Vehicle HVAC Valve Sequencing for Stable Heating Mode Switching
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Solution Overview
Problem
When switching from the combined heating mode or temperature control target-specific heat exchanger heating mode to the outside air heat absorption heating mode, the sudden full closure of the chiller expansion valve leads to a blockage of the refrigerant flow path, causing temporary and significant increases in refrigerant outlet pressure and subcooling (SC) value, which can result in decreased controllability of high pressure in the compressor and reduced durability and controllability of subcooling in the electronic expansion valves.
Innovation Solution
The vehicle air-conditioning apparatus includes a control device that, upon switching from the combined heating mode to the outside air heat absorption heating mode, gradually increases the degree of opening of the outdoor expansion valve to a given degree and maintains this for a given period, while fully closing the second electronic expansion valve within the same period.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the chiller expansion valve is fully closed immediately when switching heating modes, then the refrigerant flow path to the temperature control target heat exchanger is blocked, but the refrigerant outlet pressure and subcooling value of the indoor condenser increase suddenly and temporarily
Solution Approach 1:
The control device performs preliminary action by fully closing the second electronic expansion valve (chiller expansion valve) before increasing the degree of opening of the first electronic expansion valve (outdoor expansion valve) when switching from combined heating mode or temperature control target-specific heat exchanger heating mode to outside air heat absorption heating mode. This preliminary closure of the chiller expansion valve prevents refrigerant from flowing into the temperature control target heat exchanger, while the subsequent opening of the outdoor expansion valve ensures proper refrigerant flow to the outdoor heat exchanger, thereby preventing sudden increases in refrigerant outlet pressure and subcooling value of the indoor condenser.
Solution Approach 2:
The control device dynamically adjusts the degree of opening of the electronic expansion valves based on the operating mode. When switching to outside air heat absorption heating mode, the control device first fully closes the chiller expansion valve (second electronic expansion valve) and then gradually increases the opening of the outdoor expansion valve (first electronic expansion valve). This dynamic adjustment sequence ensures smooth transition between modes while maintaining stable refrigerant pressure and subcooling values, preventing sudden pressure spikes that could damage the compressor or expansion valves.
2Productivity
If the chiller expansion valve is fully closed immediately, then the heating mode switching is achieved quickly, but the controllability of high pressure in the compressor deteriorates
Solution Approach 1:
The control device performs preliminary action by fully closing the second electronic expansion valve (chiller expansion valve) before adjusting the first electronic expansion valve (outdoor expansion valve) when switching heating modes. This preliminary closure quickly establishes the correct flow path configuration, achieving fast mode switching, while the subsequent controlled opening of the outdoor expansion valve maintains proper refrigerant flow and pressure control, preserving compressor controllability.
Solution Approach 2:
The control device uses feedback control to monitor and adjust the refrigerant flow based on the operating mode. When switching to outside air heat absorption heating mode, the control device receives feedback about the mode change and automatically adjusts the opening degrees of the electronic expansion valves in the optimal sequence, ensuring both quick switching and maintained pressure controllability.
3Productivity
If the chiller expansion valve is fully closed immediately, then the switching to outside air heat absorption mode is completed rapidly, but the controllability of subcooling in the electronic expansion valve deteriorates
Solution Approach 1:
The control device performs preliminary action by fully closing the second electronic expansion valve (chiller expansion valve) before adjusting the first electronic expansion valve (outdoor expansion valve) when switching heating modes. This preliminary closure quickly establishes the correct flow path configuration, achieving fast mode switching, while the subsequent controlled opening of the outdoor expansion valve maintains proper refrigerant flow and subcooling control, preserving expansion valve controllability.
Solution Approach 2:
The control device dynamically adjusts the degree of opening of the electronic expansion valves based on the operating mode. When switching to outside air heat absorption heating mode, the control device first fully closes the chiller expansion valve (second electronic expansion valve) and then gradually increases the opening of the outdoor expansion valve (first electronic expansion valve). This dynamic adjustment sequence ensures smooth transition between modes while maintaining stable refrigerant pressure and subcooling values, preventing sudden pressure spikes that could damage the compressor or expansion valves.
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 prevents sudden increases in refrigerant outlet pressure and SC value during mode switching, thereby maintaining the controllability of high pressure in the compressor and improving the durability and controllability of subcooling in the electronic expansion valves.
Implementation Method 1
a compressor configured to compress a refrigerant
Implementation Method 2
a heating unit configured to heat blowing air to be blown into an air-conditioning target space
Implementation Method 3
an outdoor heat exchanger configured to cause the refrigerant to absorb heat
Implementation Method 4
a first electronic expansion valve provided on a refrigerant inlet side of the outdoor heat exchanger
Data Source
AI summary
A control device of a vehicle air-conditioning apparatus has an outside air heat absorption heating mode in which a refrigerant that has been discharged from a compressor and has dissipated heat in a heating unit absorbs heat in an outdoor heat exchanger, and a combined heating mode in which the refrigerant that has been discharged from the compressor and has dissipated heat in the heating unit absorbs heat in the outdoor heat exchanger and a chiller heat exchanger, and upon switching from the combined heating mode to the outside air heat absorption heating mode, performs control in such a manner as to increase a degree of opening of a first electronic expansion valve to a given degree of opening, maintain the given degree of opening for a given period of time, and fully close a second electronic expansion valve within the given period of time.