towards the exhaust-gas flow is heated at regular intervals to a temperature level of approximately 600°C or, after additional fuel (34) is metered in, to a temperature level of approximately 400°C.
4. Method according to Claim 1, characterized in that, in method step b₂), the thermal decoupling of the end (32) of the injection valve (24) is provided by means of thermal insulation (50).
5. Device for the catalytic combustion of fuel (34) which has been metered into an exhaust section (10) of an internal combustion engine by means of an injection valve (24), with that end of the injection valve (24) which faces towards the exhaust-gas flow having arranged on it a spray hole disc (32) with a number of individual openings (48), characterized in that the spray hole disc (32) is assigned a heating device which comprises at least one heating wire (44), or the spray hole disc (32) is thermally decoupled from the valve body (26) of the injection valve (24) by means of thermal insulation (50).
6. Device according to Claim 5, characterized in that the at least one heating wire (44) runs on one of the end faces (38, 40) of the spray hole disc (32) .
7. Device according to Claim 6, characterized in that the at least one heating wire (44) is held within a cavity (36) of the injection valve (24) and is thermally insulated with respect to the valve body (26) of the injection valve (24).
8. Device according to Claim 6, characterized in that the at least one heating wire (44) runs in a meandering fashion on one of the end faces (38, 40) of the spray hole disc (32).
9. Device according to Claim 5, characterized in that the thermal insulation (50) is arranged in a cavity (36) above the spray hole disc (32) in the valve body (26).
10. Device according to Claims 6 or 9, characterized in that individual turns of the at least one heating wire (44) run with a pitch (56) which allows fuel to pass through individual openings (48) of the spray hole disc (32), or openings (52) of the thermal insulation (50) are aligned with individual openings (48) of the spray hole disc (32).

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