JPH0150193B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a displacement magnifying device, and more particularly, to a VTR.
The present invention relates to a displacement magnifying device suitable for an actuator of a magnetic head for tracking correction of an apparatus.

BACKGROUND ART In general, in a VTR device, as shown in FIGS. 3 and 4, recording is performed at 180° symmetrical positions on the periphery of a rotary cylinder 2, which is arranged with its rotation axis slightly inclined with respect to the running direction of the magnetic tape 1.・Magnetic head 3 for playback
A and 3b are attached to the recording track, which is inclined at a predetermined angle on the magnetic tape 1 which runs by rotating the rotary cylinder 2 at a constant speed as shown in FIG.
A ₁ , B ₁ , A ₂ , B ₂ , ... Above the magnetic head 3
A and 3b are scanned alternately to perform recording and reproduction.

The above-mentioned VTR devices generally have variable speed special playback functions such as slow playback and speed search. For example, during slow playback, the running speed of the magnetic tape 1 is slowed down so that the magnetic heads 3a and 3b can play one recording track. The data is transmitted at a speed of 1/n by being read n times at a time. In addition, during the speed search, the running speed of the magnetic tape 1 is increased and the magnetic heads 3a and 3b are moved to (n-1).
By skipping and scanning the recording tracks, reproduction is performed at n times the speed. By the way, during this special reproduction, since the rotating cylinder 2 of the VTR device rotates at a constant speed, the magnetic heads 3a and 3b do not accurately scan the recording track, resulting in noise bands in the reproduced image.

Therefore, in order to prevent the generation of noise due to the magnetic heads 3a, 3b being off track, tracking is performed in which the magnetic heads 3a, 3b are displaced by a predetermined amount in a direction that corrects the above track deviation during variable speed special playback to follow the recording track. Requires correction.

As an actuator for the magnetic heads 3a and 3b for this tracking correction, the applicant has
We have previously applied for a displacement magnification device using a laminated piezoelectric material (Japanese Patent Application No. 1983-93470 and Japanese Patent Application No. 1983-
No. 164148). This displacement magnifying device consists of a laminated piezoelectric material that expands and deforms in accordance with applied voltage, a metal plate and a buckling spring connected to the laminated piezoelectric material,
The magnetic heads 3a, 3b are attached to this buckling spring. The magnetic head 3 is attached to a predetermined position of the rotating cylinder 2 via the displacement magnifying device.
a and 3b expand and contract the laminated piezoelectric body according to the voltage value applied to the laminated piezoelectric body of the displacement magnifying device during special reproduction, and the deformation of the laminated piezoelectric body is caused by the metal plate and the seat. By expanding with a bending spring, it is displaced by a predetermined amount in a direction that corrects for off-track, and follows the recording track.

Problems to be Solved by the Invention As mentioned above, the displacement magnifying device is composed of three different materials: a laminated piezoelectric material, a metal plate, and a buckling spring, so the temperature characteristics of each material also differ. However, the operating temperature range is limited. In other words, since the thermal expansion coefficients of the laminated piezoelectric body, metal plate, and buckling spring are different, the three materials undergo thermal expansion and deformation due to the temperature rise during use of the VTR device, and the amount of deformation of each material changes. As a result, the magnetic head attached to the displacement magnifying device may be displaced by more than the recording track width of the magnetic tape. In this case, it becomes difficult to set the magnetic head to the initial position by tracking correction during special reproduction.

Means for Solving the Problems The present invention has been proposed in view of the above problems, and the materials of the three constituent members are selected so that the amount of deformation due to temperature rise is offset, and the operating temperature range is The focus is on expansion. In other words, the technical means to solve this problem are:
a laminated piezoelectric body that expands and deforms depending on the magnitude of an applied voltage; a pair of arms that have one end connected to the laminated piezoelectric body to expand the amount of displacement of the laminated piezoelectric body;
It consists of a band-shaped buckling spring bridged between the other ends of the arm, and the laminated piezoelectric body, the arm, and the buckling spring can expand and change the position of the buckling spring in response to temperature changes. In order to minimize the overall size, the above three materials are combined by selecting materials having a desired thermal expansion temperature coefficient.

Effect If the materials of the laminated piezoelectric body, the arm, and the buckling spring are selected so that the amount of expansion displacement due to temperature changes during use of the device is as small as possible, as in the above technical means, The above-mentioned problems can be easily solved by expanding the operating temperature range of the device.

Embodiment An embodiment in which the displacement amplifying device according to the present invention is applied to an actuator of a magnetic head in a VTR device will be described with reference to FIGS. 1 and 2. In FIGS. 1 and 2, 4 is a metal plate for enlarging the displacement of a laminated piezoelectric body, which will be described later, and this metal plate 4 is connected to the rotating cylinder 2 (see FIGS. 3 and 4). A portal-shaped fixed base 5 fixed to the fixed base 5, a pair of L-shaped arms 6, 6 arranged symmetrically on both sides of the fixed base 5, and one end 6 of the fixed base 5 and the arms 6, 6.
a, 6a, and one end portions 6a, 6 of both arms 6, 6.
It is composed of a thin and flexible connecting part 8 that connects the parts a to each other. 9 is a laminated piezoelectric material such as a laminated ceramic sandwiched between the connecting portion 8 and the center of the fixed base 5; 10 is a free end portion 6b of both arms 6, 6;
A buckling spring in the form of a band plate fixed to the bridge b, and a head mounting portion 11 provided at the center of this buckling spring 10.
Magnetic heads 3a and 3b are fixed to the magnetic heads 3a and 3b.

In tracking correction during special playback such as slow and speed search by a VTR device, when a driving voltage according to a tracking correction signal is applied to the laminated piezoelectric body 9, the laminated piezoelectric body The body 9 expands, and in response to the expansion of the laminated piezoelectric body 9, the arms 6, 6 rotate about the hinge parts 7, 7 as fulcrums. This rotation of both arms 6, 6 causes the free ends 6b, 6b of both arms 6, 6 to expand the amount of displacement of the laminated piezoelectric body 9, as shown in FIGS.
The buckling spring 10 is displaced in the direction of the solid arrow in the figure, and the buckling spring 10 is
The free ends 6b, 6b of the arms 6, 6 are displaced in the direction of the solid line arrow in FIG.
Tracking correction of b is performed.

By the way, in the displacement magnifying device used for tracking correction in special playback of the above-mentioned VTR device,
Due to temperature rise during use, the laminated piezoelectric body 9, metal plate 4, and buckling spring 10 constituting the displacement amplifying device undergo thermal expansion and deformation, which not only limits the operating temperature range, but also causes the magnetic head 3a to , 3a is also difficult to set, so it is necessary to select the respective materials so that the amount of deformation caused by the temperature rise of the three mentioned above cancels out. Currently, laminated ceramic is used as the laminated piezoelectric body 9, and phosphor bronze is used as the buckling spring 10, so the final value is determined by the material of the metal plate 4.

Here, Tc is the thermal expansion coefficient of the material of the laminated piezoelectric body 9, that is, laminated ceramic, T _P is the thermal expansion coefficient of the material of the buckling spring 10, that is, phosphor bronze, and T is the thermal expansion coefficient of the material of the metal plate 4. T _K , and the metal plate 4
and the displacement magnification factors of the buckling spring 10 are α ₁ and α ₂ , the displacement coefficient N _A of the metal plate 4 due to temperature rise is as follows:
N _A = α ₂ (Tc - T _K ), displacement coefficient N _B of buckling spring 10
becomes N _B =α ₁ (T _P −T _K ). Therefore, the overall expansion displacement coefficient N due to the buckling spring 10 of the displacement expansion device is N=N _A +N _B = α ₁ (Tc − T _K ) + α ₂ (T _P −
T _K ) In the experiments conducted by the applicant, SUS (stainless steel), SKD (tool steel), and Invar (resistive expansion alloy) were used as the materials for the metal plate 4, and of each material, laminated piezoelectric 9. Use a desired material so that the amount of deformation due to the temperature rise of the metal plate 4 and the buckling spring 10 is canceled out, and the overall expansion displacement amount of the buckling spring 10 is equal to or less than the recording track width of the magnetic tape, for example, 30 μm. was selected. In this experiment, Tc=−
As a result of using the laminated piezoelectric material 9 and the buckling spring 10 having respective thermal expansion coefficients of 44×10 ^-7 /℃ and T _P =180×10 ^-7 /℃, in the case of the SUS metal plate 4, the The expansion displacement amount of the buckling spring 10 became +60 μm from the thermal expansion coefficient T _K =170×10 ^-7 /°C. In addition, in the case of the metal plate 4 made from SKD, its thermal expansion coefficient T _K = 130 × 10 ^-7 /
℃, the above expansion displacement amount is +10 μm, and in the case of the metal plate 4 made of Invar, its thermal expansion coefficient T _K
=35×10 ^-7 /°C, the expanded displacement amount became -110 μm. Note that the above expansion displacement amount is experimental data obtained when the temperature was raised from room temperature to 80°C.

From this experimental result, when SKD is selected as the material for the metal plate 4, the overall expansion displacement due to the temperature rise of the buckling spring 10 can be made less than the recording track width of the magnetic tape, and the expansion due to the temperature rise. It becomes possible to obtain an optimal displacement magnification device with a small amount of displacement.

In the above embodiment, a case has been described in which the present invention is applied to an actuator of a magnetic head used for tracking correction of a VTR device, but the present invention is not limited to this, and can be applied to amplify the displacement of something other than the magnetic head. Of course, it is also applicable to cases where

Effects of the Invention According to the present invention, each material is selected so that the amount of expanded displacement due to temperature rise is as small as possible, so that the operating temperature range of the device is expanded and the initial displacement position can be easily set. This makes it possible to provide a displacement amplifying device with excellent temperature characteristics.

[Brief explanation of drawings]

FIG. 1 is a plan view showing an embodiment in which a displacement amplifying device according to the present invention is applied to an actuator of a magnetic head, and FIG. 2 is a front view of FIG. 1. Fig. 3 is a perspective view showing the rotating cylinder and magnetic tape of a general VTR device, Fig. 4 is a plan view of Fig. 3, and Fig. 5
The figure is a partial plan view showing a recording track of a magnetic tape. 6...Arm, 9...Laminated piezoelectric material, 10...
Buckling spring.

Claims (1)

[Claims] 1. One end of the laminated piezoelectric body that expands and contracts depending on the magnitude of the applied voltage is connected to the bottom of the gate-shaped fixed base, and the other end of the laminated piezoelectric body is connected to both legs of the gate-shaped fixed base. A metal plate that is connected by a hinge part provided in a part of the part and has one end part of a pair of symmetrically arranged L-shaped arms connected to the connected connecting part, and a free end part of the pair of L-shaped arms. In a displacement amplifying device composed of a buckling spring that is bridged between strips and has a workpiece attachment part formed in the center, the thermal expansion coefficient Tc of the laminated piezoelectric material, the thermal expansion coefficient Tk of the metal plate material, Between the thermal expansion coefficient Tp of the buckling spring material, the displacement magnification rate α ₁ determined by the shape of the metal plate, and the displacement magnification rate α ₂ determined by the length and initial bending amount of the buckling spring, |α ₁ (Tc− A displacement magnifying device characterized in that the displacement magnifying device is combined so that the following relationship holds: Tk) + α ₂ (Tp − Tk) | ≦200×10 ^-7 /°C