JP5462508B2 - Screw parts - Google Patents

Description

  The present invention is a screw that is screwed into a workpiece with a predetermined fastening force, and in particular, when screwing into a pilot hole or a female screw of a workpiece, the plastic deformation of the workpiece or the screw thread can be reduced without removing the pilot hole or the female screw by the screw thread. The present invention relates to a threaded part that can be screwed in by copying and suppresses the generation of molding waste during screwing and minimizes the scattering and dropping thereof.

  2. Description of the Related Art In recent years, electrical products such as mobile phones, personal computers and portable music players, automobile parts, etc. are relatively light weight materials such as aluminum alloys, magnesium alloys or A resin material is used as a work, and components such as an electronic wiring board and a control board are fixed to the work. In addition, iron-based workpieces such as cold rolled steel plates (SPCC plates) are also used. In such a structure for fixing a part to a workpiece, a screw is mainly employed, and a generally popular shape as shown in FIG. 8 is employed for the thread 110 of the screw. This is a tapping screw 101 in which the flank angle at the tip of the screw thread 110 is formed at 60 °, and is usually screwed in while forming a female screw 142 in a prepared hole 141 formed in advance in the workpiece 140. There are screws.

  FIG. 10 shows another prior art, which is disclosed in Japanese Patent Laid-Open No. 10-176709. This shows a male thread in which the thread 210 is set to 45 ° on the base side of the male screw and 60 ° on the tip side, so that the screw 201 and the nut 240 screwed into the nut 240 are not separated. It is. The reason why the thread angle on the base side is smaller than the thread angle on the distal end side is that the shaft before rolling is thin and the thread needs to be increased by a predetermined amount. . Furthermore, as a prior art for preventing the scattering / dropping of molding waste, a technique as shown in JP 2008-175253 A has been used in recent years. In this method, a lower layer made of an adhesive resin is formed on the thread surface of a conventional screw, and an upper layer made of a non-adhesive resin is formed on the surface of the lower layer. By screwing this screw into the lower hole of the workpiece, a female screw is formed, the upper layer is broken and the lower layer is exposed, and molding waste generated at the time of forming the female screw is captured in this lower layer.

JP-A-10-176709 JP 2008-175253 A

  However, in these conventional techniques, in the technique shown above, since the tip of the tapping screw is formed at an acute angle of 60 ° or less, the screw thread is formed when the female screw is formed by screwing this screw. The tip has a cutting action, so that the work is likely to crack. In addition, the stress at the time of molding concentrates at the tip, causing peeling of the workpiece due to friction. When the workpiece's pilot hole is a through hole, it becomes a scrap and scatters and drops onto the electronic board. It also causes a short circuit. Further, in addition to these scraps, wear powder, plating peeling powder of the thread and the like are also generated between the thread and the female thread, and these are also formed scraps generated during screwing. In addition, the state in which the screw is not completely screwed in due to frictional heat with the workpiece, that is, a screw floating phenomenon occurs. Moreover, since a relatively large frictional resistance is generated when the screw is screwed, a smooth screwing action and a large axial force cannot be obtained, and the screw is easily loosened. In particular, the fastening of parts is often managed by the axial force of the screw, which ensures a certain fastening quality, and if a large frictional resistance occurs, the fastening quality control by the axial force is impaired. .

  On the other hand, when the screw once screwed is loosened and removed, and screwed again into the female screw hole in which the female screw has already been formed by the previous screwing, as shown in FIG. 9, it is screwed while following the already formed female screw 142. For example, if the center line (B) of the screw is inclined at an angle (θ) with respect to the center line (A) of the female screw hole, this is not corrected at the initial stage of screwing, and the tapping screw 101 The screw thread 110 bites into the side surface of the female screw, and therefore, the female screw is shaved. This means that if re-screwing is repeated, it will eventually become a female screw that does not have sufficient strength, making it impossible to firmly tighten the parts.

  In the case of the other prior art, the flank angle at the tip of the thread is 60 °, so that the same problem as described above still occurs. In addition, there are those that apply adhesive resin to existing screws and thereby capture the above-mentioned molding waste. In this case, when used for ordinary screw threads that are widely used, molding is performed by the first screwing. Although it is possible to capture debris, there are problems such that when used repeatedly, this adhesive resin is scraped off when screwed, and the capturing action rapidly declines.

  The object of the present invention is to eliminate such problems and to accurately obtain the set axial force without increasing the screwing torque, and to prevent generation of molding waste between the screw thread and the female screw even in the re-screwing operation. It is to obtain a threaded part that is reduced as much as possible.

An object of the present invention is a screw component that includes a head 2 having a driving portion and a leg 3 integral therewith, and a screw thread 10 that is screwed into a work 40 is formed in the leg 3. Thus, in the cross section perpendicular to the ridge line 21 of the thread 10, the follower flank angle (α / 2) and the advance flank angle (α / 2) on the thread base side are a predetermined height from the trough 11. The flank angle (γ) is equal to the follower flank angle (α / 2) so that the follower flank surface 14 is steep from the predetermined height (h) to the thread ridge line 21 at the same angle up to (h). In addition, the obtuse angle larger than the first flank angle (α) formed by the first follower-side flank surface 12 and the first advance-side flank surface 13 on the screw thread base side is formed on the thread ridge line side. Forming a ridge line portion 20 having a flank angle (β) of 2; Become and the steep chase flank surface 14 in section 20 and the first stabbing flank surface 13 and respectively connected, on the other hand, the seat surface 5 of the head 2 from the leg portion 3 in which at least the screw thread 10 is formed And covering with a coating agent comprising a mixture of an adhesive mainly composed of an acrylic polymer, a polyoxyalkylene nonionic activator and a polyethylene wax lubricant, and drying the coating agent at a temperature of about 160 ° C. This is achieved by providing a threaded part comprising: By covering with the coating agent in this way, the frictional resistance becomes relatively low at the time of screwing, and an accurate and relatively large axial force of the screw can be obtained after the screwing is completed.

Further, according to the present invention , in the configuration described above, the screw thread has a guide portion 10a that fits into the pilot hole 41 of the workpiece 40 at the tip of the leg portion, and then a female screw forming portion 10b that makes a round of the leg portion 3 is formed. A continuous fastening portion 10c having the same screw thread diameter is formed between the female screw forming portion 10b and the head portion 2, and the female screw forming portion 10b has an outer diameter slightly larger than the screw thread outer diameter of the fastening portion 10c. By using the screw component having the above structure, the frictional resistance when screwed into the prepared hole of the work can be reduced.

Furthermore, the ridge line portion has a narrow second follower flank surface 22 and a second advance flank surface 23 on both sides of the ridge line 21 formed by the continuous vertices, and these flank surfaces are Since the second flank angle (β) to be formed is set to 100 ° to 130 °, the movement of the meat (material flow of the workpiece) becomes smooth when forming the internal thread.

  According to the present invention, the screw thread has an obtuse angle with the second flank angle (β) on the thread tip side larger than the first flank angle (α) formed on the flank surface on the base side. Since the thread tip is unlikely to cause a cutting action when forming the internal thread, and the internal thread is smoothly formed in the pilot hole of the work, cracks are not generated in the work. In addition, since the stress concentration during molding is reduced at this tip, the occurrence of workpiece peeling due to friction is reduced, and molding scraps such as peeling pieces fall on the electronic substrate, causing a short circuit in the electronic circuit. That also decreases. In addition, wear powder, thread peeling powder, and the like are reduced between the thread and the female thread, and generation of molding waste generated during screwing is suppressed. Moreover, the angle (α / 2) formed between the first follow-up flank surface and the first advance-side flank surface perpendicular to the axis of the leg portion is equal to a predetermined height on the base side of the screw thread. Therefore, even if a large axial force is applied to the thread base, thread breakage from this part does not occur. In addition, the second flank angle (β) is set in a range from a minimum of 100 ° including the most suitable angle of 120 ° to a maximum of over 130 °. Compared to the powdery state, the generation of thin long and short strip-shaped molding scraps is minimal.

  In addition, since the follower flank surface has a steep slope from the middle, a large axial force is generated when the screwing is completed, and a firm fastening is possible. In addition, when the screw once screwed is loosened and removed, and screwed into the same female screw hole again, the screw thread is screwed in accurately following the female screw without biting into the already formed female screw. Repetitive screwing into the female screw is possible, and its durability is improved. This means that sufficient component fixing is maintained in component replacement or the like. On the other hand, since at least the leg parts of the screw parts are covered with a coating agent in which an adhesive and a lubricant are mixed, a lubricating action occurs during screwing and frictional resistance is reduced. For this reason, the screwing torque at the time of screwing can be lowered and the axial force after screwing can be increased. Thereby, in a product in which the fastening force for fixing the component to the workpiece is managed by the axial force of the screw, a highly reliable axial force is obtained, and a specific effect such as an improvement in fastening quality is obtained.

It is a principal part expanded partial sectional front view which shows embodiment of this invention. 1 is an overall front view of a tapping screw adopting the present invention. FIG. 3 is a right side view of FIG. 2. It is an expanded sectional view explaining the principal part of this invention. It is a principal part expanded sectional view which shows the screwing start state of this invention. FIG. 9 shows a modification of the thread ridge line portion of the present invention, where (a) shows a second flank angle (β) of 90 °, and (b) shows a second flank angle (β) of 150 °. It is an expanded sectional view of the shown screw thread, and the dashed-two dotted line of these figures has shown the case where the 2nd flank angle is 120 degrees. It is a principal part expanded view which shows the re-screwing start state of this invention. It is principal part sectional drawing which shows the prior art example of this invention. It is principal part sectional drawing which shows the re-screwing state of the screw in FIG. It is principal part sectional drawing which shows the screwing start state by another prior art example.

  The best mode for carrying out the present invention will be described below with reference to FIGS. 1 and 2, reference numeral 1 denotes a tapping screw having a tapping function as an example of a screw with a female thread forming function, which includes a head 2 and a leg 3 formed integrally therewith. 1 is formed with a drive hole 4 through which a screw driving force is transmitted from a driver bit (not shown). A screw thread 10 is formed on the leg 3 integral with the head 2 from the vicinity of the seating surface 5 of the head 2 to the tip of the leg 3, and the leg 3 is, as shown in FIG. It has a circular shape. Moreover, the tip portion of the leg portion 3 is lower than the height of the thread 10 of the fastening portion, which will be described later, in which about two to three threads are complete screw portions. The incomplete thread portion is formed with an outer diameter that fits in or slightly touches the pilot hole 41 formed in the above. The incomplete thread portion serves as a guide portion 10a that guides screwing into the pilot hole 41 at the start of screwing. When the guide portion 10a enters the pilot hole 41 at the start of screwing, the tapping screw 1 becomes large. The structure is not inclined.

  On the head side of the guide portion 10a, there is provided a female screw forming portion 10b having about one screw thread 10, and this female screw forming portion 10b has the same screw thread diameter formed continuously from the head side. The diameter is slightly larger than that of the fastening portion 10c. This is to prevent the frictional resistance generated between the screw thread 10 when screwed into the pilot hole 41 and the female screw 42 formed thereby from occurring in the entire screw thread 10 of the leg portion 3. Specifically, it is sufficient to increase the height of the screw thread 10 of the fastening part 10c, that is, the height (H) from the valley part 11 to the ridge line 21 of the screw thread 10 about 0.01 mm in the radial direction. .

  As shown in FIG. 4, the thread 10 of the female thread forming portion 10 b and the fastening portion 10 c covers the first follower flank surface 12 in the cross section perpendicular to the lead wire of the thread 10 as shown in FIG. 4. The first flank angle (α) formed from the first advancing flank surface 13 is an equiangular shape. Usually, the first flank angle (α) is a tappin defined in JIS. It is set to be equal to or less than the flank angle of the screw or small screw, and in this embodiment, set to 60 °. The height (h) of the first follower flank surface 12 by the first flank angle is set to 0.2 times the height (H) from the valley portion 11 of the screw thread 10, and this The angle (γ) is set to be smaller than the follower flank angle (α / 2) constituting the first flank angle (α) so that the follower flank surface 14 becomes steeper toward the thread ridge line side. From this position, the thread ridge line side has an unequal angle mountain shape. Thereby, the axial force of the screw after screwing increases.

  Further, the most ridge line side of the thread 10 is larger than the first flank angle (α) formed by the first follower flank surface 12 and the first advance flank surface 13 on the thread base portion side. A ridge line portion 20 having a second flank angle (β) that is equiangular and obtuse with respect to the thread center line is formed. The ridge line portion 20 is connected to the steep flank surface 14 and the first advancing flank surface 13 connected to the first follower flank surface 12, respectively, and the ridge line portion 20 is connected to the steep follower flank surface. The width (L) of the ridge line portion 20 connected to the surface 14 and the first advance side flank surface 13 has a relationship represented by L = P / 3.5, where the pitch of the thread 10 is (P). The height (H) to the thread ridge line 21 is set to 1 / 1.5 of the thread pitch (P). The pitch (P) of the thread 10 is set to be equal to the pitch of the small screw in JIS, and these relational values are derived from many experiments and experiences. This is obtained from the result of considering the state of flesh flow (fiber flow) of the workpiece 40 that is generated when the screw 40 is screwed into the pilot hole 41.

  Further, the ridge line portion 20 has a second follower-side flank surface 22 and a second advance-side flank surface 23 which are narrow on both sides with respect to a ridgeline 21 formed by the continuous vertices. The angle of the second flank angle (β) formed by 22 and 23 may be an obtuse angle of 90 ° or more, but the optimum angle may be set to 100 ° to 120 °. If the second flank angle (β) is 90 ° or less, the set value is such that the corner of the ridge line portion 20 of the screw thread 10 becomes tight and there is a high risk of causing cracks in the pilot hole 41. If the angle is greater than 0 °, the corners of the connection between the first flank surfaces 12 and 13 and the second flank surfaces 22 and 23 become tight, and this portion may bite into the flank surface of the female screw 42. It is determined as the optimum value. However, even if it is more than this, the bite is obtained by connecting the connecting portion 24 between the first follower side and steep flank surfaces 12 and 14 and the second follower side and advance side flank surfaces 22 and 23 with an arc. The action is eliminated, and if the corners of the first follower and steep flank surfaces 12 and 14 and the second flank surfaces 22 and 23 are formed in an arc shape, the second flank angle ( β) may exceed 120 °. In addition, the configuration in which the first follower side and steep flank surfaces 12 and 14 and the second flank surfaces 22 and 23 are connected by an arc is not particularly limited to this angle. It may be smaller than °.

  Further, the optimum angle will be discussed in detail. Table 1 shows only the second flank angle (β) according to the present invention, and the other shapes of the screw 1 having a normal thread shape, which are three types of samples of 90 °, 120 °, and 150 °, respectively. Threads 10 when three are prepared and re-screwed twice and three times into the pilot hole 41 having a female screw formed when the screw is first screwed into the pilot hole 41 of the workpiece 40 and when it is screwed in for the first time. The amount (or number) of each molding waste generated by the friction with the above is copied to a 20 times projector, and this is visually confirmed and compared. The measurement conditions of the tapping screw 1 and the workpiece 40 at this time are shown as follows. The nominal size of the tapping screw 1 is M3, the leg length is 12 mm, and the plating of the screw is trivalent chromate. The workpiece is a cold-rolled steel plate having a thickness of 1.2 mm and a pilot hole diameter of 2.8 mm. The tightening torque for tightening the tapping screw with an electric screwdriver is 0.8 N · m.

  Comparing the obtained data based on such measurement conditions, it can be seen that when the second flank angle (β) is 120 °, the generation of molding waste is the smallest in any case. That is, the thread 10 of the tapping screw 1 used in this measurement has the shape shown in FIG. 4, the height of the thread is the same for all three types, and the width (L) of the ridge line portion is set to be the same for all three types. The second flank angle (β) is set to 90 °, 120 °, and 150 °. As is clear from this, as shown in FIG. 6 (a), the ridge line is in the range of the width (L). The cross section length of the portion 20 is the longest when the angle is set to 90 °, and the next longest is the screw shown in FIG. 4 when the angle is set to 120 °, that is, a screw indicated by a two-dot chain line in FIG. In the mountain, the shortest ridge line portion 20 is set at an angle of 150 ° as shown in FIG.

  In addition, when the average values of the second flank angle (β) are 90 °, 120 °, and 150 °, the second flank angle is found when the female screw 42 is screwed into the pilot hole 41 of the work 40 while being formed. The tapping screw 1 with (β) of 120 ° produces the least amount of molding waste. Further, even when the tapping screw 1 is loosened and screwed into the same female screw hole twice or three times, the amount of molding waste generated at the time of screwing is the highest for the tapping screw 1 with the second flank angle (β) of 120 °. The measurement result that there were few was obtained. This is because factors such as the difference in the area of the ridge line portion 20 obtained by the angle of the second flank angle (β) and the magnitude of the stress component acting on the workpiece by the inclined surface of the ridge line portion 20 act comprehensively. And the second flank angle (β) of 120 ° is most preferable. Accordingly, it is most preferable that the second flank angle (β) is within an allowable range of 120 ° ± 10%. As is clear from these descriptions above, the optimum angle can be set to a maximum of 100 ° to 130 ° by preventing the flank surfaces of the screw threads 10 from being connected to each other.

  On the other hand, when the width (L) of the ridge line portion 20 is set to be too large, a large screwing resistance is generated when the tapping screw 1 is screwed into the prepared hole 41, and conversely, the width (L). In view of the fact that if the width is narrow, stress concentration tends to occur at the ridge line portion at the tip of the screw thread 10, so that the screw thread 10 does not easily bite into the flank surface of the female screw 42 even if a slight inclination occurs during screwing. It is set to do. And it becomes possible to obtain | require the width | variety (L) of a ridgeline part appropriately according to the nominal size and pitch of the tapping screw 1 by setting it as the above relational expressions, and, thereby, the nominal dimension of the tapping screw 1 is obtained. Even if the height (H) of the screw thread 10 is changed, the operation hardly changes.

  The tapping screw 1 is entirely covered with a coating agent 30. Specifically, this coating agent 30 was excellent in lubricity and a polyoxyalkylene nonionic activator excellent in adhesion between a pressure-sensitive adhesive mainly composed of an acrylic polymer excellent in weather resistance and oxidation inferiority and metal. These are mixed with a polyethylene wax-based lubricant, these are mixed in a liquid state, and thereafter, the coating agent 30 is applied to the whole by immersing the tapping screw 1 in the mixed solution. It is obtained by drying at a temperature of 5 ° C. for 5 minutes. By this drying treatment, most of the lubricating component floats and covers the surface of the coating agent 30 applied to the surface of the tapping screw 1, and the adhesive component is included and the adhesiveness is removed from the surface. Become. Note that the coating agent 30 is applied to the entire tapping screw 1, but the entire surface of the leg 3 where at least the screw thread 10 is formed instead of the entire screw is thus hung on the seating surface 5 of the head 2. It may be applied.

  Further, in the above description, the steep follower flank surface 14 and the first advancing flank surface 13 are replaced with the second follower flank surface of the flat slope having the second flank angle (β) at the ridge line portion 20. 22 and the second advancing-side flank surface 23 are connected in a straight line, but instead of the second flank surfaces 22 and 23 of the ridge line portion 20, an arc-shaped surface (not shown) having an arc shape. 1), both ends thereof may be connected to the follower-side flank surface 14 and the first advance-side flank surface 13 which are steep. In addition to this, all the connecting portions of the flat slope may be connected by an arc, and the effect can be sufficiently obtained by these.

  When the screw thread 10 of the tapping screw 1 configured in this way is screwed into the prepared hole 41 formed in the workpiece 40 in advance as shown in FIG. 5, the screw thread 10 at the tip of the leg portion 3 is first formed in the prepared hole. When this is fitted into 41 and screwed in, the female screw 42 is screwed into the prepared hole 41 while being gradually formed by the female screw forming portion 10 b of the screw thread 10. At this time, the ridge line portion 20 of the screw thread 10 gradually enters the inner periphery of the pilot hole 41 by the screw thread 10. For this reason, the flesh of the workpiece 40 in the pilot hole 41 is transferred to the valley portion of the screw thread 10. The female screw 42 is molded by being plastically deformed while being pushed away so as to enter the portion 11. The meat forming the female screw 42 at this time is formed by being pushed away by the female screw forming portion 10b of the screw thread 10, but the pilot hole diameter is set to be substantially the same as the outer diameter of the guide portion 10a of the leg portion 3. Therefore, the valley portion 11 of the screw thread 10 is not filled. Thus, when the tapping screw 1 is screwed in while forming the female screw 42, a gap is formed between the valley 11 of the screw thread 10 and the female screw 42, and the coating agent 30 applied to the screw is accumulated in this gap. It will be. And the molding waste generated at the time of screwing is adsorbed and captured by this. In addition, since the coating agent 30 contains a lubricant, smooth screwing is continued, and immediately after screwing, the tapping screw 1 has a large axial force due to the action of the fastening portion 10c, the female screw forming portion 10b, and the seat surface 5. Therefore, the fastening torque and the axial force necessary for fastening the parts can be obtained accurately.

  On the other hand, when the tapping screw 1 is loosened, the female screw 42 is already molded and plastically deformed. When the same tapping screw 1 is screwed into the tapping screw 1 again, as shown in FIG. Since the ridge line portion 20 of the screw thread 10 has the second follower side flank surface 22 and the second advance side flank surface 23, the screw thread 10 is fitted into the already formed female screw 42 at the start of screwing. The screw thread 10 is screwed while following the female screw 42 without shaving 42. As a result, the center line (B) of the tapping screw 1 is inclined by an angle (θ) with respect to the center line (A) of the pilot hole 41 in which the female screw 42 is already formed (indicated by the solid line in FIG. 7). Even if it is screwed in, the inclination is corrected (state shown by a two-dot chain line in FIG. 7), so that the generation of molding waste is extremely reduced at the time of screwing.

  Further, although the embodiment of the present invention has been described with the tapping screw 1 having a circular cross section perpendicular to the axis of the leg 3, the present invention is not limited to this, and the cross section of the leg 3 is substantially triangular. However, the same effect can be obtained.

DESCRIPTION OF SYMBOLS 1 Tapping screw 2 Head part 3 Leg part 4 Drive hole 5 Seat surface 10 Screw thread 10a Guide part 10b Female thread formation part 10c Fastening part 11 Valley part 12 1st follower side flank face 13 1st advance side flank face 14 Steep Tracking side flank surface 20 Edge line portion 21 Edge line 22 Second tracking side flank surface 23 Second advancement side flank surface 24 Connection portion 30 Coating agent 40 Work piece 41 Pilot hole 42 Female thread

Claims (3)

A screw component comprising a head formed with a drive portion and a leg portion integral with the head portion, and a screw thread that is screwed into the workpiece is formed on the leg portion,
In the cross section perpendicular to the ridgeline of the thread, the follower flank angle (α / 2) and the advance flank angle (α / 2) on the thread base side are equal to a predetermined height (h) from the valley. In addition, the flank angle (γ) is made smaller than the follower flank angle (α / 2) so as to form a steep follower flank surface from the predetermined height (h) to the thread ridge line, and the screw The second flank having an obtuse angle larger than the first flank angle (α) formed by the first follower flank surface (12) on the thread base side and the first advancing flank surface (13) on the ridge line side. Forming a ridge portion having an angle (β), and connecting the steep follower flank surface and the first advancing flank surface to the ridge line portion ,
On the other hand, a mixed liquid of an adhesive mainly composed of an acrylic polymer, a polyoxyalkylene nonionic activator, and a polyethylene wax lubricant from at least a leg portion on which a thread is formed to a seating surface (5) of the head. A screw part characterized by being covered with a coating agent comprising: and drying the coating agent at a temperature of around 160 ° C. The screw thread has a guide portion (10a) that fits into the pilot hole of the workpiece at the tip of the leg portion, and then a female screw forming portion (10b) that makes a round of the leg portion is formed. A continuous fastening portion (10c) having the same screw thread diameter is formed between the female screw forming portions, and the female screw forming portion has an outer diameter slightly larger than a screw thread outer diameter of the fastening portion. Screw parts described in The ridge line portion has a narrow second follower flank surface (22) and a second advancing flank surface (23) on both sides of the ridge line (21) formed by the continuous vertices. The screw part according to claim 1 or 2, wherein the second flank angle (β) formed by the flank surface is set to 100 ° to 130 ° . "

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