Coordinate measuring apparatus

Abstract

A coordinate measuring device is provided that is lightweight and reduces errors caused by temperature changes while ensuring design freedom. The coordinate measuring device includes a translation mechanism that translates at least in a first direction. The translation mechanism brings a contact member into contact with a workpiece to measure the three-dimensional shape of the workpiece. The translation mechanism comprises: a translation body that translates the contact member in the first direction; a first track made of a material having a first coefficient of thermal expansion for guiding the translation body in the first direction; a support portion made of a material having a second coefficient of thermal expansion different from the first coefficient of thermal expansion for supporting the first track; a first rotating body disposed between the first track and the support portion, rotating according to the relative movement of the first track and the support portion along the first direction; and a first fastening member that fastens the first track and the support portion, which are facing each other and separated by the first rotating body.

Description

Technical Field

[0001] This disclosure relates to a coordinate measuring device. Background Technology

[0002] Coordinate measuring devices that measure the dimensions, positional relationships, contour shapes, and geometric tolerances of a workpiece with high precision by placing a contact probe against any measurement position on the workpiece and obtaining the coordinates of that measurement position have been put into practical use.

[0003] Patent document 1 discloses a contact-type coordinate measuring device using a contact probe.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2009-288227 Summary of the Invention

[0007] The problem the invention aims to solve

[0008] However, to reduce the weight of the coordinate measuring device, it is considered that some of the structural components are made of lightweight materials. On the other hand, in order to achieve high-precision measurement in the coordinate measuring device, it is required to reduce the influence of measurement errors caused by temperature changes. In particular, it is necessary to suppress strain caused by the difference in thermal expansion between the fastened components. For example, a fastening method that compensates for the difference in the coefficient of thermal expansion between the components is considered. However, the fastening method that compensates for the difference in the coefficient of thermal expansion between the components has the following drawback: the fastening position between the components is restricted due to the structure used to compensate for this difference in the coefficient of thermal expansion. Therefore, the design freedom of the fastening position is low, and it is difficult to design with high precision.

[0009] In view of the above-mentioned problems, the present invention aims to provide a coordinate measuring device that is lightweight and reduces errors caused by temperature changes while ensuring design freedom.

[0010] Solution for solving the problem

[0011] For example, the coordinate measuring device according to the present invention has a translation mechanism that translates at least in a first direction. The translation mechanism is used to bring a contact member into contact with a workpiece to measure the three-dimensional shape of the workpiece. The translation mechanism includes: a translation body that translates the contact member in the first direction; a first track made of a material having a first thermal expansion ratio for guiding the translation body in the first direction; a support portion made of a material having a second thermal expansion ratio different from the first thermal expansion ratio for supporting the first track; a first rotating body disposed between the first track and the support portion, which rotates according to the relative movement of the first track and the support portion along the first direction; and a first fastening member that fastens the first track and the support portion, which are facing each other across the first rotating body.

[0012] Furthermore, other features, elements, steps, advantages, and characteristics become clearer through the following detailed description and the accompanying drawings.

[0013] Invention Effects

[0014] According to the present invention, a coordinate measuring device can be provided that is lightweight and reduces errors caused by temperature changes while ensuring design freedom. Attached Figure Description

[0015] Figure 1 This is a diagram showing the overall structure of the coordinate measuring device.

[0016] Figure 2 This is a diagram illustrating a structural example of a non-contact optical sensor.

[0017] Figure 3 This is a diagram showing the system structure of the coordinate measuring device.

[0018] Figure 4 This is a flowchart illustrating an example of a measurement setup.

[0019] Figure 5 This is a flowchart illustrating an example of continuous measurement.

[0020] Figure 6 This is a diagram showing the configuration of the translation mechanism in the first embodiment.

[0021] Figure 7 This is a front view of the translation mechanism in the first embodiment.

[0022] Figure 8 This is an exploded perspective view of the translation mechanism in the first embodiment.

[0023] Figure 9 This is a cross-sectional view of the translation mechanism in the first embodiment.

[0024] Figure 10This is a schematic diagram showing a comparative example of a conventional translation mechanism.

[0025] Figure 11 This is a conceptual diagram illustrating the effects of temperature changes in a comparative example of an existing translation mechanism.

[0026] Figure 12 This is a schematic diagram of the cross-section of the translation mechanism in the first embodiment.

[0027] Figure 13 This is a conceptual diagram illustrating the effect of temperature changes on the translation mechanism in the first embodiment.

[0028] Figure 14 This is a top view of the translation mechanism in the first embodiment.

[0029] Figure 15 This is a perspective view showing the configuration of the various parts of the translation mechanism in the first embodiment.

[0030] Figure 16 This is a diagram showing the configuration of the translation mechanism in the second embodiment.

[0031] Figure 17 This is a perspective view of the translation mechanism in the second embodiment.

[0032] Figure 18 This is the front view of the translation mechanism in the second embodiment.

[0033] Figure 19 This is a diagram illustrating the translation of the translation mechanism in the second embodiment.

[0034] Figure 20 This is a cross-sectional view of the translation mechanism in the second embodiment.

[0035] Figure 21 This is a conceptual diagram of the translation mechanism in the second embodiment. Detailed Implementation

[0036] <First Implementation Method>

[0037] <Coordinate measuring device (overall structure)>

[0038] Figure 1This is a diagram showing the overall structure of the coordinate measuring device 100. The coordinate measuring device 100 measures the dimensions, positional relationships, contour shape, and geometric tolerances of the workpiece W with high precision by placing a contact probe against any measurement position on the workpiece W to be measured and acquiring the three-dimensional coordinates of that measurement position. In addition to recording the measurement data of the workpiece W, the coordinate measuring device 100 can also calculate various values ​​through various operations. As described in this figure, the coordinate measuring device 100 includes a PC (Personal Computer) 1 and a main body 5.

[0039] PC1 can be understood as the control unit of the coordinate measuring device 100. PC1 can be either a laptop or a desktop. PC1 can also be connected to a mouse 2 as a user input device. The user input device can also be a keyboard, touchpad, touch panel, or stylus, etc.

[0040] The main body 5 comprises a head housing 57, a head 50, a contact probe 60, a non-contact optical sensor 31, a rotary table 70, and a control console 11 as its main components.

[0041] The head housing 57 is a base that supports the head 50 and the rotary table 70. For example, the head housing 57 has a ground contact portion 57a ​​and an upright portion 57b. The ground contact portion 57a ​​can be understood as a base plate that supports the rotary table 70 from below, i.e., a so-called base. The upright portion 57b can be understood as a column that stands upright from the ground contact portion 57a ​​and supports the head 50. PC1 and the head housing 57 can be connected via a communication cable 3. A measurement button 80, a detection button 81, and a power button 82 may also be provided on the front part of the ground contact portion 57a.

[0042] When the measurement button 80 is pressed, a scan is performed by the non-contact optical sensor 31 to detect the position and posture of the workpiece and determine the measurement position for the workpiece. When the measurement button 81 is pressed, a scan is performed by the non-contact optical sensor 31, and based on a comparison with the acquired map data described later, the corresponding workpiece setting file is selected from multiple pre-registered setting files. The measurement position can be defined as the position where the contact probe 60 contacts the workpiece W. When the power button 82 is pressed, the main body 5 is switched on / off.

[0043] The head 50 moves the contact probe 60 along the X-axis drive direction 51, the Y-axis drive direction 53, and the Z-axis drive direction 55. As described in this figure, the head 50 includes an X-axis drive unit 52, a Y-axis drive unit 54, and a Z-axis drive unit 56. The X-axis drive unit 52, the Y-axis drive unit 54, and the Z-axis drive unit 56 can each be understood as a translation mechanism that translates along each axis. Therefore, the head 50 can be understood as having a three-axis translation mechanism that moves the contact probe 60 in the X-axis drive direction 51, the Y-axis drive direction 53, and the Z-axis drive direction 55.

[0044] The X-axis drive unit 52 is disposed at the upper end of the head housing portion 57, particularly the upright portion 57b. The X-axis drive unit 52 cantilever supports the Y-axis drive unit 54 in a manner that allows it to move freely along the X-axis drive direction 51. The X-axis drive unit 52 can be understood as a so-called translation beam. The Y-axis drive unit 54 supports the Z-axis drive unit 56 in a manner that allows it to move freely along the Y-axis drive direction 53. The Y-axis drive unit 54 can be understood as a so-called translational body. The Z-axis drive unit 56 supports the contact probe 60 in a manner that allows it to move freely along the Z-axis drive direction 55. The Z-axis drive unit 56 can be understood as a so-called translational rod.

[0045] The contact probe 60 can be understood as a contact element that contacts the workpiece W, i.e., a touch probe. The contact probe 60 can move within the measurement space along each drive axis of the head 50, specifically along the X-axis, Y-axis, and Z-axis. The measurement space can be understood as the space within which the contact probe 60 can move and perform measurements via the head 50. That is, the measurement space can also be understood as the range of movement of the contact probe 60. Furthermore, the contact probe 60 has a two-axis rotation mechanism connected to the head 50, and its posture when in contact with the workpiece W can be changed. As described in this figure, the contact probe 60 includes a B-axis drive unit 62, an A-axis drive unit 64, a stylus 65, and a workpiece camera 66.

[0046] The B-axis drive unit 62 is supported at the lower end of the Z-axis drive unit 56. The B-axis drive unit 62 supports the A-axis drive unit 64 in a manner that allows it to rotate freely along the B-axis drive direction 61. The B-axis drive direction 61 can be understood as a circumferential direction with the B-axis as the central axis. The B-axis can also be an axis parallel to the Z-axis. The A-axis drive unit 64 is supported by the B-axis drive unit 62. The A-axis drive unit 64 can also be understood as a component of the B-axis drive unit 62. The A-axis drive unit 64 supports the stylus 65 and the workpiece camera 66 in a manner that allows them to rotate freely along the A-axis drive direction 63. The A-axis drive direction 63 can be understood as a circumferential direction with the A-axis as the central axis. The A-axis can also be an axis on the XY plane that is uniquely determined by the displacement (height) of the Z-axis drive unit 56 and uniquely determined by the displacement (rotation angle) of the B-axis drive unit 62.

[0047] Furthermore, the B-axis drive unit 62 and the A-axis drive unit 64 can be understood as a 2-axis rotation mechanism connected to the head 50. The 2-axis rotation mechanism can change the posture of the contact probe 60, specifically, it can change the posture of the stylus 65 and the workpiece camera 66.

[0048] That is, in the coordinate measuring device 100 of this embodiment, the position of the contact probe 60 is determined by a 3-axis translation mechanism, and the posture of the contact probe 60 is determined by a 2-axis rotation mechanism. Furthermore, the posture of the contact probe 60 can also be understood as the angle of the stylus 65 determined by the 2-axis rotation mechanism, in other words, as the extension direction of the stylus 65.

[0049] In this way, the contact probe 60 employs a structure that allows the stylus 65 to rotate freely via a two-axis rotation mechanism, a so-called free-angle structure. Therefore, unlike conventional structures that only allow discrete angle adjustments, the angle of the stylus 65 can be continuously and steplessly adjusted. Furthermore, unlike conventional structures, with the free-angle structure, calibration is not required for each discrete angle adjustment.

[0050] The stylus 65 is a needle-shaped member supported on the A-axis drive unit 64. The front end of the stylus 65 may, for example, be machined into a spherical shape. In this case, the action of "making the contact probe 60 contact the workpiece W" can be understood as the action of "making the ball provided at the front end of the stylus 65 contact the workpiece W".

[0051] The workpiece camera 66 is a camera device supported on the A-axis drive unit 64. The workpiece camera 66 can also be understood as a component of the A-axis drive unit 64. The workpiece camera 66 is capable of capturing images of the rotary table 70 and the workpiece W placed on the rotary table 70 in an orientation determined by the 2-axis rotation mechanism.

[0052] The non-contact optical sensor 31 is a sensor that acquires three-dimensional point clouds, or so-called map data, within the measurement space. The non-contact optical sensor 31 can also be composed of a profilometer, a 2D camera, or both. As shown in this figure, the non-contact optical sensor 31 can also be mounted on the Y-axis drive unit 54. In this case, the non-contact optical sensor 31 can move arbitrarily within the measurement space along the X-axis and Y-axis. For example, by scanning while moving the non-contact optical sensor 31 along the X-axis drive direction 51, a three-dimensional point cloud within the measurement space can be acquired. The non-contact optical sensor 31 can also be understood as a component of the Y-axis drive unit 54. The structure and measurement principle of the non-contact optical sensor 31 will be described later.

[0053] The rotary table 70 includes a disk-shaped stage for placing the workpiece W, and an θ-axis drive mechanism for rotating the stage along the θ-axis drive direction 71. The θ-axis drive direction 71 can be understood as a circumferential direction with the θ-axis as the central axis. The θ-axis can also be an axis parallel to the Z-axis.

[0054] Even if the measurement position on the workpiece W is outside the measurement space, the rotary table 70 can control the rotation angle about the θ axis in a way that positions the measurement position within the measurement space. That is, the measurement space in which the contact probe 60 can move is different from the actual measurable range including the rotary table 70. Furthermore, when the rotary table 70 is driven along the θ axis, the three-dimensional coordinates in the device coordinate system of the measurement space can be converted into three-dimensional coordinates in a virtual global coordinate system by taking into account the displacement (rotation angle) of the rotary table 70 in the θ-axis driving direction 71.

[0055] The control console 11 can be understood as a user input device that accepts manual operations on the head 50 and the contact probe 60. For example, the control console 11 may also be provided with multiple joysticks that accept manual operations on each of the six axes (X-axis, Y-axis, Z-axis, A-axis, B-axis, and θ-axis). In addition, the control console 11 may also be provided with at least one of the aforementioned measurement button 80, detection button 81, and power button 82. The head housing 57 and the control console 11 can be connected via a communication cable 12.

[0056] <Non-contact optical sensors>

[0057] Figure 2 This is a diagram illustrating a structural example of a non-contact optical sensor 31. The non-contact optical sensor 31 of this structural example can be understood as a profilometer. As described in this figure, the non-contact optical sensor 31 includes a laser emitter 32, a light-receiving lens 33, and an image sensor 34.

[0058] The laser emitting unit 32 irradiates a strip of laser light L onto the surface of the workpiece W, which is the object of measurement. The laser emitting unit 32 may also include a Powell lens as a unit for extending the laser L into a strip shape. Using a Powell lens is effective in ensuring uniform extension of the incident laser light. Alternatively, the laser emitting unit 32 may include a cylindrical lens as a unit for extending the laser L into a strip shape. Using a cylindrical lens is effective in reducing aberrations caused by the light wavelength. As described in this figure, the laser L extends into a strip shape with the Y-axis driving direction 53 as its long side. The light-receiving lens 33 images the light diffusely reflected from the surface of the workpiece W onto the imaging surface of the imaging unit 34. The larger the aperture of the light-receiving lens 33, the greater the amount of light received in the imaging unit 34. The imaging unit 34 generates imaging data corresponding to the image on the imaging surface. The cross-sectional shape, or so-called profile, of the workpiece W is acquired through imaging.

[0059] For example, during the measurement setup and continuous measurement described later, the non-contact optical sensor 31 moves along the X-axis driving direction 51, that is, in the direction intersecting the long side of the laser L which extends into a strip, while sequentially generating image data. Through scanning in this manner, the contours of each cross-section of the workpiece W are sequentially acquired along the moving direction of the non-contact optical sensor 31. By synthesizing this sequentially acquired contour data by the continuous measurement unit 113 described later, a three-dimensional point cloud corresponding to the position and shape of the workpiece W can be obtained. Furthermore, the three-dimensional point cloud generated by scanning using the non-contact optical sensor 31 can also be understood as the aforementioned map data.

[0060] <Coordinate Measuring Device (System Structure)>

[0061] Figure 3 This is a diagram showing the system structure of the coordinate measuring device 100. In this figure, the main components of the coordinate measuring device 100 are depicted as PC1, mouse 2, console 11, head housing 57, X-axis drive unit 52, Y-axis drive unit 54, Z-axis drive unit 56, θ-axis drive unit 58, and contact probe 60. The components that appear are labeled with [reference to other components]. Figure 1 and Figure 2 Same reference numerals as shown in the attached figures.

[0062] PC1 executes PC application 111 via a CPU (not shown) to function as, for example, a measurement setting unit 112, a continuous measurement unit 113, and a communication / control unit 114. PC1 also includes memory 115 for storing PC application 111 and setting files. Memory 115 can be an HDD (Hard Disk Drive), SSD (Solid State Drive), or cloud storage device, etc.

[0063] The measurement setting unit 112 performs measurement settings for the workpiece W. The measurement settings may include, for example, the measurement position required to determine the measurement elements and measurement items for the shape of the workpiece W, which is the object of measurement; the posture of the contact probe 60 relative to the measurement position; and the measurement items using the measurement elements. In other words, the measurement settings can be understood as a general term for settings related to the measurement of the workpiece W. The content of the measurement settings may also be stored as a measurement setting file in the memory 115.

[0064] The shape of workpiece W can be defined as information related to the shape of workpiece W contained in the three-dimensional data included in the measurement setting file. When the three-dimensional data is a workpiece model generated by CAD (Computer-Aided Design), the outline, position, and orientation of the workpiece model in the CAD coordinate system are included in the information related to the shape of workpiece W. Alternatively, when the three-dimensional data is pre-measured data, the outline, position, and orientation of workpiece W in the global coordinate system or device coordinate system obtained through pre-measurement are included in the information related to the shape of workpiece W. Basic measurement elements can include geometric shapes such as planes, lines, points, circles, cylinders, cones, or spheres. Measurement items can include the dimensions of each measurement element, such as distances or angles between measurement elements. Furthermore, the measurement position and orientation measured by the contact probe 60, the measurement elements formed through each measurement, and the measurement items using the measurement elements can also be registered in the measurement setting file.

[0065] The continuous measurement unit 113 performs continuous measurement of the workpiece W based on the measurement position measured by the contact probe 60 and the measurement items using the measurement elements. For example, the continuous measurement unit 113 calculates a first measurement element and a second measurement element based on the measurement position measured by the contact probe 60, and measures the dimension between the first measurement element and the second measurement element based on the measurement items. The continuous measurement of the workpiece W will be described in detail later. The measurement position and measurement elements can also be determined based on the aforementioned measurement setting file. In addition, the continuous measurement unit 113 generates a three-dimensional point cloud corresponding to the position and shape of the workpiece W by synthesizing the contour data sequentially acquired by the non-contact optical sensor.

[0066] The communication / control unit 114 controls the communication between PC1 and head housing 57.

[0067] The head housing 57 includes a main control unit 121, an X-axis encoder unit 122, and a θ-axis encoder unit 123.

[0068] The main control unit 121 controls the head housing 57, X-axis drive unit 52, Y-axis drive unit 54, Z-axis drive unit 56, θ-axis drive unit 58, and contact probe 60 according to instructions from users received by PC1 or console 11.

[0069] For example, the main control unit 121 functions as a measurement control unit that, when a measurement instruction is received, performs movement control and posture control of the contact probe 60 and rotation control of the rotary table 70 according to the measurement setting file stored in the memory 115.

[0070] As described in this figure, the main control unit 121 controls the movement of the contact probe 60 via the X-axis drive unit 52, Y-axis drive unit 54, and Z-axis drive unit 56, which are equivalent to a 3-axis translation mechanism, so that the contact probe 60 is moved to the measurement position. Furthermore, the main control unit 121 controls the posture of the contact probe 60 relative to the measurement position via the B-axis drive unit 62 and A-axis drive unit 64, which are equivalent to a 2-axis rotation mechanism. In addition, the aforementioned measurement instruction can be defined as a trigger command for reading the measurement setting file and starting the measurement of the workpiece W.

[0071] The main control unit 121 includes a communication unit 124. The communication unit 124 communicates with the console 11, the X-axis drive unit 52, the θ-axis drive unit 58, the X-axis encoder unit 122, and the θ-axis encoder unit 123.

[0072] The X-axis encoder unit 122 obtains the displacement of the X-axis drive unit 52 in the X-axis drive direction 51, i.e., the X coordinate of the contact probe 60 in the device coordinate system, by reading the linear scale of the X-axis drive unit 52. The θ-axis encoder unit 123 obtains the displacement (rotation angle) of the rotary table 70 in the θ-axis drive direction 71 by reading the rotation scale of the θ-axis drive unit 58.

[0073] The X-axis drive unit 52 includes a communication / control unit 131. The communication / control unit 131 controls the communication between the X-axis drive unit 52 and the head housing unit 57, and the communication between the X-axis drive unit 52 and the Y-axis drive unit 54.

[0074] The Y-axis drive unit 54 includes a communication / control unit 141, a Y-axis encoder unit 142, a Z-axis encoder unit 143, and a non-contact optical sensor 31. The communication / control unit 141 controls the communication between the Y-axis drive unit 54 and the X-axis drive unit 52, and the communication between the Y-axis drive unit 54 and the Z-axis drive unit 56. Furthermore, the communication / control unit 141 also communicates with the Y-axis encoder unit 142, the Z-axis encoder unit 143, and the non-contact optical sensor 31.

[0075] The Y-axis encoder unit 142 obtains the displacement of the Y-axis drive unit 54 in the Y-axis drive direction 53, i.e., the Y coordinate of the contact probe 60 in the device coordinate system, by reading the linear scale of the Y-axis drive unit 54. The Z-axis encoder unit 143 obtains the displacement of the Z-axis drive unit 56 in the Z-axis drive direction 55, i.e., the Z coordinate of the contact probe 60 in the device coordinate system, by reading the linear scale of the Z-axis drive unit 56.

[0076] In addition to the aforementioned laser emitting unit 32 and imaging unit 34, the non-contact optical sensor 31 also includes a contour calculation unit 144 and a communication / control unit 145. The contour calculation unit 144 calculates the cross-sectional shape, or contour, of the workpiece W based on the imaging data sequentially acquired by the imaging unit 34. The continuous measurement unit 113 generates three-dimensional data based on this contour data. This structure reduces the computational load on the contour calculation unit 144 of the non-contact optical sensor 31. Furthermore, the contour calculation unit 144 can also generate a three-dimensional point cloud based on the contour data. The communication / control unit 145 controls the communication between the non-contact optical sensor 31 and the communication / control unit 145.

[0077] The Z-axis drive unit 56 includes a communication / control unit 151. The communication / control unit 151 controls the communication between the Z-axis drive unit 56 and the Y-axis drive unit 54, and the communication between the Z-axis drive unit 56 and the contact probe 60.

[0078] The contact probe 60 includes a communication / control unit 161, a B-axis encoder unit 162, a camera unit 163, and a B-axis drive unit 62. The communication / control unit 161 controls communication between the contact probe 60 and the Z-axis drive unit 56. Furthermore, the communication / control unit 161 also communicates with the B-axis encoder unit 162, the camera unit 163, and the B-axis drive unit 62. The B-axis encoder unit 162 obtains the displacement (rotation angle) of the B-axis drive unit 62 in the B-axis drive direction 61 by reading the rotation scale of the B-axis drive unit 62. The camera unit 163 captures an image of an optical mark (not shown) provided on the A-axis drive unit 64. Based on the captured image pattern of the optical mark, the position and orientation of the A-axis drive unit 64 with the optical mark attached can be detected, thereby detecting the position and orientation of the stylus 65 supported on the A-axis drive unit 64.

[0079] The B-axis drive unit 62 includes a communication / control unit 164 and an A-axis encoder unit 165. The communication / control unit 164 communicates with the communication / control unit 161 of the contact probe 60. Additionally, the communication / control unit 164 also communicates with the A-axis encoder unit 165 and the A-axis drive unit 64. The A-axis encoder unit 165 obtains the displacement (rotation angle) of the A-axis drive unit 64 in the A-axis drive direction 63 by reading the rotation scale of the A-axis drive unit 64.

[0080] In addition to the aforementioned workpiece camera 66, the A-axis drive unit 64 also includes a communication / control unit 166, a Hall sensor unit 167, and an illumination unit 168. The communication / control unit 166 communicates with the communication / control unit 164 of the B-axis drive unit 62. Furthermore, the communication / control unit 166 also communicates with the Hall sensor unit 167, the illumination unit 168, and the workpiece camera 66. The Hall sensor unit 167 generates a detection signal corresponding to the displacement of the stylus 65 relative to the A-axis drive unit 64. The illumination unit 168 illuminates an optical mark (not shown) provided on the A-axis drive unit 64 from the back.

[0081] The workpiece camera 66 includes a camera unit 169. The camera unit 169 may also include photoelectric conversion elements such as a CCD (Charge Coupled Device) sensor or a CMOS (Complementary Metal Oxide Semiconductor) sensor.

[0082] <System Actions>

[0083] Then, while referring to Figure 3 A brief explanation of the system operation of the coordinate measuring device 100 is given.

[0084] Additionally, for example, when scanning using the non-contact optical sensor 31, the scanning command is transmitted via a signal path from the communication / control unit 114 of PC1 through the communication unit 124 of the main control unit 121, the communication / control unit 131 of the X-axis drive unit 52, and the communication / control unit 141 of the Y-axis drive unit 54 to the communication / control unit 145 of the non-contact optical sensor 31.

[0085] The non-contact optical sensor 31 receives the scanning command and controls the laser emitting unit 32 to irradiate a strip of laser L toward the surface of the workpiece W, which is the object of measurement. At this time, the imaging unit 34 receives the reflected light from the workpiece W and generates imaging data corresponding to the image on the imaging surface. In addition, the X-axis drive unit 52 receives the scanning command and moves the non-contact optical sensor 31 along the X-axis drive direction 51.

[0086] By scanning in this way, a contour corresponding to the position and shape of the workpiece W can be acquired in the contour calculation unit 144. This contour is transmitted through a signal path from the communication / control unit 145 of the non-contact optical sensor 31, via the communication / control unit 141 of the Y-axis drive unit 54, the communication / control unit 131 of the X-axis drive unit 52, and the communication unit 124 of the main control unit 121, to the communication / control unit 114 of the PC1. The PC1 detects the position and orientation of the workpiece W placed on the rotary table 70 by analyzing this contour.

[0087] Additionally, for example, when using the contact probe 60 to perform point measurement, the lighting command is transmitted through a signal path from the communication / control unit 114 of the PC1 via the communication unit 124 of the main control unit 121, the communication / control unit 131 of the X-axis drive unit 52, the communication / control unit 141 of the Y-axis drive unit 54, the communication / control unit 151 of the Z-axis drive unit 56, the communication / control unit 161 of the contact probe 60, the communication / control unit 164 of the B-axis drive unit 62, and the communication / control unit 166 of the A-axis drive unit 64 to the lighting unit 168.

[0088] The illumination unit 168 receives the illumination command and illuminates an optical mark (not shown) provided on the A-axis drive unit 64 from the back. The imaging unit 163 of the contact probe 60 receives the transmitted light from the optical mark when the contact probe 60 contacts the workpiece W, and generates imaging data corresponding to the image on the imaging surface. This imaging data is transmitted via a signal path from the communication / control unit 161 of the contact probe 60, through the communication / control unit 151 of the Z-axis drive unit 56, the communication / control unit 141 of the Y-axis drive unit 54, the communication / control unit 131 of the X-axis drive unit 52, and the communication unit 124 of the main control unit 121, to the communication / control unit 114 of the PC1.

[0089] Furthermore, when performing point measurement using the contact probe 60, at the moment the contact probe 60 contacts the workpiece W, the displacement amounts in each of the X-axis drive directions 51, 53, 55, and 71 are transmitted from the X-axis encoder 122, Y-axis encoder 142, Z-axis encoder 143, and θ-axis encoder 123 to the communication / control unit 114 of the PC1. Based on the aforementioned camera data and the displacement amounts in each axis drive direction, the PC1 calculates the three-dimensional coordinates of the measurement position.

[0090] Furthermore, the aforementioned camera unit 163, X-axis encoder unit 122, Y-axis encoder unit 142, Z-axis encoder unit 143, and θ-axis encoder unit 123 receive inputs from essentially different clocks and do not operate synchronously. Therefore, in order to accurately determine the three-dimensional coordinates of the measurement position, synchronous detection is preferable to ensure that the timing of the contact probe 60 contacting the workpiece W does not deviate from the timing of referencing the camera data and the displacement in each axis drive direction.

[0091] <Measurement Setup>

[0092] Figure 4This is a flowchart illustrating an example of measurement setting performed by the measurement setting unit 112. This process can also be started, for example, by pressing the measurement setting button displayed on the PC1's screen as a GUI (Graphical User Interface).

[0093] When this process begins, in step S11, the workpiece W, which is the object of the measurement setting, is placed on the rotary table 70. At this time, the contact probe 60 can also be moved to a position where the workpiece camera 66 can face the rotary table 70 from directly above. In addition, in this step S11, it can also be specified whether the rotation of the rotary table 70 is enabled during measurement. When the rotation of the rotary table 70 is disabled, the measurement is performed within the measurement space of the coordinate measuring device 100, that is, within the movement range of the contact probe 60.

[0094] Next, in step S12, a three-dimensional point cloud is acquired by sequentially generating camera data while moving the non-contact optical sensor 31 along the X-axis driving direction 51. Furthermore, in step S13, unwanted point clouds other than the workpiece W are deleted from the acquired three-dimensional point cloud. Unwanted point clouds to be deleted can be, for example, those whose height relative to the surface of the rotary table 70 is below a predetermined threshold. Through steps S12 and S13, a three-dimensional point cloud corresponding to the position and shape of the workpiece W can be acquired.

[0095] Next, in step S14, the retraction boundary is adjusted. The retraction boundary can be understood as the boundary that allows the contact probe 60 to move without contacting the workpiece W during automatic measurement. The retraction boundary is defined by including the area of ​​the workpiece W. The shape of the retraction boundary can be, for example, a cuboid or a cylinder. Various parameters of the retraction boundary, such as the longitudinal length, transverse length, and height of a cuboid, or the base radius and height of a cylinder, or the rotation angles of each of the three axes, can be manually input. Alternatively, the various parameters of the retraction boundary can be automatically input by setting a margin distance between the retraction boundary and the workpiece W. Alternatively, the various parameters of the retraction boundary can be automatically input by pre-setting a margin distance for the three-dimensional point cloud of the workpiece W acquired by the non-contact optical sensor 31.

[0096] Next, in step S15, pattern registration is performed. For example, the three-dimensional point cloud acquired in step S13 is converted into height data, and any feature region in this height data is registered as pattern data. The registered pattern data is processed as reference data containing information related to the shape of the workpiece W. Furthermore, the shape of the workpiece W in this process refers to the shape of the workpiece W itself, which is placed for the purpose of measurement.

[0097] If a pattern is registered beforehand, even if the workpiece W, the object of measurement, is configured in a different position and posture than when the measurement was set, the position will still be aligned to ensure consistency with the registered pattern. In this step, the position alignment method, the area to be registered as a pattern, the search range during position alignment, exclusion areas, and critical areas can also be set. The area to be registered as a pattern can be either the entire workpiece W or a part of the workpiece W.

[0098] Next, in step S16, the workpiece camera 66 captures a full 360° view of the workpiece W from its perimeter. During this full 360° view, for example, the workpiece camera 66, positioned to view the rotary table 70 from a slightly upward angle, can continuously capture images of the workpiece W during one full rotation of the rotary table 70. By capturing a full 360° view of the workpiece W beforehand, the user can confirm the location of the measurement positions, measurement elements, and measurement items specified in steps S17 and S18 on the workpiece W using the workpiece image on the GUI.

[0099] Next, in step S17, the position is taught. This can be implemented, for example, using the contact probe 60 and the control console 11. The control console 11 receives movement instructions from the six axes of the contact probe 60 via a joystick. The control console 11 transmits the received instructions to the communication unit 124 of the main control unit 121 in the head housing 57 via the communication cable 12. The main control unit 121 controls the X-axis drive unit 52, Y-axis drive unit 54, Z-axis drive unit 56, θ-axis drive unit 58, and the contact probe 60 based on the instructions received from the communication unit 124. The encoders of each axis acquire the three-dimensional coordinates when the contact probe 60 contacts the workpiece W. The encoders of each axis transmit the acquired three-dimensional coordinates to the communication unit 124 of the main control unit 121.

[0100] By repeating this operation, arbitrary measurement elements are temporarily determined. For example, when any face of workpiece W is set as a measurement element, any three points belonging to that face can be designated as measurement positions. Alternatively, for example, when any edge of workpiece W is set as a measurement element, the projection plane and the face to which the edge belongs can be specified using the aforementioned method, and then two points can be specified on the face to which the edge belongs to designate the edge. In addition, measurements can be performed using methods other than those described above. Furthermore, measurement positions can also be specified for 3D data of the workpiece, such as 3D point clouds or CAD data. After specifying the measurement position, the single-piece measurement begins with the pressing of the measurement start button in the GUI. This single-piece measurement refers to measuring the placed workpiece W before the measurement settings have been saved.

[0101] Single-piece measurement of workpiece W can also be performed using contact probe 60 and control console 11, for example. Control console 11 receives six-axis movement instructions from contact probe 60 via a joystick. Control console 11 transmits the received instructions to the communication unit 124 of the main control unit 121 in head housing 57 via communication cable 12. The main control unit 121 controls the X-axis drive unit 52, Y-axis drive unit 54, Z-axis drive unit 56, θ-axis drive unit 58, and contact probe 60 based on the instructions received from the communication unit 124. The encoders of each axis acquire the three-dimensional coordinates when contact probe 60 contacts workpiece W. The encoders of each axis transmit the acquired three-dimensional coordinates to the communication unit 124 of the main control unit 121.

[0102] By repeating this operation, any measurement element can be determined. For example, when any face of workpiece W is set as a measurement element, any three points belonging to that face can be designated as measurement positions. Alternatively, for example, when any edge of workpiece W is set as a measurement element, the projection plane and the face to which the edge belongs can be specified using the aforementioned method, and then two points can be specified on the face to which the edge belongs to designate the edge. Furthermore, measurements can also be performed using methods other than those described above.

[0103] Next, in step S18, the measurement items are registered. As measurement items, distances and angles between measurement elements can also be registered.

[0104] Finally, in step S19, the above series of settings are saved as a measurement setting file in memory 115. It is also possible to save multiple measurement setting files in advance for each type of workpiece W that is the object of measurement.

[0105] Furthermore, this process is basically applicable to measurement settings performed using physical equipment with coordinate measuring device 100, i.e., online measurement settings. Therefore, the above series of descriptions envisions a scenario in which measurement settings including measurement position, measurement elements, and measurement items are performed within the measurable range including the rotary table 70.

[0106] <Continuous Measurement>

[0107] Figure 5 This is a flowchart illustrating an example of continuous measurement performed by the continuous measurement unit 113.

[0108] In step S21, the workpiece W, which is to be measured, is placed on the rotary table 70. Next, in step S22, a registered measurement setting file is arbitrarily read from the memory 115. The user can select the file to use from the registered measurement setting files on the GUI of the PC application displayed on the PC1's monitor. Alternatively, by pressing the detection button 81, map data can be acquired by the non-contact optical sensor 31, and a suitable measurement setting file for the workpiece W can be automatically determined and read by comparing the shape data of the placed workpiece W in the map data with the three-dimensional shape data of the workpiece contained in the registered measurement setting file.

[0109] For example, the measurement setting file can be determined by matching the shape data of the workpiece W contained in the map data with the shape data contained in the measurement setting file. By having the user select the measurement setting file on the PC application, the action of pressing the detection button 81 and the scanning action of the non-contact optical sensor 31 can be omitted. The aforementioned method of determining the measurement setting file by pattern matching is effective when the measurement setting file to be used is known. In the method of using the detection button 81, since the measurement setting file to be used can be determined simply by pressing the detection button 81, it is effective when the measurement setting file to be used is unknown.

[0110] In step S23, it is determined whether a measurement start instruction has been issued by the continuous measurement unit 113. The measurement start instruction is issued by pressing the measurement button 80. Alternatively, the measurement start instruction can be issued via the GUI of the PC application. If a measurement start instruction has been issued, the process proceeds to step S24, and continuous measurement begins. Otherwise, if no measurement start instruction has been issued, the process returns to step S23.

[0111] Furthermore, the order of steps S21 to S23 in this process can be interchanged. For example, after reading the measurement setting file in step S22, the workpiece W can be placed on the rotary table 70 in step S21, and the measurement can begin after confirming the measurement start instruction in step S23. Alternatively, the workpiece W can be placed on the rotary table 70 and the measurement setting file can be read after confirming the measurement start instruction. In this case, a display can be shown on the PC1's screen to prompt the user to place the workpiece W on the rotary table 70 and select the measurement setting file. Furthermore, if the non-contact optical sensor 31 scans map data by pressing the detection button 81, the scanning performed by the non-contact optical sensor 31 after the measurement start instruction is confirmed can be skipped.

[0112] Then, in step S24, the acquisition of a three-dimensional point cloud by the non-contact optical sensor 31 and the deletion of unwanted point clouds are performed sequentially. As a result, a three-dimensional point cloud corresponding to the position and shape of the workpiece W can be acquired.

[0113] Next, in step S25, a comparison is performed with the registered pattern. Specifically, the 3D point cloud acquired in step S24 is converted into height data, and a data portion matching the registered pattern is searched from this height data. Through this search process, the position and orientation of the workpiece W placed on the rotary table 70 are calculated.

[0114] The computational processing in step S25 is equivalent to aligning the coordinate system related to the map data acquired by the non-contact optical sensor 31 with the coordinate system related to the shape of the workpiece W, which is the object of measurement. Here, the coordinate system related to the map data can be understood as the coordinate system of the map data acquired by the non-contact optical sensor 31. On the other hand, the coordinate system related to the shape of the workpiece W can be understood as the coordinate system of the three-dimensional data contained in the measurement setting file.

[0115] Furthermore, the map data acquired by the non-contact optical sensor 31 includes first information related to the position and orientation of the workpiece W placed on the rotary table 70. On the other hand, the three-dimensional data included in the measurement setting file includes second information related to the position and orientation of the workpiece W, which is pre-registered as a pattern, i.e., reference data. Therefore, the two coordinate systems can be matched based on the first and second information to align the position of the workpiece W.

[0116] Alternatively, step S25 can also be understood as 3D position and pose matching. This 3D position and pose matching is used to match the degrees of freedom of the six axes (X-axis, Y-axis, Z-axis, A-axis, B-axis and θ-axis) based on the 3D position and pose of the workpiece W on the map data obtained by the non-contact optical sensor 31 and the 3D position and pose of the workpiece W on the reference data registered in the measurement setting file.

[0117] Next, in step S26, based on the position and posture of the workpiece W, the measurement position where the contact probe 60 contacts the workpiece W, the posture of the contact probe 60 at the measurement position, and the measurement path of the contact probe 60 to reach the measurement position are calculated again.

[0118] Next, in step S27, point measurements are sequentially performed by the contact probe 60 along the measurement path specified in the measurement setting file. Specifically, the contact probe 60 is moved toward the measurement position in a predetermined posture, and the three-dimensional coordinates of the contact position are acquired at the point in time when the contact probe 60 contacts the workpiece W.

[0119] Alternatively, contour measurement can be performed in step S27. Contour measurement is also known as scanning measurement or scanning-type measurement. In contour measurement, from a first measurement position corresponding to the starting point to a second measurement position corresponding to the ending point, the contact probe 60 is moved while maintaining contact between the tip of the stylus 65 and the workpiece W, thereby continuously acquiring three-dimensional coordinates along the shape of the workpiece W.

[0120] Finally, in step S28, the measurement results are displayed in the GUI. The measurement results may include not only the measured values ​​of the measured items, but also, for example, a judgment flag (OK / NG) indicating whether the measured values ​​are within the normal range.

[0121] In the coordinate measuring device 100, steps S24 to S28 described above are performed automatically. That is, the user can continuously perform three-dimensional measurement of the workpiece W simply by performing the actions from step S21 to step S23.

[0122] Furthermore, this process can also be applied to the case where multiple identical workpieces W are placed on the rotary table 70 in step S21, i.e., when multiple workpieces W are measured in batches. In this case, in steps S24 and S25, the position and orientation of each of the multiple workpieces W are calculated by comparing them with the registered pattern.

[0123] Then, in step S26, based on the respective positions and orientations of the multiple workpieces W, the measurement positions where the contact probe 60 contacts each of the multiple workpieces W, the orientation of the contact probe 60 at those measurement positions, and the measurement path of the contact probe 60 to reach those measurement positions are calculated again. Here, the measurement path of the contact probe 60 can also be automatically set to most efficiently circulate among the multiple measurement positions specified for each of the multiple workpieces W.

[0124] <Translation Mechanism>

[0125] Figure 6 This is a diagram showing the configuration of the translation mechanism in the first embodiment. (As shown) Figure 6As shown, the X-axis drive unit 52, Y-axis drive unit 54, and Z-axis drive unit 56 can also be defined as translation mechanisms. The X-axis drive unit 52 is provided at the upper end of the head housing part 57, particularly the upright part 57b. The X-axis drive unit 52 cantilever supports the Y-axis drive unit 54 in a manner that allows it to move freely along the X-axis drive direction 51. The X-axis drive unit 52 can be understood as a so-called translation beam. The Y-axis drive unit 54 supports the Z-axis drive unit 56 in a manner that allows it to move freely along the Y-axis drive direction 53. The Y-axis drive unit 54 can be understood as a so-called translation body. The Z-axis drive unit 56 supports the contact probe 60 in a manner that allows it to move freely along the Z-axis drive direction 55. The Z-axis drive unit 56 can be understood as a so-called translation rod. That is, the coordinate measuring device in the first embodiment has a translation mechanism that translates at least in a first direction, and by translating the translation mechanism, the contact member (contact probe 60) connected to the translation mechanism is moved three-dimensionally within the measuring space. The contact member is brought into contact with the workpiece by the movement of the translation mechanism, so as to determine the three-dimensional coordinates of the contact point. Hereinafter, in the first embodiment, the structure of the X-axis drive unit 52 is described as an example of the translation mechanism, but the following structure can also be applied to at least one of the Y-axis drive unit 54 and the Z-axis drive unit 56.

[0126] Figure 7 This is a front view of the X-axis drive unit in the first embodiment. Additionally, Figure 8 This is an exploded perspective view of the X-axis drive unit in the first embodiment. Additionally, Figure 9 This is a cross-sectional view of the X-axis drive unit in the first embodiment.

[0127] like Figure 7 As shown, the X-axis drive unit 52 includes a support portion 201, a pair of rails 202 fixed to the support portion, and a translational body 203 that moves along the rails 202 in the X-axis direction. The support portion 201 is a support structure formed on the upper end of the head housing portion 57, particularly the upright portion 57b. Therefore, the support portion 201 is part of the head housing portion 57. Of course, it can also be formed by other components connected to the upper end of the head housing portion 57, particularly the upright portion 57b. In addition, the X-axis drive unit 52 includes a feed screw 204, which is arranged between the pair of rails 202 for driving the translational body 203 along the rails. The feed screw 204 and the translational body 203 are fixed, and the translational body 203 moves in the X-axis direction as the feed screw 204 rotates.

[0128] Furthermore, the X-axis drive unit 52 includes multiple rotating bodies 205 disposed between the support 201 and the rails, and fastening members 206 that fasten the support 201, which faces each other and is separated from the rotating bodies 205, to a pair of rails 202. Grooves are provided on both sides of each rail 202, and multiple balls are disposed between the translation body 203 and the grooves. When the translation body 203 moves along the X-axis, the balls rotate about an axis orthogonal to the X-axis. This reduces friction between the rails 202 and the translation body 203. Such a structure is generally known as a linear guide. In Embodiment 1, this structure is described as an example, but it can also be applied to structures that guide translation bodies on rails such as crossed roller guides, crossed roller tables, and ball bearing sliding tables.

[0129] like Figure 8 As shown, the fastening member 206 is composed of a threaded member, which consists of a head 2061 and a shaft portion 2062 extending from the head 2061. Threads are provided in the shaft portion 2062. Furthermore, the shaft portion 2062 has a diameter smaller than that of the head 2061. Through holes 2021 are provided on the track at predetermined intervals. The through holes 2021 consist of a recess that accommodates the head 2061 in the fastened state, and a through portion that extends through the bottom surface of the recess to the track 202. The recess and the through portion are cylindrical. Furthermore, the diameter of the through portion is smaller than that of the recess. In the support portion 201, receiving portions 2011 are provided at intervals corresponding to the through holes 2021, and the receiving portions 2011 are provided on the surface facing the track 202. Figure 9 As shown, a threaded groove is provided on the side wall of the receiving part 2011, which engages with the threaded teeth of the shaft portion 2062 of the fastening member 206. The fastening member 206 is inserted through the through hole 2021 of the track 202, and its shaft portion 2062 engages with the threaded groove of the receiving part 2011 provided on the support part 201. When the fastening member 206 is fastened, the lower surface of its head 2061 presses against the track 202 through the bottom surface of the recess of the through hole 2021. By this pressing force, the track 202 and the support part 201 are fastened in such a way that the rotating body 205 disposed between the lower surface of the track 202 and the upper surface of the support part 201 is clamped.

[0130] like Figure 8As shown, the rotating body 205 is a cylindrical shape having a rotation axis in a direction orthogonal to the X-axis. The rotating body 205 rotates about the rotation axis according to the expansion and contraction of the support portion 201 caused by temperature changes. These rotating bodies 205 are arranged between each of the two tracks 202 and the support portion 201. Details will be described later. Furthermore, multiple rotating bodies 205 can also be integrally held at predetermined intervals by a retainer (holding member). This retainer allows the rotating body 205 to rotate about its rotation axis and prevents positional deviation or detachment in the long side direction (X-axis direction) and width direction of the track 202.

[0131] Typically, the components constituting the X-axis drive unit 52 are made of materials with low coefficients of thermal expansion to reduce thermal deformation caused by temperature. The coefficient of thermal expansion, also known as the linear expansion coefficient or volumetric expansion coefficient, is used to represent this. Furthermore, to suppress strain caused by differences in the coefficients of thermal expansion between components, multiple connected components are sometimes made of materials with the same coefficient of thermal expansion or with small differences in their coefficients of thermal expansion. For example, the track 202 is made of a metal material with a relatively low coefficient of thermal expansion, such as iron. Additionally, the support unit 201 (head housing unit 57) is made of stone materials such as granite, or metal materials such as iron. For example, the coefficient of thermal expansion of iron is 10 × 10⁻⁶. -6 The expansion rate of granite is approximately 8.5 × 10⁻⁶ K. -6 The strain is approximately 1000 K, and it expands and contracts to the same extent with temperature changes, so the effect of temperature changes on strain is small. However, as mentioned above, the material tends to have a relatively high density. Since most of the materials used are high-density, the weight of the device increases, and the portability of the device decreases. In addition, for installation, sometimes a dedicated platform or room that can withstand the weight is required, which is a reason for the increased cost of implementing the device.

[0132] In contrast, in the first embodiment, the support 201 is made of a material with relatively low density, such as aluminum alloy or magnesium alloy. This allows for a reduction in the overall weight of the device. However, the track 202 is made of a metal material with a low coefficient of thermal expansion, such as iron or Invar alloy. This is because when the track 202 strains due to heat, the guiding accuracy between the track 202, the translation body 203, and the balls disposed between the track 202 and the translation body 203 decreases, potentially hindering the smooth movement of the translation body 203. Furthermore, from the viewpoint of wear resistance and mechanical strength, the track 202 is also preferably made of the aforementioned material.

[0133] However, lightweight metals, with their relatively low density, tend to have a high coefficient of thermal expansion, making them prone to deformation due to temperature changes. For example, the coefficient of thermal expansion of magnesium alloys is 25 × 10⁻⁶. -6 / K, the thermal expansion coefficient of aluminum alloy is 23×10 -6Its thermal expansion coefficient is around / K, which is greater than that of iron and Invar alloys. Furthermore, the value of the thermal expansion coefficient is given as an example.

[0134] Therefore, if the support 201, made of a material with a high coefficient of thermal expansion, is directly fastened to the track 202, made of a material with a low coefficient of thermal expansion, the amount of expansion and contraction between the two will differ due to changes in ambient temperature. This difference in expansion and contraction causes stress in the support 201 and the track 202, resulting in warping and strain.

[0135] The following example, using a conventional translation mechanism, illustrates the effect of temperature changes when components made of materials with different coefficients of thermal expansion are joined. Figure 10 This diagram shows a comparative example of a conventional translation mechanism. Additionally, Figure 11 This is a conceptual diagram illustrating the effects of temperature changes in a comparative example of a conventional translation mechanism.

[0136] like Figure 10 As shown in the comparative example, in a conventional translation mechanism, the support 201C and the track 202C are directly fastened in the long-side direction by multiple fastening members 206C. Therefore, the upper surface of the support 201C is in direct contact with the lower surface of the track 202C. Here, the thermal expansion coefficient of the support 201C with length L1 is set as α1, and the thermal expansion coefficient of the track 202C with length L2 is set as α2. Consider the case where the support 201C has a larger thermal expansion coefficient than the track 202C (α1>α2). At the reference temperature T0, as... Figure 10 As shown, the support 201C and the track 202C are fastened without strain. When the ambient temperature rises by ΔT, the support 201C will extend by α1L1ΔT. Correspondingly, the track 202C will extend by α2L2ΔT. However, when... Figure 10 When the support 201C and the track 202C are fastened in this way, their deformation is constrained by the fastening part 206C. Furthermore, at the interface between the upper surface of the support 201C and the lower surface of the track 202C, a frictional force is generated in the direction that constrains their deformation. More specifically, a frictional force is also generated between the lower surface of the head 2061C of the fastening part 206C and the bottom surface of the recess of the through hole 2021C.

[0137] Therefore, the elongation of the support portion 201C, which is intended to extend further, is hindered by the fastening and the frictional force generated at the interface with the track 202C, resulting in compressive stress within the component. Conversely, the track 202C, due to the fastening and the frictional force generated at the interface with the support portion 201C, exerts a force in the stretching direction, thereby generating tensile stress. Due to these opposing stresses, such as Figure 11As shown, the structure consisting of the support 201C and the track 202C is bent into an arc shape. Due to this bending, the straightness of the track 202C deteriorates, sometimes leading to increased travel resistance and reduced positioning accuracy of the translation body 203C.

[0138] Additionally, when the ambient temperature recovers from a state that has risen to T0+ΔT to the reference temperature T0, sometimes it does not... Figure 11 Restore to Figure 10 The state of the component. If the stress generated when the temperature rises exceeds the elastic limit of the component, plastic deformation will occur and remain as permanent strain. In addition, even within the elastic limit, due to the friction generated at the interface between the support 201C and the track 202C, and the friction generated between the fastener 206C and the through hole 2021C, small sliding and fastening will occur repeatedly, sometimes leaving a history of displacement, i.e., hysteresis.

[0139] This means that even if the temperature rises from the reference temperature and the track 202C bends, and then the temperature drops back to the reference temperature, the bending will not be completely eliminated and will remain. Each time such a temperature cycle occurs, the reference state of the device (origin, straightness) changes, and errors accumulate. As a result, frequent calibrations are required, or the reproducibility of measurements cannot be obtained, which can sometimes become problems in coordinate measuring devices requiring high-precision positioning. Of course, when the temperature returns from a state lower than the reference temperature to the reference temperature, the aforementioned strain and hysteresis problems will also occur.

[0140] The following describes a structure that reduces the influence of temperature changes when joining components made of materials with different coefficients of thermal expansion by means of the connection relationship of the translation mechanism in the first embodiment. Figure 12 This is a schematic diagram of a cross-section of the translation mechanism in the first embodiment at a reference temperature. Additionally, Figure 13 This is a conceptual diagram illustrating the effect of temperature changes on the translation mechanism in the first embodiment. Figure 14 This is a top view of the translation mechanism in the first embodiment.

[0141] like Figure 12As shown, at a reference temperature, the support portion 201 and the track 202 face each other across a plurality of rotating bodies 205. A fastening member 206 fastens the support portion 201 and the track 202 across the plurality of rotating bodies 205. At the reference temperature, the spacing of the plurality of through holes 2021 provided in the track 202 is the same as the spacing of the plurality of receiving portions 2011 provided in the support portion 201. The fastening member 206 is inserted through the through holes 2021 in the track 202, and its shaft portion 2062 engages with the threaded groove of the receiving portion 2011 provided in the support portion 201. When the fastening member 206 is fastened, the lower surface of its head 2061 presses against the track 202 across the bottom surface of the recess in the through hole 2021. Through this pressing force, the track 202 and the support portion 201 are fastened in such a way that the rotating bodies 205 disposed between the lower surface of the track 202 and the upper surface of the support portion 201 are clamped. The rotating body 205 is neither bonded nor fixed to the support 201 and the track 202. The rotating body is held between the support 201 and the track 202. When the support 201 or the track 202 moves in the X-axis direction, the rotating body 205 rotates about an axis orthogonal to the X-axis. In other words, the rotating body is only held between the support 201 and the track 202, and therefore rotation is permitted. Consequently, the frictional force generated between the upper surface of the support 201 and the lower surface of the track 202 becomes rolling friction due to rolling contact with the rotating body 205. This is far less than the frictional force generated at the interface between the support 201 and the track 202 in the conventional translation mechanism described above.

[0142] In addition, such as Figure 14 As shown, the diameter of the recess in the through hole 2021 is configured to be larger than the diameter of the head 2061 of the fastening member 206. Additionally, as... Figure 12 As shown, the diameter of the through portion of the through hole 2021 is larger than the diameter of the fastening member 206. Therefore, in the fastened state, a gap exists between the fastening member 206 and the through hole 2021. Furthermore, the diameters of the recess and the shaft portion can also be defined as inner dimensions. Additionally, the recess only needs to have an inner dimension in at least the X-axis direction larger than the diameter of the head 2061. The shape of the recess can be either circular or an elongated hole with a large inner dimension in the X-axis direction. Similarly, the through portion only needs to have an inner dimension in at least the X-axis direction larger than the diameter of the shaft portion 2062. The shape of the through portion can be either circular or an elongated hole with a large inner dimension in the X-axis direction.

[0143] like Figure 13As shown, when the temperature rises from the reference temperature, the support portion 201, made of a lightweight material with a high coefficient of thermal expansion, elongates relative to the track 202. At this time, the rotating body 205 rotates about an axis orthogonal to the X-axis. This rotation allows relative movement between the support portion 201 and the track 202 along the X-axis. That is, the friction between the support portion 201 and the track 202 is not the conventional sliding friction but rolling friction, thus the force constraining the relative movement of the support portion 201 and the track 202 is very small. Therefore, the expansion and contraction of the support portion 201 and the track 202 along the X-axis are not mutually constrained, and they can deform independently.

[0144] At this time, as Figure 13 As shown, as the support portion 201 extends and retracts, the plurality of receiving portions 2011 provided on the support portion 201 also move in the X-axis direction. Since the fastening member 206's shaft portion 2062 is screwed into the receiving portion 2011, it moves integrally with the support portion 201 in the X-axis direction.

[0145] Here, as described above, the diameters of the recess and the through portion of the through hole 2021 in the track 202 are designed to be larger than the diameters of the head 2061 and the shaft portion 2062 of the fastening member 206, respectively. That is, a gap is provided between the fastening member 206 and the through hole 2021. Through this gap, even if the fastening member 206 moves together with the support portion 201 in the X-axis direction, it will not contact the inner wall of the through hole 2021. Therefore, the fastening member 206 does not constrain the relative movement of the support portion 201 and the track 202 along the X-axis direction.

[0146] Therefore, even under varying ambient temperatures, the straightness of the track 202 can be maintained, ensuring smooth movement and high-precision positioning performance of the translation body 203. Furthermore, by suppressing the generation of stress associated with temperature changes, plastic deformation of components is reduced. Moreover, the hysteresis between the support 201 and the track 202, which was a problem in previous structures due to minor slippage and fixing, is also reduced. This means that when the temperature returns to the reference temperature after a rise or fall, no deformation such as bending remains, but rather the original state is restored. As a result, the reference state of the device remains stable even after temperature cycling.

[0147] Furthermore, the diameters of the recess and the through portion of the through hole 2021 in the track 202 can be designed based on the assumed temperature change. For example, consider the case where the specifications are assumed to be within ±20°C of a reference temperature of 20°C. In this case, when the fastening portion 206 moves due to the expansion and contraction of the support portion 201 and the track portion 202 at 0°C and 40°C, the diameters of the recess and the through portion can be determined such that the fastening portion 206 does not contact the inner wall surface of the through hole 2021.

[0148] Next, the relationship between the fastening by the fastening member 206 and the permitted expansion and contraction of the support portion 201 and the rail 202 will be described. When the fastening member 206 is tightened, a fastening force is applied mainly in the Z-axis direction, that is, the direction perpendicular to the upper surface of the rail 202. This fastening force can reduce the deviation of the rail 202 relative to the support portion 201 in the Z-axis direction.

[0149] On the other hand, the deviation on the XY plane is determined by the relationship between the frictional force acting between the lower surface of the head portion 2061 of the fastening portion 206 and the bottom surface of the recess of the through hole 2021 in the rail 202, and the rolling frictional force of the rotating body 205. For simplicity, the deviation in the X-axis direction will be described as an example of the deviation in the XY plane.

[0150] If the static frictional force acting between the lower surface of the head portion 2061 of the fastening portion 206 and the bottom surface of the recess of the through hole 2021 in the rail 202 is defined as Ff, and the rolling frictional force of the rotating body 205 is defined as Fr, the force Fmax in the direction that suppresses the deviation in the X-axis direction is obtained as the sum of Ff and Fr. Further, the force that causes the rail 202 to move in the X-axis direction, which is generated by the difference in thermal expansion between the support portion 201 and the rail 202 due to a temperature change from the reference temperature, is defined as Ft. When Fmax is greater than Ft, a force is applied in the direction that restricts the expansion and contraction of the support portion 201 and the rail 202, thus generating the strain as described above. Therefore, the relationship Fmax < Ft is required. Further, the external force applied to the support portion 201 or the rail 202 due to impact, vibration, acceleration / deceleration of the translation body, etc. of the apparatus is defined as Fex. When a deviation occurs in the X-axis direction between the support portion 201 and the rail 202 due to an external force assumed in operation, the guiding accuracy and positioning accuracy of the translation body 203 are degraded. Therefore, the relationship Fex < Fmax is required. That is, it is preferable to design to satisfy the relationship Fex < Fmax < Ft. For example, the static frictional force Ff acting between the lower surface of the head portion 2061 of the fastening portion 206 and the bottom surface of the recess of the through hole 2021 in the rail 202 is obtained as the product of the normal force from the bottom surface of the recess toward the head portion 2061 and the static friction coefficient between the bottom surface of the recess and the head portion 2061. The normal force from the bottom surface of the recess toward the head portion 2061 is determined by the fastening torque of the fastening member. Therefore, it is preferable to design the fastening torque so as to satisfy the relationship Fex < Fmax < Ft. Further, the pressure applied to the contact surface, that is, the contact pressure, is determined by the relationship between the size of the contact area between the bottom surface of the recess and the head portion 2061 and the fastening torque. When this contact pressure is large, the influence of wear between the head portion 2061 and the bottom surface of the recess becomes significant, so it is preferable to design with an appropriate contact area.

[0151] That is, sliding friction occurs between the lower surface of the head 2061 of the fastening member 206 and the bottom surface of the recess of the through hole 2021 of the track 202 due to sliding contact. However, the friction generated between the upper surface of the support 201 and the lower surface of the track 202 becomes rolling friction due to rolling contact with the rotating body 205. This allows for relative movement along the X-axis between the support 201 and the track 202 due to expansion and contraction caused by temperature changes. Furthermore, the area of ​​the sliding contact region is smaller than the area of ​​the lower surface of the head 2061. This is because the diameter of the through portion, at least along the X-axis, is larger than the diameter of the shaft portion 2062.

[0152] The effect of the fastening force of the fastening member 206 on the shape of the track 202 and the preferred configuration of the rotating body 205 for suppressing this effect will be explained. The fastening member 206 presses the track 202 against the support portion 201 through the rotating body 205. This pressing force is concentrated on the track 202 from the head 2061 of the fastening member 206. Therefore, the track 202 may flex towards the support portion 201, i.e., locally bend, with the nearby rotating body 205 as a fulcrum due to the fastening force. Therefore, a pair of rotating bodies 205a and 205b are arranged near each fastening member 206 (and the through hole 2021). The pair of rotating bodies 205a and 205b can be arranged symmetrically along the long side direction (X-axis direction) of the track 202 with respect to the central axis CL of the through hole 2021. By positioning a pair of rotating bodies 205a and 205b near the central axis CL of the through hole 2021, local deflection of the track 202 can be suppressed. Furthermore, by positioning the pair of rotating bodies 205a and 205b symmetrically along the long side (X-axis direction) of the track 202 with respect to the central axis CL of the through hole 2021, the bending moment generated by each rotating body 205a and 205b can be counteracted.

[0153] For example, let the fastening force be F, and let the distances on the X-axis from the central axis CL of the through hole to the rotating bodies 205a and 205b be La and Lb, respectively. Furthermore, consider the local region of track 202 as a beam model supported at both ends by rotating bodies 205a and 205b. In this case, the deflection depends on the cross-sectional shape, material, Young's modulus, density, beam length (the distance between the two supports, i.e., La + Lb), and fastening force of track 202. In particular, it is known that the deflection is proportional to the cube of the beam length. Therefore, by positioning a pair of rotating bodies 205a and 205b near the central axis CL of the through hole 2021, the distance between the two supports can be reduced, thus reducing the deflection.

[0154] Further, for example, let the fastening force be F, and let the distances on the X-axis from the central axis CL of the through-hole to the rotating bodies 205a and 205b be La and Lb respectively. At this time, when the position of the fastening member 206 is taken as the rotation center, the bending moment generated by the rotating body 205a is F×La. Similarly, the bending moment generated by the rotating body 205b is F×Lb. However, the directions of the bending moment generated by the rotating body 205a and the bending moment generated by the rotating body 205b are opposite to each other. In a case where the pair of rotating bodies 205a and 205b are arranged at positions symmetrical in the long side direction (X-axis direction) of the rail 202 with respect to the central axis CL of the through-hole 2021, La=Lb. Therefore, the bending moments generated by the respective rotating bodies 205a and 205b are canceled out. Therefore, regarding the arrangement of the rotating bodies 205, as described above, there is a pair of rotating bodies that, on the basis of satisfying the rolling friction Fr of Fe<Fmax<Ft, are arranged at positions symmetrical at least in the long side direction (X-axis direction) of the rail 202 with respect to the central axis CL of each through-hole 2021.

[0155] Figure 15 is a perspective view showing the arrangement of each part of the translation mechanism in the first embodiment. The X-axis drive unit 52 is provided with: a support portion 201; a pair of rails 202 fixed to the support portion; and a translation body 203 that moves in the X-axis direction along the rails 202 (in Figure 14(Not shown); and a feed screw 204, which is disposed between a pair of rails 202 for driving a translation body 203 along the rails. The pair of rails 202, fixed to the support, are arranged parallel to each other along the X-axis. The feed screw 204 and the translation body 203 are fixed, and the translation body 203 moves along the X-axis as the feed screw 204 rotates. That is, the feed screw 204 drives the translation body 203 along the X-axis. In addition, a linear scale 207 with grating graduations evenly spaced is connected to the side of at least one of the pair of rails 202. In addition, although not shown, a linear encoder is fixed to the translation body 203, which includes a light-emitting element and a light-receiving element that receives the reflected light of the measurement light projected from the light-emitting element. This linear encoder is understood as an X-axis encoder section 122. The light-emitting element of the linear encoder projects measurement light onto the linear scale 207. The light-receiving device receives the light reflected by the linear scale 207 and generates a light-receiving signal. Because the linear scale 207 has equally spaced grating graduations, the light incident on the light-receiving device appears as stripes. When the translation body 203 moves in the X-axis direction, the linear encoder fixed to the translation body also moves in the X-axis direction. As the linear encoder moves, the striped light incident on the light-receiving device also moves. Based on the change in this striped light, the relative movement of the linear encoder relative to the linear scale 207 is obtained. Furthermore, when the first embodiment is applied to the Y-axis drive unit 54, the linear encoder is understood as the Y-axis encoder unit 142. When the first embodiment is applied to the Z-axis drive unit 56, the linear encoder is understood as the Z-axis encoder unit 143.

[0156] To reduce the effects of thermal expansion and contraction, the linear scale 207 is sometimes made of a material with a low coefficient of thermal expansion, such as glass. For example, the glass used in the linear scale 207 has a coefficient of thermal expansion of 8 × 10⁻⁶. -6 The coefficient of thermal expansion is approximately 100 K. This is close to the coefficient of thermal expansion of orbit 202, which can reduce the strain caused by the difference in thermal expansion coefficient when connecting with orbit 202.

[0157] Furthermore, the linear scale 207 is connected to the side of the track 202 by an adhesive or fastening component. Here, the coefficient of thermal expansion of the material constituting the linear scale 207 (e.g., glass) and the material constituting the track 202 (e.g., iron) is sometimes not strictly consistent. If the linear scale 207 is firmly fixed to the track 202 along its entire length, stress will be generated in the linear scale 207 due to the difference in the amount of expansion and contraction when temperature changes occur, potentially causing warping, strain, or errors in the spacing of the scale graduations. To avoid such problems caused by differences in thermal expansion, the linear scale 207 and the track 202 are preferably fastened or fixed at at least one point.

[0158] For example, the linear scale 207 is firmly fixed only at a point near its center along its long side, while other parts are either not fixed or connected with a weaker adhesive force than a fixed point. In this structure, the linear scale 207 expands and contracts freely due to temperature changes, with the central fixed point as the reference point (fixed point), moving towards both ends. The track 202 also expands and contracts in the same way, but their expansion and contraction are not mutually constrained, thus suppressing stress on the linear scale 207. Furthermore, a weak adhesive means an adhesive that cannot withstand shear forces caused by differences in expansion and contraction between components, or allows relative sliding through elastic deformation of the adhesive layer or minor damage.

[0159] Alternatively, as another example, one could consider a structure where two points at either end of the linear scale 207 are fixed, while the portion in between is not fixed, or a structure connected by the aforementioned weak adhesive bonding. In this case, the linear scale 207 experiences tensile or compressive stresses due to temperature changes, but this stress becomes uniform along the entire length of the scale, making it easier to predict changes in the scale graduation spacing. In the temperature correction described later, by taking this uniform spacing change into account, higher accuracy coordinate correction can be achieved.

[0160] As the temperature changes from the reference temperature, the linear scale 207 also expands and contracts. Therefore, the readings of the linear encoder also change according to the temperature. Consequently, a temperature sensor is positioned near the linear scale 207 to measure its temperature and send it to the PC1. The memory 115 stores in advance a prescribed correction formula for correcting coordinate values ​​based on the relationship between the expansion and contraction of the linear scale 207 and temperature. The PC1 calculates the coordinate measurement value at the current temperature based on the readings of the linear scale 207 and the correction formula stored in the memory 115. Alternatively, the linear encoder can also calculate the coordinate measurement value at the current temperature based on the readings of the linear scale 207 and the correction formula stored in the memory 115.

[0161] Track 202 is a component that extends along the translation direction. Therefore, in order to increase the measurable range of the coordinate measuring device in the translation direction, track 202 needs to be longer in the translation direction. In this case, the temperature distribution generated along the longer side of track 202 needs to be considered. Therefore, for example, track 202 can be divided into two or more regions along its longer side, and a temperature sensor can be provided for each region to measure the temperature of that region. Furthermore, PC1 can also use the average temperature obtained from multiple temperature sensors to correct the coordinate values.

[0162] In addition, Figure 14In this configuration, for one of the pairs of tracks 202, a linear scale 207 is connected to the surface facing the other track, but it could also be the surface on the opposite side. Furthermore, the linear scale is not limited to the aforementioned reflective type; it could also be a transmissive type, or a method that calculates the movement based on the diffraction changes of light passing through the scale and the linear scale. Additionally, it is not limited to calculating the incremental movement relative to a reference position; it could also be an absolute method for calculating the absolute position.

[0163] <Second Implementation Method>

[0164] Figure 16 This diagram illustrates the configuration of the translation mechanism in the second embodiment. An X-axis drive unit 52 is provided at the upper end of the head housing portion 57, particularly the upright portion 57b. The X-axis drive unit 52 cantileverly supports the Y-axis drive unit 54 in a manner that allows free movement along the X-axis drive direction 51. The X-axis drive unit 52 can be understood as a so-called translation beam. The Y-axis drive unit 54 supports the Z-axis drive unit 56 in a manner that allows free movement along the Y-axis drive direction 53. The Y-axis drive unit 54 can be understood as a so-called translation body. The Z-axis drive unit 56 supports the contact probe 60 in a manner that allows free movement along the Z-axis drive direction 55. The Z-axis drive unit 56 can be understood as a so-called translation rod. A contact member is connected below the Z-axis drive unit 56. Hereinafter, in the second embodiment, the construction of the Z-axis drive unit 56 will be described as an example of the translation mechanism, but the following construction can also be applied to at least one of the X-axis drive unit 52 and the Y-axis drive unit 54.

[0165] Figure 17 This is a perspective view of the translation mechanism in the second embodiment. The Z-axis drive unit 56 includes a support unit 301, a pair of tracks 302, a fixing unit 303, and a feed screw 304 disposed between the pair of tracks 302. The fixing unit 303 is connected to the Y-axis drive unit 54. Therefore, the fixing unit 303 is moved in the Y-axis direction by the Y-axis drive unit 54. The feed screw 304 is fixed to the support unit 301. Furthermore, the feed screw 304 is connected to the fixing unit 303.

[0166] Figure 18 This is the front view of the translation mechanism in the second embodiment. Figure 19 This is a diagram illustrating the translation of the translation mechanism in the second embodiment.

[0167] like Figure 18 As shown, the fixing part 303 is connected to the Y-axis drive part 54. Figure 19As shown, with the rotation of the feed screw 304, a pair of rails 302 and a support portion 301 fixed to the feed screw 304 move relative to the fixed portion 303 in the Z-axis direction. Grooves are provided on both sides of each rail 302, and multiple balls are arranged between the fixed portion 303 and the grooves. When the support portion 301 and the pair of rails 302 move relative to the fixed portion 303 along the Z-axis direction, the balls rotate about an axis perpendicular to the Z-axis. This reduces friction between the rails 302 and the fixed portion 303. Furthermore, as... Figure 18 , Figure 19 As shown, the Z-axis drive unit 56 includes a plurality of rotating bodies 305 disposed between the support portion 301 and a pair of tracks 302, and fastening members 306 that fasten the support portion 301 and the pair of tracks 302, which are facing each other and separated by the rotating bodies 305. The connection relationship of the Z-axis drive unit 56 including the rotating bodies 305 and the fastening members 306 can also be applied to the connection relationship described in Embodiment 1 using the X-axis drive unit 52 as an example.

[0168] In particular, in coordinate measuring devices as disclosed herein, where the Z-axis drive unit 56 is cantilevered by the Y-axis drive unit 54, it is necessary to reduce the bending moment. Specifically, the overall weight of the Z-axis drive unit 56 results in a large bending moment acting on the Y-axis drive unit 54 and the X-axis drive unit 52. This bending moment causes deflection in each drive unit, leading to a decrease in measurement accuracy. In particular, when the Y-axis drive unit 54 moves, increasing the distance from its connection with the X-axis drive unit 52 to the Z-axis drive unit 56, the lever arm becomes longer, and therefore the deflection becomes even greater. Therefore, reducing the weight of the Z-axis drive unit 56 can sometimes maintain or improve the overall accuracy of the device. Of course, even in cases where the Z-axis drive unit 56 is supported from two directions, such as in a portal frame structure, weight reduction is effective in reducing the burden on the mechanism used to drive the Z-axis drive unit 56 along the Y-axis direction.

[0169] As a method to reduce the weight of the Z-axis drive unit 56, for example, the support unit 301 could be constructed from a lightweight material with a low specific gravity, such as aluminum alloy or magnesium alloy. Additionally, as... Figure 18 , Figure 19 As shown, it is also considered to provide a weight reduction structure 310 in the support part 301, or to make the plate thickness of the component thinner.

[0170] However, these lightweighting methods sometimes introduce new problems. First, as described in Embodiment 1, lightweight materials tend to have a higher coefficient of thermal expansion than materials such as iron. If the support 301 with a different coefficient of thermal expansion is directly fastened to the track 302, warping and strain will occur due to temperature changes. To address this problem, the connection structure with the rotating body 305 as described in Embodiment 1 is effective.

[0171] Second, the use of lightweight materials and the adoption of weight-reducing structures are sometimes the main reasons for the reduced rigidity of the support portion 301 itself. When the rigidity of the support portion 301 is low, even if the expansion and contraction between the components are allowed by using the connection structure of the rotating body 305, strain may still occur. That is, the support portion 301 itself may experience deformation such as strain, warping, or torsion due to forces that slightly restrict the relative movement between the components, such as the rolling friction of the rotating body 305 and the friction generated at the interface between the fastening member 306 and the track 302.

[0172] Therefore, in the second embodiment, a structure for suppressing thermal deformation caused by such reduction in rigidity is also provided. Figure 20 This is a cross-sectional view of the translation mechanism in the second embodiment. Additionally, Figure 21 This is a conceptual diagram of the translation mechanism in the second embodiment. (Example) Figure 20 , Figure 21 As shown, the same structure is also provided on the side of the support portion 301 opposite to the side where the pair of rails 302 are disposed (hereinafter referred to as the "back side"). That is, a pair of second rails 302d that do not have a guiding function are fastened to the back side of the support portion 301 using multiple second rotating bodies 305d and second fastening members 306d.

[0173] According to this structure, when the support portion 301 expands or contracts with temperature changes, the force (friction, etc.) constraining this expansion or contraction acts on both the surface and the back surface of the support portion 301. At this time, if the track 302 and the second track 302d are symmetrically arranged with respect to the central axis (or central plane) of the support portion 301, the bending moments generated in the support portion 301 by each track are mutually canceled out. As a result, deformations such as warping or torsion of the support portion 301 are suppressed.

[0174] In this case, it is preferable to arrange the pair of tracks 302 and the second track 302d in a line-symmetrical manner with respect to the central axis of the support portion 301. Furthermore, it is even more preferable that the spacing between the fastening members 306, 306d for securing each track and the spacing between the rotating bodies 305, 305d are also set symmetrically. Here, the second track 302d does not function as a guide for the fixing portion 303, but functions as a strain-suppressing member, primarily designed to suppress strain in the support portion 301.

[0175] Furthermore, the strain-suppressing component does not need to be the same as the track 302; it only needs to be a component with at least substantially the same coefficient of thermal expansion and rigidity as the track 302. For example, it could be a simple prismatic component without guide grooves. However, it is preferable to have a symmetrical shape and configuration as described above. When a temperature change occurs, a first bending moment is generated on the track 302 side due to the difference in expansion and contraction with the support. Similarly, a second bending moment is generated on the strain-suppressing component side. Here, if the geometric configuration (distance from the center of the support), physical properties (coefficient of thermal expansion, Young's modulus, cross-sectional area), and connection structure (fastening distance, friction characteristics) of the two components are symmetrical, the magnitudes of the first and second bending moments are equal and their directions are opposite. As a result, these moments cancel each other out along the entire length of the support, reducing the actual bending moment acting on the support.

[0176] Furthermore, as described above, in the structure of the second embodiment, the support portion 301 and the pair of tracks 302 move relative to the fixing portion 303 in the Z-axis direction. Compared to a structure in which the tracks 302 are fixed to the fixing portion side and the translational body for supporting the contact probe 60 moves on the tracks 302 fixed to the fixing portion 303, this structure enables miniaturization and weight reduction.

[0177] The measurable range of the coordinate measuring device depends on the movable range of the contact probe 60 caused by the X-axis drive unit 52, Y-axis drive unit 54, and Z-axis drive unit 56. Furthermore, the measurable range also varies depending on the position of each drive unit and the size of the component indicating the contact probe 60. Here, for comparison with the structure of this embodiment, the structure of a comparative example is considered. The translation mechanism of the comparative example includes a fixing part 401 fixed to the Y-axis drive unit 54, a track 402 fixed to the fixing part 401, a translation body 403 moving along the track 402, and a probe support part 404 connected to the translation body 403 and supporting the contact probe 60. In this structure, the track 402 is fixed to the fixing part 401, and the translation body 403 moves on the track 402.

[0178] In order to perform measurements even on small workpieces, the contact probe 60 needs to reach the surface of the rotary table 70 on which the workpiece W to be measured is placed. When the distance from the height Z1 of the moving axis of the Y-axis drive unit 54 to the surface (height O) of the rotary table 70 is large, i.e., when Z1 is large, a longer travel (length) of the track 402 is considered. Alternatively, the probe support 404 connecting the translation body 403 to the front end of the contact probe 60 needs to be designed to be longer. However, if the track 402 and the probe support 404 are lengthened, the volume of the components may increase accordingly, and the overall weight of the Z-axis drive unit may increase.

[0179] In contrast, in the structure of the second embodiment, such as Figure 18 and Figure 19 As shown, the track 302 and the support portion 301 are integrally movable relative to the fixed portion 303. That is, the track 302 itself becomes a movable-side component. In this structure, the fixed portion 303 does not include a structure for supporting the track 302, so it can be constructed in a smaller and lighter manner compared to the fixed portion 401 (including the track 402) of the comparative example. Furthermore, the support portion 301, as a movable-side component, directly or indirectly supports the contact probe 60 at its lower end. Since the track 302 itself moves in the Z-axis direction, it is not necessary to separately provide a long probe support portion 404 as in the comparative example, thus ensuring a larger measurable range below the Z-axis. As a result, while ensuring the same measurable range, the Z-axis drive portion 56 can be miniaturized and made lighter overall compared to the structure of the comparative example.

[0180] Furthermore, the structure of the second embodiment reduces the overall maximum height of the device, improving portability. In the comparative example, the track 402 is fixed to the Y-axis drive unit 54, so the maximum height of the device in the Z-axis direction is defined by the upper end of the track 402. In contrast, in the structure of the second embodiment, the track 302 is a movable component. Therefore, when the support unit 301 is moved downward along the Z-axis, the track 302 also moves downward in tandem. Thus, for example, when the device is being transported or stored, by moving the Z-axis drive unit 56 to its lowest position, the overall height of the device can be kept low. This helps improve the portability of the device. For example, it can also be configured such that when the power to the device is disconnected, the main control unit 121 controls the Z-axis drive unit 56 to move to its lowest position.

[0181] In a structure where the Y-axis drive unit 54 cantileverly supports the Z-axis drive unit 56, as in this disclosure, the structure of the second embodiment is particularly effective. In the cantilever construction, at the connection between the Y-axis drive unit 54 and the Z-axis drive unit 56 ( Figure 18 The connecting portion of the fixing part 303 is subjected to a torque generated by the weight of the entire unit of the Z-axis drive part 56. More specifically, the connecting portion of the X-axis drive part 52 and the Y-axis drive part 54 is subjected to a torque generated by the weight of the entire unit of the Y-axis drive part 54 and the entire unit of the Z-axis drive part 56.

[0182] In the comparative example, the heavier fixing part 401, including the track 402, is fixed to the front end of the Y-axis drive part 54, thus increasing its torque. This large torque causes the Y-axis drive part 54 to deflect. This deflection worsens the perpendicularity of the Z-axis drive direction 55 relative to the XY plane, reducing measurement accuracy. Furthermore, to minimize the decrease in measurement accuracy, it is necessary to increase the overall rigidity of the Y-axis drive part 54 and the head housing part 57. For example, using a material with higher rigidity and greater weight could be considered. This can sometimes lead to further weight increase in the overall device. In contrast, in the structure of the second embodiment, the weight of the unit 56 connected to the Y-axis drive part 54 is lighter than that of the comparative example. As a result, deflection of the Y-axis drive part 54 (X-axis drive part 52) ​​is suppressed. Therefore, it is not necessary to use a material with high rigidity and great weight, thus achieving weight reduction.

[0183] Summary

[0184] The embodiments of the present invention have been described above, but the present invention is not limited to the embodiments described above. The structures described in each embodiment can be combined arbitrarily without contradiction.

[0185] Furthermore, in each embodiment, specific translation mechanisms (X-axis drive unit, Z-axis drive unit) are described as examples, but the present invention is not limited thereto and can be applied to any translation mechanism including X-axis drive unit, Y-axis drive unit and Z-axis drive unit.

[0186] The rotating body, fastening member, and through hole structures in the first and second embodiments are structures for suppressing thermal deformation, and can also be described as thermal deformation suppression structures (thermal deformation suppression members). For example, as a variation of the thermal deformation suppression structure, consider the following structure: the track and the support are fastened by sandwiching a material with a low coefficient of friction between the track and the support. This reduces the friction at the interface between the track and the support. The material with a low coefficient of friction is, for example, a component such as a polyimide strip. That is, the case where the rotating body in the first and second embodiments is replaced by a polyimide strip is also included in the thermal deformation suppression structure. Furthermore, the connection structure (connecting member) including the rotating body and the connection structure (connecting member) in the first and second embodiments that fastens the track and the support by sandwiching a material with a low coefficient of friction between the track and the support can also be described as a friction reduction structure (component). The friction reduction member is disposed between the track and the support, and by reducing the friction at the interface between the track and the support, it allows the track and the support to expand and contract at least along the translational direction due to temperature changes. The fastening components secure the opposing tracks and support parts, which are separated by the friction-reducing components.

[0187] Furthermore, in the above embodiment, the fastening member is described as a threaded member consisting of a head and a shaft, but the present invention is not limited to this. The fastening member can be any other type of fastener as long as it functions to fasten the support to the track and allows relative movement between the two in the long-side direction.

[0188] For example, the fastening component can also be a combination of bolts and nuts. In this case, consider the following structure: a through hole is also provided in the support, and a nut is used to fasten the bolt inserted from the rail side on the back side of the support.

[0189] Alternatively, a structure using rivets for fastening can be used without requiring disassembly. Furthermore, a structure using a clamp with a cam mechanism or toggle mechanism for fastening can also be used. Regardless of the specific structure, it is preferable to provide a gap between the fastening component and the through hole in the track to allow for relative movement due to thermal expansion differences.

[0190] Furthermore, in the above embodiment, a cylindrical roller having a rotation axis orthogonal to the X-axis direction was described as the rotating body, but the present invention is not limited to this. For example, the rotating body can also be a ball (roller ball). By using a ball, small movements in a freer direction between the support and the track can be allowed. In addition, it is also possible to use multiple cylindrical rollers arranged in a cross-shaped configuration that is orthogonal to each other.

[0191] Furthermore, while a feed screw is used as the mechanism to drive the translational body in each embodiment, the driving method is not limited to this. For example, a linear motor that generates thrust in a non-contact manner through coils and magnets can also be used as the drive source. By using a linear motor, higher speed and higher precision positioning can be achieved without backlash and wear. In addition, other direct-acting mechanisms such as rack and pinion mechanisms and belt drive mechanisms can be appropriately employed.

[0192] The structure for correcting coordinate values ​​by measuring the temperature of a linear scale has been described, but the configuration of the temperature sensors is not limited to this. For example, to more precisely correct for the effects of temperature distribution, multiple temperature sensors can be arranged along the long side of the track or support. Furthermore, the average temperature can be calculated based on the measurements from each sensor, or the local expansion and contraction can be calculated based on the temperature of each area, and these can be integrated to correct the overall coordinate values. Thus, even when there is uneven temperature distribution, higher accuracy measurements can be achieved.

[0193] Explanation of reference numerals in the attached figures

[0194] 1…PC, 2…Mouse, 3…Communication cable (between head housing and PC), 5…Main body, 11…Control console, 12…Communication cable (between control console and head housing), 31…Non-contact optical sensor, 32…Laser emitting part, 33…Light receiving lens, 34…(Non-contact optical sensor)Camera part, 50…Head, 51…X-axis drive direction, 52…X-axis drive part, 53…Y-axis drive direction, 54…Y-axis drive part, 55…Z-axis drive direction, 56…Z-axis drive part, 57…Head housing, 57a…Ground contact part, 57b…Upright part, 58…θ-axis drive part, 60…Contact probe, 61…B-axis Drive direction, 62…B-axis drive unit, 63…A-axis drive direction, 64…A-axis drive unit, 65…(contact probe) stylus, 66…workpiece camera, 70…rotary stage, 71…θ-axis drive direction, 80…measurement button, 81…detection button, 82…power button, 100…coordinate measuring device, 111…PC application, 112…measurement setting unit, 113…continuous measurement unit, 114…communication / control unit, 115…memory, 121…main control unit, 122…X-axis encoder unit, 123…θ-axis encoder unit, 124…communication unit, 131…(X-axis drive unit)communication / control unit, 141…( 142…Y-axis drive unit communication / control unit, 143…Z-axis encoder unit, 144…contour calculation unit, 145…(non-contact optical sensor) communication / control unit, 151…(Z-axis drive unit) communication / control unit, 161…(contact probe) communication / control unit, 162…B-axis encoder unit, 163…(contact probe) camera unit, 164…(B-axis drive unit) communication / control unit, 165…A-axis encoder unit, 166…(A-axis drive unit) communication / control unit, 167…Hall sensor unit, 168…(A-axis drive unit) illumination unit, 169…(workpiece camera) Camera unit, W…workpiece, 201…support unit in the first embodiment, 202…track in the first embodiment, 2021…through hole, 203…translator in the first embodiment, 204…feed screw in the first embodiment, 205…rotator in the first embodiment, 206…fastening member in the first embodiment, 2061…head, 2062…shaft, 301…support unit in the second embodiment, 302…track in the second embodiment, 303…fixing unit, 304…feed screw in the second embodiment, 305…rotator in the second embodiment, 306…fastening member in the second embodiment.

Claims

1. A coordinate measuring device comprising a translation mechanism capable of translation in at least a first direction, wherein the translation mechanism causes a contact element to contact a workpiece, thereby measuring the three-dimensional shape of the workpiece. in, The translation mechanism includes: A translator that causes the contact element to translate in the first direction; A first track, which is made of a material having a first thermal expansion ratio, is used to guide the translational body in the first direction; A support portion, which is made of a material having a second thermal expansion rate different from the first thermal expansion rate, is used to support the first track; A first rotating body is disposed between the first track and the support portion, and rotates according to the relative movement of the first track and the support portion along the first direction; as well as A first fastening component fastens the first track, which faces each other across the first rotating body, to the support portion.

2. The coordinate measuring device according to claim 1, wherein, The first track is provided with a through hole through which the first fastening component passes. The through hole is configured such that its inner dimension in the first direction is larger than the diameter of the first fastening member.

3. The coordinate measuring device according to claim 2, wherein, The first fastening member has a head and a shaft extending from the head. The through hole includes a recess for receiving the head and a through portion for the shaft portion to pass through from the bottom surface of the recess toward the support portion. The inner dimension of the recess in the first direction is configured to be larger than the diameter of the head. The inner dimension of the through portion in the first direction is configured to be larger than the diameter of the shaft portion.

4. The coordinate measuring device according to claim 3, wherein, The support portion is provided with a receiving portion that screws into the shaft portion.

5. The coordinate measuring device according to claim 1, wherein, The first track is connected to the first fastening component via sliding contact. The first track is connected to the support by means of the rolling contact of the rotating body, thereby allowing relative movement along the first direction between the support and the first track due to the expansion and contraction caused by temperature changes.

6. The coordinate measuring device according to claim 5, wherein, The first fastening member has a head and a shaft extending from the head. The first track and the first fastening member are connected by a sliding contact between the lower surface of the head and the first track. The area of ​​the sliding contact is smaller than the area of ​​the lower surface of the head.

7. The coordinate measuring device according to claim 1, wherein, The first track is provided with a through hole through which the first fastening component passes. The first rotating body includes a pair of rotating bodies that are arranged symmetrically along the first direction with respect to the central axis of the through hole.

8. The coordinate measuring device according to claim 1, comprising: The second track, which is disposed on the side of the support opposite to the side where the first track is disposed, is made of a material having a thermal expansion coefficient that is approximately the same as the first thermal expansion coefficient. The second rotating body is disposed between the face on the opposite side of the support and the second track, and rotates according to the relative movement of the second track and the support along the first direction; as well as The second fastening component fastens the second track, which is opposite to the second rotating body, to the support portion.

9. The coordinate measuring device according to claim 8, wherein, The first track and the second track are arranged symmetrically with respect to the central axis of the support.

10. The coordinate measuring device according to claim 1, comprising: A linear scale, connected to the first track and extending along the first direction; and An encoder, fixed to the translation body, is used to calculate the coordinates of the contact position of the contact element based on the readings of the linear scale.

11. The coordinate measuring device according to claim 10, further comprising: A plurality of temperature sensors are arranged along the long side of the linear scale, the temperature sensors being used to measure the temperature of the linear scale; and The calibration unit corrects the coordinates obtained by the encoder based on statistical values ​​of the temperatures measured by the plurality of temperature sensors and a prescribed calibration formula.

12. The coordinate measuring device according to claim 1, wherein, It includes an X-axis drive unit, a Y-axis drive unit, and a Z-axis drive unit for performing translation in mutually orthogonal X-axis, Y-axis, and Z-axis directions. At least two of the X-axis drive unit, the Y-axis drive unit, and the Z-axis drive unit are the translation mechanism.

13. The coordinate measuring device according to claim 12, wherein, At least one of the X-axis drive unit, the Y-axis drive unit, and the Z-axis drive unit is the Z-axis drive unit. The Z-axis drive unit includes: The second track, which is disposed on the side of the support opposite to the side where the first track is disposed, is made of a material having a thermal expansion coefficient that is approximately the same as the first thermal expansion coefficient. The second rotating body is disposed between the face on the opposite side of the support and the second track, and rotates according to the relative movement of the second track and the support along the first direction; as well as The second fastening component fastens the second track, which is opposite to the second rotating body, to the support portion.

14. The coordinate measuring device according to claim 12, comprising: A stage for holding workpieces; The ground contact portion supporting the mounting platform; and The head shell portion has an upright portion that rises from the ground contact portion. The X-axis drive unit is disposed at the upper end of the vertical part, providing single-arm support for the Y-axis drive unit and enabling the Y-axis drive unit to translate in the X-axis direction. The Y-axis drive unit supports the Z-axis drive unit and allows the Z-axis drive unit to translate in the Y-axis direction. The Z-axis drive unit supports the contact member and causes the contact member to translate in the Z-axis direction.

15. The coordinate measuring device according to claim 1, wherein, The first track includes a pair of tracks arranged parallel to each other along the first direction. The translational body is connected to the pair of tracks and is guided along the pair of tracks in the first direction. The translation mechanism also includes a feed screw, which is disposed between the pair of tracks for driving the translation body along the first direction.

16. The coordinate measuring device according to claim 15, wherein, The first rotating body is located between each of the two tracks and the support portion.

17. The coordinate measuring device according to claim 15, comprising: A linear scale, which is connected to at least one of the pair of tracks; and An encoder, fixed to the translation body, is used to calculate the coordinates of the contact position of the contact element based on the readings of the linear scale.

18. A coordinate measuring device having a translation mechanism capable of translation in at least a first direction, wherein the translation mechanism causes a contact element to contact a workpiece, thereby measuring the three-dimensional shape of the workpiece. in, The translation mechanism includes: A translator that causes the contact element to translate in the first direction; The track, which is made of a material having a first thermal expansion coefficient, is used to guide the translational body in the first direction; A support portion, which is made of a material having a second thermal expansion ratio different from the first thermal expansion ratio, is used to support the track; A friction-reducing component is disposed between the track and the support portion to allow the track and the support portion to expand and contract along the first direction due to temperature changes by reducing the friction between the track and the support portion at the interface. as well as Fastening components secure the tracks, which are facing each other and separated by the friction-reducing components, to the support.

Images