Variable Displacement Compressor Cooling for Off-Road Utility Vehicles
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Solution Overview
Problem
Off-road utility vehicles with gas engines and non-electronically controlled continuously variable transmissions face challenges in providing adequate cooling without reducing vehicle performance, as existing air conditioning systems require excess power at high engine speeds and result in refrigerant backup and sudden engine speed increases.
Innovation Solution
An air conditioning system with a variable displacement compressor driven by a rubber belt from the engine output shaft, connected to a non-electronically controlled CVT, and an alternator, which adjusts compressor displacement based on refrigerant demand to maintain optimal cooling across a wide range of engine speeds, preventing performance reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a fixed displacement air conditioning compressor is used to provide adequate cooling at low idle engine speeds, then adequate cooling is achieved, but excess power is required at high engine speeds which reduces vehicle performance
Solution Approach 1:
The patent applies a variable displacement compressor that dynamically adjusts its displacement based on operating conditions. At low idle engine speeds, the compressor operates at higher displacement to provide adequate cooling capacity. At high engine speeds above 5000 rpm, the displacement is reduced to minimize power consumption and prevent excess refrigerant backup, thereby resolving the contradiction between maintaining cooling performance and reducing power requirements across different operating ranges.
Solution Approach 2:
The compressor's displacement parameter is changed based on engine speed conditions. The system transitions from fixed displacement to variable displacement, allowing the compressor to adapt its operational parameters (displacement ratio) to match the available engine power at different speeds, thus optimizing the balance between cooling output and power input requirements.
2Temperature
If a high capacity air conditioning system is used to ensure adequate cooling, then cooling performance is improved, but refrigerant backs up into the condenser causing high pressure cut-out
Solution Approach 1:
The variable displacement compressor dynamically adjusts refrigerant compression and flow rate based on operating conditions. At high engine speeds, the reduced displacement prevents excessive refrigerant compression that would cause backup into the condenser, while still maintaining adequate cooling capacity through optimized refrigerant circulation, thus preventing high pressure cut-out events.
3Quantity of substance
If the air conditioning compressor clutch disengages due to high pressure cut-out, then refrigerant backup is prevented, but sudden engine speed increase and vehicle ground speed change occur
Solution Approach 1:
The variable displacement compressor system provides continuous feedback control of refrigerant flow based on system pressure and temperature conditions. By monitoring operating parameters and dynamically adjusting compressor displacement, the system maintains stable refrigerant circulation without sudden clutch engagement/disengagement events, thereby preventing the harmful speed fluctuations that would otherwise occur.
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
The system provides effective cooling across varying engine speeds without reducing vehicle performance, managing power consumption and refrigerant flow to prevent excess refrigerant backup and sudden engine speed increases.
Implementation Method 1
a variable displacement air conditioning compressor... adjusts compressor displacement based on refrigerant demand
Implementation Method 2
an alternator with at least one rubber belt
Data Source
AI summary
An off-road utility vehicle air conditioning system includes an air conditioning unit positioned at least partially inside a mounting structure in front of an enclosed cab, and between a pair of front wheels of the utility vehicle. The air conditioning unit may be connected to a variable displacement air conditioning compressor positioned behind the cab and below a rear cargo box. A non-electronically controlled belt driven continuously variable transmission transmits power from a gas powered internal combustion engine under the rear cargo box to a pair of front wheels and pair of rear wheels, the continuously variable transmission biased to ratios where the engine runs at over about 5000 rpm.