EP4716825A1

EP4716825A1 - An assembly comprising a shaft and a magnet

Info

Publication number: EP4716825A1
Application number: EP24728962.2A
Authority: EP
Inventors: Mathieu Lallemant; Frederic Ribera
Original assignee: Valeo Embrayages SAS
Current assignee: Valeo Embrayages SAS
Priority date: 2023-05-22
Filing date: 2024-05-22
Publication date: 2026-04-01
Also published as: CN121175536A; WO2024240804A1; FR3149086A1; FR3149086B1

Abstract

The shaft (2) includes a body (5) and a projection (6). The shaft (2) rotates about an axis (4). The shaft (2) is configured to receive the magnet (3), particularly at one end of the shaft (2). A clearance (8) is located between the body (5) and the magnet (3). The clearance (8) is filled with the adhesive means (7). The magnet (3) abuts against the projection (6) to facilitate the retention of the adhesive means (7). The adhesive means (7) makes contact with the magnet 3 and secures the magnet (3) in place. The projection (6) ensures that the layer of the adhesive means (7) is intact between the body (5) and the magnet (3).

Description

AN ASSEMBLY COMPRISING A SHAFT AND A MAGNET ^^ FIELD OF INVENTION ^^^ The present subject matter relates to an assembly comprising a rotating shaft and a magnet particularly for use in an actuator for automobile applications. BACKGROUND ^^^ Generally, an automobile includes an actuator like a park lock actuator or a gearshift actuator. These actuators have an assembly that includes a rotating shaft, a magnet and a rotary position sensor. The magnet is mounted on the shaft and used as a target for a Hall Effect angular position sensor, or any such sensor. The sensor is arranged in close proximity to the magnet so that the sensor detects ^^^ a magnetic field generated by the magnet. Accordingly, information related to the angular position of the shaft may be ascertained. Typically, the magnet is mounted on a distal end of the shaft. An adhesive means, or a glue, is applied on the distal end; and the magnet is pressed thereon to achieve said mounting. However, upon pressing the magnet, the glue oozes ^^^ out of the distal end. It may also be said that the weight of the magnet push the glue towards an outer periphery of the magnet. As a result, the glue is exposed to high mechanical shear stress. Accordingly, a uniform glue thickness is not maintained. Consequently, over the course of operation, not enough glue remains in between the magnet and the shaft. ^^^ In another known arrangement disclosed in document US2022034642A1, the distal end of the shaft includes a bowl like structure to accommodate the magnet and the glue. The bowl like structure is known as a magnet base member. The glue is disposed in the bowl like structure of the shaft in other words the magnet base member. The magnet is pressed thereon to achieve said mounting of the magnet with the shaft. The above said arrangement leaves no space for the glue to move. In addition to the mechanical shear stress, the changes in the ^^ temperature has an effect on the thermal expansion of the glue. The glue deforms because of the impact of the surrounding temperature, for example, the texture of the glue may get change over the course of operation. The glue that is trapped in between the bowl like structure of the shaft and the magnet, which when gets thermally deformed, imparts a stress on the magnet. Consequently leads to ^^^ loosening of the magnet from the shaft. There is therefore a need to solve the technical problem associated with the assembly explained above. SUMMARY OF THE INVENTION ^^^ It is accordingly an object of the present arrangement to provide an assembly, which overcomes the above mentioned and other disadvantages of the known arrangements and provide for maintaining the glue thickness. The present arrangement relates to an assembly comprising a shaft, a ^^^ magnet and an adhesive means: the shaft comprising a body and a projection, the shaft being rotatable about an axis and configured to receive the magnet at one end of the shaft; a clearance being located between the body and the magnet; the clearance being filled with the adhesive means; and the magnet abutting against the projection to facilitate retention of the adhesive means. ^^^ Therefore, by virtue of the projection, the clearance maintained between the body and the magnet is uniform and hence, a uniform glue thickness is maintained. Accordingly, shear stress in the adhesive means is mitigated. According to an aspect of the arrangement, the projection is integral to the body. Accordingly, the manufacturing of the shaft with the body and the projection ^^^ is simpler. According to another aspect of the arrangement, the adhesive means is a glue. The glue ensures a reliable securement of the magnet over the projection on the shaft, by a durable, strong bond, which consequently protects the assembly from corrosion. Further, the glue facilitates uniform distribution of stress loads between the shaft and magnet. According to another aspect of the arrangement, the height of the ^^ projection is between 0,01 and 1 mm and preferably 0.05 and 0.2 mm. accordingly, the adhesive means being applied in the clearance has a thickness equal to the height of the projection. The projection supports the magnet and consequently the weight of the magnet acts on the projection thereby a balance is maintained between the body and the magnet preventing the oozing out of the ^^^ glue. According to another aspect of the arrangement, the projection is centered on the axis and a diameter of the projection is smaller than the diameter of the body. Accordingly, the manufacturing of the shaft with the body and the projection is easier with a turning machine. Further, the projection centered on the axis ^^^ consequently retains the glue thickness. In addition, it allows the thermal deformation of the glue radially to reduce a stress imparted by the glue on the magnet. According to another aspect of the arrangement, the ratio of the diameter of the projection to the diameter of the body is between 10% and 30%. ^^^ Accordingly, the annular surface area on the axial end face of the body increases, thereby increasing the glue contact area. According to another aspect of the arrangement, average roughness of the magnet surface, which abuts the projection, is greater than Ra 0.2 µm. Roughness of the magnet surface facilitates better adhesion of the glue over the ^^^ magnet surface. According to another aspect of the arrangement, a gear or a rotor is overmolded on the shaft by which an appropriate alignment and firm assembly is established between the shaft and the gear or a rotor. The gear may be a sector gear, which rotates about the said axis of the shaft. ^^^ According to another arrangement, the present subject matter relates to an angular position sensing system comprising an assembly configured in accordance with the present arrangement, wherein a sensor placed in front of the magnet. This sensor detects the magnetic field, thereby sensing the angular position of the shaft on which the magnet is attached. According to yet another arrangement, the present subject matter relates to an electromechanical actuator or a rotating machine for use in an automobile ^^ application comprising an angular position sensing system in accordance with the present arrangement. BRIEF DESCRIPTION OF DRAWINGS ^^^ The present arrangement can be better understood with reference to the following description and drawings. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the arrangement. Moreover, in the figures, like reference numerals designate corresponding parts. In the drawings: ^^^ FIG.1 illustrates a front view of an assembly comprising a shaft, a magnet and an adhesive means, configured in accordance with the present subject matter; FIG.2 is an exploded isometric view of the assembly comprising a shaft and a magnet, configured in accordance with the present subject matter; ^^^ FIG.3 illustrates a front view of an angular position sensing system comprising an assembly configured in accordance with the present subject matter; and FIG.4 illustrates another arrangement in an isometric view wherein a sector gear is overmolded on the shaft, configured in accordance with an ^^^ arrangement of the present subject matter. The figures are not necessarily to scale, and the size of some parts may be exaggerated to more clearly illustrate the example shown. Moreover, the drawings provide examples and/or examples consistent with the description; however, the description is not limited to the examples and/or examples provided ^^^ in the drawings. DETAILED DESCRIPTION OF PREFERRED EMBODIMENT In the description that follows, reference is made to accompanying drawings, which form part thereof, and in which is shown by way of illustration ^^ specific implementations in which the invention may be practiced. These implementations are described in sufficient detail to enable that skilling in the art to practice the invention, and it is to be understood that the implementations may be combined, or that other implementations may be utilized, and that structural and logical changes may be made without departing from the scope of the ^^^ present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims and their equivalents. FIG.1 illustrates a front view of an assembly 1 that includes a shaft 2, a magnet 3 and an adhesive means 7. The shaft 2 includes a body 5 and a ^^^ projection 6. The shaft 2 is configured to rotate about an axis 4. One end of the shaft 2 receives the magnet 3. A clearance 8 is formed between the body 5 and the magnet 3. The clearance 8 is filled with the adhesive means 7. The magnet 3 abuts against the projection 6 to facilitate retention of the adhesive means 7. Accordingly, the adhesive means 7 makes contact with the magnet 3 and keeps ^^^ the magnet 3 in place. Further, the projection 6 keeps the layer of the adhesive mean 7 intact in between the body 5 and the magnet 3. Preferably, the shaft 2 is circular in cross section and used to transmit power, torque, or rotational motion between two parts of a machine or a torque producing machine to a torque absorbing machine. To provide an example, ^^^ machine elements like gears, sector gear or rotor are mounted on the shaft 2. In addition to it, the projection 6 is integral to the body 5 of the shaft 2 and centred on the axis 4. The shaft 2 includes an axial end face 10 perpendicular to the axis 4 about which the shaft 2 rotates. The projection 6 extends from the axial end face 10 of the body 5. The shaft 2, the projection 6 and the magnet 3 are ^^^ coaxially aligned about the axis 4. In a non-limiting example, the projection 6 is formed by a turning process. In another embodiment, the shaft 2 includes more than one projection 6 formed integrally on the axial end face 10 of the body 5 of the shaft 2. In an exemplary embodiment, the plurality of projections 6 extends from the axial end face 10 and are located radially equidistant from the axis 4 with annular ^^ symmetry. Moreover, the shaft 2, the body 5 and the projection 6 are formed by a die casting process or by a molding process. In another example, the shaft 2, the body 5 and the projection 6 is produced by hot rolling and shaped by cold rolling process. As illustrated in FIG.1, there is a clearance 8 by virtue of the projection 6 ^^^ between the body 5 and the magnet 3, which defines the uniform glue thickness. The said projection 6 extends from the axial end face 10 of the body 5 to a particular distance, which defines the height of the projection 6. In addition, the projection 6 extends along the axis 4 about which the shaft 2 rotates. Preferably, the height of the projection 6 is between 0.05 and 0.2 mm. The height of the ^^^ clearance 8 is the consequence of the height of the projection 6. It is yet another aspect of the present subject matter that the diameter of the projection 6 is smaller than the diameter of the body 5. Preferably, the diameter of the projection 6 is about 1,5 mm and the diameter of the body is 8 mm. In another arrangement, the shaft 2 and magnet 3 takes different diameter. ^^^ In another embodiment, the adhesive means 7 is a glue. The glue is disposed in the clearance 8 formed between the body 5 and the magnet 3. Accordingly, the glue secures the magnet 3 over the projection 6 of the shaft 2. Preferably, the glue is applied over the axial end face 10 of the body 5. The height of the projection 6 defines the thickness of the glue. In an example, the glue is ^^^ disposed in the annular region surrounding the projection 6 between the diameter of the projection 6 and the diameter of the magnet 3 ensuring the uniform glue film thickness. In another aspect, the glue is disposed all around the circumference of the projection 6 in between the magnet 3 and the axial end face 10 of the body 5 of the shaft 2. ^^^ FIG.2 illustrates an exploded isometric view of the assembly 1 comprising a shaft 2 and a magnet 3, configured in accordance with the present subject matter. In an arrangement, the magnet 3 may take the shape of a cylinder. In a non-limiting manner, the magnet 3 takes the shape of a square prism (not shown) or a rectangular shape (not shown). The magnet 3 has diametral magnetization. In an exemplary embodiment, the magnet 3 may be a rare earth magnet, such as, Neodymium Iron Boron (sintered) with nickel coating. In another example, the ^^ magnet 3 is shot blasted to have a high average surface roughness. Preferably, the average roughness of the magnet surface 13, which abuts the projection 6, is greater than Ra 0.2 µm. FIG.3 illustrates a front view of the angular position sensing system 12 comprising an assembly 1 configured in accordance with the present subject ^^^ matter with a sensor 9 placed in front of the magnet 3. As illustrated in FIG.3, the angular position sensing system 12 includes an assembly 1 configured in accordance with the present subject matter. The said assembly 1 includes a shaft 2 rotatable about the axis 4 and configured to receive the magnet 3 at one end and the sensor 9 is placed in close proximity to the magnet 3. The sensor 9 may ^^^ be a magnetic field sensor, which detects the magnetic field, thereby sensing the angular position of the shaft 1 on which the magnet 3 is attached. A clearance 8 being located between the body 5 and the magnet 3 and is filled with glue. The magnet 3 abuts against the projection 6. In one example, the sensor 9 is, for instance, a Hall Effect sensor or a magneto resistive sensor (MR sensor). Both ^^^ sensors detect a magnetic field generated whereas the hall sensor senses the polarity of the magnetic field and the MR sensor senses the angular position of the magnetic field. Both types of sensors are often used together, as their mode of operation complements one another. FIG.4 illustrates another arrangement in an isometric view wherein a gear ^^^ 11 is overmolded on the shaft 2, configured in accordance with an arrangement of the present subject matter. In an example as shown in FIG.4, the gear 11 is a sector gear. The sector gear is a portion of a gear that extends in an angular range between 0^o and 360^o, preferably between 0^o and 90^o whereas the gear may extend to full 360^o. The sector gear is similar to a gear whereas the sector gear ^^^ has teeth for a limited segment on its outer periphery and a smooth remaining portion. In another arrangement, the sector gear may have more than one limited section for example two opposing segments on its outer periphery. The sector gear rotates about the said axis 4 about which the shaft 2 rotates and typically seen in actuators where limited repetitive rotation about the axis 4 is needed. The shaft 2, the projection 6, the magnet 3 and the gear 11 are arranged coaxial about the said axis 4. In an example as shown in FIG.4, by virtue of the projection 6, ^^ glue does not ooze out, hence, the securement of the magnet 3 is ensured. Accordingly, the structural and operational integrity of the arrangement is maintained. In another example, the present arrangement envisages in particular an electromechanical actuator or a rotating machine for automobile application that ^^^ includes an angular position sensing system 12 configured in accordance with the present arrangement. The rotating machine may be an electrodynamic machine preferably an electric generator or an electromechanical drive machine (i.e., an electric motor) or an electric oil pump. In this case, all known examples, such as those of a synchronous machine, an asynchronous machine, a DC ^^^ machine or a reluctance machine, are thinkable. In addition, the field of application is not limited to electric machines. In an alternate aspect, the rotating machine may also be an internal combustion engine with a shaft whose rotational position is to be detected. In another example, the corresponding electromechanical actuator is a ^^^ gearbox actuator, also known as gearshift actuator, used particularly for selecting and shifting transmission between gear ranges in an automobile transmission. For carrying out the aforementioned operation, the gearbox actuator includes a shaft 2 in the output mechanism, configured in accordance with the present subject matter. The said shaft 2 is overmolded with the gear 11 for example a ^^^ sector gear rotatable about the axis 4 and configured to receive the magnet 3 at one end. A clearance 8 being located between the body 5 and the magnet 3 and is filled with glue. The magnet 3 abuts against the projection 6. The output mechanism further includes a shift finger or the like coupled the said shaft 2. The aforementioned gearbox actuator further includes a drive motor, a controller ^^^ electrically connected to the drive motor and configured to control the drive motor, and a reduction mechanism. The said output mechanism is coupled to the drive motor with the aid of the reduction mechanism. The said controller comprising at least one magnetic field sensor adapted to detect an angular position of the shaft 2 in which a gear 11 is overmolded. In another example, the corresponding electromechanical actuator may be for example a park lock actuator or a transmission lock actuator in accordance ^^ with the present arrangement used particularly for controlling the parking pawl capable of moving between a first position wherein the parking pawl prevents rotation of the output shaft and a second position wherein the parking pawl does not prevents rotation of the output shaft. For carrying out the aforementioned operation the park lock actuator or the transmission lock actuator includes a shaft ^^^ 2 in the output mechanism, configured in accordance with the present subject matter. The said shaft 2 is overmolded with the gear 11 for example a sector gear rotatable about the axis 4 and configured to receive the magnet 3 at one end. A clearance 8 being located between the body 5 and the magnet 3 and is filled with glue. The magnet 3 abuts against the projection 6. The aforementioned park lock ^^^ actuator or the transmission lock actuator further includes a drive motor, a controller electrically connected to the drive motor and configured to control the drive motor, comprising at least one magnetic field sensor adapted to detect an angular position of the shaft 2 in which the gear 11 is overmolded, and a reduction mechanism.

Claims

CLAIMS 1. An assembly (1) comprising a shaft (2), a magnet (3) and an adhesive means (7), the shaft (2) comprising a body (5) and a projection (6), the ^^ shaft (2) being rotatable about an axis (4) and configured to receive the magnet (3) at one end of the shaft (2), a clearance (8) being located between the body (5) and the magnet (3), the clearance (8) being filled with the adhesive means (7) and the magnet (3) abutting against the projection (6) to facilitate retention of the adhesive means (7). ^^ 2. The assembly according to claim 1, wherein the projection (6) is integral to the body (5). 3. The assembly according to any one of the preceding claims,^^ wherein the adhesive means (7) is a glue. 4. The assembly according to any one of the preceding claims, wherein the height of the projection (6) is between 0,01 and 1 mm, preferably 0.05 and 0.2 mm. ^^ 5. The assembly according to any one of the preceding claims, wherein the projection (6) is centered on the axis (4) and a diameter of the projection (6) is smaller than the diameter of the body (5). ^^ 6. The assembly according to any one of the preceding claims, wherein the ratio of the diameter of the projection to the diameter of the body is between 10% and 30%. 7. The assembly according to any one of the preceding claims,^^ wherein average roughness of the magnet surface (13), which abuts the projection 6 is greater than Ra 0.2 µm. 8. The assembly according to any one of the preceding claims, wherein a gear (11) or a rotor is overmolded on the shaft (2). 9. An angular position sensing system (12) comprising an assembly ^^ configured in accordance with any one of the preceding claim and a sensor (9) placed in front of the magnet (3). 10. An electromechanical actuator or a rotating machine for use in an automobile application comprising an angular position sensing system (12) in^^ accordance with claim 9.