JP2556403B2 - Ultrasonic motor position detection method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting the position of an ultrasonic motor which detects the moving position of a vibrator held between conveyance rails.

[0002]

2. Description of the Related Art Conventionally, a card reader has a D drive as a drive source.
The C motor is used, the rotational angle position is detected based on the output pulse of the encoder incorporated in this DC motor, and highly accurate speed control and writing / reading of data to / from the card synchronized with the pulse are performed. In recent years, it has been attempted to use an ultrasonic motor instead of a DC motor for a card reader. If this ultrasonic motor is used, the ceramic oscillator sandwiched between the carrier rails can be ultrasonically elliptically vibrated based on the drive signal and moved along the carrier rail to draw or eject the card. It will be possible. If an ultrasonic motor is used for the card reader, the same as for the DC motor, in order to detect the moving position of the ceramic vibrator and perform accurate speed control and writing / reading of data to / from the card. Encoder integration is envisioned.

[0003]

However, the encoder is relatively expensive, which is a factor that hinders the cost reduction of the card reader using the ultrasonic motor.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, in which a piezoelectric element is attached to a carrier rail, and vibration of the carrier rail due to movement of a vibrator based on a driving signal is suppressed. The piezoelectric element is used for monitoring, and the moving position of the vibrator is detected based on the monitor output of this piezoelectric element.

[0005]

Therefore, according to the present invention, for example, if a plurality of piezoelectric elements are mounted on the conveying rail, the piezoelectric elements are provided in the vicinity of the piezoelectric element that outputs the maximum monitor output, that is, in the vicinity of the piezoelectric element that detects the maximum vibration. It can be determined that the vibrator is in the moving position. Further, for example, if the piezoelectric element is attached to the start end position or the end position of the transport rail, the piezoelectric element is proportional to the monitor output of the piezoelectric element, that is, the amplitude of the vibrating transport rail. The moving position can be detected.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The position detecting method for an ultrasonic motor according to the present invention will be described in detail below.

FIG. 1 is a schematic structural view showing a main part of an ultrasonic motor to which this ultrasonic motor position detecting method is applied. In the figure, 1 is a ceramic vibrator, 2-1 and 2
Reference numeral -2 is a transport rail, and reference numeral 3 is a vibrator holding mechanism.

The vibrator 1 is held between the carrier rails 2-1 and 2-2. The vibrator holding mechanism 3 includes rollers 3-1 and 3-2 contacting the transport rail 2-1 side, rollers 3-3 and 3-4 contacting the transport rail 2-2 side, and these rollers 3-1 to 3-3. -4 and a holding plate 3-5 which is pivotally supported,
The vibrator 1 is movably held along the transport rails 2-1 and 2-2 in the directions A and B shown in the figure. On the surface of the transport rail 2-1 in contact with the rollers 3-1 and 3-2, piezoelectric ceramics 4- as piezoelectric elements are arranged at predetermined intervals in the moving direction of the vibrator 1.
1 to 4-3 are embedded and fixed (bonded) (see FIG. 2).

FIG. 3 is a block diagram showing a drive control circuit attached to the ultrasonic motor 5. In the figure, 6 is a CPU, 7 is a programmable oscillator, 8 is a phase shifter, 9-1 and 9-2 are amplifiers, and 10-1 to 10-3 are level converters.

The speed of the ultrasonic motor 5 is controlled by this drive control circuit. That is, the programmable oscillator 7 receives a command from the output port 6-1 of the CPU 6.
Outputs a signal of a predetermined frequency. This oscillation signal passes through the phase shifter 8 and the amplifier 9 and is used as a drive signal by the ultrasonic motor 5
Given to. In response to this drive signal, the vibrator 1 ultrasonically oscillates between the carrier rails 2-1 and 2-2 and moves along the carrier rails 2-1 and 2-2. When the phase shifter 8 receives a direction switching command from the output port 6-2 of the CPU 6 during the movement in the A direction, the moving direction of the vibrator 1 is switched to the B direction. When the phase shifter 8 receives a direction switching command from the output port 6-2 during the movement in the B direction, the moving direction of the vibrator 1 is switched to the A direction.

Now, assuming that the end moving position in the B direction is the starting end position and the vibrator 1 moves from this starting end position in the A direction, the piezoelectric ceramics 4-1, 4-2 and 4-3 are Such electromotive force is generated. That is, the transport rail 2-
1 and 2 receive the ultrasonic elliptical vibration of the vibrator 1 and vibrate slightly (bending vibration wave + surface wave). When the roller 3-1 passes, the piezoelectric ceramics 4-1, 4-2 and 4-3 are
Vibration of the transport rail 2-1 and roller 3 caused by the vibration
A change in the surface contact pressure of -1 causes an electromotive force whose amplitude greatly fluctuates as shown in FIG. In addition, (B) shown in FIG. 4 shows the amplitude fluctuation of the electromotive force when the vibrator 1 passes.

The electromotive force generated by the piezoelectric ceramics 4-1, 4-2 and 4-3 is the level converter 10-1, 10-2, 1
The levels are exchanged at 0-3 and given to the CPU 6. C
The PU 6 is a level converter 10-1, 10-2, 10-3.
Based on the electromotive force applied via the, the piezoelectric ceramic 4 which is producing the maximum electromotive force is checked, and the vicinity of the piezoelectric ceramic 4 producing the maximum electromotive force is determined as the current movement position of the vibrator 1. That is, the CPU 6 detects the current movement position of the vibrator 1 by using the electromotive force generated by the piezoelectric ceramics 4-1, 4-2 and 4-3 as a monitor output, and detects the present movement position and the ideal corresponding to this. By comparison with the moving position, if the current moving position is in front of the ideal moving position, the moving speed of the vibrator 1 is increased, and if it is behind the ideal moving position, the moving speed of the vibrator 1 is decreased.

FIG. 5 is a block diagram showing another embodiment of the drive control circuit attached to the ultrasonic motor 5. In this drive control circuit, a voltage / frequency converter (VCO) 11 is used instead of the programmable oscillator 7, and an oscillation signal is output from the voltage / frequency converter 11 to the phase shifter 8. And the level converter 1
Piezoelectric ceramic 4 through 0-1, 10-2, 10-3
Assume that the monitor outputs from -1, 4-2 and 4-3 are applied to the voltage / frequency converter 11, and the current moving position of the vibrator 1 based on this monitor output and the ideal moving position corresponding thereto are compared. Thus, if the current movement position is in front of the ideal movement position, the movement speed of the vibrator 1 is increased, and if it is behind, the movement speed of the vibrator 1 is decreased.

In each of the above-mentioned embodiments, the piezoelectric ceramics 4-1 to 4-3 are provided on the carrier rail 2-1 side, but they may be provided on the carrier rail 2-2 side. Further, the number of piezoelectric ceramics 4 is not limited to three, and by further increasing the number of piezoelectric ceramics 4, the detection resolution of the moving position can be improved.

FIG. 6 is a schematic structural view showing a main part of another embodiment of the ultrasonic motor to which the position detecting method for the ultrasonic motor according to the present invention is applied. In the figure, the same reference numerals as those in FIG. 1 indicate the same or equivalent components, and a description thereof will be omitted. In this embodiment, the end moving position of the transport rail 2-1 in the direction B in the drawing is set as the start end position, and one end face thereof is fixed to the other at this start end position, and the other end face is brought into contact with the transport rail 2-2 to generate piezoelectric. A ceramic 12 is provided.

In the ultrasonic motor 13, in response to the drive signal, the vibrator 1 makes an ultrasonic elliptical vibration between the carrier rails 2-1 and 2-2 and follows the carrier rails 2-1 and 2-2. To move. If the direction switching command is issued during the movement in the direction A in the figure, the moving direction of the vibrator 1 is switched to the direction B in the figure.
When the direction switching command is issued during the movement in the B direction, the moving direction of the vibrator 1 is switched to the A direction.

Now, assuming that the vibrator 1 moves from the starting end position in the direction A, the piezoelectric ceramic 12 is raised in accordance with the vibration of the carrier rail 2-2 affected by the ultrasonic elliptical vibration of the vibrator 1. Produces power. That is, the transport rail 2
-1, 2-2 receive the ultrasonic elliptical vibration of the vibrator 1,
Micro vibration (bending vibration wave + surface wave). Due to this minute vibration, for example, when the vibrator 1 moves to the point t ₁ shown in FIG. 7, an electromotive force that fluctuates with a small amplitude as shown in FIG. 8A is generated in the piezoelectric ceramic 12. And
As the vibrator 1 moves to the points t ₂ and t ₃ shown in FIG. 7, the amplitude fluctuation of the electromotive force generated in the piezoelectric ceramic 12 increases as shown in FIGS. 8B and 8C.

That is, the amplitude variation of the electromotive force generated in the piezoelectric ceramic 12 increases in proportion to the distance from the starting position of the vibrator 1. Here, the electromotive force generated in the piezoelectric ceramic 12 is level-converted as a monitor output and applied to an A / D converter configured inside the CPU. In this case, A
The level of the / D converter is as shown in FIG. 9 in proportion to the moving distance L from the starting end position of the vibrator 1.

Therefore, the timer inside the CPU is used to start the timer at the same time when the movement of the vibrator 1 is started, and the current level of the A / D converter is stored (step 101 shown in FIG. 10). Compare with the A / D converter level every moment (step 10
2) If the A / D converter level is lower than the timer value, increase the moving speed of the vibrator 1 (step 1
03), if the level of the A / D converter is higher than the value of the timer, the moving speed of the vibrator 1 is reduced (step 104), so that highly accurate speed control of the ultrasonic motor 13 can be realized.

In the above-described embodiment, the piezoelectric ceramic 12 is attached to the starting end position of the carrier rail 2-1. However, it may be attached to the end position of the carrier rail 2-1. Good.

[0021]

As is apparent from the above description, according to the present invention, the piezoelectric element is attached to the carrier rail, and the vibration of the carrier rail due to the movement of the vibrator based on the drive signal is monitored by the piezoelectric element. Since the moving position of the vibrator is detected based on the monitor output of this piezoelectric element,
High-accuracy speed control can be achieved without using an encoder, and data can be written to and read from the card, facilitating cost reduction of card readers that use ultrasonic motors. become able to.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a main part of an ultrasonic motor to which a position detecting method for an ultrasonic motor according to the present invention is applied.

FIG. 2 is a sectional view taken along line II-II in FIG.

FIG. 3 is a block diagram showing a drive control circuit attached to the ultrasonic motor.

FIG. 4 is a view showing amplitude fluctuations of electromotive force generated in the piezoelectric ceramic in this ultrasonic motor.

FIG. 5 is a block diagram showing another embodiment of a drive control circuit attached to the ultrasonic motor.

FIG. 6 is a schematic configuration diagram showing another embodiment of the ultrasonic motor to which the position detecting method for the ultrasonic motor according to the present invention is applied.

FIG. 7 is a diagram showing a moving state of a vibrator in this ultrasonic motor.

FIG. 8 is a diagram showing amplitude fluctuations of electromotive force generated in the piezoelectric ceramic corresponding to the moving state of the vibrator.

FIG. 9 is a diagram showing a level change of an A / D converter in proportion to a moving distance L from a starting end position of a vibrator.

FIG. 10 is a flowchart showing the flow of speed control of this ultrasonic motor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ceramic vibrator 2-1 and 2-2 Conveying rail 3-1 to 3-4 Roller 4-1 to 4-3 Piezoelectric ceramic 5 Ultrasonic motor 6 CPU 7 Programmable oscillator 10-1 to 10-3 Level converter

Claims (1)

(57) [Claims] 1. A vibrator, which is sandwiched between carrier rails, and a piezoelectric element attached to the carrier rail, wherein the piezoelectric element causes vibration of the carrier rail due to movement of the vibrator based on a drive signal. A position detecting method for an ultrasonic motor, characterized by monitoring and detecting a moving position of the vibrator based on a monitor output of the piezoelectric element.