Sensor-containing connection element and manufacturing method

Abstract

A connection element consists of a longitudinally oriented support structure that is at least partially hollow and a sensor unit that is arranged in the inside of the support structure, is connected to a signal transmission device, and is non-positively connected to the support structure. The required force for the non-positive connection is produced by internal stresses after a plastic deformation of the support structure during a joining process of the support structure and the sensor unit. A method for manufacturing a connection element consisting of a support structure that is at least partially hollow and a sensor unit includes positioning the sensor unit in a region of the support structure and, using radially movable tool segments, exerting a force on the support structure in the radial direction and at the same time reducing the periphery of the support structure in the region in which the sensor unit is positioned.

Claims

1. A method of manufacturing a connection element comprising: providing a support structure that is at least partially hollow; providing a sensor unit that is configured to be received within the support structure; positioning the sensor unit inside the at least partially hollow support structure; joining the support structure and the sensor unit using radially movable tool segments to exert a force on the support structure in a radial direction thereby at least partially reducing a periphery of the support structure in a region of the support structure in which the sensor unit is positioned; wherein the support structure is subjected to a plastic deformation as a result of the force exerted on the support structure by the radially movable tool segments; and wherein at least a portion of the sensor unit is positively connected to the support structure by means of the plastic deformation of the support structure.

2. The method as claimed in claim 1, further comprising at least one of heating the support structure and cooling the sensor unit before a joining the support structure and the sensor unit.

3. The method as claimed in claim 1, further comprising superimposing a longitudinal force on the support structure while joining the support structure and the sensor unit.

4. The method as claimed in claim 1, wherein a portion of the sensor unit is non-positively connected to the support structure and a portion of the sensor unit is positively connected to the support structure by means of the plastic deformation of the support structure.

5. The method as claimed in claim 4, wherein a combined non-positive connection and positive connection between the support structure and the sensor unit is produced by at least one of the following: internal stresses resulting from the force exerted on the support structure using the radially movable tool segments at room temperature; application of at least one of an additional local heating of the support structure and an additional global heating of the support structure; and application of a process heat during manufacture of the support structure and subsequent shrinkage by cooling.

6. The method as claimed in claim 1, wherein at least one undercut is formed in the support structure in a contact region between an axial end of the sensor unit and the support structure.

7. The method as claimed in claim 1, wherein the connection element comprises at least one threaded region at an end of the connection element and at least one top part.

8. The method as claimed in claim 1, wherein the connection element comprises a resilient region inside which the sensor unit is integrated.

9. The method as claimed in claim 8, wherein the sensor unit is located in a secondary flux of force of the support structure and is arranged coaxially inside the at least partially hollow support structure.

10. The method as claimed in claim 9, wherein the connection element comprises a plastic expansion region disposed between the resilient region and an end of the connection element.

11. The method as claimed in claim 1, wherein the sensor unit is operable for measuring at least one of an axial pre-tensioning force and a transverse force in the connection element.

12. The method as claimed in claim 1, wherein the connection element comprises a cable connection for transmitting a signal from the sensor unit.

Description

BRIEF DESCRIPTION OF THE DRAWING FIGURES

(1) FIG. 1 is a plan view of a connection element according to an exemplary embodiment of the invention.

(2) FIG. 2 is a section view of the connection element of FIG. 1

(3) FIG. 3 is a plan view of a connection element according to another exemplary embodiment of the invention.

(4) FIG. 4 is a section view of the connection element of FIG. 3.

(5) FIG. 5 is a section view of a connection element according to another exemplary embodiment of the invention.

(6) FIG. 6 is a section view of a connection element according to another exemplary embodiment of the invention.

(7) FIG. 7 is a section view of a connection element according to another exemplary embodiment of the invention.

(8) FIG. 8 is a section view of a connection element according to another exemplary embodiment of the invention.

(9) FIG. 9 is a section view of a connection element according to another exemplary embodiment of the invention.

(10) FIG. 10 is a section view of a connection element according to another exemplary embodiment of the invention.

(11) FIG. 11 is a section view of a connection element according to another exemplary embodiment of the invention.

(12) FIG. 12 is a section view of a connection element according to another exemplary embodiment of the invention.

(13) FIG. 13 is a section view of a connection element according to another exemplary embodiment of the invention.

(14) FIG. 14 is a section view of a connection element according to another exemplary embodiment of the invention.

DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE INVENTION

(15) According to the invention, the proposed construction substantially consists of a longitudinally oriented support structure (14) and a sensor unit (10). The object of the support structure (14) is that of a connection element. The support structure (14) consists of a threaded region (1) at the ends thereof, as well as a top part (7), or alternatively, a further threaded region (1) or a further top part (7). A resilient region (2) inside which the sensor unit (10) is integrated is provided in addition. The sensor unit (10) in this case is located in the secondary flux of force of the support structure (14) and is arranged coaxially in the interior thereof. In order to exploit further the advantages of this simple construction, the sensor unit (10) is intended to be integrated during the manufacturing process of the support structure (14). The sensor unit (10) undertakes the task of measuring the axial pretensioning force acting in the connection element as well as transverse forces which are present in the connection element. In order to permit continuous monitoring, embodiments are proposed for signal forwarding (8). Moreover, the connection element may be extended by a plastic expansion region (6).

(16) In order to produce the support structure (14) in a manufacturing method using shaping technology, it is necessary to act upon the support structure (14) using tools or tool segments in the radial direction in order to produce the undercuts in the axial direction for receiving the sensor unit (10) inside the support structure (14). In this case, the shaping forces are not permitted to exceed the capacity of the sensor unit (10) to withstand stresses. During the plasticization of the support structure (14), the sensor unit (10) is integrated such that a combined non-positive and positive connection is produced between the support structure (14) and the sensor unit (10). This is achieved by the resulting internal stresses after the shaping process at room temperature, and/or by additional local or global heating of the support structure (14) from outside, and/or by process heat during the manufacture of the support structure (14) and the subsequent shrinkage by cooling which is blocked by the undercuts produced on the support structure (14), and by the presence of the sensor unit (10) at this point. By the angle of the contact geometry (26) on the sensor unit (10) and the support structure (14), the resulting axial tensile stresses (19) produced from the internal stresses and the loading of the sensor unit may be suitably adjusted during the manufacturing process. The angle (26) which is best suited may be determined for a given geometry and load using established mechanical methods, such as for example finite element methods. The method may additionally provide for the superposition of a longitudinal force (25) during the joining process on the support structure (14), in order to produce or reinforce the internal tensile stresses in the support structure (19) after the process. Generally, the axial tensile stresses in the support structure (14), and thus the pretensioning forces for the sensor unit (10), may be increased by axial tensile stress (25) during the joining process.

(17) According to the invention, the measurement values may be used both during the tightening process of the screw connection and during operation. It is particularly advantageous here that no modification has to be made to the construction.

(18) A further particular advantage of the simple construction is the scalability of the arrangement. Variables and measurement ranges may thus be adapted according to requirements as no additional elements are required.

(19) The support structure (14) may be designed to be continuously hollow (9) inside. As a result, the deformability of the support structure (14), and thus the operating capacity, is increased. Moreover, the resilient region (2) absorbs the pretensioning in the case of changing loads. If, during operation or during the clamping of the connection, the support structure (14) is subject to a longitudinal force in the pulling direction, the resilient expansion region ensures that unauthorized lengthening and/or plasticization does not occur in the longitudinal direction, so that the pretensioning of the support structure (14) and sensor unit (10) is maintained during and after the loading by the pulling force.

(20) The sensor unit (10) consists of a conventional construction for detecting loads, known from the relevant teaching books, such as for example Jorg Hoffmann: Handbuch der Messtechnik. Carl Hanser, Munich 2007 (3rd Edition). ISBN 978-3-446-40750-3, or Karl-Heinrich Grote, Jorg Fedhusen (Pub.): Dubbel-Taschenbuch fr den Maschinenbau. 23rd Edition. Springer, Berlin 2011. The application, for example, of strain gauges on a support is proposed. Similarly, a support ring (17) may also be embedded in protective caps (16), as best shown in FIG. 11. Also other measuring principles, which convert a mechanical load into an electrical variable, such as capacitive, piezoresistive or piezoelectrical, are possible and may replace the resistive measuring principle. The sensor design may be enhanced by temperature and humidity sensors in order to compensate for potential interference in the load measurement. The sensor unit is configured, in particular, for detecting mechanical and/or thermal measurement variables.

(21) According to the invention, the sensor body (10) is located in the secondary flux of force of the connection element and is thus influenced directly by alterations to the load conditions of the support structure (14). The technical measurement position, therefore, is located in the middle of the support structure (14). Thus, the sensor unit is also protected. In order to exploit further the advantages of the construction, the sensor unit (10) is integrated in the support structure (14) by a combined non-positive and positive connection. Thus a more reliable force transmission between the support structure (14) and the sensor unit (10) is ensured in the direction of the connection axis and transversely thereto.

(22) Exemplary embodiments are shown in the drawings and described in more detail in the following description.

(23) FIG. 1 shows the support structure (14) in the embodiment with a top part (7), a resilient region (2) and plastic expansion region (6) connected to a transition region (5), as well as to a threaded region (1). The top part (7) may be designed as a fastening aid with an external hexagonal contour, internal hexagonal contour, slotted contour, crosshead contour, or any other internal and/or external contour. In order to increase the rigidity of the connection element and thus the load-bearing capacity, the resilient region (2) is alternately provided with notched regions (4) and smooth regions (3) in order to exploit the stabilizing effect of the notches. If the support structure (14), during operation or during the clamping of the connection is subject to a longitudinal force in the pulling direction, the resilient expansion region (6) ensures that unauthorized lengthening and/or plasticization does not occur in the longitudinal direction, so that the pretensioning of the support structure (14) and sensor unit (10) during and after loading is maintained by the pulling force. For the signal transmission, a cable connection (8) is proposed.

(24) FIG. 2 shows the section of the embodiment described in FIG. 1. The connection element is provided along the longitudinal axis with a bore (9). The integrated sensor unit (10) is arranged inside the resilient region (2) coaxially thereto.

(25) FIG. 3 shows the support structure (14) in the embodiment with the resilient region (2) and plastic expansion region (6) connected to a transition region (5), wherein the resilient region (2) is not notched. The other elements correspond to the embodiment described above.

(26) FIG. 4 shows the section of the embodiment shown in FIG. 3. In the interior, the construction is identical to the embodiment shown in FIG. 2.

(27) FIG. 5 shows the support structure (14) in the embodiment with a top part (7), a resilient expansion region (2) and a threaded region (1). The connection element is provided along the longitudinal axis with a bore (9). The integrated sensor unit (10) is arranged inside the resilient region (2). The proposed embodiment differs from the embodiments described above in that no plastic expansion region is provided. By the size and type of this embodiment, it is suitable as a wheel bolt.

(28) The embodiment proposed in FIG. 6 differs from the embodiments described above in that the support structure (14) is only hollow in sections. The preform of such an embodiment may be implemented, for example, by the reverse cup extrusion method.

(29) FIG. 7 shows the support structure (14) in the embodiment with two threaded regions (1) and a resilient expansion region (2), wherein the resilient expansion region (2) is not notched. The other elements correspond to the embodiment described above. Moreover, a wireless method is proposed for the signal transmission. Necessary elements are a circuit for converting the wireless signals (22), as well as an antenna for transmission (21).

(30) FIG. 8 shows the support structure (14) in the embodiment with two threaded regions (1) and a resilient expansion region (2), wherein the resilient expansion region (2) is notched to increase the load-bearing capacity by the stabilizing effect of the notches, as a result of the continuous thread (1). The other elements correspond to the embodiment described above. Moreover, an optical method is proposed for the signal transmission. Required elements are a circuit for the conversion into optical signals (24) as well as an optical waveguide (23).

(31) In FIG. 9, an embodiment is shown in which the cable connection for the signal transmission (8) is provided with strain relief (11). The strain relief is produced during the manufacture of the support structure (14). Thus the connection element is additionally sealed on one side. The further construction corresponds to the embodiments described above.

(32) FIG. 10 shows an embodiment in which an interface for signal transmission (15) is introduced at the end of the support structure (14).

(33) FIG. 11 shows an embodiment in which additionally a sealing ball (12) is inserted in the screw end. Thus, the connection element may be sealed on one side or according to the embodiments of FIGS. 9 and 10, also on both sides. The further construction corresponds to the embodiments described above. Moreover, it is proposed to construct the sensor unit (10) so as to be divided into two protective caps (16) and a support ring (17).

(34) In order to be able to compensate for thermally induced measurement signals of the sensor unit (10), according to the embodiment of FIG. 12, the use of a temperature sensor (13) is provided. This sensor measures the temperatures in the region of the sensor unit (10). The construction is suitable for uniform heating of the connection element during operation. The proposed construction may also be used in the embodiments described above.

(35) The embodiment according to FIG. 13, similar to the embodiment according to FIG. 12, provides the use of temperature sensors in order to be able to compensate for the influence of thermally induced measurement signals on the sensor unit (10). In the case of uneven heating of the connection element over the longitudinal axis during operation, the temperatures are detected in the region of the threaded region (1) and in the region of the top part (7). The proposed construction may also be used in the embodiments described above.

(36) In the embodiment according to FIG. 14, an initial geometry of the support structure and an arrangement of tool segments (20) is provided in order to act on the support structure (14) in the radial direction, as proposed in FIG. 14, so that the undercuts and the contact region (18) are produced for receiving the sensor unit (10) inside the support structure (14). This process sequence is similarly known, for example, from rotary kneading. After the process, the presence of axial tensile stresses (19) in the marked region, introduced by internal stresses as a result of plasticization with or without a superimposed longitudinal force (25) during the plasticization or/and by thermal shrinkage of the support structure (14), blocked by the undercuts produced on the support structure (14) and by the presence of the sensor unit (10) at this point, is important in order to achieve thereby a pretensioning of the sensor unit. Also important is a corresponding geometry in the contact region (18) between the support structure (14) and the sensor unit (10) for the force transmission. The contact region is determined, in particular, by the initial geometry. In particular, the angle of the contact geometry (26) on the sensor unit (10) and support structure (14) has an influence on the resulting axial tensile stresses (19) caused by the internal stresses and the loading of the sensor unit during the manufacturing process.