DE10358266B4 - Fuel injection system for internal combustion engines - Google Patents

Abstract

A fuel injection system for with Diesel fuel-powered internal combustion engines, in particular with heavy oil operated internal combustion engines, with a fuel injection injector, the one control unit with a control valve and with connections a high-pressure accumulator comprising a high-pressure accumulator as a pressure source, a low pressure side and a nozzle includes, the nozzle needle on their opening position subjected to high pressure, spring loaded in its closed position and in their closed position over a Holding force is held, wherein the electrically controlled control valve in a continuous connection of high pressure side and low pressure side is located, the passage connection on the high pressure side to a port too one on the back to the nozzle needle having lying control room and wherein when the internal combustion engine via the Control valve in its open position in closed position held nozzle needle the passage connection between the low pressure side and the high pressure side is released, characterized in that the fuel injection system one over running the high-pressure accumulator with fuel injection injector (1) Has heating circuit and that when the engine is switched off and in closed position held nozzle needle (6) enabled continuous connection switched as a long-term connection becomes part of the heating circuit of the fuel injection system ...

Description

The The invention relates to a fuel injection system for internal combustion engines according to the generic term of claim 1.

The Demands of fuel injection systems are due to the Increased requirements in the operating mode of modern internal combustion engines to the processing of the fuel and in connection with it required, very high working pressures up to the range of more than 2,000 steadily increased in size, especially at missions in large combustion engines, for example, for marine propulsion, also low quality fuels, such as heavy oils, for Use come. This results in additional requirements, be it is particularly stressed from the point of view of discharge Parts, such as the nozzle parts, or the improvement of working conditions for internal combustion engines, for example and especially under cold start conditions.

At one of the DE 44 45 586 A1 known, considered in the preamble of claim 1 fuel injection system for internal combustion engines are for reducing pressure in the high-pressure accumulator after switching off the engine control valves provided in the control of the fuel injectors optionally multiple, ie clocking, briefly activated to switch a short circuit from the control room connected to the high-pressure accumulator to the low pressure side , This in order to lower the pressure in the high-pressure accumulator to a value desired when the combustion engine is switched off, which is above a threshold value at which the nozzle needle of the nozzle of the fuel injector would open. Thus, with little effort, in particular without additional devices, a pressure reduction in the system can be achieved, can be made without risk at the repair and maintenance.

For heating the fuel when the internal combustion engine is switched off, it is in injection systems for particular operated with heavy fuel internal combustion engines from the DE 196 45 243 A1 known to connect in the inlet on the high-pressure accumulator parallel to the high-pressure pump, a heating circuit, which has a heating device downstream of a prefeed pump. The high-pressure pump, and parallel to this starting from the feed pump, the heater are connected to the one end of the elongated, formed as a common rail high-pressure accumulator and at the other end of the high-pressure accumulator, a spill valve is provided via the short-circuited in the open state of the high-pressure accumulator against the fuel tank is. The overflow valve, which is connected to the injection injector on the return side and kept pressurized closed, is accordingly opened when the internal combustion engine is switched off and releases the heating circuit passing through the high-pressure accumulator. Not integrated into the heating circuit of the injection injector, so that it is kept at the internal combustion engine at most on the part of the internal combustion engine directly emitted heat to temperature.

For temperature control of the fuel injectors in a common rail system supplied fuel, it is further from the DE 199 45 436 C1 known to provide integrated in the wall of the high-pressure accumulator Temperierleitungen, which are partly connected to the cooling circuit and partly to the outgoing of the fuel injectors return, so that, as needed, in the high-pressure accumulator each existing fuel can be cooled or heated.

Of the Invention is based on the object, in an aforementioned Fuel injection system for Internal combustion engines without substantial structural additional expense Heating the fuel, especially for the cold start operation, too enable.

Reached this is achieved with the features of claim 1.

in this connection the control valve of the control unit is switched off with the internal combustion engine and in the closed position located and held nozzle needle for switching a flow connection between the high-pressure and the low-pressure side, which serves as a temporary, long-term connection forms a heating circuit and for heating and / or rinsing purposes is usable.

So for example, in diesel fuel-powered internal combustion engines for motor vehicles preheating the fuel injection system in the context of heating the internal combustion engine in preparation of the cold start operation when using auxiliary heaters, or possibly only in conjunction with fuel heating.

A Such fuel heating plays in particular for the operation of large combustion engines with heavy oil a role in which the heavy oil to achieve sufficient flowability to temperatures of in the order of magnitude heated up to 200 ° is and where this heating optionally also when the internal combustion engine must be maintained and also the heating of the fuel injectors and the one leading to them Lines serves.

An enabling heating circuit is included an injection system constructed according to the invention without additional equipment, since the fuel injectors already have a connection to the low pressure side and a corresponding dimensioning of about the control valve to be set by throttling flow cross-section allows, with switched flow connection the predetermined for the closed position of the nozzle to increase the holding force pressurization maintain. The corresponding to the respective throttling travel of the control valve can be adjusted via a piezo actuator.

Further Details and features of the invention will become apparent from the dependent claims. Further the invention will be explained below with reference to an embodiment. It demonstrate:

1 1 is a schematic sectional view of a fuel injection injector for an internal combustion engine with a control unit, via which the pressure-dependent control of the nozzle needle of an injection nozzle takes place and which comprises a control valve, which is shown in its closed position,

2 the control valve according to 1 in a corresponding sectional view, but with the control valve open, and

3 a diagram in which the stroke of the actuator of the control valve, which is shown as a magnetic actuator, in relation to the pressure in a back of the nozzle needle provided control chamber is plotted over time.

The in the 1 and 2 schematized fuel injection injector shown in section 1 includes an injection nozzle 2 with a nozzle body 3 who has a valve seat 4 adjacent to the injection end 5 and in which a nozzle needle 6 Hubbeweglich is guided. The nozzle needle 6 is towards her valve seat 4 , ie in the closing direction, via a spring 7 loaded against the nozzle housing 8th is supported, in which a piston rod 9 coaxial with the nozzle needle 6 is guided. The piston rod 9 supports itself parallel to the spring 7 on the back against the nozzle needle 6 off and adjacent to the nozzle needle 6 one in the nozzle housing 8th lying control room 10 from.

The nozzle housing 8th is a high-pressure side connection 11 assigned, which communicates with a high-pressure source, not shown, for example, a high-pressure accumulator, in communication and from which via a channel 12 the injector 2 the high-pressure fuel to be injected is supplied, the channel 12 in the nozzle body 3 on a pressure room 13 opens out, in whose area the nozzle needle 6 a pressure shoulder 14 having. The pressure shoulder 14 lies in the connection between the slimmer, on the valve seat 14 expiring part of the nozzle needle 6 along which the fuel feed from the pressure chamber 13 to the valve seat 4 he follows. In the opposite direction closes to the pressure shoulder 14 an enlarged diameter part 16 the nozzle needles 6 on, against which the spring 7 and the piston rod 9 support, with the spring 7 in a room 17 of the nozzle housing 8th that lies over a canal 18 with a low-pressure side connection 19 communicates, so that on the room 17 due to leakage overflowing fuel can be discharged to the low pressure side.

Opposite to the injector 2 is the injection injector 1 a control unit 20 assigned to a control valve 21 comprises, as the controlling locking member an anchor 22 has, which is a solenoid 23 is assigned as a magnetic actuator. The solenoid 23 is over his main body 24 against the nozzle housing 8th firmly supported. The actuating magnet 23 associated electrical connection connections are with 25 designated.

The anchor 22 is coaxial with the nozzle needle in the embodiment 6 over the solenoid 23 liftable and in 1 in his not energizing the magnet 23 represented corresponding position in which it forms a locking member, via the one from the control room 10 to the anchor room 27 leading, through a channel 28 formed connection is shut off. On the canal 28 opens from the high pressure side of a throttle channel 29 that of the channel 12 goes out, and in the passage of the channel 28 between control room 10 and anchor room 27 is opening onto the anchor space 27 a throttle point 30 intended. To the anchor room 27 also closes opposite to the spring chamber 17 the connection to the return side connection 19 producing channel 18 on, so that when energizing the solenoid 23 and from the mouth of the canal 28 lifted anchor 22 , as in 2 shown, a short-circuit connection between high-pressure side connection 11 and low-pressure side connection 19 is made.

This compound is used while maintaining the closed position for the nozzle needle, ie with the nozzle closed and the internal combustion engine switched off to produce a long-term continuous connection between high pressure side and low pressure side for heating or rinsing purposes, the nozzle needle 6 held by a holding force in its closed position, resulting from the pressure in the control room 10 and the power of the spring 7 results and at least the force of the spring 7 equivalent.

Related to the basis of the 1 and 2 described conditions and the principle indicated in this structural design is in the diagram according to 3 the stroke s of the anchor 22 , Starting from its dropped position in Nichtbestromung of the solenoid 23 , as well as in the opposite direction the pressure in the control room 10 applied, starting from the high-pressure side feed pressure p in the locked position of the armature 22 with increasing opening of the cross connection to the return 19 over time t yields.

The curve 31 illustrates the stroke course of the anchor 22 with energization of the solenoid 23 , the curve train 32 the corresponding pressure drop in the control room 10 , where the curve 32 expiring indicates the maximum possible pressure drop, which in open flow connection due to the throttling in the high pressure side inlet to the control room 10 and in the throttled drain from the control room 10 on the anchor room 27 or to the low pressure side results.

Dash-dotted is worn away on the one hand 33 the hub, where the injector 2 by lifting the nozzle needle 6 from the seat 4 opens, and at 34 the corresponding thereto, compared to the inlet pressure lowered pressure in the control room 10 ,

The diagram according to 3 thus illustrates that, starting from one another, for example via the spring 7 given holding force of the pressure in the control room can be lowered without the nozzle 2 opens and that to this pressure reduction, a certain opening stroke of the armature 22 correlated. Thus, a short-circuit connection between high-pressure side connection 11 and low-pressure side connection 19 by lifting the anchor 22 be created without the nozzle 2 opens, and it follows through this short-circuit connection, a continuous connection in which, when the engine is switched off due to the pressure drop in the displacement of the internal combustion engine, a larger stroke s can be used as in 3 worn hub 33 in which the injection nozzle 2 by lifting the nozzle needle 6 from the seat 4 opens when running internal combustion engine.

3 also illustrates that, in connection with the use of actuators, which enable the setting of a respective stroke, for example current-dependent, such as piezocells, a further exploitation of the possible stroke or pressure ranges can be achieved.

Claims (3)

Fuel injection system for diesel fuel-powered internal combustion engines, in particular fuel oil-fueled internal combustion engines, comprising a fuel injection injector comprising a control unit with a control valve and with connections to a high-pressure accumulator as a pressure source comprehensive high pressure side, a low pressure side and a nozzle whose nozzle needle on their Opening position subjected to high pressure, spring-loaded to its closed position and held in its closed position by a holding force, wherein the electrically controlled control valve is in a continuous connection of the high pressure side and low pressure side, the flow connection high pressure side has a connection to a back to the nozzle needle control chamber and wherein when switched off Internal combustion engine via the control valve in its open position held in the closed position nozzle needle, the passage connection between the low pressure side and the high pressure page is released, characterized in that the fuel injection system via the high-pressure accumulator with fuel injection injector ( 1 ) has current heating circuit and that held at shutdown of the internal combustion engine and in the closed position the nozzle needle ( 6 ) is enabled as a long-term connection and is part of the heating circuit of the fuel injection system. Fuel injection system according to claim 1, characterized in that the control valve ( 21 ) is adjustable in its stroke. Fuel injection system according to claim 1 or 2, characterized in that as an actuator of the control valve ( 21 ) a piezo actuator is provided.