JP2010131609A - Method for forming crank shaft having continuous hollow part - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method where a crank shaft having a continuous hollow part is formed in an offset upsetting method by using a hollow material constituted so that the continuous hollow part is not clogged during the upsetting. <P>SOLUTION: The method includes a setting step of holding a middle portion of a hollow material 2 by a floating tool 6, and setting it to upper and lower dies 3, 4, an offset upsetting step of executing the upsetting with the middle portion of the hollow material 2 being offset by the floating tool 6 while lowering the upper die 3, and an offset upsetting completion step of forming arm parts 9, 9 of a crank shaft 5 by executing the upsetting by lowering the upper die 3 to the predetermined position. As the hollow material 2, the one where a clogging preventive means capable of preventing a hollow part 7 located inside the arm parts 9, 9 from being squeezed and clogged by the stress by reducing the stress exerted in the hollow material 2 during the upsetting is provided inside the hollow part 7 is used. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a molding method for molding a crankshaft having a continuous hollow portion by an eccentric upsetting method.

  Conventionally, a method for manufacturing a crankshaft which is a component of an internal combustion engine by an eccentric upsetting method which is a kind of upsetting method and a technique related to a hollow crankshaft in which a continuous hollow portion is formed are known ( (See Patent Documents 1 and 2).

  The manufacturing method of the crankshaft described in Patent Document 1 is a method of forming the crankshaft by cold forging by an eccentric upsetting method, and producing an offset material that has been bent in advance, In this method, the crank body is compression-molded by pressurizing in the axial direction by an upsetting process.

  The hollow crankshaft described in Patent Document 2 has a hollow portion that also serves as a hydraulic path formed therein. As a method for forming the hollow portion, it is described that when a casting is formed, a casting crank having a hollow portion is formed by using a core such as a sand core.

As a technique for forming a crankshaft having a hollow portion (hollow hole) by cold forging, as shown in FIG. 12, a crank is formed by an eccentric upsetting method using a cylindrical hollow material having a continuous hollow portion. By forming the shaft, there is a technique for suppressing the cracking by dispersing the tensile stress on the material surface at the time of upsetting to the inner hollow side, and the pin portion and the journal portion can be made hollow.
Japanese Patent Laid-Open No. 2005-9595 JP 2004-340307 A

  However, as described in Patent Documents 1 and 2 described above, as a conventional technique, a technique for manufacturing a crankshaft by an eccentric upsetting method, a hollow part or an oil hole provided in a pin part or a journal part provided in the crankshaft Are known in the art for forming a hollow part and an oil hole by machining (pipe casting and core), and a crankshaft having a continuous hollow part (oil hole) is known. A technique for forming by forging and eccentric upsetting has not been established.

  Further, in the above-described forming technique (cold forging forming method) of a crankshaft having a hollow portion, as shown in FIG. 12, the crankshaft pin is formed by forming the crankshaft by an eccentric upsetting method using a hollow material. The hollow portion in the arm portion of the crankshaft is crushed, although the portion and the journal portion can be hollowed (see FIG. 13). When the hollow part (hollow hole) formed in the pin part or journal part is used as an oil hole for supplying lubricating oil, it is necessary to add a process such as a hole process for connecting the pin part and the journal part hole (Fig. 14), resulting in high manufacturing costs. Further, in the current crankshaft, as shown in FIG. 14, the oil holes are independently arranged, and the oil supply mechanism is complicated because each journal portion is individually supplied with oil.

  Specifically, the molding technique having the hollow portion is a method of suppressing molding cracks by dispersing the tensile stress on the inner diameter side, and the case where the eccentricity amount or the upsetting amount is large or the forgeability is poor. In the case of materials (materials with a large amount of carbon), as the compressive force during installation and the stress on the surface of the material increase, the stress dispersed in the hollow portion of the inner diameter also increases, and the stress causes the hollow portion in the arm to collapse. As a result, the continuous hollow portion in the state before molding is blocked in the middle. Therefore, when a crankshaft is formed by the eccentric upsetting method described above using a hollow material, the hollow portion of the arm portion, which is a portion to be installed due to the stress generated during installation, is prevented from being crushed and blocked. Technology is required.

  Therefore, the present invention proposes a method of forming a crankshaft having a continuous hollow portion by an eccentric upsetting method by using a hollow material in which the continuous hollow portion is not closed during installation.

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

That is, in claim 1,
A method of forming a crankshaft by performing eccentric upsetting by cold forging using a hollow material having a continuous hollow portion,
A set step of holding the middle part of the hollow material with an eccentric jig, and setting both ends in the central axis direction of the hollow material on the upper and lower molds of the molding device,
While lowering the upper mold of the molding apparatus, the eccentric jig is moved in the vertical direction with respect to the central axis direction of the hollow material, whereby the middle part of the hollow material held by the eccentric jig is An eccentric upsetting process in which the hollow material is eccentric with respect to the central axis to perform upsetting;
Eccentricity in which the crankshaft arm is continuously formed on both ends of the hollow portion held by the eccentric jig by lowering the upper mold to a predetermined position and performing upsetting. An upsetting completion process,
As the hollow material, by reducing the stress acting on the hollow material during the upsetting in the hollow portion, the hollow portion located inside the arm portion is crushed and closed by the stress. What is provided with the blockage | prevention prevention means which prevents this is used.

In claim 2,
The blocking prevention means includes
A plurality of groove portions provided on the inner wall surface of the hollow portion substantially in parallel with the central axis direction of the hollow material, and the plurality of groove portions against the direction of stress acting on the hollow material during the upsetting Thus, the groove portion is provided in a direction that is intentionally easily crushed and the groove portion is provided in a direction that is not easily crushed.

In claim 3,
The blocking prevention means includes
A support member provided with a through-hole penetrating in the same direction as the central axis direction of the hollow part, having a higher hardness than the hollow material, and supported at a predetermined position of the hollow part;
It is formed between an outer peripheral surface of the support member and an inner wall surface of the hollow portion, and includes a gap that is crushed and closed by stress acting on the hollow material during the upsetting.

In claim 4,
The blocking prevention means includes
A low melting point alloy that is cast into the hollow part, cooled and solidified, and provided with a through-hole that is crushed and closed by stress acting on the hollow material during the upsetting, and after the upsetting, The low melting point alloy is heated and melted and discharged from the hollow portion.

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

  According to the first aspect, the stress acting on the hollow material during upsetting can be reduced, and a hollow crankshaft having a continuous hollow portion can be formed.

  In claim 2, when the tensile force generated on the surface during eccentric installation is dispersed in the internal hollow portion, a groove that is crushed to reduce the tensile force and excessive compressive force during installation, and buckling Thus, a crankshaft having a continuous hollow portion can be cold-forged by an eccentric upsetting method without losing formability by a groove vacated in a direction in which a tensile force acts (groove that is not easily crushed).

  In claim 3, the load acting on the hollow portion (inner diameter portion) becomes high, such as in the case of a crankshaft with a large eccentric amount (stroke length) or when the amount of upsetting is increased to extend the counterweight. Even when the support member having high hardness supports the molding load, the crankshaft having the continuous hollow portion can be surely cold forged by the eccentric upsetting method.

  According to the fourth aspect of the present invention, the formability is ensured by reducing the force dispersed in the internal hollow portion by the through hole provided in the low melting point alloy, and the low melting point alloy remaining inside the molded crankshaft is dissolved. As a result, the crankshaft having the continuous hollow portion can be cold forged by the eccentric upsetting method at a relatively low cost even when the molding load is high.

Next, embodiments of the invention will be described.
First, the structure of the shaping | molding apparatus with which the shaping | molding method of the crankshaft which has the continuous hollow part which concerns on this invention is applied is demonstrated using FIG.
In addition, the same code | symbol is attached | subjected to the member which has the same use and function, and the description is abbreviate | omitted.

  The molding apparatus 1 is an apparatus that performs eccentric upsetting of the crankshaft 5 by cold forging using a hollow material 2, and as shown in FIG. 1 (a), mainly an upper mold 3, a lower mold 4, and A floating jig 6 that is an eccentric jig is provided. The upper mold 3 and the lower mold 4 are disposed so as to face each other vertically, and the floating jig 6 is disposed between the upper and lower molds 3 and 4.

The hollow material 2 has a round bar shape and has a hollow portion 7 penetrating a substantially central portion in the axial direction. The hollow material 2 is a material of the crankshaft 5 that is formed by an eccentric upsetting method.
The hollow material 2 is provided with a blockage prevention means described later in the hollow part 7 of the hollow material 2.
The clogging prevention means reduces (relaxes) the stress acting on the hollow material 2 during upsetting, so that the hollow portion 7 positioned inside the arm portions 9 and 9 of the crankshaft 5 is caused by the stress. It prevents crushing and blocking.

  The floating jig 6 has a flat shape, and an opening 6a is opened at a predetermined location. A hollow material 2 is inserted into the opening 6a, and a midway portion of the hollow material 2 (in this embodiment, a crank) It is possible to hold the portion of the shaft 5 that becomes the pin portion 8. In addition, the floating jig 6 is disposed at a substantially intermediate position between the upper and lower molds 3 and 4 in the initial state (FIG. 1A) in which the hollow material 2 is set in the molding apparatus 1. As the upper die 3 is lowered, the floating jig 6 is also lowered (FIG. 1 (b)), and a floating mechanism (not shown) that can always hold the floating jig 6 at an intermediate position in the vertical direction of the upper and lower dies 3 and 4. Z). Further, the floating jig 6 is movable (slidable) in the vertical direction with respect to the central axis direction of the hollow material 2 in a state where the midway portion (pin portion 8) of the hollow material 2 is held.

  By forming the molding device 1 in this way, the hollow material 2 is inserted into the opening 6a opened at a predetermined position of the floating jig 6 that is an eccentric jig, and one end (the journal portion 10) of the hollow material 2 is inserted. The upper die 3 is lowered in a state where the upper portion 3 is fixed to a predetermined position of the upper die 3 and the other end of the hollow material 2 (the portion that becomes the journal portion 10) is fixed to a predetermined portion of the lower die 4. Then, while compressing the hollow material 2 in the axial direction, the middle part of the hollow material 2 is moved (eccentric) in the vertical direction with respect to the axial direction, thereby being positioned between the upper die 3 and the floating jig 6. And the hollow material 2 positioned between the lower mold 4 and the floating jig 6 are installed to form the arm portions 9 and 9 of the crankshaft 5 (FIG. 1C). Is possible.

That is, as shown in FIG.1 (c), the crankshaft 5 shape | molded by the shaping | molding apparatus 1 which concerns on this embodiment is between the arm part 9 * 9 and arm part 9 * 9 which are a pair of flat shapes. The pin part 8 to be disposed and the journal parts 10 and 10 fixed to the upper and lower molds 3 and 4 are provided.
In addition, although the crankshaft 5 shown by this embodiment shows the example of the arm part 9 * 9 arrange | positioned on the both sides of the pin part 8 and this pin part 8, it does not specifically limit to this shape. For example, a journal portion of the crankshaft 5 and arm portions formed on both sides of the journal portion may be used.

  Next, a crankshaft forming method using the above-described forming apparatus 1 will be described.

  As shown in FIG. 2, the crankshaft forming method includes a setting step S10, an eccentric upsetting step S20, and an eccentric upsetting completion step S30. Hereinafter, each step will be described.

  In the setting step S10, the middle part of the hollow material 2 is held by the floating jig 6 that is an eccentric jig, and both ends of the hollow material 2 in the central axis direction are set in the upper and lower molds 3 and 4 of the molding apparatus 1. It is.

That is, in the setting step S10, as shown in FIG. 1A, the midway part of the hollow material 2 that becomes the pin part 8 of the crankshaft 5 after the upsetting is completed is inserted and held in the opening part 6a of the floating jig 6. At the same time, one end of the hollow material 2 that becomes the journal portion 10 of the crankshaft 5 is fixed to a predetermined position of the lower die 4 after the upsetting is completed, and the other end of the hollow material 2 that also becomes the journal portion 10 is fixed to the predetermined portion of the upper die 3. The hollow material 2 is set in the upper and lower molds 3 and 4 of the molding apparatus 1 and is prepared to start upsetting, thereby setting the initial state of upsetting.
When the setting step S10 is completed, the process proceeds to the eccentric upsetting step S20.

  In the eccentric upsetting step S <b> 20, the floating jig 6 is held by moving the floating jig 6 in the vertical direction with respect to the central axis direction of the hollow material 2 while lowering the upper mold 3 of the molding apparatus 1. This is a step of performing upsetting by decentering the middle part of the hollow material 2 with respect to the central axis of the hollow material 2.

That is, in the eccentric upsetting step S20, the hollow material 2 is compressed in the axial direction while lowering the upper mold 3 of the molding apparatus 1, and the midway portion of the hollow material 2 is perpendicular to the axial direction by the floating jig 6. By moving (eccentric) in the direction, the hollow material 2 positioned between the upper mold 3 and the floating jig 6 and the hollow material 2 positioned between the lower mold 4 and the floating jig 6 are Be put in.
When the eccentric upsetting step S20 is completed, the process proceeds to the eccentric upsetting completion step S30.

  In the eccentric upsetting completion step S30, the upper die 3 is lowered to a predetermined position to perform upsetting, so that the arm portions of the crankshaft 5 are provided at both ends of the midway portion of the hollow material 2 held by the floating jig 6. This is a step of continuously forming 9 · 9.

  That is, in the eccentric installation completion step S30, the upper mold 3 is moved to a position corresponding to a predetermined thickness of the arm portion 9 where the distance between the lower surface of the upper mold 3 of the molding apparatus 1 and the upper surface of the floating jig 6 is formed. At the same time, the floating jig 6 is arranged at the intermediate position in the vertical direction between the upper and lower molds 3 and 4 by the floating mechanism as described above. The distance between the upper surface of the lower mold 4 and the lower surface of the floating jig 6 is also equivalent to a predetermined thickness of the arm portion 9 to be formed.

According to the conventional method for forming a crankshaft, as shown in FIG. 13, it is possible to form a hollow portion inside the pin portion 8 or the journal portion 10 which is the middle portion of the hollow material 2, but upsetting molding Sometimes the hollow portions inside the arm portions 9 and 9 are crushed by the stress acting on the hollow material 2, and the continuous hollow portion 7 cannot be formed in the crankshaft 5.
On the other hand, when the upholstery molding is performed in the above-described crankshaft molding method using the hollow material 2 provided with the blocking prevention means according to the present embodiment in advance, the stress is reduced (relieved). It is possible to prevent the hollow portion located inside the arm portions 9 and 9 from being crushed and closed. For this reason, it is possible to leave a hollow portion located inside the arm portions 9 and 9 during upsetting, and it is possible to form the crankshaft 5 having the continuous hollow portion 7.
That is, by forming with the molding apparatus 1 using the hollow material 2 having the clogging prevention means, an integrated and continuous hollow portion is formed from the round bar-shaped hollow material 2 by the eccentric upsetting method of cold forging. The crankshaft 5 having it can be formed.

Thus, a method of forming the crankshaft 5 by performing eccentric upsetting by cold forging using the hollow material 2 having a continuous hollow portion 7,
A setting step S10 for holding the middle part of the hollow material 2 by a floating jig 6 that is an eccentric jig, and setting both ends of the hollow material 2 in the central axis direction of the upper and lower molds 3 and 4;
The hollow material 2 held by the floating jig 6 is moved by moving the floating jig 6 in a direction perpendicular to the central axis direction of the hollow material 2 while lowering the upper mold 3 of the molding apparatus 1. An eccentric upsetting step S20 in which an intermediate part is eccentric with respect to the central axis of the hollow material 2 to perform upsetting;
The upper mold 3 is lowered to a predetermined position to perform upsetting, so that the arms 9 and 9 of the crankshaft 5 are continuously connected to both ends of the hollow material 2 held by the floating jig 6. An eccentric upsetting completion step S30 to be formed,
As the hollow material 2, by reducing the stress acting on the hollow material 2 during the upsetting in the hollow portion 7, the hollow portion positioned inside the arm portions 9 and 9 by the stress. By applying a method of forming the crankshaft 5 using a means provided with a blocking prevention means for preventing the block 7 from being crushed and blocked, the stress acting on the hollow material 2 during upsetting can be reduced. It becomes possible and the hollow crankshaft 5 which has the continuous hollow part 7 can be shape | molded.
Specific examples of the blocking prevention means according to the present embodiment will be described below.

Next, a method for forming the crankshaft 5 using the hollow material 2 provided with the above-described blocking prevention means will be described.
The method for forming the crankshaft 5 according to the present embodiment is the same as the above-described forming method. Here, an example of a hollow material provided with a blocking prevention means used in this forming method will be specifically described.

  As shown in FIG. 3, the hollow material 12 is a round bar-like member, and has a hollow portion 17 having a cross-shaped cross section that penetrates continuously from one end to the other end.

  By reducing (releasing) the stress that acts on the hollow material 12 during upsetting, the hollow material 17 is crushed and closed by the stress. A blockage prevention means for preventing this is provided in advance.

As shown in FIG. 3, the blocking prevention means is a plurality of groove portions provided on the inner wall surface of the hollow portion 17 substantially in parallel with the central axis direction of the hollow material 12, and the plurality of groove portions are hollow materials during upsetting. 12 and the first groove portions 13 and 13 provided in a direction that tends to be intentionally crushed with respect to the direction of stress acting on 12 (a direction in which a compressive force acts by upsetting) and a direction that is difficult to be crushed (a tensile force due to buckling). And second groove portions 14 and 14 provided in the direction of action).
In the present embodiment, the two first groove portions 13 and 13 and the two second groove portions 14 and 14 are arranged so as to face each other so as to have a cross shape in cross section. Instead, the shape of the groove, the arrangement configuration of the groove in the hollow portion 17, and the like can be changed as appropriate. Moreover, as a groove part which comprises an obstruction | occlusion prevention means, it is possible to comprise so that it may become the directionally integrated or separate body.

  Next, a molding method when eccentric upsetting is performed by the above-described crankshaft molding method using the hollow material 12 in which the first groove portions 13 and 13 and the second groove portions 14 and 14 are formed as the blocking prevention means. Will be described with reference to FIG.

  In the setting step S10 (initial molding state), the hollow material 12 is set in the molding apparatus 1 as shown in FIG. In this state, the cross-sectional view of the hollow material 12 has a cross shape from the first groove portions 13 and 13 and the second groove portions 14 and 14 (FIG. 4A).

  Subsequently, in the eccentric upsetting step S20, as shown in FIG. 1 (b), the compressive force due to the upsetting and the tensile force of the dispersed surface act on the hollow material 12 as stress, intentionally. The first groove portions 13 and 13 that are crushed grooves start to be crushed (FIG. 4B).

  Subsequently, in the eccentric upsetting completion step S30, as shown in FIG. 1C, the first groove portions 13 and 13 are caused by the compressive force due to the upsetting and the tensile force of the dispersed surface acting as stress. Is completely crushed (see the dotted arrow in FIG. 4 (c)), while the second groove portions 14 and 14 remain ((FIG. 4 (c)). It is possible to reduce the stress (relieve the stress) and to leave the second grooves 14 and 14. As a result, a continuous hollow portion 17 is formed inside the crankshaft 5. Is done.

Thus, the blocking prevention means is a plurality of groove portions provided on the inner wall surface of the hollow portion 17 substantially in parallel with the central axis direction of the hollow material 12, and the plurality of groove portions are formed during the upsetting process. The first groove portions 13 and 13 that are grooves provided in a direction that is intentionally easily crushed with respect to the direction of the stress acting on the hollow material 12 and the second groove portions 14 and 14 that are grooves provided in a direction that is not easily crushed. When the tensile force generated on the surface at the time of eccentric installation is dispersed in the internal hollow portion 17, the groove is crushed to reduce the tensile force and excessive compression force at the time of installation. A crank having a continuous hollow portion 17 without sacrificing formability by the first groove portions 13 and 13 and the second groove portions 14 and 14 which are grooves (grooves which are difficult to be crushed) which are vacated in a direction in which a tensile force is exerted by buckling. Eccentric installation of shaft 5 In it can be cold 鍛成 form.
Further, when the hollow portion 17 is used as an oil hole for lubrication, a post process (drilling or the like) is not required, and cost reduction can be achieved.
Moreover, since many hollow parts 17 are formed in the inside of the crankshaft 5, a lighter crankshaft than normal forging can be shape | molded.

  In other words, the hollow material 12 provided with grooves that are intentionally easily crushed and grooves that are not easily crushed is used to form by the eccentric upsetting method. It becomes possible to leave the space formed by the second groove portions 14 and 14 for use as an oil hole.

  Next, another embodiment of a method for forming a crankshaft using a hollow material provided with blocking prevention means will be described.

  As shown in FIG. 5, the hollow material 22 is a round bar-like member, and has a hollow portion 27 having a round shape in cross section, which penetrates continuously from one end to the other end.

  In the hollow material 22, the stress acting on the hollow material 22 during upsetting is reduced (released), so that the hollow portion 27 located inside the arm portions 9 and 9 is crushed and closed by the stress. A blockage prevention means for preventing this is provided in advance.

As shown in FIG. 5, the blocking prevention means includes a through hole 23 a penetrating in the same direction as the central axis direction of the hollow portion 27, is harder than the hollow material 22, and is supported at a predetermined position of the hollow portion 27. And a gap formed between the outer peripheral surface of the support member 23 and the inner wall surface of the hollow portion 27 and crushed and closed by stress acting on the hollow material 22 during the upsetting. 24.
Further, as shown in FIG. 5A, the support member 23 in the present embodiment is supported in the hollow portion 27 in the portions 9 a and 9 a forming the arm portions 9 and 9.
In addition, as an example of a material harder than the hollow material 22, it is possible to use a material having higher hardness and strength than the hollow material 22 such as a heat-treated high carbon steel material, cemented carbide or ceramic.
In the present embodiment, four support members 23 are inserted into the hollow portion 27, but there is no particular limitation, and at least one support member 23 may be inserted.
Further, it is only necessary that the support member 23 is provided with at least one through hole 23a and the through hole 23a can form a continuous hollow portion 27 when the upsetting is completed.

  Next, a forming method in the case where the eccentric upsetting is performed by the above-described crankshaft forming method using the hollow material 22 in which the support member 23 and the gap 24 are formed as the blocking prevention means will be described with reference to FIG. To do.

  In the setting step (initial molding state), the hollow material 22 is set in the molding apparatus 1 as shown in FIG. In this state, the cross-sectional view of the hollow material 22 shows that the support member 23 is inserted (press-fitted) into the hollow portion 27 at the portion where the support member 23 is disposed, so Both end portions are in contact with and supported by the inner wall of the hollow material 22 (reference numeral 25 in FIG. 5B). Further, a gap 24 is provided between the outer peripheral surface of the support member 23 and the inner wall surface of the hollow material 22.

  Subsequently, in the eccentric upsetting step S20, as shown in FIG. 6 (b), the compressive force due to the upsetting and the tensile force of the dispersed surface act on the hollow material 22 as stress, intentionally. The gap 24, which is the space to be crushed, begins to collapse (FIG. 7B).

  Subsequently, in the eccentric installation completion step S30, as shown in FIG. 6C, the gap 24 is completely crushed because the compression force by the installation and the tensile force of the dispersed surface act as stresses. (See the dotted arrow in FIG. 7C.) On the other hand, the through hole 23a of the support member 23 remains. In this way, the stress can be reduced (stress can be released) by crushing the gap 24 during upsetting. As a result, a continuous hollow portion 27 is formed in the crankshaft 5.

Thus, the blocking prevention means includes the through hole 23a penetrating in the same direction as the central axis direction of the hollow portion 27, is harder than the hollow material 22, and is located at a predetermined position of the hollow portion 27. The support member 23 is supported, and is formed between the outer peripheral surface of the support member 23 and the inner wall surface of the hollow portion 27, and is crushed and closed by the stress acting on the hollow material 22 during the upsetting. The load acting on the hollow portion 27 (inner diameter portion) such as in the case of a crankshaft with a large eccentric amount (stroke length) or when the amount of upsetting is increased in order to extend the counterweight. Even when the height of the crankshaft 5 increases, the support member 23 having high hardness supports the molding load, so that the crankshaft 5 having the continuous hollow portion 27 can be reliably molded by the eccentric upsetting method.
Further, when the hollow portion 27 is used as an oil hole for lubrication, a post-process (drilling or the like) is not necessary, and the cost can be reduced.
Moreover, since many hollow parts 27 are formed inside the crankshaft 5, a lighter crankshaft than normal forging can be formed.

  In other words, at least one supporting member 23 having a through hole 23a made of a high hardness material is inserted into a portion to be installed (arm portion 9 molding portion), and at least one of the through holes 23a is opened. In addition, the hollow material 22 in which the support member 23 is inserted is formed by the eccentric upsetting method so that a gap 24 for releasing stress is provided between the hollow material 22 and the support member 23. With the configuration, it is possible to leave the through hole 23a, which is a portion that is not easily crushed, in order to use it as an oil hole.

  Next, another embodiment of a method for forming a crankshaft using a hollow material provided with blocking prevention means will be described.

  As shown in FIG. 5, the hollow material 22 is a round bar-like member, and has a hollow portion 27 having a round shape in cross section, which penetrates continuously from one end to the other end.

  In the hollow material 22, the stress acting on the hollow material 22 during upsetting is reduced (released), so that the hollow portion 27 located inside the arm portions 9 and 9 is crushed and closed by the stress. A blockage prevention means for preventing this is provided in advance.

As shown in FIG. 8, the blocking prevention means is provided with a through hole 28 that is cast into the hollow portion 27, cooled and solidified, and is crushed and closed by the stress acting on the hollow material 22 during the upsetting. The low-melting-point alloy 29 is obtained, and after the upsetting, the low-melting-point alloy 29 is heated and melted and discharged from the hollow portion 27.
Examples of the low melting point alloy include brazing, solder, and tin.

  Next, a forming method in which the eccentric upsetting is performed by the above-described forming method of the crankshaft using the hollow material 22 in which the low melting point alloy 29 having the through hole 28 in the hollow portion 27 is provided as a blocking prevention means. Will be described with reference to FIG.

  In the setting step (molding initial state), the hollow material 22 is set in the molding apparatus 1 as shown in FIG. In this state, the hollow material 22 has a cross-sectional view in which the low melting point alloy 29 is covered along the inner wall surface of the hollow material 22 and has a through hole 28 in the center (FIG. 8B). ).

  Subsequently, in the eccentric upsetting step S20, as shown in FIG. 9 (b), the compressive force due to the upsetting and the tensile force of the dispersed surface act on the hollow material 22 as stress, intentionally. The through hole 28 which is a hole to be crushed starts to be crushed (FIG. 10B).

  Subsequently, in the eccentric installation completion step S30, as shown in FIG. 9 (c), the through-hole 28 is completely formed because the compression force by the installation and the tensile force of the dispersed surface act as stresses. It is crushed and closed (see the dotted line arrow in FIG. 10C). In this way, the stress can be reduced (stress can be released) by crushing the through hole 28 during upsetting. Then, after upsetting, the molded crankshaft 5 is heated at a predetermined temperature, so that the low melting point alloy 29 in the hollow portion 27 is melted and discharged from the hollow portion 27 (FIG. 9D). ). As a result, a continuous hollow portion 27 is formed in the crankshaft 5.

As described above, the blocking prevention means is provided with the through hole 28 which is cast into the hollow portion 27 and cooled and solidified, and is crushed and closed by the stress acting on the hollow material 22 during the upsetting. After the upsetting, the low melting point alloy 29 is heated and melted and discharged from the hollow portion 27, so that the internal hollow portion 27 is formed by the through hole 28 provided in the low melting point alloy 29. Reducing the force dispersed in the mold ensures the formability, and melts and discharges the low melting point alloy 29 remaining in the molded crankshaft 5, thereby reducing the cost even when the molding load is high. The crankshaft 5 having the continuous hollow portion 27 can be cold forged by an eccentric upsetting method.
Further, when the hollow portion 27 is used as an oil hole for lubrication, a post-process (drilling or the like) is not necessary, and the cost can be reduced.
Moreover, since the hollow part 27 is formed in the inside of the crankshaft 5, many crankshafts lighter than normal forging can be formed.

  In this way, by applying the present invention, a crankshaft having continuous hollow holes can be manufactured as shown in FIG. 11. Therefore, concentrated oil supply to the crankshaft becomes possible using the hollow holes. The mechanism and the block structure itself can be simplified.

It is a figure which shows the shaping | molding method of the crankshaft which concerns on one Embodiment of this invention, (a) is a typical side sectional view which shows a setting process, (b) is a typical side sectional view which shows an eccentric upsetting process, (c) ) Is a schematic side cross-sectional view showing an eccentric installation completion process. The figure which similarly shows the shaping | molding flow of a crankshaft. It is a figure which shows a hollow raw material, (a) is a front view, (b) is AA arrow sectional drawing in (a). It is a figure which shows the cross sectional view of the hollow raw material in each process shown in FIG. 1, (a) is A1-A1 arrow sectional drawing in Fig.1 (a), (b) is A2-A2 arrow in FIG.1 (b). FIG. 3C is a sectional view taken along the line A3-A3 in FIG. It is a figure which shows another Example of a hollow raw material, (a) is front sectional drawing, (b) is the AA arrow sectional drawing in (a). It is a figure which shows another Example of the shaping | molding method of a crankshaft, (a) is a typical side surface sectional view which shows a setting process, (b) is a schematic side surface sectional view which shows an eccentric installation process, (c) is eccentricity The schematic side surface sectional drawing which shows an upsetting completion process. It is a figure which shows the cross sectional view of the hollow raw material in FIG. 6, (a) is A1-A1 arrow sectional drawing in FIG.6 (a), (b) is A2-A2 arrow sectional drawing in FIG.6 (b), (C) is A3-A3 arrow sectional drawing in FIG.6 (c). It is a figure which shows another Example of a hollow raw material, (a) is front sectional drawing, (b) is the AA arrow sectional drawing in (a). It is a figure which shows another Example of the shaping | molding method of a crankshaft, (a) is a typical side surface sectional view which shows a setting process, (b) is a schematic side surface sectional view which shows an eccentric installation process, (c) is eccentricity The schematic side surface sectional view which shows an upsetting completion process, (d) is a schematic side surface sectional view which shows the time of discharge | emission of a low melting-point alloy. It is a figure which shows the cross sectional view of the hollow raw material in FIG. 9, (a) is A1-A1 arrow sectional drawing in FIG.9 (a), (b) is A2-A2 arrow sectional drawing in FIG.9 (b), (C) is A3-A3 arrow sectional drawing in FIG.9 (c). Explanatory drawing which shows the crankshaft shape | molded with the shaping | molding method of the crankshaft which concerns on this invention. It is a figure which shows the shaping | molding method (formation mechanism) of the conventional crankshaft, (a) is a typical side sectional view which shows a setting process, (b) is a typical side sectional view which shows an eccentric upsetting process, (c) is The schematic side surface sectional drawing which shows an eccentric upsetting completion process. The figure which shows the crankshaft shape | molded by the conventional method. The figure explaining the subject of the crankshaft shape | molded by the conventional method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Molding apparatus 2.12 / 22 Hollow material 3 Upper mold | type 4 Lower mold | type 5 Crankshaft 6 Floating jig | tool 7.17.27 Hollow part 9 Arm part 13 1st groove part 14 2nd groove part 23 Support member 24 Crevice 28 Through-hole 29 Low melting point alloy

Claims (4)

A method of forming a crankshaft by performing eccentric upsetting by cold forging using a hollow material having a continuous hollow portion,
A set step of holding the middle part of the hollow material with an eccentric jig, and setting both ends in the central axis direction of the hollow material on the upper and lower molds of the molding device,
While lowering the upper mold of the molding apparatus, the eccentric jig is moved in the vertical direction with respect to the central axis direction of the hollow material, whereby the middle part of the hollow material held by the eccentric jig is An eccentric upsetting process in which the hollow material is eccentric with respect to the central axis to perform upsetting;
Eccentricity in which the crankshaft arm is continuously formed on both ends of the hollow portion held by the eccentric jig by lowering the upper mold to a predetermined position and performing upsetting. An upsetting completion process,
As the hollow material, by reducing the stress acting on the hollow material during the upsetting in the hollow portion, the hollow portion located inside the arm portion is crushed and closed by the stress. A method for forming a crankshaft having a continuous hollow portion, characterized in that a block provided with a blocking prevention means for preventing the above is used. The blocking prevention means includes
A plurality of groove portions provided on the inner wall surface of the hollow portion substantially in parallel with the central axis direction of the hollow material, and the plurality of groove portions against the direction of stress acting on the hollow material during the upsetting 2. The method for forming a crankshaft having a continuous hollow portion according to claim 1, comprising: a groove portion provided in a direction that is intentionally easily crushed and a groove portion provided in a direction that is not easily crushed. The blocking prevention means includes
A support member provided with a through-hole penetrating in the same direction as the central axis direction of the hollow part, having a higher hardness than the hollow material, and supported at a predetermined position of the hollow part;
A gap formed between an outer peripheral surface of the support member and an inner wall surface of the hollow portion and crushed and closed by stress acting on the hollow material during the upsetting. A method for forming a crankshaft having a continuous hollow portion according to Item 1. The blocking prevention means includes
It is a low melting point alloy that is cast into the hollow part, cooled and solidified, and provided with a through-hole that is crushed and closed by stress acting on the hollow material during the upsetting, after the upsetting, The method for forming a crankshaft having a continuous hollow portion according to claim 1, wherein the low-melting-point alloy is heated and melted and discharged from the hollow portion.