JPS6355304B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an oscillating actuator for positioning a magnetic head in a magnetic disk device, and in particular to an oscillating actuator that performs highly accurate fitting of an oscillating bearing using a simple mechanism, and achieves high speed and high accuracy. The present invention relates to a swing type actuator that enables positioning operations.

A rocking actuator in a magnetic disk device uses rolling bearings such as ball bearings, roller bearings, and needle bearings as a guide system. Swing bearings come in two configurations: an inner ring rotation type in which a shaft integrated with a rotary carriage is attached to the housing so that it can swing, and a rotary bearing in which the rotary carriage swings through a bearing on a shaft fixed to the housing. There is a rotating outer ring type that can be mounted. In either case, it is necessary to remove the radial clearance of the bearing by some means. This is because the radial clearance of the bearing lowers the resonant frequency of the mechanism, and furthermore, the friction of the mechanical elements through the clearance and the change in the amount of clearance due to heat cause variations in the mechanical characteristics, resulting in high-speed head positioning. This is because it significantly impairs high accuracy. By the way, the actuator is 1
If only one rotary carriage is provided, either of the above two bearing configurations can be adopted. However, when constructing a rotary carriage that can independently swing a plurality of rotary carriages without significantly increasing the volume occupied by the actuator, it is essential to adopt an outer ring rotation type that allows a common shaft. In the case of a rotating outer ring type, the outer ring of the bearing is often fixed to the rotary carriage with no gaps by means such as shrink fitting, press fitting, or gluing. When using a bearing capable of carrying both thrust loads and radial loads, the radial clearance between the inner ring and the outer ring can be eliminated by preloading the bearing in the thrust direction. However, for this reason, it is necessary to provide an appropriate clearance between the inner ring and the shaft, and in order to remove this, an elastic body such as a spring is inserted between the shaft and the inner ring to reapply the radial preload. It is necessary to add. As an example of a bearing without thrust load capacity, when using a solid needle bearing without an inner ring, it is necessary to apply radial preload by inserting an elastic body between the shaft and the bearing. Of course, the need for these radial preloads also exists in the case of the inner ring rotation type in which the outer ring is fixed to the housing.

In conventional devices, radial preload is applied using an elastic body such as a coil spring or a leaf spring to eliminate radial clearance. As an example, Figure 1 shows
The method for removing radial clearance in needle bearings is shown in "IBMJ.Res.Develop., 20, No.4P.389, 1976". A solid needle bearing without an inner ring is used as the swing bearing 2 of the shaft 1 in the housing 8, and a part of the shaft 1 is divided to eliminate the radial clearance between the shafts 1 and 2. A coil spring is arranged in the bearing, and the restoring force of this spring allows the divided part of the shaft 1 to be connected to the bearing 2 via the radial pad 13.
(Note that 11 is a thrust spring and 12 is a thrust pad.) but,
In this method, the bearings must be mounted with the preload springs bent in advance, and this work must be performed for each bearing separately, making the mounting method complicated and the assembly process difficult. It had the drawback of being bad. In addition to this example, a clearance removal method using a bearing capable of carrying thrust and radial loads has also been proposed, but the removal method is the same as that in this example, so this example It had the same drawbacks.

In the present invention, the swing shaft of the swing type actuator is a hollow shaft, and a spring is arranged in a through hole provided from the center of the shaft in a direction perpendicular to the shaft, and a rod-shaped structure is inserted into the hollow shaft to tighten the spring. It is characterized by preloading multiple bearings simultaneously in the radial direction by deflection, and the purpose is to create an oscillating actuator that allows for easy bearing mounting and high-speed, high-precision head positioning. Our goal is to provide the following.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A swing type actuator according to the present invention will be described below based on embodiments shown in the drawings.

FIG. 2 is a side sectional view showing an embodiment of the actuator according to the present invention when it has one rotary carriage, and FIG. 3 is a top sectional view of the shaft portion where the bearing is located. A rotary carriage 3 is swingably supported on a hollow shaft 1 via a rolling bearing 2, and a coil bobbin 4 is attached to the rotary carriage 3. A wire rod is wound around the bobbin 4 to form a coil 5. A head arm 6 is attached to the rotary carriage 3 so as to protrude in a direction opposite to the bobbin 4. The lower end of the fixed shaft 1 is fixed to the sub-base 7, and the upper end is fixed to the housing 8 fixed to the sub-base 7 by bolts 9. By rotating the thrust nut 10, the thrust spring 11 is deflected, and the thrust pad 12
is displaced in the thrust direction. This eliminates the radial clearance between the inner and outer rings of the bearing 2, and increases the rigidity between the inner and outer rings. On the other hand, when configuring the bearing, the radial pad 13 and the radial spring 14, which are movable bodies, are placed in the shaft in advance, and the radial spring 14 is inserted by inserting the through pin 15 into the shaft from the lower end of the shaft.
is deflected, and the radial clearances between all bearing inner rings and shaft 1 are removed at the same time. The radial pad 13 is normally oriented in the direction of the force acting on the bearing 2 through the carriage during head positioning operations. Through pin 1 that the radial spring 14 hits
The side surfaces of 5 are uniformly chamfered in the length direction. The through pin 15 is positioned in the circumferential direction so that this surface and the radial spring 14 come into close contact with sufficient accuracy.
Since the preload force generated by the deflection of the radial spring 14 is set to be larger than the maximum value of the force acting on the bearing 2 during the head positioning operation, no clearance is generated during positioning. Also,
Changes in preload force caused by thermal changes, etc. are of a negligible order and do not create any clearance. Although a coil spring is used as the radial spring 14 in this embodiment, it is also possible to change this to a leaf spring or an elastic body having similar properties.

As described above, in this embodiment, the spring for eliminating the radial clearance is placed inside the shaft 1 as it is without being deflected in advance, and furthermore, after all the bearings 2 are mounted, one through-hole is installed. Since the radial clearances of all the bearings 2 can be removed simply by inserting the pins 15, the method of mounting the bearings is greatly simplified compared to conventional devices.

On the other hand, the vibration characteristics of the actuator that greatly affect the head positioning performance are determined by the inertance transfer function (acceleration/ power). FIG. 4 shows an example of actual measurement of this inertance, and the solid line in the figure is the inertance in this example. The prominent peak appearing in the inertance indicates the resonance of the bending mode of the movable part consisting of the coil structure, rotary carriage, and head arm. On the other hand, the dashed-dotted line shows the inertance when the shaft is hollow and the radial clearance is not particularly removed. Also, the two-dot chain line is
The inertance is shown when the shaft is solid and radial clearance is not specifically removed. Comparing the one-dot chain line and the two-dot chain line, it can be said that the resonance frequencies of the bending modes in both are almost the same, and that the influence of the bending rigidity of the shaft on the inertance is sufficiently small. on the other hand,
It can be seen that in the inertance shown by the double-dashed line, the resonance frequency of the bending mode is lower than that shown by the solid line due to the influence of the clearance existing in the bearing section. These results show that, according to the present example, it is possible to prevent a decrease in the mechanism resonance frequency due to the clearance, and the control band of the closed-loop positioning control system can be expanded accordingly. Therefore, this embodiment has the effect of increasing the speed and precision of the head positioning operation. In addition, in this example, even if there is a thermal change, the change in the preload force due to the spring is on the order of negligible, so no clearance will occur, and as a result, the mechanism such as a bearing and a shaft, a rotary carriage, etc. The relative positions between elements also hardly change. Therefore, there is an effect that static head positioning errors due to thermal changes can be sufficiently reduced. Although ball bearings are used in this example,
When using a bearing capable of carrying both radial and thrust loads, it is possible to adopt a configuration exactly similar to this embodiment.

FIG. 5 shows another embodiment of the actuator according to the present invention. In this embodiment, a needle bearing is used as the bearing 2, and since positioning in the thrust direction requires another means, it is difficult to configure a plurality of rotary carriages as described above. However, in this embodiment, the effects of the present invention are not impaired because the radial clearances of two bearings can be removed at once, as in the case of using ball bearings.

FIGS. 6 and 7 also show other embodiments of the present invention. Note that for simplicity, the bearing portion is mainly shown. In these embodiments, the present invention is applied to an actuator having a plurality of rotary carriages 3 that are each independently driven. In the embodiment shown in FIG. 6, two bearings 2 are arranged on each of the two rotary carriages 3, and the method for eliminating radial clearance is the same as in the embodiment shown in FIG. Further, FIG. 7 shows an actuator having three rotary carriages 3. As shown in FIG. As in this example, it is also possible to eliminate the radial clearance between a plurality of bearings 2 by using one set of springs 14 and radial pads 13. Furthermore, the present invention is not limited to the above-mentioned two embodiments, but can also be applied to cases where three or more rotary carriages are arranged around a common shaft, and the resulting effects are similar to those of one rotary carriage. The effect is exactly the same as that obtained with an actuator with a ridge.

Note that when inserting the through pin 15, in order to reduce the frictional force between the through pin 15 and the radial spring 14, a strip-shaped thin plate 16 with good lubricity or coated with lubricant is inserted into the shaft in advance. It is also possible to insert the through pin 15 along it. An example of the configuration in that case is shown in FIG.

As described above based on the embodiment shown in the drawings, in the swing type actuator according to the present invention, all the bearings can be bent without pre-deflecting the springs for eliminating the radial clearance of the bearings. By simply inserting a single rod-shaped structure after the bearings are placed, the radial clearances of all bearings can be removed, and by removing the clearances, it is possible to prevent the resonant frequency of the mechanism from decreasing, thereby preventing the reduction of the resonance frequency due to thermal changes. Relative displacement of the mechanical elements can also be prevented. As a result, the bearing mounting method can be greatly simplified compared to conventional equipment, the band of the head positioning control system can be widened, and variations in static mechanical characteristics due to heat can be eliminated, resulting in high speed and precision. This enables accurate head positioning operation.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway perspective view showing a bearing part of a conventional swing-type actuator, and FIG. 2 is a side sectional view showing an embodiment of the swing-type actuator of the present invention.
FIG. 3 is a top sectional view, FIG. 4 is a graph showing a comparison between the inertance in the embodiment of the present invention and the inertance of a conventional device, and FIGS. FIG. 7 is a side sectional view showing another embodiment according to the invention. In the drawings, 1 is a shaft, 2 is a bearing, 3 is a rotary carriage, 4 is a coil bobbin, 5 is a coil, 6 is a head arm, 7 is a sub-base, 8 is a housing,
9 is a bolt, 10 is a thrust nut, 11 is a thrust spring, 12 is a thrust pad, 13 is a radial pad, 14 is a radial spring, 15 is a through pin, and 16 is a thin plate.

Claims (1)

[Claims] 1 At least one rotary carriage that is swingably supported by a rolling bearing, a coil structure that is fixed to or integrated with the rotary carriage, a plurality of head arms, and the above-mentioned rotary carriage for swinging. In the oscillating actuator, which includes a magnetic circuit for driving a coil structure, etc., and positions a magnetic head supported by the head arm on a predetermined track on a magnetic disk surface by oscillating the rotary carriage, The shaft body, which is the center of swing of the Tsuji, is a hollow shaft, and springs are arranged in a plurality of through holes provided from the center of the shaft in a direction perpendicular to the shaft.A rod-like structure is inserted into the hollow shaft, and the spring A rocking actuator characterized in that it is configured to simultaneously preload a plurality of bearings in the radial direction by deflecting the bearings.