CYLINDRICAL GRINDING APPARATUS

Description

TECHNICAL FIELD

The present invention relates to a cylindrical grinding apparatus that can detect both ends (a cone portion and a tail portion, which are conical) of a crystal rod in a preparing step (a loading step) to perform traverse grinding of the crystal rod (silicon single crystal ingot, etc.) and can perform an action of sandwiching the crystal rod in an axial direction with a main shaft and a subordinate shaft and supporting the crystal rod safely and quickly.

BACKGROUND ART

In recent years, in order to improve the performance of semiconductor devices and reduce manufacturing costs, the diameter of wafers used to manufacture semiconductor devices has been increasing. The wafers used for manufacturing these semiconductor devices are manufactured by: producing a crystal rod that has a cone portion and a tail portion, which are conical, at the front and rear of its cylindrical straight body, by the Czochralski method, etc.; next performing cylindrical grinding on an outer circumference of the crystal rod using a cylindrical grinding apparatus; then slicing the crystal rod perpendicularly to the axial direction to obtain plates; and subjecting the plates to a polishing process. Therefore, as the number of wafers obtained from one crystal rod increases and the diameter of the wafer becomes larger, the produced crystal rod also becomes larger in diameter and heavier.

When performing cylindrical grinding of such a crystal rod, a general cylindrical grinding apparatus consists of a transport unit to transport the crystal rod into and out of the apparatus, a support unit to support the crystal rod in the apparatus, and a grinding unit to perform traverse grinding on an outer circumference of the crystal rod.

FIG. 8 shows a preparation step (a loading step) in which the crystal rod is sandwiched in the direction of the crystal axis with the transport unit 38 and the support units 34a and 34b.

(Carry-In of Crystal Rod)

The transport unit 38 that clamps the crystal rod 7 in a diameter direction moves to align the crystal axis center 10 with the rotation center 9 of the main shaft 33a and the subordinate shaft 33b (Step 1 in FIG. 8).

(Support of Crystal Rod)

Next, the crystal rod 7 is sandwiched with the support units 34a and 34b. In general, in a cylindrical grinding apparatus, a support unit 34a on the main shaft side is fixed, and a support unit 34b on the subordinate shaft side is moved by a drive mechanism such as a servo motor, etc. (Step 2 in FIG. 8).

A holding part (a support device) 32b of the support unit 34b on the subordinate shaft side, which continuously moves toward the main shaft side by the drive mechanism such as the servo motor, comes into contact with the conical tail portion 12 of the crystal rod 7, and continues to move with the transport unit 38 clamping the crystal rod 7 in the diameter direction toward the main shaft (Step 3 in FIG. 8).

Due to the continuous movement described above, contact with a holding part 32a of the support unit 34a on the main shaft side and the conical cone portion 11 of the crystal rod 7 is also made. The crystal rod 7 is supported by being sandwiched between the holding part 32a on the main shaft side and the holding part 32b on the subordinate shaft side, but it is necessary to prevent the holding parts 32a, 32b, the cone portion 11, and the tail portion 12 from slipping due to grinding resistance when the cylindrical surface of the crystal rod 7 is ground by a grinding stone of the grinding unit in a cylindrical grinding step in the subsequent step. Therefore, after the crystal rod 7 is sandwiched and supported between the holding parts 32a and 32b, the supporting unit 34b on the subordinate shaft side continues to move further toward the main shaft side to increase frictional force between the cone portion 11 of the crystal rod 7 and the holding part 32a and between the tail portion 12 and the holding part 32b (Step 4 in FIG. 8).

(Retreat of Transport Unit)

After the crystal rod 7 is sandwiched between the support units 34a and 34b in the crystal axis direction in the above step, the transport unit 38 releases the crystal rod 7 and retreats (Step 5 in FIG. 8).

CITATION LIST

Patent Literature

• • Patent Document 1: JP 2010-221393 A

SUMMARY OF INVENTION

Technical Problem

In the loading step as described above, because the conical cone portion 11 and tail portion 12 of the crystal rod 7 come into contact with the holding portions 32a and 32b due to the movement of the support unit 34b on the subordinate shaft side, the cone portion 11 and the tail portion 12, which are conical, of the crystal rod 7 may be damaged due to impact by the contact or the like. In this case, in the cylindrical grinding step, the crystal rod may slip or become misaligned due to the grinding resistance when the grinding stone of the grinding unit grinds the cylindrical surface of the crystal rod 7, and therefore its quality may be adversely affected in a manner such as poorly ground condition of the cylindrical surface and poor diameter accuracy. Therefore, the support unit 34b on the subordinate shaft side must be moved at a low speed.

On the other hand, when the support unit 34b on the subordinate shaft side is moved at a low speed in order to reduce damage due to the above-mentioned impact, a lot of time will be spent in the loading step.

Further, Patent Document 1 discloses a technique that includes an ingot sensing rod capable of contacting with an end portion (a cone portion and a tail portion) of an ingot (a crystal rod) through the engaging hole of a holder (a support device). FIG. 9 shows a conventional contact-type detecting technique for detecting the position immediately before the crystal rod 7 and the holder 45 come into contact with each other.

After the crystal rod 7 is cramped in a diameter direction by a transport unit and is moved to align the crystal axis center with the rotation center of the main shaft and the subordinate shaft (upper diagram of FIG. 9: a subordinate shaft side is shown here.), the ingot sensing rod 46 (movable with ingot sensing rod moving device 50) held by a sliding part 47 through the engaging hole of the holder 45 on the subordinate shaft side that moves continuously toward the main shaft side by a drive mechanism such as a servo motor and the end portion (a tail portion 12) of the crystal rod 7 come into contact with each other. When a position for a sensor 48b can be detected by the fact that an end-portion detecting dog 49 moves from a position for a sensor 48a, it is easily assumed that the position immediately before the end portion comes into contact with the holder 45 can be grasped (lower diagram of FIG. 9).

It can be said that the contact-type detecting technique including the ingot sensing rod 46 as disclosed in Patent Document 1 is an effective means for detecting the position of the end portion (the cone portion and tail portion, which are conical.) of the crystal rod. However, there are concerns about component failure and aging. Specifically, the ingot sensing rod 46 is held by the sliding part 47, and entry of grinding dust in a mist form that was made by grinding on the cylindrical outer peripheral surface in the cylindrical grinding step might cause abrasion of sliding part 47 or the like and sliding failure (malfunction). Therefore, periodic maintenance is required.

Therefore, the present invention has been made to solve the above problem, and an object of the present invention is to provide cylindrical grinding apparatus that can prevent occurring damage in an end portion of a crystal rod and mechanical misalignment of a support unit, which are caused by impact due to contact with the main shaft or a subordinate shaft in the loading step; can reduce time to be spent for the loading step; and reduce necessity of maintenance of components to detect positional relationships between the crystal rod and the main or subordinate shaft.

Solution to Problem

To achieve the object above, the present invention provides a cylindrical grinding apparatus comprising a transport unit that holds and transports a crystal rod, a pair of support units that sandwich the crystal rod held by the transport unit in an axial direction and make the crystal rod rotatable around an axis, and a grinding unit that moves along the axial direction of the crystal rod supported by the pair of support units and performs traverse grinding on an outer circumference of the crystal rod, wherein

• • the pair of support units comprise a first support unit having a main shaft, a second support unit having a subordinate shaft, and a drive mechanism enabling the second support unit to move toward the first support unit,
  • by the drive mechanism, the second support unit moves toward the first support unit so that one end of the crystal rod held by the transport unit approaches and contacts with the subordinate shaft of the second support unit to be supported; next another end of the crystal rod approaches and contacts with the main shaft of the first support unit to be supported; and the crystal rod is sandwiched and supported between the main shaft and the subordinate shaft,
  • the cylindrical grinding apparatus further comprises a first detecting means for detecting proximity between the another end of the crystal rod and the main shaft in a non-contact manner, and a second detecting means for detecting proximity between the one end of the crystal rod and the subordinate shaft in a non-contact manner,
  • the drive mechanism can change and adjust moving speed of the second support unit:
  • in support with contact between the one end of the crystal rod and the subordinate shaft, moving speed B of the second support unit in time from proximity detection between the one end of the crystal rod and the subordinate shaft by the second detecting means to the support with contact is adjusted to be slower than moving speed A of the second support unit until the proximity detection; and
  • in support with contact between the another end of the crystal rod and the main shaft, moving speed D of the second support unit in time from proximity detection between the another end of the crystal rod and the main shaft by the first detecting means to the support with contact is adjusted to be slower than moving speed C of the second support unit until the proximity detection.

In the inventive cylindrical grinding apparatus, in the loading step, the moving speed of the second support unit is reduced by the drive mechanism, after detection of the proximity between the tail potion (one end) or cone portion (another end), which is the end portion of the crystal rod, and the main or subordinate shaft, so that the impact in contact between the end portion of the crystal rod and the main or subordinate shaft is reduced, and the contact can be performed safely. By this, it is possible to reduce damage to the end portion of the crystal rod and control occurrence of mechanical misalignment of each support unit. Therefore, in the subsequent cylindrical grinding step, the crystal rod will not slip or become misaligned due to grinding resistance, and it is possible to prevent adverse effect such as poorly ground condition of the cylindrical surface and poor diameter accuracy.

Further, the second support unit moves at a higher speed until the detection of the proximity above, it is possible to significantly reduce time required for the step than the case of using the conditional cylindrical grinding apparatus in which the second support unit moves at a low speed from the beginning to the end of the loading step. Accordingly, the inventive cylindrical grinding apparatus has an improved processing capacity and be capable of improving productivity.

Furthermore, because the above-mentioned proximity detecting means is not a contact type as before but a non-contact type, defects or the like due to abrasion of the detecting components each other do not occur and it is possible to reduce the frequency of maintenance.

In this event, the main shaft and the subordinate shaft each may have a holding part to contact and support the crystal rod,

• • each of the first detecting means and the second detecting means may be a sensor,
  • at an inside of each holding part of the main shaft and the subordinate shaft, the sensor may be disposed in a vertical direction to the main shaft and the subordinate shaft, and a detection line by the sensor may be provided,
  • the first detecting means may detect the proximity between the another end of the crystal rod and the main shaft by the fact that the another end of the crystal rod travels through the detection line,
  • the second detecting means may detect the proximity between the one end of the crystal rod and the subordinate shaft by the fact that the one end of the crystal rod travels through the detection line.

Alternatively, the main shaft and the subordinate shaft each may have a holding part to contact and support the crystal rod,

• • each of the first detecting means and the second detecting means may be a sensor,
  • the sensor may be connected to the first support unit and the second support unit respectively via a bracket and disposed at an outside of each holding part of the main shaft and the subordinate shaft, and a detection line by the sensor may be provided at the outside,
  • the first detecting means may detect the proximity between the another end of the crystal rod and the main shaft by the fact that the another end of the crystal rod travels through the detection line,
  • the second detecting means may detect the proximity between the one end of the crystal rod and the subordinate shaft by the fact that the one end of the crystal rod travels through the detection line.

With the sensor disposed inside or outside the holding part in this way, it is possible to more easily detect the proximity between the end portion of the crystal rod and the main or subordinate shaft.

Further, the sensor may be a photoelectric sensor having a light emitter and a light receiver, or an image sensor.

With such a sensor, it is possible to more surely detect the proximity between the end portion of the crystal rod and the main or subordinate shaft.

Further, the moving speeds A and C of the second support unit may be within a range from 3,000 to 4,000 mm/min, and

• • the moving speeds B and D of the second support unit may be within a range from 50 to 200 mm/min.

When this is the case, the time required for the loading step can be more surely shortened, and damage to the end portion of the crystal rod can be more reliably prevented.

Advantageous Effects of Invention

The inventive cylindrical grinding apparatus can prevent damage to the end portion of the crystal rod and misalignment in the loading step. Further, the time required for the loading step can be extremely shortened. Furthermore, the need for maintenance can be reduced. Thus, it is possible to improve the quality of the crystal rod after cylindrical grinding and its productivity.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an explanatory diagram showing an example of the inventive cylindrical grinding apparatus;

FIG. 2 is a flow diagram showing the functions and cooperation of the detecting means and the driving means in the loading step (the first half);

FIG. 3 is a flow diagram showing the functions and cooperation of the detecting means and the driving means in the loading step (the second half);

FIG. 4 is an explanatory diagram showing an example (internal arrangement) of the detecting means in Embodiment 1;

FIG. 5 is an explanatory diagram showing an example before and after detection of proximity between the end portion of the crystal rod and the subordinate shaft (the holding part) in Embodiment 1;

FIG. 6 is an explanatory diagram showing an example (external arrangement) of the detecting means in Embodiment 2;

FIG. 7 is an explanatory diagram showing an example before and after detection of proximity between the end portion of the crystal rod and the subordinate shaft (the holding part) in Embodiment 2;

FIG. 8 is a flow diagram showing an example of a conventional loading step;

FIG. 9 is a flow diagram showing a conventional contact-type detecting technique for detecting the position of a crystal rod immediately before contact with a holder;

FIG. 10 is an explanatory diagram showing the relationship between the ingot sensing rod and the shape of the end portion of the crystal rod in a conventional machine.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited thereto.

FIG. 1 shows an overall view of a cylindrical grinding apparatus 1 according to the present invention. As shown in FIG. 1, the cylindrical grinding apparatus 1 first includes a transport unit 8, a pair of support units 4, and a grinding unit 5. Furthermore, it has detecting means 14 of a non-contact type.

First, the transport unit 8 only needs to be able to hold and transport a crystal rod 7. Further, the grinding unit 5 has a grinding stone 6, which only needs to be able to perform traverse grinding on the outer circumference 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 transport unit 8 and the grinding unit 5 are provided with a drive mechanism not shown in FIGS. and are movable, and may be similar to conventional ones, for example.

Next, the pair of support units 4 will be explained. The pair of support units 4 sandwich the crystal rod 7 held by the transport unit 8 in the axial direction, make it rotatable around the axis, and have 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 subordinate shaft 3b. The main shaft 3a has a holding part 2a at its tip, and the subordinate shaft 3b has a holding part 2b at its tip. Therefore, the crystal rod 7 is supported by being sandwiched between the holding part 2a of the main shaft 3a and the holding part 2b of the subordinate shaft 3b.

Incidentally, although here shows an example in which the tail portion (one end) 12 of the crystal rod 7 is supported on the subordinate shaft 3b side and the cone portion (another end) 11 is supported on the main shaft 3a side, the present invention is not limited thereto. The direction of the crystal rod 7 may be reversed.

Further, the pair of support units 4 have a drive mechanism 13. Incidentally, for simplicity, the drive mechanism 13 is shown only in FIG. 1. This drive mechanism 13 includes, for example, a motor (a servo motor or the like), and can move the second support unit 4b toward the first support unit 4a. Of course, it is possible to move it also in the opposite direction of the first support unit 4a. By adjusting the motor rotation speed and rotation direction of the motor, the moving speed and the moving direction of the second support unit 4b can be changed and adjusted at will. Further, it may be equipped with a computer, etc. In particular, it is possible to automatically adjust the moving speed of the second support unit 4b in conjunction with the detection signal from the detecting means 14.

The detecting means 14 detects the proximity between the crystal rod 7 and the pair of support units 4 in a non-contact manner. More specifically, it consists of a first detecting means 14a that detects the proximity between the another end 11 of the crystal rod 7 and the main shaft 3a and a second detecting means 14b that detects the proximity between the one end 12 of the crystal rod 7 and the subordinate shaft 3b.

Here, the functions and cooperation of the detecting means 14 and the drive means 13 will be explained together with an explanation of the loading step (FIG. 2: the first half, FIG. 3: the second half).

First, the basic flow in the loading step is the same as the general example (FIG. 8) described above. That is, after the crystal rod 7 is carried in, the second support unit 4b is moved toward the first support unit 4a by the drive mechanism 13, so that one end 12 of the crystal rod 7 held by the transport unit 8 approaches and contact with the subordinate shaft 3b (more specifically, holding part 2b) of the support unit 4b and is supported. Next, the another end 11 of the crystal rod 7 approaches and contact with the main shaft 3a (more specifically, holding part 2a) of the first support unit 4a, and is supported. Thus, the crystal rod 7 is supported by being sandwiched between the main shaft 3a (holding part 2a) and the subordinate shaft 3b (holding part 2b). After that, the carry-in unit 8 retreats.

However, in the inventive cylindrical grinding apparatus 1, in the support with contact between the one end 12 of the crystal rod 7 and the subordinate shaft 3b, and the support with contact between the another end 11 of the crystal rod 7 and the main shaft 3a, there is cooperation between the second detecting means 14b and the drive mechanism 13, and cooperation between the first detecting means 14a and the drive mechanism 13, respectively.

Each flow will be explained.

(Carry-in of Crystal Rod)

A transport unit 8 that clamps the crystal rod 7 in the diameter direction moves to align the crystal axis center 10 with the rotation center 9 of the main shaft 3a and the subordinate shaft 3b (Step 1 in FIG. 2).

(Support of Crystal Rod)

Next, in order to sandwich the crystal rod 7 between the first support unit 4a and the second support unit 4b, the second support unit 4b is moved by the drive mechanism 13 toward the first support unit 4a. At this time, it is adjusted to move at a moving speed A until the second detecting means 14b detects the proximity between the one end 12 of the crystal rod 7 and the subordinate shaft 3b (Steps 2 to 3 in FIG. 2).

Then, when the second detecting means 14b detects the proximity, based on the detection signal, the drive mechanism 13 automatically adjusts the move at a moving speed B, which is slower than the moving speed A, in the time from then to the support with contact between the one end 12 and the subordinate shaft 3b (Steps 3 to 4 in FIG. 2).

After the support with the contact between the one end 12 and the subordinate shaft 3b, the second support unit 4b is continuously moved further toward the first support unit 4a by the drive mechanism 13. At this time, the crystal rod 7, the transport unit 8, and the second support unit 4b move as one altogether. Then, it is adjusted to move at the moving speed C until the first detecting means 14a detects the proximity between the another end 11 of the crystal rod 7 and the main shaft 3a (from Step 4 in FIG. 2 to Step 5 in FIG. 3). The moving speed C can be faster than the moving speed B, and may be the same speed as the moving speed A, for example. Incidentally, the change and adjustment from the moving speed B to the moving speed C may be performed manually by the operator by visually confirming the start of movement of the crystal rod 7 or the transport unit 8, or alternatively, it is also possible to use a system in which a position control mechanism of the transport unit 8 transmits the start of movement to the drive mechanism 13 and then the moving speed is automatically changed and adjusted.

When the first detecting means 14a detects the proximity, the drive mechanism 13 automatically, based on the detection signal, adjusts the move in the time from then to the support with contact between the another end 11 and the main shaft 3a so that the move is carried out at a moving speed D that is lower than the moving speed C (Steps 5 to 6 in FIG. 3). The moving speed D can be, for example, the same speed as the moving speed B.

As a result, the crystal rod 7 is sandwiched and supported between the main shaft 3a and the subordinate shaft 3b, but in order to prevent the main shaft 3a, the subordinate shaft 3b, the another end 11, and the one end 12 from slipping due to grinding resistance when the cylindrical surface of the crystal rod 7 is ground by a grinding stone of the grinding unit in the subsequent cylindrical grinding step, the second support unit 4b continues to move toward the first support unit 4a side (keep pushing) to increase the frictional force between the another end 11 of the crystal rod 7 and the main shaft 3a to be in their contact and the frictional force between the one end 12 of the crystal rod 7 and the subordinate shaft 3b to be in their contact (Step 6 in FIG. 3). In this way, the crystal rod 7 is sandwiched by the first support unit 4a and the second support unit 4b in the crystal axis direction. The timing of completion of the sandwiching may be determined, for example, by visually confirming of paused move of the crystal rod 7 or the transport unit 8, or by confirming of paused move of them from a position control mechanism of the transport unit 8.

(Retreat of Transport Unit)

After the crystal rod 7 is sandwiched in the step above, the transport unit 8 releases the crystal rod 7 and retreats (Step 7 in FIG. 3).

In the inventive cylindrical grinding apparatus 1 having such a cooperation between the detecting means 14 and the drive mechanism 13, the moving speed of the second support unit 4b is slowed down when the end portion of the crystal rod 7 comes into the proximity of the main shaft 3a or the subordinate shaft 3b, thus it is possible to prevent occurrence of damage to the end portion of the crystal rod 7 and mechanical misalignment of the support unit 4, which are caused by impact of their contact.

Furthermore, because the second support unit 4b can be moved at high speed until coming into the proximity, the time required for the loading step can be shortened.

Furthermore, as mentioned above, in the contact type detecting means as in Patent Document 1, the parts related to the detection wear out and require maintenance, but in the non-contact type detecting means 14 as in the present invention, parts will not wear out and the need for maintenance can be reduced.

Thanks to these excellent effects, cylindrically ground products can be obtained with high quality and the productivity thereof is also excellent.

Incidentsally, the specific setting values of the moving speeds A to D of the second support unit are not particularly limited, but the moving speeds A and C may be, for example, 3,000 to 4,000 mm/min, and the moving speeds B and D can be, for example, 50 to 200 mm/min. By setting values selected from these numerical ranges, it is surer to shorten the time required for the loading step and prevent damage to the end portion of the crystal rod 7, etc.

Examples of the detecting means 14 (the first detecting means 14a, the second detecting means 14b) can include various types of sensors. For example, a photoelectric sensor or an image sensor can be used. A photoelectric sensor may be equipped with a light emitter and a light receiver. Further, in the case of an image sensor, an image processing device (such as a computer) can be further used to process an acquired image. With these, it is possible to detect the proximity between the crystal rod and the main or subordinate shaft more surely.

Specific aspects of the detecting means 14 will be described below (Embodiments 1 and 2). Incidentally, although the second detecting means 14b and the subordinate shaft 3b (the holding part 2b) will be described as an example, the same configuration may be used for the case of the first detecting means 14a and the main shaft 3a (the holding part 2a).

Embodiment 1 of Detecting Means: Internal Arrangement

FIG. 4 shows an example of the detecting means 14 (second detecting means 14b). In this case, the detecting means is arranged inside the holding part 2b in a direction perpendicular to the subordinate shaft 3b. Further, FIG. 5 shows an example before and after detection of the proximity between the end portion of the crystal rod 7 and the subordinate shaft 3b (holding part 2b).

A holding part 2b at the tip of the subordinate shaft 3b that contacts and supports the crystal rod 7 has a through hole formed, which is a combination of a conical recess and a hole of a predetermined diameter. This through hole is configured to have the end portion of the crystal rod 7 inserted and supported.

Further, the holding part 2b is provided with a sensor installation hole 21, in which a conical-portion detecting sensor 22 is disposed as a second detecting means 14b, and a detection line 23 by the conical-portion detecting sensor 22 is provided. Based on the fact that one end 12 of the crystal rod 7 passes through the detection line 23, the proximity between the one end 12 and the subordinate shaft 3b (the holding part 2b) is detected. With such a configuration, the detection of the proximity can be performed more easily.

In addition, by providing a mechanism for sending compressed air 24 into the sensor installation hole 21, it is possible to prevent the conical-portion detecting sensor 22 from getting dirty due to entry of grinding dust in a mist form or the like that was made by grinding on the cylindrical outer peripheral surface of the crystal rod 7 in the cylindrical grinding step, which reduces maintenance as much as possible.

In this case, it can be seen that there is no limitation on distance of entry into the holding part 2b nor the shape of the end portion because there is no portion to come into contact (because the detecting means 14 is in non-contact type) when the end portion of the crystal rod 7 is detected.

Incidentally, the first detecting means 14a can also have a similar configuration.

Regarding the shape restriction of the end portion of the crystal rod, the contact typed example disclosed in Patent Document 1 will be studied here. FIG. 10 shows the relationship between an ingot sensing rod 46 and shapes of the end portion of the crystal rod 7. The top shows an example where the ingot sensing rod is extended, the middle shows an example where the end portion of the crystal rod is short, and the bottom shows an example where the end portion of the crystal rod is long.

Because the end portion (the conical cone portion and the tail portion, which are conical) of the crystal rod 7 is supported by the holder 45, a distance by which the end portion enters inside the holder 45 must be shorter than an allowable stroke (a) of the ingot sensing rod 46 and an ingot sensing rod movable device 50.

In the middle of FIG. 10, because a distance (b) of the enter is shorter than the allowable stroke (a), the conical end portion of the crystal rod 7 is supported by the holder 45 without any problem. In the bottom of FIG. 10, however, a distance (c) of the enter is longer than the allowable stroke (a), so that it can be seen that the end portion of the crystal rod 7 cannot be supported properly by the holder 45. That is, it demonstrates that the case of a contact type detecting means has a limitation depending on a shape of the end portion of the crystal rod, which is considered to be one of demerits.

In this way, in the case of a contact type detecting means, the entry of the end portion of the crystal rod 7 may be obstructed, so that the shape of the end portion of the crystal rod 7 must also be taken into consideration. However, a non-contact type as the present invention can eliminate the need for such consideration and is convenient.

Embodiment 2 of Detecting Means: Outside Arrangement

FIG. 6 shows another example of the detecting means 14 (a second detecting means 14b). In this case, it is arranged outside the holding part 2b. By installing an end-portion detecting sensor 25 as the second detecting means 14b outside the holding part 2b, it is possible to detect the end portion of the crystal rod 7 before it enters the holding part 2b.

Because it is necessary to keep a relative position between the end-portion detecting sensor 25 and the holding part 2b constant, as the easiest installment way, it is desirable that the end-portion detecting sensor 25 is connected to the second support unit 4b (for example, a base part 27b of the second support unit) via a bracket 28 and fixed completely. This makes it possible to move the second support unit 4b on the subordinate shaft side that moves toward the main shaft side by a drive mechanism such as a servo motor, synchronously with this end-portion detecting sensor 25.

Further, a detection line 26 by an end-portion detecting sensor 25 is provided. When one end 12 of the crystal rod 7 passes through the detection line 26, the proximity between the one end 12 and the subordinate shaft 3b (the holding part 2b) is detected. With such a configuration, detection of the proximity can be performed more easily.

Incidentally, the first detecting means 14a can also have a similar configuration.

In Embodiment 1 of FIG. 5, the conical end portion of the crystal rod 7 needs to enter inside of the holding part 2b, so the detection is not possible when the end portion of the crystal rod 7 does not have a conical end. However, in the case of the outside arrangement, the detection is possible even if the end portion of the crystal rod 7 is conical or flat, as shown in FIG. 7.

The detecting means 14 that detects the proximity between the end portion of the crystal rod and the main or subordinate shaft does not need a structure that is configured to have contact with a crystal rod or contact between constituent detecting components as disclosed in Patent Document 1. The detecting means 14 is not particularly limited as long as it can perform detection in a non-contact manner and cooperate as described above with the drive mechanism 13.

In preventing damage to the end portion of the crystal rod and the like, in order to move the second support unit 4b at a low speed immediately before the contact between the support unit 4 and the end portion of the crystal rod 7, it is essential to detect the position where the support unit 4 and the end portion of the crystal rod 7 are close to each other. Such a proximity detection can be performed easily by the configuration such as Embodiments 1 and 2, which are described above.

Example

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. However, the present invention is not limited thereto.

An automatic cylindrical grinding apparatus (Comparative Example) that employs conventional techniques and does not detect an end portion (a cone portion and a tail potion, which are conical) of a crystal rod and the inventive automatic cylindrical grinding apparatus (FIG. 1) (Example) that is provided with an end-portion detecting sensor 25 as a non-contact detecting means shown in FIG. 6 outside of each of holding parts on both the main shaft and the subordinate shaft sides, are prepared and the time required for the loading step was compared between the two apparatuses.

Example

The end-portion detecting sensor 25 was a general photoelectric sensor in which a light emitter and a light receiver are separated and was fixed completely on the base part 27b of the second support unit 4b via a bracket 28 completely so that, on a side of the subordinate shaft 3b, the distance 29 between the optical axis of the photoelectric sensor and the end surface of the holding part 2b is 100 mm and the space 30 between the light emitter and the light receiver is 450 mm. Also on the side of the main shaft 3a, the setting was performed so as to have the same conditions.

The used crystal rod 7 had a diameter of 300 mm, a cone length of 150 mm, a straight body length of 1,000 mm, and a tail length of 250 mm.

The loading step was performed as shown in FIGS. 2 and 3.

First, the crystal rod 7 was moved and carried in with the transport unit 8 so as to align the crystal axis center 10 with the rotation center 9 of the main shaft 3a and the subordinate shaft 3b (Step 1 in FIG. 2). The time required was 30 seconds. Incidentally, after this carry-in, the space between the end surface on the subordinate shaft 3b side and the tail portion (the one end) 12, and the space between the end surface on the main shaft 3a side and the cone portion (the another end) 11 were both 1,000 mm.

The second support unit 4b was continuously moved toward the main shaft 3a side by the drive mechanism 13 until the tail portion 12 was detected (Steps 2 to 3 in FIG. 2). The moving speed until detection by the end-portion detecting sensor (the second detecting means 14b) on the subordinate shaft 3b side was 4,000 mm/min (hereinafter referred to as the high speed), and the required time was about 15 seconds.

Next, the conical tail portion 12 of the crystal rod 7 moved from there into the inside of the holding portion 2b and came into contact with it (Steps 3 and 4 in FIG. 2). The moving speed until the contact was 100 mm/min (hereinafter referred to as the low speed), and the time required was about 48 seconds.

The holding portion 2a on the main shaft 3a side and the conical cone portion 11 of the crystal rod 7 move in the same manner.

The second support unit 4b was moved at the high speed until the end-portion detecting sensor (the first detecting means 14a) on the main shaft 3a side detected the cone portion 11 (Step 4 in FIG. 2 to Step 5 in FIG. 3). The time required was approximately 18 seconds.

The crystal rod 7 was moved at the low speed until the cone portion 11 of the crystal rod 7 entered into the inside of the holding part 2a and came into contact, and the crystal rod 7 was sandwiched and supported between the holding parts 2a and 2b. Further, the second support unit 4b continued to move toward the first support unit 4a side to increase the frictional force between the cone portion 11 of the crystal rod 7 and the holding part 2a and the frictional force between the tail portion 12 and the holding part 2b, and then the sandwiching was completed (Steps 5 to 6 in FIG. 3). The time required was 78 seconds.

Thereafter, the transport unit 8 was separated from the crystal rod 7 and retreated. The time required was 30 seconds.

Comparative Example

The crystal rod used was the same as used in Example.

The loading step was performed as shown in FIG. 8.

Incidentally, the carry-in of the crystal rod (Step 1 in FIG. 8) and the retreat of the transport unit 8 (Step 5 in FIG. 8) were the same as in Example, and the time required for each is 30 seconds as in Example.

Further, the support unit 4b on the subordinate shaft side is moved by the drive mechanism, and the tail portion 12 of the crystal rod 7 is brought into contact with the holding part of the subordinate shaft of the support unit 4b (Steps 2 to 3 in FIG. 8). Furthermore, the cone portion 11 of the crystal rod 7 was brought into contact with the holding part of the subordinate shaft of the support unit 4a on the main shaft side, and the sandwiching of the crystal rod 7 was completed (Steps 3 to 4 in FIG. 8). The moving speeds of the support unit 4b in these Steps 2 to 4 were all the low speed of 100 mm/min, and the times required for Steps 2 to 3 and Steps 3 to 4 were 630 seconds and 663 seconds, respectively.

Table 1 summarizes the time required for each step in the loading step in Example and Comparative Example.

While the total time required for the loading step was 1,353 seconds in Comparative Example, it was 219 seconds in Example. As described above, the time required in Example was about 16% of that of Comparative Example, and a significant time reduction of about 84% was confirmed.

In the case of the automatic cylindrical grinding apparatus, cylindrical grinding occupies most of the time and it takes about 2 to 4 hours for one crystal rod (depending on the length of the crystal rod, etc.). Taking this into consideration, the present invention can reduce the processing time by about 11 to 5% in the entire cylindrical grinding process including the loading step, improving productivity.

Furthermore, even if cylindrical grinding was performed with the crystal rod supported under the conditions of Example, no misalignment occurred same as when cylindrical grinding was performed with the crystal rod supported under the conditions of Comparative Example, and the ground surface had a surface condition similar to that of the Comparative Example.

TABLE 1
(Unit: second)

	Comparative
	Example	Example

To carry-in of a crystal rod	30	30
To detection of a tail portion	—	15
To contact between a tail portion and a	630	48
support device
To detection of a cone portion	—	18
To contact between a cone portion and a	663	78
support device and completion of sandwiching
To retreat of a transport unit	30	30
Sum	1,353	219
		(−84%)

The present description includes the following embodiments.

• • [1]: A cylindrical grinding apparatus comprising a transport unit that holds and transports a crystal rod, a pair of support units that sandwich the crystal rod held by the transport unit in an axial direction and make the crystal rod rotatable around an axis, and a grinding unit that moves along the axial direction of the crystal rod supported by the pair of support units and performs traverse grinding on an outer circumference of the crystal rod, wherein
    • the pair of support units comprise a first support unit having a main shaft, a second support unit having a subordinate shaft, and a drive mechanism enabling the second support unit to move toward the first support unit,
    • by the drive mechanism, the second support unit moves toward the first support unit so that one end of the crystal rod held by the transport unit approaches and contacts with the subordinate shaft of the second support unit to be supported; next another end of the crystal rod approaches and contacts with the main shaft of the first support unit to be supported; and the crystal rod is sandwiched and supported between the main shaft and the subordinate shaft,
    • the cylindrical grinding apparatus further comprises a first detecting means for detecting proximity between the another end of the crystal rod and the main shaft in a non-contact manner, and a second detecting means for detecting proximity between the one end of the crystal rod and the subordinate shaft in a non-contact manner,
    • the drive mechanism can change and adjust moving speed of the second support unit:
    • in support with contact between the one end of the crystal rod and the subordinate shaft, moving speed B of the second support unit in time from proximity detection between the one end of the crystal rod and the subordinate shaft by the second detecting means to the support with contact is adjusted to be slower than moving speed A of the second support unit until the proximity detection; and
    • in support with contact between the another end of the crystal rod and the main shaft, moving speed D of the second support unit in time from proximity detection between the another end of the crystal rod and the main shaft by the first detecting means to the support with contact is adjusted to be slower than moving speed C of the second support unit until the proximity detection.
  • [2]: The cylindrical grinding apparatus according to the above [1], wherein
    • the main shaft and the subordinate shaft each have a holding part to contact and support the crystal rod,
    • each of the first detecting means and the second detecting means is a sensor,
    • at an inside of each holding part of the main shaft and the subordinate shaft, the sensor is disposed in a vertical direction to the main shaft and the subordinate shaft, and a detection line by the sensor is provided,
    • the first detecting means detects the proximity between the another end of the crystal rod and the main shaft by the fact that the another end of the crystal rod travels through the detection line,
    • the second detecting means detects the proximity between the one end of the crystal rod and the subordinate shaft by the fact that the one end of the crystal rod travels through the detection line.
  • [3]: The cylindrical grinding apparatus according to the above [1], wherein
    • the main shaft and the subordinate shaft each have a holding part to contact and support the crystal rod,
    • each of the first detecting means and the second detecting means is a sensor,
    • the sensor is connected to the first support unit and the second support unit respectively via a bracket and disposed at an outside of each holding part of the main shaft and the subordinate shaft, and a detection line by the sensor is provided at the outside,
    • the first detecting means detects the proximity between the another end of the crystal rod and the main shaft by the fact that the another end of the crystal rod travels through the detection line,
    • the second detecting means detects the proximity between the one end of the crystal rod and the subordinate shaft by the fact that the one end of the crystal rod travels through the detection line.
  • [4]: The cylindrical grinding apparatus according to the above [2] or [3], wherein
    • the sensor is a photoelectric sensor having a light emitter and a light receiver, or an image sensor.
  • [5]: The cylindrical grinding apparatus according to any one of the above [1] to [4], wherein
    • the moving speeds A and C of the second support unit are within a range from 3,000 to 4,000 mm/min, and
    • the moving speeds B and D of the second support unit are within a range from 50 to 200 mm/min.

It should be noted that the present invention is not limited to the above-described embodiments. The embodiments are just examples, and any examples that have substantially the same feature and demonstrate the same functions and effects as those in the technical concept disclosed in claims of the present invention are included in the technical scope of the present invention.