JP4475937B2 - Guide device - Google Patents

Description

  The present invention relates to a guide device for driving a movable body that performs linear motion and rotational motion by friction drive of an ultrasonic motor, and particularly reduces dust and dust generated by friction drive, and further, the dust and dust is reduced. It can be prevented from adhering to the movable body, and is suitable as a guide device used in precision processing machines, precision measuring devices, and semiconductor manufacturing devices.

  Ultrasonic motors have a minimum amplitude on the order of nanometers, can be positioned with high resolution, and have a higher driving force than other electromagnetic motors of the same size. A zoom mechanism and a vibration alarm for a wristwatch have been put into practical use for a rotational motion system, and recently, it has been applied to a linear motion system.

  FIG. 5 shows an example of a conventional guide device using an ultrasonic motor as a drive source for the movable body. The guide device 10 includes a pair of guide members 12 such as a cross roller guide on a base board 11 as shown in the figure, and a stage 13 as a movable body is linearly (left and right in the figure) by these guide members 12. To guide you.

  A driving force transmission member 14 is installed on one side surface of the stage 13 in parallel with the guide member 12, and a linear scale 15 is installed on the other side surface of the stage 13 in parallel with the driving force transmission member 14. In addition, a measuring head 16 is provided at a position facing the linear scale 15 to constitute a position detecting means 17, and one ultrasonic motor 20 is installed at a position facing the driving force transmitting member 14. The friction member 25 of the ultrasonic motor 20 is brought into contact with the contact surface of the driving force transmission member 14 perpendicularly.

  In the figure, 26 is a housing for accommodating the ultrasonic motor 20, 18 is a control unit for controlling the driving conditions of the stage 13 based on position information obtained from the position detection means 17, and 19 is output from the control unit 18. The driver outputs a driving voltage for driving the ultrasonic motor 20 based on the command signal.

  Next, the ultrasonic motor 20 will be described in detail. FIG. 6 shows a cross-sectional view of a state in which the ultrasonic motor used in the guide device of FIG. The ultrasonic motor 20 has electrode films 22a, 22b, 22c, and 22d that are divided into four on one main surface of the piezoelectric ceramic plate 23, and connects the electrode films 22a and 22d that are located diagonally, A vibrating body 24 in which the electrode film 22b and the electrode film 22c that are located diagonally are connected, and a common electrode film (not shown) serving as a ground is formed almost on the entire main surface, and the vibrating body 24 On the other hand, it is composed of a friction member 25 made of ceramic or glass provided on the end face, and by applying an alternating voltage to the electrode film 22b or the electrode film 22d, the piezoelectric ceramic plate 23 is caused to generate longitudinal vibration and lateral vibration, and these vibrations. The friction member 25 is moved elliptically by the resultant force.

  In addition, the vibrating body 24 is held by springs 27 on both sides in the housing 26, and the vibrating body 24 is pressed against the driving force transmission member 14 of the stage 13 by the pressing force of the spring 28 to apply preload. It was.

  Therefore, when the ultrasonic motor 20 is driven, the stage 13 can be driven along the guide member 12 by the elliptical vibration of the friction member 25, and position information from the position detection means 17 accompanying the movement of the stage 13. And an output value PID-calculated by the control unit 18 based on the deviation from the preset reference position information of the stage 13 is output to the driver 19 as a command signal, and the ultrasonic motor is driven by the driving voltage from the driver 19. By performing feedback control for driving the stage 20, the stage 13 is moved and positioned.

  However, the friction member 25 of the ultrasonic motor 20 and the driving force transmission member 14 of the stage 13 are mutually worn, and dust generated by this frictional wear adheres to the contact surface of the driving force transmission member 14 and the surrounding atmosphere. Since the dust from the toner adheres again to the contact surface of the driving force transmission member 14, the dust and dust are placed between the contact portion between the friction member 25 of the ultrasonic motor 20 and the driving force transmission member 14 of the stage 13. Since the contact state changes when it is bitten, the drive characteristics of the stage 13 are made unstable, and wear of the friction member 25 of the ultrasonic motor 20 and the drive force transmission member 14 of the stage 13 is promoted. There was a problem that the ultrasonic motor 20 and the driving force transmission member 14 had to be replaced during use.

  In order to remove such dust problem, various means have been proposed for removing the dust.

  For example, an example having dust removing means such as a brush, a roller, a cleaning cloth, and a peeling claw for removing dust (dust) existing on the contact surface of the friction member 25 of the ultrasonic motor 20 and the driving force transmission member 14. Has been disclosed (see Patent Document 1).

  In addition to the above-described method for removing dust, various means have been proposed for a method for collecting the removed dust.

  For example, a dust sealing portion for storing a dust sealing portion between the friction member 25 of the ultrasonic motor 20 and the driving force transmission member 14 and for collecting dust generated by driving the ultrasonic motor is provided inside the case. Has been disclosed (see Patent Document 2).

  Moreover, the example which attracts | sucks the air inside the above sealed cases as mentioned above, and attracts | sucks and removes the fine dust which generate | occur | produced inside was disclosed (refer patent document 3).

Further, a dust removing means having a compressed gas injection hole and an exhaust groove disposed around the injection hole is provided, whereby the contact surface between the friction member 25 of the ultrasonic motor and the driving force transmission member 14 is provided. An example in which the adhering dust is removed and recovered from the exhaust groove has been disclosed (see Patent Document 4).
Japanese Patent Laid-Open No. 11-18446 Japanese Patent Laid-Open No. 9-14167 JP 2001-340991 A JP 2003-251541 A

  However, even if a mechanism devised in various ways to remove dust generated when the ultrasonic motor is driven as described above, the generation of dust is not suppressed, and the friction member 25 and the drive are also driven. There was a problem of dust adhesion on the contact surface of the force transmission member 14. The reason for this problem is considered as follows.

  That is, in a vacuum atmosphere, materials used in various parts and devices used in a vacuum are not limited to materials that generate less organic gas molecules (hereinafter referred to as outgas), and are cleaned and outgassed in a vacuum atmosphere. Even if it occurs, it is necessary to pay close attention so that it does not adhere to the product. However, even if the material is less outgassed and cleaned, the component having a low vapor pressure contained in the material is volatilized in a trace amount, and a slight outgas is generated from the trace component adhering after the cleaning. In addition, when the inside of the vacuum chamber is opened to the atmosphere for maintenance of the device, the atmosphere may enter, and dirt and organic substances may adhere to the inner wall of the vacuum vessel, and various attached components become outgas when evacuating. . The remaining outgas gas molecules that could not be recovered by the recovery means such as a vacuum pump are drifting in the vacuum chamber.

  In particular, in the vacuum atmosphere, unlike the atmospheric atmosphere in which nitrogen, oxygen, and the like exist, other gas components do not exist, so that outgas is easily generated and can move freely. The individual size of the dust generated by the friction drive of the friction member 25 and the driving force transmission member 14 of the movable body is on the order of submicron to nanometer, and the surface of these dusts has a large surface free energy. Yes.

  Therefore, even in a guide device using an ultrasonic motor used as a drive source in a vacuum atmosphere, the contact surface of the friction member 25 that generates frictional heat, or the friction between the friction member 25 and the driving force transmission member 14 of the movable body. Since the outgas is adsorbed and deposited on the surface of the dust generated by driving, the amount of dust generated is 10 times that of the case of using it in an air atmosphere. The occurrence of dust increases the chance of dust reattaching to the contact surface of the friction member 25 of the ultrasonic motor and the surface of the driving force transmission member 14 of the stage 13, and as a result, hinders good driving of the guide device 10. It was a factor.

In the present invention, in view of the above-described problems, a guide device in which an ultrasonic motor having a friction member and a movable body movable by the friction drive of the friction member are arranged in a vacuum atmosphere, and at least the friction member and A cover member provided so as to surround a contact portion of the movable body with respect to the friction member; a gas supply means for supplying a gas into a space surrounded by the cover member; and Gas discharge means for discharging to the groove, and the gas discharge means includes a groove provided to surround the friction member and the contact portion on a surface of the cover member facing the movable body, and the groove It communicates, and having an exhaust passage provided between the inner and outer surfaces of the cover member.

Preferably, the exhaust passage is a through-hole provided through the cover member and along the inner surface of the cover member. Preferably, the exhaust passage is formed in a double manner along the inner surface.

Further, preferably , dust removing means is installed inside the cover member.

  According to the configuration of the present invention, the gas supply means for supplying a rare gas, nitrogen, oxygen, or a mixed gas thereof to the inside of the cover member that covers the friction member and the friction member contact portion of the movable body, and the supplied gas By providing a gas discharge means for discharging the gas and making the atmosphere inside the cover member a gas atmosphere injected from a vacuum atmosphere, dust with organic gas attached is generated around the friction member and the friction member contact portion of the movable body. In addition to being able to suppress this, it is possible to dissipate the heat generated by the friction drive generated by the friction drive of the movable body and the friction member by the injected gas, and to cool the gas.

  Further, the gas discharge means of the present invention comprises a groove provided on the surface of the cover member facing the movable body and a through hole communicating with the groove through the wall of the cover member, whereby the friction member having the cover member formed thereon And the gas injected near the friction member contact portion of the movable body can be circulated, so that the degree of vacuum around the guide device of the present invention is not lowered.

  Furthermore, by installing dust removing means inside the cover member and removing dust adhering to the contact surface of the movable body and the friction member, it becomes possible to further reduce the wear of the friction member, It is possible to drive the guide device more stably for a long time.

  Hereinafter, the best mode for carrying out the present invention will be described. In addition, about the same part as a prior art example, it shows with the same code | symbol.

  FIG. 1 shows a schematic structural diagram of an example of the guide device of the present invention. 2 shows an enlarged cross-sectional view of the cover member 1 of the present invention in the guide device 10 of FIG.

  The guide device 10 includes a pair of guide members 12 such as a cross roller guide on a base board 11 and guides a stage 13 as a movable body linearly and reciprocally by the guide members 12. .

  Further, the stage 13 has a driving force transmission member 14 attached in parallel to the guide member 12 on one side surface, and a linear scale 15 in parallel with the driving force transmission member 14 on the other side surface of the stage 13. The measuring head 16 is provided at a position facing the linear scale 15 to constitute a position detecting means 17, and one ultrasonic motor 20 is disposed at a position facing the driving force transmitting member 14. The friction member 25 of the ultrasonic motor 20 is in contact with the contact surface of the driving force transmission member 14 perpendicularly.

  In the figure, reference numeral 18 denotes a control unit for controlling the driving conditions of the stage 13 based on position information obtained from the position detection means 17, and 19 denotes an ultrasonic motor driven based on a signal output from the control unit 18. 1 is a cover member for reducing dust generated when the guide device 10 of the present invention is driven.

  As shown in FIG. 2, the guide device 10 of the present invention has a gas injection pipe 2 for injecting a gas for maintaining the gas supply region 5 of the cover member 1 in a gas atmosphere outside the cover member 1, and A gas exhaust port 3 and a gas exhaust path 4 for inhaling and exhausting gas are provided.

  Here, the gas supply region 5 inside the cover member 1 is maintained in a gas atmosphere because the degree of freedom of movement of the outgas is restricted by replacing the gas atmosphere with a vacuum atmosphere in which outgas, which is an organic gas molecule, is easily generated. This is because the outgas component is less likely to adhere to the surface of the friction member 25 and the driving force transmission member 14 that are high energy fields, or the surface of dust generated by the friction drive.

  Further, as the material of the cover member 1, various materials such as metal, ceramics, and resin can be used, or a combination thereof may be used, and it is preferable to use a material having higher airtightness. is there.

  When the guide device 10 is used, the gas injection pipe 2 provided in the cover member 1 is connected to a gas supply tank (not shown) installed outside the system and injects gas into the gas supply region 5.

  Moreover, the gas exhaust port 3 provided in the cover member 1 is provided in a part of the groove portion 8 formed by machining over the entire circumference of the end portion 7 facing the movable body 14 of the cover member 1 as shown in FIG. A gas exhaust passage 4 (through hole) extends from the gas exhaust port 3 through the wall of the cover member 1. By connecting an exhaust means (not shown) to the gas exhaust passage 4, it is possible to exhaust the entire groove portion 8 through a gap between the movable body 14 and the end portion 7 provided at a distance of several μm. Due to the presence of the groove portion 8, it is possible to exhaust the gas that is about to leak out of the cover member 1 from the gas supply region 5.

2 shows a sectional view of the groove portion 8 and the through hole 9 of FIG. 3 which are installed in a double manner so that better gas exhaust can be carried out. A gas exhaust port 3 (groove portion 8) and an exhaust passage 4 are provided so as to double surround the gas supply region 5, and the inner gas exhaust port 3 and the exhaust passage have a degree of vacuum of about 10 ⁻² Pa. It is preferable because the gas exhaust port 3 and the gas exhaust passage 4 on the outer side thereof can be exhausted with a separate exhaust pump so that the degree of vacuum is about 10 ⁻³ Pa. In this way, by performing gas exhaustion so that the degree of vacuum is inclined from the inside to the outside of the cover member 1, without lowering the degree of vacuum in the vacuum atmosphere outside the cover member 1, Gas exhaust in the gas supply area 5 can be performed.

  Here, as the gas supplied to the gas supply region 5 of the cover member 1, helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (element 18 of the periodic table) Xe), a rare gas such as radon (Rn), nitrogen (N), oxygen gas (O) may be used, or a mixed gas thereof may be used.

  Further, in the guide device 10 of the present invention, as shown in an example in FIG. 4, the dust removing means 6 including a blade or the like whose blade edge is brought into contact with the driving force transmitting member 14 is provided in the gas supply region 5 of the cover member 1. It is possible to reduce the generation of dust and to remove the dust adhering to the driving force transmission member 14.

  In addition to the blade, various types of dust removing means 6 such as a brush, a roller, and a cleaning cloth can be installed as the dust removing means 6.

  Next, the driving state of the guide device 10 of the present invention will be described with reference to FIG.

  First, when a command signal is output from the driver 19 and the friction member 25 of the ultrasonic motor 20 is elliptically moved, the stage 13 can be moved along the guide member 12 by friction drive with the driving force transmission member 14. Based on the deviation between the position information from the position detection means 17 accompanying the movement of the stage 13 and the preset reference position information of the stage 13, an output value PID-calculated by the control unit 18 is sent to the driver 19 as a command signal. The stage 13 is moved under a predetermined condition by performing feedback control to output and drive the ultrasonic motor 20 by the drive voltage from the driver 19.

  At this time, the contact surface of the driving force transmission member 14 is activated by friction driving with the ultrasonic motor 20 and also generates frictional heat and static electricity, so that the driving force transmission member 14 and the friction member 25 are worn. In addition to the dust generated in this manner, the components floating in the surrounding atmosphere adhere to the contact surface of the driving force transmission member 14. Particularly in a vacuum atmosphere, more dust adheres as described above.

  However, according to the guide device 10 of the present invention, the cover member 1 is installed so as to cover the contact surfaces of the friction member 25 and the driving force transmission member 14, and the gas supply region 5 inside the cover member 1 A gas for adjusting the atmosphere in the gas supply region 5 is supplied from the gas injection pipe 2 provided in the cover member 1, and in the gas supply region 5, the freedom of movement of the outgas drifting in the atmosphere is remarkably limited. For this reason, the surface of the friction member 25 and the driving force transmission member 14 or the surface of the dust generated by the friction drive is unlikely to adhere, thereby reducing the dust generated with the driving of the guide device 10. It becomes possible.

  For this reason, it is possible to greatly reduce the amount of dust biting into the gap between the contact surface of the driving force transmission member 14 and the friction member 25 of the ultrasonic motor 20, and it is possible to always obtain a stable contact state. is there. Accordingly, the stage 13 can be stably driven by driving the ultrasonic motor 20, and the stage 13 can be moved with high accuracy even when high accuracy is required such that the accuracy during movement is 1 μm or less and the positioning accuracy is 0.1 μm or less. Can be positioned.

  By the way, in order to achieve such an effect, as shown in FIG. 2, the gap between the end portion 7 of the cover member 1 where the gas exhaust port 3 of the cover member 1 is installed and the driving force transmission member 14 is adjusted, Gas is exhausted through the gas exhaust port 3 and the gas exhaust passage 4 in the direction of the arrow in the figure while keeping the gas supply region 5 of the cover member 1 in the gas atmosphere to be injected, and the gas in the gas supply region 5 is discharged. It is important to implement good circulation. For this purpose, it is more preferable that the gap between the end 7 of the cover member 1 and the driving force transmission member 14 is in the range of 0.5 to 10 μm. If it is smaller than 0.5 μm, not only gas exhaust becomes difficult, but in some cases, the gap is clogged with dust, preventing good driving of the guide device 10. On the other hand, if it is larger than 10 μm, the gas that could not be exhausted from the exhaust port 3 leaks outside the cover member, and if this is in a vacuum atmosphere, the degree of vacuum is significantly reduced.

  By maintaining good gas circulation as described above, it is possible to obtain the effect of releasing the heat generated by the friction between the friction member 25 and the driving force transmission member 14 into the gas atmosphere and cooling the ultrasonic motor 20. . This cooling of the ultrasonic motor 20 is particularly effective when the guide device 10 of the present invention is driven in a vacuum atmosphere without heat transfer.

  As described above, in this embodiment, the guide device 10 in which the movable body moves linearly has been described as an example. However, it is needless to say that the guide device 10 in which the movable body rotates can be applied. The sonic motor is not limited to the multi-mode type, and may be a single wave mode standing wave type or traveling wave type, a multi-vibration mode mode conversion type, or a composite vibration type ultrasonic motor.

  The guide device 10 of the present invention as described above can maintain high-precision driving for a long period of time when introduced into the manufacturing process for a semiconductor or liquid crystal manufacturing apparatus. It can be said that it is optimal as a guide device for a manufacturing apparatus.

  Needless to say, the present invention can be applied to various improvements and modifications as long as they do not depart from the gist of the present invention.

  Examples of the present invention will be described below.

  A test was performed in which the guide device 10 of the present invention as shown in FIG. 1 and a conventional guide device were driven in a vacuum atmosphere in a vacuum chamber to compare the amount of dust generated.

  Hereinafter, the specifications of the guide device used in the experiment will be described.

  A cross roller guide having a stroke of 100 mm was used as the guide member 12 constituting the guide device 10 of the present invention, and the stage 13 having a weight of 5 kg was moved by the guide member 12. A driving force transmission member 14 made of alumina ceramic is disposed on one side surface of the stage 13, and the surface roughness of the contact surface with the ultrasonic motor 20 is set to 0.05 μm in terms of arithmetic average roughness (Ra). .

  On the other hand, the ultrasonic motor 20 that is a drive source of the stage 13 is formed by forming a vibrating body 24 by a lead zirconate titanate-based piezoelectric ceramic body 22 that is a rectangular parallelepiped having a length of 30 mm, a width of 7.5 mm, and a thickness of 3 mm. A material obtained by joining a friction member 25 made of alumina ceramic having a columnar shape with a length of 4.2 mm and a diameter of 3 mm to the end face of the vibrating body 24 was used. The contact surface of the friction member 25 with the driving force transmission member 14 was a spherical surface with a radius of curvature of 7 mm.

  Further, as the cover member 1 installed in the guide device 10 of the present invention, an alumina or metal aluminum member is used in order to hold the gap between the driving force transmission member 14 and the cover member end 7 with higher accuracy. A metal aluminum gas injection pipe 2 is connected, and a gas exhaust port 3 made of a groove is doubled on the entire circumference of the cover member end 7, and each through hole penetrates through the wall of the cover member 1. A gas exhaust passage 4 made of a material is machined so as to cover the entire ultrasonic motor 20. Then, argon gas is injected into the gas supply region 5 by setting the distance between the surface of the cover member end 7 where the gas exhaust port 3 of the cover member 1 is installed and the driving force transmitting member to 1 μm, thereby covering the cover member 1. The inside is adjusted so that the gas can be exhausted while the vacuum atmosphere outside the cover is more stabilized.

  The gas injection pipe 2 was connected to an argon gas supply tank provided outside the vacuum chamber, and the gas exhaust passage 4 was connected to an exhaust pump also provided outside the vacuum chamber.

  In the experiment, as the movement profile of the stage 13 set in advance in the control unit 18, the trapezoidal control is set such that the movement distance is 100 mm, the acceleration / deceleration is 0.03 G, and the maximum speed is 100 mm / sec, and the ultrasonic motor 20 is driven at 40 kHz. Driven at frequency.

Then, the stage 13 was driven for 50 hours under these conditions, and the amount of dust adhering to the friction member 25 of the ultrasonic motor 20 and the driving force transmission member 14 of the stage 13 after the running test was measured. In addition, about the adhesion amount of dust, the amount which the dust with a particle size of 1 micrometer or more per 1 mm < ² > adheres was measured with the particle counter.

The results are shown in Table 1.

  From Table 1, in the conventional guide device in which the cover member 1 is not installed, not only the amount of dust attached to the driving force transmission member 14 is large, but also the amount of dust attached becomes excessive when driven for 30 hours, and the stage The drive has stopped.

  On the other hand, in the guide device 10 of the present invention, dust adheres to the driving force transmission member 14 even during 50 hours of driving, and it is possible to maintain good driving of the stage 13, and a cover member is installed. As a result, it was confirmed that adhesion of dust to the driving force transmission member 14 can be reduced.

Further, a dust removing means in the form of a blade 6 as shown in FIG. 3 is installed inside the cover member of the guide device 10 of the present invention, and the guide device 10 is driven under the same conditions as described above. When the amount of generated dust was measured, the generation of dust was 0 / mm ² after 50 hours of driving. Thereby, it was confirmed that the dust generation can be further suppressed by installing the dust removing means inside the cover member 1 together with the cover member 1.

It is a schematic structure figure showing an example of a guidance device of the present invention. It is an enlarged view which shows the cover member installed in the guide apparatus of this invention of FIG. It is the schematic which shows an example of the cover member of this invention. It is a schematic structure figure showing an example at the time of installing dust removal means inside a cover member of a guide device of the present invention. It is a plane schematic diagram which shows an example of the conventional guidance apparatus. It is a schematic diagram which shows an example of the ultrasonic motor used for the conventional guidance apparatus of this invention.

Explanation of symbols

1: Cover member 2: Gas injection pipe 3: Gas exhaust port 4: Gas exhaust path (through hole)
5: Gas supply region 6: Dust removal blade 7: Cover member end 8: Groove 9: Through hole 10: Guide device 11: Base panel 12: Guide member 13: Stage 14: Driving force transmission member 15: Linear scale 16: Measuring head 17: Position detecting means 18: Control unit 19: Driver 20: Ultrasonic motors 22a, 22b, 22c, 22d: Electrode film 23: Piezoelectric ceramic plate 24: Vibrating body 25: Friction member 26: Housing 27, 28: Spring

Claims (4)

A guide device in which an ultrasonic motor having a friction member and a movable body movable by friction driving of the friction member are arranged in a vacuum atmosphere, and at least the friction member and the movable body against the friction member A cover member provided so as to surround the contact portion, a gas supply means for supplying gas into a space surrounded by the cover member , and a gas discharge means for discharging the supplied gas out of the vacuum atmosphere Have
The gas discharge means includes a groove portion provided on the surface of the cover member facing the movable body so as to surround the friction member and the contact portion, and communicates with the groove portion so that the inner surface and the outer surface of the cover member guide device having an exhaust path provided between the surfaces. The guide device according to claim 1, wherein the exhaust passage is a through-hole penetrating the cover member and provided along the inner surface. The guide device according to claim 1 or 2, wherein the exhaust passage is formed in a double manner along the inner surface. The guide device according to any one of claims 1 to 3 , wherein a dust removing means is installed inside the cover member.

Images