ELECTRIC ACTUATOR

Description

TECHNICAL FIELD OF THE INVENTION

[0001] The invention relates to the field of electric actuators comprising the assembly, in a housing and a cover, of an electric motor, a printed circuit board carrying the electronic control components and a mechanical reducer. STATE OF PRIOR ART

[0002] Many electric actuators are already known in the prior art. For example, document WO2018 / 088356 describes an actuator consisting of: a housing with a motor housing and a gear housing, each having an opening on one side, and in which the motor housing and gear housing are assembled so that their respective openings face each other; a motor installed in the motor housing; and a gear installed in the gear housing and arranged to transmit the motor's rotation. The housing has a partition wall positioned between the motor and the gear. The gear is rotationally supported on both sides in the gear shaft direction by the gear housing and the partition wall.

[0003] According to this solution, the casing comprises a first and a second engine casing, open on one side, and a central casing positioned between these two casings. The housing sandwiches the central casing between the engine casing and the gear casing.

[0004] This solution involves providing a double seal, on the one hand between the central casing and the first engine casing, and on the other hand between the gear casing and the central casing.

[0005] US patent application US2018 / 062479 describes a modular vehicle motor component actuator comprising a first module including a motor, a printed circuit board, and a motor shaft. A second module includes a gear train and an output shaft. The first module is coupled to the second module in a relationship where the motor shaft extends into the second module and is coupled to the gear train in the second module. The first and second modules have respective openings and internal cavities communicating with each other. The first and second modules are coupled together in a relationship where the printed circuit board is installed between the motor in the first module and the gear train in the second module.

[0006] We also know of patent application DE4313782. It concerns a device for mounting controllers in a motor vehicle. The device allows several controllers to be mounted as needed in the same mounting location on a wall and extracts heat from them to maintain their operating temperature. According to the invention, this device comprises at least one cooling base made of a metal with high thermal conductivity and designed to close a window-shaped cutout in a wall intended for mounting the controller(s) and made of metal or plastic. The cooling base is designed as a flat element having an equipment mounting location on which at least one heat-emitting surface of a controller can be positioned and mounted in good thermal contact.The cooling base can cover a window-shaped cutout in the mounting wall, so that the cooling base extends over the cutout on one or both sides. It can also be die-cast directly into the window opening and made of highly conductive metal.

[0007] We also know of patent application WO2010 / 138455; it describes a brushless rotary actuator comprising a housing including a motor housing defining a cavity for a motor assembly and a cover defining a cavity for a gear assembly. The motor assembly includes a rotor and a stator having a plurality of coils. A clamp in the form of an annular plate sits against the coils to retain them on the stator. Fingers formed on the annular plate are housed in respective slots defined by respective coil terminals. A printed circuit board sits in the housing against an inner shoulder of the motor housing. A plate sits in the housing against a peripheral edge of the motor housing, spaced apart above the printed circuit board.

[0008] These designs, while compact and capable of producing high torques, lack the robustness to provide sufficient vibration resistance and lifespan. Indeed, endurance performance requires precise and controlled alignment and centering of the mechanical gearbox's guide elements, as well as efficient management of the heat dissipation generated by the electronic components and the motor. The designs described in these documents offer no solution for robust control of the gearbox's precise guidance (imperfect guidance, as it is only present on one side of the gears forming the gearbox, leading to detrimental overhangs; lack of precise centering between the housing and the cover forming the upper and lower guide elements of the gearbox, resulting in coaxiality and parallelism defects).These designs also fail to address thermal energy dissipation, as the electronic components on the printed circuit board lack any external thermal bridges to dissipate the heat they generate, leading to detrimental overheating. This results in mechanically weak solutions unsuitable for applications with high ambient operating temperatures and / or high operating loads.

[0009] There are solutions that resolve the disadvantages mentioned above, such as described in document WO2010138455, through the use of an intermediate plate located between the electric motor with its printed circuit board on one side and the mechanical reducer on the other.

[0010] This solution allows for the re-guidance of the mechanical gearbox shafts and also provides improved heat dissipation at the printed circuit board level due to its proximity to the board. This solution also incorporates a liquid cooling circuit that circulates around the periphery of the motor for better heat dissipation.

[0011] However, implementing this intermediate plate is not straightforward: firstly, it rests rigidly on the lid, but on the housing side, it rests on the very flexible printed circuit board; secondly, it lacks any centering elements to ensure proper guidance of the three components: housing, lid, and intermediate plate. Furthermore, the document cited above does not address the resulting hyperstatic mechanical situation caused by this bilateral support and the need to seal the actuator completely. DESCRIPTION OF THE INVENTION

[0012] The present invention aims to improve current solutions, in particular by proposing an efficient industrial solution enabling the viable centering and guidance of the three elements mentioned above.

[0013] The present invention also aims to provide a solution to the hyperstatic assembly described above, promoting the robustness of the actuator assembly.

[0014] The present invention also aims to improve the thermal behavior of the actuator, enabling its use in high-temperature environments (typically above 150°C).

[0015] More particularly the invention relates to an electric actuator having the technical characteristics stated in claim 1.

[0016] The electric actuator comprises a housing, an electric motor including a wound stator and a rotor mounted on a rotor shaft, a printed circuit board for powering said stator and controlling said motor, an intermediate plate, a mechanical reducer driven by said rotor and formed of toothed wheels mounted on shafts, a cover, two centering pins, said housing defining a first cavity in which said stator is housed, said housing serving to guide said rotor shaft on one end, said printed circuit board being housed in said first cavity above said stator, said intermediate plate being located above said printed circuit board, said cover defining a second cavity provided with means for guiding one end of said shafts of said mechanical reducer and being located above said intermediate plate, said intermediate plate having means for guiding the other end of said rotor shaft,and serving to guide the other ends of said axes of said mechanical reducer, characterized in that the first cavity of said housing has a first pair of centering holes receiving said two centering pins, the intermediate plate has a second pair of centering holes receiving said two centering pins, the cover has a third pair of centering holes receiving said two centering pins, the intermediate plate is in contact with said housing and the cover on bearing surfaces located around the centering holes, two of said first, second and third pairs of holes are composed of a cylindrical centering pin and a free-standing centering pin, the corresponding cylindrical centering pins and free-standing centering pins, the other of said first, second and third pairs of holes is composed of two cylindrical centering pins,said housing comprising a single sealing gasket positioned at the interface between the housing and the lid.

[0017] A "cylindrical centering device" is a positioning pin that creates a sliding pivot joint with two degrees of freedom (translation and rotation around one axis only).

[0018] , The term "unobstructed centering pin" refers to a positioning pin that creates a straight linear connection, with four degrees of freedom, or a point connection, with 5 degrees of freedom.

[0019] Thus, an actuator according to the invention will be able to solve the above problems, regardless of the element (cover, housing or intermediate plate) which has the two cylindrical centering devices.

[0020] Preferably, the housing comprises a housing perimeter having at least two initial mounting holes, and the cover comprises a cover perimeter having at least two secondary mounting holes, such that the cover and housing are secured by screwing using these initial and secondary holes. The housing and cover perimeters are not contiguous when the cover and housing are resting on the intermediate plate before screwing, and are resting and at least partially contiguous after screwing, so as to constrain and block the movement of the intermediate plate. The overconstraint problem described above is thus resolved to the advantage of the actuator and the retention of the intermediate plate.

[0021] In one embodiment, the cover forms a valve body.

[0022] Preferably, the various guide surfaces of said shafts and axes of the reducing gear train are made by the housing, the intermediate plate and the cover, said guide surfaces being ball bearings or plain bearings.

[0023] In one embodiment, the two centering pins and the intermediate plate form a single piece, in order to facilitate overall production and assembly.

[0024] In another embodiment, the housing is made by overmolding a plastic material and features two coaxial centering pins on one of the holes in the pair of centering holes: one cylindrical, the other open. This configuration allows for a single housing, regardless of the chosen mounting and assembly method for the actuator, by adjusting the length of the centering pin that engages this centering hole.

[0025] In another embodiment, the housing is made by overmolding a plastic material and it includes a connector integrated into the overmolding.

[0026] In order to withstand higher operating temperatures, in a particular embodiment, the printed circuit board has a first face hosting electronic components and a second face free of components, said first face facing the electric motor and the bottom of the housing, said second face facing the intermediate plate.

[0027] Then, advantageously and optionally, the first and second sides of the printed circuit board are covered at least partially with thermal paste, also being in contact at least partially with, respectively, the case and the intermediate plate.

[0028] In order to improve the performance of the actuator, in another embodiment the wound stator has stator teeth extended tangentially by magnetic field collectors, at least part of said teeth carry coils and are attached to the stator and said coils have a frustoconical shape.

[0029] In this embodiment, in another variant of the embodiment, each stator tooth carrying a coil has, with two adjacent teeth, a W shape, the outer sides of the frustoconical coil being parallel to the inner sides of said adjacent teeth.

[0030] To optimize the performance of this embodiment, if D denotes the number of stator teeth and GAP denotes the tangential distance between the field collectors between two adjacent teeth, the following relationship will be preferred: GAP est égal à 360 / 8 × D ± 5 % .

[0031] Still within this same embodiment, to optimize performance, if E denotes the radial thickness of the rotor magnet, if EP1 denotes the minimum radial thickness at the end of the field collector and EP2 denotes the maximum radial thickness at the origin of the field collector, the following relationship will be preferred: EP 2 ≥ 0.75 xE et EP 1 < EP 2 .

[0032] Finally, in an effort to simplify the actuator's electrical mechanism and improve performance, the rotor incorporates a permanent magnet partially overmolded with injected plastic. This overmolding partially encloses the rotor shaft and forms a plane orthogonal to the shaft, on which a sensor magnet is positioned. In an alternative embodiment, the overmolded magnet directly forms a sensor magnet without the addition of a separate magnet. BRIEF DESCRIPTION OF THE FIGURES

[0033] Other features and advantages of the invention will become apparent from the following detailed examples of embodiments, with reference to the attached figures which respectively represent: there figure 1 , an exploded perspective view of a first actuator according to a first embodiment, the figure 2 , an exploded perspective view of the first actuator according to a second embodiment, the figure 3 , an exploded perspective view of the first actuator according to a third embodiment, the figure 4 , an exploded perspective view of a second actuator according to a first embodiment, the figure 5 , an exploded perspective view of the second actuator according to a second embodiment, the figure 6 , an exploded perspective view of the second actuator according to a third embodiment, the figure 7 , a first detailed and cross-sectional view of the second actuator according to the second embodiment, the figure 8 , a second detailed and cross-sectional view of the second actuator according to the second embodiment, the figure 9 , a perspective and cross-sectional view of the second actuator according to the second embodiment, the Figure 10 , an overview perspective view of the second actuator, the figure 11 , a perspective and partial cross-sectional view of the actuator of the Figure 10 , there figure 12 , an isolated overview view of a housing and an intermediate plate of the second actuator, the figure 13 , a perspective and partial cross-sectional view of the entire figure 12 , there figure 14 , a partial cross-sectional view of the second actuator in one embodiment variant, the figure 15 , an overview perspective view of the first actuator in one embodiment variant, the figure 16 , a perspective and partial cross-sectional view of the actuator of the figure 15 , there figure 17, an isolated overview view of a housing and an intermediate plate of the first actuator in one embodiment variant, the figure 18 , a perspective and partial cross-sectional view of the entire figure 17 , THE figures 19a and 19b , two partial cross-sectional views from two different viewing angles of the first actuator in one embodiment variant, the Figure 20 , an isolated, cross-sectional view of an electric motor of the second actuator, the figure 21 , an isolated view of an electric motor stator integrated into the first or second actuator in one embodiment, the figure 22 , an isolated and partially exploded view of the stator of the figure 21 , there figure 23 , an isolated, cross-sectional view of the stator of the figure 21 , there figure 24 , an isolated, longitudinal cross-sectional view of an electric motor rotor in one embodiment variant, the figure 25, a partial cross-sectional view of an actuator according to an alternative embodiment of the mechanical reducer, the figure 26 , an isolated view of an alternative embodiment of an electric motor rotor that can be used in an actuator according to the present invention, the Figures 27 And 28 , two partial cross-sectional views showing alternative embodiments of the stators of an electric motor that can be used in an actuator according to the present invention, the figure 29 , an exploded perspective view of an actuator according to an alternative embodiment, the figure 30 , a partial cross-sectional view of the actuator of the figure 29 . DETAILED DESCRIPTION OF A FIRST ACTUATOR

[0034] In figure 1A first embodiment of an actuator (1) according to the invention is presented. Generally, and common to all embodiments covered by the invention, the actuator (1) is formed by three main parts: a housing (2), an intermediate plate (3), and a cover (4). This figure also shows... figure 1 as well as certain other figures, fixing screws (5) and a sealing gasket (6) whose positioning will be explained later. This gasket (6) is the only gasket ensuring a seal between the housing and the cover, whereas in prior art solutions, and in particular patent WO2018 / 088356, it is necessary to provide two sealing gaskets.

[0035] This figure 1This shows a first example of an actuator in which the housing (2) is made of an injection-molded plastic. This housing (2) serves, in particular, to accommodate an electric motor (not visible here), which will be detailed later, by overmolding the motor's stator with the aforementioned plastic. The cover (4) is designed to house, among other things, a mechanical gearbox (not visible here), which will be detailed later. The intermediate plate (3) guides the rotating elements of the mechanical gearbox while also providing the mechanical connection between the electric motor's rotor and the gearbox. The sealing gasket (6) is positioned at the interface between the housing (2) and the cover (4) to achieve a seal by axial compression during assembly.The fixing screws (5) are intended to fix the housing (2) to the cover (4) at the threaded holes (11) by clamping the intermediate plate as will be explained later. The threaded holes (11) can also be blind holes into which self-tapping screws are screwed.

[0036] The support of the intermediate plate is located - only - around the centering holes receiving the pins (8a, 8b), which notably allows a single sealing gasket to be placed at the interface between the cover and the housing and improves the sealing compared to the solution proposed in the prior art document WO2018 / 088356.

[0037] In a first embodiment of the invention related to this first actuator (1), the plastic housing (2) has, not visible here, a first pair of holes consisting of a cylindrical centering pin and a free centering pin; the intermediate plate (3) has a second pair of holes in the form of two drillings, or cylindrical centering pins (7a, 7b) which accommodate two centering pins (8a, 8b).

[0038] These two centering pins (8a, 8b) can be: ∘ Either separated from the intermediate plate and introduced downstream of the plate manufacturing process ∘ Or integrated into the intermediate plate and thus form a single piece with the plate, forming a single piece.

[0039] The cover (4) has a third pair of holes formed by a cylindrical centering feature (9a) and a recessed centering feature (9c), here in the form of an oblong hole. The clever use of only two pins and three pairs of holes on the three main elements mentioned above—two pairs of holes forming cylindrical and recessed centering features, and the other pair forming two cylindrical centering features, with the corresponding cylindrical and recessed centering features—ensures optimal relative positioning of these three elements. Positioning the pins (8a, 8b) on the intermediate plate (3) within cylindrical centering features (7a, 7b) is the preferred configuration because it allows for a single type of intermediate plate (3) compatible with several housing (2) and / or cover (4) shapes.

[0040] There figure 2This is a second embodiment of the first actuator, differing from the first embodiment in that the centering pins (8a, 8b) are positioned in the pair of holes in the cover (4), forming two cylindrical centering points (9a, 9b), and in that the intermediate plate (3) includes a pair of holes forming a cylindrical centering point (7a) and a free-standing centering point (7c). As with the first embodiment, the plastic housing (2), not shown here, has a pair of holes consisting of a cylindrical centering point and a free-standing centering point. This is an alternative embodiment to the first.

[0041] A third alternative implementation of this first actuator is presented in figure 3This version differs from the first and second versions in that the centering pins (8a, 8b) are positioned in the pair of holes in the plastic housing (2), forming two cylindrical centering points (12a, 12b), and in that the intermediate plate (3) includes a pair of holes forming a cylindrical centering point (7a) and a free-standing centering point (7c). As with the first embodiment, the cover (4) has, though not visible here, a pair of holes consisting of a cylindrical centering point and a free-standing centering point. DETAILED DESCRIPTION OF A SECOND ACTUATOR

[0042] THE figures 4 , 5 And 6 represent, for a second type of actuator, the equivalents to Figures 1 , 2 And 3Regarding the relative positioning of the various pairs of holes and cylindrical and exposed centering pins, the second actuator differs from the first in that the housing (2) is made of a metallic material, for example, cast or injected aluminum, into which the stator of an electric motor is intended to be fixed, for example, by screwing. This design allows for a more robust actuator, notably enabling better dissipation of the thermal energy released by the printed circuit board (not shown in these figures) carrying the motor's power supply and control components, and by the electric motor itself. The second actuator also differs from the first in that the mounting screws (5) are designed to be screwed into the housing (2) instead of the cover (4). Finally, it differs from the first in that the sealing gasket (6) provides a seal by radial compression of the gasket (6). Similar to the explanations of the Figures 1 , 2And 3 In a first embodiment of the invention related to this second actuator in figure 4 , the metal casing (2) has, not visible here, a first pair of holes consisting of a cylindrical centering pin and a freestanding centering pin; the intermediate plate (3) has a second pair of holes in the form of two cylindrical centering pins (7a, 7b) which accommodate two centering pins (8a, 8b) and the cover (4) has a third pair of holes consisting of a cylindrical centering pin (9a) and a freestanding centering pin (9c) here in the form of an oblong hole.

[0043] There figure 5This is a second embodiment of the second actuator, which differs from the first embodiment in that the centering pins (8a, 8b) are positioned in the pair of holes in the cover (4), forming two cylindrical centering points (9a, 9b), and in that the intermediate plate (3) includes a pair of holes forming a cylindrical centering point (7a) and a free-standing centering point (7c). As with the first embodiment, the metal housing (2), not visible here, has a pair of holes consisting of a cylindrical centering point and a free-standing centering point. This is an alternative embodiment to the first.

[0044] A third alternative implementation of this second actuator is presented in figure 6This version differs from the first and second versions in that the centering pins (8a, 8b) are positioned in the pair of holes in the metal housing (2), forming two cylindrical centering points (12a, 12b), and in that the intermediate plate (3) includes a pair of holes forming a cylindrical centering point (7a) and a free-standing centering point (7c). As with the first embodiment, the cover (4) has, though not visible here, a pair of holes consisting of a cylindrical centering point and a free-standing centering point. DETAILED DESCRIPTION OF MAIN FUNCTIONS

[0045] THE figures 7 , 8 And 9 These are detailed or cross-sectional views of the second embodiment of the second actuator. Nevertheless, the descriptions and characteristics of the elements and their related functions below are entirely applicable. mutatis mutandis, to the other embodiments described above.

[0046] THE figures 7 And 8These are isolated views at the level of the centering devices, respectively exposed (7c, 12c) and cylindrical (7a, 12a) formed on the intermediate plate (3) and the housing (2), allowing the mounting, guidance, and locking of the latter on the centering pins (8a, 8b) placed respectively in the cylindrical centering devices (9a, 9b) of the cover (4). The intermediate plate (3) is held axially between the housing (2) and the cover (4) by the constraint exerted by the latter at two axial bearing surfaces (13, 14) around the centering holes between, respectively, on the one hand, the housing (2) and the intermediate plate (3) and on the other hand, between the intermediate plate (3) and the cover (4). With reference to the figure 9The intermediate plate (3) is installed in a first cavity (15) of the housing (2). Thus, when the cover (4) is screwed onto the housing (2) – or vice versa for the first actuator – the periphery (16) of the housing (2) comes into contact with the periphery (17) of the cover (4), initially without contact, then, due to the elasticity of the components involved, with contact as the screws are tightened. The resulting statically indeterminate mechanical situation at the constrained joint between the housing (2), intermediate plate (3), and cover (4) ensures that the intermediate plate (3) remains perfectly in place via the elasticity of the periphery (17). The screwed-on actuator (1) is thus visible. figure 9 .

[0047] With reference to the figure 8The actuator's sealing is ensured by the seal (6) positioned around a first radial surface (131) of the cover (4) and inside a second radial surface (133) of the housing (2), and between a first axial surface (132) of the cover (4) and a second axial surface (134) of the housing (2), the terms "axial" and "radial" being interpreted with respect to the motor's output axis. In this embodiment of the actuator, the radial seal is achieved by the compression of the seal (6) between these first and second surfaces (131, 133).

[0048] THE Figures 10 And 11The diagrams show overall views, respectively full and partial cross-section, of the second actuator in a first, so-called "complete" variant where this actuator can be positioned at an external component (not shown) via its output shaft (18). The actuator (1) is supplied with electrical voltage and a positioning signal via a connector (19). The housing (2) contains, within its cavity (15), an electric motor consisting of a stator (20) and a rotor (not visible), as well as a printed circuit board (22) electrically connected to the stator winding (20) by a press-fit connector and mechanically screwed into the cavity (15) of the housing (2). The housing (2) contains a ball bearing (23a) used to guide the rotor shaft (not visible here). A mechanical reducer (24), positioned in the cover (4), is driven by the rotor and consists of gears mounted on shafts (not visible).The cover (4) defines a second cavity (25) in which the shafts of the mechanical reducer carrying a toothed wheel (45a) are mounted and guided at one end by means of bearings (23c-23d). The intermediate plate (3) serves to guide one end of the rotor shaft (29), not visible here but shown in the figure. figure 12 , thanks to the bearing (23b), not visible here but shown in figure 12and serves to guide the other ends of the shafts of the mechanical reducer (24) by means of bearings (23c, 23e). In this embodiment, without limitation, a torsion spring (26) is also installed in the cover (4), applying a torque to the output shaft (18) to return the moving assembly to a predefined position when the electric motor power supply is switched off or fails. It should also be noted that the various bearings (23a, 23b, 23c, 23d, 23e, 23g, 23h) shown in all the figures can be replaced by plain bearings or any other guiding element without departing from the invention. DETAILED DESCRIPTION OF ALTERNATIVE IMPLEMENTATION METHODS

[0049] THE Figures 12 and 13present the second actuator in a second variant called the "half-actuator" where a first assembly (27) of the actuator is formed by assembling the housing (2) and the intermediate plate (3) according to the third embodiment described above. The complete actuator is then made by assembling this first assembly (27) onto the cover (4) as shown in figure 14 In this particular embodiment, the cover (4) directly integrates the control element. As an example given in this figure 14The cover (4) forms a valve body (28) and the output shaft (18) carries a butterfly-type flap (30), the whole forming an air intake valve for an internal combustion engine. During the mounting of the actuator (1), the first assembly (27) is therefore mounted directly onto the valve body (28) forming the cover (4) and the mechanical reducer (24) engages, through a slot (31) in the intermediate plate (3), the shaft (29) of the rotor (21).

[0050] There figure 13 presents a partial cross-sectional view of the first assembly (27) which allows visualization of the printed circuit board (22) which includes all the electronic components used for powering and controlling the actuator motor (1), as well as the ball bearing (23b) used to guide the shaft (29) of the rotor (21) whose outer ring is fitted in a housing of the intermediate plate (3).

[0051] THE Figures 15 and 16The first actuator is shown in a "complete" variant where the connector (19) is overmolded in plastic with the housing body (2). Its orientation is radial, but it can also be axial above the housing (2). The opening (32) visible in the cover (4) is an inlet for a heat transfer fluid used to cool the actuator (1) when it is used under high load and in a high-temperature environment, for example, near an internal combustion engine.

[0052] There figure 16is a partial cross-sectional view showing the relative positioning of the bearings (23a, 23d) and the stator (20) within the housing (2), separated by the intermediate plate (3) from the mechanical reducer (24) and the torsion spring (26). At the housing (2), this variant also features two coaxial centering devices, one cylindrical (12b) and the other exposed (12c). This combined design allows for the use of a single type of overmolding compatible with the three different embodiments described in Figures 1 , 2 And 3 , in conjunction with the height of the centering pin (8b) used. Here in figure 16 , the elements of the complete actuator are mounted according to the first embodiment, the centering pin (8b) is a short pin which engages in the centering device (12c) of the housing (2).

[0053] THE figures 17 And 18present a "half-actuator" variant of the first actuator formed from a first assembly (27) comprising the housing (2) and the intermediate plate (3). In this variant, the centering pin (8b) is a long pin which engages in the cylindrical centering pin (12b) of the housing (2), the assembly being according to the third embodiment described above.

[0054] THE figures 19a and 19bThey present a variant embodiment of the actuators, here based on the first actuator although this is not a limitation, at the level of the printed circuit board (22) and promoting the heat dissipation emitted by the printed circuit board (22). In this variant, the printed circuit board (22) carries all the components on only one of its faces, this first face (33) being the one oriented axially towards the electric motor and the bottom of the housing (2). This embodiment allows, on the one hand, the second face (34) of the printed circuit board, axially opposite to the first face (33), to be attached to the intermediate plate (3), which will promote, by conduction – the intermediate plate being chosen to be made of a thermally conductive material – the dissipation of heat through the metallic part of the cover (4).On the other hand, it is possible to use thermal paste – in a dot cloud pattern on the printed circuit board (22) – on both sides of the printed circuit board (22), this paste being compressed between the housing (2) and the intermediate plate (3) on one side and the cover (4) and the intermediate plate (3) on the other, in order to further promote this thermal conduction towards the most conductive parts of the actuator (1). On these. figures 19a and 19b The output gear (45c) of the reducer is visible, as well as a torsion spring (26) which acts on this output gear to return the output shaft (18) to a determined position when the motor is switched off.

[0055] On the Figure 20Figure 1, representing a detailed cross-sectional view of the electric motor, shows the use of a magnet (35) on the rotor (21), the length of which can be varied to increase motor performance. Indeed, for a given axial height of the stator (20), the axial height of the magnet (35) on the rotor (21) influences the torque produced at constant electrical power. This embodiment is simply a variation of the more conventional case where the height of the magnet (35) is equivalent to that of the stator (20).

[0056] THE figures 21, 22 And 23They show an example of an electric motor stator (20) that can be used by the first or second actuator or any other actuator not shown here but covered by the present invention. In particular, this stator (20) proposes to solve the performance limitation problems of actuators, notably the limitations induced by torque oscillation during electrical commutations and by magnetostatic torque. This stator (20) is also associated with a solution for optimizing the copper filling of the coil.

[0057] For this stator (20), the set of stator teeth (36a, 36b) have field collectors (37) extending tangentially to the rotor's axis of rotation. To this end, the teeth (36a) not receiving a coil are integral with the rest of the stator iron circuit, which is constructed as a stack of laminations, while the teeth (36b) receiving a coil (38) are independent and attached to the iron circuit. In order to optimize the actuator's performance, particularly torque oscillation and magnetostatic torque, the field collectors have the following geometric characteristics in an axial plane: relative to a quantity D representing the number of teeth in the stator, the following formula is recommended: GAP ≈ 360 / (8xD), where GAP represents the tangential distance separating the commutators of two adjacent teeth; relative to the quantity E, the radial thickness of the visible rotor magnet. Figure 20, we recommend: EP2 ≥ 0.75xE and EP1 < EP2, EP1 representing the minimum radial thickness at the end of the field collector (37), EP2 representing the maximum radial thickness at the start of the field collector (37).

[0058] The teeth (36b) have a central section allowing the coil (38) to be inserted by translation from the outside / rear. Similarly, the connection means (mechanical and magnetic) between the added tooth (36b) and the stator circuit is contained within the minimum cross-section of the coil (38). A solution of winding directly onto the tooth can also be considered, while retaining the possibility of removing the coil (38) and recovering the tooth (36b) in case of a manufacturing defect. The teeth (36b), thus equipped with their coil (38), are attached and connected to the stator (20) in an axial direction relative to the axis of rotation of the rotor (21). The connection means must ensure good mechanical retention of the tooth (36b) on the stator (20) and must also provide a high-quality magnetic seal to prevent the introduction of parasitic magnetic permeance that would degrade performance.A dovetail joint is particularly suitable in this case, offering an economical solution, simple shapes with precise tolerances, and good mechanical retention. The coil body (39) has recesses (40), here three in number (though this is not a limitation), on either side of the coils (38) for the mounting supports on the tooth (36b) during assembly. Since the stator circuit exhibits a W-shaped periodicity over a 120° angular sector, the coil (38) has a shape complementary to this W in order to maximize the copper fill of the available cross-section. The resulting winding shape is approximately frustoconical. The proposed conical solution allows for increased torque without significantly altering the coil impedance through optimized filling of the interdental notch.

[0059] To manufacture and industrialize this particular type of winding, the coil body (39) has a central, peripheral sawtooth section. The angle of the teeth (43) is equivalent to the angle of the winding cone (approximately 7° in this non-limiting example). The number of teeth (43) is two or more, and the teeth (43) are not necessarily of identical length. To ensure good cohesion of the assembled stator (20) and to improve its thermal behavior, it will ideally, but not exclusively, be overmolded with a thermoplastic material localized at each tooth (36b) / coil (38) pair. Alternatively, each tooth (36b) can be overmolded independently before being attached and fixed to the stator.

[0060] There figure 24This shows an example of an embodiment of the rotor (21) of an electric machine, which can be advantageously used in the present invention. This rotor (21) is composed of a permanent magnet (35) partially overmolded with injected plastic, a shaft (29) also overmolded with the same plastic, and a sensor magnet (41) positioned on a plane (42) orthogonal to the shaft (29) generated by the plastic. The rotor is shown here with the bearings (23a, 23b) described above. This embodiment is particularly advantageous because it avoids bonding the magnet (35) to a yoke, which has problematic mechanical strength at high temperatures. It also allows for improved dynamic behavior through lower inductance, firstly due to the absence of a ferromagnetic yoke, and secondly due to lower inertia resulting from the low density of the plastic material, which is the predominant material by volume.In addition, besides a simplification of the rotor assembly (21) which no longer requires gluing, the magnetostatic torque and the friction torque are reduced as are the radial forces induced on the rotor.

[0061] There figure 25 is a partial cross-sectional view that allows observation of the mechanical reducer (24). This mechanical reducer can consist of several stages. The embodiments shown in the previous figures show two reduction stages, whereas the example of this figure 25 This demonstrates three reduction stages. The rotor shaft (29), forming a pinion at its end, drives the intermediate gear (45a) carried by a shaft (46a) guided by two bearings (23g, 23h), which in turn drives the toothed gear (45b) carried by the shaft (46b). The toothed gear (45b) finally drives the output gear (45c). As in all the embodiments presented in this text, all the shafts (46a, 46b) or shaft (18) carrying the toothed gears (45a, 45b, 45c) bear on the cover (2) at one end and on the intermediate plate (3) at the other.

[0062] There figure 26 This shows a rotor (21) in an alternative embodiment. In previous embodiments, this rotor (21) has a cylindrical magnet, either supported or not by a ferromagnetic yoke. In this present embodiment, the rotor (21) consists of alternating prismatic magnets (35a) magnetized tangentially, inserted between ferromagnetic poles (44), according to a radial internal magnet configuration (spoke-type). The poles (44) have a pseudo-circular shape designed to optimize torque with and without current.

[0063] THE figures 27 And 28 show two examples of alternative embodiments of the stator (21) of the electric motor. figure 27 The stator has three coils (38) grouped in an angular sector close to 120° and the stator teeth (36a) have alternately narrow and wide angular widths as described for example in application FR2919441. figure 28 , the stator has three coils (38) grouped in an angular sector close to 120° and the stator teeth (36a) have identical angular widths as described for example in application FR2994353.

[0064] THE figures 29 And 30represent an alternative embodiment of an actuator according to the invention. The actuator (1) comprises a housing (2) receiving the stator (20) of an electric motor, a cover (4) receiving a mechanical reducer, an intermediate plate (3) inside the actuator (1), and a printed circuit board (22). The centering pins (8a, 8b) allow the positioning of the housing (2), cover (4), and intermediate plate (3) with the various centering devices: two cylindrical centering devices (not visible) formed with the cover (4), a freestanding centering device (7c), and a cylindrical centering device (7a) present at the intermediate plate (3), corresponding respectively to the freestanding centering device (12c) and cylindrical centering device (12a) present at the housing (2). The fixing screws (5) are intended to fix the cover (4) onto said housing (2) for closure. A connector (19) is fixed to the cover (4).

[0065] Positioned axially between the intermediate plate (3) and the stator (20) is the printed circuit board (22), to which are connected, on the side facing the housing (2) – the electrical coils of the stator (20) – and, on the other side facing the cover (4) – the traces of the connector (19), in order to provide power to the actuator (1) and communication with it. The printed circuit board is electrically connected to the stator winding (20) by a press-fit connector as illustrated in the figure 30 On the lid-side face (4), the printed circuit board (22) is attached to the intermediate plate (3), which facilitates heat dissipation by conduction. The intermediate plate (3) is cut so that it does not cover the printed circuit board at the electrical connection point.

Claims

1. Electric actuator (1) comprising - a housing (2), - an electric motor comprising a wound stator (20) and a rotor (21) mounted on a rotor shaft (29), - a printed circuit (22) serving to supply said stator (20) and to control said motor, - an intermediate plate (3), - a mechanical gearbox (24) driven by said rotor (21) and formed by gear wheels (45a, 45b, 45c) mounted on axes (46a, 46b, 46c), - a cover (4), - two centring pins (8a, 8b), said housing (2) defining a first cavity (15) in which said stator (20) is housed, and comprising means for guiding said rotor shaft (29) on a first end, said printed circuit (22) being located in said first cavity (15) above said stator (20), said intermediate plate (3) being located above said printed circuit (22), said cover (4) defining a second cavity (25) having means for guiding the ends of said axes (46a, 46b, 46c) of said mechanical gearbox (24), said cover (4) being located above said intermediate plate (3), said intermediate plate (3) serving to guide the other end of said rotor shaft (29), and serving to guide the other ends of said axes (46a, 46b, 46c) of said mechanical gearbox (24), characterised in that • the first cavity (15) of said housing (2) has a first pair of centring holes receiving said two centring pins (8a, 8b), • said intermediate plate (3) has a second pair of centring holes receiving said two centring pins (8a, 8b), • said cover (4) has a third pair of centring holes receiving said two centring pins (8a, 8b), • said intermediate plate (3) is in contact with said housing (2) and said cover (4) on bearing surfaces (13, 14) located around the centring holes, • two of said first, second and third pairs of holes are composed of: ∘ a cylindrical centring device (7a, 9a, 12a) achieving a sliding pivot connection with two degrees of freedom, in translation and rotation according to only one axis and ∘ a clear centring device (7c, 9c, 12c), achieving a straight linear connection with four degrees of freedom, or a connection at one point with 5 degrees of freedom. • the other of said first, second and third pairs of holes is comprised of two cylindrical centring devices (7a, 7b, 9a, 9b, 12a, 12b) making a sliding pivot connection with two degrees of freedom, in translation and rotation along only one axis • said housing comprising one single sealing gasket (6) positioned at the interface between the housing (2) and the cover (4).

2. Electric actuator according to claim 1, characterised in that said housing (2) comprises a peripheral area (16) having at least two first fastening piercings (11) and in that said cover (4) comprises a peripheral area (17) having at least two second fastening piercings (11) so that the fastening of said cover (4) and of said housing (2) is carried out by screwing using said first and second piercings (11), said peripheral areas (16, 17) not being contiguous when said cover (4) and said housing (2) are bearing on said intermediate plate (3) before screwing and being bearing and being at least partially contiguous after screwing, so as to constrain and block the movement of said intermediate plate (3).

3. Electric actuator according to claim 1, characterised in that the cover (4) forms a valve body (28).

4. Electric actuator according to claim 1, characterised in that the different guide surfaces of said rotor shaft (29) and of said axes (46a, 46b, 46c) of the mechanical gearbox (24) are made in the housing (2), the intermediate plate (3) and the cover (4), all of said guide surfaces being ball bearings (23a, 23b, 23c, 23d) or plain bearings.

5. Electric actuator according to claim 1, characterised in that said two centring pins (8a, 8b) and said intermediate plate (3) form one and the same part.

6. Electric actuator according to claim 1, characterised in that the housing (2) is made by overmoulding a plastic material and has two coaxial centring devices on one of the holes of said pair of centring holes, one being cylindrical (12b), the other being clear (12c).

7. Electric actuator according to claim 1, characterised in that the housing (2) is made by overmoulding a plastic material and in that it comprises a connector (19) integrated into the overmoulding.

8. Electric actuator according to claim 1, characterised in that the printed circuit (22) has a first face (33) accommodating electronic components and a second (34) free face of components, said first face (33) facing the electric motor and the bottom of the housing (2), said second face (34) facing the intermediate plate (3).

9. Electric actuator according to the preceding claim, characterised in that the first (33) and second (34) faces of the printed circuit (22) are at least partially covered with a thermal paste also being at least partially in contact with, respectively, the housing and the intermediate plate (3).

10. Electric actuator according to claim 1, characterised in that the wound stator (20) has stator teeth (36a, 36b) tangentially extended by magnetic field collectors (37), in that at least some of said teeth (36b) carry coils (38) and are attached on the stator (20) and in that said coils (38) have a frustoconical shape.

11. Electric actuator according to the preceding claim characterised in that each stator tooth (36b) carrying a coil (38) has, with two adjacent teeth (36a), a W-shape, the outer flanks of the conical coil (38) being parallel to the inner flanks of said adjacent teeth (36a).

12. Electric actuator according to claim 10, characterised in that, D denotes the number of stator teeth (36a, 36b) and GAP denotes the tangential distance between the field collectors (37) between two adjacent teeth (36a), with GAP = 360 / 8 × D ± 5 %13. Electric actuator according to claim 10, characterised in that said rotor (21) has a magnet (35), in that E denotes the radial thickness of said magnet (35)- EP1 denotes the minimum radial thickness at the end of the field collector (37) and EP2 denotes the maximum radial thickness at the origin of the field collector (37), with EP 2 ≥ 0 , 75 × E and EP 1 < EP 2 .

14. Electric actuator according to claim 1, characterised in that the rotor (21) comprises a permanent magnet (35) partially overmoulded by an injected plastic material, this overmoulding partially encompassing the rotor shaft (29) and forming a plane (42), orthogonal to the shaft (29), on which a sensor magnet (41) is positioned.

15. Electric actuator according to claim 1, characterised in that the rotor (21) comprises a permanent magnet (35) partially overmoulded by an injected plastic material, this overmoulding partially encompassing the rotor shaft (29) and forming a sensor magnet (41).