Inner diameter measuring device and system thereof

Abstract

To provide an inner diameter measuring device capable of obtaining accurate measurement results even in an environment where large electromagnetic noise is generated, in a state where the device is attached to a robot arm.SOLUTION: The present invention relates to an inner diameter measuring device detachably attached to a distal end part of a robot arm (14) and configured to measure an inner diameter of a hole formed in a work, the inner diameter measuring device including at least two measuring elements (270) and a data conversion and transmission unit (400), the at least two measuring elements being brought into contact with the inner wall surface of the hole formed in the work, and the data conversion and transmission unit converting analog data relating to displacements of the at least two measuring elements into digital data representing the inner diameter of the hole and transmitting the digital data to an external device.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to an inner diameter measuring device and system that is detachably attached to the tip of a robot arm and measures the inner diameter of a hole formed in a workpiece. [Background technology]

[0002] Automobile parts (workpieces) are produced using six-axis arm industrial robots and collaborative robots. Industrial robots make mass production even more labor-efficient. These workpieces require accurate measurement at each stage of manufacturing, and for this reason, attempts are being made to use automated measurement methods such as industrial robots.

[0003] When the measurement target is the inner diameter of a workpiece, a method can be used in which the measuring part of an inner diameter measuring device attached to the tip of the arm (also called a robot arm) of an industrial robot or the like is inserted into the object to perform the measurement. In this case, if the outer diameter of the measuring part is slightly smaller than the inner diameter of the workpiece, high-precision measurements can be easily achieved.

[0004] A typical measurement procedure is as follows. First, a minute gap is formed between the workpiece and the measuring part, and the measuring part is inserted into the workpiece while maintaining that gap. Then, for example, if the inner diameter measuring device is an air micrometer, measurement is performed while maintaining the minute distance between the measuring part and the inner wall of the workpiece. Also, if the inner diameter measuring device is a contact type, measurement is performed by pressing the contact against the inner wall of the workpiece at the measurement position. Examples of such workpiece inner diameter measuring devices are described in Patent Documents 1 to 3.

[0005] Furthermore, Patent Documents 4 and 5 disclose a method of measuring the inner diameter of a workpiece by attaching an inner diameter measuring device having a contact-type measuring head to the tip of a robot arm. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 6910668 [Patent Document 2] Japanese Patent Application Publication No. 10-339623 [Patent Document 3] Patent No. 7238187 [Patent Document 4] Japanese Patent Application Publication No. 2023-142301 [Patent Document 5] Japanese Patent Publication No. 2023-142303 [Patent Document 6] Japanese Patent Application Laid-Open No. 2018-169180 Summary of the Invention [Problem to be solved by the invention]

[0007] Air micrometers are often used to measure the diameter of holes in workpieces. This is because they generally have the advantage of being able to utilize the air source that is often supplied in factories. When measuring hole diameters (inner diameters of workpieces) using an air micrometer, the reaction force of the air blowing is measured. For this reason, it is preferable to maintain a small distance between the air outlet and the inner wall of the workpiece. For example, the gap between the air outlet and the inner wall of the workpiece can be set to 0.5 mm or less, specifically, around 0.1 mm. Furthermore, the gap between the wall portion other than the air outlet can be set even smaller, at 0.01 to 0.1 mm. The air outlet is sometimes called a "nozzle," and the wall portion other than the air outlet is sometimes called a "guide."

[0008] As described above, the distance between the measuring part and the inner wall of the workpiece is minute, and precise positioning is required to insert the measuring part into the workpiece. In particular, when using a robot to perform automatic measurement, it is necessary to detect the workpiece, precisely position the workpiece, and position the air micrometer relative to the workpiece. Furthermore, it is necessary to teach the robot how to handle the air micrometer. When attempting to sequentially measure the hole diameters of a large number of (mass-produced) workpieces, the hole positions vary, and the robot's stopping position (the starting position of the measurement operation) can also vary. Therefore, inserting the measuring part into the workpiece (hole) itself has been extremely difficult. Furthermore, forcible insertion can result in "galling," as described below, which can damage the workpiece and / or the measuring part.

[0009] Patent Document 1 discloses a method for using a floating mechanism to align the center of the hole to be measured with the center of the measuring part of an air micrometer. This method is said to enable high-precision, quick measurements even if the robot arm is not properly positioned. However, the method described in Patent Document 1 has the problem that it is limited to holes facing upward because it only allows for horizontal displacement of the workpiece, making it unsuitable for general-purpose hole measurement. Furthermore, the use of an air micrometer requires a separate external unit to convert air pressure and flow rate into measured values, which creates the complexity of additional space and piping.

[0010] When using an air micrometer, there is only a small gap between the outer diameter of the measuring part and the inner wall of the hole to be measured. Therefore, when mechanically inserting the measuring part into the hole to be measured, significant measures are required to prevent collisions or "galling" between the two. Patent Document 2 does not disclose any such measures.

[0011] One solution to this problem is to teach the robot the position of the hole to be measured, and then use a force sensor for feedback control to accommodate individual differences in the workpiece. In this case, feedback control is typically performed in conjunction with a PLC. However, the control programming for teaching and / or collaboration can be complicated, and force sensors are often expensive.

[0012] Patent Document 3 discloses a method for measuring the inner diameter of a hole to be measured by bringing multiple contactors into contact with the inner wall of the hole to be measured in a workpiece. The contactors are provided so that they can be retracted inside the measuring unit. In this case, the multiple contactors are retracted inside the measuring unit when inserted into the hole to be measured.

[0013] If this is to be achieved using an internal diameter measuring device attached to a robot arm, another problem arises. Robot arms generally have many degrees of freedom, up to six degrees of freedom in some cases. It is difficult to repeatedly position such a robot arm at the same hole position. When continuously measuring mass-produced products, speed is also required, but the method in Patent Document 3 assumes multiple measurements. For these reasons, it is inappropriate to implement the method in Patent Document 3 with a robot arm.

[0014] Patent Documents 4 and 5 disclose a method for measuring the inner diameter of a workpiece by attaching an inner diameter measurement unit with a contact-type measurement head to the tip of a robot arm. The measurement units described in the above documents are equipped with a collision detection unit and a force sensor, and the measurement probe is retracted when inserted into the hole to be measured. This protects the measurement probe even if the measurement head collides with the workpiece during insertion.

[0015] However, mounting a measurement unit on a robot arm presents a new problem: electromagnetic noise. Industrial robots often use servo motors to control their movements. In these cases, the electromagnetic noise generated by the motors and control means is generally loud. One factor is that servo motors repeatedly make fine adjustments to their position even when they appear to be stopped. This loud electromagnetic noise can adversely affect the minute detection signals detected by the measurement unit.

[0016] An object of the present disclosure is to solve at least some of the problems of the prior art. One specific object is to provide an inner diameter measurement device that can obtain accurate measurement results even when attached to a robot arm and in an environment where large electromagnetic noise is generated. Another specific object is to provide an inner diameter measurement system that can automatically insert a measuring part into holes to be measured in multiple workpieces without damaging the measuring part. Another specific object is to provide an inner diameter measurement system that can automatically measure holes to be measured in workpieces with different diameters (different nominal diameters). [Means for solving the problem]

[0017] One embodiment of the inner diameter measuring device disclosed herein is an inner diameter measuring device that is detachably attached to the tip of a robot arm and measures the inner diameter of a hole formed in a workpiece, and includes at least two probes and a data conversion transmission unit, wherein the at least two probes are brought into contact with the inner wall surface of the hole formed in the workpiece, and the data conversion transmission unit converts analog data relating to the displacement of the at least two probes into digital data representing the inner diameter of the hole and transmits the digital data to an external device. [Effects of the Invention]

[0018] According to the present disclosure, at least one of the problems of the conventional techniques is solved. [Brief explanation of the drawings]

[0019] [Figure 1]FIG. 1 is a perspective view of an embodiment of an inner diameter measurement system. [Figure 2] FIG. 1 is a perspective view of an embodiment of an inner diameter measurement device. [Figure 3] FIG. 3 is a vertical cross-sectional view of the main part of the inner diameter measurement instrument shown in FIG. 2. [Figure 4] FIG. 10 is a perspective view of the main parts of another embodiment of an inner diameter measurement instrument. [Figure 5] FIG. 5 is an explanatory diagram of a method for correcting the tilt of the inner diameter measurement instrument shown in FIG. 4. DETAILED DESCRIPTION OF THE INVENTION

[0020] A first embodiment of the inner diameter measuring device disclosed herein is an inner diameter measuring device that is detachably attached to the tip of a robot arm and measures the inner diameter of a hole formed in a workpiece, and includes at least two probes and a data conversion transmission unit, wherein the at least two probes are brought into contact with the inner wall surface of the hole formed in the workpiece, and the data conversion transmission unit converts analog data relating to the displacement of the at least two probes into digital data representing the inner diameter of the hole and transmits the digital data to an external device.

[0021] One of the features of the above-mentioned inner diameter measurement device is that it is equipped with a data conversion and transmission unit. The data conversion and transmission unit is provided integrally with the inner diameter measurement device. The inner diameter measurement device is detachably attached to the tip of a robot arm. In other words, the inner diameter measurement device is a replaceable device. This inner diameter measurement device is equipped integrally with a data conversion and transmission unit that converts analog data into digital data.

[0022] The data conversion / transmission unit converts analog data, which is raw measurement data regarding the displacement of the contact point, into digital data representing the inner diameter of the hole to be measured. The data conversion / transmission unit then transmits this digital data to an external device, such as a computer that controls a robot arm (robot).

[0023] As mentioned above, there is often a large amount of electromagnetic noise around a robot arm. If such electromagnetic noise gets mixed into the data representing the inner diameter of a hole, the stability and accuracy of the measurement may be impaired. However, the above-mentioned inner diameter measuring device transmits the measurement data externally as digital data using an integrated data conversion and transmission unit. Digital data is easily transmitted and received accurately even in an environment where there is a large amount of electromagnetic noise. Therefore, when the above-mentioned inner diameter measuring device is applied to the automation of inner diameter measurement using a robot arm, it is possible to achieve both stable measurements and the acquisition of highly accurate measurement data.

[0024] A second embodiment of the inner diameter measurement instrument of the present disclosure is the inner diameter measurement instrument of the first embodiment, wherein the data conversion and transmission unit transmits the digital data to the external device connected by wire.

[0025] The data conversion / transmission unit preferably transmits digital data to a wired external device (for example, a robot arm control device), and in this case may receive power from the external device via a similar wired connection.

[0026] A third embodiment of the inner diameter measuring instrument of the present disclosure is an inner diameter measuring instrument of the first embodiment, which comprises a plug gauge that holds the at least two measuring probes at its tip, and a connecting part provided between the plug gauge and the data conversion transmission part, and the connecting part is configured to allow displacement of the robot arm relative to the plug gauge in the axial direction and in a direction approximately perpendicular to the axial direction.

[0027] One of the features of the above-mentioned inner diameter measuring device is that it is equipped with a connecting part. This connecting part is configured to allow displacement in the axial direction of the robot arm and in a direction approximately perpendicular thereto. In inner diameter measurement using a robot arm, the inner diameter measuring device is inserted into the hole to be measured. By providing the connecting part, even if unintended contact occurs between the workpiece and the inner diameter measuring device due to misalignment of the workpiece during insertion, the damage caused by this is likely to be reduced. Damage includes malfunction of the plug gauge, etc. due to contact, and / or damage to the workpiece, etc.

[0028] Furthermore, by allowing displacement in a direction approximately perpendicular to the axial direction using the connecting portion, the man-hours required for teaching are further reduced. Teaching is performed on the robot arm. The insertion position (hole position) is memorized in advance through teaching. Even if the actual hole to be measured is positioned away from that position, the deviation can be absorbed by the connecting portion. Therefore, even if the teaching accuracy is lower, the insertion of the inner diameter measuring instrument into the hole is likely to be carried out smoothly.

[0029] A fourth embodiment of the inner diameter measuring instrument of the present disclosure is an inner diameter measuring instrument according to the third embodiment, in which the connecting portion is formed in an overall vertically elongated cylindrical shape, and the instrument is equipped with a bushing holder formed in an annular shape, and a floating mechanism, a relieving mechanism, and a measuring mechanism each held within the bushing holder, wherein the floating mechanism allows the displacement in a direction approximately perpendicular to the axial direction, the relieving mechanism allows the displacement in the axial direction, and the measuring mechanism acquires the analog data, and the measuring mechanism is disposed in the center of the bushing holder, with the floating mechanism and the relieving mechanism disposed around it.

[0030] In an inner diameter measurement device with a floating mechanism and a relieving mechanism, these mechanisms and the measurement mechanism are generally arranged in series, but the inner diameter measurement device described above is more compact (shorter in length) than such devices, which allows the moment applied to the robot arm to be reduced.

[0031] Adding a data transmission converter to an inner diameter measuring instrument creates new issues, such as the instrument becoming slightly heavier and larger. However, the inner diameter measuring instrument described above solves these issues by providing a connecting section that combines three functions, thereby shortening the overall length. The three functions are a floating mechanism, a relieving mechanism, and a measuring mechanism, and the floating mechanism and the relieving mechanism make it easier to insert the inner diameter measuring instrument into the hole smoothly.

[0032] A fifth embodiment of the inner diameter measuring device of the present disclosure is an inner diameter measuring device according to the fourth embodiment, wherein the relieving mechanism includes at least three ball bushings spaced apart circumferentially around the bushing holder, and a bushing shaft provided for each of the ball bushings and passing through the center of the ball bushing.

[0033] A sixth embodiment of the inner diameter measuring instrument of the present disclosure is the fourth embodiment, wherein the floating mechanism includes an elastic body, and one end of the elastic body is engaged with the bushing holder, as described in claim 4.

[0034] A seventh embodiment of the inner diameter measuring instrument of the present disclosure is an inner diameter measuring instrument according to the first embodiment, in which the at least two probes are four probes, displacement measuring devices are connected to the four probes, and the four probes are arranged at intervals in the circumferential direction, and the data conversion / transmission unit converts the analog data detected by the displacement measuring devices into digital data representing the inner diameter of the hole and transmits the digital data to the external device.

[0035] The above-described inner diameter measuring instrument allows for more accurate inner diameter measurements. Because it is equipped with four measuring probes, it is particularly useful when the axis of the inner diameter measuring instrument and the axis of the hole are not parallel (tilted). The tilt θ of the inner diameter measuring instrument can be calculated more accurately based on the displacement of the four measuring probes. There are no particular restrictions on the positions of the four measuring probes, but it is preferable that two sets of measuring probes are arranged at opposing positions (180° apart) around the circumference of the inner diameter measuring instrument. There are no particular restrictions on the arrangement of the two sets of measuring probes, but it is preferable that the four measuring probes are arranged at 90° apart around the circumference.

[0036] The first embodiment of the inner diameter measurement system of the present disclosure is an inner diameter measurement system including the robot arm and the inner diameter measurement device of any of the first to seventh embodiments.

[0037] The inner diameter measurement system can achieve both stable measurement and acquisition of highly accurate measurement data due to the configuration and functions of the inner diameter measurement device described above. Hereinafter, an embodiment of an inner diameter measuring device and an inner diameter measuring system equipped with the same will be described with reference to the drawings. In mass-produced products such as automobile parts and home appliances, the inner diameters of holes to be measured in workpieces of different diameters (different types and different nominal diameters) may be measured. To reduce the takt time of manufacturing, the use of a robot is being attempted to automate measurement and increase efficiency.

[0038] FIG. 1 is a perspective view of an embodiment of an inner diameter measurement system 50 including an inner diameter measurement device 100. The inner diameter measurement system 50 uses the robot 10 to perform unmanned measurement of a hole to be measured in a workpiece. The inner diameter measurement system 50 includes a conveyor 140, a robot 10, and a tool table 130.

[0039] The conveyor 140 continuously carries in the workpieces 150 that have been subjected to processing such as drilling. Instead of the conveyor 140, the inner diameter measurement system 50 may be provided with a measurement table.

[0040] A plurality of holes 152, 154 of different diameters are formed in a workpiece 150, which is an object to be measured. The workpiece 150 waits on the conveyor 140 until each of the holes 152, 154 is measured.

[0041] The inner diameter measurement system 50 also includes a tool table 130. A plurality of tool holders 122 are fixed to the tool table 130. Each tool holder 122 holds one of the inner diameter measurement devices 100, 100, ... with different outer diameters (nominal diameters). Of these, one inner diameter measurement device 100 is in use.

[0042] The inner diameter measuring device 100 in use is the one removed from the tool holder 122 at the right end of the tool table 130. Multiple inner diameter measuring devices 100, 100, ... can be interchangeably attached to the tip of the robot arm 14. This makes it possible to measure holes 152, 154 of different inner diameters formed in the workpiece 150.

[0043] The automatic robot 10 is disposed between the tool table 130 and the conveyor 140. The automatic robot 10 is a multi-joint robot with multiple degrees of freedom, and can operate unmanned.

[0044] An inner diameter measuring device 100 held by a tool holder 122 is attached to the tip of the robot arm 14. The robot 10 is connected to a robot controller 12 via a wiring 16 (wired connection). The movements of the robot 10 are pre-programmed, and all measurement-related movements are performed automatically or unmanned. Typically, the robot controller 12 is preferably a computer equipped with a processor and memory. The robot controller 12, which is a computer, can control each part of the inner diameter measuring system by loading a program stored in the memory and executing it using the processor.

[0045] The robot 10 moves the tip of the robot arm 14 to any position and angle by rotating each joint. As a result, first, the robot arm 14 is brought close to the top surface of the inner diameter measurement device 100 held by the tool holder 122. Next, the tip of the robot arm 14 is translated from the tip (opening) side of the guide portion 124 of the tool holder 122. Next, the tool side changer 128 and the robot arm side changer 126 are engaged and fixed, and the inner diameter measurement device 100 is integrated with the robot arm 14. The state in which the robot arm side changer 126 and the tool side changer 128 are integrated is called a robot hand changer.

[0046] The method for separating the robot hand changer into the tool side changer 128 and the robot arm side changer 126 is as follows. First, the inner diameter measuring device 100 is stored in the tool holder 122 while the robot arm 14 and the inner diameter measuring device 100 remain integrated. In this state, a stopper (not shown) provided on the robot hand changer is released. This release is performed by a command from the robot controller 12.

[0047] By the above procedure, the attachment, replacement, and removal of the inner diameter measurement device 100 to the robot arm 14 are automated.

[0048] The robot 10 first measures holes of the same nominal diameter for the number of workpieces 150 specified by the robot controller 12. After that, the inner diameter measuring device 100 is replaced and measurements of holes of a different nominal diameter are performed. Note that if multiple robots 10 are installed and each is equipped with an inner diameter measuring device 100 of a different nominal diameter, the measurement efficiency can be further improved.

[0049] Next, an embodiment of the inner diameter measurement instrument 100 will be described with reference to Figures 2 and 3. Figure 2 is a perspective view of the inner diameter measurement instrument 100. As shown in Figure 2, the inner diameter measurement instrument 100 is broadly comprised of a plug gauge 200, a floating relieving unit 300, a data conversion and transmission unit 400, and a robot hand changer unit 500.

[0050] The plug gauge 200 is inserted into holes 152, 154 formed in the workpiece 150. The plug gauge 200 includes a cylindrical plug gauge body 260, a plurality of stoppers 262, and at least two probe holes 272. The stoppers 262 and the probe holes 272 are arranged at approximately equal intervals in the circumferential direction. Each probe hole 272 is equipped with a probe 270 that abuts against the hole 152, 154.

[0051] The floating relieving part 300 is located above the plug gauge 200 and allows for and corrects positional deviation of the plug gauge 200. The floating relieving part 300 further detects the displacement of the probe 270 using a built-in measuring device 380. The floating relieving part 300 includes a floating elastic body 350. The floating elastic body 350 is attached to a cylindrical bushing holder 340.

[0052] The data conversion / transmission unit 400 is located above the floating relieving unit 300. The data conversion / transmission unit 400 is covered by a cylindrical body cover 422 and has a flange 424 on its top. The data conversion / transmission unit 400 converts analog data related to the displacement of the probe 270 into digital data representing the inner diameter of the holes 152 and 154. The analog data related to the displacement of the probe is acquired by the measuring device 380 (see FIG. 3). The data conversion / transmission unit 400 transmits the digital data representing the inner diameter to the robot controller 12 (corresponding to an external device). The measuring device 380 is built into the floating relieving unit 300. In the environment where the robot arm 14 is moving, electromagnetic noise makes it difficult to accurately transmit and receive analog data. However, in this embodiment, the data conversion / transmission unit 400 is located directly above the measuring device 380, minimizing the distance and time required for transmitting analog data. Furthermore, the data conversion / transmission unit 400 transmits digital data to the external device, which is resistant to electromagnetic noise, enabling more accurate and stable measurements.

[0053] A commercially available plug gauge, such as a BMD plug gauge manufactured by DIATEST of Germany, is used as the plug gauge 200. The plug gauge 200 has through holes formed in multiple locations on the side of a cylinder. These through holes are probe holes 272.

[0054] A probe 270 is inserted into this probe hole 272. The probe 270 is movable in the radial direction of the cylinder. The radial displacement of the probe 270 is converted into the vertical movement of a built-in needle. The needle is disposed on the back side of the probe 270 (toward the center of the plug gauge 200) and extends in the vertical direction. The needle is tapered.

[0055] A force is constantly applied to the probe 270 to push it outward in the radial direction of the cylinder. This force is generated by utilizing the elasticity of the needle. Therefore, under normal conditions, the probe 270 always protrudes about 0.1 to 0.2 mm from the outer circumferential surface of the plug gauge 200.

[0056] A measuring device 380 is disposed inside the floating relieving portion 300. The measuring device 380 is connected to the needle of the plug gauge 200 or is disposed above the plug gauge shaft 210 that is integral with the needle.

[0057] As a result, the displacement of the needle becomes an input to measuring device 380. A displacement signal from measuring device 380 is sent to data conversion / transmission unit 400. A differential transformer type displacement meter can be used as measuring device 380. Note that in addition to a differential transformer type displacement meter, an optical scale type displacement meter using laser light, an air micrometer, etc. can also be used as measuring device 380.

[0058] A measuring device 380 is disposed at the center of the floating relieving part 300, which is formed in a cylindrical shape. Three relieving shafts 362 are disposed concentrically with the measuring device 380 and on the outer periphery of the measuring device 380. The relieving shafts 362 extend vertically at intervals in the circumferential direction. In this example, there are three relieving shafts 362, but there may be three or more relieving shafts 362. A ball bushing 364 is interposed in the vertical middle of the relieving shaft 362. A spring 370 is also interposed in the relieving shaft 362. The lower end surface of the spring 370 contacts the upper end surface of the ball bushing 364.

[0059] The ball bushings 364 are held in three vertical through holes, which are formed at circumferential positions of the cylindrical bushing holder 340 corresponding to the relieving shafts 362. In this example, there are three vertical through holes, but the number can be changed according to the number of relieving shafts 362.

[0060] The bushing holder 340 extends downward in the vertical direction beyond the lower end of the ball bushing 364. The relieving shaft 362 fits loosely in the hole that extends beyond the lower end of the ball bushing 364. A ring-shaped spring retaining plate 372 with at least three through holes extending vertically is disposed on the upper surface of the bushing holder 340. The spring 370 fits loosely with its lower end held in one of these through holes. A ring-shaped pressing plate 374 is disposed at a vertical distance from the spring retaining plate 372 to hold the upper end of the spring 370. The upper end of the relieving shaft 362 is fixed to the pressing plate 374. The gap between the spring retaining plate 372 and the pressing plate 374 is 4 to 5 mm. The pressing plate 374 is connected to the bottom flange of the data converting and transmitting unit 400.

[0061] An outer cylindrical holder 354 is disposed between the cylindrical ball bushing 364 and the measuring device 380. The outer cylindrical holder 354 is cylindrical with a flange on the underside. The upper end of the outer cylindrical holder 354 extends slightly below the upper end of the ball bushing 364. The inner cylindrical holder 330 is fitted inside the outer cylindrical holder 354. The inner cylindrical holder 330 is cylindrical with a flange formed in the axial middle. A presser plate 332 is attached to the upper surface of the inner cylindrical holder 330 with a set screw 334. The flange portion of the outer cylindrical holder 354 is placed on the upper surface of the flange located in the axial middle of the inner cylindrical holder 330. The inner cylindrical holder (plug gauge holder) 330 holds the output shaft of the plug gauge 200 at its lower part.

[0062] The bushing holder 340 is formed with a plurality of notches for mounting the floating elastic body 350. The notches are formed at positions in the circumferential direction excluding the hole for the relieving shaft 362. The notches are formed at a plurality of positions in the circumferential direction so as to extend in the up-down direction. The floating elastic body 350 is mounted in these notches with screws 352, 352.

[0063] That is, notches are formed at multiple locations around the circumferential direction of the bush holder 340. Floating elastic bodies 350 of sizes corresponding to these notches are attached. The upper end of the floating elastic body 350 is attached to the bush holder 340. The lower end is attached to the flange portion of the outer cylindrical holder 354. All attachments are made by screws 352. The floating elastic body 350 has elasticity and is rectangular parallelepiped, cylindrical, or cylindrical. Its material may be rubber, plastic, or a combination thereof. The floating elastic body 350 may also be a coil spring. Its material may be metal, reinforced plastic, or the like.

[0064] The operation of the floating relieving unit 300 configured as described above will now be described. First, the inner diameter measurement device 100 is attached to the tip of the robot arm 14. Next, the robot 10 and the robot arm 14 approach the workpiece 150 having holes 152 and 154 according to a pre-programmed method. Next, the plug gauge 200 of the inner diameter measurement device 100 is positioned above the holes 152 and 154 according to the program. Next, the plug gauge 200 is lowered into the holes 152 and 154.

[0065] At this time, the centers of the holes 152 and 154 formed in the workpiece 150 differ from the center of the plug gauge 200 within an allowable error. The cylindrical portion of the plug gauge 200 below the stopper 262 acts as a guide portion 264 when the plug gauge 200 is inserted into the holes 152 and 154. The gap (clearance) formed by the outer diameter of the guide portion 264 of the plug gauge 200 and the inner diameter of the holes 152 and 154 is typically several tens of μm. Therefore, the guide portion 264 descends while partially contacting the inner walls of the holes 152 and 154. At this time, if the force with which the guide portion 264 presses against the walls of the holes 152 and 154 increases due to misalignment, or if the guide portion 264 is inserted at an angle and only a portion, such as a corner of the guide portion 264, comes into contact with the wall, a large pressure is applied to the contact point. If the pressing force at the time of contact increases due to misalignment, problems such as the guide portion 264 getting stuck in the holes 152, 154 may occur, which hinders automatic measurement.

[0066] Therefore, in this embodiment, the bushing holder 340 is provided with multiple floating elastic bodies 350. The floating elastic bodies 350 automatically displace or move the plug gauge 200 in a direction that reduces the contact force when the guide portion 264 contacts the inner wall of the hole 152, 154, depending on the contact force. The floating elastic bodies 350 can elastically deform left and right on the page in FIG. 3 . Therefore, even if the center of the plug gauge 200 is inserted into the hole 152, 154 so that the center of the plug gauge 200 is shifted left and right from the center of the hole 152, 154 (or tilted relative to the vertical axis), the plug gauge 200 and the inner cylindrical holder 330 tilt to follow the shape of the hole 152, 154. This is due to the elastic deformation of the floating elastic bodies 350. As a result, the center of the plug gauge 200 coincides with the center of the hole 152, 154. As a result, the plug gauge 200 can be inserted further into the hole 152, 154 to a measurement position.

[0067] The misalignment of the plug gauge 200 relative to the holes 152, 154 generally has a component perpendicular to the vertical direction. In other words, the misalignment has a component in the left-right direction of the paper in FIG. 3 . Furthermore, if the vertical direction is the z-direction, the misalignment has x- and y-components perpendicular to it. Therefore, one or more floating elastic bodies 350 are arranged around the circumferential direction of the bush holder 340 to accommodate misalignment in the x- and y-directions. There is no limitation on the direction of deformation of the floating elastic body 350, and one floating elastic body 350 can accommodate misalignment in the x- and y-directions. On the other hand, if three or more floating elastic bodies 350 are arranged around the circumferential direction, the bush holder 340, the outer cylindrical holder 354, and the inner cylindrical holder 330 can easily be repositioned while remaining nearly parallel to each other. At least three fixing points are required to determine a plane. In a configuration in which three or more floating elastic bodies 350 are arranged in the circumferential direction, rotation about the x- and y-axes is more restricted, enabling more accurate misalignment correction. The arrangement of the multiple floating elastic bodies 350 is not particularly limited, but it is preferable that they are spaced equally apart in the circumferential direction. For example, if three are arranged, it is preferable that they are spaced at intervals of about 120°.

[0068] As described above, in the floating relieving part 300, which is the connecting part, the floating elastic body 350, the bushing holder 340, and the inner cylindrical holder 330 form a floating mechanism.

[0069] The ball bushings 364 are mounted on three relieving shafts 362. The three relieving shafts 362 are disposed at different circumferential positions from the floating elastic bodies 350. That is, the ball bushings 364 are disposed at different circumferential positions from the floating elastic bodies 350. The ball bushings 364 are displaceable up and down along the relieving shafts 362. When excessive force is applied to the inner cylindrical holder 330, the bushing holder 340 moves up and down, causing the plug gauge 200 to move up and down. Excessive force occurs, for example, when the guide portions 264 of the plug gauge 200 come into contact with the inner surfaces of the holes 152 and 154. The up and down movement of the bushing holder 340 is achieved by the spring force of the spring 370. The up and down movement of the bushing holder 340 occurs via the outer cylindrical holder 354, which is mounted on the inner cylindrical holder 330. This relieves the plug gauge 200. The relieving shaft, at least three ball bushings 364, and spring 370 constitute a relieving mechanism.

[0070] The floating relieving unit 300 (connecting unit) includes a relieving mechanism, a floating mechanism, and a measuring device 380. The floating relieving unit 300 is an integrated component with the measuring device 380 at its center and the floating mechanism and relieving mechanism arranged around it. By integrating them, the axial length (vertical length) of the floating relieving unit 300 is shortened compared to conventional units, making it more compact. This reduces the moment load applied to the robot arm 14. This is particularly advantageous when the inner diameter measuring device 100 is attached to the tip of the robot arm 14 and moved to the measurement position. The compact size makes it more suitable for storage on the tool table 130. Tool replacement work is also easier.

[0071] A method for measuring the inner diameters of holes 152, 154 in a workpiece 150 using the inner diameter measuring instrument 100 will be described.

[0072] First, an inner diameter measuring device 100 corresponding to the diameter of the holes 152, 154 is attached to the tip of the robot arm 14. The inner diameter measuring device 100 is selected from the tool table 130 and attached automatically by the robot 10.

[0073] Next, the inner diameter measuring instrument 100 is calibrated using a master (not shown). The robot 10 rotates and translates the robot arm 14 until it reaches the vicinity of the workpiece 150 that has been brought to a predetermined position on the conveyor 140. Then, the plug gauge 200 of the inner diameter measuring instrument 100 is positioned above the holes 152, 154.

[0074] Next, the robot 10 slowly inserts the inner diameter measuring instrument 100 into the holes 152, 154 using the guide portion 264 of the plug gauge 200 as a guide. At this time, misalignment occurs between the guide portion 264 and the holes 152, 154 within the tolerance. The misalignment between the plug gauge 200 and the holes 152, 154 is eliminated by the floating mechanism. That is, the floating relieving portion 300 is displaced by the floating mechanism, and the plug gauge 200 is automatically centered with the holes 152, 154.

[0075] Next, the plug gauge 200 is lowered to a position where the stopper 262 acts or to a predetermined measurement depth position.

[0076] Next, measurement is started at this position, and the displacement of the probe 270 is transmitted to the measuring device 380 as mechanical deformation. The measuring device 380 converts the deformation (displacement) into an electrical signal (analog data). The data converting and transmitting unit 400 converts the electrical signal (analog data) representing the amount of displacement obtained by conversion in the measuring device 380 into digital data representing the inner diameters of the holes 152, 154. The digital data is transmitted to the robot 10 via the data cable 508 and the electrode device 510. The digital data is then finally stored in the robot controller 12 or a storage device attached thereto.

[0077] Here, a force is constantly applied to the probe 270 to push it outward from the probe hole 272 of the plug gauge 200. When the plug gauge 200 is not in contact with another object (normal state), the pushing force causes the probe 270 to protrude from the plug gauge 200 by about 0.2 mm. The tip of the probe 270 is hemispherical. Therefore, even if the probe 270 comes into contact with the inner wall surface of the holes 152, 154 while protruding by about 0.2 mm, the downward force of the plug gauge 200 will cause no galling or the like, and it will be pulled into the plug gauge along the inner wall surface against the pushing force.

[0078] The lowering operation of the plug gauge 200 may be stopped midway and the plug gauge 200 may be raised. For example, this may occur when the holes 152, 154 formed in the workpiece 150 are outside the tolerance range due to poor machining, or when the hole position is unexpectedly off. This operation can be performed using the relieving mechanism of the floating relieving unit 300. However, the function of the relieving mechanism is to passively contract when an excessive external force is applied. Therefore, there are limitations to the circumstances under which the relieving mechanism can be raised. For example, one method utilizes the fact that the force required to activate the relieving mechanism is stronger than that required for normal insertion. For example, one method is to set the robot to raise the plug gauge 200 when it detects an abnormal load (enough to activate the relieving mechanism) during insertion.

[0079] Next, tool replacement will be described. For example, in batch processing, tool replacement is performed for each batch. Furthermore, when continuously measuring workpieces that are continuously transported on a conveyor or the like, tool replacement is performed for each predetermined number of workpieces, for example. The holes 152 and 154 of the workpieces 150 are changed for each predetermined number of workpieces. Specifically, when first measuring small-diameter holes 152 and then large-diameter holes 154 for a predetermined number of workpieces 150, tool replacement is performed when switching between these two.

[0080] In the tool table 130, inner diameter measuring devices 100 with different measurable ranges are stored in tool holders 122.

[0081] First, an inner diameter measuring device 100 suitable for small diameter holes 152 is attached to the tip of the robot arm 14. The attachment is performed automatically by the robot 10 upon receiving a command from the robot controller 12. Then, the inner diameters of the holes 152 in a predetermined number of workpieces 150 are measured.

[0082] Thereafter, the robot arm 14 is rotated and translated to guide it to the empty tool holder 122. Then, a stopper (not shown) is released to separate the robot arm side changer 126 and the tool side changer 128. In this state, only the robot arm side changer 126 is attached to the tip of the robot arm 14. Next, the robot arm 14 is moved and positioned to a predetermined tool holder 122. An inner diameter measuring device 100 corresponding to the large-diameter hole 154 to be measured is stored in this tool holder 122. Next, a new inner diameter measuring device 100 is attached to the tip of the robot arm 14, making it possible to measure the large-diameter hole 154 to be measured.

[0083] Next, another embodiment of the inner diameter measuring instrument will be described. Fig. 4 is a perspective view of the main parts of another embodiment of the inner diameter measuring instrument. Fig. 5 is an explanatory diagram of a method for correcting the tilt of the inner diameter measuring instrument shown in Fig. 4.

[0084] The inner diameter measurement instrument 102 shown in Figure 4 differs from the above-described embodiment mainly in the following two points. First, the plug gauge and the connection section are integrated, further simplifying the configuration. Second, it is possible to correct the positional deviation of the inner diameter measurement instrument 102 (probe 270) relative to the holes 152, 154. This is due to the provision of four (or more) probes 270, among other things.

[0085] The inner diameter measuring device 102 is configured by combining two sets of displacement measuring devices, such as those described in Japanese Patent Application Laid-Open No. 2018-169180 (Patent Document 6). The data conversion and transmission unit 410 has the same configuration as in the above-described embodiment. Four displacement measuring devices 381 are connected to the data conversion and transmission unit 410. The displacement measuring devices 381 are, for example, linear variable differential transformers (LVDTs) or optical scale displacement meters.

[0086] A finger 383 extending vertically is disposed at the lower end of the displacement measuring device 381 . A probe 270 for measuring displacement is attached to each of the fingers 383 .

[0087] An outward force is constantly applied to each probe 270. The outward force is applied by an elastic body via fingers 383. Under normal conditions, the radius of the envelope circle connecting the tips of each probe 270 is approximately 0.1 to 0.5 mm larger than the maximum inner radius of the hole to be measured. This makes it possible to perform measurements even when taking into account variations in the inner radius tolerance and the occurrence of misalignment.

[0088] The tip of the contact point 270 is hemispherical. When the inner diameter measuring device 102 is inserted into the holes 152, 154, the hemispherical portion of the contact point 270 comes into contact with the inner surface of the holes 152, 154. Note that a function may be provided to forcibly move the finger 383 of the displacement measuring device 381 radially inward by several millimeters (retraction) using a built-in cylinder (not shown) or the like. By inserting the contact point into the hole in the retracted state, slight misalignment of the hole or machining defects will not collide with the hole, and the workpiece will not be damaged.

[0089] A method for measuring the inner diameters of the holes 152, 154 using the inner diameter measuring instrument 102 will be described, including the correction method shown in FIG.

[0090] First, the inner diameter measuring instrument 102 is calibrated in advance using a master. At that time, the center of the master is aligned with the center of the inner diameter measuring instrument. During alignment, the output (calibration data) of the displacement measuring instrument 381 is obtained from the displacement of each measuring element 270.

[0091] Next, the inner diameter measuring device 102 is inserted into the hole 152 of the workpiece 150. During insertion, the central axis of the inner diameter measuring device 102 may be inserted at an angle relative to the central axes of the holes 152, 154.

[0092] Figure 5 is an explanatory diagram showing the relationship between the hole 152 and the inserted inner diameter measurement instrument 102A. Figure 5 shows the state in which the inner diameter measurement instrument 102A is inserted with its central axis tilted relative to the central axis of the hole 152. The inner diameter measurement instrument 102A shown by the solid line in Figure 5 shows a state in which it is shallowly inserted into the hole 152. Furthermore, the inner diameter measurement instrument 102B shown by the dashed line shows a state in which it is inserted more deeply into the hole 152.

[0093] As is clear from a comparison between inner diameter measurement instruments 102A and 102B, the amount of retraction (amount of displacement) of each probe changes depending on the insertion depth. Probe 270A is pushed inward as the inner diameter measurement instrument is inserted into hole 152. Probe 270B is pushed outward as the inner diameter measurement instrument is inserted into hole 152. For more accurate inner diameter measurements, it is preferable to correct the measurement value according to the tilt θ.

[0094] The slope θ is unknown at the beginning of insertion. To correct the measurement value, the slope θ is first calculated as follows.

[0095] First, in a cross section including the center axis of the measuring element and the inner diameter measuring instrument, the inclination θ of the inner diameter measuring instrument 102 is calculated based on the insertion amount x and the change in the measurement value Δy, according to the following formula: (Formula)θ=tan -1 (Δy / x)

[0096] The change Δy in the measurement quantity is typically caused by tilt of the inner diameter measurement instrument. However, in principle, the change Δy can also be caused by factors other than tilt of the inner diameter measurement instrument. For example, this can occur when the holes 152, 154 are tapered, or when the inner diameter of the holes 152, 154 changes in the depth direction. In order to distinguish these from changes due to the tilt of the inner diameter measuring instrument, it is preferable to find the tilt θ from the average of the outputs of a pair of probes 270A and 270B that are arranged with a phase difference of 180° from each other.

[0097] Once the tilt θ is calculated in this manner, the robot 10 rotates the inner diameter measurement device 102 so as to cancel the tilt θ. As a result, the central axes of the holes 152, 154 and the central axis of the inner diameter measurement device 102 coincide with each other.

[0098] Now that it is possible to insert the inner diameter measuring device 102 along the central axes of the holes 152, 154, the inner diameter measuring device 102 is inserted to a predetermined measurement depth. Next, the displacement amounts (analog data) of the four measuring styluses 270 are transmitted to the displacement measuring device 381. The data conversion and transmission unit 400 converts the displacement amounts into digital data representing the inner diameters and transmits the data to the robot-side controller.

[0099] According to this embodiment, the positioning accuracy of the inner diameter measuring device 102 by the robot 10 can be roughly adjusted. Therefore, the number of steps required for teaching can be reduced. Furthermore, if the center of the inner diameter measuring device 102 is aligned with the master during mastering (zeroing) of the inner diameter measuring device 102, the inner diameter and center position of the holes 152 and 154 formed in the workpiece 150 can be obtained by comparing with the results obtained during calibration using the master. The center positions of the holes 152 and 154 can be used as the measurement results for the workpiece 150 or for position correction during teaching of the robot 10. Furthermore, since the movable displacement of the stylus 270 can be increased, the frequency of replacing the inner diameter measuring device 102 can be reduced. In one embodiment, the movable displacement can be increased to an upper limit of 0.5 to 2 mm.

[0100] In addition, in each of the above embodiments, the distance from the measurement by the measuring element to the data conversion / transmission unit is made as short as possible, thereby reducing the adverse effects on measurement caused by noise from industrial robots, particularly the servo motors used therein. Furthermore, since the data is converted into digital data before being transmitted to the outside, data degradation due to noise around the robot can be prevented, improving noise resistance.

[0101] The inner diameter measuring instrument of this embodiment also includes a data conversion / transmission unit that converts the detection signal detected by the contact point into digital data. Therefore, even if electromagnetic noise (noise) is present on the robot arm to which the inner diameter measuring instrument is attached or in its surroundings, the detection signal can be reliably preserved and measurement data can be obtained. Furthermore, the inner diameter measuring instrument employs a floating mechanism that allows lateral displacement of the measuring unit. This allows smooth insertion even when the measuring unit is misaligned with the center or horizontal of the hole being measured, preventing damage and scratches to the contact point or the hole being measured. Furthermore, the inner diameter measuring instrument uses an upper end structure compatible with auto-tool changers. By preparing inner diameter measuring instruments with different measurement ranges, it is possible to measure the inner diameters of holes with different diameters. Furthermore, by integrating the three mechanisms—the relieving mechanism, floating mechanism, and measuring mechanism—into the inner diameter measuring instrument, an inner diameter measuring instrument for robots with a short overall length (vertical length) can be realized, and the moment load at the end of the arm when the robot arm is rotating can be reduced. [Explanation of symbols]

[0102] 10...Robot, 12...Robot controller, 14...Robot arm, 16...Wiring, 50...Inner diameter measurement system, 100, 102...Inner diameter measurement device, 122...Tool holder, 124...Guide part, 126...(Robot arm side) changer, 128...(Tool side) changer, 130...Tool table, 140...Conveyor, 150...Workpiece (object to be measured), 152...Hole (small diameter side), 154...Hole (large diameter side), 200...Plug gauge, 210...Plug gauge shaft, 260...Plug gauge body, 262...Stopper, 264...Guide part, 270...Measuring point, 272...Measuring point hole, 300...Float Relieving part (connecting part), 330...(inner cylindrical holder) plug gauge holder, 332...pressing plate, 334...set screw, 340...bush holder, 350...(floating) elastic body, 352...screw, 354...(outer) cylindrical holder, 362...relieving shaft, 364...ball bushing, 370...spring, 372...spring holding plate, 374...pressing plate, 380...measuring instrument, 381...displacement measuring instrument, 383...finger, 400, 410...data conversion transmitting part, 422...main body cover, 424...flange, 500...robot hand changer part, 508...data cable, 510...electrode device

Claims

1. An inner diameter measuring device that is detachably attached to the tip of a robot arm and measures the inner diameter of a hole formed in a workpiece, The measuring instrument includes at least two probes and a data conversion / transmission unit, the at least two probes are brought into contact with an inner wall surface of a hole formed in the workpiece, The data conversion and transmission unit converts analog data relating to the displacement of the at least two contact points into digital data representing the inner diameter of the hole and transmits the digital data to an external device.

2. 2. The inner diameter measurement instrument according to claim 1, wherein the data conversion and transmission section transmits the digital data to the external device connected by wire.

3. a plug gauge that holds the at least two probes at its tip; a connecting portion provided between the plug gauge and the data conversion transmitting portion, 2. The inner diameter measurement instrument according to claim 1, wherein the articulating portion is configured to allow displacement of the robot arm relative to the plug gauge in an axial direction and in a direction substantially perpendicular to the axial direction.

4. The connecting portion is formed in an overall vertically elongated cylindrical shape and includes a bush holder formed in an annular shape, and a floating mechanism, a relieving mechanism, and a measuring mechanism, each held within the bush holder, the floating mechanism allows the displacement in a direction substantially perpendicular to the axial direction, the relieving mechanism allows the displacement in the axial direction; The measurement mechanism acquires the analog data; 4. The inner diameter measuring instrument according to claim 3, wherein the measuring mechanism is disposed at a center portion within the bushing holder, and the floating mechanism and the relieving mechanism are disposed around the measuring mechanism.

5. The relieving mechanism includes at least three ball bushings spaced apart from one another in the circumferential direction of the bushing holder; 5. The inner diameter measuring instrument according to claim 4, further comprising a bushing shaft provided for each of said ball bushings and passing through the center of said ball bushing.

6. 5. The inner diameter measuring instrument according to claim 4, wherein the floating mechanism includes an elastic body, one end of which is locked to the bush holder.

7. the at least two probes are four probes, a displacement measuring device connected to each of the four measuring probes; The four probes are arranged at intervals in the circumferential direction, 2. The inner diameter measuring instrument according to claim 1, wherein the data converting and transmitting section converts the analog data detected by the displacement measuring instrument into digital data representing the inner diameter of the hole and transmits the digital data to the external device.

8. An inner diameter measurement system comprising the robot arm and the inner diameter measurement device according to any one of claims 1 to 7.

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