JP2020153471A - Seal structure of rotary shaft of magnetic viscous fluid device - Google Patents

Abstract

To provide a seal structure of a rotary shaft of a magnetic viscous fluid device which can keep rotational resistance of a rotary shaft in a low state constantly and reduces a possibility that a magnetic viscous fluid leaks from a gap between the rotary shaft and a shaft hole without being affected by volumetric change and change of atmospheric pressure of the magnetic viscous fluid.SOLUTION: A seal structure of a rotary shaft of a magnetic viscous fluid device includes: a rotary shaft 2; a shaft hole 12 into which the rotary shaft 2 is inserted; an intermediate member 7 which is inserted into a space between the rotary shaft 2 and the shaft hole 12 so as to be movable in an axial direction of the rotary shaft 2; an inner seal member 16 which seals a gap between the rotary shaft 2 and the intermediate member 7; and an outer seal member 17 which seals a gap between the intermediate member 7 and the shaft hole 12.SELECTED DRAWING: Figure 1

Description

According to the present invention, magnetism capable of changing the torque transmitted between members by interposing a ferrofluid between members rotatably provided and changing the strength of the magnetic field applied to the ferrofluid. Regarding the seal structure of the rotating shaft of the viscous fluid device.

For example, FIG. 4 of Patent Document 1 and FIG. 1 of Patent Document 2 disclose a ferrofluid fluid apparatus. In the seal structure of the rotating shaft of these magnetic viscous fluid devices, the gap is sealed by using an annular sealing member so that the magnetic viscous fluid sealed inside does not leak to the outside from the gap between the rotating shaft and the shaft hole. are doing.

Japanese Unexamined Patent Publication No. 2017-076209 Japanese Unexamined Patent Publication No. 2019-011788

By the way, in the ferrofluid apparatus disclosed in Patent Documents 1 and 2, when the temperature of the ferrofluid rises due to an increase in temperature or the like, the volume of the ferrofluid expands and the seal member is strongly resistant to the rotating shaft and the shaft hole. It is pressed and the rotational resistance of the rotating shaft increases. In particular, it is not preferable that the rotational resistance of the rotating shaft (hereinafter, also referred to as “base torque”) increases when no current is applied to the coil.

Further, as described above, the increase in the base torque of the rotating shaft may occur when the ferrofluid fluid device is used in a place where the atmospheric pressure is high or low.

In addition, when the volume of the ferrofluid expands significantly or the atmospheric pressure drops significantly, the possibility of the ferrofluid leaking from the seal portion increases. Here, examples of a case where the atmospheric pressure drops significantly include a case where the ferrofluid fluid device is transported by an airplane or the like, or a case where the ferrofluid fluid is incorporated as a part of the device such as an airplane.

The present invention has been devised in view of the above problems, and can always maintain the rotational resistance of the rotating shaft in a low state without being affected by changes in the volume and atmospheric pressure of the ferrofluid, and is magnetic. It is an object of the present invention to provide a sealing structure for a rotating shaft of a ferrofluid fluid device, which can reduce the possibility of viscous fluid leaking from the sealing portion.

The seal structure of the rotating shaft of the magnetic viscous fluid device according to the present invention includes the rotating shaft, the shaft hole into which the rotating shaft is inserted, and the rotating shaft and the shaft hole so as to be movable in the axial direction of the rotating shaft. An intermediate member inserted between the two, and an inner sealing member that seals a gap between the rotating shaft and the intermediate member.
An outer sealing member for sealing a gap between the intermediate member and the shaft hole is provided.

According to the seal structure of the rotating shaft of the ferrofluid fluid device having such a configuration, the intermediate member moves so as to reduce the pressure difference between the enclosed space of the ferrofluid fluid and the outside of the device, so that the volume of the ferrofluid fluid changes. The rotational resistance of the rotating shaft can be kept low at all times without being affected by changes in pressure and pressure, and the possibility of the ferrofluid leaking from the seal portion can be reduced.

In the seal structure of the rotating shaft of the ferrofluid apparatus having the above configuration, it is desirable to further include an urging member that urges the intermediate member to the side where the ferrofluid is sealed.

In the seal structure of the rotating shaft of the magnetic viscous fluid device having the above configuration, the rotating shaft is supported by the shaft hole via a bearing provided on the side opposite to the magnetic viscous fluid of the intermediate member. The urging member may be provided between the intermediate member and the bearing and urge the intermediate member in a direction away from the bearing.

In the seal structure of the rotating shaft of the magnetic viscous fluid device having the above configuration, the intermediate member is rotatably inserted between the rotating shaft and the shaft hole with respect to both the rotating shaft and the shaft hole. It may be.

In the sealing structure of the rotating shaft of the ferrofluid apparatus having the above configuration, the inner sealing member is fitted into an annular groove formed in the outer peripheral portion of the rotating shaft or the inner peripheral portion of the intermediate member, and the outer sealing member is provided. The member may be fitted in an annular groove formed in the outer peripheral portion of the intermediate member or the inner peripheral portion of the shaft hole.

In the seal structure of the rotating shaft of the ferrofluid fluid device having the above configuration, the bearing may be formed with a communication hole for communicating the space on the intermediate member side and the outside of the device.

According to the present invention, the rotational resistance of the rotating shaft can always be maintained at a low state without being affected by changes in the volume or atmospheric pressure of the ferrofluid, and the ferrofluid may leak from the seal portion. Can also be lowered.

It is sectional drawing which shows the magnetic viscous fluid apparatus in embodiment of this invention.

Hereinafter, the seal structure of the rotating shaft of the ferrofluid fluid device according to the embodiment of the present invention will be described with reference to the drawings.

The ferrofluid device changes the torque transmitted between the members by interposing the ferrofluid between the members rotatably provided with each other and changing the strength of the magnetic field applied to the ferrofluid. All you need is.

As shown in FIG. 1, the ferrofluid apparatus 1 according to the present embodiment includes a rotating shaft 2, a disk 3, a first yoke 4, a second yoke 5, a coil 6, an intermediate member 7, a casing 8, and an urging member. 9. It is composed of a ferrofluid 10 and the like.

The end of the rotating shaft 2 is vertically connected to the center of the disk 3. The rotating shaft 2 is rotatably supported by a shaft hole 12 provided in the second yoke 5 via a bearing 11 provided on the opposite side of the ferrofluid 10 of the intermediate member 7. It is desirable that a non-magnetic material is used for the rotating shaft 2.

It is desirable that the bearing 11 has a structure capable of ventilating air between the space 15 on the intermediate member 7 side and the outside of the device 1. In the present embodiment, a slide bearing in which a communication hole 11a for communicating the space 15 and the outside of the device 1 is formed is used.

The disk 3 rotates with respect to the casing 8, the first yoke 4, the second yoke 5, and the like. The disk 3 is provided integrally with the rotating shaft 2. The disk 3 is constructed using, for example, a magnetic material.

The first yoke 4 is made of a magnetic material, and is formed in a disk shape having a facing surface 4a facing the surface 3b of the disk 3 via a minute gap. The first yoke 4 is fitted and fixed in a cylindrical casing 8.

The second yoke 5 is made of a magnetic material and has an opposing surface 5a that faces the back surface 3a of the disk 3 via a minute gap. The second yoke 5 has a shaft hole 12 in the center. A tubular intermediate member 7, which will be described later, is inserted into the shaft hole 12. Further, a rotating shaft 2 is inserted inside the intermediate member 7. Further, the second yoke 5 is formed with an annular groove 13 for arranging the coil 6. The second yoke 5 is fitted and fixed to the inside of the cylindrical casing 8.

Reference numeral 14 is a sphere made of a non-magnetic material, which is accommodated in a space formed by a recess formed at the center of the first yoke 4 and a recess formed at the center of the end face of the rotating shaft 2. The sphere 14 is for facilitating the setting of a gap between the first yoke 4 and the disk 3, and the gap is determined by the diameter of the sphere 14.

The coil 6 is arranged along the groove 13 formed in the second yoke 5. A current is supplied to the coil 6 from a power feeding device (not shown).

The intermediate member 7 is a tubular member and is inserted between the rotating shaft 2 and the shaft hole 12. A small gap is secured between the intermediate member 7 and the rotating shaft 2, and a small gap is also secured between the intermediate member 7 and the shaft hole 12. The intermediate member 7 is provided so as to be movable in the axial direction of the rotating shaft 2, and is provided so as to be rotatable with respect to both the rotating shaft 2 and the shaft hole 12.

A seal member 16 (hereinafter, also referred to as “inner seal member 16”) for sealing the gap between the intermediate member 7 and the rotary shaft 2 is provided between the intermediate member 7 and the rotary shaft 2. Further, a seal member 17 (hereinafter, also referred to as “outer seal member 17”) for sealing the gap between the intermediate member 7 and the shaft hole 12 is provided between the intermediate member 7 and the shaft hole 12. The inner sealing member 16 is fitted into the inner annular groove 18 formed in the inner peripheral portion of the intermediate member 7, and the outer sealing member 17 is fitted into the outer annular groove 19 formed in the outer peripheral portion of the intermediate member 7. ing. In the present embodiment, an O-ring is used as the inner seal member 16 and the outer seal member 17, but other seal members such as annular packings having various cross-sectional shapes and oil seals may be used instead of the O-ring. Good. Further, in the present embodiment, two inner seal members 16 and two outer seal members 17 are provided, but the number is not limited to this, and may be one or three or more. Further, the number of the inner seal member 16 and the outer seal member 17 may be different from each other.

Further, in the present embodiment, the inner peripheral portion and the outer peripheral portion of the intermediate member 7 are provided with annular grease grooves 20 and 21 filled with grease. However, the place where the grease grooves 20 and 21 are provided is not limited to the above. For example, it is possible to use one grease groove or to provide a plurality of grease grooves at each location. It is also possible to provide a grease groove on the inner peripheral portion of the shaft hole 12 or the outer peripheral portion of the rotating shaft 2.

The urging member 9 is provided between the intermediate member 7 and the bearing 11 and urges the intermediate member 7 in the direction away from the bearing 11 (the side in which the ferrofluid 10 is sealed). As the urging member 9, for example, an elastic body can be used. Examples of the elastic body include a spring and rubber. In the magnetic viscous fluid device 1 illustrated in FIG. 1, the intermediate member 7 urged by the urging member 9 is formed at a predetermined position by the large diameter portion 2a formed by the rotating shaft 2. Here, the large diameter portion 2a is a portion of the rotating shaft 2 having an outer diameter larger than the inner diameter of the intermediate member 7.

The ferrofluid 10 is sealed in the gap between the disk 3 and the first yoke 4 and the second yoke 5. The magnetic viscous fluid 10 is a liquid in which magnetic particles are dispersed in a dispersion medium. For example, a liquid in which the magnetic particles are composed of nano-sized metal particles (metal nanoparticles) can be used. The magnetic particles are made of a magnetizable metal material, and the metal material is not particularly limited, but a soft magnetic material is preferable. Examples of the soft magnetic material include alloys such as iron, cobalt, nickel and permalloy. The dispersion medium is not particularly limited, and examples thereof include hydrophobic silicone oil. The blending amount of the magnetic particles in the magnetically viscous fluid may be, for example, 3 to 40 vol%. It is also possible to add various additives to the ferrofluid in order to obtain various desired properties.

In the magnetic viscous fluid device 1 having the above configuration, when a current is applied to the coil 6, magnetic paths are formed in the disc 3, the first yoke 4, and the second yoke 5 along the direction indicated by, for example, the arrow P. Ru. This magnetic path is a magnetic viscous fluid 10 interposed in the gap between the front surface 3b of the disk 3 and the facing surface 4a of the first yoke 4, and the gap between the back surface 3a of the disk 3 and the facing surface 5a of the second yoke 5. Penetrate. As a result, the ferrofluid 10 develops a viscosity (shear stress) according to the strength of the magnetic field, and the transmission torque between the disk 3 and the yokes 4 and 5 depends on the strength of the magnetic field. growing. As a result, the braking force of the rotating shaft 2 also increases according to the strength of the current applied to the coil 6.

The seal structure of the rotary shaft 2 of the ferrofluid device 1 in the present embodiment includes the rotary shaft 2, the intermediate member 7, the urging member 9, the shaft hole 12, the inner seal member 16, the outer seal member 17, and the like described above. Has been done. For example, when the volume of the ferrofluid 10 enclosed in the apparatus 1 expands due to an increase in temperature or the like, or when the atmospheric pressure drops for some reason, the intermediate member 7 resists the urging force of the urging member 9. The volume of the region in which the ferrofluid 10 is enclosed is expanded by moving from the right side to the left side in the figure. As a result, the pressure difference between the region where the ferrofluid 10 is enclosed and the atmospheric pressure can be suppressed to a small size. After that, when the volume of the ferrofluid 10 sealed in the apparatus 1 returns to the original volume due to a decrease in temperature or the like, or when the atmospheric pressure rises and returns to the original volume, the intermediate member 7 attaches the urging member 9. It moves from the left side to the right side in the figure depending on the force and returns to the original state. Of course, also at this time, the pressure difference between the region where the ferrofluid 10 is enclosed and the atmospheric pressure is kept small.

In short, according to the seal structure of the rotating shaft of the ferrofluid fluid device according to the present embodiment, the rotational resistance of the ferrofluid 2 is always kept low without being affected by the volume change and the pressure change of the ferrofluid 10. It can be maintained, and the possibility that the ferrofluid 10 leaks from the gap between the rotating shaft 2 and the shaft hole 12 can be suppressed to a low level. Further, in the seal structure of the rotating shaft of the ferrofluid fluid device according to the present embodiment, a structure in which the intermediate member 7 and the urging member 9 are embedded between the rotating shaft 2 and the shaft hole 12 is adopted, so that the size is almost large. As a compact ferrofluid fluid device 1, the above-mentioned action and effect can be obtained.

By the way, in the seal structure of the rotating shaft 2 of the magnetic viscous fluid device 1 in the present embodiment, when the rotating shaft 2 rotates with respect to the shaft hole 12 at a predetermined rotation speed or an arbitrary rotation speed, the intermediate member 7 The cross-sectional deformation amount (crushing allowance) of the inner seal member 16 and the outer seal member 17 is set so as to rotate with respect to the shaft hole 12 at a rotation speed lower than that of the rotation shaft 2. Therefore, the speed at which the seal members 16 and 17 slide with the inner diameter side member or the outer diameter side member can be suppressed low. For example, when the rotating shaft 2 rotates with respect to the shaft hole 12 at a rotation speed of 100 rpm and the intermediate member 7 rotates with respect to the shaft hole 12 at a rotation speed lower than that of the rotating shaft 2 (for example, 40 rpm), it is inside. The relative rotation speed between the inner diameter side member (rotation shaft 2) and the outer diameter side member (intermediate member 7) of the seal member 16 is 40 rpm. Further, the relative rotation speed between the inner diameter side member (intermediate member 7) and the outer diameter side member (shaft hole 12) of the outer seal member 17 is 60 rpm. In the case of the ferrofluid device according to the conventional example, when the rotation shaft rotates at a rotation speed of 100 rpm with respect to the shaft hole, the relative rotation speed between the inner diameter side member and the outer diameter side member of the seal member is also 100 rpm.

Generally, as the relative rotation speed between the inner diameter side member and the outer diameter side member of the seal member increases, the seal function deteriorates and leakage of the ferrofluid tends to occur. According to the seal structure of the rotating shaft according to the present embodiment, the relative rotation speed can be suppressed low, so that the ferrofluid 10 does not increase the amount of cross-sectional deformation (crushing allowance) of each of the sealing members 16 and 17. Leakage can be suppressed. Further, since it is not necessary to increase the amount of cross-sectional deformation of each of the seal members 16 and 17, the base torque of the rotating shaft 2 can be suppressed.

Further, according to the sealing structure of the rotating shaft according to the present embodiment, the relative rotation speed between the inner diameter side member and the outer diameter side member of the sealing member can be suppressed to be low, so that the deterioration of the sealing members 16 and 17 is delayed. be able to. In other words, the durability of the sealing members 16 and 17 is improved.

<Modification example>
In the above-described embodiment, when the sealing region of the ferrofluid 10 is highly sealed, the urging member 9 can be omitted.

In the present invention, for example, the torque transmitted between the members can be changed by interposing a ferrofluid between members rotatably provided to each other and changing the strength of the magnetic field applied to the ferrofluid. It can be applied to ferrofluid devices that can.

1 Ferrofluid fluid device 2 Rotating shaft 3 Disk 7 Intermediate member 9 Biasing member 10 Ferrofluid 11 Bearing 11a Communication hole 12 Shaft hole 15 Space 16 Inner sealing member 17 Outer sealing member 18 Inner annular groove 19 Outer annular groove

Claims (6)

The axis of rotation and
The shaft hole into which the rotating shaft is inserted and
An intermediate member inserted between the rotating shaft and the shaft hole so as to be movable in the axial direction of the rotating shaft,
An inner sealing member that seals the gap between the rotating shaft and the intermediate member,
An outer sealing member that seals the gap between the intermediate member and the shaft hole,
A seal structure for a rotating shaft of a ferrofluid fluid device, which comprises. In the seal structure of the rotating shaft of the ferrofluid fluid device according to claim 1.
A seal structure for a rotating shaft of a magnetic viscous fluid device, further comprising an urging member that urges the intermediate member on the side where the magnetic viscous fluid is sealed. In the seal structure of the rotating shaft of the ferrofluid fluid device according to claim 2.
The rotating shaft is supported by the shaft hole via a bearing provided on the opposite side of the ferrofluid of the intermediate member.
The urging member is provided between the intermediate member and the bearing, and urges the intermediate member in a direction away from the bearing.
The seal structure of the rotating shaft of the ferrofluid fluid system. In the seal structure of the rotating shaft of the ferrofluid fluid device according to any one of claims 1 to 3.
The intermediate member is rotatably inserted between the rotating shaft and the shaft hole so as to be rotatable with respect to both the rotating shaft and the shaft hole.
The seal structure of the rotating shaft of the ferrofluid fluid system. In the seal structure of the rotating shaft of the ferrofluid fluid device according to any one of claims 1 to 4.
The inner sealing member is fitted into an annular groove formed in the outer peripheral portion of the rotating shaft or the inner peripheral portion of the intermediate member, and the outer sealing member is the outer peripheral portion of the intermediate member or the inner circumference of the shaft hole. It is fitted in the annular groove formed in the part,
The seal structure of the rotating shaft of the ferrofluid fluid system. In the seal structure of the rotating shaft of the ferrofluid fluid device according to any one of claims 2 to 5.
The bearing is formed with a communication hole that communicates the space on the intermediate member side with the outside of the device.
The seal structure of the rotating shaft of the ferrofluid fluid system.

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