Grain Cleaning Drive Phase Control for Lower Peak Forces
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Solution Overview
Problem
The grain cleaning system in combine harvesters experiences high peak forces during sieve reciprocation, which can be destructive to components and requires significant power, complicating structural and functional geometry.
Innovation Solution
A drive system for the grain cleaning system that controls the reciprocating motion of the chaffer and sieve by maintaining specific positional relationships between their dead points and midpoints, minimizing vibrations, destructive forces, and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the size and thickness of grain cleaning system components are increased to handle higher peak forces, then the strength and durability of components is improved, but the space for accommodating components is exceeded and the structural and functional geometry of the cleaning system is negatively impacted
Solution Approach 1:
The patent applies counterbalancing mechanisms where the chaffer and sieve are positioned and linked to create opposing forces during reciprocation. When one component is at its forward dead center, the other is positioned to provide a balancing moment, effectively canceling out peak forces and reducing the structural strength requirements of individual components.
Solution Approach 2:
The patent changes the operational parameters by controlling the phase relationship between chaffer and sieve reciprocation. By maintaining specific positional relationships (chaffer at midpoint when sieve is at dead center, and vice versa), the system transforms the force profile during operation, reducing peak forces without requiring larger components.
2Reliability
If larger components are used to handle higher peak forces, then the reliability of the cleaning system is improved, but the structural and functional geometry of the cleaning system is negatively impacted
Solution Approach 1:
The linking mechanism between chaffer and sieve creates a counterbalancing system that reduces peak forces transmitted to bearings and supports. This improves reliability by reducing stress on components while maintaining compact, simple geometry through the interconnected linkage design.
Solution Approach 2:
The patent employs periodic reciprocation of the chaffer and sieve with controlled phase differences. This periodic motion, synchronized so that peak forces from one component coincide with lower-force positions of the other, reduces overall peak loading on the system, improving reliability without increasing geometric complexity.
3Productivity
If more power is supplied to reciprocate the sieves, then the productivity of the grain cleaning system is improved, but the power consumption increases
Solution Approach 1:
The counterbalancing linkage between chaffer and sieve reduces the net power required for reciprocation by utilizing the inertial forces of one component to assist in moving the other. This maintains cleaning productivity while reducing overall power consumption of the drive system.
Solution Approach 2:
The synchronized periodic reciprocation of chaffer and sieve with controlled phase relationships creates a more efficient power demand profile. The system leverages the cyclic nature of the motion to reduce peak power requirements while maintaining effective cleaning action, optimizing the balance between productivity and power consumption.
Data Source
AI summary
A grain cleaning system for a combine harvester includes a chaffer and a sieve positioned below the chaffer. A first link includes a first end and a second end coupled to the chaffer. A second link includes a first end and a second end coupled to the sieve. A drive shaft is driven by a drive system to rotate about a shaft axis, wherein rotation of the drive shaft drives the first link to reciprocate the chaffer and drives the second link to reciprocate the sieve. The drive system is configured to control reciprocating motion of the chaffer and sieve with the goals of (i) minimizing vibrations of the cleaning system, (ii) minimizing destructive forces on the bearings (and other components) of cleaning system, and (iii) minimizing the power required to reciprocate the chaffer and sieve back and forth.