Machine element or mechanism – Gearing – Rotary bodies
Reexamination Certificate
2001-04-02
2003-07-15
Hannon, Thomas R. (Department: 3682)
Machine element or mechanism
Gearing
Rotary bodies
C074S439000, C074SDIG001, C264S257000, C428S193000, C428S474400
Reexamination Certificate
active
06591708
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a gear made of fiber reinforced resin or a resin gear, and more particularly to a gear constituted by a bushing made of metal and a gear body which includes a core made of a reinforcing fiber substrate and formed into a ring-like shape and is integrally arranged on an outside of the metal bushing.
There has been conventionally known in the art techniques of forming resin into a gear body by compression molding while using a reinforcing resin substrate made of an aramid fiber as a core. For example, techniques of preparing a prepreg by previously impregnating a sheet-like non-woven fabric made of a blend material of a para-type aramid fiber and a meta-type aramid fiber with phenolic resin, rounding the prepreg into a bar-like shape and mating or matching both ends of the thus-rounded prepreg with each other to form the prepreg into a ring-like shape, resulting in providing a reinforcing fiber substrate are disclosed in Japanese Patent Application Laid-Open Publication No. 113458/1995. Unfortunately, the reinforced fiber substrate constituted of such a non-woven fabric fails to exhibit enhanced mechanical strength. Also, the prepreg causes flowing of the resin impregnated therein, leading to deformation of the reinforcing fiber substrate, so that the reinforcing fiber substrate spreads to a portion of the metal bushing positioned in proximity to a corner thereof defined between an outer peripheral surface of the metal bushing and a side surface thereof. This causes the reinforcing fiber substrate and resin to project to the side surface of the metal bushing, although it permits an increase in bonding strength between the gear body and the metal bushing.
In order to solve the problem, techniques that a cylindrical body made of a woven or knitted fabric of an aramid fiber yarn (a blended yarn or union yarn of a meta-type aramid fiber yarn and a para/meta-type aramid fiber yarn) is used as a material for a reinforcing fiber substrate are proposed, as disclosed in Japanese Patent Application Laid-Open Publication No. 156124/1996. In the techniques proposed, the cylindrical body is bent into a ring-like shape along a central line thereof from one or both ends of the cylindrical body, so that the reinforcing fiber substrate is provided. Then, the reinforcing fiber substrate is placed in a molding die together with a metal bushing while keeping the metal bushing arranged at a central position of the reinforcing fiber substrate. Thereafter, liquid thermosetting resin such as epoxy resin, crosslinked polyamino amide or the like is poured into the molding die reduced in pressure, to thereby be impregnated in the reinforcing fiber substrate. Subsequently, the molding die is heated to a predetermined temperature, so that a resin molded member which includes the reinforcing fiber substrate having the resin impregnated therein and acting as a core is integrally formed on an outside of the metal bushing by cast molding. Then, the resin molded member is subjected to cutting, to thereby be formed on a periphery thereof with teeth, resulting in a resin gear being provided. The thus-manufactured resin gear is so constructed that the reinforcing fiber substrate is formed into a continuous ring-like shape without any joint. Such construction permits the gear to entirely exhibit uniform strength. Also, in Japanese Patent Application Laid-Open Publication No. 156124/1996 described above, techniques of subjecting the above-described blended yarn or union yarn to plain weaving, to thereby prepare a sheet-like fabric and winding the fabric into a bar-like member, of which both ends are matched with each other to provide a ring-like reinforcing fiber substrate are disclosed as a comparative example as shown in
FIG. 2
thereof The reinforcing fiber substrate thus obtained is placed in a molding die, resulting in a resin molded member being formed by compression molding in a manner like the above.
Further, additional techniques are proposed as disclosed in Japanese Patent Application Laid-Open Publication No. 299865/1998, wherein such a cylindrical body as described above is made of a woven fabric and formed into a shape like a bellows. Then, the thus-formed cylindrical body is wound up from one end thereof, to thereby be formed into a ring-like shape. The woven fabric is made of a blended or union aramid yarn constituted by a meta-type aramid fiber and a para-type aramid fiber. More detailed description of the fibers is not made in the publication. In the techniques disclosed, a ring-like reinforcing fiber substrate is placed in a temporary molding die prior to arrangement thereof in a molding die, resulting in being formed into a predetermined configuration.
The above-described aramid fiber yarn obtained by blending of the meta-type aramid fiber and para-type aramid fiber and used for the cylindrical body permits the gear made of resin to be increased in strength and durability. However, an increase in proportion of the para-type aramid fiber in the aramid fiber yarn causes cutting operation for formation of teeth of the gear to be deteriorated, although it increases strength of the gear as described above. Also, it tends to cause the aramid fiber yarn to be left on a cut surface of the teeth without being cut out during the cutting operation. Further, the aramid fiber yarn thus having failed to be cut out is caused to be pulled during the cutting operation, to thereby be drawn out of the reinforcing fiber substrate, resulting in the reinforcing fiber substrate and resin being separated or peeled from each other at an interface therebetween. Such peeling causes moisture or the like to intrude into the resin gear, leading to a deterioration in durability of the resin gear.
SUMMARY OF THE INVENTION
The present invention has been made in view of the foregoing disadvantage of the prior art.
Accordingly, it is an object of the present invention to provide a gear made of fiber reinforced resin or a resin gear which is capable of exhibiting enhanced mechanical strength and service durability while optimizing a construction of a reinforcing fiber substrate formed into a ring-like shape.
It is another object of the present invention to provide a gear made of fiber reinforced resin or a resin gear which is capable of enhancing bonding strength between a metal bushing and a resin molded member.
In accordance with one aspect of the present invention, a resin gear or a gear made of fiber reinforced resin is provided. The resin gear includes a metal bushing and a gear body made of resin and arranged on an outside of the metal bushing. The gear body includes a resin molded member integrally made of a material containing thermosetting resin as a part thereof and formed on an outer periphery thereof with a plurality of teeth. The resin molded member is formed by cast molding while using at least one reinforcing fiber substrate formed into a ring-like shape as a core thereof. The reinforcing fiber substrate is constituted by a fabric selected from the group consisting of a knitted fabric of a union yarn made of a para-type aramid fiber and an organic fiber reduced in strength as compared with the para-type aramid fiber and a woven fabric thereof.
In the present invention, the reinforcing fiber substrate has a volume percentage of 30% to 65% by volume based on a volume of the resin molded member. Also, the para-type aramid fiber has a mass percentage of 30% to 60% by weight based on a mass of the union yarn.
In a preferred embodiment of the present invention, the reinforcing fiber substrate is constituted by the knitted fabric and the reinforcing fiber substrate has a volume percentage of 30% to 65% by volume based on a volume of the resin molded member.
In a preferred embodiment of the present invention, the ring-like shape of the reinforcing fiber substrate may be obtained by winding up a cylindrical body made of the knitted fabric along a central line thereof from at least one end thereof. The reinforcing fiber substrate may have a volume percentage of 45% to 55% by
Kobayashi Naomi
Sawai Syouji
Ueda Hiroshi
Hannon Thomas R.
Shin-Kobe Electric Machinery Co. Ltd.
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