Vehicle HVAC Cabin Heating During Engine-Off Auto Stop
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Solution Overview
Problem
HVAC systems in stop-start vehicles face challenges in maintaining cabin warmth during engine-off conditions without an electric auxiliary coolant pump, particularly in low ambient temperatures, as existing systems rely on engine-driven coolant pumps which cease operation during auto stop events.
Innovation Solution
The method involves adjusting the blower motor speed to a minimum operable speed, setting the recirculation door to full recirculation, and feed-forward adjusting the temperature blend door to maintain heated air circulation in the cabin during engine-off conditions, based on sensed temperatures and climate settings, without relying on an auxiliary coolant pump.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an engine-driven coolant pump is used to circulate coolant, then the system structure is simple and cost-effective, but the coolant circulation stops during engine-off conditions in auto stop events
Solution Approach 1:
The patent utilizes the vehicle's existing engine-driven coolant pump to serve dual purposes: cooling the engine during operation and heating the cabin during auto stop events. The system self-regulates by controlling the blower motor and door positions to maximize heat extraction from the engine coolant without requiring a separate auxiliary pump.
Solution Approach 2:
The engine-driven coolant pump is made multi-functional by using it for both engine cooling and cabin heating purposes. The same pump that circulates coolant through the engine also circulates it through the heater core during engine-off conditions, eliminating the need for a dedicated auxiliary coolant pump.
2Reliability
If an electric auxiliary coolant pump is added to circulate coolant during engine-off conditions, then coolant circulation continuity is improved, but the device complexity and cost increase
Solution Approach 1:
The patent extracts the auxiliary coolant pump from the system entirely, relying instead on the existing engine-driven pump. By removing the need for an additional component, the system achieves the same functional outcome (coolant circulation during engine-off) through a different approach that uses already-available resources.
Solution Approach 2:
The existing coolant pump system serves itself by continuing to circulate coolant through the heater core even when the engine is off, powered by the vehicle's electrical system. This self-service approach eliminates the need for external auxiliary pumping equipment.
3Temperature
If the blower motor speed is increased to circulate more heated air, then the heating effectiveness is improved, but the noise level increases
Solution Approach 1:
The patent applies partial action by operating the blower motor at reduced speeds sufficient to maintain adequate cabin heating without maximizing airflow. This partial operation achieves the necessary heating effect while avoiding the noise associated with high-speed blower operation.
Solution Approach 2:
The system dynamically adjusts blower motor speed based on actual heating requirements rather than operating at constant high speed. The controller modulates the blower speed to provide just enough heated air circulation to maintain comfort, reducing noise when full power is not needed.
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 approach allows continued circulation of heated air into the cabin during engine-off conditions, ensuring comfort in low temperatures without the need for an auxiliary coolant pump, while minimizing noise levels and maintaining operational efficiency.
Implementation Method 1
controlling a blower motor (20) to circulate air through the HVAC system (16)
Implementation Method 2
circulate heated air into the cabin during engine-off conditions
Data Source
AI summary
A method of operating a stop-start vehicle with an HVAC system that does not include an electric auxiliary coolant pump for circulating warm coolant to a heater core of the HVAC system in an engine-off condition of the vehicle comprises the steps of driving the vehicle via compulsion by an engine in an environment having an ambient outside temperature of about or less than 30 degrees Fahrenheit, entering an auto stop event, such that the engine enters the engine-off condition, and circulating heated air into a cabin of the vehicle in the engine-off condition for at least one minute. The heated air is circulated by decreasing the speed of a blower motor, adjusting a recirculation door position to increase air recirculation, and adjusting a temperature blend door position toward a full-heat position based on a sensed engine coolant temperature and a sensed evaporator core temperature.