Device and method for wheel position detection

Abstract

The invention relates to a measuring device (1) and a method, as well as a clamping unit (2) for measuring an offset (10) of a rotational axis (32) and / or the position of a vehicle wheel (3) clamped in a clamping unit (2) for machining, comprising a measuring device receptacle (4) which includes a height-adjustable measuring head (5), wherein the measuring head (5) is coupled to an actuator (11) having a longitudinal axis (12) and is movable by means of the actuator (11) in the direction of the longitudinal axis (12) between a measuring position (8) and a rest position (9), and at least one measuring means (6) for measuring the offset (10) of the rotational axis (32) of the vehicle wheel (3) on the basis of position coordinates of a central hole (31) in the transverse direction (13) and / or axial direction (14) of the central hole (31) of the vehicle wheel. (3) relative to the actuator longitudinal axis (12), wherein at least one measuring means (6) is designed in such a way,that no relative rotation of the vehicle wheel (3) to the measuring head (5) is required for measurement and wherein the at least one measuring means (6) for measuring the offset (10) of the axis of rotation (32) and / or the position of the vehicle wheel (3) in the transverse direction (13) and / or axial direction (14) is either configured to detect the position coordinates of the center hole (31) as a relative distance (16) between the measuring head (5) and the vehicle wheel (3) to be measured at the center hole (31), or is configured to detect the position coordinates of the center hole (31) as a relative position (17) of the measuring head (5) in the measuring position (8) deviating from the position of the measuring head (5) in the rest position (9).

Description

[0001] The invention relates to a measuring device and a method for measuring an offset of a rotation axis and / or the position of a motor vehicle wheel clamped for machining in a clamping unit, as well as a clamping unit which comprises such a measuring device.

[0002] The production of motor vehicle wheels, which in the context of this application refers to wheels or rims for cars and trucks, requires a series of manufacturing steps. After the primary shaping of the motor vehicle wheel, for example by casting, mechanical, material-removing processes such as milling, grinding, and especially drilling are generally used. Mechanical machining centers familiar to those skilled in the art, such as CNC-controlled, multi-axis measuring and cutting devices, are used for this purpose. The processing time and accuracy should be as short as possible from a cost perspective. Motor vehicle wheels require sufficiently precisely arranged and aligned contact surfaces with a wheel suspension, as well as bolt holes positioned precisely with respect to the center hole to ensure problem-free assembly.Even a few hundredths to a few tenths of a millimeter offset of the bolt hole relative to the center hole can impair assembly or even make it completely impossible.

[0003] In the context of today's zero-defect policy in the automotive industry, a precise measurement of the actual contours and positions of the wheel must often be performed before machining the wheel or rim in order to communicate the measurement data of the wheel in its initial state to the machining center or a system control device. A precise measurement of the wheel's center hole is often performed, and the center hole position or the position of the wheel's rotation axis is used as a reference point and reference value for the arrangement of the bolt holes and / or the gaps between the rim webs.

[0004] This type of wheel alignment is often performed outside the actual machining center in a dedicated measuring station. The measurement data of the measured wheel is transferred to the system control device before the wheel is transferred from the measuring device to the machining center. This process is very time-consuming and requires repeated clamping and unclamping of the wheel to be machined, with the resulting measurement tolerances, as well as repeated determination of the position of the center hole serving as a reference point. This leads to time loss during the machining of the wheel and is therefore costly and undesirable.

[0005] A number of measuring devices are known to those skilled in the art for measuring finished vehicle wheels to check tolerances and / or adjust ongoing production for subsequent parts. For example, DE3836540A1 discloses a multi-point measuring device for measuring vehicle wheels. A plurality of transducers are arranged around a central measuring station to measure the outer contours of a vehicle wheel. The central measuring station is designed to measure the center hole and the inner and outer wheel contact surfaces during a complete rotation around the central axis of the central measuring station. The central measuring station has a vertically movable clamping head that extends from below through the center hole of the wheel disc and can measure the center hole diameter by clamping an expanding mandrel.The multi-point measuring device disclosed in DE3836540A1 thus achieves a measurement duration of several minutes using many different transducers and requires precise setup of the machined vehicle wheel in the measuring station. Due to the time-consuming process of unclamping and re-clamping the vehicle wheel to be measured, such a measuring station is not suitable for determining the position of an offset and / or any positional deviation of the vehicle wheel on a clamping unit used for machining the vehicle wheel prior to machining.

[0006] Similarly, DE102005017991A1 describes a method and device for measuring a machined motor vehicle wheel. The inner side of the wheel to be measured must rest on a turntable and be clamped from the outside with a counterholder. The measurement of the motor vehicle wheel, which is fixed in the turning and clamping unit, is carried out using a first measuring unit for determining the eccentricity of the center hole, and a second measuring unit for determining the flatness on the inside of the wheel disc. The two measuring units correspond to relatively simple mechanical scanning devices arranged in a measuring unit holder. To measure the eccentricity and / or flatness, a complete rotation of the wheel around the axis of rotation of the turntable in a clamped state is required. However, the measuring device in DE102005017991A1 is also intended for measuring the finished motor vehicle wheel.The method is therefore not suitable for measuring the wheel already clamped on the clamping unit immediately prior to subsequent machining of the wheel, especially the bolt holes, because the counterholder and the turntable would prevent access by a tool from inside or outside during machining. This would require an additional, time-consuming manipulation step of the wheel from the measuring station, followed by re-positioning the wheel in the machining center's clamping unit.

[0007] One option for measuring and detecting the center hole of a vehicle wheel directly in the machining center is known to those skilled in the art, as modern machining centers can have, for example, a tool change magazine with a dedicated measuring head with a measuring probe, or a separate measuring device for measuring the position of the vehicle wheel can be provided within the machining center. As a rule, the position of the vehicle wheel is measured using the center hole from above, i.e. from the side opposite the clamping unit. The measurement within the machining center takes place shortly before mechanical machining and therefore directly increases the relatively expensive machining time, which can lead to increased costs.In addition, such methods require a rotational movement of the vehicle wheel relative to the measuring device or vice versa, which entails additional design effort and therefore costs. Measuring the center hole to determine the rotation axis of the vehicle wheel as a reference point for the arrangement of the bolt hole bores requires approximately 10 to 20 seconds per vehicle wheel or rim, which corresponds to approximately 15 to 20% of the processing time for drilling the bolt holes. Reducing this measuring time, which must be included in the processing time, would be advantageous here. Ideally, the rotation axis of the vehicle wheel should not exhibit any deviation, i.e. an offset in the transverse direction or X / Y direction, relative to the central axis of the clamping unit. Likewise, there should be no deviation in the vertical direction, i.e. a positional deviation of the center hole and thus of the vehicle wheel in the direction of the actuator longitudinal axis or Z direction, from a predefined clamping position of the vehicle wheel.Furthermore, the wheel's rotational axis should not be tilted relative to the actuator's longitudinal axis or the central axis of the clamping unit. Detecting an undesirable positional deviation of the wheel by a tilt angle relative to the plane of the clamping unit is currently impossible to measure, or only possible with considerable effort. Such a tilt can, for example, lead to a slightly tilted wheel clamped at an angle, causing the wheel's rotational axis to be tilted relative to the axis of the machining device, and the bolt holes to be drilled at an undesirable angle.

[0008] JP H10 68619 A discloses a measuring device for measuring a rotating body with a central, circular opening. A measuring mandrel is formed whose diameter is smaller than the diameter of the opening in the rotating body. The measuring mandrel is inserted into the opening, and the relative distance of the measuring mandrel to the hollow cylindrical wall surfaces of the opening is determined using three measuring elements distributed around the circumference of the measuring mandrel and aligned radially to the measuring mandrel.

[0009] EP 0 708 308 A2 describes a non-contact measuring device for the wheel bodies of rail vehicles. It uses a plurality of non-contact sensors, such as laser sensors or inductive sensors, to measure the geometry or surface contours of the wheel body.

[0010] EP 2 808 642 A1 describes a measuring head for measuring a truncated conical countersink around a cylindrical bore, which countersink is intended to accommodate the screw head of a countersunk head screw. The measuring head has a sleeve-shaped base body in which a centering mandrel for insertion into the cylindrical bore and a probe mandrel for placement on the countersink are mounted. The probe mandrel is mounted so that it can be adjusted axially relative to the sleeve-shaped base body. When the measuring head assumes the measuring position, the axial position of the probe mandrel relative to the sleeve-shaped base body is determined, and from this, the axial depth of the truncated conical countersink is determined.

[0011] WO 97 / 15803 A1 describes a measuring device for measuring axial deviations of the outer surface of vehicle wheels. Several sensors of a mechanical or electronic measuring instrument are contacted with the outer surface of the vehicle wheel at several measuring points. The axial deviations of these measuring points relative to a reference plane can then be read on the measuring instrument and transmitted as measurement data to a machining device such as a lathe for vehicle wheels.

[0012] The object of the present invention was to overcome the above-mentioned disadvantages of the prior art and to provide a device and a method by means of which a user is able to carry out a simple and cost-effective detection and measurement of an offset of the rotation axis and / or the position, in particular a possible tilt, of a motor vehicle wheel clamped for machining in a clamping unit before the subsequent machining.

[0013] This object is achieved by a device and a method according to the claims.

[0014] The measuring device according to the invention for measuring an offset of a rotational axis and / or the position of a motor vehicle wheel clamped in a clamping unit for machining comprises a measuring device holder with an actuator, and at least one measuring device coupled to the actuator with a measuring head. The measuring head is height-adjustable and coupled to the actuator, which has an actuator longitudinal axis. The measuring head is movable in the direction of the actuator longitudinal axis between a measuring position and a rest position. The at least one measuring device is configured to determine the measurement of the offset of the rotational axis of the motor vehicle wheel based on position coordinates of the center hole of the motor vehicle wheel in at least the transverse direction and / or the position or orientation of the center hole in the axial direction of the motor vehicle wheel relative to the actuator longitudinal axis.The at least one measuring device is designed such that no relative rotation of the vehicle wheel to the measuring head and / or the clamping unit is required for measurement. The at least one measuring device is further designed to measure the offset of the rotation axis and / or the position of the vehicle wheel based on the center hole in the transverse direction and / or axial direction by either detecting the position coordinates of the center hole as the relative distance between the measuring head and the center hole of the vehicle wheel to be measured, or by detecting the position coordinates of the center hole as a relative position of the measuring head in the measuring position, which differs from the position of the measuring head in the rest position. Continued on page 5 of the originally submitted description

[0015] The deviations of a few hundredths to tenths of a millimeter of the rotational axis from the central axis of the clamping unit that frequently occur in practice due to the clamping of the vehicle wheel can be advantageously detected with the measuring device according to the invention when the vehicle wheel is already clamped in the clamping unit used for subsequent processing. In the measuring device according to the invention, the actuator longitudinal axis coincides with the central axis of the clamping unit. This can be ensured relatively easily, for example, when the measuring device is subsequently installed in an existing wheel bridge or clamping unit. The measurement of an undesired offset of the rotational axis of the vehicle wheel relative to the actuator longitudinal axis of the measuring device and / or an undesired vertical deviation and / or an undesired tilting of the vehicle wheel can thus be determined in a relatively simple manner.

[0016] A measuring device is used to determine or measure the position coordinates of the center hole. The measurement data is made available to a system control system, which uses the measurement data as correction variables for subsequent machining, in particular the drilling of the bolt end holes, with the vehicle wheel remaining clamped unchanged. This means that an offset of the rotation axis in the transverse direction is detected and the corresponding correction of the bolt hole positions is carried out. This saves the cumbersome process of clamping and unclamping the vehicle wheel. By arranging the measuring device at least partially on or inside the height-adjustable measuring head, the measuring device can be positioned on the side facing away from the machining side when the bolt holes are being drilled. Modern machining centers have two or more clamping units that can be swapped into the machining area. By clamping or unclamping the vehicle wheel, the workpiece can be clamped and the workpiece can be clamped again.By clamping the vehicle wheel on the clamping unit, measurement is possible inside or outside the machining center and can therefore advantageously be carried out outside the machining area during non-productive time, i.e. while the machining center is machining another vehicle wheel. In this way, measurement within the machining area is not necessary, thus saving expensive machining time. Furthermore, detection of any tilting or misalignment of the vehicle wheel in the clamping is possible and can be corrected if necessary before the clamping unit is moved into the machining area. However, it is also conceivable that when using a multi-axis machining center, the measurement data or correction variables are used to align the machining tool, such as a drill, accordingly to the determined offset in the transverse direction and / or tilting of the vehicle wheel. A new orRe-clamping can be avoided in this way.

[0017] The device according to the invention has a measuring device for measuring the offset of the rotational axis and / or the position, i.e., the tilt, of the vehicle wheel. This measuring device can determine the position coordinates of the center hole in space, using the measuring device in the rest position as a reference system. According to the inventive concept, the measuring device can determine the relative distance at at least two, preferably three, points between the measuring head and the center hole at the level of the plane of the center hole, thus determining the rotational axis of the vehicle wheel. If the center hole diameter is known, only two relative distances need to be recorded, although to increase measurement accuracy, a measurement can preferably be performed at three points.It is also possible to determine the position coordinates of the center hole by the deflection of the measuring head in the measuring position, when the measuring head contacts the center hole, and to determine the rotational axis of the vehicle wheel relative to the actuator's longitudinal axis by back-calculating the assumed relative position relative to the rest position of the measuring head. In both cases, rotation of the measuring device relative to the vehicle wheel, or vice versa, is not necessary, thus enabling a very robust, relatively simple, and cost-effective design.

[0018] Furthermore, it may be expedient if the measuring head for measuring the relative distance between the measuring head and the motor vehicle wheel to be measured has a smaller diameter than the center hole of the motor vehicle wheel and thus the measuring head is designed to be insertable into the center hole in the measuring position, wherein the at least one measuring means comprises at least two, preferably three, radially and star-shaped arranged sensor elements for measuring the position coordinates of the center hole as the respective relative distance of the respective sensor element from the center hole.

[0019] The advantage of this design is the ability to measure vehicle wheels of different sizes with correspondingly different center hole diameters by inserting the measuring head into the center hole. By using just two sensor elements, the distance to the center hole can be determined very easily and thus the exact position of the rotational axis of the vehicle wheel relative to the actuator longitudinal axis or central axis of the clamping unit can be determined. The use of three or more sensor elements can increase measurement accuracy. It is also conceivable for the measuring device or the sensor elements of this arrangement to scan the beginning of the center hole in the vertical direction or in the horizontal direction when assuming the measuring position.the actuator's longitudinal axis, which enables detection of the position of the vehicle wheel in space and allows conclusions to be drawn about a possible tilt if at least two, preferably three, measuring points or starting points of the center hole are recorded at different times during the movement.

[0020] Furthermore, it can be provided that the sensor elements are designed as contactless distance sensors or measuring probes that can be moved in the radial direction.

[0021] The inventive design of the sensor elements enables the at least one measuring device to be concealed from view from the outside and, under certain circumstances, even protected before and after the measuring process, e.g., by a movable cover. Non-contact measurement has the advantage that no physical contact with the center hole is necessary, thus ensuring a consistent and wear-free measuring device. The design as a movable measuring probe that can be temporarily extended radially from the measuring head represents a very cost-effective and robust variant of the measuring device.

[0022] Furthermore, it can be provided that the actuator has a support surface suitable for resting on a contact surface of the vehicle wheel that is adjacent to the center hole in the radial direction and projects radially relative to the measuring head.

[0023] The provision of a support surface has the advantage that the vertical position or deviation of the vehicle wheel can be detected by contacting the support surface when assuming the measuring position. Furthermore, the support surface can be advantageous for supporting the wheel while applying a damping force during drilling of the bolt holes. Particularly in the case of very thin-walled or delicately constructed vehicle wheels, stiffening during drilling can effectively reduce unwanted distortion and / or deflection, thus ensuring the quality of the produced vehicle wheels.

[0024] Also advantageous is a form of embodiment according to which it can be provided that the measuring head has a convex shape in the axial direction and a maximum diameter that is larger relative to the center hole, and is mounted so as to be displaceable in the transverse direction and / or axial direction relative to the longitudinal axis of the actuator, and wherein the at least one measuring means for measuring the position coordinates of the center hole based on the relative position of the measuring head in the measuring position is designed such that in the measuring position a deflection of the measuring head in the transverse direction and / or axial direction relative to the rest position can be detected.

[0025] A measuring head designed in this way for measuring the position coordinates of the center hole offers the advantage that the measuring device can be arranged in a way that is hidden from the outside in the rest and measuring positions, which enables a particularly robust construction. Furthermore, the convex, preferably conical or spherical segment-shaped, shape of the measuring head allows a type of self-centering of the measuring head in the measuring position. This embodiment thus allows a "floating" mounting of the measuring head, which significantly increases the degrees of freedom and arrangement options of the at least one measuring device. The displacement of the measuring head relative to the actuator's longitudinal axis can be determined very precisely, at least in the transverse direction, but under certain circumstances, also simultaneously in the vertical direction, depending on the arrangement of the measuring device. In this way, the determination of an offset in the transverse direction and / or vertical direction, and possiblyEven simultaneous tilting of the vehicle wheel is possible. This can reduce the time required for measurement and increase safety and quality during processing.

[0026] According to a further development, it is possible for the at least one measuring means to comprise at least one optical and / or inductive and / or capacitive sensor element.

[0027] The use of optical and / or inductive and / or capacitive sensor elements can preferably take place within the measuring head, but also separately or at least partially on or within the actuator. The sensor elements are efficiently protected from the outside and, depending on the sensor type used, can detect a displacement in at least one spatial direction, for example using reference markings. The use of capacitive sensor elements has proven to be particularly advantageous because they enable a small installation size, low energy consumption and good measurement sensitivity. It can be provided that the measuring head comprises at least two, preferably three, corresponding sensor elements in order to be able to detect displacements in the transverse and / or axial directions. It is also conceivable that the sensor elements are arranged obliquely to the longitudinal axis of the actuator in such a way that they are able to detect the displacement of the measuring head simultaneously in the transverse and vertical directions orThe actuator's longitudinal direction is detected. This enables robust, low-maintenance, and fast detection of the position coordinates of the center hole and / or the position of the vehicle wheel.

[0028] Furthermore, it may be expedient if, for the simultaneous measurement of the relative position of the measuring head in the transverse direction and axial direction, the measuring head is mounted on a measuring device arranged within the actuator and designed as a bending rod.

[0029] In this way, the sensor elements can be arranged within the measuring head and / or within the actuator, and a floating mounting of the measuring head can be easily implemented. The deflection of the bending rod in a spatial direction detected by the sensor elements provides information about the position of the rotational axis of the center hole and can even be used to determine the position or tilt of the vehicle wheel in a relatively simple manner. It is even conceivable that such a bending rod could be used to determine a damping force to be applied to the vehicle wheel from below.

[0030] Furthermore, it can be provided that the at least one measuring means is arranged within the measuring head so as to be at least temporarily hidden from view from the outside.

[0031] Temporarily concealing the measuring device can increase its service life and thus the maintenance intervals of the measuring device. This ensures high measurement precision over a longer period. Furthermore, the risk of damage to the measuring device, for example, during the clamping or removal of the vehicle wheel from the clamping device, is reduced.

[0032] Furthermore, it can be provided that the measuring means comprises a wireless, preferably WLAN or Bluetooth, communication device for transmitting the position coordinates of the center hole as survey data to a system control device.

[0033] It has proven particularly advantageous if the measuring device can be wirelessly connected to a system control system, as this eliminates the need for openings in the measuring head and / or actuator in which foreign matter could accumulate. This promotes the robustness of the measuring device. Furthermore, such a measuring device can be installed in existing clamping units with relatively little technical effort and connected to the system control system via wireless data transmission methods well known to those skilled in the art.

[0034] According to a particular embodiment, it is possible for the measuring device to have a power supply device, preferably inductive and / or capacitive, which can be recharged in the rest position in order to avoid power supply cables penetrating the actuator and / or the measuring head.

[0035] This makes it easy to ensure the independent functionality of the measuring device relative to the clamping unit. Wireless power transmission eliminates unwanted power and / or data transmission cables, especially in the area of ​​the height-adjustable actuator, thus enabling a very robust design.

[0036] According to an advantageous further development, it can be provided that a charging device corresponding to the energy supply device is arranged on the measuring device holder.

[0037] This arrangement allows the distance to the power supply device, which is preferably located in the measuring head, to be kept relatively short. This helps prevent transmission and power losses and enables fast and safe charging of the power supply device in the measuring head's rest position.

[0038] In particular, it may be advantageous if an additional length measuring element, preferably a length measuring rod, is coupled to the actuator for measuring a vertical displacement of the actuator.

[0039] This length measuring element can be used as a redundant element for detecting the vertical position of the measuring head or as a supplement to a measuring device that only detects in the transverse direction. Such a length measuring element can thus be used in combination with or as part of a previously mentioned measuring device designed to determine a transverse offset, or it can also be used independently as a measuring device for solely determining the position, thus forming a standalone measuring device. According to the inventive concept, such a measuring device for determining the position or vertical displacement is not necessarily limited to an arrangement in the measuring head, but can also be arranged on or at least partially within the measuring device holder and / or the actuator.Such a length measuring element can be designed as at least one capacitive, inductive, and / or optical sensor element and serves to detect the deflection of the actuator and / or the measuring head in the vertical direction. Preferably, the length measuring element can be designed as a mechanical and / or electromechanical length measuring rod and, for example, coupled to the actuator. This embodiment can also be designed independently within the scope of the present invention and therefore represents a potentially independent invention for monitoring the position of the vehicle wheel and / or the tilting of the vehicle wheel.

[0040] Furthermore, it can be provided that the actuator comprises a pneumatic, hydraulic or electromechanical drive for applying a damping force to at least parts of the vehicle wheel to be measured.

[0041] This design allows for easy support of the wheel components adjacent to the center hole during machining in the machining center. This increases safety during machining, especially during drilling of the bolt holes, to prevent the wheel from deflecting. This can improve the quality of the machining.

[0042] The invention further relates to a clamping unit for temporarily securing at least one motor vehicle wheel during a measuring and machining process, comprising at least three, preferably six, clamping elements displaceable concentrically to a central axis, which are suitable for engaging the motor vehicle wheel, preferably a rim flange of the motor vehicle wheel, and for clamping the motor vehicle wheel in a predeterminable position and orientation. The clamping unit according to the invention has a measuring device according to the invention, wherein the actuator longitudinal axis of the measuring device is aligned with the central axis of the clamping unit.

[0043] The advantage of this clamping unit is that the clamping and measuring can be performed as described above during non-productive time in the machining center, i.e., while another vehicle wheel is being machined. This allows the required measuring time to determine the position and / or orientation of the vehicle wheel to be performed before it is transferred into the machining area of ​​the machining center, eliminating the need for reclamping and / or measuring within the machining area. By combining it with the measuring device according to the invention, the advantages already discussed above can also be applied to the clamping unit and will not be repeated here.

[0044] In addition, it can be provided that the clamping elements are designed in several stages to accommodate vehicle wheels with different wheel diameters.

[0045] The stepped design of the clamping element upper side enables the easy accommodation of vehicle wheels with common wheel diameters of, for example, 15 to 22 inches. A vehicle wheel is placed with the rim flanges on corresponding clamping element upper sides or notches of the clamping elements and clamped by moving the clamping elements, which are arranged concentrically to the central axis of the clamping unit, together. Corresponding notches thus form a virtual plane which should be perpendicular to the rotation axis of the vehicle wheel. A possibly "slanted" insertion of a vehicle wheel is detected at an early stage by the measuring device according to the invention and, thanks to the measurement and determination of corrective variables described above, can have no qualitative impact on the subsequent processing of the vehicle wheel. This enables very fast and robust handling and, under certain circumstances, even automated manipulation of the vehicle wheels.

[0046] Also advantageous is a design according to which it can be provided that the measuring head of the measuring device is designed to be retractable in the rest position relative to a horizontal plane formed between the clamping elements.

[0047] "Sinking" the measuring head relative to the plane of the locking or clamping elements can effectively reduce the likelihood of damage to the measuring device during the insertion or removal of a vehicle wheel. The extremely robust and low-maintenance clamping unit or measuring device can therefore extend maintenance intervals and save associated repair and maintenance costs.

[0048] The method according to the invention for measuring an offset of a rotation axis and / or the position of a motor vehicle wheel clamped for machining in a clamping unit comprises the following method steps: - Providing a measuring device which comprises a measuring device holder with a height-adjustable measuring head, wherein the measuring head is coupled to an actuator having an actuator longitudinal axis and is designed to be movable in the direction of the actuator longitudinal axis between a measuring position and a rest position by means of the actuator, and which has a measuring device with at least one measuring means for measuring the offset of the rotational axis of the motor vehicle wheel based on position coordinates of a center hole in the transverse direction and / or axial direction of the center hole of the motor vehicle wheel relative to the actuator longitudinal axis, wherein the at least one measuring means is designed in such a way,that no relative rotation of the vehicle wheel to the measuring head is required for the measurement, and wherein the at least one measuring means for measuring the offset of the rotation axis and / or the position of the vehicle wheel in the transverse direction and / or axial direction is designed either to detect the position coordinates of the center hole by a relative distance between the measuring head and the center hole of the vehicle wheel to be measured, or is designed to detect the position coordinates of the center hole as a relative position of the measuring head in the measuring position deviating from the position of the measuring head in the rest position; - Moving the measuring head into the measuring position using an actuator; and - Measuring the position of the center hole and / or the position of the vehicle wheel by either -- Determining the relative distance between the measuring head and the rotational axis of the vehicle wheel to be measured by means of the measuring means configured for this purpose, preferably comprising at least two, particularly preferably three, sensor elements arranged in a star shape in the radial direction, by measuring the position coordinates of the center hole at at least two, preferably three, different points of the center hole, or -- Determining the relative position of the measuring head in the measuring position deviating from the rest position of the measuring head, which preferably has a convex shape and a larger maximum diameter relative to the center hole, by displacing the measuring head and in the transverse direction and / or axial direction relative to the rest position relative to the actuator longitudinal axis, wherein the at least one measuring means for measuring the relative position of the measuring head in the measuring position detects a deflection of the measuring head in the transverse direction and / or axial direction; - Transmitting the position coordinates of the center hole as survey data to a plant control device; - Use of the measurement data as correction values ​​for subsequent machining of the vehicle wheel with the vehicle wheel clamping unchanged.

[0049] The advantage of the method according to the invention lies in the one-time clamping of the vehicle wheel in the clamping unit and the possibility of easily correcting the subsequent machining with regard to position and / or orientation. The resulting measurement and transmission of the position coordinates of the vehicle wheel is achieved in a relatively simple manner, without the need for additional rotation of the measuring device or the vehicle wheel. Any deviations or offsets of the vehicle wheel in the transverse and / or vertical direction can be efficiently determined and transmitted to the machining center as correction values ​​via the system control system, thus efficiently avoiding reclamping and / or re-calibration in the machining area.Other advantages associated with the method arise from the combination with the previously mentioned embodiments of the measuring device according to the invention, which are also applied to the method at this point.

[0050] According to a further development, it is possible that during the measurement any offset of the center hole relative to the central axis of the clamping unit and any tilting of the vehicle wheel are determined at the same time.

[0051] This enables a particularly safe and fast method to ensure high quality when processing the vehicle wheel.

[0052] Furthermore, it may be useful if, following the transfer, the correction variables are used to determine corrected bolt hole positions and then the machining of bolt holes takes place.

[0053] Particularly when determining bolt hole positions, it has proven advantageous to forward the correction values ​​from the determined process via the system control system to the machining center, where they can then reposition, and possibly even tilt, the bolt holes accordingly. This can make a decisive contribution to avoiding rejects and thus ensuring the high quality of automotive wheels.

[0054] Furthermore, it can be provided that after the measuring process, the measuring head remains in its measuring position and during the machining of the bolt holes, the measuring head or a support surface of the actuator applies a damping force in the axial direction for support, preferably on a contact surface of the vehicle wheel adjacent to the center hole in the radial direction outwards.

[0055] With the method according to the invention, the damping force can be applied from the same side as the measurement of the position coordinates of the center hole and thus of the vehicle wheel, eliminating the need for an additional support device. Furthermore, a preset damping force can reduce any vibrations, distortion, and / or unwanted deflection of the vehicle wheel in the area of ​​the center hole. This can be particularly advantageous when a drilling tool is positioned at an angle and / or for vehicle wheels with a delicate design.

[0056] For a better understanding of the invention, it is explained in more detail using the following figures.

[0057] They show in a highly simplified, schematic representation: Fig. 1 schematic representation of a measuring device with a deflectable measuring head for measuring an offset of the rotation axis of the vehicle wheel from the actuator longitudinal axis or central axis in the rest and measuring position; Fig. 2 schematic representation of a measuring device with a measuring head which is designed to be inserted into the center hole to measure an offset of the rotational axis of the vehicle wheel from the actuator longitudinal axis or central axis; Fig. 3 schematic sectional view of the functional principle of a measuring device with a deflectable measuring head for measuring an offset of the rotation axis of the vehicle wheel from the actuator longitudinal axis or central axis in the rest position (a) and measuring position (b); Fig. 4 schematic sectional view of the functional principle of a measuring device with a measuring head which is designed to be inserted into the center hole in order to measure an offset of the rotation axis of the vehicle wheel from the actuator longitudinal axis or central axis in the rest position (a) and measuring position (b); Fig. 5 schematic sectional view of an embodiment with length measuring elements on the actuator in the left half of the image or as a length measuring rod in the right half of the image; Fig. 6 Embodiment of a measuring device with communication device and energy supply device in the measuring head, or a charging device on or in the measuring device holder; Fig. 7 Oblique view of an embodiment of a clamping unit with integrated measuring device and multi-stage clamping elements.

[0058] By way of introduction, it should be noted that in the variously described embodiments, identical parts are provided with identical reference symbols or component designations. The disclosures contained throughout the description can be applied analogously to identical parts with identical reference symbols or component designations. Furthermore, the positional information chosen in the description, such as top, bottom, side, etc., refers to the directly described and illustrated figure, and these positional information must be applied analogously to the new position in the event of a change in position.

[0059] The measuring device 1 according to the invention for measuring an offset 10 of a rotation axis 32 and / or the position of a motor vehicle wheel 3 clamped for machining in a clamping unit 2 is shown schematically in the Fig. 1 and Fig. 2. In both figures, the measuring device 1 comprises a measuring device holder 4 with an actuator 11 and at least one measuring device 6 coupled to the actuator 11. A measuring head 5 is arranged vertically upwards on the actuator 11. The measuring head 5 is designed to be height-adjustable relative to the measuring device holder 4 and is coupled to the actuator 11, which has a longitudinal axis 12. Fig. 1 and Fig. 2, the rest position 9 of the measuring head is visible in the left half of the image and a measuring position 8 is visible in the right half of the image. The measuring head 5 is designed to be movable between the rest position 9 and the measuring position 8. The at least one measuring device 6 is configured to determine the measurement of the offset 10 of the rotational axis 32 based on position coordinates of the center hole 31 of the vehicle wheel 3 in at least the transverse direction 13 and / or the position of the center hole in the axial direction 14 relative to the actuator longitudinal axis 12. The Fig. 1 and Fig. The arrangement of the measuring device shown in Figure 2 does not require any relative rotation of the vehicle wheel 3 relative to the measuring head 5 and / or the clamping unit 2 in order to measure the position coordinates of the center hole 31.

[0060] In Fig. 1 shows a schematic sectional view through the measuring device 1, in which a measuring means 6 is designed to detect the position coordinates of the center hole 31 as a relative position 17 of the measuring head 5 in the measuring position 8, deviating from the position of the measuring head 5 in the rest position 9. As can be seen from Fig. 1, in conjunction with Fig. 3a and Fig. As can be seen in Figure 3b, in the measuring position 8, the measuring head is deflected in the transverse direction 13 upon contact with the vehicle wheel 3 at the center hole 31. The measuring head 5, which is movably arranged on the actuator 11, thus enables a deflection of the measuring head 5 into the relative position 17 in the transverse direction 13 and / or axial direction 14 or vertical direction.

[0061] In Fig. 2, a measuring device 1 according to the invention is shown schematically in cross section, wherein the at least one measuring means 6 for measuring the offset 10 is designed to detect the position coordinates of the center hole 31 as a relative distance 16 between the measuring head 5 and the center hole 31 of the vehicle wheel 3 to be measured. In the embodiment shown in Fig. 2, the diameter of the measuring head 5 is selected to be smaller than the diameter of the center hole 31. In this way, the measuring head can be inserted into the center hole 31 in the measuring position 8. As can be seen from Fig. 2, in conjunction with Fig. 4a and Fig. 4b, the relative distance 16 is measured by the measuring device 6.

[0062] In Fig. 3, the functional principle and a possible embodiment of a measuring device 6 for determining the position coordinates of the center hole 31 as the relative position 17 of the measuring head 5 is shown schematically. The measuring head 5 in Fig. 3 has a convex shape in the axial direction 14 and a larger maximum diameter than the center hole 31. The measuring head 5 is mounted displaceably in the transverse direction 13 and / or axial direction 14 relative to the actuator longitudinal axis 12. In Fig. 3a, the measuring head 5 is shown in the rest position 9. In the selected representation, the measuring device 6 has at least one, preferably several, sensor elements 7, which detect a displacement or deflection relative to the actuator longitudinal axis 12. It can be provided that a reference marking 36 is arranged on the actuator 11 corresponding to the sensor element 7. In Fig. 3b schematically illustrates the measuring position 8. It can be seen that, due to the convex shape of the measuring head 5, a type of self-centering occurs when the measuring head 5 makes contact with the vehicle wheel 3 in the area of ​​the center hole 31, resulting in a deflection of the measuring head 5 relative to the actuator's longitudinal axis 12. In this way, when the measuring position 8 is assumed, a relative position 17 of the measuring head 5 is assumed, which correlates with an offset 10 of the rotational axis 32 of the vehicle wheel 3 relative to the actuator's longitudinal axis 12 or the central axis 29 of the clamping unit 2. In this way, the position of the rotational axis 32 of the vehicle wheel can be determined very precisely and easily.

[0063] The Fig. The measuring means 6 or sensor elements 7 shown in Figure 3 represent an exemplary arrangement which is particularly suitable for detecting a displacement in the transverse direction 13. However, it is within the scope of the invention that the arrangement of the at least one measuring means 6 is selected such that the displacement of the measuring head 5 occurs, for example, along at least one inclined plane, whereby the detection of a transverse and axial displacement of the measuring head 5 relative to the actuator 11 can be detected simultaneously. In this embodiment, which is not shown, the position coordinates of the center hole 31 are also determined based on the relative position 17 of the measuring head 5 relative to the actuator longitudinal axis 12 or the actuator 11 between the rest position 9 and the measuring position 8.

[0064] The Fig. 3 and Fig. 1 can comprise at least one optical and / or inductive and / or capacitive sensor element 7. As can be seen from Fig. 3, the sensor elements 7 can be arranged inside the measuring head 5 and are thus effectively protected against damage or contamination from the outside. Fig. 3b, in conjunction with Fig. 1, it can be seen that a damping force 37 can be applied in the vertical direction or axial direction 14 by means of the measuring head 5 or the actuator 11 to support at least parts of the vehicle wheel 3. The convex shape of the measuring head 5 achieves a type of self-centering, whereby the force introduction of the damping force 37 occurs homogeneously over the circumference.

[0065] Furthermore, an embodiment not shown is within the scope of the invention in which the measuring means 6, which serves to simultaneously measure the relative position 17 of the measuring head 5 in the transverse direction 13 and the axial direction 14, is designed as a bending rod, which is arranged on or at least partially within the actuator 11 and is coupled to the measuring head 5. Such a design of the measuring means 6 as a bending rod can also offer advantages in determining and controlling the damping force 37.

[0066] Analogous to the description of Figure 3, in Fig. 4a and b show a schematic section of a measuring device 1. The further and possibly independent embodiment of the measuring device 1 again uses the same reference numerals or component designations for the same parts as in the previous Fig. 1 to Fig. 3. To avoid unnecessary repetition, reference is made to the detailed description in the preceding figures. The selected illustration shows a section through one of two, preferably three, sensor elements 7 of the measuring device 6, which are arranged in the measuring head 5. Fig. 4a shows the rest position 9, in which the actuator 11 or the measuring head 5 coupled to the actuator 11 can be seen in the retracted state. Fig. 4b shows the measuring position 8, wherein the at least one measuring means 6 is arranged as at least two, preferably three, radially and star-shaped sensor elements 7 for measuring the position coordinates of the center hole 31 in the measuring head. The illustration shows a section through one of these sensor elements 7 or a sensor element 7 designed as a measuring probe 19. The Fig. 4 in conjunction with Fig. The measuring means 6 or sensor elements 7 shown in Figure 2 can be designed as contactless distance sensors 18 or as measuring probes 19 movable in the radial direction 15. The principle of a contactless distance sensor 18 is shown in Fig. 2 as dashed lines, which indicate the detection range of the distance sensor 18. In Fig. 4b schematically shows an exemplary arrangement of a movable measuring probe 19, which is designed to be extendable in the radial direction 15 for detecting the relative distance 16. It has proven advantageous if the sensor elements 7 are at least temporarily covered from the outside, for example by a cover, and thus protected. As shown in Fig. As can be seen in Figure 4b, the position coordinates of the center hole 31 are measured by measuring the relative distance 16 between the measuring head 5 and the center hole 31, whereby this relative distance 16 correlates to the offset 10 of the rotation axis 32 relative to the actuator longitudinal axis 12 or central axis 29. In this way, the position of the rotation axis 32 can be deduced relatively easily from the knowledge of the position of the actuator longitudinal axis 12.

[0067] Furthermore, Fig. 4 shows that a support surface 21 on the actuator 11 is arranged protruding in the radial direction 15, which serves to bear against a contact surface 20 of the motor vehicle wheel 3 that is adjacent to the center hole 31 in the radial direction 15. By means of this support surface 21, the application of a damping force 37 for supporting at least parts of the motor vehicle wheel 3 in the vertical direction or axial direction 14 is possible.

[0068] In Fig. 5 shows a further and possibly independent embodiment of the measuring device 1, wherein again the same reference numerals or component designations are used for the same parts as in the previous Fig. 1 to Fig. 4, and Fig. 6. To avoid unnecessary repetition, reference is made to the detailed description in the preceding figures. Fig. 5 shows two exemplary sectional views, wherein the measuring device 6 or its sensor elements 7 for determining a vertical deflection or vertical displacement 28 of the actuator 11 are shown schematically. This measuring device 6, designed as a length measuring element 26, can be used to determine the position of the motor vehicle wheel 3. Such a length measuring element 26 can be used in combination with or as part of a previously mentioned measuring device 6, which is designed to determine an offset 10 in the transverse direction, or it can also be used independently as a measuring device 6 for solely determining the position. According to the inventive concept, the measuring device 6 is not necessarily limited to an arrangement in the measuring head 5, but can optionally also be arranged on or at least partially within the measuring device holder 4 and / or the actuator 11. Fig. 5, the left half of the figure shows the actuator 11 in a measuring position 8 that differs from the rest position 9. An additional length measuring element 26 is shown on the actuator 11 for measuring the vertical displacement 28 of the actuator 11. Analogous to the statements of Fig. 3, such a length measuring element 26 can also be designed as an optical capacitive and / or inductive sensor element 7. The reference markings 36 shown on the measuring device holder 4 can be arranged, for example, on the inner wall of the measuring device holder 4 for the exact measurement of the vertical displacement 28, but are not absolutely necessary depending on the type of length measuring element 26 used. A particularly simple design of a length measuring element 26 is shown in the right half of the figure. Fig. 5 as a length measuring rod 27, which detects a vertical displacement 28 of the actuator. Fig. The length measuring elements shown in Figure 5 can be regarded as an independent measuring device 6, which can be used either in combination with a measuring device 6 of the Fig. 1 to 4 or also as a standalone measuring device 6. The use of a length measuring element 26 and / or a measuring device, as shown in the preceding examples 1 to 4, serves in particular to detect a tilt and / or vertical position of the vehicle wheel 3 deviating from an expected target position.

[0069] It is particularly advantageous to use the Fig. 1 to 7 is designed with a pneumatic or hydraulic or electromechanical drive for applying a damping force 37 to the actuator 11 and thus to at least parts of the vehicle wheel 3 to be contacted.

[0070] In Fig. 6 shows a measuring device 1 according to the invention, wherein the measuring device 6 has a wireless communication device 22 for transmitting the position coordinates of the center hole 31 as measurement data to a system control device 23. The communication device 22 is preferably a WLAN or Bluetooth transmitter or receiver.

[0071] Receiving device. Furthermore, Fig. 6 shows that, to avoid power supply cables on or within the actuator 11, a power supply device 24 is arranged within the measuring head 5. In this way, the measuring device 6 or the sensor elements 7 as well as an optional communication device 22 are supplied with power. The measuring head is shown in dashed lines in the rest position 9. In this rest position 9, the measuring head 5 or its power supply device 24 comes into the vicinity of a corresponding charging device 25, which is preferably arranged on the measuring device holder 4. The Fig. The communication device 22 shown in Figure 6 and / or the energy supply device 24 as well as the corresponding charging device 25 are compatible with all embodiments described above.

[0072] In Fig. 7 schematically shows a clamping unit 2 according to the invention for temporarily fixing a vehicle wheel 3 during a measuring and / or machining process. In the selected illustration, the clamping unit 2 comprises six clamping elements 30 movably arranged concentrically to a central axis 29 or actuator longitudinal axis 12. The vehicle wheel 3 is gripped or clamped at six points on the rim flange 33 by moving the clamping elements 30 together. After clamping the vehicle wheel 3, a measuring process can be carried out using the measuring device 1. The measuring position 8 of the measuring head 5 is shown in dashed lines. As can be seen from Fig. As can be seen in Figure 7, the actuator's longitudinal axis 12 coincides with the central axis 29 of the clamping unit. The clamping elements 30 have several steps, allowing vehicle wheels 3 with different wheel diameters 34 to be accommodated. The clamping unit 2 according to the invention or the measuring device 1 according to the invention enable, in the manner mentioned above, a very rapid and reliable detection of a possible tilt of the vehicle wheel 3 within the clamping unit 2 in the clamping elements 30.

[0073] A clamping unit 2, as in Fig. 7, can be designed as part of a machining center so that it can be pivoted into the center, whereby the one-time clamping of the vehicle wheel in the clamping unit 2 can be maintained. Preferably, two clamping units 2 are used, located alternately in the machining area. The clamping and / or measuring of the vehicle wheel 3 or the offset 10 of the center hole 31 can thus take place during idle time and already outside the machining area. According to the inventive concept, any offset 10 of the rotational axis 32 of the vehicle wheel 3 relative to the central axis 29 or the actuator longitudinal axis 12 can be measured in a simple and reliable manner. The system control device 23 receives the position coordinates of the center hole 31 from the measuring device as measurement data, which are subsequently used as correction variables for the subsequent machining of the vehicle wheel 3 with the clamping in the clamping unit 2 unchanged.This eliminates the time-consuming and costly measurement of bolt hole positions within the machining center's machining area. In the example shown in . Fig. 7, the machining or drilling of the bolt holes 35 can be carried out directly after the transmission of the correction values ​​for determining corrected bolt hole positions. In conjunction with the Fig. 1, Fig. 2, Fig. 3b and Fig. 4b it can be seen that the measuring head 5 or a support surface 21 of the actuator 11 can be used to support at least parts of the vehicle wheel 3 by means of a damping force 37 in the axial direction 14.

[0074] The embodiments show possible embodiments, whereby it should be noted at this point that the invention is not limited to the specifically illustrated embodiments thereof, but rather various combinations of the individual embodiments with each other are also possible and this possibility of variation lies within the skill of the person skilled in the art in this technical field due to the teaching of technical action by means of the objective invention.

[0075] The scope of protection is determined by the claims. However, the description and drawings must be used to interpret the claims. Individual features or combinations of features from the various embodiments shown and described may represent independent inventive solutions. The problem underlying these independent inventive solutions can be derived from the description.

[0076] All information on value ranges in this description is to be understood as including any and all sub-ranges thereof, e.g. the information 1 to 10 is to be understood as including all sub-ranges starting from the lower limit of 1 and the upper limit of 10, ie all sub-ranges begin with a lower limit of 1 or greater and end with an upper limit of 10 or less, e.g. 1 to 1.7, or 3.2 to 8.1, or 5.5 to 10.

[0077] For the sake of clarity, it should finally be pointed out that, in order to better understand the structure, some elements have been shown out of scale and / or enlarged and / or reduced in size. Reference symbol list 1 measuring device 2 clamping unit 3 car wheels 4 Measuring instrument holder 5 measuring head 6 Measuring instruments 7 Sensor element 8 Measuring position 9 Resting position 10 Offset 11 Actuator 12 Actuator longitudinal axis 13 Transverse direction 14 Axial direction 15 Radial direction 16 Relative distance 17 Relative position 18 Distance sensor 19 measuring probes 20 contact surface 21 Support surface 22 Communication device 23 Plant control device 24 Power supply device 25 loading device 26 Length measuring element 27 Length measuring stick 28 Vertical displacement 29 Central axis 30 clamping element 31 center hole 32 Rotation axis of the vehicle wheel 33 Rim flange 34 wheel diameters 35 bolt hole 36 Reference mark 37 Damping force

Claims

[1] Measuring device (1) for measuring an offset (10) of a rotational axis (32) and / or the position of a motor vehicle wheel (3) clamped for machining in a clamping unit (2), comprising a measuring device holder (4) comprising a height-adjustable measuring head (5), wherein the measuring head (5) is coupled to an actuator (11) having an actuator longitudinal axis (12) and is designed to be movable by means of the actuator (11) in the direction of the actuator longitudinal axis (12) between a measuring position (8) and a rest position (9), and at least one measuring means (6) for measuring the offset (10) of the rotational axis (32) of the motor vehicle wheel (3) based on position coordinates of a center hole (31) of the motor vehicle wheel (3) in the transverse direction (13) and / or axial direction (14) of the center hole (31) of the motor vehicle wheel (3) relative to the actuator longitudinal axis (12), wherein the at least one measuring means (6) is designed such that no relative rotation of the vehicle wheel (3) to the measuring head (5) is required for the measurement and wherein the at least one measuring means (6) for measuring the offset (10) of the rotation axis (32) and / or the position of the motor vehicle wheel (3) in the transverse direction (13) and / or axial direction (14) is designed to detect the position coordinates of the center hole (31) as a relative position (17) of the measuring head (5) in the measuring position (8) deviating from the position of the measuring head (5) in the rest position (9), wherein the measuring head (5) has a convex shape in the axial direction (14) and a larger maximum diameter relative to the central hole (31), and is mounted so as to be displaceable in the transverse direction (13) or in the transverse direction (13) and simultaneously in the axial direction (14) relative to the actuator longitudinal axis (12), wherein the at least one measuring means (6) for measuring the position coordinates of the central hole (31) based on the relative position (17) of the measuring head (5) in the measuring position (8) is designed such that in the measuring position (8) a deflection of the measuring head (5) in the transverse direction (13) or in the transverse direction (13) and simultaneously in the axial direction (14) relative to the rest position (9) can be detected, wherein, for the simultaneous measurement of the relative position (17) of the measuring head (5) in the transverse direction (13) and axial direction (14), the measuring head (5) is mounted on a measuring means (6) arranged within the actuator (11) and designed as a bending rod, and wherein the at least one measuring means (6) is arranged within the measuring head (5) so as to be at least temporarily hidden from view from the outside. [2] Measuring device (1) according to claim 1 characterized by that the at least one measuring means (6) comprises at least one optical and / or inductive and / or capacitive sensor element (7). [3] Measuring device (1) according to one of the preceding claims characterized by that the measuring means (6) comprises a wireless, preferably WLAN or Bluetooth, communication device (22) for transmitting the position coordinates of the center hole (31) as surveying data to a system control device (23). [4] Measuring device (1) according to one of the preceding claims characterized by in that the measuring means (6) has a power supply device (24) which is rechargeable in the rest position (9), preferably by inductive and / or capacitive means, in order to avoid power supply cables penetrating the actuator (11) and / or the measuring head (5). [5] Measuring device (1) according to claim 4 characterized by that a charging device (25) corresponding to the energy supply device (24) is arranged on the measuring device holder (4). [6] Measuring device (1) according to one of the preceding claims characterized bythat an additional length measuring element (26), preferably a length measuring rod (27), is coupled to the actuator (11) for measuring a vertical displacement (28) of the actuator (11). [7] Measuring device (1) according to one of the preceding claims characterized by that the actuator (11) comprises a pneumatic, hydraulic or electromechanical drive for applying a damping force (37) to at least parts of the motor vehicle wheel (3) to be measured. [8] Clamping unit (2) for the temporary fixation during a measuring and machining process of at least one motor vehicle wheel (3), comprising at least three, preferably six, clamping elements (30) which are displaceable concentrically to a central axis (29) and which are suitable for clamping the motor vehicle wheel (3), preferably engaging a rim flange (33) of the motor vehicle wheel (3), and a measuring device (1) according to one of claims 1 to 7, wherein the actuator longitudinal axis (12) of the measuring device (1) is arranged in alignment with the central axis (29) of the clamping unit (2). [9] Clamping unit (2) according to claim 8 characterized by that the clamping elements (30) are designed in several stages to accommodate motor vehicle wheels (3) with different wheel diameters (34). [10] Clamping unit (2) according to one of claims 8 or 9 characterized bythat the measuring head (5) of the measuring device (1) is designed to be retractable in the rest position (9) relative to a horizontal plane formed between the clamping elements (30). [11] Method for measuring an offset (10) of a rotational axis (32) and / or the position of a motor vehicle wheel (3) clamped for machining in a clamping unit (2), preferably designed according to one of claims 8 to 10, comprising the method steps: -- Providing a measuring device (1), designed according to one of claims 1 to 7, which comprises a measuring means holder (4) with a height-adjustable measuring head (5), wherein the measuring head (5) is coupled to an actuator (11) having an actuator longitudinal axis (12) and is designed to be movable by means of the actuator (11) in the direction of the actuator longitudinal axis (12) between a measuring position (8) and a rest position (9), and the measuring device (1) has at least one measuring means (6) for measuring the offset (10) of the rotational axis of the motor vehicle wheel (3) based on position coordinates of a center hole (31) of the motor vehicle wheel (3) in the transverse direction (13) and / or axial direction (14) of the center hole (31) of the motor vehicle wheel (3) relative to the actuator longitudinal axis (12), wherein the at least one measuring means (6) is designed such that no relative rotation of the vehicle wheel (3) to the measuring head (5) is required for the measurement and wherein the at least one measuring means (6) for measuring the offset (10) of the rotation axis (32) and / or the position of the motor vehicle wheel (3) in the transverse direction (13) and / or axial direction (14) is designed to detect the position coordinates of the center hole (31) as a relative position (17) of the measuring head (5) in the measuring position (8) deviating from the position of the measuring head (5) in the rest position (9); -- moving the measuring head (5) into the measuring position (8) by means of the actuator (11); and -- Measuring the position of the center hole (31) and / or the position of the vehicle wheel (3) by --- Determining the relative position (17) of the measuring head (5) in the measuring position (8) deviating from the rest position (9) of the measuring head (5) which has a convex shape and a maximum diameter which is larger than the central hole (31) by displacing the measuring head (5) in the transverse direction (13) or in the transverse direction (13) and simultaneously in the axial direction (14) relative to the rest position (9) relative to the actuator longitudinal axis (12), wherein the at least one measuring means (6) for measuring the relative position (17) of the measuring head (5) in the measuring position (8) detects a deflection of the measuring head (5) in the transverse direction (13) or in the transverse direction (13) and simultaneously in the axial direction (14); -- transmitting the position coordinates of the center hole (31) as survey data to a plant control device (23); - Use of the measurement data as correction values ​​for subsequent machining of the vehicle wheel (3) with the vehicle wheel (3) clamped in the same way. [12] Method according to claim 11 characterized by that during the measurement, any offset (10) of the center hole (31) relative to the central axis (29) of the clamping unit (2) and any tilting of the vehicle wheel (3) are determined at the same time. [13] Method according to one of claims 11 or 12 characterized by that following the transfer, the correction variables are used to determine corrected bolt hole positions and then the machining of bolt holes (35) takes place. [14] Method according to one of claims 11 to 13 characterized by that after the measuring process, the measuring head (5) remains in its measuring position (8) and during the machining of the bolt holes (35), the measuring head (5) or a support surface (21) of the actuator (11) applies a damping force (37) in the axial direction (14) for support, preferably on a contact surface (20) of the motor vehicle wheel (3) adjacent to the center hole (31) in the radial direction (15).

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