Patent Description:
Disc brakes for use in vehicles are generally known. To generate a braking force, brake shoes, which comprise a brake pad back plate and a brake pad, get pressed against a brake disc. This causes the brake pad to wear over time.

It is well known that electrical contact conductors - such as cables - can be arranged in the brake pad in order to monitor the thickness of the brake pad, in particular to determine whether the brake pad falls below an allowable wear limit. The brake pad has a cut-out for the arrangement of a sensor head within the brake pad. When the wear limit is reached, the contact conductor comes into contact with the brake disc during braking and is also grinded. This causes an electrical signal to be sent to a signal transmitter and a warning signal is generated.

For example, such a device is described in <CIT>. Here, two channels are arranged within a sensor head to receive a U-shaped contact loop of a signal cable. However, this arrangement is disadvantageous in that the sensor head is susceptible to damage.

<CIT>, <CIT> and <CIT> discloses a known lining wear sensor with a sensor head, a holding groove for holding the lining wear sensor on the carrier plate of the brake lining, and a cable routing arranged in the sensor head. The sensor head has two retaining channels through which the cables or cable sections are guided.

<CIT> discloses a lining wear sensor that features a section that is axially tapered in the direction of the friction lining. The cable <NUM> is arranged as a U-shaped loop in the lining wear sensor, whereby the cable sections of the U-shaped loops are separated by means of a center piece so that the lining wear sensor has two cable ducts. The disadvantage is that the cable sections are arranged parallel to the axial axis of the lining wear sensor and the brake disk and not axially one after the other, as a result of which both cable sections no longer remain in position after the U-shaped loop has been cut and, at the same time, come into contact with the brake disk, which leads to final correction.

Therefore, it was an object of the invention to provide a wear indication device that overcomes at least some of the above-mentioned issues. In particular, it was an object of the invention to provide a wear indication device, which is constructively simple in design and at the same time robust and damage-resistant.

According to the invention, it is proposed that the channel is configured to receive two signal cables. According to the invention, the term two cables is also to be understood as two cable sections of a single cable, for example in the case of a U-shaped contact loop of a cable.

The channel is a double channel having a first section for the first cable, and a second section for the second cable,
wherein the first and second sections are positioned adjacent to each other radially with respect to their center axis. The radial direction is a direction orthogonal to the center axis. The first and second section of the channel serve to arrange both cables together in the channel, but at least partially separated from each other in such a way that each cable is allocated in a separate section.

The center axis of the first signal cable has a distance to the fixing section that is greater than a distance between the center axis of the second signal cable and the fixing section. If both cables (sections) would have the same distance from the fixing section, i.e. their central axes were arranged in a plane parallel to the plane of the brake disc when installed, both cables (sections) would be ground on and off together after reaching the wear limit. In such a case, it can happen that both cables loose the holding contact at the same time and are either destroyed by the brake disc or do not come into contact with the brake disc at all. This would result in incorrect information and a diagnosis of functionality would be impossible.

According to the present invention the respective cross-sections of the first and the second sections at least partially overlap, such that the channel has a narrow necking area partly separating the first section from the second section by means of at least one protrusion, preferably two opposing protrusions in the sensor head projecting inwardly into the double channel. In this way it is possible to position the two cables on the one hand as close to each other as possible and on the other hand separately from each other in different sections. The task of the sensor is to emit a signal as soon as one of the cables, preferably the upper cable or that cable which has the smallest axial distance to the brake disc when installed, is exposed and comes into contact with the brake disc. This is the case when the sensor head is ground down so that the first section of the double channel is exposed. By means of the protrusion, it is possible to keep the second cable within the second section without it slipping out of its position within the second section when the first section is exposed. The term axial refers to an axial direction or an axial axis of the wear indication device. It is defined as an axis orthogonal to a zero plane, wherein the zero plane represents a contact surface between the brake pad back plate and the wear indication device when installed and wherein zero plane is a plane parallel to the brake disc. Unless otherwise defined below, this definition applies.

According to yet another embodiment, the first section and/or the second section of the double channel has / have at least partly a circular cross-section. The inner contour of the channel should match the outer contour of the cables. In particular, the inner contour of the first section should have a contour corresponding to the outer contour of the cross-sectional area of first cable and the inner contour of the second section should have a contour corresponding to the outer contour of the cross-sectional area of the second cable.

According to yet another preferred embodiment, the double channel has a geometry such that the two signal cables are arranged at least partially in parallel to each other in direct contact or at a distance from each other within.

According to the invention, the respective cross-sections of the first and the second sections at least partially overlap, such that the channel has a narrow necking area partly separating the first section from the second section by means of at least one protrusion, preferably two opposing protrusions in the sensor head projecting inwardly into the double channel. In this way it is possible to position the two cables on the one hand as close to each other as possible and on the other hand separately from each other in different sections. The task of the sensor is to emit a signal as soon as one of the cables, preferably the upper cable or that cable which has the smallest axial distance to the brake disc when installed, is exposed and comes into contact with the brake disc. This is the case when the sensor head is ground down so that the first section of the double channel is exposed. By means of the protrusion, it is possible to keep the second cable within the second section without it slipping out of its position within the second section when the first section is exposed. The term axial refers to an axial direction or an axial axis of the wear indication device. It is defined as an axis orthogonal to a zero plane, wherein the zero plane represents a contact surface between the brake pad back plate and the wear indication device when installed and wherein zero plane is a plane parallel to the brake disc. Unless otherwise defined below, this definition applies.

According to yet another preferred embodiment, the double channel has a geometry such that the two signal cables are arranged at least partially in parallel to each other in direct contact or at a distance from each other within the channel. An important requirement when arranging the cables inside the sensor head is to keep the axial distance as small as possible.

Preferably, the wear indication device further comprises a substantially flat contact surface for contacting a brake pad back plate when the wear indication device is installed, said contact surface defining a zero plane having an axial axis orthogonal to the plane. The sensor device of the invention determines a wear limit of the brake pad. This wear limit is defined by a plane essentially parallel to the zero plane. An indicator that the wear limit has been reached is the contact between brake disc and one cable. For this reason a precise arrangement of the sensor device is desirable to achieve a representative output value. Due to partially not completely plane-parallel removal of the brake pad, an at least sectional routing of the cable within this wear limit plane is reasonable. It should be understood that the cable routing described in this section also defines that cable section within the sensor head that is axially most distant from the zero plane, ergo axially closest to the brake disc when installed.

According to a preferred embodiment, the channel has a geometry such that the two signal cables are arranged perpendicular to the axial axis within the channel. Preferably, the center axis of the first signal cable has a distance to the zero plane that is greater than a distance between the center axis of the second signal cable and the zero plane in the direction of the axial axis. Preferably, the center axes of the first and second signal cables define a plane perpendicular to the zero plane. This is for the same reason as mentioned in the preceding paragraph(s), i.e. keep the axial space required by the cables as small as possible, and at the same time ensure the longest possible routing in the wear limit plane and to hold at least one cable section in the channel when the other one has been ground. In another embodiment, the double channel can be arranged such that the center axes of the first and second signal cables define a plane arranged at an angle less than <NUM>° to the zero plane. Preferably, the center axes of the first and second cable, as mentioned in this paragraph, extending at least partially parallel to the zero plane or perpendicular to the axial axis.

Preferably, the channel and the signal cables extend at least partially parallel to the zero plane. This is for the same reason as mentioned in the preceding paragraphs. In addition, a parallel routing has a positive effect on minimizing the space the channel required in the axial direction.

According to yet another embodiment, the channel has a geometry such that the two signal cables are in contact, so that they have the smallest possible distance from each other within the channel. As mentioned in the above paragraph, it is important to use as little space as possible in the axial direction, as this also minimizes the axial distance between the wear limit and the zero plane. As a consequence, the removal volume of the brake pad can be maximized until the wear limit is reached, which is defined by the position of the cable (section) that is axially the most distant from the zero plane. Preferably, the sensor head consists essentially of a plastic material. The wear indication device is exposed to extreme temperatures during operation. The materials used for this purpose (for example plastic) must therefore be of high quality.

Preferably, the channel is arranged outside the brake pad back plate within the brake pad. In this embodiment, the wear indication device has a sensor head as well as a fixing section. The fixing section is located within the brake pad back plate and the sensor head is located in a cut-out of the brake pad when installed. This allows the structural design of the wear indication device to be simplified. In particular, the connecting mechanism that couples the wear indication device to the brake pad back plate can be made more simple and robust if the channel is completely formed within the sensor head, i.e. within the brake pad. The connecting mechanism of the wear indication device to the brake pad back plate should be as stable as permanently possible so that the positioning of the cable is reliable and constant. Any change in position is undesirable because it affects the safety signal. For example, it may cause the above warning to be given too early or too late.

According to a preferred embodiment, an end of the channel closest to the brake pad back plate is located at a distance from the brake pad back plate that is <NUM> or less. As already mentioned, the axial distance of the cables and consequently of the channel to the zero plane must be kept as small as possible in order to be able to set the wear limit as low as possible in the axial direction, i.e. to keep the distance of the wear limit to the zero plane as low as possible. This has the advantage of maximum utilization of the brake pad.

According to a preferred embodiment, the vehicle brake further comprises a brake pad, wherein the wear indication device, in particular the sensor head, is at least partially arranged in a cut-out within the brake pad. This is necessary at least for the one reason that at least one of the cables must be arranged at least partially within the wear limit of the brake pad.

The aspects of the disclosure may best be understood from the following detailed description taken in conjunction with the accompanying figures. The figures are schematic and simplified for clarity, and they just show details to improve the understanding of the claims while other details are left out.

These and other aspects, features and/or technical effects will be apparent from and elucidated with reference to the illustrations described hereafter, which show in:.

<FIG> shows a detailed section of a vehicle brake <NUM> regarding <FIG> with a wear indication device <NUM> in a preferred embodiment. The wear indication device <NUM> comprises a fixing section <NUM> which is located inside the brake pad back plate <NUM> when wear indication device <NUM> is installed (not shown/ not visible), see therefore an exemplary fixing section in <FIG> as a fixing section according to the state of the art. The fixing section <NUM> is used to fixing the wear indication device <NUM> to a brake pad back plate <NUM>. The fixing section <NUM> may take any appropriate shape for this purpose.

The wear indication device <NUM> further comprises a sensor head <NUM> and a channel <NUM> for receiving a signal cable <NUM> within the sensor head <NUM>. According to the invention, the channel <NUM> is configured to receive two signal cables <NUM>', <NUM>" (not shown), see therefore an exemplary cable routing in <FIG>.

The channel <NUM> of the wear indication device <NUM> is a double channel having a first section <NUM> for a first cable <NUM>', and a second section <NUM> a the second cable, or respectively a first cable section <NUM>' and a second cable section <NUM>" of a signal cable as best seen in <FIG>.

In the top view of <FIG>, it can be seen that the first section <NUM> of channel <NUM> has a greater distance in the direction of axis A from the fixing section <NUM>, i.e. in the mounted state from the zero plane Z or brake pad back plate <NUM>, than the second section <NUM> of channel <NUM>.

The double channel also has two opposing protrusions <NUM>. These are set up to hold a respective cable section <NUM>', <NUM>" in the respective assigned section <NUM>, <NUM> of the channel <NUM>. This is particularly useful if the cable channel <NUM> has been ground by the brake disc and thus partially exposed.

In addition, the cross-section of each section <NUM>, <NUM> of the channel <NUM> is designed mostly circular, in order to enclose the circular cross-section of a signal cable <NUM>. Because the signal cables <NUM> in the channel <NUM> can be in contact with each other, the respective sections <NUM>, <NUM> of the channel <NUM> overlap at least in part. Therefore, the channel <NUM> has a narrow necking area <NUM> partly separating the first section <NUM> from the second section <NUM> by means of at least one protrusion <NUM>.

The wear indication device <NUM> further comprises a substantially flat contact surface for contacting a brake pad back plate <NUM> when the wear indication device <NUM> is installed, said contact surface defining a zero plane Z. The contact surface is located on the back side of the sensor head <NUM>, so that the sensor head <NUM> is in contact with the zero plane Z or the brake pad back plate <NUM> when the wear indication device <NUM> is installed. The zero plane Z thus also separates the sensor head <NUM> from the fixing section <NUM> of the wear indication device <NUM>.

The cables <NUM> run essentially parallel to each other within the channel <NUM>, or the cable sections <NUM> of the U-shaped contact loop run parallel to each other, so that they also run parallel to the zero plane Z.

In the preferred embodiment in <FIG>, the sections <NUM>, <NUM> of the channel <NUM> are arranged one above the other in the axial direction A, such that the center axes of the first and second signal cables <NUM>', <NUM>", when arrange inside of the double channel, define a plane perpendicular to the zero plane (Z). In an alternative embodiment, see <FIG> and <FIG> for an example, the sections <NUM>, <NUM> of channel <NUM> are offset in relation to the axial axis A. In this case, the center axes of the first and second signal cables <NUM>', <NUM>", when arranged inside of the double channel, define a plane with an angle smaller than <NUM>° to the zero plane (Z). As can be seen in <FIG>, <FIG> and <FIG>, the cables (sections) <NUM> inside the sensor head <NUM> run parallel to the zero plane Z and perpendicular to the axial axis A.

The cable (sections) <NUM> are adjacent to each other within the channel <NUM>, so that the size of channel <NUM> can be selected accordingly small.

<FIG> shows a disc brake <NUM> comprising a brake carrier <NUM>, which is mountable to a corresponding receiving section of a vehicle. The disc brake <NUM> further comprises a brake caliper <NUM>, which forms an accommodation space for, among others, brake pad back plate <NUM>, configured to carry a brake pad <NUM> having a friction lining that comes into contact with the disc of the brake (not shown) during braking in order to apply a braking force.

Further, the brake pad back plate <NUM> has a wear indication device <NUM>, which is configured to assess the degree of wear of the brake pads <NUM>. The wear indication device <NUM> is coupled to the brake pad back plate <NUM> and at least partly received in a recess (not shown) of the brake pad back plate <NUM>.

The wear indication device <NUM> is coupled to a signal cable <NUM> having a connector on its distal end. When the wear indication device <NUM> is installed, a cable section <NUM>', <NUM>" of the signal cable <NUM> runs in a U-shaped contact loop through the channel <NUM> inside the sensor head <NUM> of the wear indication device <NUM>. Accordingly, the entire cable channel <NUM> is located at the level of the brake pad <NUM>, as best seen in <FIG>.

The distance of the lower end of the channel <NUM>, i.e. in particular the distance of the lower end of the second section <NUM> to the zero plane Z is preferably <NUM> or less.

The brake pad <NUM> has a cut-out <NUM> surrounding the recess (see <FIG>) such that the recess is arranged within the region of the cut-out <NUM>. Thus, the wear indication device <NUM> is surrounded by the brake pad <NUM> wherein the cut-out <NUM> allows an easy access to the wear indication device <NUM>.

The brake pad back plate <NUM> carrying the brake pad <NUM> is held in position by a spring hanger <NUM>. The spring hanger <NUM> is preferably connected to the brake caliper <NUM> by a spring hanger seat <NUM> on one side and by a spring hanger fixation means <NUM> on the other side. After releasing the spring hanger fixation means <NUM> and guiding the spring hanger <NUM> out of its seat <NUM>, the spring hanger <NUM> may be removed. When the spring hanger <NUM> is removed, the brake pads <NUM> together with brake pad back plates <NUM> may be removed likewise and be exchanged.

Claim 1:
A vehicle brake (<NUM>), preferably a disc brake of a commercial vehicle, the vehicle brake (<NUM>) comprising:
a brake pad back plate (<NUM>) for carrying a brake pad (<NUM>),
wherein the vehicle brake (<NUM>) further comprises a wear indication device (<NUM>) for indicating a wear condition of a brake pad (<NUM>) comprising:
a fixing section (<NUM>) for fixing the wear indication device (<NUM>) to a brake pad back plate (<NUM>),
a sensor head (<NUM>) associated to the fixing section (<NUM>), and
a channel (<NUM>) for receiving a signal cable (<NUM>) within the sensor head (<NUM>),
wherein the channel (<NUM>) is configured to receive two signal cables (<NUM>', <NUM>"), wherein the channel (<NUM>) is a double channel having a first section (<NUM>) for the first cable (<NUM>'), and a second section (<NUM>) for the second cable (<NUM>"), wherein the first and second sections (<NUM>, <NUM>) are positioned adjacent to each other radially with respect to their center axis, wherein the center axis of the first signal cable (<NUM>') has a distance
to the fixing section (<NUM>) that is greater than a distance between the center axis of the second signal cable (<NUM>") and the fixing section (<NUM>), characterized in that
the respective cross-sections of the first and the second
sections (<NUM>, <NUM>) at least partially overlap, such that the channel (<NUM>) has a narrow necking area (<NUM>) partly separating the first section (<NUM>) from the second section (<NUM>) by means of at least one protrusion (<NUM>), preferably two opposing protrusions (<NUM>) in the sensor head (<NUM>) projecting inwardly into the double channel.