JP5204887B2 - Screw part head drive hole - Google Patents

Description

  The present invention relates to a screw for fastening a component to a workpiece with a predetermined fastening force, and in particular, the engagement between a driver bit that transmits a driving force to the head during screw fastening and a screw driving hole is an engagement groove of the screw. The present invention relates to a head drive hole for a screw part that is configured to be able to be reliably engaged without crushing.

  2. Description of the Related Art Screws having a relatively small nominal diameter are used in electrical products such as mobile phones, personal computers, and portable music players, automobile parts, and the like that have been widely used in recent years because of their weight reduction, thickness reduction, and size reduction. As such a screw, a screw stipulated mainly in JIS (Japanese Industrial Standard) is adopted, and even in a screw having a small nominal diameter as described above, as shown in FIG. It has the same shape. FIG. 11 shows a cross-recessed screw 101, and an engagement groove 110 is formed on the head 102 in four radial directions with respect to the center of the screw 101, and a hill portion between these grooves 110. The contour of 120 is the shape of the wall that forms this groove, and the blade of the driver bit engages with this groove to transmit the screw tightening driving force. It has become.

  In addition to the cross-shaped drive hole, such a hill portion is formed in the same manner, for example, in a screw having a Y-shaped engagement groove in which a screw cannot be loosened with this + driver bit, that is, a so-called tamper-proof screw. Is done. This screw is generally used in the place where the machine bit is loosened by the + driver bit and cannot be touched inside the machine. The shape of the head drive hole is the cross-shaped drive hole at the center of the screw. The Y-shaped drive holes are only three directions in contrast to the four radial directions, and both are formed with hills between the engaging grooves.

  Therefore, in order to engage the driver bit with the screw drive hole, especially when performing screw tightening work with an automatic screw tightening machine, the driver bit is simultaneously brought into contact with the screw head and the driver bit is rotated. Although the engagement blade of the driver bit is engaged with the engagement groove of the screw, the center of the screw and the center of the driver bit are slightly shifted at the beginning of the engagement, or the engagement blade of the driver bit is If the engagement groove of the drive hole is not securely fitted, the corner of the engagement groove is often crushed, and this phenomenon is particularly prominent when the screw is small.

  Moreover, there exists a driving screw shown by patent document 1 as a prior art. The driving screw of this patent document 1 forms a ridge portion that slopes downward toward the bottom of the drive hole in the protruding portion between the cross-shaped bit positioning grooves, and the bit positioning groove that sandwiches the protruding portion from the ridge portion. An inclined surface having a downward slope toward each groove is formed. This inclined surface allows the bit to be guided to properly engage the bit positioning groove.

Japanese Utility Model Publication No. 63-26566

  However, in such a conventional example, in the case of the drive hole defined in JIS, as already described, in the fastening operation using the manual driver bit, the engagement blade and the engagement groove are fitted together and then screwed. Because the work is performed, the drive hole is not crushed at the initial stage of screw tightening. However, in automated assembly factories using machines such as assembly work lines, automatic screw tightening machines are used. Is easy to collapse. In particular, in a screw having a small nominal diameter, there is a problem that the drive hole is crushed and the screw cannot be tightened with a predetermined fastening torque. Further, in the drive hole as in Patent Document 1, for example, when the driver bit starts to rotate simultaneously with the screw head in an automatic screw tightening machine, the driver bit is inclined upward with respect to the rotation direction. If it is guided to an inclined surface (an inclined surface that is inclined downward to the opposite side of the rotation direction of the driver bit across the ridge), the rotation of the driver bit is transmitted to the inclined surface and the screw is repelled. Problems occur. Further, in the drive hole as in Patent Document 1, since the projecting portion is formed with a substantially symmetrical inclined surface with the ridge portion interposed therebetween, the area of the engagement wall surface that is to receive torque transmission from the driver bit during screw tightening Becomes smaller and the groove portion is easily damaged.

  An object of the present invention is to obtain a head drive hole for a screw component that eliminates such problems and ensures the engagement between the engagement groove and the driver bit at the initial stage of screw tightening.

In order to achieve the above object, the present invention comprises a head 2 having a drive hole 4 and a leg 3 integral therewith, and a screw having a thread 5 formed on the leg. Drive holes are formed from the head surface side to the legs, and a plurality of engagement grooves 10 are formed radially from the center of the drive holes at equal intervals in the circumferential direction. The hill portion 20 formed between the engagement wall extends from the outer periphery to the entire length of the drive hole center side at the boundary with the engagement wall on the tightening direction side of the engagement groove located on the rear side in the screw tightening rotation direction. At the boundary with the engaging wall on the loosening direction side of the engaging groove located on the front side in the screw tightening rotation direction. Is higher than the inclination angle (α) continuously with the inclination of the inclination angle (α) so as to be higher toward the outer peripheral side. While inclined at Sai inclination angle (beta), configured as an inclined surface that changes the inclination angle (beta) of the surface extending from the slope of the inclined angle (alpha) to the inclination of the inclined angle (beta) from the inclination angle (alpha) The outer peripheral wall 22 extending from the head surface to the surface of the hill portion provides a head drive hole for a screw part configured in a mortar shape over the entire surface . The composite inclination angle is desirably an angle greater than 8 ° 32 ′ and smaller than 17 ° with respect to a plane perpendicular to the axis of the screw.

  According to the present invention, there is no fear that the engagement blade of the driver bit crushes the drive hole of the screw head at the initial stage of screw tightening in the automatic assembly work like the screw drive hole specified in JIS. When a screw with a small nominal diameter is tightened with an automatic screw tightener, damage to the head is avoided. In addition, since the hill between the engagement grooves is a surface inclined so that the screw tightening direction side and the center side are deep, the center of the driver bit is shifted from the center of the screw drive hole. Also, the driver bit can be guided toward the center of the screw, and the center of the driver bit and the center of the screw coincide with each other, and at the same time, the engagement blade surely fits into the engagement groove. Moreover, even when the driver bit is fitted into the screw drive hole while rotating the driver bit in the automatic assembly operation, the driver bit can be smoothly guided and fitted along the inclined surface of the hill.

  In addition, an outer peripheral wall inclined in the shape of a mortar toward the center of the drive hole is formed around the hill, so that the screwdriver bit does not go out of the drive hole of the screw and always stays on the center line when screwing. Making it possible to match. Moreover, since the engagement wall on the tightening direction side where the driver bit engages when screwing has the same height as the wall of the engagement groove constituting the conventional drive hole in the vicinity of the outer peripheral end, There is no problem in transmitting the tightening torque. In addition, the inclination angle is set to the optimum inclination angle that allows the engagement blade to slide and be guided into the engagement groove only by the contact of the engagement blade of the driver bit with the hill of the screw head, even if little thrust is applied. Therefore, even if the screw has a small nominal diameter, the screw head is not damaged at all and has a specific effect such as a stable screw tightening action.

It is a front view which shows one Example as embodiment of this invention. It is a left view of FIG. FIG. 3 is a cross-sectional view taken along line AA in FIG. 2. FIG. 3 is a cross-sectional view of an essential part of the line BB in FIG. It is a principal part expanded sectional view which shows the inclined surface of a hill part. It is principal part sectional drawing which shows the relationship between this invention and a driver bit. (A), (b) is sectional drawing which shows the sliding state of the inclined surface of a hill part, and a driver bit. It is explanatory drawing which shows the action state of the force in this invention. It is a top view which shows the other Example of this invention. It is CC sectional view taken on the line in FIG. It is principal part sectional drawing which shows the prior art example of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 and 2 as an embodiment of the present invention, reference numeral 1 denotes a screw comprising a head 2 and a leg 3 formed integrally therewith. A drive hole 4 through which a screw tightening driving force is transmitted is formed. A screw thread 5 is formed on the leg 3 integral with the head 2 from the vicinity of the seat surface 6 of the head 2 to the tip of the leg 3, and the leg 3 has a circular cross section. . A conical neck 7 is formed between the leg 3 and the head 2 and the leg side is thin and the head side is thick. The tip of the drive hole 4 of the head 2 has a substantially conical hole shape. The neck 7 has been reached.

  As shown in FIGS. 3 and 4, the drive hole 4 has its center on the center line of the screw 1 and is recessed from the surface of the head 2 to the leg 3. A plurality of engagement grooves 10 are formed at equal intervals in the circumferential direction in the radial direction from the conical hole 8 at the center of the drive hole 4, and these engagement grooves 10 are formed as shown in FIG. A hill portion 20 is formed between another engaging groove 10 which is adjacent to each other. In this embodiment, the hill portion 20 is formed between the engagement grooves 10 because the engagement grooves 10 are Y-shaped. Specifically, the engagement grooves 10a, 10b, 10b And 10c, 10c, and 10a are formed with hill portions 20 having the same inclined surface shape.

  The shape of the hill part 20 will be described by taking the hill part 20 formed between the engagement groove 10a and the engagement groove 10c adjacent to the rear of the engagement groove 10a in the screwing rotation direction as an example. As shown in FIGS. 2 to 6, the surface of the hill portion 20 is engaged with the engagement wall 11 (the engagement blade 31 of the driver bit 30 engages when the screw is tightened) in the engagement groove 10c. The inclination angle (α) is such that the engagement wall 11 is lowered toward the drive hole center side over the entire length from the outer peripheral end (intersection with the surface of the head 2) to the drive hole center side at the boundary with the wall). It is inclined at. Further, at the boundary with the engagement wall 12 on the loosening direction side in the engagement groove 10a (the engagement wall engaged when the engagement blade 31 of the driver bit 30 loosens the screw), the engagement wall 13 is placed on the outer peripheral side. In order to make it higher, it is configured to be inclined at an inclination angle (β) that is continuous with the inclination of the inclination angle (α) and smaller than the inclination angle (α). Further, the surface of the hill 20 from the boundary with the engagement wall 11 having the inclination angle (α) to the boundary with the engagement wall 12 having the inclination angle (β) is changed from the inclination angle (α) to the inclination angle (β). It is an inclined surface that changes. Since the inclination angle (β) is smaller than the inclination angle (α), and the drive hole center side of the inclination angle (β) is continuous with the inclination angle (α), the inclined surface of the hill portion 20 has an inclination angle (β ) Side and the inclination gradually becomes deeper toward the drive hole center side. For example, when viewed at a certain point on a perpendicular perpendicular to the center line of the engaging groove 10c, the direction of the arrow (b) in FIG. 2 along the perpendicular and the direction of the arrow (b) perpendicular to the direction are deeper. ing. Further, the inclined surface of the hill portion 20 coincides with the surface of the head 2 at the outer peripheral end of the engagement wall 11 on the tightening direction side.

  As described above, the surface of the hill portion 20 is an inclined surface that deepens in the screwing rotation direction and the drive hole center side, and the tip of the driver bit 30 comes into contact with the inclined surface, so that the driver bit 30 is connected to the drive hole. 4 is guided to move to the center. When the driver bit 30 is rotating in the screwing direction, the driver bit 30 can be guided without countering the rotation. Moreover, the surface of all the hill parts 20 has the structure where the center side of the drive hole 4 is the deepest, and the inner edge 21 in the drive hole center side of the surface of all the hill parts 20 has the same depth. For this reason, when the center of the driver bit 30 and the center of the drive hole 4 coincide, the engagement blade 31 of the driver bit 30 can be stably engaged with the engagement groove 10 without being inclined.

  On the other hand, the inclination angles (α) and (β) of the surface of the inclined hill portion 20 need only be inclined so that the screw tightening direction side is deep from the head surface. θ), that is, the minimum angle of the screw 1 when the tip of the driver bit 30 or the engagement blade 31 is in contact with the head 2 of the screw 1, even if almost no thrust (force that presses the driver bit toward the workpiece) is applied, it starts to slide. It is an angle, and it is as follows when calculating | requiring the angle for starting this sliding. Here, it is conventionally known that the friction coefficient μ of a general screw 1 is about 0.15, and the maximum angle at which an object can be stopped on a slope is assumed to be (θ), and the weight (or thrust) of the object ) Is Mg, it is balanced by Equation 1 (see FIG. 8).

The angle (θ) obtained from this is tan ⁻¹ μ, which is about 8 ° 32 ′.
Thereby, if the inclination angle of the surface of the hill part 20 exceeds 8 ° 32 ′, the object slides on this inclined surface, and this is the minimum angle for sliding.

  On the other hand, it is best to set the maximum angle, which is the upper limit of the optimum angle, to a value smaller than the tip angle of the driver bit 30 (18 ° ± 1 ° which is an angle defined in JIS). By setting the optimum angle (θ) of the inclined surface in the range of 8 ° 32 ′ to 17 ° in this way, as shown in FIG. 7A, the surface of the hill portion 20 where the tip of the driver bit 30 is inclined. When the angle exceeds the upper limit of the optimum angle (θ + γ), as shown in FIG. 7B, the angle of the surface of the hill portion 20 where the tip of the driver bit 30 is inclined is shown. Therefore, the range of the angle is the optimum angle. In addition, the inner wall (the surface in the depth direction from the inner edge 21) of the hill portion 20 is formed to have a sufficient height by being inclined in the range of this angle, and is fitted (biting) with the driver bit. Will not cause any trouble.

  Further, as shown in FIGS. 2 to 6, the outer peripheral wall 22 from the surface of the head 2 to the surface of the hill portion 20 is higher in the screwing rotation direction along the inclined surface of the hill portion 20, and its surface Has a conical shape, that is, a mortar shape toward the center of the drive hole. For this reason, even when the tip of the driver bit 30 touches this portion, the driver bit 30 is subjected to a moving action toward the center side of the screw 1.

  Moreover, as shown in FIGS. 3 to 6, the surface of the hill portion 20 is such that the engagement wall 11 on the tightening direction side of the engagement groove 10 is closer to the bottom surface 13 of the engagement groove 10 than the engagement wall 12 on the loosening direction side. Therefore, the transmission of the screw tightening torque from the driver bit 30 is stabilized.

  When screwing the screw 1 configured in this way, as shown in FIG. 6, the driver bit 30 is pressed so as to match the drive hole 4 formed in the head 2 of the screw 1. At this time, the engaging blade 31 of the driver bit 30 does not necessarily match and engage with the engaging groove 10 of the screw 1, but the tip of the driver bit 30 is an inclined surface formed on the hill portion 20 of the head surface. As a result, the engagement blade 31 is fitted in the engagement groove 10 because it slides in the screw tightening direction and the center side of the drive hole 4. Further, the engagement wall 11 on the tightening direction side of the engagement groove 10 is higher in the outer end side than the engagement wall 12 on the loosening direction side of the screw 1 from the bottom surface 13 of the engagement groove 10. The blade 31 fits securely without sliding out of the engagement groove 10.

  Thus, when the screw tightening torque of the driver bit 30 is transmitted to the drive hole 4 of the screw 1, the leg portion 3 of the screw 1 is screwed into the work (not shown). When the screw 1 is screwed in by a predetermined amount by this screw tightening operation and the seat surface 6 of the head 2 is seated on the work, the screw tightening torque is set, and the screw tightening operation is completed.

  In this embodiment, the drive hole 4 having the Y-shaped engagement groove 10 on the surface of the head 2 has been described. However, as shown in FIGS. 9 and 10, the drive hole 4 has a cross shape. In this case, the number of the engagement grooves 10 is larger than that in the above embodiment, so that the hill portion 20 is narrowed. However, the surface of the hill portion 20 has an inclined surface with a combined inclination angle as in the above-described embodiment, and it is needless to say that the same effect can be obtained.

DESCRIPTION OF SYMBOLS 1 Screw 2 Head 3 Leg part 4 Drive hole 5 Screw thread 6 Seat surface 7 Neck part 8 Conical hole 10 Engagement groove 11 Engagement wall by tightening direction 12 Engagement wall by loosening direction 13 Bottom face 20 Hill part 21 Inner edge 22 Outer peripheral wall 30 Driver bit 31 Engagement blade

Claims (2)

In a screw comprising a head (2) having a drive hole (4) and a leg (3) integral with the head (2), and a thread (5) formed on the leg,
A drive hole is formed in the center of the head from the head surface side to the leg, and a plurality of engagement grooves (10) formed in a radial direction and at equal intervals in the circumferential direction from the center of the drive hole. Forming,
The hill (20) formed between these engaging grooves is
Inclination angle so that the engagement wall is lowered from the outer periphery to the drive hole center side over the entire length of the drive hole center side at the boundary with the engagement wall on the tightening direction side of the engagement groove located on the rear side in the screw tightening rotation direction Inclined at an angle of (α)
In the boundary with the engagement wall on the loosening direction side of the engagement groove located on the front side in the screw tightening rotation direction, the inclination is continued to the inclination angle (α) so as to increase the engagement wall toward the outer peripheral side. Inclination with an inclination angle (β) smaller than the angle (α),
The surface from the inclination of the inclination angle (α) to the inclination of the inclination angle (β) is configured as an inclined surface that changes from the inclination angle (α) to the inclination angle (β) ,
An outer peripheral wall (22) extending from the head surface to the surface of the hill portion is formed in a mortar shape over the entire surface thereof, and is a screw head drive hole. The head drive hole for a screw component according to claim 1, wherein the combined inclination angle is an angle greater than 8 ° 32 'and less than 17 ° with respect to a plane perpendicular to the axis of the screw.

Images