Transmission - Design and Function: Overview Volvo XC90 I

see DESIGN

see FUNCTION

OVERVIEW

see OVERVIEW

Scheme 1394

Scheme 1395

1. Tapered bearings - To reduce the inner friction losses, some of the tapered bearings now have bigger diameter and shorter length of bearing rollers. This change gives fewer rollers and thus less friction.
2. Torque converter - To reduce noise/sound when locking at lower engine rpms, the LTD (Long Travel Damper) has been provided with an inner circle of damping springs
3. TCM ( T ransmission C ontrol M odule) - TCM has the same hardware as before but the software has been changed.
4. Solenoids - Faster shifting has been achieved by making all linear solenoids that control the clutch systems more effective. This change has been achieved by removing the hydraulic part of the solenoids. Further, the magnetic flow in the solenoid has been increased and gap between thrust piston and magnetic coil has been reduced to increase power.
5. Seal rings - New seal rings with smaller sealing surface contributes to reducing the inner friction. By tapering the seal, the sealing surface is reduced as is the pressure on the sealing surface.
6. Friction pads - The new friction pads on the discs reduce the impact of drag losses between the friction pads. This has been achieved by optimizing the oil flow channels between the friction surfaces.

Scheme 1396

Scheme 1397

The torque converter is between the engine and the automatic transmission. It consists of a round metal casing which contains three impellers. The torque converter is filled with oil. The first impeller, pump rotor, is secured in the torque converter casing, which is connected to the engine's crankshaft via a carrier plate. The pump rotor rotates with the crankshaft.

The second impeller, the turbine rotor, is connected to the transmission's input shaft and is driven by the oil that is circulated by the pump rotor.

The third impeller, the stator, is located between the pump rotor and the turbine rotor.

There is a hydraulically controlled lock-up clutch with a friction plate in the torque converter. The turbine rotor can connect with the torque converter housing via the lock-up clutch. This reduces fuel consumption.

The torque converter functions like a hydraulic automatic clutch. At idle, the pump action is too weak to drive the turbine rotor and thus the vehicle is stationary. When the engine speed is increased the turbine rotor starts to drive in a smooth way. Thanks to the stator rotor, the torque converter can also reinforce the engine's torque when starting and low driving speed.

The rotating impellers and the oil in the torque converter "slip" slightly. This gives a certain power loss, which slightly increases fuel consumption.

When the vehicle is moving the torque converter's reinforcement of the engine's torque is not needed. In this situation the lock-up function is activated and, at a certain speed, mechanically connects the transmission's input shaft with the engine. This is automatic and cannot be affected by the driver. The engine speed drops and, since the torque converter's slipping disappears, fuel consumption is also reduced.

Scheme 1398

X = locked

Unique to the TF-80SC is a Ravigneaux planetary gear connected in series to a conventional planetary gear. The conventional planetary gear creates a reduction in RPM in the Ravigneaux planetary gear for 1st gear up to 5th gear and reverse.

The planetary gear's ratios are controlled by 3 clutches (C1, C2, C3) and 2 brakes (B1, B2).

The number of planetary gears depends on the engine's cylinder displacement and can therefore differ from what is shown here.

Planetary train, Ravigneaux

Scheme 1399

The characteristic of a Ravigneaux planetary train is that several gears can be used in comparison to a conventional planetary train. It is compact (takes up little room) in relation to the number of possible ratios. The Ravigneaux planetary train has two sun gears of different diameters and sets of two planetary gears, an inner and outer set. The inner planetary gears are constantly connected to the outer planetary gears and the small sun gear. The outer planetary gears are constantly connected to the ring gear and large sun gear.

The planetary train has a common planetary gear carrier for both sets of planetary gears.

Principles of function

Scheme 1400

The ratios are obtained through different combinations of locked and/or connected components. The table displays the principle for how the ratios are obtained from large ratio, 1, to small ratio, 6, and counter rotation (i. e. reverse with large ratio).

Scheme 1401

The oil pump is of "non-crescent" type and is located after the torque converter. It is driven by the engine's crankshaft via the torque converter housing.

The oil pump supplies the hydraulics with oil and supplies the other components of the transmission with oil for lubrication and cooling. Excess oil is routed back to the oil sump.

see OVERVIEW

see DESIGN AND FUNCTION

see OVERVIEW