Double-head surface grinding device

Abstract

The present disclosure relates to a double-head surface grinding device that takes into account both the detection of tiny defects generated by a workpiece or the detection of wear generated by a stop mechanism and cost reduction. The double-head surface grinding device comprises: a moving mechanism that causes a first workpiece holder and a second workpiece holder to perform a closing movement toward a supporting position; a stop mechanism that limits the closing movement of the first workpiece holder and the second workpiece holder performed by the moving mechanism so that the first workpiece holder and the second workpiece holder are positioned at the supporting position; a distance sensor that detects the relative distance between the first workpiece holder and the second workpiece holder; and a controller that compares the detection value of the relative distance in a state where the first workpiece holder and the second workpiece holder perform a closing movement with a first threshold value, and when the relative distance is greater than the first threshold value, it is determined that a foreign object is clamped between the workpiece and the first workpiece holder or the second workpiece holder, and the grinding of the workpiece is stopped.

Description

Technical Field

[0001] The present invention relates to a double-head surface grinding device. Background Art

[0002] An example of a double-head surface grinding device is disclosed in Patent Document 1. Specifically, the device disclosed in Patent Document 1 comprises: a first workpiece holder and a second workpiece holder for non-contact support of a thin plate-shaped workpiece by fluid pressure; and a pair of grinding wheels for grinding two surfaces of the workpiece supported by the first workpiece holder and the second workpiece holder.

[0003] Furthermore, the device disclosed in the patent document 1 is provided with a sliding drive mechanism, a stopper bolt, and a stopper block for sliding the first workpiece holder and the second workpiece holder. Here, the sliding drive mechanism is a mechanism for bringing the first workpiece holder and the second workpiece holder closer to each other toward a supporting position (position during grinding) for non-contact support of the workpiece. The stopper bolt and the stopper block abut against each other when bringing the first workpiece holder and the second workpiece holder closer to the supporting position, thereby achieving accurate positioning.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2016-132084

[0007] Furthermore, when a thin plate-shaped workpiece is used as the grinding object, the workpiece may be slightly damaged due to defects in the raw material, abnormalities occurring during grinding, etc. When the next workpiece is ground while the fragments of the workpiece thus generated remain, there is a possibility that the fragments of the workpiece generated during the previous grinding may be sandwiched between the workpiece and the grinding wheel. Until now, there have been known technologies for detecting large damages such as cracks and breaks in workpieces, but such technologies are not sufficient to detect small defects.

[0008] As a method for detecting tiny defects, it is possible to use an image sensor to photograph the workpiece. However, in general, image sensors are expensive. In addition, when using image sensors, it is necessary to newly set up lighting devices and backgrounds for making light and dark clear, which is not conducive to cost control.

[0009] The same problem also exists in the stopper mechanism composed of a stopper bolt and a stopper block, etc. That is, in the process of grinding a plurality of workpieces, the stopper mechanism sometimes wears out. In the existing method, it is not enough to take into account both the detection of such wear and the cost reduction. Summary of the invention

[0010] The present disclosure has been made in view of this point, and an object of the present disclosure is to achieve both detection of a minute defect generated in a workpiece during the previous grinding and detection of wear generated in a stopper mechanism and cost reduction.

[0011] The first scheme of the present disclosure relates to a double-headed surface grinding device, which comprises: a first workpiece holder and a second workpiece holder, which support the workpiece in a non-contact manner by the pressure of a fluid at a support position specified for clamping a thin plate-shaped workpiece; and a pair of grinding wheels, which grind the grinding surfaces of the two faces of the workpiece supported by the first workpiece holder and the second workpiece holder. The double-headed surface grinding device comprises: a moving mechanism, which causes the first workpiece holder and the second workpiece holder to perform a closing movement toward the supporting position; a stop mechanism, which limits the closing movement of the first workpiece holder and the second workpiece holder performed by the moving mechanism so that the first workpiece holder and the second workpiece holder are positioned at the supporting position; a distance sensor, which detects the relative distance between the first workpiece holder and the second workpiece holder; and a controller, to which the detection signal of the distance sensor is input.

[0012] Furthermore, according to the first scheme, when the relative distance achieved when the closing movement is limited by the stop mechanism and the first workpiece holder and the second workpiece holder are located at the supporting position is set as a reference value, and a specified value set to be larger than the reference value is set as a first threshold value, the controller compares the detection value of the relative distance in the state where the first workpiece holder and the second workpiece holder have performed a closing movement with the first threshold value based on the detection signal of the distance sensor, and when the relative distance is greater than the first threshold value, it is determined that a foreign object is clamped between the workpiece and the first workpiece holder or the second workpiece holder, and the grinding of the workpiece is stopped.

[0013] When the first workpiece holder and the second workpiece holder are positioned at the desired support position, the detected value of the relative distance is considered to be consistent with the reference value. On the other hand, when a slight defect occurs in the workpiece, its fragments may be attached to the first workpiece holder or the second workpiece holder and remain. In this case, when the grinding of the next workpiece is transferred with the fragments remaining, it is considered that the detected value is greater than the reference value by the thickness of the fragments.

[0014] Therefore, according to the first solution, the controller compares the detection value with a first threshold value set to be larger than a reference value. By making such a comparison, a defect generated in the workpiece during the last grinding can be detected. In addition, the first solution does not require a high-cost sensor such as an image sensor. Therefore, the first solution can achieve both detection of a small defect generated in the workpiece during the last grinding and cost reduction.

[0015] The second scheme of the present disclosure relates to a double-headed surface grinding device, which comprises: a first workpiece holder and a second workpiece holder, which support the workpiece in a non-contact manner by the pressure of a fluid at a support position defined as clamping a thin plate-shaped workpiece; and a pair of grinding wheels, which grind the grinding surfaces of the two faces of the workpiece supported by the first workpiece holder and the second workpiece holder. The double-headed surface grinding device comprises: a moving mechanism, which causes the first workpiece holder and the second workpiece holder to perform a closing movement toward the supporting position; a stop mechanism, which limits the closing movement of the first workpiece holder and the second workpiece holder performed by the moving mechanism so that the first workpiece holder and the second workpiece holder are positioned at the supporting position; a distance sensor, which detects the relative distance between the first workpiece holder and the second workpiece holder; and a controller, to which the detection signal of the distance sensor is input.

[0016] Furthermore, according to the second scheme, when the relative distance achieved when the closing movement is restricted by the stop mechanism and the first workpiece holder and the second workpiece holder are located at the supporting position is set as a reference value, and a specified value set to be smaller than the reference value is set as a second threshold value, the controller compares the detection value of the relative distance in the state where the first workpiece holder and the second workpiece holder have performed a closing movement with the second threshold value based on the detection signal of the distance sensor, and when the relative distance is smaller than the second threshold value, it is determined that the stop mechanism has worn, and the grinding of the workpiece is stopped.

[0017] When the first workpiece holder and the second workpiece holder are positioned at the desired support positions, the detected value of the relative distance is considered to be consistent with the reference value as described above. On the other hand, when the stopper mechanism is worn, the detected value is considered to be smaller than the reference value in a manner corresponding to the amount of wear.

[0018] Therefore, according to the second solution, the controller compares the detection value with a second threshold value set to be smaller than the reference value. By making such a comparison, it is possible to detect that the stopper mechanism has been worn. In addition, the second solution does not require a dedicated sensor such as a linear scale for detecting the positions of the first workpiece holder and the second workpiece holder. Therefore, the second method can take into account both the detection of wear caused by the stopper mechanism and cost reduction.

[0019] The third scheme of the present disclosure relates to a double-headed surface grinding device, which comprises: a first workpiece holder and a second workpiece holder, which support the workpiece in a non-contact manner by the pressure of a fluid at a support position specified for clamping a thin plate-shaped workpiece; and a pair of grinding wheels, which grind the grinding surfaces of the two faces of the workpiece supported by the first workpiece holder and the second workpiece holder. The double-headed surface grinding device comprises: a moving mechanism, which causes the first workpiece holder and the second workpiece holder to perform a closing movement toward the supporting position; a stop mechanism, which limits the closing movement of the first workpiece holder and the second workpiece holder performed by the moving mechanism so that the first workpiece holder and the second workpiece holder are positioned at the supporting position; a distance sensor, which detects the relative distance between the first workpiece holder and the second workpiece holder; and a controller, to which the detection signal of the distance sensor is input.

[0020] Furthermore, according to the third scheme, when the relative distance achieved when the closing movement is restricted by the stop mechanism and the first workpiece holder and the second workpiece holder are located at the supporting position is set as a reference value, a specified value set to be larger than the reference value is set as a first threshold value, and a specified value set to be smaller than the reference value is set as a second threshold value, the controller compares the detection value of the relative distance in the state where the first workpiece holder and the second workpiece holder have performed the closing movement, the first threshold value, and the second threshold value based on the detection signal of the distance sensor. When the relative distance is greater than the first threshold value, it is determined that a foreign object is clamped between the workpiece and the first workpiece holder or the second workpiece holder, and the grinding of the workpiece is stopped. On the other hand, when the relative distance is less than the second threshold value, it is determined that the stop mechanism is worn, and the grinding of the workpiece is stopped.

[0021] When the first workpiece holder and the second workpiece holder are positioned at the desired support position, the detection value of the relative distance is considered to be consistent with the reference value. On the other hand, when a workpiece has a slight defect, its fragments may be attached to the first workpiece holder or the second workpiece holder and remain. In this case, when the grinding of the next workpiece is transferred to the state where the fragments remain, it is considered that the detection value will be greater than the reference value by the thickness of the fragments. Moreover, when the stop mechanism is worn, it is considered that the detection value will be smaller than the reference value corresponding to the amount of wear.

[0022] Therefore, according to the third solution, the controller compares the detection value with a first threshold value set to be larger than the reference value, or compares the detection value with a second threshold value set to be smaller than the reference value. By making such a comparison, it is possible to detect a defect in the workpiece or to detect wear of the stopper mechanism. In addition, the third solution does not require a high-cost sensor such as an image sensor. Therefore, the third solution can take into account both the detection of a small defect in the workpiece or the detection of wear of the stopper mechanism and cost reduction, as in the first and second solutions.

[0023] In addition, according to the fourth scheme of the present disclosure, it can also be set that the first workpiece holder and the second workpiece holder each have: a base, which slides and moves with the action of the moving mechanism; and a pad, which is arranged on the end face of the base to provide non-contact support for the workpiece, and the stopping mechanism is arranged in plurality between the bases of the first workpiece holder and the second workpiece holder in a manner of surrounding the pads of each of the first workpiece holder and the second workpiece holder, and the distance sensor is arranged to be adjacent to at least one of the plurality of stopping mechanisms, and the distance between the distance sensor and the stopping mechanism adjacent to the distance sensor is shorter than the distance between the distance sensor and the central portion of the pad.

[0024] According to the fourth aspect, the distance sensor is arranged closer to at least one stopper than to the center of the pad. When the base is tilted, the detection value of the distance sensor changes significantly near the stopper. Therefore, by arranging the distance sensor near the stopper, even a slight tilt can be reliably detected. This helps to ensure the accuracy of detecting defects or wear.

[0025] Effects of the Invention

[0026] As described above, according to the present disclosure, it is possible to achieve both detection of minute flaws occurring in a workpiece and detection of wear occurring in a stopper mechanism and cost reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a top view showing an example of the structure of a double-head surface grinding device.

[0028] Figure 2 It is a front sectional view of a double-head surface grinding device.

[0029] Figure 3 It is a side sectional view of a double-head surface grinding device.

[0030] Figure 4 This is a schematic diagram for explaining the reference position.

[0031] Figure 5 This is a schematic diagram for explaining the support position.

[0032] Figure 6 This is a block diagram showing an example of a configuration associated with a controller.

[0033] Figure 7 : is a flowchart which exemplifies the first process and the second process.

[0034] Figure 8 This is a diagram for explaining the clamping of foreign matter.

[0035] Fig. 9 This is a diagram for explaining the wear of the stopper mechanism.

[0036] Fig.10 is a modified example of the processing performed by the controller. Figure 7 Corresponding diagram.

[0037] Fig.11 is a modified example of the processing performed by the controller. Figure 7 Corresponding diagram.

[0038] Description of Reference Numerals

[0039] 1: Double-head surface grinding device;

[0040] 10: a first workpiece holding body;

[0041] 11: Reference side base (base);

[0042] 12: Reference side liner (liner);

[0043] 20: second workpiece holding body;

[0044] 21: Pressurized side base (base);

[0045] 22: Pressure side liner (liner);

[0046] 31: first grinding wheel (a pair of grinding wheels);

[0047] 32: second grinding wheel (a pair of grinding wheels);

[0048] 8: Mobile mechanism;

[0049] 9: Stop mechanism;

[0050] 100: controller;

[0051] 102: distance sensor;

[0052] W: workpiece;

[0053] M: Foreign body. DETAILED DESCRIPTION

[0054] Hereinafter, embodiments of the present disclosure will be described based on the drawings. It should be noted that the following description is an example.

[0055] (Overall composition)

[0056] Figure 1 It is a plan view showing an example of the structure of the double-head surface grinding device 1. Figure 2 is a front cross-sectional view of the double-head surface grinding device 1, which is equivalent to Figure 1 A-A view. Figure 3 is a side sectional view of the double-head surface grinding device 1, which is equivalent to Figure 1 In addition, Figure 4 This is a schematic diagram for explaining the reference position. Figure 5 This is a schematic diagram for explaining the support position. Figure 6 1 is a block diagram showing an example of a configuration associated with the controller 100 .

[0057] like Figure 1 As shown, the double-head surface grinding device 1 includes a first workpiece holding body 10 and a second workpiece holding body 20 and a first grinding wheel 31 and a second grinding wheel 32. The first workpiece holding body 10 and the second workpiece holding body 20 non-contactly support the workpiece W at a predetermined "support position" by the pressure of a fluid. The first grinding wheel 31 and the second grinding wheel 32 grind the grinding surfaces of the two surfaces of the workpiece W supported by the first workpiece holding body 10 and the second workpiece holding body 20, and constitute a "pair of grinding wheels" in this embodiment.

[0058] It should be noted that the "support position" mentioned here refers to Figure 5 As shown, the position is defined as a position for clamping a thin plate-shaped workpiece W in a non-contact state. In addition, the non-contact support achieved at the "support position" can be referred to as so-called "static pressure support". In addition, the workpiece W can also be a thin plate-shaped and disk-shaped object to be ground, such as a semiconductor wafer.

[0059] Specifically, the double-head surface grinding device 1 includes: a workpiece driving device 2 having the first workpiece holding body 10 and the second workpiece holding body 20 ; a grinding wheel device 3 having a pair of grinding wheels consisting of a first grinding wheel 31 and a second grinding wheel 32 ; and a controller 100 .

[0060] (Workpiece drive device)

[0061] The workpiece driving device 2 is a device that holds and rotationally drives the workpiece W when grinding both surfaces of the workpiece W. The workpiece driving device 2 includes a housing 5 , a workpiece holding mechanism 6 , a workpiece rotating mechanism 7 , a moving mechanism 8 , and a stopper mechanism 9 .

[0062] Here, the housing 5 covers the periphery of the work holding mechanism 6, and supports the work holding mechanism 6 so as to be relatively movable within the housing 5. The housing 5 is formed in a substantially rectangular box shape with openings at the top and the bottom, for example.

[0063] The workpiece holding mechanism 6 holds the workpiece W from both sides of the workpiece W. The workpiece holding mechanism 6 includes a first workpiece holding body 10 and a second workpiece holding body 20. The first workpiece holding body 10 holds the workpiece W from one side of the front and back. The second workpiece holding body 20 holds the workpiece W from the other side of the front and back. The first workpiece holding body 10 and the second workpiece holding body 20 are arranged in a manner facing each other and supported by the housing 5 so as to be movable in the left-right direction.

[0064] The first workpiece holding body 10 and the second workpiece holding body 20 each include a base 11 , 21 that slides along with the operation of the moving mechanism 8 , and pads 12 , 22 that are disposed on the end surfaces of the bases 11 , 21 , respectively, to support the workpiece W in a non-contact manner.

[0065] Specifically, the first workpiece holding body 10 includes a reference side base 11 arranged in parallel with a vertical plane in the front-rear direction, and a reference side spacer 12 provided on an end surface of the reference side base 11 on the second workpiece holding body 20 side.

[0066] The second workpiece holding body 20 includes a pressurizing-side base 21 disposed in parallel with a vertical plane in the front-rear direction, and a pressurizing-side pad 22 provided on an end surface of the pressurizing-side base 21 on the first workpiece holding body 10 side.

[0067] The reference side pad 12 and the pressurizing side pad 22 are respectively used to non-contact support the workpiece W from both sides by the pressure of fluid such as water pressure, and are formed in a substantially disk shape. The reference side pad 12 and the pressurizing side pad 22 have discharge ports (not shown) opened on the opposing surfaces for discharging the fluid.

[0068] The reference side pad 12 and the pressure side pad 22 are provided with arc-shaped first notches 61 corresponding to the first grinding wheel 31 and the second grinding wheel 32, respectively, from the outer edge thereof to a position slightly beyond the center of the reference side base 11 and the pressure side base 21 (see Figure 2 and Figure 3 ).

[0069] The reference side base 11 and the pressurizing side base 21 are each composed of a substantially rectangular plate having thickness in the left-right direction. A second arc-shaped notch 62 (shown only in the figure) corresponding to the first notch 61 is provided on the lower side of the reference side base 11 and the pressurizing side base 21 from the outer edge thereof to a position slightly beyond the center of the reference side base 11 and the pressurizing side base 21. Figure 2 ).

[0070] Furthermore, four support rollers 63 are arranged on the surface of the reference-side base 11 that faces the pressurizing-side base 21 so as to surround the reference-side pad 12. The carrier 60 that holds the workpiece W is rotatably supported by the four support rollers 63.

[0071] The carrier 60 is formed into a ring shape that can be loosely fitted with the workpiece W. A protrusion (not shown) that protrudes radially inward is provided on the inner circumferential surface of the carrier 60. The protrusion is configured to mesh with a notch (not shown) provided on the outer circumferential surface of the workpiece W. Through this meshing, the workpiece W rotates in conjunction with the rotation of the carrier 60.

[0072] The work rotating mechanism 7 drives and rotates the work W held by the work holding mechanism 6 . The work rotating mechanism 7 includes a carrier drive motor 71 and a carrier drive shaft 72 .

[0073] The carrier drive motor 71 is connected to the carrier drive shaft 72. When the carrier drive motor 71 is operated, its rotational driving force rotates the carrier drive shaft 72. The carrier drive shaft 72 has a carrier drive gear (not shown) at its top. When the carrier drive shaft 72 rotates, its rotational driving force rotates the carrier 60 via the carrier drive gear. As the carrier 60 rotates, the workpiece W also rotates as described above.

[0074] The moving mechanism 8 causes the first workpiece holding body 10 and the second workpiece holding body 20 to move toward the "support position" for realizing static pressure support. This closing movement is achieved by sliding the workpiece holding mechanism 6 relative to the housing 5. In this embodiment, the sliding movement is equivalent to moving along Figure 1 and Figure 2 as well as Figure 4 and Figure 5 In addition, the closing action of the first workpiece holding body 10 and the second workpiece holding body 20 is an action to bring the first workpiece holding body 10 and the second workpiece holding body 20 closer to each other. In order to realize such an action, the moving mechanism 8 of this embodiment has a plurality of guide rods 81, a plurality of bushings 82, a reference side cylinder 83 and a pressurizing side cylinder 84.

[0075] The plurality of guide rods 81 extend in the left-right direction in the housing 5, respectively, and penetrate the first workpiece holder 10 and the second workpiece holder 20 in the left-right direction. The plurality of guide rods 81 support the first workpiece holder 10 and the second workpiece holder 20 so as to slide freely in the left-right direction. In the present embodiment, the plurality of guide rods 81 are mounted on the housing 5 in a manner of four guide rods, one at the front, one at the back, and one at the top and bottom.

[0076] The plurality of bushings 82 are components interposed between the guide rods 81 and the through holes of the first workpiece holder 10 and the second workpiece holder 20 through which the guide rods 81 are inserted. The guide rods 81 are slidably inserted into the through holes of the first workpiece holder 10 and the second workpiece holder 20 via the bushings 82. Thus, the first workpiece holder 10 and the second workpiece holder 20 can slide in the left-right direction along the guide rods 81. For example, the bushings 82 may be double bushings.

[0077] The reference side cylinder 83 moves the first workpiece holder 10 relative to the housing 5 and the second workpiece holder 20. The pressurizing side cylinder 84 moves the second workpiece holder 20 relative to the housing 5 and the first workpiece holder 10. The reference side cylinder 83 and the pressurizing side cylinder 84 may be, for example, pneumatic cylinders, so-called air cylinders.

[0078] When grinding the workpiece W, the moving mechanism 8 brings the first workpiece holder 10 and the second workpiece holder 20 close to each other to such an extent that they do not directly contact the workpiece W. At this time, if there is no clamping of foreign matter, wear of the stopper mechanism 9, etc., the first workpiece holder 10 and the second workpiece holder 20 are positioned. Figure 5 The desired "bearing position" is shown.

[0079] When the workpiece W is replaced, the moving mechanism 8 moves the second workpiece holder 20 away from the first workpiece holder 10 in the left-right direction. Figure 4 The desired “reference position” is shown.

[0080] like Figure 5 As shown, the above-mentioned “support position” can be regarded as a relative positional relationship achieved when the first workpiece holding body 10 is positioned at the “reference position” and the second workpiece holding body 20 is moved closer to a desired position.

[0081] The stopper mechanism 9 is a mechanism for limiting the closing movement of the first workpiece holding body 10 and the second workpiece holding body 20 by the moving mechanism 8 so as to position the first workpiece holding body 10 and the second workpiece holding body 20 at the “support position”.

[0082] The stopper mechanism 9 is provided between the bases 11 and 21 of the first workpiece holder 10 and the second workpiece holder 20 in a plurality of ways so as to surround the pads 12 and 22 of the first workpiece holder 10 and the second workpiece holder 20, respectively. Figure 3 As shown, the stopper mechanisms 9 of this embodiment are respectively arranged at the four corners (particularly, the four corners in the front-rear direction and the up-down direction) between the first workpiece holding body 10 and the second workpiece holding body 20 .

[0083] In addition, the plurality of (four in this embodiment) stopper mechanisms 9 have a plurality of (four in this embodiment) reference side bolts 91 , the same number of pressurizing side bolts 92 as the reference side bolts 91 , and the same number of stopper blocks 93 as the reference side bolts 91 .

[0084] like Figure 1 and Figure 2 As shown in FIG. 1 , each reference side bolt 91 is fixed to the first workpiece holding body 10, in particular, to the four corners of the reference side base 11. Figure 4 and Figure 5 As schematically shown, each reference-side bolt 91 has a bolt head 91a that protrudes toward the left, that is, toward the second workpiece holding body 20. The bolt head 91a is provided so that the amount of protrusion can be adjusted.

[0085] like Figure 1 and Figure 2 As shown, each pressure-side bolt 92 is fixed to the second workpiece holding body 20, in particular, to the four corners of the pressure-side base 21. Figure 4 and Figure 5 As schematically shown, each pressurizing side bolt 92 has a bolt head 92a that protrudes toward the right, that is, toward the first workpiece holding body 10. The bolt head 92a is provided so that the amount of protrusion thereof can be adjusted.

[0086] like Figure 1 to Figure 3 As shown, each stopper 93 is fixed to the four corners of the housing 5. Figure 4 and Figure 5 As schematically shown, each stopper block 93 includes a reference-side stopper pin 93 a that projects so as to face the corresponding reference-side bolt 91 , and a pressurizing-side stopper pin 93 b that projects so as to face the corresponding pressurizing-side bolt 92 .

[0087] like Figure 4 As shown, when the first workpiece holding body 10 is located at the "reference position", the stopper 93 abuts against the reference side bolt 91. Specifically, when the first workpiece holding body 10 is located at the "reference position", the reference side stopper pin 93a abuts against the bolt head 91a of the reference side bolt 91.

[0088] like Figure 5As shown, when the first workpiece holding body 10 and the second workpiece holding body 20 are located at the "support position", the stopper 93 abuts against the reference side bolt 91, and the stopper 93 abuts against the pressurizing side bolt 92. Specifically, when the first workpiece holding body 10 and the second workpiece holding body 20 are located at the "support position", the reference side stopper pin 93a abuts against the bolt head 91a of the reference side bolt 91, and the pressurizing side stopper pin 93b abuts against the bolt head 92a of the pressurizing side bolt 92.

[0089] Furthermore, at the "support position", the workpiece W is non-contact supported between the reference side pad 12 and the pressurizing side pad 22. Considering the non-contact support, the actual distance (predetermined distance X) between the reference side pad 12 and the pressurizing side pad 22 at the "support position" is at least greater than the thickness D of the workpiece W.

[0090] The double-head surface grinding device 1 further includes a reference sensor 101 and a distance sensor 102 in order to sense that the “reference position” and the “support position” have been achieved.

[0091] The reference sensor 101 detects the position of the first workpiece holding body 10 relative to the stopper 93. The reference sensor 101 of this embodiment is fixed to the stopper 93, and detects the distance of the first workpiece holding body 10 relative to the stopper 93 in the left-right direction. The reference sensor 101 is electrically connected to the controller 100 via wire or wireless, and inputs an electrical signal indicating its detection result to the controller 100. The electrical signal can be used to determine whether the first workpiece holding body 10 is located at the "reference position".

[0092] The distance sensor 102 is used to detect the relative distance between the first workpiece holder 10 and the second workpiece holder 20. Specifically, the distance sensor 102 is provided on one of the first workpiece holder 10 and the second workpiece holder 20 to detect the relative distance to the other of the first workpiece holder 10 and the second workpiece holder 20.

[0093] More specifically, the distance sensor 102 is provided on the first workpiece holder 10, and detects the relative distance between the first workpiece holder 10 and the second workpiece holder 20. The distance sensor 102 may be, for example, an eddy current distance sensor.

[0094] Specifically, if Figure 3 As shown, the distance sensor 102 of this embodiment is arranged adjacent to one of the plurality of stopper mechanisms 9 (in the example of the figure, the stopper mechanism 9 located above and at the rear). Here, the distance between the distance sensor 102 and the stopper mechanism 9 adjacent to the distance sensor 102 is shorter than the distance between the distance sensor 102 and the central portion C of the reference side pad 12.

[0095] It should be noted that the relative distance detected by the distance sensor 102 may be the distance between the reference-side pad 12 and the pressurizing-side pad 22 or the distance between the reference-side base 11 and the pressurizing-side base 21 .

[0096] In addition, when the distance sensor 102 is assumed to be mounted on the first workpiece holding body 10, it can also be set as the distance between the distance sensor 102 and the pressure side base 21 or the pressure side pad 22. Similarly, when the distance sensor 102 is assumed to be mounted on the second workpiece holding body 20, it can also be set as the distance between the distance sensor 102 and the reference side base 11 or the reference side pad 12.

[0097] For example, the distance sensor 102 of the present embodiment is fixed to the reference side base 11 of the first workpiece holding body 10. The distance sensor 102 of the present embodiment detects the distance between the distance sensor 102 and the pressurizing side base 21 of the second workpiece holding body 20.

[0098] The distance sensor 102 is electrically connected to the controller 100 by wire or wirelessly, and inputs an electrical signal indicating its detection result to the controller 100. By combining with the detection signal of the reference sensor 101, the electrical signal can be used to determine whether the first workpiece holder 10 and the second workpiece holder 20 are located at the "support position".

[0099] (Grinding wheel device)

[0100] The grinding wheel device 3 is a device that grinds two surfaces of the workpiece W held and rotated by the workpiece driving device 2 by means of the first grinding wheel 31 and the second grinding wheel 32. The first grinding wheel 31 advances and retreats through the first notch 61 and the second notch 62 of the first workpiece holding body 10. The second grinding wheel 32 advances and retreats through the first notch 61 and the second notch 62 of the second workpiece holding body 20.

[0101] The grinding wheel device 3 includes a cup-shaped first grinding wheel 31 and a second grinding wheel 32 and a grinding wheel drive motor 33 for rotationally driving the grinding wheels 31 and 32. The grinding wheel device 3 is arranged on both sides of the workpiece drive device 2. The grinding wheel drive motor 33 is only shown in FIG. Figure 6 .

[0102] The first grinding wheel 31 and the second grinding wheel 32 are arranged to face both surfaces of the workpiece W held by the carrier 60 via the first notch 61 and the second notch 62 of the first workpiece holding body 10 and the second workpiece holding body 20 .

[0103] Specifically, the first grinding wheel 31 is disposed so as to face one surface side (for example, the right side) of the workpiece W held by the carrier 60 via the first notch 61 and the second notch 62 of the first workpiece holding body 10 .

[0104] On the other hand, the second grinding wheel 32 is disposed so as to face the other surface side (eg, the left side) of the workpiece W held by the carrier 60 via the first notch 61 and the second notch 62 of the second workpiece holding body 20 .

[0105] The grinding wheel device 3 is configured to move the first grinding wheel 31 and the second grinding wheel 32 in the axial direction (left-right direction), and to move the first grinding wheel 31 and the second grinding wheel 32 from the “grinding position” to a predetermined “standby position” when the workpiece W is replaced.

[0106] (Controller)

[0107] The controller 100 has a CPU (Central Processing Unit), a memory, and an input / output bus, and is constituted by, for example, a CNC (Computer Numerical Control) device. Figure 6 As shown, the controller 100 is electrically connected to the carrier drive motor 71, the reference side cylinder 83, the pressurizing side cylinder 84 and the grinding wheel drive motor 33 by wire or wireless. More specifically, the reference side cylinder 83 and the pressurizing side cylinder 84 are electrically connected via electromagnetic switching valves (not shown).

[0108] When grinding the workpiece W, the controller 100 places the first grinding wheel 31 and the second grinding wheel 32 in the "standby position" and opens the second workpiece holder 20 while keeping the first workpiece holder 10 in the "reference position". The workpiece W is passed between the first workpiece holder 10 and the second workpiece holder 20 by a loader (not shown) and is thus attached to the carrier 60 (see FIG. Figure 1 and Figure 3 ).

[0109] When the workpiece W is attached to the carrier 60, the controller 100 operates the pressurizing side cylinder 84 to move the second workpiece holder 20 toward the first workpiece holder 10, so that the second workpiece holder 20 is configured at the "support position" of the two surfaces of the reference side pad 12 and the pressurizing side pad 22 close to the workpiece W.

[0110] Then, the controller 100 discharges fluid such as air or water from the discharge ports of the reference-side pad 12 and the pressurizing-side pad 22. As a result, the workpiece W is subjected to the pressure of the fluid from both sides thereof, and is held in a non-contact state.

[0111] In the state where the workpiece W is held as described above, the controller 100 operates the carrier drive motor 71 to rotate the carrier 60. With this rotation, the workpiece W also starts to rotate. The controller 100 also rotates the first grinding wheel 31 and the second grinding wheel 32 by operating the grinding wheel drive motor 33. While the controller 100 rotates the first grinding wheel 31 and the second grinding wheel 32, it gradually approaches the first grinding wheel 31 and the second grinding wheel 32 from the "standby position" to the grinding surface of the workpiece W. With this approach, the workpiece W is clamped from both sides by the first grinding wheel 31 and the second grinding wheel 32 located at the "grinding position". Thus, the grinding of the workpiece W starts.

[0112] When grinding of the workpiece W is completed, the controller 100 moves the first grinding wheel 31 and the second grinding wheel 32 from the "grinding position" to the "standby position" and moves the second workpiece holder 20 from the "support position". The ground workpiece W is taken out of the carrier 60 by a loader (not shown) and carried out.

[0113] Furthermore, as described above, the controller 100 is also electrically connected to the reference sensor 101 and the distance sensor 102. The controller 100 receives detection signals (electrical signals) from the reference sensor 101 and the distance sensor 102.

[0114] The controller 100 can determine whether the first workpiece holder 10 is located at the “reference position” based on the detection signal of the reference sensor 101 . The controller 100 can determine whether the first workpiece holder 10 and the second workpiece holder 20 are located at the “support position” based on the detection signal of the distance sensor 102 .

[0115] Furthermore, the controller 100 detects the relative distance between the first workpiece holder 10 and the second workpiece holder 20 as described above based on the detection signal of the distance sensor 102. In particular, the controller 100 of the present embodiment detects the relative distance between the reference side pad 12 and the pressurizing side pad 22.

[0116] It should be noted that the relative distance can be detected by, for example, considering the relative position of the distance sensor 102 with respect to the reference side base 11 and the left-right thickness of the reference side pad 12 and the pressure side pad 22 in the detection value of the distance sensor 102.

[0117] The detected value of the relative distance referred to here may be the length of the actual distance between the reference-side pad 12 and the pressurizing-side pad 22 , or may not be the length of the actual distance.

[0118] For example, when calculating the former length, the detection value of the distance sensor 102 can be added with the relative position of the distance sensor 102 relative to the reference side base 11, and the value obtained by subtracting the thickness of the reference side pad 12 and the pressure side pad 22 in the left and right directions from the added value can be set as the detection value of the relative distance.

[0119] On the other hand, in the case of using the latter length, the detection value of the relative distance may also be the relative distance ( Figure 5 The specified distance X) is set as the "reference value" and a relative value relative to the reference value is adopted.

[0120] In the latter case, if Figure 5 As shown in the example, when the first workpiece holder 10 and the second workpiece holder 20 are located at the desired "support position", there is a predetermined distance X between the first workpiece holder 10 and the second workpiece holder 20. However, in the processing described below, the size of the deviation from the predetermined distance X is processed as the "detection value of the relative distance".

[0121] For example, when the definition of the predetermined distance X is used, when the relative distance between the first workpiece holder 10 and the second workpiece holder 20 is "X+ΔX", the value of "ΔX" may be treated as the detection value of the relative distance instead of the value of "X+ΔX" itself. In the present embodiment, such a value of "ΔX" (relative value relative to the reference value) is set as the detection value of the relative distance.

[0122] For example, in the present embodiment, when the first workpiece holder 10 and the second workpiece holder 20 are located at the "support position", the detection value of the relative distance is "zero" (the so-called ΔX=0 in the above definition). In addition, when the first workpiece holder 10 and the second workpiece holder 20 are closer than the "support position", the detection value of the relative distance is "negative". In addition, when the first workpiece holder 10 and the second workpiece holder 20 are farther than the "support position", the detection value of the relative distance is "positive".

[0123] The processing performed by the controller 100 is composed of at least one of a first processing and a second processing, wherein the first processing is a processing for detecting a situation in which a foreign object M is clamped in addition to the workpiece W at the "support position", and the second processing is a processing for detecting a situation in which wear of the stop mechanism 9 occurs at the "support position".

[0124] Here, when a thin plate-shaped workpiece W is used as the grinding object, the workpiece W may be slightly damaged due to defects in the raw material, abnormalities occurring during grinding, etc. When the next workpiece W is ground while the fragments of the workpiece W generated in this way remain, there is a possibility that the fragments of the workpiece generated last time are sandwiched between the workpiece W and the grinding wheels 31 and 32. The foreign matter M mentioned here refers to foreign matter represented by such fragments.

[0125] It should be noted that it is not necessary for the controller 100 to perform at least one of the first process and the second process. A controller independent of the grinding controller 100 may also be prepared to allow the controller to perform at least one of the first process and the second process or perform other various processes. It should be noted that the "various processes" mentioned here include processes for discharging fluids, processes for determining whether the first workpiece holder 10 is located at the "reference position", and the like.

[0126] The controller 100 uses the "reference value" as a common parameter in the first process and the second process. The controller 100 uses a specified first threshold value as a parameter unique to the first process. The controller 100 uses a specified second threshold value as a parameter unique to the second process. The values ​​of the reference value, the first threshold value, and the second threshold value may be read by the controller 100 from the outside or may be stored in advance in the memory of the controller 100.

[0127] Here, the “first threshold value” is a predetermined value set to be at least larger than the “reference value”, and the “second threshold value” is a predetermined value set to be at least smaller than the “reference value”.

[0128] Both the first process and the second process are performed when the first workpiece holder 10 and the second workpiece holder 20 are closed toward the "support position" during grinding of the workpiece W. Both the first process and the second process are processes for detecting whether the first workpiece holder 10 and the second workpiece holder 20 are positioned at the desired "support position".

[0129] The first process detects a situation in which the first workpiece holder 10 and the second workpiece holder 20 are closed toward the "support position" but the closing movement is actually stopped when the first workpiece holder 10 and the second workpiece holder 20 are farther than the "support position".

[0130] The second process detects a situation in which the first workpiece holder 10 and the second workpiece holder 20 are moved to close toward the “support position” but are actually closer than the “support position”.

[0131] The first process and the second process will be described in detail below.

[0132] (Details of the First Process and the Second Process)

[0133] Figure 7 is a flowchart illustrating the first process and the second process by way of example. Figure 8 is a diagram for explaining the clamping of a foreign body M. Fig. 9 This is a diagram for explaining the wear of the stopper mechanism 9 .

[0134] First of all. Figure 7 In step S1 , the controller 100 reads a detection signal from the distance sensor 102 .

[0135] In the next step S2, the controller 100 detects the relative distance between the first workpiece holder 10 and the second workpiece holder 20 based on the detection signal of the distance sensor 102. As described above, the detection value of the relative distance in this embodiment is equivalent to a relative value based on the situation when the first workpiece holder 10 and the second workpiece holder 20 are in the desired "support position". This detection value is equivalent to the value in the state where the first workpiece holder 10 and the second workpiece holder 20 are closed. When acquiring the relative distance, it has nothing to do with whether the "support position" is actually achieved. The situation where the "support position" is not actually achieved is equivalent to the situation where Figure 8 The situation of holding the foreign body M and Fig. 9 In this way, the stopper mechanism 9 is worn out.

[0136] In the next step S3 , the controller 100 compares the detected value of the relative distance with the first threshold, and compares the detected value with the second threshold.

[0137] In the next step S4, the controller 100 determines whether the detection value of the relative distance is greater than the first threshold value. If the determination is "NO", the controller 100 advances the control process to step S5.

[0138] On the other hand, if the determination in step S4 is "yes", it is considered that the Figure 8 As shown, a foreign object M is sandwiched between the workpiece W and the first workpiece holder 10 or the second workpiece holder 20. Figure 5 and Figure 8 As can be seen from the comparison, in this case, the distance between the reference side pad 12 and the pressurizing side pad 22 is longer than the prescribed distance X achieved at the desired "support position" ( Figure 8 In this case, the non-contact support is not necessarily maintained, and when grinding is performed in this state, there is a concern that the workpiece W and the first grinding wheel 31 and the second grinding wheel 32 may be damaged.

[0139] When the relative value with respect to the predetermined distance X is set as the detection value of the distance sensor 102 as described above, the detection value referred to in step S4 is equivalent to Figure 8 When the deviation ΔX1 is greater than the first threshold value, the judgment of step S4 is "yes". In this case, the controller 100 determines that a foreign object M is clamped between the workpiece W and the first workpiece holder 10 or the second workpiece holder 20, and advances the control process to step S6 to stop the grinding of the workpiece W.

[0140] It should be noted that, when it is assumed that the foreign matter M is a fragment caused by the defect of the workpiece W, it is considered that the thickness (dimension in the left-right direction) of the foreign matter M can reach a maximum of about the thickness D of the workpiece W. In this case, when considering both the workpiece W and the foreign matter M, it can be assumed that the actual distance X' between the reference side pad 12 and the pressurizing side pad 22 reaches about twice the thickness D.

[0141] The deviation ΔX1 under this assumption is:

[0142] ΔX1=X'-X

[0143] =2×D-X……(1).

[0144] The first threshold value of this embodiment is set to be smaller than the right side of equation (1). For example, when the predetermined distance X is set to 1000 [μm] and the thickness D is set to 800 [μm], the right side of equation (1) is 600 [μm]. For example, the first threshold value is set to 500 [μm] in a manner smaller than this value.

[0145] By setting the first threshold value to be smaller than the right side of the equation (1), even when a foreign object M having a thickness smaller than the thickness D of the workpiece W is held, this can be detected. This enables detection with higher accuracy.

[0146] Furthermore, in step S5, the controller 100 determines whether the detected value of the relative distance is smaller than the second threshold value. If the determination is "NO", the controller 100 advances the control process to step S7 to continue grinding the workpiece W.

[0147] On the other hand, if the determination in step S5 is "yes", for example, it is considered that Fig. 9 As shown, at least one of the reference-side bolt 91 , the pressurizing-side bolt 92 , and the stopper 93 constituting the stopper mechanism 9 is worn. Fig. 9 The example shows a state where the pressurizing side stopper pin 93b is worn. Figure 5 and Fig. 9As can be seen from the comparison, in this case, the distance between the reference side pad 12 and the pressurizing side pad 22 is shorter than the predetermined distance X achieved at the desired "support position" (see Fig. 9 In this case, normal non-contact support is not necessarily maintained, and when grinding is performed in this state, there is a concern about deterioration of machining accuracy and damage to the first grinding wheel 31 and the second grinding wheel 32. That is, since the stopper mechanism 9 is worn, the abutting workpiece holders 10 and 20 may tilt, or the pad spacing may become narrow, so there is a possibility that the balance of the static pressure holding of the workpiece W may be destroyed and the machining accuracy may be deteriorated.

[0148] When the relative value with respect to the predetermined distance X is set as the detection value of the distance sensor 102 as described above, the detection value referred to in step S5 is equivalent to Fig. 9 When the deviation ΔX2 is less than the second threshold value, the determination of step S5 is "yes". In this case, the controller 100 determines that at least a portion of the stop mechanism 9 is worn, and advances the control process to step S6 to stop the grinding of the workpiece W.

[0149] Thus, according to the embodiment, Figure 7 As shown in steps S3 to S4, the controller 100 compares the detection value of the distance sensor 102 with a first threshold value set larger than a reference value. By performing such a comparison, foreign matter M caused by a defect of the workpiece W can be detected.

[0150] In addition, if Figure 7 As shown in step S3 and step S5, the controller 100 compares the detection value of the distance sensor 102 with the second threshold value set to be smaller than the reference value. By performing such a comparison, it is possible to detect that the stopper mechanism 9 has been worn.

[0151] In addition, such a configuration does not require expensive sensors such as image sensors. Therefore, the above embodiment can achieve both detection of minute defects in the workpiece and detection of wear of the stopper mechanism 9 and cost reduction.

[0152] In addition, if Figure 3 As shown in FIG. 1 , the distance sensor 102 is arranged closer to a stopper mechanism 9 located above and behind the central portion C of the reference side pad 12. When the reference side base 11 is tilted, the detection value of the distance sensor 102 changes greatly near the stopper mechanism 9. Therefore, by arranging the distance sensor 102 near the stopper mechanism 9, even a slight tilt can be reliably detected. This helps to ensure the detection accuracy of defects or wear.

[0153] <Other embodiments>

[0154] Fig.10 and Fig.11 is a modified example of the processing performed by the controller 100 Figure 7 Corresponding diagram. Figure 7 Flowchart and Fig.10 The flowcharts of are different only in the presence or absence of step S5. Figure 7 Flowchart and Fig.11 The flowcharts of FIG. 1 and FIG. 2 differ only in the presence or absence of step S4.

[0155] As described above, it is not necessary for the controller 100 to perform both the first processing and the second processing. Fig.10 Only the first processing is performed as shown, or Fig.11 Only the second process is shown.

Claims

1. A double-head surface grinding device, comprising: a first workpiece holding body and a second workpiece holding body, which are provided at a support position for clamping a thin plate-shaped workpiece, and which non-contactly supports the workpiece by the pressure of a fluid; and a pair of grinding wheels, which grind the grinding surfaces of the two surfaces of the workpiece supported by the first workpiece holding body and the second workpiece holding body, The double-head surface grinding device is characterized in that it has: a moving mechanism for causing the first workpiece holding body and the second workpiece holding body to perform a closing movement toward the supporting position; a stop mechanism for limiting the closing movement of the first workpiece holder and the second workpiece holder performed by the moving mechanism so that the first workpiece holder and the second workpiece holder are positioned at the supporting position; a distance sensor for detecting a relative distance between the first workpiece holder and the second workpiece holder; as well as a controller, to which the detection signal of the distance sensor is input, When the relative distance achieved when the closing movement is restricted by the stopper mechanism and the first and second workpiece holders are located at the supporting positions is set as a reference value, and a prescribed value set larger than the reference value is set as a first threshold value, Based on the detection signal of the distance sensor, the controller compares the detection value of the relative distance in the state where the first workpiece holder and the second workpiece holder are closed with the first threshold value. When the relative distance is greater than the first threshold value, it is determined that a foreign object is clamped between the workpiece and the first workpiece holder or the second workpiece holder, and the grinding of the workpiece is stopped.

2. A double-head surface grinding device, comprising: a first workpiece holding body and a second workpiece holding body, at a support position defined as a thin plate-shaped workpiece, the workpiece is non-contact supported by the pressure of a fluid; and a pair of grinding wheels for grinding the two surfaces of the workpiece supported by the first workpiece holding body and the second workpiece holding body. The double-head surface grinding device is characterized in that it has: a moving mechanism for causing the first workpiece holding body and the second workpiece holding body to perform a closing movement toward the supporting position; a stop mechanism for limiting the closing movement of the first workpiece holder and the second workpiece holder performed by the moving mechanism so that the first workpiece holder and the second workpiece holder are positioned at the supporting position; a distance sensor for detecting a relative distance between the first workpiece holder and the second workpiece holder; as well as a controller, to which the detection signal of the distance sensor is input, When the relative distance achieved when the closing movement is restricted by the stopper mechanism and the first and second workpiece holders are located at the supporting positions is set as a reference value, and a prescribed value set smaller than the reference value is set as a second threshold value, Based on the detection signal of the distance sensor, the controller compares the detection value of the relative distance in the state where the first workpiece holder and the second workpiece holder are closing, with the second threshold value. When the relative distance is smaller than the second threshold value, it is determined that the stop mechanism has been worn, and the grinding of the workpiece is stopped.

3. A double-head surface grinding device, comprising: a first workpiece holding body and a second workpiece holding body, at a support position specified for clamping a thin plate-shaped workpiece, the workpiece is non-contact supported by the pressure of a fluid; and a pair of grinding wheels for grinding the grinding surfaces of the two surfaces of the workpiece supported by the first workpiece holding body and the second workpiece holding body, The double-head surface grinding device is characterized in that it has: a moving mechanism for causing the first workpiece holding body and the second workpiece holding body to perform a closing movement toward the supporting position; a stop mechanism for limiting the closing movement of the first workpiece holder and the second workpiece holder performed by the moving mechanism so that the first workpiece holder and the second workpiece holder are positioned at the supporting position; a distance sensor for detecting a relative distance between the first workpiece holder and the second workpiece holder; as well as a controller, to which the detection signal of the distance sensor is input, When the relative distance achieved when the closing movement is restricted by the stop mechanism and the first workpiece holder and the second workpiece holder are located at the supporting position is set as a reference value, a prescribed value set larger than the reference value is set as a first threshold value, and a prescribed value set smaller than the reference value is set as a second threshold value, Based on the detection signal of the distance sensor, the controller compares the detection value of the relative distance in the state where the first workpiece holder and the second workpiece holder are closed, the first threshold value, and the second threshold value. When the relative distance is greater than the first threshold value, it is determined that a foreign object is clamped between the workpiece and the first workpiece holder or the second workpiece holder, and the grinding of the workpiece is stopped. On the other hand, when the relative distance is less than the second threshold value, it is determined that the stopping mechanism is worn, and the grinding of the workpiece is stopped.

4. The double-head surface grinding device according to any one of claims 1 to 3, characterized in that: The first workpiece holder and the second workpiece holder each have: a base that slides and moves along with the movement of the moving mechanism; and A pad is arranged on the end surface of the base to provide non-contact support for the workpiece. The stopper mechanism is disposed between the bases of the first workpiece holder and the second workpiece holder in a plurality so as to surround the pads of the first workpiece holder and the second workpiece holder, The distance sensor is configured to abut at least one of the plurality of stop mechanisms, A distance between the distance sensor and the stopper mechanism adjacent to the distance sensor is shorter than a distance between the distance sensor and a center portion of the pad.

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