SMALL ENGINE PROVIDED WITH SELF STARTING MOTOR

Abstract: A small engine (10) provided with a self starter motor (24) is suitable for use as a driving means for hand-held or back-carried machines such as cleavers. As the engine is provided with a reduction drive gear (32) loosely inserted over a cylindrical support (34) concentrically provided with a crankshaft (16), and is so constructed that the rotation of the self starter motor (24) is transmitted to the crankshaft (16) via the reduction drive gear (32) and an engagement/disengage­ ment means (44) using centrifugal force, it is possible to improve the durability thereof and to simplify assembly operation.

Description: This invention is related to a small engine provided with a self starting motor, and more particularly to an improvement in a small engine provided with a self starter suitable for use as a device to drive hand-held or back-carried machines, such as cleavers, blowers, or chain saws. As a driving device for hand-held or back-carried machines, such as cleavers, there was developed in the art a small sized engine provided with a self starter engine which is compact and easy-to-handle at the same degree as the conventional type small engines provided with a recoil starter for the benefit of the consumer public. This type of small engine with a self starter is so structured that a reduction drive gear is loosely inserted over a crankshaft via bearings, a pinion of the self starter is engaged with the reduction drive gear, and a rotating body axially mounted on the crankshaft and the reduction drive gear are engaged/disengaged by the centrifugal force in order to effect or release the power transmission. Such small engine as above mentioned, however, is detrimental in that excessive damages occur to the bearings provided between the reduction drive gear and the crankshaft which are constantly rotating when the engine is being driven and that errors in processing or assembly of the crankshaft, the crankcase or the fan casing induce misalignment between the pinion of the motor and the reduction drive gear to result in serious damages. JP-A 61-229970 discloses an engine as outlined in the preamble of claim 1. Said reference is silent on how the reduction drive gear can be positioned and permanently maintained concentrically to the crank shaft. Fig. 1 and Fig.2 are explanatory cross-sectional views showing preferred embodiments of the present invention small engine provided with a self starter engine. Preferred embodiments of the small engine provided with a self starter in accordance with the present invention are now described in detail by referring to the attached drawings. Fig. 1 shows an embodiment of a small engine provided with a self starter in accordance with the present invention wherein a cylindrical support 34 is integrally provided on the outside of a crankcase 14, and the gears 38 of a cylindrical projection 38 provided on a reduction gear 32 and engaging/disengaging cams 40, 40 provided on a fly wheel 58 are engaged/disengaged by the centrifucal force. Fig. 2 shows still another embodiment of this invention small engine provided with a self starter wherein a cylindrical support 34 is integrally provided on the outside of a crankcase 14 placed opposite to an output shaft 22 or the position where a recoil starter is provided in Fig. 1, and gears 38 of the cylindrical support 34 provided on a reduction drive gear 32 and engaging/disengaging cams 40, 40 provided on a rotating plate 60 fixed to an end of a crankshaft 16 are engaged/disengaged by the centrifugal force. In all these embodiments, connection or release of power transmission between the reduction drive gear and the crankshaft can be performed smoothly, and by changing or optimally arranging the components of the engine, the size thereof may be reduced considerably. In the embodiment shown in Fig. 3, mounting/dismounting of the gear case is easily performed so as to simplify maintenance of the starter mechanism and the centrifugal clutch. As mentioned above, the small engine provided with a starter motor in accordance with the present invention not only improves durability thereof with less damages to the bearings as the reduction drive gear is loosely inserted over the cylindrical support provided concentrically with the crankshaft, but also enables precise engagement of the reduction drive gear and the pinion as processing an assembly of the crankshaft, the crankcase and the fan casing become easier and simpler, thereby preventing the damages to the engagement members, etc. as much as possible. The above going description was given in respect of the preferred embodiments of the small engine with a starter in accordance with the present invention, but it should be understood that the present invention is in no way limited to these embodiments, and various changes and modifications in design can be made within the scope of the following claims.

Claims: A small engine (10) provided with a self starter (26) comprising a reduction drive gear (32) provided in a freely rotatable fashion with respect to a crankshaft (16), a pinion (30) of the starter (26) being engaged with said reduction drive gear (32), and a rotator body provided with clutch means (40, 42, 44, 46) being fixedly connected to the crankshaft (16) a cylindrical support (34) over which said reduction drive gear (32) is loosely inserted being provided concentrically to the crankshaft (16), characterized in that said cylindrical support (34) is formed integrally with the crank case (14) and provided on the outer surface thereof. The engine of claim 1, wherein said rotator body provided with said clutch means (40, 42, 44, 46) is formed by the fly wheel (58) of said engine. The engine of claim 1, wherein said rotator body is formed by a plate (60) carrying said clutch means (40, 42, 44, 46).

Inventors: Yokoyama, Yukio
Applicants: TANAKA KOGYO CO., LTD.
Application year: 1988
Main classification: F02N15
IPC codes: F02N15, F02B75