Workpiece holder and measuring device

Abstract

Workpiece holder (1) for an elongated workpiece (100) to be measured, comprising a holder arrangement (2) comprising at least three support elements (30) spaced apart from one another along a spatial direction (3) for supporting the workpiece (100) to be measured, characterized in that the holder arrangement (2) comprises at least one pendulum device (10), wherein the pendulum device (10) comprises a pendulum beam (14) freely rotatable about a pendulum axis (15) and a rotation axis (13) oriented transversely to the pendulum axis (15), which has pendulum arms (16, 17) opposite each other with respect to the pendulum axis (15), wherein one of the at least three support elements (30) is arranged on each of the pendulum arms (16, 17).

Description

[0001] The invention relates to a workpiece holder for an elongated workpiece to be measured, in particular a shaft or crankshaft. The invention further relates to measuring devices, in particular for the precision measurement of elongated workpieces, comprising a workpiece holder for this type of workpiece.

[0002] It is common practice in the art to measure elongated mechanical components, especially shafts and crankshafts, using measuring instruments. It is common practice to use tactile coordinate measuring machines.

[0003] DE 44 20 137 A1 describes a measuring device for measuring crankshafts and, in addition to a rotatable workpiece holder, has a first group of measuring jaws for measuring the main bearings of the crankshaft and a second group of measuring jaws for measuring the connecting rod bearings. Each measuring jaw of the second group has several sensors and its own drives for moving the measuring jaw in the plane perpendicular to the axis of the crankshaft and, when the crankshaft rotates, is either guided along target paths corresponding to the stroke of the connecting rod bearing or is tracked according to the signals from the sensors of the movement of the connecting rod bearing.

[0004] Currently, crankshafts are either clamped between centers and measured, which is only possible for shorter shafts. For longer components, they are placed against the crankshaft main bearings to minimize inherent deflection.

[0005] The inherent deflection is measured by measuring a component, then rotating it 180° and measuring it again. The measurement results are then combined. The disadvantage is that two measurements have to be performed.

[0006] Even vertical storage / suspension of the component or workpiece does not eliminate the problem of self-deformation, since especially with larger and longer components, if vertical storage is even possible, significant self-deformation also occurs due to their own mass.

[0007] The invention is based on the objective of improving a workpiece holder for elongated components and workpieces for use in precision measurement and a measuring device for such components and workpieces, in particular with regard to the effect of a self-deflection of the components and workpieces in the gravitational field during a measurement and with regard to flexibility in adapting the workpiece holder to different components and workpieces and in supporting workpieces and components.

[0008] The problem is solved according to the invention by a workpiece holder with the features of claim 10 and a measuring device with the features of claim 10. Advantageous embodiments are described in the dependent claims.

[0009] A workpiece holder for an elongated workpiece to be measured is proposed, comprising a holder arrangement at least three support elements spaced apart from each other along a spatial direction for supporting the workpiece to be measured, wherein the mounting arrangement comprises at least one pendulum device, wherein the pendulum device comprises a pendulum beam freely rotatable about a pendulum axis and a rotation axis oriented transversely to the pendulum axis, which has pendulum arms opposite each other with respect to the pendulum axis, wherein one of the at least three support elements is arranged on each of the pendulum arms.

[0010] This workpiece holder offers the advantage that the at least two support elements arranged on the pendulum device always align optimally with the workpiece during placement. The free rotation of the pendulum beam around its axis ensures that the two support elements, located on opposite pendulum arms, come into contact with the workpiece via their workpiece rests, thus supporting the workpiece at the designated support points. The additional free rotation around the axis of rotation, which is transverse to, and usually perpendicular to, the pendulum axis, ensures that any transverse forces that may occur are reduced as much as possible. This minimizes deformations, particularly deflections, caused by gravity.

[0011] Workpiece holders comprising multiple pendulum devices, each with two support elements arranged on opposite pendulum arms, have proven particularly advantageous. Adjusting the support elements is simplified in this configuration. When using two pendulum devices, optimal contact between all four workpiece holders and the four support elements is ensured. One embodiment therefore provides that the holder arrangement comprises at least two of the at least one pendulum devices, each of which has one of the at least three support elements arranged on its respective pendulum arms opposite the respective pendulum axis.

[0012] While it is also possible to implement a workpiece holder that includes a static support element not arranged on a pendulum arm, embodiments are preferred that achieve optimal utilization of all advantages, e.g., a reduction of as many transverse forces as possible on the supported workpiece and full flexibility in adapting to other workpieces to be measured, when all of the at least three support elements are arranged on one of the pendulum arms of the at least one pendulum device opposite the respective pendulum axis.

[0013] A preferred embodiment provides two pendulum devices with a total of four support elements. However, embodiments with more pendulum devices and an even number of support elements are also possible.

[0014] To facilitate the alignment and arrangement of the at least one or more pendulum devices and thus the support elements, one embodiment provides that the mounting arrangement comprises a straight linear guide device along which a base, preferably one base for each pendulum device in the case of multiple pendulum devices, is slidably mounted in one spatial direction. Such a straight linear guide device can, for example, be designed as a rail-like system and comprise one or more parallel rails or grooves. A base of the at least one pendulum device preferably has engagement elements that are adapted to and interact with the guide device.If the guide device, for example, has parallel rails, a base can have guide and sliding shoes that engage the rails and enable linear guidance of the pendulum device in an unlocked state. The mechanical design of the components that allow the base to move along the guide device in the unlocked state can be chosen freely, for example, including rollers, ball bearings, pneumatic bearings, etc.

[0015] However, when supporting the workpieces and also during measurement, it is generally advantageous for the at least one pendulum device to be lockable with respect to displacement along one spatial direction. In the locked state, where displacement along one spatial direction is no longer possible, it can be prevented that the pendulum devices move relative to each other when the workpiece is supported.

[0016] However, it is also possible to allow the pendulum devices to shift during support in order to make the support process as force-free as possible.

[0017] To allow adaptation to different workpieces, for example different crankshafts whose crankshaft bearings have different distances, the support elements are detachably arranged on the pendulum arms.

[0018] For support and measurement, the support elements are preferably fixed and locked to the pendulum arms, but can be loosened and moved into an unlocked state to adapt to other workpieces. Thus, in one embodiment, the support elements arranged on one of the pendulum arms can each be locked in different positions on the pendulum arm by means of a locking device.

[0019] Adjusting the positioning is facilitated if the pendulum arms have a linear guide element oriented parallel to a longitudinal direction of the pendulum arm or pendulum lever. Adjustment of the support elements is only possible along the longitudinal direction of the respective pendulum arm. The respective support element is centrally located transversely to the longitudinal direction of the pendulum arm, so that when a workpiece is loaded onto the workpiece holder of the support element, no torsional forces are introduced into the pendulum arm. One embodiment therefore provides that the pendulum arms each have at least one linear guide element along which the support element arranged on the respective pendulum arm can be moved in an unlocked state.

[0020] To achieve a centered introduction of forces into the respective support element, the at least three support elements preferably comprise fork-shaped, notched or hollow cylindrical workpiece holders.

[0021] Furthermore, a measuring device for an elongated workpiece to be measured is created, comprising a workpiece holder for an elongated workpiece to be measured as described above. The measuring device may preferably be a probing coordinate measuring machine, for example, in a portal design.

[0022] The invention is explained in more detail below with reference to a drawing. The drawing shows: Fig. 1 a schematic representation of a workpiece holder with a workpiece supported on it, designed as a crankshaft; Fig. 2 a schematic rear view of the workpiece holder according to Fig. 1 without a supported workpiece; and Fig. 3 A schematic representation of a measuring device with workpiece holder with two support elements arranged on a pendulum device and one static support element.

[0023] In Fig. Figure 1 schematically depicts a workpiece holder 1. This includes a holder arrangement 2, which in the illustrated embodiment comprises two pendulum devices 10. Two support elements 30 are arranged on each of the pendulum devices 10, which, with their workpiece receptacles 32, support a workpiece 100 designed as a crankshaft. The workpiece 100 is supported at four points, the crankshaft bearings 110. This significantly reduces deflection compared to a two-point support at the ends or the Bessel points. For an 1800 mm long crankshaft, the maximum deformation of 0.00437 mm, measured with a support at two Bessel points, could be reduced to 0.00061 mm, which is the same as with a support at four points, as shown in Figure 1. Fig. Figure 1 shows the measurement. This allows the maximum deformation to be reduced by almost an order of magnitude.

[0024] Each of the pendulum devices 10 comprises a pendulum beam 14, which is freely rotatable about a pendulum axis 15. The pendulum beam 14 comprises two pendulum arms 16, 17 opposite each other with respect to the pendulum axis 15. One of the support elements 30 is detachably attached to each of these pendulum arms 16, 17. Preferably, the two support elements 30 of a pendulum device 10 are arranged equidistant from the pendulum axis 15. An asymmetrical arrangement with respect to the pendulum axis 15 is possible in order to compensate for the support forces to be absorbed, which are introduced via the support elements 30, if the mass distribution along the workpiece 100 is very uneven. The forces acting on the workpiece can thus be designed differently at the different support points. This can further minimize deflection.

[0025] To easily adjust the position of the support elements 30 along the pendulum arms 16, 17 and to easily change the distances between the support elements 30, for example when adapting the workpiece holder to a different component, the pendulum arms 16, 17 each have a linear guide element 18. In the illustrated embodiment, this guide element is a one-piece T-slot 19 (for example, according to DIN 650) extending along the entire length of the pendulum beam 14. A screw, guided by a foot 35 of the support element 30, engages in the T-slot 19 as a locking element 36. This screw is screwed into a T-slot nut (not shown / for example, according to DIN 508) that is inserted laterally into the T-slot 19. When the locking element 36, which is the screw, is tightened, the T-slot nut is clamped in the T-slot 19. This locks the corresponding support element 30 onto the pendulum arm 16, 17.The linear guide element and the locking means can also be designed differently.

[0026] To avoid the influence of lateral forces, the pendulum device 10 has a rotation axis 13 that is oriented transversely, preferably perpendicularly, to the pendulum axis 15. A pendulum axis support 12 is freely rotatable about this rotation axis 13 relative to a base 11 of the pendulum device 10. Although rotation about two axes oriented transversely, i.e., non-collinearly and preferably perpendicularly, to each other is described here, these need not be designed as physical axes of rotation. In other embodiments, the pendulum beam 14 can also be coupled to a base via a gimbal joint 22, which allows free rotation about two mutually perpendicular axes.

[0027] To allow the support elements 30 of the various pendulum devices 10 to be adjusted relative to one another, a base plate 40 of the mounting arrangement 2 has a straight, linear guide device 50 designed like a rail. This guide device has two spaced-apart rails 51 running parallel to one spatial direction 3. This spatial direction 3 is preferably oriented parallel to a workpiece axis 120. Guide and sliding shoes 21 of the pendulum device 10, which are attached to or formed on the base 11, engage along this axis. Locking means (not shown) on the bases 11 or the guide device 50 allow the pendulum device 10 to be locked against displacement along this spatial direction.

[0028] In Fig. 2 is a schematic representation of the workpiece holder according to Fig. Figure 1 shows no workpiece. Identical technical features are indicated with the same reference numerals.

[0029] In Fig.Figure 3 shows a schematically simplified representation of a measuring device 200 with a workpiece aging device 1. The measuring device 200 comprises a control unit 210, which can move at least one probe head 220 against measuring points on a workpiece (not shown) via mechanical actuators 230. The workpiece (not shown) is arranged on a workpiece holder 1 for measurement. In this embodiment, the workpiece holder 1 has a static support element 30 and a pendulum device 10, which has a gimbal-acting joint 22 that allows free rotation of a pendulum beam 14 about two axes oriented transversely, preferably perpendicularly, to each other, such as a pendulum axis 15 and a rotation axis 13. This workpiece holder also enables simple, optimal support of the workpiece and multi-point support of the workpiece without introducing transverse forces into the workpiece.This reduces deformation of workpieces due to gravity during measurement, allowing the measuring device to deliver more precise measurements. Although no linear guide device is shown in this embodiment, it is clear to those skilled in the art that the static support element 30 and the at least one pendulum device 10 can be positioned at different distances relative to each other on the base plate in order to support workpieces of varying elongated lengths.

[0030] It will be apparent to a person skilled in the art that the embodiments described here are highly simplified. The joints, axle bearings, guide elements and / or guide devices can be designed as desired, as long as they provide the described functionality. Reference sign 1 workpiece holder 2 Mounting arrangement 3 a spatial direction 10 Pendulum device 11 Base of the pendulum device 12 Pendulum axle bracket 13 Rotation axis 14 pendulum beams 15 Pendulum axle 16,17 pendulum arms 18 Guide element 19 T-slot 20 Leadership Chamber 21 Guide shoe 22 Cardan joint 30 support element 32 workpiece holder 35 feet 36 locking devices 40 Base plate 50 guide device 51 rails 100 workpieces 110 crankshaft bearings 120 workpiece axis 200 measuring device 210 Control 220 probe 230 actuators QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 44 20 137 A1

[0003]

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