Tappet for a high-pressure fuel pump of an internal combustion engine with an anti-twist body

Abstract

Tappet (1) for a high-pressure fuel pump of an internal combustion engine, comprising a hollow cylindrical housing (2) which has a cam follower roller (4) on its drive-side end (3), wherein the housing (2) is penetrated axially below the cam follower roller (4) by a bridge piece (5), the end face (7) of which, facing an output-side end (6) of the housing (2), has a support for a pump piston, and wherein an anti-rotation body (10) with a radially inner base section (11) is seated in a recess (8) of an outer casing (9) of the housing (2), which anti-rotation body (10) projects with a radially outer head section (12) over the outer casing (9) of the housing (2), characterized in that the recess (8) of the housing (2) is an axial groove running directly from the drive-side end (3) and provided radially on the inside with a closed base (13),which is located in a thickening (14) of the housing (2) which is circular segment-like in cross-section, wherein the axial groove (8) forms an undercut profile in cross-section, in which the anti-rotation body (10) is fixed radially outwards with its foot section (11) which is complementary thereto in cross-section, and wherein the axial groove (8) has a length which corresponds to at least half the height of the housing (2).

Description

[0001] The invention relates to a tappet for a high-pressure fuel pump of an internal combustion engine, with a hollow cylindrical housing which has a cam roller on its drive-side end, wherein the housing is penetrated axially below the cam roller by a bridge piece, the end face of which, facing an output-side end of the housing, has a contact surface for a pump piston, and wherein an anti-twist body with a radially inner base section is seated in a recess of an outer casing of the housing, which anti-twist body projects with a radially outer head section over the outer casing of the housing.

[0002] From DE 10 2012 217 801 A1 ( Fig. 2, Fig. 4) shows a tappet for a high-pressure fuel pump with a solid, separate bridge piece. The bridge piece is joined to a nose-like anti-twist element on a transverse face via a dovetail profile. The anti-twist element extends through a window in the tappet housing.

[0003] DE 10 2004 002 487 A1 shows a tappet for a high-pressure fuel pump with a cam follower roller inserted into its housing via a locking connection. Fig. 2, the anti-rotation body is designed as a bead formed in one piece from the housing and extending axially completely.

[0004] The task is to propose a tappet with an anti-rotation body that is optimized in terms of load capacity and fixation.

[0005] According to the invention, this object is achieved in that the recess of the housing is an axial groove running directly from the drive-side end and provided radially on the inside with a closed base, which lies in a thickening of the housing which is circular segment-like as seen in cross-section through the housing, wherein the axial groove forms an undercut profile in cross-section, in which the anti-rotation body with its foot section which is complementary thereto in cross-section is fixed in a form-fitting manner radially outwards and wherein the axial groove has a length which corresponds at least to half the height of the housing.

[0006] The key feature is the significant extension of the anti-rotation element compared to standard solutions. Its counter-contour in the pump or engine-side guide can be retained. Due to the significantly extended axial contact surface of the anti-rotation element, less surface pressure and wear during operation can be expected. Furthermore, such an anti-rotation element is easy to handle.

[0007] The anti-rotation device is joined “from above” via the drive-side end of the housing with the axial groove and is conveniently fixed therein by means of a press fit.

[0008] It is advantageous to design the anti-rotation element to be the same length as the axial groove. However, it can also be positioned deeper within the groove, thus being shorter than the axial groove. A slight projection beyond the drive-side face is also possible. However, depending on the circumferential orientation of the axial groove, unobstructed cam engagement must be ensured. The anti-rotation element can also have a length that is slightly less than half the height of the housing.

[0009] Advantageous designs of the undercut profile in the joining area are the subject of a further subclaim. A dovetail profile is considered, among other things. However, a T-slot, trapezoidal groove, or circular segment profile, or similar, are also possible. A good form fit in the assembly is crucial for securing the anti-rotation device.

[0010] For the joint formed with the dovetail profile, a further development provides for a bulge to be applied longitudinally to a radial inner end face of the base section of the anti-rotation element, which rests against the base of the axial groove. This design advantageously increases the preload in the joint.

[0011] The head section of the anti-rotation body, intended for receiving the tappet in the counter groove of the guide of the high-pressure fuel pump or the internal combustion engine, can have a lens-shaped, mushroom-shaped, or beam-shaped geometry, for example. It can also have a circular arc or a Gothic profile in cross-section.

[0012] It is advantageous to separate the anti-rotation element from a semi-finished product such as an extruded profile. The plunger housing is typically manufactured using a MIM process or by extrusion. The axial groove can be machined subsequently or incorporated during the forming process.

[0013] In view of the great length of the guide body, it is possible to leave the housing unhardened at low cost.

[0014] Preferably, and to put it simply, the axial groove should be offset by 90° from the roller axis, viewed in the circumferential direction of the housing. This is especially true when the cam follower roller runs on a bolt that sits in respective bores in the skirt. Mounting the cam follower roller in a plain bearing shell in a drive-side end face of the bridge piece is also possible.

[0015] The tappet can also be used in a valve train of an internal combustion engine.

[0016] About the drawing: • Fig. 1 shows the plunger in a spatial view from above; • Fig. 2 shows the housing of the tappet in a spatial view from above; • Fig. 3 shows the anti-rotation body in a spatial view and • Fig. 4 shows a section of a cross-section through the housing in the area of ​​its thickening with anti-twist body.

[0017] Out of Fig. 1 shows a tappet 1 for a high-pressure fuel pump of an internal combustion engine, with a hollow cylindrical housing 2 (see also Fig. 2), which is extruded or manufactured using an MIM process. A cam follower roller 4 is located on a drive-side end face 3, shown here at the top. The latter is mounted on a bolt 17, which is received at the end face in bores 18 of the housing 2. Axially below the cam follower roller 4, the housing 2 is penetrated by a one-piece bridge piece 5, the end face of which (not visible) facing an output-side end face 6 of the housing 2 has a support for a pump piston.

[0018] The housing 2 has two diametrically opposed thickened portions 14 with a circular segment-like cross-section, the flat inner walls 20 of which extend parallel to the axial line of the cam follower roller 4. In one of the thickened portions 14, starting from the outer casing 9 of the housing 2, there is a recess 8 in the form of an axial groove and extending from the drive-side end face 3 of the housing 2. A beam-like profiled anti-rotation element 10 with a radially inner base section 11 is press-fitted in the axial groove 8. This anti-rotation element 10 projects beyond the outer casing 9 of the housing 2 with a radially outer, mushroom-head-like head section 12.

[0019] As from Fig. 1, the axial groove 8 extends approximately over half the height of the housing 2. It can be seen in the Fig. 1, Fig. 2, a dovetail profile 15 is formed in the joining area of ​​the base section 11 of the anti-rotation body 10 with the axial groove 8 of the housing 2. A base 13 of the axial groove 8 is closed. The anti-rotation body 10 is thus positively fixed radially via its base section 11.

[0020] As the Fig. 3, Fig. 4 show, the anti-rotation body 10, which is in the form of a profile piece, has a continuous bulge 16 on a radial inner end face 19 of its base section 11. The latter bears against the base 13 of the axial groove 8, which leads to good clamping of the anti-rotation body 10 in its axial groove 14. List of reference numbers 1 pestle 2 housings 3 Front (drive side) 4 cam roller 5 bridge sections 6 Front (output side) 7 not assigned 8 Recess, axial groove 9 Outer jacket 10 anti-rotation devices 11 Foot section 12 head section 13 Reason 14 Thickening 15 dovetail profile 16 bulge 17 bolts 18 Hole 19 inner forehead 20 interior wall

Claims

[1] Tappet (1) for a high-pressure fuel pump of an internal combustion engine, with a hollow cylindrical housing (2) which has a cam follower roller (4) on its drive-side end (3), wherein the housing (2) is penetrated axially below the cam follower roller (4) by a bridge piece (5), the end face (7) of which, facing an output-side end (6) of the housing (2), has a support for a pump piston, and wherein an anti-rotation body (10) with a radially inner foot section (11) is seated in a recess (8) of an outer casing (9) of the housing (2), which anti-rotation body (10) projects with a radially outer head section (12) over the outer casing (9) of the housing (2), characterized bythat the recess (8) of the housing (2) is an axial groove running directly from the drive-side end (3) and provided radially on the inside with a closed base (13), which lies in a thickening (14) of the housing (2) which is circular segment-like in cross-section through the latter, wherein the axial groove (8) forms an undercut profile in cross-section, in which the anti-rotation body (10) with its foot section (11) complementary thereto in cross-section is fixed radially outwards in a form-fitting manner, and wherein the axial groove (8) has a length which corresponds at least to half the height of the housing (2). [2] Tappet according to claim 1, characterized by that the anti-rotation body (10) runs through the entire length of the axial groove (8). [3] Tappet according to claim 1 or 2, characterized by that the foot section (11) of the anti-rotation body (10) sits with a press fit in the axial groove (8) of the housing (2). [4] Tappet according to claim 1 or 2, characterized by that in the joining area of ​​the foot section (11) of the anti-rotation body (10) with the axial groove (8) of the housing (2) there is either a dovetail profile (15) or a T-groove, trapezoidal groove or circular segment profile. [5] Tappet according to claim 4, provided that a dovetail profile (15) is present in the joining area, characterized by that a bulge (16) runs longitudinally centrally on a radial inner end face (19) of the foot section (11) of the anti-rotation body (10), which bulge rests on the base (13) of the axial groove (8). [6] Tappet according to one of the preceding claims, characterized by that the head section (12) of the anti-rotation body (10) has a lens-shaped, mushroom-shaped or rectangular cross-section. [7] Tappet according to one of the preceding claims, characterized by that the anti-rotation body (10) is separated from an extruded profile. [8] Tappet according to one of the preceding claims, characterized bythat the housing (2) is in the form of an extruded or MIM body, wherein the bridge piece (5) is monolithically connected to the housing (2). [9] Tappet according to one of the preceding claims, characterized by that the housing (2) with the joined anti-rotation body (10) is finally unhardened. [10] Tappet according to one of the preceding claims, characterized by that the axial groove (8) is offset by 90° in the circumferential direction of the housing to the intersection point of the axial line of the cam roller (4) on the housing (2).

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