Switchable Cam Follower Wear Reduction via Clamping Point Geometry
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Solution Overview
Problem
The existing rocker arm designs for internal combustion engines experience high wear in the off-axis contact area of the winding package on the socket due to high restoring torques, leading to undesirable wear patterns.
Innovation Solution
The clamping points of the torsion leg spring are positioned to create an angle between the force vectors between 90° and 180°, reducing the resulting contact force and minimizing wear while maintaining secure axis fixation, and optionally eliminating the need for a socket by having the winding package run directly on the axis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the winding package presses the bushing onto the axle in segments to achieve axial fixation, then the axis is securely fixed, but high wear occurs in the off-axis contact area of the winding package on the socket
Solution Approach 1:
The patent changes the geometric parameters of the clamping points, specifically positioning them to create an angle between force vectors of 90°-180°. This parameter optimization reduces the resulting contact force in the segment-like contact area while maintaining sufficient axial fixation, thereby resolving the contradiction between reliable fixation and wear reduction
Solution Approach 2:
The patent performs preliminary optimization of the clamping point positions during the design phase. By pre-calculating and positioning the clamping points to achieve the optimal angle range, the design prevents excessive wear before operation begins, rather than attempting to compensate for wear after the fact
2Reliability
If high restoring torques are used to cope with high moving masses at high speeds, then the cam feedback is secure, but the wear in the contact area increases significantly
Solution Approach 1:
The patent optimizes the geometric parameters of the force application points to change the direction of contact forces. By positioning clamping points to achieve force vector angles of 90°-180°, the design maintains high restoring torque for secure cam feedback while reducing the resultant contact force that causes wear in the socket area
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 configuration significantly reduces wear in the segment-like contact area while ensuring a high restoring torque, and in some cases, eliminates the need for a socket, thereby saving costs and enhancing durability.
Implementation Method 1
a torsion spring (17) as a cam return spring which acts on the inner and outer lever in a clamping direction with two legs (19, 22)
Implementation Method 2
The corresponding socket (24) is surrounded by a winding package (16) of a torsion spring (17). When the system is clamped, the winding package presses the bushing onto the axle in segments, which leads to its axial fixation
Data Source
Figure 1~2
Figure 3
AI summary
A switchable cam follower (1) of a valve train of an internal combustion engine is proposed, having an inner lever and an outer lever (2, 3), wherein the levers (2, 3) can be connected to one another via coupling means (12) and run on a common pin (15) such that they can be moved pivotably relative to one another, which pin (15) is projected around by at least one group of turns (16) of a swivel pin spring (17) as cam restoring spring, wherein a first limb (19) which protrudes from an end side (18) of the group of turns (16) acts on a first clamping point (20) of the outer lever (3) and a second limb (22) which protrudes from another end side (21) of the group of turns (16) acts on a second clamping point (23) of the inner lever (2), in the rotational direction in such a way that the levers (2, 3) are present such that they are stressed towards one another, wherein the pin (15) runs in a "floating" manner with respect to the holes (13, 14), wherein the group of turns (16) comprises a bush (24) with play, wherein axial fixing of the pin (15) is produced via the offset contact of the group of turns (16) on the bush (24), which offset contact is brought about by the system stressing, and therefore the offset contact of said bush (24) on the pin (13), and wherein, in order to reduce a resulting contact force (FR) in the region of the contact of the group of turns (16) on the bush (24), the clamping points (20, 23) of the two limbs (19, 22) of the group of turns (16) are positioned in such a way that an angle (a) which is enclosed by intersecting force vectors at the clamping points (20, 23) [direction of action of the two contact forces (F1, F2)] lies in the range (90° < a < 180°).