RS20090381A - MAGNETIZER / DEMAGNETIZER WITH MAGNETIC FIELD SWITCH - Google Patents

Abstract

Invention herewith described refers to the magnetizer/demagnetizer with the switching magnetic field which is a new device using a continual stream of square magnetic pulses and internal loops of magnetization (SM) and (SD) used for sequentional progressive hysteresisless magnetization and demagnetization of magnetically hard materials (sintered cores), then for magnetic orientation of powder particles during injection of melted binder and orientation of groups of grains of polycrystalline magnetically hard materials during annealing in a furnace. Magnetizing and demagnetizing are performed by current impulses through the solenoid (SL) mounted in the injection tool or in the magnetic circuit (MC) and by adjusting the switching magnetic field intensity to be higher than or equal to the coercive field HcB of the magnetically hard material. The switching magnetizer has a generator of square pulses (CC) with adjustable width, height and the number of pulses per second, power transistor block (IGBT), active cooler (C) and the circuit for protection against auto induction (SS), a magnetic circuit (MC) with air gap made of dynamo sheets with axial (A), radial (R), diametric (D) and multi polar (M) adapters. The magnetizer/demagnetizer is power supplied by a group of series/parallel connected batteries, it is mobile and safe for work, multiple energy-saving and has a small dissipation.

Description

MAGNETIZER/DEMAGNETIZER WITH SWITCH

MAGNETIC FIELD

1. Technical field to which the invention relates

The invention belongs to the field of electromagnetics, the field of magnetic circuits for magnetization and demagnetization of magnetically hard materials. The device is also used for magnetic orientation of particles of magnetically hard powders in the tool during injection molding with molten binder (PIM technology), then orientation of polycrystalline magnets during heating and for magnetization of sintered (finished) cores for permanent magnets. By type, magnetization is hysteresis-free, asymmetric, pulsed, progressive and sequential because internal, i.e. small loops of magnetization and demagnetization caused by a dense continuous procession of square magnetic pulses.

According to the international classification of patents, it can be classified into groups:

and

2. Technical problem

The invention solves the technical problem of magnetization and demagnetization of green and sintered cores of magnetically hard materials and orientation of magnetic powder particles in the tool during injection of the same with molten binder, then orientation of polycrystalline magnet grains during heating in a magnetic field and magnetization / demagnetization of sintered cores of permanent magnets. By using a switching magnetic field created as a result of a continuous dense procession of narrow square current pulses through a solenoid and a magnetic circuit made of dynamo sheets, a hysteresis-free successive progressive magnetization (internal, i.e., small magnetization loops) is created, which has the same effect as DC magnetization, but consumes many times less energy, heats up less, requires the same amount of cooling and smaller conductor sections, due to which the coil and solenoid are smaller in size. This switching magnetizer consumes kA of current from the battery blocks connected in series/parallel via the switch-IGBT (transistor group). Currents flow in dense continuous processions of narrow square pulses whose number per second, height, width and distance between pulses can be adjusted. This magnetization is completely safe to work with, and switching magnetization, for example, lasts the entire time of injection molding, as long as it is needed. It achieves magnetic fields from 400 to 1000 kA/m and more, depending on the air gap in the magnetic circuit, the solenoid coil, the selected excitation of the IGBT and the selected voltage on the series/parallel connected battery block. Charging of the battery blocks is regular from the 220 Vac network, when the magnetizer is not in operation. The magnetizer is mobile, can work autonomously for several hours and is safe to work with.

3. State of the art

A magnetizer is a device for magnetizing/demagnetizing magnetically hard materials and usually consists of a strong current source and a magnetic circuit with an air gap, with or without adapters (pole extensions) for focusing the magnetic flux, i.e. magnetization of typical cores for permanent magnets.

Today, permanent magnet magnetizers are made in several variants depending on the type of magnetization (axial, radial, diametrical, multipole) and the shape of the core (adapter with pole extensions), but basically they can all be classified into two groups: with direct current - DC and with impulse current (most often) capacitive magnetizers. DC magnetizers use direct current and multi-winding solenoids that are cooled by air, oil, or water. The one-way magnetic fields that are then created are used to orient the particles during the pressing of powders of magnetically hard materials. Unidirectional magnetic fields of increasing/decreasing intensity are used for magnetic measurements in hysteresiographs. Pulse magnetizers usually have electrolytic capacitors of higher capacity, but for high voltages (2kV-3kV/5-50 mF, paper in oil) which, when discharged via the thyristor, give a triangular current pulse of the order of 20 milliseconds with an intensity of 10-100 kA, and then charge for a few seconds. As pulses, positive halves of sine waves can be used directly from the network via thyristors, but with limited currents up to 1KA, which otherwise causes great disturbances in the network. They are used only for magnetizing final products - permanent magnets.

DC demagnetization is performed with direct currents in the opposite direction to those during magnetization, but with about a third of the intensity, i.e. with those currents that achieve a reverse magnetic field sufficient to bring the residual magnetic induction of the magnet to zero (a slightly larger magnetic field is required than the coercive field Hcb on the demagnetization curve in the II quadrant of the B-H diagram). The second method is demagnetization with a pulse magnetizer, but not through a thyristor, but by free discharge of the capacitor through a solenoid (RLC-circuit), resulting in damped periodic oscillations that perform demagnetization (known as AC demagnetization).

Apart from these methods of magnetization, there is the so-called hysteresis-less asymmetric AC magnetization, which is a combination of a direct magnetic field and an alternating magnetic field due to an AC current. The AC current introduces a change from zero to some positive value of the magnetic field, which creates internal magnetization loops that lead to magnetization, i.e. magnetic induction Br without describing the entire magnetization curve in the first quadrant of the B-H diagram, i.e. without bringing the magnetically hard material into saturation (saturation) with large values of the magnetic field.

There are many manufacturers of DC magnetizers and pulse magnetizers, for example:

1. MAGNET-PHYSIK.De, Dr Steingroever, GmbH, www. magnet-physik. de

K,U,X-series magnetizers, demagnetizers.

2. ASC SCIENTIFIC, Impulse magnetizer, Model IM-10, www. ascscientific. com 3. MAGNETIC INSTRUMENTS, Magnet Charger Model 942A, www. M.Sc. com 4. ELECTROSINESYSTEMS, Magnetizers for Magnetizing Multipolar Magnet Based Magnetos Required In Automobiles, www. electrosine. com 5. METIS INSTRUMENTS & EQUIPMENT, Magnetizers, Modular energy sources for magnetizing systems, www. Metis. be 6. M-PULSE, Magnetizers, Magnetisiergerate von mPulse - Energie fur Magnete,

www. m-pulse. biz

The disadvantage of the first group-DC magnetizer/demagnetizer is a large current from the network, a large cross-section of the conductor, a large cooling of the coil with oil or water.

The shortcoming of the second group of pulsed-capacitive magnetizers is a pause between pulses of several seconds, so they cannot be used for orientation when pressing or injecting green cores.

In the patent literature, magnetizers and demagnetizers are related to the product and type of magnetization, as already mentioned, but they basically use direct current DC or direct/damped periodic pulses and half-sine pulses, for example: 1. US Patent 3,969,657 (13.07.1976), Oettinghaus; Dieter (Hohenlimburg, DT), Magnetizing and demagnetizing electrical circuit. 2. US Patent 4,381,492 (April 26, 1983), Steingroever; Erich (53 Bonn, DE), Steingroever; Dietrich (Bergisch-Gladbach), Apparatus for magnetizing multipolar permanent magnets - Apparatus for magnetizing and demagnetizing multipolar magnets. 3. US Patent 4,920,326 (April 24, 1990), Agarwala; Ashok K. (Penfield, NY), Method of magnetizing high energy rare earth alloy magnets. 4. US Patent 5,055,813 (08.10.1991), Johnson; Terry R. (Newport News, VA) Magnetization/demagnetization device- Circuit for magnetization and demagnetization. 5. US Patent 5,469,321 (November 21, 1995), Stupak, Jr.; Joseph J. (Portland, OR), Magnetizing device having variable charge storage network and voltage control -Magnetizing device with variable charge storage network and voltage control. 6. US Patent 5,852,393 (December 22, 1998), Reznik; Svetlana (Rochester, NY), Furlani; Edward P. (Lancaster, NY), Schmidtmann; William E. (Naples, NY), Apparatus for polarizing rare-earth permanent magnets. 7. US Patent 6,026,718 (February 22, 2000), Anderson; Wayne (Northport, NY), High energy magnetizer and selective demagnetizer integral with driver tool or the like 8. US Patent 6,310,532 (October 30, 2001), Santa Cruz; Cathy D. (Reno, NV), Henry; Gregory L. (Sparks, NV), Alderson; Neil R. (Sparks, NV), Multipurpose magnetizer/demagnetizer- Multipurpose magnetizer demagnetizer. 9. US Patent 6,621,396 (September 16, 2003), Leupold; Herbert A. (Eatontown, NJ), Permanent magnet radial magnetizer- Radial magnetizer for permanent 1.

In American patents and European patents there are several magnetizers/demagnetizers with direct - DC and pulsed current (triangular and half-sine pulses), but there is none, as far as we know, with a dense continuous train of narrow square current pulses that give the same (square in shape) switching magnetic field in the solenoid or dynamo sheets and successively and progressively magnetize/demagnetize the permanent magnetic material via asymmetric internal i.e. small magnetization loops (hysteresis-free magnetization by a switching magnetic field).

4. Presentation of the essence of the invention

Magnetizer/demagnetizer with switching magnetic field is a new device intended for hysteresis-free, consecutive progressive magnetization and demagnetization of magnetically hard materials (finished, sintered cores), then magnetic orientation of magnetic powder particles in the tool during injection molding with organic binder (PIM technology) and magnetic orientation of polycrystalline magnet grains during heating at elevated temperatures. For magnetization, it uses a switching magnetic field in the solenoid (SL) or in the magnetic circuit (MC) in intensity greater than or equal to the coercive field Hcb of the magnetically hard material that is injected or magnetized and asymmetric internal ie. small magnetization (SM) and demagnetization (SD) loops. Magnetization loops occur in magnetohard material during magnetization in a magnetic circuit with an air gap as a result of a dense continuous procession of narrow square current pulses whose number per second, height, width and distance between pulses can be adjusted. The device consists of a pulse generator - input control circuit (CC), battery group in series-parallel connection (BG), battery charger (BC), switching transistor block (IGBT), which has its own special block (CL) for managing the executive switching circuit, executive switching block with power transistors (TR), active cooling block (C) and block for protection against induced impulses (SS).

The second part of the magnetizer consists of a solenoid built into the injection tool (SL) and a special magnetic circuit with an air gap made of dynamo sheets (MC) and axial (A), radial (R), diametral (D) and multipole (M) adapters for the final magnetization of the finished cores. The procedure of magnetization and demagnetization by a dense continuous procession of narrow square current pulses by means of the same magnetic field (for example, pulse / pause 1/10) belongs to the type of asymmetric magnetization (hysteresis-free), in contrast to magnetizers with direct current and magnetizers with pulsed current, but it uses for its operation battery groups, IGBTs, magnetic circuits with dynamo sheets, internal loops of progressive magnetization, it saves energy multiple times. and reduces dissipation, and is completely mobile, autonomous and safe to work.

Short description of the pictures

- Figure 1 shows a block diagram of a magnetizer/demagnetizer with a switching magnetic field;

Figure 2 shows a solenoid SL for installation in an injection molding tool - for magnetic

orientation of powder particles during injection molding with molten binder.

- Figure 3 shows an MC magnetic circuit with an air gap for magnetizing with a switching magnetizer, made of dynamo sheets

Figure 4 shows the axial adapter A for the magnetic circuit MC

- Figure 5 shows the diameter adapter D for the magnetic circuit MC

- Figure 6 shows the radial adapter R for the magnetic circuit MC

Figure 7 shows the multipole adapter M for the magnetic circuit MC

Figure 8 shows the internal loops of hysteresis-free magnetization (SM) formed at

operation of a magnetizer with a switching magnetic field

Figure 9 shows the internal loops of hysteresis-free demagnetization (SD) created during operation of a demagnetizer with a switching magnetic field.

5. Detailed description of the invention

Magnetizer / demagnetizer with switching magnetic field (picture 1) performs magnetization and demagnetization of magnetically hard materials during the formation of green cores with molten binder - injection molding (PIM technology), then during heating in a magnetic field or magnetization of finished sintered cores. In doing so, the magnetizer uses a continuous dense procession of narrow square current pulses and internal progressive successive small loops of magnetization (SM) or demagnetization (SD) (Fig. 8 and 9). The intensity of the switching magnetic field obtained by a continuous dense train of narrow square pulses should be equal to or greater than the coercive magnetic field Hcb. The orientation of the magnetic powder particles is done in a tool with a built-in solenoid, and the finished sintered cores in a magnetic circuit made of dynamo sheets (MC) with an air gap and adapters (pole extensions for different types of magnetization). The magnetization of the cores of magnetically hard materials is carried out by successive progressive magnetization loops SM (first quadrant in the B-H diagram), which occur at the aforementioned switching magnetic field equal to (close to) the coercive magnetic field Hcb. Magnetization lasts as long as it takes to achieve remanent induction of the Br sample in the magnetic circuit, for example with 10 pulses per second and a pulse-pause ratio of 1/10. Demagnetization is performed in the same circuit by reversing the direction of the switching current in the magnetic circuit or solenoid (with a special switch or by changing the position of the output terminals) and using demagnetization loops SD (II second quadrant of the B-H diagram). At the same time, the number of pulses is limited electronically so that there is no overmagnetization of the magnet in the opposite direction, but only demagnetization, i.e. that Br becomes approximately zero or that some small residual induction lags behind. To adjust the pulse intensity of the switching magnetic field, the change of the IGBT excitation voltage and the voltage on the serially connected accumulators in steps of 12 V (12, 24, 36, 48...Vdc) is used.

A magnetizer / demagnetizer with a switching magnetic field has two parts: a source of strong current pulses and a magnetic circuit. The source of current pulses consists of an input control circuit (CC), a group of batteries in a series-parallel connection (BG), a battery charger (BC), a switching transistor block (IGBT), which has a special adapter (CL) for controlling the executive switching circuit, an executive switching block with transistors (TR), a cooling block ( C ) and a protection block against induced impulses ( SS ) caused by self-induction during current interruption, as given in the block diagram (Figure 1). The executive part of the magnetizer / demagnetizer consists of a solenoid (SL) built into the injection tool (Figure 2), and serves to orient the particles in the injection tool and a special magnetic circuit (MC) with an air gap, made of dynamo sheets. Magnetic circuit (MC) with axial (A), radial (R), diametral (D) and multipole (M) adapters (Figures 4-7) is used for magnetizing finished (sintered) cores.

The control circuit (CC) is a pulse generator whose number per second, height, width and pause length can be adjusted with a potentiometer. The circuit provides a continuous dense procession of square-shaped pulses and is designed to excite or brake the gate of the IGBT (group of powerful transistors). The pulse-pause ratio can be, for example, 1/10, and the intensity of the pulse train from the block (CC) can be, for example, +12Vdc (when it opens a strong current in the IGBT) and -3Vdc (when it turns off the current in the IGBT, i.e. when there is a pause). The intensity of the pulse from the control circuit can be in the range of 9-15 Vdc and thus regulates the output current of the IGBT from 0.1 to 1.5 kA.

The battery group (BG) was created by sequentially connecting lead batteries 12 Vdc/180 Ah/1200 Ade in a group of four or more batteries, which gives the possibility of choosing the voltage for the IGBT switching circuit of 12,24,36,48,... Vdc. If the accumulators are of smaller capacity, they should be connected in parallel first by two or more, then in order to obtain a variable voltage and draw a stronger current pulse from them.

The battery charger (BC) charges the batteries in turn with 10% of the battery capacity, for example for a 180 Ah battery the charging current is of the order of 20 Ade. The charger only works when the IGBT is not in use. A charged IGBT battery discharges, for example, at a rate of 1/10 continuously for at least 2 hours, and in sequences of 10 seconds, with a break of a few minutes, until a new injection, for at least 60 hours.

The switching transistor block (IGBT) has several power transistors connected in parallel in a single housing. They are driven by a driver - control logic (CL), a smaller card with electronics that is placed on the transistor block (TR) or in the transistor block - depending on the manufacturer.

The case is made of metal and cools the transistors, and the heat is dissipated to a heatsink (C) with a fan and a temperature gauge on the case that turns on the fan as soon as the case warms up a bit.

The block for protecting the IGBT against self-induction (SS) when the current is switched off is connected between the IGBT collector and the mass in parallel. During normal operation, strong current pulses, when they pass through the protection block, go to the solenoid or magnetic circuit. The protection block is a high-frequency (EMI) filter made of a group of high-voltage foil capacitors of higher capacitance, for example 10 by 10 uF/600 V, connected in parallel on thick copper strips to pass large currents and absorb the self-induction pulses that travel as a return shock from the coil to the IGBT when the current is turned off.

The solenoid for installation in the injection tool (SL) (Figure 2) is connected to the filter (SS) as a protected output from the IGBT. The solenoid has several tens of coils (22) of profiled copper conductor or copper tubes that comprise the part of the tool in the injection molding machine in which a strong magnetic field is to be achieved to orient the powder particles during injection molding. The nozzle in the tool (24) serves to inject the composite, i.e. magnetic powder with molten binder (In); the front plate (25) of the tool moves forward (opens) and the hardened piece is ejected from the non-magnetic cylinder (23) axially by the ejector (28). Parts of the tool (25), (26), (27) are made of magnetically soft material and through them flows the flux of the magnetic field, the direction of which is indicated by the arrows, and which is created by the aforementioned solenoid (22).

An air gap (MC) magnetic circuit (Figure 3) is made of dynamo sheets (32) and copper tube solenoids (31) in place of solid wire windings. Oil or water flows through copper pipes (coils) for cooling. Magnetizing adapters (33) (pole extensions in the MC circuit) are made of dynamo sheets or magnetically soft (heated) iron.

The axial adapter (A) (Fig. 4) has two pole extensions made of dynamo sheets (41) and two side holders made of aluminum (42) and is placed in the air gap of the magnetic circuit (MC) when magnetizing cores of hard magnetic materials in the form of tiles and rollers - axially.

The diametrical adapter (D) (Fig. 5) has two pole extensions made of dynamo sheets (51) and two side holders made of aluminum (52) and is placed in the air gap of the magnetic circuit (MC) when diametrically magnetizing the cylinder-shaped hard magnetic material cores.

The radial adapter (R) (Fig. 6) has two different soft iron pole extensions (61) and two aluminum side holders (62) and is inserted into the air gap of the magnetic circuit (MC) when radially magnetizing the toroid-shaped hard magnetic material cores (63).

The multipole adapter M (picture 7) magnetizes two poles (N, S) consecutively in a round roller (73). It has two pole attachments made of dynamo sheets (71) and two side holders made of aluminum (72) and is placed in the air gap of the magnetic circuit (MC) when the cores of magnetically hard materials in the shape of a roller are magnetized, successively in a circle around the circumference of the roller, i.e. multi-sex.

Loops of successive magnetization (SM) (Figure 8) partially follow the magnetization curve created by the DCM in the first quadrant of the B-H diagram, i.e. only up to the value of the coercive field Hcb given by the pulse train (IGBT). The train of pulses can be adjusted by intensity, number of pulses per second and pulse width. After the intersection with the dashed line Hcb, asymmetric - small loops of hysteresis-free magnetization occur, caused by a dense procession of square pulses from the switching power supply, which lead to remanence Br after ten or more pulses (for example, 1 second). Powder particles are oriented, for example, by means of 50 pulses (5 seconds) of intensity equal to the coercive field Hcb of the magnetic material, and that field is at least twice as large as the saturation field Hsp of the magnetic powder.

Loops of successive demagnetization (SD) (Figure 9) partially follow the curve of demagnetization by the direct (reverse) magnetic field DCM in the second quadrant of the B-H diagram, ie. only up to the value of the coercive field -Hcb given by the inverted pulse train (IGBT). After the intersection with the dashed line -Hcb, asymmetric - small loops of hysteresis-free demagnetization caused by a dense procession of square pulses from the switching power supply are formed, which lead to almost complete demagnetization (demagnetization) after a dozen or more impulses, which can be electronically limited by the total number of pulses required for demagnetization. With this type of demagnetization, there is always a few percent residual magnetization behind, because both dynamo sheets and soft iron parts have their own residual magnetization.

5. Method of industrial and other application of the invention

The switching magnetizer/demagnetizer is intended to perform the magnetic orientation of powder particles in the production of oriented magnetically hard materials by powder injection (PIM technology) for materials that have magnetocrystalline anisotropy or to perform the orientation of a group of grains during core heating in a magnetic field for materials that have the specified anisotropy (shape anisotropy). It can also be used for final magnetization of finished (sintered) cores using magnetization loops (SM) in the first quadrant of the B-H diagram. When working as a demagnetizer, it can demagnetize green samples formed by injection powder with a binder (PIM technology) before being removed from the tool, then demagnetize sintered samples using demagnetization loops (SD) in the second quadrant of the B-H diagram. It is suitable for work in plants because it uses DC current from the battery, it is safe to work because the voltages are low, so everything can be touched with bare hands. It saves energy multiple times because it works in pulse/pause mode = 1/10 and works with several times smaller currents and magnetic field in intensity compared to Hs - saturation field of the magnetic material (it does not bring the magnetic material into Bs saturation but into Br remanence). It is mobile and can work autonomously for several hours. The size and density of the pulses can be adjusted as needed. It is necessary to adjust the current so that the value of the magnetic field H in the solenoid or air-gap magnetic circuit is equal to or greater than Hcb

-coercive magnetic field.

The prototype of the switching magnetizer was made in IRITEL AD, Belgrade in June 2008 and applied for magnetization and orientation during injection molding of magnetically hard materials. During one year of exploitation, all the mentioned advantages from the patent description were proven.

Claims (2)

1. Magnetizer/demagnetizer with switching magnetic field is a new device that uses a dense continuous train of narrow square magnetic pulses and internal magnetization loops SM and SD for consecutive progressive - hysteresis-free magnetization and demagnetization of magnetically hard materials, then magnetic orientation of powder particles during injection molding and orientation of a group of polycrystal grains during furnace heating, it is characterized by the fact that it consists of an input control circuit (CC) - pulse generator, battery group in series-parallel connection (BG), battery charger (BC), switching transistor block (IGBT) with a special adapter (CL) for controlling the output switching block with power transistors (TR), cooling block ( C ) and protection block against induced pulses (SS), then a solenoid installed in the injection tool (SL) and a special magnetic circuit with an air gap made of dynamo sheets (MC) and additional adapters: axial (A), radial (R), diametral (D) and multipolar (M). 2. The method of magnetization and demagnetization by a procession of current pulses from a switching magnetizer and by means of a magnetic circuit according to claim 1, is characterized by the use of a switching magnetic field and asymmetric hysteresis-free magnetization in the solenoid (SL) or in the magnetic circuit (MC) in intensity greater than or equal to the coercive field Hcb of the hard magnetic material and internal i.e. small loops of magnetization (SM) and demagnetization (SD) caused by a dense continuous train of narrow square magnetic pulses.