JP2014100725A - Tooth taking-out forging metal mold, manufacturing method thereof and manufacturing method of helical gear - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tooth taking-out forging metal mold, a manufacturing method thereof and a manufacturing method of a helical gear using such a tooth taking-out forging metal mold, which is inexpensive, short in a lead time, and high in accuracy.SOLUTION: The tooth taking-out forging metal mold is a metal mold used for tooth taking-out forging of the helical gear of an internal tooth or an external tooth, and is manufactured by forming a groove (a female helical tooth) for forming a tooth shape of the helical gear to a metal mold raw material 20 by a gear shaper 10. The tooth taking-out forging of the helical gear of the internal tooth or the external tooth is executed by using such a tooth taking-out forging metal mold.

Description

  The present invention relates to a die for forging forging, a method for producing the same, and a method for producing a helical gear, and more particularly, a die for forging forging for creating a tooth shape of a helical gear by forging, and The present invention relates to a manufacturing method thereof, and a manufacturing method of a helical gear using such a set-up forging die.

  A helical gear is a gear having helically inclined teeth. Creation of a helical gear is generally performed by cutting (tooth cutting), forging, or the like. Known cutting methods include hobbing, broaching, and processing with a gear shaper (see Non-Patent Document 1). When gears are created using cutting, high gear accuracy is obtained, but production efficiency is low. For this reason, forging may be used for manufacturing helical gears where production efficiency is important.

  In order to form the tooth profile of a helical gear using forging, a forging die in which a groove (female helical tooth) is formed on the gear material for transferring the tooth profile (forging forging) is required. Become. When manufacturing helical gears by tooth forging, the accuracy of helical gears (tooth profile accuracy, tooth accuracy, pitch accuracy, tooth groove runout accuracy) is the groove formed in the forging die (female is The accuracy is lower than the accuracy of the teeth. That is, the forging die is required to have higher accuracy than the gear to be manufactured. Therefore, in general, electric discharge machining capable of high-precision machining is used for forming the groove (female helical tooth) of the die for forging forging (see, for example, Patent Documents 1 to 3).

In order to form a groove (female helical tooth) of a metal mold for forging and forging using electric discharge machining, an electrode (on which a helical tooth meshing with a groove (female helical tooth) of the mold is formed on the surface ( A helical electrode) is required. Grooves (female helical teeth) are formed by using electric discharge machining by bringing the helical electrode close to the surface of the material and reciprocating the helical electrode in the direction of the teeth.
However, the production of a helical electrode is expensive and time consuming. Therefore, the electric discharge machining method has a problem that the cost is high and the lead time is long.

Further, in order to manufacture an internal tooth mold, a helical electrode having a diameter substantially equal to the inner diameter of the mold is required. Therefore, in the case of manufacturing an internal tooth mold, the outer diameter of the helical electrode increases as the inner diameter of the mold increases.
However, the larger the helical electrode, the greater the inertia of the helical electrode. For this reason, when manufacturing an internal tooth mold having a large inner diameter, there is a problem that it is difficult to obtain the tooth streak accuracy during the reciprocating motion of the helical electrode during electric discharge machining, and it is difficult to maintain the accuracy.

Japanese Patent Laid-Open No. 04-152025 Japanese Patent Laid-Open No. 11-207529 JP 2009-178739 A

Okuno Fumito et al., Mitsubishi Heavy Industries Technique, VOL.34, No.2 (1997-3), p108-111

The problem to be solved by the present invention is to provide a low-cost, short lead-time, high-precision tooth forging die and a method for manufacturing the same.
Another problem to be solved by the present invention is to provide a method for manufacturing a helical gear using a die for forging set manufactured by such a method.

In order to solve the above-mentioned problems, the gist of a method for manufacturing a metal mold for forging according to the present invention is as follows.
(1) The above-described set forging forging is used for set forging of helical gears having internal teeth or external teeth.
(2) The manufacturing method of the die for forging forging includes a cutting step of forming a groove (female helical tooth) for forming a tooth profile of the helical gear with a gear shaper on a die material. ing.

Moreover, the die for forging forging which concerns on this invention consists of what is obtained by the method which concerns on this invention.
Furthermore, the helical gear manufacturing method according to the present invention uses the tooth forging die obtained by the method according to the present invention, and the tooth of the helical gear with internal teeth or external teeth with respect to the gear material. The gist of the invention is that it includes a forging process for performing forging.

  The gear shaper has been conventionally used for manufacturing a helical gear itself. The present invention is characterized in that the gear shaper is used to form a groove (female helical tooth) of a metal mold for forging forging. By forming a groove (female helical tooth) for a set-up forging die by cutting, the die can be manufactured at a lower cost and in a shorter time than when electric discharge machining is used. In addition, the accuracy of the groove (female helical teeth) can be ensured even when either an internal tooth or an external tooth mold is manufactured or when an internal tooth mold having a large inner diameter is manufactured. high. Furthermore, when the cutting process conditions are optimized, the accuracy of the grooves (female helical teeth) is almost equal to that of electric discharge machining.

FIG. 1A is a front view of a pinion cutter and a front sectional view of a mold material being processed. FIG. 1B is a plan view of a mold material being processed by a pinion cutter. It is a figure which shows the relationship between the number of strokes and gear precision when the hardness of a metal mold | die material is HRC46. It is a figure which shows the relationship between radial feed speed and gear precision when the hardness of a metal mold | die material is HRC46.

Hereinafter, an embodiment of the present invention will be described in detail.
[1. Mold for forging and forging method]
The mold for forging forging according to the present invention is obtained by the method according to the present invention.
Moreover, the manufacturing method of the die for forging forging which concerns on this invention is equipped with the following structures.
(1) The above-described set forging forging is used for set forging of helical gears having internal teeth or external teeth.
(2) The manufacturing method of the die for forging forging includes a cutting step of forming a groove (female helical tooth) for forming a tooth profile of the helical gear with a gear shaper on a die material. ing.

[1.1. Application]
The die for forging forging according to the present invention is used for tooth forging of a helical gear having internal teeth or external teeth. In order to manufacture a helical gear with an external tooth having a large outer diameter by forging, a die for forging and forging with an internal tooth having a large internal diameter is required. The method according to the present invention can be manufactured with high accuracy even for an internal teeth forging and forging die having a large inner diameter.

[1.2. Mold material]
In the present invention, the mold material is not particularly limited, and an optimum material can be selected according to the purpose.
In general, the lower the hardness of the mold material, the easier the cutting process, but the shorter the mold life. Therefore, the hardness of the mold material is preferably HRC42 or more. The hardness of the mold material is more preferably HRC44 or higher.
The higher the hardness of the mold material, the longer the mold life. However, if the hardness of the mold material is too high, cutting becomes difficult and the accuracy of the grooves (female helical teeth) is also reduced. Therefore, the hardness of the mold material is preferably HRC 50 or less.

  The mold material suitable for the present invention is a material that can be directly engraved in a quenched state (for example, hot die steel such as SKD61, prehardened steel such as SKT4).

[1.3. Cutting with gear shaper]
FIG. 1A shows a front view of the pinion cutter 10 and a front sectional view of a mold material (workpiece) 20 being processed. FIG. 1B shows a plan view of the mold material 20 being processed by the pinion cutter 10.
As shown in FIG. 1, the “gear shaper” refers to a processing device that reciprocates the pinion cutter 10 in the tooth trace direction while rotating the pinion cutter 10 in the circumferential direction. When the pinion cutter 10 on which the helical teeth are formed is reciprocated in the stroke direction while being fed at a predetermined feed speed in the radial direction and the circumferential direction, grooves (female helical teeth) are formed on the surface of the mold material 20. can do. The feed in the radial direction is performed continuously (while increasing the cutting amount little by little during one stroke). On the other hand, the feed in the circumferential direction is performed intermittently (so that the incisor is replaced) in accordance with the tooth pitch (interval to the adjacent tooth) for each stroke so that the same incisor is not continuously cut. Is called.
In addition, in the example shown in FIG. 1, although the state which forms an internal tooth in the metal mold | die raw material 20 is shown, an external tooth can also be formed by the same method.

  When cutting grooves (female helical teeth) on the surface of the mold material using a gear shaper, the cutting conditions are not particularly limited, and the composition of the mold material and the characteristics required for the mold It is preferable to select optimum conditions accordingly.

The number of strokes per unit time (hereinafter also simply referred to as “the number of strokes”) is proportional to the cutting speed. In general, as the number of strokes decreases, the wear of the tool is suppressed, and the accuracy of the grooves (female helical teeth) increases. However, if the number of strokes is too small, the machining efficiency is lowered. Therefore, the number of strokes is preferably 5 str / min or more. More preferably, the number of strokes is 50 str / min or more.
On the other hand, if the number of strokes is too large, the pinion cutter 10 is significantly worn, and the accuracy of the grooves (female helical teeth) decreases. Therefore, the number of strokes is preferably 54 str / min or less.

As the feed rate in the radial direction (radial feed rate) decreases, the cutting load decreases and the deformation and escape of the tool are suppressed, so the accuracy of the groove (female helical teeth) increases. However, if the radial feed speed is too slow, the machining efficiency is lowered. Therefore, the radial feed speed is preferably 0.0005 mm / str or more.
On the other hand, if the radial feed rate is too high, the cutting load increases, and the deformation and escape of the tool increases, so the accuracy of the groove (female helical teeth) decreases or the pinion cutter wears significantly. . Accordingly, the radial feed speed is preferably 0.001 mm / str or less.

[2. Method of manufacturing helical gear]
The helical gear manufacturing method according to the present invention is a gear set forging of a helical gear of internal teeth or external teeth with respect to a gear material using a metal mold for gear set forging obtained by the method according to the present invention. A forging process is performed.
The present invention is characterized in that toothed forging of a helical gear is performed using a die for forging forging manufactured using a gear shaper. Since the forging itself is the same as the conventional one, detailed description is omitted.

[3. Action]
The gear shaper has been conventionally used for manufacturing a helical gear itself. The present invention is characterized in that the gear shaper is used to form a groove (female helical tooth) of a metal mold for forging and forging. By forming a groove (female helical tooth) for a set-up forging die by cutting, the die can be manufactured at a lower cost and in a shorter time than when electric discharge machining is used. In addition, the accuracy of the groove (female helical teeth) can be ensured even when either an internal tooth or an external tooth mold is manufactured or when an internal tooth mold having a large inner diameter is manufactured. high. Furthermore, when the cutting process conditions are optimized, the accuracy of the grooves (female helical teeth) is almost equal to that of electric discharge machining.

[1. Production of mold for forging and forging]
Using the gear shaper shown in FIG. 1, a die for forging for producing an external gear was produced. SKD61 was used for the mold material, and it was tempered so that the hardness was HRC42-52. Powder high speed was used for the cutting tool (pinion cutter).
Cutting conditions were set to the number of strokes: 50 to 600 str / min, the circumferential feed rate: 0.40 to 0.45 mm / str, and the radial feed rate: 0.0005 to 0.010 mm / str.
The gear specifications of the mold are as follows: Module: 2.705, Twist angle: 29 °, Pressure angle: 9 °, Tip circle diameter: φ211.1, Root circle diameter: φ223.3, Total tooth length: 6. 083.

[2. Test method]
The accuracy (groove gear accuracy of female helical teeth) of grooves formed on the inner surface of the produced mold was evaluated in accordance with JIS B1702-1.

[3. result]
FIG. 2 shows the relationship between the number of strokes and the gear accuracy when the hardness of the mold material is HRC46. FIG. 3 shows the relationship between the radial feed speed and the gear accuracy when the hardness of the mold material is HRC46. Further, Table 1 shows the relationship between the hardness of the mold material and the gear accuracy. 2 to 3 and Table 1 show the following.
(1) The smaller the number of strokes, the higher the gear accuracy.
(2) The lower the hardness of the mold material, the higher the gear accuracy.
(3) In order to obtain gear accuracy of JIS grade 6 or higher, the number of strokes is preferably 54 str / min or less.
(4) In order to obtain gear accuracy of JIS grade 6 or higher and to prevent early damage of the tool, the hardness of the mold material is preferably HRC 50 or lower.

(5) The smaller the radial feed speed, the higher the gear accuracy.
(6) Generally, in a gear mold that requires a hardness of HRC 42 to 50, when molding is performed only by cutting without cutting + electric discharge, machinability, Due to the effects of thermal deformation, wear, etc., the finished appearance is affected. Therefore, there has been a limit in terms of finishing accuracy in processing precision gear shapes and the like. Therefore, it has been a conventional technique to perform electric discharge machining as a final process. However, it is proved from FIGS. 2 and 3 and Table 1 that the machining under the cutting conditions using the gear shaper of the present invention has the same accuracy as the range of the JIS standard by electric discharge machining. As described above, the final effect of the present invention is that the final forming can be performed only by cutting without electric discharge machining.

  The embodiment of the present invention has been described in detail above, but the present invention is not limited to the above embodiment, and various modifications can be made without departing from the scope of the present invention.

  The die for forging forging according to the present invention can be used for tooth forging of a helical gear having internal teeth or external teeth.

10 Pinion cutter 20 Mold material (work)

Claims (5)

A method for manufacturing a metal mold for forging forging having the following configuration.
(1) The above-described set forging forging is used for set forging of helical gears having internal teeth or external teeth.
(2) The manufacturing method of the die for forging forging includes a cutting step of forming a groove (female helical tooth) for forming a tooth profile of the helical gear with a gear shaper on a die material. ing. The manufacturing method of the metal mold | die for a tooth extraction forging of Claim 1 further provided with the following structures.
(3) The hardness of the mold material is HRC42 or more and 50 or less. The manufacturing method of the metal mold | die for tooth set forging of Claim 1 or 2 further provided with the following structures.
(4) The cutting step uses the gear shaper,
Number of strokes: 5 str / min to 54 str / min, and
Radial feed rate: The groove is cut under the condition of 0.001 mmstr or less.   A die for forging forging obtained by the method according to any one of claims 1 to 3.   Forging for performing geared forging of a helical gear of internal teeth or external teeth on a gear material using a mold for geared forging obtained by the method according to any one of claims 1 to 3. The manufacturing method of the helical gear provided with the process.

Images