Automobile sunroof: types and actuation system

The sunroof includes one of the motion mechanisms that we find in vehicle bodies. The design and manufacturing of their electric actuators enable us to offer a precise motion to open and close these systems, which are being increasingly added to more and more models.  

Design and sportiness aside, what options do the leading sunroof manufacturers in the automotive industry offer?


Sunroof examples

Removable sunroofs: The first models with sunroofs used this simple system. It involves a cover that has hinges on its rear side which allow for manual opening as if it were a “trap door”. It has a full (limited by a stop) or adjustable range of motion.

Sliding sunroofs. These are the models currently in use and incorporate electric actuators for actuation of the system. When the roof opens, it slides underneath the body (though it may also do so over it). Within this model, we can find many options:

  • Glass or metal louvered sunroof system. It is an unusual system, and works like a curtain. When opening the roof, the louvers are superimposed one over the other as we can see in the following image.

Glass or metal louvered sunroof system

  • Folding fabric sunroof. The system is similar to the example above but using fabric. They are midway between convertibles and conventional sunroofs.
  • Modular sunroof.
  • Moonroof: composed of an electric actuation mechanism, a sunshade and a glass cover.
  • Spoiler sunroof, where the cover is tilted over the body.

Spoiler sunroof


  • Multi-panel or panoramic systems.


Basic elements for sunroof operation

The following are the most important elements of sunroof opening systems: the gear motor, the athermic glass, and the actuation mechanism: elements that enable the roof to be opened, closed or lifted (drive rail pivots, drive cable and drive rails). These elements transfer the motion to the sunroof, the deflector and the sunshade.


Sunroof system
Image source: Automoción: elementos amovibles y fijos no estructurales


  • Drive cable: They convert the rotational motion they receive from the gear motor into a linear motions that is transferred to the drive rail pivot. They are built as a spiral.
  • Drive rail pivot: It is connected to the drive cable. When it receives the actuation’s motion, it moves along the guide rail and the slots of the drive rail. The drive rail connects to the sliding roof.
  • Deflector: Prevents the transmission of external noises to the interior: wind, swooshing…
  • Sunshade cover.
  • Gear motor: It moves the roof by acting on the drive cables through a system of gears and drive pinion which delivers the adequate torque and power to the displacement mechanism.

In these projects, a fundamental aspect is ensuring the waterproofing of the entire system and, in particular, the speed reducer. In this manner, we prevent rainwater or snow to seep into the vehicle or degrade and condition the operation of the sunroof.

Sunroof gear motor
Source image: Automoción: elementos amovibles y fijos no estructurales

On the other hand, when designing a sunroof, with the purpose of opening and closing the moving panel (both ways) the motor’s polarity is reversed. Then, in order to achieve its motion, a set of drive rails and drive rail pivots to the sides are required.

To sum up:

The moving panel is mounted on its frame. This frame moves when it is actuated by the drive cables that are installed on the drive rail pivots and rails. The motion is generated by the gear motor, which provides a speed ranging from 10 to 12 cm/s.
At CLR we know the engineering details surrounding different automotive industry actuators. Check out some of our success stories by visiting our projects page. World-class Tier 1 companies have been depositing their trust in our team of professionals for decades. Get to know our work and don’t miss our free resource for automotive industry professionals: “Guidelines for the selection of suppliers in tier 1 automotive projects”. We hope it will help you select a company to outsource your engineering needs.

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