Spindle unit and machining device

Abstract

Provided is a spindle unit and a processing device, the spindle unit having an air bearing that enables continuous rotation of a spindle even in a situation where thermal deformation occurs and that is also excellent in load resistance. The spindle unit includes a spindle that has a processing tool attached to a front end, and a spindle housing that has a thrust bearing and a radial bearing that noncontactingly support the spindle so as to be rotatable by air, the thrust bearing having an air supply portion that supplies air to a gap between an outer side surface of the spindle in a direction perpendicular to an axial direction of the spindle and an inner side surface of the spindle housing, and an adjustment portion that is capable of adjusting a distance in a direction perpendicular to the outer side surface of the spindle of the gap.

Description

TECHNICAL FIELD

[0001] The present application relates to a spindle unit and a processing device. BACKGROUND

[0002] A grinding device that performs grinding processing on a wafer held by a chuck table has a spindle unit that includes a spindle. In the grinding device, a grinding wheel that is provided with a ring-shaped grinding tool is attached to the front end of the spindle. The wafer is ground by the grinding tool that rotates by rotating the spindle.

[0003] As disclosed in Patent Document 1, the spindle unit has a spindle housing that forms a gap around the outer circumferential surface of the spindle, and an air supply portion that supplies air to the gap. The gap is filled with air and pressurized, thereby forming an air bearing.

[0004] In addition, with respect to the spindle, as disclosed in Patent Document 2, by measuring the pressure of the air of the gap, the load applied to the grinding tool can be measured.

[0005] Patent Document 1: Japanese Patent Application Laid-Open (JP-A) No. 11-132232

[0006] Patent Document 2: Japanese Patent Application Laid-Open (JP-A) No. 2008-049445

[0007] In the above-described spindle unit, the grinding tool of the grinding wheel attached to the front end of the spindle is pressed against the wafer to grind the wafer, and by this grinding processing, a load is applied to the direction in which the spindle inclines, and in order to suppress the inclination of the spindle due to this load, the gap is narrowed. That is, by increasing the pressure of the air supplied to the narrow gap, an air bearing that has high load resistance (high rigidity) in which the spindle does not incline when the grinding tool receives a load is formed.

[0008] However, since the gap is narrow, at the initial stage of the activation of the device, due to the supply of air for forming the air bearing, the passage of cooling water, and the like, thermal deformation of the housing or the spindle sometimes occurs. In this case, a contact site in which the spindle comes into contact with the housing is generated, and when the spindle is rotated, this contact site is sometimes rubbed to form a concave-convex, and the spindle becomes unable to rotate. SUMMARY

[0009] Thus, an object of the present application is to provide a spindle unit that has an air bearing that enables the continuous rotation of the spindle even in a situation in which thermal deformation occurs and that has excellent load resistance.

[0010] According to one embodiment of the present application, a spindle unit is provided, wherein the spindle unit includes: a spindle that mounts a processing tool at a front end; and a spindle housing that has a thrust bearing and a radial bearing that support the spindle so as to be rotatable in a non-contact manner by air, the thrust bearing having: an air supply portion that supplies air to a gap between an outer side surface of the spindle in a direction perpendicular to an axial direction of the spindle and an inner side surface of the spindle housing; and an adjustment portion that is capable of adjusting a distance of the gap in a direction perpendicular to the outer side surface of the spindle.

[0011] Preferably, the adjustment portion has a piezoelectric actuator that is disposed on the spindle so as to move the outer side surface of the spindle that forms the thrust bearing in the axial direction of the spindle. Also, preferably, the adjustment portion has a piezoelectric actuator that is disposed on the spindle housing so as to move the inner side surface of the spindle housing that forms the thrust bearing in the axial direction of the spindle.

[0012] According to another embodiment of the present application, a processing device is provided that processes a workpiece by a processing tool, wherein the processing device has: a spindle unit that includes a spindle that mounts the processing tool at a front end and a spindle housing that has a thrust bearing and a radial bearing that support the spindle so as to be rotatable in a non-contact manner by air; a holding unit that holds the workpiece; a pressure measurement portion that measures a pressure of air; and a voltage control portion that controls a voltage of direct current power, the thrust bearing having: an air supply portion that supplies air to a gap between an outer side surface of the spindle in a direction perpendicular to an axial direction of the spindle and an inner side surface of the spindle housing; and an adjustment portion that includes a piezoelectric actuator that is capable of adjusting a distance of the gap in a direction perpendicular to the outer side surface of the spindle, the pressure measurement portion measuring a pressure of air of the gap that forms the thrust bearing, the voltage control portion controlling a voltage of direct current power supplied to the piezoelectric actuator so as to adjust the distance of the gap so that a pressure value measured by the pressure measurement portion becomes a value that is set in advance.

[0013] Preferably, the adjustment portion has the piezoelectric actuator that is disposed on the spindle so as to move the outer side surface of the spindle that forms the thrust bearing in the axial direction of the spindle. Also, preferably, the adjustment portion has the piezoelectric actuator that is disposed on the spindle housing so as to move the inner side surface of the spindle housing that forms the thrust bearing in the axial direction of the spindle.

[0014] In the spindle unit of each aspect of the present application, the distance of the gap (thrust gap) between the outer side surface of the spindle in the direction perpendicular to the axial direction of the spindle and the inner side surface of the spindle housing can be adjusted by the adjustment portion. Therefore, for example, the thrust gap can be expanded at the time of idling before the temperature of the spindle is stabilized. Therefore, the occurrence of the case where the spindle, which is thermally deformed at the time of idling, contacts the spindle housing can be suppressed. Therefore, the spindle can be continuously rotated.

[0015] Further, in the spindle unit, the thrust gap can be made narrow to be the usual distance at the time of grinding processing by the adjustment portion. Therefore, a thrust bearing of high load resistance (high rigidity) can be realized. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 is a perspective view showing the structure of a grinding device.

[0017] Figure 2 is a view showing the structure of a spindle unit.

[0018] Figure 3 is a view showing the structure of an adjustment portion.

[0019] Figure 4 is a view showing other structure of a spindle unit.

[0020] Figure 5 is a view showing other structure of an adjustment portion.

[0021] REFERENCE NUMERALS

[0022] 1: grinding device; 10: base; 11: column; 31: chuck table; 32: holding surface; 50: grinding feed mechanism; 78: spindle unit; 70: grinding unit; 71: spindle housing; 74: grinding wheel mount; 75: grinding wheel; 76: grinding wheel base; 77: grinding tool; 72: spindle; 81: first circular plate portion; 82: second circular plate portion; 83: circular plate portion surface; 84: radial side surface; 73: rotary motor; 85: rotor; 86: stator; 87: cooling jacket; 88: cooling water path; 91: annular portion; 92: annular portion surface; 93: radial side air blow outlet; 95: thrust concave portion; 96: bottom surface; 97: side surface; 110: air supply source; 111: air supply path; 115: pressure element; 116: pressure measurement portion; 120: adjustment portion; 121: piezoelectric actuator; 125: sealing material; 122: movable portion; 124: movable portion surface; 123: thrust side air blow outlet; 130: grinding water source; 131: grinding water introduction path; 132: grinding water path; 140: direct current power supply; 141: voltage control portion; 142: power line; 143: power line; 145: second contact point; 146: first contact point; 150: adjustment portion; 151: thrust concave portion; 152: bottom surface; 153: side surface; 300: radial gap; 301: thrust gap. DETAILED DESCRIPTION

[0023] An embodiment of the present application will be described below with reference to the drawings. As shown in Figure 1 the drawing, a grinding device 1 of the present embodiment is an example of a processing device, and is a device for grinding a wafer 100 as a workpiece. The wafer 100 is, for example, a semiconductor wafer.

[0024] The grinding device 1 has a base 10 of a rectangular parallelepiped shape and a column 11 extending upward.

[0025] An opening portion 13 is provided on the upper surface side of the base 10. Further, a chuck table 31 as a holding unit is disposed in the opening portion 13. The chuck table 31 has a holding surface 32 that holds the wafer 100.

[0026] The holding surface 32 of the chuck table 31 is composed of a porous material, and communicates with a suction source (not shown), whereby the wafer 100 is held by suction. That is, the chuck table 31 holds the wafer 100 by the holding surface 32.

[0027] Further, the chuck table 31 is rotatable about a table center axis that extends through the center of the holding surface 32 in the Z-axis direction, by a support member (not shown) provided below, while holding the wafer 100 by the holding surface 32. Thus, the wafer 100 held by the holding surface 32 is rotated about the center of the holding surface 32 as a rotation axis.

[0028] A cover plate 39 is provided around the chuck table 31, which moves along the Y-axis direction together with the chuck table 31. Additionally, a pleat 12 that extends and retracts in the Y-axis direction is connected to the cover plate 39. Furthermore, a Y-axis moving mechanism (not shown) is provided below the chuck table 31. The Y-axis moving mechanism causes the chuck table 31 to move along the Y-axis direction.

[0029] In this embodiment, generally speaking, the chuck stage 31 moves along the Y-axis direction via a Y-axis moving mechanism between a placement position for placing the wafer 100 in front of the holding surface 32 (-Y direction side) and a grinding position for grinding the wafer 100 behind it (+Y direction side).

[0030] In addition, such as Figure 1 As shown, a column 11 is erected on the rear (+Y direction side) of the base 10. A grinding unit 70 for grinding the wafer 100 and a grinding feed mechanism 50 are provided on the front surface of the column 11.

[0031] The grinding feed mechanism 50 moves the chuck table 31 and the grinding unit 70 relative to each other in the Z-axis direction (grinding feed direction) perpendicular to the holding surface 32. In this embodiment, the grinding feed mechanism 50 is configured to move the grinding unit 70 relative to the chuck table 31 in the Z-axis direction.

[0032] The grinding feed mechanism 50 includes: a pair of Z-axis guideways 51 parallel to the Z-axis direction; a Z-axis moving table 53 sliding on the Z-axis guideways 51; a Z-axis ball screw 52 parallel to the Z-axis guideways 51; a Z-axis motor 54; and a support housing 56 mounted on the front surface (front) of the Z-axis moving table 53. The support housing 56 supports the grinding unit 70.

[0033] The Z-axis moving table 53 is configured to slide on the Z-axis guide rail 51. A nut (not shown) is fixed to the rear surface (back side) of the Z-axis moving table 53. A Z-axis ball screw 52 is screwed into this nut. A Z-axis motor 54 is connected to one end of the Z-axis ball screw 52.

[0034] In the grinding feed mechanism 50, the Z-axis motor 54 rotates the Z-axis ball screw 52, ​​thereby causing the Z-axis moving table 53 to move along the Z-axis guide rail 51 in the Z-axis direction. As a result, the support housing 56 mounted on the Z-axis moving table 53 and the grinding unit 70 supported on the support housing 56 also move together with the Z-axis moving table 53 in the Z-axis direction.

[0035] The grinding unit 70 has a spindle unit 78 comprising a spindle housing 71, a spindle 72, and a rotary motor 73. The spindle unit 78 is fixed to the support housing 56.

[0036] The spindle housing 71 is held in the support housing 56 in a manner extending along the Z-axis. The spindle 72 extends along the Z-axis perpendicularly to the holding surface 32 of the chuck table 31 and is supported by the spindle housing 71 to enable rotation. A rotary motor 73 is connected to the upper end of the spindle 72. Through this rotary motor 73, the spindle 72 rotates about a rotation axis extending along the Z-axis.

[0037] The grinding unit 70 also has a grinding wheel mounting base 74 mounted on the lower end of the spindle 72 and a grinding wheel 75 supported on the grinding wheel mounting base 74.

[0038] The grinding wheel mounting base 74 is formed in the shape of a circular plate and is fixed to the lower end (front end) of the spindle 72. The grinding wheel mounting base 74 supports the grinding wheel 75.

[0039] The grinding wheel 75 is formed with an outer diameter that is approximately the same as the outer diameter of the grinding wheel mounting base 74. The grinding wheel 75 includes an annular grinding wheel base (ring base) 76 formed of metal material. A grinding tool 77, as an example of a machining tool, is fixed on the lower surface of the grinding wheel base 76 along the entire circumference.

[0040] The grinding wheel 77 is formed in a ring shape and rotates via a rotating axis that passes through the center of the grinding wheel 77 and extends along the Z-axis direction. It is rotated by a rotary motor 73 through a spindle 72, a grinding wheel mounting base 74 and a grinding wheel base 76 to grind the wafer 100 held by the chuck stage 31 located in the grinding position.

[0041] Thus, in the grinding apparatus 1, the grinding wheel 77 is mounted on the front end of the spindle 72 by means of the grinding wheel mount 74 and the grinding wheel base 76. Furthermore, in the spindle unit 78, the spindle 72, on which the grinding wheel 77 is mounted, is supported so that it can rotate. The grinding apparatus 1 rotates this spindle 72 to process the wafer 100, which is the workpiece, by means of the grinding wheel 77.

[0042] Next, the spindle unit 78 of this embodiment will be described in more detail.

[0043] like Figure 2 As shown, the spindle unit 78 includes: a spindle 72 in an upright position; a spindle housing 71 covering and supporting the spindle 72; a spindle cover 66 covering the lower end portion of the spindle 72; and a rotary motor 73 that drives the spindle 72 to rotate.

[0044] The main shaft 72 extends along the Z-axis. A first circular plate portion 81 with a large diameter is formed in the middle part of the main shaft 72. In addition, a second circular plate portion 82 with a large diameter is also formed at the lower end of the main shaft 72.

[0045] A rotary motor 73 is connected to the upper end of the main shaft 72. The rotary motor 73 has a rotor 85 and a stator 86 provided to the upper end portion of the main shaft 72. The stator 86 is supplied with a prescribed voltage, whereby the rotor 85 rotates, and the main shaft 72 rotates about the axis.

[0046] Further, the stator 86 is provided to the inner peripheral surface of the main shaft housing 71 via a cooling jacket 87. A large number of cooling water passages 88 are formed in the cooling jacket 87. The rotary motor 73 is cooled by these cooling water passages 88.

[0047] A rotation detection sensor 89 is provided in the vicinity of the upper end of the main shaft 72 in the main shaft housing 71. The rotation detection sensor 89 is disposed so as to oppose a detected portion 90 mounted to the upper end of the main shaft 72. The rotation detection sensor 89 is configured to detect the rotational movement of the detected portion 90, whereby the rotation of the main shaft 72 is detected.

[0048] The above-described grinding wheel mounting seat 74 is connected to the front end (lower end) of the main shaft 72. The grinding wheel 75 including the grinding abrasive 77 is mounted to the grinding wheel mounting seat 74.

[0049] A grinding water introduction passage 131 that communicates with a grinding water source 130 is mounted to the upper end of the main shaft 72. Further, the grinding water introduction passage 131 communicates with a grinding water passage 132 provided in the main shaft 72, the grinding wheel mounting seat 74, and the grinding wheel base 76. With this configuration, the grinding water from the grinding water source 130 is supplied to the grinding abrasive 77 via the grinding water introduction passage 131 and the grinding water passage 132.

[0050] The main shaft housing 71 is configured to surround the outer surface of the main shaft 72, and the main shaft 72 is supported so as to be rotatable by an air bearing.

[0051] The main shaft housing 71 has a ring-shaped portion 91 at the lower end portion. The ring-shaped portion 91 is provided to the main shaft housing 71 in such a manner as to enter between the first circular plate portion 81 and the second circular plate portion 82 of the main shaft 72, and in such a manner as to form a slight gap between the first circular plate portion 81 and the second circular plate portion 82 and the ring-shaped portion 91.

[0052] Further, the main shaft housing 71 has a plurality of radial side air blow-out ports 93 that communicate with an air supply passage 111 connected to an air supply source 110, and constitutes a radial bearing.

[0053] The air supply passage 111 is formed so as to extend from the outside of the main shaft unit 78 into the main shaft housing 71 including the ring-shaped portion 91, and has an on-off valve 112 and a check valve 113.

[0054] The radial side air outlet 93 is provided in the annular portion 91 to face the radial side 84 extending between the first circular plate portion 81 and the second circular plate portion 82 of the main shaft 72, and is connected to the air supply path 111.

[0055] The radial air outlet 93 opens into the gap 300 between the radial side 84 of the spindle 72 and the annular portion 91 of the spindle housing 71. The radial air outlet 93 ejects high-pressure air radially into this radial gap 300, thereby forming a radial bearing in the radial gap 300 between the spindle housing 71 and the spindle 72, which supports the spindle 72 in a non-contact manner.

[0056] In addition, the spindle housing 71 has multiple adjustment sections 120 that constitute the thrust bearing.

[0057] The adjustment part 120 is provided in the thrust recess 95 of the spindle housing 71. The thrust recess 95 and the adjustment part 120 are formed in the annular part 91 of the spindle housing 71 to face the first circular plate part 81 and the second circular plate part 82 of the spindle 72.

[0058] exist Figure 3 The structure of the adjustment part 120, which is opposite to the first circular plate part 81, is shown in the figure. Figure 3 As shown, the adjustment part 120 includes: a piezoelectric actuator 121 fixed to the bottom surface 96 of the thrust recess 95; a movable part 122 movable in the thrust direction (axial direction of the main shaft 72); and a sealing material 125 disposed between the movable part 122 and the side surface 97 of the thrust recess 95.

[0059] The movable part 122 is provided on the surface of the piezoelectric actuator 121 and has a movable part surface 124 opposite to the first circular plate part 81. This movable part surface 124 is an example of the inner side surface of the spindle housing 71 and is perpendicular to the axial direction (Z-axis direction) of the spindle 72.

[0060] The circular plate surface 83, which is the surface of the first circular plate portion 81 (the second circular plate portion 82), is opposite to the movable portion surface 124. The circular plate surface 83 is an example of the outer surface of the main shaft 72 and is perpendicular to the axis of the main shaft 72.

[0061] The movable part 122 has a plurality of thrust-side air nozzles 123 on its movable part surface 124 that are connected to the air supply path 111. The thrust-side air nozzles 123 are an example of an air supply part. That is, the thrust-side air nozzles 123 open toward the gap between the movable part surface 124 of the spindle housing 71 and the circular plate part surface 83 of the spindle 72, i.e., the thrust gap 301, and supply air to the thrust gap 301.

[0062] That is, the thrust-side air injection port 123 injects high-pressure air in the thrust direction toward the thrust gap 301, thereby forming a thrust bearing that supports the main shaft 72 in a rotatable manner by air in a noncontact manner between the movable portion surface 124 of the main shaft housing 71 and the circular plate portion surface 83 of the main shaft 72, that is, in the thrust gap 301.

[0063] Thus, the main shaft housing 71 includes a thrust bearing and a radial bearing that support the main shaft 72 in a rotatable manner by air in a noncontact manner. In addition, the thrust bearing includes the thrust-side air injection port 123 as an air supply portion and the adjustment portion 120.

[0064] In addition, the movable portion 122 is provided so as to be movable in the thrust direction within the thrust recess 95. A seal material 125 is used to seal the side surface of the movable portion 122 when the movable portion 122 is moved.

[0065] As shown in Figs. 1 and 2, the piezoelectric actuator 121 is connected to the power line 142. As shown in Figs. 1 and 2, the power line 142 is connected to the direct-current power supply 140 and the voltage control portion 141 for controlling the direct-current power supply 140. That is, the voltage control portion 141 is electrically connected to each piezoelectric actuator 121 via the power line 142. The voltage control portion 141 adjusts the voltage value of the direct-current power from the direct-current power supply 140 and transmits it to the piezoelectric actuator 121 via the power line 142. Figure 2 Figure 3 As shown in Figs. 1 and 2, the power line 142 is connected to the direct-current power supply 140 and the voltage control portion 141 for controlling the direct-current power supply 140. That is, the voltage control portion 141 is electrically connected to each piezoelectric actuator 121 via the power line 142. The voltage control portion 141 adjusts the voltage value of the direct-current power from the direct-current power supply 140 and transmits it to the piezoelectric actuator 121 via the power line 142. Figure 1 Figure 2 The piezoelectric actuator 121 expands and contracts in the thrust direction in accordance with the voltage value of the direct-current power supplied from the voltage control portion 141. That is, the piezoelectric actuator 121 expands and contracts in the thrust direction, thereby moving the movable portion 122 provided on the surface of the piezoelectric actuator 121 in the thrust direction. The movable portion 122 moves in the thrust direction, thereby changing the distance (width) of the thrust gap 301 in the direction perpendicular to the circular plate portion surface 83 of the main shaft 72, that is, the distance between the movable portion surface 124 and the circular plate portion surface 83.

[0066] Thus, the piezoelectric actuator 121 is arranged in the main shaft housing 71, and the movable portion surface 124 of the main shaft housing 71 that forms the thrust bearing is moved in the axial direction of the main shaft 72.

[0067] In addition, as shown in Figs. 1 and 2, in the movable portion 122 of the adjustment portion 120, the pressure element 115 is provided on the movable portion surface 124 opposite the first circular plate portion 81 (the second circular plate portion 82). The pressure element 115 is connected to the pressure measuring portion 116 outside the main shaft unit 78.

[0068] In addition, as shown in Figs. 1 and 2, in the movable portion 122 of the adjustment portion 120, the pressure element 115 is provided on the movable portion surface 124 opposite the first circular plate portion 81 (the second circular plate portion 82). The pressure element 115 is connected to the pressure measuring portion 116 outside the main shaft unit 78. Figure 2 Figure 3 In addition, as shown in Figs. 1 and 2, in the movable portion 122 of the adjustment portion 120, the pressure element 115 is provided on the movable portion surface 124 opposite the first circular plate portion 81 (the second circular plate portion 82). The pressure element 115 is connected to the pressure measuring portion 116 outside the main shaft unit 78.

[0069] ​​​The pressure element 115 generates an electric signal corresponding to the pressure of the air of the thrust gap 301 between the movable portion surface 124 and the circular plate portion surface 83 of the main shaft 72, and transmits it to the pressure measuring portion 116. The pressure measuring portion 116 measures the pressure of the air of the thrust gap 301, i.e., the pressure of the air of the thrust gap 301 in which the thrust bearing is formed, according to the electric signal.

[0070] In the present embodiment, the distance of the thrust gap 301 is adjusted when the wafer 100 is subjected to the grinding processing. That is, the voltage control portion 141 adjusts the distance of the thrust gap 301 using the piezoelectric actuators 121 corresponding to the respective pressure measuring portions 116 so that the pressure value of the pressure of the air of the thrust gap 301 measured by the respective pressure measuring portions 116 becomes a pressure value set in advance. Therefore, the voltage control portion 141 controls the voltage of the direct current power supplied to the respective piezoelectric actuators 121. In addition, the pressure of the air of the thrust gap 301 substantially corresponds to the distance of the thrust gap 301.

[0071] For example, in the grinding device 1, after the main shaft 72 is rotated, an idling state is continued until the temperature of the main shaft 72 is stabilized, and after the temperature of the main shaft 72 is stabilized, the idling state is ended and the processing is started.

[0072] Therefore, in the present embodiment, the pressure of the air of the thrust gap 301 set in advance is a small value at the idling time before the processing during the process in which the temperature of the main shaft 72 is stabilized, and is a large value after the temperature of the main shaft 72 is stabilized.

[0073] In this case, the voltage control portion 141 expands the distance of the thrust gap 301 at the idling time. Thereby, the pressure of the air measured by the pressure measuring portion 116 becomes a pressure value set in advance which is relatively small.

[0074] In addition, it is possible to have a set value in which a prescribed pressure value is set in advance, and adjust the distance of the thrust gap 301 in a manner that the pressure of the air measured by the pressure measuring portion 116 at the start of the idling time becomes the set value.

[0075] In addition, the voltage control portion 141 controls the voltage of the direct current power supplied to the piezoelectric actuators 121 in a manner that the distance of the thrust gap 301 is narrowed after the temperature of the main shaft 72 is stabilized (at the time when the idling state is ended). Thereby, the pressure of the air measured by the pressure measuring portion 116 becomes a pressure value set in advance which is relatively large. Then, in the grinding device 1, the grinding processing for the wafer 100 is started.

[0076] Further, the pressure value of the thrust gap 301, which is set in advance, is constant during the grinding process. Therefore, the voltage control section 141 controls the voltage of the direct current power supplied to the piezoelectric actuator 121 in such a manner that the distance of the thrust gap 301 is constant during the grinding process. Thus, the pressure of the air during the grinding process measured by the pressure measuring section 116 becomes the constant pressure value set in advance.

[0077] Further, the voltage control section 141 controls the voltage of the direct current power supplied to the piezoelectric actuator 121 so that the distance of the thrust gap 301 of the thrust bearing formed on the upper surface of the annular portion 91 of the spindle housing 71 and the distance of the thrust gap 301 of the thrust bearing formed on the lower surface of the annular portion 91 of the spindle housing 71 are uniform.

[0078] As described above, in the present embodiment, the piezoelectric actuator 121 of the adjustment section 120 is stretched and contracted by the control of the voltage control section 141, so that the distance of the thrust gap 301 can be adjusted. Therefore, for example, at the time of idling before the temperature of the spindle 72 is stabilized, the thrust gap 301 can be expanded. Therefore, in the present embodiment, the occurrence of the case where the spindle 72, which is deformed by heat, contacts the spindle housing 71 at the time of idling can be suppressed. Therefore, in the present embodiment, the spindle 72 can be continuously rotated.

[0079] Further, in the present embodiment, by expanding the thrust gap 301 at the time of idling, the spindle 72 can be smoothly rotated. Therefore, the time of the idling state can also be shortened.

[0080] Further, in the present embodiment, by the control of the voltage control section 141, the piezoelectric actuator 121 is stretched and contracted, so that the thrust gap 301 can be narrowed to the normal distance at the time of the grinding process. Therefore, the thrust bearing having high rigidity can be formed in the spindle unit 78.

[0081] Further, in the above-described embodiment, the adjustment section 120, which can adjust the distance of the thrust gap 301, is provided in the thrust recessed portion 95 of the spindle housing 71. In this regard, the adjustment section, which can adjust the distance of the thrust gap 301, can also be provided in the spindle 72.

[0082] That is, the spindle unit 78 can have Figure 4 the structure as shown in FIG. 1. Figure 4 The spindle unit 78 shown in FIG. 1 has the following structure: in Figure 2 the structure shown in FIG. 1, the adjustment section 150 provided in the first circular plate portion 81 and the second circular plate portion 82 of the spindle 72 is provided instead of the adjustment section 120 provided in the annular portion 91 of the spindle housing 71.

[0083] As Figure 4As shown, in this structure, the radial air outlet 93 also opens toward the gap between the radial side surface 84 of the main shaft 72 and the annular portion 91 of the main shaft housing 71, i.e., the radial gap 300. Therefore, a radial bearing is formed in the radial gap 300 to support the main shaft 72 in a rotatable manner by air in a non-contact manner.

[0084] In addition, the main shaft 72 has multiple adjustment sections 150 that constitute the thrust bearing.

[0085] An adjustment part 150 is provided in the thrust recess 151 of the spindle 72. The thrust recess 151 and the adjustment part 150 are formed on the first circular plate portion 81 and the second circular plate portion 82 of the spindle 72 in a manner opposite to the annular portion 91 of the spindle housing 71.

[0086] exist Figure 5 The structure of the adjustment portion 150 formed in the first circular plate portion 81 is shown. For example... Figure 5 As shown, the adjustment part 150 includes: a piezoelectric actuator 121 fixed to the bottom surface 152 of the thrust recess 151; a movable part 122 movable in the thrust direction (Z-axis direction); and a sealing material 125 disposed between the movable part 122 and the side surface 153 of the thrust recess 151.

[0087] A movable part 122 is disposed on the surface of the piezoelectric actuator 121, and has a movable part surface 124 opposite to the annular part 91. This movable part surface 124 is an example of the outer surface of the main shaft 72 and is perpendicular to the axial direction of the main shaft 72.

[0088] The surface of the annular portion 91, namely the annular portion surface 92, is opposite to the movable portion surface 124. The annular portion surface 92 is an example of the inner side surface of the spindle housing 71 and is perpendicular to the axial direction of the spindle 72.

[0089] The annular portion 91 has multiple thrust-side air nozzles 123 on its surface 92 that are connected to the air supply path 111. Each thrust-side air nozzle 123 is an example of an air supply unit, supplying air toward the thrust gap 301, which is the gap between the movable part surface 124 of the main shaft 72 and the annular part surface 92 of the main shaft housing 71. Thus, a thrust bearing is formed in the thrust gap 301 between the movable part surface 124 and the annular part surface 92, which supports the main shaft 72 for rotation in a non-contact manner by air.

[0090] The movable part 122 is configured to move within the thrust recess 151 along the thrust direction. The sealing material 125 seals the side of the movable part 122 as it moves.

[0091] like Figure 4 and Figure 5As shown, an electric power line 143 is connected to the piezoelectric actuator 121. This electric power line 143 is connected to the direct current power source 140 and the voltage control section 141 via a first contact point 146 provided to the spindle 72, a second contact point 145 provided to the spindle housing 71 and electrically connected to the first contact point 146, and an electric power line 142 connected to the second contact point 145.

[0092] In this way, the voltage control section 141 adjusts the voltage value of the direct current power from the direct current power source 140 and transmits it to the piezoelectric actuator 121. Figure 2 The structure shown is electrically connected to each piezoelectric actuator 121 in the same way, adjusts the voltage value of the direct current power from the direct current power source 140 and transmits it to the piezoelectric actuator 121.

[0093] In addition, the contact point structure of the first contact point 146 and the second contact point 145 can be the same as that of a direct current motor, for example.

[0094] The piezoelectric actuator 121 expands and contracts in the thrust direction according to the voltage value of the direct current power supplied from the voltage control section 141, thereby moving the movable portion 122 provided to the surface of the piezoelectric actuator 121 in the thrust direction. The movable portion 122 moves in the thrust direction, thereby changing the distance of the thrust gap 301 in the direction perpendicular to the movable portion surface 124 of the spindle 72, i.e., the distance between the movable portion surface 124 and the annular portion surface 92.

[0095] In this way, in the structure shown in Figure 4 and Figure 5 The piezoelectric actuator 121 is arranged to the spindle 72, and the movable portion surface 124 of the spindle 72 forming the thrust bearing is moved in the axial direction of the spindle 72.

[0096] In addition, in the structure shown in Figure 4 and Figure 5 A pressure element 115 that generates an electric signal corresponding to the pressure of the air of the thrust gap 301 is provided to the annular portion surface 92 of the annular portion 91 of the spindle housing 71. Based on this electric signal, the pressure measuring section 116 measures the pressure of the air of the thrust gap 301 forming the thrust bearing.

[0097] In this way, in the structure shown in Figure 4 and Figure 5 The spindle unit 78 of the structure shown can also adjust the distance of the thrust gap 301 when the wafer 100 is subjected to grinding processing. That is, the voltage control section 141 and Figure 2 and Figure 3 The structure shown can also use the piezoelectric actuator 121 corresponding to each pressure measuring section 116 to adjust the distance of the thrust gap 301 so that the pressure of the air of the thrust gap 301 measured by each pressure measuring section 116 becomes a predetermined pressure value.

Claims

1. A spindle unit, wherein the spindle unit includes: a spindle that mounts a machining tool at a front end; and a spindle housing that has a thrust bearing and a radial bearing that support the spindle so as to be rotatable by air in a noncontact manner, the thrust bearing has: an air supply portion that supplies air to a gap between an outer side surface of the spindle in a direction perpendicular to an axial direction of the spindle and an inner side surface of the spindle housing; and an adjustment portion that adjusts a distance in a direction perpendicular to the outer side surface of the spindle of the gap in such a manner that the gap is expanded at an idle time and the gap is narrowed at a machining time.

2. The spindle unit according to claim 1, wherein the adjustment portion has a piezoelectric actuator that is disposed to the spindle so as to move the outer side surface of the spindle that forms the thrust bearing in the axial direction of the spindle.

3. The spindle unit according to claim 1, wherein the adjustment portion has a piezoelectric actuator that is disposed to the spindle housing so as to move the inner side surface of the spindle housing that forms the thrust bearing in the axial direction of the spindle.

4. A machining device that machines a work by a machining tool, wherein the machining device has: a spindle unit that includes a spindle that mounts the machining tool at a front end and a spindle housing that has a thrust bearing and a radial bearing that support the spindle so as to be rotatable by air in a noncontact manner; a holding unit that holds the work; a pressure measuring portion that measures a pressure of air; and a voltage control portion that controls a voltage of direct current power, the thrust bearing has: an air supply portion that supplies air to a gap between an outer side surface of the spindle in a direction perpendicular to an axial direction of the spindle and an inner side surface of the spindle housing; and an adjustment portion that includes a piezoelectric actuator that adjusts a distance in a direction perpendicular to the outer side surface of the spindle of the gap in such a manner that the gap is expanded at an idle time and the gap is narrowed at a machining time, the pressure measuring portion measures a pressure of air of the gap in which the thrust bearing is formed, the voltage control portion controls a voltage of direct current power supplied to the piezoelectric actuator so as to adjust the distance of the gap so that a pressure value measured by the pressure measuring portion becomes a value that is set in advance.

5. The machining device according to claim 4, wherein the adjustment portion has the piezoelectric actuator that is disposed to the spindle so as to move the outer side surface of the spindle that forms the thrust bearing in the axial direction of the spindle.

6. The machining device according to claim 4, wherein the adjustment portion has the piezoelectric actuator that is disposed to the spindle housing so as to move the inner side surface of the spindle housing that forms the thrust bearing in the axial direction of the spindle. ​

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