Double head surface grinding device

Abstract

To enable detection of small cracks occurring in a workpiece and wear occurring in a stopper mechanism and reduction of costs.SOLUTION: A double head surface grinding device 1 includes: a moving mechanism 8 which causes first and second workpiece holders 10, 20 to close toward support positions; a stopper mechanism 9 which restricts the closing motion of the first and second workpiece holders 10, 20 by the moving mechanism 8 so that the first and second workpiece holders 10, 20 are positioned at the support positions; a distance sensor 102 which detects the relative distance between the first and second workpiece holders 10, 20; and a controller 100. The controller 100 compares the detection value of the relative distance in a state that the first and second workpiece holders 10, 20 are closed with a first threshold value and determines that a foreign object is sandwiched between a workpiece W and the first and second workpiece holders 10, 20 to stop grinding of the workpiece W when the relative distance is larger than the first threshold value.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present disclosure relates to a double disc surface grinding machine. [Background technology]

[0002] An example of a double-disc surface grinding device is disclosed in Patent Document 1. Specifically, the device disclosed in Patent Document 1 includes first and second work holders that support a thin plate-like workpiece in a non-contact manner by fluid pressure, and a pair of grinding wheels that grind both sides of the workpiece supported by the first and second work holders.

[0003] Furthermore, the device disclosed in Patent Document 1 includes a slide drive mechanism that slides the first and second work holders, and a stopper bolt and a stopper block. Here, the slide drive mechanism is a mechanism that moves the first and second work holders closer to each other toward a support position (grinding position) where the work is supported without contact. The stopper bolt and the stopper block abut against each other when the first and second work holders are brought close to the support position, thereby achieving accurate positioning. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2016-132084 A Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, when a thin plate-shaped workpiece is to be ground, the workpiece may be slightly chipped due to defects in the material, an abnormality that occurs during grinding, etc. If the workpiece is ground while the chipped piece remains, the chipped piece from the previous grinding may be caught between the workpiece and the grinding wheel. Until now, there have been known technologies for detecting relatively large damage such as cracks and breaks in the workpiece, but these technologies were insufficient to detect slight chipping.

[0006] One method for detecting small chips is to take an image of the workpiece using an image sensor. However, image sensors are generally expensive. In addition, when using an image sensor, it is necessary to install a new lighting device to clarify light and dark, and a new background, etc., which is inconvenient for cost reduction.

[0007] A similar problem exists in the stopper mechanism consisting of a stopper bolt and a stopper block. In other words, wear may occur in the stopper mechanism while grinding a large number of workpieces. Conventional methods have been insufficient to detect such wear while keeping costs down.

[0008] The present disclosure has been made in consideration of these points, and its purpose is to achieve both the detection of minor chips that occurred in the workpiece during the previous grinding or wear that occurred in the stopper mechanism, while keeping costs down. [Means for solving the problem]

[0009] A first aspect of the present disclosure relates to a double-disc surface grinding machine including first and second work holders that support a thin plate-like workpiece in a non-contact manner by using fluid pressure at a support position determined to sandwich the workpiece, and a pair of grinding wheels that grind the surfaces to be ground on both sides of the workpiece supported by the first and second work holders. This double-disc surface grinding machine includes a moving mechanism that closes the first and second work holders toward the support position, a stopper mechanism that restricts the closing movement of the first and second work holders by the moving mechanism so that the first and second work holders are positioned at the support position, a distance sensor that detects the relative distance between the first and second work holders, and a controller to which a detection signal from the distance sensor is input.

[0010] According to the first aspect, the relative distance realized when the closing movement is restricted by the stopper mechanism and the first and second work holders are located at the support position is set as a reference value, and a predetermined 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 when the first and second work holders are closed with the first threshold value based on the detection signal of the distance sensor, and if the relative distance is larger than the first threshold value, it determines that a foreign object is sandwiched between the work and the first or second work holder, and stops grinding of the work.

[0011] When the first and second workpiece holders are positioned at the desired support positions, the detected value of the relative distance is considered to coincide with the reference value. On the other hand, if a small chip occurs in the workpiece, the chip may stick to the first or second workpiece holder and remain. In this case, if the chip remains and the grinding process moves to the next workpiece, the detected value is considered to be larger than the reference value by the thickness of the chip.

[0012] Therefore, according to the first aspect, the controller compares the detection value with a first threshold value set to be larger than a reference value. By performing such a comparison, it becomes possible to detect chipping that occurred in the workpiece during the previous grinding. Moreover, the first aspect does not require a high-cost sensor such as an image sensor. Therefore, the first aspect can achieve both detection of slight chipping that occurred in the workpiece during the previous grinding and cost reduction.

[0013] A second aspect of the present disclosure relates to a double-disc surface grinding machine including first and second work holders that support a thin plate-like workpiece in a non-contact manner by fluid pressure at a support position determined to sandwich the workpiece, and a pair of grinding wheels that grind the surfaces to be ground on both sides of the workpiece supported by the first and second work holders. This double-disc surface grinding machine includes a moving mechanism that closes the first and second work holders toward the support position, a stopper mechanism that restricts the closing movement of the first and second work holders by the moving mechanism so that the first and second work holders are positioned at the support position, a distance sensor that detects the relative distance between the first and second work holders, and a controller to which a detection signal of the distance sensor is input.

[0014] According to the second aspect, the relative distance realized when the closing movement is restricted by the stopper mechanism and the first and second work holders are located at the support positions is set as a reference value, and a predetermined 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 when the first and second work holders are closed with the second threshold value based on the detection signal of the distance sensor, and if the relative distance is smaller than the second threshold value, it determines that wear has occurred in the stopper mechanism and stops grinding of the work.

[0015] When the first and second work holders are positioned at the desired support positions, the detected value of the relative distance is considered to coincide with the reference value as described above. On the other hand, when wear occurs in the stopper mechanism, the detected value is considered to be smaller than the reference value depending on the amount of wear.

[0016] Therefore, according to the second aspect, the controller compares the detection value with a second threshold value set to be smaller than a reference value. By performing such a comparison, it becomes possible to detect wear in the stopper mechanism. Furthermore, the second aspect does not require a dedicated sensor such as a linear scale for detecting the positions of the first and second work holders. Therefore, the second aspect can detect wear in the stopper mechanism while keeping costs down.

[0017] A third aspect of the present disclosure relates to a double-disc surface grinding machine including first and second work holders that support a thin plate-like workpiece in a non-contact manner by fluid pressure at a support position determined to sandwich the workpiece, and a pair of grinding wheels that grind the surfaces to be ground on both sides of the workpiece supported by the first and second work holders. This double-disc surface grinding machine includes a moving mechanism that moves the first and second work holders in a closing motion toward the support position, a stopper mechanism that restricts the closing motion of the first and second work holders by the moving mechanism so that the first and second work holders are positioned at the support position, a distance sensor that detects the relative distance between the first and second work holders, and a controller to which a detection signal of the distance sensor is input.

[0018] According to the third aspect, the relative distance realized when the closing movement is restricted by the stopper mechanism and the first and second work holders are located at the support positions is defined as a reference value, a predetermined value set to be larger than the reference value is defined as a first threshold value, and a predetermined value set to be smaller than the reference value is defined as a second threshold value. Based on the detection signal of the distance sensor, the controller compares the detection value of the relative distance when the first and second work holders are closed with the first threshold value, and if the relative distance is larger than the first threshold value, it determines that a foreign object is sandwiched between the work and the first or second work holder and stops grinding of the work, whereas if the relative distance is smaller than the second threshold value, it determines that wear has occurred in the stopper mechanism and stops grinding of the work.

[0019] When the first and second workpiece holders are positioned at the desired support positions, the detected value of the relative distance is considered to coincide with the reference value. On the other hand, if a small chip occurs in the workpiece, the chip may stick to the first or second workpiece holder and remain. In this case, if the chip remains and the grinding of the next workpiece is started, the detected value is considered to be larger than the reference value by the thickness of the chip. Furthermore, if wear occurs in the stopper mechanism, the detected value is considered to be smaller than the reference value depending on the amount of wear.

[0020] Therefore, according to the third aspect, the controller compares the detection value with a first threshold value set to be larger than a reference value, or compares the detection value with a second threshold value set to be smaller than a reference value. By performing such comparisons, it becomes possible to detect chipping of the workpiece or wear on the stopper mechanism. In addition, the third aspect does not require a high-cost sensor such as an image sensor. Therefore, the third aspect, like the first and second aspects, can simultaneously detect slight chipping of the workpiece or wear on the stopper mechanism and reduce costs.

[0021] In addition, according to a fourth aspect of the present disclosure, the first and second work holders each have a base that slides with the operation of the moving mechanism, and a pad that is arranged on an end surface of the base and supports the work in a non-contact manner, and the stopper mechanisms are arranged between the bases of the first and second work holders so as to surround the pads of the first and second work holders, respectively, the distance sensor is arranged adjacent to at least one of the plurality of stopper mechanisms, and the distance between the distance sensor and the stopper mechanism adjacent to the distance sensor is shorter than the distance between the distance sensor and the center of the pad.

[0022] According to the fourth aspect, the distance sensor is disposed closer to at least one stopper mechanism than the center of the pad. If the base is tilted, the detection value of the distance sensor will change significantly near the stopper mechanism. Therefore, by disposing the distance sensor near the stopper mechanism, even if the tilt is slight, the tilt can be reliably detected. This is advantageous in ensuring the accuracy of chipping or wear detection. Effect of the Invention

[0023] As described above, according to the present disclosure, it is possible to detect slight chips in a workpiece or wear in a stopper mechanism while keeping costs down. [Brief description of the drawings]

[0024] [Figure 1] FIG. 2 is a plan view illustrating the configuration of a double-disc surface grinding machine. [Diagram 2] FIG. 2 is a front cross-sectional view of the double-disc surface grinding device. [Diagram 3] FIG. 2 is a side cross-sectional view of the double-disc surface grinding device. [Figure 4] FIG. 4 is a schematic diagram for explaining a reference position. [Diagram 5] FIG. 11 is a schematic diagram for explaining a support position. [Figure 6]FIG. 2 is a block diagram illustrating a configuration related to a controller. [Figure 7] 4 is a flowchart illustrating a first process and a second process. [Figure 8] FIG. 13 is a diagram for explaining the entrapment of a foreign object; [Figure 9] 11A and 11B are diagrams for explaining wear of the stopper mechanism. [Figure 10] FIG. 8 is a diagram corresponding to FIG. 7 and showing a modified example of the process performed by the controller. [Figure 11] FIG. 8 is a diagram corresponding to FIG. 7 and showing a modified example of the process performed by the controller. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. Note that the following description is merely an example.

[0026] (Overall composition) FIG. 1 is a plan view illustrating the configuration of a double-disc surface grinding machine 1. FIG. 2 is a front cross-sectional view of the double-disc surface grinding machine 1, and corresponds to the view seen from the arrow AA in FIG. 1. FIG. 3 is a side cross-sectional view of the double-disc surface grinding machine 1, and corresponds to the view seen from the arrow BB in FIG. 1. FIG. 4 is a schematic diagram for explaining the reference position, and FIG. 5 is a schematic diagram for explaining the support position. FIG. 6 is a block diagram illustrating the configuration related to the controller 100.

[0027] As shown in Fig. 1, the double-disc surface grinding device 1 includes first and second workpiece holders 10, 20, a first grinding wheel 31, and a second grinding wheel 32. The first and second workpiece holders 10, 20 support the workpiece W in a non-contact manner at a predetermined "support position" by fluid pressure. The first and second grinding wheels 31, 32 grind the surfaces to be ground on both sides of the workpiece W supported by the first and second workpiece holders 10, 20, and constitute a "pair of grinding wheels" in this embodiment.

[0028] The "support position" here refers to a position determined so that the thin plate-shaped workpiece W is clamped in a non-contact state, as shown in Fig. 5. The non-contact support realized at the "support position" can be rephrased as "static pressure support." The workpiece W may be a thin plate-shaped, disc-shaped object to be ground, such as a semiconductor wafer.

[0029] Specifically, the double-head surface grinding device 1 includes a work drive device 2 having the first and second work holders 10, 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.

[0030] (Work drive device) The work drive device 2 is a device that holds and rotates the workpiece W when grinding both sides of the workpiece W. The work drive device 2 includes a case 5, a workpiece holding mechanism 6, a workpiece rotating mechanism 7, a moving mechanism 8, and a stopper mechanism 9.

[0031] Here, the case 5 covers the periphery of the workpiece holding mechanism 6 and supports the workpiece holding mechanism 6 so as to be relatively movable within the case 5. The case 5 is formed, for example, in a substantially rectangular box shape that is open at the top and bottom.

[0032] The workpiece holding mechanism 6 holds the workpiece W from both sides of the workpiece W. The workpiece holding mechanism 6 has 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, either the front or back. The second workpiece holding body 20 holds the workpiece W from the other side, either the front or back. The first and second workpiece holding bodies 10, 20 are arranged facing each other and are supported by the case 5 so as to be movable in the left-right direction.

[0033] The first and second workpiece holders 10, 20 each have a base 11, 21 that slides with the operation of the moving mechanism 8, and pads 12, 22 that are disposed on the end faces of the bases 11, 21 and support the workpiece W in a non-contact manner.

[0034] Specifically, the first workpiece holder 10 has a reference side base 11 arranged parallel to a vertical plane in the front-to-rear direction, and a reference side pad 12 provided on the end face of the reference side base 11 on the side of the second workpiece holder 20.

[0035] The second work holder 20 has a pressure side base 21 arranged parallel to a vertical plane in the front-rear direction, and a pressure side pad 22 provided on the end face of the pressure side base 21 on the first work holder 10 side.

[0036] The reference side pad 12 and the pressure side pad 22 are formed in a substantially circular plate shape and are used to support the workpiece W from both sides in a non-contact manner by using fluid pressure such as water pressure. On the opposing surfaces of the reference side pad 12 and the pressure side pad 22, there are provided discharge ports (not shown) for discharging the fluid.

[0037] The reference side pad 12 and the pressure side pad 22 have arc-shaped first cutout portions 61 corresponding to the first and second grinding wheels 31, 32, respectively, extending from their outer edges to positions slightly beyond the centers of the reference side base 11 and the pressure side base 21 (see Figures 2 and 3).

[0038] The reference-side base 11 and the pressure-side base 21 are each formed of a substantially rectangular plate having a thickness in the left-right direction. An arc-shaped second cutout 62 corresponding to the first cutout 61 is provided on the lower side of the reference-side base 11 and the pressure-side base 21 from the outer edge side to a position slightly beyond the center of the reference-side base 11 and the pressure-side base 21 (only shown in FIG. 2).

[0039] In addition, four support rollers 63 surrounding the reference side pad 12 are arranged on the surface of the reference side base 11 facing the pressure side base 21. The carrier 60 holding the workpiece W is rotatably supported by these four support rollers 63.

[0040] The carrier 60 is formed in a ring shape in which the workpiece W can be loosely fitted. The inner peripheral surface of the carrier 60 is provided with a protrusion (not shown) that protrudes radially inward. This protrusion is configured to mesh with a notch (not shown) provided on the outer peripheral surface of the workpiece W. This meshing causes the workpiece W to rotate in conjunction with the rotation of the carrier 60.

[0041] The workpiece rotating mechanism 7 rotates and drives the workpiece W held by the workpiece holding mechanism 6. The workpiece rotating mechanism 7 has a carrier drive motor 71 and a carrier drive shaft 72.

[0042] The carrier drive motor 71 is connected to the carrier drive shaft 72. When the carrier drive motor 71 operates, its rotational drive force rotates the carrier drive shaft 72. The carrier drive shaft 72 has a carrier drive gear (not shown) at its tip. When the carrier drive shaft 72 rotates, the rotational drive force rotates the carrier 60 via the carrier drive gear. As the carrier 60 rotates, the workpiece W also rotates, as described above.

[0043] The moving mechanism 8 closes the first and second work holders 10, 20 toward a "support position" for achieving hydrostatic support. This closing operation is achieved by sliding the work holder mechanism 6 relative to the case 5. In this embodiment, this sliding movement corresponds to movement along the left-right direction in FIGS. 1 and 2, and FIGS. 3 and 4. The closing operation of the first and second work holders 10, 20 is an operation that brings the first work holder 10 and the second work holder 20 closer to each other. In order to achieve this operation, the moving mechanism 8 according to this embodiment has a plurality of guide bars 81, a plurality of bushes 82, a reference side cylinder 83, and a pressure side cylinder 84.

[0044] The multiple guide bars 81 each extend in the left-right direction within the case 5, and each penetrates the first work holder 10 and the second work holder 20 in the left-right direction. The multiple guide bars 81 support the first work holder 10 and the second work holder 20 so that they can slide freely in the left-right direction. In this embodiment, a total of four guide bars 81 are installed in the case 5, one each on the front, back, top and bottom.

[0045] The multiple bushes 82 are members interposed between each guide bar 81 and the through holes of the first and second work holders 10, 20 through which each guide bar 81 is inserted. Each guide bar 81 is slidably inserted into each through hole of the first and second work holders 10, 20 via each bush 82. This allows the first and second work holders 10, 20 to slide left and right along each guide bar 81. Each bush 82 may be, for example, a double bush.

[0046] The reference side cylinder 83 moves the first work holder 10 relative to the case 5 and the second work holder 20. The pressure side cylinder 84 moves the second work holder 20 relative to the case 5 and the first work holder 10. The reference side cylinder 83 and the pressure side cylinder 84 may be, for example, pneumatic cylinders, so-called air cylinders.

[0047] When grinding the workpiece W, the moving mechanism 8 moves the first workpiece holder 10 and the second workpiece holder 20 close to the workpiece W but not so close that they come into direct contact with the workpiece W. At that time, unless there is any foreign matter trapped between the first workpiece holder 10 and the second workpiece holder 20 or there is any wear on the stopper mechanism 9, the first workpiece holder 10 and the second workpiece holder 20 will be positioned at the desired "support position" shown in FIG.

[0048] When replacing the workpiece W, the movement mechanism 8 moves the second workpiece holder 20 left and right away from the first workpiece holder 10. At that time, the first workpiece holder 10 is maintained at the desired "reference position" shown in FIG.

[0049] The aforementioned "support position" can be considered to be the relative positional relationship realized when the first work holder 10 is positioned at the "reference position" and the second work holder 20 is brought closer to the desired position, as shown in Figure 5.

[0050] The stopper mechanism 9 is a mechanism that restricts the closing movement of the first and second work holders 10, 20 by the moving mechanism 8 so that the first and second work holders 10, 20 are positioned at the "support position".

[0051] A plurality of stopper mechanisms 9 are provided between the bases 11, 21 of the first and second work holders 10, 20 so as to surround the pads 12, 22 of the first and second work holders 10, 20. For example, the stopper mechanisms 9 according to this embodiment are disposed at each of the four corners (particularly, the four corners in the front-rear and up-down directions) between the first and second work holders 10, 20 as shown in FIG.

[0052] In addition, the multiple (four in this embodiment) stopper mechanisms 9 have multiple (four in this embodiment) reference side bolts 91, the same number of pressure side bolts 92 as the reference side bolts 91, and the same number of stopper blocks 93 as the reference side bolts 91.

[0053] 1 and 2, each reference-side bolt 91 is fixed to the first work holder 10, particularly to the four corners of the reference-side base 11. Then, as shown generally in Figures 4 and 5, each reference-side bolt 91 has a bolt head 91a that protrudes to the left, that is, toward the second work holder 20. The amount of protrusion of the bolt head 91a is adjustable.

[0054] 1 and 2, each pressure-side bolt 92 is fixed to the second work holder 20, particularly to the four corners of the pressure-side base 21. Then, as shown generally in Figures 4 and 5, each pressure-side bolt 92 has a bolt head 92a that protrudes to the right, that is, toward the first work holder 10. The amount of protrusion of the bolt head 92a is adjustable.

[0055] 1 to 3, each stopper block 93 is fixed to one of the four corners of the case 5. As shown in FIGS. 4 and 5, each stopper block 93 has a reference-side stop pin 93a protruding to face the corresponding reference-side bolt 91, and a pressure-side stop pin 93b protruding to face the corresponding pressure-side bolt 92.

[0056] 4, when the first work holder 10 is located at the "reference position", the stopper block 93 comes into contact with the reference-side bolt 91. In detail, when the first work holder 10 is located at the "reference position", the reference-side stop pin 93a comes into contact with the bolt head 91a of the reference-side bolt 91.

[0057] 5, when the first work holder 10 and the second work holder 20 are located at the "support position", the stopper block 93 abuts against the reference side bolt 91, and the stopper block 93 abuts against the pressure side bolt 92. In detail, when the first work holder 10 and the second work holder 20 are located at the "support position", the reference side stop pin 93a abuts against the bolt head 91a of the reference side bolt 91, and the pressure side stop pin 93b abuts against the bolt head 92a of the pressure side bolt 92.

[0058] Then, at the "support position", the workpiece W is supported in a non-contact manner between the reference side pad 12 and the pressure side pad 22. Considering that the workpiece W is supported in a non-contact manner, the actual distance (predetermined distance X) between the reference side pad 12 and the pressure side pad 22 at the "support position" is greater than at least the thickness D of the workpiece W.

[0059] The double disc surface grinding machine 1 further includes a reference sensor 101 and a distance sensor 102 in order to detect whether the "reference position" and the "support position" have been achieved, respectively.

[0060] The reference sensor 101 detects the position of the first work holder 10 relative to the stopper block 93. The reference sensor 101 according to this embodiment is fixed to the stopper block 93, and detects the distance of the first work holder 10 relative to the stopper block 93 in the left-right direction. The reference sensor 101 is electrically connected to the controller 100 by wire or wirelessly, and inputs an electrical signal indicating the detection result to the controller 100. This electrical signal can be used to determine whether or not the first work holder 10 is located at the "reference position".

[0061] The distance sensor 102 is used to detect the relative distance between the first and second work holders 10, 20. More specifically, the distance sensor 102 is provided on one of the first and second work holders 10, 20, and detects the relative distance between the other of the first and second work holders 10, 20.

[0062] More specifically, the distance sensor 102 is provided on the first work holder 10, and detects the relative distance between the first work holder 10 and the second work holder 20. The distance sensor 102 may be, for example, an eddy current type distance sensor.

[0063] 3, the distance sensor 102 according to this embodiment is disposed adjacent to one of the stopper mechanisms 9 (the stopper mechanism 9 located above and to the rear in the illustrated example). 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 center C of the reference side pad 12.

[0064] The relative distance detected by the distance sensor 102 may be the distance between the reference side pad 12 and the pressure side pad 22 or the distance between the reference side base 11 and the pressure side base 21 .

[0065] Also, if the distance sensor 102 is attached to the first work holder 10, it may be the distance between the distance sensor 102 and the pressure side base 21 or the pressure side pad 22. Similarly, if the distance sensor 102 is attached to the second work holder 20, it may be the distance between the distance sensor 102 and the reference side base 11 or the reference side pad 12.

[0066] For example, the distance sensor 102 according to this embodiment is fixed to the reference side base 11 of the first work holder 10. The distance sensor 102 according to this embodiment detects the distance between the distance sensor 102 and the pressure side base 21 of the second work holder 20.

[0067] The distance sensor 102 is electrically connected to the controller 100 by wire or wirelessly, and inputs an electrical signal indicating the detection result to the controller 100. This electrical signal can be used in combination with the detection signal of the reference sensor 101 to determine whether or not the first work holder 10 and the second work holder 20 are located at the "support position".

[0068] (Grinding equipment) The grinding wheel device 3 is a device that grinds both sides of the workpiece W held and rotated by the workpiece drive device 2, using first and second grinding wheels 31, 32. The first grinding wheel 31 advances and retreats through a first cutout portion 61 and a second cutout portion 62 of the first workpiece holder 10. The second grinding wheel 32 advances and retreats through a first cutout portion 61 and a second cutout portion 62 of the second workpiece holder 20.

[0069] The grindstone device 3 includes first and second cup-shaped grinding wheels 31, 32, and a grindstone drive motor 33 that rotates the grinding wheels 31, 32. The grindstone devices 3 are disposed on both the left and right sides of the work drive device 2. The grindstone drive motor 33 is only shown in FIG.

[0070] The first and second grinding wheels 31, 32 are arranged to face both sides of the workpiece W held by the carrier 60 via the first and second cutout portions 61, 62 of the first workpiece holder 10 and the second workpiece holder 20, respectively.

[0071] Specifically, the first grinding wheel 31 is positioned to face one side (e.g., the right side) of the workpiece W held by the carrier 60 via the first and second cutout portions 61, 62 of the first workpiece holder 10.

[0072] On the other hand, the second grinding wheel 32 is arranged to face the other side (e.g., the left side) of the workpiece W held by the carrier 60 via the first and second cutout portions 61, 62 of the second workpiece holder 20.

[0073] In addition, the grinding wheel device 3 is configured so that the first and second grinding wheels 31, 32 can be moved in the axial direction (left and right direction), and when replacing the workpiece W, the first and second grinding wheels 31, 32 are moved from the "grinding position" to a predetermined "standby position."

[0074] (controller) The controller 100 has a CPU, a memory, and an input / output bus, and is configured by, for example, a CNC device. As shown in Fig. 6, the controller 100 is electrically connected to the carrier drive motor 71, the reference side cylinder 83, the pressure side cylinder 84, and the grindstone drive motor 33 by wire or wirelessly. More specifically, the reference side cylinder 83 and the pressure side cylinder 84 are electrically connected to each other via electromagnetic switching valves (not shown).

[0075] When grinding the workpiece W, the controller 100 places the first and second grinding wheels 31, 32 in the "standby position" and opens the second workpiece holder 20 while holding the first workpiece holder 10 in the "reference position". The workpiece W is attached to the carrier 60 by a loader (not shown) through between the first workpiece holder 10 and the second workpiece holder 20 (see Figs. 1 and 3).

[0076] When the workpiece W is attached to the carrier 60, the controller 100 actuates the pressure side cylinder 84 to move the second workpiece holder 20 toward the first workpiece holder 10, and positions the reference side pad 12 and the pressure side pad 22 in a "support position" adjacent to both sides of the workpiece W.

[0077] Then, the controller 100 discharges a fluid such as air or water from the respective discharge ports of the reference side pad 12 and the pressure 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.

[0078] The controller 100 operates the carrier drive motor 71 to rotate the carrier 60 while the workpiece W is held as described above. This rotation also starts the rotation of the workpiece W. The controller 100 also rotates the first and second grinding wheels 31, 32 by operating the grinding wheel drive motor 33. While rotating the first and second grinding wheels 31, 32, the controller 100 gradually moves the first and second grinding wheels 31, 32 from the "standby position" to the surface to be ground of the workpiece W. This brings the workpiece W into a state where it is sandwiched from both sides by the first and second grinding wheels 31, 32 located at the "grinding position". This starts grinding the workpiece W.

[0079] When grinding of the workpiece W is completed, the controller 100 moves the first and second grinding wheels 31, 32 from the "grinding position" to the "standby position", and moves the second workpiece holder 20 from the "support position". After grinding, the workpiece W is taken out of the carrier 60 by a loader (not shown) and carried out.

[0080] As described above, the controller 100 is also electrically connected to the reference sensor 101 and the distance sensor 102. To the controller 100, detection signals (electrical signals) of the reference sensor 101 and the distance sensor 102 are input.

[0081] The controller 100 can determine whether the first work holder 10 is in the "reference position" or not based on the detection signal of the reference sensor 101. The controller 100 can determine whether the first and second work holders 10, 20 are in the "support position" or not based on the detection signal of the distance sensor 102.

[0082] Moreover, the controller 100 detects the relative distance between the first and second work holders 10, 20 as described above based on the detection signal of the distance sensor 102. In particular, the controller 100 according to this embodiment detects the relative distance between the reference side pad 12 and the pressure side pad 22.

[0083] The relative distance can be detected, for example, by taking into consideration the detection value of the distance sensor 102, the relative position of the distance sensor 102 with respect to the reference side base 11, and the left-right thicknesses of the reference side pad 12 and the pressure side pad 22.

[0084] Moreover, the detected value of the relative distance here may be the actual distance between the reference side pad 12 and the pressure side pad 22, or it does not have to be the actual distance.

[0085] For example, when calculating the former length, the detection value of the distance sensor 102 may be added to the relative position of the distance sensor 102 with respect to the reference side base 11, and the resultant sum may be subtracted by the left-right thickness of each of the reference side pad 12 and the pressure side pad 22 to obtain the detection value of the relative distance.

[0086] On the other hand, when the latter length is used, the detected value of the relative distance may be a relative value with respect to a "reference value" which is the relative distance (predetermined distance X in FIG. 5) realized when the closing movement of the first and second work holders 10, 20 is restricted by the stopper mechanism 9 and the first and second work holders 10, 20 are positioned at the desired "support position."

[0087] In the latter case, as shown in Fig. 5, when the first and second work holders 10, 20 are located at the desired "support position", there is a predetermined distance X between the first work holder 10 and the second work holder 20. However, in the process described below, the magnitude of deviation from the predetermined distance X is treated as the "detected value of the relative distance".

[0088] For example, when the above-mentioned definition of the predetermined distance X is used, if the relative distance between the first and second work holders 10, 20 is "X+ΔX", the value of "ΔX" can be treated as the detection value of the relative distance, rather than the value of "X+ΔX" itself. In this embodiment, the value of "ΔX" (relative value from a reference value) is treated as the detection value of the relative distance.

[0089] For example, in this embodiment, when the first and second work holders 10, 20 are located at the "support position", the detected value of the relative distance is "zero" (ΔX=0 as defined above). When the first and second work holders 10, 20 are closer to each other than the "support position", the detected value of the relative distance is a "negative value". When the first and second work holders 10, 20 are farther apart than the "support position", the detected value of the relative distance is a "positive value".

[0090] The processing performed by the controller 100 is composed of at least one of a first processing for detecting that a foreign object M has been pinched in addition to the workpiece W at the "support position" and a second processing for detecting that wear has occurred in the stopper mechanism 9 at the same "support position."

[0091] When a thin plate-like workpiece W is to be ground, the workpiece W may be slightly chipped due to defects in the material, an abnormality that occurs during grinding, etc. If the grinding of the next workpiece W is started with the chipped pieces of the workpiece W remaining, the chipped pieces of the previous workpiece may be caught between the workpiece W and the grinding wheels 31, 32. The foreign matter M here refers to foreign matter such as such chipped pieces.

[0092] It is not essential that the controller 100 performs at least one of the first process and the second process. A controller independent of the grinding controller 100 may be prepared and the controller may perform at least one of the first process and the second process, or may perform various other processes. The "various processes" referred to here include a process for discharging a fluid, a process for determining whether the first workpiece holder 10 is in the "reference position", and the like.

[0093] The controller 100 uses the "reference value" as a parameter common to the first and second processes. The controller 100 uses a predetermined first threshold value as a parameter specific to the first process. The controller 100 uses a predetermined second threshold value as a parameter specific to the second process. The reference value, the first threshold value, and the second threshold value may be read into the controller 100 from an external device, or may be stored in advance in the memory of the controller 100.

[0094] Here, the "first threshold" is a predetermined value that is set to be at least greater than the "reference value," and the "second threshold" is a predetermined value that is set to be at least smaller than the "reference value."

[0095] Both the first process and the second process are performed when the first and second work holders 10, 20 are closed toward the "support position" during grinding of the workpiece W. Both the first and second processes are for detecting whether the first and second work holders 10, 20 have been positioned at the desired "support position".

[0096] The first process detects a situation in which the first and second work holders 10, 20 have been caused to close toward the "support position," but in reality, the closing movement has stopped when the first and second work holders 10, 20 are farther away from the "support position."

[0097] The second process detects a situation in which the first and second work holders 10, 20 have been closed toward the "support position", but in reality, the first and second work holders 10, 20 have become closer to each other than the "support position".

[0098] The first process and the second process will be described in detail below.

[0099] (Details of the first and second processes) Fig. 7 is a flow chart illustrating the first process and the second process, Fig. 8 is a diagram for explaining the pinching of a foreign object M, and Fig. 9 is a diagram for explaining the wear of the stopper mechanism 9.

[0100] First, in step S1 of FIG.

[0101] In the next step S2, the controller 100 detects the relative distance between the first and second work holders 10, 20 based on the detection signal of the distance sensor 102. As described above, the detected value of the relative distance in this embodiment corresponds to a relative value based on the time when the first and second work holders 10, 20 are located at the desired "support position". This detected value corresponds to a value in a state in which the first and second work holders 10, 20 are closed. When obtaining the relative distance, it does not matter whether the "support position" is actually realized or not. A situation in which the "support position" is not actually realized corresponds to a situation in which a foreign object M is caught as shown in FIG. 8 and a situation in which the stopper mechanism 9 is worn as shown in FIG. 9.

[0102] In the next step S3, the controller 100 compares the detected value of the relative distance with a first threshold value, and also compares the detected value with a second threshold value.

[0103] In the next step S4, the controller 100 determines whether or not the detected value of the relative distance is greater than a first threshold value If the determination is NO, the controller 100 advances the control process to step S5.

[0104] On the other hand, if the determination in step S4 is YES, it is considered that a foreign object M is caught between the workpiece W and the first or second workpiece holder 10, 20, as shown in Fig. 8, for example. In this case, as is clear from a comparison between Fig. 5 and Fig. 8, the distance between the reference side pad 12 and the pressure side pad 22 becomes longer than the predetermined distance X realized at the desired "support position" (see ΔX1>0 in Fig. 8). In this case, non-contact support is not necessarily maintained, and there is a concern that damage to the workpiece W and the first and second grinding wheels 31, 32 may occur if grinding is performed in this state.

[0105] As described above, when a relative value from the predetermined distance X is set as the detection value of the distance sensor 102, the detection value referred to in step S4 corresponds to the value of the deviation ΔX1 in Fig. 8. If this deviation ΔX1 is larger than the first threshold value, the determination in step S4 becomes YES. In this case, the controller 100 determines that a foreign object M is sandwiched between the workpiece W and the first or second workpiece holder 10, 20, and advances the control process to step S6 to stop grinding of the workpiece W.

[0106] In addition, if it is assumed that the fragments resulting from chipping of the workpiece W become the foreign matter M, it is considered that the thickness (dimension in the left-right direction) of this foreign matter M will reach a maximum thickness D of the workpiece W. In that case, it can be assumed that the actual distance X' between the reference side pad 12 and the pressure side pad 22 will reach about twice the thickness D, taking into account both the workpiece W and the foreign matter M.

[0107] The deviation ΔX1 in this case is ΔX1=X'-X =2×DX …(1) It becomes.

[0108] The first threshold value according to the present embodiment is set to be smaller than the right side of the formula (1). For example, if the predetermined distance X=1000 [μm] and the thickness D=800 [μm], the right side of the formula (1) is 600 [μm]. The first threshold value is set to, for example, 500 [μm] so as to be smaller than this value.

[0109] By setting the first threshold value to be smaller than the right-hand side of formula (1), it becomes possible to detect even a case in which a foreign object M having a thickness smaller than the thickness D of the workpiece W is trapped. This makes it possible to realize detection with higher accuracy.

[0110] Furthermore, in step S5, the controller 100 judges whether or not the detected value of the relative distance is smaller than the second threshold value. If the judgment is NO, the controller 100 advances the control process to step S7 and continues grinding the workpiece W.

[0111] On the other hand, if the determination in step S5 is YES, it is considered that at least one of the reference side bolt 91, the pressure side bolt 92, and the stopper block 93 constituting the stopper mechanism 9 is worn, as shown in FIG. 9. FIG. 9 illustrates a state in which the pressure side stop pin 93b is worn. In this case, as is clear from a comparison between FIG. 5 and FIG. 9, the distance between the reference side pad 12 and the pressure side pad 22 becomes shorter than the predetermined distance X realized at the desired "support position" (see ΔX2<0 in FIG. 9). In this case, normal non-contact support is not necessarily maintained, and if grinding is performed in this state, there is a concern that the processing accuracy may deteriorate and the first and second grinding wheels 31 and 32 may be damaged. In other words, the wear of the stopper mechanism 9 may cause the abutting workpiece holders 10 and 20 to tilt or the distance between the pads to become narrow, resulting in an imbalance in the static pressure holding of the workpiece W and a deterioration in the processing accuracy.

[0112] As described above, when a relative value from the predetermined distance X is set as the detection value of the distance sensor 102, the detection value referred to in step S5 corresponds to the value of the deviation ΔX2 in Fig. 9. If this deviation ΔX2 is smaller than the second threshold value, the determination in step S5 becomes YES. In this case, the controller 100 determines that at least a part of the stopper mechanism 9 is worn, and advances the control process to step S6 to stop grinding of the workpiece W.

[0113] Thus, according to the embodiment, the controller 100 compares the detection value of the distance sensor 102 with a first threshold value set to be larger than the reference value, as shown in steps S3 to S4 of Fig. 7. By performing such a comparison, it becomes possible to detect a foreign object M caused by a chip in the workpiece W.

[0114] 7, the controller 100 compares the detection value of the distance sensor 102 with a second threshold value set to be smaller than the reference value. By performing such a comparison, it becomes possible to detect the occurrence of wear in the stopper mechanism 9.

[0115] In addition, such a configuration does not require a costly sensor such as an image sensor, etc. Therefore, the embodiment can simultaneously detect a slight chip in the workpiece or detect wear in the stopper mechanism 9 and reduce costs.

[0116] 3, the distance sensor 102 is disposed close to one of the stopper mechanisms 9 located above and to the rear compared to the center C of the reference side pad 12. If the reference side base 11 is tilted, the detection value of the distance sensor 102 will change significantly near the stopper mechanism 9. Therefore, by disposing the distance sensor 102 near the stopper mechanism 9, even if the tilt is slight, it is possible to reliably detect the tilt. This is advantageous in ensuring the accuracy of chipping or wear detection.

[0117] <Other embodiments> Figures 10 and 11 are diagrams corresponding to Figure 7, showing a modified example of the process performed by the controller 100. The only difference between the flowchart in Figure 7 and the flowchart in Figure 10 is the presence or absence of step S5. Similarly, the only difference between the flowchart in Figure 7 and the flowchart in Figure 11 is the presence or absence of step S4.

[0118] As described above, it is not essential that the controller 100 performs both the first and second processes, and it may perform only the first process as shown in FIG. 10, or may perform only the second process as shown in FIG. 11. [Explanation of symbols]

[0119] 1 Double-head surface grinding device 10 First work holder 11 Reference side base (base) 12 Reference side pad (pad) 20 Second work holder 21 Pressure side base (base) 22 Pressure pad (pad) 31 First grinding wheel (pair of grinding wheels) 32 No. 2 grinding wheel (pair of grinding wheels) 8 Moving mechanism 9 Stopper mechanism 100 Controller 102 Distance Sensor W work M Foreign object

Claims

1. A double-disc surface grinding device comprising: first and second work holders for supporting a thin plate-like work in a non-contact manner by fluid pressure at a support position determined so as to sandwich the work; and a pair of grinding wheels for grinding surfaces on both sides of the work supported by the first and second work holders, a moving mechanism for moving the first and second work holders toward the support position in a closing manner; a stopper mechanism that restricts a closing movement of the first and second work holders by the moving mechanism so that the first and second work holders are positioned at the support positions; a distance sensor for detecting a relative distance between the first and second work holders; a controller to which a detection signal from the distance sensor is input, The relative distance realized when the closing movement is restricted by the stopper mechanism and the first and second work holders are located at the support positions is defined as a reference value, and a predetermined value set to be larger than the reference value is defined as a first threshold value. The controller, based on the detection signal of the distance sensor, A detection value of the relative distance in a state in which the first and second work holders are closed is compared with the first threshold value; If the relative distance is greater than the first threshold value, it is determined that a foreign object is sandwiched between the workpiece and the first or second workpiece holder, and grinding of the workpiece is stopped. A double-disc surface grinding device.

2. A double-disc surface grinding device comprising: first and second work holders for supporting a thin plate-like work in a non-contact manner by fluid pressure at a support position determined so as to sandwich the work; and a pair of grinding wheels for grinding surfaces on both sides of the work supported by the first and second work holders, a moving mechanism for moving the first and second work holders toward the support position in a closing manner; a stopper mechanism that restricts a closing movement of the first and second work holders by the moving mechanism so that the first and second work holders are positioned at the support positions; a distance sensor for detecting a relative distance between the first and second work holders; a controller to which a detection signal from the distance sensor is input, The relative distance realized when the closing movement is restricted by the stopper mechanism and the first and second work holders are located at the support positions is defined as a reference value, and a predetermined value set to be smaller than the reference value is defined as a second threshold value. The controller, based on the detection signal of the distance sensor, A detection value of the relative distance in a state in which the first and second work holders are closed is compared with the second threshold value; If the relative distance is smaller than the second threshold value, it is determined that wear has occurred in the stopper mechanism, and grinding of the workpiece is stopped. A double-disc surface grinding device.

3. A double-disc surface grinding device comprising: first and second work holders for supporting a thin plate-like work in a non-contact manner by fluid pressure at a support position determined so as to sandwich the work; and a pair of grinding wheels for grinding surfaces on both sides of the work supported by the first and second work holders, a moving mechanism for moving the first and second work holders toward the support position in a closing manner; a stopper mechanism that restricts a closing movement of the first and second work holders by the moving mechanism so that the first and second work holders are positioned at the support positions; a distance sensor for detecting a relative distance between the first and second work holders; a controller to which a detection signal from the distance sensor is input, The relative distance realized when the closing movement is restricted by the stopper mechanism and the first and second work holders are located at the support positions is defined as a reference value, a predetermined value set to be larger than the reference value is defined as a first threshold value, and a predetermined value set to be smaller than the reference value is defined as a second threshold value. The controller, based on the detection signal of the distance sensor, A detection value of the relative distance in a state in which the first and second work holders are closed is compared with the first threshold value; When the relative distance is greater than the first threshold value, it is determined that a foreign object is sandwiched between the workpiece and the first or second workpiece holder, and grinding of the workpiece is stopped. When the relative distance is smaller than the second threshold value, it is determined that wear has occurred in the stopper mechanism, and grinding of the workpiece is stopped. A double-disc surface grinding device.

4. 4. The double disc surface grinding apparatus according to claim 1, The first and second work holders are each A base that slides in accordance with the operation of the moving mechanism; A pad is disposed on an end surface of the base and supports the workpiece in a non-contact manner, the stopper mechanism is disposed between the bases of the first and second work holders so as to surround the pads of the first and second work holders, the distance sensor is disposed adjacent to at least one of the plurality of stopper mechanisms; The distance between the distance sensor and the stopper mechanism adjacent to the distance sensor is shorter than the distance between the distance sensor and the center of the pad. A double-disc surface grinding device.

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