JP3515038B2 - Cold forging method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cold forging method suitable for machining pinion gears, helical gears and the like. 2. Description of the Related Art Conventionally, in pinion gears, helical gears, and the like, the shape of the teeth is complicated, and the machining time is long and the cost is high for manufacturing by mechanical processing. That is being done. Therefore, in the case of a helical pinion gear or the like in which a gear portion is formed on a large-diameter cylindrical portion, it is difficult to obtain the accuracy of the shape of the base portion of the gear portion. And JP-A-7-310807
As described in Japanese Patent Application Laid-Open Publication No. H10-260, consideration has been given to forming a built-up portion at the base of the gear portion to improve the flow of the material. Japanese Patent Application Laid-Open No. H11-10274 discloses a technique in which a bulging portion is formed at the base of a gear portion to improve the accuracy of tooth surfaces. [0003] The production of helical pinion gears
Generally, cutting or forging is performed. A conventional general method of performing cold forging will be described with reference to FIGS. First, a forming part 4 composed of a cylindrical forming part 2 and a tooth mold part 3 is formed in a die 1, and a columnar material 5 is inserted into the cylindrical forming part 2 of the forming part 4. The knockout 6 is positioned at the end of the mold 3, and the other end of the material 5 is pressed by the punch 7. As a result, the raw material 5 flows in the forming section 4 and is formed as a helical pinion gear 8 as shown in FIG. 6 in the forming section 4 in the die 1 as shown in FIG. In this case, a space 9 is left between the helical pinion gear 8 and the knockout 6. In this state, the helical pinion gear 8 is taken out from the die 1 by pushing up while rotating the knockout 6. [0004] The helical pinion gear 8 formed by cold forging as described above has a cylindrical portion 10.
The first problem is that the connecting portion between the columnar portion 10 and the gear portion 11, that is, the base portion 12 of the gear portion 11 tends to be underfilled. The second problem is that the tip portion 13 of the gear portion 11 sags. In order to solve the first problem that the base portion 12 of the gear portion 11 is susceptible to underfilling, as described above, Japanese Patent Laid-Open Nos. 7-308729 and 7-3
As disclosed in Japanese Patent Application Laid-Open No. 10807/107, consideration has been given to forming a built-up portion on the base portion 12 of the gear portion 11 to improve the flow of the material. A bulging portion is formed on the base portion 12 of the eleventh portion to improve the accuracy of the tooth surface. However, such a countermeasure is that the base portion 12 of the gear portion 11 has a built-up portion or a bulging portion, which substantially reduces the effective tooth surface range. Next, with respect to the second problem that the tip portion 13 of the gear portion 11 sags, a countermeasure is taken that the tip portion 13 of the gear portion 11 is not cut off by machining. For this reason, it is not possible to effectively use the bent part, and the part is wastefully formed. SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and provides a cold forging capable of improving the molding accuracy of each part and obtaining a product which can be used with only a small finishing operation. The aim is to provide a method. Means for Solving the Problems The invention according to claim 1 is:
A die with a molded part consisting of a cylindrical part and a tooth part
The insert material charge into a cylindrical forming unit, the inserted the material charge in the die, and rotate relative to the die the cylinder of
Rotately insert the punch inserted from the forming part and the tooth mold part
Sandwiched by the inlet knockout, the grant predetermined pressure knockout, impart greater pressure than the sum of the <br/> knockout pressure and molded under pressure to the punch, whereby the Punch and knock
The material moves to the helicopter as the out moves while rotating.
It is formed as a carpinion gear . Accordingly, the raw material is sandwiched by the punch and the knockout and is formed while receiving a large compressive force, so that the molding is accurately performed in accordance with the die shape, and a highly accurate product can be obtained. Things. Ma
Also, forming helical pinion gears with complicated shapes is problematic.
It can be done well. An embodiment of the present invention will be described with reference to FIGS. 1 to 3. First, a forming part 17 composed of a cylindrical forming part 15 and a tooth mold part 16 is formed on the die 14, and a columnar material 18 is inserted into the cylindrical forming part 15 of the forming part 17. The knockout 19 that has been rotated and inserted into the mold 16 is brought into contact with the end of the material 18, and the other end of the material 18 is pressed by the punch 20. As a result, the raw material 18 flows in the molding section 17 and
As shown in FIG. 2, the helical pinion gear 21 as shown in FIG. In this case, the knockout 19 is in contact with the material 18 with a predetermined pressing force, and
Is applied with a pressure greater than the sum of the pressure of the knockout 19 and the molding pressure. Therefore, the knockout 19 moves to a state where it is lowered from the position where it was initially located, and the molding is completed. Moreover, during cold forging, the punch 20 and the knockout 19 move in the axial direction while rotating, and the interval between the two also relatively changes. Therefore, the punch 20 and the knockout 1 are provided at the upper and lower ends of the helical pinion gear 21 until the molding is completed.
9 will be in contact with it. In this state, punch 2
The helical pinion gear 21 as a product is taken out of the die 14 by letting the knockout 19 rise upward while rotating the knockout 19. The helical pinion gear 21 thus formed by cold forging comprises a cylindrical portion 22 and a gear portion 23. The connecting portion between the cylindrical portion 22 and the gear portion 23, that is, the gear portion 23 The molding of the base 24 is also accurately performed up to the corner, and the gear 23 is
It is accurately formed without sagging up to the tip 25. The helical pinion gear 21 formed as described above is completed as a product only by performing machining such as to finish the end face of the distal end portion 25. In addition, the shape and dimensions are accurate throughout, and in particular, the shape of the base 24 of the gear portion 23 is also accurate. In the above-described embodiment, the helical pinion gear 21 is formed. However, in the embodiment, the helical pinion gear 21 may be used for forming a stepped columnar member, a straight gear such as a spur gear, and the like. .
In this case, more accurate molding can be performed than in the case of the helical pinion gear 21. According to the first aspect of the present invention, a columnar forming portion and a tooth are provided.
Forming the above-mentioned cylinder of a die having a molded part formed of a mold part
Parts to insert the material fee insert, the material charge which is inserted into the die, from rotating the cylinder forming portion with respect to the die
It has been punched and sandwiched by the knock <br/> out rotation to being inserted into the tooth-shaped portion, the grant predetermined pressure knockout, and the knock-out pressure and molded under pressure to the punch Apply a pressure greater than the sum ,
This rotates the punch and the knockout
While moving, the material is helical pinion
Since the so formed as Ya, material cost is to be formed while subjected to a large compressive force is sandwiched by a punch and the knockout, the precisely shaped along done the shape of the mold die, accurate product You can get
The shape of the die may be a general shape, therefore, the mold life since there are no unreasonable die have a effect of long such, further
In addition, molding of helical pinion gears with complicated shapes is also a problem
It has the effect that it can be performed well. [0017]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows one embodiment of the present invention, and is a longitudinal sectional side view in a state before molding. FIG. 2 is a vertical sectional side view of a molded state. FIG. 3 is a front view of a formed helical pinion gear. FIG. 4 is a longitudinal sectional side view of a state before molding, showing an example of the related art. FIG. 5 is a vertical sectional side view of a molded state. FIG. 6 is a front view of a formed helical pinion gear. [Description of Signs] 14 Die 18 Material 19 Knockout 20 Punch 21 Helical pinion gear

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B21J 1/00-13/14 B21J 17/00-19/04 B21K 1/00-31/00

Claims (1)

(57) [Claims 1] A molding part comprising a cylindrical forming part and a tooth part is provided.
Insert the raw material into the column forming part of the formed die,
The inserted the material fuel in the serial die, with respect to the die
The punch and the tooth mold that have been rotated and inserted from the cylinder forming portion
Rotating the part sandwiched by the insertion knockout imparts greater pressure than the sum of the knock-out pressure and molded under pressure to the punch, whereby
The punch and the knockout move while rotating.
Forming the helical pinion gear
A cold forging method characterized by being performed.