Measuring device

Abstract

The invention relates to a measuring device (2) for measuring the topography of the surface of a workpiece, in particular a brake disc (4), and includes a measuring sensor (10) for probing the surface of the workpiece. The invention provides that the measuring sensor (10) is associated with at least one air bearing element (12) with at least one bearing surface for air-supporting the measuring sensor (10) on the workpiece to be measured. The invention is characterized in that a plurality of spaced-apart air bearing elements (12, 14) are provided for air-supporting the measuring sensor (10) at mutually spaced locations on the workpiece.

Description

[0001] The invention relates to a measuring device of the type mentioned in the preamble of claim 1 for measuring the topography of the surface of a workpiece, in particular a brake disc.

[0002] Corresponding measuring devices have at least one measuring sensor for probing the surface of the workpiece, which may, for example, be a tactile measuring sensor.

[0003] To increase the wear resistance of cast iron brake discs and to prevent abrasion that causes fine dust, it is known to coat brake discs with a wear-resistant layer. This coating can be applied, for example, by welding a powder-based additive layer onto the brake disc using a high-performance laser.

[0004] DE 10 2006 022 882 A1 describes a method and a device for measuring the thickness of thin films with a measuring probe, which comprises a housing that accommodates at least one sensor element, the longitudinal axis of which lies in particular in a longitudinal axis of the housing, wherein at least during the measuring process a gaseous medium is supplied to a supply opening of the measuring probe at a measuring surface, which is supplied via at least one connecting channel adjoining the supply opening to one or more outlet openings provided on an end face of the measuring probe facing the measuring surface, and that at least one mass flow of the gaseous medium flowing out of one or more outlet openings is directed towards the measuring surface and that the measuring probe is held without contact with the measuring surface during the measuring process.

[0005] The invention is based on the objective of providing a measuring device of the type mentioned in the preamble of claim 1, which is particularly well suited for measuring brake discs, especially laser-coated ones.

[0006] This problem is solved by the combination of features of claim 1 or 13. The dependent claims contain advantageous further developments.

[0007] The air bearing of the measuring sensor, achieved in this way, keeps it at a constant distance from the workpiece surface during movement relative to the workpiece being measured. This prevents, for example, coarser surface features, such as runout on a brake disc, from affecting the measurement accuracy of finer surface features, such as waviness. In other words, the air bearing pneumatically tracks the surface during relative movement between the workpiece and the sensor. This function is equivalent to that of a sliding shoe on a stylus measuring instrument.

[0008] In combination with a preferably used pneumatic measuring sensor, this enables completely non-contact measurement of the surface of workpieces. This is particularly advantageous when measuring highly wear-resistant surfaces, such as a laser-coated brake disc, as it completely avoids wear on components of the measuring device caused by contact with the workpiece surface.

[0009] The measuring device according to the invention is suitable for measuring any workpiece. The measuring device according to the invention is particularly well suited for measuring brake discs, especially laser-coated ones, in that, for example, local irregularities in the coating thickness of a brake disc coating can be measured with high accuracy.

[0010] According to the invention, it is generally sufficient, within the scope of the respective requirements and circumstances, if the measuring device according to the invention comprises a single measuring sensor. An advantageous further development of the invention provides that a plurality of spaced-apart measuring sensors are provided for probing the workpiece at several points.

[0011] To realize the basic principle of the invention, it is generally sufficient if a single air bearing element is assigned to the measuring sensor or sensors. To improve the air bearing of the measuring sensor or sensors on the workpiece to be measured, another advantageous embodiment of the invention provides that a plurality of spaced-apart air bearing elements are provided for the air bearing of the measuring sensor or sensors at mutually spaced locations on the workpiece.

[0012] The integration of the inventive combination of air bearing element and measuring sensor into the mechanical structure of a measuring device can be carried out in a variety of ways, depending on the specific requirements and circumstances. An advantageous embodiment of the invention provides that the air bearing element(s) is connected to a support arrangement with at least one support, which carries the measuring sensor(s). The support arrangement can be constructed in one or more parts and may have one or more supports. The measuring sensor(s) and the air bearing element(s) are preferably rigidly connected to the support arrangement. A rigid connection in this sense means that, during measurement, the spatial arrangement of the measuring sensor(s) and the air bearing element(s) on the support arrangement remains within the limits of measurement accuracy.the wearer is not altered.

[0013] Another advantageous embodiment of the invention provides that the air bearing element or elements are an aerostatic air bearing element.

[0014] In principle, the measuring sensor of the measuring device according to the invention can be a tactile sensor. To avoid wear on the measuring sensor due to contact with the surface to be measured, an advantageous embodiment of the invention provides that the measuring sensor, or each measuring sensor, is a non-contact measuring sensor.

[0015] A further development of the aforementioned embodiment provides that the measuring sensor(s) is, or is, an optical or pneumatic sensor. Suitable measuring sensors are available as standard assemblies with high measuring accuracy. According to the invention, the use of a pneumatic measuring sensor is particularly advantageous because, in a corresponding embodiment, both the measuring sensor and an aerostatic air bearing element are operated with compressed air.

[0016] Means for the relative movement of the workpiece relative to the measuring sensor of the measuring device can be designed in a variety of ways, depending on the specific requirements and circumstances. For example, to measure a brake disc, it can be rotated around its axis relative to the measuring sensor using a rotary device.

[0017] Another advantageous embodiment of the invention provides that, for the simultaneous measurement of two opposite surfaces of a plate-shaped or disc-shaped workpiece, at least two measuring sensors with associated air bearing elements are provided, arranged such that the workpiece is probed simultaneously on both surfaces. In this way, two surfaces of a workpiece can be measured at the same time. This saves time and setup costs.

[0018] Another advantageous embodiment of the invention provides that the support arrangement is movably connected to a base body of the measuring device and that sensor means are provided for detecting movements of the support arrangement, in particular movements perpendicular to the bearing surface, relative to the base body. By means of the air bearing, the distance between the measuring sensor and the surface of the component being measured is kept constant according to the invention, coarser or longer-wavelength components of the surface topography can be reconstructed from the output signals of the sensor means.

[0019] According to another advantageous embodiment of the invention, the measuring sensor(s) and the sensor means are connected to an evaluation unit which is designed and configured such that the topography of the workpiece surface is reconstructed from the output signals of the measuring sensor(s) and the sensor means. In this way, for example, both finer and coarser components of the surface topography of a workpiece can be measured.

[0020] When measuring plate-shaped or disc-shaped workpieces, for example brake discs, it is advantageous for the air bearing element or elements to form a planar air bearing with a planar bearing surface, as provided for in another advantageous embodiment of the invention.

[0021] If a measuring arrangement has three or more air bearing elements, the geometric configuration of the air bearing elements can be selected within wide limits according to the respective requirements and circumstances. An advantageous embodiment of the invention provides that at least one measuring arrangement has three air bearing elements whose geometric centers of their preferably circular bearing surfaces are arranged at the vertices of a preferably isosceles triangle. In this way, the mounting of the measuring sensor(s) on the workpiece to be measured is further improved.

[0022] A movable connection between the support arrangement and the base body of the measuring device can be designed in various ways. An advantageous embodiment of the invention provides that the movable connection between the support arrangement and the base body is formed by a gimbal suspension. This further improves the tracking of the measuring sensor(s).

[0023] A use of a measuring device according to the invention for measuring brake discs is specified in claim 13. As explained above, a combination of an air bearing element with a pneumatic measuring sensor enables completely contactless measurement of brake discs.

[0024] The invention is explained in more detail below with reference to the accompanying highly schematic drawing and exemplary embodiments. It is evident to those skilled in the art that the individual features of each embodiment, considered separately, further develop that embodiment, i.e., independently of the other features. Thus, it is also evident to those skilled in the art that all the features described, illustrated in the drawing, and claimed in the patent claims, considered separately and in any technically meaningful combination, constitute the subject matter of the invention, irrespective of their grouping in the patent claims and their cross-references, and irrespective of their specific description or representation in the drawing.The subject matter and disclosure content of the present application include subcombinations of the patent claims in which at least one feature of a patent claim is omitted or replaced by another feature.

[0025] It shows: Fig. 1 in a schematic diagram a first embodiment of a measuring device according to the invention, Fig. 2 in the same representation as Fig. 1 a second embodiment of a measuring device according to the invention and Fig. 3 in a perspective view a third embodiment of a measuring device according to the invention

[0026] The invention is described below with reference to Fig. 1 to Fig. 3. This is explained in more detail using exemplary embodiments. Identical or corresponding components are marked with the same or corresponding reference numerals.

[0027] In Fig. Figure 1 shows a first embodiment of a measuring device 2 according to the invention in a schematic diagram. The components of this device are shown purely schematically in the drawing to illustrate the basic principle of the invention. In the illustrated embodiment, the measuring device 2 is designed as a pneumatic measuring device and serves to measure a brake disc 4, which is also shown purely schematically in the drawing.

[0028] The brake disc 4 is rotatably mounted relative to the measuring device 2 about an axis of rotation 6 by means of a rotary device which is not shown in detail in the drawing.

[0029] The measuring device 4 has a support arrangement with a carrier 8, which carries a measuring sensor 10 for probing the surface of the brake disc 4. In the illustrated embodiment, the measuring sensor 10 is designed as a pneumatic measuring sensor. The design and function of corresponding pneumatic measuring devices and measuring sensors are generally known to those skilled in the art, for example and in particular from DIN 2271, and are therefore only explained in more detail here to the extent necessary for understanding the invention.

[0030] Fig. Figure 1 shows the measuring device 2 in a measuring position in which the brake disc 4 is measured using the measuring device 2.

[0031] According to the invention, an air bearing element 12 is associated with the measuring sensor 10. In this embodiment, the air bearing element 12 forms a planar air bearing with a flat bearing surface and is designed as an aerostatic air bearing element. In addition to the air bearing element 12, the illustrated embodiment provides a further air bearing element 14, which is spaced apart from the air bearing element 12 in the radial direction of the axis of rotation 6. In the illustrated embodiment, the air bearing elements 12 and 14 each define a circularly bounded bearing surface (see also Fig. 3).

[0032] The design and function of corresponding air bearing elements are generally known to those skilled in the art and are therefore only explained here in more detail to the extent necessary for understanding the invention. For example, and in particular, corresponding air bearing elements can be designed as sintered air bearings, which have a bearing body made of porous bearing material. The bearing body is pressurized with compressed air, the porous bearing material ensuring a uniform distribution of the compressed air.

[0033] In addition to the measuring sensor 10, the measuring device 2, in the illustrated embodiment, has two further measuring sensors 16, 18, which, in this embodiment, are spaced apart from the measuring sensor 10 in the radial direction of the axis of rotation 6 and arranged on a radial line. Due to this arrangement, the brake disc 4 is measured simultaneously at points spaced apart in the radial direction during the measurement. Accordingly, when the brake disc 4 rotates relative to the measuring device 2, the brake disc 4 is measured along three radially spaced circumferential lines. Other arrangements of the measuring sensors are possible within broad limits.

[0034] The measuring sensors 10, 16, 18 are attached to a central web 20 of the support 8, while the air bearing elements 12, 14 are attached to the ends of angled arms 22, 24 of the support 8. The geometric configuration of the support 8 shown in the drawing is purely schematic and exemplary.

[0035] The dimensions of the bearing surface of the air bearings formed by the air bearing elements 12, 14 are very different from the measuring accuracy of the measuring sensors 10, 16, 18.

[0036] In the illustrated embodiment, the measuring arrangement 26 formed by the measuring sensors 10, 16, 18 is movably connected to a base body of the measuring device 2 (not shown in detail). For this purpose, one end 28 of a two-armed lever 32, mounted at a pivot point 30, is pivotally connected to the central web of the support 8. Sensor means 36 are assigned to the other end 34 of the lever 32, which detect a rotation of the two-armed lever 32 about the pivot point 30 and thus a movement of the measuring arrangement 26 relative to the surface of the brake disc 4. This configuration of the connection between the measuring arrangement and the base body is also purely schematic and exemplary.

[0037] The invention functions as follows: In the measuring operation of the measuring device 2, the air bearing elements 12, 14 are actuated or operated via a compressed air source in such a way that a constant distance is established between the air bearing elements 12, 14 and the brake disc 4.

[0038] The pneumatic measuring sensors 10, 16, 18 probe the brake disc 4 at points spaced apart in the radial direction and measure finer structures in the topography of the surface of the brake disc 4, for example with a measuring range such as is used in the measurement of waviness.

[0039] To measure the topography of the surface of the brake disc 4 facing the measuring arrangement 26, the brake disc 4 is rotated about the axis of rotation 6, so that the measuring sensors 10, 16, 18 measure the surface of the brake disc 4 along circumferential lines concentric to the axis of rotation 6.

[0040] By means of the air bearing elements 12, 14, the distance of the measuring sensors 10, 16, 18 to the surface of the brake disc 4 is kept constant within the limits of the measuring accuracy, a pneumatic tracking of the measuring sensors 10, 16, 18 is effected with respect to the surface of the brake disc 4 and a function is realized which is analogous to the function of a sliding skid in a stylus measuring device.

[0041] In this way, a contactless measurement of the surface of the brake disc 4 is achieved with high measuring accuracy.

[0042] Movements of the measuring arrangement 26 perpendicular to the bearing surface are sensed by the sensor means 36 in the form of a rotation of the two-armed lever 32 about the pivot point 30, so that coarser structures in the topography of the surface of the brake disc 4 can be measured from the output signals of the sensor means 36.

[0043] The evaluation is carried out by an evaluation device, which is not shown for the sake of simplicity, to which both the output signals of the measuring sensors 10, 16, 18 and the output signals of the sensor means 36 are fed.

[0044] In Fig. Figure 2 shows a second embodiment of a measuring device 2 according to the invention, which differs from the embodiment according to Figure 2. Fig. 1 differs in that, in addition to the measuring arrangement 26, a further measuring arrangement 26' is provided, which is arranged in a mirror image with respect to the central plane of the brake disc 4 extending into the plane of the drawing. The structure of the further measuring arrangement 26' corresponds to that of the measuring arrangement 26, and its components are provided with reference numerals that correspond to the reference numerals of the components of the measuring arrangement 26. The operating principle of the measuring device 2 in the second embodiment is fundamentally the same as in the first embodiment, except that, compared to the embodiment according to Fig. One advantage is that both sides of the brake disc 4 can be measured simultaneously. Furthermore, with the second embodiment, it is possible to measure both the thickness of the brake disc 4 and thickness variations along its surface.

[0045] In Fig. Figure 3 shows a third embodiment, which differs from the embodiment according to Fig. 1 differs in that, in addition to the two air bearing elements 12, 14, a third air bearing element 38 is provided. As in the embodiment according to Fig. In the air bearing elements 12, 14, 38, a substantially circular bearing surface is defined, with the centers of the bearing surfaces being arranged at the vertices of an equilateral triangle in the illustrated embodiment. Preferably, the support 8 can be connected to the base body of the measuring device 2 via a gimbal suspension. A corresponding gimbal suspension, which has two rotary bearings with intersecting, mutually perpendicular axes of rotation, is known per se to those skilled in the art and is therefore not described in detail here.

[0046] While in the embodiment according to Fig. 1. The carrier 8 with the measuring sensor 10 can move in an angular direction, namely around the pivot point 30, away from the surface of the brake disc 4 or is guided along the surface, as is the case in the embodiment according to Fig. 3 along two angular directions defined by the axes of rotation of the gimbal suspension. In this way, the free mounting of the measuring sensor 10 on the brake disc 4 is further improved. Reference symbol list 2 Measuring device 4 brake discs 6 axis of rotation 8 carriers 10 measuring sensor 12 air bearing elements 14 air bearing element 16 measuring sensor 18 measuring sensor 20 central jetty of 8 22 Arm 24 Arm 26 Measuring setup 28 End of 32 30 pivot point of 32 32 two-armed lever 34 End of 32 36 Sensor devices 38 Air bearing element

Claims

[1] Measuring device (2) for measuring the topography of the surface of a workpiece, in particular a brake disc (4), with a measuring sensor (10) for probing the surface of the workpiece, wherein The measuring sensor (10) is associated with at least one air bearing element (12) with at least one bearing surface for the air bearing of the measuring sensor (10) on the workpiece to be measured, characterized by , that For the air bearing of the measuring sensor (10) at mutually spaced locations of the workpiece, a plurality of mutually spaced air bearing elements (12, 14) are provided. [2] Measuring device according to claim 1, characterized by , that a plurality of spaced measuring sensors (10, 16, 18) are provided for probing the workpiece at several points spaced apart from each other. [3] Measuring device according to claim 1, characterized by, that the or each air bearing element (12, 14) is connected to a support arrangement with at least one support (8) which carries the or each measuring sensor (10, 16, 18). [4] Measuring device according to one of the preceding claims, characterized by , that the or each air bearing element (12, 14) is an aerostatic air bearing element. [5] Measuring device according to one of the preceding claims, characterized by , that the or each measuring sensor (10, 16, 18) is a non-contact measuring sensor. [6] Measuring device according to one of the preceding claims, characterized by , that the or each measuring sensor (10, 16, 18) is an optical or pneumatic measuring sensor. [7] Measuring device according to one of the preceding claims, characterized by, that for the simultaneous measurement of two opposite surfaces of a plate-shaped or disc-shaped workpiece at least two measuring sensors (10, 16, 18; 10', 16', 18') together with associated air bearing element (12, 14; 12', 14') are provided, which are arranged in such a way that the workpiece is touched simultaneously on both surfaces. [8] Measuring device according to claim 3, characterized by , that the carrier arrangement is movably connected to a base body of the measuring device (2), wherein sensor means (36) are preferably provided for sensing movements of the carrier arrangement relative to the base body, in particular movements perpendicular to the bearing surface. [9] Measuring device according to claim 8, characterized by, that the or each measuring sensor (10, 16, 18) and the sensor means (36) are connected to an evaluation device which is designed and set up in such a way that the topography of the surface of the workpiece is reconstructed from output signals of the or each measuring sensor (10, 16, 18) and the sensor means (36). [10] Measuring device according to one of the preceding claims, characterized by , that the or each air bearing element (12, 14) forms a planar air bearing with a planar bearing surface. [11] Measuring device according to one of the preceding claims, characterized by , that at least one measuring arrangement (26) has three air bearing elements (12, 14, 38) which are arranged with the geometric centers of their preferably circularly bounded bearing surfaces on the vertices of a preferably isosceles triangle. [12] Measuring device according to claim 8 or 9, characterized by, that the movable connection between the support arrangement and the base body is formed by a gimbal suspension. [13] Use of a measuring device according to one of the preceding claims for measuring brake discs.

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