JPH0714254A - Magnetic torque limiter - Google Patents

Abstract

PURPOSE:To obtain a magnetic torque limiter whose torque value can be adjusted easily. CONSTITUTION:A sub-yoke plate 3 is attached to a hysteresis plate 2 and the sub-yoke plate 3 is shifted in the radial direction of the hysteresis plate 2 to change a hysteresis torque. In order to fix the sub-yoke plate 3, a nailed spring 11 is provided on the hysteresis plate 2 and, further, saw-teeth 12 which are geared with the nailed spring 11 are provided on the sub-yoke plate 3 to obtain a magnetic torque limiter 100. Therefore, even if the torque value is out of a specification, the torque value can be adjusted and the torque limiter can be used. Further, as defective products are thus eliminated, wastes can be avoided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic torque limiter, and more specifically, it is used in a reel stand apparatus such as an 8 mm video tape recorder (8 mm VTR), a digital audio tape recorder (DAT), a cassette tape recorder, and the like. The present invention relates to a magnetic torque limiter.

[0002]

2. Description of the Related Art FIG. 6 is a cross-sectional view of an essential part of an example of a conventional magnetic torque limiter. This magnetic torque limiter 2
00, a disk-shaped hysteresis plate 202 is fixedly provided inside the ring-shaped drive gear 201, and the bearing member 2 is provided inside the hysteresis plate 202.
04 is fitted. The bearing member 204 is rotatably fitted on the tape reel shaft 6. 5 is a washer. The hysteresis plate 202 is made of a Mn steel-based magnetic material or a Cr—Co steel-based magnetic material and has a coercive force H.
c = 140 Oe.

A yoke plate 7 is fixedly mounted on the tape reel shaft 6, and a disk-shaped magnet plate 8 having a plurality of poles alternately magnetized in the circumferential direction is provided on the upper surface of the yoke plate 7. It is attracted by magnetic force. A rotation stopper 9 prevents the magnet plate 8 from slipping on the yoke plate 7.
The yoke plate 7 is made of magnetic stainless steel and has a high magnetic permeability, but the coercive force Hc is much smaller than 10 [Oe].

The magnetic torque limiter 200 as described above
In, when the hysteresis plate 202 is rotated from the outside via the drive gear 201, the hysteresis plate rotates the magnet plate 8 and thereby the tape reel shaft 6 rotates. At the tape winding end, the tape reel shaft 6 is stopped with a force larger than the hysteresis torque, and the drive gear 201 slips and rotates.

[0005]

In the conventional magnetic torque limiter 200 described above, the hysteresis plate 202 and the magnet plate 8 magnetized to have a plurality of poles are used to utilize the hysteresis loss generated in the hysteresis plate 202 as torque. There is. However, there is a problem that it deviates from the standard torque value due to variations in materials, dimensions, and assembly. In addition, there is a problem that a product that deviates from these standard torque values becomes a defective product and becomes a waste product. Therefore, an object of the present invention is to provide a magnetic torque limiter that can be adjusted so as not to deviate from the standard torque value even if there are variations in materials, dimensions, and assembly.

[0006]

According to a first aspect of the present invention, there is provided a first rotating shaft, a hysteresis plate fixed to the first rotating shaft, a second rotating shaft, and a second rotating shaft thereof. A yoke plate fixed to the yoke plate and a magnet plate that is attracted to one surface of the yoke plate and faces the hysteresis plate with a gap therebetween, and the first rotation is caused by a hysteresis torque between the hysteresis plate and the magnet plate. In a magnetic torque limiter that transmits rotation between a shaft and the second rotating shaft, a sub-yoke plate is provided on the side opposite to the magnet plate of the hysteresis plate, and the sub-yoke plate is magnetically moved and fixed at different positions. There is provided a magnetic torque limiter characterized in that the hysteresis torque can be adjusted by.

According to a second aspect of the present invention, in the above magnetic torque limiter, a spring with a claw is provided integrally with the hysteresis plate to fix the sub-yoke plate,
There is provided a magnetic torque limiter characterized in that saw teeth that are held by the claw spring are provided on a sub-yoke plate.

[0008]

In the magnetic torque limiter of the present invention, the sub-yoke plate is provided on the side of the hysteresis plate opposite to the magnet plate, and the sub-yoke plate is moved to and fixed at a magnetically different position. When they overlap, magnetic flux flows through the sub-yoke plate to adjust the hysteresis torque. Further, saw teeth are provided integrally with such a sub-yoke plate, and a claw spring is provided on the hysteresis plate. Then, the saw teeth are held by the spring with the claws to fix the sub-yoke plate. Therefore, the torque value can be easily adjusted.

[0009]

The present invention will be described in more detail with reference to the embodiments shown in the drawings. The present invention is not limited to this. FIG. 1 is a sectional view of a main part of a magnetic torque limiter according to an embodiment of the present invention. In this magnetic torque limiter 100, a disk-shaped hysteresis plate 2 is provided inside the drive gear 1 which is the first rotating shaft.
Is fixed, and on the upper surface of the hysteresis plate 2,
The sub-yoke plate 3 is movably provided. A bearing member 4 is fitted inside the hysteresis plate 2. The bearing member 4 is rotatably fitted on a tape reel shaft 6 which is a second rotating shaft. 5 is a washer. The drive gear 1 and the bearing member 4 are made of engineering plastic such as polyacetal resin. The hysteresis plate 2 is made of Mn steel-based magnetic material or Cr-C.
o Made of steel magnetic material, coercive force Hc = 140 [Oe]
And Br = 9000 [Gauss]. The washer 5 is made of 66-nylon.

A yoke plate 7 is fixedly mounted on the tape reel shaft 6, and a disk-shaped magnet plate 8 having a plurality of poles alternately magnetized in the circumferential direction is provided on the upper surface of the yoke plate 7. It is attracted by magnetic force. The tape reel shaft 6 is provided with a rotation stopper 9 for preventing the magnet plate 8 from slipping on the yoke plate 7.

The tape reel shaft 6 is made of a high sliding grade polyacetal (POM) resin. In addition to these, polyacetal resin containing carbon fiber, polycarbonate resin, unsaturated polyester resin and the like can be used. The sub-yoke plate 3 and the yoke plate 7 are hardened materials of martensitic stainless steel (SUS420J2), and have coercive forces Hc = 70 [Oe] and Br = 9000 [Gauss]. Martensitic stainless steel is easily available, inexpensive, and easy to process. In addition to the above, precipitation hardening stainless steel can also be used. The magnet plate 8 is Nd
-Fe-B type magnet. In addition to this, a ferrite plastic magnet can be used.

FIG. 2 is a top view when the sub-yoke plate 3 of the first rotating shaft is fixed to the center of the hysteresis plate 2.
In the drive gear 1, an elongated guide hole 10 and a claw spring 11 are integrally formed on the sliding contact side surface thereof. Sub-yoke plate 3
Is provided so as to be diametrically movable along the elongated guide hole 10, and saw teeth 12 are provided on the side surface thereof. This saw tooth 1
The sub-yoke plate 3 is fixed by holding 2 with the spring 11 with the pawl. The sub-yoke plate 3 can be moved by pushing it with a finger or the like.

The torque is effectively generated near the outer circumference of the hysteresis plate 2. Therefore, if the sub-yoke plate 3 is fixed substantially at the center of the hysteresis plate 2, the magnetic flux Φ effectively acts near the outer periphery of the hysteresis plate 2 as shown in FIG. 3, and a hysteresis torque is generated.

FIG. 4 is a top view when the sub-yoke plate 3 of the first rotating shaft is fixed while being displaced from the center of the hysteresis plate 2. In this case, as shown in FIG. 5, the magnetic flux Φ flows into the sub-yoke plate 3, the hysteresis loss is reduced, and the torque is reduced. That is, the hysteresis torque decreases as the sub-yoke plate 3 is moved to the vicinity of the outer periphery of the hysteresis plate 2.

In the magnetic torque limiter 100, the hysteresis plate 2 is externally provided via the drive gear 1.
When is rotated, the magnet plate 8 rotates due to the hysteresis torque, which causes the tape reel shaft 6 to rotate. At the tape winding end, the tape reel shaft 6 is stopped by a force larger than the hysteresis torque, so that the drive gear 1 slips and rotates.

Even if such a hysteresis torque deviates from the standard torque value due to variations in material, size, and assembly, the sub-yoke plate 3 can be used to adjust the torque value. Furthermore, since no defective products are generated, no waste is generated. Further, since the mechanism for moving and fixing the sub-yoke plate 3 is integrally molded with the hysteresis plate 2 together with the drive gear 1, the manufacturing becomes easy.

[0017]

According to the magnetic torque limiter of the present invention, since it has the above-mentioned configuration, the torque can be finely adjusted and used even if it deviates from the standard torque value. Furthermore, since no defective products are generated, no waste is generated.

[Brief description of drawings]

FIG. 1 is a sectional view of a main part of a magnetic torque limiter according to an embodiment of the present invention.

FIG. 2 is a top view when the sub-yoke plate of the first rotating shaft in FIG. 1 is fixed to the center of a hysteresis plate.

3 is a schematic cross-sectional view of a main part showing the relationship between the position of a sub-yoke plate in FIG. 1 and magnetic flux.

FIG. 4 is a top view when the sub-yoke plate of the first rotating shaft in FIG. 1 is fixed while being displaced from the center of the hysteresis plate.

5 is a schematic cross-sectional view of essential parts showing the relationship between the position of the sub-yoke plate of FIG. 1 and magnetic flux.

FIG. 6 is a cross-sectional view of a main part of an example of a conventional magnetic torque limiter.

[Explanation of symbols]

 100 magnetic torque limiter 1 drive gear 2 hysteresis plate 3 sub-yoke plate 4 bearing member 5 washer 6 tape reel shaft 7 yoke plate 8 magnet plate 9 rotation stop 10 long hole for guide 11 claw spring 12 saw blade

Claims (2)

[Claims] 1. A first rotary shaft, a hysteresis plate fixed to the first rotary shaft, a second rotary shaft, a yoke plate fixed to the second rotary shaft, and one surface of the yoke plate. And a magnet plate that opposes the hysteresis plate with a gap therebetween and transmits the rotation between the first rotating shaft and the second rotating shaft by the hysteresis torque between the hysteresis plate and the magnet plate. In a magnetic torque limiter, a sub-yoke plate is provided on the side opposite to the magnet plate of the hysteresis plate, and the hysteresis torque can be adjusted by moving and fixing the sub-yoke plate to a magnetically different position. Formula torque limiter. 2. The magnetic torque limiter according to claim 1, wherein a spring with a claw is provided integrally with the hysteresis plate to fix the sub-yoke plate, and saw teeth that are stopped by the spring with the claw are provided on the sub-yoke plate. A magnetic torque limiter characterized by being provided.