Vehicle Air Conditioner Bypass Ratio Control for Cool Defrosting
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Solution Overview
Problem
Vehicle air conditioners face the challenge of preventing 'cool defrosting' when gradually lowering the temperature of conditioned air during heating startup, which can disrupt driver visibility due to insufficient mixing of cold and hot air.
Innovation Solution
The air conditioner employs upper and lower air blowing paths with bypass channels and temperature adjusting doors, controlled by a unit that maintains zero bypass ratios initially during heating startup and gradually increases the bypass ratio for the lower path while fixing the upper path's ratio at zero, ensuring proper air mixing and preventing cool defrosting without additional mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the orientations of the temperature adjusting doors are changed to prevent part of the air flowing out of the cooling heat exchanger from passing through the heating heat exchanger, then the temperature of blown out air is lowered, but the cold air flows into the defroster blowout passage without being sufficiently mixed with hot air, causes condensation on the front glass, and interrupts driver visibility
Solution Approach 1:
The air conditioner divides the air flow control into separate upper and lower passages with independent temperature adjusting doors. The upper passage handles defroster air flow while the lower passage handles footwell air flow, allowing independent control of each passage's bypass ratio to prevent cool defrosting in the upper passage while maintaining temperature control in the lower passage.
Solution Approach 2:
Different bypass ratios are applied to different passages based on their specific requirements. The upper passage maintains a higher bypass ratio to ensure sufficient mixing and prevent cool defrosting, while the lower passage can use a lower bypass ratio for more aggressive temperature control, as it does not have the same visibility safety requirements.
2Object-affected harmful factors
If a rib is provided in the defroster door to prevent cold air from directly flowing into the defroster blowout passage, then cool defrosting is prevented, but the rib functions as a resistance against air flow when the defroster door is fully opened and increases the track range of the defroster door, hindering size reduction of the air conditioner
Solution Approach 1:
The air flow mixing function is extracted from the defroster door assembly and implemented through the temperature adjusting door control system. Instead of modifying the defroster door with ribs or other flow-resistant structures, the patent uses the temperature adjusting door to control the bypass ratio, allowing cold air to mix with hot air before entering the defroster passage without adding resistance or complexity to the defroster door mechanism.
Solution Approach 2:
The temperature adjusting door acts as an intermediary control element that regulates the mixing of cold and hot air streams before they enter the defroster passage. By controlling the bypass ratio through this intermediary device, the system achieves cool defrosting prevention without requiring direct modification of the defroster door or air passage structures.
3Object-affected harmful factors
If a separate door is provided in the cold air flow channel to prevent cold air from directly flowing into the defroster blowout passage, then cool defrosting is prevented, but the new door hinders size reduction of the air conditioner and increases production cost
Solution Approach 1:
The temperature adjusting door is designed to serve multiple functions: it controls the bypass ratio for temperature regulation in the lower passage and simultaneously prevents cool defrosting in the upper passage by controlling the air flow distribution. This multi-functional design eliminates the need for a separate dedicated door for cool defrosting prevention, reducing the total number of moving parts and production costs.
Solution Approach 2:
The cool defrosting prevention function is merged with the existing temperature control system. The temperature adjusting door's control of the bypass ratio simultaneously achieves both temperature regulation and prevention of cold air direct flow into the defroster passage, combining multiple functions into a single control mechanism.
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 effectively prevents cool defrosting without increasing the air conditioner's size or production cost, ensuring safe and efficient air conditioning by maintaining proper air mixing and temperature control.
Implementation Method 1
a cooling heat exchanger (evaporator) and one heating heat exchanger (heater core)
Implementation Method 2
a heating heat exchanger (heater core), in which the air flowing through the upper air passage is capable of passing through the upper parts of the cooling heat exchanger and the heating heat exchanger
Data Source
Figure 1
Figure 2A~2E
Figure 3
AI summary
[Object] To prevent cool defrosting when heating startup control is performed in a vehicle air conditioner having upper and lower two layers. [Solution] An upper (lower) temperature adjusting door (30A, 30B) is provided in an upper (lower) air blowing path (12A, 12B) between a cooling heat exchanger (26) and a heating heat exchanger (28) and adjusts a first (second) bypass ratio that is the ratio of the volume of the air passing through an upper (lower) bypass channel to the volume of the air flowing out of an upper (lower) part of the cooling heat exchanger. When heating startup control is performed, the upper and lower temperature adjusting doors are positioned so that both the first bypass ratio and the second bypass ratio become substantially zero and a defroster door (32D) is controlled so that the air flowing through a mixing chamber can pass through a defroster blowout passage (32). After that, when the temperature of conditioned air to be supplied to a vehicle cabin is lowered gradually as the temperature in the vehicle cabin rises, the upper and lower temperature adjusting doors are controlled so that the second bypass ratio increases earlier than the first bypass ratio.