机械英语证书考试(PEC)辅导-机械专业术语

Mechanical Engineering English Certification— Mechanical Terms Glossary A A-Arm - A suspension linkage formed in the shape of an "A" or "V" found commonly on the front suspension. The sides of the two legs of the A-arm are connected to the chassis by rubber bushings and the peak of the A-arm is attached to the wheel assembly. In this way, the wheel can freely move up and down. Sometimes there is an upper A-arm, a lower A-arm, or both upper and lower A-arms. The British call it a "wishbone." Accelerator - Fuel pedal or throttle. A foot-operated pedal or hand-operated lever connected by linkage or electronics to control vehicle speed. Adaptive Automatic Transmission - Some transmissions can "learn" and adapt to the driver's style, altering shift points and other transmission functions to produce the most efficient operation. Adaptive Cruise Control - One step beyond cruise control, adaptive cruise control uses a radar sensor mounted in the front of the vehicle to maintain a safe cruising distance between your vehicle and the vehicle in front of you. Most systems allow you to set the interval (distance between vehicles) and will then accelerate and brake (within reason) to maintain that interval. In many cases, the systems can take into account hilly terrain and passing situations. All have the ability to act like regular cruise control, and they still require the driver to steer the vehicle normally. Some automakers refer to it as "intelligent" cruise control. Adjustable Suspension - Provides better ride or handling. A variety of systems are used to vary shock-absorber firmness. Some automatically sense road conditions and adjust shock-absorber settings accordingly. Others include a switch on the dashboard or console that allows the driver to adjust shock-absorber settings to provide a softer or firmer ride, or sharper handling. Aftermarket - All products and services used in the repair and maintenance of vehicles that was not produced by the original vehicle manufacturer. Alternator - A component of the electrical system, it converts 12-volt DC (Direct Current) from the battery into AC (Alternating Current) at the rate of 13.8 to 14.2 volts. The alternator also provided electric power to operate the engine and accessories Air Bag - The air bag, also known as a Supplemental Inflatable Restraint System, is a passive safety device, supplemental to safety belts, that inflates to provide a cushion to absorb impact forces during moderate to severe frontal collisions. This system can help to lessen the chance of contact with the steering wheel, instrument panel and windshield. The air bag is actuated automatically by sensors located in the front of the vehicle. To maximize effectiveness, seat and shoulder belts must always be used in conjunction with this system Air Filter - A particulate air filter is a device composed of fibrous materials which removes solid particulates such as dust, pollen, mold, and bacteria from the air. Air Gap - Space between the spark plug electrodes, also known as gap, often adjusted to gain maximum performance. Airfoil - An aerodynamic device designed to improve traction by increasing the downforce on the vehicle. The use of airfoils (also called wings) increases the cornering capability and improves stability at speed, but often at the expense of additional aerodynamic drag. Air Injection - A system that injects air into the exhaust ports of the engine for combustion of unburned hydrocarbons in the exhaust gases, thus producing "cleaner" exhaust emissions. Air Suspension - Instead of steel coil or leaf springs, some vehicles have a bellows-like unit at each corner that contains pressurized air. As a rule, air suspensions can produce a softer ride. Alignment - Angles of the tire and suspension axis relative to each other and the ground: camber, caster, toe. Also, the adjustment of components to bring them into a predetermined position for the most efficient operation of wheel and vehicle for proper even tire wear. Alpha-Numeric - A load-based tire sizing system containing the load capacity, type of tire construction, aspect ratio, and the rim diameter in inches. Anti-Lock Brakes (ABS) - Helps maintain control in emergency stops. Particularly useful on slick pavement. While the driver applies steady pressure to the brake pedal, the system automatically "pumps" the brakes many times per second to prevent wheel lock-up. Anti-Roll Bar - A steel bar, linking the left and right side of a suspension. It comes into play during cornering. As the car leans in a turn, the anti-roll bar resists this leaning by transferring more weight to the outside tire. It provides a means to achieve good handling from stiff roll resistance while maintaining a comfortable ride through soft springs. Antiskid System - Helps maintain control in fast turns. Works whether or not the brakes are applied. Sensors automatically apply individual brakes to prevent a sideways skid. Some systems also cut back on the throttle, slowing the engine. It's also known as an electronic stability system or stabilization program. A-Pillar - In the side view, the foremost roof support of a vehicle, located in most instances between the outer edge of the windshield and the leading edge of the front door upper. Also known as an A-Post. Alloy Wheels - A generic term used to describe any non-steel road wheel. The most common alloy wheels are cast aluminum. Technically, an alloy is a mixture of two or more metals. These wheels are known for their light weight and strength. Alternating Current (AC) - Flow of electricity that periodically reverses direction. All-Wheel Drive - Often confused with Four-Wheel Drive (4WD), this drive system features four, full-time active drive wheels to reduce wheel slippage and provide greater driver control over the vehicle. All-Wheel Drive automatically splits engine torque between the front and rear wheels as needed, improving on-road traction in unfavorable road conditions. Unlike Four-Wheel Drive, All-Wheel Drive is an on-road system and is not designed for off-road use. AWD does not require the driver to actively engage the system. It is operational at all times, and requires no switches, lights or visor instructions for system operation. Ampere - After Andre-Marie Ampere, French (1775-1836). The ampere is a unit of electrical current, or the flow of electricity. Anti-Lock Brake System (ABS) - On a vehicle equipped with Anti-Lock Brakes, the wheels are equipped with speed sensors. When a sensor determines that a wheel is decelerating so rapidly that lockup may occur, the electro-Hydraulic Control Unit (EHCU) is activated. The EHCU then modulates the brake pressure in the appropriate brake lines by means of the solenoid-operated valves. This is intended to prevent wheel lockup and help the vehicle maintain directional stability during potentially hazardous braking situations. (See also: Rear-Wheel Anti-Lock and Four-Wheel Anti-Lock.) Antifreeze - An additive that lowers the freezing point of a liquid Aspect Ratio - The dimensional relationship between tire section height and section width; section height divided by section width. A.T.D.C. - After top dead center Automatic Climate Control - A heating and air conditioning system that adjusts itself as needed, to maintain a pre-set temperature. Automatic Locking Front Hubs - Found in some four-wheel drive vehicles, this allows the driver to engage, or "lock," the front axle hubs without leaving the vehicle. Automatic Transmission With Manual-Shift Capability - Allows manual gear changes, when desired, in an automatic transmission. Functions as a traditional automatic transmission when left in Drive, but includes a slot in which the shift lever can be moved to change gears manually. Sometimes, buttons for shifting manually through the gears are located on the steering wheel. This affords some of the advantages of a manual transmission, such as greater control of engine speed for better throttle response, but eliminates the need for a clutch pedal. Axle - A cross support of a vehicle on which its road wheels turn. Axle Ratio - The ratio between the rotational speed (RPM) of the drive shaft and that of the driven wheel. Gear reduction in final drive is determined by dividing the number of teeth on the ring gear by the number of teeth on the pinion gear. B Backspacing - The measurement from the back of the bolt pad to the back edge of the rim; used to calculate offset and determine where the back of the bolt pad is located in relation to the rim width, sometimes referred to as rear spacing. Balance - A uniform mass distribution of a tire and wheel assembly about its axis of rotation. Ball Joint - A ball-and-socket connection that lets a steering knuckle move in several directions at the same time. Bead - The area of the mounted tire which seats against the wheel. Bead Seat - The position where the tire rests and seals on the inside of the rim. Belted Bias Tire - A bias tire with additional reinforcing belt(s) between the casing plies and the tread Block Heater - An accessory which uses electric power to keep an engine that's been turned off from becoming too cold, which makes it hard to start in extremely cold climates. Bias Tire - A tire built with two or more casing plies, which cross each other in the crown at an angle of 30 to 45 degrees to the tread centerline. Biodiesel - Refers to a vegetable oil, or animal fat-based diesel fuel consisting of long-chain alkyl ( methyl , propyl or ethyl ) esters . Biodiesel is typically made by chemically reacting lipids (e.g., vegetable oil , animal fat ( tallow )) with an alcohol . Biodiesel is meant to be used in standard diesel engines and is thus distinct from the vegetable and waste oils used to fuel converted diesel engines. Biodiesel can be used alone, or blended with petrodiesel. Blemish Tire - A tire with a cosmetic or minor uniformity imperfection but whose safety and performance are unaffected. Bluetooth Capability - The ability of a radio system to work with Bluetooth wireless connectivity, to function in concert with a cellular phone. Bore - The diameter of an engine cylinder or bearing. Brake Assist - Designed to shorten stopping distance in a "panic" stop. Applies full braking power even if the brake pedal is not fully depressed. Sensors gauge the speed at which the driver initially depresses the brake pedal and determine whether full emergency stopping power is warranted. Brake Drum - A drum brake is a brake in which the friction is caused by a set of shoes or pads that press against a rotating drum-shaped part called a brake drum. Brake Fade - A condition brought about by repeated brake applications, resulting in build-up of heat that causes a temporary reduction or fading of braking effectiveness. Brake Horsepower (BHP) - The actual horsepower of an engine, measured by a brake attached to the driving shaft and recorded by a dynamometer. Brake Linings - The replaceable friction material which contacts the brake drum in a drum brake system to slow or stop the vehicle. Brake Master Cylinder - A cylinder containing a movable piston activated by pressure on the brake pedal. The piston produces hydraulic pressure that pushes fluid through the lines and wheel cylinders. This forces the brake lining or pad against the drum or disc to slow or stop the vehicle. Brake Pads - In a disc system, they are the replaceable flat segments consisting of a rigid backing plate plus frictional lining that takes the place of the shoe and lining in a drum brake. Brake Shoe - The arc-shaped carrier to which the brake linings are mounted in a drum brake. They also force the lining against the rotating drum during braking. Brakes, Disc - A type of braking system in which brake shoes, in a vise-like caliper, grip a revolving disk mounted on a wheel to slow or stop disc and wheel rotation for braking. Brakes, Drum - A type of braking system that utilizes a metal drum mounted on a wheel to form the outer shell of a brake. The brake shoes press against the drum to slow or stop drum and wheel rotation for braking. B-Pillar - The roof support between a vehicle's front door window and rear side window, if there is one. Bolt Circle - Often referred to as the wheel bolt pattern; the diameter of an imaginary circle drawn through the center of each lug hole. Braking Torque - Torque applied by a brake to a tire/wheel assembly, which slows or stops the vehicle. Breakaway - The point at which tire cornering traction is lost. Bumpsteer - A steering effect resulting from toe or camber changes as the suspension moves up and down. C Caliper - In a disk brake, a housing for cylinder, pistons and brake shoes, connected to the hydraulic system. The caliper holds the brake shoes so they straddle the brake disc. Camber Angle - The inward or outward angle which a front-wheel spindle makes with a vertical line, as viewed by either the front or the rear of the vehicle. Positive camber results when the top of the tire tilts out further than its bottom. The adjustment of this setting affects both tire wear and vehicle handling. Camshaft - The shaft in the engine which is driven by gears, belts or chain from the crankshaft. The camshaft has a series of cams that opens and closes intake and exhaust valves as it turns. Camber Thrust - The lateral force developed by a tire due to its camber. A force in the same direction as the leaning of the tire. Carrying Capacity - Amount of load that a tire can carry at a given inflation pressure as established by the Tire and Rim Association. Cart - Championship Auto Racing Teams; sanctions races for Indy type cars. Casing (Carcass) - The structure of tire cords locked around wire beads, (most often used in relation to worn tires). Caster Angle - The forward or backward tilt of the steering axis as viewed from the side. If the point of load is ahead of the point of contact, the caster angle is positive. The caster angle tends to keep wheels in a straight line. Proper caster adjustment improves both tire wear and fuel economy. Catalytic Converter - A stainless steel canister that is part of a vehicle's exhaust system and contains a thin layer of catalytic material spread over a large area of inert supports. It induces chemical reactions that convert an engine's exhaust emissions into less harmful products prior to entering the environment. Center of Gravity - The center balance point of a vehicle; the single point where a vehicle would be supported without tipping up or down. Centerline - A plane dividing a tire, wheel, or vehicle into two symmetrical halves. Centrifugal Force - The force that tends to throw a tire away from the axis of rotation, same as radial force. Chapman Strut - A rear suspension system which operates on the same principles as the MacPherson Strut; it uses lower links or a control arm and a long spring-shock strut. Chassis - The frame, suspension system, engine, and drive train of a vehicle. The assembled parts of the automobile without the body. Closed Crankcase Ventilation (CCV) -A system in which crankcase vapors are discharged into the engine intake system (usually via the intake manifold) where they are burned during the combustion process rather than being discharged into the atmosphere. Clutch - A disc-shaped mechanical device that disengages the engine from the transmission. Clutch-Starter Interlock - A safety device that prevents a truck from being started while it's in gear. The clutch must be depressed for the engine to start. Coefficient of Friction - The force required to initiate the sliding of an object, divided by the weight of the object; this ratio indicates the difficulty in sliding one surface against another. Coil Springs - Suspension components that compress and respond to road inputs, permitting the up-and-down movement of a vehicle as it goes over road bumps and dips. Cold Cranking Amps (CCA) - A rating, measured in amperes. Used for comparing cranking strength of vehicles batteries during extremely cold (0 F or lower) weather. Cold Inflation - The pressure in a tire that has been driven less than 1 mile at moderate speed or has been standing for three hours or more. Combustion Chamber - The volume of space at the top of the cylinder where burning of the air/fuel mixture begins. Compliance Steer - A steering effect caused by the deflection or compliance of bushings, joints, and other suspension components under loads and forces. Compound - The general term referring to the tire tread's chemical makeup. Composite Headlamps - Usually manufactured with replaceable halogen bulbs and separate hard acrylic or glass lenses. This type of lamp provides superior illumination compared to the long-conventional sealed beam unit. Compression Ratio - The volume of the combustion chamber and cylinder when the piston is at the bottom of its stroke, divided by the volume of the combustion chamber and cylinder when the piston is at the top of its stroke. Higher compression ratios tend to increase engine efficiency. Compressor (Air Conditioning) - The mechanism is an air conditioner that pumps vaporized refrigerant out of the evaporator, compresses it to a high pressure, and then delivers it to the condenser. Condenser (Air Conditioning) - Air conditioning component used to remove heat from the inside of a vehicle. Connecting Rod - The metal rod that connects a piston to the crankshaft. Contact Patch - The part of the tire in contact with the road surface. Continuously Variable Transmission (CVT) - Operates like an automatic transmission, with no need for a clutch pedal, but contains no gears. Instead, power is transmitted in a continuous flow from the engine to the drive wheels. Control Arm - A suspension element that has one joint at one end and two joints at the other end, typically on the chassis side. Also known as a wishbone or an A-arm. Coolant - The mixture of water and anti-freeze that picks up heat from the engine and transfers it to the air passing through the radiator. This transfer of heat keeps the engine operating within its optimum temperature and preventing premature engine wear. Cooling System - The system that removes heat from the engine by the forced circulation of coolant and thereby prevents engine overheating. In a liquid-cooled engine, it includes the water jackets, water pump, radiator, and thermostat. C-Pillar - The roof support between a vehicle's rearmost side window and its rear window. Also known as a C-Post. On a vehicle with four side pillars, the rearmost roof support may be called a D-pillar. Cord - Fabric or steel wire strands forming plies and belts in tires. Cornering Force - The force that turns a vehicle around a corner. The opposite of lateral or centrifugal force. Crankcase - A case that encloses the crankshaft. In most engines, the oil pan and the lower portion of the cylinder block form the crankcase. Crankshaft - A shaft with one or more cranks, or "throws," that are coupled by connecting rods to the engine's pistons. The combustion process creates reciprocating motion in the rods and pistons which in turn is converted to a rotating motion by the crankshaft. Crossmember - One of several horizontal members in a vehicle frame which join the side members and add to overall strength and stability. Cross Pattern - The sequential torquing of the lug nuts in a pattern across from one another. Cross-Section Width - External sidewall-to-sidewall measurement of inflated tire, exclusive of ornamental ribs and lettering. Sometimes called section width. Crown - The region between the shoulders of a tire. Crowned Road - A road design with a slope or pitch from its