UNIT 2: TRANSPORTATION

LESSON 6: MODERN AUTOMOBILE FEATURES

By the end of this lesson you should be able to:

describe different features of the automobile describe the science and technology behind select

automobile features

VocabularyPretensioner Sway BarDisc BrakeDrum BrakeSmart City Brake SupportAdaptive Cruise Control

LEARNING OUTCOMES

Car manufacturer Henry Ford once remarked that customers could have any colour of automobile they wanted as long as it was black. Times have changed considerably since Ford's day in the early 1900s. Not only can you now pick the exact colour you want, you can choose a particular model of engine, transmission type, wheel size, interior details, and many other features.

FEATURES OF THE MODERN AUTOMOBILE

Many of these features are designed to improve vehicle performance; others make vehicles safer or more comfortable. And with our growing concern for the environment and climate change, automobile manufacturers are also starting to incorporate features aimed at reducing harmful exhaust emissions. Other features provide luxury, comfort, and entertainment.

Have you ever stopped to think what actually happens when you put your key in the ignition and turn on the engine, or when you step on the brakes, or when you put on your turn signal? The modern automobile is a very sophisticated machine. Let's find out how some of its many features work.

FEATURES OF THE MODERN AUTOMOBILE

Seat belts are the one of the single most important automobile safety technologies. When worn properly, they can reduce the likelihood of death in an accident by up to 50 percent.

In a typical system, the seat belt webbing is wrapped around a toothed spool that is attached to a spring.

SEATBELTS

When you pull the webbing (like you would to put on the seat belt), the spool rotates counterclockwise and untwists the spring. The spring wants to return to its original posit ion, so it resists this movement. This resistance is what you feel when you put on the seat belt.

When the seat belt buckle is clicked in you can sti l l move forward a l itt le bit. But when the seat belt is pulled quickly and suddenly (e.g., by your forward momentum in a crash), a pawl catches a notched area between the teeth on the spool. This locking mechanism causes the belt to automatically t ighten.

SEATBELTS

A newer technology called a pretensioner goes one step further by actually pulling back on the seat belt.

SEATBELTS

In the event of a crash, sensors send off an electrical signal that ignites a gas inside the pretensioner chamber. This gas creates tremendous pressure, driving a piston upwards at high speed. This piston has teeth on its side. These teeth engage with the teeth on the seat belt spool, forcing it to rotate backwards at great force. This retracts the seat belt.

Initial State Pretensioner Operates

(1)

(2)

(3)

(1) Pinion(2) Gas Generator(3) Piston

According to the Insurance Corporation of British Columbia, serious front-end collisions are responsible for half of all vehicle occupant deaths and serious injuries to the head, neck, and chest. The best protection in a collision like this is an air bag.

Air bags are connected to sensors that detect sudden and rapid deceleration (which happens in a collision). When activated, these sensors send an electrical signal to the air bag, which ignites a chemical propellant.

AIRBAGS

This propellant produces nitrogen gas, which inflates the air bag at a speed of more than 300 km/h. Air bags have vents in the back, so they deflate immediately after absorbing the impact of the occupant's head.

AIRBAGS

Sodium Azide Sodium + Nitrogen Gas

2 NaN3 2 Na + 3 N2

Power steering reduces the effort required to turn the steering wheel.

It works by putting the steering system together with a hydraulic system.

A pump, driven by the engine, delivers pressurized hydraulic fluid to either side of the steering mechanism. This pressurized fluid pushing on the steering mechanism helps to steer the car, reducing steering effort. Power steering is actually "power-assisted steering.”

See video “Car Tech 101: Power Steering Explained”

POWER STEERING

An automobile's suspension system is designed to absorb the shock from bumps in the road and ensure the wheels maintain contact and traction with the road.

A typical suspension system consists of springs, shock absorbers, and anti-sway bars.

When the automobile hits a bump, the springs coil more tightly. The energy coiled in the springs is then transferred to the shock absorber. The shock absorber is made up of a piston inside a cylinder. The energy from the springs forces the piston to move down into the cylinder. Tiny holes in the piston allow hydraulic fluid to leak out as this happens. Since the holes are tiny, great pressure is created. This, in effect, slows down the rate of travel of the piston, which in turn slows down the spring. The energy is absorbed and the impact from the bump in the road is cushioned.

SUSPENSION

SUSPENSION

The third component of the suspension system is the anti-sway bars. An anti-sway bar stretches from one side of the axle to the other and connects each side of the suspension. When the suspension on one wheel moves up and down, the anti-sway bar transfers this movement to the other wheel. This creates a smoother, more level ride.

SUSPENSION

The typical brake system on a modern automobile consists of disk brakes on the front wheels and either disk or drum brakes on the rear wheels.

Each brake is connected to a master brake cylinder by a series of tubes and hoses. When you step on the brake pedal, brake fluid is sent from the master cylinder through these tubes and hoses to each brake.

BRAKES

On a disk brake the fluid squeezes the brake pads, or calipers, against the disk. This forces the wheel to slow down or stop. This is very similar to the brakes you will find on a bicycle.

BRAKES

Drum brakes are a bit more complex. Drum brakes consist of a backing plate, brake shoes, brake drum, wheel cylinder, return springs and an automatic or self-adjusting system.

When you apply the brakes, brake fluid is forced under pressure into the wheel cylinder, which in turn pushes the brake shoes into contact with the machined surface on the inside of the drum. When the pressure is released, return springs pull the shoes back to their rest position.

BRAKES

Mazda Motor Corporation has developed an advanced safety technology called Smart City Brake Support (SCBS), which helps a driver to avoid a frontal collision when driving at low speeds in the city or in slow traffic.

The SCBS system uses a laser sensor to detect a vehicle or obstacle in front and automatically reduces the extent of the brake rotor travel to quicken braking operation. If the driver fails to perform any operation to avoid a collision, such as applying the brake, SCBC automatically activates the brakes and reduces the engine output at the same time.

SMARTER SYSTEMS

Two companies are developing a more advanced cruise control that can automatically adjust a car's speed to maintain a safe following distance. This new technology, called adaptive cruise control , uses forward-looking radar, installed behind the grill of a vehicle, to detect the speed and distance of the vehicle ahead of it.

Adaptive cruise control is similar to conventional cruise control in that it maintains the vehicle's pre-set speed. However, unlike conventional cruise control, this new system can automatically adjust speed in order to maintain a proper distance between vehicles in the same lane.

If the lead vehicle slows down, or if another object is detected, the system sends a signal to the engine or braking system to decelerate. Then, when the road is clear, the system will re-accelerate the vehicle back to the set speed.

SMARTER SYSTEMS

QUICK CHECK QUESTIONSComplete the Quick Check Questions in your notes package.