Electromechanical actuator

Abstract

The present invention relates to an electromechanical actuator (1, 1') comprising an electric motor (3) housed in a housing (2), the electric motor (3) acting on a torque output element capable of being coupled to an element of a transmission gearbox of a motor vehicle, the torque output element being connected to the electric motor (3) by drive means (4), the torque output element being a main shaft (7) configured to rotate about its axis of rotation (X) with a first end (7a) and a second end (7b). The actuator (1, 1') further comprises a circuit board (13) located in the housing (2), the circuit board (13) comprises a sensor (14) which faces a magnet (17) mounted on a support (16) coupled to the second end (7b) of the main shaft (7) by means of a first swivel-linear mechanism (15).

Description

Description Title of the invention: Electromechanical actuator [1] The invention relates to an electromechanical actuator. [2] The invention applies more specifically 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 referred to as 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. [3] The invention also applies to the field of actuators for a system of connecting / disconnecting elements in the transmission of the aforementioned vehicles. [4] Actuators of this type are known, for example in document ES1217209UA. This type of actuator has the disadvantage of proposing a complex mechanism for detecting the position of the main shaft with a worm gear system. [5] It is therefore necessary to propose a system that is simpler to implement and less expensive while still being effective. [6] Thus, the invention provides an electromechanical actuator comprising an electric motor housed in a casing, the electric motor acting on a torque output element suitable for coupling with an element of a motor vehicle transmission, the torque output element being connected to the electric motor by drive means, the torque output element being a main shaft configured to rotate about its axis of rotation with a first end and a second end. The actuator further comprises an electronic board located in the casing, the electronic board comprising a sensor which faces a magnet mounted on a support coupled to the second end of the main shaft by means of a first roto-linear mechanism. [7] This design allows for reliable measurement of the main shaft position with a simple and inexpensive design. [8] According to one aspect of the invention, the sensor is preferably a Hall effect sensor and the magnet is permanent and polarized. [9] Advantageously, the first roto-linear mechanism is a screw-nut system. The screw part is located on the main shaft, more precisely at its second end. The nut part can be the magnet support directly or indirectly connected to the magnet support. Any other type of roto-linear mechanism can be used as an alternative, for example, a ball screw system.

[0010] According to the invention, the main shaft is connected to the electric motor by means of a pinion-wheel system to rotate the main shaft. The pinion is located on the shaft of the electric motor, and the wheel is located on the torque output element, i.e., the main shaft. Preferably, the pinion-wheel system has spur gears.

[0011] According to the invention, the first roto-linear mechanism is coupled to a surface of the housing to perform an anti-rotation function. More specifically, the nut portion of the first roto-linear mechanism is coupled to the surface of the housing.

[0012] In an alternative embodiment, the first roto-linear mechanism is linked to the magnet support by a grooved cam system. This allows the linear displacement of the first roto-linear mechanism to be transformed into a rotation of the magnet support.

[0013] According to an additional feature of the invention, a second roto-linear mechanism is coupled to the first end of the main shaft. This second roto-linear mechanism transforms the rotary motion of the main shaft into linear motion. The second roto-linear mechanism is a screw-nut system; the screw portion is located on the main shaft, specifically at its first end, and the nut portion acts as a thrust element. Any other type of roto-linear mechanism can be used as an alternative, for example, a ball screw system.

[0014] According to another feature of the invention, the stroke of the first roto-linear mechanism is different from the stroke of the second roto-linear mechanism. For example, the stroke of the first roto-linear mechanism and the stroke of the second roto-linear mechanism have a ratio between 0.1 and 3.

[0015] In particular, the stroke of the first roto-linear mechanism can be smaller than the stroke of the second roto-linear mechanism. This characteristic allows for a reduction in the stroke of the first roto-linear mechanism associated with the magnet support and the use of a standard sensor.

[0016] Alternatively, the stroke of the first roto-linear mechanism can be greater than the stroke of the second roto-linear mechanism. This feature increases the measurement accuracy.

[0017] Advantageously, the main shaft is guided in rotation by a bearing; the inner ring of the bearing is in contact with the main shaft, and the outer ring of the bearing is in contact with the housing and a flange fixed to the housing. The bearing is preferably a double-row ball bearing because the main shaft is subjected to high axial loads on the order of 700 N.

[0018] According to a particular feature of the invention, the electric motor comprises a front face facing the drive means and a rear face. The housing includes a removable cap on the rear face of the electric motor. Once removed, the cap advantageously allows access to the motor for manually engaging or disengaging the locking system.

[0019] Other features and advantages of the invention will become apparent from the following detailed examples of implementations, with reference to the attached figures:

[0020] [Figure 1] represents a cross-sectional view of an actuator according to a first embodiment;

[0021] [Figure 2] represents a perspective and partial cross-sectional view of the actuator of [Figure 3];

[0022] [Figure 3] represents a cross-sectional view of an actuator according to a second embodiment;

[0023] [Figure 4] represents a top view of an actuator without the cover according to a third embodiment;

[0024] [Figure 5] represents a perspective and partial cross-sectional view of the actuator of [Figure 4].

[0025] It should be noted that the figures disclose the invention in sufficient detail for its implementation, and these figures help to further define the invention if necessary. However, the invention should not be limited to the embodiments disclosed in the description.

[0026] In the first embodiment illustrated in [Figure 4], the electromechanical actuator 1 comprises a DC electric motor 3 housed within a casing 2 made, for example, of aluminum or plastic. The electric motor 3 has a front face 3a and a rear face 3b. The casing 2 includes a removable plug 30 on the rear face 3b of the electric motor 3. The casing 2 can be attached to the transmission via mounting eyelets 20. The upper part of the casing 2 is closed by means of a cover 40, this cover 40 comprising a gas-permeable and liquid-impermeable membrane 50. The cover 40 incorporates an electrical connector for supplying the actuator 1 with electrical power.

[0027] The electric motor 3 acts on a thrust member 18 configured to perform a predetermined linear displacement (an extension and retraction movement) to come into contact with an external mechanism (not shown) in the transmission box.

[0028] The thrust member 18 is connected to the electric motor 3 via a main shaft 7 axially aligned with the thrust member 18. The main shaft 7 is preferably made of metal and is configured to rotate about its axis of rotation X. A first end 7a of the main shaft 7, i.e., the one facing the transmission element, is coupled to the thrust member 18 by a roto-linear mechanism 9, so that the thrust member 18 can move in translation and simultaneously in rotation relative to the main shaft 7 when the main shaft 7 is rotating. The roto-linear mechanism 9 is a screw-nut system. The first end 7a of the main shaft 7 has an external threaded section which is coupled to a threaded section present in an internal housing of the thrust member 18.

[0029] The main shaft 7 is connected to the electric motor 3 by means of drive 4, i.e. a pinion-wheel system to perform the rotation of the main shaft 7. The toothed wheel 6 of the pinion-wheel system is fixedly coupled to the main shaft 7 which engages with a pinion 5 mounted on a shaft of the electric motor 3.

[0030] The electric motor 3 is controlled by means of an electronic board 13 located in the housing 2.

[0031] To ensure the operation of the actuator 1, detection means are provided, configured to detect the axial position of the thrust member 18. These means include a permanently mounted Hall effect sensor 14 connected to the electronic board 13 and a permanent magnet 17. This magnet 17 is mounted on a support 16, which is coupled to the main shaft 7 by means of a roto-linear mechanism 15. This allows the magnet support to move in translation relative to the main shaft 7 when the main shaft 7 is rotating. The roto-linear mechanism 15 is a screw-nut system.

[0032] With regard more specifically to the magnet support 16, it comprises a plastic body having an upper area receiving the magnet 17 and a lower area in the form of a threaded nut configured to engage with a threaded section of the second end 7b of the main shaft 7. The magnet support 16 is preferably snapped onto the threaded nut.

[0033] The stroke of the two roto-linear mechanisms 9 and 15 is different. In particular, the stroke of the first roto-linear mechanism 15, that is, the one associated with the sensor 14 and magnet 17 detection system, is shorter than the stroke of the second roto-linear mechanism 9 of the thrust member 18. For example, the stroke of the first roto-linear mechanism 15 is 14 mm and the stroke of the second roto-linear mechanism 9 is 22 mm. Thus, the stroke of the first roto-linear mechanism and the stroke of the second roto-linear mechanism have a ratio between 0.5 and 0.8. Preferably, the ratio is 0.7.

[0034] Thus, depending on the magnetic field generated by the permanent magnet 17 which is detected by the sensor 14, the system will know the exact position of the thrust member 18.

[0035] The main shaft 7 is supported and guided in rotation by a double-row ball bearing 11. The inner ring of the bearing 11 is in contact with the main shaft 7 and the outer ring of the bearing 11 is in contact with the housing 2 and a flange 10 attached to the housing 2. The flange 10 also serves as a guide for the second roto-linear mechanism 9. A lip seal 12 is housed in the flange 10 and is located axially between the bearing 11 and the thrust member 18 in order to prevent external contaminants from entering the actuator 1.

[0036] Figure 2 provides a clearer view of the magnet support 16, specifically the upper area receiving the magnet 17 and the lower area in the form of a threaded nut configured to engage with a threaded section of the second end 7b of the main shaft 7. The magnet support 16 has a substantially [shaped] The "T" and the two wings of the "T" of the magnet support 16 are in contact with two flat surfaces 8 of the housing 2 to perform an anti-rotation function. The contact is linear with a protrusion 81. The housing 2 thus comprises two flat surfaces 8 on which the two wings of the magnet support 16 slide. The magnet 17 is located on one of the two wings of the support 16.

[0037] Unlike the first embodiment, the second embodiment illustrated in [Figure 3] does not incorporate a second roto-linear mechanism. In other words, the first end 7a of the main shaft 7 does not have a thread but only a surface suitable for contacting an external mechanism. The other elements referenced in [Figure 3] being similar to those in [Figure 5] and [Figure 2], they will not be described here.

[0038] A third embodiment is illustrated in [Figure 4]. Unlike the first and second embodiments, the third embodiment transforms a linear displacement into a rotation. In other words, in the first and second embodiments, the magnet 17 undergoes a translation, and in the third embodiment, the magnet 17 undergoes a rotation. To achieve this, the first roto-linear mechanism 15, and more specifically its threaded nut portion, engages with the threaded section of the second end 7b of the shaft. The main shaft 7 includes a roller 151 which engages in a groove 162 of the magnet support 161. This forms a grooved cam system between the first roto-linear mechanism 15 and the magnet support 161. The torque transmission kinematics between the electric motor 3 and the main shaft 7 is similar to the first and second embodiments.

[0039] Figure 5 provides a clearer visualization of the grooved cam system between the first roto-linear mechanism 15 and the magnet support 161. It is visible that the magnet support 161 is partially housed in a recess in the casing 2 to prevent its translation and thus force it to pivot around the Z-axis. The groove 162 in the magnet support 161 is oblong. The roller 151 is formed from the same material as the threaded nut portion of the first roto-linear mechanism 15. During operation, when the threaded nut portion of the first roto-linear mechanism 15 translates, the magnet support 161 pivots around the Z-axis. This allows the position of the pusher to be determined by detecting the rotation of the magnet 17, which is associated with a sensor 14 (not shown in this figure).

[0040] Although the invention has been described in connection with two particular embodiments, it is clearly evident that it is by no means limited to them and that it includes all technical equivalents of the means described.

[0041] In claims, reference symbols in parentheses should not be interpreted as a limitation of the claim.

Claims

Claims

1. Electromechanical actuator (1, 11”) comprising an electric motor (3) housed in a housing (2), the electric motor (3) acting on a torque output element adapted to be coupled with an element of a transmission box of a motor vehicle, the torque output element being connected to the electric motor (3) by drive means (4), the torque output element being a main shaft (7) configured to rotate about its axis of rotation (X) with a first end (7a) and a second end (7b), the actuator (1, 1') further comprises an electronic card (13) located in the housing (2), the electronic card (13) comprises a sensor (14) which faces a magnet (17) mounted on a support (16, 161) coupled to the second end (7b) of the main shaft (7) by means of a first roto-linear mechanism (15).

2. Electromechanical actuator (1, 1', 1") according to claim 1, characterized in that the main shaft (7) is connected to the electric motor (1) by means of a pinion (5) wheel (6) system to effect rotation of the main shaft (7).

3. Electromechanical actuator (1, 1', 1") according to claim 1 or 2, characterized in that the first roto-linear mechanism (15) is coupled to a surface (8) of the housing (2) to perform an anti-rotation function.

4. Electromechanical actuator (1”) according to one of the preceding claims, characterized in that the first roto-linear mechanism (15) is associated with the magnet support (161) by a groove cam system (151, 162).

5. Electromechanical actuator (1, 1', 1") according to one of the preceding claims, characterized in that a second roto-linear mechanism (9) is coupled to the first end (7a) of the main shaft (7).

6. Electromechanical actuator (1, 1', 1") according to claim 5, characterized in that the stroke of the first roto-linear mechanism (15) is different from the stroke of the second roto-linear mechanism (9)-

7. Electromechanical actuator (1, 11”) according to claim 5 or 6, characterized in that the stroke of the first roto-linear mechanism (15) is smaller than the stroke of the second roto-linear mechanism (9) or the stroke of the first roto-linear mechanism (15) is larger than the stroke of the second roto-linear mechanism (9).

8. Electromechanical actuator (1, 11”) according to one of the preceding claims, characterized in that the main shaft (7) is rotationally guided for a bearing (11), the inner ring of the bearing (11) is in contact with the main shaft (7) and the outer ring of the bearing (11) is in contact with the housing (2) and a flange (10) fixed to the housing (2).

9. Electromechanical actuator (1, 1', 1") according to claim 8, characterized in that the bearing (11) has a double row of balls.

10. Electromechanical actuator (1, 1', 1") according to one of the preceding claims, characterized in that the electric motor (3) comprises a front face (3a) facing the drive means (4) and a rear face (3b), the housing (2) comprises a removable cap (30) at the rear face of the electric motor (3b).

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