Patent Description:
In a disc brake, the brake caliper is generally arranged straddling the outer peripheral margin of a brake disk, which is adapted to rotate about a rotation axis (A-A) defining an axial direction (X-X). In a disk brake, a radial direction (R-R), orthogonal to the axial direction (X-X), a circumferential direction (C-C), orthogonal both to the axial direction (X-X) and to the radial direction (R-R), and a tangential direction (T-T) locally or punctually, i.e. in an intersection point of the axial and radial directions, orthogonal to both the axial direction (X-X) and the radial direction (R-R) are further defined.

As is known, a disc for a disc brake comprises a bell adapted to associate the disc with a vehicle hub, from which an annular portion, called braking band (also denoted as disc brake band) extends, which is intended to cooperate with brake pads of a caliper. In the case of ventilated type discs, the braking band is made by two plates, mutually facing and connected to each other, respectively, by connection elements in the form of pillars or fins. The outer surfaces of the two plates define opposite braking surfaces, while the inner surfaces, together with the pillars or fins, delimit ventilation channels for cooling the disc, the ventilation channels being crossed by airflows according to a centrifugal direction during rotary motion of the disc.

The braking band is intended to cooperate with disc brake calipers, which are adapted to apply a braking action on the vehicle by applying, by the aforesaid pads, friction on opposite surfaces of the two plates, referred to as braking surfaces.

It is known that during operation of the brakes, friction between the pads of the brake calipers and the braking surfaces of the braking band generates a high amount of heat.

Disc brakes for motor vehicles should provide operation with constant braking performance for a reasonable duration. In some applications this need has been met with disc brakes which have adequate efficiency even though they are made of easily machinable material but subject to corrosion materials. Disc brake rotors are generally made with gray iron castings which have excellent characteristics for a braking system. The gray cast iron is, however; highly susceptible to corrosive attack, particularly in vehicles where the brake is subjected to significant transient heating and exposed to water and salt water spray, and dirt and debris.

In regular use, some areas of the brakes that are not swept by the brake pads are and remain particularly attacked by corrosion. Before anti-lock braking systems, such concerns were not of primary concern with brakes that were frequently in use, as the rotor is a regularly replaced part and the remaining areas prone to attack were not critical.

With the use of anti-lock braking systems, parts of the disc brake rotor, even other than the braking surfaces, become important, such as the exciter ring of the anti-lock braking system. The exciter ring is a rotor component having a common axis of rotation with the rotor. A plurality of teeth is formed in a ring, which is flat in the plane of rotation of the rotor to pass close to a fixed sensor. One type of sensor used is a variable reluctance sensor that generates a train of electrical pulses as a function of the dispersion of the variable magnetic flux between the sensor head and the exciter ring. In this system, the frequency of the resulting electric pulse train indicates the speed of rotation of the wheel on which the rotor is mounted. The generation of clean pulse trains is greatly facilitated by the presence of teeth of uniform shape, size and spacing. Where the ring is cast in one piece with the rotor, corrosion of the rotor can affect all of these factors, resulting in difficulty in detecting the passage of teeth and gaps and causing an irregular pulse train to be generated.

To overcome this drawback, it is known in drum brakes to use an exciter ring separate from the drum mounted under pressure on the end of a wheel hub. An example of this solution is known from <CIT>. Press-fit parts can easily be made from a material that is more corrosion resistant than gray cast iron. However, pressing the rings onto disc rotors has proven less effective than hubs using drum brakes. The difficulty arises from the fact that in disc brake systems the exciter ring is in direct contact with the rotor. On drum systems, less heat is transferred from the hub carrying the exciter ring than in disc systems from the rotor to an exciter ring. Exciter rings are made of low carbon steel which has a different coefficient of thermal expansion than iron. The difference in expansion coefficients in the materials used for the ring and hub or rotor causes problems in disc brake systems as a lot of heat is transferred from a rotor to the exciter ring and thus the exciter ring and rotor vary by dimensions differently from each other. An exciter ring that loses its tight fit with a rotor may begin to lose its correct angular position relative to the disc rotor. If a ring rotates on a rotor, the ring will not reflect the actual rotational speed of the wheel. This affects the functioning of the ABS. Furthermore, in these solutions the exciter ring could disconnect from the rotor during thermal expansion added to the vibrations of the brake.

Solutions to these problems have been proposed by <CIT>, <CIT>, <CIT>, <CIT> and <CIT>.

None of these documents however disclose an anti-lock sensor ring with cantilever spring retention clips and two surfaces, namely a retention surface and a support surface, as defined in the appended claim <NUM>.

However, these solutions only partially solve other needs that are becoming more and more relevant with the evolution of braking systems and the demand for more and more accurate and reliable sensors over time.

In fact, the need is further felt to position the exciter ring in a position that is easy to read for the sensor and at the same time in a position that does not alter the flow of air to the ventilation channel of the braking band, thus avoiding anomalous increases in temperature which are harmful to the rotor and exciter ring coupling.

Many of the current solution of the art is an anti-lock sensor ring that is retained using dedicated hardware, be it snap rings or threaded fasteners. Tooling is required in order to facilitate the assembly of the sensor ring and fasteners to the brake disc.

Still further, even it is desired a safe connection between the rotor and the exciter ring, there is a strong need for a solution that allows you to connect the exciter ring without using additional components or tools.

It is the object of the present invention to provide an anti-lock sensor ring and a disc brake rotor to overcome the drawbacks of the state of the art solutions.

This and other objects and advantages are achieved by a anti-lock sensor ring according to claim <NUM> and a disc brake rotor according to claim <NUM>.

Preferred embodiments of the present invention are laid down in the dependent claims.

By virtue of the solution of the present invention, taking advantage of material elasticity, the proposed anti-lock sensor ring has its own retention mechanism. Applying this principle, the anti-lock sensor ring is applied to a brake disc with locating and locking surfaces yields a tool-less, fastener-less assembly.

The invention takes advantage of assembly and locking features provided into the brake disc and the spring retention clips provided into the sensor ring. The proposed anti-lock sensor ring is retained avoiding to use dedicated hardware, be it snap rings or threaded fasteners. Tooling is not required in order to facilitate the assembly of the sensor ring nor fasteners to the brake disc.

The proposed anti-lock sensor ring is designed to be connected in a position of the brake band easy to read that avoid to close or even interfere with the venting channel provided in the braking band.

At the same time, the proposed anti-lock sensor ring has a secure attachment to the braking band but easy to remove.

The proposed solution allows to easily compensate for the difference in expansion coefficients in the materials used for the ring and hub or rotor, avoiding to lose its tight fit with the braking band and therefore avoiding to lose its correct angular position relative to the disc rotor.

Further features and advantages of the present invention will be apparent from the following description of preferred embodiments thereof, given by way of non-limiting examples, with reference to the accompanying figures, wherein the present invention is defined by the appended claims.

According to an embodiment of the present invention, see <FIG>, an anti-lock sensor ring <NUM> comprises an annular ring body <NUM>. Said annular ring body <NUM> comprises a flattened exciting portion <NUM>. Said flattened exciting portion <NUM> comprises a plurality of exciting elements <NUM>, for example a plurality of windows uniformly circumferentially distributed. Said plurality of exciting elements <NUM> are configured to interact with a stationary sensor <NUM>.

Said annular ring body <NUM> comprises a rotation axis X-X defining an axial direction A-A parallel or coincident with said rotation axis X-X, a radial direction R-R orthogonal to said axial direction A-A, and a circumferential direction C-C orthogonal both to said axial direction A-A and said radial direction R-R.

Said flattened portion <NUM> comprises an external ring radial edge <NUM>.

A retention mechanism <NUM> is projecting from said ring radial edge <NUM>.

Said retention mechanism <NUM> comprises cantilever spring retention clips <NUM> elastically deformable to snap on a disc brake band retention seat <NUM>.

Said retention mechanism <NUM> further comprises a cantilever support portion <NUM>.

At least a portion of each of said cantilever spring retention clips <NUM> is side by side to, and spaced apart from, said cantilever support portion <NUM> defining a clamp channel <NUM>.

Each of said cantilever spring retention clips <NUM> comprises a retention surface <NUM>.

Said cantilever support portion <NUM> comprises a support surface <NUM>.

When said anti-lock sensor ring <NUM> is dismounted from a disc brake band <NUM>, the plane defined by said retention surface <NUM> and the plane defined by said support surface <NUM> are facing each other in order to create opposing gripping elements.

According to an alternative embodiment, said cantilever support portion <NUM> is a cantilever flattened ring in a single piece with said flattened exciting portion <NUM>.

According to an alternative embodiment, said cantilever support portion <NUM> extend parallel to said flattened exciting portion <NUM>.

According to an alternative embodiment, said cantilever support portion <NUM> is a continuous ring partially circumferentially interrupted by ring windows <NUM>, each ring window <NUM> comprising a window base <NUM> disposed close to said flattened exciting portion <NUM>.

Each of said cantilever spring retention clips <NUM> extend from said window base <NUM> with an orthogonal spring arm <NUM> disposed orthogonal to said flattened exciting portion <NUM> and a gripping end <NUM> defining said at least a portion of each of said cantilever spring retention clips <NUM> disposed side by side to and spaced apart from said cantilever support portion <NUM>.

According to an alternative embodiment, said anti-lock sensor ring <NUM> is obtained by blanking and drawing of an initially flat plate.

According to an embodiment, a disc brake band <NUM> of a disc brake rotor <NUM>, being part of a disc brake rotor (<NUM>) according to the present invention, comprises at least one rotor plate <NUM>, <NUM>. Said at least one rotor plate <NUM>, <NUM> comprises at least a braking surface <NUM>, <NUM> configured to interact with pads of a brake caliper. Said pads are configured to abut against said at least a braking surface <NUM>, <NUM> to exert a barking action when activated.

Said at least one rotor plate <NUM>, <NUM> comprises a rotation axis X-X defining an axial direction A-A parallel or coincident with said rotation axis X-X, a radial direction R-R orthogonal to said axial direction A-A, and a circumferential direction C-C orthogonal both to said axial direction A-A and said radial direction R-R.

Said at least one rotor plate <NUM>, <NUM> comprises an inner plate radial edge <NUM>.

Said at least one rotor plate <NUM>, <NUM> comprises a radial annular protrusion <NUM> extending in radial direction R-R from said inner plate radial edge <NUM>.

Said radial annular protrusion <NUM> comprises an external plate abutment surface <NUM> and an internal plate gripping surface <NUM> facing in opposite directions.

Said radial annular protrusion <NUM> forms an undercut coupling seat <NUM>.

Said radial annular protrusion <NUM> comprises a passage and coupling openings <NUM>, for example a plurality of coupling openings uniformly circumferentially distributed, which form a passage between the external plate abutment surface <NUM> and the internal plate gripping surface <NUM> and suitable to overriding and snap coupling of cantilever spring retention cl configured ips <NUM>.

According to an alternative embodiment, said radial annular protrusion <NUM> comprises a flat conical edge <NUM> configured to drive the elastic deformation of the cantilever spring retention clips <NUM>.

According to an alternative embodiment, said external plate abutment surface <NUM> is parallel to said at least a braking surface <NUM>, <NUM>.

According to an alternative embodiment, said passage and coupling openings <NUM> comprising opposing support sides <NUM>, <NUM> to stop the cantilever spring retention clips <NUM> in circumferential C-C direction.

According to an alternative embodiment, said radial annular protrusion <NUM> comprises machined external plate abutment surface <NUM> and internal plate gripping surface <NUM>.

According to an alternative embodiment, said at least one rotor plate comprises two parallel rotor plates <NUM>, <NUM> each comprising a opposite braking surface <NUM>, <NUM>.

Said two parallel rotor plates <NUM>, <NUM> are spaced apart and forms in-between a venting duct <NUM>.

One of said two parallel rotor plates <NUM> is connected to a braking bell <NUM> configured to fix said disc brake rotor <NUM> to a vehicle axel.

The other of said two parallel rotor plates <NUM> comprises said radial annular protrusion <NUM>.

According to an embodiment of the present invention, see <FIG>, a disc brake rotor <NUM> comprises a disc brake band <NUM> as defined by at least one of the previous described embodiments and an anti-lock sensor ring <NUM> as defined by at least one of the previous described embodiments.

Said cantilever spring retention clips <NUM> is housed into said passage and coupling openings <NUM> attesting said support surface <NUM> of said cantilever support portion <NUM> against said external plate abutment surface <NUM> and snap coupling said retention surface <NUM> of said cantilever spring retention clips <NUM> against said internal plate gripping surface <NUM>.

According to an alternative embodiment, said anti-lock sensor ring <NUM> abut in axial direction A-A outside said disc brake band <NUM>.

According to an alternative embodiment, said flattened exciting portion <NUM> of said anti-lock sensor ring <NUM> comprises a sensor ring external surface <NUM>.

Said sensor ring external surface <NUM> is parallel to said braking surface <NUM>, <NUM>.

According to an alternative embodiment, between said support surface <NUM> of the cantilever support portion and said external plate abutment surface <NUM> of the radial annular protrusion <NUM> extending form said inner plate radial edge <NUM> is provided an insulating member <NUM> to create at least a partial a thermal barrier between the disc brake band <NUM> and the anti-lock sensor ring <NUM>.

Claim 1:
An anti-lock sensor ring (<NUM>) comprising
an annular ring body (<NUM>) comprising a flattened exciting portion (<NUM>) comprising a plurality of exciting elements (<NUM>) (<NUM>) configured to interact with a stationary sensor;
said annular ring body (<NUM>) comprising a rotation axis (X-X) defining an axial direction (A-A) parallel or coincident with said rotation axis (X-X), a radial direction (R-R) orthogonal to said axial direction (A-A), and a circumferential direction (C-C) orthogonal both to said axial direction (A-A) and said radial direction (R-R);
said flattened portion (<NUM>) comprising an external ring radial edge (<NUM>) ;
a retention mechanism (<NUM>) is projecting from said ring radial edge (<NUM>) ;
said retention mechanism (<NUM>) comprises cantilever spring retention clips (<NUM>) elastically deformable to snap on a disc brake band retention seat (<NUM>);
said retention mechanism (<NUM>) comprises a cantilever support portion (<NUM>) ;
at least a portion of each of said cantilever spring retention clips (<NUM>) is side by side to and spaced apart from said cantilever support portion (<NUM>) defining a clamp channel (<NUM>);
each of said cantilever spring retention clips (<NUM>) comprising a retention surface (<NUM>);
said cantilever support portion (<NUM>) comprising a support surface (<NUM>); wherein
said anti-lock sensor ring (<NUM>) is configured to be mounted on a disc brake band (<NUM>);
and is configured such that
when said anti-lock sensor ring (<NUM>) is dismounted from said disc brake band (<NUM>), the plane defined by said retention surface (<NUM>) and the plane defined by said support surface (<NUM>) are facing each other in order to create opposing gripping elements.