Electromagnetic relay having silencing means

Abstract: A relay comprises a yoke (11), an armature (12), a movable contact spring (13) having a movable contact (14), at least one stationary contact (15a,15b) mounted thereon, and a core (17). An air damper (20) is mounted on a free end of the movable spring (13), or one a free end of the armature (12), to reduce sound generated by the impulsive force of the movable contact (14) and the impulsive force of the armature (12).

Description: BACKGROUND OF THE INVENTION 1) Field of the Invention The present invention relates to an electromagnetic relay having a remarkable silencing effect during an activating mode and a releasing mode. Such a relay is used particularly in an automobile, an air conditioner, and the like. 2) Description of the Related Art An electromagnetic relay is conventionally comprised of a yoke, an armature rotatably coupled with an end of the yoke, a movable contact spring associated with the armature, and a core having a bottom fixed to another end of the yoke and a top opposing the armature. Also, at least one movable contact is mounted on the movable contact spring, and a corresponding stationary contact is provided. When a winding wound on the core is excited to activate the relay, the armature is attracted by the core and a sound is generated due to the impulsive force of the movable contact against the stationary contact when making contact therewith and the impulsive force of the armature against the top of the core. One known relay of this type is described in Unexamined Japanese Utility Model Publication No. 61-75042, in which the generation of sound, particularly that resulting from the impulsive force of the armature against the core, is reduced by the provision of a helical spring on the top of the core. However, since the load of the helical spring is added to the entire load of the relay, the relay load is increased, and therefore, when the attraction force of the core is definite, the margin of operation is reduced, and further, the contact force of the movable contact against the stationary contact, which in this case is a make contact is reduced, thus reducing the performance of the operation. Further, the helical spring is not intended to reduce a sound due to the impulsive force of the movable contact against the stationary contact, which in this case is a break contact, when the winding is non-excited to release the relay. Another known relay, although of different configuration, is described in German patent DE-B-1044221 (Metzenauer & Jung). To delay the closure of an auxiliary movable contact with respect to closure of the main relay contacts a damping assembly is provided for the auxiliary movable contact. The damping assembly of DE-B-1044221 comprises a cylinder at least partially filled with liquid and attached to the auxiliary contact within which cylinder is a piston attached at its outer end to a portion of the relay housing. The piston is provided with a return valve such as to allow free movement of the piston into the cylinder whilst opposing its withdrawal. A helical spring is also provided about the piston shaft arranged to oppose movement of the piston into the cylinder. A problem with this arrangement is that, on opening of the auxiliary contact by raising the auxiliary movable contact and cylinder, the weight of the cylinder is added to the relay load thereby reducing the effectiveness of the magnetic field of the core. SUMMARY OF THE INVENTION It is an object of the present invention to reduce a sound generated by the impulsive force of the movable contact against stationary contacts including a make contact and a break contact, and the impulsive force of the armature against the top of the core during an activating mode and a releasing mode, without reducing the margin and performance of the operation. In accordance with the present invention there is provided an electromagnetic relay comprising a yoke, an armature rotatably coupled with an end of said yoke, a movable contact spring associated with said armature, at least one movable contact mounted on said movable contact spring, at least one stationary contact opposing the or each said movable contact, and a core having a bottom fixed to another end of said yoke and a top opposing said armature, said armature being attracted by said core on actuation of the relay, characterized by a damper for reducing a speed of motion of said movable contact spring and said armature, said damper being an air damper mounted on a free end of said movable contact spring. In addition to the provision of an air damper, a magnetic plate may be mounted on a face of the armature opposing the core or mounted on the core itself to reduce the sound generated by the impulsive force of the armature. Such a magnetic plate may be of a material, such as Fe-Co-V alloy, having vibration damping characteristics. BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be more clearly understood from the description as set forth below with reference to the accompanying drawings, wherein: Fig. 1A is a partly cut-away side view showing a non-activated state of a prior art electromagnetic relay; Fig. 1B is a partly cut-away side view showing an activated state of the relay of Fig. 1A; Fig. 2A is a plan view illustrating a first embodiment of the electromagnetic relay according to the present invention; Fig. 2B is a side view of the relay of Fig. 2A; Fig. 2C is a partly cut-away side view of the relay of Fig. 2A; Fig. 2D is a front view of the relay of Fig. 2A; and Fig. 3 is a partly cut-away side view illustrating a second embodiment of the electromagnetic relay according to the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a prior art electromagnetic relay will be explained with reference to Figs. 1A and 1B (see: Unexamined Japanese Utility Model Publication No. 61-75042). In Fig. 1A, reference numeral 1 designates a yoke, 2 an armature rotatably coupled with an end of the yoke 1, and 3 a movable contact spring associated with the armature 2. The movable contact spring 3 has a movable contact 4 thereon opposing a stationary contact 5, which in this case is a make contact. Reference numeral 6 designates a return spring for pulling up the armature 2 when the relay is not activated. A core 7, on which a winding 8 is wound, has a bottom fixed to the yoke 1 and a top opposing the armature 2. In Fig. 1A, a helix spring 9 is provided on the top of the core 7 to reduce a sound generated by the impulsive force of the armature 3 against the top of the core 7 and the impulsive force of the movable contact spring 3 (or the movable contact 4) against the stationary contact 5. As shown in Fig. 1B, when the winding 8 is excited to activate the relay, the load of the helix spring 9 is added to the load of the relay, thus increasing the relay load. Therefore, when the attractive force of the excited core 7 is definite, the margin of operation is reduced, and further, the contact force between the movable contact 4 and the stationary contact 5 is reduced, thus reducing the performance of the operation of the relay. In Figs. 2A, 2B, 2C, and 2D, which illustrate a first embodiment of the present invention, reference numeral 11 designates an L-shaped yoke, 12 an armature rotatably coupled with an end of the yoke, 13 a movable contact spring associated with the armature 12, and 14 a movable contact mounted on the movable contact spring 13. The movable contact 14 opposes stationary contacts, i.e., a make contact 15a and a break contact 15b. Reference numeral 16 designates a return spring for pulling up the armature 12 when the relay is not activated. Note that the return spring 16 is integral with the movable contact spring 13. A core 17 has a bottom fixed to the yoke 11 and a top opposing the armature 12. A winding 18 is wound on the core 17 via a bobbin 18a. Also, reference numeral 19 designates a substrate for supporting external lead pins and an air damper 20. The air damper 20 is comprised of a piston 21, a cylinder 22, and a coupling member 23 which couples the piston 21 with a free end of the movable contact spring 13. A speed of motion of the movable contact spring 13 is reduced by the viscosity resistance of air flowing through a gap between the piston 21 and the cylinder 22, thus reducing the impulsive force between the movable contact spring 13 (the movable contact 14) and the stationary contacts 15a and 15b, and the impulsive force between the armature 12 and the top of the core 17, thereby exhibiting an excellent silencing effect. Note that the cylinder 22 of the air damper 20 can be formed simultaneously with the molding of the substrate 19, thus reducing the number of components of the relay. Also, it is possible to provide the air damper in a space of the prior art relay, and accordingly, the size of the relay is reduced. The operation of the relay of Figs. 2A, 2B, 2C, and 2D will be explained below. When the winding 18 is excited by supplying a current thereto, the armature 12 is attracted to the top of the core 17, so that the free end of the movable contact spring 13 associated with the armature 12 pushes down the piston 21 via the coupling member 23. In this case, since the piston 21 is enveloped by the cylinder 22, the speed at which the piston 21 is pushed down is determined by the viscosity resistance of air flowing from the cylinder 22 to the exterior, and is reduced when compared with the case where the air damper 20 is not provided. Then, when the piston 21 exceeds a contact gap distance, the movable contact 14 comes into contact with the stationary contact 15a and the armature 12 is attracted to the top of the core 17 at a weak abutment force. In this state, there is no load from the air damper 20, and therefore, the load of the relay is not increased. Subsequently, when the excitation of the winding 18 is released, the armature 12 is rotated by the return spring 16 in the direction opposite to the previous direction (i.e., in the counterclockwise direction in Figs. 2B and 2C). In this case, since the piston 21 is coupled with the free end of the movable contact spring 13 mounted on the armature 12, the piston 21 is pushed up at a speed determined by the viscosity resistance of air flowing from the exterior to the cylinder 22, so that the movable contact 14 abuts the stationary contact 15b at a weak abutment force. Note that the air damper 20 can be provided integrally with the movable contact spring 13. Generally, in an electromagnetic relay used in an automobile or an air-conditioner, a level of sound pressure due to the activation and release of the relay is usually about 75 dB, however, in the relay of Figs. 2A, 2B, 2C, and 2D, an experimental value was less than 60 dB. In Fig. 3, which illustrates a second embodiment of the present invention, a magnetic plate 24 is added to the elements of the first embodiment of Figs. 2A, 2B, 2C, and 2D. In Fig. 3, when a current is supplied to the winding 18 to attract the armature 12 to the core 17, vibrations due to the impulsion of the armature 12 to the top of the core 17 are transmitted to the magnetic plate 24, and therefore, the vibrations are absorbed by the magnetic plate 24. As a result, such vibrations are not substantially transmitted to the armature 12 and the core 17. Thus, since the magnetic plate 24 is provided at the attraction face of the armature 12 opposing the top of the core 17, so that the armature 12 does not abut against the top of the core 17 directly, thereby eliminating the impulsive sound by the magnetic plate 24 when the armature 12 abuts against the core 17. This exhibits also an excellent silencing effect. Particularly, when the magnetic plate 24 is made of an anti-vibration material such as Fe-Co-V alloy, the silencing effect is remarkably increased. Note that the magnetic plate 24 can be provided on the top of the core 17, thus exhibiting the same effect. As explained hereinbefore, according to the present invention, use is made of the viscosity resistance of air in the air damper, so that a load in proportion to the activation speed and release speed of the movable contact spring can be obtained. This load is not a load of the relay in a static operation where the operation of the relay is very slow. Also, since the relay can be operated without changing the spring load of the relay, this is a very effective measure for silencing impulsive sound when the relay is released.

Claims: An electromagnetic relay comprising: a yoke (11); an armature (12) rotatably coupled with an end of said yoke; a movable contact spring (13) associated with said armature; at least one movable contact (14) mounted on said movable contact spring (13); at least one stationary contact (15a, 15b) opposing the or each said movable contact; and a core (17) having a bottom fixed to another end of said yoke and a top opposing said armature, said armature being attracted by said core on actuation of the relay; characterized by a damper (20) for reducing a speed of motion of said movable contact spring and said armature, said damper (20) being an air damper coupled to a free end of said movable contact spring (13). A relay according to claim 1, characterized by a magnetic plate (24) mounted on a face of the armature (12) opposing the top of said core (17) or mounted on the top of the core (17). A relay according to claim 2, characterized in that the magnetic plate (24) is made of a material having vibration damping characteristics. A relay according to claim 3, characterized in that the said material is Fe-Co-V alloy.

Inventors: AOKI SHIGEMITSU, SHIKANO YUKIO, AOKI, SHIGEMITSU, SHIKANO, YUKIO
Applicants: TAKAMISAWA ELECTRIC CO, TAKAMISAWA ELECTRIC CO., LTD.
Application year: 1988
Main classification: H01H50
IPC codes: H01H50