JPS622955Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an eddy current coupling. That is, the present invention relates to an eddy current joint in which an inductor fixed to a load-side rotating shaft is disposed on the circumferential side of a drum that is directly connected to a driving electric motor, and fixed magnetic poles are disposed on the circumferential side of the inductor with a gap between them. It is something. Conventionally, in this type of device, as shown in FIGS. 1 and 2, a driving body 2 consisting of a holding part 2a and a drum 2b is integrated with a driving shaft 1, and a driven body 4 consisting of a rotating bracket 4a and an inductor 4b is integrated. The drive shaft 1 rotates because the fixed magnetic pole 6 which is fixed to the bracket 7 and holds the excitation coil 5 is disposed on the inner circumferential side of the inductor 4b which is integrated with the load-side rotating shaft 3 and has irregularities. In this state, when the excitation coil 5 is DC-excited by an external power source, the magnetic flux φ generated is as shown by the broken line in FIG. At this time, the magnetic flux density becomes uneven between the inductor 4b and the drum 2b due to the unevenness of the inductor 4b, and if there is a speed difference between the inductor 4b and the drum 2b, this magnetic flux is transferred to the drum 2b. As a result, an eddy current is induced on the inner peripheral surface of the drum 2b, and this overcurrent generates an electromagnetic force, which becomes a transmitted torque and rotates the inductor 4b so as to be pulled in the same direction as the drum 2b. However, the magnitude of this transmitted torque changes depending on the relative speed between the drum 2b and the inductor 4b and the magnitude of the excitation current of the excitation coil 5, and any desired transmitted torque or rotational speed can be obtained by adjusting the excitation current. It was hot.

However, the transmission torque is large and the rotating shaft 3
If the deceleration rate of the rotational speed of The output at 3 is reduced by the speed difference, and this difference is entirely due to the drum 2b.
The temperature of the drum 2b increases due to eddy current loss within the drum 2b, and the amount of heat generated from the excitation coil 5 is also very large.
Therefore, there is a problem in that the drum 2b is deformed or the thermal stress becomes extremely large due to this temperature rise.Furthermore, when a fan is attached for cooling, there are problems such as an increase in noise and an increase in cost.

The present invention solves these problems and can reduce the power supplied to the excitation coil on the fixed magnetic pole side, as well as reduce temperature rise, making it simple to improve reliability and service life. It is provided so that it can be improved.

Next, an embodiment of the present invention shown in FIGS. 3 to 6 will be described.

FIG. 3 shows a cross-sectional view of the main parts constructed almost in the same way as the conventional example shown in FIG. 1, as indicated by the same reference numerals.
The gap between the inductor 4b and the fixed magnetic pole 6 is filled with magnetic fluid 8. As is well known, the magnetic fluid 8 is a colloidal solution in which ferromagnetic particles 8a, such as ferrite, having a diameter of about 100 Å are suspended in a solvent, as shown in FIG. 6a. On the surface of the ferromagnetic particles 8a, there is an adsorption layer of surfactant with the hydrophobic groups facing outward, so the ferromagnetic particles 8a are uniformly dispersed in the solvent as shown in FIG. 6b. . or,
Since the ferromagnetic particles 8a are suspended in the colloidal solution, the colloidal solution has extremely high magnetic permeability compared to the magnetic permeability of air. The magnetic fluid 8 is sealed by circular seal rings 9 fixedly attached to the fixed magnetic pole 6 without contacting the inductor 4b. As shown in FIG. 4, the seal ring 9 is formed of a permanent magnet, and its magnetic field holds the magnetic fluid 8 and prevents the magnetic fluid 8 from flowing out from the gap.

Since the seal ring 9 is provided at a position where it is hardly affected by the magnetic force of the excitation coil 5, the magnetic fluid 8 can be retained even if the magnetic flux of the excitation coil 5 is larger than the magnetic flux of the permanent magnet as the seal ring 9. become. Therefore, since the magnetic permeability of the magnetic fluid 8 is extremely large compared to the magnetic permeability of air, the magnetic resistance of the gap decreases in proportion to the ratio of the magnetic permeability of the air and the magnetic fluid, and the gap is formed by the excitation of the excitation coil 5. In the magnetic circuit, most of the magnetomotive force of the excitation coil 5 is spent on magnetic resistance in the gaps between the solid magnetic pole 6 and the inductor 4b, and between the drum 2b and the inductor 4b. Note that the magnetic flux φ shown in FIG. 3 is formed by the magnetomotive force of the exciting coil 5. Further, the magnetic flux φ' in the magnetic circuit formed by the seal ring 9 becomes a closed loop magnetic circuit between the seal ring 9 and the inductor 4b as shown in FIG. When the gap between the inductor 4b and the fixed magnetic pole 6 is filled with magnetic fluid, the magnetic fluid 8 has magnetism, so the seal ring 9 and the inductor 4
It is attracted and held by the magnetic field formed between b.
Do not leak out of the gap. Furthermore, since the magnetic fluid 8 has a high magnetic permeability, the magnetic resistance of the air gap can be reduced.

When the magnetic resistance in the gap between the fixed magnetic pole 6 and the inductor 4b is reduced, the magnetomotive force of the excitation coil 5 is used only in the magnetic resistance between the drum 2b and the inductor 4b, and as a result, the predetermined value of the gap is reduced. The excitation current required for the excitation coil 5 to obtain the magnetic flux density is small, so the power supplied to the excitation coil 5 can be saved compared to the conventional example, and the heat generated from the excitation coil 5 can be significantly reduced. Furthermore, since the thermal conductivity of the magnetic fluid is more than 10 times greater than that of air, the heat from the inductor 4b can be effectively transferred to reduce the temperature of the inductor 4b.

FIG. 5 shows another embodiment of the eddy current joint according to the present invention, in which a lip seal 10 made of an elastic material such as rubber or plastic is installed in place of the seal ring 9, but it functions in the same manner as described above. It is something to do.

In this way, the present invention seals and interposes magnetic fluid in the gap between the fixed magnetic pole and the inductor to reduce magnetic resistance, which significantly reduces the power supplied to the excitation coil on the fixed magnetic pole side. It is possible to save energy, reduce temperature rise, solve the conventional problems mentioned above, and improve the reliability and life of the electromagnetic induction coupling device itself. It has the advantage of being able to be implemented conveniently with a simple structure.

[Brief explanation of the drawing]

Figure 1 is a sectional view of the conventional example, and Figure 2 is A of Figure 1.
- A sectional view taken along line A, FIG. 3 is a sectional view of the main part of an embodiment of the present invention, FIG. 4 is an enlarged view of a part of FIG. 3, and FIG. 5 is a diagram showing another embodiment. FIG. 6 is an explanatory diagram of the magnetic fluid. 2b...Drum, 3...Rotating shaft, 4b...Inductor, 6...Fixed magnetic pole, 8...Magnetic fluid.

Claims (1)

[Claims for Utility Model Registration] (1) An inductor fixed to a load-side rotating shaft disposed around the circumference of a magnetic drum connected to a drive shaft of a drive motor, and an excitation coil located approximately in the center. and a fixed magnetic pole disposed on the circumferential side of the inductor with a predetermined gap from the inductor, the magnetic fluid interposed in the gap between the inductor and the fixed magnetic pole; , provided on both sides of the fixed magnetic pole at a position hardly affected by the magnetism of the excitation coil and on both sides of the excitation coil with a slight gap from the inductor, respectively, and the inductor. and a seal ring that prevents the magnetic fluid from flowing out from the gap between the fixed magnetic pole and the fixed magnetic pole. (2) The seal ring is formed of a permanent magnet, and has a practical function of holding the magnetic fluid by the magnetic field of the permanent magnet and preventing the magnetic fluid from flowing out from the gap between the inductor and the fixed magnetic pole. An eddy current joint according to claim 1 of the patent registration claim. (3) The eddy current joint according to claim 1, wherein the seal ring is formed of a lip seal.