JP2014081303A - Position detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a position detection device that can precisely detect a position in a movement direction of a detected body.SOLUTION: The position detection device comprises: a first magnetic core 40 in which a first resonance coil 43 constituting a first resonance circuit 52 together with a first capacitor 44 and a first exciting coil 45 which is adjacent to the first resonance coil and to which a first exciting electric current causing the first resonance circuit to be excited flows are wound, respectively; and a second magnetic core 41 in which a second resonance coil 46 constituting a second resonance circuit 53 together with a second capacitor 47 and a second exciting coil 48 which is adjacent to the second resonance coil and to which a second exciting electric current causing the second resonance circuit to be excited with a reverse phase to that of the first exciting electric current flows are wound, respectively. The first magnetic core and the second magnetic core are arranged to face each other at a predetermined distance in the movement direction of a detected body made of a metal having magnetism.

Description

  The present invention relates to a position detection device that detects a position of a detected object in a moving direction.

  For example, Patent Document 1 discloses a spindle device that detects that a tool has been clamped or unclamped by a draw bar disposed inside a spindle of a machine tool so as to be movable in the axial direction of the spindle. A clamp / unclamp mechanism is disclosed. In the clamp / unclamp mechanism of the spindle device of Patent Document 1, the object to be detected is formed at the rear end of the draw bar so as to taper in the front-rear direction in the axial direction, and the displacement sensor faces the object to be detected. It is arranged. According to this clamping / unclamping mechanism, the displacement sensor outputs a voltage value corresponding to the change in the facing distance to the object to be detected, thereby detecting that the tool has been clamped or unclamped based on the voltage value. it can.

JP 2000-354939 A

  By the way, in the machine tool as described above, it is desired to detect not only that the tool is clamped or unclamped to the spindle device, but also the state in which, for example, cutting waste is sandwiched between the tool and the spindle device. There is a request. For this purpose, it is considered effective to accurately detect the position of the detection object formed on the draw bar in the moving direction (axial direction of the main shaft).

  However, in the above clamping / unclamping mechanism, the protrusion is located near the center of the detected object in the axial direction of the spindle in the axial direction of the spindle so that the center is closest to the displacement sensor. The position of the detected object is detected by a voltage value that changes in accordance with the corresponding distance between the displacement sensor and the protruding portion. It is difficult to accurately detect the difference in position in the moving direction (the axial direction) of the detected object.

  This invention is proposed in view of such a situation, and it aims at providing the position detection apparatus which can detect the position in the moving direction of a to-be-detected body precisely.

  A position detection device according to a first aspect of the present invention excites the first resonance circuit adjacent to the first resonance coil that constitutes the first resonance circuit together with the first capacitor. A first magnetic core wound with a first exciting coil through which a first exciting current to be caused is wound, a second resonant coil that forms a second resonant circuit together with a second capacitor, and the second resonant A second magnetic core wound around a second exciting coil adjacent to the coil and in which a second exciting current for exciting the second resonance circuit in an opposite phase to the first exciting current flows; The first magnetic core and the second magnetic core are arranged to face each other at a predetermined distance in the moving direction of the detection object made of metal having magnetism, and in the moving direction, Generated from the first resonance coil by a first excitation current And a magnetic field generated from the second resonance coil by the second excitation current to form a combined magnetic field, and the detected object moves in the combined magnetic field, whereby the first The position of the detected object in the moving direction is detected based on a change in electrical characteristics generated in at least one of the exciting coil and the second exciting coil.

  The invention of claim 2 is the temperature detection means capable of detecting the ambient temperatures of the first resonance coil and the second resonance coil according to claim 1, and the ambient temperatures detected by the temperature detection means. And correction means for correcting characteristic data corresponding to the electrical characteristics that change according to each ambient temperature.

  A third aspect of the present invention is the method according to the first or second aspect, wherein the movement direction is an axial direction of a main shaft of a machine tool, the inner shaft is movably disposed in the axial direction, and the movement in the axial direction is performed. The detected object is fixed to a draw bar that clamps or unclamps a tool at the front end of the main shaft, and the detected object fixed to the draw bar moves in the combined magnetic field formed in the axial direction. The position of the detected object in the axial direction is detected based on a change in the electrical characteristics caused by the operation.

According to the position detection device of the first aspect of the present invention, the movement of the detected object is replaced with a change in electrical characteristics that occurs in at least one of the first excitation coil and the second excitation coil. The position in the moving direction of the object to be detected can be accurately detected from the difference in the physical characteristics.
According to the second aspect of the present invention, the change in the characteristic data corresponding to the electrical characteristics generated in the first exciting coil and the second exciting coil due to the object to be detected moving in the combined magnetic field is Since it is not affected by the change in the ambient temperature, the position of the detected object in the moving direction can be accurately detected based on the corrected change in the characteristic data regardless of the change in the ambient temperature.
According to the invention of claim 3, it is possible to detect that the tool is clamped or unclamped at the front end of the main shaft by the draw bar from the fixed position of the detected object in the detected draw bar, and other than the clamp and the unclamp (For example, a state in which cutting waste is sandwiched between the tool and the spindle) can be detected.

It is a front view of a machining center provided with a position detection device of an embodiment of the present invention. It is a side view of the machining center. It is an enlarged view of the A part of FIG. FIG. 4 is a view on arrow YY in FIG. 3. It is an enlarged view of the B part of FIG. FIG. 5 is an enlarged view of a portion C in FIG. 4. It is the figure which showed the state by which the tool was unclamped to the main axis | shaft. It is the figure which showed arrangement | positioning with the sensor part and to-be-detected body of a position detection apparatus in the state by which the tool was unclamped to the main axis | shaft. It is the figure which showed the state in which the tool is not attached to the main axis | shaft. It is the figure which showed arrangement | positioning with the same sensor part and the same to-be-detected body in the state in which the tool is not attached to the main axis | shaft. It is a schematic block diagram of the sensor part with which the machining center of embodiment is provided. It is a schematic connection diagram of a position detection device comprising the sensor unit and a reception signal adjustment unit and a control device of a machining center. It is explanatory drawing of the synthetic magnetic field formed with the magnetic field which arises from the 1st resonance coil of the sensor part, and the magnetic field which arises from the 2nd resonance coil.

  An embodiment of the present invention will be described with reference to FIGS. A horizontal machining center 1 shown in FIGS. 1 to 10 includes a base 2, a column 3, a spindle device 4, a spindle 5, a draw bar 6, a detected object 7, a sensor unit 8, and a tool magazine 9. A work placement table 10, an operation panel 11, and a control panel 12 are provided. The machining center 1 is an example of a machine tool that uses the present invention.

  As shown in FIGS. 1 and 2, a cover 15 is disposed on the base 2, and the front side and the rear side of the base 2 and the left and right side surfaces of the base 2 are surrounded by the cover 15. Yes. A column 3 is erected on the upper surface of the base 2. In the column 3, a spindle device 4 is provided so as to be movable in the front-rear direction (left-right direction in FIG. 2). In the present embodiment, as shown in FIGS. 3 and 4, the two guide rails 16, 16 extending in the front-rear direction are provided on the outer surface of the spindle device 4, and the guide rails 16 are slidable on the column 3. A fitting guide block 17 is provided. The spindle device 4 can be moved in the longitudinal direction by feeding the spindle device 4 in the longitudinal direction and sliding the guide rails 16 of the spindle device 4 along the guide blocks 17. Further, the spindle device 4 is movable in the vertical direction.

  As shown in FIG. 4, in the spindle device 4, the spindle 5 is rotatably supported by a plurality of bearings 19 extending in the front-rear direction of the spindle device 4 (left-right direction in FIG. 4) and provided in the spindle head 18. Yes. The main shaft 5 is rotationally driven by a main shaft motor M provided at the rear portion of the main shaft device 4. A mounting hole 21 (see FIGS. 3 and 5) in which various tools 20 (see FIGS. 2 and 5) and the like held in the tool magazine 9 can be mounted is formed in the distal end surface of the main shaft 5. . In addition, illustration of the tool 20 was abbreviate | omitted in FIG. Further, as shown in FIG. 4, a through hole 22 that penetrates the shaft center is formed inside the main shaft 5. A draw bar 6 (see FIGS. 4 and 5) is inserted into the through hole 22 so as to be movable in the front-rear direction (the left-right direction in FIG. 4), which is the axial direction of the main shaft 5. A plurality of disc springs 23 (see FIG. 4) are stacked between the inner peripheral surface of the through hole 22 and the outer peripheral surface of the draw bar 6. The draw bar 6 is formed with a cutting oil supply passage 24 (see FIGS. 4 and 5) that penetrates the shaft center.

  Further, as shown in FIGS. 4 and 6, on the rear side (right side in FIG. 4) of the draw bar 6, pin members 25 having both ends projecting outward from the outer peripheral surface of the main shaft 5 are perpendicular to the axial center direction of the draw bar 6. It is being fixed in the state which penetrated the draw bar 6 in the direction to do. As shown in FIG. 6, an annular fixing member 26 is fitted on the outer peripheral surface of the main shaft 5. The fixing member 26 includes a through hole 27 that penetrates in the vertical direction and can be inserted into both ends of the pin member 25. In addition, an annular and iron detected body 7 is fixed to the outer peripheral surface of the fixing member 26 in a state where it is screwed to a pin member 25 facing from each through hole 27. Since the detected object 7 is made of iron, it can be magnetized.

  As shown in FIGS. 4 and 6, the main spindle device 4 accommodates a cylinder 28 so as to be coaxial with the central axis of the main spindle 5. Further, the cylinder 28 accommodates a piston 29 that is coaxial with the central axis of the main shaft 5 and is slidably fitted on the outer surface of the main shaft 5. As shown in FIGS. 6 and 8, when the piston 29 moves forward in the axial direction (the left-right direction in FIGS. 6 and 8) along the outer surface of the main shaft 5 by supplying hydraulic oil to the push side from the hydraulic device. Then, the fixing member 26 is pushed forward (left side in FIGS. 6 and 8). Accordingly, the detection object 7 fixed to the fixing member 26 and the draw bar 6 connected to the detection object 7 via the pin member 25 move forward.

  As shown in FIGS. 4, 5 and 9, a tool insertion hole 31 is formed at the tip of the draw bar 6. The tool mounting hole 31 is opened at the distal end surface of the draw bar 6 and communicates with the cutting oil supply path 24 and is larger in diameter than the cutting oil supply path 24. Furthermore, an annular engagement protrusion 32 is provided at the front end of the draw bar 6 so as to protrude toward the outside of the draw bar 6. FIG. 5 shows a state in which the tool 20 is clamped to the front end of the main shaft 5 by the operation of the draw bar 6. As shown in FIGS. 2 and 5, the tool 20 is a cylindrical body that extends in the front-rear direction (the left-right direction in FIG. 2) of the spindle device 4 and has a drill attached to the front surface to open the rear surface. An annular engagement claw portion 33 protrudes toward the inside of the tool 20. In addition, a cylindrical portion 34 that extends along the axial direction and can be inserted into the tool mounting hole 31 (see FIGS. 5 and 9) is provided inside the tool 20. An inflow passage 36 (see FIG. 5) for cutting oil is formed in the cylindrical portion 34 in the axial direction. In the state shown in FIG. 5, after the cylindrical portion 34 is inserted into the tool mounting hole 31, the engagement protrusion 32 and the engagement claw portion 33 are engaged, and the disc spring 23 (see FIG. 4). The draw bar 6 is urged toward the rear side of the main shaft 5 by the urging force. As a result, the engaging claw 33 is pulled into the mounting hole 21 by the engaging protrusion 32, so that the tool 20 is clamped to the front end of the main shaft 5 by the operation of the draw bar 6.

  The sensor unit 8 shown in FIGS. 4 and 6 constitutes the position detection device of the present invention, and is arranged above the detected body 7 and close to the detected body 7. Here, the sensor unit 8 includes an aluminum case 38 having a substantially rectangular parallelepiped shape, and the lower surface of the case 38 is a flat detection surface. The gap between the detection surface and the surface of the detection object 7 was set to about 0.5 mm. The case 38 includes the first magnetic core 40, the second magnetic core 41, the magnetic member 42, the first resonance coil 43, the first capacitor 44, and the first magnetic core 40 shown in FIG. An excitation coil 45, a second resonance coil 46, a second capacitor 47, a second excitation coil 48, and a thermistor 49 are accommodated. In FIG. 6, only the first magnetic core 40 and the second magnetic core 41 are shown in the case 38, and illustration of the magnetic members 42 other than the magnetic cores 40 and 41 shown in FIG. 11 is omitted. In addition, in FIG. 8 and FIG. 10, the illustration of the magnetic material 42 and the like is omitted as in FIG.

  The first magnetic core 40 has a cylindrical shape and is disposed in the case 38 in the vertical direction of the case 38 (the vertical direction in FIGS. 6 and 11). The second magnetic core 41 has the same shape as the first magnetic core 40 and is disposed in the same manner as the first magnetic core 40. As shown in FIGS. 6 and 11, the second magnetic core 41 is disposed to face the first magnetic core 40 at a predetermined interval in the axial direction of the main shaft 5 (left and right direction in FIG. 6). . Here, the outer diameter of each of the magnetic cores 40 and 41 is 5 mm, and the distance between the central axis of the first magnetic core 40 and the central axis of the second magnetic core 41 in the axial direction is 7 mm. Furthermore, a magnetic member 42 made of ferrite, for example, is integrally joined to the upper ends of both magnetic cores 40 and 41. As a result, a closed magnetic path is formed by the magnetic cores 40 and 41 and the magnetic member 42.

  As shown in FIG. 11, the first resonance coil 43 is wound around the lower end side (the detection surface side of the sensor unit 8) of the first magnetic core 40. The first resonance circuit 52 is formed by connecting the first capacitor 44 to the first resonance coil 43. Further, on the upper end side of the first magnetic core 40, a first excitation coil 45 is wound adjacent to the first resonance coil 43 in the axial direction of the first magnetic core 40. Here, the turns ratio of the first resonance coil 43 and the first excitation coil 45 is 10: 1. Thereby, the impedance of the first excitation coil 45 becomes smaller than the impedance of the first resonance coil 43. Therefore, as will be described later, the reception signal adjustment unit 66 (see FIG. 12) receives the detection signal in accordance with the amplitude of the voltage across the first excitation coil 45, so that the reception signal adjustment unit 66 and the first excitation coil are received. Even when a lead wire is connected to 45, the detection signal is prevented from fluctuating due to stray capacitance formed between the lead wire and the ground plane or noise (external noise) induced in the lead wire. doing.

  On the other hand, a second resonance coil 46 is wound around the lower end (the detection surface side) of the second magnetic core 41. The second resonance circuit 53 is formed by connecting the second capacitor 47 to the second resonance coil 46. Further, on the upper end side of the second magnetic core 41, a second excitation coil 48 is wound adjacent to the second resonance coil 46 in the axial direction of the second magnetic core 41. The turn ratio between the second resonance coil 46 and the second excitation coil 48 was the same as the turn ratio between the first resonance coil 43 and the first excitation coil 45. In addition, a thermistor 49 shown in FIG. 11 is disposed between the first resonance coil 43 and the second resonance coil 46 in the axial direction of the main shaft 5.

  As shown in FIGS. 1 and 2, the tool magazine 9 is arranged above the spindle device 4. The tool magazine 9 includes a disk-shaped tool holding plate 56 and a drive motor 57 that rotationally drives the tool holding plate 56. As shown in FIG. 1, a plurality of holding portions 58 that detachably hold various tools 20 </ b> A including the tool 20 (see FIG. 2) and the like are formed on the outer periphery of the tool holding plate 56. In addition, as shown in FIGS. 1 and 2, a work placement table 10 is disposed at a machining position of the machining center 1 in the cover 15. Various workpieces to be drilled with a tool 20 clamped to the front end of the main shaft 5 by the operation of the draw bar 6 can be detachably fixed to the upper surface of the workpiece mounting table 10, for example. In addition, an operation panel 11 is fixed to the base 2.

  As shown in FIG. 2, the control panel 12 is erected on the rear side of the spindle device 4 and fixed to the rear portion of the base 2. The control panel 12 accommodates a control device 60 shown in FIG. 12 and a programmable logic controller 61 (hereinafter referred to as “PLC 61”) shown in FIG.

  As shown in FIG. 12, the control device 60 includes an oscillator 62, impedance matching resistors 63 and 64, an inverter 65, a reception signal adjustment unit 66, a microcomputer 67, a storage unit 68, a reception port 69, and a transmission. A port 70 and a state identification signal interface 71 are provided. A microcomputer 67 is connected to the oscillator 62. The oscillator 62 supplies an excitation current based on an operation command signal from the microcomputer 67.

  As shown in FIGS. 11 and 12, the oscillator 62 is connected to the first excitation coil 45 of the sensor unit 8 described above via the impedance matching resistor 63. Thus, the oscillator 62 can supply a positive-phase excitation current (hereinafter referred to as “first excitation current”) to the first excitation coil 45 via the impedance matching resistor 63. When the first excitation current flows through the first excitation coil 45, an electromotive force is generated in the first resonance coil 43 by receiving a magnetic field from the first excitation coil 45. The first resonance coil 43 resonates with the first capacitor 44, and generates a magnetic field H1 shown in FIG. 13 by the resonance current and the electromotive force. In FIG. 13, the capacitors 44 and 47, the oscillator 62, the impedance matching resistors 63 and 64, and the inverter 65 shown in FIG.

  Further, as shown in FIGS. 11 and 12, the oscillator 62 is connected to the second exciting coil 48 of the sensor unit 8 via an inverter 65 and an impedance matching resistor 64. Since the inverter 65 inverts and outputs the excitation current supplied from the oscillator 62, the oscillator 62 sends the first excitation coil 48 to the first excitation coil 48 via the inverter 65 and the impedance matching resistor 64. An excitation current having a phase opposite to the excitation current (hereinafter referred to as “second excitation current”) can be supplied. When the second excitation current flows through the second excitation coil 48, an electromotive force is generated in the second resonance coil 46 by receiving a magnetic field from the second excitation coil 48. The second resonance coil 46 resonates with the second capacitor 47, and generates a magnetic field H2 shown in FIG. 13 by a resonance current and an electromotive force generated in the second excitation coil 48. In addition, magnetic flux leaks from the lower ends of both magnetic cores 40 and 41, so that the magnetic path of the magnetic field H3, which combines the magnetic field H1 and the magnetic field H2, as shown in FIG. 13 in the left-right direction). In the present embodiment, as described above, the outer diameter of each of the magnetic cores 40 and 41 is 5 mm, and the distance between the central axis of the first magnetic core 40 and the central axis of the second magnetic core 41 is 7 mm. A strong magnetic field H3 can be generated in the axial direction of the main shaft 5. The magnetic field H3 is an example of the combined magnetic field of the present invention.

  Further, as shown in FIGS. 11 and 12, both ends of the first excitation coil 45 and both ends of the second excitation coil 48 of the sensor unit 8 are connected to the reception signal adjustment unit 66. The sensor unit 8 detects the voltage across the exciting coils 45 and 48 that changes due to the eddy current loss caused by the eddy current flowing in the detected object 7 that moves together with the draw bar 6. The reception signal adjustment unit 66 receives a detection signal corresponding to the amplitude of the voltage across each of the excitation coils 45 and 48 detected by the sensor unit 8. In the present embodiment, as will be described later, the draw bar to which the detected object 7 is connected via the pin member 25 (see FIG. 6) by utilizing the fact that the amplitude of the detection signal changes due to the eddy current loss. 6 is the state in which the tool 20 is clamped to the front end of the spindle 5 (clamped state) by the operation 6, the state in which the tool 20 is unclamped to the front end by the operation of the draw bar 6 (unclamped state), other than the clamped state and the unclamped state It is possible to precisely determine which of the states is. Examples of states other than the clamped state and the unclamped state include a state in which the tool 20 is not attached to the front end (the tool is not attached), and a state in which the tool 20 is not different from any of the clamped state, the unclamped state, and the tool not attached state. Definition status. In addition, the both-ends voltage of each exciting coil 45 and 48 is an example of the electrical property of this invention.

  In addition, a thermistor 49 is connected to the reception signal adjusting unit 66 as shown in FIGS. As shown in FIG. 11, the thermistor 49 is disposed between the first resonance coil 43 and the second resonance coil 46, so that the ambient temperature of the first resonance coil 43 and the second resonance coil 46 Ambient temperature can be detected. The reception signal adjusting unit 66 receives a temperature detection signal corresponding to the ambient temperature detected by the thermistor 49. As the impedance values of the first resonance circuit 52 and the second resonance circuit 53 change depending on the ambient temperature, the voltage across the excitation coils 45 and 48 (the amplitude of the detection signal of the sensor unit 8) varies. The reception signal adjustment unit 66 adds or subtracts a temperature correction level corresponding to the ambient temperature to or from the amplitude of the detection signal of the sensor unit 8, thereby obtaining an appropriate signal (temperature correction signal) that is not affected by the ambient temperature. Generate. The thermistor 49 is an example of the temperature detecting means of the present invention. The amplitude of the detection signal of the sensor unit 8 is an example of the characteristic data of the present invention, and the received signal adjustment unit 66 is an example of the correction unit of the present invention and constitutes the position detection device of the present invention.

  Further, the reception signal adjusting unit 66 is connected to the microcomputer 67. The reception signal adjustment unit 66 transmits the temperature correction signal to the microcomputer 67. A storage unit 68 is connected to the microcomputer 67. In the storage unit 68, amplitude data corresponding to the amplitude equivalent to the amplitude of the temperature correction signal in each of the clamped state, the unclamped state, and the tool non-attached state is used as reference data for the spindle 5 by the operation of the draw bar 6. A plurality of different tools that can be clamped to the front end are stored in association with each other.

  In addition, the microcomputer 67 is connected with a reception port 69, a transmission port 70, and a state identification signal interface 71. The reception port 69, the transmission port 70, and the state identification signal interface 71 are connected to the PLC 61. The reception port 69 and the transmission port 70 are provided to match the level of signals transmitted and received between the microcomputer 67 and the PLC 61. The PLC 61 is used to perform monitoring and operation control of the machining center 1. The microcomputer 67 can receive communication data having a processing request command for requesting data transmission from the PLC 61 via the reception port 69 by performing I / O communication with the PLC 61 at a predetermined timing. ing. When the microcomputer 67 receives the processing command of the communication data by the I / O communication, the microcomputer 67 transmits the amplitude data of each state (unclamped state, clamped state, tool unattached state) to the PLC 61 via the transmission port 70. It is possible. The state identification signal interface 71 can always output a state identification signal for identifying each state received from the microcomputer 67 to the PLC 61.

  As shown in FIG. 12, the operation panel 11 is connected to the microcomputer 67. The operation panel 11 is provided with various buttons and a touch panel that can be operated by an operator of the machining center 1. For example, the operator inputs the model data of the tool 20 to be clamped to the front end of the main shaft 5 by the operation of the draw bar 6 from among a plurality of different tools 20 and 20A by operating the buttons and the like.

  In addition, an external input / output interface 72 is connected to the microcomputer 67. A personal computer 73 is connected to the external input / output interface 72. When the operator operates the keyboard of the personal computer 73, the personal computer 73 sends a test signal based on the test data stored in the storage device of the personal computer 73 to the microcomputer 67 via the external input / output interface 72. Send. As a result, the personal computer 73 causes the microcomputer 67 to perform a test operation.

  Next, the operation of the machining center 1 will be described. In this embodiment, when the operator operates the operation panel 11 and inputs the model data of the tool 20 used for machining the workpiece, the microcomputer 67 attaches the tool 20 to the spindle 5 before machining the workpiece. A process for detecting the state is executed. The microcomputer 67 executes processing for detecting an unclamped state, a tool unattached state, and a clamped state based on a program stored in the storage device of the microcomputer 67, for example, every 2 msec.

  In order to detect the unclamped state, the PLC 61 moves the spindle device 4 up and down or back and forth in accordance with a predetermined control command in the machining control program stored in the storage device of the PLC 61, so that the operator inputs on the operation panel 11. Control for mounting the tool 20 corresponding to the above type from the holding portion 58 of the tool magazine 9 and mounting the tool 20 in the mounting hole 21 of the spindle 5 as shown in FIG. 7 is executed for a first predetermined time. At the same time, the PLC 61 moves the draw bar 6 forward by pushing the fixing member 26 forward (left side in FIG. 8) with the piston 29 as shown in FIG. The control for setting the unclamped state in which the engagement is released is executed over a first predetermined time. At this time, with the detection surface of the sensor unit 8 facing the surface of the detected object 7 as shown in FIG. 8, the microcomputer 67 operates the oscillator 62 to adjust the amplitude data of the temperature correction signal as the received signal. Received from the unit 66 (see FIG. 12). In this embodiment, the microcomputer 67 receives the amplitude data corresponding to the voltage across the first excitation coil 45 and the amplitude data corresponding to the voltage across the second excitation coil 48 as the amplitude data. Even if one of the amplitude data cannot be received, the process of detecting the unclamped state can be continued based on the other amplitude data. In addition, in this embodiment, when the detection object 7 moves to a position corresponding to the unclamped state, the amplitude of the temperature correction signal (the amplitude of the voltage across each excitation coil 45, 48) becomes a constant level. This also applies to a tool unattached state and a clamped state described below. When the detected object 7 moves to a position corresponding to the tool unattached state, the amplitude of the temperature correction signal is unclamped or clamped. When the detected object 7 moves to a position corresponding to the clamped state, the amplitude of the temperature correction signal becomes a constant level different from the unclamped state and the tool unattached state.

  The microcomputer 67 receives the amplitude data of the temperature correction signal from the reception signal adjustment unit 66 and then the tool input by the operator on the operation panel 11 from the reference data in the unclamped state stored in the storage unit 68. The reference data in the unclamped state associated with the 20 model data is selected. Subsequently, when the microcomputer 67 determines that the amplitude data of the temperature correction signal matches the selected reference data, the microcomputer 67 determines that the machining center 1 is in an unclamped state. On the other hand, when the microcomputer 67 determines that the amplitude data does not match the reference data, the microcomputer 67 determines that the machining center 1 is in an undefined state.

  Further, in order to detect the unattached state of the tool, the PLC 61 is mounted in the mounting hole 21 by moving the spindle device 4 up and down or back and forth after the first predetermined time has elapsed according to a predetermined control command. The tool 20 is gripped by the holding portion 58 of the tool magazine 9. Subsequently, the spindle device 4 is returned to the position before the movement by the predetermined control command, and the tool is not mounted in the mounting hole 21 as shown in FIG. To run. At the same time, the PLC 61 causes the detected body 7 connected to the draw bar 6 to move horizontally below the sensor unit 8 in the magnetic field H3 (see FIG. 13) by the biasing force of the disc spring 23 (see FIG. 4). A control for moving the main shaft 5 rearward in the axial direction (right side in FIG. 10) and energizing the rearward side as shown in FIG. 10 is performed over a second predetermined time. At this time, as shown in FIG. 10, the microcomputer 67 operates the oscillator 62 in a state in which the portion where the detected object 7 overlaps the magnetic field H3 is smaller than the unclamped state shown in FIG. The amplitude data of the temperature correction signal is received from the reception signal adjustment unit 66. As shown in FIG. 10, as the overlapping portion is reduced, the eddy current loss is reduced as compared with the unclamped state. As a result, the amplitude of the temperature correction signal in the tool unattached state is larger than the amplitude in the unclamped state growing. Therefore, when the detected object 7 moves in the magnetic field 3 in the axial direction of the main shaft 5 from the position corresponding to the unclamped state to the position corresponding to the tool non-attached state, the amplitude of each temperature correction signal (each exciting coil 45). , 48), the position of the detected object 7 in the axial direction of the main shaft 5 can be accurately detected from the difference in the amplitude of the temperature correction signal. The axial direction of the main shaft 5 is an example of the moving direction of the detected object of the present invention.

  Then, after receiving the amplitude data of the temperature correction signal, the microcomputer 67 stores the model data of the tool 20 input by the operator on the operation panel 11 from the reference data stored in the storage unit 68 when the tool is not attached. The reference data in the tool unattached state associated with is selected. Subsequently, when the microcomputer 67 determines that the amplitude data matches the reference data, the microcomputer 67 determines that the machining center 1 is in a tool unattached state. On the other hand, when the microcomputer 67 determines that the amplitude data does not match the reference data, the microcomputer 67 determines that the machining center 1 is in an undefined state.

  Furthermore, in order to detect the clamping state, the PLC 61 again responds to the above type as shown in FIG. 5 by moving the spindle device 4 up and down or moving back and forth after the second predetermined time has elapsed according to a predetermined control command. Control for mounting the tool 20 to be mounted on the mounting hole 21 is executed for a third predetermined time. At the same time, the PLC 61 causes the detected object 7 to move horizontally below the sensor unit 8 in the magnetic field H3 (see FIG. 13) by the biasing force of the disc spring 23 toward the axial rear side (right side in FIG. 6) of the main shaft 5. As shown in FIG. 5, the engagement claw 33 is pulled into the mounting hole 21 by the engagement protrusion 32 and the control to make the clamp state is executed for a third predetermined time. At this time, as shown in FIG. 6, the portion where the detected body 7 overlaps the magnetic field H3 is increased from the unattached state shown in FIG. 10 and more than the unclamped state shown in FIG. In a state where the overlapping portion is reduced, the microcomputer 67 operates the oscillator 62 to receive the amplitude data of the temperature correction signal from the reception signal adjustment unit 66. The amplitude of the temperature correction signal in the clamped state is smaller than the amplitude in the tool unmounted state and larger than the amplitude in the unclamped state. After receiving the amplitude data, the microcomputer 67 is in the clamp state associated with the model data of the tool 20 input by the operator on the operation panel 11 from the reference data in the clamp state stored in the storage unit 68. Select reference data. Subsequently, when the microcomputer 67 determines that the amplitude data matches the reference data, the microcomputer 67 determines that the machining center 1 is in a clamped state. On the other hand, when the microcomputer 67 determines that the amplitude data does not match the reference data, the microcomputer 67 determines that the machining center 1 is in an undefined state.

  When the microcomputer 67 performs detection processing of each state (unclamped state, tool unattached state, clamped state) and determines that the amplitude data in each state matches the reference data, the state identification signal (unclamped) A process of outputting a state identification signal, a tool unattached state identification signal, a clamp state identification signal) to the PLC 61 through the state identification signal interface 71 is executed. On the other hand, when the microcomputer 67 determines that the amplitude data in each state does not match the reference data, the microcomputer 67 outputs a state identification signal (undefined state identification signal) to the PLC 61 through the state identification signal interface 71. Run.

  In addition, when the PLC 61 receives the undefined state identification signal beyond a predetermined time, the PLC 61 sends communication data having a processing request command to the microcomputer 67 via the reception port 69 (see FIG. 12) by I / O communication. By transmitting, the amplitude data of each state (unclamped state, clamped state, tool unattached state) is received from the microcomputer 67 via the transmission port 70 (see FIG. 12) by I / O communication. The operator predicts the cause determined to be in the undefined state based on the numerical value of the amplitude data of each state. As an example of the cause, when the tool 20 is clamped to the front end of the main shaft 5 by the operation of the draw bar 6, workpiece cutting waste is caught between the tool 20 and the mounting hole 21 of the main shaft 5. It is done. In addition, as an example of the cause, there are fluctuations in the signal level due to wear and temperature drift caused by the forward / backward movement of the draw bar 6.

<Effect of this embodiment>
In the present embodiment, the movement of the detected object 7 in the axial direction of the main shaft 5 is replaced with a change in the voltage between both the excitation coils 45 and 48, thereby detecting the detected object in the axial direction of the main shaft 5. It becomes possible to detect the position of the body 7 precisely.

  The reception signal adjusting unit 66 also detects the amplitude of the detection signal (the voltage across the excitation coils 45 and 48) of the sensor unit 8 that varies depending on the ambient temperature of the first resonance coil 43 and the ambient temperature of the second resonance coil 46. Was corrected to an amplitude not affected by the ambient temperature to generate a temperature correction signal. Therefore, since the amplitude of the temperature correction signal is not affected by the change in the ambient temperature of each resonance coil 43, 46, the main shaft 5 is based on the change in the amplitude of the temperature correction signal regardless of the change in the ambient temperature. The position of the detected object 7 in the axial direction can be accurately detected.

  Further, by detecting the position of the detected body 7 corresponding to each state (unclamped state, tool unattached state, clamped state) in the axial direction of the spindle 5 based on the amplitude data of the temperature correction signal, In addition to being able to detect a state, when the amplitude data does not match the reference data of each state, it is possible to detect a state other than each state (undefined state).

  The present invention is not limited to the above-described embodiment, and can be implemented by appropriately changing a part of the configuration without departing from the spirit of the invention. For example, unlike the embodiment described above, the outer diameter dimensions of the magnetic cores 40 and 41 and the distance between the central axis of the first magnetic core 40 and the central axis of the second magnetic core 41 are the axial directions of the main shaft 5. May be changed to an appropriate value that can generate a strong magnetic field H3. In the above-described embodiment, the detection surface of the sensor unit 8 is disposed above the detected body 7 and close to the detected body 7. However, the present invention is not limited to this, and the detection surface of the sensor unit 8 is used as the detected body 7. It may be arranged in the vicinity of the detected object 7 below the object. Further, in the above-described embodiment, in order to detect each state (unclamped state, tool unattached state, clamped state), the microcomputer 67 uses amplitude data corresponding to the voltage across the first exciting coil 45 and the second data. Both of the amplitude data corresponding to the voltage across the excitation coil 48 are received, but the present invention is not limited to this. For example, the microcomputer 67 may receive only one of the amplitude data and detect the states based on the amplitude data.

  In addition, in the above-described embodiment, the ambient temperature of both the resonance coils 43 and 46 is detected by one thermistor 49 disposed between the first resonance coil 43 and the second resonance coil 46. However, the present invention is not limited to this. First, two thermistors are arranged between the two resonance coils 43 and 46 in the axial direction of the main shaft 5, and the ambient temperature of the first resonance coil 43 is determined by the thermistor on the first resonance coil 43 side as the second resonance. The ambient temperature of the second resonance coil 46 may be detected by a thermistor on the coil 46 side. In addition, instead of the thermistor 49, one or two diodes capable of detecting the ambient temperature of the two resonance coils 43, 46 may be disposed between the two resonance coils 43, 46 in the axial direction of the main shaft 5. .

  1 .. Machining center, 5 .. Spindle, 6 .. Drawbar, 7 .. Object to be detected, 8 .. Sensor part, 40.. First magnetic core, 41. 1 resonance coil, 44... First capacitor 45... First excitation coil 46.. Second resonance coil 47.. Second capacitor 48.. Second excitation coil 49. Thermistor, 52, First resonance circuit, 53, Second resonance circuit, 66, Reception signal adjustment unit, H1, Magnetic field generated by first resonance coil, H2, Second resonance coil A magnetic field generated by the first resonance coil and a magnetic field generated by the second resonance coil and a magnetic field generated by the second resonance coil.

Claims (3)

A first resonance coil that forms a first resonance circuit together with a first capacitor, and a first excitation current that flows adjacent to the first resonance coil and that excites the first resonance circuit. A first magnetic core with each coil wound thereon;
A second resonance coil that forms a second resonance circuit together with a second capacitor, and the second resonance circuit is excited adjacent to the second resonance coil in a phase opposite to that of the first excitation current. A second magnetic core around which a second exciting coil through which a second exciting current flows is wound,
The first magnetic core and the second magnetic core are arranged to face each other with a predetermined distance in the moving direction of the detection object made of metal having magnetism,
In the moving direction, a combined magnetic field is formed by a magnetic field generated from the first resonance coil by the first excitation current and a magnetic field generated from the second resonance coil by the second excitation current. ,
The detected object in the moving direction based on a change in electrical characteristics generated in at least one of the first exciting coil and the second exciting coil as the detected object moves in the combined magnetic field. A position detecting device for detecting the position of a body. Temperature detecting means capable of detecting ambient temperatures of the first resonance coil and the second resonance coil;
The correction means which correct | amends the characteristic data corresponding to the said electrical characteristic which changes with each said ambient temperature according to each said ambient temperature detected by the said temperature detection means is provided. The position detection device described. The moving direction as the axial direction of the main axis of the machine tool,
The object to be detected is fixed to a draw bar that is arranged inside the main shaft so as to be movable in the axial direction, and clamps or unclamps a tool on the front end of the main shaft by movement in the axial direction.
Based on the change in the electrical characteristics caused by the detected object fixed to the draw bar moving in the combined magnetic field formed in the axial direction, the position of the detected object in the axial direction is determined. The position detection apparatus according to claim 1, wherein the position detection apparatus detects the position.

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