EP3268586B1 - Rocker arm for valve drive in an internal combustion engine and valve drive comprising such a rocker arm - Google Patents

Description

The invention relates to an actuating lever for a valve train of an internal combustion engine with a lever section, the lever section having a supporting surface for transmitting a valve actuation movement, and with a pivoting section for pivotably mounting the lever section about a pivot axis. The invention further relates to a valve train with at least one such actuation lever.

In internal combustion engines, such as, for example, fuel-operated engines in vehicles, the fuel-air mixtures required for combustion in the cylinders are supplied via valve inlets and combustion exhaust gases are discharged via valve outlets. The valve inlets and outlets are usually opened and closed in a timed manner via inlet valves and outlet valves. For example, camshafts are used to actuate the intake valves and exhaust valves. Levers are often arranged between the cams of the camshafts and the intake valves or exhaust valves, which transmit the actuations.

The JP S59 87209 A discloses a rocker arm with a substrate made of a fiber-light metal composite material which is coated with a flame-sprayed ceramic layer.

In this context, the document discloses DE 10 2006 052 820 A1 a rocker arm or rocker arm for actuating a gas exchange valve of an internal combustion engine. The rocker arm or rocker arm has a reshaped lever body which, in the area of a valve-side arm section with side walls and a crossbar, forms an open cross-sectional profile, a valve actuation surface running on an underside of the crossbar, which is bordered by two longitudinal webs. The crossbar and the longitudinal webs are formed in one piece. The longitudinal webs are bent on the underside of the crossbeam and welded to contact surfaces running on the underside.

It is an object of the present invention to propose an operating lever for a valve train of an internal combustion engine, which is characterized by particularly good operating behavior. This object is achieved by an operating lever with the features of claim 1 and by a valve train with at least one such operating lever with the features of claim 10. Preferred or advantageous embodiments of the invention result from the subclaims, the following description and the attached figures.

The invention thus relates to an actuating lever which is suitable and / or designed for a valve train of an internal combustion engine. In particular, the actuating lever is designed to actuate a valve, in particular a gas exchange valve, of the valve train for the internal combustion engine. The valve can be an intake valve or an exhaust valve. The internal combustion engine is preferably designed as a traction motor for a vehicle, in particular for a passenger car, truck, bus, etc. In particular, the internal combustion engine is implemented as a gasoline engine or as a diesel engine. The opening and closing of the valve in the internal combustion engine is controlled or actuated via the actuating lever.

The actuating lever has a lever section, the lever section having a supporting surface for transmitting a valve actuating movement. For example, the wing is designed as a flat surface or a flat surface section, which has an area of at least ten square millimeters. When the actuating lever is installed, the contact surface is oriented in the direction of the valve. The lever section is in particular a lever section on the valve side.

Furthermore, the actuating lever has a pivoting section which is preferably rigidly connected to the lever section. The pivot section is suitable and / or designed for the pivotable mounting of the lever section about a pivot axis. The swivel section can be designed, for example, as a swivel mount, through which a mechanical swivel axis runs. Alternatively, a bolt with a roller arranged thereon can also be provided in the pivoting section. The actuating lever is mounted so as to be pivotable about the pivot axis, the supporting surface preferably being arranged in a plane to which the pivot axis runs parallel or in which the pivot axis is arranged. When the actuating lever is pivoted about the pivot axis, the lever section with the contact surface is also pivoted, the supporting surface being able to transmit the valve actuation movement. The valve actuation movement is preferably transmitted to the valve.

In the context of the invention it is proposed that the actuating lever have a ceramic layer, the ceramic layer being arranged on the supporting surface and forming a contact surface for transmitting the valve actuating movement. In particular, the ceramic layer is designed as a wear-resistant layer.

The arrangement of the ceramic layer on the support surface forms a contact surface, in particular a valve contact surface, which, compared to the base material of the lever section, in particular the support surface, has an increased hardness, a higher mechanical strength, a higher dimensional stability and / or a higher wear resistance having. These improved mechanical properties ensure that the operating lever does not wear out or deform mechanically even after prolonged use, so that it is not necessary to readjust the actuated valve even over a long service life. The actuating lever with the ceramic layer thus enables a particularly reliable and long-lasting function of the actuating lever and thus of the valve train.

In a preferred embodiment of the invention, the contact surface is designed as a valve contact surface for direct contacting of a valve stem of the valve. Alternatively, the valve actuation movement can be transmitted to the valve via one or more additional intermediate elements.

In a preferred implementation of the invention, the ceramic layer is designed as a thermally sprayed ceramic layer. That this realization the underlying process of thermal spraying is a surface coating process. Thermal spraying is preferably carried out in accordance with the definition of DIN EN 657. In the process, additives, so-called spray additives, are melted, melted or melted inside or outside a spray burner, accelerated in a gas stream in the form of spray particles and onto the surface of the coating Component, in this example the wing, flung. The component surface, in this case the wing, is not melted and is only thermally stressed to a small extent. In particular, the temperature of the wing is less than 150 ° C. This does not affect or deform an original shape of the wing. A layer formation occurs because the spray particles flatten when they hit the component surface, in this case the wing, depending on the process and material, stick mainly due to mechanical clamping and build up the spray layer in layers.

The ceramic layer is formed by ceramic materials, in particular oxide-ceramic materials, such as, for example, aluminum oxide, magnesium oxide, zirconium oxide, titanium dioxide or multi-material systems, such as aluminum titanate, mullite, etc. or dispersion ceramics, such as aluminum oxide reinforced with zirconium. Zirconium oxide is particularly preferably used as the ceramic material for the ceramic layer. The ceramic layer is particularly preferably plasma sprayed or flame sprayed. The type of application ensures that the connection between the ceramic layer and the wing is designed to withstand the load. The layer thickness of the ceramic layer is preferably more than 50 μm, in particular more than 80 μm and / or preferably less than 150 μm, in particular less than 120 μm.

In a preferred constructive implementation of the invention, the actuating lever is designed as a pivot lever. In particular, the actuating lever is designed as a rocker arm or as a rocker arm. In the case of a rocker arm, the rocker arm is actuated on the lever section, so that the lever section is arranged between an actuating member, such as a cam of a camshaft and a valve. Alternatively, is the Actuating lever is designed as a rocker arm which has a further lever section which is arranged on the side of the pivoting section facing away from the lever section and is rigidly connected to the latter. In the case of a rocker arm, the actuation is initiated like a seesaw on the side of the further lever section.

In a preferred constructive implementation of the invention, the lever section has a crossbar area, the crossbar area extending in the axial direction and in particular parallel to the pivot axis. Furthermore, the lever section has guide arm regions which form an axial-lateral boundary on the contact surface. The contact area is arranged on the crossbar area. The guide arm areas preferably form side webs to the crossbar area. In particular, the guide arm regions are designed for lateral guidance of the valve.

In a preferred implementation of the invention, the actuating lever has a base body, the base body being designed as a shaped part. The formed part is particularly preferably designed as a sheet metal formed part. In particular, the sheet metal part is designed as a stamped and bent part. The formed part made of steel, e.g. made of 16MnCr5 as base material. The combination of a ceramic layer and the formed part made of steel is particularly advantageous, since the formed part can be produced inexpensively, but tends to deform when the temperature load is too high. The thermal spraying of the ceramic layer can ensure that the ceramic layer adheres firmly to the wing, the base body does not deform or warp, and at the same time the production of the actuating lever is inexpensive.

It is preferably provided that the shaped part comprises the guide arm areas and the crossbar area. In particular, the guide arm areas and the crossbar area are formed in one piece and / or in one material with the shaped part. In this constructive embodiment, the actuating lever is particularly easy to manufacture due to the few structural parts.

From a constructional point of view, it is preferred that the shaped part has two side cheek regions which extend from the lever section via the pivot section and optionally additionally over the further lever section. The side cheek regions are preferably aligned in the same way as a radial plane to the pivot axis. In the pivoting section, the side cheek sections each have a receptacle, e.g. a through opening for receiving and / or mechanically coupling a swivel device, such as from a mechanical swivel axis or a swivel pin. The crossbar area extends between the two side cheek areas, this connecting the side cheek areas in one piece. In particular, the lever section is U-shaped in a cross section perpendicular to its longitudinal extent, the side cheek areas forming the free legs and the crossbar area forming the connecting leg. The contact surface is arranged on a side of the crossbar area which faces away from the side cheek areas. The guide arm areas are designed as extensions of the side cheek areas and bent over so that they rest or almost rest on the crossbeam area. Optionally, the guide arm areas can be connected at the free ends to the side cheek areas for position fixing, in particular welded.

In one possible embodiment, the shaped part has one or the further lever section, the swivel section being arranged between the lever section and the further lever section. In particular, the actuating lever is designed as a straight lever, so that the lever section, joint section and further lever section form a line. The further lever section has a connecting area, the connecting area extending in the axial direction between the side cheek areas and integrally connecting them. The further lever section is preferably U-shaped in a cross section perpendicular to the longitudinal extension of the actuating lever, the two side cheek regions forming the free legs and the connecting region forming the connecting leg. A receiving structure for an actuating element, such as, for example, an actuating plunger, is arranged in the connection area, in particular molded in using a forming technique.

Another object of the invention relates to a valve train for an internal combustion engine, the valve train having at least one valve and at least one actuating lever, as described above or according to one of the preceding claims. It is provided in the valve train that the valve is actuated via the actuating lever. In principle, it is possible for the actuating lever to actuate the valve with the interposition of intermediate elements. However, it is particularly preferred that the actuating lever contacts the valve directly, so that a free end of the valve stem of the valve is in physical contact with the ceramic layer of the actuating lever. In this way, the advantages of the ceramic layer can be used particularly well.

Figur 1

eine schematische dreidimensionale Darstellung eines Betätigungshebels für einen Ventiltrieb eines Verbrennungsmotors als ein Ausführungsbeispiel der Erfindung;

Figur 2

der Betätigungshebel in der Figur 1 in einer schematischen Draufsicht von der Unterseite.

Further features, advantages and effects of the invention result from the following description of a preferred exemplary embodiment of the invention and the attached figures. Show:

Figure 1

is a schematic three-dimensional representation of an operating lever for a valve train of an internal combustion engine as an embodiment of the invention;

Figure 2

the operating lever in the Figure 1 in a schematic plan view from the bottom.

In the Figure 1 An actuating lever 1 for a valve train of an internal combustion engine is shown as a first exemplary embodiment of the invention. The actuating lever 1 can be divided into a swivel section 2, a valve-side lever section 3 and - in this exemplary embodiment - into a further lever section 4. Lever section 3, swivel section 2 and further lever section 4 are arranged in a line one behind the other and are integrally connected to one another. The actuating lever 1 can be pivoted about a pivot axis 5, which runs through the pivot section 2, so that Lever section 3 and further lever section 4 move rocker-like about pivot axis 5.

A receiving structure 6, in this example a semicircular receiving structure 6, for example for a plunger, is arranged in the further lever section 4. In the swivel section 2 there is arranged a swivel pin 16 which runs coaxially to the swivel axis 5 and on which a roller 7 is placed. The roller 7 can be arranged on a support element, not shown, so that the actuating lever 1 can be pivoted about the pivot axis 5.

The lever section 3 has a contact surface 8 which is flat or slightly curved and extends essentially in a plane which is aligned parallel to the pivot axis 5.

From a functional point of view, a valve actuation movement can be initiated via the receiving structure 6 of the further lever section 4, so that the actuation lever 1 is pivoted about the pivot axis 5 and the valve actuation movement is transmitted via the contact surface 8 to the free end of a valve stem, not shown, in order to control it , especially to open or close. The contact surface 8 thus serves to transmit a valve actuation movement to the valve, not shown, and thus forms a valve contact surface.

From a design point of view, the actuating lever 1 has a base body 9, which is designed as a shaped part, in particular as a sheet metal part made of 16MnCr5. The base body 9 has two side cheeks 10a, b, which extend in the same direction as a radial plane to the pivot axis 5. The side cheeks 10a, b carry the pivot pin 16, so that the pivot pin 16 supports the side cheeks 10a, b in the pivot section 2 against one another.

In the further lever section 4, the side cheeks 10a, b are integrally connected to one another via a connecting region 11, in which Connection area 11 introduced the receiving structure 6 and is molded in this case.

In the lever section 3, the side cheeks 10a, b are integrally connected via a crossbeam area 12 which extends from one side cheek 10a to the other side cheek 10b and provides a support surface 13 for the contact surface 8. A ceramic layer 14, which forms the contact surface 8, is applied flatly on the supporting surface 13, at least in regions.

The ceramic layer 14 is applied by thermal spraying, for example the ceramic layer 14 is plasma sprayed or flame sprayed and has a thickness of approximately 100 μm and is e.g. made of zirconium oxide. The ceramic layer 14 forms wear protection for the contact surface 8.

The side walls 10a, b merge in one piece into guide arm regions 15a, b, which, starting from an upper side of the side walls 10a, b, are bent twice and form axial side boundaries, side webs or side walls for the contact surface 8. The actuating lever 1 is guided relative to the valve stem of the valve in the axial direction of the pivot axis via the guide arm regions 15a, b. The free ends of the guide arm regions 15a are integrally connected to the base body 9, in particular to a section of the side cheeks 10a, b, for example by welding.

The Figure 2 shows the operating lever 1 of the Figure 1 in a schematic plan view from the bottom. In this view it can be seen that the side cheek regions 15 a, b are congruent to the side cheek regions 10 a, b and laterally limit the contact area 8, indicated by a broken line, with the ceramic layer 14 in the axial direction to the pivot axis 5.

Reference list

1

Operating lever

2nd

Swivel section

3rd

Lever section

4th

further lever section

5

Swivel axis

6

Reception structure

7

role

8th

Contact area

9

Basic body

10 a, b

Sidewall areas

11

Connection area

12th

Transom area

13

Wing

14

Ceramic layer

15 a, b

Guide arm areas

16

Swivel pin

Claims (8)

1. A rocker arm (1) for a valve drive of an internal combustion engine having a rocker arm portion (3), wherein the rocker arm portion (3) has a support surface (13) for transmitting a valve actuating movement, and
   having a pivoting portion (2) for the pivotable mounting of the rocker arm portion (3) about a pivot axis (5), wherein the rocker arm (1) has a thermally sprayed-on ceramic layer (14) with a layer thickness of more than 50 µm and less than 120 µm, wherein the ceramic layer (14) is arranged on the support surface (13) and forms a contact surface (8) for transmitting the valve actuating movement, wherein the rocker arm portion (3) has a transverse beam region (12) and guide arm regions (15a, 15b), wherein the transverse beam region (12) extends in the axial direction relative to the pivot axis (5), wherein the contact surface (8) is arranged on the transverse beam region (12) and wherein the guide arm regions (15a, 15b) form an axial boundary with respect to the contact surface (8), wherein the rocker arm (1) has a base body (9), wherein the base body (9) is designed as a formed sheet-metal part made of steel, which integrally comprises the guide arm regions (15a, 15b) and the transverse beam region (12), and wherein the formed sheet-metal part has two side-wall regions (10a, 10b), wherein, in the pivoting portion (2), the side-wall regions (10a, 10b) each have a holder for a pivoting device (7, 16), wherein the transverse beam region (12) connects and/or bridges the two side-wall regions (10a, 10b) in the axial direction relative to the pivot axis (5), and wherein the guide arm portions (15a, 15b) are formed as extensions (10a, 10b) of the side-wall regions, which are bent in such a way that they form the axial boundaries of the contact surface (8).
2. The rocker arm (1) according to claim 1, wherein the ceramic layer (14) is formed by plasma spraying.
3. The rocker arm (1) according to claim 1 or 2, wherein the contact surface (8) is designed as a valve contact surface for directly contacting a valve.
4. The rocker arm (1) according to any one of the preceding claims, wherein the rocker arm (1) is designed as a cam follower or as a rocker lever.
5. The rocker arm (1) according to any one of the preceding claims, wherein the rocker arm (1) has an additional rocker arm portion (4), the additional rocker arm portion (4) having a connecting region (11), wherein the connecting region (11) extends in the axial direction relative to the pivot axis (5) and connects and/or bridges the two side-wall regions (10 a, b) in the axial direction relative to the pivot axis (5), wherein a holder structure (6) for an actuator element is arranged in the connection region (11) and wherein the formed part comprises the additional rocker arm portion (4).
6. The rocker arm (1) according to any one of the preceding claims, wherein the ceramic layer (14) is formed of zirconia.
7. The rocker arm (1) according to any one of the preceding claims, wherein the formed sheet-metal part is made of steel having the composition 16MnCr5.
8. A valve drive for an internal combustion engine, having at least one valve and at least one rocker arm (1) according to any one of the preceding claims for actuating the valve.

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