SENSOR DEVICE

Description

[0001] The invention relates to a sensor device for coating inspection of a disc in the context of a coating process, comprising a first optical sensor system for determining the layer thickness of the coating applied to the disc and a rotation device for rotating the disc, as well as a coating method for a disc, in particular a brake disc, with a coating inspection for determining the layer thickness of the coating applied to the disc.

[0002] In current discussions regarding the minimization of exhaust emissions in city centers, some of which originate from vehicles, particulate matter pollution plays a significant role. Of particular relevance here are the components PM10 and PM2.5, which are considered pollutants that pose a risk to human health.

[0003] Besides a multitude of causes, such as combustion processes in power plants or heating systems, road traffic in urban areas also contributes to particulate matter pollution. The main culprits here are combustion engines, tire abrasion, and the abrasion generated by the braking system.

[0004] One way to reduce emissions generated during braking is to apply a hard metal coating to brake discs. Compared to a conventional brake disc, this can achieve a reduction of up to 90% in abrasion and therefore in particulate matter.

[0005] Currently, two methods are commonly used for this purpose. The first is called HVOF (high velocity oxygen fuel) flame spraying, and the second is called laser cladding, which can be translated as laser welding. With both application methods, it is essential that the layers applied are as uniform and defect-free as possible.

[0006] Laser cladding will be examined in more detail below. In this process, a laser heats a substrate area of ​​a disk, and a melt pool is created by adding a powder or wire, which is also melted by the laser. This builds up another layer, which is then fused to the substrate. The layer buildup typically occurs in several cycles, resulting in multiple layers. Overall, such a disk is usually coated with several layers in a spiral pattern from the inside out.

[0007] Achieving a uniform layer thickness without defects is essential for coating quality. Therefore, it is necessary to inspect the coating process and, if necessary, eliminate any defects in a second step. This optimizes the manufacturing process, resulting in the most uniform and optimal layer thicknesses possible. Overall, this saves material and time, as otherwise, uneven layer thicknesses would have to be painstakingly removed or leveled in a subsequent grinding process.

[0008] Laser coating processes for brake discs typically employ a system setup in which the brake disc to be coated, along with its hub bores, is held in a fixture and rotated. The laser coating device is stationary relative to the brake disc but can be moved radially around it. During the coating process, the brake disc is rotated at a specific speed, allowing, for example, a spiral coating to be applied by the coating device, which moves radially from the inside out.

[0009] US patent 2009 / 061075 A1 discloses a coating measurement system in which the layer thickness is determined by differential measurement using a laser measuring device. Another method is known from DE 10 104 684 A1, in which the layer thickness is determined by measuring the intensity of the radiation transmitted through the layer being measured.

[0010] Other similar procedures are known, for example, from DE 10 2005 009 262 A1 or US 2018 / 172430 A1.

[0011] The invention is based on the Task The basis is to specify a sensor device and a coating process suitable for efficiently monitoring a coating process of a disc.

[0012] This problem is solved according to the invention by a sensor device having the features of claim 1 and a coating method having the features of claim 15.

[0013] Advantageous embodiments of the invention are specified in the dependent claims, in the description and in the figures and their explanation.

[0014] In the sensor system according to the invention, the first optical sensor system is designed to simultaneously determine at least one first position-related measured value and a second position-related measured value. The first and second position-related measured values ​​can represent the distance of the first sensor system to the surface of the disk.

[0015] Furthermore, the first sensor system is configured to determine the first position-related measurement from a coated area of ​​the disk and the second position-related measurement from an uncoated area of ​​the disk. The first optical sensor system also includes at least one linear guide extending from a central area of ​​the disk to an edge area. Additionally, a control and evaluation unit is provided for calculating the disk's layer thickness at the position of the first position-related measurement using the first and second position-related measurements.

[0016] A key concept of the invention is the recognition that an absolute measurement of layer thickness is extremely difficult in relatively thick and optically opaque layers. Furthermore, various material properties play a role in the measurement, which can differ depending on the selected coating. These include, among others, the magnetization properties, the electrical conductivity, and the penetration and refraction behavior of the materials used with respect to specific wavelengths, such as the refractive properties of layer boundaries with respect to wavelength or spectra.

[0017] In principle, methods that take this property into account could be used to determine the layer thickness, but these have the significant disadvantage of a relatively low measurement frequency and a large measurement spot diameter. This means that the method is relatively slow and does not offer high-precision spatial resolution.

[0018] Therefore, according to the invention, a differential measurement is proposed to determine the layer thickness. This means that, to determine the layer thickness, a first position-related measurement and a second position-related measurement are taken. The difference between the two position-related measurements is then calculated, and conclusions about the layer thickness are drawn from this. Due to the very precise spatial resolution, a surface profile can also be created, so that even topographical errors can be detected.

[0019] The first optical sensor system used here, as described, features a linear guide to move the sensor system from an inner or central area of ​​the disc to an edge area. This allows any point on the disc to be coated to be reached, taking into account the additional rotation of the disc.

[0020] Another advantage of using the difference between two position-related measurements is that it reduces or eliminates any wobble of the disk, which can occur due to suboptimal clamping, when determining the layer thickness. The difference between the two measurements numerically compensates for any wobble in the two position-related measurements.

[0021] It is advantageous if the first optical sensor system has a first optical sensor for determining the first position-related measurement value and a second optical sensor for determining the second position-related measurement value.

[0022] The use of an optical sensor offers the advantage of achieving a relatively high measurement frequency, allowing for quick and efficient determination of the coating thickness. This is particularly beneficial for reducing the overall production time, including coating inspection. Furthermore, an inline process can be implemented, where the coating thickness is determined simultaneously during the coating process. With very slow, low-frequency measurement methods, this could only be done offline, i.e., after the coating process has been completed.

[0023] In principle, the two optical sensors can be positioned at any location relative to the disk. For example, the first and second optical sensors can be placed on opposite sides of the disk in opposite positions. In this case, the first sensor on the coated side determines the distance relative to a fixed point, such as that of the first optical sensor system. Similarly, the second optical sensor on the opposite side of the disk also determines the distance. By comparing these measurements with previous ones, the additional layer thickness can be calculated by taking the difference between the distances into account. This positioning also offers the advantage that any wobble of the disk is compensated for by the positioning of the two sensors.

[0024] Another possibility is to arrange the first and second optical sensors on the same side of the disk, particularly on the first side, in radially offset positions. In this case, the distance between the disk and the first optical sensor system is determined with respect to the same side of the disk. If the first optical sensor is directed at a coated area and the second optical sensor at an uncoated area, the layer thickness can be determined from the difference in the sensors' distances to a fixed point or plane. In this case as well, wobble would be compensated for, since the wobble behavior would simultaneously affect both measured values, those of the first and the second optical sensor.

[0025] In a further embodiment, a third and fourth optical sensor can be provided, arranged on a second side of the disk at radially offset positions. In other words, these two sensors are located opposite the first and second radially spaced sensors. In this case, for example, simultaneous measurement can be performed when the coating is applied to both sides of the disk at the same time. Furthermore, this arrangement offers additional measurement accuracy, since, in addition to comparing the measured values ​​on the same side, the measured values ​​on the opposite side can also be taken into account. This further improves the measurement accuracy.

[0026] A confocal chromatic sensor, for example, can be used as the first, second, third, and / or fourth optical sensor. This sensor has a high temporal resolution, making inline measurement or examination of the coating possible.

[0027] Another advantage of this type of sensor is that it has a relatively high spatial resolution, so that the layer thickness at a position can be calculated or determined very accurately.

[0028] In a further embodiment, the first optical sensor system can include a first triangulation sensor arranged on a first side of the disk for measuring in the radial direction of the disk, for simultaneously determining the at least first position-related measured value and the second position-related measured value. For example, such a triangulation sensor can have a measuring width of a few millimeters. It is arranged or guided such that one part of the sensor scans the coated area, while another part scans an uncoated area. Thus, two position-related measured values ​​are also determined, which can be combined analogously to the use of two optical sensors to determine the increase in layer thickness.

[0029] In a further development of this embodiment, the first optical sensor system can have a second triangulation sensor on a second side of the disk, arranged at a position opposite the first triangulation sensor. In this case, four measured values ​​can be determined simultaneously, which can then be combined analogously to the use of four separate optical sensors to generate the increase in layer thickness and a height profile.

[0030] Furthermore, it is advantageous if each sensor has a linear guide and / or a positioning device. The linear guide is preferably arranged radially, so that it allows the sensor to be moved from an inner area of ​​the disk to an outer area. By additionally rotating the disk itself, every point on the disk can thus be scanned. The positioning device, which can also be provided, serves to position the sensor at an optimal distance from the side of the disk to be measured.

[0031] If several sensors are arranged on the same side of the disc, these sensors can have a common linear guide and / or a common positioning device.

[0032] This design is particularly advantageous when one sensor scans a coated area and another sensor scans an uncoated area of ​​the disc on the same side. This allows both sensors to be mounted on the same linear guide and the same feed mechanism, thus improving the measurement process.

[0033] Within the scope of the invention, a coated area of ​​a disk can be understood to be, in particular, an area that has already been provided with at least one coating. In contrast, an uncoated area can be understood to be an area that is either not yet coated or has a lower coating thickness or number of coatings than the coated area that is to be scanned.

[0034] It is advantageous if a second optical sensor system with a line scan camera is additionally provided on one or both sides of the disk, which has a measuring range that extends essentially over the entire radius of one side of the disk. It is already possible to scan the entire surface of a disk with the first optical sensor system. However, this takes a relatively long time, partly due to the high spatial resolution. Therefore, according to the invention, it is preferred that the scanning with the first sensor system is performed only at points or in strips, and only the layer thickness is determined. To enable further defect detection, possibly also for the pre-selection of areas to be scanned with the first optical sensor system, the second optical sensor system with a line scan camera can be provided.This can, for example, feature a light-dark field illumination that is alternately switched by rotating. This allows for very rapid surface imaging, which can be used for defect detection.

[0035] Based on any detected errors, the layer thickness can then be determined more precisely using the first sensor device, and an error can be verified or rejected.

[0036] Preferably, a device for determining the position of the disk's center relative to the first and / or second optical sensor system is provided. Such a device serves to define a reference point for the first and / or second optical sensor systems. If the disk's center point can be determined, the relative position of the first and / or second optical sensor system can be determined using the device for determining the center's position, thus enabling the generation of reliable data.

[0037] To achieve even greater accuracy, a device for determining the angular position of the disk can also be provided. Together with the exact angular position and a zero point, this allows for precise localization of the measured values ​​in conjunction with the first and / or second optical sensor system.

[0038] Preferably, the control and evaluation unit is designed for the continuous and / or discontinuous determination of position-related measured values. Several options are available for the final determination of these position-related measured values. One option is the so-called inline method, in which the position-related measured values, and thus the layer thickness, are determined concurrently with the coating of the disk. Another option is to first coat one side of the disk or a specific area and then determine the applied layer thickness.

[0039] In principle, the first sensor device can scan any point on a disk or its surface. However, this can be quite time-consuming, depending on the sensor system used. Therefore, the disk can be scanned in a spiral pattern with gaps between the scanning strips. Other scanning curves are also possible. The choice between continuous scanning using position-based measurements or scanning specific areas depends on the exact application.

[0040] The sensor device according to the invention is particularly well suited for use in a coating system for brake discs. As previously explained, it is advantageous to apply a high-strength coating, thereby reducing the amount of fine dust generated by abrasion. The sensor device according to the invention can be used to ensure that the coating is uniform and of sufficient thickness.

[0041] In the coating method according to the invention for a disc, in particular a brake disc, with a coating inspection for determining the layer thickness of the coating applied to the disc, at least one first position-related measured value and one second position-related measured value are simultaneously determined using a first optical sensor system. The first and the second position-related measured values ​​represent the distance of the first optical sensor system to the surface of the disc, wherein the first position-related measured value is determined from a coated area of ​​the disc and the second position-related measured value from an uncoated area of ​​the disc. The layer thickness of the disc at the position of the first position-related measured value is calculated using the first and the second position-related measured values.In order to be able to examine any point on the disc, the disc can be rotated during the coating inspection using a rotation device and the first optical sensor system can be moved by means of at least one linear guide which extends from a central area of ​​the disc to an edge report.

[0042] The invention is explained in more detail below with reference to schematic embodiments and the figures. These show: Fig. 1 is a schematic representation of a first embodiment of a sensor device according to the invention; Fig. 2 is a schematic representation of a second embodiment of a sensor device according to the invention; and Fig. 3 is a schematic representation of a third embodiment of a sensor device according to the invention.

[0043] In Fig. 1Figure 1 shows a first embodiment of a sensor device 100 according to the invention. The sensor device according to the invention comprises a first optical sensor system 110 consisting of two parts. Each part of this sensor system 110 is arranged on opposite sides of a disc 50, which may in particular be a brake disc. As already described, the purpose of the sensor device 100 according to the invention is to determine the layer thickness of a coating on the disc 50.

[0044] Each subunit of the first optical sensor system 110 has an optical sensor 111, 112. Each of these sensors 111, 112 is attached to a linear version 131, 132 and additionally has a feed mechanism 141, 142.

[0045] For example, a confocal chromatic sensor can be used as an optical sensor 111, 112, which determines the distance to the corresponding side of the disk 50.

[0046] Furthermore, a second optical sensor system 20 is provided, which can, for example, be designed in the form of a line scan camera. This line scan camera is selected such that it can monitor the area from the center to the outer radial end of the disk 50.

[0047] Furthermore, an additional line scan camera 60 is provided in the central area, that is, in the center of the disk 50. This camera serves to determine the exact center point of the disk 50, so that the measured values ​​obtained by means of the first optical sensor system 110 and the second optical sensor system 20 can be specified relative to a fixed point. This fixed point is, for example, the mounting point of the disk 50.

[0048] Not shown here is a rotation device which makes it possible to rotate the disk 50 so that the two sensor systems 110 and 20 can remain stationary during the measurement processes or only be moved in a radial direction.

[0049] The functionality of the two sensor systems 110 and 20 will be discussed in more detail below.

[0050] The first optical sensor system 110, as already described, has two optical sensors 111 and 112, which are arranged on opposite sides of the disk 50 at essentially opposite positions. Using the two positioning devices 141 and 142, the two optical sensors 111 and 112 are brought to an optimal distance from the surface of the disk 50, enabling a good, reliable, and efficient measurement. The respective distance to the disk 50 is then determined using the two sensors 111 and 112.

[0051] In the embodiment according to Fig. 1 This measurement is repeated when a coating 51 is applied to one side of the disk 50. The thickness of the coating can be determined from the measured distance between the two optical sensors 111 and 112 at different times, once with and once without the coating.

[0052] Using the first optical sensor system 110, it is possible to determine the layer thickness during the coating of the disk 50. However, due to the sensors used, it is not economical to divide every point on the disk 50 to achieve a high-precision resolution of the layer thickness distribution. Preferably, the disk 50 is scanned in a spiral or meandering pattern. However, strip-shaped or circular scanning is also possible, in which several circles are scanned at different distances from the center.

[0053] To perform a measurement, the disk 50 is rotated via the rotation device and the two sensors 111, 112 are moved by means of the linear guides 131, 132.

[0054] To further improve measurement accuracy and detect any coating defects across the entire surface of the disc 50, a second optical sensor system 20 is provided. As previously described, this system consists of a line scan camera positioned to capture images and obtain measured values ​​from the center to the outer edge of the disc 50. During rotation of the disc, values ​​are continuously acquired via the second optical sensor system 20, for example, using light / dark defect detection. These values ​​can then be used for defect detection and quality control to determine whether the coating is unsuccessful or defective at specific locations.

[0055] In Fig. 2 Figure 200 shows another embodiment of a sensor device according to the invention.

[0056] Identical components are used in this process. Fig. 1 Designated with the same reference symbols or not described again.

[0057] The sensor device 200 shown according to the invention differs from the device 100 in that Fig. 1 by a slightly differently designed first optical sensor system 210.

[0058] In the embodiment shown here, this consists of a total of four optical sensors 211, 212, 213, 214. Two optical sensors 211, 212 and 213, 214 are arranged on the same side of the disk 50. The two sensors 211, 212 and 213, 214 arranged on the same side of the disk 50 share a common linear guide 231, 232 and a common feed mechanism 241, 242.

[0059] The embodiment shown enables so-called inline measurement. This means that the applied layer thickness can be determined during the coating process of the disk 50. For this purpose, the two optical sensors 211, 212 and 213, 214, which are located on the same side of the disk 50, are arranged such that one optical sensor 211, 213 scans a coated area and the adjacent optical sensor 212, 214 scans an uncoated area. The layer thickness can then be determined by the difference between the two measurements.

[0060] Finally, with reference to Fig. 3 A third embodiment of the sensor device 300 according to the invention is described. Here too, the sensor device 300 differs from the previously described embodiments only in the exact design of the first optical sensor system 300.

[0061] The first optical sensor system 300 in this case comprises two optical sensors 311, 312 arranged on opposite sides of the disk 50. The optical sensors 311, 312 are triangulation sensors. Each of these is mounted on a linear guide 331, 332 with a corresponding feed 341, 342. The triangulation sensors 311, 312 are configured to monitor an area of ​​the disk 50 where one area has a coating 51 and the other area has no coating. This makes it possible to determine the layer thickness from the measured values ​​obtained via the sensors 311, 312.

[0062] A further advantage of the sensor device 100, 200, 300 according to the invention, which results from the fact that sensors 111, 112, 211, 212, 213, 214, 311, 312 are arranged on both sides of the disk 50 and the measured values ​​determined by them are used to determine the layer thickness, is that any wobbling which may occur due to a non-optimal clamping of the disk 50 can be factored out using the measured values.

[0063] With the sensor device according to the invention, it is possible to obtain highly accurate values ​​for determining the layer thickness quickly and efficiently.

Claims

1. Sensor device (100, 200, 300) for examining the coating of a disc (50) as part of a coating process, comprising a first optical sensor system (110, 210, 310) for determining the layer thickness of the coating (51) applied to the disc (50), comprising a rotation apparatus for rotating the disc, and comprising a control and analysis apparatus, wherein the first optical sensor system (110, 210, 310) is designed to identify at least one first position-based measured value and one second position-based measured value, wherein the first and the second position-based measured value describe the distance between the first sensor system (110, 210, 310) and the surface of the disc, wherein the first sensor system (110, 210, 310) is configured to identify the first position-based measured value of a coated region of the disc (50) and the second position-based measured value of an uncoated region of the disc (50), wherein a control and analysis apparatus is configured for calculating a layer thickness of the disc (50) at the position of the first position-based measured value with the aid of the first and the second position-based measured value, characterized in that the first optical sensor system (110, 210, 310) is designed to simultaneously identify at least the first position-based measured value and the second position-based measured value, and in that the first optical sensor system (110, 210, 310) comprises at least one linear guide (131, 132, 231, 232, 331, 332), which extends from a central region of the disc (50) to an edge region.

2. Sensor device (100, 200) according to claim 1, characterized in that the first optical sensor system (110, 210) comprises a first optical sensor (111, 211) for identifying the first position-based measured value and a second optical sensor (112, 212) for identifying the second position-based measured value.

3. Sensor device (100, 200) according to claim 2, characterized in that the first and the second optical sensor (111, 112) are arranged in opposite positions on opposite sides of the disc (50).

4. Sensor device (200) according to claim 2, characterized in that the first and the second optical sensor (211, 212) are arranged in a position so as to be radially offset from one another on a first side of the disc (50).

5. Sensor device (200) according to claim 4, characterized in that a third (213) and a fourth (214) optical sensor are provided, which are arranged in positions so as to be radially offset from one another on a second side of the disc.

6. Sensor device (100, 200) according to claim 1, characterized in that at least the first and the second optical sensor (111, 112, 211, 212) are designed as confocal chromatic sensors.

7. Sensor device (300) according to claim 1, characterized in that the first optical sensor system (310) for simultaneously identifying the at least one first position-based measured value and the second position-based measured value comprises a first triangulation sensor (311) arranged on a first side of the disc for the measurement in the radial direction of the disc (50).

8. Sensor device (300) according to claim 7, characterized in that the first optical sensor system (300) comprises a second triangulation sensor (312) arranged in a position opposite the first triangulation sensor (311) on a second side of the disc (50).

9. Sensor device (100, 200, 300) according to any one of claims 2 to 8, characterized in that each sensor (111, 112, 211, 212, 213, 214, 311, 312) comprises a linear guide (131, 132, 231, 232, 331, 332) and / or an adjustment apparatus (141, 142, 241, 242, 341, 342).

10. Sensor device (100, 200, 300) according to any one of claims 2 to 6, 8 or 9, characterized in that sensors (111, 112, 211, 212, 213, 214, 311, 312) arranged on the same side of the disc (50) comprise a common linear guide (131, 132, 231, 232, 331, 332) and / or adjustment apparatus (141, 142, 241, 242, 341, 342).

11. Sensor device (100, 200, 300) according to any one of claims 1 to 10, characterized in that a second optical sensor system (20) comprising a line scan camera is provided on one or both sides of the disc (50) and comprises a measuring region that extends substantially over the entire radius of one side of the disc (50).

12. Sensor device (100, 200, 300) according to any one of claims 1 to 11, characterized in that an apparatus is provided for identifying the position of the center of the disc (50) relative to the first optical sensor system (110, 210, 310).

13. Sensor device (100, 200, 300) according to any one of claims 1 to 12, characterized in that an apparatus is provided for identifying the angular position of the disc (50).

14. Coating device for a brake disc, characterized by a sensor device (100, 200, 300) according to any one of claims 1 to 13.

15. Coating method for a disc, in particular a brake disc, comprising inspecting the coating for determining the layer thickness of the coating (51) applied to the disc (50), wherein at least one first position-based measured value and one second position-based measured value are identified by a first optical sensor system (110, 210, 310), wherein the first and the second position-based measured value describe the distance between the first optical sensor system (110, 210, 310) and the surface of the disc (50), wherein the first position-based measured value of a coated region of the disc (50) and the second position-based measured value of an uncoated region of the disc (50) are identified, wherein a layer thickness of the disc (50) at the position of the first position-based measured value is calculated with the aid of the first and the second position-based measured value, wherein the disc can be rotated by means of a rotation apparatus while the coating is being inspected, characterized in that at least the first position-based measured value is identified by a first optical sensor system (110, 210, 310) and the second position-based measured value is simultaneously identified by the first optical sensor system (110, 210, 310), and in that the first optical sensor system (110, 210, 310) can be moved by means of at least one linear guide (131, 132, 231, 232, 331, 332), which extends from a central region of the disc (50) to an edge region.