Processing equipment

Abstract

To achieve good machining by rotatably supporting a rotating shaft of a spindle even when grinding or polishing a hard workpiece.SOLUTION: A machining apparatus includes a mitigation unit 48 that mitigates thrust load applied in a direction away from a holding table with respect to a rotating shaft 41 during machining of a workpiece. Thereby, force in a direction in which the thrust load is cancelled can be applied to reduce the possibility of causing galling in the rotating shaft 41.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a processing apparatus for grinding or polishing a workpiece. [Background technology]

[0002] In a processing device in which a processing tool such as a grinding wheel or a polishing wheel is attached to the tip of a spindle, the workpiece is held on a chuck table and processed while being brought close to the rotating processing tool. Usually, the rotating shaft of the spindle is supported in a non-contact manner by an air bearing (for example, see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2008-049445 A Summary of the Invention [Problem to be solved by the invention]

[0004] When the workpiece is hard, such as sapphire, SiC (silicon carbide), or LT (lithium tantalate), it is necessary to press the processing tool against the workpiece to process it, but if the pressing force becomes too strong, a thrust load is applied to the bearing supporting the rotating shaft of the spindle in the direction away from the holding table. If this thrust load exceeds the supporting force of the air bearing, there is a risk that the rotating shaft will not be supported by the air at the opposite end of the grinding wheel, etc.

[0005] The present invention has been made in consideration of such problems, and has as its object to rotatably support a rotating shaft to enable good machining even when grinding or polishing a hard workpiece. [Means for solving the problem]

[0006] The present invention provides a processing apparatus including a holding table for holding a workpiece, a processing tool for processing the workpiece held on the holding table, a processing feed unit for moving the processing tool closer to the holding table for processing, and a spindle unit having the processing tool fixed to a tip thereof, the spindle unit including a rotating shaft for supporting the processing tool at one end, an air bearing for rotatably supporting the rotating shaft, a reduction unit for reducing a thrust load acting on the rotating shaft in a direction away from the holding table during processing of the workpiece, and a pressure sensor that measures a pressure applied in a thrust direction of the spindle unit; Have the reduction unit has a first magnet fixed to the rotating shaft, and a second magnet that is installed at a position farther from the holding table than the first magnet, faces the first magnet, and repels the first magnet, the first magnet being a permanent magnet and the second magnet being an electromagnet, and by adjusting a current supplied to the second magnet in accordance with a measurement value of the pressure sensor, the measurement value of the pressure sensor is controlled to be within an allowable range, and a repulsive force between the first magnet and the second magnet is used to reduce a thrust load acting on the rotating shaft in a direction away from the holding table during machining of a workpiece. . Effect of the Invention

[0007] The processing device of the present invention is equipped with a reduction unit that reduces the thrust load acting on the rotating shaft in a direction away from the holding table during processing of the workpiece, and therefore reduces the risk of the rotating shaft being seized by a force acting in a direction that cancels the thrust load. Therefore, even when grinding or polishing a hard workpiece, the rotating shaft can be rotatably supported, enabling good processing. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is a front view showing an example of a grinding device. [Diagram 2] FIG. 1 is a front view showing an example of a polishing apparatus. [Diagram 3] FIG. 2 is a vertical sectional view showing a first example of a spindle unit. [Figure 4] FIG. 11 is a vertical sectional view showing a second example of the spindle unit. [Diagram 5] FIG. 11 is a vertical sectional view showing a third example of the spindle unit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The grinding apparatus 1 shown in FIG. 1 includes a holding table 2 for holding a workpiece, a processing mechanism 3 for grinding the workpiece 100 held on the holding table 2, and a processing feed unit 7 for moving the processing mechanism 3 toward and away from the workpiece.

[0010] The holding table 2 is capable of suction-holding the workpiece 100 on its upper surface, and is rotatable about a rotation axis 20 extending in the Z-axis direction.

[0011] The processing mechanism 3 is configured by mounting a grinding wheel 5, which is a processing tool, on the tip of a spindle unit 4. The spindle unit 4 includes a spindle 41 having an axis 40 in the Z-axis direction, a motor 42 that rotates the spindle 41, and a flange 43 connected to the lower end of the spindle 41.

[0012] A grinding wheel 5, which is a processing tool, is attached to the flange 43. The grinding wheel 5 is supported at one end of the spindle 41 via the flange 43, and includes a base 51 attached to the flange 43 and a plurality of grinding stones 52 fixed to the lower surface of the base 51 in an annular shape.

[0013] In the grinding device 1 configured in this manner, the holding table 2 holding the workpiece 100 is rotated, and the processing feed unit 7 lowers the processing mechanism 3 while rotating the grinding wheel 5, thereby grinding the upper surface of the workpiece 100.

[0014] The grinding apparatus 10 shown in FIG. 2 is equipped with a grinding wheel 6 instead of the grinding wheel 5 shown in FIG. 1, and other parts are configured in the same manner as the grinding apparatus 1. Therefore, common symbols as in FIG. 1 are used and their explanations are omitted.

[0015] The polishing wheel 6 includes a base 61 attached to the flange 43 and a circular polishing pad 62 fixed to the lower surface of the base 61 .

[0016] In the polishing apparatus 10, the holding table 2 holding the workpiece 100 is rotated, and the processing feed unit 7 lowers the processing mechanism 3 while rotating the polishing wheel 6, thereby grinding the upper surface of the workpiece 100.

[0017] The following describes the configuration common to the grinding apparatus 1 and the polishing apparatus 10. 3, the spindle 41 includes a rotating shaft 411 that is rotated by a motor 42, a first large diameter portion 412 and a second large diameter portion 413 that are spaced apart in the axial direction of the spindle 41, and a supported shaft 414 that is located between the first large diameter portion 412 and the second large diameter portion 413. A grinding fluid flow path 415 that passes through the spindle 41 in the axial direction and through which the grinding fluid passes is formed inside the spindle 41.

[0018] The spindle unit 4 includes an air bearing 44 that rotatably supports the spindle 41 , and a housing 45 that supports the air bearing 44 .

[0019] The air bearing 44 communicates with an air flow path 451 formed inside the housing 45. The air flow path 451 opens at an air inlet 452 and an air outlet 453. The air bearing 44 includes a first thrust bearing 441 that supports the first large diameter portion 412 in the thrust direction by blowing air upward toward the first large diameter portion 412, a second thrust bearing 442 that supports the second large diameter portion 413 in the thrust direction by blowing air downward toward the second large diameter portion 413, and a radial bearing 443 that supports the spindle 41 in the radial direction by blowing air toward the supported shaft 414. The air that flows in from the air inlet 452 passes through the air flow path 451 and is blown out at the first thrust bearing 441, the second thrust bearing 442, and the radial bearing 443 to support the spindle 41 in a non-contact manner.

[0020] A pressure sensor 444 is disposed on the upper part of the first thrust bearing 441. The pressure sensor 444 measures the pressure between the first thrust bearing 441 and the first large diameter portion 412.

[0021] The motor 42 includes a rotor 421 connected to the rotating shaft 411, and a stator coil 422 disposed on the outer circumferential side of the rotor 421. The outer circumferential side of the stator coil 422 is covered by a water jacket 46, and the rotor 421 and the stator coil 422 are covered from above by an end cover 47.

[0022] A first magnet 481 is provided on the outer periphery of the rotating shaft 411, slightly closer to the holding table 2 than the upper end of the rotating shaft 411. Meanwhile, a second magnet 482 is provided on the inner periphery of the end cover 47. The first magnet 481 and the second magnet 482 are opposed to each other in the Z-axis direction, i.e., the axial direction of the spindle 41, and the first magnet 481 is located closer to the holding table 2 than the second magnet 482. The first magnet 481 and the second magnet 482 repel each other. The position of the second magnet 482 may be any position where a repulsive force is generated between the second magnet 482 and the first magnet 481, and is not limited to the inner circumferential side of the end cover 47.

[0023] For example, a permanent magnet is used as the first magnet 481. On the other hand, for example, an electromagnet is used as the second magnet 482. The second magnet 482 may be a permanent magnet, but if it is an electromagnet, the repulsive force can be controlled by the strength of the electric current.

[0024] The second magnet 482 is movably attached to the end cover 47 by a set screw 483. That is, the second magnet 482 can be fixed at an adjusted position while the set screw 483 prevents the second magnet 482 from coming loose. Furthermore, since there is a gap 484 between the second magnet 482 and the rotating shaft 411, a cover 485 is provided to prevent fingers from entering this gap 484.

[0025] In the grinding apparatus 1 shown in Fig. 1 and the polishing apparatus 10 shown in Fig. 2, when the grinding wheel 5 or polishing wheel 6, which is a processing tool, is lowered while rotating and brought into contact with the workpiece 100, a load is applied to the spindle 41 in the upward thrust direction. However, since the first magnet 481 and the second magnet 482 repel each other, the thrust load in the direction away from the holding table 2 is reduced by the magnetic force. Therefore, even if the workpiece 100 is hard, the risk of galling occurring between the spindle 41 and the air bearing 44 can be reduced. In this manner, the first magnet 481 and the second magnet 482 function as a reduction unit 48 that reduces the thrust load in the direction in which the spindle 41 moves away from the holding table 2.

[0026] When the spindle 41 rises in a direction away from the holding table 2, the measurement value of the pressure sensor 444 increases. However, if an electromagnet is used as the second magnet, the measurement value of the pressure sensor 444 can be controlled to be within the allowable range by adjusting the current supplied to the second magnet 482 in accordance with the measurement value of the pressure sensor 444, thereby stabilizing the position of the spindle 41 in the Z-axis direction and reducing the risk of seizing.

[0027] It is also possible to use an electromagnet as the first magnet 481. In that case, however, a mechanism must be provided to prevent the wiring for supplying power to the electromagnet from rotating. Therefore, it is preferable to use an electromagnet as the second magnet 482.

[0028] Permanent magnets may be used for both the first magnet 481 and the second magnet 482. However, since the thrust load acting on the spindle 41 differs depending on the combination of the machining tool and the workpiece attached to the spindle 41, and the measured value of the pressure sensor 444 also differs, the thrust load generated in the direction away from the holding table 2 is measured for each combination of the machining tool and the workpiece, the repulsive force required to reduce the thrust load is calculated, and the position of the second magnet 482 is adjusted before the start of machining so that the repulsive force generated in the reduction unit 48 becomes the calculated repulsive force. This makes it possible to adjust the repulsive force in the reduction unit 48 in accordance with the combination of the machining tool and the workpiece.

[0029] The spindle unit 4 shown in Fig. 4 includes a reduction unit 49 instead of the reduction unit 48 shown in Fig. 3. Although Fig. 4 does not show anything equivalent to the pressure sensor 444 provided in the grinding apparatus 1 in Fig. 3, an equivalent may be provided.

[0030] The lightening unit 49 includes an attraction part 491 disposed on the outer periphery of the upper end of the rotating shaft 411, and a third magnet 492 that magnetically attracts the attraction part 491. The attraction part 491 is configured with a magnet or a ring plate of a magnetic material, and is disposed at a position protruding further upward than the end cover 47.

[0031] The third magnet 492 faces the attraction part 491 in the axial direction of the rotating shaft 411, is closer to the holding table 2 than the attraction part 491, is composed of an electromagnet, and is fixed to a coil 493 and yokes 494 and 495, and the yoke 494 is screwed to the end cover 47. The attraction part 491 and the third magnet 492 face each other via the yoke 495 in the Z-axis direction, i.e., the axial direction of the rotating shaft 411. By passing a current through the coil 493, the attraction part 491 is attracted to the third magnet 492, and thus, during the processing of the workpiece 100, a thrust load acting on the rotating shaft 411 in a direction away from the holding table 2 can be reduced. When the spindle unit 4 includes a pressure sensor, the current supplied to the third magnet 492 is adjusted according to the measurement value of the pressure sensor, so that the measurement value of the pressure sensor is controlled to be within the range of the allowable value, and thus the position of the spindle 41 in the Z-axis direction can be stabilized.

[0032] Although it is possible to use an electromagnet as the attraction portion 491, in that case, it is necessary to provide a mechanism for preventing the power supply wiring from rotating, so it is preferable to use an electromagnet as the third magnet 492. Also, not only the attraction portion 491 but also the third magnet can be a permanent magnet.

[0033] Furthermore, the position of the third magnet 492 may be any position where an attractive force is generated between the third magnet 492 and the adsorption portion 491, and may be any position closer to the holding table 2 than the adsorption portion 491, and is not limited to the inner circumferential side of the end cover 47.

[0034] 5 is configured similarly to the spindle unit 4 shown in Fig. 4, but includes a pressure sensor 71 between the lower part of the housing 45 of the spindle unit 4 and a support member 70 that supports the spindle unit 4 from below. In this case as well, the position of the spindle 41 can be stabilized by controlling the magnetic force of the third magnet according to the measurement value of the pressure sensor 71.

[0035] The positions at which the two magnets that make up the lightening unit are arranged may be such that one is on the spindle 41 side and the other is on the housing 45, water jacket 46 or end cover 47 side, and are not limited to the positions shown in Figures 3 to 5. Furthermore, although the present embodiment has been described using air bearings, the type of bearing is not limited to air. [Explanation of symbols]

[0036] 1: Grinding device 10: Polishing device 2: Holding table 20: Rotating shaft 3: Processing mechanism 4: Spindle unit 40: Axial center 41: Spindle 411: Rotating shaft 412: First large diameter portion 413: Second large diameter portion 414: Supported shaft 415: Grinding fluid flow path 42: Motor 421: Rotor 422: Stator coil 43: Flange 44: Air bearing 441: First thrust bearing 442: Second thrust bearing 443: Radial bearing 444: Pressure sensor 45: Housing 451: Air flow path 452: Air inlet 453: Air outlet 46: Water jacket 47: End cover 48: Mitigation unit 481: First magnet 482: Second magnet 483: Grub screw 484: Gap 485: Cover 49: Lightening unit 491: Adsorption part 492: Third magnet 493: Coil 494, 495: York 5: Grinding wheel 51: Base 52: Grinding stone 6: Polishing wheel 61: Base 62: Polishing pad 7: Processing feed unit 70: Support member 71: Pressure sensor 100: Workpiece

Claims

[Claim 1] A holding table for holding the workpiece; a processing tool for processing the workpiece held on the holding table; a processing feed unit for moving the processing tool closer to the holding table for processing; A processing apparatus comprising: a spindle unit to which the processing tool is fixed at a tip, The spindle unit comprises: a rotating shaft supporting the machining tool at one end; a bearing that rotatably supports the rotating shaft; a reduction unit that reduces a thrust load acting on the rotation shaft in a direction away from the holding table during processing of the workpiece; a pressure sensor that measures a pressure applied in a thrust direction of the spindle unit; having The mitigation unit comprises: a first magnet fixed to the rotating shaft; a second magnet that is disposed at a position farther from the holding table than the first magnet, faces the first magnet, and repels the first magnet; the first magnet is a permanent magnet and the second magnet is an electromagnet; adjusting a current supplied to the second magnet in response to a measurement value of the pressure sensor so that the measurement value of the pressure sensor falls within a tolerance range; The repulsive force between the first magnet and the second magnet reduces a thrust load acting on the rotation shaft in a direction away from the holding table during machining of the workpiece. Processing equipment.

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