JPS5999168A - Electromagnetic clutch - Google Patents

Abstract

PURPOSE:To transmit rotation of one shaft to the other shaft at the same speed or different speed, by providing each magnetic force generating means on each plate mounted on each end of shafts, and forming at least one of the magnetic force generating means as an electromagnet capable of conducting or cutting off current in a desired order. CONSTITUTION:Eight permanent magnets 6a having same polarity are fixed on the lower surface of a disc 6 mounted on the lower end of a drum shaft 1c in such a manner as to be arranged along the circumference of the disc 6 and in equally spaced relation with each other. Similarly, eight electromagnetic coils 7a are fixed on the upper surface of a disc 7 mounted on the upper end of a motor shaft 2a in such a manner as to be arranged along the circumference of the disc 7 and in equally spaced relation with each other. Any one of the electromagnets 7a is allowed to be arbitrarily energized or deenergized independently of the other electromagnets 7a. Some of the plural electromagnets 7a are sequentially switched to be energized, so as to be rotated in the forward or reverse direction of the shaft, thus increasing or decreasing a rotary speed of the drum shaft 1c without changing a rotary speed of the motor shaft 2a.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to an electromagnetic clutch that transmits rotation between a pair of shafts, brakes, etc. using electromagnetic force.

BACKGROUND TECHNOLOGY There are various types of clutch mechanisms such as mechanical and electric types for connecting and disconnecting shafts, but fluid force JP electromagnetic force is used to connect and disconnect shafts without contact. Conventional electromagnetic clutches that use electromagnetic force to connect shafts,
The rotation of one shaft can be transmitted to the other shaft at approximately the same speed, but if you want to change the rotation of the other shaft, you must change the rotation speed of one shaft, or use a gear mechanism or belt as a transmission means. A hanging pulley or the like must be interposed between the shafts, which has the disadvantage of complicating the structure.

The present invention eliminates the above-mentioned drawbacks. Magnetic force generating bodies are respectively provided on the plate-shaped bodies provided on the end faces of the shaft, and at least one of the magnetic force generating bodies is constituted by a plurality of electromagnets, and each electromagnet is arranged in a desired direction. To provide an electromagnetic clutch that transmits the rotation of one shaft to the other shaft at the same speed or at a variable speed by turning on and off electricity according to the order, and enables braking of the rotation by magnetic force as necessary. The purpose is to

In order to achieve this object, the present invention provides a pair of plate-like bodies that are respectively provided on the end faces of a pair of shafts whose end faces are spaced apart and face each other, and that face each other with a predetermined interval; and magnetic force generating bodies that are provided oppositely to each other and exert magnetic attraction or repulsion on each other, and at least one of the magnetic force generating bodies is disposed circumferentially on the surface of the plate-shaped body. According to the present invention, by uniformly energizing the plurality of electromagnets, The shafts can be rotated at the same speed, and some of the electromagnets can be switched and energized to rotate some of the electromagnets in the direction of rotation of the shaft or in the opposite direction. The driven shaft can be sped up or decelerated without changing the speed, and if low-speed rotation is required, simply switch the electromagnets to be excited sequentially along the circumferential direction while leaving one shaft stopped. Moreover, since the shafts transmit power without contacting each other, excellent effects such as less transmission of mechanical shocks at the time of starting or stopping can be achieved.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an elevational view showing an embodiment of a head drum for a video tape recorder in which one quasi-magnetic clutch of the present invention is not used, and FIG. This is an enlarged view.

In the figure, l is the head drum for a video tape recorder, which consists of a pair of upper and lower drums /a, /b, lower drum /
1) is rotated by the power of a motor 2 accompanied by a magnetic head (not shown). The electromagnetic clutch 3 is provided between the drum shaft /C and the motor shaft 2a, and controls power transmission between the two shafts /c, 2a.

The drum shaft /c is supported by bearings (G) and (S) at two locations, upper and lower, and a disc (B) is attached to the lower end thereof. A disc 7 is attached to the upper end of the motor shaft 2a, and the disc 7 and the disc A face each other with a predetermined distance apart.

In the case of this example, on the F side of disk B, ! Permanent magnets 6a of the same polarity are fixedly spaced circumferentially at equal intervals. Further, on the upper surface of the disk 7, electromagnetic coils 7a are fixedly arranged circumferentially at equal intervals. These permanent magnets 6a and electromagnets 7a
and disks B, 7, etc. constitute the electromagnetic clutch 3.

Here, the various electromagnets 7a are energized through the motor shaft 2a and brush teeth brought into contact with the VC, and each electromagnet 7a can be energized or deenergized at will independently from the other electromagnets 7a. can do. Normally, there is no need to change the rotational speed of the lower drum 16, but in consideration of durability and other tests, it is desirable that the rotational speed be variable.

First, when rotating the lower drum lb at a normal rotation speed, all the electromagnets 7al are energized so that they are magnetized with a different polarity from the permanent magnet 4a, and a magnetic attraction force is created between the electromagnet 7a and the permanent magnet 6a. make it work. As a result, the motor shaft 2a and the drum shaft /c are magnetically coupled via the electromagnetic clutch 3, and the lower drum /1) rotates at a constant speed by the power of the motor 2.

In addition, if you want to stop the lower drum /1) that is rotating at a constant speed, you can simply cut off the power to the motor 2, but you can shorten the inertia rotation period and immediately stop the lower drum /b completely. There are cases where you want to. In that case, after cutting off the power to the motor 2, for example, only two of the lr permanent magnets 4a are left and the others are demagnetized, and the two in the excited state are
motor! 4] The permanent magnets 4a to be energized are sequentially switched along their circumferential arrangement so that they rotate in a direction relatively opposite to the rotation direction of magnets 2a. By doing this, the permanent magnet 6a on the drum shaft/c side is magnetically attracted in the opposite direction to the rotation direction, and the lower drum/b can be braked and stopped in a shorter time than the normal inertial rotation period. . In this case, the electromagnetic clutch 3 acts as an electromagnetic brake.

On the other hand, without changing the rotational speed of the motor shaft 2a, the lower drum/
When rotating at a rotation speed higher than bQ, the excitation points of some of the permanent magnets Aa are switched while rotating in the same direction as the motor shaft 2a, contrary to the braking described above. The rotational speed of the lower drum lb can be arbitrarily varied according to the switching speed of the excitation state, the number of excited parts, etc.

This speed change by switching the excitation of the permanent magnets 6a is possible even when the motor shaft 2a is stopped; for example, it is only necessary to sequentially switch one of the g permanent magnets A to clockwise or counterclockwise to excite it. But the lower drum tbf can be rotated.

In this way, the electromagnetic clutch 3 configured as described above is not only capable of rotating the drum shaft/c at the same speed as the motor shaft 2a (but also capable of rotating at an increased speed or at a reduced speed).
It has excellent functions such as being able to brake when necessary. Further, since the motor shaft 2a and the drum shaft /c rotate without contacting each other, the lower drum /b is less susceptible to mechanical vibrations from the motor 2, and less susceptible to starting shocks, braking shocks, etc. Therefore, it is suitable for precision machining, such as a head drum l for a video tape recorder.

Note that in the above embodiments, the number of permanent magnets 6a and electromagnets 7a used is of course not limited to g.

Further, an electromagnet may be used in place of the permanent magnet Oa for the disk A on the drum shaft IQ side, or an electromagnet 7a on the disk 7 on the motor shaft 2a side may be replaced with a permanent magnet (in short, It is sufficient if at least one of the discs B or 7 is provided with an electromagnet.

[Brief explanation of the drawing]

FIG. 1 is an elevational view showing an embodiment of a head drum for a video tape recorder to which the electromagnetic clutch of the present invention is applied, and FIG. 2 is an enlarged view taken along the line ■-■ in FIG. . /c...drum shaft, 2a...motor shaft, 3...electromagnetic clutch, Otsu, 7...disk, Otsua...permanent magnet,
7a...Electromagnet.

Claims (1)

[Claims] A pair of plate-like bodies facing each other with a predetermined interval are provided, respectively, on the end faces of a pair of shafts whose end faces 5 are spaced apart from each other, and are respectively provided on opposing faces of the pair of plate-like bodies. , and magnetic force generating bodies that mutually exert magnetic attraction or repulsion, at least one of the magnetic force generating bodies being composed of a plurality of electromagnets disposed circumferentially on the surface of the plate-shaped body, An electromagnetic clutch in which the magnets in each chamber can be turned on and off in accordance with a desired order.