Spindle unit

Abstract

To provide a spindle unit capable of reducing a frequency of cleaning a tip of a spindle by suppressing adhesion of treated liquid containing treatment wastes to the tip.SOLUTION: A groove is formed around a spindle in a region opposite an inner surface of a cover of a side surface of a tip of the spindle via a gap. At a place where the groove is formed, a sectional area of the gap between the tip of the spindle and the cover is enlarged. Thus, the gap between the tip of the spindle and the cover can be a space in which spaces (flow paths) small in the sectional area and spaces (expansion rooms) large in the sectional area are alternately arranged. In this case, even when treated liquid containing treatment wastes enters into the gap between the tip of the spindle and the cover, entry of the treated liquid to the flow path provided at a depth of the expansion rooms becomes difficult. Thus, adhesion of the treated liquid containing the treatment wastes to the tip of the spindle is suppressed, and a frequency of cleaning the tip can be reduced.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a spindle unit.

Background Art

[0002] Chips of devices such as IC (Integrated Circuit) are essential components in various electronic devices such as mobile phones and personal computers. Such chips are manufactured, for example, in the following order.

[0003] First, a plurality of devices are formed by performing photolithography or the like to form a large number of elements on the surface of a workpiece such as a wafer. Next, the back surface side of the workpiece is ground to thin the workpiece. Next, the workpiece is cut along the boundaries of the plurality of devices to divide the workpiece into a plurality of chips.

[0004] A processing device such as a grinding device for grinding a workpiece or a cutting device for cutting generally includes a spindle having a tip portion to which a mount for mounting a cutting tool is connected, and a casing that surrounds at least a part other than the tip portion of the spindle and has an air ejection port for ejecting air toward the spindle to form an air bearing. A spindle unit is provided.

[0005] Specifically, in a grinding device, an annular grinding wheel provided with a plurality of grinding wheels discretely arranged in an annular shape is mounted on a mount. Then, while rotating the grinding wheel together with the spindle in a state where an air bearing is formed between the two by ejecting air from the air ejection port of the casing toward the spindle, the workpiece is ground by bringing the plurality of grinding wheels into contact with the workpiece.

[0006] In the cutting device, an annular cutting blade with abrasive grains dispersed in it is mounted on a mount. Air is then blown from the air outlet of the casing toward the spindle to form an air bearing between the two, and the cutting blade is rotated together with the spindle while contacting the workpiece, thereby cutting the workpiece.

[0007] Furthermore, in these processing devices, the workpiece is processed while a processing fluid is supplied to the contact point (processing point) between the workpiece and the processing tool in order to wash away the processing debris generated during processing. However, since such processing is usually performed with the processing tool rotating at high speed along with the spindle, the processing fluid containing processing debris is scattered in the form of a mist.

[0008] If machining fluid containing machining debris adheres to the area near the air outlet formed in the casing, it may become difficult to form an air bearing in the spindle unit. Therefore, in the spindle unit, a cover is generally provided to surround the tip of the spindle to prevent the machining fluid from adhering to this area.

[0009] Furthermore, this cover surrounds the tip of the spindle with a gap to allow air ejected from the air outlet formed in the casing to be exhausted and to avoid obstructing the rotation of the spindle. Therefore, when processing a workpiece in these processing devices, processing fluid containing processing debris may enter the gap and adhere to the side surface of the tip of the spindle.

[0010] Furthermore, if machining fluid adhering to the side of the spindle tip dries and solidifies into machining debris, it may hinder the normal rotation of the spindle. For example, if the gap between the spindle tip and the cover is filled with machining debris, the exhaust of air ejected from the casing's air outlet will be obstructed. In this case, the spindle's axis of rotation may tilt, causing the spindle to come into contact with the casing and / or cover.

[0011] In light of this, a spindle unit has been proposed in which the tip of the spindle is surrounded by a cover that can be separated into two parts (see, for example, Patent Document 1). In this spindle unit, the cover can be divided into two parts to expose the tip of the spindle and then clean the tip. [Prior art documents] [Patent Documents]

[0012] [Patent Document 1] Japanese Patent Publication No. 2017-222003 [Overview of the project] [Problems that the invention aims to solve]

[0013] However, disassembling the cover into two parts before cleaning the tip of the spindle and then reassembling the cover afterward is cumbersome and places a heavy burden on the operator. In view of this, the object of the present invention is to provide a spindle unit that can reduce the frequency of cleaning the tip of the spindle by suppressing the adhesion of processing fluid containing processing debris to the tip of the spindle. [Means for solving the problem]

[0014] According to one aspect of the present invention, the present invention comprises a spindle having a tip to which a mount for attaching a workpiece is connected, a casing surrounding at least a portion of the spindle other than the tip and having an air outlet formed therein for injecting air toward the spindle to form an air bearing, and a cover mounted on the casing so as to surround the tip of the spindle with a gap between them, wherein at least one groove is formed on the side surface of the tip of the spindle facing the inner surface of the cover with respect to the gap, so as to circle the spindle once along the circumferential direction, and the at least one groove is The spindle includes an annular groove formed to complete a full rotation along the circumferential direction, the annular groove being in a plane parallel to both the axial and radial directions which are perpendicular to the circumferential direction and to each other. Cross-sectional shape The stand It is a shape, The annular groove has a bottom surface that is parallel to the axial direction in the plane, Applicable diameter Inclined with respect to the direction The first aspect and , More than the first side close to the casing to come into contact with, and, the diameter is parallel to the The second aspect, including Furthermore, the distance between the first side surface and the second side surface in the axial direction becomes narrower as it approaches the bottom surface. , a spindle unit is provided.

[0015] Furthermore, in one aspect of the present invention, it is preferable that the at least one groove is a plurality of grooves. In addition, in one aspect of the present invention, On the inner surface of the cover, a facing groove is formed that encircles the inner surface of the cover and faces the spindle. the at least one groove faces the inner surface of the cover through the gap Circle and is opposed to the cylindrical region Furthermore, the cylindrical region is the region further from the casing than the opposing groove. .

[0016] According to another aspect of the present invention, a spindle having a tip portion to which a mount for mounting a cutting tool is connected, a casing that surrounds at least a part of the spindle other than the tip portion of the spindle and has an air ejection port for ejecting air toward the spindle to form an air bearing, and a cover attached to the casing so as to surround the tip portion of the spindle through a gap. In a region of the side surface of the tip portion of the spindle that faces the inner surface of the cover through the gap, a spiral groove is formed so as to at least one round around the spindle along a direction inclined with respect to the circumferential direction of the spindle. The spiral groove has a In a plane that is perpendicular to the circumferential direction and parallel to both the axial and radial directions which are perpendicular to each other. cross-sectional shape The stand and is inclined with respect to the The spiral groove has a bottom surface that is parallel to the axial direction in the plane, the diameter direction, The first aspect and , More than the first side close to the casing to come into contact with, and, the diameter is parallel to the The second aspect includes, , The distance between the first side surface and the second side surface in the axial direction becomes narrower as it approaches the bottom surface. a spindle unit is provided in which the spindle rotates so that the air remaining inside the spiral groove is carried to the mount side.

[0017] Furthermore, in another aspect of the present invention, it is preferable that the spiral groove is formed so as to at least two rounds around the spindle. In addition, in one aspect of the present invention, On the inner surface of the cover, a facing groove is formed that encircles the inner surface of the cover and faces the spindle.The spiral groove faces the inner surface of the cover through the gap Circle the cylindrical region Furthermore, the cylindrical region is the region further from the casing than the opposing groove. preferably.

Advantages of the Invention

[0018] In the spindle unit of the present invention, a groove that goes around the spindle once is formed in the region on the side surface of the tip of the spindle that faces the inner surface of the cover through a gap. And at the location where the groove is formed, the cross-sectional area of the gap between the tip of the spindle and the cover becomes larger.

[0019] Therefore, the gap between the tip of the spindle and the cover can be expressed as a space in which spaces (flow paths) with a small cross-sectional area and spaces (expansion chambers) with a large cross-sectional area are alternately arranged. Here, when the fluid moves from the space with a large cross-sectional area to the space with a small cross-sectional area, a large pressure loss occurs.

[0020] Therefore, even when a machining fluid containing machining chips enters the gap between the tip of the spindle and the cover, it becomes difficult for the machining fluid to enter the flow path provided at the depth of the expansion chamber. As a result, in the spindle unit of the present invention, the adhesion of the machining fluid containing machining chips to the tip of the spindle is suppressed, and it is possible to reduce the frequency of cleaning of the tip.

Brief Description of the Drawings

[0021] <​​​​​​​​​​​​​​​​

[0022] Embodiments of the present invention will be described with reference to the attached drawings. Figure 1 is a schematic perspective view showing an example of a grinding apparatus. Note that the X-axis direction (front-back direction) and Y-axis direction (left-right direction) shown in Figure 1 are mutually orthogonal directions on the horizontal plane, and the Z-axis direction (up-down direction) is a direction perpendicular to the X-axis direction and the Y-axis direction (vertical direction).

[0023] The grinding apparatus 2 shown in Figure 1 has a base 4 that supports each component. A rectangular parallelepiped groove 4a extending along the X-axis is formed on the upper surface of the base 4. A chuck table 6 is provided above this groove 4a. Inside the groove 4a, there is an X-axis movement mechanism (not shown), a rotation drive source (not shown), and a suction source (not shown) connected to the chuck table 6.

[0024] The X-axis movement mechanism includes, for example, a motor and a ball screw, and moves the chuck table 6 along the X-axis. The rotational drive source includes, for example, a motor and a pulley, and rotates the chuck table 6 using a straight line passing through the center of the upper surface (holding surface) of the chuck table 6 as the axis of rotation.

[0025] Furthermore, the suction source includes an ejector and applies a suction force to the space near the holding surface of the chuck table 6. Therefore, if the suction source is operated while the workpiece 11 is placed on the holding surface of the chuck table 6, the workpiece 11 will be held in place by the chuck table 6.

[0026] The workpiece 11 is, for example, a wafer made of a semiconductor material such as silicon, with multiple devices formed on its surface 11a. Furthermore, a protective tape 13, made of, for example, resin, is attached to the surface 11a of the workpiece 11 to prevent damage to the devices when grinding the back surface 11b of the workpiece 11.

[0027] Furthermore, a rectangular parallelepiped table cover 8 is provided around the chuck table 6, surrounding it so that its holding surface 6a is exposed. The width of this table cover 8 (length along the Y-axis) is approximately equal to the width of the groove 4a formed on the upper surface of the base 4. In addition, a dustproof and splashproof cover 10 that can be extended and retracted along the X-axis is provided on the front and rear of the table cover 8.

[0028] Furthermore, a rectangular prism-shaped support structure 12 is provided in the area of ​​the upper surface of the base 4 located behind the groove 4a. A Z-axis direction movement mechanism 14 is provided on the front of this support structure 12. This Z-axis direction movement mechanism 14 has a pair of guide rails 16, each extending along the Z-axis direction. A slider (not shown) is provided on the front side of each of the pair of guide rails 16 in a manner that allows it to slide along the Z-axis direction.

[0029] Furthermore, the front end of this slider is fixed to the rear side of the rectangular Z-axis moving plate 18. In addition, a screw shaft 20 extending along the Z-axis direction is positioned between the pair of guide rails 16. A pulse motor 22 for rotating the screw shaft 20 is connected to the upper end of the screw shaft 20.

[0030] Furthermore, a nut (not shown) is provided on the outer surface of the screw shaft 20 where the screw threads are formed, which houses balls that circulate in accordance with the rotation of the screw shaft 20, thus forming a ball screw. This nut is fixed to the rear side of the Z-axis moving plate 18. Therefore, when the screw shaft 20 is rotated by the pulse motor 22, the Z-axis moving plate 18 moves along the Z-axis direction together with the nut.

[0031] Furthermore, a grinding unit 24 is provided on the front side of the Z-axis moving plate 18. This grinding unit 24 has a cylindrical holding member 26 fixed to the front surface of the Z-axis moving plate 18. The holding member 26 holds the spindle unit 28. Figure 2 is a schematic partial cross-sectional side view showing the spindle unit 28. Note that in Figure 2, some components of the spindle unit 28 are shown as blocks.

[0032] The spindle unit 28 has a cylindrical casing 30. A cylindrical through hole 30b is formed in the center of the bottom wall 30a of the casing 30. An air supply passage 30c is also formed in the bottom wall 30a of the casing 30, which communicates with an air supply source 32. This air supply passage 30c communicates with a plurality of air outlets 30d opening on the upper surface of the bottom wall 30a, a plurality of air outlets 30e opening on the inner surface of the bottom wall 30a, and a plurality of air outlets 30f opening on the lower surface of the bottom wall 30a.

[0033] Furthermore, the casing 30 surrounds at least a portion of the spindle 34 other than its tip. The spindle 34 has a cylindrical shaft portion 34a extending along the Z-axis direction, and a pair of flange portions 34b and 34c, each provided to protrude from the shaft portion 34a along the radial direction of the shaft portion 34a. Specifically, the flange portion 34b is provided at the tip (lower end) of the shaft portion 34a, and the flange portion 34c is provided between the base (upper end) and tip (lower end) of the shaft portion 34a.

[0034] Furthermore, the diameters of the pair of flange portions 34b and 34c are slightly smaller than the inner diameter of the casing 30. Also, the distance between the pair of flange portions 34b and 34c is slightly greater than the thickness of the bottom wall 30a of the casing 30. The portion of the spindle 34 shaft 34a located between the pair of flange portions 34b and 34c is passed through the through hole 30b of the casing 30.

[0035] Furthermore, a motor 36 is provided around the base end of the spindle 34, specifically around the base end of the shaft portion 34a. This motor 36 has a rotor 36a fixed to the base end of the spindle 34 and a stator 36b surrounding the rotor 36a with a gap in between. The stator 36b is fixed to the casing 30 via a cooling jacket 38. The cooling jacket 38 has a cooling water channel 38a formed therein, through which cooling water is supplied to cool the motor 36.

[0036] Furthermore, a disc-shaped mount 40 having a diameter approximately equal to the outer diameter of the flange portion 34b is connected to the tip of the spindle 34, specifically the flange portion 34b. A grinding wheel (working tool) 42 having a diameter approximately equal to the mount 40 is mounted on the mount 40. In addition, a cylindrical cover 44 made of resin such as polyvinyl chloride is provided around the tip of the spindle 34. This cover 44 is attached to the casing 30 so as to surround the tip of the spindle 34 with a gap in between.

[0037] Figure 3 is a partially enlarged view showing the gap between the tip of the spindle 34 and the cover 44, as shown in Figure 2. Two grooves 46a and 46b are formed on the side surface of the tip of the spindle 34, in the region facing the inner surface of the cover 44 through the gap. Each of the two grooves 46a and 46b is formed to encircle the spindle 34 in the circumferential direction.

[0038] Furthermore, the cross-sectional shape of the groove 46a is trapezoidal, becoming narrower as it approaches the bottom surface of the groove 46a. Specifically, the side of the groove 46a on the mount 40 side is inclined with respect to the circumferential direction of the spindle 34. For example, the angle between this side and the plane parallel to the X-axis and Y-axis directions is between 10° and 50°, typically 30°. Also, the side of the groove 46a on the casing 30 side is generally parallel to the circumferential direction of the spindle 34.

[0039] Furthermore, the cross-sectional shape of groove 46b is a rectangle with a generally constant width. Specifically, each of the pair of sides constituting groove 46a is generally parallel to the circumferential direction of the spindle 34. In addition, the depths (lengths along the direction perpendicular to the Z-axis) of the two grooves 46a and 46b may be the same or different. Similarly, the widths (lengths along the Z-axis) of the bottom surfaces of the two grooves 46a and 46b may be the same or different.

[0040] Furthermore, a groove 48 is formed on the inner surface of the cover 44. This groove 48 encircles the inner surface of the cover 44 and faces the region of the spindle 34's tip that is located above the groove 46b. The cross-sectional shape of the groove 46 is a right-angled triangle. Specifically, the groove 48 is composed of a side surface on the mount 40 side that is inclined with respect to the circumferential direction of the spindle 34 and a side surface on the casing 30 side that is generally parallel with the circumferential direction of the spindle 34.

[0041] The cross-sectional shape of groove 46a may be rectangular, like groove 46b, or a right-angled triangle, like groove 48. Similarly, the cross-sectional shape of groove 46b may be trapezoidal, like groove 46a, or a right-angled triangle, like groove 48. Furthermore, the cross-sectional shape of groove 48 may be trapezoidal, like groove 46a, or rectangular, like groove 46b.

[0042] Furthermore, at locations where grooves 46a, 46b, or 48 are formed, the cross-sectional area of ​​the gap between the tip of the spindle 34 and the cover 44 (specifically, the area of ​​the cross-section parallel to the X-axis and Y-axis directions) becomes larger. Therefore, the gap between the tip of the spindle 34 and the cover 44 can be described as a space in which spaces with small cross-sectional areas (flow channels) 50a, 50b, 50c, 50d and spaces with large cross-sectional areas (expansion chambers) 52a, 52b, 52c are alternately arranged from the mount 40 side.

[0043] The width of each flow path 50a, 50b, 50c, and 50d (length along the direction perpendicular to the Z-axis) is, for example, between 0.1 mm and 2.0 mm. The width of the expansion chambers 52a and 52b (distance between the bottom surfaces of grooves 46a and 46b and the inner surface of cover 44) is, for example, between 2.0 mm and 5.0 mm. The maximum width of the expansion chamber 52c (distance between the side surface of spindle 34 and the deepest part of groove 48) is, for example, between 2.0 mm and 5.0 mm.

[0044] Furthermore, the grinding wheel 42 shown in Figures 1 and 2 comprises a plurality of grinding wheels 42a and a wheel base 42b having a lower surface on which the plurality of grinding wheels 42a are arranged in a circular, discrete manner. The plurality of grinding wheels 42a have abrasive grains such as diamond or cubic boron nitride (cBN) dispersed in a binder such as a vitrified bond or a resin bond.

[0045] Furthermore, the wheel base 42b is made of a metal material such as stainless steel or aluminum. In addition, a processing fluid supply nozzle (not shown) is provided near the grinding wheel 42 to supply a liquid (processing fluid) such as pure water to the processing point when grinding the workpiece 11 with multiple grinding wheels 42a.

[0046] When grinding the workpiece 11 in the grinding apparatus 2 described above, first, with the workpiece 11 placed on the holding surface 6a of the chuck table 6 via the protective tape 13, the suction source connected to the chuck table 6 is activated. This holds the workpiece 11 on the chuck table 6 with its back surface 11b exposed.

[0047] Next, the X-axis movement mechanism connected to the chuck table 6 is operated so that the trajectories of the multiple grinding wheels, when the grinding wheel 42 is rotated together with the spindle 34, coincide with the center of the holding surface 6a of the chuck table 6.

[0048] Next, air supplied from the air supply source 32 via the air supply passage 30c is ejected from the air outlets 30d, 30e, and 30f of the casing 30 toward the spindle 34. This forms an air bearing between the casing 30 and the spindle 34. The air ejected from the air outlets 30d, 30e, and 30f is exhausted to the outside of the spindle unit 28 through gaps between the spindle 34 and the cover 44, etc.

[0049] Next, the rotary drive source connected to the chuck table 6 is operated to rotate the chuck table 6, and the motor 36 is operated to rotate the grinding wheel 42 together with the spindle 34.

[0050] Next, the Z-axis movement mechanism 14 is operated so that multiple grinding wheels 42a come into contact with the workpiece 11. Specifically, the pulse motor 22 is operated to lower the Z-axis movement plate 18. In addition, machining fluid is supplied from the machining fluid supply nozzle to the contact interface between the multiple grinding wheels 42a and the workpiece 11.

[0051] As a result, the back surface 11b of the workpiece 11 is ground. At this time, the machining fluid containing the machining debris generated by grinding is scattered in a mist-like manner. The scattered machining fluid may then enter the gap between the tip of the spindle 34 and the cover 44.

[0052] In the spindle unit 28, grooves 46a and 46b are formed around the spindle 34 in the region of the side surface of the tip of the spindle 34 that faces the inner surface of the cover 44 through a gap. That is, the gap between the tip of the spindle 34 and the cover 44 includes alternately arranged flow channels 50a, 50b, and 50c and expansion chambers 52a and 52b.

[0053] Therefore, even if machining fluid containing machining debris enters the gap between the tip of the spindle 34 and the cover 44, it becomes difficult for the machining fluid to enter the passages 50b and 50c located deep inside the expansion chambers 52a and 52b. As a result, in the spindle unit 28, adhesion of machining fluid containing machining debris to the tip of the spindle 34 is suppressed, and the frequency of cleaning of the tip can be reduced.

[0054] Furthermore, in the spindle unit 28, a groove 48 is formed in the cover 44 that encircles the inner surface of the cover 44 and faces the region of the side surface of the tip of the spindle 34 that is located above the groove 46b. Therefore, even when the processing fluid enters the flow path 50c, it is possible to suppress the adhesion of the processing fluid to the region near the air outlets 30d, 30e, and 30f formed in the bottom wall of the casing 30.

[0055] Furthermore, in the spindle unit 28, machining fluid that could not enter the flow path 50b tends to adhere to the bottom and / or side surfaces of groove 46a, and machining fluid that could not enter the flow path 50c tends to adhere to the bottom and / or side surfaces of groove 46b. However, the machining fluid that adheres to the bottom and / or side surfaces of grooves 46a and 46b is easily discharged from grooves 46a and 46b by the centrifugal force acting as the spindle 34 rotates.

[0056] Furthermore, the processing fluid discharged from grooves 46a and 46b is easily discharged to the outside of the gap between the tip of the spindle 34 and the cover 44 by flowing along the inner surface of the cover 44. In other words, in the spindle unit 28, even if the processing fluid adheres to the bottom and / or sides of grooves 46a and 46b, the discharge of this processing fluid can be promoted.

[0057] Furthermore, the side of groove 46a on the mount 40 side is inclined with respect to the circumferential direction of the spindle 34. Therefore, machining fluid adhering to the bottom and / or side of groove 46a is easily flowed along the side of groove 46a on the mount 40 side by the centrifugal force acting as the spindle 34 rotates.

[0058] Furthermore, the machining fluid that flows along the side of the groove 46a on the mount 40 side is easily discharged through the flow path 50a to the outside of the gap between the tip of the spindle 34 and the cover 44. In other words, in the spindle unit 28, even if the machining fluid adheres to the bottom surface and / or side surface of the groove 46a, the discharge of this machining fluid can be promoted.

[0059] It should be noted that the above description represents only one aspect of the present invention, and the present invention is not limited to the above description. For example, the spindle unit of the present invention is not limited to a spindle unit provided in a grinding device 2, but may also be a spindle unit provided in a cutting device.

[0060] Furthermore, in the spindle unit of the present invention, the number of grooves formed on the side surface of the tip of the spindle 34 is not limited to two. For example, the number of grooves may be one or three or more. However, from the viewpoint of preventing machining fluid containing machining debris from entering the gap between the tip of the spindle 34 and the cover 44, it is preferable to form multiple grooves on the side surface of the tip of the spindle 34.

[0061] Furthermore, in the spindle unit of the present invention, a helical groove may be formed on the side surface of the tip of the spindle. Figure 4 is a schematic front view showing the tip of a spindle in which a helical groove is formed, that is, in the portion corresponding to the flange portion 34b shown in Figures 2 and 3.

[0062] The spiral groove 56 formed on the side surface of the tip of the spindle 54 shown in Figure 4 is formed to make two turns around the spindle 54 in a direction that is inclined with respect to the circumferential direction of the spindle 54.

[0063] Furthermore, the cross-sectional shape of groove 56 is a trapezoid, similar to groove 46a shown in Figure 3. Note that the cross-sectional shape of groove 56 may also be rectangular, as shown in groove 46b in Figure 3, or a right-angled triangle, as shown in groove 48 in Figure 3.

[0064] Furthermore, if the spindle unit includes a spindle 54, it is preferable that the spindle 54 rotates along the direction shown in Figure 4 when grinding the workpiece 11. In this case, the fluid remaining inside the groove 56 is carried towards the mount side. This facilitates the discharge of the processing fluid, even if it adheres to the bottom and / or sides of the groove 56.

[0065] The number of turns of the groove 56 extending around the spindle 54 is not limited to two turns. For example, the number of turns may be one turn or three or more turns. However, from the viewpoint of preventing machining fluid containing machining debris from entering the gap between the tip of the spindle 54 and the cover, it is preferable that the spiral groove 56 is formed to extend around the spindle 54 at least two times.

[0066] Furthermore, in the spindle unit of the present invention, grooves do not need to be formed on the inner surface of the cover 44. Also, in the spindle unit of the present invention, a plurality of grooves may be formed on the inner surface of the cover 44.

[0067] Furthermore, the structures and methods of the embodiments described above can be modified as appropriate without departing from the scope of the present invention. [Explanation of Symbols]

[0068] 2: Grinding equipment 4: Base (4a: Groove) 6: Chuck table (6a: Holding surface) 8: Table cover 10: Dustproof and waterproof cover 11: Workpiece (13a: front side, 13b: back side) 12:Support structure 13: Protective tape 14:Z-axis direction movement mechanism 16: Guide rail 18: Z-axis movement plate 20: Screw shaft 22: Pulse motor 24: Grinding Unit 26: Retaining member 28: Spindle Unit 30: Casing (30a: bottom wall, 30b: through hole, 30c: air supply passage) (30d, 30e, 30f: Air outlet) 32: Air supply source 34: Spindle (34a: shaft portion, 34b, 34c: flange portion) 36: Motor (36a: Rotor, 36b: Stator) 38: Cooling jacket (38a: Cooling water channel) 40: Mount 42: Grinding wheel (42a: Grinding wheel, 42b: Wheel base) 44: Cover 46a, 46b, 48: Groove 50a, 50b, 50c, 50d: Flow channel 52a, 52b, 52c: Expansion chambers 54: Spindle 56: Groove

Claims

1. A spindle having a tip to which a mount for attaching a workpiece is connected, A casing that surrounds at least a portion of the spindle other than its tip, and has an air outlet formed therein for injecting air toward the spindle to form an air bearing, A cover is attached to the casing so as to surround the tip of the spindle with a gap in between, In the region of the side surface of the tip of the spindle that faces the inner surface of the cover through the gap, at least one groove is formed along the circumferential direction of the spindle, so as to make one full turn around the spindle. The at least one groove includes an annular groove formed to make one full turn around the spindle along the circumferential direction, The annular grooves have a trapezoidal cross-sectional shape in a plane that is perpendicular to the circumferential direction and parallel to both the axial and radial directions which are perpendicular to each other. The annular groove, in the plane, A bottom surface parallel to the axial direction, A first side surface inclined with respect to the radial direction, A second side surface that is closer to the casing than the first side surface and is parallel to the radial direction, A spindle unit in which the distance between the first side surface and the second side surface in the axial direction becomes narrower as it approaches the bottom surface.

2. The spindle unit according to claim 1, wherein the at least one groove is a plurality of grooves.

3. Opposing grooves are formed on the inner surface of the cover, encircling the inner surface of the cover and facing the spindle. The at least one groove faces the cylindrical region on the inner surface of the cover through the gap, The spindle unit according to claim 1 or 2, wherein the cylindrical region is a region further from the casing than the opposing groove.

4. A spindle having a tip to which a mount for attaching a workpiece is connected, A casing that surrounds at least a portion of the spindle other than its tip, and has an air outlet formed therein for injecting air toward the spindle to form an air bearing, A cover is attached to the casing so as to surround the tip of the spindle with a gap in between, A helical groove is formed on the side surface of the tip of the spindle, in the region facing the inner surface of the cover through the gap, so as to circle the spindle at least once in a direction inclined with respect to the circumferential direction of the spindle. The helical grooves have a trapezoidal cross-sectional shape in a plane parallel to both the axial and radial directions, which are perpendicular to the circumferential direction and perpendicular to each other. The spiral groove is, in the plane, A bottom surface parallel to the axial direction, A first side surface inclined with respect to the radial direction, A second side surface that is closer to the casing than the first side surface and is parallel to the radial direction, The distance between the first side surface and the second side surface in the axial direction becomes narrower as it approaches the bottom surface. The spindle is a spindle unit that rotates such that fluid remaining inside the helical groove is carried towards the mount.

5. The spindle unit according to claim 4, wherein the spiral groove is formed so as to make at least two turns around the spindle.

6. Opposing grooves are formed on the inner surface of the cover, encircling the inner surface of the cover and facing the spindle. The spiral groove faces the cylindrical region on the inner surface of the cover through the gap, The spindle unit according to claim 4 or 5, wherein the cylindrical region is a region further from the casing than the opposing groove.

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