Title of Invention

"GEAR NOISE PREVENTIVE SYSTEM"

Abstract

[Object] To provide a gear noise reducing system for reducing noise caused by meshing between gears, which is intended to make invariable the spring load of a torsional coil spring thereby making smooth the operation of a sub-gear. [Solving Means] A sub-gear 6 is rotatably provided adjacently to a primary drive gear 5, and is linked via a torsional coil spring 30 to a retainer 7 press-fitted around an end of a rotational shaft 4. A guide portion 25 is formed by slitting an outer peripheral flange 21 and part of a side wall 20 of the retainer 7 along both the side edges of a strip portion, and folding the strip portion inside the outer peripheral flange 21 in parallel to the axis of the rotational shaft 4. The torsional coil spring 30 is allowed to pass between the outer peripheral flange 21 and the guide portion 25. When the torsional coil spring 30 is contracted in diameter to give a preload to the sub-gear 6, part of the inner peripheral surface of the torsional coil spring 30 is brought in contact with the guide portion 25 and the remaining portion thereof is not brought in contact with the rotational shaft 4 and the like.

Full Text

[Detailed Description of the Invention] [0001] [Technical Field of the Invention] The present invention relates to a gear noise preventive system intended to reduce noise due to meshing of a primary gear and a sub-gear provided around the same rotational shaft with a mating gear by meshing both the primary gear and sub-gear with the mating gear while giving a phase difference between the primary gear and sub-gear. [0002] [Related Art] Japanese Utility Model Laid-open No. Sho 63-59260 discloses a gear noise preventive system provided around a crank shaft of an engine. In this gear noise preventive system, a primary drive gear (primary gear) and a sub-gear are disposed adjacently to each other around the crank shaft with a phase difference set therebetween and a torsional coil spring is interposed between the sub-gear and a retainer provided in such a manner as to be rotated integrally with the crank shaft, wherein the sub-gear is biased by the torsional coil spring in such a manner as to be turned in the direction where the phase difference is eliminated and hence to be given a preload, to thereby reduce noise caused by meshing of the primary drive gear and the sub-gear with a primary driven gear (mating gear) of a speed-change clutch. [0003] [Problem to be Solved by the Invention] Fig. 7 is a typical view of the above system showing a state in which a sub-gear "a" is turned in the actuating rotational direction (shown by the arrow A) to be given a preload by the torsional coil spring "b". To be more specific, the turning of the sub-gear "a" contracts the diameter of the torsional coil spring "b" by moving an end "c", engaged with the sub-gear "a", of the torsional coil spring "b" in the direction shown by the arrow A from a position (shown by the broken line) upon non-operated state to a position shown by the solid line. At the position shown by the solid line, a center Ol of the torsional coil spring "b" in the non-operated state is moved to a center 02 which is eccentric with respect to each of centers of a retainer "d" and a rotational shaft "e". As a result, part of the torsional coil spring "b" may be brought in contact with the inner peripheral surface of the retainer "d" (at a point B) or with the outer peripheral surface of the rotational shaft "e" (at a point C). [0004] The contact of the torsional coil spring "b" with irregular locations over irregular length ranges varies the spring load of the torsional coil spring "b" necessary for giving a preload to the sub-gear "a", tending to make unstable the operation of the sub-gear "a". Further. As shown in Fig. 8, for the torsional coil spring "b" wound a plurality of turns, a wound portion of the torsional coil spring "b" may be partially overlapped onto the adjacent one when the torsional coil spring "b" is contracted in diameter. In such a state, the spring load of the torsional coil spring "b" also varies, leading to instability of the operation of the sub-gear "a". [0005] [Means for Solving the Problem] To solve the above problems, according to a first invention, there is provided a gear noise preventive system in which a primary gear and a sub-gear are disposed adjacently to each other around the same rotational shaft with a phase difference set therebetween and a torsional coil spring is interposed between said sub-gear and a retainer to be rotated integrally with said rotational shaft in a state that an inner periphery of said torsional coil spring is supported by a guide portion provided on said retainer, wherein said sub-gear is biased by said torsional coil spring so as to be turned in the direction where said phase difference is eliminated and hence to be given a preload, to thereby reduce noise caused by meshing of said primary gear and said sub-gear with a mating gear, said gear noise preventive system being characterized in that said torsional coil spring is taken as a torsional coil spring wound a plurality of turns, and a gap between said guide portion and said retainer, in which said torsional coil spring is contained, is set be smaller than a value being twice a diameter of said torsional coil spring. According to a second invention, in addition to the configuration of the first invention, a gap D between the guide portion and the retainer and a diameter "d" of the torsional coil spring satisfy a relationship of D With the configuration of the first invention, the guide portion for supporting the inner periphery of the torsional coil spring is provided on the retainer, and accordingly, when the torsional coil spring is contracted in diameter to give a preload to the sub-gear, the inner periphery of the torsional coil spring is supported by the guide portion in a state being in contact therewith. As a result, the inner periphery of the torsional coil spring is brought in contact with only the guide portion, and at this time the contact point of the torsional coil spring is made constant and the contact length thereof is made relatively short. This makes it possible to make invariable the spring load of the torsional coil spring and hence to make stable the operation of the sub-gear. [0008] With the configuration of the second invention, the gap D between the guide portion and the retainer and the diameter "d" of the torsional coil spring satisfy the relationship of D [Brief Description of the Drawings] [Fig. 1] An enlarged sectional view showing a primary drive gear and its neighborhood according to an embodiment of the present invention. [Fig. 2] A sectional view of an engine according to the embodiment. [Fig. 3] A partially enlarged sectional view showing a guide portion. [Fig. 4] A view seen from the direction shown by the arrow E of Fig. 1. [Fig. 5] A sectional view taken on line 5-5 of Fig. 1 showing a state before actuating rotation (before preloading). [Fig. 6] A view, similar to Fig. 5, showing a state upon preloading. [Fig. 7] A typical view of a related art structure showing a state upon preloading. [Fig. 8] A sectional view of the related art structure showing a state in which a wound portion of a torsional coil spring is overlapped to the adjacent one. [0009] [Embodiment of the Invention] Figs. 1 to 6 show one embodiment in which the present invention is applied to a primary drive gear provided around a crank shaft of an engine, wherein Fig. 1 is an enlarged sectional view showing the primary drive gear and its neighborhood; Fig. 2 is a sectional view of an engine according to the embodiment; Fig. 3 is a partially enlarged sectional view showing a guide portion; Fig. 4 is a view seen in the direction shown by the arrow E of Fig. 1; Fig. 5 is a sectional view taken on line 5-5 of Fig. 1 showing a state before actuating rotation (before preloading); and Fig. 6 is a view, similar to Fig. 5, showing a state upon preloading. [0010] Referring to Fig. 2, an engine includes a crank shaft 2 connected to a piston rod 1, a starting clutch 3 connected to one end of the crank shaft 2; and a rotatipnal shaft 4 rotatably provided around the outer periphery of the crank shaft 2, which rotational shaft is connectable to the crank shaft 2 via the starting clutch 3. [0011] A primary drive gear (primary gear) 5 and a sub-gear 6 are disposed adjacently to each other around the rotational shaft 4, and a retainer 7 is disposed at an end portion, opposite to the primary drive gear 5 with respect to the sub-gear 6, of the rotational shaft 4. [0012] The sub-gear 6 is identical to or slightly different from the primary drive gear 5 in terms of diameter and the number of teeth. Both the primary drive gear 5 and the sub-gear 6 mesh with a primary driven gear 11 of a clutch 10. [0013] The primary driven gear 11 is integrated with a clutch outer of the clutch 10. The rotation of the primary driven gear 11 is transmitted to a main shaft 12 via a clutch inner of the clutch 10 and is then transmitted to a counter shaft gear 14 of a counter shaft 13 via a main shaft gear 12'. [0014] Next, a gear noise preventive mechanism will be described. As shown in Fig. 1 and Figs. 3 to 6, the sub-gear 6 is rotatably supported around a portion 14, near the primary gear 5, of the rotational shaft 4, which sub-gear is prevented from being slipped off from the rotational shaft 4 by means of a snap ring 15. [0015] One of teeth of the sub-gear 6 and the one paired therewith of teeth of the primary gear 5, which teeth are taken as positioning teeth, are formed with chamfer portions 17 and 16, respectively. Upon preloading, the sub-gear 6 can be easily positioned with respect to the primary gear 5 by aligning the chamfer position 17 with the chamfer portion 16. The sub-gear 6 has a locking hole 18 penetrating the side portion thereof at a position near the chamfer portion 17. [0016] The rotational shaft 4 has, at a position with the same phase as that of the positioning tooth of the primary gear 5, a positioning groove 19 cut axially inward from the end portion of the rotational shaft 4. The positioning groove 19 is opened at the end portion of the rotational shaft 4. [0017] The retainer 7 is formed substantially into a cup shape by pressing a plate made from a suitable metal material such as a steel. The retainer 7 has a side wall 20 parallel to a rotational end plane of the rotational shaft 4, an outer peripheral flange 21 integrated with the outer peripheral portion of the side wall 20 in such a manner as to project therefrom toward the sub-gear 6 side; and an inner peripheral flange 22 integrated with the inner peripheral portion of the side wall 20 in such a manner as to project therefrom in the opposed direction to the projecting direction of the outer peripheral flange 21. [0018] The inner peripheral flange 22 has a positioning recess 23 projecting inward toward the center of the retainer 7. The positioning recess 23 is allowed to be fitted in the positioning groove 19. The side wall 20 has a locking hole 24, which penetrates the side wall 20, at a position with the same phase as that of the vicinity of the central portion of the positioning recess 23 in the peripheral direction of the inner peripheral flange 22. A guide portion 25 is formed at a position separated from the position of the locking hole 24 in the actuating rotational direction with a phase difference, approximately 60°, kept therebetween. [0019] The guide portion 25 is obtained by slitting the outer peripheral flange 21 and part of the side wall 20 along both the side edges of a strip portion forming the guide portion 25, cutting off the end portion of the strip portion for a length equivalent to a gap D to be described later, and folding the strip portion inside the outer peripheral flange 21 in such a manner as to be parallel to the axis of the rotational shaft 4. A gap D between the outer peripheral surface of the guide portion 25 and the inner peripheral surface of the outer peripheral flange 21 is specified as will be described later. [0020] A gap F between the inner peripheral surface of the guide portion 25 and the inner peripheral surface of the inner peripheral flange 22 is kept at a value enough to guide the torsional coil spring 30 in such a manner that the torsional coil spring 30 except for the contact portion with the guide portion 25 is not in contact with the outer peripheral flange 21 and the rotational shaft 4 when the torsional coil spring 30 is contracted in diameter. [0021] The position of the guide portion 25 is separated a specific angle from the position of the locking hole 24 in the direction (shown by the arrow A) where the sub-gear 6 is actuated to be given a preload. In this embodiment, the above angle is set at approximately 60°, which angle allows the guide portion 25 to most effectively guide the torsional coil spring 30 as will be described later. The above angle, however, may be set in a range of approximately 180° or less, preferably, in a range of approximately 90° or less. [0022] The retainer 7 is linked to the sub-gear 6 by means of the torsional coil spring 30. The torsional coil spring 30 is wound a plurality of turns, and is folded approximately 90° in the reversed direction to the winding direction at both the ends. Both the folded ends of the torsional coil spring 30 are taken as an engagement end 31 to be locked in the locking hole 18 of the sub-gear 6 and an engagement end 32 to be locked in the locking hole 24 of the retainer 7. The engagement ends 31 and 32 are separated from each other with a specific phase difference set therebetween in the non-actuated state in order to be aligned with each other upon actuating rotation. [0023] The torsional coil spring 30 is mounted to the retainer 7 in such a manner as to pass between the guide portion 25 and the outer peripheral flange 21. The gap D between the guide portion 25 and the outer peripheral flange 21 is set to satisfy a relationship of D Next, the function of this embodiment will be described. First, the engagement end 31 of the torsional coil spring 30 is engaged in the locking hole 18 of the sub-gear 6, which sub-gear is rotatably mounted around the portion 14, near the primary gear 5, of the rotational shaft 4, in such a manner as to be prevented from being slipped off from the rotational shaft 4 by means of the snap ring 15; and the engagement end 32 of the torsional coil spring 30 is engaged in the locking hole 24 of the retainer 7. Then, the inner peripheral flange 22 is fixedly press-fitted around the outer periphery of the rotational shaft 4 in such a manner that the positioning recess 23 is fitted in the positioning groove 19. [0025] In the non-actuated state, the torsional coil spring 30 is disposed around the rotational shaft 4 in such a manner as to link the retainer 7 with the sub-gear 6 and to pass between the outer peripheral flange 21 and the guide portion 25. This state is shown in Fig. 5. As shown in Fig. 5, in such a state, the torsional coil spring 30 is not in contact with, that is, separated from the inner periphery of the retainer 7 and the outer periphery of the rotational shaft 4 with gaps kept therebetween. [0026] The sub-gear 6 is then turned in the actuating rotational direction shown by the arrow A to align the chamfer portion 17 with the chamfer portion 16 of the primary gear 5, so that the engagement end 31 is moved to the guide portion 25 side and thereby the torsional coil spring 30 is contracted in diameter. At this time, a center 01 of the torsional coil spring 30 in the non-actuated state is moved to a center O2 which is eccentric with respect to each of centers of the retainer 7 and the rotational shaft 4. [0027] As a result, the front half of the torsional coil spring 30 is moved in the rotational direction from the engagement end 32 as the fixed end to the rotational shaft 4 side, and the rear half thereof is moved in the rotational direction from the engagement end 32 to the outer peripheral flange 21 side; however, since the inner peripheral portion of the torsional coil spring 30 is supported by the guide portion 25 in the state being in contact therewith, the torsional coil spring 30 is positioned with the guide portion 25 taken as a fulcrum for supporting the torsional coil spring 20. [0028] In this way, the torsional coil spring 30 is not brought in contact with, that is, separated from the inner peripheral surface of the outer peripheral flange 21 of the retainer 7 and the outer peripheral surface of the rotational shaft 4 with specific gaps kept therebetween, except for the contact portion of the torsional coil spring 30 with the guide portion 25. In other words, the contact position of the torsional coil spring 30 on the retainer 7 side is kept constant and the contact length thereof is limited to the minimum value, that is, to only the peripheral length of the guide portion 25 on the outer peripheral side. [0029] The spring load of the torsional coil spring 30 is thus made constant, and consequently, the torsional coil spring 30 can smoothly actuate the sub-gear 6 to turn the sub-gear 6 in the reversed direction to the actuating rotational direction, thereby giving a preload to the sub-gear 6. This makes it possible to reduce noise caused by meshing of the primary gear 5 and the sub-gear 6 with the primary driven gear 11. [0030] Further, since the gap D between the guide portion 25 and the retainer 7 becomes a value which satisfies the relationship D Since the engagement end 31 is substantially aligned with the engagement end 32 when the sub-gear 6 is turned in the actuating rotational direction, it is possible to prevent twisting of the torsional coil spring 30 even when the torsional coil spring 30 is contracted in diameter to give a preload to the sub-gear 6, and hence to stably give the preload to the sub-gear 6 and make smooth the operation of the sub-gear 6. [0032] Since the guide portion 25 is located at a position separated an angle of approximately 60° from the locking hole 24, which position is relatively near the engagement end 31 in the actuating rotational direction, the guide portion 25 can effectively guide the torsional coil spring 30 while not moving the torsional coil spring 30 so much upon actuating rotation by supporting the most movable position of the torsional coil spring 30. Further, since the guide portion 25 is formed by slitting the outer peripheral flange 21 and part of the side wall 20 along both the side edges of a strip portion, and folding the strip portion, it is possible to easily form the guide portion 25. [0033] Since the locking hole 24 is formed in the side wall 20 at the position with the same phase as that of the central portion of the positioning recess 23 in the peripheral direction of the inner peripheral flange 22, it is possible to offset the position of the locking hole 24 toward the inner peripheral side in the side wall 20, and hence to miniaturize the entire system. [0034] Since the sub-gear 6 is prevented from being slipped off from the rotational shaft 4 by the snap ring 15, unlike the related art structure in which the sub-gear 6 is positioned with respect to the rotational shaft 4 by means of a pin, it is possible to facilitate the manufacture and assembly of the sub-gear 6, and to reduce the manufacturing cost because of elimination of the necessity of provision of the expensive pin. [0035] Further, since the retainer 7 is manufactured by pressing a plate made from a material such as a steel, it is possible to reduce the weight of the retainer 7 and form the retainer 7 very easier as compared with the related art retainer made from a steel by machining, and hence to reduce the manufacturing cost. Also since the retainer 7 can be previously assembled with the rotational shaft 4 by press-fitting the inner peripheral flange 22 of the retainer 7 around the end portion of the rotational shaft 4, it is possible to improve the handling characteristic of the retainer 7. [0036] It should be noted that the present invention is not limited to the above embodiment but can be variously modified. For example, in the above embodiment, the guide portion 25 is formed by slitting the outer peripheral flange 21 and part of the side wall 20 along both side edges of a strip portion and folding the strip portion inside the outer peripheral flange 21 in such a manner as to be parallel to the axis of the rotational shaft 4; however, the guide portion 25 can be obtained by performing the same procedure as described above for the inner peripheral flange 22 side. [Explanation of Symbols] 2: crank shaft, 4: rotational shaft, 5: primary drive gear, 6: sub-gear, 7: retainer, 25: guide portion, 30: torsional coil spring WE CLAIM: 1. A gear noise preventive system in which a primary gear (2) and a sub-gear (6) are disposed adjacently to each other around the same rotational shaft (4) with a phase difference set therebetween and a torsional coil spring (30) is interposed between said sub-gear (6) and a retainer (7) to be rotated integrally with said rotational shaft in a state that an inner periphery of said torsional coil spring (30) is supported by a guide portion provided on said retainer, wherein said sub-gear is biased by said torsional coil spring (30) so as to be turned in the direction where said phase difference is eliminated and hence to be given a preload, to thereby reduce noise caused by meshing of said primary gear (5) and said sub-gear (6) with a mating gear, said gear noise preventive system being characterized in that said torsional coil spring (30) is wound a plurality of turns, and a gap (D) between said guide portion (25) and said retainer (7), in which said torsional coil spring (30) is contained, is set be smaller than a value being twice a diameter of said torsional coil spring (30). 2. A gear noise preventive system substantially as herein described with reference to the accompanying drawings.

Documents:

3819-del-1998-abstract.pdf

3819-del-1998-claims.pdf

3819-del-1998-correspondence-others.pdf

3819-del-1998-correspondence-po.pdf

3819-del-1998-description (complete).pdf

3819-del-1998-drawings.pdf

3819-del-1998-form-1.pdf

3819-del-1998-form-13.pdf

3819-del-1998-form-19.pdf

3819-del-1998-form-2.pdf

3819-del-1998-form-3.pdf

3819-del-1998-form-4.pdf

3819-del-1998-form-6.pdf

3819-del-1998-gpa.pdf

3819-del-1998-petition-137.pdf

3819-del-1998-petition-138.pdf

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