Threaded fasteners for direct screwing into components
The threaded fastener design with elliptical crests and calibrated ridges addresses the challenge of high torque in light metal materials by reducing material deformation and friction, enhancing fastening performance and stability.
Patent Information
- Application Number
- JP2025511515
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-08-24
- Filing Date
- 2023-08-23
- Publication Date
- 2025-08-15
AI Technical Summary
Existing threaded fasteners face challenges in achieving high fastening performance while maintaining a small tapping torque, particularly when engaging with light metal materials, due to difficulties in reliably manufacturing calibrated ridges and increased friction during the threading process.
A threaded fastener design with a shank that transitions from a cylindrical load-bearing region to a tip region, featuring threads with elliptical crests and calibrated ridges that reduce tapping torque by minimizing material deformation and friction, and a configuration that ensures precise engagement with preformed threads in light metal components.
The design achieves improved fastening performance and reduced threading torque by ensuring smooth material flow and minimal wear, allowing for efficient threading into light metal materials with enhanced stability and load-bearing capacity.
Smart Images
Figure 2025526985000001_ABST
Abstract
Description
[Technical Field]
[0001] The present invention relates to a threaded fastener for direct screwing onto a part, and more particularly to a threaded fastener for direct screwing onto a part made of a light metal material. [Background technology]
[0002] EP 1053405 discloses a threaded fastener with a tapping thread, the front end of which is provided with a tapping portion, the cross section of which is elliptical and the crest of the thread is sharp.
[0003] WO 95 / 14863 discloses a tapping screw fastener having forming elements disposed on the threads of the fastener to reduce the threading torque, which generally increases with increasing threading depth as the threads are formed in the substrate.
[0004] The fastener has a forward region with a forming area that extends radially from the base threads, the reference threads extending substantially continuously from the shank to the tip, and a circumferentially limited and relatively short reference thread. The fastener has a calibration ridge in the load-bearing region that extends only slightly beyond the load-bearing threads, typically by less than 0.08 mm.
[0005] The use of such threaded fasteners reduces friction during tapping and still achieves good fastening performance. Reliably manufacturing such calibrated ridges, especially by rolling, is difficult because the material required to form the calibrated ridges is not sufficiently available for rolling. Summary of the Invention
[0006] An object of the present invention is to further improve the fastening performance of threaded fasteners while maintaining a small tapping torque.
[0007] The above problem is solved by the characterizing part of claim 1 in combination with the preamble configuration of said claim.
[0008] A threaded fastener for direct engagement with a component, particularly a component made of a light metal material, is known to include a head with a drive portion and a shank with threads, the outer thread radius of which decreases from a cylindrical load-bearing region through a tip region toward the tip of the fastener, such that the outer thread radius at the end opposite the head is smaller than the outer thread radius of the load-bearing region. The tip region extends from the point of the fastener closest to the load-bearing region, where the outer thread radius is smaller than the radius of the load-bearing region, to the tip of the fastener.
[0009] The threads in the tip region form internal threads in the base material of the component, and the threads in the load-bearing region are threadedly engaged with the internal threads.
[0010] The threads have a pilot flank at the tip end of the fastener and a pressure flank at the head end of the fastener.
[0011] The guide flank and the pressure flank are connected via a thread crest, and a profile contour obtained from a cross section of the thread follows the thread crest from the guide flank to the pressure flank along an elliptical path along the ellipse that represents the thread crest. At the transition between the thread crest and each of the thread flanks, there is a transition point on the ellipse that represents the thread crest.
[0012] In the present invention, the tangent to the ellipse at the transition point of the transition section with the pressure side flank forms a pressure side flank angle with the semi-major axis of the ellipse, which pressure side flank angle is particularly at most 30°, and the tangent to the ellipse at the transition point of the transition section with the guide side flank forms a guide side flank angle with the semi-major axis of the ellipse, which guide side flank angle is particularly at most 30°.
[0013] The thread crest is also configured such that a perpendicular line to the tangent at the transition point intersects the semi-major axis at an intersection.
[0014] In the present invention, the thread crest is preferably configured such that the distance between each transition point and each intersection point is smaller than the distance between each intersection point and the apex of the thread crest, and preferably the distance between each transition point and each intersection point is less than 90% of the distance between each intersection point and the apex of the thread crest.
[0015] More specifically, the transition from the elliptical thread crest to the thread flank is particularly tangential. This smooths the transition, allowing the material displaced by the thread crest to continue flowing along the thread flank with low friction, thereby reducing the tapping torque. The thread crest is sufficiently dulled to minimize wear. This reduces the deformation forces during the tapping process, thereby reducing the thread-in torque.
[0016] In a preferred embodiment of the invention, the first eccentricity ε of the ellipse is between 0.5 and 1.
[0017] The elliptical configuration of the thread crests described above provides a robust forming structure at the outermost thread crests, thereby providing excellent tapping characteristics. Furthermore, the material displaced decreases and becomes less resistant as the distance from the crest increases from the outermost thread crest toward the thread root and down to the flank. This reduces the radial force required to deform the substrate, thereby making it easier for the threads to penetrate the substrate.
[0018] In a particularly preferred embodiment of the invention, the threads are configured so that the two tangents at each transition point intersect to form an intersection angle or reference flank angle of at least 25° and at most 60°, in particular less than 60°, in particular less than 45°.
[0019] Thus, each tangent forms a pressure flank angle and a pilot flank angle with a raceway semi-major axis that extends parallel to or at an angle of less than 25° to a plane perpendicular to the threaded component centerline.
[0020] In this way, the guide flank and the pressure flank coincide with a base flank angle, which is preferably between 25° and 45°. This configuration improves the threading behavior, especially in high-strength light metal materials.
[0021] The distance from the raceway semi-major axis to the transition point with the guide flank is greater than (1 / 3) × tan (pilot flank angle) × thread height. The distance from the raceway semi-major axis to the transition point with the pressure flank is greater than (1 / 3) × tan (pressure flank angle) × thread height.
[0022] The thread height is the difference between the base thread outer radius and half the core diameter. This configuration allows for relatively narrow thread flanks.
[0023] It is also preferred to modify the thread crest so that a connecting line from each transition point to the apex of the semi-major axis at the thread crest forms an apex angle with the semi-major axis, the apex angle being less than 55°.
[0024] This configuration ensures a correspondingly slim transition at the crest of the thread, improving the cutting behavior into the substrate.
[0025] Preferably, the thread crest can transition from its elliptical shape to the guide flank and / or the pressure flank, this straight section being in particular congruent with the tangent line.
[0026] In another embodiment of the invention, the guide flank and / or the pressure flank may be shaped along an elliptical path that is curved in the opposite direction to the elliptical curvature of the thread crest, and this curvature may connect directly to the thread crest or directly to a straight section of the guide flank and / or the pressure flank.
[0027] Preferably, the eccentricity of the elliptical path of the guide flank and / or the pressure flank is less than the eccentricity of the elliptical path of the thread crest, which allows the thread to widen significantly in the direction of the thread root, thereby improving the shear strength and stability of the thread.
[0028] In another advantageous embodiment of the invention, the semimajor axis of the ellipse described by the thread crest is inclined at an angle of up to 10° towards the pilot flank relative to a plane perpendicular to the center line of the threaded component.
[0029] In particular, the distance between adjacent thread flanks at 90% of the thread height is greater than 0.7 times the pitch. Furthermore, the flank width at 90% of the thread height can be less than 0.5 times the thread height. This configuration allows for a sufficiently small crest width.
[0030] In a preferred embodiment of the invention, the thread in the tip region has at least five radially extending ridges, which are limited in the circumferential direction, i.e., there are local minima between the ridges.
[0031] More preferably, the cross-sectional configuration of the raised portion of the thread at the tip of the threaded fastener is such that the crest of the raised portion has an elliptical shape, more specifically, in the region of the raised portion, the guide flank and the pressure flank are connected via a crest having an elliptical cross-sectional contour.
[0032] In addition to the crests of the threads in the load-bearing region, the ridges can also be elliptical. By adjusting the shape of the threads in the load-bearing region, the contact of the base threads in the tapped internal thread is improved, and the ridges, which essentially contribute to the tapping of the threads, can also achieve improved tapping properties.
[0033] In some regions along the threaded component line, the outer thread radius follows a base thread profile, which is interpolated across the tip region using local minima of the outer thread radius between ridges. In the region where the thread coincides with the interpolated base thread profile, the thread is referred to as a "base thread," which has a base thread outer radius that increases from the tip of the threaded component toward the load-bearing region radius.
[0034] As before, the base thread extends in the same manner as if no ridges were provided, and the base thread outer radius preferably decreases strictly monotonically, in particular linearly, over the tip region and coincides with the load-bearing region radius in the load-bearing region.
[0035] The outer radius of the base thread in the load-bearing region is determined by the outer diameter of the cylindrical envelope in the load-bearing region. The radius of the load-bearing region is constant throughout the region where the pre-tapped threads are engaged by the raised tip region threads. Therefore, the present invention eliminates raised regions on the cylindrical portion of the external thread, as such raised regions can adversely affect the behavior of the threaded fastener in the region.
[0036] The outer thread radius in the region of the ridge varies relative to the base thread outer radius in the region of the ridge, and is correspondingly greater than the base thread outer radius. Each ridge has a maximum outer thread radius along the threaded component line in the circumferential direction, which corresponds to a ridge maximum value corresponding to a ridge. This ensures that the outer thread radius increases or decreases along the helix line throughout the ridge.
[0037] In the present invention, at least two of the protrusions are calibration protrusions, and the maximum protrusion radii of the calibration protrusions are the same and larger than the radius of the load-bearing region. The maximum protrusion radii of the calibration protrusions are the calibration radii.
[0038] The provision of at least two calibration ridges means that initially only the calibration ridge closest to the tip of the threaded fastener performs a tapping action. This means that at least one calibration ridge further from the tip of the threaded fastener than the closest calibration ridge does not provide a tapping action or the tapping action provided by the at least one calibration ridge farther from the tip of the threaded fastener is significantly reduced until the calibration ridge closer to the tip of the threaded fastener is worn away. The next calibration ridge in the direction of the load-bearing region then takes over the tapping function to the extent of the wear of the calibration ridge closer to the tip of the threaded fastener. In this way, the load-bearing thread can engage the preformed threads of the part as precisely as possible and over a longer threading path, improving the high tapping performance required for this. This reduces the threading torque.
[0039] Furthermore, with the fastener of the present invention, the threading torque is kept small and within narrow limits because the calibration ridges only provide additional tapping action after the calibration ridges closer to the tip of the fastener have worn away.
[0040] By arranging the calibration ridges in the region of the decreasing base thread outer radius, the difference from the base thread outer radius is greater than the difference from the load-bearing zone radius. In this way, the material required to form the calibration ridges is available, and the calibration ridges can be more reliably produced even if the difference between the calibration radius, the maximum ridge radius of the calibration ridges, and the load-bearing zone radius is very small. The maximum ridge radius of the calibration ridges, i.e., the difference between the calibration radius and the load-bearing zone radius, is preferably very small, in particular less than 0.1 mm.
[0041] Preferably, at least three calibration ridges with equal maximum ridge radii are provided. More specifically, one calibration ridge closest to the fastener tip, which still provides a low tapping effort, is provided, and two additional calibration ridges are provided at greater distances from the fastener tip. After the calibration ridge closest to the fastener tip wears away, the more distant calibration ridges can be used to more precisely form threads in the component. All of the above configurations are more advantageous for harder component materials, and therefore harder substrates.
[0042] Furthermore, at least three preformed ridges are provided between the calibration ridge and the forward-most fastener tip, and each preformed ridge has a maximum radius that is smaller than the maximum ridge radius of the calibration ridge, i.e., the maximum radius of the calibration radius. Furthermore, the maximum ridge radius of each preformed ridge decreases toward the fastener tip. This configuration allows for progressive shaping of the substrate. The difference between the maximum ridge radii of each of the plurality of consecutive ridges is preferably set so that each preformed ridge provides approximately the same tapping action.
[0043] In a preferred embodiment of the invention, the base thread outer radius increases from the tip of the threaded component through the tip region in the same manner as the maximum radius of the pre-formed ridge, and in particular, the interpolated progression of the maximum ridge radius is parallel to the interpolated progression of the local minimum.
[0044] Preferably, a local minimum of the thread outer radius exists between the load-bearing zone radius and the first ridge in the direction of the tip of the threaded fastener, and the local minimum of the thread outer radius is smaller than the load-bearing zone radius. In other words, the ridge drops to the height of the base thread before the load-bearing zone in the direction of the head, and the thread outer radius is smaller than the load-bearing zone radius. That is, the first ridge in the direction from the load-bearing zone to the tip of the threaded fastener is located entirely within the tip zone.
[0045] The ratio of the outer thread radius at the first local minimum to the load-bearing region radius is preferably less than 0.996, so that the difference in outer thread radii is large enough to allow sufficient material to be available to form the ridges.
[0046] In one advantageous embodiment of the invention, the thread has a ratio of the extrusion of the calibration radius to the load-bearing region radius to the extrusion of the calibration radius to its minimum average value that is greater than 1.4.
[0047] The minimum average thread radius is the average of a first local minimum outer thread radius and a second local minimum outer thread radius, the first local minimum being located between the load-bearing region and a first ridge closest to the load-bearing region in the direction of the tip, and the second local minimum being located between the first ridge and the ridge closest to the tip.
[0048] The increase in the maximum radius of the ridge in the direction of the head can also be a degressive increase instead of a linear increase in the maximum radius of the ridge, which allows further adjustment to the tapping behavior and hardness of the part material.
[0049] The local minimum between the ridges can coincide with the base thread outer radius and can decrease continuously, in particular linearly, over the tapping region in the direction toward the tip of the threaded fastener, at least partially extending over the tip region.
[0050] When the local minimum of the thread outer radius between the ridges coincides with the base thread outer radius, this allows the threads in the thread forming tip region to also contribute to the pull-out strength, making the threaded fastener easier to manufacture and improving the threaded fastener pull-out force.
[0051] The threads are defined radially by crests, which extend along the helix of the thread as is customary, and the point at which the outer thread radius is measured varies in a vertical plane (profile) at an angle which is called the "circumferential angle".
[0052] Thus, the circumferential angle is the angle formed by the outer radius of the thread, which is perpendicular to the axis of the threaded component on the helix, with a starting perpendicular line defined at the free end of the threaded component, in particular at the start of the thread, and the circumferential angle increases by 360° with each revolution from the starting perpendicular line at the start of the thread.
[0053] In one preferred embodiment of the ridge, the thread outer radius at a first circumferential angle position of the ridge circumferential angle can coincide with the base thread outer radius. As the circumferential angle then increases, the thread outer radius coincides with the maximum ridge radius at the circumferential angle position where the ridge is at its maximum value. As the circumferential angle increases, the thread outer radius coincides with the base thread outer radius at the circumferential angle position of the maximum ridge. This results in the thread outer radius increasing or decreasing relative to the base thread outer radius. In this way, an improvement in load-bearing capacity can already be achieved in the region where the base thread outer radius is still increasing.
[0054] In one preferred embodiment of the ridge, the thread outer radius increases monotonically from the base thread outer radius through the ridge circumferential angle and then decreases monotonically again to the base thread outer radius, which facilitates manufacturing and provides defined tapping characteristics of the ridge. In particular, the increase and decrease follows a parabola having an apex at the maximum ridge radius.
[0055] Preferably, between two of the ridges extending parabolically along the threaded component line, the outside radius of the base thread increases linearly in the direction of the head.
[0056] In another advantageous embodiment of the invention, the maximum ridge radius of one pre-formed ridge is greater than the outer thread radius of the nearest ridge at the start of the nearest ridge in the direction of the head of the fastener. At the start of one of the ridges, the progression of the increase in the outer thread radius can have a slope greater than the slope of the progression of the base thread. This arrangement of ridges can ensure that all pre-formed ridges provide a tapping action only in some areas, thereby reducing tapping torque and ridge wear.
[0057] In another advantageous embodiment of the invention, the ridge circumferential angle in a plane perpendicular to the centerline of the fastener between two adjacent ridge maximum radii is equal to the circumferential angular distance α, where 360° / n-10°<α<360° / n+10°, where n is selected from 2, 3, or 4, and the angular distance of one ridge is less than 210° / n. This configuration results in a relatively short ridge circumferential angle, which reduces wear in the region of the ridge maximum radii, thereby reducing the torque of the fastener.
[0058] The ridges can extend outward in the direction of the outer thread radius, and can also have a dimension in the longitudinal direction of the fastener that is greater than the dimension of the base threads in the longitudinal direction of the fastener.
[0059] This arrangement allows the width of the internal thread to be progressively increased at this stage by the pre-formed ridges.
[0060] In particular, the length of the thread in the tip region is less than five turns, which maximizes the portion of the threaded fastener's length that can contribute to its load-bearing function, especially when the fastener is being threaded into a blind hole.
[0061] In one advantageous embodiment of the invention, the core diameter increases from the tip to the tip region until it matches the core diameter in the load-bearing region, thereby improving the manufacturability of the threaded fastener of the invention.
[0062] The relative increase in core diameter can be less than the increase in base thread radius.
[0063] Preferably, the thread pitch is about 5° to 7°, which corresponds to a 3% to 5% increase in the base thread outer radius per turn. Such a gradual increase allows for the gradual formation of an internal thread in the base material, particularly with a proportional increase in the maximum ridge radius.
[0064] The threaded fasteners are preferably made of steel.
[0065] Other advantages, features and possible applications of the invention will become apparent on reading the following description which refers to embodiments illustrated in the drawings. [Brief explanation of the drawings]
[0066] [Figure 1] FIG. 2 is a perspective view of the front end of the threaded fastener of the present invention. [Figure 2a] FIG. 2 is a side view showing the load-bearing region and tip region of the threaded fastener. [Figure 2b-c] FIG. 2b is a perspective view of the tip, and FIG. 2c is a plan view of the tip. [Figure 3a]FIG. 1 shows thread lines and (interpolated) core diameter. [Figure 3b] FIG. 3b is an enlarged view of a detail of FIG. 3a. [Figure 4] FIG. 1 is a cross-sectional view of a portion of the thread. [Figure 5] FIG. 1 is a cross-sectional view showing the profile of a load-bearing thread. [Figure 6] FIG. 10 is a cross-sectional view showing the thread profile of the calibration ridge. DETAILED DESCRIPTION OF THE INVENTION
[0067] 1 is a perspective view of the leading end of a threaded fastener 100 of the present invention, which has a cylindrical load-bearing region and a conical tip region. A decreases continuously from the load-bearing region TB through the tip region SB of the thread 200, resulting in a conical envelope curve. The thread profile of the thread 200 corresponds to the thread profile described with reference to Figure 5. The profile contour described with reference to Figure 5 results in an elliptical crest that reduces the tapping torque, particularly over the tip region, as it is threaded into a pre-drilled or core hole in a light metal material, particularly aluminum, substrate.
[0068] 2a is a side view of a threaded fastener 10 of the present invention for threading into a fastener made from a light metal material. The fastener 10 has a leading end and a head 18 at the other end of the fastener 10, the leading end being referred to as the "fastener tip 12." The fastener has threads 20 with a load-bearing region TB, in which the threads 20 have a constant outer thread radius R across the threaded fastener line. A The load-bearing region radius R is T The radius of the load-bearing region R is equal to half the outer diameter of the load-bearing region TB. T is preferably specified by the nominal outer diameter of the threaded fastener. Tcorresponds to half of the nominal outer diameter. The load-bearing region TB is followed by a tip region SB in the direction of the threaded component tip 12, and the thread outer radius R of the thread 20 extends over the tip region SB. A varies along the threaded component line, decreasing to the threaded component tip 12. In the tip region SB, the threads 20 have circumferentially defined and radially extending ridges 14.2, 14.5, 14.8, 16.1, and 16.2 (also referred to as "14.X" and "16.X"). In the region of ridges 14.X and 16.X, the threads 20 have a varying outer thread radius R A The outer radius of the thread R A basically increases, and the base thread outer radius R AB The base thread 20 has an outer radius R AB The thread also increases linearly with the outer radius of the ridge R AE is the base thread outer radius R AB It also has larger ridges 14.X and 16.X.
[0069] At least two of the raised portions 16.X of the tip region SB are the raised portions 14.X and 16.X, and both the raised portions 16.1 and 16.2 have the same maximum raised portion radius R E10max ,R E11max and the maximum radius of this protuberance R E10max ,R E11max is the radius of the load-bearing area R T Larger calibration radius R K. Such ridges are called "calibration ridges" 16.X, because at least those calibration ridges 16.X located further along the helix in the head direction ensure less reshaping to form the base threads, and instead reduce any inaccuracies in the preformed threads, especially in the crest region. In particular, any inaccuracies mentioned above due to wear of the calibration ridges 16.X closer to the tip 12 of the threaded component must be reduced. This reduces the friction of the threads 20 in the load-bearing region TB, which subsequently engage the tapped threads, and allows the driving torque to be kept low and within narrow limits.
[0070] Between the calibration ridge 16.X and the forward-most tip 12, there are at least three pre-formed ridges 14.X for tapping, each of which has a maximum ridge radius R E1max ···R E9max is the calibration radius R K In this embodiment, eight preformed ridges 14.X are provided. The maximum ridge radius R is measured through the tip region SB in the direction of the load bearing region TB. E1max R E9max That is, the outer radius R of the thread of the local maximum value of the ridge 14.X A When the maximum ridge radius R is increased to , the depth of the base material increases and the internal thread is formed. E1max The increase in σ can be particularly clearly seen in Figure 3a, where the σ for each maximum ridge radius (here R E1max ~R E9max ) is shown, which includes an interpolated progression interval R AEmax is attached.
[0071] Figure 2b is a perspective view of the fastener tip 12 of fastener 10. As with the embodiment of Figure 1, threads 20 extend along the fastener line from the fastener tip 12 in the head direction.
[0072] Starting from the starting point S on the thread 20, for example the start point of the thread 20, the angular position WP at which the maximum radius of the second preformed ridge 14.2 is located E2max The thread radius angle forms a circumferential angle U with the radius at the starting point when projected onto a plane perpendicular to the threaded component centerline MA. The increment of circumferential angle U per revolution is 360°, and as the circumferential angle U increases, the position of the outer thread radius at each angular position shifts along the threaded component centerline in the direction of the head. A plan view of the perpendicular plane is shown in Figure 2c.
[0073] The circumferential angular distance α between the maximum values of two adjacent ridges, e.g., the angular position WP E2max and WP E3max The circumferential angular distance α between the maximum values of two adjacent ridges 14.X, 16.X is in this example 120°, which results in no circumferential offset between the ridges axially positioned one above the other, in contrast to the embodiment shown in Figure 2a. Alternatively, the circumferential angular distance α between the maximum values of two adjacent ridges 14.X, 16.X could be, for example, 125°, so that the ridges are circumferentially offset.
[0074] Furthermore, each ridge extends over a circumferential angular distance β. Thus, each ridge 14.X, 16.X has an angular position WP at which the ridge 14.X, 16.X begins and another angular position WP at which the ridge ends. For example, the third ridge 14.3 has an angular position WP E3start Starting from the angle position WP E3end Extending to the end of the third ridge 14.3, which terminates at
[0075] Preferably, the circumferential angular distance α between two adjacent ridges is more than twice the circumferential angular distance β of the ridges.
[0076] 3a is a schematic diagram showing an example of the progression of the thread line GL at the outermost point of the thread crest over the helical line when developed, with the circumferential angle as the horizontal axis. AA general increase in the base thread outer radius can be seen across the tip region SB. The basic increase in the base thread outer radius is shown as a thin dashed line as the base thread line BL. This line shows the progression of the "base thread" as the thread 20 extends without the ridges 14.X, 16.X in a particular region.
[0077] The solid line shows the progression of the actual thread line GL along the base thread through the ridge where the outer thread radius exceeds the base thread. The local maximum of the ridge is the maximum ridge radius R AEmax In this example, R AEmax The increase in is parallel to the base thread line.
[0078] In this figure, the ridges are short in the circumferential direction and only span a short angular range of up to about π / 3 (60°). E2end and WP E3start The circumferential angular distance between is approximately π / 3 (60°).
[0079] The threads are formed in the tip region SB of the threaded fastener 10, i.e., the outer thread radius R of the base thread. A In the region where the value of the calibration ridge 16.X increases continuously, in this example, linearly, the calibration ridge 16.X has three calibration ridges 16.X.
[0080] These three calibration ridges 16.X have the same maximum ridge radius RE 10Max ,R E11max ,R E12Max and this maximum ridge radius is the calibration radius R K The calibration radius R K , and thus the maximum ridge radius RE of each of the calibration ridges 16.X 10max ,R E11max ,R E12max is the load-bearing thread radius R of the threads in the load-bearing region TB of the threaded fastener T Greater than.
[0081] The calibration ridge 16.X is located in the radius increasing region of the tip region SB, so that the base thread radius R ABand the calibration radius R K The difference between the load-bearing area TB and the calibrated ridge 16.X is greater than the load-bearing area TB. In other words, the calibrated ridge 16.X can be produced with sufficient accuracy and high reliability by the rolling method. This makes it possible to further reliably reduce the tapping torque when directly threading such a threaded fastener into light metal.
[0082] The circumferential dimension of the ridges is approximately equal to or preferably less than the circumferential angular distance of 60°, so that friction occurs only over a small engagement angle, thereby keeping the engagement torque low.
[0083] FIG. 3b is an enlarged view of the detail of FIG. 3a, focusing on the calibration ridge 16.X. This enlarged view of the detail shows that even for the ridge closest to the load bearing region TB, the difference in the outer thread radius relative to the base thread BL is R K -R T It can be clearly seen that this is significantly larger than the load-bearing area TB, which is only a difference of 0.1 mm, which is preferably less than 0.1 mm in the present invention.
[0084] According to the teachings of the present invention, the above arrangement allows for the precise production of the calibration ridges 16.X, even by a rolling process, thereby achieving the most precise possible shaping of the base thread.
[0085] Between the calibration ridge 16.3 closest to the load-bearing area and the load-bearing area itself, the circumferential angular position WP E12end Outer thread radius R A is the outer radius of the thread R A (WP E12end ) is a local minimum with
[0086] Load bearing area radius R T The outer thread radius R of the first local minimum above A (WP E12end ) is preferably less than 0.996.
[0087] Furthermore, the end point of the second calibration ridge 16.2, i.e., the circumferential angular position WP E11end The outer radius of the thread R A (WP E11end ) there exists another local minimum with
[0088] In particular, the threads are formed at a radius R of the load bearing area. T the calibration radius R K The protrusion rate of the calibration radius R for the minimum average value K The ratio of the protrusion rates is greater than 1.4.
[0089] The minimum average value is the outer thread radius R of the first local minimum. A (WP E12end ) and the outer thread radius R of the second local minimum A (WP E11end ) is the average value.
[0090] Therefore, the thread configuration satisfies the following formula: (R K / (R A (WP E12end )+R A (WP E11end )) / 2))-1) / ((R K / R T )-1)>1.4 The axial dimensions of the ridges are shown in FIG.
[0091] 4 is a schematic cross-sectional view AA of the thread 20 at the transition from the load-bearing region TB to the tip region SB. From the thread base line GG, the thread 20 has a pressure flank 52, which is the head-side thread flank in the region of the calibrated ridge, and merges into a thread crest 54 with an elliptical profile. The thread tip 54 then changes toward the tip of the threaded component and returns to a thread flank or pilot flank 56. The profile of the base thread is shown by a dashed line, which would be the cross-sectional plane in the absence of the ridge. In the load-bearing region TB, the actual progression corresponds to the progression of the base thread, which has the pressure flank 42, the thread crest 44, and the pilot flank 46.
[0092] The calibration ridge 54 is circumferentially defined and extends beyond the progression of the base thread. The calibration ridge has a maximum ridge radius R AEmax which in this example has a calibration radius R K As can be seen in FIG. 4, in deviation from the course of the base thread shown by the dashed line, the ridges also extend beyond the base thread in the axial direction, and are preferably rolled in during the rolling process.
[0093] As can be seen in Figure 3b, the angular position WP11 AEmax In other words, in the region where the base thread height is still increasing, the base thread and the calibrated height R K The difference between the radius of the load-bearing area TB and the radius of the load-bearing area R T This allows the protrusions 54 to be fabricated with higher reliability.
[0094] The base threads have an elliptically shaped crest 44 in the load bearing region, the crest configuration of which is shown in detail in FIG.
[0095] The cross-sectional shape of the thread crest 54 is elliptical, the configuration and effect of which will be explained in more detail below with reference to FIG.
[0096] The improved wear resistance of the elliptical shape of the thread crest as described above, in combination with the configuration of the calibration area in the tip region of the present invention, allows for particularly reliable forming of the internal thread.
[0097] The elliptical profile of the thread crest in the load-bearing region is particularly suitable for adjusting to the cross-sectional shape of the ridge, thereby increasing the contact area in the fastened state, which in turn can increase the pull-out force. The shape of the ridge crest is similar to that of the base thread, and is described in more detail below with reference to Figure 6.
[0098] Figure 5 is a cross-sectional view of the thread profile of the load-bearing region TB as it occurs in the fastener configuration of Figures 1, 2a, or 2b. The thread profile has an elliptical cross-section of the thread crest 44. This thread configuration is essentially provided on the base threads through the tip region SB of the fastener. If ridges are provided in the tip region, the thread regions between the ridges also have this thread configuration.
[0099] The cross-sectional profile of the thread crest 44 is an elliptical shape SE. The thread crest 44 is joined to a pilot flank 46 toward the tip of the fastener and to a pressure flank 42 toward the head of the fastener. The crest apex SP is located at the apex of the ellipse SE at the intersection of the ellipse SE with the semi-major axis HA.
[0100] The thread crest tip 44 transitions into the pressure flank 42 at transition point UP1 and into the pilot flank 46 at transition point UP2. Transition points UP1 and UP2 are points where the thread profile departs from the elliptical path SE of the thread crest 44.
[0101] Tangents T1, T2 can be formed at each transition point UP1 and UP2, respectively, and these tangents T1, T2 determine the flank angles.
[0102] The tangent T1 is located at a transition point UP1 and forms a pressure flank angle LF with the semimajor axis HA.
[0103] A perpendicular line to this tangent line passing through the transition point UP1 intersects the semi-major axis at the intersection point BP1. The thread crest is preferably configured so that the distance between the intersection point BP1 and the transition point UP1 is less than 90% of the distance between the apex SP and the intersection point BP1. This ensures sufficient curvature of the thread crest to achieve good flow of the material as it is displaced, thereby reducing wear on the thread crest during the tapping process.
[0104] More preferably, the shape of the thread crest is such that the connecting line VL1 between the transition point UP1 and the apex SP forms an apex angle VL1-HA with the semi-major axis HA, which is in particular less than 45° and in this embodiment is approximately 22°.
[0105] The thread crest 44 is configured so that the relationship that applies to UP1 also applies to UP2 on the pilot flank.
[0106] The tangent T2 is located at a transition point UP2 and forms a guide flank angle FF with the semimajor axis HA.
[0107] A line perpendicular to this tangent line T2 passing through the transition point UP2 intersects with the semi-major axis at the intersection point BP2. The thread crest is preferably configured so that the distance between the intersection point BP2 and the transition point UP2 is less than 90% of the distance between the apex SP and the intersection point BP2. This ensures sufficient curvature of the thread crest to achieve good flow of the material as it is displaced, thereby reducing wear on the thread crest during the tapping process.
[0108] More preferably, the shape of the thread crest is such that the connecting line VL2 between the transition point UP2 and the apex SP forms an apex angle VL2-HA with the semi-major axis HA, which is in particular less than 45° and in this embodiment is approximately 22°.
[0109] Furthermore, a base flank angle can be determined, which is the sum of the pressure side flank angle LF and the guide side flank angle FF. In this embodiment, this angle is 35°.
[0110] The thread is preferably configured such that a line parallel to the tangent line T1 passing through the apex intersects with the thread base line at the foot point FP1. In the present invention, the distance A1 from the foot point FP1 to the semi-major axis is at most three times the distance A2 from the transition point UP1 to the semi-major axis.
[0111] In the embodiment described herein, the threads are configured such that the distance A1 is approximately twice the distance A2 from the transition point to the semi-major axis HA, which allows for a slim thread profile.
[0112] In this embodiment, at least a portion of the flank profile of both the pilot flank 46 and the pressure flank 42 is defined by an elliptical contour, with the eccentricity of the flank ellipses FE1, FE2 being significantly less than the eccentricity of the thread crest ellipse SE.
[0113] 6 is a thread cross-section of another thread configuration in the tip region SB of a threaded fastener 10, showing the crests 54 of the thread region in the region of the ridges. The elliptical crests 54 improve tapping characteristics, thereby reducing wear on the calibrated ridges formed as described above. Furthermore, the ridge profile is shown to be opposite the thread cross-section of the base thread having the crests 34, since if the base thread had a uniformly increasing transition at this point, the line of intersection through the ridged threads would be located at the cross-section.
[0114] Here, the apex SP is spaced from the centerline of the fastener by the maximum ridge radius for each ridge.
[0115] The progression on the tip ellipse is similar to the progression of the tip ellipse shown in FIG.
[0116] Because the thread profile in the load-bearing region is the same as the base thread profile, the tangent line T1 to the pressure flank is located at the transition point UP1 of the crest ellipse to the pressure flank, in the region where the ridge is parallel to the tangent line T1 to the ellipse at the transition to the pressure flank in the load-bearing region TB. Therefore, both form the same pressure flank angle with the semi-major axis HA. The same rule applies to the tangent line T2 in relation to the pilot flank.
[0117] In this respect, the cross-sectional profile of the ridge essentially corresponds to the profile of the load-bearing area. Only the areas where the thread flanks follow the tangent lines T1 and T2 are longer at the ridge. As a result, the roots of the thread, which are larger than the load-bearing area, are pre-tapped, and this thread can engage in the load-bearing area with its flank area parallel to the pre-tapped internal thread.
[0118] The calibration ridge closest to the load bearing area has a similar configuration, but the difference between the base threads and the ridge is greater than the difference between the threads and the ridge in the load bearing area, which ensures reliable manufacturing of the ridge while producing a slightly larger pre-formed internal thread.
Claims
1. A threaded fastener (10) for direct screwing onto a part made, in particular, of light metal material, a head and a shank provided with threads (20); The outer thread radius (R Ａ ) is the radius of the constant load-bearing area (R Ｔ ) through a tip region (SB) toward the tip (12) of the threaded component, The threads (20) have a pilot flank (46, 56) on the fastener tip (12) side and a pressure flank (42, 52) on the fastener head (18) side, the guide flank (46, 56) and the pressure flank (42, 52) are connected via a thread crest (44, 54); a profile contour of the thread crest (44, 54) from the pilot flank (46, 56) to the pressure flank (42, 52) follows an elliptical path around the thread crest; The vertex (SP) of the semi-major axis of the ellipse (SE) is at the crest of the thread, the ellipse (SE) has a transition point (UP1, UP2) with the pressure side flank (42, 52) and a transition point (UP1, UP2) with the guide side flank (46, 56), a tangent (T1) at a transition point (UP1, UP2) between the ellipse and the pressure flank (42, 52) forms a pressure flank angle (LF) with the semi-major axis (HA) of the ellipse (SE); a tangent (T2) of the ellipse (SE) at a transition point (UP2) with the leading flank (46, 56) forms a leading flank angle (FF) with the semi-major axis (HA) of the ellipse; the thread crest is configured such that an orthogonal line to each of the tangent lines (T1, T2) at the transition points (UP1, UP2) intersects with the orbital semi-major axis (HA) at an intersection point (BP1; BP2), The distance between each of the intersection points (BP1; BP2) and the transition points (UP1, UP2) is less than 90% of the distance between the vertex (SP) and the intersection point (BP1; BP2). A threaded fastener (10) characterized in that
2. the distance from the raceway semi-major axis (HA) to the transition point (UP1) with the pressure flank (42, 52) is greater than (1 / 3) × thread height × tan (pressure flank angle), and the distance from the raceway semi-major axis (HA) to the transition point (UP2) with the guide flank (46, 56) is greater than (1 / 3) × thread height × tan (guide flank angle); The threaded fastener according to claim 1.
3. each connecting line (VL1; VL2) from the transition point (UP1; UP2) at the crest of the thread to the apex (SP) of the semi-major axis (HA) forms with the semi-major axis (HA) a vertex angle (VL1-HA, VL2-HA) of less than 55°, in particular a vertex angle (VL1-HA, VL2-HA) of less than 45°; The threaded fastener according to claim 1 or 2.
4. The pressure flank angle (LF) and the guide flank angle (FF) are each up to 30°.
4. The threaded fastener according to claim 1.
5. the transition from the elliptical thread crest (34, 44) to the thread flank (32, 36; 42, 46) is tangential; 5. The threaded fastener according to claim 1.
6. the guide flank (46, 56) and / or the pressure flank (42, 52) are shaped along an elliptical path that is curved in the opposite direction to the ellipse (SE) described by the thread crest (44, 54), The threaded fastener according to claim 5.
7. the guide flank (46, 56) and / or the pressure flank (42, 52) extend from each transition point (UP1, UP2) along an elliptical path that is curved in a direction opposite to the ellipse (SE) described by the thread crest (44, 54); 7. A threaded fastener according to any one of claims 1 to 6.
8. the eccentricity of the elliptical path of the guide flank (46, 56) and / or the pressure flank (42, 52) is less than the eccentricity of the elliptical path of the thread crest; The threaded fastener according to claim 6 or 7.
9. The semimajor axis (HA) of the ellipse (SE) described by the thread crest is inclined at an angle of up to 10° toward the pilot flank (46, 56) relative to a plane perpendicular to the center line of the threaded component.
9. A threaded fastener according to any one of claims 1 to 8.
10. The distance between adjacent thread flanks at 90% of the thread height is greater than 0.7 times the pitch, and the flank width is less than 0.5 times the thread height.
10. A threaded fastener according to any one of claims 1 to 9.
11. The thread (20) has at least five circumferentially defined ridges (14.X, 16.X) in the tip region (SB), The maximum radius (R Ｅ１ｍａｘ ;R Ｅ２ｍａｘ ...R Ｅ９ｍａｘ In the region of the protuberances (14.X, 16.X), the outer thread radius (R Ａ The protuberances (14.X, 16.X) extend in the radial direction while varying the maximum protuberance radius (R), and at least two of the protuberances are calibration protuberances (16.X), and the maximum protuberance radius (R Ｅ１０ｍａｘ , R Ｅ１１ｍａｘ , R Ｅ１２ｍａｘ ) are of equal magnitude, and the load-bearing area radius (R Ｔ ) larger than the calibration radius (R Ｋ ) and at least three pre-formed ridges (14.X) are provided between said calibration ridge (16.X) and said forward-most threaded fastener tip (12); The maximum radius (R ＡＥｍａｘ ) is the maximum radius (R ＡＥｍａｘ ) and the maximum ridge radius (R ＡＥｍａｘ ) decreases in the direction of the tip (12) of the threaded fastener; Threaded fastener (10) according to any one of claims 1 to 10.
12. The load-bearing region radius (R Ｔ ) and the first of the ridges in the direction of the threaded fastener tip (12). Ａ ) and there is a local minimum of the outer thread radius (R Ａ The local minimum of the load-bearing region radius (R Ｔ ) smaller than The threaded fastener according to claim 11.
13. The load-bearing region radius (R Ｔ ) of the first local minimum relative to the outer thread radius (R Ａ (WP Ｅ１２ｅｎｄｅ )) is less than 0.996; The threaded fastener according to claim 12.
14. The threads are spaced apart by the load-bearing radius (R Ｔ ) to the calibration radius (R Ｋ ) for the proportion of overflow, the minimum average value ((R Ａ (WP Ｅ１２ｅｎｄ ) + R Ａ (WP Ｅ１１ｅｎｄ )) / 2) Ｋ ) the ratio of the protrusion rate is more than 1.4, wherein said minimum average value is the outer thread radius (R ) of a first local minimum between said load bearing area and the first of said calibration ridges (16.3). Ａ (WP Ｅ１２ｅｎｄ ) and the outer thread radius (R ) of the second local minimum between the first calibration ridge (16.3) and the second calibration ridge (16.2). Ａ (WP Ｅ１１ｅｎｄ ) and the average value of The threaded fastener according to claim 12 or 13.
15. From the tip (12) through the tip region, the maximum radius (R ＡＥｍａｘ ) increases the thread outer radius (R Ａ ) progresses in the same way as the increase in Threaded fastener according to any one of claims 1 to 14.
16. The maximum radius of the raised portion (R ＡＥｍａｘ ) is a decreasing increase from the tip of the threaded fastener; Threaded fastener according to any one of claims 11 to 15.
17. The first circumferential angle position (WP) of the circumferential angle (U) ＥＸｓｔａｒｔ ) of the outer thread radius (R Ａ ) is the base thread outer radius (R ＡＢ ) and as it continues to increase, it reaches the maximum radius (R ＡＥｍａｘ ) and, as it increases, the corresponding circumferential angle position (WP) of the circumferential angle (U) at the end of the ridge ＥＸｅｎｄ ) at the base thread outer radius (R ＡＢ ) again matches, Threaded fastener according to any one of claims 11 to 16.
18. In one of the raised portions (14.X, 16.X), the thread outer radius (R Ａ ) is the base thread outer radius (R ＡＢ ) over a circumferential angular distance (β), and then the base thread outer radius (R ＡＢ ) and then decreases until it matches again, and in particular, it follows a parabolic shape.
18. The threaded fastener of claim 17.
19. Between two adjacent pre-formed ridges (14.X), the base thread outer radius (R ＡＢ ) increases linearly, Threaded fastener according to any one of claims 11 to 18.
20. The load-bearing region radius (R Ｔ ) is the calibration radius (R Ｋ ) is more than 90% of 20. A threaded fastener according to any one of claims 11 to 19.
21. The calibration radius (R Ｋ ) is the maximum radius of the load-bearing area (R Ｔ ) is 0.1 mm larger than Threaded fastener according to any one of claims 11 to 20.
22. The maximum ridge radius (R ＡＥｍａｘ ) is the thread outer radius (R Ａ ) is greater than Threaded fastener according to any one of claims 11 to 21.
23. the circumferential angle (U) in a plane perpendicular to the centerline of the threaded component between two adjacent ridge maxima coincides with the circumferential angular distance α, where 360° / n-10°<α<360° / n+10°, n is selected from 2, 3, or 4, and the angular distance (β) of one ridge is less than 210° / n; Threaded fastener according to any one of claims 11 to 22.
24. the protuberances (14.X, 16.X) extend axially beyond the base thread, in particular extending beyond the base thread on both sides; Threaded fastener according to any one of claims 11 to 23.
25. the length of the thread (20) over the tip region (SB) is less than 5 turns; Threaded fastener according to any one of claims 11 to 24.
26. the pitch of the threads is about 5° to 7°, which corresponds to a 3% to 5% increase in the base thread outer radius per turn; Threaded fastener according to any one of claims 11 to 25.
27. The core diameter (D Ｋ ) is increasing, Threaded fastener according to any one of claims 11 to 26.
28. The core diameter (D Ｋ ) relative increase in the base thread radius (R ＡＢ ) is smaller than the increase in 28. The threaded fastener of claim 27.