JP2011099473A - Method of manufacturing connecting rod - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a connecting rod capable of surely splitting a large end part in a predetermined split surface and capable of preventing deterioration of the service life of a tool in finish machining after splitting the large end part and deterioration of mechanical strength of the connecting rod. <P>SOLUTION: This method of manufacturing a connecting rod includes: a process S1 for forming a preformed body integrally including a large end part having a first through-hole, a small end part having a second through-hole smaller in diameter than the first through-hole, and a shaft part connecting the large end part and the small end part to each other; a process S3 for forming a notch in a part of the large end part, which is planned to be split, by laser machining; a process S4 for splitting the large end part by applying a breaking load to the part planned to be split; a process S5 for connecting the split large end parts with a fastening member; a process S6 for eliminating a part hardened by influences of the heat in laser machining by roughly finishing the first through-hole into a perfect circle; and a process S7 for finally finishing the first through-hole into a perfect circle. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method of manufacturing a connecting rod constituted by connecting a broken rod body and a cap part.

  The connecting rod has a function of connecting the piston and the crankshaft of the internal combustion engine and transmitting the reciprocating motion of the piston to the crankshaft.

  The connecting rod has a first through hole at one free end and a second through hole having a smaller diameter than the first through hole at the other free end. In general, one free end having the first through hole is called a large end, and the other free end having the second through hole is called a small end. The connecting rod includes a large end portion, a small end portion, and a shaft portion that connects the large end portion and the small end portion.

  The large end portion of the connecting rod can be divided on a plane (hereinafter referred to as “divided surface”) that passes through the approximate center of the first through hole and is substantially orthogonal to the longitudinal axis of the shaft portion. Accordingly, the connecting rod can be divided into a rod body in which a small end portion, a shaft portion, and a half portion on the shaft portion side of the large end portion are integrally formed, and a cap portion that is a remaining portion of the large end portion. Each divided part is integrally coupled by a fastening member such as a bolt.

  The connecting rod configured as described above is connected to the crankshaft by a crankpin inserted into the first through hole, and is connected to the piston by a piston pin inserted into the second through hole. The crankpin is inserted into the first through hole so as to be sandwiched between the rod body and the cap portion.

  The manufacturing method of the fracture split type connecting rod includes, for example, a step of forming a preform formed integrally with a large end, a small end, and a shaft, and a notch is formed at the large end of the preform. A step of breaking the preform from the notch to divide the preform into a rod body and a cap portion, and a step of connecting the rod body and the cap portion with a fastening member. .

  By the way, in the step of dividing the preform into the rod main body and the cap portion, the large end portion is not necessarily broken starting from the notch, and may break starting from a portion other than the notch. is there. The preform that has been broken starting from a portion other than the notch is left with a notch, so there is a concern that the preform may break from the notch when it is attached to an internal combustion engine. Therefore, such a preform cannot be used as a connecting rod, and the production yield is reduced.

  Thus, a connecting rod manufacturing method is known in which a martensite structure is formed in the vicinity of the bottom of the notch to easily cause brittle fracture starting from the notch (see, for example, Patent Document 1).

JP 2005-308189 A

  In the manufacturing method of the fracture split type connecting rod, after the step of dividing the preform into the rod main body and the cap portion, finishing is performed to ensure the roundness of the inner diameter of the first through hole.

  The cutting tool in the finishing process cuts the martensite structure formed in the vicinity of the bottom of the notch. This part is very hard as compared with other parts not transformed into the martensite structure (austenite structure part), and the life of the tool is significantly consumed.

  In addition, when the martensite structure formed for fracture division remains in the finished product of the connecting rod, the mechanical strength of the connecting rod may be reduced. Furthermore, even when the remaining martensite structure is approaching the bolt hole of the fastening member, the mechanical strength of the connecting rod may be reduced.

  Accordingly, the present invention provides a method for manufacturing a connecting rod that can reliably rupture and break the large end portion with a predetermined dividing surface and does not reduce the tool life and the mechanical strength of the connecting rod in finishing after the rupture division. Propose.

  In order to solve the above problems, a manufacturing method of a connecting rod according to the present invention includes a large end portion having a first through hole, and a small end portion having a second through hole having a smaller diameter than the first through hole, A step of forming a preform integrally including a shaft portion that connects the large end portion and the small end portion together, and a step of forming a notch by laser processing in a portion to be divided of the large end portion A step of dividing the large end portion by applying a breaking load to the part to be divided, a step of connecting the divided large end portion with a fastening member, and rough finishing the first through hole to a perfect circle The method includes a step of removing the heat-affected hardened portion during the laser processing and a step of final finishing the first through hole into a perfect circle.

  According to the present invention, a method of manufacturing a connecting rod that can reliably rupture and split a large end portion with a predetermined split surface and does not reduce the tool life and the mechanical strength of the connecting rod in finishing after the rupture split. Can provide.

The front view which showed roughly an example of the connecting rod manufactured by the manufacturing method of the connecting rod which concerns on embodiment of this invention. The flowchart which showed the manufacturing method of the connecting rod which concerns on embodiment of this invention. The figure which showed roughly the rough material formation process of the manufacturing method of the connecting rod which concerns on embodiment of this invention. The figure which showed roughly the bolt hole processing process of the manufacturing method of the connecting rod which concerns on embodiment of this invention. The figure which showed roughly the large end part notch process of the manufacturing method of the connecting rod which concerns on embodiment of this invention. The figure which showed schematically the fracture | rupture division | segmentation process of the manufacturing method of the connecting rod which concerns on embodiment of this invention. The figure which showed schematically the fastening process of the manufacturing method of the connecting rod which concerns on embodiment of this invention. The figure which showed roughly the big end part perfect circle rough finishing process of the manufacturing method of the connecting rod which concerns on embodiment of this invention. The figure which showed schematically the big end perfect circle final finishing process of the manufacturing method of the connecting rod which concerns on embodiment of this invention. The figure which showed schematically the process of the process of the big end part in the manufacturing method of the connecting rod which concerns on embodiment of this invention.

  Hereinafter, an embodiment of a method for manufacturing a connecting rod according to the present invention will be described with reference to FIGS.

  FIG. 1 is a front view schematically showing an example of a connecting rod manufactured by a method for manufacturing a connecting rod according to an embodiment of the present invention.

  As shown in FIG. 1, the connecting rod 1 manufactured by the method for manufacturing a connecting rod according to the present embodiment includes a large end 3 having a first through hole 2 and a small diameter compared to the first through hole 2. A small end portion 5 having two through holes 4 and a shaft portion 6 that connects the large end portion 3 and the small end portion 5 to each other are provided.

  The large end portion 3 is divided at a dividing surface S that passes through the approximate center of the first through hole 2 and is substantially orthogonal to the longitudinal axis of the shaft portion 6. The large end 3 includes a first half 3a that is integral with the shaft 6, a second half 3b that forms the first through hole 2 together with the first half 3a, a first half 3a, and a second half. A fastening member 9 for coupling the half 3b. Thereby, the connecting rod 1 includes a rod body 11 in which the small end portion 5, the shaft portion 6, and the first half portion 3 a of the large end portion 3 are integrally formed, and the second half portion 3 b of the large end portion 3. It can be divided into a cap portion 12.

  The fastening member 9 is, for example, a bolt, passes through the through hole 14 formed in the second half 3b, and is fastened to the bolt hole 15 formed in the first half 3a.

  FIG. 2 is a flowchart showing a method of manufacturing a connecting rod according to an embodiment of the present invention.

  3 to 9 are diagrams schematically illustrating a process of a method for manufacturing a connecting rod according to an embodiment of the present invention. FIG. 3 is a diagram schematically showing the rough material forming step S1 in the connecting rod manufacturing method, and FIG. 4 is a diagram schematically showing the bolt hole machining step S2 in the connecting rod manufacturing method. FIG. 5 is a diagram schematically showing the large-end notch processing step S3 in the connecting rod manufacturing method, and FIG. 6 is a diagram schematically showing the fracture splitting step S4 in the connecting rod manufacturing method. FIG. 7 is a diagram schematically showing a fastening step S5 in the connecting rod manufacturing method, and FIG. 8 is a schematic diagram of the large end round rough finishing step S6 in the connecting rod manufacturing method. FIG. 9 is a diagram schematically showing the large end perfect circle final finishing step S7 in the method of manufacturing the connecting rod.

  As shown in FIGS. 2 to 9, the manufacturing method of the connecting rod 1 according to the present embodiment includes a preliminary large end portion 23 having a first preliminary hole 22 and a second through hole having a smaller diameter than the first preliminary hole 22. A rough material forming step S1 for forming a preform 21 integrally including a small end portion 5 having a hole 4 and a shaft portion 6 that connects the preliminary large end portion 23 and the small end portion 5 to each other (FIG. 3). ), A bolt hole machining step S2 (FIG. 4) for forming the spare bolt hole 27 in the spare large end portion 23, and a notch 29 (notch) is formed by laser machining in the planned division portion 28 of the spare large end portion 23. The large end notch processing step S3 (FIG. 5), the breaking division step S4 (FIG. 6) in which a breaking load is applied to the part to be divided 28 to divide the preliminary large end 23, and the divided preliminary large end 23 are fastened. Fastening step S5 (FIG. 7) for connecting with the member 9 and rough finishing the first preliminary hole 22 to a perfect circle Large-end round rough finishing process S6 (FIG. 8) (changed to large-end round rough finishing process) to remove the heat-affected hardening part 31 at the time of laser processing and the first after rough finishing A large end perfect circle final finishing process S7 (FIG. 9) (changed to the large end perfect circle final finishing process) for processing the preliminary hole 22 into a perfect circle and final finishing the first through hole 2 is included. .

  As shown in FIG. 3, the manufacturing method of the connecting rod 1 according to the present embodiment forms the preform 21 by hot forging using alloy steel or carbon steel as a raw material in the rough material forming step S1.

  The preform 21 is completed as the connecting rod 1 by the manufacturing method of the connecting rod 1 according to the present embodiment. Specifically, the preliminary large end portion 23 of the preformed body 21 is processed into the large end portion 3 of the connecting rod 1. The small end portion 5 and the second through hole 4 of the preformed body 21 have been finished (not shown) after the hot forging in the coarse material forming step S1.

  Next, as shown in FIG. 4, the manufacturing method of the connecting rod 1 according to the present embodiment forms the spare bolt hole 27 in the spare large end portion 23 in the bolt hole machining step S2.

  The spare bolt hole 27 constitutes the bolt hole 15 and the through hole 14 of the connecting rod 1 after the spare large end 23 is divided.

  Next, as shown in FIG. 5, in the manufacturing method of the connecting rod 1 according to the present embodiment, in the large end notch processing step S3, the notched portion 29 (notched) is formed by laser processing on the portion 28 to be divided of the preliminary large end 23. ).

  The division | segmentation plan site | part 28 is the division surface S which passes through the approximate center of the 1st preliminary hole 22, and is substantially orthogonal to the longitudinal axis of the axial part 6.

  The notch 29 is formed at a portion where the dividing surface S and the inner peripheral surface 22a of the first preliminary hole 22 intersect. In addition, the notch 29 is formed by laser processing, and in the vicinity of the notch 29, martensitic transformation occurs in the process of cooling after processing, thereby forming a heat-affected hardening portion 31 that is harder than the other portions of the preliminary large end portion 23. .

  Generally, hardness and toughness are in a trade-off relationship, and when one improves, the other decreases. Therefore, the heat-affected hardening part 31 has lower toughness than other parts of the spare large end part 23. For this reason, the heat-affected hardening part 31 is relatively easy to cause brittle fracture as compared with other parts of the spare large end part 23.

  That is, in the manufacturing method of the connecting rod 1 according to the present embodiment, the heat-affected hardening part 31 that easily causes brittle fracture is formed in the vicinity of the notch 29.

  Next, as shown in FIG. 6, the manufacturing method of the connecting rod 1 according to the present embodiment divides the preliminary large end portion 23 by applying a rupture load to the planned division portion 28 in the fracture division step S <b> 4. The breaking load is applied in the longitudinal axis direction of the shaft portion 6.

  Further, when the preliminary large end portion 23 is divided in the fracture division step S4, the inner peripheral surface 22a of the first preliminary hole 22 excluding the planned division portion 28 is not formed on the preform 21 in the coarse material forming step S1. It has a green substrate.

  When a breaking load is applied, the preliminary large end portion 23 causes a brittle fracture starting from the tip of the notch 29 and generates a crack continuous with the notch 29. As the cracks propagate sequentially, the spare large end 23 is finally divided into a first half 23a and a second half 23b.

  Thus, the manufacturing method of the connecting rod 1 according to the present embodiment can reliably divide the preliminary large end portion 23 from the planned division portion 28, and can improve the manufacturing yield of the connecting rod 1.

  In addition, the manufacturing method of the connecting rod which concerns on this embodiment rupture-divides the preliminary | backup large end part 23, without tempering the preforming body 21 before fracture | rupture division | segmentation process S4. This is because when tempering is performed, the toughness of the heat-affected hardened portion 31 is improved and brittle fracture starting from the notch 29 is less likely to occur.

  FIG. 10 is a view schematically showing a process of machining a large end portion in the manufacturing method of the connecting rod according to the embodiment of the present invention.

  As shown in FIGS. 8 to 10, the manufacturing method of the connecting rod according to the present embodiment forms a notch 29 on the inner peripheral surface 22 a of the first preliminary hole 22 in the large end notch machining step S <b> 3, The first preliminary hole 22 is expanded to a range where all the heat-affected hardened portions 31 formed around the notches 29 in the perfect round rough finishing step S6 can be removed to form rough finish holes 33. In the finishing step S7, the rough finishing hole 33 is further enlarged to form the first through hole 2.

  For example, in the manufacturing method of the connecting rod according to the present embodiment, the first preliminary hole 22 is formed with an inner diameter of about 55 mm, and the notch 29 having a depth of about 1 mm in the radial direction is formed on the inner periphery of the first preliminary hole 22. The rough finishing hole 33 having an inner diameter of about 59.96 mm is formed in the rough finishing process after split fracture, and the rough finishing hole 33 is finally finished to form the first through hole 2 having an inner diameter of about 60 mm.

  Since the machining allowance in the rough finishing process is about 2.48 mm in radius and the depth of the notch 29 is about 1 mm, the heat-affected hardening part 31 formed around the notch 29 has a perfect circle at the large end. It is reliably removed in the rough finishing step S6.

  That is, the manufacturing method of the connecting rod according to the present embodiment envelops the heat-affected hardened portion 31 formed around the notch 29 within the range of the machining allowance in the large end perfect circular rough finishing step S6, This does not affect the machining cost in the perfect circle final finishing machining step S7. As a result, the connecting rod manufacturing method can complete the large end portion 3 by processing only the portion that is not affected by heat in the large end perfect circle final finishing step S7. Therefore, the manufacturing method of the connecting rod according to the present embodiment does not reduce the life of the cutting tool in the large end perfect circle final finishing step S7.

  Moreover, according to the manufacturing method of the connecting rod which concerns on this embodiment, since all the heat influence hardening parts 31 formed for the fracture | rupture division | segmentation of the big end part 3 can be removed in the big end perfect circle rough finishing process S6, The mechanical strength of the connecting rod 1 due to the residual heat-affected hardening part 31 does not decrease.

  Furthermore, according to the manufacturing method of the connecting rod according to the present embodiment, since the heat-affected hardening part 31 formed for the fracture split of the large end part 3 can be completely removed in the large end perfect round rough finishing process S6, The mechanical strength around the bolt hole 15 does not decrease.

  Furthermore, according to the manufacturing method of the connecting rod according to the present embodiment, since it is not necessary to process the first preliminary hole 22 before the fracture of the large end portion 3, it is very efficient from the viewpoint of working time and tools used. It is possible to finish the first through hole 2 well.

  Therefore, according to the manufacturing method of the connecting rod 1 according to the present invention, the large end 3 can be reliably broken and split at the predetermined split surface S, the tool life in the finishing process after the split split, and the machine of the connecting rod 1 The mechanical strength is not reduced.

DESCRIPTION OF SYMBOLS 1 Connecting rod 2 1st through-hole 3 Large end part 3a 1st half part 3b 2nd half part 4 2nd through-hole 5 Small end part 6 Shaft part 9 Fastening member 11 Rod main body 12 Cap part 14 Through-hole 15 Bolt hole 22 First preliminary hole 22a Inner peripheral surface 23 Preliminary large end 23a First half 23b Second half 21 Preliminary molded body 27 Preliminary bolt hole 28 Divided part 29 Notch 31 Heat-affected hardening part 33 Rough finishing hole

Claims (3)

A large end portion having a first through hole, a small end portion having a second through hole having a smaller diameter than the first through hole, and a shaft portion connecting the large end portion and the small end portion to each other; A step of forming a preformed body integrally provided with,
A step of forming a notch by laser processing in the planned division portion of the large end,
Applying a rupture load to the planned division portion and dividing the large end portion;
Connecting the divided large end with a fastening member;
Rough finishing the first through hole to a perfect circle and removing the heat-affected hardening part during the laser processing;
And a final finishing process of the first through hole into a perfect circle. 2. The method of manufacturing a connecting rod according to claim 1, wherein when the first through hole is roughly finished into a perfect circle, the heat-affected hardened portion at the time of the laser processing is all removed. 2. The method of manufacturing a connecting rod according to claim 1, wherein, when the large end portion is divided, an inner peripheral surface of the first through hole excluding the portion to be divided has an unprocessed substrate.

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