1955 Mercedes-Benz Gullwing Coupe
Some modern cars today have 4 or 5 different ways of unlocking the doors, including keypads, conventional locks, or keyless entry systems. But what exactly happens in this kind of technology, regardless of the different methods of locking and unlocking of car doors? The mechanism going on the locking and unlocking system of car doors is actually interesting. This has to be reliable since it will be the main way to unlock car doors hundreds of times over. Some of the ways to unlock car doors can be with a key, pressing the unlock button in the car, using a combination lock outside the door, pulling the door’s knob, or using a keyless entry remote control via the signal from the control center. (Note: All photos in this article are from Wikipedia)
The lock or unlock switch in some cars relays power to the car’s actuators thus unlocking the door. For other more complicated cars, however, there are several ways to lock and unlock the doors – the car’s body controller is the part that decides the unlocking part. The car’s body controller serves as the car’s computer which handles a number of minor things to make your car driver-friendly. For example, the body controller ensures the car’s interior lights are on until the car starts and beeps if the headlights are left on or even when you leave the keys. Now when it comes to power door locks, it is the body controller’s job to monitor the possible sources of the lock/unlock signal. It also monitors the door-mounted touchpad as well as unlocks the doors if the right code is entered. It is also responsible for monitoring radio frequency thereby unlocking the doors when the right digital code from the transmitter is received in the key fob. Additionally, the body controller also keeps the car’s switches in check. When a signal is received from any of these sources, the actuator is powered resulting to the locking or unlocking of the car doors.
Now, let’s examine the interior of the actual car door and how everything is built and hooked up. The power actuator is located below the latch. A rod then connects the actuator to the latch while another rod is connects the latch to the knob. When the latch is moved up by the actuator, the car’s outside door handle is then connected to the opening. If the latch is not up, the outside door handles disconnects from the mechanism to allow it to open. The body controller then supplies power to the door-lock actuator unlocking the door at a timed interval. The actuator is quite a simple and straightforward device. A series of gears are turned by a small electric motor which then serves to reduce the gear. The last gear then drives the gear set connecting the actuator rod. The lock is moved by the rack that converts the motor’s rotational motion into linear motion. An interesting thing about this technology is that although the motor turns the gear moving the latch, if the latch is moved the motor will not turn. This is so due to the neat centrifugal clutch connected the gear and the motor.
Another basic structure of door locks is the centrifugal clutch on the drive gear. The clutch swings out and the small metal gear in the larger plastic gear is locked when the gear is spun by the motor and the motor is free to drive the door latch. If the door latch is manually moved, all the gears turn apart from the plastic gear that has the clutch on it. If you every locked yourself out of your vehicle and called the AAA or CAA to help you, you should know that the tool they used is a flat-hooked thin metal strip. All that is needed to turn the lock to open the door is a simple vertical motion in either the door knob or the power-lock actuator. What the AAA or CAA does with the metal strip is actually to fish around until it hooks onto the connection of the actuator and the knob. One quick pull on this and, viola, the door is now open!