Nutrunner and nutrunner control system

Abstract

[Problem] To provide a nutrunner capable of simply and accurately detecting seating of an object to be fastened using a self-locking nut. [Solution] A nutrunner and a nutrunner control system are characterized by comprising: a control means for controlling fastening of a self-locking nut to a fastening object; a measurement means for measuring torque imparted to fastening; and a detection means for detecting seating of the fastening object on the basis of an amount of change in the torque measured by the measurement means. Due to this configuration, the seating of the fastening object can be detected according to the amount of change over time of the torque, for example. Therefore, the seating of the fastening object using the self-locking nut can be detected simply and accurately.

Description

Nut runner and nut runner control system

[0001] The present invention relates to a nut runner and a nut runner control system for controlling the tightening of an object to be fastened.

[0002] Nut runners are widely used in assembly fields across various industries, including automobile body manufacturing, aerospace, heavy machinery and construction equipment assembly, and home appliance assembly. In these assembly sites, nut runners are used to fasten bolts and nuts to objects. In recent years, nut runners capable of automatically fastening bolts and nuts to objects using a rotation angle, as shown in Patent Document 1, have attracted attention in order to reduce the burden on human workers.

[0003] Patent Document 1 discloses a nut runner having a control means for controlling the tightening of a bolt or nut on an object to be tightened, wherein the control means has an AI tightening control means that performs tightening control using an optimal value search means that searches for the optimal value of a weight coefficient according to an evolutionary strategy, and the AI ​​tightening control means has a detection means that detects seating and / or bottoming of the object to be tightened by inputting a group of measurement data after the start of tightening to the optimal value search means.

[0004] Japanese Patent Publication No. 2024-117215

[0005] On the other hand, in applications such as aircraft assembly, self-locking nuts are sometimes used to prevent nuts from easily loosening due to vibration or other external factors after fastening. These self-locking nuts utilize a wedge, eccentricity, or friction with the shaft to provide a pre-locking effect. The torque required for tightening these self-locking nuts changes before seating, depending on the wedge, eccentricity, or friction with the shaft during tightening.

[0006] However, the nut runner described in Patent Document 1 does not take into account the change in torque during the tightening of the self-locking nut. Therefore, the nut runner described in Patent Document 1 has the problem that it cannot detect the seating of the self-locking nut with high accuracy.

[0007] Therefore, the present invention was devised in view of the above-mentioned problems, and its objective is to provide a nut runner that can detect the seating of an object to be fastened using a self-locking nut in a simple and highly accurate manner.

[0008] The nut runner according to the first invention is characterized by comprising: a control means for controlling the tightening of a self-locking nut to an object to be tightened; a measuring means for measuring the torque applied to the tightening; and a detection means for detecting the seating of the object to be tightened based on the amount of change in torque measured by the measuring means.

[0009] The nut runner according to the second invention is characterized in that, in the first invention, the detection means detects the seating of the object to be fastened based on the amount of change in torque measured by the measuring means and a preset threshold.

[0010] The nut runner according to the third invention is characterized in that, in the second invention, the detection means sets the threshold value based on nut information relating to the characteristics of the self-locking nut.

[0011] The nut runner according to the fourth invention is characterized in that, in the first invention, the detection means comprises a calculation means for calculating a periodic change in the torque based on the torque measured by the measuring means, and a setting means for setting a threshold based on the periodic change in the torque calculated by the calculation means, and the seating of the object to be fastened is detected based on the change in the torque measured by the measuring means and the threshold set by the setting means.

[0012] The nut runner control system according to the fifth invention is characterized by comprising: control means for controlling a nut runner that fastens a self-locking nut to an object to be fastened; measuring means for measuring the torque applied to the fastening; and detection means for detecting the seating of the object to be fastened based on the amount of change in torque measured by the measuring means.

[0013] The nut runner according to the sixth invention is characterized in that, in the first invention, the detection means determines whether or not there is an abnormality in the tightening of the self-locking nut based on the amount of change in torque measured by the measuring means.

[0014] The nut runner according to the seventh invention is characterized in that, in the first invention, the detection means determines whether or not there is an abnormality in the tightening of the self-locking nut based on the range in which the torque measured by the measuring means is greater than or equal to a set value.

[0015] According to the first to seventh inventions, the nut runner and nut runner control system detect the seating of the object to be fastened based on the amount of change in torque. This makes it possible to detect the seating of the object to be fastened in accordance with, for example, the amount of change in torque over time. Therefore, it is possible to detect the seating of an object to be fastened using a self-locking nut in a simple and highly accurate manner.

[0016] According to the second invention, the nut runner detects the seating of the object to be fastened based on the amount of change in torque and a preset threshold. By setting the nut runner to detect the seating of the object to be fastened when, for example, the amount of change in torque over time exceeds the threshold, it becomes possible to detect the seating of the object to be fastened using a self-locking nut with higher accuracy.

[0017] According to the third invention, the nut runner sets a threshold value based on nut information. This makes it possible to automatically set an appropriate threshold value according to the characteristics of the self-locking nut, such as distortion. As a result, it becomes possible to detect the seating of the object to be fastened more simply and with higher accuracy.

[0018] According to the fourth invention, the detection means detects the seating of the object to be fastened based on the amount of change in torque measured by the measuring means and a threshold value set by the setting means. This makes it possible to automatically set the threshold value from the torque while the self-locking nut is being tightened. Therefore, it becomes possible to detect the seating of the object to be fastened in a simpler manner.

[0019] According to the sixth invention, the detection means determines whether or not there is an abnormality in the self-locking nut based on the amount of change in torque. This makes it possible to automatically determine an abnormality in the tightening of the self-locking nut from the amount of change in torque, for example, if there is an abnormality in the self-locking nut such as a lack of crimping.

[0020] According to the seventh invention, the detection means determines whether or not there is an abnormality in the self-locking nut based on the range in which the torque exceeds a set value. This makes it possible to determine that the self-locking nut is normal if, for example, the length of time for which the torque exceeds the set value is greater than a certain amount. Therefore, it is possible to determine whether or not there is an abnormality in the tightening of the self-locking nut with higher accuracy.

[0021] Figure 1(a) is a cross-sectional view of a nut runner showing an embodiment of the present invention. Figure 1(b) is a configuration diagram of the operating section in the nut runner of the embodiment of the present invention. Figure 2 is an electrical block diagram of the nut runner of this embodiment. Figure 3(a) is an explanatory diagram showing the usage state of the nut runner of this embodiment (before socket attachment). Figure 3(b) is an explanatory diagram showing the usage state of the nut runner of this embodiment (after socket attachment). Figure 4(a) is a diagram showing an example of a self-locking nut. Figure 4(b) is a diagram showing an example of a bolt. Figure 5 is a tightening control flowchart for the nut runner of this embodiment. Figure 6(a) is a graph showing the relationship between the torque applied to tightening a self-locking nut and the distance from the seating surface. Figure 6(b) is a graph showing the relationship between the torque applied to tightening a general nut and the distance from the seating surface. Figure 7(a) is a graph showing the relationship between the torque applied to tightening a self-locking nut of combination A and time. Figure 7(b) is a graph showing the relationship between the torque applied to tightening a self-locking nut of combination B and time. Figure 8(a) is a graph showing the relationship between the change in torque applied to tightening the self-locking nut in combination A and time. Figure 8(b) is a graph showing the relationship between the change in torque applied to tightening the self-locking nut in combination B and time. Figure 9(a) is a graph showing the relationship between the change in torque applied to tightening the self-locking nut and time. Figure 9(b) is an enlarged version of Figure 9(a). Figure 10(a) is a graph showing the relationship between the change in torque applied to tightening the self-locking nut and time. Figure 10(b) is an enlarged version of Figure 10(a). Figure 11 is a diagram showing the first example of determining whether or not there is an abnormality in the self-locking nut using a graph showing the relationship between the torque applied to tightening the self-locking nut and time. Figure 12 is a diagram showing the second example of determining whether or not there is an abnormality in the self-locking nut using a graph showing the relationship between the torque applied to tightening the self-locking nut and time.

[0022] Hereinafter, an example of a nut runner and nut runner control system in an embodiment to which the present invention is applied will be described with reference to Figures 1 to 3. Figure 1 is a cross-sectional view showing an example of a nut runner 100 illustrating an embodiment of the present invention. Figure 2 is an electrical block diagram of the nut runner 100 of this embodiment. Figure 3(a) is an explanatory diagram showing the usage state of the nut runner 100 in this embodiment (before socket installation). Figure 3(b) is an explanatory diagram showing the usage state of the nut runner 100 in this embodiment (after socket installation).

[0023] The nut runner 100 of this embodiment is a nut runner that fastens a self-locking nut 8 to an object to be fastened. The shape of the nut runner 100 may be a handheld nut runner for operation or a stationary nut runner mounted on equipment. Handheld nut runners include straight type, pistol type, angle type, etc. The nut runner 100 has, for example, a resin casing 1, a metal casing 2, a rechargeable battery 3, a grip 4, a switch 5, an operating unit 6, and a display unit 7, as shown in Figure 1. The nut runner 100 may also be operated based on commands transmitted from an external device (not shown).

[0024] These casings house electronic components, mechanical components, motors, and the like. Specifically, the resin casing 1 contains a CPU board 11, a motor 12, an encoder 13, a motor control board 14, a display operation board 15, and an acceleration and angular velocity measurement unit 16. The metal casing 2 contains a motor drive shaft 21, a reduction unit 22, a bevel gear unit 23, a tip output unit 24, a first strain gauge type torque sensor 25, and a second strain gauge type torque sensor 26. Although not shown in the illustration, the reduction unit 22 has a sun gear, a pinion gear, and an internal gear, forming a planetary gear mechanism.

[0025] <Description of Configuration> The resin casing 1 houses a CPU board 11, a motor 12, an encoder 13, a motor control board 14, a display operation board 15, and an acceleration and angular velocity measurement unit 16.

[0026] The metal casing 2 houses a motor drive shaft 21, a reduction gear unit 22, a bevel gear unit 23, a tip output unit 24, a first strain gauge type torque sensor 25, and a second strain gauge type torque sensor 26.

[0027] The rechargeable battery 3 supplies power to the sensors, electronic circuit boards, motor, etc., inside the nut runner 100. For example, a rechargeable lithium-ion battery or nickel-metal hydride battery can be used. In the prototype, for example, a battery with a voltage of 25.2V and a capacity of 3.9Ah is used, but it is not limited to this. Any battery that can achieve the desired tightening torque is acceptable.

[0028] Grip 4 is the part that the operator holds with their hand. The operator grasps grip 4 and operates the nut runner 100 against the object to be tightened.

[0029] When switch 5 is pressed by the operator, the tightening control is initiated.

[0030] The control unit 6 is equipped with a group of buttons for performing operations such as changing setting values, changing the display of tightening results, confirming, and resetting.

[0031] The display unit 7 is a liquid crystal screen for displaying set values, tightening results, status, etc. The display format, such as color or monochrome, is not particularly limited.

[0032] The CPU board 11 has a function as a control means for performing tightening control of bolts or nuts on the object to be tightened. A program for performing tightening control is written on the CPU board 11. Hereinafter, the function of the CPU board 11 as a controller of the nut runner 100 will be described. The CPU board 11 takes in the values measured by a motor 12 such as a DC brushless motor, an encoder 13, a first strain gauge type torque sensor 25, a second strain gauge type torque sensor 26, and an acceleration and angular velocity measurement unit 16. The CPU board 11 can be connected to an external PC (not shown) via Wi-Fi communication or a USB connection. The tightening result and the threshold value required for tightening can be transmitted from the nut runner 100 to the external PC. Also, the threshold value required for tightening can be transmitted from the external PC to the nut runner 100. Various measurement values and consideration results can be temporarily stored in the memory. The tightening result can be stored in an internal storage (such as an SD card). The CPU board 11 detects the seating of the object to be tightened based on the change amount of the torque.

[0033] The motor 12 is a power source of the nut runner 100. The motor 12 may be, for example, a DC brushless motor. The rotation speed and current value of the motor 12 are taken in by the CPU.

[0034] The encoder 13 measures the rotation speed of the motor 12. The measured rotation speed value is taken in by the CPU.

[0035] The motor control board 14 is a board provided with a drive control IC for the motor 12, a driver circuit, a power supply circuit, and the like.

[0036] The display operation board 15 is a board for display and operation of the operation unit 6 and the display unit 7.

[0037] The acceleration and angular velocity measurement unit 16 is for measuring the acceleration and angular velocity of the x, y, and z axes. The acceleration and angular velocity measurement unit 16 corresponds to the 9-axis gyro sensor in FIG. 2. In this specification, the gyro sensor may also be referred to by the term "vibration sensor".

[0038] The motor drive shaft 21 transmits the driving force of the motor 12. It is for inputting the power of the motor 12 from the drive shaft to a reduction unit (such as a planetary gear mechanism).

[0039] The reduction unit 22 is decelerated by a planetary gear mechanism (sun gear, pinion, internal gear), etc., to obtain a target torque (specified torque).

[0040] The bevel gear unit 23 changes the output direction and transmits the rotational force to the tip output unit 24.

[0041] The tip output unit 24 attaches a socket (not shown), etc., and performs tightening by connecting to the self-locking nut 8 and the bolt 9.

[0042] The first strain gauge type torque sensor 25 is for measuring the tightening torque. The measured torque value is taken into the CPU.

[0043] The second strain gauge type torque sensor 26 is for measuring the tightening torque. The measured torque value is taken into the CPU.

[0044] <Electronics board: CPU board, motor control board, etc.> As shown in FIG. 2, the electronics board includes torque sensors 101A, 101B, amplifiers 102A, 102B, filters 103A, 103B, A / D conversion units 104A, 104B, midpoint voltages 105A, 105B, input unit 106, motor encoder 107, CPU 108, memory 109, storage device 113, display unit 114, motor control unit 115, communication unit 116, and various sensors (such as gyro sensors) 117.

[0045] <Explanation of the configuration of the electronics board> The torque sensors 101A, 101B generate the torque during tightening as an analog value. The torque applied to the sensor component itself generates strain, and the voltage difference of the circuit caused by this is output. Here, a strain gauge is adopted, but the output analog value is not limited to voltage. The torque sensor 101A corresponds to the first strain gauge type torque sensor 25 shown in FIG. 1. Also, the torque sensor 101B corresponds to the second strain gauge type torque sensor 26 shown in FIG. 1.

[0046] Amplifiers 102A and 102B amplify the minute potential difference output by the torque sensor 101. The amplification factor is set to, for example, about 250 times, but is not limited to this.

[0047] Filters 103A and 103B perform rounding (filtering) to smooth the analog output values ​​of amplifiers 102A and 102B.

[0048] The A / D conversion units 104A and 104B convert analog values ​​into digital values ​​that can be read by software. The A / D conversion units 104A and 104B make the values ​​readable in software (for example, 0-4096).

[0049] The midpoint voltages 105A and 105B are midpoints for safe output and protect the circuit from abnormal voltages.

[0050] The input unit 106 is an interface, such as buttons, for the user of a hand tool to operate it. Examples of the input unit 106 include buttons, a touch panel, a microphone, and the like.

[0051] The motor encoder 107 outputs a pulse signal to read the motor's rotation angle. An ON-OFF-ON-OFF signal is input to the CPU 108. The CPU 108 calculates the motor's rotation angle from this value.

[0052] The CPU 108 performs the following processes: (1) Reading from the input unit 106. (2) Reading from the communication unit 116 and writing to the communication unit 116. (3) Reading from the A / D conversion units 104A and 104B. (4) Reading from the motor encoder 107. (5) Tightening control that controls motor rotation by calculating real-time readings from the torque sensors 101A and 101B and the motor encoder 107. (6) Communicating the tightening results, etc., to the hand tool user. (7) Saving the tightening result data to the storage device 113.

[0053] Memory 109 is a volatile memory device for temporarily storing data necessary for programming and tightening.

[0054] The memory device 113 is a non-volatile memory device for permanently storing data necessary for programs and tightening.

[0055] The display unit 114 is an electronic component for transmitting information to the user. For example, the display unit 114 includes a display, LED lights, and a warning buzzer.

[0056] The motor control unit 115 is composed of, for example, the motor body and electronic components for motor control. In this embodiment, it is integrated with the motor body, but it may be configured as a separate unit.

[0057] The communication unit 116 is an electronic component that transfers data with connected external electronic devices. In this embodiment, a wireless communication interface is used, but either a wired or wireless interface may be used.

[0058] The various sensors 117 are connection interfaces other than the torque sensors 101A and 101B. In this embodiment, a 9-axis gyro sensor (vibration sensor) is connected. Alternatively, the various sensors 117 may be axial force sensors.

[0059] <Diagram illustrating the state of use of the nut runner> Figure 3(a) is an explanatory diagram showing the state of use of the nut runner 100 in this embodiment (before socket attachment). Figure 3(b) is an explanatory diagram showing the state of use of the nut runner 100 in this embodiment (after socket attachment). As shown in Figures 3(a) and (b), a user (not shown) attaches the socket CP (joint) 152 to the tip output of the nut runner 100 (see Figure 1), overlaps the object to be fastened A (joint object A) 153 and the object to be fastened B (joint object B) 154, passes the bolt 9 through both holes, presses the nut runner 100 to hold down the self-locking nut 8, turns on the switch and fastens the bolt 9 or the self-locking nut 8.

[0060] <Self-locking nut> Figure 4(a) shows an example of a self-locking nut 8. Figure 4(b) shows an example of a bolt 9. The self-locking nut 8 is a nut that has been pre-treated to prevent loosening by vibration or other external factors after fastening, by using crimping, wedges, eccentricity, or friction with the shaft. The self-locking nut 8 is treated to prevent loosening by increasing friction after tightening, for example, through a threaded design including perforations or flange grooves. The self-locking nut 8 may be, for example, a self-flocking nut, a self-locking nut, a hard lock nut, a grooved nut, a crimped nut, a stiff nut, a conical lock nut, a tri-lock nut, a top lock, a Stover lock nut, a Griptite nut, a surface bearing lock nut, etc. The self-locking nut 8 may have multiple wedges 81, for example, as shown in Figure 4(a). The self-locking nut 8 may be, for example, a U-nut with a crimped friction ring on the upper surface of the nut.

[0061] <Tightening Control Flowchart of This Embodiment> Figure 5 is a flowchart of the tightening control in the nut runner of this embodiment. Below, we will explain the tightening control flow using the tightening control means in Figure 5, with a socket attached to the nut runner 100 as shown in Figure 3.

[0062] First, when the tightening start button is pressed (ON) (step 301), the motor rotates, tightening of the self-locking nut 8 and bolt 9 begins, and measurement of various values ​​begins (step 302).

[0063] Next, in order to calculate the numerical values ​​necessary for determining abnormalities such as seating or bottoming out, the measured values ​​are saved in a time series and used in calculations (step 303).

[0064] Next, the measurement data set is input (step 304), bottoming out is determined (step 305), seating is determined (step 306), and seating torque is reached is determined (step 307), and this process is repeated.

[0065] If seating is detected (step 306) and the seating torque is reached (step 307), the determination result is considered normal and the process is terminated (step 308).

[0066] If bottoming out is detected before reaching the seating torque (step 305), the determination result is an error (abnormality), i.e., a tightening failure (step 309), and the motor is stopped to end the tightening process.

[0067] By performing the processes described in steps 301 to 308 above, seating and bottoming can be detected. Steps 301 to 308 will be described in detail below with reference to the drawings.

[0068] <Step 301> First, in step 301, the nut runner 100 is activated by pressing the tightening start button. Also in step 301, the nut runner 100 may set a threshold value to be used to detect seating and / or bottoming, as described later. The nut runner 100 may set a threshold value input via, for example, the input unit 106. Alternatively, the nut runner 100 may set a threshold value based on nut information relating to the characteristics of the self-locking nut 8. In this case, the CPU 108 may, for example, refer to a relationship table showing the relationship between nut information and the threshold value, and set a threshold value based on the nut information input via the input unit 106. This relationship table may be stored in, for example, the storage device 113. Alternatively, the nut information may be extracted by image authentication of an image of the self-locking nut 8 captured by, for example, a camera (not shown). Alternatively, the nut information may be extracted by reading the barcode on the package of the self-locking nut 8 captured by, for example, a camera (not shown).

[0069] <Nut Information> The nut information is information regarding the characteristics of the self-locking nut 8. The nut information may include, for example, the model number and size of the self-locking nut 8. The nut information may also include, for example, information regarding the wedge, eccentricity, or shaft of the self-locking nut 8. The nut information may also include, for example, information indicating the number, position, or size of the wedges 81. Furthermore, the nut information may also include information regarding the combination of the self-locking nut 8 and the bolt 9. The nut information may be stored in the storage device 113 in association with, for example, a threshold, unit time, moving average width, etc., as described later.

[0070] <Threshold> The threshold is a set value for detecting seating or bottoming out in the tightening control of the nut runner 100. This threshold is described in detail below. The threshold may also include a threshold for seating detection and a threshold for bottoming out detection.

[0071] Figure 6(a) is a graph showing the relationship between the torque applied to tightening the self-locking nut 8 and the distance from the seating surface. Figure 6(b) is a graph showing the relationship between the torque applied to tightening a general nut and the distance from the seating surface. In Figures 6(a) and (b), K indicates that the distance a between the nut and the seating surface is 0 mm, meaning the nut has seated. In the case of tightening a general nut, as shown in Figure 6(b), the torque applied to tightening increases after the distance a from the seating surface is 0 or less, that is, after the nut has seated K. In contrast, as shown in Figure 6(a), with the self-locking nut 8, the torque applied to tightening increases even when the distance a from the seating surface is 0 or more, due to the effect of friction from the wedge 81, etc., during tightening. Therefore, in order to detect seating of the self-locking nut 8, it is necessary to set a threshold considering the maximum value T of the torque before seating. Also, as shown in Figure 6(a), with the self-locking nut 8, the torque increases without an increase in axial force during tightening. For this reason, seating cannot be determined with high accuracy using a preset threshold.

[0072] Figure 7(a) is a graph showing the relationship between the torque and time required to tighten the self-locking nut 8 in combination A. Figure 7(b) is a graph showing the relationship between the torque and time required to tighten the self-locking nut 8 in combination B. Torque 1 and Torque 2 in Figures 7(a) and (b) are torques measured by, for example, the first strain gauge type torque sensor 25 and the second strain gauge type torque sensor 26, respectively. Also, the axial force in Figures 7(a) and (b) shows the relationship between the compressive force applied to the nut runner 100 and time. The compressive force applied to the nut runner 100 may be, for example, the compressive force measured by a compression load cell installed between the objects to be joined. Combination A is a combination in which MS21042L3 is used as the self-locking nut 8 and NAS6303-10 is used as the bolt 9. Combination B is a combination in which MS21043-5 is used as the self-locking nut 8 and NAS6305A10 is used as the bolt 9. Furthermore, P represents the threshold value, and T represents the maximum value of the periodic torque change. As shown in Figures 7(a) and (b), the torque applied when tightening the self-locking nut 8 changes according to the nut information of the self-locking nut 8. For this reason, it is necessary to set the threshold value considering the nut information of the self-locking nut 8. Also, as shown in Figures 7(a) and (b), a periodic torque change is observed when tightening the self-locking nut 8. The characteristics of this periodicity, such as the time and magnitude of the period, change according to the characteristics of the self-locking nut 8.

[0073] Figure 8(a) is a graph showing the relationship between the change in torque applied to tightening the self-locking nut 8 in combination A and time. Figure 8(b) is a graph showing the relationship between the change in torque applied to tightening the self-locking nut 8 in combination B and time. In Figures 8(a) and (b), the vertical axis represents the change in torque per unit time, and the horizontal axis represents time. In Figures 8(a) and (b), the unit time is set to 375 ms. As shown in Figures 8(a) and (b), the change in torque applied to tightening the self-locking nut 8 changes periodically before seating. Therefore, by setting the threshold P to be larger than the maximum value T of the periodically changing torque before seating, it is possible to detect the seating of the self-locking nut 8. The change in torque per unit time may also be calculated using, for example, the following equation (1). Alternatively, the change in torque per unit time may be calculated using the torque normalized by equation (2).

[0074] Figure 9(a) is a graph showing the relationship between the change in torque applied to tightening the self-locking nut of combination A and time. Figure 9(b) is an enlarged version of Figure 9(a). Figure 10(a) is a graph showing the relationship between the change in torque applied to tightening the self-locking nut of combination B and time. Figure 10(b) is an enlarged version of Figure 10(a). Figures 9(a) and (b) are graphs with a unit time of 426 ms and a moving average width of 120 ms. Figures 10(a) and (b) are graphs with a unit time of 111 ms and a moving average width of 426 ms. Figures 9(a) and (b) and Figures 10(a) and (b) are graphs showing the moving average value of the relationship between the change in torque and time. The moving average value is the sum of the change in torque obtained over the moving average width interval divided by the number of data points obtained. By calculating the moving average value, the correlation with the graph showing axial force increases. Therefore, it becomes possible to determine the seating time more accurately. The threshold P may be set to, for example, three times the maximum value T of the periodically changing torque before seating, but is not limited to this; any threshold P may be set as long as it is greater than the maximum value T of the periodically changing torque before seating. Furthermore, the threshold is not limited to the magnitude of the torque change, but may also be, for example, the change in the torque period, the amplitude of the period, etc.

[0075] Thus, the nut runner 100 stores the previously measured threshold in the storage device 113, and sets the stored threshold in step 301. Alternatively, the nut runner 100 may store the previously measured threshold in association with nut information such as the combination of the self-locking nut 8 and the bolt 9, and set the threshold associated with the stored nut information in step 301 based on the input nut information. Furthermore, the nut runner 100 may store the nut information, such as the combination of the self-locking nut 8 and the bolt 9, in association with an appropriate unit time and a moving average width. This makes it possible to set an appropriate threshold according to the characteristics of the self-locking nut 8, such as distortion. As a result, it becomes possible to detect the seating of the object to be fastened more simply and with higher accuracy.

[0076] Alternatively, instead of setting a threshold value measured in advance in step 301, the threshold value may be set in step 307, which will be described later, while the self-locking nut 8 is being tightened.

[0077] Next, in step 302, the various sensors read the measurement data set. In step 302, for example, the first strain gauge type torque sensor 25 and the second strain gauge type torque sensor 26 measure the torque applied during tightening. The nut runner 100 may also read the measurement data set, which includes tightening angle, axial force, angular velocity in each direction, motor rotation angle, motor current, motor rotation speed, etc., measured by a 9-axis gyro sensor or axial force sensor. In step 302, the CPU 108 may also normalize the measured torque.

[0078] Next, in step 303, the storage device 113 stores the measurement data set in chronological order. The storage device 113 may store, for example, the amount of change per unit time of the measured torque.

[0079] Next, in step 304, the measurement data set is input to the CPU 108.

[0080] Next, in step 305, the CPU 108 determines whether the object has bottomed out. Also, in step 306, the CPU 108 determines whether the object has sat up. In this case, the CPU 108 may determine bottoming out and sat up using any method. This determination of seating and bottoming out may be performed by an AI tightening control means that performs tightening control using an optimal value search means that searches for the optimal value of weight coefficients according to an evolutionary strategy. This AI tightening control means is realized by writing a tightening control program to the CPU. Specifically, the AI ​​tightening control means detects seating and / or bottoming out of the object to be tightened by inputting a group of measurement data after the start of tightening to the optimal value search means. The optimal value search means can determine seating and bottoming out by searching for the optimal solution (evaluation value) from the tightening learning data based on the algorithm of a Covariance Matrix Adaptation Evolution Strategy (CMA-ES), thereby improving the accuracy of the determination compared to conventional seating and bottoming out determinations.

[0081] Next, in step 307, the CPU 108 detects seating of the object to be fastened based on the amount of torque change input in step 304. The CPU 108 detects seating of the object to be fastened based, for example, on the amount of torque change input in step 304 and a threshold value preset in step 301. For example, the CPU 108 detects seating of the object to be fastened if the amount of torque change input in step 304 becomes greater than the threshold value preset in step 301. The CPU 108 also detects seating of the object to be fastened if, for example, the period of the amount of torque change input in step 304 becomes greater than the threshold value preset in step 301. Alternatively, the CPU 108 may use a threshold value for seating detection and a threshold value for bottoming detection, respectively, to detect seating or bottoming of the object to be fastened if the amount of torque change input in step 304 becomes greater than the respective threshold values ​​preset in step 301.

[0082] Furthermore, in step 307, the CPU 108 may set a threshold value based on the torque input in step 304. In step 307, the CPU 108 calculates the periodic change in torque based on the torque input in step 304. The periodic change in torque is a value relating to the periodic change in the increase or decrease of torque per unit time before seating during the tightening of the self-locking nut, as shown in Figures 7 to 10, for example. The CPU 108 sets a threshold value from the calculated periodic change in torque. The CPU 108 sets a threshold value P from the maximum value T indicated by the calculated periodic change in torque. The CPU 108 may set a threshold value P to three times the maximum value T indicated by the calculated periodic change in torque, for example. The CPU 108 detects seating of the object to be tightened based on the torque input in step 304 and the set threshold value. This makes it possible to automatically set a threshold value from the torque during the tightening of the self-locking nut 8 without setting a threshold value in advance. This makes it possible to detect seating of the object to be tightened more easily.

[0083] Furthermore, in step 307, the CPU 108 may set a threshold based on the torque and nut information input in step 304. The CPU 108 refers to, for example, the unit time and moving average width associated with the nut information stored in the storage device 113, and extracts the unit time and moving average width for calculating the periodic change in torque from the newly input nut information. The CPU 108 calculates the periodic change in torque from the torque input in step 304 using the extracted unit time and moving average width. The CPU 108 sets a threshold from the calculated periodic change in torque. This makes it possible to calculate the periodic change in torque using appropriate parameters according to the characteristics of the self-locking nut 8. As a result, it becomes possible to detect the seating of the object to be fastened with higher accuracy.

[0084] Next, in step 308, the tightening by the nut runner 100 is terminated by determining that it is normal. In step 308, the CPU 108 may determine whether or not there is an abnormality in the tightening of the self-locking nut 8 based on the torque characteristics input in step 304. The CPU 108, for example as shown in Figure 11, at time T １ From T ２ The presence or absence of an abnormality in the tightening of the self-locking nut 8 may be determined based on the range in which the torque for a certain period of time is greater than or equal to a set value E. In this case, the CPU 108 determines that the tightening of the self-locking nut 8 is normal if, for example, the length of time for which the torque is greater than or equal to the set value E is greater than or equal to a certain value. This range may also be the range of the tightening angle calculated from the tightening rotation speed and tightening time. Alternatively, the CPU 108 may determine the presence or absence of an abnormality in the tightening of the self-locking nut 8 using, for example, a graph showing the torque against the tightening angle. The CPU 108 determines that the tightening of the self-locking nut 8 is normal if, for example, the torque is greater than or equal to the set value E within a certain range of tightening angles using a graph showing the torque against the tightening angle. As a result, if, for example, there is an abnormality in the crimping of the self-locking nut 8, the proportion in which the torque is less than or equal to the set value E will be large, so the length of time for which the torque is greater than or equal to the set value E, or time T １ From T２ Based on the ratio of the time during which the torque is equal to or greater than the set value E within a certain period of time until a certain time, it becomes possible to accurately determine whether there is an abnormality in the self-locking nut 8. Further, the CPU 108, for example, when the torque is １ from T ２ to T １ within a certain period of time and is equal to or greater than the set value E, may determine that the tightening of the self-locking nut 8 is abnormal. Also, the time T ２ may be, for example, the time when the tightening of the self-locking nut 8 starts, but is not limited to this, and may be, for example, the time when the torque or the change amount of the torque becomes a certain value or more. The time T ２ may be, for example, the time when the seating of the self-locking nut 8 is detected, but is not limited to this, and may be, for example, the time when the torque or the change amount of the torque becomes a certain value or more. The set value E is an arbitrarily set value. Also, the presence or absence of abnormality in the tightening of the self-locking nut 8 is not limited to the presence or absence of caulking, and may be the presence or absence of bolt defects, the presence or absence of foreign matter混入, etc.

[0085] Also, in step 308, as shown in FIG. 12, the CPU 108, based on the comparison between the change in torque within a certain period of time from time T ３ to T ４ and a graph showing the time change of torque when a normal self-locking nut 8 is tightened, which has been acquired in advance, may determine the presence or absence of abnormality in the tightening of the self-locking nut 8. In such a case, for example, the CPU 108, when the root mean square of the sum of the squares of the differences between the graph of the change in torque within a certain period of time from time T ３ to T ４ and the graph showing the time change of torque when a normal self-locking nut 8 is tightened, which has been acquired in advance, is a certain value or less, determines that the tightening of the self-locking nut 8 is normal. Also, the CPU 108, when the difference between the period of the change in torque within a certain period of time from time T ３ to T ４ and the period of the time change of torque when a normal self-locking nut 8 is tightened, which has been acquired in advance, is a certain value or less, determines that the tightening of the self-locking nut 8 is normal. Also, the CPU 108, when the difference between the period of the change in torque within a certain period of time from time T ３ to T ４If the difference between the frequency of torque change over a certain period of time up to a certain point and the frequency of torque change over time when a normal self-locking nut 8 is tightened (which was previously obtained) is less than or equal to a certain value, the CPU 108 determines that the tightening of the self-locking nut 8 is normal. Also, the CPU 108 determines that time T ３ From T ４ If the difference between the number or magnitude of the amplitude of the torque change waveform over a certain period of time up to time T is less than or equal to a certain value, and the number or magnitude of the amplitude of the torque change waveform over time when a normal self-locking nut 8 is tightened (which was obtained in advance), then it is determined that the self-locking nut 8 is tightened normally. ３ This could be, for example, the time when tightening of the self-locking nut 8 begins, but is not limited to this; it could also be, for example, the time when the torque or the amount of change in torque exceeds a certain level. Time T ４ This could be, for example, the time at which the seating of the self-locking nut 8 is detected, but is not limited to this; it could also be, for example, the time at which the torque or the amount of change in torque exceeds a certain level.

[0086] The above steps complete the control of the tightening of the self-locking nut 8 to the object to be tightened by the nut runner 100. This makes it possible to detect the seating of the object to be tightened, for example, according to the amount of change in torque over time. Therefore, it is possible to detect the seating of the object to be tightened using the self-locking nut 8 in a simple and highly accurate manner.

[0087] While embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents.

[0088] 1. Resin casing 2. Metal casing 3. Rechargeable battery 4. Grip 5. Switch 6. Operating unit 7. Display unit 8. Self-locking nut 9. Bolt 11. CPU board 12. Motor 13. Encoder 14. Motor control board 15. Display and operation board 16. Acceleration and angular velocity measurement unit 21. Motor drive shaft 22. Reduction unit 23. Bevel gear unit 24. Tip output unit 25. First strain gauge type torque sensor 26. Second strain gauge type torque sensor 100. Nut runner 101. Torque sensor 102. Amplifier 103. Filter 104. A / D conversion unit 105. Midpoint voltage 106. Input unit 107. Motor encoder 108. CPU 109. Memory 113. Storage unit 114. Display unit 115. Motor control unit 116. Communication unit 152. Socket CP 153 Object to be fastened A 154 Object to be fastened B

Claims

1. A nut runner comprising: control means for controlling the tightening of a self-locking nut to an object to be fastened; measuring means for measuring the torque applied to the fastening; and detection means for detecting the seating of the object to be fastened based on the amount of change in torque measured by the measuring means.

2. The nut runner according to claim 1, characterized in that the detection means detects the seating of the object to be fastened based on the amount of change in torque measured by the measuring means and a preset threshold.

3. The nut runner according to claim 2, characterized in that the detection means sets the threshold based on nut information relating to the characteristics of the self-locking nut.

4. The nut runner according to claim 1, wherein the detection means comprises a calculation means for calculating a periodic change in the torque based on the torque measured by the measuring means, and a setting means for setting a threshold based on the periodic change in the torque calculated by the calculation means, and the seating of the object to be fastened is detected based on the change in the torque measured by the measuring means and the threshold set by the setting means.

5. A nut runner control system characterized by comprising: control means for controlling a nut runner that fastens a self-locking nut to an object to be fastened; measuring means for measuring the torque applied to the fastening; and detection means for detecting the seating of the object to be fastened based on the amount of change in torque measured by the measuring means.

6. The nut runner according to claim 1, characterized in that the detection means determines whether or not there is an abnormality in the tightening of the self-locking nut based on the amount of change in torque measured by the measuring means.

7. The nut runner according to claim 1, characterized in that the detection means determines whether or not there is an abnormality in the tightening of the self-locking nut based on the range in which the torque measured by the measuring means is greater than or equal to a set value.

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