Dual clutch mechanism for a transmission

A dual clutch mechanism for an automotive transmission, the dual clutch mechanism comprising:

• an input shaft adapted for rotation about a longitudinally extending axis;
• a hollow outer output shaft being coaxial with the input shaft;
• an inner output shaft positioned within the outer output shaft and adapted for rotation independent thereof and being coaxial with the axis of the input shaft;
• a first clutch arrangement having a plurality of intermeshing driven clutch discs and driving clutch discs;
• a first clutch driving plate operably connected to the driving clutch discs and the outer output shaft;
• a second clutch arrangement axially spaced from the first clutch arrangement, the second clutch arrangement having a plurality of intermeshing driven clutch discs and driving clutch discs;
• a second clutch driving plate operably connected to the driving clutch discs and the inner output shaft;
• a common driven plate operably connected to the driven discs of the first and second clutch arrangements and the input shaft, an interface between the common driven plate and the first and second clutch driven discs being disposed radially outward relative to the driving plates of the first clutch and second clutch arrangements;
• a first clutch pressure apply chamber being adjacent to a first clutch apply piston and a second clutch pressure apply chamber being adjacent to a second clutch apply piston, the first and second apply pistons each having an apply position where the piston is arranged to frictionally engage the respective driven set of clutch discs operably connected to the common driven plate and the driving set of clutch discs operably connected to the clutch driving plate to drive the clutch driving plate for rotation with the common driven plate when sufficient pressure is applied in the pressure apply chamber and an unapplied position where the piston is not arranged to frictionally engage the driven and driving set of clutch discs so the clutch driving plate is not driven for rotation with the common driven plate;
• a first clutch apply chamber fluid path for supplying fluid to shift the first clutch apply piston from the unapplied position to the applied position and a second clutch apply chamber fluid path for supplying fluid to shift the second clutch apply piston from the unapplied position to the applied position, the first and second clutch apply chamber fluid paths being independently selectable;
• a first clutch balance chamber and a second clutch balance chamber, the balance chambers each being separated from the respective pressure apply chamber by the respective apply piston;
• a first clutch balance chamber fluid path for supplying fluid to the first clutch balance chamber and a second clutch balance chamber fluid path for supplying fluid to the second clutch balance chamber to offset pressures against the respective piston from fluid in the respective apply chamber;
• and
• a first clutch cooling fluid path for supplying fluid to the discs of the first clutch arrangement at a first flow rate and a second clutch cooling fluid path for supplying fluid to the discs of the second clutch arrangement at a second flow rate, the first and second flow rates being independently adjustable effective to permit the first flow rate to be reduced when the driving and driven discs of the first clutch arrangement are unengaged without a corresponding reduction in the second flow rate to the driving and driven discs of the second clutch arrangement when engaged and to permit the second flow rate to be reduced when the driving and driven discs of the second clutch arrangement are unengaged without a corresponding reduction in the first flow rate to the driving and driven discs of the first clutch arrangement when engaged.

A method of selectively engaging one of a first output shaft and a second output shaft to be driven for rotation via an input shaft of a dual clutch mechanism, the method comprising:

• providing a first clutch having a set of annular driven discs having outer diameters associated with a common driven plate and an intermeshed set of driving discs having inner diameters associated with a first driving plate, the first driving plate being operably connected to the first output shaft to drive the first output shaft for rotation therewith when a first clutch apply piston compresses the driven discs with the intermeshed driving discs to engage the discs of the first clutch due to fluid pressure in a first clutch pressure apply chamber supplied via a first clutch apply fluid path;
• providing a second clutch having a set of annular driven discs having outer diameters associated with the common driven plate and an intermeshed set of driving discs having inner diameters associated with a second driving plate, the second driving plate being operably connected to the second output shaft to drive the second output shaft for rotation therewith when a second clutch apply piston compresses the driven discs with the intermeshed driving discs to engage the discs of the second clutch due to fluid pressure in a second clutch pressure apply chamber supplied via a second clutch apply fluid path;
• supplying fluid at a first flow rate to the set of driving and driven discs of the first clutch;
• supplying fluid at a second flow rate to the set of driving and driven discs of the second clutch;
• decreasing the first flow rate when the driving and driven discs of the first clutch are unengaged effective to reduce clutch drag without a corresponding decrease in the second flow rate when the driving and driven discs of the second clutch are engaged;
• and
• decreasing the second flow rate when the driving and driven discs of the second clutch are unengaged effective to reduce clutch drag without a corresponding decrease in the first flow rate when the driving and driven discs of the first clutch are engaged.