Patent Description:
The present invention concerns a transmission module provided with a hydraulic actuator. The invention is preferably applied, albeit not exclusively, in a hybrid transmission module provided with a hydraulic control clutch, which will be referred to below without loss of generality.

As is known, hybrid drive vehicles comprise an internal combustion engine and at least an electric machine which can be used as a generator or as a motor to deliver torque in combination with (or alternatively to) the internal combustion engine, according to the operating conditions of the vehicle.

A configuration in which an electric machine is used connected between the internal combustion engine and the vehicle transmission is conventionally called "P2". Modular units are known designed to be interposed between the internal combustion engine and the vehicle transmission (and therefore currently called "P2 modules") which comprise, in addition to the electric machine, one or more hydraulic control clutches to selectively connect the internal combustion engine and/or the electric machine to the transmission, in addition to the relative actuators and transmission elements.

In particular, the hydraulic control clutches are normally provided with a spring which exerts an axial load designed to keep the clutch plates together in a pack. The clutches of the above-mentioned type are normally actuated in opening by means of a hydraulic actuator, which is designed to generate an axial load which opposes that of the spring.

The hydraulic actuators for known clutches generally consist of an autonomous unit defining an internal chamber into/from which pressurized oil can be supplied/discharged.

When the chamber is pressurized, the actuator expands axially so as to provide an axial load which overcomes the force of the clutch spring.

<CIT> discloses a transmission module for a hybrid drive vehicle configured to be interposed between an internal combustion engine and a transmission of the vehicle, the module comprising a structure configured to be secured to the engine and defining a housing for a clutch, a hydraulic actuator for controlling the clutch including an annular chamber provided in the support structure and open towards the housing for the clutch, an annular piston axially movable in the annular chamber, and a thrust member constrained in a rotationally free manner to the piston, coaxial thereto and configured to cooperate with a control member of the clutch.

One problem connected with the known actuators is their large overall dimensions, in particular in axial direction. The use of said actuators in situations with limited installation space, as in the case of the transmission modules cited above, is therefore problematic.

The object of the present invention is to provide a hydraulic actuator with particularly compact overall dimensions, in particular in the axial direction.

The above-mentioned object is achieved by a transmission module according to claim <NUM>.

For a better understanding of the present invention a preferred embodiment is described, by way of non-limiting example and with reference to the attached drawings, in which:.

With reference to <FIG>, the number <NUM> indicates overall a transmission module P2 designed to be connected between an internal combustion engine E and a transmission T of a hybrid drive vehicle, forming together a hybrid power train H.

The module <NUM> forms part of a hybrid unit <NUM> comprising, in addition to the module itself, an electric machine <NUM>. Optionally, the hybrid unit <NUM> can also comprise one or more accessories such as, for example, a compressor <NUM> for an air conditioning system of the vehicle (<FIG>).

The electric machine <NUM> is expediently of a reversible type, namely it can operate as an electric motor to deliver torque to the transmission (in combination with or alternatively to the internal combustion engine) or as a generator to generate electric power.

The module <NUM> (<FIG>) essentially comprises a tray-like support structure <NUM> and a transmission <NUM>, in this example a chain transmission, housed in the support structure <NUM> and configured to operatively and selectively connect to one another a crankshaft <NUM> of the internal combustion engine E, the electric machine <NUM> and the transmission T.

In the example illustrated, the transmission <NUM> comprises a crown wheel <NUM> with axis A selectively connectable to the crankshaft <NUM>, as described below, and a pinion <NUM> with axis B designed to be connected to the electric machine <NUM>. The axes A, B coincide in use with the axis of the crankshaft <NUM> of the engine E and with the axis of the electric machine <NUM> respectively. The transmission <NUM> further comprises a chain <NUM> engaging with the crown <NUM> and the pinion <NUM>.

The support structure <NUM> has a substantially flat base wall <NUM> and a perimeter flange <NUM> extending perpendicular to it and forming a plurality of projections <NUM> in which the holes for securing the module <NUM> to the engine E are obtained. The base wall <NUM> and the perimeter flange <NUM> delimit a cavity housing the transmission <NUM>, which is closed frontally by a cover <NUM>.

The base wall <NUM> forms a pair of through seats <NUM>, <NUM> (<FIG>), having axes A and B respectively.

The electric machine <NUM> (<FIG>) is assembled at the seat <NUM>, on the opposite side of the transmission <NUM>. The seat <NUM> houses a hub <NUM> of the pinion <NUM> and the relative bearings <NUM>.

The crown <NUM> forms part of a torsional vibration damper <NUM>, for example of the circumferential spring type, described briefly below since it is known per se and not part of the present invention. The damper <NUM> is supported by means of a bearing <NUM> housed in the seat <NUM> and is provided with a shaft <NUM> having axis A arranged passing through said seat.

A free end <NUM> of the shaft <NUM> is designed to engage an axial centring hole (not illustrated) of the crankshaft <NUM>. The shaft <NUM> can be selectively connected to the crankshaft <NUM> by means of a clutch.

The base wall <NUM> of the support structure <NUM> is shaped so as to define, on the opposite side of the transmission <NUM>, a housing <NUM> for the clutch <NUM>. The clutch <NUM> can be part of the module <NUM> or, as in the example described, can be an assembly distinct from the module <NUM> and complementary thereto.

The clutch <NUM>, described here briefly insofar as necessary for understanding the present invention but not forming part thereof, comprises an external casing <NUM> secured to the crankshaft <NUM> by means of axial screws <NUM>, and a hub <NUM> (<FIG>), which is rotationally integral with the shaft <NUM> by means of a grooved coupling <NUM>.

The casing <NUM> (<FIG>) houses at least one clutch plate <NUM> rotationally fixed to the hub <NUM> and at least one clutch plate <NUM> rotationally fixed to the casing.

The clutch plates <NUM>, <NUM> are axially sliding, and are kept in a pack, in the normal clutch closing position, by means of a clutch pressure plate spring <NUM> comprising, in a known manner, an outer annular portion <NUM> and a plurality of elastic arms <NUM> extending integrally and radially towards the inside of the annular portion <NUM>. The arms <NUM>, pivoted to the support structure <NUM> in the vicinity of the annular portion <NUM>, in a known way, are shaped and preloaded so as to exert an axial action designed to maintain the clutch plates <NUM>, <NUM> in a pack against an axial wall of the casing <NUM> in an engagement position.

The module <NUM> lastly comprises an actuator <NUM> integrated in the support structure <NUM>. The actuator <NUM> is illustrated in detail in <FIG>, and is designed to exert an axial thrust action on the ends <NUM> of the arms <NUM>, when operated, to move the annular portion <NUM> away from the clutch plates <NUM>, <NUM> and thus open the clutch <NUM>.

With particular reference to <FIG>, the actuator <NUM> comprises an annular piston <NUM> with axis A axially movable in an annular chamber <NUM> obtained in the support structure <NUM> in a position coaxially external to the seat <NUM> and open frontally towards the clutch <NUM>.

The piston <NUM> is radially guided by a pair of guide rings <NUM>, <NUM> housed in respective external circumferential seats of the piston <NUM> arranged in the vicinity of the axial ends of the piston and sliding in contact with an external circumferential surface of the annular chamber <NUM>.

The piston <NUM> is further provided with a pair of external annular seals <NUM> arranged between the guide rings <NUM>, <NUM>, and a pair of internal annular seals <NUM> sliding in contact with an internal circumferential surface of the annular chamber <NUM>.

At an axial end of the piston <NUM> facing the clutch <NUM>, said piston <NUM> has an internal annular flange <NUM>, to which a tubular portion <NUM> extending towards the base wall <NUM> of the support structure <NUM> integrally connects, thus defining an internal appendix of the piston <NUM> bent axially in a direction opposite to the clutch <NUM>. The tubular portion <NUM> has an internal end shoulder <NUM> and houses a thrust ball bearing <NUM> in axial abutment against the shoulder <NUM>.

The actuator <NUM> lastly comprises a thrust member <NUM> integrally comprising a tubular sleeve <NUM> housed inside the bearing <NUM>, a substantially flat annular portion <NUM> radially extending outwards from an axial end of the sleeve <NUM> facing the clutch <NUM> and a thrust portion <NUM> defined by an outer radial edge of the annular portion <NUM> bent axially in a direction opposite to the piston <NUM>, which it axially faces. The thrust portion <NUM> cooperates with the ends <NUM> of the arms <NUM> of the clutch pressure plate spring <NUM>.

Expediently, the piston <NUM> is rotationally blocked with respect to the annular chamber <NUM> so as to avoid any undesired rotations causing premature wear on the seals <NUM>, <NUM> and the guide rings <NUM>, <NUM>. This can be carried out by means of an axial pin <NUM> engaging respective holes of the annular flange <NUM> of the piston <NUM> and of the thrust member <NUM> (<FIG>).

The sleeve <NUM> forms a labyrinth seal <NUM> with a tubular protrusion <NUM> extending axially in a cantilever manner from the support structure <NUM>, so as to prevent dirt from entering the area of the inner circumferential surface of the annular chamber <NUM>.

The actuator <NUM> further comprises an annular bellow-shaped element <NUM> secured on one side to the piston <NUM> and on the other to an annular flange <NUM> applied frontally on the support structure <NUM>, so as to prevent dirt from entering the area of the external circumferential surface of the annular chamber <NUM>.

In addition to supporting the bellow-shaped element <NUM>, the flange <NUM> acts as a safety end stop for the piston <NUM>, to prevent overtravel in the event of excess pressure or non-contact.

Expediently, the support structure <NUM> defines an internal channel <NUM> for the supply/discharge of oil to/from the annular chamber <NUM> of the actuator <NUM>; the channel <NUM> (<FIG>) establishes communication between the annular chamber <NUM> and a radial connection <NUM> arranged on the perimeter flange <NUM> of the support structure <NUM> and designed to be connected to a hydraulic control circuit.

The channel <NUM> is expediently defined by two or more holes obtained in the thickness of the wall <NUM>; said holes can be provided from the outside by means of conventional drilling operations, and intersect with one another so as to define a continuous path; the openings of the holes can be plugged if necessary.

The damper <NUM> (<FIG> and <FIG>) comprises an annular casing <NUM> formed by a pair of half-shells <NUM>, <NUM>, on the periphery of which the crown wheel <NUM> of the transmission <NUM> is fitted. The damper <NUM> further comprises an actuator <NUM> comprising a disc <NUM> rigidly (and preferably integrally) connected to the shaft <NUM> and provided with two radial spokes <NUM> (only one of which can be seen in <FIG>) housed in the annular casing <NUM>. The latter forms a pair of diametrically opposite stops <NUM> defined by internal protrusions of the half-shells <NUM>, <NUM>.

As illustrated in the diagram of <FIG>, between the spokes <NUM> and the stops <NUM> circumferential helical springs are arranged, having the purpose of elastically coupling the actuator <NUM> (and therefore the shaft <NUM>) with the annular casing <NUM> (and therefore with the crown wheel <NUM> of the transmission <NUM>), so as to filter the torsional vibrations transmitted in use from the crankshaft <NUM> to the electric machine <NUM>.

A flex plate <NUM> constituting the interface member between the module <NUM> and the transmission T is secured to the disc <NUM> of the actuator <NUM>.

The operation of the transmission module <NUM>, already partly evident from the above description, is the following.

In use, when the clutch <NUM> is closed, the shaft <NUM> is connected both to the crankshaft <NUM> of the internal combustion engine (E), and to the electric machine <NUM> by means of the damper <NUM> and the transmission <NUM>, and to the vehicle transmission T by means of the flex plate <NUM>.

In this condition, the electric machine <NUM> can be used both as a generator (for recharging the battery during operation of the internal combustion engine, or as a regenerative brake) and as a motor for starting the internal combustion engine or for delivering an additional torque during operation of the internal combustion engine (boosting).

When the clutch <NUM> is open, the electric motor can be used for electric driving, electric braking and coasting with the internal combustion engine switched off.

The use of an actuator <NUM> integrated in the support structure <NUM>, compared to conventional autonomous solutions, allows the axial dimensions of the module <NUM> to be substantially reduced and therefore the module to be housed in situations where there is limited axial space available.

The integration of the actuator <NUM> in the support structure also allows dedicated fixing means to be avoided.

Claim 1:
Transmission module (<NUM>) for a hybrid drive vehicle configured to be interposed between an internal combustion engine (E) and a transmission (T) of the vehicle, the module comprising:
a tray-like support structure (<NUM>) configured to be secured to the engine (E) and defining a housing (<NUM>) for a clutch (<NUM>),
a hydraulic actuator (<NUM>) for controlling the clutch (<NUM>) including an annular chamber (<NUM>) provided in the support structure (<NUM>) and open towards the housing (<NUM>) for the clutch (<NUM>), an annular piston (<NUM>) axially movable in the annular chamber (<NUM>), a thrust member (<NUM>) constrained in a rotationally free manner to the piston (<NUM>), coaxial thereto and configured to cooperate with a control member (<NUM>) of the clutch (<NUM>) under the thrust of the piston (<NUM>), and a bearing (<NUM>) radially interposed between the annular piston (<NUM>) and the thrust member (<NUM>),
wherein the annular piston (<NUM>) includes an internal tubular appendix (<NUM>) extending from an axial end of the piston (<NUM>) facing the housing (<NUM>) of the clutch (<NUM>) and bent axially in a direction opposite to the clutch (<NUM>), the bearing (<NUM>) being interposed between said appendix (<NUM>) and a sleeve (<NUM>) of the thrust member (<NUM>) housed inside the piston (<NUM>), and
the thrust member (<NUM>) includes a thrust portion (<NUM>) axially facing the annular piston (<NUM>) and connected to said sleeve (<NUM>) by a substantially flat annular portion (<NUM>).