Linear electromagnetic actuator

Abstract

The present invention relates to a linear electromagnetic actuator (1) comprising a housing (2) defining at least two concentric annular spaces with axis X in which are housed a first annular coil (31) and a second annular coil (32), an annular piston (4) mounted to move axially in translation about an axis X1 between a retracted position (R) and a deployed position (D) and intended to transmit an actuation force, characterized in that the piston (4) is arranged radially between the two coils (31, 32). Figure for the abstract: Figure 1

Description

Title of the invention: Linear electromagnetic actuator

[0001] The invention relates to a linear electromagnetic actuator.

[0002] The linear electromagnetic actuator according to the invention is of particular interest in the field of actuators for a transmission system of a motor vehicle.

[0003] The invention relates more specifically to an electromagnetic actuator which is intended to be housed inside a transmission casing of the transmission chain while being linked to a coupling device.

[0004] An actuator for a similar application is described in document US 20170159726 AL This document discloses an electromagnetic actuator for actuating a coupling device fitted to a differential system. The coupling device has an uncoupled state in which the differential is free to distribute torque from a motor to two wheel shafts of an axle of the vehicle and a coupled state which deactivates the "differential" function so that the two wheel shafts cannot rotate at different speeds. The electromagnetic actuator comprises a housing which is intended to be fixed in a transmission casing in which the differential system is also housed. Furthermore, the electromagnetic actuator comprises a housing having an annular space in which are housed a coil and a piston mounted movably between a retracted position and a deployed position.

[0005] This type of conventional actuator uses a single coil to ensure the storage of energy in the magnetic circuit. This coil only ensures a single movement of the piston in a single direction and it is therefore not possible to control the release time corresponding to the reverse movement without a robust closed loop.

[0006] The performance of this electromagnetic actuator is determined by the size of the components and the available voltage applied to the coil. It is therefore necessary in the automotive field to have the most optimized compactness, weight and performance ratio possible, that is to say a compact actuator offering good performance.

[0007] One of the aims of the invention is to propose an electromagnetic actuator making it possible to precisely control the actuation and release time corresponding to the opposite movements of the piston.

[0008] The invention thus proposes a linear electromagnetic actuator comprising a housing defining at least two concentric annular spaces of axis X in which are housed a first annular coil and a second annular coil, an annular piston mounted axially movable in translation along an axis XI between a retracted position and an extended position and intended to transmit an actuating force. According to the invention, the piston is arranged radially between the two coils.

[0009] In other words, the first annular coil, the annular piston and the second annular coil follow one another radially starting from the X axis.

[0010] Due to the presence of the two annular coils, the electromagnetic actuator is said to be bistable. The two annular coils allow the piston to be translated either into the retracted position or into the deployed position.

[0011] In the present invention, each coil associated with the piston and the housing form a magnetic circuit constituting an electromagnet. The electromagnetic actuator according to the present invention thus comprises two electromagnets with a shared piston.

[0012] According to the invention, the first coil has a radius RB1 and the second coil has a radius RB2, the radius RB1 being less than the radius RB2. In other words, the two annular coils are coaxial.

[0013] According to the invention, the housing comprises a first half-housing defining the first annular space housing the first annular coil and a second half-housing defining the second annular space housing the second annular coil.

[0014] According to the invention, each half-housing comprises a radial extension so as to form a stop surface in translation of the piston. Advantageously, these stop surfaces are conical in shape.

[0015] According to the invention, the two half-housings are connected by non-magnetic flanges. Alternatively, these flanges are made of the same material as the housing with a thickness that is thinner than the other walls of the housing. These flanges make it possible to decouple the two magnetic circuits associated with the two electromagnets. The thickness of these flanges must be as small as possible to limit magnetic flux leakage. The term non-magnetic must be understood to mean a material having an absence of magnetic properties.

[0016] According to another characteristic of the invention, the piston has an asymmetry along the axis XL

[0017] According to the invention, seen in section, the piston has a staircase shape with a first annular part and a second annular part connected to each other by a bridge, the first annular part is located in the magnetic flux of the first annular coil and the second annular part is located in the magnetic flux of the second annular coil. The first annular part has a radius RP1 and the second annular part has a radius RP2. The radius RP1 is less than the radius RP2. This staircase shape also makes it possible to decouple the two magnetic circuits associated with the two electromagnets. This staircase shape makes it possible to increase the performance of an electromagnetic actuator having two coils. This staircase shape makes it possible to balance the difference in radius of the two coils.

[0018] According to the invention, the axial length along the axis XI of the first part of the piston is 50% to 300% greater than the axial length of the second part of the piston.

[0019] According to the invention, the piston comprises two conical ends capable of cooperating with the stop surfaces of the half-housings.

[0020] According to the invention, the housing comprises partly non-magnetic guide surfaces for guiding the piston.

[0021] The invention will be better understood, and other aims, details, characteristics and advantages thereof will appear more clearly during the following description of a particular embodiment of the invention, given solely for illustrative and non-limiting purposes, with reference to the attached drawing:

[0022] [Fig.l] represents a sectional view of a linear electromagnetic actuator according to the invention.

[0023] It should be noted that the figure discloses the invention in a manner sufficiently detailed for its implementation, the figure helping to better define the invention if necessary.

[0024] [Fig. 1] represents an actuator 1 according to the invention. This actuator 1 is a linear electromagnetic actuator capable of being housed in a transmission casing. The transmission casing may consist of any casing in the transmission chain of a vehicle, in particular a differential casing. It comprises a housing 2 which is intended to be fixed to a transmission casing (not shown).

[0025] The housing 2 comprises two concentric annular spaces of axis X in which are housed a first annular coil 31 and a second annular coil 32 as well as an annular piston 4. The housing 2 is made of a magnetic material, for example magnetic steel. The annular coils 31, 32 consist of a winding of conductive wire and can be encapsulated in a sealed manner by a coating of polymer material for example epoxy resin, polyurethane or polyamide.

[0026] The actuator 1 may comprise an electrical connector (not shown) which is intended for the electrical connection of the coils 31, 32 to a control device which is positioned outside the housing. The electrical connector makes it possible to electrically supply these coils 31, 32.

[0027] The housing 2 comprises a first half-housing 21 defining the first annular space housing the first annular coil 31 and a second half-housing 22 defining the second annular space housing the second annular coil 32. The first coil 31 has a radius RB 1 and the second coil 32 has a radius RB2. The radius RB1 is less than the radius RB2. The two half-housings 21, 22 are connected by non-magnetic flanges 25, 26.

[0028] The piston 4 is arranged radially between the two coils 31, 32 and more generally arranged radially between the two half-housings 21, 22. The piston is mounted to move axially in translation along an axis XI between a retracted position R and a deployed position D. The piston 4 translates in a housing defined between the two half-housings 21, 22. The piston 4 makes it possible to transmit an actuating force to a coupling device.

[0029] The housing 2 comprises guide surfaces 27, 28 of the piston 4. These surfaces 27, 28 are partly non-magnetic.

[0030] The piston 4 is made of ferromagnetic material, such as iron or steel for example. The piston 4 may further comprise a non-magnetic end piece (not shown), also of annular shape, which is fixed to the piston 4 and by which the actuating force is transmitted to the coupling device. The non-magnetic end piece of the piston 4 thus makes it possible to avoid unwanted leaks of magnetic flux to the other components of the coupling device. The non-magnetic end piece is for example made of bronze or aluminum.

[0031] The housing 2, each coil 31, 32 associated with the piston 4 form a magnetic circuit constituting an electromagnet. The electromagnetic actuator according to the present invention thus comprises two electromagnets with a shared piston 4. The housing 2 serves as a magnetic circuit in order to guide the magnetic flux of the coils 31, 32.

[0032] The piston 4 has an asymmetry along the axis XI, that is to say that seen in section, the piston 4 has a staircase shape with a first annular part 41 and a second annular part 42 connected to each other by a bridge 43. The first annular part 41 is located in the magnetic flux of the first annular coil 31 and the second annular part 42 is located in the magnetic flux of the second annular coil 32.

[0033] The axial length L1 along the axis XI of the first annular part 41 is 50% to 300% greater than the axial length L2 of the second annular part 42.

[0034] Each half-housing 21, 22 comprises a radial extension 23, 24 so as to form a translational stop surface of the piston 4. These stop surfaces are conical. The piston 4 comprises two conical ends capable of cooperating with the conical stop surfaces 23, 24 of the half-housings 21, 22.

[0035] A transmission shaft 5, extending along the X axis, passes through the actuator 1 on either side.

[0036] Although the invention has been described in connection with a particular embodiment, it is obvious that it is in no way limited thereto and that it includes all the technical equivalents of the means described.

[0037] In the claims, the reference symbols in parentheses must not be interpreted as a limitation of the claim.

Claims

Claims

1. Linear electromagnetic actuator (1) comprising a housing (2) defining at least two concentric annular spaces of axis X in which are housed a first annular coil (31) and a second annular coil (32), an annular piston (4) mounted axially movable in translation along an axis XI between a retracted position (R) and a deployed position (D) and intended to transmit an actuating force, characterized in that the piston (4) is arranged radially between the two coils (31, 32).

2. Actuator (1) according to claim 1, characterized in that the first coil (31) has a radius RB1 and the second coil (32) has a radius RB2, the radius RB1 being less than the radius RB2.

3. Actuator (1) according to claim 1 or 2, characterized in that the housing (2) comprises a first half-housing (21) defining the first annular space housing the first annular coil (31) and a second half-housing (22) defining the second annular space housing the second annular coil (32).

4. Actuator (1) according to claim 3, characterized in that each half-housing (21, 22) comprises a radial extension (23, 24) so as to form a translational stop surface of the piston (4).

5. Actuator (1) according to claim 3 or 4, characterized in that the two half-housings (21, 22) are connected to each other by flanges (25, 26) which are non-magnetic or of a thickness which is thinned compared to the other walls of the two half-housings (21, 22).

6. Actuator (1) according to one of the preceding claims, characterized in that the piston (4) has an asymmetry along the axis XI.

7. Actuator (1) according to claim 6, characterized in that, seen in section, the piston (4) has a staircase shape with a first annular part (41) and a second annular part (42) connected to each other by a bridge (43), the first annular part (41) is located in the magnetic flux of the first coil (31) and the second annular part (42) is located in the magnetic flux of the second coil (32).

8. Actuator (1) according to claim 7, characterized in that the axial length (L1) along the axis XI of the first annular part (41) is 50% to 300% greater than the axial length (L2) of the second annular part (42).

9. Actuator (1) according to claim 4, characterized in that the piston (4) comprises two conical ends capable of cooperating with the stop surfaces (23, 24) of the half-housings (21, 22).

10. Actuator (1) according to one of the preceding claims, characterized in that the housing (2) comprises partly non-magnetic guide surfaces (27, 28) for guiding the piston (4).

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