What Is The Role Of A Flap Actuator?
Depending on the type of A/C system your car has and its complexity, it may have a single flap actuator or a bunch of them. These flaps play an important role in the operation of the air conditioning system, and below is an overview of how they work.
How Actuators Function
Air flowing within the A/C will move through either tubes or ducts, and the flap is used to close and open parts of the pipe or duct so that the movement of air can be controlled. These openings and closing might be partial or full, and the flap, which is also referred to as the damper, is an electrical device which moves it. Actuator flaps come in three forms, which are intake air, air mixing or air distribution.
Intake Air
With intake air, the actuator will determine whether or not the air used for conditioning will be external or recirculate from air inside the cabin. The flap position is controlled via a driver that uses a recirculate button, but may also be controlled through the usage of data which comes from air sensors within the cabin itself.
Air Mixing
This actuator will mix air that is warm (the heat exchanger) with air that is cool (the evaporator) so that the most optimal air temperature is achieved. It is preferred by many technicians and manufacturers due to its simplicity and ease of use.
Air Distribution
The air distribution actuator is the most diverse, and will differ depending on the vehicle’s make and model. As its name implies, it operates through the distribution of air throughout the cabin. Because they can differ it is important to become familiar with your specific model.
The Role Of The DC Motor
The DC (Direct Current) motor is the device responsible for making the flap move. Since there are multiple options for controlling air flow, manufacturers have also given multiple choices for controlling flap movement. Some DC motors have potentiometers which can be used to detect the flap’s position, as well as DC motors which are three phase and brushless (BLDC) that use back EMF (electromotive force) so that positions can be measured. Stepper motors can also be used to determine the amount of steps needed for position measurement. All the DC motors will drive flaps through gears which may vary in size.
Choosing The Architecture
Once a systems engineer has selected the motor they want to use, they must next select the architecture which drives it. Actuators may be controlled remotely as well as locally. When local control is desired, the electronics which handle the motor will be situated near it, meaning that the motor IC control will be integrated within an identical housing.
Communication protocols like LIN (Local Interconnect Network) will alter the motor so the flaps are moved to positions which are desired. When control is remote, the electronics responsible for handling the motor will be situated within the A/C control unit itself, separate from the actuator. Communication which occurs among the microcontroller and driver motor will occur through SPI, or serial peripheral interface, but may also be done with a parallel digital system which is much simpler.