Screws, screw connections, and vehicle couplings including such screw connections

Abstract

The present invention relates to a bolt (1) comprising a bolt head (2) and a bolt shank (3) having a threaded portion B with threads (6). A measuring device (8) having an extendable strain gauge (9) is disposed along or within the bolt shank (3), where the extendable strain gauge (9) is disposed on the threaded portion B and detects compression of the bolt shank (3).

Description

[Technical Field]

[0001] The invention relates to a bolt according to the preamble of claim 1, and to a bolted connection comprising such a bolt, as well as to a vehicle connection comprising a corresponding bolted connection. [Background technology]

[0002] Bolts with an integrated measuring device comprising at least one strain gauge are used to measure forces in various application situations, one of which is to detect torque during assembly, and another is to detect forces acting on the assembled bolted connection.

[0003] Document DE102020126374A1 discloses a bolt with a measuring device that includes a strain gauge and is used in vehicle hitches, such as fifth-wheel hitches and open-end hitches, to detect forces acting on the hitch while the vehicle is moving. For this purpose, the strain gauge is located in a hole formed in the center of the bolt shank and extending from the end remote from the bolt head to the bolt head. In this case, the strain gauge is located in the bolt shank adjacent to the bolt head and detects the elongation of the bolt caused by forces acting on the bolt. This type of bolt works well on its own. Summary of the Invention

[0004] The invention is based on the object of enabling higher measurement sensitivity. This object is achieved by a bolt having the features of claim 1, a bolted connection having the features of claim 7 and a vehicle coupling having the features of claim 10. Advantageous configurations are the subject of the dependent claims.

[0005] In the case of a bolt having a bolt head and a bolt shank having a head end adjacent to and facing the bolt head along the bolt axis and a distal end remote from the bolt head, a threaded portion having threads is formed at least adjacent to the distal end of the bolt shank and a measuring device having a strain gauge is arranged along or within the bolt shank, and according to the invention the strain gauge is arranged in the threaded portion closer to the distal end than the head end to detect compression of the bolt shank, particularly in the direction towards the bolt axis.

[0006] Instead of detecting the elongation of the bolt or bolt shank, as is common in the prior art, a strain gauge placed near the distal end can detect the compression of the bolt shank caused by the force acting on the threads. This deformation is several times larger than the elongation of the bolt shank that occurs near the bolt head when the same tightening torque or tension force is applied. This achieves higher measurement sensitivity, making it easier to detect changes in compression caused by changes in the force acting on the bolt.

[0007] In this regard, the strain gauges are preferably positioned transverse to the longitudinal axis of the bolt. Thus, the direction of measurement or detection is transverse to the longitudinal axis of the bolt. As a result, rather than detecting an elongation parallel to the longitudinal axis of the bolt, as is customary in the prior art, a compression transverse to the longitudinal axis of the bolt is detected. This compression is caused by forces between the bolt thread and the mating thread, which leads to a sliding movement between the respective thread flanks and ultimately to a compression of the bolt shank.

[0008] Preferably, the distance between the start of the thread at the distal end and the strain gauge is 0.5 to 20 times, particularly 0.5 to 10 or 0.5 to 5 times, the pitch of the thread. Compression of the bolt shank occurs most strongly in the outermost turn of the thread that engages with the mating thread. As the bolt head is approached, this compression is gradually superimposed by elongation of the material until eventually there is no compression at all and only elongation remains. By placing the strain gauge at a predetermined distance close to the start of the thread, the effect of elongation can be minimized, achieving high sensitivity.

[0009] In one advantageous refinement, the strain gauge is located inside the bolt shank, specifically in a bore extending from the distal end of the bolt shank along the bolt axis, thereby protecting the strain gauge from external influences. At the same time, the bolt can be fastened to a conventional mating thread.

[0010] In this case, it is particularly preferred that the hole only extends over the threaded portion. Alternatively or additionally, the hole may preferably extend over less than half, particularly less than one-third or one-quarter, of the length of the bolt shank. This substantially maintains the mechanical strength and structure of the bolt. The bolt can therefore absorb and / or transmit large forces.

[0011] Advantageously, two electrical connections of the measuring device are arranged in the region of the distal end. These can be arranged and designed, for example, so that when the sensor-equipped bolt is inserted into the socket, they come into contact with two corresponding electrical contacts in the socket. However, in the simplest case, the electrical connections can be routed out of the distal end of the bolt shank in the form of a cable.

[0012] The bolt shank preferably has a smooth wall of constant diameter adjacent the bolt head, so that the threads do not extend all the way through the bolt shank, thereby avoiding or reducing deformation.

[0013] The bolt preferably has a standard thread, in particular a metric or inch thread. In the case of a metric thread, the flank angle of the thread is, for example, about 60°. Such a flank angle ensures that a sufficient compression of the bolt shank is achieved by the forces acting on the bolt or bolted connection.

[0014] The measuring device preferably includes signal electronics, including, among other things, a quarter-bridge, a signal amplifier, and a signal converter. As a result, the signal electronics can be directly connected to the strain gauge, allowing virtually lossless transmission of the analog signal from the strain gauge to the signal electronics, which typically generates a processed digital signal from it. In this way, even relatively weak output signals can be processed reliably and relatively interference-free. Furthermore, self-calibration is possible at low cost.

[0015] The measuring device may also be equipped with one or more further sensors, for example a temperature sensor, which can largely prevent temperature-induced measurement errors and improve the measurement results.

[0016] The object stated at the outset is achieved by a bolted connection having the above-mentioned bolt, in which the thread engages with a counter-thread and a strain gauge is arranged in the threaded portion closer to the distal end than the head end, for detecting compression of the bolt shank, in particular in the bolt axial direction. In this respect, the counter-thread may be designed, for example, in the shape of a nut or formed on a corresponding part such as a fixing flange. As a result of the strain gauge being arranged in the threaded portion, or in particular in the region where the thread engages with the counter-thread, deformations of the bolt shank when the compression and force acting on the bolt shank change can be easily detected.

[0017] In this case, it is preferable to arrange the strain gauges in particular in the region of the external thread engagement. The maximum compression occurs in the region of the external thread engagement. From there, the compression decreases towards the bolt head. Therefore, by arranging the strain gauges in the region of one or more external thread engagements, high sensitivity can be achieved.

[0018] The bolt connection preferably has a socket with a contact surface, in particular for electrical connection with the measuring device, which allows a simple and reliable contact connection of the measuring device.

[0019] The object stated at the beginning is also achieved by a vehicle coupling, in which at least one coupling element is fixed via at least one bolted connection configured as described above, so that forces occurring during driving between the vehicle and the trailer via the vehicle coupling can be reliably detected and evaluated.

[0020] In this respect, it is particularly preferred that the vehicle hitch is designed as a fifth wheel hitch with a kingpin or as an open-end hitch, as such a vehicle hitch is capable of transmitting large forces and is therefore also suitable for use in heavy commercial vehicles. [Brief explanation of the drawings]

[0021] Further features, details and advantages of the invention will become apparent from the claims and the following description of exemplary embodiments with reference to the drawings. [Figure 1] FIG. [Figure 2] FIG. 1 is a longitudinal section of a bolt with a measuring device. DETAILED DESCRIPTION OF THE INVENTION

[0022] 1 shows a bolt 1 having a bolt head 2 and a bolt shank 3 extending along the bolt axis A. The bolt shank 3 has a head end 4 facing the bolt head 2 and a distal end 5 remote from the bolt head 2.

[0023] Adjacent to the distal end 5 the bolt shank 3 has threads 6 and comprises a threaded portion B adjoining a smooth wall portion C up to the bolt head 2 .

[0024] A bore 7 begins at the distal end 5 and extends into the bolt shank 3 along the bolt axis A. Preferably, the bore 7 extends only through the threads, i.e., only part of the length of the bolt shank 3, to minimize any reduction in the stability and strength of the bolt 1.

[0025] Figure 2 shows a longitudinal section of the bolt 1 shown in Figure 1. A measuring device 8 with a strain gauge 9 is arranged in the hole 7, i.e., inside the bolt shank 3. In this respect, the strain gauge 9 is arranged transversely to the longitudinal axis A of the bolt, i.e., it detects changes in length occurring transversely to the longitudinal axis A of the bolt. When the bolt shank 3 is compressed, the strain gauge 9 is compressed and detected accordingly. Connections 10, 11 for the measuring device are formed in a cap 12 arranged on the end 5 of the bolt shank 3. Power supply and, if necessary, signal transmission can also take place via these connections.

[0026] The strain gauge 9 is located in the region of the thread B, at the beginning of the thread, starting from the distal end of the head. Thus, when the bolt is installed, the strain gauge 9 is located in the region of the external thread engagement. The strain gauge is thus located in the region where the maximum compression of the bolt occurs due to forces acting along the longitudinal axis of the bolt. This compression occurs in this case due to the tendency of the thread flank of the bolt thread to slip in the bolt axial direction due to forces acting on the thread flank of the mating thread.

[0027] Compared to previously known sensor-equipped bolts, the bolt according to the present invention has improved sensitivity and a wider measurement spectrum. In this case, not only the tightening torque but also the tensile load and tension release can be detected. These characteristics are particularly advantageous in combination with vehicle couplings, since the (auxiliary) drive can be controlled based on the detected forces. For this purpose, the strain gauges are arranged in a position and orientation within the bolt where material compression is particularly pronounced. This position is the outermost thread engagement area between the bolt thread and the mating thread. In this respect, the approximately linear relationship between compressive and tensile loads is utilized.

[0028] The invention is not limited to any of the above-described embodiments, but can be modified in many ways. Thus, the bolt according to the invention can be used, for example, not only to detect forces acting in the area of ​​vehicle joints, but also, for example, for weight measurement or for measuring torque in compression ignition and internal combustion engines and variable pressures in the engine area. However, other use situations are also conceivable.

[0029] All features and advantages arising from the claims, the specification and the drawings, including details of construction, spatial arrangements and method steps, may be essential to the invention, either individually or in various combinations. [Explanation of symbols]

[0030] 1 volt 2 bolt heads 3 bolt shank 4 Head side end 5. Distal end of head 6 screws 7 holes 8. Measuring equipment 9 Strain gauges 10 Connection 11 Connection 12 Caps A Bolt shaft B Threaded part C. Smooth wall

Claims

1. 1. A bolt (1) comprising: a bolt head (2); and a bolt shank (3) adjacent to the bolt head (2) along a bolt axis (A), the bolt shank (3) having a head end (4) facing the bolt head (2) and a distal end (5) away from the bolt head (2), wherein a threaded portion (B) having threads (6) is formed at least adjacent to the distal end (5) of the bolt shank (3), and a measuring device (8) having a strain gauge (9) is arranged along or within the bolt shank (3), the strain gauge (9) being arranged on the threaded portion (B) closer to the distal end (5) than to the head end (4), and for detecting compression of the bolt shank (3), particularly in a direction toward the bolt axis (A).

2. 2. The bolt according to claim 1, wherein the distance between the start position of the thread (6) at the distal end (5) and the strain gauge (9) is 0.5 to 20 times, in particular 1 to 10 times, the thread pitch of the thread (6).

3. 3. A bolt according to claim 1 or claim 2, wherein the strain gauge (9) is arranged inside the bolt shank (3), in particular in a hole (7) extending from the distal end (5) of the bolt shank (3) along the bolt axis A.

4. 4. A bolt according to claim 3, wherein the hole (7) extends over less than half, in particular less than one third or one quarter, of the length of the bolt shank (3).

5. 5. The bolt according to claim 1, wherein the two electrical connections (10, 11) of the measuring device (8) are arranged in the region of the distal end (5).

6. 6. A bolt according to any one of claims 1 to 5, wherein the bolt shank (3) has a smooth wall C of constant diameter adjacent to the bolt head (2).

7. 7. A bolted connection comprising the bolt (1) according to any one of claims 1 to 6, wherein the thread (6) engages with a mating thread, and the strain gauge (9) is arranged closer to the distal end (5) of the threaded portion (B) than to the head end (4), and detects compression of the bolt shank (3), particularly in a direction towards the bolt axis A.

8. 8. A bolted connection according to claim 7, wherein the strain gauges (9) are arranged in the area of ​​the external thread engagement.

9. 9. A bolted connection according to claim 7 or 8, comprising a socket with contact surfaces, in particular for electrical connection to the measuring device (8).

10. Vehicle coupling, wherein at least one coupling member is fixed via at least one bolted connection according to any one of claims 7 to 9.

11. 11. The vehicle hitch according to claim 10, which is designed as a fifth wheel hitch with kingpin or as an open-end hitch.

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