EP3011571A1 - Self-holding magnet with a particularly low electric trigger voltage - Google Patents

Abstract

The invention relates to a self-holding magnet with a spring (accumulator spring) and a first armature. The self-holding magnet is capable of holding the first magnet armature against the spring force in a lift position which is determined by a stop; the stop thus determines at least the remaining air gap of a working air gap. The magnetic circuit of the self-holding magnet comprises a magnetic shunt which has a particularly low reluctance of the same order of magnitude as the series reluctance of the remaining working air gap(s). The working air gap(s) and the shunt are magnetically connected in parallel in relation to the flow generated by a permanent magnet but are connected in series in relation to the flow generated by the (trigger) coil. The self-holding magnet additionally has at least one of the following three positive feedback devices: (1.) a resilient stop: the stop is capable of compressing to a certain extent and in the process is much more rigid than the accumulator spring but much less rigid than a solid stop made of iron would be, said stop preferably being 100 to 10,000 times more rigid than the accumulator spring; (2.) a shunt which is designed such that a movement of the armature results in a reduction of the reluctance of the shunt in that the self-holding magnet is designed as a reversal lifting magnet, the retaining force which can hold the accumulator spring in a biased manner being generated with as little characterizing influence as possible, and the shunt is designed as an armature/counter armature piece system, wherein energizing the coil in order to trigger the drive (counter excitation) then leads to a reduction of the flow in the air gap without a characterizing influence and to an increase of the flow through the armature/counter armature piece system, the force generated by the latter acting as much as possible in the same direction as the force of the accumulator spring; and (3.) a shunt which is designed such that a movement of the armature results in a reduction of the reluctance of the shunt in that the shunt is provided with a second armature (shunt armature) which is capable of closing the small air gap of the shunt up to a known (even smaller) remaining air gap. The force acting on the shunt armature is transmitted onto the armature of the self-holding magnet by means of a known device, for example a tappet, such that the force acts on said armature in the same direction as the force of the accumulator spring.

Description

 Self-holding magnet with particularly low electrical release power

Technical Field: The invention relates to the field of electromagnetic actuators. Background of the invention:

So-called self-holding magnets are well known and commonly used (see, for example: E. Kallenbach, R. Eick, P. Quendt, T. Ströhla, K. Feindt, M. Kallenbach: Elektromagnete (2008), Chapter 9.2 Polarized Magnets, P. 298).

These are permanently polarized, switchable electromagnets: With the help of permanent magnets self-holding magnets can hold a (magnetic) anchor stable in at least one position, where necessary, by means of a coil ("trip coil"), a counter-excitation can be generated, which the permanent magnetic It is known to provide a magnetic bypass in self-holding magnets, and with respect to the permanent-magnetically generated flux, the shunt is connected in parallel with the working air gap (s) of the armature with respect to the flux generated by the coil however, they are connected in series, reducing on the one hand the electrical power required to compensate for the permanently generated magnetic field and, on the other hand, protecting the permanent magnet (s) from demagnetization combined and form with these electrically releasable spring storage. The spring thus acts on the armature to open the working air column (s). The self-holding magnet is designed so that it falls below a certain minimum air gap, it remains a residual air gap, the spring is able to hold in a stretched state.

By energizing the trip coil, a counter-excitation can be generated be that the magnetic holding force is lower than the spring force and the armature is set in motion, wherein the previously stored in the spring elastic energy can be used to do work. Such "magnetic spring stores" are used for example as a trigger, in particular residual current release, in electrical switching devices, such as circuit breakers. Commonly known is the use as a residual current release in residual current circuit breakers. In addition, they are used in locking units ("locking magnets"), wherein the clamping can be done mechanically or by reverse excitation of the magnet by means of the coil (excitation instead of counter-excitation as in triggering). In order to facilitate magnetic clamping, use can be made of a characteristic influencing, which can result in much higher force constants at full open working air gap. In battery powered interlocking units, a low tripping current is particularly desirable. The same applies to the triggers of electrical switching devices, in particular for residual current release self-powered low and medium voltage switching devices. Triggers, especially fault current triggers, should also react as quickly as possible, so have low dead times. From such triggers is also to demand that they can be designed so that not too high a counter-excitation unintentionally prevents the triggering unintentionally slowed or unduly: overcompensation of the permanent magnetically generated field and thus the associated holding force can namely the formation of a holding force as a result of the Tripping current chained flow have the result so that the latching magnet delayed or not at all triggers. Likewise, trigger magnets must of course be quite insensitive to vibration, the unintentional triggering as a result of blows or other shocks should be much more difficult, which is why the desired high electrical sensitivity - ie the desired low tripping currents or powers - can not be easily realized by magnetic holding force and spring force be aligned as closely as possible. Thus, the inventive task is posed: self-holding magnet with spring ("magnetic spring memory"), which has a particularly low electrical release performance compared to known types. In addition, the magnetic spring store should, if necessary, have the following features:

 low dead time, i. short time between the start of lighting and the beginning of the armature movement

 - No failure also, compared to conventional self-holding magnets, high counter-excitations

Summary of the invention:

The invention is based on a self-holding magnet with spring, wherein the self-holding magnet has a stop for the armature and a magnetic shunt. In the tensioned state, the armature of the self-holding magnet against the spring force is kept permanently magnetic, the working air gap (or the working air column, if an anchor with multiple pole surfaces is used) is closed except for a given by the stop (working) residual air gap, the frame of the self-holding magnet (as an anchor counterpart) can serve as a stop itself, if necessary with an anti-adhesive film or similar.

In this case, the shunt has a particularly low reluctance: According to the invention, the shunt is to be dimensioned such that its reluctance in the stressed state is of the same magnitude and as large as the reluctance of the (working) residual air gap (or the sum of the reluctances of the residual working air column, if there is a series connection of several working air gaps, this is the case, for example, for pole plates in which two poles act on the same surface).

With respect to the flux generated by permanent magnet, the working air gap (e) and the shunt are magnetically connected in parallel. However, they are connected in series with respect to the flow that can be generated by the coil. The reluctance of Shunt is, as I said, of the same order of magnitude as the reluctance of the (working) residual air gap and as large as possible. Flowing parasitic residual air gaps are also to be considered according to their arrangement. In any event, electrical counter-energization of the latch magnet causes the flux density in the working air gap (s) to be reduced as the flux density shifts.

The shunt subcircuit can also be carried out with respect to the flux-conducting cross sections occurring in it so that due to magnetic saturation, the reluctance of the coil "seen" iron circle increases with increasing counter-excitation so that even a comparatively strong counter-excitement does not hold the anchor against the spring force able (because the flux density in the shunt increases with increasing counter-excitation). For this purpose, the shunt subcircuit can have a very constant, smallest effective cross section over a certain (minimum) length. The shunt can be defined geometrically; but it can also be formed of a soft magnetic material comparatively low (macroscopic) permeability, in particular a sintered material with a distributed air gap, which can simplify the production.

In contrast to known self-holding magnets, a self-holding magnet according to the invention also has one or more of the following three positive feedback devices:

1 . Feathering stop

 2.1. Variable shunt by execution as Umkehrhubmagnet

2.2. Variable shunt with second anchor ("shunt anchor") Explanation:

1 . Feathering stop In conventional self-holding magnets with spring ("memory spring"), the stop can be regarded as rigid to a good degree, and therefore the armature only starts to move when, as a result of the electrical counter-excitation, the magnetic holding force falls below the attacking (releasing) spring force of the storage spring This is not the case if the stop itself is capable of springing in. However, in order to meet the requirement for low triggering power, this should be sufficient

To cope with vibration insensitivity, the residual air gap created with the help of the stopper can be small. On the one hand, the stop should be far stiffer than the elastic energy storage serving "first" spring of the self-holding magnet ("memory spring") .On the other hand, the resilient stop should be far less stiff than it is a solid For example, the stop may be 100 to 10,000 times stiffer than the "first" spring (accumulator spring) .The stop should by no means have a linear characteristic, but may for example be degressive and with the aid of In addition, the stop can be made adjustable, for example with fine threads, so that its preload and / or rest position can be adjusted in order to tune the tripping characteristic. first "spring (memory spring) and the" second " Spring, namely the resilient stop, based on their effect on the anchor together a combined spring with highly progressive characteristic. The resilient stop allows that even a very small counter-excitation has a certain (small) movement of the anchor result. However, since according to the invention, the shunt has a very small reluctance, even very small deflections of the armature from its (closed, tensioned) Hubanfangslage to the fact that the flow on the shunt considerably and the flow over the (or the) working air gap (e) decreases appreciably, with the associated magnetic holding force, of course, develops in proportion to the square of the flux density in the working air gap. The small deflection of the anchor, due to the resilient stop already from caused by a small counter-excitation, so leads due to the changing distribution of the flow between the working air gap and shunt to a significant reduction of the magnetic holding force at the anchor. When designing and adjusting the resilient tipping, care must be taken to ensure that the system remains sufficiently insensitive to vibration (insensitivity to accidental release). In order to improve the insensitivity to accidental tripping by vibrations or by induced by interference fields counter-excitation, can be used with an additional electrical excitation. For this purpose, the trip coil can be used and energized against the direction that is needed for triggering. But it can also be used an additional winding.

2.1. Variable shunt by execution as Umkehrhubmagnet

The positive feedback according to the invention can also be effected by a variably designed shunt. This means that when the armature is detached, ie while the working air gap is still of the order of its residual air gap, movement of the armature which increases the working air gap results in a reduction in the reluctance of the shunt. For this purpose, the invention can be performed as Umkehrhubmagnet, wherein an end face of the armature forms together with the frame the working air gap of the self-holding magnet. The opposite end of the armature can form the shunt, wherein the shunt is designed as anchor-armature counterpart system, which is preferably designed so that the highest "force constant" occurs at the beginning of stroke (ie in the position in which the working air gap except for one Residual air gap is closed, the "tensioned" position). Consequently, in this embodiment of the invention, the armature is supplied with a permanent magnetically generated magnetic flux, which is distributed according to the associated reluctances on working air gap (without characteristic influencing) and shunt (with characteristic influencing works to open the working air gap). The counter-excitement with the help of the associated coil then causes an increase in the reluctance force acting on the armature at the shunt and a decrease in the reluctance force at the "holding surface", ie at the working air gap. Shunt and accumulator spring exert force on the armature in the same direction (to open the working air gap).

2.2. Useful work from reduction of the reluctance of the variable shunt with the help of a second anchor

A reduction of the flux-guiding shunt air gap (decrease of its reluctance) can also be effected by means of a second armature ("shunt armature") .This armature is movably arranged so that it shuts the already small shunt air gap down to a residual air gap The reluctance force acting on the shunt armature may be transferred to the armature via a mechanical or hydraulic device with or without transmission, to open the working air gap (ie, the force on the shunt armature should be applied in the same direction to the armature). In the tensioned state of the drive, the shunt armature is in a position in which the reluctance of the shunt is as equal as possible to the series reluctance of the one or more (Working) residual air gap (s) is. Now, if a counter-excitation is generated, s The force acting on the shunt armature strength and is transmitted in the direction of acting on the (working) armature (storage) spring force on the (working) armature, thus acting to solve this from its Hubanfangslage. Likewise, the magnetic holding force is reduced by the counter-excitation. Movement of armature and shunt anchor eventually causes a decrease in the reluctance of the shunt and an increase in the reluctance of the working air gap. Brief description of the figures:

The invention will be explained in more detail with reference to the examples shown in the figures. The representations are not inevitably true to scale and the invention is not limited to the aspects presented. Rather, emphasis is placed on representing the principles underlying the invention. In the figures: Fig. 1a shows a longitudinal section through a self-holding magnet according to the first example of the present invention; and

1b shows a cross section through a self-holding magnet according to the first example of the present invention. In the figures, like reference characters designate the same or similar components, each having the same or similar meaning.

Detailed description of the embodiment:

In Fig. 1a and Fig. 1b shows an embodiment of a self-holding magnet according to the invention with spring having a shunt anchor. A resilient stop is not shown, but can be added advantageous. Fig. 1a shows a section through the approximately rotationally symmetrical drive. The drawing is not to scale, but provides the developer with a good foundation for FEM optimizations. The embodiment is illustrative only and is in no way limiting. The individual components of the drive can consist of the following materials:

 - 10 rams, welded to the work anchor, austenitic stainless steel (NiCr)

 - 11 work anchors, silicon iron (FeSi)

 - 20 drivers welded to the shunt anchor (NiCr)

 - 21 shunt anchors (FeSi)

 - 30 outer frame part (FeSi)

- 31 inner frame part (FeSi) - 32 additional outer frame part (FeSi)

 - 40 anchor guide (brass)

 - 41 River Reclamation (FeSi)

 - 42 shunt anchor stop (NiCr)

 - 50 spring (spring steel, can be advantageously carried out as a corrugated spring)

 - 60 abutment for spring and sleeve bearing (bushing) for plunger (bronze)

- 70 bobbin, wound in the groove of the frame part (copper enamelled wire)

- 80 permanent magnet (esp. NdFeB)

On a bobbin can be dispensed with if, for example, the groove in which the coil is located, is coated insulating. δ10 and δ11 are the (in series) working air gaps in the cocked Hubanfangslage and therefore closed (not shown) residual air gaps. 520 is the shunt air gap used by the shunt armature 21 to perform work. The inner frame part 31 is chamfered in the region of the working air gap δ10. Fig. 1 b shows a plan view of the drive with remote anchor guide and remote working anchor and plunger. On display are the permanent magnets made of radially polarized circular segments, which are located in recesses of the (soft magnetic) frame. 33 are constructive magnetic shunts, wherein the magnets are to be dimensioned so that these constructive magnetic shunts 33 saturate, so that a magnetic tension between the inner frame member 31 and the outer region with outer frame member 30, 32 and flux return 41 occurs. Although the design with radially polarized circular segments, structural (saturated) shunts, etc., is comparatively complicated, it allows a particularly high dimensional stability and thus very much accommodates the basic requirement for low residual air gaps.

Functionality: Secondary air gap δ20 is in the illustrated Hubanfangslage (pervious state) of the same reluctance as possible as the series circuit δ10, δ11 (but of larger cross-section). From the point of view of the coil, this can result in a polarized (they!) Magnetic circuit of low reluctance, which enables large force constants (N / A). The shunt anchor 21 acts on the driver 20 to the tappet 10 welded to the working anchor and thus additionally helps to overcome the holding force, which is mediated via δ10 and δ11, and to accelerate the working anchor. Due to the series connection (!) Of δ10 and δ11, opening this residual air gap by a given (small) length will cause approximately twice as much increase in series reluctance as would be the case with a simple (small) working air gap. Similarly, the shunt anchor 21 is set in motion and not only helps to move the work anchor by means of driver 20, but also draws out of the working air gaps δ10, δ11 flow, since a closing movement of the shunt armature leads to a reduction in the reluctance of the shunt and this is connected in parallel with the working air gaps with respect to the permanent magnetically generated flow. As said, the (electrical) sensitivity of this drive can be further increased by equipping it with a resilient stop of suitable rigidity. This stop (not shown), for example, make use of a plate spring and act on the plunger 10. To bias the diaphragm spring or change their rest position, the fine adjustment can be done by means of screws with fine threads, then allows adjustment of the electrical sensitivity of the drive. It may be advantageous to connect the drive according to the invention in series with a diode and to switch a varistor parallel to the drive, because during the opening a voltage is induced in the coil which is opposite to the triggering voltage. Such external circuitry can significantly shorten the trip time. Using a springy stop, a trip is as follows: Electric counter-excitation reduces the flux through working air gaps δ10, δ11 and increases those through shunt air gap δ20. Due to the resilient stop, even a minimal energization leads to a certain rebound. As a result of this rebound, δ10 and δ11 increase, meanwhile 520 decrease correspondingly (since the shunt armature 21, accelerated by reluctance force, follows the plunger 10). Because these air gaps are all small, this small deflection of the system - the rebound - results in a distinctly different distribution of the permanent magnetically generated flux: the flux through the working air gaps δ10, δ11 decreases, that through the shunt increases. The rapid increase in the force acting on the shunt armature 21 contributes to the triggering of the self-holding magnet and also allows a considerable reduction due to the additionally transmitted via driver 20 and plunger 10 on the working anchor 11 and the magnetic "short-circuiting" of the working air column δ10, δ11 The achievable positioning times, because in the vicinity of the Hubanfangslage are in conventional self-holding magnet, at least at low release powers, only small forces from the difference of the spring force and the reluctance force to accelerate the armature available In the embodiment, however, the armature movement inhibiting reluctance force with the associated Flow shorted due to the movement of the shunt armature, while the working armature 11 is driven by the reluctance force acting on shunt anchor 21 in addition to the spring force).

Claims

Patent claims: 1 . Self-retaining magnet, comprising: - a magnetic circuit comprising a stator and a first armature; - a stop; - a first stroke end position defined by the stop, in which there are one or more working residual air gaps between the stator and the first armature, which have a series reluctance; - at least one spring which exerts a spring force which pushes the first anchor away from the stop; - a magnetic shunt with particularly low reluctance; - one or more permanent magnets to excite the magnetic circuit; - one or more (triggering) coils for counter-excitation of the magnetic circuit, wherein the magnetic circuit is dimensioned such that it is able to hold its first armature magnetically against the spring force in the first stroke end position, the magnetic shunt having a reluctance which is of the same order of magnitude as the series reluctance of the Working/remaining air column(s), where working air gap(s) and shunt with respect to the are magnetically connected in parallel with the flux generated by permanent magnets, but are connected in series with respect to the flux generated by the (triggering) coil(s), wherein the (triggering) coil(s) are energized in such a way that the magnetic flux in the working air gap(s) is weakened and the magnetic flux in the shunt is increased, which leads to the relaxation of the spring when the magnetic holding force is in magnitude Spring force falls below; the self-retaining magnet further has one or more Positive feedback devices to choose from: (1) a stiff, resilient stop, whereby the stop is like this is to be designed so that it itself has spring properties, and it is much stiffer than at least one spring, but much less stiff than a solid iron stop would be; (2) Design of the magnetic shunt in such a way that a movement of the first armature reduces the reluctance of the This results in a shunt, with which the permanently magnetically generated flux begins to move with the first armature increasingly commutated to the shunt. 2. Self-holding magnet according to claim 1, wherein the commutation of the permanently magnetically generated flux to the shunt is achieved by: the shunt comprises a second armature ("shunt armature"), which transmits the reluctance force acting on it to the first armature using known means, for example a plunger, so that a counter-excitation through the (triggering) coil(s) results that the flow into the working air gap(s) of the first anchor decreases, but the flow into the working air gap(s) of the second anchor increases; As soon as the total reluctance force acting on both anchors falls below the spring force, the second anchor starts moving along with the first one To close the working air gap(s), which results in a reduction in the reluctance of the flow path leading over the second armature, i.e. the shunt. 3. Self-holding magnet according to claim 1, wherein the commutation of the permanently magnetically generated flux to the shunt is achieved by: the self-holding magnet is designed as a permanently excited reversing solenoid, whereby the armature on the side that comes to rest on the stop has, if possible, no influence on the geometric characteristic curve with the stator, so that a The highest possible magnetic holding force can be generated against the spring force, while on the opposite side of the armature, where this has a reluctance force in the direction of the When spring force is felt, the armature and stator form an armature-armature counterpart system, which has a lower reluctance than would be the case without influencing the geometric characteristic curve. 4. Self-retaining magnet according to claim 1, wherein the stiff, resilient stop is 100 to 1000 times stiffer than the at least one spring. 5. Self-retaining magnet with spring ("storage spring") and armature, which is able to hold its armature against the spring force in a lifting position, which is determined by a stop; The stop therefore determines at least the remaining air gap of a working air gap. According to the invention, the magnetic circuit of the self-holding magnet has a magnetic shunt which has a particularly low reluctance, which is of the same order of magnitude as the series reluctance of the working residual air gap(s). With regard to the permanently magnetically generated flux, the working air gap(s) and shunt are magnetically connected in parallel. However, they are connected in series with regard to the flux generated by the (tripping) coil. In addition, a self-holding magnet according to the invention has at least one of the following three positive feedback devices: - Springy stop: The stop can deflect to a certain extent and is much stiffer than the storage spring but much less stiff than a solid iron stop would be. Preferably, the stop is 100 to 10,000 times stiffer than the storage spring - The shunt is designed in such a way that a movement of the armature results in a reduction in the reluctance of the shunt by designing the self-holding magnet as a reversing solenoid, wherein the holding force, which can keep the storage spring tensioned, is generated as far as possible without influencing the characteristic curve, and the shunt is designed as an armature-anchor counterpart system. (Energizing the coil to trigger the drive (counter-excitation) then leads to a reduction in the flux density in the air gap without influencing the characteristic curve and to an increase in the flux density in the armature-armature counterpart system, with the force generated by the latter acting in the same direction as possible force of the storage spring) - The shunt is designed in such a way that a movement of the armature results in a reduction in the reluctance of the shunt by providing the shunt with an additional armature ("shunt anchor"), which reduces the small air gap of the shunt to a certain (even smaller) level ) The remaining air gap can be closed. The force acting on this shunt armature is transmitted to the armature of the self-retaining magnet by means of a known device, for example a plunger, in such a way that it acts on it in the same direction as the force of the storage spring 6. Self-retaining magnet according to claim 5, characterized in that it has a resilient stop and that this stop is adjustable in terms of its preload and / or position, which can be achieved in a simple manner using threads; This allows the sensitivity of the self-holding magnet to be adjusted over a wide range. 7. Self-retaining magnet according to claim 5, characterized in that the shunt is not designed as a geometrically determined air gap but rather with the help of a material with a distributed air gap. 8. Self-retaining magnet according to claim 5, characterized in that the shunt or the associated flux guide is dimensioned and shaped in such a way that, as a result of saturation, the reluctance of the iron circuit seen by the coil can increase to such an extent that even at Comparatively high counter-excitation prevents the armature from being held inadvertently in its initial stroke position or triggering that is inadmissibly delayed. 9. Self-holding magnet according to claim 5, characterized in that it is equipped with a rectifier and a varistor. The rectifier is connected in series with the self-holding magnet, but the varistor is connected in parallel, in such a way that if the current direction in the coil of the self-holding magnet changes, the current no longer flows via the rectifier but runs freely via the varistor. 10. Self-retaining magnet according to claim 5, characterized in that it is not round but square, and that the iron material used is wholly or predominantly laminated cores, and that ferrites are used as permanent magnets. 11. Self-retaining magnet according to claim 5, characterized in that a corrugated ring spring is used as the storage spring. 12. Self-retaining magnet according to claim 5, characterized in that at least the anchor or anchors are round and that slots are made in the anchor or anchors and / or in frame parts of the anchor and that these slots are filled with a poorly electrically conductive bearing material so far that it can serve as part of a plain bearing (in this way, good storage and, if necessary, centering can be guaranteed, while eddy currents are dampened, which benefits the triggering dynamics of the self-holding magnet) 13. Self-retaining magnet according to claim 5, characterized in that the storage spring has a plate spring (or a plate spring package), which has such a degressive characteristic curve that the spring force increases first when the spring is relaxed (triggering). For this purpose, the associated spring characteristic must have a local maximum 14. Self-holding magnet according to claim 5, which has a second armature (“shunt armature”) as a positive feedback device, characterized in that it does not have a coil but is triggered mechanically with the help of a highly dynamic second drive (e.g. piezo).