JPS63138579A - Head arm device - Google Patents

Abstract

PURPOSE:To decrease an off-track quantity to a temperature change by making coincident with material of the scale for detecting a head position and the material of an arm part for supporting and matching the linear expansion coefficient of the arm part to the coefficient of a disk. CONSTITUTION:The linear expansion coefficient of an arm part 13 is selected to a value approximately coincident to the linear expansion coefficient of a disk 2 and the linear expansion coefficient of an arm part 14 is made approximately coincident to the coefficient of a scale 16 for detecting a head position. Consequently, when the temperature around a head arm device is changed from a reference temperature, the arm part 13 and the disk 2 are also expanded and shrinked and the off-track quantity of a head 5 after the temperature is changed comes to be minimum obtained under the said conditions. An expanding shrinking quantity to occur at a graduation 17 of a scale 16 supports the scale 16, the expanding and shrinking are executed by the linear expansion coefficient approximately equal to the scale 16 and thus, the rotation position of a head arm 4 equivalent to the graduation 17 after the temperature is changed can be essentially sufficiently made close to the turning position before the temperature is changed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a helad arm device, and is suitable for application to, for example, a hard disk type magnetic recording/reproducing device.

B. Summary of the Invention The present invention provides a head arm device that allows a recording track formed on a disk to be accessed by a head arm having a head and a head position detection scale. By selecting the coefficient of linear expansion of the arm part that supports the head to be approximately the same value, and by selecting the coefficient of linear expansion of the arm part that supports the head to approximately match the coefficient of linear expansion of the disk, the head arm device can be improved. The amount of off-track present in the head can be further reduced by changing the surrounding temperature.

C. Prior art As shown in FIG. 5, a conventional hard disk type magnetic recording/reproducing device has a rotatable disk mounted on a fixed shaft 3 located near a disk 2 which is driven to rotate around a rotating shaft 1. The head 5 attached to the tip of the head arm 4 is moved along a movement trajectory 6 according to the rotation of the head arm 4.
The head 5 is configured to be able to move along the disk 2, and thus to access the recording tracks sequentially formed concentrically between the outermost track TRO and the innermost track TR1 on the disk 2. It is being

The head arm 4 has a base connected to a housing 11, and the housing 11 is rotatably attached to the fixed shaft 3 via a bearing 12. The head arm 4 has a first and a first Y-shaped structure as it goes from the housing 11 to the tip. Two arm portions 13 and 14 have a branched shape, and a leaf spring 15 having a head 5 fixed to the tip thereof is attached to the first arm portion 13.

On the other hand, a head position detection scale 16 made of a glass plate is attached to the tip of the second arm portion 14. This head position detection scale 16 has a scale 17 graduated around the fixed shaft 3 formed by, for example, vapor deposition, and when the scale 17 passes through the optical sensor 18, the rotational position IF of the scale 16 (therefore, A head position detection signal S1 representing a position corresponding to the position on the disk 2 relative to the head 5 is sent to the system controller 19.

When the system controller 19 receives a designation input from, for example, an operator to access a track at a predetermined address that the head 5 is currently tracking, the arm units 13 and 14
The head arm 4 is rotated by applying a drive signal S2 to a drive coil 22 mounted on a bobbin fork 21 extending in the opposite direction. In addition, 23
is the fixed core passing through the drive coil.

The rotational position of the head arm 40 is expressed by the number and phase of the graduations 17 of the head position detection scale 16 passing through the position of the optical sensor 18, and the corresponding head position detection signal S1 is sent to the system controller 9. The rotation position is determined by the feedback from the head 5.
When the address matches the address to be accessed, the drive signal S2
to stop the head arm 4 through the head 5.
can be moved to the track of the target address.

D Problems to be Solved by the Invention However, according to the helad arm device having the configuration shown in FIG. , scale 17 of head position detection scale 16
When the system controller 19 drives and controls the drive coil 22 based on the head position detection signal S1, the moving position of the head 5 does not match the position of the head 5 that was associated with it due to adjustment during manufacturing. There is a risk that it may become misaligned.

The reason for this is that the head position detection scale 1 is attached to the tip.
6 is attached to the fixed axis 3, as shown by arrows a and a2, according to the coefficient of linear expansion of the material. This is thought to be due to the fact that the head position detection scale 16 expands and contracts in the direction of the scale 17 with a coefficient of linear expansion determined by its material, as indicated by the arrows.

However, while conventionally the arm portion 14 of the cylinder 2 is made of aluminum with a linear expansion coefficient α of approximately α-240xlO''/°C, the head position detection scale 1 is
6, soda lime having a linear expansion coefficient α of approximately α-84×10-'/ was used.

While the second arm portion 14 has a large coefficient of linear expansion in the distal direction, the head position detection scale 16
If the coefficient of linear expansion of
℃, the head position detection scale 16, which was located at the distance L1 from the fixed shaft 3 when the temperature was 25℃, changes to 55℃, as shown in FIG. Due to the elongation of 14, the further distance L2 from the fixed axis 3
However, since the expansion of the scale 17 of the head position detection scale 16 in the direction of the arrow is not so large, it is fixed when the temperature around the head arm 4 and disk 2 is 25°C. The angle range θ2% occupied by the scale 17 of the head position detection scale 16 when the temperature reaches 55° C. is θ2% when the range of the scale 17 of the head position detection scale 16 is viewed from the axis 3. becomes smaller.

This is true when the second arm portion 14 is at 25°C and at 55°C.
This means that when the head arm 4 rotates by the same angle as when the temperature is 55 degrees Celsius, the number of divisions of the scale 17 passing through the position of the optical sensor 18 is greater when the temperature is 55 degrees Celsius.

Therefore, when the system controller 19 rotates the rad arm 4 by an angle corresponding to a predetermined number of graduations, 2
The amount of movement of the head 5 at 55°C is smaller than the amount of movement of the head 5 at 5°C, and in the end the head 5 moves at 25°C.
(This off-track phenomenon caused by temperature changes is called thermal off-track.)

This amount of off-track is determined by the thermal off-track characteristic curve in FIG. As shown by C1, the off-track absolute amount Rot in the innermost track TRI,
Off-track absolute amount R0 at outermost track TRO
The difference between the two is quite large.

Incidentally, the difference in off-track amount (Rat-Rob) from the innermost track TRI to the outermost track TRO is calculated at each point in the range on the head position detection scale 16 corresponding to the range from the innermost track TRI to the outermost track TRO. For example, according to experiments, it corresponds to the cumulative elongation of 6 [μ
m].

The above has described the effect of off-track that occurs due to the difference in linear expansion coefficient between the head position detection scale 16 and the second arm section 14. Regarding the linear expansion coefficient of part 13,
All points of the thermal off-track characteristic tune &11CI in FIG. 7 are affected, and this is superimposed on the off-track amount described above for the head position detection scale 16.

The main reason for this is thought to be that the coefficient of linear expansion of the disk 2 and the coefficient of linear expansion of the first arm part 3 supporting the head 5 do not match.

That is, when the head 5 attached to the tip of the first arm 13 extends in the direction indicated by the arrow a with the fixed shaft 3 as a reference, the head 5 attaches to the disk 2 accordingly. Change the facing position.

However, as shown by arrow C, the disk 2 extends around the rotating shaft 1 with a coefficient of linear expansion determined by its material. The position when ascending is
This is the difference between the amount of extension of the first arm portion 13 and the amount of extension of the disk 2.

Therefore, the coefficient of linear expansion of the first arm portion 13 and the coefficient of linear expansion of the disk 2
If the coefficients of linear expansion differ significantly, the amount of off-track after a temperature change will increase in practice.

This off-track amount has the property of being an absolute amount that occurs at all points from the innermost track TRI to the outermost track TRO.

The present invention has been made in consideration of the above points, and the head arm is adjusted to correspond to the track on the disk at the standard temperature at the time of adjustment, and when the temperature changes thereafter, the head arm is adjusted to correspond to the track on the disk. The present invention attempts to propose a head arm device that can minimize the amount of off-track.

E Means for Solving Problem In the head arm device, the head arm 4 is rotatably supported and has a second arm part 14 that supports a head position detection scale 16 that optically detects a position corresponding to the position 5. The linear expansion coefficient of the first arm part 13 is selected to be approximately the same as the linear expansion coefficient of the disk 2, and the linear expansion coefficient of the second arm part 14 and the linear expansion coefficient of the head position detection scale 16 are selected to be approximately the same. The value should be selected accordingly.

2 effects When the temperature around the head arm device changes from the reference temperature of the adjustment value, the first arm portion 13 expands and contracts with a linear expansion coefficient that is approximately equal to the linear expansion coefficient of the disk 2, so that the head 5 after the temperature change The amount of off-track will be the minimum value obtained under the conditions.

At the same time, the scale 17 of the head position detection scale 16
The amount of expansion and contraction that occurs in the head position detection scale 16
By supporting the scale 16 and expanding and contracting it with a coefficient of linear expansion that is approximately equal to the coefficient of linear expansion of the head position detection scale 16, the rotational position of the head arm 4 corresponding to the scale 17 after the temperature change is substantially the same as the rotation position before the temperature change. can be brought sufficiently close to the moving position.

Therefore, according to the present invention, it is possible to realize a head arm device in which the amount of off-track with respect to temperature changes is sufficiently small for practical use.

G example An embodiment of the present invention will be described in detail below with reference to the drawings.

(G1) First Embodiment In FIG. 1, in which parts corresponding to those in FIG. As shown in the figure, they are constructed from mutually separate members.

That is, the first arm part 13 is made by injection molding aluminum, for example, integrally with a protruding part 32 protruding from the housing 11, and a leaf spring 15 is formed by fixing the head 5 to the tip part using a screw 33. It has a structure in which it is screwed.

Further, the second arm portion 14 is constituted by a fan-shaped plate-shaped wing 34 made of, for example, 5US304, and is screwed to the raised portion 32 of the arm base 31 with a screw 36 through a threaded hole 35 bored at the base thereof.

A head position detection scale 16 made of a glass plate 37 made of crystallized glass is bonded to the tip of the wing 34 with an adhesive.

In the above configuration, the linear expansion coefficient α of 5US304 selected as the material for the wing 34 is α-170xlO-
'/'c, whereas the linear expansion coefficient α of the crystallized glass selected as the material for the head position detection scale 16 is α-170xlO-'/°C.

In this way, the coefficient of linear expansion α of the wing 34 and the coefficient of linear expansion α of the head position detection scale 16 are selected to substantially match each other. Therefore, in correspondence with Figure 6,
As shown in the figure, when the temperature rises from 25°C to 55°C, the wings 34 extend in the directions indicated by arrows a and a with a linear expansion coefficient α-170Xl0-'/l: Distance L! As the head position detection scale 16 moves to the position shown in FIG.
This results in an elongation of 70Xl0-'/l.

The wing 34 that constitutes the second arm portion 14 in this way
The linear expansion coefficient α of the head position detection scale 16 and the linear expansion coefficient α of the glass plate 37 constituting the head position detection scale 16 are selected to be approximately the same value. The angle θ2. represents the scale range when looking at the scale range. and an angle θ5. which represents the scale range of the head position detection scale 16 at 55°C. is a value close enough for practical use.

As a result, as shown in FIG. 4 corresponding to FIG. 7, the off-track amount R0 on the innermost track TRI and the off-track amount RI on the outermost track TPO! The slope of the thermal off-track characteristic curve C2, which represents the difference in , becomes much gentler than in the conventional case shown in FIG. This means that tracking control of the head 5 can be performed with higher accuracy in practice on the tracks between the innermost track TRI and the outermost track TR0.

Furthermore, in the configuration shown in FIG. 2, aluminum is selected as the material for the arm base 31 constituting the housing 11 and the first arm portion 13, so that its linear expansion coefficient α is
As with disk 2, the temperature is approximately α-240Xl0-'/°C.

Considering that the disk 2 is made of aluminum, the arm base 31 is made of a material with a coefficient of linear expansion α that matches the aluminum, so that the temperature is lower than the standard temperature of 25°C. If the temperature rises to 55℃,
The elongation occurring between the innermost track TRI and the outermost track TR0 of the disk 2 matches the elongation of each part of the first arm section 13 to which the head 5 is attached.

Therefore, if the position of the head 5 changes as the head 5 expands due to the linear expansion coefficient α of aluminum due to this temperature change, the position of each track from the innermost track TRI to the outermost track TROofJ will change as well. This results in elongation due to the coefficient of linear expansion α, and as a result, the absolute amount of off-track R11 that occurs in tracks TRI or TRO due to temperature changes becomes a much smaller value than when a different material is selected.

(G2) Second Embodiment As a second embodiment, in the configuration shown in FIG. The linear expansion coefficient α of the glass plate 37 is α-84xl
Soda lime with a temperature of G-'/℃ is selected, and the linear expansion coefficient α is α=240 Xl0-' as the arm base 31.
/℃ select aluminum.

In this way, by selecting a material that matches the linear expansion coefficient of the second arm portion 14 and the linear expansion coefficient of the head position detection scale 16, it is possible to change the innermost track TRI or the innermost track due to temperature changes. The rate of change in the amount of off-track occurring between the outer tracks TR0 can be made sufficiently small for practical purposes. At the same time, by making the linear expansion coefficient of the first arm portion 13 match the linear expansion coefficient of the disk 2, the innermost track TRI to the outermost track TP
Absolute off-track amount R0~R1 of O! can be suppressed to the smallest value under given conditions.

(G3) Other Embodiments (1) In the embodiment shown in FIG. 2, a screw 36 is attached to a protrusion 32 protruding from a housing 11 in which a wing 34 is rotatably supported on a fixed shaft 3 via a bearing 12. In the above case, the arm base 3 is configured to be fixed with a screw using the arm base 3. However, when a rotating shaft rotatably supported by a bearing on the base is used instead of the fixed shaft 3, the arm base 3
By fixing the wing 34 directly to the same rotating wheel at the same time as directly fixing the wing 34 to the rotating shaft, the first and second arm parts 13 and 14 can be rotated together via the rotating shaft. Even with this configuration, the same effects as in the above case can be obtained.

(2) In the above-mentioned embodiment, an example was described in which a glass scale made of a glass material was used as a scale representing the position of the head 5, but the present invention is not limited to this, and a scale such as a so-called metal scale made of a metal material may be used. Even in this case, the same effect as in the above case can be obtained.

(3) In the above embodiment, the present invention is applied to a hard disk type magnetic recording/reproducing device, but the present invention is not limited to this. It can be widely applied to disk devices that detect using an optical scale.

(4) In the description of the above embodiment, the case where each member expands as the temperature around the head arm device increases, but the above-mentioned method can be applied similarly when the temperature decreases and the members contract. You can get the same effect as in the case.

H Effects of the Invention As described above, according to the present invention, the material of the head position detection scale that indicates the track position on the disk is made to match the material of the arm part that supports it, and the material of the arm part that supports the head is By adjusting the coefficient of linear expansion to match that of the disk, it is possible to easily realize a head arm device with a much smaller amount of off-track with respect to temperature changes.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing an embodiment of the head arm device according to the present invention, FIG. 2 is an exploded perspective view showing the structure of the head arm, and FIG. 3 is thermal expansion of the head position detection scale shown in FIG. 1. 4 is a characteristic curve diagram showing the thermal off-track characteristic curve of the Herad arm device configured as shown in FIG. 1; FIG. 5 is a plan view showing the configuration of the conventional Herad arm device; FIG. 6 is a route diagram for explaining the operation of the head position detection scale, and FIG. 7 is a characteristic curve diagram showing the thermal off-track characteristic curve of the head arm device of FIG. 5. 2...Disc, 3...Fixed shaft, 4.
...Head arm, 5 ...Head, 11
...Housing, 12 ...Bearing, 13
...First arm part, 14... Second arm part, 16... Head position detection scale, 17... Graduation, 18... ...optical sensor,
19...System controller, 22...
... Drive coil, 31 ... Arm base, 32
......U Kibe, 34...Wing, 37
...Glass plate.

Claims (1)

[Claims] A first device supporting a head that scans a track on a disk.
and a second arm that supports a head position detection scale that optically detects a position corresponding to the position of the head on the disk. In the head arm device, the coefficient of linear expansion of the first arm section is selected to be a value that substantially matches the coefficient of linear expansion of the disk, and the coefficient of linear expansion of the second arm section and the head position detection scale are selected. A head arm device characterized in that the linear expansion coefficients of the two are selected to substantially match each other.