How Linear Actuators Work In Power Windows

How Linear Actuators Work In Power Windows

Anna Sapiga
Anna Sapiga
PA Engineer
You may not know it, but electromechanical linear actuators are responsible for making the power windows in your car move up and down. The mechanics are actually quite simple once you understand how actuators work.

How a Traveling Nut Linear Actuator Works

Motorized actuators take rotary motion and employ it as linear motion. For example a traveling nut actuator uses a motor to turn the lead screw. The lead nut is attached to the lead screw and does not spin, but moves in a linear motion on the lead screw. This provides the necessary up and down motion to move objects creating automation and motion control.


How Electromechanical Linear Actuators in Car Automation Work

This is the principle behind how the power windows in your car operate. However, in the case of power windows, the set up is a bit more complicated. There are mini actuators inside your car doors. They work like the traveling nut actuator except they use a worm gear as well as several other gears, to increase the travel length of the nut and still take advantage of the actuator’s small size.

The worm gear is the mechanism that prevents your power window from being forced open. Any kind of force creates friction on the teeth of the gears which causes them to bind and lock.

The glass of your car door windows is basically placed on top of traveling nut actuators which move up and down depending on whether the switch is hit to activate the motor on the actuators. When the window is in the down position, the nut on the mini actuators is also in the down position. When you hit the button on your door, the mini actuators are turned on, the nut moves up the screw shaft, and the gears begin to move.

Power Window Circuitry

While the electromechanical linear actuator is the mechanical part of what makes your window move up and down, it is electricity and the way your car is wired that powers it. A circuit breaker of about 20 amps powers the window switch on the driver’s side which feeds into the contacts on the four window switches. The four window switches are connected to the linear actuator motors in each of the car doors.

When you press the button that makes your car window move down, your window has to utilize a circuit that is sensitive to how long you hold the button down. If the button receives a quick hit, it will go down for the entire limit. If you hold the button all the way down, you can control how far the window goes down. When you hold the button down, you gain control of the limit switch.

There are many different linear actuators depending on the industry and the use required of them. For automotive automation, the industry uses electromechanical linear actuators because they are small, fast and long lasting.
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