EP1818951B1 - Solenoid - Google Patents

Abstract

Lifting magnet comprises a magnetic plunger (15) with a control section (15a) having a geometric structure so that an air gap is adjusted and/or enlarged by sliding the magnetic plunger in the direction of the lifting end position. Preferred Features: The magnetic plunger has a reduced plunger diameter in the control section. The control section of the magnetic plunger is conical.

Description

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

Such a solenoid is from the DE 196 22 794 A1 known. This solenoid has a soft magnetic housing, which at least partially surrounds an exciting coil wound on a bobbin. In an axial through-opening of the bobbin, a pole core and a magnetic piston displaceable along a center axis of the bobbin in the direction of the pole core to a Hubendposition are arranged, wherein the housing has a through hole for the magnetic piston on its side opposite the pole core.

The DE 20 2005 012 251 U1 discloses a solenoid in which a magnetic piston is guided in an elongated cylindrical guide sleeve. The magnetic piston has at its end remote from the pole piece end a reduction in diameter, which follows a curved course. What this diameter reduction should serve, is not mentioned. The guide sleeve has a closed end portion formed by a pole piece and an open end portion made of a magnetic steel alloy. Between the two end portions is a central portion of a non-magnetic material. A housing having the function of an iron yoke member includes a coil. The housing and the coil enclose a portion of the guide sleeve. The open end portion of the guide sleeve forms a passage opening for the magnetic piston in the iron yoke element. The reduced diameter end portion of the magnetic piston is slidable in the open end portion of the guide sleeve. Due to the large length of the open end portion of the magnetic guide sleeve but the curved portion of the magnetic piston remains over the entire displacement of the magnetic piston within the open end portion, whereby the parasitic air gap remains constant.

The US 4,604,600 shows in Fig. 2 a proportional solenoid with a ferromagnetic outer housing, which is bounded on both opposite end faces of ferromagnetic end plates. One of these end plates has a passage opening for a guide tube, which defines a chamber in which a magnetic piston slides. The other end disc is closed by a pole piece. The guide tube is either non-magnetic or semi-magnetic, namely with magnetic (martensitic) end portions and a non-magnetic (austenitic) center portion. The pole piece has an end portion facing the magnetic piston; the kegetstumpfförmig is executed, whereby in the course of the stroke of the magnetic piston between B and C, a constant tightening force is realized. Other embodiments of frusto-conical configuration of pole piece and / or a pole piece facing the end portion of the magnetic piston are from the Figures 3 . 5-8 seen. The magnetic piston has no change in cross-section in its end region remote from the pole piece, but slides with a constant parasitic air gap in the passage opening formed by the end disk or the guide tube.

Electromagnetic solenoids (often referred to as electromagnetic actuators) are used in many areas to perform setting or switching functions. The limiting of the stroke movement is typically carried out by a mechanical stop in the Hubendposition. The approach of this end position is also associated with mechanically damped versions with a noise, which is very often perceived by the user as disturbing. Technically possible control of the lifting operation, for example by way detection and current control are not used for cost reasons in standard applications.

A known embodiment of a lifting magnet is in Fig. 1 shown in longitudinal section. The known lifting magnet has a U-shaped bracket as a magnetic iron yoke element 1. The iron yoke element 1 has a longitudinal leg 1a, from the two ends of which in each case a transverse leg 1b, 1c extends away. The two transverse limbs 1b, 1c of the iron yoke element 1 surround an excitation coil 3 wound on a coil body 4, the transverse limbs 1b, 1c of the iron skirt closure element 1 in each case resting against an end flange 4b, 4c of the coil former 4. The bobbin 4 has a central passage opening 4a with a center axis M. At a front side of the bobbin 4, a pole core 2 is arranged in the through hole 4 a, but protrudes partly beyond and is with its protruding end in a through hole 1 d in the transverse leg 1 b used the iron yoke element 1. The other, the pole core 2 opposite transverse leg 1c of the iron yoke element 1 also has a through hole 1 e, which is aligned coaxially with the passage opening 4a of the bobbin 4. An annular plain bearing bush 6 is seated in the through hole 1e of the transverse leg 1c of the iron yoke element 1 and extends into the through hole 4a of the bobbin 4. This annular plain bearing bush 6 is provided on its inner circumferential surface with a sliding layer, for example a PTFE layer. The plain bearing bush 6 is flush with the outside of the transverse leg 1c of the iron yoke element 1. In the plain bearing bush, a magnetic piston 5 is received from a soft magnetic material, which extends inwardly beyond the plain bearing bushing 6 in the through hole 4 a of the bobbin 4.

In the magnetic piston 5 coaxially a push rod 7 is inserted from a non-magnetic material. This push rod 7 extends through an axial through hole 2b of the pole core 2 and through the through hole 1d of the transverse leg 1b of the iron yoke element 1 out of the solenoid, wherein in the through hole 2b of the pole core 2, an annular plain bearing bush 10 is arranged, in which the push rod 7 out becomes. A coil spring 9 is disposed around the push rod 7 in the through hole 2b of the pole core 2. One end of the coil spring 9 rests against the plain bearing bushing 10, the other end of the coil spring 9 abuts against the magnetic piston 5 and biases the magnetic piston 5 in a Hubanfangsposition HA, by the abutment of a sliding on the push rod 7 arranged stop member 11 on the Outside surface of the transverse leg 1 b is defined.

The magnetic piston 5 is displaceable along the center axis M of the bobbin 4, wherein between the magnetic piston 5 and the pole core 2, a working air gap 8 is formed, whose axial length s changes with the displacement of the magnetic piston 5. When the exciting coil 3 is energized, the magnetic piston 5 is moved from its stroke initial position HA in the direction of the pole core 2 to a stroke end position HE, which in the present example is defined as a position in which the pole core 2 facing end face of the magnetic piston 5 is applied to the pole core 2, so that the axial length s of the working air gap 8 is zero. To control the working air gap force characteristic is at the known lifting magnet of the pole core 2 facing end portion 5a of the magnetic piston 5 conically configured, and the pole core 2 is formed with a corresponding conical axial recess 2a. The conical configuration causes an improvement and linearization of the tightening force in the stroke end of the magnetic piston 5, whereby influencing the working air gap force characteristic over a wide stroke range is possible on the design of the cone geometry, but not the problem of disproportionate force increase Hubendbereich in reduction of the working air gap is eliminated. This is based on the characteristic A in the working air gap force diagram of Fig. 7 shown. This typical characteristic of lifting magnets with cone geometry of magnetic piston 5 and pole core 2 aggravates the noise problem by increasing the kinetic energy of the magnetic piston 5 before hitting the pole core 2 at the stroke end position HE.

The present invention has for its object to improve the known lifting magnet to the effect that an increase in the tightening force in Hubendbereich the magnetic piston is avoided and thus to reduce the noise when switching the solenoid considerably. Furthermore, the invention has for its object to provide a solenoid, which has an improved controllability of the displacement of the magnetic piston.

The invention solves this problem by providing a solenoid with the characterizing features of claim 1. Advantageous embodiments of the invention are set forth in the dependent claims.

According to the above was based on the Fig. 1 described known solenoid in such a way that a displaceable in the through hole of the piston-side portion of the iron yoke element control portion of the magnetic piston has such a geometric configuration that upon displacement of the magnetic piston in the direction of Hubendposition a parasitic air gap in the through hole of the piston-side portion of the iron yoke element adjusts and / or increases.

The inventively generated parasitic air gap leads to an increased magnetic resistance in the magnetic circuit, which reduces the lifting force when the magnetic piston approaches its Hubendposition and thereby the speed of the Reduce the impact of the magnetic piston on the pole core or prevent the impact at all. This innovation allows virtually silent switching of the solenoid. In general, an additional parameter influencing the working air gap force characteristic is introduced by the innovation according to the invention, with which the working air gap force characteristic, in particular in the stroke end region, can additionally be influenced and optimized for the respective application purpose.

With this additional characteristic control, in combination with mechanical damping elements, the force acting on the magnetic piston in Hubendbereich be influenced so that the Hubendposition not by a mechanical stop of the magnetic piston on the pole core or a stop element, but by an equilibrium of forces exerted by the damping elements on the magnetic piston Forces with the electromagnetic forces is determined. In particular, it is provided in one embodiment of the invention that a spring biases the magnetic piston against the force exerted by the exciter coil magnetic force, wherein the spring force of the spring is designed so that the magnetic piston is spaced in its Hubendposition of the pole core. Such a measure allows noiseless switching operations.

Due to the inventive geometric design of the magnetic piston to achieve a parasitic air gap at the passage opening of the iron element in combination with already used control options of the characteristic optimized on the application working air gap force-characteristic control allows, which brings the advantages described, without in the production To cause additional costs and thus can be used in standard applications.

In one embodiment of the invention, the magnetic piston in the control section on a reduced piston diameter, which adjusts a parasitic air gap in the through hole of the piston-side portion of the iron yoke element in the course of displacement of the magnetic piston toward the Hubendposition upon entry of the control section in the passage opening, since the Increased distance between the wall of the through hole and the generatrix of the magnetic piston.

Depending on the desired course of the working air gap force characteristic, the diameter of the magnetic piston in the control section can be reduced in one or more stages, whereby the parasitic air gap gradually increases as the magnetic piston approaches the stroke end position. Alternatively, the diameter of the magnetic piston in the control section in a direction opposite to the pole core direction are at least partially steadily reduced, whereby a more uniform course of the working air gap force characteristic is achieved because the parasitic air gap changes continuously. For example, the control portion of the magnetic piston may be conical or the generatrix of the control portion of the magnetic piston at least partially have a curved course in order to achieve a particularly uniform course of the working air gap force characteristic.

In another embodiment of the invention, instead of or in addition to the reduction in diameter, the control section of the magnetic piston is realized by a shortened compared to conventional magnetic piston length of the magnetic piston by the length of the magnetic piston is chosen so short that in Hubendposition the magnetic piston of the control portion of the magnetic piston or only partially protrudes into the passage opening at the piston-side region of the iron yoke element. The parasitic air gap in this case extends over the entire cross-sectional area of the through-hole and the magnetic flux of force concentrates on the part of the control section of the magnetic piston which projects into the through-hole. As this part becomes smaller and smaller with the movement of the magnetic piston into the stroke end position, the magnetic resistance increases and hence the lifting force decreases.

• Fig. 1 einen Hubmagneten gemäß dem Stand der Technik im Längsschnitt;
• Fig. 2 eine erste Ausführungsform eines erfindungsgemäßen Hubmagneten im Längsschnitt;
• Fig. 3 eine zweite Ausführungsform eines erfindungsgemäßen Hubmagneten im Längsschnitt;
• Fig. 4 eine dritte Ausführungsform eines erfindungsgemäßen Hubmagneten im Längsschnitt;
• Fig. 5 eine vierte Ausführungsform eines erfindungsgemäßen Hubmagneten im Längsschnitt;
• Fig. 6 eine fünfte Ausführungsform eines erfindungsgemäßen Hubmagneten im Längsschnitt; und
• Fig. 7 ein Arbeitsluftspalt-Kraft-Diagramm mit Arbeitsluftspalt-Kraft-Kennlinien für den Hubmagneten nach dem Stand der Technik und für zwei erfindungsgemäße Hubmagneten.

The invention will now be described by way of non-limiting embodiments with reference to the drawings. In the drawings show:

• Fig. 1 a lifting magnet according to the prior art in longitudinal section;
• Fig. 2 a first embodiment of a solenoid according to the invention in longitudinal section;
• Fig. 3 a second embodiment of a solenoid according to the invention in longitudinal section;
• Fig. 4 a third embodiment of a solenoid according to the invention in longitudinal section;
• Fig. 5 a fourth embodiment of a solenoid according to the invention in longitudinal section;
• Fig. 6 a fifth embodiment of a solenoid according to the invention in longitudinal section; and
• Fig. 7 a working air gap force diagram with working air gap force characteristics for the lifting magnet according to the prior art and for two lifting magnets according to the invention.

The invention will now be described with reference to five in the FIGS. 2 to 6 illustrated embodiments explained in more detail. These embodiments represent modifications of the in Fig. 1 illustrated lifting magnets described in detail above, and for components that are used both in the known and in the lifting magnet according to the invention, the same reference numerals are used in the drawings and reference is made to the above description with respect to their function.

In the Fig. 2 illustrated first embodiment of a lifting magnet according to the invention comprises a magnetic iron yoke element 1 in the form of a U-shaped bracket, which is bent for example of sheet metal. The iron yoke element 1 has a longitudinal leg 1a and two transverse limbs 1b, 1c extending from the longitudinal leg 1a. The transverse legs 1b, 1 c engage around the opposite end faces of a bobbin 4, on which an exciter coil 3 is wound. The bobbin 4 has an axial passage opening 4a in which a pole core 2 is arranged at one end. Furthermore, in the axial passage opening 4a of the bobbin 4, an annular plain bearing bush 6 and a magnetic piston 15 mounted therein displaceably made of a soft magnetic material. When the exciting coil 3 is supplied with electric current, the magnetic piston 15 is attracted by the electromagnetic force of the exciting coil 3 and displaced along a center axis M in the axial through hole 4a of the bobbin 4 in the direction of the pole core 2 to a stroke end position HE. The iron yoke element 1 has at the pole core 2 opposite piston-side region, ie the transverse leg 1c, a through hole 1 e, which is dimensioned so that the magnetic piston 15 can pass. As far as described so far, the construction of the solenoid is conventional. In contrast to the prior art, the magnetic piston 15 of the Hubmagneten invention, however, a control portion 15a at the spaced from the pole core 2 end of the magnetic piston 15, which control portion 15a in the through hole 1 e of the transverse leg 1 c of the iron yoke element 1 is displaceable. The control section 15a is characterized by a decreasing diameter, this diameter - starting from the diameter D1 of the central portion of the (cylindrical) magnetic piston 15 to the end remote from the pole core 2 end of the control section to a diameter D2, wherein the transition from the larger diameter D1 to the smaller diameter D2 is continuous, wherein the generatrix of the control section 15a presents as a quarter circle. During the stroke movement of the magnetic piston 15 in the direction of the stroke end position HE, the control portion 15a of the magnetic piston 15 enters the through hole 1e from the outside. Due to the continuously decreasing diameter of the control section 15a, a parasitic air gap 16 is caused in the passage opening 1e, which reduces the magnetic flux from the transverse leg 1c of the iron yoke element 1 and thereby also reduces the lifting force. The magnetic flux is lowest when the magnetic piston 15 has reached the stroke end position as in the working air gap force diagram of FIG Fig. 7 shown by the characteristic B. It can be seen from the characteristic curve B that at the beginning of the stroke, if the working air gap 8 has a length of 6 mm, the lifting force amounts to slightly more than 2 N. As the working air gap decreases, the lifting force increases to a. 3.7 N until at a Arbeitsluftssptslänge of about 2 mm, the control section 15 enters the through hole 1 e and thereby generates the parasitic air gap 16 (or increased due to manufacturing tolerances and the presence of plain bearing bush 6 existing parasitic air gap). The parasitic air gap 16 leads to a decrease in the lifting force to about 3 N at the Hubendposition HE.

The reduced lifting force at the end of the stroke allows for almost silent switching operations of the solenoid. According to the invention, however, a further measure is provided which allows virtually noiseless switching operations. This measure includes the interpretation of the spring force of a known spring 19 (see spring 9 in Fig. 1 ), which serves as a return element for the magnetic piston 15, such that the Hubendposition HE not by a mechanical stop of the magnetic piston 15 on the pole core 2, but by an equilibrium of forces exerted by the spring 19 on the magnetic piston 15 Spring force with the electromagnetic forces generated by the exciting coil 3, is determined. As from the characteristic B of the working air gap force diagram of Fig. 7 can be seen, the magnetic piston 15 is spaced in its Hubendposition HE of the pole core 2 about 0.5 mm, or in other words, remains a residual working air gap of 0.5 mm in length.

Fig. 3 shows a second embodiment of a lifting magnet according to the invention. This second embodiment differs from the first only in that the magnetic piston 25 is provided with a conical control portion 25a which tapers conically from a diameter D1 in a direction opposite to the pole core 2 to a smaller diameter D2. The parasitic air gap generated thereby is designated by the reference numeral 26.

Fig. 4 shows a third embodiment of a lifting magnet according to the invention. This third embodiment differs from the foregoing embodiments only in that the magnetic piston 35 is provided with a cylindrical control portion 35a having a diameter D2 smaller than a diameter D1 of a central cylindrical portion 35b of the magnetic piston 35 adjacent to the control portion 35a. Thus, a stepped transition from the central portion 35 to the control portion 35a of the magnetic piston is realized. The transition could also be made in several gradations according to the invention. The adjusting in the through hole 1e parasitic air gap 36 is annular.

Fig. 5 shows a fourth embodiment of a lifting magnet according to the invention. This fourth embodiment differs from the first, in Fig. 2 illustrated embodiment in principle only as followed by the control portion 45a of the magnetic piston 45, which brings a reduction in diameter from D1 to D2 with it, a cylindrical end portion 45c with a diameter D2. The cylindrical end portion 45c protrudes also in the stroke end position HE through the through hole 1e of the transverse leg 1c of the iron yoke element 1 to the outside. In contrast, formed in the previously described embodiments, the control portions (15a, 25a, 35a) respectively facing away from the pole core end of the magnetic piston, wherein the magnetic piston length was dimensioned so that in the stroke end position HE End faces of the control sections flush with the outer surface of the transverse leg 1 c completed.

In Fig. 6 is a fifth embodiment of a lifting magnet according to the invention shown in longitudinal section. This embodiment differs from the previous embodiments in that the control portion 55a of the magnetic piston 55 has no shape deviating from the cylinder shape, but is designed as an end portion of the magnetic piston having an unchanged diameter D1. However, the length L of the magnetic piston 55 is selected so that the control portion 55a does not project into the through hole 1 e of the iron yoke element 1, but flush with the inner surface of the transverse leg 1 c. The parasitic air gap 56 extends in this case over the entire cross-sectional area of the passage opening 1 e, and the magnetic flux of force concentrates during the lifting movement of the magnetic piston 55 on the part of the control portion 55 a, which still protrudes into the through hole 1 e. Since this part becomes smaller and smaller in the stroke end position HE in response to the traveled stroke of the magnetic piston, the magnetic resistance increases and hence the lift force sharply drops, as in the characteristic curve C in the working air gap force diagram of FIG Fig. 7 shown.

Also in this embodiment of the invention, the spring force of the spring 59 is set so that the Hubendposition HE not by a mechanical stop of the magnetic piston 55 on the pole core 2, but by a balance of forces exerted by the spring 59 on the magnetic piston 55 spring force with the electromagnetic forces , which are generated by the exciting coil 3, is determined. As can be seen from the characteristic curve C, the magnetic piston 55 is at its stroke end position HE of the pole core 2 about 0.5 mm apart, and there is a residual working air gap 8 of 0.5 mm in length.

It should be noted that the magnetic iron yoke element need not be formed as a bracket, but, e.g. can also be designed as a housing. In the literature, the magnetic iron yoke element is also referred to as a stator. The magnetic piston is often referred to in the literature as an anchor.

Claims (6)

1. A lifting magnet comprising a magnetic back iron element (1), an excitation coil (3) surrounded at least partially by the back iron element (1) and wound onto a coil body (4), a pole core (2) arranged at least partially in an axial through opening (4a) of the coil body (4) and a magnetic piston (5, 15, 25, 35, 45, 55) which is displaceable along a central axis (M) of the coil body (4) toward the pole core (2) as far as into a stroke end position (HE) when the excitation coil (3) is supplied with current, wherein the back iron element (1) has a through opening (1e) for the magnetic piston in a piston-side region (1c) opposite to the pole core (2), characterized in that a control section (15a, 25a, 35a, 45a, 55a) of the magnetic piston (15, 25, 35, 45, 55), which control section is displaceable in the through opening (1e) of the piston-side region (1c) of the back iron element (1), exhibits such a geometric design that a parasitic air gap (16, 26, 36, 46, 56) appears and/or increases in the through opening (1e) of the piston-side region (1c) of the back iron element (1) when the magnetic piston (15, 25, 35, 45, 55) is displaced toward the stroke end position (HE) as a result of the fact that the magnetic piston (15, 25, 35, 45) exhibits a reduced piston diameter (D2) in the control section (15a, 25a, 35a, 45a) and the control section (15a, 25a, 35a, 45a) enters from outside into the through opening (1e) during the reciprocating motion of the magnetic piston (15) toward the stroke end position (HE) or as a result of the fact that the length (L) of the magnetic piston (55) is chosen to be so short that, in the stroke end position (HE) of the magnetic piston, the control section (55a) of the magnetic piston will not or only partially project into the through opening (1e) of the piston-side region (1c) of the back iron element (1).
2. A lifting magnet according to claim 1, characterized in that, in the control section (35a), the diameter of the magnetic piston (35) gradually decreases from diameter D1 to diameter D2.
3. A lifting magnet according to claim 1, characterized in that, in the control section (15a, 25a, 45a), the diameter of the magnetic piston (15, 25, 45) continuously decreases at least piece by piece in a direction opposite to the pole core (2).
4. A lifting magnet according to claim 3, characterized in that the control section (25a) of the magnetic piston (25) has a tapered design.
5. A lifting magnet according to claim 3, characterized in that the surface line of the control section (15a, 45a) of the magnetic piston (15, 45) has a curved course at least in sections.
6. A lifting magnet according to any of the preceding claims, characterized in that a spring (19, 59) pretensions the magnetic piston (15, 55) against the magnetic force exerted by the excitation coil (3), with the elastic force of the spring (19, 59) being configured such that the magnetic piston (19, 59) in its stroke end position (HE) is spaced apart from the pole core (2).

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