Method for manufacturing a sensor bearing unit and related sensor bearing unit

Abstract

The present invention relates to a method for manufacturing a sensor bearing unit. The sensor bearing unit (10) comprises a bearing (12) and an impulse ring (14), wherein the bearing (12) comprises a first ring (16) and a second ring (18) which can coaxially rotate relative to each other; the impulse ring (14) is provided with a target holder (30) and a magnetic target (32) mounted on the target holder, and the target holder (30) is fastened in a groove (16e) formed on the cylindrical surface of the first ring. The method comprises the following steps: a) subjecting the first ring blank to a heat treatment for hardening its metal; b) after the heat treatment step, hard machining the groove (16e) on the cylindrical surface of the first ring blank; and c) introducing and fastening the target holder (30) of the impulse ring into the groove (16e) of the machined first ring.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a sensor bearing unit.

[0002] More precisely, the present invention relates to a method of manufacturing a sensor bearing unit including a bearing and an impulse magneticring. Background Art

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

[0004] Such a sensor bearing unit generally comprises a bearing, an impulse ring and a detection device facing the impulse ring. The impulse ring is equipped with a target holder fixed on the inner ring of the bearing and a magnetic target fixed on the target holder and extending beyond the outer ring of the bearing.

[0005] The magnetic target includes alternating south and north poles, the number of which depends on the size of the bearing, the detection accuracy and the specific application. The detection device can be fixed on the outer ring of the bearing or on a fixed housing.

[0006] The magnetic target is attached to the outer tubular portion of the target holder. The target holder is also provided with an inner tubular portion, which is fastened in a groove formed in the inner hole of the inner ring. Conventionally, the groove is first machined by soft turning (soft turning) and then the inner ring is heat treated.

[0007] With this manufacturing method, there is a large concentricity defect between the groove and the inner ring aperture, which results in an increase in the total pitch deviation (TPD) of the magnetic target when the impulse ring is assembled on the inner ring.

[0008] Total pitch deviation (TPD) is a parameter used to characterize the characteristics of a magnetic ring. It evaluates the cumulative deviation in position of the magnetic ring by measuring the single pitch deviation (SPD) of each magnetic pole of the magnetic ring.

[0009] The determination of the TPD with the magnetic ring with the magnetic poles is similar to the determination of the TPD of the gear or mechanical encoders seen in ABS applications.

[0010] The angular distance between the two magnetic poles with the same polarity distance is defined as the interval. The general method of calculating TPD is described as the following formula:

[0011] The single pitch deviation (SPD) of the interval i can be calculated based on the following formula:

[0012]

[0013] in,

[0014] P Theoretical It is the theoretical period of a single-spaced angular signal;

[0015] P real (i) is the actual period of the angle signal at interval i.

[0016] It should be noted that the actual period P real (i) is determined by two poles of the same polarity, i.e., two north poles or two south poles. Similarly, the actual period P real (i) is determined by the edge of the same type of signal, i.e., between two rising edges or two falling edges.

[0017] The total or accumulated pitch deviation TPD(i) of the interval i can be calculated based on the following formula:

[0018]

[0019] The total pitch deviation formed by a round of mechanical rotation can be calculated based on the following formula:

[0020]

[0021] Among them, Nbpp is the number of intervals contained in a round of mechanical rotation;

[0022] It is an object of the present invention to overcome the above-mentioned drawbacks. Summary of the invention

[0023] The present invention relates to a method for manufacturing a sensor bearing unit, wherein the sensor bearing unit comprises a bearing and an impulse ring, wherein the bearing comprises a first ring and a second ring which can coaxially rotate relative to each other, and the impulse ring is provided with a target holder and a magnetic target mounted on the target holder, wherein the target holder is fastened in a groove formed on the cylindrical surface of the first ring.

[0024] The method comprises the following steps:

[0025] -a) Perform heat treatment to harden the first round of blank:

[0026] -b) After the above-mentioned heat treatment step, the groove is hard-worked on the cylindrical surface of the first ring blank;

[0027] -c) introduce the target holder of the pulse ring into the groove of the first ring after processing; and

[0028] -d) fastening the target holder in the groove.

[0029] The "hard-machining said groove" should be understood as the groove of the first round of blank after hardening (quenching).

[0030] With this method, since the groove is hard machined, the concentricity defect relative to the inner ring bore diameter is minimized. In contrast, in conventional sensor bearing units, the mounting groove formed in the inner ring bore is only soft machined.

[0031] By using the manufacturing method of the present invention, the groove defects that occur during the heat treatment step can be removed. This leads to a reduction in the variation of the total pitch deviation determined by the angular position of the target holder relative to the first ring. The measurement accuracy of the sensor bearing unit can be improved.

[0032] According to a further aspect, the method may further comprise, before step a), a step of pre-machining the groove on the cylindrical surface of the first ring blank in a soft cutting manner with a machining allowance. The machining allowance may be substantially removed in the hard machining step.

[0033] In one specific embodiment, heat treatment may be performed to obtain a hardness in the range of 58 to 62 Vickers hardness. It is preferred that at least through-hardening operation is performed in step a).

[0034] In the first embodiment, the hard cutting process is performed in step b).

[0035] In this case, the method further comprises the step of grinding the cylindrical surface and the side surface of the first ring after processing, before step b) and before step c).

[0036] In the second candidate embodiment, the hard grinding process is performed in step b).

[0037] In one embodiment, the method further comprises the step of grinding the cylindrical surface and the side surface of the processed first turn after step b) and before step c).

[0038] In one embodiment, in step c), the target holder of the pulse ring can be fastened in the groove of the first ring after processing by press-fitting.

[0039] In one embodiment, in step b), the groove is hard-worked in the inner hole of the first ring blank. Therefore, the target is fastened to the inner ring.

[0040] In another embodiment, the groove may be hard-worked on the cylindrical outer surface of the first ring blank. In this case, the target holder is fastened to the outer ring.

[0041] The invention also relates to a sensor bearing unit, which is assembled in accordance with the above-described method.

[0042] The invention further relates to a sensor bearing unit, including:

[0043] - Bearing, the bearing comprising an inner and outer ring centered on the axis; and

[0044] - Pulse ring, the pulse ring is provided with a target carrier and a magnetic target mounted on the target carrier, the target carrier being fastened in a groove formed on the cylindrical surface of the inner or outer ring.

[0045] According to general features, the grooves of the inner or outer rings are hard-worked.

[0046] In one embodiment, the groove is formed in the inner hole of the inner ring by hard processing. Alternatively, the grooves may also be formed on the cylindrical outer surface of the outer ring by hard processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] The present invention and its advantages can be better understood by studying the following detailed description of specific embodiments, which are given by way of non-limiting example and illustrated by the accompanying drawings, in which:

[0048] Figure 1 It is an axial cross-sectional view of a sensor bearing unit according to an embodiment of the present invention;

[0049] Figure 2 The second embodiment of the present invention is shown in FIG. Figure 1 The main steps of the method of the sensor bearing unit shown;

[0050] Figure 3 and 4 Display separately Figure 1 Evolution graph of the total pitch deviation of the magnetic pulse rings of the sensor bearing unit and conventional sensor bearing unit shown; and

[0051] Figure 5 The first embodiment of the present invention is shown in FIG. Figure 1 The main steps of the method of the sensor bearing unit shown. DETAILED DESCRIPTION

[0052] Figure 1 The sensor bearing unit 10 shown is suitable for equipping devices such as motors ( / motors), braking systems, suspension systems or any rotating machine, and is particularly suitable for motor vehicles.

[0053] The sensor bearing unit 10 includes a bearing 12 and an impulse ring 14 mounted on the bearing.

[0054] The bearing 12 comprises a first ring 16 and a second ring 18. In the illustrated embodiment, the first ring 16 is an inner ring and the second ring 18 is an outer ring. The inner ring 16 and the outer ring 18 are concentric with each other and extend axially along the rotation axis XX' of the bearing. The inner ring 16 and the outer ring 18 are made of steel material.

[0055] In the illustrated embodiment, the bearing 12 further comprises a row of rolling elements 20, here in the form of balls, arranged between raceways (not shown) formed between the inner ring 16 and the outer ring 18. The rolling bearing 10 further comprises a cage 22 for maintaining the rolling elements 20 at regular circumferential spacings.

[0056] The inner ring 16 of the bearing is intended to be mounted on the shaft of the device to rotate with the shaft of the device. The inner ring 16 is intended to rotate, while the outer ring 18 is intended to be fixed. The outer ring 18 can be mounted on a fixed support or housing belonging to the device.

[0057] The inner ring 16 includes a cylindrical inner surface (i.e., inner hole) 16a and a cylindrical outer surface 16b. The outer surface 16b is arranged in the opposite direction to the inner hole 16a in the radial direction, and a toroidal annular ( / circular) raceway is formed on the outer surface 16b for the rolling body 20 to roll therein. The raceway faces the outside in the radial direction. The inner ring 16 further includes two radial side surfaces 16c and 16d arranged in opposite directions, and the side surfaces 16c and 16d define the inner ring inner hole 16a and the inner ring outer surface 16b in the axial direction.

[0058] The inner ring 16 further comprises a cylindrical groove 16e formed in the inner hole 16a, which groove 16e is centered around the axis X-X'. The diameter of the inner hole 16a is smaller than the diameter of the groove 16e. The groove 16e is opened on the radial side surface 16d.

[0059] The pulse ring 14 is mounted on the inner ring 16 . The pulse ring 14 includes an annular target holder 30 mounted on the inner ring 16 and a magnetic target 32 ​​mounted on the target holder.

[0060] The target holder 30 can be reliably fixed in the annular groove 16e of the inner ring. The target holder 30 comprises an inner annular axial portion 30a fitted in the annular groove 16e, an outer annular axial portion 30b radially surrounding the inner axial portion 30a and the bearing 12, and an annular radial portion 30c extending between the inner and outer axial portions.

[0061] The inner axial portion 30a of the target holder is fitted into the groove 16e of the inner ring, so as to rotatably fasten the impulse ring 14 to the inner ring 16. In the disclosed embodiment, the radial portion 30c of the target holder abuts against the radial side surface 16d of the inner ring in the axial direction. The outer axial portion 30b of the target holder is located radially higher than the outer ring 18 of the bearing.

[0062] In the disclosed embodiment, the target 30 is formed as one. The target bracket 30 may be made of metal or plastic, formed by stamping or any other suitable process.

[0063] The magnetic target 32 ​​is mounted on the outer axial portion 30b of the target holder. In the disclosed embodiment, the magnetic target 32 ​​is mounted in the inner hole of the outer axial portion 30b. Alternatively, the magnetic target 32 ​​can also be mounted on the outer surface of the outer axial portion 30b.

[0064] The magnetic target 32 ​​is a molded part containing alternating north and south magnetic poles. A detection device (not shown) is associated with the target 32 ​​for tracking the rotation of the pulse ring 14 and the inner ring 16 around the axis XX'. The detection device is arranged to face the inner surface of the magnetic target 32 ​​in the radial direction. As an embodiment, the detection device can include a Hall effect sensor.

[0065] Figure 2 The main steps of a method of manufacturing a sensor bearing unit according to one embodiment of the present invention are shown.

[0066] According to this embodiment, the manufacturing method has a pre-cutting step 40 to provide an inner ring blank having a shape substantially equivalent to that of the finished inner ring and having a machining allowance. In the pre-cutting step 40, the inner hole 16a ( Figure 1 ), groove 16e, cylindrical outer surface 16b, raceways formed on the outer surface, and side surfaces 16c, 16d are all soft-cut.

[0067] After the pre-soft cutting step 40, a heat treatment step 42 is performed to harden (quench) the metal of the inner ring blank. The heat treatment can be performed to obtain a hardness in the range of 58 to 62 Vickers hardness. For example, the entire inner ring blank can be subjected to a through-hardening treatment.

[0068] After the heat treatment step 42, the inner ring blank is hard machined in step 44. The following rough surfaces of the inner ring blank are hard machined: the inner hole 16a, the groove 16e, the cylindrical outer surface 16b, the raceway, and the side surfaces 16c and 16d. The machining allowance reserved on the inner ring blank is removed in the hard machining step 4.

[0069] Then, the grinding step 46 is performed on the inner hole 16 a, the raceway, and the side surfaces 16 c and 16 d of the processed inner ring.

[0070] At this stage of the sensor bearing unit manufacturing method, the bearing component assembly step 48 can be performed before the target holder of the impulse ring is assembled. As another option, the assembly of the bearing component can also be performed after the target holder is assembled on the processed inner ring.

[0071] In the target holder assembly step 50, the inner axial portion 30a of the target holder is introduced into the groove 16e of the inner ring after machining. As an option, the target holder 30 may be rotated in the groove 16e of the inner ring in the circumferential direction to a specific angular position, and then the target holder 30 is fastened in the groove 16e of the inner ring. For this purpose, the inner axial portion 30a of the target holder may be press-fitted (press-fitted) in the groove 16e. As another option, the inner axial portion 30a of the target holder may also be fastened in the groove 16e of the inner ring by any other suitable means, such as bonding or welding.

[0072] As described above, by using the manufacturing method of the present invention, the value of concentricity defect of the inner ring groove 16e relative to the inner ring aperture is smaller than the value of concentricity defect in the conventional sensor bearing unit.

[0073] exist Figure 3 In FIG. 5 , curve 52 shows the evolution of the total pitch deviation of the magnetic target 32 ​​on the impulse ring fixed in the inner ring groove 16 e at various angular positions for a sensor bearing unit manufactured according to the present invention.

[0074] Curve 54 shows the evolution of the total pitch deviation of the impulse ring target of a conventional sensor bearing unit in which the inner groove is formed only by soft cutting, the impulse ring also being fixed in the inner ring groove at various angular positions.

[0075] like Figure 3 As shown, the total pitch deviation variation of the sensor bearing unit manufactured according to the present invention is limited.

[0076] exist Figure 4In FIG. 5 , curves 56 and 58 also show the evolution of the total pitch deviation of the magnetic targets of the sensor bearing unit manufactured according to the present invention and the conventional sensor bearing unit, respectively. Here, the sensor bearing units are selected so that the inner grooves of the inner rings have the same concentricity defect.

[0077] like Figure 4 As shown in, the inner groove formed by hard cutting can almost eliminate the overall pitch deviation caused by its geometric defects.

[0078] Figure 5 The main steps of a method of manufacturing the sensor bearing unit according to another embodiment of the present invention are shown.

[0079] Similar to the first embodiment, the manufacturing method has a pre-cutting step 60 providing an inner ring blank with a processing allowance with a shape substantially corresponding to the finished inner ring. In this cutting step 60, the inner hole 16 ( Figure 1 ), groove 16e, cylindrical outer surface 16b, raceways formed on the cylindrical outer surface, and side surfaces 16c and 16d are all soft cut.

[0080] Similar to the first embodiment, after the pre-soft cutting step 60 , a heat treatment step 62 is performed to harden (quench) the metal of the inner ring blank. For example, the entire inner ring blank is subjected to a penetration hardening treatment.

[0081] After the heat treatment step 62, the inner ring blank is hard ground in step 64. The following rough surfaces of the inner ring blank are hard ground: the inner hole 16a, the groove 16e, the raceway, and the side surfaces 16c and 16d. The machining allowance left in the inner ring blank is removed in the hard grinding step 64.

[0082] In this stage of the sensor bearing unit manufacturing method, the bearing component assembly step 66 can be performed before the target holder of the impulse ring is assembled. As another option, the assembly of the bearing components can also be performed after the target holder is assembled on the processed inner ring.

[0083] Finally, the target tray assembly step 68 is performed, as described previously in the first embodiment.

[0084] In the above illustrative embodiments, the sensor bearing unit is equipped with a rolling bearing containing only one row of rolling elements. Alternatively, the rolling bearing may also contain at least two rows of rolling elements. In the above illustrative embodiments, the rolling elements are spheres. Alternatively, the rolling bearing may also contain other types of rolling elements, such as rollers. In another variant, the rolling bearing may also be configured as a sliding bearing without rolling elements.

[0085] In addition, as mentioned above, in this illustrative embodiment, the first ring of the rolling bearing is the inner ring 16 and the second ring is the outer ring 18. Alternatively, the opposite arrangement can be made: the first ring is the outer ring and the second ring is the inner ring. In this case, the target holder is fastened to the outer ring.

Claims

1. A method for manufacturing a sensor bearing unit, the sensor bearing unit (10) comprising: The bearing (12) comprises a first ring (16) and a second ring (18) which are rotatable concentrically relative to each other; and An impulse ring (14) is provided with a target holder (30) and a magnetic target (32) mounted on the target holder, wherein the target holder (30) is fastened in a groove (16e) formed on a cylindrical surface (16a) of the first ring (16); Characterized in that the method comprises the following steps: a) Heat treatment of the first round blank to harden its metal: b) hard machining the groove (16e) on the cylindrical surface (16a) of the first ring blank after the above-mentioned heat treatment step; and c) introducing and fastening the target holder (30) of the impulse ring (14) into the groove (16e) of the processed first ring.

2. The method according to claim 1, characterized in that: The method further comprises, before step a), pre-machining the groove (16e) located in the cylindrical surface (16a) of the first ring blank by a soft cutting method with reserved machining allowance.

3. The method according to claim 1 or 2, characterized in that: In step a), at least a through-hardening treatment is carried out.

4. The method according to claim 1 or 2, characterized in that: In step b) a hard turning operation is carried out.

5. The method according to claim 4, characterized in that: The method further comprises the step of grinding the cylindrical surface (16a) and the side surfaces (16c, 16d) of the processed first ring (16) after step b) and before step c).

6. The method according to claim 1 or 2, characterized in that: In step b) a hard grinding operation is carried out.

7. The method according to claim 1 or 2, characterized in that: In step b), the groove (16e) is hard machined in the inner hole of the first ring blank forming the cylindrical surface.

8. A sensor bearing unit (10) manufactured using the method according to any one of the preceding claims.

9. A sensor bearing unit (10), comprising: A bearing (12), the bearing (12) comprising an inner ring (16) and an outer ring (18) centered on an axis (XX'); and An impulse ring (14), the impulse ring (14) being provided with a target holder (30) and a magnetic target (32) mounted on the target holder, the target holder (30) being fastened in a groove (16e) formed on a cylindrical surface (16a, 16b) of the inner ring (16) or the outer ring (18); The invention is characterized in that the groove (16e) of the inner ring (16) or the outer ring (18) is hard machined.

10. The sensor bearing unit (10) according to claim 9, characterized in that: The groove (16e) is formed by hard machining in the inner hole (16a) of the inner ring (16) forming the cylindrical surface (16a).

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