EP2506272B1 - Quick-switching lifting magnet - Google Patents

Description

The invention relates to a lifting magnet according to the features of the preamble of claim 1.

Such a solenoid is, for example, in WO 2011/003547 A1 described. The local lifting magnet combines the Lorentz force acting on the basis of an intended short-circuit ring with the reluctance force customary for lifting magnets when the exciting coil is energized. In this way, the holding force of the solenoid can be increased.

Similar solenoids are z. B. off WO 2008/139250 A1 and DE 197 22 013 A1 known.

There is often the need for solenoids to reduce their switching times. Conventional lifting magnets usually work according to the reluctance principle. Here, within a metallic housing, which is part of a magnetic circuit, provided by energizing an exciting coil movable iron anchor. The mode of action is based on the force exerted on magnetic interfaces in the inhomogeneous magnetic field. The magnetic field is generated by the coil current. When the coil is energized, the armature moves in a predetermined direction.

Fast-switching solenoids, which operate according to the reluctance principle, regularly have an optimized compromise between fast current increase and high magnetic force. The problem here is that large forces are required to accelerate the armature. For this purpose, according to Maxwell's tensile force formula, a large armature cross-section is required at a constant flux density. However, as the armature cross section increases, so does the anchor mass. The larger the anchor mass, the more The armature begins to move more cumbersomely, since the mass must first be set in motion. The inductance of the coil increases with increasing iron content of the magnetic circuit. However, a large inductance requires a slower current increase. However, a slow current increase of the coil also leads to a slower increase in the force-generating magnetic flux, which in turn has a slow movement of the armature result.

On the other hand, electrodynamic actuators are known which are based on the effect of Lorentz force. A Lorentz force occurs when a current-carrying conductor is in a magnetic field, wherein the current-carrying conductor is movably mounted relative to the magnetic field. This effect is illustrated by the well-known collaborative effort originally discovered by Eliho Thomson. In this ring trial, a ring of electrically conductive material, for. As copper, arranged around an elongated coil with soft iron core. With a short current pulse through the coil, the ring jumps off the coil. This principle is not common in actuators, since due to the large leakage field and other losses only a low efficiency is achieved. The required for such actuators fast switching of high currents is also technically complex.

However, the advantage of electrodynamic actuators lies in the fact that the short-circuiting ring is flooded by a rapidly changing magnetic field. As a result, a voltage is induced in the ring, which leads to a current which also generates a magnetic field. This field is directed counter to the excitation field from its direction. Seen from the outside, it seems that the inductance of the magnetic circuit is largely short-circuited. This is a fast Current increase nothing contrary. As a result, the ring abuts the exciting coil.

The invention aims to provide a lifting magnet which switches much faster compared to conventional solenoids of similar size.

This goal is achieved in a first solution by a solenoid, which combines a conventional solenoid, which operates on the principle of relunction, with an electrodynamic actuator with a short-circuit ring, the short-circuit ring is loosely coupled to the armature of the solenoid.

A fast-switching solenoid is thus achieved by the features of claim 1.

A second solution for a fast-switching solenoid with short-circuit ring is to arrange the pole core located in the lifting magnet with its end face facing the armature at least approximately on a plane which is defined by an upper end of the exciter coil. Thus, the pole core does not protrude or at least not very far into the space wrapped by the exciter coil. In conventional lifting magnets, on the other hand, it is the case that the end face of the pole core facing the armature projects as far as possible up to the middle of the space wrapped by the exciter coil.

This second solution is advantageously combined with the first solution.

Further developments of the lifting magnet according to the invention are the subject of the dependent claims.

Figur 1:

Eine Schnittansicht durch einen beispielhaften Hubmagneten nach der Erfindung in seinem Ruhezustand, d. h. bei nicht bestromter Erregerspule, mit dem Anker in seiner Hubanfangsstellung,

Figur 2:

ein Prinzipschaltbild zum Bestromen der Erregerspule von Figur 1, und

Figur 3:

ein Diagramm, aus dem die einzelnen Kräfteverläufe, der Spulenstrom sowie die Ankerposition des in Figur 1 gezeigten Hubmagneten hervorgeht.

The fast-switching solenoid according to the invention is explained in more detail in connection with the following figures with reference to an exemplary embodiment. Show it:

FIG. 1:

A sectional view through an exemplary solenoid according to the invention in its idle state, ie when energized exciter coil, with the armature in its Hubanfangsstellung,

FIG. 2:

a schematic diagram for energizing the excitation coil of FIG. 1 , and

FIG. 3:

a diagram from which the individual force profiles, the coil current and the anchor position of the in FIG. 1 shown lifting magnets emerges.

In the following figures, unless otherwise stated, like reference numerals designate like parts with the same meaning.

The solenoid of FIG. 1 is designated by the reference numeral 10. This solenoid 10 has a housing 11, which is part of a magnetic circuit. The housing 11 has an upper housing cover 12 and a lower housing bottom 14, which are connected to each other via a rotationally symmetrical to the center axis X of the solenoid 10 housing wall 16. Instead of a rotationally symmetrical housing wall 16, this can also be configured as a quadrangular or rectangular housing wall 16. The housing wall 16 is made of metal. The housing cover 12 and the housing bottom 14 may be made of metal, but also of other materials.

Within the housing 11 is a pole core 20 which has a central bore 22 extending along the central axis X. In this centric bore 22 sits a plunger 40, which also penetrates an opening 12 located in the housing cover 12a. In this opening 12a of the housing cover 12, a guide bush 43 is inserted. Within the housing 11 of the solenoid 10, one end of the plunger 40 is fixedly connected to an armature 30, preferably an anchor 30 made of steel. The fixed connection of the plunger 40 with the armature 30 can be done for example by screwing. For this purpose, the lower end of the plunger 40 has an external thread and the armature 30 has an opening with internal thread 36 into which the lower end of the plunger 40 can be screwed. The plunger 40 is guided with the armature 30 axially movable along the center axis X. In FIG. 1 the armature 30 is in the rest position and is, as shown, by way of example on the housing bottom 14. On its side facing the housing bottom 14, the solid, block-like configured armature 30 is provided with a funnel-shaped opening 32. In addition, the armature 30 is provided with a plurality of bores 34 which run axially parallel to the center axis X through the armature 30. These holes 34 ensure that when moving the armature 30 back and forth no "air pump action" occurs, so air can escape through the armature 30.

The armature 30 has on its side facing the pole core 20 via a flange-like extension 31 which annularly surrounding the plunger 40 and can dive into the central opening 22 of the pole core 20 when the armature 30 moves in the direction Polkern 20.

In FIG. 1 the rest position of the solenoid 10 is shown. Here, an air gap 70 is formed between the opposite end faces of the pole core 20 and the armature 30. This air gap 70 is at least partially surrounded by an excitation coil 50 which is wound on a coil core 52.

As FIG. 1 further shows, the pole core 20 has an end face 21 which faces the armature 30. This end face 21 is at least approximately on a plane which is perpendicular to the center axis X and by the upper, the housing cover 12 facing the end of the exciter coil 50 is formed. This level is in FIG. 1 represented by dashed lines and designated by the reference numeral E1. The armature 30 has an end face 37 facing the pole core 20. This end face 37 lies at least approximately on a plane E2 which is defined by the lower end of the exciter coil 50. This plane E2 is also dashed in FIG. 1 shown .... of the solenoid, in FIG. 1 is shown, the excitation coil 50 thus surrounds an air gap 70, which is bounded by the mentioned planes E1 and E2 and thus by the end faces 21 of the pole core 20 and the end face 37 of the armature 30. The air gap 70 thus has at least approximately, with respect to the center axis X, a height which corresponds to the length of the winding axis of the exciter coil 50.

Above the excitation coil 50 sits a short-circuit ring 60, which is preferably formed of aluminum or copper. This short-circuit ring 60 surrounds the pole core 20 annularly. However, the short-circuit ring 60 has a significantly lower height than the pole core 20, so that the short-circuit ring 60 from his resting position in FIG. 1 in which it rests on the spool core 52 in the direction of the housing cover 12 can move. The short-circuit ring 60 is over in FIG. 1 unrecognizable webs or at least one web with an inner flange 62 preferably integrally connected. This flange 62 is in the rest position of the solenoid 10 at an annular shoulder 42 of the plunger 40 flat. In addition, the short-circuit ring 60 has an annular circumferential recess 64, which surrounds the coil 50, at least in sections annularly, as from FIG. 1 can be seen.

Although related to FIG. 1 has been explained that the housing wall 16 and the housing cover 12 are two separate parts, these two parts could also be integrally connected to each other. If the housing cover 12 is a metal part, it is advantageous to provide a circumferential recess 13, so that a constriction A in the region of the recess 13 results in terms of material. This constriction A ensures that the magnetic flux primarily does not flow over the housing cover 12 in the operation of the solenoid, but rather - as will be explained below - via the short-circuit ring 60th

The operation of the in FIG. 1 shown lifting magnets is essentially the following, if it is assumed that the excitation coil 50 can be energized with a sufficient high current very quickly, preferably leaps and bounds. For this purpose, for example, a capacitor discharge device, as shown schematically in FIG FIG. 2 is shown. As energy storage is a capacitor C, which forwards via a switch S a surge to the exciter coil 50 when closing the switch S. The equivalent circuit of the exciter coil 50 consists of a conditional by the windings ohmic resistance R in series with an inductance L.

At the beginning of the discharge of the capacitor C, a very rapid increase in current through the excitation coil 50 results. This rapid increase in current to a magnetic field that builds up very rapidly through the short-circuit ring 60. In this way, a voltage is indicated in the short-circuit ring 60, which leads to a current which also generates a magnetic field. This field is directed counter to the field directed by the exciting coil 50 from its direction. From the outside, it appears that the inductance of the magnetic circuit is largely short-circuited. The fast current increase is so nothing in the way. As a result, the short-circuit ring 60 abuts the exciter coil 50 in the direction of the housing cover 12.

The short-circuit ring 60, which moves relative to the housing cover 12, absorbs the shoulder 42 and thus the plunger 40 during its movement via its flange 62. As a result, the armature 30 lifts in the direction of pole core 20. This happens extremely fast. However, since the charge of the capacitor C is limited, this rapid increase in current can not be maintained for long. The current curve flattens off, eventually falling off. Despite the still high amount of current in the short-circuit ring 60 then no large forces generated. However, the high magnetic force provided by the reluctance principle now acts in the armature 30. While the force provided by the short-circuit ring 60 decreases, the force provided by the reluctance principle increases even further.

In FIG. 3 the power curves are shown schematically over time. The reference numeral 100 is the through the shorting ring 60 provided electrodynamic force 100 denotes. The reference numeral 102, on the other hand, designates the reluctance force. The sum of both force curves 100 and 102 can be seen in the curve 108. It follows from the course of forces 108 that altogether a very strong and steeper increase in force occurs immediately after the excitation coil 50 has been energized. In addition, the sum of the forces in the tip is almost twice as high as each individual force according to the curve 100 and the curve 102, respectively FIG. 3 is denoted by the reference numeral 104 nor the course of the coil current through the excitation coil over time and the reference numeral 106, the anchor position of the armature 30 applied.

In the stroke end position of the short-circuit ring 60 with its flange 62 continue to rest against the shoulder 42 of the plunger 40. However, it is advantageous if the short-circuit ring 60 is loosely coupled to the plunger 40, so that upon movement of the short-circuit ring 60 at the beginning of the energization of the excitation coil 50, the plunger 40 on its shoulder 42 entrains and with decreasing Lorentz force through the short-circuit ring 60 in the direction of exciter coil 50 can fall off again, so that he does not have to be moved by the then taking over the movement reluctance force ..

When dimensioning the solenoid, it is only necessary to ensure that at the beginning of the energization of the exciter coil 50, an upward movement of the short-circuit ring 60 directly entrainment of the plunger 40 and thus of the armature 30 result. After the ram 40 is taken very fast by the short-circuit ring 60 takes over in the next period after the Lorentz force subsides, the through the reluctance principle provided magnetic force the movement of the armature 30 to the housing cover 12 out.

By virtue of the principle of using a short-circuit ring 60 within a solenoid to rapidly initiate the start of movement of the armature 30 and subsequently combining that movement by the magnetic force according to the reluctance principle, an extremely fast-acting solenoid is provided. Such accelerated switching behavior is a significant advance in millisecond switching times.

LIST OF REFERENCE NUMBERS

10

solenoid

11

casing

12

housing cover

12a

drilling

13

puncture

14

caseback

16

housing

20

pole core

21

face

30

anchor

31

flange-like extension

32

opening

34

drilling

36

thread

37

face

40

tappet

42

shoulder

43

Rifle

50

excitation coil

52

bobbins

70

air gap

60

Shorting ring

62

flange

64

return

100

electrodynamic force 102 reluctance force

104

coil current

106

anchor position

108

resulting power

A

constriction

X

mid-axis

E1

level 1

E2

Level 2

L

inductance

R

resistance

C

capacitor

S

switch

Claims (11)

1. A lifting magnet with an armature (30) movable axially inside a housing (11) by an excitation coil (50) having a current flow through it and a short-circuit ring (60) coupled to the armature (30) and likewise movable axially, characterized in that the short-circuit ring (60) is loosely coupled to the armature (30) and the armature (30) is jointly movable by the short-circuit ring (60) in only one direction of movement.
2. A lifting magnet according to the preamble of claim 1 or according to claim 1, characterized in that a pole core (20) is arranged with its front end (21) facing the armature (30) at least approximately in a plane (E1) which is defined by an upper end of the excitation coil (50).
3. A lifting magnet according to claim 1 or 2, characterized in that the armature (30) is connected in a fixed manner to a tappet (40), the tappet (60) [sic] has a shoulder (42), and the short-circuit ring (60) is rests against the shoulder (42) in order to entrain the tappet (60) [sic].
4. A lifting magnet according to claim 3, characterized in that the short-circuit ring (60) is arranged coaxially with the tappet (40) and has a middle annular flange (62) which strikes against the shoulder (42) of the tappet.
5. A lifting magnet according to any one of claims 1 to 4, characterized in that in a state of the excitation coil (50) without a current flowing through it an annular setback (64) formed on the short-circuit ring (60) engages around the excitation coil (50) at least in part.
6. A lifting magnet according to any one of claims 1 to 5, characterized in that the short-circuit ring (60) consists of aluminium or copper.
7. A lifting magnet according to any one of claims 1 to 6, characterized in that the armature (30) consists of steel.
8. A lifting magnet according to any one of claims 1 to 7, characterized in that in the state of the excitation coil (50) without a current flowing through it, in which both the armature (30) and the short-circuit ring (60) are in their rest positions, a pole core (20) present in the housing (11) is arranged at a distance from the armature (30) by way of an air gap (70), and the excitation coil (50) is arranged wound around this air gap (70) at least in part.
9. A lifting magnet according to any one of claims 3 to 8, characterized in that the tappet (40) is screwed to the armature (30).
10. A lifting magnet according to any one of claims 1 to 9, characterized in that the housing (11) has a cover (12) of metal in which a continuous recess (13) is formed.
11. A lifting magnet according to any one of claims 1 to 10, characterized in that the excitation coil (50) is connected to a capacitor discharge device (C).

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