JP7035863B2 - Fracture division method for machine parts - Google Patents

Description

The present invention relates to a method for breaking and dividing a mechanical part, for example, a method for breaking and dividing a mechanical part such as a case where a large end portion of a connecting rod in an internal combustion engine is broken and divided into a rod portion and a cap portion.

The method of breaking a large end portion of a connecting rod into a rod portion and a cap portion to divide the rod portion is also called a connecting rod cracking technique, and is often used for processing a connecting rod. In this method, a V-groove-shaped notch that functions as a fracture start is formed on the inner peripheral surface of the shaft hole formed at the large end or the inner peripheral surface of the bolt hole adjacent to the shaft hole by laser processing or machining. This is a construction method in which a crack is generated and broken by applying a diameter-expanding external force that concentrates stress on the tip of the notch portion.

Patent Document 1 is a method of preliminarily forming a notch portion on the outer peripheral surface of a large end portion including the inner peripheral surface of the shaft hole, and Patent Document 2 is a method of preliminarily forming a notch portion on the inner peripheral surface of the bolt hole. Each is disclosed in.

Japanese Patent No. 4171658 International Publication No. 2012/101748

However, in the conventional fracture splitting method represented by Patent Documents 1 and 2, a crack is generated starting from a preformed notch portion, and fracture progresses in the depth direction of the notch portion to some extent. However, once the fracture is started, the subsequent fracture progress direction cannot be positively controlled.

Therefore, for example, when a part of the bolt hole is a screw hole (female thread part), the fracture surface extends to the screw hole, and a part of the screw thread or the valley part is damaged. In some cases, there is still room for improvement, such as problems in tightening bolts after the fact.

The present invention has been made focusing on such a problem, and provides a method for breaking and dividing a mechanical part so that the traveling direction itself of a fracture surface can be positively controlled.

In the present invention, when a machine part having a shaft hole penetrating in the thickness direction is broken from the fracture surface on both sides of the shaft hole and divided into two halved parts, the fracture surface of the machine part is formed. A plurality of lead holes having a fine diameter are formed in advance along the fracture surface at the corresponding positions, and at least at a position on the inner peripheral surface of the shaft hole facing each other in the radial direction, a break start portion is formed. The notch portion was formed in advance .

According to the present invention, a plurality of lead holes are previously formed at positions corresponding to the fracture surface, and the fracture surface based on the progress of the crack proceeds along the plurality of lead holes in a manner guided by them. Therefore, the traveling direction of the fracture surface can be positively controlled by selecting the position of the lead hole. Therefore, it is possible to generate a fracture surface at a position planned in advance, and it is possible to prevent secondary defects due to deviation of the fracture surface or partial chipping.

A more specific first embodiment for carrying out the method for breaking and dividing a mechanical part according to the present invention is shown, and as an example, a double-link piston in which a part manufactured by the method of the present invention is adopted as a link member. Schematic diagram of an internal combustion engine equipped with a crank mechanism. The perspective view of the lower link alone shown in FIG. FIG. 2 is a vertical cross-sectional view of the lower link shown in FIG. FIG. 3 is an enlarged cross-sectional view of the lower link material before the lower link shown in FIG. 3 is divided into two. An enlarged view of part A in FIG. A construction method for dividing the lower link material shown in FIG. 4 into two by breaking is shown, (a) is a schematic perspective view of the lower link material shown in FIG. 4, and (b) is a front view of the lower link material. (C) is a plan view of one fracture surface of FIG. 4 as viewed from above. As a second embodiment for carrying out the method for breaking and dividing a mechanical part according to the present invention, a method for dividing the lower link material shown in FIG. 4 into two by breaking is shown, and FIG. 4A shows FIG. The schematic perspective view of the lower link material shown, (b) is a front view of the lower link material, and (c) is a plan view of one fracture surface of FIG. 4 as viewed from above. It is explanatory drawing which shows the 3rd Embodiment for carrying out the breaking division method of the machine part which concerns on this invention, and shows the construction method for dividing the lower link material shown in FIG. 4 into two by breaking.

1 to 6 show a more specific first embodiment for carrying out the breaking division method of a mechanical part according to the present invention, and in particular, FIG. 1 shows, as an example, a link of parts manufactured by the method of the present invention. The outline of the internal combustion engine equipped with the double-link type piston crank mechanism adopted as a member is shown.

As shown in FIG. 1, the double-link type piston crank mechanism itself is known, and has an upper link 3 having one end connected to the piston 1 via a piston pin 2 and an upper pin 4 to the other end of the upper link 3. The lower link 7 is connected to the crankshaft 5 and connected to the crankpin 6 of the crankshaft 5, and the control link 8 that regulates the degree of freedom of the lower link 7 is provided.

One end of the control link 8 is swingably supported by the eccentric shaft portion 9a of the control shaft 9, and the other end is connected to the lower link 7 via the control pin 10. In FIG. 1, 11 is a cylinder block and 12 is a cylinder.

FIG. 2 shows a perspective view of the lower link 7 alone shown in FIG. 1, and FIG. 3 shows a vertical cross-sectional view of the lower link 7 shown in FIG. As shown in FIGS. 2 and 3, the lower link 7 has a cylindrical crankpin bearing portion 13 fitted to the crankpin 6 in the center, and is substantially 180 ° opposite to each other with the crankpin bearing portion 13 interposed therebetween. A pin boss portion 14 for an upper pin and a pin boss portion 15 for a control pin are provided at positions on the side.

The lower link 7 has a parallelogram-shaped thick plate shape that is close to a rhombus as a whole, and the pin boss portion 14 for the upper pin is provided on the dividing surfaces 16 and 17 extending in the extension line direction of the diameter of the crankpin bearing portion 13. It is formed by being divided into two parts, a lower link upper 7A including the lower link upper 7A and a lower link lower 7B including a pin boss portion 15 for a control pin. The lower link upper 7A and the lower link lower 7B are fastened to each other by a pair of bolts 18 and 19 inserted in opposite directions after fitting the crankpin bearing portion 13 into the crankpin 6.

The lower link upper 7A receives the upper link 3 axially supported by the upper pin 4, and the lower link lower 7B receives the control link 8 axially supported by the control pin 10. Therefore, the lower link upper 7A is formed as having a U-shaped cross section (bifurcated or clevis) with an open upper surface, and the lower link lower 7B has a U-shaped cross section (bifurcated or clevis) with an open lower surface. ) Is formed. Further, the control link 8 shown in FIG. 1 is also divided into two parts, the link main body 8a and the cap portion 8b, at the large end portion, like the lower link 7 or the existing connecting rod, and is fastened by the bolt 8c. ..

The lower link 7 having such a structure is manufactured by hot forging as one part in which the lower link upper 7A and the lower link lower 7B are integrated by using, for example, heat-treated steel, and is subjected to necessary machining such as drilling. After the above, the split surfaces 16 and 17 are split and split into pairs, and the lower link upper 7A and the lower link lower 7B are finished.

As is clear from the above description, the lower link 7 corresponds to the plate-shaped mechanical component in the present invention, and the lower link upper 7A and the lower link lower 7B formed by dividing the lower link 7 into two are formed. , Corresponds to the half-split parts in the present invention. Similarly, the crankpin bearing portion 13 corresponds to the shaft hole in the present invention.

Here, as shown in FIG. 3, the lower link upper 7A and the lower link lower 7B are inserted from the two bolts 18, 19 opposite to each other, that is, from the lower link upper 7A side on both sides of the crankpin bearing portion 13. The bolt 18 and the bolt 19 inserted from the lower link lower 7B side are fastened and fixed to each other.

Bolt holes 20 and 21 are formed through the portions where the bolts 18 and 19 are inserted so as to straddle the lower link upper 7A and the lower link lower 7B. Of these bolt holes 20 and 21, the portions of the bolts 18 and 19 on the heads 18a and 19a side of the split surfaces 16 and 17 are the through holes 20a and 21a, whereas the split surface 16 is used. , 17 and the portions of the bolts 18 and 19 opposite to the heads 18a and 19a are screw holes (female threaded portions) 20b and 21b. Each of the bolt holes 20 and 21 including the through holes 20a and 21a and the screw holes 20b and 21b is machined before being split into the lower link upper 7A and the lower link lower 7B from the dividing surfaces 16 and 17. Processing is applied as part.

Here, as is clear from FIG. 2, the split surfaces 16 and 17 on both sides of the crankpin bearing portion 13 are not on the virtual plane Q1 passing through the center of the crankpin bearing portion 13, and are offset from the virtual plane Q1 respectively. They are offset in opposite directions by the amount α. Therefore, if attention is paid only to the relationship between the divided surfaces 16 and 17, both have a stepped shape having a step corresponding to the offset amount α × 2. This step is set to intentionally offset the start end portions of the screw holes (female thread portions) 20b and 21b of the bolt holes 20 and 21 from the dividing surfaces 16 and 17. This point will be described later.

FIG. 4 is an enlarged view of the state before the lower link 7 shown in FIG. 3 is divided into the lower link upper 7A and the lower link lower 7B, and the bolts 18 and 19 shown in FIG. 3 are attached. do not have. However, it is assumed that the minimum required machining for the lower link 7 has been completed.

Here, since the so-called cracking method of dividing into the lower link upper 7A and the lower link lower 7B is characteristic, the member in which both are integrated before being divided into the lower link upper 7A and the lower link lower 7B is referred to as the lower link material 27. It shall be referred to. Similarly, the portions corresponding to the divided surfaces 16 and 17 in FIGS. 2 and 3 are formed by fracture due to the progress of cracks as will be described later. The portions to be the divided surfaces 16 and 17 are referred to as fracture surfaces 16a and 17a.

As described above, the lower link material 27 shown in FIG. 4 has fracture surfaces on both sides of the crankpin bearing portion 13 assuming a virtual plane Q1 passing through the center of the crankpin bearing portion 13. 16a and 17a are not on the virtual plane Q1 and are set in parallel with the virtual plane Q1 at positions offset from the virtual plane Q1 by an offset amount α, respectively. That is, when the virtual plane Q1 is used as a reference, one fracture surface 16a and the other fracture surface 17a are set at positions offset in opposite directions by the offset amount α, and the sum of the respective offset amounts α. (Offset amount α × 2) is a step between both fracture surfaces 16a and 17a.

FIG. 6 shows a method for dividing the lower link material 27 shown in FIG. 4 into two by breaking, and FIG. 6A shows a schematic perspective view of the lower link material 27 shown in FIG. The figure (b) shows the front view of the lower link material 27. Further, FIG. 4C shows a plan view of one fracture surface 16a of FIG. 4 as viewed from above.

In the lower link material 27 shown in FIG. 4, as shown in FIG. 5, which is an enlarged view of the portion A in the figure, the positions of the inner peripheral surfaces of the crankpin bearing portion 13 facing each other on the virtual plane Q1, that is, the crankpins. A fine notch portion 22 is formed in advance at a position facing the inner peripheral surface of the bearing portion 13 in the radial direction. This notch portion 22 serves as a fracture start portion due to the occurrence of a crack at the time of fracture, and is formed as a V-groove shape by, for example, laser processing or machining, and is formed along the plate thickness direction of the lower link material 27. To. The notch portion 22 does not necessarily have to have a V-groove shape, and may be, for example, a long U-groove shape.

Further, as shown in FIGS. 6A and 6B, the fracture surfaces 16a and 17a of the lower link material 27 are located at positions corresponding to the fracture surfaces 16a and 17a on both sides of the crankpin bearing portion 13. Along the line, a plurality of lead holes 23 having a fine diameter (four in FIG. 6) are preformed at a predetermined pitch and at equal pitches. As will be described later, these plurality of lead holes 23 are formed to guide the traveling direction in a specific direction in order to positively control the traveling direction of cracks or fractures at the time of fracture.

The plurality of lead holes 23 are formed by, for example, drilling so as to be parallel to each other and penetrate the lower link material 27 while pointing in the plate thickness direction. In other words, while the notch portion 22 is on the virtual plane Q1, the plurality of lead holes 23 are formed in the fracture surfaces 16a and 17a offset by the offset amount α from the virtual plane Q1, and the respective lead holes 23 are formed. Is set so as not to reach the virtual plane Q1. That is, of the fracture surfaces 16a and 17a on both sides of the crankpin bearing portion 13, the plane passing through the center lines of the plurality of lead holes 23 formed at the positions corresponding to the fracture surface 16a on one side and the fracture surface 17a on the other side. The plane passing through the center lines of the plurality of lead holes 23 formed at the corresponding positions is in the opposite direction to the virtual plane Q1 connecting the notch portions 22 facing each other on the inner peripheral surface of the crankpin bearing portion 13. Is offset to.

Regarding the lower link material 27 in which such a notch portion 22 and a plurality of lead holes 23 are formed, the crankpin bearing portion 13 is expanded from the inner peripheral side of the crankpin bearing portion 13 in a direction orthogonal to the virtual plane Q1. It is assumed that a diameter-expanding force F that causes the diameter is applied. As a result, the lower link material 27 was broken along the fracture surfaces 16a and 17a in which a plurality of lead holes 23 were formed in advance, triggered by the occurrence of a crack in the notch portion 22, and is shown in FIGS. It is divided into two parts, lower link upper 7A and lower link lower 7B. As a means for applying the diameter-expanding force F, a mandrel (not shown) capable of expanding or contracting the diameter is inserted into the crankpin bearing portion 13, and is disclosed in, for example, Japanese Patent Application Laid-Open No. 2006-315098 and Japanese Patent Application Laid-Open No. 2010-196882. You can use the same one as the one you have.

FIG. 6 (c) shows the progress state of fracture at one fracture surface 16a. As shown in (b) and (c) of the figure, in the lower link material 27 loaded with the expansion force F, a crack is generated with the notch portion 22 on the virtual plane Q1 as the break start portion, and the crack is generated. The notch portion 22 advances along the fracture surface 16a in a direction away from the inner peripheral surface of the crankpin bearing portion 13 in which the notch portion 22 is formed.

In this case, the virtual plane Q1 in which the notch portion 22 is set and the fracture surface 16a in which the plurality of lead holes 23 are formed are offset by the offset amount α shown in FIG. Therefore, as shown in FIG. 6B, the crack having the notch portion 22 as the fracture start portion is first formed from the notch portion 22 on the inner peripheral surface of the crankpin bearing portion 13 among the plurality of lead holes 23. Proceed diagonally toward the near lead hole 23. After that, the crack reaching the lead hole 23 closest to the inner peripheral surface of the crankpin bearing portion 13 sequentially progresses toward the adjacent lead hole 23 along the fracture surface 16a.

Here, in order to facilitate understanding, as far as (c) of FIG. 6 is concerned, the reference numerals 23a to 23d are given in order from the plurality of lead holes 23 closest to the crankpin bearing portion 13. Therefore, the fracture caused by the crack generated with the notch portion 22 as the fracture start portion proceeds in the order of the lead holes 23a to 23d in the direction indicated by the arrow P1 in the figure. Such behavior proceeds almost simultaneously on the other fracture surface 17a.

When microscopically observing the progress of the fracture in the fracture surface 16a, the cracks generated in the notch portion 22 are not the holes in front of the lead hole 23a closest to the inner peripheral surface of the crankpin bearing portion 13. The crack extends to the site and subsequently extends to the lead hole 23a closest to the inner peripheral surface of the crankpin bearing portion 13. When the crack extends to the lead hole 23a closest to the inner peripheral surface of the crankpin bearing portion 13, the continuity of the crack is temporarily cut off at the lead hole 23a.

Even in this state, since the diameter expansion force F is still applied to the lower link material 27, a crack occurs with the inner peripheral surface of the lead hole 23a closest to the inner peripheral surface of the crankpin bearing portion 13 as the fracture start portion. Then, a crack is generated in a portion other than the hole adjacent to the rear side of the lead hole 23a, and the crack extends to the next lead hole 23b. Such behavior is repeated until it passes through the final lead hole 23d.

That is, in the example of FIG. 6 (c), the continuity of the crack is once cut off by the crack generated in the region other than the hole region extending to the lead hole 23a, but the lead hole 23a is cut again at the fracture start portion. As a result, cracks are generated in adjacent regions other than the hole region, and such intermittent fractures are repeated in the order of lead holes 23b to 23d over the entire fracture surface 16a. Finally, in addition to the fracture surface 16a, the other fracture surface 17a is divided into the lower link upper 7A and the lower link lower 7B shown in FIGS. 2 and 3.

In this way, the fracture surfaces 16a and 17a are set at positions offset by the offset amount α from the virtual plane Q1 in which the notch portion 22 is set, and a plurality of lead holes 23 (23a to 17a) are set in the fracture surfaces 16a and 17a. Since 23d) is formed in advance, the fracture proceeds along the fracture surfaces 16a and 17a offset from the virtual plane Q1 while the crack generation at the notch portion 22 on the virtual plane Q1 is set as the break start portion. Can be made to.

Therefore, as shown in FIG. 4, even if the bolt holes 20 and 21 are opened in the fracture surfaces 16a and 17a, the fracture surfaces 16a and 17a extend to the through holes 20a and 21a and are screw holes. The fractured surfaces 16a and 17a do not extend to the female threaded portions 20b and 21b. As a result, the threads and valleys of the screw holes (female thread portions) 20b and 21b are not damaged due to the breakage at the fracture surfaces 16a and 17a, and the bolts are fastened to the subsequent bolt holes 20 and 21. , It is possible to prevent the occurrence of secondary inconveniences such as improper tightening.

FIG. 7 shows a second embodiment of the method for breaking and dividing a mechanical part according to the present invention, and FIGS. 7A to 7C have the same states as those in FIGS. 6A to 6C. Shows. The parts common to FIG. 6 are marked with the same sign.

In this second embodiment, the centerline direction of each of the plurality of lead holes 24 previously formed at the positions corresponding to the fracture surfaces 16a and 17a of the lower link material 27 is 90 ° different from that of FIG. It is different in that it is.

In addition to FIG. 4, as shown in FIGS. 7A and 7B, the diameters of the crankpin bearing portions 13 are located at positions corresponding to the fracture surfaces 16a and 17a on both sides along the fracture surfaces 16a and 17a. A plurality of fine lead holes (three in FIG. 7) are preformed at a predetermined pitch, and here at equal pitches. As will be described later, these plurality of lead holes 24 are formed to guide the traveling direction in a specific direction in order to positively control the traveling direction or the fracture traveling direction of the crack at the time of breaking. These plurality of lead holes 24 are formed by, for example, drilling so as to be parallel to each other and the center line direction is directed to the fracture traveling direction along the fracture surfaces 16a and 17a.

That is, as in the first embodiment, the notch portion 22 on the inner peripheral surface of the crankpin bearing portion 13 is used as the rupture starting portion, and the rupture occurs along the fracture surfaces 16a and 17a in the direction away from the inner peripheral surface. As it progresses, a plurality of lead holes 24 are formed in parallel with the breaking progress direction of the fracture surface 16a and 17a of the lower link material 27. As shown in FIG. 4, while the notch portion 22 is on the virtual plane Q1, the plurality of lead holes 24 are formed in the fracture surfaces 16a and 17a offset by the offset amount α from the virtual plane Q1. The point is the same as that of the first embodiment of FIG.

FIG. 7 (c) shows the progress state of fracture at one fracture surface 16a. As shown in (b) and (c) of the figure, in this example, the bolt hole 20 is set on the virtual center line Q2 that divides the thickness of the lower link material 27 into two, and the virtual center line Q2 is set. Three lead holes 24 are formed symmetrically as the center of symmetry.

Here, as far as (c) of FIG. 7 is concerned, among the arrangements of the three lead holes 24, the ones on both sides of the arrangement are set to 24a, and the one in the middle is set to 24b. Therefore, the lead hole 24b located in the center is located on the virtual center line Q2. The lead holes 24a located on both sides of the array are non-penetrating to the crankpin bearing portion 13. At the same time, the lead hole 24b located in the center is formed only on the rear side in the breaking progress direction of the bolt hole 20 even if it penetrates the through hole 20a among the bolt holes 20. Further, the point that none of the lead holes 24a and 24b extends to the virtual plane Q1 of FIG. 4 is the same as that of the first embodiment.

The method of loading the diameter-expanding force F at the time of breaking at the fracture surfaces 16a and 17a on both sides of the crankpin bearing portion 13 is the same as that of the first embodiment. As shown in FIGS. 7 (b) and 7 (c), in the lower link material 27 loaded with the expansion force F, a crack is generated with the notch portion 22 on the virtual plane Q1 as the break start portion, and the crack is generated. It travels along the fracture surface 16a in a direction away from the inner peripheral surface of the crankpin bearing portion 13.

In this case, the virtual plane Q1 in which the notch portion 22 is set and the fracture surfaces 16a and 17a in which the plurality of lead holes 24a and 24b are formed are offset by the offset amount α shown in FIG. Therefore, the crack having the notch portion 22 as the fracture start portion first proceeds diagonally from the notch portion 22 toward the deepest portion of the lead holes 24a on both sides having a large depth among the plurality of lead holes 24a and 24b.

After that, the crack progresses in the direction away from the notch portion 22 along the two lead holes 24a on both sides on the fracture surface 16a, and extends to the through hole 20a of the bolt holes 20. Eventually, it reaches the deepest part of the lead hole 24b in the middle, which penetrates to the through hole 20a. As a result, the fracture accompanying the crack progress progresses in the direction indicated by the arrows P2 and P3 in FIG. 7 (c). Such behavior proceeds almost simultaneously on the other fracture surface 17a. Finally, the fracture progresses with the progress of the crack to the ends of the three lead holes 24a and 24b, and the lower link upper shown in FIGS. 2 and 3 is shown from the fracture surface 16a and the other fracture surface 17a. It will be divided into 7A and lower link lower 7B.

In this way, the fracture surfaces 16a and 17a are set at positions offset by the offset amount α from the virtual plane Q1 in which the notch portion 22 is set, and the center line direction is the fracture traveling direction in the fracture surfaces 16a and 17a. Since a plurality of lead holes 24 (24a, 24b) pointing to the above are formed in advance, the crack generation at the notch portion 22 on the virtual plane Q1 is set as the break start portion, but is offset from the virtual plane Q1. The fracture can proceed along the fracture surfaces 16a and 17a.

Therefore, even if the bolt holes 20 and 21 are opened in the fracture surfaces 16a and 17a, the fracture surfaces 16a and 17a extend to the through holes 20a and 21a, and the screw holes (female thread portions) 20b, The fracture surfaces 16a and 17a do not extend to 21b. As a result, as in the first implementation above, the threads and valleys of the screw holes (female thread portions) 20b and 21b are not damaged due to the fracture at the fracture surface 16a and 17a, and the subsequent steps are performed. When fastening bolts to the bolt holes 20 and 21, it is possible to prevent the occurrence of secondary inconveniences such as improper tightening.

Further, since the plurality of lead holes 24 (24a, 24b) are formed symmetrically with the virtual center line Q2 as the center of symmetry, the fracture progresses stably along the fracture progress direction in the fracture surface 16a, 17a. Will be done.

Moreover, the lead hole 24b in the middle is located on the virtual center line Q2 and is formed only on the rear side in the breaking progress direction from the bolt holes 20 and 21. Therefore, as shown in FIG. 7 (c), the crack that has progressed in the direction of the arrow P3 from both sides of the lower link material 27 in the thickness direction across the bolt holes 20 and 21 is the central lead at the end of the fracture progress process. It will be in the form of merging at the hole 24b. In this way, the lead hole 24b in the center functions as the confluence of cracks from the left and right indicated by the arrow P3, thereby preventing the occurrence of steps and local defects at the confluence of cracks at the end of fracture. can do.

Further, as described above, since the plurality of lead holes 24 do not penetrate the crankpin bearing portion 13, for example, when the crankpin bearing portion 13 is to be finished and cut after the break is completed, a plurality of lead holes 24 are formed. There is no so-called intermittent cutting as in the case where the lead hole 24 of the above penetrates the crankpin bearing portion 13. Therefore, it is possible to prevent the occurrence of "burrs" on the inner peripheral surface of the crankpin bearing portion 13 and the occurrence of "unevenness" on the finished surface.

In addition, in the first embodiment shown in FIG. 6, since the center line direction of the plurality of lead holes 23 is orthogonal to the fracture progress direction in the fracture sections 16a and 17a, the notch portion 22 is the fracture start portion. As mentioned above, the progress of the cracks is intermittent. On the other hand, in the second embodiment shown in FIG. 7, since the direction of the center line of the plurality of lead holes 24 coincides with the breaking progress direction, the crack progress may be intermittent. The crack progress is continuous along the centerline direction of the plurality of lead holes 24. Therefore, the stress required for crack generation is lower in the second embodiment than in the first embodiment, and as a result, the diameter expansion force F required for fracture at the fracture surfaces 16a and 17a is also increased. It will be small.

On the other hand, in the first embodiment described above, as shown in FIG. 6, since the plurality of lead holes 23 cover the entire width of the fracture surface 16a and 17a, as compared with the second embodiment. The controllability of the fracture progress direction at the fracture sections 16a and 17a based on the occurrence of cracks is good, and when attention is paid to the inducibility of the fracture progress direction, the first embodiment is more advantageous.

FIG. 8 is a diagram showing a third embodiment of the method for breaking and dividing a mechanical part according to the present invention, in which the same parts as those in FIGS. 6 and 7 (a) are designated by the same sign.

In the third embodiment shown in FIG. 8, as the arrangement form of the plurality of lead holes 23, 24 previously formed in the lower link material 27, in addition to the three lead holes 24 in the second embodiment, a second is made. A single lead hole 23 according to the embodiment of 1 is added. More specifically, the arrangement form of the three lead holes 24 whose center line direction points to the fracture traveling direction in the fracture surface 16a and 17a of FIG. 4 is exactly the same as that shown in FIG. 7A. .. On the other hand, for those whose center line direction points to the thickness direction of the lower link material 27, of the three lead holes 23 shown in FIG. 6A, only the one closest to the crankpin bearing portion 13 is used alone. It is added with.

The three lead holes 24 whose center line direction points to the breaking progress direction and the single lead hole 23 whose center line direction points to the thickness direction of the lower link material 27 are the same offset from the virtual plane Q1 by the offset amount α. Since it is formed on the fracture surfaces 16a, 17a, as a result, the single lead hole 23 intersects with the other three lead holes 24.

Therefore, in the third embodiment, both the good inducibility of the fracture progress direction in the first embodiment and the reduction of the stress generated at the fracture progress in the second embodiment can be achieved at the same time. .. In particular, in addition to the three lead holes 24 whose center line direction points to the breaking progress direction, a single lead hole 23 whose center line direction points to the thickness direction of the lower link material 27 is located near the crankpin bearing portion 13. By adding the addition, the inducibility in the traveling direction of the fracture surfaces 16a and 17a immediately after the crack is generated triggered by the notch portion 22 becomes excellent.

Here, the numbers of the lead holes 23 and 24 in the first to third embodiments are merely examples, and can be arbitrarily set in consideration of, for example, the size of the lower link material 27. ..

Further, in each of the above embodiments, the lower link 7 of the double link type piston crank mechanism shown in FIG. 1 has been described as an example, but at the large end portion of the control link 8 in the figure, the link main body 8a and the cap portion 8b have been described. The present invention can be applied even in the case of breakage. Further, the present invention is naturally applied not only to the lower link 7 and the control link 8 of the double link type piston crank mechanism shown in FIG. 1, but also to the breakage of general connecting rods and mechanical parts of the same type. Can be done. In addition, the symmetrical mechanical parts do not necessarily have to be forged products, and may be, for example, cast products, sintered parts, or parts such as titanium alloys.

7 ... Lower link (machine parts)
7A ... Lower link upper (half-split parts)
7B ... Lower link lower (half-split parts)
13 ... Crankpin bearing (shaft hole)
16a ... Fracture surface 17a ... Fracture surface 20 ... Bolt hole (hole)
21 ... Bolt hole (hole)
22 ... Notch 23, 23a, 23b, 23c, 23d ... Lead hole 24, 24a, 24b ... Lead hole 27 ... Lower link material Q1 ... Virtual plane Q2 ... Virtual center line

Claims (10)

A shaft hole is formed in a plate-shaped machine part that penetrates in the thickness direction, and the machine part is broken from the fracture surface on both sides of the shaft hole and divided into two halves.
In a method for breaking and dividing a machine part in which a plurality of lead holes having a fine diameter are previously formed along the fracture surface at a position corresponding to the fracture surface of the machine part.
A method for breaking and dividing a mechanical part, which comprises forming in advance a notch portion to be a breaking start portion at least at a position of the inner peripheral surface of the shaft hole facing each other in the radial direction . In the method for breaking and dividing a mechanical part according to claim 1 ,
Of the fracture surfaces on both sides of the shaft hole, a plane passing through the center lines of the plurality of lead holes formed at a position corresponding to one fracture surface, and the plurality of fracture surfaces formed at positions corresponding to the other fracture surface. The plane passing through the center line of the lead hole is offset in the opposite direction to the plane connecting the notches facing each other on the inner peripheral surface of the shaft hole. How to divide. In the method for breaking and dividing a mechanical part according to claim 1 or 2 .
The processing for breaking is to apply a diameter-expanding force in the direction in which the two half-split parts are separated from each other from the inner peripheral side of the shaft hole.
The center line direction of the plurality of lead holes is set so as to direct the breaking progress direction toward the direction away from the inner peripheral surface with the inner peripheral surface side of the shaft hole as the breaking start portion. How to break and divide machine parts. In the method for breaking and dividing a mechanical part according to claim 1 or 2 .
The processing for breaking is to apply a diameter-expanding force in the direction in which the two half-split parts are separated from each other from the inner peripheral side of the shaft hole.
A method for breaking and dividing a mechanical part, characterized in that the direction of the center line of the plurality of lead holes is set to be parallel to the direction of the center line of the shaft hole. In the method for breaking and dividing a mechanical part according to claim 3 ,
In addition to the plurality of lead holes whose center line direction points to the breaking traveling direction,
A method for breaking and dividing a mechanical part, characterized in that at least one lead hole whose center line direction is parallel to the center line direction of the shaft hole is formed. In the method for breaking and dividing a mechanical part according to claim 3 or 5 .
A method for breaking and dividing a mechanical part, wherein the plurality of lead holes whose center line direction points to the breaking traveling direction do not penetrate the shaft hole. In the method for breaking and dividing a mechanical part according to claim 6 ,
The plurality of lead holes whose center line direction points to the breaking progress direction are arranged symmetrically with the virtual center line that matches the breaking progress direction and divides the thickness of the mechanical component into two as the center of symmetry. A method of breaking and splitting a mechanical part, which is characterized by being. In the method for breaking and dividing a mechanical part according to claim 7 .
A method for breaking and dividing a mechanical component, wherein the plurality of lead holes whose center line direction is directed to the breaking traveling direction is an odd number. In the method for breaking and dividing a mechanical part according to claim 8 ,
Of the mechanical parts, holes are formed in advance on both sides of the shaft hole and on the virtual center line so that the direction of the center line is substantially orthogonal to the fracture surface.
Of the odd number of lead holes, the lead hole located in the center of the arrangement direction is formed on the virtual center line and on the rear side in the fracture traveling direction with respect to the hole portion. Break split method. In the method for breaking and dividing a mechanical part according to any one of claims 1 to 9 .
A method for breaking and dividing a mechanical part, wherein the mechanical part is a link member of any one of the internal combustion engines provided with a double-link piston crank mechanism including an upper link, a lower link, and a control link.

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