JPS617525A - Magnetic switch for starter - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a magnetic switch for a starter, and more particularly to a magnetic switch for a starter that prevents its contacts from being burnt out due to exposure to high temperatures due to arcing, etc. .

[Background of the invention]

The conventional magnetic switch for starters was developed in Japanese Patent Application Laid-Open No. 55
117074, an insulating member is inserted between a movable contact and a contact push spring, and a contact return spring is arranged between a movable contact shaft and an insulating case.

However, with this conventional structure, when the contact part is exposed to high heat due to arcing etc. and the insulating material melts,
The movable contact becomes unstable, and there is no guarantee that the movable contact and the fixed contact will be reliably separated, so there is a risk that the switch itself will be burnt out due to being left energized.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic switch for a starter that can reliably cut off current when the temperature of the contact portion increases abnormally due to occurrence of an arc or the like.

[Summary of the invention]

The present invention uses a thermoplastic material for the insulating member that insulates the movable contact, and when an abnormal temperature rise occurs due to an arc, etc., this thermoplastic material melts, ensuring that the contact is opened and the current is interrupted. It is characterized by its structure.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. In FIG. 1, an armature 1 and a rotating shaft 3 of a DC motor 2 are integrally constructed.

Arranged on the rotating shaft 3 are a pinion 5 that engages with an engine ring gear 4 that is directly connected to an engine (not shown) by moving in the axial direction, a one-way clutch 6 that is integrally formed with the pinion 5, and a sleeve 7. has been done. sleeve 7
A sleeve washer 8 is fixed to the outer periphery of the magnetic switch 9, one end of which is engaged with the protrusion 11 of the plunger 10 of the magnetic switch 9, and the other end 15 of the shift lever 14, which is in contact with the housing 12 and has a rotational fulcrum 13, is held in place. Ru. The torsion spring 16 presses the rotation fulcrum 13 of the shift lever 14 against the housing 12. The plunger 19 of the magnetic switch 9 forms a magnetic circuit with the case 17 and the side plate 19 that integrally includes the fixed boss 18, and generates magnetic flux by energizing the coil 20. A recess 22 is installed in the center of the plunger 10 to accommodate the movable contact shaft 21 in a loose state, and a return spring 24 is provided at the bottom 23 of the recess 22 between the movable contact shaft 21 and the fixed boss 18.
A collar portion 25 integrally formed with the movable contact shaft 21 is in contact with the movable contact shaft 21 so as to hold the movable contact shaft 21 .

FIG. 2 is an enlarged view of the movable contact 26 and the five surrounding parts that are characteristic of the present invention. The movable contact 26 is insulated from the movable contact shaft 21 by a thermoplastic insulating bush 27 and a thermosetting insulating bush 28 The outer diameter of a portion 281 of the bushing 28 that is in contact with the movable contact shaft 21 is set larger than the outer diameter of a portion 271 of the bushing 27 that is also in contact with the shaft 21. A contact pressing spring 31 having an outer diameter smaller than the inner diameter of the movable contact 26 is arranged on the movable contact shaft 21 between the retaining ring 29 and the step 30 of the movable contact shaft 21 . The elastic body 32 installed between the movable contact 26 and the thermosetting insulating bushing 28 has a load smaller than the load of the contact push spring 31 and has an inner diameter larger than the outer diameter of the contact push spring 31 .

Returning to FIG. 1, the fixed contact 33 facing the movable contact 26
．． 34 is fixed to an insulating case 35, the fixed contact 33 is connected to a power source 37 via a bolt 36, and the fixed contact 34 is connected to the DC motor 2 via a bolt 38. The switch 39 connects the power supply 37 and the coil 2 of the magnetic switch 9.
Continue between 0 and 0.

In the above configuration, when the switch 39 is turned on, the coil 20 of the magnetic switch 9 is energized by the power supply 37, and a magnetic flux is generated between the case 17 of the magnetic circuit, the side plate 19, the fixed boss 18, and the plunger 10, and the plunger 1
0 moves to the left so as to fill the gap with the fixed boss 18. As the plunger 10 moves, the movable contact 26 moves to the left via the movable contact shaft 21, and the fixed contact 33. '34
come into contact with. On the other hand, the shift lever 14 engaged with the protrusion 11 of the plunger 10 rotates around the rotational fulcrum 13,
The sleeve washer 8 held on the other end 15 of the shift lever 14 moves the pinion 5 to the right via the sleeve 7 and the one-way clutch 6, so that it meshes with the engine ring gear 4. When the pinion 5 and the engine ring gear 4 mesh, the movable contact 26 also contacts the fixed contacts 33 and 34, so the DC motor 2 is connected to the power supply 37 by the bolt 36, the fixed contact 33, the movable contact 26, the fixed contact 34, and the bolt 37. Electricity is applied through the armature 1, and the armature 1 rotates.

As the armature 1 rotates, the pinion 5 rotates via the rotating shaft 3, sleeve 7, and one-way clutch 6, turning the engine ring gear 4 and starting the engine. While the engine is being rotated by the rotational force of the armature 1, a large current is flowing through the fixed contact 33, movable contact 26, and fixed contact 34 from the power supply 37, but for some reason an arc occurs in the contact and the movable contact 26 When exposed to high heat, the thermoplastic insulation bushing 2
7 melts, and the movable contact 26 becomes the second contact due to the repulsive force of the elastic body 32.
Pushed to the right in the figure, contact with the fixed contacts 33 and 34 is forcibly broken, and arc generation is stopped.

As is clear from the above embodiments, according to the present invention, even if the contact portion receives an abnormal temperature rise due to occurrence of an arc,
When the temperature exceeds a certain temperature, the thermoplastic insulating bushing acts as a fuse and melts, forcibly cutting off the large current at the contact, which has the effect of completely preventing burnout of the insulators around the contact.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing one embodiment of the present invention, and FIG. 2 is an enlarged sectional view of the contact portion of FIG. 1.

Claims (1)

[Claims] 1. In magnetic switches for starters, which supply current to the starter by the movable contact attached to the movable contact shaft contacting the fixed contact when the coil is energized, thermoplastic is used to connect the movable contact shaft and the movable contact. In normal conditions, the movable contact is pressed against the fixed contact by pressing the thermoplastic material with a contact pressing spring, and when the thermoplastic material melts due to high temperature, the contact pressing spring presses the thermoplastic material. A magnetic switch for a starter, characterized in that an elastic body attached to act in the opposite direction presses a movable contact in a direction away from a fixed contact.