JPH0337810B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing gears by forging.

[Conventional technology and its problems]

Conventionally, when manufacturing gears, a material is previously formed into the outer shape of the gear by machining or forging, and then the tooth portions are cut by machining. Therefore, this gear cutting process requires a lot of work, so in order to shorten or eliminate this gear cutting process, the material is forged in advance to form not only the outer shape of the gear but also the shape of the tooth part, and then the gear part is Gear cutting is performed using a gear cutting machine. Furthermore, although small-sized gears can generally be manufactured with desired precision by cold forging, medium-sized and large-sized gears cannot be manufactured due to limitations in material plasticity. For this reason, in the case of medium-sized and large-sized gears, it is necessary to perform rough processing in advance by hot forging as described above, and then cut the gears by machining.

The purpose of the present invention is to prepare the outer shape of the material in advance by hot or warm forging, and then tighten the teeth by cold forging to manufacture gears with the desired accuracy using only the forging process. do.

[Means for solving problems]

In the present invention, the outer shape of the gear is first formed by hot or warm forging, which is easy to plastically deform the material cut to the required size, and then the tooth part is cold ironed to the same degree as gear cutting. We aim to manufacture large gears with high precision using only the forging process.

〔Example〕

Next, a method for manufacturing gears by forging according to the present invention will be explained based on one embodiment. In addition to various spur gears, it is also possible to manufacture sprocket wheels according to the present invention.

First, materials suitable for gear manufacturing, such as chromium molybdenum steel (SCM), nickel chrome steel (SNC),
Material 1 is cut to the size of the gear to produce the desired steel material, such as chrome steel (SCR), nickel chrome molybdenum steel (SNCM), low carbon steel, high carbon steel, etc., and is hot or warm forged in heating process 2. Heat to the appropriate temperature. Then, this heating material 1 is previously formed into the shape of a tooth profile in a hot forging step 3 (or hereinafter abbreviated as hot forging including warm forging). This hot forging 3 goes through one or more processes, such as a rough process and a finishing process, depending on the size and shape of the gear to be formed.

The gear formed in this step may be either an internal gear or an external gear, and its tooth profile is primarily an involute tooth profile or a rack tooth profile, but other tooth profiles may also be used. In this way, the shape of the tooth profile is also normalized in the same manner as in the conventional process in order to adjust the austenite grain size or pro-eutectoid carbide of the material formed by hot forging. The material that has undergone this normalization process 4 is then sent to a shotplast process 5. After removing the oxide in this shotplast process, bonderite treatment 6 is performed. Then, in a cold forging step 7, the tooth profile is shaped, using a cold ironing die so that the tooth profile has the desired precision.

This ironing allowance is about 1/100 to 5/100 mm, which provides almost the same accuracy as gear cutting by machining.

In this cold forging process, a mold as shown in FIG. 2 is used. This is just one example and is used depending on the tooth shape. The lower mold 10 has molding teeth 11 for finishing to a desired precision, and the molding tooth 11 has a precision of 1/100 to 1/100.
Material G formed by hot forging to a size of about 5/100
is strongly pressed by the upper mold 20 to insert it. In this case, an approach 12 is formed in the upper part of the lower mold so that the tip of the material G can be guided into the molded tooth 11 reliably and accurately. In addition, if the gear to be manufactured is a spur gear, the material G can be passed through the lower mold, but if the material has a boss, flange, etc. integrally formed on the tooth profile, it is first forced into the molded teeth of the lower mold. After the material is inserted and ironed, it is pulled out.

〔Effect of the invention〕

According to the present invention, the material is first formed into the shape up to the tooth profile by hot forging, and then the tooth profile is formed by cold forging using a cold ironing die, resulting in residual stress. It has the advantage that the deformation of the tooth portion after carburizing and quenching is small, the accuracy is the same as machining, and manufacturing costs can be reduced.

Furthermore, since all tooth profiles are finished in the forging process, the fibers flow and the strength is greater than that of machined products. For this reason, it is not necessary to use high-grade materials such as nickel chrome molybdenum steel as the gear material, and the unit cost of the material becomes low.

[Brief explanation of the drawing]

The drawings show one embodiment of the method for manufacturing a gear according to the present invention, in which FIG. 1 is a flowchart, FIG. 2 is an explanatory diagram showing a cold forging process, and FIG. 3 is a plan view of a spur gear.
FIG. 4 is an explanatory diagram when forming and finishing the tooth profile portion by cold forging rather than hot forging.

Claims (1)

[Claims] 1 After hot or warm forging the material to form the tooth profile slightly larger than the final finished tooth profile, this is sequentially cooled, normalized, shot blasted, and bonded, and then cold ironed into dies. 1. A method for manufacturing a gear by forging, characterized in that the gear is fitted into an approach and pushed into the die, and a desired precision is obtained in a cold ironing process.