JPH0124925B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Purpose of the Invention) (Field of Industrial Application) The present invention relates to the shape and structure of a nut in a bolt-nut mechanism widely used as a fastening element. More specifically, the present invention relates to the shape and structure of a nut configured to have a torque limiting function and a locking function.

(Prior Art and its Problems) Bolts and nuts (herein referred to as bolts and nuts in a broad sense with a fastening function by screwing) are widely used as fastening elements in the industrial world. Depending on the machine or part used, bolts and nuts may have to be tightened with a strict predetermined rotational torque. (Used synonymously with rotational moment in the specification.)

Further, when a bolt-nut fastening means is used in a machine or a part that is subject to vibration, a so-called double nut or a rotation-preventing cotter pin is attached to the bolt and nut so that the bolt and nut are not unfastened due to the vibration.

(Problem to be Solved by the Invention) However, when using the above-mentioned torque wrench, it is cumbersome to use the torque wrench instead of a regular wrench each time when tightening, and It has to be adjusted according to the torque, which reduces work efficiency. Furthermore, due to an error in the adjustment of the torque wrench, there was a risk that the torque would be tightened with a torque different from the predetermined rotational torque.

On the other hand, the anti-rotation means using the double nut and cotter pin described above tightens one nut, and then
It was necessary to tighten another nut or to attach a cotter pin to the bolt or bolt and nut to prevent rotation of the nut, which required extra time and effort. Furthermore, the installation of the double nuts and split pins is sometimes forgotten due to operational errors during the initial assembly or overhaul stage, and it is well known that these often cause serious accidents.

In addition, there is a prior art related to Japanese Patent Application Laid-Open No. 54-99860, but in the case of a nut with this structure,
Due to its axial cross-sectional shape having a semicircular projection formed around a perfect circle, due to the corresponding mechanism of contact with the tightening tool,
The problem was that it was not possible to have both a highly accurate torque limit function and a lock function.

The present invention has been made in view of the above-mentioned current situation, and provides a nut that is equipped with a torque limit function that allows setting a desired rotational torque with high precision, and a lock function that acts to prevent the nut from rotating after completion of tightening. The purpose is to provide.

(Structure of the Invention) (Means for Solving the Problems) The nut with a torque limit function and a lock function according to the present invention has a cross-sectional shape on the outer circumferential surface that is non-circular (non-circular with respect to the rotation center of the nut). A nut having an engaging portion (the same applies in this specification) with a internal thread formed on the inner circumferential surface that corresponds to the male threaded portion of the bolt, and the nut is attached to the corresponding bolt. When tightening, if a rotational torque of a certain value (set value) or more is applied, the part of the nut that engages with the tightening tool that rotates at the minimum rotation radius of the tightening tool will cause the nut to be located outside of the engaging portion of the nut that engages with the tightening tool. The tightening tool slips due to plastic deformation of the tightening tool, and the threaded part of the nut's inner circumferential surface, which has the smallest diameter, deforms to be smaller than the male threaded part of the bolt that contacts this part, causing the inner circumferential surface of the nut to In a nut with a torque limit function and a locking function configured to press the outer circumferential surface of a male screw to be screwed together, the outer circumferential shape of the axial cross section of the engaging portion of the outer circumferential surface of the nut is formed into a multilobal curve, preferably a polygon curve, or a hypogonal curve. It is characterized by a three-lobed curve represented by a trichoidal curve and an epitricoidal curve.

(Function) When tightening the nut having the above structure onto a bolt, a recess or a through-hole with a slightly larger inner circumferential shape in the axial cross section of the engaging portion of the nut that is similar to the outer periphery of the axial cross section of the engaging portion of the nut is required. If a tightening tool such as a box wrench or an alternative tool is used for tightening, and the tightening torque exceeds the desired (regulatory) rotation torque, the tightening tool's minimum rotation radius will be used. Due to the rotating part, the outer periphery of the engaging part of the nut located outside of the rotating part (outside of the rotation locus of the part of the box wrench that has the minimum turning radius when rotated) is plastically deformed. The nut and wrench become disengaged, causing a slip between the nut and the wrench and preventing further rotation. Therefore, the operator can obtain a predetermined rotational torque (tightening torque) simply by tightening the nut and wrench with a wrench until they slip relative to each other. At this time, the above-mentioned plastic deformation is caused by the fact that the outer circumferential shape of the axial cross section of the engaging part of the outer circumferential surface of the nut is composed of multilobed curves such as polygonal curves and hypotricoidal curves, as described above. The pressure angle formed by the engaging portion of the peripheral wall and the outer peripheral surface of the nut (the angle formed by the line connecting the contact portion and the center of the nut and the normal line at that portion) is not very large and is approximately constant at each position. Therefore, the operator only has to rotate the box wrench with a constant force, and the box wrench is plastically deformed and slips with an accurate predetermined rotational torque. Furthermore, if the engaging portion of the outer circumferential surface of the nut is configured with a multi-lobed curve, the pressure angle is not so large that the outer circumferential surface of the nut will not be damaged by contact with the box wrench, and therefore, the outer circumferential surface of the nut will not be damaged. The lubricating coating and plating coating on the surface are not destroyed, providing accurate tightening and rust prevention functions.

Along with the plastic deformation of the outer circumferential shape of the axial cross section constituting the engaging portion of the nut, the inner circumferential shape of the axial cross section of the nut is plastically deformed, that is, the inner circumferential surface where the female thread portion is formed. The inner peripheral shape of the shaft cross section is deformed to a shape similar to the initial nut outer peripheral shape,
Since the outer peripheral surface of the externally threaded portion is pressed, rotation of the nut relative to the bolt is locked with a predetermined force when slip occurs between the nut and the wrench. As a result, it functions as a rotation stopper (locking function). In addition, the inner peripheral surface shape of the axial cross section of the nut that is screwed into the bolt becomes a multi-lobed curve similar to the original outer peripheral surface shape, and in order to avoid forming extreme deformed parts, the locking function can be added as necessary. You can also release it and remove the nut.

In addition, if the outer circumferential shape of the axial cross-section of the engaging portion of the nut outer circumferential surface is made of a multi-lobed curve, especially a three-lobed curve, the deformation of the nut will be the minimum required to secure the bolt from around its axis. only the necessary number will occur,
In addition, a relatively large amount of deformation is obtained, resulting in a sufficient locking function. On the other hand, if the curve is more than three leaves, deformation occurs around the nut by the number of leaves, the amount of deformation at one deformation point becomes small, and the overall locking function can be lowered. In other words, as the number of leaves increases, the shape becomes closer to a circle, which lowers the overall locking function.

(First Example) Hereinafter, the present invention will be described in more detail based on Examples with reference to the drawings.

Fig. 1 is a plan view of a nut showing an embodiment of the present invention, Fig. 2 is a front view with the same partial cross section, and Fig. 3 shows the engagement of the nut when the nut shown in Fig. 1 is screwed onto a bolt. FIG. 7 is a plan view showing deformation of the joint portion.

In the figure, 1 indicates the entire nut, 2 is an engaging portion formed on the outer circumferential surface of the nut 1 for tightening, and 3 is an inner circumferential surface portion of the nut in which a female thread is formed.

The outer circumferential shape of the axial cross-section of the engaging portion of the outer circumferential surface of the nut according to this embodiment is constituted by a hypotricoid curve, which is an outer circumferential line in which a plastic deformation region portion is provided on the outside of a base circle. That is, the hypotricoid curve is a curve expressed by the following coordinate equation: R=1:
10 (see Figure 4). In the above formula, r
In FIG. 4, R means the radius between points OM and M, and R means the radius between points M and P in FIG.

Note that n is an integer of 2 or more, and n=2 is a three-lobed curve, and n=k is generally a k+1-lobed curve.

In addition, the inner peripheral surface of the nut 1 has a normal female thread 4.
is formed.

As shown in FIG. 5, the nut 1 having the above structure is attached to a bolt 5 having a male thread 6 portion adapted to the nut 1, and a box (referring to the box portion of a box wrench). If the nut is tightened using a box wrench, etc., which has an engagement part with a slightly larger recess, the inner circumferential shape of the shaft cross-section is similar to the outer circumference shape of the shaft cross-section of the engagement part of the nut, and the final tightening process is completed. That is, in the process in which the tightening of the female thread 4 acts as an axial tensile force on the male thread 6, when the female thread 4 is tightened, a rotating torque corresponding to the axial tensile force of the male thread 6 acts on the box wrench. do. When the rotational torque approaches a predetermined set rotational torque, the outer peripheral portion of the engagement portion 2 of the nut 1 begins to undergo plastic deformation due to stress (rotational force) from the engagement portion of the box wrench. Then, when the rotational torque by the box wrench exceeds a predetermined set rotational torque (determined by the setting of the deformation amount of the plastic deformation region portion of the nut engagement portion), the engagement portion 2 of the nut 1
When the engaging part of the box wrench is rotated, it plastically deforms to fit within the rotation locus of the part that has the minimum rotation radius (see the solid line in Figure 3), so the engaging part of the box wrench and the nut are The engagement between the parts is broken, and the box wrench slips against the nut.

On the other hand, as the outer peripheral shape of the axial cross section of the engaging portion of the nut is plastically deformed, the inner peripheral shape of the axial cross section of the nut is deformed into a shape close to an epitrochoid curve, as shown in FIG. Therefore, since the inner circumferential surface (female thread 4) of the nut 1 presses the outer circumferential surface (male thread) of the bolt 5, the rotation of the nut 1 with respect to the bolt 5 is prevented due to the frictional force between the inner circumferential surface and the outer circumferential surface. inhibited.

(Second Embodiment) The nut according to this embodiment has an engagement portion for releasing the fastening between the bolt and the nut together with the engagement portion of the nut of the first embodiment. For example, as shown in FIGS. 6a and 6b, nut 1
A locking portion 8 (in this embodiment, a locking portion having a hexagonal outer peripheral shape in a cross-section of the shaft) is formed at the lower part (on the bolt side) of the engaging portion 2 of the nut for releasing the nut once tightened. . Once the nut 1 has been fastened to a bolt, when releasing the nut that has been fastened to the bolt in a locking manner, the engaging part of a normal spanner or wrench is applied to the locking part and the nut 1 is tightened. It can be released from the bolt. In addition, the cancellation of the nut in such a case is different from the case of canceling the normal nut, as mentioned above.
Since the internal thread of the nut presses and locks the external thread of the bolt, it must be released against the frictional force caused by the pressing force, which requires a large rotational torque.

Further, as shown in FIGS. 7a and 7b, a seat surface 9 may be formed at one end of the nut together with the nut engaging portion of the first embodiment. Although not shown, the same effect as described above can be obtained even if the outer circumferential shape of the axial cross-section of the engaging portion of the nut is configured with a polygonal curve, epitricoidal curve, or other multilobal curve. is obtained.

(Effects of the Invention) As explained above, if the nut according to the present invention is used, even if the nut is used in a part that needs to be tightened to a strictly predetermined rotational torque as in the conventional case, the nut can be tightened to a specified rotational torque each time. You can always tighten with the set rotational torque without having to adjust the torque wrench before using it, and you can tighten it according to the required rotational torque, such as a nut for 10Kg/cm, a nut for 15Kg/cm, etc. If you make a nut for kg/cm in advance, you are guaranteed to tighten it with the specified rotational torque, and you will not make the mistake of using the wrong tightening rotational torque as in the past.

Furthermore, since the nut according to the present invention has the above-mentioned locking function in addition to the above-mentioned torque limit function, it can also be used in machines or parts that have vibrations.
The work efficiency is significantly improved because only the nut needs to be used instead of installing a double nut or cotter pin as in the conventional method. Furthermore, mistakes caused by forgetting to attach the double nut or cotter pin can also be avoided. Furthermore, if necessary, the nut and bolt can be unlocked and removed by applying a rotational torque of a predetermined amount or more.

[Brief explanation of drawings]

Fig. 1 is a plan view of a nut showing an embodiment of the present invention, Fig. 2 is a front view with the same partial cross section, and Fig. 3 is a deformation of the engaging portion of the nut when the nut is screwed onto a bolt. FIG. 4 is a hypotrichoid curve used in this example, FIG. 5 is a perspective view showing a nut according to the present invention screwed onto a bolt, and FIGS. Figures 7a and 7b are a plan view and a partially sectional side view of another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Nut, 2... Engaging part of nut, 3... Inner peripheral surface part of nut, 4... Female thread, 5... Bolt, 6...
Male thread, 7... Outer circumference of shaft cross section of nut engaging part, 8... Nut locking part, 9... Seat surface.

Claims (1)

[Scope of Claims] 1. A nut having an engaging portion having a non-circular cross-sectional shape on its outer circumferential surface and a female thread corresponding to a male threaded portion of a bolt on its inner circumferential surface, the nut comprising: When tightening the corresponding bolt, if a rotational torque above a certain level is applied, the part of the nut that engages with the tightening tool, which rotates at the minimum rotation radius of the tightening tool, will cause the nut to move outward. The located portion is plastically deformed and the tightening tool slips, and the female threaded portion of the inner circumferential surface of the nut, which has the smallest diameter, is deformed to be smaller than the male threaded portion of the bolt that comes into contact with this portion,
In a nut with a torque limit function and a locking function, which is configured such that the inner circumferential surface of the nut presses the outer circumferential surface of the external thread to which it is screwed, the outer circumferential shape of the axial cross section of the engaging portion of the outer circumferential surface of the nut is multi-lobed. A nut with a torque limit function and a lock function, characterized by being configured with a curved line. 2. The nut with torque limit function and lock function according to claim 1, wherein the multi-lobed curve is a tri-lobed curve. 3. The nut with torque limit function and lock function according to claim 2, wherein the three-lobed curve is a polygon curve. 4. The nut with torque limit function and lock function according to claim 2, wherein the three-lobed curve is a hypotricoid curve. 5. The nut with torque limit function and lock function according to claim 2, wherein the three-lobed curve is an epitricoid curve.