V-Type Engine Valve Train Compactness via Axial Cam Follower Design
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Solution Overview
Problem
Conventional V-type engines face challenges in achieving a compact valve-operating device due to increased distance between intake and exhaust push rods, which also leads to reduced durability of sliding contact portions.
Innovation Solution
The V-type engine design features intake and exhaust rocker arms arranged in a substantially inverted-V-shape, allowing for adjacent positioning of push rods and cam followers, reducing the distance between them and concentrating cam followers and cams on a single shaft, thereby achieving a compact valve-operating device and improving durability through reduced surface pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the distance between intake and exhaust push rods is increased to accommodate the V-shape arrangement of valves, then the valve-operating device becomes more compact, but the durability of sliding contact portions deteriorates due to increased surface pressure
Solution Approach 1:
The cam followers are designed with protruding end portions that extend in the axial direction of the camshaft, utilizing the third dimension (axial direction) to increase the sliding contact area without increasing the radial distance between push rods. This dimensional transition allows the slipper portions to face each other across the cam, effectively increasing contact area while maintaining compact radial spacing.
Solution Approach 2:
The invention changes the geometric parameters of the cam followers by making their end portions protrude in the axial direction, thereby increasing the sliding contact area parameter. This parameter change reduces surface pressure (pressure = force/area) while maintaining the same push rod spacing, resolving the contradiction between compactness and durability.
2Device complexity
If the distance between intake and exhaust push rods is increased, then the valve-operating device layout becomes simpler, but the overall engine size increases
Solution Approach 1:
By utilizing the axial direction (third dimension) for increasing contact area through protruding cam follower ends, the invention avoids increasing the radial dimensions of the valve-operating device. This allows the engine to maintain a compact overall size while accommodating the valve-operating mechanism.
3Reliability
If the sliding contact area of cam followers with cams is increased, then the surface pressure is reduced and durability is improved, but the distance between push rods must be increased
Solution Approach 1:
The invention transitions from increasing contact area in the radial direction (which would increase push rod distance) to increasing contact area in the axial direction of the camshaft. The protruding end portions of cam followers extend axially to face each other across the cam, increasing sliding contact area without increasing the radial distance between push rods.
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 results in a more compact engine with improved durability of sliding contact portions and effective lubrication of cam surfaces, enhancing the overall performance and longevity of the valve-operating mechanism.
Implementation Method 1
slipper portions being in sliding contact with intake and exhaust cams, respectively
Data Source
AI summary
In a V-type engine, intake and exhaust rocker arms in each bank are arranged in a substantially inverted-V-shape in a plan view, so that side end portions of corresponding intake and exhaust push rods are positioned adjacent to each other. Slipper portions of first and second intake cam followers have end portions at one end along the axial direction of a camshaft protrude respectively in opposite directions to each other so that they face each other across an intake cam therebetween. Slipper portions of first and second exhaust cam followers have end portions at one end along the axial direction of the camshaft protrude respectively in opposite directions to each other so that they face each other across an exhaust cam therebetween. This reduces the distance between the push rods in each bank to provide a compact valve-operating device.