A multifunctional reference torque standard machine

In response to the problem of using different single machines to achieve measurement and detection of existing torque instruments, this article introduces a multifunctional reference torque standard and proposes specific steps for torque measurement and detection. This standard machine can be used to detect various existing torque instruments and can solve the problem of using a single machine to achieve the detection of a certain type of torque equipment. After adopting this standard machine and its detection method, experimental data shows that the measurement of the torque transducer can meet the requirements of JJG995-2005 “Static Torque Measuring Machines” and the measurement of the reference torque wrench can meet the requirements of JJG1103-2014 “Reference torque wrench Verification Regulations”.


Introduction
The measurement and testing of existing torque instruments such as torque transducers, reference torque wrenches, torque wrenches, and torque multipliers are usually achieved using different single machines [1] .The equipment investment is large, the land occupation is large, the universality is poor, the usage efficiency is low, and it is difficult to meet the measurement and testing needs of new torque instruments.Moreover, these single machines also face some problems when testing and measuring.
The measurement and detection of the torque transducer adopts a static weight torque standard machine [2] , and its load at each level depends on the mass of the weights, while the mass of each weight is fixed and unchanged, so it cannot achieve torque loading beyond the number of weight combinations.At the same time, its loading efficiency depends on the lifting time of each level of weight, and the more weights are loaded, the lower its loading efficiency is.The metrological detection of reference torque wrenches is achieved by adding a reaction machine [3] to the traditional static weight torque standard machine.However, the existing static weight torque standard machine cannot maintain its lever and the handle of the tested reference torque wrench level, so it cannot offset the influence of gravity on the detection results.The detection results have large errors, which do not meet the technical requirements of the verification regulations, and the metrological risk is high [4] .At the same time, due to the force point being at the handle, rather than coaxial pure torsion, it will generate lateral thrust on the precision support blade and bearing on the lever of the static weight torque standard machine, which will cause structural damage to the static weight standard over time [5] .The internationally recommended method is to use the reference torque standard machine calibration method [6] .The measurement and testing of instruments such as torque wrenches and torque multipliers are carried out using torque wrench calibrators.However, the general range of torque wrench calibrators is ≤ 3 kNm, which cannot meet the testing requirements of torque multipliers ≥ 3 kNm.With technological progress, multifunctional reference torque standard machines have emerged [7][8] , but the supports of the machines mostly adopt a vertical column layout.The upper and lower platforms of the columns need to be kept horizontal, and the columns also need to resist torsional forces.Due to the different lengths of the inspected equipment, the work plane also needs to slide up and down along the column to adjust the working space.This makes the entire reference torque standard machine structurally complex, inconvenient to use, and costly.In addition, due to the heavy weight of the large range torque transducer, some can weigh over 100 kilograms, making it difficult for manual handling.The reference torque standard machine with a vertical column layout is not conducive to installing or disassembling the large range torque transducer on the torque standard machine.At the same time, this machine adopts a single shaft output, and the torque output of the single shaft has a fixed optimal output range, which cannot accommodate a wide measurement range.The range of the torque transducer or torque multiplier being tested is often large, some can reach 10 kNm, while the range of the reference torque wrench being tested is generally ≤ 3 kNm.Single-axis output means that hardware characteristics such as transmission ratio and torque output resolution are fixed and unchanging.The torque output system with high power and high reduction ratio has no problem when detecting large torque, while the torque output will have a large jump when detecting small torque, which is difficult to stabilize and seriously affects the measurement results.On the contrary, a torque output system with low power and low reduction ratio makes it difficult to generate large torque output.
Therefore, in response to the current measurement and testing needs of torque instruments and the shortcomings of existing technology, a dual output multifunctional reference torque standard machine and method are proposed.On a servo control system and a machine, different standard torque instruments can be switched and configured to achieve measurement and testing of coaxial rotating equipment such as torque instruments and torque multipliers with a range of ≤ 10 kNm and an accuracy of ≤ 0.05%.It also achieves the detection of reference torque wrenches and torque wrenches with a range of ≤ 3 kNm and an accuracy of ≤ 0.1%, as well as the measurement and detection of noncoaxial rotating equipment such as other torque tools.It adopts three control modes: computer automatic control, electronic handwheel, and manual button, which can be flexibly selected according to usage habits and work needs.The three modes can be switched at any time, with compact structure, low manufacturing cost, flexible torque output, adjustable loading and unloading speed, and convenient operation.Thereby improving the automation level of torque equipment measurement and detection, improving work efficiency, and improving measurement accuracy through precise automatic control.

Introduction to machine structure design
The multifunctional reference torque standard machine is mainly composed of a servo motor, guide rail, coupling, support seat and support plate, support strip, measuring base slider, steering gear, reducer, steering gear, and computer control system.The basic technical principle is to control the rotation of the servo motor through three modes: computer automatic control, electronic hand wheel, and manual button control.The servo motor drives the rotation of the high-speed ratio planetary reducer.The planetary reducer is a left and right double shaft output structure, which produces two different application functions.The whole process realizes closed-loop control, with a high degree of automation, good system repeatability, and high data accuracy, and can also avoid Personal equations caused by manual operation.The three-dimensional view of the standard machine is shown in Figure 1, the front view is shown in Figure 2, the top view is shown in Figure 3, and the side view is shown in Figure 4.
The multifunctional reference torque standard machine utilizes a dual output shaft reducer to achieve two functional modules, and uses one machine to achieve measurement and detection of various torque equipment.For a better understanding, two typical examples of detecting torque transducers and reference torque wrenches are introduced in the article.Firstly, the state diagrams of the two examples are provided, as shown in Figure 5.

Research on machine function
The multifunctional reference torque standard machine utilizes a dual output shaft reducer to achieve two functional modules, including the following functions: A single machine has been used to achieve measurement and detection of various torque equipment, with low equipment cost, high integration, and small footprint.The first output shaft of the dual output shaft reducer is connected to the first standard torque transducer through a first coupling.The first standard torque transducer rotates coaxially with the first output shaft, and a second coupling is fixed on the first support seat.The second coupling remains coaxial with the first output shaft, and the first support seat can move horizontally along the axial direction of the first output shaft.This functional module is used for torque transducers.The measurement and detection of equipment that can rotate coaxially, such as torque multiplier, adopts a horizontal layout for this functional module, which has higher torsional strength and simple structure.Moreover, compared to the vertical column layout, the work plane needs to slide up and down along the column to adjust the detection space.The horizontal layout adjusts the detection space through the horizontal movement of the first support seat, making the operation easier and more convenient.In addition, the horizontal layout is also conducive to using the driving system to install or remove the large range torque transducer from the torque standard machine.The second output shaft of the dual output shaft reducer is connected to a right angle commutator, which is used to change the output direction to a vertical direction.The output end of the right angle commutator is connected to the second standard torque transducer, and the output end of the second standard torque transducer and the right angle commutator rotate on the same shaft.The end of the second standard torque transducer far from the right angle commutator is sleeved with a first bearing.The first bearing is used to withstand the bending moment generated by the tested equipment during the testing process.The second support seat is set on the top of the dual output shaft reducer.The second support seat is used to fix the handle of the tested reference torque wrench, so that the tested reference torque wrench remains stationary during the testing process.This functional module is used for measuring and testing non-coaxial rotating equipment such as reference torque wrenches and torque wrenches.The two functional modules of this machine are independent of each other.This machine can accurately measure a large number of torque transducers or torque multipliers, as well as small range reference torque wrenches or torque wrenches.This machine can take into account a wide measurement range.
In the structure of the detection machine, the first support seat is installed on the machine table through the first linear guide rail.The centerline of the first linear guide rail is parallel to the axis of the first output shaft, and the first support seat can move horizontally along the first linear guide rail.The first linear guide rail can achieve the axial horizontal movement of the first support seat along the first output shaft, which is conducive to adjusting the detection space through the horizontal movement of the first support seat for detecting different sizes of tested equipment.
In the structure of the detection machine, the support plate is installed on the machine table through a first linear guide rail, and a second bearing is fixed on the support plate.The second bearing is used to withstand the reaction force, and the support plate is used to support and fix the second bearing.
In the structure of the detection machine, the first output shaft is connected to the first coupling through the second bearing.The second bearing is used to withstand the reaction force of the first standard torque transducer and protect the first output shaft.
When measuring and testing the torque multiplier, the side of the first standard torque transducer that is not connected in series with the first output shaft is first connected in series with the support plate, and then connected to the torque multiplier.The support plate bears the reaction force of the torque multiplier, protecting the first standard torque transducer.
The second support seat is installed on the top of the dual output shaft reducer through the second linear guide rail, and can move along the second linear guide rail.The second linear guide rail can move the second support seat along it, which is beneficial for adjusting the position of the second support seat according to the length of the handle of the tested standard torque plate and torque wrench, and for keeping the tested reference torque wrench stationary during the testing process.The second support seat includes a base, a reaction baffle, and a support plate.The base is located on the top of the dual output shaft reducer, and the base is kept horizontal.The reaction baffle is in vertical contact with the base and fixed.The support plate is provided with a through hole, and the reaction baffle penetrates through the through hole.The support plate can move up and down along the reaction baffle.The reaction baffle is used to limit the horizontal movement of the handles of the tested reference torque wrench and torque wrench, so that they remain stationary during the testing process.The support plate is used to support the handles of the tested reference torque wrench and torque wrench, so that they remain horizontal.The support plate can move up and down along the reaction baffle, which is conducive to adjusting the height of the support plate according to the size of different reference torque wrenches and torque wrenches to keep it horizontal.A support strip is set at the contact point between the support plate and the handle of the tested reference torque wrench.A support strip is installed at the contact point between the handle of the support plate and the tested reference torque wrench, reducing the contact area between the handle and the support plate, thereby reducing frictional resistance, and making the output torque transmission of the second standard torque transducer better.At the same time, it can make the tested reference torque wrench and torque wrench easier to return to zero, improving measurement accuracy.
A reaction support bracket was also designed, which is fixed on the top of the right angle commutator.The reaction support bracket is provided with a through hole, and the first bearing is fixed in the through hole.The reaction bracket is used to support and fix the first bearing.
In the structure of the detection machine, the dual output shaft reducer is a dual output shaft planetary reducer.The planetary reducer has a large transmission ratio, small back clearance, low noise, low vibration, and compact structure, and is suitable for occasions that require precision transmission.

Research on machine detection methods
The multifunctional reference torque standard machine also provides a method for measuring and testing torque instruments, including the following steps: For measuring and testing equipment that can rotate coaxially: The tested torque transducer is connected to the second coupling, making sure that the tested torque transducer cannot rotate and remains coaxial with the first output shaft.The first support seat moves horizontally along the axis of the first output shaft on the machine, and the space is adjusted according to the size of the tested torque transducer.After the spatial adjustment is completed, the detected torque transducer is connected to the first standard torque transducer, and the servo motor is turned on.The detected torque transducer and the first standard torque transducer each display data under the torsion force of the servo motor.The data of the detected torque transducer is compared with the data of the first standard torque transducer to obtain the measurement parameters of the detected torque transducer.
For measurement and testing of non-coaxial rotating equipment: The tested reference torque wrench is connected to the second standard torque transducer, the handle of the tested reference torque wrench is placed on the second support seat, and the second support seat is moved according to the size of the tested reference torque wrench to adjust the space.The handle of the tested reference torque wrench is kept horizontal, and the servo motor is turned on.The tested reference torque wrench and the second standard torque transducer each display data under the action of servo motor torque force.The data of the tested reference torque wrench is compared with the data of the second standard torque transducer to obtain the measurement parameters of the tested reference torque wrench.

Experimental results and analysis
A TB2-10 kNm torque transducer produced by HBM company with an accuracy of 0.03% was selected as the first standard sensor in the standard machine, and a TB2-3 kNm torque transducer with an accuracy of 0.03% was selected as the second standard sensor, both of which have been calibrated by German PTB and meet the requirement of 0.03%.The data acquisition instrument matched with the standard sensor is DMP41 produced by HBM company, with an accuracy of 0.0005 level.A T40B-10 kNm (accuracy 0.05%) torque transducer and a TTS-1 kNm (accuracy 0.1%) reference torque wrench were selected for the experiment.The torque transducer and reference torque wrench were measured using a multifunctional reference torque standard machine.Firstly, the torque transducer was installed as shown in Figure 5, and then the indication error of the torque transducer was measured according to the verification regulation of JJG 995-2005 "Static Torque Measuring Machines" [9] .The experimental results after correct measurement and data processing are shown in Table 1 in the following text.Then, the reference torque wrench was installed as shown in Figure 5, and the indication error of the reference torque wrench was measured according to the verification regulation of JJG1103-2014 "Reference Torque Wrench Verification Regulations" [10] .After correct measurement and data processing, the experimental results are shown in Table 2  Data analysis and conclusion: From the experimental data results in Table 1, it can be analyzed that the indication error, repeatability error, and azimuth error of the torque transducer are all ≤ 0.02%, meeting the metrological performance requirement of 0.05 level specified in the JJG 995-2005 "Static Torque Measuring Machines" verification regulation.From the experimental data results in Table 2, it can be analyzed that the indication error, repeatability error, and reproducibility error of the reference torque wrench are all ≤ 0.1%, meeting the metrological performance requirements of level 0.1 specified in the JJG 1103-2014 "Reference Torque Wrench Verification Regulations" verification regulation.Therefore, after adopting the machine and method mentioned in the article, the measurement of the torque transducer and reference torque wrench can meet the requirements.

Conclusion
This article proposes a multifunctional reference torque standard machine and provides a detailed introduction to its structure, functions, and detection methods.This standard machine can be used to detect various existing torque instruments, and can solve the problem of using a single machine to achieve the detection of a certain type of torque equipment.At the same time, experiments were conducted on two typical types of torque equipment, torque gauges and reference torque wrenches.Based on experimental data analysis, the machine can meet the requirements of the verification regulations of JJG 995-2005 "Static Torque Measuring Machines" and JJG 1103-2014 "Reference Torque Wrench Verification Regulations", respectively.However, it should also be noted that such reference torque standard machines have very high requirements for supporting standard sensors and data acquisition instruments, and their accuracy and long-term stability should preferably be 5 times higher than that of the double measuring object.This has become an important factor restricting the development of such machines towards higher accuracy.This solution integrates multiple detection functions, reduces manufacturing costs, and is suitable for use as a standard machine of level 0.05 or 0.1.It can meet the detection needs of the vast majority of torque measuring instruments, and has good application prospects and promotion value.

Figure 1 .
Figure 1.3D view of standard machine.

Figure 2 .
Figure 2. Front view of standard machine.

Figure 5 .
Figure 5. State diagram of standard machine detecting torque transducer and reference torque wrench.

Table 1 .
below.Measurement data of torque transducer.
whereX is mean value,  is relative deviation, R is repeatability, and Rot is relative orientation error.

Table 2 .
Measurement data of reference torque wrench. is relative deviation, ′ is repeatability under maximum lever length, and  is reproducibility under maximum lever length.