JP2020153470A - 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 reduces a possibility that a magnetic viscous fluid leaks from a gap between a rotary shaft and a shaft hole while suppressing rotational resistance of the rotary shaft.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 rotatable relative to the rotary shaft 2 and the shaft hole 12; 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. The present invention relates to a seal structure of a rotating shaft in a viscous fluid device.

A seal structure of this type of rotating shaft is disclosed in FIG. 4 of Patent Document 1 and FIG. 1 of Patent Document 2. In the seal structure of the rotating shaft disclosed in Patent Document 1 and Patent Document 2, an annular sealing member is used so that the ferrofluid encapsulated inside does not leak to the outside through the gap between the rotating shaft and the shaft hole. The gap is sealed.

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

By the way, in order to prevent the ferrofluid fluid enclosed inside the ferrofluid device from leaking from the gap between the rotating shaft and the shaft hole, the sealing member exerts sufficient force on the rotating shaft and the shaft hole. It is necessary to set the amount of cross-sectional deformation of the seal member (in the case of an O-ring, the crushing allowance) so that it is pressed. The designer usually selects the cross-sectional dimension of the seal member and the radial dimension of the space into which the seal member is fitted so as to do so.

However, if the amount of cross-sectional deformation of the seal member is set so that the ferrofluid does not leak, the rotational resistance of the rotating shaft becomes large. On the other hand, if the amount of cross-sectional deformation of the seal member is set small, the rotational resistance of the rotating shaft becomes small, but the possibility that the ferrofluid sealed inside the device leaks from the gap between the rotating shaft and the shaft hole increases. ..

The present invention has been devised in view of the above problems, and can reduce the possibility of ferrofluid leaking from the gap between the rotating shaft and the shaft hole while suppressing the rotational resistance of the rotating shaft. It is an object of the present invention to provide a sealing structure for a rotating shaft of a viscous fluid device.

The seal structure of the rotating shaft of the magnetic viscous fluid device according to the present invention is such that the rotating shaft can be rotated with respect to both the rotating shaft, the shaft hole into which the rotating shaft is inserted, and the rotating shaft and the shaft hole. An intermediate member inserted between the shaft hole and the shaft hole, an inner sealing member that seals the gap between the rotating shaft and the intermediate member, and an outer sealing member that seals the gap between the intermediate member and the shaft hole. , Equipped with.

Cross-sectional deformation of the inner sealing member and the outer sealing member so that when the rotating shaft rotates with respect to the shaft hole, the intermediate member rotates with respect to the shaft hole at a rotation speed lower than that of the rotating shaft. It is preferable that the amounts are set respectively.

For example, the inner sealing member is fitted in 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 shaft hole. It is fitted in an annular groove formed in the inner peripheral portion.

An annular groove filled with grease may be formed on the outer peripheral portion of the rotating shaft or the inner peripheral portion of the intermediate member.

An annular groove filled with grease may be formed on the outer peripheral portion of the intermediate member or the inner peripheral portion of the shaft hole.

According to the present invention, it is possible to reduce the possibility of the ferrofluid leaking from the gap between the rotating shaft and the shaft hole while suppressing the rotational resistance of the rotating shaft.

It is sectional drawing which shows the seal structure of the rotating shaft of the ferrofluid fluid apparatus which concerns on embodiment of this invention. It is sectional drawing which shows the seal structure of the rotating shaft of the ferrofluid fluid apparatus which concerns on the modification of 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 device 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 a ferrofluid. It is composed of 9 mag.

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. It is desirable that a non-magnetic material is used for the rotating shaft 2. Further, a rolling bearing or a sliding bearing is adopted as the bearing 11.

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 cylindrical intermediate member 7, which will be described later, is inserted into the shaft hole 12. Further, a rotating shaft 2 is inserted through 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 cylindrical member and is inserted between the rotating shaft 2 and the shaft hole 12. A slight gap is secured between the intermediate member 7 and the rotating shaft 2. Further, a slight gap is also secured between the intermediate member 7 and the shaft hole 12. Therefore, the intermediate member 7 is 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 on the outer peripheral portion of the rotating shaft 2, and the outer sealing member 17 is fitted into the outer annular groove 19 formed on the outer peripheral portion of the intermediate member 7. There is. 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. In the present embodiment, three inner seal members 16 and three outer seal members 17 are provided, but the number is not limited to this, and may be one, two, or four or more. .. Further, the number of the inner seal member 16 and the outer seal member 17 may be different from each other.

The ferrofluid 9 is sealed in the gap between the disk 3 and the first yoke 4 and the second yoke 5. The magnetic viscous fluid 9 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 9 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 9 develops 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 apparatus 1 in the present embodiment is composed of the rotary shaft 2, the intermediate member 7, the shaft hole 12, the inner seal member 16, the outer seal member 17, and the like described above. Then, 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 rotates with respect to the shaft hole 12 at a rotation speed lower than that of the rotating shaft 2. The cross-sectional deformation amount (crushing allowance) of the inner seal member 16 and the outer seal member 17 is set respectively. 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 to a low value, so that the amount of cross-sectional deformation (crushing allowance) of the sealing members 16 and 17 is not increased, and the ferrofluid fluid can be used. 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 rotational resistance of the rotating shaft 2 can be suppressed. This also leads to suppressing the rotational resistance (so-called "base torque") of the rotating shaft 2 when no current is applied to the coil 6.

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, a plurality of rows of the inner seal member 16 and the outer seal member 17 are provided, but a part of the seal member is removed, and the inner annular groove 18 and the inner annular groove 18 into which the removed seal member is fitted are / Or the outer annular groove 19 may be filled with only grease. However, it is desirable that the annular groove filled with only grease is an annular groove different from the annular groove closest to the ferrofluid 9. By doing so, it is possible to suppress the rotational resistance of the rotating shaft 2 while preventing the leakage of the ferrofluid. An example of this case is shown in FIG. In the ferrofluid apparatus 1 shown in the figure, an annular groove 20 filled with grease is formed on the outer peripheral portion of the rotating shaft 2 between the rotating shaft 2 and the intermediate member 7. Further, between the intermediate member 7 and the shaft hole 12, an annular groove 21 filled with grease is formed on the outer peripheral portion of the intermediate member 7.

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 7 Intermediate member 9 Ferrofluid fluid 12 Shaft hole 16 Inner sealing member 17 Outer sealing member 20 Ring groove 21 Ring groove

Claims (5)

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 rotatable with respect to both the rotating shaft and the shaft hole.
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.
Cross-sectional deformation of the inner sealing member and the outer sealing member so that when the rotating shaft rotates with respect to the shaft hole, the intermediate member rotates with respect to the shaft hole at a rotation speed lower than that of the rotating shaft. Each amount is set,
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 claim 1 or 2.
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 claim 3.
An annular groove filled with grease is formed on the outer peripheral portion of the rotating shaft or the inner peripheral portion of the intermediate member.
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 claim 3 or 4.
An annular groove filled with grease is formed on the outer peripheral portion of the intermediate member or the inner peripheral portion of the shaft hole.
The seal structure of the rotating shaft of the ferrofluid fluid system.

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