TWO SPEED BELT DRIVE SYSTEM

1 . A two speed belt drive system comprising:

a crankshaft module ( 200 ) comprising a first pulley ( 213 ) engaging a first belt ( 10 ) and a second pulley ( 206 ) engaging a second belt ( 20 );

a clutch module ( 100 ) engaging the first belt and the second belt;

the second belt ( 20 ) engaged to an engine accessory;

the crankshaft module having a clutch spring ( 205 ) for frictional driving of the second pulley; and

the clutch module having a clutch ( 57 ) for selectively driving the second belt.

2 . The system as in claim 1 , wherein the clutch module comprises an electromagnetic clutch.

3 . The system as in claim 1 , wherein the crankshaft module clutch spring is loaded in the unwinding direction.

4 . The system as in claim 1 , wherein the crankshaft module comprises an inertia member mounted thereto by an elastomeric member.

5 . The system as in claim 1 , wherein the clutch module clutch is engaged during an engine idle condition.

6 . The system as in claim 1 , wherein the clutch module clutch is disengaged during an engine off-idle condition.

7 . The system as in claim 1 further comprising a tensioner engaged with the first belt.

8 . The system as in claim 1 further comprising a tensioner engaged with the second belt.

9 . The system as in claim 1 , wherein the clutch spring is disengaged during an overrun condition.

10 . A two speed belt drive system comprising:

a crankshaft module ( 200 ) comprising a first pulley ( 213 ) engaging a first belt ( 10 ) and a second pulley ( 206 ) engaging a second belt ( 20 ), the crankshaft module further comprising an inertia member ( 2010 ) mounted thereto by an elastomeric member ( 212 );

a clutch module ( 100 ) engaging the first belt and the second belt, the crankshaft module driving the clutch module with the first belt;

the second belt driving an engine accessory;

the crankshaft module having a clutch spring ( 205 ) for frictional driving of the second pulley, the clutch spring releasable during a predetermined condition; and

the clutch module having an electromagnetic clutch ( 57 ) for selectively driving the second belt during an engine idle condition at a speed that is greater than during an engine off-idle condition.

11 . The system as in claim 10 , wherein the electromagnetic clutch is disengaged during an engine off-idle condition.

12 . The system as in claim 10 further comprising a tensioner engaged with the first belt.

13 . The system as in claim 10 further comprising a tensioner engaged with the second belt.

14 . A two speed belt drive system comprising:

a crankshaft module ( 200 ) comprising a first pulley ( 213 ) engaging a first belt ( 10 ) and a second pulley ( 206 ) engaging a second belt ( 20 ), the first pulley further comprising an inertia member ( 2010 ) mounted to a hub ( 300 ) by an elastomeric member ( 212 );

a clutch module ( 100 ) engaging the first belt and the second belt, the crankshaft module driving the clutch module with the first belt;

the second belt driving an engine accessory;

the crankshaft module having a clutch spring ( 205 ) for frictional driving of the second pulley, the clutch spring releasable during an overrun condition; and

the clutch module having an electromagnetic clutch ( 57 ) for selectively driving the second belt during an engine idle condition at a speed that is greater than during an engine off-idle condition, the electromagnetic clutch is engaged during an engine idle condition.

15 . The system as in claim 14 further comprising a tensioner engaged with the first belt.

16 . The system as in claim 14 further comprising a tensioner engaged with the second belt.

17 . The system as in claim 14 , wherein the crankshaft module clutch spring is in a overrun condition when the electromagnetic clutch is engaged.