JPH0218765A - Access mechanism for magnetic disk devices - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a linear access mechanism for a magnetic disk device positioning mechanism, and particularly to a linear access mechanism that requires high guiding accuracy.

[Conventional technology]

An example of a conventional device is a 5-linear access mechanism.

The reaction force of the driving force can be absorbed by the rigidity of the entire device, or the damping effect caused by friction 1 can be used as seen in firearms, or the reaction force piston can be vibrated synchronously with the striking piston with a phase difference of 180'. Some methods were used to absorb recoil, the driving part was supported by a coil spring, and the natural frequency was greatly changed, and vibrations were absorbed by the displacement of laminated piezoelectrics. However, the above methods cannot track vibrations at sufficiently high frequencies, and methods that utilize the viscoelasticity of rubber can handle high frequencies, but their applicability is narrow and they are easily affected by temperature. There were drawbacks such as.

In addition, this type of device is the Utility Model Application No. 62-194950.
issue.

There are those described in Utility Model Publication No. 49-9680 2 and Japanese Patent Application Laid-open No. 59-54077.

[Problem to be solved by the invention]

The above-mentioned conventional technology has drawbacks such as being unable to follow a wide range of drive frequencies and being easily influenced by temperature. Therefore, there was a need for a vibration isolation mechanism that could follow a wide range of drive frequencies, was less susceptible to temperature effects, and had stable characteristics.

The purpose of the present invention is to reduce the drive reaction force of the access operation mechanism,
It is an object of the present invention to provide a magnetic disk access mechanism with high positioning accuracy, which can reduce vibration of the entire mechanism, is equipped with a small and highly reliable reaction force reduction device.

[Means to solve the problem]

The above purpose is to place a plurality of electrostrictive cables on both sides of the weight part, and to make the electrostrictive cables on both sides alternately extend and contract, thereby moving the weight part in a reciprocating straight line in the opposite phase to the driving part. The reaction force of the driving force can be reduced by movement or reciprocating linear movement, and vibration reduction of the entire device can be achieved.

[Effect]

In the linear access mechanism, the reaction force of the force for driving the carriage, that is, the drive reaction force, vibrates the drive section, which causes the entire apparatus to vibrate. Therefore, a method was needed to counteract or absorb this drive reaction force. On the other hand, whether the driving reaction force changes stepwise or
Alternatively, when there is a sudden change, the weight member is accelerated in the same phase as the drive reaction force in order to apply a force in the opposite phase to the drive reaction force. When moving this weight member, voltages of opposite phases are applied to the electrostrictive elements that sandwich the weight member from both sides. By switching the voltage of the electrostrictive element, reciprocating motion of the weight member can be obtained. In this way, the driving reaction force is reduced, and the vibration of the entire device is reduced. As a result, a linear access mechanism with high positioning accuracy is obtained.

In the rotary type access mechanism, the weight part is rotated and the direction of rotation is reversed; thus, the reaction force of the rotary type access mechanism is reduced.

Vibration of the entire device can be reduced.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. The magnetic disk device includes a head 1 that reads and writes data;
A spindle 2b that supports and rotates the disk 2a on which data is stored, a motor 7 that drives the spindle 2b, and a carriage 3 that supports the head 1 and performs an access operation.

a voice coil motor 4 that moves the carriage 3 in an access operation; a control circuit 8 that drives the voice coil motor 4;
and a base 5 that supports each of the members.

It is comprised of a cover 9 that shields each of the above-mentioned members from the outside air together with the base 5. Next, its operation will be explained. The carriage 3 is driven by a voice coil motor 4,
It reciprocates on the guide path 6.

This allows you to read data written to the disk or write data to the disk. In order to read and write this data, the head 1 at the far end of the carriage 3 must be positioned at a certain point on the disk 2a. 1, it depends on the accuracy of the control circuit 8 that uses the position signal detected from the disk. However, it is the driving reaction force generated to drive the carriage 3 that adversely affects this positioning accuracy. That is, the drive section is vibrated by this drive reaction force, and the vibration is transmitted, causing the spindle 2 to vibrate. As a result, a relative displacement occurs between the disk 2a and the head 1, which causes a positioning error.Therefore, as shown in FIG. 1 of the embodiment of the present invention, A reaction force reduction device is added to the configuration of a conventional magnetic disk device.
Attach the one sandwiched between 0 and the laminated electrostrictive element 1.
It is constructed by adding an electrostrictive element drive circuit 13 that drives according to a drive reaction force that generates zero. The laminated electrostrictive element 10 has at least one equal number on both sides with the weight member 11 in between.
Two or more are provided at equal intervals. In addition, the laminated electrostrictive element 1
0 is fixed to the voice coil motor 4 on one side of each. The weight member 11- reciprocates together with the laminated electrostrictive element 10. Furthermore, the method of acceleration movement of the weight member 11 and the direction of displacement of the laminated electrostrictive element 10 are the same. Since force is obtained by operating the weight member 11, when the driving reaction force is to be reduced, the direction of acceleration movement of the weight member 11 and the direction of the driving reaction force coincide.

Here, the principle of vibration isolation will be explained. FIG. 2 shows a principle model of vibration isolation, in which a voice coil motor magnet 16 of mass m1 is connected to a spring element 20 and a damping element 1.
9, this voice coil motor magnet 16
A laminated electrostrictive element 18 and a weight member]-7 are connected in this order to. When the drive reaction force F1 acts on the voice coil motor 16, it is displaced. If the drive reaction force F1 is vibratory, it vibrates. To reduce this vibration, drive reaction force F
It is clear that it would be better to reduce the number by 1. but,
If the driving reaction force F1 has only a DC component, no vibration will occur. Therefore, it is sufficient to remove only the variation of the drive section edge 1. In other words, it is sufficient to perform feedback according to the differential value of the drive reaction force F1, that is, from the perspective of the voice coil motor 16, the jerk of the voice coil motor]6. If the force for vibration isolation is represented by Do2 and 17, and the above is expressed in the equation of motion, (mx + mz)
Xt+CzX+kzXx=Ft-Fz ・=■X z
= K X, 1
... becomes ■.

FIG. 3 is an example of temporal changes in drive reaction force F1 and damping force F2. Since the force required for vibration isolation is the part where the driving reaction force F1 suddenly changes, F2 has a waveform as shown in the figure. Fourth
The figure is an example of temporal changes in jerk.

Next, a method of generating a force for vibration isolation as shown in FIG. 3 will be explained. It is shown in Figure 2. When the weight member 17 (mass mz) is accelerated, the inertia force F c
2m 2 X, z is generated. The reaction force for accelerating the weight member 17 is the damping force F'z in FIG.
It can be used as In order to move the weight member 17, the laminated electrostrictive element 18 may be deformed at an accelerated rate. For example, when a piezoelectric element is used as the laminated electrostrictive element 18, it has high frequency response, so that
Can generate vibration damping force. Among the inertial forces obtained by accelerating the weight member 17, the force that can be used as a damping force per day for the voice coil motor magnet can be expressed by a linear equation.

mz　　　　.

Fz = Xz...■z 1+- Figure 5 shows a trial calculation of the temporal change in the acceleration of the magnet using the formula ■■■. Feedpack amount (
When the magnitude of the damping force increases, the maximum acceleration of the magnet increases.

FIG. 6 shows the difference in frequency components of the acceleration waveform of the magnet when a damping force is applied and when a damping force is not applied. When damping force is applied, the frequency component decreases.

First, the method for driving the reaction force reduction device has been explained in 5. Next, the configuration of the control circuit of the reaction force reduction device will be explained.

Figure 7 shows the method for driving the reaction force reduction device.
This is an example of a control system. With carriage drive current as input,
From the differential value, find the differential value of the drive reaction force that approximately corresponds to the jerk of the voice coil motor magnet,
It is used for control.

Since current detection is easy, it is advantageous in that sensors such as accelerometers are not required.

Figure 8 shows the method for driving the reaction force reduction device.
This is an example of a control system. Input the acceleration of the voice coil motor magnet and its differential value.

In other words, the jerk of the magnet is used for control. Although this method requires an acceleration sensor, it does not require the circuit shown in FIG. 7 for converting current into driving force, and the number of circuit components is reduced.

FIG. 9 shows the method for driving the reaction force reduction device.
This is an example of a control system. This example introduces a feedback circuit that takes the carriage drive current as input and simulates the vibration of the controlled object (considering the natural frequency of the controlled object), allowing stable control that does not require an acceleration sensor. It constitutes a circuit.

FIG. 10 shows a case where the laminated electrostrictive element 10 is provided only on one side of the weight member 11. In this case, the movement of the weight member 1 becomes unstable.

When the weight member 11 moves to the left in FIG. 10, a tensile force acts on the electrostrictive element 10. Generally, it is not preferable to apply a tensile force to the electrostrictive element 10 having a core layer. Therefore, the structure of the example shown in FIG. 1, which is shown as an embodiment of the present invention, is preferable. FIG. 11 is an enlarged view of the reaction force reduction device of FIG. 1. With this structure, if the laminated electrostrictive elements 10 on both sides of the weight member 11 move in opposite phases at the same time, no tensile force will be applied. The movement start time of the strain element 11 may be slightly shifted. FIG. 12 shows the above example. For example, in FIG. 11, if you want to move the weight member 11 to the right in the figure, the electrostrictive cable 10 on the left
The movement start time of the electrostrictive element on the right side may be slightly earlier than the movement start time of the electrostrictive element on the right side.

FIG. 13 shows another embodiment of the present invention. The feature of the present invention is that the laminated electrostrictive cables 10 on both sides of the weight member 11 are
are arranged alternately, and the points of force application of each electrostrictive element 10 are arranged on the same straight line. By using this method, the distance between the laminated electrostrictive elements 10 on both sides can be reduced by the thickness of the weight member 11. Therefore, the size of the reaction force reduction device can be reduced. Figure 14 shows
This is a cross section taken along line I-I in FIG. 13.

FIG. 15 shows an embodiment that can be applied to a rotary type access mechanism. In this example, the weight member 11 rotates due to the expansion and contraction of the laminated electrostrictive element 10, and can reduce the reaction force caused by the moment.

The above is a case where the laminated electrostrictive element 10 is used, and for example, a shape memory alloy may also be used as the laminated electrostrictive element 10. However, in this case, the tensile force is stronger than the compressive force, so unlike the case of the laminated electrostrictive cord 10 described above, it is preferable to put the tensile side first. When using a shape memory alloy, it becomes possible to further reduce the weight and size.

〔Effect of the invention〕

According to the present invention, it is possible to reduce the drive reaction force generated to drive the carriage of the linear access mechanism, and to reduce the vibration of the entire device. As a result, there is an effect of improving the positioning accuracy of the linear access mechanism. In addition, it has the effect of being a small and highly reliable drive reaction force reduction device6.

[Brief Description of the Drawings] Fig. 1 is a longitudinal sectional view of a magnetic disk drive linear access mechanism according to an embodiment of the present invention, Fig. 2 is a principle model of vibration isolation, and Fig. 3 is a driving reaction force F1. Fig. 4 shows the temporal change of the damping force F2, Fig. 5 shows the calculation result of the acceleration of the magnet when damping force is applied, and Fig. 6 shows the calculation result of the acceleration of the magnet when the damping force is applied.
This is the result of frequency analysis of the acceleration waveform shown in the figure. Figure 7 is an example of a control system for vibration isolation, Figure 8 is another example of a control system for vibration isolation, and Figure 9 is another example of a control system for vibration isolation. . FIG. 10 is a longitudinal sectional view of a reaction force reducing device including a laminated electrostrictive element and a weight member as a pair, FIG. 11 is a longitudinal sectional view of a reaction force reducing device of the present invention, and FIG. 12 is an embodiment of the present invention. FIG. 13 is a longitudinal cross-sectional view of an embodiment of the present invention, FIG. 14 is a cross-sectional view taken along line II in FIG. 13, and FIG. 15 is a cross-sectional view of an embodiment of the present invention. It is a top view of a rotary type reaction force reduction device.

Claims (1)

[Claims] 1. A magnetic disk drive equipped with a device that reduces the reaction force caused by the driving force of the access mechanism by applying a force with an opposite phase,
A device for reducing reaction force includes at least one or more pairs of electrostrictive elements, at least one or more movably supported weight members, and a driving device for driving the electrostrictive elements,
An access mechanism for a magnetic disk device, characterized in that a weight member is provided between a pair of electrostrictive elements. 2. The access mechanism for a magnetic disk device according to claim 1, wherein in the magnetic disk device, a device for reducing reaction force is provided in the drive section. 3. The access mechanism for a magnetic disk device according to claim 1, wherein in the magnetic disk device, the electrostrictive element constituting the device for reducing reaction force is a laminated piezoelectric element. 4. The access mechanism for a magnetic disk device according to claim 1, wherein in the magnetic disk device, the electrostrictive element constituting the device for reducing reaction force is a shape memory alloy. 5. In the above magnetic disk device, the device for reducing reaction force is composed of a plurality of pairs of electrostrictive elements and at least one weight member, and the plurality of pairs of electrostrictive cables are connected to each other. The magnetic disk device according to claim 1, wherein the electrostrictive elements are arranged at a certain distance from each other on the same straight line, and the points of force of the respective electrostrictive elements are arranged so that they are not on the same straight line. access mechanism. 6. In the magnetic disk drive described above, a plurality of pairs of electrostrictive elements constituting a device for reducing reaction force are arranged such that a group of electrostrictive elements on one side and a group of electrostrictive elements on the other side are arranged with a weight member in between. 2. The access mechanism for a magnetic disk drive according to claim 1, wherein the electrostrictive element groups are divided into groups, and a time difference is provided between drive start times of the electrostrictive element groups on both sides. 7. In the above magnetic disk device, the direction in which the electrostrictive element of the device for reducing reaction force is deformed and the direction in which the weight member moves are the same direction. Access mechanism for disk devices. 8. In the above magnetic disk device, the direction in which the electrostrictive element of the device for reducing reaction force is deformed and the direction in which the weight member rotates are the same direction. Access mechanism for disk devices.