Method for coating a sensor unit and associated sensor unit

Abstract

A method of coating a sensor unit (10) and an associated sensor unit (10) are disclosed. The sensor unit (10) comprises at least one sensor element (32) and a sensor body (30) supporting the sensor element. The method comprises a coating step of applying a coating (50) to the outer surface of the sensor unit (10) in the assembled state of the sensor unit (10) in order to coat the sensor element (32) and the sensor body (30).

Description

Technical Field

[0001] This invention relates to the field of sensor units for sensing the angular position of a rotatable element relative to a fixed element, and more particularly to the field of sensor bearing units that include a bearing and the sensor unit.

[0002] More precisely, the present invention relates to a method for coating a sensor unit. Background Technology

[0003] Today, sensor bearing units are widely used in a wide range of technical fields, such as the automotive industry and aerospace engineering. These units provide high-quality signals and transmissions while also allowing for integration into simpler and more compact devices.

[0004] The sensor bearing unit includes a bearing and a sensor unit used to sense the angular position (or angle position) of the bearing's rotatable ring relative to a fixed ring. This sensor unit typically includes an impulse ring and a sensor element. The impulse ring is reliably fixed to the rotatable ring and contains alternating south and north poles; the sensor unit faces the impulse ring to determine the angular position of the rotatable ring based on changes in the magnetic field.

[0005] The sensor unit is also provided with a sensor body that supports the sensor element and is reliably fixed on the bearing ring, and an output connecting cable suitable for transmitting sensing data to the receiving device.

[0006] In a typical case, the sensor body of the sensor unit is overmolded onto the sensor element, with only the active part of the sensor element facing the pulse loop not embedded in the sensor body.

[0007] After the molded plastic shrinks, narrow channels may form between the sensor element and the sensor body. Water and / or contaminating particles may reach and come into contact with the sensor element. Summary of the Invention

[0008] One object of the present invention is to overcome this defect.

[0009] The present invention is particularly intended to provide a sensor unit that has improved resistance to moisture and pollutant particles.

[0010] The present invention relates to a method for coating a sensor unit, the sensor unit comprising at least one sensor element and a sensor body supporting the sensor element.

[0011] The method includes the step of applying a coating to the outer surface of the sensor unit while the sensor unit is assembled, thereby coating the sensor element and the sensor body.

[0012] The term "outer surface of the sensor unit" refers to the surface of the sensor unit that can be accessed from the outside when the sensor unit is assembled.

[0013] Thanks to this invention, the narrow channel that may be formed between the sensor element and the sensor body is covered by the applied coating.

[0014] This improves the sensor unit's ability to prevent moisture, which includes corrosive chemical agents such as salts, solvents, and mineral greases that are immersed in water.

[0015] In addition, the coating applied to the sensor unit also provides improved resistance against electrostatic discharges.

[0016] Furthermore, the sensor unit can be manufactured and assembled using traditional process steps, since the coating operation is performed on the sensor unit already assembled, thus requiring no adaptive adjustments.

[0017] In one specific embodiment, the method includes at least a first curing step following the coating step. In the first curing step, the coating is cured at room temperature and a relative humidity of less than or equal to 80%.

[0018] Advantageously, the method further includes a second curing step after the first curing step. In the second curing step, the coating is cured at a higher temperature and a relative humidity of less than or equal to 80%.

[0019] The coating is preferably applied using a dipping process. Alternatively, the coating can also be applied by spraying or brushing.

[0020] However, compared to spraying or brushing, which struggles to cover all surfaces of the sensor unit, the dip-coating process effectively covers all surface asperities clearly distributed on and / or between the sensor element and the sensor body. Furthermore, the dip-coating process results in a uniform coating thickness and limited air inclusions.

[0021] When using an immersion process, the coating step may include moving the sensor unit vertically downwards into a bath of coating until both the sensor element and the sensor body are coated.

[0022] The coating step may also include the following consecutive operations following the downward movement of the sensor unit:

[0023] - Move the sensor unit upwards at a first velocity until the sensor element is in the air; and

[0024] - Completely withdraw the sensor unit from the coating tank at a higher second speed.

[0025] In one embodiment, the coating step, after the extraction operation, further includes the operation of draining residual coating from the sensor unit above the coating tank.

[0026] In one embodiment, the sensor unit further includes an output cable mounted within the sensor body and extending outward.

[0027] In this case, the method may advantageously include applying a coating to the outer surface of the sensor unit while the sensor unit is assembled, such that the sensor element, the sensor body, and the output cable at least the portions protruding beyond the sensor body are coated.

[0028] The narrow channel that may form between the output cable and the sensor body is also sealed by this coating, thereby further improving the sealing of the sensor unit.

[0029] In one particular embodiment, during the coating step, the coating is also applied to a printed circuit board disposed along the output cable or disposed in a connector of the output cable.

[0030] The coating may partially cover / recover the output cable. In this case, the coating at least covers / recovers the protruding portion of the output cable near the sensor body. Alternatively, the coating may cover / recover the entire length of the output cable.

[0031] The present invention also relates to a sensor unit, comprising at least one sensor element and a sensor body supporting the sensor element.

[0032] According to general characteristics, the sensor unit also includes a coating covering the outer surface of the sensor element and the sensor body.

[0033] Preferably, the entire outer surface of the sensor body and the entire outer surface of the sensor element are covered by the coating.

[0034] The sensor unit may also include a support member that at least partially accommodates the sensor body within a housing formed by the support. The outer surface of the housing is covered by the coating.

[0035] The coating is preferably a single-layer coating. Alternatively, the coating may be a multi-layer coating.

[0036] In one embodiment, the sensor unit further includes an output cable mounted within the sensor body and extending outward. In this case, the coating may also at least cover the portion of the output cable protruding beyond the sensor body.

[0037] In one implementation, when using wireless sensor elements, the sensor unit may not need to use this output cable. Attached Figure Description

[0038] The invention and its advantages can be better understood by studying the detailed description of specific embodiments illustrated in the accompanying drawings, which are given by way of non-limiting examples, wherein:

[0039] Figure 1 This is a front view of the sensor unit according to the first embodiment of the present invention;

[0040] Figure 2 It is along Figure 1 A partial cross-sectional view taken from section II-II;

[0041] Figure 3 It contains Figure 1 and 2 A partial cross-sectional view of the sensor bearing unit of the sensor unit shown in the figure;

[0042] Figure 4 Demonstrating an embodiment of the present invention Figure 1 and 2 The main steps of the method for coating the sensor bearing unit shown; and

[0043] Figure 5 This is a partial cross-sectional view of the sensor unit according to the second embodiment of the present invention. Detailed Implementation

[0044] Figure 1 and 2 The sensor unit 10 shown is adapted to be assembled into Figure 3 The bearing 12 shown is used to form a sensor bearing unit.

[0045] As described below, the sensor unit 10 is coated, preferably with a conformal coating.

[0046] Bearing 12 includes an inner ring 14 and an outer ring 16. The inner and outer rings 14 and 16 are coaxial and extend axially along the bearing rotation axis X-X'.

[0047] The bearing 12 also includes a row of rolling elements 18 (here arranged in the form of balls) between the inner and outer rings 14 and 16. The rolling bearing 12 also includes a cage 20 for maintaining a regular circumferential spacing of the rolling elements 18. In the disclosed specific embodiment, the bearing 12 also includes an annular seal 22 on one side for closing the radial space existing between the inner and outer rings 14 and 16.

[0048] The inner ring 14 of the bearing is intended to be mounted on a shaft of an apparatus for rotational movement. The inner ring 14 is intended for rotation, while the outer ring 16 is intended for fixation. The outer ring 16 may be mounted in a fixed support member or housing belonging to the apparatus.

[0049] The outer ring 16 includes a cylindrical outer surface 16a and a cylindrical inner surface (hereinafter referred to as the "inner bore") 16b. The inner bore 16b forms a toroidal circular raceway (not shown in the figure) of the rolling element 18 facing radially inward. The outer ring 16 also includes two opposing radially arranged side surfaces 16c and 16d that define its outer surface 16a and inner bore 16b in the axial direction.

[0050] The outer ring also includes two grooves (unmarked) formed radially outward from the inner bore 16b, positioned on either side of the raceway. A seal 22 is installed in one of these grooves.

[0051] The bearing 12 is also equipped with an encoder unit 24, which is fixed on the inner ring 14 of the bearing and is adapted to cooperate with the sensor unit 10.

[0052] The encoder unit 24 includes an annular target holder 26 mounted on an inner ring 16 and a magnetic target 28 mounted on the target holder. The target holder 26 is fixed to the outer surface of the inner ring 14, axially positioned opposite the seal 22 across the row of rolling elements 18. The target holder 26 is fixed to the inner ring 14 to secure the encoder unit 24 to the rotatable inner ring during rotation. The target holder 26 is integrally formed and may be made of metal or plastic, formed by stamping or any other suitable process.

[0053] The target 28 is mounted on the outer surface of the target holder 26. The target 28 is a plastic molded part, which includes alternating north and south magnetic poles.

[0054] The bearing 12 is also equipped with an annular cover 29 for securing the sensor unit 10 to the outer ring 16. The cover 29 is secured to the outer ring 16. More precisely, the cover 29 is secured in a groove on the outer ring 16 axially near the side surface 16c. The cover 29 is also secured to the sensor unit 10. The cover 29 is an annular component centered on the bearing's rotation axis X-X'. The cover 29 is made of metal.

[0055] The sensor unit 10 includes a sensor body 30, a sensor element 32 supported by the sensor body, and an output connecting cable 34 for transmitting sensing data.

[0056] The sensor body 30 is made of a synthetic material such as PA6.6. In the disclosed embodiment, the sensor body 30 is overmolded (also referred to as "secondary molding") onto the sensor element 32. Alternatively, the sensor element 32 can be attached to the sensor body 30 in any suitable manner (e.g., adhesive / gluing). The sensor body 30 is attached to the outer ring 16 of the bearing. The sensor body 30 is attached to the cover 29. The sensor body 30 protrudes radially beyond the outer ring 16.

[0057] Sensor element 32 is mounted in a semi-embedded manner within sensor body 30 and is flush with the annular inner surface of sensor body. Sensor element 32 faces the target 28 of encoder unit radially. A small radial gap exists between sensor element 32 and target 28. In another embodiment, sensor element 32 may also face the target 28 of encoder unit axially. Sensor element 32 is adapted to detect changes in the magnetic field generated by rotation of encoder unit 24. Sensor element 32 may be a Hall-effect sensor.

[0058] The output cable 34 extends outward relative to the sensor body 30. In the disclosed embodiment, the output cable 34 extends outward radially. Alternatively, the output cable 34 may also extend outward axially.

[0059] like Figure 1 As shown, the output cable 34 includes multiple wires 36 and an insulating sheath 38 that holds these wires 36 together internally. The wires 36 of the output cable are directly connected to the sensor element 32 (not shown). Alternatively, the sensor unit may include a printed circuit board to which the sensing element is connected. In this case, the wires 36 of the output cable can be connected to the printed circuit board.

[0060] In the disclosed embodiment, the output cable 34 also includes a plug connector 39 (shown as dashed lines in the figure) at its free end ( / free portion), where the various free ends of the wires 36 are located. Alternatively, the output cable 34 may not have such a connector.

[0061] Refer again Figure 2 and Figure 3 The output cable 34 is installed inside the sensor body 30 and extends outward. One end of the output cable 34 is inserted into an opening 40 formed in the sensor body 30. The output cable is secured in the opening 40. The output cable 34 can be reliably fixed in the opening 40 by any suitable method, such as press-fitting, bonding, or overmolding onto the sensor body 30.

[0062] The sensor body 30 also has an outlet protruding portion 42 extending radially outward from its outer surface. An opening 40 is formed on the outlet protruding portion 42 of the sensor body. The sensor body 30 and the outlet protruding portion 42 are integrally formed. In the disclosed embodiment, the outlet protruding portion 42 has a rectangular parallelepiped shape. Alternatively, the outlet protruding portion 42 may also have other shapes, such as a tubular shape.

[0063] In the disclosed embodiment, the sensor unit 10 further includes a support 44, which is mounted on the sensor body 30 axially opposite the bearing 12. The support 44 is fixed to the sensor body 30. The support 44 is an annular component centered on the bearing's rotation axis X-X'. The sensor body 30 is mounted within the support 44. Only the outlet protrusion 42 of the sensor body protrudes radially beyond the support 44. The support 44 is made of metal. In a particular embodiment, the support 44 is made of steel with high magnetic permeability.

[0064] Figure 2 To show more clearly, sensor unit 30 also includes coating 50, deposited on all the outer surfaces of sensor body 30, sensor element 32 and support 44.

[0065] Coating 50 is also provided on the outer surface of the portion of the output cable 34 that protrudes beyond the sensor body 30. This protruding portion of the output cable 34 is adjacent to the sensor body 30. More precisely, the protruding portion of the output cable 34 is adjacent to the outlet protrusion 42 of the sensor body. Coating 50 covers the outer surface of the sheath 38 of the protruding portion of the output cable 34. The entire outer surface of the sensor body 30, sensor element 32, and support member 44 is covered by coating 50.

[0066] Advantageously, coating 50 is a conformal coating specifically designed to protect electronic circuits. For example, coating 50 can be an FSC or DCA coating from Electrolube®. Alternatively, other conformal coatings can also be used. For example, the thickness of coating 50 can range from 30 μm to 110 μm. In a variation, coatings 50 with other thickness ranges are also feasible.

[0067] The coating 50 is preferably formed by an impregnation process. Alternatively, the coating 50 can also be applied by spraying or brushing.

[0068] Figure 4This illustrates the main steps of a method for coating sensor unit 10 by an impregnation process according to an embodiment of the present invention.

[0069] In the first step 52, the coating process is performed. More precisely, in the first sub-step 52a, the sensor unit 10 is moved vertically downwards into a coating tank, preferably a coating tank containing conformal coating material. The coating material can be mixed with a special solvent to thin it if necessary.

[0070] During the first sub-step, sensor unit 10 uses Figure 1 The orientation shown is vertical, meaning the output cable 34 is positioned above the sensor body 30. The sensor unit 10 is in an assembled state.

[0071] The sensor unit 10 is vertically moved into the coating tank until the sensor element 32, sensor body 30, support 44, and output cable 34 are coated. Preferably, the first sub-step is performed with a regular, slow motion to ensure that the formed coating perfectly covers all surface micro-protrusions with a regular thickness and minimal air inclusions. For example, the movement speed can be 1 mm / s.

[0072] In the illustrated embodiment, the output cable 34 is coated only on its protruding portion near the sensor body 30. For example, the length of the coating on the output cable may be 5 mm.

[0073] In the subsequent second sub-step 52b, the sensor unit 10 is moved upward at a first speed until the sensor element 32 is in the air. For example, the first speed may be 1 mm / s.

[0074] In the third sub-step 52c, the sensor unit 10 is completely extracted from the coating tank at a higher second speed, which can be less than or equal to 10 mm / s. Alternatively, the same speed can be used to move the sensor unit 10 upward from the coating tank and extract it.

[0075] Then, in the fourth sub-step 52d, the sensor unit 10 is held above (outside) the coating tank to allow residual paint on the sensor unit 10 to drain above the coating tank. This fourth sub-step can, for example, be performed in approximately 10 seconds.

[0076] In the second step 54, the coating is cured at room temperature and a relative humidity of less than or equal to 80%. This first curing step, for example, can be completed in approximately two hours.

[0077] Then, in the third step 56, the second curing step is performed at a higher temperature and a relative humidity of less than or equal to 80%. The second curing step can also be completed over several hours, ranging from 2 to 24 hours (or longer if necessary). The temperature depends on the coating material and can be 90°C.

[0078] After the curing step, the sensor unit 10 can be mounted on the bearing.

[0079] At least during the coating step, the sensor unit 10 can be held and suspended by the output cable 34.

[0080] As previously stated, in the illustrated embodiment, the output cable 34 is coated only on its protrusion near the sensor body 30.

[0081] In another embodiment, the output cable 30 can be coated over a longer length. For example, if the output cable 34 has a printed circuit board, the coating can also be applied to the printed circuit board. Once the coating method is implemented, an adapter (dongle) can also be installed on the cable around the printed circuit board. Similarly, if the output cable 34 has a printed circuit board integrated into a plug-in connector for connection to wires, the coating can also be applied to the printed circuit board. After coating, the plug-in connector is fitted onto the sheath of the output cable.

[0082] In the illustrated embodiment, the sensor unit is fixed to the outer ring of the bearing. Alternatively, the sensor unit can also be fixed to the inner ring of the bearing.

[0083] In the illustrated embodiment, the sensor bearing unit is provided with a rolling bearing containing one row of rolling elements. Alternatively, the rolling bearing may also contain at least two rows of rolling elements. In the illustrated embodiment, the rolling elements are balls (or rollers). The rolling bearing may also contain other types of rolling elements, such as rollers. In another variation, the bearing may also be a sliding bearing without rolling elements.

[0084] In the illustrated embodiment, the sensor bearing unit is provided with an output cable. Alternatively, as mentioned above, the sensor bearing unit may not have this output cable, such as... Figure 5 As shown (where the same parts are given the same reference numerals). In this case, at least during the coating step, the sensor unit can be held and suspended in any other suitable manner.

Claims

1. A method for coating a sensor unit (10), said sensor unit (10) comprising at least one sensor element (32) and a sensor body (30) supporting said sensor element, characterized in that, The method includes the following coating steps: - With the sensor unit (10) assembled, a coating (50) is applied to the outer surface of the sensor unit (10) to coat the sensor element (32) and the sensor body (30). The coating step includes the following operations: moving the sensor unit (10) vertically downward into the coating tank until the sensor element (32) and the sensor body (30) are coated; The coating step also includes the following consecutive operations following the downward movement of the sensor unit (10): - Move the sensor unit (10) upward at a first velocity until the sensor element (32) is in the air; and - The sensor unit (10) is completely removed from the coating tank at a higher second speed.

2. The method according to claim 1, characterized in that, Following the coating step, at least a first curing step is included, in which the coating is cured at room temperature and relative humidity less than or equal to 80%.

3. The method according to claim 2, characterized in that, Following the first curing step, a second curing step is included, in which the coating is cured at a higher temperature and a relative humidity of less than or equal to 80%.

4. The method according to any one of claims 1 to 3, characterized in that, The coating step includes spraying or brushing the coating onto the sensor element (32) and the sensor body (30).

5. The method according to any one of claims 1 to 3, characterized in that, The sensor unit (10) also includes an output cable (34) mounted in the sensor body (30) and extending outward, wherein, during the coating step, the coating is applied at least to the portion of the output cable (34) that protrudes beyond the sensor body (30).

6. The method according to claim 1, characterized in that, In the coating step, the coating is also applied to a printed circuit board disposed along the output cable (34) or disposed in a connector of the output cable.

7. A sensor unit (10), comprising at least one sensor element (32) and a sensor body (30) supporting the sensor element, characterized in that, The sensor unit (10) also includes a coating (50) covering the outer surfaces of both the sensor element (32) and the sensor body (30). The coating (50) is configured to be formed by a coating step, which includes the following operations: moving the sensor unit (10) vertically downward into the coating tank until the sensor element (32) and the sensor body (30) are coated; The coating step also includes the following consecutive operations following the downward movement of the sensor unit (10): - Move the sensor unit (10) upward at a first velocity until the sensor element (32) is in the air; and - The sensor unit (10) is completely removed from the coating tank at a higher second speed.

8. A sensor bearing unit comprising a bearing (12) including an inner ring and an outer ring, and a sensor unit (10) according to claim 7, which is fixed to one of the inner ring and the outer ring.

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