Electric balancing ring and rolling bearing comprising such ring

Abstract

The invention relates to an electrical balancing ring (10) for mounting between a stationary element (11) and a rotating element (12), comprising a first frame (20), a membrane (30) and a second frame (40), the first frame and membrane being capable of conducting an electrical current, and a rolling bearing comprising such an electrical balancing ring (10). The membrane comprises, at the second end, a wear zone (ZU) that is thicker than the body of the membrane.

Description

Technical Field

[0001] The present invention relates to a grounding ring, also called an electric balancing ring, for transmitting electric charge or current between a fixed element and a rotating element capable of rotating relative to the fixed element about an axis of rotation. Typically, the ring is used to conduct electric charge between a housing and a shaft of a machine, or more specifically between a stator and a rotor of an electric machine. Background Art

[0002] The present invention relates to a grounding ring, comprising:

[0003] The first frame, which is annular and rigid, is fixedly mounted on one of the fixed element and the rotating element.

[0004] The membrane is annular and made of an elastic material, a first end of which contacts the first frame, a second end of which contacts the other of the fixed element and the rotating element, and has a body between the first end and the second end.

[0005] a second frame, which is annular and rigid, fixedly mounted on the first frame and adapted to clamp the membrane between the first frame and the second frame, and

[0006] in

[0007] The first frame and the membrane are capable of conducting electrical current between the stationary element and the rotating element.

[0008] Document US2020 / 0295634 shows such a grounding ring. However, the membrane of the ring has the problem of wear, which changes the conductivity over time, thus affecting the performance of the product. In some alternative embodiments, attempts are made to compensate for this disadvantage by installing multiple membranes in parallel, but this adds a certain complexity. Summary of the invention

[0009] A first object of the present invention is to provide a durable ground ring, i.e. one whose conductivity changes little over time.

[0010] To this end, the membrane of the grounding ring includes a wear zone at the second end, which is thicker than the body of the membrane and forms a contact surface that is configured to slide on a sliding surface of another element when in contact therewith and provides high electrical conductivity between the fixed element and the rotating element.

[0011] With these settings, the wear zone wears away during operation, but the surface area of ​​its contact surface remains essentially constant. Therefore, the electrical conductivity of the ring remains constant.

[0012] In various embodiments of the product, one or more of the following settings may be optionally used:

[0013] According to one aspect, when the ring is in the mounted position between the fixed element and the rotating element, the wear zone of the membrane extends in the direction of the axis of rotation over a length greater than or equal to the thickness of the membrane body.

[0014] According to one aspect, the thickness of the wear zone is greater than the thickness of the membrane body.

[0015] According to one aspect, the mass of the wear zone is configured to ensure contact between the contact surface and the sliding surface within a range of rotational speeds of the rotating element.

[0016] According to one aspect, the membrane is fixed to the second frame.

[0017] According to one aspect, the membrane comprises radial slots extending to the second frame and terminating in an open portion.

[0018] According to one aspect, the membrane comprises a conductive coating, said coating being located at least on the contact surface in the wear zone.

[0019] According to one aspect, the membrane is made of a PTFE material containing a conductive filler such as carbon.

[0020] According to one aspect, the second frame is capable of conducting electrical current between the stationary element and the rotating element.

[0021] According to one aspect, the radial height of the second frame is greater than the radial height of the first frame.

[0022] According to one aspect, the radial height of the second frame is at least twice the radial height of the first frame, and the radial height of the first frame is less than half the distance between the fixed element and the rotating element.

[0023] According to one aspect, the first frame and / or the second frame comprises pins adapted to penetrate the membrane and fix it to the first and / or second frame.

[0024] According to one aspect, the inner end of the second frame is bent towards the second end of the membrane when the ring is in the mounted position.

[0025] A second object of the present invention is to provide a rolling bearing comprising a grounding ring according to the above features, and rolling elements arranged in a rolling space to allow relative rotation of a rotating element with respect to a fixed element around a rotation axis. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Other characteristics and advantages of the product will become apparent in the following description of at least one embodiment given as a non-limiting example with reference to the accompanying drawings.

[0027] In the attached picture:

[0028] - Figure 1 is a cross-sectional view of a grounding ring according to the present disclosure;

[0029] - Figure 2 is with Figure 1 The same view showing the dimensions of the ring element;

[0030] - Figure 3 is a partial front view showing Figure 1 A variation of the ring comprising radial grooves;

[0031] - Figure 4A , Figure 4B , Figure 4C and Figure 4D Shows Figure 1 Variant shapes of the wear zones of rings of the type shown;

[0032] - Figure 5 yes Figure 1 a cross-sectional view of a grounding ring of the type shown, further comprising a seal; and

[0033] - Figure 6 is included Figure 1 Sectional view of a rolling bearing with an earthing ring of the type shown.

[0034] In the various drawings, the same reference numbers refer to the same or similar elements. DETAILED DESCRIPTION

[0035] Figure 1 An embodiment of a grounding ring 10 is shown, the ring being intended to be mounted between a fixed element 11 and a rotating element 12 capable of rotating relative to the fixed element about an axis of rotation AX. The ring 10 comprises:

[0036] a rigid first frame 20 , of annular type around the axis of rotation and fixedly mounted on one of the fixed element 11 and the rotating element 12 ,

[0037] - a membrane 30 , also of annular type around the axis of rotation, made of elastic material, and

[0038] A rigid second frame 40 , also of annular type around the axis of rotation and fixedly mounted on the first frame 20 .

[0039] The first frame 20 and the membrane 30 are capable of conducting electric current, in particular enabling electric current to flow between the fixed element 11 and the rotating element 12 and vice versa.

[0040] The membrane 30 extends between a first end 31 in contact with the first frame 20 and a second end 32 in contact with the other of the fixed element and the rotating element. The membrane 30 includes a body 33 between the first end 31 and the second end 32.

[0041] In particular, the fixed element 11 can be an outer element, ie the element farthest from the rotation axis AX, ie positioned around the rotating element 12, which is then an inner element. This is the case when the rotating element 12 is the rotation axis ( Figure 1 ).

[0042] On the contrary, the fixed element 11 may be an inner element, ie, an element closest to the rotation axis AX, ie, located inside the rotating element, in which case the rotating element is an outer element.

[0043] To simplify the present description, we will now consider the first frame 20 as being connected to the outer fixed element 11, and the second end 32 being in contact with another element, namely the inner rotating element 12, but of course the present disclosure is also applicable to another configuration.

[0044] The second frame 40 is adapted to clamp the membrane 30 between the first frame 20 and the second frame 40. In other words, the membrane 30 is clamped between the first frame and the second frame, for example when the second frame 40 is fixed to the first frame 20.

[0045] According to the present disclosure, the membrane 30 comprises a wear zone ZU at its second end 32. The wear zone ZU is thicker than the body 33 of the membrane 30. Figure 2 In the diagram, the thickness of the body 33 of the membrane is marked with (e), which thickness is measured in a direction substantially perpendicular to the core of the body of the membrane 30. The thickness of the wear zone ZU of the membrane 30 is marked with (b), which thickness is measured in a direction perpendicular to the axis of rotation AX when the ring is in the installed position on the rotating element 12.

[0046] Furthermore, the thickness of the membrane 30 may not be constant. Thus, the thickness of the membrane at the first end 31 , referenced as ( e1 ), may be greater than the thickness (e) of the main body 33 of the membrane 30 .

[0047] The wear zone ZU forms a contact surface 34 which is configured to contact another element (i.e. Figure 1 The rotating element 12 in the embodiment of the present invention slides on the sliding surface 14 when in contact with the rotating element 12 in the embodiment of the present invention.

[0048] Therefore, the grounding ring 10 can conduct the current from the rotating element 12 to the membrane 30 through the contact of the contact surface 34 of the wear zone ZU at the second end 32 of the membrane 30, and then conduct it to the first frame 20 in contact with the first end 31 of the membrane 30 through the body 33 of the membrane 30, and then conduct the current to the fixed element 11 through the first frame 20 through the contact between the first frame 20 and the fixed element 11. The current may also be conducted along the reverse path. Therefore, the grounding ring 10 has high conductivity and can efficiently release electric charge.

[0049] During the operation of the ring 10, the sliding and possible friction of the contact surface 34 of the membrane 30 on the sliding surface 14 leads to wear of said contact surface and the wear zone ZU, reducing its thickness. However, the wear zone ZU is thicker than the body 33 of the membrane 30, which makes it possible to keep the surface area of ​​the contact surface 34 substantially constant as long as the wear zone ZU is not completely worn, that is, its thickness does not approach zero. Therefore, by means of the contact surface 34 of the wear zone ZU, the electrical conductivity of the ring can be kept constant during very long operation.

[0050] exist Figure 1 and Figure 2 In the installation position, the wear zone ZU of the membrane 30 extends along the rotation axis AX by a length (a). For example, the length (a) is greater than or equal to the thickness (e) of the body 33 of the membrane 30:

[0051] a>=e

[0052] Advantageously, the length (a) is greater than 1 mm, and may be greater than 2 mm. Thus, the surface area S of the contact surface 34 is 34 for:

[0053] A 34 =π.Da

[0054] where D is the diameter of the rotating element 12, and

[0055] a is the length of the wear zone ZU.

[0056] Optionally, the length (a) is greater than or equal to the thickness (e1) of the first end 31 of the membrane 30:

[0057] a>=e1

[0058] Due to the length (a) of the wear zone ZU, the ring 10 has a high electrical conductivity. By increasing the length (a), the electrical conductivity can be increased.

[0059] The wear zone ZU also has a thickness (b) measured in a direction perpendicular to the axis of rotation AX in the mounted position. Advantageously, the thickness (b) is greater than the thickness (e) of the body 33 of the membrane 30 and preferably greater than twice the thickness (e) of the body 33 of the membrane 30. The wear zone is thick enough to ensure a long service life of the ring 10 while maintaining a constant and high electrical conductivity.

[0060] For example, the thickness (e) of the membrane 30 is between 0.4 mm and 1 mm. Accordingly, the thickness (b) of the wear zone ZU is between 0.5 mm and 3 mm.

[0061] Furthermore, since the second end 32 of the membrane 30 includes the wear zone ZU, the use Figure 2The thickness (c) of the second end 32 is substantially equal to the sum of the thickness (e) of the membrane and the thickness (b) of the wear zone ZU:

[0062] c=b+e

[0063] The second frame 40 is fixedly installed inside the first frame 30 by, for example, press-fitting or snap-fitting.

[0064] according to Figure 1 In the embodiment shown, the first frame 20 and the second frame 40 are L-shaped and nested with each other. Each frame 20, 40 forms a cylindrical sleeve 21, 41 extending along the rotation axis AX, and then extends inwardly toward the rotation axis AX to form an annular lateral flange 22, 42 perpendicular to the rotation axis.

[0065] The cylindrical sleeve 21 of the first frame 20 is thus suitable for being mounted into the hollow cylindrical housing 13 of the fixing element 11 by press-fitting.

[0066] The outer diameter of the annular membrane 30 is suitable for being mounted in the cylindrical sleeve 21 of the first frame 20 , with the first face 35 of the first end 31 of the membrane 30 resting on the annular lateral flange 22 of the first frame 20 .

[0067] The cylindrical sleeve 41 of the second frame 40 is thus suitable for being mounted by press-fitting to the inner surface of the cylindrical sleeve 21 of the first frame 20 until the annular lateral flange 42 of the second frame 40 is pressed against the second face 36 of the membrane 30 (at its first end 31 ), thus clamping the first end 31 of the membrane 30 .

[0068] According to one embodiment, the radial height (h) of the lateral flange 42 of the second frame 40 is greater than the radial height (g) of the lateral flange 22 of the first frame 20, so that the lateral flange 42 extends further in the direction of the rotation axis AX than the lateral flange 22 of the first frame 20. The second face 36 of the membrane 30 contacts the lateral flange 42 of the second frame 40 at the radial height (h) until the inner end 43 of the second frame 40. The body 33 of the membrane 30 is thus unconstrained and extends in a curved manner along the direction X of the rotation axis AX to the second end 32 and the wear zone ZU.

[0069] The inner end 43 of the second frame 40 is optionally curved in the direction X of the axis of rotation AX. The membrane 30 is therefore not affected by wear at the inner end 43 and the body 33 of the membrane 30 more easily assumes the desired curvilinear shape determined by calculations and / or tests. Indeed, this curvilinear shape, thickness and material of the membrane 30 determine the radial force that the membrane exerts concentrically towards the axis of rotation and against the rotating element 12. Said radial force determines the quality of contact of the wear zone ZU against the rotating element 12, as well as the conductivity of the ring and its ability to maintain conductivity during operation, i.e. during the rotation and operation of the rotating element 12.

[0070] According to a variant, the second frame 40 is also capable of conducting current. In this case, the current path may be between the membrane 30 and the first frame 20, as described above, and may also be between the membrane 30 and the second frame 40. Since the second frame 40 is fixedly mounted on the first frame 20, another branch current passing through the second frame 40 will be merged into the first frame 20. This arrangement makes it possible to increase the conductive area of ​​the membrane 30 to the first frame 20, which is substantially the first area A of direct contact between the membrane 30 and the first frame 20 (or the area of ​​the flange 22 of the first frame 20). 22 The second area A of the membrane 30 in contact with the second frame 40 (or the area of ​​the flange 42 of the second frame 20) 42 sum.

[0071] The first area A 22 is basically equivalent to:

[0072] A 22 =π.g.[D+2.h+h]

[0073] The second area A 42 is basically equivalent to:

[0074] A 42 =π.h.[D+2.d+2.hg]

[0075] Since the contact between the second frame 40 and the first frame 20 is metal-to-metal contact, its effect on conductivity is considered to be low, ie, the resistance to current conduction is small. Therefore, due to the conductivity of the second frame 40, the conductivity of the ring 10 may be reduced.

[0076] Furthermore, in the case where the second frame 40 is conductive, a larger radial height (h) can obtain a larger second area A of contact between the membrane 30 and the second frame 40 (the area of ​​the flange 42 of the second frame). 42 The electrical conductivity of the ring 10 can thus be increased.

[0077] According to one embodiment, the radial height (h) of the second frame 40 is at least twice the radial height (g) of the first frame 30 .

[0078] The radial height (g) of the first frame 20 may be less than half the distance (Di) between the inner surface of the fixed element 11 and the rotating element 12. Therefore, the membrane 30 is clamped only along the radial height (g) in the direction of the rotation axis AX.

[0079] The radial height (h) of the second frame 40 may be less than half the distance (Di) between the inner surface of the fixed element 11 and the rotating element 12. In other words, the radial height (h) of the second frame 40 is less than the distance (d) between the inner end 43 and the rotating element 12. The size of the second frame 40 and its cost are therefore limited. The body 33 of the membrane 30 retains a large curved area leading to the wear zone ZU to reduce radial forces and the friction and wear generated thereon.

[0080] According to one embodiment, the first frame 20 and / or the second frame 40 may comprise pins adapted to penetrate the membrane 30 and fix it to said first and / or second frame. Thus, the membrane 30 is mechanically fixed to at least one or both frames and thus immobilized in the ring 10.

[0081] According to one embodiment, the membrane 30 is optionally fixed to the first and / or second frame 20, 40. For example, the membrane 30 is fixed to the first and / or second frame by gluing.

[0082] According to one embodiment, the membrane 30 may be fixed to the first and / or second frame by using rivets distributed at an angle along the circumference of the membrane 30. The rivets pass through the membrane 30 and at least one of the frames (first and / or second frame).

[0083] According to one embodiment, the outer surface of the membrane 30 may include a conductive coating. Optionally, the entire outer surface of the membrane 30 is covered with such a conductive coating. Alternatively, a predetermined portion of the outer surface of the membrane 30 is covered with such a conductive coating. For example, the conductive coating may be located only in the wear zone ZU, the contact surface 34, the first face 35 or the second face 36, or a combination of these locations. Thus, the conductivity of the ring 10 can be improved.

[0084] According to one embodiment, the membrane 30 may be made of PTFE material. Preferably, the conductive material contains conductive fillers, such as carbon or the like.

[0085] According to one embodiment, the body 33 of the membrane 30 may include corrugations for adjusting the desired value of stiffness or flexibility of the body of the membrane. In particular, these corrugations are located between the inner end 43 of the second frame 40 and the wear zone ZU.

[0086] Alternatively, the body 33 of the membrane 30 may include one or more thinner regions, such as one or more locations between the inner end 43 of the second frame 40 and the wear zone ZU. This or these thinner regions, for example, have a reduced thickness along a circumference or a portion of a circumference. This or these thinner regions may also be used to adjust the desired value of stiffness or flexibility of the body of the membrane.

[0087] according to Figure 3In the embodiment shown, the membrane 30 may include radially extending grooves 37 that divide the body 33 of the membrane 30 into angular sectors distributed along the circumference of the membrane 30. The grooves 37 are through grooves. Each groove 37 passes through the membrane 30 between the second end 32 and a radial point located near the inner end 43 of the second frame 40.

[0088] Due to these grooves, the membrane 30 is more flexible. The radial forces are reduced. Furthermore, in the case where the rotating element 12 is not round or the fixed element 11 and the rotating element 12 are not coaxial, the radial forces vary less. It is easier for the membrane 30 to maintain electrical contact between the contact surface 34 and the sliding surface 14 of the rotating element 12. The electrical conductivity is increased and more stable during operation.

[0089] Optionally, the slot 37 terminates at a radial point in the opening portion 38, such as Figure 3 As shown. The opening portion is, for example, a circular opening of a predetermined diameter. The opening portion can prevent the film 30 from being torn at a radial point.

[0090] according to Figure 4A , Figure 4B , Figure 4C and Figure 4D In the various embodiments shown, the radial cross-section of the wear zone ZU at the second end 32 of the membrane 30 may have various shapes. Figure 4A Displays a rectangular cross section; Figure 4B Display circular cross-section; Figure 4C Display an elliptical cross section; and Figure 4D A trapezoidal cross section is shown. These different shapes affect the radial force, the surface area of ​​the contact surface 34, and thus the conductivity and its change over time. They can be selected based on test and application requirements. These shapes also affect how the conductivity of the grounding ring 10 changes over time (during operation).

[0091] Figure 5 An embodiment of a grounding ring 10 is shown, the ring further comprising a seal 60. The seal is, for example, an elastic O-ring extending between the fixed first element 11 and the rotating element 12. It can be directly or indirectly connected to the first frame 20 or the membrane 30 or the second frame 40 in a sealed manner. The seal 60 is, for example, made of an elastomer or rubber material. The seal may also comprise a lip 61 to ensure that the seal is maintained on the rotating element 12 and to limit the friction on the rotating element 12.

[0092] The grounding ring 10 may be Figure 5 The seal is shown to be included on one or the other side of the membrane 30 along the axis of rotation AX. The membrane 30 is thus protected from external contaminants on the side where the seal is located. Contaminants are solid particles or fluids such as oil; these contaminants may interact with the contact surface 34 and thus affect the conductivity of the membrane 30 and therefore the conductivity of the grounding ring 10.

[0093] Alternatively, the grounding ring 10 may include a seal 60 on each side of the membrane 30 along the axis of rotation AX. The membrane 30 is thus protected from external contaminants on both sides.

[0094] In addition, the seal(s) 60 may be made of a material that can also conduct electric current, ie, has good electrical conductivity. For example, the seal may include a material containing conductive particles, or a material having a conductive coating.

[0095] Figure 6 1 shows a specific application example of the above-mentioned grounding ring 10. The figure shows a rolling bearing 1, which comprises a grounding ring 10 as described above on at least one side to ensure the transmission of charges. The rolling bearing is, for example, a rolling bearing of a motor vehicle, more particularly a rolling bearing of a wheel of a motor vehicle, such as Figure 5 shown.

[0096] In particular, the rolling bearing 1 comprises:

[0097] -Fix part 2.

[0098] a rotating part 3 which is rotated by an axle 5 and to which, for example, a wheel is fixed, and

[0099] - Rolling bodies 4 arranged in a rolling space 4e formed between the fixed part 2 and the rotating part 3 to allow a relative rotation of the rotating part 3 with respect to the fixed part 2 about the rotation axis X while withstanding large forces between the fixed element and the rotating element.

[0100] The fastening element 11 of the ring 10 is directly the fastening part 2 or is fastened to the fastening part 2 of the rolling bearing 1 .

[0101] The rotating element 12 of the ring 10 is directly the rotating part 3 or is fixed to the rotating part 3 of the rolling bearing 1 .

[0102] The rolling elements 4 may be balls, cylinders or other known types.

[0103] By using the grounding ring 10 of the present disclosure, the rolling bearing 1 is able to transfer electric charge to both the stationary and rotating parts without passing the electric charge through the rolling elements (which may damage them). A vehicle equipped with such an arrangement will be more durable.

[0104] Reference numerals

[0105] 10 grounding ring,

[0106] 11 fixing elements,

[0107] 12 rotating elements,

[0108] 13 housing,

[0109] 14 sliding surfaces,

[0110] 20 first frame,

[0111] 21 cylindrical sleeve,

[0112] 22 side flange,

[0113] 30 films,

[0114] 31 First end,

[0115] 32 Second end,

[0116] 33 main body,

[0117] 34 contact surfaces,

[0118] 35 Side 1,

[0119] 36 Side 2,

[0120] 37 slots,

[0121] 38 opening part,

[0122] 40 second frame,

[0123] 41 cylindrical sleeve,

[0124] 42 side flange,

[0125] 43 inner end,

[0126] ZU wear zone.

Claims

1. A grounding ring (10) for mounting between a fixed element (11) and a rotating element (12), the rotating element (12) being rotatable relative to the fixed element about a rotation axis (AX), the ring comprising: a first frame (20), which is annular and rigid, and which is fixedly mounted on one of the fixed element and the rotating element, a membrane (30) which is annular and made of an elastic material, extending between a first end (31) and a second end (32), wherein the first end (31) contacts the first frame and the second end (32) contacts the other of the fixed element and the rotating element, and wherein the membrane has a body (33) between the first end and the second end, A second frame (40) is annular and rigid, fixedly mounted on the first frame and adapted to clamp the membrane between the first frame and the second frame, wherein The first frame and the membrane are capable of conducting electrical current between the stationary element and the rotating element, and The ring is characterized in that The membrane comprises a wear zone (ZU) at a second end, the wear zone being thicker than the main body of the membrane and forming a contact surface (34) configured to slide on a sliding surface (14) of another element when in contact therewith and to provide electrical conductivity between the stationary element and the rotating element.

2. The ring according to claim 1, characterized in that The length (a) of the wear zone of the membrane extending in the direction of the rotation axis (AX) is greater than or equal to the thickness (e) of the body (33) of the membrane (30), and the ring is in a mounted position between the fixed element and the rotating element.

3. The ring according to claim 1 or 2, characterized in that The thickness (b) of the wear zone (ZU) is greater than the thickness of the main body of the membrane.

4. The ring according to any one of claims 1 to 3, characterized in that The mass of the wear zone (ZU) is configured to ensure contact between the contact surface and the sliding surface within a range of rotational speeds of the rotating element.

5. The ring according to any one of claims 1 to 4, characterized in that The membrane (30) is fixed on the second frame.

6. The ring according to any one of claims 1 to 5, characterized in that The membrane (30) comprises a radial slot (37) extending to a second frame (40) and terminating in an opening portion (38).

7. The ring according to any one of claims 1 to 6, characterized in that The membrane (30) comprises an electrically conductive coating, which is located at least on a contact surface (34) in the wear zone (ZU).

8. The ring according to any one of claims 1 to 7, characterized in that The membrane (30) is made of PTFE material containing conductive fillers such as carbon.

9. The ring according to any one of claims 1 to 8, characterized in that The second frame (40) is capable of conducting electric current between the fixed element and the rotating element.

10. The ring according to any one of claims 1 to 9, characterized in that The radial height (h) of the second frame (40) is greater than the radial height (g) of the first frame (20).

11. The ring according to claim 10, characterized in that The radial height of the second frame is at least twice the radial height of the first frame, and the radial height of the first frame is less than half of the distance (Di) between the fixed element and the rotating element.

12. The ring according to any one of claims 1 to 11, characterized in that The first frame and / or the second frame comprises pins adapted to penetrate the membrane and fix it to the first and / or the second frame.

13. The ring according to any one of claims 1 to 12, characterized in that The second frame (40) has an inner end (43) which is bent towards the second end (32) of the membrane when the ring is in the installed position.

14. A rolling bearing (1), comprising a grounding ring (10) according to any one of claims 1 to 13, and rolling bodies (4) arranged in a rolling space to allow relative rotation of a rotating element with respect to a fixed element around a rotation axis.

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