Prime-mover dynamo plants – Electric-starting motor
Patent
1988-10-04
1990-02-20
Pellinen, A. D.
Prime-mover dynamo plants
Electric-starting motor
74 7A, 335261, F02N 1506
Patent
active
049029045
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a coaxial engine starter and, more particularly, to a coaxial engine starter for use in starting a vehicular engine.
BACKGROUND ART
A conventional engine starter for use in starting up a vehicular engine has been constructed as shown in FIG. 1.
The conventional starter 1 shown in FIG. 1 comprises a d.c. motor 2, an over-running clutch mechanism 4 slidably mounted over an armature rotary shaft 3, a planetary gear speed reduction unit 5 for reducing and transmitting the rotating speed of the armature rotary shaft 2a of the d.c. motor 2 to a clutch outer member 4a of the over-running clutch mechanism 4, and a shift lever 8 engaged at its one end with a plunger rod of a solenoid switch assembly 6 which is disposed on one side of the d.c. motor 2 for slidably moving the over-running clutch assembly 4 and at its the other end with an annular member 7 mounted to the overrunning clutch mechanism 4.
However, the conventional starter 1 needs the shift lever 8 for sliding the over-running clutch mechanism 4 on the output rotary shaft 3, and since the bi-axial arrangement, in which the electromagnetic switch assembly 6 for actuating the shift lever 8 and supplying electric power to the d.c. motor 2 is disposed on the side of the d.c. motor 2, is employed, strict limits are imposed on engine layout during the design of the vehicle.
In order to eliminate the above problem, it has been proposed to position the solenoid switch on one of the axial end portions of the d.c. motor to form the starter into a simple configuration such as an elongated cylinder. According to this proposition, the basic construction is such that the armature rotary shaft is made hollow and the plunger rod of the solenoid switch assembly which has been used to operate the shift lever is elongated to extend through the inner passage of the armature elecromagnetic core to reach the output rotary shaft. The starter having such construction is referred to as a coaxial starter since the armature rotary shaft of the d.c. motor and the rod of the solenoid switch are coaxially aligned.
However, while the above-discussed coaxial starter is a simple elongated cylindrical member, the overall axial length is significant if the solenoid switch assembly is simply attached to the rear end of the d.c. motor. On the other hand, if the solenoid switch assembly is simply reduced in size, it is difficult to maintain the necessasry magnetic attractive force. Therefore, the development of a coaxial starter of the above structure with a shorter overall length has been expected.
DISCLOSURE OF THE INVENTION
It is an object of the present invention is to provide a coaxial engine starter in which the overall axial length is short while an appropriate attractive force is maintained in the solenoid switch assembly.
The coaxial starter of one embodiment of the present invention comprises a solenoid switch assembly disposed on the rear end of an electric motor for generating a rotating force for starting an engine. The solenoid switch assembly comprises a cylindrical excitation coil, a plunger axially slidable within the excitation coil, a front magnetic path section disposed on one end of the excitation coil in opposition to the plunger, a rear magnetic path section disposed around the circumference of the plunger when it is in the return position, a bushing of an iron-system material disposed between the rear magnetic path section and the plunger, and a non-magnetic sleeve disposed side by side relative to the iron-system bushing for guiding the plunger in a moving space from its return position to the position in which the plunger abuts against the front magnetic path section.
According to the coaxial starter of this embodiment, when an electric current flows through the solenoid switch assembly to energize the excitation coil, a magnetic flux flows from the rear magnetic path section to the front magnetic path section through the iron-system bushing and the plunger to generate a magnetic attractive force between the plunger an
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patent: 4707616 (1987-11-01), Ogle et al.
patent: 4760274 (1988-07-01), Isozumi
patent: 4838100 (1989-06-01), Tanaka
Duncanson Jr. W. E.
Mitsubishi Denki & Kabushiki Kaisha
Pellinen A. D.
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