JPS5952153B2 - Control method of lifting magnet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling a lifting magnet.
In particular, the present invention relates to a control method for releasing equipment attracted by residual magnetism in a permanent magnet type lifting magnet.

As shown in Fig. 1, a magnetic path is made up of a magnetic steel 1, a yoke 2, an outer pole 3, and an inner pole 4, and a current is passed through a coil 5 wound around the magnetic steel 1 to perform magnetization and demagnetization. In lifting magnets, residual magnetism usually remains after demagnetization.

Of course, it is desirable to have no residual magnetism at all, but in actual work, residual magnetism remains due to various factors, and it is extremely difficult to eliminate it completely.

This residual magnetism is very small and does not attract the steel material 6 to be attracted, but if there is material such as cut steel material or nails, it may be attracted.

If an attempt is made to attract a steel material while the material is still attracted to the magnetic pole surface, the material will be sandwiched between the magnetic pole surface and the steel material, creating a gap and causing the inconvenience of weakening the adsorption force.

Regarding residual magnetism, magnetic steel is magnetized by being excited by a coil and demagnetized by being reversely excited, but the magnetic force changes depending on the permeance of the magnetic circuit (the ease with which magnetic flux passes through it) even when the same current is passed through it. It is something.

The main factors are (1) the size and thickness of the steel material, (
2) The size of the gap on the suction surface, warping of the steel material, distortion, scale, and the presence of dust), etc., and these things change in various ways in actual work.

Therefore, since the magnetic force also fluctuates every time a steel material is attracted, even if the magnetic force is reversely excited with a current that is the same as the excitation current,
It is not possible to completely eliminate the magnetic force, and residual magnetism remains.

Further, depending on the magnitude of the reverse excitation current with respect to the magnetic force, the polarity of the residual magnetism may be N polarity or S polarity.

The present invention has been developed in view of the points mentioned above. Before adsorbing steel materials, demagnetization is performed in the air using a reversal and attenuation current, and when the equipment is dropped and the steel materials are adsorbed, the equipment does not adhere to the magnetic pole surface. This eliminates the drop in adsorption force due to gaps caused by intervening equipment,
The purpose of this is to improve safety and work efficiency through reliable suction.

The following will explain the embodiments shown in the drawings.

In FIG. 2, 7 is a permanent magnet type lifting magnet body, and 8 is a power supply device, which is usually a cyrisk controlled power source.

Reference numeral 9 denotes a controller that gives a command signal to the power supply device 8, and each device is connected by a power supply cable 10.

The configuration of these devices is the same as that of the conventional type, but in the present invention, the power supply device 8 has the function of obtaining the current output necessary to achieve magnetization, demagnetization, and air demagnetization, respectively.

Therefore, when an air demagnetization command is issued from the controller 9 when the lifting magnet 7 is in the air in an unloaded state before attracting a steel material, the power supply device 8 outputs an air demagnetization current.

This output may be in the form of pulses or alternating current, as shown by A and B in Figure 3, and in essence, it attenuates while inverting, that is, it attenuates while inverting the hysteresis. It is sufficient if it is output.

This reversal/attenuation output causes the magnetic steel's residual magnetism to change its polarity (
N-5) is sequentially demagnetized while being reversed.

At this time, since the lifting magnet, that is, the magnetic steel, is in the air, it is not affected by the factors that change the permeance of the magnetic circuit as described above, and demagnetization can be performed under the same conditions every time.

Therefore, if inversion and attenuation demagnetization of a sufficient magnitude and number of times is performed in this state, it is possible to completely reduce the residual magnetism to zero, but in actual work, this aerial demagnetization is carried out in a few seconds. Otherwise, normal lifting magnet work will be hindered.

Therefore, in actual work, it is possible to reduce residual magnetism to the utmost limit, but it cannot be completely reduced to zero.

However, in the present invention, since reversal and attenuation demagnetization is performed in the air, even if a weak residual magnetism remains, when the polarity of the magnet is reversed in the process of reaching this point, the magnet always passes a point where the residual magnetism becomes zero. It happens.

This zero point passage occurs as many times as the number of reversals, and the equipment attached due to residual magnetism falls into the air when any zero point is passed.

After this aerial demagnetization, the lifting magnet 7 is placed on the steel material 8, a magnetization command is given to the power supply device 8 from the controller 9, and the power supply device 8 applies a current output necessary for magnetization to the magnet.

As a result, the steel material 8 is attracted to the lifting magnet l-7 and transported to a predetermined position.

The steel material 8 that has been transported to a predetermined position is placed on the floor, and then a demagnetization command is given from the controller 9 to the power supply device 8, and the power supply device 8 applies a current output necessary for demagnetization to the magnet.

As a result, the lifting magnets 1 to 7 release the adsorption of the steel material 8.

In this case, since the magnet is demagnetized on the steel material, it is affected by the above-mentioned magnetic fluctuation factors, and residual magnetism that varies in size depending on the work remains.

Then, before starting the next adsorption operation, the air demagnetization current is again output to the magnet 1, and the air demagnetization-magnetization-demagnetization control is repeated in this manner.

In addition, if the aerial degaussing command is given automatically in conjunction with, for example, hoisting, traversing, and traveling of the crane, it will be reliably executed for each operation, increasing reliability.
The driver's operations can be reduced.

As described above, according to the present invention, materials that are attracted to the magnetic pole surface due to residual magnetism are removed by demagnetizing them in the air before adhering to steel materials, thereby improving safety through reliable attraction and increasing work efficiency. Now I can try to improve myself.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing the structure of a permanent magnet type lifting magnet, Fig. 2 is a schematic diagram showing the relationship between the lifting magnet, power supply device, and controller, and Fig. 3 is a diagram showing the relationship between the command signal and excitation current according to the present invention. Explanatory diagram. 1...Magnetic steel, 2...Yoke, 3...
... Outer pole, 4... Inner pole, 5... Coil, 6... Steel material, 7... Lifting magnet body, 8... ...Power supply device, 9...
··controller.

Claims (1)

[Claims] 1. In a permanent magnet type lifting magnet that performs magnetization and demagnetization using a coil wound around magnetic steel,
A method for controlling a lifting magnet characterized by releasing the equipment by demagnetizing it in the air using a reversal/attenuation current before adsorbing the steel material.