JP2015186815A - Crankshaft forging method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily realize the formation of a lightened portion without restrictions depending on the opening direction of a forging die and without an increase in the number of steps.SOLUTION: A method of forging a crankshaft 1 comprises: a rough forming step (S13) of die-forging a preliminary molded component 102 and forming a roughly formed molded component 103; and a finishing step (S14) of die-forging the roughly formed molded component 103 and forming a finished molded component 104. The rough forming step (S13) includes forming a protrusion 7 that is a region swollen in a die opening direction as compared with a shape of the finished molded component 104 on the roughly formed molded component 103, and the finishing step (S14) includes bending the protrusion 7 by a die closing motion to form a lightened portion 6 that is a concave portion in the finished molded component 104.

Description

  The present invention relates to a technique for a crankshaft forging method, and more particularly to a method for reducing the weight of a crankshaft.

2. Description of the Related Art Conventionally, a technique for manufacturing a crankshaft, which is one of components constituting an engine, by forging is known. There is a need to reduce the weight of the crankshaft in order to improve engine performance, and various techniques for reducing the weight of the crankshaft have been studied.
In the prior art for reducing the weight of the crankshaft, it is common to reduce the weight by separately machining the forged crankshaft to form a meat stealing portion (concave portion).

  In a configuration in which machining is performed on a crankshaft after forging, the number of steps and time required for machining increase, so it is desirable to realize formation of a meat stealing part (concave portion) without increasing the number of steps. ing.

Therefore, a technique for forming a meat stealing portion on a crankshaft has been developed without relying on machining after forging. For example, the technique is disclosed in Patent Document 1 shown below.
In the crankshaft manufacturing method according to Patent Document 1, it is possible to form a meat stealing portion (concave portion) simultaneously with forging without increasing the number of steps by providing the convex portion on the forging die.

JP 2009-133331 A

However, in the conventional crankshaft manufacturing method according to Patent Document 1, there is a restriction on the direction in which the protrusions are formed due to the relationship with the forging die opening direction. That is, if a protrusion protruding in the direction intersecting the opening direction of the forging die is provided, it becomes impossible to release the mold after forging. Therefore, the protrusion that can be provided inside the forging die is parallel to the opening direction. It was limited to the convex part protruding in the direction.
In addition, when trying to form a meat stealing part without providing a convex part that protrudes in the direction intersecting the opening direction of the forging die, it is possible to cope with it by devising the arrangement of the mating surface (parting line) of the forging die However, in such a case, the degree of freedom in product design is hindered and it is difficult to achieve both forgeability.

  The present invention has been made in view of such current problems, and is not subject to restrictions due to the opening direction of the forging die, and can easily form the meat stealing portion without increasing the number of steps. An object of the present invention is to provide a method for forging a crankshaft.

  The problem to be solved by the present invention is as described above. Next, means for solving the problem will be described.

  That is, in claim 1, forging of a crankshaft comprising: a wasteland step for die forging a rod-shaped material to form a wasteland molded product; and a finishing step for die forging the wasteland molded product to form a finished molded product. In the wasteland step, a protrusion is formed on the wasteland molded product that is a portion that bulges in the mold opening direction as compared to the shape of the finished molded product, and the finishing step is a mold closing operation. The protrusion is bent by the above, and a meat stealing portion that is a recess is formed in the finished molded product.

  As effects of the present invention, the following effects can be obtained.

  In Claim 1, formation of a meat stealing part can be easily realized without being restricted by the opening direction of the forging die and without increasing the number of steps.

The schematic diagram which shows the molding condition of the crankshaft in a forge process. The figure which shows the flow of the forge process of a crankshaft. The front schematic diagram which shows a crankshaft. The journal axial direction schematic diagram which shows a crankshaft. The perspective schematic diagram which shows the formation condition of the meat stealing part in a wasteland process-a finishing process. The schematic diagram for demonstrating the protrusion part formed in a new ground processed product. The schematic diagram which shows the deformation | transformation condition of the protrusion part in a finishing process, and the formation condition of a meat stealing part. The schematic diagram which shows the finished molded product in which the meat stealing part was formed.

Next, embodiments of the invention will be described.
Here, first, the flow of the forging process of the crankshaft will be described with reference to FIGS.

In the crankshaft forging step shown in the present embodiment, the crankshaft 1 is finally manufactured by forging a cylindrical rod-shaped material 101 as shown in FIG.
As shown in FIG. 2, first, a cutting step (S10) for cutting a cylindrical billet having a diameter based on the final shape, dimensions, etc. of the crankshaft 1 (see FIG. 1 (f)) to a predetermined length. This is executed to obtain a rod-like material 101 (see FIG. 1A) used for forging the crankshaft 1.

Next, a heating step (S11) is performed in which the rod-shaped material 101 is heated to a predetermined temperature of, for example, about 1200 ° C. or higher.
Next, a preforming step (S12) is performed, and the preformed product 102 (see FIG. 1 (b)) is subjected to a bending process or the like on the heated rod-shaped material 101 and brought close to the final shape of the crankshaft 1. Get.

  Next, a wasteland step (S13) is performed in which the corners and the like of the preformed product 102 are die-forged into a simplified wasteland shape to obtain a wasteland molded product 103 (see FIG. 1C). A burr 103 a is formed around the wasteland molded product 103.

  Next, a finishing step (S14) for forging the wasteland molded product 103 into a finished shape is executed to obtain a finished molded product 104 (see FIG. 1 (d)).

  Next, since the burr 103a is deformed to form the burr 104a (see FIG. 1E) around the finished molded product 104, a trimming step (S15) for cutting the burr 104a by trimming is executed. To do.

Then, in the trimming step (S15), the burr 104a is removed from the finished molded product 104 to obtain the crankshaft 1 as the final molded product as shown in FIG.
And after performing an inspection process (S16) with respect to the crankshaft 1 and confirming that there is no crack and a deformation | transformation, it sends to a post process.
The above is a series of flows in the forging process of the crankshaft 1.

Thus, in the forging method of the crankshaft 1 according to the embodiment of the present invention, the crankshaft 1 is completed without a separate process for machining so as to provide the meat stealing portion.
In addition, in this embodiment, although the forging method of the crankshaft 1 provided with the cutting process (S10)-inspection process (S16) is illustrated, in the forging method of the crankshaft 1, in addition to, for example, the crankshaft 1 It also includes a sandblasting process for surface treatment, a process for cooling the crankshaft 1, and the like, and may include processes other than the above processes.

As shown in FIG. 3, a journal 2, an arm portion 3, a pin 4, a counterweight portion 5, and the like are formed on the crankshaft 1 obtained through a series of forging processes.
The journal 2 is a part constituting a discontinuous axis in the crankshaft 1, and arm portions 3, 3 that protrude radially outward from the journal 2 are formed at the end portion of the journal 2, and the pair of arm portions 3. A pin 4 as a shaft portion for connecting the arm portions 3 and 3 is formed between the arm portions 3 and 3, and the arm portions 3 and 3 are balanced on the opposite side of the protruding direction of the arm portions 3 and 3 Counterweight portions 5 and 5 are formed.

As shown in FIGS. 3 and 4, the crankshaft 1 manufactured by the forging method according to the embodiment of the present invention has a meat on the outer side of the arm portion 3 (opposite the side where the pin 4 is present). A stealing portion 6 is formed. The meat stealing portion 6 is a portion in which the arm portion 3 is partially thinned in order to reduce the weight of the arm portion 3 and is provided by selecting a position and a range in consideration of securing the rigidity of the arm portion 3. .
In addition, when the meat stealing part 6 is provided in the arm part 3, the weight of the counterweight part 5 can be reduced by the reduced weight. Therefore, the meat stealing part 6 in the crankshaft 1 It is preferable to provide the part 3.

  As shown in FIG. 2, the meat stealing unit 6 is formed in a series of forging processes without additional processes such as machining, and more specifically, a series of processes from a wasteland process (S13) to a finishing process (S14). In the process, the meat stealing part 6 is formed.

Next, the formation method of the meat stealing part 6 in the forging method of the crankshaft 1 which concerns on one Embodiment of this invention is demonstrated using FIGS.
As shown in FIG. 5, in the forging method of the crankshaft 1 according to one embodiment of the present invention, the protruding portion 7 is formed in the wasteland molded product 103 obtained through the wasteland process (S13).

  As shown in FIGS. 5 and 6, the protruding portion 7 is a portion formed so as to protrude toward the mold opening direction of the finishing forging die 20 (see FIG. 6) in the rough ground molded article 103. Compared to the final shape of the shaft 1, it is formed as a portion bulging outward in the mold opening direction.

In FIG. 6, the forging die 20 in a closed state and the rough ground molded product 103 are overlapped and illustrated.
As shown in FIG. 6, the protruding portion 7 protrudes by a height h from the position of the bottom portion in the depth direction of the mold inner surface 21 b of the upper mold 21 when the mold is closed, and the protruding portion 7 of the mold inner surface 21 b when the mold is closed. An offset amount A is disposed on the inner side with respect to the widthwise opening. Although not shown in FIG. 6, the protruding portion 7 protrudes by a height h from the position of the bottom in the depth direction of the inner surface 22b of the lower mold 22 when the mold is closed, and when the mold is closed. The inside of the mold inner surface 22b is disposed on the inner side by an offset amount A with respect to the widthwise opening.
In the configuration in which the protruding portion 7 protrudes at a height h, when the forging die 20 is clamped, the protruding portion 7 comes into contact with the upper die 21 and the lower die 22 at an early stage, and the clamping operation of the forging die 20 is performed. Accordingly, the protrusion 7 is gradually deformed. Further, by arranging the protruding portion 7 at a position recessed by the offset amount A, a space is secured in which the deformed protruding portion 7 can be accommodated in the mold.

  In addition, in the conventional wasteland process, processing is performed so that the shape difference with respect to the shape of the finished molded product (that is, the crankshaft) is small in order to bring the material before being introduced into the finishing process closer to the shape of the finished molded product. Since it has been carried out as a process of applying, it has not been actively provided with a bulging part as compared with the shape of the finished molded product.

The protruding portion 7 includes a tapered portion 7a on the inner side (side on which the pin 4 is formed).
The taper part 7a is directed outward (opposite to the side where the pins 4 are formed) as shown in FIG. 6 so that the width of the protrusion 7 is narrowed toward the outside in the mold opening direction of the protrusion 7. And inclined at an angle θ.

The die forging in the finishing step (S14) is performed using a forging die 20 for finishing as shown in FIG.
The forging die 20 includes an upper die 21 and a lower die 22. In the forging die 20 shown in the present embodiment, the upper die 21 and the lower die 22 are symmetrical with respect to the mating surface.

As shown in FIG. 7, the die forging performed in the finishing step (S14) is performed by clamping the die in a state where the waste ground molded product 103 is disposed in the forging die 20.
When the forging die 20 is clamped, the upper die 21 is pressed against the protrusions 7 and 7 on the upper part of the waste-moulded product 103, and convex portions that contact the tapered portions 7 a and 7 a formed inside the protrusions 7 and 7. 21a descends in contact with the tapered portions 7a and 7a. At this time, the protrusions 7 and 7 are pressed toward the outside (opposite the side on which the pins 4 are formed) by the convex portion 21a and are bent outward.
Then, when the clamping operation of the forging die 20 proceeds and the upper die 21 is lowered to the clamping position (bottom dead center), the bent projections 7 and 7 are accommodated in the die, and the bent projection 7 The meat stealing portion 6 is formed as a concave portion surrounded by.
Further, when the clamping of the forging die 20 is completed, the meat stealing portion 6 is also formed as a concave portion surrounded by the bent protruding portion 7 in the relationship between the convex portion 22a of the lower die 22 and the rough ground molded product 103. It is formed.

By forming the protrusion 7 at an angle θ, as shown in FIG. 7, as the forging die 20 is closed, the protrusion 7 selects the outside (opposite the side where the pin 4 is formed). The projecting portion 7 can be deformed (bent) so as to fall down.
When the projecting portion 7 is tilted outward, a recess surrounded by the projecting portion 7 is formed on the outer side of the arm portion 3, and when the finishing step (S14) is completed, this recess is finally formed into the finished molding obtained. It is formed as the meat stealing part 6 in the product 104.

  In the conventional finishing process, the forging die 20 is filled with a raw material and forged. If the finished molded product 104 is made into an undercut shape, it cannot be released, so that a concave portion is formed in the final shape of the crankshaft 1. In the case of having it, it is necessary to provide a process (such as punching or cutting) for machining the finished molded product 104 separately.

  On the other hand, in the forging die 20 used in the forging method of the crankshaft 1 according to the embodiment of the present invention, no protrusion is provided in a direction intersecting with the die opening (die closing) direction, and the upper die 21 and the lower die 22 are not provided. Can be easily released because the meat stealing portion 6 is formed without filling the meat stealing portion 6 and without filling the inner mold of the upper mold 21 and the lower mold 22 with the material. .

That is, the forging method of the crankshaft 1 according to one embodiment of the present invention includes a wasteland step (S13) in which a rod-shaped material (preliminarily molded product 102) is die-forged and formed into a wasteland molded product 103, and a wasteland molded product 103 is formed. And a finishing step (S14) in which the die is forged and formed into a finished molded product 104. In the waste land step (S13), the mold opening is performed on the waste ground molded product 103 as compared with the shape of the finished molded product 104. The projecting portion 7 that is a portion that bulges in the direction is formed, and the finishing step (S14) is to form the meat stealing portion 6 as a recess in the finished molded product 104 by bending the projecting portion 7 by a mold closing operation. is there.
With such a configuration, formation of the meat stealing portion 6 can be easily realized without being restricted by the opening direction of the forging die 20 and without increasing the number of steps.

The shape and arrangement of the meat stealing portion 6 are the shape of the forging die 20 used in the finishing step (S14), the shape of the protruding portion 7 formed in the wasteland step (S13), the protruding height h, the inclination angle θ, and the offset amount A. Can be adjusted to a desired arrangement and shape by appropriately changing.
In this embodiment, the case where the protruding portion 7 is tilted outward (opposite the side where the pin 4 is formed) and the meat stealing portion 6 is formed is illustrated. It is good also as a structure which inclines to the side formed) and forms the meat stealing part 6. FIG.

DESCRIPTION OF SYMBOLS 1 Crankshaft 6 Meat stealing part 7 Protruding part 102 Preliminary molded product 103 Wasteland molded product 104 Finished molded product

Claims (1)

A wasteland process in which a rod-shaped material is die-forged and formed into a wasteland molded product,
A finishing step of die forging the waste land molded product to form a finished molded product;
A crankshaft forging method comprising:
The wasteland process
In the wasteland molded product, a protrusion that is a portion that bulges in the mold opening direction compared to the shape of the finished molded product is formed,
The finishing step is
Bending the protruding part by a mold closing operation to form a meat stealing part as a recess in the finished molded product,
A crankshaft forging method characterized by the above.

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