Test device for bolt axial force measurement and loosening dectection and the controlling method thereof

Abstract

A test device for measuring bolt axial force and detecting loosening is disclosed. The test device for measuring bolt axial force and detecting loosening includes a fastening jig on which a bolt is fastened, an exciter for applying vibration to the fastening jig, a load cell for measuring the axial force of the fastened bolt while vibration is applied by the exciter, a laser Doppler vibrometer for detecting whether the fastened bolt rotates while vibration is applied by the exciter, a display for displaying information regarding the measured axial force and the detected rotation, and a processor that converts the output voltage of the load cell into a load to calculate the change in axial force of the fastened bolt while vibration is applied, and calculates whether the fastened bolt rotates based on the output signal of the laser Doppler vibrometer. Accordingly, it is possible to quantitatively confirm the trend of change in the bolt's axial force and to easily identify the point of bolt loosening through monitoring using the laser Doppler vibrometer, thereby enabling precise measurement of the bolt's axial force and verification of loosening.

Description

Technology Field

[0001] The present invention relates to a test device for measuring bolt axial force and detecting loosening, and a control method thereof. More specifically, it relates to a test device and a control method thereof that perform bolt axial force measurement and loosening detection using a load cell and a laser Doppler vibrator. Background Technology

[0002] In drive devices that drive mechanical products, such as automobile engines, high-speed repetitive loads occur, and due to these repetitive loads, there is a risk that a nut may loosen at the nut fastening part of the drive device, thereby threatening safety.

[0003] For example, in the case of a vehicle equipped with a common rail engine system, irregular repeated vibrations can cause the nut connecting the common rail and the fuel injection pipe to loosen, which poses a risk of leakage, loss, and explosion of fuel compressed to a pressure of 2000 bar.

[0004] Therefore, it is necessary to ensure the reliability of nut loosening in structures by performing vibration tests under harsh conditions to predict and evaluate nut loosening.

[0005] Japanese Patent Publication No. JP 2002-367492 (published on December 20, 2002) describes a method for evaluating bolt loosening in a bolt fastening part of a power circuit breaker. The bolt loosening evaluation method described in this patent publication is characterized by detecting vibration of the bolt fastening part by exciting the casing of the circuit breaker and obtaining a resonance frequency, then calculating the difference from the resonance frequency when there is no loosening of the bolt, and diagnosing that the bolt fastening part is loose if the difference exceeds a predetermined value.

[0006] However, such conventional bolt loosening evaluation methods have the disadvantage of low reliability due to low evaluation accuracy.

[0007] In addition, Korean Registered Patent Publication No. 10-1450253 is characterized by calculating the average axial stress of a bolt before excitation using an exciter, calculating the average axial stress of a bolt after excitation, comparing the average axial stress before excitation with the average axial stress after excitation, and determining that there is no nut loosening if the ratio is greater than or equal to a set ratio.

[0008] However, this method of determining whether loosening has occurred based solely on axial force has a problem in that it is only possible to determine exactly when loosening began and after the loosening phenomenon has occurred.

[0009] Accordingly, there has been an increased need for technology that determines the point of bolt loosening not only during changes in axial force but also during testing. The problem to be solved

[0010] The objective of the present invention is to provide a test device and a control method thereof that perform bolt axial force measurement and loosening detection using a load cell and a laser Doppler vibrator. means of solving the problem

[0011] A test device for measuring bolt axial force and detecting loosening according to one embodiment of the present invention for achieving the above purpose comprises: a fastening jig on which a bolt is fastened; an exciter for applying vibration to the fastening jig; a load cell for measuring the axial force of the fastened bolt while vibration is applied by the exciter; a laser Doppler vibrometer for detecting whether the fastened bolt rotates while vibration is applied by the exciter; a display for displaying information regarding the measured axial force and the detected rotation; and a processor for converting the output voltage of the load cell into a load to calculate the change in the axial force of the fastened bolt while vibration is applied, and for calculating whether the fastened bolt rotates based on the output signal of the laser Doppler vibrometer.

[0012] Here, the processor can convert the output voltage of the load cell into weight based on the output voltage of the load cell, and convert the converted weight into a load over time to calculate the change in axial force of the fastened bolt.

[0013] Additionally, the processor detects a vibration signal by converting the frequency change of the reflected laser into a voltage when the laser generated by the laser Doppler vibratory system is reflected by a reflective tape attached to the upper surface of the head of the fastened bolt, and can calculate that the fastened bolt has rotated if the vibration signal is not detected or weakens.

[0014] In addition, the processor can determine the point in time when the fastened bolt begins to rotate based on the interval in which the vibration signal is not detected or the interval in which the vibration signal weakens.

[0015] Meanwhile, a control method for a test device for measuring bolt axial force and detecting loosening according to one embodiment of the present invention includes the steps of applying vibration to a fastening jig on which a bolt is fastened, converting the output voltage of a load cell into a load to calculate the change in axial force of the fastened bolt while the vibration is applied, calculating whether the fastened bolt rotates based on the output signal of a laser Doppler vibrator, and displaying information regarding the change in axial force and whether the fastened bolt rotates.

[0016] Here, the step of calculating the change in axial force of the fastened bolt can calculate the change in axial force of the fastened bolt by converting the output voltage of the load cell into weight based on the output voltage of the load cell and converting the converted weight into a load over time.

[0017] In addition, the step of calculating whether the fastened bolt is rotated involves detecting a vibration signal by converting the frequency change of the reflected laser into a voltage when the laser generated by the laser Doppler vibratory system is reflected by a reflective tape attached to the upper surface of the head of the fastened bolt, and if the vibration signal is not detected or weakens, it can be calculated that the fastened bolt is rotated.

[0018] In addition, the step of calculating whether the fastened bolt rotates may determine the point in time when the fastened bolt begins to rotate based on the interval in which the vibration signal is not detected or the interval in which the vibration signal weakens. Effects of the invention

[0019] According to various embodiments of the present invention as described above, it is possible to quantitatively verify the trend of change in the axial force of a bolt and to easily identify the point of bolt loosening through monitoring using a laser Doppler vibrator, thereby enabling precise measurement of the axial force of a bolt and verification of loosening. Brief explanation of the drawing

[0020] FIG. 1 is a diagram illustrating the configuration of a test device for detecting bolt axial force and loosening according to one embodiment of the present invention. FIG. 2 is a diagram illustrating the process of calculating the change in axial force of a bolt according to one embodiment of the present invention. FIG. 3 is a drawing for explaining the process of calculating whether a bolt rotates according to an embodiment of the present invention. FIG. 4 is a flowchart illustrating a control method for a test device for measuring bolt axial force and detecting loosening according to an embodiment of the present invention. FIG. 5 is a block diagram showing the specific configuration of a test device for detecting bolt axial force and loosening as illustrated in FIG. 1. FIG. 6 is a drawing relating to a software module stored in a storage unit according to an embodiment of the present invention. Specific details for implementing the invention

[0021] The present invention will be described in more detail below with reference to the drawings. Furthermore, in describing the present invention, detailed descriptions of related known functions or configurations are omitted if it is determined that such detailed descriptions would unnecessarily obscure the essence of the invention. Additionally, the terms described below are defined considering their functions in the present invention, and these may vary depending on the intentions or relationships of the user or operator. Therefore, their definitions should be based on the content throughout this specification.

[0022] FIG. 1 is a diagram illustrating the configuration of a test device for detecting bolt axial force and loosening according to one embodiment of the present invention.

[0023] Referring to FIG. 1, a test device (100) for detecting bolt axial force and loosening according to one embodiment of the present invention includes a fastening jig (110), an exciter (120), a load cell (130), a laser Doppler vibrator (140), a display (150), and a processor (160).

[0024] Here, the fastening jig (110) is a plate provided with a hole into which at least one bolt can be fastened, and aluminum, which has high rigidity relative to its density, is often used as the material. In addition, the natural frequency of the fastening jig (110) must be designed to be higher than the excitation frequency.

[0025] And, the exciter (120) applies vibration to the fastening jig (110), and the vibration at this time can be sinusoidal vibration, random vibration, or complex vibration, etc.

[0026] Additionally, the load cell (130) can measure the axial force of the bolt fastened to the fastening jig (110) while vibration is applied by the exciter (120). Here, when a force is applied, the load cell converts the force into an electrical signal and displays the load as a number. In the present invention, a ring-type load cell can be mainly used, and such a ring-type load cell can be fastened to fit into a hole provided in the fastening jig (110).

[0027] Here, the axial force of the bolt refers to the axial force of the bolt that attempts to maintain the fastening force with the hole of the fastening jig (110), and the load cell (130) can measure this axial force of the fastened bolt.

[0028] And, the laser Doppler vibrator (140) can detect whether the bolt fastened to the fastening jig (110) rotates while vibration is applied by the exciter (120).

[0029] Specifically, the laser reflected from a moving object is affected by a frequency change proportional to the object's speed, and the laser Doppler vibrometer (140) can accurately determine the vibrational motion of the moving object by measuring this frequency change.

[0030] Accordingly, the laser Doppler vibratory system (140) can quantitatively determine whether the bolt is rotating based on the frequency variation of the laser reflected by the moving bolt. A detailed explanation of this will be provided later.

[0031] And, the display (150) can display information regarding the measured axial force and the detected rotation as a graph.

[0032] Meanwhile, the processor (160) can convert the output voltage of the load cell (130) into a load to calculate the change in axial force of the fastened bolt while vibration is applied, and calculate whether the fastened bolt rotates based on the output signal of the laser Doppler vibration meter (140).

[0033] Specifically, the processor (160) can convert the output voltage of the load cell (130) into weight and convert the converted weight into a load over time to calculate the change in axial force of the fastened bolt.

[0034] FIG. 2 is a diagram illustrating the process of calculating the change in axial force of a bolt according to one embodiment of the present invention.

[0035] Referring to FIG. 2, the processor (160) can convert the output voltage of the load cell (130) into weight by applying it to the voltage-weight graph shown on the left, and convert the converted weight into a load in N units over time as shown in the graph on the right to calculate the change in axial force of the fastened bolt.

[0036] Accordingly, the processor (160) can determine that the axial force of the fastened bolt is constant if the graph having a constant amplitude continues based on the calculated change in the axial force of the bolt, and can determine that the fastening force is lowered if the amplitude decreases, assuming that the axial force of the fastened bolt has weakened.

[0037] Meanwhile, the processor (160) detects a vibration signal by converting the frequency change of the reflected laser into a voltage when the laser generated by the laser Doppler vibrator (140) is reflected by the reflective tape attached to the upper surface of the head of the fastened bolt, and can calculate that the fastened bolt has rotated if the vibration signal is not detected or weakens.

[0038] FIG. 3 is a drawing for explaining the process of calculating whether a bolt rotates according to an embodiment of the present invention.

[0039] Referring to FIG. 3, the drawing on the left shows a vibration signal detected by a laser Doppler vibrator (140) for a bolt before rotation.

[0040] Specifically, a reflective tape (310) is attached to the upper surface of a bolt (320) fastened to a fastening jig (110), and a laser generated by a laser Doppler vibrator (140) is fired at the reflective tape (310).

[0041] And, the fastened bolt (320) is subjected to vibration in the up-and-down direction (330) by the exciter (120), and accordingly, when the laser generated by the laser Doppler vibrator (130) is reflected by the reflective tape (310) vibrating in the up-and-down direction (330), the frequency of the reflected laser is bound to change continuously due to this vibration, and the laser Doppler vibrator (130) can detect the vibration signal (340) by converting the change in the frequency of the reflected laser into a voltage.

[0042] The vibration signal (340) shown on the left displays a vibration signal graph when the fastened bolt (320) is not rotated while vibrating in the up-and-down direction (330).

[0043] Meanwhile, the drawing on the right shows a vibration signal detected through a laser Doppler vibrator (140) for a bolt after rotation.

[0044] Specifically, the reflective tape (310) attached to the upper surface of the bolt (320) fastened to the fastening jig (110) is rotated about 90 degrees counterclockwise by the rotation of the bolt (320), and the laser generated by the laser Doppler vibrator (130) no longer reaches the reflective tape (310), so the reflection of the laser cannot occur properly, and thus the section (350) where the signal is lost among the vibration signals (340) may be displayed or the signal may be displayed weakly.

[0045] That is, the section (350) where the signal is lost among the vibration signals (340) shown on the right displays a vibration signal graph when the bolt (320) is rotated while vibrating in the up-and-down direction (330), and in this drawing, it is indicated that the signal is lost.

[0046] Accordingly, the processor (160) can calculate that the fastened bolt (320) is rotated when the vibration signal (340) is not detected or weakens.

[0047] Meanwhile, the processor (160) can determine the point at which the fastened bolt begins to rotate based on the interval where the vibration signal is not detected or the interval where the vibration signal weakens.

[0048] Specifically, referring to FIG. 3, the processor (160) can determine that the time at which the section (350) where no vibration signal is detected begins in the vibration signal graph (340) shown on the right is the time at which the fastened bolt (320) begins to rotate.

[0049] Additionally, the processor (160) can determine that even in the case of a section where the vibration signal weakens, the time at the point where it weakens is the time when the bolt (320) connected starts to rotate.

[0050] FIG. 4 is a flowchart illustrating a control method for a test device for measuring bolt axial force and detecting loosening according to an embodiment of the present invention.

[0051] Referring to FIG. 4, a control method for a test device for measuring bolt axial force and detecting loosening according to one embodiment of the present invention includes the steps of: applying vibration to a fastening jig on which a bolt is fastened (S410); converting the output voltage of a load cell into a load to calculate the change in axial force of the fastened bolt while vibration is applied (S420); calculating whether the fastened bolt rotates based on the output signal of a laser Doppler vibrator (S430); and displaying information regarding the change in axial force and whether the fastened bolt rotates (S440).

[0052] Here, the step (S420) of calculating the change in axial force of the fastened bolt can calculate the change in axial force of the fastened bolt by converting the output voltage of the load cell into weight and converting the converted weight into a load over time.

[0053] Additionally, the step (S430) of calculating whether the fastened bolt is rotated involves detecting a vibration signal by converting the frequency change of the reflected laser into a voltage when the laser generated by the laser Doppler vibratory system is reflected by a reflective tape attached to the upper surface of the head of the fastened bolt, and if the vibration signal is not detected or weakens, it can be calculated that the fastened bolt is rotated.

[0054] Additionally, the step of calculating whether the fastened bolt rotates (S440) can determine the point at which the fastened bolt begins to rotate based on a section where no vibration signal is detected or a section where the vibration signal weakens.

[0055] FIG. 5 is a block diagram showing the specific configuration of a test device for detecting bolt axial force and loosening as illustrated in FIG. 1.

[0056] Referring to FIG. 5, a test device (100) for measuring bolt axial force and detecting loosening includes a fastening jig (110), an exciter (120), a load cell (130), a laser Doppler vibrator (140), a display (150), a processor (160), and a storage unit (170).

[0057] The processor (160) controls the overall operation of the test device (100) for measuring bolt axial force and detecting loosening.

[0058] Specifically, the processor (160) includes RAM (161), ROM (162), main CPU (163), graphics processing unit (164), first to n interfaces (165-1 to 165-n), and a bus (166).

[0059] RAM (161), ROM (162), main CPU (163), graphics processing unit (164), first to n interfaces (165-1 to 165-n), etc. can be connected to each other via a bus (166).

[0060] The first to n interfaces (165-1 to 165-n) are connected to the various components described above. One of the interfaces may be a network interface connected to an external device through a network.

[0061] The main CPU (163) accesses the storage unit (170) and performs booting using the O / S stored in the storage unit (170). Then, it performs various operations using various programs, content, data, etc. stored in the storage unit (170).

[0062] In particular, the main CPU (163) can convert the output voltage of the load cell into a load to calculate the change in axial force of the fastened bolt while vibration is applied, and calculate whether the fastened bolt rotates based on the output signal of the laser Doppler vibrator.

[0063] A set of instructions for booting the system is stored in the ROM (162). When a turn-on command is input and power is supplied, the main CPU (163) copies the O / S stored in the storage unit (170) to the RAM (161) according to the instructions stored in the ROM (162), and executes the O / S to boot the system. When booting is complete, the main CPU (163) copies various application programs stored in the storage unit (170) to the RAM (161), and executes the application programs copied to the RAM (161) to perform various operations.

[0064] The graphics processing unit (164) generates a screen containing various objects such as icons, images, and text using a calculation unit (not shown) and a rendering unit (not shown). The calculation unit (not shown) calculates attribute values ​​such as coordinate values, shape, size, and color for each object to be displayed according to the layout of the screen based on a received control command. The rendering unit (not shown) generates a screen of various layouts containing objects based on the attribute values ​​calculated by the calculation unit (not shown).

[0065] In particular, the graphics processing unit (164) can implement objects generated by the main CPU (163) into a GUI (Graphic User Interface), icons, user interface screens, etc.

[0066] Meanwhile, the operation of the above-described processor (160) can be performed by a program stored in the storage unit (170).

[0067] The storage unit (170) stores various data, such as an O / S (Operating System) software module for operating a test device (100) for measuring bolt axial force and detecting loosening, and various multimedia content.

[0068] In particular, the storage unit (170) may include a software module for converting the output voltage of the load cell into a load to calculate the change in axial force of the fastened bolt while vibration is applied, and for calculating whether the fastened bolt rotates based on the output signal of the laser Doppler vibrator.

[0069] FIG. 6 is a drawing relating to a software module stored in a storage unit according to an embodiment of the present invention.

[0070] Referring to FIG. 6, the storage unit (170) may store programs such as an axial force change calculation module (171), a rotation whether calculation module (172), and a rotation timing determination module (173).

[0071] Meanwhile, the operation of the processor (160) described above can be performed by a program stored in the storage unit (170). Below, the detailed operation of the processor (160) using the program stored in the storage unit (170) will be explained in detail.

[0072] Specifically, the axial force change calculation module (171) can calculate the change in axial force of the fastened bolt by converting the output voltage of the load cell (110) into weight and converting the converted weight into a load over time.

[0073] Additionally, the rotation determination module (172) detects a vibration signal by converting the frequency change of the reflected laser into a voltage when the laser generated by the laser Doppler vibrator (140) is reflected by the reflective tape attached to the upper surface of the head of the fastened bolt, and can determine that the fastened bolt has rotated if the vibration signal is not detected or weakens.

[0074] Additionally, the rotation timing determination module (173) can determine the time at which the fastened bolt begins to rotate based on the interval where the vibration signal is not detected or the interval where the vibration signal weakens.

[0075] Meanwhile, a non-transitory computer-readable medium storing a program that sequentially performs the control method according to the present invention may be provided.

[0076] A non-transient readable medium refers to a medium that stores data semi-permanently and can be read by a device, rather than a medium that stores data for a short period of time, such as a register, cache, or memory. Specifically, the various applications or programs described above may be stored and provided on non-transient readable media such as CDs, DVDs, hard disks, Blu-ray discs, USBs, memory cards, and ROMs.

[0077] In addition, although a bus is not shown in the aforementioned block diagram illustrating a test device for measuring bolt axial force and detecting loosening, communication between each component in the test device for measuring bolt axial force and detecting loosening may be performed via a bus. Furthermore, each device may additionally include a processor, such as a CPU or a microprocessor, that performs the various steps described above.

[0078] Furthermore, although preferred embodiments of the present invention have been illustrated and described above, the present invention is not limited to the specific embodiments described above. It is understood that various modifications can be made by those skilled in the art without departing from the essence of the invention as claimed in the claims, and such modifications should not be understood individually from the technical spirit or perspective of the present invention. Explanation of the symbols

[0079] 100: Test device for measuring bolt axial force and detecting loosening 110: Fastening jig 120: Vibrator 130: Load cell 140: Laser Doppler vibrometer 150: Display 160: Processor 170: Storage section

Claims

Claim 1 A test device for measuring bolt axial force and detecting loosening, comprising: a fastening jig on which a bolt is fastened; an exciter for applying vibration to the fastening jig; a load cell for measuring the axial force of the fastened bolt while vibration is applied by the exciter; a laser Doppler vibrometer for detecting whether the fastened bolt rotates while vibration is applied by the exciter; a display for displaying information regarding the measured axial force and the detected rotation; and a processor for converting the output voltage of the load cell into a load to calculate the change in the axial force of the fastened bolt while vibration is applied, and for calculating whether the fastened bolt rotates based on the output signal of the laser Doppler vibrometer; wherein the processor detects a vibration signal by converting the frequency change of the reflected laser into a voltage when a laser generated by the laser Doppler vibrometer is reflected by a reflective tape attached to the upper surface of the head of the fastened bolt, and calculates that the fastened bolt has rotated when the vibration signal is not detected or weakens. Claim 2 A test device for measuring bolt axial force and detecting loosening, wherein, in claim 1, the processor converts the output voltage of the load cell into a weight based on the output voltage of the load cell, and converts the converted weight into a load over time to calculate the change in axial force of the fastened bolt. Claim 3 delete Claim 4 A test device for measuring bolt axial force and detecting loosening, wherein, in paragraph 2, the processor determines the point in time when the fastened bolt begins to rotate based on a section where the vibration signal is not detected or a section where the vibration signal weakens. Claim 5 A control method for a test device for measuring bolt axial force and detecting loosening, comprising: a step of applying vibration to a fastening jig on which a bolt is fastened; a step of converting the output voltage of a load cell into a load to calculate the change in axial force of the fastened bolt while vibration is applied; a step of calculating whether the fastened bolt is rotated based on the output signal of a laser Doppler vibrator; and a step of displaying information regarding the change in axial force and whether the fastened bolt is rotated; wherein the step of calculating whether the fastened bolt is rotated involves detecting a vibration signal by converting the frequency change of the reflected laser into a voltage when a laser generated by the laser Doppler vibrator is reflected by a reflective tape attached to the upper surface of the head of the fastened bolt, and calculating that the fastened bolt is rotated when the vibration signal is not detected or weakens. Claim 6 In claim 5, the step of calculating the change in axial force of the fastened bolt is to convert the output voltage of the load cell into weight, and to convert the converted weight into a load over time to calculate the change in axial force of the fastened bolt, thereby controlling a test device for measuring bolt axial force and detecting loosening. Claim 7 delete Claim 8 A control method for a test device for measuring bolt axial force and detecting loosening, wherein, in claim 6, the step of calculating whether the fastened bolt rotates is to determine the point in time when the fastened bolt begins to rotate based on a section where the vibration signal is not detected or a section where the vibration signal weakens.

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