Fichtel & Sachs Ag

Dieter Neugebauer

Gerd Brunken

Werner Gob

Peter Rossmanek

The fluid friction clutch, suitable especially for the cooling fan of an internal combustion engine, has an aluminum housing mounted rotatably by means of a rolling bearing on a drive shaft. The outer race ring of the bearing is seated directly in a tubular bearing extension piece of the aluminum housing. A ring part, held on the bearing extension piece, of a material with lower coefficient of thermal expansion than aluminum, is secured on the bearing extension piece and prevents its widening with rising working temperature.

Fluid friction clutch

The fluid friction clutch comprises a clutch input part drivable about a rotation axis and a clutch output part rotatable coaxially in relation to the clutch input part. The clutch output part together with the clutch input part defines at least one shear gap. A cover which forms a cavity enclosing at least the region of the shear gap is filled partially with viscous fluid and otherwise with gas. The gas-filled volume of the cavity contains less than 18 percent of oxygen by volume, preferably not more than 5 percent of oxygen by volume, in order to preclude a chemical reaction of the viscous fluid with the oxygen under thermal overloading which limits the utility of the viscous fluid. To reduce the proportion of oxygen either the cavity is evacuated or it is filled with a substantially oxygen-free protective or noble gas.

The temperature-controlled fluid friction clutch, suitable especially for a cooling fan, comprises a rotor which is arranged in a housing, rotatably in relation to the housing, forming at least one shear gap for the viscous fluid transmitting the torque. A scraper conveys the viscous fluid according to the dynamic pressure principle out of a working chamber containing the rotor into a reservoir chamber. The scraper is connected with the housing and lied radially opposite to the external circumference of the rotor, forming a scraper gap. The housing consists of a material the coefficient of thermal expansion of which is greater than that of the material of the rotor. In this way the scraper gap is enlarged with rising temperature, whereby the pump power of the scraper is reduced with rising temperature. The clutch unites good cold-start behavior with low temperature-actuation hysteresis in the operationally hot condition. '

The viscous coupling for a cooling air fan, especially of an internal combustion engine, comprises a drive shaft rotatable about a rotation axis, on which a housing is rotatably mounted. A partition divides the housing into a reservoir for a viscous shear fluid and a working chamber. In the working chamber there is arranged a rotor non-rotatably held on the drive shaft. The rotor together with the housing or its partition defines at least one shear gap. A controllable valve device connecting the reservoir with the working chamber controls the inflow of the shear fluid from the reservoir into the working chamber, especially in dependence upon temperature. Adjoining the partition the working chamber possesses in the region of the external circumference of the rotor an annular space formed at least partly by the rotor. The partition contains at least one over-flow opening for the shear fluid, opening into the annular space. On the housing or its partition there is mounted a baffle flap mounted for pivoting about a flap axis. The baffle flap forms a pump element effective in both directions of rotation of the rotor. The arms of the baffle flap alternately baffle the shear fluid in the annular space for pumping away and alternately close the over-flow openings. The flap axis can extend either radially or parallel with the rotation axis of the rotor. The baffle flap is preferably made symmetrical in relation to a plane including the flap axis.

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Schweinfurt, Germany

Dieter Neugebauer