JP2017113802A - Manufacturing method of helical gear - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method capable of improving accuracy of a tooth form, in manufacture of a helical gear by forging.SOLUTION: A tooth form is processed by forging after heating beforehand a blank before tooth form processing, and a molding is cooled in a tooth form die, and then taken out from the tooth form die.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for manufacturing a helical gear used in an automobile or the like.

  Conventionally, as a means for manufacturing a helical gear, in many cases, cutting has been performed in all processing. Since cutting has a lower material yield than forging, there is a case in which a method of once processing into a shape close to a helical gear of a finished product by forging and then finishing by cutting is used in some cases. According to this method, the yield of the material can be improved.

  By manufacturing the helical gear by cold forging among the forging processes, it becomes possible to approach the finished shape, and the amount of finishing cutting can be reduced. However, when a helical gear is manufactured by cold forging, a twisted tooth profile is formed, so that an excessive load is applied when taking out from the mold, and the accuracy of the tooth profile is lowered.

  The present invention has been made to solve the above-described problems, and provides a manufacturing method capable of improving the accuracy of a tooth profile in manufacturing a helical gear by forging.

  In the manufacturing method according to the present invention, the blank before the tooth profile processing is preheated and then the forging is performed by forging, and the molded product is cooled in the tooth profile die and then taken out from the tooth profile die. It is a manufacturing method of a helical gear.

  According to the present invention, it is possible to improve the accuracy of the tooth profile by reducing the load required when removing from the mold after processing. In addition, since the load on the mold is reduced by reducing the load required at the time of processing, improvement of the mold life can be expected.

It is a figure which shows the flow of the manufacturing method of the helical gear in a present Example. It is a figure which shows the blank before the tooth profile process in a present Example. It is a figure which shows the member after the tooth profile process in a present Example. (A) It is a figure which shows the mode of the member and metal mold | die until preliminary upsetting in a present Example. (B) It is a figure which shows the mode of the member and metal mold | die after a preliminary upsetting in this Example to shunt shaping | molding.

  Examples of the present invention will be described below. FIG. 1 is a diagram showing the flow of an embodiment of the present invention. Each item will be described in turn.

<Blank creation>
A blank 2 shown in FIG. 2 is created. The method for creating the blank 2 may be either forging or cutting. The former has a good material yield, but becomes difficult to handle as the required accuracy increases. Although the latter does not have a good material yield, it can be used even if the required accuracy is increased to some extent. Since both have advantages and disadvantages, it is desirable to use them properly according to the situation.

<Heating>
The blank 2 is heated. The purpose of heating is to reduce the load when the tooth profile is processed by forging, and to reduce the resistance to the processed tooth profile by contraction due to cooling of the member when the molded product is taken out from the mold. In order to efficiently obtain the effect of heating and the effect of cooling, the heating temperature is preferably 50 to 350 ° C. When the heating temperature is too high, an oxide film is formed, and the tooth profile accuracy may be lowered.

<Tooth profile processing>
The blank 2 after heating is processed by forging to form a molded product 3 shown in FIG. 4 (a) and 4 (b) are schematic views of the main part of a mold used for tooth profile processing, and are composed of an inner punch 41, an outer punch 42, a mandrel 43, a tooth profile die 44, and a lower mold 45. ing. As a press machine (not shown) that holds the mold and pressurizes, a pressurizing machine whose pressure load is variable, for example, a hydraulic servo type, is used. When the pressurizing load of the press machine is not variable, for example, in the case of a link press type or the like, a predetermined load is applied at a time, so it is impossible to adopt the forging method of this embodiment (detailed) The reason will be described later). By pressing the work 46 between the inner punch 41 and the outer punch 42 and the lower mold 45, the work 46 is deformed along the tooth profile die 44 and processed into a predetermined form. The mandrel 43 passes through the inner diameter hole of the work 46 and plays a role of maintaining the accuracy of the inner diameter hole during processing. A feature of the mold in this embodiment is that the movable punch is divided into an inner punch 41 and an outer punch 42, and separate operations are possible.

  FIG. 4 (a) shows a state up to preliminary upsetting, and FIG. 4 (b) shows a state in which shunt forming is performed after preliminary upsetting. In one cycle of pressurizing operation, pre-upsetting and split flow forming are performed. In the preliminary upsetting, as indicated by an arrow in FIG. 4A, the inner punch 41 and the outer punch 42 are simultaneously lowered to pressurize the work 46. As shown by the arrow in FIG. 4B, the flow dividing molding is performed by releasing the load of the inner punch 41 while maintaining the load of the outer punch 42. The processed workpiece 46 is taken out after being cooled in the tooth profile die 44. Since the distortion of the workpiece 46 due to heat generated during machining is proportional to the machining speed (heat generation amount), in order to increase the machining accuracy, the load when forging the workpiece 46 is not shocking but gradually increases. is necessary. For the above reason, it is desirable that the pressurization speed is 5 to 10 mm / sec.

  If the forming of the tooth profile 31 is attempted by filling the tooth profile die 44 with the workpiece 46 only by upsetting without split flow forming, the tooth profile die 44 is formed during the formation due to a sudden increase in the load acting on the tooth profile die 44. It will be damaged. On the other hand, by performing shunt forming, the load required for processing is reduced, and processing accuracy can be improved and the mold life can be improved.

  The greater the speed at which the workpiece 46 after the tooth profile processing is taken out from the tooth profile die 44, the greater the impact of the impact load and the amount of heat generated and the greater the load on the tooth profile. The speed at the time of taking out from the tooth profile die 44 is desirably 20 to 50 mm / sec. In order to control the amount of heat shrinkage of the molded product, the difference between the temperature during heating and the temperature after cooling (when taking out the molded product) is preferably 20 to 200 ° C.

2 Blank 3 Molded product 31 Tooth profile 41 Internal punch 42 External punch 43 Mandrel 44 Tooth profile die 45 Lower mold 46 Workpiece

Claims (5)

  A method for manufacturing a helical gear, wherein a blank before processing a tooth profile is preheated and then forging is performed to process the tooth profile, the molded product is cooled in the tooth profile die, and then taken out from the tooth profile die.   The method for manufacturing a helical gear according to claim 1, wherein a set temperature in the heating of the workpiece is 50 to 350 ° C.   3. The method for manufacturing a helical gear according to claim 1, wherein a difference between the temperature at the time of heating and the temperature after cooling (at the time of taking out the molded product) of the workpiece is 20 to 200 ° C. 4.   The method for manufacturing a helical gear according to any one of claims 1 to 3, wherein a pressing speed of the workpiece is 5 to 10 mm / sec during the tooth profile machining.   The method for manufacturing a helical gear according to any one of claims 1 to 4, wherein a speed at which the workpiece after tooth profile processing is taken out from the tooth profile die is 20 to 50 mm / sec.

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