Electromagnetic relay

Abstract: In the electromagnetic relay of the present invention, a fixed contact and a movable contact piece are separated from an electromagnetic block and a movable iron piece, so that an insulating distance is elongated, with improving the resistance to voltage. The electromagnetic relay can be compact in size while ensuring highly resistive property to voltage.

Description: The present invention generally relates to an electromagnetic relay and, more particularly to an electromagnetic relay having high resistance to voltage. Description of the Prior Art In a conventional electromagnetic relay such as illustrated in Figs. 10 and 11, an electromagnetic block 1 formed by winding a coil 1b around an iron core la is erected on the upper surface of a base 3 via a generally L-shaped yoke 2. When an inverse L-shaped movable iron piece 4 supported at an upper end of the yoke 2 is rotated against the elasticity of a coil spring 5 in response to the excitation and demagnetization of the electromagnetic block 1, thereby driving a movable contact piece 6, a movable contact 6a at a free end of the movable contact piece 6 is alternately brought into or out of contact with fixed contacts 7a and 8a of fixed contact pieces 7 and 8. Insulation is retained in the electromagnetic relay of the above-described type, however, in a simple manner by, e.g., enlarging the distance between the electromagnetic block 1 and movable contact piece 6, or between the electromagnetic block 1 and fixed contact pieces 7,8. As such, if the components are arranged closer to each other in order to form a compact relay, desired insulating property cannot be achieved. Therefore, it has conventionally been difficult to realize a compact electromagnetic relay. A relay according to the preamble of claim 1 is also known from DE-A-38 02 688. EP-A-0 313 385 discloses a relay having fixed contact terminals insert-molded in prop parts with the fixed contacts exposed from the upper surface of the prop parts, and further having a movable contact piece block which includes the movable iron piece. The movable contacts and the movable iron piece are arranged in a side-by-side relationship. SUMMARY OF THE INVENTION An essential object of the present.invention is to provide an electromagnetic relay having highly resistive property to voltage. A further object of the present invention is to provide an electromagnetic relay enabling an apparatus to be compact in size while ensuring desired insulating property. In accomplishing the above-described objects, according to the present invention, an electromagnetic relay is provided as defined in claim 1. Since the fixed contact terminal is formed in the prop part through insertion-molding, an outer side surface of the fixed contact terminal is covered and the fixed contact alone is exposed. Besides, since the fixed contact and movable contact piece are separated from the electromagnetic block and movable iron piece by the insulating frame body, the spatial distance therebetween can be shortened in comparison with the prior art. Accordingly, even when the components are arranged close to each other, the insulating distance can be kept long, thereby achieving an electromagnetic relay compact in size and with desired insulating property. BRIEF DESCRIPTION OF THE DRAWINGS These and other objects and features of the present invention will become apparent from the following description taken in conjunction with preferred embodiments thereof with reference to the accompanying drawings, in which: Figs. 1-8 show an electromagnetic relay according to a first embodiment of the present invention; Fig. 1 is an exploded perspective view of the relay; Fig. 2 is a sectional plan view; Fig. 3 is a cross sectional view taken along the line III-III of Fig. 2; Fig. 4 is a front sectional view of an essential portion; Fig. 5 is a side sectional view of an essential portion; Figs. 6-8 are views explanatory of the operation of a movable iron piece; Fig. 9 is a side sectional view of an electromagnetic relay according to a second embodiment of the present invention; and Figs. 10 and 11 are a plan and a side elevational views of a conventional electromagnetic relay. DESCRIPTION OF THE PREFERRED EMBODIMENTS An electromagnetic relay of the present invention will be described hereinbelow with reference to Figs. 1-9. An electromagnetic relay according to a first embodiment is generally comprised of a base 10, an electromagnetic block 20, a movable iron piece 30, an insulating frame body 40, a movable contact piece block 50 and a casing 60. The base 10 having a generally rectangular plan is provided with fixed contact terminals 11, 12 and common contact terminals 13 through insertion-molding, each in pairs in symmetry (contact terminals 11-13 at the deep side are not shown in Fig. 1). Prop parts 14a,14b,14b,14a and 15a,15b,15b,15a are erected in the vicinity of the periphery of shorter sides of the base 10, and positioning prop parts 16,16 are formed at the intermediate position between the prop parts 14a and 15a. An upper end of the fixed contact terminal 11 is electrically connected to a fixed contact 11a formed at an upper surface of the prop part 14a via a lead frame (not shown). Likewise, an upper end of the fixed contact terminal 12 is electrically connected to a fixed contact 12a at an upper surface of the prop part 15a via a lead frame (not shown). Meantime, an upper end of the common contact terminal is divided into two, one being electrically connected to a fixed contact 13a formed at an upper surface of the prop part 14b via a lead frame (not shown) and the other being electrically connected to a fixed contact 13b formed at an upper surface of the prop 15b via a lead frame (not shown). There is an insertion hole 16a formed at an upper surface of each prop part 16. An insulating wall 17 extends between the prop part 16 and the prop parts 14a, 15a. References 18a,18b represent a coil terminal hole and a vent hole, respectively. An iron core 21 originally having a generally U-shaped cross section is turned into an E-shaped cross section after a permanent magnet 22 is arranged therein. The iron core 21 with the permanent magnet 22 is then insertion-molded with a spool 23, thereby eventually composing the electromagnetic block 20. A magnetic pole 22a of the permanent magnet is exposed from an upper surface of a central jaw 23a of the spool 23. A left magnetic pole 21a of the iron core is exposed from an upper surface of a jaw 23b of the spool 23, while a right magnetic pole 21b of the iron core 21 is exposed from an upper surface of a jaw 23c of the spool 23. Frame parts 24a,24b are integrally molded at the outer side faces of the jaws 23b,23c, respectively, to which are insertion-molded coil terminals 25,25. A leading wire of a coil 26 wound around the spool 23 is tied and soldered to a tie-up portion 25a of each coil terminal 25, as shown in Fig. 1. Although the iron core 21 is made of a plate having a predetermined thickness, since the left magnetic pole 21a is formed wider than the right magnetic pole 21b, the magnetic force is not balanced between the left and right portions because of the large attracting area of the right pole 21a. In Fig. 1, the right coil terminal 25 is shorter than the left coil terminal 25, so that the right coil terminal is not projected from the rear surface of the base 10 when inserted into the coil terminal hole 18a. When the electromagnetic block 20 is positioned above the base 10 and temporarily fixed by pressing the coil terminals 25 into the coil terminal holes 18a, the prop parts 14b,14b and 15b,15b are projected from the frame parts 24a and 24b, respectively. The movable iron piece 30 with a generally rectangular plan has a protruding part 31 formed at the central part of a lower surface thereof through ejection treatment. A lower surface of each end 32a,32b is tapered. Moreover, four caulking holes 33 are formed in the movable iron piece 30 at such a position that the protruding part 31 is found intermediate between the two confronting holes 33. The insulating frame body 40 is a box shape capable of concealing the movable iron piece 30. The prop parts 14b,15b of the aforementioned base 10 are loosely fitted in respective fitting holes 41,42 formed at end portions of the insulating frame body 40. Each caulking hole 43 of the frame body 40 confronts to the caulking hole 33 of the movable iron piece 30. Moreover, the insulating frame body 40 has notched stepped portions 44,44 formed at the central part of the side faces. According to this embodiment, as shown in Fig. 4, the fixed contacts 11a,13a and 12a,15a are separated from each other by partition elements 40a in a combed arrangement defining the fitting holes 41(42). Therefore, high insulating property is secured. Front ends of the partition elements 40a are integrally coupled by a coupling part 40b, so that the partition elements 40a are hard to deform. However, the coupling part 40b is provided so as only to achieve desired insulating property, and is not necessarily required. Furthermore, since the insulating frame body 40 separates the electromagnetic block 20 and movable iron piece 30 from a movable contact piece 52 and the fixed contact 13a as shown in Fig. 5, a long insulating distance is gained, which results in good insulating property of the relay. The movable contact piece block 50 is obtained by insertion-molding two movable contact pieces 52 and two movable contact pieces 53, each having a generally U-shaped plan, in front of and behind an insulating bed 51 (referring to Fig. 2). At the central part of a lower surface of the insulating bed 51 is projected a caulking protrusion (not shown) to be inserted into the caulking hole 43 of the insulating frame body 40 and caulking hole 33 of the movable iron piece 30. A tongue piece 51a (one at the deep side is not shown) is projected downwards from each side edge of the lower surface of the insulating bed 51. Meanwhile, a hinge spring 54 of a generally L-shaped plan is projected sideways from each outer side face of the tongue piece 51a. A free end of this hinge spring 54 is bent downwards in a vertical direction. Both end portions of the U-shaped movable contact piece 52 is divided into two in a widthwise direction. A movable contact 52a and a movable contact 52b are formed at the lower surface of the one of the divided ends and at the lower surface of the other of the divided ends, respectively. Similar to the movable contact piece 52, the movable contact piece 53 also has movable contacts 53a,53b formed at the lower surface of the end portions. The tongue piece 51a of the insulating bed 51 is fitted in the notched stepped portion 44 of the insulating frame body 40, and at the same time, the caulking protrusion (not shown) of the insulating bed 51 is inserted into the caulking holes 43 and 33. Then, the protruding ends are thermally caulked. As a result, the movable iron piece 30, insulating frame body 40 and movable contact piece block 50 are integrally formed into one unit. Subsequently, the obtained unit is positioned above the base 10 and fixed by pressing the ends of the hinge springs 54 into respective insertion holes 16a of the prop parts 16. The protruding part 31 of the movable iron piece 30 is brought to butt against the magnetic pole 22a of the permanent magnet 22, so that the movable iron piece 30 is supported in a rotatable manner, with the movable contacts 52a,52b and 53a,53b rendered so confronting to the fixed contacts 11a, 13a and 12a,13b as to be in and out of contact with each other. In the state where the unit is totally assembled (Fig. 3) in the manner as above, the surface of the magnetic pole of the permanent magnet 22, protruding part 31 of the movable iron piece 30 and hinge springs 54 are found approximately on the same plane, whereby an excessive bending moment is not applied to the relay, thus ensuring smooth operation, etc. Since the movable contacts 52a,52b and 53a,53b are projected further than the ends 32a and 32b of the movable iron piece 30 in the present embodiment, the rotating radius of the movable contact pieces 52,53 becomes long. Therefore, even if the movable iron piece 30 is rotated a little quantity of angles, it is possible to open/close the contacts. Accordingly, the electromagnetic relay features a large gap of contacts with high sensitivity and less consumption of power. The casing 60 is generally in the form of a box able to be fitted with the base 10. After a sealing agent 70 is injected and hardened into a recess formed when the casing 60 is fitted with the base 10, the gas inside is let out from the vent hole 18b of the base 10. Thereafter, the vent hole 18b is thermally melted to seal the casing. Thus, the electromagnetic relay is completely assembled. The operation of the electromagnetic relay in the above-described structure will be discussed below. In the case without excitation, the left end 32a of the movable iron piece 30 is attracted to the left magnetic pole 21a of the iron core 21 due to the magnetic flux of the permanent magnet 22 (indicated by a broken line in Fig. 6), thereby closing the magnetic circuit. Accordingly, the movable contacts 52a,52b of the movable contact piece 52 are brought in touch with the fixed contacts 11a,13a, whereas the movable contacts 53a,53b are separated from the fixed contacts 12a,13b. When the coil 26 is magnetized through application of such a voltage that a magnetic flux negating the above magnetic flux is generated (indicated by a one-dot chain line) as shown in Fig. 7, the right end 32b of the movable iron piece 30 is attracted to the right magnetic pole 21b of the iron core 21. As a result, the movable iron piece 30 is rotated around the protruding part 31 as a fulcrum against the magnetic force of the permanent magnet 22, thereby detaching the left end 32a of the movable iron piece 30 from the left magnetic pole 21a. The right end 32b of the movable iron piece 30 is attracted to the right magnetic pole 21b (Fig. 8). Accordingly, the movable contacts 52a,52b of the movable contact piece 52 are separated from the fixed contacts 11a,13a, and then, the movable contacts 53a,53b are brought into touch with the fixed contacts 12a,13b. If the coil 26 is demagnetized, because of the spring force of the movable contact pieces 53,53 and hinge springs 54 and due to the fact that the left magnetic pole 21a of the iron core 21 has the larger attracting area than the right magnetic pole 21b, the movable iron piece 30 is returned to its original position. The movable contacts 52a,52b and 53a,53b are changed over. The electromagnetic relay is returned to the original state. According to the first embodiment, the movable contact pieces 52,53 are formed in a generally U-shaped plan, that is, a so-called double-break configuration. Therefore, the distance between the fixed contact 52b and movable contact 11a can be reduced half in comparison with the case where the movable contact pieces 52,53 are formed in a so-called single-break configuration. Accordingly, the electromagnetic relay can be small in height, making it possible to form an apparatus compact in size. With reference to Fig. 9, in a second embodiment of the present invention, fixed contacts are formed at one side of the electromagnetic block although they are formed at both sides of the block in the above-described first embodiment. More specifically, an iron core 72 is inserted into a spool 71 having a coil 70 wound therearound. One projecting end of the iron core is made a magnetic pole 72a, and the other end is securely caulked to a perpendicular portion of a generally L-shaped yoke 73. An electromagnetic block 74 constituted in the above-described manner is placed at the central part of an upper surface of a base 75. A generally inverse L-shaped movable iron piece 73b is supported by a horizontal end portion 73a of the yoke 73. An insulating frame body 76 is integrally formed on an upper insertion-molded at one side edge of an upper surface of the base 75. A fixed contact 79 is exposed from an upper surface of the prop part 78. On the other hand, a prop part 84 has a movable contact terminal 81 insertion-molded at the other side edge of the upper surface of the base 75, which is erected on the base 75. The movable contact terminal 81 is welded with a movable contact piece 80 at an upper end thereof. A movable contact (82) formed at a free end of the movable contact piece 80 confronts to the fixed contact 79 in a detachable manner. A reference 83 is a coil terminal. In the case without excitation, the movable contact (82) is in touch with the fixed contact 79 by the spring force of the movable contact piece 80. When the electromagnetic block 74 is magnetized through application of a voltage to the coil 70, an end of the perpendicular portion of the movable iron piece 73b is attracted to the magnetic pole 72a of the iron core 72. The movable iron piece 73b is rotated against the spring force of the movable contact piece 80, and a protrusion 76a of the insulating frame body 76 pushes up the movable contact piece 80. As a result, the movable contact (82) is separated from the fixed contact 79. Then, when the electromagnetic block 74 is demagnetized, the movable contact piece 80 is returned to the original position by its own spring force, thereby bringing the movable contact (82) into touch with the fixed contact 79. Although the electromagnetic relay in the foregoing description of the first and second embodiments of the present invention is a self-returning type, a self-retaining type may be possible by adjusting the shape of the iron core or the spring force of the movable contact piece, etc. Although the present invention has been fully described by way of example with reference to the accompanying drawings, various changes and modifications would be apparent to those skilled in the art. Therefore, such changes and modifications should be construed as included therein unless they depart from the scope of the present invention.

Claims: An electromagnetic relay which comprises: a base (10) having a fixed contact terminal (11, 12) projecting from the surface of the base and having a fixed contact (11a, 12a) at its upper end; an electromagnetic block (20) provided on the upper surface of said base (10); a movable iron piece (30) rotated subsequent to the magnetization or demagnetization of said electromagnetic block; and a movable contact piece (52, 53) driven by said movable iron piece and so arranged that a movable contact (52a, 52b, 53a, 53b) formed in said movable contact piece (52, 53) is brought into or out of touch with said fixed contact (11a, 12a), characterized in that said fixed contact terminal is insertion-molded in a prop part (14a, 14b, 15a, 15b) erected on the upper surface of said base (10) with only said fixed contact (11a, 12a) being exposed from an upper face of said prop part, and that an insulating frame body (40) is integrally provided with said movable iron piece (30) and said movable contact piece (52, 53), and is arranged to separate said movable contact piece (52, 53) and fixed contact (11a, 12a) from said electromagnetic block (20) and movable iron piece (30). An electromagnetic relay according to claim 1, wherein the electromagnetic block (20) is positioned at generally the central part of the upper surface of said base (10) and has a magnetic pole (22) exposed at the central part of the upper surface thereof; the movable iron piece (30) is rotatably supported at generally the central part of the lower surface thereof by said magnetic pole (22) of the electromagnetic block; and the movable contact piece (52, 53) is insertion-molded in an insulating bed (51), the insulating bed being integrally provided with said insulating frame body (40) at a central part thereof.

Inventors: SATO RYUICHI, SATO, RYUICHI
Applicants: OMRON TATEISI ELECTRONICS CO, OMRON CORPORATION
Application year: 1991
Main classification: H01H50
IPC codes: H01H50, H01H51