Roller tappet for high-pressure fuel pump

Abstract

The invention relates to a roller tappet (1) for a high-pressure fuel pump, comprising a cup-shaped housing (2), on the drive-side end face (3) of which a cam roller (4) is mounted, the inner circumferential surface (5) of the housing (2) being bridged downstream of the cam roller (4) by means of a bridge (6) connected to the housing (2), a dome-shaped projection (9) projects from a bottom side (8) of an end face (7) of the bridge facing the output side of the housing (2), from a bore (10) of the projection an extension pin (11) for the contact of the pump piston is removed, the extension pin (11) being joined to the bore (10) of the projection (9) by friction welding.

Description

Technical Field

[0001] The present invention relates to a roller tappet for a high-pressure fuel pump, the roller tappet having a cup-shaped housing, a cam roller being arranged on the end face of the driving side of the housing, wherein the inner circumference of the housing is bridged behind the cam roller by a bridge piece connected to the housing, a dome-shaped protrusion protrudes from the bottom side of the end face of the bridge piece facing the driven side of the housing, and an extension pin for the pump piston contact part extends from the hole of the protrusion. Background Art

[0002] This type of roller tappet is provided for bridging the larger installation distance between the pump cam and the pump piston and is known from DE 10 2020 106 409 A1. A centering projection with a receptacle is molded on the bridge of the housing of the roller tappet. The receptacle partially surrounds an extension pin which is fixed by a retaining ring. Summary of the invention

[0003] The object of the invention is to provide a roller tappet which is suitable for bridging larger installation dimensions and which is of simple construction and very inexpensive.

[0004] According to the invention, this object is achieved in that the extension pin is engaged with the hole of the projection via a region of its outer circumference by friction welding.

[0005] Friction welding is a particularly preferred welding method in this case. Other welding methods such as laser welding or resistance welding are also conceivable if necessary. Soldering is also conceivable as an alternative.

[0006] It is emphasized that an end section of the outer circumference of the extension pin is fixedly joined to the bridge piece via friction welding. Preferably, the housing and the bridge piece and its dome-shaped projection are manufactured in one piece by stamping. Cutting manufacturing is also considered if necessary.

[0007] Existing "short" standard housings of (preferably stamped) roller tappets with a height-diameter ratio of approximately 1:1 can be used, with large installation distances being simply adapted via extension pins. No complex new designs are necessary, especially if stamping manufacturing technology for tappets of great length is limited.

[0008] It is obvious that with one basic type of roller tappet it is possible to operate a wide variety of high-pressure pumps and / or to compensate for tolerances by providing extension pins of graduated lengths.

[0009] Alternatively, the projection of the bridge piece can also be designed as a closed cylindrical piece, wherein the extension pin has a hole on its axial end face, and the extension pin is joined to the cylindrical piece via the hole by friction welding.

[0010] According to an improved solution of the present invention, the hole of the protrusion of the bridge piece is divided into two steps, wherein the area of ​​the extension pin facing the protrusion has an end protrusion with a step, and the end protrusion is friction welded to the second (inner) step on the bridging side of the hole of the protrusion.

[0011] In the radial direction, the remaining section of the end projection toward its annular step to the "normal" area of ​​the outer circumference of the extended pin and the first step portion on the bridge side of the hole of the projection define an annular space together. This annular space serves as a receiving space for the ridge formed during friction welding, and at the same time prevents particles escaping from the welding area from escaping due to its closed design. Finishing of the weld ridge can be omitted.

[0012] Another dependent claim specifies suitable geometries for friction welding. Thus, for example, annular, truncated-conical or spherical area configurations are conceivable.

[0013] Roller tappets can also be used in valve trains of internal combustion engines. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 shows a longitudinal section through a roller tappet with a schematically drawn cam roller, and

[0015] Figure 2 Shown according to Figure 1 View of the roller tappet rotated 90°. DETAILED DESCRIPTION

[0016] The drawing shows a roller tappet 1 for a high-pressure fuel pump, which serves to bridge a large installation distance between a pump cam and a pump piston.

[0017] The roller tappet 1 comprises a cup-shaped housing 2 which receives a cam roller 4 on its drive-side end face 3 (see Figure 1 The pins supporting the cam roller 4 are not shown (see Figure 2 ), the bolt is seated in a receptacle of an adjoining flat portion 21 of the housing 2 on the drive-side end face 3 of the housing.

[0018] Axially, the inner circumference 5 of the housing 2 is bridged behind the cam roller 4 by a bridge 6 connected integrally to the housing 2. A one-piece, continuous dome-shaped projection 9 protrudes centrally from the bottom side 8 of the bridge 6 facing the output-side end face 7 of the housing 2. The housing 2 is a stamped body.

[0019] As shown in both figures, the projection 9 of the bridge 6 has a two-step hole 10. A first step 14 of larger diameter is provided starting from an outer end face 13 of the projection 9. A second step 15 of smaller diameter adjoins the first step.

[0020] It is important to emphasize that the extended pin 11 for the pump piston contact portion is fixedly engaged with the aforementioned hole 10. Figure 2 As disclosed, the extended pin 11 with two steps on the outer circumference 22 does not extend beyond the end face 7 on the driven side of the housing 2 in the installed state. The extended pin 11 has a stepped end projection 16 on the bridge side, which is slightly shorter than the hole 10 of the projection 9.

[0021] The aforementioned joining connection of the extension pin 11 to the hole 10 of the projection 9 is achieved by friction welding. Figure 1 The arrows in the figure symbolically show the axial introduction of the extension pin 11 in the direction of the bridge 6. Figure 2 The arrows indicate the final process of friction welding the extended pin 11 to the hole 10. More specifically, the end projection 16 of the extended pin 11 which has not yet been stepped has a friction welded region 18 starting from its axial end face 17.

[0022] Another region of the end projection 16 that is adjacent in the direction of the annular step 20 of the extension pin 11 remains untouched. Figure 2 As shown in the context of , another area of ​​the end projection 16 defines an annular space 19 radially on the inside, which is defined radially on the outside by the first step 14 of the hole 10 of the projection 9 and in the axial direction by the annular step 20 of the extended pin 11.

[0023] The extension pin 11 is supported on the outer end face 13 of the projection 9 by its annular step 20 relative to the end projection 16. The annular space 19 forms a closed receiving space for the weld bead formed during friction welding and simultaneously prevents particles (metal chips) of the weld bead from entering the environment of the roller tappet 1.

[0024] according to Figure 2 The thickened annular representation in the hole 10 of the projection 9 indicates the engagement area of ​​the extension pin 11 with the hole 10 of the projection 9 .

[0025] Reference numerals list

[0026] 1 Roller tappet

[0027] 2 Housing

[0028] 3 End face on the drive side

[0029] 4 Cam rollers

[0030] 5 Inner Surface

[0031] 6 Bridge

[0032] 7 Driven side end face

[0033] 8 Bottom side

[0034] 9 Protrusion

[0035] 10 holes

[0036] 11 Extension pin

[0037] 12 Outer Surface

[0038] 13 Outer end face

[0039] 14 First step

[0040] 15 Second step

[0041] 16 End protrusion

[0042] 17 Axial end face

[0043] 18 Regions

[0044] 19 Ring Space

[0045] 20 Circular Stairs

[0046] 21 Flat part

[0047] 22 Outer Surface

Claims

1. A roller tappet (1) for a high-pressure fuel pump, the roller tappet having a cup-shaped housing (2), a cam roller (4) being arranged on the drive-side end face (3) of the housing, wherein: The inner circumference (5) of the housing (2) is bridged behind the cam roller (4) by a bridge piece (6) connected to the housing (2), and a dome-shaped projection (9) protrudes from the bottom side (8) of the end face (7) of the bridge piece facing the driven side of the housing (2), and an extension pin (11) for the pump piston contact part extends from the hole (10) of the projection, characterized in that the extension pin (11) is joined to the hole (10) of the projection (9) via an area (18) of its outer circumference (12) by friction welding.

2. The roller tappet (1) according to claim 1, characterized in that The hole (10) of the protrusion (9) has a first step (14) starting from its outer end face (13) and a second step (15) adjacent thereto having a diameter smaller than that of the first step, wherein the extension pin (11) has an end protrusion (16) with a step on the bridge side, and the end protrusion (16) has an area (18) for friction welding with the second step (15) of the hole (10) of the protrusion (9) starting from its axial end side (17), and wherein an annular space (19) surrounding the end protrusion (16) of the extension pin (11) and radially surrounded by the first step (14) is used as a accommodating space for a welding bulge that occurs during friction welding.

3. The roller tappet according to claim 2, characterized in that The extension pin (11) is supported on the outer end face (13) of the projection (9) of the bridge (6) via an annular step (20) relative to its stepped end projection (16).

4. The roller tappet according to claim 1, characterized in that The extension pin (11) extends out from a section of the end face (7) on the output side of the housing (2), or the extension pin protrudes beyond the end face (7).

5. The roller tappet according to claim 1, characterized in that The housing (2) is designed integrally with the bridge (6) and its projection (9).

6. The roller tappet according to claim 5, characterized in that The housing (2) is manufactured by stamping.

7. The roller tappet according to claim 1, characterized in that The engagement area between the extension pin (11) and the protrusion (9) of the bridge (6) is in the shape of an annular, truncated cone or spherical area.

Images