JP2019113365A - Axial force measuring device - Google Patents

Abstract

To provide an axial force measuring device with which it is possible to ensure that the position of a probe relative to the tip of a bolt shank or the position of a probe relative to the bolt head is hardly misaligned and thereby measure the axial force of the bolt accurately.SOLUTION: An axial force measuring device 100 comprises: a probe 10 arranged at the tip of a bolt shank 20, for transmitting/receiving an ultrasonic wave to and from the bolt shank 20; a magnet unit 11 holding the probe 10 in a hollow space and fixed to the bolt shank 20 by magnetic forces; an urging member 12 for pressing the probe 10 against the tip of the bolt shank 20; and a tubular probe holder 13 for accommodating the probe 10, the magnetic unit 11, and the urging member 12, with at least a portion of the bolt shank 20 inserted therein. The probe 10 adds an ultrasonic wave to the bolt shank 20 before and after a nut 21 for the bolt shank 20 is tightened.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an axial force measuring device that measures an axial force of a bolt.

  Conventionally, as an example of a method of measuring an axial force (clamping force) of a bolt, one using ultrasonic waves is known (see, for example, Patent Documents 1 and 2). These methods relate the axial force of the bolt to the axial elongation of the bolt. Specifically, when the bolt is tightened, the bolt extends in its axial direction. Before and after tightening, depending on the amount of elongation (amount of change), until the ultrasonic wave transmitted from the ultrasonic sensor (probe) bends the tip of the bolt shank from the bolt head and returns to the probe again Time is different. That is, a difference in time of the ultrasonic reciprocation time occurs before and after tightening. The axial force is calculated by a known calculation formula using this time difference.

JP-A-2-152734 JP, 2006-167815, A

  By the way, for weight reduction or resource saving, a bolt (deep recess bolt) having an uneven surface on the top surface of the bolt head is produced. In particular, the head of the bolt used outdoors is uneven due to the hot-dip galvanization being applied to the surface in order to prevent corrosion. However, when measuring the axial force of such a bolt by the above-mentioned method, the position of the probe relative to the bolt head is easily displaced, so that it becomes difficult for the ultrasonic wave to be transmitted to the bolt head and Then, the round trip time of the ultrasonic wave changes. As a result, it becomes difficult to measure the axial force of the bolt accurately. Also, when measuring from the tip of the shaft, as in the stud terminal block, the tip of the shaft has irregularities, and the probe can not be installed perpendicularly to the bolt axis, so the axial force of the bolt can be measured accurately It has become difficult.

  On the other hand, there is also a solution in which the bolt head or shaft tip is machined into a planar shape in order to bring the probe into close contact with the bolt head or shaft tip, but such machining takes time and effort At the same time, the height of the bolt head or shaft tip is reduced by cutting, which may cause problems such as the inability to secure the tightening tool (socket socket) allowance, which may make the tightening operation difficult. there were.

  Therefore, the present invention is an axial force measuring device capable of accurately measuring the axial force of a bolt by making it difficult to shift the position of the probe relative to the tip of the bolt shank or the position of the probe relative to the bolt head. Intended to provide.

(1) The axial force measuring device according to the present invention is an axial force measuring device for measuring the axial force of a bolt, which is connected to a cable and disposed at the tip of the shaft portion of the bolt and for the bolt A probe for transmitting and receiving ultrasonic waves, a magnet unit for holding the probe in a hollow space and fixed to the shaft of the bolt by magnetic force, and a probe for the tip of the shaft of the bolt The probe comprises: a biasing member to be pressed; and a tubular probe holder into which at least a part of the shaft portion of the bolt is inserted and which stores the probe, the magnet portion, and the biasing member. The blade is configured to apply the ultrasonic wave to the tip of the shaft portion of the bolt before and after tightening of the nut to the bolt.

  According to the configuration of the above (1), the magnet unit for holding the probe disposed at the tip of the bolt shaft is fixed to the tip of the bolt shaft by magnetic force. By this, it becomes difficult to shift the position of the probe with respect to the tip of the bolt shank. Further, the probe is pressed against the tip end of the bolt shaft by the biasing member, so that the contact of the probe with the tip end of the bolt shaft becomes good. Furthermore, since at least a part of the bolt shaft is inserted into the probe holder that accommodates the probe, centering of the probe with respect to the bolt shaft can be facilitated, and The feeler can be prevented from tilting. As a result, the position of the probe relative to the tip end of the bolt shaft portion is unlikely to be displaced and stabilized, so that measurement errors are less likely to occur. In such a configuration, when ultrasonic waves are applied to the tip of the bolt shank before and after tightening of the nut on the bolt, the axial force of the bolt is accurately measured by the effect of the goodness of the contact of the probe. Can.

(2) The axial force measuring device of the above (1) has a pressing shaft portion disposed in the probe holder and a pressing head engaged with an edge of one end of the probe holder. The presser bolt may further be provided, and the presser shaft portion of the presser bolt may be arranged to press the biasing member toward the probe.

  According to the structure of said (2), a probe can be pressed on the front-end | tip of a bolt axial part by simple structure.

(3) In the axial force measuring device according to (1) or (2), the outer diameter of the probe holder is preferably smaller than the outer diameter of the nut.

  According to the configuration of the above (3), the probe holder can be inserted through the hole of the socket (tightening tool of the nut) of the wrench when the nut is tightened to the bolt. It does not interfere.

(4) The axial force measuring device according to the present invention is an axial force measuring device for measuring the axial force of a bolt, which is connected to a cable and disposed at the head of the bolt and also with respect to the bolt A probe that transmits and receives the probe, a magnet unit that holds the probe in a hollow space and that is fixed to the head of the bolt by magnetic force, and an urging member that presses the probe against the head of the bolt And a rotary connector functioning as a joint between the cable and the probe, and disposed on the head of the bolt to accommodate the probe, the magnet unit, the biasing member, and the rotary connector. A tubular probe holder, wherein the probe is configured to apply the ultrasonic wave to the head of the bolt before and after tightening the head of the bolt against a nut is there.

  According to the configuration of the above (4), the magnet unit holding the probe disposed on the bolt head is fixed to the bolt head by the magnetic force. By this, it becomes difficult to shift the position of the probe relative to the bolt head. Further, the probe is pressed against the bolt head by the biasing member, so that the probe contacts the bolt head well. As a result, the position of the probe with respect to the bolt head is unlikely to be displaced and stabilized, so that measurement errors are less likely to occur. In such a configuration, when ultrasonic waves are applied to the bolt head before and after the bolt is tightened on the nut, the axial force of the bolt can be accurately measured by the effect of the goodness of the contact of the probe. it can. Furthermore, by adopting the above-mentioned rotary connector, when the probe is rotated at the time of tightening the bolt, the cable on the upstream side of the rotary connector is not twisted due to the above-mentioned rotation.

(5) In the axial force measuring device according to (4), the outer diameter of the probe holder is preferably smaller than the outer diameter of the head of the bolt.

  According to the configuration of the above (5), the probe holder can be inserted into the hole of the socket of the wrench when the bolt is tightened on the nut, so the probe holder does not interfere with the socket.

  According to the present invention, an axial force measuring device capable of accurately measuring the axial force of a bolt by making it difficult to shift the position of the probe relative to the tip of the bolt shank or the position of the probe relative to the bolt head Can be provided.

It is a sectional view showing an axial force measuring device concerning a 1st embodiment of the present invention. It is a sectional view showing an axial force measuring device concerning a 2nd embodiment of the present invention.

  Hereinafter, an axial force measuring device according to an embodiment of the present invention will be described with reference to the drawings.

First Embodiment
As shown in FIG. 1, an axial force measuring apparatus 100 according to the present embodiment includes a probe (probe) 10 which is an ultrasonic sensor, a magnet unit 11, an urging member 12 such as a coil spring, and a tubular A probe holder 13 is provided.

  At least one portion of the bolt shaft portion 20 is inserted into one end (lower end) of the probe holder 13. Therefore, although the inner diameter of the probe holder 13 is set larger than the outer diameter of the bolt shaft portion 20 (the outer diameter of the thread), in order to suppress the inclination of the probe holder 13, the above inner diameter and the above The difference from the outer diameter is small to such an extent that it is difficult to insert the bolt shaft 20 into the probe holder 13. The outer diameter of the probe holder 13 is set smaller than the outer diameter of the nut 21.

  In the state where the bolt shaft portion 20 is inserted into one end of the probe holder 13 as described above, the probe 10, the magnet portion 11 and the biasing member 12 are accommodated in the probe holder 13 There is. The probe 10 is connected to one end of the cable 14 and disposed at the tip of the bolt shank 20. Then, the probe 10 transmits and receives ultrasonic waves to the tip of the bolt shaft 20. The other end of the cable 14 is connected to an ultrasonic measuring instrument main body (not shown).

  The magnet unit 11 is formed in a hollow shape, and holds the probe 10 in the hollow space. In this case, the lower surface of the magnet unit 11 and the lower surface of the probe 10 are substantially flush. Further, the magnet unit 11 in a state of holding the probe 10 is fixed to the tip of the bolt shaft 20 by a magnetic force. This improves the contact of the lower surface of the probe 10 with the tip of the bolt shaft 20.

  A holding bolt 15 is inserted into the other end of the probe holder 13. The presser bolt 15 has a presser shaft portion 17 disposed in the probe holder 13 and a presser head 16 engaged with an edge of the other end of the probe holder 13. An insertion hole (not shown) is formed in the axial center of the presser bolt 15, and the cable 14 is inserted through the insertion hole.

  The biasing member 12 is disposed between the pressing shaft 17 of the pressing bolt 15 and the probe 10. The probe 10 is pressed toward the bolt shaft portion 20 by the biasing member 12 being pressed downward by the pressing shaft portion 17. This further improves the contact of the probe 10 with the tip of the bolt shaft 20. The vicinity of the distal end portion of the cable 14 is disposed in the biasing member 12 so as to be inserted in the axial direction of the biasing member 12.

  In such a configuration, before the nut 21 is first tightened on the bolt shaft 20, the ultrasonic reciprocation time (the ultrasonic wave applied by the probe 10 passes from the tip of the bolt shaft 20 to the bolt head The time until it returns to the probe 10 again by turning back (abbreviated in FIG. 1) is measured.

  Next, after tightening the nut 21 on the bolt shaft portion 20, the reciprocation time of the ultrasonic wave by the probe 10 is measured in the same manner as described above. Specifically, in a state in which the probe holder 13 in the state of FIG. 1 is inserted into the hole of the socket of the wrench as a tightening tool, after tightening the nut 21 by the socket, the probe 10 The ultrasonic wave is applied to the bolt shaft 20 by the above to measure the reciprocating time of the ultrasonic wave. In addition, since the bolt shaft portion 20 is stretched after tightening, the reciprocation time of the ultrasonic wave after tightening is longer than the reciprocation time of the ultrasonic wave before the tightening.

  The axial force of the bolt is calculated by a known calculation formula. Specifically, assuming that the time difference between the reciprocation time before tightening and the reciprocation time after tightening is Δt, the axial force F is given by F = Δt × V × A × E / (2 × K × L) It is calculated. In the above equation, V is the speed of sound, A is the effective cross-sectional area of the bolt, E is the Young's modulus of the bolt, K is the material constant of the bolt, and L is the length of the bolt.

  As described above, according to the axial force measuring device 100 according to the present embodiment, the magnet unit 11 holding the probe 10 disposed at the tip of the bolt shaft 20 is fixed to the tip of the bolt shaft 20 by magnetic force. Be done. As a result, the position of the probe 10 with respect to the tip of the bolt shaft portion 20 is less likely to shift. Further, when the probe 10 is pressed against the tip of the bolt shaft 20 by the biasing member 12, the contact of the probe 10 with the tip of the bolt shaft 20 is improved. Furthermore, since at least a portion of the bolt shaft portion 20 is inserted into the probe holder 13 that accommodates the probe 10, centering of the probe 10 with respect to the bolt shaft portion 20 can be facilitated and the bolt shaft The probe 10 can be prevented from being inclined with respect to the portion 20. As a result, the position of the probe 10 with respect to the tip of the bolt shaft portion 20 is unlikely to be displaced and stabilized, thereby making it difficult to cause a measurement error. In such a configuration, when an ultrasonic wave is applied to the tip of the bolt shaft 20 before and after tightening of the nut 21 with respect to the bolt shaft 20, the axial force of the bolt is obtained by the effect of the contact of the probe 10 Can be accurately measured.

  Further, in the present embodiment, since the biasing member 12 is pressed toward the probe 10 by the pressing shaft portion 17 of the pressing bolt 15, the tip of the probe 10 at the bolt shaft portion 20 with a simple configuration. Can be pressed.

  Furthermore, in the present embodiment, the outer diameter of the probe holder 13 is set smaller than the outer diameter of the nut 21. As a result, when the nut 21 is tightened on the bolt shaft portion 20, the probe holder 13 can be inserted through the hole of the socket of the wrench (the tightening tool for the nut 21). Do not interfere with

Second Embodiment
Subsequently, an axial force measuring device according to a second embodiment will be described with reference to the drawings. In addition, since the site | part of a code | symbol with the same last 2 digits as said 1st Embodiment is the same as that of what was demonstrated in the said 1st Embodiment except the case shown especially, the description is abbreviate | omitted.

  As shown in FIG. 2, the axial force measuring device 200 according to the present embodiment includes a probe 110, a magnet unit 111, an urging member 112 such as a coil spring, and a tubular probe holder 113. There is.

  One end (lower end) of the probe holder 113 is disposed on the bolt head 122. The outer diameter of the probe holder 113 is smaller than the outer diameter of the bolt head 122. The probe 110, the magnet unit 111, the biasing member 112, and the rotary connector 30 are accommodated in the probe holder 113.

  The magnet unit 111 holding the probe 110 is fixed on the bolt head 122 by magnetic force. This improves the contact of the probe 110 with the bolt head 122.

  The probe 110 is connected to one end of the cable 114 and disposed on the bolt head 122. The probe 110 transmits and receives ultrasonic waves to and from the bolt head 122. On the other hand, the other end of the cable 114 is connected to a rotary connector 30 provided on the outer peripheral surface of the pressing shaft 117 so as to be rotatable with respect to the pressing shaft 117 described later.

  A holding bolt 115 is inserted into the other end of the probe holder 113. The presser bolt 115 has a presser shaft portion 117 disposed in the probe holder 113 and a presser head 116 engaged with an edge of the other end of the probe holder 113. An insertion hole (not shown) is formed in the axial center of the presser bolt 115, and the cable 114a is inserted through the insertion hole. One end of the cable 114 a is electrically connected to the cable 114 in the rotary connector 30. That is, the rotary connector 30 functions as a joint between the probe 110 to which the cable 114 is connected and the cable 114a. The other end of the cable 114a is connected to an ultrasonic measuring instrument main body (not shown).

  The biasing member 112 is disposed between the pressing shaft portion 117 of the pressing bolt 115 and the probe 110. The probe 110 is pressed toward the bolt head 122 by the biasing member 112 being pressed downward by the pressing shaft portion 117. This further improves the contact of the probe 110 with the bolt head 122. The cable 114 is disposed in a state of being inserted into the biasing member 112.

  In such a configuration, as in the first embodiment described above, first, the ultrasonic reciprocation time is measured before the bolt head 122 is tightened on the nut (not shown). Next, after tightening the bolt head 122 to the nut, the ultrasonic reciprocation time is measured in the same manner. Specifically, in a state in which the probe holder 113 in the state of FIG. 2 is inserted into the hole of the socket of the wrench as a tightening tool, the bolt head 122 is tightened by the socket, and then the probe is detected. The ultrasonic waves are applied by the element 110 to measure the reciprocating time of the ultrasonic waves.

  As described above, in the axial force measuring device 200 according to the present embodiment, the magnet unit 111 holding the probe 110 disposed on the bolt head 122 is fixed on the bolt head 122 by magnetic force. As a result, the position of the probe 110 relative to the bolt head 122 is less likely to shift. Further, when the probe 110 is pressed against the bolt head 122 by the biasing member 112, the contact of the probe 110 with the bolt head 122 is improved. As a result, the position of the probe 110 with respect to the bolt head 122 is unlikely to be displaced and stabilized, so that measurement errors are less likely to occur. In such a configuration, when ultrasonic waves are applied to the bolt head 122 before and after the bolt head 122 is tightened, the effect of the goodness of the contact of the probe 110 accurately measures the axial force of the bolt. can do. Furthermore, by adopting the above-mentioned rotary connector 30, when the probe 110 rotates when the bolt head 122 is tightened, the cable 114a on the upstream side of the rotary connector 30 is twisted due to this rotation. I have not.

  Further, in the present embodiment, the outer diameter of the probe holder 113 is set smaller than the outer diameter of the bolt head 122. Thus, the probe holder 113 can be inserted through the hole of the socket of the wrench when the bolt head 122 is tightened on the nut, so the probe holder 113 does not interfere with the socket.

  As mentioned above, although embodiment of this invention was described based on drawing, it should be thought that a specific structure is not limited to these embodiment. The scope of the present invention is indicated not by the description of the embodiments described above but by the claims, and further includes all modifications within the meaning and scope equivalent to the claims.

  In the above embodiment, a coil spring is adopted as an example of the urging members 12 and 112. However, the invention is not limited to this. For example, another urging member such as a cushion material may be adopted.

  Further, in order to apply the biasing force of the biasing members 12 and 112 to the probes 10 and 110 more uniformly, the biasing members 12 and 112 may be accommodated in the cylindrical body. As a result, since the inclination and twist of the biasing members 12 and 112 are prevented, the biasing force is uniformly transmitted to the probes 10 and 110. As a result, the measurement surface of the probe 10 can be brought into close contact with the tip end of the bolt shaft 20 more uniformly, and the measurement surface of the probe 110 can be brought into contact with the bolt head 122 more uniformly. .

10, 110 Probe 11, 111 Magnet 12, 112 Biasing member 13, 113 Probe holder 14, 114, 114 a Cable 15, 115 Holding bolt 16, 116 Holding head 17, 117 Holding shaft 20, 120 Bolt shaft 21 Nut 30 Rotary connector 100, 200 Axial force measuring device 122 Bolt head

Claims (5)

An axial force measuring device for measuring the axial force of a bolt,
A probe connected to a cable, disposed at the tip of the shank of the bolt and transmitting and receiving ultrasonic waves to the bolt;
A magnet unit which holds the probe in a hollow space and is fixed to the shaft of the bolt by magnetic force;
A biasing member that presses the probe against the tip of the shaft of the bolt;
A tubular probe holder into which at least a part of the shaft portion of the bolt is inserted and which accommodates the probe, the magnet portion, and the biasing member;
The axial force measuring device is characterized in that the probe is configured to apply the ultrasonic wave to the tip of the shaft portion of the bolt before and after tightening of the nut on the bolt. It further comprises a pressing bolt having a pressing shaft portion disposed in the probe holder and a pressing head engaged with an edge of one end of the probe holder,
The axial force measuring device according to claim 1, wherein the pressing shaft portion of the pressing bolt is disposed to press the biasing member toward the probe.   The axial force measuring device according to claim 1, wherein an outer diameter of the probe holder is smaller than an outer diameter of the nut. An axial force measuring device for measuring the axial force of a bolt,
A probe connected to a cable, disposed at the head of the bolt and transmitting and receiving ultrasonic waves to the bolt;
A magnet unit which holds the probe in a hollow space and is fixed to the head of the bolt by magnetic force;
A biasing member for pressing the probe against the head of the bolt;
A rotary connector that functions as a joint between the cable and the probe;
A tubular probe holder disposed on the head of the bolt and accommodating the probe, the magnet unit, the biasing member, and the rotary connector;
The axial force measuring device is characterized in that the probe is configured to apply the ultrasonic wave to the head of the bolt before and after tightening of the head of the bolt with respect to a nut.   The axial force measuring device according to claim 4, wherein the outer diameter of the probe holder is smaller than the outer diameter of the head of the bolt.

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