Chrysler laser 1990 Technical Information Manual page 269

hydraulic control device functions by hydraulic
pressure force to change the state of the
clutches and brakes to accomplish the gear
To
shifting. minimize the shock that would
otherwise be produced during gear shifting,
hydraulic pressure is controlled during the gear
shifting period by the "duty control" of the
pressure control solenoid valve. The duty control
is explained later.
'HYDRAULIC PRESSURE CONTROL DURING
(1) The hydraulic pressure that functions during
gear shifting to engage the clutches and apply
the brakes is regulated by the pressure control
valve, The hydraulic pressure that works on the
pressure control valve is further regulated by the
pressure control solenoid valve which functions
under the control of the transaxle control unit.
The transaxle control unit controls the solenoid
valve through the duty control, thus providing
appropriate regulation of the hydraulic pressure.
Duty Control
The transaxle control unit outputs the pressure
control solenoid valve drive pulses as shown in
Figure A. These pulses drive the pressure
solenoid valve at a frequency of 35Hz (one Cycle
period T = 28.6 ms). Change in hydraulic pressure
achieved by changing the pulse duration "t". Such a
method of control is called "duty control" in the
sense that the more the duty or the pulse duration
(Figure B).
Duty: The ratio of power supply duration "t" to
the
The transaxle control unit decides the timing of
the gear shifting period (during which 'it per-
forms hydraulic pressure control for gear shift-
ing) according to the change in the kickdown
drum rotating speed that it detects. The unit
identifies the time just before the kickdown
brake is applied and uses that as the timing for
initiating control of the hydraulic pressure which
is to be applied to the kickdown brake.
When the transaxle is cold, the fluid viscosity is
(3)
high, causing slower oil pressure response. in
such conditions, the transaxle control unit pro-
vides a correction for the oil pressure by
changing the control duty of the pressure control
solenoid valve.
This control is performed when the fluid temper-
atures as indicated by the oil temperature
sensor is lower than 60°C (140°F).
After the engine has been started and the
(4)
vehicle is in motion, the transaxle
continues to refine its performance
est possible gear shifting.
Figure B
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one cycle period T (28.6 ms), expressed in a
percentage, as obtained by the following
formula:
Duty = t/-r x 1 0 0
time at which the solenoid valve is over-excited for
rapid valve operation, while V,, and t+., repre-
Sent
the v,oltage and the time at which the solenoid
control unit
for smooth-
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