JPH09323250A - Polishing head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the occurrence of magnetic attraction force easily and surely by making the length in the direction of axial length of a rotor of a motor larger than the length obtained by adding the length in the direction of axial length of a stator, the maximum travel length to the direction of axial length of the rotor, and double length of magnetic attraction force stable length. SOLUTION: The length L1 in the direction of axial length of a rotor 107 of a motor is the same length as the length obtained by adding the length L2 in the direction of axial length of a stator 109, the maximum travel length 2S to the direction of axial length of the rotor 107 due to travel of a rotary shaft 89, and double length of magnetic attraction force stable length X. Consequently, it is possible to eliminate the occurrence of magnetic attraction force due to relative travel of the rotor 107 of the motor and the stator 109 easily and surely. As a result, it is possible to obtain stable polishing load and perform more precise polishing.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a polishing head used in a polishing apparatus.

[0002]

2. Description of the Related Art Recently, optical components such as lenses and mirrors have been
Higher accuracy is required. In particular, an optical component used in a measuring device or an exposure device that uses a short wavelength such as ultraviolet light or soft X-ray as a light source is required to have a shape accuracy of 1 nm.

Therefore, in polishing, it is important not only to smooth the surface but also to obtain an accurate polishing removal amount in order to finish the surface shape with high precision. Generally, it is known that the removal amount of polishing is proportional to the contact pressure between the polishing head attached to the polishing apparatus and the processing surface, the relative movement speed, and the processing time.

Therefore, in order to perform highly accurate polishing, it is necessary to precisely control the swinging and rotating motions of the polishing head and the polishing load. Further, particularly, in the finishing stage, the amount of polishing removal becomes minute, so that it is necessary to control the low load with high accuracy. Generally, the swinging of the polishing head is performed by the polishing apparatus, and the rotation and the control of the polishing load are performed by the polishing head.

FIG. 3 shows a conventional polishing head.
The main body of the polishing head is composed of the polishing shaft 11, the load detector 13, and the load controller 15. The polishing shaft portion 11 includes a polishing tool 17, a rotary shaft 19, a bearing 21,
23, motor 25, rotation detector 27, linear guide 29
And housings 31, 33, and 35.

The load detecting section 13 comprises a joint 37, a load detector 39, a table 41, a linear guide 43 and a housing 45. The load controller 15 includes a pressurizer 47, a control valve 49, and a housing 51. Then, these polishing shaft portion 11 and load detecting portion 1
3 and the load control unit 15 are attached to the casings 53 and 55 to form a polishing head, which is controlled by the controller 57.

Polishing of a workpiece using such a polishing head is performed as described below. First, the polishing head is positioned directly above the processing position by a moving unit (not shown) of the polishing apparatus. Next, the polishing head is lowered by the moving means until just before the polishing head comes into contact with the workpiece.

Thereafter, the polishing shaft 11 is pushed down by the pressurizer 47 until the load detector 39 indicates a predetermined value.
A polishing tool 17 is pressed against the workpiece. Then, the pressing of the polishing shaft 11 is stopped at a position where the load detector 39 indicates a predetermined value, and the rotation of the rotating shaft 19 is
Then, the polishing tool 17 is rotated to start polishing.

In order to obtain a necessary polishing removal amount, an appropriate processing time for a polishing load is previously calculated, and the polishing is performed only for this time. However, in the above-described polishing head, since the value indicated by the load detector 39 includes the frictional force generated in the movable parts such as the bearings 21 and 23 of the polishing shaft 11 and the linear guide 29, the load detector 39 is The indicated value is different from the value indicating the actual polishing load at the tip of the polishing tool 17, and a problem arises that the required removal amount cannot be obtained with the processing time obtained by calculation.

Therefore, in the polishing process in such a low load region, it is important to keep the frictional force generated in the movable portion of the polishing shaft 11 low. Conventionally, as a polishing head capable of holding down a frictional force generated in a movable portion of a polishing shaft portion, for example, Japanese Patent Laid-Open No. 63-232929
The one disclosed in Japanese Patent Application Publication No. JP-A-2006-26095 is known.

FIG. 4 shows a polishing head disclosed in this publication. In this polishing head, a rotating shaft 59 is rotatably supported by a fluid bearing 61 in a non-contact manner. Further, the rotor 65 of the motor 63 is fixed to the rotating shaft 59,
By disposing the stator 67 around the rotating shaft 59
Are rotatable in a non-contact manner. Further, the rotation shaft 59
Is performed using the fluid pressure from the air inlets 69 and 71, and the polishing shaft 59 can be moved in a state where the frictional force is kept low.

[0012]

However, in such a conventional polishing head, the vertical displacement of the rotary shaft 59 causes relative displacement between the rotor 65 of the motor 63 and the stator 67 in the axial direction. Occurs, and the magnetic attraction force is generated in the direction of maintaining the magnetic balance. Therefore, the magnitude of the magnetic attraction force varies depending on the degree of positional deviation, and there is a problem that it is difficult to obtain a stable polishing load.

The present invention has been made in order to solve such a conventional problem, and easily and surely eliminates the generation of a magnetic attraction force due to the relative movement of the rotor and the stator of the motor.
An object of the present invention is to provide a polishing head that can obtain a stable polishing load.

[0014]

A polishing head according to a first aspect of the present invention comprises a rotary shaft having a polishing tool fixed to one end thereof, a fluid bearing for movably supporting the rotary shaft in the axial direction, and the rotary shaft. A motor having a fixed rotor and a stator arranged around the rotor in a non-contact manner; a load detector connected to the rotary shaft via a joint attached to the other end of the rotary shaft; A linear guide that guides the load detector in the axial direction of the rotary shaft, and a pressurizer that applies a load to the rotary shaft via the load detector, the axial length of the rotor of the motor, The axial length of the stator, the maximum moving length of the rotor in the axial direction, and the projecting length of the rotor from the stator that eliminates the change in the magnetic attraction force acting on the rotor when the rotor moves. Low magnetic attraction And characterized by being longer than the length plus the twice the length of the long.

(Operation) In the polishing head of the first aspect, when the motor including the rotor fixed to the rotating shaft and the stator arranged around the rotor in a non-contact manner is driven, the rotating shaft supported by the fluid bearing is The polishing tool is rotated and rotated. On the other hand, when the pressurizer is operated, the load detector is guided by the linear guide and moves in the axial direction of the rotating shaft, and the rotating shaft connected to the load detector via the fluid coupling is moved in the axial direction. .

In this polishing head, as shown in FIG. 5, the axial length L ₁ of the rotor 1 of the motor is the axial length L 2 of the stator ₂ and the rotor due to the movement of the rotary shaft 3. 2 of the maximum moving length 2S of the rotor 1 in the axial direction and the magnetic attracting force stable length X which is the protruding length of the rotor 1 from the stator 2 where the change of the magnetic attracting force acting on the rotor 1 when the rotor 1 moves is eliminated. It is longer than the double length plus the length.

That is, generally, as shown in FIG. 6, from the state where the stator 2 and the rotor 1 are magnetically balanced,
When a relative displacement occurs in the axial direction, a magnetic attraction force is generated in the axial direction. Here, the positional deviation is xm,
When the magnetic attraction force in the axial direction is Fkgf, the magnetic attraction force F in the axial direction can be obtained by the following equation.

F = (− 1/4) (dP / dx) (δk _c / μ ₀ ) ² × (P ₀ / P _X ) ² (Bmax ² /9.8) (1) where dP / dx is the rate of change of permeance: H / m P ₀ is the permeance when x = 0: H P _X is the permeance when x: x is the air gap: m k _c is the Carter coefficient μ ₀ is the air Permeability: μ ₀ = 4π × 10 ^-7 Bmax is the air gap maximum magnetic flux density when T = 0: T
It is.

On the other hand, the permeance P when deviated by x
_X is obtained by the following equation. P _x = P ₁ + 2P ₂ = μ ₀ × D (4 log (1+ (πx / 2δk _c )) + (π (L _C -2x) / δk _c )) (2) where L _C is The axial length of the magnet (rotor 1): m D is the average diameter of the gap: m 2.

Further, the rate of change of permeance dP / dx
Is calculated by the following equation. _{dP / dx = (dP 1 /} dx) +2 (dP 2 / dx) = (2μ 0 Dπ / δk c) × ((1 / (1+ (πx / 2δk c))) - 1) ··· (3) Here, by substituting the values obtained by the equations (2) and (3) into the equation (1), the magnetic attraction force F due to the positional deviation x can be obtained.

When the necessary numerical value is determined and calculated, the magnetic attraction force F increases as the displacement x increases. Next, consider a case where the positional relationship between the stator 2 and the rotor 1 is as shown in FIG. In this case, the formula for obtaining the permeance P _X when it is shifted by x is as follows.

P _x = P ₁ + P ₂ = μ ₀ × D (2 log (1+ (πx / 2δk _c )) + (π (L _C −x) / δk _c )) (4) Therefore, the permeance The change rate dP / dx of is calculated by the following equation. dP / dx = (dP ₁ / dx) + (dP ₂ / dx) = (μ ₀ Dπ / δk _c ) × ((1 / (1+ (πx / 2δk _c )))-2) ... (5) Then, by substituting the values obtained by the equations (4) and (5) into the equation (1), the magnetic attraction force F due to the positional deviation x in the case of FIG. 7 can be obtained.

When the necessary numerical value is determined and calculated, the magnetic attraction force F is obtained when the positional deviation x becomes larger than a certain value.
Is almost constant. That is, when the positional deviation x becomes larger than a certain value, the movement of the rotor 1 does not generate a new magnetic attraction force. Therefore, in the present invention, FIG.
Positional deviation as shown, the length L ₁ of the rotor 1 of the motor, the length L ₂ of the stator 2, consisting a maximum movement length 2S in the axial direction of the rotor 1, the magnetic attraction force constant It is set to a length obtained by adding twice the amount X (hereinafter referred to as magnetic attraction force stable length).

By doing so, even if a displacement occurs between the rotor 1 and the stator 2 due to the movement of the rotating shaft 3, both ends of the rotor 1 always exceed a displacement amount at which magnetic attraction force is not generated. Therefore, the generation of magnetic attraction can be suppressed.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings.

FIG. 1 shows an embodiment of the polishing head of the present invention. The polishing head is mainly composed of a polishing shaft 81, a load detector 83 and a load controller 85. The polishing shaft 81 has a rotating shaft 89 at the tip of which a polishing tool 87 is mounted. This rotating shaft 89 is
It is arranged so as to penetrate the center of the housing 91, and is supported vertically by air bearings 93 and 95.

The air bearings 93 and 95 have an air supply source 97.
Are connected via the filter 99 and the pipes 101 and 103. A rotor 107 of the motor 105 is fixed at the center of the rotating shaft 89, and a stator 109 is arranged around the rotor 107. The motor 105 is a brushless motor in which a rotor 107 is made of a permanent magnet and a stator 109 is made of an electromagnet.
1 constitutes an AC servomotor.

The range of the rotational speed of the motor 105 used is 10 to 100 rpm. A rotation detector 113 composed of a photoelectric rotary encoder is provided above the rotation shaft 89.
Is arranged.

The load detection unit 83 is arranged in the housing 115 and has a load detector 117 composed of a load cell. The load detector 117 is connected to a fluid coupling 119 arranged at the upper end of the rotary shaft 89. The load detector 117 is a linear guide 1 including a cross roller guide.
It is guided by 21 so as to be vertically movable.

The load control section 85 is arranged above the housing 115 and has a pressurizer 123 composed of a pneumatic cylinder. The pressurizer 123 is fixed to the housing 115 via the housing 125, and the piston rod 123 a is connected to the load detector 117. An air supply source 97 is connected to the pressurizer 123 via a control valve 127 and pipes 129 and 131.

The air pressure supplied to the control valve 127 is 4 kgf / cm ² , but the pressurizer 123 composed of a pneumatic cylinder is supplied with the air controlled to the required pressure by the control valve 127. In FIG. 1, reference numeral 111 indicates a controller. The controller 111 inputs a load signal from the load detector 117 and a rotation signal of the rotating shaft 89 from the rotation detector 113.

Then, the rotation speeds of the control valve 127 and the motor 105 are controlled based on these signals. In this embodiment, as shown in FIG. 2, the axial direction length L ₁ of the rotor 107 of the motor 105, the axial direction length L ₂ of the stator 109, the axial length of the rotor 107 due to the movement of the rotary shaft 89 Direction maximum movement length 2S and magnetic attraction force stable length X
It is said that the length is the same as the length obtained by adding twice the length.

That is, more specifically, the magnetic permeability μ _{0 of} air is 4π × 10 ⁻⁷ H / m, and the average diameter D of the gap is 2
1.7 × 10 ^-3 m, air gap δ 0.5 × 10
^-3 m, the Carter coefficient k _c is 1.12, the magnetic flux density B in the air gap is 0.773 T, and the length of the stator 3a is 7.
It is set to 5 × 10 ^-3 m. Further, the maximum moving length 2S of the rotor 107 in the axial direction is set to be twice the magnetic attraction force stable length X.

Then, as shown in FIG. 7, the length L _C of the rotor 1 is set to the length of the stator 2 plus the positional deviation x, and the positional deviation x is changed while the above equation (4) is given.
Substituting into the equation (5) and further obtaining the magnetic attraction force F at the positional displacement x by the above equation (1), the magnetic attraction force F is about when the positional displacement x exceeds 6 × 10 ⁻³ m. 0.
It became a constant value of 8 kgf.

Therefore, in this embodiment, the magnetic attraction force stable length X is set to 6 × 10 ⁻³ m, and the length of the stator 109 is set to 7.
For 5 × 10 ⁻³ m, the length of the rotor 107 is 31.5 × 10 ⁻³ m, which is twice the magnetic attraction force stable length of 6 × 10 ⁻³ m at both ends of the stator 109. I have to.
In the polishing head described above, when the motor 105 including the rotor 107 fixed to the rotating shaft 89 and the stator 109 arranged around the rotor 107 in a non-contact manner is driven, the rotating shaft 89 supported by the air bearings 93 and 95. Is rotated,
The polishing tool 87 is rotated.

On the other hand, when the pressurizer 123 is operated, the load detector 117 is guided by the linear guide 121 and the rotating shaft 89
, And the rotating shaft 89 connected to the load detector 117 via the fluid coupling 119 is moved in the axial direction. Polishing of a workpiece using the above-described polishing head is performed as described below.

First, the polishing head is positioned right above the processing position by the moving means (not shown) of the polishing apparatus. next,
The moving means lowers the polishing head until just before the polishing head comes into contact with the workpiece. Thereafter, the rotating shaft 89 is pressed down by the pressurizer 123 until the load detector 117 indicates a predetermined value, and the polishing tool 87 is pressed against the workpiece.

Then, when the load detector 117 shows a predetermined value, the pushing down of the rotary shaft 89 is stopped, and the motor 1 is stopped.
The drive shaft 05 rotates the rotating shaft 89 and the polishing tool 87 to start polishing. In addition, in order to obtain a necessary polishing removal amount, an appropriate processing time for a polishing load is previously calculated, and the polishing is performed only for this time.

In the polishing head configured as described above,
The axial direction length L ₁ of the rotor 107 of the motor 105, the axial direction length L ₂ of the stator 109, and the maximum movement length 2S in the axial direction of the rotor 107, the magnetic attraction force stable length X 2 Since the length is doubled, the generation of the magnetic attraction force due to the relative movement of the rotor 107 and the stator 109 of the motor 105 can be easily and reliably eliminated.

Therefore, it is possible to obtain a stable polishing load, and it is possible to perform polishing processing with higher precision. In the above-described embodiment, the example in which the pneumatic cylinder is used as the pressurizer 123 has been described, but the present invention is not limited to this embodiment, and the value by the load detector 117 is returned to the controller 111. A fluid pressure cylinder that uses pressure of oil or the like, an electrostrictive element that generates a driving force by electricity, a voice coil motor, or the like may be used as long as it can control a low load.

It is desirable that the pressurizer 123 has a controllable load range of 1 × 10 ^-2 to 1 kgf and a load accuracy of within ± 5% of the set load.

[0042]

As described above, in the polishing head according to claim 1, the axial length of the rotor of the motor is the axial length of the stator, and the maximum moving length of the rotor in the axial direction.
Since the length is made longer than the length obtained by adding twice the magnetic attraction force stable length, the generation of the magnetic attraction force due to the relative movement of the rotor and the stator of the motor can be easily and reliably eliminated.

Therefore, it is possible to obtain a stable polishing load, and it is possible to perform polishing processing with higher accuracy.

[Brief description of drawings]

FIG. 1 is a sectional view showing one embodiment of a polishing head of the present invention.

FIG. 2 is an explanatory view showing a length relationship between a rotor and a stator of the motor shown in FIG.

FIG. 3 is a sectional view showing an example of a conventional polishing head.

FIG. 4 is a sectional view showing another example of a conventional polishing head.

FIG. 5 is an explanatory diagram showing a length relationship between a rotor and a stator of the motor of the present invention.

FIG. 6 is an explanatory diagram showing a relationship between a magnetic attraction force F and a positional shift x generated by a positional shift between the rotor and the stator when the rotor and the stator of the motor have the same length.

FIG. 7 is an explanatory diagram showing a relationship between a magnetic attraction force F and a positional deviation x generated by a positional deviation between the rotor and the stator when the rotor of the motor is longer than the length of the stator.

[Explanation of symbols]

 87 Polishing tool 89 Rotary shaft 93,95 Air bearing 105 Motor 107 Rotor 109 Stator 113 Rotation detector 117 Load detector 119 Fluid coupling 121 Linear guide 123 Pressurizer 133 Joint body 135 Air chamber 137 Disk member

Claims (1)

[Claims] 1. A rotary shaft to which an abrasive tool is fixed at one end, a fluid bearing that supports the rotary shaft so as to be movable in the axial direction, a rotor fixed to the rotary shaft, and no contact around the rotor. And a load detector connected to the rotary shaft via a joint attached to the other end of the rotary shaft, the load detector in the axial direction of the rotary shaft. A linear guide for guiding and a pressurizer for applying a load to the rotary shaft via the load detector, wherein the axial length of the rotor of the motor is the axial length of the stator and the axial length of the rotor is A maximum movement length in the axial direction and a length that is twice the magnetic attraction force stable length that is the protruding length of the rotor from the stator that eliminates the change in the magnetic attraction force that acts on the rotor when the rotor moves. Longer than the added length A polishing head that is characterized by being bent.