JPH0530150B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a motor, and particularly to a vibration wave motor that utilizes vibrations generated in a piezoelectric element.

[Prior art]

As electric motors have become extremely compact due to recent technological advances, small motors are now installed in various small portable devices such as cameras, and these motors contribute to improving the performance of the devices. ing.

However, although the small motors installed in cameras and the like can rotate at high speeds, they cannot generate large torque at low speeds, so a reduction mechanism is required. A disadvantage is that the volume of the power generation mechanism including the speed reduction mechanism becomes considerably large. Therefore, it has been desired to develop a small and lightweight motor that can generate large torque at low speed without requiring a speed reduction mechanism.

Against this background, in recent years, attempts have been made to use piezoelectric elements as a power generation source, and as a result, an ultrasonic motor that converts the ultrasonic vibrations generated by piezoelectric elements into rotational motion has recently been developed. , has been developed.

This known ultrasonic motor has an annular stator and an annular rotor, and a piezoelectric element annularly bonded to the end surface of the stator generates an annular surface acoustic wave on the end surface of the stator. is generated, thereby rotating the rotor that is in contact with the end surface of the stator.

This known ultrasonic motor can generate large torque at low speeds, eliminating the need for a reduction mechanism.
Therefore, it is suitable as a motor for mounting on small devices such as cameras, and because it has an annular shape, it is suitable as an autofocus motor for cameras. However, in this known ultrasonic motor, the stator There was a problem in that the generated vibrations were easily attenuated and it was difficult to support the stator without causing vibration attenuation. Particularly in devices such as cameras that may be subjected to external shocks, there is a problem in that it becomes difficult to support the stator.

Therefore, a vibrating rod extending parallel to the axis of the rotor is provided, and the circular motion generated at the end of the vibrating rod to which the piezoelectric element is fixed causes rotational motion in the rotor. A motor that solved the problem of difficulty in supporting the stator was proposed by the applicant in Japanese Patent Application No. 1986-286242.

However, since the vibrating rod of the above-mentioned vibrating wave motor is rod-like with a substantially square cross section, the vibration amplitude with respect to the input voltage is small, the efficiency is poor, and it is difficult to miniaturize the motor.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a rod-shaped vibration wave motor that solves the above-mentioned drawbacks of conventional motors, is highly efficient, can be miniaturized, and can suppress a decrease in rigidity.

[Summary of the invention]

The present invention is characterized by a vibrating rod whose outer circumferential end rotates due to vibration generated in a piezoelectric element fixed to the end surface, and a movable body that is frictionally driven by the rotational movement generated in the vibrating rod. The vibration wave motor has a recessed portion at least in the center of the vibrating rod. In the present invention, the efficiency is improved due to such a configuration, and the decrease in rigidity can be suppressed to a small level.

The present invention will be explained below with reference to the drawings.

[Embodiments of the invention]

FIG. 1 shows a main part configuration diagram of a vibrating rod in a vibrating wave motor to which the present invention is applied.
It is a vibrating rod that has recesses on four end faces to which PZTs 2 to 5 as mechanical energy conversion elements are attached. One end is supported by a structural member (not shown) at the node position.
As shown in FIG. 2, piezoelectric elements PZT2-5 are adhered to four end faces of the vibrating rod 1 having a square cross section with an adhesive. Each of the PZTs 2 to 5, which impart bending vibration to the vibrating rod 1, is polarized in the direction of the arrow as shown in FIG. 2 so that the corresponding PZTs bend in the same direction. Furthermore, each PZT2
~5 terminal parts 2a, 2b, 3a, 3b, 4a, 4
b, 5a, 5b (however, 5a, 5b are not shown) and the ends 1a, b of the vibrating rod 1 are not clearly shown in FIG.
They are spaced apart to prevent electrical conduction. 9
is an AC power supply, and the AC signal, for example, a sine wave, output from the power supply 9 is passed through a 90° transfer device 7 to the PZT 2,
On the other hand, the electrodes of PZTs 4 and 5 are directly connected to the output terminal of AC power supply 9. Therefore, when these AC signals with a phase difference are applied to PZTs 2 to 5, the vibrating rod 1 is simultaneously bent in the y direction by PZTs 2 and 3, and the point in time is different by the phase difference caused by the phase shifter 7 by PZTs 4 and 5. simultaneously bends in the x direction. These bends are repeated according to the applied AC signal, so the tip 1 of the vibrating rod 1
b makes a circular motion or an elliptical motion depending on the phase amount of the phase shifter 7. The principles of these rotational movements are detailed in Japanese Patent Application No. 1986-286242, which was previously proposed by the applicant of the present invention, and will therefore be omitted here.

Here, let us consider the unidirectional vibration in the bending vibration of the vibrating rod 1 (FIG. 1). If the amplitude of the tip 1b of the vibrating rod 1 is a, the velocity of the tip 1b of the vibrating rod 1 in the cross-sectional direction is v, and the primary resonance angular velocity of the vibrating rod 1 is ω, then v=aωsinωt is defined, and from this equation, the speed is The maximum value vmax of v is vmax=aω. Fourth
The figure shows the results of a comparison of a conventional vibrating rod with a square cross-sectional shape and the vibrating rod 1 having a concave portion in the center according to the present invention (i.e., a vibrating rod with a cross-sectional area ratio of 1, see FIG. 4) regarding the maximum speed vmax. However, as is clear from the curve _C1 in FIG. 4, the vibrating rod of the present invention achieved a higher maximum speed than the conventional vibrating rod described above. Next, consider the rigidity of the vibrating rod.

The rigidity EI of the vibrating rod 1 is EI=ES ₀ ² /12×H ² (where, E is Young's modulus, S ₀ is the standard cross-sectional area, H is the cross-sectional area ratio,
0<H≦1). Therefore, when the cross-sectional area ratio decreases, the rigidity of the vibrating rod rapidly decreases, and when a pressing force is applied to a moving body (not shown), the vibrating rod exceeds its bending limit and breaks. Therefore, the shallower the depth of the concave portion of the vibrating rod 1, the better. Regarding this rigidity, as shown in Figure 3, both ends are 1Aa and 1Ab.
Vibrating rod 1A with thinner vibration rod 1A and vibrating rod 1 according to the present invention
(Fig. 1) and the curve shown in Fig. 4.
As shown in C ₂ , at the same cross-sectional area ratio (for example, cross-sectional area ratio 0.4), the third illustrated vibrating rod 1A exhibited v ₁ and the one of the present invention exhibited v ₂ . That is, according to the present invention, a high mass point velocity can be obtained without impairing rigidity. In other words, a high mass point velocity, that is, high efficiency, can be obtained with a small amount of energy, and a decrease in rigidity can be suppressed to a small level. In FIG. 4, the horizontal axis shows the cross-sectional area ratio, and the vertical axis shows the maximum velocity of the mass point of the vibrating rod. And the curve _C1 shows the relationship between the cross-sectional area ratio of the vibrating rod according to the present invention and the maximum velocity of the mass point, and the curve
C ₂ is a curve showing the difference in characteristics between the vibrating rod of the present invention and the vibrating rod shown in the third diagram, and shows the relationship between the cross-sectional area ratio and the maximum velocity of the mass point of the vibrating rod shown in the third diagram. Incidentally, the vibrating rod having a cross-sectional area ratio of 1 is a vibrating rod having a uniform square cross section as shown in the above-mentioned earlier application.

In addition, the vibration rod 1 constituting the vibration wave motor is the first
It does not have to be a square prism as shown in the figure, but a triangular prism or a cylinder (not shown) as shown in the fifth figure can also provide the same operation and effect as in the case of the first figure. It is not necessary to stick them at equidistant positions across the center of the vibrating rod 1 as shown in the figure, but they may be stuck to either side as shown in the sixth figure.

FIG. 7 is a vertical cross-sectional view of a main part of a vibration wave motor incorporating the first illustrated stator. Elements having the same functions as those shown in the first figure are given the same reference numerals, and detailed explanation thereof will be omitted.

In FIG. 7, reference numeral 11 denotes a rotor configured as a stepped torus, and the rotor 11 is supported by a structural member (not shown) so as to be rotatable about its own axis Z ₀ . A flexible covering material 13 having a large coefficient of friction is fixed to the inner peripheral surface of the small diameter portion 11A of the rotor 11 with an adhesive or the like.

A vibrating rod 1 for causing rotational movement in the rotor 11 is arranged parallel to the axis of the rotor 11, and a tip end 1b of the vibrating rod 1 is connected to a small diameter portion 1 of the rotor 11.
1A and positioned so that the upper surface of the tip 1b is close to the covering material 13 of the small diameter portion 11A.

In this embodiment, the vibrating rod 1 having a concave portion in the center is configured as a square rod having a rectangular cross-sectional shape, and the outer peripheral surface of the vibrating rod 1 is constituted by a pair of horizontal surfaces and a pair of vertical surfaces. There is. Then, the vibrating rod 1
As shown in the second figure, piezoelectric elements 2 to 5 as vibration excitation means for producing vibrational displacement in a circular or elliptical orbit at the tip 1b of the vibrating rod 1 are adhered to the vertical and horizontal surfaces of the vibrating rod 1, respectively. There is. The piezoelectric elements 2 to 5 are bonded at the central position in the longitudinal direction of the vibrating rod 1, and are bonded to the center of the drive generated in the vibrating rod 1.

A thin hole is penetrated through the outer peripheral surface of the vibrating rod 1 at a position that becomes a node of vibration generated in the vibrating rod 1, and a thin support rod 1 is fitted into the thin hole and fixed to the vibrating rod 1.
5 and 17 protrude from the vertical and horizontal surfaces of the vibrating rod 1, respectively. The support rods 15 and 17 are steel wires, both ends of the support rod 15 are fixed to the support ring 19, and both ends of the support rod 17 are fixed to the support ring 21.
is fixed. The support rings 19 and 21 have the same inner diameter and the same outer diameter, and the support rings 19 and 21 are fitted into the spigots at both ends of the cylindrical support base 23 and fixed ring 25. It is fixed to a support stand 23.

The support stand 23 is elastically supported by a spring 27 on a stationary member (not shown), and is biased vertically upward by the spring 27. Therefore, the vibrating rod 1 is also urged toward the covering material 13 of the rotor 11 by the force of the spring 27.

There are four connection terminals 27 to 3 on the bottom surface of the support stand 23.
3 are provided, and the connection terminals 27 to 33 are connected to control circuits 7 and 9 as shown in FIG. Moreover, the connection terminal 27 is connected to PZT4 as a piezoelectric element via a lead wire,
The connection terminal 29 is connected to PZT3 as a piezoelectric element via a lead wire, and the connection terminal 33 is
It is connected to PZT2, and the connection terminal 31 is connected to PZT5 (not shown). Note that the grounding terminal connected to the main body of the vibrating rod 1 is omitted.

In this configuration, when an AC signal is applied from the power source 9 to the PZTs 2 to 5 for driving, the tip 1b of the vibrating rod 1 rotates, so the rotor 11 as a moving body rotates around the axis _Z0 . exercise.

Figure 8 shows the center side of the vibrating rod 1 being cut.
PZT2 to 5 (PZT4 is not shown) are attached to the rod 1, and the positions of the vibration nodes are cut deeper to make it easier to support the nodes, so that the bending vibration using the nodes as fulcrums becomes larger. In this way, the rotation speed of the tip portion 1b is increased.

The other configurations in the eighth illustrated embodiment are the same as those in the seventh embodiment.
Since it is the same as the illustrated embodiment, it is omitted.

Although two pairs of piezoelectric elements are used as the piezoelectric elements in the above embodiment, it goes without saying that the same effect can be obtained even if only one pair of piezoelectric elements is used.

〔Effect of the invention〕

As explained above, in the present invention, since the recess is provided between both ends of the vibrating rod that constitutes the stator, the speed of the moving body that is in contact with one end of the stator is increased, and the Efficiency can be obtained.

Note that 1 and 1B are rod-shaped elastic bodies, and 2 and 4 are first and second
The electrical-mechanical energy conversion elements are configured respectively.

[Brief explanation of the drawing]

Fig. 1 is a main part configuration diagram of a stator and drive circuit portion in a vibration wave motor to which the present invention is applied, Fig. 2 is a sectional view taken along line AA of the stator shown in Fig. 1, and Fig. 3 is a comparison and contrast with the present invention. FIG. 4 is a characteristic diagram of the vibration wave motor of the first illustrated embodiment; FIGS. 5 and 6 are diagrams of the main part of the stator of the vibration wave motor in other embodiments of the present invention. , 7th
8 are main part configuration diagrams of a vibration wave motor to which the present invention is applied. In the figure, 1... vibrating rod constituting the stator, 2 to 5... piezoelectric elements, and 11... rotor.

Claims (1)

[Claims] 1. A vibration device for an ultrasonic motor, comprising a rod-shaped elastic body 1; 1B, a first electro-mechanical energy conversion element 2, and a second electro-mechanical energy conversion element 4. The elastic body 1; 1B has two ends 1a, 1
b; 1Ba, 1Bb, a recess is formed in the portion sandwiched between the two end portions 1a, 1b; 1Ba, 1Bb;
The electric-mechanical energy conversion element 2; 4 is fixed to the elastic body 1; 1B, and the first electric-mechanical energy conversion element 2
generates bending vibration in the first direction in the elastic body 1; 1B in response to an applied alternating current signal, and the second electro-mechanical energy conversion element 4
is to generate bending vibration in a second direction different from the first direction in the elastic body 1; 1B in response to an applied alternating current signal, and these two bending vibrations cause the elastic body 1 to One end 1b of 1B makes a rotational movement, and the member 11 in contact with this one end and the elastic body 1; 1B make a relative movement due to this rotational movement. A vibration device for ultrasonic motors.