A detection instrument for coaxiality measurement

Abstract

The application is suitable for coaxiality measurement technical field, and provides a detection instrument for coaxiality measurement, which comprises a sensor, an instrument and software, the sensor elastic body is provided with a protective shell, the top end is connected with the connecting plate through the first fixed plate and the second fixed plate, the shell is fixed through the connecting plate, the cylindrical centering sensor, the two end clamping parts are provided with high-precision threads, which is convenient for replacement and improves the service life of the sensor. The detection instrument for coaxiality measurement is provided with a built-in non-measurement strain gauge, the non-measurement strain gauge and the measurement strain gauge on the centering sensor elastic body are in the same environment, the measurement error caused by different environments is avoided, the measurement accuracy is improved, the calculation of the coaxiality mainly is the ratio of the maximum bending strain and the average axial strain, the accuracy of the measurement result is improved, the accuracy and the qualified rate of the coaxiality sensor are improved, and the measurement result is more reliable.

Description

Technical Field

[0001] This invention belongs to the field of coaxiality measurement technology, and particularly relates to a testing instrument for coaxiality measurement. Background Technology

[0002] Coaxiality is a core parameter in the performance testing of material testing machines. It is a key indicator measuring the degree of coincidence between the axis of the clamping device and the force-applying axis, directly affecting the accuracy of test results. In the testing of material mechanical properties, misalignment will cause the specimen to bear additional bending moments during tension or compression, resulting in uneven stress on the material and thus producing test results with large deviations. This affects the measurement of key performance indicators such as material strength, elastic modulus, and lifespan. Coaxiality deviation will exacerbate abnormal wear of components such as the clamping device, potentially causing equipment resonance, damaging parts, and increasing maintenance costs. National verification regulations clearly stipulate the coaxiality requirements for different grades of testing machines, and American standards have put forward unified requirements for coaxiality classification. Products must meet international standards to obtain a larger market share.

[0003] The coaxiality error of a testing machine mainly originates from factors such as the machine's design, manufacturing, assembly, and wear and aging during use. These errors can cause the axes of the upper and lower clamps to misalign. When coaxiality is poor, the specimen will experience additional bending strain due to the added bending stress in addition to the axial stress during tension or compression. This can lead to premature material fracture, directly affecting the accuracy and reliability of mechanical property tests (such as tensile, compression, and fatigue tests). Studies have shown that severe coaxiality errors can even cause the difference between surface bending strain and average axial strain to be as high as 50% to 100%.

[0004] The methods for measuring the coaxiality of testing machines are mainly divided into two categories: geometric measurement methods and strain measurement methods. Geometric measurement method: Dial indicator / micrometer, install a long straight coaxiality bar, use the dial indicator to measure the offset of the two ends of the bar in mutually perpendicular directions, calculate the coaxiality, use a weight line and centering plate, and judge the coaxiality by observing or measuring the deviation between the tip of the weight and the center of the centering plate.

[0005] Strain measurement method: Two extensometers are installed in a direction perpendicular to each other in the middle section of the coaxial bar to measure the deformation difference on both sides under a specific tensile force (such as 4% of the maximum force) and calculate the coaxiality. Resistance strain gauges are attached to multiple sections of the coaxial bar to measure the strain at each point under force and calculate the ratio of bending strain to axial strain to characterize the coaxiality.

[0006] However, in existing technologies, dial indicators / micrometers cannot reflect the actual coaxiality under stress conditions in static measurements; human reading errors are large; extensometers can usually only measure the average bending (C-type bending) within a gauge length; they may not be comprehensive for complex bending (such as S-type bending); and there are errors in symmetrical clamping of extensometers on the same cross section. Conventional coaxiality sensors for strain gauges have a low pass rate of 1% or higher accuracy, the sensor clamping ends are prone to wear, and the lifespan is limited to 12 years. The number of bridge cables is large and messy, which is not conducive to the use of testing machines for coaxiality measurement. Summary of the Invention

[0007] This invention provides a testing instrument for measuring coaxiality, aiming to solve the problems in the prior art where the accuracy and pass rate of coaxiality sensors are low, the service life of coaxiality sensors is short, and they cannot well meet the testing requirements of different standards.

[0008] The present invention is implemented as follows: a coaxiality measuring instrument includes a protective housing, a sensor elastomer in a connecting plate, and high-precision threads are provided at both ends of the centering sensor elastomer, and a first fixing plate and a second fixing plate are provided at the top end. The connecting plate is provided with several fifth screws, and the inner wall of the fifth screws is fixedly connected with a retaining strip. The top of the surface of the centering sensor elastomer is provided with a retaining groove that matches the retaining strip. The bottom of the inner cavity of the protective housing is provided with a baffle that matches the centering sensor elastomer. The baffle is provided with a through-hole that matches the centering sensor elastomer. The surface of the centering sensor elastomer is provided with 12 measuring strain gauges that are evenly arranged along its surface.

[0009] Preferably, the first fixing plate, the second fixing plate, and the baffle are provided with a plurality of threaded holes that are adapted to the fifth screw.

[0010] Preferably, a third screw is provided on the top of both the front and rear sides of the protective housing, and threaded holes adapted to the third screw are provided on the outer sides of both the first fixing plate and the second fixing plate.

[0011] Preferably, a second screw is provided on the bottom of both the front and rear sides of the protective housing, and a threaded hole adapted to the second screw is provided on the outer side of the baffle.

[0012] Preferably, a support frame located in the inner cavity of the protective housing is detachably connected to the upper part of one side of the connecting plate via a fifth screw. An adhesive plate is detachably installed on the side wall of the support frame via a sixth screw. Twelve strain gauge bridges, consisting of 36 non-measuring strain gauges, 12 zero-point compensation strain gauges, and 12 zero-point temperature compensation strain gauges, are attached to the side wall of the adhesive plate. The twelve strain gauge bridges correspond one-to-one with the twelve measuring strain gauges and are electrically connected.

[0013] Preferably, one side of the connecting plate is provided with a plurality of wire clamps by means of several bolts, and the plurality of wire clamps are evenly spaced and distributed along one side of the protective housing.

[0014] Preferably, a cable connector located inside the connecting plate is fixedly connected to one side of the protective housing. The cable connector is electrically connected to the 12 strain gauge bridge circuits, and the terminal of the cable connector extends to the other side of the protective housing.

[0015] Preferably, the centering sensor elastic body is cylindrical, and the 12 strain gauges are divided into 3 groups. The 3 groups of strain gauges are arranged along the length direction of the centering sensor elastic body, and the 4 strain gauges in each group are distributed at 90-degree intervals around the same cross-section of the centering sensor elastic body.

[0016] Preferably, the centering sensor elastic body is a thick rectangle, and the 12 strain gauges are divided into 3 groups. The 3 groups of strain gauges are arranged along the length direction of the centering sensor elastic body, and the 4 strain gauges in each group are distributed at the center of the four faces of the same cross section of the centering sensor elastic body.

[0017] Preferably, the centering sensor elastic body is a thin rectangle, and the 12 strain gauges are divided into 3 groups. The 3 groups of strain gauges are arranged along the length direction of the centering sensor elastic body. Each group of 4 strain gauges is distributed in pairs on a wide surface of the same cross section and is mirror-symmetrical to the center of the centering sensor elastic body.

[0018] Beneficial effects

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: The coaxiality measuring instrument of the present invention, by incorporating a non-measuring strain gauge, places the non-measuring strain gauge and the measuring strain gauge on the elastic body of the centering sensor in the same environment, avoiding measurement errors caused by different environments and improving measurement accuracy. Furthermore, the instrument uses three four-channel modules for data acquisition, with each module's four channels acquiring four bridge circuits at the same cross-section, and the four bridge circuits at the same cross-section using the same voltage. The coaxiality calculation mainly uses the ratio of the maximum bending strain to the average axial strain, improving the accuracy of the measurement results, increasing the accuracy and pass rate of the coaxiality sensor, and making the measurement results more reliable. High-precision threaded fittings at both ends extend the service life of the coaxiality sensor. The testing software allows for standard switching to meet the testing requirements of different standards. Attached Figure Description

[0020] Figure 1 This is a three-dimensional structural diagram of the present invention; Figure 2This is a schematic diagram of the structure of the first fixing plate and the fifth screw in this invention; Figure 3 This is a schematic diagram of the support frame and strain gauge bridge in this invention; Figure 4 This is a front cross-sectional view of the present invention; Figure 5 This is a schematic diagram of the structure of the first embodiment of the present invention; Figure 6 This is a schematic diagram of the structure of the second embodiment of the present invention; Figure 7 This is a schematic diagram of the structure of the third embodiment of the present invention; Figure 8 This is a schematic diagram of the 1 / 4 bridge in this invention.

[0021] In the diagram: 1. Protective housing; 2. Connecting plate; 3. First screw; 4. Baffle; 5. Through port; 6. Second screw; 7. Wire clamp; 8. Centering sensor elastomer; 9. First fixing plate; 10. Second fixing plate; 11. Clip; 12. Slot; 13. Strain gauge; 14. Third screw; 15. Cable connector; 16. Fourth screw; 17. Fifth screw; 18. Support frame; 19. Sixth screw; 20. Adhesive plate; 21. Strain gauge bridge circuit; 22. Bolt. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0023] First Embodiment

[0024] Please see Figure 1-5 The present invention provides a technical solution: a coaxiality measuring instrument, including a protective housing 1, a connecting plate 2, and a centering sensor elastic body 8. The clamping parts at both ends of the centering sensor elastic body 8 are provided with high-precision threads, and the top end is provided with a first fixing plate 9 and a second fixing plate 10.

[0025] The jaws of the clamps are usually quite hard. During the measurement process, clamping can cause damage to the clamping parts, especially when the clamping pressure is high. After repeated use, misalignment of the clamping axes can be introduced, affecting the coaxiality measurement results. The clamping end of the centering sensor elastomer 8 is designed and machined with high-precision threads and matched with a threaded sleeve. After a certain degree of damage occurs, the matching threaded sleeve is replaced to ensure the accuracy of the measurement results and improve the service life of the coaxiality sensor.

[0026] It also includes a connecting plate 2, on one side of which a protective housing 1 is detachably installed. The first fixing plate 9 and the second fixing plate 10 are both detachably connected to the protective housing 1. The centering sensor elastomer 8 is disposed inside the protective housing 1. The first fixing plate 9 and the second fixing plate 10 are spliced ​​together to form a cover plate that seals the top opening of the second fixing plate 10. A fifth screw 17 adapted to the centering sensor elastomer 8 is provided on the cover plate.

[0027] A first screw 3 is provided at the bottom of the other side of the connecting plate 2, and a threaded hole adapted to the first screw 3 is opened on the other end face of the baffle 4 to improve the stability of the baffle 4 after it is fixed.

[0028] A fourth screw 16 is provided at the bottom of the other side of the connecting plate 2. The other end faces of the first fixing plate 9 and the second fixing plate 10 are both provided with threaded holes that are compatible with the fourth screw 16, thereby improving the stability of the first fixing plate 9 and the second fixing plate 10 after they are fixed.

[0029] The inner wall of the fifth screw 17 is fixedly connected with a retaining strip 11. The top of the surface of the centering sensor elastic body 8 is provided with a retaining groove 12 that matches the retaining strip 11. The bottom of the inner cavity of the protective housing 1 is provided with a baffle 4 that matches the centering sensor elastic body 8. The baffle 4 is provided with a through-hole 5 that matches the centering sensor elastic body 8. The side wall of the centering sensor elastic body 8 is provided with 12 strain gauges 13 that are evenly arranged along its surface.

[0030] The built-in non-measuring strain gauge is in the same environment as the strain gauge 13 on the centering sensor elastic body 8, which avoids measurement errors caused by different environments and improves measurement accuracy.

[0031] Furthermore, a number of fifth screws 17 are provided on one side of the protective housing 1, and a number of threaded holes adapted to the fifth screws 17 are provided on one side of the connecting plate 2.

[0032] Furthermore, a third screw 14 is provided on the top of both the front and rear sides of the protective housing 1, and threaded holes adapted to the third screw 14 are provided on the outer sides of both the first fixing plate 9 and the second fixing plate 10.

[0033] Furthermore, a second screw 6 is provided on the bottom of both the front and rear sides of the protective housing 1, and threaded holes adapted to the second screw 6 are provided on the outer side of the baffle 4.

[0034] Furthermore, a support frame 18 located in the inner cavity of the protective housing 1 is detachably connected to the upper part of one side of the connecting plate 2 via a fifth screw 17. An adhesive plate 20 is detachably installed on the side wall of the support frame 18 via a sixth screw 19. The side wall of the adhesive plate 20 is attached with 36 non-measuring strain gauges, 12 zero-point compensation strain gauges, and 12 zero-point temperature compensation strain gauges, which together with the elastic body 8 form 12 strain gauge bridge circuits 21. The 12 strain gauge bridge circuits 21 correspond one-to-one with the 12 strain gauges 13 and are electrically connected.

[0035] Furthermore, a number of wire clamps 7 are installed on one side of the connecting plate 2 by means of several bolts 22, and the multiple wire clamps 7 are evenly spaced along one side of the protective shell 1.

[0036] Furthermore, a cable connector 15 is fixed inside the cavity of the connecting plate 2. The cable connector 15 is electrically connected to the 12 strain gauge bridge circuits 21, and the wiring terminals of the cable connector 15 extend to the outside of the connecting plate 2.

[0037] Furthermore, the centering sensor elastic body 8 is cylindrical, and the 12 strain gauges 13 are divided into 3 groups. The 3 groups of strain gauges 13 are arranged along the length direction of the centering sensor elastic body 8. Each group has 4 strain gauges 13 distributed at 90-degree intervals around the same cross-section of the centering sensor elastic body 8. The cylindrical centering sensor is divided into threaded connection and V-type clamping.

[0038] The instrument uses three four-channel modules for data acquisition. Each module's four channels acquire data from four bridge circuits at the same cross section, and the power supply voltage for the four bridge circuits at the same cross section is the same voltage. The coaxiality calculation is mainly the ratio of the maximum bending strain to the average axial strain, which improves the accuracy of the measurement results, increases the accuracy and pass rate of the coaxiality sensor, makes the measurement results more reliable, and extends the service life of the coaxiality sensor. Standard switching is used to meet the testing requirements of different standards.

[0039] The working principle of the centering sensor elastic body 8 is based on Hooke's law, which states that strain is proportional to stress. When an axial force is applied to the sensor, the centering sensor elastic body 8 will undergo elastic deformation, thereby generating strain. This strain can be measured by a bridge circuit composed of strain gauges.

[0040] The centering sensor elastomer 8 has a parallel section in the middle with consistent dimensions and uniform strain. The clamping dimensions at both ends are larger than the parallel section, and the strain is concentrated in the parallel section. The clamping section and the parallel section have a smooth transition to prevent stress concentration.

[0041] The strain gauge 13 is a thin and sensitive metal sheet fixed on the centering sensor elastic body 8. When deformation occurs, the resistance value of the strain gauge 13 will change. The magnitude of the strain can be deduced by the change in output.

[0042] The 12 strain gauges 13 arranged on the centering sensor elastomer 8 are all measuring strain gauges. Temperature self-compensating strain gauges that match the thermal expansion coefficient of the centering sensor elastomer 8 are selected to improve measurement accuracy. They are combined with 3 non-measuring strain gauges to form a 1 / 4 bridge.

[0043] Second Embodiment

[0044] Please refer to Figure 6 Unlike the first embodiment described above, the centering sensor elastic body 8 is a thick rectangle (width-to-thickness ratio < 3) and is held by a flat jaw. The 12 strain gauges 13 are divided into 3 groups. The 3 groups of strain gauges 13 are arranged along the length direction of the centering sensor elastic body 8, and the 4 strain gauges 13 in each group are distributed at the center of the four sides of the same cross section of the centering sensor elastic body 8.

[0045] Third Embodiment

[0046] Please refer to Figure 7 Unlike the first embodiment described above, the centering sensor elastic body 8 is a thin rectangle (with a high width-to-thickness ratio) and is held by a flat jaw. The 12 strain gauges 13 are divided into 3 groups. The 3 groups of strain gauges 13 are arranged along the length of the centering sensor elastic body 8. Each group has 4 strain gauges 13, with 2 of them distributed on a wide surface of the same cross section, and they are mirror-symmetrical to the center of the centering sensor elastic body 8.

[0047] Please refer to Figure 8 ST represents the measuring strain gauge; R represents the non-measuring strain gauge; U represents the bridge supply voltage; P+ represents the positive bridge supply voltage; P- represents the negative bridge supply voltage; U0 represents the bridge output; S+ represents the positive bridge output; S- represents the negative bridge output.

[0048] The 1 / 4 bridge requires high-precision matching resistors with low drift and low temperature drift. It uses strain gauges from the same batch, which have high resistance accuracy and the same coefficient of thermal expansion to reduce measurement errors.

[0049] Conventional coaxiality sensors measure strain gauges located on the elastic body, while the matching resistors of the bridge are located in the data acquisition instrument. The electronic components in the measuring instrument generate heat and dissipate heat. Since the strain gauges and matching resistors are in different environments, measurement errors may occur due to environmental influences.

[0050] The software is configured to acquire up to 12 bridge outputs, with three selectable layers (upper, middle, and lower) to meet the requirements of different standards for coaxiality measurement. The protective housing 1 protects the strain gauges 13 on the centering sensor elastomer 8 from damage, while also providing installation space for non-measuring strain gauges.

[0051] The working principle and usage process of this invention: After the invention is installed, when axial force is applied to the sensor, the centering sensor elastic body 8 will undergo elastic deformation, thereby generating strain. This strain can be measured by a bridge circuit composed of strain gauges. The centering sensor elastic body 8 has a parallel section in the middle with consistent dimensions and uniform strain. The clamping dimensions at both ends are larger than the parallel section, and the strain is concentrated in the parallel section. The clamping section and the parallel section have a smooth transition to prevent stress concentration. The instrument uses three four-channel modules for acquisition. The four channels of each module acquire four bridge circuits of the same cross section, and the power supply voltage for the four bridge circuits of the same cross section is the same voltage. The coaxiality calculation is mainly the ratio of the maximum bending strain to the average axial strain, which improves the accuracy of the measurement results, improves the accuracy and pass rate of the coaxiality sensor, and makes the measurement results more reliable.

[0052] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A coaxiality measuring instrument, comprising a protective housing (1), a connecting plate (2), and an alignment sensor elastic body (8), characterized in that: The centering sensor elastomer (8) has high-precision threads at both ends of its clamping parts, and a first fixing plate (9) and a second fixing plate (10) are provided at the top. The connecting plate (2) is provided with a plurality of fifth screws (17), and the inner wall of the fifth screws (17) is fixedly connected with a retaining strip (11). The top of the surface of the centering sensor elastomer (8) is provided with a retaining groove (12) that is compatible with the retaining strip (11). The bottom of the inner cavity of the protective housing (1) is provided with a baffle (4) that is compatible with the centering sensor elastomer (8). The baffle (4) is provided with a through-hole (5) that is compatible with the centering sensor elastomer (8). The surface of the centering sensor elastomer (8) is provided with 12 measuring strain gauges (13) that are evenly arranged along its surface. The first fixing plate (9), the second fixing plate (10), and the baffle (4) are provided with a plurality of threaded holes that are compatible with the fifth screws (17). The upper part of one side of the connecting plate (2) is connected to a support frame (18) located in the inner cavity of the protective shell (1) by a fifth screw (17). The side wall of the support frame (18) is provided with an adhesive plate (20) by a sixth screw (19). The side wall of the adhesive plate (20) is provided with 12 strain gauge bridge circuits (21) consisting of 36 non-measuring strain gauges, 12 zero-point compensation strain gauges and 12 zero-point temperature compensation strain gauges. The 12 strain gauge bridge circuits (21) correspond one-to-one with the 12 measuring strain gauges (13) and are electrically connected. The connecting plate (2) is provided with a number of fifth screws (17), and the first fixing plate (9), the second fixing plate (10), and the baffle (4) are provided with a number of threaded holes that are compatible with the fifth screws (17); The centering sensor elastic body (8) is cylindrical, and the 12 strain gauges (13) are divided into 3 groups. The 3 groups of strain gauges (13) are arranged along the length direction of the centering sensor elastic body (8). Each group of 4 strain gauges (13) are distributed at 90-degree intervals around the same cross-section of the centering sensor elastic body (8).

2. The coaxiality measuring instrument as described in claim 1, characterized in that: The protective housing (1) has a third screw (14) on the top of both the front and rear sides. The outer sides of the first fixing plate (9) and the second fixing plate (10) are provided with threaded holes that are compatible with the third screw (14).

3. The coaxiality measuring instrument as described in claim 1, characterized in that: The protective housing (1) has a second screw (6) on the bottom of both the front and rear sides, and the outer side of the baffle (4) has a threaded hole that matches the second screw (6).

4. The coaxiality measuring instrument as described in claim 1, characterized in that: A number of wire clamps (7) are installed on one side of the connecting plate (2) by means of several bolts (22), and the multiple wire clamps (7) are evenly spaced along one side of the protective shell (1).

5. The coaxiality measuring instrument as described in claim 1, characterized in that: A cable connector (15) located inside the cavity of the connecting plate (2) is fixedly connected to one side of the protective housing (1). The cable connector (15) is electrically connected to the 12 strain gauge bridge circuits (21). The terminal of the cable connector (15) extends to the other side of the protective housing (1).

6. The coaxiality measuring instrument as described in claim 1, characterized in that: The centering sensor elastic body (8) is a thick rectangle. The 12 strain gauges (13) are divided into 3 groups. The 3 groups of strain gauges (13) are arranged along the length direction of the centering sensor elastic body (8). Each group of 4 strain gauges (13) are distributed at the center of the four sides of the same cross section of the centering sensor elastic body (8).

7. The coaxiality measuring instrument as described in claim 1, characterized in that: The centering sensor elastic body (8) is a thin rectangle. The 12 strain gauges (13) are divided into 3 groups. The 3 groups of strain gauges (13) are arranged along the length direction of the centering sensor elastic body (8). Each group of 4 strain gauges (13) are distributed in pairs on a wide surface of the same cross section and are mirror-symmetrical to the center of the centering sensor elastic body (8).

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