Tappet for a high-pressure fuel pump

Abstract

A tappet (1) for a high-pressure fuel pump is proposed, comprising a housing (2) which, at its upper annular end (3), accommodates a cam follower roller (4), which runs on a bolt (5) which is seated in the flats (6) of the housing (2), which flats (6) extend from the upper annular end (3) and run in height sections on the outer casing (7) of the housing (2), wherein the housing (2) is extended beyond its lower annular end (9) by means of a sleeve-like adapter piece (8), which adapter piece (8) on the one hand bears against chord-like lower ends (11) of the flats (6) via its tappet-side open end (10) and on the other hand forms a pump piston system (13) on its closed base (12) remote from the tappet, and wherein the adapter piece (8) has a honeycomb-like cross-section and is provided with two axial stages (14, 15), a first retracted axial stage (14) with the base (12) and a second, enlarged axial stage (15) with the open front (10),which axial stages (14, 15) are connected to each other via a ring plateau (16).

Description

[0001] The invention relates to a tappet for a high-pressure fuel pump, with a hollow cylindrical housing which accommodates a cam roller at its upper annular end, which runs on a bolt which is seated in diametrically opposite flats of the housing, which flats emanate from the upper annular end and run in height sections on the outer casing of the housing, wherein the housing is extended beyond its lower annular end by means of a sleeve-like adapter piece, which adapter piece on the one hand rests on chord-like lower ends of the flats via its tappet-side open end and on the other hand forms a pump piston system on its closed base remote from the tappet.

[0002] DE 10 2017 124 274 B3 discloses a tappet with a tubular adapter piece that largely fills the interior of the housing radially. The adapter piece has a folded collar at its upper end. The adapter piece is pressed onto the inner casing of the housing via a collar jacket.

[0003] The task is to create a lightweight tappet that is suitable for large installation distances between the cam and the pump piston and is extremely rigid.

[0004] According to the invention, this object is achieved in that the adapter piece has a honeycomb-like cross-section and is provided with at least two axial stages: a first, retracted axial stage with the base and a second, expanded axial stage with the open end, which axial stages are connected to one another via an annular plateau. It is particularly preferred to provide the adapter piece with a hexagonal and thus honeycomb-like cross-section at both axial stages.

[0005] The long tappet, mounted on a standard base housing, e.g., made of sheet steel, features a particularly rigid adapter piece, making it ideal for the very high forces encountered in modern pump drives. The adapter piece can be easily inserted via the lower annular end face of the housing during assembly and joined to the lower ends of the flat. A press fit on the inner surface of the housing is possible or provided.

[0006] Instead of the hexagonal honeycomb structure, a pentagonal or heptagonal shape is also conceivable and planned. It is also conceivable and planned to equip the adapter piece with more than two axial steps. The decisive factor is its tapered inlet.

[0007] The adapter piece is further reinforced by internal stiffening ribs, which, in a further development, have an arched shape and protrude from the longitudinal edges of the adapter piece. If necessary, the stiffening ribs can also be arranged circumferentially offset from the longitudinal edges and / or have straight edges.

[0008] According to a further embodiment of the invention, it is proposed to provide the adapter piece with one or more perforations (holes, windows). This contributes to lightweight construction and allows the passage of media such as air or oil.

[0009] Likewise, the upper edge area of the adapter piece can have one or more material inlets, so that media can also pass through here.

[0010] As proposed in concretization of the invention, the adapter piece can be manufactured by a process such as investment casting, plastic injection molding, MIM or 3D printing.

[0011] The base of the adapter piece can be directly designed for contact with a pump piston and optionally coated with a hard material for this purpose. However, it is also suggested to insert / attach a separate contact plate or similar made of a particularly wear-resistant material. The adapter piece can also be of a length such that it does not protrude beyond the housing.

[0012] Instead of the cam follower roller, a sliding surface in the tappet is also conceivable. The latter can also be used alternatively in the valve train of an internal combustion engine.

[0013] About the drawing: • Fig. 1 shows a spatial view of the fully assembled tappet; • Fig. 2 shows a longitudinal section through the tappet, transversely through its cam roller; • Fig. 3 shows a 90° angled Fig. 2 rotated sectional view; • Fig. 4 shows a spatial view of the plunger, partially cut away lengthwise; • Fig. 5 shows a longitudinal section through the adapter piece and • Fig. 6 shows the adapter piece in a spatial view obliquely from below.

[0014] From the Fig. 1 - 4 show a tappet 1 for a high-pressure fuel pump. The tappet 1 has a hollow cylindrical housing 2 made of sheet steel. At its upper annular end 3, the tappet 1 houses a cam follower roller 4. This roller runs via a needle bearing 25 on a pin 5. The pin 5 is seated in diametrically opposed, indented flats 6 of the housing 2. The two flats 6 extend from the upper annular end 3 of the housing 2 and extend approximately halfway up the height of the housing 2.

[0015] The housing 2 is extended beyond its lower annular end 9 by means of a sleeve-like adapter piece 8 with a honeycomb-like hexagonal cross-section.

[0016] As in the Fig. 1 - 4, the adapter piece 8 rests on the chord-like undersides 11 of the aforementioned flat 6 via its open end 10 on the tappet side, transmitting force. A bottom 12 of the adapter piece 8 remote from the tappet is closed and forms a pump piston system 13 on the outside, which according to Fig. 5 can also be a separate contact plate 25.

[0017] As the Fig. 5, Fig. 6, the adapter piece 8 is provided with two axial steps 14, 15, resulting in a tapered profile. The first, lower axial step 14 has a one-piece base 12. The second axial step 15, connected to it via a ring plateau 16, is wider and has an open end 10. Each axial step 14, 15 has a hexagonal cross-section.

[0018] To further increase the rigidity of the adapter piece 8 and thus of the tappet 1, stiffening ribs 19 are arranged on the inner casing 17 of the adapter piece 8. These stiffening ribs 19 extend from an inner side 18 of the base 12 of the adapter piece 8 in a dome-like manner and are integrally connected to the longitudinal edges 20 of the adapter piece 8. As best seen from the Fig. 2, Fig. 4, the stiffening ribs 19 have an arched shape.

[0019] Out of Fig. 6 shows that each wall segment 23 of the adapter piece 8 is provided with a perforation 24 designed as a bore. Fig. 6, that the adapter piece 8, starting from the front 10 of its upper axial step 15, has a shell-like material inlet 26 on each wall segment 23. List of reference numbers 1 pestle 2 housings 3 ring forehead 4 cam roller 5 bolts 6 Flat 7 Outer jacket 8 adapter piece 9 Ring forehead 10 forehead 11 Lower forehead 12 odes 13 Pump piston system 14 axial stage 15 axial stage 16 Ring Plateau 17 inner jacket 18 Inside 19 Stiffening rib 20 Longitudinal edge 21 Interior 22 Center 23 Wall segment 24 Perforation 25 Needle bearing 26 Material feed QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2017 124 274 B3

[0002]

Claims

[1] Tappet (1) for a high-pressure fuel pump, with a hollow cylindrical housing (2) which accommodates a cam follower roller (4) at its upper annular end (3), which runs on a bolt (5) which is seated in diametrically opposite flats (6) of the housing (2), which flats (6) extend from the upper annular end (3) and run in height sections on the outer casing (7) of the housing (2), wherein the housing (2) is extended beyond its lower annular end (9) by means of a sleeve-like adapter piece (8), which adapter piece (8) on the one hand rests on chord-like lower ends (11) of the flats (6) via its tappet-side open end (10) and on the other hand forms a pump piston system (13) on its closed base (12) remote from the tappet, characterized bythat the adapter piece (8) has a honeycomb-like cross-section and is provided with at least two axial stages (14, 15), a first retracted axial stage (14) with the base (12) and a second, in contrast, expanded axial stage (15) with the open end (10), which axial stages (14, 15) are connected to one another via an annular plateau (16). [2] Tappet according to claim 1, characterized by that the adapter piece (8) has an inherent hexagonal cross-section. [3] Tappet according to claim 1 or 2, characterized by that stiffening ribs (19) are arranged on the inner casing (17) of the adapter piece (8), starting from an inner side (18) of its base (12) and running up to its open end (10). [4] Tappet according to claim 3, characterized by that the stiffening ribs (19) protrude from longitudinal edges (20) of the adapter piece (8) into its interior (21) in an arc shape and converge in a dome-like manner at the center (22) of the inner side (18) of the base (12). [5] Tappet according to claim 1 or 2, characterized by that at least one wall segment (23) of the adapter piece (8) is provided with a perforation (24). [6] Tappet according to claim 1 or 2, characterized by that the adapter piece (8) is manufactured by a process such as investment casting, plastic injection molding, MIM or 3D printing. [7] Tappet according to claim 1 or 2, characterized by that an outer side (18) of the bottom (12) of the adapter piece (8) is provided with a separate contact plate (25) than the pump piston system (13). [8] Tappet according to claim 1 or 2, characterized by that the adapter piece (8), starting from the end (10) of the extended axial stage (15), has a material indentation (26) inherent in at least one of its wall segments (23).

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