Variable Valve Drive Cam Element Ramp Interaction
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Solution Overview
Problem
Existing variable valve drive devices for internal combustion engines are complex, prone to wear, and limited in variability of valve lift, with many components and contact surfaces leading to unfavorable tolerance and actuation play.
Innovation Solution
A cam element with a counter-ramp surface inclined to the axis of rotation interacts with the ramp surface of a push rod, reducing wear and jamming, allowing direct contact and minimizing transmission elements for precise adjustment, and featuring a ramp surface that extends over the push rod's front surface with varying angles of inclination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple contact surfaces and transmission elements are used to actuate the cam element, then the valve lift can be varied, but wear increases and actuation precision deteriorates due to tolerance accumulation
Solution Approach 1:
The patent removes intermediate transmission elements (balls, pins, retaining pins, locking pins) from the actuation mechanism. The push rod directly contacts the cam element's counter-ramp surface, eliminating multiple contact surfaces and their associated wear and tolerance issues while maintaining valve lift variability through the cam element's pivoting motion.
Solution Approach 2:
The counter-ramp surface on the cam element serves as an integrated intermediary that combines the functions of multiple separate components. It provides both the actuation surface for the push rod and the geometric transformation mechanism, eliminating the need for separate balls, pins, and retaining structures while reducing wear points.
2Device complexity
If a frustoconical push rod ramp is used to actuate the cam element, then the structure is simple, but the cam element can only be displaced by half the diameter of the push rod and jamming may occur
Solution Approach 1:
Instead of forming the ramp on the push rod (as in prior art), the invention places the ramp surface on the cam element itself. This inversion allows the push rod to simply push against the cam element's counter-ramp surface, enabling greater displacement range without increasing push rod complexity and eliminating the half-diameter limitation.
Solution Approach 2:
The counter-ramp surface is designed with varying angles of inclination that extend beyond the simple frustoconical geometry. This dimensional enhancement of the ramp surface allows the cam element to pivot through a larger angular range, increasing displacement beyond half the push rod diameter while maintaining structural simplicity.
3Device complexity
If the ramp surface has a single inclination angle, then the structure is simple, but self-locking and incorrect actuation may occur
Solution Approach 1:
The counter-ramp surface is designed with different inclination angles in different regions. The varying angles provide optimal actuation at different stages of cam element pivoting, preventing self-locking in some regions while ensuring correct actuation in others. This local variation in geometry maintains reliability without excessive overall complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design enables a wide range of valve lift adjustments with reduced wear and improved precision, avoiding self-locking and jamming, while maintaining a simple structure and minimizing contact points for enhanced operational reliability.
Implementation Method 1
The push rod (6) has a ramp surface (8) which is arranged on a first end face (9) of the push rod (6) and is inclined to the axis of rotation (2a) of the camshaft (2). The cam element (3) has a counter-ramp surface (13) on which the ramp surface (8) of the push rod (6) acts.
Data Source
Figure 1~3
Figure 4~5
AI summary
The invention relates to a variable valve drive device (1) for actuating at least one gas exchange valve, having a camshaft (2) rotatably mounted about an axis of rotation (2a) and having at least one cam element (3) adjustable via an adjusting device (20), wherein the cam element (23) is pivotably mounted about a pivot axis (3a) between at least a folded-in, first position (K) and a folded-out, second position (B) and wherein the adjustable cam element (3) is arranged adjacent to at least one basic cam (4a, 4b) in the direction of the axis of rotation (2a), wherein the adjusting device (20) has at least one push rod (6) arranged within the camshaft (2), wherein the push rod (6) has at least one ramp face (8) formed at least partly at an angle to the axis of rotation (2a) of the camshaft (2). The cam element (3) has a mating ramp face (13) interacting with the ramp face (8) of the push rod (6), which is formed at least partly at an angle to the axis of rotation (2a) of the camshaft (2).