EP1275845A2 - High pressure fuel pump - Google Patents

Abstract

The pump incorporates a fastener, e.g. a screw (58) to hold the cylinder head (14) with its ring-shaped contact face (44) on the cylinder (12). The contact face and the active area (64) of the screw on the cylinder head are mainly located on the same level, as seen in longitudinal direction of the cylinder. The screw is clamped between a ring-shaped fastener part (52) and the cylinder head. The fastener ring has a fastener flange (69) to connect the fuel pump to a housing (26) in the engine.

Description

State of the art

The invention relates to a fuel pump, in particular High pressure fuel pump for a fuel system Internal combustion engine with gasoline direct injection, with one Piston, with drive means for driving the piston, with a cylinder in which the piston is guided with a Cylinder head on the cylinder with a total annular contact surface rests, and with at least a fastener with which the cylinder head with the applied annular contact surface against the cylinder becomes.

Such a fuel pump is known from the market. at it is the cylinder between the cylinder head and one Flange element jammed, which in turn on the engine block the internal combustion engine is attached. The flange element is clamped to the cylinder head with screws.

The present invention has the task of a Fuel pump of the type mentioned above to further develop that they are manufactured cheaper can.

This task is the beginning of a fuel pump mentioned type solved in that the annular Contact area and the effective area of the fastener on the cylinder head, seen in the longitudinal direction of the cylinder, in Are essentially at the same level.

Advantages of the invention

The fuel pump according to the invention has the advantage that a cheaper fastener can be used with which the cylinder head with the annular contact surface is applied against the cylinder. The reason for that is that the fastener has smaller forces must record. This is based on the following consideration:

Fasteners work with the part to be fastened usually not the same in the entire contact area Measurements together. Generally there is an effective range in which the predominant portion of power transmission he follows. The distance between the two effective areas a fastener can be called "free length" describe.

Are, as is the case with the prior art, the annular contact surface and the effective range of the Fasteners on the cylinder head, in the longitudinal direction of the Cylinder seen, not at the same height, but are seen in the longitudinal direction, spaced from each other, adds up when the cylinder head heats up expansion of the cylinder head caused by the heating to the "free" length of the fastener. The holding power of the fastener is thus when the Fuel pump lower. To compensate for this, the Fasteners in the idle state of the fuel pump when so this is cold, the cylinder head with very high force against the cylinder, especially when warm Operating state of the fuel pump is the cylinder head has expanded, still adequate To be able to provide the application force.

However, if, as is the case according to the invention, the annular contact surface and the effective range of the Fasteners on the cylinder head essentially same height, a change in length of the Cylinder head not or only insignificantly on the Loading force by the fastener between the cylinder head and the cylinder. The actual position of the effective range of the In this case, the fastener remains in Seen longitudinal direction of the cylinder, opposite the cylinder essentially the same even with a change in temperature. Since there is no change in the temperature change Loading force by the fastener is expected, it is no longer required Fastener to choose which at rest when so the fuel pump is cold, a very high one Can provide a force of application. Thus a Fasteners are used, which is cheaper what the cost of the fuel pump overall lowers.

Advantageous developments of the invention are in Subclaims specified.

In a first training it says that the Fuel pump comprises an annular fastening part, which is supported at least indirectly on the cylinder, the fastener between the fastener and the cylinder head is clamped. With such a annular fastener can be avoided on the cylinder itself, which is generally made of a hard Material is made, for example, bores or threads must be introduced on which the fastener can attack. Ultimately, the ring-shaped Fastening part the manufacture of the actual cylinder simplified or cheaper.

It is particularly preferred if the annular Fastening part in the area of the internal combustion engine supports the facing end of the cylinder on the cylinder and includes a mounting flange with which the Fuel pump on a housing of the internal combustion engine can be attached. Such a fastener thus also serves as the mounting flange Fuel pump on the housing of the internal combustion engine, for example on Engine block or on the crankcase, and for attaching the Cylinder head on the cylinder of the fuel pump. The cylinder even in this case no holes or Have openings at which the corresponding Can attack fasteners.

But it is also possible that the ring-shaped Fastening part in the area of the cylinder head supports the facing end of the cylinder on the cylinder. In in this case the fasteners do not run over the entire length of the cylinder, but the attachment of the Cylinder head takes place only in the area of the Cylinder head facing end of the cylinder.

A particularly easy and inexpensive to implement Attachment of the fastening part to the cylinder can be done in it exist that the fastener on one Ring element supports which on a circumferential groove in Cylinder is arranged. Again, it is preferred that the angular position of the fastener relative to the Cylinder is specified by a pin which is in corresponding recesses in the cylinder and in Fastening part engages. The said circumferential groove is just as easily into the hard cylinder material as the recesses for the pen.

A screw is preferably used as the fastening means Question which one in a threaded hole in the cylinder head is screwed in. Under certain circumstances commercially available screws are used, which are inexpensive are available. The effective areas of the screw lie here on the one hand with the screw head and on the other hand on the outside End of the area screwed into the threaded hole.

An optimal seal between the cylinder head and the The cylinder is achieved in that the annular Contact surface is designed as a bite edge. Possibly. can there is even no need for additional sealants. This simplifies the production again and reduces the Production costs.

But it is also possible that the cylinder head one Cylinder radially surrounding at least in some areas Apron section has that opposite the cylinder is sealed by an annular seal, between which Apron section and the cylinder an annulus available which is with a low pressure range of Fuel pump is connected. With this fuel pump is an optimal seal between the cylinder head and Cylinder achieved. Should there be a leak at the Bite edge come, the leakage fluid through the Ring seal prevented from escaping. The ring seal will in the process of too great a load from the connection of the annulus with the low pressure area of the Fuel pump protected.

Alternatively, it is possible that the cylinder head on Cylinder is fastened by means of at least one screw, which penetrates the annular contact surface and with a thread in the cylinder or cylinder head works together, which directly to the contact area is adjacent. In this case, the Cylinder head on the cylinder is not caused by tension between a fastening part and the cylinder head, but by screwing the Cylinder head on the cylinder.

If the thread, as provided according to the invention, is immediately adjacent to the contact surface, then also the effective range of the thread generally the first few turns to which Contact area immediately adjacent. This one too Fuel pump according to the invention thus occurs in a Heating of the fuel pump and with it associated expansion of the cylinder head and / or the Cylinder does not change the preload force Screws or an application force between Cylinder head and cylinder, so that inexpensive screws can be used.

In further training for this it is proposed that the Fuel pump includes a mounting flange with which attach the fuel pump to the internal combustion engine can be, which engages a ring element which in a circumferential groove is arranged in the cylinder, the Angle position of the mounting flange with a pin is specified, which in corresponding recesses in the Cylinder and in the mounting flange.

This means that only those threads have to be inserted on the cylinder which are used to attach the cylinder head required are. To attach the fuel pump the internal combustion engine is only the introduction of one Ring groove on the cylinder required. This is also the case with one hard cylinder material relatively inexpensive possible. As well the angular position of the mounting flange relative to the Cylinder through the inventive design to simple and inexpensive way set.

If several screws are provided over the circumference some should have a right and some should have a Left-hand thread. The distribution is preferred in half. Then tighten the screws at the same time the total torsional element is equal to or close to zero what the Danger of warping the cylinder or the Cylinder head reduced.

Basically, the ring-shaped contact surface with an annular shoulder on the cylinder can interact. Ultimately, this means that the axial position of the Effective range or the contact area at any axial position with respect to the longitudinal axis of the cylinder can be provided. The fuel pump can thus be switched on different installation conditions in a simple way and Way to be adjusted.

It is also suggested that the fuel pump be on High-pressure connector part, which is on the cylinder head attached, preferably screwed into this. Since the Cylinder head generally made of a rather soft material is made, whereas the cylinder due to the high Pressure loads tend to be made of a hard material is the introduction of the for the attachment of the High-pressure connector required tapping relatively easy.

It is again preferred that the high-pressure connecting part is sealed in or on the cylinder. This leads to the high pressure area on the actual Cylinder is limited, so those parts made up of a less hard material, not through the high pressure will be charged.

In this regard, it is particularly advantageous if the Cylinder steel and the cylinder head and / or that Fastener or aluminum fasteners comprises or comprise. Through the use of aluminum the weight of the fuel pump can be reduced being used for the cylinder which also for high pressures required strength remains guaranteed. Furthermore, threads can be used in aluminum, for example Fastening of parts (e.g. high pressure connection) easier be cut, what the manufacturing costs again lowers.

drawing

Figur 1

einen teilweisen Längsschnitt durch ein erstes Ausführungsbeispiel einer Kraftstoffpumpe;

Figur 2

eine Ansicht in Richtung des Pfeiles II von Fig. 1;

Figur 3

eine Darstellung ähnlich Fig. 1 eines zweiten Ausführungsbeispiels einer Kraftstoffpumpe;

Figur 4

eine Darstellung ähnlich Fig. 1 eines dritten Ausführungsbeispiels einer Kraftstoffpumpe;

Figur 5

eine Darstellung ähnlich Fig. 1 eines vierten Ausführungsbeispiels einer Kraftstoffpumpe;

Figur 6

eine Darstellung ähnlich Fig. 1 eines fünften Ausführungsbeispiels einer Kraftstoffpumpe; und

Figur 7

eine Darstellung eines Kraftstoffsystems mit einer Kraftstoffpumpe entsprechend der Figuren 1 - 6.

Particularly preferred exemplary embodiments of the invention are explained in detail below with reference to the accompanying drawing. The drawing shows:

Figure 1

a partial longitudinal section through a first embodiment of a fuel pump;

Figure 2

a view in the direction of arrow II of Fig. 1;

Figure 3

a representation similar to Figure 1 of a second embodiment of a fuel pump.

Figure 4

a representation similar to Figure 1 of a third embodiment of a fuel pump.

Figure 5

a representation similar to Figure 1 of a fourth embodiment of a fuel pump.

Figure 6

a representation similar to Figure 1 of a fifth embodiment of a fuel pump. and

Figure 7

a representation of a fuel system with a fuel pump according to Figures 1-6.

Description of the embodiments

A fuel pump carries in total in Fig. 1 Reference numeral 10. The fuel pump 10 includes one Cylinder 12, on which a cylinder head 14 is placed. A quantity control valve is in turn on the cylinder head 14 16 put on. A piston 18 is guided in the cylinder and sealed by a piston seal 19. This is about a tappet 20 from an eccentric 22 one Drive shaft 24 is reciprocated. The Fuel pump 10 is to be shown in more detail and manner on a housing 26 of an internal combustion engine (not shown) attached.

The cylinder 12 has an overall circular cylindrical shape and comprises an upper section 28 with a smaller one in FIG. 1 Diameter, a central section 30 with a larger Diameter and a lower section 32 in FIG. 1 again with a smaller diameter. Between the top Section 28 and middle section 30 is a paragraph 34 formed, and between the central portion 30 and the lower portion 32 of the cylinder 12 is a shoulder 36 available. The cylinder 12 is made of steel. In the upper section 28 of the cylinder 12 is from the side a radially extending stepped bore 38 is driven in, into which a high-pressure connection 40 is inserted and via a O-ring seal 42 is sealed.

The cylinder head 14 is overall a bell-shaped part educated. With its lower end face 44 in FIG. 1 it lies against the shoulder 34 of the cylinder 12. Compared to the Cylinder 12 is the cylinder head 14 through an O-ring seal 46 sealed. In the upper area in FIG. 1 of the cylinder head 14 is a radially extending bore 48 introduced, which is a low pressure connection. The cylinder head 14 is open at the top. In the opening the quantity control valve 16 is inserted and this is attached to the cylinder head 14 by means of screws 50. The Screws 50 are only indicated by dash-dotted lines in FIG. 1.

Around the lower portion 32 of the cylinder 12 is a annular fastening part 52 arranged. Whose Inner diameter corresponds approximately to the outer diameter of the lower section 32 of the cylinder 12. The annular Fastening part 52 bears against shoulder 36 of cylinder 12. In the annular fastening part 52 are on the circumference distributed introduced several stepped bores 54. These are formed so that a head 56 one in them Tension screw 58 can be added. The tension screw 58 is with its threaded portion 60 in a threaded bore 62 screwed into the cylinder head 14. That way the cylinder 12 between the cylinder head 14 and the annular fastening part 52 are jammed.

For this purpose, the clamping screws 58 are in the threaded holes 62 screwed into the cylinder head 14 and between the Fastening part 52 and the cylinder head 14 clamped. As is known, the effective range lies between the Threaded section 60 of the clamping screw 58 and Threaded bore 62 in the cylinder head 14 in the area of the outer End of the threaded bore 62. This effective range contributes to Fig. 1, reference numeral 64. In the longitudinal direction of the cylinder 12 seen (the longitudinal axis carries in Fig. 1 Reference number 66) is therefore the annular contact surface 44 of the cylinder head 14 to the cylinder 12 approximately same height as the effective area 64.

The attachment of the fuel pump 10 to the cylinder 12 is carried out by screws 68, which only in Fig. 1 are indicated by dash-dotted lines. Through these screws 68 the annular fastening part 52 with a Flange section 69 on the housing 26 of the internal combustion engine screwed. The seal between the annular Fastening part 52 and the cylinder 12 is made by a O-ring seal 74. The attachment of the high pressure connection 40 takes place on cylinder head 14. The high pressure connection 40 has lateral fastening tabs 70 for this purpose on (see FIG. 2), which by means of screws 72 in corresponding threaded holes (not visible) in the Cylinder head 14 are screwed in.

Now the second shown in Fig. 3 Exemplary embodiment of a fuel pump 10 referred. In this as well as in the following Embodiments carry such elements and areas what equivalent functions to elements and areas the in Figs. 1 and 2 described Have embodiment, the same Reference numerals. They are not explained in detail again. For the sake of illustration, the reference symbols are also not always drawn in for all elements.

In contrast to that shown in Fig. 1 The embodiment shown in FIG. 3 has Cylinder 12 no sections with different Diameter, but is as a straight cylindrical Part trained. The seal between the cylinder head 14 and the cylinder 12 is done by a on the cylinder head 14 formed annular biting edge 44, which by the Tensioning screws 58 against an upper end face 34 of the Cylinder 12 is pressed.

Approximately from the axial position of the bite edge 44 extends from an upper portion 80 of the Cylinder head 14 an apron section 82 in the axial Direction towards the annular fastener 52. At the lower end of the apron section 82 in FIG. 3 there is an annular web 84 pointing radially inwards, via an O-ring seal 46 opposite the cylinder 12 is sealed.

Is between the skirt portion 82 and the cylinder 12 an annular space 86 is present. This is about one Relief channel 88 with the low pressure inlet 48 connected. One on the inner surface of the cylinder 12 existing relief groove 89 is obliquely behind connecting channel 90 running radially outside and above connected to the annular space 86.

Another difference from that shown in FIG. 3 Embodiment of a fuel pump 10 to the in the FIGS. 1 and 2 shown embodiment relates the seal of the piston 18 to the housing 26 of the Internal combustion engine. During the sealing ring 19 in the the fig. 1 and 2 illustrated embodiment in a stage (without reference numerals) in the cylinder 12 is, the sealing takes place in that shown in Fig. 3 Embodiment through the inclusion of the piston seal 19 into the annular fastening part 52.

After the annular fastening part 52 made of aluminum is the corresponding stepped bore in this can be introduced more easily than into the cylinder 12, which is made of a hard steel. The ring-shaped Fastening part 52 is thus part of the seal of the Piston 18 relative to the housing 26 of the internal combustion engine and is opposite the cylinder 12 via O-rings 74a, 74b on the one hand and the housing 26 of the internal combustion engine sealed. Furthermore, in the piston 18 in the area of his in Fig. 3 upper end of a circumferential groove (without Reference numerals) into which a retaining ring 92 to secure the piston 18 against loss, for example for transport the piston pump 10 is inserted.

Another difference concerns the arrangement of the High pressure connection: This can be done with the one shown in Figure 3 illustrated embodiment in the cylinder head 14th screwed in and sealed against this. In Figure 3 is only the corresponding one Location hole (without reference number), but not the Corresponding high-pressure connection (reference number in FIG. 1 40) and the corresponding seal (in FIG. 1 Reference number 42).

4 is another embodiment of a Fuel pump 10 shown. In contrast to the one in 3 shows the embodiment shown Cylinder head 14 in Fig. 4 no apron section. Instead, the upper section 80 of the Cylinder head 14 only one axially over a short Distance-shaped guide ring 82 is formed, which opposite the cylinder 12 by an O-ring seal 46 is sealed.

Instead of the relief groove 89 in the cylinder 12 is in the the embodiment shown in Fig. 4 the annular Fastening part 52 is formed such that that section the through opening in the annular fastening part 52, which lies directly above the piston seal 19, is radially spaced somewhat from the piston 18. That one formed space between the annular Fastening part 52 and the piston 18 acts as Relief chamber 88, which via a connecting channel 90 in a manner not shown in FIG. 4 with the low pressure inlet 48 (or not in one illustrated embodiment with one to one Fuel tank leading return line) connected is. In this way, the piston seal 19 is also relieved. At the same time, the relief groove in the Cylinder 12, which further simplifies its manufacture.

The shown in Figures 3 and 4 Embodiments are, in contrast to that in the Figures 1 and 2 illustrated embodiment, in With regard to the simplest design without stepped pistons executed. The expected higher pressure pulsation when suctioning, if necessary, by arranging a Pilsationsdampfers are smoothed in the inlet.

In the embodiment shown in Fig. 5 one A fixing ring 52 is provided in the fuel pump 10, that in the region of the upper end of the cylinder 12 in FIG. 5 this is arranged radially surrounding. In the area of his is a circumferential groove (without Reference numerals) into which a retaining ring 96 is used. This in turn supports a paragraph (without reference number) on the inner surface of the Fastening ring 52 from. The clamping screws 58 with which the cylinder head 14 acts against the cylinder 12 is between the mounting ring 52 and the Cylinder head 14 clamped. Sealing the Cylinder head 14 opposite the cylinder 12 takes place in the 5 shown by an O-ring seal 46, which in an annular groove (without Reference numeral) is used in the cylinder head 14.

A flange 69 is made in two parts in FIG. 5. On Part 69a of the flange 69 serves as a pure clamping ring on the one hand via screws 68 on the housing 26 Internal combustion engine is attached and on the other hand a circlip 98 supports, which in a circumferential groove (Without reference number) is inserted in the cylinder 12. To one clear and defined angular position of the cylinder 12 to be able to ensure relative to the clamping ring 69a a centering pin 100 is provided, which in corresponding Recesses (without reference numerals) on the one hand in the cylinder 12 and on the other hand engages in the clamping ring 69a.

The other part 69b of the flange 69 is used for sealing between the cylinder 12, the piston 18 and the housing 26 the internal combustion engine. That is also in him Relief channel 90 through which the piston seal 19 is relieved.

In the embodiment shown in Fig. 6 is no ring-shaped fastening part available. Instead is the cylinder head 14 on the cylinder 12 by screws 58 attached, which the lower end face 44 of Cylinder head 14, which has an annular contact surface forms, penetrate. The clamping screws 58 work directly with a threaded bore (not shown) in the cylinder 12 together, their effective area 64 to the lower end face 44 of the cylinder head 14 immediately adjacent in the installed position is. The quantity control valve 16 is also with the Screws 58 attached to the cylinder head 14.

In order to avoid that when assembling the Quantity control valve 16 and the cylinder head 14 to critical loads on the cylinder 12 comes, for example. can lead to distortion of the hole in which the Piston 18 is included, the threads in the cylinder 12, into which the screws 58 are screwed, alternately be designed as left and right hand threads. Especially when there is an even total Screws 58 are used to equalize themselves simultaneous tightening of the screws 58 provided that acting on the cylinder 12 when tightening the screws Torsional moments.

7, a fuel system 102 is shown. This includes a fuel tank 104 from which fuel 106 promoted by an electric fuel pump 108 becomes. Via a low pressure fuel line 110 Fuel 106 to a high pressure fuel pump 10 promoted, which in the manner of one of the exemplary embodiments the fig. 1 - 6 is formed. From the high pressure fuel pump 10, the fuel 106 passes through a High pressure fuel line 112 to a high pressure fuel rail 114, which is commonly called "Rail" is called.

There are several to the high pressure fuel rail 114 Injectors 116 connected to the fuel directly into combustion chambers 118 of the internal combustion engine (not shown) inject.

It goes without saying that the individual characteristics of Figures 1 to 6 can also be combined can.

Claims (16)

Fuel pump, in particular high-pressure fuel pump (10) for a fuel system (102) of an internal combustion engine with gasoline direct injection, with a piston (18), with drive means (24) for driving the piston (18), with a cylinder (12), in which the piston (18) is guided, with a cylinder head (14) which rests on the cylinder (12) with an overall annular contact surface (44), and with at least one fastening means (58) with which the cylinder head (14) with the annular contact surface (44) against the cylinder (12), characterized in that the annular contact surface (44) and the effective area (64) of the fastening means (58) on the cylinder head (14), in the longitudinal direction (66) of the cylinder (12 ) seen, are essentially at the same level. Fuel pump (10) according to claim 1, characterized in that it comprises an annular fastening part (52) which is at least indirectly supported on the cylinder (12), the fastening means (58) between the fastening part (52) and the cylinder head (14) is tense. Fuel pump (10) according to Claim 2, characterized in that the annular fastening part (52) is supported on the cylinder (12) in the region of the end of the cylinder (12) facing the internal combustion engine and comprises a fastening flange (69) with which the fuel pump ( 10) can be attached to a housing (26) of the internal combustion engine. Fuel pump (10) according to Claim 2, characterized in that the annular fastening part (52) is supported on the cylinder (12) in the region of the end of the cylinder (12) facing the cylinder head (14). Fuel pump (10) according to one of claims 3 or 4, characterized in that the fastening part (52) is supported on a ring element (98) which is arranged in a circumferential groove in the cylinder (12). Fuel pump (10) according to claim 5, characterized in that the angular position of the fastening part (52) relative to the cylinder (12) is predetermined by a pin (100) which engages in corresponding recesses in the cylinder (12) and in the fastening part (52) , Fuel pump (10) according to one of the preceding claims, characterized in that the fastening means is a screw (58) which is screwed into a threaded bore (62) in the cylinder head (14). Fuel pump (10) according to one of the preceding claims, characterized in that the annular contact surface is designed as a bite edge (44). Fuel pump (10) according to Claim 8, characterized in that the cylinder head (14) has an apron section (82) which at least partially radially surrounds the cylinder (12) and is sealed with respect to the cylinder (12) by an annular seal (85), wherein between the skirt section (82) and the cylinder (12) there is an annular space (86) which is connected to a low pressure region (48) of the fuel pump (10). Fuel pump (10) according to claim 1, characterized in that the cylinder head (14) on the cylinder (12) by means of at least one screw (58) which penetrates the annular contact surface (44) and with a thread in the cylinder (12) or cooperates in the cylinder head, which is immediately adjacent to the contact surface (44). Fuel pump (10) according to claim 10, characterized in that it comprises a mounting flange (69) with which the fuel pump (10) can be attached to the housing (26) of the internal combustion engine, which engages a ring element (98) which in a circumferential groove is arranged in the cylinder (12), the angular position of the fastening flange (69) relative to the cylinder (12) being predetermined by a pin (100) which engages in corresponding recesses in the cylinder (12) and in the fastening flange (69). Fuel pump (10) according to one of claims 7 to 11, characterized in that a plurality of screws (58) are provided, some of which are provided with a right-hand thread and some with a left-hand thread. Fuel pump (10) according to one of the preceding claims, characterized in that the annular contact surface (44) interacts with an annular shoulder (34) on the cylinder (12). Fuel pump (10) according to one of the preceding claims, characterized in that it comprises a high-pressure connecting part (40) which is attached to the cylinder head (14), preferably screwed into the latter. Fuel pump (10) according to claim 14, characterized in that the high-pressure connecting part (40) is sealed in or on the cylinder (12). Fuel pump (10) according to one of the preceding claims, characterized in that the cylinder (12) steel and the cylinder head (14) and / or the fastening part (52, 94) comprises aluminum.

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