EP0329138B1 - Electromagnetic relay - Google Patents

Description

The invention relates to an electromagnetic relay with a coil, an axially arranged core in the coil and with a first and a second, each L-shaped yoke, the first yoke being designed as an armature, the first leg of which has a working air gap with respect to a first end of the Forms core and carries a contact spring, and whose second leg runs approximately parallel to the coil axis, the second yoke with its first leg facing the second end of the core, with its second leg extending substantially parallel to the coil axis next to the coil and a bearing point forms for the free end of the second leg of the first yoke, both yokes also having an extension of their first leg beyond the respective second leg and a tension return spring acting on both extensions and extending substantially parallel to the coil axis.

A relay structure with some of these features, in particular with an angular yoke and a flat armature carrying a contact spring, is described, for example, in DE-A-32 32 679, but is also known in many other configurations. These relays are simple and inexpensive to manufacture, robust against external influences and therefore used in large numbers, for example in motor vehicles.

Known relays of this conventional design each have a plate-shaped armature, which is usually mounted on the yoke in the region of an end edge. There are also known designs in which the armature is angled, but the bearing point is also usually in the case of such angled anchors in an extension of the pole face. If high direct currents are switched with such relays, there is a strong material migration and a great tendency to weld the contacts. These undesirable effects are particularly pronounced when the melt that arises in the arc of the contact can cool down at the same point on the arc if there is no relative movement at the contact points. This is often the case with relays of the type mentioned at the beginning, since the contact springs are generally connected directly to the armature.

Another disadvantage of the conventional arrangement is that the force exerted on the armature by the return spring, which force may also have to generate the rest contact force, counteracts the excitation force and increases during conventional armature tightening in conventional systems. Care must therefore be taken to ensure that the magnet system, ie the coil, is designed so that the force generated by the excitation system is greater than the counterforce exerted by the return spring and, if appropriate, the contact springs, at any time during the response. If the difference between the force curves of these two counteracting systems is too small, there is a risk that the relay will not pull through completely or not quickly enough under unfavorable tolerance conditions, so that unsafe contact will result.

A relay is known from FR-A-2 517 464, in which two angled armatures are mounted opposite one another on a plastic body surrounding the coil and actuate contact springs fastened separately with one or more actuating elements. The two anchors, like all conventional angle anchors, are each mounted in their bending angle there, so that each anchor executes its pivoting movement about its own axis at this bending angle. Since the contact springs are not connected to the anchors there, but are actuated by sliders, there is no relative movement at the contact points; the restoring forces exerted by the contact springs also have the conventional characteristics.

From US-A-4,691,181 a relay of the type mentioned is also known, in which one of two L-shaped yokes serves as an anchor and is supported with its second leg on the end of the second leg of the other yoke. The first leg of the armature carries a contact spring directly, and is reset by means of a tension coil spring. This already eliminates some of the disadvantages of conventional relays described at the beginning.

An improvement in the force-displacement characteristic of the spring forces results from the fact that the armature is not only angled, but also has its bearing point at the end of the angled second leg, that is to say approximately in the central region of the coil length. As a result, during the switching movement, the armature does not pivot about its break point between the two legs, but rather about the free end of the second leg, which, according to the length of this second leg, is at a large distance from the plane of the pole face on the coil core. The contact spring connected to the first armature leg thus has a large friction path at the contact point, which counteracts the material migration and the tendency of the contact to weld.

A significant further advantage of this construction is, however, that the return spring acting on the extension of the armature as well as on an extension of the second yoke has a falling characteristic of its effective spring force during the armature tightening movement. This is explained by the fact that, due to the rotary movement of the angle armature around the distal end of the second armature leg, the point of application of the return spring moves considerably with respect to the bearing point, so that the effective lever arm for the force of the return spring when the armature suit is significantly reduced. So although the spring force of the return spring remains the same during the armature movement or even increases slightly, it works with the lever arm multiplied spring force in a lower torque, which counteracts the torque applied by the magnet system.

The object of the invention is to develop a relay of the type mentioned in such a way that the advantages already described with reference to US Pat. No. 4,691,181 are achieved to an increased extent, the relay being intended to have as few individual parts as possible.

According to the invention, this relay is designed in such a way that the second yoke forms a second armature, which has a working air gap with its first leg relative to the core, and that the free ends of the two yoke legs are movably supported against one another at a common bearing point.

In the relay according to the invention, the second yoke is also designed as an angular armature, which is mounted with its angled second leg together with the corresponding leg of the first armature. The relay thus has two movable anchors, while a separate immovable flow return element is not required. The previously described advantages for contact friction and for the improved force-displacement characteristic are also given in the two-armature relay according to the invention. In addition, a two-armature relay has the known advantage that increased security against welding is given when the two contacts are connected in series.

Further refinements are specified in the subclaims.

• FIG 1 schematisch ein Relaissystem ähnlich dem der US-A-4691181 mit einem feststehenden Joch und einem beweglichen Winkelanker,
• FIG 2 ein Diagramm mit den Kraft-Weg-Kurven des Magnetsystems und des Kontaktsatzes bei einem herkömmlichen und bei dem Relais nach Fig. 1,
• FIG 3 eine FIG 1 entsprechende schematische Darstellung eines erfindungsgemäßen Relais mit zwei Ankern,
• FIG 4 eine detailliertere konstruktive Ausgestaltung eines Relais gemäß FIG 3.

The invention is explained in more detail below using exemplary embodiments with reference to the drawing. It shows

• 1 schematically shows a relay system similar to that of US-A-4691181 with a fixed yoke and a movable angle anchor,
• 2 shows a diagram with the force-displacement curves of the magnet system and the contact set in a conventional and in the relay according to FIG. 1,
• 3 shows a schematic representation corresponding to FIG. 1 of a relay according to the invention with two armatures,
• 4 shows a more detailed design of a relay according to FIG. 3.

1 shows schematically the basic structure of a relay designed similarly to US-A-4691181. This relay has a coil with a coil body 1 and a winding 2. Inside the coil, a core 3 is arranged in the axial direction, the first end 3a of which forms a working air gap with a movable yoke or armature 4, while the second end 3b with a fixed yoke 5 connected is. This yoke 5 has a first leg 5a, which runs perpendicular to the coil axis, and a second leg 5b, which is bent in a direction parallel to the coil axis and extends in length approximately to the middle of the coil length. The armature 4 is also angled or L-shaped, a first armature leg 4a forming the working air gap mentioned, while a second armature leg 4b runs approximately parallel to the coil axis and is supported with the free end 4c on the free end 5c of the yoke leg 5b. The bearing point or pivot point is designated 6.

As an extension of the first arm leg 4a, the armature 4 has an extension 4d which extends beyond the bend; Correspondingly, the yoke 5 also has an extension 5d which extends the first yoke leg 5a beyond the angle of the second yoke leg 5b. On these two extensions 4d and 5d, a return spring 7 is suspended, which is subjected to tension and is designed, for example, as a coil spring.

In addition, a contact spring 8 is attached to the armature, which forms a normally closed contact and a working contact with two counter-contact elements 9 and 10, which are only indicated.

In the switching position shown in FIG. 1, the system is in the non-energized state, the contact spring 8 resting on the mating contact element 9 in the idle state and receiving a corresponding contact pressure through the return spring 7. When the coil 2 is excited, the armature 4 is attracted. It rotates around point 6 and brings the contact spring 8 into contact with the mating contact element 10. The contact spring 8 receives due to the distance a of the armature leg 4 from the pivot point 6 a remarkable movement component in its longitudinal direction, whereby a considerable friction is generated on the contact surfaces. As a result, both material migration and mechanical contact wear can be kept low.

In addition, it results in the switching movement that the distance b between the pivot point 6 and the point 11 of the return spring on the armature 4 becomes smaller as the arm leg 4a approaches the yoke end 3a, so that the spring force of the return spring 7 has an increasingly smaller effect, ie that the product of the spring force of the return spring 7 and lever arm b becomes smaller, while the force exerted by the magnet system on the armature increases with the lever arm c remaining essentially the same.

The force relationships are shown in FIG. 2 as an example. There, the path s is plotted on the abscissa, which the armature travels between a rest position R (corresponds to FIG. 1) and a working or closing position A (with the armature fully tightened). The forces F are plotted on the ordinate, all forces being related to the same lever arm in order to make them comparable. The curve m denotes the course of the force generated by the magnet system through the excitation coil 2. It increases as the armature approaches the core until it reaches the value F _m in the closed state.

Curve f1 shows the course of the spring forces, i.e. the contact springs and the return spring, in a conventional relay of a comparable design. When the relay responds, i.e. at point R, the normally closed contact force F _k1 must first be overcome until the contact opens. Thenceforth only the return spring 7 counteracts the pulling forces of the magnet system. In a conventional system according to curve f1, however, the force of the return spring increases with increasing armature until the contact closes at point S. At this point the spring force reaches a size F _k2 . From then on, a contact force is built up in the contact spring 8 resting on the counter-contact element 10, which counteracts the magnet system in addition to the force of the return spring, which also increases. In the final state of the attracted armature, the spring force reaches the value F _k3 . It can be seen from FIG. 2 that the spring force curve f1 in some places comes quite close to the curve of the force of the magnet system. However, you must not cut this curve, otherwise the spring force would be greater than the force of the magnet system, so the armature could no longer be tightened.

Curve f2 now shows a force-displacement curve which can be achieved in the relay shown in FIG. 1 and which is considerably further away from curve m , that is to say it produces greater energy reserves of the magnet system when the magnet system remains unchanged, and thus leads to a more reliable response. Curve f2 does not initially increase after opening break contact 8-9, since the effective force of the return spring drops due to the decreasing lever arm b , namely from point R to point S from force F _k1 to F _k4 . Only from the closing point S on does the spring force curve f2 rise again, since the desired contact force must now be built up at the normally open contact 10. However, due to the much lower starting point, it has a sufficiently large distance from the magnet system curve m , so that the desired responsiveness is guaranteed.

3 shows an exemplary embodiment of a relay designed according to the invention in a schematic representation. Coil and armature 4 are constructed and labeled in the same way as in FIG 1. Only Instead of the fixed yoke 5, a movable yoke or a second armature 15 is now provided, which forms a further working air gap with the second core end 3b. The second anchor 15 is constructed correspondingly to the first anchor 4, that is to say with a first anchor leg 15a and an angled second anchor leg 15b and with an extension 15d. The return spring 7 is accordingly suspended in this case between the two extensions 4d and 15d. A second contact spring 18 is also attached to the armature 15, which cooperates with counter-contact elements 19 and 20. The advantages described with reference to FIG. 1 are also achieved with the relay according to FIG. 3, namely the contact friction during the switching process and the favorable course of the force-displacement curves. With the two armatures and the associated two working air gaps there is an even steeper increase in the magnetic force curve, while the drop in the effective force of the return spring 7 has an increased effect on both armatures. The embodiment of FIG. 3 also has the advantage that the advantages of two anchors can be used with only one excitation system, but at the same time a fixed yoke is saved.

A structural design of the relay from FIG. 3 is also shown in FIG. The magnet system contains a coil body 21 with a winding 22, the coil body resting on a base 23 as a supporting part. The system has two anchors 24 and 25, which are each angularly shaped according to FIG 3. The first armature legs 24a and 25a interact with the core (not shown) and each carry a contact spring, for example 28. The second armature legs 24b and 25b extend next to the coil and form interlocking bearing elements at their free ends, for example a bearing cutting edge 24c and a bearing groove 25c. However, it would also be conceivable to equip both anchors with a bearing cutting edge or with bearing grooves and a corresponding one between them Intermediate element, for example in the form of a rod with a cylindrical cross section or with an X-shaped cross section, depending on the design of the anchor ends. A return spring 27 is suspended between extensions 24d and 25d of the two anchors. The function of the two anchors has already been described with reference to FIG 3.

As can also be seen in FIG. 4, the relay has a base 30 and a cap 31 as a housing, with connection elements, for example in the form of flat plugs 32, being fastened in the base 30. These connecting elements are connected in a suitable, known manner to the corresponding parts in the relay, for example via strands 33 to the contact springs and via correspondingly bent, invisible connecting pieces to the coil connections 34. Support elements 35 (only molded on the base) for the two anchors. As a result, the anchors, which are otherwise only preloaded against one another, are secured against lateral migration.

Finally, it should be pointed out that instead of the extension of the respective yoke or anchor leg mentioned in the claims for the attack of the return spring, a correspondingly designed contact spring according to DE-GM 83 25 986 or EP-OS 0 136 592 can be used. In this case, the variable lever arm is formed directly by the contact spring, not by the armature.

Claims (6)

1. Electromagnetic relay having a coil, a core (3) which is arranged axially in the coil (1, 2), and having a first and a second yoke (4, 15; 24, 25), which are in each case L-shaped, the first yoke (4; 24) being constructed as an armature whose first limb (4a, 24a) forms an operating air gap with respect to a first end (3a) of the core (3) and supports a contact spring (8; 28), and whose second limb (4b; 24b) runs approximately parallel to the coil axis, the second yoke (15; 25) facing the second end (3b) of the core (3) with its first limb (15a; 25a), extending essentially parallel to the coil axis, adjacent to the coil, with its second limb (15b; 25b), and forming a bearing point for the free end of the second limb (4b; 24b) of the first yoke (4; 24), both yokes (4; 24) furthermore in each case having an extension (4d, 15d; 24d, 25d) of their first limb (4a, 15a; 24a, 25a) beyond the respectively second limb (4b, 15b); 24b, 25b), and a tension restoring spring (7; 27) engaging on both extensions (4d, 15d; 24d, 25d) and extending essentially parallel to the coil axis, characterised in that the second yoke (15; 25) forms a second armature which, with its first limb (15a; 25a), has an operating air gap with respect to the core (3), and in that the free ends of the two second yoke limbs (4b, 15b; 24b, 25b) are supported on a common bearing point (6) such that they can move with respect to one another.
2. Relay according to Claim 1, characterised in that the respectively second limbs (4b, 15b; 24b, 25b) in each case extend approximately up to half the coil length.
3. Relay according to Claim 1 or 2, characterised in that the two armatures (24, 25) in each case have integrally formed bearing elements (24c, 25c) which engage in one another.
4. Relay according to Claim 1 or 2, characterised in that the two armatures are in each case supported on a common bearing element which is supported in between.
5. Relay according to one of Claims 1 to 4, characterised in that bearing or supporting elements (35) are integrally formed on the housing (30, 31) in the region of the bearing ends of the two armatures (24, 25).
6. Relay according to one of Claims 1 to 5, characterised in that the extension for the engagement of the restoring spring is formed by a section of the contact spring which is mounted on the armature.

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