JPH01289674A - Axial force managing method for bolt - Google Patents

Abstract

PURPOSE:To facilitate management of the axial force of a bolt by performing the axial force management of the bolt with attention paid onto deformation of a spacer, and determining accurate axial force from an angle of rotation and the torque applied to the bolt. CONSTITUTION:When fastening is made using a bolt 1 and a washer (one type spacer) 6, change in the differential value (dT/dtheta) of the torque with respect to the rotational angle (angle of screw driving) of the bolt 1 is determined, and in this change of differential value, the axial force of bolt corresponding to a certain rotational angle with respect to the point of change of the differential value is determined on a plurality of washers 6. Then these washers 6 are grouped by bolt axial forces, and at the actual time of fastening, i.e. when a member to be fixed 9 is fastened by bolt to a hold-down member 8, washer 6 is selected corresponding to the bolt axial force desired to be accomplished. As a result, accurate axial force of bolt 1 can be determined from the angle of rotation and the torque applied to the bolt 1.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for managing the axial force of bolts used to fasten parts.

Conventional technology In order to securely attach a part to be attached to an attachment member such as the main body of a mechanical device, a fastening operation using bolts and spacers such as washers and metals (hereinafter referred to as washers) is employed. FIG. 2 shows a general example of a state in which parts are fastened together using bolts and washers that are often used to fasten such parts.

In this figure, numeral 1 indicates a bolt for fixing parts,
This bolt 1 consists of a component abutting part 3 to which a rotating action such as a spanner is applied, and a leg part 4 having a threaded part 7 at its lower end. A seat surface 5 is provided on the back surface.

A washer 6 is attached to the leg portion 4 of the bolt 1 to improve the efficiency of tightening the bolt 1. This washer 6 is a countersunk spring washer in which a predetermined dimensional difference (deepening depth) is made between the outer peripheral edge 6a and the inner peripheral edge 6b by press molding or the like, as shown in FIG. 3, for example. . When such a washer 6 is attached to the bolt 1 and the attached member 9 is attached to the attachment member 8, the outer circumferential edge 6a of the washer 6 comes into contact with the attached member 9, while the inner circumferential edge 6b of the bolt 1 comes into contact with the attached member 9. It comes into contact with the seat surface 5.

When the bolt 1 is rotated in this state, the difference in moment acts on the washer 6 to prevent it from rotating, and gradually the washer 6
The bolt 1 is tightened with a constant torque while deforming the bolt 1 into a flat shape.

Conventionally, in order to tighten the bolt while keeping the axial force of the bolt 1 at a certain constant value or within a predetermined range, the axial force of the bolt 1, that is, the force applied to the leg 4 ( There is an axial force management method called the torque gradient method, which focuses on the axial force (axial force) or the torque based on this and tracks the change in 1 -rook for 10 rotation angles of the bolt. An example of the bolt axial force management method using this torque gradient method is shown in the fourth section.
As shown in the figure.

This is to obtain the differential value of the torque (the same applies to the axial force) corresponding to the rotation angle of the bolt 1 during bolt tightening. If the bolt 1 is tightened until it breaks, there is a relationship between the rotation angle of the bolt 1 and the torque applied to the bolt 1 as shown in FIG. 4(a). That is, the axial force of the bolt 1 increases slowly until the rotation angle reaches α1, and while the rotation angle is from α1 to α2, the bolt 1 is elastically deformed and the change in axial force remains constant. and,
When the elastic limit is reached, a yield point S is drawn, and then when an external force (tensile force due to screwing) is further applied, it breaks at a breaking point T. When such a torque change of the bolt 1 is expressed as a differential value dT/dθ of the axial force with respect to the rotation angle, it becomes as shown in FIG. 4(b). In other words, this differential value is 3 from the origin 0 to the point!
Until point A is reached, the leg portion 4 of the bolt 1 is elastically deformed, so that the differential value becomes a maximum and constant value (3). Thereafter, the differential value, that is, the rate of increase in torque decreases from point 8 corresponding to the point where the bolt 1 reaches its elastic limit, and reaches O at the maximum axial force.

Conventionally, the differential value is, for example, 1/2 from 8 points.
The axial force is controlled so that the rotation of the bolt '1 is stopped at the 0 point, which is the point at which the bolt becomes V, and the axial force at this time is used to tighten the bolt. This bolt tightening is called the yield point line.

Problems to be Solved by the Invention However, in such a conventional bolt axial force management method, due to manufacturing variations between the bolts 1, as shown by the dotted line in FIG. 4(a), The yield point is different for each bolt, and the point of change of its differential value also fluctuates like 8 → D, and the bolt axial force at the time when the rotational torque of bolt 1 changes is not uniquely determined, making it difficult to install parts. Even if it is desired to tighten with a certain axial force, it is not possible to stably obtain that axial force. On the other hand, the method of determining axial force from torque as described above has the problem that the relationship between torque and axial force cannot be accurately determined because the bolt 1 is subjected to torsional action.

The present invention has been made in view of such conventional problems, and its purpose is to provide a bolt axial force management method that allows bolt tightening to be performed with a predetermined axial force.

Means for Solving the Problems In order to achieve the above object, the present invention calculates the change in the differential value of torque (dT/dθ) with respect to the rotation angle of the bolt when tightening the bolt using a washer or other spacer. , and among the changes in the differential value, find the axial force of the bolt corresponding to a certain rotation angle with respect to the point of change in the differential value for multiple washers, and calculate the axial force of the bolt for each of these multiple washers according to the axial force of the bolt. Divide into groups and do the actual tightening of the bolts.

The gist is that washers are selected and used according to the bolt axial force that is desired to be achieved.

Action When tightening a bolt, if the bolt is tightened a certain amount from the beginning, the bolt will be in a state where the washer is sandwiched between its head and the member to which it is attached, and from then on, the washer will be elastically deformed. Accordingly, a torque is generated which is approximately directly proportional to the screwing amount, that is, the rotation angle. Therefore, during the elastic deformation of this washer, the differential value dT of torque with respect to the rotation angle
When /dθ is determined, this differential value becomes a certain constant value and is represented on a graph. Then, the washer is completely deformed (
For example, when the rough washer becomes completely crushed), the rotational torque of the bolt increases rapidly by 1'' and the bolt begins to be elastically deformed, after which the differential value of l·ruk with respect to the rotational angle becomes constant. If we calculate the differential value of torque with respect to the rotation angle in this torque changing part, this differential value increases almost linearly from the above-mentioned constant value and becomes constant again at a predetermined value.Therefore, when managing the axial force of the bolt, calculates the change point of this differential value, and uses this as a reference to determine the axial force of the bolt corresponding to a predetermined rotation angle for a plurality of spacers.Then, the plurality of spacers are divided into a plurality of groups according to the axial force of the bolt. When bolting a mounted member to a mounting member, a spacer is selected and used depending on the bolt axial force that is desired to be achieved.

Embodiment FIG. 1 is a diagram showing an embodiment of the present invention. In this embodiment 6, an attached member 9 is bolted to an attaching member 8 by a combination of a bolt 1 and a washer 6 in the same manner as shown in FIGS. 2 and 3. During this bolt 1 tightening operation, the relationship between the rotation angle θ of the bolt 1 and the torque T in the elastic deformation region of the washer 6 sandwiched between the head 2 of the bolt 1 and the attached member 9; When the relationship between the rotation angle θ and the differential value dT/dθ of −Lux T with respect to the rotation angle θ is determined, it becomes as shown in FIGS. 1(a> and (b), respectively).

That is, first, the change in torque T with respect to the rotation angle θ of the bolt 1 is as shown by the solid line in FIG. Then, the bolt 1 starts to elastically deform at a point F (rotation angle is β) where the washer 6 is completely deformed, for example, the countersunk washer becomes completely crushed, and the torque applied to the bolt 1 is applied to the washer 6. The deformation becomes more rapid than during elastic deformation. In addition, if another washer 6 (this washer is used as the second washer and the previous washer is used as the first washer) is used to tighten the bolt in the same manner as above, the result is shown by the dotted line in Fig. 1(a). A torque change is obtained, and at a change point Fl (rotation angle is β1), the elastic deformation of the washer 6 ends and the bolt 1 enters the elastic deformation region.

If we look at the differential value change of torque corresponding to such a torque change in Fig. 1(b), this differential value is initially a constant value P.
A change point G appears when the rotation angle is near β, and from there it increases to a value Q within an extremely small angle, reaches a change point H, and then remains constant at the value Q. In addition, when the second washer described in IyI is used, the differential value is a constant value P1 until the rotation angle reaches β1 at first, and the rotation angle becomes β1.
A changing point G1 appears near , from which it increases to a value Q1 within an extremely small angle, reaches a changing point H1, and then remains constant at a value Q1. Then, the changing points of the differential value corresponding to the changing points F and F1 during the torque increase approximately correspond to 1 and 11, respectively.

Therefore, while the change in the torque differential value while the washer 6 is elastically deformed is determined for each washer, the bolt 1 corresponding to a certain rotation angle with respect to the change point G, I or H of this differential value is determined for each washer. Find the axial force for multiple washers. In this way, for example, the standard is set to 1. If you set it to Il,
When the first washer is used, the change point F appears at the torque value T1, and when the second washer is used, the change point F1 appears at the torque value T2.
appears, the bolt axial force corresponding to T1 is found to be, for example, 2000Ko (kilograms), and the bolt axial force corresponding to T2 is found to be, for example, 4000Ko.
The bolt axis when rotated by an angle γ (this angle T is the same whether the first washer or the second washer is used) further than the rotation angle β and β1 corresponding to the standards I and 11. The force is also 3000 when using the first washer, for example.
Kg.

When using the second washer, it can be calculated as 5000 KO. Therefore, a plurality of washers 6 are divided into a first washer group, a second washer group, a third washer group, and a third washer group depending on the axial force of the bolt.
By dividing the bolt into multiple groups such as the fourth group of washers, which washer 6 should be used and by what angle should the bolt 1 be rotated (including forward and reverse rotation) from the torque change point? It becomes clear whether the axial force of can be obtained.

Moreover, compared to the bolt 1, the washer 6 has fewer dimensional variations during manufacturing, making it easier to manage the product, and when tightening the bolt 1, rotational torque is not dispersed into torsional action during operation. The relationship between angle and torque is accurately determined.

Therefore, when assembling a mechanical element such as a connecting rod that is incorporated into an automobile engine, if you want to tighten bolts with a certain axial force, select a washer that corresponds to the required axial force, and Bolt 1 at a determined angle from the reference point
By rotating the bolt, you can always obtain the same axial force no matter which bolt you use. Moreover, the torque change point F is the washer 6.
This is the transition point from the elastic deformation area of bolt 1 to the elastic deformation area of bolt 1, so if you stop the rotation of the bolt after a small angle from the change point, you can manage the axial force within the bolt's elastic deformation area. , unlike the case of controlling the axial force when the bolt 1 yields as in the conventional example (in addition, the axial force is not always constant), the bolt can be used by tightening or loosening the bolt any number of times. You can. In this embodiment, a washer was used as a spacer to be inserted between the bolt and a mechanical component such as a member to be attached when tightening a bolt. A spacer called metal is loaded into the spacer. Therefore, in the present invention, the same result can be obtained even if the axial force of the bolt is managed by determining the torque and the change in the torque differential value within the elastic deformation region of a member such as metal.

As described in detail, according to the present invention, since the axial force of the bolt is managed by paying attention to the deformation of the spacer, it is possible to accurately determine the axial force from the torque applied to the bolt and the rotation angle. In addition to being easy to manage and manage, the axial force can be managed within the bolt's elastic deformation region, so it has various effects such as increasing the number of times the bolt is used when tightening the bolt and extending the usage time. can get.

[Brief explanation of the drawing]

Fig. 7 is a diagram showing an embodiment of the bolt axial force management method of the present invention, Fig. 2 is a sectional view showing an example of a bolt tightening part of a machine element that requires bolt axial force management, and Fig. 3 is a sectional view showing an example of a washer used in the bolt tightening part in FIG. 2;
FIG. 4 is a diagram showing an example of a conventional bolt axial force management method. 1... Bolt 2... Head 4... Leg (bolt shaft) 5... Seat surface (spacer) 6...
Washer 8...Mounting member 9...Mounted member Patent applicant Saga Iron Works Co., Ltd. Agent
Patent Attorney Masahiro Kurago Figure 1 Figure 2 Figure 4 0 θ

Claims (1)

[Scope of Claims] Bolts are tightened on the mounting member to the attached member under the interposition of a spacer that is deformed by the tightening of the bolts, and the change in the torque differential value dT/dθ with respect to the screwing angle during this bolt tightening is determined. , among the changes in the differential value, determine the axial force of the bolt corresponding to a certain rotation angle based on the point of change of the differential value for a plurality of spacers, A bolt axial force management method that divides bolts into groups and selects and uses spacers corresponding to the desired bolt axial force for each bolt when tightening bolts to the mounting member.