Switchable bridge for a valve train of a heavy-duty internal combustion engine

Abstract

A switchable bridge (1) for a valve train of a heavy-duty internal combustion engine is proposed, comprising a crossbeam-like base body (2) whose underside (3) has a valve contact surface (5) in front of each longitudinal end (4) and which has a guide bore (8) extending from its upper surface (7) at its longitudinal center, which continues in a pipe extension (9), in which a pressure piston (10) runs, the head (12) of which has an engagement surface (13) for a contact foot of a rocker arm, wherein a transverse bore (14) runs through the base body (2) and intersects the guide bore (8) perpendicularly, in which a coupling slide (15) is located on both sides of the pressure piston (10), which is acted upon inwards by a compression spring (16), each pressure piston (10) has a coupling groove (17) facing the respective coupling slide (15) and a contact foot extending from its head (12) and via the contact foot the rocker arm has an axial channel (18) for pressurized oil,which runs downstream to a supply channel (19) in the pressure piston (10), which leads into a pressure chamber (6) for the pressure oil in front of an inner face (20) of the respective coupling slide (15). It is emphasized that, for an uninterrupted supply of the axial channel (18) in the pressure piston (10) with pressure oil, the contact surface (13) of the head (12) of the pressure piston (10) is formed directly on a top surface (23) of a pressure piece (25) which is guided axially movably on the pressure piston (10) and acted upon by a spring (24) away from it.

Description

[0001] The invention relates to a switchable bridge for a valve train of a heavy-duty internal combustion engine, comprising a crossbeam-like base body, the underside of which has a valve contact surface in front of each longitudinal end, the base body having a guide bore extending from its upper side at its longitudinal center, which is continued in a pipe extension projecting from the underside of the base body, in which a pressure piston runs telescopically, which is acted upon by a return spring from the guide bore and whose head has an engagement surface for a contact foot of a rocker arm, wherein a transverse bore runs through the base body perpendicularly intersecting the guide bore, in which a coupling slide is located on both sides of the pressure piston, which is acted upon inwards by a compression spring means.which pressure piston has a coupling groove facing the respective coupling slide and an axial channel for pressurized oil extending from its head and supplied via the contact foot of the rocker arm, which runs downstream to a supply channel in the pressure piston, which leads into a pressure chamber for the pressurized oil in front of an inner face of the respective coupling slide, wherein the basic body is fanned out in an x-shape in plan view and is formed on the one hand from a first beam with the transverse bore and a second beam circumferentially offset to this with the two valve contact surfaces and wherein, when the coupling slides are coupled into the coupling groove of the pressure piston via the force of the compression spring means, a full valve stroke is realized and, when they are uncoupled from the coupling groove back into their transverse bore via pressurized oil directed into the pressure chamber in front of their inner faces, a zero valve stroke is realized.

[0002] The term "heavy-duty internal combustion engine" refers to a machine used in particular to power a truck, van, light transporter, agricultural equipment, ship, mining or construction site equipment, etc.

[0003] Document US 2014 / 0165941A1 describes a switchable bridge with two diametrically opposed coupling slides as described above. The latter are supplied with pressurized oil via the contact foot of the rocker arm, which runs directly onto the pressure piston.

[0004] CN 1 13 898 439 A lists a switchable bridge as described above. The track of the coupling slides in the base body runs approximately perpendicular to the connecting line of the valve contact surfaces in the base body. It should be noted that the bridge is equipped with a separate valve actuator to represent an engine braking function.

[0005] Another switchable bridge with two hydraulically actuated coupling valves in the decoupling direction is described in DE 10 2022 200 995 A1. Here, too, the bridge is supplied with hydraulic pressure via the contact foot of the rocker arm, which runs directly onto the pressure piston. The raceway of the coupling valves is integrated into the beam-shaped bridge.

[0006] Furthermore, reference is made to DE 10 2011 052 246 A1. The switchable bridge resulting therefrom includes, for example, according to... Fig. 4. A set of three coupling valves arranged in a star pattern within the bridge. The bridge is supplied with pressurized oil via the contact foot of the directly acting rocker arm.

[0007] DE 10 2021 124 855 A1 discloses a switchable bridge actuated by a rocker arm, with a plate that can be moved longitudinally on its upper surface via an external actuator. When the rocker arm is engaged, the plate closes an insertion opening for a contact foot of the rocker arm. When disengaged, the plate is displaced on the upper surface of the bridge via the actuator in such a way that its insertion opening is uncovered, and the rocker arm, with its contact foot, moves "emptily" into the insertion opening during cam stroke.

[0008] The task is to create a switchable bridge that is easy to actuate and simple to build.

[0009] According to the invention, this problem is solved by providing an uninterrupted supply of pressure oil to the axial channel in the pressure piston by forming the contact surface of the head of the pressure piston for the contact foot of the rocker arm directly on the upper side of a pressure piece which is axially movable on the pressure piston and acted upon by a spring and which is guided in a bore of an end face of the pressure piston, wherein each coupling slide has a section-wise flattening on its upper side, starting from its inner face, over which it can be displaced in the coupling groove of the pressure piston, which is designed as a pocket or circumferential groove, in order to ensure an uninterrupted supply of the axial channel in the pressure piston.

[0010] The shutdown of the two gas exchange valves, actuated simultaneously by the bridge, is achieved using simple means that require minimal installation space on the valve side. The transverse bore for the coupling slides is not located directly above the valve contact surfaces, but slightly offset circumferentially. In plan view, the bridge's main body is fanned out in an X-shape and consists of a first beam with the transverse bore and a second beam, offset circumferentially, containing the two valve contact surfaces below. This reduces, for example, any potential influence of deformation of the main body on the coupling slide track when force is applied.

[0011] Due to the axially movable pressure piece provided according to the invention as an engagement surface for the rocker arm's contact foot, even when the rocker arm has completed its basic rotation and is thus "retracted," an uninterrupted supply of hydraulic oil to the axial channel in the pressure piston is ensured, even with basic rotation contact play. The pressure piece ensures permanent contact between the pressure piston and the rocker arm's leading contact foot. The pressure piece can be guided in a bore in an end face of the pressure piston or, outside the scope of the invention, "slid" over the pressure piston. For low-stress force transmission during coupling, the two coupling slides are partially flattened on their upper surfaces, with these flattened sections engaging under a complementary counter-contour of the coupling groove in the outer shell of the pressure piston, which is designed, for example, as a recess or circumferential groove.

[0012] To specify this, a snap ring groove holder for the pressure piston is provided to limit its slight axial travel of, for example, 1 mm.

[0013] Complex hydraulic oil supply systems, such as those running from the cylinder head into a telescopically positioned guide rod for the bridge, are unnecessary. The channels of the pressure piston and ultimately the pressure chamber(s) are continuously supplied with hydraulic oil via an axially downward-running supply from the rocker arm with a contact foot, which could, for example, be an elephant's foot joint.

[0014] It is clear that, outside the scope of the invention, instead of the two piston-like coupling slides diametrically opposed in the transverse bore of the base body, a slide assembly may also be provided. According to a further development of the invention, the compression spring element, also referred to as a lost-motion spring, which acts axially outwards on the pressure piston in the rocker arm direction, is located between a base of the tube extension and an underside of the pressure piston. A compression spring assembly may also be used. Alternatively, the compression spring element can be supported at one end on the outside of an upper surface of the base body and encompass the pressure piston at its head region, and at the other end bear against a ring plate or the like fixed to the pressure piston.

[0015] Furthermore, a subclaim relates that the compression spring means for the respective coupling slide is clamped in front of its outer face and is provided as at least one helical compression spring which rests on the outside against a separate, disc-like stop in the transverse bore, which may simultaneously be travel-limiting and have a damping function for the respective coupling slide.

[0016] Particularly in cases where the coupling groove in the pressure piston does not have a circumferential annular groove, a simple anti-rotation device for the pressure piston in its guide bore of the base body is proposed. In this case, an anti-rotation element, such as a pin, can project radially from one of the components (pressure piston or guide cylinder) into a longitudinal groove of the other component.

[0017] To implement an additional engine braking function, one of the two valves, in this case the exhaust valves, can be actuated by a separate engine brake rocker arm. A pin-like valve actuator runs relatively freely in a bore in the base body above the respective valve.

[0018] The bridge's main body is a solid component and is available as either a MIM or cast piece. Contact points or bores in the main body can be coated with a wear-resistant layer such as a hard coating (e.g., DLC).

[0019] The bridge can also be used in the valve train of a passenger car internal combustion engine, if necessary.

[0020] Regarding the drawing: • Fig. Figure 1 shows a longitudinal section through the bridge and • Fig. Figure 2 shows a spatial view of the bridge.

[0021] From the Fig. 1, Fig. Figure 2 shows a switchable bridge 1 for a valve train of a heavy-duty internal combustion engine. The bridge 1 consists of a essentially crossbeam-like, solid cast base body 2. This can be seen from Fig. 2, that the base body 2 is fanned out in an x-shape in plan view and consists, on the one hand, of a first beam 21 with a transverse bore 14 (sa Fig. 1) and a second beam 22 slightly offset in circumference with valve contact surfaces 5 on a bottom side 3 in front of each longitudinal end 4.

[0022] Exactly at its longitudinal midpoint (intersection of the two beams 21, 22), the base body 2 has a guide bore 8 extending from its upper surface 7. The latter continues in a pipe extension 9, which projects from the aforementioned lower surface 3 of the base body 2 and is integrally connected to it. A pressure piston 10 runs telescopically guided in the guide bore 8 (see figure). Fig. 1) This is springed from the guide bore 8 by a return spring 11 (lost motion spring) clamped between a cylinder head-side base 29 of the pipe extension 9 and an underside 30 of the pressure piston 10.

[0023] A head 12 of the pressure piston 10 has a contact surface 13 for a rocker arm contact foot. More precisely, the contact surface 13 is formed directly on the upper surface 23 of a pressure piece 25, which is axially movably guided on the pressure piston 10 and acted upon by a spring 24. The latter pressure piece 25 is located in a sac-like bore 26 in an end face 27 of the pressure piston 10 and its axial travel, which is, for example, a maximum of 1 mm, is limited by a snap ring groove retainer 28. The pressure piece 25 ensures continuous contact of the pressure piston 10 with the rocker arm contact foot.

[0024] Furthermore, it is assumed that Fig. Figure 1 shows that a transverse bore 14, perpendicular to and completely through the guide bore 8, runs through the first beam 21 of the base body 2. A coupling slide 15 is arranged upstream of the pressure piston 10 in the transverse bore 14 on both sides, and this coupling slide has a section-wise flattening 33 on its upper side, starting from its inner face 20. It is connected via this latter section in the Fig. In the coupling shown in Figure 1, the pressure is transferred via a compression spring element 16, which is a helical compression spring and is positioned in front of its outer face 31 in the transverse bore 14, into a respective coupling groove 17 of the pressure piston 10. The coupling groove 17 is located on the outer surface of the pressure piston 10 as a wrench flat or pocket. At the other end, the compression spring element 16 acts against a disc-like stop 32 that is attached to the outside of the transverse bore 14.

[0025] According to Fig. The pressure piston 10 has an axial channel 18 for pressurized oil extending from its head 12 and permanently supplied via the contact base of the rocker arm. This channel is connected to a passage 39 in the pressure piece 25. Downstream, the axial channel 18 leads to a supply channel 19 in the pressure piston 10, which intersects it orthogonally and ultimately leads into a pressure chamber 6 for the pressurized oil in front of an inner face 20 of the respective coupling slide 15. When the cam base circle rotates, pressurized oil pressurizes the two coupling slide 15, causing them to move out of their coupling grooves 17 and back into the transverse bore 14. The pressure piston 10 is thus unlocked and performs a free stroke during cam rotation, so that the gas exchange valves remain unactuated.

[0026] A locking ring 38 prevents the two coupling slides 15 from rotating relative to their transverse bore 14, and this locking ring 38 lies over the flattened surfaces 33 of the coupling slides 15 and sits in the guide bore 8.

[0027] Finally, it shows Fig. 2, that a pin-like anti-rotation element 34 projects radially from the pressure piston 10 into a longitudinal groove 35 of the pipe extension 9. Thus, the pressure piston 10 is rotationally secured relative to the guide bore 8. The stop of the anti-rotation element 34 against an upper face 36 of the longitudinal groove 35, as shown, simultaneously limits the extension of the pressure piston 10 from the guide bore 8. List of reference figures 1 Bridge 2 basic shapes 3 Underside 4 Longitudinal end 5 Valve contact surface 6 Pressure chamber 7 Top 8 guide holes 9 Pipe connection 10 pressure pistons 11 Return spring 12 heads 13 attack surface 14 transverse bore 15 coupling slides 16 Compression spring components 17 coupling groove 18 Axial groove 19 Feed channel 20 Inner forehead 21 bars (first) 22 bars (second) 23 Top 24 springs 25 printed pieces 26 bore 27 End forehead 28 bracket 29 reasons 30 Under-forehead 31 Outer forehead 32 stops 33 Flattening 34 anti-rotation devices 35 longitudinal groove 36 Upper forehead 37 valve actuators 38 Anti-rotation ring 39 Passage

Images