EP1799999B1 - Fuel system for an internal combustion engine - Google Patents

Description

State of the art

The invention relates to a fuel system for an internal combustion engine, with a fuel pump which promotes from a low pressure region in a high pressure region, with a metering device, with a reaching to the fuel pump volumetric flow can be changed with a pressure limiting device which limits a pressure in the high pressure region and on the one side by a spring and on the other side acted upon by the pressure prevailing in the high-pressure region valve element, and with a coupling device which mechanically at least temporarily and at least indirectly couples an actuator of the metering device at least temporarily.

The invention also provides a method for operating a fuel system, and a method for producing a fuel system.

A fuel system of the type mentioned is from the EP 0 974 008 B1 known. The force acting in the closing direction of the pressure limiting device spring is supported in the known fuel system on a valve spool of the metering device. When the metering device is open, the spring is compressed, which leads to a correspondingly higher opening pressure of the pressure limiting device. When the metering device is closed, the spring is largely relaxed, so that the pressure limiting device is open.

This fuel system has the disadvantage that a large stroke of the valve spool of the metering device is required to cause a change in the opening pressure of the pressure limiting device. In addition, in this fuel system the Pressure limiting function of Druckbegrerizungseinrichtung when the maximum holding pressure of the pressure limiting device in case of failure is less than the allowable pressure in the high pressure area, limited. If the maximum holding pressure of the pressure limiting device in the event of a fault is greater than the permissible pressure in the high pressure region, an additional pressure limiting device must be used.

From the DE 196 12 413 A1 a fuel system is known in which the metering device can act directly on a valve element of a pressure relief device in the Öffriungsrichtung. As a result, the high pressure area can be depressurized in an emergency. In this fuel system, a pressure limiting device must additionally be provided for securing the high-pressure region.

The EP 0 809 016 A1 describes a fuel system with a piezoelectrically actuated metering device. The piezoelectric actuator of the metering device can act simultaneously with the closed metering device as an actuator of a relief valve and open this forcibly.

General is still on the EP 0 299 337 A2 and the EP 0 837 986 B1 directed.

Object of the present invention is to develop a fuel system of the type mentioned so that it can be produced inexpensively, compact builds, and the safety and reliability is guaranteed in all operating situations.

This object is achieved by a fuel system having the features of claim 1.

In a method and a computer program of the type mentioned, the object is achieved accordingly.

Advantages of the invention

In the fuel system according to the invention, only a single pressure limiting device is required, which serves as a safety device for the protection of the high-pressure area, and which, secondly, for setting a desired pressure in the high pressure range can be used with closed or almost closed metering device. In this case, no additional actuator for the operation of the pressure limiting device is required, since this is the actuator of the metering device is used.

At the same time, the actuating device of the metering device does not have to carry out a particularly large additional stroke in order to influence the pressure in the high-pressure region, since this influencing is not or at least not substantially accomplished by a stroke but by a force acting in the opening direction of the valve element of the pressure-limiting device. The normal opening pressure of the pressure limiting device can be set to a constant above a maximum occurring during normal operation of the fuel system fuel pressure, but below a critical pressure, for example, would lead to damage of the parts used in the high pressure area, or in which a function of injectors, which are connected to the high pressure area, is no longer guaranteed. This safety function is not affected by the coupling with the actuator.

At the same time, the pressure limiting device can be used by the defined force that can exert the actuator of the metering device on the valve element of the pressure limiting device, also to an active pressure reduction or pressure control in certain operating situations of the fuel system. Such active pressure reduction is, for example, desirable in a coasting operation or when the internal combustion engine is switched off, in order to have a lower pressure available when the internal combustion engine is put back into service. In addition, a pressure reduction after switching off the engine for safety reasons and in the event of failure, service, or crash advantage.

Advantageous developments of the invention are specified in subclaims.

A first advantageous embodiment of the fuel system according to the invention provides that the coupling device only at least indirectly acts on the valve element of the pressure limiting device with the force when the metering device is completely closed. This has the advantage that in normal operation, the pressure in the high-pressure region can be controlled or regulated exclusively by the volume flow control by means of the metering device. Such a fuel system works with very high efficiency.

Alternatively, it is also possible that the coupling device, the valve element of the pressure limiting device already then at least indirectly applied to the force when the metering device is not completely closed. In this case, for example, is for lubrication or cooling the fuel pump a certain minimum volume flow available.

The fuel system according to the invention is particularly compact when the metering device and the pressure limiting device are integrated in a common housing, in particular in a housing of the fuel pump.

It is further proposed that the metering device comprises a valve slide on which a driver is attached or formed, which can engage a corresponding driver, which is coupled to the valve element of the pressure limiting device. Such an embodiment of the fuel system according to the invention is simple and inexpensive to implement.

If the valve spool is received in a cylinder element and at its end facing away from the actuator has a pressure piece which can be pressed into the cylinder element and preferably receives the sealing seat of the pressure limiting device, it is possible to adjust the opening pressure of the pressure limiting device by a defined pressing of the pressure element in the cylinder element. Thus, the individual components may be subject to higher tolerances, which reduces the manufacturing costs. Nevertheless, the opening pressure of the pressure limiting device can be optimally adjusted.

A development of the invention provides that the valve spool is connected via a connecting element with the actuating device. In this way, the fuel system can be mounted in a particularly flexible manner and at the same time a possibly existing axial offset between the actuator and the valve spool can be compensated.

But it is also possible that parts of the actuating device and the valve slide are integrally formed, whereby the number of components can be reduced.

If the connection between the connecting element and the actuating device and / or between the connecting element and the valve slide is formed as a latching connection, the assembly of the elements designed as particularly simple and fast.

In a further development of the invention, it is proposed that the pressure-limiting device comprises a plunger, which is coaxial with the valve slide, or a coaxial coupling element which is at least temporarily coupled to the valve element and to which the driver is present. Consequently certain liberties remain in the design of the valve element.

In a further development for this purpose, it is proposed that the plunger or the coaxial coupling element are integral with the valve element and preferably the driver. This reduces the manufacturing and in particular the assembly costs.

It when the coupling element has at least one support structure for the driver, which is latchably inserted into the valve spool is particularly advantageous. This construction makes it possible that the coupling element can be inserted into the valve slide, without a driver would have to be mounted separately.

Particularly advantageous is that embodiment of the inventive Kraflstoffsystems, wherein the valve spool of the metering device comprises a cavity into which the plunger or the coupling element protrudes and which forms a flow path for the outflowing when the pressure relief valve fuel. This also leads to a particularly compact design of the fuel system according to the invention, and moreover, the production costs are reduced because additional external channels are not required.

In a further development for this purpose, it is proposed that the cavity is connected via at least one opening in the valve slide with the inlet of the metering device. Thus, the fluid flowing out when the pressure limiting device is open can flow off directly into the fuel line present upstream of the inlet of the metering device, so a separate return line is not required. This again reduces the construction volume and the manufacturing costs.

In a method according to the invention, it is particularly advantageous if the force acting in the opening direction of the valve element of the pressure-limiting device depends on a current pressure prevailing in the high-pressure region. The pressure limiting device can thus be used in this case for a regulation of the pressure prevailing in the high pressure region.

When the fuel method is manufactured according to one of the inventive methods for producing a fuel system, the assembly of the fuel system designed as particularly simple and flexible. In particular, a reference volume flow of the Metering unit and the opening pressure of the Druckbegenzungseinrichtung be easily adjusted and / or adapted.

drawings

Figur 1

eine schematische Darstellung eines ersten Ausführungsbeispiels eines Kraftstoff-systems einer Brennkraftmaschine mit einer Zumesseinrichtung und einer mit dieser gekoppelten Druckbegrenzungseintichtung;

Figur 2

eine hervorgehobene Darstellung der Zumesseinrichtung und der Druckbegrenzungseinrichtung von Figur 1;

Figur 3

eine Darstellung ähnlich Figur 1 einer alternativen Ausführungsform eines Kraftstoffsystems;

Figur 4

ein Diagramm, in dem ein durch die Zumesseinrichtung strömender Volumenstrom, ein Öffnungsdruck der Druckbegenzungseinrichtung, und ein Stellhub einer Betätigungseinrichtung der Zumesseinrichtung über einer von der Betätigungseinrichtung ausgeübten Kraft aufgetragen sind;

Figur 5

einen teilweisen Schnitt durch eine konkrete Ausführungsform der Zumesseinrichtung und der Druckbegrenzungseinrichtung von Figur 1 in einem ersten Betriebszustand;

Figur 6

eine Darstellung ähnlich Figur 5, in einem zweiten Betriebszustand;

Figur 7

eine perspektivische Darstellung eines Elements der Druckbegrenzungseinrichtung der Figuren 5 und 6;

Figur 8

eine perspektivische Darstellung eines Mitnehmers der Zumesseinrichtung der Figuren 5 und 6;

Figur 9

einen teilweisen Schnitt durch eine weitere konkrete Ausführungsform der Zumesseinrichtung und der Druckbegrenzungseinrichtung bei Anordnung in einem Pumpengehäuse;

Figur 10

einen Ausschnitt aus Figur 9;

Figur 11

eine perspektivische Darstellung eines Elements der Druckbegrenzungseinrichtung gemäß Figuren 9 und 10;

Figur 12

eine perspektivische Darstellung eines Mitnehmers der Zumesseinrichtung gemäß Figuren 9 und 10; und

Figur 13

eine perspektivische Darstellung von Montagegruppen der Ausführungsform gemäß Figuren 9 bis 12.

Hereinafter, particularly preferred embodiments of the present invention will be explained in more detail with reference to the accompanying drawings. In the drawing show:

FIG. 1

a schematic representation of a first embodiment of a fuel system of an internal combustion engine having a metering device and coupled to this Druckbegrenzungseintichtung;

FIG. 2

a highlighted representation of the metering device and the pressure limiting device of FIG. 1 ;

FIG. 3

a representation similar FIG. 1 an alternative embodiment of a fuel system;

FIG. 4

a diagram in which a volume flow flowing through the metering device, an opening pressure of the Druckbegenzungseinrichtung, and a Stellhub an actuator of the metering device are applied to a force exerted by the actuator force;

FIG. 5

a partial section through a concrete embodiment of the metering device and the pressure limiting device of FIG. 1 in a first operating state;

FIG. 6

a representation similar FIG. 5 in a second operating state;

FIG. 7

a perspective view of an element of the pressure limiting device of FIGS. 5 and 6 ;

FIG. 8

a perspective view of a driver of the metering device of FIGS. 5 and 6 ;

FIG. 9

a partial section through another specific embodiment of the metering device and the pressure limiting device when arranged in a pump housing;

FIG. 10

a section from FIG. 9 ;

FIG. 11

a perspective view of an element of the pressure limiting device according to Figures 9 and 10 ;

FIG. 12

a perspective view of a driver of the metering device according to Figures 9 and 10 ; and

FIG. 13

a perspective view of mounting groups of the embodiment according to FIGS. 9 to 12 ,

Description of the embodiments

In FIG. 1 a fuel system carries the overall reference numeral 100. It comprises a fuel tank 1, which is connected via a feed line 2 with a prefeed pump 3. This pumps the fuel via a delivery line 4 into a control unit 5, to which reference will be made in detail below. In this a fuel flow is adjusted and passed via a line 6 to a high-pressure pump 7. The lines 4 and 6 are part of a low pressure area. Downstream of the feed pump 3 is connected to the delivery line 4, not shown in the figure mechanical pressure control valve, which ensures a defined inlet pressure of the high-pressure pump 7. From the pressure control valve, a return line, also not shown, leads back to the fuel tank 1.

In the high-pressure pump 7, the fuel is compressed to a high pressure. From the high-pressure pump 7, the fuel passes under high pressure via a delivery line 8 into a high-pressure accumulator 9 (common rail), which both form a high-pressure region. This is connected to injection valves 10, which inject the fuel in only symbolically shown combustion chambers 11 of an internal combustion engine (without reference numeral).

Via a line 12, the control unit 5 is hydraulically connected to the high-pressure accumulator 9. At the high-pressure accumulator 9, a pressure sensor 13 is further arranged, which is connected via a data line 14 with a control and regulating device 15. This is also connected via a data line 16 to the control unit 5. Via data lines 17 and 18, the control and regulating device 15 also receives signals from various sensors of the internal combustion engine.

In FIG. 2 the control unit 5 is shown highlighted. It comprises a metering device 102 and a pressure limiting device 24. The fuel passes from the fuel reservoir 1 via the line 4 into the control unit 5. A throttle slide 20 of the metering device 102 measures the fuel, which then reaches the high pressure pump 7 via the line 6. The throttle valve is positioned by an electromagnetic actuator 21 ("actuator") operating against a spring 22.

In normal operation, the pressure limiting device 24 is closed; a spring 25, which in the Figures 1 and 2 invisible valve element of the pressure control device 24 is acted upon in the closing direction, is correspondingly strongly biased. The metering device 102 and the pressure control device 24 can be coupled together by two drivers 23 and 26. These two drivers form a coupling device 106 so far.

The first driver 23 is fixedly connected to the throttle slide 20 of the metering device 102 and the second driver 26 with the valve element of the pressure limiting device 24.

In order to reduce the opening pressure of the pressure limiting device 24, the electromagnetic actuator 21 of the throttle slide 20 has the driver 23 so far in the Figures 1 and 2 move to the right that he hits the driver 26 of the pressure limiting device 24 and exerts on this a force acting against the force acting in the closing direction of the pressure limiting device 24 force of the spring 25. In total, this reduces the opening force or the opening pressure of the pressure limiting device 24. If the opening pressure of the pressure limiting device 24 drops to a value below the pressure of the high-pressure accumulator 9, fuel is diverted into the line 4 via the pressure regulating valve to the reservoir 1 until the pressure in the high-pressure accumulator 9 has dropped so far, that it corresponds to the reduced opening pressure, which leads to the closing of the pressure limiting device 24.

FIG. 3 shows a variant of the fuel system 100. It bear such elements and areas, which equivalent functions to elements and areas of Figures 1 and 2 have the same reference numerals. They are not explained again in detail.

Compared to the fuel system 100 after FIG. 1 Here, the amount of fuel diverted by the pressure limiting device 24 is conducted via a separate line 19 to the fuel tank 1. The pressure limiting device 24 and the metering device 102 are thus not directly connected to each other hydraulically. An advantage of this embodiment may lie in a better fuel cooling.

In FIG. 4 is the basic course of a flow rate Q through the throttle slide 20 of the metering device 102, the course of an opening pressure p of the pressure limiting device 24, and a control stroke s of the electromagnetic actuator 21 plotted on the force F. The electromagnetic actuator 21 is formed by a proportional magnet. A force F _i after FIG. 4 thus corresponds to a current flow I _i of an electromagnet 37. In the area between the forces F ₁ and F ₂ which are generated by the electromagnetic actuator 21, is set by the metering device 102 of the reaching to the high-pressure pump 7 Flow Q, in which the flow cross-section of the throttle slide 20 is varied by a corresponding positioning of the electromagnetic actuator 21. The stroke s of the throttle slide 20 is between s ₁ and s ₂ .

When the force F ₂ and the stroke s ₂ , the flow cross-section of the throttle valve 20 is closed. If the force F is further increased, the throttle slide 20 shifts by a neutral lift from the stroke s ₂ to the stroke s _3rd At a corresponding force F ₃ and the stroke s ₃ of the driver 23 102 contacts the metering device to the carrier 26 of the pressure-limiting device 24. If the force F is now increased further, this counteracts the force acting in the closing direction of the pressure-limiting device 24 of the spring 25, thereby the opening pressure of the pressure limiting device 24 is lowered. When the electromagnetic actuator 21 generates a force F ₄ , prevail, still at a control stroke s ₃ , equilibrium between the force acting in the closing direction spring 25 of the pressure limiting device 24 and the of Driver 23 and 26 applied in the opening direction force, the opening pressure of the pressure limiting device 24 is therefore zero in this case.

Opens the pressure limiting device 24, when the pressure in the high-pressure accumulator 9 is above the opening pressure of the pressure limiting device 24, there is an additional control stroke, which, however, is very low. Only in the case of very large quantities, which are diverted by the pressure limiting device 24, does a relevant additional stroke result, which, however, is altogether small with respect to the control stroke s ₂ or s ₃ .

In the present embodiment, the force F ₃ is larger than the force F _2, since in normal operation the control of the pressure prevailing in the high pressure accumulator 9 is realized exclusively by the flow variation means of the metering device 102nd In the event that the throttle slide 20 in the closed state lets through a relevant amount of leakage to the high-pressure pump 7, if no fuel is injected from the injection valves 10, for example, in overrun mode of the internal combustion engine or when the internal combustion engine, the excess amount of fuel via the pressure relief device 24 dissipated. The control can be done both controlled and regulated. In a pressure control, the pressure in the high-pressure accumulator 9 is reported by the pressure sensor 13 to the control and regulating device 15 and compared with a desired value. In the event of a deviation, the drive for the electromagnetic actuator 21 is recalculated and output.

In a variant embodiment, not shown, the force F ₃ , in which the driver 23 of the metering device 102 starts to engage the driver 26 of the pressure limiting device 24, smaller than the force F ₂ , in which the metering device 102 is fully closed. When the force F ₂ is reached, the valve element of the pressure-limiting device 24 is thus opened by the stroke s ₂ -s ₃ . Thus, when the pressure limiting device 24 is open, a certain fuel volume flow continues to the high-pressure pump 7. This may be necessary for reasons of lubrication or cooling of the high-pressure pump 7. Again, the removal of excess fuel can be controlled or regulated.

The adjustment of the force exerted by the electromagnetic actuator 21 force can be carried out according to a computer program, which is stored in the control and regulating device 15 on a storage medium.

The FIGS. 5 and 6 show a concrete embodiment of the control unit 5, wherein FIG. 5 shows an operating state in which the metering device 102 is decoupled from the pressure limiting device 24, whereas FIG. 6 shows an operating state in which the metering device 102 is coupled to the pressure limiting device 24.

The throttle or valve spool 20 includes a piston 30 having a control edge 27 which is slidably received in a cylinder 31 forming a housing. The driver 23 is fixed in the form of a disc in a slot (without reference numeral) of the piston 30. An inlet port 33 is hydraulically with in the FIGS. 5 and 6 not shown line 4 connected. An outlet opening 32 is hydraulically with in the FIGS. 5 and 6 also not shown line 6, which leads to the high-pressure pump 7.

In the de-energized state of the solenoid 37, the spring 22 presses a magnet armature 34 together with the piston 30 on a spacer 35, which is supported on the cylinder 31. In this state, the outlet opening 32 is open, so that the fuel can pass from the inflow bore 33 via the outlet opening 32 to the high-pressure pump 7. In addition to the magnetic coil 37 and the armature 34 of the electromagnetic actuator 21 includes in a conventional manner a counter-pole 38 which is connected via a preferably non-magnetic sleeve 39 with a connecting piece 36, which in turn is fixedly connected to the cylinder 31. For magnetic return and for fixing the solenoid coil 37 is a pot 40th

The pressure limiting device 24 comprises those already in connection with the FIGS. 1 and 3 said spring 25, which is supported on a disc-shaped spring holder 41. This is welded to a plunger 108, at one end of a spherical valve element 42 is attached. This works together with a stationary and rigidly connected to the cylinder 31 sealing seat 43. At the remote from the valve element 42 end of the plunger 108 is already out of the FIGS. 1 and 3 known driver 26 attached in the form of an end plate on the plunger 108. Their annular end face facing the valve element 42 forms a shoulder 51. The annular disk 23 and the end disk 26 thus form the coupling device 106.

The end plate 26 forming the driver of the pressure limiting device 24 has on its lateral surface two mutually opposite flattenings 52 (cf. FIG. 7 ). The plunger 108 of the pressure limiting device 24 also has a flattening 53 between the valve element 42 and the spring holder 41. The spring holder 41 shows several Through holes 54. Their function will be discussed below. Valve element 42, plunger 108, spring holder 41 and end plate 26 are made in one piece.

Like from the FIGS. 5 and 6 apparent, the piston 30 is in his in the FIGS. 5 and 6 left area with a coaxial with its longitudinal axis and stepped cavity 48. In this projecting the plunger 108 with the driver or the end plate 26 into it. The drive plate 23, which in detail in FIG. 8 is shown on the in the FIGS. 5 and 6 left end of the piston 30 in a slot (without reference numeral) of the wall of the piston 30 is inserted, wherein a bore 55 in the drive plate 23 in the installed position serves as a guide for the plunger 108 of the pressure limiting device 24. For mounting the drive plate 23, this has a slot 56. In installation position, the end plate 26 of the pressure limiting device 24 is located within the cavity 48 between the drive plate 23 and the piston 30th

In a first axial position of the piston 30 are a plurality of holes 48 leading outwardly from the cavity 48 (see. FIG. 6 ). Its axial position is selected so that the cavity 48 is always connected to the inlet openings 33 in the cylinder 31, regardless of the position of the piston 30. Toward the electromagnetic actuator 21, in the piston 30, at a different axial position of the piston 30, there are again several bores 50 leading radially outward from the cavity 48. These are axially positioned so that they connect via the cavity 48 and the holes 49 a space (without reference numeral), in which the magnet armature 34 is arranged, with the inlet openings 33 fluidly.

For sealing the individual elements and areas against each other different sealing elements are provided. Sealing elements 44 and 45 serve to seal between a low-pressure region of the metering device 102 and a high-pressure region of the pressure-limiting device 24. A sealing element 46 serves to seal between the inlet openings 33 and the outlet openings 32. A sealing element 47 serves to seal off the in the FIGS. 5 and 6 illustrated unit to the outside.

The control unit 5 shown in FIGS. 5 and 6 operates as follows:

The spring 22 acts on the armature 34 and connected to this piston 30 in the FIGS. 5 and 6 to the left. In the de-energized state of the solenoid 37 is thereby the Magnetic armature 34 pressed against the spacer 35, through which the open end position of the metering device 102 is defined. In this state, fuel passes unthrottled from the conduit 4, the inlet openings 33, and the outlet openings 32 to the conduit 6 and on to the high-pressure pump 7.

If less than the maximum possible amount of fuel is to be delivered by the high-pressure pump 7, the magnetic coil 37 is energized. As a result, the armature 34 is against the force of the spring 22 in the FIGS. 5 and 6 moved to the right, which causes the piston 30 moves with the control edge 27 partially over the outlet openings 32, which leads to a throttling of reaching the high-pressure pump 7 fuel flow. Another corresponding energization of the solenoid 37 such that the piston 30 a stroke s ₃ accordingly FIG. 4 causes causes the drive plate 23 connected to the piston 30 of the metering device 102 just touches the shoulder 51 on the end plate 26 of the pressure limiting device 24 forming the driver (this state is shown in FIG FIG. 6 shown).

If the current is increased again, the excess magnetic force on the piston 30, the drive plate 23, the end plate 26 and the plunger 108 is transmitted to the valve element 42 and acts, together with the pressure applied in the line 12 high pressure, against the force of the spring 25. Overall, the holding force of the valve element 42 is thus reduced on the sealing seat 43 in this way, resulting in a corresponding reduction of the opening pressure of the pressure limiting device 24.

If the pressure in the line 12 exceeds the opening pressure of the pressure limiting device 24, the fuel flows between the sealing seat 43 and the valve element 42, the flattening 53 on the plunger 108, the bores 54 in the spring holder 41, and the flats 52 on the end plate 26 in the Cavity 48 into it. From there, the fuel passes through the holes 49 and the inlet openings 33 in the line 4. In this case, the line 4 is constantly connected via the holes 50 with the space (without reference numeral), in which the magnet armature 34 is arranged.

How out FIG. 6 it can be seen, in the state in which the two drivers 23 and 26 are coupled together, the control edge 27 is arranged on the piston 30 so that the outlet openings 32 are completely closed. This allows a rapid pressure reduction in the high pressure accumulator 9 by opening the pressure relief device 24, without that of the High pressure pump 7 further fuel is pumped into the high-pressure accumulator 9. However, if, for example, for cooling or lubrication of the high-pressure pump 7, even with open pressure limiting device 24 still reach a certain Krflstoffstrom from the outlet port 32 to the high pressure pump 7, the control edge 27 must be positioned relative to the drive plate 23 accordingly different.

It should be noted at this point that the lowering of the opening pressure of the pressure limiting device 24 by a corresponding energization of the electromagnet 37 is especially in question when the engine is operating in overrun mode and the injectors 10 do not retrieve fuel from the high-pressure accumulator 9, and at switched off internal combustion engine. It should also be noted that the control of the electromagnet 37 can also take place in the context of a closed loop on the basis of the signals that are transmitted from the pressure sensor 13 via the data line 14 to the control and regulating device 15. It should also be noted that the cylinder 31 forms a common housing for the metering device 102 and the pressure limiting device 24.

In FIG. 9 is a further embodiment of the metering device and the pressure limiting device shown in the arrangement in a pump housing, these are together part of a fuel system 100 '.

The fuel system 100 'comprises a metering device, designated as a whole by 102', which can be actuated by an actuating device 21 'and can be coupled to a pressure-limiting device 24'.

The actuating device 21 'has an electrical connection 201 in order to be able to energize a magnetic coil 202. The magnet coil 202 is arranged on a winding support 203, which in turn is arranged in a magnet pot 40 '.

The actuating device 21 'further comprises a magnetic armature 34' which is connected to a magnetic needle 211. The magnetic needle 211 is mounted in bushings 35 'and 35 ", and the bushing 35' is received in a connecting piece 36 'which has one end in the actuating device 21' and at its other end in its pump housing 110 is included. The bush 35 "is received in a counter-pole element 38 ', which is connected to a closing element 205 of the actuating device 21'.

The connecting piece 36 'is fastened via a weld 103 to the already mentioned pump housing 110. The weld 103 seals the pump housing 110 to the outside. The pump housing is shown only in sections and takes the metering unit 102 'and the pressure limiting device 24' on.

The pump housing 110 is supplied with fuel via the delivery line 4 and passes into a first annular space 60 via the metering device 102 'to a second annular space 62 and from there to an inlet valve 64. The inlet valve 64 is followed by a working space 66 of a pump piston 68. The pump piston 68 can be driven via a cam 70 so that high pressure can be applied to fuel present in the working space 68 and can be fed to the delivery line 8 via an outlet valve 72.

The pressure limiting device 24 'has at its end remote from the actuating device 21' a pressure piece 260 which is pressed into a bore 58 which is provided in the pump housing 110. From the bore 58, a line 74 leads to the delivery line 8 in the high pressure region of the fuel system 100 '.

Regarding FIG. 10 the construction of the metering unit 102 'and the pressure-limiting device 24' will be explained in detail. The connecting piece 36 'is in FIG. 10 shown only in sections and has on the pressure limiting device 24 'side facing a cylindrical receptacle 218, in which a flange of a cylinder member 31' is pressed and secured there by means of a flanging 219. The cylinder element 31 'serves to receive a valve slide 30', which is acted upon by a spring 22 'with a compressive force. The spring 22 'relies on its in FIG. 10 right end to the valve spool 30 'and at its in FIG. 10 left end on the connecting piece 36 'from.

The cylinder element 31 'has an inlet opening 33', which over the in FIG. 9 shown annular space 60 is connected to the line 4.

The cylinder element 31 'further has an outlet opening 32' which extends beyond the in FIG. 9 shown annular space 62 with a line (without reference numeral) is in communication, the Inlet valve 64 leads. The seal between the annular spaces 60 and 62 via a seal 46 ', which is provided on the outside of the cylinder member 31'.

The valve spool 30 'is connected via a connecting element 220 to the actuating device 21' or via a needle head 212 to the magnetic needle 211 of the actuating device 21 '. The connecting element 220 also points in FIG. 11 shown holding elements 221, between which recesses 223 are provided, so that the holding elements 221 are yielding in the radial direction. Thus, the needle head 212 of the magnetic needle 211 is latchingly inserted into the connecting element 220.

The connecting element 220 has on the side facing away from the needle head 212 a total of four holding elements 222, between which recesses 224 are also provided. The holding elements 222 are elastically yielding, so that they can dodge radially inward and can be used in the valve slide 30 'to there a in FIG. 10 shown paragraph 231 with projections 225 engage behind latching.

In the valve slide 30 'is an elongated, centrally arranged cavity 48' is provided. In this cavity emerges a generally designated 280 coupling element, which is a in FIG. 12 having 284 designated carrier structure 284 for driver 26 '. The support structure 284 is elongated and elastic, so that the coupling element 280 can be inserted latching in the valve slide 30 '. The coupling element 280 has on its side facing away from the drivers 26 'a spring holder 41' on which a spring 25 'is supported. This spring is supported at its other end on an annular shoulder 244 of the cylinder member 31 'from.

Adjacent to the spring plate 41 'and the support structure 284 facing away from the coupling element 280 has a cylindrical guide portion 283 which dips into the already mentioned pressure piece 260. The pressure piece 260 is pressed in via a press-fit surface 261 in the cylinder element 31 '.

Adjacent to the guide section 283, a ball cage 272 is provided, in which a valve element 42 'formed as a ball is received. The valve element 42 'forms the sealing body for a sealing seat 43'. The sealing seat 43 'is pressed into the pressure piece 260 via a press-fit surface 264. The pressure piece itself is about a press-in 263 in the in FIG. 9 shown bore 58 of the pump housing 110 is pressed.

In the Figures 9 and 10 the metering unit 102 'and the pressure limiting device 24' are shown in their unactuated state. The metering unit 102 'delivers in this unactuated state a maximum flow rate, since a control edge 27' (see. FIG. 10 ) of the valve spool 30 'produces an unthrottled connection between inlet port 33' and outlet port 32 '. The valve spool 30 'is held in this position by means of the spring 22'. When the actuating device 21 'is energized, the magnet armature 34' is moved together with the magnetic needle 211 in the direction of the end element 205 of the actuating device 21 '. In this case, the spring 22 'is compressed. The magnetic needle 211 can transmit the movement to the valve spool 30 'via the needle head 212 and the connecting element 220. Thus, the control edge 27 ', the outlet port 32' gradually close, so that the volume flow supplied to the downstream pump is throttled.

After the outlet opening 32 'is completely covered by the control edge 27' of the valve slide 30 ', passes in the valve slide 30' trained driver 23 'in engagement with the drivers 26' of the coupling element 280. If the actuator 21 'now energized even higher, can via the driver 23 'of the valve slide 30', the driver 26 'of the coupling element 280 and finally on the spring holder 41' a compressive force in the spring 25 'are introduced. In this state, the pressure limiting device 24 'is still closed. On the valve element 42 'acts on the one hand an opening force due to the fuel which rests in the bore 58 in the high pressure region of the pump and on the other hand, a residual residual force of the spring 25', the guide portion 283 presses against the valve element 42 'via the spring holder 41'. By further energization of the actuator 21 'gradually higher forces are introduced into the spring 25' until the coupling element 280 is finally moved away from the sealing seat 43 ', so that the valve element 42' opens. In this condition, high pressure fuel may pass from the bore 58 via the valve element 42 'around the spring retainer 41' and past the support members 284 into the cavity 48 'of the valve spool 30'. From there, the fuel can then have an in FIG. 10 designated 243 via the inlet port 33 'in the low pressure region of the fuel system 100' are discharged.

The described Absteuerung of fuel can be done, for example. In overrun mode or when switching off the engine. The Absteuerung can also be done when the fuel demand of the internal combustion engine is smaller than the leakage amount between Valve spool 30 'and the cylinder member 31' is formed. However, it is preferred if the Absteuerung takes place only in overrun mode or when switching off the internal combustion engine.

When assembling the fuel system 100 ', an in FIG. 13 a total of 290 designated assembly unit are made, which is composed of a magnet assembly 291 and a hydraulic assembly 292. The latter includes, inter alia, the connecting piece 36 ', the cylinder element 31', the pressure piece 260 and the sealing seat 43 '. The magnet assembly comprises the magnet pot 40 'with the electrical connection 201 and also the termination element 205.

The assembly of the fuel system 100 'will be described in detail below. First, the armature 34 'is pressed by a defined amount on the magnetic needle 211. Then, the bush 35 "is press-fitted into the opposite pole 38 'and the bush 35' is pressed into the joint 36. Thereafter, the magnetic needle 211 is inserted into the bushings 35 'and 35". Subsequently, the opposite pole 38 'and the connecting piece 36' are pressed into a sleeve 215. The adjustment of the stroke of the magnet armature 34 'takes place by pressing the opposite pole 38' and / or the connecting piece 36 'by a defined amount on the sleeve 215.

In a subsequent assembly step, the connector 220 is inserted into the valve slide 30 'detent, wherein provided on the holding elements 222 projections 225 engage behind the valve slide 30' provided paragraph 231 latching. Before the valve spool 30 'is connected to the magnetic needle 211 or its needle head 212, the spring 22' in the connector 36 'is inserted. Subsequently, the connecting piece 220, which is already connected to the valve slide 30 ', is pressed onto the needle head 212 so that it is latched within the holding elements 221. Between the connecting piece 220 and the needle head 212 or between the connecting piece 220 and the valve slide 30 ', a radial clearance may be present in order to be able to compensate for a deagification between said components.

In a subsequent assembly step, the valve slide 30 'is inserted into the space 243 formed in the cylinder element 31'. In this case, the cylinder element 31 'is pre-pressed into the receptacle 218 of the connecting piece 36'.

In order to be able to set a specific control behavior of the metering unit 102, the hydraulic module produced up to this point in time can be inserted into a test device and be adjusted so that a predetermined or desired volume flow (reference volume flow) results. The hydraulic assembly is flowed through with a test medium. With the aid of a magnetic coil of the test device, the spring 22 'is acted upon by a defined force, wherein the control edge 27' of the valve spool 30 'occupies a defined position. The adjustment to the reference volume flow takes place by the cylinder element 31 'is pressed further into the receptacle 218 of the connecting piece 36' until the reference volume flow is established. After completion of this process, the cylinder member 31 'by means of flanging 219 on the connecting piece 36' additionally be secured.

Alternatively, an adjustment of the control behavior can also be made by the positions of the components to be positioned to each other are detected by a laser. It is provided that the cylinder member 31 'within the receptacle 218 of the connecting piece 36' is displaced until a predetermined distance between the inlet port 33 'and / or outlet port 32' to the control edge 27 'is made. This distance corresponds to a predetermined volume flow.

The inlet opening 33 'and the outlet opening 32' can also be integrated in the valve slide 30 ', wherein the control edge is then formed by the cylinder element 31'. Also in this case, the setting of a desired control behavior as described above can be done with a test medium or by optical measurement.

In a following step, the Druckbegenzungseinrichtung 24 'is mounted. First, the spring 25 'in the cylinder member 31' is inserted. Subsequently, the coupling element 280 in the spring 25 'and the valve slide 30' is used until the driver 26 'engage in recesses 232 which are formed in the valve slide 30'. In this case, the spring 25 'comes with the spring plate 41' in Appendix.

Finally, the sealing seat 43 'is pre-pressed into a bore 265 formed in the pressure piece 260. The valve element 42 'and the ball cage 272 are inserted into the pressure piece 260. Finally, the pressure piece 260 is pressed into the cylinder element 31 'via the press-fit surface 261.

The setting of the opening pressure of the Druckbegenzungseinrichtung 24 'can be done without the pressure limiting device 24' is coupled to the metering unit 102 '. For this In this case, the maximum opening pressure of the pressure-limiting device 24 'can be set precisely. In order to be able to form an association between the opening pressure of the pressure limiting device 24 'and the position of the valve slide 30' and the corresponding activation of the actuating device 21 'in this case, it is proposed to actuate the actuating device 21' by means of an in FIG. 1 adapted to adjust control and regulating device and save. For this purpose, the actuating device 21 'can be supplied with a reference current and, in this state of the actuating device 21', an actual pressure value in the high-pressure region of the fuel system 100 'can be detected. This actual pressure value may vary from an in FIG. 1 pressure sensor 13 are detected, are transmitted to the control or regulating unit 15 to be compared there with a stored in the control and / or regulating device desired pressure value can. From the difference value between the detected actual pressure value and the stored desired pressure value, the energization of the actuating device 21 'can be adjusted. The adaptation can be carried out once, for example during commissioning of the internal combustion engine, but can also be carried out continuously or at certain time intervals, for example in order to be able to compensate for changes in the components during a long service life.

The opening pressure of the pressure limiting device 24 'can also take place if it is mechanically coupled to the metering unit 102'. In this case, a desired opening pressure correlates with a certain magnetic force, which can be applied, for example, by a mounting coil. In this case, an association between the actuation of the actuating device 21 'and thus the position of the magnet armature 34' and the valve slide 30 'with the opening pressure of the pressure limiting device 24' is determined in the event that the pressure limiting device 24 'is coupled to the metering unit 102' ,

For both options shown for adjusting the opening pressure of the pressure limiting device 24 ', the setting of the opening pressure by defined pressing of the sealing seat 43' takes place in the pressure piece 260th

In a subsequent assembly step, the sealing element 46 'is mounted on the cylinder element 31'.

The assembly of the magnet assembly 291 ( FIG. 13 ) is carried out by winding the coil 202 onto the winding support 203. The coil 202 with the winding support 203 become relative positioned to the magnet pot 40 'and molded with a plastic material. At the same time, the electrical connection 201 is formed.

The assembly of the thus formed hydraulic assembly 292 and the magnet assembly 291 in the pump housing 110 is carried out as follows: First, the hydraulic assembly 292 is inserted into the pump housing 110. When mounting the hydraulic assembly 292, the pressure piece 260 is pressed into the bore 58 of the pump housing 110. On the one hand, a fuel-tight connection can be achieved by the pressure and, on the other hand, the pressure force acting on the pressure piece 260 can be introduced into the pump housing 110. The hydraulic assembly 292 can be pressed into the pump housing 110 until the connecting piece 36 'with a stop 266 formed in the pump housing 110 (FIG. FIG. 9 ) comes to the plant. The required press-in force can, for example, be introduced via the connecting piece 36 '. By the sealing element 46 ', the annular spaces 60 and 62 are sealed to each other.

After the hydraulic assembly 292 has been inserted into the pump housing 110, the connector 36 'is fixed to the pump housing 110 by means of the weld 103. The weld 103 forms a fuel-tight connection.

Subsequently, the magnet assembly 291 is joined to the hydraulic assembly 292. For this purpose, the pot 40 'is pressed onto the connecting piece 36'. In a final assembly step, the closing element 205 is pressed onto the opposite pole 38 '.

Claims (22)

1. Fuel system (100) for an internal combustion engine, with a fuel pump (7) which conveys from a low-pressure region (4, 6) into a high-pressure region (8, 9), with a metering device (102), by means of which a volume flow arriving at the fuel pump (7) can be varied, with a pressure-limiting device (24) which limits a pressure in the high-pressure region (8, 9) and has a valve element (42) acted upon on one side by a spring (25) and on the other side by the pressure prevailing at a high-pressure region (8, 9), and with a coupling device (106) which mechanically couples an actuating device (21) of the metering device (102) at least temporarily and at least indirectly to the pressure-limiting device (24), the metering device (102) comprising a valve slide (29) which is positioned by an electromagnetic actuator (21) and by means of which the volume flow arriving at the fuel pump (7) can be varied, characterized in that, with the metering device (102) closed or almost closed, the coupling device (106) acts at least indirectly upon the valve element (42) of the pressure-limiting device (24) with a force acting in the opening direction of the pressure-limiting device (24), in such a way that the holding force of the valve element (42) on a sealing seat (43) is reduced and a reduction in the opening pressure of the pressure-limiting device (24) is thus brought about, but no forced opening.
2. Fuel system (100) according to Claim 1, characterized in that the coupling device (106) acts at least indirectly upon the valve element (42) of the pressure-limiting device (24) with the force only when the metering device (102) is completely closed.
3. Fuel system (100) according to Claim 1, characterized in that the coupling device (106) acts at least indirectly upon the valve element (42) of the pressure-limiting device (24) with the force even when the metering device (102) is not yet closed completely.
4. Fuel system (100) according to one of the preceding claims, characterized in that the metering device (102) and the pressure-limiting device (24) are integrated into a common housing (31), in particular into a housing (110) of the fuel pump (7, 66-70).
5. Fuel system (100, 100') according to one of the preceding claims, characterized in that the metering device (100) comprises a valve slide (30, 30'), on which is fastened or formed a dog (23, 23') which can engage on a corresponding dog (26, 26') which is coupled to the valve element (42, 42') of the pressure-limiting device (24, 24').
6. Fuel system (100, 100') according to Claim 5, characterized in that the valve slide (30') is received in a cylinder element (31') and has at its end facing away from the actuating device (21') a thrust piece (260) which is pressed into the cylinder element (31') and which preferably receives the sealing seat (43') of the pressure-limiting device (24').
7. Fuel system (100, 100') according to Claim 5 or 6, characterized in that the valve slide (30') is connected to the actuating device (21') via a connection element (220).
8. Fuel system (100, 100') according to Claim 6 or 7, characterized in that the connection between the connection element (220) and the actuating device (21') and/or between the connection element (220) and the valve slide (30') is designed as a latching connection.
9. Fuel system (100, 100') according to Claims 5 to 8, characterized in that the pressure-limiting device (24, 24') comprises a tappet (108) coaxial to the valve slide (30, 30') or a coaxial coupling element (280) which is coupled at least temporarily to the valve element (42, 42') and on which the dog (26, 26') is present.
10. Fuel system (100, 100') according to Claim 9, characterized in that the tappet (108) or the coaxial coupling element (280) is in one piece with the valve element (42, 42') and preferably with the dog (26, 26').
11. Fuel system (100, 100') according to Claim 9 or 10, characterized in that the coupling element (280) has at least one carrier structure (284) for the dog (26'), which carrier structure can be inserted into the valve slide (30') in a latching manner.
12. Fuel system (100, 100') according to one of Claims 5 to 11, characterized in that the valve slide (30, 30') of the metering device (102, 102') comprises a cavity (48, 48'), into which the tappet (108) or the coupling element (280) projects and which forms a flow path for the fuel which flows out when the pressure-limiting valve (24, 24') is open.
13. Fuel system (100) according to Claim 12, characterized in that the cavity (48) is connected to the inlet (33) of the metering device (102) via at least one orifice (49) in the valve slide (30).
14. Method for operating a fuel system (100) according to one of the preceding claims, characterized in that the actuating device (21) is activated such that, with the metering device (102) closed or almost closed, it exerts a defined force in the opening direction of the valve element (42) of the pressure-limiting device (24), without forcibly opening the latter.
15. Method according to Claim 14, characterized in that, in an overrun operating mode and/or with the internal combustion engine switched off, the actuating device (21) exerts the force acting in the opening direction of the valve element (42) of the pressure-limiting device (24).
16. Method according to either one of Claims 14 and 15, characterized in that the force is dependent on a current pressure prevailing in the high-pressure region (8, 9).
17. Method according to one of Claims 14 to 16, characterized in that the actuating device (21) is activated by a control and/or regulating device (15) for an internal combustion engine.
18. Method for producing a fuel system (100') according to one of Claims 5 to 13, characterized in that the setting of a desired control behaviour of the metering unit (102') takes place in that a cylinder element (31') surrounding the valve slide (30') is pressed into a receptacle (218) of the actuating device (21') such that a reference volume flow or a predetermined dimension is achieved.
19. Method for producing a fuel system (100') according to one of Claims 6 to 13, characterized in that the setting of the opening pressure of the pressure-limiting device (24') takes place in that the sealing seat (43') of the pressure-limiting device (24') is pressed into the thrust piece (26') by a variable amount.
20. Method according to Claim 19, characterized in that the setting of the opening pressure takes place when the pressure-limiting device (24') is coupled to the metering unit (102').
21. Method according to Claim 20, characterized in that the setting of the opening pressure takes place when the pressure-limiting device (24') is uncoupled from the metering unit (102').
22. Method according to either one of Claims 20 and 21, characterized in that the setting of the opening pressure takes place in that, when a reference current is applied to the actuating device (21'), an actual pressure value is detected in the high-pressure region of the fuel system (100'), the differential value between the detected actual pressure value and a desired pressure value stored in the control and/or regulating device (15) is formed by means of the control and/or regulating device, and the application of current to the actuating device (21') is adapted on the basis of the differential value.

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