JP2529835B2 - Bolt tightening force detection seat - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A bolt used in a mechanical device has a large fatigue life which varies depending on its tightening force, and therefore an appropriate tightening force is required. Even if you try to make the tightening force constant with a torque wrench, the tightening force will not be constant because the friction coefficient of the screw part of the bolt will change, and a large difference will occur.

The present invention is to properly define this tightening force. It is highly versatile and is not restricted by the length of the bolt, as is the case with the known method using the amount of elongation of the bolt.

An example will be described. In FIG. 1, 1 is a bolt, 6 is a frame tightened by the bolt 1, 2 is a washer, 3 is an elastic body (disc spring-hereafter disc spring), 4 is a seat, and 5 is a ring. The seat 4 has a screw portion 4a and an index 4b, and the ring 5 has a screw portion 5a and a scale 5b which are screwed into the screw portion 4a.
There is. When the bolt 1 is screwed in to tighten the frame 6 with the bolt 1, as the screwing progresses, the disc spring 3 interposed between the lower surface of the washer 2 and the upper surface of the receiving seat 4 is compressed.

At the same time, the gap G between the lower surface of the washer 2 and the upper surface of the ring 5 decreases. Then, a tensile force is generated in the bolt 1.
If the spring constant of the disc spring 3 is known, the tensile force of the bolt can be calculated from the amount of change in the gap G.

With the washer 2, disc spring 3 and catch 4 lightly contacting each other, the ring 5
Lightly contact the top surface of the washer 2 with the bottom surface of the washer 2, and then graduate the ring 5
5b is read by the index 4b of the seat 4, and then the ring 5 is twisted with a fingertip to set the gap G. At this time, the rotation angle of the ring 5 is measured by the scale 5b and the index 4b. Screw part 5a
The value of the gap G is calculated from the pitch and the rotation angle of the. Next, when the bolt 1 is screwed in for tightening, the gap G decreases and finally becomes zero, the upper surface of the ring 5 contacts the lower surface of the washer 2, and the upward rotation of the ring 5 is impossible with the fingertip. This state corresponds to the relationship between the object to be measured and the end surface of the spindle of the micrometer when the dimension is measured by the micrometer (the spindle cannot be rotated in the tightening direction). At this point, the bolt 1 is applied with a tensile force due to the product of the spring constant of the disc spring 3 and the gap G. In other words, the bolt 1 is loaded with the specified tightening force.

 Next, another embodiment will be described.

In FIG. 2, 11 is a bolt, 16 is a frame, 12 is a washer,
13 is an elastic body (for example, polyimide resin) 15 is a ring, 14
Is a seat. There is a receiving portion 14a into which the ring 15 is rotatably fitted with a fingertip.

If you screw it in to tighten the frame 16 with the bolt 11,
As the screwing proceeds, the elastic body 13 interposed between the lower surface of the washer 12 and the seat 14 is compressed. At the same time washer 12
The gap G between the lower surface of the ring and the upper surface of the ring 15 decreases. Then, a tensile force is generated on the bolt 11. If the spring constant of the elastic body 13 is known, the tensile force of the bolt 11 can be calculated from the amount of change in the gap G.

When the washer 12, the elastic body 13, and the seat 14 are lightly contacted with each other, the gap G is set, and when the bolt 11 is screwed in, the gap G decreases and finally becomes zero, and the upper surface of the ring 15 contacts the lower surface of the washer 12. The ring 15 cannot rotate with the fingertip. At this point, the bolt 11 is loaded with a tensile force due to the product of the spring constant of the elastic body 13 and the gap G. In other words, the bolt 11 is loaded with the specified tightening force. In this case, the gap G is set by using a ring which is not screwed and whose height is determined in advance so that the gap G comes out.

In either case, while supporting the ring with your fingertips, tighten the bolts so that the bottom surface of the washer hits the top surface of the ring,
When you can no longer rotate the ring, stop tightening the bolts. This enables tightening with the specified tightening force.

The above-described determination of whether or not the upper surface of the ring 15 and the lower surface of the washer 12 are in contact with each other, in other words, the stop accuracy of the ring 15 depends on the experimental result of the standard bolt tightening force detection seat for the M6 bolt. For example, it was equivalent to ± 1.17% of the gap G. By taking advantage of this highly accurate feature, the same bolt tightening force detection seat can be used for a half load by changing the gap G (changing the ring height).

Further, in the above-described determination work using another method such as a bar, it is difficult to perform a complete horizontal movement work, and therefore a highly accurate result cannot be expected.

By replacing the disc spring 3 in FIG. 1 with the elastic body 13 in FIG. 2, a wide range of tightening force can be specified for both the variable tightening force and the constant tightening force. Further, in the embodiment shown in FIG. 2, the elastic body 13, the washer 12 and the receiving seat 14 are separated from each other, but the cost can be reduced by making them into an integral structure.

 According to the present invention, the following remarkable effects can be obtained.

1. Bolts can be fastened with a specified tightening force at low cost. Furthermore, when an external force is applied to the bolt fastening portion, the ratio of the internal force to the external force, which indicates the load ratio to the bolt, becomes small, so that the life of the bolt increases. In particular, it is effective for increasing the fatigue life under repeated loading.

2 The specified tightening force can be applied regardless of the length of the bolt.

Commercially available bolts can be used for 3 bolts, and no special bolts are required.

[Brief description of drawings]

FIG. 1 is a sectional view of the variable tightening force type, and FIG. 2 is a sectional view of the constant tightening force type. 1 ... Bolt, 2 ... Washer, 3 ... Disc spring, 4 ... Bearing, 5 ... Ring, 6 ...
Frame 11… Bolt, 12… Washer, 13… Elastic body, 14… Catch 15… Ring, 16… Frame

Claims (2)

(57) [Claims] 1. A washer (2) having a hole through which a bolt (1) can pass, a receiving seat (4), and a screw connection (4a) with the receiving seat (4) to move vertically in the axial direction. The ring (5) and an elastic body (3) interposed between the washer (2), the seat (4) and the ring (5) are interposed between the ring (5) and the seat (5). 4) At least the scale (5b) or the index (4) that can know the rotation amount of the ring (5).
b) is attached, and the ring (5) is rotated to set a desired gap (G) between the upper surface of the elastic body (3) having a free height and the upper surface of the ring (5). Can and
When the bolt (1) is tightened, the elastic body (3) is deformed by the specified tightening force of the bolt (1) so that the washer (2) and the ring (5) come into contact with each other. Characteristic bolt tightening force detection seat. 2. A washer (12) having a hole through which a bolt (11) can pass, a receiving seat (14), a ring (15) for rotating the outer periphery of an elastic body (13), and the washer ( 12), seat (1
4) and an elastic body (13) interposed in a region surrounded by the ring (15), and the height of the ring (15) is a free height of the upper surface of the elastic body (13) and the ring (15). The height is such that a preset gap (G) is formed between the elastic body (13) and the upper surface of the elastic body (13) when the bolt (11) is tightened by the specified tightening force of the bolt (11). Is transformed into the washer (1
A seat for detecting bolt tightening force, characterized in that the ring (15) and the ring (2) are in contact with each other.