JPS6066362A - Sealing device - Google Patents

Abstract

PURPOSE:To keep the pressure resistance inside a sealing device constant even if the environmental temperature is changed by constituting a portion on the way of a magnetic path or a portion adjacent to the magnetic path of a heat sensitive magnetic body. CONSTITUTION:As shown in the sectional view, a sealing device is constituted of pole pieces 2 contacted both sides of a ring-like permanent magnet 1, magnetic rotary body 4 and magnetic fluid 3 caught between the pole pieces 2 and the rotary body 4. A annular temperature sensitive magnetic fluid 5 is interposed between the right and left pole pieces 2 so as to touch the inner periphery of the permanent magnet 1. For instance, Mn-Zn group heat sensitive ferrite or the like is used as the heat sensitive magnetic body.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an I-type sealing device using a magnetic fluid suitable for application to a dust sealing device for a magnetic disk for a computer, a rotary shaft sealing device for a vacuum device, an air valve, and the like.

For example, in a magnetic disk drive, the disk unit is sometimes attached to the end of a rotating shaft extended from a motor installed externally, and dust on the disk unit or from bearings, etc. In order to prevent the intrusion of oil mist, etc., a sealing device that blocks air circulation is sometimes provided.

FIG. 1 is a cross-sectional view showing an example of a general type device. An annular ferromagnetic body (pole piece) 2 is attached to both sides i of an annular permanent magnet 1, and a ferromagnetic rotating body 4 is attached to the annular permanent magnet 1. The magnetic fluid 3 is magnetically captured in the annular gap formed between the pole piece 2 and the rotating shaft 4. This annular film of the magnetic fluid 3 functions as a sealing device. are doing.

By the way, the annular film formed by the magnetic fluid is such that if a predetermined amount of magnetic fluid is not injected between the pole piece 2 and the rotating shaft 4 (1), sufficient withstand pressure will not be generated as a sealing device, and it will not function as a sealing device. However, when a sufficient amount of magnetic fluid is injected and the magnetic fluid 3 is left unused or in operation, the magnetic fluid 3 flows out of the sealed device due to an increase in environmental temperature and contaminates the sealed space. The first reason is that the air in the space partitioned by the two annular magnetic fluids expands thermally and presses the annular magnetic fluid film 3 to the outside of the sealing device.Second, the environmental temperature increases. As a result, the amount of magnetic flux that can be supplied by the permanent magnet 1 is reduced.Therefore, due to the decrease in the magnetic field that holds and fixes the magnetic fluid film 3, the sealing pressure is reduced, and the first
Due to the force mentioned in the above reason, the magnetic fluid film 3 becomes easy to move or the magnetic fluid film 3 is torn, and the magnetic fluid flows out of the sealing device. As the environmental temperature increases, the saturation magnetization from the magnetic fluid itself decreases, and the sealing pressure decreases.As a result, due to the aforementioned force, the magnetic fluid film 3 becomes easier to move, or the magnetic fluid film 3 becomes easier to move. The fluid film 3 is ruptured and the magnetic fluid flows out of the sealed device.Fourth, as the environmental temperature rises, the surface tension and viscosity of the magnetic fluid decrease. This makes it easier to move.These are possible causes.

By the way, the left and right spaces that have a sealing mechanism using magnetic driftwood are blocked from fluid at one point, but in a certain temperature range, for example, air valves, etc., can promote the flow of fluid or vice versa ((it is necessary to block it). However, this type of conventional sealing mechanism has the above-mentioned drawbacks, and the magnetic fluid pulp (
It is extremely difficult to make the valve work.

In view of this point, the present invention provides a temperature-sensitive magnetic material in the magnetic path in order to suppress the deterioration of the sealing function due to the rise in the ambient temperature,
The main purpose of the present invention is to propose a sealing device that can intentionally increase or decrease the sealing groove in a predetermined temperature range by arbitrarily setting the temperature-sensitive magnetic material.

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

FIG. 2 is a sectional view showing an example of the present invention. A sealing device (hereinafter referred to as MFS) is composed of an annular permanent magnet 1, a pole piece 2 in contact with the IC on both sides, a magnetic rotating body 4, and a magnetic fluid 13 trapped between the ball piece 2 and the rotating body 4. However, an annular temperature-sensitive magnetic fluid 5 is sandwiched between the left and right pole pieces 2 in contact with the inner peripheral surface of the permanent magnet 1. The temperature-sensitive magnetic material 5 is, for example, M
An n-Zn temperature-sensitive ferrite can be used.

FIG. 3 is a diagram showing the relationship between temperature change and MFS breakdown voltage. In the temperature range below the Curie point (Tc) of the temperature-sensitive magnetic material 5, the magnetic flux force from the permanent magnet 1? The MFS does not pass through the pole piece 2 and act on the ferromagnetic rotating body 4, but passes from the pole piece 2 through the temperature-sensitive magnetic body 5, passes through the other pole piece 2, and returns to the permanent magnet 1. Almost no breakdown voltage occurs.When the temperature rises from around the Curie point Tc,
Since the saturation magnetization of the temperature-sensitive ferrite begins to decrease, the amount of magnetic flux passing through the temperature-sensitive ferrite 5 decreases, and conversely, the magnetic flux also passes through the pole piece 2, the magnetic fluid 3, and the rotating shaft 4. As the amount of magnetic flux increases, the withstand voltage of the MFS increases (see curve B in FIG. 3). Therefore, temperature-sensitive ferrite 5
At temperature distribution above the Curie point, where the amount of magnetic flux acting on the rotating body 4 due to the zero effect increases with temperature rise, the magnetic flux acting on the pole piece 2, the magnetic fluid film 3, and the rotating shaft 4 increases and the magnetic fluid 3 increases. In equilibrium with the amount of decrease in saturation magnetization of MF
The withstand voltage of S becomes constant. In higher temperature ranges, the third
As shown in the figure, the magnetic flux density that passes through and holds the magnetic fluid 3 supplied by the permanent magnet decreases, and the saturation magnetization of the magnetic fluid also decreases, so the withstand voltage of the MFS gradually decreases.

Therefore, by setting the temperature range where the MFS's withstand voltage is constant to the variable range of the MFS operating environment, the temperature of Ml''S -
The leakage of the magnetic fluid 3 can be prevented by compensating for the drop in withstand pressure due to the increase in F.

By considering the cross-sectional area and material of the temperature-sensitive ferrite 5, the cross-sectional area and material of the permanent magnet 1, etc., the withstand voltage of the MPS can be gradually increased as the temperature rises, as shown by curve C in Fig. 3. I can get 1st. In addition, the outflow of the magnetic fluid 3 due to the surface tension and viscosity reduction inherent to the magnetic fluid 3 is also caused by the phenomenon of an apparent increase in the viscosity of the magnetic fluid (as the magnetic field strength applied to the magnetic fluid increases, the viscosity of the magnetic fluid 3 increases). Curve A in Figure 3 shows the change due to the structure of the example in Figure 1 as a reference, but as the temperature rises, the withstand voltage characteristics deteriorate. It is understood that the reason is as mentioned above.

FIG. 4 shows another embodiment in which a temperature-sensitive ferrite 5 used as a magnetic flux bypass and an I- is arranged outside the permanent magnet 1 and the pole piece 2. Since the operating principle and effects are the same as those of the embodiment shown in FIG. 2, a detailed explanation will be omitted. This will be explained below.

Figure 5 shows an MFS having a structure in which a temperature-sensitive ferrite 5 and a permanent magnet 1 are sandwiched between pole pieces 2 in a diagonal shape.
It is a sectional view showing an example. At a temperature below the Gikori point Tc of the temperature-sensitive ferrite 5, the magnetomotive force of the permanent magnet 1 is used only in the gap between the pole piece 2 and the rotating body 4, so as shown in FIG. High pressure resistance. However, when the temperature rises by 1, the saturation magnetization of the temperature-sensitive ferrite 5 rapidly decreases from around Tc,
'C Therefore, the magnetomotive force loss of the temperature-sensitive ferrite 5 increases,
The withstand voltage of the MFS begins to decrease rapidly. Therefore, by utilizing such characteristics, it is possible to open and close the partition walls due to temperature changes caused by the magnetic fluid.

Figure 7 shows a structure in which the MFSs of the example in Figure 2 and the example in Figure 5 are combined. Assume one point TC2 of temperature-sensitive ferrite between 1 and 1,
Furthermore, the relationship 'f'c, (Tc) is set. Therefore, at temperatures below Tc, the magnetic flux mainly generated from the permanent magnet 1 passes through the temperature-sensitive ferrite 51, so no withstand pressure is generated. , the amount of magnetic flux passing through the magnetic fluid 3 increases from the nearby temperature, so the withstand voltage increases.As the temperature approaches TC2, the magnetomotive force loss of the temperature-sensitive ferrite 52 increases, so the amount of magnetic flux passing through the magnetic fluid 3 increases. decreases, and the withstand voltage drops rapidly. This relationship can be expressed in a diagram as shown in FIG. 8. Therefore, in this example, Tc.

The flow path can be blocked by magnetic fluid only in the temperature range of ~TC2, and it has a so-called valve function.

The structure shown in FIG. 9 is basically a combination of Ml"S in the example in FIG. 2 and the example in FIG.
Let the points of Curie be Tc, , Tc2 respectively,
The relationship is Tc, (, Tc2.

Therefore, at a temperature below Tc, the magnetic flux generated from the permanent magnet 1 will form two magnetic paths.

One is permanent magnet 1 → pole piece 21 → temperature-sensitive ferrite 62 → pole piece 22 → permanent magnet 1 (hereinafter referred to as the first path). The other path is permanent magnet 1 → temperature-sensitive light 61 → pole piece 21 → rotating shaft 4 → pole piece 22 → permanent magnet 1 (hereinafter referred to as the second path). In this case, the withstand voltage is generated by the magnetic flux caused by the second path. When the temperature approaches Tc,
The magnetomotive force loss of the temperature-sensitive ferrite 62 in the first path increases, and the magnetic flux passes through the second path [2], and the withstand voltage begins to drop rapidly. Since the magnetic flux cannot pass through, the magnetic flux in the first path is permanent magnet 1 → pole piece 21 → rotation 1 sales shaft 4 → pole piece 22
→The path of permanent magnet 1 is taken and withstand voltage is generated (10th
(see figure).

Therefore, since the present invention can freely change the pressure resistance of the sealing device depending on the temperature, it can be applied to many applications as a device such as a fluid A control valve. Alternatively, a non-rotating shaft can be used, and it can also be applied to a flat plate with an infinitely large diameter. Further, in the above example, the temperature-sensitive magnetic material is attached, but it goes without saying that the annular pole piece or the rotating shaft itself may be made of the temperature-sensitive magnetic material without the addition of the temperature-sensitive magnetic material.

As described above, the present invention includes a shaft, a magnet device facing the shaft with a gap therebetween and forming a magnetic path between the two poles, and a magnetic fluid having fluidity that closes the gap at a predetermined location. In the constructed sealing device, since the part in the middle of the magnetic path or the part adjacent to the magnetic path is made of a temperature-sensitive magnetic material,
Even if there are fluctuations in the environmental temperature, the withstand pressure within the sealing device can be kept constant or increased. Therefore, even if the environmental temperature fluctuates, the magnetic fluid inside the sealing device will not flow out of the sealing device, and a highly reliable sealing device (MFS) using magnetic fluid can be provided. Furthermore, since the MFS of the present invention can freely change and set the withstand pressure and temperature characteristics, it can be used in many ways as an opening/closing mechanism for air valves and the like.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of the basic structure of the magnetic i11 fluid seal device, No. 2 I-1 is a cross-sectional view showing an example of Kinoe Suj, and Fig. 3 is a pressure-resistant-temperature custom-made wire for explaining the effects of the present invention. Figure 4 is a new view showing a second example of the present invention, Figure 5 is a sectional view showing a third example of the present invention, Figure 6 is a breakdown voltage-temperature characteristic of the example in Figure 5, and Figure 4 is a new view showing a second example of the present invention. , FIG. 7 is a sectional view showing a fourth example of the present invention, FIG. 8 is a breakdown voltage-temperature characteristic diagram of the example in FIG. 7, FIG. 9 is a sectional view showing a fifth example of the present invention, and FIG. 10 is a breakdown voltage-temperature characteristic diagram of the $9 example. 1...Permanent magnet, 2...Pole piece, 3...Magnetic fluid, 4...Rotating shaft, 5 - Temperature-sensitive magnetic material applicant's agent Taka Akiyama, Phosphorus Figure 3, Figure 7cm '/Visibility CT) Figure 7 Figure 8 Figure 9 and 2 Figure 10

Claims (1)

[Claims] a shaft, a magnet device that has a gap with the shaft (-) and forms a magnetic path between the opposing poles, and -1- a sealing device that is made of a magnetic fluid with fluidity that closes the gap at a predetermined location. A sealing device characterized in that a portion in the middle of the magnetic path or adjacent to the magnetic path is made of a temperature-sensitive magnetic material.