JPH0822760A - Magnet switch for starter - Google Patents

Abstract

PURPOSE:To protect a contact case from damage by a fire by checking the heat from directly conducting to the contact case even if a fixed contact point is put at an abnormal temperature. CONSTITUTION:A fixed contact point 6 penetratingly passes a side surface of an insulated contact case 14, and is fixed by sandwiching the contact case 14, and a heat resistant insulating spacer 16 having a heat resistant temperature higher than a melting point of the fixed contact point 6 is arranged at least between the penetrating part and the fixed contact point 6, and the fixed contact is indirectly held by the contact case 14. Therefore, since the conical heat resistant insulating spacer having heat resistance higher than the contact case is arranged between the contact point case and the fixed contact, even if the contact is put at an abnormal temperature, heat can be easily and reliably checked from directly conducting to the contact case, and the contact case can be reliably protected from damage by a fire.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a starter magnet switch, and more particularly to a starter magnet switch having a heat resistant structure suitable for a starter for starting an internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, a technique in which a fixed contact is fixed to an insulated contact case via another heat-resistant member and the contact case has a heat-resistant structure is known, for example, from Japanese Utility Model Publication No. 55-5407.
This publication describes that a contact case member that holds a fixed contact is formed of an insulating member that withstands a temperature higher than the melting point of the fixed contact base metal.

[0003]

In the above-mentioned prior art, a ceramic heat-resistant insulating spacer is arranged only on the fixed contact and the inner end surface of the contact case, and the space between the inner peripheral surface of the contact case and the fixed contact and the fixed contact penetrating portion. The contact case is in contact with the contact case.

However, in a magnet switch for a starter, the contact case is generally made of phenolic resin. Therefore, when the fixed contact has an abnormal temperature, the heat is directly transferred to the contact case, and in some cases, the heat may be transmitted to the contact case. Problems such as burning of the contact case occur. This is because the chattering phenomenon occurs in the range of 0.1 to 0.3 ms, especially when the movable contact has play against the movable contact moving shaft, and when the energizing current becomes 800 (A) or more, the fixed contact becomes the center. It has been confirmed that the ambient temperature rises above 1000 ° C.

An object of the present invention is to protect the contact case from burning by preventing the heat from directly transferring to the contact case even if the fixed contact has an abnormal temperature.

[0006]

According to the present invention, a suction coil responsive to opening and closing of a starting switch, a movable contact urged by the suction coil to move, and a driving circuit for a starting motor by joining the movable contacts. In the starter magnet switch having a fixed contact that forms a fixed contact, the fixed contact is fixed by penetrating a side surface of the insulating contact case and sandwiching the contact case, and at least the through portion and the A heat-resistant insulating spacer having a heat-resistant temperature higher than the melting point of the fixed contacts is arranged between the fixed contacts, and the fixed contacts are indirectly held by the contact case. It

[0007]

As shown in the figure, the heat-resistant insulating spacer prevents the fixed contact from moving even if an arc occurs at the contact due to abnormal contact (chattering) between the fixed contact and the movable contact, causing the temperature of the fixed contact to rise above 1000 ° C. It blocks heat conduction and prevents high heat from being transferred to the contact case.

Further, since the heat-resistant insulating spacer has a conical shape, the fixed contacts are concentrically arranged only by tightening the fixed contacts, and the airtightness between the parts can be effectively maintained. Further, even if the heat-resistant insulating spacer is a ceramic type, the stress generated in the heat-resistant insulating spacer 16 when the fixed contacts are tightened becomes a compressive stress in both the circumferential direction and the axial direction. Utilizing the characteristics, cracking does not occur even when repeated cooling and heating.

[0009]

Embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 2 shows a drive circuit for a starter using the magnet switch of the present invention. The exciting coil 4 of the starting motor 3 having one end connected to the ground side of the battery 2 via a brush has a magnet at the other end. Switch 5
Is connected to the other end of the battery 2 via the fixed contact 61, the movable contact 7, and the fixed contact 6.

The reference numeral 8 is adapted to press the movable contact 7 toward the fixed contacts 6 and 61 when excited by a suction coil 9 having one end connected to one end of the fixed contact 61 and attracted by a movable plunger. It is configured. The other end of the suction coil 9 is connected to one end of the plunger holding coil 10 and the other end of the battery 2 via a start switch 11.

FIG. 1 shows the structure of the magnet switch 5 which is the subject matter of the present invention. The yoke 12 around which the attraction coil 9 and the holding coil 10 are wound has a hollow central portion, on which the plunger 8 slides. It is movably arranged. An insulating contact case 14 arranged on the end surface of the yoke 12 via an airtight sheet 13 made of rubber or the like is formed in a bowl shape, and is integrally covered and fixed by a metal case 15 covering the outer peripheral portion of the yoke. There is.

In consideration of cost, productivity, etc., the contact case 14 is generally made of epoxy resin or phenol resin having a heat resistant temperature of about 200 ° C., and the fixed contacts 6 and 61 are inserted into the side surface 14a. A conical through hole 14b for arrangement is formed. The through hole 14b is a conical hole that becomes thinner toward the outside, and the small diameter portion has a diameter larger than at least the outer diameter portions of the bolt portions 6a and 61a of the fixed contact. The fixed contacts 6 and 61 are made of a copper-based or iron-based conductive material, and are processed into a T-shaped cross section to form stepped portions 6b and 61b.

Reference numeral 16 denotes a heat-resistant insulating spacer having a conical cylindrical shape,
RBSN material that does not shrink even when sintered or zirconia with high bending strength, and is formed by molding from silica, macor, etc. (generally heat resistant temperature exceeds 5000 ° C), and bolts of fixed contacts 6,61 The conical through hole 14b and the stepped portions 6a and 61b are inserted into the portions 6a and 61a, and the vault portion is tightened by the nut 17.
Between them, it is tightened by the wedge effect and firmly fixed.
The movable contact 7 is made of a disc-shaped conductor and made of the same material as that of the fixed contact, and is arranged in the contact case via a push spring 18 and a return spring 19.

In the above structure, fixed contacts 6 and 6 are generally used.
Although the heat resistant temperature of No. 1 is about 820 ° C., for example, an arc is generated at the contact portion due to abnormal contact (chattering) between the fixed contacts 6 and 61 and the movable contact 7, and the temperature of the fixed contact is 100%.
Even if the temperature rises above 0 ° C, the heat-resistant insulating spacers are arranged between the fixed contacts and the contact case, so that the heat of the fixed contacts 6 and 61 is cut off by the heat-resistant insulating spacers 16 and the contact case 14 receives high heat. To be transmitted.

Further, since the heat-resistant insulating spacer 16 has a conical shape, the fixed contacts are concentrically arranged only by tightening the fixed contacts 6 and 61, and the airtightness between the parts can be effectively maintained. Further, even if the heat-resistant insulating spacer is a ceramic type, the stress generated in the heat-resistant insulating spacer 16 when the fixed contacts are tightened becomes a compressive stress in both the circumferential direction and the axial direction, so that cracking which is a defect of ceramics can be prevented. It can be fully used as a heat-resistant insulating spacer.

[0017]

According to the present invention, since a heat-resistant insulating spacer having a cone shape and higher heat resistance than the contact case is provided between the contact case and the fixed contact, even if the fixed contact has an abnormal temperature, the direct contact case It is possible to easily and reliably prevent heat conduction to the heat resistant insulating spacers, and the heat resistant insulating spacers are in a compressive stress state in both the circumferential and axial directions due to the fastening load of the bolts. It can be protected from burning.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of essential parts of a starter magnet switch showing an embodiment of the present invention.

FIG. 2 is a schematic diagram of a starter using the magnet switch of the present invention.

[Explanation of symbols]

6, 61 ... Fixed contact, 7 ... Movable contact, 14 ... Contact case, 16 ... Heat resistant insulating spacer.

Claims (5)

[Claims] 1. A suction coil responsive to opening and closing of a start switch, a movable contact urged by the suction coil to move, and a fixed contact forming a drive circuit of a starting motor by joining the movable contacts. In the starter magnet switch, the fixed contact is fixed by penetrating a side surface of the insulating contact case and sandwiching the contact case, and the fixed contact is provided at least between the penetrating portion and the fixed contact. A heat-resistant insulating spacer having a heat-resistant temperature higher than the melting point of is arranged,
A magnet switch for a starter, wherein the fixed contact is indirectly held by the contact case. 2. The heat-resistant insulating spacer according to claim 1, wherein the heat-resistant insulating spacer is arranged so as to protrude from an inner end surface of the contact case.
A magnet switch for a starter, which receives a step of a fixed contact. 3. The starter magnet switch according to claim 1 or 2, wherein the heat-resistant insulating spacer is a conical cylinder in the fastening direction of the fixed contacts. 4. The starter magnet according to claim 2, wherein the tip of the conical tubular heat-resistant insulating spacer in the fixed contact tightening direction is arranged in the fixed contact through hole with a tightening margin. switch. 5. The magnet switch for a starter according to claim 1, wherein the heat-resistant insulating spacer is a ceramic material having a heat-resistant temperature of 5000 ° C. or higher.