Chapter 77 Vocab Flashcards
Vocab for chapter 77
road feel
slight steering wheel pull caused by road surface irregularities
linkage steering systems
found in large, full-size pickup trucks and full-size vans, both two- and four-wheel drive. Include steering wheel, shaft, column, gearbox, linkage through tie-rods, and ball sockets
rack-and-pinion steering systems
lighter and are better for passenger cars and small trucks. Include steering wheel, shaft, column, steering pinion gear, rack, gear housing, and tie-rods
steering column assembly
consists of the steering wheel, steering shaft, column (outer housing), and, sometimes, ignition key mechanism, a flexible coupling, and a universal joint
ignition lock mechanism
mounted on the steering column in most vehicles, normally on the top, right-hand side of the column
ignition switch
usually bolted inside the steering column
locking steering wheel
to help prevent theft, prevents wheel from turning when ignition key is off by means of a steel pin
collapsible steering column
help prevent driver chest and face injury during an accident. Column designed to crumple or slide together when forced forward during a collision. Different types steel mesh (crushing) columns, tube-and-ball (sliding) columns, and the shear capsule (break and slide) columns. Made up of two pieces
tilt steering column/tilt steering wheel
has a flex joint, or U-joint, that allows the top half of the column and the steering wheel to be positioned at different angles
manual tilt column
uses a lever on the steering column to unlock the flex joint so the wheel can be moved up or down
power tilt column
uses a small electric motor, a control switch, and a gear mechanism to change steering wheel angle or height.
memory tilt wheels
use a tilt control module (computer) to “remember” more than one steering wheel position. a sensor in steering column provides feedback so the tilt control module knows wheel location.
recirculating-ball gearbox
normally used with a linkage steering system on large truck. It has small steel balls that circulate between the gear members
worm shaft
the input gear connected to the steering column shaft. The balls fit and ride in the grooves in the worm gear
sector shaft
is the output gear from the steering gearbox. It transfers motion to the steering linkage. A sector gear is machined on the inner end of the sector shaft
ball nut
rides on the ball bearings and the worm gear. Grooves are cut in the ball nut to match the shape of the worm gear. Cannot rotate, it slides up and down as the worm gear rotates
ball guides
route extra ball bearings in and out from between the worm and ball nut
adjusting nut
is usually provided to set worm shaft bearing preload
adjusting screw
is used to set the sector shaft clearance
gearbox housing
provides an enclosure for the other gearbox components. Seals press into the housing to prevent lubricant leakage at the worm and sector shafts.
end cover
normally bolts on the housing to cover the end of the sector gear. It can be removed for gearbox service
gearbox ratio/steering ratio/steering gear reduction
a comparison between steering wheel rotation and sector shaft rotation. Range from 15:1 to 24:1
variable-ratio gearbox
changes the internal gear ratio as the front wheels are turned from the center position. faster when cornering, and provides better control and response when maneuvering
constant-ratio gearbox
changes gear reduction from full left to full right
worm-and-roller steering gearbox
contains a roller that is mounted on the pinion shaft and meshes with the worm gear. The roller replaces the ball bearings and the ball nut used in the recirculating- ball gearbox. The roller imparts a rotary force on the pitman shaft as the worm gear rotates
steering linkage
series of arms, rods, and ball sockets that connect the worm-type steering gearbox to the steering knuckles
parallelogram steering linkage
linkage used with a worm-type gearbox. Typically includes a pitman arm, a center link, and idler arm, and two tie-rod assemblies. Possibly a steering damper
pitman arm
transfers gearbox motion to the steering linkage. Is splined to the gearbox sector (output) shaft. A large nut and lock washer secure the arm to its shaft. The outer end of the pitman arm is normally connected to the linkage through a ball socket
ball sockets
provide for motion in all directions between two connected parts. They are needed so the steering linkage is not bent and damaged when the wheels turn or move up and down over rough road surfacesce
center link/relay rod
a steel bar that connects the right and left sides of the steering linkage. It has holes that accept the pitman arm, tie-rods, and idler arm
idler arm
supports the end of the center link on the passenger side of the vehicle
steering damper
is an oil-filled shock absorber found in some parallelogram linkage arrangements. Attached between the vehicle’s frame and the center link to help absorb road shocks
tie-rod assemblies
fasten the center link to the steering knuckles. Typically consists of two tie-rods and a toe adjustment sleeve. Ball sockets are normally used on both ends of each tie-rod assembly
toe adjustment sleeve
is provided for changing the length of the tie-rod assembly during wheel alignment. tie-rods and sleeves are threaded so the assembly can be lengthened or shortened to adjust toe-in or toe-out of the front wheels
flexible coupling
helps keep road shock from being transmitted to the steering wheel and allows for slight misalignment of the steering shaft and steering gear input shaft (pinion shaft)
universal joint
allows for a change in the angle between the steering column and steering shaft
rack-and-pinion steering gear
consists of pinion shaft, a rack, a thrust spring, bearings, seals and a gear housing
thrust spring
preloads the rack-and-pinion gear teeth to prevent excessive gear backlash (play). Adjustment screws or shims may be used to set thrust spring tension
rubber dust boots
fit over the inner ball sockets to keep out road dirt and water, as well as to hold in lubricating grease
power steering systems
normally use an engine-driven pump and a hydraulic system to assist steering action. Can also use an electric motor
power steering pump
is engine driven and produces the hydraulic pressure for steering system operation. has a belt running from the engine crankshaft pulley to power the pump
power steering fluid reservoir
holds an extra supply of power steering oil or fluid
pressure-relief valve
used in a power steering system to control maximum oil pressure. Prevents damage by limiting pressure when needed
power steering hoses
are high-pressure, hydraulic, synthetic rubber hoses that connect the power steering pump and the integral gearbox or the power cylinder. One line serves as the pressure feed line, the other as a return line to the reservoir
integral-piston power steering system
has the hydraulic piston mounted inside the steering gearbox housing. It consists of a power steering pump, hydraulic lines, and an integral power-assist gearbox
integral power steering gearbox
contains a conventional worm-and-sector gear, a hydraulic piston, and a flow-direction valve. use spool valve or rotary valve
spool valve
in an integral power steering gearbox, uses a small spool valve to control the pressure entering the power assist chambers
rotary valve
in an integral power steering gearbox, has a small torsion bar to detect steering wheel turning direction and turning effort
external cylinder power steering system
power cylinder is commonly bolted to the frame and center link
power rack-and-pinion steering
uses hydraulic pump pressure to assist the driver in moving the rack and the front wheels
power cylinder
hydraulic cylinder machined inside the rack or gear housing
power piston
hydraulic double-acting piston formed on the rack shaft
hydraulic lines
steel tubing connecting the control valve and the power cylinder
control valve
is either a rotary valve or a spool valve that regulates pressure entry into each end of the power cylinder
rotary control valve
operated by a torsion shaft connected to the pinion gear
spool control valvr
thrust action of the pinion shaft shifts it to route oil to the power cylinder
power steering oil cooler
used to remove excess heat from the oil.
electronic steering assist
uses a small electric motor to help move the rack-and-pinion gearbox
proportional rack-and-pinion power steering/speed-sensitive power steering
senses vehicle speed and steering load to ensure adequate road feel
mechanical four-wheel steering system
uses a special front-rack-and-pinion gearbox with a transfer box, which operates a long shaft that extends back to the rear rack
hydraulic four-wheel steering system
uses a conventional power rack-and-pinion steering system up front. A vane pump forces fluid to the rack to provide power assist. Hydraulic lines extend back to a rear power steering pump, which is driven by the differential. Requires a certain road speed to be reached
electronic four-wheel steering systems
have an electric motor-driven power rack that acts upon the rear wheels via its own recirculating-ball drive and mechanical links
