自动变速器英文文献加翻译

2021年1月25日发(作者：就业率)
AUTOMATIC TRANSMISSION
The modern automatic transmission is by far
，
the most complicated mechanical
component in today
’
s automobile
。
It is a type of transmission that sifts itself
。
A fluid
coupling
or
torque
converter
is
used
instead
of
a
manually
operated
clutch
to
connect the transmission to the engine
。

There
are
two
basic
types
of
automatic
transmission
based
on
whether
the
vehicle
is
rear
wheel
drive
or
front
wheel
drive
。
On
a
rear
wheel
drive
car
，
the
transmission is usually mounted to the back of the engine and is located under the
hump in the center of the floorboard alongside the gas pedal position
。
A drive shaft
connects the transmission to the final drive which is located in the rear axle and is
used
to
send
power
to
the
rear
wheels
。
Power
flow
on
this
system
is
simple
and
straight forward going from the engine
，
through the torque converter
，
then trough
the transmission and drive shaft until it reaches the final drive where it is split and
sent to the two rear transmission
。

On a front wheel drive car
，
the transmission is usually combined with the final
drive
to
form
what
is
called
a
transaxle
。
The
engine
on
a
front
wheel
drive
car
is
usually mounted sideways in the car with the transaxle tucked under it on the side of
the
engine
facing
the
rear
of
the
car
。
Front
axles
are
connected
directly
to
the
transaxle and provide power to front wheels
。
In this example
，
power floes from the
engine
，
through the torque converter to a larger chain that sends the power through
a 180 degree turn to the transmission that is along side the engine
。
From there
，
the
power is routed through the transmission to the final drive where it is split and sent
to the two front wheels through the drive axles
。


There are a number of other arrangements including front drive vehicles where
the engine is mounted front to back instead of sideways and there are other systems
that
drive
all
four
wheels
but
the
two
systems
described
here
are
by far
the
most
popular
。
A much less popular rear and is connected by a drive shaft to the torque
converter
which
is
still
mounted
on
the
engine
。
This
system
is
found
on
the
new
Corvette
and
is used
in order to
balance
the
weight
evenly between the
front
and
rear
wheels
for
improved
performance
and
handling
。
Another
rear
drive
system
mounts everything
，
the engine
，
transmission and final drive in the rear
。
This rear
engine arrangement is popular on the Porsche
。


The
modern
automatic
transmission
consists
of many
components
and
systems
that designed to work together in a symphony of planetary gear sets
，
the hydraulic
system, seals and gaskets
，
the torque converter
，
the governor and the modulator or
throttle cable and computer controls that has evolved over the years into what many
mechanical inclined individuals consider to be an art from
。
Here try to used simple
，
generic explanation where possible to describe these systems
。

1
）
Planetary gear sets



Automatic transmission contain many gears in various combinations
。
In a manual
transmission
，
gears slide along shafts as you move the shift lever from one position
to another
，
engaging various sizes gears as required in order to provide the correct
gear ratio
。
In an automatic transmission
，
how ever
，
the gears are never physically
moved and are always engaged to the same gears
。
This is accomplished through the
use of planetary gear sets
。

The basic planetary gear set consists of a sun gear
，
a ring and two or more planet
gears
，
all remaining in constant mesh
。
The planet gears are connected to each other
through a common carrier which allows the gears to spin on shafts called
“
pinions
”

which are attached to the carrier
。

One example of a way that this system can be used is by connecting the ring gear
to
the
input
shaft
coming
from
the
engine
，
connecting
the
planet
carrier
to
the
output shaft
，
and locking the sun gear so that it can
’
t move
。
In this scenario
，
when
we
turn
the
ring
gear
，
the
planets
will
“
walk
”

along
the
sun
gear
(
which
is
held
stationary ) causing the planet carrier to turn the output shaft in the same direction
as the input shaft but at a slower speed causing gear reduction ( similar to a car in
first gear )
。

If we unlock the sun gear and lock any two elements together
，
this will cause all
three
elements
to
turn
at
the
same
speed
so
that
to
output
shaft
will
turn
at
the
same rate of speed as the input shaft
。
This is like a car that is third or high gear
。
Another
way we
can
use
a
planetary
gear
set
is
by locking
the
planet
carrier
from
moving
，
then applying power to the ring gear which will cause the sun gear to turn in
opposite direction giving us reverse gear
。

The
illustration
in
Figure
shows
how
the
simple system
described
above
would
look in an actual transmission
。
The input shaft is connected to the ring gear
，
the
output
shaft
is
connected
to
the
planet
carrier
which
is
also
connected
to
a
“
Multi- disk
”
clutch pack
。
The sun gear is connected to drum which is also connected
to the other half of the clutch pack
。
Surrounding the outside of the drum is a band
that can be tightened around the drum when required to prevent the drum with the
attached sun gear from turning
。

The clutch pack is used
，
in this instance
，
to lock the planet carrier with the sun
gear forcing both to turn at the same speed
。
If both the clutch pack and the band
were released
，
the system would be in neutral
。
Turning the input shaft would turn
the planet gears against the sun gear
，
but since noting is holding the sun gear
，
it will
just spin free and have no effect on the output shaft
。
To place the unit in first gear
，
the band is applied to hold the sun gear from moving
。
To shift from first to high gear
，
the band is released and the clutch is applied causing the output shaft to turn at the
same speed as the input shaft
。


Many
more
combinations
are
possible
using
two
or
more
planetary
sets
connected in various way to provide the different forward speeds and reverse that
are found in modern automatic transmission
。















































2
）
Clutch pack

A clutch pack consists of alternating disks that fit inside a clutch drum
。
Half of
the disks are steel and have splines that fit into groves on the inside of the drum
。
The
other half have a friction material bonded to their surface and have splines on the
inside edge that fit groves on the outer surface of the adjoining hub
。
There is a piston
inside the drum that is activated by oil pressure at the appropriate time to
squeeze
the
clutch
pack
together
so
that
the
two
components
become
locked
and
turn
as
one
。


3
）
One-way Clutch


A one- way clutch ( also known as a
“
sprag
”
clutch ) is a device that will allow a
component such as ring gear to turn freely in one direction but not in the other
。
This
effect is just like that bicycle
，
where the pedals will turn the wheel when pedaling
forward
，
but will spin free when pedaling backward
。


A common place where a one-way clutch is used is in first gear when the shifter
is in the drive position
。
When you begin to accelerate from a stop
，
the transmission
starts out in first gear
。
But have you ever noticed what happens if you release the gas
while it is still in first gear ? The vehicle continues to coast as if you were in neutral
。
Now
，
shift into Low gear instead of Drive
。
When you let go of the gas in this case
，
you will feel the engine slow you down just like a standard shift car
。
The reason for
this is that in Drive
，
one-way clutch is used whereas in Low
，
a clutch pack or a band is
used
。

4
）
Torque Converter



On
automatic
transmission
，
the
torque
converter takes the place
of the
clutch
found on standard shift vehicles
。
It is there to allow the engine to continue running
when the vehicle comes to a stop
。
The principle behind a torque converter is like
taking a fan that is plugged into the wall and blowing air into another fan which is
unplugged
。
If you grab the blade on the unplugged fan
，
you are able to hold it from
turning but as soon as you let go
，
it will begin to speed up until it comes close to
speed of the powered fan
。
The difference with a torque converter is that instead of
using air it used oil or transmission fluid
，
to be more precise
。


A torque converter is a lager doughnut shaped device that is mounted between
the
engine
and
the
transmission
。
It
consists
of
three
internal
elements
that
work
together to transmit power to the transmission
。
The three elements of the torque
converter are the pump
，
the Turbine
，
and the Stator
。
The pump is mounted directly
to the torque housing which in turn is bolted directly to the engine
’
s crankshaft and
turns at engine speed
。
The turbine is inside the housing and is connected directly to
the input shaft of the transmission providing power to move the vehicle
。
The stator is
mounted to a one-way clutch so that it can spin freely in one direction but not in the
other
。
Each of the three elements has fins mounted in them to precisely direct the
flow of oil through the converter
。


With the engine running
，
transmission fluid is pulled into the pump section and
is pushed outward by centrifugal force until it reaches the turbine section which stars
it running
。
The fluid continues in a circular motion back towards the center of the
turbine where it enters the stator
。
If the turbine is moving considerably slower than
the pump
，
the fluid will make contact with the front of the stator fins which push the
stator into the one way clutch and prevent it from turning
。
With the stator stopped
，
the
fluid
is
directed
by
the
stator
fins
to
re- enter
the
pump
at
a
“
help
”

angle
providing a torque increase
。
As the speed of the turbine catches up with the pump
，
the fluid starts hitting the stator blades on the back-side causing the stator to turn in
the
same
direction
as
the
pump
and
turbine
。
As
the
speed
increase
，
all
three
elements begin to turn at approximately the same speed
。
Sine the
‘
80s
，
in order to
improve fuel economy
，
torque converters have been equipped with a lockup clutch
which
locks
the
turbine
to
the
pump
as
the
vehicle
reaches
approximately
40-50
mph
。
This
lockup
is
controlled
by
computer
and
usually
won
’
t
engage
unless
the
transmission is in 3
rd
or 4
th
gear
。

5
）
Hydraulic System


The

hydraulic system is a complex maze of passage and tubes that sends that
sends
transmission
fluid
and
under
pressure
to
all
parts
of
the
transmission
and
torque converter and
。
Transmission fluid serves a number of purpose including : shift
control ,general lubrication and transmission cooling
。
Unlike the engine ,which uses
oil primary for lubrication ,
every aspect of a transmission ‘s function is dependant on
a
constant
supply
of
fluid
is
send
pressure
。
In
order
to
keep
the
transmission
at
normal operating temperature
，
a portion of the fluid is send to through one of two
steel tubes to a special chamber that is submerged in anti-freeze in the radiator
。
Fluid
passing
through
this
chamber
is
cooled
and
then
returned
to
the
transmission
through the other steel tube
。
A typical transmission has an avenge of ten quarts of
fluid between the transmission
，
torque converter
，
and cooler tank
，
In fact
，
most of
the
components
of
a
transmission
are
constantly
submerged
in
fluid
including
the
clutch packs and bands
。
The friction surfaces on these parts are designed to operate
properly only when they are submerged in oil
。

6
）
Oil Pump




The transmission oil pump ( not to confused with the pump element inside the
torque converter ) is responsible for producing all the oil pressure that is required in
the transmission
。
The oil pump is mounted to front of the transmission case and is
directly
connected
to
a
flange
on

the
engine
crankshaft
，
the
pump
will
produce
pressure
whenever
the
engine
is
running
as
there
is
a
sufficient
amount
of
transmission fluid available
。
The oil enters the pump through a filter that is located at
bottom
of the
transmission
oil pan
and travels up
a
pickup
tube
directly to the
oil
pump
。
The oil is then sent
，
under pressure to the pressure regulator
，
the valve body
and the rest of the components
，
as required
。


7
）
Valve Body




The valve body is the control center of the automatic transmission
。
It contains a
maze
of
channels
and
passages
that
direct
hydraulic
fluid
to
the
numerous
valves
which when activate the appropriate clutch pack of band servo to smoothly shift to
the appropriate gear for each driving situation
。
Each of the many valves in the valve
body has a specific purpose and is named for that function
。
For example the 2-3 shift
valve
activates
the
2
nd
gear
up-shift
or
the
3-2
shift
timing
valve
which
determines
when a downshift should occur
。





The most important valve and the one that you have direct control over is the
manual valve
。

The manual valve is directly connected to the gear shift handle and
covers and uncovers various passages depending on what position the gear shift is
paced in
。
When you place the gear shift in Drive
，
for instance
，
the manual valve
directs fluid to the clutch pack ( s ) that activates 1
st
gear
。
It also sets up to monitor
vehicle speed and throttle position so that it can determine the optimal time and the
force
for
the
1-2
shift
。
On
computer
controlled
transmission
，
you
will
also
have
electrical
solenoids
that
are
mounted
in
the
valve
body
to
direct
fluid
to
the
appropriate clutch packs or bands under computer control to more precisely control
shift points
。

8
）
Seals and Gaskets




An
automatic
transmission
has
many
seals
and
gaskets
to
control
the
flow
of
hydraulic fluid and to keep it from leaking out
。
There are two main external seals :
the
front
seal
and
the
rear
seal
。
The
front
seal
seals
the
point
where
the
torque
converter mounts to the transmission case
。
This seal allows fluid to freely move from
the converter to the transmission but keeps the fluid from leaking out
。
The rear seal
keeps fluid from leaking past the output shaft
。

A
seal
is
usually
made
of
rubber
(
similar
to
the
rubber
in
a
windshield
wiper
blade
)
and
is used to
keep oil
from
leaking
past
a
moving part
such
as
a
spinning
shaft
。
In some cases
，
the rubber is assisted by a spring that holds he rubber in close
contact with the spinning shaft
。

A
gasket
is
a
type
of
seal
used
to
seal
two
stationary
parts
that
are
fasted
together
。
Some common gasket materials are : paper
，
cork
，
rubber
，
silicone and soft
metal
。

Aside from the main seals
，
there are also a number of other seals and gasket that
vary from transmission to transmission
。
A common example is the rubber O-ring that
seals the shaft for the shift control lever
。
This is the shaft that you move when you
manipulate the gear shifter
。
Another example that is common to most transmission
is the oil pan gasket
。
In fact
，
seals are required anywhere that a device needs to pass
through the transmission case with each one being a potential source for leaks
。

9
）
Computer Controls




The computer uses sensors on the engine and transmission to detect such things
as throttle position
，
vehicle speed
，
engine speed
，
engine load
，
stop light switch
position
，
etc
。
to control exact shift points as well as how soft or firm the shift should
be
。
Some
computerized
transmission
even
learn
your
driving
style
and
constantly
adapt to it so that every shift is timed precisely when you would need it
。

Because of computer controls
，
sports models are coming out with the ability to
take manual control of the transmission as through it were a stick shift lever through
a special gate
，
then tapping it in one direction or the other in order to up-shift at
will
。
The computer monitors this activity to make sure that the driver dose not select
a gear that could over speed the engine and damage it
。

Another
advantage
to
these
“
smart”
transmission
is
that
they
have
a
self
diagnostic mode which can detect a problem early on and warn you with an indicator
light on the dash
。
A technician can then plug test equipment in and retrieve a list of
trouble codes that will help pinpoint where the problem is
。