JPH0481357B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to a piezoelectric displacement device suitable as a recording/reproducing head actuator for a VTR, magnetic disk device, optical disk device, electronic camera, etc. [Technical background of the invention and its problems] This type of conventional piezoelectric displacement device has a bimorph structure. FIG. 1 is a diagram showing an example thereof. Piezoelectric element 1
In this example, electrodes 3a, 3b, 3c, and 3d are attached to both sides of piezoelectric ceramics 2a and 2b such as PZT, respectively, and polarization is performed, and these are glued together so that the polarization axes 4a and 4b are in opposite directions. They are bonded together using an adhesive (not shown). For example, a ferrite head 5 is attached to the tip of the piezoelectric element 1 via a seat plate 6. The base end (upper end in the figure) of the piezoelectric element 1 is fixed to a pedestal 7, and a signal voltage of a predetermined polarity is applied in series to the electrodes 3a to 3d through lead terminals 8a and 8b. There is. Now, when a signal voltage as shown in the figure is applied to the lead terminals 8a and 8b, the thickness of one piezoelectric ceramic 2a increases and the thickness of the other piezoelectric ceramic 2b decreases. As a result, the tip of the piezoelectric element 1 is deformed into a bimetallic shape,
Ferrite head 5 is displaced in the direction of arrow 9A.
By reversing the polarity of the signal voltages applied to lead terminals 8a and 8b, ferrite head 5 is displaced in the direction of arrow 9B. Note that the piezoelectric ceramics 2a, 2b are arranged so that the polarization axes 4a, 4b are in the same direction.
There is also a structure in which the electrodes 3a, 3b, 3c, and 3d are glued together and a signal voltage is applied in parallel to each electrode, but the operating principle is the same as the above-mentioned example. Thus, according to the piezoelectric displacement device having the above configuration,
Tracking control can be performed by displacing the ferrite head 5 on the magnetic recording medium. The relationship between the displacement amount y and the applied voltage V in the piezoelectric displacement device having the above configuration is expressed as y=3l ² /t ² d ₃₁ V. However, l is the length of piezoelectric element 1, and t
is the thickness and _d31 is the piezoelectric constant. Therefore, in order to increase the displacement y for a constant applied voltage,
It is necessary to reduce the thickness t and increase the length l of the piezoelectric element 1. However, in this case, the mechanical strength of the piezoelectric element 1 is significantly impaired. For this reason, a thin plate of titanium, copper, brass, stainless steel, etc. is usually inserted as a reinforcing material at the interface between the two piezoelectric ceramics 2a and 2b, but although this increases the mechanical strength to a certain extent, it also However, there were problems in that the amount of displacement was reduced and the size was increased. Additionally, in the past, tracking control, azimuth adjustment,
There was no small-sized head moving device suitable for highly accurate and minute displacement of the head, such as protrusion amount adjustment, wobbling displacement, etc. A head moving device using a bimorph element is large in size and has insufficient mechanical strength, making it impractical. [Object of the Invention] An object of the present invention is to provide a piezoelectric displacement device that is small in size, has high mechanical strength, has a large displacement amount with respect to applied voltage, and has high conversion efficiency. Another object of the present invention is to provide a compact and robust head moving device suitable for finely displacing a head with high precision. [Summary of the Invention] In order to achieve the above object, the present invention is characterized by the following configuration. A plurality of thickness-slide piezoelectric vibrators having polarization axes in a direction parallel to the electrode surface are stacked together to form a laminate so that the polarization axes are parallel to each other, one end surface of this laminate is fixed, and the other end surface is fixed. A piezoelectric displacement device was constructed by attaching a displaced body and applying a signal voltage to each piezoelectric vibrator to displace the displaced body in the same direction as the sliding direction of each piezoelectric vibrator. ...Figure 3 The laminate described above is formed by stacking thickness-shear piezoelectric vibrators such that the direction of their polarization axes alternately changes for each layer, and the thickness-shear piezoelectric vibrators are laminated adjacently. A common electrode was placed between them. …Fourth
The common electrode in the above has a folded part in which each electrode of both thickness-sliding piezoelectric vibrators stacked adjacent to each other is folded back at the side end of the piezoelectric vibrator. The parts that should have the same polarity are electrically connected. ...Fig. 11 The above laminate is formed by stacking thickness-shear piezoelectric vibrators such that their polarization axes are in the same direction, and each of the thickness-shear piezoelectric vibrators stacked adjacently The electrodes were insulated, and the electrodes that should have the same polarity were electrically connected. ...Figure 8 One end side of an actuator that has a laminate formed by stacking a plurality of thickness-shear piezoelectric vibrators whose polarization axes are parallel to each other so that their polarization axes are parallel to each other as a drive displacement source. The head is attached to the head, and the other end of the actuator is connected to a head carrier (corresponding to the head support arm 55 in FIG. 13) for applying a relatively large displacement to the head to form a head moving device. did. ...FIGS. 13 and 17 The actuator described above is configured to displace the head in the tracking control direction of the information recording track. The actuator described above is configured to displace the head in the azimuth adjustment direction. The actuator described above is configured to displace the head in a direction that adjusts the amount of protrusion relative to the corresponding information recording medium. The actuator described above is configured to cause wobbling displacement of the head. The actuator in the above is
One end of the head is provided with a connecting member for attaching the head so that the actuator and the head stand side by side facing the information recording medium. ...Fig. 13c, Fig. 14 Fig. 2 is a diagram for explaining the principle of the present invention. The thickness-shear piezoelectric vibrator 11 has electrodes 13a and 13b attached to both sides of a piezoelectric ceramic 12, and a polarization axis 1 in a direction parallel to these electrodes 13a and 13b.
It has a structure with 4. Therefore, "thickness shear vibration" is excited as the main vibration mode, as shown by the broken line. Note that an arrow 15 in the figure indicates the direction of the electric field. Now, when voltage V is applied from the power supply 16 to the electrodes 13a and 13b, a displacement amount of y∝d ₁₅ V occurs in the longitudinal direction of the vibrator 11. By the way, the piezoelectric constants include d ₃₁ , which is closely related to piezoelectric bimorph depending on the excited vibration mode or displacement mode, d ₃₃ , which is related to thickness vibration, and thickness-shear piezoelectric vibration, which is closely related to the displacement device according to the present invention. There are values such as d ₁₅ , which are specific to each material. The following table shows the piezoelectric constant of each mode of typical commercially available PZT ceramics.

[Embodiments of the invention]

3 to 5 are diagrams showing a first embodiment of the present invention. FIG. 3 is a side view showing the entire head actuator, and reference numeral 21 in the figure is a laminate in which a plurality of thin plate thickness shear piezoelectric vibrators 11 are laminated.
One end surface of this laminate 21 is fixed to a pedestal 22. A seat plate 23 is provided at the center of the other end surface of the laminate 21.
A magnetic head 24 as a displaced body is attached via the magnetic head 24. Signal voltage application terminals 25a and 25b are connected to the electrodes of each piezoelectric vibrator 11 via lead wires 26a and 26b. FIG. 4 is an enlarged view of part F of the laminate 21,
The piezoelectric ceramics 12 of the piezoelectric vibrators 11-1, 11-2, . Also, 27-1, 27-2, ...27- in Figure 4
N is an electrode lead conductor interposed between each piezoelectric vibrator, and in terms of an electric circuit, every other piezoelectric vibrator is commonly connected as shown in FIG. 5, and is collectively connected to terminals 25a and 25b, respectively. Now, when a voltage V is applied from the power supply 28 to the signal voltage application terminals 25a and 25b as shown in FIG. 5, a displacement y proportional to the voltage V is generated in the laminated body 21. In this way, tracking control of the head 24, etc. can be performed. In this embodiment, since the polarization directions of the piezoelectric vibrators 11 are oriented in different directions for every other layer, it is necessary to insulate adjacent electrodes between the piezoelectric vibrators 11-1, 11-2,...11-N. None. Therefore, the thickness of the laminate 21 and, by extension, the thickness of the entire head actuator can be reduced. 6 to 8 show a second embodiment of the present invention. In this embodiment, the piezoelectric vibrators 11 are arranged so that their polarization directions are all in the same direction. Therefore, in this embodiment, insulating members 29-1 and 29-2 are used to insulate each electrode of adjacent piezoelectric vibrators 11 from each other.
9-2...29-(N-1) is interposed. In this embodiment as well, the same operation as in the previous embodiment can be performed. FIG. 9 shows a third embodiment of the present invention. This embodiment is characterized in that a head 24 is attached via a seat plate 23 to an end on the other end of a thickness-shear vibrator laminate 21 whose one end is fixed to a pedestal 22. FIG. 10 shows a fourth embodiment of the present invention. In this embodiment, a support arm 31 is attached to a vertical pedestal 30, one end surface of the laminate 21 is fixed to this arm 31, and a head 24 is attached to the end of the laminate 21 as in the case of FIG. It is characterized by FIG. 11 shows a fifth embodiment of the present invention, which is a modification of the first embodiment shown in FIGS. 3 to 5. That is, in this embodiment, the ends of each electrode 13a, 13b of the piezoelectric vibrator 11 are connected to the side surface of the laminate 21 without using the electrode lead-out conductors 27-1, 27-2...27-N shown in FIG. It extends in an L-shape, and adjacent parts are integrally joined by solder 41, and a lead wire 42 is connected to this part. According to this embodiment, compared to the first embodiment, the thickness of the laminate 21 can be further reduced by not using the electrode lead-out conductors 27-1, 27-2, . . . 27-N, and the material cost can be reduced. There is. Here, let us examine the performance when material B in the table above is used as the piezoelectric ceramic 12 of the thickness-shear piezoelectric vibrator 11 in each of the embodiments shown in FIGS. 3 to 11. Laminated body 2 in which thickness shear piezoelectric vibrators 11 are laminated
When the number of stacked layers of 1 is n and the applied voltage is V volts, the displacement y [m] can be expressed as y=n×d ₁₅ ×V [m]. Here n=30, d=930
×10 ^-12 [m/v], V = ±500 (V), then the displacement y is y = ±14 [μm]. This value applies to tracks such as 2-inch to 3-inch small magnetic disks. This displacement amount is enough to be used as a head actuator for tracking.On the other hand, as shown in Fig. 12, for one piezoelectric vibrator 11, the length of the vertical side is P, and the length of the horizontal side is Q. It has been experimentally revealed that noise mode vibrations can be suppressed by setting the ratio of the lengths of each side to P:Q:R=10:30:1, where the thickness is R. So now,
The above R is set to 0.15 [mm] including the electrode, and Figure 3~
In the case of an actuator structure as shown in FIG. 5, if n=30 layers, the size of the actuator is 1.5 [mm] in length, 4.5 [mm] in width, and 4.5 [mm] in thickness.
As described above, since the device is sufficiently small in size, it can be used in portable magnetic disk recording and reproducing devices, electronic cameras, and the like. 13a, b, c to 17 are diagrams showing specific examples of use of the piezoelectric displacement device of the present invention as a head actuator of a magnetic disk recording/reproducing device. Figures 13a, b, and c are examples in which the present invention is applied to Japanese Patent Application No. 126132/1983, which was previously filed by the applicant. Japanese Patent Application No. 57-126132 discloses a disk-shaped recording medium (hereinafter abbreviated as "disk") with a head that performs recording/reproduction on the outer circumferential surface and a head that performs recording/reproduction on the inner circumferential surface of the disk. By cutting the head and fixing it to both ends of a head support arm that moves back and forth in a straight line, and using these two heads in a time-sharing or signal-dividing manner, high-quality recording and playback can be achieved even when the disk has a small diameter. This is an imaging device that enables In FIG. 13a, 50 is a disk;
Its central portion is fitted into the shaft 52 of a direct drive type brushless servo motor 51. Thus, this disk 50 is 30 [rps] or 60 [rps]
Rotates at high speed. The two head actuators 53 and 54 according to the present invention are connected to the head support arm 5.
It is attached to a predetermined position on disk 5, and
It faces the 0 recording surface. A rack 56 is provided at the bottom of one end of the head support arm 55, and this rack 56 is connected to the head movement motor 57.
It meshes with a pinion 58 attached to the shaft. Thus, the head support arm 55 moves in a direction transverse to the center of rotation of the disk 50 as shown by the arrow h as the head movement motor 57 rotates. FIG. 13b is a view of the head support arm 55 viewed from the disk 50 side. The mounting positions 53' and 54' of the head actuators 53 and 54 are slightly offset from the center B-B' of the head support arm 55. Reference numerals 59 and 60 indicate notched holes provided in the head support arm 55 for mounting the head, and the centers of these holes are located on B-B'. 61 is the motor shaft 52 when the head support arm 55 moves.
This is a motor shaft fitting hole provided so as not to hit the motor shaft. FIG. 13c is a perspective view showing a state in which the head actuator 53 is installed at the position A-A' in b. The proximal end of the head actuator 53 is fixed at a mounting position on the head support arm 55. One end of a connecting member 62 is fixed to the displacement end of the head actuator. A head 63 is fixed to the other end of the connecting member 62.
The gap 64 of the head 63 is arranged to coincide with the line BB' of b. Thus, the head 63 is coarsely moved in the radial direction of the disk by the rotation of the motor 57, and then finely moved in a direction perpendicular to the tracks on the disk by the head actuator 53. That is, tracking control is performed by applying a control voltage based on tracking information to the head actuator 53. FIG. 14 is a modification in which the relative mounting positional relationship between the head actuator 53 and the magnetic head 63 in FIG. 13c is rotated by 90 degrees. FIGS. 15 to 17 show examples in which the head actuator according to the present invention is used for purposes other than tracking. FIG. 15 shows an embodiment in which a head actuator 53 is used for adjusting the head touch. That is, the example of the present invention is an example in which the device is used in the same way as a focusing actuator for an optical disk. In high-density recording, an important issue is how to eliminate the spacing loss caused between the magnetic head and the recording medium, but according to this embodiment, the spacing can be controlled with an accuracy of less than .mu.m. FIG. 16 shows an embodiment in which the head actuator 53 is configured as an actuator for adjusting the azimuth of the magnetic head 63. That is, the head 63 is held between a pair of actuators 53A and 53B, and the inclination of the head gap 64 is adjusted. In short-wavelength recording where the recording wavelength is 1 [μm] or less, a slight deviation in the azimuth angle causes azimuth loss and leads to a reduction in reproduction sensitivity, but in this embodiment, angle adjustment of 1 minute or less is possible. FIG. 17 shows an embodiment in which the head actuator 53 is applied to a wobbling type head actuator. In other words, the head actuator 53
An alternating voltage is applied from an AC power supply 65 to the magnetic head 63 to vibrate the magnetic head 63 in the track width direction, and track deviation information is obtained by envelope detection of the reproduced output. As shown in the above embodiments, the head actuator according to the present invention can be formed into a very small size, so it can be used, for example, in VTRs, magnetic disk recording/playback devices, etc.
Magnetic head drive (tracking,
Ideal for azimuth adjustment, head touch pressure adjustment, etc.). It is also suitable for driving (tracking, focusing, etc.) optical heads such as optical disks and opto-magnetic disks. Since this head actuator is of a laminated type, it has the advantage that the number of laminated layers can be changed as appropriate depending on the amount of displacement necessary for the device to which it is applied. Furthermore, since it is much superior in mechanical strength and output power to a bimorph structure, it is possible to simultaneously displace a plurality of heads with a single head actuator. Note that the present invention is not limited to the embodiments described above. For example, in FIGS. 13a, b, and c, two head actuators are installed, but a plurality of head actuators may be installed depending on the number of heads to be attached. Also, Figure 13a,
A perpendicular magnetic recording head may be used in place of the magnetic head 63 in FIGS. b, c to 17. Further, in the above-described embodiment, the present invention was applied to a head actuator, but it is of course applicable to a wide range of displaced objects that require fine displacement control, such as various sensors, light emitting elements, mirrors, etc. be. [Effects of the Invention] As explained above, according to the present invention, thickness-shear piezoelectric vibrators are stacked, one end surface thereof is fixed, a displaced body is attached to the other end surface, and a signal voltage is applied to the piezoelectric vibrator. By applying the voltage, the object to be displaced is displaced in the sliding direction of the piezoelectric vibrator, so it is possible to provide a piezoelectric displacement device that is small, has high mechanical strength, and has high conversion efficiency. Further, it is possible to provide a compact and robust head moving device suitable for minutely moving the head with high precision.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of a conventional example, FIG. 2 is a diagram for explaining the principle of the present invention, FIGS. 3 to 5 are diagrams showing the first embodiment of the present invention, and FIGS. Figure 8 shows the second embodiment of the invention, Figures 9 to 11 show the third to fifth embodiments of the invention, and Figure 12 shows the thickness of the first to fifth embodiments. Figures 13a, b, c to 17, which are diagrams for explaining the performance of the sliding piezoelectric vibrator, are diagrams showing specific examples of use of the present invention as a head actuator. 11... Thickness shear piezoelectric vibrator, 12... Piezoelectric ceramics, 13a, 13b... Electrode, 14...
Polarization direction, 15... Electric field direction, 21... Piezoelectric vibrator laminate, 22... Pedestal, 23... Seat plate, 24...
...Magnetic head, 27-1 to 27-N... Electrode lead conductor, 29-1 to 29-(N-1)... Insulating member, 31... Support arm, 41... Solder, 42
... Lead wire, 50 ... Disc-shaped recording medium (disk), 51 ... Direct drive brushless servo motor, 53, 54 ... Head actuator, 5
5... Head support arm, 62... Connection member, 6
3...Magnetic head, 64...Head gap.

Claims (1)

[Claims] 1. A laminate is formed by laminating a plurality of thickness-shear piezoelectric vibrators having their polarization axes in a direction parallel to the electrode plane so that their polarization axes are parallel, and one of the laminates By fixing one end face, attaching a displaced object to the other end face, and applying a signal voltage to each of the piezoelectric vibrators,
A piezoelectric displacement device, characterized in that the displaced body is displaced in the same direction as the sliding direction of each piezoelectric vibrator. 2 The above laminate is composed of thickness-shear piezoelectric vibrators stacked such that the direction of their polarization axes alternately changes for each layer, and a common layer between the thickness-shear piezoelectric vibrators stacked adjacent to each other. A piezoelectric displacement device according to claim 1, which comprises electrodes arranged therein. 3. The common electrode has a folded part obtained by folding each electrode of the double-thickness sliding piezoelectric vibrator stacked adjacent to each other at the side end of the piezoelectric vibrator. 3. The piezoelectric displacement device according to claim 2, wherein the objects to be moved are electrically connected to each other. 4 The above laminate is formed by stacking thickness-shear piezoelectric vibrators such that their polarization axes are in the same direction, and each electrode of the thickness-shear piezoelectric vibrators stacked adjacently is insulated. 3. The piezoelectric displacement device according to claim 2, wherein electrodes having the same polarity are electrically connected to each other. 5. The head is attached to one end side of an actuator which has a laminate formed by laminating a plurality of thickness-slip piezoelectric vibrators having polarization axes in a direction parallel to the electrode surface so that the polarization axes are parallel to each other as a drive displacement generation source. A head moving device characterized in that the actuator is attached to the head and the other end side of the actuator is connected to a head carrier for applying a relatively large displacement to the head. 6. A head moving device according to claim 5, wherein said actuator is adapted to displace said head in a tracking control direction of an information recording track. 7. The head moving device according to claim 5, wherein the actuator is configured to displace the head in an azimuth adjustment direction. 8. The head moving device according to claim 5, wherein the actuator is configured to displace the head in a direction that adjusts the amount of protrusion of the head relative to the corresponding information recording medium. 9. The head moving device according to claim 5, wherein the actuator is configured to cause wobbling displacement of the head. 10 The actuator has a connecting member on one end thereof for attaching the head so that the actuator and the head stand side by side facing the information recording medium. Head moving device according to any one of clauses 9.