JP5883644B2 - Manufacturing method of connecting rod - Google Patents

Description

The present invention relates to a method of manufacturing a connecting rod which is adapted to form a larger end portion is divided by cation-breaking method to cap site and the rod body site large end of the connecting rod.

  The engine has a connecting rod for converting the linear reciprocating motion of the piston into the rotational motion of the crankshaft. The connecting rod has a rod main body portion provided with a small end portion connected to a piston at one end portion, and a large end portion connected to a crankshaft is provided at the other end portion of the rod main body portion. A through hole in which a piston pin is mounted is provided in the small end portion, and a through hole in which the crank shaft is mounted is provided in the large end portion.

  A type in which the large end portion of the connecting rod is formed by a rod main body portion and a cap portion, and the cap portion is attached to the rod main body portion by a bolt is an assembly type connecting rod. As a manufacturing method of this assembly type connecting rod, as described in Patent Document 1, there is a crack splitting method in which a large end portion formed integrally in advance is broken and divided into a cap portion and a rod body portion. is there.

JP 2005-305646 A

  In order to manufacture a connecting rod by this method, the small end and the large end are integrally formed at the end of the rod body by forging or casting, and through holes are formed in the small end and the large end, respectively. The The integrally formed large end has leg portions on both sides of the through-hole and closed portions connected to these leg portions, and before the large end portion is divided into a cap portion and a rod body portion. In the leg portion, a bolt mounting hole is machined in advance.

  When dividing the large end formed integrally with the rod body, notches or notches that face each other through the central axis are formed in advance on the inner peripheral surface of the through hole in which the crankshaft is mounted, The split jig splits the large end portion into the cap portion and the rod main body portion with the cut portion as the break start position. An uneven portion, that is, a knurled portion, is formed on the fracture surface of the cap portion and the rod main body portion which are broken and divided by such a crack splitting method, that is, the fracture method, and the cap portion is assembled to the rod main body portion. When the connecting rod is attached to the crankshaft, the fractured surface having the concavo-convex portion is engaged and the surface deviation can be prevented. The fracture surface may be formed on a right-angle plane perpendicular to the central axis of the connecting rod or on an inclined plane inclined with respect to the central axis.

  When the large end is divided into a rod body part and a cap part by such a crack splitting method, if the unevenness of the fracture surface becomes rough, chipping and cracking are likely to occur on the fracture surface, and the manufacturing yield of the connecting rod is increased. Will be reduced. Therefore, as a result of searching for the cause of quality defects such as chipping on the fracture surface, increasing the crack speed at the fracture surface starting from the notch and reducing the change in crack growth rate will result in poor quality at the fracture surface. It was found that can be prevented.

  An object of the present invention is to prevent the occurrence of poor quality at the fracture surface between the cap part and the rod main body part and to manufacture a connecting rod with a high yield.

The method for manufacturing a connecting rod according to the present invention includes a large end portion having a leg portion on both sides of the through hole and a closed portion connected to the leg portion by a through hole formed in the end portion of the connecting rod. A connecting rod that is divided into a rod main body portion by a claw splitting method, and an outer end portion of the leg portion on a reference line in a direction crossing a central axis of a bolt mounting hole formed in both the leg portions The wall thickness of the end portion of the leg portion is equal to or less than the side wall thickness of both side portions of the leg portion on a parallel axis perpendicular to the central axis of the bolt mounting hole and parallel to the central axis of the through hole. in position, said comprising the steps of: forming a bolt mounting hole, a step of forming a notch extending in the axial direction of the through hole said through hole mutually to face the inner peripheral surface of the respective said leg Circle on the outer circumference of Jo portion is formed, the mounting hole pitch between the center axis of the bolt mounting holes are set to a same curvature pitch between the center of curvature axis of the arcuate portion, or is set larger than the curvature pitch, When dividing the leg portion into the cap portion and the rod body portion with the notch as a break start position, the change in the propagation speed of the breakage crack that advances from the both side portions to the outer end portion of the leg portion is reduced. It is characterized by doing.

The method for manufacturing a connecting rod according to the present invention includes a large end portion having a leg portion on both sides of the through hole and a closed portion connected to the leg portion by a through hole formed in the end portion of the connecting rod. A connecting rod that is divided into a rod main body portion by a claw splitting method, and an outer end portion of the leg portion on a reference line in a direction crossing a central axis of a bolt mounting hole formed in both the leg portions The wall thickness of the end portion of the leg portion is equal to or less than the side wall thickness of both side portions of the leg portion on a parallel axis perpendicular to the central axis of the bolt mounting hole and parallel to the central axis of the through hole. Forming the bolt mounting hole at a position, and forming a notch extending in the axial direction of the through hole so as to face each other on the inner peripheral surface of the through hole. Between center axes Hole pitch, the one is set to be the same as the curvature of the pitch between the curvature center axis of the virtual contact with the outer peripheral surface of the leg portion, or is set larger than the curvature pitch, the leg portion of the notch as the breaking starting position When dividing into the cap part and the rod body part, a change in the propagation speed of the fracture crack that advances from the both side parts to the outer end part of the leg part is reduced.

  The present invention relates to a connecting rod formed by dividing a large end into a rod main body part and a cap part by a claw splitting method, and a bolt mounting hole formed in a leg portion of the large end in advance before performing the cut part splitting method. By setting this position, it is possible to increase the cracking speed of the fractured surface when cracking the large end and to reduce the change in crack propagation speed. Thereby, the generation | occurrence | production of the chip | tip and a crack in a torn surface can be prevented, and the manufacturing yield of a connecting rod can be improved significantly.

(A) is a partially cutaway front view showing a connecting rod in a forged state, and (B) is a state in which a bolt mounting hole is formed in a leg portion of a large end shown in (A). It is a partially notched front view which shows a connecting rod. (A) is a partially cutaway front view of the connecting rod in a state where a cut is formed on the inner peripheral surface of the through hole formed at the large end, and (B) is a diagram in which a split jig is inserted into the through hole. FIG. 5C is a partially cutaway front view of the connecting rod in a state where the connecting rod is partially cut out, and (C) is a partially cutaway front view of the connecting rod in a state where the large end is divided into a cap portion and a rod body portion. It is a top view which shows the progress condition of the fracture crack of the torn surface in FIG.2 (C). It is a top view which shows the torn surface in the modification of the large end part of a connecting rod. It is a top view which shows the torn surface in the other modification of the large end part of a connecting rod. It is a top view which shows the torn surface in the other modification of the large end part of a connecting rod.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. As shown in FIG. 1, the connecting rod 10 has a rod body 13 having a small end 11 provided at one end and a large end 12 provided at the other end. A through hole 14 is formed in the small end portion 11. A piston pin (not shown) passes through the through hole 14, and the connecting rod 10 is connected to the piston by the piston pin. A through hole 15 having a diameter larger than that of the through hole 14 is formed in the large end portion 12, and a crank pin of a crankshaft (not shown) passes through the through hole 15, and the connecting rod 10 is connected to the crankshaft.

  FIG. 1A shows a state in which the connecting rod 10 is manufactured by forging. In the forged state, as shown in the figure, the large end portion 12 is set to be larger in width than the small end portion 11 and the rod body 13, and both sides of the through hole 15 are leg portions 16a and 16b. A closing portion 17 that connects these leg portions 16a and 16b is integrated with each leg portion 16a and 16b.

FIG. 1B shows a state where bolt mounting holes 18a and 18b are formed in the leg portions 16a and 16b of the large end portion 12 by machining. Each bolt mounting holes 18a, 18b, the center axis _{O 1} and the through hole 14 of the center axis _{O 2} and is parallel to the direction of the rod center line L extending to intersect the legs 16a of the through hole 15, the 16b It penetrates.

When the large end portion 12 is divided, the notches having V-shaped cross sections, that is, the notches 21a and 21b are opposed to each other on the inner peripheral surface of the through-hole 15 in advance as shown in FIG. Laser processed. Each notch 21a, 21b are extended along the axial direction of the direction, that the through-hole 15 along the center axis _{O 1} of the through hole 15, both notches 21a, 21b are rod centerline with including the center axis _{O 1} L Are formed in a right-angle plane H that is perpendicular to the direction H.

  FIG. 2B shows a state where the connecting rod 10 is attached to the dividing jig 22, and the dividing jig 22 is inserted into the through hole 15. Each of the split jigs 22 as a claw splitting jig has a substantially semicircular fixing bracket 22a and a moving bracket 22b, and moves the moving bracket 22b in a direction away from the fixing bracket 22a. FIG. 2C shows a state in which the large end portion 12 is divided into a rod main body portion 12a and a cap portion 12b by a claw splitting method. The leg portions 16a and 16b are separated into the rod main body portion 12a and the cap portion 12b with the surface including the bolt mounting holes 18a and 18b as a fracture surface by the claw splitting method. Each part has a part of leg parts 16 a and 16 b, and a cap part 12 b is formed by a part of the leg part and the blocking part 17. Thus, after the connecting rod 10 is manufactured to the shape shown in FIG. 1 (A) by forging, a drilling step for forming bolt mounting holes 18a and 18b by machining as shown in FIG. 1 (B). 2A, and the cut forming process using a laser as shown in FIG. 2A, the large end 12 is divided into a rod main body portion 12a and a cap portion 12b by a cut and cut method shown in FIG. 2B. Is done.

  On both fractured surfaces, fine irregularities, i.e., jagged portions, are formed by the cracking method, so that when the large end portion 12 is attached to the crankshaft, the jagged portions of both fractured surfaces are engaged. It is possible to prevent the rod main body portion 12a and the cap portion 12b from being displaced and to position both portions accurately.

  FIG. 3 is a plan view showing a fracture surface 23 of the cap portion 12b. The shape of the fracture surface 23 is the same for the rod main body portion 12a.

As shown in FIG. 3, each leg portion 16a, the bolt mounting holes 18a formed in 16b, and the inner diameter of 18b and _{R 1,} each of the bolt mounting holes 18a, the direction of the imaginary line crossing the central axis O of 18b the If the reference line S, both of the bolt mounting holes 18a on the reference line S, the distance between the center axis O mutual 18b becomes mounting hole pitch P _1. The thickness on the reference line S at the outer end portions 24a and 24b of the leg portions 16a and 16b is defined as an end thickness E, which is orthogonal to the central axis O of the bolt mounting holes 18a and 18b and the central axis O _{1 of the} through hole 15. If the thickness of the leg portions 16a, 16b on the parallel axis J parallel to the side wall thickness F is the side wall thickness F, the end wall thickness E is set equal to or thinner than the side wall thickness F. Yes. Thus, each bolt attachment hole 18a, 18b is formed at a position where the end thickness E is equal to or thinner than the side thickness F.

  In FIG. 3, the arrow attached to the fracture surface 23 indicates a fracture crack when the large end portion 12 is divided into the rod body portion 12a and the cap portion 12b by the split jig 22, as shown in FIG. 2 (B). Shows progress. The cracks reach the end thickness E portion while crossing the side thickness F portion along the bolt mounting holes 18a and 18b, as indicated by arrows with the notches 21a and 21b as the break start positions. In the portion of the end thickness E, the fracture crack that has passed through both side thicknesses F collides with this. When both fractured cracks collide at the end thickness E portion, the crack growth rate at the end thickness E portion becomes slower than the other portions. If the crack propagation speed of this portion becomes slower than the upstream crack propagation speed, chipping or cracking occurs at the end thickness E of the leg portions 16a, 16b, and the connecting rod 10 is manufactured. The yield will be reduced.

  As shown in the drawing, when the bolt mounting holes 18a and 18b are formed at positions where the end thickness E becomes thinner than the side thickness F (E <F), the change in the crack growth rate at the end thickness E is changed. Can be set to a value close to the change in the crack growth rate in the upstream portion, and the change in the crack growth rate in the entire fracture surface 23 can be reduced. Thereby, generation | occurrence | production of the chip | tip and a crack in the part of the edge part thickness E among the torn surfaces 23 and its vicinity was prevented, and the manufacture yield of the connecting rod 10 was able to be improved. According to the experiment, even if the thickness dimension of the end thickness E part and the thickness dimension of the side thickness F part are the same (E = F), the occurrence of chipping or cracking in the end thickness E part is observed. Although it was possible to prevent the occurrence of cracks and cracks in the fracture surface 23 when the bolt mounting holes 18a and 18b are formed at a position where the dimension of the end thickness E is larger than the dimension of the side thickness F. It was done. Thus, when the end thickness E is the same as the side thickness F or thinner than the side thickness F, a change in the breaking crack propagation rate in the end thickness E portion of the legs 16a, 16b. Thus, it was confirmed that there was no quality defect such as chipping or cracking in the fracture surface 23.

Of the outer peripheral surfaces of the legs 16a and 16b shown in FIG. 3, an arcuate surface 25 is formed on the side of the leg, a flat surface 26 is formed on the end, and the sides of the legs 16a and 16b are A flat surface 27 is formed. Assuming that the virtual radius inscribed in the arc-shaped surface 25, that is, the radius of curvature of the arc-shaped surface 25 is T, the dimension between the two flat surfaces 27 is set larger than the radius of curvature T of the arc-shaped surface 25. A concave R surface, that is, an arcuate surface 28 is formed between the arcuate surface 25 and the arcuate surface 25. The curvature center axis of the curvature radius T of the arcuate surface 25 is Q, and the distance between both the curvature center axis Q mutual and curvature pitch P _2, the curvature pitch P ₂ set to a value smaller than the mounting hole pitch P ₁ Has been. That is, the mounting hole pitch _{P 1} is set to a value larger than the curvature pitch _{P 2 (P 1> P 2} ). Thus, when the position of each bolt attachment hole 18a, 18 is set so that both pitches may be in a magnitude relationship, from the side wall thickness F portion to the end wall thickness E portion of the fracture surface 23. Even when the crack progresses toward the end, it can be seen that the speed change of the crack progress can be reduced, and the occurrence of cracks and cracks in the region between the side wall thickness F and the end wall thickness E can be reduced. did. Even if the mounting hole pitch P ₁ and the curvature pitch P ₂ are set to substantially the same value (P ₁ = P ₂ ), the occurrence of chipping and cracking can be reduced in the same region, but the curvature is larger than the mounting pitch P _1. increasing the pitch P _2, chipping and cracking in the region was observed. The reason for this is that if the thickness in the region between the side wall thickness F and the end wall thickness E is the same or gradually decreased toward the end wall thickness E, the change in crack growth rate is reduced. It is thought that it is possible. When the generation of chips and cracks in the entire fracture surface 23 is reduced, the manufacturing yield of the connecting rod 10 can be improved.

  4-6 is a top view which shows the torn surface in the modification of the large end part 12 of the connecting rod 10, respectively. In these drawings, parts that are the same as those in FIG. 3 are given the same reference numerals.

  The leg portions 16a and 16b of the large end portion 12 shown in FIGS. 4 to 6 have bolt mounting holes 18a and 18b at positions where the end thickness E becomes thinner than the side thickness F (E <F). Is formed. Therefore, similarly to the case shown in FIG. 3, the crack growth rate in the end thickness E portion can be set to a value close to the crack growth rate in the upstream portion, and the entire fracture surface 23 can be set. It is possible to reduce the change in the speed of crack propagation in. Thereby, the generation | occurrence | production of the chip | tip and the crack in the part of the edge part thickness E can be prevented. Even if the thickness dimension of the end thickness E portion is the same as the thickness dimension of the side thickness F portion (E = F), the crack growth rate in the end thickness E portion is changed as described above. It can be set to a value close to the crack growth rate in the upstream portion.

  In the leg portion 16a16b of the large end portion 12 shown in FIG. 4, the outer peripheral surface of the outer end portion 24a is a substantially semicircular arcuate surface 25. The dimension between both flat surfaces 27 is set larger than the radius of the arcuate surface 25, and a concave arcuate surface 28 is formed between the flat surface 27 and the arcuate surface 25.

Legs 16a of the large end portion 12 shown in FIG. 5, 16b is an outer end portion 24a is a flat surface 26 as in the case shown in FIG. 3, the direction of the length along the center axis O ₁ Figure 3 is set longer than the flat surface 26 in FIG. A flat surface 31 substantially perpendicular to the flat surface 26 is formed between both the flat surfaces 27 and the flat surface 26 substantially perpendicular thereto, and both the flat surfaces 26 and 31 are convex. Are connected via a circular arc surface 32.

  The cross-sectional shapes of the leg portions 16a and 16b of the large end portion 12 shown in FIG. 6 are almost the same as those shown in FIG. 5, but the dimension between the flat surfaces 31 is larger than that shown in FIG. Is set. A projection 33 is provided at the center of the flat surface 26 formed at the outer end, and the end thickness E is larger than the end thickness E shown in FIG.

In big end 12 shown in Figures 4-6, a case where the leg portions 16a, the curvature pitch P ₂ between the centers of curvature axis Q mutual virtual circle G radius of curvature T inscribing the outer peripheral surface of 16b was described above It is set to a value smaller than the similarly mounting hole pitch P _1. That is, the mounting hole pitch _{P 1} is set to a value larger than the curvature pitch _{P 2 (P 1> P 2} ). As described above, when the positions of the respective bolt mounting holes 18a and 18 and the shapes of the outer peripheral surfaces of the leg portions 16a and 16b are set so that both pitches are large and small, the side wall thickness F of the fracture surface 23 is set. Even when the crack progresses from the portion toward the end thickness E, it is possible to reduce the occurrence of cracks and cracks in the region between the side thickness F portion and the end thickness E. Even if the mounting hole pitch P ₁ and the curvature pitch P ₂ are set to substantially the same value (P ₁ = P ₂ ), the occurrence of chips and cracks in the same region can be reduced.

As described above, the bolt mounting holes 18a and 18b are formed in the leg portions 16a and 16b of the large end 12 of the connecting rod 10 manufactured by forging, and the notches 21a and 18a are formed in the inner peripheral surfaces of the bolt mounting holes 18a and 18b. After forming 21b, the connecting rod 10 is manufactured by dividing the large end portion 12 into the rod main body portion 12a and the cap portion 12b by the cracking method. When manufacturing the connecting rod 10 by such a crack splitting method, the positions of the bolt mounting holes 18a and 18b are set in advance so that the thickness relationship between the end thickness E and the side thickness F satisfies E ≦ F. Then, generation | occurrence | production of the chip | tip and the crack in the part of the edge part thickness E can be prevented. Furthermore, when the relationship between the mounting hole pitch P ₁ and the curvature pitch P ₂ is set to P ₁ ≧ P ₂ , a crack is generated from the side wall thickness F portion to the end wall thickness E portion of the fracture surface 23. Also when progressing, the generation | occurrence | production of the chip | tip and the crack in the area | region between the part of the side part thickness F and the edge part thickness E can be reduced.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention. For example, in the connecting rod 10 shown in the figure, the fracture surface 23 is formed on a right-angle plane H perpendicular to the rod center line L as shown in FIG. You may make it form in the surface inclined with respect to the centerline L. FIG.

DESCRIPTION OF SYMBOLS 10 Connecting rod 11 Small end part 12 Large end part 12a Rod main-body part 12b Cap part 13 Rod main body 14,15 Through-hole 16a, 16b Leg part 17 Closure part 18a, 18b Bolt attachment hole 21a, 21b Cut 23 Broken surface 24a Outer end Part E End thickness F Side thickness G Virtual circle L Rod center line O ₁ Center axis P ₁ Mounting hole pitch P ₂ Curvature pitch Q Curvature center axis S Reference line

Claims (2)

A large end portion having a leg portion on both sides of the through hole and a closed portion connected to the leg portion by a through hole formed in the end portion of the connecting rod is divided into a cap portion and a rod main body portion by a cracking method. A method of manufacturing a connecting rod to be divided,
An end wall thickness of an outer end portion of the leg portion on a reference line in a direction crossing the central axis of the bolt mounting hole formed in both the leg portions is orthogonal to the central axis of the bolt mounting hole and the through hole Forming the bolt mounting hole at a position that is equal to or thinner than the side wall thickness of both sides of the leg on a parallel axis parallel to the central axis of
Forming a notch extending in the axial direction of the through hole so as to face each other on the inner peripheral surface of the through hole, and
Arc-shaped portions are formed on the outer peripheral surfaces of the respective leg portions, and the mounting hole pitch between the central axes of the bolt mounting holes is set to be the same as the curvature pitch between the curvature central axes of the arc-shaped portions, Or larger than the curvature pitch,
When dividing the leg portion into the cap portion and the rod body portion with the notch as a break start position, the change in the propagation speed of the breakage crack that advances from the both side portions to the outer end portion of the leg portion is reduced. A method of manufacturing a connecting rod, comprising: A large end portion having a leg portion on both sides of the through hole and a closed portion connected to the leg portion by a through hole formed in the end portion of the connecting rod is divided into a cap portion and a rod main body portion by a cracking method. A method of manufacturing a connecting rod to be divided,
An end wall thickness of an outer end portion of the leg portion on a reference line in a direction crossing the central axis of the bolt mounting hole formed in both the leg portions is orthogonal to the central axis of the bolt mounting hole and the through hole Forming the bolt mounting hole at a position that is equal to or thinner than the side wall thickness of both sides of the leg on a parallel axis parallel to the central axis of
Forming a notch extending in the axial direction of the through hole so as to face each other on the inner peripheral surface of the through hole, and
The mounting hole pitch between the central axes of the bolt mounting holes is set to be the same as the curvature pitch between the virtual central axes of curvature in contact with the outer peripheral surface of the leg or set larger than the curvature pitch,
When dividing the leg portion into the cap portion and the rod body portion with the notch as a break start position, the change in the propagation speed of the breakage crack that advances from the both side portions to the outer end portion of the leg portion is reduced. A method of manufacturing a connecting rod, comprising:

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