Prime-mover dynamo plants – Electric control – Electric-starting motor
Patent
1996-03-01
1998-06-02
Dougherty, Thomas M.
Prime-mover dynamo plants
Electric control
Electric-starting motor
290 48, F02N 1100, H02P 904
Patent
active
057604851
DESCRIPTION:
BRIEF SUMMARY
This application claims benefit of international application PCT/JP94 02166, filed Dec. 19, 1994.
TECHNICAL FIELD
The present invention relates to a starter having a speed reduction gear mechanism for starting an engine.
BACKGROUND ART
In the prior art, as disclosed in Japanese Patent Laid-Open No. 238171/1990, there has been provided a starter having a planetary reduction gear mechanism, which has its motor small-sized by setting the planetary speed reduction ratio to 5.45 at the maximum.
In the aforementioned construction of the prior art, however, only the size reduction of a motor is intended to achieve by increasing the planetary reduction ratio, but no consideration has been taken into the size reduction of the starter in its entirety. Specifically, as the reduction gear ratio increases, the tooth number of an internal gear of the planetary reduction gear mechanism increases to enlarge the external diameter of the internal gear. As a result, the planetary reduction gear mechanism has its volume increased in proportion to the square of the external diameter of the internal gear. Thus, there arises a difficulty that the reduction gear mechanism is large-sized although the motor can be small-sized by increasing the gear ratio.
As a result of the increase in the reduction gear ratio, moreover, the rotational energy E, as expressed by the following equation, of an armature of the motor will increase in proportion to the square of the rotating angular velocity (i.e., R.P.M.) w with respect to an inertial moment J of the armature: the armature may increase to cause a meshing impact at the start of the starter or a serious impact torque at the re-meshing time during the inertial rotation of the starter thereby to break the torque transmitting parts of the starter. Thus, the reduction gear ratio increasing means is exemplified by the method, in which the gear specification M (or module) is decreased to increase the reduction gear ratio while suppressing the external diameter of an internal gear, but a problem of the tooth strength is left unsolved. Another method of increasing the reduction gear ratio by decreasing the tooth number of a sun gear has to make the diameter (as will be called the "deddendum diameter of the sun gear") of a bearing adjacent to the sun gear smaller than that of the prior art, thus leaving the strength problem unsolved.
According to the increase in the reduction gear ratio, moreover, the heat radiation from the surface of the starter motor decreases. This is found from the fact that the heat radiation is proportional to the area m.sup.2, as generally expressed by the following equation:
The present invention has been conceived in view of the background thus far described and has an object to provide a starter which can be small-sized in its entirety by clarifying the optimum range of the reduction gear ratio.
DISCLOSURE OF THE INVENTION
In order to achieve the above-specified object, according to the present invention, there is provided a starter comprising: a starter motor including an armature core having an armature coil wound thereon and an armature shaft for holding the armature core rotatably; a drive shaft having a pinion meshing with a ring gear of an engine; and one reduction gear mechanism interposed between the drive shaft and the armature shaft of the starter motor for reducing the rotation of the armature shaft to transmit the reduced rotation to the drive shaft, wherein the reduction gear mechanism has a reduction ratio of 6:1 to 10:1.
In this construction, the reduction ratio of the reduction gear mechanism is set within such an optimum range of 6 to 10 as viewed from the volume of the motor and the reduction gear mechanism of the starter, so that the starter can be most effectively reduced in size and weight.
In addition to the aforementioned construction, the armature coil includes: upper-layer and lower-layer coil members fitted in the slots of the armature core; first connection portions connected to one end of the lower-layer coil member and extending gen
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patent: 4268772 (1981-05-01), Workman
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patent: 4674344 (1987-06-01), Kazino et al.
patent: 4819975 (1989-04-01), Morishita et al.
patent: 4970908 (1990-11-01), Isozumi et al.
patent: 5130596 (1992-07-01), Umeki
patent: 5508566 (1996-04-01), Nagao et al.
Hayashi Nobuyuki
Kajino Sadayoshi
Ohmi Masanori
Shiga Tsutomu
Dougherty Thomas M.
Nippondenso Co. Ltd.
Ponomarenko Nicholas
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