JP4878125B2 - Piezoelectric device, method for manufacturing piezoelectric device, and electronic apparatus - Google Patents

Description

  The present invention relates to various piezoelectric devices that function by vibration of a piezoelectric element, and particularly to an ultrasonic motor that frictionally drives a moving body by vibration of a vibrating body and an electronic device using the same, and in particular, longitudinal vibration and bending vibration used for driving. The present invention relates to a structure of a vibrating body capable of adjusting a resonance frequency and an adjusting method.

In recent years, with the miniaturization, high functionality, and low power consumption of electronic devices, ultrasonic motors have attracted attention as actuators that move operating parts, and their adoption results are increasing. In particular, an ultrasonic motor using the longitudinal vibration and bending vibration of a rectangular plate-shaped vibrating body has a simple structure and can be easily reduced in thickness, and can be used for both rotary motion and linear motion. Application to is expected.
Japanese Unexamined Patent Publication No. 2000-116162

  However, an ultrasonic motor using the longitudinal vibration and bending vibration of a vibrating body made of a rectangular plate is subject to longitudinal vibration related to each vibrating body due to dimensional variations during processing of the vibrating body, attachment of a support member or friction member to the vibrating body, etc. In addition, the resonance frequencies of the bending vibrations fluctuated independently. As a result, the output characteristics (speed, propulsive force, current) of the ultrasonic motor also vary. In addition, there is a difference in output characteristics depending on the moving direction of the moving body.

  Therefore, in order to solve the above problems, the ultrasonic motor of the present invention has an additional mass part or a mass removal part in the vicinity of the node of the bending vibration excited by the vibrating body. Alternatively, an additional mass portion or a mass removal portion is provided in the vicinity of the antinode of flexural vibration excited by the vibrating body. Or it is set as the structure which has an additional mass part or a mass removal part in the longitudinal direction substantially tip part of a vibrating body.

  Here, the additional mass part or the mass removal part is provided symmetrically in the longitudinal direction and in the width direction of the vibrator. A plurality of additional mass parts or mass removal parts are provided on the vibrating body.

  As a specific adjustment method, a step of evaluating the resonance characteristics of the vibrating body, a step of selecting the position of the additional mass portion or the mass removal portion based on the evaluation result of the resonance characteristics, and adding or adding the additional mass It is set as the process to remove. Alternatively, a step of evaluating the resonance characteristics of the vibrating body and a step of determining whether to add additional mass or to remove mass among a plurality of additional mass applying portions or mass removing portion positions based on the evaluation result of the resonance characteristics And adding mass or removing mass.

  According to the present invention, it is possible to correct a deviation between the design value of the resonance frequency of the longitudinal vibration and the resonance frequency of the flexural vibration generated during the manufacture of each part or attachment to an electronic device, and to reduce ultrasonic fluctuations between products. Motors and various piezoelectric devices can be realized. As a matter of course, this not only improves the characteristics of piezoelectric devices such as ultrasonic motors, but also enables stable driving of electronic devices equipped with them, and improves reliability.

BEST MODE FOR CARRYING OUT THE INVENTION

  Hereinafter, an ultrasonic motor will be described as an example among piezoelectric devices.

  FIG. 1 is a diagram showing a configuration example of an ultrasonic motor according to the present invention. A protrusion 1 (2a and 2b) serving as a friction member and a support member 3 having a recess are joined to a vibrating body 1 made of a rectangular piezoelectric element. The shaft portion 4a of the pressure member 4 has a stepped portion and is guided by the guide hole 5a of the guide plate 5 so as to be movable only in the axial direction. A moving body 7 guided by guide members 8 (8a and 8b) is provided under the protrusion 2 and the pressing member 4 that engages the concave portion of the support member 3 is pressed by the pressing means 6 so that the protrusion 2 And the moving body 7 is in contact with each other. The support member 3 may be a shaft that penetrates through the central portion (vibration node) of the vibrator 1.

  Here, the vibrating body 1 made of a piezoelectric element excites longitudinal vibration and bending vibration. As the electrode configuration of the piezoelectric element, for example, the one shown in Patent Document 1 is used. FIG. 2 shows the distribution of vibration amplitude for each position in the longitudinal direction (x direction) of the vibrating body 1. (A) shows the amplitude of longitudinal vibration (displacement in the x direction), and (b) shows the amplitude of bending vibration (displacement in the y direction). Longitudinal vibration is the primary mode and bending vibration is the secondary mode. The central portion of the vibrating body 1 serves as a vibration node for both longitudinal vibration and bending vibration, and the support member 3 is provided at this position. Further, a protrusion 2 is provided at the position of the antinode of bending vibration. By simultaneously exciting the longitudinal vibration and bending vibration, the protrusion 2 performs an elliptical motion consisting of a displacement component in the longitudinal direction of the vibrating body 1 and a displacement in the width direction (y direction) perpendicular thereto, and drives the moving body 7. To do. The present invention is a method for correcting the resonance frequency of longitudinal vibration and the resonance frequency of flexural vibration to optimum values due to variations in the size and the like of the vibrating body produced in the manufacturing process, and details will be described in the following embodiments.

  The present invention does not limit the electrode configuration of the piezoelectric element, and may use a degenerate vibration of a longitudinal vibration and a bending vibration or may use a combined vibration. Then, the movable body 7 may be fixed and a self-propelled configuration for driving the vibrating body 1 itself may be used, or a rotary actuator configuration for rotating the movable body may be used. The shape of the vibrating body may be a round bar or a structure in which an elastic body such as metal and a piezoelectric element are joined.

(Embodiment 1)
Fig. 3 shows the resonance frequencies of longitudinal vibration and bending vibration when additional mass made of solder is attached to various positions of the vibrating body. The notation of the magnitude of the load mass (large and small) in the figure is qualitative for the convenience of the experiment, but the amount of change in the resonance frequency of the longitudinal vibration and the amount of change in the resonance frequency of the bending vibration for the same additional mass. I think that it is enough for comparison. Actually, the size of the large solder was about three times that of the small size. FIG. 4 (a) is a view showing where the solder is attached when the vibrating body 1 in FIG. 1 is viewed from the same direction, and (b) is a view in which the solder 9 is attached to the point B ((a) (Viewed from the direction of arrow E).

  Fig. 3 (a) shows the resonance frequency and bending vibration of the longitudinal vibration when the solder is attached to the bending vibration node (point A in Fig. 4) of the vibrator 1 (additional mass part is formed) and when the solder is not attached. It is the table | surface which showed these resonant frequencies. As the additional mass increases, both the longitudinal vibration resonance frequency and the bending vibration resonance frequency decrease, but the amount of decrease in the longitudinal vibration resonance frequency is larger. Therefore, if the resonance frequency of the longitudinal vibration is higher than the target value with respect to the resonance frequency of the bending vibration, an additional mass may be provided near the node of the bending vibration. By the way, the additional mass is not limited to solder, and may be a metal or an adhesive itself.

  Conversely, if the resonance frequency of longitudinal vibration is lower than the target value relative to the resonance frequency of bending vibration, the mass near the node of bending vibration is removed by laser, mechanical drilling, cutting, grinding, etc. In addition, a mass removing unit may be provided. In this case, whether or not the hole to be pierced is through is selected.

  FIGS. 3 (b) and 3 (c) show soldering at the bending vibration abdomen (point B in FIG. 4) and longitudinal ends (point C in FIG. 4 which becomes the antinodes of longitudinal vibration and bending vibration), respectively. It is the table | surface which showed the resonance frequency of the longitudinal vibration and the resonance frequency of a bending vibration when not making it adhere and when not attaching. As the added mass increases, both the longitudinal vibration resonance frequency and the bending vibration resonance frequency decrease, but the amount of decrease in the bending vibration resonance frequency is larger. Therefore, when the resonance frequency of the bending vibration is higher than the target value with respect to the resonance frequency of the longitudinal vibration, an additional mass may be applied in the vicinity of both ends in the longitudinal direction of the vibrating body 1 (longitudinal vibration of the longitudinal vibration and the bending vibration). . Conversely, when the resonance frequency of the bending vibration is lower than the target value with respect to the resonance frequency of the longitudinal vibration, the mass in the vicinity of both ends in the longitudinal direction of the vibrating body 1 (the antinodes of the longitudinal vibration and the bending vibration) is measured by laser or mechanical. It is only necessary to provide a mass removing portion by removing the hole by a drilling process.

  From the above experimental results, it has been clarified that the resonance frequency of longitudinal vibration and bending vibration can be greatly controlled by providing an additional mass part or a mass removing part at the bending vibration node. The frequency of the longitudinal vibration and the bending vibration can be arbitrarily adjusted by combining various positions of the mass part or the mass removing part or controlling the amount of additional mass or mass removal.

  FIG. 5 shows an additional mass applying unit. FIG. 5 (a) is a diagram showing the configuration of the vibrating body 10. The vibrating body 10 is composed of laminated piezoelectric elements, and includes piezoelectric elements 10b and 10c that contribute to driving and a piezoelectric element 10a that does not contribute to driving. On the upper surface of the piezoelectric element 10a, additional mass applying electrodes 11 (11a to 11c), 12 (12a to 12c), 13 (13a and 13b), 14 (14a and 14b), 15 (15a to 15a) 15c) and 16 (16a to 16c) are provided so that heavy metals such as solder are easily attached. In particular, in the case of solder, molten solder may be applied and fixed, or a solder ball placed on a vibrating body may be melted and fixed through a reflow process.

The additional mass applying electrodes 11 and 12 for applying additional mass are in the vicinity of both ends in the longitudinal direction of the vibrating body 10 (the antinodes of longitudinal vibration and bending vibration), and the additional mass applying electrodes 13 and 14 are in the vicinity of the node of the bending vibration. The additional mass applying electrodes 15 and 16 are provided in the vicinity of the abdomen of bending vibration. The additional mass application electrodes 11 and 12, the additional mass application electrodes 13 and 14, and the additional mass application electrodes 15 and 16 are each assembled. For example, when additional mass is applied to the additional mass application electrode 11, it must be added. Additional mass is also applied to the mass applying electrode 12. By providing the additional mass portion or the mass removal portion symmetrically in the longitudinal direction of the vibrating body 10 in this way, the vibration amplitude distribution becomes uniform without the influence of the additional mass portion and the mass removal portion, and spurious is not generated.

Further, the additional mass is applied to the additional mass applying electrodes 11, 12, 15, 16 so as to be symmetrical with respect to the width direction of the vibrating body 10. For example, when the additional mass is applied to the additional mass application electrode 15a, the additional mass is also applied to the additional mass application electrode 15c. By providing the additional mass part or the mass removal part symmetrically in the width direction of the vibrating body 10 in this way, the vibration amplitude distribution becomes uniform without the influence of the additional mass part and the mass removal part, and spurious is not generated. Of course, the same effect can be obtained even if the additional mass part and the mass removal part are provided only at the center position in the width direction. If the additional mass is applied not only to the front surface but also to the back surface of the vibrating body 10, not only the frequency adjustment range is widened, but also the excitation of bending vibration (spurious) in the thickness direction is prevented. However, it is not always necessary to provide the additional mass symmetrically unless the vibration amplitude distribution is disturbed or spurious vibrations occur due to the additional mass. For example, this can be realized by changing the weight of each additional mass.

  By the way, for example, when a single plate element is used, the additional mass may be directly attached to the driving electrode. However, if the additional mass is a metal such as solder, care must be taken because the additional mass may cause a short circuit between the electrodes. If additional mass is applied to the same surface as the driving electrode, it must be used for driving. It is better to provide an electrode for imparting additional mass separately from the electrode.

Although an ultrasonic motor has been described here as an example of a piezoelectric device, other piezoelectric devices using piezoelectric vibrators in two different vibration modes (longitudinal vibration and bending vibration) as in the present invention, such as gyro sensors and filters (Embodiment 2)
The process of adjusting the resonance frequency of the longitudinal vibration and the bending vibration will be described in detail with reference to FIG. This step includes a resonance frequency evaluation step 20, a frequency adjustment method determination step 21, and a frequency adjustment step 22.

  The resonance frequency evaluation step 20 is basically a step of measuring the resonance frequency of the longitudinal vibration and the bending vibration in the resonance characteristic measurement by the admittance measuring device, but the signal corresponding to the output (voltage, output impedance, etc.) of the actual drive circuit is used. The step of sweeping the frequency and measuring the current peak may be used, or the step of measuring the size of the vibrating body and measuring the deviation from the target value may be used.

  In the frequency adjustment method determination step 21, it is determined, based on the result of the resonance frequency evaluation step 20, how much additional mass is applied to which position, how much mass is removed from which position, and the like. Here, the additional mass or the removed mass may be adjusted at one place (for example, only the additional mass applying electrodes 15 and 16), but based on the result of the resonance characteristic evaluation step 20, a plurality of additional mass applying units, Alternatively, it may be a step of determining whether to add additional mass to a plurality of mass removing unit positions or to remove mass. For example, in the additional mass application electrode 15a, it is determined whether the additional mass is applied only to 15b, the additional mass application 15a, 15c, or all the additional mass application 15a, b, c. This is the case. In this way, the added mass or the removed mass can be controlled.

  When the corresponding piezoelectric device is an ultrasonic motor, the resonance characteristic evaluation step 20 is performed with the support members 3 and the friction members 2 provided on the vibrating bodies 1 and 10 so that the resonance frequency due to the joining of these members is increased. This is desirable because changes are taken into account. The resonance characteristic evaluation step 20 is better performed when the vibrating bodies 1 and 10 and the movable body 7 are in a pressurized state. This is because the change in resonance frequency of longitudinal vibration due to pressurization is different from the change in resonance frequency of flexural vibration. Highly accurate frequency adjustment is possible.

(Embodiment 3)
A configuration of an electronic apparatus having an operation unit driven by the ultrasonic motor of the present invention will be described with reference to FIG. Vibrating bodies 1 and 10 composed of piezoelectric elements, a friction member 3 joined to the vibrating bodies 1 and 10, a moving body 25 that is brought into contact with the friction member 2 by the pressurizing means 6 and frictionally driven, and the moving body 25 are integrated A transmission mechanism 23 that operates in an automatic manner, and an output mechanism 24 that operates based on the operation of the transmission mechanism 23. Here, an example of rotating the moving body 25 as a rotating body will be described.

  Here, the transmission mechanism 23 uses a transmission wheel such as a gear train or a friction wheel. The output mechanism 24 serving as an operating unit includes a paper feed mechanism in a printer, a shutter drive mechanism, a lens drive mechanism, a film winding mechanism in a camera, a pointer in an electronic device and a measuring instrument, and an arm in a robot. In the mechanism and machine tool, a tooth feeding mechanism, a processing member feeding mechanism, and the like are used. Of course, the output mechanism 24 may be directly driven without the transmission mechanism 23.

  Note that an electronic timepiece, a measuring instrument, a camera, a printer, a printing machine, a robot, a machine tool, a game machine, an optical information device, a medical device, a moving device, and the like can be realized as the electronic device in this embodiment. Furthermore, if the moving body 7 is provided with an output shaft and has a power transmission mechanism for transmitting torque from the output shaft, an ultrasonic motor driving device can be realized.

  The ultrasonic motor of the present invention requires a linear motion of the operating portion, and is particularly effective for applications that require positioning. The reading of an information recording device, the driving of a writing head, the lens of a digital camera, a video camera, etc. It can be applied as a driving source for various electronic devices such as driving various functions (calendar driving, etc.) and a toy for a wristwatch that requires driving, small size, thinness, and low power consumption. Similarly, piezoelectric devices such as gyros and sensors using the technology according to the present invention can be used in digital cameras, video cameras, portable information devices, toys, and the like.

It is a figure which shows the structure of the ultrasonic motor of this invention. It is a figure which shows the vibration mode of the vibrating body of this invention. It is a figure which shows the change of the resonant frequency by the frequency adjustment example of this invention. It is a figure which shows the provision position of the additional mass used for the frequency adjustment example of this invention. It is a figure which shows the additional mass provision position of the vibrating body of this invention. It is a block diagram which shows the resonance frequency adjustment method of this invention. It is a block diagram which shows the electronic device using the ultrasonic motor of this invention.

Explanation of symbols

1, 10 Vibrating body
2 Friction member
3 Support member
7, 25 Mobile
11, 12, 13, 14, 15, 16 Additional mass application electrode

Claims (11)

In a piezoelectric device using a combined vibration of a primary longitudinal vibration and a secondary bending vibration in the same plane direction of a vibrating body having a rectangular piezoelectric element,
Said on within the plane of the vibrating body possess the additional mass portion in the section near the bending vibration or mass removal portion which is in a position different from the center position of the vibrator in the longitudinal direction of the vibrator, the added mass The piezoelectric device is characterized in that the part or the mass removing part is provided symmetrically from the center position in the longitudinal direction of the vibrating body . In a piezoelectric device using a combined vibration of a primary longitudinal vibration and a secondary bending vibration in the same plane direction of a vibrating body having a rectangular piezoelectric element,
Said on within the plane of the vibrating body possess the bent belly added near parts by or mass removal portion of the vibrating in the longitudinal direction at a position different from the longitudinal end of the vibrating member, the added mass parts or The piezoelectric device according to claim 1, wherein the mass removing unit is provided symmetrically from a center position in a longitudinal direction of the vibrating body . In a piezoelectric device using a combined vibration of a primary longitudinal vibration and a secondary bending vibration in the same plane direction of a vibrating body having a rectangular piezoelectric element,
Said on said plane and substantially longitudinal tip of the vibrator have a additional mass parts or mass removal portion, wherein the additional mass portion or the mass removal portion is provided symmetrically from the longitudinal center of the vibrating member A piezoelectric device characterized by the above . 4. The piezoelectric device according to claim 1, wherein the additional mass part or the mass removal part is provided symmetrically in the width direction of the vibrating body. 5. 4. The piezoelectric device according to claim 1, wherein the additional mass part or the mass removal part is provided at a center position in a width direction of the vibrating body. 5. The piezoelectric device according to any one of claims 1 to 5, wherein the additional mass portion or the mass removal portion is characterized in that is provided with a plurality on the vibrator. The piezoelectric device according to any one of claims 1 to 6, wherein the additional mass portion is an electrode material, and a mass attached to the additional mass portion is a metal . A method for manufacturing a piezoelectric device according to any one of claims 1 to 7,
  Evaluating the resonance characteristics of the vibrator;
  Selecting the position of the additional mass part or the mass removing part based on the evaluation result of the resonance characteristics;
  A method for manufacturing a piezoelectric device, comprising: adding mass or removing mass. The piezoelectric device according to claim 8, wherein the piezoelectric device is an ultrasonic motor, and the resonance characteristics are evaluated in a state where at least one of a support member and a friction member is attached to the vibrating body. Device manufacturing method. The method for manufacturing a piezoelectric device according to claim 9, wherein the resonance characteristics are evaluated in a state where the vibrating body and the moving body are pressurized . An electronic apparatus comprising: an operating unit driven by the piezoelectric device according to claim 1.

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