JPH07112234A - Method and apparatus for forging multistep gear - Google Patents

Abstract

PURPOSE:To form a multistep gear by forging. CONSTITUTION:Dies are constituted with a parting surface at a boundary of a large diameter gear and a small diameter gear and a tooth die 5 for forming a helical tooth form on the peripheral surface of a cavity 2a for forming the large diameter gear and a tooth die 6 for forming a straight tooth form on the peripheral surface of a cavity 2b for forming the small diameter gear. Then the helical tooth form and the straight tooth form are synchronously formed on the periphery of a blank 8 by a pushing-in operation for pushing the two-step doughnut type blank 8 into the cavity 2 provided so as to be possible to pierce with s mandrel 3 at the center and an operation for piercing with the mandrel 3 into a through-hole 8a of the blank 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for forging a multi-stage gear having tooth profiles adjacent to each other, such as a speed change gear having synchro engaging teeth. The term "gear" is used herein as a generic term for gears having irregularities for engagement, and also includes sprockets, counter driven, and the like.

[0002]

2. Description of the Related Art Gears, which have hitherto relied on cutting work, have suddenly come alive with the success of forging being announced in recent years. In those forging methods, as previously proposed by the applicant, a forging device in which cavities corresponding to two types of gears are integrally formed makes it possible to form a highly accurate tooth profile by utilizing the seguiri effect. There is.

[0003]

There is no problem if the diameters of the gears are arranged next to each other in the order of increasing or decreasing diameters, but it is applicable to the molding of multistage gears in which small diameter gears are arranged between large diameter gears. Can not. Further, if the tooth profile is straight, it is easy to push in and out, but if the helical tooth profile is included, the inclination of the tooth trace will damage and it will not be possible to push it straight in or out like a straight tooth profile. Further, when a gear having a large tooth width and a large tooth height is formed, there is a possibility that the thickness may be insufficient.

[0004]

According to the present invention, even if a helical tooth profile is included, it is possible to mold and demold it, and to mold a multi-stage gear which has been impossible by the arrangement order of gears having different diameters. In addition, it is a technology to form a highly accurate multistage gear, which has a boundary between adjacent gears on a dividing surface, has a tooth profile forming tooth profile on the peripheral surface, and pierces a mandrel at the center. A forging method of forming a tooth profile around the material by pushing in a doughnut-shaped material into the cavity that is possible and piercing the mandrel,
The forging apparatus has a boundary between adjacent gears on a dividing surface, a tooth profile forming tooth mold on the peripheral surface, and a cavity having a mandrel pierced at the center thereof.

[0005]

If the block for helical tooth profile formation can be independently rotated by the divided structure, both straight and helical tooth profiles can be simultaneously formed by pushing operation, and multi-stage gears, which have been impossible in the past, can be molded. In addition, the mandrel piercing operation causes the force of meat to project in the radial direction,
The accuracy of the tooth profile is also improved.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method and apparatus for forging a multistage gear according to the present invention will be described with reference to the drawings. FIG. 1 shows a forging device. Reference numeral 1 denotes a die in which a cavity 2a for forming a large-diameter gear and a cavity 2b for forming a small-diameter gear are coaxially formed vertically side by side. The two blocks 1a. 1a. 1b and a block 1a in which a cavity 2a for forming a small diameter gear is formed are fixed to a bolster. On the other hand, the block 1a in which the cavity 2a for forming the large diameter gear is formed is rotatably supported with respect to the block 1b. Below the cavity 2b for forming the small diameter gear, the mandrel 3 is located at the center.
Further, an ejector 4 is arranged around the mandrel 3 so as to be retractable into and out of a cavity 2 composed of a cavity 2a for forming a large diameter gear and a cavity 2b for forming a small diameter gear, and the mandrel 3 is a shaft of a gear product. It has a thickness corresponding to the hole diameter.

A helical tooth profile forming tooth die 5 is formed on the inner peripheral surface of the large diameter gear forming cavity 2a, and a straight tooth profile forming tooth die 6 is formed on the inner peripheral surface of the small diameter gear forming cavity 2b. Each is formed. The straight tooth profile is used as a meshing tooth for synchronization (generally called a dog gear), and has a chamfer forming portion 6a at the tip. Also block 1a. Although not shown, a lock means is provided between the blocks 1b so that the block 1a does not rotate carelessly when the mandrel 3 is retracted. Reference numeral 7 is a punch disposed directly above the die, and a relief portion 7a having a tapered surface that is retracted in the counter-pushing direction is provided around the contact surface with the material 8.

With the forging device thus formed, first, the punch 7 is used to press-fit the two-step donut-shaped material 8 having the through hole 8a in the center into the cavity 2. In the press-fitting process, the peripheral surface of the large-diameter portion of the material 8 is initially in sliding contact with the helical tooth profile forming tooth die 5, and the block 1a is rotated and moved forward to form the helical tooth profile 9 on the sliding surface (FIG. 2). ). Then, the small-diameter portion of the raw material 8 slides on the straight tooth profile forming tooth mold to move straight forward. At this time, the block continues to rotate, and the straight tooth profile 10 is formed in the small diameter part of the material, and at the same time, the corner part of the helical tooth profile can be tensioned by the seguiri effect (FIG. 3). Finally material 8
If a mandrel 3 having a diameter larger than that of the mandrel 3 is inserted into the through hole 8a of the two tooth profiles 9.1 due to the force of expanding in the radial direction.
The accuracy of 0 can be improved (FIG. 4).

When the ejector 4 is raised, the product 8'is pushed out directly while rotating the block 1a in the opposite direction. In this way, a perfect tooth profile with a long tooth length and no flesh is formed, and the surplus remains as a burr 11 in the escape portion of the punch and can be removed by simple cutting (FIG. 5). By removing the burrs 11, a helical gear product having synchro engaging teeth with a chamfer 10a as shown in FIG. 6 is obtained.

In the above-mentioned embodiment, the cavities corresponding to the large and small gears are formed in the die. However, the cavities corresponding to the large and small gears can be provided in the die and the punch respectively. Will be explained. The names of the members are the same as those in the above embodiment. In the apparatus of this modified embodiment, as shown in FIG. 7, a cavity 2a for forming a large diameter gear is provided in a die 1, a cavity 2b for forming a small diameter gear is provided in a punch 7, and a mandrel 3.3 includes a die 1 and a punch 7. And are provided separately. Here, when the material 8 is set on the cavity 2a of the die 1 and the punch 1 is lowered, the large-diameter portion and the small-diameter portion have their respective cavities 2a. 2b
It is pushed inward, a tooth profile is formed in the process, and a seguiri effect can be expected when it is completely pushed in. The mandrel 3.3 is pierced at the same time from above and below, and its effect is the same as that of the above embodiment (FIG. 8).

Since the tooth profile is formed by pushing and pushing the mandrel in this way, a highly accurate tooth profile is obtained and the shaft hole is completed. In addition, it is possible to have two or more stages, and by making the diameter the same and inverting the inclination, it becomes a double toothed tooth, or a multistage gear in which a small diameter gear is sandwiched between large diameter gears,
It is possible to form a gear with missing teeth by omitting it partially.

[0012]

According to the present invention, it is possible to accurately form a gear by forging means, particularly a special gear including helical teeth, which has been impossible in the past, or a gear having a small diameter is sandwiched between gears having a large diameter. Is possible.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a device according to the present invention.

FIG. 2 is an explanatory diagram of a molding process.

FIG. 3 is an explanatory diagram of a molding process.

FIG. 4 is an explanatory diagram of a molding process.

FIG. 5 is an explanatory diagram at the time of demolding.

FIG. 6 is an explanatory diagram of a product.

FIG. 7 is an explanatory diagram of a modification example.

FIG. 8 is an explanatory diagram showing a molding process of a modified example.

[Explanation of symbols]

1 ... Die, 2 ... Cavity, 2a ... Cavity for forming large diameter gear, 2b ... Cavity for forming small diameter gear, 3 ... Mandrel, 4 ... Ejector, 5 ... , 6 ・ ・ Straight tooth profile forming tooth mold, 7 ・ ・ Punch, 8 ・ ・ Material, 8 '・ ・ Product, 9 ・ ・
Helical tooth profile, 10 straight straight tooth profile, 10a chamfer, 11 burr.

Claims (3)

[Claims] 1. A pushing operation for pushing a donut-shaped material into a cavity having a boundary between adjacent gears on a dividing surface, a tooth profile forming tooth mold on the peripheral surface, and a mandrel at the center of which a mandrel can be pierced. And a method for forging a multi-stage gear in which a tooth profile is formed around the material by a mandrel piercing operation. 2. A multi-stage gear having a pair of blocks each having a boundary between adjacent gears as a division surface, having a tooth profile forming tooth mold on its peripheral surface, and having a cavity at the center of which a mandrel can be inserted. Forging equipment. 3. The forging device according to claim 2, wherein each of the divided blocks is relatively rotatable.