Direct Drive Compressor Speed Governance via Variable Belt
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Solution Overview
Problem
In direct drive type transport refrigeration units (TRUs), the compressor speed varies with engine speed, leading to low cooling capacity at idle speeds and prolonged recovery times for refrigeration set points, resulting in inconsistent temperature uniformity in cargo spaces.
Innovation Solution
A speed-governed transmission unit is integrated into the direct drive unit compressor system, which maintains the compressor's operational speed independently of the engine speed by using a power transfer system with variable gear assemblies and a belt mechanism to ensure consistent power delivery to the compressor, allowing it to operate at predefined speeds regardless of engine output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the compressor is directly driven by the engine through a belt, then the system structure is simple, but the cooling capacity becomes very low at idle engine speed
Solution Approach 1:
The patent applies a variable ratio belt pulley system that dynamically adjusts the belt ratio between engine and compressor pulleys. When engine speed drops to idle, the system automatically increases the belt ratio to maintain compressor speed and cooling capacity. This dynamic adjustment resolves the contradiction by making the transmission system adaptive rather than fixed.
Solution Approach 2:
The system changes the transmission ratio parameter based on engine operating conditions. The control system monitors engine speed and adjusts the effective belt ratio accordingly - using a higher ratio at idle speeds to maintain compressor performance, and a lower ratio at higher engine speeds. This parameter change allows the simple direct-drive structure to maintain productivity across varying operating conditions.
2Ease of operation
If the compressor speed varies with engine speed, then the system operates simply without speed control, but the recovery time for refrigeration set point becomes prolonged
Solution Approach 1:
The patent implements a control system that continuously monitors engine speed and provides feedback to adjust the belt ratio accordingly. When engine speed drops, the system detects this change and automatically increases the transmission ratio to maintain compressor speed, ensuring rapid recovery of refrigeration set points. This feedback mechanism maintains ease of operation while eliminating prolonged recovery times.
3Device complexity
If the compressor speed varies with engine speed, then no speed governance is needed, but temperature uniformity in cargo space becomes inconsistent
Solution Approach 1:
The variable ratio belt pulley system dynamically adjusts transmission characteristics to maintain stable compressor speed despite engine speed variations. This dynamic adjustment ensures consistent refrigeration output and temperature uniformity in the cargo space, while the system remains relatively simple in structure compared to alternative speed control methods.
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 solution enhances the compressor's operational capacity at low engine speeds, reduces recovery time for temperature set points, and maintains consistent temperature within the cargo space, while preventing large compressor speed variations, thereby improving reliability.
Implementation Method 1
a power transfer system with variable gear assemblies and a belt mechanism to ensure consistent power delivery to the compressor
Data Source
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AI summary
A system is provided and includes a power generation unit, a direct drive unit and a speed-governed transmission unit. The power generation unit includes a first power transfer device operable at varying speed modes based on current engine output. The direct drive unit includes a second power transfer device that is operable at varying speed modes based on current driven element requirements. The speed-governed transmission unit is coupled to the first and second power transfer devices and is configured to transmit power generated by the power generation unit to the direct drive unit in proximate satisfaction of the current driven element requirements and in proximate independence of the current engine output.