A device for measuring the friction coefficient of fasteners of a jacking pre-tightening device

Abstract

The present invention relates to a device for measuring the friction coefficient of fasteners of a push-type pre-tightening device. A force load sensor is arranged on the left bearing end face of a bearing fixing seat. A boss shaft of the bearing fixing seat is connected to a support seat through a thrust ball bearing. A large push nut is installed in a large push nut fixing seat. A push bolt is connected to the large push nut fixing seat through a thread. The front end face of the push bolt contacts the support seat, and the rear end is connected to a rotating shaft through a push bolt connecting part. Torque load sensors are respectively arranged on the rotating shaft and the support seat. The friction coefficient measuring device of the present invention provides a platform test condition for measuring the friction coefficient of fasteners of a push-type pre-tightening device, and can measure the thread pair friction coefficient and the head end face friction coefficient of a push bolt under axial compressive stress pre-tightening, and has high engineering practical value.

Description

Technical Field

[0001] The present invention relates to a fastener for a push-type preloading device, and in particular, to a device for measuring the friction coefficient of the thread of a push bolt and the end face of its head part of the push-type preloading device. Background Art

[0002] Existing test and measurement devices for the friction coefficient of fasteners are mainly applicable to fasteners with the structural form of "hexagon head bolt - connected part - hexagon nut". The test load mode applied to the tested bolt is axial tensile stress, and the acting torque occurs at the contact end face between the hexagon head of the bolt and the connected part and the contact surface of the thread pair. This measurement device can meet the measurement requirements for the friction coefficient of the thread pair and the friction coefficient of the support surface of conventional hexagon head bolt fasteners.

[0003] The push-type preloading device is a fastener different from the traditional connection structural form. It can achieve precise preloading between the connected parts only by tightening the push bolt to generate a preloading force. During the tightening process, the end face part of the head of the push bolt comes into contact and extrusion with the support surface to generate axial compressive stress. The thread of the push bolt extrudes the internal thread of the push nut, driving the push nut to move axially in the reverse direction and act on the large bolt, so that the large bolt is axially stretched to generate a preloading force and transmitted to the connected parts.

[0004] The preloading force of the push bolt comes from the reaction forces of the support surface and the thread pair, and has no direct contact with the surface of the connected part. The hexagon head at one end is only used for wrench tightening and has no effective preloading force. Therefore, for the fastener of the push-type preloading device that uses the push force to achieve axial compressive stress preloading, due to the changes in the structural form and the loading mode, the existing measurement devices can no longer meet the measurement needs, lacking corresponding means for measuring the friction coefficient and unable to perform accurate and reliable performance prediction on it.

[0005] The fastener of the push-type preloading device is an innovation in the field of bolt connection and is often used in application scenarios that require large-size bolt fastening. This connection and fastening form uses the push force to achieve precise preloading of the connected parts, providing a fastening form with a simple structure and high cost performance. The action form of the fastener of the push-type preloading device can be analogized to the load application process of a jack and a displacement amplifier, and is often designed as a super bolt assembly in a circumferentially parallel form, which can greatly improve the overall preloading force of the connected parts. Therefore, in order to accurately grasp the connection performance of the fastener of the push-type preloading device, facilitate the structural strength design and precise preloading, it is necessary to solve the need for accurate measurement of the friction coefficient of the push bolt. Therefore, it is necessary to design a test device that is easy to operate, has strong dismountability, high measurement accuracy, and can reliably measure the friction coefficient of the fastener of the push-type preloading device. Summary of the Invention

[0006] The present invention aims to provide a device for measuring the friction coefficient of fasteners in a push-type preloading device. Compared with traditional friction coefficient measuring devices, this device can measure axial compressive stress, frictional torque on the support surface, and total fastening torque. By simply replacing the corresponding large push nut fixing seat and push bolt connecting piece, it can adapt to the measurement of the friction coefficient of push bolts with different specifications and sizes, eliminating the need for complex tooling design for bolt fasteners.

[0007] To achieve the above object, the technical solution of the present invention is: a device for measuring the friction coefficient of fasteners in a push-type preloading device, including a bearing fixing seat, a thrust ball bearing, a support seat, a large push nut fixing seat, a push bolt connecting piece, a rotating shaft, a large push nut, a push bolt, and a torque load sensor. The force load sensor is arranged on the left bearing end face of the bearing fixing seat. The boss shaft of the bearing fixing seat is connected to the support seat through a thrust ball bearing. The large push nut is installed in the large push nut fixing seat. The large push nut fixing seat is connected to the push bolt through a thread. The front end face of the push bolt contacts the support seat, and the rear end is connected to the rotating shaft through the push bolt connecting piece. Torque load sensors are respectively provided on the rotating shaft and the support seat.

[0008] Further, the large push nut is installed in the central counterbore of the large push nut fixing seat and fixed at the end face.

[0009] Further, the bearing fixing seat and the large push nut fixing seat are in a fixed constraint.

[0010] Further, the push bolt passes through the central through hole of the large push nut fixing seat for test installation.

[0011] Further, one end of the push bolt is embedded in the hexagonal groove counterbore at one end of the push bolt connecting piece, and the other end of the push bolt connecting piece is fixedly connected to the rotating shaft.

[0012] Further, the large push nut is eccentrically installed and limited in the large push nut fixing seat.

[0013] Further, the force load sensor is placed on the bearing surface of the fixed end of the bearing fixing seat for measuring the axial preloading compressive stress F of the push bolt.

[0014] Further, the thrust ball bearing is installed on the boss shaft body of the bearing fixing seat for separating the frictional torque T s of the thread pair and the frictional torque T w .

[0015] Further, the torque load sensors are respectively arranged on the support seat and the rotating shaft for measuring the frictional torque T w of the support surface and the total fastening torque T 总 .

[0016] The beneficial effects of the present invention are as follows:

[0017] The friction coefficient measuring device of the present invention provides a platform test condition for the friction coefficient of fasteners of a push-type pre-tightening device, and can measure the friction coefficient of the thread pair and the friction coefficient of the head end face of a push bolt under axial compressive stress pre-tightening, having high engineering practical value.

[0018] This friction coefficient measuring device uses a thrust ball bearing to separate the friction torques of the thread pair and the support surface, and the internal friction of the bearing can be ignored, having the measurement benefits of high precision and small error.

[0019] This friction coefficient measuring device eccentrically installs a large push nut on a large push nut fixing seat, and applies a torque load to the push bolt by a rotating shaft. During the test, only by rotating and adjusting the position of the large push nut, the sequential measurement requirements for all push bolts can be achieved, having the characteristics of convenient measurement and rapid disassembly and assembly.

[0020] This friction coefficient measuring device only needs to replace the large push nut fixing seat and the push bolt connecting piece, and without complex tooling design, it can realize the friction coefficient measurement of fasteners of push-type pre-tightening devices with various size specifications, having high working efficiency, strong interchangeability, and a high measurement effect of universality. Brief Description of the Drawings

[0021] Figure 1 It is a cross-sectional view of the device for measuring the friction coefficient of fasteners of a push-type pre-tightening device according to the present invention;

[0022] Figure 2 It is the front view of the structure of the large push nut;

[0023] Figure 3 It is the left cross-sectional view of the structure of the large push nut;

[0024] Figure 4 It is an application schematic diagram of fasteners of a push-type pre-tightening device;

[0025] In the figure: 1. Force load sensor, 2. Bearing fixing seat, 3. Thrust ball bearing, 4. Support seat, 5. Large push nut fixing seat, 6. Push bolt connecting piece, 7. Rotating shaft, 8. Torque load sensor I, 9. Large push nut, 10. Push bolt, 11. Torque load sensor II, 12. Large bolt, 13. Support gasket, 14. First connected part, 15. Second connected part. Detailed Embodiments

[0026] The present invention will be further described below in conjunction with the drawings and embodiments.

[0027] As Figures 1 to 3As shown in the figure, the device for measuring the friction coefficient of fasteners of the jacking pre-tightening device of the present invention includes a force load sensor 1, a bearing fixing seat 2, a thrust ball bearing 3, a support seat 4, a jacking big nut fixing seat 5, a jacking bolt connecting member 6, a rotating shaft 7, a torque load sensor I 8, a jacking big nut 9, a jacking bolt 10, and a torque load sensor II 11.

[0028] The force load sensor 1 is arranged on the left bearing end face of the bearing fixing seat 2. The force load sensor 1 is used to measure the axial pre-tightening compressive stress generated by the jacking bolt 10 during the tightening process. A thrust ball bearing 3 is installed on the boss shaft of the bearing fixing seat 2. The thrust ball bearing 3 is in contact with the end face of the support seat 4. The support seat 4 is in contact with the surface of the jacking bolt 10. The jacking bolt 10 and the jacking big nut 9 are connected by a threaded fit. The jacking big nut 9 is installed in the central counterbore of the jacking big nut fixing seat 5 and fixed at the end face. The bearing fixing seat 2 and the jacking big nut fixing seat 5 are fixed constraints. The jacking bolt 10 passes through the central through hole of the jacking big nut fixing seat 5 for test installation. One end of the jacking bolt 10 is embedded in the hexagonal groove counterbore at one end of the jacking bolt connecting member 6, and the other end of the jacking bolt connecting member 6 is fixedly connected to the rotating shaft 7.

[0029] The measurement principle is as follows: The rotating shaft 7 applies a total tightening torque T 总 to the jacking bolt connecting member 6. The total tightening torque T 总 is measured by the torque load sensor I 8. The jacking bolt connecting member 6 drives the jacking bolt 10 to tighten. Since the jacking big nut 9 is subject to a fixed constraint, at this time, the jacking bolt 10 shows compressive stress, and the left end transfers the jacking force and torque to the support seat 4. The thrust ball bearing 3 is installed on the boss shaft of the bearing fixing seat 2 and is used to transfer the axial pre-tightening force applied by the jacking bolt 10 to the support seat 4. The axial pre-tightening force is measured by the force load sensor 1, and the friction torque of the support surface is measured by the torque load sensor II 11. The friction torque T s of the thread pair is calculated from the difference between the total tightening torque T 总 and the friction torque T w of the support surface. Based on the total pre-tightening force F, the friction torque T w of the support surface, and the friction torque T s of the thread pair, the thread friction coefficient μ s , the support surface friction coefficient μ w , and the total friction coefficient μ 总 can be calculated.

[0030] The calculation method refers to the basic principle of threaded fasteners:

[0031] Friction torque of the thread pair: T s = T - T ω

[0032] Thread friction coefficient:

[0033] Coefficient of friction of the supporting surface:

[0034] Total coefficient of friction:

[0035] Note that μ is not the average of μ s and μ w The definitions of each symbol are as follows:

[0036] d2 is the pitch diameter of the thread; d ω is the equivalent friction diameter of the supporting surface; P is the pitch; α is the half angle of the thread profile; F is the axial pre-tightening force of the bolt; T 总 is the total tightening torque; T s is the friction torque of the thread pair; T w is the friction torque of the supporting surface; μ s is the coefficient of friction of the thread; μ w is the coefficient of friction of the supporting surface; μ 总 is the total coefficient of friction.

[0037] As Figure 4 shown, an application example of the fastener of the push-type pre-tightening device, the first connected part 14 and the second connected part 15 are fixedly connected by the large bolt 12 and the push-type large nut 9. Among them, a support gasket 13 is arranged between the push-type large nut 9 and the first connected part 14, and a plurality of push bolts 10 are used to tighten the support gasket 13 in the push-type large nut 9, and the accurate pre-tightening of the connected parts is realized through the pushing force.

Claims

1. A device for measuring the friction coefficient of fasteners in a push-type pre-tightening device, characterized in that: It includes a bearing fixed seat, a thrust ball bearing, a support seat, a large thrust nut fixed seat, a thrust bolt connecting member, a rotating shaft, a large thrust nut, a thrust bolt, a torque load sensor, and a force load sensor. The force load sensor is arranged on the left bearing end face of the bearing fixed seat. The boss shaft of the bearing fixed seat is connected to the support seat through a thrust ball bearing. The large thrust nut is installed in the large thrust nut fixed seat. The large thrust nut fixed seat is internally connected to the thrust bolt through a thread. The front end face of the thrust bolt contacts the support seat, and the rear end is connected to the rotating shaft through the thrust bolt connecting member. Torque load sensors are respectively provided on the rotating shaft and the support seat. The large thrust nut is installed in the central counterbore of the large thrust nut fixed seat and fixed at the end face. The bearing fixed seat and the large thrust nut fixed seat are fixed constraints.

2. The device for measuring the friction coefficient of fasteners of the jacking preloading device according to claim 1, characterized in that: The thrust bolt passes through the central through hole of the large thrust nut fixed seat for test installation.

3. The device for measuring the friction coefficient of fasteners of the jacking pre-tightening device according to claim 1, characterized in that: One end of the thrust bolt is embedded in the hexagonal groove counterbore at one end of the thrust bolt connecting member, and the other end of the thrust bolt connecting member is fixedly connected to the rotating shaft.

4. The device for measuring the friction coefficient of fasteners of the jacking preloading device according to claim 1, wherein: The large thrust nut is eccentrically installed and limited in the large thrust nut fixed seat.

5. The device for measuring the friction coefficient of fasteners in a push-type pre-tightening device according to claim 1, characterized in that: The force load sensor is placed on the bearing surface of the fixed end of the bearing fixed seat and is used to measure the axial pre-tightening compressive stress F of the thrust bolt.

6. The device for measuring the friction coefficient of fasteners of the jacking pre-tightening device according to claim 1, characterized in that: The thrust ball bearing is installed on the boss shaft body of the bearing fixed seat and is used to separate the frictional torque T of the thread pair s and the frictional torque T of the support surface w .

7. The device for measuring the friction coefficient of fasteners of the push-type pre-tightening device according to claim 1, characterized in that: The torque load sensors are respectively arranged on the support base and the rotating shaft and are used to measure the support surface friction torque T w and the total fastening torque T 总 .

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