JP2886610B2 - Friction drive with non-contact support - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a driving device for performing a linear motion or the like, and in particular, converts a rotary motion into a linear motion by frictional force while utilizing non-contact support. The present invention relates to a structure of a friction drive device capable of moving an object.

[Prior Art] In the field of semiconductor integrated circuit manufacturing technology, the density of semiconductor devices has been increased. As a result, the alignment adjustment between the wafer and mask of the semiconductor exposure
A resolution on the order of μm has been required. It is difficult to achieve such accuracy with a conventional drive device using a servomotor and a ball screw. Conventionally, a linear motion drive device having such a high resolution employs a friction drive system in which a drive roller frictionally drives a contact roller while contacting and supporting it with an idler as shown in FIG.

The shaft 32 is connected to the rotor of the motor 31, and the shaft 32 is supported by a rolling bearing device 33. A drive roller 34 is mounted on the shaft 32 and rotates with the rotation of the motor 31. The driving roller 34 is pressed against one (left side in the figure) side surface of the driving rod 35, and transmits the driving force by using the contact frictional force. The right side surface of the drive rod 35 is supported by the idler roller 36 to be rolled and positioned with respect to the fixed base. As a result, the drive rod 35 linearly moves in the direction of the arrow. A stage device or the like (not shown) is connected to the end of the drive rod. The idler roller 36 has a rolling bearing 37
Supported by

A major factor that determines the resolution of the friction drive device is the mechanical loss of the driving force from the driving source to the object. Specifically, reducing the friction loss of the driving force,
In addition, it is required that the driving force from the motor be accurately transmitted to the non-driving object (driving rod) while suppressing the fluctuation.

In the conventional friction drive system described above, when transmitting the rotational force of the motor 31 to the drive roller 34, in addition to the friction loss in the motor 31, there is a friction loss due to the rolling bearing 33, and the elastic deformation of the rolling bearing 33 Also, small vibrations may occur during rotation due to backlash. Idler roller
There is also a friction loss at 36 rolling bearings 37. In addition, hysteresis occurs due to the direction in which the force acts.

Further, there is pressure deformation and friction loss between the drive roller 34 and the drive rod 35, and also pressure deformation and friction loss between the idler roller 36 and the drive rod 35 for guiding and supporting. The rolling friction between the driving roller 34 and the driving rod 35 varies according to the pressing force F between them, so that if the pressing force F changes, it changes accordingly. The pressing force F changes due to minute irregularities on the contact surfaces of the driving roller 34 and the driving rod 35, and eventually causes a change in friction loss of the driving force. Fluctuations in the coefficient of friction cause the drive roller 34 to slip, resulting in a driving force (rotational torque).
This causes a change in the relationship between the movement amount and the movement amount. This is 0.01 μm
This is a serious problem for a linear drive device that requires movement control with order resolution.

[Problems to be Solved by the Invention] As described above, according to the related art, even in the friction drive in which the backlash is eliminated, the drive by the friction or the like is performed while the drive force is transmitted from the drive force source to the driven object. Force decay and fluctuation were inevitable.

An object of the present invention is to provide a friction drive device suitable for a motion device having an ultra-high resolution.

Means for Solving the Problems A stator of a motor supported by a base, a rotor of the motor supported by bearings, and a roller having a rotating surface for outputting a rotational driving force of the rotor to the outside. An air film is generated between a movable member that moves by receiving a driving force from a roller by friction, and a movable member that is slidably provided through the air film to the movable member. And an air pad device for ensuring a pressing force between the roller and the roller.

[Operation] The driving force generated between the stator and the rotor of the motor as the driving force source is transmitted to the driving roller with substantially no frictional force because the rotor is supported by the air bearing link. . The rotation of the drive roller is transmitted to the movable member by frictional contact between the surfaces. The movable member is driven in a predetermined direction by receiving the rotational force of the driving roller. The air pad device secures a pressing force between the movable member and the drive roller by applying a supporting force to the movable member via an air film. Further, since this pressing force is applied to the movable member via the air film, the movable member can slide with substantially no frictional force.

The friction force is only the rolling resistance between the drive roller and the movable member, and the friction loss is extremely small. Moreover, since the air pad device applies a pressing force to the movable member via the air film, even if there are minute irregularities on the contact surface of the drive roller and the drive rod, the air film absorbs these and keeps the pressing force constant. To keep. Since the pressing force is stabilized, the friction coefficient is also stabilized, and a high driving force resolution can be obtained.

Embodiment FIG. 1 shows the configuration of an embodiment of the friction drive device of the present invention. Reference numeral 11 denotes a servo motor, which is a driving force generating source. The rotating shaft 12 is directly connected to the rotor of the motor 11,
11 and rotating shaft 12 are air bearing device 13 and servo motor 11
Is positioned and supported on the stator. Since the rotating part is supported by an air bearing, there is substantially no friction loss or hysteresis for the rotating movement. A driving roller 14 is connected to the tip of the rotating shaft 12. Drive roller is drive rod
When the drive roller 14 rotates, the rotation of the drive roller 14 is transmitted to the drive rod 15 by friction, and the drive rod 15 linearly moves in the direction of arrow A. A stage device 16 is connected to the end of the drive rod 15 by a suitable connecting device. An arbitrary object or device to be driven is mounted on the stage device 16.

The other side surface of the drive rod 15 is positioned and supported on the fixed base 18 by the air pad 17 so as to be slidable in the moving direction. The air pad 17 blows out compressed air from a surface facing the side surface of the drive rod 15 to form an air film between the air pad 17 and the side surface of the drive rod 15. The driving rod 15 is supported by the air film and linearly moves in the direction of arrow A while sliding on the driving rod. Since it is an air film, there is substantially no friction loss.
The air pad 17 is supported on a fixed base 18 by a piezoelectric actuator 19.

The piezoelectric actuator 19 is formed by arranging a plurality of dielectric piezoelectric elements such as ceramics having a piezo effect with their displacement axes aligned, and laminating and bonding them in the direction of the displacement axis. When a voltage is applied, the laminated piezoelectric element is displaced in the direction of arrow B in the figure. At the same time, it has strong rigidity in the direction of displacement. The displacement can be controlled by adjusting the applied voltage.

FIG. 2 is a view as seen from the direction of arrow A in FIG. 1, and shows details of a drive support device including a drive roller 14, a drive rod 15, an air pack 17, and a piezoelectric actuator 19.

The air pad 17 forms an air film 20, and applies a pressure F1 to the drive rod 15 by the air pressure. The drive rod 15 applies the pressure F1 to the drive roller 14. Since the drive roller 14 and the drive rod 15 are in contact with each other, the drive rod 15 receives the reaction F2. When the driving roller 14 and the driving rod 15 are considered to be substantially rigid, F1 = F2, and the driving rod 15 is positioned and supported in a fixed position in the horizontal direction in FIG. Further, friction is generated between the drive roller 14 and the drive rod 15 by the force F2.

Strictly speaking, the drive roller 14 is partially crushed and comes into contact with the drive rod 15, and the friction coefficient μ changes according to the pressing force F2.

The drive roller 14 has extremely high roundness and its rotating surface is formed with extremely smooth machining finish accuracy. Further, the side surface of the drive rod 15 which comes into contact with the rotating surface of the drive roller 14 also has smoothness due to precision finishing.

However, unevenness (shape error) still remains on the contact surface and the like. When the support is provided by a mechanical rolling bearing or the like, if there is unevenness, the pressing force F2 is changed. When the pressing force F2 fluctuates, the friction coefficient μ changes, and thus the transmission loss of the driving force fluctuates. This variation is not negligible in a mobile device requiring a resolution of 0.01 μm.

By the way, the air layer and air pad in the air bearing 13
The air film 20 generated in 17 can be elastically deformed as compared with the drive rod 15 and can be partially deformed. By changing the thickness x of the air film 20, the fluctuation of the pressing force F2 due to the unevenness of the contact surface between the driving roller 14 and the driving rod 15 can be absorbed, and the value of the pressing force F2 can be kept constant.

The thickness x of the air film 20 can be adjusted by controlling the amount of displacement of the piezoelectric actuator 19. The displacement of the piezoelectric actuator 19 can be controlled by the applied voltage,
A resolution of 0.01 μm or less can be realized. Thickness x of air film 20
Can also be adjusted with the same degree of stability. Further, since the displacement response speed of the piezoelectric actuator 19 is very fast, dynamic control response accuracy is high even when monitoring and feeding back air pressure fluctuations and drive bar displacements.

In the above description, the vertical supporting method in the drawing of FIG. 2 is not particularly mentioned, but this may be an air bearing method, a magnetic bearing method, or a supporting method using another bearing method.

Although two piezoelectric actuators 19 are provided in the embodiment, an appropriate number can be selected in consideration of the length of the driving rod 15, the magnitude of the pressing force, and the like. Further, if a similar linear drive device is mounted on the stage device 16 in FIG. 1 in other directions as well, the device performs XY two-dimensional motion.

INDUSTRIAL APPLICABILITY The friction driving device of the present invention can be used in a wide range of fields as a moving device requiring high-precision positioning, such as a distance measuring device or an ultra-precision processing machine, in addition to a stepper of a semiconductor exposure device.

[Effect of the Invention] Since the frictional force between the driving source and the non-driving body is determined only by the rolling resistance between the roller such as the driving roller and the movable member such as the driving rod, the friction loss is extremely reduced.

Since the air pad applies a pressing force to the movable member via the air film, the air film absorbs minute irregularities on the contact surfaces of the members such as the drive roller and the drive rod, and keeps the average pressing force constant.

It is also possible to adjust the thickness of the air film of the air pad to an optimum value by a piezoelectric actuator.

 A high-speed, high-resolution friction drive device can be realized.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a linear motion device using a friction drive device according to an embodiment of the present invention, FIG. 2 is a configuration diagram of a drive / support mechanism according to an embodiment of the present invention, and FIG. FIG. 2 is a configuration diagram of an example of a friction drive device according to the first technology. In the figure, 11 ... servo motor 12, 32 ... rotating shaft 13 ... air bearing 14, 34 ... drive roller 15, 35 ... drive rod 16 ... stage device 17 ... air pad 18 ... fixed base 19 ... … Piezoelectric actuator 20 …… Air film 31 …… Motor 33, 37 …… Rolling bearing 36 …… Idler roller

Continuation of the front page (56) References JP-A-63-140159 (JP, A) JP-A-2-4780 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) F16H 19 / 00-19/08 G05D 3/00-3/20

Claims (3)

(57) [Claims] 1. A motor stator supported by a base, a motor rotor supported by an air bearing, a roller having a rotating surface for outputting a rotational driving force of the rotor to the outside, A movable member having a surface in contact with a rotating surface of the roller, receiving a rotational driving force from the roller by a frictional force generated between the contact surface and the rotating surface, and thereby performing a linear motion; Opposite to the movable member on the opposite side, generates an air film between the movable member and gives a slidable support force to the movable member via the air film, thereby providing the movable member with An air pad means for securing a pressing force between the roller and the roller. 2. The air pad means includes: an air blowing device for generating the air film; and moving the air blowing device in a direction toward the movable member to reduce a distance between the air blowing device and the movable member. The friction drive device according to claim 1, further comprising an actuator using a piezoelectric element that can be adjusted. 3. A friction drive device according to claim 2, wherein said air pad means includes a support for guiding a linear movement of said movable member.