WO2010139677A1

WO2010139677A1 - An instrumented bearing, a bearing assembly, and a rotary electrical machine including such a bearing or such an assembly

Info

Publication number: WO2010139677A1
Application number: PCT/EP2010/057589
Authority: WO
Inventors: Florian Barcat; Vincent Sausset; Olivier Joubert
Original assignee: Aktiebolaget Skf
Priority date: 2009-06-02
Filing date: 2010-06-01
Publication date: 2010-12-09
Also published as: FR2946108A1

Abstract

The instrumented bearing (22) comprises a rotary inner ring (28), a non- rotary outer ring (26), and means for detecting a parameter concerning rotation of the inner ring (28) relative to the outer ring (26), said means including at least one sensor mounted on or in a support (54). The bearing (22) also includes an annular mounting member (60) for mounting the support (54) on the outer ring (26), said member being provided with an annular skirt (68). The annular mounting member (60) is provided with a tongue (70) or with a lancing cut in the annular skirt (68). The tongue (70) or the lancing extend radially outwards from the annular skirt (68) and enables the outer ring (26) to be blocked in rotation about the axis of rotation (X₂₂) of the inner ring (28).

Description

AN INSTRUMENTED BEARING, A BEARING ASSEMBLY, AND A ROTARY ELECTRICAL MACHINE INCLUDING SUCH A BEARING OR SUCH AN ASSEMBLY

The invention relates to an instrumented bearing, such as an assembly having rolling bodies that is fitted with one or more sensors enabling a parameter concerning the rotation of one of the rings of the bearing relative to the other ring to be detected.

As mentioned in FR-A-2 838 884, such a bearing may be used for supporting the central shaft of a rotary electrical machine, of the motor or generator type. By providing knowledge of a parameter concerning the rotation of the shaft of the machine, such a bearing makes it possible to feed the coils of its stator in optimized manner.

In order to avoid any risk of static indeterminacy, such that a bearing cannot be mounted as a tight fit both via its inner ring and via its outer ring. In the equipment disclosed in FR-A-2 838 884, the inner ring of the bearing is mounted as a tight fit on the central shaft of the rotor, while its outer ring is mounted to be slidable relative to the carcass of the machine, with a bushing of synthetic material being interposed between them to make it possible, in particular, for differential thermal expansion to be taken up between the carcass and the outer ring.

In order to improve the accuracy of such an instrumented bearing, WO-A-2009/004198 provides for a block of a detector assembly to be mounted angularly inside a support, the support being mounted on one of the rings of the bearing, thereby enabling the angular position of the means for detecting a parameter concerning rotation to be adjusted. Such an approach assumes that the outer ring of the bearing on which the support is mounted is itself in a position that is accurate and unchanging relative to a stationary structure such as the carcass. Known structures do not ensure such an accurate and unchanging position for a reference ring of an instrumented bearing.

Documents EP-A-I 270 974 and DE-A-197 13 333 also disclose using means for preventing the outer ring of the instrumented bearing from moving in axial translation. Nevertheless, that does not enable such a ring to be prevented from moving in rotation, such that the measurement performed by a sensor connected to said ring might be erroneous . Those are the drawbacks that the invention seeks more particularly to remedy by proposing a novel instrumented bearing in which the detector means can operate in more effective manner by virtue of one of the rings of the bearing being positioned in accurate and stable manner.

To this end, the invention relates to an instrumented bearing comprising a rotary inner ring, a non-rotary outer ring, means for detecting a parameter concerning rotation of the inner ring relative to the outer ring, said means including at least one sensor mounted on or in a support, and an annular mounting member for mounting the support on the outer ring, said annular mounting member being provided with an annular skirt. This bearing is characterized in that the mounting member is provided with a tongue or a lancing cut in the annular skirt, said tongue or said lancing extending radially outwards relative to the annular skirt and enabling the outer ring to be blocked in rotation about the axis of rotation of the inner ring. By means of the invention, the mounting member performs both a function of securing the sensor support relative to the outer ring, and a function of preventing the outer ring from moving in rotation, thereby ensuring that the sensor (s) forming part of the detector means is/are positioned reliably. The tongue or the lancing serves to prevent the mounting member from moving in rotation, thereby preventing the outer ring of the bearing from moving in rotation.

A parameter concerning rotation of the inner ring relative to the outer ring is a parameter that is representative of the rotary movement of the inner ring. Such a parameter may be an angle measuring the angular position of the inner ring relative to the outer ring, about its axis of rotation. Such a parameter may also be speed, a shift, an acceleration, or a vibration. In the present description, words such as "axial", "radial", "axially", and "radially", are relative to the axis of rotation of the rings relative to each other. A direction is said to be "axial" when it is parallel to said axis, and is said to be "radial" when it is perpendicular to said axis and intersects it.

The invention may be implemented with any type of bearing, and more particularly with a rolling bearing, the rolling bodies of the bearing possibly being balls, rollers, or needles. In aspects of the invention that are advantageous but not essential, an instrumented bearing in accordance with the invention may incorporate one or more of the following characteristics taken in any technically feasible combination. • The tongue is advantageously deformable between a first configuration in which it extends in a direction inclined at an angle lying in the range 20° to 70° relative to the axis of rotation of the inner ring, and a second configuration in which it is perpendicular to said axis, the tongue being deformed under the effect of the bearing being caused to move axially in translation towards the inside end of the housing.

• The support is mounted inside the mounting member while being angularly movable relative to the mounting member about the axis of rotation of the inner ring.

This makes it possible to adjust the angular position of the detector means once the position of the outer ring has been set by the blocking means .

• The mounting member is made of metal, in particular is made of spring steel. The invention also provides a bearing assembly comprising an instrumented bearing as mentioned above, and a bushing for mounting the bearing in a carrier structure, such as the carcass of a rotary electrical machine, the bushing being fitted with first blocking means complementary to the tongue or the lancing of the mounting member and enabling the outer ring to be prevented from moving in rotation relative to the bushing about the axis of rotation of the inner ring, and second blocking means for blocking the bushing in rotation relative to the carrier structure and to the above- mentioned axis.

When the mounting member is annular, with its blocking means comprising at least one element projecting radially outwards from an annular skirt, the first blocking means of the bushing advantageously include at least one hollow housing for receiving the tongue or the lancing of the mounting member, and the second blocking means of the bushing include at least one element projecting radially outwards from an outer radial surface of the bushing. Under such circumstances, provision may be made for the hollow housing and the projecting element of the bushing to be in alignment in a direction that is radial relative to the axis of rotation of the inner ring . Finally, the invention provides a rotary electrical machine, e.g. a motor, a generator, or an alternator/starter, the machine comprising a carcass, a stator, and a rotor mounted on a shaft that is supported relative to the carcass by means of an instrumented bearing as mentioned above, or by means of a bearing assembly as mentioned above, and a housing formed in the carcass for receiving the bearing or the bearing assembly is provided with means complementary to the tongue or the lancing of the mounting member or of the second blocking means of the bushing, said complementary means of the housing being suitable for co-operating with said tongue, said lancing or bearing assembly to prevent the outer ring of the instrumented bearing from moving in rotation relative about the axis of rotation of the inner ring. The invention can be better understood and other advantages thereof appear more clearly in the light of the following description of various embodiments of an instrumented bearing, of a bearing assembly, and of a rotary electrical machine, in compliance with the principle of the invention and given purely by way of example, being made with reference to the accompanying drawings, in which:

• Figure 1 is a partially exploded perspective view of a rotary electrical machine in accordance with the invention, the central shaft and the rotor of the machine being omitted for clarity of the drawing; • Figure 2 is a perspective view on a smaller scale and from a different angle, showing the Figure 1 machine while it is being assembled;

• Figure 3 is a side view of the machine of Figures 1 and 2 while it is being assembled, the view being partially cut away;

• Figure 4 is a view showing a detail IV of Figure 3 on a larger scale;

• Figure 5 is a view analogous to Figure 4 during a subsequent assembly step; • Figure 6 is a view analogous to Figure 1 for a machine constituting a second embodiment of the invention;

• Figure 7 is a view analogous to Figure 3 for the Figure 6 machine; • Figure 8 is a view showing a detail VIII of Figure 7, on a larger scale; • Figure 9 is a view analogous to Figure 8 during a subsequent assembly step; and

• Figure 10 is a perspective view of a mounting annulus suitable for use in a variant of the invention. The rotary electrical machine 2 shown in Figures 1 to 5 comprises a carcass 4 having mounted therein a stator 6, and a shaft 8 mounted to rotate relative to the carcass 4 and carrying a rotor 10.

The shaft 8 is secured to a pulley 12 for engaging with a motion-transmission belt. In the vicinity of the pulley 12, the shaft 8 is supported relative to the carcass 4 by means of a ball bearing (not shown) .

At its end opposite from the pulley 12, the shaft 8 is supported by a bearing assembly 20 that comprises an instrumented bearing 22 and a bushing 24 made of electrically-insulating synthetic material that defines a housing 242 for receiving the bearing 22 and that is designed to be inserted in a housing 42 of corresponding shape defined by the carcass 4. The bearing 22 comprises a non-rotary outer ring 26 and a rotary inner ring 28 that is clamped onto the shaft 8. Balls 29 are interposed between the rings 26 and 28 and they are held in position by a cage 31.

Encoder washer 30 is fastened to the inner ring 28 and comprises a metal strength member 32 assembled by force in a setback 282 of the inner ring 28, thereby ensuring that the elements 28 and 30 are firmly prevented from turning relative to each other. Alternatively, the code washer 30 may be constrained to rotate with the inner ring 28 by any other suitable means such as adhesive and/or magnetic retention. In addition, a magnetic ring 34 is fastened to the strength member 32, the ring having at least two magnetic poles formed by permanent magnets. Parts 32 and 34 together form encoder washer 30. The encoder washer 30 turns about the central axis X₂₂ of the bearing 22, which axis coincides with the longitudinal axis X₈ of the shaft 8 when the ring 28 of the bearing 22 is clamped onto the shaft 8.

Furthermore, a plurality of magnetically-sensitive sensors, of the Hall effect cell type, are located close to the washer 30. One of these sensors is visible in the figures, with the reference 50. In practice, the magnetically-sensitive sensors are three in number, for example, since that number is sufficient to control a three-phase electrical machine, and they are regularly distributed around the axis X₂₂, in particular when the encoder washer has only one pair of magnetic poles. They are disposed with their respective aiming directions parallel to the axis X₂₂ and facing towards the ring 34. Each sensor 50 or the equivalent is mounted on a printed circuit 52 that is itself held stationary in a cover 54 constituting a support for the elements 50 and 52 and placed around the shaft 8 with radial clearance J. The cover 54 includes a zone 56 dedicated to passing a cable 58 for connecting the printed circuit 52 to an electronic control unit (not shown) .

The cover 54 is prevented from moving relative to the ring 28 by means of a mounting annulus 60, or mounting ring, made of spring steel and having a section that is circular, as does the ring 26 of the cover 54, with the exception of the zone 56. The annulus 60 has a cylindrical portion 62 of circular section and a frustoconical portion 64 that extends from the portion 62 towards the axis X₈. The annulus 60 also has an annular portion 66 perpendicular to the axis X₂₂ and a cylindrical skirt 68 of circular section. The portion 66 connects the portion 64 to the skirt 68.

The cover 54 has a cylindrical inner skirt 542 of circular section centered on the axis X₂₂, and an annular section 544 perpendicular to the axis X₂₂ and extending radially outwards from the skirt 542. The cover 54 also has an outer skirt 546 parallel to the skirt 542 and extending radially outside the skirt 542. A volume V₅₄ for receiving the elements 50 and 52 is thus defined between the skirts 542 and 546, being defined axially by the portion 554. The skirt 546 is extended by a margin 548 having a radially outer surface that comprises a cylindrical portion 5482 and a frustoconical portion 5484. The shapes of the portions 62 and 64 of the annulus 60 match the shapes of the portions 5482 and 5484 in such a manner as to enable the annulus 60 to be snap- fastened around the margin 548, while being free to turn angularly relative thereto about the axis X₂₂.

Furthermore, the inside diameter of the skirt 68 matches the diameter of the portion of the ring 26 that faces the cover 54, such that the annulus 60 can be snap- fastened on the outer edge 261 of the outer ring 26. The skirt 68 is provided with two tongues or tabs 70 that extend radially outwards from the skirt, so as to project relative to the outer radial surface 262 of the ring 26 when the annulus 60 is secured to the cover 54 and the ring 26. Furthermore, the bushing 24 is provided on its radially inner surface 244 that defines the housing 242 with two notches 246 for receiving the tabs 70 when the bearing 22 is engaged in the bushing 24.

The bushing 24 enables the outer ring 26 of the bearing 22 to be mounted slidably relative to the carcass 4. Given its resilient nature that results from the elastic material from which it is molded, this bushing serves to take up differential thermal expansion between the carcass 4, which may be made of aluminum, and the outer ring 26, which may be made of steel. The bushing 24 thus ensures that the bearing 22 is mounted in the carcass 4 in resilient manner, without excessively prestressing the rings 26 and 28 or the balls 30 in the event of a larger amount of differential thermal expansion. In addition, the bushing 24 is electrically insulating, thereby protecting the bearing 22 from residual electrostatic currents that might exist in the machine 2. This serves in particular to avoid forming electric arcs between the balls 29 and the raceways formed respectively in the rings 26 and 28.

The bushing 24 is also provided with a finger 248 that projects radially from the outer radial surface 249 of the bushing 24.

The tongues 70 are in alignment on a diameter D₆₀ of the annulus 60. In the same manner, the notches 246 are in alignment on a diameter D₂₄ of the bushing 24. The finger 248 is also in alignment on the diameter D₂₄, such that the notches 246 and the finger 248 are in line with one another, in a radial direction relative to a central axis X₂₄ of the bushing 24 that coincides with the axes X₂₂ and X₈ when the machine 2 is in the assembled configuration.

Furthermore, the inner radial surface 44 of the carcass 4 that defines the housing 42 is provided with a notch 46 for receiving the finger 248.

Thus, when the machine 2 is being assembled, as shown in Figure 2, it is possible to engage the bushing 24 in the housing 42 by bringing the finger 248 into the notch 46 defined by the carcass 4, thereby preventing the bushing 24 from turning about the central axis X₄₂ of the housing 42, which axis coincides with the axes X₂₂ and X₈ when the machine 2 is in its assembled configuration.

Furthermore, the bearing 22 is preassembled by assembling the cover 54 with the ring 26 by means of the annulus 60. It is then possible to put the bearing 22 into place in the housing 242 of the bushing 24 by engaging each of the tongues 70 in a respective notch

246. This produces the configuration shown in Figures 3 and 4 in which each tongue 70 extends on a straight line Δ₇₀ that forms an angle θ relative to the axis X₈, where the angle θ is about 45°. In practice, the angle θ may be selected to lie in the range 0° to 90°, and preferably in the range 20° to 70°, and its value is set on fabrication of the annulus 60. In the configuration of Figures 3 and 4, the ring 26 is not yet pressed against an inner radial collar 241 of the bushing 24 that defines the inside end of the housing 242 in the carcass 4. From the configuration of Figure 4, it is possible to push the bearing 22 towards the collar 241, as represented by arrow F₁, thereby having the effect of bringing the ring 26 against the collar 241, as can be seen in Figure 5. This movement also has the effect of bringing each of the tongues 70 to bear against a shoulder 247 defining the bottom, or inside end, of each notch 242, such that each tongue 70 is then deformed to take a configuration perpendicular to the axis X₂₂. This deformation of the tongues 70 is essentially elastic. Passing the tongues 70 from the configuration of

Figure 4 to the configuration of Figure 5 increases the distance over which they project radially from the skirt 68 and the surface 262.

Thus, putting the bearing 22 into place in the bushing 24 serves to prevent the ring 26 from moving about the axes X₂₂, X₈, X₂₄, and X₄₂ that coincide insofar as, if the ring tends to turn under the effect of friction between the bearings 29 and the raceway formed in the inner radial surface of the ring, then this beginning of rotation is blocked by the tabs 70 or by one of the tabs, coming to bear against the side of at least one of the notches 246.

Optionally, blocking means (not shown) may be inserted in the notches 246 after the tongues 70 in order to prevent the bearing 22 from moving axially relative to the bushing 24 in a pull-out direction opposite to the direction of arrow F₁.

Once the bearing 22 has been prevented from turning inside the bushing 24, which is itself prevented from turning relative to the carcass 4, it is possible to adjust the angular position of the sensors 50 and of the printed circuit 52 about the axes X₈ and X₂₂ by causing the cover 54 to slide inside the annulus 60, in accordance with the technical teaching of WO-A-2009/004198.

In the second embodiment of the invention shown in Figures 6 to 9 , elements analogous to those of the first embodiment are given the same references. Unless mentioned to the contrary, component parts of the machine 2 in this second embodiment are identical, and they operate in the same manner as the parts of the first embodiment. This second embodiment differs from the first embodiment in that no use is made of a bushing interposed between the bearing 22 and the housing 42 defined by the carcass 4 of the machine 2.

The tongues 70 of the mounting annulus 60, or mounting ring, in this embodiment are engaged directly in two notches 46 formed in the inner radial surface 44 of the carcass 4 that defines the housing 42 for receiving the bearing 22. This configuration is particularly simple and also serves to prevent the ring 26 of the bearing 22 from turning about the axes X₈, X₂₂, and X₄₂ that coincide when the machine is in its assembled configuration .

As in the first embodiment, the tabs 70 are deformed on passing from the configuration shown in Figure 8 to that shown in Figure 9 as a result of the bearing 22 being pushed, as represented by arrow F₁, towards an inner radial collar 41 of the carcass 4 that defines the inside end of the housing 42 inside the machine 2.

The mounting annulus, or mounting ring, shown in Figure 10 may be used in either of the embodiments described above, as an alternative to the mounting annulus shown in Figures 1 to 9. This mounting annulus 60 as shown in Figure 10 is provided with two lancings 70' replacing the tongues 70. These lancings 70' are obtained by cutting and localized deformation of a circular-based annular skirt 68 of the annulus 60. These lancings project radially outwards from the skirt 68 and may be engaged in notches 246 of a bushing 24, as in the first embodiment, or in notches 46 in a carcass 4, as in the second embodiment .

In a variant of the invention that is not shown, the means for blocking the ring 26 in rotation relative to the carcass 4 of the machine 2 may be provided in the form of hollow elements in the mounting annulus 60, with elements that project radially toward the axis X₈ being provided on the inner radial surface of the ring 24 or of the carcass 4 that defines the reception housing 242 or 42.

Claims

1. An instrumented bearing (22) comprising:

• a rotary inner ring (28) ;

• a non-rotary outer ring (26) ; • means (30, 50, 52, 54) for detecting a parameter concerning rotation of the inner ring relative to the outer ring, said means including at least one sensor (50) mounted on or in a support (54) ; and

• an annular mounting member (60) for mounting the support (54) on the outer ring (26), said annular mounting member being provided with an annular skirt

(68) ; the bearing being characterized in that the mounting member (60) is provided with a tongue (70) or a lancing (70') cut in the annular skirt (68), said tongue or said lancing extending radially outwards relative to the annular skirt (68) and enabling the outer ring (26) to be blocked in rotation about the axis of rotation (X₂₂) of the inner ring (28) .

2. An instrumented bearing according to claim 1, characterized in that the tongue (70) is deformable between a first configuration (Figures 4 and 8) in which it extends in a direction inclined at an angle (θ) lying in the range 20° to 70° relative to the axis of rotation (X₂₂) of the inner ring (28) , and a second configuration (Figures 5 and 9) in which it is perpendicular to said axis, the tongue being deformed under the effect of the bearing (22) being caused to move axially (F₁) in translation towards the inside end (241; 41) of the housing (242; 42) .

3. An instrumented bearing according to either preceding claim, characterized in that the support (54) is mounted inside the mounting member (60) while being angularly movable relative to the mounting member about the axis of rotation (X₂₂) of the inner ring (28) .

4. An instrumented bearing according to any preceding claim, characterized in that the mounting member (60) is made of metal, and in particular is made of spring steel.

5. A bearing assembly (20) comprising an instrumented bearing (22) according to any preceding claim and a bushing (24) for mounting the bearing in a carrier structure (4), the bushing being fitted with first blocking means (246) complementary to the tongue (70) or the lancing (70') of the mounting member (60) and enabling the outer ring (26) to be prevented from moving in rotation relative to the bushing (24) about the axis of rotation (X₂₂) of the inner ring (28) , and second blocking means (248) for blocking the bushing in rotation relative to the carrier structure (4) and about said axis .

6. A bearing assembly according to claim 5, characterized in that the first blocking means of the bushing (24) include at least one hollow housing (246) for receiving the tongue (70) or the lancing (70') of the mounting member (60) , and in that the second blocking means of the bushing include at least one element (248) projecting radially outwards from an outer radial surface (249) of the bushing.

7. A bearing assembly according to claim 6, characterized in that the hollow housing (246) and the projecting element (248) of the bushing (24) are in alignment in a direction (D₂₄) that is radial relative to the axis of rotation (X₂₂) of the inner ring (28) .

8. A rotary electrical machine comprising a carcass (4), a stator (6) , and a rotor (10) mounted on a shaft (8) , the machine being characterized in that the shaft (8) is supported relative to the carcass (4) by means of at least one instrumented bearing (22) according to any one of claims 1 to 4 or by means of at least one bearing assembly (20) according to any one of claims 5 to 7, and in that a housing (42) formed in the carcass for receiving said bearing or said bearing assembly is provided with means (46) complementary to the tongue (70) or to the lancing (70') of the mounting member (60) or of the second blocking means (248) of the bushing (24), and suitable for co-operating with said tongue, said lancing or said blocking means to prevent the outer ring (26) of the instrumented bearing (22) from moving in rotation relative about the axis of rotation (X₂₂) of the inner ring (28) .