Abstract:
A polarized relay comprising an electromagnet, a two-pole or three-pole permanent magnet, an armature, and switches, which are mounted in and on a shelf-like support component. The support component accommodates magnetic flux pieces and the permanent magnet in an upper cavity, and the permanent magnet is magnetized while the electromagnet is still outside the support component. Subsequently, the electromagnet is inserted into lower cavity of the support component and the rest of the components of the relay are mounted.

Description:
FIELD OF THE INVENTION 
     The invention relates to a method for producing a polarized electromagnetic relay comprising an electromagnet, a permanent magnet, an armature, and actuable switches, and further relates to a polarized electromagnetic relay produced by such method. 
     BACKGROUND OF THE INVENTION 
     Polarized electromagnetic relays are known in configurations with three-pole permanent magnet (WO 93/23866) and with two-pole permanent magnet (U.S. Pat. No. 4,912,438, U.S. Pat. No. 5,153,543, U.S. Pat. No. 6,670,871 B1). In any case, the electromagnet includes a coil comprising a core and pole pieces in a yoke-shaped configuration. In case of a three-pole permanent magnet, this permanent magnet is arranged between the two legs of the yoke above the coil and in parallel to the axis of the coil. This permanent magnet may be separated from a magnetized strip and inserted into the coil former between the two legs of the yoke. In case of a two-pole permanent magnet, the latter is magnetically connected transversely to the axis of the coil, with one pole approximately in the middle of the old core (U.S. Pat. No. 4,912,438, U.S. Pat. No. 5,153,543). 
     From U.S. Pat. No. 4,975,666 a polarized electromagnetic relay is known comprising a base housing which opens to the top, with an electromagnetic block including coil, core, and pole legs, and a permanent magnet between the pole legs, and an armature block including armature and switch elements on the pole legs mounted therein. The assembly does not permit to produce the permanent magnet located between the pole legs from an unmagnetized ferromagnetic precursor by magnetization, because this would damage the coil by excessive induced currents. 
     From DE 195 20 220 C1, another polarized electromagnetic relay is known, in which the coil together with two ferromagnetic yokes and a permanent magnet interposed therebetween are inserted into a base body from above and fixed with a potting compound. Magnetizing of an unmagnetized precursor in the installed state is not possible. 
     Also, a relay is already known (U.S. Pat. No. 6,670,871 B1) including a two-pole permanent magnet which extends in parallel to the coil axis. The plate-shaped permanent magnet having poles on the top and bottom thereof is received in an armature plate. The electromagnet is accommodated in a two-part housing which comprises a trough-shaped lower portion and a box-shaped upper portion on which the fixed contacts of the switches and the rotary supports for the armature are located. The movable contact springs are embedded in the insulating armature plate. A recess in the armature plate is adapted to accommodate the two-pole permanent magnet. The document does not disclose whether the permanent magnet is magnetized in its embedded state in the armature plate. In any case, a drawback is the large spacing between the two-pole permanent magnet and the core of the electromagnet causing a large ferromagnetic-free path in the closed magnetic flux path, which results in a large magnetic resistance in any position of the armature. 
     In order to be capable to implement small polarized relays, very strong permanent magnets are necessary. Such strong permanent magnets are available and include fractions of rare earths. However, because of the strong attractive forces between the magnets, their handling from a supply of individual magnets is difficult, not only in terms of the adhesion of the magnets to each other, but also in terms of keeping the pole faces free of chips and dust particles during installation. In terms of production technology it is more favorable to use a piece of material of an unmagnetized ferromagnetic alloy and to “magnetize” the “precursor” once installed in the relay. However, magnetization in place using high field strength involves the risk that other components of the magnetic system of the relay might be damaged due to strong induced voltages and currents, in particular the coil of the electromagnet. 
     SUMMARY OF THE INVENTION 
     The invention is based on the object to magnetize the permanent magnet of a polarized relay without any risk for other components of the relay. 
     The invention uses separate manufacturing and configuration of components of the relay in conjunction with specific manufacturing steps, so that magnetization of the permanent magnet is possible without incurring a risk of damaging the coil of the electromagnet. 
     Specifically, a coil assembly is provided as one component of the relay, comprising a coil, a core, and pole pieces, and further a support component is provided, in which magnetic flux pieces of the magnetic system of the relay are included, such as the pole pieces of the electromagnet and a bearing portion of the armature. These magnetic flux pieces are made of soft iron and are not damaged by high magnetic field strengths. 
     In a line with the magnetic flux pieces, a one-piece or two-piece permanent magnet precursor of an unmagnetized ferromagnetic alloy is installed in the support component, which will become the permanent magnet by magnetization. The support component additionally has an accommodation space into which the separately manufactured coil assembly which is the sensitive part of the electromagnet is inserted and mounted once the permanent magnet has been magnetized. Then the rest of the relay components including the switches actuated by the relay are mounted to complete the relay. 
     The invention also relates to a polarized electromagnetic relay comprising an electromagnet, a pole assembly including magnetic flux pieces and a permanent magnet, a support component, and an armature. The electromagnet comprises a coil assembly, which is configured as a structural unit including a coil, a core, and pole pieces. The support component preferably has a shelf-like or storey-like configuration comprising an upper cavity that defines an accommodation space for the pole assembly including the magnetic flux pieces and the magnetized permanent magnet, and an intermediate insertion cavity that defines an accommodation space for the coil assembly. The armature of the relay is pivotally mounted relative to the electromagnet on the support component, and is connected to the movable switch elements. 
     This configuration permits to produce even small and narrow polarized relays of high sensitivity. By modifying component parameters, various functions of polarized relays can be realized. 
     Further details of the invention will become apparent from the following description of two exemplary embodiments with reference to the drawings, and from the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings: 
         FIG. 1  is a perspective view of a first embodiment of a relay as seen obliquely from above to a longitudinal side and a short side, with the housing cap removed; 
         FIG. 2  is a longitudinal sectional view through the relay of the first embodiment; 
         FIG. 3  is a perspective view of a support component as seen obliquely from above to a longitudinal side and a front end; 
         FIG. 4  is a perspective view of a coil assembly; 
         FIG. 5  is an exploded view of the individual components of the relay according to the first embodiment; 
         FIG. 6  is a perspective view of a second embodiment of the relay; 
         FIG. 7  is a longitudinal sectional view through the relay of  FIG. 6 ; and 
         FIG. 8  is an exploded view of the individual components of the relay of  FIG. 6 . 
     
    
    
     DETAILED DESCRIPTION 
     The electromagnetic relay consists of a magnetic system and a switch system which are held together and protected by housing components. The magnetic system comprises an electromagnet consisting of a coil assembly  10  ( FIG. 4 ) and pole pieces ( FIG. 2 ). Coil assembly  10  comprises a coil  1  wound around a coil former  5 , a ferromagnetic core  2 , and ferromagnetic pole pieces  3  and  4 , which form a structural unit. Core  2  is integrally joined to one of the two pole pieces  3 ,  4 , or to both pole pieces. The magnetic system further comprises magnetic flux pieces  7 ,  8 ,  9 , a permanent magnet  11 , and an armature  12 . Magnetic flux pieces  7  and  8  define the pole pieces of the electromagnet. Magnetic flux piece  9  forms a support piece for armature  12  which is in form of a rocking armature  12  in the present example. The permanent magnet  11  of the first embodiment has two poles and is arranged between pole piece  7  and magnetic flux piece  9 , while between pieces  8  and  9  the magnetic flux is interrupted. It is also possible to reverse the arrangement of permanent magnet and magnetic flux gap. What is important is the orientation of the poles of the permanent magnet relative to pole piece  7  or  8 , and to magnetic flux piece  9 . Magnetic flux pieces  7 ,  8 ,  9  and permanent magnet  11  form a pole assembly. 
     In the illustrated exemplary embodiment ( FIG. 4 ), a connection block  6  is connected to the coil assembly  10 , which is not necessary for the invention. Connection block  6  comprises switch signal terminal pins  15 ,  16  having deflected legs  15   a ,  16   a  for direct connection to the winding ends of coil  1 . A test contact terminal pin  25  is cranked and may thus be clamped between connection block  6  and pole piece  3 . 
     The component illustrated in  FIG. 4  is configured for being inserted into and secured in a shelf compartment or accommodation space  42  of a shelf-like or storey-like support component  40  ( FIG. 3 ). For this purpose, space  42  has two cavity extensions  43  and  44  for accommodating and positioning the connection block  6  in addition and adjacent to coil assembly  10 . 
     The shelf-like or storey-like support component  40  is also adapted for accommodating the pole assembly, i.e. magnetic flux pieces  7 , 8 ,  9  and permanent magnet  11 . For this purpose, an armature-side accommodation space  41  is provided and is divided into pockets. Pieces  7 ,  8 ,  9 , and  11  are fixed in the support component  40  by being embedding therein. Several embedding methods are contemplated, for example, overmolding, gluing, press-fitting. Additionally, a fixed contact  21  is provided on the upper side of support component  40 , which is electrically connected to a terminal pin  26  which is likewise fixed in the support component  40  by being embedding therein. 
     The switch system comprises a diagnostic switch  20  and at least one load switch  30 . Diagnostic switch  20  comprises the fixed contact  21  and a movable contact  22  which is attached at a fork-shaped end of a contact spring  23  in form of a double contact. Contact spring  23  is secured to and actuated by the leg  12   a  of armature  12 . Movable contact  22  provides the electrical connection to terminal pin  25 . 
     In a modified embodiment of the invention, test contact terminal pin  25  is embedded in support component  40  in parallel to test contact terminal pin  26  (not shown), and two separate fixed contacts are provided on the upper side of support component  40 . In this embodiment, the end of contact spring  23  is used as a bridging contact in order to close switch  20 . 
     Load switch  30  includes a fixed contact  31  and a movable contact  32  which is seated on a contact spring  33  that is mounted to support component  40  through a power rail  34  and is moreover electrically connected to a load terminal pin  35 . Fixed contact  31  is conductively connected to another load terminal pin  36 . Contact spring  33  is actuated via an electrically insulating coupling member  37  whose upper end is mechanically coupled to the second leg  12   b  of armature  12 . The mechanical connection may be established through an over-stroke spring  38 , as illustrated, or by directly connecting the ends of rocking armature  12  and coupling member  37 . 
     Besides the two legs  12   a  and  12   b , armature  12  further has a curved bearing portion  12   c  by which the armature rests on magnetic flux piece  9  which is formed as a supporting piece. Depending on the operational type of the relay (monostable, bistable), the legs  12   a ,  12   b  of armature  12  have different lengths and are held by spring forces, with different pole gap widths. Such spring forces are generated by contact spring  23 , over-stroke spring  38  (if provided), and contact spring  33 . Contact spring  23  is riveted to the leg  12   a  of the armature and has spring projections  23   a  and  23   b  and a fastening tab  23   c  which is welded to supporting piece  9  between armature  12  and pole face  7  in a specific angular position. Over-stroke spring  38  is similarly riveted to the leg  12   b  and also has spring projections  38   a ,  38   b  and a fastening tab  38   c  which is welded to supporting piece  9 . In addition to the force of contact spring  33 , the torsional forces of spring legs  23   b  and  38   b  are mainly responsible for the overall spring behavior of the relay. 
     In addition to the spring forces, the magnetic attractive force on armature  12  makes a difference as to whether a monostable or a bistable relay is obtained. The attracting forces on the legs  12   a ,  12   b  of the armature depend on the strength of permanent magnet  11  and the size of the pole faces of pole pieces  7 ,  8 . When in one end position of the armature the magnetic attraction force is greater than the effective spring force in the lifting direction, and in the other end position the magnetic attraction force is smaller than the lifting force of the springs, we have a monostable relay. By contrast, when in both end positions of the armature the magnetic attractive force is greater than the effective spring force in the lifting direction, we have a bistable relay. 
     While support component  40  is the main element of the housing, a housing bottom  50  and a housing cap  60  are also provided. As illustrated in  FIG. 1 , support component  40  has, at its front face shown, a guideway  46  for guiding the insulating coupling member  37 . This guideway and the upper side of the relay are covered by housing cap  60  of the assembled relay according to  FIG. 1 . A shallow cavity  45  ( FIG. 2 ) extends along the bottom of support component  40 , which cavity serves to accommodate load contact spring  33  and the movement range thereof and which is delimited at the lower side by housing bottom  50 . Load contact terminal pin  36  is inserted in the bottom part  50  and riveted with the bottom part by means of fixed contact  31 . 
     On the top of housing cap  60 , a switch may be provided for manually changing the position of armature  12 . 
       FIGS. 6, 7, and 8  illustrate a second embodiment of the invention. Components similar to the first embodiment are designated with the same reference numerals. The general configuration of the relay according to the second embodiment is similar to that of the first embodiment, and therefore corresponding parts of the description will not be repeated and only the differences will be described in more detail. 
     In the second embodiment of the relay, permanent magnet  11  comprises two portions  11   a  and  11   b , and interposed therebetween a magnetic flux piece  9  of soft iron so as to form a three-pole permanent magnet. Portion  11   a  has a higher coercive force when compared to portion  11   b . The two portions  11   a  and  11   b  have the same polarity towards magnetic flux piece  9 , that means either both are aligned with the south pole facing magnetic flux piece  9 , or both with the north pole, while towards the outer ends of the relay, the permanent magnet  11  with a total of three poles presents only north poles, or only south poles, as the case may be. Magnetic flux piece  9  presents the adjacent polarity, i.e. south pole if the north pole of the permanent magnet faces outwards, and north pole if the south pole of the permanent magnet faces outwards. 
     In the second embodiment, the mounting of armature  12  is different from the first embodiment in that a cross-shaped spring  39  provides for the support of armature  12  on magnetic flux piece  9 . Cross-shaped spring  39  has tabs  39   a  via which it is joined to magnetic flux piece  9  by welding, and further has a torsion web  39   b  and, transversely thereto, a support tab  39   c  for supporting armature  12 . 
     Another tab  39   d  may extend from cross-shaped spring  39 , which is adapted to dampen the impact of armature  12  on magnetic flux piece  8  and at the same time is tensioned thereby, which is useful upon a subsequent switching of the armature  12 , since in this way the armature will more easily clear magnetic flux piece  8 . Cross-shaped spring  39  is effective as a torsion spring, i.e. there will be no bearing friction and hysteresis loss of spring  39  is very small. 
     As another modification in the second embodiment, contact spring  23  and over-stroke spring  38  are formed integrally. Contact spring  23  is electrically conductive and is connected to electrically conductive armature  12  which in turn is connected, via electrically conductive cross-shaped spring  39 , to electrically conductive magnetic flux piece  9  which in turn is in electrically conductive communication with test contact terminal pin  25 . 
     For adjusting the adhesive force of leg  12   b  of armature  12  to magnetic flux piece  8 , an intermediate piece  8   a  of sheet metal material or plastic is additionally provided. Namely, due to the different lengths of legs  12   a ,  12   b  of armature  12 , the effective lifting forces thereon are different, which is somewhat compensated for by the interposition of piece  8   a.    
     The polarized electromagnetic relay is manufactured and assembled in a novel manner. The individual components illustrated in  FIG. 5  and  FIG. 8  are partially assembled into units, for example the coil assembly  10  shown in  FIG. 4 . This coil assembly comprises at least coil  1 , core  2 , and pole pieces  3  and  4 . In the illustrated exemplary embodiment, a coil former  5  is additionally provided to which a connection block  6  is mounted, through which the connections from the coil ends to the terminal pins  15 ,  16  extend. 
     The individual components illustrated in  FIG. 5  and  FIG. 8  moreover include a support component  40  which, for the purposes of the invention, is adapted to the production method of the relay. That is, support component  40  has an armature-side accommodation space  41  for magnetic flux pieces  7 ,  8 ,  9  and for permanent magnet  11 , and additionally an insertion cavity-like accommodation space  42  for coil assembly  10 . Magnetic flux pieces  7 ,  8 , and  9 , and permanent magnet  11  may be referred to as a pole assembly, since they present two outer poles and a center pole to armature  12 . The pole assembly is inserted into accommodation space  41  of the support component  40  and is fixed therein, for example by overmolding. 
     A special feature of the invention is that during installation of the pole assembly, it is not a finished permanent magnet what is mounted, but a permanent magnet precursor of an unmagnetized ferromagnetic alloy that includes a fraction of rare earths. Such precursor magnets can be “magnetized” with extremely high coercive forces. To this end, a very strong magnetic field has to be applied, which magnetizes the precursor magnet in the desired direction. In practical terms, a coil has to be placed around the pole assembly to produce the required field strength. This can be accomplished in the installed state of the pole assembly within accommodation space  41  of support component  40 . It will be appreciated that the accommodation space  42  for coil assembly  10  may be left empty. This prevents high voltages with a high electric current from being generated in the coil assembly, which could result in a damage thereof. 
     When magnetizing the pole assembly, the type of permanent magnet to be generated has to be taken into consideration. If a one-piece two-pole permanent magnet is to be produced, which corresponds to the first embodiment of the relay, the method described as above is sufficient. However, if a three-pole permanent magnet is to be produced by magnetization, the procedure is modified. Two precursor magnet portions  11   a ,  11   b  are used on either side of the central magnetic flux piece  9  and in contact with the adjacent magnetic flux pieces  7  and  8 , respectively. One of these precursor magnet portions, here portion  11   a , is made of an alloy that can be magnetized more than the other portion  11   b . Also, the more magnetizable portion  11   a  may be made smaller than the weaker magnetizable portion  11   b . Once the pole assembly has been mounted in the accommodation space  41  of support component  40 , for example in the order of the portions of  7 ,  11   a ,  9 ,  11   b ,  8 , magnetization is performed in a defined direction corresponding to the stronger permanent magnet portion  11   a . Then, a magnetic field is applied to the pole assembly, which is weaker and opposite to the initial magnetic direction, and this weaker magnetic field is not sufficient to reverse the magnetization of permanent magnet portion  11   a , but is sufficient to reverse the magnetization of the weaker permanent magnet portion  11   b . A result thereof is that like poles will face each other at central magnetic flux piece  9 . In this manner, a complete permanent magnet  11  is obtained with two like poles on the outer ends, i.e. towards magnetic flux pieces  7  and  8  which are effective as pole pieces, and an opposite pole on the central magnetic flux piece  9 . This configuration defines a three-pole permanent magnet. 
     Once the permanent magnet  11  has been generated, the coil assembly  10  may be mounted in the insertion cavity-like accommodation space  42  without risk. 
     Then, the remaining components are mounted to complete the relay. These include the armature  12  with its springs  23 ,  38 , and  39 , the load switch  30  together with coupling member  37 , and housing parts  50  and  60 . 
     The novel relay permits to implement various functionalities of a polarized relay, by modifying the size, the arrangement, and the parameters of individual components. By creating the permanent magnet through magnetization within the support component, it is possible to use strong permanent magnets without causing complications in the assembly of the relay, since at the time of magnetization the latter does not contain any sensitive components such as the magnetic coil. The relays may be made very small, because it is possible to produce permanent magnets with high coercive force. 
     It will be apparent to those skilled in the art that the embodiments described above are intended as examples and that the invention is not limited thereto but may be varied in many ways without departing from the scope of the claims. Furthermore, the features also define individually significant components of the invention, irrespective of whether they are disclosed in the description, the claims, the figures, or otherwise, even if they are described together with other features.