JP2002349536A - Locking screw - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a locking screw providing stable locking action in engagement of a screw and an internal thread hole with paying attention to an inner diameter of the internal thread hole. SOLUTION: A section shape of a leg part 3 is a roughly triangle shape. A diameter of a rotation locus circle drawn by a projection 12 on a root part 11 with rotating the roughly triangle shape root part 11 of thread 10 of the leg part 3 is formed equal to or a little but larger than an inner diameter of the internal thread hole 21 of an object 20 to be fastened and a thread top angle of external threads is narrower than a root angle between a thread and a thread of the internal threads. Since a part generating locking action is positioned at the root part of threads and the inner diameter part of the internal threads, locking action is surely provided if a nominal dimension of the object 20 to be fastened and a nominal dimension of the thread is the same. Since the inner diameters of internal threads are prescribed by JIS, locking torque with little variation can be always provided if the internal thread meets JIS.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a locking screw for preventing loosening of a fastening action between a screw and a female screw hole of a workpiece when the workpiece or nut is fastened to the workpiece. .

[0002]

2. Description of the Related Art Conventionally, various types of loosening screws have been employed as a structure of a locking screw in which a screw is fastened to a female screw hole of a nut or a work to prevent the screw from being loosened from the female screw hole. Examples of such a loosening prevention structure include a structure in which a retaining member such as an E-ring (not shown) is fitted to a portion of a screwed screw leg where a male screw projects from a female screw hole, or a female screw hole. A resin is previously applied to a leg portion to be screwed into the female screw so as to act as a locking action with a female screw. These require a locking member such as a resin or a loosening member in addition to the screw, so that the number of parts is increased, and the number of manufacturing steps and the number of assembling steps are increased.

In order to solve such a problem, recently, as shown in FIGS. 8 and 9, when a screw is screwed into the female screw hole 121, the male screw and the female screw hole 121 of the leg 103 are connected to each other. In order to prevent the screws from loosening due to the contact, a modified shape of the external thread 110 of the leg portion 103 is being used. In particular, FIG. 8 shows a case in which a slit 114 is formed at the crest of the male screw of the leg portion 103 having a crest angle of 60 ° along the shape of the crest of the female screw hole 121. This is so that when this male screw is screwed into the female screw hole 121, the flank surface of the male screw thread 110 has a resilient force when coming into contact with the flank surface of the female screw, so that a loosening prevention action is produced.
In FIG. 9, the flank surfaces on both sides of the external thread 110 of the leg portion 103 are inclined surfaces having different inclination angles, respectively.
As a result, the top portion of the thread 110 slightly bites into the female screw to generate a locking force.

[0004]

However, as described above, a slit is formed in the thread of the external thread, or the flank surfaces on both sides forming one thread are formed at different angles, and the screw is fastened to the thread. When screwing into a female screw hole of an object, all of the portions that cause the locking action are located at the outer thread portion outside the effective diameter of the thread. On the other hand, a female screw hole formed in a workpiece such as a nut or a work into which the screw is screwed usually has a female screw thread inner diameter defined by JIS (Japanese Industrial Standards), and the dimensions are respectively specified. The root diameter of the female screw is not particularly specified, and it is generally considered that it is sufficient that the outer diameter of the thread corresponding to the nominal size of the male screw to be screwed is fitted. Some have the same diameter, while others have a diameter larger than the outer diameter.

[0005] For this reason, if the fitting with the male screw is normal, there is no problem. However, when the locking action is provided, depending on the female screw hole of the article to be fastened, the locking may be prevented. The effect was insufficient. If the external thread size is increased to solve this, the screwing torque at the time of screwing will be higher than the set value, and the screw will not be screwed sufficiently, causing a screw floating state, or conversely, the loosening torque will be insufficient, etc. Stable locking effect has not been obtained. In addition, in order to surely obtain the loosening prevention effect, it is necessary to select in advance a thread having a fixed root diameter of the female screw hole of the object to be fastened, and to select a screw having an outer diameter matching this root diameter. There is a problem that the desired effect is not always obtained because the nominal dimensions of the screw hole and the female screw hole match.

All of these are the results of devising a locking effect in relation to the thread of the male screw and the valley of the female screw hole to be screwed correspondingly.
This is because the focus is not on the inner diameter of the female screw hole defined by S. For example, in JIS B0209, the maximum and minimum values such as the inner diameter and the effective diameter of the female screw are specified for each nominal size of the screw, but the maximum and minimum values are not specified for the root diameter. For this reason, it is the present condition that the valley diameter is easy to use by a manufacturer such as a nut having a female screw hole.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide a stable loosening preventing action in fitting a screw and a female screw hole of an object to be fastened by focusing on the inner diameter of the female screw hole specified in JIS. The objective is to obtain a locking screw that is made available.

[0008]

The object of the present invention is to provide a head 2
A screw formed by forming a male screw on a leg 3 to which a screwing force is applied by engaging the driver with a driver bit, wherein the cross-sectional shape of the leg 3 is substantially triangular; By rotating the substantially triangular valley 11 of the male screw formed on the leg 3, the diameter of the rotation trajectory circle drawn by the protrusion 12 in the valley 11 is changed into a female screw hole formed in the workpiece 20 in advance. The present invention provides a locking screw which is formed to have the same diameter as or slightly larger than the inner diameter of the inner screw 21 and the crest angle of the male screw is smaller than the root angle between the threads forming the female screw. It is achieved by doing. In addition to this, in addition to the above configuration, the projections 12 formed in the valleys 11 are provided at equal intervals on the circumference thereof in a cross section orthogonal to the axis of the leg 3. This is achieved even with loose locking screws. Further, in order to achieve the above-mentioned object, the valley 11 of the screw leg 3 is provided between the protrusions 12 adjacent to each other, and the valley surface 13 which does not contact the inner diameter of the female screw hole 21 of the workpiece 20. May be used as a locking screw. Moreover, in addition to these configurations, by using a locking screw in which the external thread has a crest angle of 30 °, the locking function can be more reliably performed.

[0009]

FIG. 1 is a block diagram showing an embodiment of the present invention.
7 through FIG. 2 and 3, 1
Is a locking screw comprising a head 2 and a male screw-shaped leg 3 integral with the head 2 and having a thread 10 on the outer periphery. The head 2 of the locking screw 1 has a driving hole 4 in the shape of a cruciform conical groove which is engaged with a driver bit (not shown) on the center line of the leg 3 to form a driving unit. The driving portion of the head 2 is a driving hole 4 having a cross-conical groove shape.
In addition, for example, the shape may be a square, a hexagon, or another groove or a hole, and the shape is not limited to this as long as the shape is commonly used.

The head 2 is formed integrally with a leg 3 having a diameter smaller than that of the head 2 and a substantially triangular cross section, and a thread 10 is formed on the leg 3. It is formed with a predetermined pitch. The male screw of the leg 3 has a crest angle formed by a flank on both sides forming a screw thread of a female screw hole 21 as shown in FIGS. Is smaller than the angle α, and in this embodiment, the angle α is 30 degrees.
° formed. For this reason, the thickness of the base of the thread 10 of the external thread is thinner than usual, and the pitch of the thread 10 does not change, but the width of the root of the thread 10 is formed slightly wider.

On the other hand, as shown in FIGS. 2 and 6, the thread 10 and the valley 11 formed on the leg 3 are substantially triangular in cross section orthogonal to the axis of the leg 3. An arc-shaped projection 12 having a small radius of curvature is provided at three equally-divided portions of the substantially triangular valley 11, and an arc shape having a large radius of curvature is provided between the projections 12. Are connected by a valley surface 13. On the other hand, the thread has a substantially triangular shape in which protrusions 14 each having a small radius of curvature are similarly formed at three places, and these are connected by an arc having a large radius of curvature. Note that the boundary line showing the cross section of FIG. 6 is actually a part of the boundary line reaching the top of the thread 10, that is,
Although it has a contour cross section indicated by a two-dot chain line, it is illustrated in this manner for convenience of explanation in order to facilitate understanding of the fitting of the substantially triangular male screw and the circular female screw hole 21.

As shown in FIG. 4, the length H from the center of the leg of the screw thread 10 to the tip of the protrusion 14 is the length D from the center of the female screw hole 21 formed in the work 20 to the root. The length is shorter or slightly longer, and the ridge 14 of the thread 10 of the leg 3 may not contact the valley 22 of the female screw hole 21, or as shown in FIG. Or dig into it. On the other hand, the length h from the center of the leg 3 to the protrusion 12 of the valley 11 is equal to or slightly smaller than the length d from the center of the female screw hole 21 of the workpiece 20 to the inner diameter of the female screw. As shown in FIG. 6, the rotation locus circle (dashed line) formed by the rotation of the projection 12 has the same diameter as the inner diameter (dashed line) of the internal thread or has a larger diameter. It has a slightly larger diameter. Thus, the three protrusions 12 can always contact the inner diameter of the female screw.

As shown in FIG. 1, when the loosening set screw 1 constructed as described above is screwed into a nut serving as the object 20 to be fastened, the female screw hole 21 of the nut has an inner diameter corresponding to its nominal size. Usually, the diameter is set to a size that allows the corresponding male screw of the screw 1 to be screwed in. Therefore, the projection 12 of the valley 11 of the locking screw 1 comes into contact with the inner diameter of the female screw hole. At this time, as shown in FIG. 6, a gap is formed between the protrusion 12 of the male screw valley 11 and the inner diameter of the female screw. No contact. As a result, the locking screw 1 is screwed with a predetermined torque while generating a predetermined resistance by the protrusion 12 with the female screw.

When screwed and fixed in this way, the internal diameter of the internal thread is restored to some extent, so that the projection 12 formed in the root 11 of the external thread bites into the internal diameter of the internal thread. And no loosening occurs. In this operation, since the inner diameter of the female screw hole 21 is defined within a predetermined tolerance range, the phenomenon that the inner diameter of the female screw hole 21 does not contact the protrusion 12 of the valley 11 of the locking screw 1 at all does not occur.
As a result, a reliable locking action can be obtained.

On the other hand, as shown in FIG. 4 (and the dashed line A in FIG. 7), the valley 22 of the female screw hole 21 of the workpiece 20 has a valley diameter smaller than the outer diameter of the ridge 14 of the male screw. If it is large, it does not come into contact, but since the protrusion 12 of the root 11 of the male screw and the inner diameter of the female screw hole 21 are in contact, there is no hindrance to the loosening prevention action. 5 (and the dashed line B in FIG. 7)
If the root diameter of the root part 22 of the female screw hole 21 of the workpiece 20 is smaller than the outer diameter of the root part 14 of the screw thread 10 formed in the male screw as shown in FIG. The portion 14 bites into the female thread valley 22 even slightly, and in such a screwing action, the locking action which occurs between the protrusion 12 of the screw thread 10 and the female thread valley 22 together with the locking action is provided. Both effects will occur and a greater locking effect will be obtained.

Next, the conventional locking screw having a nominal diameter of 2 mm and the locking screw having the same nominal diameter in the present embodiment are screwed into nuts as the fittings 20 to be fitted, respectively. The measurement of the stop torque was repeated five times, and the results and average values of the respective results are shown in Table 1.

[0017]

[Table 1]

As shown in Table 1, the average of the conventional conventional locking screw is 0.127 N · m and the average of the other conventional locking screw is 0.040 N · m. The average of the locking screw of the present invention is 0.141 N ·
m, thus, the locking torque of the locking screw of the present invention is higher than that of the conventional screw.

In this embodiment, so-called leg portions 3 having a so-called substantially triangular cross-sectional shape are formed in which three protruding portions 12 having a small radius of curvature are formed at three positions at equal intervals in the root portion 11 of the screw thread 10. However, the present invention is not limited to this, and may be, for example, a substantially polygonal shape such as a substantially square or substantially pentagonal shape.

[0020]

According to the present invention, as apparent from the above-described embodiments, a screw having a drive portion on a head 2 to which a driver bit is engaged, and a male screw formed on a leg 3 to which a screwing force is applied. 1, the cross-sectional shape of the leg 3 is substantially triangular, and the substantially triangular valley 11 of the thread 10 of the leg 3 is formed.
Rotates, the diameter of the rotation trajectory circle drawn by the protrusion 12 in the valley 11 is formed to be the same as or slightly larger than the inner diameter of the female screw hole 21 of the workpiece 20.
A locking screw in which the thread crest angle of the male screw is smaller than the root angle between the screw threads of the female screw.

For this reason, in order to give a resilient force to the thread of the leg portion, a slit is formed or the flanks on both sides forming the thread are formed at different angles, respectively, as in the prior art. Since the different part, that is, the part that produces the locking action, is located at the root of the screw and the inner diameter of the female screw, the nominal size of the object to be fastened is smaller than the nominal size of the screw. If it is the same as above, the locking action can be obtained reliably. The inner diameter of the female screw is JIS
Therefore, if the female screw is highly reliable and conforms to JIS, a loosening prevention torque with little variation can always be obtained. Furthermore, since the internal diameter of the female screw is within the specified allowable range, the screwing torque at the time of screwing becomes higher than the set value, causing a screw floating state, or conversely, the loosening torque is insufficient. Is also solved, and stable screwing and loosening prevention torque can be obtained. In addition, there is no need to select a thread having a constant root diameter of the female screw hole of the object to be fastened in order to reliably obtain the locking effect, and to select a screw having an outer diameter matching the root diameter. If the nominal dimensions of the male screw and the female screw hole match, a predetermined loosening prevention action can be reliably obtained. In addition, since the root of the male screw is in contact with the inner diameter of the female screw, the torque at the time of screwing can be set low, and the loosening force due to vibration or the like does not change at all.

Further, in addition to the above configuration, the projections 12 of the valleys 11 are equally spaced on the circumference of the cross section of the leg 3, and are located between the adjacent projections 12. Has a valley surface 13 which does not come into contact with the inner diameter of the female screw hole 21 of the work 20, so that only a plurality of locations contact the inner diameter of the female screw. In addition, since there is no sharp increase in torque, it is possible to sufficiently cope with the automation of the screw tightening operation by an automatic screw tightening machine or the like. Further, depending on the combination of the male screw and the female screw hole 21, the protrusion 14 of the thread 10 of the leg 3 may come into contact with the valley 22 of the female screw. In this case, a stronger loosening preventing action is provided. can get. Besides, the screw leg 3
Since the thread crest angle of the thread is 30 °, when the protrusion formed on the thread of the external thread comes into contact with the valley of the internal thread, it can bite smoothly. It has specific effects such as becoming.

[Brief description of the drawings]

FIG. 1 is an enlarged cross-sectional view illustrating a state where the present invention is screwed into a female screw hole of an object to be fastened.

FIG. 2 is a front view of the screw showing the embodiment of the present invention.

FIG. 3 is a bottom view of FIG. 2;

FIG. 4 is an enlarged sectional view of a main part showing a screwed state of the present invention.

FIG. 5 is an enlarged sectional view of a main part showing another screwed state of the present invention.

FIG. 6 is an enlarged cross-sectional view perpendicular to the axis of the leg showing the screwed state of the present invention.

FIG. 7 is an enlarged sectional view similar to FIG. 6, showing a state in which a male screw acts on a female screw.

FIG. 8 is a sectional front view of a main part showing a conventional example.

FIG. 9 is a cross-sectional front view of a main part showing another conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Loosening set screw 2 Head 3 Leg 4 Drive hole 10 Thread 11 Valley 12 Projection 13 Valley surface 14 Projection 20 Workpiece 21 Female screw hole 22 Valley

Claims (4)

[Claims] 1. A screw having a drive unit on a head (2) with which a driver bit is engaged, and a male screw formed on a leg (3) engaged with the drive unit to apply a screwing force. Is formed into a substantially triangular cross-section, and the substantially triangular valley (11) of the male screw formed on the leg is rotated, so that the rotation locus circle diameter drawn by the protrusion (12) in the valley is formed. Is formed to have the same diameter as or slightly larger than the inner diameter of the female screw hole (21) formed in advance in the workpiece (20), and the screw crest angle of the male screw is set to A locking screw having a configuration smaller than a valley angle between a mountain and a mountain. 2. The projections formed in the valleys are provided at equal intervals on the circumference in a cross section orthogonal to the axis of the leg. The set screw described. 3. A valley surface between the protrusions adjacent to each other and not in contact with an inner diameter of a female screw hole of an object to be fastened.
The locking screw according to claim 1, further comprising: 4. The locking screw according to claim 1, wherein the external thread has a crest angle of 30 °.