Downloaded from www.Manualslib.com manuals search engine Automatic Transmission/Transaxle: 5A-3
General Description
A/T DescriptionS7RS0B5101001
This automatic transaxle is electronic control full automatic transaxle with forward 4-speed and reverse 1-speed.
The torque converter is a 3-element, 1-step and 2-phase type and is equipped with an automatically controlled lock-up
mechanism.
The gear change device consists of a ravigneau type planet ary gear unit, 3 multiple disc type clutches, 3 multiple disc
type brakes and 2 one-way clutches.
The hydraulic pressure control device consists of a valve body assembly, pressure control solenoid valve (linear
solenoid), 2 shift solenoid va lves, TCC pressure control solenoid valve (lin ear solenoid) and a timing solenoid valve.
Optimum line pressure complying with engine torque is produced by the pressure control solenoid valve in
dependence upon control signal from transmission control module (TCM). This makes it possible to control the line
pressure with high accuracy in accordance with the engine power and running conditions to achieve smooth shifting
characteristics and high efficiency.
A clutch-to-clutch control system is prov ided for shifting between 3rd gear and 4th gear. This clutch-to-clutch control
system is made to function optimally , so that hydraulic pressure controls such as shown below are conducted.
• When upshifting from 3rd gear to 4th gear, to adjust the drain hydraulic pressure at releasing the forward clutch, a
timing solenoid valve is used to switch a hydraulic passage with an orifice to another during shifting.
• When downshifting from 4th gear to 3rd gear, to adjust the line pressure applied to the forward clutch at engaging the forward clutch, a timing solenoid valve is used to s witch a hydraulic passage with an orifice to another during
shifting.
• When upshifting from 3rd gear to 4th gear with engine throttle opened, to optimize the line pressure applied to the forward clutch at releasing the forward clutch, the learning control is processed to compensate the switching timing
of the timing solenoid at every shifting.
• When downshifting from 4th gear to 3rd gear with engine throttle opened, to optimize the line pressure applied to
the forward clutch at engaging the forw ard clutch, the learning control is processed to compensate the line pressure
at every shifting.
Employing the ravigneau type planetary gear unit and this clutch-to-clutch control system greatly simplifies the
construction to make possible a lightweight and compact transaxle.
A line pressure learning control is conducted to provide opti mum shifting time at every upshifting with engine throttle
opened. If long upshifting time is detected, the subsequent line pressure applied during upshifting is intensified. On the
contrary, if short upshifting time is detected, the subs equent line pressure applied during upshifting is weakened.
Slip controlled lock-up function
Even at a lower speed than when the TCC gets engaged completely, control over the TCC pressure control solenoid
works to cause the TCC to slip (be engaged slightly), ther eby improving the transmission efficiency. While such slip
control is being executed, the oil pressure applied to the TCC is controlled by the TCC pressure control solenoid so
that the difference between the engine speed and the input shaft speed becomes close to the specified value.
Also, during deceleration, the TCC is made to slip (be enga ged slightly) to raise the engine speed and enlarge the fuel
cut operation range so that better fuel consumption is achieved.
Due to this reason, it is absolutely necessary for the automati c transmission to use ATF suitable for slip control. Use of
any fluid other than the specified ATF may cause j uddering or some other faulty condition to occur.
