Electromechanical actuator

Abstract

The present invention relates to an electromechanical actuator (1) comprising an electric motor (2) acting on a torque output element (6) able to be coupled to a movable member of a vehicle gearbox, wherein the torque output element (6) is configured to rotate about its axis of rotation between a first end position and a second end position defining an actuation range, the torque output element (6) being connected to the electric motor (2) by drive means (4, 5) which comprise a first gear (4) and a second gear (5), the actuator (1) further comprising a circuit board (10). The circuit board (10) comprises two sensors (12, 13) which each face a magnet (41, 51) associated with each gear (4, 5) in order to detect the angular position of each gear (4, 5). The two gears (4, 5) have a different number of teeth corresponding to the number of turns required for the torque output member (6) to cover the actuation range.

Description

Description Title of the invention: Electromechanical actuator [1] The invention relates to an electromechanical actuator. More particularly, the invention relates to an electromechanical actuator which may be rotary or linear. [2] The invention applies, for example, to the field of actuators for a parking lock system for a vehicle gearbox, in particular a motor vehicle equipped with an automatic gearbox, for example a hybrid vehicle. The invention also applies to a parking lock system for a reducer associated with an electric vehicle motor. The gearbox or reducer will more generally be called a transmission box. This locking system is better known by its English term “park-lock” or “parking lock”. Such an actuator allows the transmission box to be locked in parking by means of a lever engaging with a toothing of the transmission box. [3] The invention also applies to the field of actuators for a system for connecting / disconnecting components in the transmission box of the aforementioned vehicles, such as, for example, forks, synchronizers, selectors, etc. [4] It is typical with these architectures that the actuator is placed outside the transmission box and that the moving part to be actuated is inside the transmission box. In order for the actuator to act reliably on the moving part of the transmission, it is necessary to know exactly the position of the moving part in the transmission box. [5] In the case of a rotary actuator, one solution would be to count the number of revolutions of the torque output element of the actuator to determine the position of the moving member, having prior knowledge of the number of revolutions required by the torque output element to cover the entire actuation range of the moving member. This solution has the disadvantage of having to store the position of the rotation in a storage unit. In addition, in the case In the event of a power outage, the stored position will be lost, which requires a complex learning procedure to implement. [6] One of the aims of the invention is to propose an actuator that can solve the problems mentioned above. The actuator must be capable of reliably and autonomously determining the position of the moving member in the transmission box over its entire actuation range without involving elements external to the actuator. [7] Thus the invention proposes an electromechanical actuator comprising an electric motor acting on a torque output element capable of being coupled with a movable member of a transmission box of a vehicle, the torque output element is configured to rotate around its axis of rotation between a first extreme position and a second extreme position defining an actuation range, the torque output element is connected to the electric motor by drive means comprising a first toothed wheel and a second toothed wheel. The actuator further comprises an electronic card which comprises two sensors which each face a magnet associated with each toothed wheel in order to detect the angular position of each toothed wheel. [8] According to the invention, the two toothed wheels have a different number of teeth. More precisely, the difference in the number of teeth between the two toothed wheels corresponds to the number of revolutions required by the torque output element to travel through the actuation range. Preferably, the number of revolutions required by the torque output element to travel through the actuation range corresponds to an integer. [9] According to the invention, the two toothed wheels also have different diameters.

[0010] This design thus makes it possible to recover two signals generated by the two angular position sensors of each toothed wheel for analysis purposes by a controller capable of generating a signal corresponding to an angular position of the torque output element over its actuation range.

[0011] The moving part of the gearbox 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.

[0012] 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°.

[0013] Preferably, both sensors are absolute sensors, for example Hall effect.

[0014] According to the invention, the electric motor comprises a motor shaft which extends along an axis X1 and a motor pinion, this motor pinion meshes with the first toothed wheel which is mounted to rotate about an axis X2, this first toothed wheel in turn meshes with the second toothed wheel mounted to rotate about an axis X3. According to a feature of the invention, the axes X1, X2, X3 are parallel. This “U” design is particularly compact and optimized for integration into a vehicle.

[0015] According to the invention, the drive pinion and the two gear wheels have straight teeth. The teeth can also be helical.

[0016] Thus, the angular position of the two gears will be different, which allows different signals to be generated. These different signals are the basic data for the controller to generate a signal corresponding to an angular position of the torque output element over its actuation range.

[0017] According to another characteristic of the invention, the two toothed wheels are guided in rotation by an intermediate frame.

[0018] According to the invention, the torque output element is a shaft rotatably connected to the second gear wheel and is configured to rotate about the axis of rotation X3. In other words, the torque output element and the second gear wheel are coaxial.

[0019] Advantageously, the electric motor, the motor pinion, the drive means with their magnets, the electronic card with the two sensors, the intermediate frame and at least partly the torque output element are housed in a housing.

[0020] The invention generally 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] The invention also relates to an assembly comprising an actuator according to one of the above characteristics and a controller, said controller being configured to generate a signal corresponding to an angular position of the torque output element over its actuation range from a comparison of the signals generated by the two angular position sensors of each toothed wheel.

[0022] Preferably, the controller is located on the actuator's electronic board.

[0023] Finally, the invention also relates to a method for determining the angular position of the torque output element of the actuator of the assembly mentioned above, the method comprising the following steps: i) recovery of a first signal associated with the angular position of the first toothed wheel, ii) recovery of a second signal associated with the angular position of the second toothed wheel, iii) comparison of the two signals by the controller, iv) generation by the controller of a signal corresponding to an angular position of the torque output element over its actuation range.

[0024] Other characteristics and advantages of the invention will emerge from the following reading of a detailed example of embodiment, with reference to the appended figures:

[0025] [Figure 1] shows a perspective view of the actuator according to the present invention;

[0026] [Figure 2] shows a front view of the actuator according to the present invention;

[0027] [Figure 3] represents a schematic diagram of the controller associated with the actuator according to the present invention;

[0028] [Figure 4] shows a graph of the controller's input and output signals.

[0029] 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 as needed. The invention should not, however, be limited to the embodiment disclosed in the description.

[0030] With reference to [Figure 3] and [Figure 2], an electromechanical actuator is shown without its housing in order to better highlight the internal elements. This actuator 1 comprises an electric motor 2 acting on a torque output element 6 capable of being coupled with a member movable in translation of a transmission box of a vehicle. The electric motor 2 is of the brushed direct current type and comprises a motor shaft which extends along an axis X1 and a motor pinion 3 fixed on this shaft. The electric motor 2 is axially pressed into the housing (not shown) by a compression plate 21, known per se.

[0031] 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 torque output element 6 is greater than one revolution.

[0032] The torque output element 6 is connected to the electric motor 2 by drive means. These drive means comprise a first gear wheel 4 and a second gear wheel 5. The motor pinion 3 of the electric motor 2 meshes with the first gear wheel 4 which is mounted to rotate about an axis X2 via a shaft 9. The first gear wheel 4 in turn meshes with the second gear wheel 5 mounted to rotate about an axis X3. The motor pinion 3 and the two gear wheels 4, 5 have straight teeth. The two gear wheels 4, 5 are guided in rotation by an intermediate frame 20 fixed to the housing (not shown). The torque output element 6 is a shaft connected in rotation to the second gear wheel 5 and is configured to rotate about the axis of rotation X3. The torque output element 6 is rotationally guided by a rolling bearing 8 and a plain bearing 7. A seal is located between the rolling 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 box.

[0033] The axes X1, X2, X3 are parallel so that the actuator has a “U” design.

[0034] Each toothed wheel 4, 5 carries a magnet 41, 51 at one of its ends. These magnets are fixed to the toothed wheels preferably by snap-fastening via hooks 42, 52. Other means of fixing the magnets are also possible, in particular by gluing. The magnets 41, 51 face two sensors 12, 13 mounted on an electronic card 10. The association of the magnet 41, 51 with its respective sensor 12, 13 makes it possible to detect the angular position of each toothed wheel 4, 5. The electronic card 10 also comprises a controller 100 for processing the signals S1 and S2 generated by the sensors 12, 13. This sensor and its functionalities will be discussed in connection with [Figure 3] and [Figure 4],

[0035] A particular aspect of the invention is that the two gear wheels 4, 5 have a different number of teeth. In the present case, the first gear wheel 4 has a smaller number of teeth than the second gear wheel 5. For example, the first gear wheel 4 comprises 24 teeth and the second gear wheel 5 comprises 28 teeth. This difference of 4 teeth corresponds to the 4 revolutions required by the torque output element 6 to travel the actuation range between its first and second extreme positions. Thanks to this difference, the angular position of the two gear wheels 4, 5 will be different.

[0036] It is thus established when the actuator 1 is in operation, due to the different number of teeth, that the angular position of the two toothed wheels 4, 5 will be different, each toothed wheel 4, 5 generating its own angular position signal S1, S2 via the magnets 41, 51 and the sensors 12, 13. Thus the signal S1 is associated with the first toothed wheel 4 and the signal S2 is associated with the second toothed wheel 5.

[0037] [Figure 3] schematically shows how these two input signals are processed by the controller 100. The controller 100 is configured to generate an output signal SF corresponding to the angular position of the torque output element 6 over its actuation range from a comparison of the input signals S1, S2 based on the graph of [Figure 4],

[0038] This [Figure 4] shows a graph with in particular the two input data S1 and S2 allowing to generate the output signal SF. Depending on its angular position, each toothed wheel 4, 5 generates a signal S1, S2 whose voltage varies. Due to the different number of teeth, a shift between these two signals is thus measured, which makes it possible to artificially create an SF signal using a modulo function of the voltage difference between signals S1 and S2 divided by the number of teeth of difference between gears 4, 5.

[0039] 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 technical equivalents of the means described.

[0040] In the claims, reference symbols in parentheses are not to be construed as a limitation of the claim.

Claims

Claims

1. Electromechanical actuator (1) comprising an electric motor (2) acting on a torque output element (6) capable of being coupled with a movable member of a transmission box of a vehicle, 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 toothed wheel (4) and a second toothed wheel (5), the actuator (1) further comprises an electronic card (10), characterized in that the electronic card (10) comprises two sensors (12, 13) which each face a magnet (41, 51) associated with each toothed wheel (4, 5) in order to detect the angular position of each toothed wheel (4, 5) characterized in that the two toothed wheels (4,5) have a different number of teeth corresponding to the number of revolutions required by the torque output element (6) to travel the actuation range.,

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

3. Actuator (1) according to claim 1 or 2, characterized in that the electric motor (2) comprises a motor shaft which extends along an axis X1 and a motor pinion (3), this motor pinion (3) meshes with the first toothed wheel (4) which is mounted to be able to rotate about an axis X2, this first toothed wheel (4) in turn meshes with the second toothed wheel (5) mounted to be able to rotate about an axis X3.

4. Actuator (1) according to claim 3, characterized in that the drive pinion (3) and the two toothed wheels (4, 5) have straight or helical teeth.

5. Actuator (1) according to one of the preceding claims, characterized in that the two toothed wheels (4, 5) are guided in rotation by an intermediate frame (20).

6. Actuator (1) according to claim 3, characterized in that the torque output element (6) is a shaft rotatably connected to the second toothed wheel (5) and is configured to rotate about the axis of rotation X3.

7. Actuator (1) according to one of the preceding claims, characterized in that the electric motor (2), the motor pinion (3), the drive means (4, 5) with their magnets (41, 51), the electronic card (10) with the two sensors (12, 13), the intermediate frame (20) and at least partly the torque output element (6) are housed in a housing.

8. Assembly comprising an actuator (1) according to one of the preceding claims and a controller (100), said controller (100) being configured to generate a signal (SF) corresponding to an angular position of the torque output element (6) over its actuation range from a comparison of the signals (S1, S2) generated by the two angular position sensors (12, 13) of each toothed wheel (4, 5).

9. Method for determining the angular position of the torque output element (6) of the actuator (1) of the assembly of claim 8, characterized in that the method comprises the following steps: i) recovery of a first signal (S1) associated with the angular position of the first toothed wheel (4), ii) recovery of a second signal (S2) associated with the angular position of the second toothed wheel (5), iii) comparison of the two signals (S1, S2) by the controller (100), iv) generation by the controller of a signal (SF) corresponding to an angular position of the torque output element (6) over its actuation range.)

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