JP2007192399A - Connecting rod, internal combustion engine, motor vehicle and method of manufacturing connecting rod - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a connecting rod having a superior mechanical characteristic with every part, and capable of sufficiently reducing its weight. <P>SOLUTION: This connecting rod has a rod body part 10, a small end part 20 arranged one one end of the rod body part 10 and a large end part 30 arranged on the other end of the rod body part 10, and includes a round part 30R curved so that the large end part 30 narrows toward the rod body part 10. The large end part 30 is formed of a metallic material of composition different from the rod body part 10, and is joined to the rod body part 10. A joining place W of the large end part 30 and the rod body part 10 is positioned on the small end part 20 side more than the end RE on the rod body part 10 side of the round part 30R. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a connecting rod and a manufacturing method thereof. The present invention also relates to an internal combustion engine or a motor vehicle provided with a connecting rod.

  In an internal combustion engine of a motor vehicle, a member called a connecting rod (or connecting rod) is used to connect a crankshaft and a piston. FIG. 16 shows a general connecting rod 401. The connecting rod 401 has a rod-shaped rod body 410, a small end 420 provided at one end of the rod body 410, and a large end 430 provided at the other end of the rod body 410.

  The small end portion 420 has a piston pin hole 425 for allowing the piston pin to pass therethrough, and is connected to the piston through the piston pin. On the other hand, the large end portion 430 has a crankpin hole 435 through which the crankpin is passed, and is connected to the crankshaft through the crankpin.

  The large end portion 430 is divided into a rod portion 433 that is continuous with one end of the rod body portion 410 and a cap portion 434 that is coupled to the rod portion 433 by a bolt 440. For this reason, the connecting rod 401 shown in FIG. 16 is called a split connecting rod. As another connecting rod, a connecting rod of a type in which the large end portion is not divided is also known.

Conventionally, steel has been widely used as a material for the connecting rod, but in recent years, it has been proposed to use a titanium alloy (for example, Patent Document 1). By reducing the weight of the connecting rod using a titanium alloy, the crankshaft and other engine parts can be reduced in weight, so that the entire engine can be reduced in weight. Therefore, output can be improved and fuel consumption can be reduced.
JP-A-60-247432

  However, it has been found that the use of a titanium alloy as the connecting rod material causes the following problems.

  The mechanical properties required for the connecting rod vary from site to site. For example, the small end portion of the connecting rod and the rod main body portion are required to have high strength and high toughness so as not to undergo fatigue failure or impact failure during use. On the other hand, the large end portion of the connecting rod has a high rigidity and a high elastic modulus that the inner peripheral surface of the crankpin hole is not deformed even by the rotational movement of the crankshaft in order to reduce the friction with the crankpin. It is required to be difficult to deform even at high speeds.

  For this reason, when a titanium alloy having a lower elastic coefficient than steel is used as the connecting rod material, the weight of the connecting rod can be reduced, but the rigidity of the large end portion is insufficient. In addition, if the size is such that sufficient rigidity is obtained, the advantage of weight reduction is lost.

  Therefore, the inventor of the present application has conceived of using a different metal material for each part of the connecting rod. By joining a plurality of members made of metals having different compositions to form a connecting rod, desired mechanical properties can be given to each portion of the connecting rod. For example, a metal material that is lightweight and has excellent fatigue strength is used for the small end and the rod main body, while a metal material having high rigidity and a high elastic modulus is used for the large end, thereby increasing the rigidity of the large end. While ensuring, weight reduction can be achieved.

  However, the inventor of the present application has made a detailed study and found that it is difficult to reduce the weight sufficiently even if such a method is used. Since the connecting rod transmits the explosive force transmitted from the piston to the crankshaft, high strength is required. For this reason, when connecting rods are formed by joining a plurality of members, the strength of the joints decreases, and sufficient strength cannot be obtained. Further, if the connecting rod is made thick to compensate for the reduced strength and the cross-sectional area of the joint portion is increased, the weight is increased correspondingly, and the advantage of using different metal materials cannot be obtained.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a connecting rod that has excellent mechanical characteristics for each part and can be sufficiently reduced in weight, and a method for manufacturing the connecting rod. is there.

  The connecting rod according to the present invention has a rod main body, a small end provided at one end of the rod main body, and a large end provided at the other end of the rod main body. Is a connecting rod that includes a rounded portion that curves toward the rod body, and the large end is formed of a metal material having a composition different from that of the rod body and is joined to the rod body. The joint portion between the large end portion and the rod main body portion is located closer to the small end portion than the end of the round portion on the rod main body side, thereby achieving the above object. Is done.

  In a preferred embodiment, the rod main body portion is made of a material having a specific gravity smaller than that of the large end portion.

  In a preferred embodiment, the large end and the rod body are joined by friction welding.

  In a preferred embodiment, the small end portion and the rod main body portion are made of a material having a specific strength higher than that of the large end portion.

  In a preferred embodiment, the small end portion and the rod body portion are made of a titanium alloy, an aluminum alloy, or a magnesium alloy.

  In a preferred embodiment, the small end portion and the rod main body portion are formed of maraging steel, alloy steel, or carbon steel.

  In a preferred embodiment, the large end is formed of high carbon steel, non-tempered steel or sintered forged material.

  In a preferred embodiment, the large end portion is made of an iron alloy, and the small end portion and the rod body portion are made of a titanium alloy.

  In a preferred embodiment, the average carbon content from the surface of the large end part to a depth of 0.2 mm is less than 0.3% by mass, and the joining portion is located from the end of the round part on the rod body part side. The distance to is 3 mm or more.

  In a preferred embodiment, the average carbon content from the surface of the large end portion to a depth of 0.2 mm is 0.3% by mass or more and 0.5% by mass or less, and the rod body side of the rounded portion The distance from the end to the joint location is 5 mm or more.

  In a preferred embodiment, the average carbon content from the surface of the large end part to a depth of 0.2 mm exceeds 0.5% by mass, from the end of the round part on the rod main body side to the joining point. The distance is 7 mm or more.

  The internal combustion engine by this invention is provided with the connecting rod which has said structure.

  A motor vehicle according to the present invention includes an internal combustion engine having the above-described configuration.

  A connecting rod manufacturing method according to the present invention is a connecting rod manufacturing method having a rod main body, a small end provided at one end of the rod main body, and a large end provided at the other end of the rod main body. Preparing a first member formed of a first metal material; preparing a second member formed of a second metal material having a composition different from that of the first metal material; And the step of joining the first member and the second member by direct acting friction welding, whereby the above object is achieved.

  In a preferred embodiment, the large end portion includes a rounded portion that is curved so as to dent toward the rod main body portion, and the joining step includes joining portions of the first member and the second member. However, it is performed so that it may be located in the said small end part side rather than the end by the side of the said rod main body part of the said round part.

  In a preferred embodiment, the large end portion has a through hole through which a crank pin is inserted, and the joining step includes connecting the first member and the second member to a central axis of the through hole. It is performed so as to rub along the direction orthogonal to the direction and the direction in which the rod main body extends.

  In a preferred embodiment, the large end portion has a through hole through which a crank pin is inserted, and the joining step connects the first member and the second member in the direction of the central axis of the through hole. It is done so as to rub along.

  In the connecting rod according to the present invention, the small end portion, the rod main body portion, and the large end portion are formed of metals having different compositions. Therefore, different mechanical characteristics can be realized in the small end part and the rod main body part and the large end part, and excellent mechanical characteristics can be imparted to each part of the connecting rod.

  In the connecting rod according to the present invention, the joining portion between the large end and the rod main body is located closer to the small end than the end of the rounded portion of the large end on the rod main body side. As described above, in the connecting rod according to the present invention, since the joint portion is provided at a position shifted from the end of the rounded portion where stress is most concentrated, it is necessary to increase the cross-sectional area of the joint portion in order to compensate for a decrease in strength due to the joint. Less is. Therefore, it is possible to achieve a sufficient weight reduction while ensuring excellent mechanical characteristics.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, this invention is not limited to the following embodiment.

  In FIG. 1, the connecting rod 1 in this embodiment is shown. As shown in FIG. 1, the connecting rod 1 includes a rod-shaped rod body portion 10, a small end portion 20 provided at one end of the rod body portion 10, and a large end portion 30 provided at the other end of the rod body portion 10. And have.

  A through hole (referred to as a “piston pin hole”) 25 through which the piston pin passes is formed in the small end portion 20. On the other hand, a through-hole (referred to as “crank pin hole”) 35 through which the crank pin is passed is formed in the large end portion 30. The crank pin hole 35 is typically larger in diameter than the piston pin hole 25.

  In the following description, the extending direction of the rod body 10 is referred to as “longitudinal direction”, and the direction of the central axis of the crankpin hole 35 is referred to as “axial direction”. A direction orthogonal to the longitudinal direction and the axial direction is referred to as a “width direction”. In the drawings, the longitudinal direction is indicated by an arrow Z, the axial direction is indicated by an arrow X, and the width direction is indicated by an arrow Y.

  As shown in FIG. 2, the large end portion 30 is divided into a rod portion 33 that is continuous with the end of the rod body portion 10 and a cap portion 34 that is coupled to the rod portion 33 by a bolt 40. It is preferable that the rod part 33 and the cap part 34 are divided | segmented by the fracture | rupture division method. The fracture splitting method is a construction method in which the rod portion 33 and the cap portion 34 are integrally formed and then split by brittle fracture. According to this construction method, fine irregularities are complementarily formed on the fracture surface F of the rod portion 33 and the cap portion 34 by brittle fracture. Since the fracture surface F of the rod portion 33 and the cap portion 34 has complementary irregularities, the rod portion 33 and the cap portion 34 are accurately positioned. Moreover, when the unevenness | corrugation of the torn surface F fits, the coupling | bonding of the rod part 33 and the cap part 34 becomes firmer, and the rigidity of the big end part 30 whole improves.

  The connecting rod 1 in the present embodiment is different from the conventional connecting rod in that the large end 30 is formed of a metal having a composition different from that of the small end 20 and the rod body 10 and is joined to the rod body 10. Yes. In FIG. 1 and FIG. 2, a joint portion between the large end portion 30 and the rod main body portion 10 is indicated by a reference symbol W.

  Fatigue strength is not so important for the large end portion 30 of the connecting rod 1, and it is required to have high rigidity and high elastic modulus. In addition, when the above-described fracture splitting method is used, it is also important that brittle fracture is easy. On the other hand, the small end 20 and the rod main body 10 are required to have higher fatigue strength than high rigidity and high elastic modulus. In the conventional connecting rod, since all the parts are integrally formed using the same material, it has been difficult to satisfy all the preferable conditions described above.

  In the present embodiment, since the large end portion 30 is formed of a metal having a composition different from that of the small end portion 20 and the rod main body portion 10, excellent mechanical characteristics can be realized for each portion of the connecting rod 1. Specifically, the large end portion 30 is formed of a metal material having high rigidity and a high elastic modulus (and easy to break and divide), and the small end portion 20 and the rod main body portion 10 are made of a metal material having high fatigue strength. By forming it, it is possible to have a distribution preferable for the mechanical characteristics of the connecting rod 1 (a distribution not obtained with a conventional connecting rod). Further, by forming the small end portion 20 and the rod main body portion 10 from a metal material having a specific gravity (density) smaller than that of the large end portion 30, the entire connecting rod 1 can be reduced in weight while ensuring the rigidity of the large end portion 30. be able to. For example, by forming the large end portion 30 from an iron alloy and forming the small end portion 20 and the rod main body portion 10 from a titanium alloy, the connecting rod 1 having a light weight and excellent mechanical properties can be obtained.

  The connecting rod 1 in the present embodiment is further characterized in the position of the joining point W between the large end 30 and the rod main body 10. As shown in FIG. 1, the large end portion 30 includes a rounded portion 30 </ b> R that is curved so as to dent toward the rod main body portion 10 (that is, indented inward). End (end on the rod body 10 side) RE is located closer to the small end 20 than RE.

  In order to obtain the maximum weight reduction effect by using a metal material having a specific gravity (density) smaller than that of the large end portion 30 as the material of the small end portion 20 and the rod main body portion 10, joining is performed at the end RE of the round portion 30R. It seems that it is preferable to perform (that is, the end RE of the rounded portion 30R and the joint portion W are matched). However, when a plurality of members are joined to each other, the strength of the joint location W is reduced. Therefore, when joining is performed at the end RE of the rounded portion 30R where the stress is applied most in the connecting rod 1, the joint location is compensated for the lack of strength. It is necessary to increase the cross-sectional area of W. Therefore, the weight increases correspondingly and sufficient weight reduction cannot be performed.

  On the other hand, when the joint location W is provided at a position shifted from the end RE of the rounded portion 30R where stress is most concentrated as in the present embodiment, the cross-sectional area of the joint location W is reduced in order to compensate for a decrease in strength due to joining. There is little need to increase. Therefore, it is possible to achieve a sufficient weight reduction while ensuring excellent mechanical characteristics.

  Considering the change in the cross-sectional area of the connecting rod 1 along the direction from the small end portion 20 toward the large end portion 30 (longitudinal direction Z in FIG. 1), the rod main body portion 10 has a large end from the small end portion 20 side. The cross-sectional area increases at a constant rate toward the part 30 side. Therefore, typically, the end RE of the rounded portion 30R is defined as a portion where the increase rate of the cross-sectional area changes (becomes higher) from a certain value.

  The large end 30 and the rod main body 10 can be joined using various methods, but it is preferable to perform the friction welding. Friction welding is a technique in which members to be joined are rubbed together at a high speed and the members are softened by the generated frictional heat and simultaneously applied with pressure. Of course, a fusion welding method may be used, but if different materials are joined using the fusion welding method, a brittle alloy or an intermetallic compound may be formed. According to the friction welding, since formation of such a brittle alloy or an intermetallic compound can be suppressed, it is possible to suitably perform the bonding for various combinations of different materials. In addition, a method (welding, brazing, etc.) using an intermediate material (third member) may be used for joining, but according to the friction welding method, a different metal material is used compared to a method using such an intermediate material. It is easy to join each other with high strength.

  Further, according to the friction welding, since the joining can be performed with a high positional accuracy (specifically, with an accuracy of about 0.05 mm), it is possible to further reduce the weight. In the conventional connecting rod, since all the parts are integrally forged, it is difficult to form the piston pin hole and the crankpin hole while maintaining a three-dimensional positional relationship with high accuracy. For this reason, it is necessary to make the connecting rod thick in consideration of such misalignment. For example, it is necessary to increase the minimum thickness Tmin of the small end portion shown in FIG. 3A and the allocations A1 and A2 shown in FIG. On the other hand, according to the friction welding, such a positional shift can be reduced. Specifically, the positional deviation that has conventionally been about 0.2 mm in the axial direction X and about 0.3 mm in the width direction Y and the longitudinal direction Z can be reduced to about 0.05 mm. Therefore, it is not necessary to make the connecting rod 1 thick in view of the deviation, and further weight reduction can be achieved. If the reciprocating weight is reduced by reducing the weight of the connecting rod 1, the weight of the crankshaft and the balancer can also be reduced, so that the internal combustion engine and the entire vehicle can be reduced in weight.

  In addition, according to the friction welding, since there are few voids at the joint W and there is no need to use an intermediate material, heat conduction from the small end 20 to the large end 30 is improved. Furthermore, since no intermediate material is required, it is easy to simplify the equipment for performing the joining process and to automate the joining process.

  Friction welding is largely divided into rotary friction welding, in which one (or both) of the members to be joined is rotated, and linear friction welding, in which one of the members to be joined is linearly reciprocated as shown in FIG. Although it is different, since the connecting rod 1 generally does not have a circular cross section, it is preferable to use a linear friction welding.

  In addition, even if it joins by friction welding, since the metal structure of the joining location W changes, the intensity | strength of the joining location W will fall somewhat. However, by shifting the position of the joint location W from the rounded portion end RE (location where stress is most concentrated) as in the present embodiment, it is less necessary to increase the cross-sectional area to compensate for the strength reduction. Further, the longer the distance D (see FIG. 1) from the end RE of the rounded portion 30R to the joint location W, the less the influence of the rounded portion end RE is affected by the change in the metal structure due to the joint, and the fatigue strength at the rounded portion end RE. Reduction can be suppressed. Hereinafter, in the case where the large end portion 30 is formed from an iron alloy and the small end portion 20 and the rod main body portion 10 are formed from a titanium alloy, a preferable range of the distance D from the round end RE to the joining point W is specifically described. explain.

  Table 1 shows the weight (g) of the whole connecting rod, the Vickers hardness (HV) at the depth 0.1 mm of the radius portion end RE, and the fatigue strength of the radius portion end RE when the distance D (mm) is changed. (MPa). The data shown in Table 1 uses an iron alloy (steel) having an average carbon content of less than 0.3% by mass from the surface to a depth of 0.2 mm as the material of the large end portion 30, and the small end. As a material for the portion 20 and the rod body portion 10, a titanium alloy having a composition of Ti-6Al-4V (that is, containing about 6 mass% Al and about 4 mass% V) is used.

  First, paying attention to the weight of the connecting rod 1, it can be seen that the weight of the connecting rod 1 is smaller as the distance D is shorter. This is because the shorter the distance D, the more parts are formed from the titanium alloy.

  However, paying attention to the hardness and fatigue strength of the rounded portion end RE, it can be seen that when the distance D is too short, the hardness of the rounded portion end RE is low and the fatigue strength is low. This is because if the distance D is too short, the rounded end RE is affected by the change in the metal structure at the joint W.

  Table 1 shows the weight of the connecting rod 1 (referred to as “adjusted weight”) when the cross-sectional area of the joint W is adjusted (specifically increased) so that a favorable fatigue strength is obtained at the rounded end RE. It also shows. Focusing on this adjusted weight, it can be seen that if the distance D is too short, the weight will increase.

  FIG. 5 shows the relationship between the distance D from the rounded portion end RE to the joining point W, the fatigue strength of the rounded portion end RE, and the adjusted weight of the connecting rod 1.

  From FIG. 5, it can be seen that the fatigue strength improves as the distance D increases, and that the fatigue strength takes a substantially constant value when the distance D is 3 mm or more. This means that when the distance D is set to 3 mm or more, the rounded portion end RE is hardly affected by the change in the metal structure at the joint location W. Further, in correspondence with this, it can be seen that as the distance D becomes longer, the adjustment weight becomes smaller, and by making the distance D 3 mm or more, the effect of reducing the weight can be sufficiently obtained. Since the weight when the entire connecting rod 1 is made of steel is 338 g as shown in Table 1, in the case exemplified here, the distance D is set to 3 mm or more, so that the weight is reduced by about 20%. Can be achieved. As can be seen from FIG. 5, even if the distance D is less than 3 mm, if it is sufficiently close to 3 mm (for example, 2.5 mm or more), a practically sufficient lightening effect can be obtained.

  Subsequently, in Table 2 and FIG. 6, as a material of the large end portion 30, an iron alloy (steel) having an average carbon content from the surface to a depth of 0.2 mm of 0.3% by mass to 0.5% by mass. The data when using is shown. About the material of the small end part 20 and the rod main-body part 10, it is the same as the connecting rod which showed the data in Table 1 and FIG.

  From Table 2 and FIG. 6, it can be seen that the fatigue strength improves as the distance D increases, and that the fatigue strength takes a substantially constant value when the distance D is 5 mm or more. Further, it can be seen that as the distance D becomes longer, the adjustment weight becomes smaller, and by making the distance D 5 mm or more, the effect of reducing the weight can be sufficiently obtained. Therefore, in this case, by setting the distance D from the rounded portion end RE to the joint location W to be 5 mm or more, the fatigue strength of the rounded portion end RE can be secured sufficiently high, and sufficient weight reduction can be achieved. . Of course, as can be seen from FIG. 6, even if the distance D is less than 5 mm, if it is sufficiently close to 5 mm (for example, 4.5 mm or more), a practically sufficient lightening effect can be obtained.

  Moreover, in Table 3 and FIG. 7, the data when using the iron alloy (steel) whose average carbon content from the surface to the depth of 0.2 mm exceeds 0.5 mass% as a material of the large end part 30 are used. Show. About the material of the small end part 20 and the rod main-body part 10, it is the same as the connecting rod which showed the data in Table 1 and FIG.

  From Table 3 and FIG. 7, it can be seen that the fatigue strength improves as the distance D increases, and that the fatigue strength takes a substantially constant value when the distance D is 7 mm or more. Further, it can be seen that as the distance D becomes longer, the adjustment weight becomes smaller, and by making the distance D 7 mm or more, a light weight effect can be sufficiently obtained. Therefore, in this case, by setting the distance D from the rounded portion end RE to the joint location W to be 7 mm or more, the fatigue strength of the rounded portion end RE can be secured sufficiently high, and sufficient weight reduction can be achieved. . Of course, as can be seen from FIG. 7, even if the distance D is less than 7 mm, if it is sufficiently close to 7 mm (for example, 6.5 mm or more), a practically sufficient weight reduction effect can be obtained.

  As specifically shown in Tables 1 to 3 and FIGS. 5 to 7, in the connecting rod 1 according to the present invention, the connecting rod 1 can be reduced in weight by intentionally shifting the joining portion W toward the small end portion 20. An unexpected effect is obtained.

  In any case, there is no particular upper limit to the distance D. However, if the distance D is too long, the number of portions formed from the titanium alloy is reduced and an extra weight is increased. Therefore, the distance D is preferably 10 mm or less.

  Next, the manufacturing method of the connecting rod 1 in this embodiment is demonstrated.

  First, as shown in FIG. 8A, a first member P1 including a small end portion 20 and a rod main body portion 10 and formed of a titanium alloy is prepared. Separately from this, a second member P2 including a large end portion 30 and made of an iron alloy as shown in FIG. 8B is prepared. The first member P1 and the second member P2 can be formed by various known methods including a forging process, a machining process, a heat treatment process, and the like.

  Next, the prepared first member P1 and second member P2 are joined by direct acting friction welding. FIG. 9 shows a friction welding apparatus 50 for performing linear friction welding.

  The friction welding apparatus 50 includes a first holder 51 that holds the first member P1, a second holder 52 that holds the second member P2, an actuator 53 connected to the first holder 51, and a second holder. The hydraulic cylinder 54 connected to 52 is provided. As the actuator 53, for example, a hydraulic servo type or an electric motor type is used. While the first member P1 is reciprocated linearly by the actuator 53, the second member P2 is brought into pressure contact with the first member P1 by the hydraulic cylinder 54, whereby friction welding is performed. The second member P2 is joined. This joining process is performed so that the joining location W between the first member P1 and the second member P2 is located closer to the small end portion 20 than the end RE on the rod body portion 10 side of the round portion 30R. After joining, the connecting rod 1 is completed by cutting the burr | flash of the joining location W. FIG.

  FIG. 10 shows an example of the first holder 51 and the second holder 52. The first holder 51 shown in FIG. 10 firmly holds the first member P1 by the pin 55 inserted through the piston pin hole 25 and the clamp 56 that presses the rod main body 10 from both sides. Further, the second holder 52 shown in FIG. 10 firmly holds the second member P <b> 2 by the pin 57 inserted through the crank pin hole 35 and the bolt 58 inserted into the bolt hole of the large end 30. .

  Here, a preferable vibration direction of the first member P1 in the joining step will be described with reference to FIGS. 11 (a) and 11 (b). FIGS. 11A and 11B are views showing a cross section of the rod main body 10 and a preferable vibration direction.

  In the joining process, as shown in FIG. 11A, the first member P1 and the second member P2 are rubbed together along the width direction D1 of the connecting rod 1 (corresponding to the direction Y in FIG. 1). Preferably, it is done. Since the width direction D1 is a direction having the highest moment (that is, high rigidity) in a plane parallel to the joining surface, the first member P1 is vibrated along the width direction D1, thereby elastic deformation at the time of joining. And plastic deformation can be reduced. Therefore, the amplitude required at the time of joining can be reduced, and the joining accuracy can be improved.

  Alternatively, the joining step is performed so that the first member P1 and the second member P2 are rubbed along the axial direction D2 (corresponding to the direction X in FIG. 1), as shown in FIG. It is preferable. Since the axial direction D2 is the direction having the lowest moment (that is, the rigidity is low) in the plane parallel to the joining surface, the member is elastic at the time of joining by vibrating the first member P1 along the axial direction D2. It becomes easy to deform. For this reason, the joining surfaces can be easily blended, and the gap at the joining portion W is reduced. Therefore, the bonding strength can be improved.

  Whether the first member P1 is vibrated in the width direction D1 or the width direction D2 depends on the shape and material of the member in the vicinity of the joining point W, required performance (for example, which of the joining accuracy and joining strength is important), and the like. What is necessary is just to set suitably according to.

  Although the manufacturing method has been described as an example in which the first member P1 is vibrated, it is needless to say that the second member P2 may be vibrated instead of the first member P1.

  Subsequently, a preferable cross-sectional shape in the vicinity of the joint portion W will be described with reference to FIGS. 12 and 13.

  As shown in FIGS. 12A and 12B, when the cross-sectional shape at the joint W is an H shape, the weight can be reduced without reducing the buckling strength (cross-sectional moment). Further, as shown in FIGS. 13A and 13B, if the cross-sectional shape at the joint location W is substantially rectangular, the area of the joint surface can be increased without reducing the buckling strength (cross-section moment). Can be improved.

  In the present embodiment, the case where the small end portion 20 and the rod main body portion 10 are formed from a titanium alloy and the large end portion 30 is formed from an iron alloy (steel) is illustrated, but the present invention is not limited to this. Absent.

  The small end portion 20 and the rod main body portion 10 are preferably formed of, for example, a titanium alloy, an aluminum alloy, or a magnesium alloy. Since these metal materials have high specific strength, the connecting rod 1 can be reduced in weight by using these metal materials.

  In the conventional connecting rod, when the small end portion and the rod main body portion are formed from these metal materials, the large end portion is necessarily formed from these metal materials. Since the above metal material is relatively expensive, the use of such an expensive material in spite of the fact that a high specific strength is not required at the large end portion increases the manufacturing cost. Moreover, when it is going to ensure equivalent mechanical strength using said metal material, a large end part will become large and the manufacturing cost will also rise by this.

  According to the present invention, since the large end 30 is formed of a metal material having a composition different from that of the small end 20 and the rod main body 10, only the small end 20 and the rod main body 10 are made of a titanium alloy, an aluminum alloy or a magnesium alloy. Therefore, the amount of use of these expensive metal materials can be reduced by the amount of the large end portion 30 as compared with the prior art. Therefore, the manufacturing cost can be reduced. Particularly when connecting rods are formed by forging, conventionally, the yield of the material of the portion that becomes the small end portion is low in order to match the size of the large end portion. The present invention is also effective in improving the yield.

  Further, when the large end portion is formed of a titanium alloy, an aluminum alloy, or a magnesium alloy, seizure is likely to occur due to sliding with the crank side surface, so that surface treatment or use of a thrust washer is required. According to the present invention, it is less necessary to perform surface treatment or use a thrust washer.

  Or it is also preferable that the small end part 20 and the rod main-body part 10 are formed from maraging steel, alloy steel, or carbon steel. Since these metal materials have high fatigue strength, they are preferably used as materials for the small end portion 20 and the rod main body portion 10.

  In the conventional connecting rod, when the small end portion and the rod main body portion are formed from these metal materials, the large end portion is necessarily formed from these metal materials. The above metal materials are difficult to process after heat treatment, so even if high fatigue strength is not required at the large end, using such a material will result in a large end that requires more work than a small end. It becomes difficult to process.

  According to the present invention, the large end portion 30 can be easily processed by forming only the small end portion 20 and the rod main body portion 10 from maraging steel, alloy steel, or carbon steel. Further, since these metal materials are also relatively expensive, it is not necessary to use these metal materials for the large end portion 30, thereby reducing the manufacturing cost.

  The large end portion 30 is preferably formed of, for example, high carbon steel, non-tempered steel, or sintered forged material. Since these metal materials have a high elastic modulus and high brittleness, they can be easily broken and divided.

  In the conventional connecting rod, when the large end portion is formed from these metal materials, the small end portion and the rod main body portion are inevitably formed from these metal materials. Since the above metal materials have relatively low fatigue strength, fatigue breakage becomes a problem when the small end portion and the rod main body portion are formed of these metal materials.

  According to the present invention, only the large end portion 30 is formed from high carbon steel, non-tempered steel, or sintered forged material, so that fatigue failure of the small end portion 20 and the rod main body portion 10 does not become a problem. If the large end portion 30 is formed from the metal material that can be easily broken and divided, the breaking and dividing step can be simplified. Specifically, it is possible to omit the cooling process, simplify the creation of the fracture start groove, and reduce the output of the fracture equipment. Moreover, when the large end part 30 is formed from the said metal material which has a high elasticity coefficient, a deformation | transformation of the large end part 30 will be suppressed, As a result, the seizure in the large end part 30 will become difficult to occur.

  In this embodiment, as an example of a combination of metal materials having different compositions, a combination of alloys having different base metals is shown, but the combination of metal materials is not limited to this. A combination of alloy materials having the same base metal may be used. For example, a combination of iron alloys such as SCM435 and maraging steel may be used.

  Moreover, in this embodiment, although friction welding was illustrated as a preferable method of joining the big end part 30 and the rod main-body part 10, it is also preferable to use an electron beam welding method or a laser welding method. In these methods, since the amount of melting is small, it is difficult to generate brittle alloys and intermetallic compounds that reduce the strength, and it is not necessary to use an intermediate material (third member), so even if these methods are used, The large end portion 30 and the rod main body portion 10 formed of metal materials having different compositions can be suitably joined. Further, when the electron beam welding method or the laser welding method is used, since the workpiece is not moved, an advantage that the positional accuracy can be further improved (specifically, up to about 0.01 mm) can be obtained. Further, there is an advantage that the joining process can be easily automated.

  Moreover, although the split type connecting rod is exemplified in the present embodiment, the present invention is also suitably used for a connecting rod of a type in which the large end portion is not split.

  The connecting rod 1 in this embodiment is widely used in various internal combustion engines (engines) for motor vehicles and machines. In FIG. 14, an example of the engine 100 provided with the connecting rod 1 in this embodiment is shown.

  The engine 100 includes a crankcase 110, a cylinder block 120, and a cylinder head 130.

  A crankshaft 111 is accommodated in the crankcase 110. The crankshaft 111 has a crankpin 112 and a crank web 113.

  A cylinder block 120 is provided on the crankcase 110. The cylinder block 120 is fitted with a cylindrical cylinder sleeve 121, and the piston 122 is provided so as to reciprocate within the cylinder sleeve 121.

  A cylinder head 130 is provided on the cylinder block 120. The cylinder head 130 forms a combustion chamber 131 together with the piston 122 and the cylinder sleeve 121 of the cylinder block 120. The cylinder head 130 has an intake port 132 and an exhaust port 133. An intake valve 134 for supplying air-fuel mixture into the combustion chamber 131 is provided in the intake port 132, and an exhaust valve 135 for exhausting the combustion chamber 131 is provided in the exhaust port. .

  Piston 122 and crankshaft 111 are connected by connecting rod 1. Specifically, the piston pin 123 of the piston 122 is inserted into the through hole (piston pin hole) of the small end portion 20 of the connecting rod 1, and the crankshaft 111 is inserted into the through hole (crank pin hole) of the large end portion 30. The crank pin 112 is inserted, whereby the piston 122 and the crankshaft 111 are connected. A bearing metal 114 is provided between the inner peripheral surface of the through hole of the large end portion 30 and the crank pin 112. The bearing metal 114 is locked by a bearing locking groove.

  Since the connecting rod 1 in the present embodiment can achieve a sufficient weight reduction as described above, the blow-up of the engine 100 can be improved and the fuel consumption can be reduced.

  FIG. 15 shows a motorcycle including the engine 100 shown in FIG.

  In the motorcycle shown in FIG. 15, a head pipe 302 is provided at the front end of the main body frame 301. A front fork 303 is attached to the head pipe 302 so as to be able to swing in the left-right direction of the vehicle. A front wheel 304 is rotatably supported at the lower end of the front fork 303.

  A seat rail 306 is attached so as to extend rearward from the upper rear end of the main body frame 301. A fuel tank 307 is provided on the main body frame 301, and a main seat 308 a and a tandem seat 308 b are provided on the seat rail 306.

  A rear arm 309 extending rearward is attached to the rear end of the main body frame 301. A rear wheel 310 is rotatably supported at the rear end of the rear arm 309.

  The engine 100 shown in FIG. 14 is held at the center of the main body frame 301. For the engine 100, the connecting rod 1 in the present embodiment is used. A radiator 311 is provided in front of the engine 100. An exhaust pipe 312 is connected to the exhaust port of the engine 100, and a muffler 313 is attached to the rear end of the exhaust pipe 312.

  A transmission 315 is connected to the engine 100. A drive sprocket 317 is attached to the output shaft 316 of the transmission 315. The drive sprocket 317 is connected to the rear wheel sprocket 319 of the rear wheel 310 via a chain 318. Transmission 315 and chain 318 function as a transmission mechanism that transmits the power generated by engine 100 to the drive wheels.

  Since the motorcycle shown in FIG. 15 includes the engine 100 using the connecting rod 1 in the present embodiment, suitable performance can be obtained.

  According to the present invention, there is provided a connecting rod that has excellent mechanical properties for each part and can be sufficiently reduced in weight.

  The connecting rod according to the present invention is widely used in various internal combustion engines (for example, engines for motor vehicles).

It is a top view which shows typically the connecting rod in suitable embodiment of this invention. It is a perspective view which shows typically the connecting rod in suitable embodiment of this invention. (A) is a figure which shows the minimum thickness of a small edge part, (b) is a figure which shows allocation. It is a figure for demonstrating direct-acting friction welding. It is a graph which shows the relationship between the distance from a round part end to a joining location, the fatigue strength of a round part end, and the adjustment weight of a connecting rod. It is a graph which shows the relationship between the distance from a round part end to a joining location, the fatigue strength of a round part end, and the adjustment weight of a connecting rod. It is a graph which shows the relationship between the distance from a round part end to a joining location, the fatigue strength of a round part end, and the adjustment weight of a connecting rod. (A) And (b) is a top view which shows typically the 1st member and 2nd member which are prepared in the manufacturing method of the connecting rod in this embodiment. It is a figure which shows typically the friction welding apparatus for performing direct acting friction welding. It is a figure which shows typically an example of the 1st holder and 2nd holder which a friction welding apparatus has. (A) And (b) is a figure for demonstrating the preferable vibration direction in a joining process. (A) is a top view which shows the joining location vicinity of a connecting rod, (b) is sectional drawing along the 12B-12B 'line in (a). (A) is a top view which shows the joining location vicinity of a connecting rod, (b) is sectional drawing along the 13B-13B 'line | wire in (a). It is sectional drawing which shows typically an example of the engine provided with the connecting rod in suitable embodiment of this invention. It is sectional drawing which shows typically the motorcycle provided with the engine shown in FIG. It is a top view which shows the conventional split type connecting rod typically.

Explanation of symbols

1 connecting rod 10 rod body portion 20 small end portion 25 piston pin hole 30 large end portion 30R round portion RE round portion end 33 rod portion 34 cap portion 35 crankpin hole 40 bolt W joint location 100 engine

Claims (17)

A rod main body, a small end provided at one end of the rod main body, and a large end provided at the other end of the rod main body, wherein the large end is the rod main body A connecting rod including a rounded portion curved so as to sag,
The large end is formed of a metal material having a composition different from that of the rod main body and joined to the rod main body.
A connecting rod where the large end portion and the rod main body portion are joined is located closer to the small end portion than the end of the round portion on the rod main body side.   The connecting rod according to claim 1, wherein the rod main body portion is formed of a material having a specific gravity smaller than that of the large end portion.   The connecting rod according to claim 1 or 2, wherein the large end portion and the rod main body portion are joined by friction welding.   The connecting rod according to any one of claims 1 to 3, wherein the small end portion and the rod main body portion are formed of a material having higher specific strength than the large end portion.   The connecting rod according to claim 1, wherein the small end portion and the rod main body portion are formed of a titanium alloy, an aluminum alloy, or a magnesium alloy.   The connecting rod according to any one of claims 1 to 3, wherein the small end portion and the rod main body portion are formed of maraging steel, alloy steel, or carbon steel.   The connecting rod according to any one of claims 1 to 6, wherein the large end portion is formed of high carbon steel, non-tempered steel, or sintered forged material.   The connecting rod according to any one of claims 1 to 3, wherein the large end portion is formed of an iron alloy, and the small end portion and the rod main body portion are formed of a titanium alloy. The average carbon content from the surface of the large end to a depth of 0.2 mm is less than 0.3% by mass,
The connecting rod according to claim 8, wherein a distance from an end of the round portion on the rod main body side to the joining portion is 3 mm or more. The average carbon content from the surface of the large end to a depth of 0.2 mm is 0.3% by mass or more and 0.5% by mass or less,
The connecting rod according to claim 8, wherein a distance from an end of the round portion on the rod main body side to the joining portion is 5 mm or more. The average carbon content from the surface of the large end to a depth of 0.2 mm exceeds 0.5% by mass,
The connecting rod according to claim 8, wherein a distance from an end of the rounded portion on the rod main body side to the joining portion is 7 mm or more.   An internal combustion engine comprising the connecting rod according to any one of claims 1 to 11.   A motor vehicle comprising the internal combustion engine according to claim 12. A method for manufacturing a connecting rod having a rod main body, a small end provided at one end of the rod main body, and a large end provided at the other end of the rod main body,
Providing a first member formed of a first metal material;
Providing a second member formed of a second metal material having a composition different from that of the first metal material;
Joining the first member and the second member by linear friction welding;
The manufacturing method of the connecting rod including this. The large end portion includes a rounded portion curved so as to dent toward the rod main body portion,
15. The joining step is performed such that a joining portion between the first member and the second member is located on the small end side with respect to the end of the round portion on the rod main body side. The manufacturing method of the connecting rod as described in any one of. The large end has a through hole through which the crank pin is inserted,
The joining step is performed so that the first member and the second member are rubbed together along a direction perpendicular to a central axis direction of the through hole and a direction in which the rod main body extends. The manufacturing method of the connecting rod of 14 or 15. The large end has a through hole through which the crank pin is inserted,
The connecting rod manufacturing method according to claim 14 or 15, wherein the joining step is performed so that the first member and the second member are rubbed together along a central axis direction of the through hole.