automobile
[‚ȯd·ə·mə′bēl]Automobile
A self-propelled land vehicle, usually having four wheels and an internal combustion engine, used primarily for personal transportation. Other types of motor vehicles include buses, which carry large numbers of commercial passengers, and medium- and heavy-duty trucks, which carry heavy or bulky loads of freight or other goods and materials. Instead of being carried on a truck, these loads may be placed on a semitrailer, and sometimes also a trailer, forming a tractor-trailer combination which is pulled by a truck tractor.
The automobile body is the assembly of sheet-metal, fiberglass, plastic, or composite-material panels together with windows, doors, seats, trim and upholstery, glass, and other parts that form enclosures for the passenger, engine, and luggage compartments. The assembled body structure may attach through rubber mounts to a separate or full frame (body-on-frame construction), or the body and frame may be integrated (unitized-body construction). In the latter method, the frame, body parts, and floor pan are welded together to form a single unit that has energy-absorbing front and rear structures, and anchors for the engine, suspension, steering, and power-train components. A third type of body construction is the space frame which is made of welded steel stampings. Similar to the tube chassis and roll cage combination used in race-car construction, non-load-carrying plastic outer panels fasten to the space frame to form the body. See Composite material
The frame is the main structural member to which all other mechanical chassis parts and the body are assembled to make a complete vehicle. In older vehicle designs, the frame is a separate rigid structure; newer passenger-car designs have the frame and body structure combined into an integral unit, or unitized body. Subframes and their assembled components attach to the side rails at the front and rear of the unitized body. The front subframe carries the engine, transmission or transaxle, lower front suspension, and other mechanical parts. The rear subframe, if used, carries the rear suspension and rear axle.
The suspension supports the weight of the vehicle, absorbs road shocks, transmits brake-reaction forces, helps maintain traction between the tires and the road, and holds the wheels in alignment while allowing the driver to steer the vehicle over a wide range of speed and load conditions. The action of the suspension increases riding comfort, improves driving safety, and reduces strain on vehicle components, occupants, and cargo. The springs may be coil, leaf, torsion bar, or air. Most automotive vehicles have coil springs at the front and either coil or leaf springs at the rear. See Automotive suspension
The steering system enables the driver to turn the front wheels left or right to control the direction of vehicle travel. The rotary motion of the steering wheel is changed to linear motion in the steering gear, which is located at the lower end of the steering shaft. The linear motion is transferred through the steering linkage to the steering knuckles, to which the front wheels are mounted. Steering systems are classed as either manual steering or power steering, with power assist provided hydraulically or by an electric motor.
A brake is a device that uses a controlled force to reduce the speed of or stop a moving vehicle, or to hold the vehicle stationary. The automobile has a friction brake at each wheel. When the brake is applied, a stationary surface moves into contact with a moving surface. The resistance to relative motion or rubbing action between the two surfaces slows the moving surface, which slows and stops the vehicle.
The engine supplies the power to move the vehicle. The power is available from the engine crankshaft after a fuel, usually gasoline, is burned in the engine cylinders. Most automotive engines are located at the front of the vehicle and drive either the rear wheels or the front wheels through a drive train or power train made up of gears, shafts, and other mechanical and hydraulic components. Most automotive vehicles are powered by a spark-ignition four-stroke-cycle internal combustion engine. The inline four-cylinder engine and V-type six-cylinder engine are the most widely used, with V-8 engines also common. Other automotive engines have three, five, ten, and twelve cylinders. Some passenger cars and trucks have diesel engines. Some automotive spark-ignition and diesel engines are equipped with a supercharger or turbocharger. See Automotive engine, Diesel engine, Engine, Ignition system, Turbocharger
Most automotive engines have electronic fuel injection instead of a carburetor. A computer-controlled electronic engine control system automatically manages various emissions devices and numerous functions of engine operation, including the fuel injection and spark timing. This allows optimizing power and fuel economy while minimizing exhaust emissions. See Carburetor, Control systems, Fuel injection
The power available from the engine crankshaft to do work is transmitted to the drive wheels by the power train, or drive train. In the front-engine rear-drive vehicle, the power train consists of a clutch and manual transmission, or a torque converter and an automatic transmission; driveshafts and Hooke (Cardan) universal joints; and rear drive axle that includes the final drive, differential, and wheel axle shafts. In the typical front-engine front-drive vehicle, the power train consists of a clutch and manual transaxle, or a torque converter and an automatic transaxle. The final drive and differential are designed into the transaxle, and drive the wheels through half-shafts with constant-velocity (CV) universal joints. See Clutch, Gear
The transmission is the device in the power train that provides different forward gear ratios between the engine and drive wheels, as well as neutral and reverse. The two general classifications of transmission are manual transmission, which the driver shifts by hand, and automatic transmission, which shifts automatically. To shift a manual transmission, the clutch must first be disengaged. However, some vehicles have automatic clutch disengagement for manual transmissions, while other vehicles have a limited manual-shift capability for automatic transmissions. See Automotive transmission
In the power train, the final drive is the speed-reduction gear set that drives the differential. The final drive is made up of a large ring gear driven by a smaller pinion, or pinion gear. This provides a gear reduction of about 3:1; the exact value can be tailored to the engine, transmission, weight of the vehicle, and performance or fuel economy desired.
In drive axles, the differential is the gear assembly between axle shafts that permits one wheel to rotate at a speed different from that of the other (if necessary), while transmitting torque from the final-drive ring gear to the axle shafts. When the vehicle is cornering or making a turn, the differential allows the outside wheel to travel a greater distance than the inside wheel; otherwise, one wheel would skid, causing tire wear and partial loss of control. See Differential
A wheel is a disc or a series of spokes with a hub at the center and a rim around the outside for mounting of the tire. The wheels of a vehicle must have sufficient strength and resiliency to carry the weight of the vehicle, transfer driving and braking torque to the tires, and withstand side thrusts over a wide range of speed and road conditions. Wheel size is primarily determined by the load-bearing strength of the tire.
The use of solid-state electronic devices in the automobile began during the 1960s, when the electromechanical voltage regulator of the alternator, was replaced by a transistorized voltage regulator. This was followed in the 1970s by electronic ignition, fuel injection, and cruise control. Since then, electronic devices and systems on the automobile have proliferated. These include engine and power train control, air bags, antilock braking, traction control, suspension and ride control, remote keyless entry, memory seats, driver information and navigation systems, cellular telephone and mobile communications systems, and onboard diagnostics. See Feedback circuit
The self-diagnostic capability of the vehicle computer, power-train or engine control module, or system controller may be aided by a memory that stores information about malfunctions that have occurred and perhaps temporarily disappeared. When recalled from the memory, this information can help the service technician diagnose and repair the vehicle more quickly, accurately, and reliably.
automotive safety systems
Vehicular systems that help prevent an accident are increasing rapidly. Combined with all the computer-based entertainment, navigation, dashboard and engine control, electronic systems comprised more than 20% of the car's value by 2017. Automotive safety systems are designed to either work automatically or require drivers to activate them when desired. See automotive systems and microcontroller.Old Passive
Passive systems require no action on the part of the driver other than buckling seat belts. Head rests, airbags, anti-lock braking (see ABS) and tire pressure monitoring (see TPM) are passive safety measures that date back to the 1960s and 1970s in the U.S.
New Passive
Automatic braking, blind spot alerts, rear blind zone monitoring, cyclist and temperature detection, driver alerts and adaptive headlights are modern passive systems. See collision avoidance system, blind spot monitoring, driver alert, cyclist detection, pedestrian detection, hot car detection and adaptive headlights.
New Active
Active systems must be turned on by the driver. Cruise control that keeps a set distance, lane changing warnings, self-parking and self-driving are examples. See adaptive cruise control, lane departure system, self-parking car and self-driving car.
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| Safety Systems in a Lincoln |
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| A TV commercial for the 2019 Lincoln Nautilus touts its safety systems by displaying the checklist that appears on the dashboard when starting the car. (Image courtesy of Ford Motor Company.) |