Transmission cooling, basic function

Overview

This document contains information on:

 General

 Function requirements

 Function

General

The waste heat of the transmission control, and the friction at the clutch plates and gear sets generate high transmission oil temperatures when driving. Particularly high waste heat is developed on the clutches. The waste heat is absorbed by the transmission oil.

The transmission oil cooling keeps the transmission oil temperature at an optimum temperature level. This serves to prevent any overheating damage to the electrical and mechanical components of the transmission.

The transmission oil temperature is dependent on the  following factors:

 Driver load request

 Number of active auxiliary assemblies

 Number of shift operations

 Ambient temperature

Function requirements

 Engine management ON (circuit 87M)

 Engine in operation

 Vehicle driving

 Threshold for transmission oil temperature exceeded

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Function

Transmission oil cooling with transmission oil heat exchanger

A mechanical pump draws in the transmission oil from the oil pan. During a coasting downshift or engine OFF, this is done by the electric auxiliary oil pump. The transmission oil is pumped through a feed duct in the transmission housing to the transmission oil heat exchanger.

The transmission oil is routed through ducts inside the transmission oil heat exchanger. A constant flow of coolant runs through the ducts, it absorbs the waste heat and dissipates it to a separate coolant circuit. The flow of coolant is regulated to meet requirements by the transmission oil cooling coolant circulation pump by the combustion engine control unit.

The transmission oil flows back through the return line to the oil pan.

 By using the transmission oil heat exchanger, the transmission oil can be heated by the coolant. This ensures a that the operating temperature of the dual clutch transmission is reached quickly.

 The transmission oil heat exchanger is designed as a stacked plate cooler and is the interface between the coolant circuit and the oil circuit of the transmission.

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Transmission oil cooling with oil cooler

The transmission oil is routed to the inner wall of the integrated oil cooler through actuation of the transmission oil cooling coolant circulation pump and the oil pump dual clutch.control circuit. A circular cooling duct dissipates the heat absorbed by the transmission oil to the engine cooling circuit.

The integrated transmission oil cooling coolant circulation pump ensures constant circulation of the coolant.