JP2009254089A - Ultrasonic linear stage - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a linear stage having a stop holding function not influenced by resolution of a position sensor in executing positioning by feedback control. <P>SOLUTION: In the linear stage, a roller 2 is fixed on a rotating shaft of an ultrasonic motor 1 as shown in Fig.1. Further, the linear stage includes a shaft 3 installed to have a frictional force for conversion of a rotational force of the roller 2 into linear movement and a sensor unit 4 formed of a scale 4a and a read head 4b provided to read a protrusion amount A of the shaft. By assembling this configuration into the stage, a total configuration is made. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention is a stage that includes an ultrasonic motor, a rotation-linear motion conversion mechanism, and a linear encoder that is a position sensor, and has a built-in linear actuator that has both feedback positioning by the encoder and a stop and hold function that utilizes the characteristics of the ultrasonic motor. It is about.

  A general positioning linear actuator converts a rotational force into a linear motion, and is configured using an electromagnetic motor, an encoder installed behind the electromagnetic motor, and a screw feed mechanism. If a stop and hold function is required, a brake must be added.

  There are also linear actuators that directly generate linear motion using a linear motor or the like. For positioning, a linear encoder is often used. In this case, the stop holding function assumes that the vehicle is stopped by adding a brake or performing position correction by feedback control to restrict movement outside the predetermined range.

Japanese Patent Laid-Open No. 8-111990 JP 7-5928 A

  If a brake mechanism is added when a linear stage that requires positioning accuracy of 1 micron or less is provided with a stop holding function, a phenomenon occurs in which the positioning completion position is shifted by applying the brake. On the stage of a microscope, there is a problem that the test position on the field of view is greatly deviated.

  In general, feedback control is used when a stop function is provided without adding a brake. Control is performed so that the resolution of the encoder is sufficiently large, and this is returned when it deviates from a predetermined range, for example, the range of the plus / minus 1 signal from the current position. At this time, two problems arise.

  The first problem occurs when the resolution of the encoder is increased. Performance that is not necessary with the original positioning resolution is given to stop and hold (although it does not really stop), but to control at the same speed, the encoder signal becomes dense, so the control side Since the response specification of the system must be raised, it becomes a problem in cost.

Another problem is that it is not controlled within the range of the encoder plus or minus 1 signal at most. Since control itself is not performed in this, even if it fluctuates, it cannot be suppressed.

  The configuration for realizing the object of the present invention is as described in the claims. Specifically, in view of having a large holding force when the drive is stopped, which is a feature of the ultrasonic motor, the configuration of the precision positioning device is used. It is intended to obtain positioning and stationary stability by incorporating it on the stage. With this configuration, the position control resolution can be kept at a desired position while holding the holding force while minimizing the resolution of the position control. The ultrasonic motor itself is the drive source and the brake.

  In addition, the shape of the contact part between the roller and the shaft is aimed at reliable driving as shown in Fig. 2, but this is not aimed at the stability during positioning movement, but for the purpose of improving the holding force at the time of stopping. is there. As shown in FIG. 1, the encoder unit is attached to the shaft side, so that it is not necessary to make corrections based on slippage during movement and the amount of wear of the rollers. The roller material may be a soft material such as rubber or resin if the load fluctuation after stopping is small, and it may be a hard material such as metal if it is large.

  According to the first aspect of the present invention, when positioning is completed by the position feedback control, the ultrasonic motor stops at that moment and generates a large holding force. It will be a good stage.

  According to invention of Claim 2, a static holding force can be heightened by making the contact part shape of a roller and a shaft into V groove shape.

The objective of giving the linear stage for positioning a good static characteristic that does not depend on the resolution of the encoder was realized without adding a device such as a brake.
The objective of inputting an image from a position outside the housing or as close to the end of the housing as possible was realized with the minimum number of components and without sacrificing the thickness of the optical system components.

FIG. 3 is a schematic view showing an embodiment of the linear stage according to the present invention.
Reference numeral 1 denotes an ultrasonic motor. A roller 2 is fixed to a rotating shaft of the ultrasonic motor. The motor is fixed to a swing arm 6 and swings around a bearing 11 but is pressed against a shaft 3 by a spring 5. A bearing 11 has an inner ring fixed to the base 8 by a pin 7. The slide mechanism of the stage is configured by fixing a linear motion bearing 9 to a table 10 and a base 8. The table 10 and the shaft 3 are fixed, and this is a moving body. An encoder scale 4 a is fixed to the table 10, and this and an encoder head 4 b fixed to the base 8 constitute a position sensor.

  The structure of the ultrasonic motor 1 is a rotary ultrasonic motor having a disk-like vibrator. The rotational force of the motor is transmitted to the shaft 5 through the roller 4 and converted into linear motion, and the table 9 supported by the bearing 6 moves to the left and right. The lateral pressure of the roller 4 and the shaft 5 is stably held by the spring 7, and the motor 1 has a floating structure by the swing arm 2 and the bearing 3.

  Next, the positioning / stopping operation according to this embodiment will be described with reference to a timing chart shown in FIG.

  a is a waveform of positioning by feedback control. After the positioning is completed, it moves within the width A of the plus / minus 1 signal of the minimum encoder resolution, but this cannot be controlled. b is the waveform of the stage of the present invention. When positioning is complete, the motor stops and stabilizes with a large holding force.

Structure of actuator part of the present invention The shape of the rotation-linear motion converter of the present invention Examples of the present invention Timing chart

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ultrasonic motor 2 Roller 3 Shaft 4a Encoder scale 4b Encoder head 5 Spring 6 Swing arm 7 Pin 8 Base 9 Direct acting bearing 10 Table 11 Bearing

Claims (2)

  Directly on a roller fixed to the rotating shaft of a rotary ultrasonic motor, a shaft frictionally contacted via a lateral pressure means for converting the rotational force of the roller into linear motion, and a moving body connected to the shaft A stage having an attached linear encoder, wherein a stationary state after positioning is made stationary by exceeding the resolution of the encoder by utilizing a large stop holding torque of an ultrasonic motor.   2. The linear stage according to claim 1, wherein the linear stage has a mechanism in which a contact portion shape of the roller and the shaft is formed of a groove portion and a protrusion portion as shown in FIG.

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