JP2006329250A - Connecting rod - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a connecting rod whose fretting wear can be properly prevented. <P>SOLUTION: The connecting rod 10 comprises a small end portion 20, a large end portion 30, and a connection portion 40 for connecting these to each other, the connection portion 40 having a reduced thickness on the surface. Side ends 42a, 42b of the reduced thickness 42 located on the side of the large end portion 30 are located between a straight line L1 which passes through the edge of a connecting rod bolt mounting hole 38 of the large end portion 30 on the center side of the connecting rod 10, and a straight line L2 which has contact with the inner peripheral face of a crank pin hole 32 of the large end portion 30 and passes through a predetermined combustion load point (a) on the side of the small end portion 20. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a connecting rod for connecting an engine piston and a crankshaft.

  The connecting rod generally includes a small end portion, a large end portion, and a connecting portion that connects them, and is configured to have a meat steal on the surface of the connecting portion. The weight is reduced. Some connecting rods having meat theft have a so-called I-shaped cross section. In such a connecting rod, not only the explosive force in the combustion chamber acts as a compressive force in the combustion / expansion stroke of each cylinder, but also the inertia force generated by the piston's own weight, etc. as the crankshaft rotates is the tensile force. It acts as a torsional force, and this causes a deformation mode in which the crank pin hole at the large end of the connecting rod and the piston pin hole at the small end are deformed into an oval shape. In particular, a large load is applied locally around the crank pin hole at the large end, and the load may not be applied uniformly, and there are places where the load is extremely concentrated, so-called fretting wear There is a problem that occurs. And if this fretting wear progresses, it will lead to fretting fatigue and the strength of the large end will decrease, which is not preferable.

  Therefore, in order to prevent such fretting wear, according to Patent Document 1, a connecting rod having a small end portion, a large end portion, and a connecting portion that connects the small end portion and the large end portion. In this case, it has been proposed to connect the large end portion to the connecting portion outside the plane in contact with the contact surface of the large end bearing parallel to the center plane passing through the center line and the center line of the small end portion. .

JP-A-5-240236

  However, even the one described in Patent Document 1 has a limit in preventing fretting wear, and a connecting rod that can more appropriately prevent fretting wear is desired.

  Accordingly, an object of the present invention is to provide a connecting rod that solves the above-described problems and can appropriately prevent fretting wear.

  In order to solve the above problems, a connecting rod according to the present invention includes a small end portion, a large end portion, and a connecting portion that connects the small end portion and the large end portion, and steals meat on the surface of the connecting portion. A connecting rod having a side end of the stealer located on the large end side, a straight line passing through an edge of the connecting rod bolt mounting hole of the large end portion on the connecting rod center side, and It is characterized by being positioned between a straight line passing through a predetermined combustion load point on the small end side and in contact with the inner peripheral surface of the crankpin hole.

  With the above configuration, the combustion load is exerted in a well-balanced manner around the crank pin hole at the large end, and the deformation at the large end becomes difficult to occur, so that it is possible to appropriately prevent the occurrence of fretting wear. .

  Preferably, the meat stealing is configured such that the amount of meat stealing increases from the side end toward the inside of the meat steal, whereby an inclined surface having a predetermined angle is formed at the side end of the meat stealing. It is formed. As a result, the thickness around the large end is not suddenly reduced, and the strength around the large end can be maintained, the deformation of the large end is suppressed, and the occurrence of fretting wear is suppressed. I can do it. The slope of the slope is preferably about 20 °.

  The combustion load point may be set to an end portion closest to the large end portion among the piston pin holes of the small end portion.

  According to the connecting rod of the present invention, it is possible to appropriately prevent fretting wear.

  Hereinafter, a connecting rod according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  1 is a front view of a connecting rod according to an embodiment of the present invention, FIG. 2 is a cross-sectional view taken along line AA in FIG. 1, and FIG. 3 is a cross-sectional view taken along line BB in FIG. 4 is an analysis result of the surface around the crank pin hole in the lower part of FIG.

  The connecting rod 10 in the present embodiment is applied to a reciprocating engine, and includes a small end portion 20, a large end portion 30, and a connecting portion 40 for connecting them, and the connecting portion 40 is used for stealing meat. 42. The meat stealer 42 is formed on the surfaces on both sides, that is, the front surface and the back surface thereof so that the cross-sectional shape of the connecting portion 40, which may also be referred to as a column portion, is an I-shaped cross section. In addition, the surface to which meat stealing is performed is not limited to both surfaces, and can be one surface.

  The small end portion 20 is provided with a piston pin hole 22, and a piston pin (not shown) is inserted into the piston pin hole 22, and the small end portion 20 and the piston are connected by the piston pin. On the other hand, a crankpin hole 32 is provided in the large end portion 30, and a crankpin (not shown) of a crankshaft is inserted into the crankpin hole 32. A metal bearing 34 as a connecting rod bearing is fitted into the inner surface of the crankpin hole 32, and a crankpin is rotatably fitted inside the metal bearing 34 to connect the large end 30 and the crankshaft. The connecting rod 10 is divided into two so as to horizontally divide the large end 30, one of which includes the small end 20, the connecting portion 40, and the upper half of the large end 30 to form the connecting rod body 12. The other is a connecting rod cap 36 attached to the connecting rod body 12 from below. The metal bearing 34 is similarly divided into two and is fitted into the crank pin hole 32. The connecting rod cap 36 is attached to the connecting rod body 12 by fastening the connecting rod bolt 50 to two connecting rod bolt mounting holes (hereinafter referred to as bolt holes) 38 provided on the left and right sides of the crankpin hole 32. .

  The connecting rod 10 in the present embodiment is made of a titanium alloy and has the meat steal 42 as described above. The meat stealer 42 is applied to almost the entire connecting portion 40 over a wide range from the small end portion 20 side to the large end portion 30 side, and on the large end portion 30 side, a thick portion 32a extending around the crankpin hole 32 is provided. It is given along the shape. Therefore, on the large end portion 30 side, the meat stealer 42 projects to the left and right, and the side ends 42a and 42b are formed at the outermost left and right positions. Here, each of the meat thefts 42 is a central plane extending in the thickness direction of the connecting rod 10 including the center line L0 of the connecting rod 10, that is, the center line of the small end 20 and the center line of the large end 30. It has a left-right symmetric shape. Therefore, only the left side end 42a with respect to the center plane will be described, and description of the right side end 42b will be omitted.

  The side end 42a of the meat stealer 42 is in contact with the connecting rod center side of the bolt hole 38, that is, the straight line L1 passing through the edge on the center plane side including the center line L0, and the inner peripheral surface of the crank pin hole 32 and is small. It is located between a straight line L2 passing through a predetermined combustion load point a on the end 20 side. That is, the side end 42 a of the meat steal 42 is in contact with the first flat surface extending in the thickness direction of the connecting rod 10 through the end of the bolt hole 38 on the center side of the connecting rod and the inner peripheral surface of the crankpin hole 32. At the same time, it is located between a second plane extending in the thickness direction of the connecting rod 10 through a predetermined combustion load point a on the small end 20 side.

  In the present embodiment, the side end 42a of the meat stealer 42 is located between the line L1 ′ from the center line L0 of the connecting rod 10 and the line L2 rather than the line L1. This is due to the fact that the machining hole 38a, which is a hole larger than the bolt hole 38, communicates with the upper end of the bolt hole 38 and is formed coaxially, so as to prevent the meat hole from being stealed. The meat stealer 42 is positioned on the inner side of the straight line L1 ′ passing through the end of the machining hole 38a on the connecting rod center side.

  The combustion load point a is an action point of force exerted from the crank pin to the large end 30 side of the connecting rod 10 in the combustion / expansion stroke of the engine. In the present embodiment, the combustion load point a is set at a position closest to the large end 30 in the piston pin hole 22 of the small end 20, and more specifically, a hole that forms the piston pin hole 22. A combustion load point a is set at a point where the surface and the center line L0 of the connecting rod 10 intersect. However, the combustion load point a may vary to some extent depending on the timing at which force is applied from the piston pin to the connecting rod 10, and can be set to any point within the range of such variation.

  2, the meat stealing 42 of the connecting rod 10 of the present embodiment is configured such that the amount of meat stealing gradually increases from the side end 42a toward the inside of the meat stealing 42. As a result, a slope 42c having a predetermined angle is formed in a region from the side end 42a of the meat stealing 42 to the inside of the predetermined distance, that is, the side end. That is, the thickness of the connecting rod 10 gradually increases from the side end 42a (also the side end 42b) in the region sandwiched between the lines L1 and L2 toward the aforementioned center plane, that is, the center line L0 of the connecting rod 10. Inclined so as to be thinner. The AA line in FIG. 1 is a substantially bisector of the side end of the meat steal 42. 1 and 2, it is understood that the inclined surface 42c is provided up to a point c that does not reach the center plane, and the bottom surface of the meat stealer is perpendicular to the center plane inside the connecting rod 10. This point c is an intersection of the line AA and the line L3 perpendicular to the line AA in FIG. 1, and the line L3 intersects the center line L0 in the meat steal 42. The angle α of the inclined surface 42c is preferably about 20 °. In FIG. 2, the thread is omitted.

  The shape and configuration of the connecting rod 10 according to the present embodiment have been described above. The effect is described below. FIG. 3 shows a cross-sectional view of the connecting rod 10 cut along the line BB in FIG. 1, in other words, a view of the connecting rod body 12 viewed from the connecting rod cap 36 side. However, the metal bearing 34 is omitted in FIG. Here, the analysis result for the hatched portion B2 in FIG. 3 is shown in FIG. FIG. 4 is a schematic representation of the stress distribution for rod stress up to several tons of maximum load using FEM analysis. In FIG. 4, r1 indicates a region where the stress is the least, and a region where the stress increases in the order of r1, r2, r3, r4, r5. According to FIG. 4, there is no place where a remarkably large stress acts on the hole surface defining the crank pin hole 32 of the large end 30, and particularly from the center line L 0 of the connecting rod 10 as shown in FIG. 1. It can be understood that a large stress does not act in the vicinity of the points p and q 45 ° apart from each other on the left and right, and the stress is distributed relatively uniformly. Therefore, the combustion load is exerted in a well-balanced manner around the crank pin hole 32 of the large end portion 30, and the large end portion 30 is hardly deformed. Therefore, it is possible to prevent fretting wear from occurring at the large end 30 while reducing the thickness of the thick part 32a around the large end 30 of the connecting rod 10 to some extent. Further, it is possible to prevent fretting fatigue due to fretting wear on the connecting rod 10 and to extend the life of the connecting rod 10. Further, this prevents the connecting portion 40 from being twisted and prevents an unnecessary force from being generated at the small end portion 20. For example, the piston pin C-ring with respect to the small end portion 20 is unlikely to drop off.

  Further, as described above, the connecting rod 10 has the slope 42c inward from the side ends 42a, 42b, so that the thickness around the large end 30 is not sharply reduced, and the larger end The strength around 30 can be maintained, and as a result, fretting wear is prevented from occurring. In addition, the connecting rod 10 can be reduced in weight by having the inclined surface 42c. For example, it has been verified that the titanium alloy connecting rod 10 according to the present embodiment can achieve a weight reduction of about 10% compared to a titanium alloy connecting rod that is generally used.

  As mentioned above, although this invention was demonstrated based on the said embodiment, this invention is not limited to this. For example, the connecting rod 10 may be made of a special steel such as nickel / chromium steel or chromium / molybdenum steel instead of a titanium alloy. Moreover, it is producible by means, such as forging, casting, and powder metallurgy. The application to the one-pin / one-piece connecting rod as in this embodiment is not limited, and the present invention can also be applied to a one-pin / two-piece connecting rod.

  In the above embodiment, the present invention has been described with a certain degree of concreteness, but various modifications and changes can be made to the present invention without departing from the spirit and scope of the invention described in the claims. It must be understood that. That is, the present invention includes modifications and changes that fall within the scope and spirit of the appended claims and their equivalents.

It is a front view of the connecting rod in the embodiment of the present invention. It is sectional drawing along the AA line of FIG. It is sectional drawing along the BB line of FIG. FIG. 4 is an analysis result of a surface around a crank pin hole at the bottom of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Connecting rod 12 Connecting rod main body 20 Small end part 22 Piston pin hole 30 Large end part 32 Crank pin hole 32a Thick part 34 Metal bearing 36 Connecting rod cap 38 Bolt hole 40 Connecting part 42 Meat stealing 42a, 42b Side end 50 Connecting rod bolt

Claims (3)

A connecting rod having a small end, a large end, and a connecting portion that connects the small end and the large end, and having a steal on the surface of the connecting portion,
The side end of the meat theft located on the large end side is a straight line passing through the connecting rod center side edge of the connecting rod bolt mounting hole of the large end portion, and the inner periphery of the crank pin hole of the large end portion The connecting rod is located between a straight line that contacts a surface and passes through a predetermined combustion load point on the small end side.   The meat stealing is configured such that the amount of meat stealing increases from the side end toward the inside of the meat steal, whereby a slope with a predetermined angle is formed at the side end of the meat stealing. The connecting rod according to claim 1.   The connecting rod according to claim 1, wherein the combustion load point is set at an end portion closest to the large end portion among piston pin holes of the small end portion.

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