Prime-mover dynamo plants – Electric control – Electric-starting motor
Reexamination Certificate
2000-12-26
2002-05-21
Ramirez, Nestor (Department: 2834)
Prime-mover dynamo plants
Electric control
Electric-starting motor
C290S031000, C290S046000, C074S00700R
Reexamination Certificate
active
06392311
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
This invention pertains to a starter generator for an internal combustion engine (an internal combustion engine starting motor and generator apparatus) serving as a starter motor when the internal combustion engine should start and as a generator after the engine starts.
BACKGROUND OF THE INVENTION
There has been provided in an internal combustion engine a generator for driving various car electric devices. A conventional generator for an internal combustion engine comprises a flywheel magnet rotor mounted on a crankshaft of the engine and a stator having armature coils wound on an armature core. The stator is provided with various generator coils for driving various car electric devices necessary for driving the engine such as an ignition system for the internal combustion engine, a fuel injection apparatus and so on and a generator coil for supplying an electric power for driving arbitrarily driven loads such as lamp loads, a battery and so on.
A ring gear is secured onto an outer peripheral wall of the flywheel of the flywheel magnet rotor and a starter motor (an engine starting motor) is mounted on an engine case. A pinion gear is mounted on an output shaft of the starter motor. The pinion gear is adapted to be moved in a forward direction when the starter motor is driven and meshed with the ring gear so that the flywheel magnet rotor rotates together with the crankshaft.
Thus, as the magnet rotor rotates, a voltage is induced across the igniting generator coil provided in the stator, which causes the ignition system for the internal combustion engine to ignite the engine so that the engine starts.
Since the conventional internal combustion engine is required to have the starter and the ring gear provided on the outer peripheral face of the flywheel for starting the engine as aforementioned, the engine cannot be avoided from having a complicated construction.
As disclosed in JP58-63085, there has been proposed a starter generator that comprises an electric rotary machine having a rotor mounted on a crankshaft of an internal combustion engine and serving as an electric motor for starting the engine and as a generator after the engine starts.
However, since the starter motor (the engine starting motor) and the battery charging generator have a different winding specification necessary for meeting the characteristics required for the starter motor and the battery charging generator, respectively, the single electric rotary machine cannot be practically used as both of the starter motor and the generator even though it may be established as an idea.
More particularly, since the starter motor is required to produce a high torque when the engine should start, the generator can be also used as the starter motor as long as it should have a smaller winding resistance of the armature coils which is required for momentarily passing a larger current when the engine should start. This requires a smaller number of turns of the armature coils and a thicker diameter of the coil conductor for using the generator as the starter motor.
Since the generator is required to charge the battery with the output thereof after the engine starts, the number of turns of the armature coils should be so set that the generation output thereof around the idling revolution of the engine is substantially equal to the battery voltage.
However, with the generator for the internal combustion engine constructed in this manner, the battery is possibly damaged because the charging current for the battery is too large when the engine rotates at middle or high speed.
It will be considered that in order to prevent the battery from being over-charged a regulator is provided for shorting the output of the generator when the voltage applied across the battery gets excessive. However, with the generator having the winding resistance set to be smaller as aforementioned and the short-circuit type regulator used in combination, electronic parts for the regulator will be possibly broken due to the excessive short current.
As disclosed in JUM (Utility Model) 3-91064, there has been well known a starter generator that comprises a stator having a commutator connected to armature coils and a magnet rotor having a brush engaging the commutator in a sliding manner. The starter generator is operated as a DC motor with a brush while engaging the brush with the commutator when the engine should start and as a generator by moving the brush away from the commutator by a centrifugal clutch mechanism after the engine starts.
Such a starter generator can produce an enough starting torque by supplying the drive current to all the armature coils of the stator when the engine should start and can prevent the battery from being over-charged by supplying the output taken out from some of the armature coils through a rectifier after the engine starts.
However, since the starter generator is required to have the centrifugal clutch mechanism provided for moving the brush away from the commutator after the engine starts, the construction of the starter generator is complicated, which causes the cost to be inevitably expensive. Also, the brush and the commutator are consumed due to the engagement of the brush with the commutator when the engine should start and therefore the maintenance will be required.
SUMMARY OF THE INVENTION
Accordingly, it is a principal object of the invention to provide a starter generator for an internal combustion engine adapted to produce a high torque required to start the internal combustion engine when it should be used as a starter motor and to restrain an output thereof when it should be used as a generator so that the battery is prevented from being over-charged.
The present invention pertains to a starter generator serving as a starter motor when an internal combustion engine should start and as a generator for generating an output for charging a battery after the engine starts.
The starter generator according to the invention comprises a magnet rotor mounted on a crankshaft of the internal combustion engine, a stator, a rotor magnetic pole sensor for detecting whether the magnetic pole of the magnet rotor passing a particular position on the side of the stator is a N pole or a S pole, first through fourth switch circuits connected in parallel to both ends of the battery and a switch controller to control switch elements of the first through fourth switch circuits in accordance with the output of the rotor magnetic pole sensor.
More particularly, the magnet rotor is so constructed as to have a filed system of n poles (n is an even number of more than 4) disposed at an equal angle distance.
The stator comprises m(m=n×&agr;) coils (&agr; is an integral number of more than 1) wound on an armature core with a winding direction identical to each other so that they are placed in order of a rotational direction of the magnet rotor and connected in series in order to each other so that they form a closed circuit and includes 1st through mth tap terminals led out from connection points between terminating ends of the 1st through mth coils and beginning ends of the coils adjacent to the 1st through mth coils so that the alternate tap terminals of the same phase among the tap terminals provide a first group of the tap terminals and the remaining alternate tap terminals of the phase reverse to those of the first group form a second group of the tap terminals.
The respective coils may be formed by winding electric conductors having a relatively larger cross section in order to pass a larger current through the coils when the internal combustion engine should start. The respective coils may have a number of turns so set that the stator can generate a voltage substantially equal to a battery voltage when the engine rotates at an idling revolution or more or less after the engine starts.
The rotor magnetic pole sensor serves to detect whether the magnetic pole of the magnet rotor passing a detection position set between particular two adjacent coils selected among the 1st through mth
Inaba Yutaka
Muramatsu Shuichi
Nakagawa Masanori
Shimazaki Mitsuyoshi
Cuevas Pedro J.
Kokusan Denki Co. Ltd.
Pearne & Gordon LLP
Ramirez Nestor
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