JP2016102450A - Internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To firmly fasten a crank cap to a cylinder block with uniform force while preventing occurrence of distortion of the cylinder block, even when the axial cores of a head bolt and a cap bolt are deviated, in an internal combustion engine in which the axial core of a cylinder bore and the axial core of the crank shaft are deviated.SOLUTION: Head bolts 3 are provided at symmetric positions so as to hold an axial core 20 of a cylinder bore 1. An axial core 23 of a crank shaft 7 is offset on one side by a dimension e with respect to the axial core 20 of the cylinder bore 1. Right and left cap bolts 12 are arranged respectively coaxially with the head bolts 3. Accordingly, the right and left cap bolts 12 are arranged so as to be laterally asymmetric to the axial core 23 of the crank shaft 7. A main oil gallery 26 is provided between the cap bolt 12 and the head bolt 3 positioned on the side in which the crank shaft 7 is offset, and thereby joint strength of the right and left cap bolts 12 is balanced.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an internal combustion engine, and particularly has a feature in a fixing structure (fastening structure) of a cylinder head, a cylinder block, and a crank cap.

  In a reciprocating internal combustion engine, a cylinder head is fixed to the upper surface of a cylinder block with a head bolt, while a crank cap that rotatably holds a crankshaft is a cap bolt on the lower surface portion (bearing recess) of the cylinder block. It is fixed by.

  In this case, when looking at the head bolt, in order to equalize the fastening force of the cylinder head over the whole, the head bolt is disposed at a symmetrical position of the cylinder bore as viewed in the crank axis direction.

  Similarly, in order to equalize the tightening force of the crank cap and prevent uneven wear of the crankshaft, it is preferable to dispose the cap bolt at a symmetrical position of the cylinder bore as viewed in the direction of the crankshaft axis. . In particular, since the cylinder block made of aluminum is easily deformed, it is highly necessary to consider that a uniform fastening force is applied to the cylinder head and the crank cap.

  Therefore, in Patent Document 1, the head bolt is provided at a symmetrical position with the axis of the cylinder bore interposed therebetween, and the cap bolt is disposed at a symmetrical position with the axis of the crankshaft interposed therebetween. Moreover, in patent document 1, the main oil gallery is formed in the height position between the head bolt and cap bolt which were located in the one side in the crank-axis direction view. The main oil gallery is formed so as to be shifted to the left and right outside from the axis of the head bolt and the cap bolt.

JP-A-7-71311

  Now, in an internal combustion engine, in order to efficiently transmit the piston force during the expansion stroke to the crankshaft, to reduce the height of the cylinder block, etc., the crankshaft is centered with respect to the cylinder bore shaft. Offsetting (shifting) to the left or right when viewed in the axial direction is performed.

  Therefore, as in Patent Document 1, when the head bolts are arranged symmetrically on both sides of the cylinder bore, and the cap bolts are arranged symmetrically on both sides of the crankshaft, in the offset type internal combustion engine, the head bolt And the cap bolt will shift to the left and right, and the direction of pulling by the head bolt and cap bolt will shift, and the cylinder block will be easily distorted. To prevent this, Reinforcing means such as increasing the thickness or providing reinforcing ribs must be taken, which leads to new problems such as increased costs and increased weight (resulting in fuel efficiency deterioration).

  Further, in Patent Document 1, the cylinder bore and the crankshaft are arranged concentrically, and the head bolt and the cap bolt are arranged symmetrically. In this state, the main oil gallery is connected to the head bolt and the cap bolt on one side. Since they are formed at a height position between them, the tensile stresses in the vertical direction are different on both sides of the axis of the cylinder bore. As a result, the fastening strength of the crank cap is different on the left and right, and there is concern that uneven wear may occur on the crankshaft.

  The present invention has been made to improve the current situation.

  In the internal combustion engine of the present invention, the cylinder head is fixed to the upper surface of the cylinder block by a group of head bolts. On the lower surface of the cylinder block, a crank cap that rotatably holds the crankshaft is a cap bolt. The head bolt and the cap bolt are arranged in pairs on the left and right as viewed in the crank axis direction, and the center axis of the crank shaft is aligned with respect to the axis of the cylinder bore in the crank axis direction view. This is a basic configuration that is offset to the left or right side.

The pair of left and right head bolts are provided at symmetrical positions across the axis of the cylinder bore in the crank axis view,
The pair of cap bolts are arranged at asymmetric positions from the axis of the crankshaft so that one cap bolt located on the side where the crankshaft is offset is closer to the crankshaft than the other cap bolt. And
In addition, a main oil gallery extending in the crank axis direction is formed between the one cap bolt and the head bolt positioned thereon.

  In the present invention, the head bolt and cap bolt pair located on the left side in the crank axis direction view and the head bolt and cap bolt pair located on the right side are misaligned in the crank axis direction view, respectively. However, it is preferable to arrange the head bolt and the cap bolt concentrically. Also, it is preferable that the main oil gallery has its axis as close as possible to the head bolt and cap bolt. It is particularly preferred if the three are arranged concentrically.

  In the present invention, since the left and right cap bolts are arranged asymmetrically with respect to the axis of the crankshaft, if no measures are taken, the crank cap is fixed with cap bolts separated from the crankshaft. The fixing strength of the portion fixed by the cap bolt close to the crankshaft is larger than the fixing strength of the portion where it is. Accordingly, the holding force of the crankshaft is different between the right and left, and as a result, uneven wear is likely to occur in the crankshaft and the bearing member.

  However, in the present invention, since the main oil gallery is present above one cap bolt close to the crankshaft, the cylinder block has a location above one cap bolt higher than a location above the other cap bolt. Since the strength is weakened, the fastening strength of the crank cap by one of the cap bolts is weakened, and the pressing force of the left and right cap bolts can be equalized.

  That is, the present invention can eliminate or suppress non-uniform fastening strength due to asymmetrical cap bolts with respect to the crankshaft by adjusting the strength of the cylinder block using the main oil gallery, As a result, even though the shaft center of the cylinder bore and the axis of the crankshaft are offset, an internal combustion engine can prevent or greatly suppress uneven wear of the crankshaft while avoiding an increase in cost and weight.

It is a figure which shows 1st Embodiment and is the vertical front view which looked at the part between bores from the direction orthogonal to the crankshaft axis. It is a vertical front view of a modification.

  Next, an embodiment of the present invention will be described with reference to the drawings. First, the embodiment shown in FIG. 1 will be described. In the following description, the term “left and right” is used to specify the direction, which means left and right viewed from the crank axis direction.

  The basic structure of the internal combustion engine is the same as that of the prior art, and includes a cylinder block 2 having a plurality of cylinder bores 1 and a cylinder head 4 fixed to the upper surface of the cylinder block 2 with a group of head bolts 3. The cylinder block 2 and the cylinder head 4 are aluminum castings. FIG. 1 is a cross-sectional view of the portion between the bores. Therefore, the cylinder bore 1 is indicated by a dotted line. A piston 5 is slidably fitted in the cylinder bore 1, and the reciprocating motion of the piston 5 is converted into rotation of the crankshaft 7 by a connecting rod 6 indicated by a virtual line.

  The crankshaft 7 includes a plurality of crank journals 8 positioned outside the bore portion 2a and the bore group, and each crank journal 8 has a bearing portion 10 formed in the lower recess 9 of the cylinder block 2 in the upper half. The lower half is fitted to the crank cap 11, and the crank cap 11 is fixed (fastened) to the lower recess 9 of the cylinder block 2 by a pair of left and right cap bolts 12. A vertically-divided metal bearing 13 is fitted to the bearing portion 10 and the crank cap 11.

  The crankshaft 7 includes a crank arm (not shown), and a crank pin 15 provided at the tip of the crank arm and a piston pin 16 are connected by a connecting rod 6. A rotation locus of the crankpin 15 is indicated by reference numeral 17.

  The head bolts 3 are arranged in pairs on the left and right sides of the bore portion 2a and the bore group, and the left and right head bolts 3 are provided at symmetrical positions with the axis 20 of the cylinder bore interposed therebetween. That is, the left and right head bolts 3 are symmetrically arranged at a location separated from the axial center 20 of the cylinder bore 1 by an equal dimension L1. The head bolt 3 and the cap bolt 12 are reamer bolts, and the clearance between the head bolt 3 and the cap bolt 12 and the bolt holes 21 and 22 is very small.

  The axial center 23 of the crankshaft 7 is offset to the left by a slight dimension e from the axial center 20 of the cylinder bore 1 (shifted to the right). The left and right cap bolts 12 are arranged concentrically with the head bolt 3 respectively. For this reason, the distances L2 and L3 between the left and right cap bolts 12 and the shaft center 23 of the crankshaft 7 are such that the left dimension L3 offset from the axis 20 of the cylinder bore 1 is larger than the dimension L3 opposite to the offset side. Is also getting smaller.

  That is, the left cap bolt 12 (one cap bolt) is arranged closer to the crankshaft 7 than the right cap bolt 12 (the other cap bolt). Precisely, L3 has a dimension larger by e than L1, and L2 has a dimension smaller by e than L1.

  A main oil gallery 26 through which the lubricating oil passes is formed between the cap bolt 12 and the head bolt 3 located on the side offset from the axis 20 of the cylinder bore 1. The main oil gallery 26 extends in the crank axis direction, and branch oil passages 27 extending from the main oil gallery 26 to the locations of the metal bearings 13 are branched. Although not shown, an oil jet passage for injecting lubricating oil toward the lower surface of the piston 5 is also branched from the main oil gallery 26.

  In the present embodiment, the main oil gallery 26 is disposed concentrically with the head bolt 3 and the cap bolt 12. Further, the vertical distance between the cap bolt 12 and the main oil gallery 26 is set to be substantially the same as the vertical distance between the cap bolt 12 and the main oil gallery 26 (these vertical distance dimensions can be arbitrarily set).

  Since the left and right cap bolts 12 are arranged asymmetrically with respect to the crankshaft 7, when the main oil gallery 26 does not exist, if the left and right cap bolts 12 are tightened with the same torque, the fastening strength by the left cap bolt 12 is increased. Therefore, the clearance between the crank journal 8 and the metal bearing 13 is smaller in the left half than in the right half, so that the crank journal 8 and the bearing metal 13 are increased. This tends to cause uneven wear.

  However, in the present embodiment, due to the presence of the main oil gallery 26, the strength of the portion of the cylinder block 2 where the main oil gallery 26 is provided is weak, so even if the left and right cap bolts 12 are tightened with the same torque, The crank cap 11 can be held by the cylinder block 2 with the same force on the left and right. Thereby, uneven wear of the crank journal 8 and the metal bearing 13 can be prevented.

  In the modification shown in FIG. 2, the left cap bolt 12 that is offset with respect to the shaft center 23 of the crankshaft 7 among the cap bolts 12 is only the dimension e with respect to the left head bolt 3 positioned thereon. Offset to the left outside. Therefore, the difference between L2 and L3 is smaller than in the case of FIG.

  The left and right cap bolts 12 can be arranged outside the left and right head bolts 3 (the side far from the crankshaft), and the left and right cap bolts 12 can be arranged inside the left and right headbolts 3 (the side close to the crankshaft). It is.

  The present invention is actually applicable to an internal combustion engine. Therefore, it can be used industrially.

DESCRIPTION OF SYMBOLS 1 Thin bore bore 2 Cylinder block 3 Head bolt 4 Cylinder head 7 Crank shaft 8 Crank journal 9 Cylinder block bearing recess 10 Cylinder block bearing 11 Crank cap 12 Cap bolt 23 Metal bearing 20 as an example of bearing 20 Shaft bore 21 , 22 Bolt hole 23 Crankshaft axis 24,25 Bolt axis 26 Main oil gallery

Claims (1)

A cylinder head is fixed to the upper surface of the cylinder block by a group of head bolts, while a crank cap that rotatably holds a crankshaft is fixed to the lower surface of the cylinder block with a cap bolt, and the head A pair of bolts and cap bolts are arranged on the left and right as viewed in the crank axis direction, and the axis of the crankshaft is offset to the left or right side with respect to the axis of the cylinder bore as viewed in the crank axis direction Is configured, and
The pair of left and right head bolts are provided at symmetrical positions sandwiching the axis of the cylinder bore in the crank axis view,
The pair of cap bolts are arranged at asymmetric positions from the axis of the crankshaft so that one cap bolt located on the side where the crankshaft is offset is closer to the crankshaft than the other cap bolt. And
And, a main oil gallery extending in the crank axis direction is formed between the one cap bolt and the head bolt located thereon,
Internal combustion engine.

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