Inspection device and inspection method of crank shaft

Abstract

To provide an inspection device or the like of a crank shaft capable of reducing an inspection time and suppressing device costs.SOLUTION: An inspection device 100 comprises: surface shape measurement sections 1 (1a to 1d) disposed each around a center axis of a specimen T configured while crank shafts S (S1, S2) are lined up in a direction of a center axis L; a movement mechanism section 2 for relatively moving the surface shape measurement sections; a three-dimensional point group data generation section 31 for generating three-dimensional point group data on the basis of the surface shape of a specimen measured by the surface shape measurement section; a superposing section 32 for parallelly and rotationally moving three-dimensional point group data so that a distance to a surface shape model of crank shafts is minimized for each area corresponding to each of the multiple crank shafts of the three-dimensional point group data, and for superposing them on the surface shape model; and an inspection section 33 for inspecting the crank shafts on the basis of three-dimensional point group data after the superposition.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an apparatus and method for inspecting crankshafts used in automobile engines, etc., during their manufacturing process, and more particularly to an inspection apparatus and method for crankshafts that can shorten the inspection time and reduce the cost of the apparatus. [Background technology]

[0002] Figure 1 is a diagram showing an example of a crankshaft (a crankshaft for an in-line four-cylinder engine), in which Fig. 1(a) is a front view seen from the direction of the rotational axis L of the crankshaft S, and Fig. 1(b) is a side view seen from a direction perpendicular to the rotational axis L. As shown in FIG. 1, the crankshaft S includes a front SA provided on a central axis (rotational central axis) L of the crankshaft S, a plurality of (five in the example shown in FIG. 1) journals SB provided on the central axis L, a plurality of (eight in the example shown in FIG. 1) counterweights SC provided on the central axis L for balancing the rotation, a plurality of (four in the example shown in FIG. 1) pins SD for attaching connecting rods (not shown) provided at predetermined angular positions around the central axis L, and a flange SE provided on the central axis L. The cross-sectional shape of the pin SD is a circle centered at a position spaced from the central axis L, and the cross-sectional shapes of the front SA, journals SB, and flange SE, which are shaft portions of the crankshaft S corresponding to the shaft portion of the engine, are also circular and centered on the central axis L of the crankshaft S. The cross-sectional shape of the counterweight SC is a complex shape that is bilaterally symmetrical.

[0003] A crankshaft S, such as that shown in Figure 1, is manufactured by die forging, in which heated material is pressed between upper and lower dies to form a forged product containing burrs, which is then removed and shot blasted. The crankshaft S manufactured through these manufacturing processes is then machined by cutting so that it can be properly installed in an automobile engine or the like. Specifically, the shaft portion (front SA, journal SB, and flange SE) of the crankshaft S and the pin SD are machined into a cylindrical shape. These shaft portions and pin SD are provided with a machining allowance of several millimeters to allow for machining.

[0004] As described above, crankshafts have complex shapes. During forging, variations in material dimensions, material temperature, and forging operation can lead to defects known as underfill, where the material does not reach the edge of the die, as well as bends and twists along the entire length of the crankshaft. Furthermore, dents can occur when the crankshaft comes into contact with conveying equipment during handling. Furthermore, the shaft and pins, which are the machining areas of the crankshaft, may not have sufficient machining allowance. For this reason, in the crankshaft manufacturing process, the actual shape of the crankshaft is inspected by comparing it with a reference shape before machining to determine whether it passes or fails.

[0005] The criteria for determining whether a crankshaft passes or fails are: (a) the bending and twisting of the crankshaft are within a specified tolerance range, (b) the counterweight has no undercuts or dents that exceed the tolerance range, and (c) the shaft and pin, which are processed parts, have the specified processing allowance. The above (a) and (b) are set as conditions necessary for achieving dimensional accuracy and weight balance as a final crankshaft product. If the crankshaft is significantly bent or twisted, causing the pin installation position to deviate significantly from the specified angle, it will be difficult to achieve dimensional accuracy and weight balance as a final crankshaft product, regardless of what kind of processing is performed in subsequent processes. Similarly, if the counterweight shape does not conform to the design due to undercutting or dents, causing the center of gravity to deviate, it will also be difficult to achieve weight balance as a final crankshaft product. The above condition (c) is set as a necessary condition for machining. No matter how well-balanced the weight of a crankshaft may be, if there is not enough machining allowance, it will be difficult to achieve the required dimensional accuracy after machining, and the forged surface will have poor surface quality, making it impossible to use as an engine component.

[0006] Specifically, the pass / fail of the crankshaft bending is determined by the amount of deviation from the center axis of the shaft portion (front, journal, and flange) when the crankshaft is aligned with the coordinate system used during machining (the XYZ coordinate system in Figure 1), and the pass / fail of the crankshaft is judged based on whether this control index is within the tolerance (for example, within ±1 mm).Furthermore, the pass / fail of the crankshaft twist is determined by the pin split angle, and the pass / fail of the crankshaft is judged based on whether this control index is within a specified range (for example, ±1°). The counterweight's shape is judged based on its side dimensions (width, height, and outer diameter) as seen from the direction of the crankshaft's central axis, as shown in Figure 1(a). These control parameters are necessary to ensure the rotational balance of the crankshaft. The counterweight's shape is also judged based on its longitudinal position as seen from a direction perpendicular to the crankshaft's central axis, as shown in Figure 1(b). These control parameters are necessary to detect the counterweight's thickness (dimension along the central axis) and tilt. Each of the above control parameters related to the counterweight's shape has a set tolerance (for example, ±1 mm, ±2 mm). Furthermore, to determine whether the shape of the shaft portion is acceptable, the forging thickness and forging die deviation, which allow for understanding the precision of die forging, are used as control indicators in the manufacturing process.

[0007] A conventional crankshaft inspection method involves placing plate gauges formed to match the reference shapes of the pins and counterweights on the crankshaft to be inspected, checking the gaps between the plate gauges and the pins and counterweights, and judging whether the crankshaft passes or fails. This method is performed manually by an operator using plate gauges formed to match the reference shapes of the pins and counterweights, which not only results in individual differences in inspection accuracy but also requires a significant amount of time. For this reason, in order to perform accurate inspections automatically, the present inventors have proposed various crankshaft inspection devices and inspection methods, as shown in Patent Documents 1 to 5.

[0008] However, in both conventional inspection devices and methods, a surface shape measurement unit is moved relatively along the central axis of each crankshaft to measure the surface shape of each crankshaft, and the crankshaft is inspected based on the measurement results. Therefore, when inspecting crankshafts during the manufacturing process using the inspection devices shown in Patent Documents 1 to 5, if the time required to measure the surface shape of the crankshafts is long relative to the manufacturing pitch of the crankshafts (in other words, the pitch at which the crankshafts are brought into the inspection device), a single inspection device is not sufficient, and two or more inspection devices must be installed and the surface shapes of the crankshafts must be measured in parallel. This has led to problems such as increased device costs and the need for a larger space to install the inspection devices. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Patent No. 6451843 [Patent Document 2] Patent No. 6540882 [Patent Document 3] Patent No. 7277780 [Patent Document 4] Patent No. 7277781 [Patent Document 5] International Publication No. 2023 / 127200 Summary of the Invention [Problem to be solved by the invention]

[0010] The present invention has been made to solve the problems of the conventional technology as described above, and an object of the present invention is to provide a crankshaft inspection device and inspection method that can shorten the inspection time and suppress the device costs. [Means for solving the problem]

[0011] To solve the above problems, the inventors conducted extensive research and discovered that crankshafts are axial mechanical components made up of pieces with similar shapes connected in the direction of their central axis. They then came up with the idea that if multiple crankshafts are lined up in the direction of their central axis and a surface shape measuring unit is moved relatively in the direction of the central axis of the multiple crankshafts to measure their surface shapes simultaneously, it would be possible to shorten the inspection time per crankshaft and reduce the cost of the equipment, and completed the present invention. That is, to solve the above-mentioned problems, the present invention provides a crankshaft inspection device comprising: a plurality of surface shape measuring units arranged around a central axis of an object to be inspected, the surface shape measuring units being configured to optically measure a surface shape of the object to be inspected, the surface shape measuring units being arranged around the central axis of the object to be inspected; a movement mechanism unit being configured to move the surface shape measuring units relative to the object to be inspected in the central axis direction of the object to be inspected; a 3D point cloud data generation unit being configured to generate 3D point cloud data of the surface of the object to be inspected based on the surface shape of the object to be inspected measured by the surface shape measuring units being moved relatively by the movement mechanism; a superposition unit being configured to translate and rotate the 3D point cloud data for each region of the 3D point cloud data corresponding to each of the plurality of crankshafts so as to minimize the distance from the surface shape model of the crankshaft that is prepared in advance based on design specifications of the crankshaft, and to superimpose the 3D point cloud data on the surface shape model; and an inspection unit being configured to inspect the crankshaft based on the superimposed 3D point cloud data.

[0012] According to the inspection device of the present invention, the surface profile of the test object (a test object consisting of multiple crankshafts aligned along its central axis) is measured using a surface profile measurement unit that is moved relatively by a movement mechanism, so that the surface profiles of the multiple crankshafts that make up the test object are measured simultaneously. Therefore, compared to conventional methods of measuring the surface profile of each crankshaft individually, the time required to measure the surface profile of each crankshaft, and therefore the inspection time, can be shortened. Specifically, for example, when measuring the surface profile of two crankshafts individually, the relative acceleration and deceleration times of the surface profile measurement unit caused by the movement mechanism are required twice (for two crankshafts). However, according to the inspection device of the present invention, these times are required only once (for one test object), thereby shortening the time required to measure the surface profile. In the inspection device according to the present invention, the 3D point cloud data generator generates 3D point cloud data of the surface of the subject. That is, 3D point cloud data of the surfaces of multiple crankshafts is generated collectively. Then, the superimposing unit translates and rotates the 3D point cloud data for each region of the 3D point cloud data corresponding to each of the multiple crankshafts so as to minimize the distance from a surface shape model of the crankshaft prepared in advance based on the crankshaft's design specifications, and superimposes the data on the surface shape model. Therefore, the inspection unit can inspect the crankshaft based on the superimposed 3D point cloud data, i.e., the 3D point cloud data in a state that matches the coordinate system of the surface shape model. In other words, the multiple crankshafts constituting the subject can be inspected one by one. The inspection unit inspects the crankshaft based on the superimposed 3D point cloud data. Specifically, the inspection unit calculates the distance between the superimposed 3D point cloud data and the surface shape model, and detects defects such as underfill in the crankshaft based on this calculated distance. Furthermore, since the superimposed 3D point cloud data can identify the coordinates of each crankshaft component (journal, flange, pin, counterweight, etc.), it is possible to measure the dimensions of each component, such as the diameter of the journal and flange, the diameter and division angle of the pin (twist of the crankshaft), and the width, height, and outer diameter of the counterweight. Furthermore, the superimposed 3D point cloud data can be aligned with the coordinate system used during machining, which makes it possible to measure the deviation from the central axis of the shaft components (front, journal, and flange) (bending of the crankshaft) and the machining allowance. That is, even if defects such as twists, bends, and underfill occur in multiple crankshafts when they are connected and manufactured, the defects can be confirmed for each crankshaft. Furthermore, if defects such as twists, bends, and underfill occur in the machining allowance when the crankshafts are connected and manufactured, the defects can be ignored. The inspection details of the inspection unit described above can be applied to, for example, the contents described in Patent Documents 1 to 3.

[0013] As described above, the inspection device according to the present invention can reduce the time required to measure the surface shape of one crankshaft, and therefore the inspection time. Therefore, even if the production pitch of crankshafts becomes shorter, there is no need to install two or more inspection devices as in the past, and the cost of the device can be reduced. Furthermore, in the inspection device of the present invention, "the distance to the surface shape model of the crankshaft is minimized" means that the sum of the distances between each data point constituting the 3D point cloud data and the surface shape model, or the sum of the squared distances, is minimized.

[0014] In the inspection device according to the present invention, a plurality of crankshafts separated from one another can also be used as the object to be inspected, the surface shape of which is to be measured by the surface shape measuring unit. On the other hand, crankshafts are designed for each engine, and their length depends on the number of cylinders and displacement of the engine. The fewer the number of cylinders and the smaller the displacement, the shorter the crankshaft tends to be. For example, crankshafts used in small-displacement three-cylinder engines have a short overall length, less than half the length of crankshafts used in large-displacement eight-cylinder engines. Therefore, to improve the efficiency of crankshaft manufacturing, multiple crankshafts are sometimes die-forged while connected together, and then the forged product is separated into individual crankshafts. In such cases, in order to shorten inspection time, it is preferable to use multiple crankshafts before separation as the test specimen, rather than arranging the separated crankshafts in the axial direction.

[0015] That is, in the inspection apparatus according to the present invention, it is preferable that the test object has a configuration in which the plurality of crankshafts are connected together to form an integrated unit.

[0016] In the case of an inspection object consisting of multiple crankshafts separated from one another, it is necessary to repeatedly carry the inspection object into the inspection device and then carry the inspection object out of the inspection device after inspection a number of times corresponding to the number of crankshafts that make up the inspection object. In contrast to this, according to the above-described preferred configuration, the subject can be carried in and out in a single operation, thereby further shortening the examination time.

[0017] In order to solve the above-mentioned problems, the present invention also provides a crankshaft inspection method, comprising: a surface shape measurement step of measuring the surface shape of an object to be inspected using a plurality of surface shape measurement units arranged around a central axis of the object to be inspected, the surface shape measurement units being each arranged around the central axis of the object to be inspected in the axial direction of the object; and a movement mechanism unit that moves the surface shape measurement units relative to the object to be inspected in the axial direction of the object to be inspected; a 3D point cloud data generation step of generating 3D point cloud data of the surface of the object to be inspected based on the surface shape of the object using a 3D point cloud data generation unit; a superposition step of using a superposition unit to translate and rotate the 3D point cloud data for each region of the 3D point cloud data corresponding to each of the plurality of crankshafts so as to minimize a distance from a surface shape model of the crankshaft that is prepared in advance based on design specifications of the crankshaft, and superimposing the 3D point cloud data on the surface shape model; and an inspection step of inspecting the crankshaft based on the superposed 3D point cloud data using an inspection unit.

[0018] In the inspection method according to the present invention, it is preferable that the test object has a configuration in which the plurality of crankshafts are connected together into one unit. [Effects of the Invention]

[0019] According to the present invention, it is possible to shorten the inspection time and suppress the cost of the device. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is a diagram schematically illustrating an example of a crankshaft (a crankshaft for an in-line four-cylinder engine). [Figure 2] 1 is a diagram showing a schematic configuration of a crankshaft inspection device according to an embodiment of the present invention; [Figure 3] 1 is a diagram showing a schematic configuration of a crankshaft inspection device according to an embodiment of the present invention; [Figure 4] FIG. 1 is a flowchart showing a schematic procedure of a crankshaft inspection method according to an embodiment of the present invention. [Figure 5] FIG. 10 is a side view showing a schematic configuration of a crankshaft inspection device according to a first modified example of the present invention. [Figure 6] In a crankshaft inspection method using an inspection device according to the first modified example, an example of 3D point cloud data generated in a 3D point cloud data generation process and an example of divided 3D point cloud data generated in a divided 3D point cloud data generation process are shown. [Figure 7] FIG. 10 is a side view showing a schematic configuration of a crankshaft inspection device according to a second modified example of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, with reference to the accompanying drawings as appropriate, an embodiment of the present invention will be described, taking as an example a crankshaft for an in-line three-cylinder engine.

[0022] 2 and 3 are diagrams showing the schematic configuration of a crankshaft inspection device according to one embodiment of the present invention. FIG. 2(a) is a front perspective view as seen from the direction of the central axis of the test object T (X-axis direction). FIG. 2(b) is a block diagram showing the configuration of the calculation means 3 shown in FIG. 2(a). FIG. 3 is a side view as seen from the direction indicated by arrow A in FIG. 2(a). In FIGS. 2 and 3, the direction parallel to the central axis L of the test object T when there is no bending or twisting in the test object T is defined as the X-axis direction, the horizontal direction perpendicular to the central axis L of the test object T is defined as the Y-axis direction, and the vertical direction perpendicular to the central axis L of the test object T is defined as the Z-axis direction. In addition, the calculation means 3 is not shown in FIG. 3. As shown in FIGS. 2 and 3, the inspection device 100 according to this embodiment includes a surface shape measuring unit 1, a movement mechanism unit 2, a calculation means 3, and a support means 4. Hereinafter, the above-mentioned components 1 to 4 included in the inspection device 100 according to this embodiment will be specifically described.

[0023] <Surface shape measurement section 1> The object of surface shape measurement by the surface shape measuring unit 1 is an object T made up of multiple crankshafts S lined up in the direction of their central axes L (X-axis direction). In the example shown in Fig. 3, the object T is made up of two crankshafts S1 and S2 that are separated from each other and are arranged so that their central axes L coincide. The flanges SE of the two crankshafts S1 and S2 are arranged so that they face each other. The surface shape measuring unit 1 optically measures the surface shape of the test object T by projecting and receiving light onto the test object T. Specifically, the surface shape measuring unit 1 of this embodiment includes a light projecting means 11 that projects linear laser light toward the test object T extending in a direction perpendicular to the central axis L of the test object T (extending in the YZ plane), and a light receiving means 12 that receives and captures the light reflected from the surface of the test object T, and is configured to measure the surface shape of the test object T at the location where the laser light is projected by a light cutting method that analyzes deformation of the linear laser light. However, the surface shape measuring unit 1 is not limited to this, and it is also possible to adopt a configuration that projects a two-dimensional stripe pattern or grid pattern and measures the surface shape (three-dimensional shape) of the test object T by a spatial encoding method.

[0024] The surface profile measuring unit 1 of this embodiment is positioned at an angle β with respect to a plane (YZ plane) perpendicular to the direction of the central axis L of the test object T (X-axis direction), and when the distance to the test object T is 400 mm, the measurement field of view in the circumferential direction of the test object T is 180 mm. Furthermore, the measurement resolution in the circumferential direction of the test object T is 0.3 mm, and the measurement resolution in the radial direction of the test object T at a measurement cycle of 500 Hz is approximately 0.02 mm. For example, an ultra-high-speed inline profile measuring instrument "LJ-V7300" manufactured by Keyence Corporation can be used as this surface profile measuring unit 1. When the surface profile measuring unit 1 is moved in the X-axis direction at 200 mm / sec using the movement mechanism 2 described below, it is possible to measure the surface profile (three-dimensional shape) of the test object T with a measurement resolution in the X-axis direction (direction of the central axis L of the test object T) of 0.4 mm, a measurement resolution in the circumferential direction of the test object T of 0.3 mm, and a measurement resolution in the radial direction of the test object T of 0.02 mm.

[0025] The inspection apparatus 100 according to this embodiment includes, as the surface shape measuring unit 1, four surface shape measuring units 1a to 1d arranged at 90° intervals around the central axis L of the specimen T (around the X-axis direction). The surface shape measuring unit 1a includes a light projecting means 11a and a light receiving means 12a, and the surface shape measuring unit 1b includes a light projecting means 11b and a light receiving means 12b. Although not shown, the same applies to the surface shape measuring units 1c and 1d. By including the four surface shape measuring units 1a to 1d in this manner, it is possible to measure the surface shape (three-dimensional shape) of the entire specimen T without rotating the specimen T around the central axis L.

[0026] Of the four surface shape measuring units 1a to 1d, the surface shape measuring units adjacent to each other around the central axis L of the test object T have light projection directions inclined in opposite directions relative to the direction perpendicular to the central axis L of the test object T. For example, as shown in FIG. 3, the projection direction of light from the light-projecting means 11a of the surface profile measuring unit 1a is inclined by an angle β toward one crankshaft S2 (the right side of FIG. 3) with respect to a direction perpendicular to the central axis L of the specimen T (the Z-axis direction in the example shown in FIG. 3), whereas the projection direction of light from the light-projecting means 11b of the surface profile measuring unit 1b adjacent to the surface profile measuring unit 1a is inclined by an angle β toward the other crankshaft S1 (the left side of FIG. 3) with respect to a direction perpendicular to the central axis L of the specimen T (the Z-axis direction in the example shown in FIG. 3). Although not shown in the figure, the direction of light projection from the light projection means of surface shape measurement unit 1d adjacent to surface shape measurement unit 1a is inclined by angle β toward the crankshaft S1 with respect to a direction perpendicular to the central axis L of the specimen T, and the direction of light projection from the light projection means of surface shape measurement unit 1c adjacent to surface shape measurement units 1b and 1d is inclined by angle β toward the crankshaft S2 with respect to a direction perpendicular to the central axis L of the specimen T.

[0027] As with the surface profile measuring unit 1 of this embodiment, by tilting the light projection direction relative to a direction perpendicular to the central axis L of the test object T, it is possible to measure the shape of the side surface of the counterweight SC (the side surface perpendicular to the central axis L of the test object T). Furthermore, because the light projection directions of adjacent surface profile measuring units 1 are tilted in opposite directions relative to the direction perpendicular to the central axis L of the test object T, it is possible to measure the shapes of both side surfaces of the counterweight SC (the side surface on the front SA side and the side surface on the flange SE side). When the angle β is 5°, the measurement pitch in the Y-axis direction of the side surface of the counterweight SC is 4.5 mm (= 0.4 mm / tan 5°).

[0028] <Moving mechanism section 2> The movement mechanism 2 moves the surface profile measuring unit 1 relatively in the direction of the central axis L (X-axis direction) of the specimen T. In this embodiment, the specimen T remains stationary, while the movement mechanism 2 moves the surface profile measuring unit 1. For example, a uniaxial stage can be used as the movement mechanism 2. The uniaxial stage used in the movement mechanism 2 is preferably one that can position or grasp the position with a resolution of 0.1 mm or less. In this embodiment, a movement mechanism 2 is provided for each of the four surface profile measuring units 1 in order to move each of the four surface profile measuring units 1 independently. If the measurement positions of the four surface shape measuring units 1a-1d in the X-axis direction are close to each other, the light emitted from each surface shape measuring unit 1a-1d may interfere with each other, resulting in erroneous measurements. For this reason, for example, each of the four movement mechanism units 2 moves each of the surface shape measuring units 1a-1d so that they are spaced apart by approximately 200 mm in the X-axis direction.

[0029] <Calculation means 3> The calculation means 3 is connected to the four surface shape measurement units 1 and includes a three-dimensional point cloud data generation unit 31 , a superposition unit 32 , and an inspection unit 33 . The calculation means 3 is configured, for example, by a computer on which programs and applications that perform various calculations are installed so as to function as the 3D point cloud data generation unit 31, the superposition unit 32, and the inspection unit 33. Specifically, the calculation means 3 can be configured by implementing a known point cloud processing library, such as the open-source "PCL (Point Cloud Library)" or "HALCON" manufactured by MVTec, on the computer. The point cloud processing library can handle not only point cloud data but also surface data (data composed of cylinders, planes, triangular meshes, etc.), and can perform various calculations on point cloud data and surface data, such as preprocessing such as smoothing and thinning, extraction of point cloud data based on coordinates and distances, coordinate conversion, matching processing, fitting processing, dimensional measurement of point cloud data, and generation of three-dimensional surfaces. Each of the units 31 to 33 included in the calculation means 3 will be specifically described below.

[0030] [3D point cloud data generator 31] The three-dimensional point cloud data generating unit 31 receives input of the surface shapes of the subject T measured by the four surface shape measuring units 1 that are moved relatively by the movement mechanism unit 2. Then, the three-dimensional point cloud data generating unit 31 generates three-dimensional point cloud data made up of data points corresponding to points on the surface of the subject T by synthesizing the input surface shape of the subject T.

[0031] [Overlapping section 32] The superposition unit 32 stores in advance a surface shape model of the crankshaft S created based on the design specifications of the crankshaft S (S1, S2). Specifically, three-dimensional CAD data based on the design specifications is input to the superposition unit 32, which then converts the input CAD data into a surface shape model made up of a triangular mesh or the like and stores it. A surface shape model can be created and stored for each type of crankshaft S, so when inspected objects T made up of crankshafts S of the same type are inspected consecutively, there is no need to create a surface shape model for each inspection. Then, the superimposing unit 32 translates and rotates the 3D point cloud data generated by the 3D point cloud data generating unit 31, for each region corresponding to each of the multiple crankshafts S (S1, S2), to superimpose it on the surface shape model so that the distance from the surface shape model of the crankshaft S is minimized. The region corresponding to each of the multiple crankshafts S can be specified by the predetermined positions in the X-axis direction at which the multiple crankshafts S are placed on the support means 4, the X-axis position of each data point constituting the 3D point cloud data, etc.

[0032] Here, when the overlay unit 32 overlays the 3D point cloud data generated by the 3D point cloud data generator 31 onto a surface shape model, if the multiple crankshafts S constituting the subject T have the same shape, a problem may occur in which multiple surface shape models overlap one of the regions corresponding to the multiple crankshafts S in the 3D point cloud data (one region is overlapped and overlaid on multiple surface shape models; in other words, one region and one surface shape model do not have a one-to-one correspondence). To avoid this problem, it is preferable to set the overlay conditions in advance. For example, (1) if the crankshaft S has an asymmetric shape in the axial direction, when the surface shapes of multiple crankshafts S manufactured by connecting them together or multiple separated crankshafts S are measured using the surface shape measurement unit 1, the multiple crankshafts S can be manufactured or arranged so that their orientations are different from each other, (2) the orientation and range when overlaying the three-dimensional point cloud data can be set so that each region of the three-dimensional point cloud data is overlaid on each surface shape model, or (3) the three-dimensional point cloud data generated by the three-dimensional point cloud data generation unit 31 can be divided into regions corresponding to the multiple crankshafts.

[0033] For example, when dividing the three-dimensional point cloud data generated by the three-dimensional point cloud data generation unit 31, the overlay unit 32 divides the three-dimensional point cloud data generated by the three-dimensional point cloud data generation unit 31 into regions corresponding to each of the plurality of crankshafts S (two crankshafts S1 and S2 in this embodiment) to generate a plurality of (two in this embodiment) divided three-dimensional point cloud data. By dividing the three-dimensional point cloud data generated by the three-dimensional point cloud data generation unit 31, it is possible to set regions that overlap with the surface shape model corresponding to each of the plurality of crankshafts S, making it easy to overlay the three-dimensional point cloud data on the surface shape model. Note that "dividing into regions corresponding to the plurality of crankshafts" is a concept that encompasses both cases where adjacent regions have overlapping portions in the central axis direction of the crankshaft S and cases where they do not. In either case, combining the plurality of divided 3D point cloud data divided into regions corresponds to the 3D point cloud data of the subject T. However, when adjacent regions have overlapping portions, it is necessary that one of the two adjacent divided 3D point cloud data does not include the 3D point cloud data of the counterweight of the crankshaft S that corresponds to the other divided 3D point cloud data.

[0034] [Inspection Department 33] The inspection unit 33 inspects the crankshaft S (S1, S2) based on the three-dimensional point cloud data after superimposition by the superimposition unit 32. Specifically, the inspection unit 33 calculates the distance between the superimposed 3D point cloud data and the surface shape model, and detects defects such as underfill on the crankshaft S based on this calculated distance. Furthermore, since the superimposed 3D point cloud data can identify the coordinates of each part of the crankshaft S (journal, flange, pin, counterweight, etc.), the inspection unit 33 can also measure the dimensions of each part, such as the diameter of the journal and flange, the diameter and division angle of the pin (twist of the crankshaft S), and the width, height, and outer diameter of the counterweight. Furthermore, the inspection unit 33 can measure the amount of deviation from the central axis of the shaft parts (front, journal, and flange) (bending of the crankshaft S) and the processing allowance by aligning the superimposed 3D point cloud data with the coordinate system used during machining.

[0035] <Support means 4> The support means 4 includes a base 41 and two pairs of support portions 42 each extending in the Z-axis direction from the base 41. One support portion 42 of each pair supports the front SA of the crankshaft S, and the other support portion 42 supports the flange SE of the crankshaft S. The upper ends of the support portions 42 are formed in a V-shape, which allows the crankshaft S to be supported in a stable position. The two pairs of support portions 42 are arranged in a straight line in the X-axis direction, so that by placing the crankshafts S1 and S2 on each pair of support portions 42, the crankshafts S1 and S2 are arranged so that their central axes L coincide.

[0036] The surface shape measuring unit 1, moving mechanism unit 2, and support means 4 provided in the inspection device 100 according to this embodiment can have the same configurations as those described in Patent Documents 1 to 5, and therefore further detailed explanations will be omitted here.

[0037] A method for inspecting the crankshaft S using the inspection device 100 having the above configuration will be described below. FIG. 4 is a flowchart showing the outline of the procedure of the method for inspecting the crankshaft S according to one embodiment of the present invention. As shown in FIG. 4, the inspection method according to this embodiment includes a surface shape measuring step ST1, a three-dimensional point cloud data generating step ST2, a superposition step ST3, and an inspection step ST4. Each of the steps ST1 to ST4 will be specifically described below.

[0038] <Surface shape measurement process ST1> In the surface shape measuring step ST1, the surface shape of the specimen T is measured using a surface shape measuring unit 1 and a movement mechanism unit 2. Specifically, the movement mechanism unit 2 moves the surface shape measuring unit 1 relatively in the direction of the central axis L of the specimen T, while the surface shape measuring unit 1 measures the surface shape (three-dimensional shape) of the specimen T. More specifically, first, the specimen T is loaded into the inspection apparatus 100 using a predetermined transport mechanism (not shown). In other words, the two crankshafts S1 and S2 are each placed on the support means 4 in order. Next, the movement mechanism 2 moves the four surface shape measuring units 1a-1d in the X-axis direction toward the front SA of the crankshaft S1 (left side in FIG. 3). Then, while the movement mechanism 2 moves the four surface shape measuring units 1a-1d in the X-axis direction toward the front SA of the crankshaft S2 (right side in FIG. 3), light is projected onto and received from the specimen T (crankshafts S1 and S2), thereby measuring the surface shape of the specimen T. At this time, to prevent the light projected from each surface shape measuring unit 1a-1d from interfering with each other and causing erroneous measurements, the surface shape measuring units 1a-1d are moved so that they are spaced apart by approximately 200 mm in the X-axis direction. For example, when each of the surface shape measuring units 1a to 1d is moved at 200 mm / s, each of the surface shape measuring units 1a to 1d is moved with a delay of 1 second. The crankshaft S in this embodiment is a crankshaft for an in-line three-cylinder engine, and therefore its length (dimension in the direction of the central axis L) is approximately 420 mm at most. Therefore, even if the crankshafts S1 and S2 are aligned in the direction of the central axis L, a travel distance of 1000 mm for the surface shape measuring units 1a to 1d is sufficient. When the travel distance is 1000 mm, the surface shape over the entire length of the specimen T can be measured within 10 seconds.

[0039] <3D point cloud data generation process ST2> The surface shape over the entire length of the test object T measured in the surface shape measuring step ST1 is input to the three-dimensional point cloud data generating unit 31 of the calculation means 3 via Ethernet (registered trademark) or the like, and stored therein. In the three-dimensional point cloud data generating step ST2, the three-dimensional point cloud data generating unit 31 generates three-dimensional point cloud data of the entire surface of the object T by combining the surface shapes measured by the four surface shape measuring units 1a to 1d.

[0040] <Laminating process ST3> In the superposition process ST3, the superposition unit 32 translates and rotates the 3D point cloud data generated in the 3D point cloud data generation process ST2 for each region corresponding to each of the multiple crankshafts S, so as to minimize the distance from the surface shape model of the crankshaft S, and superimposes it on the surface shape model. In the superposition step ST3, when the 3D point cloud data generated in the 3D point cloud data generation step ST2 is superimposed on the surface shape model, if the multiple crankshafts S constituting the test object T have the same shape, a problem may occur in which multiple surface shape models overlap one of the regions of the 3D point cloud data corresponding to the multiple crankshafts S. To avoid this problem, it is preferable to set the superposition conditions in advance. For example, (1) if the crankshafts S have an axially asymmetric shape, when measuring the surface shapes of the multiple connected crankshafts S or the multiple separated crankshafts S using the surface shape measurement unit 1, the multiple crankshafts S may be manufactured or arranged so that their orientations are different from each other; (2) the orientation and range of the 3D point cloud data to be superimposed may be set so that each region of the 3D point cloud data is superimposed on each surface shape model; or (3) the 3D point cloud data generated by the 3D point cloud data generation unit 31 may be divided into regions corresponding to the multiple crankshafts.

[0041] For example, when dividing the three-dimensional point cloud data generated in the three-dimensional point cloud data generation process ST2, in the superposition process ST3, the three-dimensional point cloud data generated in the three-dimensional point cloud data generation process ST2 is divided into areas corresponding to the crankshafts S1 and S2, respectively, to generate two divided three-dimensional point cloud data. The 3D point cloud data generated in the 3D point cloud data generation step ST2 is optionally subjected to a process of removing isolated data points to reduce noise, or to thinning the data points to a predetermined pitch (for example, thinning to a pitch of 0.5 mm in the X-axis and Y-axis directions) to improve processing speed. Furthermore, as necessary, smoothing is performed on the thinned 3D point cloud data to reduce noise. In the superposition step ST3, the superposition unit 32 performs these signal processes as necessary, and then generates two pieces of divided 3D point cloud data.

[0042] <Inspection process ST4> In the inspection step ST4, the inspection unit 33 inspects the crankshaft S based on the 3D point cloud data after the superposition step ST3. Specifically, in the inspection step ST4, the inspection unit 33 calculates the distance between the 3D point cloud data after the superposition and the surface shape model, and detects defects such as underfill on the crankshaft S based on this calculated distance. Furthermore, since the 3D point cloud data after the superposition can identify the coordinates of each part of the crankshaft S (journal, flange, pin, counterweight, etc.), the inspection step ST4 can also measure the dimensions of each part, such as the diameter of the journal and flange, the diameter and separation angle of the pin (twist of the crankshaft S), and the width, height, and outer diameter of the counterweight. Furthermore, in the inspection step ST4, the 3D point cloud data after the superposition can be aligned with the coordinate system used for machining, thereby measuring the amount of deviation from the central axis of the shaft parts (front, journal, and flange) (bending of the crankshaft S) and the machining allowance. After the inspection step ST4 is completed, a predetermined transport mechanism is used to carry the test object T out of the inspection apparatus 100. In other words, the two crankshafts S1 and S2 are carried out from the support means 4 in order. In order to shorten the inspection time (the total time required to perform the surface shape measurement process S1 to the inspection process ST4), it is preferable to perform the inspection process ST4 by utilizing the time required to unload the inspection object T to be inspected and the time required to load the next inspection object T to be inspected. As for the inspection content in the inspection step ST4, the same inspection content as that using the three-dimensional point cloud data described in Patent Documents 1 to 5 can be appropriately adopted, and therefore further detailed description will be omitted here.

[0043] According to the inspection apparatus 100 and the inspection method using the same of this embodiment described above, the surface shape of the test object T is measured by the surface shape measurement unit 1, which is moved relatively by the movement mechanism 2, so that the surface shapes of the two crankshafts S1 and S2 constituting the test object T are measured simultaneously. Therefore, compared to the conventional method of measuring the surface shape of each crankshaft S, the time required to measure the surface shape of each crankshaft S, and therefore the inspection time, can be shortened. Specifically, when measuring the surface shapes of the two crankshafts S1 and S2, the relative acceleration and deceleration time of the surface shape measurement unit 1 by the movement mechanism 2 is required twice (for two crankshafts S). However, according to the inspection apparatus 100 and the inspection method using the same of this embodiment, this is only required once (for one test object T), so the time required to measure the surface shape can be shortened. Furthermore, according to the inspection device 100 of this embodiment and the inspection method using the same, even if the orientations of the two separated crankshafts S1 and S2 are different, it is possible to overlay the 3D point cloud data on a surface shape model for each region of the 3D point cloud data corresponding to each of the two crankshafts S, making it possible to detect defects such as underfill in the crankshaft S, and to measure the dimensions of each part of the crankshaft S, the amount of deviation from the central axis of the shaft, and the processing allowance.

[0044] In this embodiment, the test object T is described as being composed of two separate crankshafts S1 and S2, but the present invention is not limited to this. It is also possible to use a configuration in which multiple crankshafts are connected together to form an integrated unit (for example, a configuration in which two crankshafts S1 and S2 are connected together to form an integrated unit) as the test object T. When multiple crankshafts S are connected and manufactured, even if defects such as twists, bends, or underfill occur in the multiple crankshafts S, the defects such as twists, bends, or underfill can be confirmed for each crankshaft S. Furthermore, when multiple crankshafts S are connected and manufactured, if defects such as twists, bends, or underfill occur in the machining area, the defects can be ignored.

[0045] Fig. 5 is a side view (a side view corresponding to Fig. 3) showing a schematic configuration of a crankshaft inspection device according to a first modified example of the present invention. In Fig. 5, as in Fig. 3, the calculation means 3 is omitted from the illustration. In the inspection device 100 shown in Fig. 3, two pairs of support parts 42 are required to support the crankshafts S1 and S2 separately. However, in the inspection device 100A according to the first modification shown in Fig. 5, the inspection object T, which is the object to be inspected, has a structure in which two crankshafts S1 and S2 are connected together as a single unit, so it is only necessary to provide one pair of support parts 42. The inspection device 100A differs from the inspection device 100 shown in Fig. 3 in this respect, and in other respects has the same structure as the inspection device 100, so a description thereof will be omitted here.

[0046] The inspection method for the crankshaft S using the inspection device 100A according to the first modified example also includes the same steps (surface shape measuring step ST1 to inspection step ST4) as the inspection method described with reference to FIG. 6 shows an example of 3D point cloud data generated in the 3D point cloud data generation step ST2 and an example of divided 3D point cloud data generated when the 3D point cloud data is divided in the superposition step ST3 in the method for inspecting a crankshaft S using the inspection device 100A according to the first modified example. Fig. 6(a) shows the 3D point cloud data, and Fig. 6(b) shows the divided 3D point cloud data generated by dividing the 3D point cloud data shown in Fig. 6(a). Note that for convenience of illustration, Fig. 6 shows 3D surface data obtained by meshing the 3D point cloud data, rather than the 3D point cloud data itself. The example shown in Figure 6 is a case where adjacent regions have overlapping portions in the central axis direction of the crankshaft S, and it can be seen that the 3D point cloud data of the subject T (Figure 6(a)) can be separated into divided 3D point cloud data of the region corresponding to the crankshaft S1 (Figure 6(b)) and divided 3D point cloud data of the region corresponding to the crankshaft S2 (Figure 6(c)).

[0047] As shown in Figure 3, in the case of an inspected object T consisting of two crankshafts S1 and S2 separated from each other, the process of loading the inspected object T into the inspection device 100 and unloading the inspected object T from the inspection device 100 after inspection must be repeated twice, which is the number of crankshafts S1 and S2 that make up the inspected object T. In contrast, according to the inspection method using the inspection apparatus 100A according to the first modified example shown in FIG. 5, the test subject T can be loaded and unloaded in a single operation, thereby further shortening the inspection time.

[0048] Furthermore, in this embodiment, an example has been described in which the moving mechanism 2 moves the surface shape measuring unit 1, but the present invention is not limited to this, and it is also possible to adopt a moving mechanism that moves the specimen T in the X-axis direction. Fig. 7 is a side view (a side view corresponding to Fig. 3) showing a schematic configuration of a crankshaft inspection device according to a second modified example of the present invention. In Fig. 7, as in Fig. 3, the calculation means 3 is omitted from the illustration. In an inspection apparatus 100B according to a second modified example shown in Fig. 7, a support means 4 that supports the specimen T is attached to a movement mechanism 2A. Then, while the surface shape measuring unit 1 is stationary, the movement mechanism 2A moves the support means 4, and therefore the specimen T, in the direction of the central axis L (X-axis direction) of the specimen T. Note that while Fig. 7 illustrates a case in which the specimen T is made up of two separate crankshafts S1 and S2, a configuration in which the support means 4 that supports the specimen T is attached to the movement mechanism 2A can also be adopted in the case in which the specimen T is made up of two crankshafts S1 and S2 that are connected together to form an integrated structure. The inspection device 100B according to the second modification can also perform the same inspection method as the inspection devices 100 and 100A.

[0049] Table 1 below shows the results of an evaluation of the inspection time required when inspecting crankshafts S using a conventional inspection device (an inspection device that measures the surface shape of each crankshaft S), the inspection device 100 of this embodiment (two individual crankshafts), and the inspection device 100A of the first modified example (two connected crankshafts). [Table 1] As shown in Table 1, the inspection device 100 according to this embodiment can shorten the inspection time by the amount of time required to measure the surface shape compared to conventional inspection devices. Furthermore, the inspection device 100A according to the first modified example can shorten the time required to measure the surface shape compared to conventional inspection devices, and can also shorten the inspection time by the amount of time required to carry in and out the test object T in a single operation. [Explanation of symbols]

[0050] 1, 1a, 1b, 1c, 1d...Surface shape measurement section 2...Moving mechanism section 3...Arithmetic means 4...Support means 31. 3D point cloud data generation unit 32... Overlapping section 33 Inspection Department 100, 100A, 100B... Inspection equipment L...Center axis S, S1, S2... crankshaft T...Subject

Claims

1. a plurality of surface shape measuring units arranged around a central axis of an object to be inspected, the surface shape measuring units being configured to optically measure the surface shape of the object; a movement mechanism that moves the surface shape measurement unit relative to the object in a central axis direction of the object; a three-dimensional point cloud data generation unit that generates three-dimensional point cloud data of the surface of the object based on the surface shape of the object measured by the surface shape measurement unit that is moved relatively by the movement mechanism unit; an overlay unit that translates and rotates the three-dimensional point cloud data and overlays the three-dimensional point cloud data on a surface shape model prepared in advance based on design specifications of the crankshafts so that a distance between the three-dimensional point cloud data and a surface shape model of the crankshafts prepared in advance is minimized for each region of the three-dimensional point cloud data corresponding to each of the plurality of crankshafts; an inspection unit that inspects the crankshaft based on the three-dimensional point cloud data after the superposition; A crankshaft inspection device comprising:

2. The subject has a configuration in which the plurality of crankshafts are connected together into one unit. The crankshaft inspection device according to claim 1.

3. a surface shape measuring step of measuring the surface shape of the object using a plurality of surface shape measuring units each arranged around a central axis of the object and configured so that a plurality of crankshafts are aligned in the central axis direction and each measuring the surface shape of the object, and a movement mechanism unit that moves the surface shape measuring units relative to the object in the central axis direction of the object; a three-dimensional point cloud data generating step of generating three-dimensional point cloud data of the surface of the object based on the surface shape of the object using a three-dimensional point cloud data generating unit; a superimposition step of using a superimposition unit to translate and rotate the three-dimensional point cloud data so that a distance between the three-dimensional point cloud data and a surface shape model of the crankshaft prepared in advance based on design specifications of the crankshaft is minimized for each region of the three-dimensional point cloud data corresponding to each of the plurality of crankshafts, and superimpose the three-dimensional point cloud data on the surface shape model; an inspection step of inspecting the crankshaft based on the superimposed three-dimensional point cloud data using an inspection unit; A crankshaft inspection method comprising:

4. The subject has a configuration in which the plurality of crankshafts are connected together into one unit. The crankshaft inspection method according to claim 3.

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