EP2526283B1 - Method for controlling the temperature of an injector of an injection system for injecting fuel into the combustion chamber of an internal combustion engine - Google Patents

Description

The present invention relates to a method for controlling the temperature of an injector of an injection for the injection of fuel into the combustion chamber of an internal combustion engine in which the fuel is conveyed from at least one prefeed pump from a tank to at least one high-pressure pump and the high-pressure fuel delivered by the high-pressure pump is supplied to the injector in which a high-pressure fuel reservoir is arranged inside the injector and the injector has an injection nozzle with a nozzle needle displaceable axially in a nozzle antechamber which dips into a control space which can be fed with high-pressure fuel, its pressure via a control valve opening or closing fuel for at least one supply or discharge channel is controlled and an apparatus for performing this method, such as in DE 3119050 shown.

Injectors of the type described above are often used in common rail injection systems. Injectors for common rail systems for injecting high viscosity fuels into the combustion chamber of internal combustion engines are known in various forms. In the case of heavy oil, heating up to 150 ° C is required to achieve the necessary injection viscosity.

Basically, an injector for a common rail injection system has different parts, which are usually held together by a nozzle retaining nut. The actual injector nozzle contains a nozzle needle, which is guided axially displaceably in the nozzle body of the injector nozzle and has a plurality of open spaces through which fuel can flow from the nozzle antechamber to the needle tip. The nozzle needle itself carries a collar on which a compression spring is supported, and immersed in a control chamber, which can be acted upon with fuel under pressure. To this control room can an inlet channel via a Inlet restrictor and a flow channel to be connected via an outlet throttle, wherein the respective pressure built up in the control chamber together with the force of the compression spring holds the nozzle needle in the closed position. The pressure in the control chamber can be controlled by a control valve, which is usually operated by an electromagnet. With appropriate wiring, an opening of the solenoid valve can cause a flow of fuel through a throttle, so that a decrease in the hydraulic holding force leads to the immersed into the control chamber end face of the nozzle needle for opening the nozzle needle. In this way, the fuel can pass through the injection openings in the combustion chamber of the engine in the sequence.

In addition to an outlet throttle, an inlet throttle is usually also provided, wherein the opening speed of the nozzle needle is determined by the flow difference between the inlet and outlet throttle. When the solenoid valve is closed, the drainage path of the fuel is blocked by the outlet throttle and re-established via the inlet throttle pressure in the control chamber and causes the closing of the nozzle needle.

From the WO 2009/023887 For example, a method and apparatus for injecting fuel into the combustion chamber of an internal combustion engine has become known, in which the injector for preheating fuel into the combustion chamber can be preheated with tempered fuel. This may be necessary if the internal combustion engine is operated, for example, with heavy oil, as is often the case with large-volume diesel engines. This warming of the injectors is necessary because the heavy oil in the injectors and in the lines would become thick due to the temperature drop at standstill of the engine and the injectors and lines would clog in the episode with the solidified heavy oil and re-commissioning of the engine is not readily possible would.

In the method according to the WO 2009/023887 Therefore, a subset of the fuel is taken between the prefeed pump and the high-pressure pump of the injection system, passed through a heat exchanger and fed as flushing through a separate channel in the injector to the control valve, so that the purge flows through the armature chamber of the control valve and thus maintains a certain elevated temperature.

The injectors, which according to the WO 2009/023887 are to be used, operate on the common rail principle, in which in a common high-pressure fuel storage, the common rail, fuel is kept under high pressure, the injectors are connected via high pressure lines to the common rail and after actuation of the Control valve in the respective injector to a lifting of the nozzle needle from the valve seat and thus comes to an injection into the combustion chamber, wherein the corresponding injection quantity is provided from the common rail. For very large engines, where the individual injectors may be mounted at a considerable distance from each other, the use of a common rail for the injectors does not make sense, since the lengths of the lines from the rail to the injectors would be very long due to the size of the engine, so There would be a large pressure drop during injection. In such engines, however, in which the movement of the nozzle needle for the opening and closing of the injectors is also controlled by the pressure at the valve seat of the nozzle needle and controllable by a control valve pressure in a control chamber on the injection nozzles facing away from the inner needle, it is therefore provided to arrange a high pressure fuel storage inside the injector. Such a design is referred to as a modular design, since each injector has its own high-pressure fuel storage and thus can be used as a stand-alone module. Under a high-pressure fuel storage is not an ordinary line to understand, but it is a high-pressure fuel storage to a pressure-resistant vessel with an inlet and a derivative whose Diameter compared to the high pressure lines is considerably increased, so that from the high-pressure fuel storage a certain amount of injection can be delivered without causing an immediate pressure drop, as would be the case if the injection amount would be taken from a common high-pressure line. In addition to the injection quantity falls in such pressure-controlled injectors nor to a control amount, which is discharged through the open control valve, which controls the pressure in the control chamber at the end remote from the injectors end of the control needle in the low pressure region.

If now, as in the prior art, a correspondingly tempered flushing is supplied only to the control valve for heating the injector during the stoppage of the internal combustion engine, the fuel volume in the relatively large-sized high-pressure fuel storage can not be maintained at a sufficiently high temperature to solidification of the fuel in the high-pressure fuel storage and in the other components of the injector to prevent with certainty.

The object of the present invention is thus to provide a method and a device with which or which succeeds to prevent solidification of the fuel in the injectors of an internal combustion engine with a modular design. To solve this problem, the method of the type mentioned is inventively further developed such that during the stoppage of the internal combustion engine between the prefeed pump and the high-pressure pump a subset of the fuel diverted as flushing, passed through a heat exchanger for heating the fuel and the high-pressure fuel storage is supplied, so this is flowed through by the flushing volume. At standstill of the engine, the high-pressure pumps rest, and the pressure in the system falls below the prefeed pressure of the prefeed pump, so that the pressure of the prefeed pump is sufficient to pump fuel into the high-pressure fuel storage. The fuel provided for this purpose is inventively taken between the prefeed pump and the high-pressure pump, heated in a heat exchanger and fed directly to the high-pressure fuel storage. The high-pressure fuel accumulator constitutes a relatively large volume inside the injector, so that the entire injector is sufficiently heated when the high-pressure fuel accumulator is kept at a corresponding temperature.

Since for large diesel engines, which are operated with heavy oil, naturally also result in relatively long conduction paths, the invention is advantageously developed to the effect that the fuel is conveyed by the prefeed pump to an overpressure of 5-10, so that pressure losses due to the cable lengths with certainty be overcome and a reliable flushing and thus temperature control of all injectors is ensured.

After introducing the tempered fuel into the high-pressure fuel storage, it must be able to flow out of the injector. In this case, the procedure is preferably such that the flushing quantity is discharged from the injector via connections for high-pressure fuel lines of the injection. The high-pressure fuel lines, which, as already mentioned, are not under high pressure when the internal combustion engine is at rest, are optionally connected to the low-pressure region of the injection system in internal combustion engines with a modular structure, with the interposition of a manifold, so that the flushing quantities can be removed via these lines.

In this case, the procedure is preferably such that the flushing quantity is returned to the tank or to the prefeed pump, so that here too a corresponding temperature level can be maintained in order to prevent clogging of lines in this area.

The temperature of the internal combustion engine decreases continuously at standstill, so that the amount of heat that must be introduced to maintain the fluidity of the fuel in the injector increases with the downtime. Up to a certain limit temperature, there will be no need to supply a purge amount, since the engine is already hot enough to keep the fuel liquid, which falls below this limit temperature, a heating is necessary and the diverted flushing amount must be increased with the duration compensate for the ever lower temperatures of the internal combustion engine in the injector. Advantageously, the method according to the invention is therefore further developed such that the purge quantity diverted between the prefeed pump and the high-pressure pump is regulated.

According to a preferred embodiment of the present invention, it is provided that a further flushing quantity is supplied directly to the control valve of the injector, so that in addition to the high-pressure fuel storage, which is usually in communication with the nozzle front chamber and together with this forms the high-pressure side of the injector, the can be maintained by the control valve and the associated outflows formed by the control valve low pressure side of the injector by a correspondingly controlled flushing at an elevated temperature. This may be necessary in particular for injectors of particularly large size, in order to be able to keep the entire injector sufficiently warm.

When the internal combustion engine is put back into operation after a standstill phase and the high-pressure pump starts up again for this purpose, the pressure in the high-pressure fuel reservoir increases considerably, so that a pressure loss would occur via the branch line for the flushing quantity. Is an advantage the method according to the invention therefore further developed such that the supply line for the flushing quantity to the high-pressure fuel storage is closed by a check valve during operation of the internal combustion engine.

The device for injecting fuel into the combustion chamber of an internal combustion engine for carrying out the method according to the invention comprises at least one prefeed pump for conveying fuel from a tank, at least one high-pressure pump and at least one injector, wherein the fuel delivered by the prefeed pump of the high-pressure pump and of the high-pressure pump funded high-pressure fuel is supplied to the injector, inside the injector, a high-pressure fuel storage is arranged and the injector has an injector with an axially displaceable nozzle in an antechamber nozzle, which dips into a high pressure fuel feedable control chamber whose pressure via at least one inlet or outlet channel for Controlled fuel opening or closing control valve. Such injections are referred to as modular common rail systems, since the individual injectors each have their own high-pressure fuel storage, which assumes the function of the rail and the injection otherwise proceeds as in conventional injectors in common-rail engines. As already stated, in the nozzle antechamber, in which an axially displaceable nozzle needle closes the injection nozzles, the pressure of the high-pressure fuel accumulator is constantly present, whereby a control chamber which is likewise under this pressure is arranged at the end of the nozzle needle facing away from the injection nozzles, via the actuation of a control valve be temporarily reduced. When the control pressure in the control room drops, the opening forces on the nozzle needle are greater than the closing forces, so that the injection holes are released. In such a device is now provided according to the invention, that between the at least one prefeed pump and the at least one high pressure pump is connected to a branch line for a flushing amount, wherein the branch line passes through a heat exchanger and opens into the high-pressure fuel storage of the injector, so that it is traversed by the flushing. By these measures, it is possible to keep the high-pressure fuel storage at a sufficiently high temperature to prevent solidification of the fuel.

In order to overcome the pressure losses which occur in the relatively long lines in large engines, the device according to the invention is developed to advantage in that the prefeed pump is designed to deliver the fuel to 5-10 bar.

A particularly preferred form of discharging the supplied flushing quantity from the injector can be achieved by connecting a T-piece to the injector, which connects high-pressure lines to the high-pressure fuel reservoir or the nozzle antechamber of a first injector and to the T-piece of another injector, so that the discharge of the flushing amount via the high-pressure lines for the high-pressure fuel, which is required during operation of the internal combustion engine, can take place.

In order to heat the prefeed pump with the residual heat of the flushing amount, the device according to the present invention is preferably further developed such that low-pressure lines are arranged for the return of the flushing amount to the prefeed pump.

In order to allow independent of the pump speed of the prefeed pump control of the flushing amount, the device is preferably further developed such that a throttle and / or a Control valve for controlling the flushing amount is arranged in the branch line.

When the injector is made particularly large, it may be advantageous not only to temper the high pressure accumulator with a purge amount, but also to heat the low pressure side of the injector. For this purpose, the device according to the invention can be further developed in such a way that a connection directly connected to the control valve of the injector for a further flushing quantity is arranged on the injector.

In order to prevent a pressure loss through the branch line during the operation of the internal combustion engine, in which the pressure in the high-pressure fuel storage increases sharply, the device according to the invention can be developed with advantage in that in the branch line for the flushing quantity, a check valve is arranged which against Supply direction for the flushing closes.

The invention will be explained in more detail below with reference to an exemplary embodiment shown schematically in the drawing. In this shows Fig. 1 the schematic structure of an injection according to the invention for carrying out the method according to the invention and Fig. 2 a detailed schematic representation of an injector, as used in the present invention is used.

In Fig. 1 1 denotes a fuel tank, from which fuel is conveyed to a further prefeed pump 2 via a prefeed pump 2 and a filter 3. During normal operation of the engine, the fuel is fed via a further filter 3 to the high-pressure pumps 4, which convey the fuel into a collector 5. With 6 low pressure lines are referred to which the fuel leakage, in the high-pressure pumping arises, in the low pressure range of the injection lead back. The high-pressure fuel is supplied via the high-pressure lines 7 and the T-pieces 8 to the injectors 9 shown schematically, the high-pressure fuel reservoirs of the injectors 9 being designated 14.

If at standstill of the engine, the temperature drops and the heavy oil threatens to solidify in the lines and in the injectors, the fuel is diverted after the second feed pump 2 and the heat exchanger 10 before the high pressure pumps via a branch line 11 and the high-pressure accumulators 14 of the individual injectors 9 supplied. The outflow of the flushing amount via the high pressure lines 7, which open into a common manifold 15, wherein the high pressure region is separated by the flush valve 12 from the low pressure region. Alternatively or additionally, via the lines 11 and the tees 8, a flushing quantity can also be supplied to the low-pressure region of the injectors 9 formed by the control valve and the associated outlets, the corresponding outflow in the sequence via the low-pressure lines 6 into the low-pressure region, for example into the Manifold 15 of the injection system opens.

If the prefeed pumps 4 start up again during operation of the engine, the pressure in the high-pressure accumulators 14 rises sharply, so that via the lines 11 a backflow takes place and thus a pressure loss would occur. To prevent this, a schematically illustrated check valve 13 is arranged in the region of the mouth of the branch lines 11 in the high-pressure accumulator of the injectors, which closes in the direction of arrow 16 to prevent a backflow of high-pressure fuel through the branch line 11. A similar valve may also be arranged in the T-piece 8.

The actual injector nozzle contains, as in Fig. 2 it can be seen, a nozzle needle 16, which is axially displaceably guided in the nozzle body 15 of the injector 9 and has a plurality of free surfaces 17 through which fuel from the nozzle Vorraum 18 can flow to the needle tip. The nozzle needle 16 itself carries a collar 19, on which a compression spring 20 is supported, and immersed in a control chamber 21, which can be acted upon with fuel under pressure. To this control chamber 21, an inlet channel 22 via an inlet throttle 23 and a drain channel 24 via a discharge throttle 25 are connected, wherein the respective pressure built up in the control chamber 21 together with the force of the compression spring 20 holds the nozzle needle 16 in the closed position. The pressure in the control chamber 21 is controlled by a control or solenoid valve 26 which is actuated by an electromagnet 27. An opening of the solenoid valve 26 causes a drainage of the fuel via the outlet throttle 25, so that a decrease in the hydraulic holding force leads to the dipping into the control chamber 21 end face 28 of the nozzle needle 16 to open the nozzle needle 16. In this way, the fuel passes through the injection openings 29 into the combustion chamber of the engine.

In addition to a discharge throttle 25 and an inlet throttle 23 is provided, wherein the opening speed of the nozzle needle 16 is determined by the flow difference between the inlet and outlet throttle. When the solenoid valve 26 is closed, the drainage path of the fuel is blocked by the outlet throttle 25 and re-established pressure in the control chamber 21 via the inlet throttle 23 and causes the closing of the nozzle needle 16. The remaining reference numerals were made Fig. 1 accepted.

Claims (14)

1. Method for adjusting to a moderate temperature an injector of an injection for injecting fuel into the combustion chamber of an internal combustion engine, in which the fuel is delivered from a tank to at least one high-pressure pump by at least one predelivery pump, and the high-pressure fuel delivered by the high-pressure pump is supplied to the injector, wherein a high-pressure fuel accumulator is arranged within the injector, and the injector has an injection nozzle with a nozzle needle which is displaceable axially in a nozzle prechamber and which protrudes into a control chamber which can be fed with highly pressurized fuel, the pressure of which control chamber is controlled by means of a control valve which opens or closes at least one inflow or outflow duct for fuel, characterized in that, while the internal combustion engine is at a standstill, a partial amount of the fuel, as a flushing amount, is branched off between the predelivery pump and the high-pressure pump, is conducted through a heat exchanger for the purpose of heating the fuel, and is supplied to the high-pressure fuel accumulator, such that the flushing amount flows through said high-pressure fuel accumulator.
2. Method according to Claim 1, characterized in that the fuel is delivered by the predelivery pump at a positive pressure of 5-10 bar.
3. Method according to Claim 1 or 2, characterized in that the flushing amount is discharged from the injector via ports for high-pressure fuel lines of the injection.
4. Method according to one of Claims 1, 2 or 3, characterized in that the flushing amount is returned to the tank or to the predelivery pump.
5. Method according to one of Claims 1 to 4, characterized in that the flushing amount branched off between the predelivery pump and the high-pressure pump is regulated.
6. Method according to one of Claims 1 to 5, characterized in that a further flushing amount is supplied directly to the control valve of the injector.
7. Method according to one of Claims 1 to 6, characterized in that the feed line for the flushing amount to the high-pressure fuel accumulator is closed by a check valve during the operation of the internal combustion engine.
8. Device for injecting fuel into the combustion chamber of an internal combustion engine, in particular for carrying out the method according to one of Claims 1 to 7, comprising at least one predelivery pump (3) for delivering fuel out of a tank (1), at least one high-pressure pump (4), and at least one injector (9), wherein the fuel delivered by the predelivery pump (3) is supplied to the high-pressure pump (4) and the high-pressure fuel delivered by the high-pressure pump (4) is supplied to the injector (9), a high-pressure fuel accumulator (14) is arranged in the interior of the injector (9), and the injector (9) has an injection nozzle with a nozzle needle (16) which is displaceable axially in a nozzle prechamber and which protrudes into a control chamber (21) which can be fed with highly pressurized fuel, the pressure of which control chamber is controlled by means of a control valve (26) which opens or closes at least one inflow or outflow duct (22, 24) for fuel, characterized in that a branch line (11) for a flushing amount is connected between the at least one predelivery pump (3) and the at least one high-pressure pump (4), wherein the branch line (11) leads through a heat exchanger (10) and issues into the high-pressure fuel accumulator (14) of the injector (9), such that the flushing amount flows through said high-pressure fuel accumulator.
9. Device according to Claim 8, characterized in that the predelivery pump (3) is designed for delivering the fuel at 5-10 bar.
10. Device according to Claim 8 or 9, characterized in that there is connected to the injector (9) a T-piece (8) which connects high-pressure lines (7) to the high-pressure fuel accumulator (14) and to the nozzle prechamber (21) of a first injector (9) and to the T-piece (8) of a further injector (9).
11. Device according to one of Claims 8, 9 or 10, characterized in that low-pressure lines (15, 6) are provided for conducting the flushing amount back to the predelivery pump (3).
12. Device according to one of Claims 8 to 11, characterized in that a throttle and/or a regulating valve for regulating the flushing amount is arranged in the branch line (11).
13. Device according to one of Claims 8 to 12, characterized in that, on the injector (9), there is arranged a port, which is connected directly to the control valve (26) of the injector (9), for a further flushing amount.
14. Device according to one of Claims 8 to 13, characterized in that, in the branch line (11) for the flushing amount, there is arranged a check valve (13) which closes counter to the feed direction for the flushing amount.

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