JPH02148492A - Magnetic disk device - Google Patents

Abstract

PURPOSE:To reduce moisture absorbent and to prolong the service life of the moisture absorbent by housing a first moisture absorbent, out of the first and second moisture absorbents of different moisture absorption coefficient, to a case, for which the diffu sion resistance of steam is large, and providing the second moisture absorbent, for which the difference of the saturation moisture absorption coefficient at specified relative humidity is larger than the saturation moisture absorption coefficient at low humidity, in a housing, for which the diffusion resistance of the specified quantity of the steam is small. CONSTITUTION:The surrounding temperature of a device is stable, the relative humidity is kept constant at the low humidity in a sealed housing 1 of space capacity V (l) by fine holes 2 and a first moisture absorbent 3. When the surrounding temperature is rapidly lowered and the relative humidity rises up, a second moisture absorbent 4 is operated. For the second moisture absorbent 2, since difference DELTAq between the saturation moisture absorption coefficients at the relative humidity 70% and 50% is larger than the saturation moisture absorption coefficient under the relative humidity 50%, by defining the quantity as 0.001-0.002V/DELTAq(g), the rapid rising of the surrounding temperature, especially, the quantity of the steam to be discharged from the second moisture absorbent 4 is limited. Then, the rising of the absolute humidity is prevented. Thus, the life of the moisture absorbent is prolonged and the agent can be reduced.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a magnetic disk drive, and particularly to a magnetic disk drive having a moisture absorbent that absorbs water vapor in the HDA. Regarding dehumidification methods.

[Conventional technology]

Conventionally, in a fixed magnetic disk device (Winchester disk device) that has a structure in which the head and disk are sealed, the disk and head arm are integrated and sealed in a housing to prevent minute dust from entering. This integrated head and disk is called a head disk assembly (HDA). However, the head disk assembly (HDA) is provided with minute holes in order to adjust the pressure between the inside and outside air, and therefore cannot have a completely sealed structure. Furthermore, when a coated medium is used as a recording medium, it is necessary to keep the humidity low to prevent head adsorption, and when a thin film metal medium (plated medium or sputtered medium) is used, the magnetic material must be non-stick. Since it is an oxide, it has the problem of being easily corroded. Therefore, in order to maintain a low humidity state within the HDA (hermetically sealed housing) in which the disk is housed, a case or the like containing a desiccant is placed inside the HDA (hermetically sealed housing).

As a recent trend, magnetic disk drives are required to be faster, have a larger capacity, and are smaller. Accordingly, there is a need for a dehumidifying method that can maintain a sufficiently low humidity state in a narrow space.

As this type of technology, for example, Japanese Patent Application Laid-Open No. 62-26686
As described in the above publication, a method is known in which a moisture absorbent is housed in two moisture absorbent cases each having a different flow path resistance to maintain a constant low humidity state within the HDA.

[Problem to be solved by the invention]

The above-mentioned conventional technology does not take into account the moisture absorption characteristics of the moisture absorbent used or the amount used, and the moisture absorbent is housed in a case with ventilation holes with low flow path resistance to keep the relative humidity constant at high temperatures. There is a problem in that the moisture releasing effect of the air acts, leading to an increase in absolute humidity. Moreover, this causes a problem of shortening the life of the moisture absorbent housed in the case having the ventilation holes with high flow path resistance.

The purpose of the present invention is to solve such conventional problems, to suppress the increase in absolute humidity due to the moisture releasing action of the moisture absorbent housed in a case having ventilation holes with low flow path resistance C at high temperatures, and to It is an object of the present invention to provide a magnetic disk device that can narrow the space of a dehumidifying part and extend its life by reducing the amount of a first moisture absorbent housed in a case having a ventilation hole with high road resistance.

[Means to solve the problem]

In order to achieve the above object, a magnetic disk device according to the present invention has a hygroscopic agent that absorbs moisture in a sealed housing having a spatial volume V (Q) having micropores. 1 and a second hygroscopic agent, the first hygroscopic agent is housed in a case with high water vapor diffusion resistance, and the relative humidity around the device is 70% and 50%. The second hygroscopic agent has a difference Δq in saturated hygroscopicity from when the relative humidity is 50% or less, by mass (Q, 001 to 0.02
) V/Δq, (g) and is characterized by being housed in a case with low water vapor diffusion resistance.

[Effect]

In the present invention, when the ambient temperature of the device is stable, the inside of the closed housing with the spatial volume v(n) has a microhole and a first
The hygroscopic agent keeps the relative humidity constant at low humidity.

When the ambient temperature suddenly decreases and the relative humidity increases, the second moisture absorbent comes into play.

The moisture absorbent of Mizu-Tei 2 is used in low humidity conditions (relative humidity 50% or less).
Since the difference Δq between the saturated moisture absorption rates at relative humidity of 70% and 50% is larger than the saturated moisture absorption rate at
0.02) V/Δq(g) limits the amount of water vapor released by the second moisture absorbent when the ambient temperature suddenly increases, thereby preventing a significant increase in absolute humidity.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a sectional view of a sealed housing of a magnetic disk device showing an embodiment of the present invention, and FIG. 2 is a diagram showing the moisture absorption characteristics of first and second moisture absorbents used in this embodiment. . Further, in FIG. 1, only the parts related to dehumidification (moisture absorption), which is a characteristic feature of the present invention, are shown, and the magnetic head, magnetic disk, etc. that are naturally housed in the housing are omitted. Therefore, below, dehumidification (moisture absorption) will be explained in detail.

A part of the housing 1 having a spatial volume v(Q) is provided with a microhole 2 which increases the diffusion resistance of water vapor, and adjusts the pressure with the outside air. Further, inside the housing 1, there are a first moisture absorbent 3 exhibiting moisture absorption characteristics as shown in FIG. It is housed in case 5. Furthermore, the case 5 is provided with a filter 6 for preventing contamination by the moisture absorbent in the housing 1 and a moisture absorption hole 7 with a large diffusion resistance for the first moisture absorbent 3 to absorb moisture in the housing 1. . In this example, since the amount used is very small, the second moisture absorbent is placed in the case 5 that houses the first moisture absorbent 3.
A moisture absorbent 4 can be attached. Therefore, the space of the dehumidifying part can be reduced.

According to this embodiment, when the temperature around the housing 1 or inside the housing 1 is stable, water vapor that has diffused from the outside of the housing 1 through the micropores 2 is absorbed by the first moisture absorbent 3 through the moisture absorption holes 7. . At this time, the relative humidity inside the housing 1 is always kept at 50% or less by adjusting the diffusion resistance of the micropores 2 and moisture absorption holes 7. At this time, the second moisture absorbent 4 is in a saturated state, (0,001 to 0.02)
V.q. /Δq(g) of moisture is absorbed.

Next, when the temperature suddenly decreases, the relative humidity inside the housing 1 starts to rise, but the second moisture absorbent 4 starts absorbing moisture because the saturated moisture absorption rate of the second moisture absorbent 4 suddenly increases when the relative humidity is 50% or more. In order to maintain the relative humidity in the housing 1 at 70% or less, the amount of the second moisture absorbent 4 should be h/Δq(g) or more when the moisture content in the housing 1 at stable temperature is h(g). Must be. However, if the amount of the second moisture absorbent 4 is too large.

When the temperature rises rapidly, the moisture absorbed when the temperature is stable is released, leading to a significant increase in absolute humidity.6 In this embodiment, as described above, the amount of moisture absorbed by the second moisture absorbent 4 is (0,001 ~0.02) V・q,. /
Δ9 (g), and no significant increase in absolute humidity occurs due to moisture release. Therefore, the life of the first moisture absorbent 3 can be extended with a small amount of moisture absorbent. In addition, under the general usage environment of the device, the absolute humidity inside the housing 1 when the temperature is stable is O,OO1~0.02 according to the psychrometric diagram in Figure 3.
(kg/kg) It is estimated that the temperature will be 8 degrees, and the density of moisture in the air at this time will be approximately 0.001 to 0.02 (g ha D
becomes. Therefore, the amount of water h (g) in the housing 1 is
0.001 V≦h≦0.02V.

Incidentally, the diffusion resistance of a moisture absorption hole is inversely proportional to the area of the hole and proportional to its length. Also, what is the saturated moisture absorption rate?

The mass ratio of the hygroscopic agent and the absorbed moisture to the relative humidity around the hygroscopic agent, that is, the relationship is as follows.

〔Effect of the invention〕

As described above, according to the present invention, the relative humidity within the sealed housing can be kept low and a significant increase in absolute humidity can be prevented. Moreover, this makes it possible to extend the life of the moisture absorbent and reduce the amount of the moisture absorbent.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a sealed housing of a magnetic disk drive according to an embodiment of the present invention, FIG. 2 is a diagram showing moisture absorption characteristics of first and second moisture absorbents in an embodiment of the present invention, and FIG. is a psychrometric diagram. 1: Housing, 2: Micropore, 3: First moisture absorbent, 4:
Second moisture absorbent, 5: case, 6: filter, 7: moisture absorption hole. Diagram

Claims (1)

[Claims] 1. A magnetic disk device having a moisture absorbent that absorbs moisture in a sealed housing having a spatial volume V(l) having micropores, having a first moisture absorbent and a second moisture absorbent having different saturated moisture absorption rates; The first moisture absorbent is housed in a case with high water vapor diffusion resistance, and the difference Δq in the saturated moisture absorption rate between when the relative humidity around the device is 70% and when the relative humidity is 50% is The second hygroscopic agent whose saturated moisture absorption rate is higher than the saturated moisture absorption rate when the humidity is 50% or less is added by mass (0.00.1 to 0.0
2) A magnetic disk device that uses V/Δq(g) and is housed in a case with low water vapor diffusion resistance.