Set including a shaft and a magnet

Abstract

The present invention relates to an assembly (1) for use in an automotive application. The assembly (1) comprises a shaft (2), a magnet (3) and an adhesive means (7). The shaft (2) comprises a body (5) and a protrusion (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 provided between the body (5) and the magnet (3). The clearance (8) is filled by the adhesive means (7). The magnet (3) abuts the protrusion (6) to facilitate retention of the adhesive (7). The adhesive (7) contacts the magnet (3) and holds it in place. The protrusion (6) ensures that the layer of adhesive means (7) is intact between the body (5) and the magnet (3). Figure for abstract: Figure 2

Description

Title of the invention: Assembly comprising a shaft and a magnet

[0001] The invention relates to an assembly comprising a rotating shaft and a magnet, particularly intended for use in an actuator for automotive applications.

[0002] Typically, an automobile includes an actuator such as a parking lock actuator or a gear shift actuator. These actuators have an assembly that includes a rotating shaft, a magnet, and a rotating position sensor. The magnet is mounted on the shaft and serves as a target for a Hall effect angular position sensor, or other such sensor. The sensor is placed near the magnet so that it detects a magnetic field generated by the magnet. Information about the angular position of the shaft can thus be determined.

[0003] Typically, the magnet is mounted on the distal end of the shaft. An adhesive means, or glue, is applied to the distal end and the magnet is pressed onto it to achieve this mounting. However, when the magnet is pressed, the glue escapes from the distal end and thus there is not enough glue left to retain the magnet. The weight of the magnet can also push the glue towards an outer periphery of the magnet. Therefore, the glue is exposed to high mechanical shear stress and when the thickness of the glue is not uniform there is a risk of losing the magnet.

[0004] It is therefore necessary to solve the technical problem related to the assembly explained above.

[0005] The object of the present invention is therefore to provide an assembly which overcomes the aforementioned and other disadvantages of known arrangements and which makes it possible to maintain the thickness of the glue.

[0006] The present invention relates to an assembly comprising a shaft, a magnet and an adhesive means, the shaft comprises a body and a protrusion, the shaft being rotatable about an axis and configured to receive the magnet at one end of the shaft, a clearance is located between the body and the magnet, the clearance is filled with the adhesive means, the magnet abuts the protrusion to facilitate retention of the adhesive means.

[0007] Due to the protrusion, the clearance maintained between the body and the magnet is uniform and, therefore, a uniform glue thickness is maintained. As a result, the shear stress in the adhesive means is mitigated.

[0008] According to one aspect of the invention, the protrusion is an integral part of the body. In other words, the protrusion and the body are a single piece. According to an additional characteristic, the protrusion is centered on the axis and the diameter of the protrusion is less than the diameter of the body. The manufacture of the shaft with the body and the protrusion is simpler to carry out, for example by a turning operation. The shaft is in metal.

[0009] According to another aspect of the invention, the adhesive means is an adhesive. The adhesive ensures reliable attachment of the magnet to the protrusion of the shaft, by a durable and strong bond, which protects the assembly from corrosion. In addition, the adhesive facilitates the uniform distribution of stresses between the shaft and the magnet.

[0010] According to another aspect of the invention, the height of the protrusion is between 0.01 and 1 mm and, preferably, between 0.05 and 0.2 mm. The protrusion supports the magnet and, therefore, the weight of the magnet acts on the protrusion, so that a balance is maintained between the body and the magnet, which prevents the glue from escaping.

[0011] According to another aspect of the invention, the ratio between the diameter of the protrusion and the diameter of the body is between 10 and 30%. As a result, the annular surface on the axial end face of the body increases, which increases the contact surface with the glue.

[0012] According to another aspect of the arrangement, the average roughness of the surface of the magnet, which touches the protrusion, is greater than Ra 0.2 pm. The roughness of the surface of the magnet facilitates the adhesion of the glue on the surface of the magnet.

[0013] According to another aspect of the invention, a gear or rotor is overmolded onto the shaft, thereby providing proper alignment and a secure connection between the shaft and the gear or rotor. The gear may be a sector gear that rotates about the axis of the shaft.

[0014] The invention also relates to an angular position detection system comprising an assembly configured according to the above characteristics, in which a sensor is placed opposite the magnet. This sensor detects the magnetic field and thus detects the angular position of the shaft on which the magnet is fixed.

[0015] The invention also relates to an electromechanical actuator or a rotating machine for an automotive application comprising an angular position detection system defined above.

[0016] Other characteristics and advantages of the invention will emerge from the following reading of a detailed exemplary embodiment, with reference to the appended figures:

[0017] [Fig.l] represents a front view of an assembly according to the invention;

[0018] [Fig.2] represents an exploded isometric view of an assembly according to the invention;

[0019] [Fig.3] represents a front view of an angular position detection system according to the invention;

[0020] [Fig.4] represents an isometric view where a sector gear is overmolded on the shaft.

[0021] It should be noted that the figures disclose the invention in a manner 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.

[0022] Referring to [Fig.l] there is illustrated a front view of an assembly 1 which comprises a shaft 2, a magnet 3 and an adhesive means 7. The shaft 2 comprises a body 5 and a protrusion 6. The shaft 2 is configured to rotate about an axis 4. One end of the shaft 2 receives the magnet 3. A free space 8 is formed between the body 5 and the magnet 3. The free space 8 is filled by the adhesive 7. The magnet 3 abuts against the protrusion 6 to facilitate retention of the adhesive 7. Thus, the adhesive 7 contacts the magnet 3 and holds it in place. Furthermore, the protrusion 6 keeps the layer of the adhesive means 7 intact between the body 5 and the magnet 3.

[0023] Preferably, the shaft 2 is of circular section and serves to transmit power, torque or rotational movement between two parts of a machine or between a machine producing torque and a machine absorbing torque. For example, machine elements such as gears, a sector gear or a rotor are mounted on the shaft 2.

[0024] Furthermore, the protrusion 6 is integral with the body 5 of the shaft 2 and centered on the axis 4. The shaft 2 comprises an axial end face 10 perpendicular to the axis 4 around which the shaft 2 rotates. The protrusion 6 extends from the axial end face 10 of the body 5. The shaft 2, the protrusion 6 and the magnet 3 are coaxially aligned around the axis 4. In a non-limiting example, the protrusion 6 is formed by a turning process.

[0025] In another embodiment, the shaft 2 includes more than one protrusion 6 integrally formed on the axial end face 10 of the body 5 of the shaft 2. In an exemplary embodiment, the plurality of protrusions 6 extend from the axial end face 10 and are located radially equidistant from the axis 4 with annular symmetry. Further, the shaft 2, the body 5 and the protrusion 6 are formed by a die casting process or by a molding process. In another example, the shaft 2, the body 5 and the protrusion 6 are produced by a hot rolling process and shaped by a cold rolling process.

[0026] As illustrated in [Fig.l], there is a free space 8 due to the projection 6 between the body 5 and the magnet 3, which defines the uniform thickness of the glue. Said protrusion 6 extends from the axial end face 10 of the body 5 to a particular distance, which defines the height of the protrusion 6. Furthermore, the protrusion 6 extends along the axis 4 around which the shaft 2 rotates. Preferably, the height of the protrusion 6 is between 0.05 and 0.2 mm. The height of the free space 8 is the consequence of the height of the protrusion 6. According to another aspect of the present object, the diameter of the protrusion 6 is less than the diameter of the body 5. Preferably, the diameter of the protrusion 6 is about 1.5 mm and the diameter of the body is 8 mm. In another arrangement, shaft 2 and magnet 3 have different diameters.

[0027] The adhesive means 7 is an adhesive. The adhesive is disposed in the free space 8 formed between the body 5 and the magnet 3. As a result, the adhesive fixes the magnet 3 to the protrusion 6 of the shaft 2. Preferably, the adhesive is applied to the axial end face 10 of the body 5. The height of the protrusion 6 defines the thickness of the adhesive. In one example, the adhesive is disposed in the annular region surrounding the protrusion 6 between the diameter of the protrusion 6 and the diameter of the magnet 3, which ensures the uniform thickness of the adhesive film. In another aspect, the adhesive is disposed all around the circumference of the projection 6 between the magnet 3 and the axial end face 10 of the body 5 of the shaft 2.

[0028] [Fig. 2] illustrates an exploded isometric view of the assembly 1 comprising a shaft 2 and a magnet 3. The magnet 3 may take the shape of a cylinder. In a non-limiting manner, the magnet 3 may take the shape of a square prism (not shown) or a rectangular shape (not shown). The magnet 3 has a diametrical magnetization. In an exemplary embodiment, the magnet 3 may be a rare earth magnet, such as Neodymium-Iron-Boron (sintered) with a nickel coating. In another example, the magnet 3 is shot-peened to obtain a high average surface roughness. Preferably, the average roughness of the surface of the magnet 13, which touches the protrusion 6, is greater than Ra 0.2 pm.

[0029] [Fig. 3] illustrates a front view of the angular position detection system 12 comprising an assembly 1 with a sensor 9 placed opposite the magnet 3. Said assembly 1 comprises a shaft 2 rotatable about the axis 4 and configured to receive the magnet 3 at one end, and the sensor 9 is placed near the magnet 3 so as to detect the magnetic field of the magnet 3. The sensor 9 may be a magnetic field sensor, which detects the magnetic field, thus detecting the angular position of the shaft 1 on which the magnet 3 is fixed. A free space 8 is located between the body 5 and the magnet 3 and is filled with glue. The magnet 3 abuts against the protrusion 6. In one example, the sensor 9 is, for example, a Hall effect sensor or a magnetoresistive sensor (MR sensor).Both sensors detect a generated magnetic field, while the Hall effect sensor detects the polarity of the magnetic field and the MR sensor the angular position of the magnetic field. These two types of sensors are often used together, as their mode of operation complements each other.

[0030] [Fig.4] illustrates an isometric view in which a gear 11 is overmolded onto the shaft 2. In one example illustrated 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° and 360°, preferably between 0° and 90°, while the gear can extend up to 360°. The sector gear is similar to a gear, but it has teeth on a limited segment of its outer periphery and a portion remaining smooth. 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 axis 4 around which shaft 2 rotates. It is generally used in actuators where limited repetitive rotation about axis 4 is required. Shaft 2, protrusion 6, magnet 3 and gear 11 are arranged coaxially around said axis 4. In an example shown in [Fig.4], thanks to protrusion 6, the glue does not escape, which ensures the attachment of magnet 3. As a result, the structural and operational integrity of the device is maintained.

[0031] The invention applies in particular to an electromechanical actuator or a rotating machine for an automotive application which comprises an angular position detection system 12 configured as above. 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 pump, for example an oil pump. In this case, all known examples, such as those of a synchronous machine, an asynchronous machine, a direct current machine or a reluctance machine, are conceivable. Furthermore, the scope of application is not limited to electrical machines. In another aspect, the rotating machine may also be an internal combustion engine with a shaft whose rotational position is to be detected.

[0032] The corresponding electromechanical actuator is a gearbox actuator, also known as a gearshift actuator, used in particular for selecting and shifting between gears in an automobile transmission. To perform the aforementioned operation, the gearbox actuator comprises a shaft 2 in the output mechanism, configured in accordance with the present subject matter. 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 free space 8 is located between the body 5 and the magnet 3 and is filled with glue. The magnet 3 abuts against the protrusion 6. The output mechanism further comprises a gearshift finger or the like coupled to the aforementioned shaft 2.The aforementioned gearbox actuator further comprises a drive motor, a controller electrically connected to the drive motor and configured to control the drive motor, and a reduction mechanism. Said output mechanism is coupled to the drive motor using the reduction mechanism. Said controller comprises at least one magnetic field sensor adapted to detect an angular position of the shaft 2 in which a gear 11 is overmolded.

[0033] In another example, the corresponding electromechanical actuator may be, for example, a parking lock actuator or a parking lock actuator. transmission, used in particular to control the parking pawl capable of moving between a first position in which the parking pawl prevents rotation of the output shaft and a second position in which the parking pawl does not prevent rotation of the output shaft. To perform the aforementioned operation, the parking lock actuator or the transmission lock actuator comprises a shaft 2 in the output mechanism. 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 free space 8 is located between the body 5 and the magnet 3 and is filled with glue. The magnet 3 abuts against the protrusion 6.The aforementioned parking lock actuator or transmission lock actuator further comprises 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.

[0034] 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.

[0035] In the claims, the reference symbols in parentheses should not be interpreted as a limitation of the claim.

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 protrusion (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 free space (8) located between the body (5) and the magnet (3), the free space (8) being filled by the adhesive means (7) and the magnet (3) abutting the protrusion (6) to facilitate retention of the adhesive means (7).

2. An assembly according to claim 1, wherein the protrusion (6) is an integral part of the body (5).

3. An assembly according to any preceding claim, wherein the adhesive means (7) is a glue.

4. An assembly according to any one of the preceding claims, wherein the height of the protrusion (6) is between 0.01 and 1 mm, preferably between 0.05 and 0.2 mm.

5. An assembly according to any preceding claim, wherein the protrusion (6) is centered on the axis (4) and a diameter of the protrusion (6) is less than the diameter of the body (5).

6. An assembly according to any preceding claim, wherein the ratio of the diameter of the protrusion to the diameter of the body is between 10% and 30%.

7. An assembly according to any preceding claim, wherein the average roughness of the surface of the magnet (13), which abuts the protrusion (6), is greater than Ra 0.2 pm.

8. An assembly according to any preceding claim, wherein a gear (11) or rotor is overmolded onto the shaft (2).

9. Angular position detection system (12) comprising an assembly configured according to any one of the preceding claims and a sensor (9) placed opposite the magnet (3).

10. An electromechanical actuator or rotating machine for an automotive application comprising an angular position detection system (12) according to claim 9.

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