JP2006003295A - Load cell, and physical property evaluation-testing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To measure force without being affected by a lead wire from a sample, in a device for evaluating a physical property of the sample while applying the force. <P>SOLUTION: The sample S1 is a material with a resistance value varied in response to pressure, and a resistance value variation is measured while applying the force. The lead wire 8 from the sample S1 is connected to a pedestal receiving terminal part 5 of a load cell, and is connected to a measuring instrument 13 from a pedestal terminal part 6. Rigidity of a cable 12 brings no influence in the measurement of the force because a position of the pedestal terminal part 6 is not moved although a position of the sample S1 is moved downwards by a deformation of the load cell 1, when applying the force onto the sample S1 by a load part 11. The lead wire 8 led out from the sample S1 is not deformed because it is moved only such a manner as same to the sample S1 and the pedestal receiving terminal part 5, and rigidity of the lead wire 8 brings no influence in the measurement of the force by the load cell 1. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a load cell for detecting force. Furthermore, the present invention relates to a physical property evaluation test apparatus that detects and evaluates various physical properties of a test object while detecting the force using a load cell when a test is performed while applying a force to the test object. Among these physical property evaluation test devices, devices that evaluate, test, and analyze the properties and conditions of test objects, such as strength evaluation test devices, durability evaluation test devices, continuity test devices, and life evaluation test devices Including general.

  In order to evaluate various properties of the test object, there are cases where it is desired to take out an electrical signal from the test object while applying a force to the test object. In order to detect the test force applied to the test object by the load cell, the test object is fixed to the load seat of the load cell, and the magnitude of the force is measured as an output from the load cell. On the other hand, since the electrical signal from the test object needs to be taken out separately from the force load and the measurement mechanism, the electrical connection for this purpose often uses a lead wire directly drawn from the test object. . Electric power is supplied through this lead wire or an electrical signal is taken out.

  FIG. 4 is a schematic diagram showing a conventional configuration when such an evaluation test is performed. A load cell 52 is fixed to the apparatus frame 51, and a sample 53 is fixed thereon. The load portion 54 is pressed against the sample from above, and the load force is measured by the output from the load cell 52. The force measurement portion based on the output from the load cell is omitted in FIG. On the other hand, two lead wires 55 are extended from the sample, and the electrical characteristics of the sample 53 are measured by connecting them to the measuring device 56. The electrical characteristic in this case is, for example, the resistance value of the sample. That is, the example shown in FIG. 4 is an example of an apparatus that measures resistance while applying a compressive stress by applying force to the sample 53.

  An example of such measurement is described in Patent Document 1, for example. In this document, in order to detect a crack in a coating film on a test object using a material testing machine, a crack occurrence detection circuit is connected to a lead wire directly coming out of the test object.

Japanese Patent Laid-Open No. 2001-41869 (FIG. 1)

  If the test force measured by the load cell is large, that is, if the lead wire stiffness is sufficiently small compared to the stiffness of the load cell used, the influence of the lead wire stiffness on the test force measured even with the conventional connection method There are few. However, if the test force you want to measure is small for small electronic components or micromachines, that is, if the lead wire stiffness is large and unstable relative to the stiffness of the load cell used, the lead wire stiffness gives the test force measurement. The effect is large and the test force cannot be measured accurately. As a test with a small force, a test with a full scale of the test force of about 0.5 N is required, and when it is small, it may be required to load a test force of about 2 mN with high accuracy.

  This is due to the following reason. Generally, the load cell has a structure having a strain generating portion between a load seat for receiving a force and a mounting base for fixing itself to another member. When a force is received by the load seat, the strain generating portion is deformed and the force is measured by detecting the amount of deformation. At this time, since the load seat on which the measurement object is in contact moves slightly, the measurement object also moves together. If a lead wire is attached to the object to be measured, this lead wire is also pulled, and this tensile force becomes an error in the measured force.

  The present invention has been made in view of the above problems, and a load cell in which the rigidity of the lead wire does not affect the test force measurement, and a physical property in which the influence of the lead wire using this load cell does not affect the test force measurement. An object is to provide an evaluation test apparatus.

  The present invention provides a load cell having a strain-generating portion between a load seat for receiving force and a mounting base for fixing itself to another member, and the load cell itself is made of an electrically conductive material. The load receiving seat has a receiving terminal portion and the mounting base has a pedestal terminal portion as terminals for electrical connection, and there is electrical continuity between the two terminal portions. Features. (Claim 1)

  The load cell of the present invention uses itself as a conductor for obtaining electrical continuity. And the lead wire which has come out from the test object is provided with a seat terminal portion so as to be connected to the load seat portion of the load cell. Then, even if the strained part of the load cell deforms, the test object and the load seat just move together in the same way, so the lead wire is not deformed and does not affect the measured force. .

  A physical property evaluation test apparatus according to the present invention is a physical property evaluation test apparatus that evaluates an electrical property of a test object in a state where a force is applied to the test object, and includes the load cell described above to detect the force applied to the test object. An electrical signal is taken out from the pedestal terminal portion in a state where a lead wire from the object is connected to the receiving terminal portion. (Claim 2)

  The physical property evaluation test apparatus of the present invention uses the load cell described above to take out an electrical signal from the test object from the seat terminal part through the load cell main body from the base terminal part that does not move even if a force is applied to the test object. Like that. By doing so, there is no need to directly connect the lead wire coming out of the test object to a measuring device or the like, so that even if a force is applied to the test object, the lead wire is not deformed and does not affect the force measurement.

  Furthermore, the physical property evaluation test apparatus of the present invention is a physical property evaluation test apparatus that evaluates the electrical physical property of a test object in a state where force is applied to the test object, and has a plurality of lead wires from the test object, and is applied to the test object. In order to detect force, the load cell is provided with the number corresponding to the number of the lead wires or more, and each lead wire is connected to the receiving terminal portion of a separate load cell, and the load cell to which the lead wire is connected An electrical signal is taken out from the pedestal terminal portion. (Claim 3)

  When a plurality of lead wires are required from the test object, all the signal lines can be taken out through the load cell by using a plurality of the load cells. By doing so, since all the lead wires are fixed to the load seat portion of the load cell, the lead wires do not affect the force measurement. In this case, the load cells may be used according to the number of lead wires, but a number of load cells exceeding the number of lead wires may be used. Further, the measurement of the test force can be represented by the output from one load cell, or the outputs from a plurality of load cells may be added (averaged).

  Since the load cell of the present invention is provided with an electric terminal portion in each of the load receiving portion and the fixed base portion so that the load cell itself can be used as an electric conductor, the lead wire from the test object is connected to the terminal portion of the load receiving portion. The force can be detected such that the lead wire does not affect the force detection.

  In addition, the physical property evaluation test apparatus of the present invention uses the above load cell to perform electrical property evaluation while applying a test force to the test object, so that an electric signal from the test object is taken out from the base terminal part that does not move. Therefore, it is possible to perform measurement with high accuracy without the lead wire coming out of the test object affecting the measurement of the test force. It is particularly effective for evaluation tests of small materials and parts that are evaluated using a small test force.

  Furthermore, the physical property evaluation test apparatus of the present invention performs electrical property evaluation while applying test force to a test object using a plurality of load cells when there are a plurality of lead wires from the test object. The electrical lead wires from the above do not affect the measurement of the test force, and a highly accurate measurement can be performed. Even if two or more lead wires are required, this can be dealt with by using a plurality of load cells of the present invention.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a load cell of the present invention. The load cell 1 has a configuration in which a strain generating portion 4 is interposed between a load receiving portion 2 for receiving a force and a fixed base portion 3 for fixing the load cell to an apparatus frame or the like. The load receiving portion 2 is in the form of a block, and the load receiving portion 2 itself has such a high rigidity that it does not deform at least when a force within the rated measurement range is applied. Similarly, the fixed pedestal portion 3 has a block shape and does not deform itself. The strain generating portion 4 is deformed when a force is applied between the load receiving portion 2 and the fixed pedestal portion 3, and the amount of deformation is measured by a strain gauge and converted into a force. In the example of the Roberval mechanism illustrated in FIG. 1, the strain generating portion 4 is formed with a dent that is easily deformed at both ends of two parallel bars. When a force is applied to the load receiving portion 2, the dent portion It is measured as a force by measuring the output of the strain gauge 7 which is deformed and pasted in the vicinity by a measuring device (not shown).

  The load receiving portion 2 in FIG. 1 is provided with a receiving terminal portion 5. The seat terminal portion 5 is a terminal for connecting a lead wire from a sample to be tested placed on the load seat portion 2 when the load cell is used. Further, the fixed pedestal portion 3 is provided with a pedestal terminal portion 6. This pedestal terminal portion 6 is a terminal for connecting to a measuring device when using this load cell. The load cell 1 itself is formed of a material having electrical conductivity such as metal. When this load cell is used, an electrical signal can be taken out from the base terminal 6 via the load cell 1 from the test sample.

  The shape of the receiving terminal portion 5 and the pedestal terminal portion 6 may be a metal tab that can be soldered, or a tapped hole for fixing a lead wire from the sample or a cable to the measuring device with a screw. it can. Furthermore, it may be a simple hole that can be electrically connected by inserting a springy terminal. Further, the position of the receiving terminal portion 5 in the load receiving portion 2 may be a side surface or an upper surface, and any position can be adopted as long as it can avoid interference with the sample placed on the load receiving portion 2. Similarly, any position of the base terminal portion 6 in the fixed base portion 3 can be adopted.

  Various known configurations can be employed for the material and mechanical shape of the load cell. For example, the material may be a metal such as aluminum or stainless steel, or a polymer material such as conductive plastic. The form of the mechanical shape and the strain generating part is not limited to the example shown in FIG. 1, and any known shape such as a linear beam sensitive type, a bent sensitive type, a hollow cylindrical sensitive type, a shear sensitive type, etc. The format can be adopted. Further, the force detected by the load cell is not limited to the compressive force, but may be a type that detects a tensile force or a type that can detect both the compressive force and the tensile force.

  FIG. 2 is a diagram showing a main part of the physical property evaluation test apparatus of the present invention. In this apparatus, the sample S1 is placed on the load cell 1 fixed to the frame 10 of the apparatus, and an electrical signal from the sample S1 is taken out while applying a force to the sample S1 by the load unit 11, and the physical properties are evaluated. The load cell 1 used here is the load cell described above with reference to FIG. The arrow described in the load unit 11 indicates the movement of the load unit 11 and the direction in which a force is applied.

  An insulating plate 9 is inserted between the frame 10 of the apparatus and the load cell 1 so that the frame 10 and the load cell 1 are electrically insulated. The insulating plate 9 is made of an insulating material having an electrically high resistance value, and is preferably a material having high rigidity mechanically. The electrical resistance needs to be a value far higher than the resistance value of the load cell itself as a conductor, and the mechanical rigidity needs to be at least a value much higher than the rigidity of the strain-generating portion of the load cell 1. Specifically, a ceramic plate, a plastic plate, or the like can be employed as the insulating plate 9.

  A lead wire 8 from the sample S1 placed on the load cell 1 is connected to a receiving terminal portion 5 formed on the load cell 1. A pedestal terminal portion 6 formed in the load cell 1 is electrically connected to a measuring device 13 using a cable 12. By doing so, the electrical signal from the sample S1 flows in the order of the lead wire 8, the receiving terminal portion 5, the main body of the load cell 1, the pedestal terminal portion 6, the cable 12, and the measuring device 13.

  The apparatus having the configuration shown in FIG. 2 can perform the following measurement. For example, the sample S1 is a material whose resistance value changes with pressure, and the object is to measure the resistance value change while applying force. One end of the resistance value measurement is taken out from the lead wire 8 and the other end is set to the tip of the load portion 11 as a contact point of the electrode. As a connection from the measuring device 13, one end is connected to the pedestal terminal portion 6 via the cable 12, and the other end is connected to the load portion 11 using a cable (not shown). By doing so, the resistance value of the sample S1 can be measured by the measuring device while applying a force to the sample S1 by the load unit 11. When a force is applied to the sample S1, the position of the sample S1 moves downward by the amount of deformation of the strain generating portion of the load cell 1, but the position of the base terminal portion 6 does not move at all. There is no influence on the rigidity of the. Further, since the lead wire 8 coming out of the sample S1 moves together with the sample S1 and the receiving terminal portion 5, it does not deform at all, and the rigidity of the lead wire 8 has no influence on the force measurement by the load cell 1. Not give.

  The embodiment shown in FIG. 3 is an example when there are a plurality of lead wires from the sample S2. In this example, three lead wires 29 exit from the sample S2. The load cells 21, 22, and 23 described with reference to FIG. 1 are fixed on the frame 26 of the apparatus via the electric insulating plate 24, and the electric insulating plate 25 is fixed thereon. The three load cells 21 to 23 have the same height and characteristics as a force measuring device, and the force applied between the insulating plate 24 and the insulating plate 25 is applied equally to the three load cells. Yes.

  The three lead wires coming out of the sample S2 are connected to the receiving terminal portions 30 of the load cells 21 to 23, respectively. On the other hand, the cables 32 from the base terminal portions 31 of the three load cells 21 to 23 are connected to the measuring device 28. That is, three types of signals obtained through the three lead wires coming out from the sample S2 are transmitted to the measuring device 28 via the receiving terminal portion 30, the load cell main body, and the pedestal terminal portion 31 of each load cell. Since the three load cells are electrically insulated by the insulating plate 24 and the insulating plate 25, electrical signals do not interfere with each other.

  The insulating plates 24 and 25 are made of an insulating material having an electrically high resistance value, and a material having high rigidity is desirable mechanically. The electrical resistance needs to be a value far higher than the resistance value of the load cell itself as a conductor, and the mechanical rigidity needs to be at least a value much higher than the rigidity of the strain-generating portion of the load cell 1. Furthermore, high mechanical rigidity is required in order to apply a force evenly to a plurality of load cells. Specifically, ceramic plates, plastic plates, or the like can be used as the insulating plates 24 and 25.

  In FIG. 3, since there are three lead wires, three load cells are used. However, the number of load cells may be four or more. In general, the number of load cells may be a number of load cells exceeding the number of lead wires. Further, the measurement of the test force can be represented by the output from one of the three load cells. In this case, for example, a force measurement signal coming out of the load cell 21 may be input to the force measuring instrument. Alternatively, the outputs from two or three load cells may be added or averaged and measured as a force. The idea is the same when four or more lead wires are required, and more load cells than the number of lead wires may be used.

  An example of a method for measuring physical properties with the configuration of FIG. 3 will be described. For example, it is assumed that the sample S2 is a substance such as a piezoelectric element and generates an electromotive force when a force is applied. A compressive stress is applied to the sample S2 by the load portion 27 in the connected state as shown in FIG. The arrow described in the load part 27 indicates the movement of the load part 27 and the direction in which the force is applied. Considering the case where the electromotive force generated in two directions of the sample is measured at that time, if one terminal is used in common, three lead wires are required in total. Since the three lead wires coming out of the sample S2 are connected to the receiving terminal portions 30 of the three load cells, the respective signals are transmitted to the measuring device 28 via the base terminal portions 31 of the respective load cells. Two electromotive forces are measured.

  When force is applied to the sample S2, the position of the sample S2 moves downward by the amount of deformation of the load cells 21 to 23, but the position of the pedestal terminal portion 31 does not move at all. Stiffness has no effect. Further, since the lead wire 29 coming out of the sample S2 only moves in the same manner as the sample S2 and the receiving terminal portion 30, it does not deform at all, and the rigidity of the lead wire 29 has no influence on the force measurement by the load cells 21-23. Not give.

  The physical property evaluation test apparatus of the present invention is not limited to the above-described example, and includes various specific apparatuses. This includes all devices that use a lead wire to extract an electrical signal from a sample while applying a tensile or compressive force to the sample to be tested, and that use a load cell for force measurement.

  For example, the present invention can be applied to the following apparatuses. The sample is an electrical switch such as a micro switch having a mechanical contact, and is a device that measures a resistance value between the contacts while applying a force like an operation of turning on the actuator part. Evaluate what happens to the force value when the switch is turned on and the resistance value at that time. By repeating the operation of turning on the switch many times, it can be used for a durability test device for the sample switch.

  In the case of application to contact resistance measurement and durability test associated with electrical connector insertion / extraction, the resistance value between the combined connector contacts is measured. When measuring the mechanical strength such as how much tensile force a small wiring can withstand, such as the wiring in an IC, the resistance value between the wiring and its connecting portion or the presence or absence of conduction is measured.

It is an example of the load cell of this invention. It is an example of the physical property evaluation test apparatus of the present invention. It is another example of the physical property evaluation test apparatus of this invention. It is an example of a conventional test apparatus

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Load cell, 2 ... Load receiving part, 3 ... Fixed base part, 4 ... Strain part, 5 ... Receiving terminal part, 6 ... Base terminal part, 7 ... Strain gauge, 10 ... Frame, 11 ... Load part, DESCRIPTION OF SYMBOLS 12 ... Cable, 13 ... Measuring device, 21 ... Load cell, 22 ... Load cell, 23 ... Load cell, 24 ... Insulating plate, 25 ... Insulating plate, 26 ... Frame, 27 ... Load part, 28 ... Measuring device, 29 ... Lead wire, DESCRIPTION OF SYMBOLS 30 ... Receiving terminal part, 31 ... Base terminal part, 32 ... Cable, 51 ... Frame, 52 ... Load cell, 53 ... Sample, 54 ... Load part, 55 ... Lead wire, 56 ... Measuring device

Claims (3)

  In a load cell having a strain-generating portion between a load seat for receiving a force and a mounting base for fixing itself to another member, the load cell itself is formed of an electrically conductive material, A load cell having a receiving terminal portion on the load seat and a pedestal terminal portion on the mounting base as electrical connection terminals, and an electrical continuity between the two terminal portions. .   A physical property evaluation test apparatus for evaluating electrical properties of a test object in a state where a force is applied to the test object, comprising the load cell according to claim 1 for detecting a force applied to the test object, wherein a lead wire from the test object is provided. An apparatus for evaluating physical properties, wherein an electrical signal is extracted from the pedestal terminal portion in a state of being connected to the receiving terminal portion. 2. A physical property evaluation test apparatus for evaluating an electrical property of a test object in a state where a force is applied to the test object, wherein there are a plurality of lead wires from the test object and the force applied to the test object is detected. More than the number of load cells corresponding to the number of the lead wires, and with each lead wire connected to the receiving terminal portion of a separate load cell, the load cell is electrically connected from the base terminal portion of the load cell to which the lead wire is connected. A physical property evaluation test apparatus characterized by taking out a physical signal.

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