JP2023167867A - Axial force detection device - Google Patents

Abstract

To prevent a fastening body from being loose in the time of unloading after axial force detection.SOLUTION: An axial force detection device for detecting axial force of a fastening body fastened to a fastening object body comprises: a connection member which has a first screw part and a second screw part; a tension rod which has a third screw part and pulls the fastening body via the connection member by applying a rotation torque around a rotational shaft extending in the vertical direction to the connection member in such a state that the second screw part is screwed to the third screw part; and a tension reception part which is arranged around the outer periphery of the connection member and receives reaction force acting from the fastening object body in the time of pulling by the tension rod. A feeding amount of the second screw part is greater than a feeding amount of a screw shaft part of the fastening body.SELECTED DRAWING: Figure 1

Description

The present invention relates to an axial force detection device that detects axial force by pulling a fastened body fastened to a fastened body.

BACKGROUND OF THE INVENTION Screws are used to assemble machines such as automobiles and structures such as bridges. The strength of a screw as a fastening body largely depends on the tightening force. On the other hand, management of the fastening force in a bolt fastened body is generally only performed at the time of tightening by measuring the torque and rotation angle, and is rarely performed after tightening. However, if the bolts loosen due to the action of an unexpected external force during machine operation and the tightening force decreases, the risk of fatigue failure increases significantly. Therefore, in order to prevent bolt breakage accidents and improve the reliability of the screw fastened body, it is necessary to pay attention to the detection of the tightening force of the bolt after fastening.

Patent Document 1 discloses a bolt/nut fastening body that compresses a fastened body by inserting a bolt into an insertion hole of the fastened body and screwing and fastening a nut to a male threaded portion of the bolt that passes through the insertion hole. A bolt characterized in that a male threaded portion of the bolt protruding from the upper surface of the nut is pulled against the upper surface of the nut, a transition point of the bolt's spring constant is detected, and the tensile force at the transition point is used as a tightening force. A method for detecting a tightening force of a nut fastening body is disclosed.

Patent No. 4028254

In conventional axial force detection devices, there is a risk that the fastening body may loosen when the load is unloaded after the axial force is detected.

In order to solve the above problems, the axial force detection device according to the present invention is (1) an axial force detection device that detects the axial force of a fastened body fastened to a fastened body, which A connecting member having a threaded portion, and a third threaded portion, wherein a rotational torque about a rotation axis extending in the vertical direction is applied to the connecting member in a state where the second threaded portion is screwed to the third threaded portion. A tension rod that pulls the fastened body through the connecting member; and a tension receiver that is arranged around the outer periphery of the connecting member and receives a reaction force acting from the fastened body when the tension rod pulls the fastened body. , the fastening body or a fastening component used for fastening together with the fastening body has a fourth threaded part that is threadedly engaged with the first threaded part, and the second threaded part and the first threaded part Unloading the connecting member and the tension rod when unloading after threading the threaded parts into the third threaded part and the fourth threaded part and pulling up the fastening body for axial force detection. When the torque is defined as Trl, and the loosening torque of the fastened body with respect to the fastened body is defined as Tsl,
An axial force detection device characterized in that Trl defined by equation (1) is set smaller than Tsl defined by equation (2).
Trl=Ft/2×(d2t/cosαt×μst-Pt/π)...Formula (1)
However, Ft: tensile force of the fastening body, d2t: effective diameter of the second threaded part of the connecting member, αt: half-angle of thread of the second threaded part of the connecting member, μst: thread surface of the second threaded part of the connecting member. Friction coefficient, Pt: is the amount of feed per rotation of the second threaded portion of the connecting member.
Tsl=Fb/2×(d2b/cosαb×μsb-Pb/π)...Formula (2)
However, Fb: axial force of the fastening body, d2b: effective diameter of the threaded shaft of the fastening body, αb: half angle of the thread of the threaded shaft of the fastening body, μsb: coefficient of friction of the threaded surface of the threaded shaft of the fastening body, Pb: Feed amount per rotation of the screw shaft portion of the fastening body.

(2) The tension rod described in (1) above is characterized in that when Trl is positive, the tension rod is rotated by applying an external force during unloading, and when Trl is negative, the tension rod is automatically rotated when unloading. Axial force detection device.

(3) The axial force detection device according to (1) or (2) above, wherein the fastening body is a bolt, and the fastening component is a nut or a washer.

(4) When the fourth threaded portion is formed on the fastening body, the fourth threaded portion includes a side surface of the bolt head, a threaded shaft portion of the bolt, a protruding portion protruding from the top surface of the bolt head, and The axial force detection device according to (3) above, wherein the axial force detection device is formed in any of the recesses of the bolt head.

(5) When the fourth threaded portion is formed on the nut, the fourth threaded portion is formed on a side surface of the nut, the axial force detection device according to (3) above. .

(6) When the fourth threaded portion is formed on the washer, the fourth threaded portion is formed on a side surface of the washer, the axial force detection device according to (3) above. .

(7) An axial force detection device for detecting the axial force of a fastening body fastened to a fastened object, which includes a third threaded portion and is formed on the fastening body or a fastening component used for fastening together with the fastening body. a tension rod that pulls the fastening body by applying a torque around a rotation axis extending in the vertical direction to the fastening body in a state in which the third threaded part is screwed into the second threaded part; After the second threaded part and the third threaded part are screwed together and the fastened body is pulled up for axial force detection, the unloading torque of the fastened body and the tension rod when unloading is Trl, When the loosening torque of the fastened body with respect to the fastened body is defined as Tsl, Trl defined by equation (1) is set smaller than Tsl defined by equation (2). Force detection device.
Trl=Ft/2×(d2t/cosαt×μst-Pt/π)...Formula (1)
However, Ft: tensile force of the fastening body, d2t: effective diameter of the second threaded portion of the fastening body or fastening component, αt: thread half angle of the second threaded portion of the fastening body or fastening component, μst: fastening body or fastening component The coefficient of friction of the threaded surface of the second threaded portion of Pt is the feed amount per rotation of the second threaded portion of the fastening body or fastening component.
Tsl=Fb/2×(d2b/cosαb×μsb-Pb/π)...Formula (2)
However, Fb: axial force of the fastening body, d2b: effective diameter of the threaded shaft of the fastening body, αb: half angle of the thread of the threaded shaft of the fastening body, μsb: coefficient of friction of the threaded surface of the threaded shaft of the fastening body, Pb: Feed amount per rotation of the screw shaft portion of the fastening body.

(8) The tension rod described in (7) above is characterized in that when Trl is positive, the tension rod is rotated by applying an external force during unloading, and when Trl is negative, the tension rod is automatically rotated when unloading. Axial force detection device.

(9) The axial force detection device according to (7) or (8) above, wherein the fastening body is a bolt, and the fastening component is a nut or a washer.

(10) When the second threaded portion is formed on the fastening body, the second threaded portion includes a side surface of the bolt head, a threaded shaft portion of the bolt, a protrusion protruding from the top surface of the bolt head, and The axial force detection device according to (9) above, characterized in that the axial force detection device is formed in any of the recesses of the bolt head.

(11) When the second threaded portion is formed on the nut, the second threaded portion is formed on a side surface of the nut, the axial force detection device according to (9) above. .

(12) When the second threaded portion is formed on the washer, the second threaded portion is formed on a side surface of the washer, the axial force detection device according to (9) above. .

(13) The connecting member and the tension receiver have a rotation prevention mechanism, and the rotation prevention mechanism allows movement of the connection member in the direction of the rotation axis of the tension rod, and the rotation prevention mechanism allows movement of the connection member in the direction of the rotation axis of the tension rod. The axial force detection device according to any one of (1) to (6) above, characterized in that rotation of the connection member around the connection member is prevented.

(14) The rotation prevention mechanism includes a key extending in the vertical direction and a key groove that the key engages with, one of the key and the key groove being formed in the tension receiving part, and the other The axial force detection device according to (13) above, characterized in that the axial force detection device is formed on the connection member.

(15) The rotation prevention mechanism includes a first toothed portion formed on the connecting member, and a second toothed portion formed on the tension receiving portion and meshed with the first toothed portion in a direction around the rotation axis of the tension rod. The axial force detection device according to (13) above, characterized in that it consists of the following.

(16) The tension rod is designed so that when the fastening body is pulled and the axial force is detected, the rotational torque by the tension rod does not exceed the torque that rotates the tension receiver. The axial force detection device according to any one of (13) to (15) above.

(17) The axial force detection device according to (16) above, wherein the ground contact surface of the tension receiving portion is subjected to high friction treatment to increase frictional force.

(18) The above feature, characterized in that the distance from the rotation axis of the tension rod to the tension receiving part is set so that the tension receiving part does not rotate when the fastening body is pulled and the axial force is detected. The axial force detection device according to (16).

(19) An axial force detection device that detects the axial force of a fastening body fastened to a fastened body, comprising a connecting member having a first threaded portion and a second threaded portion, and a third threaded portion, the a tension rod that pulls the fastening body through the connecting member by applying a rotational torque around a rotational axis extending in the vertical direction to the connecting member with the second screw portion screwed into the third screw portion; and a tension receiver disposed around the outer periphery of the connection member to receive a reaction force acting from the object to be fastened when the tension rod is pulled, the connection member and the tension receiver being configured to prevent rotation. The rotation prevention mechanism is characterized in that the rotation prevention mechanism allows movement of the connection member in the direction of the rotation axis of the tension rod and prevents rotation of the connection member around the rotation axis of the tension rod. Axial force detection device.

(20) The rotation prevention mechanism includes a key that extends in the vertical direction and a keyway that the key engages with, one of the key and the keyway being formed in the tension receiving part, and the other including: The axial force detection device according to (19) above, characterized in that the axial force detection device is formed on the connection member.

(21) The rotation prevention mechanism includes a first toothed portion formed on the connecting member, and a second toothed portion formed on the tension receiving portion and meshed with the first toothed portion in a direction around the rotation axis of the tension rod. The axial force detection device according to (19) above, characterized in that it consists of the following.

(22) The tension rod is designed so that when the fastening body is pulled and the axial force is detected, the rotational torque by the tension rod does not exceed the torque that rotates the tension receiver. The axial force detection device according to any one of (19) to (21) above.

(23) The axial force detection device according to (22) above, wherein the ground contact surface of the tension receiving portion is subjected to high friction treatment to increase frictional force.

(24) A distance from the rotational axis of the tension rod to the tension receiving part is set so that the tension receiving part does not rotate when the fastening body is pulled and the axial force is detected. The axial force detection device according to (22) above.

According to the present invention, it is possible to prevent the fastening body from loosening during unloading after the axial force is detected.

It is a schematic diagram of an axial force detection device (1st embodiment). It is an explanatory view of the feed amount of a single thread screw and a double thread screw. It is a perspective view of a bolt (1st embodiment). It is another perspective view of a bolt (1st embodiment). FIG. 2 is a schematic diagram of an axial force detection device during bolt tension (first embodiment). It is a perspective view of a bolt (Modification 1 of a 1st embodiment). It is a perspective view of a bolt (Modification 2 of a 1st embodiment). It is a perspective view of a bolt (Modification 3 of a 1st embodiment). It is a perspective view of a bolt (Modification 3 of a 1st embodiment). It is a schematic diagram of an axial force detection device (modification 3 of a 1st embodiment). It is a schematic diagram of an axial force detection device (modification 4 of a 1st embodiment). It is a schematic diagram of an axial force detection device (modification 5 of a 1st embodiment). It is a perspective view of a washer (modification 6 of a 1st embodiment). It is a schematic diagram of an axial force detection device (modification 7 of a 1st embodiment). It is a schematic diagram of an axial force detection device (modification 7 of a 1st embodiment). It is a schematic diagram of an axial force detection device (2nd embodiment). It is a perspective view of a bolt and a washer (2nd embodiment). It is a schematic diagram of an axial force detection device (modification 1 of a 2nd embodiment). It is a schematic diagram of an axial force detection device (modification 2 of a 2nd embodiment). It is a perspective view of a bolt (Modification 2 of a 2nd embodiment). It is a perspective view of a washer (modification 3 of a 2nd embodiment). It is a schematic diagram of an axial force detection device (modification 3 of a 2nd embodiment). FIG. 3 is a schematic diagram of an axial force detection device (Modification 3-1 of the second embodiment). FIG. 7 is a perspective view of a washer (modification example 3-2 of the second embodiment). It is a schematic diagram of an axial force detection device (modification 4 of a 2nd embodiment). It is a perspective view of a nut (Modification 4 of a 2nd embodiment). It is a schematic diagram of an axial force detection device (modification 5 of a 2nd embodiment). It is a schematic diagram of an axial force detection device (modification 6 of a 2nd embodiment). It is a schematic diagram of an axial force detection device (modification 6 of a 2nd embodiment). It is a schematic diagram of an axial force detection device (3rd embodiment). It is a perspective view of a nut (3rd embodiment). It is a perspective view of a nut (Modification 1 of a 3rd embodiment). It is a schematic diagram of an axial force detection device (modification 2 of a 3rd embodiment). It is a perspective view of a nut (Modification 3 of a 3rd embodiment). It is a schematic diagram of an axial force detection device (modification 3 of a 3rd embodiment). FIG. 7 is a schematic diagram of an axial force detection device (Modification 3-1 of the third embodiment). It is a perspective view of a nut (Modification 4 of a 3rd embodiment). It is a schematic diagram of an axial force detection device (modification 4 of a 3rd embodiment). It is a schematic diagram of an axial force detection device (modification 5 of a 3rd embodiment). It is a perspective view of a nut (modification 6 of a 3rd embodiment). It is a schematic diagram of an axial force detection device (modification 7 of a 3rd embodiment). It is a schematic diagram of an axial force detection device ((modification 8 of a 3rd embodiment)). It is a schematic diagram of an axial force detection device ((modification 8 of a 3rd embodiment)). It is a schematic diagram of an axial force detection device (4th embodiment). It is a schematic diagram of an axial force detection device (5th embodiment). This is a modification of FIG. 30(a) (stud bolt). This is a modification of FIG. 30(a) (connection members are omitted). It is a schematic diagram of an axial force detection device (6th embodiment).

Embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
The axial force detection device of this embodiment is a device that fastens objects to be fastened with bolts and pulls the bolt (corresponding to the fastening object) while suppressing the upper surface of the object, and the axial force of the bolt (in other words, Used to detect bolt fastening force). The basic idea of axial force detection is the same as that described in Japanese Patent No. 4028254.

FIG. 1 is a schematic diagram of the axial force detection device of this embodiment, showing the state immediately after starting the action of pulling the bolt. Note that by representing a plurality of members included in the axial force detection device with mutually different types of hatching, boundaries between the members are made clear. The axial force detection device 1 includes a connection member 2, a tension mechanism 3, a tension receiver 4, and a handle 5. In addition, X shown by a dashed-dotted line has shown the rotation axis of the axial force detection device 1 extended in the up-down direction.

The connecting member 2 includes a cylindrical portion 21 and a convex portion 22 formed on the upper surface of the cylindrical portion 21 . A connection member hollow part 21a extending in the vertical direction is formed at the lower end of the columnar part 21. A first female screw portion 21a1 (corresponding to the first screw portion in claim 1) extending around the rotation axis X is formed on the peripheral surface of the connecting member hollow portion 21a. The convex portion 22 is formed in a cylindrical shape with a smaller diameter than the cylindrical portion 21, and has a second male screw portion 22a (corresponding to the second screw portion in claim 1) extending around the rotation axis X on its outer peripheral surface. ) is formed.

Here, the feed amount per screw rotation of the second male threaded portion 22a of the connecting member 2 (hereinafter abbreviated as “feed amount”) is Pt, and the feed amount of the threaded portion of the bolt screw shaft portion 11 of the bolt 10 is Pb. The connecting member 2 is configured such that, when defined, a magnitude relationship such as feed amount Pt>feed amount Pb is established. This can prevent the bolt 10 from loosening during unloading, but the details will be described later. For example, the threaded portion of the bolt shaft portion 11 of the bolt 10 may be a single thread, and the second male threaded portion 22a of the connecting member 2 may be a multi-thread thread (for example, a double thread thread), a triangular thread, a trapezoidal thread, or a square thread. By doing so, the feed amount Pt can be made larger than the feed amount Pb.
In the case of a single thread screw, the thread pitch corresponds to the feed amount, as shown in FIG. In the case of a double thread screw, twice the thread pitch corresponds to the feed amount, as shown in FIG.
For the connecting member 2, a material having higher tensile strength than the bolt 10 can be used. Thereby, it is possible to prevent the connecting member 2 from being plastically deformed when detecting the axial force.

The tension mechanism 3 includes a tension rod 31, a bearing portion 32, a square drive 33, and a wrench 34. The tension rod 31 is composed of a cylindrical small-diameter rod portion 31a and a cylindrical large-diameter rod portion 31b, and the upper end of the small-diameter rod portion 31a and the lower end of the large-diameter rod portion 31b are connected to each other. These small diameter rod portion 31a and large diameter rod portion 31b are integrally formed.

A tension rod hollow part 311 is formed at the lower end of the small diameter rod part 31a, and a third female screw part 311a (claim 1 A third threaded portion) is formed. An attachment opening 312 is formed at the upper end of the large diameter rod portion 31b.

The bearing portion 32 is a thrust bearing, and rotatably supports the small diameter rod portion 31a of the tension rod 31. The upper end surface of the bearing section 32 is in contact with the large diameter rod section 31b of the tension rod 31, and the lower end surface of the bearing section 32 is in contact with the upper end surface of the tension receiving section 4. That is, the bearing portion 32 is sandwiched between the large diameter rod portion 31b and the tension receiving portion 4 in the vertical direction.

The square drive 33 is detachably attached to the attachment opening 312 of the large diameter rod portion 31b, and by rotating the square drive 33, the tension rod 31 can be rotated around the rotation axis X. The angular drive 33 can be rotated using the handle 5 and the wrench 34. In the configuration of this embodiment, when the tension rod 31 is rotated once around the rotation axis X using the wrench 34, the connection member 2 moves upward by the thread pitch of the third female threaded portion 311a of the tension rod 31. Designed. In addition, in this embodiment, the tension rod 31 is rotated using the square drive 33, the handle 5, and the wrench 34, but the present invention is not limited to this, and the power to rotate the tension rod 31 can be generated. Other possible drive means may also be used.

The wrench 34 is formed to be elongated in the horizontal direction, and can obtain a larger torque than the handle 5 when rotated with the same force. The wrench 34 is provided with an angle sensor (for example, a gyro sensor) that is not shown. The amount of rotation of the tension rod 31 can be measured by the angle sensor. However, the angle sensor may be attached directly to the tension rod 31 instead of the wrench 34.

The tension receiver 4 is provided with an axial force detection section (not shown) for detecting axial force. For example, a strain gauge can be used as the axial force detection section. A strain gauge deforms when force is applied to it, and outputs an electrical signal according to the amount of deformation. A tension hollow part 41 extending in the vertical direction is formed at the lower end of the tension receiving part 4. The connecting member 2 is housed inside the tension hollow part 41 , and the cylindrical part 21 of the connecting member 2 is arranged along the inner peripheral surface of the tension hollow part 41 . That is, the tension receiving portion 4 is arranged so as to surround the connecting member 2.

Here, the configuration of the tensioning mechanism 3 is not limited to the above-mentioned configuration, and may have other configurations as long as the connecting member 2 and the bolt 10 can be moved upward without rotating (other embodiments and The same applies to modified examples). For example, a concave portion having a female thread on the inner peripheral surface is formed on the upper surface of the cylindrical portion 21, and a convex portion having a male thread on the outer peripheral surface is formed at the lower end of the tension rod 31 (that is, the lower end of the small diameter rod portion 31a). The connecting member 2 and the bolt 10 may be pulled by forming a convex portion and threading the convex portion into the female thread.

Next, the bolt and the object to be fastened will be explained in detail. The bolt 10 is a hexagonal bolt and is composed of a bolt threaded shaft portion 11 and a bolt head 12. The bolt threaded shaft portion 11 is formed with a male threaded portion. As described above, the feed amount Pb of this male screw portion is smaller than the feed amount Pt.

The to-be-fastened body H consists of to-be-fastened bodies H1 and H2 which are superimposed in the vertical direction, and bolt holes H1a and H2a are formed in these to-be-fastened bodies H1 and H2, respectively. A female threaded portion is formed on the circumferential surface of the bolt hole H2a to be screwed into the male threaded portion of the bolt screw shaft portion 11. The bolt 10 inserted into the bolt hole H1a is screwed into the bolt hole H2a, so that the bolt 10 is fastened to the object H to be fastened.

Note that without forming a female thread in the bolt hole H2a, the bolt 10 is inserted into the bolt hole H1a, H2a, and a nut (not shown) is inserted into the bolt screw shaft portion 11 that protrudes downward from the end surface of the object to be fastened H (H2). The bolt 10 may be fastened to the body H by screwing it together. Note that the type of nut is not particularly limited, but for example, a hexagonal nut, a dodecagonal nut, or a square nut can be used (the same applies to other embodiments and modifications).

Here, as shown in FIG. 3(a), fourth male threaded portions 12a (corresponding to the fourth threaded portion in claim 1) are formed intermittently in the circumferential direction on the side surface of the bolt head 12. ing. That is, each fourth male threaded portion 12a is formed in a bent shape portion on the side surface of the bolt head 12. In the illustrated example, the fourth male threaded portion 12a is formed over the entire side surface of the bolt head 12 from the upper end to the lower end, but the present invention is not limited to this, and as shown in FIG. 3(b). As shown in the figure, it may be formed in a portion from the upper end to the lower end.

Next, the operation of the axial force detection device 1 during tension and unloading will be described. It is assumed that the bolt 10 is fastened to the object H in the initial state. Further, it is assumed that the tension mechanism 3, the tension receiver 4, and the handle 5 are assembled in advance into a unit.

First, the fourth male threaded portion 12a of the bolt head 12 is screwed into the first female threaded portion 21a1 of the connecting member 2 to connect the connecting member 2 and the bolt 10. That is, the bolt head 12 is threaded until the upper surface contacts the top surface of the connecting member hollow portion 21a, and the connecting member 2 and the bolt 10 are screwed together.

When the fourth male threaded portion 12a and the first female threaded portion 21a1 are screwed together and tensioning is started, it is desirable that predetermined tensioning start conditions be satisfied. The predetermined tension start conditions consist of the following conditions (1) and (2).
(Condition 1): The first female threaded portion 21a1 is screwed into the fourth male threaded portion 12a having a length of one circumference or more on the outer peripheral surface of the bolt head 12. (Condition 2): The lower end of the connecting member 2 A clearance is formed between the object to be fastened H1

If condition 1 is not satisfied, there will be an area in the circumferential direction of the bolt head 12 where no tensile force is applied (in other words, an area where the first female threaded part 21a1 is not in contact), so the load will be applied in the tensile direction (in other words, in the vertical direction). direction), which may reduce the accuracy of axial force detection. Furthermore, if Condition 1 is not satisfied, there is a risk that the screw threads will be plastically deformed during tension, resulting in a decrease in detection accuracy such as axial force detection.

If condition 2 is not satisfied, the axial force is detected in a state where the lower end of the connecting member 2 is in pressure contact with the object to be fastened H1, resulting in a large detection error.

Here, when connecting the connecting member 2 and the bolt head 12, if the connecting member 2 is rotated around the rotation axis X and the fourth male threaded part 12a and the first female threaded part 21a1 are screwed together, the connecting member 2 spirals downward. When the connecting member 2 is further rotated around the rotation axis X, the bolt head 12 comes into contact with the top surface of the connecting member hollow portion 21a, and the connecting member 2 becomes unable to rotate. In this embodiment, the connection is made so that conditions 1 and 2 are satisfied when the connecting member hollow part 21a and the bolt head 12 come into contact (in other words, when the connecting member 2 cannot be screwed on). The size of the member hollow portion 21a is set. Therefore, conditions 1 and 2 can be easily satisfied.

Next, the lower end of the tension rod hollow part 311 is positioned at the tip of the convex part 22 of the connecting member 2. At this time, the tension receiver 4 is located above the fastened body H1 (in other words, the tension receiver 4 and the fastened body H1 are in a non-contact state). Subsequently, the handle 5 is manually rotated around the rotation axis X, and the third female threaded portion 311a and the second male threaded portion 22a are screwed together. When the handle 5 is further rotated, the tension rod 31, together with the bearing portion 32 and the tension receiving portion 4, spirals downward, and the tension receiving portion 4 is seated on the fastened body H1.

FIG. 1 shows a state immediately after the tension receiving part 4 comes into contact with the object to be fastened H1, and a clearance is formed between the lower end of the tension rod 31 and the upper end of the cylindrical part 21. . Further, a clearance is also formed between the tip of the convex portion 22 and the upper end of the tension rod hollow portion 311.

When the tension receiving portion 4 is seated on the fastened body H1, the tension rod 31 cannot be rotated any further by manual operation using the handle 5 because the torque is small. Therefore, the tension rod 31 is rotated by manual operation using the wrench 34. Thereby, the connecting member 2 can be moved upward. Note that the connecting member 2 does not rotate when moving upward.

When the connecting member 2 moves upward, as shown in FIG. 4, the bolt screw shaft portion 11 extends, the bolt head 12 separates from the fastened object H1, and tension is released from the large diameter rod portion 31b via the bearing portion 32. A pushing force is applied to the receiving portion 4 . At this time, since the tension receiving part 4 seated on the fastened body H1 cannot move downward, it is compressed by the bearing part 32 and the fastened body H1, and the tension receiving part 4 is moved from the fastened body H1 to the fastened body H1. A reaction force acts. At this time, an electrical signal (for example, voltage) is output from the strain gauge, and the axial force can be calculated from this output signal. Note that the calculated axial force can be displayed, for example, on a display section (not shown) provided on the outer peripheral surface of the wrench 34 or the tension receiver 4.

When the axial force of the bolt 10 reaches the target axial force, the connecting member 2 and the tension rod 31 are unloaded. When the unloading torque is defined as Trl, Trl can be calculated from the following equation (1). Unloading means rotating the tension rod 31 in a direction that releases the tensile load on the bolt 10.
Trl=Ft/2×(d2t/cosαt×μst-Pt/π)...Formula (1)
However, Ft: tensile force of the bolt 10, d2t: effective diameter of the second male threaded portion 22a of the connecting member 2, αt: half-angle thread of the second male threaded portion 22a of the connecting member 2, μst: the second male threaded portion 22a of the connecting member 2. The coefficient of friction of the threaded surface of the second male threaded portion 22a is Pt: the feed amount per rotation of the second male threaded portion 22a of the connecting member 2.

Moreover, if the loosening torque of the bolt 10 with respect to the object to be fastened H is defined as Tsl, Tsl can be calculated from the following equation (2).
Tsl=Fb/2×(d2b/cosαb×μsb-Pb/π)...Formula (2)
However, Fb: axial force of the bolt 10, d2b: effective diameter of the bolt threaded shaft 11, αb: thread half angle of the bolt threaded shaft 11, μsb: coefficient of friction of the threaded surface of the bolt threaded shaft 11, Pb: bolt threaded shaft 11 is the feed amount per screw rotation.

Here, in equation (1), when Trl is positive (that is, when d2t/cosαt×μst>Pt/π), an external force is applied to the tension rod 31 in the direction of releasing the tensile load on the bolt 10. Unloading is performed by rotating the tension rod 31. For example, by rotating the wrench 34, the tension rod 31 can be rotated. As described above, in this embodiment, Tsl is made larger than Trl by designing so that feed amount Pt>feed amount Pb. This can prevent the bolt 10 from loosening during unloading.

In equation (1), when Trl is negative (that is, when d2t/cosαt×μst<Pt/π), the tension rod 31 automatically rotates in a direction that releases the tensile load on the bolt 10. In this case, no loosening torque is applied to the bolt 10.

In this embodiment, Tsl is made larger than Trl by performing a design that satisfies feed amount Pt>feed amount Pb, but the present invention is not limited to this. For example, Tsl may be made larger than Trl by adjusting parameters other than the feed amount specified in equations (1) and (2).
Here, even if the effective diameter d2t of the second male threaded portion 22a of the connecting member 2 is larger than the effective diameter d2b of the bolt threaded shaft portion 11, if the feed amount Pt is made sufficiently larger than the feed amount Pb, Tsl can be made larger than Trl. By increasing the effective diameter d2t of the second male screw portion 22a of the connecting member 2, damage to the connecting member 2 can be effectively suppressed (the same applies to other embodiments and modifications described later). be).
Note that Ft and Fb in equations (1) and (2) are substantially the same.

Here, as a method of making Tsl larger than Trl, a method of reducing the effective diameter d2t of the second male threaded portion 22a of the connecting member 2 can be considered. However, the tightening axial force of the bolt 10 is often near the elastic limit, and the connecting member 2 is a member that is used repeatedly. There is a risk that the male threaded portion 22a may be damaged. Therefore, as described above, it is desirable to adjust the feed amount.

In addition, by applying surface treatment or lubricant to the second male threaded portion 22a of the connecting member 2 and/or the third female threaded portion 311a of the tension rod 31 to reduce the coefficient of friction, Tsl can be made lower than Trl. You can make it bigger. However, preferably, the method of adjusting the feed amount Pb and the feed amount Pt described above is used. This is because the coefficient of friction changes depending on the machining accuracy, surface texture, rotational speed, etc. of the second male threaded portion 22a, so there is a risk that the intended torque magnitude relationship may not be obtained.

(Modification 1 of the first embodiment)
As shown in FIG. 5, the bolt 10 may be a bolt 100 with a hexagonal socket in which a hexagonal socket 102a is formed in the bolt head. The bolt threaded shaft portion 101 has a male threaded portion formed therein.
A fourth male threaded portion 102b is continuously formed on the side surface of the bolt head 102 without interruption in the circumferential direction. Axial force detection can be performed in a state where the fourth male threaded portion 102b of the bolt head 102 is screwed into the first female threaded portion 21a1 of the connection member 2.

In the illustrated example, the fourth male threaded portion 102b is formed over the entire side surface of the bolt head 102 from the upper end to the lower end, but the present invention is not limited to this. As shown in FIG. 3(b), it may be formed in a portion from the upper end to the lower end. Note that the bolt 10 of this modification may be a flange bolt. Details of the flange bolt will be described in Modification 3.

(Modification 2 of the first embodiment)
As shown in FIG. 6, the bolt 10 may be a bolt 200 made of a square bolt.
The bolt threaded shaft portion 201 has a male threaded portion formed therein. Fourth male screw portions 202a are formed intermittently in the circumferential direction on the side surface of the bolt head 202. That is, each fourth male threaded portion 202a is formed in a bent shape on the side surface of the bolt head 202. Axial force detection can be performed in a state where the fourth male threaded portion 202a of the bolt head 202 is screwed into the first female threaded portion 21a1 of the connection member 2. In the illustrated example, the fourth male threaded portion 202a is formed over the entire side surface of the bolt head 202 from the upper end to the lower end, but the present invention is not limited to this. As shown in FIG. 3(b), it may be formed in a portion from the upper end to the lower end.

(Variation 3 of the first embodiment)
Modification 3 of the first embodiment will be described with reference to FIGS. 7(a) and 8. In this embodiment, flange bolts are used. FIG. 7(a) is a perspective view of the flange bolt. FIG. 8 is a schematic diagram of the axial force detection device.

The connecting member hollow part 21a has an upper and lower two-stage structure consisting of a large diameter hollow part 211a and a small diameter hollow part 212a, and the upper end of the large diameter hollow part 211a and the lower end of the small diameter hollow part 212a are connected. A female threaded portion 211a1 (corresponding to the first threaded portion in claim 1) is formed on the inner circumferential surface of the large diameter hollow portion 211a, and a female threaded portion 212a1 is formed on the inner circumferential surface of the small diameter hollow portion 212a. (corresponding to the first threaded portion in claim 1) is formed.

The bolt 300 is a hexagonal bolt with a flange, which is an example of a flange bolt, and is composed of a bolt threaded shaft portion 301 and a bolt head 302. The bolt threaded shaft portion 301 has a male threaded portion formed therein. The bolt 300 can be fastened to the object to be fastened H by threading the bolt 300 inserted into the bolt hole H1a into the bolt hole H2a.

The bolt head 302 is composed of a head main body 302a and a flange portion 302b. The head body 302a and the flange portion 302b are integrally formed, and the flange portion 302b is formed in a flat plate shape and protrudes outward in the radial direction from the head body 302a. Fourth male threaded portions 302a1 (corresponding to the fourth threaded portion in claim 1) extending in the circumferential direction are intermittently formed on the outer peripheral surface of the head main body 302a. A fourth male screw portion 302b1 (corresponding to the fourth screw portion in claim 1) extending in the circumferential direction is continuously formed on the outer peripheral surface of the flange portion 302b. Note that the bolt head 302 may be replaced with a bolt head of a hexagon socket head bolt as shown in FIG.

Axial force detection can be performed in a state where the fourth male threaded portion 302a1 is screwed into the female threaded portion 212a1, and the fourth male threaded portion 302b1 is screwed into the female threaded portion 211a1. The fourth male screw portions 302a1 and 302b1 must have the same pitch. If the pitches are different, the connecting member 2 cannot be screwed into the fourth male screw portions 302a1 and 302b1.

In Modification 3, male threaded portions are formed on both the head main body 302a and the flange portion 302b, but the present invention is not limited to this. It is also possible to use a flange bolt in which one part is formed and the other part is not formed with a male thread part. In the illustrated example, the fourth male threaded portion 302a1 is formed over the entire side surface of the head main body 302a from the upper end to the lower end, but the present invention is not limited to this, and as shown in FIG. 3(b). As shown in the figure, it may be formed in a portion from the upper end to the lower end. Further, in the illustrated example, the fourth male threaded portion 302b1 is formed over the entire side surface of the flange portion 302b from the upper end to the lower end, but the present invention is not limited to this, and is similar to that of the first embodiment. As illustrated in FIG. 3(b), it may be formed in a portion from the upper end to the lower end.

The present invention can also be applied to a flange bolt (see FIG. 7(b)) whose bent portion has a gentler curve than a flanged hexagonal bolt. Since the symbols 400, 401, 402, 402a, 402b, 402a1, and 402b1 in FIG. 7(b) correspond to the symbols 300, 301, 302, 302a, 302b, 302a1, and 302b1 in FIG. 7(a), respectively, Detailed explanation will be omitted.

In the example shown in FIG. 7(a), the flange portion 302b of the bolt head 302 is formed into a flat plate shape, but the present invention is not limited to this, and may have a curved surface or a truncated cone shape. good. Furthermore, when the curved surface of the flange portion 302b (or the tapered surface if the flange portion 302b has a truncated cone shape) comes into contact with the large-diameter hollow portion 211a, there is a clearance between the connecting member 2 and the object to be fastened H1. may be formed. Note that the curved surface (or the tapered surface) includes a concave portion or a convex portion formed on these surfaces. That is, a configuration may be adopted in which a clearance is formed between the connection member 2 and the object to be fastened H1 when the connection member 2 contacts the recess or projection.

(Modification 4 of the first embodiment)
Modification 4 of the first embodiment will be described with reference to FIG. 9(a). FIG. 9A corresponds to FIG. 1 and shows a state immediately after the tension receiver 4 comes into contact with the object to be fastened H1. In this embodiment, a washer 50 is interposed between the bolt head 12 and the object to be fastened H1. The washer 50 is a normal flat washer formed into a flat plate shape, and its diameter is set smaller than the inner diameter of the tension hollow portion 41. A clear clearance is formed. If the axial force is detected with the lower end of the connecting member 2 in pressure contact with the washer 50, the detection error will increase. That is, by detecting the axial force with a small clearance formed between the lower end of the connecting member 2 and the washer 50, detection errors can be reduced. In addition, in FIG. 9(a), the dimension of the washer 50 in the plane direction may be enlarged, and the washer 50 may be interposed between the tension receiving part 4 and the object to be fastened H1. The same applies to the embodiment and other modified examples.) In this case, the tension receiving portion 4 receives a reaction force when the bolt is pulled through the washer 50.

In the present modification 4, a clearance is formed when the bolt head 12 and the connection member hollow part 21a come into contact with each other, but the present invention is not limited to this. For example, when the connecting member hollow part 21a is composed of a large diameter hollow part 211a and a small diameter hollow part 212a as shown in FIG. A configuration may be adopted in which a clearance is formed between the connecting member 2 and the object to be fastened H1 when they come into contact with each other. In this case, the axial force is detected in a state where a gap is formed in the vertical direction between the bolt head 12 and the small diameter hollow part 212a. Note that the upper surface of the washer 50 includes a concave portion or a convex portion formed on the upper surface. That is, a configuration may be adopted in which a clearance is formed between the connection member 2 and the object to be fastened H1 when the connection member 2 contacts the recess or projection.

(Variation 5 of the first embodiment)
FIG. 9(b) is a schematic diagram of the axial force detection device of Modification 5, and shows the state immediately after the tension receiving portion 4 comes into contact with the fastened body H1. The connecting member hollow part 21a has an upper and lower two-stage structure consisting of a large diameter hollow part 211a and a small diameter hollow part 212a, and the upper end of the large diameter hollow part 211a and the lower end of the small diameter hollow part 212a are connected. A female screw portion 212a1 is formed on the inner peripheral surface of the small diameter hollow portion 212a.

The washer 51 is a stepped washer and includes a large diameter washer portion 51a and a small diameter washer portion 51b formed on the upper surface of the large diameter washer portion 51a. The large-diameter washer 51a is integrally formed with the small-diameter washer 51b, and has a larger diameter than the small-diameter washer 51b. The small diameter washer portion 51b is set to have a larger outer diameter than the bolt head 12.

Here, when the connecting member 2 is rotated around the rotational axis proceed. When the connecting member 2 is further rotated around the rotation axis X, the upper surface of the small diameter washer portion 51b comes into contact with the large diameter hollow portion 211a, and the connecting member 2 becomes unable to rotate. In this embodiment, when the small diameter washer part 51b and the large diameter hollow part 211a come into contact (in other words, when the connecting member 2 cannot be screwed on), there is a gap between the connecting member 2 and the object to be fastened H1. It is configured so that a clearance is formed. Therefore, it is not necessary to visually check whether a clearance is formed between the lower end of the connecting member 2 and the object to be fastened H1 each time the axial force is detected. It can be performed. Note that the upper surface of the small diameter washer portion 51b includes a concave portion or a convex portion formed on the upper surface. That is, a configuration may be adopted in which a clearance is formed between the connection member 2 and the object to be fastened H1 when the connection member 2 contacts the recess or projection.

However, even when using the stepped washer 51, a clearance is formed between the connecting member 2 and the object to be fastened H1 when the bolt head 12 and the connecting member hollow part 21a come into contact. It may be configured as follows. Alternatively, a clearance may be formed between the connecting member 2 and the object to be fastened H1 when the upper surface of the large diameter washer 51a and the connecting member hollow portion 21a abut. Note that the upper surface of the large-diameter washer portion 51a includes a recess or a convex portion formed on the upper surface. That is, a configuration may be adopted in which a clearance is formed between the connection member 2 and the object to be fastened H1 when the connection member 2 contacts the recess or projection.

(Variation 6 of the first embodiment)
In the above-described embodiment, the washer 50 was formed into a flat plate shape, but the present invention is not limited to this. FIG. 9(c) is a perspective view of the washer 52 of this modification. The washer 52 is a rosette washer, and a curved surface portion 52b extending upward in a dome shape is formed on a lower end flat plate portion 52a. In this modification, when the curved surface portion 52b of the washer 52 and the large diameter hollow portion 211a abut, a clearance may be formed between the connecting member 2 and the object to be fastened H1. In addition, when a concave part or a convex part is formed in the curved surface part 52b, the configuration is such that a clearance is formed between the connecting member 2 and the object to be fastened H1 when the concave part or the convex part comes into contact with the concave part or the convex part. It's okay. Further, the washer 52 may have a truncated cone shape. In this case, it may be configured such that a clearance is formed between the connecting member 2 and the object to be fastened H1 when the tapered surface of the washer 52 and the large diameter hollow portion 211a abut. In addition, if a concave part or a convex part is formed on the tapered surface, the configuration is such that a clearance is formed between the connecting member 2 and the object to be fastened H1 when the concave part or the convex part comes into contact with the concave part or the convex part. It's okay.

(Modification 7 of the first embodiment)
Modification 7 of the first embodiment will be described with reference to FIG. 10. FIG. 10 shows the state immediately after the tension receiver 4 comes into contact with the protection plate 60. That is, the protection plate 60 can be interposed between the bolt head 12, the tension receiver 4, and the object to be fastened H1. The protection plate 60 has an opening through which the bolt screw shaft portion 11 is inserted, and its diameter is set larger than the outer diameter of the tension receiving portion 4 . Therefore, when the handle 5 is rotated to move the tension receiver 4 downward, the member that the tension receiver 4 comes into contact with becomes the protection plate 60 instead of the fastened body H1. In this case, the reaction force applied from the fastened body H1 when the axial force is detected is transmitted to the tension receiver 4 via the protection plate 60.

The configuration of this embodiment is particularly suitable when the rigidity (EI) and elastic limit strength of the fastened body H are lower than that of the tension receiver 4. Note that E is Young's modulus and I is the moment of inertia of area. That is, when the tension receiving portion 4 is brought into contact with the object to be fastened H1 to detect the axial force, the load is concentrated on the abutting portion of the object to be fastened H1. Therefore, if the rigidity or the like of the object to be fastened H1 is low, there is a possibility that the object to be fastened H1 will deform. Therefore, in this embodiment, a protection plate 60 having a diameter larger than the outer diameter of the tension receiving part 4 is interposed between the tension receiving part 4 and the object to be fastened H1. As a result, the contact area increases and the load is distributed, so that the load applied to the object H to be fastened can be reduced.

For the protection plate 60, a material having higher rigidity (EI) and higher elastic limit strength than the objects H to be fastened (for example, heat-treated steel) can be used. By detecting the reaction force through the protection plate 60 having high rigidity (EI), it is possible to reduce the detection error in axial force detection.

FIG. 11 shows a modification of the protection plate. The protection plate 61 is formed in a ring shape (however, it may have a shape other than the ring shape), and is interposed between the tension receiver 4 and the object to be fastened H1, avoiding the position directly under the bolt head 12. are doing. Of the protection plate 61, an inner edge 61a is provided at a position corresponding to the inner edge of the tension receiver 4, and an outer edge 61b is provided at a position protruding from the outer edge of the tension receiver 4 in the radial direction. .
According to this example, by adjusting the thickness of the protection plate 61 in the radial direction (in other words, adjusting the contact area between the fastened body H1 and the protection plate 61), the fastened body H1 directly below the bolt head 12 The amount of deformation of the fastened body H1 directly under the protection plate 61 can be made substantially the same. That is, S1 is the deformation amount of the fastened body H1 directly under the bolt head 12 before the tensioning mechanism 3 starts tensioning, and S1 is the deformation amount of the fastened body H1 directly under the protection plate 61 after the tensioning mechanism 3 starts tensioning. It is desirable to adjust the contact area of the protective plate 61 with respect to the object to be fastened H1 so that the amounts of deformation S1 and S2 are approximately equal to each other when the amount of deformation is S2. Note that the amounts of deformation S1 and S2 are amounts of deformation of the bolt 10 in the axial direction. However, the protection plate 61 may be provided as a part of the tension receiver 4. In this case, it is desirable to adjust the contact area of the contact part (in other words, the lower end part) of the tension receiving part 4 that contacts the object H1 to be fastened so that it satisfies the above-mentioned conditions. An appropriate contact area can be determined by conducting experiments or simulations in advance.

The advantages of having substantially the same amount of deformation are as follows. When the bolt head 12 is pulled, the amount of deformation during tightening of the fastened body H1 directly below the bolt head 12 is released (in other words, the area directly below the bolt head 12 becomes almost unloaded). In order to maintain the deformed state when the bolt head 12 is pulled, the protection plate 61 (or the tension receiver 4) deforms the fastened body H1 in the same way as when tightening, thereby improving the accuracy of axial force detection. can be improved.

In the first embodiment and its various modifications, the shape of the bolt head is hexagonal or square, but the present invention is not limited to this, and may be replaced with a dodecagonal shape, for example.

Further, the bolt may be a double hex bolt. Here, the double hexagon bolt is a bolt with hexagonal heads shifted 30 degrees and overlapped vertically, and each head has a fourth male screw part similar to the first embodiment. can be formed. However, the fourth male threaded portion may be formed only in one of the vertically stacked heads.

(Second embodiment)
The axial force detection device of this embodiment fastens objects to be fastened with bolts and washers, and pulls the bolt through the washer (corresponding to the fastening component in claim 1) while holding down the upper surface of the object to axially It is a device that detects force.

FIG. 12(a) is a schematic configuration diagram of the axial force detection device of this embodiment, and FIG. 12(b) is a perspective view of a bolt and a washer. The basic configuration of the axial force detection device is the same as that in the first embodiment, so detailed explanation will be omitted.
The bolt, washer, and fastened object will be explained in detail. The bolt 10 is a hexagonal bolt and is composed of a bolt threaded shaft portion 11 and a bolt head 12. However, the bolt 10 may be, for example, a dodecagonal bolt or a square bolt (the same applies to other modifications of this embodiment). The bolt threaded shaft portion 11 is formed with a male thread. The washer 14 is formed into a flat plate shape, and has a diameter larger than that of the bolt 10. A fourth male threaded portion 14a (corresponding to the fourth threaded portion in claim 1) is formed on the outer peripheral surface of the washer 14 so as to extend in the circumferential direction. In the illustrated example, the fourth male threaded portion 14a is formed on the entire outer circumferential surface (side surface) of the washer 14, but the present invention is not limited to this, and may be formed on a part of the outer circumferential surface (other The same applies to the embodiments and modifications of .

The washer 14 is compressed by the bolt head 12 and the fastened body H1 in the vertical direction. By using the washer 14, the contact area becomes larger, so that the contact surface pressure on the object to be fastened H1 can be lowered. Therefore, the present invention can be applied even when the object to be fastened H1 is made of a material with low strength (for example, aluminum).

Axial force detection can be performed in a state where the fourth male threaded portion 14a of the washer 14 is screwed into the first female threaded portion 21a1 of the connection member 2. Here, the fourth male threaded portion 14a is formed on the outer circumferential surface of the washer 14 that protrudes radially outward from the bolt head 12, so that when the washer 14 and the connecting member 2 are screwed together, A sufficient circumferential length can be ensured. This can suppress plastic deformation of the screw thread during axial force detection and a decrease in the detection accuracy of axial force detection.

In this embodiment, as in the first embodiment, the feed amount and the like are adjusted so as to obtain the magnitude relationship Tsl>Trl. The definitions of Tsl and Trl are omitted since they were explained in the first embodiment. Therefore, it is possible to prevent the bolt 10 from loosening when the tension rod 31 is unloaded.

(Modification 1 of the second embodiment)
Modification 1 of the second embodiment will be described with reference to FIG. 13. FIG. 13 corresponds to FIG. 1 and shows a state immediately after the tension receiver 4 comes into contact with the object to be fastened H1. Note that detailed descriptions of the same configurations as in the second embodiment will be omitted. In the bolt 10 of this embodiment, the bolt head 12 contacts the lower surface of the object to be fastened H2, and the tip of the bolt screw shaft portion 11 protrudes from the upper surface of the object to be fastened H1. That is, the direction of the bolt is opposite to that in the second embodiment. Note that the bolt holes H1a and H2a are not threaded.

A washer 14 is inserted into the protruding portion of the bolt screw shaft portion 11, and a nut 50 is fastened onto the washer 14. In other words, the washer 14 is compressed by the fastened body H1 and the nut 50. The washer 14 is set to have a larger outer diameter than the nut 50. Note that the type of nut 50 is not particularly limited, but for example, a hexagonal nut, a dodecagonal nut, or a square nut can be used (the same applies to other modifications of this embodiment).

Similar to the second embodiment, a fourth male threaded portion 14a is formed on the outer peripheral surface of the washer 14. The connecting member hollow part 21a has a two-stage upper limit structure consisting of a large diameter hollow part 211a and a small diameter hollow part 212a, and the upper end of the large diameter hollow part 211a and the lower end of the small diameter hollow part 212a are connected. A first female screw portion 21a1 is formed in the large diameter hollow portion 211a and is screwed into the fourth male screw portion 14a of the washer 14 when detecting the axial force.

Here, the vertical dimensions of the large-diameter hollow part 211a and the small-diameter hollow part 212a are such that when the connecting member 2 is screwed onto the washer 14, the bolt screw shaft part 11 comes into contact with the top surface of the small-diameter hollow part 212a. , the size is adjusted so that the upper surface of the nut 50 (including the recess or projection when a recess or projection is formed on the upper surface of the nut 50) comes into contact with the top surface of the large diameter hollow part 211a. .

(Modification 2 of the second embodiment)
An axial force detection device according to a second modification of the second embodiment will be described with reference to FIGS. 14 and 15. FIG. 14 is a schematic diagram of the axial force detection device, showing the state immediately after the action of pulling the washer is started. Note that detailed descriptions of the same configurations as in the second embodiment will be omitted. FIG. 15 is a perspective view of the bolt.

A connection member hollow part 21a extending in the vertical direction is formed at the lower end of the columnar part 21. The connecting member hollow part 21a has an upper and lower two-stage structure consisting of a large diameter hollow part 211a and a small diameter hollow part 212a, and the upper end of the large diameter hollow part 211a and the lower end of the small diameter hollow part 212a are connected. A first female screw portion 21a1 is formed in the large diameter hollow portion 211a and is screwed into the fourth male screw portion 14a of the washer 14 when detecting the axial force.

Next, the bolt, washer, and object to be fastened will be explained in detail. The bolt 13 is a hexagonal bolt with a flange, and includes a bolt threaded shaft portion 13a, a bolt head 13b, and a bolt flange portion 13c. A male screw is formed in the bolt screw shaft portion 13a. The bolt flange portion 13c is formed so as to protrude in the radial direction from the lower end portion of the bolt head 13b, and is formed integrally with the bolt head 13b. The outer diameter of the bolt flange portion 13c is larger than the inner diameter of the small diameter hollow portion 212a and smaller than the inner diameter of the large diameter hollow portion 211a.

The washer 14 is formed into a flat plate shape, and has a diameter larger than that of the bolt flange portion 13c. A fourth male threaded portion 14a is formed on the outer peripheral surface of the washer 14 and extends in the circumferential direction. The washer 14 is compressed by the bolt flange portion 13c and the fastened body H1 in the vertical direction.

Axial force detection can be performed in a state where the fourth male threaded portion 14a of the washer 14 is screwed into the first female threaded portion 21a1 of the connection member 2. Here, the fourth male threaded portion 14a is formed on the outer circumferential surface of the washer 14 that protrudes radially outward from the bolt flange portion 13c, so that when the washer 14 and the connecting member 2 are screwed together, A sufficient circumferential length can be ensured. This can suppress plastic deformation of the screw thread during axial force detection and a decrease in the detection accuracy of axial force detection.

In the second modification of the second embodiment, the bolt flange portion 13c is formed into a flat plate shape, but it may have a shape having a curved surface (or a tapered surface) as described in the first embodiment.

(Variation 3 of the second embodiment)
FIG. 16 is a perspective view of the washer of Modification 3, and FIG. 17(a) is a schematic diagram of the axial force detection device. The washer 81 is a stepped washer and includes a large diameter washer portion 81a and a small diameter washer portion 81b formed on the upper surface of the large diameter washer portion 81a. The large diameter washer part 81a is integrally formed with the small diameter washer part 81b, and has an outer diameter larger than that of the small diameter washer part 81b.

The bolt 82 is a hexagonal bolt consisting of a bolt head 82a and a bolt threaded shaft portion 82b. A washer 81 is inserted through the bolt screw shaft portion 82b, and the washer 81 is sandwiched between the bolt head 82a and the object to be fastened H1. The small diameter washer part 81b is in contact with the bolt head 82a, and the large diameter washer part 81a is in contact with the top surface of the large diameter hollow part 211a. A fourth male screw portion 810a is formed on the outer peripheral surface (side surface) of the large diameter washer portion 81a. A gap is formed between the bolt head 82a and the small diameter hollow portion 212a. The bolt is pulled while the fourth male threaded portion 810a of the large diameter washer 81a is screwed into the first female threaded portion 21a1 of the connecting member 2.

A further modification 3-1 of the present modification 3 will be described with reference to FIG. 17(b). FIG. 17(b) corresponds to FIG. 17(a), and shows a state immediately after the tension receiver 4 comes into contact with the object to be fastened H1. In the washer 81, the outer diameter of the small diameter washer portion 81b is set to be larger than that of the third modification.

In the above configuration, when the connecting member 2 is rotated around the rotation axis X and the fourth male threaded portion 810a and the first female threaded portion 21a1 are screwed together, the connecting member 2 is screwed downward. When the connecting member 2 is further rotated around the rotation axis The connecting member 2 comes into contact with the radial hollow portion 211a and becomes unable to rotate. In this state, by rotating the tension rod 31, the bolt 82 can be pulled through the connecting member 2 and the washer 81.

A further modification 3-2 of the present modification 3 will be described with reference to FIG. FIG. 18 is a perspective view of the washer of Modification 3-2. The washer 91 is a rosette washer, and a fourth male threaded portion 910a is formed on the outer peripheral surface (side surface) of the lower end flat plate portion 91a. A curved surface portion 91b extending upward in a dome shape is formed on the lower end flat plate portion 91a. However, the curved surface portion 91b may be formed into a truncated cone shape.

Referring to FIGS. 17(a) and 18, in this modification 3-2, the curved surface portion 91b (in the case of a truncated cone, the tapered surface) of the washer 91 and the large diameter hollow portion 211a are in contact with each other, so that the connection is achieved. Member 2 becomes unrotatable. In this state, by rotating the tension rod 31, the bolt 82 can be pulled through the connecting member 2 and the washer 81.

(Modification 4 of the second embodiment)
The axial force detection device of Modification 4 will be described with reference to FIGS. 19 and 20. FIG. 19 shows a state immediately after the tension receiver 4 comes into contact with the object to be fastened H1. FIG. 20 is a perspective view of the nut 95 of the fourth modification.

The nut 95 is a flanged nut and includes a nut flange portion 95a and a nut body 95b. The nut flange portion 95a projects radially outward from the lower end portion of the nut body 95b. The outer diameter of the nut flange portion 95a is set smaller than the outer diameter of the washer 14.

Here, when the connecting member 2 is rotated around the rotation axis X and the fourth male threaded portion 14a and the first female threaded portion 21a1 are screwed together, the connecting member 2 is screwed downward. When the connecting member 2 is further rotated around the rotation axis The connecting member 2 comes into contact with the radial hollow portion 211a and becomes unable to rotate. The connecting member 2 becomes unrotatable. In this state, by rotating the tension rod 31, the bolt 82 can be pulled through the connecting member 2 and the washer 14.

In this modification 4, as shown in FIG. 19, the bolt 82 is a hexagonal bolt, but it can also be a stud bolt without a bolt head (the same applies to FIG. 21, which will be described later). Note that the stud bolt has threaded portions at both ends.

In Modification 4, the nut flange portion 95a is formed into a flat plate shape, but the present invention is not limited to this, and may have a shape other than a flat plate with a diameter expanded radially outward from the nut body 95b. . The nut flange portion 95a may have a shape having a curved surface (or a tapered surface) imitating the shape shown in FIG. 18, for example.

(Variation 5 of the second embodiment)
Referring to FIG. 21, an axial force detection device according to modification 5 of the second embodiment will be described. FIG. 21 shows a state immediately after the tension receiver 4 comes into contact with the object to be fastened H1. The nut 97 of this modification 5 is a nut without a flange. The washer of this modification 5 is similar to the washer 81 described above (see FIG. 16). Furthermore, in the connecting member 2 of Modification 5, a medium diameter hollow part 213a is formed between the large diameter hollow part 211a and the small diameter hollow part 212a.

Here, when the connecting member 2 is rotated around the rotation axis X and the fourth male threaded portion 810a and the first female threaded portion 21a1 are screwed together, the connecting member 2 is screwed downward. When the connecting member 2 is further rotated around the rotational axis contacts the large-diameter hollow portion 211a, and the connecting member 2 becomes unable to rotate. In this state, by rotating the tension rod 31, the bolt 82 can be pulled through the connecting member 2 and the washer 81.

A further modification 5-1 of modification 5 will be described. In FIG. 21, the height of the large-diameter hollow portion 211a is increased so that the upper surface of the small-diameter washer 81b (if a recess or a protrusion is formed on the upper surface of the small-diameter washer 81b, the recess or protrusion is included). ) and the medium-diameter hollow portion 213a may come into contact with each other, making it impossible for the connecting member 2 to screw forward.

(Variation 6 of the second embodiment)
Modification 6 of the second embodiment will be described with reference to FIG. 22. FIG. 22 shows the state immediately after the tension receiver 4 comes into contact with the protection plate 60. That is, the protection plate 60 can be interposed between the washer 14, the tension receiver 4, and the object to be fastened H1. The protection plate 60 is formed in a ring shape, and an inner edge 60a is provided at a position corresponding to the bolt screw shaft 11, and an outer edge 60b is provided at a position protruding from the outer edge of the tension receiver 4 in the radial direction. It is provided. Therefore, when the handle 5 is rotated to move the tension receiver 4 downward, the tension receiver 4 comes into contact with the protection plate 60 instead of the object to be fastened H1. In this case, the reaction force applied from the fastened body H1 when the axial force is detected is transmitted to the tension receiver 4 via the protection plate 60.

FIG. 23 shows a modification of the protection plate. The protection plate 61 is formed in a ring shape (however, it may have a shape other than the ring shape), and is interposed between the tension receiver 4 and the object to be fastened H1 so as not to be directly under the washer 14. There is. Of the protection plate 61, an inner edge 61a is provided at a position corresponding to the inner edge of the tension receiver 4, and an outer edge 61b is provided at a position protruding from the outer edge of the tension receiver 4 in the radial direction. .

(Third embodiment)
The axial force detection device of this embodiment is a bolt/nut that compresses the object to be fastened by inserting a bolt into the insertion hole of the object to be fastened, and screwing and fastening a nut to the male threaded part of the bolt that has passed through the insertion hole. This is a device that pulls the fastener and detects the axial force.

FIG. 24(a) is a schematic diagram of the axial force detection device. FIG. 24(b) is a perspective view of the nut.
The basic configuration of the axial force detection device is the same as in the first embodiment and the second embodiment, so detailed explanation will be omitted.
The bolt 10 is a hexagonal bolt and is composed of a bolt threaded shaft portion 11 and a bolt head 12. However, as the bolt 10, various bolts described in the first embodiment, such as a dodecagonal bolt and a square bolt, can be used. Further, a stud bolt without a bolt head can also be used.

The bolt screw shaft portion 11 protrudes from the upper surface of the object to be fastened H, and a nut 15 is fastened to this protruding portion. That is, the fastened body H is compressed by the bolt head 12 and the nut 15.

As shown in FIG. 24(b), fourth male threaded portions 15a (corresponding to the fourth threaded portion in claim 1) are formed intermittently in the circumferential direction on the side surface of the nut 15. That is, each fourth male threaded portion 15a is formed in a bent shape portion on the side surface of the nut 15. It is preferable that the fourth male threaded portion 15a be formed with substantially equal length in all the bent portions. For example, if the fourth male threaded portion 15a is not formed in some bent portions, the load may act in a direction different from the tensile direction (that is, the vertical direction), and the accuracy of axial force detection may decrease. .

Axial force detection can be performed in a state where the first female threaded portion 21a1 of the connecting member 2 is screwed into the fourth male threaded portion 15a of the nut 15. In this embodiment, since the fourth male threaded portion 15a is formed on the outer peripheral surface of the nut 15, which has a larger diameter than the bolt screw shaft portion 11, the fourth male threaded portion 15a and the first female threaded portion 21a1 are screwed together. The area covered can be increased.

In this embodiment, as in the first embodiment, the feed amount and the like are adjusted so as to obtain the magnitude relationship Tsl>Trl. The definitions of Tsl and Trl are omitted since they were explained in the first embodiment. Therefore, it is possible to prevent the bolt 10 from loosening when the tension rod 31 is unloaded.

(Modification 1 of the third embodiment)
In the illustrated example, the fourth male threaded portion 15a is formed over the entire side surface of the nut 15 from the upper end to the lower end, but the present invention is not limited to this, and as shown in FIG. 24(c). It may be formed in a part from the upper end to the lower end.

(Modification 2 of the third embodiment)
In the embodiment described above, when the upper surface of the nut 15 and the first hollow part 21a of the connecting member come into contact, a clearance is formed between the lower end of the connecting member 2 and the object to be fastened H1. However, the present invention is not limited to this, and as shown in FIG. 24(d), a clearance is formed when the distal end surface of the bolt screw shaft portion 11 and the top surface of the second hollow portion 21b of the connecting member come into contact with each other. It may be configured so that Note that the distal end surface of the bolt screw shaft portion 11 also includes a recess or a convex portion formed on the distal end surface.

(Variation 3 of the third embodiment)
Modification 3 will be described with reference to FIGS. 25(a) and 25(b). FIG. 25(a) is a perspective view of the nut of Modification 3. FIG. 25(b) is a schematic diagram of an axial force detection device according to the third modification. In this modification 3, a flange nut is used.

The nut 500 is a hexagonal nut with a flange, which is an example of a flange nut, and includes a hexagonal nut body 501 and a ring-shaped flange portion 502. These nut main body 501 and flange portion 502 are integrally formed. The flange portion 502 protrudes radially outward from the nut body 501. Fourth male screw portions 501a extending in the circumferential direction are intermittently formed on the outer peripheral surface of the nut body 501. That is, like the first embodiment, a fourth male threaded portion 501a is formed in the bent portion of the nut body 501.

When connecting the connecting member 2 and the nut 500, when the connecting member 2 is rotated around the rotation axis X and the fourth male threaded part 501a and the first female threaded part 21a1 are screwed together, the connecting member 2 is screwed downward. do. When the connecting member 2 is further rotated around the rotation axis X, the upper surface of the nut body 501 comes into contact with the top surface of the first hollow portion 21a of the connecting member, and the connecting member 2 becomes unable to rotate. In the present modification example 3, a clearance is formed when the nut main body 501 and the connecting member first hollow portion 21a abut against each other (in other words, when the connecting member 2 cannot be screwed on). Note that the upper surface of the nut main body 501 includes a concave portion or a convex portion formed on the upper surface.
In the configuration shown in FIG. 25(b), the diameter of the flange portion 502 may be expanded and the flange portion 502 may be interposed between the tension receiving portion 4 and the object to be fastened H1. In this case, the tension receiving portion 4 receives a reaction force when the bolt is pulled through the flange portion 502 of the washer 500.

A further modification 3-1 of the present modification 3 will be described with reference to FIG. 25(c). FIG. 25(c) is a schematic diagram of the axial force detecting device of this modification, which differs from the axial force detecting device of FIG. 25(b) in that a connecting member third hollow portion 21c is formed. The third hollow part 21c of the connecting member is connected to the lower end of the first hollow part 21a of the connecting member, and has a diameter larger than that of the first hollow part 21a of the connecting member.

In this modification example 3-1, when the upper surface of the flange portion 502 of the nut 500 abuts the top surface of the third hollow portion 21c of the connecting member, there is a clearance between the lower end portion of the connecting member 2 and the object to be fastened H1. It is formed. Note that the upper surface of the flange portion 502 also includes a recess or a convex portion formed on the upper surface. However, as shown in FIG. 24(d), the distal end surface of the bolt screw shaft portion 11 (if a recess or convex portion is formed on the distal end surface of the bolt screw shaft portion 11, the recess or convex portion formed on the distal end surface) A clearance may be formed between the lower end of the connecting member 2 and the object to be fastened H1 when the top surface of the second hollow portion 21b of the connecting member 2 comes into contact with the top surface of the second hollow portion 21b of the connecting member 2.

(Modification 4 of the third embodiment)
FIG. 25(d) is a perspective view of the nut of this modification. FIG. 25(e) is a schematic diagram of the axial force detection device of this modification. In the nut 500 of this modification, a fourth male screw portion 502a extending in the circumferential direction is continuously formed on the outer peripheral surface of the flange portion 502.

When the connecting member 2 and the nut 500 are connected, when the connecting member 2 is rotated around the rotation axis X and the fourth male threaded portion 502a and the first female threaded portion 21c1 are screwed together, the connecting member 2 is screwed downward. do. When the connecting member 2 is further rotated around the rotation axis X, the upper surface of the flange portion 502 comes into contact with the top surface of the third hollow portion 21c of the connecting member, and the connecting member 2 becomes unable to rotate. In this modification 4, when the flange portion 502 and the third hollow portion 21c of the connecting member come into contact with each other (in other words, when the connecting member 2 cannot be screwed), the lower end of the connecting member 2 and the object to be fastened. A clearance is formed between H1 and H1. Note that the upper surface of the flange portion 502 also includes a recess or a convex portion formed on the upper surface. However, when the top surface of the nut body 501 (including the concave portions or convex portions when the top surface of the nut body 501 is formed) comes into contact with the connecting member first hollow portion 21a, or When the distal end surface of the bolt screw shaft portion 11 (including the recessed portion or convex portion if a recessed portion or a convex portion is formed on the distal end surface of the bolt screw shaft portion 11) comes into contact with the connecting member second hollow portion 21b. , a clearance may be formed between the lower end of the connecting member 2 and the object to be fastened H1.

(Variation 5 of the third embodiment)
FIG. 25(f) is a schematic diagram of an axial force detection device according to Modification Example 5. In the nut 500 of this modification, a fourth male threaded portion 501a is formed on the outer peripheral surface of the nut body 501, and a fourth male threaded portion 502a is formed on the outer peripheral surface of the flange portion 502. These fourth male screw portions 501a and 502a must have the same pitch. If the pitches are different, the connecting member 2 cannot be screwed into the fourth male threaded portions 501a and 502a.

Here, when connecting the connecting member 2 and the nut 500, the connecting member 2 is rotated around the rotation axis X to screw the fourth male threaded part 501a and the first female threaded part 21a1 together, and When the first female screw portion 21c1 is screwed together, the connecting member 2 is screwed downward. When the connecting member 2 is further rotated around the rotation axis comes into contact with the top surface of the third hollow portion 21c of the connecting member, and the connecting member 2 becomes unable to rotate. In this fifth modification, when the flange portion 502 and the third hollow portion 21c of the connecting member come into contact with each other (in other words, when the connecting member 2 cannot be screwed on), the lower end of the connecting member 2 and the object to be fastened. A clearance is formed between H1 and H1. However, when the top surface of the nut body 501 (including the concave portions or convex portions when the top surface of the nut body 501 is formed) comes into contact with the connecting member first hollow portion 21a, or When the distal end surface of the bolt screw shaft portion 11 (including the recessed portion or convex portion if a recessed portion or a convex portion is formed on the distal end surface of the bolt screw shaft portion 11) comes into contact with the connecting member second hollow portion 21b. , a clearance may be formed between the lower end of the connecting member 2 and the object to be fastened H1.

(Variation 6 of the third embodiment)
FIG. 25(g) is a perspective view of the nut of this modification. Referring to the figure, the flange portion 502 includes a lower end flat plate portion 503 and a curved surface portion 504 extending upward from the outer edge of the upper surface of the lower end flat plate portion 503 in a dome shape. However, the curved surface portion 504 may be formed into a truncated cone shape. A fourth male screw portion 503a extending in the circumferential direction is formed on the outer peripheral surface of the lower end flat plate portion 503. However, the fourth male threaded portion may be formed on the nut main body 501. Further, a fourth male screw portion may be formed on both the nut main body 501 and the lower end flat plate portion 503.

The distal end surface of the bolt screw shaft portion 11 (if a recess or convex portion is formed on the distal end surface of the bolt screw shaft portion 11, these recesses or convex portions are also included) is in contact with the top surface of the connecting member second hollow portion 21b. When in contact, the top surface of the nut body 501 (including the concave portions or convex portions if the top surface of the nut body 501 is formed) comes into contact with the top surface of the first hollow portion 21a of the connecting member. When the curved surface part 504 (in the case of a truncated cone, the tapered surface) contacts the top surface of the third hollow part 21c of the connecting member 2, there is a clearance between the lower end of the connecting member 2 and the object to be fastened H1. may be formed. In addition, when the curved surface part 504 (or the said taper surface) has a recessed part or a convex part formed, the said recessed part or convex part may be used as a contact site.

(Modification 7 of the third embodiment)
Modification 7 of this embodiment will be described with reference to FIG. 26. FIG. 26 corresponds to FIG. 1 and shows a state immediately after the tension receiver 4 contacts the fastened body H1. In this modification 7, a flat washer 50 is interposed between the nut 15 and the object to be fastened H1. The washer 50 has a diameter smaller than the inner diameter of the tension hollow portion 41, and a minute clearance is formed between the lower end of the connecting member 2 and the washer 50.

The washer 50 is inserted into the bolt screw shaft portion 11, and the nut 15 is fastened onto the washer 50. The washer 50 is set to have a larger outer diameter than the nut 15. Here, the washer 50 is not limited to a flat plate shape, and may be a stepped washer shown in FIG. 16 or a rosette washer 52 shown in FIG. 18.

Here, when the connecting member 2 is screwed onto the washer 50, before the bolt screw shaft portion 11 comes into contact with the top surface of the connecting member second hollow portion 21b, the upper surface of the nut 15 is attached to the connecting member first hollow portion 21a. The dimensions in the vertical direction of the connecting member first hollow part 21a and the connecting member second hollow part 21b are set to be in contact with the top surface.

However, the distal end surface of the bolt screw shaft portion 11 (if a recess or convex portion is formed on the distal end surface of the bolt screw shaft portion 11, these recesses or convex portions are also included) is the top surface of the connecting member second hollow portion 21b. A clearance may be formed between the lower end of the connection member 2 and the object to be fastened H1 when the connection member 2 comes into contact with the object H1. Furthermore, when the upper surface of the washer 50 (including the recesses or projections when the upper surface of the washer 50 is formed) contacts the connecting member 2, the lower end of the connecting member 2 A clearance may be formed between the fastened body H1 and the fastened body H1.
Further, when the top surface of the stepped washer (including the recesses or projections if the top surface of the stepped washer 51 is formed with these recesses or projections) comes into contact with the connection member 2, the connection member 2 A clearance may be formed between the lower end portion and the object to be fastened H1.
Furthermore, the curved surface portion of the rosette washer (if a concave portion or a convex portion is formed in the curved surface portion, the concave portion or convex portion is included) may be used as the abutment site.

(Modification 8 of the third embodiment)
Modification 8 of this embodiment will be described with reference to FIG. 27. FIG. 27 shows the state immediately after the tension receiver 4 comes into contact with the protection plate 60. That is, the protection plate 60 can be interposed between the nut 15, the tension receiving part 4, and the object to be fastened H1. A minute clearance is formed between the lower end of the connection member 2 and the protection plate 60. The protection plate 60 has an opening through which the bolt screw shaft portion 11 is inserted, and its diameter is set larger than the outer diameter of the tension receiving portion 4 . Therefore, when the handle 5 is rotated to move the tension receiver 4 downward, the member that the tension receiver 4 comes into contact with becomes the protection plate 60 instead of the fastened body H1. In this case, the reaction force applied from the fastened body H1 when the axial force is detected is transmitted to the tension receiver 4 via the protection plate 60. The details of the protection plate 60 have been explained in the first embodiment, so the explanation will be omitted.

The protection plate of Modification 8 can also have the form shown in FIG. 28. FIG. 28 shows a modification of the protection plate. Since this has been described in detail in the first embodiment described with reference to FIG. 11, it will be omitted.

(Modification 9 of the third embodiment)
In the above-described embodiments and modifications, the type of nut is a hexagonal nut, but the present invention is not limited to this. For example, the nut may be replaced with a square nut or a dodecagonal nut. Note that the square nut and the dodecagonal nut may have a flange or may not have a flange.

(Fourth embodiment)
The axial force detection device of this embodiment is a device in which the connecting member 2 is omitted and a bolt or the like is directly pulled by a tension rod 31. FIG. 29 is a schematic diagram of the axial force detection device of this embodiment. The bolt 10 is a hexagonal bolt convex screw, and includes a first bolt screw shaft portion 11 extending downward from the bolt head 12 and a protruding portion 120 extending upward from the bolt head 12 (the protruding portion according to claim 10). equivalent). The bolts 10 may be square bolts, hexagonal bolts, dodecagonal bolts, flange bolts, or the like.

The protrusion 120 is integrally provided on the bolt head 12. However, a recess with a threaded groove cut on the inner peripheral surface may be formed in the bolt head 12, and the protrusion 120 may be removably fastened to the recess. In the case of a removable type, the protrusion 120 can be removed after the axial force is detected. The first bolt screw shaft portion 11 is fastened to the bolt holes H1a and H2a of the fastened bodies H1 and H2. A second male threaded portion 120a (corresponding to the second threaded portion in claim 7) is formed on the protruding portion 120, and the second male threaded portion 120a is connected to the third female threaded portion 311a of the tension rod 31 (corresponding to the second threaded portion in claim 7). (corresponding to the third threaded portion in item 7), the bolt 10 is pulled and axial force detection is performed.

When the axial force of the bolt 10 reaches the target axial force, the bolt 10 and the tension rod 31 are unloaded. When the unloading torque is defined as Trl, Trl can be calculated from the following equation (1). Unloading means rotating the tension rod 31 in a direction that releases the tensile load on the bolt 10.
Trl=Ft/2×(d2t/cosαt×μst-Pt/π)...Formula (1)
However, Ft: tensile force of the bolt 10, d2t: effective diameter of the second male threaded portion 120a of the protrusion 120, αt: half angle of the thread of the second male threaded portion 120a of the protrusion 120, μst: the second male threaded portion 120a of the protrusion 120. The coefficient of friction of the threaded surface of the second male threaded portion 120a is Pt: the feed amount per rotation of the second male threaded portion 120a of the protrusion 120.

Further, the loosening torque of the bolt 10 with respect to the object to be fastened H is defined as Tsl. The definition of Tsl is omitted because it was explained using equation (2) in the first embodiment. Similar to the first embodiment, Tsl is configured to be larger than Trl. A method for realizing this size relationship is, for example, when the threaded portion of the first bolt screw shaft portion 11 is a single-thread thread, and the second male threaded portion 120a of the protruding portion 120 is a multi-thread thread, a triangular thread, a trapezoidal thread, or a square thread. It can be configured by The details have been explained in the first embodiment, so they will be omitted.

Here, in equation (1), when Trl is positive (that is, when d2t/cosαt×μst>Pt/π), an external force is applied to the tension rod 31 in the direction of releasing the tensile load on the bolt 10. The load is released by rotating the tension rod 31. For example, by rotating the wrench 34, the tension rod 31 can be forcibly rotated. As described above, in this embodiment as well, by designing the feed amount Pt>feed amount Pb, for example, Tsl can be made larger than Trl. This can prevent the bolt 10 from loosening during unloading.

In equation (1), when Trl is negative (that is, when d2t/cosαt×μst<Pt/π), the tension rod 31 automatically rotates in a direction that releases the tensile load on the bolt 10. In this case, no loosening torque is applied to the bolt 10.
However, the bolt 10 of this embodiment can also be applied to an axial force detection device having the connecting member 2. In this case, the second male threaded part 120a of the protruding part 120 protruding from the bolt head 12 is screwed into the first female threaded part 21a1 of the connecting member 2, and the connecting member 2 is connected as in the first embodiment. Pull the bolt 10 through the screw. The conditions to be satisfied by the connecting member 2 in this case have been explained in the first embodiment and so on, so the description thereof will be omitted.

(Modification 1 of the fourth embodiment)
As explained in the first embodiment, the washer 50 is interposed between the bolt head 12 and the object to be fastened H (see FIG. 9(a)), or the stepped washer 51 is interposed (see FIG. 9(a)). b)), a washer 52 made of a rosette washer (see FIG. 9(c)), or a protective plate 61 may be provided (see FIGS. 10 and 11).

(Modification 2 of the fourth embodiment)
When using the bolt 10 having the fourth male threaded portion 12a (corresponding to the second threaded portion in claim 7) on the side surface of the bolt head 12 described in the first embodiment, the fourth male threaded portion 12a is The third female threaded portion 311a of the tension rod 31 may be screwed together to pull the bolt 10. In this case, by adjusting the feed amount Pt of the fourth male threaded portion 12a of the bolt head 12 to be larger than the feed amount Pb of the threaded portion of the bolt screw shaft portion 11, the bolt 10 can be prevented from loosening during unloading. etc. can be prevented. It goes without saying that the various modifications described in the first embodiment are included in the second modification of the fourth embodiment.

(Variation 3 of the fourth embodiment)
When using the washer 14 having the fourth male threaded portion 14a (corresponding to the second threaded portion of claim 7) described in the second embodiment, the third female thread of the tension rod 31 is attached to the fourth male threaded portion 14a. The bolt 10 may be pulled by threading the threaded portion 311a. In this case, by adjusting the feed amount Pt of the fourth male threaded portion 14a of the washer 14 to be larger than the feed amount Pb of the threaded portion of the bolt screw shaft portion 11, loosening of the bolt 10 during unloading can be prevented. It can be prevented. It goes without saying that the various modifications described in the second embodiment are included in the third modification of the fourth embodiment.

(Modification 4 of the fourth embodiment)
When using the nut 15 having the fourth male threaded portion 15a (corresponding to the second threaded portion of claim 7) described in the third embodiment, the third female thread of the tension rod 31 is attached to the fourth male threaded portion 15a. The bolt 10 may be pulled by threading the threaded portion 311a. In this case, by adjusting the feed amount Pt of the fourth male threaded portion 14a of the nut 15 to be larger than the feed amount Pb of the threaded portion of the bolt screw shaft portion 11, loosening of the bolt 10 during unloading can be prevented. It can be prevented. Note that it goes without saying that the various modifications described in the third embodiment are included in modification 4 of the fourth embodiment.

(Variation 5 of the fourth embodiment)
A protruding portion 120 having a second male threaded portion 120a may be provided at the lower end of the tension rod 31, and a recessed portion having a female threaded portion cut on the inner peripheral surface may be formed in the bolt head 12. In this case, the axial force is detected by screwing the second male threaded portion 120a of the protruding portion 120 extending from the tension rod 31 into the recessed portion of the bolt head 12.
The bolt of this modification can also be applied to an axial force detection device having the connecting member 2. In this case, the axial force is detected by forming a protrusion with a male thread cut on the outer peripheral surface at the lower end of the connecting member 2, and screwing this protrusion into the recess of the bolt head 12.

(Fifth embodiment)
In the first to third embodiments described above, the structure in which one of the bolt head, washer, and nut is pulled by the tension rod 31 via the connection member 2 was described, but the axial force detection device of this embodiment is This is a device that pulls the shaft of a bolt through a connecting member. FIG. 30(a) is a schematic diagram of the axial force detection device of this embodiment. A bottom surface portion 42 extending toward the rotation axis X is provided at the lower end portion of the tension receiving portion 4 . Note that the configuration of the tension receiving section 4 having the bottom surface section 42 can be applied to other embodiments and modifications. The bolt 10 is a general bolt having a bolt threaded shaft portion 11 and a bolt head 12. A regular bolt is a bolt that does not have a thread formed on the side of the bolt head. Various bolts described in the first embodiment, such as square bolts, hexagonal bolts, and dodecagonal bolts, can be used as the bolts 10. The bolt head 12 is in contact with the lower surface of the object to be fastened H2.

Nut 15 is a general nut. A general nut is a nut that does not have a thread formed on the side of the nut. Various nuts described in the third embodiment, such as a square nut, a hexagonal nut, and a dodecagonal nut, can be used as the nut 15. The nut 15 is fastened to the bolt screw shaft portion 11 and is in contact with the upper surface of the fastened body H1. Further, the bottom surface portion 42 of the tension receiving portion 4 is in contact with the top surface of the nut 15 . Therefore, the tension receiving portion 4 receives a reaction force via the nut 15. Note that the bottom surface portion 42 of the tension receiving portion 4 may be omitted. In this case, the tension receiving portion 4 comes into contact with the object H to be fastened instead of the nut 15, and therefore receives a reaction force directly from the object H.

As described above, the bolt 10 includes various bolts, but also includes a stud bolt without a bolt head, as shown in FIG. 30(b). A nut 15 is fastened to the upper threaded portion of the stud bolt 10, and a lower threaded portion of the stud bolt 10 is fastened to the object to be fastened H2. Thereby, the stud bolt 10 is fixed to the body H to be fastened. In the illustrated example, since the nut 15 is interposed between the bottom surface part 42 of the tension receiving part 4 and the object to be fastened H, the tension receiving part 4 receives a reaction force via the nut 15. Note that the bottom surface portion 42 of the tension receiving portion 4 may be omitted. In this case, the tension receiving portion 4 comes into contact with the object H to be fastened instead of the nut 15, and therefore receives a reaction force directly from the object H.
The nut 15 is not limited to a flat plate shape, and may be a flanged nut illustrated in FIG. 20, for example. In this case, the flange portion of the nut may be interposed between the tension receiving portion 4 and the body H to be fastened. The shape of the flange portion of the nut may be, for example, a shape having a curved surface (or tapered surface) imitating the shape shown in FIG. 18.

As described in the first embodiment, by adjusting the feed amount and the like so that the magnitude relationship Tsl>Trl is obtained, it is possible to prevent the bolt 10 from loosening during unloading.

(Modification 1 of the fifth embodiment)
A washer may be interposed between the nut 15 and the object to be fastened H1. As the washer, a normal washer shown in FIG. 9(a), a stepped washer 51 shown in FIG. 9(b), a washer 52 made of a rosette washer shown in FIG. 9(c), etc. can be used. The diameter of the washer may be increased and the washer may be interposed between the tension receiving portion 4 and the object to be fastened H1. In this case, the tension receiving portion 4 receives a reaction force when the bolt is pulled through the washer.

(Modification 2 of the fifth embodiment)
Instead of the nut 15 of Modification 1 of the present embodiment, the protection plate 60 described in the first embodiment may be interposed between the bolt head 12 and the body H to be fastened. In this case, the tension receiving portion 4 receives a reaction force when the bolt is pulled through the protection plate 60.

(Variation 3 of the fifth embodiment)
In FIG. 30(a), the connecting member 2 may be omitted and the bolt threaded shaft portion 11 may be directly screwed into the third female threaded portion 311a of the tension rod 31 (see FIG. 30(c)). In this case, by adjusting the feed amount of the portion of the bolt screw shaft portion 11 that is screwed into the third female thread portion 311a and the portion that is fastened to the fastening body H, the size relationship of Tsl>Trl can be established. Obtainable. In addition, in FIG. 30(c), the bottom surface part 42 of the tension receiving part 4 may be omitted. In this case, the tension receiving portion 4 comes into contact with the object H to be fastened instead of the nut 15, and therefore receives a reaction force directly from the object H.
Also, when using the stud bolt 10 shown in FIG. 30(b), the connecting member 2 is omitted and the upper threaded part of the stud bolt 10 is directly screwed into the third female threaded part 311a of the tension rod 31. You may let them. In this case, by adjusting the feed amount of the portion of the stud bolt 10 that is screwed into the third female threaded portion 311a and the portion that is fastened to the fastening body H, a size relationship of Tsl>Trl is obtained. be able to. In addition, as mentioned above, the bottom surface part 42 of the tension receiving part 4 may be omitted. In this case, the tension receiving portion 4 comes into contact with the object H to be fastened instead of the nut 15, and therefore receives a reaction force directly from the object H.
When using the tension receiving part 4 shown in FIGS. 30(a) and 30(b) having the bottom surface part 42, it is desirable that the tension receiving part 4 be of a split type that can be divided into a plurality of parts. In this case, by assembling the tension receiver 4 after the connecting member 2 is screwed onto the bolt 10, etc., the axial force detecting device shown in FIGS. 30(a) and 30(b) can be completed. .

(Sixth embodiment)
The axial force detection device of this embodiment is provided with a rotation prevention mechanism that allows movement of the connection member 2 in the direction of the rotation axis X and prevents the connection member 2 from rotating around the rotation axis X. FIG. 31 is a schematic diagram of the axial force detection device of this embodiment.
Elements whose functions are common to those of the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

A plurality of key grooves 41a extending in the vertical direction are formed on the inner surface of the tension receiving part 4. It is desirable that these keyways 41a are arranged at equal intervals. The number of key grooves 41a installed is not particularly limited, but may be, for example, eight in the circumferential direction.
A key 25 that engages with the key groove 41a is provided on the side surface of the connecting member 2. The key 25 is set slightly smaller than the width of the keyway 41a.
Note that although the keyway 41a may be formed in only one place, it is preferable to have a plurality of keyways 41a because the degree of freedom in attaching the connecting member 2 increases.

Therefore, in the state in which the key 25 is engaged with the keyway 41a, the connecting member 2 is allowed to move in the vertical direction and is prohibited from rotating around the rotation axis X. In this embodiment, the key 25 is formed in the connecting member 2 and the key groove 41a is formed in the tension receiving part 4, but the present invention is not limited to this. A key may also be formed.

In the first embodiment, in order to prevent the bolt 10 from loosening during unloading, the screw feed amount was adjusted so that Pt>Pb, but in this embodiment, such adjustment is not essential. Therefore, it is also possible to set Pt<Pb.

As described in the first embodiment, if the screw feed amount is set to satisfy the condition Pt>Pb, it is possible to prevent the bolt 10 from loosening during unloading, but for example, If poor lubrication occurs in the screwing region between the second male threaded portion 22a and the third female threaded portion 311a of the tension rod 31, the above-mentioned effects may not be achieved. Therefore, by providing the rotation prevention mechanism consisting of the key 25 and the keyway 41a, it is possible to reliably prevent the bolt 10 from loosening during unloading.

Furthermore, when the connecting member 2 is moved upward to pull the bolt 10, the bolt screw shaft portion 11 is extended and the bolt head 12 is separated from the object H1 to be fastened. Since the frictional force is eliminated, when the torque by the tension rod 31 becomes larger than the torque of the bolt 10 and the object to be fastened H, the connecting member 2 rotates and the bolt 10 is further tightened. In this embodiment, since the rotation of the connection member 2 is prevented by the rotation prevention mechanism, such a problem does not occur.

In this embodiment, the rotation prevention mechanism is realized by the key 25 and the keyway 41a, but the present invention is not limited to this. For example, the rotation prevention mechanism is formed by a first toothed portion formed on the connecting member 2 and a second toothed portion formed on the tension receiving portion 4 and meshed with the first toothed portion in the direction around the rotation axis of the tension rod 31. It may be realized. In this case, since the first toothed portion and the second toothed portion mesh in the direction around the rotation axis, it is possible to prevent the connecting member 2 from rotating. The rotation prevention mechanism including the first toothed portion and the second toothed portion may be realized by a spline or by serrations.

If there is play or twist in the rotation prevention mechanism in the direction around the rotation axis of the tension rod 31, the bolt 10 will easily rotate in the loosening direction. Therefore, it is desirable to design the anti-rotation mechanism so that play and twisting are reduced.

By providing the rotation prevention mechanism, when the bolt 10 is pulled, the rotational torque of the tension rod 31 acts on the tension receiving part 4 via the connecting member 2, and there is a possibility that the tension receiving part 4 may rotate. Therefore, in order to prevent the tension receiving part 4 from rotating, the friction coefficient of the contact surface of the tension receiving part 4 is increased, the diameter of the tension receiving part 4 is designed to be large (that is, the torque is increased), etc. It is desirable to leave it there.

It goes without saying that the configuration of this embodiment can be applied to the axial force detection devices of the first to fifth embodiments and the modified axial force detection devices described in these embodiments.
For example, in FIG. 31, the tension receiving part 4 is in contact with the object to be fastened H1, but a nut or a protection plate may be interposed between the tension receiving part 4 and the object to be fastened H1.

1 Axial force detection device 2 Connection member 3 Tension mechanism 4 Tension receiver 5 Handle 10, 100, 200, 300 Bolt 11 Bolt threaded shaft portion 12a, 102b, 202a, 302a1, 302b1 First male screw portion 14 50 51 52 81 91 Washer 15 95 97 500 Nut 21 Cylindrical portion 21a Connection member hollow portion 21a1 First female threaded portion 22 Convex portion 22a Second male threaded portion 25 Key 31 Tension rod 31a Small diameter rod portion 31b Large diameter rod portion 32 Bearing portion 33 Square drive 34 Wrench 41a Keyway 42 Bottom part 60 Protective plate 311 Tension rod hollow part 311a Second female threaded part H (H1, H2) Fastened object

Claims (24)

An axial force detection device that detects the axial force of a fastened body fastened to a fastened body,
a connecting member having a first threaded portion and a second threaded portion;
The connecting member is provided with a third threaded portion, and the connecting member is rotated by applying a rotational torque around a rotation axis extending in the vertical direction while the second threaded portion is screwed to the third threaded portion. a tension rod that tensions the fastener through the tension rod;
a tension receiver disposed around the outer periphery of the connecting member and receiving a reaction force acting from the object to be fastened when the tension rod is pulled;
has
The fastening body or a fastening component used for fastening together with the fastening body is formed with a fourth threaded part that is threaded into the first threaded part,
The second threaded part and the first threaded part are screwed into the third threaded part and the fourth threaded part, respectively, and the fastening body is pulled up for axial force detection, and then the load is unloaded. When the unloading torque of the connecting member and the tension rod is defined as Trl, and the loosening torque of the fastened body with respect to the fastened body is defined as Tsl,
An axial force detection device characterized in that Trl defined by equation (1) is set smaller than Tsl defined by equation (2).
Trl=Ft/2×(d2t/cosαt×μst-Pt/π)...Formula (1)
However, Ft: tensile force of the fastening body, d2t: effective diameter of the second threaded part of the connecting member, αt: half-angle of thread of the second threaded part of the connecting member, μst: thread surface of the second threaded part of the connecting member. Friction coefficient, Pt: is the amount of feed per rotation of the second threaded portion of the connecting member.
Tsl=Fb/2×(d2b/cosαb×μsb-Pb/π)...Formula (2)
However, Fb: axial force of the fastening body, d2b: effective diameter of the threaded shaft of the fastening body, αb: half angle of the thread of the threaded shaft of the fastening body, μsb: coefficient of friction of the threaded surface of the threaded shaft of the fastening body, Pb: Feed amount per rotation of the screw shaft portion of the fastening body. The axial force detection according to claim 1, wherein the tension rod is rotated by applying an external force when unloading when Trl is positive, and automatically rotates when unloading when Trl is negative. Device. The fastening body is a bolt,
The axial force detection device according to claim 1 or 2, wherein the fastening component is a nut or a washer. When the fourth threaded portion is formed on the fastening body, the fourth threaded portion includes a side surface of the bolt head, a threaded shaft portion of the bolt, a protrusion projecting from the top surface of the bolt head, and the bolt head. The axial force detection device according to claim 3, wherein the axial force detection device is formed in any one of the recesses. The axial force detection device according to claim 3, wherein when the fourth threaded portion is formed on the nut, the fourth threaded portion is formed on a side surface of the nut. The axial force detection device according to claim 3, wherein when the fourth threaded portion is formed on the washer, the fourth threaded portion is formed on a side surface of the washer. An axial force detection device that detects the axial force of a fastened body fastened to a fastened body,
The third threaded part is provided with a third threaded part, and the third threaded part is screwed into a second threaded part formed on the fastening body or a fastening component used for fastening together with the fastening body, and the third threaded part is arranged around a rotating shaft extending in the vertical direction. a tension rod that pulls the fastening body by applying a torque of
After the second threaded part and the third threaded part are screwed together and the fastened body is pulled up for axial force detection, the unloading torque of the fastened body and the tension rod when unloading is Trl, When the loosening torque of the fastened body with respect to the fastened body is defined as Tsl,
An axial force detection device characterized in that Trl defined by equation (1) is set smaller than Tsl defined by equation (2).
Trl=Ft/2×(d2t/cosαt×μst-Pt/π)...Formula (1)
However, Ft: tensile force of the fastening body, d2t: effective diameter of the second threaded portion of the fastening body or fastening component, αt: thread half angle of the second threaded portion of the fastening body or fastening component, μst: fastening body or fastening component The coefficient of friction of the threaded surface of the second threaded portion of Pt is the feed amount per rotation of the second threaded portion of the fastening body or fastening component.
Tsl=Fb/2×(d2b/cosαb×μsb-Pb/π)...Formula (2)
However, Fb: axial force of the fastening body, d2b: effective diameter of the threaded shaft of the fastening body, αb: half angle of the thread of the threaded shaft of the fastening body, μsb: coefficient of friction of the threaded surface of the threaded shaft of the fastening body, Pb: Feed amount per rotation of the screw shaft portion of the fastening body. The axial force detection according to claim 7, wherein the tension rod is rotated by applying an external force when unloading when Trl is positive, and automatically rotates when unloading when Trl is negative. Device. The fastening body is a bolt,
The axial force detection device according to claim 7 or 8, wherein the fastening component is a nut or a washer. When the second threaded portion is formed on the fastening body,
A claim characterized in that the second threaded portion is formed on any one of a side surface of the bolt head, a threaded shaft portion of the bolt, a protrusion projecting from the top surface of the bolt head, and a recessed portion of the bolt head. The axial force detection device according to item 9. The axial force detection device according to claim 9, wherein when the second threaded portion is formed on the nut, the second threaded portion is formed on a side surface of the nut. The axial force detection device according to claim 9, wherein when the second threaded portion is formed on the washer, the second threaded portion is formed on a side surface of the washer. The connecting member and the tension receiver have a rotation prevention mechanism,
3. The rotation prevention mechanism allows movement of the connection member in the direction of the rotation axis of the tension rod, and prevents rotation of the connection member around the rotation axis of the tension rod. The axial force detection device described in . The rotation prevention mechanism is a key extending in the vertical direction and a key groove in which the key engages,
The axial force detection device according to claim 13, wherein one of the key and the keyway is formed in the tension receiving portion, and the other is formed in the connection member. The rotation prevention mechanism includes a first toothed portion formed on the connecting member, and a second toothed portion formed on the tension receiving portion and meshed with the first toothed portion in a direction around the rotation axis of the tension rod. The axial force detection device according to claim 13, characterized in that: A claim characterized in that the tension rod is designed so that when the fastening body is pulled and the axial force is detected, the rotational torque by the tension rod does not exceed the torque that rotates the tension receiver. The axial force detection device according to item 13. 17. The axial force detection device according to claim 16, wherein the ground contact surface of the tension receiving portion is subjected to high friction treatment to increase frictional force. 17. The distance from the rotation axis of the tension rod to the tension receiving part is set so that the tension receiving part does not rotate when the fastening body is pulled and the axial force is detected. The axial force detection device described. An axial force detection device that detects the axial force of a fastened body fastened to a fastened body,
a connecting member having a first threaded portion and a second threaded portion;
The connecting member is provided with a third threaded portion, and the connecting member is rotated by applying a rotational torque around a rotation axis extending in the vertical direction while the second threaded portion is screwed to the third threaded portion. a tension rod that tensions the fastener through the tension rod;
a tension receiver disposed around the outer periphery of the connecting member and receiving a reaction force acting from the object to be fastened when the tension rod is pulled;
has
The connecting member and the tension receiver have a rotation prevention mechanism,
The axial force detection device is characterized in that the rotation prevention mechanism allows movement of the connection member in the direction of the rotation axis of the tension rod and prevents rotation of the connection member around the rotation axis of the tension rod. The rotation prevention mechanism is a key extending in the vertical direction and a key groove in which the key engages,
The axial force detection device according to claim 19, wherein one of the key and the keyway is formed in the tension receiving portion, and the other is formed in the connection member. The rotation prevention mechanism includes a first toothed portion formed on the connecting member, and a second toothed portion formed on the tension receiving portion and meshed with the first toothed portion in a direction around the rotation axis of the tension rod. The axial force detection device according to claim 19. A claim characterized in that the tension rod is designed so that when the fastening body is pulled and the axial force is detected, the rotational torque by the tension rod does not exceed the torque that rotates the tension receiver. The axial force detection device according to any one of Items 19 to 21. The axial force detection device according to claim 22, wherein the ground contact surface of the tension receiving portion is subjected to high friction treatment to increase frictional force. 22. A distance from the rotation axis of the tension rod to the tension receiving part is set so that the tension receiving part does not rotate when the fastening body is pulled and the axial force is detected. The axial force detection device described in .