Component description for the electromagnetic viscous coupling

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Location

15 Electromagnetic viscous coupling

16 Poly-V belt for fan

The electromagnetic viscous coupling (15) is mounted directly on the fan support and is driven via an additional fan poly-V belt (16).

Task

The electromagnetic viscous coupling (15) creates the connection between the engine and the fan wheel. Stepless cut-in is dependent on the cooling requirements of the engine. This ensures a constant operating temperature of the engine under all operating conditions.

 A defective electromagnetic viscous coupling cannot be repaired if this is required.

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Design

1 Return hole

2 Valve lever

3 Storage room

4 Cover

5 Clutch plate

6 Seal

7 Oil feed bore

8 Housing

9 Sensor ring

10 Flange shaft

11 Bearing

12 Main bearing

13 Electrical line (with hose as a torque support)

B122 Fan clutch rpm sensor

Y170 Fan solenoid valve

A primary side of the electromagnetic fan clutch is the components which are firmly fixed with the stub shaft (10), such as the clutch plate (5). The primary side always turns at the current drive speed.

The secondary side of the electromagnetic fan clutch consists of a number of parts including the cover (4) and the housing (8), which is screwed onto the fan wheel. The secondary side is separated from the primary side by the main bearing (12). If the electromagnetic fan clutch is switched off the fan wheel is difficult to turn.

The fan solenoid valve (Y170) with the fan clutch rpm sensor (B122) is mounted rotatable on the stub shaft (10) and is prevented by the hose for the electrical line (13), which serves as a torque support, from also turning.

The hose for the electrical line (13) is attached to a holder on the camshaft sprocket cover. The electrical line (13) is connected via a multiplug with the engine control (MR) control unit (A6).

Function

A Silicone oil pathway

B Magnet field lines

Power transmission between the primary side and the secondary side takes place via the shear of silicone oil in the operating space. A shear is the displacement of silicone oil between the drive lamellae of the clutch plate (5) and the power take-off lamellae of the housing (8) or the cover (4).

Flow of silicone oil from the storage room via the oil feed bore (7) in the operating space takes place due to the centrifugal force created by the rotation. The quantity of silicon oil quantity flowing in is determined by the valve lever (2) which opens and closes the oil feed bore (7). The valve lever (2) controlled by the magnetic field generated by the fan solenoid valve (Y170) and determines the opening time of the oil feed bore (7). The oil feed bore (7) is basically opened if the fan solenoid valve (Y170) is not actuated.

Actuation of the fan solenoid valve (Y170) takes place via the engine control (MR) control unit (A6) by means of a pulse width modulated signal (PWM signal), whereby a large positioning signal is generated by a longer "On" pulse or a small positioning signal by a shorter "On" pulse.

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In the case of request for a higher torque transmission between the primary and secondary side, which means an increased cooling requirement, the fan solenoid valve (Y170) receives a smaller positioning signal from the engine control (MR) control unit (A6).

The fan solenoid valve (Y170) generates a low magnetic field and thus the valve lever (2) extends the opening time of the oil feed bore (7). The amount of silicone oil flowing into the operating space is increased, whereby the torque transferred between the primary and secondary side increases and the fan wheel speed increases.

In the case of a request for a lower torque transmission between the primary and secondary side, which means a lower cooling requirement, the fan solenoid valve (Y170) receives a larger positioning signal from the engine control (MR) control unit (A6).

The fan solenoid valve (Y170) generates a large magnetic field and thus the valve lever (2) shortens the opening time of the oil feed bore (7). The amount of silicone oil flowing into the operating space is decreased, whereby the torque transferred between the primary and secondary side decreases and the fan wheel speed decreases. Reverse flow of the silicone oil into the storage room takes place through the return hole (1).