JP3235174B2 - 2-axis actuator mechanism - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention employs a two-axis structure comprising a coarse movement mechanism and a fine movement mechanism for performing fine positioning over a wide vibration frequency band in an actuator mechanism. By using an elastically deformed vibrator utilizing electrostriction, magnetostriction, etc. for the mechanism for fine movement related to driving, miniaturization of the device and reduction of unnecessary vibration are achieved,
In particular, an object of the present invention is to provide a novel two-axis actuator mechanism capable of improving the characteristics of an actuator in a low frequency range.

[0002]

2. Description of the Related Art Generally, in order to increase the track density of a hard disk drive, it is required to increase the speed of tracking control and improve the accuracy.

The movement of the magnetic head to a predetermined track is usually performed by controlling the rotation of a head arm that supports the magnetic head, and the magnetic head is finely positioned with respect to the track by a rotary actuator mechanism.

At this time, regarding the control of the actuator, it is difficult to obtain an ideal performance over a wide band due to the characteristics of the actuator. Therefore, two types of control divisions, coarse movement and fine movement, are adopted. In many cases, the approximate positioning of the magnetic head with respect to the track is performed, and then the control is shifted to the fine movement control to perform the fine positioning with high accuracy.

As a structure of a two-axis actuator corresponding to such a division of positioning accuracy, there is known a structure in which an actuator for fine movement is mounted on an actuator for coarse movement.

[0006]

However, the conventional actuator mechanism generally has problems such as a complicated structure and a difficulty in reducing unnecessary vibrations which hinder control. There is.

[0007] For example, regarding the former problem, since the actuator for fine movement is mounted on the actuator for coarse movement, problems such as an increase in weight and deterioration in rigidity become problems.

[0008] The latter problem is disadvantageous in that coupled vibration is generated due to the actuator forming a coupled system and resonance is easily generated.

Further, since the conventional mechanism has a limitation in tracking control as described below, there is a problem in realizing minute and high-precision positioning control corresponding to high density. become.

FIG. 7 is a graph conceptually showing the relationship between the input torque and the displacement as an index indicating the characteristics of the actuator mechanism (known as the i-θ characteristic), and the horizontal axis. Is selected as the logarithmic axis of the vibration frequency, and the vertical axis is selected as the gain axis.

A graph curve a shown by a solid line in FIG. 7 represents the actual characteristics of the actuator. As is clear from comparison with an ideal characteristic (a linear characteristic rising to the left) shown by a broken line b, a low curve is obtained. The difference from the ideal characteristic is remarkable in the flat portion d in the frequency range c (100 Hz or less), which causes a nonlinearity.

That is, the non-linear error due to the waveform distortion becomes particularly remarkable for a low-frequency signal or a signal having a small amplitude, and this limits the positioning on the tracking servo.

The characteristics in the low frequency range related to the graph curve a shown in FIG. 7 are caused by the friction caused by the viscoelastic material inside the bearing of the actuator, and it is technically necessary to solve this problem and obtain a characteristic close to ideal. Is one of the keys.

[0014]

Therefore, in order to solve the above-mentioned problems, a two-axis actuator mechanism according to the present invention includes a coarse-movement actuator used for large-amplitude drive control in a high-frequency range and a small-amplitude actuator in a low-frequency range. drive control Ri Do from fine control actuator used in, fine control actuator is configured using a transducer, the positioning control of a controlled object by the elastic force at the time of member deformation caused when driving the vibrator at low frequencies 2-axis actuator
In the tutor mechanism, the coarse actuator
With a rotation mechanism that rotates the member around the shaft
In both cases, torsional vibration is used as the vibrator of the actuator for fine movement.
By providing the rotor on the shaft, the outer surface of the shaft
Control of the controlled object by torsional force in the circumferential direction
It is something to do .

[0015]

According to the present invention, the fine control actuator eliminates the need to adopt a structure for mounting the coarse for actuators, also, since the coarse-movement actuator has a rotating mechanism, the fine control actuator in the axial portion vibrator The structure can be adopted to make fine adjustment to the rotating mechanism by the elastic deformation vibration, so that the structure can be simplified, problems such as weight increase of the mechanism can be eliminated, and Unnecessary vibration can be suppressed.

Further, since the driving force of the vibrator of the fine movement actuator can be directly transmitted to the movement (or rotation) mechanism of the coarse movement actuator, the frictional resistance at the bearing portion or the like is large. Waveform distortion for a low frequency small amplitude signal can be reduced.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A description will be given below of an embodiment in which the two-axis actuator mechanism of the present invention is applied to a tracking mechanism in a hard disk drive unit.

FIG. 1 is a plan view showing an outline of a two-axis actuator mechanism 1, and FIG. 2 is a schematic sectional view showing a main part thereof.

In the figure, reference numeral 2 denotes a disk, which is rotated by a motor (not shown).

Reference numeral 3 denotes a head arm block, which includes head arms 5, 5 (only one pair is shown in the figure) for supporting the magnetic heads 4, 4, a bearing housing 6, and a voice coil motor unit (hereinafter, "VCM unit"). 7).

The head arms 5, 5 are arranged in a bearing housing 6 so as to be in a positional relationship parallel to each other in the height direction.
It is fixed to. Then, head support pieces 5a, 5a are provided at portions near one end thereof, and when approaching the tip end where the magnetic heads 4, 4 are provided when viewed from the side, the head support pieces 5a, 5a are arranged closer to each other. In this way, a height relationship is established in which the disk 2 is interposed between the magnetic heads 4 and 4 arranged in an opposed state.

As shown in FIG. 2, outer rings of bearings 8, 8 are fitted into the bearing housing 6, and the inner ring of these bearings 8, 8 is mounted on a shaft 9 on a chassis 9.
0, so that the head arm block 3
Can rotate around the shaft portion 10. The shaft portion 10 is configured using a piezoelectric element as described later, and is provided with a function (a fine adjustment function related to tracking control) that is more than a simple rotation axis.

The VCM section 7 includes a coil section 11, a support section 12 to which the coil section 11 is attached, a yoke 13 having an arc shape in plan view, and the like.

That is, the support portion 12 is fixed to the side surface of the bearing housing 6 which is located on the opposite side of the shaft portion 10 from the support pieces 5a, 5a of the magnetic heads 4, 4, and is attached to the support portion 12. The hollow part of the coil part 11
The yoke 13 is fixed to the chassis 9 so that the yoke 3 is inserted therethrough.

Although not shown, a pair of stator magnets are arranged so as to sandwich the coil portion 11.

The head arm block 3 is rotated about the shaft 10 by a driving force generated by supplying a current to the coil 11, and the magnetic heads 4 and 4 extend in the radial direction of the disk. Movement control is performed.

That is, the VCM unit 7 is a drive source for one-axis control of the two-axis actuator mechanism 1, and is involved in coarse adjustment of tracking control.

It is the above-described shaft portion 10 that is involved in the control of the remaining one axis, that is, the fine adjustment of tracking, which is configured so that the torsion on the outer peripheral surface of the shaft can be controlled by an external signal. An element, for example, a piezoelectric ceramic single torsional vibrator 14 is used.

The piezoelectric ceramic single torsional vibrator 14
Is, as shown in FIG.
Are provided with interdigitated electrode patterns 16 and 16 on the outer peripheral surface of the cylinder 15, and the twisting is induced on the outer peripheral surface of the cylinder 15 by skillfully combining the piezoelectric longitudinal effect and the piezoelectric lateral effect. Element.

FIG. 4 is a schematic view for explaining the principle of operation, and twists produced when circumferentially opposite forces F and -F are applied to the outer peripheral surface of a cylinder 15 'made of an elastic material. Distortion includes stretching strain in the direction of + 45 ° with respect to the cylinder axis (the clockwise direction in FIG. 4 is the positive direction of the angle) as shown by a broken arrow E, and a cylindrical strain as shown by a broken arrow C. This is considered to be a combination with the shrinkage strain in the −45 ° direction with respect to the axis.

The electrode fingers 1 of the interdigital electrode patterns 16 and 16
Are arranged at an angle of + 45 ° with respect to the central axis of the cylinder 15 as shown in FIG. 3, so that the pair of opposed electrode fingers 16a, 16a is the same as in polarization. When a voltage is applied, the electrode fingers 16
The elongation strain occurs in the direction perpendicular to the longitudinal direction of a, and at the same time, the contraction strain occurs in the longitudinal direction of the electrode finger 16a due to the piezoelectric transverse effect, and the cylinder 15 is twisted.

Therefore, the torsional vibration can be controlled by the AC voltage applied to the electrode finger.

That is, the piezoelectric ceramic single torsional vibrator 1
The piezoelectric ceramic body is previously polarized so that a predetermined voltage is applied to the shaft portion 4 so that the outer peripheral surface of the shaft portion 10 is twisted in the circumferential direction on the outer peripheral surface, and as shown in FIG. When an AC voltage is applied to the mounting portion, a minute torsional vibration can be generated in the shaft portion 10 accordingly.

By using this torsional force as a driving force for minute rotation control of the head arm block 3, fine adjustment relating to tracking control can be performed.

That is, in order to correct a minute displacement of the magnetic head due to disturbance, the magnetic head 4 is vibrated with a small amplitude by driving the piezoelectric ceramic torsion vibrator 14 of the shaft portion 10 at a low frequency to properly adjust the magnetic head. What is necessary is just to guide to a position.

FIG. 5 shows the configuration of the servo control system of the two-axis actuator mechanism 1.

When a head position target value signal from a command unit 17 such as a CPU and a head position signal from the magnetic head 4 are sent to a position error detection unit 18, an error signal between the two is sent to a subsequent filter circuit 19. , 20.

One filter circuit 19 is an HPF (high-pass filter) circuit for extracting a high-frequency signal component of the error signal, and its output is sent to a coarse actuator 22 via an amplifier 21. The coarse motion actuator 22 corresponds to a mechanism for rotating the head arm block 3 around the shaft portion 10 by the driving force generated by the above-described VCM unit 7, and performs positioning control when the frequency is high and the amplitude is relatively large. .

The other filter circuit 20 is an LPF (low-pass filter) circuit for extracting a low-frequency signal component of the error signal, and its output is sent to an actuator 24 for fine movement via an amplifier 23. The fine-movement actuator 24 corresponds to a mechanism for causing the head arm block 3 to generate a small-amplitude vibration around the shaft portion 10 by the torsional force at the shaft portion 10 to position the magnetic head, and has a low frequency and a low frequency. Performs positioning control for small amplitude.

Then, a detection signal of the head position reproduced by the magnetic head 4 is fed back to the position error detector 18 via the servo amplifier 25.

As described with reference to FIG. 7, the transmission characteristic in the low frequency range, which is particularly problematic in the characteristics of the actuator, is mainly because the frictional resistance in the bearing portion is extremely large with respect to the low frequency and small amplitude signals. It depends on becoming.

[0042] Therefore, the biaxial actuator mechanism 1, while the coarse-movement actuator 22 to the VCM unit 7 and the drive source is an advantage of having a characteristic close to the ideal in a high frequency region was preserved, deformation of the shaft member (piezoelectric effect By using a torsional vibrator utilizing microstrain, electrostriction or magnetostriction for the actuator 24 for fine movement, the characteristics of the low-frequency range are not greatly affected by the friction in the bearing portion. Guarantees the positioning accuracy of the magnetic head.

Thus, by the role sharing between the high frequency band and the low frequency band, a characteristic which is almost ideal as a whole (see the broken line b in FIG. 7) is obtained, and the tracking control with a small residual error is realized. It becomes possible.

In the above embodiment, the present invention is applied to a rotary type 2
Although an example in which the invention is applied to a shaft actuator mechanism has been described, the invention can also be applied to a direct acting two-axis actuator mechanism.

In this case, a mechanism capable of linearly moving the object to be positioned by using a linear motor or the like is used for the coarse movement actuator, and the vertical movement of the rectangular plate-shaped vibrator is used for the fine movement actuator. What is necessary is just to comprise so that fine positioning control of a positioning object may be performed by low frequency drive of a vibrator using vibration or lateral vibration.

FIG. 6 schematically shows a structure of a vibrator in which interdigital electrodes are provided on the surface of a rectangular plate made of piezoelectric ceramics and whose polarization and excitation can be performed.

The vibrator 26 shown in FIG. 6A has electrode finger patterns 28, 28,... Arranged on the surface of a rectangular plate 27 at right angles to the longitudinal direction of the rectangular plate 27. As shown in VD1, stretching vibration occurs in a direction perpendicular to the longitudinal direction of the electrode finger (mainly due to the piezoelectric longitudinal effect), and the vibrator 29 shown in FIG. , 31,... Are arranged along the longitudinal direction of the rectangular plate 30, and stretching vibration occurs in the longitudinal direction of the electrode finger as shown by an arrow VD2 (due to the piezoelectric transverse effect).

By using such a vibrator for, for example, a mounting portion of a member serving as a driving guide, minute positioning of a moving object in the linear direction can be performed.

[0049]

As is apparent from the above description, according to the present invention, the structure for mounting the fine movement actuator on the coarse movement actuator is avoided, and the coarse movement actuator has a rotating mechanism . It is possible to adopt a structure in which a vibrator of a fine movement actuator is provided on the shaft portion and a force due to the elastic deformation vibration is used for fine adjustment to the rotating mechanism, so that the structure can be simplified.

Therefore, it is possible to reduce the increase in the weight of the mechanism and the occurrence of unnecessary vibration inherent to the coupled system, which have been problematic in the conventional mechanism due to the complicated structure.

Also, by directly transmitting the elastic deformation force of the vibrator of the fine movement actuator to the moving mechanism of the coarse movement actuator, the characteristics particularly in the low frequency range of the vibration frequency can be improved. In addition, it is possible to suppress the occurrence of waveform distortion with respect to a low-frequency small-amplitude signal, which has been regarded as a technical problem due to the presence of a portion having a remarkable frictional resistance, such as a bearing portion, and to reduce a nonlinear error.

The above-described embodiment is merely an example of the embodiment of the present invention, and the technical scope of the present invention should not be construed as being narrow by this example alone. It goes without saying that the present invention can be widely applied not only to various uses but also to various uses.

[Brief description of the drawings]

FIG. 1 is a plan view schematically showing a configuration of a two-axis actuator mechanism according to the present invention.

FIG. 2 is a sectional view showing a main part of a two-axis actuator mechanism according to the present invention.

FIG. 3 is a schematic diagram showing a configuration of a piezoelectric ceramic single torsional vibrator used for a shaft portion.

FIG. 4 is a diagram for explaining the operation principle of the piezoelectric ceramic single torsional vibrator.

FIG. 5 is a block diagram showing a configuration of a servo control system according to the present invention.

FIGS. 6A and 6B show an example of a vibrator capable of linear displacement, wherein FIG. 6A shows a vibrator whose vibration direction is perpendicular to the cross finger electrode, and FIG. 6 shows a vibrator in a direction along an electrode.

FIG. 7 is a graph showing characteristics of an actuator for explaining a conventional problem.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 2-axis actuator mechanism 4 Controlled object 5, 6, 10 Rotation mechanism 10 Shaft part 14 Torsional vibrator 22 Coarse motion actuator 24 Fine motion actuator

Claims (2)

(57) [Claims] 1. A coarse-movement actuator used for driving control of large amplitude in the high frequency range, Ri Do from fine control actuator for use in small amplitude of the drive control in the low frequency range, constituted fine control actuators by using a vibrator In the two-axis actuator mechanism, which controls the positioning of the object to be controlled by the elastic force at the time of driving the vibrator at a low frequency when the member is deformed , the coarse movement
The rotation by which the actuator rotates the member about the shaft.
Movement mechanism, and vibration of the actuator for fine movement.
By providing a torsional vibrator on the shaft as a rotor,
Controlled by the torsional force in the circumferential direction on the outer peripheral surface of the part
Two-axis positioning control
Actuator mechanism. 2. The two-axis actuator mechanism according to claim 1, wherein an effect element that generates an elastic force with electromagnetically induced strain is used as a vibrator of the fine movement actuator. 2-axis actuator mechanism.