JP2013209999A - Method of manufacturing connecting rod and semifinished product of connecting rod - Google Patents

Abstract

An object of the present invention is to suppress the occurrence of poor quality at a fracture surface between a main body and a cap.
Since a first notch 23 of an intake side connecting portion 39 is formed deeper than a second notch 24 of an exhaust side connecting portion 40, the first notch 23 is more than the second notch 24 at the time of fracture division. Large stress acts. As a result, as shown in FIG. 8 (b), a crack C is generated in the first notch 23 before the second notch 24 at the time of fracture division, and as shown in FIG. The intake side connecting portion 39 is broken before the portion 40. Subsequently, as shown in FIG. 8 (d), a crack C occurs in the second notch 24, and as shown in FIG. 8 (e), the exhaust side connecting portion 40 is broken. In this way, by changing the shape of the notches 23 and 24, it is possible to determine the breaking order of the intake side connecting portion 39 and the exhaust side connecting portion 40, and to stabilize the quality of the fracture surfaces 20 and 21. Become.
[Selection] Figure 8

Description

  The present invention relates to a connecting rod manufacturing technique in which a large end portion is divided into a main body portion and a cap portion.

  The engine incorporates a connecting rod (hereinafter referred to as a connecting rod) that connects the crankshaft and the piston. In order to mount the crank pin of the crankshaft on the large end portion of the connecting rod, the large end portion of the connecting rod is divided into a main body portion and a cap portion. Generally, a knock pin or the like is provided between the main body portion and the cap portion in order to position the divided main body portion and cap portion. However, positioning the main body portion and the cap portion using the knock pin has been a factor in increasing the cost of the connecting rod. Therefore, a so-called cracking method for breaking and dividing the large end of the connecting rod has been developed (see, for example, Patent Document 1). By this cracking manufacturing method, moderate irregularities can be formed on the fracture surface of the main body portion and the cap portion, so that the main body portion and the cap portion can be positioned with high accuracy without using a knock pin.

JP 2005-188741 A

  By the way, in the cracking manufacturing method in which the large end portion is broken and divided, it is important to suppress the occurrence of defective quality at the fracture surface of the main body and the cap portion, that is, the occurrence of chipping at the fracture surface. However, it has been extremely difficult to control the quality of the fracture surface, which is a cleavage fracture surface.

  An object of the present invention is to suppress the occurrence of poor quality at the fracture surface of the main body portion and the cap portion.

  The connecting rod manufacturing method of the present invention is a connecting rod manufacturing method in which a large end portion is divided into a main body portion and a cap portion, and is formed on the inner peripheral surface of a through hole provided in the large end portion. A notch processing step for forming the first notch and the second notch facing each other, and expanding the through hole in the radial direction, thereby generating a crack from the first notch and one side of the large end portion. A fracture splitting step in which a crack is generated from the second notch and the other side of the large end portion is fractured. The connecting rod manufacturing method of the present invention is characterized in that the first notch and the second notch have different shapes. The connecting rod manufacturing method of the present invention is characterized in that the first cutout is formed deeper than the second cutout.

  A semi-finished product of a connecting rod according to the present invention is a semi-finished product of a connecting rod that is put into a breaking and splitting process in which a large end is expanded in a radial direction and split into a main body and a cap. Formed in the inner peripheral surface of the through hole provided in the first hole, and formed as a starting point of crack generation during fracture division, and formed in the inner peripheral surface opposite to the first notch, during fracture division. It has the 2nd notch used as the crack starting point, The shape of the said 1st notch and the said 2nd notch differs, It is characterized by the above-mentioned. Moreover, the semifinished product of the connecting rod of the present invention is characterized in that the first cutout is formed deeper than the second cutout.

  According to the present invention, a crack is generated from the first notch to break one side of the large end, and then a crack is generated from the second notch to break the other side of the large end. Therefore, it is possible to stabilize the quality of the connecting rod in which the large end portion is broken and divided into the main body portion and the cap portion. Thereby, it becomes possible to suppress generation | occurrence | production of the quality defect in the torn surface of a main-body part and a cap part.

(a) is a front view which shows a connecting rod. (b) is a front view showing the disassembled connecting rod. It is explanatory drawing which shows an example of the manufacturing process of a connecting rod. It is the schematic which shows an example of the fracture | rupture apparatus used in a fracture | rupture division | segmentation process. (a) And (b) is explanatory drawing which shows the process condition of the workpiece | work in a fracture | rupture division | segmentation process. (a) is a front view which shows the workpiece | work thrown into a fracture | rupture division | segmentation process. (b) is sectional drawing which shows a workpiece | work along the AA line of Fig.5 (a). (c) is sectional drawing which shows a workpiece | work along the BB line of Fig.5 (a). (a) is the elements on larger scale which show the big end part of the workpiece | work shown to Fig.5 (a). (b) is sectional drawing which shows a workpiece | work along the AA line of Fig.6 (a). It is explanatory drawing which shows the stress which acts on the fracture | rupture planned surface of a large end part in a fracture | rupture division | segmentation process. (a)-(e) is explanatory drawing which shows the fracture | rupture process of the big end part in a fracture | rupture division | segmentation process in order. It is a diagram which shows the fluctuation | variation state of the tensile load which acts on a big end part in a fracture | rupture division | segmentation process. (a) is the elements on larger scale which show the big end part of the semi-finished product of the connecting rod which is other embodiment of this invention. (b) is an expanded sectional view which shows a workpiece | work along the AA line of Fig.10 (a). (a) is the elements on larger scale which show the big end part of the semi-finished product of the connecting rod which is other embodiment of this invention. (b) is an expanded sectional view which shows a workpiece | work along the AA line of Fig.11 (a). (a) is the elements on larger scale which show the big end part of the semi-finished product of the connecting rod which is other embodiment of this invention. (b) is an expanded sectional view which shows a workpiece | work along the AA line of Fig.12 (a). (a) is the elements on larger scale which show the big end part of the semi-finished product of the connecting rod which is other embodiment of this invention. (b) is an expanded sectional view which shows a workpiece | work along the AA line of Fig.13 (a). (a) is the elements on larger scale which show the big end part of the semi-finished product of the connecting rod which is other embodiment of this invention. (b) is an expanded sectional view which shows a workpiece | work along the AA line of Fig.14 (a).

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1A is a front view showing a connecting rod 10 (hereinafter referred to as a connecting rod). Moreover, FIG.1 (b) is a front view which shows the connecting rod 10 decomposed | disassembled.

  As shown in FIG. 1A, the connecting rod 10 includes a small end portion 12 having a piston pin hole 11, a large end portion 14 having a crank pin hole (through hole) 13, a small end portion 12 and a large end portion. 14 and a rod portion 15 that connects the two. A piston pin of a piston (not shown) is assembled to the small end portion 12, and a crank pin of a crankshaft (not shown) is assembled to the large end portion 14. Further, as shown in FIGS. 1A and 1B, the large end portion 14 of the connecting rod 10 is divided into a main body portion 16 and a cap portion 17. When the connecting rod 10 is assembled to the crank pin, the cap portion 17 is fastened to the main body portion 16 using the connecting rod bolt 18 after the crank pin is sandwiched between the divided main body portion 16 and the cap portion 17.

  When the large end portion 14 of the connecting rod 10 is divided, in order to improve productivity and positioning accuracy, a so-called cracking manufacturing method is used in which the inner end of the large end portion 14 is expanded and broken and divided. By using this cracking manufacturing method, it is possible to form irregularities having an appropriate roughness on the fracture surfaces 20 and 21 of the main body portion 16 and the cap portion 17. Thereby, when assembling the cap part 17 with respect to the main body part 16, the unevenness | corrugation of the torn surfaces 20 and 21 can be meshed | engaged with each other, and the positioning accuracy of the main body part 16 and the cap part 17 can be improved. It becomes. Moreover, the knock pin for positioning etc. can be reduced from the connecting rod 10, and it becomes possible to improve the productivity of the connecting rod 10. FIG.

  Next, a method for manufacturing the connecting rod 10 will be described. FIG. 2 is an explanatory view showing an example of a manufacturing process of the connecting rod 10. As shown in FIG. 2, in the material forging step S <b> 1, a work in which the small end portion 12, the rod portion 15, and the large end portion 14 are integrated by subjecting the cut carbon steel material or titanium alloy material to hot forging or the like. Is manufactured. In the grinding step S2, side grinding of the small end portion 12 and the large end portion 14 is performed using a grinding machine. Subsequently, in the small end hole processing step S <b> 3, the piston pin hole 11 is processed in the small end portion 12 by performing drilling or reamer processing on the small end portion 12. Further, in the large end hole machining step S4, the crank pin hole 13 is machined in the large end portion 14 by performing drilling, reamer processing or the like on the large end portion 14. Further, in the bolt hole machining step S <b> 5, a bolt hole is machined in the large end portion 14 by performing drilling, reaming, or the like on the large end portion 14. Subsequently, in a notch processing step (notch processing step) S6, a pair of notches (first notch and second notch) 23 and 24 opposed to each other with respect to an inner peripheral surface 22 of the large end portion 14 described later are provided. It is formed. In the notch machining step S6, the notches 23 and 24 are formed by using cutting or electric discharge machining. In the breaking and dividing step S7, the inner diameter of the large end portion 14 is expanded using a breaking device 30 described later, and the large end portion 14 is broken and divided into the main body portion 16 and the cap portion 17 starting from the notches 23 and 24. The

  In the subsequent bolt tightening step S <b> 8, the divided cap portion 17 is assembled to the main body portion 16 by tightening the connecting rod bolt 18. Also, in the finish grinding step S9, a grinder is used to remove the level difference of the large end portion 14 after the fracture division and to ensure the flatness and parallelism of the small end portion 12 and the large end portion 14. Side grinding of the small end portion 12 and the large end portion 14 is performed. Further, in the oil hole machining step S <b> 10, the oil holes for lubrication are machined in the small end portions 12 and the large end portions 14 by drilling the small end portions 12 and the large end portions 14. Subsequently, in the metal groove processing step S <b> 11, a metal groove for fixing the bearing metal to the inner peripheral surface 22 of the large end portion 14 is processed by cutting the large end portion 14. In the honing step S12, honing is performed on the small end portion 12 and the large end portion 14 in order to ensure the processing accuracy of the piston pin hole 11 and the crank pin hole 13. Then, after removing chips and the like adhering to the connecting rod 10 in the cleaning step S13, a completion inspection of the connecting rod 10 is performed in the completion inspection step S14.

  FIG. 3 is a schematic view showing an example of the breaking device 30 used in the breaking division step S7. 4 (a) and 4 (b) are explanatory diagrams showing the machining status of the workpiece X in the fracture division step S7. The workpiece X shown in FIG. 4 (a) is the workpiece X that is put into the fracture dividing step S7, and is a semi-finished product of the connecting rod according to one embodiment of the present invention, that is, an intermediate product in the manufacturing process. Yes.

  As shown in FIG. 3, the breaking device 30 includes a base member 31 and a pair of sliders 32 and 33 that are movably assembled to the base member 31. One slider 32 is provided with a positioning pin 34 inserted into the piston pin hole 11 of the small end portion 12 and a pressurizing jig 35 inserted into the crank pin hole 13 of the large end portion 14. The other slider 33 is provided with a pressure jig 36 inserted into the crank pin hole 13 of the large end portion 14. Further, the breaking device 30 has a wedge 38 that is driven up and down by a hydraulic cylinder 37. The wedge 38 is movable to a retracted position where it is lifted away from the pressurizing jigs 35, 36 and a pressurizing position where it is lowered and inserted between the pressurizing jigs 35, 36. At the time of breaking and dividing, as shown in FIG. 4A, the small end portion 12 of the work X is attached to the positioning pin 34 with the sliders 32 and 33 of the breaking device 30 close to each other, and both pressures are applied. The large end portion 14 of the work X is attached to the jigs 35 and 36. Then, as shown by black arrows in FIGS. 3 and 4B, the wedge 38 is lowered toward the pressing position, and the pair of pressing jigs 35 and 36 are moved away from each other. In this way, by expanding the inner diameter of the large end portion 14 of the workpiece X using the pressurizing jigs 35 and 36, the large end portion 14 is connected to the main body portion 16 and the cap portion 17 starting from the notches 23 and 24. Break and split. That is, the intake side connecting portion 39 constituting one side of the large end portion 14 is broken starting from the notch 23, and the exhaust side connecting portion 40 constituting the other side of the large end portion 14 is broken starting from the notch 24. It will be. The intake side connecting portion 39 is a portion located on the intake port side when the connecting rod 10 is assembled to the engine. Further, the exhaust side connecting part 40 is a part located on the exhaust port side when the connecting rod 10 is assembled to the engine.

  By the way, in the fracture | rupture division | segmentation process S7 which fractures | divides and breaks the big end part 14, generation | occurrence | production of the quality defect in the fracture | rupture surfaces 20 and 21 of the main-body part 16 or the cap part 17, ie, generation | occurrence | production of the chip | tip in the fracture surfaces 20 and 21 is suppressed. is important. However, it is difficult to stabilize the quality of the fractured surfaces 20 and 21 even when the large end portion 14 is broken and divided using the same breaking device 30. Therefore, the present inventor has conducted intensive research to solve the quality variation in the fracture surfaces 20 and 21, and as a result, the fracture order of the intake side connection portion 39 and the exhaust side connection portion 40 is determined. It was found that this is an important factor in stabilizing the quality of 20,21. That is, as a rupture situation in the conventional rupture division process, a situation in which the intake-side connecting portion 39 breaks first or the exhaust-side connecting portion 40 breaks first due to variations in workpiece shape, workpiece fixed state, or the like. Were mixed. Furthermore, the fracture splitting step is performed when the exhaust side coupling portion 40 is fractured after the intake side coupling portion 39 is fractured and when the intake side coupling portion 39 is fractured after the exhaust side coupling portion 40 is fractured. There may be a difference in the quality of the fractured surfaces 20, 21 obtained in S7. Therefore, in order to improve the quality of the fractured surfaces 20 and 21 while stabilizing the quality of the fractured surfaces 20 and 21, the intake air is sucked in a preset order without being affected by variations in the workpiece shape, workpiece fixed state, and the like. It was necessary to break the side connecting portion 39 and the exhaust side connecting portion 40. In order to improve the quality of the fractured surfaces 20 and 21, it is better to first break the intake side connecting portion 39 or to cut the exhaust side connecting portion 40 first. It is affected by the material, workpiece shape, rupture conditions, etc., and is determined based on a rupture test or the like.

  Here, Fig.5 (a) is a front view which shows the workpiece | work X thrown into fracture | rupture division | segmentation process S7. 5B is a cross-sectional view showing the workpiece X along the line AA in FIG. 5A, and FIG. 5C shows the workpiece X along the line BB in FIG. It is sectional drawing shown. 6A is a partially enlarged view showing the large end portion 14 of the workpiece X shown in FIG. 5A, and FIG. 6B is taken along the line AA in FIG. 6A. 3 is an enlarged cross-sectional view showing a workpiece X. FIG.

  As shown in FIGS. 5A to 5C, the first notch 23 and the second notch 24 face each other on the inner peripheral surface 22 of the crankpin hole 13 provided in the large end portion 14 of the workpiece X. Formed in position. Moreover, the 1st notch 23 and the 2nd notch 24 are formed in the position which overlaps with the plane S containing the centerline C1 of the crankpin hole 13 so that the internal peripheral surface 22 may be divided | segmented in the width direction. A virtual surface in the large end portion 14 that overlaps the plane S is a planned fracture surface that becomes the fracture surfaces 20 and 21 in the fracture division step S7. Further, since the connecting rod 10 manufactured using the illustrated workpiece X is a symmetric connecting rod that is symmetric with respect to the center line C2, the plane S is perpendicular to the center line C2. In addition, the code | symbol C3 shown in FIG. Further, as shown in FIGS. 6A and 6B, the width of the first notch 23 formed in the intake side connecting portion 39 is W and the depth is D1. On the other hand, the second notch 24 formed in the exhaust side connecting portion 40 has a width dimension of W and a depth dimension of D2, which is shallower than D1. As described above, the first notch 23 of the intake side connecting portion 39 is formed deeper than the second notch 24 of the exhaust side connecting portion 40. That is, the first notch 23 and the second notch 24 are formed in different shapes.

  Next, FIG. 7 is an explanatory diagram showing the stress acting on the planned fracture surface of the large end portion 14 in the fracture division step S7. FIGS. 8A to 8E are explanatory views sequentially showing the breaking process of the large end portion 14 in the breaking division step S7. As shown in FIG. 7, the first notch 23 of the intake side connecting portion 39 is formed deeper than the second notch 24 of the exhaust side connecting portion 40. A stress larger than 24 acts (σ1> σ2). Since stress concentrates on the first notch 23 more than the second notch 24 in this way, as shown in FIG. 8 (b), the crack is formed in the first notch 23 before the second notch 24 at the time of fracture division. C is generated, and as shown in FIG. 8C, the intake side connecting portion 39 can be broken before the exhaust side connecting portion 40. When the breakage of the intake side connecting portion 39 is completed, a crack C occurs in the second notch 24 as shown in FIG. 8D, and the exhaust side connecting portion 40 is shown in FIG. 8E. Will break.

  Here, FIG. 9 is a diagram showing a fluctuation state of the tensile load acting on the large end portion 14 in the fracture dividing step S7. 9 represents the tensile load acting on the portion indicated by reference numeral IN1 in FIG. 8A, and the line indicated by reference numeral IN2 in FIG. 9 indicates the tensile load acting on the portion indicated by reference numeral IN1 in FIG. Means the tensile load acting on the part indicated by reference numeral IN2. Further, the line indicated by reference numeral EX1 in FIG. 9 means a tensile load acting on the portion indicated by reference numeral EX1 in FIG. 8A, and the line indicated by reference numeral EX2 in FIG. Means the tensile load acting on the part indicated by the symbol EX2. As shown in FIG. 9, when the separating operation of the pressurizing jigs 35 and 36 is started in the breaking division step S7, the breaking is started from the inside of the intake side connecting portion 39 having the first notch 23 (reference number). α1) After that, the crack C extends to the outside of the intake side connecting portion 39, and the breaking of the intake side connecting portion 39 is completed (reference symbol α2). Subsequently, the fracture is started from the inside of the exhaust side connecting portion 40 including the second notch 24 (reference numeral β1), and then the crack C extending to the outside of the exhaust side connecting portion 40 extends to break the exhaust side connecting portion 40. Is completed (symbol β2). Thus, by changing the shape of the first notch 23 and the second notch 24, it is possible to provide a difference in the stress concentration at the time of the fracture split, and the intake side connecting portion 39 (one side of the large end portion 14). ) Can be broken, and then the exhaust side connecting portion 40 (the other side of the large end portion 14) can be broken. That is, it is possible to provide a time difference T from the completion of the breakage of the intake side connecting portion 39 to the start of the breakage of the exhaust side connecting portion 40.

  As described so far, by changing the shapes of the first notch 23 and the second notch 24, a clear difference is provided in the concentration of stress acting on the intake side connecting portion 39 and the exhaust side connecting portion 40. It becomes possible. As a result, the order of breakage between the intake side connecting portion 39 and the exhaust side connecting portion 40 can be determined without being affected by variations in the workpiece shape, the workpiece fixing state, and the like, and the quality of the fracture surfaces 20 and 21 is stabilized. It becomes possible. In the above description, the exhaust side connecting portion 40 is broken after the intake side connecting portion 39 is broken. However, the order is not limited to this, and the exhaust side connecting portion 40 is broken after the intake side connecting portion 39 is broken. The side connecting portion 39 may be broken. As described above, in order to improve the quality of the fractured surfaces 20 and 21, it is better to first break the intake side connecting portion 39 or to cut the exhaust side connecting portion 40 first. Is affected by the material, workpiece shape, rupture conditions, and the like, and is determined based on a rupture test or the like.

  Further, as shown in FIGS. 8 and 9, the exhaust side connection part 39 is broken before the exhaust side connection part 39 is broken without overlapping the break process of the intake side connection part 39 and the fracture process of the exhaust side connection part 40. The portion 40 is broken. Thus, by avoiding simultaneous breakage of the intake side connecting portion 39 and the exhaust side connecting portion 40, the quality of the fracture surfaces 20, 21 can be improved. That is, when the rupture process of the intake side connection part 39 and the exhaust side connection part 40 is overlapped in time, both the connection parts are always restrained, so that both of the connection parts are greatly plastically deformed. However, it is considered to break. On the other hand, when the rupture process of the intake side connection part 39 and the exhaust side connection part 40 is shifted in time, the connection part that has been broken first is released, so that the connection part that is broken later This is probably because the amount of plastic deformation is suppressed. Thus, it becomes possible to improve the quality of the torn surfaces 20 and 21 by making it fracture, suppressing the amount of plastic deformation.

  Then, the semifinished product of the connecting rod which is other embodiment of this invention is demonstrated. As shown in FIG. 6, in the above description, the shape of the first notch 23 and the second notch 24 is changed by changing the depth dimension of the first notch 23 and the second notch 24. It is not limited to. Here, FIG. 10A is a partially enlarged view showing a large end portion 14 of a semi-finished product (workpiece Xa) of a connecting rod according to another embodiment of the present invention, and FIG. It is an expanded sectional view showing work Xa along the AA line of a). Moreover, Fig.11 (a) is the elements on larger scale which show the large end part 14 of the semi-finished product (workpiece Xb) of the connecting rod which is other embodiment of this invention, FIG.11 (b) is FIG.11 (a). It is an expanded sectional view which shows the workpiece | work Xb along the AA line | wire of (). Further, FIG. 12 (a) is a partially enlarged view showing a large end portion 14 of a semi-finished product (workpiece Xc) of a connecting rod according to another embodiment of the present invention, and FIG. It is an expanded sectional view which shows the workpiece | work Xc along the AA line | wire of (). 10 to 12, the same members as those described above are denoted by the same reference numerals, and the description thereof is omitted.

  As shown in FIGS. 10A and 10B, the width of the first notch (first notch) 41 is W1 and the depth is D1. On the other hand, the second notch (second notch) 42 has a width W2 wider than W1 and a depth D1. That is, the first notch 41 is formed to be narrower than the second notch 42. In this way, even when the notch shape is changed by changing the width dimension, the concentration of stress acting on the first notch 41 and the second notch 42 can be changed, and the breaking order set in advance can be changed. The intake side connecting portion 39 and the exhaust side connecting portion 40 can be broken.

  Further, as shown in FIGS. 11A and 11B, when comparing the first notch (first notch) 51 and the second notch (second notch) 52, the width dimension W and the depth dimension D1 are compared. Are the same, but the tip of the first notch 51 is formed at an acute angle, whereas the tip of the second notch 52 is formed in an arc shape. Thus, even if the width dimension and the depth dimension are the same, the concentration of stress acting on the first notch 51 and the second notch 52 can be changed by changing the tip shape of the notches 51 and 52. It becomes possible to break the intake side connecting portion 39 and the exhaust side connecting portion 40 in a preset breaking order.

  Furthermore, as shown in FIGS. 12A and 12B, the first notch (first notch) 61 has a depth dimension of D1 at the central portion in the longitudinal direction, whereas the first notch (first notch) 61 has a longitudinal dimension in the longitudinal direction. At both ends, the depth dimension is D2, which is shallower than D1. On the other hand, the depth dimension of the second notch (second notch) 62 is maintained at D2 over the longitudinal direction. Thus, even when the notch shape is partially changed in the longitudinal direction of the notches 61 and 62 (the width direction of the inner peripheral surface 22), the stress acting on the first notch 61 and the second notch 62 Thus, the intake side connecting portion 39 and the exhaust side connecting portion 40 can be broken in a preset breaking order.

  In addition, as shown in FIGS. 6 and 10 to 12, in the above description, the first notch 23, 41, 51, 61 and the second notch 24, 42, 52, 62 are changed to change the shape. The stress concentration at the time of division is changed, but it is not limited to this. Here, FIG. 13A is a partially enlarged view showing a large end portion 14 of a semi-finished product (workpiece Xd) of a connecting rod according to another embodiment of the present invention, and FIG. It is an expanded sectional view showing work Xd along the AA line of a). FIG. 14A is a partially enlarged view showing the large end portion 14 of a semi-finished product (work Xe) of a connecting rod according to another embodiment of the present invention. FIG. It is an expanded sectional view which shows the workpiece | work Xe along the AA line | wire of (). In FIG. 13 and FIG. 14, the same members as those described above are denoted by the same reference numerals, and the description thereof is omitted.

  As shown in FIGS. 13A and 13B, the first notch (first notch) 71 and the second notch (second notch) 72 have the same shape. However, as shown by cross-hatching in FIG. 13 (a), the hardened layer 73 is formed in the first notch 71 at a depth D2, whereas the second notch 72 has a depth D3 deeper than D2. A quenching layer 74 is formed. In this way, even if the notch shape is the same, the concentration of stress acting on the first notch 71 and the second notch 72 can be changed by changing the quenching depth, and the intake air is sucked in a preset order of breakage. The side connecting portion 39 and the exhaust side connecting portion 40 can be broken. In addition, when forming the quenching layers 73 and 74 having different depths in the notches 71 and 72, it is possible to use laser quenching, induction quenching, or the like.

  As shown in FIGS. 14A and 14B, the first notch (first notch) 81 and the second notch (second notch) 82 have the same shape. However, as shown in FIG. 14B, the intake-side connecting portion 39 and the exhaust-side connecting portion 40 are formed with different cross-sectional shapes. In this way, even if the notch shape is the same, the concentration of stress acting on the first notch 81 and the second notch 82 can be changed by changing the cross-sectional shape of the connecting portion, and a preset breaking order can be obtained. Thus, the intake side connecting portion 39 and the exhaust side connecting portion 40 can be broken.

  It goes without saying that 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. In the above description, the notch provided in the intake side connecting portion 39 is described as the first notch, and the notch provided in the exhaust side connecting portion 40 is described as the second notch. However, this is not a limitation. Absent. In the fracture dividing step S7, when the exhaust side connecting portion 40 is first broken, the notch provided in the exhaust side connecting portion 40 becomes the first notch, and the notch provided in the intake side connecting portion 39 becomes the second notch. It becomes. Further, the connecting rod 10 manufactured using the workpieces X and Xa to Xe shown in FIGS. 6 and 10 to 14 is a symmetric connecting rod having a symmetric shape with respect to the center line C2, but is not limited thereto. There is nothing. For example, the manufacturing technique of the present invention can be effectively applied even to an asymmetric connecting rod having an asymmetric shape with respect to the center line C2.

In the above description, the hot-forged workpieces X, Xa to Xe are used. However, the present invention is not limited to this, and cold forging, sintered forging, or cast workpieces X, Xa to Xe are used. There may be. Further, in the above description, cutting or electric discharge machining is used when forming the notches 23, 24, 41 to 82, but the present invention is not limited to this, and a laser using a CO ₂ laser, a YAG laser, or the like. The notches 23, 24, 41 to 82 may be formed by processing.

10 Connecting rod (Connecting rod)
11 Piston pin hole 12 Small end 13 Crank pin hole (through hole)
14 Large end portion 15 Rod portion 16 Body portion 17 Cap portion 18 Connecting rod bolt 20 Broken surface 21 Broken surface 22 Inner circumferential surface 23 First notch (first notch)
24 Second notch (second notch)
30 Breaking device 31 Base member 32 Slider 33 Slider 34 Positioning pin 35 Pressurizing jig 36 Pressurizing jig 37 Hydraulic cylinder 38 Wedge 39 Inlet side connecting portion (one side of the large end)
40 Exhaust side connecting part (the other side of the large end)
41 First notch (first notch)
42 2nd notch (2nd notch)
51 First notch (first notch)
52 2nd notch (2nd notch)
61 First notch (first notch)
62 2nd notch (2nd notch)
71 First notch (first notch)
72 2nd notch (2nd notch)
81 First notch (first notch)
82 2nd notch (2nd notch)
S6 Notching process (notch process)
S7 Fracture split process X, Xa ~ Xe Workpiece (Semi-finished product of connecting rod)
C crack

Claims (5)

A connecting rod manufacturing method in which a large end portion is divided into a main body portion and a cap portion,
A notch processing step of forming a first notch and a second notch facing each other on an inner peripheral surface of a through hole provided in the large end portion;
By expanding the through-hole in the radial direction, a crack is generated from the first notch to break one side of the large end portion, and then a crack is generated from the second notch to generate the large end. And a fracture splitting process for breaking the other side of the part. In the manufacturing method of the connecting rod of Claim 1,
The method of manufacturing a connecting rod, wherein the first cutout and the second cutout have different shapes. In the manufacturing method of the connecting rod of Claim 1 or 2,
The method of manufacturing a connecting rod, wherein the first cutout is formed deeper than the second cutout. It is a semi-finished product of a connecting rod that is put into a fracture splitting process in which a large end is expanded in the radial direction and split into a main body part and a cap part,
A first notch formed on an inner peripheral surface of a through hole provided in the large end, and serving as a starting point of a crack during fracture division;
A second notch that is formed on the inner peripheral surface to face the first notch and serves as a starting point of crack generation during fracture division;
A connecting rod semi-finished product, wherein the first notch and the second notch have different shapes. The connecting rod semi-finished product according to claim 4,
The connecting rod semi-finished product, wherein the first cutout is formed deeper than the second cutout.

Images