JP2003172101A - Crank mechanism of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To allow a significant offset required from a request for fuel economy in a crank mechanism of an internal combustion engine. <P>SOLUTION: In an offset crank mechanism, an external shape of a connecting rod 10 is bent in an almost V shape. The external shape of the connecting rod 10 may be bent as a whole, and one side (a side surface faced to the offset side) may be only bent in a recessed shape by making a side surface shape different on the respective sides. Such a V-shaped rod 10 can also be applied to a V-type multicylinder engine. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crank mechanism of an internal combustion engine in which the center line of a crankshaft is offset from the centerline of a cylinder. To improve the connecting rod shape to achieve a specified amount of offset.

[0002]

2. Description of the Related Art Conventionally, in an internal combustion engine, a method of offsetting a crankshaft center line from a cylinder center line has been adopted in order to reduce frictional resistance between a piston and a cylinder block. In other words, by offsetting the crankshaft centerline so that the connecting rod becomes almost parallel to the cylinder centerline at the timing when the combustion pressure becomes maximum (to minimize the inclination angle of the connecting rod with respect to the cylinder centerline), the expansion stroke In this case, the generation of an external force that acts laterally with respect to the piston is suppressed as much as possible (Japanese Patent Application Laid-Open No. 20-200200).
No. 01-207854).

[0003]

According to the offset crank mechanism disclosed in the above publication, the frictional resistance is reduced,
While preventing wear of the piston ring and cylinder block, the lateral pressure on the inner surface of the cylinder block (in some cases, the inner surface of the liner) is reduced, and the combustion pressure is efficiently converted to torque, which improves fuel efficiency. it can.

By the way, the offset amount of the crankshaft centerline with respect to the cylinder centerline (in other words, the offset amount of the cylinder centerline with respect to the crankshaft centerline) must be set to some extent large in view of fuel consumption requirements. I know. However, if the offset amount is increased, the connecting rod is brought closer to the cylinder. Therefore, in the conventional offset crank mechanism in which the piston pin and the crank pin are connected in a straight line by the straight connecting rod, the connecting rod and the cylinder interfere with each other and the movement of the connecting rod is restricted. . Therefore, at present, the amount of offset required from the viewpoint of fuel consumption has not been completely realized.

Further, even if the cylinder is newly designed, certain restrictions are imposed on the cylinder shape due to requirements from other engine components such as the layout of the intake and exhaust systems. Therefore, it is difficult to increase the offset amount by newly providing a relief on the cylinder side for avoiding a collision with the connecting rod in correspondence with the offset. In addition, JP-A-5
In Japanese Patent Laid-Open No. 0-125305, a connecting rod that drives a piston of a reciprocating compressor is bent in a dogleg shape.

However, if the bending structure disclosed in the above publication is applied to an offset crank mechanism, the direction in which the connecting rod is bent is the direction in which collision with the cylinder block is avoided for one connecting rod, but the cylinder for the other connecting rod. Since the degree of interference with the block is rather large, the offset amount cannot be set large.

The present invention has been made in view of the above circumstances, and an object thereof is to improve a connecting rod in a crank mechanism of an internal combustion engine in terms of a shape to enable a large crank offset. . The present invention particularly aims to realize the required amount of crank offset in view of fuel consumption requirements.

[0008]

For this reason, in the invention described in claim 1, in the crank mechanism of the internal combustion engine in which the crankshaft center line is offset with respect to the cylinder center line, the outer shape of the connecting rod is offset. The side surface facing the side is bent in a concave shape between the small end portion and the large end portion of the connecting rod.

As described above, in the conventional crank mechanism, the connecting rod and the cylinder block interfere with each other due to the offset, and the offset amount is limited to a small value.
Therefore, according to the present invention, as described above, the specific side surface of the connecting rod is bent to have a concave cross section so that the connecting rod moves while avoiding the cylinder, so that the restriction on the offset is relaxed (including the case where it is released). I chose

According to the second aspect of the present invention, in addition to bending the specific side surface of the connecting rod so as to have a concave cross section, the connecting rod itself is bent so as to be convex in a direction opposite to the offset direction. According to the invention of claim 3, in the crank mechanism of an internal combustion engine in which the center line of the crankshaft is offset from the centerline of the cylinder, the center axis of the connecting rod is bent so as to be convex in a direction opposite to the offset direction. Then, it was decided to form this connecting rod into a generally V shape.

As described above, in the conventional crank mechanism, the amount of offset is limited to a small amount due to mutual interference between the connecting rod and the cylinder. In this case, the connecting rod is moved so as to avoid the cylinder so that the restriction on the offset is relaxed (including the case where it is released).

According to the fourth aspect of the invention, the offset direction is set so that the crankpin center line intersects with the cylinder center line during the expansion stroke. According to a fifth aspect of the present invention, the above crank mechanism has a plurality of cylinders with V
The present invention is applied to a multi-cylinder engine arranged in a character shape, and the crankshaft center line is offset with respect to each cylinder center line.

[0013]

According to the invention of claim 1, since the specific side surface of the connecting rod is bent to have a concave cross section, the restriction on the crank offset is relaxed, so that the offset amount can be made larger than ever. it can. And, by extension, it is possible to realize a large offset required from the viewpoint of fuel consumption.

Further, (when the layout permits), the space for the escape of the connecting rod to be provided on the cylinder side can be reduced, or it can be offset without providing this space itself. Therefore, since no additional processing is required, the manufacturing cost can be reduced, and the internal combustion engine (in particular, the cylinder block) can be made compact.

According to the second aspect of the invention, by bending the entire connecting rod and bending the specific side surface, it is possible to ensure a uniform width of the connecting rod, so that the strength of the connecting rod can be ensured. According to the invention of claim 3, since the connecting rod is formed in a substantially V shape, the offset amount can be made larger than ever, and
The space for escape of the connecting rod that should be provided on the cylinder side can be reduced (including the case where it is omitted) to save space.

According to the invention of claim 4, the external force acting laterally on the piston due to the combustion pressure can be suppressed to an extremely small value, so that the fuel consumption is further improved and the wear of the cylinder block and the like is suppressed. it can. According to the invention of claim 5, the above effect can be obtained in a V-type multi-cylinder engine.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an internal combustion engine (hereinafter referred to as “engine”) according to an embodiment of the present invention.
It is sectional drawing which shows the structure of the crank mechanism of E1. The engine E1 is a spark ignition engine in which a plurality of cylinders are arranged in a line, and only one of these cylinders is illustrated here.

The engine body 1 includes a cylinder block 2
And a cylinder head 3 fixed thereon. Here, since the cylinder block 2 is made of an aluminum alloy in order to reduce the weight, the liner 4 is fitted into the cylinder block 2. In this embodiment, the cast iron liner 4 is used to improve wear resistance. However, instead of the liner 4, even if the inner wall of the cylinder block 2 is plated with chrome, or the cylinder block 2 itself is made of cast iron, it can be used in combination with the crank mechanism according to the present invention. .

The cylinder head 3 has an intake passage 5 on one side and an exhaust passage 6 on the other side with respect to the cylinder center line L1.
Are formed, and the port portions 5a and 6a of the passages 5 and 6 are formed.
An intake valve 7 and an exhaust valve 8 are interposed in the. Then, the piston 9 is inserted into the cylinder block 2, and the combustion chamber is formed by the lower surface of the cylinder head 3 and the crown surface of the piston 9.

In the expansion stroke, the combustion pressure is transmitted from the piston 9 to the crankshaft 11 (for simplicity, only the cross section of the shaft is shown) via the connecting rod (connecting rod) 10 which constitutes the crank mechanism, and is rotated. It is taken out as power. The connecting rod 10 is connected to the piston 9 by inserting the piston pin 12 into the small end portion (small end) 10a. On the other hand, the large end (big end) 10b is formed by being divided into the upper and lower parts, and the crank pin 13 formed at the tip of the crank arm is sandwiched by an appropriate bearing and fastened with a bolt. .

Here, the connecting rod 10 has a different external shape from the typical connecting rod that has been used conventionally. That is, as will be described later, the crankshaft center line C1
Bending between the small end portion 10a and the large end portion 10b so that (since the cross section is shown as a point) is convex in the direction opposite to the direction offset with respect to the cylinder center line L1. Has been done. In FIG. 1, since the crankshaft center line C1 is offset to the left, the crankshaft centerline C1 is bent so as to be convex to the opposite right. Therefore, the connecting rod 10
Is shaped like a dogleg as a whole.

For reference, FIG. 1 shows the center line L2 of the connecting rod 10 by a one-dot chain line. Since the connecting rod 10 is formed in a V shape as a whole as described above,
The center line L2 is also bent in a V shape. The cross section of the connecting rod 10 may be I-shaped like a general one so that the rigidity is improved. The offset of the crankshaft centerline C1 is in the direction opposite to the rotation direction D of the crankshaft 11 with respect to the cylinder centerline L1 (in FIG. 1,
Since the crankshaft 11 rotates clockwise, the opposite direction to the left) is performed. The offset amount (offset width w; for example, about 18.5 mm) that achieves the desired fuel consumption may be used.

Reference numeral 14 is an electronically controlled spark plug, and reference numeral 15 is a water jacket for circulating engine cooling water. The liner 4 of the cylinder block 2 may be of a wet type or a dry type. Further, the center of the piston pin 12 is indicated by reference numeral C2, and the center of the crank pin 13 is indicated by reference numeral C3. The chain double-dashed line T indicates the locus traced by the crankpin center C3 as the crankshaft 11 rotates.

FIG. 2 conceptually shows the operation of the crank mechanism of the engine 1 configured as described above.
(A) to (e) show this series of operations in chronological order. At a certain point in the compression stroke, the positional relationship between the crank arm 11a and the connecting rod 10 is as shown in (a), and when the crankshaft 11 rotates from there, it further moves and pushes the piston 9 upward. In this process, since the connecting rod 10 is bent in a V shape, a collision between the connecting rod 10 and the cylinder block 2 (liner 4) is avoided as shown in (b).

Here, for reference, the case of a typical straight connecting rod 10 'is shown in dotted lines. In this case, it is understood that the connecting rod 10 'and the cylinder block 2 are too close to each other because the offset width w is increased, and the connecting rod 10' collides with the cylinder block 2. Thereafter, in (c) showing the positional relationship at the compression top dead center, the piston pin center C2, the crank pin center C3, and the crank shaft center line C1 are lined up in a line from the top. When the rotation further proceeds from here and reaches a predetermined ignition timing after the compression top dead center, the spark plug 14 operates to ignite the fuel.

When the combustion pressure is maximum, the positional relationship between the connection points is as shown in (d). A straight line connecting the piston pin center C2 and the crank pin center C3 is substantially parallel to the cylinder center line L1 (in other words, the crank pin center C3 is located almost on the cylinder center line L1). By setting the positional relationship when the maximum combustion pressure is generated in this way, the external force (thrust force) that the piston 9 laterally receives based on the combustion pressure is suppressed as much as possible, and the lateral pressure to the inner surface of the liner 4 is reduced. Therefore, it is possible to suppress wear of the piston ring and the liner 4 and efficiently transmit the combustion pressure to the crankshaft 11 to obtain a large rotational power.

Since the offset width w of the crankshaft center line C1 is set to be large, as shown in (d),
When the maximum combustion pressure is generated, the lateral distance between the crankpin center C3 and the crankshaft centerline C1 (the operating point distance; equal to the offset width w) becomes long. This increases the moment obtained for equal combustion pressures,
The torque can be increased.

Then, when the next compression stroke is reached through the expansion stroke and the exhaust stroke, the rotation proceeds from the state immediately after the compression bottom dead center shown in (e), and returns to the state of (a) again. The operation will be repeated. FIG. 3 illustrates the effect obtained by the present embodiment, and the offset width w
The relationship between (horizontal axis) and the frictional resistance F (vertical axis) between the piston 9 and the liner 4 is shown.

In order to reduce the frictional resistance F as much as possible to achieve a desired fuel consumption, it is necessary to offset the width by w2 (for example, 18.5 mm). In a typical straight connecting rod, a cylinder block is used. The offset width w was limited to w1 (w1 <w2, for example, 8 mm) or less due to interference between the two. Therefore, with such a connecting rod, it is not possible to realize an offset sufficient to satisfy the fuel consumption requirement.

On the other hand, according to the doglegged connecting rod 10 of this embodiment, it is possible to set the offset width w large without causing a collision between the connecting rod 10 and the cylinder block 2. Therefore, it is possible to improve the fuel consumption by offsetting the width w2 that is required in view of the fuel consumption requirement. In addition to this, according to the connecting rod 10, since the connecting rod itself avoids a collision with the cylinder block 2, it is not necessary to provide a relief for avoiding a collision on the cylinder side. For this reason, the engine 1 (cylinder block 2) can be prevented from becoming large in size and can be finished compactly.

FIG. 4 shows the V-shaped connecting rod 1 described above.
The structure of what 0 was applied to the crank mechanism of V type cylinder engine E2 is shown notionally. As described above, the connecting rod according to the present invention can be applied to the one in which a plurality of cylinders are arranged in a V shape, and similarly in the engine E2 having such a configuration, the friction resistance is reduced, Also, the effect of improving the output can be obtained. At this time, the direction of offset of the crankshaft centerline C1 is the direction in which the crankshaft centerline C1 is arranged only on one side with respect to each cylinder centerline L1 in its vertical plane. Specifically referring to FIG. 4, the crankshaft centerline C1 is
It is located on the left side with respect to all the cylinder center lines L1.

FIG. 5 shows some modifications of the connecting rod according to the present invention. (A) is a typical linear connecting rod, and (b) to (d) are connecting rods according to the present invention. Shows. FIG. 5B shows the V-shaped connecting rod 10 described above, and the description thereof is omitted here.

As shown in FIG. 5 (c), the connecting rod is bent in a convex shape toward one side as in the case of FIG. 5 (b), except that it is smoothly bent in an arc shape as a whole. There is. Even with such an arc-shaped connecting rod 101, the connecting rod 101 and the cylinder block 2 (liner 4) can be made to have a convex shape in a direction opposite to the offset direction so that the connecting rod 101 and the cylinder block 2 (liner 4) have a large offset width w. Avoid collisions.

In FIG. 5 (d), the connecting rod is not bent as a whole and has a substantially linear shape, but the side shape is different on each side. That is, one of the sides
It is bent in a concave shape in a vertical section parallel to the offset direction (a section parallel to the surface of the figure). Even with the connecting rod 102 having such an external shape that is cut out,
A collision between the connecting rod 102 and the cylinder block 2 can be avoided. At this time, the connecting rod 102 is arranged so that the side surface 102c including the notch N faces the offset side.

As explained above, according to the present invention,
The use of a uniquely shaped connecting rod 10, 101 or 102 in a crank mechanism of an internal combustion engine allows for a greater crank offset. Therefore, the frictional resistance to the piston 9 is reduced and the combustion pressure is efficiently converted into rotational power, so that the fuel consumption can be improved and the output can be increased.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a crank mechanism of an internal combustion engine according to an embodiment of the present invention.

FIG. 2 is a conceptual diagram of the operation of the above crank mechanism.

[Fig. 3] Offset width w and piston 9 and liner 4
Diagram of frictional resistance F acting between

FIG. 4 is a V-type cylinder engine E equipped with the above crank mechanism.
Schematic diagram of 2

FIG. 5 is a front view of a connecting rod that constitutes a crank mechanism of an internal combustion engine according to some other embodiments of the present invention.

[Explanation of symbols]

1 ... Engine body 2 ... Cylinder block 3 ... Cylinder head 4 ... Liner 9 ... Piston 10 ... connecting rod 11 ... Crankshaft 12 ... Piston pin 13 ... Crank pin L1 ... Cylinder center line L2 ... connecting rod center line C1 ... Crankshaft centerline C2 ... Center of piston pin C3 ... Center of crankpin w ... offset width

Claims (5)

[Claims] 1. In a crank mechanism of an internal combustion engine in which a crankshaft center line is offset from a cylinder centerline, a side surface of the connecting rod facing the offset side has a small end portion and a large end portion of the connecting rod. A crank mechanism for an internal combustion engine, characterized in that the crank mechanism is bent in a concave shape between itself and the portion. 2. The crank mechanism for an internal combustion engine according to claim 1, wherein the connecting rod is bent so as to be convex in a direction opposite to an offset direction. 3. A crank mechanism for an internal combustion engine, wherein a center line of a crank shaft is offset from a center line of a cylinder, the center line of a connecting rod is bent so as to be convex in a direction opposite to an offset direction, and the connecting rod is bent. A crank mechanism for an internal combustion engine, characterized in that it is formed in a generally V shape. 4. The crank mechanism for an internal combustion engine according to claim 1, wherein the direction of offset is set so that the crankpin centerline intersects with the cylinder centerline during the expansion stroke. 5. The method according to claim 1, which is applied to a multi-cylinder engine in which a plurality of cylinders are arranged in a V shape, and a crankshaft center line is offset with respect to each cylinder center line. Crank mechanism of internal combustion engine.