Electric actuator

Abstract

The present invention relates to an electric actuator, comprising: a housing (2); an electric motor including a wound stator and a rotor mounted on a shaft; a printed circuit for powering the stator; an intermediate plate (3); a mechanical reduction gear driven by the rotor and including a toothed gear mounted on a shaft body; a cover (4); and two centering pins (8a, 8b). The motor is received in a cavity of the housing (2) which guides one end of the shaft. The printed circuit is located above the stator. The intermediate plate (3) is located above the printed circuit. The cover (4) is located above the intermediate plate (3). The reduction gear is received in a cavity of the cover (4) which guides one end of each shaft body. The intermediate plate (3) guides the other ends of the shaft and the shaft body. Three pairs of centering holes (7, 9, 12) receive the centering pins (8). The housing (2) includes a single sealing gasket (6) positioned at the interface between the housing (2) and the cover (4).

Description

Technical Field

[0001] The present invention relates to the field of electric actuators, which include, in a housing and a cover, a component of an electric motor, a printed circuit carrying electronic control components, and a mechanical reduction gear. Background Art

[0002] In the prior art, numerous electric actuators are already known. For example, document WO2018 / 088356 describes an actuator provided with: a housing having a motor housing and a gearbox, each having an opening on one side, and wherein the motor housing and the gearbox are assembled with each other such that the corresponding openings face each other; a motor mounted in the motor housing; and a gear mounted in the gearbox and arranged to transmit the rotation of the motor. The housing has a partition wall provided between the motor and the gear. Both sides of the gear are rotatably supported by the gearbox and the partition wall in the gear axis direction.

[0003] According to this solution, the housing includes a first and a second motor housing open on one side and a central housing provided between the two housings. The outer housing sandwiches the central housing between the motor housing and the gearbox.

[0004] This solution involves providing a double seal on the one hand between the central housing and the first motor housing and on the other hand between the gearbox and the central housing.

[0005] Furthermore, the known patent applications US2018 / 062479, DE4313782, and WO2010 / 138455 describe the construction of an actuator that includes a printed circuit positioned between an electric motor and a mechanical reduction gear.

[0006] Although these embodiments are compact and capable of generating high torque, they lack robustness to provide sufficient vibration resistance and service life performance. In fact, durability performance requires alignment of the guiding elements of the mechanical reduction gear, precise and controlled centering, and efficient management of the dissipation of the heat energy generated at the electronic components and the motor. The embodiments claimed in these documents do not provide any solution for the robust control of the precise guidance of the reduction gear (imperfect guidance because it only exists on one side of the wheels forming the reduction gear, contributing to harmful overhang, lack of precise centering between the housing and the cover of the upper and lower guiding elements forming the reduction gear, promoting coaxiality and parallelism defects). These embodiments also do not provide a solution for dissipating heat energy because the electronic components present on the printed circuit do not have a thermal bridge to the outside to dissipate the heat energy they generate, contributing to harmful heating. This results in a mechanically less robust solution that cannot address applications with high ambient operating temperatures and / or high operating loads.

[0007] There are solutions to address the above drawbacks, as described for example in document WO2010138455, which is attributed to the use of an intermediate plate located between on the one hand an electric motor having its printed circuit and on the other hand a mechanical reduction gear.

[0008] This solution makes it possible to recover the shaft guiding the mechanical reduction gear and also allows for improved heat dissipation at the printed circuit due to its proximity to the printed circuit. This solution also provides a liquid cooling circuit that circulates near the periphery of the motor in order to better discharge the thermal energy.

[0009] However, this intermediate plate is not easy to implement: on the one hand it has a rigid support on the cover, but it rests on the housing side on the less rigid printed circuit, and on the other hand it does not contain any centering elements allowing for the correct guiding of the three elements of the housing, cover, and intermediate plate. Additionally, the above-cited document does not provide a solution to the hyperstatic mechanical situation resulting from this bilateral support and the need to seal the actuator in a hermetic manner. Summary of the Invention

[0010] The object of the present invention is to improve the current solution, and in particular to propose an effective industrial solution that allows for the feasible centering and guiding of the above three elements.

[0011] Another object of the present invention is to provide a solution to the above hyperstatic assembly, thereby contributing to the robustness of the actuator assembly.

[0012] Another object of the present invention is to improve the thermal behavior of the actuator, thereby allowing it to be used in an environment heated to a high temperature (usually greater than 150 °C).

[0013] More specifically, the present invention relates to an electric actuator, comprising: a housing; an electric motor including a wound stator and a rotor mounted on a rotor shaft; a printed circuit for powering the stator and controlling the motor; an intermediate plate; a mechanical reduction gear driven by the rotor and formed by a toothed gear mounted on a shaft body; a cover; two centering pins, wherein the housing defines a first cavity for receiving the stator, the housing is used to guide the rotor shaft at a first end, the printed circuit is received above the stator in the first cavity, the intermediate plate is located above the printed circuit, the cover defines a second cavity provided with means for guiding one end of the shaft body of the mechanical reduction gear and is located above the intermediate plate, the intermediate plate has guiding means for guiding the other end of the rotor shaft and for guiding the other end of the shaft body of the mechanical reduction gear, and is characterized in that a first pair of centering holes for receiving the two centering pins is present in the first cavity of the housing, a second pair of centering holes for receiving the two centering pins is present in the intermediate plate, a third pair of centering holes for receiving the two centering pins is present in the cover, the intermediate plate contacts the housing and the cover on a support surface around the centering holes, two of the first, second and third pairs of holes are composed of a cylindrical centering device and a clearance centering device, the cylindrical centering device and the corresponding clearance centering device, and the other of the first, second and third pairs of holes is composed of two cylindrical centering devices, and the housing includes a single sealing gasket positioned at the interface between the housing and the cover.

[0014] The "cylindrical centering device" means a positioning pin that generates a sliding pivot connection with two degrees of freedom (translation and rotation only along one axis).

[0015] The term "clear centering device" means a positioning pin that generates a linear linear connection with four degrees of freedom or a point connection with five degrees of freedom.

[0016] Therefore, the actuator according to the present invention will be able to solve the above problems regardless of the element (cover, housing or intermediate plate) having two cylindrical centering devices.

[0017] Preferably, the housing includes a housing perimeter having at least two first attachment drill holes, and the cover includes a cover perimeter having at least two second attachment drill holes, such that the attachment of the cover and the housing is performed by means of a threaded connection through the first and second drill holes. The housing and cover perimeters are discontinuous when the cover and the housing rest on the intermediate plate before the threaded connection, and are supported and at least partially continuous after the threaded connection to constrain and block the movement of the intermediate plate. Thus, the above-mentioned hyperstatic problem is turned into an advantage for the maintenance of the actuator and the intermediate plate.

[0018] In a variant embodiment, the cover forms the valve body.

[0019] Preferably, different guiding surfaces of the shaft and the shaft body of the reduction gear train are generated by the housing, the intermediate plate, and the cover, and the guiding surfaces are ball bearings or sliding bearings.

[0020] In a variant embodiment, the two centering pins and the intermediate plate form a single part to facilitate overall manufacturing and assembly.

[0021] In another variant embodiment, the housing is manufactured by overmolding a plastic material and has two coaxial centering devices on one of a pair of centering holes, one of which is cylindrical and the other is a clearance. By varying the length of the centering pin engaged with this centering hole, this configuration allows for a single housing to be envisioned regardless of the embodiment chosen for the installation and assembly of the actuator.

[0022] In another variant embodiment, the housing is manufactured by overmolding a plastic material and includes a connector integrated into the overmolding.

[0023] To withstand higher operating temperatures, in a specific embodiment, the printed circuit has a first side that houses electronic components and a second side without components, the first side facing the electric motor and being at the bottom of the housing, and the second side facing the intermediate plate.

[0024] Then, advantageously and optionally, the first and second sides of the printed circuit are at least partially covered with a thermal paste that also at least partially contacts the housing and the intermediate plate, respectively.

[0025] To improve the performance of the actuator, in another variant embodiment, the wound stator has stator teeth that extend tangentially through a magnetic field collector; at least part of the teeth carry coils and are attached to the stator, and the coils have a frustoconical shape.

[0026] In this embodiment, in another variant embodiment, each stator tooth carrying a coil has a W shape with two adjacent teeth, and the outer side of the frustoconical coil is parallel to the inner side of the adjacent teeth.

[0027] To optimize the performance of this embodiment, if D represents the number of stator teeth and GAP represents the tangential distance between two adjacent teeth between the field collectors, the following relationship will result:

[0028] GAP = 360 / (8×D) ± 5%.

[0029] Still in this same embodiment, for performance optimization, if E represents the radial thickness of the rotor magnet, if EP1 represents the minimum radial thickness at the end of the field collector and EP2 represents the maximum radial thickness at the origin of the field collector, the following relationship will result:

[0030] EP2 ≥ 0.75 × E and EP1 < EP2.

[0031] Finally, to simplify the actuator's motor and improve performance, the rotor includes a permanent magnet partially overmolded with an injection-molded material, the overmolding partially surrounding the rotor shaft and forming a plane orthogonal to the axis where the sensor magnet is located. In an alternative embodiment, the overmolded magnet directly forms the sensor magnet without adding additional magnets. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Other features and advantages of the present invention will become apparent when reading the following detailed embodiments with reference to the accompanying drawings, which respectively show:

[0033] - Figure 1 , an exploded perspective view of a first actuator according to a first embodiment,

[0034] - Figure 2 , an exploded perspective view of a first actuator according to a second embodiment,

[0035] - Figure 3 , an exploded perspective view of a first actuator according to a third embodiment,

[0036] - Figure 4 , an exploded perspective view of a second actuator according to a first embodiment,

[0037] - Figure 5 , an exploded perspective view of a second actuator according to a second embodiment,

[0038] - Figure 6 , an exploded perspective view of a second actuator according to a third embodiment,

[0039] - Figure 7 , a first detailed cross-sectional view of a second actuator according to a second embodiment,

[0040] - Figure 8 , a second detailed cross-sectional view of a second actuator according to a second embodiment,

[0041] - Figure 9 , a perspective cross-sectional view of a second actuator according to a second embodiment,

[0042] - Figure 10 , an overall perspective view of a second actuator,

[0043] -Figure 11 , Figure 10 Partial cross-sectional perspective view of the actuator

[0044] - Figure 12 , Isolated overview of the housing and the intermediate plate of the second actuator

[0045] - Figure 13 , Figure 12 Partial cross-sectional perspective view of the components of

[0046] - Figure 14 , Partial cross-sectional view of the second actuator in a variant implementation

[0047] - Figure 15 , General perspective view of the first actuator in a variant implementation

[0048] - Figure 16 , Figure 15 Partial cross-sectional perspective view of the actuator of

[0049] - Figure 17 , Isolated general view of the housing and the intermediate plate of the first actuator in a variant implementation

[0050] - Figure 18 , Figure 17 Partial cross-sectional perspective view of the components of

[0051] - Figure 19a and Figure 19b , Two partial cross-sectional views of the first actuator in a variant implementation from two different perspectives

[0052] - Figure 20 , Isolated cross-sectional view of the electric motor of the second actuator

[0053] - Figure 21 , Isolated view of the stator of the electric motor integrated into the first or second actuator in a variant implementation

[0054] - Figure 22 , Figure 21 Isolated partial exploded view of the stator of

[0055] - Figure 23 , Figure 21 Isolated cross-sectional view of the stator of

[0056] - Figure 24 , Isolated longitudinal cross-sectional view of the electric motor rotor in a variant implementation

[0057] - Figure 25 , Partial cross-sectional view of the actuator according to an alternative implementation of the mechanical reduction gear

[0058] - Figure 26, Isolated view of an alternative embodiment of an electric motor rotor that can be used in the actuator according to the present invention,

[0059] - Figure 27 and Figure 28 , Two partial cross-sectional views showing an alternative embodiment of the stator of an electric motor that can be used in the actuator according to the present invention,

[0060] - Figure 29 , Exploded perspective view of an actuator according to an alternative embodiment,

[0061] - Figure 30 , Figure 29 Partial cross-sectional view of the actuator. Detailed Description

[0062] Figure 1 Shows a first embodiment of the actuator (1) according to the present invention. Generally, common to all embodiments covered by the present invention, the actuator (1) is formed by three main parts: a housing (2), an intermediate plate (3), and a cover (4). In this Figure 1 And also seen in certain other figures are fixing screws (5) and a sealing gasket (6), the positioning of which will be described below. This sealing member (6) is the only seal to ensure tightness between the housing and the cover, while in prior art solutions, in particular patent WO2018 / 088356, two seals are required.

[0063] This Figure 1 Shows a first example of an actuator, where the housing (2) is made of an injection-moldable plastic material. By overmolding the stator of the motor with the said plastic material, the housing (2) has the specific function of accommodating an electric motor (not visible here) which will be described in detail below. The purpose of the cover (4) is in particular to accommodate a mechanical reduction gear (not visible here) which will be described in detail below. The purpose of the intermediate plate (3) is to guide the rotating elements of the mechanical reduction gear while allowing a mechanical connection between the rotor of the electric motor and the mechanical reduction gear. The sealing gasket (6) is intended to be positioned at the interface between the housing (2) and the cover (4) to achieve tightness by axial compression during assembly. The fixing screw (5) is intended to fix the housing (2) to the cover (4) by constraining the intermediate plate at the threaded hole (11), as will be described later. The threaded hole (11) can also be a blind hole for screwing in a self-forming screw.

[0064] The support of the intermediate plate is (only) around the centering holes for receiving the pins (8a, 8b), which makes it possible, in particular, to place a single sealing gasket at the interface between the cover and the housing and to improve tightness compared to the solution proposed in the document of the prior art WO2018 / 088356.

[0065] In a first embodiment of the invention relating to this first actuator (1), the plastic housing (2) has a first pair of holes (not visible here) formed by a cylindrical centering device and a clearance centering device; the intermediate plate (3) has a second pair of holes in the form of two drilled holes or a cylindrical centering device (7a, 7b) for receiving two centering pins (8a, 8b).

[0066] These two centering pins (8a, 8b) can:

[0067] ○ Be separated from the intermediate plate and introduced downstream of the plate manufacture

[0068] ○ Or be integrated into the intermediate plate, thus forming a single part with the plate and then forming a single part.

[0069] The cover (4) has a third pair of holes formed by a cylindrical centering device (9a) and a clearance centering device (9c) (here in the form of an oblong drilled hole). The ingenious use of only two pins and three pairs of holes on the above three main elements (where two pairs of holes form a cylindrical centering device and a clearance centering device, and the other pair of holes form two cylindrical centering devices corresponding to the cylindrical and clearance centering devices) enables the optimal relative positioning of the three elements to be ensured. The positioning of the pins (8a, 8b) on the intermediate plate (3) in the cylindrical centering devices (7a, 7b) represents a preferred configuration as it enables a single type of intermediate plate (3) to be considered compatible with various forms of housing (2) and / or cover (4).

[0070] Figure 2 This is a second embodiment of this first actuator, which differs from the first embodiment in that the centering pins (8a, 8b) are positioned in a pair of holes in the cover (4) forming two cylindrical centering devices (9a, 9b), and the intermediate plate (3) includes a pair of holes forming a cylindrical centering device (7a) and a clearance centering device (7c). Similar to the first embodiment, the plastic housing (2) has a pair of holes (not visible here) formed by a cylindrical centering device and a clearance centering device. This is an alternative embodiment of the first embodiment.

[0071] Figure 3 This shows a third alternative embodiment of this first actuator. It differs from the first and second embodiments in that the centering pins (8a, 8b) are positioned in a pair of holes in the plastic housing (2) forming two cylindrical centering devices (12a, 12b), and the intermediate plate (3) includes a pair of holes forming a cylindrical centering device (7a) and a clearance centering device (7c). Similar to the first embodiment, the cover (4) has a pair of holes (not visible here) formed by a cylindrical centering device and a clearance centering device.

[0072] Detailed description of the second actuator

[0073] Figure 4 , Figure 5 and Figure 6 show the relative positioning of each pair of holes with respect to the cylindrical and clearance centering devices to be equivalent to Figure 1 , Figure 2 and Figure 3 of the second type of actuator. The second actuator differs from the first actuator in that the housing (2) is here formed of a metallic material (e.g., formed of cast aluminum or injection-molded aluminum), where the stator of the electric motor is intended to be fixed, for example, by a threaded connection. This embodiment enables a more robust actuator to be manufactured, such that in particular the heat generated by the printed circuit (not shown in these figures) carrying the power supply and control components of the motor and by the electric motor can be dissipated better. The second actuator also differs from the first actuator in that the fixing screw (5) is intended to be screwed into the housing (2), rather than the cover (4). Finally, it differs from the first actuator in that the sealing gasket (6) creates tightness by radial compression of the sealing gasket (6). Similar to Figure 1 , Figure 2 and Figure 3 in the description.

[0074] In a first embodiment of the invention relating to this second actuator in Figure 4 , the metallic housing (2) has (not visible here) a first pair of holes formed by a cylindrical centering device and a clearance centering device; the intermediate plate (3) has a second pair of holes in the form of two cylindrical centering devices (7a, 7b) for receiving two centering pins (8a, 8b), and the cover (4) has a third pair of holes formed by a cylindrical centering device (9a) and a clearance centering device (9c) (here in the form of an oblong bore).

[0075] Figure 5 is a second embodiment of this second actuator, which differs from the first embodiment in that the centering pins (8a, 8b) are positioned in a pair of holes forming two cylindrical centering devices (9a, 9b) in the cover (4), and the intermediate plate (3) includes a pair of holes forming a cylindrical centering device (7a) and a clearance centering device (7c). Similar to the first embodiment, the metallic housing (2) has (not visible here) a pair of holes formed by a cylindrical centering device and a clearance centering device. This is an alternative embodiment of the first embodiment.

[0076] Figure 6A third alternative embodiment of this second actuator is shown. It differs from the first and second embodiments in that the centering pins (8a, 8b) are positioned in a pair of holes in the metal housing (2) that form two cylindrical centering means (12a, 12b), and the intermediate plate (3) includes a pair of holes that form a cylindrical centering means (7a) and a clearance centering means (7c). Similar to the first embodiment, the cover (4) has (not visible here) a pair of holes formed by a cylindrical centering means and a clearance centering means.

[0077] Detailed description of the main functions

[0078] Figure 7 , Figure 8 and Figure 9 are details or sectional views of the second embodiment of the second actuator. However, the following description and characteristics of the elements and the functions associated therewith can be fully applied to the other above-mentioned embodiments with the necessary modifications.

[0079] Figure 7 and Figure 8 are isolated views of the centering means (clearance (7c, 12c) and cylindrical (7a, 12a) respectively) generated on the intermediate plate (3) and the housing (2), which allow the rotation of the housing (2) to be mounted, guided and blocked on the centering pins (8a, 8b) respectively placed in the cylindrical centering means (9a, 9b) of the cover (4). The intermediate plate (3) is axially fixed between the housing (2) and the cover (4) by the stresses applied by the cover (4) at two axial support surfaces (13, 14) around the centering holes, on the one hand between the housing (2) and the intermediate plate (3), and on the other hand between the intermediate plate (3) and the cover (4). Referring to Figure 9 , the intermediate plate (3) is mounted in the first cavity (15) of the housing (2). Thus, when the cover (4) is screwed onto the housing (2) (or for the embodiment of the first actuator, the housing (2) is screwed onto the cover (4)), the periphery (16) of the housing (2) approaches the periphery (17) of the cover (4), initially without contact, then contacts during the screwing process through the elasticity of the components involved, and the statically indeterminate mechanical situation generated at the strain joints between the housing (2), the intermediate plate (3) and the cover (4) ensures the perfect elastic fixation of the intermediate plate (3) via the periphery (17) instead. Thus, the screw-mounted actuator (1) can be seen in Figure 9

[0080] Referring to Figure 8, the tightness of the actuator is ensured by a 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 output shaft. In this embodiment of the actuator, tightness is generated radially by squeezing the seal (6) between these first and second surfaces (131, 133).

[0081] Figure 10 and Figure 11 shows general views (in full section and partial section respectively) of a second actuator in a first so-called "complete" variant, in which this actuator can be positioned at an external member (not shown) due to its output shaft (18). Voltage and positioning signals are supplied to the actuator (1) via a connector (19). The housing (2) receives in its cavity (15) an electric motor formed by a stator (20) and a rotor (not visible) and a printed circuit (22) that is electrically connected to the stator windings (20) by a press-fit type connector and mechanically connected by threading into the cavity (15) of the housing (2). The housing (2) receives a ball bearing (23a) for guiding the rotor shaft (not visible here). A mechanical reduction gear (24) positioned in the cover (4) is driven by the said rotor and is formed by a toothed gear mounted on a shaft body (not visible). The cover (4) defines a second cavity (25), in which the shaft body of the said mechanical reduction gear carrying the toothed gear (45a) is mounted and guided at its first end by bearings (23c - 23d). An intermediate plate (3) serves to guide one end of the rotor shaft (29) (not visible here but shown in Figure 12 ) due to a bearing (23b) (not visible here but shown in Figure 12 ), and to guide the other end of the shaft body of the mechanical reduction gear (24) by bearings (23c, 23e). In this embodiment but not by way of limitation, a torsion spring (26) is also mounted in the cover (4) so as to apply a torque to the output shaft (18) such that the movable assembly can be returned to a predefined position when the power supply to the electric motor is switched off or fails. It should also be noted that, without departing from the present invention, the various bearings (23a, 23b, 23c, 23d, 23e, 23g, 23h) specified in all the figures can be replaced by sliding bearings or any other guiding elements.

[0082] Detailed description of alternative embodiments

[0083] Figure 12 and Figure 13Shows a second actuator in a second variant called a "semi-actuator", where the first component (27) of the actuator is formed by assembling the housing (2) and the intermediate plate (3) according to the above-described third embodiment. Then, a complete actuator is generated by assembling this first component (27) on the cover (4), as Figure 14 shown. In this particular embodiment, the cover (4) directly integrates the component to be controlled. By this Figure 14 example given in, the cover (4) forms a valve body (28) and the output shaft (18) carries a "butterfly" type shutter (30), which together form an intake valve for an internal combustion engine. When the actuator (1) is installed, the first component (27) is thus directly mounted on the valve body (28) forming the cover (4), and the mechanical reduction gear (24) engages the shaft (29) of the rotor (21) through the slot (31) of the intermediate plate (3).

[0084] Figure 13 Shows a partial cross-sectional view of the first component (27), which allows the visualization of the printed circuit (22) including all the electronic components for powering and controlling the motor of the actuator (1) and the ball bearing (23b) for guiding the shaft (29) of the rotor (21), the outer ring of which fits into the housing of the intermediate plate (3).

[0085] Figure 15 and Figure 16 Shows the first actuator in the "complete" variant, where the connector (19) is plastic molded with the body of the housing (2). Its orientation is radial, but it can also be considered axial above the housing (2). When the actuator (1) is used in a high-load and high-temperature environment (e.g., near a spark-ignition engine), the opening (32) visible in the cover (4) is the inlet for the heat transfer fluid for cooling the actuator (1).

[0086] Figure 16 Is a partial cross-sectional view that allows the evaluation of the relative positioning in the housing (2) of the bearings (23a, 23d) and the stator (20) separated by the intermediate plate (3) of the mechanical reduction gear (24) and the torsion spring (26). At the housing (2), this variant also has two coaxial centering devices, one cylindrical (12b) and the other free (12c). This combined embodiment allows for the idea of using a single type of overmolding compatible with all three different embodiments described in Figure 1 , Figure 2 and Figure 3 in combination with the height of the centering pin (8b) used. Here in Figure 16 , the elements of the complete actuator are installed according to the first embodiment; the centering pin (8b) is a short pin that engages in the clearance centering device (12c) of the housing (2).

[0087] Figure 17 andFigure 18 Shows a "semi - actuator" variant of a first actuator formed by a first assembly (27) including a housing (2) and an intermediate plate (3). In this variant, the centering pin (8b) is a long pin engaged in the cylindrical centering device (12b) of the housing (2), and the assembly is according to the above - mentioned third embodiment.

[0088] Figure 19a and Figure 19b Shows a variant embodiment of the actuator, here based on the first actuator but not limited thereto, which is at the printed circuit (22) and promotes the dissipation of heat emitted by the printed circuit (22). In this variant, the printed circuit (22) carries all components on only one of its faces, this first face (33) being axially oriented towards the bottom of the electric motor and the housing (2). This embodiment enables, on the one hand, attaching the second face (34) of the printed circuit, which is axially opposite to the first face (33), to the intermediate plate (3), which will promote the discharge of heat through the metal part of the cover (4) by conduction (selecting the intermediate plate with a thermally conductive material). On the other hand, a thermal paste can be used on both sides of the printed circuit (22) (in a large number of points on the printed circuit (22)), squeezing the paste between the housing (2) and the intermediate plate (3) on the one hand and between the cover (4) and the intermediate plate (3) on the other hand, in order to further promote this heat conduction towards the most conductive parts of the actuator (1). These Figure 19a and Figure 19b Shows the output gear (45c) of the reduction gear and the torsion spring (26), which acts on this output gear when the motor stops to return the output shaft (18) to a defined position.

[0089] showing a detailed cross - sectional view of the electric motor Figure 20 Shows the use of magnets (35) at the rotor (21), the length of which can be varied to increase the performance of the motor. In fact, at a given axial height of the stator (20), the axial height of the magnets (35) at the rotor (21) affects the torque generated with a constant power. This embodiment is only a variant compared to the more traditional case where the height of the magnets (35) is equal to the height of the stator (20).

[0090] Figure 21 、 Figure 22 and Figure 23 Shows an example of a stator (20) of an electric motor that can be used by the first or second actuator or any other actuator not shown here but covered by the present invention. Specifically, this stator (20) presents a solution to the problem of limiting the performance of the actuator, in particular the limitations caused by torque oscillations during electrical switching and the magnetostatic torque. This stator (20) is also associated with a solution for optimizing the copper filling of the coils.

[0091] For this stator (20), all stator teeth (36a, 36b) have field collectors (37) extending in the tangential direction relative to the axis of rotation of the rotor. To this end, the teeth (36a) that do not receive coils are integral with the rest of the stator core magnetic circuit generated in the form of a bundle of sheets, while the teeth (36b) that receive coils (38) are independent and attached to the core magnetic circuit. To optimize the performance of the actuator, especially torque oscillation and magnetostatic torque, the field collectors have the following geometric characteristics in the axial plane: relative to the quantity D representing the number of teeth on the stator, it is recommended to comply with the formula:

[0092] GAP≈360 / (8×D), where GAP represents the tangential distance separating the collectors of two adjacent teeth;

[0093] Relative to the quantity E, the radial thickness of the rotor magnet as can be seen in Figure 20 it is recommended that:

[0094] EP2≥0.75×E and EP1<EP2, where EP1 represents the minimum radial thickness at the end of the field collector (37) and EP2 represents the maximum radial thickness at the origin of the field collector (37).

[0095] The teeth (36b) have a central section that allows the placement of the coil (38) by translation from the outside / rear. Also, the connecting means (mechanical and magnetic) between the attached teeth (36b) and the stator circuit are inscribed in the minimum section of the coil (38). A winding solution directly on the teeth can also be envisaged, while retaining the possibility of removing the coil (38) and restoring the teeth (36b) in case of manufacturing defects. The teeth (36b) thus equipped with their coils (38) are attached and linked to the stator (20) in the axial direction relative to the axis of rotation of the rotor (21). The connecting means must ensure good mechanical retention of the teeth (36b) on the stator (20) and must also provide a good-quality magnetic seal to avoid introducing parasitic permeabilities that degrade performance. In this case, the dovetail solution is particularly suitable, allowing an economical solution, a simple shape with precise tolerances, and good mechanical support. The coil body (39) has recesses (40) (here the number is 3, but not limiting) on either side of the coil (38) for press-fit support on the teeth (36b) during the assembly operation. Since the stator circuit has a W-shaped periodicity in a 120° angular sector, the coil (38) has a shape complementary to this W in order to maximize the copper filling degree of the actually available section. The shape of the coil thus obtained is substantially frustoconical. Through the optimized filling of the inter-tooth notches, the proposed conical solution allows a gain in torque without significantly changing the impedance of the coil.

[0096] In order to produce and industrialize this specific type of winding, the coil body (39) has a central peripheral serrated cross-section, the teeth (43) having an angle equal to the cone angle of the winding (in this non-limiting example, approximately 7°), the number of teeth (43) being two or more, and the teeth (43) not necessarily having the same length. In order to ensure good cohesion of the stator (20) thus assembled and to improve its thermal behavior, it will be ideally (but not restrictively) overmolded with a thermoplastic material located at each attached tooth (36b) / coil (38) pair. Alternatively, each tooth (36b) can be molded independently before being attached and fixed to the stator.

[0097] Figure 24 Shows an embodiment of the rotor (21) of an electric machine that can be advantageously used in the present invention. This rotor (21) consists of a permanent magnet (35) partially overmolded with an injection-molded material, a shaft (29) also overmolded with the same plastic material, and a sensor magnet (41) positioned in a plane (42) orthogonal to the shaft (29) generated by the plastic material. The rotor is shown here as having the above-mentioned bearings (23a, 23b). This embodiment is particularly advantageous because it avoids the magnet (35) sticking to the yoke with problematic mechanical resistance at high temperatures. Also, on the one hand, by the absence of a ferromagnetic yoke, and on the other hand, by the lower inertia due to the low density of the plastic material (dominant here by volume), it is also possible to increase the dynamic behavior via a lower inductance. In addition, in addition to simplifying the assembly of the rotor (21) where gluing operations are no longer required, the magnetostatic torque and the frictional torque are reduced, and the radial force induced on the rotor is also reduced.

[0098] Figure 25 Is a partial cross-sectional view that enables the observation of the mechanical reduction gear (24). This mechanical reduction gear can be composed of multiple stages. The embodiment presented in the previous figures shows two reduction stages, while this Figure 25 example shows three reduction stages. In fact, the rotor shaft (29) forming a pinion at its end drives an intermediate gear (45a) carried by a shaft body (46a) guided by two bearings (23g, 23h). The intermediate gear (45a) in turn drives a toothed gear (45b) carried by a shaft body (46b). The toothed gear (45b) finally drives an output gear (45c). As in all embodiments presented herein, all shaft bodies (46a, 46b) or shafts (18) carrying the toothed gears (45a, 45b, 45c) are supported on the cover (2) at one end and on the intermediate plate (3) at the other end.

[0099] Figure 26Shows the rotor (21) in an alternative embodiment. In the previous embodiment, this rotor (21) had a cylindrical magnet, which may or may not be carried by a ferromagnetic yoke. In the present embodiment, in a version called a radially oriented interior magnet ("spoke type" embodiment), the rotor (21) consists of an alternation of rhomboidal magnets (35a) magnetized in the tangential direction and inserted between the iron poles (44). The poles (44) are of a pseudo-circular shape and are designed to optimize the torque with and without current.

[0100] Figure 27 and Figure 28 Shows two alternative embodiments of the stator (21) of an electric motor. In Figure 27 , the stator has three coils (38) grouped together in an angular sector of approximately 120°, and the stator teeth (36a) have an angular width that is alternately narrow and wide, as described for example in application FR2919441. In Figure 28 , the stator has three coils (38) grouped together in an angular sector of approximately 120°, and the stator teeth (36a) have the same angular width, as described for example in application FR2994353,

[0101] Figure 29 and Figure 30 Shows an alternative embodiment of an actuator according to the present invention. The actuator (1) includes a housing (2) that houses the stator (20) of an electric motor, a cover (4) that houses a mechanical reduction gear, an intermediate plate (3) inside the actuator (1), and a printed circuit (22). Centering pins (8a, 8b) allow the housing (2), cover (4), and intermediate plate (3) to be positioned using various centering means: two cylindrical centering means (not visible) made with the cover (4), a clearance centering means (7c) and a cylindrical centering means (7a) present at the intermediate plate (3), corresponding respectively to a clearance (12c) and a cylinder (12a) centering means present at the housing (2). Fixing screws (5) are intended to fix the cover (4) to the said housing (2) for closing. A connector (19) is integral with the cover (4).

[0102] The printed circuit (22) is axially positioned between the intermediate plate (3) and the stator (20), and is connected on the one hand to the electrical coils of the said stator (20) on the side of the housing (2), and on the other hand to the tracks of the connector (19) on the side of the cover (4) in order to allow power supply to and communication with the actuator (1). As Figure 30 shown, the printed circuit is electrically connected to the stator winding (20) by a press-fit type connector. On the side of the cover (4), the printed circuit (22) is attached to the intermediate plate (3), which promotes heat dissipation by conduction. The intermediate plate (3) is cut so that it does not cover the printed circuit at the electrical connection level.

Claims

1. An electric actuator (1), the electric actuator (1) comprising: - a housing (2), - an electric motor including a wound stator (20) and a rotor (21) mounted on a rotor shaft (29), - a printed circuit (22) for powering the stator (20) and controlling the motor, - an intermediate plate (3), - a mechanical reduction gear (24) driven by the rotor (21) and formed by gear wheels (45a, 45b, 45c) mounted on shafts (46a, 46b, 46c), - a cover (4), - two centering pins (8a, 8b), the housing (2) defining a first cavity (15) for receiving the stator (20) and including means for guiding the rotor shaft (29) at a first end, the printed circuit (22) being received in the first cavity (15) above the stator (20), the intermediate plate (3) being located above the printed circuit (22), the cover (4) defining a second cavity (25) provided with means for guiding one end of the shafts (46a, 46b, 46c) of the mechanical reduction gear (24), the cover (4) being located above the intermediate plate (3), the intermediate plate (3) having guiding means for guiding the other end of the rotor shaft (29) and for guiding the other end of the shafts (46a, 46b, 46c) of the mechanical reduction gear (24), characterized in that · there is a first pair of centering holes in the first cavity (15) of the housing (2) for receiving the two centering pins (8a, 8b), · there is a second pair of centering holes in the intermediate plate (3) for receiving the two centering pins (8a, 8b), · there is a third pair of centering holes in the cover (4) for receiving the two centering pins (8a, 8b), · the intermediate plate (3) contacts the housing (2) on support surfaces (13, 14) surrounding the first pair of centering holes and the second pair of centering holes, and contacts the cover (4) on support surfaces (13, 14) surrounding the second pair of centering holes and the third pair of centering holes, · two pairs of the first pair of centering holes, the second pair of centering holes and the third pair of centering holes are composed of cylindrical centering means (7a, 9a, 12a) and clearance centering means (7c, 9c, 12c), the cylindrical centering means (7a, 9a, 12a) and the corresponding clearance centering means (7c, 9c, 12c), · the other pair of the first pair of centering holes, the second pair of centering holes and the third pair of centering holes is composed of two cylindrical centering means (7a, 7b, 9a, 9b, 12a, 12b), · the housing includes a single sealing gasket (6) positioned at the interface between the housing (2) and the cover (4).

2. The electric actuator according to claim 1, characterized in that The housing (2) includes a peripheral region (16) having at least two first attachment bores (11), and the cover (4) includes a peripheral region (17) having at least two second attachment bores (11) such that attachment of the cover (4) and the housing (2) is performed by means of a threaded connection through the first and second attachment bores (11). The peripheral regions (16, 17) are discontinuous when the cover (4) and the housing (2) rest on the intermediate plate (3) prior to the threaded connection and are supported and at least partially continuous after the threaded connection to restrain and block movement of the intermediate plate (3).

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

4. The electric actuator according to claim 1, characterized in that, different guiding surfaces of the rotor shaft (29) and the shaft bodies (46a, 46b, 46c) of the mechanical reduction gear (24) are generated by the housing (2), the intermediate plate (3) and the cover (4), and the guiding surfaces are ball bearings (23a, 23b, 23c, 23d) or sliding bearings.

5. The electric actuator according to claim 1, characterized in that, the two centering pins (8a, 8b) and the intermediate plate (3) form the same part.

6. The electric actuator according to claim 1, characterized in that, the housing (2) is manufactured by overmolding a plastic material and has two coaxial centering devices on one of the pair of centering holes, one being cylindrical (12b) and the other being a clearance (12c).

7. The electric actuator according to claim 1, characterized in that, the housing (2) is manufactured by overmolding a plastic material and includes a connector (19) integrated into the overmolding.

8. The electric actuator according to claim 1, characterized in that, the printed circuit (22) has a first face (33) for accommodating electronic components and a second face (34) without components. The first face (33) faces the electric motor and is located at the bottom of the housing (2), and the second face (34) faces the intermediate plate (3).

9. The electric actuator according to claim 8, characterized in that, the first face (33) and the second face (34) of the printed circuit (22) are at least partially covered by a thermal paste which also at least partially contacts the housing and the intermediate plate (3) respectively.

10. The electric actuator according to claim 1, characterized in that, the wound stator (20) has stator teeth (36a, 36b) tangentially extending through a magnetic field collector (37). At least part of the teeth (36b) carry coils (38) and are attached to the stator (20), and the coils (38) have a frustoconical shape.

11. The electric actuator according to claim 10, characterized in that, Each stator tooth (36b) carrying the coil (38) has a W shape with two adjacent teeth (36a), and the outer side surface of the frustum-shaped coil (38) is parallel to the inner side surface of the adjacent teeth (36a).

12. The electric actuator according to claim 10, characterized in that, D represents the number of stator teeth (36a, 36b), and GAP represents the tangential distance between two adjacent teeth (36a) between the field collectors (37), where GAP = (360 / (8×D)) ± 5%.

13. The electric actuator according to claim 10, characterized in that, the rotor (21) has a magnet (35), E represents the radial thickness of the magnet (35), EP1 represents the minimum radial thickness at the end of the field collector (37), and EP2 designates the maximum radial thickness at the start of the field collector (37), where EP2 ≥ 0.75×E and EP1 < EP2.

14. The electric actuator according to claim 1, characterized in that, the rotor (21) includes a permanent magnet (35) partially overmolded with an injection molding material, and the overmolded part partially surrounds the rotor shaft (29) and forms a plane (42) orthogonal to the shaft (29) where the sensor magnet (41) is located.

15. The electric actuator according to claim 1, characterized in that, the rotor (21) includes a permanent magnet (35) partially overmolded with an injection molding material, and the overmolded part partially surrounds the rotor shaft (29) and forms the sensor magnet (41).

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