Transmission module provided with a hydraulic actuator

A transmission module for a hybrid drive vehicle configured to be interposed between an internal combustion engine and a transmission of the vehicle has a tray-like support structure configured to be secured to the engine and defines a housing for a clutch to be interposed between a crankshaft of the internal combustion engine and the module. An actuator controls the clutch. The actuator includes an annular chamber provided in the support structure and opens toward the housing, and an annular piston housed in the annular chamber is axially sliding but angularly fixed. A thrust member is coupled in a rotationally free manner to the annular piston, coaxial thereto and operable to cooperate with a control member of the clutch under the thrust of the piston.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present invention is filed under 35 U.S.C. § 371 as the U.S. National Phase of International Patent Application No. PCT/IB2020/062441, filed Dec. 24, 2020, which designated the United States and which claims the benefit of Italian patent application no. 102019000025642, filed on Dec. 27, 2019, the entire disclosure of which is incorporated herein by reference.

TECHNICAL FIELD

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.

BACKGROUND ART

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.

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.

DISCLOSURE OF INVENTION

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 configured to be interposed between an internal combustion engine and a transmission of the vehicle. The module has a tray-like support structure configured to be secured to the engine and defines a housing for a clutch, and a hydraulic actuator for controlling the clutch. The hydraulic actuator has an annular chamber provided in the support structure that 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 under the thrust of the piston.

The above-mentioned object is achieved by a transmission module according to claim1.

BEST MODE FOR CARRYING OUT THE INVENTION

With reference toFIGS.1to3, the number1indicates overall a transmission module P2designed 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 module1forms part of a hybrid unit4comprising, in addition to the module itself, an electric machine2. Optionally, the hybrid unit4can also comprise one or more accessories such as, for example, a compressor3for an air conditioning system of the vehicle (FIG.2).

The electric machine2is 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 module1(FIGS.3-5) essentially comprises a tray-like support structure5and a transmission6, in this example a chain transmission, housed in the support structure5and configured to operatively and selectively connect to one another a crankshaft7of the internal combustion engine E, the electric machine2and the transmission T.

In the example illustrated, the transmission6comprises a crown wheel8with axis A selectively connectable to the crankshaft7, as described below, and a pinion9with axis B designed to be connected to the electric machine2. The axes A, B coincide in use with the axis of the crankshaft7of the engine E and with the axis of the electric machine2respectively. The transmission6further comprises a chain10engaging with the crown8and the pinion9.

The support structure5has a substantially flat base wall12and a perimeter flange13extending perpendicular to it and forming a plurality of projections14in which the holes for securing the module1to the engine E are obtained. The base wall12and the perimeter flange13delimit a cavity housing the transmission6, which is closed frontally by a cover11.

The base wall12forms a pair of through seats15,16(FIG.4), having axes A and B respectively.

The electric machine2(FIG.4) is assembled at the seat16, on the opposite side of the transmission6. The seat16houses a hub17of the pinion9and the relative bearings19.

The crown8forms part of a torsional vibration damper18, for example of the circumferential spring type, described briefly below since it is known per se and not part of the present invention. The damper18is supported by means of a bearing25housed in the seat15and is provided with a shaft20having axis A arranged passing through said seat.

A free end21of the shaft20is designed to engage an axial centring hole (not illustrated) of the crankshaft7. The shaft20can be selectively connected to the crankshaft7by means of a clutch.

The base wall12of the support structure5is shaped so as to define, on the opposite side of the transmission6, a housing22for the clutch23. The clutch23can be part of the module1or, as in the example described, can be an assembly distinct from the module1and complementary thereto.

The clutch23, described here briefly insofar as necessary for understanding the present invention but not forming part thereof, comprises an external casing24secured to the crankshaft7by means of axial screws50, and a hub26(FIG.5), which is rotationally integral with the shaft20by means of a grooved coupling27.

The casing24(FIG.5) houses at least one clutch plate28rotationally fixed to the hub26and at least one clutch plate29rotationally fixed to the casing.

The clutch plates28,29are axially sliding, and are kept in a pack, in the normal clutch closing position, by means of a clutch pressure plate spring30comprising, in a known manner, an outer annular portion31and a plurality of elastic arms32extending integrally and radially towards the inside of the annular portion31. The arms32, pivoted to the support structure5in the vicinity of the annular portion31, in a known way, are shaped and preloaded so as to exert an axial action designed to maintain the clutch plates28,29in a pack against an axial wall of the casing24in an engagement position.

The module1lastly comprises an actuator34integrated in the support structure5. The actuator34is illustrated in detail inFIG.6, and is designed to exert an axial thrust action on the ends33of the arms32, when operated, to move the annular portion31away from the clutch plates28,29and thus open the clutch23.

With particular reference toFIG.6, the actuator34comprises an annular piston35with axis A axially movable in an annular chamber36obtained in the support structure5in a position coaxially external to the seat15and open frontally towards the clutch23.

The piston35is radially guided by a pair of guide rings37,38housed in respective external circumferential seats of the piston35arranged in the vicinity of the axial ends of the piston and sliding in contact with an external circumferential surface of the annular chamber36.

The piston35is further provided with a pair of external annular seals40arranged between the guide rings37,38, and a pair of internal annular seals41sliding in contact with an internal circumferential surface of the annular chamber36.

At an axial end of the piston35facing the clutch23, said piston35has an internal annular flange42, to which a tubular portion43extending towards the base wall12of the support structure5integrally connects, thus defining an internal appendix of the piston35bent axially in a direction opposite to the clutch23. The tubular portion43has an internal end shoulder44and houses a thrust ball bearing45in axial abutment against the shoulder44.

The actuator34lastly comprises a thrust member46integrally comprising a tubular sleeve47housed inside the bearing45, a substantially flat annular portion48radially extending outwards from an axial end of the sleeve47facing the clutch23and a thrust portion49defined by an outer radial edge of the annular portion48bent axially in a direction opposite to the piston35, which it axially faces. The thrust portion49cooperates with the ends33of the arms32of the clutch pressure plate spring30.

Expediently, the piston35is rotationally blocked with respect to the annular chamber36so as to avoid any undesired rotations causing premature wear on the seals40,41and the guide rings37,38. This can be carried out by means of an axial pin57engaging respective holes of the annular flange42of the piston35and of the thrust member46(FIG.6).

The sleeve47forms a labyrinth seal52with a tubular protrusion51extending axially in a cantilever manner from the support structure5, so as to prevent dirt from entering the area of the inner circumferential surface of the annular chamber36.

The actuator34further comprises an annular bellow-shaped element53secured on one side to the piston35and on the other to an annular flange54applied frontally on the support structure5, so as to prevent dirt from entering the area of the external circumferential surface of the annular chamber36.

In addition to supporting the bellow-shaped element53, the flange54acts as a safety end stop for the piston35, to prevent overtravel in the event of excess pressure or non-contact.

Expediently, the support structure5defines an internal channel55for the supply/discharge of oil to/from the annular chamber36of the actuator34; the channel55(FIG.5) establishes communication between the annular chamber36and a radial connection56arranged on the perimeter flange13of the support structure5and designed to be connected to a hydraulic control circuit.

The channel55is expediently defined by two or more holes obtained in the thickness of the wall12; 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 damper18(FIGS.3and5) comprises an annular casing60formed by a pair of half-shells61,62, on the periphery of which the crown wheel8of the transmission6is fitted. The damper18further comprises an actuator63comprising a disc64rigidly (and preferably integrally) connected to the shaft20and provided with two radial spokes65(only one of which can be seen inFIG.5) housed in the annular casing60. The latter forms a pair of diametrically opposite stops66defined by internal protrusions of the half-shells61,62.

As illustrated in the diagram ofFIG.7, between the spokes65and the stops66circumferential helical springs are arranged, having the purpose of elastically coupling the actuator63(and therefore the shaft20) with the annular casing60(and therefore with the crown wheel8of the transmission6), so as to filter the torsional vibrations transmitted in use from the crankshaft7to the electric machine2.

A flex plate67constituting the interface member between the module1and the transmission T is secured to the disc64of the actuator63.

The operation of the transmission module1, already partly evident from the above description, is the following.

In use, when the clutch23is closed, the shaft20is connected both to the crankshaft7of the internal combustion engine (E), and to the electric machine2by means of the damper18and the transmission6, and to the vehicle transmission T by means of the flex plate67.

In this condition, the electric machine2can 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 clutch23is 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 actuator34integrated in the support structure5, compared to conventional autonomous solutions, allows the axial dimensions of the module1to be substantially reduced and therefore the module to be housed in situations where there is limited axial space available.

The integration of the actuator34in the support structure also allows dedicated fixing means to be avoided.

Lastly it is clear that modifications and variations can be made to the actuator34and to the module1comprising it that do not depart from the scope defined by the claims.