190303E Flashcards
Hydraulic Retarder Fundamentals
function of a hydraulic retarder?
prevent engine from overspeeding and reduce use of service brakes
what kind of braking system is a hyd retarder?
a supplementary or auxiliary braking system
is a retarder meant to stop a vehicle?
no
where are input, output, and remote mounted retarders located?
input: on input to transmission after torque converter
output: on output of transmission
remote: located on driveline
the retarder used within a transmission is sometimes referred to as a?
input retarder
if a retarder is between the engine and converter, what do you need to have on the converter?
a lockup clutch
what is the most effective position for a retarder?
on the input, it enhances effectiveness when operator downshifts when retarder is being used
how does the output retarder exert braking force?
exerts force directly on driveline, doesn’t care about engine rpm or tranny gear selection
what is used to minimize the delay of oil to retarder housing when the retarder is activated?
multi-disc clutch packs can activate for a short period to begin the retarding process
how does a remote retarder exert braking force?
same as output retarder
what are the components of a hyd retarder?
retarder rotor
retarder housing
oil pump and supply circuit
oil cooler
retarder control valve and control circuit
wet brake system
accumulator
where is the retarder rotor attached to?
torque converter output shaft, tranny output shaft or driveline
where is the retarder rotor located?
in the retarder housing and sandwiched by stator/retarder housing
what is the retarder/stator housing?
a stationary component, called a stator. encircles and encloses the retarder rotor
where does the retarder get oil from?
the same oil pump that supplies oil to the torque converter/tranny if input mounted. if output mounted/remote, can have their own oil pump
how is oil supplied to the retarder?
from the converter/tranny system then cooled by converter oil cooler
on large haul trucks, what is used to cool the retarder oil?
an oil-to-coolant type of oil cooler, or oil to air
there are 3 methods to control a retarder, what are they?
manual operator control
air over hydraulic control
electronic control
purpose of a hyd retarder control valve assembly?
direct oil supply to retarder rotor housing
what basic switches are used on automatic control valve and control circuits for the retarder actuation?
an ignition switch
a mode selection switch/lever
a clutch position switch+ tranny gear indicator
fuel control position indicator
what actuation method is used for operator modulation of the reorder?
hydraulic or air activated
what is a benefit of modulating the retarder?
limits heat created
extends service life of components, maintains oil quality
Why would a wet brake system be used?
to limit lag time, faster apply retarder.
why do retarders use an accumulator?
as a method of fast fill. mostly in trucking/highway
when braking is not required, is the retarder housing full of oil?
no, only has lube oil
what energy conversion does a retarder create?
kinetic to heat
how does a retarder operate?
due to the friction between the moving rotor and oil
how is oil slowed in a retarder?
by the shearing action of the oil between the rotor and oil
is oil constantly running through the retarder control valve?
yes, but not always going to retarder
if a hyd retarder is too small for the application, what will occur?
excessive hear and oil deterioration
machines that operate in mountainous terrain need to be aware of what regarding service intervals?
may require a shorter oil change interval
