JP2011105560A - Core drill and drilling method of glass plate using the drill - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately form a through hole by preventing core deviation or reduction in machining accuracy resulting from the core deviation as much as possible while allowing smooth supply of cooling fluid to a drill tip, in the piercing of a glass plate using a core drill. <P>SOLUTION: The outer circumferential surface 11 of a cutting part provided on the tip side of the core drill 10 has a cross section of a round shape, and the center O is on the axis of rotation of the core drill 10. The inner circumferential surface 12 of the core drill 10 has a plurality of bulged parts 15 each having a shape bulged on the outer diameter side from an imaginary inscribed circle 13 which is in contact with a minimum diameter part 14 of the inner circumferential surface 12 when seen from a cross section perpendicular to the axis of rotation of the core drill 10. All of the plurality of bulged parts 15 are arranged so that they are symmetrical about the axis of rotation of the core drill 10. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a core drill and a method for drilling a glass plate using the drill.

  As is well known, some glass substrates used for flat panel displays such as plasma display (PDP), field emission display (FED), and electroluminescence display (ELD) are used for exhaust and gas filling in the panel. For this purpose, there is one that forms a through hole.

  For example, in the case of a PDP, in order to generate an effective plasma discharge, it is necessary to enclose a gas such as Xe or Ar in the space between the front plate and the back plate. A through hole having a diameter of about several millimeters for discharging air and filling the gas is formed at one or a plurality of locations. Also, in the case of FED, since the space between the front plate and the back plate needs to be high vacuum, one or more penetrations are made in the peripheral portion or corner portion of the back plate in the same manner as the glass substrate for PDP. A hole is formed.

  Thus, when forming a through-hole in the thickness direction of a glass plate, a core drill is normally used from the viewpoint of both processing accuracy and processing speed (productivity). This drill has a hollow cutting edge shape and is made by fixing cutting abrasive grains such as diamond abrasive grains and CBN abrasive grains on the surface of a cylindrical base metal as a base (surface type) ), And those using chips formed by dispersing and arranging the abrasive grains in metal bonds (impletype) are known.

  By the way, when drilling a glass plate using the above-described core drill, a columnar uncut object called a core may remain inside the hollow hole of the core drill after processing. The core is generated in the thickness direction of the glass plate as the core drill cuts, and is normally generated in a state of being fitted with almost no gap between the core drill and the hollow hole. Therefore, for example, when performing drilling while supplying coolant or cutting fluid to the drill tip processing location through the hollow hole, smooth supply of coolant or the like to the drill tip is hindered by the core, and at the cutting location. Cooling efficiency tends to be insufficient or uneven. In this case, the cutting conditions (cutting speed and the like) must be relaxed, and as a result, the processing speed may be reduced. In addition, there is a concern that the cutting efficiency generated by the drilling process may not be sufficiently discharged, leading to a reduction in cutting efficiency.

  As a countermeasure against the above-mentioned problem, for example, in Patent Document 1 below, the core diameter is made smaller than the inner diameter by making the inner diameter center of the electrodeposition layer forming portion serving as a cutting portion eccentric from the outer diameter center by a predetermined amount. Thus, there has been proposed an electrodeposition tool (core drill) that secures a predetermined gap between the inner peripheral surface of the cutting part and the outer peripheral surface of the core and enables smooth supply of the coolant.

JP-A-8-118124

  In recent years, as the demand for the above-described flat panel display increases, the demand for improving the productivity of the corresponding glass substrate has also increased. For this reason, increasing the speed of drilling a glass substrate using the core drill has been an issue. On the other hand, there is a present situation that a glass substrate used for processing is thinned due to the thinning and lightening of the display. Therefore, if the holes are drilled under the same processing conditions as before, the glass substrate is likely to be cracked, and it is difficult to increase the processing speed.

Here, as shown in FIG. 9, when drilling is performed using a core drill 100 having a hole 102 coaxial with the outer peripheral surface 101 serving as a cutting surface, a hole having an inner diameter equal to the outer diameter of the core drill 100 is formed. It will be formed on a glass plate. On the other hand, when the electrodeposition tool (core drill) described in Patent Document 1 is used, the core runout is caused by the difference in the thickness (radial width) of the drill cutting portion in the circumferential position. It is likely to occur. Specifically, as shown in FIG. 10, since the cutting resistance is increased in the relatively thick portion 203 of the cutting portion (electrodeposit layer forming portion) 200 as compared with the thin portion 204, this resistance difference is eliminated. the direction of the force, the force F directed to the center O ₂ of the inner peripheral surface 202 from the center O ₁ of the outer peripheral surface 201 in terms of the FIG. 10 is applied to the core drill (cutting portion 200). As a result of the radial force F acting on the cutting part 200 in this way, the core drill is caused to run out, and a through hole having an inner diameter larger than the outer diameter of the cutting part 200 is formed in the glass substrate. .

Further, since the through hole is formed by drilling with the deflection of the drill tip, the processing accuracy is likely to be insufficient, and the finished state of the inner peripheral surface is likely to vary. In addition, there is a concern that the strength of the through hole may be reduced. This is because if the inner peripheral surface property of the through-hole is unstable and a defect such as a micro crack is present, damage can be caused relatively easily starting from the defect. Furthermore, since the core drill disclosed in Patent Document 1 has a center of gravity at a position shifted in the radial direction from the rotation axis (passing through the center O ₁ of the outer peripheral surface 201), this is also the core of the drill. There is a risk of acting in a direction that promotes runout. The above problems tend to become more prominent as the machining speed (for example, the cutting speed) increases. Therefore, when trying to increase the processing speed in order to improve the productivity, the core runout of the core drill becomes remarkable, and the processing accuracy is lowered.

  In view of the above circumstances, in the present invention, in the drilling of a glass plate using a core drill, while allowing the coolant to be smoothly supplied to the tip of the drill, the center runout or the processing accuracy due to the runout is reduced. It is a technical problem to prevent through as much as possible and form the through hole with high accuracy.

  The solution to the above problem is achieved by the core drill according to the present invention. That is, this core drill is a core drill for performing a predetermined drilling process on a glass plate at a cutting portion provided on the tip side of the drill, and the inner peripheral surface of the cutting portion is an inner periphery when viewed in an arbitrary cross section perpendicular to the axis. It has a plurality of bulging portions that have a shape that bulges from the virtual inscribed circle that contacts the smallest diameter portion of the surface to the outer diameter side, and the plurality of bulging portions are all symmetric about the rotation axis of the cutting portion It is characterized by the points arranged as follows.

  As described above, in the core drill according to the present invention, since the cross-sectional shape of the inner peripheral surface thereof is a non-circular shape, the thickness (radial direction) of the core drill cutting portion is the same as in the case of the conventional core drill. It also appears that a radial force F (see FIG. 10) arises due to the non-uniformity of the (width) at the circumferential position. However, in the present invention, as described above, the bulging portions constituting the inner peripheral surface are arranged so as to be symmetric around the rotation axis of the cutting portion. Will be offset. Therefore, the runout of the core drill caused by the radial force can be suppressed. In addition, since the center of gravity of the cutting part can be placed on the rotation axis (or the center of gravity of the cutting part can be as close as possible to the rotation axis), the core runout of the core drill can be reduced as much as possible. Moreover, according to the said structure, the core of the diameter equivalent to the virtual inscribed circle which contact | connects the minimum diameter part in the internal peripheral surface of a core drill cutting part is produced | generated with a drilling process. Therefore, the space formed between the core and the bulging portion of the shape that bulges from the virtual inscribed circle to the outer diameter side can be used as a supply flow path for cooling liquid, etc. A rich coolant can be supplied smoothly. As a result, the cooling efficiency of the cutting portion can be improved and the cutting efficiency can be increased. For example, even if the processing speed is increased, the processing accuracy can be ensured, and the through hole having the required surface accuracy or strength can be formed in a short time. Can be formed.

  Here, the plurality of bulging portions are continuous with each other at their circumferential ends, and thereby the inner peripheral surface of the cutting portion may be constituted by a plurality of bulging portions.

  By comprising in this way, the minimum diameter part of an internal peripheral surface and a virtual inscribed circle will contact | connect in the state which made the point contact or the contact area very small. Since the virtual inscribed circle corresponds to the outer peripheral surface of the core, the inner peripheral surface and the core of the core drill cutting part at the time of drilling are formed by configuring the inner peripheral surface to contact the virtual inscribed circle as described above. The contact area of the outer peripheral surface can also be reduced. Thereby, the cutting resistance acting on the core drill can be reduced, and the processing accuracy can be further improved. In this case, the inner peripheral surface is contacted (supported) with a constant pitch in the circumferential direction with respect to the core, so that the posture of the cutting portion is stabilized. This also improves the processing accuracy of the through hole by the core drill.

  Further, the tip surface of the cutting part may have a plurality of radial grooves extending in the radial direction, and in this case, the plurality of radial grooves are all arranged symmetrically around the rotation axis. May be.

  Thus, by providing the groove portion in the radial direction on the tip surface of the cutting portion, the coolant supplied to the drill tip through the gap between the bulge portion and the core can be smoothly discharged to the outside of the core drill. Further, in this case, by arranging the plurality of radial grooves so as to be symmetrical around the rotation axis of the cutting part, the occurrence or increase of runout due to the provision of the grooves on the tip surface is made as much as possible. This prevents the runout from occurring.

  In addition, the outer peripheral surface of the cutting part may have a plurality of axial grooves extending in the axial direction, and in this case, the plurality of axial grooves are all arranged symmetrically around the rotation axis. May be.

  Thus, by providing an axial groove on the outer peripheral surface of the cutting part, the coolant that is supplied to the drill tip through the gap between the bulging part and the core, and then flows out to the outer peripheral side of the core drill, like the radial groove. Etc. can be smoothly discharged to the base end side of the drill. Further, in this case, by arranging the plurality of axial grooves so as to be symmetric around the rotation axis of the cutting portion, the occurrence or increase of runout due to the provision of the grooves on the outer peripheral surface is made as much as possible. This prevents the runout from occurring.

  Or the some radial direction groove part provided in the front end surface of the cutting part may be continued with the bulging part on the inner diameter side, and may be continued with the axial direction groove part on the outer diameter side.

  Each of the above-described radial groove portion and axial groove portion has a discharge action of a predetermined coolant or the like alone, but as described above, by making the radial groove portion continuous with the bulging portion and the axial groove portion, The coolant supplied to the drill tip through the gap between the bulge and the core can be discharged smoothly and reliably to the drill base end through the radial groove and the axial groove. Accordingly, drilling can be performed while supplying a large amount of cutting fluid, and cooling efficiency and cutting efficiency can be further improved.

  In the core drill according to the present invention, the inner diameter of the through hole formed in the glass plate may be 1 mm or more and 5 mm or less. In the small-diameter drilling process, the core drill itself is also thin and relatively easy to cause core runout, and there is a limit to increasing the rigidity of the drill, but with the core drill according to the present invention, the end face of the glass plate As long as the drilling is performed in the direction in which the load acts vertically, the runout can be prevented or the runout can be minimized. In addition, the coolant and the like can be smoothly supplied using the space between the bulging portion and the core. As mentioned above, even if it is a through-hole of a comparatively small diameter, the through-hole with a smooth and favorable surface accuracy can be perforated and formed in a glass plate.

  Moreover, the solution of the above-mentioned problem is also achieved by the glass plate perforating method according to the present invention. That is, this drilling method is a method in which a predetermined drilling process is performed on the glass plate with a cutting part provided at the tip of the core drill. The inner peripheral surface of the cutting part is an inner periphery when viewed in an arbitrary cross section perpendicular to the axis. It has a plurality of bulging portions that have a shape that bulges from the virtual inscribed circle that contacts the smallest diameter portion of the surface to the outer diameter side, and the plurality of bulging portions are all symmetric about the rotation axis of the cutting portion It is characterized by the points arranged as follows.

  The above-described drilling method also has the same technical characteristics as the core drill described at the beginning of this section, so that the same effect as the effect of the core drill can be obtained.

  As described above, according to the core drill according to the present invention and the method for drilling a glass plate using the drill, in the drilling process of the glass plate using the core drill, the coolant can be smoothly supplied to the tip of the drill. However, the through-hole can be formed with high accuracy by preventing as much as possible the deterioration of the processing accuracy due to the core runout or the runout.

It is an axis orthogonal sectional view of a core drill concerning a 1st embodiment of the present invention. (A)-(d) is each one Embodiment of the drilling method of the glass plate using the core drill which concerns on this invention, Comprising: Of the drilling processing of the glass plate using the core drill shown in FIG. It is sectional drawing which shows the outline | summary of the drilling operation | work by chronological order. (A)-(c) is sectional drawing which shows the outline | summary of the drilling | boring operation | work by a subsequent drill among the drilling processes of the glass plate using the core drill shown in FIG. 1, respectively. It is an axis orthogonal sectional view of a core drill concerning a 2nd embodiment of the present invention. It is a shaft-containing sectional view of a core drill according to a third embodiment of the present invention. It is an axial orthogonal sectional view of the core drill shown in FIG. It is the top view seen from the drill front end side of the core drill shown in FIG. It is the top view seen from the drill front end side of the core drill which concerns on 4th Embodiment of this invention. It is an axial orthogonal cross section of the conventional core drill. It is an axial orthogonal cross section of the conventional core drill.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS.

  FIG. 1 shows an axial orthogonal cross-sectional view of a core drill 10 according to a first embodiment of the present invention. The core drill 10 has a generally cylindrical shape. For example, the abrasive grains such as diamond abrasive grains and CBN abrasive grains are fixed to the surface of a metal base serving as a base of the core drill 10 with an appropriate fixing material. The tip side can be used as a cutting part.

  Here, when attention is paid to the cross-sectional shape of the core drill 10 (the cutting portion thereof), the outer peripheral surface 11 of the core drill 10 has a perfectly circular cross-section, and its center O is on the rotation axis of the core drill 10. Further, as shown in FIG. 1, the inner peripheral surface 12 of the core drill 10 has a virtual inscribed circle 13 that is in contact with the minimum diameter portion 14 of the inner peripheral surface 12 when viewed in an axis orthogonal cross section orthogonal to the rotation axis of the core drill 10. It has a plurality of bulging portions 15 that have a shape bulging from the outer diameter side (circle shown by a one-dot chain line in FIG. 1). The plurality of bulging portions 15 are all arranged symmetrically around the rotation axis of the core drill 10.

  In this embodiment, the inner peripheral surface 12 has a so-called “Dharma-shaped” cross-sectional shape, and the two bulging portions 15 both have a circular arc cross-section, and both are symmetrical about the rotation axis by 180 °. Thus, it arrange | positions in the position which opposes on both sides of a rotating shaft. Moreover, these two bulging parts 15 are exhibiting the shape which continued mutually in the circumferential direction end, and the inner peripheral surface 12 is comprised by these bulging parts 15 and 15. FIG. In this case, the continuous part (connected part) between the two bulging parts 15 and 15 becomes the minimum diameter part 14 of the inner peripheral surface 12, and the minimum diameter part 14 faces two places across the rotating shaft. Formed in position (see FIG. 1). In this embodiment, each of the minimum diameter portions 14 has a form in which two bulging portions 15 having an arcuate cross section are smoothly connected by a cross section R. The minimum diameter portion 24 in the second embodiment to be described later has a similar form.

  The core drill 10 having the above-described cross-sectional shape is used in a method for punching a glass plate in the following manner, for example. Hereinafter, an embodiment of a method for drilling a glass plate using a core drill according to the present invention will be described by taking as an example the case of forming a through hole as an exhaust hole in a glass substrate for PDP. Note that the “up and down” direction in the following description is merely defined for easy understanding of the positional relationship between elements in each drawing. Therefore, it does not specify the installation direction or use mode of the core drill described below or the installation direction of the glass plate.

  2 and 3 show an outline of a method for punching a glass plate using the core drill 10 shown in FIG. In the drilling method according to these drawings, the core drill 10 as a preceding drill is inserted in the thickness direction by cutting from the lower end surface side of the glass plate 16 to form the bottomed hole 18, and then the core drill 10 is moved backward. After that, a through hole 19 is formed in the glass plate 16 by cutting the core drill 10 as a subsequent drill into the same direction as the preceding drill with cutting from the upper end surface side of the glass plate 16. Among these, FIG. 2 is sectional drawing which showed the outline | summary of the drilling operation | work by the preceding drill in the said drilling process in order of the time series from (a) to (d). Moreover, in FIG. 2, the core drill 10 is shown as a shaft-containing cross-sectional view when seen in the AA cross section of FIG.

  Here, the core drill 10 used as the leading drill and the trailing drill is coaxially arranged in a state of facing each other across the glass plate 16. Further, both core drills 10 are configured to be able to move up and down and rotate independently of each other.

  Next, a procedure for forming a through-hole in a glass plate using two core drills 10 (preceding drill and following drill) will be described with reference to FIGS.

  First, as shown in FIG. 2 (a), the core drill 10 as a preceding drill disposed below the glass plate 16 in a horizontal posture is raised with rotation, whereby the core drill 10 is moved to the lower end surface of the glass plate 16. It penetrates in the thickness direction with cutting from the side. At this time, the core drill 10 is allowed to enter the glass plate 16 while supplying a coolant such as water to the tip of the core drill 10 that is a cutting point through the inner peripheral surface 12 that is a hollow hole of the core drill 10. And even after the front-end | tip of the core drill 10 contact | abuts to the lower end surface of the glass plate 16, as shown in FIG.2 (b), the front end side of the core-drill 10 used as a cutting part is continued by continuing the raise operation | movement of the core drill 10. The glass plate 16 is cut perpendicularly to the lower end surface. Thereby, a cylindrical incision region by the core drill 10 is generated on the lower end surface side of the glass plate 16, and at the same time, a columnar core 17 shown in FIG. 2B is generated inside the incision region. .

  At this time, since the two bulging portions 15 constituting the inner peripheral surface 12 are arranged so as to be 180 ° symmetrical about the rotation axis of the core drill 10, the core drill is provided by providing the bulging portion 15. Even if the thickness of 10 varies, the radial force F (see FIG. 10) caused by the variation is canceled out. Therefore, the drilling operation can be continued in a state in which the core runout of the core drill 10, particularly the runout on the drill tip side serving as a cutting portion is suppressed. Moreover, by arranging the two bulging portions 15 as described above, the center of gravity of the entire core drill 10 can be made as close as possible to the rotation axis thereof, and thereby the core runout of the core drill 10 can be suppressed.

  At this time, since the outer periphery of the core 17 is mainly formed by cutting at the minimum diameter portion 14 of the inner peripheral surface 12 of the core drill 10, the outer diameter of the core 17 is the virtual inscribed circle 13 shown in FIG. Equal to the radial dimension of Therefore, a radial clearance corresponding to the difference between the maximum inner diameter of the bulging portion 15 and the outer diameter of the core 17 is between the inner peripheral surface 12 of the core drill 10 and the outer peripheral surface of the core 17 during the cutting operation. It will be empty. Therefore, when drilling is performed while supplying the coolant to the tip of the core drill 10 as described above, the tip of the core drill 10 where abundant coolant becomes a cutting point through the gap between the bulging portion 15 and the core 17. To be supplied. Thereby, the cooling efficiency in the cutting part of the core drill 10 thru | or the cutting efficiency can be improved, and the lifetime improvement can be achieved. Further, since the cooling efficiency and the cutting efficiency can be increased, the rotational speed or cutting speed of the core drill 10 can be increased.

  In the case where two minimum diameter portions 14 are formed at positions that are 180 ° symmetrical about the rotation axis of the core drill 10 as in this embodiment, the core 17 is formed by the minimum diameter portions 14 and 14 extending in the axial direction. The drilling operation is performed with two points supported. Therefore, it is possible to perform the drilling operation with the cutting resistance acting on the core drill 10 reduced as much as possible, thereby further improving the processing accuracy. Moreover, since it contacts with the core 17 at intervals of 180 °, even when a corresponding gap is generated between the bulging portion 15 and the core 17, the posture of the core drill 10 can be stabilized. It is possible to perform the drilling operation with high accuracy.

  Then, as shown in FIG. 2 (c), when the core drill 10 has entered the intermediate position in the axial direction of the glass plate 16 while leaving a predetermined thickness dimension on the upper end surface side of the glass plate 16, the core drill 10 Stop rising. Then, the descending operation of the core drill 10 is started from this state, and as shown in FIG. 2D, the core drill 10 is extracted from the glass plate 16 and moved to the retracted position shown in FIG. As a result, the glass plate 16 is formed in a substantially cylindrical shape following the shape of the core drill 10 and is formed with a bottomed hole 18 in a non-penetrating state in which only the lower part is opened. A core 17 having a height equal to the depth remains.

  Next, as shown in FIG. 3 (a), the core drill 10 is lowered from the upper end surface side of the glass plate 16 by lowering the core drill 10 as a subsequent drill disposed above the glass plate 16 with rotation. It penetrates in the thickness direction with cutting. In this case, since the core drill 10 arranged above the glass plate 16 is arranged in a state where the lower core drill 10 previously drilled (preceding drill) and its axis are aligned, the glass plate 16 has already been aligned. A drilling operation to be described later is performed in a state where the axis of the formed bottomed hole 18 and the axis of the subsequent drill (core drill 10) coincide with each other. And even after the front-end | tip of the core drill 10 as a subsequent drill contact | abuts to the upper end surface of the glass plate 16, the front-end side of the core drill 10 used as a cutting part continues on the glass plate 16 by continuing the downward movement of the core drill 10. Cut vertically to the end face. Thereby, the cutting area | region by the core drill 10 is produced | generated by the upper end surface side of the glass plate 16, and the columnar core 17 shown to Fig.3 (a) is produced | generated inside the said cutting area | region.

  Of course, also in this case, since the two bulging portions 15 constituting the inner peripheral surface 12 are both arranged 180 degrees symmetrical around the rotation axis of the core drill 10, the core runout of the core drill 10 is reduced. The drilling operation can be continued in a suppressed state. In addition, since abundant coolant is supplied to the distal end side of the core drill 10 serving as a cutting point through the gap between the bulging portion 15 and the core 17, the cooling efficiency or cutting efficiency in the cutting portion of the core drill 10 is increased, Long life can be achieved. Alternatively, the rotational speed or cutting speed of the core drill 10 can be increased.

  Then, by continuing to lower the core drill 10 and further entering the glass plate 16, as shown in FIG. 3B, all of the bottom portion of the bottomed hole 18 formed by the core drill 10 is scraped off. Thereby, the cores 17 and 17 extending vertically in the thickness direction of the glass plate 16 are also removed (separated from the glass plate 16 main body and dropped), and a through hole 19 having a constant inner diameter is formed. Then, from the state where the core drill 10 is lowered to a predetermined position in the thickness direction (see FIG. 3B), the core drill 10 starts to move upward, and as shown in FIG. 10 is extracted and moved to the retracted position shown in FIG. Thereby, the glass plate 16 is formed with through holes 19 as exhaust holes having openings on both end faces. Further, the inner peripheral surface of the through hole 19 is ground in a state where the core runout is suppressed by the core drill 10 over the entire axial direction region and a sufficient amount of cooling liquid is supplied to the tip of the core drill 10 serving as a cutting portion. Therefore, the inner peripheral surface of the through hole 19 is finished with high accuracy.

  In the above, one embodiment of the core drill according to the present invention and the method of drilling a glass plate using the drill has been described. However, these are not limited to the above-described exemplary forms, and are arbitrary within the scope of the present invention. It can take a form.

  FIG. 4 shows a cross-sectional view perpendicular to the axis of the core drill 20 according to the second embodiment of the present invention. As shown in FIG. 4, the core drill 20 includes a virtual inscribed circle 23 that contacts the minimum diameter portion 24 of the inner peripheral surface 22 when viewed in an axial orthogonal section orthogonal to the rotation axis of the core drill 10 (1 in FIG. 4). It has a plurality of bulging portions 25 that exhibit a shape bulging from the outer diameter side from a circle indicated by a chain line, and each of the plurality of bulging portions 25 is the rotation axis of the core drill 20 (the center of the outer peripheral surface 21). It is the same as the core drill 10 according to the first embodiment in that it is arranged so as to be symmetrical around (through O). However, in this embodiment, the core drill according to the first embodiment is that the bulging portions 25 are arranged at circumferential positions at equal pitches so that all of the bulging portions 25 are symmetrical about the rotation axis. 20 and different.

  As described above, since the three bulging portions 25 constituting the inner peripheral surface 22 are all arranged so as to be symmetrical about 120 ° around the rotation axis of the core drill 20, the bulging portion 25 is provided. Even if the thickness of the core drill 20 varies, the radial force F (see FIG. 10) caused by the variation is canceled out. Therefore, similarly to the core drill 10 according to the first embodiment, the drilling method shown in FIGS. 2 and 3 can be performed in a state in which the core runout of the core drill 20, particularly the runout on the drill tip side serving as a cutting portion is suppressed. Become. Moreover, by arranging the three bulging portions 25 as described above, the center of gravity of the entire core drill 20 can be made as close as possible to the rotation axis thereof, and thereby the core runout of the core drill 20 can be suppressed.

  Further, when the drilling shown in FIGS. 2 and 3 is performed using the core drill 20 shown in FIG. 4, it is generated on the glass plate by the inner peripheral surface 22 of the core drill 20 during the cutting operation and the drilling work of the core drill 20. A gap in the radial direction corresponding to the difference between the maximum inner diameter of the bulging portion 25 and the outer diameter of the core 17 is left between the outer peripheral surface of the core 17 (see FIGS. 2 and 3). . Therefore, as in the first embodiment, an abundant coolant can be supplied to the distal end side of the core drill 20 serving as a cutting location through the gap between the bulging portion 25 and the core 17, and cooling efficiency or cutting efficiency in the cutting portion of the core drill 20. Can be increased. Further, since the cooling efficiency and the cutting efficiency can be increased, the rotational speed or the cutting speed of the core drill 20 can be increased.

  In this embodiment, the three bulging portions 25 have a shape that is continuous with each other at the circumferential ends, and the inner circumferential surface 22 is configured by these three bulging portions 25. In this case, a continuous portion (connected portion) between the three bulging portions 25, 25, 25 becomes the minimum diameter portion 24 of the inner peripheral surface 22, and the minimum diameter portions 24 are arranged at three positions and at a 120 ° pitch. (See FIG. 4). Therefore, when drilling a glass plate using this core drill 20, drilling is performed in a state where the core is supported at three points at equal intervals in the circumferential direction by these three minimum diameter portions 24, 24, 24 extending in the axial direction. Work will be done. Therefore, compared with 1st Embodiment, it becomes possible to perform said drilling operation | work by the core drill 20 with a sufficient state in the state which maintained the more stable attitude | position.

  Of course, as long as the plurality of bulging portions 15 and 25 are arranged so as to be symmetrical around the rotation axis of the core drills 10 and 20, the shape and number thereof are arbitrary. Although not shown in the drawings, four or more bulging portions 15 and 25 may be provided on the inner peripheral surfaces 12 and 22, and the bulging portions 15 and 25 having a shape other than an arcuate cross section are provided on the inner peripheral surface. It may be provided on the surfaces 12 and 22. For example, it is possible to adopt a form in which the two bulging portions 15 are both elliptical arc shapes and the bulging portions 15 and 15 are both smoothly connected. In this case, both the bulging portions 15 and 15 form one elliptical shape, that is, the inner peripheral surface 12 has a cross-sectional elliptical shape. Moreover, you may make it arrange the some bulging parts 15 and 25 intermittently in the circumferential direction. In this case, a cross-sectional shape in which the plurality of bulging portions 15 and 25 are connected by a perfect circular arc surface having the same diameter as the virtual inscribed circles 13 and 23 is exhibited. However, in any of the above-described forms, the bulging portions 15 and 25 have virtual inscribed circles 13 and 23 to the extent that smooth supply or abundant supply of coolant or the like to the drill tip side can be ensured. It is important to exhibit a cross-sectional shape bulging by a predetermined amount from the outer diameter side to the outer diameter side.

  In addition, when supply of abundant coolant or the like to the drill tip is taken into account, for example, the form shown in FIG. 5 (third embodiment) can be adopted. The core drill 30 shown in this figure is obtained by further providing a groove for discharging coolant or the like in the core drill 10 described in the first embodiment. More specifically, the core drill 30 shown in FIG. 5 has a plurality of radial directions extending radially at its distal end surface and continuing at the inner circumferential surface 12 and its inner diameter end and continuing at the outer circumferential surface 11 and its outer diameter end. A groove 31 is provided. In the illustrated example, in addition to the radial groove 31, the outer peripheral surface 11 has a plurality of axial grooves 32 extending in the axial direction. In this embodiment, as shown in FIG. 6, the axial groove 32 has a constant cross-sectional shape (cross-sectional arc shape) along the axial direction. The radial groove 31 also has a constant cross-sectional shape (cross-sectional arc shape) along the radial direction, although illustration is omitted.

  By providing the radial groove portion 31 and the axial groove portion 32 in this way, the bulging portion 15 and the core 17 (see FIG. 2) are formed during drilling through the hollow hole (inside the inner peripheral surface 12) of the core drill 30. The coolant or the like supplied to the drill distal end through the gap can be discharged to the outside of the core drill 30 and the drill proximal end through the radial groove 31 and the axial groove 32. Therefore, the cooling efficiency or cutting efficiency of the core drill 30 can be further increased. Further, in this embodiment, the same number of radial grooves 31 and axial grooves 32 as the bulging portions 15 are provided, and each radial groove 31 is connected to the bulging portion 15 at the inner diameter end thereof, and outside thereof. Since it is made to continue with the axial direction groove part 32 at a diameter end, said discharge | emission action can be improved further.

  In addition, in this embodiment, as shown in FIGS. 6 and 7, a plurality (two) of radial grooves 31 having the same shape and dimensions are arranged so as to be symmetrical around the rotation axis of the core drill 30. Therefore, by providing the radial groove 31, it is possible to avoid as much as possible a situation in which the rotational accuracy (the degree of runout) of the core drill 30 is adversely affected, and to ensure machining accuracy. Similarly, with respect to the axial groove 32, a plurality of (two) axial grooves 32 having the same shape and size are all arranged symmetrically around the rotation axis of the core drill 30. By providing as much as possible, a situation in which the rotational accuracy of the core drill 30 is adversely affected is avoided as much as possible, and the processing accuracy can be ensured.

  Moreover, said radial direction groove part 31 and axial direction groove part 32 are applicable to a core drill irrespective of the form and number of bulging parts. FIG. 8: has shown the top view which looked at the core drill which concerns on 4th Embodiment of this invention from the drill front-end | tip. The core drill 40 shown in this figure is obtained by providing the core drill 20 according to the second embodiment with the same number of radial grooves 41 and axial grooves 42 as the bulging portions 25. Therefore, according to the core drill 40, in addition to the operational effects obtained by the core drill 20 according to the second embodiment, the operational effects described in the third embodiment can be enjoyed.

  Of course, the arrangement | positioning aspect of the said radial direction groove parts 31 and 41 and the axial direction groove parts 32 and 42 is not restricted to the said form. As long as there is no hindrance to the discharge of the coolant, the radial groove portions 31 and 41 may not be continuous with the bulging portions 15 and 25 or the axial groove portions 32 and 42. Further, the influence of the radial groove portions 31 and 41 and the axial groove portions 32 and 42 on the degree of runout of the core drills 10 and 20 is smaller than that of the bulging portions 15 and 25. , 42 are not necessarily arranged so as to be symmetrical around the rotation axis of the core drills 10,20. From this, the number of the radial groove portions 31 and 41 and the axial groove portions 32 and 42 is not limited to a plurality (only one may be used).

  About the structure regarding the above core drills 10 and 20, it is not necessary to be provided over the axial direction full length of the core drills 10 and 20, and from the drill tip used as a cutting part to the height (cutting depth) of the core 17 at least. What is necessary is just to be provided in the axial direction area | region.

  Moreover, in the above description, although the case where the through-hole 19 was formed in the glass plate 16 using the two core drills 10 was illustrated as a method for perforating the glass plate according to the present invention, of course, other than the above-described perforation methods. Also, the core drill 10 according to the present invention can be applied. For example, the core drill 10 according to the present invention may be used only for the preceding drill, and another core drill may be used for the subsequent drill. Or you may make it form the through-hole penetrated from the one end surface side of the glass plate 16 to the other end surface side by one drilling operation using one core drill 10.

  In the above description, the present invention is applied to the case where a through hole as an exhaust hole is formed in a glass substrate for PDP. However, in the case where a through hole is formed in a glass substrate for FED or ELD in addition to this, The present invention can also be applied to the same. Moreover, if it is a core drill which concerns on this invention, since a high processing precision can be exhibited by the outstanding cooling effect and a core runout suppression effect, the glass plate which has the thickness which remove | deviates from the above suitable range (1 mm or more and 5 mm or less) Needless to say, the present invention can be applied.

  Of course, other specific forms can be adopted for matters other than the above as long as the technical significance of the present invention is not lost.

  In order to confirm the effect of the present invention, the following tests and examinations were conducted. Through holes are formed in a glass plate using the core drill according to the present invention (Example) and a conventional core drill (Comparative Example), respectively, and the difference in grinding speed (cutting speed) in the thickness direction at that time is the core. The degree of influence on the shake amount was verified. The common items will be described first. First, 50 glass substrates for PDP each having a horizontal dimension of 500 mm, a vertical dimension of 600 mm, and a thickness of 1.8 mm were prepared for the glass plates forming the through holes. And the through-hole used as an exhaust hole was formed in the said glass plate using the core drill which has the shape and dimension mentioned later. In any of the drilling operations, first, a core drill is inserted from a lower surface side of the glass substrate by a certain amount (for example, 70% of the thickness dimension) and then cut, and then the core drill is inserted from the upper surface side and penetrated to form a through hole. I did it. At this time, the grinding speed (cutting speed) in the thickness direction is gradually increased from 0.1 mm / min to 1.1 mm / min in increments of 0.2 mm / min, and in each case, the glass plate is penetrated. Holes were drilled. The number of rotations of the core drill was the same.

  Here, the core drill of the shape shown in FIG. 1 was used for the core drill according to the example. Moreover, the core drill of the shape shown in FIG. 10 was used for the core drill which concerns on a comparative example. The outer diameter is 2.0 mm. The minimum diameter of the inner peripheral surface (the diameter of the virtual inscribed circle) was 0.35 mm, and the maximum bulge amount from the virtual inscribed circle of the bulged portion was 0.65 mm. On the other hand, as shown in FIG. 10, the core drill which concerns on a prior art example used the core drill which exhibits the cross-sectional shape in which the inner peripheral surface center was eccentric with respect to the outer peripheral surface center. The outer diameter was 2.0 mm as in the example. The inner diameter was 1.0 mm and the amount of eccentricity was 0.2 mm.

Then, using each of the above core drills, through holes are formed in the glass plate for each of the set grinding speeds (cutting speeds), and then the diameters of the formed through holes are measured. 2.0 mm) was calculated as the amount of runout. The results are shown in Table 1 below. The numerical values shown in the middle and lower parts of Table 1 indicate the amount of runout. Note that the conventional core drill shown in FIG. 9 was similarly perforated, but the core was clogged in the hollow hole, and the required through hole could not be formed.

  As can be seen from Table 1 above, it was found that when the through hole was formed in the glass plate with a conventional core drill, the amount of runout increased as the cutting speed increased. In particular, it can be seen that the amount of runout of the core increases abruptly when the cutting speed exceeds 0.5 mm / min. Here, when the center runout amount is larger than 30 μm, the surface property of the processed surface (the inner peripheral surface of the through hole) becomes unstable, and the surface roughness also varies greatly. On the other hand, when the through hole was formed by drilling with the core drill according to the present invention, no runout was observed at any cutting speed. From this, it has been found that the core drill according to the present invention is effective in suppressing a decrease in machining accuracy due to runout.

10, 20, 30, 40 Core drills 11, 21 Outer peripheral surfaces 12, 22 Inner peripheral surfaces 13, 23 Virtual inscribed circles 14, 24 Minimum diameter portions 15, 25 Swelled portion 16 Glass plate 17 Core 18 Bottomed hole 19 Through hole 31 Radial groove 32 Axial groove 100 Core drill 101 Outer peripheral surface 102 Hole 200 Cutting part (core drill)
201 outer peripheral surface 202 inner peripheral surface 203 (radial direction) thick portion 204 (radial direction) thin portion F radial force O, center of O ₁ outer peripheral surface center of O ₂ inner peripheral surface

Claims (7)

In the core drill for applying a predetermined drilling process to the glass plate at the cutting part provided on the drill tip side,
The inner peripheral surface of the cutting portion includes a plurality of bulged portions that have a shape that bulges outward from a virtual inscribed circle in contact with the smallest diameter portion of the inner peripheral surface when viewed in an arbitrary axis orthogonal cross section. And having
The core drill, wherein the plurality of bulging portions are arranged so as to be symmetrical around the rotation axis of the cutting portion.   2. The core drill according to claim 1, wherein the plurality of bulging portions are continuous with each other at circumferential ends thereof, whereby the inner peripheral surface of the cutting portion is configured by the plurality of bulging portions.   The front end surface of the cutting part has a plurality of radial grooves extending in the radial direction, and the plurality of radial grooves are all arranged symmetrically around the rotation axis. Core drill as described in   The outer peripheral surface of the cutting portion has a plurality of axial grooves extending in the axial direction, and the plurality of axial grooves are all arranged symmetrically around the rotation axis. Core drill as described in   The front end surface of the cutting portion has a plurality of radial grooves extending in the radial direction, and the inner peripheral surface of the cutting portion has a plurality of axial grooves extending in the axial direction, and the plurality of radial directions The core drill according to claim 1 or 2, wherein the groove portion is continuous with the bulging portion at an inner diameter end thereof and is continuous with the axial groove portion at an outer diameter end thereof.   The core drill according to any one of claims 1 to 5, wherein an inner diameter of the through-hole formed in the glass plate is 1 mm or more and 5 mm or less. In the method of performing a predetermined drilling process on the glass plate at the cutting part provided on the tip side of the core drill,
The inner peripheral surface of the cutting portion includes a plurality of bulged portions that have a shape that bulges outward from a virtual inscribed circle in contact with the smallest diameter portion of the inner peripheral surface when viewed in an arbitrary axis orthogonal cross section. And having
The glass plate drilling method using a core drill, wherein the plurality of bulging portions are arranged so as to be symmetrical around the rotation axis of the cutting portion.

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