EP1573174B1 - Intermediate lever for a variable valve drive of an internal combustion engine - Google Patents

Abstract

Disclosed is an intermediate lever (1) for a variable valve drive of an internal combustion engine, comprising an impingement end and a pivoting end (2, 3), a cam stop area (4), and a support (5) for a return spring (6). The face of the impingement end (2) extends on the intermediate lever (1) and is provided with a sliding area (7) that comes in contact with a lever-type valve-opening device while the pivoting end (3) is designed so as to be able to communicate with eccentric means in order to modify the position of the intermediate lever (1). The cam stop area (4) is located between the impingement end and the pivoting end (2, 3). The inventive intermediate lever (1) is made of thin-walled sheet metal and is produced essentially in a stamping-bending process. The support (5) is located on a top face (8, 9) of the intermediate lever (1), in the edge region (10) towards the impingement end (2), while being provided with a convex extension which runs in the direction of the top face (8, 9) and comes in contact with a leg (11) of a torsion spring used as a return spring (6), and being laterally delimited by two guiding loops (12, 13).

Description

Field of the invention

The invention relates to a variable valve train for an internal combustion engine, with an intermediate lever, which has a Beaufschlagungsende and a pivot end and a cam contact surface and a system for a return spring, the Beaufschlagungsende the front side of the intermediate lever and provided with a sliding surface for contact with a lever-like valve opener is, wherein in the region of the pivot end to its change in position eccentric means are provided and wherein the cam contact surface between the loading end and the pivot end is arranged.

Background of the invention

Such a valve train with an intermediate lever is apparent from the document EP-A-0 638 706. There are several disadvantages inherent in this. On the one hand, the intermediate lever is manufactured by casting. This has a negative effect on the manufacturing costs and the mass. Furthermore, it should be noted that as a return spring, a quite complicated transverse attacking coil spring is applied, which is attached to the end of a plate. This coil spring increases in the transverse direction of the cylinder head unnecessarily the space. Possibly. It can be very narrow Space conditions occur on or in the cylinder head that the coil spring is extremely difficult to accommodate. Finally, it is found that, since the aforementioned intermediate lever is merely clamped between the cam elements of the camshaft, eccentric, return spring and lever-like valve opener, it thus lacks sufficiently good guidance, for example in the lateral direction.

The document EP-A-1 143 118 likewise shows a valvetrain of the type mentioned in the opening paragraph. In this case, the intermediate lever designed as a pivoting lever has at one end a control track which is provided for line contact with a transmission element designed as a lever-type valve opener. The control track includes a Leerhubkurve and a lift curve. There is no information in the text about the production of the intermediate lever. As the drawing can be seen, however, the intermediate lever has a complicated structure. He seems to be composed of several individual components, which had to be attached to each other.

Object of the invention

The object of the invention is therefore to provide an intermediate lever of the aforementioned type, in which the disadvantages mentioned are eliminated by simple means.

Summary of the invention

According to the invention, this object is achieved in that the intermediate lever consists of a thin-walled sheet metal material and essentially in one Punching and bending process is prepared in which a stamped blank is formed with lateral wing-like projections and then the approaches are bent while maintaining a base surface of the blank to form the sliding surface for the valve opener such that they form side walls of the intermediate lever.

It is provided according to a first, particularly preferred embodiment of the invention that the system is positioned on an upper or lower side of the intermediate lever at the edge region to the Beaufschlagungsende and extending in the direction of the top or bottom a spherical extension for a contact of a leg Torsion spring has as a return spring, the system is bounded laterally by two guide plates.

Thus, the disadvantages described above are effectively eliminated. Due to the sheet metal design of the intermediate lever this is comparatively easy for a. On the other hand, the person skilled in the art recognizes that such a production of sheet metal material, sufficient rigidity and component load capacity assuming that it is considerably cheaper to produce than the casting variant.

The system for the return spring, which is designed as a torsion leg spring, wherein on the system, a leg of the aforementioned spring should come to rest, preferably in the longitudinal direction of the intermediate lever has a convex profile and is in one piece from its Beaufschlagungsende.

The inventively proposed guide tabs for limiting the system give the intermediate lever excellent leadership in its clamped state in the valve train. Due to the crown of the system also edge contact of the corresponding leg of the torsion spring is avoided in a pivoting movement of the intermediate lever.

Further subclaims relate to appropriate design variants of the guide plates. On the one hand, these can go out from one end of the plant and run back horn-like bent back onto the plant. On the other hand, it is provided to form the guide tabs as perpendicular from the top or bottom of the intermediate lever wegstehende approaches.

In the latter variant, it may be provided according to an appropriate concretization to secure the system in recesses of the guide plates. Due to this design, an undesirable bending of the system is avoided when Beaufschlagungsfall.

Also, a claim relates to a solution in which the guide plates are formed from side surfaces of the system. For this purpose, the system must laterally each have a wing-like approach, which approaches are then bent towards each other. Here, if necessary, the following additional fixation measures can be omitted. This embodiment is otherwise not shown in detail drawing.

Possibly. it may be provided in this but also in the former variant, in addition to secure the guide plates with the system, for example via a welded joint.

The wells mentioned z. B. immediately after a punching out of the contour of the intermediate lever, for example by an embossing process, are introduced. It is also conceivable, however, a light passing through or a cutting process.

If, as additionally proposed, the cam contact surface is produced as a preferably roller bearing roller, the friction work in this area is additionally minimized.

Short description of the drawing

Figur 1

in einer Seitenansicht einen Zwischenhebel mit als Drehschenkel ausgebildeter Rückstellfeder;

Figur 2

den Zwischenhebel als Stanzrohling vor dessen Biegevorgang;

und die Figuren 3 - 5

in einer räumlichen Ansicht den Zwischenhebel mit erfindungsgemäßer Anlage und den Führungslaschen.

The invention is suitably explained in more detail with reference to the drawing. Show it:

FIG. 1

in a side view, an intermediate lever formed as a rotary leg return spring;

FIG. 2

the intermediate lever as a punch blank before the bending process;

and Figures 3 - 5

in a three-dimensional view of the intermediate lever with inventive system and the guide plates.

Detailed description of the drawing

The intermediate lever 1 according to the invention consists of thin-walled sheet metal (sheet steel) and is manufactured in a stamping and bending process. Reference is made to FIG. 2, which shows the punch blank. If the wing-like projections lying laterally of the line of symmetry are bent while forming a base surface to form a loading end 2 or a sliding surface 7, the final design of the intermediate lever 1 essentially results from FIGS. 3 to 5. However, it is before the bending process mentioned still necessary to make the system marked "5" in approximately orthogonal to the board, so that after bending this Appendix 5 already between thus formed guide plates 12, 13 (design of Figure 5) is present.

The intermediate lever 1 generally consists of 2 parallel side walls 19, 20, wherein it has a Beaufschlagungs- and a pivot end 2, 3. The Beaufschlagungsende 2 is formed here over its entire length as a sliding surface 7 for contact with a lever-like valve opener such as a rocker arm or rocker arm and arranged on the front side of the intermediate lever 1. The pivoting end 3, however, is here designed with a rotatable roller for engagement in or from eccentric means (s) for changing the position of the intermediate lever 1 (BMW Valvetronic system).

Between the loading and the pivoting end 2, 3, the lever has a cam contact surface 4 designed here as a rotatable roller.

In order to guarantee a permanent cam system of the intermediate lever 1, a return spring 6 (see Figure 1) is provided, which is designed here as a torsion spring, wherein one leg 11 abuts against the plant 5. The use of the torsion spring has several advantages, for example, even space-consuming, as they have already been described in the introduction.

As mentioned, the intermediate lever 1 is made of a thin-walled sheet metal material in a stamping and bending process. In this case, the system 5 is provided for the leg 11 of the return spring 6 with lateral guide plates 12, 13 without the use of separate components. Characterized in that the system 5 preferably has a convex profile, it comes with a pivoting movement of the intermediate lever 1 is not an edge contact with unwanted wear, etc. The system 5, as is apparent from Figures 3 to 5, as in the direction of the top 8 bent Extension of the impingement end 2 made.

According to what is disclosed in FIGS. 3, 4, each guide lug 12, 13 consists of a strip-like projection, which starts from an end face 14 of the installation 5 and extends like a horn back onto the installation 5 in the direction of the loading end 2.

According to an alternative embodiment according to FIG. 5, each guide lug 12, 13 is produced as a section projecting away from the upper side 8. In this case, the guide tabs are approximately orthogonal away from the top 8. It can also be seen that, for example, embossed recesses 17, 18 are generated on inner sides of the guide plates 12, 13. In these, the system 5 is held with their respective sides 15, 16. Thus, if necessary, a bending of the system 5 is prevented during operation of the intermediate lever 1.

Additional welding or the like in the transition region from the guide plates 12, 13 to the attachment 5 can create an additional hold.

All in all, therefore, there is an intermediate lever 1, which dispenses with the casting training previously used in the prior art and thus has mass advantages. Likewise, the production costs can be reduced by the sheet metal training. Furthermore, by the integrally connected to the intermediate lever 1 Appendix 5 with limiting guide plates 12, 13 created an excellent system for the leg 11 of the return spring 6 and the intermediate lever 1 undergoes additional guidance in its "clamped" state in the variable, preferably fully variable, valve train.

List of reference numbers

1

intermediate lever

2

loading end

3

pivoting

4

Cam contacting surface

5

investment

6

Return spring

7

sliding surface

8th

top

9

bottom

10

edge region

11

leg

12

guide tab

13

guide tab

14th

front

15

page

16

page

17

deepening

18

deepening

19

Side wall

20

Side wall

Claims (10)

1. Variable valve train for an internal combustion engine, said valve train having an intermediate lever (1) comprising a loading end (2) and a pivoting end (3) as well as a cam contacting surface(4) and a support (5) for a resetting spring (6), the loading end (2) extending on a front end of the intermediate lever (1) while comprising a sliding surface (7) for a contact with a lever-type valve opener, eccentric means being provided in the region of the pivoting lever (3) for effecting a change of its position, and the cam contacting surface (4) being arranged between the loading end (2) and the pivoting end (3), characterised in that the intermediate lever (1) is made of a thin-walled sheet material and is manufactured substantially by a punching and bending method, in which a punched blank having lateral wing-like extensions is formed and these extensions, while retaining a base surface of the blank for forming the sliding surface (7) for the valve opener, are then bent upwards in such a way that they form side walls (19, 20) of the intermediate lever (1).
2. Valve train according to claim 1, characterised in that the support (5) is disposed on an upper or a lower side (8, 9) of the intermediate lever (1) in the edge region (10) to the loading end (2) and, extending towards the upper or the lower side (8, 9), the support (5) has a convex shape for contact by a leg (11) of a torsion spring serving as a resetting spring (6), and the support (5) is laterally delimited by two guide tabs (12, 13).
3. Valve train according to claim 2, characterised in that the support (5) together with its guide tabs (12, 13) is made integrally in one piece with the intermediate lever (1).
4. Valve train according to claim 2, characterised in that the support (5) is configured as an extension of the loading end (2) and is bent towards the upper or the lower side (8, 9), each guide tab (12, 13) is formed by a strip-like extension in the direction of extent of the support (5), which extension starts from a front end (14) of the support (5) and is bent back onto the support (5) into a horn-like shape, preferably towards the loading end (2) (Fig. 3, 4).
5. Valve train according to claim 2, characterised in that the support (5) is configured as an extension of the loading end (2) and is bent towards the upper or the lower side (8, 9), and each guide tab (12, 13) is constituted by a section projecting away from the upper or the lower end (8, 9) (Fig. 5).
6. Valve train according to claim 5, characterised in that each guide tab (12, 13) possesses a depression (17, 18) having a shape complementary to the opposing side (15, 16) of the support (5), in which depression (17, 18) the corresponding side (15, 16) is retained.
7. Valve train according to claim 6, characterised in that the depressions (17, 18) are made by a non-chipping method such as embossing or rudimentary stamping.
8. Valve train according to claim 2, characterised in that the support (5) is configured as an extension of the loading end (2) and is bent towards the upper or the lower side (8, 9), each guide tab (12, 13) is formed by an extension projecting laterally away from the support (5), and the extensions are bent through approximately 90° in such a way towards each other that they project away from the upper or the lower side (8, 9).
9. Valve train according to claim 1, characterised in that the cam contacting surface (4) is configured as a rotating roller that is optionally arranged on a rolling bearing.
10. Valve train according to claim 4 or 5, characterised in that the support (5) and the guide tabs (12, 13) are fixed to one another by a welded, soldered or glued joint.

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