Mitsubishi Eclipse. Technical Information Manual (1994) — part 51
POWER TRAIN Automatic Transaxle
q
In-gear logic
Shift logic
1 S, Shift schedule output
1 ST, 2ND Speed ratio shift
complete signal
Shift Logic Selection
The purpose of the Shift Logic Selection program is to activate
the appropriate “shift logic” so that the “in-gear logic” condition
matches the gear called for by the shift schedule (driver selected
gear, throttle position).
Imagine that the TCM must always be in one of the logic boxes
at any given time. The double line boxes represent the “in-gear
logic” the TCM uses to maintain a certain gear range. The
single line boxes represent the “shift logic” required by the
TCM to execute a desired gear change from one gear to another.
The paths (lines with arrows) between the blocks are labeled
with one or more of the shift schedule output signals (Is, 2s).
These desired gear signals (shift schedule output signals) be-
come the primary input which will cause the correct path to
be taken, from one in-gear box (such as inl) to a shift logic
box (such as l-2).
The output is a change to “shift logic” in order to obtain an
in-gear
that matches the output of the shift schedule
routine. The TCM knows whether the desired shift has been
completed when a correct speed ratio check of the input and
output speed sensors is present. The speed ratio check is
used to verify that the desired gear has been achieved. For
example, when the correct speed ratio signal for second gear
has been verilied by the TCM by checking the speed ratio
between the input and output speed sensors, it will switch
to the appropriate in-gear logic (in2).
Changes to “In Gear” or “Shift” Logic
If the transaxle is in first gear logic (inl) and the
shift schedule output changes to call for second
gear
then “1-2” logic will be activated. This
generally remains in effect until the completion of
the shift is determined by the speed ratio check.
When the speed ratio check confirms that the
gired gear (second) has been obtained,
logic
is activated. There are other possible exits or
changes that may be made to the normal shift sched-
ule logic from the
shift logic example, such
as a change-mind condition.
A “change-mind” shift condition may occur when
a shift that has begun directly from within another
Shift Logic Chart
Another exit or change to the normal shift schedule
logic is the fail shift timer may expire. The TCM
will only allow a certain amount of time to elapse
for the shift logic to complete a shift. If a speed
shift, instead of from an in-gear condition. A “change
mind” condition occurs if a change in the throttle
position signal causes the normal shift schedule
routine to select a different desired gear signal, such
as is, during a 1-2 shift change. These shifts are
accommodated by direct paths between upshift and
downshift logic within the logic selection routine.
“Change mind” shifts are needed to provide the
proper response to changes in driver demand.
Changes in the manual lever (selector lever) position
may also cause a “change-mind” shift depending
on when the lever position changes. A more detailed
shift logic chart is illustrated.
ratio check does not confirm the completion of an
attempted shift within this time limit, the shift logic
is aborted, and the desired in gear logic is activated.
POWER TRAIN Automatic Transaxle
i
d
In-gear logic
q
Shift logic
Shift Execution Logic
1 S,
RS Shift schedule output
lst, 2nd
Rev. Speed ratio shift
complete signal
As with most automatic transmissions, including the
two clutches must be applied to
provide an operating gear range. One of the applied
clutches must be an input clutch driven by the torque
converter, such as the Reverse, the Underdrive,
or the Overdrive clutches. The other applied clutch
is usually a reaction or holding device, such as
the 2-4 or
clutches. For all gear ratios this is
the rule, except Direct Drive (3) where output is
achieved by applying two input clutches. All shifts
leave one clutch continuously engaged and involve
changing another clutch from the releasing clutch
to a different applying clutch.
cc
POWER TRAIN Automatic Transaxle
Solenoid Driver Logic
Electronic solenoid valves connect the clutches to
either a hydraulic source or a vent. Solenoid coils,
when energized, exert force on a push rod which
in turn opens or closes a ball valve and/or vent.
To increase efficiency, the current through the sole-
noid coil is pulse-width modulated. The
Pulsing the Solenoids
The Full ON pulse time is normally around 8 millisec-
onds and provides rapid pull-in response time.
in response time is dependent upon battery voltage.
The pull-in response time will increase with reduced
battery voltage to maintain pull in power.
To protect against inadvertent drop-out of an ener-
gized solenoid, each ON solenoid is issued a re-
fresher pulse every 50 milliseconds. The refresher
pulse is used to prevent hydraulic pressure from
overcoming the solenoids strength. The frequency
is increased during shifts and as certain faults start
to occur.
The hold-in duty cycle is also dependent on battery
voltage as well as the in-gear condition. The
puter within the TCM is responsible for providing
this modulation (pulsing) signal as well as an initial
pull-in current pulse each time a solenoid is ener-
gized.
age of solenoid on-time is normally 38%. In third
or fourth gear, the typical percentage is 30%. This
is because less power is required to overcome the
reduced hydraulic line pressure in third and fourth
gear ranges.
Current efficiency is maximized by the use of the
inductive energy of the solenoid during the OFF
portion of the cycle.
The turn OFF command opens the circuit to provide
for rapid drop-out response time. The circuit is moni-
tored to permit checking the continuity of the sole-
noid and its power return line.
SOLENOID DRIVER LOGIC
Solenoid control logic:
Driver pulse logic:
Solenoid voltage:
VL
0
Inductive current flow
from ground
Solenoid current:
Inductive path opened
(1) provides rapid ON pull-in response time
(2) reduces power level
(3) refresh pulse a periodic reissue of the FULL ON
pulse to any energized
(4) provides for rapid OFF drop-out response time;
inductive OFF voltage spike monitored
to confirm circuit continuity
Automatic Transaxle
Solenoid
Clutch
OD
ON
ON
ON
ON
UD
OFF
ON
OFF
ON
Solenoid and Element Logic
Since both normally-ON and normally-OFF solenoids are used,
the following logic is recognized by the TCM.
The LWCC solenoid controls the LR clutch in first gear, Neutral,
and Park and controls the Converter clutch (CC) in second,
third, and fourth gears. The solenoid switch valve position deter-
mines which clutch (LR or CC) the solenoid will control.
The
solenoid controls the 2-4 clutch in Overdrive, Drive
and Low. The
solenoid controls the LR clutch in Reverse.
In this case, the manual valve position determines which clutch
is being controlled.
Gear
Park/Neutral
(Under 8 MPH)
Neutral
(Over 8 MPH)
Reverse
Reverse
(Over 8 MPH)
First
Second
Second EMCC
Third
Third EMCC
Fourth
Fourth EMCC
Solenoids
s2
s3
s4
Manual valve
OD
UD
LR
LR
LR
UD
UD
24
c c
UD
24
UD
UD
24
24
Solenoid energized
Clutch applied OD, LR, CC, UD, 2-4,
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