Title of Invention

"A SINTERED PRIMARY DRIVEN GEAR"

Abstract A sintered primary driven gear provided between clutch outer (21) and clutch side plate (28) and subjected to a sintering after compacting metal powder using an outer mold for forming teeth and an outer part in the vicinity of the teeth and an inner mold for forming inner part that are different from each other, characterized in that: a stepped portion (31) arising as a result of separation of each of the outer and inner molds is formed further out than a contact surface between the primary driven gear (30) and the clutch outer (21), a gap is established between the stepped portion (31) and the clutch side plate (28) or the stepped portion (31) and the clutch outer (21).
Full Text The present invention relates to a sintered primary driven gear. Related Art
With gears, tooth portions carrying out transmission of driving force by meshing have points requiring special strength, and outer portions indicating the teeth are formed of an extremely strong material such as carbon steel, while the inner parts are formed of a low weight material such as an aluminum alloy, and Japanese Utility Model Publication No. Hei. 1-67370 shown an example where two such materials are solid-phase welded by pressure welding or welding, etc. in an attempt to reduce weight.
However, this involves a number of manufacturing steps and
increase in manufacturing
cost.A method of carrying out sintering processing after the compacting can provide a sintered gear having particularly high strength at tooth portions with a reduced number of processing steps and low price, by partitioning molds, and compacting an outer portion, including tooth portions, and an inner portion in separate molds to alter the powder density.
A compacting and sintering method can ensure a normally high dimensional accuracy, but in the case where separate molds are used a stepped portion is formed at borderlines caused by the separation of the molds, and it is difficult to maintain high dimensional accuracy.
Also, manufacturing cost is increased by corrections such as sizing (repressing) etc.
The present invention has been conceived in view of the above described problems, and has as its object to provide a sintered gear that can maintain high dimensioned precision at locations on toothed portions requiring particularly high strength, with a reduced number of manufacturing steps and at low cost.
Accordingly there is provided a sintered primary driven gear provided between clutch outer and clutch side plate and subjected to a sintering after compacting metal powder using an outer mold for forming teeth and an outer part in the vicinity of the teeth and an inner mold for forming inner part that are different from each other,
characterized in that:
a stepped portion arising as a result of separation of each of the outer and inner molds is formed further out than a contact surface between the primary driven gear and the clutch outer, a gap is established
between the stepped portion and the clutch side plate or the stepped portion and the clutch outer.
With compacting carried out using a mold for an outer peripheral part including teeth and a mold for an inner part that are different from each other it is possible to make the compacting density of the outer peripheral part particularly high and increase the strength of the teeth, at the same time as forming stepped portions of borderlines caused by separation of each of the molds in the vicinity of the teeth, which means that teeth and inner parts, except for an area near the teeth, requiring dimensional accuracy can maintain high dimensional precision.
It is also possible to provide a sintered gear with a reduced number
of manufacturing steps following the compacting and sintering, and
at lower
cost
The invention is the sintered gear according to claim 1, being a helical gear having a line of teeth in the shape of a helix.
The helical gear can be simply formed by carrying out compression while rotating an external side mold along a line of teeth in the shape of a helix, and by using a helical gear power transmission can be carried out more smoothly and with improved efficiency.
The invention is the sintered gear according to claim 1 being a primary driven gear attached to a clutch outer of a small vehicle.
Since stepped portions of borderlines caused by mold splits of each of the molds are formed in the vicinity of teeth, it is possible to ensure high dimensional precision of an inner part of the primary driven gear contacting the clutch outer and it is possible to precisely locate the primary driven gear in an axial direction.
\ "The invention is the sintered gear aecording to claim 3, wherein the
• \ • stepped portion is formed further out than a contact' surface between the primary driven gear and the clutch outer.
A contact surface where the primary driven gear contact the clutch outer can be made to ensure sufficient dimensional precision, and it is possible to prevent the occurrence of hammering noise by locating the primary driven gear precisely in an axial direction to avoid contact with a sideplate etc.
'[Brief Description of The Drawings
Fig. I is a cross sectional drawing of an internal combustion engine and power transmission system for a motorcycle to which a sintered gear "of an embodiment of the present invention is applied.
Fig. 2 is a cross sectional drawing showing a clutch and the area around the clutch. Fig. 3 is a front elevation of a primary driven gear part with a clutch side plate omitted. Fig. 4 is a front elevation of a primary driven gear. Fig. 5 is an enlarged cross sectional drawing of essential parts of Fig. 2. Fig. 6 is a cross sectional drawing showing essential parts of a compacting machine. Fig. 7 is a similar cross sectional drawing in a different state. Tig. 8 is a cross sectional drawing of essential parts of another embodiment. Fin. 9 is a cross sectional drawing of essential parts of a primary driven gear of a further embodiment of the present invention.
Fin. 10 is a front elevation of a primary driven gear part of the other embodiment with the clutch side plate omiti'd. Fig. 1 1 is an explanatory drawing showing an example different to the present invention.
| Embodiment Of The Invention)
An embodiment of the present invention will be described in the following with reference to Fig. I to Fig. 7.
A sintered gear relating to this embodiment is used as a primary driven gear 30 used in a clutch section of a motorcycle, and Fig. I shows a cross section of an internal combustion engine, and power transmission system of a motorcycle.
In the internal combustion engine I, the connecting rod 4 converts reciprocal movement of a piston 3 inside a cylinder 2 into rotational motion of a crankshaft 5, and an AC generator 6 is provided on one end of the crankshaft 5. The other end of the

crankshaft 5 is engaged with a primary' drive gear 7.
A main shaft 8 and a counter shaft 9 are provided parallel to the crankshaft 5, and power transmission is carried out through a transmission gear group 10 selectively meshing between the main shaft 8 and the counter shaft 9. A rear wheel is driven via a chain wound around a sprocket 1 1 attached to the end of the counter shaft 9.
A friction clutch 20 is provided on one end of the main shaft 8, and a primary driven gear 30 attached to a clutch outer 21 of the friction clutch 20 meshes with a primary drive gear 7 attached to the crankshaft 5 .
The primary drive gear 7 and the primary driven gear 30 are helical gears with meshing teeth being a line of teeth in a helix shape.
Referring to Fig. 2, the clutch outer 21 of the friction clutch 20 constitutes a cylinder having a hollow circular plate section 21a as a bottom wall and a cylinder section 21 b. A hub 22 is spline-fitted onto the main shaft 8 projecting inside this cylinder and fastened with a nut 23, and a central cylinder section 24a of a clutch center 24 is also attached to the same "hub 22.
The clutch center 24 has an annular circular plate 3,4b extending in a radial direction from the central cylinder section 24a, and folded to a cylinder section 24c which is folded back to form a flange 24d. The clutch center rotates integrally with the main shafts via the hub 22.
Within the cylinder of the clutch outer 21, a pressure plate 25 is slidably supported at its middle on the hub 22 inside the clutch center 24.
The pressure plate 25 has an annular circular plate 25a opposite to the clutch center 24, and a cylindrical section 25b extending from the external vicinity of the annular circular plate 25a is formed along the outer surface of the cylindrical section 24c of the clutch center 24.
[0021]
A plurality of clutch outer 21 side clutch discs 26 and pressure plate 25 side clutch plates 27 are alternately arranged in the space between the outer surface of the cylindrical section 25b of the pressure plate 25 and an inner surface of the clutch outer 2 1 .
These clutch discs 26 and clutch plates 27 are sandwiched between the flange 24d of the clutch center 24 and the annular circular plate 25a of the pressure plate 25.

10022]
Accordingly, if a distance by which the pressure plates 25 approaches the clutch center 24 is reduced, the clutch discs 26 and the clutch plates 27 respectively draw closer together and a frictional bond is made strong, easily transmitting rotation of the clutch outer 21 to the clutch center 24 and the main shaft 8. Conversely, if the pressure plates are separated from the clutch center 24 power transmission is disconnected.
The friction clutch 20 is engaged or disengaged in this way. [0023|
The primary drive gear 7 and the primary driven gear 30 for transmitting rotation of the crankshaft 5 to the clutch outer 21 are sintered helical gears, and the primary driven gear 30 has a shape as shown in Fig. 2 to Fig. 5.
That is, particularly with reference to Fig. 4, an annular circular plate part 30b extends in a radial direction from a central cylindrical part 30a, and helical teeth 30c are formed in the shape of a helix on an outer edge of the circular plate part 30b. |0024|
A stepped portion 31 is formed in a circular shape at a borderline between an outer portion 32 including these helical teeth 30c and an inner portion 33 inside the outer portion 32.
The stepped portion 31 is in the vicinity of the helical teeth 30e and the clutch outer 21 comes into contact with an inner part 33 inside this stepped portion 3 1. |0025|
This inner part 33 has a six large diameter circular holes 34 formed at equal intervals around the circumference of the cylindrical part 30a, and also three small diameter circular holes 35 formed at equal intervals along the stepped portion 3 1.
The small diameter holes 35 are provided with stepped parts having a small internal diameter at inner surfaces. |0026|
As shown in Fig. 2, the primary driven gear 30 has the cylindrical part 30a rotatably attached to the main shaft X via an outer collar 40, and sandwiched between two washers 41 and 42 on either side, and is located in an axial direction together with the collar 40. |0027|
The primary driven gear 30 has the circular plate section 2 la of the friction clutch 20 contacting with the inner part 33 of the primary driven gear 30, and six bosses 2le projecting from the circular plate section 2la of the friction clutch 20 are inserted into buffer rubbers 36 fitted into the six large circular holes 34 of the inner part 33 and the

clutch outer 21 is held in a floating state via the buffer rubbers. |0028]Resilient rubbers 37 are fitted into the three small holes 35 of the inner part 33 of the primary driven gear 30, and each of the resilient rubbers 37 is pushed out further than the side surface of the inner part 33 with no external force applied.
If the circular plate section 2 la of the clutch outer 21 is brought into contact with the primary driven gear 30, end surfaces of the bosses 21c penetrating through the buffer rubbers fitted into the large holes 34 project slightly further than the side surface of the primary driven gear 30. |0029|
A clutch side plate 28 having a hollow circular plate shape is made to oppose a side surface of the inner part 33 and comes into contact with an end surface of the bosses 2ic of the clutch outer 21. The clutch side plate 28 is integrally attached to the clutch outer 21 by being fixed to the bosses 21c with rivets 29. |0030|
The resilient rubbers 37 that have been fitted into the three small holes 35 of the primary driven gear 30 are pressed against the clutch side plate 28, and the restoring force acts to move the clutch side plate 28 to the left in Fig. 2 in a direction of moving away from the primary driven gear 30. Accordingly the clutch outer 21 integral with the clutch side plate 28 is pressed against the primary driven gear 30 and operates to maintain a contacting state. 10031|
As shown in Fig. 5, in this state a fixed gap C is formed between the primary driven gear 30 and the clutch aide plate 28.
In this way, the clutch outer 21 is attached in a floating state to the primary driven gear 30 through the buffer rubbers 36. |0032|
If the crankshaft 5 is rotated by operation of the internal combustion engine 1, rotation is transmitted to the primary driven gear 30 meshing with the primary drive gear 7 integral with the crankshaft 5, but both the crankshaft 5 and the primary driven gear 30 are helical gears which means that power transmission is carried out smoothly and with good efficiency. |0033|
Rotation of the primary driven gear 30 is transmitted to the clutch outer 21 via the buffer rubbers 36 which means that rotational load variations due to engaging or disengaging of the frictionul clutch 30 such as when starting the internal combustion
engine 1 are damped by the buffer rubbers 37 making it possible to maintain smooth power transmission. |0034|
In this case, by maintaining the gap C between the primary driven gear 30 and the clutch side plate 28, since relative rotation of the primary driven gear 30 and the clutch outer 21 becomes free, the buffer rubbers 36 operate effectively when there are variations in rotational load due to disengaging of the primary driven gear 30 and power transmission can be carried out smoothly. 100351
Also, the primary drive gear 7 and the primary driven gear 30 are helical gears and the helical teeth are meshed, which means that if there are variations in rotational load a phase difference occurs between the primary driven gear 30 and the clutch outer 21, as described above, and the primary driven gear 30 is also subjected to force in an axial direction. (00361
If the gap between the primary driven gear 30 and the clutch side plate 28 is not kept at a necessary minimum the primary driven gear 30 knocks into the clutch side plate 28 and hammering ivoise is generated. |0037|
The gap C must be maintained at the necessary minimum also to prevent this generation of hammering noise, and as a result the primary driven gear 30 must be manufactured to a high dimensional precision.
Particularly, there is a need for high dimensional precision with respect to the length and wicllh or'the inner part 33 of the primary driven gear 30. 100381
This primary driven gear 30 is a sintered helical gear that has been subjected to a sintering process after being compacted. Since an outer part 32 including helical teeth 30e requires extra strength compared to the inner part 33, molds must be rotated to compact the helical teeth 30e of the outer part 32. However, since the molds having the large circular holes 34 can not rotate, the outer part 33, and the inner part 32, are compacted using separate molds. |0039|
The method of compacting will be described based on the schematic diagrams of Fig. 6 and Fig. 7. Identical molding machines make an annular shape, a pair of upper and lower punches are fitted into an inner side of a die 50 forming helical teeth on an inner surface, and metal powder filled in between the upper and lower punches is compressed
to form a compacted body. [0040]
A rod 51 for forming the cylindrical part 30a of the primary driven gear 30 passes through the central axis of the die 50, with a rod for forming the large circular holes 34 and small circular holes 35 (not shown) passing through fixed locations. |0041|
A pair comprised of an upper boss punch 52a and a lower boss punch 52b are fitted around the central rod 5 1 so as to be capable of being raised or lowered. An upper inner punch 53a and a lower inner punch 53b are respectively fitted round the upper boss punch 52a and a lower boss punch 52b so as to be capable of being raised or lowered, and an upper outer punch 54a and a lower outer punch 54b are respectively fitted between the die 50 and upper and lower inner punches 53a and 53b. [0042]
Helical teeth are formed on the outer surface of the upper and lower outer punches 54a and 54b and spiral with the helical teeth of the die 50 upwards and downwards
Accordingly, the inner side upper and lower boss punches 52a and 52b and the upper and lower inner punches 53a and 53b only move in an up-down direction, while the outer side upper and lower pouter punches 54a and 54b move in an up-down direction while rotating. |0043|
in this way, the molds are divided into inner and an outer molds, with the inner part 33 of the primary driven gear 30 being formed using the upper and lower boss punches 52a and 52b and the upper and lower inner punches 53a and 53b on the inside, while the outer part 32 is formed using the upper and lower outer punches 54a and 54b on the outside. |0044|
At the initial molding stage, as shown in Fig. 6, metal powder 55 that has been filled in is compressed by the inner side upper and lower boss punches 52a and 52b and the upper and lower inner punches 53a and 53b and the metal powder 55 is compressed at the insicle and pushed toward a peripheral edge portion. |0045|
Following that, the peripheral edge of the metal powder 55 is compressed while rotating the upper and lower outer punches 54a and 54b to form the helical teeth and an outer parr, and a compacted body is formed as shown in Fig. 7 by substantially aligning the upper and lower inner punches 53a and 53b with the upper and lower outer punches
54a and 54b. [0046|
The compacted body formed in this way has high metal powder density in an outer part including the helical teeth compressed at a different time, and if this compacted body is sintered, it is possible to increase the strength of the helical 30a of the outer part 32. 100471
The compacting stage is carried out so as to substantially align the upper and lower outer punches 54a and 54b and the upper and lower inner punches 53a and 53b, but perfect alignment is difficult and the sintered primary driven gear 30 has a stepped portion 31 formed where the molds are separated. 100481
As shown in Fig. 5, since the primary driven gear 30 has the stepped portion 31 of an amount D corresponding to the mold separating area along the outside in the vicinity of the helical teeth, the stepped portion 3 I is further out than the part contacting the clutch outer 21, and this means that, as described above, it is possible to ensure that the length and width of the inner part 33, requiring particularly high dimensional precision, between the clutch outer 21 of the primary driven gear 30 and the clutch side plate 28 maintain the required dimensional precision. |0049|
Accordingly, a gap C between the primary driven gear 30 and the clutch side plate 28 maintains a necessary minimum and it is possible to prevent the occurrence of hammering noise when the primary driven gear 30 knocks against the clutch side plate 28. [0050|
If, as shown in Fig. I 1, the position at which the molds are separated is not in the vicinity of the helical teeth 030c but approaching the central side and the stepped portion 031 i.s a portion for contacting the clutch outer 021, the gap C between the primary driven gear 030 and the clutch side plate 028 caused by mold slippage amount D can not he kept at the necessary minimum and hammering noise can not be prevented. |0051|
As described above, this primary driven gear 30 can be manufactured with a reduced number of processing steps and at low cost by carrying out compacting sintering processing, and it is possible to maintain a necessary high dimensional precision of the inner part 33. |0052|
The primary driven gear 30 shown in Fig. 5 has a stepped portion 3 I formed by

mold slipping of the outer part 32 to the clutch outer 21 side relative to the inner part 33, but the primary driven gear 60 as shown in Fig. 8 (the same parts have the same reference numerals attached thereto) has a stepped portion 61 formed by slipping of the outer part 62 to the clutch side plate 28 opposite to the clutch outer 21 relative to the inner part 63. However, the stepped portion 61 is further out than a portion contacting the clutch outer 21 and a necessary length and width of the inner part 63 can maintain high dimensional precision, a gap C between the primary driven gear 60 and the clutch side plate 28 can be kept at the necessary minimum and the occurrence of hammering noise can be prevented. |0053|
When even higher precision is desired than the dimensional precision obtained with the above described compacting and sintering, a cutting margin 76 is formed in the vicinity of a stepped portion 7 1 on a side surface of an inner part 73 at the clutch side plate 2S side so as to make the primary driven gear 70 shown in Fig. 9 and Fig. 10 (the same parts have the same reference numerals attached thereto). |0054|
With respect to the side surface of the inner part 63, by subjecting a raised portion 77 sticking out further than the cutting margin 76 to cutting processing it is possible to easily form the length of width of the inner part 63 with high dimensional precision and it is possible to restrict manufacturing cost to a minimum, and further it is possible to provide the gap C between the primary driven gear 70 and the clutch side plate 28 with a necessary gap length of high accuracy.
[Description Of The Numerals|
1 internal combustion engine
2 cylinder
3 piston
4 connecting rod
5 crankshaft
6 AC generator
7 primary drive gear
8 main shaft
9 counter shaft

10 transmission gear train
11 sprocket

20 friction clutch
21 clutch outer
22 hub
23 nut
24 clutch center - '
25 pressure plate
26 clutch disk
27 clutch plate
28 clutch side plate
29 rivet
30 primary driven gear
31 ridge
32 outer circumferential section
33 inner circumferential section
34 large circular hole
35 small circular hole
36 damping rubber
37 flexible rubber
40 outer collar
52a upper boss punch 52b lower boss punch 53a upper inner punch 53b lower inner punch
54a upper outer punch 54b lower outer punch 55 metal powder
60 primary driven gear
61 ridge
62 outer circumferential section
63 inner circumferential section

70 primary driven gear
71 ridge
72 outer circumferential section
73 inner circumferential section

76 cutting margin
77 raised portion



WE CLAIM;
1. A sintered primary driven gear provided between clutch outer (21)
and clutch side plate (28) and subjected to a sintering after
compacting metal powder using an outer mold for forming teeth
and an outer part in the vicinity of the teeth and an inner mold for
forming inner part that are different from each other,
characterized in that:
a stepped portion (31) arising as a result of separation of each of the outer and inner molds is formed further out than a contact surface between the primary driven gear (30) and the clutch outer (21), a gap is established between the stepped portion (31) and the clutch side plate (28) or the stepped portion (31) and the clutch outer (21).
2. A sintered primary driven gear substantially as hereinbefore
described with reference to and as illustrated in the accompanying
drawings.

Documents:

260-del-1999-abstract.pdf

260-del-1999-claims.pdf

260-del-1999-correspondence-others.pdf

260-del-1999-correspondence-po.pdf

260-del-1999-description (complete).pdf

260-del-1999-drawings.pdf

260-del-1999-form-1.pdf

260-del-1999-form-13.pdf

260-del-1999-form-19.pdf

260-del-1999-form-2.pdf

260-del-1999-form-3.pdf

260-del-1999-form-4.pdf

260-del-1999-form-6.pdf

260-del-1999-gpa.pdf

260-del-1999-petition-138.pdf


Patent Number 215701
Indian Patent Application Number 260/DEL/1999
PG Journal Number 12/2008
Publication Date 21-Mar-2008
Grant Date 03-Mar-2008
Date of Filing 17-Feb-1999
Name of Patentee HONDA GIKEN KOGYO KABUSHIKI KAISHA
Applicant Address 1-1 MINAMIAOYAMA 2-CHOME, MINATO-KU, TOKYO, JAPAN.
Inventors:
# Inventor's Name Inventor's Address
1 MAKATO SUZUKI C/O KABUSHIKI KAISHA HONDA GIJUTSU KENKYUSHO, OF 4-1, CHUO 1-CHOME, WAKO-SHI, SAITAMA, JAPAN.
PCT International Classification Number B22F 5/08
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 Hei-10-71679 1998-03-20 Japan