Electromagnetic switch with enhanced stability in operation

• US 8,305,169 B2
• Filed: 12/08/2010
• Issued: 11/06/2012
• Est. Priority Date: 12/11/2009
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Suzuki, Yoshiaki, Murata, Mitsuhiro
• Primary Examiner(s): Enad, Elvin G
• Assistant Examiner(s): Talpalatski, Alexander
• Application Number:
  US12/963,037
• Publication Number:
  US 20110140813A1
• Time in Patent Office: 699 Days
• Field of Search: 335/78, 335/126, 335/131
• US Class Current: 335/126
• CPC Class Codes: F02N 11/087 Details of the switching means in starting circuits, e.g. relays or electronic switches
• CPC Class Codes: F02N 11/10 Safety devices F02N11/08 takes precedence
• CPC Class Codes: F02N 2011/0892 Two coils being used in the starting circuit, e.g. in two windings in the starting relay or two field windings in the starter
• CPC Class Codes: H01H 51/065 Relays having a pair of normally open contacts rigidly fixed to a magnetic core movable along the axis of a solenoid, e.g. relays for starting automobiles details H01H50/20

Abstract

A normally-closed electromagnetic relay which may be used in controlling a supply of electric current to an automotive engine starter. The electromagnetic relay is equipped with a resistor and a shirt circuit. The short circuit is created by closing of relay contacts when a relay coil is energized to establish an electric connection between ends of the resistor to supply the current from a battery to an electric motor without flowing through the resistor and opened by opening of the relay contacts when the relay coil is deenergized to supply the electric current from the battery to the electric motor through the resistor. If a motor drive signal line leading to the electromagnetic relay is disconnected when the relay coil is kept energized, it will cause the short circuit to be established to ensure the supply of current to the motor, which also avoids the melting down of the resistor.

Claims

1. A normally-closed electromagnetic relay comprising:

a hollow case which has an end extending substantially perpendicular to an axial direction thereof to define a bottom, the bottom having a radially central portion extending outwardly of the hollow case in the axial direction to define a hollow protrusion;

a resistor to be connected electrically at ends thereof to a motor circuit to control a starting current supplied from a battery to an electric motor when it is required to start the electric motor;

a relay coil disposed inside the hollow case, the relay coil producing magnetic attraction when energized;

a movable core having a first and a second end opposed to each other in an axial direction thereof in which the movable core is to be moved by the magnetic attraction, as produced by the relay coil, along an inner periphery of the relay coil with the first end being disposed inside the hollow protrusion of the case;

relay contacts which are to be opened or closed selectively by movement of the movable core when the relay coil is energized or deenergized; and

a short circuit which is created by closing of the relay contacts when the relay coil is deenergized to establish an electric connection between the ends of the resistor to supply an electric current from the battery to the electric motor without flowing through the resistor and opened by opening of the relay contacts when the relay coil is energized to supply the electric current from the battery to the electric motor through the resistor.

2. A normally-closed electromagnetic relay as set forth in claim 1, further comprising a stationary core disposed adjacent the second end of the movable core, the stationary core being magnetized when the relay coil is energized to produce the magnetic attraction to attract the movable core, and wherein a length of a portion of the movable core which is disposed inside the hollow protrusion is set greater than an interval kept between the movable core and the stationary core when the relay coil is deenergized.

3. A normally-closed electromagnetic relay as set forth in claim 1, further comprising a hollow resinous bobbin around of which the relay coil is wound and a thin-wall hollow cylinder formed integrally with the bobbin, and wherein the thin-wall hollow cylinder is disposed between a portion of an outer periphery of the movable core disposed inside the hollow protrusion and an inner periphery of the hollow protrusion, the thin-wall hollow cylinder having substantially the same inner diameter as the hollow protrusion to have a common cylindrical inner wall extending without any irregularities to define the outer periphery of the movable core and the inner periphery of the hollow protrusion.

4. A normally-closed electromagnetic relay as set forth in claim 1, wherein the hollow case has a main body with a bottom which is formed to be separate from the hollow protrusion, and wherein the hollow protrusion is joined detachably to the bottom of the main body of the hollow case.

5. A normally-closed electromagnetic relay as set forth in claim 1, further comprising a non-magnetic spacer disposed between an inner bottom surface of the hollow protrusion and the movable core.

6. A normally-closed electromagnetic relay as set forth in claim 1, further comprising a bracket for use in mounting the electromagnetic relay in a vehicle, the bracket being disposed outside the hollow protrusion and fixed on the bottom of the hollow case, and wherein the bracket has a thickness in an axial direction of the electromagnetic relay, the thickness being substantially identical with or greater than a height of the hollow protrusion which projects from a major body of the relay case.

7. A normally-closed electromagnetic relay as set forth in claim 2, further comprising (a) a bulkhead which is located remote from the bottom of the relay case on an opposite side of the relay coil and formed one of integrally with and separately from the stationary core, (b) an insulating cover which closes an opening formed in an end of the hollow case which is opposite the bottom and is secured to the hollow case, (c) a first external terminal which is secured to the insulating cover and connected to a high-potential side of the motor circuit, (d) a second external terminal which is secured to the insulating cover and connected to a low-potential side of the motor circuit, (e) a first fixed contact which is disposed inside the insulating cover and connected electrically and mechanically to the first external terminal, (f) a second fixed contact which is disposed inside the insulating cover and connected electrically and mechanically to the second external terminal, (g) a movable contact which is disposed remote from the bulkhead on an opposite side of the first and second fixed contacts and to be moved following movement of the movable core to establish and block an electric connection between the first and second fixed contacts, selectively, and (h) a shaft which, when the relay coil is energized to move the movable core to the stationary core, transmit movement of the movable core to the movable contact, and

wherein the resistor is disposed inside the insulating cover and connected at one of the ends thereof to the first external terminal and at the other end to the second external terminal, and

wherein when the relay coil is energized, the movable contact is moved away from the first and second fixed contacts to open the relay contacts, while when the relay coil is deenergized, the movable contact is moved into abutment with the first and second fixed contacts to close the relay contacts.

8. A normally-closed electromagnetic relay as set forth in claim 5, wherein the spacer has elasticity.

9. A normally-closed electromagnetic relay as set forth in claim 7, wherein surfaces of the first and second fixed contacts and the movable contact which are to be placed in contact with each other have irregularities.

10. A normally-closed electromagnetic relay as set forth in claim 7, wherein the bulkhead and the stationary core constitute a magnetic path component which has formed in a radially central portion thereof a hole which extends in an axial direction of the magnetic path component and through which a resinous hollow guide cylinder is disposed, and wherein the shaft is made of an insulating material separate from the movable core and to be moved inside the hollow guide cylinder following the movement of the movable core.

11. A normally-closed electromagnetic relay as set forth in claim 8, further comprising a return spring which works to urge the movable core away from the stationary core, and wherein the shaft has formed on an end thereof facing the movable core a flange which extends radially outwardly of the shaft, the flange being exerted by pressure, as produced by the return spring, to be brought into constant abutment with the movable core.

12. A normally-closed electromagnetic relay as set forth in claim 7, wherein each of the first and second external terminals is provided by a bolt with an external thread and secured to the cover with the external thread being exposed outside the cover.

13. A normally-closed electromagnetic relay as set forth in claim 1, wherein the movable core has recesses formed in radially central portions of ends opposed to each other in an axial direction thereof to have an H-shape in longitudinal cross section extending in the axial direction of the movable core.

14. A normally-closed electromagnetic relay comprising:

a hollow case which has ends opposed to each other in an axial direction of the hollow case, one of the ends defining a bottom, the other end having an opening;

a resistor to be connected electrically at ends thereof to a motor circuit to control a starting current supplied from a battery to an electric motor when it is required to start the electric motor;

a relay coil disposed inside the hollow case, the relay coil producing magnetic attraction when energized;

a movable core which is to be moved by the magnetic attraction, as produced by the relay coil, along an inner periphery of the relay coil;

relay contacts which are to be opened or closed selectively by movement of the movable core when the relay coil is energized or deenergized;

a short circuit which is created by closing of the relay contacts when the relay coil is deenergized to establish an electric connection between the ends of the resistor to supply an electric current from the battery to the electric motor without flowing through the resistor and opened by opening of the relay contacts when the relay coil is energized to supply the electric current from the battery to the electric motor through the resistor;

an annular magnetic plate disposed between the bottom of the relay case and an end of the relay coil to create a magnetic path between the hollow case and the movable core;

a bulkhead which is located remote from the magnetic plate on an opposite side of the relay coil to create a magnetic path extending radially thereof;

a stationary core which is formed one of integrally with and separately from the bulkhead and develops a magnetic path continuing to the magnetic path, as created by the bulkhead, the stationary core being so disposed as to face the movable core in an axial direction thereof;

an insulating cover which closes the opening of the hollow case and is secured to the hollow case;

a first external terminal which is secured to the insulating cover and connected to a high-potential side of the motor circuit;

a second external terminal which is secured to the insulating cover and connected to a low-potential side of the motor circuit;

a first fixed contact which is disposed inside the insulating cover and connected electrically and mechanically to the first external terminal;

a second fixed contact which is disposed inside the insulating cover and connected electrically and mechanically to the second external terminal;

a movable contact which is disposed remote from the bulkhead on an opposite side of the first and second fixed contacts and to be moved following movement of the movable core to establish and block an electric connection between the first and second fixed contacts, selectively; and

a shaft which, when the relay coil is energized to move the movable core to the stationary core, transmit movement of the movable core to the movable contact, and

wherein the resistor is disposed inside the insulating cover and connected at one of the ends thereof to the first external terminal and at the other end to the second external terminal, and

wherein when the relay coil is energized, the movable contact is moved away from the first and second fixed contacts to open the relay contacts, while when the relay coil is deenergized, the movable contact is moved into abutment with the first and second fixed contacts to close the relay contacts.

15. A normally-closed electromagnetic relay as set forth in claim 14, further comprising a non-magnetic spacer disposed between the bottom of the hollow case and the movable core.

16. A normally-closed electromagnetic relay as set forth in claim 15, wherein the spacer has elasticity.

17. A normally-closed electromagnetic relay as set forth in claim 14, wherein surfaces of the first and second fixed contacts and the movable contact which are to be placed in contact with each other have irregularities.

18. A normally-closed electromagnetic relay as set forth in claim 14, wherein the bulkhead and the stationary core constitute a magnetic path component which has formed in a radially central portion thereof a hole which extends in an axial direction of the magnetic path component and through which a resinous hollow guide cylinder is disposed, and wherein the shaft is made of an insulating material separate from the movable core and to be moved inside the hollow guide cylinder following the movement of the movable core.

19. A normally-closed electromagnetic relay as set forth in claim 16, further comprising a return spring which works to urge the movable core away from the stationary core, and wherein the shaft has formed on an end thereof facing the movable core a flange which extends radially outwardly of the shaft, the flange being exerted by pressure, as produced by the return spring, to be brought into constant abutment with the movable core.

20. A normally-closed electromagnetic relay as set forth in claim 14, wherein each of the first and second external terminals is provided by a bolt with an external thread and secured to the cover with the external thread being exposed outside the cover.

21. A normally-closed electromagnetic relay as set forth in claim 14, wherein the movable core has recesses formed in radially central portions of ends opposed to each other in an axial direction thereof to have an H-shape in longitudinal cross section extending in the axial direction of the movable core.