JPS59162673A - Actuator - Google Patents

Abstract

PURPOSE:To prevent the structural weakness and the enlargement of a bimorph element and simplify the electrode structure inserted between a piezoelectric element single body by utilizing the transversal oscillation of a piezoelectric element in a thickness direction to drive and control an object to be driven with respect to an actuator which drives and controls the head of an information recording and reproducing device or the like. CONSTITUTION:The piezoelectric element single bodies 31-36 are so laminated that their polarization directions are different from one another by 180 deg.. Electrode layers 41-47 are provided between the piezoelectric element single bodies 31-36 and at the outside faces of the piezoelectric element single bodies 31 and 36. When a voltage of such potential is impressed from a voltage amplifier 24 to a laminated piezoelectric device 23a to expand this device 23a in the thickness direction, and a voltage of such potential is impressed to a laminated piezoelectric device 23b from a voltage amplifier 25 to compress the device 23b in the thickness direction. Even if some external force is applied to a head 22, the position of the head 22 is not deviated considerably because the outsides of both piezoelectric devices 23a and 23b are held firmly by both legs 21a and 21b of a frame body 20 formed with a member of high mechanical strength.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides, for example, a magnetic tape that is inclined with respect to the longitudinal direction [
In addition, there is a so-called helical scanning type VTR that forms a recording track, and an information recording/reproducing device that magnetically or optically forms a concentric spiral recording track on a disk. The present invention relates to an actuator for drive control.

One of the conventional actuators of this type is attached to the tip of a magnetic helatrahymorph element (a type of piezoelectric element), and a predetermined voltage is applied to the bimorph element based on tracking information, thereby generating magnetic force. , gear 4. Some types control the head position so that the center position of the track always coincides with the center position of the track. In the above devices, the mechanical strength of the bimorph element itself is relatively weak, so external forces such as those caused by the tip of the magnetic head coming into contact with the recording surface of a magnetic tape or magnetic disk are applied to the magnetic head. In such a case, the magnetic head may be severely deviated from a predetermined position and moved to another position due to the above-mentioned external force.

In such a case, in order to return the magnet to the optimum operating position, it is necessary to apply a large voltage for correcting the amount of deviation to the bimorph element. Therefore, it is necessary to sufficiently widen the dynamic range of the amplifier for supplying the above-mentioned applied voltage, which poses a considerable problem in terms of cost.

Further, the amount of deviation gives an offset to the tracking servo system. Therefore, in order to absorb the above-mentioned offset, it is necessary to make the serv gain of the tracking servo system extremely large, which also poses a problem in terms of ensuring the stability of the servo system.

r A bimorph element has a structure in which two sheets of thin ceramic are glued together, or a piezoelectric element and a mechanical non-piezoelectric element made of a metal plate or polymer film are glued together. Therefore, in order to move the magnetic head positionally, it is necessary to make the bimorph element sufficiently long.

Long ceramics have weak strength, so thick materials must be used. However, thick guimorph elements do not work well unless the drive voltage is high.

As mentioned above, there is a correlation between the thickness of the guimorph element, the length of the element, the drive voltage, and the amount of deformation (movement).
This makes it difficult to design a drive element suitable for the device.

The present invention is based on these circumstances. The purpose of this is to have sufficiently high mechanical strength so that even if an external force is applied to the magnetic object being driven, the object to be driven can be held stably, and the driving element is long and large. It is an object of the present invention to provide an actuator which can be formed as a whole into a compact structure without becoming bulky, has a simple structure, and is easy to assemble and wire, and is suitable as, for example, a head actuator for a small portable magnetic recording device.

In order to achieve the above object, the present invention is characterized by the following configuration. That is, in the present invention, a frame body with tripods facing each other in parallel at a predetermined distance is formed of a member with high mechanical strength, and the object to be driven is all arranged in the center between the tripods of the frame body, and the object to be driven is The first. A second laminated piezoelectric element is inserted, and these first and second laminated piezoelectric elements are inserted. By applying a control voltage of a predetermined polarity according to drive control information to the second laminated piezoelectric element, the object to be driven is controlled to be driven to a predetermined position. As the second laminated piezoelectric element, a plurality of single piezoelectric elements are arranged alternately at 180 degrees in the polarization direction.
Even if the layers are stacked differently, σ) is used. Thus, in the present invention, it is possible to drive and control an object to be driven by utilizing longitudinal vibration in the thickness direction of a piezoelectric element without using an element with an immorph structure. The present invention is characterized in that it is possible to prevent this, and to simplify the electrode structure inserted between each piezoelectric element, as well as the assembly and wiring.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a plan view showing the configuration of a mechanical section of an embodiment of the present invention, in which 11 is a rotating magnetic disk, 12 is a track formed on the magnetic disk, and 13 is a 2 ．． 1. 14 is an appeal screw provided on the shaft of the motor, and 15 is a head holder that moves in steps in the radial direction of the disk 11 as the ball screw 14 rotates.

FIG. 2 is a perspective view showing a specific structure of the female head holder 15 shown in FIG. In FIG. 2, 20 is an H-shaped frame made of a member having sufficient mechanical strength,
Opposing tripods 21 a + 21 b of this frame 20
In between is a gear, knob G? 1. To the magnetism that it has. 22 on both sides. It is inserted while being held between the second laminated piezoelectric elements 23a and 23b. 1st. Second laminated piezoelectric element 2
A control voltage l of positive or negative potential amplified by voltage amplifiers 24 and 25 is applied to 3a and 23b. Note that the tripods 21a and 21b of the frame body 20 and the first. Second laminated piezoelectric element 2,? a, 23b, and between both sides of the magnetic head 220 and the first and second laminated piezoelectric elements 23a,
23b is bonded with adhesive or the like.

Figure 3 is 1. Second laminated piezoelectric element 238°2,?
It is a figure showing detailed composition of b. However (~ Figure 3 shows
Only the first laminated piezoelectric element 23a is shown at 7. In the figure,
31.32, 33.34°35.36d It is a single piezoelectric element, and the polarization direction is alternately 1800° as shown by the arrow in the figure.
They are laminated in different layers. Each of the above piezoelectric elements 31 to 3
6 and on both outer surfaces of 3) and 36.
．． 42, 43, 44.45, and 46.47 are provided. Odd numbered electrode layer 41, 43, 4 among the above electrode layers
5.47 are commonly connected and connected to the output terminal of the voltage amplifier 24, and even numbered electrode layers 42, 44, and 46 are commonly connected and grounded. Thus, each piezoelectric element 2. A control voltage corresponding to the tracking information voltage amplified by the voltage amplifier 24 is applied in parallel to β1 to β36. As a result, each of the piezoelectric elements 31 to 36 expands in the direction of arrow I in FIG. 3 if the control voltage is at a positive potential, and in the direction of the arrow ■ in FIG. 3 if the control voltage is at a negative potential. to apply a biasing force to the head 22. Note that the direction in which the above biasing force acts on the head 22 is the first direction. Second
Laminated piezoelectric element 2,? a, 23 b to match, 1st. Second piezoelectric element 23a.

23b is controlled so that when one expands, the other compresses.

That is, in FIG. 2, when a voltage having a potential that causes the element 2.7a to expand in the thickness direction is applied from the voltage amplifier 24 to the laminated piezoelectric element 23a, this voltage is applied from the voltage amplifier 25 to the laminated piezoelectric element 23b. A potential voltage is applied so that the element 23b is compressed in the thickness direction. As a result, the head 22 moves in the direction A shown in the figure due to the effects of both 23a and 23b.

FIG. 4 is a diagram showing tracking information detection means. In FIG. 4, there are a pair of heads 51.52d for detecting tracking information. In the detection heads 51 and 52, when the head 22 is in the optimum tracking state, each gap center position of the heads 5 and 52 is set to 1. 4 are set so as to coincide with both ends of the track 12, and move integrally with the head 22 in the width direction of the track 12. The tracking information detection helad 51. ,
Each output of 52 is envelope-detected by envelope detectors 53 and 54, and then sent to a differential amplifier 5.
5. The output of the differential amplifier 55 is given to the voltage amplifiers 24 and 25 as tracking information.

Since this device is configured as described above, when the head 22 generates a tracking error, the detection head 51.5
A difference occurs between the two outputs, and tracking information corresponding to the difference is sent out from the differential amplifier 55. This tracking information is voltage amplified by voltage amplifiers 24 and 25, and applied to the laminated piezoelectric element 23a as a positive or negative potential control voltage.

23b. Therefore, the laminated piezoelectric element 23a
, 23b apply a driving force to the head 22 in the direction A or B as shown in FIG. 2, and perform tracking control so that the center position of the head 22 coincides with the center position of the track 12.

Now, suppose that an external force is applied to the head 22 from the side. However, the head 22 has laminated piezoelectric elements 23 on both sides.
a, 23bK, and both piezoelectric elements 2
Since the outer sides of 3a and 23h are firmly held by both legs 211L and 21b of frame body 20 formed of a member with high mechanical strength, there is no fear that the position of head 22 will be significantly shifted by the external force. Therefore, a large voltage is applied to the piezoelectric elements 23a and 23 for correcting the amount of deviation as in the conventional case.
There is no need to make the dynamic range of the amplifiers 24 and 25 particularly large in order to provide for the offset absorption, and there is no need to ensure servo gain for offset absorption, so stability of the servo system can be obtained. On the other hand, as shown in FIG.
is a pair of laminated piezoelectric elements 23 a, 2, ? between two parallel presses 21a, 21b. Since both sides are equally held under pressure by b, the perpendicularity and parallelism of the head 22 can be easily obtained without any special adjustment means, and the assembly is easy.

As shown in FIGS. 2 and 3, the second laminated piezoelectric elements 23a and 23b utilize longitudinal vibration in the thickness direction of the piezoelectric elements, so they do not have the structural weakness of bimorph elements. , and there is no risk of it becoming too long. Furthermore, as shown in FIG. 3, since the individual piezoelectric elements 31 to 36 are laminated with their polarization directions alternately different by 180 degrees, ``all the electrode layers interposed between the individual piezoelectric elements are It can be shared by two piezoelectric elements adjacent to each other on both sides. As a result, the structure of each electrode layer is simplified and the wiring is also simplified, compared to a structure in which the polarization direction is uniform and the layers are stacked as shown in FIG. In FIG. 5, 6 to 66 are individual piezoelectric elements, 71a, 71b to 75a, and 75b are electrode layers disposed on both sides of each individual piezoelectric element 61 to 65, and 8
1 to 86 are insulating layers. According to this embodiment, the electrode layers 71a, 71b to 75a, and 75b forming each pair are unified, so that the insulating layers 81 to 86 can also be omitted, and the wiring for every other electrode is common. All you have to do is connect.

FIG. 6 is a perspective view showing another embodiment of the invention. 6th
In the figure, 91 is a step motor, 92 is a ball screw, 93 is a U-shaped frame, 94 is a tripod 93a of the frame,
95a and 95b are first and second laminated piezoelectric elements. In this embodiment, the gap position of the head 94 is different from that in FIG. 2 by l-1'90°. Of course, even with such a configuration, the same effects as those of the embodiment described above can be achieved.

Note that the present invention is not limited to the embodiments described above. For example, in the embodiments described above, the present invention is used as a head actuator for a magnetic disk device, but it is also applicable to a helical scanning type VTR. It can also be used with a Rad actuator.However, in this case, the ball screw 14 shown in Figures 2 and 6 is not necessary, and the axis of the frame provided at the yV-Runeno insertion site is installed parallel to the axis of the rotary sill. Furthermore, it can be used as an optical radar actuator or focusing actuator for an optical disc device.

As explained above, according to the present invention, the driven object placed between the tripods of the frame made of a member with high mechanical strength is moved to the first. The object to be driven is controlled to be driven to a predetermined position by sandwiching the object from both sides with the second laminated piezoelectric element and applying a control voltage of a predetermined polarity to each of these piezoelectric elements according to drive control information. [Also, since it makes full use of the vertical vibration in the thickness direction of the piezoelectric element, the mechanical strength of the driving element is sufficiently large, and even if an external force is applied to the driven object, it will not be able to move the driven object.] It can be stably held, and the drive element does not become long, making the entire structure compact. According to the present invention, 1. With the second laminated piezoelectric element (~), each piezoelectric element is laminated with the polarization direction alternately anisotropic by 180 degrees (since a tray is used, there is a gap between each piezoelectric element body). The inserted electrode structure can be simplified, the structure is simple, assembly and wiring are easy, and it is possible to provide an actuator suitable for use as, for example, a head actuator for a small portable magnetic recording device.

[Brief explanation of drawings]

1 to 4 are views showing one embodiment of the present invention, in which FIG. 1 is a sectional view showing the structure of the mechanism section, FIG. 2 is a perspective view showing the specific structure of the head holder, and FIG. Figure 1. FIG. 4 is a diagram showing the detailed configuration of the second laminated piezoelectric element, FIG. 4 is a diagram showing the tracking information detection means, and FIG. FIG. 6 is a perspective view of a door holder showing another embodiment of the present invention. 11... Rotating magnetic disk, 12... Recording track. 13.91...Step motor for head feeding, 1
4.92... Sol screw, 15... To, do holder, 2
0, 93--frame body, 21 a, 2 l b,
9.7 a. 9,? b-・Two presses, 22.94-・Magnetic head, 2
3a. 23b, 95a, 95b - laminated piezoelectric element,
24゜25...Voltage amplifier, 31-36...Piezoelectric element alone, 41-47...Electrode layer, 51.52...To playback for tracking information detection, 7 de, 53.54...Enperoso Detector, 55...Differential amplifier, Applicant's representative Patent attorney Takehiko Suzue Figure 1 Figure 2 Figure 3 Figure 41

Claims (1)

[Claims] A frame body formed of a member with high mechanical strength and having tripods facing each other in parallel at a predetermined distance, a driven object disposed at the center between the tripods of this frame body, and one side of this driven target object. and an inner surface of the one leg, and a second piezoelectric element inserted between the other surface of the driven object and the inner surface of the other leg. A laminated piezoelectric element,
Above 1. means for applying a control voltage of a predetermined polarity according to the drive control information to the second laminated piezoelectric element to drive and control the driven object to a predetermined position; An actuator characterized in that each of the second laminated piezoelectric elements is a plurality of piezoelectric elements laminated with their polarization directions alternately different by 180 degrees.