Patent Application
20130033344
1. Field of the Invention
This invention relates to an electromagnetic relay. The invention also relates to a method for producing such an electromagnetic relay.
2. Description of the Related Art
An electromagnetic relay is required to provide for passage and blockage of a large current of high-voltage direct current, when it is used for an industrial power supply equipment, such as an uninterruptible power supply (UPS) installed in a telecommunication base station, or for a power conditioner or a rechargeable battery in a fuel cell system or a solar power system. In an electromagnetic relay in these applications, it is necessary to provide a sufficient movable range of movable contacts so as to switch the power source on and off, and it tends to complicate the configuration or increase the size in order to improve heat dissipation capacity and durability. JP 2010-44973 A describes an electromagnetic relay with an actuating part having an improved form in order to address such issues.
It has been known in an electromagnetic relay that arc discharge occurs when a movable contact moves apart from a fixed contact or when the movable contact approaches to the fixed contact. This phenomenon becomes more remarkable, as a voltage applied to the electromagnetic relay becomes higher or an electric current passing through the electromagnetic relay becomes larger. The arc discharge could result in damaging the contacts or decreasing blockage capability of the electric current.
An electromagnetic relay has been known, including a bar-shaped magnet having a length equal to or greater than the distance between a pair of fixed contacts (or a pair of movable contacts), the magnet being provided opposite to a gap between the fixed contacts and the movable contacts. (See JP 2000-195402 A, for example.). The electromagnetic relay is designed to generate a magnetic field perpendicular to the gap between the fixed contacts and the movable contacts by providing the magnet inside the side wall of a cover enclosing the respective parts, thereby cutting off the arc discharge. In this configuration, the magnet is placed on a side wall of the cover by insert molding, or in a pocket which has been formed in the cover prior to placement of the magnet.
There is a need for an inexpensive electromagnetic relay having a simpler configuration, which allows for passage and blockage of a high voltage and/or a large current.
According to one embodiment of the present invention, an electromagnetic relay is provided, the electromagnetic relay comprising:
In the following, embodiments of the present invention will be described with reference to the accompanied drawings. Like elements commonly used in different drawings or different embodiments are designated with the same reference numerals. The scale of elements relative to one another may be modified for the purpose of clarifying the drawings. Although particular relationships between the positions of elements or particular orientations of elements may be specified in the following description, these particularities are not intended to limit practical applications or manners in which each element is provided in relation to one another, but to merely explain particular embodiments as illustrated in the drawings, unless mentioned otherwise.
First, an electromagnetic relay 10 according to a first embodiment of the present invention will be described below with reference to
The electromagnetic relay 10 is a polarized electromagnetic relay which includes a permanent magnet 18 incorporated to an armature 16 and functions to switch between states of passing and blocking an electric current flowing through a pair of bus bar terminals 20 and 22. The electromagnetic relay 10 includes an electromagnet part 24 which generates a magnetic field in response to electric power supplied from an external source, an actuating part 26 which is actuated in response to the generated magnetic field, and a contact part 28 which opens or closes a pathway of an electric current in response to the movement of the actuating part 26. Each component of the electromagnet part 24, the actuating part 26 and the contact part 28 is accommodated in the interior of a housing formed by a base (first housing) 12 made of resin and a cover (second housing) 14 made of resin.
The base 12 is an example of a first housing for holding the electromagnet part 24, the actuating part 26 and the contact part 28. The base 12 has a plate-like end wall 30 having a substantially L-shaped contour in plan view, and a peripheral wall 32 provided along the outer edges of the end wall 30, so as to project from the end wall 30 to a certain height in one direction. The peripheral wall 32 defines an opening opposite to the end wall 30. The peripheral wall 32 has at its one edge grooves 34 and 36 in a height direction of the peripheral wall 32. The peripheral wall 32 and the end wall 30 define a recess 38 having a substantially L-shaped cross section for accommodating components necessary for an operation of the electromagnetic relay 10 (in particular, the electromagnet part 24, the actuating part 26 and the contact part 28). The recess 38 has a rectangular portion and an extended portion 38a laterally extending from a part of one edge of the rectangular portion. The base 12 has wall portions 40 and 42 which extend from a portion 32b of the peripheral wall 32 to substantially the middle of the recess 38. The wall portion 40 has on a side opposite to the peripheral wall 32 a tip 40a which has a U-shaped cross section and defines a groove 44 for receiving the bus bar terminal 22.
The base 12 has a pair of attachment portions 46 and 48 on outer side faces of the peripheral wall 32. The attachment portions 46 and 48 have a cylindrical shape, respectively, and have through-holes 50 and 52 in parallel to the height direction of the peripheral wall 32. Also referring to
The cover 14 is an example of a second housing attached to the base 12 via a joining portion 54. The cover 14 is formed from a plate-like member having a substantially L-shaped contour in plan view, corresponding to the shape of the recess 38. The cover 14 has in its outer periphery the joining portion 54 which engages with an engageable portion 32a extending along inner side faces of the opening end of the peripheral wall 32 of the base 12. The cover 14 has a second end wall 56 which is provided opposite to and in parallel to the end wall 30 of the base 12, so as to close the recess 38 when the joining portion 54 engages with the engageable portion 32a of the peripheral wall 32 of the base 12. As described below in further details, on the outer surface of the second end wall 56 opposite to the recess 38, there is an accommodating portion 60 capable of accommodating a permanent magnet 58 opposite to the contact part 28 with the second end wall 56 interposed therebetween. The cover 14 has protrusions 62 and 64 at its one edge. These protrusions 62 and 64 have a supplementary shape so as to cooperate with the grooves 34 and 36 formed on the edge of the peripheral wall 32 of the base 12, and to surround engageable portions 20b and 22b of the bus bar terminals 20 and 22 (described below), when the housing is formed by engaging the joining portion 54 of the cover 14 to the engageable portion 32a of the base 12.
The electromagnet part 24 is provided in a space defined by the wall portion 42 of the base 12, the part 32b of the peripheral wall 32 extending perpendicular to the wall portion 42, and the part 32c of the peripheral wall 32 extending in parallel to and spaced apart from the wall portion 42. The electromagnet part 24 includes a bobbin 66 made of resin, a coil 68 formed by winding an electric wire, a core member 70 and a yoke 72.
The bobbin 66 includes a tubular portion 66a and flanges 66b and 66c provided at the ends of the tubular portion 66a. The coil 68 is formed by winding the electric wire around the tubular portion 66a. A through-hole 74 continuously extends through the tubular portion 66a and the flanges 66b and 66c. A core 70b extending from an end plate portion 70a of the core member 70 substantially at right angle is adapted to be inserted to the through-hole 74. In order to clarify the drawings, the electric wire of the coil 68 is either not shown or only schematically illustrated in the drawings.
The yoke 72 has an end plate portion 72a provided along the flange 66b, an intermediate plate portion 72b bent from the end plate portion 72a and extending along one side of the coil 68 beyond the middle point of the coil 68 in an axial direction, and a tip plate portion 72c bent again from the intermediate plate portion 72b and extending in parallel to the end plate portion 72a in a direction opposite to the end plate portion 72a. The end plate portion 72a has protrusions 76 and 78, which are pressed into recesses (not shown) situated certain positions in the base 12. The end plate portion 72a further has an engaging hole 80 with which a tip portion of the core 70b is engaged. The tip plate portion 72c is positioned so as to be spaced apart from, opposite to and substantially in parallel to a part of the end plate portion 70a of the core member 70, when the electromagnet part 24 is assembled. When the coil 68 is excited, a magnetic field is generated between the tip plate portion 72c of the yoke 72 and the end plate portion 70a of the core member 70.
The electric wire of the coil 68 is at its tip end connected to coil terminals 86, 88 and 90. In the illustrated configuration, the coil is formed by a first electric wire whose ends 82a and 82b are connected to the coil terminals 86 and 88, respectively, and a second electric wire whose ends 84a and 84b are connected to the coil terminals 88 and 90, respectively (
The actuating part 26 of the electromagnetic relay 10 includes an armature 16 which is actuated in response to magnetic force generated by the electromagnet part 24, an actuating body 94 for holding the armature 16, and a card 96 for transmitting movement of the actuating part 26 to the contact part 28. The actuating body 94 has a substantially L-shaped contour in plan view. The L-shaped actuating body 94 has a shaft 98 at one end, and elongated grooves 100 and 102 extending in parallel to each other in the vertical direction at the other end. The shaft 98 is rotatably inserted into a recess (not shown) provided at the bottom of the extended portion 38a of the recess 38 of the base 12.
The armature 16 includes two plate members 104 and 106 made of a magnetic material such as iron, and a permanent magnet 18 held between these plate members 104 and 106. The plate members 104 and 106 are attached to the actuating body 94 by inserting narrower portions 104a and 106a (right side in
The actuating part 26 is actuated so as to rotate around the shaft 98, as the card 96 is actuated by the magnetic force generated by the electromagnet part 24. The rotational movement of the actuating part 26 around the shaft 98 is transmitted to movable contacts 108 and 110 of the contact part 28, which will be described below, via the card 96. The card 96 has upper protruding pieces 112a and 114a projecting toward the actuating body 94, which are spaced apart from each other and extend in parallel to each other. The card 96 also has two vertical pieces 112 and 114 which are spaced apart from each other and extend in parallel to each other, and extend downward and perpendicularly to the upper protruding pieces 112a and 114a. At a lower end of the vertical piece 112, there is a lower protruding piece 112b extending toward the actuating body 94 and perpendicularly to the vertical piece 112. The card 96 is fitted to the actuating body 94 by inserting the upper protruding pieces 112a and 114a and the lower protruding piece 112b, which are oriented toward the actuating body 94, to corresponding engaging holes 116, 118 and 120 of the actuating body 94. In this way, the actuating body 94 and the card 96 are integrated with each other, so as to move together. The two vertical pieces 112 and 114 of the card 96 have bulging portions 112c and 114c, respectively, which bulge toward each other. A part of a movable spring 122 of the contact part 28, which will be described below, is situated in a gap between the vertical pieces 112 and 114, so as to be sandwiched on both sides by the bulging portions 112c and 114c. As described above, since the movable spring 122 is held by the card 96, the movable spring 122 is also actuated in accordance with the movement of the actuating part 26.
The contact part 28 including the movable contacts 108 and 110 and the fixed contacts 124 and 126 will be described below. The contact part 28 includes a pair of bus bar terminals 20 and 22, a movable spring 122 attached to the bus bar terminal 20, and a flat braided wire 128 placed along the movable spring 122. The contact part 28 as illustrated is a twin contacts type which employs two pairs of contacts capable of opening and closing. The fixed contacts 124 and 126 are in the form of a rivet, and attached to the bus bar terminal 22 by fastening to an upper through-hole 130 and a lower through-hole 132 formed in the bus bar terminal 22. The bus bar terminal 22, as a whole, is positioned along the wall portion 40 in the recess 38 of the base 12. At the end (left side in
The movable contacts 108 and 110 also in the form of a rivet are fastened to an upper through-hole 134 and a lower through-hole 136 formed at one end of the movable spring 122 and to an upper through-hole 138 and a lower through-hole 140 of the flat braided wire 128, whereby the movable contacts 108 and 110 are attached to the movable spring 122 and the flat braided wire 128. The movable contacts 108 and 110 are situated opposite to the fixed contacts 124 and 126 described above. At the end opposite to the through-holes 134 and 136 of the movable spring 122, there are attaching holes 142 and 144. Similarly, there are attaching holes 146 and 148 at the end opposite to the through-holes 138 and 140 of the flat braided wire 128. Rivets 150 and 152 are fastened through these attaching holes 142, 144, 146 and 148 and attaching holes 154 and 156 formed in the flat end plate portion 20a of the bus bar terminal 20. The movable spring 122 and the flat braided wire 128 have a fixed end fixed to the bus bar terminal 20, and a free end provided with the movable contacts 108 and 110 at the other end, respectively. The movable spring 122 and the flat braided wire 128 are coupled to each other at both ends. In this way, the intermediate portion of the movable spring 122 is received between the vertical pieces 112 and 114 of the card 96 as described above, the intermediate portion of the flat braided wire 128 extends apart from the movable spring 122 and along the outsides (backsides in
With the configuration in which the flat braided wire 128 having a large electric capacity is provided in parallel to the movable spring 122, it is possible to decrease electric resistance of the circuit of the movable contacts 108 and 110, while keeping the cross section area of the movable spring 122 small. Thus, such a configuration has an advantage to reduce heat generated at the contact part 28, especially when a large current flows through the electromagnetic relay 10. In addition, since the flat braided wire 128 having greater flexibility than a leaf spring is used as a bypass pathway, smaller force will be required to open and close the contact part 28.
Referring to
The bus bar terminal 20 has a flat end plate portion 20a having attaching holes 154 and 156, an intermediate engageable portion 20b which is engaged with the groove 34 formed on one edge of the peripheral wall 32 of the base 12, a flat end plate portion 20c extending from the engageable portion 20b in a direction opposite to the flat end plate portion 20a and projecting from the base 12, and a flat attachment plate portion 20d bent at the lower end of the flat end plate portion 20c substantially at right angle and extending substantially in the horizontal direction. The bus bar terminal 20 is fixed to the base 12 by pressing the engageable portion 20b into the groove 34 of the base 12. The flat attachment plate portion 20d has a through-hole 21 which receives a known fixing means such as a bolt, similarly to the flat attachment plate portion 22d of the bus bar terminal 22, whereby the bus bar terminal 20 can be mounted to any support body such as a substrate.
In the case where passage and blockage of a high voltage and/or a large current is switched through the electromagnetic relay 10, arc discharge may occur between the contacts, as the movable contacts 108 and 110 are moved apart from the fixed contacts 124 and 126 so as to block electricity between the bus bar terminals 20 and 22. The arc discharge may also occur, as the contacts apart from each other are moved closer so as to conduct electricity. In order to solve the problem, according to this embodiment, a permanent magnet 58 is provided at a position corresponding to the contact part 28, more specifically, in a position opposite to the movable contacts 108 and 110 and the fixed contacts 124 and 126. By positioning the permanent magnet 58 such that a magnetic flux of the permanent magnet 58 traverses a gap between the movable contacts 108 and 110 and the fixed contacts 124 and 126, the arc discharge between the contacts is extended toward the permanent magnet 58, and as a result, the arc discharge is cut off.
On the outer surface of the end wall 56 of the cover 14 opposite to the recess 38, there is an accommodating portion 60 which is depressed toward the contact part 28. By pressing and fixing the permanent magnet 58 into the accommodating portion 60 integrally formed in the cover 14, the permanent magnet 58 can be easily placed in position relative to the contact part 28. More specifically, the permanent magnet 58 extends over longer distance than a gap between the contacts formed as a result of movement of the movable contacts 108 and 110 to the right in
The permanent magnet 58 may also be positioned in the accommodating portion 60 in a different manner. For example, after the permanent magnet 58 is placed in the accommodating portion 60, the permanent magnet 58 may be fixed by an additional holding member (not shown) which can be pressed into the accommodating portion 60 so as to keep the permanent magnet 58 in position within the accommodating portion 60.
In other alternative embodiment, which is not illustrated, the permanent magnet 58 may be accommodated in a protrusion protruding from the outer surface of the end wall 56 of the cover 14. This configuration is effective when the internal space of the housing is severely restricted.
In the embodiment described above, the arc discharge does not directly reach the permanent magnet 58, since the end wall 56 of the cover 14 is interposed between the contact part 28 and the permanent magnet 58. In addition, with the interposed end wall 56, the permanent magnet 58 can be easily mounted without the effect of magnetic attractive force to metal components. Furthermore, in the embodiment in which the permanent magnet 58 is sealed by injecting resin into the accommodating portion 60, mechanical damages to the permanent magnet 58 can also be prevented.
The electromagnetic relay 10 according to the embodiment can be assembled in the following manner. First, each component of the electromagnet part 24, the actuating part 26 and the contact part 28 is mounted in position to the base 12 in a known way such as pressing and adhering (
The permanent magnet 58 is then sealed by injecting resin from the top of the permanent magnet 58 situated in the accommodating portion 60. In this process, sealing resin is simultaneously injected between the joining portion 54 in the outer periphery of the cover 14 and the engageable portion 32a of the peripheral wall 32 of the base 12, and thus, a housing is formed by attaching the cover 14 to the base 12 in a sealing manner. Alternatively, one of the processes of attaching the cover 14 to the base 12 and sealing the permanent magnet 58 may also be carried out first, and the other process is carried out without delay in a continuous manner. In these ways, the attaching process between the base 12 and the joining portion 54 of the cover 14 and the sealing process of the permanent magnet 58 in relation to the end wall 56 are simultaneously or continuously carried out on the side of the cover 14 as a single sealing process. Therefore, a process necessary to move a nozzle for injecting resin or change position of the housing can be omitted, and a production procedure is simplified.
As such, according to the illustrated embodiment, passing and blocking a high voltage and/or a large current can be easily performed by an inexpensive electromagnetic relay.
Next, a second embodiment of the present invention will be described with reference to
In this embodiment, in addition to the permanent magnet 216 provided to the cover 214, a separate permanent magnet 218 is provided at a position corresponding to the contact part 28 on the outer surface of the end wall 220 of the base 212 opposite to the recess 38, so as to be opposite to the contact part 28. As more clearly seen in
In the present embodiment, since the permanent magnets 216 and 218 are provided on both sides of the contact part 224, a greater magnetic flux perpendicular to the contact part 224 is generated. As a result, a greater effect of cutting off the arc discharge is achieved, compared with the case where the permanent magnet 216 is provided only on the cover 214.
Referring to
In the present embodiment, permanent magnets 316 and 318 are provided on both of the cover 314 and the base 312. Further, a yoke 320 is mounted to the outer side of the cover 314 and the base 312. The yoke 320 is fitted to the housing between a pair of the bus bar terminals 322 and 324, so as to extend between pathways of an electric current passing through the bus bar terminals 322 and 324, which serve as terminals to the exterior and are switched between a conducting state and a non-conducting state by means of the electromagnetic relay 310. In the present embodiment, in order to provide insulating distance as well as a space large enough to place the yoke 320 therein, longer distance between the bus bar terminals 322 and 324 is formed, compared with other embodiments. As most clearly seen in
With the configuration according to the present embodiment, by means of the yoke 320, a magnetic path is formed between the permanent magnets 316 and 318, which are spaced apart from each other, and a magnetic flux generated by the permanent magnets 316 and 318 is transmitted through the yoke 320. Since magnetic force exerting on the contact part 330 becomes even greater, compared with the case where only the permanent magnets 316 and 318 are provided on the cover 314 and the base 312, a greater effect of cutting off the arc discharge is achieved. In addition, the yoke 320 is provided between the bus bar terminals 322 and 324 and in parallel thereto, an electric current flowing through the bus bar terminals 322 and 324 is not influenced by the yoke 320, or vice versa.
As a variant of the third embodiment, the permanent magnet 318 on the base 312 may be omitted. In this variant, the permanent magnet 316 is provided on the cover 314, and a yoke 320 having a U-shaped cross section extends from the permanent magnet 316 to the base 312 along the outer side of the housing. In the variant, a magnetic path extends from the permanent magnet 316 to a position opposite to the permanent magnet 316, and therefore, it is conceivable that an effect of cutting off the arc discharge is substantially equivalent to the configuration in which the permanent magnets 216 and 218 are provided opposite to the contact part 224, respectively, in accordance with the second embodiment.
The above embodiments are described, referring to exemplary twin contacts types of the electromagnetic relays with two contacts. However, according to the embodiments that achieve an effect of cutting off the arc discharge, a single contact type of electromagnetic relay with one contact may be also used for passing and blocking a high voltage and/or a large current. By changing to the single contact type, it is possible to reduce an amount of expensive material containing silver used for a contact, and therefore an inexpensive electromagnetic relay can be provided.
Although it is described that the permanent magnet for cutting off the arc discharge generates a magnetic field perpendicular to the arc discharge, the perpendicularity is not always strictly required. Thus, a magnetizing direction of the permanent magnet may be at an angle other than right angle in relation to the arc discharge, as long as the effect of cutting off the arc discharge is sufficiently achieved.
The numbers, shapes and arrangements of the attachment portions 46 and 48 are not limited to the illustrated embodiments. The shapes of the receiving portions 46a, 48a, 46b and 48b may also be modified, corresponding to various known attaching means, as necessary.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2011-170367 | Aug 2011 | JP | national |
