Encoder wheel for a hub unit

Abstract

A speed measuring device (1) for a hub unit (2) provided with a rolling bearing (3), the speed measuring device (1) comprising: an encoder wheel (7) made of a magnetized material and assembled on a rotating ring (4) of the rolling bearing (3); a mechanical support member (8) arranged directly between the encoder wheel (7) and the rotating ring (4) such that the encoder wheel (7) and the ring (4) are angularly constrained to each other; and a mechanical locking member (9) for locking the encoder wheel (7) in the axial direction within a seating portion (100) defined by the mechanical locking member (9) and the mechanical support member (8).

Description

Field of the Invention

[0001] The present invention relates to an encoder wheel for a wheel hub unit.

[0002] Although non-exclusive, the present invention is particularly applicable to the field of motor vehicle wheel hub units provided with rolling bearings. These applications include the case where the outer ring of the bearing rotates while the inner ring of the bearing is fixed, and the opposite case where the inner ring rotates while the outer ring is fixed. The encoder wheel forms part of a device for detecting the rotational speed of the rotating ring of the bearing. These devices also include sensors adapted to acquire the signals generated by the encoder wheel, typically speed sensors, and the encoder wheel allows monitoring of the kinematic operating parameters of the wheel hub unit. The following description will refer to these specific applications by way of example without losing their general character. Background Art

[0003] Known speed measuring devices of the aforementioned type include encoder wheels in the form of annular discs or cylindrical screens made of magnetized rubber, which are angularly constrained to the rotating ring of the bearing. In some known solutions, the encoder wheel includes a metal insert that is fixed to the magnetized rubber part by gluing and press-fitted into the rotating ring of the bearing or into an element integral with the ring. In other solutions, instead, the encoder wheel is directly mounted on the rotating ring and angularly constrained to the rotating ring by gluing.

[0004] However, it has been found that, in the case of gluing them to the metal insert, the encoder wheels are subject to tensions that they do not withstand well, while in the case of gluing them directly to the rotating ring, it is difficult to position the encoder wheels. Summary of the Invention

[0005] The object of the present invention is to provide an encoder wheel for a wheel hub unit that does not have the above-mentioned drawbacks.

[0006] According to the present invention, an encoder wheel for a wheel hub unit provided with a rolling bearing is achieved, said wheel hub unit having the features recited in the appended independent claims.

[0007] The encoder wheel thus achieved is mounted on the rotating ring of the bearing and constrained to the rotating ring by the arrangement of a mechanical support member between the encoder wheel and the rotating ring, which not only facilitates the installation of the encoder wheel but also (for example, in the absence of any gluing) can practically eliminate the formation of a state of tension in the magnetized rubber as a whole, and allows arbitrary position adjustment while ensuring the stability of the encoder wheel during use.

[0008] Furthermore, the possibility of eliminating the glue joint and thus reducing the number of components of the speed measuring device brings the additional advantages of a faster manufacturing and assembly process and a reduced environmental impact.

[0009] Furthermore, the preferred and / or particularly advantageous embodiments of the invention are illustrated by the features shown in the appended dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The present invention will now be described with reference to the accompanying drawings, which show non-limiting examples of embodiments of the invention, in which:

[0011] - Figure 1 is a partial cross-sectional view of a wheel hub unit equipped with a speed measuring device according to the present invention, in which a radial encoder wheel is mounted on the outer ring of a bearing;

[0012] - Figure 2 is an enlarged view of the radial encoder wheel according to Figure 1 . DETAILED DESCRIPTION

[0013] With reference to Figure 1 , 1 generally denotes a speed measuring device for a wheel hub unit 2. The unit 2 is provided with a rolling bearing 3, which includes: an outer ring 4, which is coaxial with the rotational axis A of the bearing 3; an inner ring 5, which is coaxial with the outer ring 4; and a plurality of rolling elements 6 (the rolling elements are, for example, balls), which are arranged between the outer ring and the inner ring. In the example shown in Figure 1 , the outer ring 4 of the bearing 3 is rotatable, while the inner ring 5 is fixed.

[0014] The bearing 3 is provided with means 1 for measuring the rotational speed of the rotatable outer ring 4; the means 1 includes:

[0015] - a radial encoder wheel 7;

[0016] - mechanical support means 8, which is arranged between the encoder wheel 7 and the outer ring 4 for supporting the encoder wheel 7 and angularly constraining the encoder wheel 7 to the outer ring 4;

[0017] - mechanical locking means 9, which is for axially locking the encoder wheel 7 to the mechanical support means 8; and

[0018] - a sensor (not shown), which faces the encoder wheel and is mounted on a fixed part of the vehicle.

[0019] In addition, according to Figure 2As shown, the mechanical support member 8 is directly mounted axially outside 41 of the outer ring 4 and includes a bottom cylindrical wall 82 which is keyed in an adjustable manner to the cylindrical outer surface 42 of the outer ring 4, (the bottom cylindrical wall 82) being coaxial with the axis A and bounded radially outwards by a cylindrical bottom surface 821.

[0020] The mechanical locking member 9 is coupled to the mechanical support member 8 to axially lock the encoder wheel 7 to the mechanical support member 8, and the mechanical locking member 9 includes a smaller side wall or flange 93 and a larger side wall or flange 94 which are integral with the bottom cylindrical wall 82 on two opposite sides and extend radially outwards from the bottom cylindrical wall 82; the side walls or flanges 93 and 94 are mechanical members for locking the encoder wheel 7 and axially lock the encoder wheel 7 to the bottom cylindrical wall 82. The smaller side wall or flange 93 is axially disposed on the opposite side of the bottom cylindrical wall 82 with respect to the axially outside 41 of the outer ring 4, and is bounded radially outwards by a cylindrical surface 933, the diameter 93f of the cylindrical surface 933 being smaller than the diameter 94f of the cylindrical surface 943 on the radially outer side of the larger side wall or flange 94 disposed on the same side of the axially outside 41 of the outer ring 4. In addition, the side walls or flanges 93 and 94 are bounded axially by corresponding surfaces 931 and 941 on the side facing the bottom cylindrical wall, the surfaces 931 and 941 being transverse to the axis A and connected to the cylindrical bottom surface 821 by corresponding toroidal connecting portions 932 and 942.

[0021] The side walls or flanges 93 and 94 and the bottom cylindrical wall 82 are made of a metallic material, and a U-shaped metallic insertion portion 81 and a seat 100 for the encoder wheel 7 are defined between the side walls or flanges 93 and 94 and the bottom cylindrical wall 82: if both the side walls or flanges 93 and 94 prevent any axial movement of the encoder wheel 7 relative to the bottom cylindrical wall 82, the radial height of the side walls or flanges 93 and 94 is such that the side wall or flange 93 has a different function from the side wall or flange 94. In fact, the side wall or flange 93 allows the encoder wheel 7 to be inserted into the seat 100, while the side wall or flange 94 allows the encoder wheel 7 to be mounted onto the surface 42 by means of a pushing member (not shown) which applies an axial mounting force to the side wall or flange 94 without pressing against the encoder wheel 7, thus protecting the encoder wheel 7 at least during the mounting of (the encoder wheel 7) onto the bearing 3. The side wall or flange 94 can also protect the encoder wheel 7 during the operation of the measuring device 1, thereby preventing any impact between the encoder wheel 7 and external elements and / or the bearing 3 and / or the measuring device 1.

[0022] The encoder wheel 7 includes a cylinder shield 71 made of rubber magnetized with alternating magnetism in the circumferential direction, and (the cylinder shield 71) is bounded by a reading surface 72 on the radially outer side and an installation surface 73 on the radially inner side: both surfaces 72 and 73 are cylindrical surfaces. The diameter 72f of the reading surface 72 is larger than both the diameter 93f and the diameter 94f. The installation surface 73 is arranged in contact with the surface 821, and the diameter 73f of the installation surface 73 is slightly smaller than the diameter 93f, but the difference between the diameter 73f and the diameter 93f is sufficient to allow elastic (preferably radial) expansion of the cylinder shield 71 by the amount that needs to extend axially beyond the side wall or flange 93 during assembly, and is sufficient to ensure that the side wall or flange 93 can provide an effective axial locking action on the encoder wheel 7.

[0023] In fact, the magnetized rubber making up the cylinder shield 71 as a whole has an elasticity that allows elastic expansion of the cylinder shield 71 during the assembly of the encoder wheel 7 to the mechanical support member 8: this elastic expansion, which can be obtained by thermal action (preferably but not necessarily by heating the cylinder shield 71) or by mechanical action (preferably but not necessarily by mechanical expansion of the cylinder shield 71), allows the diameter 73f of the installation surface 73 to obtain a size larger than the diameter 93f of the side wall or flange 93, thus allowing the shield 71 to be easily inserted into the seating portion 100 and pass over the side wall or flange 93 without difficulty. The elasticity of the magnetized rubber making up the cylinder shield 71 also allows the cylinder shield 71 to regain its nominal size after being inserted into the seating portion 100, that is, to regain the dimensions that cause the surfaces to be in direct and close contact with the surface 821, thus creating frictional conditions that angularly constrain the encoder wheel 7 and the wall 82 to each other. The elastic return of the magnetized rubber of the cylinder shield 71 presses the cylinder shield 71 tightly against the wall 82 in the radial direction, and since the wall 82 is in turn keyed into the cylindrical outer surface 42 of the outer ring 4, that is, the installation type of the wall 82 causes the wall 82 and the outer ring 4 to be angularly constrained together, while allowing a small axial adjustment if necessary. Therefore, the encoder wheel 7 is definitely angularly constrained to the outer ring 4, all due to the frictional forces generated by the contact between the surface of the encoder wheel 7 and the surface of the wall 82 and the contact between the surface of the wall 82 and the surface of the outer ring 4.

[0024] Finally, the encoder wheel 7 has corresponding rounded annular edges 77 and 78 in the regions of the annular connections 932 and 942 so as to match the shape of the annular connections 932 and 942 and to facilitate the operation of assembling the tubular shield 71 into the seating portion 100. The rounded edges 77 and 78 also prevent any cracks and / or fissures from forming in the tubular shield 71 and finally also allow the encoder wheel 7 to be optimally centred within the seating portion 100.

[0025] Finally, it should be noted that the dimension of the radial thickness S of the tubular partition 71 is decidedly greater than the difference between the dimension of the diameter 93f and the dimension of the diameter 73f, so that the mounting of the encoder wheel 7 within the seating portion 100 is even more reliable, i.e. without any defects. By way of non-limiting example, a thickness S equal to at least 4 or 6 times the difference between the dimension of the diameter 93f and the dimension of the diameter 73f makes it absolutely safe and problem-free to mount the encoder wheel 7 within the seating portion 100 in the case where the tubular shield 71 has to expand by thermal action and also in the case where the tubular shield 71 has to expand by mechanical action.

[0026] The mechanical support member 8 and the mechanical locking member 9 according to the invention offer a number of technical advantages such as:

[0027] - the possibility of mounting the encoder wheel 7 onto the surface 42 of the outer ring 4 in such a way as to also adjust the axial position of the encoder wheel 7 during the final assembly of the hub unit 2 onto the vehicle and to compensate for any errors during the alignment of the encoder wheel 7 relative to the sensor;

[0028] - the possibility of avoiding the use of adhesive water to fix the encoder wheel 7 to the rotatable ring 4, which is generally environmentally unsustainable and in any case requires special attention during the production cycle and also results in an increase in the assembly time; and

[0029] - the possibility of protecting the tubular shield 71 from any impact, especially during the assembly with the bearing 3.

[0030] However, the greatest advantage of the mechanical locking member 9 according to the present invention is that both the side walls or flanges 93 and 94 have different dimensions relative to each other and relative to the encoder wheel 7. In fact, the side wall or flange 93 having a particularly small dimension compared to the radial thickness of the cylindrical shielding member 71 will cause the side edge 75 of the encoder wheel 7 to be almost substantially completely exposed, so that the magnetic field generated by the magnetized rubber of the cylindrical shielding member 71 can be more easily propagated (diffused) in the region of the cylindrical shielding member 71. On the axially opposite side, the side wall or flange 94 having a small dimension compared to the radial thickness of the cylindrical shielding member 71 will cause a part of the side edge 76 to be sufficiently exposed to allow the magnetic field generated by the magnetized rubber to propagate well under any circumstances, and at the same time protect the edge 76 during the installation of the encoder wheel 7 onto the rotatable outer ring 4. On the side facing the axially outer side 41 of the outer ring 4 and especially on the axially opposite side of the axially outer side 41, the greater the propagation of the magnetic field generated by the magnetized rubber of the cylindrical shielding member 71 means that the axial installation of the device 1 for measuring the rotational speed of the rotatable outer ring 4 can be carried out even more freely, thus allowing any axial errors during the installation of the sensor or encoder wheel 7 to be easily compensated, however, without having a negative impact on the quality of the magnetic signals that can be received by the sensor.

[0031] In addition, the side wall or flange 93 having a particularly small dimension compared to the radial thickness of the cylindrical shielding member 71 allows the encoder wheel 7 to be easily installed in the seating portion 100 without any damage to the encoder wheel 7 and only by utilizing the conventional elasticity of the magnetized rubber.

[0032] Thanks to these advantages, the process of assembling the device is simplified not only because it is faster due to the smaller number of components, but also because of the flexibility provided by the axial expansion of the magnetic field that is not obstructed in any way by the side walls or flanges 93 and 94. The side walls or flanges 93 and 94 also provide effective protection and ensure a reliable and stable installation of the encoder wheel 7.

[0033] In addition to the embodiments of the present invention described above, it should be understood that there are many other variations. It should also be understood that the embodiments are merely examples and do not limit the subject matter of the present invention, nor its application and possible configurations. On the contrary, although the description provided above enables a person skilled in the art to implement the present invention at least in one of the construction examples of the present invention, it should be understood that various variations of the described components are feasible without departing from the scope of the present invention, which is defined as the literal scope and / or its legal equivalents as defined in the appended claims.

Claims

1. A speed measuring device (1) for a wheel hub unit (2), the wheel hub unit (2) being provided with a rolling bearing (3), the speed measuring device (1) comprising: - An encoder wheel (7) made of a magnetizable material and assembled on a rotating ring (4) of the rolling bearing (3); - A mechanical support member (8) directly provided between the encoder wheel (7) and the rotating ring (4) such that the encoder wheel (7) and the rotating ring (4) are angularly constrained to each other; The speed measuring device (1) is characterized in that it further comprises a mechanical locking member (9) for axially locking the encoder wheel (7) within a seating portion (100) defined jointly by the mechanical locking member (9) and the mechanical support member (8), The mechanical support member (8) itself comprises a first lateral flange (93) and a second lateral flange (94) on both sides, the first lateral flange (93) being a flange with a radial dimension smaller than the radial dimension of the second lateral flange (94).

2. The speed measuring device according to claim 1, characterized in that, The mechanical support member (8) is directly mounted axially outside (41) of the rotating ring (4) and comprises a cylindrical bottom wall (82) keyed to the rotating ring (4) in an axially adjustable manner.

3. The speed measurement device according to claim 2, characterized in that The encoder wheel (7) is made of an elastic magnetizable material, is directly in contact with the cylindrical bottom wall (82) and is angularly constrained to the cylindrical bottom wall (82).

4. The speed measuring device according to claim 2 or 3, characterized in that, The mechanical locking member (9) is combined with the mechanical support member (8) such that the encoder wheel (7) is axially locked to the mechanical support member (8), the mechanical locking member (9) comprising the first lateral flange (93) and the second lateral flange (94) integral with the cylindrical bottom wall (82), the first lateral flange (93) and the second lateral flange (94) being made integral with the cylindrical bottom wall (82), and a U-shaped insertion portion (81) defining a boundary of the seating portion (100) being defined between the first lateral flange (93) and the second lateral flange (94) and the cylindrical bottom wall (82).

5. The speed measurement device according to claim 4, characterized in that, The second lateral flange (94) is a pushing lateral flange (94) for keying the speed measuring device (1) to the rotating ring (4) of the rolling bearing (3) and capable of shielding the encoder wheel (7) at least during installation of the speed measuring device (1) onto the rotating ring (4).

6. The speed measuring device according to claim 5, characterized in that, The encoder wheel (7) comprises a cylindrical shield (71) made of rubber magnetized with circumferentially alternating polarities, and an inner radial dimension of the cylindrical shield (71) is smaller than an outer radial dimension of the two lateral flanges (93, 94).

7. The speed measurement device according to claim 4, characterized in that, The first lateral flange (93) and the second lateral flange (94) and the cylindrical bottom wall (82) are made integral of a metallic material.

Images