Method of connecting at least two elements by connection element and connection device
The method of controlled rotational speed and axial force variation during the connection process addresses defects in low ductility elements by heating and inserting a connecting element, achieving a strong and fracture-free connection.
Patent Information
- Application Number
- JP2025061816
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2024-04-12
- Filing Date
- 2025-04-03
- Publication Date
- 2025-11-18
Smart Images
Figure 2025170212000001_ABST
Abstract
Description
[Technical Field]
[0001] The present invention relates to a method for connecting at least two elements by means of a connecting element.Furthermore, the present invention relates to a connecting device for connecting at least two elements by means of a connecting element. [Background technology]
[0002] Connecting elements are known and used for connecting elements or parts to one another. With thread-forming connecting elements, material is not removed from the workpiece to form the thread, but rather the material of the workpiece is shaped or deformed so that a thread is formed in the workpiece. When the thread-forming connecting element is inserted, no material, or only a very small amount of material, is removed from the workpiece. Some thread-forming connecting elements are also capable of forming a hole in the workpiece into which the connecting element is placed. This hole can be formed at the same time as the thread. Thread-forming connecting elements that are also capable of forming a hole are called thread-forming / hole-forming connecting elements.
[0003] To insert the thread-forming / hole-forming connecting element into the workpiece, the connecting element is rotated in contact with the workpiece, heating the workpiece. The connecting element is then inserted into the workpiece. The thread-forming connecting element is inserted into the workpiece while rotating. This forms a thread in the workpiece.
[0004] The connecting element and the connected element can be adapted to one another in such a way that the surface of one connected element is not penetrated by the connecting element, and in the region of the connecting element, a protrusion is formed on the non-penetrated surface.
[0005] WO 2023 / 214164 discloses a thread-forming / hole-forming connecting element. The connecting element includes a head and a shank defining a longitudinal axis. The shank has a shank portion and a tip portion. The shank portion extends from the head. The tip portion extends from the shank portion and is disposed opposite the head. At least a portion of the shank portion is threaded. The tip portion is at least partially tapered to define a tip angle. The tip angle is 50 degrees or greater.
[0006] In particular, when connecting elements or components with low ductility, the protrusions may break or burst on the non-penetrating surface of the element opposite the element into which the connecting element is first inserted. Summary of the Invention
[0007] The object of the present invention is to improve the connection of two elements, especially when at least one of the elements has low ductility, and in particular to reduce or avoid defects, cracks, or fractures in the connection of the two elements.
[0008] A method for connecting at least two elements with a connecting element is disclosed, the method including the steps of providing a first element, a second element, and the connecting element, placing the connecting element on a surface of the first element, rotating the connecting element at a first rotational speed for a first time period and applying a first axial force to the connecting element in the direction of the surface of the first element, and rotating the connecting element at a second rotational speed for a second time period and applying a second axial force to the connecting element in the direction of the surface of the first element.
[0009] The first rotational speed during the first time period may be lower than the second rotational speed during the second time period. Alternatively or additionally, the first axial force during the first time period may be greater than the second axial force during the second time period.
[0010] Also disclosed is a connecting device for connecting at least two elements via a connecting element, the connecting device comprising a rotatable connecting punch configured to rotate the connecting element and apply an axial force to the connecting element, and a control device configured to control the connecting punch to rotate the connecting element at a first rotational speed during a first period and apply a first axial force to the connecting element in a direction toward a surface of the first element, and to control the connecting punch to rotate the connecting element at a second rotational speed during a second period and apply a second axial force to the connecting element in a direction toward a surface of the first element.
[0011] The first rotational speed during the first time period may be lower than the second rotational speed during the second time period. Alternatively or additionally, the first axial force during the first time period may be greater than the second axial force during the second time period.
[0012] In general, the controller may be configured to control the connection device such that the connection device performs any of the method steps disclosed herein. In particular, the controller may be configured to control the connection punch such that the connection punch performs any of the method steps disclosed herein.
[0013] A first element and a second element are provided for connecting them. In this case, these elements may be arranged one on top of the other. The connecting element is placed on the surface of the first element. When the connecting element is rotated and a force is applied to the connecting element toward the surface, heat is generated due to friction between the connecting element and the first element. This heat reduces the hardness and / or strength of the first element and, optionally, the hardness and / or strength of the second element, allowing the connecting element to be at least partially inserted into the first element. When the connecting element is inserted a certain distance into the first element and, optionally, into the second element, the threads of the connecting element first come into contact with the first element, forming threads corresponding to the threads of the connecting element. The connecting element is then inserted into the first and second elements to a final insertion depth, connecting these elements. In this case, the process may be designed so that the connecting element does not protrude from the second element. That is, the tip of the connecting element remains within the stack of the first and second elements. In other words, the surface opposite the first element is not penetrated by the connecting element, and the molded material forms a protrusion on this surface.
[0014] In particular, if one of the elements, e.g. the second element, has low ductility, the protrusion may break or burst, which may result in a weakened or defective connection.
[0015] By increasing the rotation speed of the connecting element and / or decreasing the force with which the connecting element is pushed toward the element, the first element, and optionally the second element, are heated to a higher temperature. At the same time, the speed at which the connecting element is inserted into the stack of first and second elements is decreased. Heating to a higher temperature increases the ductility of the elements. According to the method of the present invention, the connecting element can be inserted further only when, within a certain range, the element has sufficient ductility or its hardness and / or strength has been sufficiently reduced by heating. Therefore, fracture and / or rupture of the protrusions formed on the surface of the second element can be reduced or prevented.
[0016] When the first and second elements are provided, they may be arranged one on top of the other. In particular, the first and second elements (arranged one on top of the other) may be fixed relative to each other. Fixing may be achieved by a holding device.
[0017] When provided, the connecting element may be held by a connecting device. The connecting device may include a connecting punch. The connecting punch can hold and rotate the connecting element. Similarly, the connecting punch can apply an axial force (relative to the axis of rotation of the connecting element) to the connecting element.
[0018] The connecting element can be placed on the surface of the first element by means of a connecting device, in particular a connecting punch.
[0019] Preferably, before or when the connecting element is placed on the surface of the first element, the first element and / or the second element do not have holes in the region of the first or second element that is axially aligned with the axis of rotation of the connecting element, i.e., the connecting element can be introduced into the first and / or second element without drilling pre-holes in the first and / or second element.
[0020] The first and second periods may be consecutive, i.e., there may be no intervening periods between the first and second periods, and the first period may precede the second period in time.
[0021] The first period of time may be 0.5 seconds or more. In particular, the first period of time may have a length of 0.5 seconds to 6 seconds, preferably 1 second to 4 seconds, preferably 1.5 seconds to 3 seconds.
[0022] The second period of time may be 0.5 seconds or more. In particular, the second period of time may have a length of 0.5 seconds to 6 seconds, preferably 1 second to 4 seconds, preferably 1.5 seconds to 3 seconds.
[0023] The first period and the second period (the sum of the lengths of the first period and the second period) may have a combined length of 0.5 to 12 seconds, preferably 0.5 to 10 seconds, preferably 1 to 8 seconds, preferably 2 to 7 seconds, preferably 3 to 6 seconds. The first period and the second period may have substantially the same length.
[0024] The first rotation speed in the first time period may be at least 10% lower, preferably at least 15%, preferably at least 20%, preferably at least 25%, preferably at least 30%, preferably at least 35%, preferably at least 40%, preferably at least 45%, preferably at least 50% lower than the second rotation speed in the second time period.
[0025] The first rotation speed in the first time period may be at most 70% lower, preferably at most 60%, preferably at most 50%, preferably at most 45%, preferably at most 40%, preferably at most 35%, preferably at most 30%, preferably at most 25%, preferably at most 20% lower than the second rotation speed in the second time period.
[0026] For example, if the first rotation speed is 10% lower than the second rotation speed and the second rotation speed is 1000 rpm (revolutions per minute), the first rotation speed is 900 rpm.
[0027] The first axial force in the first time period may be at least 10% greater, preferably at least 15%, preferably at least 20%, preferably at least 25%, preferably at least 30%, preferably at least 35%, preferably at least 40%, preferably at least 45%, preferably at least 50%, preferably at least 55%, preferably at least 60%, preferably at least 70%, preferably at least 80%, preferably at least 90%, preferably at least 100% greater than the second axial force in the second time period.
[0028] The first axial force in the first time period may be no more than 120%, preferably no more than 110%, preferably no more than 100%, preferably no more than 90%, preferably no more than 80%, preferably no more than 75%, preferably no more than 70%, preferably no more than 65%, preferably no more than 60%, preferably no more than 55%, preferably no more than 50%, preferably no more than 45%, preferably no more than 40%, preferably no more than 35%, preferably no more than 30% greater than the second axial force in the second time period.
[0029] For example, if the first axial force is 10% greater than the second axial force and the second axial force is 1000 N (Newtons), then the first axial force is 1100 N.
[0030] The axial force may act along the axis of rotation of the connecting element.
[0031] The lengths of the first and second periods can be determined based on the insertion depth of the connecting element into the first element or the insertion depth of the connecting element into the first and second elements. That is, the lengths of the first and second periods can be functions that depend on the insertion depth of the connecting element. The insertion depth can be based on the insertion depth of the connecting element into the first element or the insertion depth of the connecting element into the first and second elements. The latter case occurs when the connecting element completely penetrates the first element and also penetrates the second element during the first or second period.
[0032] The length of the first period continues until the connecting element reaches a first (absolute) fixed insertion depth within the first element or within the first and second elements. For example, the first (absolute) fixed insertion depth is in the range of 1 mm to 4 mm, preferably 2 mm to 3 mm. The length of the second period continues until the connecting element reaches a second (absolute) fixed insertion depth within the first element or within the first and second elements. For example, the second (absolute) fixed insertion depth is in the range of 3 mm to 7 mm, preferably 4.5 mm to 5.5 mm.
[0033] The connecting element may comprise a head and a shank. The shank may have a threaded portion. The threaded portion has a thread, in particular an external thread. The shank may have a tip portion opposite the head. The tip portion does not have a thread.
[0034] The connecting element may be a screw without a thread at its tip.
[0035] The tip is placed on a surface of the first element. By rotating the connecting element and applying an axial force to the connecting element, friction is generated between the connecting element and the first element. Depending on the axial force and the material properties of the first element, the connecting element is inserted into the first element. When the connecting element is fully inserted into the first element or the first and second elements, and the threads of the threaded portion contact the first element, further insertion of the connecting element forms threads on the first element and / or the second element that correspond to the threads of the threaded portion.
[0036] The threaded portion may contact the first element and / or the second element during a first period and / or a second period. If threads corresponding to those of the threaded portion are formed in the first and / or second element, the corresponding threads may be partially removed by rotation of the connecting element. When the first and second elements are connected to each other by the connecting element, threads corresponding to those of the threaded portion may be at least partially formed in the second element.
[0037] Preferably, during the first period, the threaded portion does not contact the first element and / or the second element at least temporarily. At the start of the first period, only the tip of the connecting element contacts the first element. As the connecting element is further inserted into the first element during the first period, the threaded portion of the connecting element contacts the first element. During the first period, the threaded portion temporarily does not contact the first element, and then temporarily contacts the first element.
[0038] When the first and second elements are connected by the connecting element, the connecting element is inserted into the first and second elements to a final insertion depth. Preferably, the head of the connecting element is located outside the first and second elements. A portion of the head may be in contact with the surface of the first element.
[0039] When the first and second elements are connected to each other, the tip may be surrounded by the first and / or second elements. In particular, the tip is surrounded by the first and / or second elements when the connecting element is inserted into the first and second elements to the final insertion depth. The tip may not protrude from the first and / or second elements when the first and second elements are connected to each other or when the connecting element is inserted into the first and second elements to the final insertion depth. The tip may be configured to be at least partially surrounded by a protrusion formed on the second element. When the first and second elements are connected to each other or when the connecting element is inserted into the first and second elements to the final insertion depth, the surface of the second element may not be penetrated by the connecting element.
[0040] The energy input to the first and / or second element during the second time period may be greater than the energy input during the first time period. In particular, the energy input per unit time, i.e., power input, to the first and / or second element during the second time period may be greater than that during the first time period. Similarly, the absolute energy input (in joules) to the first and / or second element during the second time period may be greater than that during the first time period. Similarly, the energy input to the first and / or second element relative to insertion depth during the second time period may be greater than that during the first time period. That is, greater energy or power is input to the first and / or second element during the second time period relative to insertion depth (e.g., per 1 mm of insertion depth).
[0041] The energy or power input is largely or almost completely (at least 90% or more) converted into heat. The energy or power input is defined by the energy or power consumption of the connecting device or connecting punch. Thus, the first element, and possibly the second element, heats up more in the second time period than in the first time period.
[0042] The first element and / or the second element may be a part. In particular, the first element and / or the second element may comprise or consist of a metal. Preferably, the first element is a metal element or part, particularly a steel element or part. Similarly, the first element may be an aluminum part. The aluminum part may be composed of or include an AA5000, AA6000, or AA7000 alloy. The second element may be a metal element or part, particularly an aluminum element or part. Particularly preferably, the second element is a cast aluminum element. The second element may be a non-heat-treated cast aluminum element. Similarly, the second element may be a cast aluminum element with a high proportion of secondary aluminum, i.e., a high proportion of recycled aluminum. The second element may be composed of or include an AA7000 alloy, particularly in the T6 state. The method of the present invention allows for successful joining of AA7000 alloy in the T6 state to a part.
[0043] The first rotational speed may be at least partially constant during the first time period. Alternatively or additionally, the second rotational speed may be at least partially constant during the second time period. The first axial force may be at least partially constant during the first time period. Alternatively or additionally, the second axial force may at least partially increase during the second time period.
[0044] "Partially" refers to 30% or more of the entire period, preferably 40% or more, preferably 50% or more, preferably 60% or more, preferably 70% or more, preferably 80% or more, preferably 90% or more, preferably 95% or more.
[0045] During a first period of time, the rotation speed may be increased from 0 to a first fixed value. Thereafter, the rotation speed may be maintained substantially constant during the first period of time. The portion of the first period during which the rotation speed increases may be shorter than the portion of the first period during which the rotation speed is maintained substantially constant. During a second period of time, the rotation speed may be increased to a second fixed value. Thereafter, the rotation speed may be maintained substantially constant at the second fixed value during the second period of time. The portion of the second period during which the rotation speed increases may be shorter than the portion of the second period during which the rotation speed is maintained substantially constant.
[0046] Generally, "substantially" means a deviation of ±10% or ±5%.
[0047] In a first period, the axial force may be increased from 0 to a first fixed value. Thereafter, the axial force may be maintained substantially constant during the first period. The portion of the first period during which the axial force increases may be shorter than the portion of the first period during which the axial force is maintained substantially constant. In a second period, the axial force may be decreased to a second fixed value. Thereafter, the axial force may be increased during the second period, particularly starting from the second fixed value. For example, in the second period, the axial force may be increased continuously or stepwise starting from the second fixed value. This may be done up to a third value. The third value may be lower than the first fixed value. The portion of the second period during which the axial force decreases may be shorter than the portion of the second period during which the axial force increases.
[0048] The method may further include rotating the connecting element at a third rotational speed during a third time period and applying a third axial force to the connecting element in the direction of the surface of the first element. The third rotational speed during the third time period may be lower than the first rotational speed during the first time period. Alternatively or additionally, the third rotational speed during the third time period may be lower than the second rotational speed during the second time period. The third axial force during the third time period may be smaller than the first axial force during the first time period. Alternatively or additionally, the third axial force during the third time period may be smaller than the second axial force during the second time period.
[0049] The first, second, and third periods may be consecutive with one another. The third period may be consecutive with the second period. There may be no other periods between the second and third periods. The second period may precede the third period in time.
[0050] During a third period, the threads of the connecting element may contact the first and / or second elements. During the third period, threads corresponding to the threads of the threads are formed in the first and / or second elements. At the end of the third period, the connecting element is at a final position or final insertion depth within the first and second elements.
[0051] Generally, the rotational speed in each period is the average rotational speed in that period. Similarly, the axial force in each period is the average axial force in that period.
[0052] The present invention will now be described in detail with reference to the accompanying drawings. [Brief explanation of the drawings]
[0053] [Figure 1a] FIG. 1 shows a connecting element 10. [Figure 1b] FIG. 1 shows two elements 30, 40 connected by a connecting element 10. [Figure 2a]1A-1C show steps of a method for connecting two elements 30, 40 by means of a connecting element 10. [Figure 2b] 1A-1C show steps of a method for connecting two elements 30, 40 by means of a connecting element 10. [Figure 2c] 1A-1C show steps of a method for connecting two elements 30, 40 by means of a connecting element 10. [Figure 2d] 1A-1C show steps of a method for connecting two elements 30, 40 by means of a connecting element 10. [Figure 3] FIG. 10 is a diagram showing the rotation speed relative to the insertion depth of the connecting element 10. [Figure 4] FIG. 10 is a diagram showing the (axial) force versus the insertion depth of the connecting element 10. [Figure 5] FIG. 10 is a diagram showing the (input) energy versus the insertion depth of the connecting element 10. [Figure 6] FIG. 2 is a diagram showing a connection device 60. [Figure 7] 1A and 1B show a surface 41 of a second element 40 in an exemplary connection process. [Figure 8] 2 shows a surface 41 of a second element 40 in a connection process according to the invention. DETAILED DESCRIPTION OF THE INVENTION
[0054] FIG. 1 is a cross-sectional view of a connecting element 10. The connecting element 10 may include or be constructed from steel. The connecting element 10 may include a head 11. The head 11 may have a lower surface 13. The connecting element 10 may include a shank 15. The shank 15 extends from the lower surface 13 of the head 11. As shown in FIG. 1b, the head 11 may have a drive shape 11a. The periphery of the drive shape 11a may define a discontinuous profile. In use, the drive shape 11a engages with a connecting device 60 or a connecting punch 70 of the connecting device 60, thereby transmitting torque from the connecting device 60 or the connecting punch 70 to the connecting element 10. The drive shape 11a may be male or female.
[0055] The head 11 may be provided with a lower recess 12. The lower recess 12 is adjacent to the shank 15 and in particular extends around the shank 15. The lower recess 12 can receive material from a workpiece (e.g., the first element 30 and / or the second element 40) when the connecting element 10 is in use. The lower recess 12 does not necessarily have to be provided. If the lower recess 12 is not present, the lower surface 13 of the head 11 may be substantially planar.
[0056] The shank 15 may include a base 16. The base 16 may be adjacent to the head 11. The base 16 does not have threads. In particular, the base 16 is surrounded by a lower recess 12.
[0057] The shank 15 may include a threaded portion 17. The threaded portion 17 may be adjacent to the base 16 or the head 11. The threaded portion 17 includes a thread, in particular an external thread.
[0058] Shank 15 may include tip 18. Tip 18 may be adjacent to threaded portion 17. Tip 18 does not have threads.
[0059] The stem 10 has a stem diameter SD. The stem diameter SD does not include the diameter of the base 11. The stem diameter SD may be equal to or greater than 2 mm. The stem diameter SD may be equal to or less than 10 mm. In particular, the stem diameter SD may be in the range of 3 mm to 8 mm, preferably 3.5 mm to 5.5 mm. The stem 15 defines a longitudinal axis A. The longitudinal axis A may be identical to the axis of rotation of the connecting element 10. The connecting element 10 may be formed rotationally symmetrical about the longitudinal axis A.
[0060] The threaded portion 17 has a thread diameter TD, which may be substantially constant throughout the length of the threaded portion 17.
[0061] The tip 18 is formed at one end of the shank 15. This end of the shank 15 is located opposite the head 11. The tip 18 is particularly tapered relative to the shank 15. The tip 18 has a tip angle α. The tip angle α is understood to refer to the internal angle of the tip of the tip 18, particularly as shown in FIG. 1a. The tip angle α may be 50° or greater. The tip angle α may be 160° or less. In particular, the tip angle α may be in the range of 125° to 135°. The tip 18 may be formed in a conical, frustoconical, or tapered shape. The tip 18 has a tip 19. The tip 19 may define an end point of the tip 18. Alternatively, the tip 19 may be flat.
[0062] The tip 18 has a tip length TL. The tip length TL is oriented parallel to the longitudinal axis A. Preferably, the ratio of the tip length TL to the thread diameter TD is equal to or less than 0.6.
[0063] The connecting element 10 may be a thread-forming / hole-forming connecting element, i.e. the connecting element 10 can form a hole in the connecting element 30, 40 or can form a thread, in particular an internal thread, in the connecting element 30, 40.
[0064] FIG. 1b is a partial cross-sectional view of two connected elements 30, 40. The first element 30 is connected to the second element 40 by a connecting element 10. The connecting element 10 does not penetrate the surface 41 of the second element 40. When the connecting element 10 is inserted into the first element 30 and the second element 40, a protrusion 45 may be formed. The protrusion 45 may be formed on the surface 41 of the second element 40 that is not penetrated by the connecting element 10. The tip 18 of the connecting element 10 may be (completely) surrounded by the first and / or second elements 30, 40. The protrusion 45 may be made of material of the second element 40 that was displaced when the connecting element 10 was inserted into the first element 30 and the second element 40. The protrusion 45 surrounds the connecting element 10, in particular the tip 18, and preferably separates it from the surroundings.
[0065] 2a to 2d show the various steps involved in inserting the connecting element 10 into a first element 30 and a second element 40 in order to connect them.
[0066] In Fig. 2a, first, a first element 30 and a second element 40 are provided. For example, the first and second elements 30, 40 are stacked on top of each other and fixed in position as needed. A connecting element 10 is also provided. The connecting element 10 can be held by a connecting device 60. The connecting element 10 is particularly positioned so that the tip 18 contacts the surface of the first element 30. No holes or pilot holes may be formed in the area where the connecting element 10 contacts the first element 30.
[0067] In FIG. 2b, the connecting element 10 is rotated by the connecting device 60, which applies an axial force to the connecting element 10. This rotation and axial force create friction between the connecting element 10 and the first element 30, which in turn heats up the first element 30. This heat may be partially transferred to the second element 40, for example, by conduction. In this case, a portion of the connecting element 10, in particular the tip 18, is inserted into the first element 30. Preferably, however, the connecting element 10 is initially inserted slightly so that the threaded portion 17 is located outside the first element 30. Therefore, the threaded portion 17 may not (yet) come into contact with the first element 30. Similarly, the connecting element 10 may already be inserted into the first element 30 so that the threaded portion 17 comes into contact with the first element 30. This is particularly true if the thickness of the first element 30 is 1 mm or greater.
[0068] The steps of the method described with respect to Figures 2a and 2b may correspond to the first and second time periods.
[0069] In Fig. 2c, the connecting element 10 is further inserted into the first element 30, in particular so that the threaded portion 17 is partially located within the first element 30. Thus, in this method, the threaded portion 17 comes into contact with the first element 30 at the latest. As a result, a thread (internal thread) corresponding to the thread of the threaded portion 17 is formed in the first element 30 and may also be formed in the second element with further insertion. The method steps described with reference to Fig. 2d may correspond to the first and second periods.
[0070] In Figure 2d, the connecting element 10 is in its final position or final insertion depth within the first element 30 and the second element 40. The head 11 or the underside 13 of the head 11 may be in contact with the surface of the first element 30. The connecting element 10 may form threads only on the second element 40 or on both the first element 30 and the second element 40.
[0071] The movement of material from the first and / or second elements 30, 40, and in particular the movement of material from the second element 40, causes a protrusion 45 to form on the surface 41 of the second element 40. The protrusion 45 is formed so as to surround the connecting element 10, in particular the tip 18.
[0072] FIG. 3 shows two profiles. The x-axis in the diagram represents the insertion depth of the connecting element 10 into the first element 30 and, optionally, into the second element 40. The y-axis represents the rotational speed of the connecting element 10. The two profiles overlap. The profiles differ, in particular, in the second period t2 and the third period t3. The profiles differ primarily in the second period t2. In the third period t3, the profiles may differ only at the beginning of the third period t3, with the remaining profiles remaining the same. Similarly, the profiles may differ only in the second period t2. The first profile is called "single-stage" and the second profile is called "two-stage." In the region where the first and second profiles differ, the two-stage profile is indicated by an "x." The "two-stage" profile corresponds to the present invention.
[0073] During a first period t1, the connecting element 10 is placed on the surface of the first element 30 and the rotation of the connecting element 10 is initiated. In the figure, this is shown as an increase in the rotation speed at the start of the first period t1. The rotation speed can be set to a first (fixed) value. In the example of FIG. 3, the first (fixed) value is approximately 4000 rpm.
[0074] During the first time period t1, the rotation speed may be maintained substantially constant, or may be varied during the first time period t1.
[0075] The first time period t1 may continue until a first value of insertion depth is reached. The first time period t1 is defined by reaching a first fixed insertion depth. In the example of FIG. 3, the first insertion depth is approximately 2.5 mm.
[0076] In the first time period t1, only the tip 18 of the connecting element 10, or at most the tip 18, may be in contact with the first element 30. The threaded portion 17 may not be in contact with the first element 30. Likewise, in the first time period t1, the threaded portion 17 may already be in contact with the first element 30. This is particularly true if the thickness of the first element 30 is 1 mm or more.
[0077] The second period t2 is adjacent to the first period t1 and preferably follows without interruption. In the second period t2, in a single-stage process, the rotation speed is further kept constant. In a two-stage process according to the invention, the rotation speed of the connecting element 10 is increased. In particular, in the second period t2, the rotation speed can be increased to a second (fixed) value.
[0078] During the second time period t2, the rotation speed (second value of the rotation speed) may be maintained substantially constant. Alternatively, the rotation speed may be varied during the second time period t2. The average rotation speed during the second time period t2 is higher than the average rotation speed during the first time period t1. The average rotation speed may be an average value of the rotation speed over the entire time period.
[0079] The second time period t2 may continue until a second (fixed) value of the insertion depth is reached. The second time period t2 is defined by reaching the second (fixed) insertion depth. In the example of FIG. 3, the second (fixed) insertion depth is about 5 mm.
[0080] In the second time period t2, the threaded portion 17 may come into contact with the first element 30, in particular with the first element 30 and the second element 40.
[0081] The third period t3 is adjacent to the second period t2 and preferably follows without interruption. During the third period t3, the rotation speed is decreased. In particular, during the third period t3, the rotation speed can be decreased to a third (fixed) value.
[0082] During the third period t3, the rotation speed (third value of the rotation speed) may be maintained substantially constant, or the rotation speed may be varied during the third period t3.
[0083] In particular, the rotation speed in the third time period t3 may be lower than a first value of the rotation speed in the first time period t1 and a second value of the rotation speed in the second time period t2. The average rotation speed in the third time period t3 may be lower than the average rotation speed in the second time period t2 and the average rotation speed in the first time period t1.
[0084] Relative to the (average) rotation speed in the second period t2, the rotation speed in the third period may decrease by 20% or more, preferably 30% or more, preferably 40% or more, preferably 50% or more, preferably 60% or more, preferably 70% or more, preferably 80% or more, preferably 85% or more, preferably 90% or more, preferably 95% or more.
[0085] The third period t3 may continue until a third (fixed) value of the insertion depth is reached. The third period t3 is defined by reaching the third (fixed) insertion depth. Similarly, the third period t3 may be defined by reaching a (fixed) torque. When the head 11 of the connecting element 10 contacts the surface of the first element 30, the torque rises sharply.
[0086] During a third period t3, the threaded portion 17 may contact the second element 40 or the first element 30 and the second element 40. At the end of the third period t3, the connecting element 10 may reach a final position within the first and second elements 30, 40 or a final insertion depth within the first and second elements 30, 40. The connecting process then ends.
[0087] By first rotating the connecting element 10 at an average rotational speed and then rotating it at a higher rotational speed when the tip 19 of the connecting element 10 approaches the second element 40 (by the connecting element 10 at least partially penetrating the first element 30), the second element 40 can be heated to a higher temperature. In particular, if the second element 40 has low ductility (at room temperature), the ductility of the second element 40 can be improved during the connecting process. Furthermore, the hardness and / or strength of the second element 40 can be reduced during the connecting process. Therefore, breakage or rupture of the protrusions 45 formed on the surface of the second element 40 can be reduced or prevented.
[0088] FIG. 4 shows two profiles. The x-axis in the diagram represents the insertion depth of the connecting element 10 into the first element 30 and, optionally, into the second element 40. The x-axis may be identical to the x-axis in the diagram shown in FIG. 3. The y-axis represents the (axial) force applied to the connecting element 10. The two profiles overlap. The profiles differ particularly in the second period t2 and the third period t3. The profiles differ primarily in the second period t2. In the third period t3, the profiles may differ only at the beginning of the third period t3 and remain the same thereafter. Similarly, the profiles may differ only in the second period t2. The first profile is called "single-stage" and the second profile is called "two-stage." In the region where the first and second profiles differ, the two-stage profile is designated by an "x." The "two-stage" profile corresponds to the present invention. The periods t1, t2, and t3 may be the same as the periods t1, t2, and t3 in FIG.
[0089] During a first time period t1, the connecting element 10 is placed on the surface of the first element 30 and an axial force is applied. The "axial force" refers to the axis of rotation or longitudinal axis of the connecting element 10. In the figure, this is shown as an increase in the axial force at the beginning of the first time period t1. The axial force can be set to a first (fixed) value. In the example of FIG. 4, the first (fixed) value is approximately 2000 N.
[0090] During the first time period t1, the axial force may be maintained substantially constant, or the axial force may be varied during the first time period t1.
[0091] The second period t2 is adjacent to the first period t1 and preferably follows without interruption. During the second period t2, in a single-stage process, the axial force is further kept constant. In a two-stage process according to the invention, the axial force applied to the connecting element 10 is reduced. In particular, during the second period t2, the axial force can be reduced to a second (fixed) value.
[0092] During the second period t2, the axial force may be increased, particularly in a range where the insertion depth is 0.5 mm or more, preferably 1 mm or more, preferably 1.5 mm or more, preferably 2.0 mm or more. The axial force may be increased continuously or in steps. Alternatively, the axial force (the value of the second axial force) may be maintained substantially constant. The average axial force during the first period t1 may be greater than the axial force during the second period t2. The average axial force may be an average value of the axial force over the entire period.
[0093] The second time period t2 may continue until a second (fixed) value of the insertion depth is reached. The second time period t2 is defined by reaching the second (fixed) insertion depth. In the example of FIG. 3, the second (fixed) insertion depth is about 5 mm.
[0094] During a second period t2, the threaded portion 17 may come into contact with the first element 30 and possibly with the second element 40.
[0095] The third period t3 is adjacent to the second period t2 and preferably follows without interruption. During the third period t3, the axial force is decreased. In particular, during the third period t3, the axial force can be decreased to a third (fixed) value.
[0096] During the third time period t3, the axial force (third value of the axial force) may be maintained substantially constant, or the axial force may be varied during the third time period t3.
[0097] In particular, the axial force in the third time period t3 may be less than a first value of the axial force in the first time period t1 and a second value of the axial force in the second time period t2. The average axial force in the third time period t3 may be less than the average axial force in the second time period t2 and the average axial force in the first time period t1.
[0098] Relative to the (average) axial force in the second period t2, the axial force in the third period may decrease by 20% or more, preferably 30% or more, preferably 40% or more, preferably 50% or more, preferably 55% or more, preferably 60% or more, preferably 65% or more, preferably 70% or more, preferably 75% or more, preferably 80% or more.
[0099] The third time period t3 may continue until a third (fixed) value of the insertion depth is reached. The third time period t3 is defined by reaching the third (fixed) insertion depth. Similarly, the third time period t3 may be defined by reaching a (fixed) torque.
[0100] During a third period t3, the threaded portion 17 may contact the second element 40 or the first element 30 and the second element 40. At the end of the third period t3, the connecting element 10 may reach a final position within the first and second elements 30, 40 or a final insertion depth within the first and second elements 30, 40. The connecting process then ends.
[0101] By decreasing the axial force during the second time period t2 and then increasing it as needed, at least a portion of the protrusions 45 are formed on the surface 41 of the second element 40 only when the heating has sufficiently increased the ductility or sufficiently reduced the hardness and / or strength of the second element 40, thereby reducing or preventing breakage or rupture of the protrusions 45.
[0102] FIG. 5 shows two profiles. The x-axis in the diagram represents the insertion depth of the connecting element 10 into the first element 30 and, optionally, into the second element 40. The x-axis may be identical to the x-axis in the diagrams shown in FIGS. 3 and 4. The y-axis represents the (cumulative) energy input into the first element 30 and, optionally, into the second element 40. Energy can also be understood as the energy applied to the connecting element 10 by the connecting device 60. The two profiles partially overlap. The profiles differ, in particular, in the second period t2 and the third period t3. The first profile is called "single-stage" and the second profile is called "two-stage." In the areas where the first and second profiles differ, the two-stage profile is indicated by an "x." The "two-stage" profile corresponds to the present invention. The periods t1, t2, and t3 may be identical to the periods t1, t2, and t3 in FIGS. 3 and 4.
[0103] In particular, the two-stage process provides more energy to the first element 30, and possibly the second element 40, during the second time period t2 than the single-stage process. The increased energy delivery during the second time period t2 reduces or prevents breakage or rupture of the protrusions 45 on the surface 41 of the second element 40.
[0104] 6 is a schematic diagram of a connecting device 60. The connecting device 60 includes a connecting punch 70. The connecting punch 70 is capable of engaging with the connecting element 10. The connecting punch 70 rotates the connecting element 10 and applies an axial force to the connecting element 10. For this purpose, the connecting punch 70 may be rotatable and / or axially displaceable.
[0105] The connecting device 60 includes a control device 80. The control device 80 may be configured to control the connecting punch 70. In particular, the control device 80 is configured to control the rotational speed of the connecting punch 70 or the connecting element 10, to control the axial movement of the connecting punch 70 or the axial force acting on the connecting element 10, and / or to control the energy input to the first element 30 and, optionally, the second element 40.
[0106] A preferred connection device is the Atlas Copco KFLOW® system available from Atlas Copco IAS GmbH, Geretsried, Germany.
[0107] Figure 7 shows an image of the surface 41 of a second element 40 connected to a first element 30 by a connecting element 10. This connection was made according to the single-stage process described above.
[0108] A clear crack or break is observed at the protrusion 45 formed on the surface 41. Thus, there is a defect in the connection between the first element 30 and the second element 40.
[0109] Figure 8 shows an image of the surface 41 of a second element 40 connected to a first element 30 by a connecting element 10. This connection was made according to the two-stage process according to the invention described above.
[0110] The protrusions 45 formed on the surface 41 are smooth and surround the connecting element without any defects, thus improving the connection between the first element 30 and the second element 40.
Claims
1. A method for connecting at least two elements (30, 40) by means of a connecting element (10), comprising the steps of: providing a first element (30), a second element (40), and said connecting element; placing said connecting element (10) on a surface of said first element (30); rotating the connecting element (10) at a first rotational speed during a first period of time (t1) and applying a first axial force to the connecting element (10) in the direction of a surface of the first element (30); and rotating the connecting element (10) at a second rotational speed during a second period (t2) and applying a second axial force to the connecting element (10) in the direction of the surface of the first element (30), (i) the first rotation speed during the first time period (t1) is lower than the second rotation speed during the second time period (t2); and / or (ii) the first axial force in the first time period (t1) is greater than the second axial force in the second time period (t2).
2. 2. The method of claim 1, wherein the first rotational speed during the second time period (t1) is at least 10% lower than the second rotational speed during the second time period (t2), and / or the first axial force during the first time period (t1) is at least 10% greater than the second axial force during the second time period (t2).
3. 3. The method according to claim 1 or 2, wherein the length of the first period (t1) and the length of the second period (t2) are based on an insertion depth of the connecting element (10) into the first element (30) or an insertion depth of the connecting element (10) into the first element (30) and the second element (40).
4. 3. The method according to claim 1 or 2, wherein the connecting element (10) comprises a head (11) and a shank (15), the shank (15) having a threaded portion (17) on the side opposite the head (11) and a tip portion (18), the tip portion (18) having no threads.
5. 5. The method of claim 4, wherein the threaded portion (17) is at least temporarily out of contact with the first element (30) and / or the second element (40) during the first period (t1).
6. 5. The method of claim 4, wherein the tip (18) is surrounded by the first element (30) and / or the second element (40) when the first element (30) and the second element (40) are connected to each other.
7. 3. The method of claim 1 or 2, wherein the energy input to the first element (30) and / or the second element (40) during the second time period (t2) is greater than the energy input during the first time period (t1).
8. 3. The method of claim 1 or 2, wherein said first element (30) is a metal element and said second element (40) is an aluminum element.
9. the first rotational speed during the first time period (t1) and / or the second rotational speed during the second time period (t2) are at least partly constant; and / or 3. The method according to claim 1 or 2, wherein the first axial force during the first time period (t1) is at least partially constant and / or the second axial force during the second time period (t2) is at least partially increasing.
10. During a third period (t3), the method further comprises rotating the connecting element (10) at a third rotational speed and applying a third axial force to the connecting element (10) in the direction of the surface of the first element (30); the third rotation speed in the third time period (t3) is lower than the first rotation speed in the first time period (t1) and / or lower than the second rotation speed in the second time period (t2); and / or 3. The method of claim 1 or 2, wherein the third axial force in the third period (t3) is less than the first axial force in the first period (t1) and / or less than the second axial force in the second period (t2).
11. A connecting device (60) for connecting at least two elements (30, 40) by means of a connecting element (10), comprising: a rotatable connecting punch (70) configured to rotate the connecting element (10) and apply an axial force to the connecting element (10); A control device (80) comprising: controlling the connecting punch (70) so that, during a first period (t1), the connecting element (10) rotates at a first rotational speed and a first axial force is applied to the connecting element (10) in the direction of a surface of the first element (30); a control device (80) configured to control the connecting punch (70) so that, during a second time period (t1), the connecting element (10) rotates at a second rotational speed and a second axial force is applied to the connecting element (10) in the direction of the surface of the first element (30), (i) the first rotation speed during the first time period (t1) is lower than the second rotation speed during the second time period (t2); and / or (ii) a connection device (60) in which the first axial force during the first time period (t1) is greater than the second axial force during the second time period (t2).