Actuator for operating at least one moving organ, especially for gear changes in motor vehicle transmissions

Description

[0001] The invention relates to an actuator for actuating at least one moving member. It finds its application, in particular in the field of actuators for motor vehicle transmissions. However, many other applications are possible.

[0002] More specifically, the invention relates to an actuator for changing gears in a motor vehicle transmission or gearbox. Such an actuator is useful in a hybrid motor vehicle transmission, comprising on the one hand a thermal drive engine, and on the other hand an electric machine.

[0003] There is a need to change the transmission ratios so that the thermal engine and / or the electric machine operate in their optimal operating range. The actuator according to the invention fulfills this function.

[0004] Document WO2018 / 146393A1 discloses an actuator for changing gears in a gearbox comprising an electric motor and a fork shaft moved axially to engage or disengage a gear in the gearbox. This actuator comprises means for reducing the rotational movement between the output shaft of the electric motor and a pin offset from the rotational axis of the electric motor, the pin being engaged in an oblong opening of a dog clutch system, so as to cause the axial movement of the fork shaft by moving linearly along the opening under the action of the electric motor. EP1094253 B1 also discloses an actuator with a reduction system.

[0005] This solution has the disadvantage of proposing a bulky gear reduction mechanism, which goes against the automotive industry's objectives of reducing the weight and size of components. Furthermore, no means of controlling the electric motor is proposed in this document.

[0006] The present invention aims to improve current solutions, in particular by proposing a solution aimed at making such an actuator as compact as possible for changing gears in a motor vehicle transmission, while integrating a means of controlling the electric motor.

[0007] The term transmission is synonymous with the gearbox of a motor vehicle.

[0008] More particularly, the invention relates to an actuator for actuating at least one moving member of a motor vehicle transmission, said actuator comprising a housing and a cover defining an internal volume in which are housed at least one electric motor having a stator and a rotor mounted on a rotor shaft extending along an axis X1, a motor pinion fixed to the end of the shaft opposite the rotor, an electronic card for powering the stator and controlling the electric motor, a reduction mechanism driven by the motor pinion, the housing or the cover comprises an electrical connector which integrates a semi-permeable membrane allowing a gas exchange between the interior of the actuator and the external environment.

[0009] Thus, an actuator according to the invention will be able to solve the problems set out above. In particular, positioning the membrane on the electrical connector makes it possible to simplify the design of the housing or cover.

[0010] According to the invention, the membrane is semi-permeable, that is to say it is permeable to gases, in particular air, and impermeable to liquids, in particular water or oil. This exchange makes it possible to balance the pressure inside the actuator due to the release of heat linked to the electronic card and the electric motor.

[0011] According to a feature of the invention, the housing and the cover are made of metal. Preferably, the housing and the cover are made of aluminum, for example high-pressure die-cast aluminum.

[0012] According to another feature of the invention, the electrical connector is made of plastic. It is particularly advantageous to position the membrane on a plastic element. In addition, positioning the membrane on the plastic electrical connector is simpler from a manufacturing point of view rather than positioning the membrane on the metal housing or cover. Indeed, it is easier on a plastic part to create complex shapes to hold the membrane, which is impossible with a metal part. These complex shapes can, for example, protect access to the membrane.

[0013] In the field of automotive actuators, it is interesting to use standardized elements in order to reduce costs, the use of an electrical connector integrating a membrane also allows its use in different types of actuators.

[0014] Preferably, the electrical connector with its membrane is positioned on the support element, namely the cover or the housing, which is located on the upper part of the actuator.

[0015] According to an exemplary embodiment of the invention, the membrane is clipped onto the electrical connector by means of a ring. Alternatively, the membrane is glued or welded onto the electrical connector.

[0016] Preferably, the electrical connector is substantially circular in shape. A seal is positioned between the electrical connector and the housing or cover, preferably the seal is an O-ring.

[0017] According to the invention, the electrical connector is screwed onto the housing or the cover. Alternatively, the electrical connector is clipped onto the housing or the cover.

[0018] According to a characteristic of the invention, the housing and the cover each have means for guiding the reduction mechanism.

[0019] According to the invention, the housing comprises a peripheral groove in which a sealing gasket is arranged in order to ensure a seal between the housing and the cover.

[0020] Preferably, the actuator is capable of being fixed directly to the vehicle transmission and the external surface of the cover has a groove in which a seal is positioned in order to ensure sealing between the transmission and the actuator cover.

[0021] Advantageously, the actuator comprises at least one pin capable of being engaged in a moving member of the transmission. The pin is located outside the cover and therefore outside the actuator. The pin may have a shape cooperating with the moving member, for example a conical shape or alternatively a spherical shape.

[0022] The pin is capable of being engaged in an opening, for example an oblong opening, so as to cause the axial displacement of a fork by moving linearly along the opening under the action of the electric motor. The pin is capable of moving in the opening around a central dead center position and two extreme positions.

[0023] According to the invention, the reduction mechanism is kinematically located between the drive pinion and the pinion. The reduction mechanism comprises at least one toothed wheel mounted on at least one shaft. More specifically, the reduction mechanism comprises a stepped pinion wheel and a toothed sector pinion.

[0024] According to the invention, the stepped pinion wheel and the toothed sector pinion each extend along a plane orthogonal to the X1 axis. This gear mechanism architecture makes it possible to obtain a particularly compact actuator.

[0025] More specifically, the stepped pinion wheel comprises a first pinion and a second pinion, the first pinion is coupled with the motor pinion and the second pinion is coupled with the toothed sector pinion, the stepped pinion wheel is mounted on a shaft extending along an axis X2 radially offset from the axis X1 of the shaft of the electric motor. Preferably, the stepped pinion wheel is in one piece, the first pinion and the second pinion are coaxial.

[0026] According to the invention, the toothed sector of the pinion extends in an angular range between 90° and 180°, preferably between 100° and 120°. Alternatively, the toothed sector of the pinion may extend to 360°. The toothed sector pinion is mounted on a shaft extending along an axis X3 radially offset from the axes X1 and X2.

[0027] According to an additional characteristic of the invention, the pin is mounted offset along an axis X4 at one end of the shaft of the toothed sector pinion by means of a connecting rod.

[0028] According to the invention, the axes X1, X2, X3 and X4 are parallel.

[0029] According to a characteristic of the invention, the actuator is configured for changing gears of a motor vehicle transmission, in particular a hybrid transmission.

[0030] Advantageously, the actuator according to the invention comprises three electric motors, each electric motor being associated with its own reduction mechanism and its own pin. In this way, the actuator is able to control the change of six transmission ratios. Indeed, each electric motor, via its own reduction mechanism, is able to move the associated pin into two extreme positions, each corresponding to a transmission ratio. In other words, each electric motor, via its own reduction mechanism and its associated pin, is able to control two ratios of the vehicle's transmission. The electric actuator according to the invention with its three electric motors is of interest in six-speed transmissions.

[0031] For example, in the context of the hybrid transmission disclosed in WO2015 / 197927A1 and WO2019 / 219294A1, the first electric motor of the actuator according to the invention may be linked to two associated ratios of the electric machine while the second electric motor of the actuator according to the invention may be linked to two ratios of the thermal engine, for example ratios 1 and 3 and the third electric motor of the actuator according to the invention may be linked to two other ratios of the thermal engine, for example ratios 2 and 4.

[0032] Other characteristics and advantages of the invention will emerge from the following reading of detailed examples of embodiments, with reference to the appended Figures. There Figure 1 represents the actuator according to the invention from a bottom view; The Figure 2 represents the actuator according to the invention from a top view; The Figure 3 represents a perspective and partial sectional view of the actuator according to the invention; The Figure 4 represents a sectional and perspective view of the actuator according to the invention; The Figure 5a and the Figure 5b respectively represent a perspective view and a sectional view of a means for guiding a shaft of the reduction mechanism; The Figure 6 represents a perspective view of the contact between the electronic card and the housing; The Figure 7 represents a cutaway perspective view of a holding plate of an electric motor; The Figure 8 represents a sectional view of a means for guiding a shaft of the reduction mechanism; The Figure 9a and the Figure 9b respectively represent a perspective view and a sectional view of an electrical connector of the actuator according to the invention; The Figure 10 represents a sectional view of the electric actuator according to the invention fixed to a gearbox of a motor vehicle; The Figure 11 represents an alternative embodiment of the invention; The Figure 12 and the Figure 13 represent an alternative embodiment of the actuator according to the invention; The Figure 14 and the Figure 15 represent another variant embodiment of the actuator according to the invention.

[0033] There Figure 1 represents an actuator 10 according to the invention. The actuator 10 is formed by two main parts, namely a housing 20 and a cover 30 in which several elements are housed. This Figure 1 is focused on the housing 20 of the actuator 10. The housing 20 is made of metal such as aluminum or aluminum alloy. Alternatively, the housing 20 can be made of an injectable plastic material. The function of the housing 20 is to accommodate the electric motors 1 in dedicated housings 21. The housing 20 thus forms a housing common to the electric motors 1.

[0034] In a first embodiment of the invention, three electric motors 1 are housed in three respective housings 21. The housings 21 of the electric motors 1 are made in a shape complementary to the shape of the electric motors. Reinforcements 22 in the form of ribs are provided between each housing 21 to stiffen the housing 20.

[0035] The housing 20 also integrates an electrical connector 27 in order to supply the electric motors 1 and all the electrical components necessary for the operation of the actuator 10.

[0036] The housing 20 is assembled to the cover 30 by means of fixing screws 23 located at the periphery of the housing 20 and the cover 30.

[0037] In Figure 2 The cover 30 of the actuator 10 is visible. The cover 30 is made of metal such as aluminum or an alloy. Alternatively, the cover 30 may be made of an injectable plastic material. In the case of the present invention, the housing 20 and the cover 30 are made of high-pressure cast aluminum (in English " die casting »). The housing 20 or the cover 30 can receive a cooling circuit if the surrounding temperatures are too high.

[0038] The actuator 10 is capable of being fixed directly to the vehicle transmission, such as for example the gearbox, by means of fixing means 31, in particular openings through which screws pass. The external surface of the cover 30 has a groove 33 in which a seal 34 is positioned in order to ensure sealing between the transmission and the cover 30. The elements which are located inside the closed contour of the seal 34 are directly in contact with the vehicle transmission. In the present case, three pins 8 are each capable of being engaged in a movable member of the transmission, linked for example to a fork and / or a dog clutch. The pins 8 are therefore located outside the cover 30. The pins 8 have a shape cooperating with their respective movable member, for example a conical shape.

[0039] Each pin 8 is capable of being engaged in an opening, for example an oblong opening, of a dog clutch so as to cause the axial displacement of a fork by moving linearly along the opening under the action of the electric motor. The pin is capable of moving in the opening around a central neutral position and two extreme positions. This actuation kinematics is described in the published document WO2018 / 146393A1.

[0040] There Figure 3 shows the interior of the actuator 10 according to the invention. Although this Figure 3 either a perspective view and partial section focused on a single electric motor 1 and its associated kinematics up to pin 8, the three electric motors 1 and the actuating kinematics of pins 8 are all independent but identical in actuator 10.

[0041] On this Figure 3 the housing 20 and its housing 21 in which the electric motors 1 are housed are therefore visible. In order to hold the electric motors 1 securely in the housing 20, holding plates 6 are used so as to press the electric motors 1 to the bottom of their respective housing 21.

[0042] The electric motors 1 are direct current and each consist of a stator 2 and a rotor 3 mounted on a rotor shaft 4 extending along an axis X1. A motor pinion 5 is fixed to the end of each shaft on the side opposite the rotor 3 and makes it possible to drive a reduction mechanism 40 formed by toothed wheels 41, 42, 46 mounted on shafts 44, 45.

[0043] The reduction mechanism 40 is kinematically located between the motor pinion 5 and the pin 8 and comprises a stepped pinion wheel 43 and a toothed sector pinion 46.

[0044] The stepped pinion wheel 43 comprises a first pinion 41 and a second pinion 42, the first pinion 41 is coupled with the motor pinion 5 and the second pinion 42 is coupled with the toothed sector pinion 46, the stepped pinion wheel 43 is mounted on the shaft 44 extending along an axis X2 and radially offset from the axis X1 of the shaft 4 of the electric motor 1. The first pinion 41 has a larger diameter than the second pinion 42. The toothed wheels 41, 42, 46 are overmolded on the shafts 44, 45. The toothed wheels 41, 42, 46 are for example made of glass fiber reinforced polyphthalamide (PPA), having very high rigidity and strength, as well as resistance to high temperatures and chemicals. Alternatively, the toothed wheels may be made of glass fiber reinforced polyamide (PA).

[0045] The stepped pinion wheel 41, 42, 43 and the toothed sector pinion 46 each extend along a plane orthogonal to the axis X1.

[0046] The toothed sector of the pinion 46 extends in an angular range between 90° and 180°, preferably between 100° and 120°. The toothed sector pinion 46 is mounted on the shaft 45 extending along an axis X3 radially offset relative to the axes X1 and X2. The pin 8 is mounted offset along an axis X4 at one end of the shaft 45 of the toothed sector pinion 46 by means of a connecting rod 9. This connecting rod 9 is also located outside the cover 30. The axes X1, X2, X3 and X4 are parallel.

[0047] An electronic card 11 used to power the stator 2 and to control each electric motor 1 is located axially along the axis X1 between each electric motor 1 and each motor pinion 5. The housing 20 defines a first volume in which the electric motors 1 and the electronic card 11 are housed, thus forming an electronic subassembly.

[0048] The electronic card 11 is fixed to the housing 20 by means of fixing means 13, in particular screws. The outer contour of the electronic card 11 substantially matches the inner contour of the housing 20. The electronic card 11 comprises three openings 12 of closed contour which are each crossed by the rotor shaft 4 of each electric motor 1.

[0049] The electronic card 11 allows the management of the power electronics, the control electronics and the self-diagnostic function. Consequently, all the functions (detection of the position of the pins 8 for closed-loop control, power supply and connection to the vehicle bus) can be located on the electronic card. Thus, the electronic circuit 11 integrates all the electronic components necessary for the operation of the electric actuator such as, for example, rotation sensors 56 opposite the shafts 45 in order to know the position of the pins 8. In addition, the power supply of the motors 1 is close to the electrical connector 27. The electronic card 11 is connected to the electric motors 1 by crimp or solder contacts.

[0050] The reduction mechanism 40 is housed in the cover 30 which defines a second volume. The housing 20 and the cover 30 each have guide means 24, 32 for the shafts 44, 45 of the reduction mechanism 40.

[0051] The housing 20 comprises a peripheral groove 25 in which a seal 26 is arranged in order to ensure a seal between the housing 20 and the cover 30.

[0052] There Figure 4 allows to better illustrate the kinematics between the electric motor 1, the reduction mechanism 40 and the pin 8.

[0053] The housing 20 comprises a guide means 24 in the form of a blind hole receiving one end of the shaft 44 of the stepped pinion wheel 43. The cover 30 also comprises a guide means 28 in the form of a blind hole receiving the other end of the shaft 44 of the stepped pinion wheel 43.

[0054] The cover 30 also includes a through hole 32 for the passage and guidance of the shaft 45 of the toothed sector pinion 46.

[0055] On its end facing the electronic card 11, the shaft 45 comprises a magnet 35 making it possible to detect the position of the pin 8 using a sensor 56 fixed to the electronic card 11. The sensor 56 is preferably a Hall effect sensor.

[0056] THE Figures 5a et 5b show respectively a perspective view and a sectional view of the guide means 24 in which the shaft 44 of the reduction mechanism 40 is housed. The guide means comprises an axial groove 47 making it easier to insert the shaft 44. This axial groove 47 makes it possible to expel the air while preventing the formation of an air pocket when inserting the shaft 44 into the guide means 24. The guide means 28 may also comprise such an axial groove. The electronic card has an opening 50 of closed contour crossed by the guide means 24. The guide means 24 has a shoulder 55 on which the electronic card rests. The guide means 24 serves both for guiding the reduction mechanism 40 in rotation and also as a means for centering the electronic card 11 in the housing 20.

[0057] There Figure 6 shows the electronic card 11 in contact with pins 37 of the housing 20 in order to dissipate the heat produced by the electronic card 11. The thermal paste 38 is positioned between the pins 37 and the electronic card 11 in order to improve the transfer of calories from the electronic card 11 to the housing 20 which, thanks to its material, dissipates the heat. A channel 39 is provided around the perimeter of the pins 37 in order to recover the excess thermal paste 38.

[0058] There Figure 7 shows the positioning of one of the electric motors 1 and its maintenance in position in its dedicated housing 21. In operation, the electric motor 1 undergoes acceleration and inertia, it must therefore be correctly positioned and maintained in its housing 21. The electric motor 1 must also be correctly oriented to allow conduction via its terminals B+, B- with the electronic card 11 and thus avoid a risk of polarity inversion. The terminals B+, B- are in contact with the electronic card 11 by pinching, particularly visible on the Figure 10 . The electric motor 1 must also be correctly centered to ensure the proper functioning of the reduction mechanism 40. The holding plate 6 performs all these functions. This holding plate 6 allows the electric motor 1 to be pressed against the bottom of the housing 21. The holding plate 6 is made of metal, preferably a metal allowing a spring function. The holding plate 6 is fixed to the housing 20 by means of fixing means 7, in particular screws. The housing 20 comprises a rib 48 in the shape of an arc of a circle made in order to center the holding plate 6 relative to the housing 20, the holding plate 6 having a shape substantially complementary to the rib 48. The holding plate 6 also comprises a curved tab 49 in order to index the holding plate 6 and the electric motor 1, the curved tab 49 being directed towards the electric motor 1.

[0059] There Figure 8 shows in more detail the guidance of shaft 45. Due to the high forces and torques required to control the change of transmission ratios, the guidance of shaft 45 must be robust. To achieve this, shaft 45 is guided in rotation by a rolling bearing 36 and a bearing 51, which allows it to absorb radial loads. Bearing 36 is a ball bearing and bearing 51 is a plain bearing.

[0060] The guide means 32 is a through hole and has three bores of different diameters in which the bearing 36, the bearing 51 and a lip seal 52 are mounted.

[0061] The bearing 36 is mounted in a first bore in order to guide in rotation the shaft 45 of the toothed sector pinion 46 and the pin 8 mounted on the connecting rod 9. The bearing 36 is preferably sealed in order not to allow impurities to enter the internal volume defined by the housing 20 and the cover 30. The internal ring of the ball bearing 36 is mounted on the shaft 45 and the external ring is housed in a first bore of the guide means 32.

[0062] The inner wall of the bearing 51 is in contact with the shaft 45 and the outer wall is in contact with a second bore of the guide means 32. The bearing 51 is for example an anti-friction plain bearing made of metal-polymer. Alternatively, the plain bearing can be made of bronze.

[0063] The bearing 36 is located on the outer side of the cover 30 and the bearing 51 is located on the inner side of the cover 30.

[0064] Axially along the axis X3, a lip seal 52 is positioned in a third bore of the guide means 32 between the ball bearing 36 and the bearing 51. This lip seal 52 makes it possible to seal the interior of the actuator. Indeed, the actuator 10 is mounted directly on the gearbox of the vehicle, thus the pin 8, the connecting rod 9 and the ball bearing 36 are in direct contact with the gearbox lubricant. The ball bearing 36 is thus constantly lubricated by the gearbox lubricant. In other words, the lip seal 52 makes it possible to separate a wet space, namely the interior of the vehicle gearbox, and a dry space, namely the interior of the actuator 10. The lip seal 52 is housed in a shoulder of the guide means 32. The lip of the seal 52 is in contact with the shaft 45. The lip seal 52 is in contact with one end of the bearing 51.

[0065] THE Figures 9a et 9b show in detail the electrical connector 27 for supplying power to the electric motors 1 and all the electrical components necessary for the operation of the actuator 10. On the side external to the housing 20, the electrical connector 27 comprises electrical tracks capable of being connected to an external connector. On the side internal to the housing 20, the electrical connector comprises means for connection to the electronic card 11. The electrical connector 27 is entirely made of plastic and is mounted in an opening of the housing 20. The electrical connector 27 comprises a membrane 53, more precisely a semi-permeable membrane, that is to say that it is permeable to gases, in particular air, and impermeable to liquids, in particular water. The membrane 53 is hydrophobic and, where appropriate, oleophobic, and may have a microporous coating.The membrane 53 can be fixed by various means to the electrical connector 27, such as by means of a ring clipped onto the electrical connector 27. Alternatively, the membrane 53 can be glued or welded onto the electrical connector. Such a membrane thus makes it possible to limit the risks of condensation and excess pressure within the actuator 10, and thus increases the service life while improving the operation of the actuator.

[0066] A 54 joint visible on the Figure 9b , of the toric type, is positioned between the electrical connector 27 and the housing 20 in order to guarantee the sealing of the actuator. The seal 54 is received in an annular groove of the electrical connector 27. The electrical connector 27 is screwed or clipped onto the housing 20.

[0067] There Figure 10 shows the actuator 10 in the mounted position on the gearbox BV of the vehicle. The seal between the gearbox BV and the actuator 10 is provided by the seal 34 mounted in a groove 33 of the actuator 10, more precisely of the cover 30. The seal 34 is preferably a polymer seal. The use of a polymer seal 34 is preferred to the use of a flat metal seal as is customary in the field.

[0068] There Figure 11 shows an alternative embodiment of the actuator 10. Unlike the previous embodiment, the pin 80 is spherical and no longer conical. This makes it possible to adapt to a greater diversity of moving parts of motor vehicle transmissions.

[0069] THE Figures 12 à 15 show two other variant embodiments of the actuator 10. On the Figures 12 et 13 an actuator 200 is visible in which there is only one electric motor associated with a pin 8 via a reduction mechanism. On the Figures 14 et 15 an actuator 300 is visible in which there are two electric motors associated with two pins 8 via two reduction mechanisms. The operation of the actuators 200, 300 is similar to the operation of the actuator 10, only the number of electric motors, reduction mechanisms and pins differs according to the embodiments.

[0070] Such an electric actuator 10, 100, 200, 300 has a compact structure and a small footprint. Furthermore, it is possible to use many standard commercial elements, such as electric motors and toothed wheels. The cost of such an electric actuator is also relatively low and can be easily integrated into existing transmission systems.

[0071] Although the invention has been described in connection with several embodiments, it is obvious that it is in no way limited thereto and that it includes the means described as well as their combinations if these fall within the scope of the invention as defined in the claims.

[0072] In the claims, any reference sign in parentheses cannot be interpreted as a limitation of the claim.

Claims

1. Actuator (10, 100, 200, 300) for the actuation of at least one movable member of a motor vehicle transmission, said actuator comprising a housing (20) and a cover (30) defining an internal volume in which are received at least one electric motor (1) having a stator (2) and a rotor (3) mounted on a rotor shaft (4) extending along an axis X1, a motor pinion (5) fixed to the opposite end of the shaft (4) to the rotor (3), a circuit board (11) for supplying power to the stator (2) and for controlling the electric motor (1), a step-down mechanism (40) driven by the motor pinion (5), characterized in that the housing (20) or the cover (30) comprises an electrical connector (27) which incorporates a semipermeable membrane (53) allowing an exchange of gas between the inside of the actuator and the external surroundings.

2. Actuator according to Claim 1, characterized in that the housing (20) and the cover (30) are made of metal, preferably of aluminium.

3. Actuator according to either of Claims 1 and 2, characterized in that the electrical connector (27) is made of plastic.

4. Actuator according to one of the preceding claims, characterized in that the membrane (53) is clipped on the electrical connector (27) by way of a ring.

5. Actuator according to one of Claims 1 to 3, characterized in that the membrane (53) is adhesively bonded or welded on the electrical connector (27).

6. Actuator according to one of the preceding claims, characterized in that a seal (54) is positioned between the electrical connector (27) and the housing (20) or the cover (30), preferably an O-ring.

7. Actuator according to one of the preceding claims, characterized in that the electrical connector (27) is screwed or clipped on the housing (20) or the cover (30).

8. Actuator according to one of the preceding claims, characterized in that the housing (20) and the cover (30) each have guide means (24, 28, 32) for guiding the step-down mechanism (40).

9. Actuator according to one of the preceding claims, characterized in that the housing (20) comprises a peripheral groove (25) in which a seal (26) is disposed in order to ensure leaktightness between the housing (20) and the cover (30).

10. Actuator according to one of the preceding claims, characterized in that it is able to be fixed directly on the transmission of the vehicle and in that the outer surface of the cover (30) has a groove (33) in which a seal (34) is positioned in order to ensure leaktightness between the transmission and the cover (30) of the actuator.

11. Actuator according to one of the preceding claims, characterized in that it comprises at least one pin (8) able to be engaged in the movable member of the transmission.

12. Actuator according to Claim 11, characterized in that the step-down mechanism (40) comprises at least one gear wheel (43, 46) mounted on at least one shaft (44, 45) and is located kinematically between the motor pinion (5) and the pin (8).

13. Actuator according to Claim 12, characterized in that the step-down mechanism (40) comprises a stepped-pinion wheel (41, 42, 43) and a toothed-sector pinion (46).

14. Actuator according to one of the preceding claims, characterized in that it is configured to change gear ratios in a motor vehicle transmission, in particular a hybrid vehicle transmission.