Electromechanical actuator

Abstract

The present invention relates to an electromechanical actuator (1) comprising an electric motor (2) acting on a torque output element (6) adapted to be coupled with a moving part of a vehicle's transmission. The torque output element (6) is configured to rotate about its axis of rotation between a first extreme position and a second extreme position defining an actuation range. The torque output element (6) is connected to the electric motor (2) by drive means (4, 5) comprising a first gear (4) and a second gear (5). The actuator (1) further comprises an electronic board (10). The electronic board (10) includes a sensor (12) facing a magnet (15) mounted on a third gear (11), said third gear (11) meshing with the second gear (5). (See Figure 1 for abbreviations.)

Description

Title of the invention: Electromechanical actuator

[0001] The invention relates to an electromechanical actuator. More particularly, the invention relates to an electromechanical actuator that can be rotary or linear.

[0002] The invention applies, for example, to the field of actuators for a parking lock system for a vehicle gearbox, particularly a motor vehicle equipped with an automatic transmission, for example, a hybrid vehicle. The invention also applies to a parking lock system for a reduction gear associated with an electric vehicle motor. The gearbox or reduction gear will more generally be called a transmission. This locking system is better known by its English term "park lock." Such an actuator allows the transmission to be locked in the parking position by means of a lever engaging with a gear in the transmission.

[0003] The invention also applies to the field of actuators for a system of connecting / disconnecting components in the transmission of the aforementioned vehicles such as, for example, forks, synchronizers, selectors, etc...

[0004] It is typical with these designs for the actuator to be located outside the transmission and for the moving part to be actuated to be inside the transmission. In order for the actuator to reliably act on the moving part of the transmission, it is necessary to know the exact position of the moving part within the transmission.

[0005] In the case of a rotary actuator, one solution would be to count the number of revolutions of the actuator's torque output element to determine the position of the moving part, provided that the number of revolutions required for the torque output element to traverse the entire actuation range of the moving part is known beforehand. This solution has the disadvantage of requiring the rotation position to be stored in a memory unit. Furthermore, in the event of a power failure, the stored position will be lost, necessitating a complex learning procedure.

[0006] One of the aims of the invention is to provide an actuator that solves the problems mentioned above. The actuator must be able to reliably and autonomously determine the position of the moving part in the gearbox over its entire actuation range without involving any elements external to the actuator.

[0007] Thus, the invention proposes an electromechanical actuator comprising an electric motor acting on a torque output element suitable for coupling with a moving part of a vehicle's transmission gearbox; the torque output element is configured to rotate about its axis of rotation between a first position The torque output element is connected to the electric motor by means of a drive comprising a first gear and a second gear. The actuator further includes an electronic control board. The electronic control board includes a sensor facing a magnet mounted on a third gear, said third gear meshing with the second gear.

[0008] This design thus makes it possible to recover the signal generated by the sensor associated with the angular position of the third toothed wheel, which makes it possible to know the angular position of the torque output element over its actuation range.

[0009] The moving part of the transmission is, for example, a roto-linear device. The rotary actuation range of the torque output element of the actuator corresponds to the linear actuation range of the moving part.

[0010] According to the invention, the actuation range of the torque output element is greater than one revolution. In other words, the actuation range of the torque output element is greater than 360°.

[0011] Preferably, the sensor is an absolute sensor, for example a Hall effect sensor.

[0012] According to the invention, the electric motor comprises a drive shaft extending along an axis XI and a drive pinion. This drive pinion meshes with the first gear, which is mounted to rotate freely about an axis X2. This first gear, in turn, meshes with the second gear, which is also mounted to rotate freely about an axis X3. According to a particular feature of the invention, the axes XI, X2, and X3 are parallel. This U-shaped design is particularly compact and optimized for integration into a vehicle.

[0013] According to the invention, the drive pinion and the three gear wheels have straight teeth. The teeth can also be helical.

[0014] According to the invention, the torque output element is a shaft rotationally linked to the second gear and is configured to rotate around the axis of rotation X3. In other words, the torque output element and the second gear are coaxial.

[0015] According to another feature of the invention, the third gear and the first gear are mounted to rotate relative to each other. In other words, the third gear and the first gear are coaxial. Due to the reduction ratio of the three gears, the third gear and the first gear rotate at different speeds.

[0016] A washer is positioned axially between the first gear and the third gear in order to limit wear due to friction.

[0017] According to the invention, the second gear is two-stage, the first stage meshes with the first gear and the second stage meshes with the third gear.

[0018] Advantageously, the reduction ratio between the second and third gears is chosen according to the number of revolutions the torque output element must make. For example, when the torque output element makes n revolutions to cover the entire actuation range, the reduction ratio must be greater than n. More precisely, when the torque output element makes n revolutions corresponding to the actuation range, the third gear makes a maximum of only one revolution. It is thus possible to easily determine the position of the torque output element by means of the angular position of the third gear, knowing the reduction ratio between the second and third gears.

[0019] According to another feature of the invention, the electric motor, the motor pinion, the drive means, the third gear with the magnet, the electronic board with the sensor, and at least part of the torque output element are housed in a casing.

[0020] The invention, in general, relates to a rotary or linear electromechanical actuator comprising at least one of the above characteristics. In the case of a linear electromechanical actuator, the torque output element will be coupled to a roto-linear device.

[0021] Other features and advantages of the invention will become apparent from the following detailed embodiment, with reference to the attached figures:

[0022] [Fig.1] represents a perspective view of the actuator according to the present invention;

[0023] [Fig.2] represents a front view of the actuator according to the present invention.

[0024] It should be noted that the figures disclose the invention in a sufficiently detailed for its implementation, said figures helping to better define the invention if necessary. The invention should not, however, be limited to the embodiment disclosed in the description.

[0025] With reference to [Fig. 1] and [Fig. 2], an electromechanical actuator is shown comprising an electric motor 2 acting on a torque output element 6 suitable for coupling with a moving part of a vehicle's transmission. The electric motor 2 is a brushed DC type and comprises a motor shaft extending along an axis XI and a motor pinion 3 fixed to this shaft. The electric motor 2 is axially pressed into the housing (not shown) by a compression plate 21, known per se.

[0026] The torque output element 6 is configured to rotate about its axis of rotation between a first extreme position and a second extreme position, defining an actuation range. The actuation range of the output element of couple 6 is greater than one turn.

[0027] The torque output element 6 is connected to the electric motor 2 by means of a drive. These drive means comprise a first gear 4 and a second gear 5. The drive pinion 3 of the electric motor 2 meshes with the first gear 4, which is mounted to rotate about an axis X2 by means of a shaft 9. The first gear 4, in turn, meshes with the second gear 5, which is mounted to rotate about an axis X3. The drive pinion 3 and the two gears 4 and 5 have spur gears. The torque output element 6 is a shaft rotationally connected to the second gear 5 and is configured to rotate about the axis of rotation X3. The torque output element 6 is guided in rotation by a bearing 8 and a plain bearing 7. A seal is located between the bearing 8 and the plain bearing 7.The end of the torque output element 6 is grooved so that it can be coupled to the moving part of the transmission.

[0028] Axes XI, X2, X3 are parallel so that the actuator has a "U" shaped design.

[0029] The actuator 1 further comprises a third gear 11 which meshes with the second gear 5. This third gear 11 carries a magnet 15 at one of its ends. This magnet 15 is preferably attached to the gear 11 by snap-on clips. Other means of attaching the magnets are also possible, in particular by gluing. The magnet 15 faces a sensor 12 mounted on an electronic board 10. The interaction of the magnet 15 with the sensor 12 makes it possible to detect the angular position of the third gear 11.

[0030] A particular aspect of the invention is that the third gear 11 and the first gear 4 are mounted to rotate freely relative to each other. A washer 13 is positioned axially between the first gear 4 and the third gear 11.

[0031] The second gear 5 has two stages 51, 52. The first stage 51 meshes with the first gear 4, and the second stage 52 meshes with the third gear 11. The reduction ratio between the second gear 5 and the third gear 11 is chosen according to the number of revolutions that the torque output element 6 must make. In this case, the torque output element 6 must make 4 revolutions to cover the actuation range; therefore, the reduction ratio between the second gear 5 and the third gear 11 must be greater than 4. It is thus possible to easily detect the position of the torque output element 6 by means of the angular position of the third gear, knowing the reduction ratio between the second gear 5 and the third gear 11.

[0032] The motor pinion 3 and the three gear wheels 4, 5, 11 have straight teeth.

[0033] The electric motor 2, the motor pinion 3, the drive means 4, 5, the third gear 11 with magnet 15, electronic board 10 with sensor 12, and at least in part the torque output element 6 are housed in a casing 14.

[0034] Although the invention has been described in connection with a particular embodiment, it is clearly evident that it is by no means limited to it and that it includes all the technical equivalents of the means described.

[0035] In the claims, the reference symbols in parentheses shall not be interpreted as a limitation of the claim.

Claims

Demands

1. Electromechanical actuator (1) comprising an electric motor (2) acting on a torque output element (6) suitable for coupling with a moving part of a vehicle transmission, the torque output element (6) is configured to rotate about its axis of rotation between a first extreme position and a second extreme position defining an actuation range, the torque output element (6) is connected to the electric motor (2) by drive means (4, 5) comprising a first gear (4) and a second gear (5), the electric motor (2) comprises a drive shaft extending along an axis XI and a drive pinion (3), this drive pinion (3) meshes with the first gear (4) which is mounted to rotate freely about an axis X2, this first gear (4) in turn meshes with the second gear (5) mounted to rotate freely about an axis X3,The actuator (1) further comprises an electronic board (10) including a sensor (12) which faces a magnet (15) mounted on a third gear (11), said third gear (11) meshing with the second gear (5), the third gear (11) and the first gear (4) are mounted to rotate flexibly relative to one another.

2. Actuator (1) according to claim 1, characterized in that the actuation range of the torque output element (6) is greater than one turn.

3. Actuator (1) according to any one of the preceding claims, characterized in that the drive pinion (3) and the three gear wheels (4, 5, 11) have straight or helical teeth.

4. Actuator (1) according to any one of the preceding claims, characterized in that the torque output element (6) is a shaft rotationally linked to the second gear (5) and is configured to rotate about the rotation axis X3.

5. Actuator (1) according to any one of the preceding claims, characterized in that a washer (13) is positioned axially between the first gear (4) and the third gear (11).

6. Actuator (1) according to any one of the preceding claims, characterized in that the second gear (5) is two-stage (51, 52), the first stage (51) meshes with the first gear (4) and the second stage (52) meshes with the third gear (11).

7. Actuator (1) according to any one of the preceding claims, characterized in that the reduction ratio between the second gear (5) and the third gear (11) is chosen according to the number of turns that the torque output element (6) must make.

8. Actuator (1) according to any one of the preceding claims, characterized in that the electric motor (2), the motor pinion (3), the drive means (4, 5), the third gear (11) with the magnet (15), the electronic board (10) with the sensor (12), and at least in part the torque output element (6) are housed in a casing (14).

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