Vehicle HVAC Heater Core Control With Temperature Feedback
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Solution Overview
Problem
Existing HVAC systems for motor vehicles face challenges in easily controlling the temperature of air flowing into the vehicle interior due to mechanical hysteresis in interface devices, leading to poor linearity in actuator commands.
Innovation Solution
The HVAC system incorporates a temperature sensor to detect the actual temperature of air flowing into the air treatment cavity, allowing the control unit to adjust the actuator's operation based on both the user's temperature command and the detected temperature data, thereby reducing mechanical hysteresis and improving linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a mechanical interface device (knob) with electrical potentiometer is used to control the actuator, then the system structure is simple, but mechanical hysteresis occurs and linearity of actuator command deteriorates
Solution Approach 1:
A feedback circuit is introduced that includes a second potentiometer connected to the actuator shaft. This second potentiometer provides real-time position feedback to the control unit, allowing the system to compensate for mechanical hysteresis and improve the linearity of the actuator command. The feedback mechanism enables the control unit to adjust the actuator position based on actual position data, resolving the contradiction between simple structure and precise control.
2Ease of operation
If a mechanical interface device (knob) is used for temperature control, then the interface is simple to operate, but mechanical hysteresis causes poor control precision
Solution Approach 1:
The feedback circuit with the second potentiometer provides real-time position information to the control unit, enabling precise control of the actuator position. This feedback mechanism compensates for mechanical hysteresis in the mechanical interface device, allowing the system to achieve accurate temperature control while maintaining the simplicity of mechanical operation.
Solution Approach 2:
The patent introduces an electrical feedback mechanism (second potentiometer and feedback circuit) to supplement the mechanical interface device. This electrical feedback system replaces the need for a purely mechanical control system, enabling precise digital control of the actuator while maintaining the user-friendly mechanical interface for temperature selection.
3Device complexity
If only temperature command from interface device is used to control actuator, then the control system is simple, but temperature control accuracy deteriorates due to mechanical hysteresis
Solution Approach 1:
The feedback circuit provides real-time position data from the actuator shaft to the control unit, enabling the system to compensate for mechanical hysteresis effects. This feedback mechanism allows the control unit to calculate the actual actuator position and adjust the control signal accordingly, significantly improving temperature control accuracy while adding minimal complexity to the control system.
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 ability to precisely control the temperature of air flowing into the vehicle interior, improving comfort and reducing the issues associated with mechanical hysteresis and poor linearity in existing systems.
Implementation Method 1
a temperature sensor configured to detect temperature data representative of the temperature reached by the air flowing into said air treatment cavity downstream of the heater core
Implementation Method 2
an air treatment cavity situated between the inlet opening and the outlet opening through which an air flow can pass. The air treatment cavity contains a heater core which is part of the engine cooling circuit
Implementation Method 3
a heater core which is part of the engine cooling circuit
Data Source
AI summary
A system includes a casing configured to allow air to flow towards a vehicle interior or cabin. An air treatment cavity contains a heater core of a cooling circuit. A control unit is provided which is configured to control the temperature of the air. An interface device provides the control unit with a required temperature command. An actuator is configured to adjust, in a controlled way by the control unit, the opening of a flow control valve situated upstream of the heater core. The system further includes a temperature sensor configured to detect temperature data representative of the temperature reached by the air flowing into the air treatment cavity downstream of the heater core. The control unit is also configured to control the actuator also as a function of the temperature data as a function of the temperature command.