Tappet for high-pressure fuel pump

Abstract

The invention relates to a tappet (1) for a high-pressure fuel pump, comprising a hollow cylindrical housing (2) made of steel sheet, which housing accommodates a cam follower roller (4) on the upper annular end face (3) thereof, which cam follower roller runs on a bolt (26), which bolt is arranged in diametrically opposite flat sections (5) of the housing (2), the flat portion (5) extends from the upper annular end face (3) and partially on the outer circumferential surface (6) of the housing (2), and wherein the housing (2) is penetrated axially beneath the cam follower roller (4) by a separate disc-shaped bridge (7), which rests on the lower transverse end face (9) of the flat portion (5) via its upper edge section facing the upper annular end face (3), the central annular projection (10) protrudes integrally from the bridge (7) in the direction of the lower annular end face (11) of the housing (2), the housing (2) being extended by means of an adapter tube (12) which forms, on one hand, a bearing for the pump piston at the lower closing end (13) thereof, and, on the other hand, a bearing for the pump piston at the lower closing end (13) thereof, and which forms, on the other hand, a bearing for the pump piston at the lower closing end (13) thereof. On the other hand, the annular section (14) and the annular projection (10) of the bridge (7) are inserted into each other at the upper open end (15) and are fastened via a press fit (16).

Description

Field of the Invention

[0001] The present invention relates to a tappet for a high-pressure fuel pump, the tappet having a hollow cylindrical housing made of a steel plate, the housing receiving a cam follower roller at its upper annular end face, the cam follower roller running on a bolt, the bolt being arranged in diametrically opposite flat portions of the housing, the flat portions starting from the upper annular end face and extending locally on the outer peripheral surface of the housing, wherein the housing is extended via an adapter tube, the adapter tube forming a support portion for the pump piston at its lower closed end on the one hand and being connected to the housing at its upper open end on the other hand. Background Art

[0002] A tappet with an adapter tube is known from DE 10 2017 124 274 B3, the adapter tube filling the inner space of the housing as much as possible radially. The adapter tube has a folded collar at its upper end. The adapter tube is clamped against the inner peripheral surface of the housing via the peripheral surface of the collar. Summary of the Invention

[0003] The object of the present invention is to provide a roller tappet with an optimized adapter tube, which is simply and reliably engaged with the housing at the same time.

[0004] According to the present invention, this object is achieved by the new features of claim 1. Thus, the housing is axially penetrated below the cam follower roller by a separate disk-shaped bridging member, the bridging member abutting against the lower transverse end face of the flat portion via the edge section of its upper side facing the upper annular end face, wherein a central annular projection projects integrally from the bridging member in the direction of the lower annular end face of the housing, and wherein the adapter tube is inserted into the annular projection of the bridging member at its upper end via an annular section and is fixed in this case by a press fit.

[0005] Particularly preferably, the aforementioned press fit is achieved by transverse extrusion.

[0006] The aforementioned tappet is relatively lightly constructed, and its main components (housing, bridging portion and possibly the adapter tube) can be made of steel plate. The tappet has a reliable and simple connection of the adapter tube of the tappet to the bridging member and to the housing, which can be achieved by transverse extrusion. Machining preparation work for the components to be joined can be dispensed with. The degree of deformation of the transversely clamped material is very high, so that the adapter part does not loosen from the annular projection of the bridging member during operation, even if subsequent heat treatment of the joined components (as proposed in an improved embodiment of the present invention) may cause a loss of force transmission. The form-fit connection remains unchanged. In addition, a certain angular mobility of the connecting portion abutting against the transverse end face of the flat portion is ensured.

[0007] Preferably, an adapter tube, which can also be formed by stretching a steel plate, should be plugged onto the annular projection. Alternatively, an adapter tube in the form of a solid pin can extend with its upper end into the hole of the annular projection.

[0008] As proposed, the annular projection of the bridging element has at least two diameter steps, wherein the adapter tube is clamped via an annular section of its inner wall to the lower diameter step of the annular projection. The lower diameter step is recessed relative to the upper diameter step located above it. A favorable axial support and force transmission are achieved by the annular end face of the adapter tube abutting on the annular step that connects the two diameter steps in a platform-like manner.

[0009] In a further refinement of the invention, a "tapered seat" in the press fit is proposed. Thus, for example, only the adapter tube can have a cone on the annular section of the inner wall, which tapers in the direction of the upper annular end face of the housing and in the direction of the bridging element. In a transverse extrusion, the material of the annular projection is extruded and flowed into the cone by a punch that moves into the opening of the annular projection of the bridging element, wherein the adapter tube is simultaneously accommodated in a die. It is clear that the material of the adapter tube in the joining region is also flowing / can flow.

[0010] If the diameter of the adapter tube is less than half of the diameter measured on the inner circumferential surface of the housing, the adapter tube is of a particularly thin-walled and lightweight construction.

[0011] The adapter tube can have a length such that it projects beyond the lower annular end face of the housing. Thus, it is clear that a relatively large spacing between the pump cam or pump eccentric and the pump piston can also be bridged. The pump cam or pump eccentric can be arranged, for example, on a camshaft. The adapter tube can also have a length such that the adapter tube terminates at the height of the lower annular end face of the housing or even terminates within the housing. Description of the Drawings

[0012] Figure 1 A partially sectioned perspective view of the tappet is shown;

[0013] Figure 2 A longitudinal sectional view of the tappet taken transversely through its cam follower roller is shown;

[0014] Figure 3 The adapter tube and the bridging element in the die are shown and equipped with a punch

[0015] Figure 4 The press fit is shown separately. Detailed Description of the Invention

[0016] Figure 1 、 Figure 2Shows a tappet 1 for a high-pressure fuel pump. The tappet has a hollow cylindrical housing 2 made of a steel plate, and a cam follower roller 4 is accommodated at its upper annular end face 3, with the cam follower roller partially protruding beyond the upper annular end face. The cam follower roller 4 runs on a bolt 26, and the end side of the bolt is arranged in the diametrically opposite flat part 5 of the housing 2. The flat part 5 starts from the upper annular end face 3 and extends downward locally on the outer peripheral surface 6 of the housing 2.

[0017] A disc-shaped bridging piece 7 made of a steel plate abuts against the lower transverse end face 9 of the recessed flat part 5 (see Figure 1 ). More specifically, the bridging piece 7 abuts against the transverse end face 9 via the edge section of its upper side 8.

[0018] See Figure 3 , Figure 4 It can be seen that a chimney-shaped annular projection 10 projects integrally downward in the middle from the bridging piece 7. The annular projection engages with an adapter tube 12, and the adapter tube extends beyond the lower annular end face 11 of the housing 2. The adapter tube 12 is closed at its lower end 13 and forms a support for the pump piston here.

[0019] The adapter tube 12 is inserted at its other upper end 15 via an annular section 14 of the inner wall onto the outer peripheral surface 18 of the lower diameter step 19 of the annular projection 10. The upper diameter step 20 of the annular projection 10 is connected to the lower diameter step 19. The two diameter steps 19, 20 are connected to each other via a platform-shaped annular step 22. The adapter tube 12 is located on the annular step at its upper end 15 through its annular end face 21.

[0020] As Figure 4 shown, the annular section 14 of the adapter tube 12 has an inner cone 23 that narrows in the direction towards the upper annular end face 3 of the housing 2. The annular section 14 and the annular projection 10 of the bridging piece 7 are fastened via a press fit 16, and the press fit is achieved by lateral extrusion (see Figure 3 ). Briefly, the material of the lower diameter step 19 of the annular projection 10 is extruded with the material upstream in the radial direction of the adapter tube 12, and material flow occurs on at least one mating part.

[0021] The two elements of the annular section 14 of the adapter tube 12 and the annular projection 10 of the bridging piece 7 are not rigidly pressed against each other, so heat treatment is not required in advance. Heat treatment is carried out only in the state where the housing 2 is joined.

[0022] List of reference numerals

[0023] 1) Tappet

[0024] 2) Housing

[0025] 3) Upper annular end face

[0026] 4) Cam follower roller

[0027] 5) Flat part

[0028] 6) Outer peripheral surface

[0029] 7) Bridging member

[0030] 8) Upper side

[0031] 9) Lateral end face

[0032] 10) Annular projection

[0033] 11) Annular end face

[0034] 12) Adaptor tube

[0035] 13) Lower end part

[0036] 14) Annular section

[0037] 15) Upper end part

[0038] 16) Press fit

[0039] 17) Inner peripheral surface

[0040] 18) Outer peripheral surface

[0041] 19) Lower diameter step

[0042] 20) Upper diameter step

[0043] 21) Annular end face

[0044] 22) Annular step

[0045] 23) Inner cone

[0046] 24) Recess

[0047] 25) Plunger

[0048] 26) Bolt

[0049] 27) Inner peripheral surface

Claims

1. A tappet (1) for a high-pressure fuel pump, said tappet having a hollow cylindrical housing (2) made of a steel plate, said housing receiving a cam follower roller (4) at its upper annular end face (3), said cam follower roller running on a bolt (26), said bolt being arranged in diametrically opposite flats (5) of the housing (2), said flats (5) starting from the upper annular end face (3) and extending partially on the outer peripheral surface (6) of the housing (2), wherein, The housing (2) is axially penetrated below the cam follower roller (4) by a separate disc-shaped bridging member (7), which abuts against the lower transverse end face (9) of the flat part (5) via an edge section of its upper side (8) facing the upper annular end face (3), wherein a central annular projection (10) projects integrally from the bridging member (7) in the direction of the lower annular end face (11) of the housing (2), wherein the housing (2) is extended by an adapter tube (12), which on the one hand forms a support for the pump piston at its lower closed end (13), and on the other hand, via an annular section (14) at its upper open end (15), is inserted into the annular projection (10) of the bridging member (7) and is fixed in this case by a press fit (16).

2. The tappet according to claim 1, wherein, The press fit (16) is achieved by transverse pressing.

3. The tappet according to claim 1 or 2, wherein, The adapter tube (12) is pressed against the outer peripheral surface (18) of the annular projection (10) of the bridging member (7) via an end region of its inner peripheral surface (17) that is an annular section (14), wherein the annular projection (10) has at least one lower diameter step (19) and an upper diameter step (20) connected thereto, and the adapter tube (12) is only pressed against the lower diameter step (19) of the annular projection (10) via its annular section (14) and is supported at its upper end (15) via its annular end face (21) on an annular step (22) of the annular projection (10) between its two diameter steps (19, 20).

4. The tappet according to claim 3 and referring to claim 2, wherein, The annular section (14) of the adapter tube (12) is provided with an inner cone (23) and / or the outer peripheral surface (18) of the annular projection (10) of the bridging member (7) is provided with an outer cone at its lower diameter step (19), and the respective cones (inner cone (23), outer cone) narrow in the direction of the upper annular end face (3) of the housing (2), and wherein, in transverse pressing, the cone profiles are shaped into one another radially.

5. The tappet according to claim 1 or 2, wherein, The two elements, namely the annular section (14) of the adapter tube (12) and the annular projection (10) of the bridging member (7), are pressed against each other without curing.

6. The tappet according to claim 1, wherein, The bridging member (7) is made of a steel plate.

7. The tappet according to claim 1, wherein, The adapter tube (12) projects beyond the lower annular end face (11) of the housing (2).

8. The tappet according to claim 1 or 7, wherein, The adapter tube has a diameter less than half of the diameter of the housing (2) measured on its inner peripheral surface (27).

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