JP2002281772A - Ultrasonic motor using a static pressure applying device with nonlinear characteristics - Google Patents

Abstract

[PROBLEMS] To provide an ultrasonic motor having a large driving force, a high rotational speed, a high efficiency load characteristic and a good durability by using a static pressure applying device having a nonlinear characteristic instead of the conventional linear characteristic. Realize. A static pressure is generated during a driving process in which a rotating or moving unit (rotor or slider) of an ultrasonic motor is driven in contact by ultrasonic vibration of various vibration trajectories such as a straight line, an ellipse, and a circle of a contact driving unit (stator). By using a static pressure applying device that has a non-linear characteristic in space and time to increase the driving force by increasing the driving force and reduce the static pressure in the return process to reduce the frictional force, the rotation type or linear movement The driving force of the ultrasonic motor such as a mold is increased, the efficiency is further increased and a high rotation speed is obtained, the load characteristics are improved, the direct contact drive of the drive surface is enabled, and the durable rotary type or An ultrasonic motor such as a linear moving type is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the contact of a rotating or moving part (rotor or slider) of an ultrasonic motor with ultrasonic vibrations of various vibration trajectories such as a straight line, an ellipse and a circle of a contact driving part (stator). A rotary type using a static pressure application device that has a spatially and temporally non-linear characteristic that increases the driving force by increasing the static pressure during the driving process and reduces the frictional force during the return process. Also, the present invention relates to improvement of load characteristics such as a rotation speed, a driving force, and efficiency of an ultrasonic motor such as a linear moving type.

[0002]

2. Description of the Related Art In an ultrasonic motor, a moving part (rotor or slider) such as a rotation or a straight line is pressed against a contact driving part by a spring for applying static pressure or the like, and a contact driving part (stator) is made of a piezoelectric ceramic or the like. Straight line by vibration transducer,
Ultrasonic vibration is caused by an elliptical or circular vibration trajectory, and the moving part is driven by frictional force to rotate or linearly move.

[0003]

The problem to be solved is that in the prior art, a spring or magnet or the like having a linear characteristic is used to apply a static pressure to the contact drive unit. In the course of driving the locus, the contact driving force increases, but in the returning process in which the vibration direction is opposite to the moving direction, the friction force increases and loss occurs, and when the static pressure is reduced, the driving force decreases, The point is that it is difficult to obtain an ultrasonic motor having a large number of rotations and a high driving force and having good load characteristics with high efficiency.

[0004] Further, in order to obtain a large driving force, it is inevitable that the durability is reduced due to the damage of the contact driving portion due to friction.

[0005] Further, it is difficult to drive the rotating or moving part by direct contact with the driving part, and it is usually unavoidable to insert various friction materials into the driving surface.

According to the present invention, there is provided a driving process in which a rotating or moving part (rotor or slider) of an ultrasonic motor is driven in contact by ultrasonic vibration of various vibration trajectories such as a straight line, an ellipse, and a circle of a contact driving part (stator). Sometimes, the static pressure is increased to increase the driving force, and in the return process, the static pressure is reduced by using a static pressure applying device having a non-linear characteristic in space and time in order to reduce the frictional force by reducing the static pressure. It is an object of the present invention to increase the driving force of a linearly moving ultrasonic motor, further increase efficiency, obtain a high rotational speed, and improve load characteristics.

[0007] Since the conventional ultrasonic motor uses a static pressure applying device having a linear characteristic, the static pressure of the contact drive portion of the rotor or the slider in the driving process and the return process is substantially equal, and the contact portion in the driving process is applied. When the static pressure is increased, the frictional force in the reverse direction in the return process increases, making it difficult to increase the efficiency.In addition, the contact drive unit is worn and damaged in the return process, causing a problem in durability. ing. If sufficient static pressure is not applied, slippage occurs in the driving process and the driving force becomes small, so that effective driving cannot be performed. Even if the friction force in the reverse direction of the returning process becomes small, high efficiency and durability are obtained. It was difficult to obtain a stable ultrasonic motor.

In a conventional ultrasonic motor, it is common to use a friction material such as a polymer material between a driving unit and a rotating or moving unit, and it is difficult to drive the moving unit by directly bringing the moving unit into stable contact with the driving unit. It was difficult.

[0009]

SUMMARY OF THE INVENTION The present invention relates to a method for controlling the rotation or moving portion (rotor or slider) of an ultrasonic motor by using ultrasonic vibration of various vibration trajectories such as a straight line, an ellipse, and a circle of a contact drive portion (stator). In order to increase the driving force by increasing the static pressure during the driving process of contact driving by means of a contact, and to reduce the friction force by decreasing the static pressure in the returning process, a spring for applying static pressure that has spatially and temporally non-linear characteristics. By using, the driving force of the ultrasonic motor that rotates or linearly moves is increased, the efficiency is further increased, a high rotation speed is obtained, the load characteristics are improved, and a more durable ultrasonic motor is obtained. It is.

In an ultrasonic motor, a vibration transducer such as a piezoelectric ceramic is driven by a semiconductor device or the like to generate an ultrasonic vibration, a traveling wave or a standing wave is generated, and a driving unit is vibrated along, for example, an elliptical vibration locus. In a state where a static pressure is applied and the rotating unit or the moving unit is pressed against the driving unit, a component perpendicular to the driving surface of the vibration trajectory of the driving unit presses the rotating unit or the moving unit, and the parallel component rotates or moves. The ultrasonic motor has a contact drive process and a return process in which the vertical component moves away from the drive unit and the parallel vibration component moves in the direction opposite to the movement direction. The magnitude of the applied static pressure is determined, and the magnitude of the driving force is determined by the magnitude of the frictional force proportional to the static pressure and the friction coefficient. Since the static pressure has a large effect on the driving force and efficiency, the static pressure is increased. Is desirable. In the return step, the vibration trajectory is in a direction in which the driving unit and the moving unit are separated from each other, and it is desired that the movement is not hindered as much as possible. For,
It is desirable that the static pressure be small in the return process.

[0011]

In the ultrasonic motor, the static pressure is large in the driving process, and the static pressure is small in the returning process. Or the slider) increases the driving force by increasing the static pressure during the driving process in which the contact driving unit (stator) is driven in contact with the ultrasonic vibration of various vibration trajectories such as straight lines, ellipses, and circles, and increases the driving force. It is possible to reduce the frictional force by reducing the pressure, increase the driving force such as the rotation or linear movement of the ultrasonic motor, increase the efficiency, obtain a high rotation speed, and improve the load characteristics.

[0012] It is possible to obtain an ultrasonic motor having greater durability.

Conventionally, direct drive is possible without the need for a friction material inserted between the contact drive surfaces.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration, the driving principle, the vibration trajectory, the driving force, the frictional force and the static pressure in the driving process and the returning process of the ultrasonic motor of the present embodiment. The ultrasonic motor applies a static pressure applying device 4 to a driving unit 2 (stator) driven by a moving unit 3 (rotor or slider) that moves by rotation or a straight line or the like by a generator 1 of a linear, elliptical or circular vibration locus.
The driving unit 2 is driven along a linear, elliptical or circular vibration locus 7 while the static pressure 5 is applied and pressed by the
(Rotor or slider) is rotated or linearly moved. In the case of an elliptical vibration trajectory, in the driving process A, the moving component moves in the rotation direction 8 of the trajectory when the vertical component of the vibration trajectory is in the upward direction against the direction of application of the static pressure due to the contact friction driving force 10 due to the static pressure due to vibration. 3 is driven, and the moving direction of the trajectory is downward, and the returning process B is in the opposite direction to the moving direction of the moving unit 3.
In this case, the friction braking force 11 in the reverse direction acts, but the moving portion 3 continues to move 8 until the next driving process due to inertia, and continuously rotates or moves. Further, the holding force at rest is determined by the applied static pressure at rest. In the driving process A in which the elliptical vibration trajectory of the driving unit of the ultrasonic motor rotates upward, the friction driving force 1 increases as the static pressure increases.
In the return process B during the period in which 0 becomes large and the vibration trajectory rotates downward, the smaller the friction braking force 11, the higher the rotation speed without hindering the rotation or movement, and the greater the driving force and the higher the efficiency. It becomes possible.

FIG. 2 shows a static combination of one or more springs in which the stiffness constant (spring constant) is small in the portion where the displacement is small and the stiffness constant is large in the portion where the displacement beyond the inflection point is large. FIG. 4 shows a schematic diagram of a displacement-force characteristic 12 of the pressure application device. By placing the stationary state at the inflection point 13, when the ultrasonic vibration 14 is applied, the static pressure increases in the driving process as shown by the curve 15 in the drawing, the driving force increases, and the static force increases in the returning process. The pressure becomes small, the braking force due to friction is reduced, and the loss is reduced.

FIG. 3 shows a hysteresis characteristic in which the static pressure is large in the compression process of the driving process, and the static pressure is small in the return process, measured for the metal disc spring 16, the polyurethane spring 17, and the silicon rubber spring 18. This is an example of a displacement-force characteristic having a nonlinear characteristic in which the stiffness constant increases as the displacement increases. The static pressure of the ultrasonic motor in the stationary state is set near the inflection points 19, 19 ', 19 "in the figure.

FIG. 4 shows an example in which a flat spring made of polyurethane or silicone rubber is driven in a 27 kHz ultrasonic vibration system while applying a static pressure, and the time response of the displacement of the spring material is actually measured by a laser Doppler vibrometer. In the direction in which the ultrasonic vibration direction is such that the static pressure is large (upward in the figure), the static pressure is large in accordance with the displacement (20 in the figure), but when the ultrasonic vibration direction is opposite to the static pressure direction, Indicates that there is a temporal non-linear characteristic in which the response of the spring displacement is delayed with time and the static pressure is small (21 in the figure).

The drive process of the ultrasonic motor can be performed by using one or some of the characteristics of the static pressure applying device having the spatially and temporally non-linear characteristics shown in FIGS. 2, 3 and 4. It is possible to increase the static pressure during the return process and to reduce the static pressure during the return process.

FIG. 5 shows an example of a rotary ultrasonic motor. Longitudinal vibration is generated by the piezoelectric ceramic 23, and vibration of an elliptical or circular locus is generated in the driving surface 31 in the circumferential direction by the vertical-torsional vibration converter 25 using an oblique slit (Japanese Patent Application Laid-Open No. Hei 8-294673). The rotating unit 27 is driven by the driving unit 3 by a static pressure applying device 29 installed on the central shaft 28.
Linear or non-linear static pressure applying device 29 pressed against 1
Thus, vibration is applied while a static pressure is applied to the contact drive surface, and the rotating unit (rotor) 27 is rotated. The rotation direction 32 is changed by changing the driving frequency to control the vibration mode of the vibration converter unit 22 and changing the rotation direction of the vibration trajectory.

The configuration of FIG. 5 has a diameter of 15 mm and a length of about 50 m.
FIG. 6 shows an example of measuring the input power, the mechanical output power, the number of revolutions, and the efficiency by changing the load torque when the silicon rubber spring 18 of FIG. 3 is used for the ultrasonic motor of FIG. Show. The maximum rotational speed is 1400 rpm, the maximum torque is 0.28 Nm, and the maximum efficiency is 25.6%.

The structure of FIG. 5 has a diameter of 15 mm and a length of 50 mm.
Table 1 shows examples of the maximum torque, the maximum number of revolutions, and the efficiency when the linear metal disc spring, the non-linear metal disc spring shown in FIG. 3, polyurethane and silicone rubber are applied to the static pressure applying device of the ultrasonic motor of FIG. . By using a static pressure applying spring having non-linear characteristics, the characteristics are greatly improved as compared with a normal linear static pressure applying device. When a non-linear spring is used, the maximum rotation speed is 810 to 1400 rpm
m, maximum torque 0.22 to 0.28 Nm, efficiency 18.4
２９29.4%, and the characteristics are greatly improved as compared with a normal linear static pressure applying device.

By using this non-linear static pressure applying device, efficient direct driving becomes possible without using a friction material conventionally used.

Of course, it is desirable that the material of the direct drive unit and the moving unit be a combination having a large frictional force and a large durability.

By combining these characteristics, it is possible to obtain a highly efficient and durable ultrasonic motor having a large driving force.

These effects can be effectively applied to all ultrasonic motors and ultrasonic moving devices such as a rotary type and a linear moving type.

These effects can be effectively applied to all ultrasonic motors and ultrasonic moving devices such as standing waveforms and traveling waveforms.

[0027]

As described above, the ultrasonic motor using the device for applying static pressure having a spatially and temporally non-linear characteristic according to the present invention comprises a rotating or moving unit (rotor or slider) and a contact driving unit. (Stator) Increases the driving force by increasing the static pressure in the driving process of contact driving by ultrasonic vibration of various vibration trajectories such as straight line, ellipse, and circle, and reduces the static pressure in the returning process to reduce the frictional force. There is an advantage that the driving force such as rotation or linear movement of the ultrasonic motor is increased, efficiency is increased, a high rotation speed is obtained, and load characteristics are improved. In addition, efficient direct drive is possible without using a friction material conventionally used. Further, the durability of the ultrasonic motor can be improved.

[0028]

[Table 1]

Table 1 shows the configuration of FIG. 5 with a diameter of 15 mm and a length of 50 mm.
The metal disc spring shown in FIG.
It is an example of load characteristics when polyurethane and silicone rubber are applied.

[Brief description of the drawings]

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is an explanatory view of a configuration, a driving principle, a vibration trajectory, a driving force, a frictional force, and a static pressure in a rotary and linear moving type ultrasonic motor in a driving process and a returning process.

FIG. 2 is a schematic diagram of a displacement-static pressure characteristic having a non-linear characteristic used for applying a static pressure of a drive unit of the ultrasonic motor shown in FIG.

FIG. 3 is an example in which the displacement static pressure characteristics of a metal disc spring, polyurethane and silicon rubber having a non-linear hysteresis are measured.

FIG. 4 is an example in which a spring made of polyurethane, silicon, or the like is vibrated by an ultrasonic vibration system of 27 kHz while applying a static pressure, and dynamic response is measured by a laser Doppler vibrometer.

FIG. 5 is an example of a rotary ultrasonic motor using a vertical-torsional vibration converter having an oblique slit.
The rotating unit is pressed against the driving unit by a static pressure applying device installed on the central axis, and vibration is applied while applying a static pressure to the contact driving surface to rotate the rotating unit (rotor).

FIG. 6 is an example in which load characteristics are measured when the silicon rubber spring of FIG. 3 is used for the ultrasonic motor of FIG. 5;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Linear, elliptical or circular ultrasonic vibration locus generator 2 Drive unit (stator) of ultrasonic motor with linear, elliptical or circular vibration locus 3 Rotation or linear moving part (rotor or slider) of ultrasonic motor 4 Contact drive Static pressure applying device to unit 5 Static pressure of contact drive unit 5 'Static pressure in drive process 5' Static pressure in return process 6 Contact drive unit 7 Linear, elliptical and circular vibration trajectory of drive unit 7 'Driving of elliptical vibration trajectory Process 7 "Return process of elliptical vibration locus 8 Rotation or moving direction 9 Fixed portion of ultrasonic motor 9 'Fixed portion of static pressure application device 10 Direction of driving force by contact portion vibration locus in driving process 11 Friction in returning process Force direction 12 Static pressure curve 13 Static pressure of ultrasonic motor at rest-static point; inflection point 14 Vibration amplitude component perpendicular to drive surface 15 Time change of static pressure of drive unit 1 Displacement of metal disc spring-static pressure characteristic 17 Displacement of polyurethane spring-static pressure characteristic 18 Displacement-static pressure characteristic of polyurethane spring 19, 19 ', 19 "Static pressure at rest-static point; inflection point 20 Static pressure change during drive period 21 Static pressure change during return period 22 Linear, elliptical or circular ultrasonic vibration locus converter 23 Piezoelectric ceramic longitudinal vibration converter 24 Ultrasonic motor support device 25 Vertical-torsional vibration converter 26 Elliptical vibration locus 27 A rotating unit (rotor) 28 A rotating unit and a central shaft for supporting a static pressure applying device 29 A static pressure applying unit combining springs of various nonlinear characteristics 30 A nut for fixing a static pressure applying unit 31 A contact drive surface 32 Rotation direction 33 Ultrasonic motor fixing flange 34 Input power to ultrasonic motor 35 Mechanical output power 36 Number of rotations 37 Efficiency

Claims (1)

[Claims] The present invention has a non-linear characteristic in which a static pressure increases during a driving process of contacting a rotating or moving part of an ultrasonic motor to increase a driving force, and a static pressure decreases during a returning process to reduce a frictional force. Ultrasonic motor using a device for applying static pressure