Modulating pressure - RA27007229120X(27-9120)
Modulating pressure system shown in the lower vehicle speed range. Both valves (69) and (5) are in the governed position .
The modulating pressure influences the level of the working pressure from partial through to full throttle and the level of the shift pressure. It is derived from the working pressure and governed at two separate control valves:
- at control valve (69), modulating pressure "M1" (dependent on vacuum).
- at control valve (5), modulating pressure "M2" (boosted dependent on vehicle speed).
The torque increase of the torque converter in the starting-off range necessitates increasing the modulating pressure "M2".
Modulating pressure "M1"
The "M1" modulating pressure system consists of the control valve (69) and a vacuum unit (68). The spring chamber of the vacuum unit is connected to the intake manifold of the engine. As the vacuum rises, the force of the spring (b) acting on the control valve (69) is weakened. The modulating pressure "M1" is controlled at the control edges (d) and (f) as a function of the force of the spring (b) and of the pressure governed at the end face surface (e).
Throttle valve closed:
- low engine load
- high vacuum
results in
==> low modulating pressure
==> low working pressure
Throttle valve open:
- high engine load
- low vacuum
results in
==> high modulating pressure
==> high working pressure
Modulating pressure "M2"
The modulating pressure "M1" is boosted in line with vehicle speed at the torque converter adaptation control valve (5) and results in modulating pressure "M2".
In the starting position, the control valve (5) is pushed to the right against the stop by the spring force. As soon as modulating pressure "M1" is formed, this pressure passes into the "M2" modulating pressure system. At the same time, modulating pressure "M1" acts on the end face surface (k) and pushes the valve (5) to the left against the force of the spring. This seals off the connection to the modulating pressure "M1" and the working pressure inlet at the control edge (j) opens. The modulating pressure "M2" rises and acts on the annular surface (h) to push the valve (5) into the governed position.
When the car is moving, governor pressure acts on the end face surface (g). The force of the pressures at the end face surface (g) and at the annular surface (h) as well as the spring force counter the effect of the modulating pressure "M1" at the end face surface.
As the governor pressure rises, the modulating pressure "M2" drops continuously until the valve (5) is pushed out of the governed position as far as the right stop. Modulating pressure "M1" flows directly into the "M2" modulating pressure system; both modulating pressures are equally high.