Material testing machine

Abstract

The purpose of the present invention is to provide a material testing machine capable of reducing the influence of noise. A material testing machine (1, 2) is provided with: a measurement unit (22, 142) that converts a force applied to a subject (100) into an electric signal; and an amplification / conversion unit (23, 159) including an amplification unit (24, 154) for amplifying the electrical signal and an AD conversion unit (25, 155) for digitizing the electrical signal amplified by the amplification unit (24, 154), the amplification / conversion unit (23, 159) being configured integrally with the measurement unit (22, 142) or separately from the measurement unit (22, 142) and disposed in the vicinity of the measurement unit (22, 142).

Description

Technical Field

[0001] The invention relates to a material testing machine. Background Art

[0002] A material testing machine that performs a tensile test, a compression test, etc. on a test object is known (for example, see Patent Document 1). The material testing machine of Patent Document 1 is equipped with a load cell that converts a load applied to the test object into an electrical signal. Prior art literature Patent Literature

[0003] Patent Document 1: Japanese Patent Application Publication No. 2018-17579 Summary of the invention Problems to be solved by the invention

[0004] Generally, in a material testing machine such as Patent Document 1, a load cell is connected to a control unit that processes an electrical signal from the load cell via a communication line. Therefore, when the electrical signal is transmitted via the communication line, it may be affected by noise at a level that cannot be ignored.

[0005] Therefore, one of the objects of the present invention is to provide a material testing machine capable of reducing the influence of noise. Solutions for solving problems

[0006] The present invention is a material testing machine for performing material tests on a test object, characterized in that it comprises: a measuring unit that converts the force applied to the test object into an electrical signal; and an amplifying and converting unit, including an amplifying unit that amplifies the electrical signal and an AD converting unit that digitizes the electrical signal amplified by the amplifying unit, the amplifying and converting unit being integrally formed with the measuring unit or separately formed from the measuring unit and arranged near the measuring unit.

[0007] It should be noted that the amplification conversion unit and the measurement unit may be integrally formed.

[0008] Alternatively, the amplification conversion unit may be formed separately from the measuring unit and connected to the measuring unit, and the measuring unit and the amplification conversion unit may be fixed to the moving crosshead of the material testing machine. In this case, the amplification conversion unit may be fixed to the moving crosshead via a buffer or to the top surface of the moving crosshead.

[0009] Furthermore, the measuring unit and the amplifying and converting unit may be driven by alternating current.

[0010] In addition, the material testing machine may further include a cable, the cable connecting the amplification conversion unit and the control unit, wherein the control unit processes the digital signal output from the amplification conversion unit. In this case, the cable may have a core wire and one or more layers of shielding, wherein the shielding reduces the influence of noise on the core wire, the cable may be a twisted pair cable, and the cable may be wired in a manner that bends when the moving crosshead of the material testing machine is at the farthest distance from the control unit.

[0011] In addition, the material testing machine may include a calculation processing unit integrally formed with the amplification and conversion unit, and the measuring unit may be included in a force sensor having a memory, wherein the memory stores data for calibrating the material testing machine, and when the force sensor is connected to the amplification and conversion unit, the calculation processing unit reads the data from the memory of the force sensor to calibrate the material testing machine.

[0012] Furthermore, the material testing machine may be a tension-compression testing machine for performing a tension test and a compression test on the object to be tested. Effects of the Invention

[0013] According to the present invention, there is provided a material testing machine capable of reducing the influence of noise. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a diagram schematically showing a material testing machine according to the first embodiment of the present invention. Figure 2 yes Figure 1 The shown block diagram of the material testing machine mainly shows the functional blocks of the force sensor unit and the control unit. Figure 3 This is a diagram showing an example of a cable. Figure 4 This is a diagram showing another example of the cable. Figure 5 It is a diagram schematically showing a material testing machine according to a second embodiment of the present invention. Figure 6 yes Figure 5 The shown block diagram of the material testing machine mainly shows the functional blocks of the force sensor unit and the control unit. DETAILED DESCRIPTION

[0015] The following, with the attached Figure 1The following examples illustrate the methods for implementing the material testing machine of the present invention. The embodiments illustrated below are for the purpose of facilitating the understanding of the present invention and are not intended to limit the interpretation of the present invention. The present invention can be changed and improved according to the following embodiments without departing from its main purpose. In addition, in the above-mentioned drawings, the size of each component is sometimes shown in an exaggerated or reduced manner for the sake of ease of understanding.

[0016] (First Embodiment) Figure 1 Schematic diagram of a material testing machine according to this embodiment. Figure 1 As shown, the material testing machine 1 of the present embodiment is a tension and compression testing machine, and includes a base 12, a top surface 15 parallel to the base 12, a pair of frames 10A and 10B, a moving crosshead 11, a load cell unit 20, and a control unit 30 as main structures. The material testing machine 1 is used in a state where the base 12 faces downward in the vertical direction and the top surface 15 faces upward in the vertical direction.

[0017] A pair of frames 10A and 10B are perpendicular to the base 12 and the top surface 15, and extend from the base 12 to the top surface 15. A ball screw is contained in each of the frames 10A and 10B. The ball screws contained in the frames 10A and 10B are connected to a driving unit 16 such as a motor via various gear mechanisms, and the driving unit 16 drives the ball screws contained in the frames 10A and 10B to rotate synchronously with each other.

[0018] The movable crosshead 11 is a plate-shaped member parallel to the base 12 and the top surface 15, and includes a main surface 11D on the side of the base 12, a main surface 11U on the side of the top surface 15, a side surface 11R on the side of the frame 10A, and a side surface 11L on the side of the frame 11B. In the present embodiment, the height H from the main surface 11U to the main surface 11D of the movable crosshead 11 is approximately less than 1 / 2 of the width W from the side surface 11R to the side surface 11L of the movable crosshead 11. However, the ratio of the height H to the width W is not limited thereto. The side surface 11R of the movable crosshead 11 is mounted on the ball screw accommodated in the frame 10A via an unillustrated mounting mechanism. Similarly, the side surface 11L is also mounted on the ball screw accommodated in the frame 10B via an unillustrated mounting mechanism. Therefore, when the driving unit 16 drives and rotates the ball screws contained in the frames 10A and 10B, respectively, the movable crosshead 11 moves along the long dimension direction of the frames 10A and 10B (i.e., the base 12 side or the top surface 15 side) as the ball screws rotate. It should be noted that in the present embodiment, the movable crosshead 11 is controlled to move between the upper limit position (highest reachable position) 10U and the lower limit position 10D in the frames 10A and 10B.

[0019] A load cell unit 20 is mounted on one of the main surface 11D and the main surface 11U of the moving crosshead 11. In the present embodiment, the load cell unit 20 is mounted substantially in the center of the main surface 11D. The load cell unit 20 has a housing 21 in which electronic components constituting various functional blocks described later are stored or installed.

[0020] A first jig 17 constituting a test jig 19 is mounted on the load cell unit 20. A second jig 18 constituting the test jig 19 is mounted on a portion of the base 12 that faces the first jig 17. Figure 1 In the example of , the first clamp 17 is configured to hold one side of the test object 100, and the second clamp 18 is configured to hold the other side of the test object 100. Therefore, when the moving crosshead 11 moves to the upper limit position 10U side, the test object 100 is stretched, and when the moving crosshead 11 rises to a specified position, the test object 100 breaks. The material testing machine 1 can measure the test force when the test object 100 breaks and other various characteristics of the test object 100 related to tension, thereby functioning as a tensile testing machine. On the other hand, the first clamp 17 and the second clamp 18 of the test clamp 19 can also be replaced with pressure plates respectively. In this case, the test object 100 is clamped between the moving crosshead 11 and the base 12 via a pair of pressure plates, and when the moving crosshead 11 moves to the lower limit position 10D side, the test object 100 is compressed, and when the moving crosshead 11 descends to a specified position, the test object 100 is compressed and broken. In this case, the material testing machine 1 can function as a compression testing machine by measuring the test force when the test object 100 is compressively broken and other various characteristics of the test object 100 related to compression. In this way, the material testing machine 1 of this embodiment is configured as a tension-compression testing machine.

[0021] Figure 2 1 is a block diagram mainly showing functional blocks of the load cell unit 20 and the control unit 30 of the material testing machine 1. Figure 2 As shown, the load cell unit 20 includes, for example, a power supply unit 28, a measuring unit voltage generator 29, a measuring unit 22, an amplifying and converting unit 23, a processing unit 26, and a driver unit 27 as main functional blocks. That is, in this embodiment, the measuring unit 22 and the amplifying and converting unit 23 are integrally formed.

[0022] The power supply unit 28 supplies the DC or AC power supplied from the external power supply 40 to the measuring unit voltage generating unit 29, the amplifying and converting unit 23 (i.e., the amplifying unit 24 and the AD converting unit 25 described later), the arithmetic processing unit 26, the driver unit 27, etc. That is, the measuring unit 22 and the amplifying and converting unit 23 are driven by the DC or AC.

[0023] It should be noted that the power supply unit 28 may convert the power supplied from the external power supply 40 into power that can be used by the measurement unit voltage generator 29, the amplification conversion unit 23, the calculation processing unit 26, and the driver unit 27 by converting the DC and AC of the power supplied from the external power supply 40. The measurement unit voltage generator 29 converts the power supplied from the power supply unit 28 into power that can be used by the measurement unit 22. It should be noted that when the measurement unit 22 can directly use the power supplied from the power supply unit 28, the measurement unit voltage generator 29 is not an essential structure in the material testing machine 1.

[0024] In this embodiment, the measuring unit 22 includes a strain gauge. In addition, the first fixture 17 constituting the test fixture 19 is connected to the measuring unit 22. Therefore, as the moving crosshead 11 moves and the test object 100 is stretched or compressed by the test fixture 19, strain is generated in the strain gauge of the measuring unit 22. The strain gauge is a part of the Wheatstone bridge circuit, and the change in resistance caused by the strain generated in the strain gauge is converted into a voltage via the Wheatstone bridge circuit. The voltage signal (electrical signal) from the measuring unit 22 is output to the amplification conversion unit 23.

[0025] The amplifying and converting section 23 includes an amplifying section 24 and an AD converting section 25. The amplifying section 24 amplifies the electrical signal output from the measuring section 22, and outputs the amplified electrical signal to the AD converting section 25. Then, the AD converting section 25 converts the amplified electrical signal into a digital signal, and outputs the digital signal to the arithmetic processing section 26. In this way, the load cell unit 20 of the material testing machine 1 is configured as a so-called digital load cell in which the measuring section 22 and the amplifying and converting section 23 are integrated.

[0026] The calculation processing unit 26 is composed of, for example, a CPU (Central Processing Unit). The calculation processing unit 26 outputs the digital signal output from the AD conversion unit 25 to the driver unit 27. The driver unit 27 is connected to a cable 60 (see Figure 1 ). It should be noted that the operation processing unit 26 can also convert the digital signal output from the AD conversion unit 25 into a specified format as needed, and output the converted signal to the cable 60. In addition, the operation processing unit 26 can also comprehensively control the various parts of the force sensor unit 20. In this case, the operation processing unit 26 can control the force sensor unit 20 according to the instructions (control instructions) represented by the control signal from the control unit 30.

[0027] The driver unit 27 outputs the digital signal (or a signal converted from the digital signal) to the cable 60 in a format corresponding to the communication method between the load cell unit 20 and the control unit 30. For example, the driver unit 27 outputs the digital signal to the cable 60 as serial data such as RS-232C or RS-422 / 485.

[0028] like Figure 1 As shown, the cable 60 connects the force sensor unit 20 and the control unit 30. That is, the amplification conversion unit 23 and the control unit 30 are connected via the cable 60. The cable 60 is a cable that transmits the digital signal output from the amplification conversion unit 23 to the control unit 30. For example, as the cable 60, a communication cable commonly available in the communication standard of RS-232C or RS-422 / 485 can also be used. The cable 60 has: a first section 61, extending from the force sensor unit 20 along the moving crosshead 11 to the frame 10A; a second section 62, which is wired along the outer wall of the frame 10A, etc.; and a third section 63, which connects the end of the second section 62 on the opposite side of the end on the first section 61 side to the control unit 30. The second section 62 is a section that connects the first section 61 and the third section 63. It should be noted that, Figure 1 The wiring in is an example. For example, in Figure 1 In the embodiment, the cable 60 passes through the front side of the frame 10A (i.e., the front side of the material testing machine 1). However, the cable 60 may be routed through the rear side of the frame 10A (i.e., the back side of the material testing machine 1). The cable 60 may be routed so as to be "flexible" as described below, and the routing path, routing method, and length of the cable 60 are not particularly limited.

[0029] like Figure 1 As shown, the second section 62 of the cable 60 is bent. Figure 1 In the example, when the moving crosshead 11 is located at the upper limit position 10U, the second section 62 and the third section 63 are bent and do not extend in a straight line. In this way, in the material testing machine 1 of the present embodiment, even when the moving crosshead 11 is at the farthest distance from the control unit 30 (that is, when the moving crosshead 11 is at the upper limit position 10U which is the highest reachable position), the cable 60 is in a bent state. It should be noted that the magnitude of the bend of the cable 60 and the portion of the cable 60 that is bent can be appropriately determined within the range that does not hinder the original function of the material testing machine 1, such as the movement of the moving crosshead. For example, as a Figure 1 In a different example, the cable 60 may be bent in the first section 61 .

[0030] In addition, the cable 60 may be a cable that has not been subjected to special shielding processing for reducing the influence of noise. More specifically, the cable 60 may be, for example, Figure 3 The coaxial cable shown in FIG. The coaxial cable is composed of a core wire 601 for transmitting a digital signal output from the amplifying and converting section 23, an insulator 602 covering the core wire 601, a shield 603 covering the insulator 602, and a sheath 604 covering the shield 603. The shield 603 is composed of, for example, a conductor, so as to reduce the influence of noise on the core wire 601. In this way, Figure 3 The cable 60 shown is a cable that has one or more shielding members for reducing the influence of noise on the core wire 601, and does not perform special shielding processing for reducing the influence of noise and / or does not provide an additional shielding member. In addition, as another example, the cable 60 may also be a cable that has one or more shielding members for reducing the influence of noise on the core wire 601. Figure 4 The twisted pair cable shown in FIG. The twisted pair cable is composed of the following parts: a pair of core wires 611, which are twisted together and transmit the digital signal output from the amplification conversion unit 23; an insulator 612, which covers the pair of core wires 611; a shield 613, which covers the insulator 612; and a sheath 614, which covers the shield 613. The shield 613 is composed of a conductor, for example, to reduce the influence of noise on the pair of core wires 611. In this way, Figure 4 The cable 60 shown is a cable that has one or more shields for reducing the influence of noise on a pair of core wires 611 , and is not subjected to special shielding processing for reducing the influence of noise.

[0031] return Figure 2 The control unit 30 has a power supply unit 35, a driver unit 31, a processing unit 32, a control unit 33, and a memory 34 as main functional blocks. The power supply unit 35 is connected to an external power supply 40, and supplies the power supplied from the external power supply 40 to the driver unit 31, the processing unit 32, the control unit 33, the memory 34, etc.

[0032] The driver unit 31 is connected to the driver unit 27 of the load cell unit 20 via the cable 60, and receives the digital signal outputted from the driver unit 27 of the load cell unit 20. For example, when the driver unit 31 receives the digital signal as serial data, it may convert it into parallel data. The driver unit 31 outputs the digital signal to the arithmetic processing unit 32.

[0033] The calculation processing unit 32 is composed of, for example, a CPU, and converts the input digital signal into digital data, and converts the digital data into analog data representing various characteristics (e.g., tensile strength, compressive strength, etc.) of the specimen 100 by referring to various tables stored in the memory 34. The calculation processing unit 32 outputs the analog data to the control unit 33. It should be noted that the memory 34 includes a ROM (Read Only Memory), a RAM (Random Access Memory), and the like.

[0034] The control unit 33 is composed of, for example, a CPU, and controls the material testing machine 1. Specifically, the control unit 33 stores the simulation data input from the calculation processing unit 32 in the memory 34, or reads the simulation data stored in the memory 34 as needed and displays the simulation data on the display unit 50 composed of a display or the like, or Figure 1 The operation of the drive unit 16 shown is controlled.

[0035] In this way, the control unit 30 processes the digital signal output from the amplification conversion unit 23 of the load cell unit 20, and displays or manages the data detected by the measurement unit 22 of the load cell unit 20. It should be noted that the control unit 33 can also issue a control instruction to the load cell unit 20. In this case, the control unit 33 establishes a control instruction to the load cell unit 20, and outputs the control instruction to the calculation processing unit 32. It should be noted that the "control instruction" mentioned here is, for example, an instruction to adjust the zero point / span of the calculation processing unit 26 of the load cell unit 20. It is an instruction to start or end the measurement of the measurement unit 22. The calculation processing unit 32 converts the control instruction received from the control unit 33 into a control signal, and outputs it to the driver unit 31. The driver unit 31 outputs the control signal received from the calculation processing unit 32 to the driver unit 27 of the load cell unit 20.

[0036] As described above, the material testing machine 1 of the present embodiment comprises: (i) a measuring unit 22 for converting a force applied to the specimen 100 into an electrical signal; and (ii) an amplifying and converting unit 23, including an amplifying unit 24 for amplifying the electrical signal and an AD converting unit 25 for digitizing the amplified electrical signal, wherein the amplifying and converting unit 23 is integrally formed with the measuring unit 22.

[0037] According to the material testing machine 1 having such a structure, the electric signal generated in the measuring unit 22 is converted into a digital signal before being output from the load cell unit 20 to the cable 60 (that is, in the load cell unit 20). In addition, as described above, since the cable 60 from the load cell unit 20 to the control unit 30 has a certain length, the electric signal may be affected by noise during transmission in the cable 60. In this case, if the electric signal is an analog signal, due to the influence of noise, an error that cannot be ignored may occur between the data represented by the analog signal reaching the control unit 30 and the data measured by the measuring unit 22. However, according to the material testing machine 1 of this embodiment, the data measured by the measuring unit 22 is converted into a digital signal in the load cell unit 20 and then transmitted to the control unit 30. Therefore, compared with the case where the data is transmitted to the control unit 30 in the state of an analog signal, the influence of noise on the electric signal generated in the measuring unit 22 is reduced. Therefore, according to the material testing machine 1, the frequency of the error between the data measured by the measuring unit 22 and the data processed by the control unit 30 and / or the error itself can be reduced. In addition, in such a material testing machine 1, the influence of noise can be further reduced by performing additional filtering processing on the analog signal output by the measuring unit 22 and / or the digital signal output by the amplifying and converting unit 23, or performing additional shielding processing on various wirings including the cable 60. As a result, the material testing machine 1 can obtain more reliable measurement data (i.e., measurement data with high stability and accuracy).

[0038] As described above, according to the material testing machine 1, the influence of noise in the cable 60 is reduced. Therefore, according to the material testing machine 1, regardless of the structure and material of the cable used, highly reliable measurement data can be obtained. For example, in the previous material testing machine, in view of the influence of noise, it is difficult to use a cable that has not been specially shielded to reduce the influence of noise (for example, a cable with only one layer of shielding or a single winding shield, etc.). On the other hand, according to the material testing machine 1, even in the case of using such a type of cable that is difficult to use in the previous material testing machine as the cable 60, the influence of noise can be reduced, thereby obtaining highly reliable measurement data. In addition, according to the material testing machine 1, as described above, since a cable that has been specially shielded (i.e., a relatively expensive cable) is not necessary, the manufacturing cost of the material testing machine 1 as a whole can be reduced.

[0039] In addition, when the load cell unit 20 is driven by AC, since the signal output from the load cell unit 20 is also AC, it is more susceptible to the parasitic capacitance of the cable 60 than when the signal is DC. In addition, the longer the cable 60 is, the larger the parasitic capacitance is. In this way, when the signal is AC, the influence of the noise caused by the parasitic capacitance of the cable 60 may become larger. However, as described above, according to the material testing machine 1, since the electrical signal from the measuring section 22 is converted into a digital signal in the load cell unit 20, even when the signal is AC, the influence of the noise caused by such parasitic capacitance can be reduced. Therefore, in the material testing machine 1, even if the measuring section 22 and the amplification conversion section 23 of the load cell unit 20 are driven by AC, measurement data with high reliability (i.e., measurement data with high stability and accuracy) can be obtained. That is, according to the material testing machine 1, the disadvantages of the case where the load cell unit 20 is driven by AC can be reduced, and AC driving can be achieved. When the load cell unit 20 is driven by AC, for example, when the current supply to the load cell unit 20 is forcibly cut off, the current can be cut off at the timing of the current zero point, which can have the effect of suppressing the load applied to the electrical system of the material testing machine 1.

[0040] In addition, when the load cell unit 20 is driven by AC, by setting the cable 60 as, for example Figure 4 The twisted pair cable shown can further reduce the influence of the above-mentioned parasitic capacitance. However, even when the load cell unit 20 is driven by direct current, the influence of the parasitic capacitance can be reduced by using the twisted pair cable as the cable 60.

[0041] Furthermore, as described above, according to the material testing machine 1, when the moving crosshead 11 is located at the upper limit position 10U (the highest reach position), that is, when the moving crosshead 11 is at the farthest distance from the control unit 30, there is a deflection in the cable 60. Therefore, according to the material testing machine 1, it is possible to prevent excessive tensile tension from being applied to the cable 60 when the moving crosshead 11 reaches the upper limit position 10U. In addition, it can generally be expected that the longer the cable length of the material testing machine, the greater the influence of noise. Therefore, compared with the case where the cable of the material testing machine does not have deflection, in the case where the above-mentioned deflection exists, the influence of noise may increase. However, in the material testing machine 1, since the influence of noise is reduced as described above, the cable 60 can be made to have such deflection while reducing the influence of noise.

[0042] (Second Embodiment) Next, a material testing machine according to a second embodiment will be described. Figure 5 Schematic diagram of a material testing machine according to the present embodiment. Figure 5As shown, the material testing machine 2 of this embodiment has substantially the same structure as the material testing machine 1 of the first embodiment, except that the structure of the load cell unit is different from the load cell unit 20 of the material testing machine 1 of the first embodiment. Therefore, in the following, with respect to the material testing machine 2, points related to the load cell unit will be described, and other structures are denoted by the same reference numerals as those of the first embodiment and descriptions thereof will be omitted.

[0043] like Figure 5 As shown, the load cell unit 120 of the present embodiment includes: a load cell 140 mounted on the main surface 11D on the base 12 side of the moving crosshead 11; and a signal processing unit 150 mounted on the main surface 11U on the top surface 15 side of the moving crosshead 11. In this way, in the material testing machine 2 of the present embodiment, the load cell 140 having the measuring unit 142 described later and the signal processing unit 150 having the amplifying unit 154 and the AD converting unit 155 described later are separately configured. Both the load cell 140 and the signal processing unit 150 are fixed to the moving crosshead 11.

[0044] The load cell 140 has a housing 141 in which electronic components constituting various functional blocks described below of the load cell 140 are stored or installed. The signal processing unit 150 has a housing 151 in which electronic components constituting various functional blocks described below of the signal processing unit 150 are stored or installed.

[0045] The force sensor 140 and the signal processing unit 150 are connected by the wiring 121. The length of the wiring 121 is extremely short compared to the cable 60. For example, the wiring 121 may be less than the length of the second section 62 of the cable 60, and further may be less than the length of the first section 61 of the cable 60. Since both the force sensor 140 and the signal processing unit 150 are fixed to the moving crosshead 11, the force sensor 140 and the signal processing unit 150 are arranged near the extent that they can be connected by the wiring 121 which is extremely short compared to the length of the cable 60.

[0046] It should be noted that, in the present embodiment, the signal processing unit 150 is fixed to the moving crosshead 11 via the buffer 122. For example, a vibration-proof and / or shock-resistant rubber can be used as the buffer 122. More specifically, for example, polyurethane rubber, silicone rubber, or foam rubber of these rubbers can be used as the buffer 122. The shape of the buffer 122 is not particularly limited, for example, the buffer 122 can be in a pad-like shape.

[0047] Figure 6 1 is a block diagram mainly showing functional blocks of the load cell unit 120 and the control unit 30 of the material testing machine 2 .

[0048] like Figure 6 As shown, the force sensor 140 has a measuring unit 142, a memory 143, and a connector 144 as main functional blocks. It should be noted that each unit of the force sensor 140 is driven by power obtained from the signal processing unit 150 via the connector 144. The measuring unit 142 is driven by direct current or alternating current. The end of one side of the wiring 121 is connected to the connector 144.

[0049] In this embodiment, the measuring unit 142 includes a strain gauge. In addition, the first fixture 17 constituting the test fixture 19 is connected to the measuring unit 142. Therefore, as the moving crosshead 11 moves and the test object 100 is stretched or compressed by the test fixture 19, strain is generated in the strain gauge of the measuring unit 142. The strain gauge is a part of the Wheatstone bridge circuit, and the change in resistance caused by the strain generated in the strain gauge is converted into a voltage via the Wheatstone bridge circuit. The voltage signal (electrical signal) from the measuring unit 142 is output to the connector 144.

[0050] The memory 143 includes ROM, RAM, etc., and stores data (tables) for calibrating the material testing machine 2. For example, the memory 143 stores a table that establishes a correspondence between an input voltage to a Wheatstone bridge circuit in a force sensor 140 equipped with the memory 143 and an output voltage of the Wheatstone bridge circuit with respect to the input voltage. The memory 143 is connected to a connector 144.

[0051] The signal processing unit 150 includes, for example, a power supply unit 158, a voltage generator for a measuring unit 153, an amplifier and converter unit 159, an operation processing unit 156, a driver unit 157, and a connector 152 as main functional blocks. The power supply unit 158 ​​supplies DC or AC power supplied from the external power supply 40 to the voltage generator for a measuring unit 153, the amplifier and converter unit 159 (that is, the amplifier 154 and the AD converter unit 155 described later), the AD converter unit 155, the operation processing unit 156, and the driver unit 157. That is, the amplifier and converter unit 159 is driven by DC or AC.

[0052] It should be noted that the power supply unit 158 ​​can also convert the DC and AC power supplied from the external power supply 40, and convert the power from the external power supply 40 into power that can be used by the voltage generating unit 153 for the measuring unit, the amplification conversion unit 159, the operation processing unit 156 and the driver unit 157.

[0053] The measuring unit voltage generator 153 converts the power supplied from the power supply unit 158 ​​into power that can be used by the measuring unit 142 (and the memory 143) of the load cell 140. The measuring unit voltage generator 153 supplies the converted power to the load cell 140 via the connector 152. It should be noted that, when the measuring unit 142 (and the memory 143) can directly use the power supplied from the power supply unit 158, the measuring unit voltage generator 153 is not an essential structure in the material testing machine 2.

[0054] The other end of the wiring 121 is connected to the connector 152. Therefore, the electrical signal from the measuring unit 142 of the force sensor 140 and the data from the memory 143 are input to the connector 152 via the connector 144 of the force sensor 140 and the wiring 121. The connector 152 outputs the input electrical signal and / or data to the amplification conversion unit 159. In addition, the connector 152 outputs the power input from the measuring unit voltage generating unit 153 to the connector 144 of the force sensor 140. Thus, power is supplied to the force sensor 140.

[0055] The amplification conversion unit 159 includes an amplifier 154 and an AD conversion unit 155. The amplifier 154 amplifies the electrical signal input from the measurement unit 142 of the force sensor 140, and outputs the amplified electrical signal to the AD conversion unit 155. Then, the AD conversion unit 155 converts the amplified electrical signal into a digital signal, and outputs the digital signal to the operation processing unit 156.

[0056] Thus, in the load cell unit 120 of the material testing machine 2, the signal processing unit 150 is separately configured from the measuring unit 142, and the signal processing unit 150 is connected to the measuring unit 142 via the connector 152 and the connector 144. In addition, the signal processing unit 150 is arranged near the measuring unit 142 (that is, near the load cell 140). The specific distance of "near" mentioned here is not particularly limited, but it is ideal to arrange the load cell 140 and the signal processing unit 150 in such a manner that the distance from the load cell 140 to the signal processing unit 150 is shorter than the distance from the signal processing unit 150 to the control unit 30.

[0057] The operation processing unit 156 of the signal processing unit 150 is composed of, for example, a CPU. When a digital signal is input from the AD conversion unit 155, the operation processing unit 156 reads data (table) for calibrating the material testing machine 2 from the memory 143 of the load cell 140, and refers to the table to correct the voltage value represented by the digital signal input from the AD conversion unit 155 to a predetermined voltage value. That is, the operation processing unit 156 calibrates the material testing machine 2 based on the data from the memory 143. Then, the operation processing unit 156 outputs the calibrated digital signal to the driver unit 157. It should be noted that it is also possible to calibrate the electrical signal output from the connector 152 before the electrical signal is processed in the amplifier 154 and the AD conversion unit 155. In addition, the operation processing unit 156 can also control the various parts of the load cell unit 120 in a comprehensive manner. In this case, the operation processing unit 156 can also control the load cell unit 120 according to the control instruction from the control unit 30.

[0058] The cable 60 is connected to the driver unit 157. The driver unit 157 outputs a digital signal to the cable 60. The driver unit 157 outputs the digital signal (or the signal converted from the digital signal) input from the calculation processing unit 156 to the cable 60 in a form corresponding to the communication method between the signal processing unit 150 and the control unit 30. For example, the driver unit 157 outputs the digital signal to the cable 60 as serial data such as RS-232C or RS-422 / 485. Then, similarly to the material testing machine 1 of the first embodiment, the serial data is transmitted through the cable 60 and input to the driver unit 31 of the control unit 30.

[0059] As described above, the material testing machine 2 of the present embodiment comprises: a measuring unit 142, which converts the force applied to the specimen 100 into an electrical signal; and an amplifying and converting unit 159, which includes an amplifying unit 154 for amplifying the electrical signal and an AD converting unit 155 for digitizing the electrical signal amplified by the amplifying unit 154, wherein the amplifying and converting unit 159 is separately constructed from the measuring unit 142, and the amplifying and converting unit 159 is arranged near the measuring unit 142.

[0060] According to the material testing machine 2 having such a structure, the electric signal generated in the measuring section 142 is converted into a digital signal before being output from the load cell unit 120 to the cable 60 (that is, in the load cell unit 120). It should be noted that in the material testing machine 2, the amplification conversion section 159 is configured separately from the measuring section 142, but as described above, since the amplification conversion section 159 is arranged near the measuring section 142, the electric signal generated in the measuring section 142 is not easily affected by noise when it is transmitted in the wiring 121. In addition, according to the material testing machine 2, the data measured by the measuring section 142 is converted into a digital signal in the amplification conversion section 159 and then transmitted to the control unit 30. Therefore, compared with the case where the data measured by the measuring section 142 is transmitted to the control unit 30 in the form of an analog signal, the influence of noise on the electric signal generated in the measuring section 142 is reduced. Therefore, according to the material testing machine 2, the frequency of error generation between the data measured by the measuring section 142 and the data processed by the control unit 30 and / or the error itself can be reduced. Furthermore, the influence of noise can be further reduced by performing filtering and shielding processing on such a material testing machine 2. Thus, the material testing machine 2 can obtain more reliable measurement data (ie, more stable and accurate measurement data).

[0061] Furthermore, according to the material testing machine 2, the influence of noise is reduced as described above, similarly to the material testing machine 1. Therefore, according to the material testing machine 2, regardless of the structure and material of the cable used, highly reliable measurement data can be obtained. For example, in the conventional material testing machine, in view of the influence of noise, it is difficult to use a cable that has not undergone special shielding processing for reducing the influence of noise (for example, a cable having only one layer of shielding or a single winding shield, etc.). On the other hand, according to the material testing machine 2, even in the case of using such a type of cable that is difficult to use in the conventional material testing machine as the cable 60, the influence of noise can be reduced, thereby obtaining highly reliable measurement data. Furthermore, according to the material testing machine 2, as described above, since a cable that has undergone special shielding processing (i.e., a relatively expensive cable) is not necessary, the overall manufacturing cost of the material testing machine 2 can be reduced.

[0062] Furthermore, according to the material testing machine 2, the influence of noise due to the parasitic capacitance of the cable 60 is reduced similarly to the material testing machine 1. Therefore, in the material testing machine 2, it is relatively easy to drive the load cell unit 120 with alternating current.

[0063] In addition, when the load cell unit 120 is driven by AC, the cable 60 is provided as, for example, Figure 4The twisted pair cable shown can further reduce the influence of the above-mentioned parasitic capacitance. However, even when the load cell unit 120 is driven by direct current, the influence of the parasitic capacitance can be reduced by making the cable 60 a twisted pair cable.

[0064] Furthermore, according to the material testing machine 2, similarly to the first embodiment, when the moving crosshead 11 is located at the upper limit position 10U (the highest reaching position), that is, when the moving crosshead 11 is at the farthest distance from the control unit 30, there is a deflection in the cable 60. Therefore, according to the material testing machine 2, it is possible to prevent an excessive tensile tension from being applied to the cable 60 when the moving crosshead 11 reaches the upper limit position 10U.

[0065] Furthermore, in the material testing machine 2, as described above, the load cell 140 including the measuring unit 142 has a memory 143 storing data for calibrating the material testing machine 2, and when the load cell 140 and the signal processing unit 150 are connected, the arithmetic processing unit 156 of the signal processing unit 150 reads the data from the memory 143 of the load cell 140, thereby calibrating the material testing machine 2. That is, the load cell unit 120 of the material testing machine 2 has a so-called plug and play function. With such a structure, when the load cell 140 is replaced with a new load cell 140, the trouble of manually calibrating the new load cell 140 to fit the material testing machine 2 is omitted. However, it is not essential that the load cell unit 120 has a plug and play function.

[0066] In addition, the material testing machine 2 has a structure in which the signal processing unit 150 including the amplifying and converting section 159 is fixed to the moving crosshead 11 via the buffer 122. With such a structure, it is possible to suppress the transmission of vibration and impact from the moving crosshead 11 to the substrate on which the amplifying section 154 and the AD converting section 155 are installed. However, the buffer 122 is not essential.

[0067] As mentioned above, although the present invention has been described by taking the above-mentioned embodiment as an example, the present invention is not limited thereto.

[0068] For example, in the above-mentioned second embodiment, an example is described in which the force sensor 140 is fixed to the main surface 11D on the base 12 side of the moving crosshead 11 and the signal processing unit 150 is fixed to the main surface 11U on the top surface 15 side of the moving crosshead 11, but the signal processing unit 150 may be fixed to the main surface 11D and the force sensor 140 may be fixed to the main surface 11U, or both the force sensor 140 and the signal processing unit 150 may be fixed to one of the main surface 11U and the main surface 11D.

[0069] Furthermore, in the first and second embodiments described above, examples have been described in which the material testing machine is a tension and compression tester, but the present invention can also be applied to other types of material testing machines (for example, a torsion testing machine, a vibration testing machine, etc.). Description of Reference Numerals

[0070] 1, 2: material testing machine; 10U: upper limit position (highest reaching position); 11: moving crosshead; 20, 120: force sensor unit; 22, 142: measuring unit; 23, 159: amplification conversion unit; 24, 154: amplification unit; 25, 155: AD conversion unit; 26, 156: operation processing unit; 30: control unit; 60: cable; 100: test object; 122: buffer; 140: force sensor; 150: signal processing unit; 143: memory; 601, 611: core wire; 603, 613: shielding member.

Claims

1. A material testing machine for performing material testing on a test object, characterized in that: The material testing machine has: a measuring unit that converts the force applied to the subject into an electrical signal; and an amplifying and converting unit, comprising an amplifying unit for amplifying the electrical signal and an AD converting unit for digitizing the electrical signal amplified by the amplifying unit; The amplification conversion section is integrally formed with the measurement section or is separately formed with the measurement section and is arranged near the measurement section.

2. The material testing machine according to claim 1, characterized in that: The amplification conversion unit is integrally formed with the measurement unit.

3. The material testing machine according to claim 1, characterized in that: The amplification conversion part is formed separately from the measurement part and connected to the measurement part. The measuring unit and the amplification conversion unit are fixed to a moving crosshead of the material testing machine.

4. The material testing machine according to claim 3, characterized in that: The enlargement conversion part is fixed to the moving crosshead via a buffer.

5. The material testing machine according to claim 3 or 4, characterized in that: The enlargement conversion part is fixed to the top surface of the moving crosshead.

6. The material testing machine according to any one of claims 1 to 5, characterized in that: The measuring unit and the amplifying and converting unit are driven by alternating current.

7. The material testing machine according to any one of claims 1 to 6, characterized in that: A cable is further provided, the cable connecting the amplification conversion section and a control unit, wherein the control unit processes the digital signal output from the amplification conversion section.

8. The material testing machine according to claim 7, characterized in that: The cable has a core wire and one or more shielding members, wherein the shielding members reduce the influence of noise on the core wire.

9. The material testing machine according to claim 7 or 8, characterized in that: The cable is a twisted pair cable.

10. The material testing machine according to any one of claims 7 to 9, characterized in that: The cable is routed in such a way that it is bent when the distance between the moving crosshead of the material testing machine and the control unit is the greatest.

11. The material testing machine according to any one of claims 1 to 10, characterized in that: A calculation processing unit is provided which is integrally formed with the amplification conversion unit. The measuring unit is included in a load cell having a memory, wherein the memory stores data for calibrating the material testing machine. When the load cell is connected to the amplification and conversion unit, the calculation processing unit reads the data from the memory of the load cell to calibrate the material testing machine.

12. The material testing machine according to any one of claims 1 to 11, characterized in that: The material testing machine is a tension-compression testing machine for performing a tension test and a compression test on the object to be tested.

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