JP2009031075A - Gravity compensation mechanism and vertical-direction positioning equipment using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gravity compensation mechanism which is capable of responding to vertical-direction super-precision positioning equipment that demand precision of nanometer order. <P>SOLUTION: The gravity compensation mechanism is equipped with a vacuum cylinder actuator 10 and a vacuum pump 14. The vacuum cylinder actuator consists of a vacuum cylinder 10A that is made to communicate with the vacuum pump 14, a noncontact seal ring 10B provided on the side of one end face of the vacuum cylinder and a piston 10C inserted through the noncontact seal ring, and a load given downward vertically to the piston is compensated by the operation of the vacuum pump. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a gravity compensation mechanism and a vertical direction positioning device using the gravity compensation mechanism.

  In recent years, precision machine tools, semiconductor manufacturing equipment, various measuring instruments, and the like have been required to have ultra-precision on the order of nanometers for vertical positioning, and accordingly, development of ultra-precision vertical positioning devices is desired. Yes.

  Conventionally, a gravity compensation mechanism is used in a vertical positioning device so that a controlled object can be positioned easily. Typical examples of such a gravity compensation mechanism include a counterweight method, a constant tension spring method, an electromagnetic actuator method, and a pneumatic cylinder method. However, these conventional gravity compensation mechanisms cannot be used for ultra-precision vertical positioning devices that require ultra-precision on the order of nanometers for the reasons described below.

  First, in the counterweight type gravity compensation mechanism, counterweights having substantially the same load as the control object are connected to each other by a belt or a wire, and the belt or wire is hung on a pulley, and the control object and the counterweight are connected to each other. Are balanced with each other. However, in such a counterweight type gravity compensation mechanism, friction is generated on the rotating shaft of the pulley, and the gravity compensation mechanism accompanying the generation of such friction is used for vertical positioning on the order of nanometers. It cannot be used. In the counterweight system, not only the mass of the movable part is doubled but also a movable space for the counterweight has to be prepared, and there is a problem that the gravity compensation mechanism is enlarged.

  The constant tension spring type gravity compensation mechanism has a configuration in which a controlled object is suspended by a constant tension spring. However, in such a configuration, the controlled object is easily subjected to vibration, and the constant tension spring is fatigued over time. Therefore, the gravity compensation mechanism using the constant tension spring is also used for vertical positioning in the order of nanometers. It is not possible.

  The gravitational compensation mechanism of the electromagnetic actuator type is configured to push up the control object with the operating rod of the electromagnetic actuator. However, the operation of the electromagnetic actuator is accompanied by a large amount of heat that causes thermal deformation of the system. Therefore, the electromagnetic actuator type gravity compensation mechanism cannot be used for positioning in the vertical direction on the order of nanometers.

  The pneumatic cylinder type gravity compensation mechanism is configured to push up an object to be controlled by a piston of the pneumatic cylinder. However, when the object to be controlled is displaced as will be described later, the output fluctuation of the pneumatic cylinder is large, and the gravity compensation mechanism of the pneumatic cylinder system cannot be used for vertical positioning of the order of nanometers.

  Accordingly, the present invention provides a gravity compensation mechanism that can correspond to an ultra-precision vertical positioning device that requires precision on the order of nanometers, and also provides a vertical positioning device that uses such a gravity compensation mechanism. For the purpose.

  The gravity compensation mechanism according to the first aspect of the present invention includes a vacuum cylinder actuator and a vacuum pump. The vacuum cylinder actuator includes a vacuum cylinder communicated with a vacuum pump, a non-contact seal ring provided on one end face side of the vacuum cylinder, and a piston inserted through the non-contact seal ring. The load exerted downward in the vertical direction is compensated by the operation of the vacuum pump. That is, the operation of the vacuum pump places the vacuum cylinder in a low pressure state, which causes the piston to be drawn into the vacuum cylinder to compensate for the downward vertical load applied thereto.

  In such a gravity compensation mechanism, the seal clearance and the seal length of the non-contact seal ring are set according to the load exerted downward on the piston in the vertical direction. In this case, preferably, the seal gap and the seal length of the non-contact seal ring are set so that the gauge pressure in the vacuum cylinder is at least −80 kPaG or less by the operation of the vacuum pump.

  The vertical positioning device according to the second aspect of the present invention uses the gravity compensation mechanism as described above, and includes a drive motor for moving the piston along the vertical direction, and a vertical direction of the piston. And a moving distance measuring sensor for measuring the moving distance along.

  In the vertical positioning device according to the second aspect of the present invention, the drive motor may be one of a voice coil motor and a linear motor. Further, the moving distance measuring sensor is preferably configured as a non-contact type high resolution sensor.

  The vertical positioning apparatus according to the third aspect of the present invention includes a pair of vacuum cylinder actuators and a vacuum pump. In this case, each of the vacuum cylinder actuators includes a vacuum cylinder communicated with a vacuum pump, a non-contact seal ring provided on one end face side of the vacuum cylinder, and a piston inserted through the non-contact seal ring The load exerted downward on the piston in the vertical direction is compensated by the operation of the vacuum pump. The vertical positioning apparatus according to the third aspect of the present invention further includes a drive motor for moving both pistons along the vertical direction to the center between the pair of vacuum cylinder actuators, and movement along the vertical direction of the pistons. A moving distance measuring sensor for measuring the distance. A control object is suspended from the pair of pistons, and the control object is positioned by controlling the drive motor with a movement distance measurement sensor.

  The vertical positioning apparatus according to the third aspect of the present invention further includes a support suspended from both of the pistons and supported by the drive motor to support the controlled object, and the vertical direction of the support. And a pair of non-contact guide means for guiding the movement of the two. When such a non-contact guide means is used, the generation of frictional heat is suppressed as much as possible, thereby eliminating the influence of frictional heat on the vertical positioning accuracy of the controlled object.

  In the vertical positioning device according to the third aspect of the present invention, preferably, the pair of vacuum cylinder actuators are arranged symmetrically with respect to the drive direction of the drive motor, and similarly, the pair of non-contact guide means is also provided for the drive motor. They are arranged symmetrically with respect to the driving direction. With such a symmetric structure, for example, it is possible to minimize the influence on the positioning accuracy in the vertical direction of the control symmetric object due to the dimensional change of the component accompanying the temperature change.

  In the vertical positioning device according to the third aspect of the present invention, each of the pair of non-contact guide means includes a guide rail and a guide block that is moved along the guide rail and connected to the support body. Can be configured. In such a case, preferably, the vertical positioning device further supports the first support structure that supports the movement distance measurement sensor and the pair of guide rails, the pair of vacuum cylinder actuators, and the drive motor. And a second support structure independent of the first support structure. According to such a configuration, the vibration generated when the drive motor is actuated is prevented from reaching the movement distance measurement sensor, so that the measurement by the movement distance measurement sensor can be performed quickly without waiting for the vibration to attenuate. it can.

  Next, an embodiment of a gravity compensation mechanism according to the present invention will be described with reference to FIG. FIG. 1 is a schematic diagram showing the principle configuration of a gravity compensation mechanism according to the present invention.

  The gravity compensation mechanism according to the present invention employs a vacuum cylinder system and includes a vacuum cylinder actuator 10 and a guide column 11. The vacuum cylinder actuator 10 includes a vacuum cylinder 10A that is appropriately fixed to the upper end side of the guide column 11, a non-contact seal ring 10B provided on the lower surface side of the vacuum cylinder 10A, and a vacuum cylinder through the non-contact seal ring 10B. And a piston 10C inserted through 10A. A control object 12 is appropriately fixed to the outer end of the piston 10C, and a guide piece 12A is projected from the control object 12, and the guide piece 12A is formed in the guide column 11 but is not in the vertical guide groove 11A. Engaged in contact. That is, a large number of compressed air ejection holes (not shown) communicated with the compressor are formed on the inner wall surface of the vertical guide groove 12, thereby guaranteeing the non-contact state of the guide piece 12 </ b> A in the vertical guide groove 11 </ b> A. The

  The vacuum cylinder 10A is communicated with the vacuum pump 14 via the conduit 13, and the conduit 13 is provided with a pressure regulator 15, whereby the load of the control object 12 is compensated in the vacuum cylinder 10A. A vacuum or low pressure state is created. That is, the piston 10 </ b> C is drawn by the vacuum cylinder 10 </ b> A with a suction force that cancels the load and the load of the control object 12, and the control object 12 is held in a floating state.

  The seal gap between the non-contact seal ring 10B and the piston 10C is about several tens of μm, and the vacuum pump 14 is continuously operated to maintain the control target 12 in a floating state. At this time, the vacuum cylinder 10A Is in a low pressure state with a gauge pressure of -80 to -100 kPaG. The unit kPaG indicates the gauge pressure.

  According to the vacuum cylinder type gravity compensation mechanism as described above, even if the controlled object 12 is displaced by an appropriate drive means such as a voice coil motor or a linear motor for positioning, the details will be described below. As described above, the output fluctuation of the vacuum cylinder actuator 10 can be made substantially zero, so that the controlled object 12 can be positioned with ultra-high accuracy on the order of nanometers.

  First, for a better understanding of the present invention, a conventional pneumatic cylinder type gravity compensation mechanism will be described as a comparative example of the gravity compensation mechanism according to the present invention with reference to FIG. FIG. 2 is a schematic diagram showing a conventional pneumatic cylinder type gravity compensation mechanism.

  The pneumatic cylinder type gravity compensation mechanism includes a pneumatic cylinder actuator 20 and a guide column 21, and the pneumatic cylinder actuator 20 and the guide column 21 are provided adjacent to each other. The pneumatic cylinder actuator 20 includes a pneumatic cylinder 20A installed on an appropriate support base, a non-contact seal ring 20B provided on the upper surface side of the pneumatic cylinder 20A, and the pneumatic cylinder 20A through the non-contact seal ring 20B. It consists of the piston 20C inserted. A control object 22 is appropriately fixed to the outer end of the piston 20C, and a guide piece 22A is projected from the control object 22. The guide piece 22A is formed in the guide column 21 but is not in the vertical guide groove 21A. Engage in contact. That is, as in the case shown in FIG. 1, the inner wall surface of the vertical guide groove 22 is formed with a number of compressed air ejection holes (not shown) communicated with the compressor. The non-contact state of the guide piece 22A is guaranteed.

  The pneumatic cylinder 20A is communicated with the compressor 24 through a conduit 23, and a pressure regulator 25 is provided in the conduit 23, whereby a predetermined load that compensates for the load of the controlled object 22 is provided in the pneumatic cylinder 20A. A high pressure condition is created. That is, the piston 20C is pushed out of the pneumatic cylinder 20A with a pressing force that cancels out the load and the load of the controlled object 22, and the controlled object 22 is held in a floating state.

  Note that the seal gap between the non-contact seal ring 20B and the piston 20C is about several tens of μm, and the compressor 24 is continuously operated in order to maintain the controlled object 22 in a floating state.

  In the gravity compensation mechanism of the pneumatic cylinder type as described above, when the controlled object 22 is displaced by an appropriate driving means such as a voice coil motor or a linear motor for positioning, the pneumatic cylinder actuator 20 The output fluctuation becomes large, and therefore, the pneumatic cylinder type gravity compensation mechanism cannot be used to position the control object 22 with ultra-high accuracy on the order of nanometers.

  With respect to the output (gauge pressure) fluctuation received by the piston 10C when the volume in the vacuum cylinder 10A is changed by the movement of the piston 10C in the gravity compensation mechanism shown in FIG. 1, the pneumatic cylinder 20A is used in the gravity compensation mechanism shown in FIG. It can be easily expected that the internal volume is significantly smaller than the fluctuation of the output gauge pressure that the piston 20C receives when it is changed by the movement of the piston 20C, but the fluctuation of both outputs (gauge pressure) is quantitative. It is not clear how much is different.

  3A and 3B show the vacuum cylinder type gravity compensation mechanism according to the present invention shown in FIG. 1 and the conventional pneumatic cylinder type gravity compensation mechanism shown in FIG. Thus, the output fluctuation of the piston received when the cylinder fluctuates under low pressure and high pressure conditions was numerically calculated. In the pseudo model of FIGS. 3A and 3B, the piston is moved in a sealed state within the cylinder, and the pressure in the cylinder (gauge pressure) as the piston moves. / Volume changes will be subject to polytropic changes.

The polytropic change is expressed by the following formula.
PV ⁿ = constant where P is the gauge pressure in the cylinder, V is the volume change in the cylinder, and n is a constant.

  More specifically, in the pseudo model of FIG. 3A, the initial condition is that the piston 10C is placed at the lower limit position and the gauge pressure in the cylinder 10A is a low pressure state of −95 kPaG (corresponding to an absolute pressure of 6.3 kPa). If the piston 10C is moved from the lower limit position until the volume of the cylinder 10A is reduced by 50%, the gauge pressure in the cylinder 10A increases from -95 kPaG to -85 kPaG (corresponding to an absolute pressure of 17 kPa). The output fluctuation of 10C, that is, the gauge pressure fluctuation in the cylinder 10A is about 11% [(95-85) / 95 × 100%].

  On the other hand, in the pseudo model of FIG. 3B, the piston 20C is placed under an initial condition where the piston 20C is placed at the upper limit position and the gauge pressure in the cylinder 20A is 95 kPaG (corresponding to an absolute pressure of 196 kPa). Is moved from the upper limit position until the volume of the cylinder 20A is reduced by 50%, the gauge pressure in the cylinder 20A increases from 95 kPaG to 418 kPaG (519 kPa). At this time, the output fluctuation of the piston 20C is 340% [(418 -95) / 95 × 100%].

  As shown by the above calculation results, in the case of FIG. 3A as compared with FIG. 3B, the output (gauge) of the piston 10C accompanying the volume fluctuation of the cylinder 10A due to the movement of the piston 10C. It can be seen that the pressure variation is much smaller. In the gravity compensation mechanism shown in FIG. 1, the piston 10C is actually inserted into the vacuum cylinder 10A through the non-contact seal ring 10B, so that the output (gauge pressure) of the piston 10C accompanying the volume variation of the vacuum cylinder 10A. ) The fluctuation is even smaller.

  In the gravity compensation mechanism shown in FIG. 1, the gravity compensation force, that is, the force for holding the controlled object 12 in a floating state is determined by the design of the non-contact seal ring 10B. This will be described below.

  First, referring to FIG. 4, the non-contact seal ring 10 </ b> B and the piston 10 </ b> C of FIG. 1 are shown as perspective views, in which the reference symbol a indicates the seal gap of the non-contact seal ring 10 </ b> B, and the reference symbol L indicates non- The seal length of the contact seal ring 10B is shown.

  The gravity compensation force depends on the low-pressure state obtained in the vacuum cylinder 10A (see FIG. 1), and this low-pressure state is determined by the amount of air flowing from the seal gap a between the non-contact seal ring 10B and the piston 10C. That is, the smaller the air inflow amount, the greater the gravity compensation force. Therefore, if the seal gap a is small and the seal length L is large, the gravity compensation force becomes large.

  The graph of FIG. 5A shows the analysis result of the relationship between the seal gap a and the gravity compensation force, and the graph of FIG. 5B shows the analysis result of the relationship between the seal length L and the gravity compensation force. Indicates. As shown in these graphs, a large gravity compensation force can be obtained if the seal gap a is small and the seal length L is large.

  Therefore, when designing the gravity compensation mechanism of FIG. 1, the design parameters (a, L) of the non-contact seal ring 10B are set in FIGS. 5 (a) and 5 (b) according to the load of the controlled object 12. It can be determined appropriately based on the graph.

  Referring to FIG. 6, an experimental apparatus having a configuration equivalent to a vertical positioning apparatus having a gravity compensation mechanism according to the present invention is shown, and an evaluation experiment of the vertical positioning apparatus according to the present invention was performed using this experimental apparatus. .

  The experimental apparatus shown in FIG. 6 includes a vacuum cylinder actuator 30, which is provided on a suitable cylinder B and one end face of the vacuum cylinder 30A. The non-contact seal ring 30B and the piston 30C inserted into the vacuum cylinder 30A through the non-contact seal ring 30B. The diameter of the piston 30C is 25 mm, and the stroke length is 30 mm. The non-contact seal ring 30B has a seal gap of 20 μm and a seal length of 19 mm. Reference numeral 31 is a pressure sensor for measuring the pressure in the vacuum cylinder 30A.

  The other end face of the vacuum cylinder 30A is communicated with a vacuum pump 33 through a conduit 32, and the conduit 32 is provided with a pressure regulator 34.

  A block piece 35 is connected to the outer end of the piston 30C as a control object. Although not shown in FIG. 6, a large number of compressed air ejection holes are formed in a part of the base B, that is, a region where the block piece 35 is disposed, so that the block piece 35 is floated by the air layer. Maintained.

  In order to drive the block piece 35, a voice coil motor 36 is provided on the side opposite to the piston 30 </ b> C side with respect to the block piece 35. The voice coil motor 36 includes a permanent magnet 36A fixed on the base B, an electromagnetic coil 36B accommodated in the permanent magnet 36A, and a connecting rod 36C for connecting the electromagnetic coil 36B and the block piece 35. . The maximum thrust of the voice coil motor 36 is 50N.

  In order to measure the amount of movement of the block piece 35, a non-contact type high resolution sensor such as a laser interferometer 37 is provided adjacent to the voice coil motor 36, and this laser interferometer 37 is provided on the base B. It is installed on the support base 38. On the other hand, a mirror 39 is installed on the block piece 35 to reflect the laser beam LB emitted from the laser interferometer 37 back to the laser interferometer 37. The resolution of the laser interferometer 37 is 0.3 nm.

  In the experimental apparatus of FIG. 6, the vacuum cylinder actuator 30 and the block piece 35 are arranged on a horizontal plane, so that the gravity of the block piece 35 does not act on the piston 30 </ b> C of the vacuum cylinder actuator 30. When the vacuum pump 33 is operated, the block piece 35 is sucked to the vacuum cylinder actuator 30 side with a predetermined suction force. By operating the voice coil motor 36 so as to compensate for the suction force, the block 30 and the block 30 are blocked. It is possible to maintain the piece 35 in the initial position as shown in FIG. 6, and at this time, the experimental apparatus is equivalent to a vertical positioning apparatus.

  First, in the experimental apparatus of FIG. 6, a pressure fluctuation experiment in the vacuum cylinder 30A was performed under the following conditions. That is, with the block piece 35 maintained at the initial position, the vacuum pump 33 and the voice coil motor 36 are driven so that the gauge pressure in the vacuum cylinder 30A becomes a steady pressure of −20 kPaG, and then the piston 30C. The voice coil motor 36 is controlled to be pushed into the vacuum cylinder 30A by 20 mm. At this time, the gauge pressure in the vacuum cylinder 30 </ b> A was measured by the pressure sensor 31. The moving distance of the piston 30A, that is, the moving distance of the block piece 35 was measured by the laser interferometer 37.

  The measurement results are shown in the timing chart of FIG. As shown in the figure, when the piston 30C is pushed into the vacuum cylinder 30A, the gauge pressure in the vacuum cylinder 30 increases by about 5 kPaG and immediately returns to the steady pressure of -20 kPaG. That is, the pressure fluctuation of the measurement result is about 5 kPaG. An analysis result based on simulation is also shown in the timing diagram of FIG. 7A. The pressure fluctuation of the analysis result is about 4 kPaG, and it can be seen that the measurement result and the analysis result are almost the same.

  Next, in the experimental apparatus of FIG. 6, a pressure fluctuation experiment in the vacuum cylinder 30A was performed under different conditions. That is, in this pressure fluctuation experiment, the vacuum pump 33 and the voice coil motor 36 are driven so that the gauge pressure in the vacuum cylinder 30A becomes a steady pressure of -80 kPaG with the block piece 35 maintained at the initial position. Except for these points, the experiment was performed under the same conditions as the pressure fluctuation experiment described above (FIG. 7A).

  The measurement result when the in-cylinder steady pressure is −80 kPaG is shown in the timing diagram of FIG. As shown in the figure, when the piston 30C is pushed into the vacuum cylinder 30A, the gauge pressure in the vacuum cylinder 30 increases by about 2 kPaG and immediately returns to the steady pressure of -80 kPaG. That is, the pressure fluctuation of the measurement result is about 2 kPaG. The timing diagram of FIG. 7 (b) also shows an analysis result based on the simulation. The pressure fluctuation of the analysis result is about 3 kPaG, and it can be seen that the measurement result and the analysis result almost coincide.

  From the above measurement results and analysis results, it can be seen that the pressure fluctuation in the vacuum cylinder 30A can be predicted by the analysis result based on the simulation instead of the measurement result of the pressure fluctuation in the vacuum cylinder 30A.

  Therefore, in the experimental apparatus of FIG. 6, the steady gauge pressure is used as a variable, and the pressure fluctuation is obtained from the analysis result based on the simulation. That is, -20 kPaG, -50 kPaG, -80 kPaG and -90 kPaG are set as the steady gauge pressures in the vacuum cylinder 30, respectively, and the piston 30C is only 20 mm from the initial position (see FIG. 6) under the respective steady gauge pressure settings. The drive of the voice coil motor 36 is controlled so as to be pulled out from the vacuum cylinder 30A to the initial position after being pushed into the vacuum cylinder 30A. At this time, the pressure fluctuation in the vacuum cylinder 30 was obtained by simulation. .

  The analysis result of the pressure fluctuation simulation when the piston 30C is pushed into the vacuum cylinder 30A is shown in the timing diagram of FIG. 8A, and the simulation of the pressure fluctuation when the piston 30C is pulled out from the vacuum cylinder 30A. The analysis result is shown in the timing chart of FIG.

  As shown in the timing diagrams of FIG. 8A and FIG. 8B, when the steady pressure in the vacuum cylinder 30 is -80 kPaG or less, the vacuum cylinder 30 can be used both when the piston 30C is pushed and when the piston 30C is pulled out. The pressure fluctuation is ± 2kPaG or less. That is, when the piston 30C is pushed in and pulled out, fluctuations in the output of the piston 30C are substantially eliminated, so that the block piece 35 can be positioned on the order of nanometers.

  Referring to FIG. 9, the precision machine tool is shown as a perspective view, and the precision machine tool incorporates a vertical positioning device using a gravity compensation mechanism as shown in FIG.

  As shown in FIG. 9, the precision machine tool includes a front support structure 40 and a rear support structure 41 that are independent from each other, and the front support structure 40 is formed as a beam 40B stretched on a pair of block bases 40A. Similarly, the rear support structure 41 is also configured as a beam 41B stretched over a pair of block bases 41A. Both beams 40B and 41B are extended in parallel with each other at a predetermined interval. In FIG. 9, the beam 40 </ b> B is shown with its central portion cut away for convenience of illustration.

  The precision machine tool also includes a horizontal positioning device 42 located below the center of both beams 40B and 41B. The horizontal direction positioning device 42 includes an XY table 42A that can be positioned along the X and Y axes of an XYZ rectangular coordinate system, a drive mechanism 42B for driving the XY table 42A, and an XY table. And a workpiece mounting table 42C installed on 42A. An appropriate workpiece W is mounted on the workpiece mounting table 42C.

  The precision machine tool further includes an H-shaped support plate 43 fixed to the inner wall surface of the beam 40B, that is, the inner wall surface facing the beam 41B, and a non-contact high resolution sensor such as a laser interferometer supported by the H-shaped support plate 43. 44 and a pair of guide rails 45 supported by an H-shaped support plate 43. More specifically, a rectangular attachment plate 43A is stretched over the H-shaped support plate 43, and a laser interferometer 44 is attached to the center of the rectangular attachment plate 43A. The resolution of the laser interferometer 44 is 0.6 nm.

  On the other hand, from the rear wall surface of the left and right sides of the H-shaped support plate 43, support pieces 43B are fixed in the vicinity of the upper and lower ends thereof, and the guide rail 45 is attached to the support pieces 43B near the upper and lower ends of the left and right sides. Is supported. In FIG. 9, the support piece (43 </ b> B) near the lower ends of the left and right sides of the H-shaped support plate 43 cannot be hidden behind the H-shaped support plate 43.

  The precision machine tool further comprises a vertical positioning device 46 provided between both beams 40B and 41B. The vertical positioning device 46 includes a pair of vacuum cylinder actuators 460 fixedly supported on the beam 41B by a support bracket 47, a voice coil motor 461 provided between the pair of vacuum cylinder actuators 460, and a pair of guide rails 45. And a pair of guide blocks 462 engaged with each of them in a non-contact state. In FIG. 9, only a part of the left guide block 462 is visible, and the right guide block (462) cannot be seen hidden behind the H-shaped support plate 43.

  Referring to FIG. 10, a vertical positioning device 46 extracted from the precision machine tool of FIG. 9 is shown as a partial cross-sectional detailed perspective view.

  As shown in FIG. 10, each vacuum cylinder actuator 460 includes a vacuum cylinder 460A fixed to the support bracket 47 (see FIG. 9), a non-contact seal ring 460B provided on the lower surface side of the vacuum cylinder 460A, The piston 460C is inserted into the vacuum cylinder 20B through the non-contact seal ring 460B. The lower end of each piston 460C is fixed to an attachment piece 462A protruding from the upper end of the corresponding guide block 462.

  The non-contact seal ring 460B has a seal gap of 20 μm and a seal length of 19 mm. The piston 460C had a diameter of 40 mm, a length of 145 mm, and a stroke of 100 mm.

  Although not shown in FIG. 10, a large number of compressed air ejection holes communicating with the compressor are appropriately formed around the entire guide rail 45, thereby guaranteeing a non-contact state of the guide block 462 with respect to the guide rail 45. Is done.

  The voice coil motor 461 includes a permanent magnet 461A which is fixed between a pair of vacuum cylinders 460A and has a U-shaped cross section, and an electromagnetic coil 461B disposed in the permanent magnet 461A. The electromagnetic coil 461B is driven so as to move up and down according to the direction of current flowing therethrough.

  An inverted T-shaped support body 463 is connected to the lower end of the electromagnetic coil 461 </ b> B of the voice coil motor 461, and the lower end side head is fixed to the side walls of the pair of guide blocks 462. That is, the pair of guide blocks 462 and the support body 463 are suspended from the pair of pistons 460C. A mirror 464 arranged so as to be aligned with the laser interferometer 44 (see FIG. 9) is attached to the center front of the lower-end side head of the inverted T-shaped support 463, and this mirror 464 is emitted from the laser interferometer 44. The reflected laser light is reflected toward the laser interferometer 44, whereby the distance between the mirror 464 and the laser interferometer 44, that is, the moving distance of the permanent magnet 461A moving up and down of the electromagnetic coil 461B is measured. .

  Returning to FIG. 9 again, in order to ensure stable vertical movement of the electromagnetic coil 461B of the voice coil motor 461, a pair of guide rails 461C are provided along the opening edge of the permanent magnet 461A having a U-shaped cross section. The guide member 461D having a T-shaped cross section is inserted between the pair of guide rails 461C and connected to the electromagnetic coil 46. The wall surfaces of the pair of guide rails 461C facing each other are formed with a number of compressed air ejection holes (not shown) communicating with the compressor, whereby the guide member 461D is engaged with the pair of guide rails 461D in a non-contact state. Can be combined.

  Further, as shown in FIG. 9, a tool holder 465 is suspended from the center of the lower end side head portion of the inverted T-shaped support body 463, and an appropriate tool T is held on the tool holder 465 as an object to be controlled. Is done.

Although not shown in FIGS. 9 and 10, in the precision machine tool described above, the pair of vacuum cylinders 460A are communicated with a vacuum pump via a pressure regulator. The pumping speed of the vacuum pump was 4 m ² / h, and the steady pressure in each vacuum cylinder 460 was -80 kPaG.

  In the precision machine tool of FIGS. 9 and 10, the pair of vacuum cylinder actuators 460 constitute a gravity compensation mechanism, and by this gravity compensation mechanism, a pair of pistons 460C, an electromagnetic coil 461B, a guide member 461D, and a pair of guide blocks. The load of the movable part consisting of 462, the pair of mounting pieces 462A, the support 463, the mirror 464, the tool holder 465, and the tool T is compensated to be in a floating state. By driving the voice coil motor 461 in such a floating state, the vertical positioning of the tool T can be performed on the order of nanometers. In addition, the load of the above-mentioned movable part is 16 kg.

  An important feature of the precision machine tool shown in FIGS. 9 and 10 is that the entire structure is symmetric with respect to the drive axis of the voice coil motor 461. With such a symmetric structure, for example, it is possible to minimize the influence on the vertical positioning accuracy of the tool T due to the dimensional change of the component accompanying the temperature change.

  Another important feature of the precision machine tool of FIGS. 9 and 10 is that the guide member 461D and the guide block 462 are guided in a non-contact state using compressed air. That is, since the guide member 461D and the guide block 462 are guided in a non-contact state, generation of frictional heat is suppressed, thereby eliminating the influence of frictional heat on the vertical positioning accuracy of the tool T. Become.

  Further, as another important feature of the precision machine tool of FIGS. 9 and 10, the laser interferometer 44 and the pair of guide rails 45 are supported on the front support structure 40 side by the H-shaped support plate 43. On the other hand, a point that the pair of vacuum cylinder actuators 460 and the voice coil motor 461 are supported on the rear support structure 41 side by the support bracket 47 is also mentioned. According to such a configuration, the vibration generated when the voice coil motor 461 is actuated is prevented from reaching the laser interferometer 44. Therefore, the measurement by the laser interferometer 44 is promptly performed without waiting for the attenuation of the vibration. be able to.

  9 and 10, a voice coil motor 461 is used as a drive motor for positioning the tool T. For example, a linear motor can be used as another drive motor.

  In the precision machine tool shown in FIGS. 9 and 10, an experiment is actually performed in which the tool T is moved upward by 2 nm from a predetermined stop position in the vertical direction and then moved downward by 2 nm to the original stop position. The experimental results are shown in the graphs of FIGS. 11 (a) and 11 (b).

  The timing diagram of FIG. 11A shows the measurement values obtained from the laser interferometer 44 when placed at a predetermined stop position in the vertical direction. As shown in the timing chart of FIG. 11A, it can be seen that the measured value from the laser interferometer 44 changes within a range of approximately ± 1.5 nm. This indicates that the stop performance with respect to the tool T is ± 1.5 nm in the precision machine tool of FIGS. 9 and 10. In the timing chart of FIG. 11A, the solid line drawn at the tool position 0 nm indicates the stop position where the tool T should be originally stopped.

  The timing chart of FIG. 11B is obtained from the laser interferometer 44 when the tool T is moved upward by 2 nm from the predetermined stop position and then moved downward by 2 nm to the original stop position. Indicates the measured value. In the timing diagram of FIG. 11B, the solid line in the staircase shape indicates the movement locus that the tool T should follow. As shown in the timing diagram of FIG. 11B, it can be seen that the tool T can be positioned with a positioning resolution of 2 nm.

  9 and 10 show an example in which the vertical positioning device according to the present invention is applied to a precision machine tool. However, the vertical positioning device according to the present invention is not only a precision machine tool but also a semiconductor manufacturing facility and various kinds of devices. It can also be applied to measuring instruments.

In the embodiment described above, the laser interferometer 44 is used as a non-contact type high resolution sensor, but other sensors such as a linear encoder may be used.

It is a schematic diagram showing an embodiment of a gravity compensation mechanism of a vacuum cylinder type according to the present invention. It is a schematic diagram showing a conventional pneumatic cylinder type gravity compensation mechanism. (A) is an explanatory view for explaining fluctuations in output (gauge pressure) of a piston when a pressure / volume change is caused by movement of the piston in a cylinder under a low pressure state in the pseudo model of the gravity compensation mechanism of FIG. (B) explains the fluctuation of the output (gauge pressure) of the piston when the inside of the cylinder under high pressure is subjected to a pressure / volume change due to the movement of the piston in the pseudo model of the gravity compensation mechanism of FIG. It is explanatory drawing to do. It is a perspective view which shows the non-contact seal ring and piston of FIG. 1, Comprising: It is explanatory drawing explaining the seal clearance gap and seal length of a non-contact seal ring. (A) is a graph which shows the relationship between the seal clearance gap and gravity compensation force of the non-contact seal ring of the gravity compensation mechanism of FIG. 1, (b) is the seal of the non-contact seal ring of the gravity compensation mechanism of FIG. It is a graph which shows the relationship between length and gravity compensation force. It is the schematic which shows the experimental apparatus with a structure equivalent to the vertical direction positioning apparatus with a gravity compensation mechanism by this invention. (A) is a timing chart showing the measurement result and simulation analysis result of one vacuum cylinder pressure fluctuation experiment performed with the experimental apparatus of FIG. 6, and (b) was performed with the experimental apparatus of FIG. It is a timing diagram which shows the measurement result of another vacuum cylinder pressure fluctuation experiment, and the analysis result of simulation. (A) is a timing diagram which shows the analysis result of the simulation of another vacuum cylinder pressure fluctuation | variation performed with the experimental apparatus of FIG. 6, (b) is another another performed with the experimental apparatus of FIG. It is a timing diagram which shows the analysis result of the simulation of a vacuum cylinder pressure fluctuation. 1 is a perspective view of a precision machine tool incorporating a vertical positioning device using a gravity compensation mechanism according to the present invention. FIG. 10 is a partial cross-sectional detailed perspective view of the vertical positioning device extracted from the precision machine tool of FIG. 9. (A) is a timing diagram showing measurement values obtained from a laser interferometer when the tool is placed at a predetermined stop position in the vertical direction in the precision machine tool of FIG. 10, and (b) is a timing diagram showing FIG. FIG. 5 is a timing chart showing measurement values obtained from a laser interferometer when a tool is moved upward by 2 nm from a predetermined stop position by the precision machine tool and then moved downward by 2 nm to the original stop position.

Explanation of symbols

10: Vacuum cylinder actuator 11: Guide column 11A: Vertical guide groove 10A: Vacuum cylinder 10B: Non-contact seal ring 10C: Piston 12: Control target 12A: Guide piece 20: Pneumatic cylinder actuator 20A: Pneumatic cylinder 20B: Non Contact seal ring 20C: Piston 21: Guide column 21A: Vertical guide groove 22: Control target 22A: Guide piece a: Seal gap L: Seal length 30: Vacuum cylinder actuator 30A: Vacuum cylinder 30B: Non-contact seal ring 30C: Piston 31: Pressure sensor 32: Conduit 33: Vacuum pump 34: Pressure regulator 35: Block piece 36: Voice coil motor 36A: Permanent magnet 36B: Electromagnetic coil 37: Laser interferometer 38: Support base 39: Mirror LB: Laser light 40 : Front support structure 40A: Block base 40 : Beam 41: Back support structure 41A: Block base 41B: Beam 42: Horizontal positioning device 42A: XY table 42B: Drive mechanism 42C: Workpiece mounting table W: Workpiece 43: H-shaped support plate 43A : Rectangular mounting plate 43B: Support piece 44: Laser interferometer 45: Guide rail 46: Vertical positioning device 460: Vacuum cylinder actuator 460A: Vacuum cylinder 460B: Non-contact seal ring 460C: Piston 461: Voice coil motor 461A: Permanent Magnet 461B: Electromagnetic coil 461C: Guide rail 461D: Guide member 462: Guide block 462A: Mounting piece 463: Support body 464: Mirror 465: Tool holder 47: Support bracket T: Tool

Claims (11)

A gravity compensation mechanism comprising a vacuum cylinder actuator (10) and a vacuum pump (14),
The vacuum cylinder actuator includes a vacuum cylinder (10A) communicated with the vacuum pump (14), a non-contact seal ring (10B) provided on one end face side of the vacuum cylinder, and the non-contact seal ring A gravity compensation mechanism comprising a piston (10C) inserted into the piston, and a load exerted downward on the piston in the vertical direction is compensated by the operation of the vacuum pump. 2. The gravity compensation mechanism according to claim 1, wherein a seal gap and a seal length of the non-contact seal ring (10 </ b> B) are set according to a load applied vertically downward to the piston. The gravity compensation mechanism according to claim 2, wherein the non-contact seal ring (10B) and the non-contact seal ring (10B) are configured so that the pressure in the vacuum cylinder (10A) is at least -80 kPaG or less by the operation of the vacuum pump (14). Gravity compensation mechanism in which the seal length is set. A vertical positioning device using the gravity compensation mechanism according to any one of claims 1 to 3,
A drive motor for moving the piston along the vertical direction;
A vertical positioning device comprising a movement distance measuring sensor for measuring a movement distance along a vertical direction of the piston. 5. The vertical positioning apparatus according to claim 4, wherein the drive motor is one of a voice coil motor and a linear motor. 5. The vertical positioning device according to claim 4, wherein the moving distance measuring sensor is a non-contact type high resolution sensor. A vertical positioning device comprising a pair of vacuum cylinder actuators (460) and a vacuum pump,
Each of the vacuum cylinder actuators includes a vacuum cylinder (460A) communicated with the vacuum pump, a non-contact seal ring (460B) provided on one end surface side of the vacuum cylinder, and a non-contact seal ring. A vertical positioning device comprising a piston (460C) inserted therein, wherein a load applied vertically downward to both of the pistons is compensated by the operation of the vacuum pump;
And a drive motor (461) for moving both of the pistons along the vertical direction in the center between the pair of vacuum cylinder actuators;
A vertical positioning device comprising a moving distance measuring sensor (44) for measuring a moving distance along a vertical direction of the piston. The vertical positioning device according to claim 7,
A support (463) suspended from both of the pistons (460C) and connected by the drive motor to support the control object (T);
A vertical positioning device comprising a pair of non-contact guide means (45, 462) for guiding the vertical movement of the support. 9. The vertical positioning device according to claim 8, wherein the pair of vacuum cylinder actuators (460) are arranged symmetrically with respect to the drive direction of the drive motor (461) and the pair of non-contact guide means (45). , 462) are also positioned vertically with respect to the drive direction of the drive motor (461). 8. The vertical positioning device according to claim 7, wherein each of the pair of non-contact guide means is moved along the guide rail (45) and connected to the support body (463). A vertical positioning device comprising a guide block (462). The vertical positioning device according to claim 10,
A first support structure (40) for supporting the movement distance measuring sensor (44) and the pair of guide rails (45);
A vertical positioning device comprising a second support structure (42) supporting the pair of vacuum cylinder actuators (460) and the drive motor (461) and independent of the first support structure.

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