JP5782864B2 - Contact position detection device and machine tool - Google Patents

Description

  The present invention relates to a contact position detection device that detects a contact position of a workpiece or a tool with respect to an object, and a machine tool that performs workpiece shape measurement or tool breakage detection using the contact position detection device.

  In general, a machining center (machine tool) mills a workpiece by moving the workpiece mounted on the table and the tool mounted on the spindle in the XYZ directions and rotating the tool by rotating the spindle. Various processes such as boring or tapping can be performed. The machine tool accommodates a plurality of types of tools, and continuously performs various types of processing while exchanging tools to be mounted on the spindle according to the target processing. In addition, the machine tool can measure the surface shape of the workpiece by attaching the touch sensor to the spindle after the machining, moving the workpiece and the touch sensor relative to each other, and bringing the touch sensor into contact with the surface of the workpiece.

  In such a machine tool, the workpiece and the touch sensor are relatively moved in the X and Y directions, and the touch sensor is moved up and down in the Z direction to detect a position where the touch sensor contacts the workpiece (and / or a position away from the workpiece). By measuring the surface shape of the workpiece. However, when the touch sensor is based on a mechanical contact, there is a possibility that chattering may occur at the contact when the touch sensor contacts the workpiece. When chattering occurs, there is a possibility that the position where the touch sensor touches the workpiece may be erroneously detected, and there is a problem that the measurement accuracy of the surface shape of the workpiece is lowered.

  In Patent Document 1, the detection value of the touch sensor is sampled and stored in the shift register in order, and when the detection value indicating that the touch sensor has contacted the workpiece continues for a predetermined number of times, the touch sensor contacts the surface of the workpiece. It has been determined that the chattering removing apparatus is configured to acquire the position of the touch sensor at this time as the contact position. In this apparatus, since detection results less than the predetermined number are excluded, chattering can be removed with a simple configuration.

  In Patent Literature 2, a tool is moved in the Z-axis direction and brought into contact with a touch sensor provided on a table, whereby a first predetermined position set and a second distance apart from the first predetermined position by a predetermined distance. The position of the tool is detected by detecting that the tool has reached the predetermined position, the position corresponding to the detected first predetermined position and the position corresponding to the second predetermined position, and the first predetermined position and the second predetermined position. There has been proposed a numerically controlled machine tool that calculates a displacement difference from a predetermined distance between the two and corrects the movement control of the tool based on the displacement difference. Further, the numerically controlled machine tool described in Patent Document 2 can detect whether or not the tool is broken according to the position where the tool contacts the touch sensor.

JP 2010-157975 A Japanese Utility Model Publication No. 5-83802

  However, since the chattering removal apparatus described in Patent Document 1 is configured to determine that the first contact is made when a detection value indicating contact with the workpiece continues for a predetermined number of times, the touch sensor actually contacts the workpiece. There is a problem in that there is a time difference between the time point and the time point when the chattering removal device determines contact. Due to this time difference, there is a problem that the detection accuracy of the contact position with respect to the workpiece is lowered and the measurement accuracy of the surface shape of the workpiece is lowered. Similarly, when the machine tool detects breakage of a tool, there is a problem that detection accuracy is lowered.

  Further, in the numerically controlled machine tool described in Patent Document 2, chattering is similarly generated by the touch sensor. Therefore, it is conceivable to employ the technique described in Patent Document 1. However, also in this case, there is a problem that the detection accuracy of the contact position of the tool with respect to the touch sensor is lowered, and the accuracy of correction for the tool movement control is lowered. Similarly, when the breakage detection of a tool is performed with the numerically controlled machine tool described in Patent Document 2, there is a problem that the breakage detection accuracy is lowered.

  The present invention has been made in view of such circumstances, and an object of the present invention is to eliminate chattering generated by the touch sensor and prevent the detection accuracy of the contact position from being lowered, and chattering. An object of the present invention is to provide a contact position detection device and a machine tool that can prevent the detection accuracy of a contact position from being lowered due to a detection delay associated with removal.

The contact position detection device according to the present invention includes a contact detection unit that samples a detection result of a sensor that detects presence or absence of contact with an object in time series, and a displacement that displaces a relative position between the sensor and the object. And a position detection means for sampling the position in time series, wherein the sensor detects a position in contact with the object, and the detection result of the contact detection means is detected in time series. When the detection result storage means for storing a plurality of times, the position storage means for storing the position sampled by the position detection means for a plurality of times in a time series, and the detection result with contact by the contact detection means continue for a predetermined number of times. The contact detection means for sampling the contact detection means for determining the contact with the object and the first detection result among the detection results for the presence of the contact that has been repeated for the predetermined number of times. Get the contact there detection result before the point, the detection result extracted from the detection results stored in the storage means, said position detecting means at the time of sampling corresponding to the extracted detection result sampled position, from the position storage means A position acquisition unit, and a counter that counts the number of samplings from the first detection result with contact by the contact detection unit to the detection result with the contact determination unit determining contact, and the position acquisition unit includes: When the contact confirmation means confirms contact, the position corresponding to the first detection result with contact is acquired based on the count value of the counter, and the position acquired by the position acquisition means is The sensor is configured to detect a position in contact with the object.

  In the contact position detection device according to the present invention, the time from the time when the position acquisition unit samples the first detection result by the contact detection unit to the time when the contact determination unit determines the contact. When the time is longer than a predetermined time, the position corresponding to the time point before the predetermined time from the time point when the contact determination means determines the contact is obtained from the position of the plurality of times stored in the position storage means. And

  The contact position detecting device according to the present invention is characterized in that the contact detection means shifts and stores the sampled detection results in order in a shift register.

  In addition, the machine tool according to the present invention is a machine tool that processes a workpiece with a mounted tool, and the above-described contact position detection device detects the workpiece as the workpiece according to the contact position. It is characterized by comprising measuring means for measuring the shape.

  Further, the machine tool according to the present invention is a machine tool that processes a workpiece with a mounted tool, and the above-described contact position detecting device detects the object as the tool according to the contact position. It is characterized by comprising a breakage detecting means for detecting the breakage.

In the present invention, the detection result of the sensor for detecting contact is sampled and stored in a plurality of times in a time series, and the detection of contact with the object is confirmed when the detection result with contact continues for a predetermined number of times. . As a result, detection results less than the predetermined number are excluded, so that the influence of erroneous detection due to chattering can be eliminated.
Further, the relative positions of the sensor and the object are detected, and the detected positions are sampled and stored a plurality of times in time series. When the detection of contact with the object is confirmed as described above, the detection result with contact is extracted retroactively from the timing of sampling the first detection result of the predetermined number of times when the contact detection is confirmed, and the extracted detection result The detection position sampled at the time of sampling corresponding to is acquired. By setting the acquired detection position as the position where the sensor and the object are in contact with each other, it is possible to use the position of the sensor retroactively before removing the chattering and confirming the contact as the detection result of the final sensor contact position. . Since chattering occurs due to the contact between the sensor and the object, the detection result close to the actual contact position can be obtained by tracing the detection position before the contact is determined, and the detection accuracy of the contact position can be improved.

  In addition, the detection positions are stored a plurality of times in time series. That is, the detection positions are stored in the order of detection, and after reaching the storable number, the oldest detection positions are deleted and new detection positions are stored (so-called FIFO (First In First Out)). When acquiring the detection position retroactively before the contact is confirmed, the first (oldest) detection position corresponding to the detection result with contact by the sensor is acquired from the detection positions stored in time series. Good. As a result, the number of stored detection positions (storage capacity) is only required to be able to store a sampling result of about the time from the occurrence of chattering until the detection result is stabilized. Further, it is easy to obtain the detection position retrospectively.

  In the present invention, the number of samplings from the most recent detection result with contact until the contact is confirmed is counted by a counter, and the most recent detection result is acquired based on the value of this counter after the contact is confirmed. Thereby, the process which acquires a detection position retroactively before contact determination can be performed easily.

In the present invention, the maximum time for acquiring the detection position retrospectively from the contact confirmation is determined in advance as a predetermined time. The predetermined time can be determined based on the measurement result obtained by measuring the time from the occurrence of chattering until the detection result of the sensor is stabilized in the design stage or the test stage of the manufacturing process.
After the contact is confirmed, the most recent detection position is acquired from the stored detection positions for a plurality of times, but if the time from the sampling of the most recent detection position until the contact is confirmed is longer than the predetermined time, the most recent detection position is finally determined Instead of using the contact position, a detection position corresponding to a time point that is a predetermined time after the contact confirmation is acquired, and the acquired detection position is set as the final contact position. Thereby, even if it is a case where the erroneous detection of a sensor generate | occur | produces by the influence of disturbance noise etc. before chattering, the influence of this erroneous detection can be excluded.

  In the present invention, the detection result of the sensor is stored in the shift register. By sequentially shifting the stored detection results every time sampling is performed, time-series storage can be easily realized. Similarly, a shift register may be used for storing the detection position.

  Moreover, in this invention, the contact position of the sensor with respect to a workpiece | work is detected using the above contact position detection apparatuses, and the shape measurement of a workpiece | work is performed according to a detection result. Accordingly, it is possible to detect the contact position with high accuracy with respect to the workpiece while excluding the influence of chattering, and it is possible to measure the shape of the workpiece with high accuracy.

  In the present invention, the contact position detection device as described above is used to detect the contact position of the sensor with respect to the tool, and the breakage of the tool is detected according to the detection result. Thereby, it is possible to detect the contact position with high accuracy with respect to the tool while excluding the influence of chattering, and to detect breakage of the tool with high accuracy.

  In the case of the present invention, the detection of contact with the object is confirmed when the detection result with contact continues for a predetermined number of times, the detection position is acquired retroactively before the contact is determined, and the acquired detection position is determined based on the sensor and the object. By adopting a configuration in which the contact position is detected, it is possible to prevent a decrease in detection accuracy of the contact position due to chattering, and it is possible to prevent a decrease in detection accuracy of the contact position due to a detection delay caused by chattering removal. Therefore, the workpiece shape measurement and / or tool breakage detection in the machine tool can be performed with high accuracy.

It is a perspective view which shows the external appearance of a machining center. It is a front view which shows the structure of the principal part of a machining center. It is a block diagram which shows the electrical structure of a machining center. It is a timing chart for demonstrating a contact position detection process. It is a timing chart for demonstrating a contact position detection process. It is a flowchart which shows the procedure of a contact position detection process. It is a flowchart which shows the procedure of a contact decision process. It is a flowchart which shows the procedure of a contact decision process. It is a flowchart which shows the procedure of a contact position confirmation process. FIG. 6 is a schematic diagram for explaining a configuration of a machining center according to a second embodiment.

(Embodiment 1)
Hereinafter, the present invention will be specifically described with reference to the drawings showing embodiments thereof. FIG. 1 is a perspective view showing an appearance of a machining center (machine tool). FIG. 2 is a front view showing the configuration of the main part of the machining center. The machining center according to the present embodiment can perform desired machining (for example, slicing, drilling, cutting, etc.) on a workpiece by relatively moving a workpiece (not shown) to be processed and a tool. It is a machine tool that can. The machining center includes a metal base 1, and legs are provided at the four corners of the lower part of the base 1, and these four legs are installed on the floor or the like, so that the machining center is installed at a predetermined place. The The base 1 is a rectangular parallelepiped casting that is long in the front-rear direction of the machining center.

  A column seat 3 is provided on the rear portion of the base 1 of the machining center, and a columnar column 4 extending vertically upward is erected on the column seat 3. The column 4 is provided with a spindle head 5 that can move up and down along the front surface thereof. The spindle head 5 is provided with a spindle 5A on which a machining tool 6 is mounted, and a tool exchange mechanism 7 for exchanging the tool 6 mounted on the spindle 5A with another tool 6. Although not shown in FIG. 1, a Z-axis motor 67 (see FIG. 3) is provided at the top of the column 4, and the spindle head 5 can be moved up and down by the rotation of the Z-axis motor 67.

  A spindle 5A corresponding to a machining axis is rotatably mounted on the spindle head 5, and a spindle motor 61 (see FIG. 3) for rotating the spindle 5A is provided at the top. A tool 6 is detachably attached to the lower end of the main shaft 5A. When the main shaft 5A is rotationally driven by a main shaft motor 61, the tool 6 is rotated and a workpiece fixed to the table 8 is processed. The spindle 5A moves between an upper exchange position and a lower machining position by the vertical movement of the spindle head 5. The tool change mechanism 7 holds and conveys a tool magazine 14 that stores a plurality of tool holders that support the tool 6, a tool holder that is mounted on the spindle 5A, and another tool holder that is stored in the tool magazine 14, And a tool changing arm 15 for changing the tool.

  Further, on the base 1, a table 8 is disposed below the spindle head 5 so that a work can be detachably fixed. The table 8 is controlled to move in the X-axis direction (left-right direction) and the Y-axis direction (front-rear direction) by an X-axis motor 63 and a Y-axis motor 65 (see FIG. 3) which are servo motors. Specifically, a rectangular parallelepiped support base 10 is provided below the table 8, and the support base 10 is provided with a pair of X-axis feed guides extending along the X-axis direction, and a pair of X-axis feed guides. A table 8 is movably supported on the top. In addition, a pair of Y-axis feed guides extending in the longitudinal direction (Y-axis direction) is provided on the upper portion of the base 1, and the support base 10 is movably supported on the pair of Y-axis feed guides. . A Y-axis motor 65 provided on the base 1 moves and drives the support base 10 in the Y-axis direction along the Y-axis feed guide, and an X-axis motor 63 provided on the support base 10 follows the X-axis feed guide. Then, the table 8 is driven to move in the X-axis direction.

  The X-axis feed guide is provided with telescopic covers 11 and 12 that contract telescopically on both the left and right sides of the table 8. In the Y-axis feed guide, a telescopic cover 13 and a Y-axis rear cover are provided on the front and rear sides of the support base 10, respectively. The X-axis feed guide and the Y-axis feed guide are always covered by the telescopic covers 11, 12, 13 and the Y-axis rear cover, regardless of which direction the table 8 and the support base 10 are moved. The telescopic covers 11, 12, 13 and the Y-axis rear cover are for preventing chips or the like scattered from the workpiece processing region from dropping onto the X-axis feed guide, the Y-axis feed guide, and the like.

  A box-shaped control box 9 is provided on the back side of the column 4, and a control unit 20 (see FIG. 3) for controlling the operation of the machining center is accommodated in the control box 9. FIG. 3 is a block diagram showing an electrical configuration of the machining center. In the machining center, a plurality of servo amplifiers 30 and input / output units 40 are connected to a control unit 20 accommodated in a control box 9 via a communication bus, and these can be used for work while transmitting and receiving information via the communication bus. Such processing is performed.

  The illustrated machining center includes four servo amplifiers 30, a spindle motor 61 and a spindle encoder 62 are connected to the first servo amplifier 30, and an X-axis motor 63 and an X-axis encoder are connected to the second servo amplifier 30. 64, a Y-axis motor 65 and a Y-axis encoder 66 are connected to the third servo amplifier 30, and a Z-axis motor 67 and a Z-axis encoder 68 are connected to the fourth servo amplifier 30. A touch sensor 50 is connected to the input / output unit 40.

  The control unit 20 includes a CPU (Central Processing Unit) 21, a control clock generation unit (simply described as a control clock in FIG. 3) 22, a storage unit 23, a communication I / F (interface) 24, and the like. . The CPU 21 operates based on a clock signal of a predetermined period generated by the control clock generator 22, and performs various arithmetic processes to control operations of the respective parts of the machining center. The storage unit 23 is composed of a memory element such as a DRAM (Dynamic Random Access Memory) or an SRAM (Static Random Access Memory), and data generated during the arithmetic processing of the CPU 21, or the servo amplifier 30 or the input / output unit 40. Temporarily store data transmitted and received by the communication.

  The communication I / F 24 of the control unit 20 is connected to a communication bus and communicates with the servo amplifier 30 or the input / output unit 40. When a transmission instruction is given from the CPU 21, the communication I / F 24 performs transmission processing by reading transmission data from the storage unit 23 and outputting it to the communication bus. Further, when receiving data from the servo amplifier 30 or the input / output unit 40, the communication I / F 24 stores the received data in the storage unit 23 and notifies the CPU 21 that the data has been received.

  Further, the control unit 20 periodically communicates with the servo amplifier 30 and the input / output unit 40. However, in order to reduce the load on the CPU 21, the servo amplifier 30 and the input / output unit 40 have different periods. Communicate with. Specifically, the communication cycle between the servo amplifier 30 having a high control priority and the control unit 20 is set short, and the communication cycle between the input / output unit 40 having a low priority and the control unit 20 is set long.

  The servo amplifier 30 includes a CPU 31, a servo clock generation unit (simply described as a servo clock in FIG. 3) 32, a storage unit 33, a communication I / F 34, a motor I / F 35, an encoder I / F 36, and the like. . The CPU 31 operates based on a clock signal having a predetermined period generated by the servo clock generator 32. The storage unit 33 is configured by a memory element such as a DRAM or SRAM, and data generated during the arithmetic processing of the CPU 31, data transmitted / received through communication with the control unit 20, data input to the encoder I / F 36, etc. Is temporarily stored. The communication I / F 34 is connected to a communication bus and periodically communicates with the control unit 20.

  The motor I / F 35 of the servo amplifier 30 is connected to a motor such as a main shaft motor 61, an X-axis motor 63, a Y-axis motor 65, or a Z-axis motor 67, and a control signal for driving the motor to rotate according to the control of the CPU 31. Is output. The main shaft motor 61 is for rotating the main shaft 5A. The X-axis motor 63 and the Y-axis motor 65 move the table 8 in the X-axis direction and the Y-axis direction, respectively. The Z-axis motor 67 moves the spindle head 5 in the Z-axis direction. (The X-axis motor 63, the Y-axis motor 65, and the Z-axis motor 67 are displacement means for displacing the relative positions of the tool 6 or the touch sensor 50 mounted on the main shaft 5A and the workpiece placed on the table 8. .)

  The encoder I / F 36 is connected to an encoder such as a main shaft encoder 62, an X axis encoder 64, a Y axis encoder 66, or a Z axis encoder 68. (The X-axis encoder 64, the Y-axis encoder 66, and the Z-axis encoder 68 are position detection means for detecting the relative position between the tool 6 or the touch sensor 50 mounted on the spindle 5A and the workpiece placed on the table 8. These encoders detect the rotational position information of the corresponding motor and output it to the servo amplifier 30, and the encoder I / F 36 samples the information input from the encoder based on the control of the CPU 31, The sampled information is stored in the storage unit 33 in time series. Based on information from the encoder, the CPU 31 calculates the rotational speed of the spindle 5A, the positions (coordinates) of the spindle 5A in the X-axis direction, the Y-axis direction, and the Z-axis direction with respect to the workpiece (or table 8). Can do. The information stored in the storage unit 33 may be the calculated coordinate information of the spindle 5A.

  In the storage unit 33 of the second to fourth servo amplifiers 30, the detection results of the encoder over several cycles of the communication cycle with the control unit 20 are stored as coordinate information in the X-axis direction, the Y-axis direction, or the Z-axis direction. The stored coordinate information is transmitted to the control unit 20 by communication via the communication bus. The control unit 20 stores the coordinate information received from each servo amplifier 30 in the storage unit 23 in time series. (That is, the storage unit 33 of the servo amplifier 30 and the storage unit 23 of the control unit 20 are detection position storage means for storing coordinate information for a plurality of times in time series.) Note that a touch sensor 50 described later is mounted on the spindle 5A. The coordinate information stored in the storage unit 23 is also position (coordinate) information of the touch sensor 50.

  The input / output unit 40 is configured to include a shift register clock generation unit (indicated simply as a shift clock in FIG. 3) 41, a shift register 42, a communication I / F 43, and the like. A touch sensor 50 is connected to the input / output unit 40, and a signal output from the touch sensor 50 is input to the shift register 42 of the input / output unit 40. The touch sensor 50 is a sensor that detects the presence or absence of contact with an object. For example, the touch sensor 50 outputs a high level signal when there is a contact, and outputs a low level signal when there is no contact.

  The shift register clock generator 41 generates and outputs a clock signal having a predetermined cycle. The shift register 42 captures (samples) the output signal of the touch sensor 50 in accordance with the clock signal and stores the stored information. Shift one bit at a time. The shift register 42 can store N (for example, N = 4) bits of information, and can store N sampling results of the touch sensor 50. (That is, the shift register 42 is a contact detection sampling unit and a contact detection result storage unit.)

  The communication I / F 43 is connected to the communication bus and periodically communicates with the control unit 20. The communication I / F 43 communicates with the control unit 20 at least once every N (the size of the shift register 42) cycle of the clock signal input to the shift register 42, and the value stored in the shift register 42. Is transmitted to the control unit 20. The control unit 20 stores the information received from the input / output unit 40 (the value of the shift register 42) in the storage unit 23 over several communication cycles with the input / output unit 40. (That is, the storage unit 23 of the control unit 20 is also a contact detection result storage unit that stores the contact detection results for a plurality of times in time series.)

  When the machining center measures the surface shape of the workpiece placed on the table 8, the touch sensor 50 is mounted on the spindle 5A, and the table 8 is driven in the X-axis direction and the Y-axis direction by driving the X-axis motor 63 and the Y-axis motor 65. The spindle head 5 is moved in the Z-axis direction by driving the Z-axis motor 67 while moving to the position, and the position at which the touch sensor 50 contacts the surface of the workpiece is measured.

  The touch sensor 50 outputs a low level signal when it is not in contact with the surface of the workpiece, and outputs a high level signal when it is in contact with the surface of the workpiece. The input / output unit 40 samples the output signal of the touch sensor 50 at the cycle of the clock signal generated by the shift register clock generation unit 41, and stores a high-level or low-level 1-bit value in the shift register 42. Further, the shift register 42 sequentially shifts the stored value in accordance with the clock signal, whereby the detection result of the touch sensor 50 is stored in time series. The input / output unit 40 periodically communicates with the control unit 20, and transmits the N-bit value stored in the shift register 42 to the control unit 20. The communication cycle between the input / output unit 40 and the control unit 20 is longer than the cycle of the clock signal generated by the shift register clock generation unit 41.

  Each servo amplifier 30 outputs a signal of the encoder (X-axis encoder 64, Y-axis encoder 66, or Z-axis encoder 68) input to the encoder I / F 36 at a predetermined cycle (the cycle of the clock signal generated by the servo clock generator 32). And may be a period other than that), and the detection result of the position of the spindle 5A (touch sensor 50 attached to the workpiece) with respect to the workpiece in the X-axis direction, the Y-axis direction, or the Z-axis direction. Are stored in the storage unit 33 in time series. The servo amplifier 30 periodically communicates with the control unit 20, and transmits information on the detection position stored in the storage unit 33 to the control unit 20. The communication cycle of the servo amplifier 30 and the control unit 20 is longer than the sampling cycle of the detection position.

  The control unit 20 stores, in the storage unit 23, information on the detected position regarding the X-axis direction, the Y-axis direction, and the Z-axis direction received through communication with the servo amplifier 30 in time series, and communication with the input / output unit 40. The information of the detection result of the touch sensor 50 received by is stored in the storage unit 23 in time series. That is, the storage unit 23 of the control unit 20 stores the detection result of the presence or absence of the touch sensor 50 and the detection position in the X-axis direction, the Y-axis direction, and the Z-axis direction in time series, and samples each detection result. The detected position at the time of the recording is stored in association with each other. Further, the amount of information of the detection result and detection position of the touch sensor 50 stored in the storage unit 23 of the control unit 20 is limited, and when new information is received from the servo amplifier 30 or the input / output unit 40, the oldest information is received. Is destroyed.

  The sampling of each servo amplifier 30 and the sampling of the input / output unit 40 are not necessarily performed in synchronization. The sampling of each servo amplifier 30 and the sampling of the input / output unit 40 are not necessarily performed at the same cycle. When sampling is performed asynchronously and / or when sampling is performed at different periods, the detection position sampled at the closest timing to the detection result of the presence or absence of contact may be stored in association with each other.

  FIG. 4 is a timing chart for explaining the contact position detection processing. An example of the output signal of the touch sensor 50 is shown in the upper part, and the sampling timing to the shift register 42 by the input / output unit 40 is shown in the lower part. The contact position detection process is a process performed by the CPU 21 of the control unit 20. In the illustrated example, sampling results for 12 cycles (A to F) are stored in the storage unit 23. The storage unit 23 stores information on detection positions in the X-axis direction, the Y-axis direction, and the Z-axis direction in association with the sampled detection results of the touch sensor 50. The detection result and the detection position stored in the storage unit 23 are the chattering time (four periods in the illustrated example) generated by the touch sensor 50 contact, and the output signal of the touch sensor 50 is stable and the control unit 20 is in contact. The amount of information can be set to be several cycles longer than the total time with the time until it is determined (four cycles in the illustrated example). The chattering time can be determined by measuring in advance at the design stage of the machining center, for example.

  In the contact position detection process, the CPU 21 of the control unit 20 examines the detection results of the touch sensor 50 stored in the storage unit 23 in order from the oldest one, and the detection result with contact is continuously a predetermined number of times (in the illustrated example, four times). If it is, the touch sensor 50 is confirmed to contact the workpiece (timing J in the figure). After the contact is confirmed, the CPU 21 goes back to the first detection result (timing G) of the predetermined number of contact detection results related to the contact determination, and from the detection result stored in the storage unit 23, the most recent contact is detected. The detection result (timing C) is acquired (that is, the detection result with the latest contact may be acquired from the storage unit 23). The CPU 21 sets the timing at which the detection result is sampled as the timing at which the touch sensor 50 first contacts the workpiece, and stores the detection positions in the X-axis direction, the Y-axis direction, and the Z-axis direction corresponding to the detection result. And the touch position of the touch sensor 50 with respect to the workpiece. As a result, the CPU 21 can acquire the detection position corresponding to the sampling timing (timing C) closest to the timing when the touch sensor 50 actually contacts the workpiece from the storage unit 23 and set it as the contact position.

  FIG. 5 is a timing chart for explaining the contact position detection process, in which a condition for the maximum retroactive time is further added to the contact position detection process explained in FIG. In the procedure of this process, similarly to the procedure of the process shown in FIG. 4, the CPU 21 determines the contact of the touch sensor 50 to the workpiece when the detection result of the presence of contact has continued for a predetermined number of times (timing L ), The detection result with contact stored in the storage unit 23 is acquired retroactively before the first detection result (timing I) among the predetermined number of detection results with contact according to the contact confirmation. At this time, in this process, the maximum retroactive time (in the example shown, the time for four sampling cycles) is set in advance, and the CPU 21 examines the detection result retroactively within the range of the maximum retroactive time, and there is the most recent contact. The detection result (timing E) is acquired.

  By setting the maximum retroactive time in this way, even if erroneous detection (timing A, B) of the touch sensor 50 due to noise or the like occurs, for example, as shown in the figure, the CPU 21 determines the erroneous detection result. It is possible to prevent the detection position from being acquired as the contact position retroactively. Note that the maximum retroactive time can be determined based on chattering time measured in advance in the design stage of the machining center (for example, chattering time + several cycles of time, etc.).

FIG. 6 is a flowchart showing the procedure of the contact position detection process, and shows the procedure of the process performed by the CPU 21 of the control unit 20. In this processing, processing is performed using the following registers, counters, flags, and the like, which are realized by a part of the storage area of the storage unit 23 or the register of the CPU 21.
Registers P1, P2, P3: registers for temporarily storing shift register values received from the input / output unit 40.
Register length L: Bit length of registers P1, P2, and P3.
Chattering removal threshold N: This is a threshold for determining the presence of contact, and it is determined that there is a contact when the detection result of the presence of contact continues N times.
Counter C1: A counter for counting the continuous number with contact.
Counters C2 and C3: Counters that count the number of shifts to shift by the register length of the registers P1, P2, and P3.
Counter C4: A counter for counting the number of shifts from the first detection result of contact.
Flag F1: A flag indicating whether or not there is a detection result of contact.

  In the contact position detection process, the CPU 21 first clears the values of the registers P1 to P3 and the counters C1 to C4 to 0, and performs an initialization process for reading the register length L and the chattering removal threshold value N (step S1). Next, the CPU 21 determines whether or not communication with the input / output unit 40 is performed through the communication I / F 24 (step S2). When communication is not performed (S2: NO), communication is performed. Wait until.

  When communication with the input / output unit 40 is performed (S2: YES), the CPU 21 sets (stores) the value of the register P3 in the register P2 (step S3), and the detection result (shift) received from the input / output unit 40. The value of the register 42) is set in the registers P1 and P3 (step S4). That is, the register P3 stores the value of the shift register received from the input / output unit 40 in the previous communication, the latest received data is set in the register P1, and the previous received data is set in the register P2. . Subsequent processing is performed on the previous and latest two received data set in the two registers P1 and P2.

  Next, the CPU 21 performs contact determination processing based on the values of the registers P1 and P2 (step S5). 7 and 8 are flowcharts showing the procedure of the contact confirmation process, and shows the detailed procedure of the process performed by the CPU 21 in step S5. In the contact determination process, the CPU 21 determines whether or not the MSB (Most Significant Bit) value of the register P2 (the oldest detection result stored in the register P2) is 1 (contact present) (step S21). If the MSB value of the register P2 is not 1 (S21: NO), the CPU 21 sets the value of the counter C1 to 0 (step S22), and if the MSB value of the register P2 is 1 (S21: YES) Then, 1 is added to the value of the counter C1, and 1 is set to the flag F1 (step S23), and the process proceeds to step S24.

  Next, the CPU 21 adds 1 to the value of the counter C2 (step S24), and shifts the register P2 to the left by 1 bit (discards the MSB data and moves the other data to the MSB side by 1 bit) (step S25). ). Thereafter, the CPU 21 determines whether or not the value of the flag F1 is 1 (step S26). If the value of the flag F1 is 1 (S26: YES), the CPU 21 adds 1 to the value of the counter C4 ( The process proceeds to step S27) and step S28. If the value of the flag F1 is not 1 (S26: NO), the CPU 21 advances the process to step S28.

  Next, the CPU 21 determines whether or not the value of the counter C1 is the chattering removal threshold value N (step S28). When the value of the counter C1 is the chattering removal threshold value N (S28: YES), since the detection result of presence of contact is N times continuous, the CPU 21 determines the contact (step S42) and ends the contact determination process. Then, the process returns to the process of the flowchart shown in FIG.

  If the value of the counter C1 is not the chattering removal threshold N (S28: NO), the CPU 21 further determines whether or not the value of the counter C2 is the register length L (step S29). If the value of the counter C2 is not the register length L (S29: NO), the CPU 21 returns the process to step S21 and repeats the above process for the next bit of the register P2. When the value of the counter C2 is the register length L (S29: YES), the CPU 21 sets the value of the counter C2 to 0 (step S30) because the above processing has been completed for all the bits of the register P2. The process proceeds to S31.

  Next, the CPU 21 performs the same process for the value set in the register P1. The CPU 21 determines whether or not the MSB value of the register P1 is 1 (step S31). If the MSB value of the register P1 is not 1 (S31: NO), the CPU 21 sets the value of the counter C1 to 0 (step S32), and if the MSB value of the register P1 is 1 (S31: YES) Then, 1 is added to the value of the counter C1, and 1 is set to the flag F1 (step S33), and the process proceeds to step S34.

  Next, the CPU 21 adds 1 to the value of the counter C3 (step S34), and shifts the register P1 to the left by 1 bit (step S35). Thereafter, the CPU 21 determines whether or not the value of the flag F1 is 1 (step S36). If the value of the flag F1 is 1 (S36: YES), the CPU 21 adds 1 to the value of the counter C4 ( The process proceeds to step S37) and step S38. If the value of the flag F1 is not 1 (S36: NO), the CPU 21 advances the process to step S38.

  Next, the CPU 21 determines whether or not the value of the counter C1 is the chattering removal threshold value N (step S38). When the value of the counter C1 is the chattering removal threshold value N (S38: YES), since the detection result of contact is N times consecutively, the CPU 21 determines the contact (step S42) and ends the contact determination process. Then, the process returns to the process of the flowchart shown in FIG.

  When the value of the counter C1 is not the chattering removal threshold value N (S38: NO), the CPU 21 further determines whether or not the value of the counter C3 is the register length L (step S39). When the value of the counter C3 is not the register length L (S39: NO), the CPU 21 returns the process to step S31 and repeats the above process for the next bit of the register P1. When the value of the counter C3 is the register length L (S39: YES), the CPU 21 sets the value of the counter C1 to 0 (step S40) because the above processing has been completed for all the bits of the register P1. It determines with there being no contact (step S41), complete | finishes a contact determination process, and returns to the process of the flowchart shown in FIG.

  After completing the contact confirmation process in step S5, the CPU 21 determines whether or not the contact is confirmed based on the processing result of the contact confirmation process (step S6). When the contact is not confirmed (S6: NO), the CPU 21 returns the process to step S2 and waits for the next communication with the input / output unit 40. When the contact is determined (S6: YES), the CPU 21 performs a contact position determination process for determining the contact position of the touch sensor 50 with respect to the workpiece (step S7).

  FIG. 9 is a flowchart showing the procedure of the contact position determination process, and shows the detailed procedure of the process performed by the CPU 21 in step S7. In the contact position determination process, first, the CPU 21 reads the retroactive limit value X (step S51). The retroactive limit value X corresponds to the maximum retroactive time shown in FIG. 5, and the maximum retroactive time corresponds to how many sampling periods (the period of the clock signal generated by the shift register clock generator 41). It is a fixed value indicating

  Next, the CPU 21 determines whether or not the value of the counter C4 is smaller than the retroactive limit value X (step S52). When the value of the counter C4 is smaller than the retroactive limit value X (S52: YES), the CPU 21 stores the detection position corresponding to the timing retroactive by the value of the counter C4 from the timing when the contact is determined in the contact determination process from the storage unit 23. Acquired (step S53), the contact position determination process is terminated with this detected position as the contact position, and the process returns to the flowchart shown in FIG. When the value of the counter C4 is greater than or equal to the retroactive limit value X (S52: NO), the CPU 21 stores the detection position corresponding to the timing retroactive by the retroactive limit value X from the timing of determining the contact in the contact determination process. 23 (step S54), the detected position is set as the contact position, the contact position determination process is terminated, and the process returns to the flowchart shown in FIG. In the contact position detection process of FIG. 6, the contact position determined in the contact position determination process in step S7 is set as a detection result, and the process ends.

  In the machining center having the above configuration, the output signal (detection result) of the touch sensor 50 is sampled and stored in the time series in the shift register 42 and the storage unit 23, and the contact is detected when the detection result with contact continues for a predetermined number of times. Since the detection result less than the predetermined number is excluded, the influence of chattering can be eliminated. Further, the position of the touch sensor 50 mounted on the spindle 5A with respect to the workpiece placed on the table 8 is sampled as coordinate information in the X-axis direction, the Y-axis direction, and the Z-axis direction, and stored in the storage units 23 and 33 in time series. When the contact of the touch sensor 50 is determined and the touch sensor 50 is determined to be contacted, the stored detection position is acquired and used as the contact position before the timing at which the first detection result of the predetermined number of times when the contact detection is determined is sampled. By adopting the configuration, the position of the touch sensor 50 that is traced back before the chattering is removed and the contact is determined can be used as the final detection result of the touch position of the touch sensor 50. Since chattering occurs due to contact between the touch sensor 50 and the workpiece, a detection result close to the actual contact position can be obtained by tracing back the detection position before the contact is determined, and the detection accuracy of the contact position can be improved. .

  Further, when acquiring the detection position retroactively before the contact is determined, the foremost (oldest) detection position corresponding to the detection result with the touch by the touch sensor 50 is acquired from the detection positions stored in time series. With this configuration, the process of acquiring the detection position retrospectively is easy, and the number of detection positions stored (the capacity of the storage unit 23 necessary for storing the detection positions) is detected from the occurrence of chattering. It is possible to make the capacity small enough to store the sampling result for the time until the time becomes stable.

  In addition, if the detection result with the latest contact traced back from the contact determination is before the maximum retroactive time from the contact determination, the detection position corresponding to the detection result with the previous contact is not the contact position. By setting the detection position corresponding to the detection result retroactive by the maximum retroactive time as the contact position, even if erroneous detection of the touch sensor 50 occurs due to, for example, disturbance noise before chattering, The influence of this false detection can be excluded.

  In the present embodiment, an example in which a configuration (contact position detection device) for detecting a contact position with respect to an object using the touch sensor 50 is applied to a machining center has been described. However, the contact position detection device is applied to the machining center. The present invention is not limited to this, and can be applied to various devices having a function of detecting contact positions with respect to other various objects.

  Further, the detection result of the touch sensor 50 is sampled by the input / output unit 40, and the sampling result is given to the control unit 20 by communication. However, the present invention is not limited to this, and the control unit 20 directly controls the touch sensor 50. The detection result may be sampled. Similarly, with respect to the detection positions in the X-axis direction, the Y-axis direction, and the Z-axis direction, the control unit 20 directly samples the sampling result instead of transmitting the sampling result from the servo amplifier 30 to the control unit 20. Also good. Further, the storage unit 23 of the control unit 20 and / or the storage unit 33 of the servo amplifier 30 may be configured with a shift register (with respect to storage of detection results or detection positions).

  Moreover, when acquiring a contact position retroactively from contact confirmation, it was set as the structure which limits the time to go back by the maximum retroactive time (retroactive limit value X), However, It is good also as a structure which does not perform this. Whether or not to limit the maximum retroactive time depends on the amount of detection results stored in the storage unit 23 of the control unit 20 (how many detection results are stored) and the contact for confirming the contact Based on conditions such as the number of consecutive detection results (that is, chattering removal threshold N) and the like, the designer of the apparatus can make a determination in advance.

(Embodiment 2)
The machining center according to the first embodiment described above is configured to measure the shape of the workpiece using the touch sensor 50, whereas the machining center according to the second embodiment is a detection result of the contact position of the tool 6 with respect to the touch sensor. Accordingly, the breakage of the tool 6 is detected. FIG. 10 is a schematic diagram for explaining the configuration of the machining center according to the second embodiment. In the machining center according to the second embodiment, a touch sensor 150 is provided on a table 8 on which a workpiece is placed.

  The control unit 20 of the machining center drives the X-axis motor 63 and the Y-axis motor 65 to move the table 8 in the X-axis direction and the Y-axis so that the sensor 150 is positioned directly below the main shaft 5A (the tool 6 attached to the spindle 5A). It can be moved in the axial direction. Thereafter, the control unit 20 moves the spindle head 5 downward in the Z-axis direction by driving the Z-axis motor 67 until the tool 6 attached to the spindle 5A contacts the touch sensor 150, and the tool 6 moves to the touch sensor 150. The coordinate information in the Z-axis direction when touching is acquired.

  The coordinate information in the Z-axis direction acquired by the control unit 20 at this time is information corresponding to the length of the tool 6 attached to the main shaft 5A. In the machining center, coordinate information in the Z-axis direction that is expected to come into contact with the touch sensor 150 corresponding to the length of each tool 6 is stored in advance, and the coordinate information stored in advance and the coordinates actually detected are stored. When the difference from the information exceeds the threshold value, the control unit 20 detects that the tool 6 is broken.

  In the breakage detection process of the machining center according to the second embodiment, when the detection result of the touch of the tool 6 with respect to the touch sensor 150 continues for a predetermined number of times, as in the workpiece shape measurement process of the machining center according to the first embodiment. The contact is confirmed, and the contact position (coordinate information in the Z-axis direction) is acquired retrospectively from the contact confirmation.

  Further, the machining center according to the second embodiment can correct the change in the movement amount due to the temperature change with respect to the movement control of the spindle head 5 in the Z-axis direction. Hereinafter, this correction process will be briefly described (refer to Patent Document 2 for details). The spindle head 5 of the machining center is provided with a nut portion (not shown), and this nut portion is screwed with a ball screw (not shown) provided on the column 4. The ball screw is rotatably supported. When the ball screw is rotationally driven by the Z-axis motor 67, the spindle head 5 moves in the Z-axis direction.

  When the spindle head 5 repeatedly moves in the Z-axis direction during processing, heat is generated by friction between the nut portion of the spindle head 5 and the ball screw, and the heat is transmitted to the column 4, the ball screw, the spindle head 5, and the like. Temperature rises. At this time, since the column 4 expands upward, the ball screw expands downward, and the spindle head 5 expands downward, the lower end surface of the spindle head 5 (position where the tool 6 is mounted) according to the expansion amount. Is displaced.

  Therefore, the control unit 20 of the machining center according to the second embodiment corrects the machining conditions (the amount of movement of the spindle head 5 in the Z-axis direction) by performing the following processing. First, the control unit 20 starts from the reference position of the spindle head 5 (for example, the position where the tool is changed) until the first tool mounted on the spindle 5A comes into contact with the touch sensor 150 (until the contact is confirmed). Is moved downward in the Z-axis direction, and the position at which the first tool contacts the touch sensor 150 (this position is referred to as Z1) is acquired. Next, the control unit 20 includes position information defined by the dimensions of the first tool and the dimensions of the touch sensor 150 stored in advance (that is, the expected value of the contact position of the first tool on the touch sensor 150), A difference from the actually detected position information Z1 is calculated as a displacement amount D1.

  Next, the control unit 20 replaces the tool, attaches the second tool (tool having a different length from the first tool) to the spindle 5A, and similarly, the position where the second tool contacts the touch sensor 150. Z2 is detected and a displacement amount D2 is calculated. When the contact positions Z1 and Z2 and the displacement amounts D1 and D2 obtained by the above processing are used, the displacement amount D (z) at the coordinate z in the Z-axis direction can be expressed by the following equation (1).

  D (z) = (D2-D1) / (Z2-Z1) * z + (Z2 * D1-Z1 * D2) / (Z2-Z1) (1)

  Since the displacement amount at each position in the Z-axis direction can be calculated by the above equation (1), the control unit 20 corrects the movement amount of the spindle head 5 in the Z-axis direction so as to cancel the displacement amount. As a result, the machining accuracy of the machining center can be increased. Note that when the contact positions Z1 and Z2 are detected, the detection result of the contact of the first tool or the second tool with respect to the touch sensor 150 is detected as in the workpiece shape measurement process of the machining center according to the first embodiment. Is determined for a predetermined number of times, the contact is determined, and the contact positions Z1 and Z2 are acquired retroactively from the contact determination.

  The machining center according to the second embodiment having the above-described configuration performs the correction process related to the breakage detection of the tool 6 or the movement in the Z-axis direction based on the detection result of the contact position of the tool 6 with respect to the touch sensor 150 and the touch. By adopting a configuration in which the contact position is acquired retrospectively from the contact determination of the sensor 150, the influence of chattering generated in the touch sensor 150 can be removed, and the detection accuracy of the contact position can be improved. The breakage detection process or the correction process can be performed with high accuracy.

4 column 5 spindle head 5A spindle 6 tool 7 tool change mechanism 8 table 9 control box 14 tool magazine 15 tool change arm 20 control unit 21 CPU (contact determination means, position acquisition means, counter, measurement means, breakage detection means)
22 control clock generator 23 storage unit (position storage means)
24 Communication I / F
30 Servo amplifier 31 CPU
32 Servo clock 33 Storage section (position storage means)
34 Communication I / F
35 Motor I / F
36 Encoder I / F (position detection means)
40 I / O unit 41 Clock generator for shift register 42 Shift register (contact detection means)
43 Communication I / F
50 Touch sensor (sensor)
61 Spindle motor 62 Spindle encoder 63 X-axis motor (displacement means)
64 X-axis encoder 65 Y-axis motor (displacement means)
66 Y-axis encoder 67 Z-axis motor (displacement means)
68 Z-axis encoder 150 Touch sensor (sensor)

Claims (5)

Contact detection means for sampling a detection result of a sensor for detecting presence or absence of contact with an object in time series, displacement means for displacing a relative position of the sensor and the object, and the position in time series A position detecting means for sampling, and a contact position detecting device for detecting a position at which the sensor contacts an object,
Detection result storage means for storing the detection results of the contact detection means a plurality of times in a time series;
Position storage means for storing the position sampled by the position detection means a plurality of times in time series;
Contact confirmation means for confirming contact with an object when the detection result of presence of contact by the contact detection means is continued a predetermined number of times;
The initial detection results before the time when the contact detection means is sampled in contact there the detection result of said predetermined number of consecutive contacts there the detection result, and extracted detected from the result stored in the detection result storage means, Position acquisition means for acquiring the position sampled by the position detection means at the time of sampling corresponding to the extracted detection result from the position storage means ;
A counter that counts the number of sampling from the first detection result with contact by the contact detection unit to the detection result with the contact determination unit determining contact ;
The position acquisition means acquires a position corresponding to the first detection result with contact based on the count value of the counter when the contact determination means determines contact,
The contact position detection apparatus characterized in that the position acquired by the position acquisition means is detected as a position where the sensor is in contact with the object. When the time from the time when the first detection result is sampled by the contact detection unit to the time when the contact determination unit determines contact is longer than a predetermined time, the position acquisition unit determines that the contact determination unit is in contact the position corresponding to a point in time before the predetermined time from the defined point in time, said position storing means the contact position detecting apparatus according to claim 1, characterized in that are to be acquired from a plurality of times of position stored . The contact detection unit, the contact position detecting apparatus according to claim 1 or claim 2, characterized in that shifting sequentially the detection results of the sampling in the shift register are to be stored. In machine tools that process workpieces with installed tools,
The contact position detection device according to any one of claims 1 to 3 , further comprising a measurement unit that measures the shape of the workpiece according to the contact position at which the object is detected as the workpiece. A machine tool. In machine tools that process workpieces with installed tools,
The contact position detection device according to any one of claims 1 to 3 , further comprising: a break detection unit that detects breakage of the tool according to a contact position where the object is detected as the tool. A featured machine tool.

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