Abnormal condition detection method and polishing apparatus

Abstract

The present invention provides an abnormal condition detection method and polishing apparatus that can detect the occurrence of an abnormal condition related to a workpiece based on the load condition of the polishing surface. [Solution] In a polishing apparatus 1 comprising a polishing tool 10 pressed against the surface of a glass plate G and a drive unit 20 that rotates the polishing tool 10, the load current value of the drive unit 20 is monitored, and the occurrence of an abnormal condition related to the glass plate G is detected based on the fact that the time change of the load current value is different from the normal state.

Description

[Technical Field]

[0001] This invention relates to a method for detecting abnormal conditions and a polishing apparatus. [Background technology]

[0002] For example, during various processing steps for glass plates used in flat panel displays (FPDs) such as LCDs (Liquid Crystal Displays) and OLEDs (Organic Light-Emitting Diodes), damage such as cracks may occur in the glass plates. For this reason, polishing equipment for glass plates that has a function to detect cracks in the glass plates at an early stage is known.

[0003] Patent Document 1 discloses an abnormality detection device that includes an AE sensor installed on a worktable where a workpiece placed on top is processed, which detects elastic waves from the workpiece via a liquid interposed between the workpiece and the workpiece, and an abnormality detection unit that determines whether or not there is an abnormality in the workpiece based on the detection signal from the AE sensor, wherein the AE sensor is positioned directly below the position where the workpiece is placed on the worktable.

[0004] Non-patent document 1 clarifies the relationship between changes in the power (current) of a machining tool and the machining load, and by examining the effect on power (current) in unstable machining, it is possible to estimate the tangential resistance by measuring the spindle current during machining as a result of estimating the unstable machining state, and it is possible to estimate the grinding burn and clogging ratio. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-185659 [Non-patent literature]

[0006] [Non-Patent Document 1] Kensuke Yamashita, Hiroyuki Koike, and Shosuke Soda, "Observation of Machining Load Due to Power Changes in Machining Machines in Grinding Processes," Tochigi Prefectural Industrial Technology Center Research Report, No. 20, 2023. [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] Conventional polishing equipment does not adequately consider the load on the polishing surface of the workpiece being polished, making it difficult to properly detect abnormal conditions that may occur during polishing.

[0008] The present invention has been made in view of the above, and aims to provide an abnormal condition detection method and polishing apparatus that can detect the occurrence of an abnormal condition related to a workpiece based on the load condition of the polished surface. [Means for solving the problem]

[0009] One aspect of the present invention consists of the following configuration. A polishing apparatus comprising a polishing tool pressed against the surface of a flat workpiece and a drive unit for rotating the polishing tool, The load current value of the drive unit is monitored, Based on the fact that the time change of the load current value differs from the normal state, the occurrence of an abnormal state related to the flat workpiece is detected. Method for detecting abnormal conditions.

[0010] One aspect of the present invention consists of the following configuration. A polishing tool pressed against the surface of a flat workpiece, A drive unit for rotating the polishing tool, A monitoring unit that monitors the load current value of the drive unit, A detection unit that detects the occurrence of an abnormal condition related to the flat workpiece based on the time change of the load current value, A polishing device equipped with the following features. [Effects of the Invention]

[0011] According to the present invention, it is possible to detect the occurrence of an abnormal state related to a workpiece based on the load state of the polished surface.

Brief Description of the Drawings

[0012] [Figure 1] FIG. 1 is a schematic diagram of a polishing apparatus according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a perspective view showing a state where a polishing tool polishes a glass plate in the polishing apparatus according to the first embodiment. [Figure 3] FIG. 3 is an image diagram showing a processing concept of a method for detecting an abnormal state of a glass plate by a control device. [Figure 4] FIG. 4 is a flowchart showing the procedure of the first detection method. [Figure 5] FIG. 5 is a flowchart showing the procedure of the second detection method. [Figure 6] FIG. 6 is a graph showing an example of a load current value in a normal state. [Figure 7] FIG. 7 is a graph showing an example of the behavior of a load current value when an abnormal state related to a glass plate occurs in the polishing apparatus according to the first embodiment. (A) is an example where a crack occurs in the glass plate, the load current value once decreases, and then a curl occurs and the load current value increases. (B) is an example where a crack occurs in the glass plate but no curl occurs and the load current value decreases. (C) is an example where a crack and a curl occur in the glass plate almost simultaneously and the load current value increases. [Figure 8] FIG. 8 is a graph showing an example of the behavior of a load current value when an abnormal state related to an equipment system occurs in the polishing apparatus according to the first embodiment and a schematic diagram of the equipment system. (A1) is an example where the load current value is decreasing. (A2) is a diagram showing the peeling of a double-sided tape on a polishing pad corresponding to the behavior of (A1). (B1) is an example where the load current value is decreasing. (B2) is a diagram showing a dent on the surface of a polishing pad corresponding to the behavior of (B1). (C1) shows an example where the load current value is decreasing. [Figure 9] FIG. 9 is a schematic diagram of a polishing apparatus according to a second embodiment of the present invention. [Figure 10] FIG. 10 is a perspective view showing a state in which an abrasive tool polishes a glass plate in the polishing apparatus according to the second embodiment. [Figure 11] FIG. 11 is a graph showing the behavior of the load current value when an abnormal state occurs with respect to the glass plate in the polishing apparatus according to the second embodiment, where (A) shows the load current value of revolution, (B) shows the load current value of turning, and (C) shows the load current value of rocking.

Embodiments for Carrying Out the Invention

[0013] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Note that the present invention is not limited by this embodiment, and when there are a plurality of embodiments, those configured by combining each embodiment are also included. Also, numerical values include the range of rounding.

[0014] (First Embodiment) FIG. 1 is a schematic view of a polishing apparatus according to the first embodiment of the present invention. The polishing apparatus 1 is an apparatus for polishing a flat workpiece (workpiece) such as a glass plate. The polishing apparatus 1 according to the first embodiment includes an abrasive tool 10 pressed against the surface of the glass plate G, a drive unit 20 that rotationally drives the abrasive tool 10, and a control device 30 that monitors and controls the operation of the drive unit 20.

[0015] The abrasive tool 10 is an apparatus for polishing the surface of the glass plate G, and includes a polishing head (upper platen) 11, a polishing plate 12, a polishing pad 13, a back pad 14, and a lower platen 15. The polishing head (upper platen) 11, the polishing plate 12, and the polishing pad 13 may be collectively referred to as the upper side of the abrasive tool 10. The glass plate G is manufactured by, for example, the float process. The glass plate G is sandwiched between the polishing pad 13 and the back pad 14, and the surface of the glass plate G is polished by the upper side of the abrasive tool 10 being rotationally driven.

[0016] The drive unit 20 is a mechanism for driving the upper part of the polishing tool 10 and includes an orbital drive servo motor 21, a rotation drive servo motor 22, a rotary joint 23, a spindle 24, and a shaft 25. The orbital drive servo motor 21 causes the upper part of the polishing tool 10 to orbit around the axis of the spindle 24 at a constant rotational speed. The rotation drive servo motor 22 causes the upper part of the polishing tool 10 to rotate around the axis of the shaft 25 at a constant rotational speed. The axis of the shaft 25 is offset from the axis of the spindle 24 by the orbital radius. The rotary joint 23 is through which polishing slurry, vacuum piping for plate adsorption, polishing pressure piping, etc. are passed. The spindle 24 has a reduction gear that reduces the rotation of the orbital drive servo motor 21 and the rotation drive servo motor 22, and rotates the shaft 25. The shaft 25 is connected to the upper part of the polishing tool 10, and the upper part of the polishing tool 10 is driven as the shaft 25 rotates.

[0017] Figure 2 is a perspective view showing the polishing tool 10 polishing a glass plate G in the polishing apparatus 1 according to the first embodiment. In this example, the polishing head 11, polishing plate 12, and polishing pad 13 of the polishing tool 10 are circular in plan view, rotate in the direction of arrow A, and revolve in the direction of arrow B. Multiple glass plates G before polishing are laid out and attached on the lower platen 15 via a back pad 14. The lower platen 15 is driven by a lower servo motor (not shown) and moves linearly in the direction of arrow C, so that the glass plates G before polishing are sequentially and continuously transported to the location of the rotating polishing head 11, polishing plate 12, and polishing pad 13. The transported glass plates G are polished by the polishing head 11, polishing plate 12, and polishing pad 13. In other words, the polishing apparatus 1 according to this embodiment is a continuous polishing apparatus. Since the polishing head 11 and the orbital drive servo motor 21 and the rotational drive servo motor 22, and the lower platen 15 and the lower servo motor are all connected via direct drive using only gears, without the use of chains or the like, high-precision control is possible.

[0018] The polishing tool 10 is not limited to the example in Figure 2. For example, the polishing head 11, polishing plate 12, and polishing pad 13 may be rectangular in plan view, and their shapes are not limited. Also, the rectangular polishing tool 10 may revolve rather than rotate. In addition to the configuration in Figure 2, the tool may further include the polishing head 11, polishing plate 12, and polishing pad 13, and polish the glass plate G at two locations.

[0019] The control device 30, which monitors and controls the operation of the drive unit 20, comprises a controller 31, a monitoring unit 32, and a detection unit 33. The controller 31 receives feedback of the rotation angle detected by optical encoders, etc., built into the orbital drive servo motor 21 and the rotational drive servo motor 22. The controller 31, upon receiving the feedback, can control the rotation of each motor by controlling a servo amplifier (not shown) that supplies power to each motor.

[0020] The control device 30 controls the speed of each operation of the polishing head 11 and the lower platen 15, specifically the rotation, oscillation, and swirling motions. Under normal conditions, the control device 30 controls the current value so that the rotation of each motor is at a predetermined set value (a constant value or a constant pattern).

[0021] The monitoring unit 32 monitors the load current value of the drive unit 20. The load current value is the result of speed control by the controller 31 described above. If the mechanical load, such as friction at each part of the device, including the polishing tool 10, is constant, i.e., in a normal state, the load current value will be a constant value or a constant pattern. However, if there is a fluctuation in the mechanical load, the controller 31 will fluctuate the load current value in order to control the speed, causing the load current value to deviate from a constant value or constant pattern and show a value different from the normal state.

[0022] The present inventors' findings regarding load current values ​​are described below. During polishing, the load current value is generated with a constant periodic current waveform, but its value fluctuates depending on the contact area between the polishing surface of the polishing tool 10 and the glass plate G. The main reason for the decrease in load current value is thought to be a decrease in contact area. In addition, the wavelength and the number of periodic current waveforms change according to the line speed, or the conveying speed by the lower platen 15 in the example of Figure 2. As a result, it has been found that a gradual increase in the load current value leads to cracking of the glass plate G.

[0023] The detection unit 33 detects the occurrence of an abnormal condition related to the glass plate G based on the time change in the load current value. In particular, as described above, the detection unit 33 detects the occurrence of an abnormal condition related to the glass plate G based on the time change in the load current value monitored by the monitoring unit 32 being different from the normal state. The control device 30 is equipped with one or more processors and reads an abnormal condition detection program for detecting the occurrence of an abnormal condition related to the glass plate G from a memory (not shown), implements the functions of the monitoring unit 32 and the detection unit 33, and performs abnormal condition detection. For example, the control device 30 is mainly composed of a PLC (Programmable Logic Controller), and the orbital drive servo motor 21 and the rotational drive servo motor 22 are rotated by a controller 31 that receives commands from the PLC. The control device 30 may have the controller 31, monitoring unit 32 and detection unit 33 in the same device (housing), or one or more functions may be implemented by multiple devices.

[0024] Furthermore, abnormal conditions related to the glass plate G, i.e., the workpiece, include not only the occurrence of cracks and grinding cracks, but also abnormalities in components and equipment that can cause grinding cracks, such as grinding pad detachment, grinding pad surface dents, and equipment failure. When such events occur, the load current value will show a value different from that of the normal state.

[0025] According to this embodiment, the occurrence of an abnormal condition related to a workpiece, such as a glass plate G, is detected based on the time change of the load current value corresponding to the load state of the polished surface being different from the normal state. Therefore, for example, the occurrence of an abnormal condition related to the workpiece can be detected by detecting an increase in the frictional force of the polished surface or a state that deviates from the load current value trend graph of the normal state. The occurrence of an abnormal condition related to the workpiece includes the occurrence of polishing cracks (damage to the workpiece shape), cracks, other abnormal conditions of the workpiece itself, and abnormal conditions of components and equipment that may cause polishing cracks in the workpiece.

[0026] Figure 3 is an image diagram illustrating the processing concept of the abnormal state detection method for the glass plate G by the control device 30. The monitoring unit 32 monitors the load current value of a periodic waveform with wavelength λ under normal conditions, for example. In this embodiment, the specific detection method by the detection unit 33 includes, for example, a first detection method and a second detection method.

[0027] In the first detection method, the detection unit 33 detects the occurrence of an abnormal condition when the load current value exceeds an overload threshold determined based on the average value under normal conditions. The average value under normal conditions is calculated over a moving average calculation time t. ave The detection unit 33 calculates the average value at a certain point using a moving average, determines the overload threshold, and compares it with the load current value. As shown in the value P1 in Figure 3, if the load current value exceeds the overload threshold, the detection unit 33 detects the occurrence of an abnormal condition. Moving average calculation time t ave For example, it can be set to 30 seconds, but the value is not particularly limited.

[0028] This allows for the detection of workpiece cracks that increase friction on the polishing surface due to cracks in the workpiece or damage to the polishing tool, thereby enabling the detection of workpiece cracks that increase friction on the polishing surface.

[0029] The overload threshold may include an alarm threshold and a stop threshold that is greater than the alarm threshold. In this case, the control device 30 may issue an alarm when the load current value exceeds the alarm threshold and stop the drive unit 20 when the load current value exceeds the stop threshold. This prevents unforeseen incidents by issuing an alarm to draw attention when the load current value exceeds the alarm threshold and stopping the drive unit when the load current value exceeds the stop threshold.

[0030] Figure 4 is a flowchart showing the procedure of the first detection method. The monitoring unit 32 monitors the load current value (step S1). The detection unit 33 obtains an overload threshold, in particular an alarm threshold, and a stop threshold that is greater than the alarm threshold, calculated based on the average value of the load current value under normal conditions (step S2). These thresholds are calculated sequentially, for example at 30-second intervals, as explained in Figure 3, and stored in a memory (not shown).

[0031] The detection unit 33 determines whether the load current value exceeds the alarm threshold (step S3). If the load current value does not exceed the alarm threshold (No in step S3), the process returns to step S1. If the load current value exceeds the alarm threshold (Yes in step S3), the control device 30 issues an alarm (step S4) to alert the user. The user can take measures such as checking the operation of the device.

[0032] Furthermore, the detection unit 33 determines whether the load current value exceeds the stopping threshold (step S5). If the load current value does not exceed the stopping threshold (No in step S5), the process returns to step S1. If the load current value exceeds the stopping threshold (Yes in step S5), the control device 30 stops the drive unit 20 (step S6). This prevents unforeseen events such as failure of the polishing device 1 due to excessive load.

[0033] In the second detection method, it is assumed that the time variation of the load current value under normal conditions includes a periodic waveform. In this case, the detection unit 33 detects the occurrence of an abnormal condition when the load current value deviates from within a certain range r determined based on the average value under normal conditions and the amplitude of the periodic waveform. The detection unit 33 can detect the occurrence of an abnormal condition when the load current value deviates from within a certain range r in which fluctuations are permissible, as shown in the value P2 in Figure 3.

[0034] This allows for the detection of cracks, fissures, or increases or decreases in the load on the polished surface immediately before cracking, by setting a certain range (tolerance range) based on the load current value trend graph under normal conditions and detecting deviations from this range, i.e., when the load on the polished surface changes beyond the normal range of change.

[0035] However, the detection unit 33 may not detect the occurrence of an abnormal condition if the load current value deviates from a certain range and then returns to that range within a predetermined time based on the wavelength of the periodic waveform, but may detect the occurrence of an abnormal condition if it does not return to the certain range within the predetermined time. In this case, the detection unit 33 does not immediately detect the occurrence of an abnormal condition even if the load current value deviates from a certain range to the value P2 in Figure 3. The detection unit 33 detects the occurrence of an abnormal condition if, after a predetermined time has elapsed since the load current value reached value P2, for example, a time corresponding to half a period of the periodic waveform, 1 / 2λ, the load current does not return to the certain range, such as value P3.

[0036] As a result, even if the signal moves outside a certain range, if it returns to that range within a predetermined time, for example, within half a period (1 / 2λ) of the periodic waveform, the occurrence of an abnormal condition will not be detected, thus preventing false detections caused by noise levels, etc.

[0037] The above predetermined time may include a predetermined alarm time and a predetermined stop time that is longer than the predetermined alarm time. In this case, the control device 30 may issue an alarm if the load current value deviates from a certain range and does not return to a certain range within the predetermined alarm time, and stop the drive unit 20 if it does not return to a certain range within the predetermined stop time. This prevents unforeseen incidents by issuing an alarm if the load current value deviates from a certain range and does not return to a certain range within the predetermined alarm time, and stopping the drive unit 20 if it does not return to a certain range within the predetermined stop time.

[0038] Figure 5 is a flowchart showing the procedure for the second detection method. The monitoring unit 32 monitors the load current value (step S11). The detection unit 33 obtains a certain range r that is permissible to fluctuate based on the amplitude of the periodic waveform of the load current value obtained by the monitoring unit 32 (step S12). The certain range r is calculated sequentially, for example at 30-second intervals, as explained in Figure 3, and is stored in memory (not shown). Furthermore, the detection unit 33 obtains predetermined times, in particular a predetermined alarm time and a predetermined stop time that is longer than the predetermined alarm time (step S13). The predetermined alarm time and the predetermined stop time are set in advance and stored in memory (not shown).

[0039] The detection unit 33 determines whether the load current value has deviated from a certain range (step S14). If the load current value has not deviated from a certain range (No in step S14), the process returns to step S1. If the load current value has deviated from a certain range (Yes in step S14), the detection unit 33 determines whether the load current value has returned to a certain range within a predetermined alarm time after deviating from a certain range (step S15). If it has returned to a certain range within a predetermined alarm time (Yes in step S15), the process returns to step S1. If it has not returned to a certain range within a predetermined alarm time (No in step S15), the control device 30 issues an alarm (step S16) to alert the user. The user can take measures such as checking the operation of the device.

[0040] Furthermore, the detection unit 33 determines whether the load current value has returned to a certain range within a predetermined time for stopping after deviating from that range (step S17). If it has returned to a certain range within the predetermined time for stopping (Yes in step S17), the process returns to step S1. If it has not returned to a certain range within the predetermined time for stopping (No in step S17), the control device 30 stops the drive unit 20 (step S18). This prevents unforeseen events such as failure of the polishing device 1 due to excessive load.

[0041] Figure 6 is a graph showing an example of the load current value under normal conditions, as monitored by the monitoring unit 32. The load current value takes the form of a normal periodic waveform and does not show extreme changes. Figure 6 shows that the waveforms of the load current value during revolution and the load current value during rotation are similar.

[0042] Figure 7 is a graph showing an example of the behavior of the load current value when an abnormal condition occurs with respect to the glass plate G, as monitored by the monitoring unit 32 in the polishing apparatus 1 according to the first embodiment. In the example in Figure 7(A), a crack occurs in the glass plate G, the load current value decreases temporarily, and then cullet is generated, causing the load current value to increase. In this example, the detection unit 33 detects the occurrence of an abnormal condition according to the first detection method. The first detection method is a detection method based on a relatively simple algorithm compared to the second detection method, and requires setting a higher overload threshold, so the time required for overload determination from the occurrence of an abnormal fluctuation in the current value to detection is t. x The time required for overload detection tends to be longer. In the example in Figure 7(A), the moving average calculation time is approximately 30 seconds, and the time required for overload detection is t. x This is approximately twice as long, around 60 seconds. In the example in Figure 7(A), the drive unit 20 is stopped and the load current value is set to 0 after the detection unit 33 detects the occurrence of an abnormal condition. The same applies to the examples in Figures 7(B), (C) and 8(A1), (B1), and (C1) thereafter.

[0043] In the example of FIG. 7(B), cracks occur in the glass plate G but no chippings occur, and the load current value deviates from a certain range and decreases. In the example of FIG. 7(B), the certain range is set to ±20% of 100 [A]. The overload determination required time t x is about 10 seconds. In the example of FIG. 7(C), cracks and chippings occur in the glass plate G almost simultaneously, and the load current value deviates from a certain range and increases. In the example of FIG. 7(C), the certain range is set to ±33% of 47 [A]. The overload determination required time t x is about 13 seconds. In FIGS. 7(B) and 7(C), the detection unit 33 detects the occurrence of an abnormal state according to the second detection method. The overload determination required time t x in the second detection method tends to be shorter than that in the first detection method. According to the examples of FIGS. 7(A) to (C), it can be seen that when cracks occur in the glass plate G, the load current value tends to decrease, and when chippings occur in the glass plate G, the load current value tends to increase.

[0044] FIG. 8 is a graph showing an example of the behavior of the load current value when an abnormal state occurs in the equipment system and a schematic diagram of the equipment system in the polishing apparatus 1 according to the first embodiment. In the example of FIG. 8(A1), the load current value deviates from a certain range and increases. Upon investigation, peeling X of the double-sided tape on the polishing pad shown in FIG. 8(A2) was found. In this example, the certain range is set to ±25% of 47 [A]. The overload determination required time t x is about 15 seconds.

[0045] In the example of FIG. 8(B1), the load current value deviates from a certain range and increases. Upon investigation, a dent Y on the surface of the polishing pad shown in FIG. 8(B2) was found. In this example, the certain range is set to ±20% of 59 [A]. The overload determination required time t x is about 6 seconds. In the example of FIG. 8(C1), the load current value deviates from a certain range and increases. Upon investigation, an abnormality (equipment failure) in the polishing pressure system was found. In this example, the certain range is set to ±23% of 60 [A]. The overload determination required time t x is about 12 seconds.

[0046] As shown in the graphs in Figure 8, a change in the load current value occurs before any abnormality such as cracking occurs in the glass plate G. Each example in Figure 8 shows that the detection unit 33 can detect an abnormality in the equipment system before an abnormality occurs in the glass plate G, thereby suppressing the occurrence of an abnormality in the glass plate G.

[0047] (Second Embodiment) Figure 9 is a schematic diagram of a polishing apparatus according to a second embodiment of the present invention. The polishing apparatus 1 according to the second embodiment includes a polishing tool 10, a drive unit 20, and a control device 30, similar to the polishing apparatus 1 according to the first embodiment.

[0048] The polishing tool 10 is a device for polishing the surface of a glass plate G, and comprises a polishing head (upper platen) 11, a back plate 16, a back pad 14, a polishing pad 13, a polishing plate 12, and a lower platen 15. The relative positions of the back pad 14, polishing pad 13, and polishing plate 12 in this embodiment differ from those in the first embodiment. The polishing pad 13, polishing plate 12, and lower platen 15 may be collectively referred to as the lower side of the polishing tool 10. The glass plate G before polishing is attached to the polishing head 11 via the back pad 14 and back plate 16. The glass plate G before polishing is transferred onto the polishing pad 13 together with the back pad 14 and back plate 16, and while sandwiched between the polishing pad 13 and the glass plate G, the lower side of the polishing tool 10 is rotated, thereby polishing the surface of the glass plate G.

[0049] The drive unit 20 is a mechanism for driving the polishing tool 10 and includes a revolving motor 26, a swivel motor 27, and an oscillating motor 28. Figure 10 is a perspective view showing the state in which the polishing tool 10 polishes a glass plate G in the polishing apparatus 1 according to the second embodiment. In this example, the polishing head 11 and back pad 14 of the polishing tool 10 are rectangular in plan view and revolve in the direction of arrow D by the revolving motor 26. On the other hand, the polishing pad 13, polishing plate 12, and lower platen 15 are circular in plan view and swivel in the direction of arrow E by the swivel motor 27 and oscillate in the direction of arrow F by the oscillating motor 28.

[0050] The glass plate G, before polishing, is transferred to the polishing pad 13, polishing plate 12, and lower base plate 15 using a robotic arm or the like, along with the back plate 16 and back pad 14. The polishing tool 10 polishes each glass plate G that is transferred to the polishing pad 13. In other words, the polishing apparatus 1 according to this embodiment is a batch-type polishing apparatus.

[0051] The control device 30, which monitors and controls the operation of the drive unit 20, comprises a controller 31, a monitoring unit 32, and a detection unit 33, similar to the first embodiment. The controller 31 receives feedback of the rotation angle detected by optical encoders, etc., built into the orbital motor 26, the slewing motor 27, and the oscillating motor 28. The controller 31, upon receiving the feedback, can control the rotation of each motor by controlling a servo amplifier (not shown) that supplies power to each motor.

[0052] The control device 30 controls the speed of each operation of the polishing head 11 and the lower platen 15, specifically the rotation, oscillation, and rotation. Under normal conditions, the control device 30 controls the current value so that the rotation of each motor is at a predetermined set value (a constant value or a constant pattern).

[0053] The monitoring unit 32 monitors the load current value of the drive unit 20, similar to the first embodiment. In this embodiment, the monitoring unit 32 can monitor the load current value for revolution, the load current value for revolution, and the load current value for oscillation for each of the orbital motor 26, the orbital motor 27, and the oscillating motor 28, respectively. The detection unit 33 detects the occurrence of an abnormal condition related to the glass plate G, similar to the first embodiment, based on the fact that the time change of the load current value monitored by the monitoring unit 32 differs from the normal state. In this embodiment, the detection unit 33 can detect the occurrence of an abnormal condition related to the glass plate G based on the fact that the time change of the load current value for revolution, the load current value for revolution, and the load current value for oscillation differs from the normal state.

[0054] Figure 11 is a graph showing the behavior of the load current value when an abnormal condition occurs with respect to the glass plate G, as monitored by the monitoring unit 32 in the polishing apparatus 1 according to the second embodiment. Figure 11(A) shows the load current value for revolution, (B) shows the load current value for rotation, and (C) shows the load current value for oscillation.

[0055] In Figure 11(A), the detection unit 33 can perform two types of abnormal condition detection, corresponding to the first and second detection methods described in Figure 3. When using the first detection method, the detection unit 33 determines the average value of the orbital load current values ​​when polishing multiple (e.g., two) glass plates G that are considered to be in a normal state as the center value. The detection unit 33 detects the occurrence of an abnormal condition when the orbital load current value during polishing of the glass plate G that is currently subject to abnormality judgment deviates from the tolerance range determined based on the center value. The tolerance range is not particularly limited, but for example, it may be set to a range of ±30% of the center value.

[0056] In Figure 11(A), arrow P indicates that the load current value of the orbit of the glass plate G, which is currently subject to abnormality detection, has fallen by 30% or more (for example, 84%) from the center value. In this case, the detection unit 33 detects the occurrence of an abnormal condition for the glass plate G.

[0057] When using the second detection method, the detection unit 33 determines the maximum value of the orbital load current when polishing multiple (e.g., two) glass plates G that are considered to be in a normal state as the peak value. The detection unit 33 detects the occurrence of an abnormal condition when the orbital load current value of the polishing of the glass plate G that is currently subject to abnormal determination deviates from the allowable range determined based on the peak value. The allowable range is not particularly limited, but may be set to a range of ±20% of the peak value, for example.

[0058] In Figure 11(A), arrow Q indicates that the load current value of the orbit of the glass plate G, which is currently subject to abnormality detection, has fallen by 20% or more (for example, 47%) from its peak value. In this case, the detection unit 33 detects the occurrence of an abnormal condition for the glass plate G.

[0059] In Figure 11(B), the detection unit 33 can perform abnormal condition detection based on the second detection method described in Figure 3. The detection unit 33 determines the maximum value of the rotational load current value when polishing multiple (e.g., two) glass plates G immediately before the state is considered normal as the peak value. The detection unit 33 detects the occurrence of an abnormal condition when the rotational load current value of the polishing of the glass plate G that is currently subject to abnormal judgment deviates from the allowable range determined based on the peak value. The allowable range is not particularly limited, but for example, it may be set to a range of ±30% of the peak value.

[0060] In Figure 11(B), arrow R indicates that the rotation load current value of the glass plate G, which is currently subject to abnormality detection, has fallen by 30% or more (for example, 70%) from its peak value. In this case, the detection unit 33 detects the occurrence of an abnormal condition for the glass plate G.

[0061] In Figure 11(C), the detection unit 33 can perform abnormal condition detection based on the second detection method described in Figure 3. The detection unit 33 determines the peak value as the maximum value of the oscillating load current when polishing multiple (e.g., two) glass plates G immediately before the state is considered normal. The detection unit 33 detects the occurrence of an abnormal condition when the oscillating load current value of the polishing of the glass plate G that is currently subject to abnormal judgment deviates from the allowable range determined based on the peak value. The allowable range is not particularly limited, but for example, it may be set to a range of ±20% of the peak value.

[0062] In Figure 11(C), arrow S indicates that the load current value of the oscillating glass plate G, which is currently subject to abnormality detection, has fallen by 20% or more (for example, 26%) from its peak value. In this case, the detection unit 33 detects the occurrence of an abnormal condition for the glass plate G.

[0063] As described above, the polishing apparatus 1 according to the embodiment is a device for detecting the occurrence of an abnormal condition with respect to a flat plate-shaped workpiece made of a glass plate G. This makes it possible to detect the occurrence of an abnormal condition with respect to the glass plate G.

[0064] Furthermore, when the polishing pad is used for a long period of time, clogging of the polishing pad reduces the amount of polishing per unit time, and the load current value tends to decrease over time. However, for crack detection in this embodiment, the change in the load current value (waveform) over a short period of time that does not show this decreasing trend is used.

[0065] The present invention is not limited to the embodiments described above. It is also intended and within the scope of protection to be provided for the combination of each configuration of the embodiments, as well as for modifications and applications by those skilled in the art based on the description in the specification and well-known art.

[0066] As described above, the following matters are disclosed in this specification:

[0067] (1) A polishing apparatus (1) comprising a polishing tool (10) pressed against the surface of a flat workpiece (glass plate G), and a drive unit (20) that rotates the polishing tool, The load current value of the drive unit is monitored, Based on the fact that the time change of the load current value differs from the normal state, the occurrence of an abnormal state related to the flat workpiece is detected. Method for detecting abnormal conditions.

[0068] According to the above configuration, the occurrence of an abnormal condition related to the workpiece is detected based on the time change of the load current value corresponding to the load condition of the polishing surface differing from the normal condition. Therefore, for example, by detecting an increase in the frictional force of the polishing surface or a condition that deviates from the load current value trend graph of the normal condition, it is possible to detect the occurrence of abnormal conditions related to the workpiece, such as polishing cracks (damage to the workpiece shape), cracks, other abnormal conditions of the workpiece, or abnormal conditions of components or equipment that may cause polishing cracks in the workpiece.

[0069] (2) When the load current value exceeds the overload threshold determined based on the average value of the normal state, the occurrence of the abnormal state is detected. (1) The abnormal condition detection method described above.

[0070] With the above configuration, it is possible to detect workpiece cracks that increase the frictional force on the polishing surface by detecting cracks in the workpiece or damage to the polishing tool.

[0071] (3) The time variation of the load current value in the normal state includes a periodic waveform, The system detects the occurrence of the abnormal condition when the load current value deviates from a certain range determined based on the average value of the normal state and the amplitude of the periodic waveform. (1) The abnormal condition detection method described above.

[0072] According to the above configuration, a certain range is set based on the load current value trend graph under normal conditions, and if the value deviates from this range, i.e., if the load on the polishing surface changes beyond the normal range of change, it is possible to detect cracks, fissures, or increases or decreases in the load on the polishing surface just before cracking of the workpiece.

[0073] (4) If the load current value deviates from the specified range and then returns to the specified range within a predetermined time based on the wavelength of the periodic waveform, the occurrence of the abnormal state is not detected. If the value does not return to the specified range within the predetermined time, the occurrence of the abnormal state is detected. (3) Method for detecting abnormal conditions as described above.

[0074] According to the above configuration, even if the value deviates from a certain range, if it returns to that range within a predetermined time, for example, within half a cycle of a periodic waveform, the occurrence of an abnormal condition will not be detected, thus preventing false detections caused by noise levels, etc.

[0075] (5) The overload threshold includes an alarm threshold and a stop threshold that is greater than the alarm threshold, When the load current value exceeds the alarm threshold, an alarm is issued. When the load current value exceeds the stop threshold, the drive unit is stopped. (2) Method for detecting abnormal conditions as described in (2).

[0076] With the above configuration, an alarm is issued to draw attention when the load current value exceeds the alarm threshold, and the drive unit is stopped when the load current value exceeds the stop threshold, thereby preventing unforeseen incidents.

[0077] (6) The predetermined time includes a predetermined time for alarms and a predetermined time for stopping that is longer than the predetermined time for alarms. After the load current value deviates from the certain range, If the person does not return to the specified range within the predetermined time for the alarm, an alarm will be issued. If the unit does not return to the specified range within the predetermined stopping time, the drive unit is stopped. (4) Method for detecting abnormal conditions.

[0078] With the above configuration, if the load current value deviates from a certain range and does not return to that range within a predetermined alarm period, an alarm is issued, and if it does not return to that range within a predetermined stop period, the drive unit is stopped, thus preventing unforeseen incidents.

[0079] (7) An abnormal condition detection method according to any one of (1) to (6) for detecting the occurrence of an abnormal condition with respect to the flat workpiece made of a glass plate.

[0080] According to the above configuration, it is possible to detect the occurrence of an abnormal condition related to the glass plate.

[0081] (8) A polishing tool (10) that is pressed against the surface of a flat workpiece (glass plate G), A drive unit (20) for rotating the polishing tool, A monitoring unit (32) monitors the load current value of the drive unit, A detection unit (33) detects the occurrence of an abnormal condition related to the flat workpiece based on the time change of the load current value, A polishing device (1) equipped with the following.

[0082] According to the above configuration, the occurrence of an abnormal condition related to the workpiece is detected based on the time change of the load current value corresponding to the load condition of the polishing surface differing from the normal condition. Therefore, for example, by detecting an increase in the frictional force of the polishing surface or a condition that deviates from the load current value trend graph of the normal condition, it is possible to detect the occurrence of abnormal conditions related to the workpiece, such as polishing cracks (damage to the workpiece shape), cracks, other abnormal conditions of the workpiece, or abnormal conditions of components or equipment that may cause polishing cracks in the workpiece. [Explanation of Symbols]

[0083] 1 Polishing equipment 10 Polishing tools 20 Drive unit 30 Control device 31 Controllers 32 Monitoring Department 33 Detection unit G Glass plate (flat workpiece)

Claims

1. A polishing apparatus comprising a polishing tool pressed against the surface of a flat workpiece and a drive unit for rotating the polishing tool, The load current value of the drive unit is monitored, Based on the fact that the time change of the load current value differs from the normal state, the occurrence of an abnormal state related to the flat workpiece is detected. Method for detecting abnormal conditions.

2. When the load current value exceeds an overload threshold determined based on the average value under normal conditions, the occurrence of the abnormal condition is detected. The abnormal state detection method according to claim 1.

3. The time variation of the load current value in the normal state includes a periodic waveform. The system detects the occurrence of the abnormal condition when the load current value deviates from a certain range determined based on the average value of the normal state and the amplitude of the periodic waveform. The abnormal state detection method according to claim 1.

4. If the load current value deviates from the specified range and then returns to the specified range within a predetermined time based on the wavelength of the periodic waveform, the occurrence of the abnormal state is not detected. If the value does not return to the specified range within the predetermined time, the occurrence of the abnormal state is detected. The abnormal state detection method according to claim 3.

5. The overload threshold includes an alarm threshold and a stop threshold that is greater than the alarm threshold. When the load current value exceeds the alarm threshold, an alarm is issued. When the load current value exceeds the stop threshold, the drive unit is stopped. The abnormal state detection method according to claim 2.

6. The predetermined time includes a predetermined time for alarms and a predetermined time for stopping that is longer than the predetermined time for alarms. After the load current value deviates from the certain range, If the person does not return to the specified range within the predetermined time for the alarm, an alarm will be issued. If the unit does not return to the specified range within the predetermined stopping time, the drive unit is stopped. The abnormal state detection method according to claim 4.

7. An abnormal condition detection method according to any one of claims 1 to 6, for detecting the occurrence of an abnormal condition with respect to the flat plate-shaped workpiece made of a glass plate.

8. A polishing tool pressed against the surface of a flat workpiece, A drive unit for rotating the polishing tool, A monitoring unit that monitors the load current value of the drive unit, A detection unit that detects the occurrence of an abnormal condition related to the flat workpiece based on the time change of the load current value, A polishing device equipped with the following features.

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