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

Abstract

A switchable rocker arm (1) is proposed, specifically for a valve train of a heavy-duty internal combustion engine, with a contact point (2) for a lift cam, a bearing eye (4) and a valve contact foot (5), which valve contact foot (5) is part of a pressure piston (9) guided in a bore (8) of the rocker arm (1), which has coupling slides (10) arranged as ring segments, the pockets (11) of its outer shell (12) being located in diametrically opposite pockets, wherein the rocker arm (1) has an annular pocket (14) concentrically encompassing the bore (8) with the pressure piston (9) and a separate annular cup (15), wherein a compression spring (22) is tensioned against a base (21) of the annular cup (15) as a cam return spring, which acts at its other end against a support (23) of the pressure piston (9),which compression spring (22) is enclosed over a large part of its length by an outer wall (40) of the ring pocket (14) and wherein the coupling slides (10) are encompassed by an annular spring element (24) around their outer sleeves (25) [decoupling].

Description

The invention relates to a switchable rocker arm for a valve drive of a heavy-duty internal combustion engine, having a contact point for at least indirect contact of a lifting cam at one longitudinal end, a bearing eye in the longitudinal central region and a valve contact foot at its underside at the other longitudinal end, which valve contact foot is part of a pressure piston which can be moved longitudinally in an upright bore of the rocker arm and has at least one pair of coupling slides, wherein a receiving region which is aligned with the coupling slides when passing through the base circle of the cam is provided in the bore, wherein the coupling slides can be displaced partially into the receiving region of the bore on the one hand for switching on a stroke of the lifting cam and can be displaced back from this receiving region on the other hand for switching off the stroke of the lifting cam, wherein a path for hydraulic medium for displacing the coupling slides in one direction thereof is formed in the rocker lever, which path is fed upstream by a longitudinal channel in the rocker lever, which channel leads from the bearing eye, which path leads downstream to a pressure chamber in front of the coupling slides, wherein a displacement of the coupling slides in their other direction is effected by a spring means, and wherein the pressure piston is prestressed by a compression spring as a cam restoring spring, which is supported on the one hand on the rocker lever and acts on the other hand against a support of the pressure piston.The term "heavy-duty internal combustion engine" is understood to mean a machine as is used in particular for driving a truck, transporter, light transporter, agricultural working equipment, ship, mining or construction site equipment, etc.The unpublished DE 10 2023 115 987.9 discloses a switchable rocker arm for a valve drive of a heavy-duty internal combustion engine. Two pairs of coupling slides lying one above the other are shown in the head region thereof. The pair of coupling slides on the valve side is seated in a radial bore of the pressure piston in the decoupling mode. For coupling with an annular groove in a bore which leads the pressure piston, the two coupling slides have flattened upper sides. The cam reset spring includes exposed the outer jacket of the plunger.Reference is also made to DE 199 14 046 A1. This discloses a shut-off rocker arm in an OHV valve drive with a camshaft lying at the bottom for a passenger car internal combustion engine.It is an object to design a switchable rocker arm for a valve drive of a heavy-duty internal combustion engine, which rocker arm is compact and saves installation space and the coupling mechanism of which rocker arm is capable of withstanding the high loads in a valve drive of a heavy-duty internal combustion engine.According to the invention, this object is achieved by the novel features of claim 1.Accordingly, the coupling slides of the at least one pair are situated diametrically opposite one another in pockets of an outer jacket of the pressure piston, wherein each coupling slide is a ring segment, wherein a ring pocket comprising a separate ring cup therein concentrically enclosing the bore thereof starts from the underside of the rocker lever, wherein the path for the hydraulic medium for the outward displacement of the coupling slides is formed between an outer jacket of the ring cup and the ring pocket, said path being fed at the input by the longitudinal channel in the rocker lever and leading at the output to the pressure piston, wherein the pressure piston has a pressure chamber at least indirectly in front of the inner end face of the coupling slides for the inward displacement thereof into the receiving region of the bore, wherein the rearward displacement of the coupling slides is effected by an annular spring element around the outer jacket thereof when the pressure of hydraulic medium is reduced / deactivated.The rocker arm, which may optionally also be present as a rocker arm, is very compact especially at its other longitudinal end (valve side) and can therefore also be used well in restricted installation space conditions. The at least one compression spring as a cam return spring is in this case mostly housed by the annular pocket comprising the pressure piston and supported on a support of the pressure piston present, for example, as an annular plate.According to a further feature of the invention, a thin-walled annular cup runs in the annular pocket, which may consist, for example, of sheet metal. This annular cup serves on the one hand for deflecting and forwarding hydraulic medium, which is directed longitudinally through the rocker arm, between its outer jacket and the annular pocket. It is clear here that at least one storage space for the hydraulic medium can also be formed in this deflection region. At the same time, the compression spring sits directly in the annular cup and is supported at one end on its base, which base lies opposite a base of the annular pocket and runs circumferentially outside the path for the hydraulic medium at least in sections directly on the base of the annular pocket.Due to the ring segment-like configuration of the at least two coupling slides accommodated in the pressure piston in a space-saving manner, a low-surface-pressure introduction (planar surfaces) takes place in the coupling case (transmission of cam stroke). If, as proposed according to a development of the invention, two pairs of coupling slides are installed whose axial lines form a cross, so that the total of 4 coupling slides are evenly distributed circumferentially in their pockets in the outer jacket of the pressure piston, the component load is further significantly reduced.Particularly preferably, the rocker arm is to be used as an engine brake rocker arm. In this case, it can preferably, but not exclusively, additionally act, in addition to a main rocker arm, on a valve bridge, for example on the outlet side, of the valve drive.A further contribution in the direction of optimizing the installation space is made by the selection of an annular spring element around the outer shells of the coupling slides for their rearward displacement into their pockets in the pressure piston. According to a refinement of the invention, the spring element lies in a manner similar to a belt in channel-like depressions of the outer casings of the coupling slides and can be, for example, a tubular spring, a spring ring or a standardized securing ring.As proposed in a development of the invention, the two diametrically opposite pockets in the pressure piston for the coupling slides should be connected by a radial bore. At the same time, each coupling slide has a piston-like extension on its inner ring jacket, via which it is inserted in the radial bore. An inner end face of the respective extension is provided as a pressure surface for the hydraulic medium and delimits a pressure chamber within the radial bore.The receiving region of the bore of the rocker lever for the coupling slides can be a simple annular groove for all coupling slides or, for example, a segment-like puncture or a window per coupling slide. Depending on the configuration of a transition for the hydraulic medium from the path in the annular pocket to the pressure piston, in the first-mentioned solution, it is optionally possible to dispense with a rotation prevention of the pressure piston with respect to the housing.According to a further dependent claim, it is proposed to provide the rocker lever with a hydraulic play compensating element which is seated in a guide bore of the pressure piston and the compensating piston of which has the valve contact foot which can be formed, for example, by the base thereof. Alternatively, an angular joint is intended.As a contact point for the starting of the lifting cam, wherein a cam group is also possible if necessary, a pin-mounted roller is proposed at one longitudinal end of the rocker lever. The roller is seated in a pocket which is open from the underside and / or one longitudinal end. A closed bottom of the pocket is formed by the top of the rocker arm. The upper side in the roller region can serve as a one-end support with a guide function for a further cam reset spring.For the drawing:• FIG. 1 shows the rocker lever in a three-dimensional view,• FIG. 2 shows the rocker arm at the other, valve-side end in longitudinal section;• FIG. 3 shows the rocker arm at the other, valve-side end in cross section, and• Fig. 4 shows as a detail the coupling slide.FIG. 1 shows a three-dimensional overall view of the rocker arm 1. The rocker arm 1 is shown as a solid part. On a longitudinal end 3 shown here on the right, it has a contact point 2 designed as a roller for a run-on of a lifting cam. The contact point 2 (roller) is located largely in a pocket 37 of the rocker arm 1, the closed bottom 38 of which is bounded by an upper side 39 of the rocker arm 1.In the region of a longitudinal center, the rocker lever 1 has a bearing eye 4 for pivotably supporting on an axle or a bearing block.At the other longitudinal end 7, shown here on the left, a valve contact foot 5 protrudes from an underside 6 of the rocker lever 1. The latter is part of a pressure piston 9 which is guided in a longitudinally movable manner in a bore 8 of the rocker arm 1 running in the valve direction (see also FIGS. 2, 3 ). The pressure piston 9 encloses a valve clearance compensating element 34 in a guide bore 35, the compensating piston 36 of which has the valve contact foot 5.Above the valve clearance compensating element 34, two intersecting radial bores 26 are located in the pressure piston 9, the latter ending radially on the outside in pockets 11 which intersect an outer jacket 12 of the pressure piston 9. Seated in each pocket 11 is a coupling slide 10, which is present as a ring segment and is planar at its upper and lower ring ends 30, 31 (see also FIG. 4 ). The relevant coupling slide 10 has on its inner ring jacket 27 a piston-like extension 28, which is guided in the respective radial bore 26 and whose inner end 29 forms a pressure surface for hydraulic medium for its outward displacement. The inner ends 29 of the coupling slides 10 thus delimit pressure spaces 20 for the hydraulic medium in the cross region of the two radial bores 26.According to FIGS. 2, 3, the coupling slides 10 are shown in their decoupling mode, i.e. they are located in their complementary pockets 11 in a rearward / retracted manner.In the bore 8 guiding the pressure piston 9, an annular receiving region 13 is provided for the coupling slides 10, which is aligned with the latter when passing through the cam base circle. For the activation / activation of a stroke of the lifting cam (engine brake stroke) acting on the rocker arm 1, the coupling slides 10 can be displaced in sections into the ring-like receiving region 13 of the bore 8 of the rocker arm 1 during passage through the cam base circle via hydraulic medium that can be guided into the pressure chambers 20 in front of their inner ends 29.Decoupling and thus deactivation of the cam stroke takes place with reduced / switched-off pressure of hydraulic medium again during the passage of the cam base circle. An annular spring element 24 which is tensioned around outer ring shells 33 of the coupling slides 25 serves for this purpose. This, for example a tension ring, brings about the rearward displacement of the coupling slides 25 into their pockets 11 in the outer shell 12 of the pressure piston 9. For guiding the spring element 24, the outer ring shells 33 of the coupling slides 25 are recessed in a channel-like manner (see FIG. 4 ).FIGS. 2, 3 show that an annular pocket 14 concentrically surrounding the bore 8 thereof starts from the underside 6 of the rocker arm 1, which pocket is deep enough to run over a large part of the height of the rocker arm 1 at the other longitudinal end. A separate annular cup 15 made of steel sheet is pressed into the annular pocket 14. A compression spring 22 (helical compression spring) is tensioned at one end against a base 21 of the annular cup 15 as a cam return spring. At the other end, the compression spring 22 acts against a support 23 of the pressure piston 9 designed as an annular plate axially outside the bore 8, which can be seen to mean that the compression spring 22, which can also be present as a compression spring pack, is surrounded over a large part of its length by an outer wall 40 of the annular pocket 14 (see also FIG. 1 ).It can also be seen from FIG. 2 (see arrow specifications) that a path 17 for the hydraulic medium is formed between an outer jacket 16 of the thin-walled annular cup 15 and the annular pocket 14 enclosing the latter. This path 17 is fed by a longitudinal channel 18 in the rocker arm 1 starting from the bearing eye 4 and leads as a U-shaped deflection via a radial crossover 42 in the pressure piston 9 to a path 19 therein. The path 19 supplies, on the one hand, a storage chamber 41 of the valve clearance compensating element 34 and, on the other hand, it leads centrally to the pressure chambers 20 of the two radial bores 26 in the pressure piston 9.List of Reference Numbers1 Rocker lever 2 contact point 3 longitudinal end 4 bearing eye 5 valve contact foot 6 underside 7 longitudinal end 8 bore 9 pressure piston 10 coupling slide 11 pocket 12 outer jacket 13 receiving region 14 annular pocket 15 annular cup 16 outer jacket 17 path 18 longitudinal channel 19 path 20 pressure chamber 21 base 22 compression spring 23 support 24 spring element 25 outer jacket 26 radial bore 27 inner annular jacket 28 extension 29 inner end 30 upper annular end 31 lower annular end 32 driver end face 33 outer annular jacket 34 valve play compensating element 35 guide bore 36 compensating piston 37 pocket 38 base 39 upper side 40 outer wall 41 storage chamber 42 radial crossoverReferences included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedDE 10 2023 115 987.9

[0003] DE 199 14 046 A1

[0004]

Claims

Switchable rocker arm (1) for a valve drive of a heavy-duty internal combustion engine, having a contact point (2) for at least indirect contact of a lifting cam at one longitudinal end (3), a bearing eye (4) in the longitudinal central region and a valve contact foot (5) at its underside (6) at the other longitudinal end (7), which valve contact foot (5) is part of a pressure piston (9) which can be moved longitudinally in an upright bore (8) of the rocker arm (1), which pressure piston (9) has at least one pair of coupling slides (10) which are seated in diametrically opposite pockets (11) of its outer jacket (12), wherein a receiving region (13) which is aligned with the coupling slides (10) during passage through the base circle of the cam is provided in the bore (8), wherein the coupling slides (10) can be displaced in sections into the receiving region (13) of the bore (8) on the one hand for switching on a stroke of the lifting cam and can be displaced back into their pockets (11) in the pressure piston (9) from this receiving region (13) on the other hand for switching off the stroke of the lifting cam, wherein each coupling slide (10) is a ring segment, wherein an annular pocket (14) comprising a separate annular pocket (15) therein concentrically surrounding the bore (8) of the tilting lever (1) starts from the underside (6) of the tilting lever (1), wherein a path (17) for hydraulic medium for displacing the coupling slides (10) is formed on the one hand between an outer jacket (16) of the annular pocket (15) and the annular pocket (14), Upstream of a longitudinal channel (18) in the rocker arm (1) starting from the bearing eye (4) and leading downstream to a path (19) in the pressure piston (9), which opens into a pressure chamber (20) at least indirectly in front of inner ends (29) of the coupling slides (10), wherein, on the other hand, a compression spring (22) is tensioned against a base (21) of the annular cup (15) as a cam return spring, which compression spring acts against a support (23) of the pressure piston (9) at the other end, which compression spring (22) is surrounded over a major part of its length by an outer wall (40) of the annular pocket (14), and wherein the coupling slides (10), for their inward displacement with reduced / switched-off pressure of hydraulic medium, are surrounded by an annular spring element (24) around their outer jacket (25).Rocker arm according to Claim 1, wherein the pockets (11) of the pair of coupling slides (10) are connected via a radial bore (26) into which the path (19) of the pressure piston (9) opens, wherein each coupling slide (10) has, on its inner ring jacket (27), a piston-like extension (28) which is guided in the radial bore (26) and the inner end face (29) of which forms a pressure surface for the hydraulic medium for its displacement out.Rocker lever according to Claim 1 or 2, wherein the respective coupling slide (10) is planar on its upper and lower ring end face (30, 31) and at least the driver end face (32) of the receiving region (13) of the bore (8) of the rocker lever (1).Rocker arm according to Claim 1 or 3, wherein the receiving region (13) of the bore (8) of the rocker arm (1) is present either as a circumferential groove for all the coupling slides (10) or as a segmental puncture per coupling slide (10).Rocker arm according to Claim 1, wherein an outer ring jacket (33) of the respective coupling slide (10) is recessed in a channel-like manner for the spring element (24) to be seated in.Rocker arm according to Claim 1, wherein the rocker arm (1) is provided with a hydraulic valve clearance compensation element (34) which is seated in a guide bore (35) of the pressure piston (9) and the compensation piston (36) of which has the valve contact foot (5).Rocker arm according to Claim 1, wherein the pressure piston (9) has exactly two pairs of coupling slides (10), the connecting axial lines of which form a cross.Rocker arm according to Claim 1, in which the contact point (2) for the starting of the lifting cam at one longitudinal end (3) is a roller which is seated substantially in a pocket (37) of the rocker arm (1), the closed bottom (38) of which is delimited by an upper side (39) of the rocker arm (1).The rocker arm according to claim 1, wherein the rocker arm (1) is an engine brake lever.

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