Air conditioning control
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Solution Overview
Problem
The failure of an evaporator temperature sensor in a vehicle air conditioning system can lead to loss of cabin cooling and windscreen misting, as the compressor may be disabled, necessitating an improved method for controlling the evaporator.
Innovation Solution
A method for calculating an estimated evaporator operating temperature using blower speed, mass flow rate, and heater parameters, allowing the compressor to be controlled based on this estimation, and incorporating a fault threshold to manage sensor failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a temperature sensor is used to monitor the evaporator, then the evaporator temperature can be controlled correctly, but the system reliability deteriorates when the sensor fails causing compressor shutdown
Solution Approach 1:
The patent creates a virtual copy of the temperature sensor function through software calculation. Instead of relying solely on a physical sensor, the system calculates an estimated evaporator temperature using readily available data from the blower motor speed sensor and HVAC control module. This software-based temperature estimation serves as a backup copy that maintains system operation when the physical temperature sensor fails.
Solution Approach 2:
The patent introduces an intermediary calculation process that uses the blower motor speed as a proxy indicator for evaporator temperature. The blower motor speed sensor acts as an intermediary component, providing indirect information about evaporator conditions through its relationship with refrigerant temperature and airflow characteristics, thereby maintaining temperature monitoring capability without requiring a dedicated evaporator temperature sensor.
2Reliability
If the evaporator temperature sensor fails, then the compressor is disabled to prevent damage, but the cabin cooling and air dehumidification are lost
Solution Approach 1:
The system uses a virtual temperature measurement derived from blower motor speed to replace the function of the failed physical temperature sensor. This allows the control system to continue making informed decisions about compressor operation and maintains cabin cooling functionality without requiring the original temperature sensor to be functional.
Solution Approach 2:
The system uses existing components (blower motor speed sensor and control module) to provide the temperature monitoring function that would otherwise require a dedicated evaporator temperature sensor. The blower motor speed sensor serves dual purposes: controlling blower operation and indicating evaporator temperature conditions, thereby eliminating the need for separate temperature sensing hardware.
3Reliability
If the evaporator temperature sensor fails, then the system loses temperature monitoring capability, but adding a redundant sensor increases system complexity
Solution Approach 1:
Instead of adding physical hardware redundancy, the patent creates a software-based virtual sensor that copies the temperature monitoring function. The control module calculates evaporator temperature estimation using algorithms that process blower motor speed data, providing redundant temperature monitoring capability without adding physical sensors or increasing hardware complexity.
Solution Approach 2:
The blower motor speed sensor is made multi-functional, serving both its primary purpose of controlling blower operation and its secondary purpose of indicating evaporator temperature. This universal use of existing components eliminates the need for additional dedicated temperature sensors, maintaining reliability while avoiding increased system complexity.
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
Enables reliable operation of the air conditioning system by maintaining evaporator control even in the absence of a functional temperature sensor, reducing costs and improving system reliability.
Implementation Method 1
a blower unit configured to generate an airflow along the duct and to generate the airflow at a variable blower speed
Implementation Method 2
The purpose of the evaporator is to condition an airflow moving through the evaporator. The conditioning of the air may involve changing the humidity level of the airflow and/or cooling the airflow.
Implementation Method 3
a first heater and a first discharge temperature sensor, the evaporator and the first heater being located in the duct
Data Source
AI summary
Methods for controlling an air conditioning system of a vehicle including a blower unit, a duct, an evaporator, a first heater and a first discharge temperature sensor, the evaporator and the first heater being located in the duct, the blower unit being configured to generate an airflow along the duct at a variable blower speed, the first discharge temperature sensor being configured to output a first discharge temperature sensed from the airflow in the duct located after the evaporator and first heater, the methods comprise: calculating a mass flow rate based on the blower speed of the blower unit; calculating a first heating level of the air conditioning system based on at least one first heater parameter associated with the first heater; and calculating an estimated evaporator operating temperature of the evaporator based on the first discharge temperature, the first heating level, and the mass flow rate.