JP6036495B2 - Displacement measuring device and material testing machine - Google Patents

Description

  The present invention relates to a displacement measuring apparatus and a material testing machine for measuring a displacement amount of a test piece when a tensile load or a compression load is applied to the test piece.

  As a material testing machine that performs a tensile test and a compression test on a test piece, a table, an upper crosshead connected to the table via a support, and a ram cylinder that raises and lowers the table and the upper crosshead synchronously A lower crosshead that can be moved up and down along the column, a pair of screw rods that raise and lower the lower crosshead, and a force detection sensor that detects a test force applied between the table or the upper crosshead and the lower crosshead What is provided with is known.

  When performing a tensile test in such a material testing machine, the ram is held in a state where both ends of the test piece are gripped by the upper gripping tool disposed on the upper crosshead and the lower gripping tool disposed on the lower crosshead. The upper crosshead is raised relative to the lower crosshead by driving the cylinder. On the other hand, when a compression test is performed in this material testing machine, the table is raised with respect to the lower crosshead by driving the ram cylinder in a state where a test piece is disposed between the lower crosshead and the table. The displacement amount of the test piece at this time is acquired from the stroke amount of the ram cylinder detected by the ram stroke detector.

  The ram stroke detector has a wire having one end fixed to a table and the other end fixed to a holding member that moves up and down with the table, a pulley wound around the wire and rotating as the wire moves, and detecting the rotation of the pulley. One having a rotary encoder is known (see Patent Document 1).

  Also, as a material testing machine for performing a tensile test, a pair of screw rods erected on a base, a drive mechanism for rotating the pair of screw rods in synchronization, and a crosshead erected on the pair of screw rods are provided. Things are known. When performing a tensile test in such a material testing machine, raise the crosshead while holding both ends of the test piece with the upper gripping tool provided on the crosshead and the lower gripping tool provided on the table. Let And the displacement amount of the test piece at this time is acquired by a contact-type elongation measuring device or the like.

  This elongation measuring device is a pair of upper and lower levers that are brought into contact with a test piece, a wire having one end connected to the lever and a weight (weight) connected to the other end, and the wire is wound and rotated by movement of the wire. And a rotary encoder that detects the rotation of the pulley (see Patent Document 2). The elongation measuring device acquires the amount of elongation of the test piece by measuring the amount of movement of the lever that moves following the elongation of the test piece given a tensile load.

  In the displacement measuring device such as the ram stroke detector described in Patent Document 1 and the elongation measuring device described in Patent Document 2, the movement of the wire accompanying the movement of a member such as a lever to be brought into contact with the load member or the test piece. A configuration is adopted in which the amount is detected by a rotary encoder as the amount of rotation of the pulley around which the wire is wound. The number of pulses corresponding to the amount of rotation is output to the control circuit of the material testing machine. The control circuit of the material testing machine calculates the amount of elongation (displacement) of the test piece according to the number of pulses input from the rotary encoder. The displacement amount per pulley rotation is a value obtained by multiplying the sum of the pulley diameter and the wire diameter by the circular ratio. Therefore, the displacement amount per rotation of the rotary encoder can be obtained in advance.

Japanese Utility Model Publication 4-21091 JP-A-11-281349

  However, the diameter and circumferential length of the pulley include processing errors, and the diameter of the wire changes depending on the elongation rate of the wire itself. For this reason, the number of pulses per rotation of the rotary encoder varies depending on each displacement measuring device or each set of pulleys, wires and rotary encoders that transmit and signal the actual displacement in the displacement measuring device, The amount of displacement per rotation of the rotary encoder is slightly different from the calculated value. Such a difference affects the accuracy of detecting the displacement of the test piece.

  Furthermore, it is technically very difficult to accurately place the pulley rotation center at the rotary encoder rotation center, so that a slight deviation occurs between the pulley rotation center and the rotary encoder rotation center. Such an error in the amount of wire movement that is less than one rotation of the rotary encoder due to the eccentricity between the pulley and the rotary shaft of the rotary encoder also affects the accuracy of displacement detection.

  As described above, in order to avoid the error of the members such as pulleys and wires constituting the displacement detection mechanism in the displacement measuring device from becoming a displacement measurement error, the output to the displacement indicator or the like according to the input from the rotary encoder It is conceivable to perform pulse rate conversion to adjust the pulse. FIG. 11 is an explanatory diagram showing an example of pulse rate conversion in a conventional displacement measuring apparatus. FIG. 11 shows an actual displacement and displacement display of a test piece when a tensile test is performed in a material testing machine equipped with a displacement measuring device that displays a value obtained by converting one pulse of a rotary encoder into a displacement of 10 μm in length. It is a graph which shows the difference with the display value of a vessel. In the graph of FIG. 11, black squares and triangular points are displacements in the pulse output time from the rotary encoder, and a broken line connecting the black squares indicates a change in actual displacement, and connects the triangular points. A solid line indicates a change in the display value.

  When the length of one pulse of the rotary encoder is actually 12 μm, the actual displacement changes linearly at 12 μm / 1 count, whereas the displayed value increases in units of 10 μm. In the example shown in FIG. 11, when the error accumulation of 12−10 = 2 μm reaches 10 μm (one pulse), the pulse counter on the displacement indicator side with respect to one pulse input from the rotary encoder. By adjusting so that the output pulse to 2 is 2 pulses, an error of 10 μm or more is prevented from occurring between the actual displacement and the display value. In such a pulse rate conversion, for example, using an electronic gear with a denominator: numerator = 1: 1.2, the surplus value for the denominator of the numerator is integrated, and the adjustment is performed when the integrated value becomes a multiple of the denominator. 1 pulse is output to the display. For this reason, as shown in FIG. 11, the displayed value may increase by 20 μm from the previous value, and the error in the displacement measurement also varies in the range of 0 to 8 μm.

  On the other hand, from the viewpoint of improving the reliability of the displacement measurement value, the error between the actual displacement and the display value obtained by calculation is preferably smaller, and the fluctuation range of the error is preferably smaller.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide a displacement measuring apparatus and a material testing machine in which the accuracy of displacement measurement is further improved.

The invention according to claim 1 is a displacement measuring device for measuring a displacement amount of a test piece when a tensile load or a compression load is applied to the test piece, and is wound around a pulley in a state where the tension is given. A displacement detection mechanism having a movement transmission member that rotates the pulley by moving with the displacement of the test piece, a rotary encoder that detects rotation of the pulley, and amplification of the number of input pulses from the rotary encoder Electronic gear in which the values of the electronic gear numerator and the electronic gear denominator are determined based on the basic magnification used as a reference for the rate and the displacement measurement error caused by the member constituting the displacement detection mechanism obtained by calibration And an accumulator for accumulating a difference between the value of the electronic gear numerator and the value of the electronic gear denominator, and one input pulse from the rotary encoder according to a value held by the accumulator. Respect, the number of pulses of the value of the integer portion of the gear ratio of the electronic gear molecule, or, and a pulse rate converter for outputting a pulse count value plus 1 of the integer part of the gear ratio of the electronic gear, the basic multiplier is characterized der Rukoto least twice in the pulse rate conversion unit.

  According to a second aspect of the present invention, in the first aspect of the present invention, the basic magnification in the pulse rate conversion unit is 10 to 1000 times.

According to a third aspect of the present invention, there is provided a movement transmitting member that is wound around a pulley in a state where a tension is applied and rotates the pulley by moving in accordance with a displacement of a test piece to which a tensile load or a compression load is applied. And a rotary encoder that detects the rotation of the pulley, and a material that performs a material test that applies a tensile load or a compressive load to the test piece by driving the load mechanism. A testing machine based on a basic magnification as a reference for an amplification factor of the number of input pulses from the rotary encoder and a measurement error of a displacement amount caused by a member constituting the displacement detection mechanism obtained by calibration; An electronic gear for which values of an electronic gear numerator and an electronic gear denominator are determined, and an accumulator for accumulating a difference between the value of the electronic gear numerator and the value of the electronic gear denominator, Depending on the value held by the accumulator, the number of pulses of the integer part of the gear ratio of the electronic gear or the integer part of the gear ratio of the electronic gear for one input pulse from the rotary encoder Rate conversion section that outputs the number of pulses plus one, and the displacement conversion that counts the output pulses converted by the pulse rate conversion section and converts it to the displacement amount of the test piece based on the counted value A controller, and a controller, connected to the controller, an input unit for inputting the value of the electronic gear denominator and the value of the electronic gear numerator in the pulse rate converter, and connected to the controller, comprising a display unit for displaying the displacement amount of the calculated specimen in displacement conversion unit, wherein the basic multiplier in the pulse rate conversion unit is characterized in der Rukoto least twice.

  According to a fourth aspect of the present invention, in the third aspect of the present invention, the basic magnification in the pulse rate conversion unit is 10 times to 1000 times.

  According to a fifth aspect of the present invention, in the invention according to the third aspect, the pulse rate conversion unit is configured to detect whether the electronic gear numerator and the electronic gear denominator are positive or negative depending on whether the pulse of the rotary encoder is normal rotation or reverse rotation. A selector for selecting the value of the electronic gear numerator as a value to be added to the accumulator, and the positive or negative value of the electronic gear numerator selected by the selector is added to the accumulator for each input pulse. And based on the comparison between the value held in the accumulator and the value of the electronic gear denominator, the absolute value of the value held in the accumulator is larger than the value of the electronic gear denominator. Sometimes, one pulse is output, and the accumulator is added with the value of the electronic gear denominator that is a positive or negative opposite sign of the value of the electronic gear selected by the selector. Retained When the absolute value of the current value is equal to the value of the electronic gear denominator or smaller than the value of the electronic gear denominator, by not outputting a pulse, one input pulse from the rotary encoder The number of pulses of the integer part of the gear ratio for the electronic gear or the number of pulses of the integer part of the gear ratio of the electronic gear plus one is output.

  According to the first to fifth aspects of the present invention, the output pulse of the rotary encoder is adjusted by the pulse rate conversion unit provided with the electronic gear, the actual displacement of the test piece in the material test, and the output pulse of the rotary encoder Thus, the error between the display value obtained by calculation based on the above and the fluctuation range of the error can be made smaller, and the accuracy of displacement measurement can be improved.

  According to the second and fourth aspects of the invention, since the basic magnification is 10 to 1000 times, the basic magnification is obtained by calculation based on the actual displacement of the test piece in the material test and the output pulse of the rotary encoder. The error from the display value on the display side and the fluctuation range of the error can be further reduced.

1 is a schematic diagram of a material testing machine according to the present invention. 2 is a schematic diagram of a displacement measuring device 50. FIG. 5 is an explanatory diagram showing an overview from displacement measurement to display of measured values on the display unit 36 in the displacement measuring device 50. FIG. 4 is a block diagram of a pulse rate conversion circuit 60. FIG. 6 is a flowchart showing a procedure for determining an electronic gear denominator and an electronic gear numerator of the pulse rate conversion circuit 60; 5 is a flowchart for explaining the operation of a pulse rate conversion circuit 60. 4 is a graph showing the relationship between the setting of the electronic gear and the error between the actual displacement and the display value displayed on the display unit 36. It is a graph which shows the power spectrum of the error shown in FIG. It is a figure which shows the outline | summary of the material testing machine which concerns on other embodiment of this invention. 1 is a schematic diagram of a displacement measuring device 150. FIG. It is explanatory drawing which shows an example of the pulse rate conversion in the conventional displacement measuring apparatus.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram of a material testing machine according to the present invention.

  This material testing machine includes a table 16, a pair of support posts 19 erected on the floor, and a pair of screw rods erected so as to be able to rotate vertically on the table 16 inside each support column 19. 11, a crosshead 13 movable along the screw rods 11, and a load mechanism 30 for moving the crosshead 13 to apply a test force to the test piece 10. FIG. 1 shows a state in which the left column 19 of the pair of columns 19 is removed.

  The cross head 13 is connected to the pair of screw rods 11 via nuts (not shown). A lower end portion of each screw rod 11 is connected to the load mechanism 30, and power from a motor as a power source in the load mechanism 30 is transmitted to the pair of screw rods 11. As the pair of screw rods 11 rotate in synchronization, the cross head 13 moves up and down along the pair of screw rods 11.

  The crosshead 13 is provided with an upper gripping tool 21 for gripping the upper end portion of the test piece 10. On the other hand, the table 16 is provided with a lower gripping tool 22 for gripping the lower end portion of the test piece 10. When performing a tensile test, the test force (tensile load) is applied to the test piece 10 by raising the crosshead 13 in a state where both ends of the test piece 10 are gripped by the upper gripping tool 21 and the lower gripping tool 22. ). At this time, the test force acting on the test piece 10 is detected by the load cell 14 and input to the control unit 35. Further, the displacement amount of the test piece 10 is measured by a contact-type displacement measuring device 50 disposed on the table 16.

  The control unit 35 is configured by a computer including a CPU and a sequencer. As shown in FIG. 1, the load cell 14, the load mechanism 30, and the displacement measuring device 50 are connected to the control unit 35. And the control part 35 takes in the test force data from the load cell 14, and the data from the displacement measuring apparatus 50, and performs a data process. The test force on the test piece 10 and the amount of displacement of the test piece 10 are obtained by such processing as calculation in the control unit 35. The control unit 35 is also connected to a display unit 36 and an input unit 37, and the display unit 36 displays a displacement amount of the test piece 10 and the like.

  FIG. 2 is a schematic diagram of the displacement measuring device 50. 2A is a left side view and FIG. 2B is a front view.

  The displacement measuring device 50 includes struts 51a and 51b, guide rails 52, pulleys 53a and 53b, rotary encoders 54a and 54b, an upper arm 56, a lower arm 57, a pair of wires 58a and 58b, and a pair of balance weights 59a and 59b. Is provided. The support columns 51 a and 51 b are erected in the load direction of the test piece 10. The guide rail 52 is provided between the support column 51a and the support column 51b. The pulleys 53a and 53b and the rotary encoders 54a and 54b are disposed at the upper ends of the respective columns 51a and 51b. The rotary encoder 54a is connected to the rotating shaft of the pulley 53a, and the rotary encoder 54b is connected to the rotating shaft of the pulley 53b. ing.

  On the guide rail 52, an upper arm 56 and a lower arm 57 are respectively held so as to be movable up and down. A wire 58a is wound around the pulley 53a, and a wire 58b is wound around the pulley 53b. An upper arm 56 is connected to one end of the wire 58a, and a balance weight 59a is suspended from the other end. Similarly, a lower arm 57 is connected to one end of the wire 58b, and a balance weight 59b is suspended from the other end. The wires 58a and 58b correspond to the movement transmission member of the present invention, and move with the movement of the upper arm 56 and the lower arm 57, thereby rotating the pulleys 53a and 53b. The movement transmission member is not limited to a wire, and a toothed belt such as a timing belt meshing with a timing pulley or the like, a toothed rope, or the like may be employed. The wires 58 a and 58 b, the pulleys 53 a and 53 b, and the rotary encoders 54 a and 54 b are members that constitute a displacement detection mechanism in the displacement measuring device 50.

  The upper arm 56 and the lower arm 57 are arranged apart from each other by a predetermined distance so as to sandwich the test piece 10 gripped at both ends by the upper gripping tool 21 and the lower gripping tool 22. Although not shown, each of the upper arm 56 and the lower arm 57 has a pair of opening / closing levers and an actuator for operating the opening / closing levers. Can be removed.

  When the tensile test is being performed, the upper arm 56 and the lower arm 57 move along the guide rail 52 following the elongation of the test piece 10. In the material testing machine including the displacement measuring device 50, the number of pulses output from the rotary encoder 54 a that detects the amount of rotation of the pulley 53 a according to the amount of movement of the upper arm 56 of the displacement measuring device 50, and the lower arm 57. The amount of displacement of the test piece 10 is calculated based on the difference from the number of pulses output from the rotary encoder 54b that detects the amount of rotation of the pulley 53b according to the amount of movement.

  FIG. 3 is an explanatory diagram showing an outline from the displacement measurement to the display of the measured value on the display unit 36 in the displacement measuring device 50.

  The pulse signal output from the rotary encoder 54a is input to the pulse rate conversion circuit 60a and then output to the counter circuit 62. The pulse signal output from the rotary encoder 54b is input to the pulse rate conversion circuit 60b and then output to the counter circuit 62. In this embodiment, an error caused by the pulley 53a and the wire 58a that are members for detecting the amount of movement of the upper arm 56 and a pulley 53b and a wire 58b that are members for detecting the amount of movement of the lower arm 57 are added. The resulting error is individually adjusted by the pulse rate conversion circuit 60a and the pulse rate conversion circuit 60b. In this specification, the pulse rate conversion circuit 60a and the pulse rate conversion circuit 60b are collectively referred to as the pulse rate conversion circuit 60, and the pulley 53a and the pulley 53b are collectively referred to as the pulley 53, the rotary encoder 54a, and the rotary encoder 54b. When collectively referred to, the rotary encoder 54, the wire 58a, and the wire 58b are collectively referred to as a wire 58. The pulse rate conversion circuit 60 functions as a pulse rate conversion unit of the present invention.

  The counter circuit 62 calculates the difference between a register that separately counts and holds the number of input pulses from the pulse rate conversion circuit 60a and the number of input pulses from the pulse rate conversion circuit 60b, and a count value held by each register. A difference value between the number of input pulses from the pulse rate conversion circuit 60a and the number of input pulses from the pulse rate conversion circuit 60b obtained in the calculation unit is output to the displacement conversion circuit 63. This difference value corresponds to a value obtained by multiplying the number of pulses corresponding to the relative movement amount of the upper arm 56 and the lower arm 57 by a basic magnification of the electronic gear in the pulse rate conversion circuit 60 described later. For this reason, the displacement conversion circuit 63 has a length per one pulse output from the pulse rate conversion circuit 60 obtained by dividing the length (μm) per output pulse of the rotary encoder 54 by the basic magnification with respect to the number of differential pulses. The displacement amount is obtained by multiplying by (μm). Then, the calculated displacement amount is displayed on the display unit 36. Note that the counter circuit 62 and the displacement conversion circuit 63 may be realized by an integrated circuit such as a PLD or FPGA arranged on the displacement measuring device 50 side, or an integrated circuit arranged in the control unit 35 that controls the entire material testing machine. Etc. may be realized.

  FIG. 4 is a block diagram of the pulse rate conversion circuit 60. FIG. 5 is a flowchart showing the procedure for determining the conversion rate of the pulse rate conversion circuit 60, and FIG. 6 is a flowchart for explaining the operation of the pulse rate conversion circuit 60.

  The pulse conversion rate in the pulse rate conversion circuit 60 is adjusted by the electronic gear. That is, as shown in FIG. 5, the value of the electronic gear denominator is determined from the maximum pulse rate that can be set in the pulse rate conversion circuit 60 and the processing capability of the circuit that implements the pulse rate conversion circuit 60. (Step S10). At this time, the basic magnification of the electronic gear denominator and the electronic gear numerator can also be determined. The basic magnification is a magnification used as a reference for the amplification factor of the number of input pulses from the rotary encoder 54. Thereafter, the displacement measuring device 50 is calibrated, and the actual displacement value is determined by the number of pitches per revolution of the pulley, the nominal value of the movement amount per pitch of the wire, and the revolution encoder per revolution. The value of the electronic gear numerator is determined in consideration of how much the displacement is deviated from the nominal value of the displacement obtained from the count number (step S20). For example, when the value of the electronic gear denominator is set to 1 in step S10 and the basic magnification is set to 100, the nominal value of the amount of movement of the wire per pitch is 2 mm, and it is acquired per calibration operation. If the measured value of the displacement amount is 2.02 mm, the displacement measurement error obtained by this calibration is 0.02 mm per pitch. The value of the electronic gear numerator is determined to be 101 (= actual value / nominal value × basic magnification).

  As shown in FIG. 4, the pulse rate conversion circuit 60 includes an accumulator 72 that is an electronic gear and an accumulator, performs output adjustment using the electronic gear for each pulse input from the rotary encoder 54, and outputs a pulse rate. Perform the conversion. Values determined by the procedure shown in FIG. 5 are set in the electronic gear denominator and the electronic gear numerator of the pulse rate conversion circuit 60 using the input unit 37 and the like.

  For example, when the actual measurement value (2.02 mm) of the displacement obtained by the calibration work on the upper arm 56 side or the lower arm 57 side of the displacement measuring device 50 is longer than the nominal value (2 mm) of the displacement obtained by calculation For the electronic gear denominator and the electronic gear numerator, the basic magnification is set to 10 and values such as electronic gear denominator = 10, electronic gear numerator = 101 are set. Note that the values of the basic magnification and the electronic gear denominator are determined as values that can absorb the error between the nominal value of the displacement and the actual measurement value, and are not limited to the values shown in this embodiment.

  The basic magnification of the present invention is a number of 2 or more, and indicates how much the number of pulses output from the rotary encoder 54 is amplified by the pulse rate conversion circuit 60 (amplification factor). In the present invention, since the error between the nominal value and the actual measurement value of the displacement obtained by calibration is adjusted by the electronic gear, the electronic gear numerator is often not a value divisible by the electronic gear denominator. Therefore, the basic magnification is such that the difference between the value obtained by multiplying the basic magnification by the electronic gear denominator and the value of the electronic gear numerator is within a predetermined range (for example, a range within ± 20% of the value of the electronic gear numerator). The value satisfies the following condition. Further, the display value on the display unit 36 side obtained by calculation based on the actual displacement directly derived by the amount of movement of the upper arm 56 or the lower arm 57 and other measurement methods and the number of pulses output from the rotary encoder 54. From the viewpoint of reducing the error, it is more preferable to convert the output of one pulse of the rotary encoder 54 to a large pulse rate such as 10 times to 1000 times. Therefore, the basic magnification (pulse rate amplification factor) in the pulse rate conversion circuit 60 is preferably 10 to 1000 times.

  Hereinafter, the operation of the pulse rate conversion circuit 60 will be described by taking as an example a case where the rotary encoder 54 is rotated in the forward direction (forward rotation), the electronic gear numerator is set to 101, and the electronic gear denominator is set to 10. When the rotary encoder 54 rotates and the phase of the A / B phase changes, the U / D signal (UP / DOWN pulse) that can be used by the pulse rate conversion circuit 60 for the A / B phase pulse output from the rotary encoder 54 The UP pulse is input to the control circuit 71 through the converter 78 that converts the signal into the control circuit 71. The control circuit 71 controls the operation of the pulse rate conversion circuit 60.

  When the UP pulse is input to the control circuit 71 (step S1), +101 which is “numerator” is selected and added to the accumulator 72 including the adder 77 and the register 76 (step S2). At this time, the value of the accumulator 72 becomes +101 (integrated value 0 + electronic gear numerator 101 = 101), and this value is held in the register 76. When a DOWN pulse is input to the control circuit 71 (step S3),-"molecule" (for example, -101) is added to the accumulator 72 (step S4). That is, the selector 73 selects which of the positive and negative values should be given to the accumulator 72 according to whether the input pulse is an UP pulse or a DOWN pulse.

  When the value of the accumulator 72 is +101 and an output timing signal is input at a timing when neither the UP pulse nor the DOWN pulse is input (step S5), the value held in the register 76 after the addition in step S2 +101 and the value +10 of the electronic gear denominator are compared by the first comparator 74 (step S6). In the block diagram shown in FIG. 4, the output timing signal is set to 1 MPPS (1 mega pulse per second) which is the maximum output pulse rate from the pulse rate conversion circuit 60 that can be allowed by the counter circuit 62.

  In this example, as a result of the comparison by the first comparator 74, the value 10 of the electronic gear denominator is a value smaller than +101. Therefore, an electron having an opposite sign to the positive value of the electronic gear numerator added in step S2 The gear denominator negative value (− “denominator”) −10 is selected by the selector 73 and added to the adder 77 (here, the value of the accumulator 72 becomes 91, and this value is held in the register 76 as an integrated value). The UP pulse is output via the control circuit 71 (step S7). The output UP pulse is converted by a converter 79 that converts the U / D signal into an A / B phase pulse, and is sent to the counter circuit 62.

  When the DOWN pulse is input to the pulse rate converter 60 and the value of the accumulator 72 to be compared with the value of the electronic gear denominator is a negative value such as 101, the accumulator 72 held in the register 76 has a negative value. The value −101 is compared with −10 which is the value of “denominator” by the second comparator 75 (step S8). In this case, since −101 of the accumulator 72 is smaller than −10 of − “denominator”, +10 of “denominator” is selected by the selector 73 and added to the adder 77, and a DOWN pulse is sent from the control circuit 71. Is output (step S9). That is, in the pulse rate conversion circuit 60, the first comparator 74 functions as a UP pulse comparator, and the second comparator 75 functions as a DOWN pulse comparator.

  Further, in the pulse rate conversion circuit 60, the pulse frequency (for example, 1 MPPS) of the timing signal input from the reference oscillator is determined by the displacement amount when the test piece 10 is displaced by the tensile test and the increment of the displacement amount per time. The frequency is sufficiently higher than a frequency (for example, a maximum of 5 kHz) obtained from a certain increase speed. For this reason, one UP pulse or DOWN pulse is input in the pulse rate conversion circuit 60, and + "numerator" is added to the accumulator 72 in step S2, or-"numerator" is added to the accumulator 72 in step S4. The output timing signal is input without an UP pulse or DOWN pulse input than the opportunity. In step S7, “-denominator” is added to the accumulator 72, or + “denominator” is added to the accumulator 72 in step S9. There will be more opportunities to be played.

  Therefore, when the rotary encoder 54 rotates in the forward direction (forward rotation), the pulse rate conversion circuit 60 makes a determination of No in step S1, No in step S3, Yes in step S5, and Yes in step S6. In step S7, the operation of adding “denominator” and returning to step S1 is repeated until the absolute value of the value of the register 76 becomes smaller than the value of the denominator in step S6, thereby continuously outputting UP pulses. Will continue. Assuming that the next UP pulse is input, it is determined No in step S1, No in step S3, Yes in step S5, Yes in step S6, and in step S7-"denominator" is added and step S1 is added. When the operation of returning to 10 is repeated 10 times, 10 UP pulses are continuously output to the counter circuit 62, and the value of the register 76 becomes +1. Thereafter, the output timing signal is input faster than the input of the next UP pulse (step S5). When the comparison is performed in step S6, the value of the register 76 is +1 and is smaller than the denominator value +10. Then,-"denominator" is not added to the accumulator 72, the UP pulse is not output to the counter circuit 62, and the process returns to step S1. That is, the state waits for the accumulator 72 to be given a value of + “numerator” or − “numerator” by the input of the next UP pulse.

  Similarly, when the rotary encoder 54 rotates (reverses) in the reverse direction, the pulse rate conversion circuit 60 determines No in step S1, No in step S3, Yes in step S5, No in step S6, and Yes in step S8. The operation of adding + “denominator” in step S9 and returning to step S1 is repeated until the absolute value of the value of the register 76 becomes smaller than the value of the denominator in step S8, thereby continuously outputting DOWN pulses. Will continue. When there is an output timing signal input faster than the input of the next DOWN pulse and the value of the register 76 becomes a value larger than − “denominator” (step S6), + “denominator” is added to the accumulator 72. Without the DOWN pulse being output to the counter circuit 62, the process returns to step S1. That is, the state waits for the value of “numerator” to be given to the accumulator 72 by the input of the next DOWN pulse.

  In the above-described example, the maximum frequency that can be set is set for the frequency of the timing signal in consideration of the counting processing capability of the counter circuit 62 and the processing capability of the accumulator 72 of the pulse rate conversion circuit 60. The frequency of the timing signal is, for example, a frequency that is 100 to 500 times the frequency that is obtained from the displacement rate when the test piece 10 is displaced by the tensile test and the increase rate that is the increment of the displacement amount per time. Even when the basic magnification is large, the value of the register 76 does not accumulate until the value exceeds the capability of the register 76.

  When the rotary encoder 54 rotates in the forward direction and the accumulated value held by the register 76 in the accumulator 72 is +1, if an UP pulse is further input from the rotary encoder 54 via the converter 78 to the control circuit 71 (step) S1) +101 which is “numerator” is selected and added to the accumulator 72 by the selector 73 (step S2). At this time, the value of the accumulator 72 is +102 (integrated value 1 + electronic gear numerator 101 = 102). When an output timing signal is input (step S5), the value +102 of the register 76 and the electronic gear denominator value 10 are compared by the first comparator 74 (step S6). In this case, since the electronic gear denominator is smaller than the value of the register 76, −10 which is “denominator” is selected by the selector 73 and added to the adder 77 (where the value of the accumulator 72 is The UP pulse is output via the control circuit 71 (step S7).

  As described above, when the rotary encoder 54 rotates in the forward direction (forward rotation), when the signal of the rotary encoder 54 is input to the pulse rate conversion circuit 60, steps S1 and S2 in the flowchart of FIG. A signal is output to the counter circuit 62 through S5, S6, and S7. Further, when the rotary encoder 54 rotates (reverses) in the reverse direction, when the signal of the rotary encoder 54 is input to the pulse rate conversion circuit 60, steps S3, S4, S5, S8, A signal is output to the counter 62 through S9.

  In this pulse rate conversion circuit 60, the value of the electronic gear numerator is accumulated in the accumulator 72 every time one pulse is received from the rotary encoder 54, and every time one pulse is output from the pulse rate conversion circuit 60, the accumulator 72 The value of the electronic gear denominator is subtracted from the integrated value. As a result of such accumulation in the accumulator 72, the difference (value of the decimal part of the gear ratio) between the value of the electronic gear numerator and the value obtained by multiplying the electronic gear denominator by the basic magnification repeats the input and output of the pulse. It will be accumulated in the accumulator 72 later.

  If the electronic gear numerator is set to 101 and the electronic gear denominator is set to 10, if there are 10 pulse inputs from the rotary encoder 54, 9 out of 10 pulse inputs will be 1 input pulse. On the other hand, 10 pulses, which is the value of the integer part of the gear ratio 10.1 (electronic gear numerator / electronic gear denominator = 101/10) of the electronic gear, are output to the counter circuit 62, and the remaining one input pulse is output. Thus, 11 pulses of the value +1 of the integer part of the gear ratio 10.1 of the electronic gear are output to the counter circuit 62. That is, when the electronic gear numerator is set to 101 and the electronic gear denominator is set to 10, the gear ratio of the electronic gear is set to one input pulse at a frequency of once every 10 input pulses from the rotary encoder 54. The number of pulses of the integer part value + 1 is output from the pulse rate conversion circuit 60 to the counter circuit 62.

  On the other hand, if the electronic gear numerator is set to 99 and the electronic gear denominator is set to 10 and there are 10 pulse inputs from the rotary encoder 54, the first input pulse of the 10 pulse inputs 9 pulses of the integer part of the electronic gear ratio 9.9 (electronic gear numerator / electronic gear denominator = 99/10) are output to the counter circuit 62, and the remaining nine pulse inputs are output. Thus, 10 pulses of the value +1 of the integer part of the gear ratio 9.9 obtained by dividing the electronic gear numerator 99 by the electronic gear denominator 10 for one input pulse are output to the counter circuit 62. In other words, if the electronic gear numerator is set to 99 and the electronic gear denominator is set to 10, the frequency of the electronic gear gear ratio with respect to one input pulse is once per 10 times of the input pulses from the rotary encoder 54. The number of pulses of the integer part value is output from the pulse rate conversion circuit 60 to the counter circuit 62.

  FIG. 7 is a graph showing the relationship between the setting of the electronic gear and the error between the actual displacement and the display value displayed on the display unit 36. FIG. 8 is a graph showing the power spectrum of the error shown in FIG.

The horizontal axis of the graph of FIG. 8 indicates time (seconds), and the vertical axis indicates the error (mm) between the actual displacement and the calculated value based on the pulse output from the pulse rate conversion circuit 60 displayed on the display unit 36. Show. Each point indicated by a square, a circle, and a triangle in the graph corresponds to a displacement in the output time of one pulse output to the pulse rate conversion circuit 60, and a line connecting the triangle points is an electronic gear denominator: Electronic gear numerator = 1: 101.6, a line connecting round dots is electronic gear denominator: electronic gear numerator = 1: 10.16, a line connecting square dots is electronic gear denominator: electronic gear numerator = 1: 1. A change in error when adjusted by the electronic gear 016 is shown. Further, in the graph of FIG. 8 , the error spectrum of the electronic gear denominator: electronic gear numerator = 1: 1.016 is represented by a solid line, and the error spectrum of the electronic gear denominator: electronic gear numerator = 1: 1.16 is represented. The broken line shows the spectrum of the error of the electronic gear of electronic gear denominator: electronic gear numerator = 1: 101.6 with a two-dot chain line.

  The values of the electronic gear numerators shown in this graph are the same as that of the pulley 53a for detecting the position of the upper arm 56, the rotary encoder 54a, and the wire 58a in the displacement measuring device 50, respectively, a pulley with one rotation of 40 pitches and a rotation of 8000. Assuming that a rotary encoder with a count (a value obtained by multiplying the output of a rotary encoder of 2000 pulses / rotation by four) and a wire with a nominal movement amount per pitch of 2 mm is used, the explanation will be given with reference to FIG. This is determined through the calibration work in step S20.

  The nominal value of the displacement amount per pulse output from the rotary encoder 54a is {the nominal value of the movement amount per pitch of the wire 58a (mm)} × {number of pitches of one pulley rotation / count of one rotary encoder rotation. Number} can be calculated as 0.01 mm. Here, when the movement amount per pitch of the actual wire 58a obtained by the calibration operation is 2.032 mm and the basic ratio (basic magnification) of the electronic gear is denominator: numerator = 1: 1, the displacement amount The electronic gear considering the error between the nominal value and the actual measurement value is denominator: numerator = 1: 1.016.

  When the electronic gear is set to denominator: numerator = 1: 1.016, the displacement conversion unit 63 converts the displacement to a displacement amount as 0.01 mm per pulse. Then, every time one pulse is received from the rotary encoder 54 and one pulse is output from the pulse rate conversion circuit 60, the pulse rate conversion circuit 60 accumulates the decimal value 0.016 of the gear ratio as an error in the accumulator 72. , 63 pulses are received, the error accumulation becomes 1.008, which is larger than the value of the electronic gear denominator. That is, as shown in FIG. 7, one extra pulse is output at a frequency of once every 63 times, and the error is settled.

  However, when the electronic gear is set to denominator: numerator = 1: 1.016, the error between the actual displacement and the display value on the display unit 36 side is about 0.01 mm at the maximum. On the other hand, when the electronic gear is set to denominator: numerator = 1: 10.16 (basic magnification = 10 times) and denominator: numerator = 1: 101.6 (basic magnification = 100 times) as in the present invention, The error between the actual displacement and the display value on the display unit 36 side can be reduced to 1/10 or 1/100 according to the basic magnification. In this way, by increasing the basic magnification, the error between the actual displacement and the display value on the display unit 36 can be reduced. As shown in FIG. 8, the error increases as the basic magnification of the electronic gear increases. It can be understood from the fact that the spectrum is also small.

  As described above, in the present invention, the values of the electronic gear denominator and the electronic gear numerator of the pulse rate conversion circuit 60 including the electronic gear are set to be twice or more (preferably 10 times) the number of pulses input to the pulse rate conversion circuit 60. And a value capable of absorbing an error caused by a member constituting a displacement detection mechanism such as a wire or a pulley. As a result, the error between the display-side displacement display value calculated based on the number of output pulses of the rotary encoder and the actual displacement can be made smaller than before, and the accuracy of displacement measurement can be improved.

  Next, a material testing machine according to another embodiment of the present invention will be described. FIG. 9 is a diagram showing an outline of a material testing machine according to another embodiment of the present invention. In addition, about the structure similar to the material testing machine shown in FIG. 1, the same code | symbol is attached | subjected and detailed description is abbreviate | omitted.

  This material testing machine includes a table 16, an upper cross head 24 connected to the table 16 via a pair of support columns 32, and a ram cylinder 25 that is an actuator that raises and lowers the table 16 and the upper cross head 24 synchronously. A pair of screws that are screwed to a lower crosshead 26 that is disposed between the table 16 and the upper crosshead 24 so as to be movable up and down, and nuts with a rotation drive mechanism (not shown) provided at both ends of the lower crosshead 26.棹 31. The lower crosshead 26 can be moved up and down by rotating a nut with an electric motor or a hydraulic motor (not shown). Further, the pair of screw rods 31 are erected on the base 41 through the table 16.

  An upper grip 31 is disposed on the upper cross head 24, and a lower grip 32 is disposed on the lower cross head 26. The test piece 10 to be subjected to the tensile test is gripped at both ends by the upper gripping tool 31 and the lower gripping tool 32. The lower crosshead 26 is provided with a platen 28, and the test piece 10 to be subjected to the compression test is pressed at the upper and lower ends by the platen 28 and the table 16.

  The ram cylinder 25 has a configuration in which the ram 25b extends by supplying pressure oil to the cylinder chamber 25a. As the ram 25a extends, the table 16, the pair of struts 22, and the upper cross head 24 rise synchronously. Due to the rise of the table 16 and the upper cross head 24, a tensile load is applied to the test piece 10 held at both ends by the upper gripping tool 21 and the lower gripping tool 22 when performing a tensile test, and a platen 28 when performing a compression test. A compressive load is applied to the test piece 10 disposed between the table 16 and the table 16. The operation of the ram cylinder 25 is driven and controlled by a hydraulic source 38 that supplies pressure oil to the ram cylinder 25. The hydraulic power source 38 is controlled by the control unit 35.

  The test force at this time is measured by a pressure sensor 33 as a force detection sensor. This measured value is transmitted to the control unit 35 and displayed on the display unit 36 as necessary. Further, the movement amount of the table 16 and the upper cross head 24 at this time is detected by the displacement measuring device 150. This detected value is transmitted to the control unit 35, converted into a displacement amount of the test piece 10, and displayed on the display unit 36.

  FIG. 10 is a schematic diagram of the displacement measuring device 150. FIG. 10A is a view of the displacement measuring device 150 as viewed from the pulley arrangement side. FIG. 10B is a side view of the displacement measuring device 150.

  This displacement measuring device 150 detects the amount of movement of the table 16 when a tensile or compressive load is applied to the test piece 10, and calculates the amount of displacement of the test piece 10 from the detected value. Also called a vessel. The displacement measuring device 150 includes a pulley 153, a wire 158, and a rotary encoder 154 as members constituting a displacement detection mechanism that detects the amount of movement of the table. The displacement measuring device 150 includes a support plate 151 that is suspended from the lower surface of the table 16 and moves up and down together with the table 16, and a stand 155 that is erected on the base 41. The rotary encoder 154 is fixed to the stand 155. A pulley 153 is fixed to the rotary shaft of the rotary encoder 154, and a wire 158 is wound around the pulley 153. One end (upper end side) of the wire 158 is fixed to the table 16 that moves up and down by driving the ram cylinder 25 via the coil spring 159, and the other end is opposite to the connection end of the support plate 151 to the table 16. It is fixed to the end of the. Further, a coil spring 159, which is an elastic member, is interposed at a connection portion of the wire 158 to the table 16, so that the wire 158 is not loosened.

  When the table 16 moves up and down by driving the ram cylinder 25, the wire 158 moves and rotates the pulley 153. The rotary encoder 154 functions as detection means for detecting the rotation of the pulley 153 and outputs a signal to the pulse rate conversion circuit 60.

  In this embodiment, since the displacement measuring device 150 has one rotary encoder 154, one pulley 153, and one wire 158, the number of pulses output from the pulse rate conversion circuit 60 is counted as it is. In the displacement conversion unit 63 shown in FIG.

  Like this material testing machine, a pulley 153 that winds a wire 158 connected to a member constituting a load member such as a table 16, and a movement amount of the wire 158 is detected as a rotation amount of the pulley 153, and a pulse is detected. As means for adjusting the output pulse of the displacement measuring device 150 including the rotary encoder 154 for outputting, the pulse rate conversion circuit 60 including the electronic gear of the present invention can be employed. For example, in a material testing machine that applies a test force to a test piece by raising and lowering a load member that supports a lower grip as described in JP-A-8-152389, the load member that supports the lower grip The pulse rate conversion circuit 60 can also be used to adjust an output pulse from a wire type displacement detector of a type in which a belt member is expanded and contracted by a winding mechanism as a detector for detecting the amount of movement. Thereby, the effect demonstrated with reference to FIG. 7 and FIG. 8 can be acquired.

DESCRIPTION OF SYMBOLS 10 Test piece 11 Screw rod 13 Cross head 14 Load cell 16 Table 19 Post 21 Upper grip 22 Lower grip 24 Upper cross head 25 Ram cylinder 26 Lower cross head 28 Platen 41 Base 30 Load mechanism 31 Screw rod 32 Post 33 Pressure sensor 35 Control unit 36 Display unit 37 Input unit 50 Displacement measuring device 51a, 51b Column 52 Guide rail 53a, 53b Pulley 54a, 54b Rotary encoder 56 Upper arm 57 Lower arm 58a, 58b Wire 59a, 59b Balance weight 60 Pulse rate conversion circuit 62 Counter Circuit 63 Displacement conversion circuit 71 Control circuit 72 Accumulator 73 Selector 74 First comparator 75 Second comparator 76 Register 150 Displacement measuring device 151 Support plate 153 Pulley 154 Tali encoder 155 stand 156 coil spring 158 wire

Claims (5)

A displacement measuring device for measuring a displacement amount of a test piece when a tensile load or a compression load is applied to the test piece,
Displacement detection having a movement transmitting member that is wound around a pulley in a state where tension is applied and rotates the pulley by moving with the displacement of the test piece, and a rotary encoder that detects rotation of the pulley. Mechanism,
Based on the basic magnification as a reference for the amplification factor of the number of input pulses from the rotary encoder and the measurement error of the displacement amount caused by the member constituting the displacement detection mechanism obtained by calibration, the electronic gear molecule and the electron An electronic gear in which a value of the gear denominator is determined, an accumulator that accumulates a difference between the value of the electronic gear numerator and the value of the electronic gear denominator, and depending on the value held by the accumulator, Pulse that outputs the number of pulses of the integer part of the gear ratio of the electronic gear or the number of pulses of the integer part of the gear ratio of the electronic gear plus one pulse for one input pulse from the rotary encoder A rate converter,
Wherein the basic multiplier in the pulse rate conversion unit displacement measuring device according to claim der Rukoto least twice. The displacement measuring device according to claim 1,
The displacement measuring device in which the basic magnification in the pulse rate conversion unit is 10 to 1000 times. A movement transmission member for rotating the pulley by being wound around the pulley in a state where tension is applied and moving along with the displacement of the test piece to which a tensile load or a compression load is applied, and detecting the rotation of the pulley. A material testing machine comprising a displacement measuring device including a displacement detection mechanism having a rotary encoder, and performing a material test for applying a tensile load or a compression load to the test piece by driving a load mechanism,
Based on the basic magnification as a reference for the amplification factor of the number of input pulses from the rotary encoder and the measurement error of the displacement amount caused by the member constituting the displacement detection mechanism obtained by calibration, the electronic gear molecule and the electron An electronic gear in which a value of the gear denominator is determined, an accumulator that accumulates a difference between the value of the electronic gear numerator and the value of the electronic gear denominator, and depending on the value held by the accumulator, Pulse that outputs the number of pulses of the integer part of the gear ratio of the electronic gear or the number of pulses of the integer part of the gear ratio of the electronic gear plus one pulse for one input pulse from the rotary encoder A rate converter,
A displacement conversion unit that counts the output pulses converted by the pulse rate conversion unit and converts the displacement to the amount of displacement of the test piece based on the counted value,
A control unit comprising:
An input unit connected to the control unit for inputting the value of the electronic gear denominator and the value of the electronic gear numerator in the pulse rate conversion unit;
A display unit connected to the control unit and displaying a displacement amount of the test piece calculated in the displacement conversion unit;
Wherein the basic multiplier materials testing machine, characterized in der Rukoto least twice in the pulse rate conversion unit. The material testing machine according to claim 3,
The material testing machine in which the basic magnification in the pulse rate conversion unit is 10 to 1000 times. The material testing machine according to claim 3,
The pulse rate converter
A selector that selects a positive or negative value of the electronic gear numerator and the gear denominator as a value to be added to the accumulator depending on whether the pulse of the rotary encoder is normal rotation or reverse rotation;
The positive or negative value of the electronic gear numerator selected by the selector is added to and stored in the accumulator for each input pulse, and the value held in the accumulator and the electron Based on the comparison with the value of the gear denominator, when the absolute value of the value held in the accumulator is larger than the value of the electronic gear denominator, one pulse is output, and the accumulator is selected by the selector. The value of the electronic gear denominator that is a positive or negative opposite sign of the numerator value of the electronic gear is added, and the absolute value of the value held in the accumulator is equal to the value of the electronic gear denominator Alternatively, when the value is smaller than the value of the electronic gear denominator, by not outputting a pulse, the number of pulses of the integer part of the gear ratio of the electronic gear with respect to one input pulse from the rotary encoder, or , Serial testing machine for outputting a pulse count value plus 1 of the integer part of the gear ratio of the electronic gear.

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