Variable sliding shaft valve drive

Abstract

Variable valve train (1) for a four-cylinder 4V in-line engine of a motorcycle, with a camshaft (3) located in a carrier head of the in-line engine for exclusively actuating synchronously acting gas exchange valves, with one cam group (4) fixed to each gas exchange valve, each cam group (4) comprising a high-lift cam (5) and a low-lift or zero-lift cam (6), wherein the valve train (1) has exactly two separate, longitudinally arranged sliding shaft assemblies (7) in the carrier head, each sliding shaft assembly (7) being assigned to two cylinders of the in-line engine and comprising a pair of rocker arms (8) for each cylinder, each of which is assigned to one of the synchronously acting gas exchange valves and one of the cam groups (4), each sliding shaft assembly (7) further comprising a separate, rotationally secured sliding shaft piece (9),on which the two pairs of rocker arms (8) are pivotably mounted relative to it and axially secured, and to which each sliding axis assembly (7) belongs an e-actuator (10) arranged orthogonally to the corresponding sliding axis piece (9), which acts at one end via its control pin (11) on a drive pin (13) running through a drive contour (12) of the sliding axis piece (9), which, when the e-actuator (10) is energized, can be inserted at the other end into an axial displacement groove profile (14) on the camshaft (3), so that for the two pairs of rocker arms (8) of the respective sliding axis piece (9) either a first displacement position towards the large-stroke cams (5) of the cam groups (4) or a second displacement position towards the small-stroke or zero-stroke cams (6) of the cam groups (4) is achieved.

Description

The invention relates to a variable sliding-shaft valve train for a motorcycle engine, with a camshaft located in a carrier head of the engine for exclusively actuating co-acting gas exchange valves, with one cam group fixed to each gas exchange valve, each cam group comprising a large-lift cam and a small-lift or zero-lift cam, each of which is assigned to one of the co-acting gas exchange valves and one of the cam groups. German patent DE 10 2015 213 266 A1 discloses a variable valve train, system "sliding shaft", for a single-cylinder DOHC 4V internal combustion engine for a motorcycle. As can be seen from Fig. 2, a sliding shaft component with an electric actuator and a sliding groove profile on the camshaft is provided for the single cylinder of the internal combustion engine. The term "motorized two-wheeler" refers specifically to a motorized two-wheeler such as a moped or a motorcycle. Three-wheeled vehicles may also fall under this category. The task is to design a variable sliding shaft valve train that is adapted for a four-cylinder or two-cylinder in-line engine of a motorcycle and at the same time requires few components. Essential to the invention according to claim 1 is that the valve train for the four-cylinder in-line engine has two separate, longitudinally arranged sliding shaft assemblies in the carrier head, wherein each sliding shaft assembly is assigned to two cylinders of the in-line engine and comprises a pair of rocker arms for each cylinder.Each sliding axis assembly has a separate, rotationally secured sliding axis piece on which the two pairs of rocker arms are pivotably mounted relative to this piece and axially secured. Each sliding axis assembly includes an e-actuator arranged orthogonally to the corresponding sliding axis piece, which acts at one end via its control pin on a drive pin running through a drive contour of the sliding axis piece. When the e-actuator is energized, the other end of the drive pin can be inserted into an axial displacement groove profile on the camshaft, so that for the two pairs of rocker arms of the respective sliding axis piece either a first displacement position to the large-stroke cams of the cam groups or a second displacement position to the small-stroke or zero-stroke cams of the cam groups is achieved. In contrast, the valve train for the two-cylinder in-line engine according to dependent claim 2 has only one sliding shaft assembly with an e-actuator. The valve train thus comprises only a rotationally secured sliding shaft assembly spanning the two cylinders, two pairs of rocker arms, four cam assemblies, a sliding groove profile on the camshaft, and an e-actuator for engaging the sliding groove profile. The intake camshaft is one example of a camshaft. The other camshaft, the exhaust camshaft, can be a standard design or it can also be part of a variable valve train. Thus, switching between large-stroke and small-stroke or zero-stroke operation for the entire series of synchronously acting gas exchange valves can be achieved with a small installation space and high functional integration in the cylinder head. A particular advantage of the solution according to claim 1 is that two separate, longitudinally arranged sliding shaft assemblies each operate two cylinders together, thereby reducing the number of switching components relative to the number of valves. This reduces weight, cost, and complexity. The same advantage applies to the valve train according to dependent claim 2, provided for a two-cylinder engine with only one sliding shaft assembly and one electric actuator. The orthogonal arrangement of each e-actuator allows for space-saving, easy-to-install integration and a clear force flow direction for triggering the axial adjustment. The coupling via control pin, drive pin, drive contour, and axial groove profile provides a positively guided, defined adjustment kinematics that promotes short switching times, reproducible end positions, and low switching forces. An advantage is that the fork-like design of the rocker arms with two bearing eyes, according to a further development of the invention, enables a particularly stable and low-tilting-moment bearing arrangement on the sliding axle piece, so that lateral forces from the cam contact are better absorbed and wear at the bearing points is reduced. The ring axially fixed between the fork arms, whereby rings can also be provided on both sides of the respective rocker arm, ensures a defined axial positioning of the rocker arms without additional complex locking mechanisms on each individual arm. According to a further subclaim, the respective e-actuator is to engage the sliding shaft section centrally. This results in a symmetrical load distribution on the subsequent elements to be adjusted. This promotes low switching forces and stable switching operations. Furthermore, the central arrangement allows for a shorter component length and a reduced required stiffness of the sliding shaft section, which supports weight and cost advantages through material-efficient design. It is clear that, for example, in cases of space constraints, the e-actuator can also engage the sliding shaft section off-center. A simple anti-rotation device is proposed for each sliding axle component. This involves a longitudinal flat or a polygonal keyway on the component, combined with a counter contour permanently formed in the support head. This ensures that the orientation of the sliding axle component, and thus the position of the guide and drive geometries, remains permanently defined. According to a further specification of the invention, the two adjustable positions of the sliding shaft are reliably held by a spring-loaded detent mechanism, ensuring stable switching even under vibrations, etc. The detent head, e.g., with a spherical geometry, engages in complementary, e.g., dome-shaped, counter-contours, creating a clear and measurable end-position fix, which reduces the risk of intermediate positions. According to further training, the axial displacement groove profile should be either integrated with the camshaft as a single piece or as part of a separately assembled ring body. This allows for flexible design with regard to manufacturing, material selection, and costs. A monolithic design, for example, promotes high stiffness and a low number of parts. The alternative design with a separately assembled, e.g., pressed-on, ring body, on the other hand, allows for modular manufacturing, including, for example, separate precision machining of the groove profile. A further subclaim provides for a functional separation of the rocker arm into an exclusive cam contact area, an exclusive valve contact area below it, and a laterally adjacent cam passage area. The cam passage area can be recessed relative to the cam contact area. This creates a clear contact and clearance geometry, enabling switching between different cam profiles with a reduced risk of collision and lower frictional losses. The cam contact area can be specifically optimized with regard to surface hardness, lubrication conditions, and contact geometry, for example, by incorporating an applied hard coating, while the valve contact area can be designed independently for efficient force transmission and low surface pressure.The cam passage area ensures that the currently inactive lower smaller cam profile can pass through without unwanted contact when switching to the large-stroke cam. Regarding the drawing: • It shows the only figure, a spatial view from above of a variable valve train of a four-cylinder 4V in-line engine; without the carrier head for the sake of clarity. The variable valve train 1 is designed for a four-cylinder, 4V inline motorcycle engine and is integrated into, or intended for integration into, the engine's cylinder head. A camshaft 3 is mounted in the cylinder head; here, the intake camshaft is shown in the foreground. This camshaft is used exclusively to actuate the synchronized gas exchange valves (in this case, the intake valves). A cam group 4 is fixed to the camshaft 3 for each gas exchange valve, resulting in a total of eight cam groups. Each cam group 4 comprises a long-lift cam 5 (shown on the left) and a short-lift cam 6 (shown on the right). By combining both cams 5 and 6 within the cam group 4, the valve actuation can be performed with either a long or a reduced lift. The carrier head contains two separate sliding shaft assemblies 7, arranged longitudinally one behind the other. Each sliding shaft assembly 7 is assigned to two cylinders of the inline engine. Within each sliding shaft assembly 7, where predominantly identical elements are designated only once, a pair of rocker arms 8 is provided for each of the two cylinders. Each rocker arm 8 is functionally assigned to one of the co-acting gas exchange valves below (not shown) and to a cam group 4 above it. The cylinder-by-cylinder arrangement of the rocker arm pairs 8 within a sliding shaft assembly 7 enables the valve lift characteristics to be switched simultaneously for two cylinders. It is also conceivable that the two sliding shaft assemblies 7 implement different lift profiles. Each sliding axis assembly 7 has a separate sliding axis piece 9. The sliding axis piece 9 forms the common sliding axis for the two associated pairs of rocker arms 8 of the two cylinders. The four rocker arms 8 are pivotally mounted on the sliding axis piece 9 and simultaneously axially secured, so that the rocker arms 8 can pivot relative to the sliding axis piece 9, while the sliding axis piece 9 itself can be axially displaced for switching. The rocker arms 8 are mounted on the sliding axle piece 9 by means of two fork arms 16. Each of the fork arms 16 has a bearing eye 15. The respective rocker arm 8 is mounted on the sliding axle piece 9 via the bearing eyes 15, thus creating a bearing supported on both sides. A ring 17 is provided for axially fixing the rocker arms 8 on the sliding axle piece 9. This ring runs between the fork arms 16 and is axially fixed to the sliding axle piece 9 by means of a pin (not shown). Each sliding shaft assembly 7 is assigned an e-actuator 10, which is arranged orthogonally to the respective sliding shaft section 9. Thus, there are only two e-actuators 10 in total for the four cylinders of the engine. The respective e-actuator 10 engages the sliding shaft section 9 approximately longitudinally at its center. The e-actuator 10 has a control pin 11, which interacts with a separate drive pin 13. The drive pin 13 is guided through a drive contour 12 of the sliding shaft section 9, which is designed as a bore. The control pin 11 acts on the drive pin 13 at one end, while the drive pin 13 can be inserted into an axial sliding groove profile 14 of the camshaft 3 at the other end. As a result of the energizing of the e-actuator 10, the control pin 11 is displaced, causing the drive pin 13 to be moved through the drive contour 12 and at the same time engage in and be guided in the sliding groove profile 14.The sliding groove profile 14 serves as an axial conversion structure, via which a defined axial displacement of the sliding axle piece 9 is implemented. The axial displacement groove profile 14 is part of a separately joined ring body 23. The latter is firmly connected to the camshaft 3, so that the displacement groove profile 14 is available in a defined angular and axial position. Two defined displacement positions are set by the axial displacement of the respective sliding shaft section 9, effected via the e-actuator 10, control pin 11, drive contour 12, drive pin 13, and displacement groove profile 14. In a first displacement position, the rocker arms 8 of the respective sliding shaft section 9 are assigned to the large-stroke cams 5 of the cam groups 4 (see figure). In this position, the valve actuation is effected via the large-stroke cam 5, thus achieving a large valve lift. In a second displacement position (displacement to the right in the figure, not shown), the rocker arms 8 are assigned to the small-stroke cams 6 of the cam groups 4. In this position, a reduced valve lift occurs. In this position, the respective large-stroke cam 5 (shown here on the left) moves freely along its rocker arm 8. The switching action affects both cylinders of the respective sliding shaft assembly 7 together, as they are coupled via the common sliding shaft section 9. The sliding axle piece 9 is designed to prevent rotation, for example to ensure the defined orientation of the drive contour 12, which is provided as a bore. For this purpose, the sliding axle piece 9 has a longitudinal flat 18 at its end. A counter contour 19, fixed to the carrier head and in this case a pin, engages the longitudinal flat 18 and thus prevents the sliding axle piece 9 from rotating about its longitudinal axis. To secure the respective sliding position, a spring-loaded locking pin 20 is provided for each sliding axle piece 9. The locking pin 20 projects radially from the carrier head towards the sliding axle piece 9. At its end, the locking pin 20 has a spherical locking head 21 that engages in a first or second complementary counter contour 22 of the sliding axle piece 9. The counter contours 22 are designed and arranged to correspond to the two sliding positions. Each rocker arm 8 is divided into functional areas. On its upper side, the rocker arm 8 has an exclusive cam contact area 24, shown here on the left, which is designed for direct contact with the respective active large-stroke cam 5 or small-stroke cam 6. Below this, an exclusive valve contact area 25 is provided, through which the rocker arm 8 transmits the stroke movement to the associated gas exchange valve. Adjacent to this on the upper side is a cam passage area 26, shown here on the right. The cam passage area 26 provides a clearance so that the optionally inactive small-stroke cam 6 of the cam group 4 can pass by the rocker arm 8 without contact. Finally, another camshaft 27, here an exhaust camshaft, emerges from the figure in the background of the image. A more detailed description of the construction of the variable valve train 1 for the two-cylinder 4V in-line engine can be omitted, since the valve train 1 is only to be considered longitudinally “halved” according to the single figure. List of reference figures 1 Valve train 3 Camshaft (intake camshaft) 4 Cam assembly 5 High-lift cam 6 Low-lift cam 7 Sliding shaft assembly 8 Rocker arm 9 Sliding shaft piece 10 Electric actuator 11 Control pin 12 Drive contour 13 Drive pin 14 Sliding groove profile 15 Bearing eye 16 Fork arm 17 Ring 18 Longitudinal flat 19 Counter contour 20 Detent pin 21 Detent head 22 Counter contour 23 Ring body 24 Cam contact area 25 Valve contact area 26 Cam passage area 27 Camshaft (exhaust camshaft) QUOTES INCLUDED IN THE DESCRIPTION This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature DE 10 2015 213 266 A1

[0002]

Claims

Variable valve train (1) for a four-cylinder 4V in-line engine of a motorcycle, with a camshaft (3) located in a carrier head of the in-line engine for exclusively actuating synchronously acting gas exchange valves, with one cam group (4) fixed to each gas exchange valve, each cam group (4) comprising a high-lift cam (5) and a low-lift or zero-lift cam (6), wherein the valve train (1) has exactly two separate, longitudinally arranged sliding shaft assemblies (7) in the carrier head, each sliding shaft assembly (7) being assigned to two cylinders of the in-line engine and comprising a pair of rocker arms (8) for each cylinder, each of which is assigned to one of the synchronously acting gas exchange valves and one of the cam groups (4), each sliding shaft assembly (7) further comprising a separate, rotationally secured sliding shaft piece (9),on which the two pairs of rocker arms (8) are pivotably mounted relative to it and axially secured, and to which each sliding axis assembly (7) belongs an e-actuator (10) arranged orthogonally to the corresponding sliding axis piece (9), which acts at one end via its control pin (11) on a drive pin (13) running through a drive contour (12) of the sliding axis piece (9), which, when the e-actuator (10) is energized, can be inserted at the other end into an axial displacement groove profile (14) on the camshaft (3), so that for the two pairs of rocker arms (8) of the respective sliding axis piece (9) either a first displacement position towards the large-stroke cams (5) of the cam groups (4) or a second displacement position towards the small-stroke or zero-stroke cams (6) of the cam groups (4) is achieved. Variable valve train (1) for a two-cylinder 4V in-line engine of a motorcycle, with a camshaft (3) located in a carrier head of the in-line engine for exclusively actuating synchronously acting gas exchange valves, with one cam group (4) fixed to each gas exchange valve, each cam group (4) comprising a high-lift cam (5) and a low-lift or zero-lift cam (6), wherein the valve train (1) has exactly one sliding shaft assembly (7) in the carrier head, which is assigned to the two cylinders of the in-line engine and comprises a pair of rocker arms (8) for each cylinder, each of which is assigned to one of the synchronously acting gas exchange valves and one of the cam groups (4), which sliding shaft assembly (7) further comprises a rotationally secured sliding shaft piece (9),on which the two pairs of rocker arms (8) are pivotably mounted relative to it and axially secured, and to which sliding axis assembly (7) belongs an e-actuator (10) arranged orthogonally to the sliding axis piece (9), which acts at one end via its control pin (11) on a drive pin (13) running through a drive contour (12) of the sliding axis piece (9), which, when the e-actuator (10) is energized, can be inserted at the other end into an axial displacement groove profile (14) on the camshaft (3), so that for the two pairs of rocker arms (8) of the sliding axis piece (9) either a first displacement position towards the large-stroke cams (5) of the cam groups (4) or a second displacement position towards the small-stroke or zero-stroke cams (6) of the cam groups (4) is achieved. Variable valve train according to claim 1 or 2, characterized in that the respective rocker arm (8) terminates on the sliding shaft side with two fork arms (16) each comprising a bearing eye (15), via which bearing eyes (15) it is placed on the sliding shaft piece (9), wherein a ring (17) runs between the fork arms (16) and is axially fixed on the sliding shaft piece (9) for its axial fixation on the sliding shaft piece (9). Variable valve train according to claim 1 or 2, characterized in that the respective e-actuator (10) engages its sliding shaft piece (9) longitudinally in the center. Variable valve train according to claim 1 or 2, characterized in that the respective sliding shaft piece (9) has at least one longitudinal flat (18) or a multi-sided key surface on which a carrier head-fixed counter contour (19) engages to prevent its rotation. Variable valve train according to claim 1 or 2, characterized in that at least one spring-loaded detent pin (20) is provided for each sliding shaft piece (9), which projects radially from the carrier head onto the latter and engages at its end with a detent head (21) in a first or second complementary counter contour (22) of the sliding shaft piece (9) to secure the first or second displacement position of the latter. Variable valve train according to claim 1 or 2, characterized in that the respective axial displacement groove profile (14) on the camshaft (3) is either monolithically connected to it or is present as part of a separately joined ring body (23). Variable valve train according to claim 1 or 2, characterized in that the respective rocker arm (8) is structured into two longitudinal areas, on the one hand an exclusive cam contact area (24) and an exclusive valve contact area (25) below it on the upper side, and on the other hand a cam passage area (26) adjacent laterally on the upper side.

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