Electromechanical actuator

Abstract

The present invention relates to an electromechanical actuator (1) comprising a housing (20), an electric motor (2), a gear power transmission system, a torque output element (7) rotatable about a Z axis between two extreme positions and a support element (10, 30), said gear power transmission system comprises at least one shaft (5) with a worm screw system (51) rotatable about an X axis, the housing (20) and the support element (10, 30) each comprise two axially separated half-bearings (11, 12, 21, 22) so that when the support element (10, 30) is assembled to the housing (20) the shaft (5) is guided in rotation by two axially separated bearings. According to the invention, the two half-bearings of the housing (21, 22) and of the support element (11, 12) cooperate by means of complementary shapes. Figure for the abstract: Figure 1

Description

Title of the invention: Electromechanical actuator

[0001] 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".

[0002] 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.

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

[0004] Actuators of this type are known and are conventionally designed with a toothed wheel and worm gear system for transmitting the rotational movement of an electric motor to a torque output element of the actuator. Such an actuator is described in application US 2019383391 AL This actuator comprises a housing, an electric motor, a gear power transmission system with a worm system and a torque output element rotatable between a locking position and an unlocking position.

[0005] This prior art actuator has a first drawback in the fixing of the shaft comprising the worm screw. This shaft is supported and guided in rotation only by the housing via a rolling bearing and a bearing. This design has the drawback of being complex and expensive due to a high number of components. In addition, all the forces generated by the worm screw are taken up only by the housing, which generates high stresses at the fixings of the shaft on the housing.

[0006] Another disadvantage exists at the level of the axial stop of the worm shaft. The axial stop is carried out by additional components, in particular the rolling bearing or the bearing, which generates additional cost and excess weight.

[0007] There is thus a need to improve the existing actuator in order to provide a simpler design with few components in order to obtain a lightweight and relatively inexpensive actuator.

[0008] Thus, the invention provides 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, said gear power transmission system comprises at least one shaft with a worm screw system rotatable about an X axis, the housing and the support element each comprise two axially separated half-bearings so that when the support element is assembled to the housing the shaft is guided in rotation by two axially separated bearings. The two half-bearings of the housing and the support element cooperate by form complementarity.

[0009] This arrangement allows the shaft with the worm screw to be mounted directly on the housing and the support element without any additional element such as a bearing, a rolling bearing or a ring for guiding the shaft in rotation. This thus avoids a complex assembly process. In addition, the forces generated by the worm screw are distributed uniformly between the housing and the support element, and no longer only on one element of the actuator.

[0010] In the case of an actuator for a parking lock system of a vehicle transmission, the two extreme positions are a locking position and an unlocking position.

[0011] According to the invention, each half-bearing of the housing and of the support element comprises at least one positive imprint and / or one negative imprint. For example, the positive imprint is on the half-bearing of the housing and the negative imprint is on the half-bearing of the support element. Preferably, each half-bearing comprises two imprints located on either side of the concave surface receiving the shaft.

[0012] According to a characteristic of the invention, the imprints have flat stop surfaces allowing immobilization of the support element relative to the housing along the X axis and along a Y axis transverse to the X axis. Preferably, the positive or negative imprint is cubic or cuboid in shape (rectangular prism or rectangular parallelepiped). Obtaining flat surfaces is simpler to achieve with an injection molding process compared to round surfaces, for example pins.

[0013] Advantageously, the contacting faces of each half-bearing of the housing and of the support element have a “U” shape in the XY plane. This shape allows locking in two directions.

[0014] According to the invention, the shaft comprises a toothed wheel which meshes with a motor pinion of the electric motor, said shaft comprises a shoulder serving as an axial stop of the shaft against a face of one of the bearings. This arrangement makes it possible to axially lock the shaft relative to the housing and the support element without any additional element such as a circlip, a bearing or a rolling bearing. This thus avoids a complex assembly process.

[0015] According to the invention, the toothed wheel, the shoulder and a rotational guide portion are surmounted on the shaft, said portion being located axially along the X axis between the toothed wheel and the shoulder. This design allows simple assembly of the actuator.

[0016] According to an additional characteristic of the invention, the worm screw system of the shaft meshes with the torque output element via a toothed sector integral with the torque output element.

[0017] According to the invention, the electric motor is housed in the housing and extends along an axis X' parallel to the axis X, the support element comprises electrical connection means in order to supply the electric motor with electrical energy and means for locking the electric motor in the housing.

[0018] According to the invention, the support element is an intermediate frame or a cover. Advantageously, the cover is fixed to the housing in order to delimit an internal volume in which the electric motor, the gear power transmission system, the intermediate frame and the torque output element are located. Preferably, the intermediate frame is fixed to the housing by at least one fixing means, for example a screw.

[0019] According to another characteristic of the invention, the intermediate frame comprises an opening coaxial with the axis of rotation of the torque output element, in order to allow the passage of a system for detecting the angular position of the torque output element. The detection system comprises a magnet arranged on the torque output element and a sensor arranged on an electronic card fixed to the intermediate frame. Advantageously, the housing guides the torque output element in rotation.

[0020] According to the invention, the housing and the support element, in particular the intermediate frame, are made of plastic. The cover is also made of plastic.

[0021] Other characteristics and advantages of the invention will emerge from the following reading of a detailed embodiment, with reference to the appended figures:

[0022] [Fig.l] represents an exploded perspective view of the actuator according to the invention;

[0023] [Fig.2] represents a perspective view from below of the support element;

[0024] [Fig.3] shows a sectional view of the actuator of [Fig.l] without the cover.

[0025] It should be noted that these 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.

[0026] Referring to [Fig.l], the actuator 1 mainly comprises a housing 20, an electric drive motor 2, a geared power transmission system, an intermediate frame 10, a torque output element 7, an electronic card 60 and a cover 30.

[0027] The gear power transmission system reduces the speed and increases the torque of the electric motor 2. The gear power transmission system comprises a motor pinion 3 mounted on the output shaft of the electric motor 2, a gear wheel 4 which meshes with the motor pinion 3, a shaft 5 with a worm 51 which is connected to the gear wheel 4, the shaft 5 extends along an axis X, a toothed sector 6 which meshes with the worm 51. The torque output element 7 is integral with the toothed sector 6. The electric motor 2 is housed in the housing 20 and extends along an axis X' parallel to the axis X of the shaft 5. The electric motor 2 comprises a front face and a rear face. The front face and the rear face each comprise a cylindrical protrusion corresponding to a shape complementarity with a bearing internal to the electric motor 2.

[0028] The housing 20 and the cover 30 form, once assembled together, an internal volume in which the electric motor 2, the gear power transmission system, the intermediate frame 10, the torque output element 7 and the electronic card 60 are housed. The housing 20 and the cover 30 can be assembled together by any type of sealed fastening, for example screwing, gluing or by laser welding, ultrasound. The housing 20 and the cover 30 are made of plastic, in particular of PBT reinforced with fiberglass. A semi-permeable membrane, i.e. permeable to gases and impermeable to liquids, is housed in the housing 20 or in the cover 30 in order to automatically regulate the pressure inside the actuator 1.

[0029] The cover 30 also comprises an electrical connector 31 in order to connect the actuator 1 to an electrical source of the vehicle. The electronic card 60 is connected both to the electrical connector 31 and to the electric motor 20 via conductive pins passing through the intermediate frame 10.

[0030] The housing is capable of being fixed to a transmission box of the vehicle by means of fixing means passing through openings in the housing 20. The housing 20 is thus positioned precisely with the transmission box.

[0031] The torque output element 7 is produced in the form of a shaft, one end of which has the form 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 7 can be produced in the form of a male socket.

[0032] The housing 20 comprises an opening in the form of a guide barrel in which the torque output element 7 is mounted. Thanks to precise tolerancing between the opening and the torque output element 7, precise rotational guidance allows the torque output element 7 to move between a locking position and an unlocking position.

[0033] The housing 20 and the intermediate frame 10 each comprise two half-bearings 11, 12, 21, 22 separated axially along the axis X so that when the intermediate frame 10 is assembled to the housing 20 the shaft 5 is guided in rotation by two axially separated bearings.

[0034] The two half-bearings of the housing 21, 22 and of the intermediate frame 11, 12 cooperate by complementarity of shape. For this purpose, each half-bearing of the housing 21, 22 and of the intermediate frame 11, 12 comprises at least one positive imprint or one negative imprint. In the embodiment described here, the half-bearings of the housing 20 have positive imprints 211, 221 and the half-bearings of the intermediate frame have negative imprints 111, 121 which are visible in [Fig. 2]. It is entirely possible to provide alternatively that the half-bearings of the housing 20 have positive and negative imprints and that the half-bearings of the intermediate frame 10 have positive and negative imprints.

[0035] The indentations 111, 121, 211, 221 have flat stop surfaces allowing immobilization of the intermediate frame 10 relative to the housing 20 along the X axis and along a Y axis transverse to the X axis. The contacting faces of each half-bearing of the housing 21, 22 and of the intermediate frame 11, 12 have a “U” shape in the XY plane. Each half-bearing comprises a concave surface for receiving the shaft 5.

[0036] [Fig. 2] allows a better visualization of the intermediate frame 10 and in particular the negative impressions 111, 121 of the two half-bearings. The intermediate frame 10 comprises electrical connection means 13, in the form of pins, passing through the intermediate frame on either side in order to supply the electric motor 2 with electrical energy. The intermediate frame also comprises locking means 13, 14 for locking the electric motor in the housing 20. These locking means 13, 14 extend in the form of a protrusion and engage with the front face and the rear face of the electric motor 2 by a complementary shape. The electric motor 2 is thus locked axially along the X axis and transversely along the Y axis.

[0037] The intermediate frame 10 further comprises an opening 9 coaxial with the axis of rotation Z of the torque output element 7, in order to allow the passage of a system for detecting the angular position of the torque output element 7. The detection system comprises a magnet 8 arranged on the torque output element 7 and a sensor arranged on the electronic card 60 fixed on the intermediate frame 10. The magnet 8 can be glued, snapped, screwed or overmolded to the torque output element 7. The torque output element 7 passes through the intermediate support 10 on either side. The electronic card 60 is fixed on the intermediate frame 10 on the face opposite the face where the two half-bearings 11, 12 are located.

[0038] The intermediate frame also includes openings to allow passage of means for fixing the frame to the housing.

[0039] [Fig. 3] allows a better visualization of the rotational guidance of the shaft 5 as well as its axial stop. In this [Fig. 3], the cover is not shown. The shaft 5 comprises for this purpose a shoulder 42 serving as an axial stop along the axis X of the shaft 5 against a face of one of the bearings 11, 12. The toothed wheel 4, the shoulder 42 and a rotational guidance portion 41 are overmolded on the shaft 5, said portion 41 is located axially between the toothed wheel 4 and the shoulder 42. The shaft 5 is thus sandwiched between the housing 20 and the intermediate frame 10. The shaft is preferably made of metal. Thus, the first rotational guidance is a plastic-on-plastic contact due to the overmolding of the portion 41 and the second rotational guidance is a plastic-on-metal contact. Grease may be added between shaft 5 and the bearings to prevent wear and facilitate rotation.

[0040] Although the invention has been described in connection with a particular embodiment, it is quite obvious that it is in no way limited thereto and that it includes all the technical equivalents of the means described.

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

Claims

Claims

1. Electromechanical actuator (1) comprising a housing (20), an electric motor (2), a gear power transmission system, a torque output element (7) rotatable about an axis Z between two extreme positions and a support element (10, 30), said gear power transmission system comprises at least one shaft (5) with a worm screw system (51) rotatable about an axis X, the housing (20) and the support element (10, 30) each comprise two half-bearings (11, 12, 21, 22) axially separated so that when the support element (10, 30) is assembled to the housing (20) the shaft (5) is guided in rotation by two axially separated bearings, characterized in that the two half-bearings of the housing (21, 22) and of the support element (11, 12) cooperate by complementarity of shape and in that the shaft (5) comprises a toothed wheel (4) which meshes with a motor pinion (3) of the electric motor (2),said shaft (5) comprises a shoulder (42) serving as an axial stop for the shaft (5) against a face of one of the bearings.,

2. Actuator (1) according to claim 1, characterized in that each half-bearing of the housing (21, 22) and of the support element (11, 12) comprises at least one positive imprint (211, 221) and / or one negative imprint (111, 121).

3. Actuator (1) according to claim 2, characterized in that the impressions (111, 121, 211, 221) have flat stop surfaces allowing immobilization of the support element (10, 30) relative to the housing (20) along the X axis and along a Y axis transverse to the X axis.

4. Actuator (1) according to claim 3, characterized in that the contacting faces of each half-bearing of the housing (21, 22) and of the support element (11, 12) have a “U” shape in the XY plane.

5. Actuator (1) according to one of the preceding claims, characterized in that the toothed wheel (4), the shoulder (42) and a portion (41) for guiding in rotation are overmolded on the shaft (5), said portion (41) is located axially along the X axis between the toothed wheel (4) and the shoulder (42).

6. Actuator (1) according to one of the preceding claims, characterized in that the worm system (51) of the shaft (5) meshes with the torque output element (7) via a toothed sector (6) integral with the torque output element (7).

7. Actuator (1) according to one of the preceding claims, characterized in that the electric motor (2) is housed in the housing (20) and extends along an axis X' parallel to the axis X, the support element (10, 30) comprises electrical connection means (13) in order to supply the electric motor (2) with electrical energy and means (13, 14) for locking the electric motor in the housing (20).

8. Actuator (1) according to one of the preceding claims, characterized in that the support element is an intermediate frame (10) or a cover (30).

9. Actuator (1) according to claim 8 when the support element is an intermediate frame (10), characterized in that the intermediate frame (10) comprises an opening (9) coaxial with the axis of rotation of the torque output element (7), in order to allow the passage of a system for detecting the angular position of the torque output element (7), the detection system comprises a magnet (8) arranged on the torque output element (7) and a sensor arranged on an electronic card (60) fixed on the intermediate frame (10).

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