JP4356402B2 - External gear extrusion molding method - Google Patents

Description

  The present invention relates to a method for forming an external gear, and more particularly, to an external gear extrusion method for performing a crowning process on a tooth surface in a tooth line direction of a gear.

  In recent years, in external gears such as pinion gears and helical gears (helical gears), the shape of their tooth portions is complicated, and the machining time and cost are high for manufacturing by machining. For this reason, it has come to manufacture an external gear by cold forging. For example, the cold forging method of a helical gear is disclosed by the following patent documents 1-3.

  On the other hand, in external gears such as pinion gears and helical gears, gear noise becomes a problem at the torque transmission site due to the meshing of the gears, which adversely affects the development of various products. The generation of gear noise is considered to be caused by a misalignment in the meshing of the gears due to poor gear tooth shape accuracy or deflection of the gears when a load is input. Therefore, in order to absorb such misalignment that causes gear noise, crown the tooth surface in the direction of the tooth trace of the external gear (the thickness of the tooth gradually increases from the center of the tooth toward both sides of the tooth. There is known a technique for reliably transmitting the tooth surface force to the mating tooth surface under the best conditions by performing a process of reducing the tooth surface.

When such a crowning process is performed on the tooth surface of an external gear formed by cold forging, it is necessary to perform a cutting process or a polishing process as an additional process, which causes a cost increase in gear manufacturing. ing.
JP 2002-96139 A JP 2000-39056 A JP 07-310807 A

  The problem to be solved by the present invention is that, when a crowned treatment is applied to a cold forged extruded gear, an increase in work steps and a high cost are caused. Accordingly, an object of the present invention is to provide an external gear extrusion molding method capable of simultaneously performing crowning treatment on the tooth surface in the extrusion molding step when forming the external gear by cold forging extrusion molding. It is in.

  In order to achieve the above object, the external gear extrusion molding method according to the present invention includes an extrusion process in which a material is press-fitted into a die using an extrusion jig and extruded to form the material into an external gear. An external gear extrusion molding method, wherein the extruding step includes a first extruding step of extruding the material by moving the extruding jig at a first feeding speed, and the first extruding step after the first extruding step. A second extrusion step of extruding the material by moving the extrusion jig at a second feed rate different from the feed rate.

  In another preferred feature of the external gear extrusion molding method, the first feed speed is higher than the second feed speed.

  In another preferred feature of the external gear extrusion molding method, the extrusion step includes moving the extrusion jig at a third feed rate different from the second feed rate after the second extrusion step. A third extrusion step of extruding the material is included, and the first and third feed rates are higher than the second feed rate.

  According to the external gear extrusion molding method based on the present invention, when the feed speed of the extrusion jig (the plastic processing speed of the material) is increased, the deformation resistance of the material to the die increases and the material filling rate decreases. The mold transferability becomes worse. On the other hand, when the feeding speed of the extrusion jig is slowed, the deformation resistance of the material to the die is low, and the filling rate of the material is improved, so that the mold transfer property is improved.

  Therefore, the tooth surface shape of the external gear extruded at the first feed speed higher than the second feed speed is a thin shape because the filling rate of the material is lower than the region fed at the second feed speed. On the other hand, the tooth surface shape of the external gear extruded at the second feed speed that is slower than the first feed speed becomes thicker because the filling rate of the material is higher than the region fed at the first feed speed. As a result, by controlling the feed rate in a single extrusion process, it is possible to give a tooth surface shape that continuously transitions from a lean state to a shape that gradually swells.

  Thus, for example, if the first to third extrusion steps are provided as the extrusion step, and the first and third feed rates are controlled to be higher than the second feed rate, the region corresponding to the first extrusion step is thin. The region corresponding to the second extrusion process is a thick tooth surface shape, and the region corresponding to the third extrusion process is a thin tooth surface shape. As a result, it is possible to give a tooth surface shape gradually swelled from a thin tooth surface shape and continuously transition to a thin tooth surface shape, that is, a crowning shape at the same time as the external gear extrusion process. Become.

  Hereinafter, an external gear extrusion molding method according to an embodiment of the present invention will be described with reference to the drawings. As the external gear, various gears such as a spur gear, a helical gear, a rack gear, and the like can be cited. The feature of the present invention is the extrusion method. Therefore, in the present embodiment, in order to facilitate understanding of this feature, a case where the present invention is applied to spur gear extrusion will be described as an example.

  FIG. 1 is a view showing an outer shape of a material 100 before being extruded, FIG. 1 (A) is a cross-sectional view along the gear axis, and FIG. 1 (B) is a direction orthogonal to the gear axis. FIG. Moreover, FIG. 2 is a figure which shows the external shape of the spur gear 200 after extrusion molding, FIG. 2 (A) is sectional drawing along a gear shaft, FIG. 2 (B) is a gear shaft. It is sectional drawing along the orthogonal direction. On the outer peripheral surface of the spur gear 200, teeth 201 whose teeth are parallel to the gear axis direction are formed. Since this extrusion molding is a two-stage extrusion (described later), a core hole 100h into which a mandrel (described later) is inserted is provided at the center. 100 is not provided with a core hole 100h.

Next, the structure of a mold used for extrusion molding by a two-stage mold will be described with reference to FIG. In FIG. 3, the left side of the gear shaft of the material 100 shows a state cross section before processing, and the right side of the gear shaft of the material 100 shows a state cross section after processing. The material 100 is inserted into the die 40. Above the die 40, a mandrel 20 to be inserted into the core hole 100 h of the material 100 and a punch 10 for applying pressure to the material 100 are disposed along the outer peripheral surface of the mandrel 20. Further, a knockout 30 is disposed below the die 40 .

The punch 10 and the mandrel 20 is lowered at a predetermined feed speed, also by adding the processing pressure in knock-out 30, predetermined pressure is applied to the material 100, material 100 is molded portion provided in the die 40 in liquidity to, it will be formed into a spur gear 200 having a desired shape.

  Here, as described in the above background art, it is necessary to perform a crowning process on the tooth surface in the tooth line direction of the external gear so as to absorb misalignment that causes gear noise (see FIG. 4). In the present embodiment, it is possible to give crowning to the tooth surface of the spur gear 200 simultaneously with the extrusion molding process of the spur gear 200 by controlling the feed rates of the punch 10 and the mandrel 20 as shown below. It is what. Hereinafter, the details of the extrusion molding method for giving crowning to the tooth surface of the spur gear 200 will be described.

(Details of extrusion molding method)
When the feeding speed of the punch 10 and the mandrel 20 (the plastic processing speed of the material 100), which is an extrusion jig, is increased, the deformation resistance of the material 100 to the die 40 increases, and the filling rate of the material 100 decreases, so that the mold transfer property is improved. Deteriorate. On the other hand, when the feed speeds of the punch 10 and the mandrel 20 are slowed, the deformation resistance of the material to the die is low, and the filling rate of the material 100 is improved, so that the mold transfer property is improved.

Therefore, the feed rate of the punch 10 and the mandrel 20 is conventionally constant. For example, the feed rate at the beginning of extrusion is set slower than the conventional feed rate (first feed rate: V1). Extrude for a certain time. Then, it returns to the conventional feed rate (2nd feed rate: V2, V1> V2), and extrudes the raw material 100 for a fixed time. Thus, the second feeding speed (V2) is extruded at a faster than the first feed speed (V1) tooth surface shape (area 1000), as shown in FIG. 5, an extrusion at a second feed speed (V2) Since the filling rate of the material is lower than that of the region 1000, the shape becomes thin. In addition, FIG. 5 is the figure which looked at only the tooth | gear from the front .

On the other hand, the tooth surface shape (region 2000) extruded at the second feed speed (V2) slower than the first feed speed (V1) is fed at the first feed speed (V1) as shown in FIG. It becomes the same shape as the conventional tooth surfaces due to high filling rate of the material than the region 1000 (fat shape than the region 1000). As a result, by controlling the feed rate in a single extrusion process, it is possible to give a tooth surface shape that continuously transitions from a lean state to a shape that gradually swells.

  From the above, as shown in FIG. 6, the feed speed of the punch 10 and the mandrel 20 includes first to third extrusion processes as extrusion processes, and the first feed speed (V1) and the third feed of each process. The speed (V3) is controlled to be higher than the second feed speed (V2) (the second feed speed (V2) is about the same as the conventional feed speed). FIG. 7 shows the feeding time (100 / s) on the horizontal axis, the punch position (mm) on the vertical axis (left side), and the molding load (Ton) on the vertical axis (right side) in this case. . In this figure, a region 1000 indicates the first extrusion step, a region 2000 indicates the second extrusion step, and a region 3000 indicates the third extrusion step. A line L1 indicates the relationship between the feed time (100 / s) and the punch position (mm), and the region 1000 and the region 3000 indicate that the feed rate is faster than the region 2000. A line L2 indicates the relationship between the feed time (100 / s) and the molding load (Ton), and the region 2000 indicates that a sufficient molding load is applied.

  As a result, by providing the first to third extrusion steps as the extrusion step, the region 1000 corresponding to the first extrusion step has a thin tooth surface shape as shown in FIGS. 8 and 9, and the second extrusion step. The region 2000 corresponding to the process has the same tooth surface shape as the conventional spur gear (a shape thicker than the region 1000), and the region 3000 corresponding to the third extrusion step has a thin tooth surface shape. As a result, the tooth surface shape gradually swelled from the thin tooth surface shape, and the shape that continuously transitions to the thin tooth surface shape again, that is, crowning (the central part of the tooth mold becomes a smooth convex shape), It can be applied simultaneously with the spur gear extrusion process. FIG. 8 is a view of only the teeth as viewed from the front, and FIG. 9 is a cross-sectional view along the gear shaft of the spur gear 200.

  In the embodiment described above, the case where the spur gear 200 is provided with one crowning has been described. However, in a gear in which two or more meshes are generated, a plurality of crownings are provided at corresponding locations. Need to do. In such a case, for example, as shown in FIG. 10, the first to fifth extrusion steps are provided, and the first, third and fifth feed speeds (V1, V3, V5) are changed to the second and fourth feed speeds ( The second feed rate (V2) is the same as the conventional feed rate, V1> V2, V2 <V3, V3> V4, V4 <V5). Thereby, as shown in FIG. 11, it becomes possible to give crowning to two places.

  In the above embodiment, the case where crowning is imparted in the extrusion molding of a spur gear has been described. However, all external gears which are required to be crowned, such as helical gears and rack gears, and which are molded by the extrusion molding method. It is possible to apply to.

  Therefore, the said form disclosed this time is an illustration in all the points, Comprising: It does not become a basis of limited interpretation. Therefore, the technical scope of the present invention is not interpreted only by the above-described embodiments, but is defined based on the description of the claims. Further, all modifications within the meaning and scope equivalent to the scope of the claims are included.

It is a figure which shows the external shape of the raw material of a spur gear before extrusion molding, (A) is sectional drawing along a gear shaft, (B) is sectional drawing along the direction orthogonal to a gear shaft. It is. It is a figure which shows the external shape of the spur gear after extrusion molding, (A) is sectional drawing along a gear shaft, (B) is sectional drawing along the direction orthogonal to a gear shaft. . It is sectional drawing which shows the structure of the two-stage type | mold used for extrusion molding. It is a schematic diagram which shows the crowning given to the tooth surface of the tooth-gear direction of an external gear. It is the 1st figure which looked at only the external teeth of the spur gear formed in this embodiment from the front. It is a 1st flowchart which shows the relationship of the feed rate in this Embodiment. It is a figure which shows the relationship between the punch position (mm) with respect to feed time (100 / s), and the molding load (Ton) with respect to feed time (100 / s). It is the 2nd figure which looked at only the external tooth of the spur gear fabricated in this embodiment from the front. It is a 1st sectional view along the gear axis of the spur gear formed along the 1st flow figure in this embodiment. It is a 2nd flowchart which shows the relationship of the feed rate in this Embodiment. It is the 2nd sectional view along the gear axis of the spur gear formed along the 2nd flow figure in this embodiment.

Explanation of symbols

20 mandrels, 30 knockouts, 40 dies , 100 material, 100h core hole, 200 spur gear, 201 teeth, V1, V2, V3, V4, V5 feed speed.

Claims (2)

A method of extruding an external gear, including an extrusion step of pressing and extruding a material into a die using an extrusion jig and forming external teeth on the outer peripheral surface of the material,
The extrusion process includes
A first extruding step of moving the extruding jig at a first feeding speed to extrude the material into a forming part provided in the die ;
After the first extrusion step, the second extrusion step of extruding the raw material to the molding part provided in the die by moving the extrusion jig at a second feed rate slower than the first feed rate. ,
By adopting the first extruding step and the second extruding step, a tooth surface shape is formed in which the tooth surface to be extruded continuously transitions from a thin tooth surface shape to a bulging shape. Gear extrusion method. The extruding step includes a third extruding step of extruding the material by moving the extruding jig at a third feeding speed different from the second feeding speed after the second extruding step,
The first and third feed speeds are faster than the second feed speed ,
The extrusion of the external gear according to claim 1, wherein the tooth surface to be extruded is formed into a shape in which the tooth surface shape gradually swells from the thin tooth surface shape and continuously transitions to the thin tooth surface shape. Molding method.

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