TECHNICAL SYMPOSIUM ON AUTOMOTIVE TECHNOLOGIES, FEBRUARY 5 2011

PAPER PRESENTATION EVENT

TOPIC: POWER WINDOWS

PRESENTERS:

C. SIDDHARTH NARAYANAN – 10A249

B LAKSHMAN – 10A222

I BE AUTOMOBILE

POWER WINDOWS

CONTENTS

1. What are power windows?2. Evolution of power windows3. Working of power windows4. The lifting mechanism5. Special features6. Safety

WHAT ARE POWER WINDOWS?

• Power windows are electric windows which can be raised and lowered at the touch of a button.

• They can either be in-built or can be externally installed by paying an extra amount.

• All the cars today come with a power window variant which is slightly higher priced compared to the car with normal windows.

Typical window switches with remote disable control on driver's door (1993 Jeep Grand Cherokee).

EVOLUTION OF POWER WINDOWS

• Packard introduced the first power windows in the 1940 Packard 180 series. This was a hydro-electric system.

• In 1941, Ford followed with power windows on the Lincoln Custom.

• Cadillac had a straight-electric divider window (but not side windows) on their pre-WWII series 75 limousines.

• Pre-WWII Cadillac sedans used 3 types of power window mechanisms - straight electric, straight vacuum and electro-hydraulic.

• The 1946 Buick convertibles had an electrically controlled hydraulic system that provided fingertip operation of windows.

• Ford also had an electro-hydraulic system on higher-end convertibles (Mercury and Lincoln) by 1951.

• Chrysler introduced all-electric operation on the 1951 Imperial.

• General Motors followed with full electric operation in 1954.

• Chevrolet introduced the oddity of power front windows in the 1954 model.

• Ford introduced full four-door power windows in 1954.

• Electrically-operated vent windows were introduced on 1958 Cadillacs.

• In a typical auto installation, there is an individual switch at each window and a set of switches on the driver's door, so the driver can operate all the windows.

• However, some models like Saab and Holden have switches located in the center console, where they are accessible to all the occupants. The door-mounted switches are omitted.

WORKING OF POWER WINDOWS

• Power windows work on the principle of electricity or battery that is controlled by switches and wires. They work only when the car is on start mode.

• The basic system comprises control of all four windows by the driver.

• The driver’s door receives power from an optimized circuit beaker.

• This power is sent to the window switch control panel.

• Then it is distributed to a power contact in the center of each of the four window switches where the wirings of all four windows meet.

• There are two power contacts to the sides of the center power contact. One of them gets connected to the vehicle ground and the other gets connected to the electric motor.

• When the driver presses one of the switches, one of the two side contacts is disconnected from the ground and connected to the center power contact, while the other one remains grounded.

• This provides power to the window motor.

• This motor then raises the windows through a lifting mechanism.

• The latest luxury car brands have a more technologically advanced power window system.

• This is because the car has many powered components like power windows, doors, and mirrors.

• There it becomes very difficult to assemble all the wires together.

• So all wires are merged into one module to monitor all the controls.

• Thus when the driver presses the button, power gets transmitted directly to the central wire module and then to all the four windows.

THE LIFTING MECHANISM

• The window lift uses a neat linkage to lift the window glass while keeping it level.

• The motor is attached to a worm gear and several spur gears to create a large gear reduction, giving it enough torque to lift the window.

• The linkage has a long arm, which attaches to a bar that holds the bottom of the window.

• The end of the arm can slide in a groove in the bar as the window rises.

• On the other end of the arm is a large plate that has gear teeth cut into it.

• The motor turns a gear that engages these teeth.

• The same linkage is often used on cars with manual windows, but instead of a motor turning the gear, the crank handle turns it.

SPECIAL FEATURES

• Cannot be forced upwards:

– This is because of the self-locking characteristic of the worm gears.

– The angle of contact between the worm and the gear sees that the worm can rotate the gear but the gear cannot rotate the worm.

– The friction between the teeth of the gear and worm causes the gears to bind.

• Courtesy Power-On:

– Some cars store the power in the circuit itself after the ignition is turned off.

– The passengers can roll up the windows without again turning on the ignition.

• Automatic up/down:

– In the automatic down system, the window goes all the way down when the switch is hit.

– The system has a circuit that measures the amount of time for which the switch is pressed.

– When the switch is pressed for less than half a second the window goes all the way down.

– But if it is pressed for more than that period the window will stop when the switch is released.

– In automatic up windows, the windows stop moving if some obstacle comes in the way.

– The motor speed reduces drastically or the window goes back down.

• Window Control From Outside:

– In some cars, the windows can be opened just by turning the key inside the driver's door.

– This also works on the principle of measuring the time for which the key is turned and held at that position.

SAFETY

• Power windows have come under some scrutiny after several fatal accidents in which children's necks have trapped, leading to suffocation.

• This is because in some designs, the switch is placed on a location on a hand rest where it can be accidentally triggered by a child climbing to place his or her head out of the window.

• To prevent this, many vehicles feature a driver-controlled lockout switch, preventing rear-seat passengers (which are usually small children) from accidentally triggering the switches.

• This also prevents children from using them as toys and pets riding with their heads out of windows from activating the power window switch.