JPS63262072A - Ultrasonic motor device - Google Patents

Abstract

PURPOSE:To reduce the varying width of a moving velocity by controlling the sweeping direction of a circulation type sweeper and the start/stop of the sweep according to the amplitude of a mechanical arm current. CONSTITUTION:An ultrasonic motor is composed of a circulation type frequency sweeper 1, a phase shifter 2, power amplifiers 3-4, and a sweep controller 6, etc. In this case, a mechanical arm current detector 5 is provided, its detection current is input to the controller 6, which outputs sweep ON/OFF direction command in response to the current. The logic unit of the controller 6 turns ON the command 8 when the current is smaller than a set range, sets a sweeping direction command 7 to a smaller frequency from larger frequency, and set the frequency from small to larger one when it is larger than the set range. Thus, the shifter 2 outputs predetermined AC signal A, B by a driving frequency signal 9, and applies driving signal VA, VB to the electrode A, B of the motor through the amplifiers 3-4.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an ultrasonic motor device that generates driving force using a piezoelectric body.

2. Description of the Related Art In recent years, ultrasonic motors, which obtain rotational or running motion by exciting various ultrasonic vibrations using electro-mechanical transducers such as piezoelectric ceramics, have attracted attention because of their high energy density.

Fig. 5 shows an exploded perspective view of a disk-type ultrasonic motor as an example of an ultrasonic motor. As shown in Japanese Patent Application Laid-open No. 190178/1983, the lower surface of the vibrating body has a disk-shaped radial structure. For example, divide it into 8, and make 46
The piezoelectric bodies 12 and 13, which are polarized in opposite directions for each degree, are pasted together with their spatial phases shifted by 9o0,
Driving signals 21.22 of several tens of kHz and having temporal phases different by 90 degrees are applied to each of the piezoelectric bodies 12 and 13. By applying the drive signals 21.22, standing waves are generated in the piezoelectric body 12.13, which are temporally and spatially different in phase by 900 degrees.

When the amplitudes of the two standing waves are made equal, the two standing waves are combined in the vibrating body 23, and a bending traveling wave that travels in the circumferential direction is generated. Point A of the vibrating body 23 is caused by the traveling wave to move along the long axis 2.
w shows an elliptical motion of the short axis 2u, and when the movable body 24 installed under pressure on the vibrating body 23 comes into contact with the apex of the ellipse, V = wau in the opposite direction to the traveling wave of the wave.・・・
・It shows that it moves at the speed of (1) (W is the frequency of the traveling wave). The moving body 24 is driven in the direction opposite to the direction of wave propagation by the frictional force between it and the vibrating body 1, and when the work done to the outside cannot be ignored with respect to this frictional force, the moving body 24
A slip occurs between the vibrating body 23 and the vibrating body 23, and the velocity becomes smaller than V. Figure 2 is an electrical equivalent circuit diagram of the piezoelectric body 12 or 13, and the current that flows through C0, which is considered to be the capacitance C0 that does not contribute to the piezoelectric effect, and the capacitance C0 that contributes to the piezoelectric effect, or is coupled in parallel with C1 and R. is called the electric arm current, L, C1
, H is called the mechanical arm current. The mechanical arm current and the short axis amplitude 2u are in a proportional relationship. Even if the voltage and frequency of the drive signals 21 and 22 applied to the piezoelectric body 12.13 in FIG. Therefore, the mechanical arm current changes and the rotational speed fluctuates.

Problems to be Solved by the Invention As explained above, the moving speed of the ultrasonic motor is determined by the product of the frequency W of the traveling wave and the minor axis U of the elliptical motion.
The magnitude of is proportional to the mechanical arm current.

The variation range of the short axis U is larger than the variation range of the frequency W, and the rotation speed is determined almost by the mechanical arm current.

If the mechanical load on the piezoelectric body 12, 13 is constant, the electrical impedance is constant, and if the voltage and frequency are constant, the mechanical arm current is constant and the rotation speed is also constant.

However, in reality, as the moving object is moving, the mechanical load fluctuates, and the electrical impedance fluctuates due to temperature changes.As a result, the mechanical arm current changes and the rotational speed fluctuates greatly. Another problem is that the ultrasonic motor may not start depending on the frequency of the drive signal, and when the voltage of the drive signal changes, the mechanical arm current changes and the rotation speed also fluctuates. There is a problem.

The present invention solves the above problems and reduces mechanical loads.

An object of the present invention is to provide an ultrasonic motor device that can reduce fluctuations in rotational speed in response to fluctuations in temperature and voltage of a drive signal, can quickly start the motor, and can select a moving speed.

Means for Solving the Problems The present invention includes an ultrasonic motor consisting of a vibrating body made of a piezoelectric body and an elastic body, and a movable body installed in pressurized contact with the vibrating body. Sweep cyclically and with a frequency sweeper and 90 degrees of phase from each other from the output of said sweeper.
0 A phase shifter that outputs two different alternating current signals, a power amplifier that amplifies the output of the phase shifter and outputs a drive signal for the ultrasonic motor, and a mechanical arm current in the current flowing into the piezoelectric body. a mechanical arm current detector that detects the mechanical arm current; and a sweep controller that outputs a sweep direction of the sweeper and a signal to start or stop the sweep according to the magnitude of the mechanical arm current. When the mechanical arm current is below the set range, the sweep direction is set from the higher frequency side to the lower frequency side, and when the mechanical arm current is above the set range, the sweep direction is set from the lower frequency side. and when the mechanical arm current is within a set range or when the output of the power amplifier is cut off to stop the motor, the sweep of the sweeper is stopped. An ultrasonic motor device configured to operate as described above.When the motor is started, the mechanical arm current is smaller than the set range, and the frequency sweeper sweeps in the direction from the higher frequency to the lower frequency. The frequency of the drive signal gradually decreases, the moving body of the motor begins to move, the mechanical arm current increases, and when the magnitude of the mechanical arm current falls within the set range, the frequency decreases. The sweep of the sweeper stops, the frequency of the drive signal becomes constant, and the moving speed of the moving object becomes a range corresponding to the setting range of the mechanical arm current. When the moving speed decreases due to fluctuations in drive signal voltage, mechanical load, temperature, etc., and the mechanical arm current becomes smaller than the set range, the sweeper starts sweeping in the direction of decreasing frequency again, and as the frequency decreases. The moving speed and mechanical arm current increase, and when they enter the set range, the sweep stops. In addition, when the moving speed increases, the mechanical arm current also increases, and when the set range is exceeded, the sweeper starts sweeping at a higher frequency, and as the frequency increases, the moving speed and mechanical arm current increase. decreases and the sweep stops when it enters the set range. Even when the frequency at the start of the sweep is lower than the frequency at which the movement speed is greatest, the sweeper is configured to sweep cyclically during startup, so the sweep direction is set to the higher frequency as described above. After the frequency reaches the smallest range of the set frequency range, the sweep is continued from the highest part of the set frequency range again until the mechanical arm current falls within the set range. The sweep continues until

As described above, by controlling the sweep direction and the start and stop of the sweep of the circulating sweeper according to the magnitude of the mechanical arm current, the frequency of the drive signal can be adjusted so that the mechanical arm current is always within a certain range. This setting suppresses the size of the traveling wave in the driving body within a predetermined range, and as a result, it is possible to reduce the range of fluctuations in the moving speed in response to fluctuations in mechanical load, temperature, and drive signal voltage. Even when the motor is started, the movement speed can be quickly increased by sweeping the frequency.

Furthermore, by changing the setting range of the mechanical arm current, the magnitude of the moving speed of the moving object and its fluctuation range can be selected.

EXAMPLES Below, examples of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram of an ultrasonic motor device of the present invention. The electrode part A includes 12 piezoelectric bodies A and a resistance element R.
A1 is connected in series with a capacitor C having a capacitance equal to the capacitance co of the electric arm impedance of the piezoelectric body in FIG.
A and a resistance element RA having a resistance value equal to that of the resistance element RA1.
2 are connected in series and connected to the electrode portion A in parallel with the series connection body consisting of the piezoelectric body and the resistance element. The same applies to the electrode section B. Resistance element RA1 and resistance element R of electrode part A
A mechanical arm current 19 is detected using a differential amplifier 14 based on the difference between the potentials of A2. In the sweep controller 6, a mechanical arm current 19 is smoothed using a smoother 16, and two voltage comparators 1e are used to determine whether the smoothed mechanical arm current is smaller or larger than a set range. , or within the set range, and based on the result, the logic unit 17 outputs a sweep on/off command 8 and a sweep direction command 7 to the circulating frequency sweeper 1.

In the logic unit 17, when the mechanical arm current is smaller than the set range, the sweep on/off command 8 is turned on, the sweep direction command 7 is set from the higher frequency to the lower frequency, and the mechanical arm current is turned on. When the current is larger than the set range, the sweep on/off command 8 is turned on, and the sweep direction command 7 is set from the direction of the lowest frequency to the highest frequency.

Furthermore, when the mechanical arm current is within the set range or when the motor on/off command 18 is off, the sweep on/off command 8 is turned off. The cyclic frequency sweeper 1 cyclically sweeps a predetermined frequency range or stops sweeping based on the sweep on/off command 1 and the sweep direction command T, and outputs a drive frequency signal 9. Phaser 2 is 1. From the drive frequency signal 9, the temporal phase of 9o
O Outputs different AC signal A and AC signal B. The power amplifiers 3 and 4 are configured to amplify the AC signal A1 and the AC signal B, respectively, and output drive signals A and B of the same voltage, and apply the drive signals A and B to the electrode sections A and B, respectively.

FIG. 3 is a characteristic curve of the rotation speed of the ultrasonic motor used in this embodiment and the mechanical arm current, and two outputs to the sweeper of the logic section 17 are also shown. The rotational speed of the ultrasonic motor has a history as shown in Fig. 3 in the frequency sweep direction, and when increasing the rotational speed of the ultrasonic motor or starting up,
It can be seen that it is necessary to set the sweep direction from the higher frequency side to the lower frequency side. On the other hand, when lowering the rotation speed, it is necessary to increase the frequency.

Figure 5 shows the characteristic curve of the mechanical arm current and rotational speed of one of the piezoelectric bodies when the driving voltage of the two piezoelectric bodies is the same and the parameters are the same, and the rotational speed is independent of voltage fluctuations. Approximately proportional to mechanical arm current.

The operation of this embodiment will be explained below with reference to FIG. When the mechanical arm current 19 is smaller than a predetermined range, such as when starting the ultrasonic motor, the sweep direction is set from the higher frequency to the lower frequency (point A, point B, or point 0 in FIG. 3).

For example, if the sweep start point is at point A, since the sweeper 1 is configured cyclically, the operating point will move from point F to point B over time, and the frequency will gradually decrease from point B. According to the decrease, as shown at the 0 point, the mechanical arm current 1
9 increases. Then, as shown at point D, when the mechanical arm current falls within the set range, the sweeper is stopped, and the moving body rotates at a rotation speed proportional to the mechanical arm current within the set range.

During rotation, the rotation speed and mechanical arm current 19 decrease due to variations in mechanical load, temperature, and drive voltage, and when the mechanical arm current 19 falls below the set range as shown at the 0 point, the sweep direction is changed again to the frequency. The rotation speed and the mechanical arm current 19 increase as the frequency decreases, and the mechanical arm current falls within the set range again as at point D. Conversely, when the rotational speed and mechanical arm current exceed the set range as at point E due to each of the above fluctuations, the sweep direction is set in the direction of increasing frequency, and as the frequency increases, the rotational wave and mechanical arm current increase. 19 decreases, and the mechanical arm current 19 falls within the set range again as at point D.

As described above, by determining the sweep direction of the sweeper that sweeps cyclically and the start and stop of the sweep depending on the magnitude of the mechanical arm current, the mechanical arm current 19 can be controlled within the set range, and the mechanical load , for variations in temperature and drive signal voltage,
It becomes possible to reduce fluctuations in rotational speed. Furthermore, at startup, the frequency is swept from high to low, allowing the rotational speed to rise quickly.

Also, by changing the setting range of the mechanical arm current 19,
The magnitude and fluctuation range of the rotational speed can be arbitrarily selected within the range shown in FIG.

In this embodiment, the mechanical arm current 19 is detected from the electrode section A, but it may be detected from either of the electrode sections A and H.

Furthermore, although this embodiment has been explained using a disc type ultrasonic motor, the present invention is not limited to a disc type ultrasonic motor, and the present invention is not limited to a disc type ultrasonic motor. It can also be applied to motors.

Effects of the Invention As explained above, considering the history of the frequency characteristics of the mechanical arm current of the ultrasonic motor and the moving speed of the moving object, when the mechanical arm current is below the set range in the circulating frequency sweeper,
The sweep direction is set from high frequency to low frequency, and when the mechanical arm current exceeds the set range, the sweep direction is set from low frequency to high frequency. When the mechanical arm current is within the setting range, or
When the motor is stopped by cutting off the output of the power amplifier, the mechanical arm current can be controlled always within the set range by stopping the sweep of the sweeper, and as a result, the mechanical arm current of the ultrasonic motor load.

It is possible to reduce the range of variation in the moving speed of the moving body with respect to each variation in temperature and voltage of the drive signal.

Furthermore, at startup, the frequency is always swept from high to low, allowing the movement speed to quickly rise. Furthermore, by selecting the setting range of the mechanical arm current, the magnitude and fluctuation range of the moving speed can be selected, which has great practical effects.

These effects have expanded the scope of use of ultrasonic motors,
For example, ultrasonic motors can be applied to places where voltage and temperature fluctuations are severe, such as in transportation vehicles such as automobiles, aircraft, and ships.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an ultrasonic motor device according to an embodiment of the present invention, FIG. 2 is an electrical equivalent circuit diagram of the same motor, and FIG.
The figure is an explanatory diagram of the history of the rotational speed of the motor and the drive frequency of the mechanical arm current and the operation of the sweep controller, and FIG. 4 is a characteristic diagram showing the relationship between the rotational speed of the motor and the mechanical arm current. FIG. 5 is an exploded perspective view of a disk-type ultrasonic motor used in an embodiment of the present invention, and FIG. 6 is a diagram illustrating the principle of the motor. 1... Circulating frequency sweeper, 2... Phase shifter, 3... Power amplifier, 4... Power amplifier, 5... Mechanical arm current detector, 6...
...Sweep controller. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] Equipped with an ultrasonic motor consisting of a vibrating body made of a piezoelectric body and an elastic body, and a moving body installed in pressure contact with the vibrating body,
A frequency sweeper that cyclically sweeps a predetermined frequency range and can control the frequency sweep direction and the start and stop of the sweep, and outputs two AC signals whose phases differ by 90 degrees from the output of the sweeper. a power amplifier that amplifies the output of the phase shifter and outputs a drive signal for the ultrasonic motor; and a mechanical arm current detector that detects a mechanical arm current in the current flowing into the piezoelectric body. and a sweep controller that outputs a sweep direction of the sweeper and a signal to start or stop the sweep according to the magnitude of the mechanical arm current, and in the sweep controller, the mechanical arm current is below a set range. When , set the sweep direction from high frequency to low frequency,
Further, when the mechanical arm current is above a set range, the sweep direction is set from a low frequency to a high frequency direction,
Further, the ultrasonic motor device is characterized in that the sweeping of the sweeper is stopped when the mechanical arm current is within a set range or when the output of the power amplifier is cut off to stop the motor.