ELECTROMAGNETIC SWITCH DEVICE

Abstract

 In an electromagnetic switch device incorporated with fuse terminals (31, 32, 36, 37) for at least one fuse (41), a terminal holder (12) retaining fuse terminals therein is fit onto an open end of a switch casing (11) that receives an electromagnetic coil (13) and associated component parts, and the terminal holder includes a peripheral wall (12A) that opposes a side wall of the switch casing in an overlapping relationship and defining a small gap (51) therebetween. At least one of the terminal pieces includes a heat dissipating extension (34A, 35A) extending into the gap between the peripheral wall of the terminal holder and opposing side wall of the switch casing. The heat dissipating extension promotes the dissipation of the heat conducted through the corresponding terminal piece to the ambient air. The improved heat dissipation contributes to the improvement in the electric properties of the electromagnetic switch device, and ensures a high reliability.

Description

TECHNICAL FIELD

[0001] The present invention relates to an electromagnetic switch device, and in particular to an electromagnetic switch device suitable for use in conjunction with starter motors of motorcycles.

BACKGROUND OF THE INVENTION

[0002] Onboard electric components are desired to be small and compact because of limited spaces available in vehicles, in particular motorcycles. As such an onboard electric component for motorcycles is known an electromagnetic switch device incorporated with a fuse box fitted with terminals or sockets for fuses. The fuse terminals for a main fuse provided for an electric circuit separate from a starter motor circuit is mounted on a terminal holder for the electromagnetic switch for a starter motor. Such a device occupies a smaller space than when a fuse box and an electromagnetic device are provided separately. See Japanese patent laid open publication No. 61-085746.

[0003] In such an electromagnetic switch device incorporated with fuse terminals, electric current constantly flows through the fuse terminals, and the electric resistance of the fuse terminals inevitably generates heat during use. The need for a higher compactness in such an electromagnetic switch device incorporated with fuse terminals often requires the fuse terminals to be small, and the resulting reduction in the surface area of the fuse terminals causes a corresponding reduction in heat dissipation.

[0004] The electric systems for current motorcycles require significant power consumptions owing to the extensive use of electronic control systems for fuel injection and brake control as compared with more traditional motorcycles. Therefore, the power system for each motorcycle is often grouped into a plurality of circuit systems which are individually provided with fuses so as to cope with large power consumption and enhance the reliability of the system.

[0005] As the number of the fuse circuits increases, a corresponding number of fuse terminals must be provided in the fuse terminal holder of the electromagnetic switch device incorporated with fuse terminals, and this requires the size of each individual fuse terminal to be reduced for the given size of the electromagnetic switch device. Therefore, the surface area of each fuse terminal is reduced, and the resulting reduction in heat dissipation imposes an increased thermal load to such an extent that the electric performance and durability of the electromagnetic switch device could be reduced.

BRIEF SUMMARY OF THE INVENTION

[0006] In view of such problems of the prior art, a primary object of the present invention is to provide an electromagnetic switch device incorporated with fuse terminals in which heat can be favorably dissipated from the fuse terminals even when the size of the overall electromagnetic switch is reduced.

[0007] A second object of the present invention is to provide an electromagnetic switch device incorporated with fuse terminals whose electric performance and durability is not compromised in spite of a compact design thereof.

[0008] According to the present invention, such an object can be accomplished at least partly by providing an electromagnetic switch device, comprising: a switch casing (11) having an open end and receiving an electromagnetic coil (13); a plunger (14) and a contact assembly (15, 16, 17) therein; and a terminal holder (12) fitted onto the open end of the switch casing and receiving at least one power source side terminal piece (33) and at least one output side terminal piece (34, 35); wherein the terminal holder includes a peripheral wall (12A) that opposes a side wall of the switch casing in an overlapping relationship and defining a small gap (51) therebetween, and at least one of the terminal pieces include a heat dissipating extension (34A, 35A) extending into the gap between the peripheral wall of the terminal holder and opposing side wall of the switch casing.

[0009] The heat dissipating extension that extends into the gap between the peripheral wall of the terminal holder and opposing side wall of the switch casing promotes the dissipation of the heat conducted through the corresponding terminal piece to the ambient air. The improved heat dissipation contributes to the improvement in the electric properties of the electromagnetic switch device, and ensures a high reliability.

[0010] According to a preferred embodiment of the present invention, the at least one power source side terminal piece includes a power source side fuse terminal (31, 32) extending therefrom, and the at least one output side terminal piece includes an output side fuse terminal (36, 37) extending therefrom. The device may comprise a pair of output side terminal pieces each including an output side fuse terminal, and the power source side terminal piece includes a pair of power source side terminals which are respectively paired to the corresponding output side terminals of the two output side terminal pieces. Also, the contact assembly comprises a pair of fixed contact members (15, 16) and a moveable contact member (17) connected to the plunger, and the switch casing further receives a pair of switch casing terminals connected to the corresponding fixed contact members, one of the switch casing terminals (19, 20) being electrically connected to the power source side terminal piece while the other switch casing terminal being configured to be electrically connected to a starter motor.

[0011] According to a certain aspect of the present invention, the terminal holder is fitted onto the switch casing in an axial direction, and the at least one output side terminal piece includes a base portion extending perpendicularly to the axial direction, the heat dissipating extension being formed by bending a part of the base portion onto an inner surface of the side wall of the switch casing. Preferably, the two output side fuse terminals are disposed on outer sides of the power source side fuse terminals with all the terminals arranged in a single row. According to a particularly preferred embodiment of the present invention, the heat dissipating extension is in close contact with the outer peripheral wall of the terminal holder.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Now the present invention is described in the following with reference to the appended drawings, in which:

Figure 1 is a diagram view showing a starter magnetic switch device for a motorcycle embodying the present invention;

Figure 2 is a vertical sectional view of the starter magnetic switch device;

Figure 3 is a bottom view of the starter magnetic switch device;

Figure 4 is a perspective view of the starter magnetic switch device; and

Figure 5 is an exploded perspective view of the starter magnetic switch device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] In the following is described a starter magnetic switch device for a motorcycle embodying the present invention with reference to Figures 1 to 5.

[0014] The starter magnetic switch device 10 comprises a switch casing 11 made of electrically insulating material such as plastic, and a terminal holder 12 made of similarly electrically insulating material such as plastic and joined to an upper end of the switch casing 11.

[0015] In the following description, it is assumed that the switch casing 11 is located in a lower part, and the terminal holder 12 is attached to the top part thereof as illustrated in Figure 4, for instance, for the convenience of description although the magnetic switch device may be mounted in any desired attitude in actual use.

[0016] The switch casing 11 receives therein an electromagnetic switch 18 in a sealed manner, and the electromagnetic switch 18 includes an electromagnetic coil 13, a plunger 14, a pair of fixed contact members 15 and 16 and a moveable contact member 17. When the electromagnetic coil 13 is energized, the moveable contact member 17 comes into contact with the fixed contact members 15 and 16, and establishes an electric contact between the fixed contact members 15 and 16. When the electromagnetic coil 13 is deenergized, the moveable contact member 17 moves away from the fixed contact members 15 and 16 under the spring force of a spring not shown in the drawing, and disconnects an electric contact between the fixed contact members 15 and 16. Coil terminals 13A and 13B for the electromagnetic coil 13 project upward above an upper end of the switch casing 11.

[0017] To the switch casing 11 are attached a power source terminal 19 which is integrally connected to one of the fixed contact members 15 and a switch output terminal 20 which is integrally connected to the other fixed contact member 16. Upper ends of the power source terminal 19 and switch output terminal 20, respectively, protrude slightly upward out of the switch casing 11. The upper end of the power source terminal 19 is electrically connected to a battery power source 100, and the upper end of the switch output terminal 20 is electrically connected to a starter motor 101. The power source terminal 19 may also be formed separately from the one fixed contact member 15, and electrically connected thereto. Likewise, the switch output terminal 20 may also be formed separately from the other fixed contact member 16, and electrically connected thereto.

[0018] To the terminal holder 12 are attached a power source side terminal piece 33 which is electrically connected to the power source terminal 19 and includes a pair of power source side fuse terminals 31 and 32, and a pair of output side terminal pieces 34 and 35 each integrally provided with an output side fuse terminal 36, 37 that is paired with a corresponding one of the power source side fuse terminal 31, 32. To each fuse terminal 31, 32, 36, 37 is fixedly attached a spring piece 40 which is formed by bending a strip of resilient conductive material sheet into a prescribed shape. A pair of blade fuses 41 are each connected to the corresponding pair of fuse terminals by pushing flat bar shaped leg pieces 41A into the spring pieces of the corresponding fuse terminals 31, 32, 36, 37. Each spring piece 40 resiliently retains the corresponding leg piece 41A in a detachable manner.

[0019] One of the output side terminal pieces 34 is additionally provided with an output terminal 38 for connecting a first electric load 102 which typically includes a headlight and a taillight. The other output side terminal piece 35 is also additionally provided with an output terminal 39 for connecting a second electric load 103 which typically includes fuel injection valves and an engine control unit. In the illustrated embodiment, the two power source side fuse terminals 31 and 32 are disposed one next to the other, and the two output side fuse terminals 36 and 37 are disposed on the outer sides of the power source side fuse terminals 31 and 32 all in a single row.

[0020] Each output side terminal piece 34, 35 is made by stamp forming electrically conductive material sheet, and includes a main horizontal portion and a pair of heat dissipating extensions 34A, 34B, 35A, 35B downwardly bent from the main horizontal portion.

[0021] The terminal holder 12 includes a peripheral wall portion 12A which is fit onto the upper end of the switch casing 11, and a small lateral gap 51 is defined between the lower end of the peripheral wall portion 12A and the opposing side surface 11A of the switch casing 11. In the illustrated embodiment, the two heat dissipating extensions 34A, 34B, 35A, 35B of each output side terminal piece 34, 35 extend laterally in mutually perpendicular directions, and one of the two heat dissipating extensions 34A, 35A of each output side terminal piece 34, 35 extends into the corresponding gap 51. As this gap 51 communicates with the surrounding air via the lower end thereof, a favorable convection heat transfer from the terminal pieces to the ambient air can be effected. Because these heat dissipating extensions 34A, 35A extend vertically along the outer side wall surface 11A of the switch casing 11, the surface area of the heat dissipating extensions 34A, 35A can be increased without increasing the size of the electromagnetic switch device 10.

[0022] When two circuits for two individual sets of electric load with individual fuses are provided, two pairs of fuse terminals are required to be mounted on a terminal holder to accommodate the two fuses, and this necessitates the size of each fuse terminal to be reduced. However, according to the illustrated embodiment, heat is favorably dissipated, from each terminal piece, and this prevents any electric and other ill effects that can be otherwise caused by heat. This also improves the durability of the magnetic switch device.

[0023] The length of each heat dissipating extension 34A, 35A can be selected depending on the thermal properties of the output side terminal pieces 34 and 35, and can be extended up to the entire height of the switch casing 11 without increasing the overall size of the electromagnetic switch device.

[0024] The other heat dissipating extensions 34B, 35B are disposed within the outer peripheral wall, and are protected from inadvertent short-circuiting or grounding owing to a contact with an external conductor.

[0025] Each heat dissipating extension 34A, 35A is in contact with the outer peripheral wall 12A of the terminal holder 12 on one side (inner side) thereof (in an overlapping relationship) so that heat is dissipated from the heat dissipating extension 34A, 35A to the terminal holder and switch casing by heat conduction. Additionally, each heat dissipating extension 34A, 35A reinforces the outer peripheral wall 12A of the terminal holder 12 by supporting it from the back against external forces that could be applied to the electromagnetic switch device 10, and this prevents deformation or other damages to the terminal holder.

[0026] In the illustrated embodiment, the heat dissipating extensions are provided on the output side terminal pieces as they are located externally of the power source side terminal pieces. If the power source side terminal pieces are located externally of the output side terminal pieces, similar heat dissipating extensions may be advantageously provided to the power source side terminal pieces. It is also within the purview of the present invention to provide a heat dissipating extension to only one of two or more of power source side terminals or output side terminals.

[0027] Although the present invention has been described in terms of a preferred embodiment thereof, it is obvious to a person skilled in the art that various alterations and modifications are possible without departing from the scope of the present invention which is set forth in the appended claims.

[0028] The contents of the original Japanese patent application on which the Paris Convention priority claim is made for the present application are incorporated in this application by reference.

Claims

1. An electromagnetic switch device, comprising:

a switch casing (11) having an open end and receiving an electromagnetic coil (13), a plunger (14) and a contact assembly (15, 16, 17) therein; and

a terminal holder (12) fitted onto the open end of the switch casing and receiving at least one power source side terminal piece (33) and at least one output side terminal piece (34, 35);

wherein the terminal holder includes a peripheral wall that opposes a side wall (12A) of the switch casing in an overlapping relationship and defining a gap therebetween, and at least one of the terminal pieces include a heat dissipating extension (34A, 35A) extending into the gap (51) between the peripheral wall of the terminal holder and opposing side wall of the switch casing.

2. The electromagnetic switch device according to claim 1, wherein the at least one power source side terminal piece includes a power source side fuse terminal (31, 32) extending therefrom, and the at least one output side terminal piece includes an output side fuse terminal (36, 37) extending therefrom.

3. The electromagnetic switch device according to claim 2, wherein the device comprises a pair of output side terminal pieces each including an output side fuse terminal, and the power source side terminal piece includes a pair of power source side terminals which are respectively paired to the corresponding output side terminals of the two output side terminal pieces.

4. The electromagnetic switch device according to claim 1, wherein the contact assembly comprises a pair of fixed contact members (15, 16) and a moveable contact member (17) connected to the plunger, and the switch casing further receives a pair of
switch casing terminals connected to the corresponding fixed contact members, one of the switch casing terminals being electrically connected to the power source side terminal piece while the other switch casing terminal (19, 20) being configured to be electrically connected to a starter motor.

5. The electromagnetic switch device according to claim 1, wherein the terminal holder is fitted onto the switch casing in an axial direction, and the at least one output side terminal piece includes a base portion extending perpendicularly to the axial direction, the heat dissipating extension being formed by bending a part of the base portion onto an inner surface of the side wall of the switch casing.

6. The electromagnetic switch device according to claim 2, wherein the two output side fuse terminals are disposed on outer sides of the power source side fuse terminals with all the terminals arranged in a single row.

7. The electromagnetic switch device according to claim 1, wherein the heat dissipating extension is in close contact with the outer peripheral wall of the terminal holder.

Drawing