Patent Application
20100330850
The present application relates to and incorporates by reference Japanese Patent application No. 2009-151240 filed on Jun. 25, 2009.
1. Field of the Invention
The present invention relates to an electromagnetic switch which turns on/off a conduction (energizing) current of a starter motor.
2. Description of the Related Art
Conventionally, an electromagnetic switch which turns on/off a conduction (energizing) current fed to a starter motor which starts an engine is widely known.
When a movable contact is driven by magnetomotive force which an exciting coil generates by being energized, so as to contact a pair of fixed contacts which is placed opposite the movable contacts, the pair of fixed contacts are short-circuited with each other. This makes the electromagnetic switch close an electric circuit. The exciting coil is conducted with a switch terminal which is energized in response to ON operation of an ignition switch, and the pair of fixed contacts are conducted respectively with a battery terminal and a motor terminal, both of them are formed protrusively outward at a contact cover fitted into a yoke of the exciting coil. A battery cable is connected to the battery terminal, and a motor lead is connected to the motor terminal. The electric circuit is closed by the operation of the electromagnetic switch, thereby a motor generates torque in response to power feeding from a battery. The torque is slowed down with an epicycle reduction gear for example, and is transmitted to a pinion gear. An engine crankshaft is rotated by engaging the pinion gear with a ring gear provided in the engine crankshaft, and an engine starts up.
In an electromagnetic switch disclosed in a Japanese Patent Application Laid-Open Publication No. 2004-319128, as shown in
By the way, in the case where the electromagnetic switch is used under a severe environment where excessive vibration from the engine is directly received, the nut 109 may loosen by excessive vibration. Therefore, it is necessary to prevent the battery cable 107 and/or the motor lead 108 separate from the respective collars 101,102. Then, if the battery terminal bolt 103 and the motor terminal bolt 104 are formed through the collars 101, 102 as the above composition, a tightening loads of the nuts 109,109 are received in the axial direction of the collars 101, 102 having high strength. Consequently, the nut 109 can be firmly tightened. In addition, looseness of the nut 109 by vibration or aging can be controlled since the creep tolerance of metal under compressive load is excellent compared with resin.
However, in the above electromagnetic switch, other than the above composition, an O-ring is fitted on an outer circumference of each head 103a, 104a of the battery terminal bolt 103 and the motor terminal bolt 104 in order to secure the airtightness in the contact cover 100. In order to improve sealability for airtightness, an O-ring with sufficient thickness should be adopted, compressed strongly, and as a result, largely elastically deformed. However, in such composition, increase in the thickness of the O-ring may require larger outer diameter of the contact cover 100. In order to avoid the enlargement of the outer diameter of the contact cover 100, thin sealing member should be used.
The present invention has been made in view of such conventional problems, and thus, it is an object of the present invention to provide an electromagnetic switch which can secure the sealing member with sufficient thickness without expanding the outer diameter of a contact cover.
In order to achieve the aforementioned object, the present invention provides an electromagnetic switch including an exciting coil which generates magnetomotive force by being energized, a movable contact driven by the magnetomotive force of the exciting coil, a pair of fixed contacts placed opposite the movable contact, a contact cover of a shape having a contact chamber provided therein and containing the movable contact and the pair of fixed contacts, tubular members fitted into respective terminal holes formed in the bottom of the contact cover, terminal bolts inserted in respective tubular members and conducted with the pair of fixed contacts respectively, sealing members sealing respective gaps between the terminal holes and the terminal bolts, and tightening members screwed on the respective male screws of the terminal bolts, so as to fix ring terminals to the terminal bolts respectively. wherein the terminal bolts have locking parts projected in the direction of outer diameter, one end at the contact chamber side of the tubular members abut against the locking parts and the sealing members are engaged closer to the contact chamber side than the locking parts of the terminal bolts are.
Since ends at the fixed contacts side of the terminal bolts abut against locking parts of the feet of the terminal bolts, the positions of the terminal bolts relative to the tubular members are regulated and pressing forceaxial pressing forces on the tightening members can be absorbed by the locking parts. Since spaces are created between the terminal holes and the terminal bolts at places being closer to the contact chamber side than the locking part side of the terminal bolts, the airtightness of the contact chamber can be secured by interposing the sealing members in the spaces in elastically compressed states. Moreover, even if the sealing members with large thickness are used for the improvement of the airtightness of the contact chamber, the contact cover does not expanded in the radial direction in the range in which the cross-section of the tubular members after elastic compression falls within the projected plane in the axial direction of the sealing members.
It is preferable that the fixed contact may be serration-fitted to a knurled part formed to the contact chamber side rather than the sealing member of the terminal bolt.
According to this configuration, since the airtightness of the contact chamber is secured by arranging the sealing members at the opposite side to the knurled parts, crevices between fixed contacts and the knurled parts does not have a bad influence on the airtightness of the contact chamber.
It is preferable that the tubular member has a notch part formed on the inner surface of the contact chamber.
According to this configuration, the stress by the pressing force of the tightening members can be distributed in the axial direction and the radial direction, the tubular members can be engaged with the locking parts more reliably.
It is preferable that the locking part is provided separately from the terminal bolt.
According to this configuration, a complicated forming step of forming a projection in the midway of the terminal bolts is not needed, and locking parts can be prepared by attaching locking members to the terminal bolts, and so manufacture of the products can be made easily. Moreover, before preparing locking members to the terminal bolts, sealing members can be fitted, whereby sealing members can be attached easily.
It is preferable that the locking member is fitted into a groove part formed at a foot of the terminal bolt.
According to this configuration, the strength of the locking member to the pressing force of the tightening member can be made high by regulating the position in axial direction of the locking member relative to the terminal bolt, whereby the ring terminal can be more firmly tightened to the terminal bolt.
It is preferable that a cross-section of the locking part is circular, cross section of the groove part and the notch part has a circular arc which fits to the cross-sectional shape of the locking part respectively.
According to this configuration, since the locking member and terminal bolt, the locking member and the tubular member are surface-contacted respectively, whereby stress produced among them can be distributed.
It is preferable that the locking member is a C-ring made of rounded steel wire.
According to this configuration, the C-ring can be inserted into the terminal bolt in the state where the diameter of the locking member is expanded using the elastic deformation of the C-ring. When the locking member reaches the groove part, the diameter of the locking member returns, whereby the locking member can be certainly fixed to the terminal bolt.
It is preferable that the locking part is made of piano wire.
According to this configuration, the piano wire has a high strength and is reliable. Furthermore, since the piano wire has elasticity, the piano wire has a good attachment performance, and suitable for using as locking part.
It is preferable that the tubular member is made of metal.
According to this configuration, since metal has high strength, metal can bear the large pressing force of the tightening member, and also since metal has high creep tolerance, loosening of the tightening member by age deterioration can be controlled.
It is preferable that the tubular member is provided to the contact cover by insert-molding
According to this configuration, since the tubular member can be simultaneously formed at the time of forming the contact cover, the manufacturing process can be simplified.
In the accompanying drawings:
As shown in
As shown in
As shown in
As shown in
The fixed contact 5 is made of a material having excellent electrical conductivity, and consists of a pair of a contact point electrically conducted with a battery and a contact point electrically conducted with a motor. As shown in
The contact cover 6 is made of a insulating material having high heat resistance, such as phenol resin, is formed in an approximately bottomed cylindrical shape as shown in
The collar 7 (8) is made of metal such as iron, and as shown in
As shown in
O-ring 11 is made of resin having elasticity, and as shown in
As shown in
Next, operation of the electromagnetic switch 1 is explained.
The exciting coil 3 is energized by ON operation of an ignition switch and generates magnetomotive force, and then the fixed iron core 19 and the movable iron core 20 are magnetized. While the movable contact 4 presses and contracts the return spring 27 through the rod 22, the movable contact approaches the fixed contact 5 side, at the same time movable iron core 20 is attracted toward the fixed iron core 19 side. When the movable contact 4 abuts against the fixed contact 5, the movable contact 4 separates from stopper 22b and pressurizes contact pressure by pressing and contracting the contact pressure spring 23. And the movable contact 4 short-circuits between the battery terminal bolt 9 and the motor terminal bolt 10 by making the pair of fixed contacts 5 conduct and the motor 2 operates in response to electric supply of a battery and generates torque. On the other hand, when the movable iron core 20 is attracted toward the fixed iron core 19 side, the pinion gear 2a is pushed out to the ring gear 2b side of the engine, the torque of the motor 2 is transmitted, and the engine is started since the connector 20a of the movable iron core 20 drives the gearshift (not shown).
After the engine starting, energization of the exciting coil 3 is stopped and the attraction force between the fixed iron core 19 and the movable iron core 20 disappears by OFF operation of the ignition switch. Thus the rod 22 is put back by the reaction force of the return spring 27 and the movable contact 4 is separated from the fixed contact 5 whereby the operation of the motor 2 is suspended.
Since an end on the contact chamber 6a side of the collar 7 (8) abuts against the C-ring 25 of the foot 9a (10a) of the terminal bolt 9 (10), the position of the terminal bolt 9 (10) relative to the collar 7 (8) is regulated and the pressing force in the axial direction of the nut 14 can be received by the locking part. Accordingly, a space is created between the terminal hole 6b and the terminal bolt 9 (10) at a place being closer to the contact chamber 6a side than the C ring 25 side of the terminal bolt 9 (10) is. The airtightness of the contact chamber 6a can be secured by interposing the O-ring 11 in the space in an elastically compressed state. Even if the O-ring 11 with large thickness is used for the improvement of the airtightness of the contact chamber 6a, the contact cover 6 is not expanded in the radial direction in the range in which the cross-section of the O-ring 11 after elastic compression falls within the projected plane in the axial direction of the collar 7 (8).
Since the stress by the pressing force of the nut 14 can be distributed in the axial direction and the radial direction by forming the notch part 7a (8a) which is engaged with the C-ring 25 on the inner surface of the collar 7 (8), so engagement of the collar 7 (8) and the C-ring 25 can be made more reliable.
The complicated forming step of forming a projection in the midway of the terminal bolt 9 (10) is not needed when the C-ring 25 is used in the locking part. The locking part can be prepared by attaching the C-ring 25 to the terminal bolt 9 (10) whereby products can be manufactured easy. Moreover, since the O-ring 11 can be fitted before preparing the C-ring 25 to the terminal bolt 9 (10), the O-ring 11 can be attached easily.
The position in the axial direction of the C-ring 25 relative to the terminal bolt 9 (10) can be regulated by forming the U-shaped groove 9c (10c) in which the C-ring 25 is fitted into the terminal bolt 9 (10). Thereby, strength against the pressing force of the nut 14 can be made high, and the ring terminal 12a (13a) can be more firmly tightened to the terminal bolt 9 (10).
Since the cross-section of both the U-shaped groove 9c (10c) and the notch part has a circular arc which fits to the cross-sectional shape of the C-ring 25 respectively, the C-ring 25 and the terminal bolt 9 (10), the C-ring 25 and collar 7 (8) are surface-contacted respectively, whereby stress produced among them can be distributed.
Since the C-ring 25 is a rounded steel wire, the C-ring can be inserted into the terminal bolt 9 (10) in the state where the diameter of the C-ring 25 is expanded using the elastic deformation of the C-ring 25. When the locking part reaches the groove part, the diameter of the C-ring 25 returns, whereby the C-ring 25 can be certainly fixed to the terminal bolt 9 (10).
If a piano wire is used for the C-ring 25, since the piano wire has a high strength, reliable products can be manufactured. Furthermore, since the piano wire has elasticity, the piano wire has a good attachment performance, and suitable for using as locking part.
By making collars 7 (8) with metal, since metal has high strength, metal can bear the large the pressing force of the nut 14, and also since metal has high creep tolerance, loosening of the nut 14 by aged deterioration can be controlled. Moreover, by forming collar 7 (8) by insert-molding, since collars 7 (8) can be simultaneously formed at the time of forming the contact cover 6, a manufacturing process can be simplified.
In the electromagnetic switch of the first embodiment, the fixed contact 5 is brazed to the head 9a (10a) of the terminal bolt 9 (10), but in the electromagnetic switch of the second embodiment, the fixed contact 5 is serration-fitted to a knurled part 9d (10d) formed at one end at the contact chamber 6a side of the terminal bolt 9 (10) as shown in
With such configuration, since a crevice is made to a serration-fitted part of the fixed contact 5, there is concern that airtightness of the contact chamber 6a may be reduced. However, by inserting the O-ring 11 in the foot 9b (10b) of the terminal bolt 9 (10), and between the knurled part 9d (10d) and the O-ring 25, a sealing member is disposed outside the knurled part 9d (10d) and the airtightness of the contact chamber 6a is secured, whereby the crevice between the fixed contact 5 and the knurled part 9d (10d) does not have a bad influence on the airtightness of the contact chamber 6a.
Other configuration and an effect are the same as that of the first embodiment.
The collar 7 (8) may be provided loosely fitted in the contact cover 6, or pressed into the contact cover 5.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2009-151240 | Jun 2009 | JP | national |
