Electrical balancing ring and rolling bearing equipped with same

Abstract

A grounding ring (10), also called an electrical balance ring, mounted between a fixed element (11) and a rotating element (12) comprises a first frame (20), a membrane (30) and a second frame (40), the first frame and the membrane being capable of carrying an electric current. The membrane includes a wear zone (ZU) at its second end, the wear zone being thicker than the main body of the membrane.

Description

[Technical Field]

[0001] The present invention relates to a grounding ring, also called an electric balance ring, used to transfer charge or current between a fixed element and a rotating element that is rotatable relative to the fixed element about an axis of rotation. Typically, the ring is used to conduct charge between a housing and a machine shaft, and more particularly between the stator and rotor of an electric machine. [Background technology]

[0002] Accordingly, the present invention provides a ground ring comprising: a first annular and rigid frame fixed to one of the fixed element and the rotating element; an annular membrane made of a resilient material, the membrane extending between a first end contacting the first frame and a second end contacting the other of the fixed element and the rotating element, the membrane having a body between the first end and the second end; an annular, rigid second frame, the second frame being securely attached to the first frame and configured to clamp and secure the membrane between the first frame and the second frame; The first frame and the membrane are capable of conducting an electrical current between the fixed element and the rotating element.

[0003] US Patent No. 5,949,999 shows such a grounding ring, but the ring suffers from membrane wear issues, which change electrical conduction over time and alter product performance. In some alternative embodiments, multiple membranes are installed in parallel to attempt to compensate for this drawback, but at the expense of some complexity. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] US Patent Application Publication No. 2020 / 0295634 [Patent Document 2] European Patent Application Publication No. 3468013 [Patent Document 3] German Patent Application Publication No. 102019133877 Summary of the Invention [Problem to be solved by the invention]

[0005] A first object of the present invention is to provide a durable ground ring, meaning that its electrical conductivity changes little over time.

[0006] For this purpose, the membrane of the grounding ring has at its second end a wear zone that is thicker than the main body of the membrane, this wear zone forming a contact surface that slides in contact with the sliding surface of the other element and is configured to provide high electrical conductivity between the fixed element and the rotating element.

[0007] With these configurations, the wear zones that wear during operation have contact surfaces that maintain a substantially constant surface area, and therefore the electrical conductivity of the ring remains constant.

[0008] Various embodiments of this product may optionally use one or more of the following configurations:

[0009] According to one embodiment, the wear zone of the membrane extends in the direction of the axis of rotation over a length equal to or greater than the thickness of the body of the membrane, the ring being in a mounting position between the fixed element and the rotating element.

[0010] According to one embodiment, the wear zone has a thickness greater than the thickness of the body of the membrane.

[0011] According to one aspect, the wear zone has a mass configured to ensure contact between the contact surface and the sliding surface over a range of rotational speeds of the rotating element.

[0012] According to one embodiment, the membrane is fixed to a second frame.

[0013] According to one embodiment, the membrane includes a radial slot that extends to the second frame and terminates in an open portion.

[0014] According to one embodiment, the membrane includes a conductive coating, said coating being on at least the contact surface of the wear zone.

[0015] According to one embodiment, the membrane is formed from a PTFE material containing a conductive filler such as carbon.

[0016] According to one embodiment, the second frame is capable of conducting electrical current between the fixed element and the rotating element.

[0017] According to one embodiment, the second frame has a radial height greater than the radial height of the first frame.

[0018] According to one embodiment, 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.

[0019] According to one embodiment, the first frame and / or the second frame comprises pins adapted to penetrate the membrane and secure the membrane to the first frame and / or the second frame.

[0020] According to one embodiment, the second frame has an inner end that curves toward the second end of the membrane when the ring is in the attached position.

[0021] A second object of the present invention is to provide a rolling bearing comprising a grounding ring having the above-mentioned characteristics and rolling bodies that are arranged in the rolling space and allow relative rotation of the rotating element around the rotation axis with respect to the fixed element. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a cross-sectional view of a ground ring according to the present disclosure. [Figure 2] 2 is the same view as FIG. 1, showing the dimensions of the ring elements. [Figure 3] FIG. 2 is a partial front view of a variation of the ring of FIG. 1 including radial slots. [Figure 4A] 2 shows the deformed shape of the wear zone of a ring of the type shown in FIG. 1; [Figure 4B] 2 shows the deformed shape of the wear zone of a ring of the type shown in FIG. 1; [Figure 4C] 2 shows the deformed shape of the wear zone of a ring of the type shown in FIG. 1; [Figure 4D] 2 shows the deformed shape of the wear zone of a ring of the type shown in FIG. 1; [Figure 5] 2 is a cross-sectional view of a ground ring of the type shown in FIG. 1 further including a sealing member. [Figure 6] 2 is a cross-sectional view of a rolling bearing incorporating a ground ring of the type shown in FIG. 1; DETAILED DESCRIPTION OF THE INVENTION

[0023] Other characteristics and advantages of the product will become apparent during the following description of at least one of its embodiments, given as a non-limiting example, with reference to the attached drawings, in which:

[0024] In the various figures, the same reference numbers indicate the same or similar elements.

[0025] 1 shows an embodiment of a grounding ring 10 intended to be mounted between a fixed element 11 and a rotating element 12 rotatable relative to the fixed element about a rotation axis AX. The ring 10 comprises: a rigid first frame 20 of the type annular about the axis of rotation and rigidly attached to one of the fixed element 11 and the rotating element 12; a membrane 30 of the type also annular about the axis of rotation and made of elastic material, and a rigid second frame 40 of the type also annular about the axis of rotation and rigidly attached to the first frame 20;

[0026] The first frame 20 and the membrane 30 are particularly capable of conducting current so that current can flow between the fixed element 11 and the rotating element 12 and vice versa.

[0027] 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 and rotating elements. The membrane 30 includes a body 33 between the first and second ends 31, 32.

[0028] In particular, the fixed element 11 can be the outer element, i.e. the element furthest from the axis of rotation AX, that is the element arranged around the rotating element 12, which is the inner element, if the rotating element 12 is the axis of rotation (FIG. 1).

[0029] Conversely, the fixed element 11 can be located inside the inner element, ie the rotating element closest to the axis of rotation AX, ie the outer element.

[0030] For simplicity of explanation herein, we consider a first frame 20 connected to an outer fixed element 11 and its second end 32 in contact with the other element, i.e., the inner rotating element 12, although of course other configurations are also suitable within the scope of this disclosure.

[0031] The second frame 40 is configured to clamp and secure the membrane 30 between the first frame 20 and the second frame 40. That is, the membrane 30 is secured by being sandwiched between the first frame 20 and the second frame 40 when the second frame 40 is secured to the first frame 20, for example.

[0032] According to the present disclosure, the membrane 30 includes a wear zone ZU at the second end 32 of the membrane 30. The wear zone ZU is thicker than the main body 33 of the membrane 30. In FIG. 2, the thickness of the main body 33 of the membrane is indicated by (e), and this thickness is measured in a direction substantially perpendicular to the core of the main body of the membrane 30. The thickness of the wear zone ZU of the membrane 30 is indicated by (b), and this thickness is measured in a direction perpendicular to the axis of rotation AX at the mounting location of the ring on the rotating element 12.

[0033] Furthermore, the membrane 30 may have a non-constant thickness, such that the thickness of the membrane at the first end 31, designated (e1), may be greater than the thickness (e) of the main body 33 of the membrane 30.

[0034] The wear zone ZU therefore forms a contact surface 34 which is adapted to slide on and in contact with the sliding surface 14 of the other element, namely the rolling element 12 of FIG.

[0035] Thus, the grounding ring 10 can conduct current from the rotating element 12 to the membrane 30 via contact of the contact surface 34 of the wear zone ZU at the second end 32 of the membrane 30, then through the body 33 of the membrane 30 to the first frame 20 in contact with the first end 31 of the membrane 30, and then through the first frame 20 to the fixed element 11 via contact between the first frame 20 and the fixed element 11. Electrical conduction can also take the reverse path. This makes the grounding ring 10 highly conductive and allows electric charges to be efficiently discharged.

[0036] During operation of the ring 10, the sliding and possibly friction of the contact surface 34 of the membrane 30 causes wear of this contact surface and wear of the wear zone ZU, which reduces its thickness. However, the thickness of the wear zone ZU, which is greater than that of the main body 33 of the membrane 30, allows the surface area of ​​the contact surface 34 to remain substantially constant as long as the wear zone ZU does not wear completely, i.e., as long as its thickness does not tend towards zero. The contact surface 34 of the wear zone ZU therefore allows the conductivity of the ring to remain constant over very long operating periods.

[0037] 1 and 2, the wear zone ZU of the membrane 30 extends over a length (a) in the direction of the axis of rotation AX. For example, the length (a) is equal to or greater than the thickness (e) of the body 33 of the membrane 30, i.e. a ≥ e is.

[0038] Advantageously, the length (a) is greater than 1 mm, and may be greater than 2 mm. Therefore, the surface area S of the contact surface 34 34 teeth, A 34 =π D a is. where D is the diameter of the rolling element 12 and a is the length of the wear zone ZU.

[0039] Optionally, the length (a) is equal to or greater than the thickness (e1) of the first end 31 of the membrane 30, i.e. a ≥ e1 is.

[0040] Due to this length (a) of the wear zone ZU, the ring 10 has a high electrical conductivity, which can be increased by increasing the length (a).

[0041] The wear zone ZU also has a thickness (b), which is measured in the mounted position in a direction perpendicular to the direction of the axis of rotation AX. Advantageously, the thickness (b) is greater than the thickness (e) of the body 33 of the membrane 30, preferably more than twice the thickness (e) of the body 33 of the membrane 30. The wear zone is therefore thick enough to ensure a long service life of the ring 10 while maintaining a constant high electrical conductivity.

[0042] For example, the thickness (e) of the membrane 30 is between 0.4 mm and 1 mm, and the thickness (b) of the wear zone ZU is therefore between 0.5 mm and 3 mm.

[0043] Furthermore, because the second end 32 of the membrane 30 includes the wear zone ZU, using the notation of FIG. 2, the 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, i.e., c=b+e is.

[0044] The second frame 40 is securely attached, for example, to the inside of the first frame 30, possibly by press-fitting or crimping.

[0045] 1, the first frame 20 and the second frame 40 have an L-shape, nested one inside the other. Each of the frames 20, 40 defines a cylindrical sleeve 21, 41 extending along the direction of the axis of rotation AX and then extending inwardly towards the axis of rotation AX within a transverse annular flange 22, 42 perpendicular to the axis of rotation.

[0046] The cylindrical sleeve 21 of the first frame 20 is therefore adapted to be mounted by press-fitting into the hollow cylindrical housing 13 of the fixing element 11 .

[0047] The annular membrane 30 has an outer diameter adapted to be received within the cylindrical sleeve 21 of the first frame 20, and a first surface 35 of the first end 31 of the membrane 30 rests against the lateral annular flange 22 of the first frame 20.

[0048] Next, the cylindrical sleeve 41 of the second frame 40 is configured to be attached by being pressed into the inner surface of the cylindrical sleeve 21 of the first frame 20 until the lateral annular flange 42 of the second frame 40 is pressed against the second surface 36 of the membrane 30 (at its first end 31), thus clamping the first end 31 of the membrane 30.

[0049] According to one embodiment, the second frame 40 has a radial height (h) of the lateral flanges 42 that is greater than the radial height (g) of the lateral flanges 22 of the first frame 20, so that the lateral flanges 42 extend further towards the axis of rotation AX than the lateral flanges 22 of the first frame 20. The membrane 30 therefore has a second surface 36 that is in contact with the lateral flanges 42 of the second frame 40 along the radial height (h) up to the inner end 43 of the second frame 40. The body 33 of the membrane 30 then extends unconstrained and curved along the direction X of the axis of rotation AX up to the second end 32 and the wear zone ZU.

[0050] The inner end 43 of the second frame 40 is optionally curved in the direction X of the axis of rotation AX. Therefore, the membrane 30 is not affected by wear at the inner end 43, and the body 33 of the membrane 30 more easily assumes the desired curved shape determined by calculation and / or testing. In fact, this curved shape, thickness, and material of the membrane 30 determine the radial force that the membrane exerts towards the axis of rotation and concentrically against the rotating element 12. This radial force determines the quality of contact of the wear zone ZU with the rotating element 12, and therefore the electrical conductivity of the ring and its ability to maintain this conductivity during operation, i.e., during and during the rotation of the rotating element 12.

[0051] According to a variant, the second frame 40 can also carry a current. In this case, the path of the current can be between the membrane 30 and the first frame 20, as described above, but also between the membrane 30 and the second frame 40. The second frame 40 is securely attached to the first frame 20, so that the other branch of the current flowing through the second frame 40 joins the first frame 20. This configuration makes it possible to increase the conductive area of ​​the membrane 30 towards the first frame 20, this conductive area being substantially equal to the first area A of direct contact between the membrane 30 and the first frame 20. 22 (i.e., the area of ​​the flange 22 of the first frame 20) and the second area A of contact between the membrane 30 and the second frame 40 42(i.e., the area of ​​the flange 42 of the second frame 40).

[0052] First area A 22 is essentially, A 22 =π g [D+2 h+h] and the second area A 42 is essentially, A 42 =π h [D+2 d+2 hg] is equal to.

[0053] Since the contact between the second frame 40 and the first frame 20 is metal-to-metal contact, its effect on the conductivity is considered small, which means that the resistance to electrical conduction is very small. Therefore, the electrical conduction of the second frame 40 may reduce the conductivity of the ring 10.

[0054] In addition, in the case of the second frame 40 that is capable of electrical conduction, the contact area A between the membrane 30 and the second frame 40 (the area of ​​the flange 42 of the second frame) can be increased by increasing the radial height (h). 42 Therefore, the conductivity of the ring 10 can be increased.

[0055] 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 .

[0056] 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 rotation element 12. The membrane 30 is then kept clamped in the direction of the rotation axis AX only along this radial height (g).

[0057] 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 smaller than the distance (d) between the inner end 43 and the rotating element 12. This limits the size of the second frame 40 and its cost. The main body 33 of the membrane 30 maintains a large curvature zone up to the wear zone ZU, reducing the radial force and therefore the friction and wear in the wear zone ZU.

[0058] According to one embodiment, the first frame 20 and / or the second frame 40 may comprise pins adapted to penetrate the membrane 30 and secure it to said first and / or second frame. The membrane 30 is thus mechanically fixed to at least one or both frames and is therefore fixedly held within the ring 10.

[0059] According to one embodiment, the membrane 30 may optionally be secured to the first frame 20 and / or the second frame 40. For example, the membrane 30 may be secured to the first frame and / or the second frame by gluing.

[0060] According to one embodiment, the membrane 30 may be secured to the first frame and / or the second frame by using rivets angularly distributed around the circumference of the membrane 30. The rivets pass through the membrane 30 and at least one of the frames (the first frame and / or the second frame).

[0061] According to one embodiment, the membrane 30 may include a conductive coating on its outer surface. Optionally, the entire outer surface of the membrane 30 may be covered with the conductive coating. Alternatively, only a specific portion of the outer surface of the membrane 30 may be covered with the conductive coating. For example, the conductive coating may be applied only to the wear zone ZU, the contact surface 34, or the first or second surfaces 35, 36, or a combination of these locations. This may improve the electrical conductivity of the ring 10.

[0062] According to one embodiment, the membrane 30 may be formed from a PTFE material. Preferably, the conductive material includes a conductive filler such as carbon.

[0063] According to one embodiment, the body 33 of the membrane 30 may be provided with corrugations configured to adjust the desired value of the stiffness or flexibility of the membrane body, in particular, these corrugations being arranged between the inner end 43 of the second frame 40 and the wear zone ZU.

[0064] Alternatively, the body 33 of the membrane 30 may include one or more thinner regions, for example, located at one or more positions between the inner end 43 of the second frame 40 and the wear zone ZU. The thinner region or regions may be, for example, a reduction in thickness along the circumference or along a portion of the circumference. The thinner region or regions may also be used to adjust the desired stiffness or flexibility of the membrane body.

[0065] According to one embodiment shown in Figure 3, the membrane 30 extends radially and may include slots 37 that separate the body 33 of the membrane 30 into angular sectors distributed around the circumference of the membrane 30. The slots 37 are through slots. Each slot 37 penetrates the membrane 30 between the second end 32 and a radial point located near the inner end 43 of the second frame 40.

[0066] These slots make the membrane 30 more flexible. The radial forces are reduced. Furthermore, the radial force fluctuations are smaller when the rotating element 12 is non-circular and / or when there is a non-coaxial relationship between the fixed element 11 and the rotating element 12. The membrane 30 more easily maintains electrical contact between the contact surface 34 and the sliding surface 14 of the rotating element 12. The conductivity is increased and it is more stable during operation.

[0067] Optionally, slot 37 terminates at said radial point in an open portion 38, as shown in Figure 3. The opening may be, for example, a circular opening having a predetermined diameter. This open portion prevents membrane 30 from tearing at the radial point.

[0068] According to various embodiments shown in Figures 4A, 4B, 4C, and 4D, the radial cross section of the wear zone ZU at the second end 32 of the membrane 30 can have various shapes. Figure 4A shows a rectangular cross section. Figure 4B shows a circular cross section. Figure 4C shows an elliptical cross section, and Figure 4D shows a trapezoidal cross section. These various shapes affect the radial force, the surface area of ​​the contact surface 34, and therefore the electrical conductivity and its change over time. These can be selected based on testing and depending on the application. These shapes also affect the change over time (during operation) of the electrical conductivity of the ground ring 10.

[0069] FIG. 5 shows an embodiment of the ground ring 10 further including a sealing member 60. This sealing member may be, for example, an elastic O-ring extending between the fixed first element 11 and the rotating element 12. It may be directly or indirectly connected in a sealed manner to the first frame 20, the membrane 30, or the second frame 40. The sealing member 60 may be made of, for example, an elastomer or rubber material. The sealing member may also include a lip 61 to ensure that the seal is maintained on the rotating element 12 and to limit friction on the rotating element 12.

[0070] The grounding ring 10 may include a single sealing element disposed on one side or the other of the membrane 30 along the direction of the rotation axis AX, as shown in FIG. 5. The membrane 30 is thus protected from external contaminants coming from the side on which the sealing element is disposed. Contaminants are understood to mean solid particles or fluids, such as oil, which may affect the electrical conductivity of the membrane 30 and thus the grounding ring 10 by interacting with the contact surface 34.

[0071] Alternatively, the ground ring 10 may be provided with a sealing member 60 on each side of the membrane 30 along the direction of the axis of rotation AX, so that the membrane 30 is protected on both sides against external contaminants.

[0072] Additionally, the seal member 60 may be made of a material that is capable of conducting electrical current, i.e., has good electrical conductivity. For example, the seal member may include a material that contains conductive particles or a material that has a conductive coating.

[0073] 6 shows a specific exemplary application of the above-described grounding ring 10. This figure shows a rolling bearing 1 provided on at least one side with a grounding ring 10 as described above for ensuring the transfer of electric charges. The rolling bearing may be, for example, a rolling bearing of an automobile, as shown in FIG. 5, more particularly, a rolling bearing of a wheel of an automobile.

[0074] Specifically, the rolling bearing 1 is - Fixing member 2 - a rotating member 3 rotated by an axle 5 and to which, for example, a wheel is fixed; - A rolling element 4 that is disposed in the rolling space 4e formed between the fixed member 2 and the rotating member 3, enables the rotating member 3 to rotate relative to the fixed member 2 around the rotation axis X, and absorbs large forces between the fixed member and the rotating member.

[0075] The fixing element 11 of the ring 10 is fixed either directly to the fixing member 2 or to the fixing member 2 of the rolling bearing 1 .

[0076] The rolling element 12 of the ring 10 is either directly attached to the rolling member 3 or is fixed to the rolling member 3 of the rolling bearing 1 .

[0077] The rolling elements 4 may be balls, cylinders or any other known type.

[0078] The ground ring 10 of the present disclosure allows the rolling bearing 1 to transfer electrical charge to the stationary and rotating members without the electrical charge passing through and damaging the rolling elements, thus making vehicles equipped with such a device more durable. [Explanation of symbols]

[0079] 10 Grounding Ring 11 Fixed Elements 12 Rotational Elements 13. Housing 14 Sliding surface 20 First Frame 21 Cylindrical sleeve 22 Lateral annular flange 30 membrane 31 first end 32 Second end 33 Main Unit 34 Contact surface 35 First Side 36 Second Side 37 slots 38 Open part 40 Second Frame 41 Cylindrical sleeve 42 Lateral annular flange 43 Inner end ZU Wear Zone

Claims

1. A ground ring (10) intended to be mounted between a fixed element (11) and a rotating element (12) rotatable relative to said fixed element about an axis of rotation (AX), an annular, rigid first frame (20) securely attached to one of the fixed element and the rotating element; an annular membrane (30) made of an elastic material, extending between a first end (31) in contact with the first frame and a second end (32) in contact with the other of the fixed element and the rotating element, and having a body (33) between the first end and the second end; an annular, rigid second frame (40) securely attached to the first frame and configured to clamp and secure the membrane between the first and second frames; Equipped with the first frame and the membrane are capable of conducting an electric current between the fixed element and the rotating element, and the membrane has a wear zone (ZU) at the second end that is thicker than the main body of the membrane, the wear zone forming a contact surface (34) that slides in contact with the sliding surface (14) of the other element and is configured to provide electrical conductivity between the fixed element and the rotating element; Grounding ring.

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

3. 3. A ring according to claim 1 or 2, wherein the wear zone (ZU) has a thickness (b) greater than the thickness of the body of the membrane.

4. 4. A ring according to any one of claims 1 to 3, wherein the wear zone (ZU) has a mass configured to ensure contact between the contact surface and the sliding surface over a range of rotational speeds of the rotating element.

5. A ring according to any one of claims 1 to 4, wherein said membrane (30) is fixed to said second frame.

6. A ring according to any one of the preceding claims, wherein the membrane (30) includes a radial slot (37) extending to the second frame (40) and terminating in an open portion (38).

7. A ring according to any one of the preceding claims, wherein the membrane (30) comprises an electrically conductive coating, which is on at least the contact surface (34) in the wear zone (ZU).

8. A ring according to any one of the preceding claims, wherein the membrane (30) is made from a PTFE material containing conductive fillers such as carbon.

9. A ring according to any one of the preceding claims, wherein the second frame (40) is capable of conducting an electric current between the fixed element and the rotating element.

10. A ring according to any one of the preceding claims, wherein the second frame (40) has a radial height (h) greater than the radial height (g) of the first frame (20).

11. 11. The ring of claim 10, wherein 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 (Di) between the fixed element and the rotating element.

12. 12. The ring according to any one of claims 1 to 11, wherein the first frame and / or the second frame are provided with pins adapted to penetrate the membrane and fix the membrane to the first frame and / or the second frame.

13. A ring according to any one of claims 1 to 12, wherein the second frame (40) has an inner end (43) that is curved towards the second end (32) of the membrane when the ring is in the mounted position.

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

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