Electromagnetic switch with fixed magnetic core having disc portion formed of stack of base and balance metal sheets

Abstract

According to the invention, an electromagnetic switch includes a pair of fixed contacts, a movable magnetic core, a magnetic coil, and a fixed magnetic core. The movable magnetic core is configured to be moved by a magnetic attraction, thereby establishing an electrical connection between the fixed contacts. The fixed magnetic core is configured to create the magnetic attraction when the magnetic coil is energized. The fixed magnetic core has a base portion and a disc portion. The base portion is arranged to face the movable magnetic core. The disc portion is fixed to the base portion and formed of a stack of metal sheets including at least one base metal sheet and a balance metal sheet. The balance metal sheet has a thickness that is predetermined to balance a difference between a desired thickness of the disc portion and a total thickness of the at least one base metal sheet.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood more fully from the detailed description given hereinafter and from the accompanying drawings of the preferred embodiments of the invention, which, however, should not be taken to limit the invention to the specific embodiments but are for the purpose of explanation and understanding only.

In the accompanying drawings:

FIG. 1 is a partially cross-sectional view showing the overall configuration of an electromagnetic switch according to the first embodiment of the invention;

FIG. 2 is a cross-sectional view showing an example of a fixed magnetic core according to the first embodiment of the invention;

FIG. 3 is a cross-sectional view showing another example of the fixed magnetic core according to the first embodiment of the invention;

FIG. 4 is a cross-sectional view showing a fixed magnetic core according to the second embodiment of the invention;

FIG. 5 is a cross-sectional view illustrating the abutment between an inner shoulder of a yoke and a disc portion of a fixed magnetic core according to the third embodiment of the invention;

FIG. 6 is a perspective view illustrating a variation of the electromagnetic switch; and

FIG. 7 is an exploded perspective view showing a fixed magnetic core of a prior art electromagnetic switch.

Claims

1. An electromagnetic switch comprising: a pair of fixed contacts;a movable magnetic core configured to be moved by a magnetic attraction, thereby establishing an electrical connection between the fixed contacts;a magnetic coil; anda fixed magnetic core configured to create the magnetic attraction when the magnetic coil is energized, the fixed magnetic core having a base portion and a disc portion, the base portion being arranged to face the movable magnetic core, the disc portion being fixed to the base portion and formed of a stack of metal sheets including at least one base metal sheet and a balance metal sheet, the balance metal sheet having a thickness that is predetermined to balance a difference between a desired thickness of the disc portion and a total thickness of the at least one base metal sheet.

2. The electromagnetic switch as set forth in claim 1, wherein the thickness of the balance metal sheet is different from a thickness of the base metal sheet.

3. The electromagnetic switch as set forth in claim 2, wherein the base portion of the fixed magnetic core has a body facing the movable magnetic core and a boss protruding from the body in an opposite direction to the movable magnetic core, each of the metal sheets has a center through-hole in which the boss of the base portion is press-fitted,the balance metal sheet is arranged farthest from the movable magnetic core among the metal sheets, andthe thickness of the balance metal sheet is greater than the thickness of the base metal sheet.

4. The electromagnetic switch as set forth in claim 2, further comprising a yoke that accommodates therein the magnetic coil and the fixed magnetic core and has formed therein an inner shoulder by which the fixed magnetic core is positioned in the yoke, wherein, among the metal sheets, only the balance metal sheet abuts the inner shoulder of the yoke, andthe thickness of the balance metal sheet is less than the thickness of the base metal sheet.

5. The electromagnetic switch as set forth in claim 1, wherein one of the metal sheets, which is arranged farthest from the movable magnetic core among the metal sheets, is made of steel and has, on an opposite side to the movable magnetic core, a coated surface to which an earth terminal of the magnetic coil is joined by one of welding and soldering.