Eddy current displacement sensor, press machine measuring device, and press machine monitoring device

Abstract

To provide an inexpensive eddy current displacement sensor with a variable measurable range.SOLUTION: An eddy current displacement sensor 20a is provided, comprising a detection coil 1 and an oscillator circuit 2a for generating a high frequency current, the oscillator circuit 2a having frequency switching means 5 for changing the oscillation frequency of the high frequency current generated by the oscillator circuit 2a.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an eddy current displacement sensor that measures the displacement of an object using an electrical signal, a press machine measuring device that measures the state of a press machine using an eddy current displacement sensor, and a press machine monitoring device that uses the press machine measuring device to detect abnormalities in a press machine and stop the press machine or return it to a normal state. [Background technology]

[0002] Conventionally, eddy current displacement sensors are used to measure the displacement of a metal object to be measured. In an eddy current displacement sensor, an eddy current flows in the object to be measured when the object to be measured interferes with a high-frequency magnetic field generated in a detection coil of the eddy current displacement sensor, and the inductance of the detection coil changes due to the eddy current. As a result, the magnitude of the AC voltage applied to the detection coil changes, and the magnitude of the changed AC voltage is output to the outside as a DC voltage signal. Since there is a correlation between the DC voltage signal output to the outside and the distance from the detection coil to the object to be measured, the distance from the detection coil to the object to be measured can be calculated.

[0003] Also, in an eddy current type displacement sensor, a technology having redundancy described in Patent Document 1 is known. The eddy current type displacement sensor described in Patent Document 1 includes two oscillator coils, two oscillator circuits for oscillating each oscillator coil, and two detection units for detecting the position of the detection target through detection of an induced voltage generated in each receiving coil by an eddy current generated in the detection target, and is an eddy current type displacement sensor in which, when one oscillator circuit oscillates one oscillator coil, the other oscillator circuit does not oscillate the other oscillator coil, and when the other oscillator circuit oscillates the other oscillator coil, the one oscillator circuit does not oscillate the one oscillator coil, so that the two oscillator coils do not oscillate simultaneously, and the eddy current based on the oscillation of one oscillator coil and the eddy current based on the oscillation of the other oscillator coil do not interfere in the detection target, and the two oscillator coils can each detect the displacement of the detection target, and even if a malfunction occurs in one of the two detection circuits, the displacement of the detection target can be detected from the voltage of the oscillator coil provided in the other detection circuit. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2016-001123 A Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, since the distance from the detection coil to the measurement object that can be measured by an eddy current displacement sensor has a measurable range that depends on the specifications of the eddy current displacement sensor, the eddy current displacement sensor is fixed to an arbitrary position using a dedicated jig or the like so that the displacement of the measurement object to be measured falls within the measurable range of the eddy current displacement sensor. For example, in a press machine that has a mold consisting of an upper mold and a lower mold that move up and down and that molds the workpiece into the shape of the mold by sandwiching and pressing the workpiece between the upper mold and the lower mold, when the lowest position of the upper mold that moves up and down is measured by an eddy current displacement sensor, the eddy current displacement sensor is fixed to the press machine with a dedicated jig so that the approximate lowest position of the upper mold falls within the measurable range of the eddy current displacement sensor.

[0006] However, when the mold is changed to a mold of a different shape, or when the workpiece is changed to a workpiece of a different shape and material, the setting of the lowest position of the upper mold, which moves up and down facing the lower mold and the workpiece, is also changed. In this case, if the lowest position of the upper mold deviates from the measurable range of the eddy current displacement sensor, it is necessary to adjust the fixed position of the eddy current displacement sensor so that the approximate lowest position of the upper mold falls within the measurable range of the eddy current displacement sensor. Alternatively, it is necessary to change the existing eddy current displacement sensor to an appropriate eddy current displacement sensor whose measurable range is different from that of the existing eddy current displacement sensor. In this way, when the displacement of the measurement object changes and deviates from the measurable range of the eddy current displacement sensor, it is necessary to adjust the position of the eddy current displacement sensor, and in some cases, it is necessary to prepare a new eddy current displacement sensor, which is time-consuming and expensive.

[0007] In this case, in the eddy current displacement sensor described in Patent Document 1, by arranging the detection circuits so that the measurable range of one detection circuit is different from the measurable range of the other detection circuit, even if the displacement of the object to be measured changes and deviates from the measurable range of the eddy current displacement sensor, it is possible to measure the displacement of the object to be measured by selecting the detection circuit to be used without adjusting the position of the eddy current displacement sensor or replacing it with a different eddy current displacement sensor.

[0008] However, the displacement sensor described in Patent Document 1 requires two detection coils and two detection circuits. This requires a large number of parts, which increases material costs, and the structure becomes complex, which increases assembly costs. In addition, since it requires roughly twice as many parts as a general eddy current displacement sensor, the eddy current displacement sensor becomes larger, which places restrictions on where the eddy current displacement sensor can be fixed.

[0009] The present invention has been made in consideration of the above-mentioned circumstances, and has an object to provide an inexpensive eddy current displacement sensor with a variable measurable range, a press machine measuring device using the eddy current displacement sensor, and a press machine monitoring device using the press machine measuring device. [Means for solving the problem]

[0015] A press machine measuring device according to the present invention is a press machine measuring device for measuring the state of a press machine or a workpiece in a press machine which clamps a workpiece placed at a predetermined position and punches out the workpiece to form a hole in the workpiece, the press machine measuring device being fixed to the press machine so as to be able to measure the displacement of one end or both ends of an upper die of the press machine, the device having a detection coil and an oscillation circuit which generates a high frequency current, the oscillation circuit having a frequency switching means for changing the oscillation frequency of the high frequency current generated by the oscillation circuit, the frequency switching means being a capacitance changing means for changing the capacitance of the oscillation circuit or an inductance changing means for changing the inductance of the oscillation circuit, the capacitance changing means being a capacitance of a capacitor included in the oscillation circuit, Directlya switching capacitor connected to the row, and a disconnecting / connecting device for disconnecting or connecting the switching capacitor from the capacitor, and the inductance changing means is a coil provided in the oscillator circuit. Directly and a processing device to which information measured by the eddy current type displacement sensor is input, the processing device recording the information, and performing a predetermined process. The frequency switching means reduces the capacitance of the oscillator circuit and increases the oscillation frequency when the displacement of the object to be measured deviates from the measurable range of the eddy current displacement sensor, and increases the capacitance of the oscillator circuit and decreases the oscillation frequency when the displacement of the object to be measured is within the measurable range of the eddy current displacement sensor. It is characterized by:

[0016] The present invention relates to a press machine monitoring device that detects an abnormality in a press machine that clamps and molds a workpiece placed at a predetermined position, and takes action in response to the detected abnormality, and is characterized in that: 1 and a treatment means for treating any abnormality in the press machine or the workpiece, wherein the processing device of the press machine measuring device determines whether or not there is an abnormality in the press machine or the workpiece by comparing information measured by the eddy current displacement sensor with a predetermined setting value that is preset in the processing device, and the processing device outputs a treatment signal to the processing means when it detects an abnormality. Effect of the Invention

[0017] According to the eddy current displacement sensor of the present invention, the oscillation frequency of the high frequency current generated by the oscillator circuit can be changed by the frequency switching means. It has been found through experiments that by increasing the oscillation frequency of the high frequency current flowing through the detection coil of the eddy current displacement sensor, the measurable range of the eddy current displacement sensor is widened, and by decreasing the oscillation frequency, the measurable range of the eddy current displacement sensor is narrowed and the resolution is increased. In other words, by changing the oscillation frequency of the high frequency current generated by the oscillator circuit by the frequency switching means, it is possible to adjust the measurable range of the eddy current displacement sensor.

[0018] Furthermore, the method of changing the capacitance of the oscillator circuit is simple and easy, and does not require a complicated structure. Therefore, the frequency switching means, which is the capacitance changing means for changing the capacitance of the oscillator circuit, can be made from inexpensive parts.

[0019] Furthermore, since the capacitor is an inexpensive component and the disconnecting / connecting device for connecting and disconnecting the capacitor can be incorporated with a simple structure, it can be manufactured at low cost.

[0020] In addition, the method of changing the inductance of the oscillator circuit is simple and easy, and does not require a complicated structure. Therefore, the frequency switching means, which is the inductance changing means for changing the inductance of the oscillator circuit, can be manufactured using inexpensive parts.

[0021] Furthermore, the coil is an inexpensive component, and the disconnecting / connecting device for connecting and disconnecting the coil can be incorporated with a simple structure, so that it can be manufactured inexpensively.

[0022] According to the press machine measuring device of the present invention, when the displacement of any part of the press machine or any part of the workpiece to be measured deviates from the measurable range of the eddy current displacement sensor, the measurable range of the eddy current displacement sensor is adjusted by the frequency switching means, thereby eliminating the need to adjust the position of the eddy current displacement sensor or replace it with a different eddy current displacement sensor.

[0023] According to the press machine monitoring device of the present invention, when the displacement of any part of the press machine or any part of the material to be processed that is the object of measurement deviates from the measurable range of the eddy current displacement sensor, the measurable range of the eddy current displacement sensor is adjusted by the frequency switching means, so that when an abnormality occurs in the press machine, measures such as stopping the press machine or restoring it to normal can be automatically taken, without the need to adjust the position of the eddy current displacement sensor or replace it with a different eddy current displacement sensor. [Brief description of the drawings]

[0024] [Figure 1]FIG. 1 is a block diagram showing an eddy current displacement sensor according to a first embodiment and a second embodiment of the present invention. [Diagram 2] 1 is a circuit diagram showing an oscillator circuit of an eddy current type displacement sensor according to a first embodiment of the present invention. [Diagram 3] 5 is a graph showing a change in characteristics due to a change in the oscillation frequency of the eddy current type displacement sensor according to the first embodiment of the present invention. [Figure 4] FIG. 4 is a circuit diagram showing an oscillator circuit of an eddy current type displacement sensor according to a second embodiment of the present invention. [Diagram 5] 1 is a diagram showing a press machine in which a press machine measuring device according to an embodiment of the present invention and a press machine monitoring device according to a second embodiment are used. FIG. [Figure 6] 1 is a block diagram showing a press machine measurement device according to an embodiment of the present invention. FIG. [Figure 7] 1 is a diagram showing a press machine in which a press machine monitoring device according to a first embodiment of the present invention is used; [Figure 8] FIG. 1 is a block diagram showing a press machine monitoring device according to a first embodiment of the present invention. [Figure 9] FIG. 4 is a block diagram showing a press machine monitoring device according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] The eddy current displacement sensor, the press machine measuring device, and the press machine monitoring device according to the present invention will be described below with reference to the drawings. However, the following merely illustrates one embodiment of the present invention by way of example, and the scope of the present invention is not limited to the following embodiment, and can be modified as appropriate without departing from the spirit of the present invention.

[0026] First, a first embodiment of an eddy current displacement sensor according to the present invention will be described. The eddy current displacement sensor 20a according to this embodiment is the eddy current displacement sensor 20a according to claim 3, and as shown in Fig. 1, has a detection coil 1, an oscillation circuit 2a for generating a high-frequency current, a detection circuit 11 for extracting the time change in the magnitude of the AC voltage applied to the detection coil 1 as a voltage signal, and a smoothing circuit 12 for converting the voltage signal extracted by the detection circuit 11 into a state close to DC and outputting it to the outside. Since the eddy current displacement sensor 20a according to this embodiment is a self-excited eddy current displacement sensor 20a, the detection coil 1 functions as a part of the oscillation circuit 2a.

[0027] 2, the oscillator circuit 2a includes a detection coil 1, two capacitors 4, and two frequency switching means 5. The frequency switching means 5 changes the oscillation frequency of the high-frequency current generated by the oscillator circuit 2a, and the frequency switching means 5 in this embodiment is a capacitance changing means 6 that changes the capacitance of the oscillator circuit 2a to change the oscillation frequency of the high-frequency current generated by the oscillator circuit 2a.

[0028] The frequency switching means 5 includes two switching capacitors 8 connected in parallel to the two existing capacitors 4 of the oscillation circuit 2a, and two disconnection / connection devices 10 that are switches for disconnecting or connecting the two switching capacitors 8 from the existing capacitors 4. The two disconnection / connection devices 10 work together to simultaneously disconnect or connect the two switching capacitors 8 to the existing capacitors 4. By operating the disconnection / connection devices 10 to disconnect the switching capacitors 8 from the existing capacitors 4, the capacitance of the oscillation circuit 2a can be reduced, and by reducing the capacitance of the oscillation circuit 2a, the oscillation frequency of the high-frequency current generated by the oscillation circuit 2a can be increased. In the eddy current displacement sensor 20a according to this embodiment, in order to distinguish between the two frequency switching means 5, the frequency switching means 5 located on the left side of the two frequency switching means 5 shown in FIG. 2 is referred to as the first frequency switching means 51, and the frequency switching means 5 located on the right side is referred to as the second frequency switching means 52.

[0029] The eddy current displacement sensor 20a of this embodiment includes two frequency switching means 5, a first frequency switching means 51 and a second frequency switching means 52. Therefore, the oscillation circuit 2a can be switched between four states: a state in which the first frequency switching means 51 and the second frequency switching means 52 are connected, a state in which the first frequency switching means 51 is disconnected and the second frequency switching means 52 is connected, a state in which the first frequency switching means 51 is connected and the second frequency switching means 52 is disconnected, and a state in which the first frequency switching means 51 and the second frequency switching means 52 are disconnected. In other words, by using capacitors with different capacitances for the switching capacitor 8 of the first frequency switching means 51 and the switching capacitor 8 of the second frequency switching means 52, the oscillation circuit 2a can change the capacitance for each of the four states, and the oscillation frequency of the high-frequency current generated by the oscillation circuit 2a can be changed in four stages.

[0030] Next, the principle of the eddy current type displacement sensor 20a will be described. First, a high-frequency current is generated by the oscillator circuit 2a, and the high-frequency current is passed through the detector coil 1 to generate a high-frequency magnetic field in the detector coil 1. As described above, the eddy current type displacement sensor 20a of this embodiment is self-excited, and the detector coil 1 is also a part of the oscillator circuit 2a, so that a high-frequency magnetic field is generated in the detector coil 1 at the time when the high-frequency current is generated in the oscillator circuit 2a. Then, when the metal object to be measured 13 interferes with the high-frequency magnetic field, an eddy current flows in the object to be measured 13 by electromagnetic induction. Furthermore, the inductance of the detector coil 1 changes due to the eddy current flowing through the object to be measured 13, and the magnitude of the AC voltage applied to the detector coil 1 changes. Since there is a correlation between the magnitude of this changed AC voltage and the distance from the detector coil 1 to the object to be measured 13, the detector circuit 11 extracts the time change in the magnitude of the AC voltage applied to the detector coil 1 as a voltage signal, and the voltage signal is converted into a voltage signal close to DC by the smoothing circuit 12 and output to the outside, and the distance from the detector coil 1 to the object to be measured 13 can be known based on the output voltage signal.

[0031] Incidentally, the magnitude of the AC voltage applied to the detection coil 1 and the distance from the detection coil 1 to the measurement object 13 only have a limited range in which a correlation is established, and the eddy current displacement sensor 20a has a measurable range only in which a correlation is established between the magnitude of the AC voltage applied to the detection coil 1 and the distance from the detection coil 1 to the measurement object 13. Since the measurable range differs depending on the specifications of the eddy current displacement sensor, the measurable range is determined by the manufacturer of the eddy current displacement sensor for each specification of the eddy current displacement sensor.

[0032] 3 is a graph of data obtained by measuring the displacement of a certain measurement object 13 using the eddy current displacement sensor 20a of this embodiment, where the vertical axis represents the voltage output from the eddy current displacement sensor 20a and the horizontal axis represents the distance from the detection coil 1 to the measurement object 13. A first series A represents data obtained by the eddy current displacement sensor 20a in a state in which the first frequency switching means 51 and the second frequency switching means 52 are connected, a second series B represents data obtained by the eddy current displacement sensor 20a in a state in which the first frequency switching means 51 is connected and the second frequency switching means 52 is disconnected, and a third series C represents data obtained by the eddy current displacement sensor 20a in a state in which the first frequency switching means 51 and the second frequency switching means 52 are disconnected.

[0033] 3, it can be seen that the second series B can measure a closer range of distances from the detection coil 1 to the object to be measured 13 than the first series A, and the third series C can measure a closer range of distances from the detection coil 1 to the object to be measured 13 than the second series B, and conversely, the second series B has a higher resolution than the third series C, and the first series A has a higher resolution than the second series B. In other words, it can be seen that the eddy current displacement sensor 20a can widen the measurable range by increasing the oscillation frequency of the oscillation circuit 2a, and can also narrow the measurable range but increase the resolution by lowering the oscillation frequency 2a.

[0034] Therefore, when the displacement of the measurement object 13 deviates from the measurable range of the eddy current displacement sensor 20a, the frequency switching means 5 can be used to decrease the capacitance of the oscillator circuit 2a and increase the oscillation frequency of the oscillator circuit 2a, thereby widening the measurable range of the eddy current displacement sensor 20a, eliminating the need to adjust the position of the eddy current displacement sensor 20a or replace it with an eddy current displacement sensor of appropriate specifications. On the other hand, when the displacement of the measurement object 13 is within the measurable range of the eddy current displacement sensor 20a, the frequency switching means 5 can be used to increase the capacitance of the oscillator circuit 2a and decrease the oscillation frequency of the oscillator circuit 2a, thereby increasing the resolution of the eddy current displacement sensor 20a and enabling more accurate measurement of the displacement of the measurement object 13.

[0035] In addition, the capacitance of the existing capacitor 4 in the oscillator circuit 2a of this embodiment is 1000 [pF], the capacitance of the switching capacitor 8 of the first frequency switching means 51 is 3600 [pF], the capacitance of the switching capacitor 8 of the second frequency switching means 52 is 9100 [pF], the oscillation frequency when the first frequency switching means 51 and the second frequency switching means 52 are connected (first series A) is 80 [kHz], the oscillation frequency when the first frequency switching means 51 is connected and the second frequency switching means 52 is disconnected (second series B) is 120 [kHz], and the oscillation frequency when the first frequency switching means 51 and the second frequency switching means 52 are disconnected (third series C) is 180 [kHz].

[0036] In addition, the eddy current displacement sensor 20a of this embodiment is provided with two frequency switching means 5 in the oscillator circuit 2a, but in other embodiments, by adding more frequency switching means 5, the number of patterns for changing the capacitance of the oscillator circuit 2a increases, making it possible to select a larger number of measurable ranges and a larger number of resolutions.

[0037] Furthermore, the switching capacitor 8 of the frequency switching means 5 in this embodiment is connected in parallel to the existing capacitor 4, but it may be connected in series.

[0038] Furthermore, the frequency switching means 5 of the eddy current displacement sensor 20a of this embodiment adjusts the capacitance of the oscillator circuit 2a by connecting or disconnecting the switching capacitor 8 to the existing capacitor 4, but as an embodiment of the eddy current displacement sensor according to the invention of claim 2, a mechanism for varying the capacitance, such as a variable capacitor, may be used for the existing capacitor 4 to adjust the measurable range of the eddy current displacement sensor. Furthermore, as another embodiment, a mechanism for varying the capacitance, such as a variable capacitor, may be used for the switching capacitor 8 to make the capacitance variable.

[0039] Next, a second embodiment of the eddy current displacement sensor according to the present invention will be described. The eddy current displacement sensor 20b according to this embodiment is an eddy current displacement sensor 20b according to claim 5, and like the eddy current displacement sensor 20a of the first embodiment, has a detection coil 1, an oscillation circuit 2b for generating a high-frequency current, a detection circuit 11 for extracting the time change in the magnitude of the AC voltage applied to the detection coil 1 as a voltage signal, and a smoothing circuit 12 for converting the voltage signal extracted by the detection circuit 11 into a state close to DC and outputting it to the outside, as shown in Fig. 1. The eddy current displacement sensor 20b according to this embodiment is a self-excited eddy current displacement sensor 20b, so the detection coil 1 functions as a part of the oscillation circuit.

[0040] 4, the oscillator circuit 2b of this embodiment includes a detection coil 1, two capacitors 4, and a frequency switching means 5. The frequency switching means 5 changes the oscillation frequency of the high-frequency current generated by the oscillator circuit 2b, and the frequency switching means 5 of this embodiment is an inductance changing means 7 that changes the oscillation frequency of the high-frequency current generated by the oscillator circuit 2b by changing the inductance of the oscillator circuit 2b.

[0041] The frequency switching means 5 includes a switching coil 9 connected in series to the detection coil 1, and a disconnection / connection device 10 which is a switch for disconnecting or connecting the switching coil 9 to the detection coil 1. By disconnecting the switching coil 9 from the detection coil 1 by the disconnection / connection device 10, it is possible to reduce the inductance of the oscillation circuit and increase the oscillation frequency of the oscillation circuit 2b.

[0042] Therefore, when the displacement of the measurement object 13 deviates from the measurable range of the eddy current displacement sensor 20b, the inductance of the oscillator circuit 2b is decreased and the oscillation frequency is increased by the frequency switching means 5, thereby making it possible to widen the measurable range of the eddy current displacement sensor 20b, and there is no need to adjust the position of the eddy current displacement sensor 20b or to replace it with an eddy current displacement sensor of appropriate specifications. Also, when the displacement of the measurement object 13 is within the measurable range of the eddy current displacement sensor 20b, the inductance of the oscillator circuit 2b is increased and the oscillation frequency of the oscillator circuit 2b is decreased by the frequency switching means 5, thereby increasing the resolution of the eddy current displacement sensor 20b and enabling more accurate displacement measurement.

[0043] In addition, the eddy current displacement sensor 20b of this embodiment is provided with one frequency switching means 5 in the oscillator circuit 2b, but in other embodiments, by adding more frequency switching means 5, the number of patterns for changing the inductance of the oscillator circuit 2b increases, making it possible to select more measurable ranges and more resolutions.

[0044] Furthermore, although the switching coil 9 of the frequency switching means 5 in this embodiment is connected in series to the detection coil 1, it may be connected in parallel.

[0045] In addition, the frequency switching means 5 of the eddy current displacement sensor 20b of this embodiment adjusts the inductance of the oscillator circuit 2b by disconnecting or connecting the switching coil 9 from the detection coil 1, but as an embodiment of the eddy current displacement sensor according to the invention of claim 2, a mechanism for making an inductor such as a variable inductor variable may be used in the detection coil 1 to adjust the measurable range of the eddy current displacement sensor. Furthermore, as another embodiment, a mechanism for making an inductor variable such as a variable inductor may be used in the switching coil 9 to make the inductor variable.

[0046] Next, an embodiment of the press machine measuring device 30 according to the present invention will be described. As shown in Fig. 5, the press machine 100a in which the press machine measuring device 30 of this embodiment is used has an upper slide 101 that moves continuously up and down, an upper die 102 that is a die fixed to the lower end of the slide 101, and a lower die 103 that is a die fixed at a distance below the upper die 102. A material to be processed 110 is placed between the upper die 102 and the lower die 103, and the material to be processed 110 is molded by sandwiching and pressing the material to be processed 110 between the upper die 102 and the lower die 103.

[0047] The workpiece 110 is normally molded when the upper die 102 is lowered to a predetermined position, but if the upper die 102 does not fully lower to the predetermined position or is lowered below the predetermined position, the workpiece 110 may be crushed or the unevenness may not be molded properly, resulting in a decrease in molding accuracy of the workpiece 110 and possibly a defective product. In other words, the accuracy of the movement of the slide 101 to which the upper die 102 is fixed is related to the molding accuracy of the workpiece 110. The press machine measuring device 30 of this embodiment is for evaluating the accuracy of the movement of the slide 101 of the press machine 100a in advance, and moves the slide 101 up and down multiple times in succession so as to lower it to a predetermined position set in advance, and the position where the slide 101 is fully lowered for each up and down movement is recorded by the processing device 32, and the variation is measured.

[0048] As shown in FIG. 6, the press machine measuring device 30 includes an eddy current displacement sensor 20a of the first embodiment fixed to the press machine 100a as shown in FIG. 5 so as to measure the displacement of the slide 101 of the press machine 100a, an A / D converter 31 that converts a voltage signal output from the eddy current displacement sensor 20a into a digital value, and a processing device 32 which is a computer that records the voltage signal converted into a digital value by the A / D converter 31 and performs predetermined processing.

[0049] The displacement of the slide 101 of the press machine 100a, which moves up and down continuously multiple times to lower to a predetermined position set in advance, is measured by the eddy current displacement sensor 20a, the voltage signal output from the eddy current displacement sensor 20a is converted to a digital value by the A / D converter 31, and the time change in the displacement of the slide 101 is recorded by the processing device 32. Furthermore, the processing device 32 extracts the position where the slide 101 has lowered to the bottom for each up and down movement from the time change in the displacement of the slide 101 recorded in the processing device 32, and obtains the variation. The press machine 100a is evaluated based on the variation in the position where the slide 101 has lowered to the bottom for each up and down movement. It is also possible to evaluate the press machine 100a by the processing device 32 by setting in advance an evaluation standard for the variation in the position where the slide 101 has lowered to the bottom for each up and down movement in the processing device 32.

[0050] In addition, in measuring the variation of the slide 101 of the press machine 100a, it is desirable that the predetermined position where the slide 101 is set to the lowest position is the position where the slide 101 is set to the lowest position when the press machine 100a is actually used. Therefore, when the position where the slide 101 is set to the lowest position when actually used changes each time due to changes in the upper mold 102 and the lower mold 103 or the workpiece material 110, the variation of the slide 101 of the press machine 100a is measured for each position where the slide 101 is set to the lowest position. At this time, the displacement of the slide 101 may deviate from the measurable range of the eddy current displacement sensor 20a fixed to the press machine 100a. In that case, by changing the measurable range of the eddy current displacement sensor 20a using the frequency switching means 5, the displacement of the slide 101 can be measured without adjusting the position of the eddy current displacement sensor 20a or replacing it with a different eddy current displacement sensor.

[0051] The press machine measuring device 30 in this embodiment measures the variation of the slide 101 of the press machine 100a, but in other embodiments, it may be a device that measures the condition of the press machine, such as a device that measures the accuracy of the movement of other parts of the press machine 100a, or a device that measures the positioning accuracy of the workpiece 110 placed between the upper die 102 and the lower die 103.

[0052] Next, a first embodiment of the press machine monitoring device according to the present invention will be described. As shown in Fig. 7, the press machine 100b in which the press machine monitoring device 40a of this embodiment is used has a stripper 104 that moves up and down, a punch 105 that moves up and down, a die 106 fixed below the stripper 104 and the punch 105, and a waste hole 107 formed in the die 106. A material 110 to be processed is placed between the stripper 104 and the die 106, and the material 110 to be processed is sandwiched and fixed by the stripper 104 and the die 106, and the material 110 to be processed is punched out by the punch 105 to form a hole in the material 110 to be processed.

[0053] Slag 111 from the workpiece material 110 punched out by the punch 105 falls into a slag hole 107, but after punching, slag 111 may adhere to the tip of the punch 105, causing slag lift-up, i.e., the slag 111 getting caught between the stripper 104 and the die 106. The press machine monitoring device 40a of this embodiment detects slag lift-up, stops the press machine using the press machine control device 42, and issues an alarm using the alarm device 43 to notify an operator of the slag lift-up.

[0054] 8, the press machine monitoring device 40a of this embodiment includes the press machine measuring device 30 according to the invention of claim 6, a press machine control device 42 which is connected to the press machine measuring device 30 and the press machine 100b and is one of the processing means 41 that outputs a control signal 44 which is a stop signal to the press machine 100b, and an alarm device 43 which is one of the processing means 41 connected to the press machine measuring device 30. The press machine measuring device 30 includes the eddy current displacement sensor 20a of the first embodiment fixed to the press machine 100b so as to measure the displacement of the stripper 104 of the press machine 100b, an A / D converter 31 which converts a voltage signal output from the eddy current displacement sensor 20a into a digital value, and a processing device 32 which is a computer which records and processes the voltage signal converted into a digital value by the A / D converter 31, determines the presence or absence of slug lift-up, and outputs a processing signal 33 to the press machine control device 42 and the alarm device 43 when slug lift-up is detected.

[0055] If slag lift-up occurs in the press 100b, the bottom dead center position, which is the position of the stripper 104 when it collides with the workpiece 110, will change from the bottom dead center position during normal random punching. Therefore, a predetermined set value determined based on the distribution of bottom dead center positions measured during normal random punching is set in advance in the processing device 32, and the bottom dead center position actually measured by the eddy current displacement sensor 20a is compared with the predetermined set value by the processing device 32 to determine whether slag lift-up has occurred. If the bottom dead center position actually measured by the eddy current displacement sensor 20a deviates from the range of predetermined set values, it is determined that scum lift has occurred in the press machine 100b, and the processing device 32 outputs a treatment signal 33 to the press machine control device 42 and the alarm device 43. The press machine control device 42, to which the treatment signal 33 has been input, stops the press machine 100b by outputting a control signal 44 to the press machine 100b to stop the press machine 100b, and the alarm device 43, to which the treatment signal 33 has been input, issues an alarm to inform the operator that scum lift has occurred.

[0056] In addition, since the bottom dead center position of the stripper 104, which is the criterion for determining whether scrap has risen, varies depending on the shape of the workpiece material 110, the bottom dead center position of the stripper 104 may deviate from the measurable range of the eddy current displacement sensor 20a when the workpiece material 110 is changed. In that case, by changing the measurable range of the eddy current displacement sensor 20a using the frequency switching means 5 of the eddy current displacement sensor 20a, measurement becomes possible without adjusting the position of the eddy current displacement sensor 20a or replacing it with a different eddy current displacement sensor.

[0057] Next, a second embodiment of the press machine monitoring device according to the present invention will be described. The press machine 100a in which the press machine monitoring device 40b of this embodiment is used is the press machine 100a shown in FIG.

[0058] The press machine 100a, which is continuously in operation, may heat up and cause each part to thermally expand, and this thermal expansion may cause the upper die 102 to tilt from the normal posture. The press machine monitoring device 40b of this embodiment detects the change in posture of the upper die 102 and performs a procedure to return the posture of the upper die 102 to the normal posture using the press machine control device 42.

[0059] 9, the press machine monitoring device 40b of this embodiment includes the press machine measuring device 30 according to the invention of claim 6, and a press machine control device 42 which is connected to the press machine measuring device 30 and the press machine 100a and serves as processing means 41 for controlling the movement of the slide 101. The press machine measuring device 30 includes a first eddy current displacement sensor 21 which is the eddy current displacement sensor 20a of the first embodiment which is fixed to the press machine 100a as shown in FIG. 5 so as to measure the displacement of one end 102a of the upper die 102 of the press machine 100a and to measure the change in posture of the upper die 102 of the press machine 100a, and a second eddy current displacement sensor 20a of the first embodiment which is fixed to the press machine 100a as shown in FIG. 5 so as to measure the displacement of the other end 102b of the upper die 102 of the press machine 100a. The apparatus includes a second eddy current displacement sensor 22, an A / D converter 31 that converts the voltage signals output from the first eddy current displacement sensor 21 and the second eddy current displacement sensor 22 into digital values, and a processing device 32 which is a computer that records the two voltage signals converted into digital values ​​by the A / D converter 31, performs predetermined processing, detects a change in the posture of the upper die 102, and outputs an action signal 33 to the press machine control device 42 as a command to control the movement of the slide 101 when a change in the posture of the upper die 102 is detected.

[0060] If the upper die 102 of the press 100a becomes tilted from the normal position due to thermal expansion, the relationship between the displacement of one end 102a of the upper die 102 and the displacement of the other end 102b of the upper die 102 will change from the relationship between the displacement of one end 102a of the upper die 102 and the displacement of the other end 102b of the upper die 102 when the upper die 102 is in the normal position. Therefore, based on the distribution of the difference between the displacement of one end 102a of the upper die 102 and the displacement of the other end 102b of the upper die 102 measured when the upper die 102 is in the normal position, a tolerance is determined and set in advance in the processing device 32 as a predetermined set value, and the processing device 32 compares the difference between the actually measured displacement of one end 102a of the upper die 102 and the displacement of the other end 102b of the upper die 102 with the predetermined set value to determine whether the upper die 102 is tilted.

[0061] Then, if the difference between the displacement of one end 102a of the upper die 102 actually measured and the displacement of the other end 102b of the upper die 102 deviates from a predetermined set value, it is determined that the upper die 102 is in an inclined position, and a processing signal 33 is output from the processing device 32 to the press machine control device 42 as a command to control the movement of the slide 101. The press machine control device 42, to which the processing signal 33 has been input, outputs a control signal 44 to the press machine 100a to control the movement of the slide 101, thereby returning the position of the upper die 102 fixed to the slide 101 to the normal position.

[0062] The control of the posture of the upper die 102 by the press machine control device 42 is a PID control in which a predetermined set value is set as a target value within a range determined based on the distribution of the difference between the displacement of one end 102a of the upper die 102 and the displacement of the other end 102b of the upper die 102 measured when the upper die 102 is in the normal posture, the difference between the actually measured displacement of one end 102a of the upper die 102 and the displacement of the other end 102b of the upper die 102 is set as an output value, and the processing signal 33 output from the processing device 32 to the press machine control device 42 is set as an input value, and the calculation is performed by the processing device 32.

[0063] In addition, since the displacement of one end 102a of the upper die 102 and the displacement of the other end 102b of the upper die 102, which are the criteria for determining whether or not the posture of the upper die 102 has changed, vary depending on the shape of the upper die 102, when the upper die 102 is changed, the displacement of one end 102a of the upper die 102 and the displacement of the other end 102b of the upper die 102 may deviate from the measurable range of the eddy current displacement sensor 20a. In that case, by changing the measurable range of each eddy current displacement sensor 20a using the frequency switching means 5 of each of the two eddy current displacement sensors 20a, measurement becomes possible without adjusting the position of the eddy current displacement sensor 20a or replacing it with a different eddy current displacement sensor.

[0064] Furthermore, by using a mechanical relay or a semiconductor relay for the disconnection / connection device 10 of the frequency switching means 5 of the eddy current displacement sensor of the present invention, it becomes possible to automatically change the measurable range of the eddy current displacement sensor by inputting a disconnection signal or connection signal from the outside to the disconnection / connection device 10. In particular, in the press machine measuring device and the press machine monitoring device of the present invention, it is possible to input a disconnection signal or connection signal from the processing device 32 to the disconnection / connection device 10, or to input it from the processing device 32 to the disconnection / connection device 10 via the processing means 41.

[0065] Therefore, in the press machine measuring device 30, the press machine monitoring device 40a, and the press machine monitoring device 40b, when the measurement object deviates from the measurable range of the eddy current displacement sensor 20a at the timing of changing the lowered position of the slide 101 or changing the upper mold 102 or the workpiece material 110, the frequency switching means 5 is operated to change the measurable range of the eddy current displacement sensor 20a. However, by using a mechanical relay or a semiconductor relay in the disconnecting and connecting device 10 so that the disconnecting and connecting device 10 can be controlled by an electric signal, a predetermined threshold value is set in advance in the processing device 32, and when the measurement value of the eddy current displacement sensor 20a inputted to the processing device 32 exceeds or falls below the threshold value, the processing device 32 outputs a disconnection signal or connection signal, automatically opens and closes the disconnecting and connecting device 10, and changes the measurable range of the eddy current displacement sensor 20a, so that measurement can always be performed without human intervention even if there is an unexpected large displacement in the measurement object. [Explanation of symbols]

[0066] 20a Eddy current displacement sensor 20b Eddy current displacement sensor 1 Detection coil 2a Oscillator circuit 2b Oscillator circuit 4 Capacitors 3 Coil 5. Frequency switching means 6 Capacitance change means 7. Means of changing inductance 8 Switching Capacitors 9 Switching coil 10 Disconnecting device 30 Press machine measuring device 31 A / D converter 32 Processing equipment 33 Action Signal 40a Press machine monitoring device 40b Press machine monitoring device 41 Treatment methods 100a press machine 100b Press Machine 110 Work material

Claims

1. A press machine measuring device for measuring a state of a press machine or a workpiece that is molded by clamping a workpiece placed at a predetermined position and punching the workpiece to form a hole in the workpiece, comprising: The press machine includes a detection coil and an oscillator circuit for generating a high-frequency current, the detection coil being fixed to the press machine so as to be able to measure the displacement of one end or both ends of an upper die of the press machine; the oscillation circuit has a frequency switching means for changing an oscillation frequency of a high-frequency current generated by the oscillation circuit, the frequency switching means is a capacitance changing means for changing a capacitance of the oscillation circuit or an inductance changing means for changing an inductance of the oscillation circuit, the capacitance change means includes a switching capacitor connected in parallel or in series to a capacitor included in the oscillation circuit, and a disconnect / connect device for disconnecting or connecting the switching capacitor to or from the capacitor; the inductance changing means is an eddy current displacement sensor having a switching coil connected in parallel or series to a coil of the oscillation circuit, and a disconnecting / connecting device for disconnecting or connecting the switching coil from the coil; a processing device to which information measured by the eddy current displacement sensor is input, the processing device records the information, and performs a predetermined process; the frequency switching means, when the displacement of the object to be measured deviates from the measurable range of the eddy current displacement sensor, decreases the capacitance of the oscillator circuit to increase the oscillation frequency, and, when the displacement of the object to be measured is within the measurable range of the eddy current displacement sensor, increases the capacitance of the oscillator circuit to decrease the oscillation frequency.

2. A press machine monitoring device that detects an abnormality in a press machine that clamps and molds a workpiece placed at a predetermined position, and takes action against the detected abnormality, A press machine measuring device according to claim 1, and a processing means for processing an abnormality of the press machine or the workpiece, The processing device of the press machine measuring device compares information measured by the eddy current displacement sensor with a predetermined set value that is preset in the processing device to determine whether or not there is an abnormality in the press machine or the workpiece; The press machine monitoring device is characterized in that the processing device outputs a processing signal to the processing means when it detects an abnormality.

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