EP0962649A1 - Fuel injection apparatus - Google Patents

Abstract

The arrangement has a reciprocating piston pump (5) that displaces fuel with a reciprocating piston (8). The delivery stroke of the piston is limited by a stop element and a dispenser determines the quantity of fuel to be injected by displacing the piston wrt. the stop element by a defined, variable storage stroke corresp. to the delivery stroke. The dispenser has an electromagnet. A storage piston forming the armature of the electromagnet is subjected to force by the electromagnet to perform the storage stroke.

Description

The invention relates to a fuel injection device for Injecting fuel into a combustion chamber by means of a Injector.

Such fuel injection devices can be used as a reciprocating pump be formed in a connecting line between the fuel injector and the injection pump fuel under pressure. From a predetermined Flow pressure opens the injector and sprays fuel into the combustion chamber. If the piston pump falls generated pressure below the forward pressure, so closes the injector and ends the injection process.

The one consisting of a reciprocating piston pump and an injection nozzle System is referred to as a unit injector.

Known injection devices (e.g. DD-PS 213 472, DE 42 06 817 C2 and DE 195 15 782 A1) refer to the pressure build-up a high precision. Nevertheless, it is with such pump-nozzle systems not possible over a longer period of use, from e.g. several years, fuel in precisely metered amounts of fuel to inject. These changes in quantity are based e.g. to a passage pressure that changes with time of the injectors. The injectors that are directly connected to the The combustion chamber is adjacent to the pressures generated in the combustion chamber and exposed to thermal loads. As a consequence, that the injectors age, i.e. that there is one in the injector located, the passage pressure controlling spring puts. In addition, the stroke of an injection nozzle can become deformed of the sealing seat and / or the needle change over time. In addition, coking in the nozzle changes their Passage cross section. The injectors must be used because of the tight space Space be very compact, so that long-term stable Constructions become complex.

With conventional unit injector systems this problem can only be solved can be remedied by regularly replacing the injection nozzle.

The advantages of a fuel injector based a reciprocating pump for a unit injector are in the much smaller design, the much simpler design and in that the injection energy only when needed to the extent necessary.

The invention is therefore based on the object of a fuel injection device for creating a unit injector with a long-term stable metering of the fuel quantity is possible.

The task is performed using a fuel injector solved the features of claim 1. Advantageous configurations are specified in the subclaims.

The fuel injection device according to the invention has a Pump device and a metering device. The pumping device is designed as a reciprocating pump, and can be in one preferred embodiment, a two-part from an actuating piston and an accumulator piston existing exhibit. The accumulator piston is the actuating piston in the conveying direction upstream. There is a stop provided limits the path of the accumulator piston in the conveying direction.

The accumulator piston is between two injections of the metering device by a predetermined variable storage stroke moved against the direction of conveyance, one predetermined amount of fuel is stored. In this withdrawn Position, the accumulator piston is held until until the actuating piston moves the accumulator piston in the conveying direction presses. The accumulator piston is activated by the actuating piston pushed as far as it will go, with the accumulator piston holding the intake fuel displaced. This will make a pre exactly defined conveying stroke and exactly that in advance sucked or stored by the accumulator stroke of the accumulator piston Amount of fuel sprayed.

The Krattstoffein injection device according to the invention can with their metering device the amount of fuel to be injected set exactly. The amount of fuel to be injected is alone due to the precisely definable stroke of the accumulator piston and not due to the passage pressure, which cannot be precisely adjusted in the long run the injector. With the invention Injection device is thus a long-term stable, exact Dosage of fuel quantity guaranteed.

Fig. 1

ein Pumpe-Düse-System mit einem ersten Ausführungsbeispiel der erfindungsgemäßen Kraftstoffeinspritzvorrichtung im Querschnitt,

Fig. 2

ein Pumpe-Düse-System mit einem zweiten Ausführungsbeispiel der erfindungsgemäßen Kraftstoffeinspritzvorrichtung im Querschnitt,

Fig. 3

ein Pumpe-Düse-System mit einem dritten Ausführungsbeispiel der erfindungsgemäßen Kraftstoffeinspritzvorrichtung im Querschnitt, bei der die Dosiereinrichtung und die Pumpeinrichtung in einer Linie angeordnet sind,

Fig. 4

ein Pumpe-Düse-System mit einem vierten Ausführungsbeispiel der erfindungsgemäßen Kraftstoffeinspritzvorrichtung im Querschnitt, bei der die Dosiereinrichtung und die Pumpeinrichtung in einer Linie angeordnet sind, und eine Verzögerungseinrichtung vorgesehen ist,

Fig. 5

ein Pumpe-Düse-System mit einem fünften Ausführungsbeispiel der erfindungsgemäßen Kraftstoffeinspritzvorrichtung im Querschnitt, bei der die Dosiereinrichtung und die Pumpeinrichtung in einer Linie angeordnet sind,

Fig. 6

ein Pumpe-Düse-System mit einem sechsten Ausführungsbeispiel der erfindungsgemäßen Kraftstoffeinspritzvorrichtung im Querschnitt, mit einer pneumatisch betätigten Pumpeinrichtung,

Fig. 7

ein Pumpe-Düse-System mit einem siebten Ausführungsbeispiel der erfindungsgemäßen Kraftstoffeinspritzvorrichtung im Querschnitt, bei der die Dosiereinrichtung und die Pumpeinrichtung in einer Linie angeordnet sind, wobei die Pumpeinrichtung pneumatisch betätigt wird,

Fig. 8a

eine Dosiereinrichtung mit sehr kleinem Schadraum im Querschnitt,

Fig. 8b

eine bei der in Fig. 7a gezeigten Dosiereinrichtung verwendete Ventilscheibe,

Fig. 9

ein Diagramm, das den Druckverlauf in einem Brennraum zeigt und in welchem die Bereiche gekennzeichnet sind, an welchen unter Druck stehendes Gas zur Betätigung einer erfindungsgemäßen pneumatischen Einspritzvorrichtung abgezogen werden kann.

The invention is described in more detail below using the drawings as an example. They show schematically:

Fig. 1

a pump-nozzle system with a first embodiment of the fuel injection device according to the invention in cross section,

Fig. 2

a pump-nozzle system with a second embodiment of the fuel injection device according to the invention in cross section,

Fig. 3

a pump-nozzle system with a third embodiment of the fuel injection device according to the invention in cross section, in which the metering device and the pump device are arranged in a line,

Fig. 4

a pump-nozzle system with a fourth embodiment of the fuel injection device according to the invention in cross section, in which the metering device and the pump device are arranged in a line, and a delay device is provided,

Fig. 5

a pump-nozzle system with a fifth embodiment of the fuel injection device according to the invention in cross section, in which the metering device and the pump device are arranged in a line,

Fig. 6

a pump-nozzle system with a sixth embodiment of the fuel injection device according to the invention in cross section, with a pneumatically operated pump device,

Fig. 7

a pump-nozzle system with a seventh embodiment of the fuel injection device according to the invention in cross section, in which the metering device and the pump device are arranged in a line, the pump device being actuated pneumatically,

Fig. 8a

a dosing device with a very small cross-sectional area,

Fig. 8b

a valve disk used in the metering device shown in FIG. 7a,

Fig. 9

a diagram showing the pressure curve in a combustion chamber and in which the areas are marked, at which pressurized gas can be withdrawn for actuating a pneumatic injection device according to the invention.

In Fig. 1 is a pump-nozzle system with a first schematically Embodiment of a fuel injection device according to the invention 1 shown.

The fuel injection device 1 is via a high pressure line 2 connected to an injection nozzle 3. The injector 3 is on a combustion chamber (not shown) of an internal combustion engine for injecting fuel into the combustion chamber arranged.

The fuel injection device 1 has a pump device 5 and a metering device 6. The pump device 5 is an electromagnetically operated reciprocating pump with a two-part from an actuating piston 8 and a storage piston 9 existing pistons.

The actuating piston 8 is an armature of an electromagnet 11 and is stored in a cylindrical armature space 12, which is one first tube section 13 of a housing body 14 limited becomes. On the outside sits on the first pipe section 13 tubular electromagnet 11.

The pipe section 13 and the electromagnet 11 are of one Pump housing 15 includes that also in the direction of delivery 16th rear end of the pipe section 13 with a cover section 17 completes. Sitting on the inside of the cover section 17 one from e.g. an elastomer material, thermosetting material or brass existing tubular guide bushing 19. Die Guide bushing 19 also serves as a stop for the actuating piston 8th.

The actuating piston 8 has a tubular, on the inner surface of the first pipe section 13 adjacent anchor body 22 and one arranged in the anchor body 22 and with it firmly connected anchor guide tube 23. The anchor guide tube 23 closes flush with the anchor body in the conveying direction 16 22 and is on the rear with respect to the conveying direction 16 Side of the anchor body 22 on the anchor body 22 in front. With this protruding section is the armature guide tube 23 in the guide bush 19 stored.

The actuating piston shown in Fig. 1 is made in two parts the armature body 22 and the armature guide tube 23 are formed. It can equally well be in one piece and it is it is also possible to run one only through the pipe section 13 To provide anchors without a guide tube.

Longitudinal grooves are made in the lateral surface of the armature body 22 and the anchor guide tube is hollow, for example, if the anchor space is flooded with fuel so that when moving of the actuating piston 8 in the conveying direction 16 or counter a fuel located in the armature space to the conveying direction 16 can flow past the actuating piston 8 and its movement does not inhibit. However, the armature space 12 is preferably opposite the fuel-carrying areas are sealed and free of fuel. In such an embodiment there are none Provide longitudinal grooves on the anchor body.

Forms at the front end of the armature space 12 in the conveying direction 16 the housing body 14 one with respect to the inner diameter of the Anchor space 12 thinner delimited by an annular web 24 Passage in which a stop bush 25 is inserted. The Stop bushing 25 projects from the ring web 24 into the armature space 12 before and forms with their opposite to the conveying direction 16 Front edge a stop edge 26.

The storage piston is slidably supported in the stop bushing 25 9. The accumulator piston 9 points at its opposite to the conveying direction 16 end showing a stop edge 26 of the Stop disc 25 overlapping stop disc 27. At the The edge area of the stop disc 27 is a thin one in the armature space 12 projecting annular web 28 is formed.

The diameter of the stop disc 27 is smaller than the inside diameter of the armature space 12. An armature spring 29 is between the ring web 24 of the housing body 14 and in the conveying direction 16 facing end face of the actuating piston 8 used. A storage piston spring 30 is between the stop disc 27 and the end face pointing in the conveying direction 16 of the actuating piston 8 used. On this face a recess 31 is made in which the Accumulator piston spring 30 sits and in which the accumulator piston spring 30 when the same is compressed.

In the housing body 14 is one of the pump device 5 in the conveying direction 16 upstream pressure chamber 32 formed. The Pressure chamber 32 has a connection opening 33 for connection the high pressure line 2 leading to the injection nozzle 3 as well an opening 34 leading to the metering device 6. In the Port 33 is a parking pressure valve 35 is used only from a certain passage pressure within the pressure chamber 32 releases the connection opening. In the to the dosing device 6 leading opening sits an overflow valve 36 that a in Check valve opening direction to the pressure chamber 32 is. The pressure chamber 32 extends into the interior of FIG Stop bushing 25 so that it can the inner wall of the stop bush 25 and that in the conveying direction 16 front end face of the storage piston 9 limited is.

The metering device 6 is on the same housing body 14 as the pump device 5 is formed and has a second one Pipe section 38 which is transverse to the conveying direction 16 of the Pump device 5, namely in the injection direction 37, extends. A metering piston is slidably supported in the second tube section 38 40, which consists of a tubular anchor body 41 and a guide pin protruding on its two faces 42 exists. The guide pin 42 is supported with its two ends each in a fixed position in the second pipe section used guide bushing 44, 45.

At the front of the metering device in the injection direction 6, an inwardly projecting ring web 47 is formed. Between the ring web 47 and the front face of the anchor body 41, a metering spring 48 is used, which the metering piston 40 towards the rear guide bush 45 presses.

On the outside of the second pipe section 38 is for actuating the Dosing piston 40 encompasses the second pipe section 38 Electromagnet 49 arranged. The electromagnet 49 and the second pipe sections 38 are from a metering device housing 50 includes that also the rear in the injection direction 37 End of the metering device 6 with a cover section 51 completes.

In the area between the overflow valve 36 and the stroke area of the metering piston 40 opens into the second pipe section 38 a fuel supply line 52. At the mouth of the fuel supply line 52 to the second pipe section 38 is a Check valve 53 arranged that a backflow into the Fuel supply line 52 prevented.

In this embodiment, the first pipe section is 13 and the second pipe section 38 of the housing body 14 in the right Angle to each other. This arrangement is compact and therefore useful, but it is not necessary. The two Pipe sections can be at any other angle to each other be arranged; e.g. it is also possible that the Pump device 5 and the metering device 6 diametrically opposite are arranged to the pressure chamber 32.

Below is the operation of the first embodiment the fuel injection device according to the invention explained.

In the state of the fuel injection device shown in FIG. 1 is the storage piston 9 by the the accumulator piston spring 30 exerted pressure with its stop disk 27 abutting on the stop edge 26 of the stop bush 25, i.e. the accumulator piston 9 is completely in the stop bush 24 inserted. Is at the same time the dosing piston 40 in its initial state in which it is the metering spring 48 away from the pressure chamber 32 against the rear Guide bush 45 is pressed. This initial state takes the fuel injector after a completed one Injection process.

To prepare another injection process, a Dosing process carried out by the dosing piston 40 of the dosing device 6 is actuated by the electromagnet 49, so that he delivers fuel into the pressure chamber 32. The delivery pressure is less than the passage pressure of the parking pressure valve 35 so that the fuel is not in the injector 3 leading high pressure line 2 can drain.

The fuel fed into the pressure chamber 32 pushes the Accumulator piston 9 by a precisely definable, variable accumulator stroke in the armature chamber 12 of the pump device 5 against the Effect of the accumulator piston spring 30. The overflow valve 36 prevents the fuel from flowing back into the metering device 6. By the located in the pressure chamber 32 Fuel and the storage piston spring acting on the delivery piston 9 30 is the end of the dosing process Delivery piston 9 held in position so that a predetermined Amount of fuel stored in the pressure chamber 32 is.

After the dosing process, the magnet 49 of the dosing device 6 switched off and the dosing piston 40 by the dosing spring 48 pressed into its initial state, whereby Fuel is drawn from the fuel supply line 52.

For injecting the fuel stored in the pressure chamber 32 the actuating piston 8 of the electromagnet 11 Pump device accelerated in the conveying direction 16. This works the actuating piston alone against the relatively soft trained springs 29, 30 so that it strikes until the accumulator piston 9 stores kinetic energy. The kinetic Energy is transferred to the storage piston 9 and this is pressed into the stop bush 25 by the actuating piston 8. The movement of the accumulator piston 9 is caused by the impact its stop disc 27 on the stop edge 26 of the Stop bush 25 stopped.

The storage piston 9 displaces during its movement in the conveying direction 16 located in the stop bush 25 in the area of his Fuel stroke located fuel.

The fuel is thus, by the parking pressure valve 35, the High pressure line 2 and the injector 3 in the combustion chamber promoted an internal combustion engine.

Since the delivery stroke of the accumulator piston 9 corresponds to the accumulator stroke, which is precisely preset by means of the metering device 6 is the amount of fuel to be displaced by the delivery piston 9 or the amount of fuel injected into the combustion chamber exactly defined.

In the fuel injection device according to the invention therefore not the amount of fuel to be injected by one Passage pressure of an injection nozzle, but by means of adjustable storage stroke of the metering device. Of the The stroke of the accumulator piston 9 is not subject to any signs of aging, so that long-term stable metering of the injection quantity is guaranteed.

By providing a metering device 6 according to the invention and a pump device 5 is the metering of the amount of fuel decoupled from the generation of the fuel injection pressure.

Since the storage piston 9 after the dosing process at a larger amount of fuel to be injected further into the armature space 12 than with a smaller amount of fuel to be injected protrudes, the acceleration path of the actuating piston 8 at larger amounts of fuel to be injected than at smaller amounts of fuel. With larger amounts of fuel the length of the acceleration path is less than be smaller Amounts of fuel, resulting in that stored by the actuating piston kinetic energy with larger amounts of fuel to be injected is lower than with smaller amounts of fuel. As a result, smaller amounts of fuel with higher Pressure can be injected as larger amounts of fuel. Hereby small amounts of fuel are atomized very finely and braked in the combustion chamber directly in the area behind the nozzle. Larger amounts of fuel injected at lower pressure however, form larger drops that continue into the Penetrate the combustion chamber. This effect is for the ignition behavior the internal combustion engine is very advantageous since the smaller ones Amounts of fuel braked near the injector 3 be and by an appropriate arrangement of the spark plug can be ignited exactly, whereas larger amounts of fuel are evenly distributed in the combustion chamber and accordingly burn well. This ideal distribution for the burning process of the fuel with which smaller amounts of fuel are enriched in the area of the spark plug and larger amounts of fuel are distributed more evenly in the combustion chamber than Called charge stratification.

In Fig. 2 is a second embodiment of the invention Fuel injector shown. It owns in essentially the same structure as the first embodiment, which is why the same parts have the same reference numerals and a detailed description are omitted can be.

The second embodiment differs from the first Embodiment in that the actuating piston 8 immediately abuts the accumulator piston 9 and in the pump device 5 only a single spring 55 between the actuating piston 8 and the rear guide bushing in the conveying direction 16 19 is arranged. The spring 55 acts on the actuating piston 8 together with the accumulator piston 9 in the conveying direction 16, that is towards the pressure chamber 32.

The actuating piston 8 and the accumulator piston 9 lead together both the storage stroke and the delivery stroke. At this embodiment, the actuating piston 8 and Accumulator piston 9 can also be formed in one piece.

A third embodiment of the fuel injection device according to the invention is shown in Fig. 3.

In this fuel injection device are the pump device 5 and the metering device 6 arranged along a line. This fuel injection device has a essential tubular housing body 14, which consists of a first Pipe section 13 and a second pipe section 38, which are arranged coaxially with each other, with between the first and second pipe sections 13, 38 a cross plate 57 is formed. In the area of the first pipe section is the pump device 5 and in the region of the second pipe section 38 is adjacent to the cross plate 57, the metering device 6 and in the conveying direction 16 subsequently the pressure chamber 32 trained.

The pump device 5 has a bearing in an armature chamber 12 Actuating piston 8, which consists of a tubular armature body 22 and an anchor body 22 in the longitudinal direction penetrating anchor pin 23, the on both end faces of the Anchor body 22 protrudes. The anchor space 12 is from first tube section 13 of the housing body 14 limited. On the outer surface of the first tube section 13 is an electromagnet 11. The pipe section 13 and the electromagnet 11 are comprised of a pump housing 15, which also in the direction of delivery 16 rear end of the pipe section 13 with a Cover section 17 completes.

At the front end of the pipe section 13 in the conveying direction 16 is formed in one piece with the first pipe section 13 Cross plate 57 arranged, in the middle of which a passage is introduced is. A guide bush 59 sits in this passage. Another is located at the rear end of the anchor space 12 Guide bushing 19. In the two guide bushings 19, 59 the anchor pin 23 of the actuating piston 8 is displaceable stored. Between those pointing forward in the direction of conveyance 16 End face of the anchor body 22 and the cross plate 57 is an armature spring 29 is used, which the actuating piston 8th acted against the conveying direction 16 with a force.

The metering device arranged on the second pipe section 38 6 has a metering piston 40 which consists of a tubular Anchor body 41 and one protruding on its two end faces Guide pin 42 is made. The guide pin 42 is supported with its two ends each inserted in the cross plate Guide bush 59 or in a stop bush 25. The stop bush 25 is used in one pass, the from an inwardly projecting on the second pipe section 38 Ring web 24 is limited.

Between the armature body 41 of the metering piston 40 and the in the guide plate 59 inserted into the transverse plate 57 is a metering spring 48 used, the dosing piston 40 with a Force applied in the conveying direction 16 and against the stop bush 25 presses.

In the area of the metering device 6 is on the outside on the second Pipe section 38 another magnet 49 for actuating the metering piston 40 arranged by a cylindrical metering device housing 50 is enclosed.

The one upstream of the metering device 6 in the conveying direction 16 Pressure chamber 32 is laterally delimited by the second pipe section 38. This pipe section 38 delimiting the pressure chamber 32 is at the front in the conveying direction 16 with a connection opening 33 for connecting the high pressure line leading to the injector 3 2 provided. There is a parking pressure valve in the connection opening 35 used, that only from a certain passage pressure opens within the pressure chamber 32 and the connection to Injector 3 releases.

In the area of the stop bush 25 opens between the parking pressure valve 35 and the metering piston 40 a fuel supply 54 into the pressure chamber 32. In the fuel supply 54 a check valve 53 is arranged which a backflow in a fuel supply line connected to the fuel supply 54 52 prevented.

The operation of this third embodiment of the invention is similar to that of the first embodiment and is explained below.

During the dosing process, the magnet 49 of the dosing device 6 energized so that the metering piston 40th executes a storage stroke counter to the conveying direction 16 and Sucks fuel from the fuel supply line 52. The one in Area of the stop bush 25 fuel can be because of the standing pressure valve 35 and the check valve 52 does not escape and prevents the metering piston from moving back 40. At the end of the dosing process, the magnet 44 is de-energized switched, the metering piston 40 in the position of the Storage stroke remains because on the one hand its return movement is locked and on the other hand, the metering spring 48 the metering piston 40 acted upon in the conveying direction 16. Here acts the metering piston 40 as a storage piston, since it is a predetermined one Fuel quantity in the pressure chamber 32 stores.

During the injection process, the magnet 11 of the pump device 5 energized so that the actuating piston 8 in the conveying direction is moved, during an acceleration phase stores kinetic energy. At the end of the acceleration phase the actuating piston 8 hits the metering piston 40 and transfers its kinetic energy to it. Of the Dosing piston 40 is pressed into the stop bush 25 until it with the front end face of the anchor body 41 on the stop edge 26 strikes the stop bush 25 and stopped becomes. The delivery stroke thus corresponds to the storage stroke and the amount of fuel displaced by the metering piston 40 during the Dosing process sucked and stored amount of fuel. Since the amount of fuel displaced by the metering piston into the High pressure line 2 is conveyed and by means of the injection nozzle 3 is injected into the combustion chamber, is the injected Fuel quantity measured exactly by the dosing process and independent of parameters that change over time, such as e.g. the passage pressure of the injector.

4 is a fourth embodiment of the invention Fuel injector shown. It owns in essentially the same structure as the third embodiment, which is why the same parts with the same reference number are provided and a detailed description is omitted can be.

In this embodiment, the pressure chamber 32 opens out a passage 121 leading to a delay chamber 120. The delay chamber 120 is like a blind hole with a jacket wall 122 and a bottom wall 123 executed and points a hollow cylindrical shape. There is a deceleration piston in it 125 slidably mounted, the one flush with the jacket wall 122 of the delay chamber 120 closes. At the of the pressure chamber 32 facing away from the delay piston 125 is a recess for receiving a compression spring 126 in introduced the bottom wall 123, which is between the deceleration piston 125 and that in the bottom wall 123 inserted recess is inserted.

The operation of this fourth embodiment will explained below.

The dosing process is identical to that of the third Embodiment executed.

During the injection process, the actuating piston 8 is removed from the magnet 11 accelerated in the conveying direction 16, during a Acceleration phase stores kinetic energy. At the end the acceleration piston hits the actuating piston 8 the metering piston 40 and transmits its kinetic energy on this, whereby fuel from the pressure chamber 32 to Injector 3 is displaced.

If a deceleration pressure P _{V set} in the deceleration chamber 120 by the prestress of the compression spring 126 is reached in the pressure chamber 32, fuel escapes into the deceleration chamber 120, the deceleration piston 125 being inserted into the deceleration chamber 120. As a result, the pressure build-up in the pressure chamber 32 and consequently in the high-pressure line 2 is delayed, so that the pressure does not increase suddenly, but rather increases gradually. The deceleration process ends when the deceleration piston 125 strikes the bottom wall 123. The delay period is determined by the spring hardness of the spring 126 and the stroke of the delay piston 125.

The deceleration pressure is preferably in the range of P V = ½P jet to P V = P jet , where P _{nozzle is} the _nozzle opening pressure of the injection nozzle 3. The spring hardness of the compression spring 126 is selected such that the deceleration process continues at least during the opening phase of the injection valve. The spring hardness of the compression spring 126 and the stroke of the delay piston 125 are preferably selected so that the delay piston 125 strikes the bottom wall 123 at a final pressure of P _end from 1.5P _nozzle to 3P _nozzle .

1.) Zunächst wird der Kraftstoff unter Druck gesetzt, bis der Druck den Verzögerungsdruck P_V einnimmt. Während diesem Druckanstieg führt wegen der Inkompressibilität des Kraftstoffes der Dosierkolben 40 nur eine minimale Bewegung aus, weshalb dieser Druckanstieg quasi schlagartig erfolgt.

2.) Mit dem Erreichen des Verzögerungsdruckes P_V beginnt die Verzögerungsphase, während der der weitere Druckaufbau verzögert wird. Während dieser Verzögerungsphase öffnet sich das Einspritzventil, wobei der Öffnungsvorgang nicht schlagartig, sondern über einem bestimmten Zeitraum andauernd erfolgt. Da während des Öffnungsvorganges des Einspritzventils der Druckaufbau verzögert wird, wird erreicht, daß an der teilweise geöffneten Einspritzdüse ein geringerer Anteil an Druckenergie reflektiert wird, die bei der nachfolgenden Reflexion die Bewegung des Dosierkolbens abbremst und zu Druckschwankungen beim Einspritzvorgang führt würde.

3.) Die Federhärte der Druckfeder 126 und der Hub des Verzögerungskolbens 125 ist bspw. so gewählt, daß der Verzögerungsvorgang unmittelbar nach dem vollständigen Öffnen des Einspritzventils abgeschlossen ist, so daß der weitere Druckanstieg wieder mit maximaler Anstiegsrate erfolgt.

The process of building up pressure in the fuel in the pressure chamber 32 and the high-pressure line 2 can be divided into three phases:

1.) First, the fuel is pressurized until the pressure assumes the deceleration pressure P _V. During this pressure increase, because of the incompressibility of the fuel, the metering piston 40 carries out only a minimal movement, which is why this pressure increase takes place suddenly.

2.) When the deceleration pressure P _{V is} reached, the deceleration phase begins, during which the further pressure build-up is delayed. During this delay phase, the injection valve opens, the opening process not taking place suddenly, but continuously over a certain period of time. Since the pressure build-up is delayed during the opening process of the injection valve, it is achieved that a smaller proportion of pressure energy is reflected at the partially open injection nozzle, which slows down the movement of the metering piston in the subsequent reflection and would lead to pressure fluctuations during the injection process.

3.) The spring hardness of the compression spring 126 and the stroke of the delay piston 125 is selected, for example, so that the deceleration process is completed immediately after the injection valve is fully opened, so that the further pressure rise takes place again at the maximum rate of increase.

This delay device delays the pressure build-up during the opening process of the injector, thereby avoided is that pressure waves at the only partially opened injector be reflected and the movement of the dosing piston slow down. This will improve energy transfer and a more uniform pressure level during the injection process achieved.

This delay device can in all embodiments of the present application are provided, wherein it opens to the pressure chamber 32 or to the high pressure line 2 is arranged; an arrangement as close as possible to the dosing piston is preferred, however.

The delay device can be replaced with a separate one Chamber also with e.g. between the actuating piston and the metering piston arranged spring or damping element be formed, the energy transfer from the actuating piston delayed on the dosing piston.

5 is a fifth embodiment of the invention Fuel injector shown. It owns in essentially the same structure as the third embodiment, which is why the same parts have the same reference numerals and a detailed description are omitted can be.

The fifth embodiment differs from the third Embodiment in that the actuating piston 8 immediately abuts the metering piston 40 and in the pump device 5 only a single spring 55 between the actuating piston 8 and the rear guide bush 19 in the conveying direction 16 is arranged. The spring 55 acts on the actuating piston 8 together with the metering piston 40 in the conveying direction 16, that is, in the direction of the pressure chamber 32.

The actuating piston 8 and the one acting as a storage piston Dosing piston 40 together lead both the storage stroke also the delivery stroke. In this embodiment, the Actuating piston 8 and the metering piston 40 are formed in one piece be.

A pump-nozzle system with a sixth embodiment the fuel injection device according to the invention is in Fig. 6 shown.

The structure of this fuel injection device corresponds to essentially that of the first embodiment and differs differ from this only in the design of the pumping device 5.

The pump device 5 is operated pneumatically. She points a pump housing 60. There is a hollow cylindrical one in the pump housing 60 Actuating piston chamber 62 formed in which an actuating piston 8 is slidably disposed. The actuating piston 8 is a hollow cylindrical one that is open at one end Piston with a piston crown 63 and a piston wall 64. The piston wall 64 is form-fitting on the inner wall the actuating piston chamber 62.

Between the piston crown 63 and the rear in the conveying direction 16 Front side of the actuating piston chamber 62 is one Actuating piston spring 67 used the actuating piston 8 applied with a force in the conveying direction 16.

Coaxial with the actuating piston chamber 62 is an opening into it Storage hole 65 introduced. The storage bore 65 is in the conveying direction 16 in front of the actuating piston chamber 62 arranged and has a smaller diameter than the actuating piston chamber 62 so that at the mouth of the Storage bore 65 with respect to the actuating piston chamber 62 Ring step 66 is formed. The actuating piston 8 is with its piston crown 63 pointing towards the storage bore 65 arranged. A massive, bolt-shaped accumulator piston 9.

Immediately adjacent to the ring step 66 is a lateral one control opening 68 opening into the actuating piston chamber 62 scheduled. A control valve 70 is arranged at the control opening 68, via a pneumatic line with a combustion chamber connected is. The control valve 70 is a known one Electromagnetically operated pneumatic valve for opening and Closing a passage.

This pneumatically operated pump device 5 is connected to the Pump housing 60 to outward opening storage bore 65 an opening of the rest of the housing body 14, the pressure chamber 32 limiting area set so that the pressure chamber 32 extends into the inner region of the storage bore 65 and them with respect to the pump device 5 from the inner wall the storage bore 65 and the front in the conveying direction 16 End face of the storage piston 9 is limited.

The following is the operation of the sixth embodiment the fuel injection device according to the invention explained.

The fuel injection device is located after an injection process in the state shown in Fig. 6, i.e. that the actuating piston 8 from the actuating piston spring 67 pressed against the ring step 66 and the metering piston 40 in its initial state, in which it is controlled by the dosing spring 48 from the pressure chamber 32 away from the rear guide bush 45 is pressed.

At the end of a combustion process in the combustion chamber of the internal combustion engine the control valve 70 briefly opens the control opening 68, which is between the ring step 66 and the piston crown 63 forms a gas pressure that the actuating piston 8 against the action of the actuating piston spring 67 of the Ring stage 66 lifts off. From this gas pressure the storage piston 9 pressed into the storage bore 65, due to the different However, cross sections on the accumulator pistons 9 force acting much less than that on the actuating piston 8 is acting force.

Only after the pump device 5 has been preloaded by means of the Dosing is started. This promotes the metering device 6 in an identical manner to the first Embodiment fuel in the pressure chamber 32, whereby the storage piston 9 in the storage bore 65 opposite to Delivery direction 16 and thus against the effect of the gas pressure is shifted (= storage stroke). The one stored in pressure chamber 32 Fuel cannot because of the overflow valve 36 flow out, which is why the storage piston 9 in the position of Storage stroke is maintained and a precisely defined amount of fuel is saved.

The control valve 70 opens the control opening for the injection process 68, whereby that located in the actuating piston chamber 62 Gas flows out, the actuating piston 8 from the actuating piston spring 67 is accelerated in the conveying direction 16 and the accumulator piston after an acceleration phase into the Storage hole presses. When the actuating piston hits 8 on the ring step 66 or the accumulator piston 9 on the housing body 14, the conveying process is stopped, the conveying stroke again corresponds exactly to the storage stroke. Because the storage stroke can be set exactly by the metering device 6, can be a predetermined variable amount of fuel regardless of Signs of aging can be dosed in the unit injector system.

In Fig. 7 is a pump-nozzle system with a schematic seventh embodiment of an inventive, pneumatic driven fuel injector shown.

In this injector, the metering piston 40 and the actuating piston 8 similar to the third embodiment arranged in a line. This injector has an essentially tubular housing body 14. The housing body is at the rear end in the injection direction 16 completed with an end plate 75. On in the injection direction 16 front end portion of the tubular housing body 14 is a connection opening 33 for connecting the to the injection nozzle 3 leading high pressure line 2 is provided.

A stop bush 25 is adjacent to the connection opening 33 provided in an inward protruding Ring web limited passage is used. The dosing piston 40 in turn has a tubular anchor body 41 with a guiding pin 42 protruding from both ends thereof on. With the area pointing forward in the injection direction 16 of the guide pin 42 supports the metering piston 40 in the Stop bushing 25. Between the stop bushing 25 and the connection opening 33, a standing pressure valve 35 is arranged.

In the area of the stop bush 25 opens between the parking pressure valve 35 and the metering piston 40 a fuel supply 54 in the pressure chamber 32. In the fuel supply 54 a check valve 53 is arranged which a backflow in a fuel supply line connected to the fuel supply 54 52 prevented.

Is located between the metering piston 40 and the end plate 75 the actuating piston 8 in the tubular housing 14. The actuating piston 8 has an approximately cup-shaped body with a jacket wall 76 and a bottom wall 77. With the actuating piston 8 is positively supported by its jacket wall 76 in the tubular housing 14 and is with its Bottom wall 77 arranged in the injection direction 16 to the rear. In the limited by the cup-shaped actuating piston 8 the metering piston supports a cylindrical recess 40 with its protruding rearward in the injection direction 16 Guide pin 42.

There is a between the bottom wall 77 and the metering piston 40 Dosing spring 48 used.

The actuating piston 8 has at the rear jacket area a recess in which an actuating piston spring 67 sits, which is supported on the end plate 75 of the housing 14.

To actuate the metering piston 40 is in the rear area an electromagnet 11 enclosing the housing 14 is arranged.

Is adjacent to the tubular housing 14 and in the injection direction 16 a pneumatic opening 80 at the rear on the ring web 24 educated. On the outside of the housing 14 is a control valve 70 scheduled, which is a pneumatic connection between the pneumatic opening 80 and a pressurized gas reservoir and can shut off. The control valve 70 is a known one Electromagnetically operated pneumatic valve for opening and closing a passage. In the room in which the metering piston 40 and the actuating piston 8 are the Armature chamber 12 can thus be supplied with gas under pressure become.

The metering piston 40 has in the jacket area of its armature body 41 at least one longitudinal groove 82 through which one into the anchor space entering gas in the back of the metering piston 40 Range can be forwarded.

The following is the operation of this seventh embodiment explained in more detail.

During a metering process, the metering piston 40 is removed from the magnet 11 actuated counter to the injection direction 16, so that Fuel drawn from the fuel supply and in the Pressure chamber 32 in the area between the standing pressure valve 35 and the metering piston 40 is stored. Because of the fuel of the check valve 53 does not escape from the pressure chamber 32 can, the metering piston 40 is fixed in its position.

The actuating piston is used to actuate the metering piston 40 8 biased by a pressurized gas. The Gas is supplied to the armature chamber via the pneumatic opening 80 and through the longitudinal groove 82 in made in the metering piston 40 the area between the metering piston 40 and the actuating piston 8 introduced so that the actuating piston 8 due the increased gas pressure to the rear against the actuating piston spring 67 pressed and the actuating piston spring 67 biased becomes. The dosing piston remains in its position because he both from the metering spring 48 and the one under pressure standing gas is injected in the direction of injection 16 and its movement due to the fuel in the pressure chamber 32 is blocked in the injection direction 16.

When the control valve 70 is opened, the gas can escape from the armature space escape, whereby the actuating piston 8 due to Spring tension of the actuating piston spring 67 in the injection direction is accelerated until it hits the metering piston 40 and transfers its energy to it in order to Spray space 32 located fuel.

The actuation piston 8 can also be preloaded in time the metering piston 40 is actuated by means of the magnet 11, however, the order described above, at first the dosing process and then the pretensioning of the actuating piston is carried out, is preferred because then the Dosing piston 40 when dosing only against the actuating piston spring 67 works and not against an elevated one Gas pressure must work.

The combustion chamber can be used as the gas pressure reservoir with that of the invention PDS system equipped internal combustion engine used become. 9 is the pressure curve during a Working cycle shown in a combustion chamber. In the area before top dead center the pressure rises due to the by the Piston motion gradually produced compression from atmospheric pressure to a compression pressure. After the ignition that usually shortly after reaching top dead center is triggered, the pressure suddenly rises to a multiple of the compression pressure and then falls through the Piston movement steeply, after opening the exhaust valve the pressure in the combustion chamber drops to atmospheric pressure.

To actuate the pneumatic injection device according to the invention can about during the pressure drop (I in Fig. 9) withdrawn gas at the level of the compression pressure and the injector supplied for biasing the actuating piston become.

The gas flowing out when the injector is discharged e.g. fed back to the combustion chamber (II in Fig. 9), wherein the combustion chamber pressure at this time is less than the storage pressure is in the injector. The time of The injector is unloaded by the time of Injection process set so that it is in a single-cylinder engine always coincides with the increase in pressure. At a Multi-cylinder engine can be assigned to a specific cylinder Injector with another cylinder's gas can be controlled so that the discharge process of the injector can coincide with the phase during which there is atmospheric pressure in the combustion chamber.

In the pneumatic connection line between the combustion chamber and the injector can be provided with an additional valve with which the gas is discharged when the injector in a room with low, i.e. e.g. atmospheric Pressure that can be derived.

In the case of 2-stroke engines, the crankcase can be used instead of the combustion chamber be used as a gas pressure reservoir in which the Air in it cyclically due to the piston movement is compressed.

These pneumatically operated injectors are in front all intended for internal combustion engines that do not have their own electrical electrical system with which electrical Sufficient energy is made available. In these devices, the main energy contribution, namely the movement of the actuating piston by means of pneumatically transmitted Energy executed whereas the control functions, which have low energy consumption, but very much must be carried out exactly, be controlled electrically.

A preferred metering device is in FIGS. 8a and 8b shown. Same parts as for the dosing devices described above are provided with the same reference numerals. This metering device 6 in turn has a pipe section 38, which is surrounded by a magnet 49. Of the Pipe section 38 and magnet 49 are from a housing 50 includes.

A metering piston 40, which consists of a Armature body 41 and a piston body 42a is formed. Of the Piston body 42a is rod-shaped with a smaller diameter formed as the anchor body 41 and in the conveying direction 81 of the metering device 6 arranged coaxially in front of the armature body 41. The piston body 42a is in with its front end a guide bush 44 slidably mounted. On his the piston body 42a has a radially rearward end externally projecting ring web 83, between the ring web 83 and the guide bush 44, a metering spring 48 clamped is.

At the rear of the pipe section in the conveying direction 81 38 a Lekagerrohr 85 is used. The Lekagerrohr 85 extends through an opening in the housing 50 to the outside and forms a stop with its front-facing end face 86 for the metering piston 40. The metering piston 40 lies in its starting position, i.e. in the due to the spring force the metering spring 48 in the rearwardly shifted position, at the stop 86.

The guide bush 44 points at its in the conveying direction 81 a radially outwardly projecting washer 88 on. The washer 88 is on its back with a Sealed ring against the pipe section 38 and has on the front in the area of the through opening shallow approximately spherical recess 90. 81 in the conveying direction A valve device 91 is arranged upstream of the recess 90.

The valve device 91 has one directly on the Washer 88 of the tubular section 38 abutting circular Metal disc 92 and a circular valve disc 93. The metal disc has an inlet hole 94 and an outlet hole 95 provided. The inlet hole 94, the outlet hole 95, the spherical recess 90 and that extending to the metering piston Passage of the guide bush 44 delimit a valve chamber 89.

The valve disk 93 is preferably a thin metal plate made of spring steel, preferably with rubber on both sides or plastic is coated. On the valve disk 93 is each an inlet tongue 96 and an outlet tongue 97 with a cut into a narrow u-shaped cut. The two disks 92, 93 are held by a housing cover 98, which is detachable is attached to the housing 50 and a circular recess has, in which the two disks 92, 93 are arranged. A fuel supply channel 100 is formed in the housing cover 98, the one in the area of the inlet tongue 96 on the valve disk 93 ends. On the fuel supply channel 100 there is a on the housing cover 98 fuel supply neck protruding radially outward 102 attached to a fuel supply line can be connected. In the housing cover 98 is also a Fuel outlet passage 101 introduced with an opening 105 opens in the region of the outlet tongue 97 on the valve disk 93.

The opening 104 of the fuel supply channel opening at the inlet tongue 96 100 is so small that it is completely different from the Inlet tongue 96 can be covered. That is, the opening 104 lies within the free cut of the inlet tongue (Fig. 8b). The inlet opening 94 of the metal disc 92 is so large that it completely includes the inlet tab 96. If the inlet tongue 96 located in the disc plane, it completely covers the fuel supply passage 100 so that the supply of fuel is interrupted. Since the inlet opening 94 of the metal disc 92 completely encloses the tongue 96, the inlet tongue 96, are bent into the inlet opening 94 so that they a passage between the fuel supply passage 100 and the Valve chamber 89 releases. The inlet tongue 96 thus forms the openings 94 and 104 a designed as a check valve Intake valve 110, which is a flow of fuel from the valve chamber 89 prevented in the fuel supply channel 100.

The outlet opening 95 of the metal disk 92, however, is so small that they are within the free cut of the outlet tongue 97 (Fig. 8b), i.e. the outlet opening is so small that it can be completely covered by the outlet tongue 97. If the outlet tongue 97 is in the disk plane, covers they completely exhaust port 95 so that the passage from the valve chamber 89 to the outlet duct 101 is interrupted.

The opening 105 of the outlet duct 101 is larger than that Cut the outlet tongue 97 so that the outlet tongue 97 in the opening 105 can be bent and a passage between the valve chamber 89 and the outlet channel 101 releases. The outlet tongue 97 thus forms with the openings 95, 105 designed as a check valve outlet valve 111, the one Fuel flow from the exhaust port 101 into the valve chamber 89 prevents.

The mode of operation of this metering device 6 is described below explained.

When the dosing piston 40 from its starting position by the magnet 49 is actuated, i.e. the metering piston moves in the conveying direction 81 moves, it displaces fuel from the valve chamber 89 through the outlet valve 111 into the outlet channel 101. During fuel displacement, intake valve 110 locks. When the dosing piston moves back into its starting position is fuel from the fuel supply passage 100 through the intake valve 110 is sucked. The outlet valve is blocked 111.

By forming the two valve tongues 96, 97 on one single disc 93, a very small valve chamber 89 is obtained. This means that with this metering device 6 a Pumping device with an extremely small clearance was created. Large damaged spaces are to be pumped in pumping equipment of liquids disadvantageous because if they are not complete filled with liquid, it may be that the pump stroke only compresses and relaxes an air column without Liquid is pumped.

This special configuration of the metering device is not only advantageous for injectors, but can also used with any other reciprocating pump equipment become. As a metering device for injectors this pump arrangement, however, is particularly advantageous because with one extremely small dead space, the pumping device 5 can be flooded can, the pump device 5 not being actuated during flooding must be, so that their harmful space (= pressure chamber 32) in any Size can be designed.

Claims (12)

Fuel injector with a pump device (5) designed as a reciprocating piston pump which displaces fuel by means of a reciprocating piston (8, 9),
marked by a stop element (25, 26) which limits the delivery stroke of the reciprocating piston (8, 9) in the conveying direction (16), and a metering device (6) for determining the amount of fuel to be injected by displacing the reciprocating piston (8, 9) relative to the stop element (25 , 26) by a specific, variable storage stroke which corresponds to the conveying stroke. Fuel injection device according to claim 1,
characterized, that the reciprocating piston (8, 9) is formed in two parts from an actuating piston (8) and a storage piston (9), the storage piston (9) being arranged upstream of the actuating piston (8) in the conveying direction (16), so that only the storage piston ( 9) is displaced by the metering device by the storage stroke. Fuel injection device according to claim 2,
characterized, that the actuating piston (8) for absorbing kinetic energy is arranged in the pump device (5) in such a way that it can carry out a greater stroke than the storage piston (9), and during an acceleration phase it stores kinetic energy which it needs to displace the fuel transfers to the accumulator piston (9). Fuel injection device according to claim 3,
characterized, that the acceleration path covered by the actuating piston (8) during the acceleration phase is inversely proportional to the variable storage stroke of the storage piston (9). Fuel injection device according to one of Claims 1 to 4,
characterized, that the metering device (6) is a separate fuel delivery device, which is designed separately from the pump device (5) and can convey fuel in a pressure chamber (32) arranged upstream of the pump device (5), the pressure chamber (32) being connected to an injection nozzle (3) is limited by a parking pressure valve (35) which only opens from a certain passage pressure, the passage pressure being dimensioned so that the standing pressure valve (35) does not open when the fueling is carried out by the metering device (6) into the pressure chamber (32), whereas the standing pressure valve opens when the fueling is carried out by the pumping device (5) at a higher pressure. Fuel injection device according to claim 2 or 3,
characterized, that the metering device (6) has an electromagnet (49) and the storage piston (9) armature (41) of this electromagnet (49), so that the storage piston (9, 41) for executing the storage stroke of the electromagnet (49) with a force is applied. Fuel injection device according to one of Claims 1 to 6,
characterized, that the pump device (5) is operated with gas pressure. Fuel injection device according to claim 7,
characterized, that a control valve (70) on the pump device (5) for supplying gas under pressure in an area upstream of the actuating piston (8) in the conveying direction (16), so that the actuating piston (8) counter to the conveying direction (16) against an actuating piston spring (67) is biased, and for discharging the gas so that the actuating piston (8) is moved in the conveying direction (16) to act on the storage piston (9). Fuel injection device according to claim 8,
characterized, that the control valve (70) in the conveying direction (16) upstream of an armature body (41) of the storage piston (9) functioning as a metering piston (40) into an armature chamber (12) in which the storage piston (9) and the actuating piston (8) are arranged movably are, the armature body (41) has a passage (82) in the longitudinal direction, so that the gas can flow past the armature body to the actuating piston. Fuel injection device according to one of Claims 1 to 9,
characterized, that the metering device (6) is a reciprocating piston pump which draws fuel in and out of a delivery chamber by means of a reciprocating metering piston (40), a fuel supply channel (100) leading to the delivery chamber and a fuel outlet channel (101) leading away from the delivery chamber are each separated from the delivery chamber by a non-return valve which blocks back flow, and the two check valves each have an inlet or outlet tongue (96, 97) as a valve element, which are formed on a common valve disk (93). Fuel injection device according to claim 10,
characterized, that the delivery space is delimited by a flat, spherical recess (90) arranged close to the valve disc (93). Fuel injection device according to one of Claims 1 to 11,
characterized, that a delay device (120, 125) is provided, which is designed such that the energy transfer in the pump device (5) from the reciprocating piston (8, 9) to the fuel is delayed at least during the opening process of the injection nozzle (3).

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