Sliding Cam System Axial Displacement Boundary Portion
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Solution Overview
Problem
Conventional sliding cam systems in variable valve trains face limitations in switching speed and service life due to high forces encountered during axial displacement, particularly with steep ramp angles, which can lead to reduced reliability and increased wear.
Innovation Solution
The sliding cam system incorporates a cam carrier that can be axially displaced using actuators and engagement tracks, with boundary portions on the cams allowing displacement beyond the base circle area, reducing inertial forces and extending the displacement time, thus enabling increased switching speed and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the base circle of the cam is shortened to increase switching speed, then the switching speed increases, but the forces during axial displacement increase due to steeper ramps
Solution Approach 1:
The patent extends the axial displacement range beyond the traditional base circle boundary into the boundary portion of the cam. This dimensional extension provides additional displacement distance, allowing for reduced acceleration forces while maintaining the same switching time, or alternatively enabling faster switching with controlled forces.
Solution Approach 2:
The axial displacement of the cam carrier begins before the cam follower reaches the base circle area, utilizing the boundary portion for preliminary displacement action. This preliminary action in the boundary portion reduces the required ramp angle and associated forces during the main displacement phase.
2Speed
If steep ramps are used to achieve axial displacement in less time, then switching speed increases, but service life decreases due to large forces
Solution Approach 1:
By utilizing the boundary portion of the cam in addition to the base circle area, the patent extends the available displacement distance in the axial dimension. This extended distance allows for gentler ramps that reduce forces and wear, thereby improving service life while maintaining switching speed performance.
Solution Approach 2:
The boundary portion of the cam acts as an intermediary zone between the base circle area and the valve lift area. This intermediary region provides a transition zone that reduces the steepness of the ramp, thereby reducing forces during axial displacement and improving component durability.
3Device complexity
If axial displacement is limited to the base circle area, then the cam system is simple, but the switching speed is limited
Solution Approach 1:
The patent extends the axial displacement range from the traditional base circle-only limitation into the boundary portion of the cam. This dimensional extension provides additional time and distance for axial displacement, enabling faster switching speeds without requiring complex additional mechanisms.
Solution Approach 2:
The boundary portion of the cam, which traditionally served only as a transition zone, is given the additional function of enabling axial displacement. This multi-functionality allows the existing cam structure to achieve faster switching speeds without adding separate mechanisms, thereby maintaining simplicity while improving performance.
Data Source
Figure 1
Figure 2
Figure 3~5B
AI summary
A sliding cam system (11) comprises a camshaft (12), a cam carrier (14), a cam follower (16A), and a first actuator (24). The first cam (32) has a base circle region (32A) and a valve lift region (32B) with a boundary section (32C) adjacent to the base circle region (32A) of the first cam (32). The second cam (34) has a base circle region (34A) and a valve lift region (34D) with a boundary section (34E) adjacent to the base circle region (34A) of the second cam (34). The boundary section (32C) of the first cam (32) and the boundary section (34E) of the second cam (34) are identical and arranged at the same circumferential position around the longitudinal axis of the camshaft (12). An axial displacement of the cam carrier (14) is possible, while the cam follower (16A) is in operative connection with the limit section (32C) of the first cam (32) and/or the limit section (34E) of the second cam (34).