FR3149065A1 - Electromechanical actuator - Google Patents

Abstract

The present invention relates to an electromechanical actuator (1) comprising a housing (2), an electric motor, a gear power transmission system, a torque output element (10) rotatable about a Z axis between two extreme positions and a support element (20). The torque output element (10) is guided in rotation by a rolling member (30) and this rolling member is mounted in the support element (20). Abstract: Figure 3

Description

Electromechanical actuator

The invention relates to an electromechanical actuator. More specifically, the invention relates to an actuator for a parking lock system of 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 of 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 on the transmission box.

Actuators of this type are known and are conventionally designed with a gear system of toothed wheel and worm screw for transmitting the rotational movement of an electric motor to a torque output element of the actuator. Such an actuator is described in application DE 102019100300 A1. This actuator comprises a housing, an electric motor, a gear power transmission system with a worm screw system and a torque output element rotatable between a locking position and an unlocking position. This torque output element is guided in rotation by a support element.

This prior art actuator has a first drawback in terms of the transmissible torque. The torque output element and the support element are made of plastic and the torque output element is guided in rotation by the support element by plastic/plastic contact. This design does not allow a high torque to be transmitted. One solution would be to use a more powerful electric motor but this implies a greater weight at the risk of degrading the gear power transmission system.

There is therefore a need to improve the existing actuator in order to enable the transmission of a significant torque, i.e. of the order of 15 Nm, without damaging the actuator components.

Thus, the invention proposes an electromechanical actuator comprising a housing, an electric motor, a gear power transmission system, a torque output element rotatable about a Z axis between two extreme positions and a support element. The torque output element is guided in rotation by a rolling member and this rolling member is mounted in the support element.

This arrangement is more robust than all other solutions with plastic interface parts. In addition, the forces generated by the electric motor and the gear power transmission system are taken up by the support element and the rolling element thanks to their rigidity and this without damaging the housing.

According to the invention, the two extreme positions are a locking position and an unlocking position.

According to the invention, the rolling member is distinct from the support element. In other words, the rolling member is an additional element.

According to the invention, the housing is made of plastic and the support element is made of metal. Preferably, the housing is made of glass fiber reinforced PA or PBT. Preferably, the support element is made of aluminum alloy. Preferably, the support element is obtained by die casting.

According to a characteristic of the invention, the support element comprises a barrel and the rolling member is mounted in this barrel. The barrel extends along the Z axis. Preferably, the rolling member is crimped into the barrel of the support element. Preferably, the barrel is obtained by machining, which allows better precision for integrating the rolling member.

Advantageously, the torque output element comprises a toothing which partly covers the barrel axially along the Z axis so that the toothing and the rolling member are in the same plane P. This characteristic has the effect of stiffening the toothing of the torque output element.

According to the invention, the rolling member comprises an inner ring and an outer ring, said outer ring is in axial abutment against a shoulder of the support element and the inner ring is in axial abutment against a shoulder of the torque output element. An axial abutment is understood to mean a stop along the Z axis. The rolling member is for example a ball bearing or roller bearing. Other types of bearing are of course possible.

According to the invention, the torque output element comprises a metal core on which a toothing, in particular a toothed sector, is overmolded. The metal core comprises a coupling means in the form of a male or female imprint.

According to an additional characteristic of the invention, a magnetic target is overmolded on the torque output element, said magnetic target faces a sensor mounted on an electronic card fixed on the support element.

According to the invention, said gear power transmission system comprises a shaft having a worm system and a toothed wheel, said toothed wheel meshes with a drive pinion of the electric motor and the worm system meshes with the torque output element. Preferably, the worm system is rotatable about an X axis. Preferably, the electric motor extends along an X' axis parallel to the X axis.

According to the invention, the support element carries the electric motor and the gear power transmission system. Preferably, the support element comprises means for locking the electric motor in the housing. Preferably, the support element comprises means for guiding the rotation of the shaft, in particular two bearings.

According to another characteristic of the invention, the actuator comprises a cover defining with the housing an internal volume in which the support element is located, the support element being fixed to the housing. The electric motor and the gear power transmission system are of course also in the internal volume because they are mounted on the support element.

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

there represents a perspective view from above of the support element of the actuator according to the invention;

there represents a perspective view from below of the support element of the actuator according to the invention;

there represents a sectional view of the actuator according to the invention;

there shows an enlarged view of the mounting of the rolling member in the support element.

It is noted that the figures disclose the invention in sufficient detail 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.

Referring to the , the interior of the actuator 1 is shown without housing 2 or cover 3. The actuator 1 mainly comprises an electric drive motor (not shown), a gear power transmission system, a support element 20 and a torque output element 10. The torque output element 10 is rotatable between two extreme positions and is guided in rotation by a rolling member 30 mounted in the support element 20. The support element can also be called an intermediate frame. The role of this support element 20 is to support the components of the actuator 1 so that they have a common reference, which facilitates assembly and functional dimensioning. This support element 20 is made of metal, in particular of aluminum alloy obtained by die casting. Certain parts of this support element 20 are then machined in order to obtain surfaces requiring precise tolerances.

The support element 20 comprises in particular a barrel 21 and the rolling member 30 is mounted in this barrel 21. The barrel 21 has previously been machined to receive the rolling member 30. The mounting of the rolling member 30 and its retention in the barrel 21 will be described in relation to the .

There allows for a better visualization of the gear power transmission system. On the , we have illustrated a reference X, Y, Z. The X direction or axis corresponds to a longitudinal direction. The Y direction or axis, transverse, is defined as being perpendicular to the longitudinal direction X. More specifically, the longitudinal and transverse directions X and Y can for example belong substantially to a substantially horizontal plane. The Z direction or axis corresponds to a vertical direction.

The geared power transmission system reduces the speed and increases the torque of the electric motor and comprises a motor pinion mounted on the output shaft of the electric motor, a gear wheel 4 which meshes with the motor pinion, a shaft 5 with a worm 51 which is connected to the gear wheel 4, a toothed sector 12 which meshes with the worm 51. The torque output element 10 is connected to the toothed sector 6. The shaft 5 extends along an axis X.

The support element 20 extends substantially in the XY plane. The support element 20 comprises an extension 26 which extends in the YZ plane in which there is an opening 27 capable of receiving the electric motor, in particular its front face. The electric motor extends along an axis X' parallel to the X axis. The electric motor is thus blocked axially along the X axis and transversely along the Y axis. The rear face of the electric motor is held by a fixing plate screwed into the support element 20, in particular in the inserts 29.

The shaft 5 is guided in rotation by two bearings 24, 25 made of the same material as the support element 20. The bearing surfaces of the bearings 24, 25 have been machined beforehand. The shaft 5 comprises a shoulder 28 serving as an axial stop along the axis X of the shaft 5 against a face of one of the bearings 25.

As illustrated in the , the housing 2 and the cover 3 form, once assembled together, an internal volume in which are housed the electric motor, the gear power transmission system, the support element 20, the torque output element 10 and an electronic card 40. The housing 2 and the cover 3 can be assembled together by any type of sealed fixing, for example screwing, gluing or by laser welding, ultrasound. The housing 2 and the cover 3 are made of plastic, in particular reinforced with fiberglass.

The housing 2 also includes an electrical connector 6 for connecting the actuator 1 to an electrical source of the vehicle. The electronic card 40 is connected both to the electrical connector 6 and to the electric motor via conductive pins.

The actuator 1 is adapted to be attached to a transmission box of the vehicle.

The torque output element 10 is made in the form of a shaft, one end of which has the shape of a star-shaped female socket in which an actuating rod (not shown) of a locking system is capable of engaging so as to lock or unlock a toothing of the transmission box (not shown) via an actuating lever or latch (not shown). Alternatively, the torque output element 10 can be made in the form of a male socket. More precisely, the torque output element 10 comprises a metal core 11 on which the toothed sector 12 is overmolded. This toothed sector 12 has a semi-global toothing, that is to say that the toothing is the combination of half a helical toothing and half a global toothing. This toothing has the advantage of being able to transmit a higher torque than a conventional helical toothing.

The torque output element 10 partly covers the barrel 21 axially along the Z axis. In other words, this amounts to saying that the toothed sector 12 is located axially along the Z axis at the same level as the rolling member 30, which allows better absorption by the support element 20 of the stresses generated by the worm screw 51 on the toothed sector 12. The teeth of the toothed sector 12 and the rolling member 30 are in the same plane P defined along the X, Y directions.

The housing 2 comprises an opening in the form of a guide barrel 7 in which the torque output element 10 is mounted.

The support element 20 further comprises an opening coaxial with the axis of rotation Z of the torque output element 10, in order to allow the passage of a system for detecting the angular position of the torque output element 10. The detection system comprises a magnetic target 14 arranged on the torque output element 10 and a sensor 41 arranged on the electronic card 40. The magnetic target 14 is overmolded on the toothed sector 12 at the end of the torque output element 10 opposite the female socket. The electronic card 40 is fixed to the support element 20, in particular by screws.

There shows more precisely the assembly of the rolling member 30 in the barrel 21 of the support element 20. The rolling member 30 is inserted into the barrel 21 following a machining operation of the support element 20 in order to create a rolling bearing surface.

The rolling member 30 is a ball bearing and thus comprises an inner ring 31 and an outer ring 32 between which the balls are arranged. The outer ring 32 is in axial abutment against a shoulder 22 of the support element 20 and the inner ring 31 is in axial abutment against a shoulder 13 of the torque output element 10.

Once the rolling member 30 is inserted into the barrel 21 and abuts against the shoulder 22, the lips 23 are folded against the rolling member 30, in particular the outer ring 32 by a crimping operation. The rolling member 30 is thus held in the support element permanently.

These machining operations of the bearings 24, 25 and the barrel 21 allow for much better gear center distance precision than with a plastic support element, which has the effect of limiting wear over time of the gear power transmission system.

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.

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

Claims (10)

Electromechanical actuator (1) comprising a housing (2), an electric motor, a gear power transmission system, a torque output element (10) rotatable about an axis Z between two extreme positions and a support element (20), characterized in that the torque output element (10) is guided in rotation by a rolling member (30) and this rolling member is mounted in the support element (20). Actuator (1) according to claim 1, characterized in that the housing (2) is made of plastic and the support element (20) is made of metal. Actuator (1) according to claim 1 or 2, characterized in that the support element (20) comprises a barrel (21) and the rolling member (30) is mounted in this barrel (21). Actuator (1) according to claim 3, characterized in that the torque output element (10) comprises a toothing (12) which partly covers the barrel (21) axially along the Z axis so that the toothing (12) and the rolling member (30) are in the same plane P. Actuator (1) according to one of the preceding claims, characterized in that the rolling member (30) comprises an inner ring (31) and an outer ring (32), said outer ring (32) is in axial abutment against a shoulder (22) of the support element (20) and the inner ring (31) is in axial abutment against a shoulder (13) of the torque output element (10). Actuator (1) according to claim 4, characterized in that the torque output element (10) comprises a metal core (11) on which the teeth (12), in particular a toothed sector, are overmolded. Actuator (1) according to one of the preceding claims, characterized in that a magnetic target (14) is overmolded on the torque output element (10), said magnetic target (14) faces a sensor (41) mounted on an electronic card (40) fixed on the support element (20). Actuator (1) according to one of the preceding claims, characterized in that said gear power transmission system comprises a shaft (5) having a worm system (51) and a toothed wheel (4), said toothed wheel (4) meshes with a motor pinion of the electric motor and the worm system (51) meshes with the torque output element (10). Actuator (1) according to one of the preceding claims, characterized in that the support element (20) carries the electric motor and the gear power transmission system. Actuator (1) according to one of the preceding claims, characterized in that it comprises a cover (3) defining with the housing (2) an internal volume in which the support element (20) is located, the support element (20) being fixed to the housing (2).