EP3001023A1 - Fuel pump - Google Patents

Abstract

Fuel pump (10), in particular high-pressure fuel pump of a common rail fuel system, with a in a pump cylinder (11) guided pump piston (13), wherein in the region of a recess (12) of the pump cylinder (11), in which the pump piston (13) out is formed via at least one inlet bore (20) coupled to a first pressure level upper inlet groove (18) and via at least one drain hole (21) coupled to a second pressure level lower drainage groove (19) for the lubrication and possibly cooling serving fuel wherein a guide web (24) for the pump piston (13) is formed between an upper edge (23) of the lower drain groove (19) and a lower edge (22) of the upper Zulaufnut (18), and wherein the or each of the upper Zulaufnut (18) leading inlet bore (20) adjacent to the lower edge (22) of the upper Zulaufnut (18) in the upper Zulaufnut (18) opens.

Description

The invention relates to a fuel pump, in particular a high-pressure fuel pump of a common rail fuel system, according to the preamble of claim 1.

Fuel pumps have a pump cylinder, wherein a pump piston is movably mounted or guided in the pump cylinder. The pump piston is moved in the pump cylinder via one or more cams up and down, which sucked fuel and from the fuel pump consumers, such. B. injectors of a fuel system is supplied.

Fuel pumps known from practice have, in the region of the pump cylinder in which the pump piston is movably mounted, one or more leakage grooves in order to remove a fuel leakage occurring between the pump cylinder and the pump piston. In particular, when the fuel-lubricated and optionally cooled fuel pump is used in a fuel system in which heavy fuel oil is used, by reaction of the lubrication and optionally cooling the fuel pump serving heavy oil with lubricants used in the region of the cam on the pump piston and Form or deposits on the pump cylinder as laking, which reduce the guide clearance between the pump piston and the pump cylinder in a guide region between the pump piston and the pump cylinder. This can ultimately form a piston seizure on the fuel pump, so then the fuel pump can not be operated. Piston eaters can still be caused by impurities in the fuel.

From the DE 10 2007 019 909 A1 a fuel pump with two formed in the region of the pump cylinder leakage grooves is known, via which a occurring between the pump cylinder and the pump piston fuel leakage is discharged, namely either in the fuel system and / or without pressure in a leakage return, wherein the reduction of laking on the pump piston and / or Pump cylinder both leakage grooves are positioned on a lower third of the pump piston receiving recesses of the pump cylinder.

From the DE 10 2006 049 759 A1 is a fuel pump with a pump cylinder and a guided in a recess of the pump cylinder pump piston is known, wherein in the region of the pump piston leading recess of the pump cylinder on the one hand an upper Zulaufnut and on the other hand, a lower drain groove for the lubrication and possibly cooling of the fuel pump serving fuel is formed Fuel can be supplied via the upper inlet groove for lubrication and cooling of the pump piston and discharged via the lower drainage groove of the fuel used for lubrication and cooling. It is after the DE 10 2006 049 759 A1 to reduce laking of the pump piston via a introduced into the pump piston cavity by means of the supply via the feed groove and discharged via the drainage fuel from the inside cooled.

Although the danger of a piston seizure of the pump piston in the pump cylinder can be reduced to a certain extent with the fuel pumps known from the prior art, there is a need for a fuel pump in which a reduced risk of piston seizure exists for the pump piston.

On this basis, the present invention is based on the problem of creating a novel fuel pump with reduced risk of piston eaters. This problem is solved by a fuel pump according to claim 1. According to the invention, a guide web for the pump piston is formed between an upper edge of the lower drain groove and a lower edge of the upper Zulaufnut, wherein the or each leading to the upper Zulaufnut inlet bore opens adjacent to the lower edge of the upper Zulaufnut in the upper Zulaufnut. In the case of the fuel pump according to the invention, the risk of laceration in the region of the pump piston and the pump cylinder and the risk of a piston seizure due to impurities in the fuel are reduced.

Preferably, the or each inlet bore leading to the upper feed groove opens flush with the lower edge of the upper feed groove into the upper feed groove. As a result, the risk of laking in the region of the pump piston and the pump cylinder and the risk of a piston seizure due to impurities in the fuel can be further reduced.

According to an advantageous embodiment of the invention, a scraper is received in a groove of the pump cylinder in the recess of the pump cylinder below the lower drain groove, wherein formed between the lower edge of the lower drain groove and an upper edge of the scraper receiving groove another guide web for the pump piston is, whose axial height is smaller than an axial height of the guide web positioned between the drain groove and the upper Zulaufnut. Preferably, the or each leading to the lower drain groove discharge bore, which in particular has a larger flow cross-section than the or each leading to the upper Zulaufnut inlet bore, adjacent to a lower edge of the lower drain groove, in particular flush with the lower edge of the lower drain groove, in the lower drainage groove. In this way, on the one hand, the risk of laking in the region of the pump piston and of the pump cylinder can be further reduced; on the other hand, impurities in the fuel can be removed in a defined manner. The danger of a pestiller is further reduced.

Preferably, the upper inlet groove, whose axial groove height is greater than a piston stroke of the pump piston, in a lower portion in which the or each inlet bore opens into the inlet groove, has a larger radial groove depth than in an upper portion thereof. The risk of a seizure can hereby be further reduced.

Preferably, the lower drain groove has an axial groove height which is greater than a piston stroke of the pump piston. The risk of a seizure can hereby be further reduced.

According to an advantageous embodiment of the invention, the or each guide bar is dimensioned such that one at Verlackungen on the pump piston and / or in laking on the or each guide web forming and dependent on the surface of the or each guide bar adhesive force of the pump piston on or each guide bar is smaller than a restoring force of a drive spring. Even if a laking on the pump piston and / or should be done on the or each guide bar, the operability of the fuel pump is maintained because the adhesive force of the pump piston on the or each small-area guide webs compared to the restoring force of the drive spring is low.

Fig. 1:

einen schematischen Querschnitt durch eine erfindungsgemäße Kraftstoffpumpe.

Preferred embodiments of the invention will become apparent from the dependent claims and the description below. Embodiments of the invention will be described, without being limited thereto, with reference to the drawings. Showing:

Fig. 1:

a schematic cross section through a fuel pump according to the invention.

The present invention relates to a fuel pump, in particular a high-pressure fuel pump of a common rail fuel system for a heavy oil-powered internal combustion engine, such as a marine diesel engine.

Fig. 1 shows a cross section through a fuel pump 10 according to the invention, wherein the fuel pump 10 has a pump cylinder 11 and a movable in a recess 12 of the pump cylinder 11 pump piston 13. The pump piston 13 is in the recess 12 of the pump cylinder 11 movable up and down and back and forth, namely controlled by a cam 14. The cam 14 is also referred to as a drive cam. The movement of the pump piston 13 caused by the cam 14 counteracts a restoring force provided by a return spring 15, also referred to as a drive spring. This drive spring 15 is supported, on the one hand, on the pump cylinder 11 and, on the other hand, on a support element 16 coupled to the pump piston 13.

At the in Fig. 1 Fuel pump 10 shown is a high-pressure fuel pump of a common rail fuel system, wherein such a high-pressure fuel pump sucks fuel from a low pressure region of the common rail fuel system, compressed and provides a high-pressure region of the common rail fuel system. The pump piston 13 serves to compress the fuel in the recess 12 of the pump cylinder 11, the fuel compressed in the recess 12 of the pump cylinder 11 via the pump piston 13 via a high-pressure bore 17 in the pump cylinder 11 in the direction of the high-pressure region of the common-rail fuel system can be promoted. Such a fuel pump 10 is lubricated with fuel and optionally cooled, so that accordingly serves for lubrication and possibly cooling of the pump piston 13 which is movably guided in the recess 12 of the pump cylinder 11, fuel.

In particular, when the fuel pump 10 as a fuel draws and compresses heavy oil, there is a risk that the heavy oil, which also serves to lubricate the pump piston 13, with lubricants which are used in the region of the cam 14 for lubricating the same and which in the Area around the drive spring 15 and thus spread in the region of a protruding from the pump cylinder 11 portion of the pump piston 13, reacts, which then reaction products of the fuel and the lubricant used in the region of the cam 14 as so-called laking in the region of the pump piston 13 and / or as a result of the lifting movement of the pump piston 13 in the region of the recess 12 of the pump cylinder 11 can be deposited, which reduce a guide clearance between the pump piston 13 and the pump cylinder 11. A reduced guide clearance can lead to a piston seizure of the pump piston 13. Piston eaters can still be caused by impurities in the fuel. The present invention now relates to details of the fuel pump 10, by means of which the risk of a piston seizure of the pump piston 13 can be reduced.

In the pump cylinder 11, namely in the region of the recess 12 thereof, within which the pump piston 13 is guided, an upper Zulaufnut 18 and a lower drain groove 19 is introduced, wherein the upper Zulaufnut 18 is coupled via at least one inlet bore 20 to a first pressure level, and wherein the lower drain hole 19 is coupled via at least one drain hole 21 to a second pressure level.

In the case where the fuel pump is a high pressure fuel pump of a common rail fuel system, the first pressure level is the pressure level prevailing in a low pressure region of the common rail fuel system. The second pressure level is then preferably ambient pressure. The pressure level of the low pressure area is set by a low pressure fuel pump and is larger than the ambient pressure.

Between a lower edge 22 of the upper Zulaufnut 18 and an upper edge 23 of the lower drain groove 19, a guide web 24 is formed for the pump piston 13.

The or each leading to the upper Zulaufnut 18 inlet bore 20 opens adjacent to the lower edge 22 of the upper Zulaufnut 18 in the same. In this way it can be ensured that for the lubrication and optionally cooling of the pump piston 13 introduced via the or each inlet bore 20 in the Zulaufnut 18 fuel introduced via the positioned between the upper Zulaufnut 18 and the lower drain groove 19 guide web 24 flows and prevents so that in Region of the guide web 24 either foreign particles of the fuel, which serves the lubrication and possibly cooling of the pump piston 13, or can deposit deposits in the region of the guide web 24. As a result, the risk of a piston seizure for the pump piston 13 is reduced.

Preferably, the or each leading to the upper Zulaufnut 18 inlet bore 20 opens flush with the lower edge 22 of the upper Zulaufnut 18 in the upper Zulaufnut 18. This is particularly preferred to over the guide web 24, between the upper Zulaufnut 18 and the lower drain groove 19 is designed to always ensure a sufficient flow of fuel so as to avoid the formation of a laking and / or the setting of foreign particles contained in the fuel in the region of this guide web 24.

In the region of the recess 12 of the pump cylinder 11, a groove 25 is formed below the lower drain groove 19, in which a stripping element 26 is received. Between a lower edge 27 of the lower drain groove 19 and an upper edge 28 of the wiper 26 receiving groove 25, a further guide web 29 is formed, whose axial height C2 is preferably smaller than the axial height C1 of between the lower drain groove 19 and the upper Zulaufnut 18 positioned guide bar 24.

The or each leading to the lower drain groove 19 drain hole 21 preferably opens adjacent to the lower edge 27 of the lower drain groove 19 in the same, preferably such that the or each of the lower drain groove 19 leading drain hole 21 flush with the lower edge 27 of the lower drain groove 19 opens into the same and / or partially sunk in the guide web 29 positioned between the lower drain groove 19 and the groove 25 receiving the wiper element 26. In Fig. 1 the drain hole 21 is partially sunk in the guide bar 29. In this way, an optimal removal of the introduced for lubrication and possibly cooling in the Zulaufnut 18 fuel flowing through the guide bar 24 into the lower drain groove 19, guaranteed from the lower drain groove 19. Furthermore, it is ensured that optionally via the scraper element 26 introduced into the region of the lower drain groove 19, used in the region of the cam 14 lubricant, defined from the drainage groove 19 is discharged so that there is no danger that used in the region of the cam 14 lubricant with the the lubrication of the pump piston 13 serving fuel reacts and leads to laking in the region of the lower guide web 29 and the lower drain groove 19.

Preferably, the or each leading to the lower drain groove 19 drain hole 21 also has a larger flow area than the or each leading to the upper Zulaufnut 18 inlet bore 20. Contaminants in the fuel can be discharged from the drain piston 19 defined by the pump piston 13.

As Fig. 1 can be removed, the upper Zulaufnut 18 has a stepped contour. Thus, in a lower portion 30 of the upper Zulaufnut 18 the same is characterized by a larger radial groove depth than in an upper portion 31 thereof. In the lower portion 30 of the upper Zulaufnut 18, which has the larger radial groove depth than the upper portion 31 thereof, the or each feed hole 20 opens. The axial groove height of the lower portion 30 of Zulaufnut 18 is less than the axial groove height of the upper portion 31 of the inlet groove 18th

Preferably, the upper Zulaufnut 18 has a total of an axial groove height B, on the one hand greater than a conditional by the cam 14 piston stroke A of the pump piston 13. Due to the fact that the axial groove height B of the upper Zulaufnut 18 is greater than that caused by the cam piston stroke 14 A of the pump piston 13 (B> A), there is no risk that lubricant used in the region of the cam 14 and due to the Lifting movement of the piston 13 via the scraper element 26 possibly reaches the region of the upper Zulaufnut 18, passes into a portion of the recess 12 of the pump cylinder 11, which is positioned above the upper inlet groove 18. As a result, the risk of a piston seizure for the pump piston 13 can be further reduced.

In Fig. 1 corresponds to the axial groove height D of the lower drain groove 19 in about the flow cross section of the or each leading to the lower drain groove 19 drainage bore 21. Although in Fig. 1 not shown, the lower drain groove 19 may also have a much greater axial groove height D, which is then greater than the piston stroke A caused by the cam 14 of the pump piston 13. Then, when D> A, the risk of damaging the scraper element 26 and, ultimately, the risk of a piston seizure for the pump piston 13 can be further reduced.

The invention may find use in any form of fuel lubricated fuel pumps. In particular, the invention finds use in a high pressure fuel pump of a common rail fuel system in which heavy fuel oil is used.

The inventive design of the fuel pump 10, the risk of seizures for the pump piston 13 of the fuel pump 10 can be reduced.

Foreign particles in the fuel, which is supplied for lubrication and possibly cooling via the or each inlet bore 20 of the upper Zulaufnut 18, as defined by the pressure difference between the upper Zulaufnut 18 and the lower drain groove 19 via the between the Zulaufnut 18 and the drain groove 19 positioned Guide web 24 are discharged into the region of the lower drain groove 19 to be discharged via the or each drain hole 21 of the fuel pump 10. Since this guide web 24 has a small axial height C1, and furthermore the or each inlet bore 20 preferably opens flush with the lower edge 22 of the upper Zulaufnut 18 in the same, a sufficient flow of fuel is ensured via this guide web 24. Accordingly, foreign particles contained in the fuel can not settle in the region of this guide web 24. Furthermore, as a result of the fuel flow no laking can form in the region of this guide web 24. Furthermore, the sufficiently large flow of fuel flowing over the guide web 24 prevents lubricants used in the region of the cam 14 from being able to enter the drain groove 19 via the wiping element 26 and the further guide web 29 as a result of the lifting movement of the pump piston 13 , Pass the guide bar 24 and reach the area of the upper Zulaufnut 18. Nevertheless, should minor amounts of such lubricant reach the area of the upper feed groove 18, the defined, graduated contouring of the upper feed groove 18 ensures that any laking that may form there is not critical to the guide play for the pump piston 13 in the region of the upper feed groove 18 reduce, so then formed as a result of such Verlackungen no piston eater.

Both guide webs 24, 29 have a relatively short axial length. The fact that both guide webs 24, 29 have a relatively short axial length, even if a laking on the pump piston 13 and / or on the guide webs 24, 29 should be maintained, the operability of the fuel pump 10 is maintained, since then the adhesive force or Friction force of the pump piston 13 on the small-area guide webs 24, 29 in comparison to the restoring force of the drive spring 15 is low.

Accordingly, the area of the guide webs 24, 29 is preferably dimensioned such that an adhesive force of the pump piston 13 which is dependent on the surface of the guide webs 24, 29 during laking on the pump piston 13 and / or on the guide webs 24, 29 is smaller than it the restoring force of the drive spring 15. As a result, an emergency operation of the fuel pump 10 can be maintained. For this purpose, preferably the sum of C1 and C2, ie the sum of the axial heights of the guide webs 24 and 29, is significantly smaller than the piston stroke A of the pump piston 13 caused by the cam 14.

Then, when the sum of C1 and C2 corresponds approximately to A, the pump piston 13 remains at laking on the pump piston 13 and / or laking at the guide webs 24 and 29 stuck. This can alternatively be used to avoid damage to other components of the internal combustion engine, which can be caused by an uneven delivery or pumping power of the fuel pump 10.

LIST OF REFERENCE NUMBERS

10

Fuel pump

11

pump cylinder

12

recess

13

pump pistons

14

drive cam

15

driving spring

16

supporting

17

High pressure drilling

18

Zulaufnut

19

drain groove

20

inlet bore

21

drain hole

22

edge

23

edge

24

guide web

25

groove

26

stripping element

27

edge

28

edge

29

guide web

30

section

31

section

Claims (13)

Fuel pump (10), in particular high-pressure fuel pump of a common rail fuel system, with a in a pump cylinder (11) guided pump piston (13), wherein in the region of a recess (12) of the pump cylinder (11), in which the pump piston (13) out is formed via at least one inlet bore (20) coupled to a first pressure level upper inlet groove (18) and via at least one drain hole (21) coupled to a second pressure level lower drainage groove (19) for the lubrication and possibly cooling serving fuel characterized in that between an upper edge (23) of the lower drain groove (19) and a lower edge (22) of the upper Zulaufnut (18) a guide web (24) for the pump piston (13) is formed, wherein the or each of the upper Zulaufnut (18) leading inlet bore (20) adjacent to the lower edge (22) of the upper Zulaufnut (18) in the upper Zulaufnut (18) opens. Fuel pump according to claim 1, characterized in that the or each of the upper Zulaufnut (18) leading inlet bore (20) opens flush with the lower edge (22) of the upper Zulaufnut (18) in the same. Fuel pump according to claim 1 or 2, characterized in that in the region of the recess (12) of the pump cylinder (11) below the lower drainage groove (19) a scraper element (26) is received in a groove (25) of the pump cylinder (11) between a lower edge (27) of the lower drainage groove (19) and an upper edge (29) of the wiper (26) receiving groove (25) is formed a further guide web (29) for the pump piston (14) whose axial height ( C2) is smaller than an axial height (C1) of the upper guide web (24) positioned between the drain groove (19) and the upper feed groove (18). Fuel pump according to one of Claims 1 to 3, characterized in that the or each drainage bore (21) leading to the lower drainage groove (19) has a larger flow cross-section than the or each inlet bore (20) leading to the upper inlet groove (18). Fuel pump according to one of claims 1 to 4, characterized in that for the or each of the lower drainage groove (19) leading drainage bore (21) adjacent to a lower edge (27) of the lower drainage groove (19) in the lower drainage groove (19) empties. Fuel pump according to one of claims 1 to 5, characterized in that the or each of the lower drainage groove (19) leading drainage bore (21) opens flush with the lower edge (17) of the lower drainage groove (19) in the lower drainage groove (19) , Fuel pump according to one of claims 1 to 6, characterized in that the or each to the lower drainage groove (19) leading drainage bore (21) at least in the between the lower drainage groove (19) and the stripping element (26) receiving groove (25). positioned guide web (29) is sunk. Fuel pump according to one of claims 1 to 7, characterized in that the upper Zulaufnut (18) in a lower portion (30), in which the or each inlet bore (20) opens into the Zulaufnut (18) has a larger radial groove depth than in an upper portion (31) thereof. Fuel pump according to one of claims 1 to 8, characterized in that the upper Zulaufnut (18) has an axial groove height (B), which is greater than a piston stroke (A) of the pump piston (13). Fuel pump according to one of claims 1 to 9, characterized in that the lower drainage groove (19) has an axial groove height (D) which is greater than a piston stroke (A) of the pump piston (13). Fuel pump according to one of claims 1 to 10, characterized in that the Zulaufnut (18) via the or each inlet bore to a low pressure region of the common rail fuel system can be connected. Fuel pump according to one of claims 1 to 11, characterized in that the drainage groove (19) via the or each drain hole (21) is connectable to a region of the common rail fuel system, in which ambient pressure prevails. Fuel pump according to one of claims 1 to 12, characterized in that the or each guide web (24, 29) is dimensioned such that a forming during laking and the surface of the or each guide web (24, 29) dependent adhesive force of the pump piston ( 13) on the or each guide web is smaller than a restoring force of a drive spring (15).

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