What happens in the background: February 2015

Most of us own cars these days. We often open and close the windows on our cars for various purposes. Do you know what happens in the background to open and close the window? Here is the description about what happens in the background

Before going to know about window mechanism, lets know how glass entered into automobile.

When automobile was invented, It didn't had a closed body. The drivers had nothing to protect them from the dust, bugs and a face full of mud while driving the car. So, this is when a windshield came into existence. It was around the early 1900's when the windshield was introduced.

The first windshields were two-piece affairs, when mud, rain, or other substances blocked his or her view forward, a driver could simply tip the top half down for an unobstructed view. While the usefulness of windshields was clear to everybody, they posed a serious danger. Manufacturers quickly discovered that during an accident, their glass windshields could shatter, sending a shower of sharp shards into the vehicle. Glass windshields proved most hazardous during front-end collisions, when passengers could end up smashing headlong through the glass.

Here is a picture to help you understand

Later changes

when the first cars with glass on all four sides were introduced, many people were afraid to ride in them. In early 20th century, two European scientists independently invented a solution to deadly windshields. While working in his lab, French scientist Edouard Benedictus accidentally knocked a flask to the floor. To his amazement, the glass did not break. Looking closer, he discovered that the chemical that had been inside the flask, nitrocellulose, had dried up, leaving an adhesive film that kept the numerous bits of fragmented glass from separating. Benedictus went on to develop a window consisting of two layers of plate glass held together by layer of cellulose.

After windshield was developed, there were cars with no windows on sides. Like the one below.

Later the car had windows on all sides.Different window styles were opted by various manufacturers for their car models. Some used fixed windows, some used horizontal sliding windows, Opera windows.

Finally in 1948 the crank windows were introduced. These are outdated now as most of the cars are coming with power windows, although low end models of some cars are still using this feature.

The first thing that lies beneath your car window is a window regulator. The window regulator is the component inside your door panel that allows you to raise or lower your window glass. Both manual and electric car windows have window regulators. A manual window is operated by a hand-crank, while an electric window is controlled by a switch or button that activates a motor.

A manual window regulator is the most basic of window lifting mechanisms. It has crank handle sticking through the door panel that regulates the up and down motion of the glass window. Humans power this type of regulator by their wrist, as the window crank needs to be physically rotated to raise and lower the door glass.

When we rotate the crank, we actually rotate a pinion which is engaged to a larger gear, which is inturn connected to the window regulator that moves your window up and down. It converts rotary motion to linear motion.

In power windows we have a motor to which we supply power from battery. When we press the power button to lift window we actually make circuit and current flows to motor. The motor is attached to a worm gear and several other spur gearsto create a large gear reduction and provides enough torque to lift the window.

In power windows we have three kinds of mechanisms. They are:

1. The Scissors Mechanism

The scissor type window regulator basically look like a giant pair of scissors. As they expand, the window goes up. When they contract, the window glass rolls down. The drawback of this type of regulator is that the wheels on the ends of them wear out over time, and break off. This causes your door glass to tilt sideways, and eventually fall down into the door. They also wear out at the center of the scissor mechanism and become noisy, sloppy, and unpredictable.

2. The Cable Mechanism

The cable type window regulator is a more modern design that is used in a huge variety of vehicles. They use far less space inside the door. Being more complicated than the scissor-type, these window regulators have more opportunity to break. The pulleys and cables in these regulators typically wear out, and snap. When that happens, the glass almost always falls inside the door, leaving your interior open.

3. The Flexible Drive Mechanism

This window mechanism was used for the rear doors in Reliant and Sundance 4-door models. The mechanism was a rack-and-pinion gear set made of tough injection-molded Delrin plastic. The Delrin rack gear was flexible and slides along a T-shaped steel track to move the glass up or down as the window crank turns the pinion gear. The window glass was fastened to the sliding rack gear by a link. A small fixed window was used in the door behind the sliding glass with this mechanism.

This video will help you to know about the electrical circuits in power windows.

To know more of electrical circuits goto: http://in.mathworks.com/products/simulink/model-examples.html?file=/products/demos/simulink/PowerWindow/html/PowerWindow1.html

Finally check out this video.

Notify me about anything you want to know in the comments. Thanks and peace.

References :

Have you ever wondered how your car starts just by turning a key or pushing a start button? If you ever did, here is what that happens in the back ground.

First let us know what is essential for engine to start and run. Fuel and spark are main requirements for the engine to keep running, but to start an engine initially we need to rotate crankshaft which in turn reciprocates the pistons in cylinder block. This is done by the Flywheel attached to crankshaft. The flywheel has teeth which engages with pinion teeth on starter.

To start car engine we rotate the ignition key beyond the ON symbol. After a few jerky sounds you hear your engine breathing. When we rotate the ignition key beyond the ON indication the starter switch turns ON and the current from the car battery is drawn to the solenoid through thick wires. When current passes through solenoid wires electromagnetic field develops and attracts the iron rod inside it. The movement of iron rod completes the circuit between battery and the starter. Now the starter motor powers the pinion on the motor shaft.

Bendix drive is engagement mechanism used in starter motors. The device allows the pinion gear of the starter motor to engage or disengage the flywheel of the engine automatically when the starter is powered.It disengages as soon as the engine picks up speed, and there are two ways by which it does so - the inertia system and the pre-engaged system.

Inertia System

Pre Engaged System

When the starter motor begins turning, the inertia of the drive pinion assembly causes it to wind the spring forcing the length of the spring to change and engage with the ring gear. When the engine starts, backdrive from the ring gear causes the drive pinion to exceed the rotative speed of the starter, at which point the drive pinion is forced back and out of mesh with the ring gear.The pinion returns so violently that there has to be a strong spring on the shaft to cushion its impact.The violent engagement and disengagement of an inertia starter can cause heavy wear on the gear teeth.
To overcome that problem the pre-engaged starter was introduced, which has a solenoid mounted on the motor. As well as switching on the motor, the solenoid also slides the pinion along the shaft to engage it.The shaft has straight splines rather than a Bendix thread, so that the pinion always turns with it.The pinion is brought into contact with the toothed ring on the flywheel by a sliding fork. The fork is moved by a solenoid, which has two sets of contacts that close one after the other.The first contact supplies a low current to the motor so that it turns slowly - just far enough to let the pinion teeth engage. Then the second contacts close, feeding the motor a high current to turn the engine.The starter motor is saved from over-speeding when the engine starts by means of a freewheel clutch, like the freewheel of a bicycle. The return spring of the solenoid withdraws the pinion from engagement.

The ignition switch(Key rotating port) has a return spring, so that as soon as you release the key it springs back and turns the starter switch off.

In olden days the driver used to rotate the flywheel manually to start the engine (Cranking). See 11.52 min in the video below.

Want to know more about starter go to following links:

So, We have successfully started the car and as stated above fuel and spark are required. Fuel, we would fill it the car at gas station. So where does the spark come from.To generate the spark we need high voltage. But the car battery can only provide 12V. We need to convert this 12V from battery to thousands of volts. Lets learn about spark generation.

When we turn on the ignition switch to ON position, current flows from 12 volt car battery to the ignition coil. An ignition coil (also called a spark coil) is an induction coil in an automobile's ignition system which transforms the battery's low voltage to the thousands of volts needed to create an electric spark in the spark plugs to ignite the fuel. Ignition coil consists of laminated iron core surrounded by Primary and secondary windings.

To know more about ignition coil: http://en.wikipedia.org/wiki/Ignition_coil

The current flows from the battery to the primary winding in the Ignition coil and flows to a mechanical contact breaker which is grounded at other end. The contact will be broken by a cam which is connected directly to the cam shaft according to the number of engine cylinders. When the contact is broken, the current flow in primary circuit breaks and an EMF is induced in the secondary winding which has more no. of coil turns than primary winding. The voltage jumps to a value of some thousands. Whenever the contact is broken back EMF generated is absorbed by the condenser.

The generated high voltage is then carried to distributor by spark plug wires also known as high tension leads. In the distributor we have a rotor that rotates according to ignition timing, such that it supplies current to a exact spark plug at exact time through distributor points. The rotor does not come directly into contact with the distributor point.

The high voltage is then transferred to the spark plug central electrode by high tension leads. The central electrode is surrounded by an insulator. The central electrode and ground electrode are separated by very small distance. When the voltage exceeds the dielectric strength of gases between the electrodes, the gas is ionised and spark is produced with current flow in the gap. Originally, every ignition coil system required mechanical contact breaker points, and a capacitor (condenser).

The following video helps in better understanding.

More recent electronic ignition systems use a power transistor to provide pulses to the ignition coil. In this system the mechanical contact breaker is replaced by an armature and electronic ignition module( EIG). Previously contact breaker used to break current in primary circuit and the mechanical system is always prone to wear. In this system the armature sends signal to ignition module to make and break the circuit. This setup has armature which has teeth and a pickup coil. When the armature tooth comes in front of pickup coil it sends a signal to EIG to break current flow in primary circuit. When the tooth moves away the primary circuit is made. Rest of the mechanism is the same.

The following video helps in better understanding.

We have another Ignition system which is the Direct Ignition System (DIS). In this system the distributor is eliminated and we have Ignition Control Module (ICM) and Engine Control Unit (ECU). We have sensors to know the exact position of cam shaft and crank shaft. The signals from both the sensors help ICM determine the position of piston w.r.t the position of crank shaft and cam shaft. These sensors also help ICM in advancing or retarding the spark with varying engine speeds. This is possible as each spark plug is individually powered by the coil pack (ignition coils) i.e one coil pack per plug.The ECU supplies battery voltage to coil pack and simultaneously calculates the ignition timing, which is based on information it gets from ICM.

We can also have common coil pack between two spark plugs and the cylinder block acts as the connection between the two plugs. In this type of DIS one plug fires in forward direction whereas the other spark plug in companion cylinder fires in opposite direction. This system results in waste spark generation. The wasted spark system is more reliable than a single coil system with a distributor and less expensive than coil-on-plug.

The following video helps in better understanding.

Diesel engines doesn't need spark plugs. Diesel engines rely on fuel compression for ignition, but usually also have glowplugs that preheat the combustion chamber to allow starting of the engine in cold weather.

Some topics you would want to learn more in detail :

Notify me about anything you want to know in the comments. Thanks and peace.

What happens in the background

Friday, February 27, 2015

How windows on a car work?

Thursday, February 19, 2015

How does a car start?