Metal deforming – By use of closed-die and coacting work-forcer – With stripping or ejecting from tool
Patent
1998-07-10
1999-09-07
Larson, Lowell A.
Metal deforming
By use of closed-die and coacting work-forcer
With stripping or ejecting from tool
72352, 2989334, B21K 130
Patent
active
059469633
DESCRIPTION:
BRIEF SUMMARY
This application claims the benefit under 35 U.S.C. .sctn.371 of prior PCT International Application No. PCT/JP97/04087 which has an International filing date of Nov. 10, 1997 which designated the United States of America, the entire contents of which are hereby incorporated by reference.
1. Technical Field
The present invention concerns a hot-forging apparatus for forming a bevel gear having inclined gear teeth, wherein forging is performed while heat is applied to the material at a fixed temperature.
2. Background Art
A bevel gear, which is constructed with inclined gear teeth, is one type of gear which enables the direction of transmission of a motive force to be varied, and moreover, while being smoothly and quietly effected. Among such known bevel gears are helical bevel gears, spiral bevel gears, hypoid gears, and the like.
FIG. 12 illustrates spiral bevel gears 2 and 4. Such spiral bevel gears 2, 4 intersect at respective axial lines thereof, and are constructed so that their mutually enmeshed gear teeth 2a and 4a are in an inclined condition.
As methods for producing bevel gears 2, 4 constructed in this manner, spiral-teeth bevel gears are produced, for example, by press working, machining, and/or utilizing specialized gear cutting apparatus. In the case of specialized gear cutting apparatus, a remarkably high cost is involved, and further, because the gear teeth must be cut one by one, there is the disadvantage that a lengthy processing time is required, with poor yield rate.
Hence, an apparatus by which spiral bevel gears 2, 4 are formed by forging has been disclosed in Japanese Laid-Open Patent Publication No. 4-371335. According to this known technique, after forging of a spiral bevel gear material using rotatably disposed upper and lower dies having gear-teeth formations on their interior surfaces thereof, a spiral bevel gear 2, 4 having inclined gear teeth is formed by "knockout" while one of the molds is being rotated.
However, with this known technique, one of the molds, for example the upper mold, is supported for rotation through bearings, and when knockout is performed after formation, the upper mold is rotated depending on the turn angle of the gear teeth 2a, 4a. Accordingly, especially in the case of a heavy material upper die, the force necessary to rotate the die is directly imposed on the gear teeth, resulting in malformation thereof.
Further, another prior technique is the gear forging die apparatus which is disclosed in Japanese Laid-Open Patent Publication No. 2-52141. This apparatus is constructed by a driven gear which is disposed on the outer peripheral part of a lower die, wherein by means of a screw, and via a drive gear which is enmeshed with the driven gear, the lower die is made to rotate, such that when the die is closed shut and opened, rotation of the lower die is performed by a cylinder which is attached to the screw.
However, according to this technique, especially concerning rotation of the lower die at the time of opening the die, there is a delay caused by the cylinder, whereby synchronization with the opening operation cannot be achieved, resulting in damage to the spiral bevel gear 2, 4.
A principal object of the invention is to provide a bevel gear hot-forging apparatus in which a large force is reliably prevented from being applied to the gear teeth during opening of a forming die, thereby enabling bevel gears of superior quality and high yield rate to be achieved.
DISCLOSURE OF THE INVENTION
At the time of closing a die mold, a bevel gear is formed by a stable die closing force which is sufficiently given to a material by force applying means. If the force applying means comprises a plate spring, a stable die closing force can be constantly obtained. The force applying means has a hydraulic cylinder. A hydraulic fluid supply circuit has a check valve and a relief valve for conducting supply and evacuation of hydraulic fluid. Therefore, a desired surface pressure can be obtained at the time of closing the die mold, so that burrs or mold flashing can be avoi
Asada Takashi
Minowa Akihiko
Okada Seishi
Sugita Hiroshi
Suzuki Kouji
Honda Giken Kogyo Kabushiki Kaisha
Larson Lowell A.
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