DE102016209586B4 - Direct injection compression ignition internal combustion engine with a fuel supply system comprising two high-pressure piston pumps and a method for operating such an internal combustion engine - Google Patents

Abstract

Direct-injection compression-ignition internal combustion engine with at least one cylinder, in which each cylinder is equipped with an injection device for the direct introduction of fuel into the cylinder, Low-pressure side (1b) and a valve unit (2), and- the fuel supply system (1) is equipped with at least two high-pressure piston pumps (3a, 3b), each of which has a piston (10a, 10b) that can be moved translationally between a bottom dead center and a top dead center and can be connected to the high pressure side (1a) and can be connected to the low pressure side (1b) via a valve unit, characterized in that the valve unit (2) has a control piston (2a) which is arranged in and along a valve housing (2b) a displacement axis (2c) is mounted so as to be translationally displaceable, - in a middle position (M) via valve housing (2b) which connects at least two high-pressure piston pumps (3a, 3b) to each other and to the low-pressure side (1b), - in a first end position (E1) a first high-pressure piston pump (3a) to the low-pressure side (1b) connects and separates from the at least one other high-pressure piston pump (3b) and separates a second high-pressure piston pump (3b) from the low-pressure side (1b), and - in a second end position (E2), connects the second high-pressure piston pump (3b) to the low-pressure side (1b) and separates from the at least one other high-pressure piston pump (3a) and separates the first high-pressure piston pump (3a) from the low-pressure side (1b).

Description

• - jeder Zylinder zum direkten Einbringen von Kraftstoff in den Zylinder mit einer Einspritzvorrichtung ausgestattet ist,
• - zwecks Kraftstoffversorgung des mindestens einen Zylinders ein Kraftstoffversorgungssystem vorgesehen ist, das eine Hochdruckseite, eine Niederdruckseite sowie eine Ventileinheit umfasst, und
• - das Kraftstoffversorgungssystem mit mindestens zwei Kolbenhochdruckpumpen ausgestattet ist, die jeweils einen zwischen einem unteren Totpunkt und einem oberen Totpunkt translatorisch verschiebbaren Kolben umfassen sowie mit der Hochdruckseite verbindbar sind und mit der Niederdruckseite via Ventileinheit verbindbar sind.

The invention relates to a direct-injection compression-ignition internal combustion engine with at least one cylinder in which

• - each cylinder is equipped with an injection device for the direct introduction of fuel into the cylinder,
• - For the purpose of supplying fuel to the at least one cylinder, a fuel supply system is provided which comprises a high pressure side, a low pressure side and a valve unit, and
• - The fuel supply system is equipped with at least two high-pressure piston pumps, each comprising a piston that can be moved translationally between a bottom dead center and an upper dead center and can be connected to the high pressure side and connected to the low pressure side via a valve unit.

The invention also relates to a method for operating such an internal combustion engine.

An internal combustion engine of the type mentioned is used as a motor vehicle drive. the DE 695 14 716 T2 describes a fuel supply system for a diesel internal combustion engine with a valve unit which can connect two piston pumps to one another and to the low-pressure area. It is not possible to connect the two piston pumps to one another and at the same time to the low-pressure side. The latter enables the piston pump system according to DE 197 45 118 A1 .

In the context of the present invention, the term internal combustion engine includes compression-ignition diesel engines, but also compression-ignition hybrid internal combustion engines that use a hybrid combustion process with compression ignition, as well as hybrid drives that, in addition to the compression-ignition internal combustion engine, include an electric machine that can be driven with the internal combustion engine and which provides power from the Internal combustion engine takes up or delivers additional power as a switchable auxiliary drive.

In the development of internal combustion engines, constant efforts are made to minimize fuel consumption and reduce pollutant emissions.

The direct injection is characterized by an inhomogeneous combustion chamber charge, which is not characterized by a uniform air ratio, but regularly has both lean (λ> 1) mixture parts and rich (λ <1) mixture parts. The inhomogeneity of the fuel-air mixture is also one of the reasons for the particulate emissions.

There is comparatively little time available for the injection of the fuel, the preparation of the mixture in the combustion chamber, namely the mixing of air and fuel and the preparation of the fuel as part of preliminary reactions including evaporation and ignition of the prepared mixture.

The resulting requirements for mixture formation apply in principle to every direct-injecting internal combustion engine and thus also to direct-injecting diesel engines. The internal combustion engine which is the subject of the present invention is generally a direct injection compression ignition internal combustion engine.

Direct injection requires a fuel supply system that is able to build up the high pressure in the fuel to be injected that is required for direct injection. Therefore - as for example in 1a shown - fuel supply systems 101 for direct-injection internal combustion engines with at least one high-pressure pump 103 fitted. As a high pressure pump 103 a piston pump is used regularly 103 used, in which a piston that is translationally displaceable between a bottom dead center and an upper dead center 103a During the operation of the pump, ie during the fuel delivery, oscillates and fuel as part of a suction stroke from the low-pressure side 101b sucks in and on the high pressure side as part of a delivery stroke 101a pumps, ie promotes. To regulate the fuel volume flow is on the low pressure side 101b a valve unit 102 provided over which the high-pressure piston pump 103 is supplied with fuel from a fuel reservoir or can at least be connected to this fuel reservoir. One on the high pressure side 101a arranged check valve 108 prevents a backflow from already on the high pressure side 101a pumped fuel back into the high-pressure piston pump 103 ; especially during the suction stroke of the high-pressure piston pump 103 . One on the low pressure side 101b arranged check valve 108 prevents the high-pressure piston pump during the delivery stroke 103 Fuel on the low pressure side 101b is promoted.

According to the prior art, it can be used as a valve unit 102 a throttle 102a be used, which the inflow of fuel into the piston chamber of the US 31 39 492 A throttles and thus regulates the fuel volume flow. Both concepts with a high-pressure piston pump can be used 103 as well as concepts with several high-pressure piston pumps 103 realize how in the 1a and 1b shown. The use of a throttle 102a as a valve unit 102 is inherently associated with high losses, which is why alternative concepts have been developed that act as a valve unit 102 a digitally switchable valve instead of a throttle 102b insert, as in the 2a and 2 B shown. For each high-pressure piston pump 103 a digitally switchable valve 102b provided, ie a valve 102b which can be switched on and off. The same reference numerals have been used for the same components, which is why reference is made to FIG 1a and 1b .

When using a digitally switchable valve 102b becomes the piston chamber of the high-pressure piston pump 103 as part of the suction stroke with the valve open 102b always completely filled with fuel and optionally with the valve open during the delivery stroke 102b on the low pressure side 101b or with the valve closed 102b on the high pressure side 101a pumped, ie promoted, so that by targeted switching of the valve 102b Adjust, ie regulate, the amount of fuel delivered in the delivery stroke. There is a digitally switchable valve 102b If only a small pressure loss is generated, the losses in the fuel delivery are smaller, that is to say comparatively low.

However, the use of a digitally switchable valve is also associated with disadvantages. The return of fuel to the low-pressure side as part of a delivery stroke for the purpose of adjusting the amount of fuel delivered generates pressure fluctuations in the lines of the fuel supply system on the low-pressure side, i. H. in the low pressure lines or suction lines. The pressure oscillations lead to a disturbing noise excitation and make pressure regulation of the low-pressure circuit more difficult.

For concepts with several piston high-pressure pumps, each high-pressure pump requires its own digitally switchable valve as a valve unit including control. This is associated with considerable costs and an increased space requirement for the fuel supply system.

In the case of small amounts of fuel to be delivered, the compressed dead volume is large compared to the compressed amount of fuel actually delivered, as a result of which the losses are disadvantageously increased.

Against the background of what has been said, it is an object of the present invention to provide a direct-injection compression-ignition internal combustion engine according to the preamble of claim 1 with which the disadvantages known from the prior art relating to the fuel supply system can be reduced or overcome.

Another sub-object of the invention is to provide a method according to the preamble of claim 16 for operating such an internal combustion engine.

• - jeder Zylinder zum direkten Einbringen von Kraftstoff in den Zylinder mit einer Einspritzvorrichtung ausgestattet ist,
• - zwecks Kraftstoffversorgung des mindestens einen Zylinders ein Kraftstoffversorgungssystem vorgesehen ist, das eine Hochdruckseite, eine Niederdruckseite sowie eine Ventileinheit umfasst, und
• - das Kraftstoffversorgungssystem mit mindestens zwei Kolbenhochdruckpumpen ausgestattet ist, die jeweils einen zwischen einem unteren Totpunkt und einem oberen Totpunkt translatorisch verschiebbaren Kolben umfassen sowie mit der Hochdruckseite verbindbar sind und mit der Niederdruckseite via Ventileinheit verbindbar sind,

und die dadurch gekennzeichnet, dass die Ventileinheit über einen Steuerkolben verfügt, der

• - in einem Ventilgehäuse angeordnet und entlang einer Verschiebeachse translatorisch verschiebbar gelagert ist,
• - in einer Mittelposition via Ventilgehäuse die mindestens zwei Kolbenhochdruckpumpen miteinander und jeweils mit der Niederdruckseite verbindet,
• - in einer ersten Endposition eine erste Kolbenhochdruckpumpe mit der Niederdruckseite verbindet und von der mindestens einen anderen Kolbenhochdruckpumpe trennt sowie eine zweite Kolbenhochdruckpumpe von der Niederdruckseite trennt, und
• - in einer zweiten Endposition die zweite Kolbenhochdruckpumpe mit der Niederdruckseite verbindet und von der mindestens einen anderen Kolbenhochdruckpumpe trennt sowie die erste Kolbenhochdruckpumpe von der Niederdruckseite trennt.

The first task is achieved by a direct-injection compression-ignition internal combustion engine with at least one cylinder in which

• - each cylinder is equipped with an injection device for the direct introduction of fuel into the cylinder,
• - For the purpose of supplying fuel to the at least one cylinder, a fuel supply system is provided which comprises a high pressure side, a low pressure side and a valve unit, and
• - The fuel supply system is equipped with at least two high-pressure piston pumps, each of which includes a piston that can be moved translationally between a bottom dead center and an upper dead center and can be connected to the high pressure side and can be connected to the low pressure side via a valve unit,

and which is characterized in that the valve unit has a control piston which

• - is arranged in a valve housing and mounted so as to be translationally displaceable along a displacement axis,
• - in a central position via the valve housing that connects at least two high-pressure piston pumps to one another and to the low-pressure side,
• - In a first end position, a first high-pressure piston pump connects to the low-pressure side and separates from the at least one other high-pressure piston pump and a second high-pressure piston pump separates from the low-pressure side, and
• - In a second end position, the second high-pressure piston pump connects to the low-pressure side and separates it from the at least one other high-pressure piston pump and separates the first high-pressure piston pump from the low-pressure side.

According to the invention, the fuel supply system has two or more high-pressure piston pumps and a valve unit. Two or more high-pressure piston pumps can also share a common pump housing. I. E. Regardless of the number of high-pressure piston pumps used, only one valve unit is required. This reduces the costs and the space required for the fuel supply system.

The pistons of the high-pressure piston pumps can move in opposite directions in pairs, but can also be offset from one another as required. The lift curves can be different and also have areas without a lift, for example in the dead centers. When using two high-pressure piston pumps, the piston of one high-pressure piston pump can consequently move upwards, ie be in the delivery stroke, while the piston of the other high-pressure piston pump moves downwards, ie is in the suction stroke.

The high-pressure piston pumps can be connected to one another via a valve unit, i. H. short-circuit so that one high-pressure piston pump delivers into another high-pressure piston pump. For this purpose, the control piston of the valve unit according to the invention is to be moved into the central position, in which the high-pressure piston pumps are connected to one another and to the low-pressure side.

When using two high-pressure piston pumps, the pistons of which move in opposite directions, when the control piston is in the central position, fuel from the high-pressure piston pump in the delivery stroke can get directly into the high-pressure piston pump in the suction stroke, i. H. be conveyed without fuel having to be or will be conveyed back to the low-pressure side. This has the advantageous effect that only weak or no pressure oscillations are generated in the lines of the fuel supply system on the low-pressure side. With the pressure oscillations, the noise excitation and the problem with regard to pressure regulation in the low-pressure circuit are reduced or eliminated.

By connecting the high-pressure piston pumps to one another and to the low-pressure side, no delivery pressure can be built up by the high-pressure piston pumps and no fuel can be delivered to the high-pressure side. In this respect, when a control piston is in the middle position, there is no delivery, d. H. a zero grant.

The valve unit according to the invention can be designed in completely different ways. The various embodiments are discussed according to the subclaims. For example, passive valve centering can be provided which forces the control piston into the central position without any further action. A deflection device is then required to move the control piston for the purpose of pumping fuel from the middle position into an end position in which one high-pressure piston pump is connected to the low-pressure side and sucks in fuel, while the other high-pressure piston pump is separated from the low-pressure side and the high-pressure piston pump and provides fuel in the delivery stroke pumps on the high pressure side.

The passive valve centering can also be replaced by an active valve centering, for example in embodiments in which flow forces or pressure differences in the valve housing, which also act on the control piston, are used to move the control piston into an end position. Once the control piston is in an end position, the high pressure piston pump, which is separate from the other high pressure piston pump and the low pressure side and located in the delivery stroke in this end position, ensures a sufficiently high pressure to keep the control piston in this end position and to deliver fuel to the high pressure side; at least in the embodiments in which the control piston can be pressurized by the fuel located in the valve housing in such a way that a resultant force acts in the direction of the end position.

According to the invention, the valve unit can also be designed in such a way that the control piston is not pressurized by the fuel located in the valve housing, in such a way that a resultant force acts along the displacement axis. The control piston is then designed in the manner of a slide that is free or independent of the fuel pressure. However, it is then necessary to provide a displacement device with which a force can be introduced into the control piston along the displacement axis and the control piston can be displaced into the end positions. There is no need for valve centering at all.

With the internal combustion engine according to the invention, the first object on which the invention is based is achieved, namely a direct-injection compression-ignition internal combustion engine according to the preamble of claim 1, with which the disadvantages known from the prior art relating to the fuel supply system can be reduced or overcome.

Embodiments of the direct-injection compression-ignition internal combustion engine are advantageous in which the pistons of two or more high-pressure piston pumps are arranged in a common pump housing. In the context of the present invention, the fuel supply system comprises at least two piston high-pressure pumps, which can be separate independent pumps, but also a pump housing with two or more pistons or pumps combined in groups, the pistons of which are each arranged in a common housing.

Further advantageous embodiments of the direct-injection compression-ignition internal combustion engine are discussed in connection with the subclaims.

Embodiments of the direct-injection compression-ignition internal combustion engine in which only a single valve unit is provided are advantageous. This embodiment once again expressly states that, according to the invention, only a single valve unit is to be provided, or is provided, regardless of the number of high-pressure piston pumps used. The costs and the space required for metering or regulating the amount of fuel delivered are significantly reduced.

Embodiments of the direct-injection compression-ignition internal combustion engine are advantageous in which valve centering is provided for positioning the control piston in the central position.

At least in the case of embodiments in which the control piston is pressurized by the fuel in the valve housing - at least temporarily - in such a way that a resulting force acts in the direction of one or the other end position, the flow forces and pressure differences that are present in the valve housing and on the Attack the control piston, used to move the control piston or to hold it in an end position. At the end of a conveying process, when the pressures on the low-pressure side and the high-pressure side are equal and the pressure differences are reduced via the control piston, the valve centering system moves the control piston back into the middle position.

In this context, embodiments of the direct-injection compression-ignition internal combustion engine are advantageous in which the valve centering comprises at least one spring element which acts on the control piston along the displacement axis and forces it into the central position.

If the valve centering is designed using a spring element, it is a passive valve centering that moves the control piston without further action, i. H. automatically transferred to the middle position as soon as the pressures acting on the control piston or the resulting force acting on the control piston along the displacement axis allow this. An active reset is then not required.

Embodiments of the direct-injection compression-ignition internal combustion engine are advantageous in which the valve centering comprises at least two spring elements which force the control piston along the displacement axis in opposite directions and force it into the central position. Embodiments with two spring elements are advantageous, of which one spring element acts on the control piston with a spring force in the direction of the first end position, whereas the other spring element acts on the control piston in the opposite direction, namely in the direction of the second end position.

If only one spring element is used, this spring element must be able to withstand both pressure and tension, i.e. H. can be claimed.

Embodiments of the direct-injection compression-ignition internal combustion engine in which the valve centering is active valve centering can also be advantageous.

Active valve centering can also be provided or used instead of passive valve centering. Then, however, the control piston is not automatically transferred into the middle position without further action as soon as the prerequisites for this are met. Rather, the control piston has to be actively returned to the central position by introducing an external displacement force. The valve centering is preferably activated when the pressures or forces acting on the control piston are minimal; H. advantageously at the end of a conveying process when the pressures on the low-pressure side and the high-pressure side are equal. As a result, the displacement force required for active resetting can be minimized.

If the control piston is then to be moved into an end position again for the purpose of fuel delivery, the valve centering must be deactivated in good time.

Embodiments of the direct-injection compression-ignition internal combustion engine in which the control piston is pressurized by the fuel in the valve housing are advantageous in such a way that - at least temporarily - a resulting force acts along the displacement axis in the direction of an end position.

In the present case, the control piston is of such a shape that the fuel pressure acting on the control piston generates or can at least temporarily generate a resultant force in the direction of the first or the second end position. This resulting force acting along the displacement axis of the control piston becomes more advantageous Way used to move the control piston or to hold it in an end position.

If passive valve centering is not provided, the resulting force serves both to move the control piston into an end position and to hold the control piston in this end position. At the end of a delivery process, when the pressure differences on the control piston decrease, active valve centering can be used to bring the control piston back into the middle position.

If, on the other hand, passive valve centering is used, which automatically moves the control piston into the middle position as soon as the pressures acting on the control piston allow this, the resulting force acting on the control piston serves exclusively or primarily to hold the control piston in an end position.

In this respect, measures are then required with which the control piston can be moved into the end positions.

In this context, embodiments of the direct-injection compression-ignition internal combustion engine are advantageous in which a deflection device is provided with which a force can be introduced into the control piston along the displacement axis, whereby the control piston can be deflected from the central position.

The deflection device can be used at the beginning of the conveying process to move the control piston into one of the two end positions. If fuel is then delivered as part of a delivery stroke by means of the corresponding high-pressure piston pump, the pressure differences acting on the control piston regularly result in a holding force in the direction of the end position, which preferably holds the control piston in this end position until the end of the delivery stroke. In this respect, the deflection device can be deactivated as soon as the pressure conditions on the control piston ensure a sufficiently high holding force. This variant proves to be particularly energy-saving. At the end of the delivery stroke or when the high-pressure piston pump used to deliver fuel is changed, the deflection device can then be activated again and used to move or transfer the control piston into the other end position.

The point in time at which the deflection device is activated as part of the delivery stroke of the high-pressure piston pump is decisive for the amount of fuel delivered by means of this high-pressure piston pump. The distance that the piston belonging to the pump has from the bottom dead center when the deflecting device is activated is relevant in this context. The greater the distance, the smaller the amount of fuel delivered.

The deflection device can be an electromagnetically, mechanically, hydraulically or also pneumatically operated deflection device.

If passive valve centering is not provided, the resulting force serves both to move the control piston into an end position and to hold the control piston in this end position and a deflection device is not absolutely necessary. According to a preferred embodiment, active valve centering is then provided.

If the control piston is pressurized by the fuel in the valve housing in such a way that a resulting force acts along the displacement axis, embodiments can be advantageous in which the first high-pressure piston pump is connected to a first pressure chamber of the valve unit and the control piston protrudes into this first pressure chamber .

If the control piston is pressurized by the fuel in the valve housing in such a way that a resulting force acts along the displacement axis, embodiments can also be advantageous in which the second high-pressure piston pump is connected to a second pressure chamber of the valve unit and the control piston is connected to this second pressure chamber protrudes.

A first and / or second pressure chamber makes it easier to give the control piston such a shape that the fuel pressure acting on the control piston leads to pressure differences along the control piston and thus to a resulting force along the displacement axis.

A pressure chamber of the valve unit can also form a common pressure chamber with a working chamber of a high-pressure piston pump. I. E. the first or the second pressure chamber can form a common chamber with the working chamber of the associated high-pressure piston pump. This could minimize the dead volume in most embodiments. This would be beneficial.

However, embodiments of the direct-injection compression-ignition internal combustion engine can also be advantageous in which the control piston is not pressurized by the fuel in the valve housing, so that no resulting force acts along the displacement axis in the direction of an end position.

In the present case, the valve unit is designed in such a way that the control piston is force-free with regard to the fuel located in the valve housing, so that the pressure differences in the fuel do not result in any force along the displacement axis. Then the control piston is a kind of force-relieved slide. To move this slide along the displacement axis, however, an external force is required, which is introduced in a targeted manner from the outside when the slide is to be moved, for example into an end position.

In this context, embodiments of the direct-injection compression-ignition internal combustion engine are advantageous in which a displacement device is provided with which a force can be introduced into the control piston along the displacement axis and the control piston can be displaced into the end positions.

The displacement device introduces a force into the control piston from the outside in order to move the control piston along the displacement axis, to hold the control piston in an end position as long as fuel is to be conveyed or is being conveyed, and to bring about the return of the control piston, d. H. to move the control piston back into the middle position if necessary. There is no need for valve centering at all.

Embodiments of the direct-injection compression-ignition internal combustion engine are advantageous in which each high-pressure piston pump can be connected to the high-pressure side via a separate line. This embodiment ensures that the high-pressure piston pumps can only be or are connected to one another via a valve unit.

In this context, embodiments of the direct-injection compression-ignition internal combustion engine in which a check valve is arranged in each separate line are advantageous. This embodiment makes it possible to bring the separate lines together to form a high-pressure line without the high-pressure piston pumps being fluidically, ie. H. To connect fluidically with each other, in such a way that one high-pressure piston pump conveys into the other high-pressure piston pump.

Embodiments of the direct-injection compression-ignition internal combustion engine are advantageous in which the low-pressure side can at least be connected to a container for storing fuel.

• - eine Ventilzentrierung mit Federelementen vorgesehen ist, die den Steuerkolben entlang der Verschiebeachse in entgegengesetzten Richtungen kraftbeaufschlagen und in die Mittelposition zwingen,
• - die erste Kolbenhochdruckpumpe mit einer ersten Druckkammer der Ventileinheit in Verbindung steht, wobei der Steuerkolben in diese erste Druckkammer hineinragt,
• - die zweite Kolbenhochdruckpumpe mit einer zweiten Druckkammer der Ventileinheit in Verbindung steht, wobei der Steuerkolben in diese zweite Druckkammer hineinragt,
• - der Steuerkolben durch den im Ventilgehäuse befindlichen Kraftstoff druckbeaufschlagt ist, in der Art, dass - zumindest zeitweise - eine resultierende Kraft entlang der Verschiebeachse in Richtung einer Endposition wirkt, und
• - eine Auslenkeinrichtung vorgesehen ist, mit der in den Steuerkolben eine Kraft entlang der Verschiebeachse einleitbar ist, womit der Steuerkolben aus der Mittelposition auslenkbar ist,

wird gelöst mit einem Verfahren, das dadurch gekennzeichnet ist, dass ausgehend von einem in der Mittelposition befindlichen Steuerkolben zwecks Förderung von Kraftstoff von der Niederdruckseite auf die Hochdruckseite der Steuerkolben unter Verwendung der Auslenkeinrichtung in die erste Endposition gebracht wird, damit

• - unter Verwendung der ersten Kolbenhochdruckpumpe, die in der ersten Endposition mit der Niederdruckseite verbunden ist, Kraftstoff im Rahmen eines Saughubes von der Niederdruckseite angesaugt wird, und
• - unter Verwendung der zweiten Kolbenhochdruckpumpe, die in der ersten Endposition von der Niederdruckseite getrennt ist, Kraftstoff im Rahmen eines Förderhubes auf die Hochdruckseite gefördert wird.

The second sub-task on which the invention is based, namely to show a method for operating a direct-injection compression-ignition internal combustion engine of the type described above with two high-pressure piston pumps, in which

• - a valve centering with spring elements is provided, which force the control piston along the displacement axis in opposite directions and force it into the central position,
• - the first high-pressure piston pump is connected to a first pressure chamber of the valve unit, the control piston protruding into this first pressure chamber,
• - the second high-pressure piston pump is connected to a second pressure chamber of the valve unit, the control piston protruding into this second pressure chamber,
• - The control piston is pressurized by the fuel located in the valve housing in such a way that - at least temporarily - a resultant force acts along the displacement axis in the direction of an end position, and
• - A deflection device is provided with which a force can be introduced into the control piston along the displacement axis, with which the control piston can be deflected from the central position,

is achieved with a method which is characterized in that, starting from a control piston located in the middle position, the control piston is brought into the first end position using the deflection device for the purpose of conveying fuel from the low-pressure side to the high-pressure side, so that

• - Using the first high-pressure piston pump, which is connected to the low-pressure side in the first end position, fuel is sucked in from the low-pressure side as part of a suction stroke, and
• - Using the second high-pressure piston pump, which is separated from the low-pressure side in the first end position, fuel is delivered to the high-pressure side as part of a delivery stroke.

What has already been said for the internal combustion engine according to the invention also applies to the method according to the invention, which is why reference is generally made at this point to the statements made above with regard to the internal combustion engine. The various internal combustion engines sometimes require different process variants.

The pistons of the two high-pressure piston pumps oscillate between their bottom dead center and their top dead center in opposite directions, preferably with a phase difference of 180 °.

Method variants are advantageous in which the deflection device is deactivated as soon as the fuel pressure generated in the associated second pressure chamber using the second high-pressure piston pump located in the delivery stroke is sufficiently high to hold the control piston in the first end position.

• - unter Verwendung der zweiten Kolbenhochdruckpumpe, die in der zweiten Endposition mit der Niederdruckseite verbunden ist, Kraftstoff im Rahmen eines Saughubes von der Niederdruckseite angesaugt wird, und
• - unter Verwendung der ersten Kolbenhochdruckpumpe, die in der zweiten Endposition von der Niederdruckseite getrennt ist, Kraftstoff im Rahmen eines Förderhubes auf die Hochdruckseite gefördert wird.

Method variants are advantageous in which, starting from a control piston located in the middle position, the control piston is brought into the second end position using the deflection device for the purpose of conveying fuel from the low-pressure side to the high-pressure side

• - Using the second high-pressure piston pump, which is connected to the low-pressure side in the second end position, fuel is sucked in from the low-pressure side as part of a suction stroke, and
• - Using the first high-pressure piston pump, which is separated from the low-pressure side in the second end position, fuel is delivered to the high-pressure side as part of a delivery stroke.

In this context, process variants are advantageous in which the deflection device is deactivated as soon as the fuel pressure generated in the associated first pressure chamber using the first high-pressure piston pump located in the delivery stroke is high enough to hold the control piston in the second end position.

Method variants are advantageous in which the amount of fuel delivered by means of a high-pressure piston pump is set via the distance that the pump-associated piston has from bottom dead center when the deflection device is activated during the delivery stroke of the high-pressure piston pump.

The distance that the piston belonging to the pump has from the bottom dead center when the deflecting device is activated is used for metering the fuel, i. H. for setting the amount of fuel delivered. The greater the distance, the smaller the amount of fuel delivered within the scope of a delivery stroke.

The point in time at which the deflection device is activated as part of the delivery stroke of the high-pressure piston pump is relevant for the amount of fuel delivered.

In this context, process variants are advantageous in which the amount of fuel delivered by the high-pressure piston pump is reduced by increasing the distance between the pump-associated piston and bottom dead center when the deflecting device is activated.

• 1a schematisch als Prinzipskizze ein Fragment des Kraftstoffversorgungssystems einer Brennkraftmaschine nach dem Stand der Technik mit einer Hochdruckpumpe und einer Drossel als Ventileinheit,
• 1b schematisch als Prinzipskizze ein Fragment des Kraftstoffversorgungssystems einer Brennkraftmaschine nach dem Stand der Technik mit mehreren Hochdruckpumpen und einer Drossel als Ventileinheit,
• 2a schematisch als Prinzipskizze ein Fragment des Kraftstoffversorgungssystems einer Brennkraftmaschine nach dem Stand der Technik mit einer Hochdruckpumpe und einem digital schaltbaren Ventil als Ventileinheit,
• 2b schematisch als Prinzipskizze ein Fragment des Kraftstoffversorgungssystems einer Brennkraftmaschine nach dem Stand der Technik mit mehreren Hochdruckpumpen und mehreren digital schaltbaren Ventilen als Ventileinheiten,
• 3a schematisch als Prinzipskizze ein Fragment des Kraftstoffversorgungssystems einer ersten Ausführungsform der Brennkraftmaschine mit Ventileinheit,
• 3b schematisch als Prinzipskizze die Ventileinheit der in 3a dargestellten Ausführungsform mit dem Steuerkolben in der ersten Endposition E₁ ,
• 3c schematisch als Prinzipskizze die Ventileinheit der in 3a dargestellten Ausführungsform mit dem Steuerkolben in der Mittelposition M,
• 4a schematisch die Hubkurven H₁ , H₂ der Kolben, die Bewegungskurve V_piston des Steuerkolbens sowie den Kraftstofffluss Flow₁ , Flow₂ der Kolbenhochdruckpumpen für die in 3a dargestellte Ventileinheit bei Voll-Förderung,
• 4b schematisch die Hubkurven H₁ , H₂ der Kolben, die Bewegungskurve V_piston des Steuerkolbens sowie den Kraftstofffluss Flow₁ , Flow₂ der Kolbenhochdruckpumpen für die in 3a dargestellte Ventileinheit bei einer Teil-Förderung,
• 4c schematisch die Hubkurven H₁ , H₂ der Kolben, die Bewegungskurve V_piston des Steuerkolbens sowie den Kraftstofffluss Flow₁ , Flow₂ der Kolbenhochdruckpumpen für die in 3a dargestellte Ventileinheit bei einer Teil-Förderung,
• 4d schematisch die Hubkurven H₁ , H₂ der Kolben, die Bewegungskurve V_piston des Steuerkolbens sowie den Kraftstofffluss Flow₂ der zweiten Kolbenhochdruckpumpe für die in 3a dargestellte Ventileinheit bei einer Teil-Förderung,
• 5 schematisch als Prinzipskizze die Ventileinheit einer zweiten Ausführungsform der Brennkraftmaschine mit dem Steuerkolben in der Mittelposition M, und
• 6 schematisch als Prinzipskizze die Ventileinheit einer dritten Ausführungsform der Brennkraftmaschine mit dem Steuerkolben in der Mittelposition M.

In the following, the invention is based on five exemplary embodiments and in accordance with FIGS 1a , 1b , 2a , 2 B , 3a , 3b , 3c and 4a , 4b , 4c explained in more detail. Here shows:

• 1a a schematic diagram of a fragment of the fuel supply system of an internal combustion engine according to the prior art with a high-pressure pump and a throttle as the valve unit,
• 1b schematically, as a basic sketch, a fragment of the fuel supply system of an internal combustion engine according to the prior art with several high-pressure pumps and a throttle as a valve unit,
• 2a schematically, as a basic sketch, a fragment of the fuel supply system of an internal combustion engine according to the prior art with a high-pressure pump and a digitally switchable valve as the valve unit,
• 2 B schematically, as a basic sketch, a fragment of the fuel supply system of an internal combustion engine according to the prior art with several high-pressure pumps and several digitally switchable valves as valve units,
• 3a schematically, as a basic sketch, a fragment of the fuel supply system of a first embodiment of the internal combustion engine with valve unit,
• 3b the valve unit of the in 3a illustrated embodiment with the control piston in the first end position E ₁ ,
• 3c the valve unit of the in 3a embodiment shown with the control piston in the central position M. ,
• 4a schematically the lift curves H ₁ , H ₂ the piston, the motion curve V _piston the control piston and the fuel flow Flow ₁ , Flow ₂ of high-pressure piston pumps for the in 3a shown valve unit with full delivery,
• 4b schematically the lift curves H ₁ , H ₂ the piston, the motion curve V _piston the control piston and the fuel flow Flow ₁ , Flow ₂ of high-pressure piston pumps for the in 3a valve unit shown with a partial delivery,
• 4c schematically the lift curves H ₁ , H ₂ the piston, the motion curve V _piston the control piston and the fuel flow Flow ₁ , Flow ₂ of high-pressure piston pumps for the in 3a valve unit shown with a partial delivery,
• 4d schematically the lift curves H ₁ , H ₂ the piston, the motion curve V _piston the control piston and the fuel flow Flow ₂ the second high-pressure piston pump for the in 3a valve unit shown with a partial delivery,
• 5 schematically, as a basic sketch, the valve unit of a second embodiment of the internal combustion engine with the control piston in the central position M. , and
• 6th schematically, as a basic sketch, the valve unit of a third embodiment of the internal combustion engine with the control piston in the central position M. .

the 1a , 1b , 2a and 2b have already been discussed in connection with the prior art, which is why reference is made to the corresponding statements.

3a shows a schematic diagram of a fragment of the fuel supply system 1 a first embodiment of the internal combustion engine including valve unit 2 . The hydraulic symbols are used in some cases. The control piston 2a the valve unit 2 shows 3b in the first end position E ₁ and 3c in the middle position M. .

The fuel supply system shown 1 serves to supply fuel to the cylinders of the internal combustion engine and includes a high-pressure side 1a , a low pressure side 1b as well as the valve unit according to the invention 2 .

Here is the fuel supply system 1 with two high-pressure piston pumps 3a , 3b equipped, each with a piston 10a , 10b have, which is translationally displaceable between a bottom dead center and an upper dead center, ie can oscillate. Any high pressure piston pump 3a , 3b is via a separate line 7a , 7b with the high pressure side 1a connectable, with each separate line 7a , 7b a check valve 8a , 8b is arranged.

The two high-pressure piston pumps 3a , 3b are via valve unit 2 with each other and with the low pressure side 1b connectable. The valve unit has for this purpose 2 via the control piston 2a that is in a valve housing 2 B arranged and along a displacement axis 2c Is mounted translationally displaceable.

In the middle position M. of the control piston 2a are the two high-pressure piston pumps 3a , 3b via valve housing 2 B with each other and in each case with the low-pressure side 1b connected (see 3a and 3c ).

In the first end position E ₁ is the first high-pressure piston pump 3a with the low pressure side 1b connected and from the second high pressure piston pump 3b separated so that using the first high pressure piston pump 3a Fuel as part of a suction stroke from the low-pressure side 1b is or can be sucked in. The second high-pressure piston pump 3b is in the first end position E ₁ from the low pressure side 1b separated, so that for the purpose of fuel delivery using the second high-pressure piston pump 3b Fuel as part of a delivery stroke on the high pressure side 1a is or can be funded (see also 3b) .

In the second end position E ₂ is the second high-pressure piston pump 3b with the low pressure side 1b connected and from the first high pressure piston pump 3a separated so that using the second high pressure piston pump 3b Fuel as part of a suction stroke from the low-pressure side 1b is or can be sucked in. The first high-pressure piston pump 3a is in the second end position E ₂ from the low pressure side 1b separated, so that for the purpose of fuel delivery using the first high-pressure piston pump 3a Fuel as part of a delivery stroke on the high pressure side 1a is or can be funded.

The switching states of the valve unit 2 according to the positions M. , E ₁ and E ₂ of the control piston 2a are in 3a symbolically represented with squares.

3b shows the valve unit schematically as a basic sketch 2 the in 3a illustrated embodiment with the control piston 2a in the first end position E ₁ .

The control piston 2a is of such a shape that the one in the valve housing 2 B on the control piston 2a acting fuel pressure p a resulting force in the direction of the first or the second end position E ₁ , E ₂ can generate. This resulting along the shift axis 2c of the control piston 2a acting force is in 3b used to control the control piston 2a in the first end position E ₁ to keep. In the valve body 2 B are pressure chambers 9a , 9b provided in which the control piston 2a protrudes so that the one in the chambers 9a , 9b present print p on the control piston 2a can work. Differences in pressure generate a resulting force along the displacement axis 2c .

The first high-pressure piston pump 3a stands with the first pressure chamber 9a the valve unit 2 in connection and the second high-pressure piston pump 3b with the second pressure chamber 9b the valve unit 2 . The pressure chambers 9a , 9b could each with the working space of the associated high-pressure piston pump 3a , 3b be designed as an integral chamber.

In the in 3b illustrated first end position E ₁ becomes the control piston 2a from the delivery pressure p ₂ the second high-pressure piston pump 3b , which is located in the delivery stroke for the purpose of fuel delivery, acted upon as well as by the pressure p ₀ the low pressure side 1b . The first high-pressure piston pump 3a is with the low pressure side 1b connected, from the second high-pressure piston pump 3b separated and sucks fuel from the low-pressure side as part of a suction stroke 1b at.

A passive valve centering 4th transfers the control piston 2a at the end of the delivery stroke when the on the control piston 2a attacking pressures equalize, automatically return to the middle position M. . 3c shows the valve unit 2 with the control piston 2a in the middle position M. . The valve centering 4th includes two spring elements 4a , 4b , which is the control piston 2a along the shift axis 2c Apply force in opposite directions and in the middle position M. to force. Here are the spring elements 4a , 4b in the pressure chambers 9a , 9b arranged.

A deflection device 5 is required and provided to the control piston 2a from the middle position M. deflect and at the beginning of the conveying process in one of the two end positions E ₁ , E ₂ to move. Then fuel is used as part of a delivery stroke of a high-pressure piston pump 3a , 3b promoted, the generate on the control piston 2a acting pressure differences a force in the direction of the end position E ₁ , E ₂ who have favourited the control piston 2a in the end position E ₁ , E ₂ holds. The deflection device 5 is deactivated as soon as the pressure conditions on the control piston 2a generate the required holding force.

4a shows schematically the lift curves H ₁ , H ₂ the piston, the motion curve V _piston the control piston and the fuel flow Flow ₁ , Flow ₂ the high-pressure piston pumps for the in 3a Valve unit shown with full delivery.

The pistons of the two high-pressure piston pumps oscillate according to the stroke curves H ₁ , H ₂ each between their bottom dead center UT and their top dead center OT in opposite directions with a phase difference of 180 °. The piston of the first high-pressure piston pump is at bottom dead center UT the piston of the second high-pressure piston pump is at top dead center OT and vice versa. If the first high-pressure piston pump is working in the delivery stroke, the second high-pressure piston pump is in the suction stroke and vice versa.

At the beginning of the delivery process, the control piston is moved using the deflection device by introducing an external force F _ex in one of the two end positions E ₁ , E ₂ postponed. The deflection device 5 is deactivated when the control piston is in the respective end position E ₁ , E ₂ is located. If, for example, fuel is then to be delivered as part of a delivery stroke of the second high-pressure piston pump, the delivery pressure increases p ₂ of the second pump, as shown in the graphic on the right, with fuel being delivered to the high-pressure side as soon as the delivery pressure is reached p ₂ the pressure p _high reached or exceeded on the high pressure side. The curve Flow ₂ illustrates the fuel flow from the second high-pressure piston pump to the high-pressure side.

According to 4a the introduction of the external force takes place F _ex each at bottom dead center UT the high-pressure piston pump with which fuel is to be delivered. In this respect, the control piston does not briefly take the middle position in between M. one, but only alternates between the two end positions E ₁ , E ₂ . As a result, this leads to full funding, ie maximum funding.

the 4b and 4c show different partial grants in which the external force F _ex not in bottom dead center UT a high-pressure piston pump is initiated, but with a certain distance from the bottom dead center UT , ie the associated piston is already in the delivery stroke on the way to top dead center OT . The distance that the piston belonging to the pump from the bottom dead center when the deflection device is activated UT has, determines the amount of fuel delivered by means of this high-pressure piston pump. The greater the distance, the smaller the amount of fuel delivered, as can be seen from the graphic on the right.

The control piston briefly takes the middle position every now and then M. on if between the two end positions E ₁ , E ₂ is changed.

4d shows a partial delivery in which the first high-pressure piston pump is not delivering or is deactivated. The control piston changes between the middle position M. and the first end positions E ₁ . The second end positions E ₂ is not taken, which deactivates the first high-pressure piston pump.

5 shows the valve unit schematically as a basic sketch 2 a second embodiment of the internal combustion engine with the control piston 2a in the middle position M. Only the differences to that in the 3a , 3b and 3c illustrated embodiment will be discussed, which is why in For the rest, reference is made to these figures. The same reference numerals have been used for the same components.

At the in 5 shown valve unit 2 is an active valve centering 4th , 4c provided instead of passive valve centering. The transfer of the control piston 2a in the middle position M. does not take place automatically, but actively by introducing an external displacement force by means of valve centering 4th , 4c . The valve centering 4th , 4c is preferably activated when the pressure differences on the control piston 2a reduce, ie at the end of a conveying process when the pressures equalize.

Becomes an active valve centering 4th , 4c used as in 5 shown, is used on the control piston 2a along the shift axis 2c towards an end position E ₁ , E ₂ acting and from those in the valve body 2 B existing pressure differences resulting force both the displacement of the control piston 2a in an end position E ₁ , E ₂ as well as holding the control piston 2a in this end position E ₁ , E ₂ .

6th shows the valve unit schematically as a basic sketch 2 a third embodiment of the internal combustion engine with the control piston 2a in the middle position M. .

Only the differences to that in the 3a , 3b and 3c illustrated embodiment are discussed, which is why reference is otherwise made to these figures. The same reference numerals have been used for the same components.

At the in 6th shown valve unit 2 has the control piston 2a such a shape that the control piston 2a of those in the valve body 2 B located fuel is not pressurized, in such a way that a resultant force along the displacement axis 2c towards an end position E ₁ , E ₂ would work. The control piston 2a is in terms of the in the valve body 2 B The fuel that is located is therefore free of forces, so that the pressure differences in the fuel do not result in any force along the axis of displacement 2c results.

This is the control piston 2a the 6th around a slider 2a . For moving the control piston 2a along the shift axis 2c is a sliding device 6th provided with an external force along the displacement axis 2c of the control piston 2a can be initiated.

The sliding device 6th directs a force into the control piston from the outside 2a one to the control piston 2a along the shift axis 2c to move and in an end position E ₁ , E ₂ to hold as long as fuel is to be pumped. A valve centering 4th , 4a and 4b transfers the control piston 2a back to the middle position M. .

List of reference symbols

1

Fuel supply system

1a

High pressure side

1b

Low pressure side

2

Valve unit

2a

translationally displaceable control piston

2 B

Valve body

2c

Shift axis

3a

first high-pressure piston pump

3b

second high-pressure piston pump

4th

Valve centering

4a

Spring element

4b

Spring element

4c

active valve centering

5

Deflection device

6th

Sliding device

7a

separate line of the first high-pressure piston pump

7b

separate line for the second high-pressure piston pump

8a

Check valve of the first high-pressure piston pump

8b

Check valve of the second high-pressure piston pump

9a

first pressure chamber, pressure chamber of the first high-pressure piston pump

9b

second pressure chamber, pressure chamber of the second high-pressure piston pump

10a

first piston, piston of the first high-pressure piston pump

10b

second piston, piston of the second high-pressure piston pump

101

Fuel supply system

101a

High pressure side

101b

Low pressure side

102

Valve unit

102a

throttle

102b

digitally switchable valve

103

High pressure piston pump

103a

Pistons

108

check valve

M.

Middle position

E1

first end position

E2

second end position

Fex

external force impulse of the deflection device

Flow1

Fuel flow of the first high-pressure piston pump

Flow2

Fuel flow of the second high-pressure piston pump

H1

Stroke curve of the first piston

H2

Stroke curve of the second piston

OT

Top Dead Center

p

Fuel pressure

p0

Fuel pressure on the low pressure side

p1

Delivery pressure of the first high-pressure piston pump

p2

Delivery pressure of the second high-pressure piston pump

phigh

Fuel pressure on the high pressure side

t

Time

UT

bottom dead center

Vpiston

Movement curve of the control piston

Claims (21)

Direct-injection compression-ignition internal combustion engine with at least one cylinder, in which - each cylinder is equipped with an injection device for the direct introduction of fuel into the cylinder, Low-pressure side (1b) and a valve unit (2), and - the fuel supply system (1) is equipped with at least two high-pressure piston pumps (3a, 3b), each of which has a piston (10a, 10b) that can be moved translationally between a bottom dead center and an upper dead center and can be connected to the high pressure side (1a) and can be connected to the low pressure side (1b) via a valve unit, characterized in that the valve unit (2) has a control piston (2a) which - arranged in a valve housing (2b) and along a displacement axis (2c) is mounted so as to be translationally displaceable, - in a central position (M) via the valve housing (2b) connects the at least two high-pressure piston pumps (3a, 3b) with each other and each with the low-pressure side (1b), - in a first end position (E1) a first high-pressure piston pump (3a) with the low-pressure side ( 1b) connects and separates from the at least one other high-pressure piston pump (3b) and separates a second high-pressure piston pump (3b) from the low-pressure side (1b), and - in a second end position (E2), the second high-pressure piston pump (3b) with the low-pressure side (1b) connects and separates from the at least one other high-pressure piston pump (3a) and separates the first high-pressure piston pump (3a) from the low-pressure side (1b). Direct injection compression ignition internal combustion engine according to Claim 1 , characterized in that only a single valve unit (2) is provided. Direct injection compression ignition internal combustion engine according to Claim 1 or 2 , characterized in that a valve centering (4) is provided for positioning the control piston (2a) in the central position (M). Direct injection compression ignition internal combustion engine according to Claim 3 , characterized in that the valve centering (4) comprises at least one spring element (4a, 4b) which forces the control piston (2a) along the displacement axis (2c) and forces it into the central position. Direct injection compression ignition internal combustion engine according to Claim 4 , characterized in that the valve centering (4) comprises at least two spring elements (4a, 4b) which force the control piston (2a) along the displacement axis (2c) in opposite directions and force it into the central position (M). Direct injection compression ignition internal combustion engine according to Claim 3 , characterized in that the valve centering (4) is an active valve centering (4c). Direct-injection self-igniting internal combustion engine according to one of the preceding claims, characterized in that the control piston (2a) is pressurized by the fuel in the valve housing (2b) in such a way that - at least temporarily - a resulting force along the Shifting axis (2c) acts in the direction of one of the end positions (E1, E2). Direct injection compression ignition internal combustion engine according to Claim 7 , characterized in that a deflection device (5) is provided with which a force can be introduced into the control piston (2a) along the displacement axis (2c), whereby the control piston (2a) can be deflected from the central position (M). Direct injection compression ignition internal combustion engine according to Claim 7 or 8th , characterized in that the first high-pressure piston pump (3a) is connected to a first pressure chamber (9a) of the valve unit (2), the control piston (2a) protruding into this first pressure chamber (9a). Direct injection compression ignition internal combustion engine according to one of the Claims 7 until 9 , characterized in that the second high-pressure piston pump (3b) is connected to a second pressure chamber (9b) of the valve unit (2), the control piston (2a) protruding into this second pressure chamber (9b). Direct injection compression ignition internal combustion engine according to one of the Claims 1 until 6th , characterized in that the control piston (2a) is not pressurized by the fuel in the valve housing (2b), so that no resulting force acts along the displacement axis (2c) in the direction of one of the end positions (E1, E2). Direct injection compression ignition internal combustion engine according to Claim 11 , characterized in that a displacement device (6) is provided with which a force can be introduced into the control piston (2a) along the displacement axis (2c) and the control piston (2a) can be displaced into the end positions (E1, E2). < Direct-injection self-igniting internal combustion engine according to one of the preceding claims, characterized in that each high-pressure piston pump (3a, 3b) can be connected to the high-pressure side (1a) via a separate line (7a, 7b). Direct injection compression ignition internal combustion engine according to Claim 13 , characterized in that a check valve (8a, 8b) is arranged in each separate line (7a, 7b). Direct-injection self-igniting internal combustion engine according to one of the preceding claims, characterized in that the low-pressure side (1a) can at least be connected to a container for storing fuel. Method for operating a direct-injection compression-ignition internal combustion engine according to Claim 1 with two high-pressure piston pumps (3a, 3b), in which - a valve centering (4) with spring elements (4a, 4b) is provided, which force the control piston (2a) along the displacement axis (2c) in opposite directions and into the central position (M) force - the first high-pressure piston pump (3a) is connected to a first pressure chamber (9a) of the valve unit (2), the control piston (2a) protruding into this first pressure chamber (9a), - the second high-pressure piston pump (3b) with a second The pressure chamber (9b) of the valve unit (2) is connected, the control piston (2a) protruding into this second pressure chamber (9b), - the control piston (2a) is pressurized by the fuel in the valve housing (2b), in the manner that - at least temporarily - a resultant force acts along the displacement axis (2c) in the direction of an end position, and - a deflection device (5) is provided with which a force along the displacement in the control piston (2a) ebaxle (2c) can be introduced, with which the control piston (2a) can be deflected from the central position, characterized in that, starting from a control piston (2a) located in the central position, for the purpose of conveying fuel from the low-pressure side (1b) to the high-pressure side (1a) the control piston (7) is brought into the first end position using the deflection device (5) so that - using the first high-pressure piston pump (3a), which is connected to the low-pressure side (1a) in the first end position (E1), fuel in the frame a suction stroke from the low-pressure side (1a), and - using the second high-pressure piston pump (3b), which is separated from the low-pressure side (1b) in the first end position, fuel is conveyed to the high-pressure side (1a) as part of a delivery stroke. Procedure according to Claim 16 , characterized in that the deflection device (5) is deactivated as soon as the fuel pressure generated in the associated second pressure chamber (9b) using the second high-pressure piston pump (3b) in the delivery stroke is sufficiently high to put the control piston (2a) in the first end position to keep. Procedure according to Claim 16 or 17th , characterized in that, starting from a control piston (2a) located in the central position (M) for the purpose of conveying fuel from the low-pressure side (1b) to the high-pressure side (1a), the control piston (2a) using the deflection device (5) into the second End position (E2) is brought so that - using the second high-pressure piston pump (3b), which is connected to the low-pressure side (1b) in the second end position, fuel is sucked in from the low-pressure side (1b) as part of a suction stroke, and - using the first high-pressure piston pump (3a), which is shown in the second end position is separated from the low-pressure side (1b), fuel is delivered to the high-pressure side (1a) as part of a delivery stroke. Procedure according to Claim 18 , characterized in that the deflection device (5) is deactivated as soon as the fuel pressure generated in the associated first pressure chamber (9a) using the first high-pressure piston pump (3a) in the delivery stroke is sufficiently high to put the control piston (2a) in the second end position (E2) to hold. Method according to one of the Claims 16 until 19th , characterized in that the amount of fuel delivered by means of a high-pressure piston pump (3a, 3b) is set via the distance that the pump-associated piston (10a, 10b) from when the deflection device (5) is activated during the delivery stroke of the high-pressure piston pump (3a, 3b) has bottom dead center. Procedure according to Claim 20 , characterized in that the amount of fuel delivered by the high-pressure piston pump (3a, 3b) is reduced by increasing the distance between the piston (10a, 10b) belonging to the pump and the bottom dead center when the deflecting device (5) is activated.

Images