An assembly comprising a shaft, a magnet and a plastic part

Abstract

The present subject matter relates to an assembly (10) for use in an automobile. The assembly (10) includes a shaft (2), rotatable about a longitudinal axis, and a magnet (3) disposed proximally at one end of the shaft (1). The magnet (3) has an anisotropic direction (X) perpendicular to the longitudinal axis. The magnet (3) has at least one primary flat surface (5) or one primary concave surface (5a) extending at least partially along the longitudinal axis. The assembly (10) further includes a plastic part (2) overmolded over the shaft (1) and magnet (3). The at least one primary flat surface (5), or at least one tangent of the at least one primary concave surface (5a), is parallel to the anisotropic direction (X) and at least partially devoid of the plastic part (2) intended to indicate the orientation of the anisotropic direction (X).

Description

DescriptionTitle of the invention: An assembly comprising a shaft, a magnet and a plastic part[1] The present subject matter relates to an assembly that includes a rotating shaft, a magnet and a plastic part. The assembly is particularly for use in an actuator for automobile applications.[2] In general, actuators are applied in automobiles for various applications. Such actuators may be park lock actuators, gearshift actuator, electronic throttle controller, etc. These actuators are assemblies that typically include a rotating shaft, a magnet mounted on a shaft and a rotary position sensor. Generally, the magnet is mounted on a distal end of the shaft. The magnet operates as a target for the rotary position sensor. The rotary position sensor, or sensor, is arranged in close proximity to the magnet so that the sensor detects the magnetic field generated by the magnet. As a result, information related to the angular position of the shaft may be determined. Typically, the rotary position sensor is a Hall Effect angular position sensor, or any such sensor.[3] In a known manner, the magnet is overmolded in plastic prior to being mounted on the shaft. The magnet is magnetized after overmolding so that an application of high temperatures, during overmolding, does not deter the anisotropic magnetic properties of the magnet. However, there is a risk of the magnet not being optimally oriented for overmolding consequently by which during magnetization the magnet may not be magnetized according to a proper direction. Accordingly, the magnet, having been magnetized in the improper manner, may have a shorter life in terms of operating as a target in actuators.[4] Therefore, there is a need to solve the technical problem associated with the typical actuator assemblies explained above.[5] 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 precisely orienting the magnet in a proper direction for magnetization.[6] The present arrangement relates to an assembly comprising a shaft being rotatable about a longitudinal axis, a magnet disposed proximally at one end of the shaft, the magnet has an anisotropic direction perpendicular to the longitudinal axis of the shaft, the magnet has at least, one primary flat surface or one primary concave surface extending at least partially along the longitudinal axis, a plastic part being overmolded over the shaft and the magnet, the at least one primary flat surface or at least one tangent of the at least one primary concave surface is parallel to the anisotropic direction of the magnet and at least partially devoid of the plastic part intended to indicate the orientation of the anisotropic direction.[7] Therefore, by virtue of the at least one primary flat surface or the at least one primary concave surface of the magnet, the mounting position of the magnet with the mold and the plastic part is made easy and helps in aligning the magnet in a magnetizer core for magnetization after overmolding with the plastic part. The at least one primary flat surface or the at least one primary concave surface of the magnet facilitates precise orientation and magnetization according to the desired anisotropic direction of the magnet.[8] According to the invention, the magnet is formed of a disc shape. This shape allows a strong magnetic field instead of a ring shape having less magnetic field due to lack of material in the center.[9] According to the invention, the plastic part is overmolded on a surface of the periphery of the magnet. This ensures better radial magnet fixation.

[0010] According to the invention, the at least one primary flat surface or the at least one primary concave surface is located on the periphery of the magnet. This provides easy access for overmolding and magnetization tooling.

[0011] According to an aspect of the arrangement, the said magnet has at least, one secondary flat surface or one secondary concave surface extending at least partially along the longitudinal axis and the said at least one secondary flat or at least one tangent of the at least one secondary concave surface is parallel to the anisotropic direction of the magnet and at least partially overmolded with the plastic part. Accordingly, by virtue of the secondary flat surface or the secondaryconcave surface of the magnet, and the overmolding by the plastic part, the magnet may be optimally oriented by means of a tool.

[0012] According to another aspect of the arrangement, the said at least one primary flat surface and the at least one secondary flat surface are opposite to each other or the said at least one primary concave surface and the at least one secondary concave surface are opposite to each other. Accordingly, upon magnetization, a magnetic field collinear to the anisotropic direction is achieved.

[0013] According to another aspect of the arrangement, the magnet having a cylindrical shape with a diameter D and extending along the longitudinal axis with a height H.

[0014] According to another aspect of the arrangement, the distance A between the at least one primary flat surface and the at least one secondary flat surface is between 0.7 times and 0.9 times the diameter D of the magnet.

[0015] According to another aspect of the arrangement, the height H of the magnet is between 0.3 times and the actual diameter D of the magnet.

[0016] According to another aspect of the arrangement, the width W of the at least one primary flat surface and at least one secondary flat surface is given by, width W = 7(D2- A2).

[0017] Accordingly, the magnet with the cylindrical shape with flat surfaces avoids the linearity error on the signal angle of the sensor element, which measures the axial field of the magnet and provides a perfectly sinusoidal shape of the magnetic field.

[0018] According to another aspect of the arrangement, the magnet having a parallelepiped shape. Accordingly, the magnet with the parallelepiped shape is more robust in terms of magnetic ageing since it has high permeance coefficient.

[0019] According to another aspect of the arrangement, the plastic part is a gear, a sector gear, or a rotor. Accordingly, the plastic part being the gear, sector gear or a rotor not only overmolds the shaft and the magnet but also enables torque transfer between the shaft and the adjacent components.

[0020] According to another aspect of the arrangement, the present subject matter relates to an angular position sensing system comprising an assembly configuredin accordance with the present arrangement, wherein a sensor is 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.

[0021] According to 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.

[0022] In yet another aspect, the present subject matter relates to a method of producing the present arrangement of an assembly of a shaft, a magnet and a plastic part comprising following steps:

[0023] (a) providing a ferromagnetic material having at least, one primary flat surface or one primary concave surface and at least one secondary flat surface or at least one secondary concave surface extending at least partially along the longitudinal axis, the said at least one primary flat surface or at least one tangent of the at least one primary concave surface of the ferromagnetic material is aligned parallel with the anisotropic direction of the ferromagnetic material;

[0024] (b) depositing the ferromagnetic material in a mold proximally at one end of the shaft with an anisotropic direction perpendicular to the longitudinal axis of the shaft by a tool wherein the tool holds the at least one of the secondary flat surface or at least one of the secondary concave surface of the ferromagnetic magnetic material and the mold at least partially receives the at least one primary flat surface or at least one of the primary concave surface of the ferromagnetic material;

[0025] (c) removing the tool and overmolding the shaft and the ferromagnetic material with the plastic part wherein one of the at least one of the secondary flat surface or at least one of the secondary concave surface is at least being partially overmolded with the plastic part;

[0026] (d) magnetizing the ferromagnetic material by placing the ferromagnetic material in a magnetic field. Therefore, by virtue of the at least one primary flat surface or the at least one primary concave surface of the magnet, the mounting position of the magnet with the mold and the plastic part is made easy and helps in aligning the magnet in a magnetizer core for magnetization after overmoldingwith the plastic part. The at least one primary flat surface or the at least one primary concave surface of the magnet facilitates precise orientation and magnetization according to the desired anisotropic direction of the ferromagnetic material.

[0027] 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:

[0028] [Figure 1] illustrates a top view of an embodiment of an assembly configured in accordance with the present subject matter;

[0029] [Figure 2] and [Figure 2a] illustrate a perspective view of a magnet in the assembly, configured in accordance with the present subject matter;

[0030] [Figure 2b] and [Figure 2c] illustrate a top view of an embodiment of a magnet, in accordance with the present subject matter;

[0031] [Figure 3] illustrates a perspective view of an assembly comprising a shaft and a magnet configured in accordance with the present subject matter;

[0032] [Figure 4] illustrates a perspective sectional view of an assembly wherein a plastic part being a sector gear and is overmolded over a shaft and a magnet, configured in accordance with an arrangement of the present subject matter;

[0033] [Figure 5] illustrates a front view of an angular position sensing system comprising an assembly configured in accordance with the present subject matter;

[0034] [Figure 6] illustrates various stages of forming the magnet, configured in accordance with an embodiment of the present subject matter; and ;

[0035] [Figure 7] is a flowchart depicting an assembly process of the magnet, configured in accordance with an arrangement of the present subject matter.

[0036] 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.

[0037] 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.

[0038] [Figure 1 ] illustrates a top view of an assembly 10, configured in accordance with the present subject matter that includes a shaft 1 , a magnet 3, a mold and a plastic part 2. The shaft 1 is configured to rotate about a longitudinal axis. The magnet 3 is disposed proximally at one end of the shaft 1 with an anisotropic direction X perpendicular to the longitudinal axis of the shaft 1 . The magnet 3 has at least, one primary flat surface 5 extending at least partially along the longitudinal axis. The plastic part 2 overmolded over the shaft 1 and partially overmolded over the magnet 3, thereby holding the magnet 3 in place on the shaft 1 . The plastic part 2 is overmolded on a surface of the periphery of the magnet 3. The shaft 1 and the plastic part 2 are two distinct elements of the assembly 10. The at least one primary flat surface 5 is parallel to the anisotropic direction X of the magnet 3 and at least partially devoid of the plastic part 2. Thus the at least one primary flat surface 5 that is devoid of plastic part 2 indicate the anisotropic direction X of the magnet 3 and facilitates precise orientation and magnetization of the magnet 3 according its anisotropic direction X.

[0039] According to an aspect of the present subject matter, the magnet 3 includes at least one secondary flat surface 6 that extend at least partially along the longitudinal axis 4. The at least one secondary flat surface 6 is parallel to the anisotropic direction X of the magnet 3 and is at least partially overmolded in the plastic part 2. Further, the mold includes finger like structures 20a, 20b, 20c that facilitate receiving the magnet 3 and holding said magnet 3 in place.

[0040] In the example shown in [Figure 1], the magnet 3 is formed with a cylindrical shape 7 and extends at least partially along the longitudinal axis. The magnet 3 in [Figure 1] includes one primary flat surface 5 and one secondary flat surface 6, each being opposite to each other. The mold receives the magnet 3 by way of three finger like structures 20a, 20b, 20c, spaced at 120° to one another. One of the finger like structure 20a of the mold is a flat surface 17 that at least partially abuts the primary flat surface 5, hence, limiting the relative rotation of the magnet 3 before or during overmolding process. The other two finger like structures 20b; 20c of the mold has a curved surface (by virtue of the cylindrical shape 18, 19) abutting the cylindrical shape 7 that compliments the curved area of the mold. Consequently, the magnet 3 is maintained and indexed in the mold.

[0041] In accordance with another embodiment of the present subject matter, the magnet 3 includes at least, one primary concave surface and one secondary concave surface extending at least partially along the longitudinal axis of the shaft 1 .

[0042] According to the example shown in [Figure 1], the plastic part 2 partially covers the shaft 1 and partially covers the magnet 3. The plastic part 2 holds the magnet 3 in such a manner that the secondary flat surface 6 is at least being partially overmolded with the plastic part 2. The said plastic part 2 has a flat surface 14 that at least partially abuts the secondary flat surface 6, hence, limiting the relative rotation of the magnet 3 in the plastic part 2 during the working of the assembly 10. From the primary flat surface 5, which is devoid of the plastic part 2, the orientation direction (magnetization direction) can be grasped at a glance. The plastic part 2 further has two finger like structure with a curved surface (by virtue of the cylindrical shape 15, 16) abutting the cylindrical shape 7 that compliments the cylindrical shape 7of the magnet 3. Consequently, the mounting position of the magnet 3 is maintained and indexed in the plastic part 2.

[0043] [Figure 2] illustrates a perspective view of a magnet 3 configured in accordance with the present subject matter. [Figure 2a] illustrates a perspective view of a magnet 3 configured in accordance with the present subject matter. [Figure 2b] illustrates a top view of the magnet 3 configured in accordance with an embodiment of the present subject matter. For the sake of brevity, the description for [Figure 2], [Figure 2a], [Figure 2b] is described herein in tandem.The magnet 3 is formed with the cylindrical shape 7 and has the longitudinal axis 4 perpendicular to the anisotropic direction X. Preferably, the diameter D of the cylindrical shape 7 is between 4mm and 14mm. It is also preferable that the height H of the magnet 3 is between 0.3 times and the actual diameter D of the magnet 3, the height H is being along the longitudinal axis 4. As explained in the preceding description, the one primary flat surface 5 and the one secondary flat surface 6 are formed so that both of the said surfaces 5 and 6 are parallel to the anisotropic direction X of the magnet 3 and opposite to each other. In the example shown, the distance A between the one primary flat surface 5 and the one secondary flat surface 6 is configured to be anywhere between 0.7 times and 0.9 times the diameter D of the magnet 3. The width W of the one primary flat surface 5 and the width W the one secondary flat surface 6 is given by width W = V(D2- A2).

[0044] The magnet 3 is diametrically magnetized. In an exemplary embodiment, the magnet 3 may be a rare earth magnet, such as, Neodymium Iron Boron (sintered) with nickel coating or potentially anisotropic hard ferrite. Preferably, the tolerance for the flat surface of the at least one primary flat surface 5 and the at least one secondary flat surface 6 is between 10 to 15% of the height H of the magnet 3. Furthermore, the magnet 3 with the cylindrical shape 7 avoids the linearity error on the signal angle of the sensor element, which measures the axial field of the magnet 3 and provides a perfectly sinusoidal shape of the magnetic field.

[0045] In an exemplary embodiment, the magnet 3 is formed with a parallelepiped shape having a primary flat surface and a secondary flat surface and are parallel to the anisotropic direction X of the magnet 3 and are opposite to each other. Preferably, the distance between the primary flat surface and the secondary flat surface is between 5mm and 5.6mm.

[0046] In an exemplary embodiment as illustrated in [Figure 2c] the magnet 3 includes a cylindrical shape 7 that extend along the longitudinal axis 4 and includes one primary concave surface 5a and one secondary concave surface 6a. At least one tangent of the said one primary concave surface 5a is parallel to the anisotropic direction X of the magnet 3. One tangent of the said onesecondary concave surface 6a is parallel to the anisotropic direction X of the magnet 3. The magnet 3 is formed of a disc shape.

[0047] In yet another embodiment, the plastic part 2 is overmolded over the shaft 1 and partially overmolded over the magnet 3, thereby holding the magnet 3 in place on the shaft 1 . The at least one tangent of the one primary concave surface 5a is parallel to the anisotropic direction X of the magnet 3 and at least partially devoid of the plastic part 2. Thus the one primary concave surface 5a that is devoid of plastic part 2 indicate the anisotropic direction X of the magnet 3 and facilitates precise orientation and magnetization of the magnet 3 according to its anisotropic direction X. Further in accordance with the present subject matter, the magnet 3 includes one secondary concave surface 6a that extend at least partially along the longitudinal axis 4. The at least one tangent of the one secondary concave surface 6a is parallel to the anisotropic direction X of the magnet 3 and is at least partially overmolded in the plastic part 2. Accordingly, the primary concave surface 5a that abuts the mold aids limiting the relative motion of the magnet 3 in the mold before or during overmolding process. In a similar fashion the one secondary concave surface 6a that abuts the plastic part 2 aids limiting the relation motion of the magnet 3 in the plastic part 2 during the working of the assembly 10.

[0048] In another embodiment, the magnet 3 is formed with a parallelepiped shape having a primary concave surface and a secondary concave surface. At least one tangent of the said primary concave surface is parallel to the anisotropic direction X of the magnet 3. At least one tangent of the said secondary concave surface is parallel to the anisotropic direction X of the magnet 3.

[0049] In yet another embodiment, the primary and secondary surface may be with a profile non-conformity with the flat surface. The profile can be a cross sectional profile as seen from the top view. For example, in a non-limiting manner the said profile non-conformity with the flat surface of the magnet 3 has raised and lowered portions. In a non-limiting manner, the profile of the raised and lowered portions may resemble a stair stepping or saw-tooth like pattern.

[0050] [Figure 3] illustrates a perspective view of an assembly 10 that includes a shaft 1 and a magnet 3, the assembly 10 being configured in accordance with thepresent subject matter. The plastic part 2 as shown in [Figure 1] is not shown here. The shaft 1 is circular in cross section and extends along the longitudinal axis 4 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. The magnet 3 is disposed proximally at one end of the shaft 1 with an anisotropic direction X perpendicular to the longitudinal axis 4 of the shaft 1 . The outer periphery of the shaft 1 include at least one groove 1 a which facilitates retention of the plastic part 2 that is being overmolded. The shaft 1 is formed of a metal.

[0051] [Figure 4] illustrates a perspective sectional view of an assembly 10 configured in accordance with an example of the present subject matter. As shown in [Figure 4] the plastic part 2 being a sector gear 2a and is overmolded partially over the shaft 1 and the magnet 3. The sector gear 2a is a segment of a gear that extends in an angular range anywhere between 0°and 360°, preferably between 0°and 90° whereas the gear may extend to full 360°. The sector gear 2a is similar to a gear whereas the sector gear 2a has teeth 2b for a limited segment on its outer periphery and a smooth remaining portion. In another arrangement, the sector gear 2a may have more than one limited section for example two opposing segments on its outer periphery. The sector gear 2a rotates about the said longitudinal axis 4 about which the shaft 1 rotates and typically seen in actuators where limited repetitive rotation about the longitudinal axis 4 is needed. The shaft 1 , the plastic part 2 and the magnet 3 are arranged coaxial about the longitudinal axis 4. The magnet 3 has the one primary flat surface 5 and the one secondary flat surface 6 and the said one primary flat surface 5 and the one secondary flat surface 6 are parallel to the anisotropic direction X of the magnet 3 and are opposite to each other. The one secondary flat surface 6 is being overmolded with the plastic part 2 whereas the one primary flat surface 5 is devoid of the plastic part 2 and is being visible. Consequently by which the orientation direction (magnetization direction) can be grasped at a glance for magnetizing the magnet 3.

[0052] In an example the plastic part 2, preferably be a gear. In yet another example the plastic part 2 preferably be a rotor, in a non-limiting manner, the rotor may be a plastic rotor incorporating magnetic particles or magnets. The said gear or therotor is overmolded over the shaft 1 and the magnet 3 configured in accordance with the present subject matter.

[0053] In yet another embodiment, the magnet 3 is indirectly coupled to the shaft 1 . Specifically, in the aforesaid embodiment, a metallic insert is disposed between the shaft 1 and the magnet 3, to facilitate the coupling aforementioned. The plastic part 2 is at least partially overmolded over the magnet 3 and at least partially overmolded over the metallic insert.

[0054] [Figure 5] illustrates a front view of an angular position sensing system 21 configured in accordance with the present subject matter. The angular position sensing system 21 includes the assembly 10 configured in accordance with the present subject matter. The assembly 10 includes the shaft 1 , the magnet 3, the sensor 22 and the plastic part 2. The magnet 3 has at least, one primary flat surface 5 or one primary concave surface 5a extending at least partially along the longitudinal axis 4. The plastic part 2 being overmolded over the shaft 1 and the magnet 3 characterized in that the at least one primary flat surface 5 or at least one tangent of the at least one primary concave surface 5a is parallel to the anisotropic direction X of the magnet 3 and at least partially devoid of the plastic part 2 intended to indicate the orientation of the anisotropic direction X. In one example, the sensor 22 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.

[0055] [Figure 6] illustrates a process of making an embodiment of a magnet 3 configured in accordance with the present subject matter. In the example illustrated in [Figure 6], the magnet 3 is manufactured by a material removal process such as milling, shaping. Preferably, the raw material used is ferromagnetic material 23 in the form of rectangular bar having a width 24 and length 25, 26. The width 24 of the ferromagnetic material 23 is turned into a cylindrical shape 7. Then the length 25, 26 of the ferromagnetic material 23 is surface machined to form the at least one primary flat surface 5 and the at least one secondary flat surface 6.

[0056] [Figure 7] is a flowchart illustrating steps for manufacturing a magnet and an assembly process, configured in accordance with the present subject matter. In step 71 , the raw material that is the ferromagnetic material 23 is provided. In an example the magnet 3 is manufactured by a material removal process from the ferromagnetic material 23, in a non-limiting manner as described above. Thus, as in step 72, the manufactured magnet 3 has at least, one primary flat surface 5 or one primary concave surface 5a and at least, one secondary flat surface 6 or one secondary concave surface 6a extending at least partially along the longitudinal axis 4 and the said at least one primary flat surface 5 or at least one tangent of the at least one primary concave surface 5a of the ferromagnetic material 23 is aligned parallel with the anisotropic direction X of the ferromagnetic material 23.

[0057] Further as in step 73, deposition of the ferromagnetic material 23 in a mold is performed. The ferromagnetic material 23 is deposited in mold proximally at one end of the shaft 1 with an anisotropic direction X perpendicular to the longitudinal axis 4 of the shaft 1 by a tool wherein the tool holds the at least one of the secondary flat surface 6 or at least one of the secondary concave surface 6a of the ferromagnetic magnetic material 23 and the mold at least partially receives the at least one primary flat surface 5 or at least one of the primary concave surface 5a of the ferromagnetic material 23. To provide an example in a nonlimiting manner the mold may have at least one finger like structure. The said finger like structure of the mold is of flat surface 17 that at least partially receives the at least one of the primary flat surface 5 of the magnet 3 and intended to limit the relative rotation of the ferromagnetic material 23. In another example, the said finger like structure of the mold is of a convex surface that at least partially receives the at least one of the primary concave surface 5a of the ferromagnetic material 23 and intended to limit the relative rotation of the ferromagnetic material 23. Consequently, the ferromagnetic material 23 is maintained and indexed in the mold.

[0058] Further as in step 74, the removal operation of the tool is done and overmolding the shaft 1 and the ferromagnetic material 23 with the plastic part 2 is performed wherein at least one of the secondary flat surface 6 or at least one of the secondary concave surface 6a is at least partially overmolded with the plastic part 2. To provide an example in a non-limiting manner the plastic part 2 isat least partially overmolded over the ferromagnetic material in such a way that the plastic part 2 holds the at least one of the secondary flat surface 6 or the at least one of the secondary concave surface 6a the ferromagnetic material 23 intended to limit the relative rotation of the magnet 3 and from the at least one of the primary flat surface 5 or at least one of the primary concave surface 5a of the ferromagnetic material 23 which is at least partially devoid of the plastic part 2, the orientation direction (magnetization direction) can be grasped at a glance. Consequently, the mounting position of the magnet 3 is maintained and indexed in the plastic part 2.

[0059] Further as in step 75, the magnetization of the ferromagnetic material is performed by placing the shaft 1 and the ferromagnetic material 23, which is being overmolded with the plastic part 2 in a magnetic field. The ferromagnetic magnetic material 23, overmolded with the plastic part 2 is positioned and clamped in a tool and then a coil is approached. In an example, the coil may be a magnetizer core or a C shaped coil. An electric current is passed through the coil, which creates a strong magnetic field. The ferromagnetic material 23 is placed in the coil in such a fashion that the anisotropic direction X of the ferromagnetic material 23 is aligned with the magnetic field generated by the magnetizer. The electric current passing through the coil must be high enough to saturate the magnetization of the ferromagnetic material 23. Thus, the ferromagnetic material 23 gets magnetized.

[0060] The assembly 10 comprising a shaft 1 , a magnet 3 and a plastic part 2 in accordance with the present subject matter, as described above, is specifically advantageous in applications where automotive components like an electromechanical actuator or a rotating machine or a pump are assembled in a motor vehicle. In an example, the present arrangement envisages in particular a rotating machine for automobile that includes an angular position sensing system 12 configured in accordance with the present subject matter. 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 Brush Less DC motor (BLDC motor) with a rotor made of magnetic pole or a reluctance machine, arethinkable. 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.

[0061] 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 1 and a magnet 3 in the output mechanism, configured in accordance with the present subject matter. The said shaft 1 and the magnet 3 is overmolded with a plastic part 2 for example the plastic part 2 being a sector gear 2a rotatable about the longitudinal axis 4. The magnet 3 has an anisotropic direction X perpendicular to the longitudinal axis 4 of the shaft 1 . The magnet 3 has at least, one primary flat surface 5 or one primary concave surface 5a extending at least partially along the longitudinal axis 4 and the said at least one primary flat surface 5 or at least one tangent of the at least one primary concave surface 5a is parallel to the anisotropic direction X of the magnet 3 and at least partially devoid of the plastic part 2 intended to indicate the orientation of the anisotropic direction X. The output mechanism further includes a shift finger or the like coupled to the said shaft 1 . 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 1 in which the sector gear 2a is overmolded.

[0062] 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 in an automobile application. The said parking pawl is being 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 1 and a magnet 3 in the output mechanism, configured in accordance with the present subject matter.The said shaft 1 and the magnet 3 is overmolded with a plastic part 2 for example the plastic part 2 being a sector gear 2a rotatable about the longitudinal axis 4.The magnet 3 has an anisotropic direction X perpendicular to the longitudinal axis 4 of the shaft 1 . The magnet 3 has at least, one primary flat surface 5 or one primary concave surface 5a extending at least partially along the longitudinal axis 4 and the said at least one primary flat surface 5 or at least one tangent of the at least one primary concave surface 5a is parallel to the anisotropic direction X of the magnet 3 and at least partially devoid of the plastic part 2 intended to indicate the orientation of the anisotropic direction X. 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 1 in which the sector gear 2a is overmolded, and a reduction mechanism.

[0063] In yet another example, the corresponding electromechanical actuator may be for example an electronic throttle controller in accordance with the present arrangement used particularly as a fluid metering valve of internal combustion engines, in such cases gasoline or diesel engines are possible. It also finds its applications as an exhaust gas recirculation valve or EGR valve. The said electronic throttle control comprises fluid metering valve for example is a throttle valve, a shutter, or a flap, which operates between first and second positions, a control shaft unit which is connected to the said fluid metering valve, a drive unit and a gear mechanism coupled to the drive unit. The drive unit is configured to rotate the valve between the first and second position. The rotation of the valve makes it possible to control the flow of fluid flowing in a duct. For carrying out the aforementioned operation, the said control shaft unit is configured in accordance with the present subject matter. The said control shaft unit comprises a shaft 1 and the magnet 3 and is being overmolded with a plastic part 2 for example the plastic part 2 being a sector gear 2a rotatable about the longitudinal axis 4. The magnet 3 has an anisotropic direction X perpendicular to the longitudinal axis 4 of the shaft 1 . The magnet 3 has at least, one primary flat surface 5 or one primary concave surface 5a extending at least partially along the longitudinal axis 4 and the said at least one primary flat surface 5 or at least one tangent of the at leastone primary concave surface 5a is parallel to the anisotropic direction X of the magnet 3 and at least partially devoid of the plastic part 2 intended to indicate the orientation of the anisotropic direction X. The electronic throttle controller further comprises a at least one magnetic field sensor adapted to detect an angular position of the shaft 1 in which the sector gear 2a is overmolded. Other applications of the valve according to the invention are also possible without departing from the scope of the invention.

[0064] However, it may be understood that the application is not limited to a gearshift actuator or a park lock actuator or an electronic throttle controller only, the present subject matter may find applications in various other automobile components, which comprises an assembly 10 having a shaft 1 , a magnet 3 and a plastic part 2.

Claims

Claims

1. An assembly (10) comprising a shaft (1 ) being rotatable about a longitudinal axis (4), a magnet (3) disposed proximally at one end of the shaft (1 ), the magnet (3) has an anisotropic direction (X) perpendicular to the longitudinal axis (4) of the shaft (1 ), the magnet (3) has at least one primary flat surface (5) or one primary concave surface (5a) extending at least partially along the longitudinal axis (4), a plastic part (2) overmolded over the shaft (1 ) and the magnet (3), characterized in that the at least one primary flat surface(5) or at least one tangent of the at least one primary concave surface (5a) is parallel to the anisotropic direction (X) of the magnet (3) and at least partially devoid of the plastic part (2) intended to indicate the orientation of the anisotropic direction (X).

2. The assembly (10) according to claim 1 , characterized in that the said magnet (3) has at least, one secondary flat surface (6) or one secondary concave surface (6a) extending at least partially along the longitudinal axis (4) and the said at least one secondary flat surface (6) or at least one tangent of the at least one secondary surface (6a) is parallel to the anisotropic direction (X) of the magnet (3) and at least partially overmolded with the plastic part (2).

3. The assembly (10) according to claim 2, characterized in that the said at least one primary flat surface (5) and the at least one secondary flat surface(6) are opposite to each other or the said at least one primary concave surface (6) and the at least one secondary concave surface (6a) are opposite to each other.

4. The assembly (10) according to any one of the preceding claims, characterized in that the magnet (3) having a cylindrical shape (7) with a diameter D and extending along the longitudinal axis (4) with a height H.

5. The assembly (10) according to claim 4, characterized in that the distance A between the at least one primary flat surface (5) and the at least one secondary flat surface (6) is between 0.7 times and 0.9 times the diameter D of the magnet (3).

6. The assembly (10) according to claim 4 or 5, characterized in that the height H of the magnet (3) is between 0.3 times and the actual diameter D of the magnet (3).

7. The assembly (10) according to claim 4 or 5, characterized in that the width W of the at least one primary flat surface (5) and at least one secondary flat surface (6) is given by width W = (D2- A2).

8. The assembly (10) according to any one of the claim 1 to 3, characterized in that the magnet (3) having a parallelepiped shape.

9. The assembly (10) according to any one of the preceding claims, characterized in that the plastic part (2) is a gear, a sector gear (2a) or a rotor.

10. An angular position sensing system (21 ) comprising an assembly (10) configured in accordance with any one of the preceding claims and a sensor (22) placed in front of the magnet (3).

11. An electromechanical actuator or a rotating machine for use in an automobile application comprising an angular position sensing system (21 ) in accordance with claim 10.

12. A method of producing an assembly (10) of a shaft (1 ), a magnet (3) and a plastic part (2) comprising following steps:(a) providing a ferromagnetic material (23) having at least, one primary flat surface (5) or one primary concave surface (5a) and at least one secondary flat surface (6) or at least one secondary concave surface (6a) extending at least partially along the longitudinal axis (4) and the said at least one primary flat surface (5) or at least one tangent of the at least one primary concave surface (5a) of the ferromagnetic material (23) is aligned parallel with the anisotropic direction (X) of the ferromagnetic material (23);(b) depositing the ferromagnetic material (23) in a mold (20) proximally at one end of the shaft (1 ) with an anisotropic direction (X) perpendicular to the longitudinal axis (4) of the shaft (1 ) by a tool wherein the tool holds the at least one of the secondary flat surface (6) or at least one of the secondary concave surface (6a) of the ferromagnetic magnetic material (23) and the mold (20) at least partially receives the at least one primary flat surface (5) or at leastone of the primary concave surface (5a) of the ferromagnetic material (23);(c) removing the tool and overmolding the shaft (1 ) and the ferromagnetic material (23) with the plastic part (2) wherein one of the at least one of the secondary flat surface (6) or at least one of the secondary concave surface (6a) is at least being partially overmolded with the plastic part (2);(d) magnetizing the ferromagnetic material (23) by placing the ferromagnetic material (23) in a magnetic field.)

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