DE202020006037U1 - Tappet for a high-pressure fuel pump - Google Patents

Abstract

Tappet (1) with a plain bearing cam roller (7), which tappet (1) is intended for a high-pressure fuel pump of an internal combustion engine and has a housing (2), on the drive-side end (3) of which two diametrically opposed bores (4) with a bolt (5) are arranged therein, on which the cam roller (7) runs via an intermediate ring (6), wherein the tappet (1) has a bridge piece (8) axially below the cam roller (7), the underside (10) of which facing an output-side end (9) of the housing (2) has a support (11) for a follower part, characterized in that the bolt (5) which is uncoated on the outer casing (12) and the intermediate ring (6) which is uncoated on its bore (13) are joined to one another by means of a press fit, wherein the bolt (5) is freely rotatable relative to the bores (4) of the housing (2) and an axial securing of the Roller assembly (bolt (5), intermediate ring (6) and cam roller (7)) is only present due to the intermediate ring (6) running with its outer faces (14) against an inner wall (15) of the housing (2).

Description

The invention relates to a tappet with a plain-bearing cam roller, which tappet is intended for a high-pressure fuel pump of an internal combustion engine and has a housing, on the drive-side face of which two diametrically opposed bores with a bolt are arranged therein, on which the cam roller runs via an intermediate ring, wherein the tappet has a bridge piece axially below the cam roller, the underside of which facing an output-side face of the housing has a support for a follower part.

A generic tappet with a plain bearing roller assembly, having an intermediate ring between the bolt and the cam roller, is derived from the EN 10 2018 120 265 A1 , 2 u . Chapter [0013] The aforementioned components are capable of relative rotation relative to one another, with a hydrodynamic plain bearing being present in the annular gaps between a) the bolt and intermediate ring and b) the intermediate ring and cam roller during operation. The surface partners involved in the two annular gaps are provided with a friction and wear-reducing hard material layer (DLC layer), which is subjected to a brushing process after application. The bolt is axially secured by expanding its front ends using caulking or radial point rivets, whereby snap ring locks are also known.

A tappet as mentioned above, but with a needle bearing cam roller, reveals the EN 10 2009 013 130 A1 .

The task is to design a tappet that is suitable for very high loads and high speeds in the pump drive and at the same time can be manufactured inexpensively.

According to the invention, this object is achieved in that the bolt, which is uncoated on the outer casing, and the intermediate ring, which is uncoated on its bore, are joined to one another by means of a press fit, wherein the bolt is freely rotatable relative to the bores of the housing and axial securing of the roller assembly is only provided by the intermediate ring running with its outer faces against an inner wall of the housing.

The hydrodynamic plain bearing is thus only displaced to the radially outer annular gap between the intermediate ring and the cam roller, whereas at the radially inner annular gap, between the bolt and the intermediate ring, a permanent press connection is now formed and thus no more relative rotation takes place.

From a purely functional point of view, the above has the advantage that higher circumferential speeds are available due to the plain bearing, which is only formed on the larger diameter, and thus the elastohydrodynamic lubrication is significantly improved. The proportion of solid and mixed friction is reduced. This bearing is excellently suited to the constantly increasing pump pressures and speeds of the drive (cam, crank, balance or auxiliary shaft).

At the same time, a bolt with a comparatively small diameter can be installed in the press-fitted assembly, which in terms of surface quality is only available as a "standard rolling bearing assembly", so that, for example, the two bolt holes in the housing can be located relatively close to the upper ring face of the housing. At the same time, a relatively thin, ring-like cam roller can now be used, so that it is relatively "rotatable" due to its low mass and there is too little slippage with the known wear marks during operation, e.g. when starting up / ramping up. A stepped bolt with a thin cam ring resulting from the standard version, which bolt can only be easily mounted in U-shaped pockets in the housing, can be dispensed with.

In addition, the elimination of the previously predominant hard material coating between the outer casing of the bolt and the bore of the intermediate ring, with subsequent brushing of the surfaces, has reduced production costs. Although the assembly process in the coating chamber can be automated, it is predominantly a laborious manual loading (threading) and removal process.

The bolt to be pressed onto the intermediate ring is guided laterally to one of the holes in the housing, with the intermediate ring and roller mounted on it being kept ready inside the housing. The bolt is then pressed onto the intermediate ring using a stamp or similar.

The invention also has the advantage that the previously prevalent force-intensive fixings using caulking/radial point rivets on the hardened bolt etc., with the risk of, for example, affecting the housing or even its ground raceway (outer casing) or loosening this connection, can be dispensed with. The roller assembly and the bolt are thus only axially secured by the intermediate ring running over its outer ends on the inner casing of the housing. The outer ends of the cam roller are slightly recessed compared to the outer ends of the intermediate ring.

In order to increase the load-bearing capacity and wear resistance of the roller assembly, it is proposed in a particularly preferred development of the invention to provide at least one of the annular gap partners of the “remaining” plain bearing with a hard material layer such as a DLC layer.

Likewise or independently of this, ring sections of the bolt that run in the bore area of the housing can also be coated with a hard material so that friction and wear in the area of the rotating bolt are minimized. If necessary, the bolt can also run on bushings in the bores.

Also alone or together with the last-mentioned design measures, the outer faces of the intermediate ring which run into the inner casing of the housing can be formed with an applied hard material layer or also the inner casing.

• • Figur zeigt den Stößel in einer räumlichen Gesamtansicht;
• • 2 zeigt einen Längsschnitt durch den Stößel entlang der Rollenachse und
• • 3 zeigt eine um 90° gegenüber 2 gedrehte Schnittdarstellung des Stößels.

About the drawing:

• • Figure shows the plunger in a three-dimensional overall view;
• • 2 shows a longitudinal section through the tappet along the roller axis and
• • 3 shows a 90° opposite 2 rotated sectional view of the plunger.

1 shows the tappet 1, also called a roller or pump tappet, in its basically known construction. The tappet 1 has a hollow cylindrical housing 2, on the drive-side face 3 of which two diametrically opposed holes 4 are located in the indented flat 24. In the holes 4 there is a bolt 5 which can be rotated and slightly moved axially, and which carries a cam roller 7 via an intermediate ring 6. Axially below the cam roller 7 there is a thin-walled bridge piece 8 (see 2 , 3 ), the underside 10 of which, facing an output-side front 9 of the housing 2, has a system 11 for a follower part (pump piston).

The bolt 5, which is preferably fully hardened here, is permanently pressed into a bore 13 of the intermediate ring 6 via its outer casing 12. In this respect, there is no plain bearing in this radially inner ring area. The surface quality in the contact area just mentioned is reduced to "standard rolling bearing".

Only the thin-walled cam roller 7 is held in a rotationally movable manner relative to the now fixed intermediate ring 6, whereby it is not necessary to explain that the hydrodynamic plain bearing is formed exclusively between an outer casing 23 of the intermediate ring 6 and an inner casing 16 of the cam roller 7. The outer and inner casings 23, 16 are provided with a DLC layer.

The roller assembly is axially secured by the intermediate ring 6 running with its outer faces 14 against an inner wall 15 of the housing 2.

List of reference numbers

1

Pestle

2

Housing

3

Forehead

4

drilling

5

bolt

6

Intermediate ring

7

Cam roller

8th

Bridge section

9

Forehead

10

bottom

11

Attachment

12

Outer jacket

13

drilling

14

Outer forehead

15

Inner wall

16

Inner jacket

17

Hard material layer

18

Hard material layer

19

Ring section

20

Hard material layer

21

not awarded

22

Hard material layer

23

Outer jacket

24

Flat

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• DE 102018120265 A1 [0002]
• DE 102009013130 A1 [0003]

Claims (4)

Tappet (1) with a plain bearing cam roller (7), which tappet (1) is intended for a high-pressure fuel pump of an internal combustion engine and has a housing (2), on the drive-side end (3) of which two diametrically opposed bores (4) with a bolt (5) are arranged therein, on which the cam roller (7) runs via an intermediate ring (6), wherein the tappet (1) has a bridge piece (8) axially below the cam roller (7), the underside (10) of which facing an output-side end (9) of the housing (2) has a support (11) for a follower part, characterized in that the bolt (5) which is uncoated on the outer casing (12) and the intermediate ring (6) which is uncoated on its bore (13) are joined to one another by means of a press fit, wherein the bolt (5) is freely rotatable relative to the bores (4) of the housing (2) and an axial securing of the Roller assembly (bolt (5), intermediate ring (6) and cam roller (7)) is only present due to the intermediate ring (6) running with its outer faces (14) against an inner wall (15) of the housing (2). Tappet after Claim 1 , characterized in that an outer shell (23) of the intermediate ring (6) and / or an inner shell (16) of the cam roller (7) have an applied hard material layer (17, 18). Tappet after Claim 1 , characterized in that the bolt (5) is completely hardened and only ring sections (19) of its outer casing (12) at the bores (4) of the housing (2) are provided with an applied hard material layer (20). Tappet after Claim 1 , characterized in that a hard material layer (22) is applied to the outer ends (14) of the intermediate ring (6).

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