Screws for direct screwing into components

Abstract

This invention relates to a screw (10) for direct screwing into a component, particularly a component made of a light metal material, comprising a head and a shank, wherein the shank is provided with a thread (20), the outer radius (RA) of which decreases from a cylindrical support region (TB) toward a tip (12) within a tip region (SB), wherein the thread (20) in the tip region (SB), i.e., in the region where the outer radius (RA) decreases toward the screw tip (12), has at least five circumferentially restricted, radially extending protrusions (14.X, 16.X), wherein in the region of the aforementioned protrusions (14.X, 16.X), the thread (20) extends within a varying outer radius (RA), wherein the corresponding maximum protrusion outer radius of the aforementioned protrusions defines the maximum protrusion plate (R Emax), wherein the maximum protrusion radius (R Emax) of at least two protrusions—the calibration protrusion (16.X)—is defined as follows: The size of the preformed protrusion (Emax) is the same as and also greater than the constant thread outer radius (RA) in the aforementioned support area, i.e. the support area radius (RT). At least three preformed protrusions (14.X) are arranged between the aforementioned calibration protrusion (16.X) and the aforementioned foremost tip (12). The corresponding maximum protrusion radius (R Emax) of the aforementioned preformed protrusion is smaller than the maximum protrusion radius (R Emax) of the aforementioned calibration protrusion (16.X). Furthermore, the maximum protrusion radius (R Emax) of the aforementioned preformed protrusion (14.X) decreases in the direction of the aforementioned tip (12).

Description

Screws for direct screwing into components The invention relates to a screw for screwing directly into a component, in particular a component made of light metal material. EP 1 053 405 B1 discloses a self-tapping screw having a retaining section and a penetration section, by which the thread displaces the nut material to form the thread. The end of the penetration section facing the screw head forms a calibration section, which penetrates only slightly into the nut part and is intended to calibrate the formed thread. In this area, the minimum height between the calibration projections is the same as the thread radius in the cylindrical support area. These calibration projections form two opposing support points, which are equidistant from the screw's center axis. They should only slightly protrude beyond the support diameter. A similar design is known from WO 95 / 14863 A1, which describes a self-tapping screw with a forming element placed on the thread. This screw is intended to reduce the screw-in torque, which in principle increases with increasing screw-in depth during thread forming in the nut material. The screw has a profiled area in the front region, which extends radially beyond the basic thread, which is essentially continuous from the shank to the tip, and is circumferentially limited and relatively short. In the support region, the screw has a calibration projection, which protrudes only slightly beyond the support thread, in particular by less than 0.08 mm. These screws reduce friction during the trenching process while still achieving good fixing properties. Reliably manufacturing these calibrating projections is difficult, particularly using rolling technology, because the material required to form the calibrating projections is not readily available during the rolling process. Consequently, a reliably defined structure of the calibrating projections cannot be achieved. Therefore, the present invention aims to further improve the fixing performance of the screw and simplify its manufacturability while maintaining a relatively low tapping torque. The solution for achieving the above-mentioned purpose of the present invention lies in the features of claim 1 and the features of its preamble. In a known manner, a screw for directly screwing into a component, particularly a component made of light metal, comprises a head with a driver and a shank, wherein the shank is provided with a thread. The outer radius of the thread decreases from a cylindrical support region within a tip region toward the screw tip, so that the outer radius of the thread at the end of the thread, spaced a certain distance from the head, is smaller than the outer radius in the support region. The tip region begins at the point of the screw closest to the support region and extends to the screw tip, at which point the outer radius of the thread is smaller than the radius of the support region. The thread in the tip region produces a nut thread in the nut material of the component, into which the thread in the support region is screwed. The thread has at least five radially extending projections in the tip region. These projections are circumferentially limited, which means that there are local minima between the projections. The thread outer radius locally follows the basic thread path along the helix. This basic thread path is interpolated via local minima in the tip region, located between these projections. In the region where the thread follows the interpolated basic thread path, the thread is referred to as a basic thread, with a basic thread outer radius that increases continuously from the screw tip to the support region. To some extent, it can be said that the basic thread extends in the same manner as a thread without projections. The basic thread outer radius ideally decreases strictly monotonically, in particular linearly, in the tip region and corresponds to the bearing region radius in the bearing region. The basic thread outer radius in the bearing area is based on the outer diameter of the cylindrical envelope in the bearing area. The bearing area radius is constant over the entire area where the thread of the bearing area meshes with the thread pre-grooved in the tip area by the projections. Consequently, according to the present invention, projections are no longer provided in the cylindrical portion of the external thread, as such projections would negatively affect the screw-in performance because they cannot be reliably manufactured in this area. In the tip region, the thread has a thread outer radius that varies from the basic thread outer radius in the region of these projections, correspondingly increasing relative to the basic thread outer radius. Thus, each projection has a maximum thread outer radius along the circumferential helical line that corresponds to the maximum radius of the projection associated with that projection. This ensures that the thread outer radius increases or decreases along the helical line within the region of this projection. According to the present invention, at least two projections are configured as calibration projections, wherein the projection maximum radius of these calibration projections is the same size and is also larger than the support area radius. The projection maximum radius of these calibration projections defines the calibration radius. By providing at least two calibrating projections, initially only the calibrating projection closest to the screw tip provides trenching efficiency. At least one calibrating projection spaced further apart provides no or only significantly reduced trenching efficiency until the calibrating projection closer to the screw tip wears out. In this case, the subsequent calibrating projection, located toward the support area, assumes the trenching function until the calibrating projection closer to the screw tip wears out. This allows the support thread to engage the preformed thread in the component, which is preformed in a largely defined manner, with a longer screw-in stroke and the associated higher trenching efficiency. This reduces the screw-in torque. Furthermore, the screwing-in torque is kept low and within a narrow range by means of a screw according to the invention, since the additional trenching efficiency provided by the calibration projection is only achieved when the calibration projection near the screw tip is worn. The calibration projection is located in an area where the outer radius of the basic thread is reduced, and therefore has a greater difference to the outer radius of the basic thread than to the radius of the support area. Even if the difference between the calibration radius (i.e., the maximum radius of the calibration projection) and the radius of the support area is small, such calibration projections can be manufactured more reliably because the material for forming the calibration projection is thus available. Ideally, the difference between the maximum radius of the calibration projection (i.e., the calibration radius) and the radius of the support area is very small, in particular less than 0.1 mm. Ideally, at least three calibrating projections with the same maximum projection radius are provided. Thus, there is one calibrating projection closest to the screw tip, which still provides a relatively low trenching efficiency, and two further calibrating projections located further away from the screw tip. After the calibrating projection closest to the screw tip wears out, the further spaced calibrating projections can be used to precisely shape the thread in the component. This design is more advantageous the harder the component and nut materials are. Furthermore, at least three preformed protrusions are arranged between the calibration protrusion and the frontmost screw tip. The respective maximum protrusion radius of these preformed protrusions is smaller than the maximum protrusion radius of the calibration protrusion, i.e., the calibration radius. Furthermore, the maximum protrusion radius of each preformed protrusion decreases toward the screw tip. This allows for gradual shaping of the nut material. In this case, the difference in maximum protrusion radius of successive protrusions is ideally selected so that each preformed protrusion provides approximately the same trenching efficiency. As an ideal technical measure, the outer radius of the basic thread increases from the screw tip in the tip region in the same manner as the maximum radius of the preformed protrusion increases. The interpolation curve of the maximum radius of the protrusion is particularly parallel to the interpolation curve of the local minimum. Ideally, there is a local minimum of the thread outer radius between the radius of the support region and the maximum radius of the first projection toward the screw tip. At this local minimum, the thread outer radius is smaller than the support region radius. This means that the projection in front of the support region toward the head also descends to the level of the basic thread, whose outer thread diameter is smaller than the support region radius at this point. Consequently, the first projection, starting from the support region and heading toward the screw tip, is located entirely in the tip region. The ratio of the thread outer radius at the first local minimum to the bearing area radius is ideally less than 0.996. This achieves a sufficiently large difference in the thread outer radius to provide sufficient material to form the projection. As another advantageous technical measure, the aforementioned thread is designed in a certain aspect so that the ratio of the percentage of the calibration radius exceeding the minimum average value to the percentage of the calibration radius exceeding the support area radius is greater than 1.4. The minimum average value is the average of the thread outer radius at the first local minimum and the thread outer radius at the second local minimum. The first local minimum is located between the support area and the first protrusion closest to the support area in the direction of the tip, and the second local minimum is located between the first protrusion and the protrusion closest to the tip. As an alternative to a linear increase in the distribution of the maximum radius of the protrusion, the curve of the increase of the maximum radius of the protrusion towards the tip can also be decreasing, so as to adapt the groove opening performance and the hardness of the component material. The local minimum between these protrusions can correspond to the basic thread outer radius and can continue to decrease in the direction of the screw tip in the groove area extending at least partially beyond the screw tip, with the characteristic being a linear decrease. If the local minimum of the thread outer radius between these projections corresponds to the basic thread outer radius, the production of the screw is simplified and the pull-out force is increased, since the thread in the tip region of the thread profile can also contribute to the pull-out resistance. The thread is radially delimited by the thread tip. The thread generally extends along the thread helix with its thread tip, wherein the position of the point at the thread tip that defines the thread's outer radius varies with respect to an angle in the normal plane (plan view), which is known as the wrap angle. The wrap angle therefore represents the angle formed by the outer radius of the thread, perpendicular to the line perpendicular to the thread helix relative to the screw axis, and the starting line perpendicular to the free end of the screw, in particular at the beginning of the thread. Starting from the starting line perpendicular to the beginning of the thread, the wrap angle increases by 360° with each revolution. For example, an ideal technical approach for a protrusion is to have the thread outer radius equal to the basic thread outer radius at the first wrap angle of the protrusion. In this case, as the wrap angle increases, the thread outer radius at the wrap angle position where the protrusion reaches its maximum value becomes equal to the protrusion's maximum radius. As the wrap angle increases further, the thread outer radius at the wrap angle position at the end of the protrusion becomes equal to the basic thread outer radius. This allows the thread outer radius to increase or decrease relative to the basic thread outer radius. This improves load-bearing capacity in areas where the basic thread outer radius still increases. As an ideal improvement for the cam, the thread outer radius increases monotonically from the basic thread outer radius within the cam wrap angle, and then decreases monotonically back to the basic thread outer radius. This allows for simple cam production and achieves defined groove characteristics. In particular, the increase and decrease occur along a parabola, with the apex of this parabola located at the cam's maximum radius. The outer radius of the basic thread ideally increases linearly between two projections extending in a parabolic manner along the helical line towards the head. As in another advantageous improvement of the invention, the maximum radius of the bulge of a preformed bulge is greater than the outer radius of the next thread at the beginning of the next bulge toward the direction of the screw head. At the beginning of the convexity, the enlargement curve of the outer radius of the thread has a larger slope compared to the course of the basic thread. The layout of such bulges ensures that all preformed bulges are required to provide grooving efficiency only in some areas, thereby reducing tapping torque and reducing wear of the bulges. As in another advantageous means of improvement of the present invention, in the normal plane with respect to the mid-axis of the screw, the bulge circumference angle between the maximum radius of two adjacent bulges is equivalent to the angular distance alpha, where 360° / n-10°<alpha<360° / n+10°, where n is between 2, 3 or 4. Accordingly a relatively short bulge within this bulge ring angle is defined, thereby reducing friction in the region of the bulge maximum radius. This reduces the screw-in torque. Such protrusions may not only extend outward in the direction of the outer radius, but may have an extension along the longitudinal direction of the screw that is greater than the extension of the basic thread along the longitudinal direction of the screw. This is especially true on the sides. This can also gradually increase the width of the nut thread by means of preformed protrusions. The length of the thread within the tip region is especially less than five turns. Therefore, particularly when screwed into blind holes, the vast majority of the screw length can play a supporting role. As another advantageous means of improvement, the thread root diameter increases somewhat within the tip region from the tip until it is equivalent to the thread root diameter in the support region. This improves the manufacturability of screws such as the invention. The relative increase in the thread root diameter can be smaller than the increase in the basic thread radius. The slope of the threaded line is ideally about 5° to 7°, which is equivalent to a 3% to 5% increase in the outer radius of the basic thread per turn. In particular, when the maximum radius of the bulge increases proportionally, the nut thread can be gradually formed into the nut material due to the smaller magnitude of increase. In another advantageous means of improvement, the thread side width is designed in a narrower pattern along the axial direction. This thread has a guide side towards the tip of the screw and a loading side towards the head of the screw. The guide side forms a basic side angle with the loading side. This basic side angle is ideally between 25° and 45°. This improves the screw-in performance, especially in high-strength light metal materials. Further ideally, the cross-section of the protrusion of the thread within the range of the tip of the screw is designed in a certain pattern such that such protrusion is oval at the tip of the thread. As a particularly preferred technical measure, in the region of the projection, the guide flank and the load flank are connected by the thread tip, the contour of which is elliptical in cross section. In this case, the numerical eccentricity Epsilon of this ellipse is between 0.5 and 1. The elliptical shape of the thread tip in the raised area provides a rigid structure at the outermost thread tip, resulting in excellent trenching properties. Furthermore, as the distance from the tip increases from the outermost thread tip toward the thread root, the displaced material encounters decreasing resistance. This reduces the radial force required to deform the nut material, making it easier for the thread to penetrate the nut material. This also reduces wear on the raised area, particularly the alignment raised area, indicating an improved definition of the thread in the nut material. In addition to the elliptical design of the raised thread tips, the thread tips of the basic threads in the support region can also have an elliptical shape. By adapting the shape of the basic threads in the support region, the contact between the basic threads and the grooved nut threads can be improved. As a particularly advantageous improvement, the threads are designed in such a way that the two tangent lines intersect at the ellipse defining the thread tip and form an angle of less than 60°, in particular less than 45°, at the base flank angle. Each of the two tangent lines lies at a contact point on the ellipse at the transition from the elliptical area defining the thread tip to the thread flanks adjacent to the thread tip (i.e., the load flank and the guide flank), wherein each tangent line forms a semi-flank angle with the semi-major axis. The distance between the two contact points and the semi-major axis is greater than 1 / 3 * tan (half flank angle) * thread height. The thread height is the difference between the basic thread outer radius and half the thread root diameter. This design allows for a relatively narrow thread flank. Furthermore, the aforementioned thread tip can be further modified in the raised region in such a manner that a line connecting the corresponding contact point and the vertex of the semi-major axis at the thread tip forms a vertex angle with the semi-major axis of less than 55°. This ensures that the thread tip extends correspondingly slenderly, thereby improving penetration into the nut material. This forms a contact point on the load side and a contact point on the guide side. A perpendicular line perpendicular to the corresponding tangent line, passing through the contact point, intersects the semi-major axis at the intersection point. The thread tip is ideally designed so that the distance between the contact point and the intersection point is less than the distance from the intersection point to the apex of the thread tip. Ideally, the distance between the contact point and the intersection point is less than 90% of the distance from the intersection point to the apex of the thread tip. As a particularly ideal technical measure, the transition from the elliptical thread tip to the thread flank extends tangentially. This makes the transition smoother, allowing material displaced by the thread tip to flow further along the thread flank with low friction, thus reducing tapping torque. Ideally, the ellipse can be connected to a straight section of the guide side and / or the load side, wherein the guide side and / or the load side coincide with the tangent. In a refinement of the present invention, the guide flank and / or the load flank may extend along an elliptical path, the curvature of which is configured in a direction opposite to the elliptical curvature at the thread tip. In this case, the curvature may be located immediately adjacent to the thread tip or the straight section of the guide flank and / or the load flank. The eccentricity of the elliptical path of the guide flank and / or the load flank is ideally smaller than the eccentricity of the ellipse defining the thread tip. This results in a significant widening of the thread towards the thread root, thereby increasing the shear strength and stability of the thread. According to another advantageous development of the invention, the semi-major axis of the ellipse defining the thread tip is inclined in the direction of the guide flank at an angle of not more than 10° relative to the normal plane to the screw center axis. The distance between adjacent thread flanks at 90% of the thread height is preferably greater than 0.7 times the lead. Furthermore, at 90% of the thread height, the flank width can be less than 0.5 times the thread height. This provides a sufficiently small thread tip width. The aforementioned screws are ideally made of steel. FIG1 is a side view of a screw 10 according to the invention for screwing into a component made of light metal material. The screw 10 comprises a front end, referred to as the screw tip 12, and a head 18 at the other end of the screw 10. The screw has a thread 20 with a bearing region TB, wherein the thread 20 has a constant outer thread radius R in the bearing region TB over the entire length of the helix. A , that is, the radius of the support area R T , which corresponds to half the outer diameter in the bearing area TB. Bearing area radius R T The ideal is based on the nominal outer diameter of the screw. Therefore, the bearing area radius R T The support area TB adjoins the tip area SB in the direction of the screw tip 12 , and the thread outer radius R of the thread 20 is AIn this tip region, the thread 20 changes along the helical line and thus decreases to the screw tip 12. In the tip region SB, the thread 20 has circumferentially defined and radially extending projections 14.2, 14.5, 14.8, 16.1, 16.2 (also referred to as 14.X, 16.X). In the region of these projections 14.X, 16.X, the thread 20 has a varying outer thread radius R. A Starting from the screw tip 12, the thread outer radius R A The thread 20 is substantially enlarged and formed, and the thread substantially comprises a basic thread outer radius R AB The basic thread, where the basic thread outer radius R AB In addition, the thread further has protrusions 14.X, 16.X, and the protrusion outer radius R AE Relative to the basic thread outer radius R AB Has increased. Of the local projections 14.X, 16.X in the tip region SB, at least two projections 16.X have a projection maximum radius R E9max 、R E10max The maximum radius of the projection is the same for both projections 16.1 and 16.2 and corresponds to the calibration radius R K , this calibration radius is larger than the support area radius R T These projections are referred to as calibration projections 16.X because, at least along the helix, the calibration projections 16.X that are further away toward the head do not require additional forming work to produce the nut thread. Instead, they are intended to reduce any possible errors in the preformed thread, particularly in the area of ​​the thread tip. In particular, these errors are intended to be reduced due to wear on the calibration projections 16.X that are closer toward the screw tip 12. This reduces the friction of the thread 20 in the bearing area TB that is subsequently screwed into the grooved thread, allowing the screw-in torque to be kept within a low range. For the purpose of thread forming, at least three pre-forming projections 14.X are arranged between the calibration projection 16.X and the frontmost tip 12, which pre-forming projections are formed with respect to their respective maximum projection radius R E1max ,…,R E8max The calibration radius R K In this embodiment, there are 8 preformed protrusions 14.X. Since the maximum radius R of the protrusion E1max to R E8max , i.e. the outer thread radius R at the local maximum of the protrusion 14.X A In the direction of the support area TB, the nut thread is enlarged in the tip area SB, so that the nut thread is formed into the nut material with an increasing depth. In particular, the maximum radius R of the projection can be clearly seen in the diagram shown in FIG. 3 a. E1max In this figure, the corresponding maximum radius of the protrusion R E1max to R E8max The increasing curve of AEMax To express. FIG2 a is a perspective view of the screw tip 12 of the screw 10 . Similar to the embodiment shown in FIG1 , the thread 20 starts from the screw tip 12 and extends along its helical line toward the head. Starting from the starting point S on the thread 20, for example, from the beginning of the thread 20, the thread radius is at the angular position WP where the maximum radius of the second preformed protrusion 14.2 is located. E2max When projected onto a normal plane relative to the screw's center axis MA, the angle at the thread's starting point forms a wrap angle U with the radius at the starting point. With each revolution, wrap angle U increases by 360°, with the position of the thread's outer radius at the corresponding angular position shifting along the screw's center axis toward the head as wrap angle U increases. A top view of the normal plane is shown in Figure 2b. In this example, the maximum value between two adjacent protrusions (for example, the angular position WP E2max With WP E3max The surrounding angular distance alpha Max As an alternative, the angular distance alpha between the maximum values ​​of two adjacent protrusions 14.X and 16.X is 120°. Max For example, it can also be 125°, so that these protrusions will not be offset along the circumference. Furthermore, each protrusion extends over a surrounding angular distance beta. Thus, each protrusion 14.X, 16.X has an angular position WP where the protrusion 14.X, 16.X begins and another angular position WP where the protrusion ends. The third protrusion 14.3 is, for example, at an angular position WP E3 開始 Starting at angular position WP E3 結束 It extends to the end of the third protrusion 14.3. The angular distance alpha between two adjacent protrusions is preferably at least twice the angular distance beta between the protrusions. FIG3 a schematically shows the direction of the thread line GL at the outermost point of the thread tip within the scope of the helix along its development within the wrap angle. As can be seen from the figure, in the tip area SB, the thread outer radius R A The large increase in the outer radius of the basic thread is shown as a basic thread line BL in a short dashed line. This short dashed line shows the course of the "basic thread", ie the course of the thread 20 without the local projections 14.X, 16.X. The solid line shows the course of the actual thread line GL along the basic thread in the region of these projections, which project beyond the basic thread line with respect to their thread outer radius. AEmax has its local maximum at . In this example, R AEmax The enlargement in the area of ​​the tip is parallel to the basic thread line. As can be seen from the figure, these protrusions are designed to be shorter along the circumferential direction and extend only within a shorter angular range not exceeding pi / 3 (60°). E2 結束 With WP E3 開始 The surrounding angular distance between them is approximately pi / 3 (60°). The thread is formed in the tip region SB of the screw 10, ie in the outer thread radius R of the basic thread. A In the continuously increasing (in this example linearly increasing) area, there are three calibration protrusions 16 .X. The three calibration protrusions 16.X have the same protrusion maximum radius R E9Max 、R E10max 、R E11Max , which is equivalent to the calibration radius R K Calibration radius R of calibration protrusion 16.X K and the maximum radius of the bulge R E9Max 、R E10Max 、R E11Max Greater than the supporting thread radius R of the thread in the screw supporting area TB T . Since the calibration projection 16.X is located in the area of ​​increased radius in the tip region SB, the basic thread radius R is larger than that in the support region TB. AB With calibration radius R K The difference between them is large. This allows the calibration projection 16.X to be reliably manufactured with sufficient precision using rolling technology. This allows the tapping torque of this screw to be reduced more reliably when screwing directly into light metal. The circumferential extension of projection is roughly equivalent to or ideally less than 60 ° of surrounding angle distance. Accordingly, only in smaller helical angle, cause friction, thereby can make screwing-in torque remain smaller. FIG3b is a partial enlargement of the diagram shown in FIG3a, focusing on the calibration projection 16.X. In this enlarged view, it is clearly seen that even for the projection closest to the support area TB, the difference in outer radius from the basic thread BL is still much greater than the difference in outer radius in the support area TB, where the difference is only R K -R T And as in the present invention, it is ideally less than 0.1 mm. In this way, the calibration projection 16 .X can be precisely produced using rolling technology according to the technical principle of the present invention in order to achieve the most precise possible structure of the nut thread. Between the calibration projection 16.3 closest to the support area and this support area, the surrounding angular position WP E12 結束 The outer radius of the thread R A The thread outer radius R has a local minimum A (WP E12 結束 ). The outer radius R of the thread at this local minimum A (WP E12 結束 ) and the support area radius R T The ratio is ideally less than 0.996. Furthermore, at the end of the second calibration projection 16.2, ie at the wrap-around angle position WP E11 結束 At this point, another local minimum thread outer radius R is generated A (WP E11 結束 ). The thread is designed in a certain way so that the calibration radius R K Percentage exceeding the minimum mean value versus calibration radius R K Beyond the support area radius R T The percentage ratio is greater than 1.4. The minimum average value is the thread outer radius R at the first local minimum A (WP E12 結束 ) and the thread outer radius R at the second local minimum A (WP E11 結束 ) is the average value of . Therefore, the design of the thread satisfies the following formula: (R K / ((R A (WP E12 結束 ) + R A (WP E11 結束 )) / 2)) – 1) / ((R K / R T )-1) > 1.4 FIG. 4 shows the extension of the projections in the axial direction. FIG4 shows a schematic cross-sectional view AA of the thread 20 at the transition from the bearing region TB to the tip region SB. Starting from its thread base GG, in the region of the calibration projection, the thread 20 has a thread flank facing the head (i.e., load flank 52), which merges with a thread tip 54 having an elliptical profile. The thread tip 54 then merges again with a thread flank (i.e., guide flank 56) toward the screw tip. The outline of the basic thread is indicated by a dashed line; if there were no projection, this basic thread would be present in the section plane. In this case, the actual course in the bearing region TB corresponds to that of the basic thread, which has a load flank 42, a thread tip 44, and a guide flank 46. The calibrating projection 54 protrudes beyond the course of the basic thread to a limited extent in the circumferential direction. The calibrating projection has a projection maximum radius R at its local maximum. AEmax , which in this example corresponds to the calibration radius R K As shown in FIG. 4 , in contrast to the basic thread shown in dotted form, the projection also extends axially beyond the basic thread, wherein the projection is ideally rolled in during the rolling process. It can be further seen from Figure 3b that at the angular position WP E12max In the area where the basic thread height is still increased, the basic thread and the calibration height R K The difference between them is much larger than the difference between the support area TB and the support area radius R T In this way, the protrusion 54 can be manufactured more reliably. This basic thread has an oval thread tip 44 in the bearing area. This thread tip design is illustrated in detail in FIG. The thread tip 54 has an elliptical cross section, and its design and effect will be described in detail with reference to FIG. 6 . The increased resistance to wear of the oval thread tip in combination with the design according to the invention of the calibration region in the tip region allows for particularly reliable and precise profiling of the nut thread. The elliptical profile of the thread tip in the bearing area is particularly suitable for adapting to the cross-sectional shape of the projection, thereby increasing the contact surface in the tightened state, which in turn can increase the extraction force. The shape of the thread tip of this projection is similar to that of the basic thread, which will be explained in detail below with reference to Figure 6. 5 shows a cross section of the thread in the support region TB with a cross-sectionally oval thread tip 44. This thread shape is also essentially present in the basic thread in the tip region SB of the screw, ie in the region between the projections. The cross-sectional profile of the thread tip 44 is an ellipse SE. The thread tip 44 connects with the guide flank 46 toward the screw tip and with the load flank 42 toward the screw head. The vertex SP of the thread tip is located at the vertex of the ellipse SE at the intersection with its semi-major axis HA. The thread tip 44 meets the load flank 42 at a transition point UP1 and meets the guide flank 46 at a transition point UP2. The transition points UP1 and UP2 are the points where the thread profile leaves the elliptical path SE defining the thread tip 44. At the transition points UP1 and UP2 , tangent lines T1 , T2 , respectively, defining the flank angles, may be applied. A tangent line T1 , which forms a load flank angle LF with the semi-major axis HA, abuts the transition point UP1 . The perpendicular line to the tangent line T1 at the transition point UP1 intersects the semi-major axis at the intersection point BP1. The thread tip is ideally designed so that the distance between the intersection point BP1 and the transition point UP1 is less than 90% of the distance between the vertex SP and the intersection point BP1. This ensures sufficient curvature at the thread tip for good material flow during displacement, thereby reducing wear on the thread tip during the trenching process. Furthermore, the thread tip is preferably shaped in such a manner that a line VL1 connecting the transition point UP1 and the vertex SP forms a vertex angle VL1-HA with the semi-major axis HA. The vertex angle VL1-HA is preferably less than 45°, and in this embodiment is approximately 22°. The design of the thread tip 44 is similar to that of the leading edge UP2 and is applicable to UP1. The tangent line T2 is located at the transition point UP2, which intersects the leading edge angle FF of the major semi-axis HA. The perpendicular line to the tangent line T2 at transition point UP2 intersects the semi-major axis at intersection point BP2. Ideally, the thread tip should be designed so that the distance between transition point BP2 and transition point UP2 is less than 90% of the distance between vertex SP and intersection point BP2. This ensures sufficient curvature at the thread tip, allowing for smooth material flow during displacement and reducing wear on the thread tip during the grooving process. Furthermore, the shape of the thread tip is ideally such that a line VL2 connecting the transition point UP2 and the vertex SP forms a vertex angle VL2-HA with the semi-major axis HA. The vertex angle VL2-HA is particularly smaller than 45°, and is approximately 22° in this embodiment. Furthermore, a basic flank angle can be determined, which is obtained from the sum of the load flank angle LF and the guide flank angle FF. In the present embodiment, the basic flank angle is 35°. The thread is ideally designed in a manner such that a line parallel to the tangent line T1 passing through the vertex intersects the thread base line at the perpendicular FP1. As in the present invention, the distance A1 from the perpendicular FP1 to the semi-major axis is at most three times the distance A2 from the transition point UP1 to the semi-major axis. In the embodiment described, the thread is designed in such a way that the distance A1 is approximately twice the distance A2 from the transition point to the semi-major axis HA. This allows for an elongated thread shape. In this embodiment, the side curves of the guide flank 46 and the load flank 42 are at least partially defined by elliptical profiles. The eccentricity of these side ellipses FE1 and FE2 is much smaller than the ellipse SE defining the thread tip. FIG6 shows a thread cross section of another thread shape in the tip region SB of screw 10, wherein the thread tip 54 of the trenching region is shown in the region of the projection. The oval thread tip 54 contributes to improved trenching properties, thereby reducing wear on the thus designed calibration projection. Furthermore, the projection profile is opposite the thread cross section of the basic thread with the thread tip 34, as would be present at the intersection of the thread and the projection if the basic thread were to extend uniformly and continuously. The apex SP is located at the corresponding projection R, which is away from the center axis of the screw. E8max The maximum radius of the bulge is at . The orientation of the tip ellipse is similar to the orientation of the tip ellipse shown in Figure 5. Because the thread has the same profile as the basic thread in the bearing region, the tangent T1 to the ellipse defining the thread tip at the transition point UP1 to the load flank in the convex region in the bearing region TB is parallel to the tangent T1 to the ellipse at the transition to the load flank in the bearing region TB. Consequently, these two tangents form the same load flank angle with the semi-major axis HA. The same approach applies to the tangent T2 as described above with respect to the guide flank. In this respect, the cross-sectional profile of the projection essentially corresponds to the profile of the support region. In this projection, only the regions where the thread flanks follow the tangent lines T1, T2 are longer. This results in a pre-grooving of the thread that is enlarged relative to the support region, with which the thread in the support region can engage via flank regions that are parallel to the pre-grooved nut thread. The calibration projection closest to the support area is also designed in this way, but the difference between the basic thread and the projection is greater than the difference between the thread and the projection in the support area. This ensures that the projection can be produced reliably and still produces a preformed nut thread that is only slightly larger. 10: Screw 12: Tip 14.X: Protrusions 14.2, 14.5, 14.8, 16.1, 16.2: Protrusions 14.3: Third protrusion 16.X: Calibration protrusion 16.3: Calibration protrusion, first calibration protrusion 18: Head 20: Thread 34: Thread tip 46, 56: Guide flanks 44, 54: Thread tip 42, 52: Load flanks alpha: Angular distance A1, A2: Distance AA: Cross-sectional view beta: Angular distance BL: Basic thread line BP1, BP2: Intersection points FE1, FE2: Side ellipse FP1: Perpendicular foot GG: Thread base line GL: Thread line HA: Major semi-axis MA: Screw centerline R A :Thread outer radius R AB : Basic thread outer radius, basic thread radius R AE :Protrusion outer radius R K :Calibration radius R AEmax ,R E8Max ,R E2Max : Maximum radius of bulge R T : Support area radius S: Starting point SB: Tip area SE: Ellipse SP: Vertex T1, T2: Tangent TB: Support area U: Wrap angle UP1, UP2: Contact point VL1-HA, VL2-HA: Vertex angle WP E2max ,WP E3max : Angular position WP where the maximum radius of the protrusion is located E2, WP E3 :Angular position WP E12 ,WP E11 ,WP E12max :Angular position For other advantages, features and application means of the present invention, please refer to the following description in conjunction with the embodiments shown in the drawings. 1 is a side view of the screw in the support area and the tip area; 2a is a perspective view; 2b is a top view of the tip; 3a is a diagram of the thread line and the (interpolated) thread root diameter; 3b is a partial enlarged view of FIG3a; 4 is a partial cross-sectional view of the thread; 5 is a cross-sectional view of the profile curve of the support thread; and 6 is a cross-sectional view of the thread profile curve of the calibration protrusion. 10: Screws 12: Tip 14.2, 14.5, 14.8, 16.2: convex 18: Head 20: Thread MA: screw center axis R A :Thread outer radius R AB : Basic thread outer radius, basic thread radius R AE : convex outer radius R T : Support area radius SB: Tip area TB: Bearing area

Claims

1. A screw (10) for direct screwing to a component made of a light metal material, the screw comprising a head (18) and a shank, wherein the shank is provided with a thread (20) having an outer radius (RA) of the thread decreasing toward a screw tip (12) from a cylindrical support region (TB) having a constant support region radius (RT) within a tip region (SB), wherein the thread (20) in the tip region (SB), i.e., in the region where the outer radius (RA) decreases toward the screw tip (12), has at least five circumferentially restricted, radially extending protrusions (14.X, 16.X), wherein in the region of the protrusions (14.X, 16.X), the outer radius (RA) is such that the protrusion has the largest corresponding protrusion. Large radii (RE1max, RE2max, RE8max), wherein at least two of the protrusions are calibration protrusions (16.X), the maximum radii (RE11max, RE12max) of the calibration protrusions (16.X) are the same size and are equivalent to the calibration radius (RK), which is greater than the radius (RT) of the support area, wherein at least three preformed protrusions (14.X) are arranged between the calibration protrusions (16.X) and the foremost screw tip (12), the corresponding maximum radii (RAEmax) of the preformed protrusions are smaller than the maximum radii (RAEmax) of the calibration protrusions (16.X), and the maximum radii (RAEmax) of the preformed protrusions (14.X) decrease in the direction of the screw tip (12).

2. The screw as described in claim 1, wherein, There exists a first local minimum of the thread outer radius (RA) between the support area radius (RT) and the first calibration protrusion (16.3), which is smaller than the support area radius (RT).

3. The screw as described in claim 2, wherein, The ratio of the outer radius of the thread at the first local minimum (RA(WPE12 end)) to the radius of the support area (RT) is less than 0.

996.

4. The screw as described in claim 2, wherein, The thread is designed such that the percentage by which the calibration radius (RK) exceeds the minimum average value ((RA(WPE12 end) + RA(WPE11 end)) / 2) is greater than the percentage by which the calibration radius (RK) exceeds the support area radius (RT). The minimum average value is composed of the average of the thread outer radius (RA(WPE12 end)) at the first local minimum value between the support area and the first calibration protrusion (16.3) and the thread outer radius (RA(WPE11 end)) at the second local minimum value between the first calibration protrusion (16.3) and the second calibration protrusion (16.2), wherein the second calibration protrusion (16.2) is adjacent to the first calibration protrusion (16.3).

5. The screw as described in claim 1, wherein, Starting from the tip (12), within the area of ​​the tip region, the increase of the corresponding maximum radius (RAEmax) of the preformed protrusion (14.X) is consistent with the increase of the outer radius (RA) of the thread at the local minimum between the preformed protrusions (14.X).

6. The screw as described in claim 1, wherein, The maximum radius (RAEmax) of the preformed protrusion (14.X) increases from the screw tip (12) and the rate of increase decreases.

7. The screw as described in claim 1, wherein, In the protrusions (14.X, 16.X), at the first surrounding angle position (WPEX start) of the surrounding angle (U), the thread outer radius (RA) is at the level of the basic thread outer radius (RAB). In the case of further increase, the thread outer radius (RA) is equivalent to the maximum radius (RAEmax) of the protrusion. In the case of further increase, at the surrounding angle position (WPEX end) of the surrounding angle (U) at the end of the protrusion, the thread outer radius (RA) is equivalent to the basic thread outer radius (RAB).

8. The screw as described in claim 7, wherein, In the protrusions (14.X, 16.X), the outer radius of the thread (RA) increases continuously within the surrounding angle distance (beta) from the basic outer radius of the thread (RAB) and then decreases until it is again equivalent to the basic outer radius of the thread (RAB), following a parabolic trajectory.

9. The screw as described in claim 8, wherein, For the thread (20) between two adjacent preformed protrusions (14.X), the basic thread outer radius (RAB) increases linearly from the screw tip.

10. The screw as described in claim 1, wherein, The radius of the support area (RT) is greater than 90% of the calibration radius (RK).

11. The screw as described in claim 1, wherein, The calibration radius (RK) is at most 0.1 mm larger than the support area radius (RT).

12. The screw as described in claim 1, wherein, The maximum radius (RAEmax) of a preformed protrusion is greater than the outer radius (RA) of the next thread at the beginning of the next protrusion in the direction toward the head (18).

13. The screw as described in claim 1, wherein, The circumference (U) between the maximum values ​​of two adjacent bulges in the normal plane relative to the screw's central axis is equivalent to the circumference distance (alphamax), where 360° / n - 10° < alphamax < 360° / n + 10°, where n is between 2, 3, or 4, and the angular distance (beta) of the bulges is less than 210° / n.

14. The screw as described in claim 1, wherein, The protrusions (14.X, 16.X) also extend axially on both sides across the basic thread.

15. The screw as described in claim 1, wherein, The length of the thread (20) within the tip region (SB) is less than five turns.

16. The screw as described in claim 1, wherein, The slope of the thread is approximately 5° to 7°, which is equivalent to an increase of 3% to 5% in the outer radius of the basic thread per turn.

17. The screw as described in claim 1, wherein, The root diameter (DK) of the thread increases within the tip region (SB) starting from the tip (12).

18. The screw as described in claim 17, wherein, Starting from the tip (12) of the screw and moving towards the head, the relative increase in the root diameter (DK) of the thread is less than the increase in the outer radius (RAB) of the basic thread.

19. The screw as described in any one of claims 1 to 18, wherein, The threaded side is narrower along the axial direction and includes a guide side (46, 56) facing the screw tip (12) and a load side (42, 52) facing the head (18).

20. The screw as described in claim 19, wherein, The guide side (46, 56) and the load side (42, 52) are connected by threaded tips (44, 54), the outline of which follows an elliptical path.

21. The screw as described in claim 20, wherein, The design of the threaded tip (44, 54) and / or the protrusion in the tip region (SB) of the support area (TB) is such that at one contact point in the transition with the load side (42, 52), the tangent (T1) of the ellipse and the major semi-axis (HA) of the ellipse form a load side angle (LF) of less than 30°, and at another contact point in the transition with the guide side (46, 56), the tangent (T2) of the ellipse and the major semi-axis (HA) of the ellipse form a load side angle (LF) of less than 30°; wherein the contact point is located at the transition point (UP1) and the other contact point is located at the transition point (UP2).

22. The screw as described in claim 21, wherein, The distance between the contact point and the long half-shaft (HA) is greater than 1 / 3 * thread height * tan (load side angle), and the distance between the other contact point and the long half-shaft (HA) is greater than 1 / 3 * thread height * tan (guide side angle).

23. The screw as described in claim 22, wherein, The line connecting the contact point and the other contact point to the vertex (SP) of the long semi-axis (HA) at the thread tip (VL1; VL2) forms a vertex angle (VL1-HA, VL2-HA) of less than 55° with the long semi-axis (HA).

24. The screw as described in claim 23, wherein, The thread tip is designed such that an orthogonal line orthogonal to the tangent (T1, T2) at the contact point and the other contact point intersects the major semi-axis at an intersection point (BP1; BP2), wherein the distance between the intersection point (BP1; BP2) and the contact point and the other contact point is less than 90% of the distance between the vertex (SP) and the intersection point (BP1; BP2).

25. The screw as described in claim 21, wherein, The transition from the elliptical thread tip (44) to the load side (42) and the guide side (46) extends tangentially.

26. The screw as described in claim 25, wherein, The guide side (46, 56) and / or the load side (42, 52) extend along an elliptical path that bends in the opposite direction to the ellipse (SE) that forms the thread tip (44, 54).

27. The screw as described in claim 26, wherein, The numerical eccentricity of the elliptical path of the guide side (46, 56) and / or the load side (42, 52) is less than the numerical eccentricity of the ellipse defining the thread tip.

28. The screw as described in claim 24, wherein, The major semi-axis (HA) of the ellipse (SE) at the thread tip is defined to be inclined toward the guide side (46, 56) at an angle not exceeding 10° relative to the normal plane about the screw centerline.

29. The screw as described in claim 1, wherein, The spacing between adjacent thread flanks at 90% of the thread height is greater than 0.7 times the lead, and at that point, the flank width is less than 0.5 times the thread height.

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