A transmission system (10), especially for a motor vehicle, having around an axis (O) at least an input shell (12) that is rotationally connected to a driving shaft and to a drive web (18) in order to rotationally connect said input shell (12) to a double wet clutch mechanism (20) that, having at least a first clutch (E1) and a second clutch (E2) respectively of the multiple-disc type, is controlled to selectively couple said driving shaft to a first driven shaft (A1) and to a second driven shaft (A2), wherein the input shell (12) and the drive web (18) are rotationally connected by connecting means (24), which are constituted in particular by rivets (25), with zero angular clearance.

In a seal device for a hydraulic circuit, in which an oil passage that supplies hydraulic oil to or discharges the hydraulic oil from a hydraulic actuator operated by hydraulic pressure is formed over at least two members that relatively move, and a seal member that seals a gap between the two members in a liquid-tight manner is disposed in an interior of a groove section that is formed in at least either one of the two members, a communication section that allows the groove section to communicate with any portion of the oil passage such that the hydraulic oil in the interior of the groove section moves along with supply of the hydraulic oil to or discharge of the hydraulic oil from the hydraulic actuator is formed.

The invention relates to a hydraulic control system (21) for a dual wet clutch (1), having: housing (41) having an internal tube (42) extending axially around the axis X and configuring an internal space intended for passage of the two input shafts (2, 3) of a gearbox, and a first and a second annular chamber (43, 44) concentric around the axis X and disposed radially around the internal tube (42); a first and a second annular piston (45, 46), which are respectively mounted axially slidingly inside the first and the second annular chamber (43, 44), the first and the second annular piston (45, 46) each carrying a rotating stop (49, 50); the internal tube (42) having at least one flow conduit (55) for a cooling fluid, intended to direct the cooling fluid to the clutches (4, 5).

A hydraulic system for an automatic transmission of a motor vehicle, including a high pressure circuit in which a pressure accumulator, at least one clutch and a gear selector are connected, and comprising a low pressure circuit for cooling the clutch, wherein the high pressure circuit and the low pressure circuit have at least one hydraulic pump that can be driven by an electric motor, and including a control unit that actuates the electric motor of the hydraulic pump when a pressure accumulator charging requirement is detected, wherein the high and low pressure circuits are connected via a bypass line to an integrated accumulator charging valve.

A clutch assembly may have an axially slidable first plate, an axially fixed second plate disposed opposite the first plate, and a clutch pack arranged between the first plate and the second plate. The clutch pack may have a number of axially slidable consecutively arranged friction plates and separator plates. The assembly may also have an actuator axially movable between a first position and a second position, where, in the first position, the clutch pack is opened and, in the second position, the clutch pack is closed and the friction plates are frictionally engaged. The assembly may also have a return spring configured to bias the actuator in a direction away from the clutch pack towards the first position. The assembly may also have an engagement spring element configured to exert an elastic force on the clutch pack.

A wet clutch system includes fluid-flow apertures in the clutch piston which allow for reduction of oil shear forces between rotating clutch plates and a stationary piston. In particular the apertures pass through the piston in the area of the piston's engagement with the clutch plates. When the piston is in its deactivated position and spaced from the clutch plates, the radially-outward position of these apertures allows high-pressure, centrifugally-driven clutch fluid to migrate away from the clutch plates through the piston to a backfill cavity on the opposite side of the piston. An air-inlet aperture may be provided in or near the clutch hub to facilitate this oil migration.

A disconnectable coupling device rotatable about an axis is provided with a first shaft having an end and a hub formed on the end, the hub including a flange extending radially from the end and a round wall projecting axially from the flange and defining a hollow; a second shaft aligned with the first shaft and opposed to the end of the first shaft, the second shaft having a drum overhanging the hub; a multi-plate clutch held between the hub and the drum to disconnectably connect the hub with the drum; a cup so fixed with the hub as to define a gutter around the first shaft; and one or more perforations axially passing through the flange to establish fluid communication between the gutter and the hollow.

A disconnectable coupling device rotatable about an axis is provided with a first shaft having an end and a hub formed on the end, the hub including a flange extending radially from the end and a round wall projecting axially from the flange and defining a hollow; a second shaft aligned with the first shaft and opposed to the end of the first shaft, the second shaft having a drum overhanging the hub; a multi-plate clutch held between the hub and the drum to disconnectably connect the hub with the drum; a cup so fixed with the hub as to define a gutter around the first shaft; and one or more perforations axially passing through the flange to establish fluid communication between the gutter and the hollow.

A clutch assembly may have an axially slidable first plate, an axially fixed second plate disposed opposite the first plate, and a clutch pack arranged between the first plate and the second plate. The clutch pack may have a number of axially slidable consecutively arranged friction plates and separator plates. The assembly may also have an actuator axially movable between a first position and a second position, where, in the first position, the clutch pack is opened and, in the second position, the clutch pack is closed and the friction plates are frictionally engaged. The assembly may also have a return spring configured to bias the actuator in a direction away from the clutch pack towards the first position. The assembly may also have an engagement spring element configured to exert an elastic force on the clutch pack.

A clutch subassembly for a motorcycle includes a hub, a plurality of driven discs and an elastic element. The hub includes a plurality of projecting protrusions, wherein the plurality of projecting protrusions define wide through openings capable of promoting a lubrication and, at a same time, the plurality of projecting protrusions reduce a weight of the clutch subassembly.