EP1684319A1

EP1684319A1 - Electromagnetic relay with reduced switching noise

Info

Publication number: EP1684319A1
Application number: EP05398001A
Authority: EP
Inventors: Fernando Oliveira; Edgar Nina
Original assignee: Tyco Electronics Componentes Electromecanicos Ltda
Current assignee: Tyco Electronics Componentes Electromecanicos Ltda
Priority date: 2005-01-25
Filing date: 2005-01-25
Publication date: 2006-07-26

Abstract

The present invention refers to a magnetic system for an electromagnetic relay, to an electromagnetic relay and to a method for manufacturing same. In particular, the present invention concerns a magnetic system for an electromagnetic relay, wherein said magnetic system comprises a magnetic coil for generating a magnetic field to actuate an armature and a movable contact and wherein said armature is pivotally supported in a bearing. In order to provide an electromagnetic relay which is particularly uncomplicated and cost effective to fabricate and which exhibits a reduced switching noise, a damping material (122) is disposed at the armature (104) in a region of said bearing (115) for providing a damping (122) of the armature's movement.

Description

The present invention refers to a magnetic system for an electromagnetic relay, to an electromagnetic relay and to a method for manufacturing same. In particular, the present invention concerns a magnetic system for an electromagnetic relay, wherein said magnetic system comprises a magnetic coil for generating a magnetic field to actuate an armature and a movable contact and wherein said armature is pivotally supported in a bearing.
Electromagnetic relays are well known and widely used components. Generally speaking, relays are electromagnetically operated switches. An actuating current on a coil operates one or more galvanically separated contacts or load circuits. The electromechanical relay therefore is a remote control switch capable of switching multiple circuits either individually or simultaneously or in sequence. The primary functions of a relay may be summarized as follows: The galvanic separation of the primary or actuating circuit and the load circuits, single input/multiple output capability, separation of different load circuits for multi-pole relays, separation of AC and DC circuits, interface between electronic and power circuits, multiple switching functions, e. g. delay or signal conditioning, amplifier function.
Accordingly, relays may be found in a large variety of application fields. Typical applications for relays include laboratory instruments, telecommunication systems, computer interfaces, domestic appliances, air conditioning and heating, automotive electrics, traffic control, lighting control, building control, electric power control, business machines, control of motors and solenoids, tooling machines, production and test equipment.
In particular in the field of automotive appliances, electromagnetic relays may be used for a multitude of switching appliances, such as air condition, brake lights, electric heating of seats or front/rear windows, rear defrost, window defoggers, wiper controls and wiper/washer control.
When using electromagnetic relays for switching tasks which are not directly controlled by a user, for instance for switching the window heater or wind screen wipers and washing pumps, it is essential that these relays have a low switching noise which possibly is not audible at all for a user.
In order to prevent such an electromagnetic relay from emitting an audible switching noise, it is known to surround the electromagnetic system and the contacts by an acoustic encapsulation. Moreover, as shown in the published International Patent Application WO 00/63937A1, it is known to embed the stationary parts of the electromagnetic system together with the covering cap in an insulating material, in particular a plastic molding material.
Although this known solution reduces the acoustic noise which can be heard outside significantly, it has the disadvantage, that firstly the intrinsic cause for the switching noise is not eliminated, and that the construction of the electromagnetic relay is unnecessarily complex and costly.
Accordingly, it is an object of this invention to provide an electromagnetic relay which is particularly uncomplicated and cost-effective to fabricate and which exhibits a reduced switching noise.
According to the principles of this invention, a damping material is disposed at the armature in a region of said bearing for providing a damping of the armature's movement. Thus, the real cause for the switching noise is counteracted and therefore a costly and complex acoustic encapsulation is no longer necessary. A relay according to the present invention therefore minimizes the assembly costs. By directly remedying the acoustic reasons for switching noises at a part of the relay which does not contribute to the electric switching characteristics of the relay, a silent relay according to the present invention may advantageously be optimized with respect to the switching specifications of the particular appliance. Even existing relay structures may be retrofitted with a damping material according to the present invention.
According to an advantageous further development, said damping material is a visco-electric resin, preferably polyurethane or a similar hydro carbonic resin. Some of the most important requirements which have to be considered when choosing a damping material according to the present invention are listed in the following: The temperature dependence of the shore A hardness and the elasticity modulus of the material must ensure sufficiently constant damping characteristics and thus a constant reduction of the switching noises over the complete life time and range of operational parameters. The characteristics of the used polymer must have a sufficient aging resistance. In view of a possible deterioration of the contact, out gassing of corrosive components from the polymer has to be avoided. The electric and acoustic characteristics have to be influenced as little as possible by the tolerances of the dosage and applying precision of damping material onto the armature.
In order to provide a secure mechanical coupling of the damping material and the armature, the damping material may have adhesive characteristics.
According to an advantageous development of the present invention, the electromagnetic relay is of the type of a so called "hinged armature relay" having a yoke for guiding the magnetic field, wherein said armature is a flat armature which is carried by at least one bearing edge of said yoke. With such a relay, the advantageous noise damping characteristics of the damping material may be used advantageously.
For a particularly simple and cost-effective mounting of the armature same comprises at least one hook-shaped hinge projection which interacts with the bearing.
In order to ensure reproducible and secure switching characteristics, the magnetic system further comprises a return spring for establishing a defined position of the armature when the magnetic coil is not energized. According to the present invention, the damping material is disposed between said return spring and the armature for further reducing switching noises.
A particularly uncomplicated and cost-effective possibility of producing said return spring is to form same by a stamped and bent leaf spring.
According to an advantageous development of a method for manufacturing such a magnetic system for an electromagnetic relay, the damping material is applied to the armature by infusing a visco-elastic resin, preferably polyurethane, as a drop onto the armature. This represents a particularly simple and effective fabrication procedure which also may be employed for retrofitting existing relay structures and magnetic systems.
According to a further advantageous embodiment, the return spring has an opening, through which the visco-elastic resin may easily be infused.
By means of the embodiments shown in the attached drawings the invention is described more particularly in the following. Similar or corresponding details have the same reference numerals in the Figures, wherein:

Figure 1: shows sectional view of an electromagnetic relay according to the present invention along the line A-A of Figure 2;
Figure 2: shows a side view of the electromagnetic relay according to the embodiment of Figure 1;
Figure 3: shows a further side view of the electromechanical relay of Figure 1;
Figure 4: shows a detail B marked in Figure 1;
Figure 5: shows a detail C indicated in Figure 3;
Figure 6: shows a further side view of the electromechanical relay according to the present invention.

The accompanying drawings are incorporated into and form a part of the specification for the purpose of explaining the principles of the invention. The drawings are not to be construed as limiting the invention to only the illustrated and described examples of how the invention can be made and used. Further features and advantages will become apparent from the following and more particular description of the invention as illustrated in the accompanying drawings.
Referring now to the drawings and in particular to Figure 1, a sectional view of an electromagnetic relay according to the present invention is shown. The electromagnetic relay 100 comprises an energizing magnetic coil 102 for generating a magnetic field to actuate an armature 104 and a movable contact 106 connected thereto. The fixed permeable iron circuit of the relay 100 is formed by a core 108 and an L-shaped yoke 110. This fixed open loop part of the iron circuit is completed when the air gap 112 is closed by the attracting of the armature 104 when the coil 102 is energized.
According to the present invention, the armature 104 is hinged to the yoke 110 in a way that it may be pivoted around an axis being across to the longitudinal axis of the core 108. This pivoting axis 114 is indicated in Figure 2. For performing a switching function, the movable contact 106 (also referred to as switching contact) is arranged between two fixed contacts 116 and 118. For holding the electrical contact between the fixed contact 116 and the movable contact 106 closed when the coil 102 is de-energized, a return spring 120 is provided.
In the particular embodiment shown in the Figures, this return spring 120 is formed by a stamped and bent leaf spring. However, also a coil spring may be used to provide the return (or restoring) force on the armature 104 in the de-energized position. According to the present embodiment, the fixed contact 116 is a normally closed contact which is closed under the action of the return spring 120. However, for a person skilled in the art it is clear, that other contact arrangements which are known with electromechanical relays are also possible.
According to the present invention, a damping material 122 is disposed at the armature 104 in the region of the bearing 115 in order to provide a damping of the armature's movement.
Thus, the movement of the assembly consisting of the armature 104 and the return spring 120, which results from a superposition of the magnetic and the spring forces, is dampened and its velocity is reduced by the visco-elastic damping material 122. As damping material preferably polyurethane or a similar modified hydro carbonic resin may be used.
The principles of the present invention may be derived in still more detail from Figures 4 and 5, showing details B and C as indicated Figures 1 and 3, respectively. As can be seen from Figure 4, the armature 104 is connected to the yoke 110 by means of the hook-shaped hinge projection 124 and is thus pivotally connected to the yoke 110 around an axis 114 leading into the drawing plane of Figure 4.
According to the present invention, a damping material 122 in the form of a drop of an adhesive visco-elastic substance it is disposed onto the armature 104 and the yoke 110 in the region of the hinge projection 124. The damping material 122 adheres to the surfaces of the armature 122 and of the yoke 110, thus providing a mechanical resistance for the pivoting movement of the armature. However, the damping material 122 has enough elasticity to allow a sufficient movement of the armature 104 for actuating the switching contact 106. Only the velocity of the movement, when the coil 102 is energized, is reduced, thus leading to a significantly reduced switching noise of the relay 100.
Preferably, the viscosity of the damping material 122 is high enough not to be infused between the yoke 110 and the armature 124 in the region of the magnetic circuit in order not to deteriorate the electromagnetic characteristics of the relay 100. As shown in the Figures, the return spring 120 has an opening 126 for the hinge projection 124. Through this opening 126 the damping material 122 can be filed in to be disposed on the armature 104.
According to the present invention, the damping material 122 is applied with enough thickness to allow the spring 120 to rest partly on the damping material 122 in order to reduce possible noises caused by the movement of the return spring 120.
The assembly method for manufacturing the electromagnetic relay 100 according to the present invention will be explained in the following in reference to Figures 1 to 6.
An important feature of the invention may be seen in the fact that a conventional prefabricated magnetic system or electromagnetic relay with already mounted contacts 106, 116, 118 and return spring 120 may be provided with a damping material 122 for reducing the switching noises without any constructional changes of the magnetic system or relay.
According to an advantageous embodiment of the present invention, a drop of a visco-elastic adhesive substance, for instance polyurethane, is applied as damping material 122 to the armature 104 and the yoke 110 in the region of the bearing 115 of the armature 104.
According to the shown embodiment, this is done by infusing the damping material 122 through the opening 126 and subsequently performing a curing step. This curing step may be a thermal curing or may use UV radiation.
The fully assembled electromagnetic relay 100 may now be mounted in a housing (not shown in the drawings). This housing, however, does not need to possess any particular features for an acoustic encapsulation, but may be optimized with respect to electromagnetic performance, cost-effective production or geometric requirements.

Claims

Magnetic system for an electromagnetic relay, the magnetic system comprising:
a magnetic coil (102) for generating a magnetic field to actuate an armature (104) and a movable contact (106),

said armature (104) being pivotally supported in a bearing (115), and

a damping material (122) being disposed at the armature (104) in a region of said bearing (115) for providing a damping (122) of the armature's movement.
Magnetic system according to claim 1, wherein said damping material (122) is a visco-elastic resin, preferably polyurethane.
Magnetic system according to claim 2, wherein said damping material (122) is an adhesive.
Magnetic system according to at least one of the preceding claims, further comprising a yoke (110) for guiding the magnetic field, wherein said armature (104) is a flat armature which is carried by at least one bearing edge of said yoke (110).
Magnetic system according to at least one of the preceding claims, wherein the armature (104) comprises at least one hook-shaped hinge projection (124) for interacting with said bearing (115).
Magnetic system according to at least one of the preceding claims, further comprising a return spring (120) for establishing a defined position of the armature (104) when the magnetic coil (102) is not energized, wherein the damping material (122) is arranged between said return spring (120) and the armature (104).
Magnetic system according to claim 3, wherein said return spring (120) is formed by a stamped and bent leaf spring.
Electromagnetic relay having a magnetic system comprising:
a magnetic coil (102) for generating a magnetic field to actuate an armature (104) and a movable contact (106),

said armature (104) being pivotally supported in a bearing (115), and

a damping material (122) being disposed at the armature (104) in a region of said bearing (115) for providing a damping (122) of the armature's movement.
Electromagnetic relay according to claim 8, wherein said damping material (122) is a visco-elastic resin, preferably polyurethane.
Electromagnetic relay according to claim 9, wherein said damping material (122) is an adhesive.
Electromagnetic relay according to at least one of the claims 8 to 10, further comprising a yoke (110) for guiding the magnetic field, wherein said armature (104) is a flat armature which is carried by at least one bearing edge of said yoke (110).
Electromagnetic relay according to at least one of the claims 8 to 11, wherein the armature (104) comprises at least one hook-shaped hinge projection (124) for interacting with said bearing (115).
Electromagnetic relay according to at least one of the claims 8 to 12, further comprising a return spring (120) for establishing a defined position of the armature (104) when the magnetic coil (102) is not energized, wherein the damping material (122) is arranged between said return spring (120) and the armature (104).
Electromagnetic relay according to claim 13, wherein said return spring (120) is formed by a stamped and bent leaf spring.
Electromagnetic relay according to at least one of the claims 8 to 14, further comprising at least one fixed contact (116, 118), wherein said movable contact (106) may be connected to said fixed contact (116, 118) in response to the movement of the armature (104).
Method for manufacturing a magnetic system for an electromagnetic relay, said method comprising the following steps:
assembling the magnetic system comprising a magnetic coil for generating a magnetic field to actuate an armature and a movable contact, said armature being pivotally supported in a bearing,

applying a damping material to the armature in a region of said bearing for providing a damping of the armature's movement.
Method according to claim 16, wherein the step of applying a damping material comprises infusing a visco-elastic resin, preferably polyurethane.
Method according to claim 16 or 17, wherein the step of assembling the magnetic system further comprises the step of mounting a return spring for establishing a defined position of the armature when the magnetic coil is not energized.
Method according to claim 18, wherein the step of applying said damping material comprises infusing a visco-elastic resin, preferably polyurethane, through an opening provided in the return spring.