Measuring method and measuring system for measuring bores as well as precision machining machine with measuring system

Abstract

Measuring method for measuring the geometry of a bore in a workpiece using a measuring system (100) which has a measuring unit (110), which in its ready-to-use state has a measuring mandrel (120) which can be moved bidirectionally along a travel path parallel to a measuring mandrel axis (125) by means of a lifting drive (128); wherein the measuring mandrel (120) is calibrated at least once using a reference device (200) with at least one reference element (230-1, 230-2) of defined internal dimensions, by moving the measuring mandrel (120) by means of the lifting drive (128) into a calibration position in which a measuring sensor of the measuring mandrel (120) is arranged in the area of ​​the reference element (230-1, 230-2), characterized in that The reference device (200) is arranged in a neutral position outside the travel path of the measuring mandrel (120) during measuring operation such that the measuring mandrel (120) can be inserted into the bore to be measured without passing through the reference element (230-1, 230-2); the reference device (200) is moved from the neutral position to a calibration position in which the reference element (230-1, 230-2) is arranged in a calibration position coaxial to the measuring mandrel axis (125); and In the calibration position of the measuring mandrel (120), a calibration measurement is carried out to calibrate the measuring mandrel (120).

Description

SCOPE OF APPLICATION AND STATE OF THE ART

[0001] The invention relates to a measuring method for measuring the geometry of a bore, a measuring system suitable for carrying out the measuring method, and a precision machining machine with such a measuring system.

[0002] A preferred application is the measurement-assisted fine machining of bores by internal honing, wherein a measurement to determine the macro shape of the bore, in particular a measurement of the inner diameter of the bore, is carried out before and / or after the fine machining.

[0003] Honing is a machining process with geometrically undefined cutting edges, in which a honing tool performs a two-component cutting motion and maintains constant surface contact between one or more cutting material elements, such as honing stones, of the honing tool and the bore's inner surface being machined. The kinematics of a honing tool are characterized by a superposition of a rotary motion and a stroke motion in the axial direction of the bore. An optional expansion motion is usually also included, which results in a change in the effective diameter of the honing tool.

[0004] On the inner surface of the bore, the kinematics of the honing tool create a surface structure with intersecting machining marks. Surfaces finished by honing can meet extremely high requirements regarding dimensional and form tolerances. Therefore, many highly stressed sliding surfaces in engines or engine components, e.g., cylinder bores in engine blocks or inner bore surfaces in injection pump housings, are machined by honing.

[0005] Honing typically requires adherence to very tight tolerances regarding the macro-shape and the bore size, quantified, for example, by the bore diameter. Whether the desired macro-shape has been achieved within the tolerances by a honing process is usually determined after completion by measuring the bore geometry using a measuring system. This measuring system can be integrated into the machining center or be part of a separate measuring station.

[0006] Known measuring systems for this purpose comprise a measuring unit which, in its ready-to-use state, has a measuring mandrel that can be moved back and forth parallel to a measuring mandrel axis by means of a linear actuator. During measurement, the measuring mandrel can be moved into the bore and then back out of the bore using the linear actuator. Different measuring planes can be accessed during the measurement, if necessary, using the linear actuator. The measuring mandrel is usually interchangeably coupled to a measuring mandrel connection at the workpiece-side end of a measuring mandrel carrier, which is mounted on a slide that moves parallel to the measuring mandrel axis. The coupling can be rigid or, if necessary, have limited movement, e.g., gimbal-mounted or floating.

[0007] The measuring mandrel can, for example, be a pneumatic measuring mandrel. Pneumatic measuring mandrels often have at least one pair of measuring nozzles arranged diametrically opposite each other to the mandrel axis. There are also versions with only one measuring nozzle. A measuring nozzle can be understood as the measuring point of a pneumatic measuring system. Tactile measuring mandrels, as well as mandrels with one or more inductive or capacitive sensors, or radar sensors, are also known.

[0008] To prevent measurement errors, measuring systems are typically calibrated periodically using a reference device. The reference device comprises at least one reference element with defined internal dimensions, such as one or more reference rings with a precisely known inner diameter. These reference rings are also commonly referred to as measuring rings, zero rings, calibration rings, or adjustment rings. For calibration, the measuring mandrel is positioned within the area of ​​the reference device so that the (known) inner diameter of the reference element can be measured with the mandrel. If there are unacceptable deviations between the measured value and the (known) inner diameter, corrections can be made.

[0009] In normal operation, the measuring mandrel and the reference device are usually arranged coaxially, so that the reference device is positioned near the bore entrance when the bore is in the measuring position. This coaxial arrangement is considered advantageous because, for calibration purposes, the measuring mandrel only needs to be moved axially (parallel to the mandrel axis) to switch between the working position (measuring sensors inside the bore) and the calibration position (measuring sensors in the vicinity of the reference device).

[0010] Patent DE 100 60 967 B4 describes examples where reference rings are made of the material of the workpiece to be measured in order to avoid temperature-related calibration errors.

[0011] DE 44 13 645 A1 describes examples in which a reference gauge with a variable reference dimension is used. To calibrate this gauge, it can be moved perpendicular to the measuring mandrel axis into a calibration station that contains a group of several zero rings with different defined fixed inner diameters. In the calibration station, the variable reference gauge can be calibrated by comparison with the zero rings.

[0012] German patent application DE 40 24 778 A1 discloses a honing measuring tool and a method for measuring a machining surface of a workpiece, in particular with a functional element of a measuring tool designed as a measuring element which is essentially stationary relative to a tool body during the measuring process, wherein at least one functional element is adjusted to change the measuring accuracy.

[0013] Patent DE 10 2006 011 904 B4 discloses a measuring system with a reference device and a measuring method for measuring a workpiece surface on a workpiece using at least one measuring probe, which has a probe body and at least one measuring sensor attached to the probe body, comprising the following steps: drive-controlled positioning of the measuring probe relative to the workpiece; drive-controlled fixing of the probe body on the workpiece in a measuring position by supporting the probe body on the workpiece surface using a support device which has at least one support element; carrying out the measurement within a measuring range. TASK AND SOLUTION

[0014] One object of the invention is to provide a measuring method for measuring the geometry of a bore and a measuring system suitable for carrying out the measuring method, which operate without interference, offer permanently high measuring accuracies and enable dynamic measurement and thus short machine cycle times of a precision machining machine equipped with it.

[0015] To solve this problem, the invention provides a measuring method with the features of claim 1 and a measuring system with the features of claim 5. Furthermore, a precision machining machine with the features of claim 16 is provided. Advantageous embodiments are specified in the dependent claims. The wording of all claims is made clear by reference to the content of the description.

[0016] This measuring method is used to measure the geometry of a bore in a workpiece. Specifically, the bore's inner diameter can be measured in a plane perpendicular to the bore axis or in several axially offset planes. As an alternative to measuring in fixed planes, continuous acquisition of measurements along the entire bore length (so-called scanning) is also possible. The measuring method utilizes a measuring system that includes a measuring unit. In its ready-to-use state, this unit features a measuring mandrel. This mandrel is bidirectionally movable to different axial positions along a travel path parallel to a measuring mandrel axis by means of a linear actuator.

[0017] To minimize measurement errors, the measuring mandrel is calibrated at least once using a reference device with at least one reference element of defined internal dimensions. For calibration, the measuring mandrel is moved into a calibration position by means of the stroke drive, in which at least one measuring sensor of the mandrel is positioned in the area of ​​the reference element. In a pneumatic measuring system, a measuring nozzle is the part of the measuring sensor that interacts with the inner surface of the bore at a measuring point, so that in this case the (at least one) measuring nozzle is positioned in the area of ​​the reference element. The inner diameter or another internal dimension of the reference element can then be measured. If the measured value does not correspond to the known reference dimension of the reference element within the tolerances, the measuring system can be corrected.

[0018] According to one formulation of the claimed invention, the reference device is arranged in a neutral position outside the travel path of the measuring mandrel during the measuring operation of the measuring system, such that the measuring mandrel can be inserted into the bore to be measured without passing through the reference element. To perform a calibration operation, the reference device is moved from the neutral position to a calibration position in which the reference element is arranged coaxially to the measuring mandrel axis. The measuring mandrel is then moved by means of the lifting drive to a calibration position in which at least one measuring sensor of the measuring mandrel is arranged in the region of the reference element. In this calibration position, a calibration measurement is performed to calibrate the measuring mandrel. A calibration measurement is a measurement whose result is used for calibration.A single calibration measurement may suffice for complete calibration. However, two or more calibration measurements are often performed on one or more reference elements, and their results are then processed together or used for calibration.

[0019] During measurement, the workpiece with the bore to be measured is positioned in such a way that the bore axis is as coaxial as possible with the measuring mandrel axis. The measuring mandrel can then be inserted into the bore, the bore geometry measured in one or more planes, possibly in a scan mode, and then withdrawn so that another bore of the same workpiece or a bore in a different workpiece can be measured.

[0020] The movement of the reference device between the neutral position and the calibration position and back is preferably performed automatically, i.e., by means of a dedicated drive that can be controlled via a control unit. Manual operation to switch between the neutral position and the calibration position is also possible.

[0021] The reference element is preferably a reference element with a fixed diameter, i.e., not a reference element with adjustable internal dimensions. When using reference elements with fixed internal dimensions, a separate calibration operation, as proposed in the prior art for the use of adjustable reference elements, can be omitted. The reference element is preferably a reference ring, i.e., a circumferentially closed reference element, which can also be referred to as a measuring ring. Instead of measuring rings, it is also possible, for example, to combine several gauge blocks (very precisely manufactured spacers of known height) using so-called gauge block holders / gauge blocks in such a way that two parallel planes at a fixed distance exist, which could be used to calibrate a measuring mandrel, e.g., a pneumatic measuring mandrel with two measuring nozzles.

[0022] Since the reference device for measurement operation can be moved from the calibration position to a neutral position outside the travel path of the measuring mandrel, the advantage is that the measuring mandrel no longer needs to pass through the reference element(s) to enter the bore. This allows the measuring mandrel to be shorter and / or geometrically simpler than in the case of a permanent arrangement of reference elements within the travel path of the measuring mandrel.

[0023] A further advantage of using pneumatic measuring mandrels is that the volume of air moved and trapped between the measuring nozzle (i.e., the part of the measuring sensor that interacts with the inside of the bore) and the associated transducer (which converts pressure changes, volume flow changes, etc., into electrical signals) can be smaller the shorter the measuring mandrel is. This reduced air volume can lead to shorter dead times in the measuring system, resulting in shorter cycle times for the measurement and the associated manufacturing processes. Shorter measurement cycle times, in turn, improve the efficiency of production.

[0024] In conventional measuring systems, where the reference device is always statically mounted at a fixed height between the plane of the workpiece being measured and the measuring mandrel connection, the measuring mandrel must be long enough to pass through the reference device and its reference elements (one or more). This means, as explained above, that the measuring mandrels must be relatively long. To limit the length, the reference device should also be positioned relatively close to the top surface of the workpieces being measured. This makes the arrangement relatively inflexible, as larger (taller) workpieces could collide with the reference device. Conversely, if the reference device were mounted higher to allow more clearance above the plane of the workpieces, shorter workpieces might no longer be measurable. These problems are avoided by applying the invention.

[0025] Preferably, after completion of the calibration operation, the reference device is automatically moved from the calibration position back to the neutral position before the measurement operation is resumed.

[0026] According to a further development, the reference device is housed in a casing in its neutral position, which at least partially encloses it. Accordingly, the measuring system has a casing for housing the reference device in its neutral position, wherein the casing at least partially encloses the reference device in its neutral position and the reference device can be moved out of the casing into the calibration position. By providing a casing in which the reference device is at least partially housed in its neutral position, the reference elements (one or more) contained within the reference device can be protected against contamination and / or damage. This takes into account that the reference elements are intended to serve as calibration standards for the measuring mandrel and should therefore be housed in a protected manner when not in use during measurement.

[0027] The reference device can be linearly moved, for example, to switch between the neutral position and the calibration position in a direction perpendicular to the measuring mandrel axis. This can be achieved structurally by guiding the reference device linearly into and out of the housing, similar to a drawer. Alternatively, the reference device can be pivoted, for example, around a pivot axis parallel to the measuring mandrel axis. Lateral pivoting parallel to the measuring mandrel axis or pivoting from above using a parallelogram linkage are possible, for example.

[0028] According to a further development, the reference device has a movable support frame with mounting structures for an interchangeable reference element carrier. By replacing the reference element carrier with one or more reference elements it holds, the reference device can be easily converted to other calibration standards. Preferably, the reference element carrier can be replaced without tools. This allows a single operator to conveniently and quickly convert to other calibration standards.

[0029] A replaceable reference element holder can have receiving structures for a single reference element. Preferably, the reference element holder has receiving structures for two or more reference elements in a coaxial arrangement. This makes it possible to compare the measuring mandrel with at least two different internal dimensions or calibration standards during the calibration operation. The results of two or more calibration measurements can therefore be processed together. Interpolation to intermediate dimensions can be performed from the obtained measured values. This enables highly accurate calibrations.

[0030] According to a further development, components of the measuring system are attached to a support structure. The measuring unit has a carriage that is linearly displaceable on a linear guide system on a base support attached to the support structure, and the base support carries the lifting drive. This allows all components supported by the base support, in particular the measuring unit, which is bidirectionally movable (forward and backward) on a linear guide system, and the lifting drive required to generate this movement, to be attached to and removed from the support structure as a single assembly.

[0031] Preferably, the aforementioned housing, which at least partially accommodates the reference device in its neutral position, is also attached to the base support. This allows the reference device to be installed together with the assembly. Furthermore, the housing and the reference device are then always in the correct position and orientation relative to the measuring mandrel axis. The fully pre-assembled module, which can be mounted on the support structure, can also be referred to as a "measuring axis," whereby the "measuring axis" is a separate machine axis whose operations can be controlled by the control unit of a separate measuring station or a precision machining center.

[0032] To avoid or minimize measurement errors resulting from misalignments between the measuring mandrel axis and the bore axis of the bore being measured, some embodiments incorporate an alignment system for stepless, reversible adjustment of the measuring mandrel axis's orientation relative to the support structure. Preferably, the alignment system is designed for independently adjusting the position of the measuring mandrel axis along two mutually perpendicular translational axes and for adjusting the orientation of the measuring mandrel axis relative to two mutually perpendicular rotational axes.

[0033] In particular, the alignment system may include a first adjustment unit and a second adjustment unit, separate from and separately operable from the first, arranged at a distance from the first. Each adjustment unit has first adjustment elements for stepless adjustment of the distance between the support structure and the base in a first direction, and second adjustment elements for generating stepless relative movement of the base with respect to the support structure in a second direction perpendicular to the first. To facilitate assembly and also for improved stability, the two adjustment units may be integrated into a common base body.

[0034] In some embodiments, the measuring mandrel can only be moved linearly parallel to the mandrel axis by means of the lifting drive, but is otherwise fixed. There are also embodiments in which the measuring mandrel can additionally be rotated about the mandrel axis by means of a rotary drive. The rotary drive makes it possible to perform measurements, for example, measurements of the inner diameter of a bore, in any radial direction relative to the bore axis.

[0035] The invention also relates to a precision machining machine for finishing a bore in a workpiece, wherein the precision machining machine is assigned a measuring system according to the invention. The measuring system can be integrated into the precision machining machine or be part of a measuring station separate from the precision machining machine.

[0036] The precision machining machine in question may be, in particular, a honing machine. A honing machine is a machine tool suitable for honing bores in workpieces. It has at least one honing unit mounted on a machine-fixed support structure, such as a column, a pillar, or a frame. A honing unit comprises a spindle unit in which a spindle shaft is rotatably mounted. The spindle shaft is rotatable about its spindle axis by means of a rotary drive and has a device for attaching a honing tool at one end, on the tool side. A linear guide system may be arranged between the base support and the spindle unit to guide a linear stroke of the spindle unit relative to the base support. A stroke drive is provided to generate the stroke of the spindle unit parallel to the spindle axis. A reaming drive is also typically provided for reaming the honing tool.

[0037] The honing machine can have several workstations, e.g., two or more honing stations, each with at least one honing unit. Mechanical components of the measuring system, in particular the measuring unit, the reference device, and, if necessary, a housing for the reference device in the neutral position, etc., can be mounted at a suitable location on the support structure, thus creating a honing machine with an integrated measuring station. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Further advantages and aspects of the invention will become apparent from the claims and from the following description of preferred embodiments of the invention, which are explained below with reference to the figures. Fig. Figure 1 schematically shows a measuring station with components of a measuring system according to an exemplary embodiment; Fig. 2 shows further details of the construction Fig. 1; Fig. Figure 3 shows the reference device in a calibration position; Fig. 4A and Fig. Figure 4B shows an interchangeable reference element carrier that can be inserted into a support frame of the reference device and has receiving structures for reference rings; Fig. 5 shows the reference device in a calibration position with the measuring mandrel inserted; Fig. Figure 6 shows the reference device in a calibration position, with measuring nozzles of the pneumatic measuring mandrel arranged in the area of ​​one of the reference elements; Fig. Figure 7 shows the measuring mandrel in a measuring position. DETAILED DESCRIPTION OF THE EXECUTION EXAMPLES

[0039] The following describes exemplary implementations of measuring methods and measuring systems for measuring the geometry of bores in workpieces in connection with a measuring station assigned to a precision machining machine (not shown), in the form of a honing machine. The measuring system 100, described in more detail below, can be integrated into the precision machining machine as a measuring station. Alternatively, the measuring system can, for example, be part of a separate measuring station from the precision machining machine.

[0040] Fig. Figure 1 schematically shows a measuring station with components of a measuring system 100 according to an exemplary embodiment. Many mechanical components of the measuring system 100 are mounted on a support structure 190 in the form of a vertical stand. The support structure can be a component mechanically fixed to the machine frame of the precision machining machine or the supporting structure of a separate measuring station. The support structure 190 generally extends vertically or parallel to the z-direction of the Cartesian coordinate system KS. Mechanical components of the measuring system 100 are attached to the front face 192 of the support structure, which lies in the y-direction, such that the components are located above a workpiece plane.

[0041] In this example, the workpieces, whose bores (one or more) are to be measured using the measuring system, are transported to the measuring point and then removed using a workpiece transport system 170. The workpiece, which is not visible, is held in a workpiece holding device 175. Fig. Figure 1 schematically depicts a workpiece transport system 170 with a rotary indexing table. Variants with linear workpiece transfer are also possible. A workpiece can also be manually moved into the measuring position.

[0042] The measuring system 100 comprises a vertically oriented measuring unit 110, which, in the illustrated, ready-to-use state, has a (replaceable) measuring mandrel 120 that can be moved back and forth or up and down along a substantially vertical travel path parallel to a measuring mandrel axis 125 by means of a lifting drive 128. All vertical movements are controlled by the electric lifting drive 128 via a control unit of the measuring station (not shown). This drive powers a vertically oriented ball screw on which a spindle nut runs, which is connected to vertically movable parts of the measuring unit 110.

[0043] In the schematic side view of Fig. 2 Further details of the construction are visible. On the flat front surface 192 of the support structure 190, mechanical components of an alignment system 300, which will be explained later, are mounted. This system carries on its side facing away from the support structure a generally vertically oriented base support 180, which is a torsionally rigid component and which carries vertically extending guide rails of a linear guide system 185 on its side facing away from the support structure 190.

[0044] The measuring unit 110 has a carriage that is essentially vertically movable on the linear guide system. The ball screw's spindle nut is attached to the carriage, so that the lifting drive 128 can generate vertical movement of the measuring unit 110 in both directions. The lifting drive 128 is attached to the upper end of the base support 180. The ball screw runs inside the base support 180.

[0045] The measuring unit 110 comprises a measuring mandrel carrier 122, which projects from a housing 114 of the measuring unit at its lower end. The measuring mandrel carrier 122 features coupling structures for a measuring mandrel connection 115. The measuring mandrel connection can be spring-loaded for collision protection. The measuring mandrel 120 is interchangeably coupled to this measuring mandrel connection at the workpiece-side end of the measuring mandrel carrier, for example, by means of a union nut or a bayonet coupling. The coupling can be rigid, but can also be designed to allow limited movement, so that the measuring mandrel 120 can also be mounted gimbal-mounted and / or floating on the measuring mandrel carrier. Depending on the coupling method, the longitudinal center axis of the measuring mandrel can always run parallel to the axis of the measuring mandrel carrier or (in the case of gimbal mounting) be slightly inclined (by a few degrees) relative to it at certain times.

[0046] In this example, the measuring mandrel 120 is a pneumatic measuring mandrel. It has at least one pair of measuring nozzles at its lower end, arranged diametrically opposite each other at a fixed distance from the mandrel axis. There are also measuring mandrels with three nozzles (e.g., for parts with transverse bores spaced 3 mm apart), four-nozzle measuring mandrels (thus eliminating the influence of ovality), and mandrels with six or eight nozzles (e.g., for very narrow webs). In all cases, the measured value at the measuring mandrel corresponds to the average of the respective distances of the measuring nozzles to the workpiece surface.

[0047] Pneumatic measuring mandrels are known to operate on the nozzle-impact plate principle. For measurement, compressed air is blown from the measuring nozzles towards the bore wall. The resulting dynamic pressure in the area of ​​the measuring nozzles serves as a measure of the distance between the measuring nozzle and the bore wall. A transducer connected to the measuring nozzle via a pressure line converts the (pneumatic) pressure signal into an electrically processable signal. Using two diametrically opposed measuring nozzles, the bore diameter can be determined for a given diametrical distance between the nozzles. The transducer and a compressed air supply system are housed within the measuring unit's housing 114, along with other components. The position of a measuring nozzle is considered the effective position of the measuring sensor. Ring or slot nozzles are further variations of the more classic round nozzles.

[0048] In an embodiment not shown, the measuring mandrel is additionally rotatable about its axis by means of a rotary drive. This rotary drive makes it possible to perform measurements sequentially in any radial direction of the bore being measured. In this case, the measuring mandrel carrier is designed as a rotatable spindle, and the rotary drive can be mounted inside the housing.

[0049] To avoid measurement errors as much as possible, measuring systems should be calibrated from time to time. Measuring system 100 has an integrated reference device 200 for calibrating the measuring mandrel 120. The mechanical components of the reference device are particularly well integrated into the Fig. 3, Fig. 4A and Fig. 4B as well as Fig. 6. The reference device 200 is not fixedly mounted with respect to the support structure 190, but is linearly movable in a displacement direction 205 perpendicular to the measuring mandrel axis (corresponding to the y-direction of the system coordinate system KS). The reference device can be moved between the in by means of a pneumatic drive (not shown) Fig. 1 shown neutral position and the one shown, for example, in Fig. 3 and Fig. The calibration position shown in section 5 should be moved horizontally parallel to the y-direction.

[0050] In the neutral position ( Fig. 1) The mechanical components of the reference device 200 are largely housed within a box-shaped enclosure 280, which is mounted at the lower end of the base support 180. In the neutral position, the enclosure surrounds the reference device upwards and laterally, similar to a drawer. The reference device 200 itself is guided linearly into and out of the enclosure 280, parallel to the y-direction, similar to a drawer. For this purpose, horizontal guide structures are formed on the inside of vertical enclosure walls. The reference device has a movably mounted support frame 210, which has guide structures on its outer surface that run in the guide structures on the inside of the enclosure 280.

[0051] The support frame 210 has receiving structures for receiving an interchangeable reference element support 220, which is also in Fig. 4A and Fig. 4B is clearly visible. The reference element carrier 220 serves to hold several reference elements 230-1, 230-2 in the form of reference rings with a defined inner diameter. The reference element carrier has internal receiving structures into which the reference rings can be inserted laterally and are then held in such a way that they are positioned there in a coaxial arrangement centered on the central axis of the reference element carrier (see Figure 4B). Fig. 4B). A recessed cylindrical receptacle is formed on the upper side of the reference element carrier, into which an insertion aid 235 can be inserted from above. The insertion aid has conical insertion surfaces that prevent collision of the measuring mandrel when inserted into the reference elements (reference ring).

[0052] The reference element carrier 220, which can accommodate two or more measuring rings, is also referred to as a measuring ring nest. The reference element carrier can be inserted into and removed from the support frame 210 without the use of tools. For this purpose, the support frame 210 is open in a funnel shape on the side facing the measuring mandrel axis. The reference element carrier 220 can be inserted or removed horizontally into its installation position in the support frame 210 in a specific rotational position. When inserted, it can be fixed and locked in place by rotating it, for example, by 45°. The illustration of Fig. Figure 3 shows the reference element carrier in the ready-to-use, assembled, and locked state.

[0053] As already mentioned, the Reference Facility 200 as a whole is located between the in Fig. 1 visible neutral position (partially inside the housing 280) and the one in Fig. The reference device is linearly movable in the calibration position shown in Figure 3. In the neutral position, the reference device is completely outside the vertical travel path of the measuring mandrel 120 and the housing, so that the latter can be inserted into a bore to be measured without passing through the reference device or the reference elements contained therein. The measuring mandrel connection 115 can be positioned at a level below the housing 280 if required. This lower measuring position, which the measuring unit can assume for measuring operation, is shown in Figure 3. Fig. Figure 7 shows that if calibration of the measuring mandrel is to be carried out, the measuring mandrel is moved upwards until its lower end is above the horizontal travel distance of the reference device 200. The reference device can then be moved horizontally into the space shown in Figure 7 using the pneumatic drive. Fig. The calibration position shown in Figure 3 is used. In the calibration position, the reference elements are in their calibration position coaxial with the measuring mandrel axis 125. This allows the measuring mandrel to be moved downwards into a calibration position by means of the lifting drive 128, in which a measuring sensor of the measuring mandrel (here the measuring nozzles) is arranged in the area of ​​one of the reference elements (see Figure 3). Fig. 6) Then the calibration can be carried out using a measurement of the known inner diameter of the reference element.

[0054] The measuring method is thus characterized by the fact that the reference device 200 is in a neutral position outside the vertical travel path of the measuring mandrel during measuring operation, i.e. when the measuring mandrel 120 is used or is to be used for measuring bores in workpieces, so that the measuring mandrel can be inserted into the bore to be measured without passing through the reference element.

[0055] To perform a calibration operation, the reference device 200 is automatically moved from the neutral position to the calibration position, in which the reference element is in a calibration position coaxial with the measuring mandrel axis 125. To avoid collisions with the measuring mandrel, the measuring unit 110 is first moved upwards at least far enough so that the end of the measuring mandrel facing the workpiece is above the plane of the top of the reference device 200. The measuring mandrel is then moved downwards by means of the lifting drive 128 into a calibration position in which a measuring sensor of the measuring mandrel is arranged in the area of ​​the reference element of interest, approximately at the level of the vertical center of a measuring ring. A calibration measurement is then performed in this calibration position for the purpose of calibration.

[0056] During calibration, several calibration measurements can be performed. For example, measurements can be taken sequentially on two axially offset measuring rings with different inner diameters, and the results can then be compared.

[0057] After completion of the calibration operation, the measuring mandrel is moved upwards out of the reference device and the reference device is automatically moved from the calibration position back to the neutral position before the measurement operation is resumed.

[0058] In many cases, calibration is a cyclical process that takes place at a wider, adjustable interval depending on the application. For example, calibration is typically performed after a machine is switched on, at a shift change, and then subsequently at fixed intervals, e.g., from 0.5 hours to approximately 4 hours.

[0059] In principle, the measuring unit should be aligned for measuring operation such that the measuring mandrel axis 125 runs coaxially to a reference axis which, when the workpiece is in a measuring position, corresponds to the bore axis of a bore to be measured. In the exemplary embodiment, this can be ensured systematically and relatively conveniently using the alignment system 300. The alignment system 300 comprises a first adjustment unit 310-1 and a second adjustment unit 310-2, which is separate from the first adjustment unit and arranged at a distance 312 from the first adjustment unit 310-1. The components of the adjustment units are installed in a common base 315, which, among other things, simplifies assembly.

[0060] After pre-assembly, the adjustment units are arranged between the support structure 190 and the base support 180 of the measuring unit for rough alignment. Each adjustment unit comprises first adjustment elements for reversibly adjusting the distance between the support structure and the base support in a first direction corresponding to the y-direction, and second adjustment elements for generating stepless relative movement of the base support with respect to the support structure in a second direction perpendicular to the first direction, which essentially corresponds to the x-direction. The adjustment units can be actuated independently of one another, which simplifies the adjustment process. Stepless adjustment of the settings is preferably possible.Using exactly two adjustment units allows for reliable adjustment of the target parameters without geometrically overdetermining the overall arrangement, which could lead to deformation of the devices coupled to the spindle unit.

[0061] By adjusting the distance 314 between the support structure 190 and the base support 180 using the first adjustment elements, different positional changes of the measuring pin axis can be achieved. If the distance is changed by the same amount at both adjustment units, this causes a parallel displacement of the measuring pin axis in the first direction (y-direction). If, on the other hand, the distance is changed at only one of the adjustment units, or if the distance is changed by different amounts at both adjustment units, this causes a tilting or rotation of the measuring pin axis about an axis of rotation perpendicular to the first direction, provided it runs parallel to the second direction (x-direction). The position of this virtual axis of rotation with respect to the two adjustment units can vary and depends on the absolute extent of the distance changes at the two adjustment units as well as on the type of distance change (increasing or decreasing the distance).

[0062] Similar adjustment options are achieved by actuating the second adjustment elements, which cause stepless relative movement of the base body with respect to the support structure in a second direction perpendicular to the first direction in both adjustment units. If the same displacement is applied in this second direction (x-direction) in both adjustment units, this results in a parallel displacement of the position of the measuring mandrel axis without changing its inclination. If, however, the displacements between the first and second adjustment units differ, the measuring mandrel axis 125 also rotates about a (virtual) axis of rotation that runs parallel to the first direction (y-direction). Here, too, the absolute position of this virtual axis of rotation depends on the ratios of the displacements between the first and second adjustment units.

[0063] So far, examples of measuring methods and systems for measuring the geometry of bores in workpieces have been described in connection with a dedicated measuring station assigned to a finishing machine in the form of a honing machine. There are also honing processes in which measuring sensors of a diameter measuring system, e.g., measuring nozzles of a pneumatic measuring system, are arranged on an expandable honing tool. This allows in-process measurements of the bore to be carried out during its honing operation, e.g., to operate a controlled honing process. It is possible to mount components of the measuring system, including the reference device, on a honing station normally used for workpiece machining, which can then be used for honing during machining operations. If the measuring system integrated into the honing tool then needs to be calibrated, this calibration operation can be carried out at the honing station analogously to the procedure described above.The expandable honing tool would then be considered a measuring mandrel that, in addition to one or more measuring sensors, also carries one or more radially adjustable cutting material bodies, e.g., in the form of honing blocks. For calibration, the cutting material bodies should be moved into their radially inward retracted position to avoid contact with reference elements.

[0064] It would therefore also be conceivable to use the drawer on a honing station that has a honing tool with measuring nozzles ("in-process measurement"). Here, too, the advantage would be that the honing tool could be designed to be as short as possible and thus as precise as possible. Additionally, in this case, the measuring rings would be protected from damage by the honing tool and from wear debris during the honing process because they move away from the honing tool axis.

Claims

[1] Measuring method for measuring the geometry of a bore in a workpiece using a measuring system (100) comprising a measuring unit (110), which in its ready-to-use state has a measuring mandrel (120) which can be moved bidirectionally along a travel path parallel to a measuring mandrel axis (125) by means of a lifting drive (128); wherein the measuring mandrel (120) is calibrated at least once using a reference device (200) with at least one reference element (230-1, 230-2) of defined internal dimensions by moving the measuring mandrel (120) by means of the lifting drive (128) into a calibration position in which a measuring sensor of the measuring mandrel (120) is arranged in the area of ​​the reference element (230-1, 230-2), characterized by , that The reference device (200) is arranged in a neutral position outside the travel path of the measuring mandrel (120) during measuring operation such that the measuring mandrel (120) can be inserted into the bore to be measured without passing through the reference element (230-1, 230-2); the reference device (200) is moved from the neutral position to a calibration position in which the reference element (230-1, 230-2) is arranged in a calibration position coaxial to the measuring mandrel axis (125); and In the calibration position of the measuring mandrel (120), a calibration measurement is carried out to calibrate the measuring mandrel (120). [2] Measuring method according to claim 1, characterized by, that movements of the reference device (200) between the neutral position and the calibration position and back are carried out automatically, wherein in particular the reference device (200) is automatically moved from the calibration position back to the neutral position after completion of the calibration operation before the measurement operation is resumed. [3] Measuring method according to claim 1 or 2, characterized by , that the reference device (200) is received in the neutral position in a housing (280) which at least partially encloses the reference device (200). [4] Measuring method according to any one of the preceding claims, characterized by , that the reference device (200) is linearly displaced in a displacement direction (205) perpendicular to the measuring mandrel axis (125) to change between the neutral position and the calibration position. [5] Measuring system (100) for measuring the geometry of a bore in a workpiece comprising: one unit of measurement (110), which in its ready-to-use state has a measuring mandrel (120) which can be moved bidirectionally along a travel path parallel to a measuring mandrel axis (125) by means of a lifting drive (128); a reference device (200) for calibrating the measuring mandrel (120), wherein the reference device (200) has at least one reference element (230-1, 230-2) of defined internal dimensions, characterized by , that the reference device (200) is mounted in such a way that the reference device (200) can be moved between a calibration position and a neutral position, wherein in the calibration position the reference element (230-1, 230-2) is arranged in a calibration position coaxial to the measuring mandrel axis (125) such that the measuring mandrel (120) can be moved by means of the lifting drive (128) into a calibration position in which a measuring sensor of the measuring mandrel (120) is arranged in the area of ​​the reference element (230-1, 230-2), and wherein the reference device (200) is arranged in the neutral position outside a travel path of the measuring mandrel (120) in such a way that the measuring mandrel (120) can be inserted into the bore to be measured without passing through the reference element (230-1, 230-2). [6] Measuring system according to claim 5, characterized by , that movements of the reference device (200) between the neutral position and the calibration position and back can be carried out automatically using a drive provided for this purpose. [7] Measuring system according to claim 5 or 6, characterized by, that the measuring system (100) has a housing (280) for receiving the reference device (200) in the neutral position, wherein the housing (280) at least partially encloses the reference device in the neutral position and the reference device (200) is movable out of the housing (280) into the calibration position. [8] Measuring system according to claim 7, characterized by , that the reference device (200) is guided linearly into and out of the housing (280) in the manner of a drawer. [9] Measuring system according to any one of claims 5 to 7, characterized by , that the reference device (200) has a movably mounted support frame (210) with receiving structures for receiving an interchangeable reference element carrier (220), wherein the reference element carrier (220) is preferably interchangeable without tools. [10] Measuring system according to claim 9, characterized by, that the reference element carrier (220) has receiving structures for receiving two or more reference elements (230-1, 230-2) in a coaxial arrangement. [11] Measuring system according to any one of claims 5 to 10, characterized by , that components of the measuring system (100) are attached to a support structure (190), wherein the measuring unit (110) is mounted on a slide which is guided linearly displaceably on a linear guide system (185) on a base support (180) attached to the support structure (190), wherein the base support (180) carries the lifting drive (128). [12] Measuring system according to claims 7 and 11, characterized by , that the housing (280) is attached to the base support (180). [13] Measuring system according to claim 11 or 12, characterized byan alignment system (300) for stepless, reversible adjustment of the alignment of the measuring mandrel axis (125) with respect to the support structure (190), wherein the alignment system (300) is designed for independent adjustment of the position of the measuring mandrel axis (125) along two mutually perpendicular translation axes and for adjusting the orientation of the measuring mandrel axis (125) with respect to two mutually perpendicular rotation axes. [14] Measuring system according to claim 13, characterized by, that the alignment system (300) has a first adjustment unit (310-1) and a second adjustment unit (310-2) separate from the first adjustment unit (310-1), which is arranged at a distance (312) from the first adjustment unit (310-1), wherein each of the adjustment units (310-1, 310-2) has first adjustment elements for stepless adjustment of a distance (314) between the support structure (190) and the base support (180) in a first direction and second adjustment elements for generating a stepless relative movement of the base support (180) relative to the support structure (190) in a second direction perpendicular to the first direction. [15] Measuring system according to claim 14, characterized by , that the two adjustment units (310-1, 310-2) are installed in a common base body (315). [16] Precision machining machine for finishing a bore in a workpiece, in particular a honing machine, characterized by, that the precision machining machine is assigned a measuring system (100) according to one of claims 5 to 15.

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