Linear electromagnetic actuator

Abstract

The present invention relates to a linear electromagnetic actuator (1) comprising a cylindrical housing (2) defining an annular space of axis X in which a cylindrical coil (3) is housed, an annular piston (4) mounted axially movable along an axis X between a retracted position (R) and a deployed position (D) and intended to transmit an actuating force, the piston (4) has a truncated conical portion (11), said truncated conical portion (11) comprises an internal surface (12), an external surface (14) and a truncation (13). The height (H) of the internal surface (12) and the width (L) of the truncation (13) have a ratio of between 3 and 8. 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 equipping 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 actuator requires a very short response time, that is to say that the time lag between the actuation command and its execution must be as small as possible.

[0006] One of the aims of the invention is to propose a linear electromagnetic actuator optimized to improve its response time.

[0007] The invention thus proposes a linear electromagnetic actuator comprising a cylindrical housing defining an annular space of axis X in which a cylindrical coil is housed, an annular piston mounted axially movable along an axis X between a retracted position and a deployed position and intended to transmit an actuating force. The piston has a truncated conical portion, said truncated conical portion comprises an internal surface, an external surface and a truncation. According to the invention, the height of the internal surface and the width of the truncation have a ratio of between 3 and 8. More precisely, the ratio can be between 3 and 6.

[0008] The concept of internal surface should be understood as being the surface of the truncated conical portion facing the coil. The external surface faces the housing. The ratio is obtained by dividing the height of the internal surface by the width of the truncation.

[0009] In the present invention, the piston, the coil and the housing form a magnetic circuit constituting an electromagnet.

[0010] According to the invention, the direction of extension of the internal surface and the direction of extension of the external surface of the truncated conical portion form an angle of between 2° and 20°.

[0011] According to the invention, the direction of extension of the external surface of the truncated conical portion is parallel to the X axis.

[0012] According to the invention, the housing comprises a radially internal skirt, a bottom surface and a radially external skirt.

[0013] According to the invention, the piston is housed inside the housing and radially between the coil and the radially external skirt.

[0014] According to another characteristic of the invention, the piston is housed inside the housing and radially between the coil and the radially internal skirt.

[0015] Alternatively, the piston is housed outside the housing and radially between the X axis and the radially internal skirt.

[0016] According to the invention, the annular space of the housing is partly closed by a magnetic cover, the magnetic cover defines an end-of-stroke stop for the piston when the piston is in the deployed position.

[0017] According to the invention, the piston comprises a shoulder intended to come into abutment against a shoulder of the magnetic cover when the piston is in the deployed position.

[0018] According to the invention, the magnetic cover comprises a conical portion complementary to the truncated conical portion of the piston. This means that, when the piston is in the deployed position, the conical portion of the magnetic cover and the truncated conical portion of the piston are almost in contact, only a small residual clearance remains.

[0019] The invention will be better understood, and other aims, details, characteristics and advantages thereof will appear more clearly during the following description of several particular embodiments of the invention, given solely for illustrative and non-limiting purposes, with reference to the appended drawings:

[0020] [Fig.l] represents a linear electromagnetic actuator according to the invention;

[0021] [Fig.2] shows an enlarged view of the truncated conical portion of the actuator of [Fig.l].

[0022] It should be noted that the figures disclose the invention in a manner sufficiently detailed for its implementation, said figures helping to better define the invention if necessary. The invention should not, however, be limited to the embodiments disclosed in the description.

[0023] [Fig.l] represents an actuator 1 according to the invention. This actuator 1 is an elec electromagnet capable of being housed in a transmission casing. The transmission casing can be constituted by any casing of the transmission chain of a vehicle, in particular a differential casing. The actuator 1 is here an electromagnet capable of being linked to a coupling device (not shown) of a motor vehicle transmission. It comprises a housing 2 which is intended to be fixed to a transmission casing (not shown). In this housing 2 are arranged an annular coil 3 as well as an annular piston 4. The piston 4, the coil 3 and the housing 2 constitute the electromagnet. The housing 2 serves as a magnetic circuit in order to guide the magnetic flux of the coil 3.

[0024] The actuator 1 may comprise an electrical connector (not shown) which is intended for connecting the coil 3 to a control device which is positioned outside the casing. The electrical connector makes it possible to electrically power this coil 3.

[0025] The housing 2 defines an annular space of axis X in which the annular piston 4 intended to transmit an actuating force to a coupling device and the annular coil 3 are housed. The piston 4 is arranged coaxially with the axis X and is mounted axially movable along the axis X between a retracted position R and a deployed position D. The piston 4 is located radially outside the coil 3. It is entirely possible to locate the piston 4 radially inside the coil 3.

[0026] Seen in section, the housing 2 is U-shaped. It is made in a single piece or in at least two assembled L-shaped parts. The housing 2 is made of a single magnetic material, for example magnetic steel. The housing 2 comprises a radially external skirt 23 serving as a guide surface for the piston 4, a bottom surface 22 and a radially internal skirt 21.

[0027] The annular coil 3 consists of a winding of conductive wire and can be sealed by a coating of polymer material, for example epoxy resin, polyurethane or polyamide. The coating can form an annular radial extension (not shown) defining an end-of-travel stop for the piston 4 when it is in the retracted position R.

[0028] The piston 4 is mounted movably in a housing defined between the coil 3 and the external skirt 23 of the housing 2.

[0029] The annular space of the housing 2 is closed by a magnetic cover 8, the magnetic cover 8 defines an end-of-travel stop for the piston 4 when the piston 4 is in the deployed position D. The piston 4 comprises a shoulder intended to come into abutment against a shoulder of the magnetic cover 8 when the piston 4 is in the deployed position D.

[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 tip (not shown), also annular in shape, which is fixed to the piston 4 and through which the actuating force is transmitted to the coupling device. Non-magnetic means a material having an absence of magnetic properties. The non-magnetic tip of the piston 4 thus prevents unwanted leakage of magnetic flux to the other components of the coupling device. The non-magnetic tip is, for example, made of bronze or aluminum.

[0031] A transmission shaft 10, coaxial with the X axis, passes through the actuator 1 on either side.

[0032] The truncated conical portion 11 of the piston 4 is better visible in [Fig.2] and comprises an internal surface 12 facing the coil 3, an external surface 14 facing the housing 2 and a truncation 13.

[0033] The height H of the internal surface 12 and the width L of the truncation 13 have a ratio between 3 and 8. For example, the height H of the internal surface 12 measures between 2.85 mm and 4 mm, the width L of the truncation 13 measures between 0.5 mm and 0.9 mm. In the embodiment of [Fig.l] and [Fig.2] the height H of the internal surface 12 is 2.85 mm and the width L of the truncation 13 is 0.5 mm. The angle a is between 2° and 20°. Such a ratio makes it possible to reduce the response time of the actuator.

[0034] The piston 4 comprises a shoulder 15 intended to come into abutment against a shoulder 81 of the magnetic cover 8 when the piston 4 is in the deployed position D. The magnetic cover 8 comprises a conical portion 82 complementary to the truncated conical portion 11 of the piston 4. This means that, when the piston 4 is in the deployed position, the conical portion 82 of the magnetic cover 8 and the truncated conical portion 11 of the piston 4 are in contact

[0035] Although the invention has been described in connection with two particular embodiments, it is quite obvious that it is in no way limited thereto and that it includes all the technical equivalents of the means described.

[0036] In the claims, the reference symbols in parentheses should not be interpreted as a limitation of the claim.

Claims

Claims

1. Linear electromagnetic actuator (1) comprising a cylindrical housing (2) defining an annular space of axis X in which a cylindrical coil (3) is housed, an annular piston (4) mounted axially movable along an axis X between a retracted position (R) and a deployed position (D) and intended to transmit an actuating force, the housing (2) comprises a radially internal skirt (21), a bottom surface (22) and a radially external skirt (23), the piston (3) is housed inside the housing (2) and radially between the coil (3) and the radially external skirt (23), the annular space of the housing (2) is partly closed by a magnetic cover (8), the magnetic cover (8) defines an end-of-travel stop for the piston (4) when the piston (4) is in the deployed position (D), the piston (4) comprises a shoulder (15) intended to come into abutment against a shoulder (81) of the magnetic cover (8) when the piston (4) is in the deployed position (D),the piston (3) has a truncated conical portion (11), said truncated conical portion (11) comprises an internal surface (12), an external surface (14) and a truncation (13), the magnetic cover (8) comprises a conical portion (82) complementary to the truncated conical portion (11) of the piston (4), the height (H) of the internal surface (12) and the width (L) of the truncation (13) have a ratio between 3 and 8.,

2. Actuator (1) according to claim 1, characterized in that the direction of extension of the internal surface (12) and the direction of extension of the external surface (14) of the truncated conical portion (11) form an angle (a) between 2° and 20°.

3. Actuator (1) according to claim 1 or 2, characterized in that the direction of extension of the external surface (14) of the truncated conical portion (11) is parallel to the X axis.

Images