JP2549528Y2 - Bolt neck length gauge - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a length gauge under a bolt neck, and more particularly, to easily measure the magnitude of plastic elongation of a bolt used in a plastic area tightening method and determine whether the bolt can be reused. The present invention relates to a bolt neck length gauge that is effective for judgment.

[0002]

2. Description of the Related Art Conventionally, a plastic region tightening method has been applied for bolting a cylinder head or a connecting rod of an automobile engine. In this method, a torque corresponding to a plastic region exceeding an elastic region is applied to a bolt in a strain-stress curve of a steel type of a bolt to be used, and the bolt is tightened.

When the engine is disassembled and repaired, the tightened bolt is loosened and removed to overhaul the engine. After the repair is completed, the bolt is used again in the plastic region to reassemble the engine. However, bolts tightened in the plastic region are not tightened in the elastic region when they are loosened and removed, so the length of the lower part of the bolt neck does not return to the same length as the initial value before use, Plastic elongation corresponding to permanent set remains, and the length of the lower part of the neck becomes slightly longer than its initial value.

[0004] When the tightening of the plastic region and the release thereof are repeated a plurality of times, the above-described plastic elongation is accumulated each time, so that the lower portion of the bolt neck becomes gradually longer.
When the cumulative plastic elongation exceeds a certain allowable value, necking or the like occurs at the lower portion of the bolt neck, the strength of the bolt is remarkably reduced, and the bolt can no longer be used for reliable plastic fastening.

That is, when the plastic elongation exceeds a certain allowable value, in order to ensure the reliability of the assembled engine,
It is necessary to discard the bolts used so far and replace them with new ones. Therefore, it is necessary to determine the service limit of the bolt used in the plastic zone tightening method by some method.

Conventionally, as this determination method, for example, the number of times the plastic region is tightened is stamped (takin) on the head of the bolt, and the bolts having a certain number of the bolts or more are discarded and reused. There is a method of not using it.

[0007]

However, the method of judging the reusability by reading the mark described above is not necessarily a reliable and highly reliable method. For example, an engine manufacturer could routinely make such a taping operation as part of the process control, but in the case of an engine delivered to a dealer or the like, there is no guarantee that the taping will be done.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problem, and it is possible to reliably and easily measure whether or not the accumulated plastic elongation exceeds an allowable value for the bolt to determine whether or not the bolt can be reused. The aim is to provide a length gauge below the bolt neck that can be used.

[0009]

In order to achieve the above-mentioned object, in the present invention, the whole is in the form of a thick-walled pipe, and the lower part of the neck of the bolt used for tightening the plastic region is inserted into the hollow part. A bolt neck length gauge for measuring the length of the lower part of the neck, wherein the hollow part has a smaller diameter than the head of the bolt, and the total length is longer than the initial value of the lower part of the neck of the bolt before use. In addition, a bolt neck length gauge is provided which has a length equal to or less than a length obtained by adding an allowable value of the plastic elongation of the bolt to the initial value.

[0010]

The bolt used for tightening the plastic region is inserted into the hollow portion of the thick pipe from its tip. Since the diameter of the hollow part is smaller than the head of the bolt, the lower part of the bolt head, that is, the lower part of the neck, fits in the hollow part of the pipe. At this time, if the tip of the lower part of the neck, that is, the tip of the bolt protrudes from the hollow part of the pipe, it means that the length of the lower part of the neck is longer than the allowable value of the cumulative plastic elongation. The bolt is determined not to be reusable. When the tip of the bolt does not protrude from the pipe, the accumulated plastic elongation is smaller than the allowable value and can be used again.

[0011]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a gage according to the present invention. FIG. 1 is a side view of the gauge of the present invention. In the drawing, a gauge 1 is made of a tool steel such as a SKD material having a high hardness and a toughness, and is a thick pipe having a simple overall shape.

The hollow part 1a of the gauge (thick pipe) 1 is a hole having the same diameter in the longitudinal direction, and the diameter d is the diameter of the head 2a of the bolt 2 before use as shown in FIG. than D ₁ in diameter, which is larger in diameter than the diameter D ₂ of the neck lower portion 2b. In addition, the total length L of the thick pipe 1 is represented by the length (initial value) of the neck lower portion 2b of the bolt 2 before use shown in FIG. 2, and the allowable value of the cumulative plastic elongation of the neck lower portion 2b in this bolt. To Δ
When it is 1, the value satisfies the following relationship: l <L ≦ l + Δl.

Although it depends on the size and shape of the bolts used, the diameter of the hollow portion 1a of the thick pipe 1 and the dimensional accuracy of the total length L are preferably set within a range of ± 0.01 mm. Next, the operation will be described. Used for tightening the plastic zone, the length of the lower part of the neck is from l to l +
Consider the possibility of reusing the bolt 3 as shown in FIG.

First, as shown in FIG.
Is inserted into the hollow portion 1a of the thick pipe 1 from its tip 3c. The neck lower portion 3b of the bolt 3 is completely inserted into the hollow portion 1a of the thick pipe 1. At this time, the cumulative plastic elongation l ′
Is larger than the allowable value Δl, the tip 3c of the bolt is connected to the tip 1 of the thick pipe 1 as shown in FIG.
It protrudes from b by a length of l′-Δl.

In this case, since the accumulated plastic elongation of the bolt 3 exceeds its allowable value, the bolt 3 is discarded without being used again for tightening the plastic region. Conversely, if the tip 3c of the bolt 3 does not protrude from the tip 1b of the thick pipe 1, the accumulated plastic elongation of the bolt does not exceed its allowable value. Absent.

[0016]

[Effect of the Invention] As is clear from the above description, the length gauge under the bolt neck of the present invention has a shape of a thick pipe as a whole,
A bolt neck length gauge for measuring the length of the neck lower part by inserting the lower part of the bolt used for plastic region tightening into the hollow part, wherein the hollow part has a smaller diameter than the head of the bolt. Since its total length is longer than the initial value of the lower part of the neck of the bolt before use, and is equal to or less than the length obtained by adding the allowable value of the plastic elongation of the bolt to the initial value,
Insert the lower neck of the used bolt into the hollow part of the gauge,
It is possible to determine whether or not the bolt can be reused only by checking whether or not the tip of the bolt protrudes from the tip of the gauge.

Therefore, it is not necessary to perform the work of measuring the length of the lower part of the neck with a vernier caliper to judge the reusability as in the prior art, and it is possible to reliably and easily judge the reusability. The length of the lower part of the bolt neck varies depending on the type of engine to be assembled. For this purpose, a gauge of a predetermined length is manufactured for each bolt, and the outer circumference of those gauges is What is necessary is just to hit a mark indicating an object of use so that it can be identified.

[Brief description of the drawings]

FIG. 1 is a side view showing a gauge according to the present invention.

FIG. 2 is a side view of the bolt before use.

FIG. 3 is a side view of a bolt that has undergone plastic elongation.

FIG. 4 is a side view showing a state in which a lower part of a bolt is inserted into a gauge.

FIG. 5 is a side view showing a state in which a lower part of a bolt is completely inserted into a gauge.

[Explanation of symbols]

Reference Signs List 1 gauge 1a hollow portion of gauge 1 1b tip of gauge 1 2 bolt before use 2a head of bolt 2 2b lower neck of bolt 2 3 bolt with plastic elongation 3a head of bolt 3 3b lower neck of bolt 3 3c bolt Tip of 3 D ₁ Diameter of bolt head D ₂ Diameter of bolt lower part d Diameter of gauge hollow part l Initial value of lower neck length l 'Length of cumulative plastic elongation

Claims (1)

(57) [Scope of request for utility model registration] 1. A bolt neck length gauge for measuring the length of a lower portion of a bolt used for fastening a plastic region by inserting a lower portion of the bolt into a hollow portion thereof, and measuring the length of the lower portion of the bolt. The hollow portion has a smaller diameter than the head of the bolt, and its total length is longer than the initial value of the lower portion of the neck of the bolt before use,
The length gauge under the bolt neck is equal to or less than a length obtained by adding an allowable value of the plastic elongation of the bolt to the initial value.