Starting Device With Planetary Reduction Gear

The present invention relates to a starting device with a planetary reduction gear which is used for starting an internal combustion engine.

A starting device of this type is known in the prior art as disclosed in Laid-Open Japanese Patent No. Sho 60-175763. Such a prior-art starting device 1, as shown in FIG. 1, is constituted of a DC motor 2, an overrunning clutch device 4 which is fitted slidably on an output rotating shaft 3, a planetary reduction gear 5 which transmits the rotation of an armature rotating shaft 2a of the DC motor 2 after speed reduction to an outer clutch 4a of the overrunning clutch device 4 through the output rotating shaft 3, and a shift lever 8 with its one end engaged with a plunger rod 6a of an electromagnetic switch device 6 disposed on the side section of the DC motor and with its other end engaged with an annular member 7 mounted on the overrunning clutch device 4 such that the overrunning clutch device 4 can slide on the output rotating shaft 3.

The planetary reduction gear 5 of the prior-art starting device 1 will be further explained. This planetary reduction gear 5 consists of a sun gear 5a which is formed integral with the outer peripheral section of one end of the armature rotating shaft 2a of the DC motor 2, an internal gear 5b fixed around this sun gear 5a positioned at center, and a plurality of planet pinions 5e which are in mesh with the sun gear 5a and the internal gear 5b and rotatably mounted on pins 5d fixed on a carrier 5c through sleeve bearings 5f. The carrier 5c on which each planet pinion 5e is mounted is formed integrally with the output rotating shaft 3, and accordingly the revolution of the planet pinions 5d directly becomes the rotation of the output rotating shaft 3.

The output rotating shaft 3 slidably supporting the overrunning clutch device 4 at a position adjacent to the planetary reduction gear 5 has helical splines 3a formed over the range of sliding of the clutch device 4 in order to transmit the rotation of the outer clutch 4a of the clutch device 4. Numeral 9 denotes a pinion formed on the inner clutch 4b of the overrunning clutch device 4. This pinion comes into engagement with a ring gear (not illustrated) of the engine when the overrunning clutch device 4 has slid on the output rotating shaft 3. As described above, the helical splines 3a formed on the output rotating shaft 3 are engaged with the outer clutch 4a of the overrunning clutch device 4 supported on this output rotation shaft 3, thereby enabling the constant transmission of a turning force to the outer clutch 4a while sliding the clutch device in the axial direction.

The prior-art starting device with a planetary reduction gear has such a problem that, as described above, the use of a longer output rotating shaft and consequently the starting device of increased overall length are required because of the formation of the helical splines on the output rotating shaft over the range of sliding of the clutch device to transmit rotation decelerated by the planetary reduction gear to the outer clutch 4a of the overrunning clutch device 4.

The present invention has been accomplished in an attempt to solve the aforementioned problem of the prior art, and it is an object of the present invention to provide a starting device having a planetary reduction gear that has a small size realized by decreasing the length of the whole body of device.

The starting device with a planetary reduction gear pertaining to the present invention has the effect that the overall length of the starting device can be decreased by designing the internal gear so as to turn without rotating each planet pinion of the planetary reduction gear, by mounting a holder section, which has been attached to the outer clutch of the overrunning clutch device, over the outer periphery of this internal gear and in mesh with the helical splines, and by mounting a shift lever for shifting the overrunning clutch device with its one end engaged with the outer peripheral section of the holder section.

FIG. 1. is a sectional view showing a prior-art starting with a planetary reduction gear; and

FIG. 2 is a fragmentary sectional view showing a starting device with a planetary reduction gear according to one embodiment of the present invention.

Hereinafter an embodiment of a starting device with a planetary reduction gear of the present invention will be described with reference to the accompanying drawings. FIG. 2 shows a starting device with planetary reduction gear (hereinafter referred to simply as the starting device) 20 according to one embodiment of the present invention. The starting device 20 comprises a DC motor 21, an overrunning clutch device 22 slidably fitted on an extended shaft portion of its armature rotating shaft 21, a planetary reduction gear 23 which transmits rotation to an outer clutch 22a of the overrunning clutch device 22 after decreasing the speed of rotation of the armature rotating shaft 21a of the DC motor 21, and an electromagnetic switch device 24 disposed on the side section of the DC motor 21 to slide the overrunning clutch device 22 on the extended shaft portion of the armature rotating shaft 21a and also to turn on the power supply to the DC motor 21.

The planetary reduction gear 23 is disposed in a position adjacent to an end wall 21c continuous to a casing 21b of the DC motor 21, and consists of a sun gear 23a formed on the extended shaft portion of the armature rotating shaft 21a, a plurality of planet pinions 23b disposed around, and in mesh with, the sun gear 23a, and an internal gear 23c in mesh with these planet pinions 23b. Each planet pinion 23b is rotatably supported on a bearing 23e on the other end of a pin fixed at one end on the end wall 21c, that is, a fixed shaft 23d. Therefore, each planet pinion 23b does not revolve around the sun gear 23a, but only revolves on the center of the fixed shaft 23d. Accordingly, the internal gear 23c which is in mesh with these planet pinions 23b is rotatably supported on the extended shaft portion of the armature rotating shaft 21a through a bearing 25 fitted between its hub and the extended shaft portion, so that rotation from the planet pinions 23b will be transmitted thereto.

The overrunning clutch device 22 is disposed adjacent to the planetary reduction gear 23, and is supported on a bearing 26 such that the inner clutch 22b is rotatable and axially slidable in relation to the extended shaft portion of the armature rotating shaft 21a. At the front end of this inner clutch 22b, a pinion 27 is formed in mesh with a ring gear (not illustrated) of the engine. On the outer clutch 22a of the overrunning clutch device 22, a cylindrical holder 28 is integrally formed extending out to cover the outer periphery of the internal gear 23c of the planetary reduction gear 23. This overrunning clutch device 22 is of a similar constitution as conventional ones except for the holder section 28 described above. The inner peripheral surface of the holder 28 is engaged with the helical splines 23f formed in the outer peripheral surface of the internal gear 23c.

In the outer peripheral surface of this holder section 28, a circumferential groove 28a is formed by collars jutting outwardly in the radial direction at both its ends in the axial direction. With the groove 28a, one end of a shift lever 29 is engaged. The other end of the shift lever 29 is engaged, as in conventional ones, with a plunger rod of the electromagnetic switch device 24.

In FIG. 2, numeral 30 designates a bearing rotatably supporting the armature rotating shaft 21a at the boss section of the end wall 21c; numeral 31 indicates a starter housing, or a front bracket; numeral 32 is a bearing supporting the end section of the extended shaft of the armature rotating shaft 21a in the front bracket 31; numeral 33 is a stop ring; numeral 34 is a stopper; and numeral 35 is a cap.

Next the operation of the starting device 20 of this embodiment will be explained.

When the electromagnetic switch device 24 is energized, the shift lever 29 is pivotally operated to move forward the overrunning clutch device 22 with the holder section 28 of the outer clutch held in mesh with the internal gear 23c through the helical splines 23f, then the pinion 27 goes into engagement with the ring gear 36 of the internal combustion engine 37. Immediately before or nearly simultaneously with this engagement, the main contact of the electromagnetic switch device 24 is closed, thus turning on the power supply of the DC motor 21 to rotate the armature rotating shaft 21. This rotation from the sun gear 23a formed on the armature rotating shaft 21a drives to rotate the internal gear 23c through the planet pinions 23b, and from the internal gear 23 the rotation is transmitted to the outer clutch 22a of the overrunning clutch device 22 through the helical splines 23f after internally decreasing the speed of rotation of the armature rotating shaft 21a. In consequence, the engine is started by the pinion 27 which is turning with the inner clutch 22b. The reverse transmission of the turning force to the armature rotating shaft after the starting of the engine will be shut off by the overrunning clutch device 22.