Starter

Abstract: A starter comprises a planetary gear reduction mechanism including an internal gear provided with a cylindrical chamber, a rotary disk, and a friction disk for restricting the rotary disk. The rotary disk is prevented from angularly moving with respect to the internal gear through an elastic member. When a larger load is applied to the internal gear which the elastic member cannot absorb, the rotary disk is released from the friction disk to angularly move to absorb such larger load.

Description: The present invention relates to a starter according to the preamble of claim 1, and more particular, a starter equipped with a planetary gear speed-reduction mechanism. When an engine is cranked by a starter, a crank rotates with pulsation due to the piston stroke displacement, i.e., compression, suction, combustion, and exhaust strokes. For this reason, a starter equipped with a planetary gear reduction mechanism cannot follow the pulsation. The impact caused by the pulsation is applied to an internal gear incorporating the planetary gear reduction mechanism installed therewith, and vibrations due to such impact cause an unpleasant noise during cranking. A countermeasure to absorb the impact is disclosed in Japanese Utility Model Examined Publication No. 2-31583, in which an elastic member is interposed between a frame and an outer periphery of the internal gear incorporating the planetary gear reduction mechanism. Also, a technique in which an internal gear is pressed against a frame by using a frictional force is disclosed in Japanese Patent Unexamined Publication No. 63-277859. In the former, there is a problem that the loads larger than that the elastic member can absorb cannot be dealt with, because there is a limit of the impact which the elastic member absorbs alone. To the contrary, in the latter, large loads can be absorbed by sliding therebetween, but small loads cannot be absorbed. A generic starter is known from the EP-A-0 180 016 and comprises a planetary gear reduction mechanism having a sun gear, a planetary gear and an internal gear, wherein the rotation of the internal gear with respect to a frame of the starter is restricted by a friction member. According to one embodiment of the EP-A-0 180 016 the internal gear is formed of synthetic resinous material and has an annular recess at its outer peripherial portion, so that the internal gear is elastically deformable. However, this known starter cannot absorb loads from the engine over a wide range, since the elastic deformability of the internal gear is limited to the material characteristics of the synthetic resinous material. It is the object of the present invention to further develop a starter according to the preamble of claim 1 such that it is capable of effectively absorbing a wide range of loads from an engine. This object is achieved by the features indicated in the characterising portion of claim 1. According to the invention movable means are engageable with an engaging portion of the internal gear. The movable means comprise a first portion which is resiliently engageable with the engaging portion of the internal gear, so that the internal gear can be angularly moved against a first load. Additionally the movable means comprise a second portion which transmits a second load greater than the first load wherein the second portion is engaged with the engaging portion of the internal gear. By this means the starter is capable of effectively absorbing a wide range of loads from the engine. When the load exceeds a predetermined value an engagement between the movable means and the internal gear is reached, so that a defined relative movement of the internal gear vis-à-vis the frame is ensured due to the friction member. Advantageous further developments are set out in the dependent claims. Fig. 1 is a fragmentary enlarged view showing a reduction mechanism of a starter shown in Fig. 2; Fig. 2 is a sectional view showing the starter according to a first embodiment of the present invention; Fig. 3 is a perspective view showing an internal gear shown in Fig. 1; Fig. 4 is a perspective view showing a rotary disk shown in Fig. 1; Fig. 5 is a view showing an engagement between the rotary disk and the internal gear in the starter according to the first embodiment of the present invention; Fig. 6 is a perspective view showing a rotary disk of a starter according to a second embodiment of the present invention; Fig. 7 is a perspective view showing an internal gear of the starter according to the second embodiment of the present invention; and Fig. 8 is a view showing an engagement in the starter according to a third embodiment of the present invention. A starter incorporating a reduction mechanism 15 shown in Fig. 1 comprises, as shown in Fig. 2, a motor block 12 which supports a rotary shaft 11 of an armature at opposite end portions of a housing, a solenoid block 14 incorporating a solenoid for driving a shift lever 13 by a starter switch (not shown), the planetary gear reduction mechanism 15 mounted on the rotary shaft 11 of the armature, an output mechanism 16 which transmits a speed reduction output from the planetary gear reduction mechanism 15 to a ring gear of a fly wheel through an output shaft 17, and means 18 for absorbing loads transmitted to the planetary gear reduction mechanism 15 from an engine. The motor block 12 includes the rotary shaft 11, a field coil 21 and an armature winding 22 formed on the rotary shaft 11 for cooperating the field coil 21 to generate an electromagnetic force so as to rotate the rotary shaft 11. The planetary gear reduction mechanism 15, as shown in Fig. 1, includes a predetermined number of planetary gears 24, an arm 25 integrated with the output shaft 17 to support the gears 24, and an internal gear 26 angularly movably mounted in a frame 28. The internal gear 26 includes a first cylindrical chamber 27 and a second cylindrical chamber 29 which are disposed axially in series. The gears 24 are installed inside the first cylindrical chamber 27 to be engaged with an internal gear portion 26a formed on the first cylindrical chamber 27. As shown in Fig. 3, recesses 30 and 31 representing engaging portions are formed on the inner periphery of the second cylindrical chamber 29. The recesses comprise four first long recesses 30 equiangularly spaced from each other by 45°, and four second short recessses 31 equiangularly spaced from each other by 45°. Projections 32 are formed between the first recesses 30 and the second recesses 31. An elastic member 33 of rubber or the like is held in each of the first recesses 30. A circumferential groove 34 shorter than the short recess 31 is formed in the elastic member 33. A rotary disk 35 (Figs. 2 and 4) which serves as the absorbing means is engaged with the second cylindrical chamber 29. Namely, projections 36 formed on the outer periphery of the rotary disk 35 and together forming movable means, shown in Fig. 4, made of phosphor bronze or the like, are fitted to the circumferential grooves 34 and the second recesses 31, as shown in Fig. 5. The projection 36, as shown in Fig. 4, is formed by bending opposite ends (claws 37 and 37) of each of circumferential pieces equiangularly spaced from each other and provided on the outer periphery of the rotary disk 35. As a result of these claws 37 and 37 being fitted to the circumferential groove 34 and the second recesses 31, the rotary disk 35 is engaged with the internal gear 26 without rotation through the elastic member 33 placed therebetween. In this case, the projection 36 is close fitted to the circumferential groove 34 of the elastic member 33 without gap, but maintains opposite gaps 31a and 31a with the second recess 31 (Fig. 5). The rotary disk 35 is slidably in contact at one surface thereof with a side wall 28a of the frame 28 supporting the output shaft 17 through a cylindrical support portion 28b thereof, and at the other surface thereof is pressed to contact a friction disk 39 of low carbon steel or the like. The rotary disk 35 and the friction disk 39 are disposed around the supporting portion 28b of the frame 28, and a coned disk spring 40 is further disposed around the supporting portion 28b. A nut 41 is screw mounted onto a thread portion formed on the supporting portion 28b to press the coned disk spring 40 so as to adjust the frictional force between the friction disk 39 and the rotary disk 35. In the output mechanism 16, as shown in Fig. 2, an overrunning clutch 42 and a pinion 43 are mounted on the output shaft 17, and the shift lever 13 is rested on the overrunning clutch 42. In the starter constructed as described above, the rotation of the rotary shaft 11 of the armature is in the direction of an arrow A is transmitted through the planetary gear reduction mechanism 15 to the output shaft 17 in the form of a speed reduced rotation in a reversed direction. At the same time, the shift lever 13 causes the pinion 43 to be engaged with the ring gear through the overrunning clutch 42. This causes the engine to crank. Impacts are generated in the output shaft 17 due to the pulsations of the engine during the above cranking time. A load caused thereby is transmitted to the internal gear 26 through the planetary gear 24. When this load is small, the movement of the rotary disk 35 is prevented by the friction disk 39. Therefore, the load from the planetary gear 24 is absorbed by a circumferential deformation of the elastic member 33 held in the recess 30 of the internal gear 26. When the load received by the internal gear 26 exceeds the capacity of the elastic member 33, a rotational force larger than the frictional force of the friction disk 39 is applied to the rotary disk 35 since the claws 37 are engaged with the recess 31 without rotation. As a consequence, the rotary disk 35 is released from the restriction of the friction disk 39 and rotates slidably on the sliding surface with the frame 28, and at the same time rotates the internal gear 26. In this way, excessive impact loads can be absorbed by the rotation of the rotary disk 35 together with the internal gear 26. When the rotary disk 35 is angularly moved to a certain extent and then the elastic member 33 can absorb the load, the movement of the rotary disk 35 is restricted by the frictional force of the friction disk 39, and the absorption function by the elastic member 33 works again. As described above, in this embodiment, a wide range of loads can be absorbed by the elastic member 33 and the friction disk 39 which restricts the rotary disk, 35 by a frictional force. Namely, a small load can be absorbed by the elastic member 33 and a large load can be absorbed by the rotation of the rotary disk 35 with the internal gear 26. The absorbing means 18 having such double absorption functions is accomplished without increasing the diametrical size of the frame 28 because the absorbing means 18 is installed within the internal gear 26. Next, the second embodiment of the present invention will be described with reference to Figs. 6 and 7. The rotary disk 35' has two groups of projections 36' formed by bending opposite ends (claws 37a and 37a, and 37b and 37b) of each of circumferential pieces equiangularly spaced from each other and provided on the outer periphery of the disk 35. The axial lengths of the claws 37a and 37b are different from each other. The claw 37a having an axial length L1 and the claw 37b having an axial length L2 smaller than L1 are circumfernetially disposed alternately. The claws 37a and 37a are flared to provide a resiliency to the projection 36'. The second cylindrical chamber of the internal gear 26 is provided with first recesses 30a each having an axial depth L1' and second recesses 30b each having an axial depth L2' smaller than L1', these depths corresponding to the axial lengths L1 and L2 of the claws 37a, 37a and 37b, 37b, respectively. The pairs of claws 37a and 37a and the pairs of claws 37b and 37b are fitted into the first recesses 30a and the second recesses 30b, respectively. The pair of claws 37a and 37a are closely fitted to the first recess 30a. To the contrary, the pair of claws 37b and 37b are loosely fitted to the second recess 30b as the same as the first embodiment. According to the second embodiment, when the small load is applied to the rotary disk 35', the pair of claws 37a and 37a work as resilient members so that they are deformed to be closed to each other, thereby absorbing such small load as the same as the elastic member 33 of the first embodiment. When the large load which the pairs of claws 37a and 37a cannot absorb is applied to the rotary disk 35', it is rotated by a rotational force, which is larger than the restriction force due to the frictional force of the friction disk 39, so as to absorb such large load. As a result, like the first embodiment, the rotary disk 35' circumferentially moves with the internal gear 26 to a certain extent to absorb the large load, and thereafter, the pairs of claws 37a and 37a absorb the reduced load again. In a third embodiment, as shown in Fig. 8, the position of the projection 36 of the rotary disk 35 is modified with respect to the recess 30 of the internal gear 26 in view of the engine type. Each of the projections 36, which is housed in the circumferential groove 34 of the elastic member 33, is asymmetrical with a circumferential center line of the respective groove 34. All of such projections 36 are deviated in the same direction. According to the third embodiment, in case that the starter is applied to an engine which has an intention of generating a specifically inclined load, the elastic members 33 can absorbed such load more effectively. As apparent from the above description, according to the present invention, due to the double absorption function, it is possible to absorb a wider range of load, as compared with the single absorption function in which the load is absorbed by the elastic members only. A starter comprises a planetary gear reduction mechanism including an internal gear provided with a cylindrical chamber, a rotary disk, and a friction disk for restricting the rotary disk. The rotary disk is prevented from angularly moving with respect to the internal gear through an elastic member. When a larger load is applied to the internal gear which the elastic member cannot absorb, the rotary disk is released from the friction disk to angularly move to absorb such larger load.

Claims: A starter comprising: a planetary gear reduction mechanism (15) including a sun gear (23) connected to a rotary shaft (11) of an armature (12), and an internal gear (24) engaged with said sun gear (23), and an internal gear (26) including an internal gear portion (26a) thereof engaged with said planetary gear (24) and an engaging portion (30, 31, 30a, 30b); an output shaft (17) to which a rotation of said rotary shaft (11) is transmitted by means of an orbital revolution of said planetary gear (24); a pinion (43) provided in said output shaft (17) engageable with a ring gear of an engine; a frame (28); and a friction member (39) for restricting angular movement of movable means (35, 36, 36') with respect to said frame (28), characterized in that said movable means (35, 36, 36') are angularly movably mounted to said frame (28), said movable means (35, 36, 36') including first and second portions engageable with said engaging portion (30, 31, 30a, 30b) of said internal gear (26), said first portion resiliently engaging with said engaging portion (30, 30a) of said internal gear (26) and being deformable for permitting said internal gear (26) to angularly move against a first load, which is applied to said internal gear (26) to angularly move it, and said second portion adapted to be engaged with said engaging portion (31, 30b) of said internal gear (26) to transmit a load applied to said internal gear (26) to said movable means (35, 36, 36'), where said first portion is deformed beyond a predetermined extent, and wherein, after said second portions abut against said engaging portion (31, 30b), said friction member (39) provides a slip between said movable means (35, 36, 36') and said friction member (39) when a second load is applied to said internal gear (26), the magnitude of which is larger than that of said first load, after engagement between said second portion and said engaging portion (31, 30b). A starter according to claim 1 characterized by an elastic member (33) disposed between said first portion of said movable means (35, 36, 36') and said engaging portion (30, 30a) of said internal gear (26). A starter according to claim 1, characterized in that said first portion of said movable means (35, 36, 36') is constituted by deformable member. A starter according to any of the preceding claims, characterized in that said movable means (35, 36, 36') include at an inner peripheral portion thereof a ring portion being held angularly movably with respect to said frame (28), and at an outer peripheral portion thereof said first and a second portions (36, 36') engageable with said engaging portions (30, 31, 30a, 30b) and wherein said friction member (39) is axially abutted to said ring portion of said movable means (35, 36, 36').

Inventors: HASEGAWA YOUICHI, HIRAMA KAZUO, NAGAO YASUHIRO, OHGI TAKAHIRO, HASEGAWA, YOUICHI, HIRAMA, KAZUO, NAGAO, YASUHIRO, OHGI, TAKAHIRO
Applicants: NIPPON DENSO CO, NIPPONDENSO CO., LTD.
Application year: 1992
Main classification: F02N15
IPC codes: F02N15, F16H1