JPS6153141B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a ring gear having a small wire diameter, such as a ring gear for an automobile.

To be more specific, a ring-shaped workpiece 30 (Fig. 6) pre-processed into a special shape and a lower die 18 (Fig. 16) with a special structure for forging this workpiece.
The ring gear 31 (Fig. 3) is forged using the following steps.

That is, the workpiece 30 has a chamfered portion 32 (FIG. 6) on the upper edge of its outer periphery, and the die 18 has a tooth profile 19 (FIG. 6) consisting of a tapered portion 42 and a straight portion 43 on its inner periphery.

Generally, in the conventional gear forging method in which the tooth profile 3 formed on the die 2 is filled with the material 5, as shown in FIGS. The molded gear 6 is molded with a portion 9 or a large amount of burr. Therefore, the forging force inevitably increases, a forging machine with a large capacity is required, and the life of the die is inevitably shortened. Further, a lot of machining is required, such as cutting off the excess thickness 9 after forging, and there is a lot of wasted material.

In addition, the conventional method of applying an axial rolling load to the material and increasing the outer diameter of the material to form a tooth profile on the outer periphery requires a high heading ratio, especially for ring gears with a small wire diameter, making it difficult to form the tooth profile. It was extremely difficult. Therefore, when the material is heated to a high temperature and hot forged in order to improve its fluidity, it not only causes roughness but also has the drawback that the desired tooth precision cannot be obtained.

Therefore, the present invention has been devised to eliminate such drawbacks of the prior art, and aims to provide a forging method that can form a highly accurate and strong tooth profile on the outer periphery of a ring-shaped material with a small forming force. do.

A feature of the present invention is that a lower die is formed in which a tooth profile is formed on the inner periphery, consisting of a tapered part where the diameter of the tooth tip gradually decreases downward, and a straight part that continues below the taper part with the same tooth tip circle. Fix it on the base plate,
A ring-shaped material with a chamfer formed on at least the upper edge of the outer periphery is inserted into the inner circumferential position above the taper part of the tooth profile of the lower mold, and then the punch is lowered to bite the material into the tooth profile taper part to continue the tooth profile. The purpose of this method is to roll the material in the axial direction in a sealed state in the straight section, thereby forming finished teeth around the outer periphery of the ring-shaped material.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of embodiments of the present invention will be explained below with reference to the drawings.

The ring-shaped material 30 used to form the ring gear 31 partially shown in FIG. 3 is made by winding a steel wire formed into a predetermined cross-sectional shape by drawing or rolling to obtain a desired diameter. 4 and 6 by welding the abutted surfaces.

FIG. 4 shows a cross section of the main part of the forging device, with the left half showing the ring-shaped material 30 attached and the left half showing the punch 26 starting to descend. The punch 26 has a guide portion 27 with a cylindrical outer periphery on its tip side, and a tooth-shaped outer periphery with a diameter larger than that of the guide portion 27 is provided on the upper outer periphery of the guide portion 27 via a shoulder end surface 28 that spreads horizontally. A peripheral tooth profile 29 in which is formed continues to be provided. This punch 26 is fixed to a ram (not shown) of a forging device via an upper mold body 24 and a pressure receiving plate 25,
It is mounted opposite to the upper surface of the machine base plate 11 so as to be able to freely reciprocate.

A die 18 is fixed to the upper surface of a machine base plate 11 of a forging device with a pressure receiving plate 13 and a spacer ring 22 interposed therebetween by a tightening ring 21.

The die 18 has a tooth profile 19 on the inner periphery for forming teeth on the outer periphery of the ring-shaped material 30, and
It is fixed on the same axis as 6.

This tooth profile 19 consists of a tapered part 42 where the diameter of the tip circle gradually decreases downward from a position slightly lower than the opening above the die 18, and a straight part where the tip circle continues with the same diameter below the tapered part. It consists of 43. Further, the root circle of this tooth profile 19 is formed to have the same diameter from top to bottom.

Reference numeral 14 denotes a knockout, which is provided on the inner periphery of the pressure receiving ring 12 so as to be movable up and down in the axial direction of the punch 26, facing the tip of the punch. A knockout ring 15 is arranged above the knockout 14 with a pressure receiving plate 13 in between.

A meshing tooth profile 20 is formed on the outer periphery of the knockout ring 15, and the meshing tooth profile 20 engages with the straight part 43 of the tooth profile 19 on the inner periphery of the die 18 without any gap. The upper surface of the knockout ring 15 forms the bottom surface 16 (FIG. 6) of the tooth forming space. The knockout ring 15 is configured to move back and forth in the tooth forming space in the axial direction while remaining engaged with the tooth profile 19 as the knockout 14 moves up and down.

On the other hand, the outer peripheral tooth profile 29 on the upper outer periphery of the punch also meshes with the tooth profile straight part 43 of the die 18 with almost no gap when the punch 26 descends, and in this state, the lower surface of the outer peripheral tooth profile 29, that is, the shoulder end surface 28, is engaged with the tooth profile straight part 43 of the die 18. A carved top surface (Fig. 9) is formed.

Next, determine the inner and outer diameters of the material, the punch 26 and the die 1.
The dimensional relationships such as 8 will be explained.

The diameter of the punch guide portion 27 is the same as that of the ring-shaped material 3.
The inner diameter of the knockout ring 15 is slightly smaller than the inner diameter of the knockout ring 15.

The inner diameter of the upper inner edge 37 of the knockout ring 15 is formed to be approximately equal to the inner diameter of the desired ring gear 31.

The ring-shaped material 30 is formed so that its outer diameter is approximately equal to the tip circle on the large diameter side of the taper portion 42 of the tooth profile 19 of the die 18 .

That is, the outer diameter of the ring-shaped material 30 is formed to be slightly smaller than the root circle of the die tooth profile 19.

and the material 30 adjacent to the punch shoulder end face 28.
The upper periphery of the outer periphery has a chamfered portion 32 whose periphery is recessed to a position where the diameter is considerably smaller than the outer diameter of the punch shoulder end face 28.

Next, the operation of the device with the above configuration will be explained using the ring-shaped material 3.
This will be explained along with the process of forming a tooth profile on the outer periphery of 0.

First, as shown on the left side of FIG.
Insert it into the inner circumferential side of the taper portion 42 of the tooth profile 19 of No. 8. At this time, as shown in an enlarged view in FIG. 6, the position of the material 30 is determined by the outer periphery of the material 30 coming into contact with the large-diameter tip circle side of the tooth-shaped tapered portion 42.

Next, as shown on the right side of FIG. 4, when the punch 26 is lowered, the guide portion 27 enters the inner periphery of the material, and the shoulder end surface 28 comes into contact with the upper surface of the material. At this time, as shown in an enlarged view in FIG. 7, the blank 30 has a chamfered portion 32 formed on the upper periphery of the outer periphery of the blank 30, so that the blank 30 is properly positioned on the inner circumferential side of the bottom circle of the punch outer circumferential tooth profile 29. It abuts against the shoulder end surface 28 at the position.

As a result, the material 30 is forcibly moved down the tooth profile tapered portion 42 with the inner circumferential side being restrained by the punch guide portion 27, so that the outer circumferential side thereof is pushed into the space within the tooth profile. Further, at this time, the chamfered portion 32 on the upper periphery of the outer circumference of the material becomes smaller as the material expands toward the shoulder end surface 28 as the punch 26 descends. Therefore, the size of the chamfered portion 32 is large enough to prevent the material from entering between the die tooth profile 19 and the punch outer tooth profile 29 even immediately before the die tooth profile 19 and the punch outer circumferential tooth profile 29 close together, as shown in FIG. However, it can be appropriately determined in advance through experiments.

However, at this stage, the material 30 that has not completely filled the inside of the tooth profile 19, etc., also remains in the tooth profile straight section 4.
Completely finished in 3. That is, the fifth
When the punch is lowered to a predetermined position as shown on the left side of the figure, the material 30, that is, the ring gear 31, is aligned vertically with the shoulder end surface 28 of the punch 26 and the bottom of the knockout ring 15, as shown in FIG. surface 16, and its inner and outer peripheries are surrounded by punch 2.
6 and the surface of the tooth profile 19 of the die 18. Moreover, at this time, the material 30 with the shoulder end surface 28 of the punch in a sealed state
Since the material 30 is pressed in a rolling manner, the material 30 is pressed into the nearly sealed die-cutting space, filling the space and almost perfectly shaping the ring gear.

When the molding is completed in this manner, as shown on the right side of FIG. 5, the punch 26 is first raised, and then the knockout ring 15 is raised to push up the molded ring gear 31.

The ring gear 31 formed in this way is
Unlike ring gears formed by conventional ring gear forging methods, there are no unformed parts or large burrs that connect adjacent teeth on one side of the tooth trace, so material yield is good and post-processing is easy. This can be significantly reduced.

In addition, instead of simply rolling the material in the axial direction to form teeth on the outer periphery of the material as in the past, a preliminary process of toothing in which the material is deformed in the direction of reducing the diameter of the material and the preformed material being rolled into a sealed space. The final forming process of the tooth profile, in which rolling deformation is applied in the axial direction, is performed in one stroke of the punch, so the flow of material is smooth, the blow connection is good, and it has excellent strength, just like a rolling gear. Teeth are molded. Moreover, since the flow of the material around the outer circumference of the material is natural, cold heading forming of the ring gear is possible. Furthermore, mold wear is greater in the die taper part 42 than in the die straight part 43, but the die taper part 43
Since the wear of No. 2 has little effect on molding accuracy, there is no problem in mass production of ring gears.

It should be noted that the forging device, material cross-sectional shape, etc. may be considered in addition to the above-mentioned embodiments, and one example will be described below.

FIG. 10 shows the punch 126 divided into multiple parts, and the tooth profile 119 and the knockout ring 115.
This figure represents an embodiment in which a die-carved bottom surface 116 is formed by the following.The symbols in the figure are indicated by adding 100 to the locations corresponding to the symbols of the embodiment in FIG.

In this embodiment, the punch 126 is attached to the punch holder 1
34 and an upper mold ring 138 shrink-fitted to the punch holder 134, and is fixed to the upper mold body 124 by an upper mold flange 135.

Further, the upper part of the knockout ring 115 has a cylindrical outer circumference having a diameter that allows it to move forward and backward along the inner circumferential side of the tooth profile 119, and no meshing tooth profile is formed therein. Furthermore, a third
When molding the chamfer surface 41 as shown in the figure, a die-scaved shape corresponding to the top surface of the knockout ring in the embodiment shown in FIG. 4 and a tooth profile in the embodiment shown in FIG. Alternatively, in both the embodiments shown in FIGS. 4 and 9, a die-carved shape corresponding to the shoulder end face of the punch may be formed.

FIG. 10 shows an embodiment of the cross-sectional shape of the ring-shaped material 230, in which the cross-sectional shape is circular and the outer peripheral surface itself has a chamfered portion 232.

As described above, in the present invention, a ring-shaped material having a chamfered portion on the upper edge of the outer periphery is inserted into the inner periphery of the die with tapered teeth on the inner periphery, and then an outer periphery tooth profile that meshes with the tooth profile of the die is formed. The punch is lowered to bite the material into the tapered part of the tooth profile to pre-form the teeth, and then finish forming in the straight part of the tooth profile, so the deformation of the inner diameter side of the material is slight and the outer peripheral part where the teeth are formed is Because it deforms in the radial direction, a tooth profile with high accuracy and strength can be formed on the outer periphery of a pre-prepared ring-shaped material with a small wire diameter with a small forming force, and the forming process does not generate burrs at the beginning or middle of the downward movement of the punch. In the latter stage, the material is forged in a nearly sealed state with no excess thickness, so it is possible to form a highly accurate ring gear with minimal burrs and excess thickness.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a conventional ring gear forging method.
FIG. 2 is an explanatory cross-sectional view of a ring gear forged by the method shown in FIG. 1. FIG. 3 is a partially enlarged perspective view of the ring gear. FIG. 4 and FIG. 5 represent an embodiment of the present invention, and are explanatory diagrams showing the molding process step by step. FIGS. 6 to 9 are explanatory diagrams showing enlarged portions of the molding process shown in FIGS. 4 and 5. FIGS. FIG. 10 shows a different embodiment from FIG. 4 and is an explanatory diagram of a forging device. FIG. 11 shows a different embodiment from FIG. 6, and is an explanatory diagram of a cross section of the material. (Explanation of symbols), 11... Machine base plate. 15...
Notsuku out ring. 16...Bottom surface of die carving. 17
...lower mold. 18... Dice. 19...Tooth shape. 23
...upper mold. 26...Ponchi. 27...Information part.
28... Shoulder end surface. 30...Material. 31...Ring gear. 32... Chamfered portion. 33...molded teeth. 4
2...Tapered part. 43...Straight section.

Claims (1)

[Claims] 1. A step of inserting a ring-shaped material having a chamfered portion formed on at least the upper edge of the outer periphery into a tapered portion where the tip circle of the tooth profile formed on the inner periphery of the lower mold gently decreases in diameter downward; A tooth preforming step in which a punch with a matching outer circumferential tooth profile is lowered onto the upper surface of the material to deform the material in a direction that reduces the diameter of the material using the tooth profile taper part, and a tooth tip circle of the tapered part of the tooth profile. A forging method for forming a tooth profile on the outer periphery of a ring-shaped material, comprising the step of final forming the preformed material with a straight part of the tooth profile that continues on the small diameter side with the same tooth tip diameter.