JPS63133362A - Head moving drive mechanism for disk device - Google Patents

Abstract

PURPOSE:To attain highly accurate positioning by selecting an output shaft diameter of a step motor and an outer diameter of a pinion according to the dimension of a flexible disk and adopting a metallic bearing for the bearing of the step motor. CONSTITUTION:The output shaft diameter of the permanent magnet type step motor 11 and the outer diameter of the pinion are selected respectively as 2.1mm or below for a disk device where the nominal diameter of the flexible disk is 4 inches or over and as 1.6mm or below for the disk device less than 4 inches, and further, the metallic bearing is employed. For example, in the device as shown in figure where the nominal diameter of the flexible disk is 3.5 inches and the track interval is 187.5mum, the outer diameter of the motor 11 is selected to be 20mm, number of steps per revolution is selected to be 20, and the pinion 12 is provided directly to the output shaft of the motor and the number of teeth is selected to be 10. A rack 16 is fixed to a carriage 15 mounted with a magnetic head 14 and meshes with the pinion 12. The carriage 15 is made of a magnetic material and a pre-load magnet 18 provided to the frame 17 and the attracting force by the carriage 15 exclude backlash between the rack 16 and the pinion 12.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a head movement drive aftX for a disk device.

[Conventional technology]

Conventionally, a head moving drive groove as shown in FIG. 3 and described in Japanese Utility Model Application Publication No. 49-34340 has been known. FIG. 3 is a perspective view of a conventional head movement drive mechanism.

In FIG. 3, a pinion 2 provided on a step motor 1 and a rack 4 provided on a carriage 3 are engaged, and a magnetic head 6 is moved and positioned using a slide shaft 5 that guides the carriage 3. Ta.

[The problem that the invention attempts to solve]

However, in the conventional head movement drive mechanism a, the division accuracy of the step motor 1 directly affects the positioning accuracy of the head 6, so a hybrid type step motor with high accuracy and high output had to be used. Further, the hybrid type step motor has a structure in which the number of steps per rotation is large, and the number of teeth on the pinion 2 is also increased, and the pitch circle diameter is also increased. Therefore, the step motor 1 is easily affected by the shellfish load applied to the carriage 3, and a step motor 1 with a larger output torque is required.

The present invention solves these conventional problems,
The purpose is to provide an inexpensive and highly accurate head moving unit vJ mechanism for a disk device.

[Means for solving problems]

In order to solve the above problems, the head movement drive mechanism of the disk device of the present invention rotates a disk-shaped flexible disk, and attaches a rack to a carriage equipped with a magnetic head for recording and reproducing information on the flexible disk. a pinion that engages with the rack is provided integrally with the output shaft of the permanent magnet type step motor, and has means for preloading the rack and pinion in a direction perpendicular to the direction of movement of the carriage, and an articulated drive of the step motor. In a head moving unit vJ mechanism of a disk device that moves and positions a magnetic head by using a flexible A disk device in which the nominal diameter of the disk is less than 4 inches is characterized in that it is 1.6 mm or less, and the bearing of the step motor is a metal bearing.

[Effect]

According to the above configuration of the present invention, even if the clearance between the output shaft of the step motor and the bearing is large, the preload force from the direction of carriage movement causes the step motor to be shifted to one side, and play in the direction of carriage movement can be eliminated. .

The effect of this biasing is greater as the shaft diameter becomes smaller.
It is more stable.

In addition, by configuring the output shaft diameter of the step motor to be small, bearing loss is small, and by configuring the diameter of the nion to be small, for example, even if a carriage equipped with a rack is subjected to external disturbances such as vibrations or shocks, the step motor will not be able to step. The motor is less affected by disturbances and can position the magnetic head with higher precision.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a perspective view of essential parts of a head movement drive mechanism according to the present invention. First, the nominal diameter of the flexible disk is 3.
This will be explained by citing a 5-inch disk device with a track spacing of 187.5 μm as an example.

In Figure 1, a permanent magnet type (hereinafter P
The outer diameter of the step motor 11 (referred to as M type) is 20 mm.
The number of steps per rotation is 20.

The pinion 12 is provided directly on the output shaft of the step motor 11, and the outer diameter of the shaft is 1.5 mm, the outer diameter of the pinion 12 is 1.48 mm, and the number of teeth is 10.

A rack 16 is fixed to the carriage 15 to which the magnetic head 14 is attached, and is engaged with the pinion 12.

The carriage 15 is made of a magnetic material, and the backlash of the rack 16 and pinion 12 is removed by the attraction force between the carriage 15 and a pressurizing magnet 18 provided on the frame 17.

The carriage 15 moves in the direction of the arrow 20 in the figure, following the rotation of the step motor 110, using the slide shaft 19 as a guide.

The pinion 12 is inserted into a long space provided with a rack 16, and prevents the pinion 12 and the rack 16 from coming out of mesh due to vibration or impact, for example, and thereby preventing the meshing phase position from going out of order.

FIG. 2 is a diagram showing the relationship between the shaft of the step motor and the bearing, and FIG. 2 is a sectional view of the step motor bearing in the present invention.

In FIG. 2, the shaft 31 of the step motor 11 has a clearance between the metal bearings 21, and originally there is play in the direction of the arrow 20 in the figure, but the preload magnet 18 and the carriage 15 in FIG. Due to the suction force, it is shifted in the direction of arrow 32 in FIG. 2, and looseness in the direction of arrow 20 in the figure is removed.

At this time, the smaller the diameter of the shaft 31, the smaller the diameter of the metal bearing 21.
The smaller the clearance between the shaft 31 and the shaft 31, the smaller the movement of the shaft 31 in the direction of arrow 20 in FIG. 2, and the more effectively the preload force in the direction of arrow 32 in FIG.

By configuring as above, the step motor 11
By rotating the magnetic head 14 by 18 degrees in one step, the magnetic head 14 is precisely 187 degrees in the direction of the arrow 20 in FIG.
．． It has a structure that allows for 5 μm movement and 1 positioning.

Here is a practical example.

Carriage 15! i amount is approximately 20g, and the first
It is necessary to estimate approximately Log as the friction load in the direction of arrow 20 in the figure. The holding torque of the step motor 11 is 35 g-cm, and the slope of the torque from the stable stop point of the step motor 11 is actually measured to be 2.5 g-cm.
/deg.

In other words, this step motor 11 has an external load of 2.5
By adding g-am, the stopping position of ldeg changes.

However, in this embodiment, the pitch circle radius at the point where the rack 16 and the pinion 12 come into contact is approximately 0.6 mm. In this state, the carriage 1 is used as an external load.
5 to a force of 30 g (carriage 15's own weight, and friction 5
Even if we add power (L street), 0.6X30÷10=1
, the load torque is 8 g-cm, and the step motor 1
1 means no change of 0.7 degL from the stable stop point.

In this embodiment, one step (18 degrees) of the step motor 11 moves the carriage 15 to 187 degrees.
5μm 5WjJ structure, so 0.7d
eg corresponds to a change in the position of the carriage 15 of approximately 7 μm.

Standardly, in a disk device with a flexible disk having a nominal diameter of 3.5 inches, the allowable track position deviation is approximately 30 μm, and the positional change of 7 μm is
It is quite acceptable.

However, when the diameter of the pinion 12 is increased, the change in the position of the carriage 15 due to the load increases proportionally. For example, by doubling the diameter of the pinion 12, the change in the position of the carriage 15 described above can be reduced by It can be seen that this is as much as half of the allowable track position deviation of the entire device, which is extremely unacceptable.

Furthermore, in this embodiment, the shaft 31 of the step motor 11
Although there is a clearance of approximately 10 to 25 μm between the metal bearing 21 and the metal bearing 21, the preload of 990 g completely removes this clearance, and the movement of the shaft 31 in the direction of the arrow 20 in FIG. It was impossible to measure.

Furthermore, the friction torque T due to the preload between the shaft 31 and the metal bearing 21 is calculated when the preload is 90 g and the radius of the shaft 31 is 0.75 m.
For m, m#l! If coefficient μ=0.2, T=90x0.75÷10x0.2=1.35g-cm
As mentioned above, by applying an external load of 2.5 g-cm, the step motor 11 can change its stop position to ld.
eg changes, and one step (18 degrees) of the step motor 11 moves the carriage 15 to 187 degrees.
．． If the structure moves 5μm, then 187.5÷18÷2.5X1.35=5.6,
The positional change of the carriage 15 occurs by only 5.6 μm.

In this way, by making l1l131 of the step motor 11 thinner, changes in the stop position of the carriage 15 due to the influence of external loads and bearing loss can be suppressed.
It is now possible to use a metal bearing for the bearing 31 of the step motor 11 without using a pole bearing.

〔Effect of the invention〕

As explained above, the present invention has a structure in which a magnetic head of a disk drive is moved by a rack and a pinion provided with a PM type step motor shaft, and a preload is applied to the rack and pinion. By reducing the diameter of the head, it is possible to provide a disk device that is inexpensive and can perform highly accurate head positioning.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a main part of a head movement drive mechanism according to the present invention. FIG. 2 is a sectional view of the step motor bearing in the present invention. FIG. 3 is a perspective view of a conventional head movement drive mechanism. 11...Step motor 12...Pinion 15...Carriage 16...Rack 18...Preload magnet 21...Metal bearing 31...Shaft and above Applicant 7 Iko Ebson Co., Ltd. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] A rack is provided on a carriage equipped with a magnetic head for rotationally driving a disk-shaped flexible disk and recording and reproducing information on the flexible disk, and a pinion that engages with the rack is integrated with the output shaft of a permanent magnet type step motor. In a head movement drive mechanism of a disk device, the head movement drive mechanism of a disk device has means for preloading the rack and pinion in a direction perpendicular to the movement direction of the carriage, and moves and positions the magnetic head by articulated driving of the step motor. The output shaft diameter and pinion outer diameter should be 2.1 mm or less for disk devices with flexible disks with a nominal diameter of 4 inches or more, and 1.1 mm or less for disk devices with flexible disks with a nominal diameter of less than 4 inches.
A head movement drive mechanism for a disk device, characterized in that the diameter of the step motor is 6 mm or less, and the bearing of the step motor is made of a metal bearing.