Electricity: magnetically operated switches – magnets – and electr – Electromagnetically actuated switches – Multiple contact type
Reexamination Certificate
2000-07-28
2001-05-08
Barrera, Ray (Department: 2832)
Electricity: magnetically operated switches, magnets, and electr
Electromagnetically actuated switches
Multiple contact type
C335S127000, C335S156000
Reexamination Certificate
active
06229416
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magnetic switch for a starter used in an internal combustion engine, and in particular, relates to an improvement in a structure of a magnetic switch for a starter including an electromagnet having a hollow cylindrical coil which controls the current supply between a battery and a starter motor.
2. Conventional Art
As an example of conventional structures of magnetic switches for starters, U.S. Pat. No. 5,256,992 discloses a magnetic switch in which a rectangular plate shaped movable contact is disposed on a movable control rod between an annular collar shaped head at the end thereof and a helical spring arranged around the rod, while interposing at the respective faces of the plate shaped movable contact a pair of an insulative washer and an insulative bush having a protrusion, and the other end of the helical spring is supported by a guide sleeve fixed to the other end of the rod.
Further, U.S. Pat. No. 5,757,256 discloses another example in which a rectangular plate shaped movable contact is disposed on a presumably insulative movable control rod between a constant spring and a metal washer fixed axially on the rod against a tapered shoulder thereof by a clawed metal washer at the axial end of the control rod, and the other end of the constant spring is supported by another shoulder formed integrally on the control rod.
Still further, JP-A-4-337223(1992), JP-A-
07-253072
(1995) and JP-A-11-30169(1999) discloses still other examples in which a rectangular plate shaped movable contact is disposed on an electrically conductive movable shaft between a movable contact holding member fixed at an end thereof and a contact pushing spring, while interposing at the respective faces of the plate shaped movable contact a pair of an insulative washer and an insulative bush having a protrusion for insulating the movable contact from the movable shaft, and the other end of the contact pushing spring is supported by an annular collar formed integrally on the movable shaft.
Further, in the above examples an inner stationary core forming a magnetic flux passage together with a casing thereof for a hollow cylindrical coil is usually formed through cold forging to have a cylindrical protrusion so as to secure the hollow cylindrical coil at the circumference thereof together with the casing and to permit axial movement of the movable rod or shaft of non-magnetic material, therefore, an elastic member such as a leaf spring is interposed between the side face of the casing and the hollow cylindrical coil so as to prevent vibration of the hollow cylindrical coil with respect to the casing.
With the structure including the fitting member secured to the shaft and/or shaft end caulking and for receiving an impact force of the plate shaped movable contact which is caused when recovering compressed distance of the contact pressing spring corresponding to over travelling of the rod immediately after being released from activation or deenergization of the magnetic switches for the starters as has been explained above, it was difficult to adjust the grip strength of the fitting member and the caulking strength at the shaft top end which can endure the repeating impact force from the plate shaped movable contact as well as it took time for the adjustment. On the other hand, the structure which receives the impact force with the collar formed integral with the shaft satisfies a required mechanical strength, however, since a spring stopper has to be provided at he remote side of the contact pressing spring from he movable contact along the shaft, while interposing intermediate members at respective faces of the movable contact plate, the total length of the shaft carrying the movable contact is prolonged as well as the diameter of the shaft receiving through hole in the inner stationary core cylindrical protrusion has to be enlarged which reduces the cross sectional area of the magnetic flux passage circuit in the stationary magnetic core, or otherwise enlarges the radial size of the stationary magnetic core. Moreover, in the conventional structure, in order to fixedly secure the hollow cylindrical coil in the casing together with the inner stationary core, such as a leaf spring has to be interposed between the hollow cylindrical coil and the side face of the casing, which causes an increase of parts number and assembly manhour to increase the manufacturing cost thereof.
SUMMARY OF THE INVENTION.
An object of the present invention is to provide a highly reliable magnetic switch for a starter used in an internal combustion engine of which structure is simplified and of which size, parts number, assembly manhour as well as manufacturing cost are reduced.
According to the present invention, a movable contact plate is directly sandwiched and held by a collar formed integral with a shaft and a contact pressing spring, an impact force of the movable contact plate caused by the contact pressing spring when the compressed amount of the contact pressing spring corresponding to the over travelling distance after being released from the activation of the magnetic switch is received by a collar formed integral with the shaft, and a cylindrical portion of an insulative spring stopper member is inserted along the movable shaft inside the contact pressing coil spring in concentric and overlapping manner therewith, in other words, in coaxial and overlapping manner therewith. When the shaft having the integrally formed collar which receives and stops the movable contact plate is made of an insulative material, the movable contact plate and the contact pressing coil spring are simply assembled together only with the insulative spring stopper member having the cylindrical portion which is to be inserted inside the contact pressing coil spring along the shaft, further, when the shaft having the integrally formed collar which receives and stops the movable contact plate is made of an electrically conductive material, the movable contact plate and the contact pressing coil spring are also easily assembled together with the insulative spring stopper member and a set of insulative washers (or bushes). Still further, a hollow cylindrical coil is sandwiched and held in both axial and radial directions by the side plate of the casing and the side plate stationary core having a tapered protrusion which is formed by a sheet metal pressing of simple manufacturing processes so as to constitute a unitary body of the hollow cylindrical coil and the casing.
With the above structure, even if the degrees of the parts accuracy and of the strength adjustment of the assembly are reduced, a predetermined strength necessary for enduring the impact force due to the contact pressing coil spring can easily be ensured with the collar formed integral with the shaft, further, since the contact pressing coil spring and the cylindrical portion of the insulative spring stopper member are disposed in concentric and overlapping manner along the shaft, the total length of the shaft as well as the outer diameter of magnetic core formed by the casing and the inner stationary core are reduced, thereby, a necessary cross sectional area for the magnetic flux passage circuit can be realized with a small size magnetic core. Further, since the hollow cylindrical coil is firmly secured in the casing by the tapered protrusion outer circumference of the inner stationary core without using parts such as leaf springs within the casing in the axial and radial directions thereof, a possible movement of the hollow cylindrical coil with respect to the casing is substantially suppressed to thereby endure a possible large vibration.
REFERENCES:
patent: 4251788 (1981-02-01), Barthruff et al.
patent: 4801909 (1989-01-01), Fasola
patent: 5256992 (1993-10-01), Fasola et al.
patent: 5757256 (1998-05-01), Vilou
patent: 5973581 (1999-10-01), Jacquin et al.
patent: 4-337223 (1992-11-01), None
patent: 7-253072 (1995-03-01), None
patent: 11-030169 (1999-02-01), None
Ebihara Koohei
Tokita Tamotsu
Barrera Ray
Evenson, McKeown, Edwards & Lenahan P.L.L.C.
Hitachi , Ltd.
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