JP2006329292A - Screw to be implanted with welding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a screw to be implanted in a base plate such as a metal material with resistance welding in such a manner as to be easily perpendicular to the base plate during implantation and superior in bending or returning mechanical strength. <P>SOLUTION: The implanted screw 100 is implanted in the base plate 50 such as the metal material with welding. A skirt portion 30 is protruded in inclination from the lower end of a shaft core 10 of the screw to the downward direction. A circularly rounded abutting face 31 is formed at the front end of the skirt portion 30, while a retaining face 40 is provided on the lower end face of the shaft core encircled by the skirt portion 30. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a screw that can be welded and planted, and more particularly to a screw that is planted by welding to the surface of a low-carbon steel plate, stainless steel plate, aluminum plate or other base plate by resistance welding or the like.

  In fields such as so-called sheet metal processing, various machine parts and tools can be obtained by screw welding onto a base plate such as a low carbon steel plate or stainless steel plate, and screwing a fastening component such as a nut onto the planted screw. Etc. are carried out. In this case, various mechanical elements are used for fixing the screw. However, the most common method is to fix the screw or the like by projection welding using the shape characteristic of the screw. When this projection welding is used for welding to a screw base plate, why is a large current flowing through the core of the screw and it is heated, and the thread and the like are easily damaged? In addition, when a screw is implanted in this way, even if projection welding is used, since the current always flows through the screw shaft core, the screw shaft core is heated, so the screw shaft core is heated. There is a desire for a welding method that minimizes heating of the threaded portion.

  The projection welding method is used as one of the welding methods. The projection welding method is one mode of resistance welding, and is essentially the same as the spot welding method. That is, it is a welding method in which a large current is concentrated and flowed only in a welded portion, and a welded portion (nugget) is formed in that portion for welding. In contrast to spot welding, this is achieved by the shape of the electrode, whereas projection welding is intended to concentrate the current and pressure depending on the welding material to be welded, specifically the shape of the screw to be welded. It is no exaggeration to say that it is determined whether projection welding can be effectively achieved with the shape of the screw.

  For this reason, in screw projection welding, screws that are to be welded to a base material such as a steel plate must have a structure that allows resistance welding by concentrating current and pressure so that the performance is not impaired. ing. However, the screw to be joined by projection welding itself has a structure in which linear protrusions are wound around the shaft core of an elongated cylinder, but the current can be concentrated by constricting the shaft core. Since it seems to be a structure, it is often used as it is for project welding, and there have been few proposals for improvements to suitable shapes.

  That is, when welding screws on a base material such as a steel plate, projection welding is used on one side, from another point of view, the screw to be welded and the base on which it is implanted. This is because the heat capacity difference between the plates is large. For example, between the screw and the base plate such as a steel plate, the heat capacity of the screw is larger than that of the steel plate. Therefore, if the tip of the screw is used as a projection (or projection), the heat balance with the steel plate is adjusted. it can. This heat balance depends on the shape of the screw, especially the shape of the tip of the screw. Ultimately, it will affect the quality of projection welding. Can be welded to.

  Furthermore, when welding the screw to the base plate in this way, an attempt is made to flow a current intensively at the tip of the screw in order to increase the joint strength at the time of welding.

  One of them is a screw that has been proposed as a spot boss. That is, a conical protrusion is formed along the axis on the tip surface of a screw shaft around which a linear protrusion is wound. In the spot boss of this structure, when current is passed through the screw shaft through the upper welding tip during welding, the current is concentrated on the conical protrusion at the tip, and projection welding can be achieved. The conical protrusion on the tip surface also serves as a pilot for screw positioning. If a recess for positioning is formed in advance in a base plate such as a steel plate, the conical protrusion aligns with this recess. In addition, screw positioning is facilitated.

  However, the conical protrusions of such spot bosses have a drawback that the pressurizing portion bulges on the back side of the base plate due to deep penetration in the base plate due to the pressure applied during welding. For this reason, the applied pressure cannot be increased to increase the joint strength. Further, since the welded portion is limited to the apex portion of the conical protrusion, there is a limit in increasing the joint strength. Further, in this spot boss, the conical protrusion is usually formed by mechanical cutting, and it is not preferable that the cost is high in a screw based on low cost.

  Further, even when looking at a nut for projection welding in order to attach a nut to which a screw is screwed to a base plate, a nut having a structure and shape suitable for projection welding has been hardly proposed.

  Japanese Patent Application Laid-Open No. 2004-268133 discloses a projection welding apparatus. As an example used in this welding apparatus, a screw or bolt for projection is disclosed. In other words, the projection welding apparatus is configured such that a material to be welded of a steel plate is supported by a support base, and a fixed electrode is brought into close contact with the back surface of the material to be welded to be energized. On the other hand, the movable electrode moves up and down on the fixed electrode, and the movable electrode is configured to hold a screw to be welded to the steel plate to be welded. The movable electrode is a portable movable electrode unit, and the movable electrode unit is configured to receive a welding electrode.

  Therefore, at the time of welding, a steel plate to be welded is placed on the fixed electrode supported by the base member, and a welding bolt held by a magnet (magnet) of the movable electrode is supplied from above, This is pressurized and energized by a movable electrode and projection welded. For this reason, the steel plate on the fixed electrode has a structure that is positioned by the base member, and the movement of the upper movable electrode is restrained by the receiving portion of this base member, so the arrangement position of the receiving portion can be selected, A welding position such as a welding bolt held by a magnet with the movable electrode is set, and only an example of the welding nut is disclosed.

  The welding bolt exemplified in this conventional welding apparatus does not have an improved shape and structure, and the welding bolt 1 shown in FIG. 8 is exemplified therein. That is, the welding bolt 1 is inserted into the axial hole 3 of the welding tip 2 and held by the magnet 4. The welding bolt 1 has a flange portion 5 formed at the tip of the threaded portion, and a projection portion 6 formed on the end surface of the flange portion 5.

  However, such a bolt 1 has substantially the same structure as that of the above-described spot screw pad, and simply concentrates current and voltage on the projection part on the end face of the flange part.

  Further, when the welding bolt 1 is pressed from above with the welding tip 2, the projection portion 6 is formed in a conical shape obliquely downward, so that the tip of the projection portion 6 is a base plate such as a steel plate due to the applied pressure. 7, and after welding remains as a joint on the back side of the base plate 7, it takes time to repair it.

Furthermore, using projection welding for planting screws and bolts is to concentrate current on the projection part, but the volume of the part expands due to local melting preceding the beginning of welding of the projection part. However, in the conventional bolts and screws, the core phenomenon occurs in the shaft core, and therefore, a portion that is locally lifted or not welded is likely to occur locally. Improvement is desired.
JP 2004-268133 A

  The object of the present invention is to solve the above-mentioned drawbacks, and specifically, to propose a screw having a structure suitable for welding and planting on a base plate such as low carbon steel, stainless steel, or aluminum material.

  First, the present invention is a planting screw that is welded and planted on a base plate such as a metal material, and is inclined downward from the lower end of the axial center of the screw to project the skat part, An abutting surface that is rounded in an arc shape is formed at the tip of the skat portion, and a pressing surface is provided on the lower end surface of the shaft core surrounded by the skat portion.

  In the present invention, the skirt portion is continuously formed in an annular shape.

  In the present invention, at least one notch groove is provided in the skirt portion.

  Further, in the present invention, a protrusion is provided at the tip of the skirt portion with a space.

  In the present invention, the base plate is a low carbon steel plate, an aluminum plate, or an aluminum alloy plate.

  In the present invention, at least a part of the pressing surface is flattened.

  In the present invention, the skat part and the shaft core are integrally formed by forging.

From the configuration as described above, the screw according to the present invention has the following effects.
(1) The skat portion is projected from the lower end of the screw shaft core, and an arcuate round contact surface is provided at the tip of the skat portion.
With this configuration, the screw can be planted while maintaining strict orthogonality to the base plate, and the welded planting with the base plate depends on the outer skirt, so bending and other machinery The mechanical strength can be greatly increased.
(2) Since the skirt portion is provided with at least one notch groove and the separated skirt portion is welded as a projection, the current concentration effect can be stably improved without causing a shunt. it can.
(3) Since the contact surface of the skirt portion is rounded in an arc shape, the contact surface does not enter the base plate, and the pressing surface surrounded by the skirt portion is formed flat. As a result, almost no weld remains on the back side of the planted base plate.

  Therefore, the present invention will be described in detail through the best mode for carrying out the invention as illustrated in the drawings.

  FIG. 1 is a front view showing, in section, a part of a welding screw according to one embodiment of the present invention.

  FIG. 2 is a bottom view seen from the direction of arrows AA in FIG.

  FIG. 3 is an explanatory view of an example when the welding screw shown in FIG. 1 is welded to a base plate such as a steel plate.

  FIG. 4 is a front view showing a part of a welding screw according to another embodiment of the present invention in cross section.

  FIG. 5 is a bottom view seen from the direction of arrow BB in FIG.

  FIG. 6 is a partial front view of a welding screw according to another embodiment of the present invention.

  FIG. 7 is a bottom view seen from the direction of the arrow CC in FIG.

  FIG. 8 is an explanatory view showing a welding mode when one welding screw of a conventional example is welded and implanted.

  First, in FIG. 1, FIG. 2 and FIG. 3, reference numeral 100 generally indicates a planting screw according to one embodiment of the present invention. The planting screw 100 includes a screw shaft core 10, a screw portion 20, a skar portion 30, and a holding portion 40 surrounded by the screw shaft core 10. The screw shaft core 10 is equivalent to a screw used as a normal fastening element, and a screw 11 is cut around the outer periphery thereof by winding a linear projection, and this male screw 11 is cut on the inner periphery of a nut or the like. Therefore, the screw is screwed and tightened.

  The screw shaft core 10 has a cylindrical shape, and helical projections are wound around the outer periphery of the screw shaft 10 as male screws 11. A female screw of a nut having a helical projection wound around a cylindrical inner surface is screwed onto the male screw 11. In this case, the axis 12 of the screw shaft core 10 is welded in order to achieve a predetermined fastening purpose in order to plant it vertically on a base plate such as a steel plate (indicated as 50 in FIG. 3). It is necessary to be perpendicular to the power base plate 50, that is, to maintain the orthogonality between the axis 12 and the surface of the base plate 50. Needless to say, the external thread on the outer surface of the screw and the internal thread on the inner surface of the nut are completely meshed with each other, and the inclined surface of each thread (that is, the flank surface) is not in good contact. This is because a fastening force is generated. As is well known, the fastening force of screws and nuts determines whether or not the contact of the inclined flank surfaces of each screw that meshes with each other is completely contact, and this contact (flat contact, even if it is flat) has a slight defect. On the contrary, the strength of the fastening portion deteriorates, and the structure is destroyed from the portion. In other words, if the axis of each screw does not match even when engaged, the effective diameter of each engaged screw will not match, and the flank surface of each screw will not contact completely, and the screw as the fastening element will be The effect of supporting the load on the surface cannot be exhibited sufficiently.

  In short, when the screw shaft core 10 is welded to the base plate 50 and planted vertically, the axis 12 and the surface of the base plate 50 must be strictly orthogonal. If this relationship goes wrong, even if the planting screw 100 is planted on the base plate 50, the planted screw 100 itself cannot have a predetermined strength, causing trouble.

  From this point, the conventional screw is not limited to the example shown in FIG. 8, and the projection is usually configured integrally with the shaft core and the current concentration effect is achieved on the projection. It is formed in a conical shape. For this reason, if the pressure is applied downward toward the base plate during welding, an extremely high pressure is applied to the contact portion of the base plate, which makes it difficult to insert. In particular, the initial heating is stable because the contact resistance of the conical projection part is formed immediately after welding, but on the other hand, the projection part is inevitably embedded in the base plate. Furthermore, the electrode from the upper part also descends while the projection part melts and disappears. For this reason, the orthogonality between the base plate and the axis line is lost. In particular, if the pressure applied to the electrode from the upper part is eased for biting into the base plate or removal after welding as described later, the orthogonality will be lost. Is easy to lose.

  In other words, it is extremely important that in the installation of screws for projection welding, the formation position of the projection part, even if its shape is slight, the orthogonality of the screw axis to the base plate, even if it is slightly out of order, The meshing contact with the flank surfaces of the threads that mesh with each other does not go smoothly and causes problems. If this is neglected and engaged to create a fastening part of the device, its strength is greatly impaired and it becomes a defective part.

  This conical protrusion bites into the base plate, and the lower surface of the base plate always protrudes locally following this, leaving a protruding portion. In addition, because the local projection part melts very locally, only that part overheats, so a clear “after welding” always remains on the back of the base plate, and the rest is relatively low. It remains deep. If the part is repaired at a later date, it will take a lot of time after painting and other work, which is not preferable.

  From these points, in the planting screw 100 according to the present invention, the skirt part 30 is provided at the lower end part of the screw shaft core 10. The skat part 30 is formed along the outer periphery of the lower end surface of the screw shaft core 10, and in particular, as shown in FIG. 1 and FIG. In addition, a part of the lower end surface of the screw shaft core 10 surrounded by the skat portion 30, usually the lower end surface itself, is configured as the pressing portion 40, and this portion is configured as the entire surface or a locally flat surface. .

  On the other hand, the skat part 30 forms a contact surface 31 of the skat part 30 along the tip edge of the skat part 30 as a projection part.

  In this way, when the contact surface 31 is configured as a projection portion on the shoot portion 30 and the holding portion 40 is formed inside the projection portion, the welding can be performed without leaving “after welding” as will be described later. At the same time, the strict orthogonality between the screw axis 12 and the base plate 50 can be maintained.

  In this case, it is necessary to provide a certain level of difference between the skat part 30 and the pressing part 40 as shown in FIGS. That is, when projection welding is performed by applying pressure from above, the contact surface 31 at the tip of the skat 30 is first brought into line contact, the portion is heated intensively, and the portion starts melting. With subsequent progress, the contact portion of the contact surface 31 expands, and the holding portion 40 also descends sequentially and contacts the base plate 50, whereby the welding tip (not shown) from above is slightly pushed upward. In short, if the screw has such a shape, the welding to the base plate 50 is first concentrated at the skat part, and then finished when the welding of the holding part is slightly started. become.

  For this reason, the welded joint obtained can retain a considerable strength by welding of the skar part 30, and further, the strength is supplemented by the welding of the holding part 40 surrounded by the skat part, and as a projection part. The formed contact surface 31 does not enter the base plate 50 locally, and almost no “after welding” remains on the back surface of the base plate 50. That is, when evaluating the mechanical strength of the welded portion of the screw 100 implanted in the base plate 50 as a welded joint, the load applied to the welded portion of the screw shaft core 10, for example, bending, This bending load is mostly concentrated. Even in such a case, in this planting screw 100, the outer peripheral skirt portion is almost welded to form a welded joint, so that the welded portion is configured to have a large section modulus, and the bending strength is extremely high. Retained.

  In addition, since the holding portion 40 surrounded by the welded portion is at least partially formed of a flat surface, the flat plate is in contact with the base plate 50, so that the strength as a welded joint, particularly when compressed. Even if the applied pressure becomes extremely high, it can withstand it stably.

  Incidentally, the screw 1 shown in FIG. 8 is removably held in the shaft hole 21 of the upper welding tip 2 via the magnetic body 22 as described above, and has a conical shape on the central axis of the screw 1. The projection part 3 is provided, and it is comprised so that projection welding can be achieved through this projection part 3. FIG. Comparing the strength of each welded joint using the conventional screw 1 and the present invention screw, the strength of the tension, compression, bending, etc. of the screw according to the present invention is 1.5% of the joint strength of the conventional example. It was about 2 to 2 times, and there was no problem in planting with a base plate or the like, and it was possible to weld smoothly.

  More specifically, in the planting screw 100 according to the present invention, the welding operation is completed when the contact or welding of the holding portion 40 has slightly occurred. Most of the welded parts are limited to the skat part 30. Since the skat part 30 is the outer periphery of the pressing part 40, the bending strength is extremely high. In addition, since the holding portion 40 is flat and the base plate 50 stays in contact with the surface, there is almost no welded portion on the back surface of the base plate 50, and the product can be used as it is with little care. Can be used. Even if it is slightly left, it is left in a very small area, so that it is almost impossible to visually observe it after polishing only a small amount of welding after the maintenance, and there is no need for maintenance.

  Further, since the pressing portion 40 itself is flat and orthogonal to the axis 12, welding can be completed by contacting the surface directly with the surface of the base plate 50. Since it is a contact, it can weld without losing orthogonality at all.

  This is one feature, and the flank surface of the screw 100 that is planted and the flank surface of the other nut are smoothly meshed with each other by a common virtual cylinder represented by an effective diameter, and the fastening work is extremely difficult. It can be done smoothly.

  When the skat part 30 is configured as described above, the skat part 30 can be configured as a continuous ring shape as shown in FIG. 4 and FIG. As shown in FIG. 3, the notched grooves 32 and 33 can be configured with a predetermined interval. The purpose of forming the notched grooves 32 and 33 is to enhance the formation effect of the projection and thereby weld the respective skirt parts 30. By forming the notched grooves 32 and 33, each welding point is formed. In this case, a local welding current shunt occurs at, and the joint strength decreases.

  That is, the notch groove 32 shown in FIG. 2 is formed by cutting the skat part 30 so as to form a cross shape orthogonal to each other, and the contact surfaces 31 of the four skat parts 30 notched are respectively formed. A projection part is formed. Further, the notch groove 33 shown in FIG. 7 is formed by notching the skirt portion 30 in three equal parts. In any case, each of the skat parts 30 is formed by being separated by the notch grooves 32 and 33, and each skat part 30 cut out at the time of welding has an independent welding point. Form. For this reason, even if the current is concentrated by the notch groove and the joint strength is increased, the strength may be lowered due to the diversion.

  In this regard, as shown in FIG. 2 and FIG. 7, the skat part 30 is formed with notched grooves 32 and 33, and the skat part 30 is made continuous as shown in FIGS. When the joint strength was determined by comparing with the one shown in FIG. 2, an invalid shunt appears when the skirt part 30 shown in FIGS. 2 and 5 is pressed downward and energized. 2, 5 and 6, even if the skirt portion 30 divided by the notch grooves 32 and 33 is simultaneously energized with a common electrode, the width of the notch groove exceeds 2 mm and exceeds 3 mm. Then there will be no reactive diversion. As a result, it was possible to improve the joint strength by about 20 to 30% even though the skirt part 30 was continuous.

  Next, in the skat part 30 configured as described above, the contact surface 31 provided at the tip of the skat part 30 is inclined downward and projects outward, while the contact of the tip. The cross-sectional shape of the surface 31 itself is formed in an arc shape. (See Figure 3)

  The reason for configuring this arc shape is that, as shown in FIG. 3, the contact surface 31 is configured so that the cross section thereof forms an arc shape, and when pressed downward, the arc portion is the base plate. 50, and the pressure applied from above is dispersed to avoid locally pressurizing the base plate 50 on which the planting screw 100 is to be planted, thereby causing the base plate 50 to be damaged. Minimize.

  That is, the arcuate contact surface 31 contacts the surface of the base plate 50 in a line contact state at the beginning of projection welding. Subsequently, the contact surface 31 of the skat portion 30 sequentially increases the contact area with which the base plate 50 comes into contact with the progress of the melt squeezing, and accordingly the initial projection effect of current concentration is slightly diminished. At the same time, the local pressure applied to the base plate 50 can also be reduced, and the advancing of the contact surface 31 from the surface of the base plate 50 to the inside can be prevented. Since the flat surface of the pressing portion 40 surrounded by the skat portion 30 comes into surface contact and pressurization by the planting screw 100 is stopped, the base plate 50 does not protrude from the back surface. That is, since the contact surface 31 of the skat portion 30 has an arcuate cross-section and is inclined outwardly and downwardly protruding, when the axial pressure is applied downward, the squeezing direction Is squeezed obliquely in the outer direction, and the welded portion is also involved in the inner portion of the skat part 30 to form a welded joint with extremely high mechanical strength.

  Furthermore, pressure heating from the holding portion 40 having a large contact area may be slow, so that no weld remains. In short, a welded joint can be formed that is very effective and does not require maintenance.

  As described above, the planting screw 100 according to the present invention is configured. At this time, the base plate 50 is often used for welding low carbon steel (soft steel) or the like. For example, a stainless steel plate or a softer non-ferrous plate can be used.

  That is, the base plate 50 can be used even if it is soft and has a high thermal conductivity such as an aluminum material or an alloy material thereof, copper or an alloy material thereof. The reason for this is that even if the aluminum material is soft, the contact surface 31 of the skat part 30 has an arc shape and is inclined downward so as to project outward. Therefore, the first line contact after the pressing is immediately shifted to the contact of the inner surface of the skat part 30, and intensive melt welding as projection welding is possible. Further, even a low-carbon steel sheet having a chemical conversion coating on the surface can be extremely effective because the chemical conversion coating and the like are first broken at the contact surface 31 and then gradually proceed with welding.

  It can be widely used when fastening machine parts or the like on a base plate such as a distribution board of an electric appliance, and the range of use is extremely wide, and the manufacturing cost can be greatly reduced.

It is a front view which shows a part of welding screw which concerns on one Example of this invention in a cross section. It is the bottom view seen from the arrow AA direction of FIG. It is explanatory drawing of an example at the time of welding the welding screw shown in FIG. 1 to base plates, such as a steel plate. It is a front view which shows a part of welding screw which concerns on the other Example of this invention in a cross section. It is the bottom view seen from the arrow BB direction of FIG. It is a one part front view of the welding screw concerning other examples of the present invention. It is the bottom view seen from the arrow CC direction of FIG. It is explanatory drawing which shows the welding aspect at the time of welding and welding one welding screw of a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Screw shaft core 11 Male thread 12 Axis 20 Thread part 30 Skar part 31 Contact surface 40 Pressing part 100 Planting screw

Claims (7)

  A planting screw that is welded and planted on a base plate made of a metal material or the like, and is inclined downward from the lower end of the axial center of the screw so that the skar portion protrudes. A welded and planted screw characterized by comprising a contact surface having a rounded arc shape at the tip, and a pressing surface provided on a lower end surface of the shaft core surrounded by the skat portion.   2. The screw to be welded and planted according to claim 1, wherein the skat portion is formed in an annular shape.   The welded and planted screw according to claim 1, wherein at least one notch groove is provided in the skat portion.   2. The screw to be welded and planted according to claim 1, wherein a protrusion is provided at a distance from a tip of the skat portion.   2. The screw to be welded and planted according to claim 1, wherein the base plate is a low carbon steel plate, an aluminum plate, or an aluminum alloy plate.   The welded and planted screw according to claim 1, wherein at least a part of the pressing surface is flattened. 2. The welded and planted screw according to claim 1, wherein the skat portion and the shaft core are integrally formed by forging.

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