JP6231824B2 - How to set bolt axial force - Google Patents

Description

  The present invention relates to a method for setting a bolt axial force, and more particularly to a method in which a bolt can be stably set to a desired axial force when a member is tightened with a bolt and a nut.

  A method for fastening a member by combining a bolt and a nut, generating an axial tightening force (bolt axial force) on the bolt by the tightening force of the nut is well known. The bolt axial force is controlled by the tightening torque of the nut so that it is within a predetermined range depending on the member to be fastened and the application.

In general, it is well known that the relationship between the torsional torque of the nut and the bolt axial force has the following relationship depending on the torque coefficient value and the nominal diameter of the screw.
K = Torque N · m / Bolt diameter (mm) · Bolt axial force (KN)
However, K is a torque coefficient value.

  However, it is very difficult to control the torque coefficient value K to be constant and reduce the variation in the bolt axial force.

  On the other hand, the method of controlling bolt axial force with the elastic repulsive force of a leaf | plate spring is proposed (patent document 1, patent document 2, patent document 3).

Japanese Patent Application Laid-Open No. 07-224823 JP 2003-322220 A JP 2006-144838 A

  However, in the methods described in Patent Documents 1 to 3, it is necessary to always provide a leaf spring on the bolt, and the structure becomes complicated and large.

  This invention makes it a subject to provide the setting method of the bolt axial force which made it possible to obtain desired bolt axial force stably with a simple structure in view of this problem.

  Therefore, the bolt axial force setting method according to the present invention heats a cylindrical bolt having an external thread formed on the outer peripheral surface, inserts a stress rod inside the cylindrical bolt, and connects both ends of the stress rod to a jig. After attaching the cylindrical bolt to the cylindrical bolt, the cylindrical bolt is returned to room temperature, and an axial tensile force is applied to the cylindrical bolt by the stress rod, and a pair of nuts are screwed onto the outer peripheral surface of the cylindrical bolt. Then, after sandwiching a member between the pair of nuts, the jig is removed, the axial pulling force by the stress rod is released, and the cylindrical bolt is contracted. It is characterized by controlling to axial force.

  Also, the bolt axial force setting method according to the present invention comprises cooling the stress rod, inserting the stress rod into a cylindrical bolt having an external thread formed on the outer peripheral surface, and using a jig to connect both ends of the stress rod. After attaching to the cylindrical bolt, the stress rod is returned to room temperature, the axial tension is applied to the cylindrical bolt by the stress rod, and a pair of nuts are screwed onto the outer peripheral surface of the cylindrical bolt, After holding the member between the pair of nuts, the jig is removed to release the tensile force of the stress rod in the axial direction, and the cylindrical bolt is contracted. It is characterized in that it is controlled to.

  One of the features of the present invention is that the cylindrical bolt is heated or the stress rod is cooled, the stress rod is inserted into the cylindrical bolt and attached with a jig, and then returned to room temperature. In this state, a pair of nuts are screwed onto the outer peripheral surface of the cylindrical bolt to sandwich the member, and finally the jig is removed to release the axial tensile force. It is in the point which was made to control.

Thereby, a member can be tightened with a cylindrical bolt and a pair of nuts, and the structure can be made very simple.
Moreover, if the elongation of the cylindrical bolt or the contraction of the stress rod is controlled by heating or cooling, a predetermined bolt axial force can be stably obtained.

  A hexagon bolt or a cap screw can be used as the jig, and an internal thread is formed on the inner surface of the cylindrical bolt, and the hexagon bolt or the cap screw is screwed to attach the stress rod to the cylindrical bolt.

It is a figure which shows typically preferable embodiment of the setting method of the bolt axial force which concerns on this invention. It is a figure which shows 2nd Embodiment typically.

  Hereinafter, the present invention will be described in detail based on specific examples shown in the drawings. FIG. 1 shows a preferred embodiment of a bolt axial force setting method according to the present invention. When the bolt axial force is set by the method of this example, as shown in FIG. 1A, a cylindrical bolt 10 is prepared in which a male screw 10A is formed on the outer peripheral surface and a female screw 10B is formed on the inner surfaces of both ends. The inner surface portion for accommodating the stress rod 11 of the cylindrical bolt 10 may be cylindrical or rectangular.

  Next, as shown in FIGS. 1B, 1C, and 1D, the cylindrical bolt 10 is heated to a predetermined temperature, the stress rod 11 is inserted into the cylindrical bolt 10, and the cylindrical bolt is inserted. Hexagonal bolts (jigs) 12 are screwed onto the inner surfaces of both end portions of 10 and the stress rods 11 are attached to both end portions of the cylindrical bolt 10 without compressing the stress rod 11.

  When the cylindrical bolt 10 and the stress rod 11 are returned to room temperature in this state, the cylindrical bolt 10 contracts, a compressive force acts on the stress rod 11, and an axial tensile force acts on the cylindrical bolt 10 as a reaction. It becomes.

  The combination of the cylindrical bolt 10 and the stress rod 11 is inserted into the holes of the members 13 and 14, and a pair of nuts 12 are screwed onto the outer peripheral surface of the cylindrical bolt 10 as shown in FIG. The members 13 and 14 are clamped.

  Finally, as shown in FIG. 1F, when the hexagon bolt 12 is loosened and the stress rod 11 is pulled out, the members 13 and 14 can be tightened by a predetermined bolt axial force.

  Now, assume that the length of the cylindrical bolt 10 is L1, and when this is heated to a predetermined temperature, L1 + I1 is obtained. Next, a tensile test is performed on the cylindrical bolt 10 at room temperature, and the tensile load when the length becomes L1 + I1 can be measured. Due to the cooling, a load that the cylindrical bolt 10 tries to contract is applied to the stress rod 11 and compressed, and the tensile force in the axial direction acts on the cylindrical rod 11 due to the reaction. When the axial pulling force by the stress rod 11 is released, the cylindrical bolt 11 is contracted, and the bolt axial force between the nuts 15 can be measured.

  FIG. 2 shows a second embodiment, in which the same reference numerals as those in FIG. 1 denote the same or corresponding parts. In this example, the stress rod 11 is cooled (FIGS. 2A and 2B), set in the cylindrical rod 10, and returned to room temperature (FIGS. 2C and 2D). It is the same as the form. Thus, even if the stress rod 11 is cooled, the bolt axial force can be set.

DESCRIPTION OF SYMBOLS 10 Cylindrical bolt 10A Male thread 10B Female thread 11 Stress rod 12 Hexagon bolt (jig)
13, 14 member 15 nut

Claims (2)

Heating the male screw end portions (10A) is formed is opened internal thread on the both end inner surface (10B) is formed cylindrical bolt (10) on the outer circumferential surface, the interior of the heated cylindrical bolt (10) A stress rod (11) having a diameter smaller than the inner diameter of the cylindrical bolt (10) is inserted , and the bolt (12) is screwed into the female screw (10B) on the inner surface of both ends of the cylindrical bolt (10) to thereby stress the rod. (11) after mounting the upper Symbol cylindrical bolt the ends of the stress rods by abutting the end surfaces of the stress rods without compressing (11) (11) (10) and,
By returning the cylindrical bolt (10) to room temperature, an axial tensile force is applied to the cylindrical bolt (10) by the stress rod (11),
After a pair of nuts (15) are screwed onto the outer peripheral surface of the cylindrical bolt (10) and the members (13, 14) are sandwiched between the pair of nuts (15),
By contracting the cylindrical bolt (10) Remove the bolts (12) to release the axial tensile force by the stress rods (11), setting the cylindrical bolt (10) to a predetermined axial force A method of setting a bolt axial force, characterized in that The stress rod (11) is cooled, the stress rod (11) is inserted into a cylindrical bolt (10) having an external thread formed on the outer peripheral surface, and both ends of the stress rod (11) are attached to a jig (12). After attaching to the cylindrical bolt (10),
The stress rod (11) is returned to room temperature and an axial tensile force is applied to the cylindrical bolt (10) by the stress rod (11).
After a pair of nuts (15) are screwed onto the outer peripheral surface of the cylindrical bolt (10) and the members (13, 14) are sandwiched between the pair of nuts (15),
The cylindrical bolt (10) is brought to a predetermined axial force by removing the jig (12) and releasing the axial pulling force by the stress rod (11) to contract the cylindrical bolt (10). A bolt axial force setting method characterized by controlling the bolt axial force.

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