Material-testing machine

Abstract

To provide a material-testing machine capable of reducing effect of noise.SOLUTION: Material-testing machines (1, 2) comprises measurement units (22, 142) that convert a force applied to an analyte (100) into an electrical signal, and amplification conversion units (23, 159) that include amplifiers (24, 154) that amplify the electrical signal and AD conversion units (25, 155) that digitize the electrical signal amplified by the amplifiers (24, 154), and the amplification conversion unit (23, 159) is configured as an integral part of the measurement units (22, 142), or as a separate body from the measurement units (22, 142) and located in the vicinity of the measurement units (22, 142).SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] There is known a material testing machine that performs a tensile test, a compression test, etc. on a test specimen (see, for example, 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 specimen into an electrical signal. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-17579 A Summary of the Invention [Problem to be solved by the invention]

[0004] Generally, in a material testing machine such as that described in the above Patent Document 1, the load cell is connected to a control unit that processes an electric signal from the load cell via a communication line. Therefore, when the electric signal is transmitted via the communication line, it may be affected by a non-negligible level of noise.

[0005] Therefore, an object of the present invention is to provide a material testing machine capable of reducing the effects of noise. [Means for solving the problem]

[0006] The present invention is a materials testing machine for performing materials testing on a specimen, comprising: a measurement unit that converts a force applied to the specimen into an electrical signal; and an amplification conversion unit that includes an amplification unit that amplifies the electrical signal and an AD conversion unit that digitizes the electrical signal amplified by the amplification unit, wherein the amplification conversion unit is configured integrally with the measurement unit, or is configured separately from the measurement unit and positioned in the vicinity of the measurement unit.

[0007] The amplification conversion section may be configured integrally with the measurement section.

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

[0009] The measurement unit and the amplification conversion unit may be driven by alternating current.

[0010] The material testing machine may further include a cable connecting the amplifier and converter to a control unit that processes a digital signal output from the amplifier and converter. In this case, the cable may have a core wire and one or more layers of shielding that reduce the effect of noise on the core wire, may be a twisted pair cable, and may be wired so that sagging occurs when the moving crosshead of the material testing machine and the control unit are farthest apart.

[0011] The above-mentioned material testing machine may further include an arithmetic processing unit that is integral with the amplification conversion unit, the measurement unit being included in a load cell having a memory in which data for calibrating the material testing machine is stored, and the arithmetic processing unit may read out the data from the memory of the load cell when the load cell is connected to the amplification conversion unit, and calibrate the material testing machine.

[0012] The material testing machine may be a tension / compression testing machine for performing a tensile test and a compression test on the specimen. Effect of the Invention

[0013] According to the present invention, a material testing machine capable of reducing the influence of noise is provided. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a diagram illustrating a material testing machine according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a block diagram showing mainly functional blocks of a load cell unit and a control unit of the material testing machine shown in FIG. 1. [Diagram 3] FIG. 1 illustrates an example of a cable. [Figure 4] FIG. 13 is a diagram showing another example of a cable. [Diagram 5] FIG. 4 is a diagram showing a schematic diagram of a material testing machine according to a second embodiment of the present invention. [Figure 6] FIG. 6 is a block diagram showing mainly functional blocks of a load cell unit and a control unit of the material testing machine shown in FIG. 5. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, embodiments for carrying out the material testing machine according to the present invention will be illustrated with reference to the accompanying drawings. The embodiments illustrated below are intended to facilitate understanding of the present invention, and are not intended to limit the present invention. The present invention can be modified or improved from the following embodiments without departing from the spirit of the present invention. In addition, in the above-mentioned attached drawings, the dimensions of each member may be exaggerated or reduced in order to facilitate understanding.

[0016] (First embodiment) Fig. 1 is a schematic diagram of a material testing machine of this embodiment. As shown in Fig. 1, the material testing machine 1 of this embodiment is a tension / compression testing machine, and mainly comprises 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. The material testing machine 1 is used with the base 12 facing vertically downward and the top surface 15 facing vertically upward.

[0017] The pair of frames 10A, 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 housed inside each of the frames 10A, 10B. Each of the ball screws housed in the frames 10A, 10B is connected to a drive unit 16 such as a motor via various gear mechanisms, and when the drive unit 16 is driven, the ball screws housed in the frames 10A, 10B rotate in synchronization with each other.

[0018] The moving crosshead 11 is a plate-like member parallel to the base 12 and the top surface 15, and includes a main surface 11D on the base 12 side, a main surface 11U on the top surface 15 side, a side surface 11R on the frame 10A side, and a side surface 11L on the frame 11B side. In this embodiment, the height H from the main surface 11U to the main surface 11D of the moving crosshead 11 is approximately 1 / 2 or less of the width W from the side surface 11R to the side surface 11L of the moving crosshead 11. However, the ratio of the height H to the width W is not limited to this. The side surface 11R of the moving crosshead 11 is attached to a ball screw housed in the frame 10A via an attachment mechanism (not shown). Similarly, the side surface 11L is also attached to a ball screw housed in the frame 10B via an attachment mechanism (not shown). Therefore, when the driving unit 16 is driven to rotate the ball screws housed in the frames 10A, 10B, the movable crosshead 11 moves along the longitudinal direction of the frames 10A, 10B (i.e., toward the base 12 or toward the top surface 15) in accordance with the rotation of the ball screws. In this embodiment, the movable crosshead 11 is controlled to move between an upper limit position (highest reach position) 10U and a lower limit position 10D in the frames 10A, 10B.

[0019] A load cell unit 20 is attached to one of the main surfaces 11D, 11U of the moving crosshead 11. In this embodiment, the load cell unit 20 is attached approximately in the center of the main surface 11D. The load cell unit 20 has a case 21, and electronic components that constitute various functional blocks, which will be described later, are stored or mounted in this case 21.

[0020] A first jig 17 constituting a test jig 19 is attached to the load cell unit 20. A second jig 18 constituting the test jig 19 is attached to a portion of the base 12 facing the first jig 17. In the example of FIG. 1, the first jig 17 is configured to hold one side of the test specimen 100, and the second jig 18 is configured to hold the other side of the test specimen 100. Therefore, when the moving crosshead 11 moves to the upper limit position 10U side, the test specimen 100 is pulled, and when the moving crosshead 11 rises to a predetermined position, the test specimen 100 breaks. The material testing machine 1 can measure the test force at which the test specimen 100 breaks and various other characteristics of the test specimen 100 related to tension, and functions as a tensile testing machine. Meanwhile, the first jig 17 and the second jig 18 of the test jig 19 may be replaced with pressure plates. In this case, the specimen 100 is sandwiched between the movable crosshead 11 and the base 12 via a pair of compression plates, and when the movable crosshead 11 moves to the lower limit position 10D, the specimen 100 is compressed, and when the movable crosshead 11 descends to a predetermined position, the specimen 100 undergoes compression failure. In this case, the material testing machine 1 can measure the test force when the specimen 100 undergoes compression failure and various other compression-related characteristics of the specimen 100, and functions as a compression testing machine. In this way, the material testing machine 1 of this embodiment is configured as a tension / compression testing machine.

[0021] Fig. 2 is a block diagram showing mainly functional blocks of the load cell unit 20 and the control unit 30 of the material testing machine 1. As shown in Fig. 2, the load cell unit 20 has, as main functional blocks, for example, a power supply unit 28, a measurement unit voltage generation unit 29, a measurement unit 22, an amplification conversion unit 23, an arithmetic processing unit 26, and a driver unit 27. That is, in this embodiment, the measurement unit 22 and the amplification conversion unit 23 are integrally configured.

[0022] The power supply unit 28 supplies DC or AC power supplied from an external power supply 40 to the measurement unit voltage generation unit 29, the amplification and conversion unit 23 (i.e., the amplification unit 24 and the AD conversion unit 25 described below), the arithmetic processing unit 26, the driver unit 27, etc. In other words, the measurement unit 22 and the amplification and conversion unit 23 are driven by DC or AC.

[0023] Note that power supply unit 28 may convert the power from external power supply 40 into power usable by measurement unit voltage generation unit 29, amplification and conversion unit 23, arithmetic processing unit 26, and driver unit 27, for example by converting the power supplied from external power supply 40 between DC and AC. Measurement unit voltage generation unit 29 converts the power supplied from power supply unit 28 into power usable by measurement unit 22. Note that when measurement unit 22 can directly use the power supplied from power supply unit 28, measurement unit voltage generation unit 29 is not an essential component of material testing machine 1.

[0024] In this embodiment, the measuring unit 22 includes a strain gauge. A first jig 17 constituting the test jig 19 is connected to the measuring unit 22. As a result, as the movable crosshead 11 moves and the test jig 19 pulls or compresses the test object 100, a strain is generated in the strain gauge of the measuring unit 22. The strain gauge is a part of a Wheatstone bridge circuit, and a 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 amplifying and converting unit 23.

[0025] The amplification conversion section 23 includes an amplification section 24 and an AD conversion section 25. The amplification section 24 amplifies the electric signal output from the measurement section 22, and outputs the amplified electric signal to the AD conversion section 25. The AD conversion section 25 then converts the amplified electric signal into a digital signal, and outputs the digital signal to the calculation processing section 26. In this manner, the load cell unit 20 of the material testing machine 1 is configured as a so-called digital load cell in which the measurement section 22 and the amplification conversion section 23 are integrated.

[0026] The arithmetic processing unit 26 is composed of, for example, a CPU (Central Processing Unit). The arithmetic processing unit 26 outputs the digital signal output from the AD conversion unit 25 to the driver unit 27. A cable 60 (see FIG. 1) is connected to the driver unit 27. The arithmetic processing unit 26 may convert the digital signal output from the AD conversion unit 25 into a predetermined format as necessary and output the converted signal to the cable 60. The arithmetic processing unit 26 may also comprehensively control each part of the load cell unit 20. In this case, the arithmetic processing unit 26 may control the load cell unit 20 according to an instruction (control instruction) indicated by a control signal from the control unit 30.

[0027] The driver unit 27 outputs a digital signal (or a signal converted from the digital signal) to the cable 60 in a format corresponding to the communication form 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] As shown in FIG. 1, the cable 60 connects the load cell unit 20 and the control unit 30. That is, the amplifying and converting unit 23 and the control unit 30 are connected via the cable 60. The cable 60 is a cable that transmits a digital signal output from the amplifying and converting unit 23 to the control unit 30. For example, a communication cable that is generally available for the communication standard of RS-232C or RS-422 / 485 may be used as the cable 60. The cable 60 has a first section 61 that extends along the moving crosshead 11 from the load cell unit 20 to the frame 10A, a second section 62 that is wired along the outer wall of the frame 10A, and a third section 63 that connects the end of the second section 62 opposite to 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. Note that the wiring in FIG. 1 is an example. 1, 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 so as to pass through the rear side of the frame 10A (i.e., the back side of the material testing machine 1). As long as the cable 60 is routed so as to be able to "flex" as described below, the wiring path, wiring method, and length of the cable 60 are not particularly limited.

[0029] As shown in FIG. 1, the second section 62 of the cable 60 is bent. For example, in the example of FIG. 1, when the moving crosshead 11 is at the upper limit position 10U, the second section 62 and the third section 63 do not extend in a straight line but are bent. In this way, in the material testing machine 1 according to this embodiment, even when the distance between the moving crosshead 11 and the control unit 30 is the farthest (i.e., 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. The magnitude of the bend of the cable 60 and the bent part of the cable 60 may be appropriately determined within a range that does not interfere with the original function of the material testing machine 1, such as the movement of the moving crosshead. For example, as an example different from FIG. 1, the first section 61 of the cable 60 may be bent.

[0030] Incidentally, the cable 60 may be a cable that is not specially shielded to reduce the influence of noise. More specifically, the cable 60 may be, for example, a coaxial cable as shown in FIG. 3. This coaxial cable includes a core 601 through which a digital signal output from the amplifier / converter 23 propagates, an insulator 602 that covers the core 601, a shield 603 that covers the insulator 602, and a jacket 604 that covers the shield 603. The shield 603 is made of, for example, a conductor, and reduces the influence of noise on the core 601. Thus, the cable 60 shown in FIG. 3 is a cable that has one or more layers of shielding that reduces the influence of noise on the core 601, and is not specially shielded to reduce the influence of noise, and / or does not have an additional shield. As another example, the cable 60 may be a twisted pair cable as shown in FIG. 4. This twisted pair cable is composed of a pair of core wires 611 twisted together through which a digital signal output from the amplifier / converter unit 23 propagates, an insulator 612 covering the pair of core wires 611, a shield 613 covering the insulator 612, and a jacket 614 covering the shield 613. The shield 613 is made of, for example, a conductor, and reduces the effects of noise on the pair of core wires 611. In this way, the cable 60 shown in Fig. 4 has one or more layers of shielding that reduce the effects of noise on the pair of core wires 611, and is a cable that is not subjected to special shielding processing for reducing the effects of noise.

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

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

[0033] The arithmetic processing unit 32 is composed of, for example, a CPU, and converts the input digital signal into digital data, and also converts this digital data into analog data indicating various characteristics (for example, tensile strength, compressive strength, etc.) of the subject 100 by referring to various tables, etc. stored in the memory 34. The arithmetic processing unit 32 outputs this analog data to the control unit 33. The memory 34 includes a ROM (Read Only Memory), a RAM (Random Access Memory), etc.

[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 analog data input from the arithmetic processing unit 32 in the memory 34, reads out the analog data stored in the memory 34 as necessary, displays the analog data on the display unit 50 composed of a display or the like, and controls the operation of the drive unit 16 shown in FIG.

[0035] In this way, the control unit 30 processes the digital signal output from the amplifying and converting section 23 of the load cell unit 20, and displays and manages the data detected by the measuring section 22 of the load cell unit 20. The control section 33 may issue a control instruction to the load cell unit 20. In this case, the control section 33 creates a control instruction to the load cell unit 20 and outputs the control instruction to the arithmetic processing section 32. The "control instruction" here is, for example, an instruction to adjust zero and span to the arithmetic processing section 26 of the load cell unit 20, or an instruction to start or end measurement to the measuring section 22. The arithmetic processing section 32 converts the control instruction received from the control section 33 into a control signal and outputs it to the driver section 31. The driver section 31 outputs the control signal received from the arithmetic processing section 32 to the driver section 27 of the load cell unit 20.

[0036] As described above, the material testing machine 1 of this embodiment is equipped with (i) a measuring unit 22 that converts the force applied to the specimen 100 into an electrical signal, and (ii) an amplification conversion unit 23 that includes an amplification unit 24 that amplifies this electrical signal and an AD conversion unit 25 that digitizes the amplified electrical signal, and the amplification conversion unit 23 is configured integrally with the measuring unit 22.

[0037] According to the material testing machine 1 having such a configuration, the electric signal generated in the measuring section 22 is converted into a digital signal before being output from the load cell unit 20 to the cable 60 (i.e., within the load cell unit 20). However, 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 while propagating through the cable 60. In this case, if the electric signal is an analog signal, there is a risk that a non-negligible error occurs between the data indicated by the analog signal that has reached the control unit 30 and the data measured by the measuring section 22 due to the influence of noise. However, according to the material testing machine 1 of this embodiment, the data measured by the measuring section 22 is converted into a digital signal within the load cell unit 20 and then conveyed to the control unit 30. Therefore, the influence of noise on the electric signal generated in the measuring section 22 is reduced compared to the case where the data is conveyed to the control unit 30 as an analog signal. Therefore, according to the material testing machine 1, the frequency of occurrence of an error between the data measured by the measuring section 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, it is possible to further reduce the influence of noise by performing additional filtering on the analog signal output by the measuring unit 22 and / or the digital signal output by the amplifying and converting unit 23, and by performing additional shielding on various wiring including the cable 60. This enables the material testing machine 1 to obtain even more reliable measurement data (i.e., measurement data with high stability and accuracy).

[0038] As described above, the material testing machine 1 reduces the influence of noise on the cable 60. Therefore, the material testing machine 1 can obtain highly reliable measurement data regardless of the structure or material of the cable used. For example, a cable that is not specially shielded to reduce the influence of noise (for example, a cable with only one layer of shield or a cable with a one-sided shield, etc.) is difficult to use in a conventional material testing machine in consideration of the influence of noise. On the other hand, the material testing machine 1 can reduce the influence of noise and obtain highly reliable measurement data even when such a type of cable that is difficult to use in a conventional material testing machine is adopted as the cable 60. In addition, the material testing machine 1 does not require a cable with a special shielding process (i.e., a relatively expensive cable) as described above, so that it is possible to reduce the manufacturing cost of the material testing machine 1 as a whole.

[0039] Incidentally, when the load cell unit 20 is driven by AC, the signal output from the load cell unit 20 is also AC, and is therefore more susceptible to the parasitic capacitance of the cable 60 than when the signal is DC. Moreover, the parasitic capacitance increases as the cable 60 becomes longer. In this way, when the signal is AC, the effect of noise caused by the parasitic capacitance of the cable 60 may be greater. However, as described above, according to the material testing machine 1, the electrical signal from the measuring unit 22 is converted into a digital signal within the load cell unit 20, so that even when the signal is AC, the effect of noise caused by such parasitic capacitance is reduced. Therefore, in the material testing machine 1, even if the measuring unit 22 and the amplifying and converting unit 23 of the load cell unit 20 are driven by AC, highly reliable measurement data (i.e., measurement data with high stability and accuracy) can be obtained. In other words, according to the material testing machine 1, it is possible to realize AC driving while reducing the disadvantages of driving the load cell unit 20 by AC. When the load cell unit 20 is driven by alternating current, for example when the current supply to the load cell unit 20 is forcibly cut off, it is possible to cut off the current at the timing of the zero current point, thereby obtaining effects such as reducing the load on the electrical system of the material testing machine 1.

[0040] Furthermore, when the load cell unit 20 is driven by AC, the influence of the parasitic capacitance can be further reduced by using the cable 60 as a twisted pair cable as shown in Fig. 4. However, even when the load cell unit 20 is driven by DC, the influence of the parasitic capacitance can be reduced by using the cable 60 as a twisted pair cable.

[0041] As described above, according to the material testing machine 1, when the moving crosshead 11 is at the upper limit position 10U (highest reach position), that is, when the distance between the moving crosshead 11 and the control unit 30 is the greatest, the cable 60 is deflected. Therefore, according to the material testing machine 1, it is possible to prevent excessive pulling tension from being applied to the cable 60 when the moving crosshead 11 reaches the upper limit position 10U. Incidentally, it is generally expected that the longer the cable length of the material testing machine, the greater the influence of noise. Therefore, when the above-mentioned deflection exists in the cable of the material testing machine, the influence of noise may be greater than when there is no deflection in the cable of the material testing machine. However, in the material testing machine 1, the influence of noise is reduced as described above, so that it is possible to provide such a deflection in the cable 60 while reducing the influence of noise.

[0042] Second embodiment Next, a material testing machine according to the second embodiment will be described. FIG. 5 is a diagram showing a material testing machine according to the present embodiment. As shown in FIG. 5, the material testing machine 2 according to the present embodiment has a configuration that is generally similar to that of the material testing machine 1 according to the first embodiment, except that the configuration of the load cell unit is different from that of the load cell unit 20 of the material testing machine 1 according to the first embodiment. Therefore, hereinafter, the material testing machine 2 will be described with respect to the load cell unit, and the other configurations will be denoted by the same reference numerals as those in the first embodiment and will not be described.

[0043] 5, the load cell unit 120 of this embodiment has a load cell 140 attached to the main surface 11D of the movable crosshead 11 on the base 12 side, and a signal processing unit 150 attached to the main surface 11U of the movable crosshead 11 on the top surface 15 side. In this manner, in the material testing machine 2 of this embodiment, the load cell 140 having a measuring unit 142 described later, and the signal processing unit 150 having an amplifier unit 154 and an AD conversion unit 155 described later are configured separately. Both the load cell 140 and the signal processing unit 150 are fixed to the movable crosshead 11.

[0044] The load cell 140 has a case 141, and electronic components constituting various functional blocks of the load cell 140, which will be described later, are stored or mounted in this case 141. The signal processing unit 150 has a case 151, and electronic components constituting various functional blocks of the signal processing unit 150, which will be described later, are stored or mounted in this case 151.

[0045] The load cell 140 and the signal processing unit 150 are connected by a wiring 121. The length of the wiring 121 is extremely short compared to the length of the cable 60. For example, the wiring 121 may be equal to or shorter than the length of the second section 62 of the cable 60, and may further be equal to or shorter than the length of the first section 61 of the cable 60. Since the load cell 140 and the signal processing unit 150 are both fixed to the moving crosshead 11, they are disposed close enough to be connected by the wiring 121, which is extremely short compared to the length of the cable 60.

[0046] In this embodiment, the signal processing unit 150 is fixed to the moving crosshead 11 via the cushioning material 122. For example, anti-vibration and / or earthquake-proof rubber can be used as the cushioning material 122. More specifically, for example, urethane rubber, silicone rubber, or foam rubber of these rubbers can be used as the cushioning material 122. The shape of the cushioning material 122 is not particularly limited, but the cushioning material 122 may be, for example, a mat-like shape.

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

[0048] 6, the load cell 140 has a measuring section 142, a memory 143, and a connector 144 as main functional blocks. Each section of the load cell 140 is driven by power obtained from a signal processing unit 150 via the connector 144. The measuring section 142 is driven by a direct current or an alternating current. One end of the wiring 121 described above is connected to the connector 144.

[0049] In this embodiment, the measuring unit 142 includes a strain gauge. A first jig 17 constituting the test jig 19 is connected to the measuring unit 142. As a result, as the movable crosshead 11 moves and the test jig 19 pulls or compresses the test object 100, a strain is generated in the strain gauge of the measuring unit 142. This strain gauge is a part of a Wheatstone bridge circuit, and a change in resistance caused by the strain generated in the strain gauge is converted into a voltage via this Wheatstone bridge circuit. A voltage signal (electrical signal) from the measuring unit 142 is output to a connector 144.

[0050] The memory 143 includes a ROM, a RAM, etc., and stores data (tables) for calibrating the material testing machine 2. For example, the memory 143 stores a table that associates an input voltage to a Wheatstone bridge circuit in the load cell 140 in which the memory 143 is mounted with an output voltage of the Wheatstone bridge circuit corresponding to the input voltage. The memory 143 is connected to a connector 144.

[0051] The signal processing unit 150 has, as main functional blocks, for example, a power supply section 158, a measurement section voltage generation section 153, an amplification and conversion section 159, an arithmetic processing section 156, a driver section 157, and a connector 152. The power supply section 158 supplies DC or AC power supplied from the external power supply 40 to the measurement section voltage generation section 153, the amplification and conversion section 159 (i.e., an amplification section 154 and an AD conversion section 155 described later), the AD conversion section 155, the arithmetic processing section 156, the driver section 157, and the like. That is, the amplification and conversion section 159 is driven by DC or AC.

[0052] In addition, the power supply unit 158 ​​may convert the power from the external power supply 40 into power that can be used by the measurement unit voltage generation unit 153, the amplification and conversion unit 159, the calculation processing unit 156, and the driver unit 157, such as by converting the power supplied from the external power supply 40 between DC and AC.

[0053] The measurement unit voltage generating unit 153 converts the power supplied from the power supply unit 158 ​​into power that can be used by the measurement unit 142 (and memory 143) of the load cell 140. The measurement unit voltage generating unit 153 supplies the converted power to the load cell 140 via the connector 152. Note that if the measurement unit 142 (and memory 143) can directly use the power supplied from the power supply unit 158, the measurement unit voltage generating unit 153 is not an essential component of the material testing machine 2.

[0054] The other end of the wiring 121 described above is connected to the connector 152. Therefore, the electrical signal from the measurement unit 142 of the load cell 140 and the data from the memory 143 are input to the connector 152 via the connector 144 of the load cell 140 and the wiring 121. The connector 152 outputs the input electrical signal and / or data to the amplification conversion unit 159. The connector 152 also outputs the power input from the measurement unit voltage generation unit 153 to the connector 144 of the load cell 140. As a result, power is supplied to the load cell 140.

[0055] The amplification conversion unit 159 includes an amplification unit 154 and an AD conversion unit 155. The amplification unit 154 amplifies the electric signal input from the measurement unit 142 of the load cell 140, and outputs the amplified electric signal to the AD conversion unit 155. Then, the AD conversion unit 155 converts the amplified electric signal into a digital signal, and outputs the digital signal to the calculation processing unit 156.

[0056] As described above, in the load cell unit 120 of the material testing machine 2, the signal processing unit 150 is configured separately from the measurement section 142, and is connected to the measurement section 142 via the connector 152 and the connector 144. The signal processing unit 150 is disposed in the vicinity of the measurement section 142 (i.e., in the vicinity of the load cell 140). The specific distance of "in the vicinity" here is not particularly limited, but it is desirable that the load cell 140 and the signal processing unit 150 are disposed so 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 arithmetic processing unit 156 of the signal processing unit 150 is composed of, for example, a CPU. When the arithmetic processing unit 156 receives a digital signal from the AD conversion unit 155, the arithmetic processing unit 156 reads data (table) for calibrating the above-mentioned material testing machine 2 from the memory 143 of the load cell 140, and calibrates the voltage value indicated by the digital signal received from the AD conversion unit 155 to a predetermined voltage value by referring to the table. That is, the arithmetic processing unit 156 calibrates the material testing machine 2 based on the data from the memory 143. Then, the arithmetic processing unit 156 outputs the calibrated digital signal to the driver unit 157. Note that the arithmetic processing unit 156 may calibrate the electric signal output from the connector 152 before the electric signal is processed by the amplifier unit 154 and the AD conversion unit 155. The arithmetic processing unit 156 may also control each unit of the load cell unit 120 in an integrated manner. In this case, the arithmetic processing unit 156 may control the load cell unit 120 according to a control instruction from the control unit 30.

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

[0059] As described above, the material testing machine 2 of this embodiment is equipped with a measuring unit 142 that converts the force applied to the specimen 100 into an electrical signal, and an amplification conversion unit 159 that includes an amplification unit 154 that amplifies this electrical signal and an AD conversion unit 155 that digitizes the electrical signal amplified by the amplification unit 154, and the amplification conversion unit 159 is configured separately from the measuring unit 142 and is arranged in the vicinity of the measuring unit 142.

[0060] According to the material testing machine 2 having such a configuration, the electric signal generated in the measuring unit 142 is converted into a digital signal before being output from the load cell unit 120 to the cable 60 (i.e., within the load cell unit 120). In the material testing machine 2, the amplifying and converting unit 159 is configured separately from the measuring unit 142, but since the amplifying and converting unit 159 is disposed near the measuring unit 142 as described above, the electric signal generated in the measuring unit 142 is not easily affected by noise when propagating through the wiring 121. According to the material testing machine 2, the data measured in the measuring unit 142 is converted into a digital signal in the amplifying and converting unit 159 and then transmitted to the control unit 30. Therefore, the influence of noise on the electric signal generated in the measuring unit 142 is reduced compared to the case where the data measured in the measuring unit 142 is conveyed to the control unit 30 as an analog signal. Therefore, according to the material testing machine 2, the frequency of occurrence of an error between the data measured by the measuring unit 142 and the data processed by the control unit 30 and / or the error itself can be reduced. Moreover, it is possible to further reduce the influence of noise by applying filtering or shielding to such a material testing machine 2. This enables the material testing machine 2 to obtain measurement data with even higher reliability (i.e., measurement data with high stability and accuracy).

[0061] Moreover, 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, highly reliable measurement data can be obtained regardless of the structure or material of the cable used. For example, a cable that is not specially shielded to reduce the influence of noise (for example, a cable with only one layer of shield or a cable with a one-sided shield, etc.) has been difficult to use in the conventional material testing machine in consideration of the influence of noise. On the other hand, according to the material testing machine 2, even if such a type of cable that is difficult to use in the conventional material testing machine is adopted as the cable 60, the influence of noise can be reduced and highly reliable measurement data can be obtained. Furthermore, according to the material testing machine 2, a cable with a special shielding process (i.e., a relatively expensive cable) is not essential as described above, so that the manufacturing cost of the material testing machine 2 as a whole can be reduced.

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

[0063] Furthermore, when the load cell unit 120 is driven by AC, the influence of the parasitic capacitance can be further reduced by using the cable 60 as a twisted pair cable as shown in Fig. 4. However, even when the load cell unit 120 is driven by DC, the influence of the parasitic capacitance can be reduced by using the cable 60 as a twisted pair cable.

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

[0065] In addition, in the material testing machine 2, as described above, the load cell 140 including the measuring unit 142 has the memory 143 in which data for calibrating the material testing machine 2 is stored, and the arithmetic processing unit 156 of the signal processing unit 150 reads out the above data from the memory 143 of the load cell 140 when the load cell 140 is connected to the signal processing unit 150, and calibrates the material testing machine 2. That is, the load cell unit 120 of the material testing machine 2 has a so-called plug & play function. With this configuration, when the load cell 140 is replaced with a new load cell 140, the effort of manually calibrating the new load cell 140 to fit it to the material testing machine 2 is eliminated. However, it is not essential that the load cell unit 120 has the plug & play function.

[0066] Furthermore, the material testing machine 2 has a configuration in which the signal processing unit 150 including the amplification conversion section 159 is fixed to the moving crosshead 11 via the cushioning material 122. This configuration makes it possible to prevent vibrations and shocks from the moving crosshead 11 from being transmitted to the board on which the amplification section 154 and the AD conversion section 155 are mounted. However, the cushioning material 122 is not essential.

[0067] Although the present invention has been described above by taking the above embodiment as an example, the present invention is not limited to this.

[0068] For example, in the above-mentioned second embodiment, an example was described in which the load cell 140 is fixed to the main surface 11D facing the base 12 of the movable crosshead 11, and the signal processing unit 150 is fixed to the main surface 11U facing the top surface 15 of the movable crosshead 11. However, it is also possible to fix the signal processing unit 150 to the main surface 11D and fix the load cell 140 to the main surface 11U, or to fix both the load cell 140 and the signal processing unit 150 to one of the main surfaces 11U, 11D.

[0069] Furthermore, in the above-described first and second embodiments, examples have been described in which the material testing machine performs tension and compression tests, but the present invention can also be applied to other types of material testing machines (e.g., torsion testing machines, vibration testing machines, etc.). [Explanation of symbols]

[0070] 1,2...Material testing machine, 10U...Upper limit position (highest reach position), 11...Moving crosshead, 20,120...Load cell unit, 22,142...Measuring section, 23,159...Amplification conversion section, 24,154...Amplification section, 25,155...AD conversion section, 26,156...Calculation processing section, 30...Control unit, 60...Cable, 100...Test object, 122...Buffer material, 140...Load cell, 150...Signal processing unit, 143...Memory, 601,611...Core wire, 603,613...Shield

Claims

1. A material testing machine for performing a material test on a specimen, comprising: a measurement unit that converts a force applied to the specimen into an electrical signal; an amplification and conversion unit including an amplification unit that amplifies the electrical signal and an AD conversion unit that digitizes the electrical signal amplified by the amplification unit; and is provided with: the amplification and conversion unit is configured integrally with the measurement unit or is configured separately from the measurement unit and arranged in the vicinity of the measurement unit A material testing machine characterized by the above.

2. The amplification and conversion unit is configured integrally with the measurement unit The material testing machine according to claim 1, characterized by the above.

3. The amplification and conversion unit is configured separately from the measurement unit and connected to the measurement unit, The measurement unit and the amplification and conversion unit are fixed to a moving crosshead of the material testing machine The material testing machine according to claim 1, characterized by the above.

4. The amplification and conversion unit is fixed to the moving crosshead via a buffer material The material testing machine according to claim 3, characterized by the above.

5. The amplification and conversion unit is fixed to the top surface of the moving crosshead The material testing machine according to claim 3 or 4, characterized by the above.

6. The measurement unit and the amplification and conversion unit are driven by alternating current The material testing machine according to any one of claims 1 to 4, characterized by the above.

7. Further provided with a cable connecting the amplification and conversion unit and a control unit that processes a digital signal output from the amplification and conversion unit The material testing machine according to any one of claims 1 to 4, characterized by the above.

8. The cable has a core wire and one or more shields that reduce the influence of noise on the core wire The material testing machine according to claim 7, characterized by the above.

9. The cable is a twisted pair cable The material testing machine according to claim 7, characterized by the above.

10. The cable is wired so that deflection occurs when the distance between the moving crosshead of the material testing machine and the control unit is the farthest The material testing machine according to claim 7, characterized by the above.

11. Comprising an arithmetic processing unit configured integrally with the amplification and conversion unit, The measurement unit is included in a load cell having a memory storing data for calibrating the material testing machine, When the load cell is connected to the amplification conversion unit, the arithmetic processing unit reads the data from the memory of the load cell and calibrates the material testing machine. The material testing machine according to any one of claims 1 to 4, characterized by the above.

12. The material testing machine is a tensile-compression testing machine for performing a tensile test and a compression test on the specimen. The material testing machine according to any one of claims 1 to 4, characterized by the above.

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