Cylindrical grinding machine and cylindrical grinding method

Abstract

The present invention provides a cylindrical grinding machine which is capable of supporting a crystal rod regardless of the presence or absence of a conical cone portion and a tail portion at the two ends of the crystal rod, and which additionally comprises a discriminator capable of automatically discriminating between the presence or absence of the cone portion, etc., and a controller in which set values are registered separately depending on whether the cone portion, etc., are present or absent during traverse grinding, for a clamping force with which the crystal rod is clamped by a pair of support units and a maximum griding allowance per operation of a grinding unit, wherein the controller automatically selects a grinding recipe that includes the set values of the clamping force and the maximum griding allowance per operation, corresponding to the presence or absence of the cone portion, etc., as discriminated automatically by the discriminator, and traverse grinding can be automatically performed on the basis of the grinding recipe. The present invention thereby provides a cylindrical grinding machine and a cylindrical grinding method with which, when performing traverse grinding of a crystal rod, grinding can be performed efficiently and at low cost, and with a stable quality by preventing the occurrence of positional displacement and breakage of the crystal rod.

Description

Cylindrical grinding machine and cylindrical grinding method

[0001] The present invention relates to a cylindrical grinding machine and a cylindrical grinding method having a support unit that axially sandwiches a crystal bar (such as a silicon single crystal ingot) between a main shaft and a sub-shaft to which a support device is attached, and supports (fixes) the crystal bar so that the crystal bar can rotate about the axis, and a grinding unit that moves along the axial direction of the crystal bar while traverse-grinding the outer periphery of the crystal bar.

[0002] In recent years, the diameter of wafers used in semiconductor device manufacturing has been increasing in order to improve the performance of semiconductor devices and reduce manufacturing costs. The wafers used in semiconductor device manufacturing are produced by preparing a crystal rod using the Czochralski method or other methods, with a cylindrical body and a conical cone and tail at the front and rear of the body. The outer periphery of the crystal rod is then cylindrically ground using a cylindrical grinder, after which the rod is sliced ​​perpendicular to the axial direction to cut into plates, which are then polished. In recent years, as the number of wafers obtained from a single crystal rod increases and the diameter of the wafers increases, the crystal rods produced are also becoming longer, larger, and heavier.

[0003] When cylindrically grinding such a crystal rod, a cylindrical grinding machine 101 as shown in Figure 5 is used. A typical conventional cylindrical grinding machine 101 is composed of a transport unit 116 for transporting the crystal rod 7 inside and outside the machine, a pair of support units 104 for holding the crystal rod 7, and a grinding unit 105 for traverse grinding the outer periphery of the crystal rod 7. The pair of support units 104 have a main shaft 103a and a sub-shaft 103b, each with a support device attached to its tip, and can sandwich the crystal rod 7 in the axial direction and rotate it around the axis.

[0004] Here, examples (7a to 7d) of the shape of the crystal rod 7 to be cylindrically ground are described using FIGS. 6 to 9 . FIG. 6 shows a dislocation-free crystal rod 7a, which has a conical shape at both ends (on both sides of the body 8) of the crystal rod 7a. Furthermore, in the case of the crystal rod 7b shown in FIG. 7, which has undergone dislocation growth, clamping and fixing the crystal rod 7b axially using the support devices 102a and 102b at the ends of the main and sub-shafts 103a and 103b shown in FIG. 5 causes the dislocation-containing portion D to collapse, resulting in an inability to properly fix the crystal rod 7b. Therefore, as a pretreatment step, the dislocation-containing portion D is cut perpendicular to the crystal axis using a band saw or similar machine. FIG. 8 shows a crystal rod 7c with the dislocation-containing portion D cut off in this manner. Furthermore, for some reason, a cylindrical crystal rod 7d shown in FIG. 9 cut from a dislocation-free crystal rod 7a or a dislocation-containing crystal rod 7b may be subjected to traverse grinding using a cylindrical grinder.

[0005] In the following, for convenience, the conical cone portion may be referred to as "with cone 9a," the conical tail portion may be referred to as "with tail 10a," the flat surface of the cone portion cut vertically (flat) may be referred to as "without cone 9b," and the flat surface of the tail portion cut vertically (flat) may be referred to as "without tail 10b."

[0006] In the preparation process (loading process) for traverse grinding with a cylindrical grinding machine, the crystal bar is transported into the cylindrical grinding machine by a transport unit, and the crystal bar is clamped in the crystal axis direction by a support unit. The support device, as shown in Figures 10 and 11 of Patent Document 1, is composed of a fixed support 114 with a conical hole and a floating support 115 that supports the vertically cut end face. The cone-containing bar 9a and the tail-containing bar 10a are supported by the fixed support 114 with a conical hole, as shown in Figure 10. On the other hand, the non-cone-containing bar 9b and the non-tail-containing bar 10b have their vertically cut faces supported by the floating support 115, as shown in Figure 11. The floating support 115 is slightly movable. When cutting perpendicular to the crystal axis direction as part of the pre-processing, it is difficult to achieve an accurate vertical cut due to the unevenness of the cylindrical outer periphery. However, even crystal bar with such a cut face can be held by the movable floating support 115, as shown in Figure 11.

[0007] Japanese Patent Application Publication No. 11-207505

[0008] In the preparation process (loading process), the crystal bar 7 is transported and supported in the cylindrical grinding machine 101, where it is subjected to diameter measurement and other procedures prior to cylindrical grinding. Figure 12 shows the cylindrical grinding of a crystal bar with a cone (tail). Figure 13 shows the case of a crystal bar without a cone (tail). The crystal bar 7 is cylindrically ground on its outer periphery by the grinding wheel 106 of the grinding unit 105. However, if the grinding allowance SR required to grind the crystal bar down to its finishing diameter (final target diameter) exceeds the maximum grinding allowance SRm per run, the crystal bar is ground in multiple passes. During cylindrical grinding, an external force EF acts in the opposite direction of the grinding wheel 106 due to the grinding load of the grinding wheel 106. In the case of the no-cone 9b and no-tail 10b shown in Figure 13, if the external force EF (or grinding load, maximum grinding allowance SRm per run) becomes larger than the frictional force (also called support frictional force) generated between the vertically cut surface and the floating support 115, the crystal bar 7 will move during cylindrical grinding (misalignment of the crystal bar), resulting in poor grinding of the cylindrically ground surface and poor diameter accuracy. On the other hand, in the case of the cone 9a and tail 10a shown in Figure 12, the cone portion 9 and tail portion 10 are held in the conical hole, so the crystal bar 7 will not move during cylindrical grinding.

[0009] The frictional force that clamps and supports the crystal rod 7 in the crystal axis direction is obtained by moving a pair of support units 104 in the crystal axis direction to apply a clamping force CF (also called a pressing force) to the crystal rod 7. Generally, the clamping force is increased when there is no cone (tail) to prevent the crystal rod 7 from moving during cylindrical grinding. However, when the cone (tail) is supported with the same clamping force, the cone portion 9 (tail portion 10) breaks near the contact point with the conical hole, resulting in poor grinding of the cylindrical grinding surface and poor diameter accuracy. Furthermore, depending on the conical shape of the cone portion 9 and tail portion 10, the narrow tail side is generally more likely to break.

[0010] One way to deal with this is to prepare cylindrical grinding machines with dedicated settings for both those with and without cones (tails), but this was not practical because the machine's operating rate would decrease if the balance between the number of crystal rods to be processed and the number of machines was poor.Another way is to manually change the settings to the optimal grinding recipe each time depending on whether or not there is a cone (tail), but this requires operator intervention each time, which increases the number of man-hours and leads to higher costs.

[0011] The present invention has been made to solve the above-mentioned problems, and aims to provide a cylindrical grinding machine and a cylindrical grinding method that can perform traverse grinding of crystal rods efficiently, at low cost, and with stable quality by preventing the crystal rods from shifting or breaking.

[0012] In order to achieve the above object, the present invention provides a cylindrical grinding machine having a pair of support units, each having a support device for supporting the end of a crystal rod, which supports the crystal rod in the axial direction with a main shaft and a sub-shaft attached to the tip of the support device, and which sandwiches the crystal rod between them and allows it to rotate around its axis, and a grinding unit that moves along the axial direction of the crystal rod supported by the pair of support units and traverse-grinds the outer periphery of the crystal rod, wherein the support device has a concave first support portion capable of supporting a conical crystal end and a second support portion capable of supporting a flat crystal end, and is capable of supporting the crystal rod regardless of the presence or absence of a conical cone and tail portions at both ends of the crystal rod; the present invention further comprises a discriminator that can automatically discriminate between the presence or absence of the cone and tail portions; and a controller in which set values ​​are registered for the clamping force with which the pair of support units clamp the crystal rod during traverse grinding and the maximum grinding allowance per grinding by the grinding unit, depending on the presence or absence of the cone and tail portions. The present invention provides a cylindrical grinding machine characterized in that the controller automatically selects a grinding recipe having set values ​​for the clamping force and the maximum cutting allowance per grinding corresponding to the presence or absence of the cone portion and tail portion automatically determined by the discriminator, and the controller can automatically perform traverse grinding based on the grinding recipe.

[0013] The cylindrical grinding machine of the present invention supports and fixes the crystal bar with a clamping force set according to the presence or absence of a cone and tail (hereinafter, also referred to as the cone, etc.), and is capable of traverse grinding with the maximum cutting allowance per grinding operation set to that value. Appropriate settings for the clamping force and the maximum cutting allowance per grinding operation can be set depending on the presence or absence of a cone, etc. This prevents the cone, etc., from breaking due to excessive clamping force, or the crystal bar from being displaced due to the maximum cutting allowance per grinding operation being too large compared to the support friction force when a cone, etc., is absent. As a result, grinding can be performed with consistent quality without poor grinding of the cylindrical grinding surface or poor diameter accuracy.

[0014] In addition, since the determination of the presence or absence of cone parts, selection of grinding recipe, and traverse grinding are all automatic, there is no need for operator intervention, making grinding possible at low cost. Furthermore, since it is compatible with both patterns with and without cone parts, grinding can be performed efficiently, preventing the decline in operating rate that occurs with conventional dedicated machines for both with and without cone parts.

[0015] The present invention also provides a method for cylindrically grinding a crystal rod using a cylindrical grinding machine having a pair of support units, each of which has a main shaft and a sub-shaft attached to the tip of a support device that supports the end of the crystal rod, sandwiching the crystal rod in the axial direction and allowing it to rotate around its axis, and a grinding unit that moves along the axial direction of the crystal rod supported by the pair of support units to traverse grind the outer periphery of the crystal rod, wherein the support device has a concave first support portion that can support the conical crystal end and a second support portion that can support the flat crystal end, and is capable of supporting the crystal rod regardless of the presence or absence of a conical cone and tail portion at both ends of the crystal rod; further comprising: a discriminator that can automatically discriminate between the presence or absence of the cone and tail; and a controller in which set values ​​are registered for the clamping force with which the pair of support units clamp the crystal rod during traverse grinding and the maximum grinding allowance per grinding by the grinding unit, depending on the presence or absence of the cone and tail portions. The present invention provides a cylindrical grinding method, characterized in that, when the crystal rod is clamped and fixed by the pair of support units, the presence or absence of the cone portion and tail portion of the crystal rod is automatically determined by the discriminator, a grinding recipe having set values ​​for the clamping force and the maximum grinding allowance per grinding corresponding to the automatically determined presence or absence of the cone portion and tail portion is automatically selected by the controller, and traverse grinding is automatically performed based on the grinding recipe.

[0016] The cylindrical grinding method of the present invention can prevent breakage of the cone portion or misalignment of the crystal rod due to excessive clamping force or the maximum grinding allowance per operation, enabling stable grinding quality. Furthermore, by automatically determining whether or not a cone portion is present, manual intervention is unnecessary, reducing costs. Furthermore, since the method can handle both patterns with and without a cone portion, grinding can be performed efficiently.

[0017] The cylindrical grinding machine and cylindrical grinding method of the present invention enable traverse grinding of crystal rods with stable quality by preventing breakage of cone parts and misalignment of the crystal rods, while also reducing costs through various automation methods and improving efficiency by adapting to both the presence and absence of cone parts.

[0018] FIG. 1 is an explanatory diagram showing an example of a cylindrical grinding machine of the present invention. FIG. 1 is an explanatory diagram showing an example of a support device in the present invention. FIG. 1 is an explanatory diagram showing an example of a discriminator (contact type). FIG. 1 is an explanatory diagram showing an example of a discriminator (non-contact type). FIG. 2 is an explanatory diagram showing an example of a conventional cylindrical grinding machine. FIG. 2 is an explanatory diagram showing an example of a crystal rod of dislocation-free crystals. FIG. 2 is an explanatory diagram showing an example of a crystal rod made to have dislocations. FIG. 2 is an explanatory diagram showing an example of a crystal rod from which a dislocation-containing portion has been cut off. FIG. 2 is an explanatory diagram showing an example of a cylindrical crystal rod. FIG. 2 is an explanatory diagram showing an example of a crystal rod with a cone (tail) held by a support device. FIG. 2 is an explanatory diagram showing an example of a crystal rod without a cone (tail) held by a support device. FIG. 2 is an explanatory diagram showing an example of a state during cylindrical grinding of a crystal rod with a cone (tail). FIG. 2 is an explanatory diagram showing an example of a state during cylindrical grinding of a crystal rod without a cone (tail).

[0019] Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited thereto. FIG. 1 shows an overall view of a cylindrical grinding machine 1 of the present invention for traverse grinding a crystal rod 7. As shown in FIG. 1, the cylindrical grinding machine 1 includes a conveying unit 16, a pair of support units 4, and a grinding unit 5. It also includes a discriminator 11 and a controller 12. The conveying unit 16 may be any device capable of holding and conveying the crystal rod 7. The grinding unit 5 may include a grinding wheel 6 and may be capable of traverse grinding the outer periphery of the crystal rod 7 while moving along the axial direction of the crystal rod 7 supported by the pair of support units 4. The conveying unit 16 and the grinding unit 5 are equipped with drive mechanisms (not shown) and are movable, and may be, for example, similar to conventional devices.

[0020] Next, the pair of support units 4 will be described. The pair of support units 4 sandwich the crystal rod 7 transported by the transport unit 16 in the axial direction, allowing it to rotate around the axis. They include a first support unit 4a and a second support unit 4b. The first support unit 4a has a main shaft 3a, and the second support unit 4b has a sub-shaft 3b. The main shaft 3a has a support device 2a at its tip, and the sub-shaft 3b has a support device 2b at its tip. Therefore, the crystal rod 7 is supported by being sandwiched between the support device 2a of the main shaft 3a and the support device 2b of the sub-shaft 3b. Here, an example is shown in which the tail portion 10 of the crystal rod 7 is supported on the sub-shaft 3b side and the cone portion 9 is supported on the main shaft 3a side, but this is not limiting; the orientation of the crystal rod 7 may be reversed.

[0021] Examples of support devices 2a and 2b are shown in Figure 2. Support devices 2a and 2b each have a first support 14 with a concave shape having a conical hole capable of supporting the conical crystal end (cone 9 and tail 10) of the crystal portion 7, and a second support 15 capable of supporting the flat crystal end. The first support 14 and second support 15 may be similar to the fixed support 114 and floating support 115 in Figure 10, for example. Therefore, both support devices 2a and 2b can support the crystal rod 7 regardless of whether the crystal rod 7 has the conical cone 9 and tail 10 at both ends.

[0022] The pair of support units 4 also have a drive mechanism 13. This drive mechanism 13 has, for example, a motor (servo motor, etc.), and can move the second support unit 4b toward the first support unit 4a. Of course, it can also move in the opposite direction to the first support unit 4a. By adjusting the number of rotations and direction of rotation of the motor, the movement speed and movement direction of the second support unit 4b can be freely changed and adjusted.

[0023] Next, the discriminator 11 will be described. The discriminator 11 is a means capable of automatically discriminating the presence or absence of the cone portion 9 and the tail portion 10, and may be a contact type that comes into contact with the cone portion 9 or the like, or a non-contact type. Below, a specific configuration example of the discriminator 11 and an example of a discrimination mechanism in the preparation process (hereinafter sometimes referred to as the loading process) will be described, but the following configuration example and mechanism are not limited to these and can be determined as appropriate. Note that the explanation will be given using the support device 2b side (tail portion 10 side) as an example, but the same can be done on the support device 2a side (cone portion 9 side).

[0024] Figure 3 shows a contact-type discriminator 11. As shown in the upper part of Figure 3, this type is equipped with an ingot detection rod 20, a slider 21, a detection dog 22, a first sensor 23a, a second sensor 23b, and an ingot detection rod moving device 24. The ingot detection rod 20 is held by the slider 21 through a conical hole in the first support part of the support device 2b, and can be slid in the axial direction by the ingot detection rod moving device 24. The first sensor 23a and second sensor 23b are used to detect the detection dog 22 provided on the ingot detection rod 20.

[0025] During the loading process, when the crystal rod 7 is supported and fixed axially by the countershaft 3b attached to the tip of the support device 2b, the tail portion 10 directly contacts the ingot detection rod 20. The ingot detection rod 20 moves along the sliding portion 21, and the detection dog 22 attached to the ingot detection rod 20 also moves simultaneously. Here, if the first sensor 23a is initially positioned to detect the detection dog 22 (before loading), and the second sensor 23b is positioned to detect the detection dog 22 when the crystal rod 7 (without a tail 10b) is supported by the support device 2b (after loading), the presence or absence of a tail can be easily detected. In other words, when the crystal rod 7 has a tail 10a, the first sensor 23a and the second sensor 23b do not detect the detection dog 22, as shown in the middle of Figure 3. On the other hand, in the case of no tail 10b, as shown in the lower part of Figure 3, the first sensor 23a does not detect the detection dog 22, but the second sensor 23b does detect the detection dog 22. This mechanism makes it possible to automatically determine whether or not the tail 10 (and the cone 9) is present. Table 1 shows the relationship between the presence or absence of the cone etc. and the detection by the first and second sensors.

[0026]

[0027] FIG. 4 shows a non-contact discriminator 11. As shown in the upper part of FIG. 4, a sensor installation hole 30 is provided in the support device 2b, and a conical portion detection sensor 31 is disposed therein, providing a detection line 32 for the conical portion detection sensor 31. As with the contact type described above, when the crystal rod 7 is supported and fixed in the axial direction during the loading process, as shown in the middle part of FIG. 4, if the crystal rod 7 has a tail 10a, it can be detected because it blocks the detection line 32 of the conical portion detection sensor 31 provided in the sensor installation hole 30 of the support device 2b. On the other hand, as shown in the lower part of FIG. 4, if the crystal rod 7 does not have a tail 10b, even when the crystal rod 7 is fixed in the axial direction, it does not block the detection line 32 of the conical portion detection sensor 31, and therefore is not detected. The presence or absence of the tail 10 can be automatically determined based on the presence or absence of this detection. In recent years, the performance of image sensors has improved, making it easier to detect the conical tail 10 (cone portion 9) from an image, and this can be used to automatically determine the presence or absence of the tail 10 (cone portion 9) in a non-contact manner.

[0028] Next, the controller 12 will be described. The controller 12 can be, for example, a computer. The controller 12 stores preset values ​​for the clamping force CF applied to the crystal rod 7 by the pair of support units 4 during traverse grinding, and the maximum grinding allowance SRm (maximum grinding allowance per grinding) per grinding operation by the grinding unit 5, depending on whether or not the cone portion 9 and tail portion 10 are present. These preset values ​​are not particularly limited and can be determined appropriately depending on various conditions, such as the type, length, and diameter of the crystal rod 7, or the length of the cone portion 9 and tail portion 10.

[0029] In particular, the clamping force CF (pressing force) is preferably set to a relatively strong value in the case of the cone-less type 9b and the tail-less type 10b so as to generate a large frictional force between the vertically (flat) cut surface and the second support portion 15. On the other hand, in the case of the cone-with 9a and the tail-with 10a, a relatively weak value is preferably set to prevent breakage near the contact portion between the cone portion 9 or the tail portion 10 and the first support portion 14. Furthermore, in the case of the cone-less type 9b and the tail-less type 10b, the maximum cutting allowance SRm (external force EF) per operation is preferably set to a relatively small value compared to the case of the cone-with 9a and the tail-with 10b in order to prevent the crystal rod 7 from moving during cylindrical grinding.

[0030] The controller 12 is also connected to the pair of support units 4 (including the drive mechanism 13), the grinding unit 5, the discriminator 11, the transport unit 16, and the like, and is capable of automatically operating these. In addition, the controller 12 is programmed to automatically select a grinding recipe having the set values ​​for the clamping force CF and the maximum grinding allowance SRm per grinding operation, which are registered as described above, in response to the presence or absence of the cone portion 9, etc., automatically discriminated by the discriminator 11. Then, a program is written for operating each part so that traverse grinding is automatically performed based on the automatically selected appropriate grinding recipe.

[0031] The cylindrical grinding machine 1 of the present invention described above allows traverse grinding to be performed with an appropriate clamping force CF and maximum grinding allowance SRm per grinding, depending on whether or not the cone portion 9 is present. This reduces the occurrence of problems such as breakage of the cone portion 9 and misalignment of the crystal rod 7, which have been problems in the past. This prevents defects in the cylindrically ground surface and poor diameter accuracy, and provides crystal rods of consistent quality after cylindrical grinding. Furthermore, because the entire traverse grinding process, including determining whether or not the cone portion 9 is present, can be performed automatically, regardless of whether or not the cone portion 9 is present, crystal rods can be ground efficiently and at low cost.

[0032] Next, the cylindrical grinding method of the present invention will be described. First, a cylindrical grinding machine 1 (including a pair of support units 4, a grinding unit 5, a discriminator 11, a controller 12, and a conveying unit 16) and a crystal bar 7 to be ground are prepared as shown in FIG.

[0033] In the preparation process (loading process), the crystal rod 7 is first moved using the transport unit 16 to align the center of the crystal axis with the center of rotation of the main shaft 3a and the sub-shaft 3b. Next, the crystal rod 7 is sandwiched between the first support unit 4a and the second support unit 4b, and the second support unit 4b is moved toward the first support unit 4a by the drive mechanism 13. The crystal rod 7 is sandwiched and supported and fixed by this pair of support units 4.

[0034] At this time, the presence or absence of the cone portion 9 of the crystal bar 7 is automatically determined by a discriminator 11. A contact type as shown in FIG. 3 or a non-contact type as shown in FIG. 4 may be used. Here, the controller 12 pre-registers preset values ​​(the set value of the clamping force CF and the set value of the maximum grinding allowance SRm per grinding) for both the case where the cone portion 9 is present and the case where the cone portion 9 is absent. Therefore, a grinding recipe including appropriate set values ​​is automatically selected based on the results of automatic determination by the discriminator 11. After the crystal bar 7 is clamped between the pair of support units 4 in the crystal axis direction, the transport unit 16 releases the crystal bar 7 and retreats.

[0035] Then, traverse grinding is automatically performed based on the automatically selected grinding recipe. That is, while the crystal rod 7 is clamped and supported with the automatically selected clamping force CF and rotated around its axis, the grinding wheel 6 of the grinding unit 5 grinds the crystal rod to the finishing diameter (final target diameter). If the cutting allowance SR exceeds the maximum cutting allowance SRm per run, the outer periphery of the crystal rod 7 is automatically ground while applying a grinding load so that the cutting allowance becomes SRm. If the remaining cutting allowance required to reach the final target diameter does not exceed SRm, grinding is automatically performed for the remaining cutting allowance as the final grinding, and the process is terminated. The remaining cutting allowance can be calculated by subtracting SRm from SR by the number of grinding runs, and this can be automatically calculated, for example, by the controller 12.

[0036] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples. First, 50 crystal rods each having a diameter of 200 mm, a cone length of 150 mm, a tail length of 250 mm, and a straight body length of 1,000 mm were prepared. Of these, 25 were used as crystal rods with a cone and a tail (Set A). The remaining 25 were cut perpendicular to the crystal axis direction to form flat ends, resulting in crystal rods without a cone and a tail (Set B). Four sets of 50 crystal rods each were prepared.

[0037] (Example) The cylindrical grinding machine 1 of the present invention shown in Figure 1 was prepared, and one of the four crystal bars was subjected to the cylindrical grinding method of the present invention, in which the cone and tail portions were automatically identified, a grinding recipe was automatically selected based on the automatic identification, and traverse grinding was automatically performed based on the automatically selected grinding recipe. The presence or absence of the cone and tail portions was automatically identified using a non-contact discriminator as shown in Figure 4. The clamping force applied by the drive mechanism of the support unit of the cylindrical grinding machine used was measured with a load cell and was 16 kN at 100% output.

[0038] The relationship between the presence or absence of a cone and a tail and the grinding recipe (setting value of clamping force (pressing force) CF and setting value of maximum cutting allowance per one time SRm) registered in the controller is as follows: [Selective grinding recipe with cone and tail] CF: Output 90% SRm: 10 mm [Selective grinding recipe without cone and tail] CF: Output 98% SRm: 6 mm

[0039] Then, we investigated the occurrence of quality defects due to breakage of the cone or tail in set A (25 pieces) and the occurrence of quality defects due to misalignment of the crystal rod during cylindrical grinding in set B (25 pieces), and the results were as follows: Occurrence of quality defects (breakage) in set A: 0 pieces (quality defect occurrence rate: 0%) Occurrence of quality defects (misalignment) in set B: 0 pieces (quality defect occurrence rate: 0%)

[0040] (Comparative Examples 1-3) Unlike the Examples, a cylindrical grinding machine was prepared that did not have the functions of automatically distinguishing between cone and tail portions, automatically selecting a grinding recipe based on this automatic distinction, and automatically performing traverse grinding based on the automatically selected grinding recipe. This cylindrical grinding machine does not have the discriminator or controller of the cylindrical grinding machine 1 of the present invention shown in FIG. 1, and is always capable of executing only a fixed grinding recipe (fixed CF, fixed SRm) manually adjusted in advance by the operator. Other than that, it was the same as the cylindrical grinding machine 1 of the Examples, including the maximum output of the drive mechanism of the support unit. Using this cylindrical grinding machine, traverse grinding was performed on three of the four sets of crystal bars described above using a fixed grinding recipe.

[0041] The grinding recipes of Comparative Examples 1 to 3 are as follows: [Grinding recipe of Comparative Example 1] CF: Always 90% output SRm: Always 10 mm [Grinding recipe of Comparative Example 2] CF: Always 98% output SRm: Always 10 mm [Grinding recipe of Comparative Example 3] CF: Always 98% output SRm: Always 6 mm

[0042] Then, in the same manner as in the Examples, the occurrence of quality defects due to breakage of the cone portion or tail portion in Set A (25 pieces) and the occurrence of quality defects due to misalignment of the crystal rod during cylindrical grinding in Set B (25 pieces) were investigated, and the results were as follows. Note that all of the breaks that occurred in Set A were in the tail portion, and no breaks occurred in the cone portion. [Results of Comparative Example 1] Occurrence of quality defects (breakage) in Set A: 0 pieces (quality defect occurrence rate: 0%) Occurrence of quality defects (misalignment) in Set B: 5 pieces (quality defect occurrence rate: 20%) [Results of Comparative Example 2] Occurrence of quality defects (breakage) in Set A: 3 pieces (quality defect occurrence rate: 12%) Occurrence of quality defects (misalignment) in Set B: 2 pieces (quality defect occurrence rate: 8%) [Results of Comparative Example 3] Occurrence of quality defects (breakage) in Set A: 3 pieces (quality defect occurrence rate: 12%) Occurrence of quality defects (misalignment) in Set B: 0 pieces (quality defect occurrence rate: 0%)

[0043] As can be seen from the results of Example and Comparative Examples 2 and 3, the rate of quality defects due to breakage was reduced by up to 12%. Furthermore, as can be seen from the results of Example and Comparative Example 1, the rate of quality defects due to misalignment was reduced by up to 20%. Only Example was able to reduce the rate of quality defects for both to 0%. Thus, with the present invention, efficient cylindrical grinding can be performed with stable quality at low cost, without the need to prepare dedicated cylindrical grinding machines adjusted for use with and without a cone (tail), and without the need for an operator to manually set an optimal recipe each time depending on whether or not a cone (tail) is used.

[0044] The present invention is not limited to the above-described embodiments. The above-described embodiments are merely examples, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits similar effects is included within the technical scope of the present invention.

Claims

1. A cylindrical grinding machine having a pair of support units, each of which has a main shaft and a sub shaft attached to the tip of a support device that supports the end of a crystal rod, which sandwich the crystal rod in the axial direction and allows it to rotate around the axis, and a grinding unit that moves along the axial direction of the crystal rod supported by the pair of support units and traverse grinds the outer periphery of the crystal rod, wherein the support device has a first support part with a concave shape that can support a conical crystal end and a second support part that can support a flat crystal end, and is capable of supporting the crystal rod regardless of the presence or absence of a conical cone portion and tail portion at both ends of the crystal rod, further comprising a discriminator that can automatically discriminate whether or not the cone portion and tail portion are present, and a controller in which set values ​​are registered for the clamping force with which the pair of support units clamp the crystal rod during the traverse grinding and the maximum grinding allowance per operation by the grinding unit, depending on whether or not the cone portion and tail portion are present, a grinding recipe having set values ​​for the clamping force and the maximum cutting allowance per one run corresponding to the presence or absence of the cone portion and the tail portion automatically determined by the discriminator is automatically selected by the controller, and traverse grinding can be automatically performed based on the grinding recipe.

2. A method for cylindrically grinding a crystal rod using a cylindrical grinding machine having a pair of support units, each of which has a main shaft and a sub shaft attached to the tip of a support device that supports the end of the crystal rod, sandwiching the crystal rod in the axial direction and allowing it to rotate around the axis, and a grinding unit that moves along the axial direction of the crystal rod supported by the pair of support units while traverse grinding the outer periphery of the crystal rod, wherein the support device has a first support part with a concave shape that can support a conical crystal end and a second support part that can support a flat crystal end, and is capable of supporting the crystal rod regardless of the presence or absence of a conical cone and tail parts at both ends of the crystal rod, further comprising: a discriminator that can automatically discriminate whether or not the cone and tail parts are present; and a controller in which set values ​​are registered for the clamping force with which the pair of support units clamp the crystal rod during the traverse grinding and the maximum grinding allowance per operation by the grinding unit, depending on whether or not the cone and tail parts are present. a controller for automatically selecting a grinding recipe having a set value of the clamping force and the maximum cutting allowance per one grinding operation corresponding to the automatically determined presence or absence of the cone portion and tail portion when the crystal bar is clamped and fixed by the pair of support units, and automatically performing traverse grinding based on the grinding recipe.

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