Beam-like bridge for a valve drive of a heavy-duty internal combustion engine

Description

[0001] The invention relates to a beam-like bridge for a valve train of a heavy-duty internal combustion engine for transmitting a cam stroke to two co-acting gas exchange valves, which bridge is a one-piece hollow body with an inverted U-profile, manufactured from sheet steel using stamping and bending techniques, formed by a transverse wall with side walls suspended from its longitudinal edges, which transverse wall has a plateau at each of its longitudinal ends and a raised contact zone at its longitudinal center for at least indirect cam counter-rotation, which plateaus are connected to the contact zone via a roof section, wherein a gas exchange valve contact surface is located on a lower side of the transverse wall at each of its longitudinal ends.

[0002] A heavy-duty internal combustion engine is understood to be a machine such as is used in particular to power a truck, van, light transporter, agricultural work equipment, ship, mining or construction site equipment, etc.

[0003] DE 20 2019 103 327 U1 discloses a bridge for the valve train of a heavy-duty internal combustion engine. The gas exchange valve contact surfaces are arranged on the undersides of its plateaus. The transverse wall is provided with a rectangular contact zone in the region of its longitudinal center, which is connected to the plateaus via plate segments.

[0004] A similar bridge to the one mentioned above is described in DE 20 2019 101 904 U1. In this design, the side walls are connected at the longitudinal ends of the bridge.

[0005] Another bridge is revealed by DE 10 2010 011 455 A1. This one is designed as a solid component using casting or forging techniques.

[0006] Reference is also made to documents DE 10 2014 224 625 A1 and DE 10 2006 002 994 A1. Each of these citations shows a stamped and bent steel rocker arm, as used in the valve train of passenger car internal combustion engines, which has an embossed channel on its upper side at the valve-side longitudinal end.

[0007] The task is to create a bridge like the one mentioned above that is very cost-effective, lightweight, and can be used between large vertical distances from its contact zone to the gas exchange valve surfaces.

[0008] According to the invention, this problem is solved by the fact that, in order to increase the distance between the contact zone and the two gas exchange valve contact surfaces, the plateaus each have a rectangular channel-like central section that is lowered relative to the longitudinal edges by deep drawing, the longitudinal walls of which have their outer surfaces positioned in front of the inner sides of the transverse walls in height sections, so that an M-like profile is present in the section of the plateaus, wherein the gas exchange valve contact surfaces are located on undersides of the central sections of the plateaus, and the roof sections are spherical segment-like.

[0009] Thus, a vertically movable bridge for the simultaneous opening of two gas exchange valves, achievable inexpensively by stamping and bending, is available, specifically for an application in a valve train of a commercial vehicle internal combustion engine or other heavy-duty working machine, which inherently possesses the required stiffness, is comparatively lightweight and is also suitable for large vertical installation distances.

[0010] The large distance to be bridged between the contact zone for the at least indirect cam counter-rotation on the upper side and the valve contact surfaces on the underside of the transverse wall of the bridge is now cleverly achieved by the two rectangular channel-like lowered, reshaped sections of the plateaus, while maintaining the generally inverted U-shape of the bridge.

[0011] Increasing the drawing depth of the contact zone raised from the top surface is subject to forming limitations, for example, the risk of cracking. In cross-section through the central sections, this results in an M-shaped design with a doubling of wall material. The inner surfaces of the longitudinal walls of each rectangular channel serve as lateral guides for the respective gas exchange valve. It is clear at this point that the two rectangular channels could also be trough-shaped or similar.

[0012] According to a preferred embodiment of the invention, the bridge should have a wall thickness of 2 to 10 mm, based on its base body excluding the recessed central sections. A thick sheet metal construction with a thickness of approximately 4 to 6 mm is particularly preferred.

[0013] At the same time, it is proposed that the bridge should end openly at its longitudinal ends.

[0014] Furthermore, it is proposed that the contact zone on the upper surface of the bridge be circular. Alternatively, the contact zone can have an elliptical shape. It can also be spherically convex and / or embossed and / or coated with a hard material layer.

[0015] If the free, lower edge of the side walls is flat, as specifically suggested, handling the bridge is easier. If necessary, the latter can also be shaped downwards in the central area, which may increase stiffness and provide material for the deep-drawing process.

[0016] Regarding the drawing: Figure 1 shows a spatial view of the bridge in its general design after its first draw step and Figure 2 The image shows the bridge as described above, in its final form with channels molded into the plateaus.

[0017] Out of Figure 2A beam-like bridge 1 made of sheet steel is used for a valve train of a heavy-duty internal combustion engine. The bridge 1 serves to simultaneously transmit a cam stroke to two synchronously acting gas exchange valves and is not guided by columns or the like relative to a cylinder head of the internal combustion engine.

[0018] In view of the high forces / loads occurring in heavy-duty applications, bridge 1 can, for example, be made of thick sheet metal with a wall thickness of 4 mm, although a total thickness range of approximately 2 to 10 mm is intended. Bridge 1 is manufactured using a stamping and bending process in at least two successive drawing stages, whereby Figure 1 The bridge 1, after its essential drawing stage, shows its U-shape inverted in cross-section.

[0019] Bridge 1 has a transverse wall 3 at the top, from whose longitudinal edges 9a side walls 4 are suspended. Thus, bridge 1 forms a hollow body. From a top surface 5 of the transverse wall 3, at a longitudinal center of bridge 1, a raised contact zone 6 projects for the counter-rotation of a lever-like cam follower (rocker arm, rocker arm). The contact zone 6 is clearly circular and slightly convex. Extending from the longitudinal ends 8 of bridge 1, the transverse wall 3 has a plateau 10 on each side. The plateaus 10 are connected to the contact zone 6 via easily deep-drawable, spherical segment-like roof sections 11.

[0020] On an underside 7 of the aforementioned transverse wall 3, a gas exchange valve contact surface 9 is formed in front of each of the opposing longitudinal ends 8 (su). The bridge 1 is guided along the shafts of the gas exchange valves in the shoring by the inner surfaces 14 of the side walls 4.

[0021] Figure 2Bridge 1 is shown after an additional drawing step, which can also be integrated into the preceding drawing step described above. Accordingly, each plateau 10 of the transverse wall 3 has a rectangular channel-like central section 12 that is lowered relative to the longitudinal edges 9a. The thick in the Figures 1, 2 The arrows drawn here symbolize the main drawing directions in the die. As in Figure 2 As can be seen, due to the additional drawing step, the longitudinal walls 13 of the lowered central sections 12 lie section by section with their outer surfaces 14 in front of the inner surfaces 15 of the transverse walls 3. If necessary, a visibly larger distance can also be chosen between them to keep the bending stresses in check. In cross-section, this results in an M-like profile.

[0022] The two-sided gas exchange valve contact surfaces 9 run along under surfaces 16 of the central sections 12. Due to the lowered central sections 12, comparatively high vertical distances between the cam counter-rotation and the gas exchange valves can be spanned via the bridge 1, which has good deep-drawing properties. List of reference figures

[0023] 1) Bridge 2) Edge 3) Transverse wall 4) Side wall 5) Top surface 6) Contact zone 7) Bottom surface 8) Longitudinal end 9) Gas exchange valve contact surface 9a) Longitudinal edge 10) Plateau 11) Roof section 12) Middle section 13) Longitudinal wall 14) Outer surface 15) Inner surface 16) Bottom surface

Claims

1. A beam-like crosshead (1) for a valve train of a heavy duty internal combustion engine for transmitting a cam lift to two co-acting gas exchange valves, which crosshead (1) is a one-piece, stamped and bent hollow body made of sheet steel with an inverted U-profile, formed by a transverse wall (3) with side walls (4) hanging from its longitudinal edges (9a), which transverse wall (3), starting from the longitudinal ends (8) of the crosshead (1), each has a plateau (10) and, at its longitudinal centre on its upper side (5), a raised contact zone (6) for at least indirect cam counter-rotation, which plateaus (10) are each connected to the contact zone (6) via a roof section (11), wherein a gas exchange valve contact surface (9) is located on an underside (7) of the transverse wall (3) at each of the longitudinal ends (8), and wherein the side walls (4) extend unconnected at the longitudinal ends (8) of the crosshead (1), characterised in that, to increase the distance between the contact zone (6) and the two gas exchange valve contact surfaces (9), the two plateaus (10) each have a centre section (12) similar to a rectangular channel, which is lowered relative to the longitudinal edges (9a) by means of deep drawing, the longitudinal walls (13) of which are positioned with their outer surfaces (14) in front of the inner sides (15) of the transverse walls (3) in height sections, such that there is an M-like profile in the section of the plateaus (10), wherein the gas exchange valve contact surfaces (9) are located on lower surfaces (16) of the centre sections (12) of the plateaus (10), wherein the roof sections (11) are spherical segment-like.

2. The crosshead according to claim 1, characterised in that the crosshead (1) has a wall thickness of 2 to 10 mm.

3. The crosshead according to claim 1, characterised in that a free edge (2) of the side walls (4) facing away from the transverse wall (3) is either a flat surface or is curved in the region of the longitudinal centre.