High-pressure fuel pump for an internal combustion engine

Abstract

High-pressure fuel pump for an internal combustion engine, designed as a piston pump with a housing (12) that can be inserted into an opening of an engine block (32) by means of a mounting fitting (34), with a mounting flange for attaching the housing (12) to the engine block (32), with a stepped bore (14) in the housing (12) which has a region (16) with a larger diameter on the side facing the engine block (32) and a region (24) with a smaller diameter on the side facing away from the engine block (32), with at least one piston (22), and with at least one piston bushing (18) attached to the housing (12) and arranged in the region (16) with a larger diameter, the piston bushing having an axial through-opening (20) in which the piston (22) is guided.wherein a working chamber (26) of the pump is formed between the region (24) with a smaller diameter of the staged bore (14) and an end of the piston (22) facing away from the engine block (32), wherein the delivery rate of the pump is adjustable by a quantity control valve (28) arranged on the inlet side of the working chamber (26), wherein the piston bushing (18) is radially held in at least two axially spaced radial support regions (44, 46) by mounting webs (38, 40) extending circumferentially on the housing (12) in the region of the axial ends of the piston bushing (18), and the piston bushing (18) is held axially by a rout (54) of the housing (12) and further by a step formed between the region (24) with a smaller diameter of the staged bore (14) and the region with a larger diameter of the staged bore (14). High-pressure fuel pump for a internal combustion enginedesigned as a piston pump with a housing (12) that can be inserted into an opening of an engine block (32) by means of a mounting fitting (34), with a mounting flange for attaching the housing (12) to the engine block (32), with a stepped bore (14) in the housing (12) which has a region (16) with a larger diameter on the side facing the engine block (32) and a region (24) with a smaller diameter on the side facing away from the engine block (32), with at least one piston (22), and with at least one piston bushing (18) attached to the housing (12) and arranged in the region (16) with a larger diameter, the piston bushing having an axial through-opening (20) in which the piston (22) is guided, wherein a working chamber (26) of the pump is formed between the region (24) with a smaller diameter of the stepped bore (14) and an end of the piston (22) facing away from the engine block (32),wherein the delivery rate of the pump is adjustable by a flow control valve (28) arranged on the inlet side of the working chamber (26), wherein the piston bushing (18) is radially held in at least two axially spaced radial support areas (44, 46) by mounting webs (38, 40) extending circumferentially on the housing (12) in the region of the axial ends of the piston bushing (18) on the outer surface of the piston bushing (18), and the piston bushing (18) is axially held by a rivet (54) of the housing (12) and further by a step formed between the area (24) with a smaller diameter of the stepped bore (14) and the area with a larger diameter of the stepped bore (14).

Description

State of the art

[0001] a high-pressure fuel pump for an internal combustion engine, comprising a housing, with at least one piston, and with at least one piston bushing attached to the housing, having an axial through-hole in which the piston is guided.

[0002] A high-pressure fuel pump of the type mentioned above is known from DE 199 38 504 A1. This patent discloses a single-cylinder high-pressure piston pump for high-pressure supply in a common-rail injection system of an internal combustion engine. The known piston pump comprises a pump housing into which a piston bushing is inserted and held by means of a sealing screw.

[0003] The present invention aims to further develop a high-pressure fuel pump of the type mentioned above in such a way that it has a better efficiency.

[0004] This task is solved in a high-pressure fuel pump of the type mentioned above by holding the piston bushing radially on the housing in two axially spaced radial mounting areas.

[0005] Other high-pressure fuel pumps are known from WO 96 / 28 661 A1, DD 2 19 533 A1, DE 199 25 250 A1, DE 197 21 227 A1, DE 199 30 608 A1 and DE 199 38 504 A1. Advantages of the invention

[0006] In the piston pump according to the invention, the through-hole in which the piston is guided is largely decoupled from deformations of the piston pump housing. Deformations of the housing, which can occur, for example, during assembly, are therefore transmitted to the piston bushing only to a significantly reduced extent. Thus, the clearance between the axial through-hole of the piston bushing and the piston can be reduced, which improves the efficiency of the piston pump. In addition, a thinner-walled piston bushing can also be used, which reduces the dimensions of the piston pump according to the invention.

[0007] In an advantageous embodiment of the piston pump according to the invention, the radial support areas are arranged at least approximately at the axial ends of the piston bushing. Such a fastening or support absorbs a tilting moment, which is introduced at the contact point of the piston with a bucket or roller tappet, with the lowest possible forces on the piston bushing. The resulting deformations of the piston bushing are therefore minimal.

[0008] Furthermore, it is proposed that the radial mounting area closest to the working space be press-fitted to the housing in a fluid-tight manner. This dual function of the radial mounting area eliminates the need for a separate seal, thus saving installation space and costs.

[0009] The seal can be easily achieved by having a sealing edge on the radial mounting area closest to the working space.

[0010] According to the invention, the piston bushing is held axially by a riveting of the housing, which results in a secure fixing of the piston bushing to the housing without the need for additional parts, such as a screw connection.

[0011] Another embodiment of the piston pump according to the invention is characterized by the presence of a gap outside the two radial mounting areas between the piston bushing and the housing. This gap is preferably created by a recess in the piston bushing and / or the housing. Such a gap prevents contact between the piston bushing and the housing outside the radial mounting areas, thus preventing the transmission of forces and deformations from the housing into the piston bushing. The deformation of the piston bushing during the manufacture of the piston pump and during its operation is therefore particularly small.

[0012] The radial support area, located away from the working chamber, preferably interacts with the housing in a fluid-permeable manner. This prevents the build-up of intermediate pressure between the piston bushing and the housing due to minor leaks that do not affect the pump's efficiency. Such pressure could, in turn, lead to deformation of the piston bushing. Under certain circumstances, such deformation could even result in increased friction between the piston and piston bushing, potentially leading to piston jamming during a compression stroke.

[0013] This fluid permeability can be achieved particularly easily by having at least one passage, in particular a recess, groove or flattening, at the axial height of the radial mounting area located away from the working space, which extends over the radial mounting area.

[0014] If a certain degree of fluid permeability is already permitted in the radial support area furthest from the working space, this radial support area can have a shorter axial contact length with the housing than the radial support area closest to the working space. This reduces the area of ​​influence for potential deformations of the piston bushing.

[0015] Another advantageous embodiment of the piston pump according to the invention is characterized in that the piston bushing comprises a bushing part and a mounting sleeve, which is pressed onto the bushing part and on which the two radial mounting areas are formed. This further improves the decoupling of the piston bushing from the housing, resulting in even lower deformations and ultimately a further improved efficiency of the piston pump according to the invention.

[0016] This applies particularly to cases where the mounting sleeve has a lower stiffness than the bushing part. In such cases, deformations of the housing are primarily absorbed by the mounting sleeve and only transmitted to the bushing part to a limited extent.

[0017] Manufacturing costs are particularly low if the mounting sleeve is a sheet metal part.

[0018] The manufacturing costs of the piston pump according to the invention are reduced if the radial mounting areas on the mounting sleeve are formed by areas with a larger diameter. Such an area with a larger diameter can, for example, be easily produced by widening the sleeve.

[0019] A further improved decoupling of the piston bushing from the housing is achieved if the bushing part is supported by a housing-fixed support shoulder with an axial surface pointing away from the working space.

[0020] Further development suggests that the support shoulder be mounted on a retaining ring that is riveted to the housing. This prevents deformation of the piston bushing during the riveting process.

[0021] A passage for draining leakage fluid can also be provided across the piston bushing support and the retaining ring. This also prevents pressure build-up between two radial support areas in this variant.

[0022] Another preferred embodiment of the piston pump according to the invention provides that the axial through-opening of the piston bushing has a larger diameter at approximately the axial height of at least one of the radial support areas. This prevents the axial movement of the piston in the axial through-opening from being hindered during assembly by deformation of the piston bushing in the area of ​​said radial support area.

[0023] Furthermore, it is proposed that an inlet port and / or an outlet port, through which the fuel enters or flows out of the working chamber, be arranged in the piston sleeve. This simplifies the design of the piston pump.

[0024] In a further development, a preferably additional radial support area can be arranged at least approximately at the axial height of the inlet opening and / or the outlet opening. This combines the radial support with the sealing of the fuel path, reducing costs and simplifying the design.

[0025] A reduction in the overall height of the piston pump is achieved when the working chamber is connected to an inlet and / or outlet port via at least one axial and at least one radial channel in the piston. This also provides the piston with additional guide length in the area of ​​the through-hole.

[0026] It is particularly advantageous if a relief groove is present at least approximately at the axial height of the inlet and / or outlet opening on the outside of the piston and / or the inside of the piston sleeve, the axial extent of which corresponds at least to the piston stroke. This ensures that the fluid connection from the working chamber to the inlet or outlet of the piston pump is guaranteed at all times.

[0027] To prevent dirt from accumulating between the piston bushing and the housing during machining of the piston pump bores and during assembly, it is proposed that the piston bushing have a sealing edge at its axial end facing the housing. Furthermore, such a sealing edge relieves stress on the seal between the radial mounting area of ​​the piston bushing and the housing.

[0028] Further development of this idea proposes that the sealing edge interact with an inclined housing surface. This improves the sealing effect during a compression stroke.

[0029] Furthermore, it is proposed that a space formed radially outside the sealing edge between the piston bushing and the housing be connected to a low-pressure port. This has the advantage that the piston bushing is largely pressure-relieved, especially in the axial direction, so that lower demands can be placed on the press fit between the piston bushing and the housing. Drawings

[0030] Preferred embodiments of the present invention are explained in more detail below with reference to the accompanying drawing. The drawing shows: Fig. 1 a partial section through a first embodiment of a piston pump; Fig. 2 an enlarged view of a section of the piston pump of Fig. 1 with a piston bushing; Fig. 3 a representation similar Fig. 2 of a second embodiment; Description of preferred embodiments

[0031] A piston pump carries in Fig. 1 overall the reference numeral 10. It serves as a high-pressure pump in a fuel system of an internal combustion engine (not shown) and supplies a fuel rail with fuel under very high pressure.

[0032] The piston pump 10 comprises a cylindrical housing 12 in which a central stepped bore 14 is provided. In a region 16 with a larger diameter, a cylindrical piston bushing 18 is arranged in the stepped bore 14. This, in turn, has a through-hole 20 in which a pump piston 22 is guided axially displaceably. At the top of the housing 12, under a cover 21, is a Fig. One invisible pressure damper is present.

[0033] Between the in Fig. A working chamber 26 is formed between the upper axial end of the pump piston 22 and a section 24 with a smaller diameter of the stepped bore 14. During a suction stroke of the pump piston 22, fuel at low pressure enters the working chamber 26 via an inlet 28. During a compression stroke of the pump piston 22, the fuel in the working chamber 26 is compressed and finally discharged via a Fig. Fuel is delivered to the fuel rail via a non-visible outlet. The delivery rate is adjusted via a quantity control valve 30.

[0034] The housing 12 of the piston pump 10 is directly attached to a Fig. 1. The housing 12 is attached to the engine block 32 of the internal combustion engine, indicated only by a dashed line. For this purpose, the housing 12 is inserted into an opening 36 in the engine block 32 using a mounting sleeve 34. The housing 12 is attached to the engine block 32 by a fastener 34. Fig. 1 mounting flange not shown.

[0035] In Fig. Figure 2 shows an enlarged view of the piston bushing 18 and the adjacent area of ​​the piston pump 10. It can be seen that the radially outer surface of the piston bushing 18 has a circumferentially extending mounting rib 38 or 40 in the region of its axial ends. The Fig. 2. The upper mounting bracket 38 is inclined and tapers towards the one in Fig. 2 upper axial end of the piston bushing 18. This forms a sealing edge 42.

[0036] In their unassembled state, the two mounting lugs 38 and 40 have a slightly larger diameter than the area 16 of the stepped bore 14 in the housing 12. The piston bushing 18 is therefore pressed into this area 16 of the stepped bore 14, causing the mounting lugs 38 and 40 to deform plastically and elastically. In the installed position, radial support areas 44 and 46 are formed on the mounting lugs 38 and 40. These areas have a comparatively small axial extent a1 and a2, respectively, and bear in a press fit against the inner wall of the stepped bore 14. In practice, the axial extent a1 and a2 of the radial support areas 44 and 46 is a maximum of 0.5 mm.

[0037] While the press fit through the radial mounting area 44 is fluid-tight, partly due to the presence of the sealing edge 42, this is not desired for the radial mounting area 46. The press force of the press fit of the radial mounting area 46 is therefore lower than that of the radial mounting area 44. Between the two mounting lugs 38 and 40, a kind of recess 48 is present on the outside of the piston bushing 18, forming a gap 50 between the piston bushing 18 and the housing 12. To ensure that the annular space formed by the gap 50 remains pressureless even during operation of the piston pump 10, the mounting lug 40 is interrupted by an axially extending groove 52 that extends axially across the radial mounting area 46.The securing of the piston bushing 18 in the stepped bore 14 is achieved by a riveting 54, which forms a housing-fixed support shoulder 58, on which a ring surface (without reference numeral) pointing away from the working space and at least approximately axially, which is present on the piston bushing 18, is supported.

[0038] An alternative embodiment is in Fig. Figure 3 (without pump piston) is shown. As with subsequent embodiments, elements and areas with equivalent functions to those described above bear the same reference numerals and are not explained again in detail.

[0039] At the in Fig.In the piston pump 10 shown in Figure 3, the piston bushing 18 is designed in two parts, comprising a bushing part 18a and a mounting sleeve 18b. The latter has a significantly lower stiffness than the bushing part 18a and is formed, for example, by a sheet metal ring which has expansions 38 and 40 at its axial ends, forming the radial mounting areas 44 and 46. The area (without reference numeral) of the mounting sleeve 18b located between the expansions 38 and 40 is pressed onto the bushing part 18a in a fluid-tight manner.

[0040] The bushing part 18a has a radially outward extending and circumferentially circumferential annular collar 58. A small gap exists between its radially outer surface and the inner surface of the stepped bore 14. The axial surface of the annular collar 58, facing away from the working chamber 26, bears against a boundary surface of a retaining ring 60 facing the working chamber 26, thus forming a support shoulder 62. The retaining ring 60 is pushed onto the end region of the bushing part 18a facing away from the working chamber 26, with the inner diameter of the retaining ring 60 being slightly larger than the outer diameter of the bushing part 18a in this region. The retaining ring 60 is secured to the housing 12 by a rivet 56. To prevent axial loading of the bushing part 18a, the retaining ring 60 bears against a shoulder 64 of the housing 12.

[0041] In the radial mounting area 46, a relief groove 52 is again provided. Additionally, a radially extending relief groove 53 is provided in the surface (without reference numeral) of the ring collar 58 facing the retaining ring. Leaking fuel can thus flow from the annular space formed by the gap 50, via the relief groove 52, the gap between the ring collar 58 and the housing 12, the groove 53, and the gap between the inner diameter of the retaining ring 60 and the outer diameter of the bushing part 18a, towards the low-pressure area.

Claims

[1] High-pressure fuel pump for an internal combustion engine, designed as a piston pump with a housing (12) that can be inserted into an opening of an engine block (32) by means of a mounting fitting (34), with a mounting flange for attaching the housing (12) to the engine block (32), with a stepped bore (14) in the housing (12) which has a region (16) with a larger diameter on the side facing the engine block (32) and a region (24) with a smaller diameter on the side facing away from the engine block (32), with at least one piston (22), and with at least one piston bushing (18) attached to the housing (12) and arranged in the region (16) with a larger diameter, the piston bushing having an axial through-opening (20) in which the piston (22) is guided,wherein a working chamber (26) of the pump is formed between the region (24) with a smaller diameter of the stepped bore (14) and an end of the piston (22) facing away from the engine block (32), wherein the delivery rate of the pump is adjustable by a quantity control valve (28) arranged on the inlet side of the working chamber (26), wherein the piston bushing (18) is radially held in at least two axially spaced radial support regions (44, 46) by mounting webs (38, 40) extending circumferentially on the housing (12) in the region of the axial ends of the piston bushing (18), and the piston bushing (18) is held axially by a rout (54) of the housing (12) and further by a step formed between the region (24) with a smaller diameter of the stepped bore (14) and the region with a larger diameter of the stepped bore (14). [2] High-pressure fuel pump according to claim 1, characterized by, that the radial support areas (44, 46) are arranged at least approximately at the axial ends of the piston bushing (18). [3] High-pressure fuel pump according to one of claims 1 or 2, characterized by , that the radial support area (44) closest to the working space (26) is pressed fluid-tight with the housing (12). [4] High-pressure fuel pump according to claim 3, characterized by , that the radial support area (44) nearest to the working space (26) has a sealing edge (42). [5] High-pressure fuel pump according to any one of the preceding claims, characterized by , that essentially outside the two radial support areas (44, 46) between the piston bushing (18) and the housing (12) there is a gap (50) which is preferably produced by a recess (48) on the piston bushing (18) and / or on the housing (12). [6] High-pressure fuel pump according to any one of the preceding claims, characterized by, that the radial support area (46) located remote from the work space (26) cooperates with the housing (12) in a fluid-permeable manner. [7] High-pressure fuel pump according to claim 6, characterized by , that at the axial height of the radial support area (46) located remote from the working space (26) there is at least one passage, in particular a recess, groove (52) or flattening, which extends over the radial support area (46). [8] High-pressure fuel pump according to one of claims 6 or 7, characterized by , that the radial support area (46) located furthest from the working space (26) has a shorter axial contact length with the housing than the radial support area (44) closest to the working space (26). [9] High-pressure fuel pump according to any one of the preceding claims, characterized by, that the piston bushing (18) comprises a bushing part (18a) and a mounting sleeve (18b) which is pressed onto the bushing part (18a) and on which the two radial mounting areas (44, 46) are formed. [10] High-pressure fuel pump according to claim 9, characterized by , that the fastening sleeve (18b) has a lower stiffness than the bushing part (18a). [11] High-pressure fuel pump according to one of claims 9 or 10, characterized by , that the fastening sleeve (18b) is a sheet metal part. [12] High-pressure fuel pump according to any one of claims 9 to 11, characterized by , that the radial support areas (44, 46) on the mounting sleeve (18b) are formed by areas (38, 40) with a larger diameter. [13] High-pressure fuel pump according to any one of the preceding claims, characterized by, that the piston bushing (18) or bushing part (18a) is supported at least indirectly by an axial surface pointing away from the working space (26) on a housing-fixed support shoulder (62). [14] High-pressure fuel pump according to claim 13, characterized by , that the support shoulder (62) is present on a retaining ring (60) which is riveted (56) to the housing (12). [15] High-pressure fuel pump according to claim 14 in conjunction with one of claims 6 to 8, characterized by , that a passage (53) for draining leakage fluid is also provided across the support of the piston bushing (18) and the retaining ring (60).

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