The first volume produced engines to be equipped with a multifunctional thermostat are the 1.8 l and 2.0 l TFSI engines from the VW-Group (four-cylinder in-line engine EA888 Gen.3). This module was developed jointly by Audi and Schaeffler (Figure 1). In the warm-up phase of the engine, the Thermal Management Module is able to completely close the coolant inlet in the engine or set a minimum flow rate. If the engine is warm from operation, the coolant temperature can be adjusted quickly and fully variably to different temperature levels depending on load requirements and external boundary conditions.
The Thermal Management Module has two coupled rotary slide valves, which are operated by only one drive motor. One of these rotary slide valves is on the pressure side of the water pump and is designed for shutting off the coolant. The second rotary slide valve is used for distributing coolant on the intake side. The entire cooling circuit also has switching valves to enable the flow of coolant through the heater and the transmission oil heat exchanger to be switched on and off in a targeted manner.
Two rotary slide valves, which are coupled mechanically, control the flow of coolant inside the rotary slide valve module. An electric motor drives rotary slide valve 1 via a worm gear with a high reduction ratio. Rotary slide valve 1 is, in turn, connected with rotary slide valve 2 via a lantern pinion. Rotary slide valve 1 replaces the conventional wax thermostat and can very quickly and fully variably adjust the coolant temperature between 80 °C and 110 °C depending on requirements.
In addition, rotary slide valve 1 switches the coolant return from the engine oil cooler (Figure 2). The coolant water is heated 30 % faster compared to the previous engine with a wax thermostat. The time required to reach the target oil temperature is reduced by around 50 %.
Schaeffler will be exhibiting at this year’s Auto Trade EXPO, which takes place from Saturday and Sunday, October 15-16 at the RDS Simmonscourt in Dublin.