Variable Valve Drive Switchable Cam Follower Mechanism
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Solution Overview
Problem
Existing variable valve trains for internal combustion piston engines require multiple hydraulic or electrical switching lines and actuators, making them complex, costly, and space-intensive, especially when switching gas exchange valves in groups.
Innovation Solution
A variable valve train design using switchable rocker arms with a coupling bolt guided in a transverse bore of the primary lever, actuated by a single linear shift rod and leaf spring connecting elements, allowing for mechanical switching without separate hydraulic or electromagnetic actuators, thus simplifying the actuation mechanism and reducing space requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple hydraulic or electrical switching lines and actuators are used for each rocker arm, then the valve lift control flexibility is improved, but the device complexity and space requirements increase
Solution Approach 1:
The patent merges multiple separate actuation systems into a single common actuating device that controls multiple rocker arms simultaneously. The linear actuator with shift rod provides unified mechanical actuation for primary and secondary levers across multiple cylinders, reducing the number of separate hydraulic or electrical actuators while maintaining independent valve lift control flexibility through the switchable coupling mechanism.
Solution Approach 2:
The common actuating device serves multiple functions: it actuates both primary and secondary levers, controls multiple rocker arms across different cylinders, and enables both coupled and decoupled states for different operating conditions. The single linear actuator replaces multiple specialized actuators, providing universal control capability that reduces system complexity while maintaining adaptability.
2Manufacturing precision
If separate hydraulic or electrical actuators are provided for each rocker arm, then the switching precision is improved, but the manufacturing cost and device complexity increase
Solution Approach 1:
The patent combines multiple actuation functions into a single mechanical actuating device with a common linear actuator and shift rod that simultaneously controls multiple rocker arms. This merging approach maintains switching precision through the direct mechanical coupling mechanism while reducing the number of separate actuators, thereby lowering manufacturing complexity and cost.
Solution Approach 2:
The mechanical coupling element with spring biasing provides self-service switching functionality where the system automatically transitions between coupled and decoupled states based on operational requirements, reducing the need for complex external actuation systems while maintaining precise switching control through the inherent mechanical design.
3Device complexity
If a compact actuation mechanism is used to reduce space requirements, then the device complexity is reduced, but the switching reliability may be compromised
Solution Approach 1:
The coupling element with integrated spring biasing provides self-service reliability by automatically maintaining proper engagement forces and enabling automatic transition between coupled and decoupled states. The spring-loaded design ensures consistent contact forces without requiring complex external actuation, thereby maintaining switching reliability through the self-regulating mechanical design.
Solution Approach 2:
The mechanical coupling element acts as an intermediary between the linear actuator and the rocker arm, providing reliable force transmission and engagement. This intermediary mechanism ensures that the simplified actuation system maintains switching reliability through direct mechanical coupling with adequate force transmission, rather than relying on complex hydraulic or electrical systems.
Data Source
Figure 1
Figure 1a
Figure 1b
AI summary
The invention relates to a variable valve drive (1) of an internal combustion engine, comprising at least one functionally identical gas exchange valve per cylinder, the valve stroke of which is specified by at least one primary cam (7) and a secondary cam (8) of a camshaft (6) and can be selectively transmitted to at least one paired gas exchange valve by means of a switchable cam follower (10) which has a primary follower (14) and a secondary follower (19). Each of the coupling elements (17) of the switchable cam follower (10) is designed as a coupling bolt which is guided in a transverse bore (16) of the primary follower (14) in an axially movable manner and which can be moved into an opposite coupling bore (28) of the secondary follower against the restoring force of a spring element (18) by means of a switching bolt (25) which is axially movable in a transverse bore (24) of the secondary follower (19). The outer end (26) of each switching bolt protrudes out of the secondary follower, and each switching bolt is connected to a selector rod (34) at said end via a connection element (29), said selector rod being arranged parallel to the camshaft (6) and being longitudinally movable by means of a linear actuator (31).