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(11) | EP 0 198 594 A2 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Relay |
| (57) A relay comprising a hollow, preformed housing (30) which locates, in preset positions,
an armature - (14), a contact spring (17) and contact terminals - (19,21,23). The
contact terminals project from one side of the housing for connection to a planar
assembly board, and a solenoid coil (10) is located outside the housing on a side
opposite the one side. The longitudinal axis (XX) of the coil is orthogonal to said
one side and so to the plane of an assembly board to which the contact terminal may
be connected. |
[0001] This invention relates to a relay and it relates particularly, though not exclusively, to a relay suitable for use in the control and/or supervisory systems of an automobile.
[0002] With the advent of solid state circuitry the complexity and sophistication of the control and/or supervisory systems used in an automobile has increased considerably. Typically circuits employed in such systems may incorporate many relays.
[0003] Each relay should, of course, be designed to operate reliably in the hostile environment encountered in the engine of an automobile and there is an increasing demand for more compact designs at lower costs.
[0004] Figure 1 shows a known form of relay, described in GB 1,265,138. It comprises an electromagnet 1 provided with a yoke 2 and an armature 3, which is biassed by a coil spring 4 away from the electromagnet. A contact spring 5 mounted on the armature can establish an e4ectrical connection between a common contact member - (not shown), formed integrally with the yoke, and a respective one or two other contact members 6, 7 depending on whether the electromagnet is energised or de-energised. This design of relay is found to be unsatisfactory in practice. The arrangement is rather bulky and can be difficult to protect satisfactorily from dust, fumes and the like. After assembly the component parts must be set manually and this can be a time consuming procedure. Furthermore, an electrically conductive braid 8 is needed to establish electrical continuity between the contact spring 5, rpounted on the armature, and the common contact member, formed integrally with the yoke. After repeated use of the relay the braid tends to wear; moreover, the braid must be attached by welding and this increases the assembly time. Use of a coil spring is also inconvenient as special anchorages must be provided on the armature and the yoke. In this example the yoke is connected to the live terminal and this can result in arcing problems if two relays are mounted side-by- side.
[0005] It is an object of the present invention to provide a relay whereby some or all of these problems are at least alleviated.
[0006] Accordingly there is provided a relay comprising a hollow, preformed housing configured to locate a number of component parts in respective preset positions, wherein said component parts include a solenoid coil; a magnetic circuit associated with the solenoid coil which comprises a yoke, a core arranged to lie on a longitudinal axis of the solenoid coil and an armature, proximate one end of the core, the armature being displaceable pivotally with respect to the core in response to energisation or de-energisation of the coil; and a contact spring, cooperable with said armature, to establish an electrical connection between first and second electrically conductive contact terminals in dependence of the state of energisation of the coil, characterised in that said contact spring, said armature and said contact terminals are located inside said housing, the contact terminals projecting from one side only of the housing so as to be connectable to a planar assembly board, and said solenoid coil is located outside the housing on a side thereof opposite said one side, the longitudinal axis of the solenoid coil being substantially orthogonal to said one side, and so to the plane of an assembly board to which said contact terminals may be connected.
[0007] A relay of the kind defined is found by the inventors to be beneficial, particularly so when used in the control and or supervisory systems of an automobile. With the solenoid coil outside the housing, other components parts can be arranged, within the housing, with improved economy of space giving a more compact configuration commensurate with mounting on a planar assembly board. This can also lead to shorter electrically conductive path lengths allowing relatively high currents, sometimes demanded in an automobile relay, to be passed with reduced self heating.
[0008] In practice it has been found that the component parts may be assembled, with precision, in their intended positions, obviating the need for elaborate manual setting subsequent to assembly. Moreover, since the housing encloses some of the component parts it gives some protection against accidental displacement either in use of the relay or during assembly. If desired, a dust cover and base plate may be fitted to give additional protection against dirt, grease, fumes and the like. Use of a common preformed housing can lead to a substantial reduction of assembly time and so overall costs and, to this end, said armature, said first contact terminal and said contact spring may be locatable, in one operation, in a housing as a sub-assembly.
[0009] The first contact member may comprise part of a frame member, and said contact spring cooperates with the armature to bias the armature resiliently against the frame member and away from the core, the armature being free to pivot relative to the frame member in response to energisation or de-energisation of the solenoid coil.
[0010] This arrangment overcomes the need for a separate spring biassing means and or electrically conductive braid as used commonly in a number of known relays.
[0011] In order that the invention may be carried readily into effect embodiments thereof are now described, by way of example only, by reference to Figures 2 and 6 of the accompanying drawings of which,
Figure 1 shows a side view of a known form of relay,
Figure 2 shows a cross-sectional view through a relay in accordance with one embodiment of the present invention,
Figure 3 shows a sub-assembly used in the relay of Figure 2,
Figures 4a and 4b show different perspective views of a housing used in the relay of Figure 2,
Figure 5 shows a cross-sectional view through a relay in accordance with another embodiment of the present invention and Figure 6 shows a sub-assembly used in the relay of Figure 5.
[0012] It will be appreciated that although the relay described hereinafter by reference to Figures 2 to 6 of the drawings is especially suitable for use in the control and/or supervisory circuits of an automobile, the present invention encompasses relays suitable in other applications.
[0013] Referring now to Figure 2 of the drawings, the relay includes a solenoid coil 10, wound on a bobbin 11, in association with a magnetic circuit comprising a magnetic core 12, arranged to lie on a longitudinal axis XX of the coil, a yoke 13 around the core and an armature 14.
[0014] The armature is supported within a hollow, preformed housing 30 and, as is shown in greater detail in Figure 3, comprises a plate-like element 15 with an integral, down-turned end portion 16. The armature is biassed resiliently away from the core (i.e. downwardly in Figure 2) by a flat contact spring 17 which is mounted on a support frame 18 and engages against one edge of an opening 0 in the end portion. The armature is free to pivot on axis YY in response to energisation or de-energisation of the solenoid coil and, in the shown (de-energised) position, the contact spring establishes an electrical connection between the contact terminal 19, which forms part of frame 18, and a normally closed contact member 20 connected electrically to a respective contact terminal 21. If, on the other hand, the solenoid coil is in the energised condition the armature is attracted (upwardly) by the core causing the contact spring to establish an electrical connection between contact terminal 19 and a normally open member 22 which is connected electrically to a respective contact terminal 23. Thus, by controlling electrical current supplied to the solenoid coil, the switching condition of the relay can be changed.
[0015] Housing 30 is formed as a moulding of a suitable plastics material capable, in this example, of withstanding, without distortion, the relatively high temperatures encountered in the engine of an automobile. One suitable material is found to be polybutylene terephthalene (PTB). Bobbin 11 is formed integrally with, and externally of, the housing as part of the same moulding. However, it will be appreciated that the bobbin could alternatively be formed as a separate piece part to be mounted on the housing, with a snap-action for example, after the coil has been wound. Referring to Figures 4a and 4b, in addition to Figure 2, the housing has a number of internal, shelf-like formations so disposed as to guide, and locate with precision, certain of the component parts. Contact terminals 21, 23 are assembled in their respective locations in slotted recesses 31, 32 defined by respective formations F,, F2 (Figures 2 and 4a). Similarly armature 14, contact spring 17 and supporting frame 18 are located, as a sub-assembly (SA), shown in Figure 3, at the opposite end of the housing - (Figures 2 and 4b), slotted formations F,, F4 serving to guide and locate respective anchoring tabs,24, 25 forming part of frame 18. Formations F3, F4 also serve as end stops ensuring that the contact forming tip of spring 17 is positioned correctly between the contact members 20, 22.
[0016] In this example, contact spring 17 has an upturned finger 26 which bears resiliently against element 15 and urges the armature back against frame 18, as shown in Figure 3. The armature has two arcuate lugs L,, L2. one on each side of member 15, which locate against respective arcuate surfaces (eg S), formed internally as recesses in opposite side walls of the housing. In effect, the lugs and surfaces cooperate as bearings which assist to locate the armature correctly, in abutting relationship against the yoke, and also facilitate pivotal movement thereof in response to energisation in de-energisation of the solenoid coil.
[0017] The contact terminals 19, 21 and 23 protrude from the lower side of the housing and are connectable to a planar assembly board. If desired, a protective dust cover 33 may be fitted over the housing, as shown, and this may be sealed by a base plate 34, which serves to protect the component parts from solder runs when the relay is mounted on an assembly board. The contact terminals can be accommodated in respective openings formed in the base plate. It will be appreciated that sub-assembly (SA), consisting of armature 14, contact spring 17 and supporting frame 18, maybe positioned in the housing in one operation leading to a more convenient handling procedure and a significant reduction in assembly time. In an alternative embodiment, shown in Figures 5 and 6, contact spring 17 has two wing formations W,, W2 which bear against respective edges of two openings 26, 27 in element 15. The wing formations bias the armature resiliently against frame 18 which is configured to allow the armature to pivot about axis P, as represented by arrow A. Other parts of the relay are substantially as shown in Figures 2 and 3 and are ascribed like reference numerals.
[0018] An arrangement of the kind described, wherein the contact spring biasses the armature resiliently, is advantageous in that it obviates the need for additional spring biassing means of the kind sometimes used in hitherto known designs. Moreover, this arrangement removes the need for an electrically conductive braid, since the contact spring establish an electrical connection to contact terminal 19 directly. As shown in both Figures 2 and 5 the armature, when positioned, abuts the yoke to establish contact therewith over a relatively large surface region and thereby complete the magnetic circuit satisfactory even as it is being displaced.
[0019] A relay in accordance with the present invention, wherein the contact terminals protrude from one side of the housing for connection to a printed circuit board, and the solenoid coil is positioned externally of the housing, on the opposite side, with the longitudial axis of the coil orthogonal to the plane of a printed circuit board, is found by the inventors to be beneficial, particularly so when used in the control and/or supervisory systems of an automobile. With the solenoid coil outside the housing, other components parts can be arranged within the housing with improved economy of space; for example, in one embodiment, the relay occupies a relatively small area (2.4cm x 1.6cm) on the circuit board while providing adequate separation of the current carrying terminals, contacting terminals 19, 21 and 23 being spaced apart from one another by about 1.6cm and 0.7cm respectively. This can lead to shorter path lengths allowing relatively high currents, sometimes demanded in an automobile relay, to be passed with reduced self heating.
[0020] In practice, it has been found that because a single housing is used generally fewer piece parts are needed. Furthermore, when the component parts have been assembled in the housing they do not require elaborate setting; the moulding, which can be formed with a required degree of precision serves to locate the parts with a desired tolerance. Thus, as compared with some known constructions, the assembly procedure is simplified considerably, leading to a more reliable product and a reduction in assembly time and so costs.
[0021] The housing encloses some of the component parts and so provides some protection against accidental displacement during assembly and in use. A dust cover and a base plate, if fitted, give additional protection against dust, fumes, grease and the like and also allow a number of relay to be arranged in a close-packed formation on a printed circuit board.
[0022] The inventors have found that a relay in accordance with the present invention is well suited to mounting on planar assembly board (eg for use in the control and or supervisory systems of an automobile), is relatively compact as compared with some known relays and involves a relatively short assembly time.
1. A relay comprising a hollow, preformed housing configured to locate a number of
component parts in respective preset positions, wherein said component parts include
a solenoid coil; a magnetic circuit associated with the solenoid coil which comprises
a yoke, a core arranged to lie on a longitudinal axis of the solenoid coil and an
armature, proximate one end of the core, the armature being displaceable pivotally
with respect to the core in response to energisation or de-energisation of the coil;
and a contact spring, cooperable with said armature, to establish an electrical connection
between first and second electrically conductive contact terminals in dependence on
the state of energisation of the coil, characterised in that said contact spring,
said armature and said contact terminals are located inside said housing, the contact
terminals projecting from one side only of the housing so as to be connectable to
a planar assembly board, and said solenoid coil is located outside the housing on
a side thereof opposite said one side, the longitudinal axis of the solenoid coil
being substantially orthogonal to said one side, and so to the plane of an assembly
board to which said contact terminals may be connected.
2. A relay according to Claim 1 wherein said solenoid coil is wound on a bobbin formed
integrally with the housing.
3. A relay according to Claim 1 or Claim 2 wherein said armature, said first contact
terminal and said contact spring are locatable, as a sub-assembly, in said preformed
housing.
4. A relay according to Claim 3 wherein said first contact member comprises part of
a frame member, and said contact spring co-operates with the armature to urge the
armature resiliently against the frame member, and away from the core, the armature
being free to pivot relative to said frame member in response to energisation or de-energisation
of the solenoid coil.
5. A relay according to Claim 4 wherein said housing and armature have respective
cooperable bearing surfaces.
6. A relay substantially as hereinbefore described by reference to Figures 2 to 6
of the accompanying drawings.