JPH11280752A - Bearing structure of crank shaft - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bearing structure for a crank shaft with high durability which can keep strength of a crank bearing cap to be attached to a lower surface of a cylinder block. SOLUTION: In this bearing structure, companion surfaces 4b of crank bearing caps 4 each formed with a central arcuate recession to compose a bearing part 4a are tapered by angle θ to form an inverted chevron shape. The crank bearing cap 4 is fastened to a cylinder block 2 by means of a bolt 5. The crank bearing caps 4 are brought into close contact with each other with deformation. Compression stress is generated on a lower portion of the bearing portion 4a, that is, a bridge portion 6. A tensile stress at the time of fastening and a tensile stress generated on the bridge portion 6 under engine operation are cancelled by the compression stress. The tensile stress is reduced compared to the conventional cap 4. It is thus possible to reduce metal fatigue of the cap 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

2. Description of the Related Art Some crankshafts and camshafts in an engine use split type bearings due to their structure. Correctly fixing the bearings improves the engine performance. The present invention relates to a crankshaft bearing structure in which a split type bearing is fixed by bolting.

[0002]

2. Description of the Related Art In an engine for a vehicle, the number of cylinders is increased, and the arrangement of the cylinders is changed to improve the operability and the riding comfort. Therefore, the crankshaft of the engine usually has a plurality of shaft portions, and the cylinder block is formed with a semicircular bearing for each shaft portion, and the corresponding semicircular bearing is provided. A crank bearing cap sandwiches the shaft portion and is fastened to the cylinder block by a pair of bolts on both sides. Also, this crank bearing cap is independent one by one,
There is a structure in which several crank bearing caps are connected, and they are used as appropriate.

As an example, a crankshaft 1 shown in FIG. 7 has a plurality of shaft portions. When the crankshaft 1 is mounted on a cylinder block 2, a metal bearing 3 is interposed between the shaft portions, and a semicircular portion of the cylinder block 2 A shaft portion is supported by a crank bearing cap (hereinafter, referred to as a cap) 4 having a semicircular portion.
To conclude. The cap 4 is made of aluminum or iron.

[0004]

FIG. 8 (a)
When the cap 4 is fastened to the semicircular portion of the cylinder block 2 by a pair of bolts 5 as shown in FIG. 8, two bolts 5 are attached to the bridge portion 6 (the net portion in FIG. , A tensile stress (in the direction of the arrow) is generated (see FIG. 8B). Further, as shown in FIG. 9A, the crankshaft 1 is floatingly supported by the lubricating oil 7, but when the engine is operating, the cap 4 receives a force due to inertia from the crankshaft 1 and also causes a bridge due to friction or the like. Tensile stress is generated in the portion 6 (see FIG. 9B).

[0005] When these two tensile stresses are combined,
A large tensile stress acts on the cap 4. For this reason, although the strength is given so that the cap 4 is not damaged, the cap 4 becomes large, which leads to restrictions on layout and an increase in weight. In addition, in order to prevent the vertical movement direction a (see FIG. 8B) of the piston of the bearing inner diameter from being reduced, in Japanese Patent Application Laid-Open No. 7-35128, the cylinder block side is concave at the center and the cap side is A convex shape is formed at the center to align the mating surfaces, and the inner diameter is held by a tightening force. In addition, in order to eliminate a gap due to warpage at the time of tightening the mating surface between the cylinder head and the cylinder block, it has been proposed to raise the mating surface (Japanese Patent Laid-Open No. 3-138437).

An object of the present invention, as described above, is to provide a crankshaft bearing structure that maintains the strength of a crank bearing cap and has good durability.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, according to the present invention, a crank bearing cap for a bearing is provided on the lower surface of a cylinder block. In a crankshaft bearing structure in which a mating surface on both sides of a bearing portion formed on the crank bearing cap is fastened to a lower surface of the cylinder block, a mating surface on both sides of the crank bearing cap or the lower surface of the cylinder block is far from the bearing portion. It is characterized in that the slope is made closer to the mating surface of the other party.

A second aspect of the present invention is characterized in that, in the first aspect of the invention, the seat for the mounting bolt of the crank bearing cap is formed as a slope along the slope of the mating surface.

[0009] The invention of claim 3 is claim 1 or claim 2.
In the invention described in the above, a protruding edge portion that joins to an end wall surface of the mating surface on the crank bearing cap side is extended on the mating surface on the cylinder block side.

[0010] The invention of claim 4 is claim 1 or claim 2.
In the invention described above, a fastening margin is extended to an end of the mating surface on the cylinder block side and the mating surface on the crank bearing cap side, and the fastening margin is fastened.

As described above, according to the present invention, the lower surface of the cylinder block and the mating surface of the crank bearing cap are not parallel to each other, but the mating surfaces on both sides of the bearing portion are inclined in an inverted C-shape so that the bolts can be tightened at the time of fastening. The crank bearing cap is brought into close contact with the cylinder block and deformed to generate a compressive stress at a lower portion (bridge portion) of the bearing portion. Then, the tensile stress is offset with the tensile stress generated conventionally. Therefore, both surfaces of the lower surface of the cylinder block and the mating surface of the crank bearing cap may be machined to form a slope, or these shapes may be combined.

[0012]

Embodiments of the present invention will be described below with reference to the accompanying drawings. As shown in FIG. 1, a semicircular bearing portion 2 a for supporting a crankshaft is formed on a lower surface of a cylinder block 2, and a metal bearing 3 is mounted thereon. One of the caps 4 supporting the crankshaft is formed with a semicircular bearing 4a, and the mating surfaces 4b on both sides of the cap 4 are closer to the mating surface 2b of the cylinder block 2 in the direction perpendicular to the shaft axis, as the position is more centrifugal. An adjacent slope (angle θ) is formed. Here, the lower surface of the cylinder block 2 is flat, and the metal bearing 3 is also mounted on the bearing 4a of the cap 4.

As shown in FIG. 2, the bolt seat surfaces 4c on both sides of the cap 4 are parallel planes, and a pair of bolts 5
Thereby, the cap 4 is fastened to the cylinder block 2 to form a circular hole to support the crankshaft. Therefore, the cap 4 is connected to the cylinder block 2
When the cap 4 is in contact with the cap, a clearance is created between the mating surface 2b and the end of the bearing 4a. However, since the cap 4 is made of deformable aluminum or iron, the clearance is lost due to the close contact deformation at the time of fastening. The bridge 6 is compressed by the deformation, and a compressive stress (in the direction of the arrow) is generated.

The compressive stress cancels out the tensile stress at the time of fastening and the tensile stress generated in the bridge portion 6 of the cap 4 by operating the engine, so that the tensile stress value is lower than that of the conventional cap 4. Become. Thereby, the metal fatigue of the cap 4 is reduced.

The mating surface 4b of the cap 4 is
Although it varies depending on the precision and axial force of the conventional parallel plane, it is cut so as to have an inclination (angle θ) of about 2 to 3 degrees with respect to a conventional parallel plane. It has been confirmed by some experiments that a steep inclination (5 to 6 degrees) causes a lift in the vicinity of the bearing portion (causing a gap), and a gentle inclination (0 to 1 degrees) has little effect. . Accordingly, the compressive stress may be weak depending on the shape of the mating surface of the cap 4. However, since the tensile stress generated conventionally decreases, the tensile stress at the time of operation (the stress at the time of assembly and at the time of operation) also decreases. Will be.

Next, as another embodiment, the cap 4 shown in FIG. 3A has a mating surface in which the bolt seat surface 4c is also inclined.
It is made parallel to 4b. Fig. 3
As shown in (b), the lower surface of the cylinder block 2 and the bolt bearing surface 4c are parallel, and the load on the bolt 5 is reduced.
In the embodiment shown in FIG. 4A, the mating surface 4b of the cap 4 and the bolt seating surface 4c are both parallel planes, but the mating surface 2b of the lower surface of the corresponding cylinder block 2 is a slope (angle θ). Is configured. Also in this case, FIG.
As shown in FIG. 7, the cap 4 is deformed by fastening. In this configuration, since the engine (cylinder block 2) on which the invention is to be implemented is processed, the cap 4
Can be shared with conventional products.

In another embodiment shown in FIG. 5, both side walls (projecting edges) 2c continuous with the mating surface 2b of the cylinder block 2 are shown.
Is formed, and the bearing 2a of the cylinder block 2 is positioned in the concave shape. The cap 4 is fitted in this concave shape,
A corner portion (end wall surface) 4d of the cap 4 contacts the side wall 2c.
The cap shape is such that the mating surface 4b is an inclined surface (see FIG. 6 (a)) and is tightly adhered at the time of fastening. However, since the side walls 2c and the corners 4d of the cap 4 are in contact, this cap is Prevents deformation in orthogonal directions.

On the other hand, the bolt seat surface 4c side of the cap 4 extends in a direction perpendicular to the crankshaft, and the bolt seat surface (fastening allowance) 4e is increased. And, by fastening the bolts 5 twice, deformation (strain) during operation can be further reduced.

The cap 4 shown in FIG.
Is inclined (angle θ), has a corner 4d, and is formed with two pairs of bolt bearing surfaces 4c and 4e. By mounting the cap 4 on the cylinder block 2 described above, a solid bearing can be provided. In addition, as shown in FIG. 6B, the load on the bolt 5 is reduced by making the mating surface 4b of the cap 4 and the bolt seating surfaces 4c, 4e parallel. In addition, if the other cap shape is a composite type of the above-described elements, the durability can be improved.

[0020]

As described above, according to the present invention, when the crank bearing cap is fastened to the cylinder block, the compression stress is generated by the deformation of the crank bearing cap, the tensile stress at the time of the conventional assembly is reduced, and the strength is reduced. As a result, the tensile stress generated in the crank bearing cap during engine operation can be reduced, and the durability of the crank bearing cap can be improved. Further, the influence of the tensile stress is reduced, so that the size and material of the crank bearing cap can be reduced, the weight and cost can be reduced, and the layout restrictions can be reduced. Further, the load on the bolt is reduced by making the bolt bearing surface of the crank bearing cap parallel to the mating surface, and the strength is improved. In addition, when the cylinder block and the crank bearing cap are aligned, the protruding edge and the end wall come into contact with each other to prevent a displacement at the time of assembling, so that the accuracy of the bearing can be improved. Also,
Since the crank bearing cap with the extended fastening margin is fixed with two pairs of bolts, stress during operation can be reduced and deformation (strain) can be reduced.

[Brief description of the drawings]

FIG. 1 is a front view of a crank bearing cap according to an embodiment of the present invention and a cylinder block to which the cap is attached.

FIG. 2 is a front view of a main part in a mounted state of the crank bearing cap of FIG. 1;

FIG. 3 is a front view of a shape (a) and a mounted state (b) of a crank bearing cap according to another embodiment.

FIG. 4 shows the shape of the lower surface of a cylinder block according to another embodiment (a) and the mounting state of a crank bearing cap (b).
FIG.

FIG. 5 is a front view showing a mounted state of a crank bearing cap according to another embodiment.

6 is a front view of the crank bearing caps (a) and (b) used in FIG.

FIG. 7 is a perspective view showing a conventional crankshaft bearing structure.

FIG. 8 is a front view of a shape (a) and a mounted state (b) of a conventional crank bearing cap.

FIG. 9 is a front view showing a conventional bearing structure (a) with a crankshaft inserted and a shaft rotating state (b).

[Explanation of symbols]

 2 Cylinder block 2b Mating surface 2c Projecting edge 4 Crank bearing cap 4b Mating surface 4c Bolt seat 4d End wall 4e Fastening allowance (bolt seat) θ Slope angle

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shoji Takeuchi 300 Takatsukacho, Hamamatsu-shi, Shizuoka Suzuki Co., Ltd. (72) Inventor Yoshiaki Ueda 300 Takatsukacho, Hamamatsu-shi, Shizuoka Suzuki Co., Ltd.

Claims (4)

[Claims] 1. A crank bearing cap for a bearing having a center formed in an arc-shaped concave portion is disposed on a lower surface of a cylinder block, and both side mating surfaces of a bearing portion formed on the crank bearing cap are fastened to a lower surface of the cylinder block. A bearing structure for a crankshaft according to claim 1, characterized in that the both-side mating surfaces of the lower surface of the crank bearing cap or the cylinder block are inclined closer to the mating surface as the distance from the bearing part increases. 2. A bearing structure for a crankshaft according to claim 1, wherein the seat for the mounting bolt of the crank bearing cap is formed as a slope along the slope of the mating surface. 3. The crankshaft according to claim 1, wherein a protruding edge portion joined to an end wall surface of the mating surface on the crank bearing cap side is extended on the mating surface on the cylinder block side. Bearing structure. 4. The fastening margin is extended at an end of the mating surface on the cylinder block side and the mating surface on the crank bearing cap side, and the fastening margin is fastened. 3. The bearing structure for a crankshaft according to 2.